Effects of 10-week circadian rhythm disruption on pancreatic beta-cell mass, beta-cell apoptosis, and replication. Mean beta-cell fractional area (A, C) and beta-cell mass (B, D) in WT (left panels) and diabetes-prone HIP rats (right panels) following 10-week exposure to LD (open bars), LL (black bars), and 6-h advances (gray bars). Mean beta-cell replication (E, G) and beta-cell apoptosis (F, H) in WT (left panels) and diabetes-prone HIP rats (right panels) following 10-week exposure to LD (open bars), LL (black bars), and 6-h advances (gray bars). Data are expressed as mean ± SEM. *p < 0.05 statistical significance for beta-cell area, beta-cell mass, and beta-cell apoptosis vs. LD HIP rats.