Increased apoptosis in taste buds of p27-/- mice. (A) TUNEL labeling of wild-type (+/+) and p27-nullizygous (-/-) taste buds from CV papillae at 5 weeks of age. Papilla surface is up. TUNEL-positive nuclear fragments (arrows) occur more frequently in taste buds from mutant animals. Note the small size and condensed appearance of the labeled fragments. (B) Electron micrographs of CV taste buds from p27-heterozygous (+/-) and -nullizygous (-/-) mice. The distinct apoptotic body in the boxed area of the mutant taste bud is shown at higher magnification in the inset (arrow). (C) Light micrograph of a JB-4-embedded thick section from a p27-nullizygous CV taste bud, illustrating a dying cell with the characteristic apoptotic bodies resulting from nuclear fragmentation (boxed region). These condensed fragments, seen at higher magnification in the inset, are notably smaller and denser than the nuclei evident in the intact cells of the bud. (D) Quantitation of taste bud apoptotic bodies seen in serial JB-4 sections through CV papillae, plotted as total apoptotic cells in whole papillae (means ± SEM for 5 replicates in each genotype). The number of apoptotic cells in p27-/- mice is approximately 1.5 times greater than in the wild-type. * indicates p = 0.005. Scale bar: 10 μm.