Ultrastructure, ultracytochemistry and histochemistry of the submandibular gland of the fi eld mouse. Apodemus argenteus Temminck.

Abstract:This study was carried out to observe morphologically and quantitatively the membrane fusion of secretory granules and exocytotic figures during secretion while keeping alive the submandibular gland acinar secretory granules of male rats . The results showed that in comparison with the secretory granules of stimulated and control rats by quick freezing with OsO4. acetone and paraformaldehyde•acetone, (a) secretory granules apposed and fused with each other in a convex and concave form, and filamentous structure (90-100 A) and actin-like filaments (40 A) were intercalated between the two closely apposed granules, (b) part of the two fused outer leaflets of the granule disappeared in the initial stages of the two fused granule membrane and a fused, double thickness lipid bilayer was observed. After the contents of one granule were poured into the other fused granule, association of the two fused membranes was observed; and (c) appearance of a convex shaped granule membrane facing toward the plasma membrane and depression of the plasma membrane facing the cytoplasm represented the initial stage of exocytosis. On the other hand, filamentous structures intercalated between the plasma membrane and the granule membrane were detected. Lastly, (d) the width of the tubular structures in the control groups was narrower than that in the stimulated gland at discharge after the fusion of the two membranes.From these results it was concluded that the concave and convex form in the granule membrane fusion and the association of plasmalemma-granules with tubular structures in the exocytosis may be intrinsic phenomena of the double lipid bilayer in secretory granule fusion, thus confirming the exclusion of intramembranous particles.

No abstract

No abstract

Novel zipper-like filamentous structures (3-10 run in diameter) were located in the central part of the processes of the interdigitation area of the granular convoluted tubule cells of rat submandibular gland. The zipper-like filamentous structures were composed of center-line-like and cross-tie-like structures, the latter being situated at intervals of 6.6-16 nm. These zipper-like filamentous structures may play a role in maintaining the configuration of the processes.