Electron microscopic studies on pancreatic beta cells of normal and diabetic rats. Ultrastructural organization of pancreatic beta cells (A). Scale bar = 1 μm. ER: endoplasmic reticulum; MC: mitochondria; N: nucleus; SG: secretory granules. Mean density of SG was assessed by Image-Pro Plus 6.0 software and calculated as means ± SEM of 20 determinations in each group (B). See Figure 2 for groups and treatment. * P < 0.05 versus vehicle-treated normal rats, and # P < 0.05 versus vehicle-treated diabetic rats.