The second is inhibition of cytochrome oxidase in a manner very similar to the effect of cyanide.. The nitrites within the kit convert hemoglobin to methemoglobin which becomes an agent
Trang 1TOXICITY OF SULFIDES
Hydrogen sulfide has two major toxic actions The first is a depressant effect on the CNS A result of this effect is paralysis of the respiratory center and death The second
is inhibition of cytochrome oxidase in a manner very similar to the effect of cyanide
H2S is actually a more potent inhibitor of cytochrome oxidase than is cyanide Carbon disulfide has some toxic features in common with H2S It attacks the CNS and the cardiovascular system However, it has its own uniquely toxic character
in causing a peripheral neuropathy with cranial nerve damage (see Chapter 10 on neurotoxins) Curiously, it is also atherogenic in experimental animals
THERAPY
The cyanide antidote kit is effective with H2S poisoning The nitrites within the kit convert hemoglobin to methemoglobin which becomes an agent for binding hydro-gen sulfide before it can bind cytochrome oxidase and cause death Sulfmethemo-globin is formed by the reaction between methemoSulfmethemo-globin and either H2S or hydrogen sulfide anion and this substance is excreted into the urine as such or as nontoxic metabolites
LABORATORY TESTING
Hydrogen sulfide is like cyanide in the sense that many victims will die too soon for laboratory evaluation to be of any help However, testing for sulfide ion in blood may help to make the diagnosis for those who are less disabled An ion-selective electrode has been developed for measurement of sulfide ion Because this electrode
is not completely specific to sulfide to the exclusion of all other ions, it is necessary
to pre-treat the specimen and isolate sulfide This has been done, in one method, with Conway microdiffusion cells Concentrations of sulfide ion found in H2S deaths ranged from 1.7 to 3.75 µg/mL
HYDROCARBONS
By definition these are compounds which contain only carbon and hydrogen Many such compounds have been identified in the natural world, a good number of which are found in crude oil They include the aliphatic alkanes, alkenes, and alkynes, which differ among each other in regard to the saturation of the carbon atoms The most common members of this class are methane, ethane, propane, and butane All members of this category are very abundant in the industrial world The aromatic hydrocarbons include benzene and the many compounds derived from benzene Halogenated hydrocarbons and organohalide insecticides are similar to hydro-carbons in some chemical and toxicological properties; however, they also have unique toxicological traits and will be discussed in a separate section of this text
Trang 2TOXICITY OF SULFIDES
Hydrogen sulfide has two major toxic actions The first is a depressant effect on the CNS A result of this effect is paralysis of the respiratory center and death The second
is inhibition of cytochrome oxidase in a manner very similar to the effect of cyanide
H2S is actually a more potent inhibitor of cytochrome oxidase than is cyanide Carbon disulfide has some toxic features in common with H2S It attacks the CNS and the cardiovascular system However, it has its own uniquely toxic character
in causing a peripheral neuropathy with cranial nerve damage (see Chapter 10 on neurotoxins) Curiously, it is also atherogenic in experimental animals
THERAPY
The cyanide antidote kit is effective with H2S poisoning The nitrites within the kit convert hemoglobin to methemoglobin which becomes an agent for binding hydro-gen sulfide before it can bind cytochrome oxidase and cause death Sulfmethemo-globin is formed by the reaction between methemoSulfmethemo-globin and either H2S or hydrogen sulfide anion and this substance is excreted into the urine as such or as nontoxic metabolites
LABORATORY TESTING
Hydrogen sulfide is like cyanide in the sense that many victims will die too soon for laboratory evaluation to be of any help However, testing for sulfide ion in blood may help to make the diagnosis for those who are less disabled An ion-selective electrode has been developed for measurement of sulfide ion Because this electrode
is not completely specific to sulfide to the exclusion of all other ions, it is necessary
to pre-treat the specimen and isolate sulfide This has been done, in one method, with Conway microdiffusion cells Concentrations of sulfide ion found in H2S deaths ranged from 1.7 to 3.75 µg/mL
HYDROCARBONS
By definition these are compounds which contain only carbon and hydrogen Many such compounds have been identified in the natural world, a good number of which are found in crude oil They include the aliphatic alkanes, alkenes, and alkynes, which differ among each other in regard to the saturation of the carbon atoms The most common members of this class are methane, ethane, propane, and butane All members of this category are very abundant in the industrial world The aromatic hydrocarbons include benzene and the many compounds derived from benzene Halogenated hydrocarbons and organohalide insecticides are similar to hydro-carbons in some chemical and toxicological properties; however, they also have unique toxicological traits and will be discussed in a separate section of this text
Trang 3CONTENTS
Organochlorine Insecticides
Chemistry
Benzene Hexachloride (Hexachlorocyclohexane)
Cyclodienes
Cage Structures
Symptoms of Organochlorine Poisoning
Therapy
Organophosphate Insecticides
Chemistry
Physiology of Cholinergic Activity
Characteristics of Organophosphate Poisoning
Therapy
Laboratory Testing
Carbamates
Pyrethrins
Questions and Problems
Insecticides are very beneficial to mankind because they help to control vector-borne diseases such as malaria, improve agricultural productivity, and reduce the angst which many forms of insects visit upon “picnicking man.” Ideally, they should be entirely species-specific or, at least, specific to invertebrates This is, of course, not the case Some insecticides are much more lethal to insects than to higher forms of life Nonetheless, because they are harmful to all forms of life, at least to some degree, exposure to them can be fatal and they must be discussed in texts on toxicology
ORGANOCHLORINE INSECTICIDES
The chlorinated hydrocarbon group of insecticides is large and includes what is possibly the most controversial compound of the twentieth century, DDT, dichlo-rodiphenyltrichloroethane (Figure 17.1) It was synthesized 125 years ago in 1874 but its ability to eliminate insect pests was not recognized until 1939 That recog-nition led to the 1948 Nobel prize for the responsible scientist, Dr Paul Mueller, a Swiss chemist Mueller discovered the potency of DDT while screening for insec-ticides for the JR Geigy Company
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Trang 4CONTENTS
Arsenic
History
Forms of Arsenic
Sources of Arsenic
Mechanism of Arsenic Toxicity
Symptoms of Arsenic Poisoning
Treatment
Chelators
Chelating Agents for Use with Arsenic Poisoning Testing for Arsenic
Lead
History
Sources of Lead
Pharmacokinetics of Lead
Mechanism of Toxicity
Symptoms of Lead Poisoning
Treatment of Lead Intoxication
The Laboratory and Lead Overdose
Mercury
History
Types and Sources of Mercury
Toxicokinetics of Mercury
Signs of Mercury Poisoning
Treatment of Mercury Poisoning
Laboratory Testing and Mercury
Iron
Toxicokinetics
Iron Toxicity
Treatment
Deferoxamine (Deferoxamine Mesylate, Desferal) Laboratory Involvement
Laboratory Testing Methods
Questions and Problems
Further Reading
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