DNA synthesis in the adult hair germ during dormancy (telogen) and activation (early anagen)

Abstract

There is in general very little synthesis of DNA in the germ of the adult murine hair follicle during the main course of telogen. A small percentage of hair germ nuclei incorporate tritiated thymidine during the last third of telogen, and this percentage increases with the approach of Anagen I of the next hair generation. In anagen initiated experimentally by the plucking of telogen follicles, the incorporation of tritiated thymidine in hair germ nuclei begins about 12 hours after plucking, and rises sharply to a maximum at 30 hours after plucking. This curve is approximately 6 hours earlier in time than the curve for the occurrence of mitotic figures in hair germs after plucking, which was reported previously. Telogen germs as well as early anagen germs are differentiated into at least three kinds of cells, located in a specific position. During activation all cells increase markedly in size, and their membranes appear less coarse. They do not, however, lose their differentiated state, i.e., general shape and location, although differential staining is temporarily reduced.