A juxtaposition between A-cells and D-cells in the chicken pancreatic islets following vagotomy.

Conventional electron microscopy and enzyme-cytochemistry were applied to elucidate the juxtaposition between the pancreatic D-cell and A-cell, 1-2 weeks after abdominal vagotomy in chickens. A pancreatic D-cell frequently encircled an A-cell. Around this juxtaposition, several D-cells, characterized by the occurrence of peculiar dense bodies, formed a cluster. Both the D-cell and the A-cell juxtaposed with each other and had an irregularly shaped nucleus with several indentations. Exocytosis of secretory granules from D-cells encircling an A-cell was often observed in the capillary side, but no release of secretory granules from A-cells was detected, except on the capillary side. A few large dense bodies, resembling a multivesicular body, were observed in the A-cell cytoplasm, showed positive acid-phosphatase activity, and contained remnants of several types of cell organelles. They thus seemed to be secondary lysosomes. It is possible that the juxtaposition between the A-cell and the D-cell may be morphological evidence of the inhibitory action on the A-cell by the D-cell.

Immuno- and enzyme-cytochemical studies on the pancreatic D-cells in the chicken following vagotomy.

To study the appearance of polymorphic, dense multivesicular body-like structures (MBLS) occurring in the D-cells of pancreatic islets following abdominal vagotomy in the chicken, the D-cells were evaluated by means of quantitative electron microscopy, identified by immunogold labeling and characterized by a method of enzyme cytochemistry. Following vagotomy, secretory granules of the pancreatic D-cells decreased significantly in number, whereas MBLS increased significantly in number. the mean area of the cell, nucleus and mitochondria displayed no significant changes. MBLS were rarely labeled for somatostatin when subjected to immunogold staining. MBLS arranging along the Golgi stacks may possibly be formed in the Golgi apparatus. consequently, it seems unlikely that MBLS are secondary lysosomes revealing crinophagy. Some MBLS showed acid phosphatase (AcPase) activity, although the direct fusion of primary lysosomes exhibiting AcPase activity with MBLS was seldom observed. As a result, it is possible that MBLS may be a kind of modified form of secretory granules and that they may be destroyed by lysosomes under the storing condition, judging from the AcPase reaction.

Immunohistochemical studies on the intrinsic pancreatic nerves in the chicken.

A peroxidase anti-peroxidase method or an avidin-biotinylated complex method was used to visualize neural elements immunostained for several neuropeptides in the chicken pancreas. Pancreatic ganglion cells were only immunoreactive with vasoactive intestinal polypeptide (VIP), galanin and substance P (SP) antisera. VIP-immunoreactive (IR) ganglion cells were the most numerous, and most of them also showed the distinct immunoreaction with galanin. VIP- and galanin-IR nerve fibers were observed in the exocrine portion, the adventitia of the artery and the connective tissue of the ductal wall. The number and distribution of the VIP- and galanin-IR nerve fibers around the artery and duct were similar. SP-IR nerve fibers were found mainly close to the blood vessel. SP- and CGRP-IR nerve fibers were detected in the VIP-IR ganglion and extrapancreatic nerve bundle. Tyrosine hydroxylase (TH)- and aromatic L-amino acid decarboxylase (AADC)-IR nerve fibers were observed as nerve bundles in the interlobular space or extrapancreatic nerves. Consequently, VIP and galanin coexist in the intrinsic neural elements. SP is partially located in the intrinsic neural elements, but most of it seems likely to originate from the extrinsic ganglion. It is probable that calcitonin gene related peptide (CGRP)-, TH- and AADC-IR nerve fibers have an extrinsic origin.