WK, hen the epithelial cells of the cornea of the dogfish are mechanically injured, a rapid incorporation of tritium-labeled thymidine (H3 thymidine) into deoxyribonucleic acid (DNA) takes place. Incubation in vitro of conical epithelial cells of the dogfish also demonstrates a significant degree of incorporation of thymidine into DNA. The depression of thymidine uptake when the temperature is ...

In studies of cell proliferation in the intestine of animals during the past few years, observations have been made that suggest points of interest concerning cell renewal in humans. In rodents, proliferating jejunal and colonic epithelial cells have mean generation times of about 12 to 18 hours, DNA synthesis (S phase) times of 5 to 8 hours, and premitosis (G2) and mitosis (M) times of 1 to 2 ...