Various heavy metals such as cadmium, copper, mercury, iron and zinc are well documented to stimulate, tissue metallothionein. Metallothionein (MT) is found in various animal tissues, including the brain, and functions as a scavenger of heavy metals as well as a survey for essential metals (Yasutake et al. 2004).
In spite of exposure to mercury vapor for 3 months, no pathological change was determined in the brains of either MT-null or wild type mice, suggesting a low mercury toxicity of the present dose schedule. The presence of mercury could be detected histochemically in the brains of grains were observed in the cytoplasm of nerve cells and occasional glial cells throughout the brain of both strains, though non-exposed control tissues indicated no mercury grains. It was not observed differences in the distribution and intensity of mercury deposits between the brains of MT-null and wild type mice exposed to mercury (Yasutake et al. 2004). It was reported that mercury deposition at cerebrum and cerebellum cells were observed in rats which exposed to mercury 10 weeks (Warfvinge 1995).
Nehru et al. (1997) were investigated when the weight of the cerebrum and cerebellum was taken separately, a significant rise in the cerebellar weight was seen in the Pb-treated group, and it resulted in a important increase in its rate to brain weight. Following combined application of Pb and Se a substantial improvement in the cerebrum weight and brain weight was declared. Histologically, the transverse section of cortex of group I (control) animals indicated a well-organized cortical layer. The cells were uniform and showed no vacuoles. In the Pb-treated animals, however, the layers were almost absent, and the neurons were diffuse in the cross-section. There were spaces and autophagic vacuoles with debris seen in many places. Pb and Se treated animals, the autophagic vacuoles were present. The pyramidal cells were reduces in size. In this study, it was observed that the number of ischemic neurons and vascular dilatation were more density in Fe group. Density of damage in brain tissue of Fe group was higher than in the control group but in the other groups were no significant difference with control group.
In the central nervous system signs of silver were identicated after higher doses of silver lactate. The sediment was confined to lysosomes of motor neurons in the pontine nuclei and in the spinal cord, but glial cells were also found to contain silver. Neuropathic changes were seen in the myelin sheaths of cauda equina axons (Danscher 1991).
Histochemical changes in several neurons in the central nervous system and spinal ganglia could be detected after about 14 days of exposure to mercury chloride. By investigation light microscopy, the reaction products were seen as black grains in the neuronal somata. In many cases the grains were localized to special regioni juxtanuclearly, but more even distributions were also found (Danscher and Schroder 1979).
Total number of Purkinje cells in iron and iron + nicardipine groups were significantly lower than control animals (p < 0.005). However, when the iron and iron + nicardipine groups were compared, purkinje cell loss was higher in the iron group (p < 0.05) (Kozan et al. 2008). Similar results were obtained in this study.
The administration of cadmium (100 ppm) in drinking water to growing rats from 21 days of life for 120 days consistantly induced lesions in the cerebellar cortex. Purkinje cells at places were found to be disintegrated with pyknotic nuclei, eosinophilic cytoplasm and resolution of cellular membranes. The blood vessels, however, appeared normal. The leptomeninges and deep cerebellar nuclei were splitted up (Murthy et al. 1987).
Similar results were observed cerebellum tissues. Density of damage in cerebellum of Fe and Fe + Juglone groups were higher than in the control group but in the other groups were no significant difference with control group (p˂0.05). Degeneration and reduction in the number of purkinje cells were determined in Fe and Fe + Juglone groups.
Arsenic dose-dependent histopathological changes observed in brain. The section from brain show more frequent nuclear pyknosis. A significant increase in caspase-3 activity was determined at 10.5 and 12.6 mg/kg sodium arsenite in brain (Bashir et al. 2006). In this study, apoptotic cells number was higher Fe groups than other groups.
Fe/600 ppm.doses heavy metals have created a toxic effect on the cerebrum and cerebellum tissues. The damage associated with the Zn and Zn + Juglone was determined to be less significant than the damage by Fe and Fe + Juglone groups. Degeneration in cerebrum and cerebellum tissues were decreased with antioxidant effects of juglone.