Development of annular gap junctions in guinea pig epithelia.

Epithelia from skin, palate, buccal mucosa and dorsal tongue were studied in normal and zinc deficient guinea pigs by transmission electron microscopy. Gap junctions (nexuses) were observed primarily in the basal and prickle cell layers. They were also seen to form bulging and looping configurations which appeared to pinch off into the cytoplasm forming what are recognized as annular gap junctions. These may be attached to the surface or represent separate, intracytoplasmic, nexus-bound inclusions. Their contents varied, but most often they contained glycogen and ribosomal-like particles. Various cell organelles were also seen entrapped, most common of which were membrane coating granules. The development of these annular gap junctions is a prominent feature of many epithelia. It has been suggested that they probably serve to maintain a synchronized differentiation throughout the various epithelial layers.