抄録
A light and electron microscopic observations on pancreatic islets of spontaneous diabetic mice (yellow KK) were performed. Degranulation and glycogen deposition of B cell observed at the age of 5 weeks were followed by hypertrophy and central cavitation of islets. These changes became prominent until they were 16 weeks of age, and then degranulation and glycogen deposition became diminished with increasing age. By the electron microscopy, degranulated B cells were found to contain well developed Golgi apparatus, abundant granular endoplasmic reticulum and fine granules of glycogen. B granules were occasionally fused to cell membrane to represent emiocytosis. These changes show increased activities of synthesis and release of insulin which corresponded with high levels of plasma immunoreactive insulin. During the phase of hypertrophy of islets, there were observed acinar typed cells containing B granules in islets, and aldehyde fuchsin positive cells in pancreatic ducts. These phenomena suggest the validity of the transformation of extra-insular cells into B cells in the process of hypertrophy of islets.
