Role for differential cell proliferation in perforation and rupture of chick pharyngeal closing plates.

Patterns of cell proliferation show two distinct domains around avian pharyngeal closing plates as they form, perforate, and rupture. Pouch endoderm and groove ectoderm are in one domain showing 81-86% proliferation, which suggests relatively rapid growth. Cells in epithelia that comprise the pharyngeal closing plates contiguous with pouch and groove epithelia are vital but are dividing at a significantly lower percentage (62-64%). This phenomenon is similar to the lag in growth reported for cells in the oral membrane around the time of rupture (Miller and Olcott, 1989: Anat. Rec., 223:204-208), is consistent with Waterman's suggestion (1985: Anat. Rec., 211:450-457) that cellular reorganization, rather than massive degeneration, is a major mechanism of initial perforation, and suggests that differential growth is a contributor to performation and rupture of chick pharyngeal closing plates.