Psychological test performance during experimental challenge to toluene and n-butyl acetate in cases of solvent-induced toxic encephalopathy.
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OBJECTIVES: This study determined whether performance in neurobehavioral tests deteriorates during subjectively annoying chemical challenge below known neurotoxic thresholds among persons with toxic encephalopathy with subjective hypersensitivity to chemicals. METHODS: Subjects with symptoms and previous neuropsychological test results compatible with toxic encephalopathy (TE) of either type 2A (N=12) or 2B (N=12) and unexposed referents (N=12) were challenged in an exposure chamber. In a counterbalanced design, the subjects were exposed on 2 occasions to increasing air concentrations of n-butyl acetate and toluene at levels well below the thresholds for neurotoxic effects. Attention and motor speed tests were given (i) in room air outside the chamber before the challenge, (ii) in room air inside the chamber before the exposure, (iii) at 12 ppm (44 or 56 mg/m3), and (iv) at 48 ppm (at 180 or 228 mg/m3). RESULTS: For both substances the TE groups showed a slight increase (deterioration) in the simple reaction-time task during chemical exposure, but not in the complex reaction-time task or in the digit symbol test of the Wechsler Adult Intelligence Scale. Contrary to reference subjects, the TE subjects did not show any improvement or learning effect in the digit symbol test over the chamber phases. n-Butyl acetate tended to affect cognitive functioning more obviously than toluene did. Suggestion or expectancy effects were not observed in any group in the clean-air baseline conditions. CONCLUSIONS: The results do not support the notion that men with subjective hypersensitivity to chemicals would be more affected than healthy men regarding cognitive functioning during annoying solvent exposure below thresholds for acute neurotoxic effects. (+info)
Characteristics of cold-sensitive mutants of Escherichia coli K-12 defective in deoxyribonucleic acid replication.
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Four cold-sensitive mutants of Escherichia coli have been isolated which show a reduced ability to synthesize deoxyribonucleic acid at low temperature. The mutants also have a reduced ability to incorporate nucleoside triphosphates into deoxyribonucleic acid at low temperature in cell preparations made permeable with toluene. All four mutations are located at or near the dnaA locus on the E. coli genetic map. They are recessive to the wild-type allele and two of them can be integratively suppressed by F episomes. (+info)
Stimulation of adenosine 5'-triphosphate-dependent in vitro deoxyribonucleic acid replication by factors from the periplasmic space of Escherichia coli.
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In vitro deoxyribonucleic acid (DNA) synthesis systems based on an earlier system using pencillin have been developed which use osmotic lysis of lysozyme-formed spheroplasts of Escherichia coli cells embedded in an agarose matrix. An adenosine 5'-triphosphate (ATP)-dependent semiconservative mode, or replicative mode, of in vitro DNA synthesis is exhibited which is sensitivie to nalidixic acid. These systems require growth of the agar-embedded cells in a preincubation medium before spheroplast formation and osmotic lysis. Inhibitor studies suggest that one or more required macromolecular species are synthesized during this preincubation growth period. Osmotic shock fluid from E. coli contains macromolecular factors which preferentially stimulate the ATP- dependent semiconservative mode of in vitro DNA synthesis. In some cases, the ATP independent mode of synthesis is inhibited by shock fluid. Evidence is presented that the stimulating factors found in the osmotic shock fluid come from the E. coli periplasmic space. This stimulation is observed using either toluene-treated cells or lysed agar-embedded ethylene glycol-bis-(beta-aminoethyl ether) N,N'-tetraacetate-lysozyme spheroplasts, and is thus independent of the in vitro DNA synthesis system used. Shock fluid obtained from a given E. coli dna mutant does not stimulate in vitro DNA synthesis by that mutant. However, in some cases, shock fluid from one class of dna mutants does stimulate ATP dependent in vitro DNA synthesis by another class of dna mutants, in a thermosensitive reacaction. Gently prepared cell extracts also stimulate ATP-dependent in vitro DNA synthesis, whereas cell extracts prepared by more severe procedures inhibit this in vitro synthesis. Severl stimulating DNA replication factors may be present in the osmotic shock fluid, including products of E. coli dna genes. (+info)
Behavioral toxicology of carbon disulfide and toluene.
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Organic solvents are pervasive in the communal and industrial environments. Although many are potent central nervous system agents, clearly delineated behavioral effects have played only a minor role in the formation of exposure standards. A comprehensive behavioral pharmacology and toxicology of these compounds is one aim of US/USSR collaboration. The current report describes some actions of carbon disulfide and toulene. Earlier data about the actions of carbon disulfide on pigeon operant performance indicated disruption of schedule-controlled key-pecking. Primate data are now described from a situation designed to determine aversive thresholds to electrical stimulation. Effective concentrations of carbon disulfide produced both a rise in the amount of electric shock tolerated and a diminution of the response force exerted by the monkeys. In experiments with toluene, pigeons were shown to elevate key-pecking rate in an operant situation at certain concentrations. Toluene also was studied for its capacity to maintain self-administration in the same way as drugs of abuse. Monkeys worked to gain access to toulene vapor just as they work for opiates or amphetamines. The current experiments demonstrate how comprehensive the range of behavioral toxicology needs to be to deal with environmental health issues. (+info)
Toluene-degrading bacteria are chemotactic towards the environmental pollutants benzene, toluene, and trichloroethylene.
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The bioremediation of polluted groundwater and toxic waste sites requires that bacteria come into close physical contact with pollutants. This can be accomplished by chemotaxis. Five motile strains of bacteria that use five different pathways to degrade toluene were tested for their ability to detect and swim towards this pollutant. Three of the five strains (Pseudomonas putida F1, Ralstonia pickettii PKO1, and Burkholderia cepacia G4) were attracted to toluene. In each case, the response was dependent on induction by growth with toluene. Pseudomonas mendocina KR1 and P. putida PaW15 did not show a convincing response. The chemotactic responses of P. putida F1 to a variety of toxic aromatic hydrocarbons and chlorinated aliphatic compounds were examined. Compounds that are growth substrates for P. putida F1, including benzene and ethylbenzene, were chemoattractants. P. putida F1 was also attracted to trichloroethylene (TCE), which is not a growth substrate but is dechlorinated and detoxified by P. putida F1. Mutant strains of P. putida F1 that do not oxidize toluene were attracted to toluene, indicating that toluene itself and not a metabolite was the compound detected. The two-component response regulator pair TodS and TodT, which control expression of the toluene degradation genes in P. putida F1, were required for the response. This demonstration that soil bacteria can sense and swim towards the toxic compounds toluene, benzene, TCE, and related chemicals suggests that the introduction of chemotactic bacteria into selected polluted sites may accelerate bioremediation processes. (+info)
A GC-MS method for the detection of toluene and ethylbenzene in volatile substance abuse.
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The interference of some substances with the gas chromatography-flame ionization detection and gas chromatography-Fourier transform infrared detection of toluene and ethylbenzene in volatile substance abuse poses problems. A gas chromatography-mass spectrometry (GC-MS) method that will overcome such interference has been developed for the detection of toluene and/or ethylbenzene in the headspace of preparations and products containing these substances and in the headspace of blood samples in the cases of volatile substance abuse. The method is based on converting toluene to benzoic acid via the formation of benzotrichloride. The latter compound was obtained upon the reaction of toluene with chlorine gas under direct sunlight conditions. In the presence of water, benzotrichloride was converted to benzoic acid. Ethylbenzene was converted to benzoic acid and two phenylethanols via the formation of side chain chloro-substituted phenylethanes followed by reaction with water. The chloro-substituted phenylethanes were obtained by the reaction of ethylbenzene with chlorine under direct sunlight conditions. The benzoic acid resulting from toluene and/or ethylbenzene and the two phenylethanols resulting from ethylbenzene were detected by GC-MS as their trimethylsilyl (TMS) derivatives. For the method to be viable for the detection of volatile substance abuse, the chlorination reactions were effected in the gaseous state. (+info)
DNA repair synthesis dependent on the uvrA,B gene products in toluene-treated cells.
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Ultraviolet irradiation of toluene-treated Escherichia coli causes an inhibition of replicative DNA synthesis. This is followed by the appearance of nonconservative DNA repair synthesis which does not require either the polymerase or 5' leads to 3' exonucleolytic activities of DNA polymerase I. The repair synthesis may be catalyzed by DNA polymerase III activity but does not require a functional DNA polymerase II. The ultraviolet-induced synthesis requires ATP and is dependent on a functional uvrA and uvrB gene product. However, other uvr gene products are not required for the synthesis. The recB function is also not required. (+info)
Interaction of enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system with adenylate cyclase of Escherichia coli.
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Transient repression by glucose of induced enzyme synthesis involves lowering of intracellular cAMP levels. This glucose effect is partially explained by a glucose inhibition of adenylate cyclase [EC 4.6.1.1; ATP pyrophosphate-lyase(cyclizing)]. Since the phosphoenolpyruvate:sugar phosphotransferase system has been implicated in repression phenomena, an investigation was made of adenylate cyclase activity in mutants of that transport system. The results suggest that glucose phosphorylation is not necessary for inhibition of adenylate cyclase since an HPr mutant retained sensitivity to glucose inhibition. The results also suggest that adenylate cyclase activity requires the presence of Enzyme I in a phosphorylated form and that adenylate cyclase activity may be regulated by a phosphorylation-dephosphorylation mechanism. (+info)