Nucleolar apparatus of neuroepithelial cells and organization of the ventricular zone in human neocortical anlage

: Using silver nitrate impregnation nucleolar apparatus was studied in cells of ventricular zone of human neocortex in embryos at 6-13 wks of development. The number of nucleoli in cells grew gradually in the direction to ventricular surface in all cases studied. These data indicate characteristic localization of cell cycle phases in the neuroepithelium and correspond to the results of experiments performed in animals using DNA-labelled precursors. Specific cell population with scanty large nucleoli was found in inner portion of ventricular zone in 6-8 wks old embryos where mitotic figures are usually localized. Some hypotheses on these cells' origin and role are discussed.