Neuropathology of trimethyltin intoxication. III. Changes in the brain stem neurons.

Young adult BALB/c mice were administered trimethyltin chloride (TMT) at a dosage of 3.0 mg TMT/kg body wt. Animals displayed severe toxic signs (tremor and aggression) within 24 hr and were sacrificed at 48 and 72 hr postinjection. The brain stems of these animals were examined with light and electron microscopy. Degenerative and vacuolar changes were observed in many large brain stem neurons, especially those in the mesencephalic trigeminal nuclei. These neurons acquired a chromatolytic character with eccentric nuclei, loss of Nissl substance, and hyalinoid cytoplasm. Extensive vacuolation was also found in these nerve cells. Electron microscopy examination revealed progressive loss of the Nissl substance (rough endoplasmic reticulum) and distention of the cytoplasmic membranes (endoplasmic reticulum and Golgi complex). Severe distention of these membranes resulted in large membrane-limited vacuoles within these nerve cells. This intraneuronal vacuolation reflects an intracellular edema condition of these nerve cells and is potentially reversible. Mitochondrial damage in these neurons was only moderate. Further investigation is needed to elucidate the full toxic impact and pathogenetic mechanisms of TMT in the nervous system.