Abstract
Summary
The time of appearance of cytologic specialization in cells of regenerating rat tracheal epithelium was compared to the time of maximal mitotic response. Trauma sufficient to lethally injure most cells reaching the surface but sparing most basal cells resulted in a peak of mitotic activity from the 26th to the 30th hour following injury. The cells in the hyperplastic regenerating epithelium at the peak of mitosis had high nuclear-cytoplasmic ratios with little cytoplasmic or surface specialization. Ciliogenesis and mucinogen formation were not. seen in most cells until the 60th hr after the injury and there was little cell division at that time or later. Since cessation of mitosis does not follow or even coincide with the replenishment of the ciliated or goblet cell populations, the data does not support the hypothesis that control of cell division resides in the elaboration or release of a suppressor substance by the mature cells.
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