Differential cell proliferation of embryonic rat palatal processes as determined by incorporation of tritiated thymidine.

The differential cellular proliferation of the palatal processes in the Wistar albino rat was studied utilizing tritiated thymidine labeling. 3HTdr was given to pregnant rats at 14, 15, 16, and 17 days of gestation. The animals were killed one hour after injection. The fetuses were removed and the heads were embedded, sectioned, and an autoradiographic technique utilized. The autoradiograms were examined microscopically and labeling indices for various areas and regions of the palatal processes were calculated. The findings revealed that the pattern of cellular activity of mesenchymal and epithelial cells changes in different areas and regions of the palatal processes with different stages of secondary palate development.