[Cytokinetic study on healing of burned injury in the lip mucosal epithelium of C3Hf/He mice].

The cell growth kinetics in response to a burned injury was studied in the lip mucosal epithelium of C3Hf/He mice by using a pulse labelling method with 3H-thymidine for microautoradiography. Basal cells were labelled immediately after injury, and the mice were sacrificed for preparation at various intervals of time thereafter. The variations in frequencies of the labelled cells and mitosis were observed in their neighbors by the injury and also in untreated cells for comparison. The results of the observation are summarized as following. 1) The cell cycle time of the neighbor basal cells was estimated as 25.4 hrs, being about 36% shorter than that of 39.5 hrs in untreated cells. 2) The transition of the basal cells towards the upper layers of the epithelium was found to occur earlier (about 6 hrs after injury) in the neighboring cells in contrast to the transition time (20 hrs after labelling of untreated cells. But there was no difference in the rate of transition between the neighbors and the untreated cells. 3) The turnover time of the lip epithelial cells, which was measured by the peak to peak time difference in labelling index between basal and granular layers, was about 2 days and became about half of the time (4 days) for untreated cells. 4) The labelling index was found to form a peak first in the neighborhood at a distance of 200-300 cells away from the edge of the injury. Then, this peak moved centripetally toward the edge of burn, as time passed.