Dynamics of granule cells migration into the internal granular layer in developing human cerebellum

The aim of these investigations was to find out the dynamics of migration of granule cells into the internal granular layer in three different parts of cerebellar cortex. The dynamics of changes was followed in vermis, in lateral hemispheres and in flocculus. For that purpose, 25 fetal brains of different postovulatory age (12.5, 15, 17.5, 19.5, 21, 31 week and one brain of 6 days old newborn) were fixed in formalin, embedded in paraffin, than stained with Cresyl violet and cut in 6, 15 and 30 microm. Each fifth slice was analyzed using the light microscope and numerical density of granule cell nuclei was established by point counting method according to Weibel. Results show a steady increase of the granule cell population in the internal granular layer of all regions investigated, being still greater in vermis and in hemispheres. This increase in the cell number lasted during the whole period of intrauterine development. Moreover, according to the trend of the curves, the increase of the cell number continues even after the birth, suggesting that at least some synaptic connections of granule cells are not established yet. For each region the adequate mathematical model of migration dynamics was calculated.