FIGURE 3. Analysis of islets and -cells in pulse–chase experiments.

a–g, Staining for HPAP (dark blue) and insulin (brown). a–c, Typical islets from mice killed immediately after tamoxifen injection (a), 4 months later (b) or 1 year later (c). Note that the HPAP stain obscures the brown insulin stain in double-positive cells. d–g, HPAP⁺ and HPAP^- clusters of -cells from mice immediately after the pulse (d, e) and in mice after a 6 month chase (f, g). Shown are clusters containing HPAP⁺ -cells (d, f) and clusters containing only unlabelled -cells (e, g). Original magnification, 400. Scale bars, 50 m (a–c), 25 m (d–g). h, Graph summarizing the frequency of HPAP⁺ islets and small clusters (containing fewer than 10 -cells) in pulse–chase experiments with normal adult mice. Error bars represent standard deviations for all animals analysed (n = 8 for pulse, n = 16 for all chase experiments combined). Blue, pulse; red, chase. i, Graph summarizing the frequency of -cells expressing HPAP in adult RIP–CreER;Z/AP mice after tamoxifen injection. Bars represent the average percentage of HPAP⁺ -cells per mouse. Error bars represent standard deviations for all animals analysed for that time point; n is the number of mice.