[Electron microscopic study of rat tanicyte differentiation during the perinatal period].

The tanycyte differentiation during the perinatal period was studied by means of electron microscope in rats. From the 16th till the 18th day of prenatal period the wall of the 3rd ventricle is formed by intensively proliferating matrix cells with a narrow long apical process, oval perykarya and basal process. As the differentiation proceeds, the apical process shortens and disappears. The number of such cells increases gradually. At the same time the concentration of rough endoplasmic reticulum, mitochondria, polysomes, lipid droplets, dense, lamellated and multivesicular bodies increases. By the 3rd day the proliferative activity of cells decreases and they differ markedly in the ventral and ventrolateral parts of the infundibular recess and in the periphery of its broadened part. After the 5th day the ultrastructure of tanycytes and character of their distribution within the infundibular recess practically do not change, thus witnessing indirectly the completion of the main stages of differentiation of these cells.