H³‐Thymidine autoradiographic studies on the cell proliferation and differentiation in the external and the internal granular layers of the mouse cerebellum

Abstract

Abstract Cell proliferation and migration in the external granular layer of the mouse cerebellum were studied with autoradiography after cumulative labeling with H 3 ‐thymidine. The germinative cells in the external granular layer were considered as externally dislocated matrix cells. Their generation time, presynthetic time, duration of DNA synthesis, postsynthetic time and mitotic time were determined in one‐, three‐, seven‐ and ten‐day‐old mice. The entire sequence of the ontogeny of the external granular cell‐system was separated into three consecutive stages; stage 1 or stage of pure external matrix cell proliferation, stage 2 or stage of neuroblast production, and stage 3 or stage of neuroglia differentiation. Production of neuroblasts in the external granular layer at seven and ten days of life and their migration into the internal granular layer were demonstrated by means of autoradiography. Transit times of the neuroblasts migrating across the external mantle layer and the molecular layer of ten‐day‐old mice were estimated at 21 and four hours, respectively. More than 50% of the inner granular cells migrated from the external granular layer later than ten days of life and almost 81 to 92% were produced later than seven days of postnatal life. In conclusion, on the basis of the matrix cell concept, the authors tried to unify observations of previous and present investigators and presented a scheme of pre‐ and postnatal histogenesis of the mouse cerebellum.