[Ultrastructural modifications in the pigeon islets of Langerhans after epiphysectomy and treatment with epifizan (author's transl)].

The endocrine pancreas in pigeon consists of three types of Langerhans' islets (light, dark and mixed) each one having D, A and B cells in different proportions, representing 42%, 32% and 25%, respectively, from the total amount of endocrine pancreas. The D-cells are electrondense and contain many large spheric secretory granules (300...500 nm) with an adherent membrane to its content. The A-cells are spheric or columnal in shape, having few cell-organelles, a low electron density and contain spheric or oval secretory granules (200...400 nm) with a narrow space between the membrane and its content. The B-cells are elongated, electrondense, have many cell-organelles and contain many polymorph secretory granules (180...260 nm) which have in their majority a crystalline content which is separated from the membrane by a halo. After epiphysectomy the A (glucagon-secreting) and B (insulin-secreting) cells appear to be stimulated: the nuclei are enlarged, the synthesis processes are accelerated and the secretory granules increased. The stimulation of the glucagon synthesis is the consequence of the hypoglycaemia, caused by pinealectomy. The D (somatostatin-secreting) cells appear to be inhibited, having decreased secretory granules and modifications of some cell-organelles. This seems to be connected only with hypertrophy of the B-cells. After epiphysectomy followed by a treatment with Epizifan, the A-cells appear to be exhausted, caused by a persistent secretory activity, these cells containing only a small quantity of immature secretory granules. The B-cells are overloaded with secretory granules, having some damaged cell-organelles and appear to be inhibited in the releasing of their secretory granules. The D-cells are very active, rich in secretory granules, allowing the conclusion that an active synthesis and secretion have been taking place. These facts could be explained only by an inner regulation mechanism of the Langerhan's islet which is disturbed by pinealectomy but not restored by the nonspecific (cattle) Epifizan.