Electron microscopy studies on the neurotoxic effect of sodium tellurite in the central nervous system of the adult rat.

We observed demyelination and rapid reparative remyelination in the cerebral white matter, cortex and optic nerve of adult rats intoxicated with sodium tellurite (1.25 and 6.25 mg/kg Te4+). Hypomyelination dominated by the seventh day and its intensity was dependent on the dose Te4+. Reparative myelination was not completed in the brains 30 days after the intoxication with tellurium. In addition to myelin changes, signs of neuronal and astrocytic damage were seen: dark neurons and swelling of the astrocytic processes and synapses in the cerebral cortex. We postulate that tellurium evokes not only the myelin sheath and a myelin forming glia damage but also ultrastructural changes in some axons, and reaction of fibrillar astrocytes.