Organ distribution and nervous system binding of styrene and styrene oxide

Ten adult male rats were injected intraperitoneally with 460 mumol of styrene oxide with radioactive label. Fifteen similar rats were injected similarly with 577 mumol of styrene. The distribution of styrene in central nervous system, blood, liver, lungs, kidneys and duodenum was studied 3, 6 and 24 h after the injection while the same studies were done with styrene oxide 3 and 6 h after the injection. The liver, brain, kidney and duodenal contents of styrene and styrene oxide were higher than that in blood, lungs and spinal cord while the macromolecule-associated styrene oxide in the central nervous system was small. The removal of injected compounds was slow between 3 and 6 h after the injection in the organ systems although lipid-soluble compounds tended to diminish in brain more rapidly than the total radioactivity.

Trichloroethylene and 1,1,1-trichloroethane: effects on brain and liver after five days intermittent inhalation

The inhalation exposure of adult male rats to 7.9 mumol/l (200 ppm) of trichloroethylene for 4 days 6 h each day led to an accumulation of the solvent in the perirenal fat 17 h after the last exposure. Exposures to 20 mumol/l (500 ppm) of 1,1,1-trichloroethane caused similar accumulation. The latter rats presented no changes in their behaviour in an open-field test whereas the motor behaviour of the animals exposed to trichloroethylene was more active in comparison to controls 1 h after the exposure on the 4th day. Trace effects of trichloroethylene on emotional behaviour of the same rats could be seen 17 h after the last exposure. Further exposures on the 5th day increased brain, liver, lung and blood contents of trichlorethylene and 1,1,1-trichloroethane. A slight decrease in brain RNA content was found in the 1,1,1-trichloroethane exposed rats while RNA decreased significantly after the fifth day of trichloroethylene inhalation. The exposure to 1,1,1-trichloroethane on the 5th day depressed also the microsomal cytochrome P-450 content in liver of rats whereas trichloroethylene increased the hemochrome content slightly at the same time.

Some aspects of the mechanisms by which industrial solvents produce neurotoxic effects

A Short Review is given of the biochemical neurotoxic mechanisms of common industrial solvents of various structures. The acute effects of organic solvents may be caused by their direct action on the nerve cell membrane and energy metabolism, whereas chronic neurotoxic effects may be explained by the formation of chemically and biologically reactive intermediates. The stability of the toxic metabolites appears to correlate with the development of neuropathy although this is structuredependent. The role of reactive intermediates is also emphasized by the potentiating effect of the induction of the cytochrome P-450 complex.

Brain and blood lead in acute intoxication

Administering lead acetate in drinking water to adult male rats resulted in an elevated lead content in blood and brain during 11 subsequent days. The brain and blood lead contents were proportional to each other although the interdependency changed according to the cumulative dose and equilibration period. The present data indicate that the permeability of the blood-brain barrier towards inorganic lead may be dose-dependent and saturable with high doses of the metal.

The binding of CS2 in central nervous system of control and phenobarbitone-pretreated rats

The binding of 35S- and 14C-labelled CS2 in rat central nervous system (CNS) was studied in control and phenobarbitone-pretreated rats in vivo and in vitro. Animals received CS2 through intraperitoneal injection in olive oil. Samples were taken for analysis 3 and 6 h after the injection. Sulphur atoms were bound to rat brain more highly than carbon atoms in control and phenobarbitone-pretreated rats in vivo. The phenobarbitone pretreatment increased the cerebral binding of sulphur and decreased that of carbon. Main part of the bound sulphur and carbon was detected in the trichloroacetic acid (TCA) precipitable fraction in both test groups. Pretreatment with phenobarbitone or with polychlorinated hydrocarbon (PCB) mixture did not increase significantly the binding of CS2 sulphur in brain microsomes in vitro. The present findings suggest that a considerable amount of injected CS2 is retained in the nervous system and that phenobarbitone pretreatment of test subjects may also alter brain metabolism of CS2.

Effects of acute CS2 intoxication on protein metabolism in rat brain

The effect of acute CS2 exposure on the rat brain protein metabolism was studied with control and phenobarbitone pretreated adult male rats 1, 4 and 46 h after exposure. Increased activity of acid proteinase was detected in both test groups 1 and 4 h after exposure and it was accompanied by changes in 14C-labelled leucine turnover as well as in RNA content. The changes were more conspicuous in cerebellum than in brain in both test groups while phenobarbitone pretreatment modified the brain response towards intoxication. This modification probably represents inherent effects of barbiturate on brain protein metabolism as well as altered metabolism of CS2. The activities of creatine kinase and nonspecific cholinesterase displayed only subtle changes as assayed in cerebral homogenate and serum. Thus a single acute CS2 intoxication apparently causes definitive transient changes in brain protein metabolism; serum enzyme determinations may not reflect the magnitude of these changes.

CS2 binding to rat spinal neurofilaments

The binding of CS2 sulphur to rat spinal cord neurofilaments was studied 3 and 6 h after the intraperitoneal injection of 1.3 mmol of CS2 in control and phenobarbitone pretreated rats. The binding of CS2 carbon was studied similarly 3 h after the injection. The binding of CS2 sulphur was 31% higher in the control neurofilaments than that in the phenobarbitone pretreated group. Half of the neurofilament associated CS2 sulphur was bound to protein in both groups as studied by electrophoresis. Approximately 30% of the neurofilament associated CS2 sulphur was detected 6 h after the injection of that at 3 h in both groups. All of the neurofilament associated CS2 carbon was bound to protein in control group 3 h after the injection. The binding of CS2 carbon was 4.7 times less than that of sulphur at the same time. The present data may indicate that the high binding of CS2 to the neurofilament protein contributes to the increase in neurofilaments in chronic CS2 intoxication.

The in vivo toxicity of CS2 to liver microsomes: binding of labelled CS2 and changes of the microsomal enzyme activities

The binding of 35S and 14C labelled CS2 to liver microsomes was studied in control and phenobarbitone pretreated rats 3 and 6 hrs after an intraperitoneal injection. The level of hepatic cytochrome P-450, the activities of epoxide hydratase and UDP-glucuronosyltransferase were analyzed in the same animals. The binding of the sulphur label was considerably higher than that of carbon 3 hrs after the injection, the difference being less evident at 6 hrs.T he measurable P-450 declined after the CS2 injection. It was approximately 40% in the phenobarbitone pretreated rats and 60% in control rats of the values of animals which were not treated with CS2. CS2 did not affect microsomal epoxide hydratase activity, while it increased the measurable activity of UDP-glucuronosyltransferase. The increase was evident 3 hrs after the injection of CS2 in the phenobarbitone pretreated rats. It could also be detected in the control animals 6 hrs after the injection. The present data suggest that the change in the measureble P-450 results from the binding of the metabolite(s) of CS2 to the cytochrome, and its subsequent degradation. The increase in measurable UDP-glycuronosyltransferase activity results probably from the activated perturbation of the structure of microsomal membrane by the metabolites of CS2 in vivo.

High binding of CS2 sulphur in spinal cord axonal fraction

The binding of carbon disulphide sulphur was studied in the spinal cord and its axons of four control and four phenobarbitone pretreated adult rats 3 and 6 h after an intraperitoneal injection of 650 mumol of CS2 in olive oil. The binding of CS2 carbon was measured in the same fractions of two adult control rats 4.5 h after a similar administration of 1.3 mumol of the compound for reference. The specific binding of sulphur was highest in the axons of control animals 3 h after the injection while binding was 17.5% smaller in the axons of phenobarbitone treated animals. The uptake of sulphur was higher in the spinal cord homogenate of the pretreated animals in comparison to control rats. Sulphur was removed from the axonal fraction at a rate of 5.1 natoms/mg of protein/h. Phenobarbitone treatment increased the disappearance of sulphur in the control animals while the rate in the treated rats was 4.9 natoms/mg of protein/h. Phenobarbitone treatment increased the disappearance of sulphur in the spinal homogenate from the removal rate of 0.22 natoms/mg of protein/h in control animals to 0.37 natoms/mg of protein/h in treated rats. The binding of CS2 carbon was negligible 4.5 h after the injection in the axonal fraction. The present data indicate that the release and binding of CS2 sulphur may be responsible for the toxic neural manifestations in chronic CS2 poisoning.

Isolation of the liver N-aspartyl-beta-glucosaminidase in aspartylglucosaminuria

The isolation of liver N-aspartyl-beta-glucosaminidase in human aspartylglucosaminuria, where this enzyme activity is diminished, yields an enzyme molecule with the same molecular weight and pH optimum as the normal enzyme. Its activity is 10% of that of the control preparation. Combination of both enzymes results in the summation of both activities, and the pathological enzyme does not inhibit the control preparation. It is concluded that no change into a totally different isoenzyme has occurred in aspartylglucosaminuria.

Biochemical studies on myelin isolated from the brains of patients with Down's syndrome

Amyelination has been deduced from the data on chemical studies of myelin isolated from the brains of Down's syndrome. The lack of cholesterol and much reduced phosphohydrolase activity in mongol myelin possibly suggest a fault in the structure of myelin.