Contribution a l'Histologie du Pancréas Endocrine d'<i>Eliomys quercinus</i> L

Abstract

Besides some findings concerning the microscopic anatomy of the pancreatic islets and the histological peculiarities of the neuro-insular complexes in the garden dormouse, Eliomys quercinus, this study confirms the existence of islet cells of three different types on the basis of their distribution, cytological characteristics and their changes during the annual cycle.The B-cells are located in the central region of the islets and represent about 70% of the total cell population. Their secretory granules are relatively small and stainable with paraldehyde-fuchsin and other basic dyes after permanganate oxidation. They are rich in protein-bound disulphide groups and devoid of histochemically detectable indoles.The A-cells are of greater size than the two other cell types. The abundant secretory granules of these cells remain erythrophilic after permanganate oxidation. Devoid of disulphide groups, they are positive in histochemically detectable indoles. This cell type is located near the border of the islets and fails to show any argyrophilia after impregnation following the methods of Davenport and Grimelius.The D-cells are represented by argyrophilic elements of conical or pear-shape. Their cytoplasmic processes are oriented toward the capillaries, the cell bodies lying at the periphery of the islet tissue. The secretory product shows a metachromatic reaction with toluidine blue which is enhanced by hydrochloric hydrolysis. This product contains neither histochemically detectable indoles nor disulphides. It exhibits cyanophilia after permanganate oxidation. The number of D-cells and the abundance of the argyrophilic secretory product undergo a characteristic change during the annual cycle. A progressive decrease from January to June is followed by a progressive increase. The maximum amount of cells and of argyrophilic substance is encountered in prehibernating animals. This type of change differs from the annual cycle of B- and A-cells. Together with the lack of any transitional forms between D-cells and the other cell types it is consistent with the conception of the independence of the three cell types. The annual cycle of D-cells is not correlated to the changes in blood sugar and hepatic glycogen, but is closely parallel to changes in fatty acids in the liver parenchyma and blood plasma suggesting a possible elaboration by this cell type of substances which regulate lipid metabolism.