Nerve cell degeneration and progeny survival following ethylenethiourea treatment during pregnancy in rats.

Ethylenethiourea (ETU)-induced early histologic changes in fetal CNS and their effect on postnatal survival was studied at 0, 15 or 30 mg/kg administered as single oral dose on day 13 of pregnancy. Fetuses, from 4-6 dams killed at post-treatment intervals of 12, 24, 48 and 72 h were fixed and studied for histopathological changes following routine methods. The remaining dams were allowed to litter and their progeny was studied for postnatal survival until 80 days of age. Histologic study revealed the presence of karyorrhexis in the germinal layer of basal lamina of CNS extending from the thoracic spinal cord to the telencephalon twelve hours after treatment with 30 mg of ETU/kg. At 48 h post-treatment, the spinal cord showed obliteration and duplication of the central canal and disorganization of germinal and mantle layers. In the brain, the ventricular lining was focally denuded, neuroepithelial cells were arranged in the form of rosettes and the nerve cell proliferation was disorganized. In the 15 mg of ETU/kg group, cellular necrosis was less severe and consisted of degeneration in a single or a small group of cells widely dispersed in the germinal layer of neuraxis. The initial degenerative changes were observed in a specific nerve cell type, identified as the undifferentiated migrating neuroblast. In the postnatal study, since survival was reduced to 50% at the 30 mg/kg and unaffected at the 15 mg/kg, it was concluded that necrosis of neuroblasts up to a certain degree was compatible with postnatal life until adulthood.