Histopathological study of islets of Langerhans and effect of hydroalcholic extract of N. sativa on the number of islets and the number of islet cells and islets diameter (μm) in pancreatic tissues in rats. A- Diabetic group, shrunken islets of Langerhans displaying degenerative and necrotic changes and vacuolization in diabetic rats without treatment (H&E × 400); B- NS treated group (5 mg/kg b.w.). NS protected the majority of cells in the islet of Langerhans. However, the remaining cells exhibit light hydropic degeneration, degranulation, and necrosis. In addition, a few cells with a picnotic nucleus are indicated (H&E × 400). C- Complete glycogen depletion is seen due to STZ-induced diabetes (PAS staining × 400) and The hepatic glycogen level remarkably elevated after 32 days treatment with NS at dose of 5 mg/kg b.w. (PAS staining × 400). D- The hepatic glycogen content did not change considerably after 32 days treatment with NS at dose of 10 and 20 mg/kg b.w. (PAS staining × 400).