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ABSTRACT A detailed study of the cellular proliferation kinetics in interfollicular plucked and unplucked mouse skin has been made in Swiss albino mice, using tritiated thymidine autoradiography. Diurnal variations in mitotic and labelling indices were demonstrated in both systems. The mean cell cycle times for unplucked and plucked skin were estimated by four different methods and found to be 100 ± 10 and 47 ± 3 hr respectively. Most of the difference was due to the shortening of G 1 phase after plucking. Repeated labelling at intervals shorter than the DNA synthesis times resulted in all the basal layer cells becoming labelled, so that the growth fraction was unity, in unplucked and plucked skin. A well‐defined second wave of labelled mitoses was seen at about 100 hr after labelling the unplucked (i.e. normal) mouse skin. A double labelling technique using 14 C‐TdR and 3 H‐TdR with a single layer of emulsion gave reasonable values for the duration of the DNA synthesis phase.
Hegazy et al. (Mon,) studied this question.