The Fine Structure of the D-Cells of the Pancreatic Islets in the Domestic Fowl and their Morphological Evidence of Secretion

D Cell, the Third Endocrine Element of the Pancreatic Islet

“…In his light microscopic study on the islet tissue of elasmobranchial fishes, THOMAS (1940) describes distinct cytological changes suggesting elaboration, storage and deplation of the granules in the D cell. Finally, the recent electron microscopic findings on the specific granules of the D cell, especially the observation on the extrusion of the granules (MACHINO, SAKUMA and ONOE, 1966) seem to have confirmed the hypothesis of secretion in this cell.…”

“…Although MEYER and BENCOSME (1965) pointed out that the limiting membrane of the D granules located close to the cell surface is often attached to the plasma mambrane, a more direct evidence of the release of the granules was obtained by MACHINO, SAKUMA and ONOE (1966). According to these Japanese authors, the D granules of the fowl show a series of figures which are believed to indicate that the limiting membrane of the granule first fuses with the plasma membrane and a pore opens at the fused part through which the substance of the granule is extruded (Fig.…”

The microanatomy of human islets of Langerhans, with special reference to somatostatin (D-) cells.

“…Moreover, several authors observed exocytotic figures at the vascular pole of D-cells (MACHINO et al, 1966;FUJITA, 1968;KOBAYASHI and FUJITA, 1969;WATANABE et al, 1975;SCHUSDZIARRA et al, 1978). Therefore, there was no real doubt that D-cells correspond to typical endocrine cells.…”

Comparative Studies on the Pancreatic Islets

“…Their secretory activity 1. The electron microscopic findings of Machino et al (1966) indicate that the Dcells synthesize and secrete a substance different from that of A-and B-cells. 2.…”

“…Electronmicroscopically it was also described for various mammals and man, birds, reptiles, amphibians and teleosts, though we might face here also a nomenclatural problem (cf. Watanabe, 1960;Bjorkman et al, 1966;Machino et al, 1966;Kobayashi, 1966;Sato et al, 1966;Titlbach 1966). Thus, information is still lacking for the chondrostei, holostei, lungfishes, Latimeria and gymnophiona.…”