Electron microscopy on the effect of vinblastine on the telencephalic wall of the rat fetus.

To clarify the ultrastructural changes in the primitive neural cells of the telencephalic wall of rat fetuses to vinblastine, pregnant MP 1 rats in Day 14 of gestation were given vinblastine (1 mg/kg) as a single i.p. injection. Observations were made on the parietal region of the telencephalic wall of the fetuses removed at 3, 6, 9, 12 and 24 h after drug adnministration. Several ultrastructural changes were observed in the telencephalic wall 6 h after the administration: production of cytoplasmic protrusions and free spherules at the paraventricular surface, abnormal accumulation of mitotic cells in metaphase in the paraventricular region, extreme condensation and fragmentation of chromatin materials in some of the paraventricular cells and the subventricular cells, decrease or complete disappearance of endoplasmic reticulum and Golgi apparatus in cells all over the telencephalic wall, formation of llpid droplet-like inclusions and ribosomal complexes in the cytoplasm of the cells in the intermediate zone and the cortical plate. These changes were mostly very transient. At 9 h after the administration none of the changes were observed except for sporadic nectotic cells in the ventricular and subventricular zones. These necrotic cells were phagocytosed by neighbouring primitive neural cells or by macrophage-like cells newly appearing in the ventricular zone and the cortical plate 12 h after the drug was administered. These changes are discussed in relation to those of other tissues and cultured cells on which earlier reports have been made.