Electron Microscopy of Human Pancreatic Islet

The human pancreatic islet cells were observed by the electron microscope of ultrathin sections and the results obtained are as follows.1. Three types of cells are distinguished in human pancreatic islet cells.2. The first type of cells contains spherical, sharp bordered granules with high electron density in one side of dark background cytoplasm. In cytoplasm, a few mitochondria are observed, but endoplasmic reticulum and GOLGI apparatus are not clearly distinguishable.3. In the second type of cells, we observed a few irreguar granules with low electron density and relatively well developed, nearly round mitochondria and endoplasmic reticulum.4. The third type of human pancreatic islet cells contains similar granules to those of the first cells and the granules are uniformly diffused in cytoplasm. Cytoplasm of these cells appears light with numerous cytoplasmic fenestra. The majority of mitochondria in this type of cells are cells are clubbed in shape.5. In each type of the above described cells, the inclusions which contain several vacuoles are recognized. Intermediate forms between mitochondria and the inclusion are also observed. So, these inclusions are considered to be the transformed mitochondria.