[Relative incidence of mitosis and binucleated cells, nuclear volume and nucleolar rate per nucleus in the mammary gland eipithelium of the mouse during differentiation in the gestational and lactation phase].

At the begin of gestation, a higher mitotic activity in the epithelial cells of the mammary gland of the mouse was observed. On 10th d of this period, the maximum was reached; into the lactation phase proliferations continuous. The amount of binucleated cells in the mammary epithelium from the 18th d of gestation onward to 21th d of the lactation phase increased. The binucleated cells are probably caused by the amitosis . A significant increase of the nuclear volume in the mono- and binucleated cells of the epithelium from 3rd to 18th d of lactation was observed. The nucleolar rate of mononucleated cells of the mammary epithelium raised significantly from 1st to 5th d during the lactation phase. The increase of the nucleolar rate per nucleus and the nuclear volume as well as the increase of the binucleated cells express a higher activity of the mammary gland cells during the lactation period.