Shrawan K. Gupta

Neuromelanin in manganese-exposed primates

Monkeys developed muscular weakness and rigidity of the lower limbs after 18 months exposure to manganese. These are neurological signs typical of chronic manganese intoxication. Marked neuronal degeneration with depigmentation was noticed in the region of substantia nigra. Significance of depigmentation in relation to the depletion in the contents of brain dopamine in chronic manganese intoxication has been discussed.

Ultrastructural observations in testicular tissue of chromium-treated rats

The administration of hexavalent chromium (2 mg/kg, ip as potassium dichromate) in adult rats daily for 15 days produced significant increases in the blood and testicular chromium levels. Although no light microscopic pathologic changes or alterations in epididymal sperm counts and motility were observed, lanthanum perfusion in treated rats revealed leakage of Sertoli-cell tight junctions under EM. A few tubules showed marked ultracellular alterations in the form of vacuolization of cytoplasm and degeneration of mitochondria in the epithelial cells. Late stage spermatids were the most affected germ cells. The mitochondrial sheath of the midpiece was vacuolated, incomplete, swollen, or broken in places. The observed alterations may result in the disruption of normal testicular physiology leading to reproductive impairment after chromium exposure.

Lead induced ultrastructural changes in the testis of rats.

Oral lead administration (250 ppm lead acetate through drinking water) to weaning male rats for 70 days resulted in the marked accumulation of this metal in blood and testicular tissue. No marked changes were evident in light microscopy. Ultrastructural changes were revealed in the form of vacuolisation of Sertoli cell cytoplasm and increase in the number and size of lysosomes. Some of the vacuoles contained vesicle like structures. Although there was no impairment of spermatogenesis, the changes in the Sertoli cells may lead to changes in spermatogenesis after chronic exposure.

Nuclear alterations during acrosomal cap formation in spermatids of lead-treated rats

Ultrastructural studies were conducted to assess the effect of lead (Pb 5 mg/kg IP for 16 days as lead acetate) on rat spermiogenesis. Results showed swelling of nuclei and acrosomes in round spermatids. In Sertoli cells, nuclei appeared fragmentated, whereas the cytoplasm exhibited a vacuolated appearance and a few structures delimitated by a double membrane that contain parallelly arranged microtubules and cross-striated fine fibrils. Sertoli cell tight junctions remained intact. There was no significant change in epididymal sperm motility and counts, although testicular and blood lead levels were found to be elevated after lead exposure. These results suggest that spermatid and Sertoli cell damage may lead to disruption of spermiogenesis in lead-intoxicated rats.

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.

Genotoxic Effects of Diuron Contaminated Soil on the Root Meristem Cells of Allium sativum: A Possible Mechanism of Chromosome Damage

Diuron, a persistant substituted urea herbicide, was tested in the root meristem cells of Allium sativum for the possible cytogenetic effects and to compare the sensitivity with Allium cepa. Test concentrations of diuron 22.5, 45.0, and 90.0 ppm were mixed in soil and the cloves of A. sativum were placed over diuron-contaminated soils. Root meristematic cells were sampled at 48 h to score Mitotic/Chromosomal aberrations and to analyze the effect on mitotic index (MI). Microscopic analyses revealed significant and dose-dependent induction of mitotic as well as chromosomal breaks. The frequency of mitotic aberrations was every time found much higher than that of chromosomal aberrations. Mild percentage of Micronucleated and Binucleated cells was observed, as MI also declined during the analysis. Based on the data of valence charge densities on the atoms of herbicide molecule and spectroscopic studies, a possible mechanism of interaction of diuron with DNA molecule for chromosomal aberrations has been proposed.

The effect of manganese administration, alone or combined with zinc, mercury and cadmium, on the tissue levels of these elements in rats.

Manganese chloride was administered alone or in combination with zinc chloride, mercuric chloride and cadmium chloride i.p. to rats for 30 days to investigate the effect of interaction of these elements on their content in brain, liver and kidney. Significant changes in the accumulation of these metals after combined exposure indicated that metabolic interactions occur. Alterations in the tissue contents of manganese, zinc, mercury and cadmium after combined administration may reflect changes at the absorptive sites or in excretory pattern.