Licht- und elektronenmikroskopische Untersuchungen der Langerhansschen Inseln bei Grünleguan (Iguana iguana)

Abstract

1. Langerhans islets in the green iguana form a large mass in the part of the pancreas near the spleen; this mass is covered only with a thin layer of zymogen tissue. Islet cells form abundantly anastomosing cords.
2. As in other reptiles, three types of cells are found in the islets both by light and electron microscopy; each type can be easily demonstrated under the light microscope, using specific staining methods. B-cells are not evenly distributed in the islet tissue; sometimes other cells, mostly A-cells, predominate.
3. With the electron microscope individual types of cells differ in the shape and size of specific granules; a-granules (390±90nm) are mostly spherical and dark. The core of b-granules in sections (total size of granules being approximately 350±80nm) takes the shape of various geometrical figures. D-cells, whose granules (270±75nm) are smaller, lighter and slightly irregular, are found more sporadically.
4. Cells with granules of different shapes and with different appearances of cytoplasm in various parts of the cell occur especially at the islet periphery. Besides typical zymogen granules characteristic formations, which should correspond to A- and B-cells, possibly to D-cell granules, may be found in the same cell. Fine ducts are found at the islet periphery as well. Their cells do not contain any granules; they are, however, characterized by mitochondria with broad and dark cristae as well as a larger amount of glycogen.