ULTRASTRUCTURE OF THE PANCREATIC ISLET TISSUE OF NORMAL AND ALLOXAN-TREATED COTTUS SCORPIUS

Abstract

The principle islets of Cottus scorpius are very suitable for electron microscopical investigations since they contain only endocrine parenchyma inside the connective tissue capsule. The central region with the [beta]-cells is more osmiophilic than the peripheral region. Thus, it is fairly easy to trim the islets in the desired region and obtain purely endocrine cells with known histological and histo-chemical features in the electron micrographs. The peripheral region is mainly composed of two kinds of cells a granular type, ultra-structurally corresponding to mammalian [alpha]-cells, and an agranular one possibly related to the mammalian gamma- and/or delta-cells as judged from its fine structure. The granules of the [alpha]-cells like cells are submicroscopical. The agranular cells terminate at capillaries in the same way as the granular cells. Both cell types are essentially unaffected by alloxan administration. The central region contains granular cells with a fine structure resembling that of mammalian [beta]-cells. These cells are severely damaged by alloxan administration. Intimately intermingled with these [beta] - cells are granular and agranular cells which are unaffected by alloxan administration. In part, at least they show ultrastructural similarities to the cells of the peripheral region and represent the aldehyde fuchsin and pseudo-isocyanine negative cells of this region.