scientific american - 1995 11 - guardian cells in the brain

Ships can now receive 48 SCIENTIFIC AMERICAN November 1995 MEDITERRANEAN AND BLACK SEAS INDIAN OCEAN ATLANTIC OCEAN PACIFIC OCEAN Major Fishing Regions of the World: Changes in Catch...

NOVEMBER 1995

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Memory crystal could trap

a trillion bytes of data in 3-D.

Guardian cells in the brain.

Saving the worldÕs fisheries.

JugglingÕs tricks exposed.

Copyright 1995 Scientific American, Inc

November 1995 Volume 273 Number 5

Wolfgang J Streit and Carol A Kincaid-Colton

Holographic Memories

Demetri Psaltis and Fai Mok

During the 1950s and 1960s, the catch from commercial Þshing grew at three timesthe rate of the human population Such increasing exploitation of a limited naturalresource could not endure indeÞnitely : the total return peaked in 1989 and hassince stagnated, with some areas in severe decline Prudent management will be es-sential to prevent the collapse of this industry

Geologic records from around the world show that the earthÕs weather patternshave sometimes changed dramatically in a decade or less The ßow of heat throughthe oceans, particularly the Atlantic, may be the critical factor determining climatepatterns Researchers are now beginning to understand what triggered past swingsand to assess the possibility that we are poised for another in the near future

ÒI am very sorry to be disobliging about the photographers,Ó wrote Charles Darwin,Òbut I cannot endure the thought of sitting again.Ó Despite DarwinÕs lifelong eÝorts

to avoid public lectures, dinner parties and photography sessions, a few early men managed to capture his image A stunning photograph has recently been re-discoveredÑapparently the last ever made of the reclusive naturalist

lens-The laser technologies that produce 3-D pictures, or holograms, can also be applied

to capture and re-create digital information Holographic computer memories arealready capable of storing almost a billion bytes in the volume of a sugar cube andallowing the data to be accessed 10 times faster than from todayÕs compact-discsystems Advances in optoelectronics are making these feats possible

The brain polices against disease with the help of chameleonlike cells called glia Normally, these highly branched cells sit quietly, their extended arms reachingout to their neighbors; if they detect signs of damage or illness, they retract theirbranches and mobilize Growing evidence suggests that microglia may also be re-sponsible for some of the tissue damage caused by AlzheimerÕs disease and strokes

micro-4

The Science of Juggling

Peter J Beek and Arthur Lewbel

GodÕs Utility Function

Richard Dawkins

reserved No part of this issue may be reproduced by any mechanical, photographic or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted or otherwise copied for public or private use without written permission of the publisher Second-class postage paid at New York, N.Y., and at additional mailing offices Canada Post International Publications Mail (Canadian Distribution) Sales Agreement No 242764 Canadian GST No R 127387652; QST No Q1015332537 Subscription rates: one year $36 (outside U.S and possessions add $11 per year for postage) Postmaster: Send address changes to Scientific American, Box 3187, Harlan, Iowa 51537 Reprints available: write Reprint Department, Scientific American,

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Does the dazzling complexity of life oÝer irrefutable evidence of a grand purpose

in the universe? No, argues this expert on evolution and natural selection Patterns

of seemingly intelligent design can rather be explained as the result of a contest forsurvival among selÞsh genes that exploit their living hosts

One hundred years ago this month, Wilhelm Conrad Ršntgen, a quiet German icist, witnessed a startling image He attributed the eÝect to a new kind of electro-magnetic rayÑemissions that could pass through cardboard, wood and skin Withinmonths, an astounding array of applications were born

phys-Practitioners of this ancient art have found an appreciative audience in the tory Scientists have quantiÞed how many objects can be juggled, analyzed thephysiology of the talent, devised mathematics that helps performers invent newjuggling patterns and even built juggling robots

labora-50, 100 and 150 Years Ago

1945: DDT warning

1895: Loss of the bison

1845: Telegraph balloons

111102

8

10

Letters to the Editors

The counterfeiting threat Red wolves:

a new species? HarvardÕs women

Reviews and Commentaries

Extremely close encounters Atlases onCD-ROM Science-in-Þction MorrisonÕsÒWondersÓ and BurkeÕs ÒConnections.Ó

Essay:Anne Eisenberg

Electronic commerce could drop the Net on personal privacy

D E PARTM E N T S

12

Science and the CitizenRising IQ Fiberglass and cancer fears ÒGay genesÓ under new scrutiny Antarctic meltdown Thalidomide rehabili-tated Mapping heart disease Volcano music Attractive odors.The Analytical Economist Taxes and the female workforce.Technology and Business Congress tackles technology withoutadvice Algae against sewage Linking nerves to silicon

ProÞle Kay RedÞeld Jamison talks of moods and madness

How to Þll space with knots and doughnuts

The Amateur Scientist

Measuring wind speed

Established 1845

EDITOR IN CHIEF: John Rennie

BOARD OF EDITORS: Michelle Press, Managing tor; Marguerite Holloway, News Editor; Ricki L Rusting, Associate Editor; Timothy M Beardsley ;

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THE COVER shows the pattern of varyingrefractivity that represents a bit of data,stored three-dimensionally in a crystal Suchholograms are created when two laserbeams, one imprinted with the data, meetand interfere with each other in the crystal

The resulting interference pattern is not tually visible But when the crystal is reillu-minated at the correct angle, the patterndiÝracts the light so that the beam with thedata is reconstructed (see ỊHolographicMemories,Ĩ by Demetri Psaltis and Fai Mok,page 70) Image by Slim Films

ac-Letter from the Editor

JOHN RENNIE, Editor in Chief

All living things are the products of evolution, a point that renowned

biologist Richard Dawkins of the University of Oxford makes

forcefully in this issue Magazines evolve over time, too, which

makes this a Þtting moment to introduce some additions and

reÞne-ments that readers will Þnd in ScientiÞc AmericanÕs pages this month.

First, we are glad to mark the debut of two new features, both of which

appear in our expanded ỊReviews and CommentariesĨ section One is in

fact a contribution from an old friend: physicist Philip Morrison,

profes-sor emeritus of the Massachusetts Institute of Technology For almost 30

years, Professor Morrison has served as ScientiÞc AmericanÕs faithful

book reviewer, a role in which he produced a steady outpouring of lyrical,

literary essays that revealed as much about his own far-ranging

enthusi-asms and knowledge as about the books under discussion In his new

col-umn, ỊWonders,Ĩ he carries on that tradition, taking as his credo the

words of Michael Faraday, ỊNothing is too wonderful to be true.Ĩ (

Inci-dentally, on a more personal note, this month Professor Morrison

cele-brates his 80th birthday Happy birthday, Phil, from all of us youÕve

amazed, informed and inspired.)

We are also delighted to welcome historian of science James Burke,

best known to millions as the creator of the television series Connections.

In his column of the same name, Burke wittily traces the

threadsĐslen-der, frayed and oddly tangledĐthat tie together diverse technological

de-velopments through the centuries Check page 109 to learn, for example,

how innovations in 17th-century textile making revolutionized

20th-cen-tury automation

Fans of ỊMathematical RecreationsĨ and ỊThe Amateur ScientistĨ may be

pleased to see that those features, which formerly alternated from month

to month, will now be appearing in every issue ỊMathematical

Recrea-tionsĨ continues under the reliable authorship of Ian Stewart of the

Uni-versity of Warwick Shawn Carlson joins us as the new writer of ỊThe

Am-ateur Scientist.Ĩ The subject of the column is one close to his heart : he is

director of the international Society for Amateur Scientists We hope

read-ers will be able to use the projects he describes as a springboard to

fur-ther explorations of the natural world and technological innovation

Foreign Exchange

In their article ÒProtecting the

Green-backÓ [SCIENTIFIC AMERICAN, July],

Rob-ert E Schafrik and Sara E Church stress

that photocopiers and computers are

the main threats to U.S currency The

article did not go into how some foreign

countries make high-quality counterfeit

bills For example, Iran allegedly uses

the same intaglio press as the U.S and is

said to have obtained counterfeit $100

plates The bills created are so well made

that some banks will not take U.S

cur-rency in large amounts from Iran for

fear that these ÒsuperbillsÓ will be mixed

in Some estimates put the number of

superbills now in circulation at around

$5 billion

GREGORY MORROW

Portland, Me

Schafrik and Church reply :

The National Research Council

re-port, ÒCounterfeit Deterrent Features

for the Next-Generation Currency

De-sign,Ó which is referenced in our article,

gives a full discussion of counterfeiting

threats from opportunistic individuals,

well-Þnanced criminal organizations

and state-sponsored counterfeiters

Al-though the features we discussed will

pose signiÞcant obstacles to

profession-al counterfeiters, the long-term strategy

to combat counterfeiting should rely on

the use of a well-chosen suite of visible

and machine-detectable features that

are changed at intervals frequent enough

to make counterfeiting an expensive

and diÛcult job

According to the Secret Service, which

works closely with law enforcement and

banks all over the world, the face value

of counterfeit bills in circulation at one

time is on the order of one hundredth

of 1 percent of the $380 billion of

circu-lating currencyÑmuch smaller than the

Þgure of $5 billion quoted by Morrow

Ideally, the number of counterfeit notes

should be zero; from a practical

stand-point, the average citizen will only

rare-ly, if ever, run across a counterfeit note

Distorted Images

The most striking demonstration of

the phenomenon described in John

Hor-ganÕs ÒThe Waterfall IllusionÓ [ÒScience

and the Citizen,Ó SCIENTIFIC AMERICAN,

July] can be seen in a rotating spiraldisk When one gazes at it for a whilewith the disk rotating in one direction,then looks at a personÕs face, the faceseems to expand When the spiral is ro-tated the other way, the face seems tocontract Jerry Andrus, a magician andinventor of optical illusions, had thehappy idea of putting several spirals

on one disk, alternating their directions

After one observes this disk rotate for

a minute or so, then looks away, thescene bubbles with curious distortions

MARTIN GARDNERHendersonville, N.C

The Origin of the Hybrid

In their article ÒThe Problematic RedWolf Ó [SCIENTIFIC AMERICAN, July], Rob-ert K Wayne and John L Gittleman pre-sent evidence that strongly supports theidea that the red wolf is not a species oflong standing Their evidence does notargue nearly so well, though, that thered wolf is merely a hybrid of the coyoteand the gray wolf, the main contention

of the article Perhaps the genetic larities of the red wolf to both the graywolf and the coyote reßect the possibil-ity that the red wolf has become a dis-tinct species only in the past few thou-sands or even hundreds of years Thered wolf has suÝered a more recent de-cline, so that now only hybrids exist Byadopting a very restrictive deÞnition ofspecies, the authors may have been led

simi-to a conclusion that the evidence doesnot exclusively support

KEITH W SPOENEMANDes Peres, Mo

Wayne and Gittleman reply :

We do not mean to apply a restrictivedeÞnition of species to the red wolf Apopulation may have no observableunique genetic markers and yet be mor-phologically distinct from other popu-lations and so considered by some to

be a species If the red wolf originatedwithin the past few thousand years, asSpoeneman suggests, we agree thatthere may not have been time for uniquegenetic markers of the kind we analyzed

to evolve in the red wolf But the groupmay have had time to become physical-

ly distinct Rapid morphologic changes,however, such as those seen in the many

varieties of domestic plants and animalsthat have arisen in the past few hundredyears, generally involve a limited num-ber of genes and require intense artiÞ-cial selection In particular, the purity

of these new groups is carefully tained by breeders

main-Even if some of these restrictive ditions applied to the origin and evolu-tion of the red wolf, the species wouldhave had to persist in genetic isolation,despite the overwhelming possibility ofcrossbreeding with the plentiful graywolf and coyote that lived in the samerange In eastern Canada, crossbreed-ing between gray wolves and coyotesoccurs because of habitat changes thatare analogous to past events in the his-toric range of the red wolf Thus, in ouropinion, a simpler and more likely sce-nario for the origin of the red wolf isthat it results from hybridization be-tween the gray wolf and coyote

con-Women at HarvardRuth Hubbard was not Òthe Þrst wom-

an to receive tenure in the sciences atHarvardÓ in 1973, as described in theproÞle by Marguerite Holloway [ÒSci-ence and the Citizen,Ó SCIENTIFIC AMER-ICAN, June] The astronomer CeciliaPayne-Gaposchkin had been promoted

to tenure in 1956 When I came to vard as a freshman in 1959, she wasnot only Phillips Professor of Astrono-

Har-my but also what we then called man of the astronomy department Itwas years before I realized that it wasnot typical to have women as professors

chair-or as chairmen! Jane S Knowles, chivist of RadcliÝe College, informs methat Payne-Gaposchkin was preceded

ar-as tenured professor at Harvard by thephysician and toxicologist Alice Hamil-ton ( in the medical school ) and by thehistorian Helen Maud Cam and the an-thropologist Cora DuBois in the faculty

of arts and science

JAY M PASACHOFFWilliams College

Letters selected for publication may

be edited for length and clarity licited manuscripts and correspondence will not be returned or acknowledged unless accompanied by a stamped, self- addressed envelope.

Unso-8 SCIENTIFIC AMERICAN November 1995

LETTERS TO THE EDITORS

Copyright 1995 Scientific American, Inc.

NOVEMBER 1945

Miniature oxygen tents for

ba-bies born prematurely are

now being fabricated from Ethocel

sheeting Still in the experimental stage,

the clear plastic tents permit a full view

of the tiny patient.Ó

ÒRelease of DDT to civilians for

gen-eral use recently led to a ßood of

prep-arations presumably containing this

highly eÝective insecticide but actually

too dilute to be useful Fear is expressed

by legitimate insecticide producers that

unfortunate experiences with early

im-proper DDT preparations made by

un-scrupulous persons may prevent its

le-gitimate later use for valuable purposes.Ó

ÒWar trends as foreseen by General

H H Arnold include: One, airplanes

traveling at supersonic speeds; at such

speeds, aerial combat as it is known

to-day would be impossible Two,

develop-ment of guided missiles; reÞnedevelop-ment of

their controls could enable exact hits

on targets of a mile square or less, at

any part of the world from any part of

the world Three, great developments

in defense against aircraft and guided

missiles; every new weapon of oÝense

brings forth a weapon of defense, and

this should remain true even in the case

of the atomic bomb.Ó

NOVEMBER 1895

Common earthworms, despised by

man and heedlessly trodden under

foot, Ôhave played a more important

part in the history of the world than

most persons would at Þrst suppose,Õ

says Charles Darwin Vast quantities ofearth are continually being passedthrough the bodies of earthworms andvoided on the surface as castings Alayer of dirt one-Þfth of an inch thick,

or ten tons by weight, has been lated in many places to be brought an-nually to the surface per acre.Ó

calcu-ÒThe buÝalo of the West has rapidlydisappeared before the huntsmanÕs ri-

ße The hunters received on an averagefrom $2.50 to $3.50 per hide, to beshipped out of the country and sold forleather making, belting, harness, andkindred purposes The most successfulhunting parties consisted of a hunterand six men known as strippers, andmany thousands of men were engaged

in the enterprise At one station alone

on the Topeka and Santa Fe Railroad asmany as 750,000 hides were shipped inone year The same territory which aquarter of a century ago was support-ing vast herds of wild game is now sus-taining millions of domestic animals.ÓÒThe federal government has beenexperimenting at its military posts withcondensed rations, so called At FortLogan, the rations issued consisted ofcoÝee and soup, condensed into smalltablets; the bread was crushed into aßat cake of the weight and hardness of

a stone The bacon was solidly packed

in a tin can The soldiers marched andate as ordered, but their marching andeating were brought to an abrupt end

by more than half falling sick beforeone-half the allotted time expired The

report to the War Department atWashington is wholly against theexperiment.Ó

ÒE W Scripture of Yale Universitywrites: ÔI have found a method of astereoscopic projection of lantern viewsshowing relief eÝects on a screen Spec-tacles of colored glass can be arrangedwith a particular red for the left eye and

a particular green for the right eye, madefrom the standard red and green glassused by railways The relief appearsjust as real as a real object When thepictures are life size, the observer Þnds

it hard to believe that, for example, hecannot actually advance along the shad-

ed roadway before him or step into theboat waiting on the shore.Õ Ó

NOVEMBER 1845

The steamship Britannia arrived atBoston on Thursday last, havingmade the passage from Europe in Þf-teen days The accounts of the generalfailure of the potato crops by the rot,especially in Ireland, are of a very seri-ous and alarming character.Ó

ÒThe editors and publishers of

sever-al newspapers have promptly refused

to advertise for grocers or innkeeperswho deal in ardent liquors That is as itshould be; and it is to be hoped that alleditors, especially those who advocatethe temperance cause, will refrain fromaiding the rum trade by advertising anything in the line.Ó

ÒThe western papers complain of thedepredations of burglars from NewYork This must be a mistake, as thereappears to be none missing here.Ó

ÒA new method has been proposedfor extending the lines of the MagneticTelegraph across rivers and bays It isproposed to support the wires in an el-evated position, by means of elliptic bal-loons These balloons, being each sixtyfeet in length, will support about 40pounds each besides its own weight.The cost will not exceed $200 each, be-ing made of thin varnished cloth andinßated with hydrogen gas A small pipe1.4 inch in diameter will be extended toeach balloon, by means of which thegas in the balloon may be occasionallyreplenished.Ó

The Magnetic Telegraph crossing a river

50, 100 AND 150 YEARS AGO

12 SCIENTIFIC AMERICAN November 1995

Is the average high schooler of

to-day brilliant compared with his or

her grandparents? Or, conversely,

are those grandparents dull-witted

rel-ative to their childrenÕs children? One

must conclude as muchÑif one believes

intelligence is a Þxed trait that can be

accurately measured by IQ tests The

reason is that scores on intelligence

tests have risen steadily and

dramati-cally ever since such tests were

intro-duced early in this century

This phenomenon, called the Flynn

eÝect, was Þrst described more than a

decade ago But it has received

wide-spread attention only recently as a

re-sult of the tintinnabulation emanating

from The Bell Curve: Intelligence and

Class Structure in American Life In that

book, published last year, political

scien-tist Charles Murray and the late

Rich-ard J Herrnstein, a psychologist,

ar-gued that the economic stratiÞcation

of American society reßects

ineradica-ble diÝerences in intellectual ability

The authors mentioned the Flynn eÝect

only to dismiss it as a curiosity with

lit-tle relevance for their overall argument

Actually, the Flynn eÝect

demon-strates that intelligence is much more

mysterious than Murray and Herrnstein

imply, says Ulric Neisser, a psychologist

at Emory University Neisser is the lead

author of a new study by the American

Psychological Association (APA)

enti-tled Intelligence: Knowns and Unknowns.

The report considers various possible

explanations of the ÒstrikingÓ eÝect but

acknowledges that none are

satisfacto-ry ÒThe fact that there could be such a

large eÝect, and that we donÕt know

what causes it, shows the state of our

Þeld,Ó Neisser says ÒIt shows that weshould be quieter than we are.ÓThe phenomenon is named afterJames R Flynn, a political scientist atthe University of Otago in New Zealand

In the early 1980s, while studying ligence testing in the U.S military, Flynnfound that recruits who were merelyaverage when compared with their con-temporaries were above average whencompared with recruits in a previousgeneration who had taken exactly thesame test The trend had escaped noticebecause testers calculate IQ scores bycomparing an individualÕs performance

intel-with those of others in the same agegroup (A score of 100 is average bydeÞnition.)

Investigating the implications of thistrend, Flynn found that scores on virtu-ally every type of IQ testÑadministered

to military recruits and to students ofall agesÑhad risen roughly three pointsper decade since they were Þrst insti-tuted in the U.S Flynn learned that 20other countries for which suÛcient dataare availableÑincluding Canada, Israeland a number of European nationsÑshowed similar increases

The gains ranged from 10 points pergeneration, or 30 years, in Sweden andDenmark to 20 points per generation inIsrael and Belgium The upward surgestended to be greatest for tests that min-imize cultural or educational advantag-

es by probing the ability to recognizeabstract patterns or solve other non-verbal problems Flynn has recently an-

alyzed scores from RavenÕs ProgressiveMatrices, which is considered to be one

of the least Òculturally loadedÓ IQ tests.The birth dates of those examined span

a century, ranging from 1877 to 1977.Flynn concluded that someone scoring

in the 90th percentile 100 years agowould be in the Þfth percentile today.The eÝect can mislead intelligenceresearchers, according to Flynn Manyinvestigators have asserted, for exam-ple, that the elderly suÝer a progressivedecline in intelligence, because whenthey take modern IQ tests they do not

score well compared with modern year-olds But if the average 70-year-oldtakes a test that was used 50 years ago,Flynn says, he or she will usually score

20-as well 20-as the average 20-year-old ofthat era did on the same test

Similarly, some experts have claimedthat the academic success of Chinese-Americans, relative to their white con-temporaries, is correlated with higherintelligence as measured by higher IQscores But the IQ disparity reported insome studies resulted in part from theadministration of old tests to the Chi-nese-Americans, Flynn says

All researchers, including Murray andHerrnstein, agree that the IQ gains muststem not from genetic factors but fromenvironmental ones Nevertheless, Flynnhimself has shot down every hypothe-sis put forward so farÑfor instance, theproposal that children in successivegenerations attain higher scores becausethey take more tests and thus learn how

to perform more eÛciently IQ testshave actually become less common inrecent years, Flynn remarks, while therise in scores has persisted Moreover,studies have shown that ÒpracticeÓ intaking tests generally confers only asmall advantage at best

Nor can the eÝect be attributed

sole-SCIENCE AND THE CITIZEN

Get Smart, Take a Test

A long-term rise in IQ scores baÜes intelligence experts

SMART, SMARTER, SMARTEST? These photographs show children taking IQ tests in 1927, 1951 and 1989.

ly to improvements in

educa-tion, Flynn says To be sure, the

rise in IQ in Denmark has been

matched by increases in the

time that students spend in

school But IQs of American

children have risen even during

periods when the time spent in

school has not Flynn also looks

askance at the idea that the

growing pervasiveness of the media,

and television in particular, has made

children smarter Television was

usual-ly considered a Òdumbing downÓ

inßu-ence, Flynn comments wryly, Òuntil this

eÝect came along.Ó Moreover, scores

be-gan rising in the U.S decades before the

advent of television in the early 1950s

The Flynn eÝect should become even

more widely discussed over the next

year or two Neisser hopes to convene

a conference on it at Emory next spring

The noted intelligence researcher

Ar-thur R Jensen of the University of

Cali-fornia at Berkeley also dedicates a ter to the Flynn eÝect in a forthcomingbook

chap-Jensen, whose proposals on gence in the 1970s anticipated those

intelli-aired in The Bell Curve, was an early

critic of FlynnÕs research But he hasbecome convinced that the Flynn eÝect

is genuine and important Jensen tends that the gains must be at leastpartially biologicalÑrelated to improve-ments in nutrition and medicineÑaswell as cultural He points out thatheight, a human attribute that is largely

con-heritable, has increased steadilyfor more than a century; nutri-tion might have spurred com-parable boosts in intelligence.But the recent APA reportÞnds little support for a corre-lation between nutrition and in-telligence (as long as minimalneeds are met) Flynn also coun-ters JensenÕs hypothesis with aquestion: In 1864 did the Dutch, whowere on average shorter than 99 per-cent of their modern descendants, real-

ly have an intelligence stunted to thesame degree? Did they have the sameintelligence as people who today score

65 on IQ tests?

Flynn thinks not In fact, he evenÞnds the notion that his generation issigniÞcantly more intelligent than that

of his parents ludicrousÑand yet that

is the implication of his own research.ÒYou can see why IÕm baÜed,Ó he sayswith a sigh ÑJohn Horgan

F I E L D N O T E S

Attracted to the Pole

Although the magnetic pole lies

more than 1,000 kilometers to the

south, the earth’s geographic North

Pole emits its own invisible force,

entic-ing scientists to cross vast

stretch-es of the frozen Arctic to reach it

In 1991 a pair of European

ice-breakers were the first research

vessels to make the trip Last

year U.S and Canadian ships

mounted a joint expedition, and

their journey produced some

un-expected, young heroes

The two vessels, the American

Coast Guard’s Polar Sea and the

Canadian Coast Guard’s Louis S St.

Laurent, left Alaska in July 1994

and headed to the earth’s

north-ern limit the hard way—through

some 1,700 kilometers of

ice-bound ocean They planned to

make a circuit of the western basin,

where sea ice is typically older (and

thus harder to break) than in the

east-ern route taken by the Europeans The

vessels struggled past heavy ice and

came within 50 miles of the North Pole,

when, according to E Peter Jones of

the Bedford Institute of Oceanography

in Halifax, “the Polar Sea suffered

ma-jor propeller damage.” Lt Commander

Steven G Sawhill reports that a cracked

retaining ring caused a blade to fly off

one of the three main shafts: “Once we

knew we had lost that propeller, it was

pretty obvious what the implications

were.” As James A Elliot of the BedfordInstitute explains, the problems werenot severe enough to threaten the ship,but they did cut the mission short: “Wewanted to get out When you’re upthere, you don’t want to get frozen infor a year—or two, or three.”

Tension must have run high as the

scientists pondered their options fromthe middle of this daunting wilderness

Then, like an Arctic mirage, there peared a curious, completely unantici-pated sight: a huge ship with a strange,toothy smile painted on the bow It was

ap-the Russian icebreaker Yamal Employed

during winter months to keep sea lanesopen, Murmansk Shipping’s newest nu-clear-powered icebreaker was spend-ing some of its off-season time ferryingabout 50 Russian children to the NorthPole The youngsters were on the jaunt

to celebrate a national festival for dren with music, singing and dancing

chil-Along with the many exuberant boysand girls was a Russian television crewproducing a live broadcast

Kent Berger-North, a Canadian ographer who acted as translator, ex-plains that the Russians “very gracious-

ocean-ly left the Pole” long enough for theAmerican and Canadian scientists tocomplete their struggle to reach

it, then came back: “They didn’twant to steal anybody’s thunder.”Russian generosity did not endthere After the appropriate num-ber of toasts, barbecues and

baseball games on the ice, the mal spearheaded the procession

Ya-home Whereas the research sels might have picked their way

ves-at three to four knots, the Yamal

charged ahead at 12 to 15 knotsthrough giant walls of frozen sea

“It just threw blocks away,” Elliotrecounts with awe

So the children’s ship led, andthe scientists followed in whatJames H Swift of the Scripps Institute ofOceanography in San Diego describes

as “the giant Slurpee the Yamal leaves

behind.” The researchers were fortunate.Had fate been less kind, they might

easily have missed the Yamal —or met

up with it during one of its chartered excursions to the Pole thatsummer Such an encounter would havemade the polar research expeditionseem awfully mundane After all, howexotic would it have been to bump into

American-an alumni tour group from California orIndiana? At least the kids spoke anoth-

er language —David Schneider

SCORES from both Wechsler and Stanford-Binet tests rose 24 points in the U.S between 1918 and 1989 The scores have been calibrated according to 1989 levels.

1009590858075

1920 1930 1940 1950 1960 1970 1980 1990

For the past several years, the fear

that Þberglass insulation might be

carcinogenic has permeated

scien-tiÞc and public health circles Although

the typical homeowner encounters

lev-els far too low for concern, the risk for

people who routinely install the

materi-alÑabout 30,000 in the U.S.Ñremains

controversial The insulation industry

points to studies indicating that

air-borne Þberglass has not raised the rate

of cancer among workers Some

gov-ernment scientists, however, perceive

shortcomings in those studies and cite

analyses showing a link Because of

these uncertainties, no U.S regulatory

body has completed a formal risk

as-sessment But an experiment begun this

past August may Þnally permit

regula-tors to decide once and for all

Fiberglass, manufactured since the

1930s, belongs to a class of materials

known as man-made vitreous Þbers

(MMVFs) Others include wools cast

from rock or slagÑsometimes called

mineral woolsÑand refractory ceramics,

made from clay But Þberglass

domi-nates the insulation market,

constitut-ing 80 percent of the U.S production of

MMVFs and garnering more than $2billion annually in sales

Concern that this widely used rial might be Òasbestos liteÓ came to thefore in 1988, when the InternationalAgency for Research on Cancer (IARC),

mate-a division of the World Hemate-alth Orgmate-ani-zation, classiÞed MMVFs as a possiblecarcinogen The U.S Department ofHealth and Human Services followedsuit last year, describing Þbrous glass

Organi-as ÒreOrgani-asonably anticipated to be a cinogenÓ and placing it on the list withsaccharin and automobile exhaust

car-The industry cried foul car-The NorthAmerican Insulation Manufacturers As-sociation in Alexandria, Va., claimedthat the designation derives from obso-lete scientiÞc protocols The IARC haddrawn its conclusions from studies inwhich rats and hamsters were injected

or implanted with massive numbers ofÞbers Some rodents developed meso-theliomas, tumors on the interior lin-ings of body cavities

ÒThese injection studies by deÞnitionoverload the target organ,Ó says Thom-

as W Hesterberg, a researcher for ler International, an insulation manu-

Schul-facturer based in Denver ÒTheyÕre propriate: humans are not exposed thatway.Ó All the Þbers are placed in the an-imal at once, but in humans exposure isgradual Moreover, body cavities lack themucosal and cilia linings of the lungsthat can clear Þbers from the system

inap-A more suitable test, Hesterberg says,

is inhalation of Þberglass, whereby ratsare forced to breathe air with variousconcentrations of MMVFsÑin somestudies up to 300 Þbers per cubic cen-timeter (A weekend project of layinginsulation in the attic typically kicks uponly 0.1 Þber per cubic centimeter, ac-cording to Thomas Calzavara, SchullerÕsmanager of product safety and health.)None of these studies concluded thatbreathing glass Þbers would cause tu-mors One class of MMVF, the refractoryceramic Þbers, did appear to be almost

as carcinogenic as asbestos is; this type

of insulation, however, appears only inspecialized applications, such as lin-ings for coke ovens

Some scientists discount the tion work Rodents have to breathethrough their noses; humans do not.Thus, rats may be inappropriate mod-els because they take in Þbers that arenarrower than the Þbers humans inhale,notes Loretta D Schuman, a toxicologist

inhala-at the Occupinhala-ational Safety and Health

Fiber That May Not Be Good for You

Researchers investigate whether Þberglass causes cancer

Copyright 1995 Scientific American, Inc

Administration So, she argues, just

be-cause inhalation studies turn up

nega-tive results does not prove glass wool

poses no risk ÒAn analogy is asbestos

They Þnally got rats to get cancer by

breathing, but it took ages Long before

that, they did injection studies,Ó

Schu-man recounts

That rats are nose breathers,

howev-er, does not invalidate them in

Hester-bergÕs opinion ÒA lot of the proposed

diÝerences between rodent and human

size exposures are pretty theoretical,Ó he

states, pointing out that no one knows

exactly how the Þbers actually trigger

cancer In any case, he says, the rodents

would be inhaling narrower Þbers, which

are thought to be more toxic because

they can reach deep into the lungs

Perhaps more disconcerting are

pos-sible technical problems in the

inhala-tion studies Schuman and her OSHA

colleague Peter F Infante have sharply

criticized them, Þnding ßaws in the

methodology and incomplete

presenta-tion of results In a review published

last year, they concluded that a slight

association exists between Þberglass

inhalation and cancer in test animals

Hesterberg counters, saying that the

re-crunching of the numbersÑin part,

pooling control animals from diÝerent

studiesÑwas inappropriate ÒIn rats,

there is enormous variability You want

to use concurrent controls: same lot,same litter,Ó he argues

The industry also maintains thatMMVFs diÝer chemically from asbestos

An inorganic Þber mined from rocks,asbestos takes up residence in the lungs

to cause cancer, mesotheliomas and

Þ-brosis (scarring) In contrast, Þberglass

is a synthetic substance that breaks upeasily and is quickly removed from thelungs by macrophages But the solubili-

ty argument does not assure all:

Vanes-sa T Vu, a scientist at the tal Protection Agency, points out thatthe most commonly used kind of as-

Environmen-BLOWING IN FIBERGLASS, done when the installation of blankets is infeasible, kicks

up enough potentially carcinogenic Þbers to require full protective gear.

bestos, called chrysotile, is also

relative-ly soluble, yet it still causes cancer

More important, the bodyÕs clearance

mechanisms may not help a

profession-al instprofession-aller ÒWorkers are going to be

exposed for 45 years,Ó Schuman notes,

Òand anything that goes away is going

to be replaced.Ó Currently OSHA has no

occupational guidelines for MMVFs (it

regards them as nuisance dust); an

at-tempt to push through some standards

in 1992 fell through because of legal

technicalities The insulation

manufac-turers association recommends

precau-tions, including a mask and an exposure

limit of one Þber per cubic centimeter

But there are some instances where that

level is easily exceeded ÒOSHA is

wor-ried particularly about the blowing in

of insulation,Ó Schuman remarks

Epidemiology studies have not helped

settle the controversy Most Þnd no rise

in cancer risk, although some subgroups

demonstrate slightly elevated levels

Some investigators believe the studies

are ßawed, because the analyses drew

mostly on workers who came from

pro-duction facilities, where airborne Þber

levels are kept low Hence, the sample

may have consisted of individuals not

exposed to levels experienced by those

who blow in insulation Others take the

opposite tack and state that

confound-ing factors, such as smokconfound-ing, may havecaused the correlations

To evaluate the risk completely, theEPA suggested industry conduct a newinhalation study Begun this past sum-mer, it is designed to address some ofthe criticisms of past inhalation trials,one of the most important being wheth-

er the animals were dosed suÛciently

(In an unpublished analysis, Hesterbergconcludes they were: the maximum tol-erated dose, he recently found, is a con-centration of 30 milligrams of Þbers percubic meter.) The study, using ham-sters, should be Þnished by mid-1997

Although scientists on both sides ofthe issue feel that this experiment willlead to a more complete risk assess-ment of MMVFs, it probably will not endthe debate Lacking funds, governmentagencies rarely test for safety them-selves; instead they rely on industry-sponsored work Even though such stud-ies take advice from government scien-tists, are open to auditing and must passpeer review, a feeling of bias can stillexist ÒIt is a reality we have to live with,ÓHesterberg says, conceding that Òourcompany has made some mistakesÓ butthat it has learned its lessons from as-bestos ÒI feel weÕve adequately testedÞberglass,Ó he adds ÒI feel it wonÕt causecancer or Þbrosis.Ó ÑPhilip Yam

The Big Thaw

Stability of the Antarctic ice remains unclear

The vast shield of ice capping the

Antarctic is the largest body offreshwater on the planet If itmelted, sea levels would surge by 60 me-ters, submerging coastal areas aroundthe world Some scientists have there-fore become increasingly alarmed in re-cent years as David M Harwood of theUniversity of Nebraska and others havepresented evidence that a mere threemillion years ago, during the Plioceneepoch, the Antarctic ice sheet melted,transforming the frozen continent into

a collection of tree-covered islands Thedisturbing implication is that globalwarming, which may push temperatures

to Pliocene levels by the middle of thenext century, might trigger a catastroph-

ic meltdown of the ice sheet

Now a group led by David E Sugden

of the University of Edinburgh has lenged this scenario Sugden and his six

chal-co-workers report in Nature that they

have discovered ice at least eight millionyears old in a region that, in HarwoodÕsview, should have been clear of ice asrecently as three million years ago The

Copyright 1995 Scientific American, Inc

new Þnding has intensiÞed what was

already a Þerce debate between

Òstabil-istsÓ and ÒdynamÒstabil-istsÓ over the ice capÕs

past and, more important, its future

The Harwood group based its claim

of a big thaw on fossilized beech trees

and marine diatoms found high in the

Transantarctic Mountains, a rocky spine

that cuts the Antarctic roughly in half

The beech fossils were undatable, but

the diatoms were of a type known to

have existed in the southern oceans

three million years ago

According to Harwood, the beech

trees grew on the ice-free shores of arctic islands during the warm Pliocene,and the diatoms thrived in the marinebasins surrounding the landmasses

Ant-When the balmy weather of the Pliocenegave way to a more frigid climate, thebeech trees all died oÝ; the expandingsea ice pushed sediments laden withdiatoms up over the islands, where thediatoms mingled with the beech fos-sils Those Pliocene islands became thepeaks of the Transantarctic Mountains

But George H Denton of the sity of Maine, a member of SugdenÕs

Univer-group, questions HarwoodÕs analysis.Denton says that even today diatomscan be blown from the open sea sur-rounding the Antarctic far inland Thethree-million-year-old diatoms found byHarwood might also have been trans-ported from open sea into the Trans-antarctic Mountains, mingling with themuch older fossilized beech trees, Den-ton explains

The recent Þndings of Sugden, ton and others cast still more doubt onthe big-melt scenario The workersfound glacial ice covered with a layer ofvolcanic ash in a region of the Transant-arctic Mountains near where HarwoodÕsgroup had taken samples By analyzingthe levels of argon isotopes in the ash,SugdenÕs crew concluded that it waseight million years old; the underlyingice, therefore, had to be at least that old.David R Marchant of the University

Den-of Maine, another member Den-of SugdenÕsteam, believes conditions during thePliocene were probably much the same

as they are today The Antarctic ice, hemaintains, is among Òthe most stablegeologic features on the planet.Ó Harwood replies that both his Þnd-ings and those of SugdenÕs group might

be correct The climate might havewarmed enough during the Pliocene formost of the ice cap to melt, Harwood

BEACON VALLEY, in the Transantarctic Mountains, contains ice at least eight

mil-lion years old, says David E Sugden and his team, whose camp is shown here.

For many people, the horrifying

side eÝects associated with

thalid-omide should eliminate the drug

from consideration as a treatment for

anything Yet scientists have returned

to the controversial medication,

seek-ing therapies for a variety of illnesses,

including AIDS and cancer Despite the

drugÕs dark past, recent experiments

indicate that a family of related

com-pounds might safely and eÝectively

treat diseases of the immune system

In the 1950s thalidomide was given

to thousands of pregnant women formorning sickness Those who took thedrug early in the Þrst trimester gavebirth to severely deformed babiesÑthecompound somehow stunts the growth

of arms and legs In the 1960s, however,thalidomide given to leprosy patientseased their condition, and the drug wasreexamined as a possible medication

Thalidomide is now used routinely totreat leprosy patients around the world.(In certain developing countries, wherethe drug is not carefully regulated, somepatients, unaware of the side eÝects,still give birth to deformed infants.)Several years ago Gilla Kaplan of theRockefeller University determined thatthalidomide combats immune disor-dersÑsuch as the inßammation associ-ated with leprosyÑby regulating theamount of tumor necrosis factor alpha(TNF-alpha) circulating in the blood-stream This hormonelike protein initi-ates immune response, but high levels

of it have been linked to cachexia (thewasting syndrome seen in some AIDS

or cancer patients), rheumatoid tis, lupus, bacterial meningitis and sep-tic shock, among other maladies Be-cause of its ability to control TNF-alphaactivity, thalidomide is now being stud-ied as a treatment for AIDS, cancer andgraft versus host disease, which can oc-cur after bone marrow transplants Pre-liminary results show the drug can re-lieve many of these conditions

arthri-20 SCIENTIFIC AMERICAN November 1995

elaborates, while still allowing some ice

to persist high in the mountains

Moreover, just as HarwoodÕs Þndings

have been challenged, so have those of

Sugden and his colleagues In a

com-mentary in Nature, Dick van der

Water-en of the Free University in Amsterdam

and Richard Hindmarsh of the British

Antarctic Survey suggest that the

vol-canic ash dated by Sugden might have

been pushed onto much younger icelong after the ash was originally depos-ited At the moment, however, the sta-bilists may be prevailing John A Bar-ron of the U.S Geological Survey inMenlo Park, Calif., a previously neutralobserver, says the recent report by Sug-den and his co-workers has left himÒ75 to 80 percentÓ convinced that thestabilists are right ÑJohn Horgan

Transforming Hyde into Jekyll

Researchers redesign thalidomide

Tell me where is fancy bred, Or in the heart or in the

head?” William Shakespeare wonders in The Merchant

of Venice “How begot, how nourished?” He then answers

his own question: “It is engender’d in the eyes, With

gaz-ing fed.” Yeah, well, Shakespeare, writgaz-ing in the days

be-fore daily showers, must have been keeping the pungent

truth to himself The eyes may be the windows to the

soul, but smell might be the doorway

Swiss researchers recently published a report in the

Pro-ceedings of the Royal Society of London that tested the role

male body odor has in female mate choice Perhaps just

as important, the researchers finally found a place in

sci-ence for the T-shirt—as something other than the standard

uniform of the graduate student

In a smelly nutshell, male volunteers slept in T-shirts for

two nights Female volunteers then sniffed the

reposito-ries of chemical emissions, after which they rated the

odoriferous shirts for pleasantness and sexiness All this

might be the modus operandi for some low-tech dating

service had not the researchers bothered to tissue-type

their subjects to determine their major histocompatibility

complexes, or MHCs, a crucial part of the immune system.Studies with mice have revealed a preference for matesthat have differing MHCs—presumably because offspringwill have a wider array of immune options to draw on iftheir parents’ MHCs are not alike The T-shirt study showedthe same: females rated as more alluring the smells fromthose T-shirts that had been worn by men whose MHCsdiffered most from their own Such smells reminded fe-males of their own mates or ex-mates twice as often asdid smells of men whose MHCs were similar to their own.The Swiss study also indicated a potentially disturbingside effect of the contraceptive pill Females on the pillpreferred males of similar MHCs (This phenomenon may

be a result of the pill’s physiological mimicry of cy: pregnant mice prefer to nest with MHC-similar individ-uals, most likely supportive relatives, not the unrelatedscoundrels who got them into the situation.) A womanwho chooses her husband while on the pill, stays on thepill through the first few years of marriage, then goes offthe pill may suddenly wonder who the stinker in bed with

The Noses Have It

Copyright 1995 Scientific American, Inc.

Such uses for thalidomide could come even safer Researchers at CelgeneCorporation in New Jersey and at Rocke-feller announced at the fall meeting ofthe American Chemical Society thatthey have altered the structure of theagent to create a family of several hun-dred thalidomide derivatives that may

be-be more eÝective and less dangerous.ÒThalidomide was developed as a sed-ative, and so we felt the structure hadnÕtbeen optimizedÓ to treat immune con-ditions, comments George W Muller ofCelgene Muller and David I Stirling,also at Celgene, and their colleaguescreated the novel compounds by deter-mining how the body metabolizes tha-lidomide Such analysis can pinpointwhich parts of the molecule make it intothe bloodstream and thus might inhibitTNF-alpha production The team thentinkered with the drugÕs structure, add-ing molecular groups here and there,looking for improvements ÒEarly on

we found that if we changed one of thering structures of thalidomide, we start-

ed to see large increases in modulatory] activity,Ó Muller says.Initial tests are not deÞnitive aboutthe safety of the new compounds ButStirling explains that by studying a fam-ily of chemicals in which each memberhas slightly diÝerent properties, chem-ists can better evaluate which parts ofthe structure may trigger side eÝects.Stirling expects the team eventually toÒseparate the teratogenicity from theimmune modulation capabilitiesÓ or toimprove potency so that lower doses can

[immuno-be given, eliminating harmful eÝects.One could, of course, remove the dan-gers of thalidomide by abandoning thedrug entirely Monoclonal antibodies,for instance, can also be used to lowerTNF-alpha levels According to Stirling,however, the antibodies completelyeradicate the protein, instead of lower-ing its level back to normal as thalido-mide and its derivatives do

Furthermore, Muller says, thalidomidehas been studied since the 1960s as atreatment for a variety of diseases; re-sults demonstrate the drug can be apowerful tool against many of theseailments Modern tests can presumablydetect potential teratogens better thanthose used decades agoÑparticularlysince tests were improved as a directconsequence of the thalidomide trage-

dy Indeed, Muller maintains that anyadverse eÝects would show up in labo-ratory trialsÑand he will soon Þnd out

if this is true for the new family of lidomide derivatives Researchers atJohns Hopkins University just beganpreclinical testing of several thalido-midelike drugs for use in graft versushost disease ÑSasha Nemecek

tha-In 1994 heart disease killed 735,000 Americans More than two thirds died

from coronary heart disease (CHD), which occurs when the coronary

arter-ies, suppliers of oxygen-rich blood to the heart, become blocked by

atherosclerosis (fatty deposits on the arterial wall) or thrombosis (blood

clot-ting) These changes may result in a heart attack—erratic heartbeats and the

sudden destruction of part of the heart muscle

Far more men than women die of CHD, because women are protected

against the disease by hormones, particularly those present before

meno-pause In the early 1920s, when CHD mortality started to increase, the

num-bers of men and women 65 and older were roughly equal, but by 1970 men

this age were outnumbered by women almost 10 to seven, largely because of

CHD Why CHD rates rose in the 1920s is not clear, but it is likely that the

popularity of cigarettes among men was partly responsible Smoking, which

is a prime risk factor for CHD and other types of heart disease, started to

de-cline in the 1960s, after a 1964 report by the U.S surgeon general In the

1960s, CHD rates also began to fall—a trend that continues today

Cigarette smoking most likely contributes to the pattern on the map, which

shows age-adjusted mortality rates for all forms of heart disease for white

men age 45 to 74 ( Total heart disease mortality, rather than recorded CHD

mortality, is depicted because an unknown but probably substantial number

of CHD deaths are misclassified.) State-by-state information on smoking,

available since 1984, reveals that there are more smokers in the eastern than

the western U.S Several of the eastern regions with the highest mortality for

heart disease are also areas where lung cancer death rates are highest

Be-cause 80 percent or more of lung cancer is attributable to cigarette smoking,

this fact suggests that high heart disease mortality in these places is the

re-sult, in part, of smoking There are, however, important exceptions to this

congruence—such as northern Virginia—where lung cancer mortality is high,

but heart disease mortality is low

Other CHD risk factors—elevated blood pressure, augmented serum

cho-lesterol and minimal physical activity—also contribute to the pattern of heart

disease, but their impact is impossible to gauge because little geographic

in-formation is available Another risk factor for CHD—diabetes—does not help

explain the map Diabetes mortality is high in parts of the east but also in

Utah and New Mexico, where heart disease mortality is low

The pattern of heart disease mortality among women and blacks in the

same age group is roughly the same as that of white men, although blacks

700 OR MORE DEATHS PER 100,000

500 TO 699 DEATHS PER 100,000FEWER THAN 500 DEATHS PER 100,000SOURCE: National Center for Health Statistics, 1979–1992

Male Deaths Caused by Heart Disease, by County

The fate of a fast-growing shrub in

Southeast Asia and tropical

Afri-ca could pit small farmers against

large plantation managers, with

agricul-tural researchers forced to take sides

Chromolaena odorata is not much to

look at, but it has spread so rapidly in

Africa, according to Joan Baxter of the

International Center for Research in

Ag-roforestry (ICRAF) in Nairobi, that local

names for it have cropped up: Bokassa

(the dictator of the Central African

Re-public from 1966 to 1979, who had

himself crowned emperor in 1977 in a

lavish ceremony that bankrupted his

subjects), lÕenvahisseur (the invader)

and mighbe (the plant that crushes all)

in Cameroon

The shrub, which grows up to Þve

meters high, plagues coconut, oil palm

and rubber plantations If it is not

sup-pressed, it can shade infant trees and

prevent them from growing It also

cre-ates a wall of impassable undergrowth

that makes harvesting mature trees

al-most impossible And labor for

weed-ing of enormous tracts is expensive

So there is little surprise that the C.

odorata Newsletter should be almost

en-tirely devoted to eÝorts aimed at theplantÕs eradication Since the mid-1960s,one herbicide after another has provedineÝective at targeting the shrub andleaving plantation trees unharmed But

in the past few years researchers atBiotrop in Indonesia have had modestsuccess with a parasitic moth that

munches on C odorataÕs leaves,

slow-ing its growth and spread dramatically

ThereÕs only one small glitch in thisstory of agroscience triumphant Many

small farmers depend on C odorata to

restore the soil of their Þelds duringfallow years and to crowd out grassesand other weeds that are much morediÛcult to cut back, reports Simon P

Field of the Fiji Soil and Crop EvaluationProject Five people can chop down andburn a hectare covered with the shruband ready it for planting in a week; thejob would take a month for a Þeld cov-

ered in Imperata cylindrica, an invasive

grass that grows in the same regions.Parasitic moths are not known fortheir ability to distinguish between plan-tations and small holdings, so large-

scale biocontrol of C odorata could

leave poor farmers in serious trouble,according to Hubert de Foresta of theSoutheast Asian branch of the ICRAF.Avoiding damage to smaller farmscould call for plantation managers toreturn to labor-intensive hand pruning.Although most fallow crops are of no

particular use on plantations, C ata appears to be the only one actively

odor-targeted for destruction, says Miguel A.Altieri of the University of California atBerkeley (Baxter reports that Australia,for example, lists it among plants to bedestroyed on sight.) Field and other re-searchers are attempting to Þnd othercrops that would be as eÝective at re-storing the land and suppressing weedsbut that would not threaten plantations.Indonesian farmers already grow sever-

al varieties of leguminous trees to vent weed buildup, but nurturing thetrees through their Þrst year can be dif-

pre-ficult C odorata, in contrast, appears

able to survive virtually everything butlabor-saving research ĐPaul Wallich

24 SCIENTIFIC AMERICAN November 1995

A Never-Ending Feast

Imagine what it would be like if whenever you finished a

meal, it magically reappeared If this sounds like a dream,

consult a grasshopper New findings suggest that every time

a grasshopper feeds, it secretes a chemical that

encour-ages the leaves of the plant it is eating to regrow

Investigations into just what happens to plants when

they are consumed have become increasingly common in

the past decade as researchers have attempted to address

the concerns of environmentalists, evolutionists and

farm-ers In particular, they have sought to understand

vegeta-tion’s chemical responses

Grazing appears to bring about one of two reactions in

plants Herbivores may set in motion a negative feedback

system that allows a plant to defend itself When tomato

leaves are damaged, for instance, they produce proteinase

inhibitors, which interfere with the predator’s digestive

sys-tem When attacked by caterpillars, other forms of flora can

release chemicals to attract wasps—the natural enemies of

the invading caterpillar Alternatively, a positive feedback

system might kick in In these cases, grazing alters plant

metabolism, leading to growth: bison and mouse saliva

can stimulate such development These changes can also

protect against further predation; scientists have shown

that once attacked, the carbon stores of some greens are

moved from stem to root, where they are less vulnerable

Until recently, however, the mechanism behind such a

response remained mysterious It was thought to depend

on a series of chemicals, or perhaps on an electrical signal,

elicited by physical damage or by the salivary secretions

of the feeding animal But now Melvin I Dyer and his

col-leagues at the University of Georgia have pinpointed a

compound from one herbivore, a grasshopper, and

de-tailed its effects Dyer collected more than 1,000 specimens

of Romalea guttatas, also known as Lubber grasshoppers (above), and purified an extract of their midgut tissue.

When applied to sorghum shoots, the concoction fosteredgrowth in 24 hours This activity suggests that duringfeeding, the grasshopper may regurgitate to produce “apositive feedback in plant growth,” Dyer explains

Although the chemical has not yet been identified, Dyersays it seems similar to epidermal growth factor (EGF), abiochemical messenger found in vertebrate saliva Dyer hasshown that EGF induces changes in the development ofplants—as well as in mammals If EGF-like compounds arealso present in invertebrates, it is very likely that Dyer’s re-sults could have wide ecological implications, explainingcertain aspects of herbivore-plant relations

Dyer says he hopes to look at the genetics of the systemand identify the receptor that binds with the grasshopper’schemical For now, though, he is pleased the results furtherconfirm the idea of reward feedback —Nicola Perrin

In recent years, two studies

pub-lished in Science seemed to provide

dramatic evidence that male

homo-sexuality has biological underpinnings

In 1991 Simon LeVay, then at the Salk

Institute for Biological Studies in San

Diego, reported Þnding subtle but

sig-niÞcant diÝerences between the brains

of homosexual and heterosexual men

Two years later a group led by Dean H

Hamer of the National Cancer Institute

linked male homosexuality to a gene

on the X chromosome, which is

inherit-ed exclusively from the mother

Both announcements made headlines

worldwide LeVay and Hamer appeared

on talk shows and wrote books They

also co-authored an article published in

this magazine in May 1994 But LeVayÕs

Þnding has yet to be fully replicated by

another researcher As for Hamer, one

study has contradicted his results More

disturbingly, he has been charged with

research improprieties and is now

un-der investigation by the Feun-deral Ỏce

of Research Integrity

In HamerÕs original study, he

exam-ined 40 pairs of nonidentical gay

broth-ers and asserted that 33 pairsĐa

num-ber signiÞcantly higher than the 20 pairs

that chance would dictateĐhad

inherit-ed the same X-linkinherit-ed genetic markers

from their mothers Sources with

knowl-edge of the investigation say a former

colleague has accused Hamer of

im-properly excluding pairs of brothers

whose genetic makeup contradicted his

Þnding Hamer has declined to comment

on the charges, which were Þrst

report-ed in the Chicago Tribune

Hamer has continued to pursue his

research in spite of the controversy

With workers at the University of

Colo-rado, Hamer recently performed a study

similar to the one reported in 1993, but

with 33 pairs of gay brothers instead of

40 Stacey Cherny, one of HamerÕs

col-laborators, says the new study

essen-tially corroborates the original Þnding

of linkage with markers on the X

chro-mosome The paper has been

submit-ted to a journal

Elliot S Gershon of the National

In-stitute of Mental Health is now

recruit-ing 100 pairs of gay brothers for a

ge-netic-marker study similar to HamerÕs

But the only independent group that

has completed a study like HamerÕs

failed to replicate his results George

Ebers of the University of Western

On-tario says his examination of 52 pairs

of gay brothers yielded no evidence for

a linkage of homosexuality to markers

on the X chromosome or elsewhere

Ebers and an associate, George Rice,have also analyzed the pattern of sexu-

al orientation in 400 families with one

or more gay males and found no dence for the X-linked, mother-to-sontransmission posited by Hamer

evi-Meanwhile one scientist has tried toreplicate LeVayÕs claim

about diÝerences betweenthe brains of gay menand their straight coun-terparts LeVay assertedthat a minute region ofthe hypothalamus calledthe interstitial nucle-

us was smaller in malehomosexuals than instraight men and similar

in size to the nucleus offemales LeVay specu-lated that biological fac-tors, possibly geneticallybased, cause the brains

of homosexuals to come Ịfeminized.ĨOne of the premises ofLeVayÕs study was thatthe interstitial nucleus ofmales is signiÞcantly larg-

be-er than that of females

William Byne, a trist at Mount Sinai Medi-cal Center, decided to test

psychia-LeVayÕs idea (In the same issue of tiÞc American in which LeVay and Ha-

Scien-mer argued that homosexuality is a logical condition, Byne challenged theirview.) Byne compared the brains of 19heterosexual men and seven womenand found that the male nuclei werelargerĐas LeVay had found

bio-But Byne suspects that spurious

caus-es may explain the sexual dimorphism

He notes, for example, that it is much

easier to obtain the brains of youngmales for research, because their mor-tality rates are so much higher thanthose of females As a result, femalebrains may have been stored longer in

a preservative, thus shrinking the stitial nucleus and other features Bynehas chosen not to publish his resultsuntil he can rule out this and other pos-sibilities He is also collecting brains for

inter-a compinter-arison of ginter-ay inter-and strinter-aight minter-ales

Evan S Balaban, a neurobiologist atthe Neurosciences Institute in San Di-ego, notes that the search for the bio-logical underpinnings of complex hu-man traits has a sorry history of late Inrecent years, researchers and the me-dia have proclaimed the ỊdiscoveryĨ ofgenes linked to alcoholism and mentalillness as well as to homosexuality.None of the claims, Balaban points out,have been conÞrmed ĐJohn Horgan

Gay Genes, Revisited

Doubts arise over research on the biology of homosexuality

Many scientiÞc instruments have

been turned on the sun, butuntil recently all of them havelooked at the star from close to theearthÕs angle of view A European Space

Agency craft called Ulysses is now

per-plexing physicists with measurementsfrom an entirely diÝerent perspective

After a delay of several years, Ulysses

was launched in 1990 on the space

shuttle Discovery During its long

voy-age, the spacecraft made use of JupiterÕsgravity to ßip it into an orbit that sent

it under the sun The spacecraft passed

below the solar southern pole last yearand looped over the northern side thispast summer The spacecraftÕs uniquevantage point enabled it to detect pre-viously unrecorded phenomena.Some of the key observations relate tothe solar wind, a torrent of ionized hy-drogen and helium rushing away fromthe sun that exerts profound eÝects onthe earthÕs electrical environment (itsgusts are responsible for much radio in-terference) Near the sunÕs equator, thewind moves relatively slowly and vari-ably at about 450 kilometers per sec-

Solar Secrets

More data make for more mystery

IDENTICAL TWINS show that some homosexuality cannot be ascribed to genetic factors While James (left) is heterosexual, Jerry is gay.

ond, but at the higher latitudes

now being monitored, its speed

changes abruptly to 750

kilo-meters per second The

bound-ary between the high- and

low-speed winds oscillates like the

edge of a spinning ballerinaÕs

skirt The width of the

turbu-lent, low-speed band may

de-pend on the level of sunspot

activityĐan idea that will be

tested after the year 2000 as

Ulysses makes a second polar

pass, which, unlike the Þrst,

will occur during a period when many

sunspots are expected

The fast ßow at high latitudes,

togeth-er with details of the solar windÕs

com-position, Þts well with the idea that

most of the wind originates in the

pho-tosphere, the sunÕs sharp, bright

out-er edge, says D Edgar Page, Ulysses

sci-ence coordinator for the EuropeanSpace Agency at the Jet Propulsion Lab-oratory in Pasadena, Calif Some scien-tists had thought they would Þnd only

occasional high-speed streams,which would have pointed to adiÝerent site of origin, Pagenotes The fast wind probablyescapes through huge holes fre-quently detected near the sunÕspoles in the corona, an often invisible gaseous halo thatshrouds the visible disk

Recently David J Thomsonand his colleagues at AT&T BellLaboratories made the controversial

claim that information from Ulysses

and other satellites reveals a hiddenperiodicity in the solar wind resultingfrom oscillations already believed tooccur within the sun Further analysis

28 SCIENTIFIC AMERICAN November 1995

Country Music

The natural world is so full of complexity that detection

of a regular signal can be startling Perhaps this is what

Vera Schlindwein, Joachim Wassermann and Frank

Scher-baum, all then of Ludwig-Maximilians University in

Mu-nich, felt as they made seismic recordings along the side

of Java’s Mount Semeru (right ) in 1992 That these

experi-ments revealed periodic rumblings is not surprising:

seis-mologists have recognized for decades that volcanoes can

generate such vibrations, called harmonic tremors What

seemed strange was that the waves were too regular

The researchers’ instruments recorded ground motion

that contained a series of evenly spaced harmonic

fre-quencies—like a musical instrument playing a single note

rich in overtones The fundamental frequency of these

subaudible vibrations would often shift slightly up or

down, as might a struggling singer trying to stay on key

The frequencies were restricted to below eight hertz, so

the song of the mountain, even if amplified, would be

in-audible to human ears Even so, in their recent report in

Geophysical Research Letters, the team did describe “a

va-riety of acoustic events, among which a regular pumping

sound was the most striking feature.”

Seismologists have debated whether harmonic tremors

such as these arise from peculiarities of the volcanic

source—molten magma creeping upward through cracks,

perhaps belching up gas now and then—or whether they

result from the sound bouncing back and forth along the

path between the source and the receiving instrument

Schlindwein and her co-workers point out that they

re-ceived the same pattern at different locations, so that

echoes along the signal path are not likely to explain the

reverberations They posit instead that these oscillations

emanate from a single source—a large, presumably

cylin-drical gas-filled cavity The top of the void may be

stop-pered by a plug of frozen lava; the bottom by a column of

molten magma The lowest frequency in the signal (0.5

hertz) suggests that the chamber could be 500 meters tall

Bernard A Chouet, a seismologist at the U.S Geological

Survey in Menlo Park, Calif., remarks that the great

differ-ence in physical properties between gas and surrounding

rock could explain why the German team detected such a

high-quality signal Most of the acoustic energy would

res-onate in the cavity at characteristic frequencies withoutbeing dampened “That gives you the same thing as an or-gan pipe,” Chouet explains The shifts in frequency, theGerman scientists propose, result from changes in thelength of the pipe as the level of magma gradually rises orfalls It is as if they had stumbled on a gargantuan subter-ranean trombone

Carrying the musical analogies even further, wein’s team argues that the occasional observation of a set

Schlind-of harmonics without the fundamental note can be counted for by the same mechanism that controls “over-blowing of low tones in a recorder.” This phenomenon oc-curs when pressure pulses in the cavity affect the source(in this case, not quivering lips but bubbling magma).Whether the basal magma could ever rise to the pointwhere the tones reach audible frequencies is unclear, butshould that shift happen, some enterprising local may de-cide to set up an amplifier and speakers The attractionmight inspire a whole new generation of eco-tourists tovisit the peak, saxophone and trumpet in hand After all,it’s not everywhere that you can count on the location itself

ac-to provide some good bass riffs —David Schneider

SUNEARTH’S ORBIT

ULYSSES PROBEJUPITER’S

In the days before the current wave

of feminism, many economists

(most of them male) subscribed to

the notion that womenÕs earnings were

Ịpin moneyĨĐa luxury that households

did not really need Nowadays, with

more than 60 percent of adult women

in the labor force (compared with about

75 percent of men), that myth has

most-ly been banished Ironicalmost-ly,

how-ever, Nada Eissa of the

Univer-sity of California at Berkeley

has recently conducted studies

showing that for a few women

there may be a grain of truth to

the old saw after all In addition,

the reaction of women to

sud-den changes in their eÝective

pay may cast light on how

peo-ple in general decide how much

to work

Eissa looked at the eÝects of

the 1986 Tax Reform Act, which

lowered the tax paid by

high-in-come couples but left

middle-and low-income ones

essential-ly unchanged She found that in

households earning more than $130,000

a year, the proportion of women in the

labor forceĐeither employed or

active-ly looking for jobsĐincreased 19.5

per-cent by 1988, compared with only 7.2

percent for families earning $47,000

annually High-income women who were

already employed worked 12.7 percent

more hours each week, compared with

3.6 percent for middle-income women

Economists have argued for decades

over whether wage increases cause

peo-ple to work more or less, says James M

Poterba of the Massachusetts Institute

of Technology On the one hand, money

is considered a good thing, and more

of it is generally considered even

bet-ter Thus, higher wages should increasethe incentives for people to work Onthe other hand, leisure is also a goodthing, and a higher wage allows people

to meet their basic needs more easily,

so they could decide to work less andmaintain the same standard of living

EissaÕs data suggest that at least forone segment of the population, the lure

of extra money outweighs the joys ofidleness Her Þndings are consistent,Poterba notes, with analyses by MartinFeldstein of Harvard University, whodiscovered a sharp increase in taxableincome among the upper-income brack-ets in the year that their tax rate fell

About a third of this extra income wasthe result of people deferring paymentsfrom the previous yearĐin which theywould have been taxed more heavilyĐbut the rest does appear to representreal changes, Poterba explains

Whether such a happy ability, muchless desire, to match earnings to tax in-centives extends to the rest of the pop-ulation is very diÛcult to determine,

Eissa says, because there are no tics collected that address the questiondirectly There is some evidence to sug-gest that high-income women, at least,tailor their employment and workinghabits more closely to tax laws than doworking women as a whole, she says,but the issue is far from clear

statis-Another question that has yet to bedecided is whether the behavior of therich provides any support for the infa-mous LaÝer curve hypothesis, whichpredicted that cutting taxes would in-crease government revenues becausepeople who were able to keep more ofwhat they earned would put in longerhours The numbers appear to bear thenow obscure LaÝer out, but ex-trapolating to low incomescould be diÛcult Furthermore,Poterba notes, because econo-mists can analyze only report-

ed income, there is no way totell if people were actually work-ing more or merely switchingtheir portfolios from tax-freemunicipal bonds to high-yield-ing taxable investments

Economists may get a

slight-ly better handle on these points,thanks to the tax counterrefor-mation of 1993, which rescind-

ed some of the breaks that per-income couples acquired

up-in 1986 EissaÕs models suggestthat high-income married womenshould leave jobs and cut back theirhours in almost the proportions thatthey augmented their participation afew years before This kind of natural,relatively well controlled experiment inthe labor market is rare, Poterba saysĐindeed, he considers the data that havebeen generated by the policy swings ofthe 1980s and 1990s something of awindfall for economic research ỊItÕs like

a volcano is for geologists,Ĩ he quips

No one would advocate revamping thetax laws every Þve years just to gatherinformation, but if Congress is going to

do it anyway, some understanding may

as well emerge ĐPaul Wallich

of the data may shed light on the

mat-ter, says AndrŽ Balogh of Imperial

Col-lege, London, a member of the Ulysses

team For now, however, he regards the

question as unsettled

What drives the solar wind is also still

a mystery, but surprising features of

the sunÕs magnetic Þeld detected by

Ulysses provide clues The ÞeldÕs

over-all form was not the predicted

bar-mag-net shape, with distinct north and south

magnetic poles; rather magnetic-Þeld

lines spread out uniformly like the

spokes of a tire According to Balogh,

the shape results because the ic-Þeld lines near the poles are pushedapart by the solar wind He envisagesthe high-speed wind emerging from po-lar holes in the corona and then beingdeßected by magnetic forces toward theequator Powerful, and apparently ran-dom, ßuctuations in the Þeld over thecourse of just a few hours may be theenergy source for the wind

magnet-The strong ßuctuations in the netic Þeld probably also keep out most

mag-of the cosmic rays that Ulysses looked

for but that were seen only at low

inten-sity, Page explains High-intensity raysmight have given hints about their ori-gins, which are thought to lie in energet-

ic events elsewhere in the galaxy Butother discoveries compensate, includ-ing the Þrst direct detection of neutralatoms from outside the solar system.Their apparent speed of 26 kilometersper second reßects the sunÕs motionrelative to the galactic background The

Ulysses data ỊconÞrm some of what we

expected,Ĩ Balogh says ỊBut more than

50 percent of our models were wrong.ItÕs a nice balance.Ĩ ĐTim Beardsley

THE ANALYTICAL ECONOMIST

Some Women Are More Equal Than Others

WOMANÕS WORK is inßuenced by tax rates, but low- and middle-income women do not reap tax-cut beneÞts.

How would a group of lawyers

formulate policy on complex

technical and scientiÞc issues

without a consistent source of in-depth

information? ItÕs not another unkind

joke at the expense of the legal

profes-sion but a real concern in the wake of

the U.S CongressÕs decision to

elimi-nate its 22-year-old Ỏce of

Technolo-gy Assessment this past July

CongressÕs 535 members, the

majori-ty of whom have only legal backgrounds,

must regularly

formu-late legislation on

tele-communications,

de-fense, energy,

astro-nautics, health care,

basic research,

trans-portation and other

technical subjects For

help, the committees

on which they serve

have often turned to

the OTA, which then

typically drew on the

expertise of specialists

in academia, at private

think tanks or

else-where Such experts

oÝered information,

advice and criticism

to OTA staÝers, who

wrote, rewrote and

edited reports to

eluci-date policy options and

consequences Draft

reports were reviewed

by a bipartisan board

of representatives and senators

ỊWe have had this agency, which has

a $22-million budget, pay for itself

hun-dreds of times over by giving this

Con-gress the kind of advice it needs to

pre-vent mistakes from being made,Ĩ said

Representative Vic Fazio of California

in June at a meeting of the committee

on legislative branch appropriations

Only last year, supporters say, an OTA

report on the Social Security

Adminis-trationÕs computer procurement

strate-gy helped to avert a purchase of

$2-bil-lion worth of outdated equipment In

the late 1970s the ßedgling OTA raised

concerns about the synthetic-fuels

pro-gram, which went on to become what

is widely regarded as a

multibillion-dol-lar boondoggle

But with $200 million needing to be

pruned from the $1.3-billion legislative

budget, the OTA seemed to some a ury that was no longer aÝordable ỊI

lux-donÕt think Congress has to have a

cap-tive agency to advise it on science andtechnology issues,Ĩ says John Morgan,

a physicist and staÝ member in the fice of Representative Dana Rohrabach-

of-er of California ỊThof-ere are litof-erally dreds of areas where we have no suchagency I would put economic policy atthe head of that list.Ĩ

hun-ỊThere was a feeling that the

informa-tion the OTA provides would be able from other sources,Ĩ adds MarkMills, a spokesman for Senator ConnieMack of Florida ỊWith the explosion oftechnology, there has been an explosion

avail-of information on technology.Ĩ

It is not at all obvious, though, howother sources will compensate for theloss of the OTA Much of the informa-tion that swamps congressional staÝscomes from lobbyists and others withspeciÞc interests The organizationsmost often cited as being able to Þll infor the OTA include CongressÕs ownGeneral Accounting Ỏce (GAO) andCongressional Research Service (CRS),executive-branch or other agencies such

as the National Research Council (NRC)and private think tanks None of them,OTA supporters have pointed out, putout information like the OTÃs Besides

being tailored to the needs of gress, OTA reports are peer-reviewedand impartial (insofar as anything is inWashington) Such a combination of at-tributes is not to be found even in theoutput of other congressional oÛces,none of which have anything like theOTÃs concentration of technical andscientiÞc expertise The CRS generallydoes short, speciÞc studies for individu-

Con-al members, whereas the GAO providesoversight of executive-branch agencies.The notion that Congress might draw

on executive-branch organizations nores the circumstances of the OTÃsestablishment in the early 1970s Indealing with the Nixon administration

ig-on such issues as the antiballistic sile system and the Trans-Alaska pipe-line, members of Congress and theirstaÝs felt they were at a disadvantage

mis-when pitted againstthe executive branchÕsparade of technical experts

The NRC, which isthe operating arm ofthe National Academy

of Sciences and theNational Academy ofEngineering, is proba-bly the most capable

in theory of Þlling infor the OTA The NRCÕsdetailed studies, how-ever, often take evenlonger than the 18 to

24 months requiredfor some of the OTÃs,and the realities ofNRC-congressional co-operation are not en-couraging, notes oneveteran of both theOTA and CRS Because

of its culture, the ỊNRCdoes not often wind

up answering the questions Congressasks,Ĩ he says ỊIt doesnÕt know how.Ĩ

In any case, many observers Þnd theprospect of committee chairmen dog-gedly pursuing other avenues of tech-nical enlightenment preposterous ỊThis

is a Congress less interested as an stitution in being informed than anyCongress in the two decades IÕve beenfollowing the legislative branch close-ly,Ĩ says the ex-OTA employee Repre-sentative George E Brown, Jr., of Cali-fornia, a former civil engineer who has along history of involvement in scienceand technology issues, agrees ỊManymembers of Congress do not take ad-vantage of the products the OTA is put-ting out,Ĩ he claims ỊPolitics in Con-gress today is being driven by ideology,not technology assessments or rationalprojections.Ĩ ĐGlenn Zorpette

in-30 SCIENTIFIC AMERICAN November 1995

TECHNOLOGY AND BUSINESS

Luddites on the Hill

Congress quietly kills the Ỏce of Technology Assessment

TRANS-ALASKA PIPELINE was one of several big technical projects in the early 1970s that compelled the U.S Congress to seek professional help.

Copyright 1995 Scientific American, Inc.

The Intergovernmental Panel on

Climate Change, an international

body reviewing the science of

global warming, may soon reach a

sig-niÞcant milestone A draft report from

the panel concludes that world average

temperature changes over the past

cen-turyĐamounting to an increase of

be-tween 0.3 and 0.6 degree CelsiusĐare

Ịunlikely to be entirely due to natural

causes.Ĩ If that declaration survives in

the Þnal report, expected to be

pub-lished next month, it will mark the

pan-elÕs Þrst oÛcial acknowledgment that

humans have very likely contributed to

the gradual warming

That trend is driven by increasing

at-mospheric levels of greenhouse gases,

chießy carbon dioxide, which is

pro-duced when fossil fuels are burned

Re-searchers everywhere are seeking ways

to reduce the amount of the gas

re-leased Power plants, which account forabout one third of emissions, are theeasiest target One approach is to in-crease energy eÛciency, reducing theamount of fuel used An alternativewould be to take carbon dioxide out ofexhaust gases and sequester it in somesafe form So far, however, nobody hasdemonstrated an economical way to do

so And Klaus S Lackner of Los AlamosNational Laboratory points out thatschemes to extract the gas and bury itare risky, because it could leakĐdefeat-ing the purpose and posing danger

But Lackner and his colleagues thinkthere is a solution They say carbon di-oxide from power-plant exhaust can bemade to react with abundant, easily ac-cessible minerals to create a harmlesswaste product, magnesium carbonate

Because the reaction produces heat,which could drive other steps in the op-

eration, the process would largely payits own energy bills ỊWe were surprisedthat nobody else had thought of this,ĨLackner says The scheme uses rocksthat contain magnesium oxide Twokinds, in particular, show promise: ser-pentinite and olivine Serpentinite could

be simply ground up and heated tostart the reaction while carbon dioxide

is passed over it; olivine would have to

be pretreated to make it reactive enough

As envisioned by the Los Alamosteam, the operation would not be small:six tons of rocks would be needed toabsorb the carbon dioxide from everyone ton of coal burned Having to trans-port the rocks would make the processimpossibly expensive, but Lackner sayscarbon dioxide could be piped frompower plants to absorbing facilities sit-

ed near mines Others who have ined the proposal wonder, however,whether the process can be made as en-ergy eÛcientĐand hence economicalĐ

exam-as Lackner exam-assumes ỊThe ideexam-as are portant, but the scheme is optimistic,Ĩsays Roddie R Judkins of Oak RidgeNational Laboratory ỊNone of the nec-essary technology exists now.Ĩ

im-But Lackner thinks modern heat changers make the technique Þnancial-

ex-ly feasible The cheapest electricity able costs about three cents per kilo-watt-hour LacknerÕs calculations suggestcarbon dioxide could be extracted andstored on an industrial scale for an ad-ditional six cents per kilowatt-hourĐroughly tripling the cost Although thatprice might sound unpromising, Lack-ner points out that nuclear power costsabout eight cents per kilowatt-hour Ifconcerns about carbon dioxide levelsgrow, Ịhaving some solution availablewill be critical,Ĩ he says The team isseeking grants to scale up the experi-mentsĐa challenge, as funds for energy

avail-research are being cut ĐTim Beardsley

Clearing the Air

Common rocks may deliver cleaner power

Mind Meets Machine, Sort of

Taking a modest step closer to the science-fiction staple of melding the

hu-man brain with the computer, researchers in Gerhu-many can now control a

single neuron via a silicon chip connected to it Granted, the neuron belongs

to a leech Still, the achievement may give biologists a new tool to investigate

how neural networks grow and communicate

Of course, scientists playing with electricity have, since the late 18th

cen-tury, been able to set nerves and muscles atwitter using microelectrodes Yet

that approach has significant problems, says Peter Fromherz of the Max

Planck Institute of Biochemistry near Munich The current flow can initiate

chemical reactions that can damage the cells, corrode the electrical contacts

and form toxic by-products

To avoid these problems, Fromherz and his colleagues relied on a

capacita-tive effect—that is, using a nearby electric field to induce current flow in

an-other element They crafted a silicon chip with insulated “stimulation spots”

about 10 to 50 microns wide The workers then extracted from leeches

indi-vidual neurons, which are large and hence easy to isolate, and plopped each

one onto a stimulation spot A voltage applied to the spot caused a buildup of

positive charge in the nerve cell without any electricity actually flowing

be-tween the silicon and the cell Above 4.9 volts, the neuron fired

The work complements research Fromherz had conducted a few years ago,

when he was able to register neuronal activity with a silicon chip He recently

succeeded in combining both detection and stimulation devices so that they

can connect to the same neuron His group has even fabricated stimulation

spots in the two-micron range, small

enough to be used for neurons in rats

and even humans Still, “it is most

diffi-cult to handle them individually,”

From-herz remarks And it is not clear how

the system would work once taken out

of the petri dish “I do not know how

to make such contacts in a tissue at

the moment,” Fromherz admits, noting

that the researchers are only at the

stage of developing the tools for

ex-periments that might record and

stim-ulate neural networks The brain

pros-thesis will have to wait —Philip Yam

GROUND ROCKS could be an answer

When computer diagnostician

Angela Bennett (played by

San-dra Bullock) disabled a

main-frame computer with a virus-infected

disk slipped into a Macintosh in this

past summerÕs nerd thriller, The Net,

most computer aÞcionados chuckled

knowingly One of the fundamentals of

computer viruses is that malicious

pro-grams designed to paralyze one kind

of hardware become ineÝective

gibber-ish when aimed at the wrong machine

Those were the good old days In

Au-gust thousands of Microsoft Word usersÕ

computers were infected with a virus

that spread equally fast regardless of

whether they were using Macintoshes

or Intel-style PCs The oÝending code

was a macroÑa miniature programÑ

whose instructions were carried out by

an interpreter that Microsoft had

built into the newest version of

the word-processing software

This Òvirtual machineÓ was

inde-pendent of the underlying

hard-ware The macro was designed to

run automatically when a

docu-ment containing it was opened

for reading or editing (Instead

of performing any illicit deed,

however, the main body of the

virus consisted of a statement:

ÒREM ThatÕs enough to prove

my point.Ó) Although Microsoft

quickly released software to

contain the virus, contributors

to the Usenet newsgroup comp

security.misc pointed out that

the antidote neither completely

excises the oÝending code nor

guards against trivially

modi-Þed versions

ÒI was not surprised,Ó says security

expert William Cheswick of AT&T Bell

Laboratories somewhat wearily

Com-puter scientists have been toying with

the viral possibilities of macro

languag-es for at least seven years, he notlanguag-es; the

only puzzle is why it took this long for

one to start spreading Cheswick

spec-ulates the reason is more

epidemiolog-ical than technepidemiolog-ical: not enough machines

running the right software and no good

method for transmitting the infection

from one machine to another The

com-bination of local-area network Þle

serv-ers and MicrosoftÕs market dominance

appears to have supplied both factors

Many other programsÑand computer

operating systemsÑare acquiring macro

capabilities, sometimes also known as

scripting These simple programming

languages can make use of the

capabil-ities of the applications in which they

are embedded: a word-processing

mac-ro, for example, might use the and-replace function in conjunctionwith the word-counting command to ad-just a text for the available space Anyrepetitive task is easy to automate; in-deed, Microsoft has proposed makingthe language in which the Word viruswas written a standard for the rest ofits software and for other companies

search-Luckily, most of these potential digitalbreeding grounds are crippled by thediÛculty of communicating infectiouscontent The real potential for Ògeomet-ric increase,Ó according to Cheswick,lies with software that combines sim-ple programming tools and capabilitiesfor sending and receiving data over theInternet Instead of waiting for users toexchange Þles or ßoppy disks, such a

program can reach out to kindred chines in a few hundred milliseconds

ma-ÒVirus Implementation LanguageÓ isCheswickÕs private name for Hot Java,

a World Wide Web scripting tool oped by Sun Microsystems The lan-guage lets programmers embed smallpieces of software in World Wide Webdocuments; these customized programsrun not on the Web server (a machinethat responds to requests for informa-tion sent over the World Wide Web) butrather on the computer that belongs tothe person looking for information Thistechnique makes it easier to processcomplex exchanges of information

devel-Although SunÕs engineers have stalled a number of security features toreduce the chances that rogue JavacodeÑdownloaded with a single click

in-of a mouseÑwill run amok over the ternet, some of the features that make

In-it dangerous are precisely the ones thatmake it useful If a Java program canaccess usersÕ Þles to help bring order totheir electronic life, it can as easily wreakdisorder; if it can reach out to other ma-chines on the Internet to retrieve valu-able information, it may also be able tospawn copies of itself and bring theNet to its collective knees Careful atten-tion to the rules governing what Þles aprogram can manipulate or how freely

it can access the Internet can minimizethe risks and still allow Java programs

to perform useful work, but Cheswickand others are doubtful that most us-ers will know how to conÞgure theirmachines correctly

And Hot Java is only one of manymethods under development for send-ing programs across the Net and exe-cuting them remotely General MagicÕsTelescript is based on the notion ofsoftware ÒagentsÓ prowling in search ofthe best airfare from Phoenix to Fiji, thee-mail address of an old collegebuddy or whatever else theirowners may want In theory,strict cryptographic safeguardsshould prevent mischief, but thesystem has yet to be thoroughlytested MicrosoftÕs own propri-etary network, a sort of shadow

of the World Wide Web, allowsusers to e-mail programs to oneanother in a special format sothat a program will run automat-ically when the recipient reads

an incoming message EvenMime, a multimedia extensionfor conventional Internet mailprograms, is designed to decodeand execute simple programssent via e-mail

With so many attractive

choic-es facing them simultaneously,hackersÕ to-do list may be get-ting long enough that any given loop-hole is less likely to be cracked,Cheswick suggests hopefully He re-calls his surprise earlier this year when

no one exploited a bug that made itpossible to commandeer Web serverssimply by sending a message that wastoo long for their input buÝers (Ironi-cally, this same class of bug was re-sponsible for the spread of the Internetworm that nearly shut down the Net in1988.) Then again, Cheswick says, thefact that so many security holes havegone unused for so long could meanthat there are far fewer malicious hack-ers on the Internet than the din of direpublic pronouncements would havepeople think Unfortunately, as CornellUniversity graduate student Robert Mor-ris, Jr., and his self-reproducing pro-grams dramatically showed seven yearsago, it takes only one ÑPaul Wallich

34 SCIENTIFIC AMERICAN November 1995

Meta-Virus

Breaking the hardware species barrier

ART ANTICIPATES LIFE in The Net, as Sandra Bullock plays a hacker who meets a universal computer virus.

Copyright 1995 Scientific American, Inc.

Privacy, as George Orwell pointed

out, rests on some level on a

bar-gain between people and their

machines Long before 1984,

communi-cations technology had the potential to

become surveillance technology Now it

is Not, as Orwell might have predicted,

because Big Brother wants to keep his

subjects in thrall but simply because

most people want it to be By giving up

some protective anonymity, people get

safety and service A majority seem to

think the bargain a very good oneĐ

which is why everybody should look

very carefully at the Þne print

Somewhat ironically for the nation

that gave birth to Orwell, Britain is

lead-ing the way in creatlead-ing the kind of

soci-ety that he taught the

world to fear More than

300 British city streets are

wired for 24-hour

surveil-lance by closed-circuit

television cameras From

control rooms, police and

private security oÛcers

scan everything that

moves, or doesnÕt, and

dispatch police oÛcers

to investigate anything

suspicious

More cities are getting

wired all the time, often

by popular demand

Whatever qualms Britons

have about privacy, they

are more concerned

about crime The

cam-eras do seem to reduce

crimeĐat least in the

ar-eas underneath the

cam-eras Academics point out

that surveillance seems to have no

im-pact whatsoever on the overall level of

crime, which is rising, but people just

donÕt seem to care about where the

mug-gers go when they leave their

hoodĐparticularly when their

neighbor-hood wasnÕt too good to begin with

Safety is not the only reason to

em-brace surveillance At the Olivetti

Re-search Laboratory in Cambridge, for

in-stance, Andy Hopper and his staÝ have

for years worn tiny badges that inform

their computers where they are each

minute The point is convenience

Com-puters automatically bring to the screen

the work of the person sitting in front

of them Calls are forwarded to the

tel-ephone nearest wherever they happen

to beĐunless the computers detect

three or more badge wearers gathered

in the same oÛce, in which case they

are assumed to be in a meeting, and

calls are forwarded to their voice mail

To make life more convenient still,Hopper is trying even cleverer technolo-gies Some chairs now contain compass-

es that monitor whether they are

point-ed at a screen, and, if not, the screen isdimmed to save power Such devices,Hopper reckons, are crucial to makingcomputers eÝortlessly easy to use As

he puts it, ỊYou canÕt have tion without identiÞcation.Ĩ

personaliza-But the search for personalization in

a high-tech world may create an comfortable situation in the global vil-lage Villages are safe places but notvery private ones Mrs Grundy, peeringfrom behind her lace curtains, did stophousebreakers, but she also tried to halt

un-many other things of which she proved There are signs that Grundy-ism is returning to Britain Many of thecrimes recorded by surveillance cam-eras are worryingly petty Arrests forurinating in public have soared Forbetter and for worse, cameras that cansee in the dark now line romantic walks

disap-to the beaches in seaside disap-towns

In Britain, as elsewhere, technologyand politicians are about to deepen theprivacy dilemma Cameras are beinglinked to smarter computers that canidentify people Some drivers receivetickets without human intervention Vid-

eo cameras check their speed and readtheir license plates Along with a ticket,the owner is sent a photograph of thecar and driver at the time the speedingwas clocked A number of companiesare touting technology that can recog-nize faces by matching video images to

digitized photographs (from, say, ersÕ licenses)

driv-The British government, like manyothers, is also discussing plans for anational identity card that would, bygiving everyone a number, make it eas-ier to keep track of personal data Theselling point is convenience Much ofthe work of Þlling out forms in bureau-cratic Britain is simply to give onebranch of government information thatanother part already hasĐor to correctinformation that bureaucrats have gotwrong

Convenient though it may be in

theo-ry, the combination of national identityschemes and surveillance cameraspromises to give governments many ofthe powers of an all-seeing God Andthere are many reasons to worry thatmere humans would not be as merciful

or as competent Two aspects of

sur-veillance will prove cial in determining thepractical terms of thenew privacy bargain nowbeing struck: choice andreciprocity

cru-Unlike the subject ofvideo surveillance, thewearer of one of Olivet-tiÕs badges can removethe device and disappearfrom the system Hiselectronic identity is en-tirely a voluntary one: if

he wishes to forward allthe telephone calls theold-fashioned way, byhand, there is nothing tostop him Surveillancebecomes less intrusive if

it is optional But choicecannot be a cure for allthe potential ills of sur-veillance As electronicpersonalization makes electronic iden-tiÞcation more important, that choicebecomes harder to manage

One problem is forgery If electronicidentities can be taken on and oÝ likesweaters, the risk that fraudsters will

be able to put on somebody elseÕs tity rises Besides, as such identiÞcationbecomes more important, the sheer ef-fort required to live anonymously willrender choice moot Anonymity willsimply become too much work.Real village traditions oÝer hope forthe lazy and the identiÞable In villagelife, surveillance was reciprocal: if Mrs.Grundy knew a lot about you, you alsoknew a lot about herĐand you knewwhat she knew about you Technologyshould further extend this reciprocity.The badges in the Olivetti lab provide away of locating any badge wearer Butthey also allow badge wearers to track

iden-Rights of Privacy

Technology has its eyes on you

VIDEO CAMERAS will scan the crowd at the 1996 Olympic Games in Atlanta The security system can transmit images for identiÞcation.

Andile Tiyani wrinkles his nose in

distaste as he points to a listing

outhouse patched together from

scraps of wood and corrugated metal

The tiny shack, huddled among

thou-sands of other slightly larger shacks

that house the black residents of the

Crossroads township outside of Cape

Town, South Africa, is just large enough

to accommodate a toilet seat mounted

over a bucket The bucket is overßowing

ỊIn better areas, they periodically take

these buckets to the edge of town and

dump them,Ĩ Tiyani explains ỊWhen the

rains come, it all runs into the streams,

where people wash their clothes, and it

contaminates the groundwater, which

lies just four meters below the surface

here.Ĩ In Þve neighboring townships,

home to some one million black South

Africans, conditions vary only slightly

In Harare, residents share pit toilets

TiyaniÕs house in the middle-class

dis-trict of Guguletu is among the most

hy-gienic around, sporting a septic tank

Bringing basic sanitation services to

the millions who lack them is a top

pub-lic health priority for the new South

Af-rican government It is also a huge

Þs-cal challenge As in so many other poor

countries, expensive Western

technolo-gies are simply not an option

One cheap Western technology may

be, though Nearly 500 miles to the east

of Cape Town, Peter D Rose of RhodesUniversity is adapting an American al-gae-based system to meet the needs ofsub-Saharan Africa In a nearby pilotplant, due to be completed next year,the waste of 500 to 1,000 people will

be pumped through 1,000 square

me-ters of ponds and

raceways full of rulina, a single-celled

Spi-plant that thrives onsalty, nutrient-richsewage Exposed tosunlight and stirredgently, algae ingestmost of the waste Asmall remainder ofheavy metals andother inorganic detri-tus sinks to the bot-tom of the pits

Ponds replete withalgae have been used

to treat waste for atleast a century But

it is only in the pastdecade that advancedalgal systems, inwhich just certainspecies are actively cultivated, have be-gun to challenge the activated-sludgetechniques commonly used in industri-

al nations

Advanced algal ponding processesnow oÝer several advantages, says Wil-liam J Oswald of the University of Cali-fornia at Berkeley, who has worked onthe technology since the 1950s Theequipment and power used in conven-tional plants to mix incoming sewagewith pressurized air and bacteria-richsludge are avoided in algal systems, sothe latter cost about one half as much

to build and operate They can run onless waterĐimportant in arid climessuch as South AfricaÕs They produce farless sludge, which is generally trucked

to landÞlls or dumped at sea In fact,the main product is tons upon tons ofdead algae, which when dried makes agood fertilizer or additive for Þsh food

And because the plants produce lots of

oxygen, they donÕt stink ỊWe had a winetasting not long ago at the [algal pond]plant in St Helena,Ĩ which processes500,000 gallons of sewage a day in theheart of California wine country ỊIt wasvery picturesque,Ĩ Oswald says.For Rose, the technology holds a dualattraction The potential for improvingcommunity sanitation throughout theThird World is obvious (Researchers inKuwait and Morocco are also runningtests.) ỊBut it has allowed us to do somevery interesting fundamental research

as well,Ĩ Rose says, donning his chemistÕs cap As South African sciencebudgets are increasingly squeezed by agovernment facing more urgent needs,many scientists there are scrambling toÞnd relevant applications to justifytheir basic research

bio-ỊOne of the future beneÞts of theprocess is that once you have this algalbiomass, you might be able to engineer

it to produce by-products that are morevaluable than just animal feed,Ĩ Rosecontinues His team recently elucidatedthe biochemical mechanism by which

another algae, Dunaliella salina,

produc-es massive amounts of beta carotene(the nutrient used by the body to makevitamin A) when stressed by excessivesalt or heat

Rose has also demonstrated that rulina ponds can treat industrial waste,

Spi-particularly from tanneries ỊThe ning industry is set to explode in Afri-ca,Ĩ says Randall Hepburn, RhodesÕsdean of science ỊThe reason is simple:

tan-we kill 650 million sheep, goats, pigsand cows each year But the hides of allbut 3 percent of those are left to rot.That is going to change.Ĩ

The possibility of a tanning boomworries some African environmental-ists ỊTanneries produce some of theworst eÜuents of any industry: sulÞdes,ammonia, heavy metals,Ĩ Rose says ỊItÕsshocking stuÝ.Ĩ So he was a bit sur-prised several years ago when he no-

ticed giant blooms of Spirulina forming

in a tanneryÕs evaporation pond Thediscovery has led to test projects attanneries near Cape Town, in Namibiaand in the Transvaal, where algal treat-ment systems are successfullyĐand in-expensivelyĐsquelching odors and re-claiming water that was previouslywasted through evaporation

ỊRapid industrialization in ThirdWorld countries is very often done atthe expense of the environment, be-cause the costs of First World remedia-tion technologies cannot be aÝordedsimultaneously,Ĩ Rose says ỊTo come

up with a low-cost method that turnswaste into something not only safe butusefulĐwell, thatÕs the Þrst prize inbiotechnology.Ĩ ĐW Wayt Gibbs

42 SCIENTIFIC AMERICAN November 1995

Sewage Treatment Plants

Algae oÝer a cheaper way to clean up wastewater

PETER D ROSE believes algae-Þlled ponds may bring

af-fordable waste treatment to South African townships.

anybody who is trying to locate them

There can indeed be no

personaliza-tion without identiÞcapersonaliza-tion, but there is

increasingly little excuse for

identiÞca-tion without notiÞcaidentiÞca-tion The same

computers and networks that send

fac-es, names and numbers whizzing

around the world could also be

re-quired to send notiÞcation back to each

of those identiÞed, each time they havebeen spotted Even as the world be-comes more personalized and less pri-vate, there is no reason for the elec-tronic global village to become less per-sonable than a thatched one, or less

Copyright 1995 Scientific American, Inc.

Kay RedÞeld JamisonÕs musical

voice sounds above the din in

the midtown Manhattan

restau-rant where we are eating lunch It is the

conÞdent voice of a seasoned lecturer

But Jamison, a professor of psychiatry

at the Johns Hopkins University School

of Medicine, is not at this moment

set-ting forth the symptoms of

manic-de-pressive illness, her area of expertise

Instead she is telling me about the

re-actions to her latest book It is, to be

certain, quite diÝerent from what

she has published in the past In

1990 Jamison co-authored

Man-ic-Depressive Illness, considered

the deÞnitive clinical text, and in

1993 wrote Touched with Fire, a

look at the diseaseÕs inßuence on

great artists Her new oÝering,

An Unquiet Mind, describes

man-ic-depression from another

van-tage altogether: her own

Jamison was diagnosed with

the illness some 20 years ago but

only now has found the

convic-tionÑand, more important, time

away from her intense scheduleÑ

to write about it ÒBasically,

peo-ple have been very supportive,Ó

she says, nodding her head as

though she is still trying to

de-cide ÒBut you are not aware of

the people who arenÕt saying

any-thing So youÕre sort of left at the

mercy of what other peopleÕs

opinions of the disease are.Ó It is,

as she well knows, an illness that

frightens many, conjuring up

bleak images of locked

psychi-atric wards It is also strongly genetic,

running through families and too often

stigmatizing aÝected and unaÝected

members alike Left untreated,

manic-depressive illness precipitates violent,

psychotic manias and black suicidal

de-pressions Yet, as Jamison can testify,

the disease is highly treatable Lithium

and psychotherapy have ably secured

her life and sanity for many years

She has also beneÞted from terriÞc

strength and luck Lithium was

ap-proved by the Food and Drug

Adminis-tration for treating manic-depression

in 1970, only four short years before

her condition became a medical

emer-gency Her very Þrst attack had come 10

years earlier, when she was a senior in

high school JamisonÕs family had

re-cently left Washington, D.C Her father,

a meteorologist and manic-depressive

as well, retired from the U.S Air Forceand took a job at the Rand Corporation

in Santa Monica Although Jamison hadmoved many times beforeÑshe attend-

ed four schools by the Þfth ifornia proved to be a diÛcult adjust-ment Her brother, on whom she dotedand would later depend, had left forcollege, and her father fell into depres-sion and heavy drinking

gradeÑCal-Initially, she experienced a brief, very

mild mania ÒI raced about like a crazedweasel, bubbling with plans and enthu-siasms,Ó she writes But these high-ßy-ing emotions soon gave way to despair

For months, she thought constantlyabout death, often drank vodka in hermorning orange juice and felt Òvirtuallyinert, with a dead heart and a brain cold

as clay.Ó Then, as swiftly as her moodshad come, they lifted During her under-graduate years at the University of Cal-ifornia at Los Angeles, however, the ill-ness returned in force

As her temperament worsened andgraduation grew near, Jamison shiftedher career goals from medicine to psy-chology and, in 1971, began studyingfor a doctorate at U.C.L.A ÒDespite thefact that we were being taught how tomake clinical diagnoses, I still did not

make any connection in my own mindbetween the problems I had experiencedand what was described as manic-de-pressive illness in the textbooks,Ó shewrites Though disruptive, her moodswere not unrelenting In fact, they hadvanished during a junior year abroad atthe University of St Andrews in Scot-land ÒThroughout and beyond a longNorth Sea winter,Ó she writes, Òit wasthe Indian summer of my life.Ó

In her writing and teaching, Jamisonhas long emphasized how seductivemild manias and respites from depres-sion can be during the early stages ofthe disease As such, they explain inpart why so many manic-depressivesÑmore than two thirdsÑgo untreated It

is a critical point During lunch, shepauses on it, using the blunt side of herknife to impress a timeline onthe stretch of linen between ourplates ÒThe natural course of thedisease is to have an initial epi-sode, say, at 18,Ó she says, mak-ing one invisible notch near thebreadbasket ÒThen you havemaybe a year and a half or twobefore another episode,Ó sheadds, scoring the cloth again,Òand then another year or so offree time.Ó Toward the edge ofthe table, her hand is recordingstripes of psychosis, spaced ayear or less apart

Once manic-depression enterssuch a regular cycle, it is oftenless responsive to medication,and the moods it brings begin tooverlap Indeed, mania and de-pression do not lie on oppositeends of the emotional spectrum,

as the blanched name ÒbipolardisorderÓ implies In mixedstatesÑÞlled with manic energyand morbid thoughtsÑpeopleare most likely to attempt sui-cide; without treatment, one inÞve succeed ÒIt sounds like a terriblething to say,Ó Jamison remarks, Òbutwhen you most want people to have awhole lot of episodes so that if theystop taking their medication theyÕll getsick again, they actually face the great-est probability that they are going tostay well for a long time So many peo-ple delude themselves into thinkingthat the illness wonÕt come back.ÓShe herself fell into this trap In July

1974 Jamison joined the psychiatry ulty at U.C.L.A ÒSummer, a lack of sleep,

fac-a deluge of work, fac-and exquisitely nerable genes eventually took me to theback of beyond, past my familiar levels

vul-of exuberance and into ßorid madness,Óshe writes One evening in the early fall,

as she watched the sun set over the ciÞc from her living room, she sudden-

Pa-Coming through Madness

PROFILE: KAY REDFIELD JAMISON

JAMISON has sought to change how sive illness is perceived and treated.

ly Òfelt a strange sense of light at the

back of my eyes and almost

immedi-ately saw a huge black centrifuge

in-side my head.Ó A tall Þgure, whom she

slowly recognized as herself, placed a

large tube into the centrifuge ÒThen,

horrifyingly, the image that previously

had been inside my head now was

com-pletely outside of it.Ó The whirring

ma-chine splintered, spewing blood onto

the walls, carpets and window, where it

merged into the sunset ÒI screamed

again and again Slowly the

hallucina-tions receded I telephoned a colleague

for help, poured myself a large scotch,

and waited for his arrival.Ó

This colleague insisted she see a

psy-chiatrist, persuaded her to leave U.C.L.A

for a while and prescribed an array of

antipsychotic medications ÒEndless and

terrifying days of endlessly terrifying

drugsÑThorazine, lithium, Valium and

barbituratesÑÞnally took eÝect.Ó But in

the spring, when she again felt well, she

ceased taking lithium Many of her

rea-sons were medical: The high doses that

were regularly prescribed in the 1970s

blurred her vision and made her

horri-bly nauseated When the dose reached

toxic levels, she became ataxic, or

un-coordinated Lithium further faulted her

memory and concentration She was

also loath to relinquish the addictive

thrill of her manias And she was scared

that lithium might not work Today

an-ticonvulsant drugs can level extreme

moods in many patients, she explains,

but 10 and 20 years ago, Òif you didnÕt

respond to lithium, you were just out

of luck.Ó It was a costly gamble

In a rage I pulled the bathroom lamp

oÝ the wall and felt the violence go

through me but not yet out of me ÒFor

ChristÕs sake,Ó he said, rushing inÑand

then stopping very quietly Jesus, I must

be crazy, I can see it in his eyes: a

dread-ful mix of concern, terror, irritation,

res-ignation, and why me, Lord? ÒAre you

hurt?Ó he asks Turning my head with its

fast-scanning eyes I see in the mirror

blood running down my arms, collecting

into the tight ribbing of my beautiful,

erotic negligee, only an hour ago used in

passion of an altogether diÝerent and

wonderful kind ÒI canÕt help it I canÕt

help it,Ó I chant to myself, but I canÕt say

it; the words wonÕt come out, and the

thoughts are going by far too fast I bang

my head over and over against the door

God make it stop I canÕt stand it, I know

IÕm insane again He really cares, I think,

but within ten minutes he too is

scream-ing, and his eyes have a wild look from

contagious madness, from the lightning

adrenaline between the two of us ÒI canÕt

leave you like this,Ó but I say a few truly

awful things and then go for his throat in

a more literal way, and he does leave me,provoked beyond endurance and unable

to see the devastation and despair side I canÕt convey it and he canÕt see it;

in-thereÕs nothing to be done I canÕt think, IcanÕt calm this murderous cauldron, mygrand ideas of an hour ago seem absurdand pathetic, my life is in ruins andÑworse stillÑruinous; my body is unin-habitable It is raging and weeping andfull of destruction and wild energy goneamok In the mirror I see a creature IdonÕt know but must live and share mymind with

I understand why Jekyll killed himselfbefore Hyde had taken over completely Itook a massive overdose of lithium with

no regrets

Jamison had in fact planned the tempt well in advance, obtaining anti-emetic medication to prevent her bodyfrom vomiting up the deadly dosage

at-She also placed her telephone far fromher bed so she would not answer it andattract any unwanted help Neverthe-less, when it did ring, her half-druggedbrain instinctively responded Herbrother, checking in from Paris, heardher slurred speech, hung up and calledher psychiatrist ÒThe debt I owe mypsychiatrist is beyond description,Ó shewrites ÒHe taught me that the road fromsuicide to life is cold and colder andcolder still, butÑwith steely eÝort, thegrace of God, and an inevitable break

in the weatherÑthat I could make it.Ó

When Jamison Þnally resolved thatlithium was, for her, a matter ofsurvival, she returned to academia de-termined Òto make a diÝerence in howthe illness was seen and treated.Ó Withtwo colleagues, she set up an outpatientclinic at U.C.L.A in 1977 specializing inthe treatment of mood disorders With-

in a few years, it became a large ing and research facility Jamison, notsurprisingly, emphasized the value intreating manic-depression with drugsand psychotherapy at once, which wasnot then the norm ÒWhen medicationsÞrst became available, there was a ten-dency to say, well, you can just takeyour lithium and be happy as a clam,and clearly thatÕs the wrong approach,Óshe says ÒIt does no good to have a drugthat works, if people donÕt take it.ÓAlso at the clinic, Jamison began giv-ing talks on musical composers, such

teach-as Robert Schumann, who had suÝeredfrom mood disorders These lecturesled to a series of concertsÑthe Þrst ofwhich she produced with the Los Ange-les Philharmonic in 1985Ñand to a se-ries of television specials on the linkbetween manic-depressive illness andthe arts In 1982 she surveyed the high

prevalence of mood disorders in ish artists and writers while on sabbat-ical at the University of Oxford and St.GeorgeÕs Hospital Medical School inLondon She later found evidence that adisproportionately high number of emi-nent writers and artists of the 18th and19th centuries, including Lord Byron,Vincent van Gogh and Alfred, Lord Ten-nyson, had very likely suÝered frommanic-depressive illness

Brit-Certainly most artists are not mad,and most manic-depressives are not es-pecially artistic, but Jamison suggeststhat heightened mood swings may af-ford some people greater creativity [seeÒManic-Depressive Illness and Creativi-ty,Ó by Kay RedÞeld Jamison: SCIENTIF-

IC AMERICAN, February] Such an vantage raises diÛcult questions, giventhat manic-depressive illness is genetic.Workers at Stanford University, ColdSpring Harbor Laboratory and JohnsHopkins University, as part of the DanaConsortium, are collaborating to Þndthe genes and to consider the ethicalramiÞcations of success: ÒDo we riskmaking the world a blander, more ho-mogenized place if we get rid of thegenes for manic-depressive illness?ÓJamison asks in her book ÒWhat are thedangers in prenatal diagnostic testing?ÓShe herself never had children, but notbecause she feared they might well in-herit her illness Rather the man in herlife at the time she was ready died un-expectedly, and her current husband,Richard Wyatt, a schizophrenia research-

ad-er at the National Institute of MentalHealth, already had three children whenthey met A pilot study of 50 manic-de-pressives and their spouses at JohnsHopkins has found that most coupleswould not abort an aÝected fetus.Aside from early diagnosis, Jamisonbelieves that Þnding the genes will helpscientists uncover the biochemistry ofmanic-depression ÒThere are a lot oftheories about neurotransmitters, but

at the end of the day, when they Þndthe genes, theyÕre going to be able totrace back what is out of whack.Ó Mean-while new imaging techniques are yield-ing intriguing clues Both magnetic res-onance imaging and positron emissiontomographic scans show structural ab-normalities called hyperintensities, re-ferred to as unidentiÞed bright objects(UBOs), in the brains of many manic-depressives No one has looked for UBOs

in children at risk for the disease whohave not yet been treated Until then, itwill remain unknown whether UBOs areetiologic ÒIt is clear that the UBOs arerelated,Ó Jamison says, adding with aquick smile, ÒIÕm not playing with a fulldeck.Ó It is also clear that she has playedher hand well ÑKristin Leutwyler

SCIENTIFIC AMERICAN November 1995 45

Copyright 1995 Scientific American, Inc.

The 19th-century naturalist Jean-Baptiste de Lamarck is well known for his

theory of the inheritance of acquired characteristics, but he is less

re-membered for his views on marine Þsheries In pondering the subject, he

wrote, ÒAnimals living in the sea waters are protected from the destruction

of their species by man Their multiplication is so rapid and their means of

evading pursuit or traps are so great, that there is no likelihood of his being

able to destroy the entire species of any of these animals.Ó Lamarck was also

wrong about evolution

One can forgive Lamarck for his inability to imagine that humans might catch

Þsh faster than these creatures could reproduce But many peopleÑincluding

those in professions focused entirely on ÞsheriesÑhave committed the same

error of thinking Their mistakes have reduced numerous Þsh populations to

extremely low levels, destabilized marine ecosystems and impoverished many

coastal communities Ironically, the drive for short-term proÞts has cost billions

of dollars to businesses and taxpayers, and it has threatened the food security

of developing countries around the world The fundamental folly underlying

The WorldÕs Imperiled Fish

Wild fish cannot survive the onslaught of modern

industrial fishing The collapse of fisheries

in many regions shows the danger plainly

by Carl SaÞna

MARINE FISH face a variety of threats

brought on by excessive exploitation

by modern Þshing ßeets and the

degra-dation of their natural habitats

LONG DRIFT NETSare banned but continue to be used,

entangling countless creatures besides their intended catch

SONAR can detect schools of fish directly by their characteristic echoes

PAIR TRAWLSare outlawed in some

places because the method collects

fish too effectively

LONGLINESstretching as far as

80 miles contain thousands of baitedhooks that often take accidental victims

BLUEFIN TUNA

can commandextraordinaryprices, prompt-ing fishers to hunt them downrelentlessly withships and spot-ter airplanes

RADARallows vessels

to navigate (and fish)

through dense fog

COASTAL MANGROVESthat couldotherwise serve as nurseries for youngmarine fish are often cut down

to accommodate aquaculture

SATELLITE POSITIONINGenables

ships to maneuver precisely to spots

where fish are known to congregate

and breed

DEFORESTATIONcan increase surfacerunoff, sometimes choking fragile river andcoral habitats in sediment

POLLUTIONfrom factories, sewageand agriculture can bring toxic substances

to the sea and can add excessive nutrients,causing phytoplankton to proliferate androbbing the water of oxygen

Copyright 1995 Scientific American, Inc.

the current decline has been a

wide-spread failure to recognize that Þsh are

wildlifeÑthe only wildlife still hunted

on a large scale

Because wild Þsh regenerate at rates

determined by nature, attempts to

in-crease their supply to the marketplace

must eventually run into limits That

threshold seems to have been passed

in all parts of the Atlantic,

Mediterrane-an Mediterrane-and PaciÞc: these regions each show

dwindling catches Worldwide, the

ex-traction of wild Þsh peaked at 82

mil-lion metric tons in 1989 Since then, the

long-term growth trend has been

re-placed by stagnation or decline

In some areas where the catches

peaked as long ago as the early 1970s,

current landings have decreased by

more than 50 percent Even more

dis-turbingly, some of the worldÕs greatest

Þshing grounds, including the Grand

Banks and Georges Bank of eastern

North America, are now essentially

closed following their collapseÑthe

for-merly dominant fauna have been

re-duced to a tiny fraction of their

previ-ous abundance and are considered

com-mercially extinct

Recognizing that a basic shift has

oc-curred, the members of the United

Na-tionsÕs Food and Agriculture tion (a body that encouraged the expan-sion of large-scale industrial Þshing only

Organiza-a decOrganiza-ade Organiza-ago) recently concluded thOrganiza-atthe operation of the worldÕs Þsheriescannot be sustained They now acknowl-edge that substantial damage has al-ready been done to the marine environ-ment and to the many economies thatdepend on this natural resource

Such sobering assessments are oed in the U.S by the National Academy

ech-of Sciences It reported this past Aprilthat human actions have caused drasticreductions in many of the preferred spe-cies of edible Þsh and that changes in-duced in composition and abundance

of marine animals and plants are tensive enough to endanger the func-tioning of marine ecosystems Althoughthe scientists involved in that study not-

ex-ed that Þshing constitutes just one ofthe many human activities that threat-

en the oceans, they ranked it as themost serious

Indeed, the environmental problemsfacing the seas are in some ways morepressing than those on land DanielPauly of the Fisheries Center at the Uni-versity of British Columbia and VillyChristensen of the International Center

for Living Aquatic Resources ment in Manila have pointed out thatthe vast majority of shallow continen-tal shelves have been scarred by Þshing,whereas large untouched tracts of rainforest still exist For those who workwith living marine resources, the dam-age is not at all subtle Vaughn C An-thony, a scientist formerly with the Na-tional Marine Fisheries Service, has saidsimply : ÒAny dumb fool knows thereÕs

Manage-no Þsh around.Ó

A War on Fishes

How did this collapse happen? Anexplosion of Þshing technologiesoccurred during the 1950s and 1960s.During that time, Þshers adapted vari-ous military technologies to hunting onthe high seas Radar allowed boats tonavigate in total fog, and sonar made itpossible to detect schools of Þsh deepunder the oceansÕ opaque blanket Elec-tronic navigation aids such as LORAN( Long-Range Navigation) and satellitepositioning systems turned the track-less sea into a grid so that vessels couldreturn to within 50 feet of a chosen lo-cation, such as sites where Þsh gath-ered and bred Ships can now receive

48 SCIENTIFIC AMERICAN November 1995

MEDITERRANEAN AND BLACK SEAS

INDIAN OCEAN

ATLANTIC OCEAN

PACIFIC

OCEAN

Major Fishing Regions of the World: Changes in Catch

satellite weather maps of

water-temper-ature fronts, indicating where Þsh will

be traveling Some vessels work in

con-cert with aircraft used to spot Þsh

Many industrial Þshing vessels are

ßoating factories deploying gear of

enor-mous proportions: 80 miles of

sub-merged longlines with thousands of

bait-ed hooks, bag-shapbait-ed trawl nets large

enough to engulf 12 jumbo jetliners

and 40-mile-long drift nets (still in use

by some countries) Pressure from

in-dustrial Þshing is so intense that 80 to

90 percent of the Þsh in some

popula-tions are removed every year

For the past two decades, the Þshing

industry has had increasingly to face

the result of extracting Þsh faster than

these populations could reproduce

Fish-ers have countered loss of preferred Þsh

by switching to species of lesser value,

usually those positioned lower in the

food webÑa practice that robs larger

Þshes, marine mammals and seabirds

of food During the 1980s, Þve of the

less desirable species made up nearly

30 percent of the world Þsh catch but

accounted for only 6 percent of its etary value Now there are virtually noother marine Þsh that can be exploitedeconomically

mon-With the decline of so many species,some people have turned to raising Þsh

to make up for the shortfall ture has doubled its output in the pastdecade, increasing by about 10 millionmetric tons since 1985 The practice now

Aquacul-provides more freshwater Þsh than dowild Þsheries Saltwater salmon farm-ing also rivals the wild catch, and abouthalf the shrimp now sold are raised inponds Overall, aquaculture suppliesone Þfth of the Þsh eaten by people.Unfortunately, the development ofaquaculture has not reduced the pres-sure on wild populations Strangely, itmay do the opposite Shrimp farminghas created a demand for otherwiseworthless catch because it can be used

as feed In some countries, shrimp ers are now investing in trawl nets withÞne mesh to catch everything they canfor shrimp food, a practice known asbiomass Þshing Much of the catch arejuveniles of valuable species, and sothese Þsh never have the opportunity

farm-to reproduce

Fish farms can hurt wild populationsbecause the construction of pens alongthe coast often requires cutting downmangrovesÑthe submerged roots ofthese salt-tolerant trees provide a natu-ral nursery for shrimp and Þsh PeterWeber of the Worldwatch Institute re-ports that aquaculture is one of the ma-jor reasons that half the worldÕs man-groves have been destroyed Aquacul-ture also threatens marine Þsh because

SCIENTIFIC AMERICAN November 1995 49

REGIONAL TAKES of Þsh have fallen inmost areas of the globe, having reachedtheir peak values anywhere from four

to 22 years ago ( The year of the peakcatch is shown in parentheses.) Only inthe Indian Ocean region, where modernmechanized Þshing is just now takinghold, have marine catches been on theincrease ( Red bars show average annu-

al growth since 1988.)

ALBATROSS are killed in tremendous

numbers because they frequently grab

at bait on longlines that are being set

for tuna Such losses are threatening

the survival of several species of these

MEDITERRANEAN AND BLACK SEAS (1988)

PACIFIC OCEAN

NORTHWEST (1988)NORTHEAST (1987)WEST CENTRAL (1991)EAST CENTRAL (1981)SOUTHWEST (1991)SOUTHEAST (1989)

–20–30 –40–50–60

SOURCE: Food and Agriculture Organization

Copyright 1995 Scientific American, Inc.

some of its most valuable

products, such as groupers,

milkÞsh and eels, cannot be

bred in captivity and are

raised from newly hatched

Þsh caught in the wild : the

constant loss of young fry

then leads these species even

further into decline

Aquaculture also proves a

poor replacement for Þshing

because it requires

substan-tial investment, land

owner-ship and large amounts of

clean water Most of the

peo-ple living on the crowded

coasts of the world lack all

these resources Aquaculture

as carried out in many

unde-veloped nations often

pro-duces only shrimp and

ex-pensive types of Þsh for

export to richer countries,

leaving most of the locals to

struggle for their own needs

with the oceansÕ declining

resources

Madhouse Economics

If the situation is so dire,

why are Þsh so available

and, in most developed

na-tions, aÝordable? Seafood

prices have, in fact, risen

fast-er than those for chicken,

pork or beef, and the lower

cost of these foods tends to

constrain the price of ÞshÑ

people would turn to other

meats if the expense of

sea-food far surpassed them

Further price increases will

also be slowed by imports, by

overÞshing to keep supplies

high (until they crash) and

by aquaculture For instance,

the construction of shrimp

farms that followed the

de-cline of many wild

popula-tions has kept prices in check

So to some extent, the economic law

of supply and demand controls the cost

of Þsh But no law says Þsheries need

to be proÞtable To catch $70-billion

worth of Þsh, the Þshing industry

re-cently incurred costs totaling $124

bil-lion annually Subsidies Þll much of the

$54 billion in deÞcits These artiÞcial

supports include fuel-tax exemptions,

price controls, low-interest loans and

outright grants for gear or

infrastruc-ture Such massive subsidies arise from

the eÝorts of many governments to

preserve employment despite the

self-destruction of so many Þsheries

These incentives have for many years

enticed investors to Þnance more Þshing

ships than the seasÕ resources could sibly support Between 1970 and 1990,the worldÕs industrial Þshing ßeet grew

pos-at twice the rpos-ate of the global cpos-atch,

ful-ly doubling in the total tonnage of sels and in number This armada Þnallyachieved twice the capacity needed toextract what the oceans could sustain-ably produce Economists and manag-ers refer to this situation as overcapital-ization Curiously, Þshers would havebeen able to catch as much with no newvessels at all One study in the U.S

ves-found that the annual proÞts of the lowtail ßounder Þshery could increasefrom zero to $6 million by removingmore than 100 boats

yel-Because this excessive pacity rapidly depletes theamount of Þsh available, pro-Þtability often plummets, re-ducing the value of ships onthe market Unable to selltheir chief asset without ma-jor Þnancial loss, owners ofthese vessels are forced tokeep Þshing to repay theirloans and are caught in aneconomic trap They oftenexercise substantial politicalpressure so that governmentregulators will not reduce al-lowable takes This commonpattern has become widelyrecognized Even the U.N.now acknowledges that byenticing too many partici-pants, high levels of subsidyultimately generate severeeconomic and environmentalhardship

ca-A World Growing Hungrier

While the catch of wildmarine Þsh declines, thenumber of people in the worldincreases every year by about

100 million, an amount equal

to the current population ofMexico Maintaining the pres-ent rate of consumption inthe face of such growth willrequire that by 2010 approxi-mately 19 million additionalmetric tons of seafood be-come available every year Toachieve this level, aquacul-ture would have to double inthe next 15 years, and wildÞsh populations would have

to be restored to allow highersustainable catches

Technical innovations mayalso help produce human foodfrom species currently used

to feed livestock But even ifall the Þsh that now go tothese animalsÑa third of the worldcatchÑwere eaten by people, todayÕsaverage consumption could hold foronly about 20 years Beyond that time,even improved conservation of wild Þshwould not be able to keep pace with hu-man population growth The next cen-tury will therefore witness the hereto-fore unthinkable exhaustion of theoceansÕ natural ability to satisfy human-ityÕs demand for food from the seas

To manage this limited resource inthe best way possible will clearly require

a solid understanding of marine

biolo-gy and ecolobiolo-gy But substantial ties will undoubtedly arise in fashioningscientiÞc information into intelligent

diÛcul-FISH SUPPLIES from aquaculture continue to rise, but marineÞsheries (which provide the greatest share of the globalyield) peaked in 1989 Total world catch has since entered aperiod of stagnation or decline

DOGFISH

SKATEFLOUNDER

10

PERCENT

19921965

SOURCE: National Marine Fisheries ServiceRELATIVE ABUNDANCE of common Þshes in the Gulf ofMaine has changed drastically because of overÞshing Barsindicate the level of each of these species in 1965 (red ) as compared with 1992 ( yellow).

WORLD TOTAL

MARINE CATCH

ALL AQUACULTUREFRESHWATER CATCH

SOURCE: Worldwatch Institute

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995

1101009080706050403020100

policies and in translating these

regula-tions into practice Managers of

Þsher-ies as well as policymakers have for the

most part ignored the numerous

nation-al and internationnation-al stock assessments

done in past years

Where regulators have set limits, some

Þshers have not adhered to them From

1986 to 1992, distant water ßeets

Þsh-ing on the international part of the

Grand Banks oÝ the coast of Canada

removed 16 times the quotas for cod,

ßounder and redÞsh set by the

North-west Atlantic Fisheries Organization

When Canadian oÛcials seized a

Span-ish Þshing boat near the Grand Banks

early this year, they found two sets of

logbooksĐone recording true

opera-tions and one faked for the authorities

They also discovered nets with illegally

small mesh and 350 metric tons of

ju-venile Greenland halibut None of the

Þsh on board were mature enough to

have reproduced Such selÞsh disregard

for regulations helped to destroy the

Grand Banks Þshery

Although the U.N reports that about

70 percent of the worldÕs edible Þsh,

crustaceans and mollusks are in urgent

need of managed conservation, no

country can be viewed as generally

suc-cessful in Þsheries management

Inter-national cooperation has been even

harder to come by If a country objects

to the restrictions of a particular

agree-ment, it just ignores them

In 1991, for instance, several

coun-tries arranged to reduce their catches of

swordÞsh from the Atlantic; Spain and

the U.S complied with the limitations

(set at 15 percent less than 1988

lev-els), but JapanÕs catch rose 70 percent,

PortugalÕs landings increased by 120

percent and CanadaÕs take nearly

tri-pled Norway has decided unilaterally to

resume hunting minke whales despite

an international moratorium JapanÕs

hunting of minke whales, ostensibly for

scientiÞc purposes, supplies meat that

is sold for food and maintains a market

that supports illegal whaling worldwide

Innocent Bystanders

In virtually every kind of Þshery,

peo-ple inadvertently capture forms of

marine life that, collectively, are known

as ỊbycatchĨ or Ịbykill.Ĩ In the worldÕs

commercial Þsheries, one of every four

animals taken from the sea is

unwant-ed Fishers simply discard the remains

of these numerous creatures overboard

Bycatch involves a variety of marinelife, such as species without commercialvalue and young Þsh too small to sell

In 1990 high-seas drift nets tangled 42million animals that were not targeted,including diving seabirds and marinemammals Such massive losses prompt-

ed the U.N to enact a global ban onlarge-scale drift nets (those longer than2.5 kilometers)Đalthough Italy, Franceand Ireland, among other countries,continue to deploy them

In some coastal areas, Þshing nets setnear the sea bottom routinely ensnaresmall dolphins Losses to Þsheries of

SCIENTIFIC AMERICAN November 1995 51

WHALE MEAT sold in Japan includes

many diÝerent species from all over

the world, although the legal catch

(tak-en nominally for sci(tak-entiÞc purposes) is

limited to minke whales

No Place Like Home

Although much of my work has been focused on overfishing, I have also come to see that marine habitats are being destroyed or degraded in nu-merous ways In many temperate regions the larger, bottom-dwelling animalsand plants—which feed and shelter fish—have been heavily damaged bytrawling, a form of fishing that rakes nets over the shallow continental shelves

In the tropical Indo-Pacific, many people catch fish by stunning them withcyanide—a poison that kills the coral that makes up the fishes’ habitat Somefishers herd their prey into nets by pounding the corals with stones; a boat fish-ing in this way can destroy up to a square kilometer of living reef every day Marine habitats also suffer assaults from aquaculture, agriculture and clear-cutting for logging In the Pacific Northwest of the U.S and Canada, intensivedeforestation, hydroelectric dams and water diversion have destroyed thou-sands of miles of salmon habitat Most species of sturgeon are also becomingendangered in this way throughout the Northern Hemisphere Profuse sedi-mentation following deforestation degrades habitats in many parts of thetropics as well Sediments can kill coral reefs by clogging them, blocking sun-light and preventing settlement of larvae

In 1989 the tropical marine ecologist Robert Johannes helped to select thetiny Pacific island country of Palau as one of the world’s seven undersea won-ders—akin to the seven wonders of the ancient world—because of its spec-tacular and largely unspoiled coral reefs When I visited him in Palau early thisyear, I frequently witnessed long plumes of red sediment bleeding off new,poorly made roads into coral lagoons after every heavy rain Runoff from in-tact jungle was, in contrast, as clear as the rain itself Untreated sewage wasalso flowing into reefs near the capital’s harbor Such nutrient-rich pollution al-lows algae to grow at unnatural rates, killing corals by altering their delicate

Copyright 1995 Scientific American, Inc.

several marine mammalsÑthe baiji of

eastern Asia, the Mexican vaquita (the

smallest type of dolphin), HectorÕs

dol-phins in the New Zealand region and

the Mediterranean monk sealÑput those

speciesÕ survival at risk Seabirds are

also killed when they try to eat the bait

attached to Þshing lines as these are

played out from ships Rosemary

Gales, a research scientist at the

Parks and Wildlife Service in

Ho-bart, Tasmania, estimates that

in the Southern Hemisphere

more than 40,000 albatross are

hooked and drowned every year

after grabbing at squid used as

bait on longlines being set for

blueÞn tuna This level of

mor-tality endangers six of the 14

species of these majestic

wan-dering seabirds

In some Þsheries, bykill

ex-ceeds target catch In 1992 in the

Bering Sea, Þshers discarded 16

million red king crabs, keeping

only about three million

Trawl-ing for shrimp produces more

bykill than any other type of

Þshing and accounts for more

than a third of the global total

Discarded creatures outnumber

shrimp taken by anywhere from

125 to 830 percent In the Gulf

of Mexico shrimp Þshery 12

mil-lion juvenile snappers and 2,800 metrictons of sharks are discarded annually

Worldwide, Þshers dispose of about sixmillion sharks every yearÑhalf of thosecaught And these statistics probablyunderestimate the magnitude of thewaste: much bycatch goes unreported

There remain, however, some

glim-mers of hope The bykill of sea turtles

in shrimp trawls had been a constantplague on these creatures in U.S wa-ters (the National Research Council es-timated that up to 55,000 adult turtlesdied this way every year ) But thesedeaths are being reduced by recentlymandated Òexcluder devicesÓ that shuntthe animals out a trap door inthe nets

Perhaps the best-publicizedexample of bycatch involved up

to 400,000 dolphins killed nually by Þshers netting PaciÞcyellowÞn tuna Over three de-cades since the tuna industrybegan using huge nets, the east-ern spinner dolphin populationfell 80 percent, and the num-bers of oÝshore spotted dol-phin plummeted by more than

an-50 percent These declines led

to the use of so-called safe methods (begun in 1990)whereby Þshers shifted fromnetting around dolphin schools

dolphin-to netting around logs and

oth-er ßoating objects

This approach has been

high-ly successful : dolphin kills wentdown to 4,000 in 1993 Unfor-tunately, dolphin-safe nettingmethods are not safe for imma-ture tuna, billÞsh, turtle or shark

EXPORT PRICES for Þsh have exceeded those for beef,chicken and pork by a substantial margin over thepast two decades To facilitate comparison, the price

of each meat is scaled to 100 for 1975

Economies of Scales

Fishing adds only about 1 percent to the global economy,

but on a regional basis it can contribute enormously to

human survival Marine fisheries contribute more to the

world’s supply of protein than beef, poultry or any other

ani-mal source

Fishing typically does not require land ownership, and

be-cause it remains, in general, open to all, it is often the

em-ployer of last resort in the developing world—an occupation

when there are no other options Worldwide, about 200

mil-lion people depend on fishing for their livelihoods Within

Southeast Asia alone, more than five million people fish

full-time In northern Chile 40 percent of the population lives off

the ocean In Newfoundland most employment came from

fishing or servicing that industry—until the collapse of the

cod fisheries in the early 1990s left tens of thousands of

peo-ple out of work

Although debates over the conservation of natural

resourc-es are often cast as a conflict between jobs and the

environ-ment, the restoration of fish populations would in fact boost

employment Michael P Sissenwine and Andrew A Rosenberg

of the U.S National Marine Fisheries Service have estimated

that if depleted species were allowed to rebuild to their

long-term potential, their sustainable use would add about $8

bil-lion to the U.S gross domestic product—and provide some

300,000 jobs If fish populations were restored and properly

managed, about 20 million metric tons could be added to the

world’s annual catch But reinstatement of ecological balance,

fiscal profitability and economic security will require a

On average, for every 1,000 nets set

around dolphin herds, Þshers

inadver-tently capture 500 dolphins, 52 billÞsh,

10 sea turtles and no sharks In

con-trast, typical bycatch from the same

number of sets around ßoating objects

includes only two dolphins but also

654 billÞsh, 102 sea turtles and 13,958

sharks In addition, many juvenile tuna

are caught under ßoating objects

One solution to the bycatch from nets

would be to Þsh for tuna with poles and

lines, as was practiced commercially in

the 1950s That switch would entail

hir-ing back bigger crews, such as those laid

oÝ when the Þshery Þrst mechanized

its operations

The recent reductions in the bycatch

of dolphins and turtles provide a minder that although the state of theworldÕs Þsheries is precarious, there arealso reasons for optimism ScientiÞcgrasp of the problems is still develop-ing, yet suÛcient knowledge has beenamassed to understand how the diÛ-culties can be rectiÞed Clearly, one ofthe most important steps that could betaken to prevent overÞshing and exces-sive bycatch is to remove the subsidiesfor Þsheries that would otherwise beÞnancially incapable of existing oÝ theoceansÕ wildlifeÑbut are now quite ca-pable of depleting it

re-Where Þshes have been protected,

they have reboundedÑalong with thesocial and economic activities they sup-ported The resurgence of striped bassalong the eastern coast of the U.S isprobably the best example in the world

of a species that was allowed to recoupthrough tough management and an in-telligent rebuilding plan

During the past year, the U.N hasbeen making historic progress in forg-ing new conservation agreements deal-ing with high-seas Þshing Such mea-sures, along with regional and localeÝorts to protect the marine environ-ment, should help guide the world to-ward a sane and sustainable future forlife in the oceans

SCIENTIFIC AMERICAN November 1995 53

The Author

CARL SAFINA earned his doctorate in ecology in

1987 at Rutgers University, where he studied natural

dynamics among seabirds, prey Þshes and predatory

fishes He founded and now directs the National

Audu-bon SocietyÕs Living Oceans Program He also serves as

deputy chair of the World Conservation UnionÕs Shark

Specialist Group, is a founding member of the Marine

Fish Conservation Network and was formerly on the

Mid-Atlantic Fisheries Management Council SaÞna

re-ceived the Pew Charitable TrustÕs Scholars Award in

Conservation and the Environment He has Þshed

com-mercially and for sport

Further Reading

BLUEFIN TUNA IN THE WEST ATLANTIC: NEGLIGENT MANAGEMENT AND THE

MAK-ING OF AN ENDANGERED SPECIES Carl SaÞna in Conservation Biology, Vol 7, No.

2, pages 229Ð234; June 1993

CONSERVA-TION INTO DECISION MAKING Edited by E Norse Island Press, 1993

Technolo-gy, Vol 10, pages 37Ð43; Spring 1994.

Agriculture Organization, Rome, 1995

Coun-cilÕs Committee on Biological Diversity in Marine Systems National AcademyPress, 1995

stantial reduction in the capacity of the commercial fishingindustry so that wild populations can recover

The necessary reductions in fishing power need not come

at the expense of jobs Governments could increase ment and reduce the pressure on fish populations by direct-ing subsidies away from highly mechanized ships For each

employ-$1 million of investment, industrial-scale fishing operationsrequire only one to five people, whereas small-scale fisherieswould employ between 60 and 3,000 Industrial fishing itselfthreatens tens of millions of fishers working on a small scale

by depleting the fish on which they depend for subsistence.For some fisheries, regulators have purposefully promot-

ed inefficiency as a way to limit excessive catches and tain the living resource For example, in the Chesapeake Bay,law requires oyster-dredging boats to be powered by sail

main-(left ), a restriction on technology that has helped this fishery

survive In New England, regulators outlawed the use of netspulled between two boats ( “pair trawls” ) because this tech-nique was too effective at catching cod Managers of the U.S.bluefin-tuna fishery allocate 52 percent of the catch to com-mercial boats that deploy the least capable gear—handlines

or rod and reel—even though the entire allowed amountcould easily be extracted with purse-seine nets In this in-stance, vessels with the more labor-intensive tackle accountfor nearly 80 percent of direct employment; those that havelarge nets provide only 2 percent Numerous other regula-tions on sizes and total amount of the catch, as well as allo-cation and allowable equipment, can be viewed as acknowl-edgments of the need to curb efficiency in order to achievewider social and ecological benefits — C.S.

When biologists view healthy

tissue from the brain or spinal

cord under a microscope, they

rarely see white blood cells, the best

known sentries of the immune system

And for good reason Although white

blood cells defend against infection and

cancer, they also can secrete

substanc-es capable of killing irreplaceable nerve

cells, or neurons The body minimizes

such destruction by restricting the

pas-sage of immune cells out of blood

ves-sels and into the central nervous

sys-tem; white cells generally escape into

the nerve tissue only when blood

ves-sels are damaged by trauma or disease

Such observations led to the once

widespread belief that the central

ner-vous system lacks immune protection

Recently, however, investigators have

demonstrated that fascinating cells

called microglia form an extensive

de-fensive network there Most of the time,

microglia serve without harming

neu-rons Yet mounting evidence suggests

they occasionally lose their benign

char-acter In fact, there are intimations that

the cells can help cause or exacerbate

several disabling conditions, among

them, stroke, AlzheimerÕs disease,

mul-tiple sclerosis and other

neurodegener-ative disorders

Microglia belong to a class of cellsÑthe glia ( from Greek, meaning ÒglueÓ)Ñthat was Þrst recognized in the 1800s

Initially, biologists mistakenly thought

of the glia as a single unit that servedonly as the uninteresting putty betweenneurons in the brain and spinal cord But

by the 1920s microscopists had Þed three kinds of glial cell: astrocytes,oligodendrocytes and microglia By the1970s it was evident the Þrst two types,

identi-at least, had profound responsibilities

For instance, the star-shaped cyte, which has the largest cell body,had been found to sop up extra neuro-transmitter molecules around neurons,thereby protecting nerve cells from re-ceiving too much stimulation [see ÒAs-trocytes,Ó by Harold K Kimelberg andMichael D Norenberg; SCIENTIFIC AMER-ICAN, April 1989] And the oligodendro-cyte, the next largest glial cell, had beenshown to produce the myelin sheaththat insulates axons (long projectionsthat extend from neuronal cell bodiesand carry electrical signals) Some re-searchers suspected the more diminu-tive, microglial cell also had a specialÑimmunologicÑrole, but until the 1980s,the tools needed to validate this specu-lation were lacking

astro-The idea grew primarily out of

inten-sive research performed early in the20th century by Pio del R’o-Hortega, aformer student of the famous Spanishneuroanatomist Santiago Ramon y Ca-jal In 1919 del R’o-Hortega developed

a stain, based on silver carbonate, thatmade it possible to distinguish micro-glia from neurons, astrocytes and oligo-dendrocytes in thin slices of the mam-malian brain He then spent more than

a decade learning all he could aboutthese odd cells

He determined that microglia Þrstappear in the developing brain as amor-phous bodies Eventually, though, theydiÝerentiate into extensively branched,

or ramiÞed, forms that populate everyregion of the brain and touch neuronsand astrocytes (but not one another )

He also saw that the cells respondeddramatically when the brain was injuredseverely For instance, he noted that inreaction to a stab wound, the ramiÞedcells retracted their delicate branches,

or processes, and seemed to return totheir rounder, immature conformation.Del R’o-Hortega recognized that mi-croglia in this last state resembledmacrophages, a form of white bloodcell found in tissues outside the brain

He knew as well that when

macrophag-es sensed that tissumacrophag-es were hurt or

in-The BrainÕs Immune System

It consists of cells called microglia that are normally protective

but can be surprisingly destructive The cells may contribute

to neurodegenerative diseases and to the dementia of AIDS

by Wolfgang J Streit and Carol A Kincaid-Colton

MYELIN

OLIGODENDROCYTE

ASTROCYTE

fected, they usually migrated to the

af-fected areas, proliferated and became

highly phagocyticĐthat is, they became

garbage collectors, capable of ingesting

and degrading microbes, dying cells and

other debris By 1932 he was able to

postulate that the rounding of mature

microglia reßected a metamorphosis to

a phagocytic state In other words, he

thought microglia functioned as the

macrophages of the central nervous

system

Support for an Immune Role

Although del R’o-HortegaÕs ideas

made sense, few investigators

fol-lowed up on them during the next 50

years, largely because his staining

method proved unreliable Without a

dependable way of distinguishing

mi-croglia from other cells, no one could

learn much about their functions This

barrier came down only in the 1980s,

after V Hugh Perry and his colleagues at

the University of Oxford began

screen-ing monoclonal antibodies for their

abil-ity to bind to microglia Monoclonal

an-tibodies each recognize a highly

spe-ciÞc protein target, or antigen PerryÕs

group knew that if such antibodies

found their targets on microglia but

not on other cells of the central nervoussystem, the antibodies could be exploit-

ed as a new kind of Ịstain.Ĩ The glia would stand out from other cells ifthe workers simply linked the boundantibodies to some detectable label,such as a ßuorescent compound

micro-In 1985 PerryÕs team demonstratedthat various monoclonals produced byother groups could indeed pinpoint mi-croglia in brain tissue Soon, even moreantibodies able to serve this purposebecame available Their introduction,together with the advent in the mid-1980s of methods for maintaining purepopulations of microglia in culture dish-

es, Þnally made it possible to examinethe activities of the cells in detail

The antibodies did more than light microglia; they provided strongcircumstantial support for the assertionthat those cells could operate as im-mune defenders in the brain and spinalcord Notably, various antibodies thatrecognize proteins occurring exclusive-

high-ly on cells of the immune system wereable to Þnd their targets on microglia

Further, certain antibodies

demonstrat-ed that the cells probably behavdemonstrat-ed likemacrophages

Macrophages and some of their kinare antigen presenters: they chop upproteins made by invading microbes anddisplay the pieces in molecular show-cases known as class II major histocom-patibility antigens Such displays help

to induce additional immune cells tolaunch a full-ßedged attack against aninvader Between 1985 and 1989, re-searchers from around the world dem-onstrated that monoclonal antibodiesable to latch on to class II major histo-compatibility antigens often bound well

to microglia This behavior meant that,contrary to prevailing views, microgliaproduced class II major histocompati-bility antigens; hence, they were proba-bly antigen-presenting cells themselves.The antibody results dovetailed withwork by Georg W Kreutzberg and hiscolleagues at the Max Planck Institutefor Psychiatry in Martinsried The Ger-man group, one of the few with a long-standing interest in microglial function,

SCIENTIFIC AMERICAN November 1995 55

MICROGLIAL CELLS (red ) in their resting state touch the cells around them and

monitor their health, ready to respond quickly to injury or disease Microglia are asnumerous as neurons in the central nervous system and are dispersed throughout it

Microglia ( golden brown in micrographs ) are often

found in their resting, highly ramified state (top ) But

when they sense a neuron is in trouble, they begin to

re-tract their branches They also migrate to the site of

dan-ger and take on a new conformation (middle) The precise

shape usually depends on the architecture of the brain

re-gion in which the microglia find themselves If the cells

have enough space, they may become bushy (left ) If the

cells have to fit in among long, thin neuronal projections,

they tend to become rodlike (center ) Other times, they

prefer to conform to the surface of injured neurons, as is

the case when motor neurons are damaged (right ) If

dis-ordered neurons recover, microglia may revert to their

resting state ( gray arrows ) If neurons die, however, croglia progress to a phagocytic state (bottom ) and assid-

mi-uously try to remove the dead material

Cells in this state are

reacting to the death

of other cells; they

change shape again

and attempt to degrade

the dead matter

tested the ability of microglia in the

ro-dent brain to behave like macrophages

when confronted with severely injured

neurons At the same time, the workers

looked into the contention of some

in-vestigators that microglia did not live in

the central nervous system at all, that

they were nothing more than

mono-cytes that ßooded into the brain or

spinal cord when blood vessels in the

nerve tissue were damaged This last

assertion had been diÛcult to refute

because then, as now, the antibodies

and stains that recognized microglia

also recognized macrophages derived

from blood-borne monocytes

Kreutzberg and his colleagues

ap-plied a simple method to resolve both

issues As a start, they focused on

neu-rons whose cell bodies were located in

the brain but whose axons terminated

at muscles outside the brain They

in-jected a toxin into a site near the ends

of the axons and allowed the poison to

diÝuse throughĐand killĐthe neurons

without aÝecting any blood vessels This

maneuver ensured that any

macro-phagelike cells responding to the

dam-age would be residents of the brain

tis-sue, not interlopers from the blood

Fi-nally, they examined the brain region

containing the remains of the aÝected

nerve cells Analyses of tissue from

many animals revealed that microglia

do in fact migrate to dead neurons,

pro-liferate and remove dead cells In short,

microglia are, indeed, the brainÕs own

kind of macrophages

Experiments on pure populations of

microglia in culture have now helped

convince even the greatest skeptics that

microglia are the immune warriors del

R’o-Hortega thought them to be These

studies have conÞrmed that the cells are

extremely mobileĐa property essential

for cells that supposedly move easily to

injured areas within the brain The work

has also established that microglia can

be induced to produce a wide array of

chemicals made by macrophages in

other tissues

How Normal Microglia Behave

It appears, then, that modern research

has Þnally justiÞed del R’o-HortegaÕs

belief in the immunologic properties of

microglia The studies have also

clari-Þed the operation of the cells in the

healthy, as well as the diseased, central

nervous system

Microglia are critical to proper

devel-opment of the embryo They may

se-crete growth factors important to the

formation of the central nervous

sys-tem, but another role has been

identi-Þed more deÞnitively The growing

fe-tus generates many more neurons and

glial cells than it needs Over time, theunused cells die, and young microglia,still in their initial, nonramiÞed confor-mation, remove the dead matter

As the sculpting of the central vous system is completed, the need todegrade large numbers of cells disap-pears, and microglia diÝerentiate intotheir extensively ramiÞed, resting state

ner-This conformation enables the cells to

keep close tabs on the health of manycells in their vicinity No one yet knowsmuch about the other functions of rest-ing microglia, but indirect evidence implies the cells release low levels ofgrowth factors, which at this stagewould help mature neurons and gliasurvive Those substances may includeÞbroblast growth factor and nervegrowth factorĐtwo proteins that inves-tigators have prodded cultured micro-glia to secrete

What is more certain is that restingmicroglia respond almost instantly(within minutes) to disturbances in theirmicroenvironment and prepare to sur-round damaged neurons or other cells

The outward signs of such activationare retraction of their branches, otherchanges in shape, production of pro-teins not found in the resting state, andstepped-up synthesis of proteins for-merly made only in small amounts Forexample, expression of major histocom-patibility antigens is enhanced marked-

ly We do not yet know whether the cellsrelease higher amounts of growth fac-tors, but they may well do so in an at-tempt to repair injured neurons

The conformation of the newly vated microglia seems to depend a greatdeal on the architecture of the region

acti-in which the cells live If the area isÞlled mainly with axons, the cells tend

to become long and thin, in order to Þtbetween the cables If there is room tomaneuver, as is the case in much of thebrain, the cells often become bushy

Activated cells do not automaticallybecome phagocytic; they can revert to

the resting state if the injury they havedetected is mild or reversible If the in-jury is severe and kills neurons, howev-

er, microglia begin to function as ßedged, phagocytic macrophages Theultimate fate of the phagocytes is un-clear, but investigations of cultured mi-croglia and of diseased brains suggestthe cells sometimes go on to damagethe neurons they are meant to protect.Suspicion that microglia might con-tribute to neurologic disorders wasaroused in part by the discovery, men-tioned earlier, that microglia can releasemany of the same chemicals emitted bymacrophages outside the central ner-vous system Some of those substancesare dangerous to cells and, if made inexcessive amounts, could surely killneurons For example, one of us ( Kin-caid-Colton) and her colleagues atGeorgetown University have found thatwhen activated microglia in culture areexposed to particular bacterial compo-nents, the cells, like other macrophag-

full-es, generate extremely destructive ecules known as reactive oxygen spe-cies The compounds go by such names

mol-as the superoxide anion, the hydroxylradical (one of the most toxic com-pounds in the body) and hydrogen per-oxide Along with killing microbes, theycan damage membranes, proteins andDNA in neurons and other cells

Additional, potentially destructivecompounds manufactured by stronglyactivated microglia and other macro-phages include enzymes called proteas-

es that digest proteins and can chewholes in cell membranes They furtherencompass at least two versatile mes-senger molecules, or cytokines, that canincrease inßammation That is, thesecytokinesĐamong them, interleukin-1and tumor necrosis factorĐoften help

to recruit other components of the mune system to a site of injury [see ỊTu-mor Necrosis Factor,Ĩ by Lloyd J Old;

im-SCIENTIFIC AMERICAN, May 1988] ßammation can be important for eradi-cating infections and incipient cancers,but it can have serious ỊbystanderĨ ef-fects by which uninfected cells areharmed Under some circumstances,the cytokines can also damage neuronsdirectly, and tumor necrosis factor cankill oligodendrocytes

In-That microglia can synthesize all thesesubstances in culture is not proof thatthe cells can disrupt the living brain In-deed, the central nervous system appar-ently holds microglia on a tight leash,forcing them to keep worrisome secre-tions to a minimum, even when re-sponding to injury and disease; other-wise no one would survive having microglia everywhere in the brain Nev-ertheless, research into a number of

SCIENTIFIC AMERICAN November 1995 59

Investigations

of cultured microglia and of diseased brains suggest the cells sometimes damage the neurons they are meant to protect.

Copyright 1995 Scientific American, Inc.

neurological disorders suggests that in

some patients the leash is loosened,

ei-ther because a defect exists in the

mi-croglia themselves or because some

oth-er disease process undoth-ermines the

nor-mal controls on the behavior of the cells

Microglia and Disease

Excessive microglial activity has

cer-tainly been implicated in the

demen-tia that sometimes arises in patients

suÝering from AIDS The human

immu-nodeÞciency virus, which causes the

disease, does not attack neurons, but it

does infect microglia Such invasion has

been shown to spur microglia to make

elevated levels of inßammatory

cyto-kines and other molecules that are

tox-ic to neurons

Disturbed regulation of microglia

could play a part in AlzheimerÕs disease

as well The brains of AlzheimerÕs

pa-tients are marked by large numbers of

senile plaques: abnormal regions in

which deposits of a protein fragmentknown as beta amyloid mingle with mi-croglia, astrocytes and the endings ofinjured neurons Such plaques arethought to contribute to the neuronaldeath that underlies the deterioration ofthe mind Exactly how they hurt nervecells is unclear and a matter of heatedargument Many investigators suspectbeta amyloid is the agent of trouble

We think beta amyloid might do itsmischief by aÝecting microglia It isnow evident, for instance, that the lev-els of interleukin-1 and other cytokinesknown to be made at times by micro-glia are elevated in senile plaques Suchelevation implies that somethingÑper-haps beta amyloidÑpushes the micro-glia in plaques into a highly active state

In that condition, the cells would sumably also release oxygenated spe-cies and protein-degrading enzymesand could thereby disrupt neurons

pre-Other Þndings suggest that microgliamight even contribute to the formation

of plaques It seems microglia respond

to injury in the central nervous system

by making one form of the amyloid cursor proteinÑthe molecule that, whencleaved in a particular way, yields betaamyloid Moreover, studies of cells inculture have shown that interleukin-1causes various other cells, possibly in-cluding neurons, to produce amyloidprecursor molecules Finally, the reac-tive oxygen species made by activatedmicroglia promote the aggregation ofamyloid fragments

pre-It is easy to imagine that a vicious cycle could ensue after some triggerpushed microglia into a hyperactivestate If the cells made the amyloid pre-cursor protein, their proteases couldwell cleave the molecule to produce betaamyloid At the same time, interleukin-

1 might induce other cells to make loid as well Then reactive oxygen spe-cies could cause the amyloid released bymicroglia or neighboring cells to clumptogether Such clustering, in turn, couldlead to activation of additional micro-glia, production of more amyloid, for-mation of more plaques, and so on.People born with DownÕs syndromeacquire elevated numbers of senileplaques in their brains, albeit earlierthan do patients with AlzheimerÕs dis-ease Because the brain changes are soalike in the two conditions, Kincaid-Colton and her colleagues have begunexploring the possibility that microgliadamage brain tissue in these patients.They have uncovered some support forthe concept in studies of mice bearing

amy-a genetic defect amy-anamy-alogous to thamy-at sponsible for DownÕs syndrome in hu-mans Microglia in such fetuses are un-usually reactive and abundant; addi-tionally, the microglia in the ÒDownÕsÓmice release increased amounts of re-active oxygen species, interleukin-1 andother cytokines that might aÝect nervetissue adversely

re-Stroke victims, too, might lose rons to overzealous microglia, accord-ing to experiments performed in rats

neu-by one of us ( Streit) and his co-workers

at the University of Florida When a jor blood vessel feeding the forebrain isshut down, the brain tissue dependent

ma-on the vessel dies quickly Over the nextseveral days, particularly vulnerableneurons in a part of the surroundingareaÑthe so-called CA1 region of thehippocampusÑdie as well Interestingly,StreitÕs group has discovered that mi-croglia are activated within minutes af-ter onset of such a stroke, long beforethe hippocampal neurons die ( This ac-tivation is made evident by changes incell shape and by enhanced stainabili-ty.) It is conceivable that the microglia,sensing danger, attempt to protect the

The Controversial Origin of Microglia

In 1932 Pio del Río-Hortega, the pioneer of microglial research, ignited a

controversy that preoccupied most investigators interested in microglia for

more than 50 years In the same paper in which he proposed that microglia

were the immune defenders and garbage collectors of the central nervous

system, he suggested that the cells did not originate in the same embryonic

tissue—the ectoderm—that gives rise to nerve cells He concluded that

mi-croglia derived instead from the mesoderm, the layer of embryonic germ

cells that forms the bone marrow, blood, blood vessels and lymphatics He

could not decide, however, on the precise mesodermal lineage of the cells

Did microglia descend from white blood cells called monocytes and enter the

brain and spinal cord from the fetal blood circulation? Or did they descend

from noncirculating cousins of monocytes and migrate to the central nervous

system directly, without passing through the bloodstream?

For a time, the monocytic origin was favored, and the majority opinion held

that the precursors of microglia were monocytes attracted to the developing

nervous system by neurons that died during the sculpting of the brain and

spinal cord But new findingscontradict that view For in-stance, Jutta Schnitzer of theMax Delbrück Center forMolecular Medicine in Berlinand Ken W S Ashwell of theUniversity of Sydney in Aus-tralia have shown that theretina of the eye, a part ofthe central nervous system,

is “seeded” with microgliaquite early in development,well before neurons begin todie In fact, the weight of ev-idence now favors the “cou-sin” hypothesis

The photograph at the leftwas taken in 1924 by Wilder

G Penfield, before Penfieldgained renown as a neuro-

neurons, perhaps by initiating or

in-creasing secretion of growth factors

potentially able to repair injuries It is

equally likely, however, that the altered

chemistry in the region eventually

re-leases the normal brakes on microglial

behavior, propelling the cells into a

state in which they become dangerous

Preliminary evidence points as well

to microglia as possible participants in

multiple sclerosis, ParkinsonÕs disease

and amyotrophic lateral sclerosis ( Lou

GehrigÕs disease) Microglia also change

with age, as is evident in the increased

display of major histocompatibility

anti-gens This display could be a sign that

the normal inhibitions on progression

to the dangerous, highly active state

re-lax with time Easing of these controls

would undoubtedly promote neuronaldestruction and could thus contribute

to memory declines and senility

The Good News

Agood deal of research into the link between microglia and disorders

of the brain casts microglia as villains,but the data do have some encouragingimplications If microglia are indeedcentral players in neurological diseases,

it might be possible to ameliorate theseconditions by speciÞcally inhibiting mi-croglia or by blocking the activity oftheir products Drug therapies withthese aims are already beginning to betested in patients with AlzheimerÕs dis-ease For example, small trials are under

way to examine the safety and tiveness of an anti-inßammatory agentcapable of quieting activated microglia.Conversely, scientists might be able totake advantage of the cellsÕ protectiveaspects and boost microglial produc-tion of growth factors

eÝec-Ten years ago some investigators nied that microglia even existed Fiveyears ago most physicians would havelaughed if anyone hinted that microgliacould be major participants in Alzhei-merÕs disease and other degenerativeconditions of the brain Today the skep-ticism is evaporating Indeed, manyworkers are conÞdent that study of mi-croglia will eventually yield new thera-pies for some of the most heartbreak-ing diseases aÜicting humankind

de-SCIENTIFIC AMERICAN November 1995 61

SENILE PLAQUES (round regions in micrograph ) are thought

to cause the neuronal damage underlying memory impairment

in patients with AlzheimerÕs disease and DownÕs syndrome At

their core, the plaques consist mainly of protein fragments

called beta amyloid (red ), known to be harmful to neurons,

and microglia (deep purple) The plaques also include other

glial cells called astrocytes ( golden brown ÒstarsÓ ) as well as damaged axons and dendrites (not visible) New evidence

suggests microglia promote plaque formation It is also sible that activated microglia disrupt neurons directly, by se-creting chemicals that can be toxic to cells Some of thechemicals made by microglia are listed in the table

pos-The Authors

WOLFGANG J STREIT and CAROL A KINCAID-COLTON conduct separate research

pro-grams but have collaborated on developing a symposium on microglia Streit, who earned

his Ph.D in experimental neuropathology at the Medical University of South Carolina , is

associate professor of neuroscience at the University of Florida Brain Institute He joined

the university after working as a staÝ scientist at the Max Planck Institute for Psychiatry in

Martinsried, Germany Kincaid-Colton is associate professor of physiology and biophysics

at the Georgetown University School of Medicine She holds a doctorate in physiology from

Rutgers University and was on staÝ at the Laboratory of Biophysics at the National

Insti-tutes of Health before taking her post at Georgetown

MICROGLIA Special issue of Glia Edited by

M B Graeber, G W Kreutzberg and W J.Streit Vol 7, No 1; January 1993

B R Ransom Oxford University Press, 1995

Amyloid precursor protein

Cytokines(messenger molecules

of the immune system)Growth factors

Protein-cleavingenzymes

Reactive oxygenspecies

Unknown

Recruit other cells to sites

of infection; some promotethe survival and repair

of astrocytes; some combat tumorsPromote the survival and repair of neuronsHelp to degrade microbes and damaged cells

Can damage membranes, proteins and DNA

in microbes

When cleaved, may give rise to beta amyloidCan harm healthy cellsand induce other immune cells to secrete cell-damaging

substancesUnknown

Can degrade membranes

of healthy cells; may contribute to formation

of beta amyloidCan damage healthy cells; can promote the

aggregation of beta amyloid

Microglial Products: Double-Edged Swords

Beneficial Effects Harmful Effects Chemical

Copyright 1995 Scientific American, Inc.

The past 10,000 years are

anoma-lous in the history of our planet

This period, during which

civiliza-tion developed, was marked by weather

more consistent and equable than any

similar time span of the past 100

mil-lennia Cores drilled through several

parts of the Greenland ice cap show a

series of cold snaps and warm spellsĐ

each lasting 1,000 years or moreĐthat

raised or lowered the average winter

temperature in northern Europe by as

much as 10 degrees Celsius over the

course of as little as a decade The signs

of these sudden changes can be read in

the records of atmospheric dust,

meth-ane content and precipitation preserved

in the annual ice layers

The last millennium-long cold period,

known as the Younger Dryas (after a

tundra ßower whose habitat expanded

signiÞcantly), ended about 11,000 years

ago Its marks can be found in North

Atlantic marine sediments,

Scandina-vian and Icelandic glacial moraines, and

northern European and maritime

Cana-dian lakes and bogs New England also

cooled signiÞcantly

Further evidence is accumulating that

the Younger DryasÕs eÝects were global

in scope The postglacial warming of

AntarcticaÕs polar plateau came to a halt

for 1,000 years; at the same time, New

ZealandÕs mountain glaciers made a

major advance, and the proportions of

diÝerent species in the plankton

popu-lation of the South China Sea changed

markedly The atmosphereÕs methane

content dropped by 30 percent Only

pollen records from parts of the U.S

fail to show the periodÕs impact

The Great Conveyor

What lies behind this turbulent

his-tory, and could it repeat itself?

Al-though no one knows for sure, there are

some very powerful clues A variety of

models suggest that the circulation of

heat and salt through the worldÕs oceans

can change suddenly, with drastic eÝects

on the global climate Giant,

conveyor-like circulation cells span the length ofeach ocean In the Atlantic, warm upperwaters ßow northward, reaching the

vicinity of Greenland [see illustration on these two pages], where the Arctic air

cools them, allowing them to sink andform a current that ßows all the way tothe Southern Ocean, adjacent to Antarc-tica There, warmer and thus less densethan the frigid surface water, the cur-rent rises again, is chilled to the freez-ing point and sinks back into the abyss

Tongues of Antarctic bottom water, thedensest in the world, ßood northwardinto the Atlantic, PaciÞc and Indianoceans, eventually welling up again torepeat the cycle In the PaciÞc and Indi-

an oceans, the northward ßow of tom waters is balanced by a southwardmovement of surface waters In the At-

bot-Chaotic Climate

Global temperatures have been known

to change substantially in only a decade or two

Could another jump be in the o¤ng?

by Wallace S Broecker