[Fine-structure and function of the primary proliferative layer of the embryonal central nervous system]

Results obtained by mechanical isolation of neuroblasts from the primary proliferative layer of the central nervous system in chick embryos by the aid of an original method and by electronmicroscopic investigations are consistent with Sauer's concept on neuroepithelial cell proliferation. The bipolar form of the undifferentiated neuroblast is maintained--at the beginning--by external factors of cell contact only. Each end-feet contains two centrioles, one of which represents the basal body of a cilium. During mitosis, the position parallel to the lumen of the spingle axis and the subsequent appearance of two identical daughter cells depend on the behaviour of the centrioles. The later may move in an abnormal direction, and induce thus an obliquely or perpendicularly laying spindle axis. These changes may influence--on the other hand--the mechanism of proliferation.