A comparative study on the intercellular canalicular system and intercellular junctions in the pancreatic islets of some rodents.

An electron microscope study of the development of the exocrine and endocrine pancreas with special reference to intercellular junctions.

“…In the rat, small gap junctions are present, but no tight junctional strands are seen in situ as shown by IN'T VELD et al (1984), YAMAMOTO and KATAOKA (1984) and the present study. In the mouse, on the other hand, focal tight junctions are present along with small gap junctions (YAMAMOTO and KATAOKA, 1984; the present study). Since acinar cells, intercalated duct cells and endocrine cells originate from undifferentiated cells of the pancreatic bud during embryonic development (PICTET and RUTTER, 1972;ANDREW, 1976), intercellular junctions of undifferentiated cells must be modified to form junctions characteristic of each mature cell type during histogenesis.…”

“…Endocrine cells in the islet are joined by scattered small gap junctions and focal tight junctions (ORCI and PERRELET, 1977;KATAOKA et al, 1982;YAMAMOTO and KATAOKA, 1984), but development of the latter varies according to animal species (YAMAMOTO and KATAOKA, 1984) as well as experimental conditions (ORCI et al, 1973;IN'T VELD et al, 1984). In the rat, small gap junctions are present, but no tight junctional strands are seen in situ as shown by IN'T VELD et al (1984), YAMAMOTO and KATAOKA (1984) and the present study. In the mouse, on the other hand, focal tight junctions are present along with small gap junctions (YAMAMOTO and KATAOKA, 1984; the present study).…”

“…On the other hand, islet cells, which have been separated from the exocrine matrix during development, possess only scattered small gap junctions (YAMAMOTO and KATAOKA, 1984). The morphogenesis of these intercellular junctions, previously not systematically studied, was deemed worthy of elucidation for a better understanding of the development and differentiation of a complex organ, the pancreas.…”

“…Small irregular gap junctions were often present at the top of these elevations. In adult rats, small gap junctions were scattered on flat adjoining membranes, and tight junctional strands were no longer seen (YAMAMOTO and KATAOKA, 1984). In adult mice, a few tight functional strands persisted, and small gap junctions were either associated with the strands or were present independently of them (YAMAMOTO and KATAOKA, 1984).…”

Electron microscopic observation of the primary cilium in the pancreatic islets.

“…A similar view was espoused by MUNGER (1958), who first described the presence of the primary cilium in the pancreatic islet. If this hypothesis is accepted, then the localization of the primary cilium becomes appropriate in the pancreatic islet: the cilium projects to the lumen of the intercellular canaliculus, an efficient pathway for the intercellular fluid (FUJITA et al, 1981;KATAOKA et al, 1982;YAMAMOTO and KATAOKA, 1984).…”