R.S. Srivastava

An Exploratory Study of Manganese Exposure to Welders

Sixty welders (20 each from Plants A, B, and C) and 20 control subjects were investigated for the possible occurrence of manganese poisoning among welders exposed to the welding fumes containing this metal. Ten, 9, and 5 welders from Plants B, C, and A, respectively, were diagnosed as suspected cases of early manganese poisoning. The diagnosis was based on the proof of overexposure to manganese by the findings of increased urinary levels of this metal, signs of early neurological involvement, and increased contents of serum calcium. These results are discussed in relation to the manganese concentration in the air around the welders breathing zones.

Regional distribution of metals and biogenic amines in the brain of monkeys exposed to manganese

Abstract Manganese chloride (20 mg/kg/day) was administered orally to male Rhesus monkeys. The levels of copper, calcium, manganese and biogenic amines m different regions of brain were determined after 18 months of manganese exposure. The levels of manganese were increased above control values in the cerebral cortex, cerebellum, diencephalon, corpus striatum, mid-brain and pons, but not in the medulla oblongata. Copper was increased only in the pons and medulla oblongata while calcium declined in pons, medulla oblongata and corpus striatum. Alterations in copper and calcium did not appear to be related to the altered metabolism of catecholamines in the brain.

The effect of lead exposure on the testis of growing rats

Daily intraperitoneal administration of lead (8 mg/kg) as lead acetate in male rats from 21 till 120 days of age triggered histopathological and biochemical alterations in the testis. Histopathological examination revealed disturbance in spermatogenesis besides Leydig cells degeneration. There was an increase in cholesterol, decrease in ascorbic acid contents and reduction in the glucose-6-phosphate dehydrogenase activity in the testis of lead-treated rats. These alterations suggest that the disturbed steroidogenesis during growing stage may be responsible for altering the germinal function of the testis at maturity.

Effect of hexavalent chromium on testicular maturation in the rat

Daily intraperitoneal administration of hexavalent chromium (Cr6+; 1, 2, and 3 mg/kg intraperitoneally as potassium dichromate) in weaned rats for an entire duration of 55 and 90 days of age produced dose- and duration-dependent enzymatic and pathologic alterations. At 55 days, the pathologic changes were not seen in testes of Cr6+ treated rats, but the activities of sorbitol dehydrogenase, lactic dehydrogenase, gamma-glutamyl transpeptidase, and glucose-6-phosphate dehydrogenase were significantly altered. When the treatment was prolonged to sexual maturity, that is, 90 days of age, the alterations in enzyme activities were greater, and there were dose-dependent pathologic changes in the testes of Cr(6+)-treated rats. These alterations suggest a risk to growing testes if rats are exposed to Cr6+ during the prepubertal stage of development, which, in turn, may disturb normal testicular physiology at adulthood.

The interaction between ethanol and manganese in rat brain

The effect of combined administration of ethanol and manganese on the brain tissue of rats was investigated to evaluate the role of alcohol ingestion in inducing susceptibility to manganese poisoning. Ethanol and manganese alone and the combination of the two were administered orally daily to the rats for 30 days. Almost identical increase in the brain contents of manganese in rats receiving the metal alone and in combination with ethanol indicates that ethanol administration does not influence the accumulation of manganese in that organ. The copper contents of brain also increased to almost the same extent in these two groups. Synergistic effect of ethanol and manganese was noticed on increasing the activity of ATPase and RNase while marked antagonistic effect was observed on the activity of MAO. The mechanism and the significance of these neurochemical alterations occurring after the administration of ethanol and manganese have been discussed.

Combined effect of metals on biogenic amines and their distribution in the brain of mice

The toxic effects of manganese in combination with iron or copper on the brain tissue of mice were investigated. The combined administration of manganese and iron decreased the accumulation of manganese in the brain compared to manganese treatment alone. This indicated that excess iron may influence the absorption of manganese. Combined exposure to manganese and copper resulted in marked accumulation of copper in the brain. This is of great concern, since excess copper in brain produces incoordination in body movements. Thus, the combined exposure of these two metals, even in permissible limits, may produce serious brain dysfunctions. The combined administration of manganese with iron or copper has also significantly altered the levels of brain tryptophan and 5-hydroxytryptamine.

Manganese induced testicular changes in monkeys

Oral administration of manganese chloride (25 mg/kg b. w. daily) to monkeys for a period of 18 months produced congestion and marked increase in weight of testis. Histopathologic examination revealed interstitial oedema and degeneration of seminiferous tubules. Activities of succinic dehydrogenase, glucose-6-phosphate dehydrogenase and acid phosphatase were significantly inhibited whereas NADH-diaphorase and alkaline phosphatase activities showed only slight inhibition in seminiferous tubules of treated monkeys. It was concluded that chronic exposure to manganese does not produce sever degenerative changes in the testis earlier than metal induced encephalopathy in primates.

Effect of organo-tellurium compounds on the enzymatic alterations in rats.

An attempt has been made to correlate early toxicity of organo-tellurium (Te) compounds with enzymic alterations in liver, kidney, brain and serum at 1 and 3 days following single i.p. injections of bis-(tetraphenyl phosphonium) tetracyanato-bis-p-methoxy p-phenyl tellurate(IV) (TTMT) and bis-(tetraheptyl ammonium) tetraiodocyclopentane tellurate(IV) (TACT). These compounds, at 2 and 1 mg Te/kg body weight as TTMT and TACT, respectively, produced cholinergic signs and caused death within 3 days. Administration at maximum tolerable doses of 0.5 mg and 0.1 mg Te/kg body weight as TTMT and TACT, respectively, resulted in significant reduction of acetylcholine esterase (AChE) and monoamine oxidase (MAO) in serum and brain and by a significant decrease in hepatic glutathione and in glutathione-S-transferase (GST) and alkaline phosphatase in liver and kidney.

Serum ceruloplasmin in manganese-treated rats.

Rats were exposed to manganese (Mn) (6 mg/kg) daily for 30 days. The content of ceruloplasmin decreased significantly by 19.5% while copper (Cu) content was reduced by 27.8% in the serum of Mn-treated animals. These alterations were associated with a marked increase in the Cu content of liver and brain. The significant decrease in serum Cu and ceruloplasmin may serve as useful parameters for early diagnosis of Mn poisoning.

Lead induced testicular hypersensitivity in stressed rats

Rats were immobilized for 2 h and treated i.p. with lead Pb2+ (8 mg/kg/day) for 45 d to investigate the testicular effects of lead on rats kept under immobilization stress. Marked alteration in SDH. G6PDH activity, cholesterol and ascorbic acid contents and reduced sperm counts associated with marked pathological changes in the testis of rats were observed after combined treatment with lead and immobilization stress in comparison to either alone. An increase in the disturbances of testicular androgen synthesis seems to be responsible for enhanced testicular injury in lead induced stressed rats.