Autoradiographic Observations on Variation of DNA Synthesis in the Developing Extraembryonic Membranes of the Golden Hamster

Golden Hamster 태반형성(胎盤形成)에 있어서 Autoradiography에 의한 분열세포(分裂細胞)의 소장(消長)

The purpose of the present study is to determine variations in synthesis of DNA in the nuclei of various elements of the golden hamster (Mesocricetus auratus) placenta with increasing gestational age from the eighth day post coitus to parturition. The method employed for such determination was autoradiography following injection of pregnant animals with tritiated thymidine. From the results reported, the following points are concluded. The mitotic activities of the endodermal cells of the visceral yolk sac and of the parietal yolk sac, the trophoblastic cells of the labyrinth and the trophospongium and the giant cells were decreased with increasing gestational age, The placentation was nearly completed by day 13 of pregnancy and the increase in size of labyrinth was by appositional growth from the trophospongial cells. It was considered that the inner trophoblastic cells in the vicinity of the fetal blood vessels were originated from the pure chorion. The interrelation among the various cells and the polyploidal giant cells in the placenta were discussed.