Time course of p27 expression examined by BrdU birth-dating analysis. (A) Confocal images (maximum projections, z-series of ten 1 μm steps) of anti-BrdU (red) and anti-p27 (green) immunolabeling in CV papillae of wild-type mice at 1, 3, 7 and 15 days following intraperitoneal injection of the BrdU. Papilla surface is to the left. No incorporation of BrdU is seen in the p27-immunoreactive taste cell population at 1 day post-injection. Co-labeled cells are evident on days 3, 7 and 15. (B) Percent (± SEM) BrdU-immunoreactive nuclei that are co-labeled for p27 with increasing cellular age. Data (means ± SEM) from 3 mice at each time point. * indicates p ≤ 0.005 compared to the previous time point. Scale bar: 20 μm.