Figure 6. Ultrastructural observations of the pancreatic beta cells of normal and experimental groups of rats. Transmission electron micrographs of the pancreas of control normal (CN), control diabetic (CD), vanadium-treated diabetic (VTD) and insulin-treated diabetic (ITD) rats. Cellular organelles nucleus (N); nucleolus (Nu); rough endoplasmic reticulum (RER); mitochondria (M); and Golgi complex (GC) are marked. Arrow shows central dense core atypical insulin secretory granules (ISG). Beta cells in CN islets contain numerous ISG and welldistinguished central core (arrow). The cellular integrity of beta cells in CD was normal, their nuclei are migrated, RER is compressed with atypical ISG and devoid of central dense core (arrow). Beta cells in VTD are like CN, with abundant typical ISG and central dense core. The nuclei of beta cells in ITD are identical to CN, with typical and atypical ISG, less filled core dense (arrow) and fewer mitochondria.