Studies on the delayed neurotoxicity of organophosphorus compounds--(II).

Delayed neurotoxicity experiment was carried out on an organophosphorus compound (TOCP) in hens. Fifteen hens, 1.9 kg of their average body weight and 20 months of age, were orally administered with TOCP in a dose of 400 mg/kg body weight. Two animals out of 15 were sacrificed after 7 days to examine alterations in the nervous system under electron microscope. On the remaining 13 animals, histopathological examinations were carried out after 35 days. During the course of the experiment, progressive neuropathy developed in the animals at 10 to 12 days after the exposure to TOCP. Examinations of the sciatic nerve under electron microscope revealed slight axonal degeneration while the myelin sheath was found to be rather intact. On the animals after the observations periods of 35 days, marked axonal and myelin degeneration was observed in the anterior and posterior funiculus, and in the spinocerebellar tracts of the spinal cord as well as in the cerebellar peduncle and in the white matter of the cerebellum associated with glial proliferation. The localization and degree of these changes were considered to be "Dying Back", showing systemic neuropathy. Moreover, the morphological alterations of the nerve cells were observed in the Purkinje cells, in the cerebellar nucleus, gracilis nucleus, and anterior horn cells of the lumbar spinal cords, characterized by loss of nerve cells and/or tigrolysis. Muscular lesions showed small group atrophy, corresponding to Type I fiber atrophy.