AUTORADIOGRAPHIC STUDIES OF THE INCORPORATION OF THYMIDINE-H3 INTO DEOXYRIBONUCLEIC ACID IN THE SKIN OF YOUNG RATS

[摘要] Newly synthesized DNA in the epidermis of the newborn rat was labeled by tritiated thymidine injected intraperitoneally. Fifteen minutes after the injection, labeled interphase nuclei were observed in the basal and the Malpighian layers of the epidermis, the hair follicles and the connective tissue of the dermis. Labeled mitotic figures appeared 6 hours later. The synthesis of DNA is probably, therefore, completed about 6 hours before cell division. Migration of the labeled cells from the deeper part of the epidermis to the superficial part of the Malpighian layer and the granular layer was seen. The labeled nuclei in 1000 epidermal cells were counted at various intervals and their distribution was studied. The life time of some epidermal cells appeared to be about 90 hours.