Nervous system, organization

Luiten, P., Koolhaas, J., de Boer, S. and Koopmans, S. (1985) The cortico-medial amygdala in the central nervous system organization of agonistic behavior. Brain Res. 332, 283-297. 

Nerve Agent Substances that interfere with the central nervous system. Organic esters of phosphoric acid used as a chemical warfare agent because of their extreme toxicity (tabun-GA, sarin-GB, soman-GD, GF, and VX). All are potent inhibitors of the enzyme, acetylcholinesterase, which is responsible for the degradation of the neurotransmitter, acetylcholine in neuronal synapses or myoneural junctions. Nerve agents are readily absorbed by inhalation and/or through intact skin. 

Neurotoxicity. No clinical signs of central nervous system toxicity or histological alterations of nervous system organs and tissues were observed in rats or mice in the NCI (1978) chronic oral bioassay. Tests for neurotoxicity in animals may be appropriate if there is clinical evidence of neurological dysfunction in general oral or dermal toxicity studies of I 2-diphenylhydrazine. 

Pyrethroids act as neurotoxins that cause excitation of the nervous system. Organisms may become hypersensitive to stimuli and experience paresthesia (abnormal sensations of burning or prickling of the skin). Tremors and salivation are common symptoms of mammals exposed to toxic levels of pyrethroids. 

D-Pantolactone (Figure 6.3.1) is an important intermediate in the production of d-pantothenic acid, also called vitamin B5. Deficiency of pantothenic acid can result in symptoms such as pathological changes of the skin and mucosa, disorders in the gastrointestinal tract and nervous system, organ changes, and hormonal disorders. Pantothenic acid is used mainly in feed for chicken and pigs and also as a vitamin supply in human nutrition. Its commercial form, the calcium salt, is produced worldwide on a multi-thousand ton scale. 

Kohonen networks, also known as self-organizing maps (SOMs), belong to the large group of methods called artificial neural networks. Artificial neural networks (ANNs) are techniques which process information in a way that is motivated by the functionality of biological nervous systems. For a more detailed description see Section 9.5. 

An interesting set of central nervous system properties has also been discovered and studied (Table VI-10). The work devoted to piscaine must be emphasized besides finding hypnotic properties of 2-amino-4-phenyl-thiazole on fish, the authors studied the structure of the metabolite, as well as the localization of the (radio labeled) metabolic product in various organs. Recently, thiazol-4-yl methoxyamine was shown to inhibit the development of morphine tolerance (1607). 5-Aminothiazole derivatives such as 419a were proposed as cardiovascular agents (1608, 1610). Substitution of the 5-aminothiazole radical on the cephalophosphorin structure gives a series of antibacterial products (1609). 

Physiological Classifications of Contaminants. The physiological classification of air contaminants is difficult, because the type of action of many gases and vapors depends on concentrations (55). For example, a vapor at one concentration may exert its principal effect as an anesthetic but, at a lower concentration, the same vapor may iujure the nervous system, the hematopoietic (blood-forming) system, or some visceral organ (see Toxicology). 

Division of the receptors in the adrenergic nervous system into two classes (a and P) was proposed in 1948 (39) when a difference in the rank order of potency of epinephrine (1, R = CH ), norephinephrine (1, R = H), and isoproterenol [7683-59-2], C H yNO, (1, R = CH(CH3)2) was noted to depend on the organ examined. Eurther subdivision into groups P2 proposed in 1967 (40). Both types of P-adrenoceptors are found throughout the... 

Health nd SMety Factors. The lowest pubhshed human oral toxic dose is 430 mg/kg, causing nervous system disturbances and gastrointestinal symptoms. The LD q (rat, oral) is 750 mg/kg (183). Thiocyanates are destroyed readily by soil bacteria and by biological treatment systems in which the organisms become acclimatized to thiocyanate. Pyrolysis products and combustion products can include toxic hydrogen cyanide, hydrogen sulfide, sulfur oxides, and nitrogen oxides. 

Bromothiophenes are toxic materials by aU routes. Inhalation toxicity of 2-bromothiophene is significant. Ecotoxicity is also noted for these materials, particularly for 2-bromo-3-methylthiophene. 2-Thiophenecarboxaldehyde and the 3-methyl derivative can cause minor irritation to the skin and eyes of rabbits. The former is a sensitizer to guinea pig skin, the latter is not. 2-Acetylthiophene is toxic in aU modes of contact. Severe exposure causes serious inflammation of the lung, damage to many organs, and depression of the central nervous system. 

Metals and metalloids that form alkyl compounds, eg, methylmercury and methylarsenic acid, tributjltin, deserve special concern because these compounds are volatile and accumulate in cells they are poisonous to the central nervous system of higher organisms. Because methylmercury or other metal alkyls may be produced at a rate faster than it is degraded by other organisms, it may accumulate in higher organisms such as fish. Hg species are also reduced to elementary Hg which is soluble in water but lost by volatilization to the atmosphere (40). 

AH volatile organic solvents are toxic to some degree. Excessive vapor inhalation of the volatile chloriaated solveats, and the central nervous system depression that results, is the greatest hazard for iadustrial use of these solvents. Proper protective equipment and operating procedures permit safe use of solvents such as methylene chloride, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene ia both cold and hot metal-cleaning operations. The toxicity of a solvent cannot be predicted from its chlorine content or chemical stmcture. For example, 1,1,1-trichloroethane is one of the least toxic metal-cleaning solvents and has a recommended threshold limit value (TLV) of 350 ppm. However, the 1,1,2-trichloroethane isomer is one of the more toxic chloriaated hydrocarboas, with a TLV of only 10 ppm. 

Air-poUutant effects on neural and sensory functions in humans vary widely. Odorous pollutants cause only minor annoyance yet, if persistent, they can lead to irritation, emotional upset, anorexia, and mental depression. Carbon monoxide can cause death secondary to the depression of the respiratory centers of the central nervous system. Short of death, repeated and prolonged exposure to carbon monoxide can alter sensory protection, temporal perception, and higher mental functions. Lipid-soluble aerosols can enter the body and be absorbed in the lipids of the central nervous system. Once there, their effects may persist long after the initial contact has been removed. Examples of agents of long-term chronic effects are organic phosphate pesticides and aerosols carrying the metals lead, mercury, and cadmium. 

In nonindustrial settings, MCS substances are the cause of indoor air pollution and are the contaminants in air and water. Many of the chemicals which trigger MCS symptoms are known to be irritants or toxic to the nervous system. As an example, volatile organic compounds readily evaporate into the air at room temperature. Permitted airborne levels of such contaminants can still make ordinary people sick. When the human body is assaulted with levels of toxic chemicals that it cannot safely process, it is likely that at some point an individual will become ill. For some, the outcome could be cancer or reproductive damage. Others may become hypersensitive to these chemicals or develop other chronic disorders, while some people may not experience any noticeable health effects. Even where high levels of exposure occur, generally only a small percentage of people become chemically sensitive. 

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