Tadayuki Yamashita

Immunocytochemical Study of the Gastroenteropancreatic Endocrine Cells of the Sheep

The gastroenteropancreatic (GEP) endocrine cells of the sheep were studied immunocytochemically and their distribution and frequency were determined. Eleven types of endocrine cells were revealed. In the abomasum, somatostatin-, gastrin-, glucagon- and glicentin-immunoreactive cells were detected with the highest frequency in the pyloric region. In the small intestine, somatostatin-, gastrin-, CCK-, motilin-, neurotensin-, secretin-, substance P-, glucagon-, glicentin- and BPP-immunoreactive cells were found and were most numerous in the duodenum except for neurotensin-, glucagon- and glicentin-immunoreactive cells which were more concentrated in the ileum. In the large intestine, somatostatin-, substance P-, glucagon-, glicentin- and BPP-immunoreactive cells were localized with the last three cell types being more concentrated in the rectum. In the pancreas, somatostatin-, glucagon-, glicentin-, BPP- and insulin-immunoreactive cells predominated within the islets and were also scattered in the exocrine portion and rarely detected in duct epithelial cells. The differences between the distribution and frequency of the GEP endocrine cells of the sheep and those of monogastric species are discussed.

Immunohistochemical Study of the Distribution of Endocrine Cells in the Gastrointestinal Tract of the Lesser Mouse Deer (Tragulus javanicus)

The occurrence and distribution of endocrine cells in the gastrointestinal tract of the lesser mouse deer, Tragulus javanicus, were studied immunohistochemically. Fourteen types of endocrine cells immunoreactive for serotonin, somatostatin, enteroglucagon, pancreatic glucagon, bovine pancreatic polypeptide (BPP), gastrin, substance P, motilin, gastric inhibitory polypeptide (GIP), cholecystokinin (CCK), methionine-enkephalin-Arg6-Gly7-Leu8 (MENK-8), secretin, neurotensin, peptide tyrosine tyrosine (PYY) and chromogranin were revealed. Chromogranin-, serotonin-, somatostatin- and enteroglucagon-immunoreactive cells were detected in all regions examined, while pancreatic glucagon-immunoreactive cells, except in the proper gastric gland region, were not found in other regions of the gastrointestinal tract. Few BPP-immunoreactive cells in either the proper gastric gland or pyloric gland regions and abundant gastrin-immunoreactive cells in the pyloric gland region were observed. Restricted distributions of substance P-, GIP-, gastrin-, motilin-, CCK-, MENK-8-, secretin-, neurotensin- and BPP-immunoreactive cells in the small intestine, and BPP-, substance P-, PYY- and motilin-immunoreactive cells in the large intestine were noted. The important findings include the presence of BPP-immunoreactive cells in the abomasum, pancreatic glucagon-immunoreactive cells in the proper gastric gland region, and substance P- and motilin-immunoreactive cells in the large intestine. It is suggested that the distribution pattern of gut endocrine cells in the lesser mouse deer is more similar to that in the pig than in the domestic ruminants so far reported.

Immunohistochemical localization of lactoferrin in bovine exocrine glands

The localization of lactoferrin (LF) was studied in bovine exocrine glands by the peroxidase-antiperoxidase method. In general, LF immunoreactivity was demonstrated in most of the serous demilunes of the mixed glands and in some but not all acinar cells of the serous glands. LF was not detected in the acinar cells of the mucous glands. LF immunoreactive cells were seen in the nasal and tracheal glands. The lacrimal and mammary glands were stained intensely, while the sweat glands were not stained. In the major and minor salivary glands, LF immunoreactivity was demonstrated in the serous demilunes and acini of the mixed glands and in some serous cells of the pure serous parotid gland. LF immunoreactivity was not seen in the gastrointestinal tract and pancreas, but the serous gland in the lamina propria of the bile duct was stained positively. In the male reproductive tracts, the prostate and bulbourethral glands were stained positively, but the vesicular gland was negative. In the female reproductive system, the uterine and Bartholin glands, the epithelial cells of the cervix and ampulla of the uterine tube reacted positively. However, the lesser vestibular gland did not react for LF. The present findings, that LF was demonstrated in the exocrine glands located mainly in the gateways of the digestive, respiratory and reproductive systems, may morphologically support the antibacterial role of LF.

Immunohistochemical Study of the Distributions of the Peptide- and Catecholamine-Containing Nerves in the Omasum of the Sheep

The distribution in the sheep omasum of peptide- and catecholamine-containing neurons was investigated by an immunohistochemical technique using antibodies against six neuropeptides and two catecholamine-synthesizing enzymes. In the myenteric plexus, both nerve cell bodies and nerve fibers were positively immunostained for substance P (SP), methionine enkephalin (ENK), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and galanin (GAL). In contrast, immunoreactivity specific for calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) was detected only in nerve fibers. In the omasal wall, nerve fibers with SP- and ENK-like immunoreactivity were prominent in the outer muscle layer, while numerous nerve fibers with VIP-, NPY- and GAL-like immunoreactivity were observed in the inner muscle layer. In the lamina propria mucosae, and in particular in the omasal papillae, a dense network of peptide-containing nerves was found. The distribution of nerves with CGRP-like immunoreactivity was different from that of other immunoreactive nerves. The networks of nerves with TH-, DBH- and NPY-like immunoreactivity were concentrated around the vascular components. The results of this study indicate the complexity of the enteric nervous system in the sheep omasum, reflecting the multiple functions of the nerves in the regulation of motility and/or absorption and secretion.

Immunohistochemical Study on the Endocrine Pancreas of Cattle with Special Reference to Coexistence of Serotonin and Glucagon or Bovine Pancreatic Polypeptide

Bovine pancreatic endocrine cells were investigated by light microscopic immunohistochemistry. Serotonin-immunoreactive cells as well as insulin-, glucagon-, somatostatin-, bovine pancreatic polypeptide (BPP)-immunoreactive cells were detected in the pancreatic islets. Generally, insulin-immunoreactive cells were distributed throughout the islet and the others took peripheral location. Since the distribution and shape of serotonin-immunoreactive cells were very similar to glucagon- and BPP-immunoreactive cells, serial sections were restained by using the elution method. All glucagon- and BPP-immunoreactive cells also showed serotonin immunoreactivity but glucagon and BPP immunoreactivities were never observed to be colocalized in the same cell. A small number of serotonin-immunoreactive cells were observed that showed serotonin immunoreactivity only.

Electron Immunocytochemical Co-Localization of Prochymosin and Pepsinogen in Chief Cells, Mucous Neck Cells and Transitional Mucous Neck/Chief Cells of the Calf Fundic Glands

The electron immunocytochemical co-localization of prochymosin and pepsinogen in chief cells, mucous neck cells and transitional mucous neck/chief cells of calf fundic glands was studied using specific antisera for prochymosin and pepsinogen with a protein A-gold method. Prochymosin and pepsinogen immunoreactivities were detected in the same secretory granules of the chief, mucous neck and transitional cells, simultaneously using small and large colloidal gold particles. In chief cells, both immunoreactivities were distributed uniformly over the same zymogen granules showing a round, large, homogeneous and electron-dense appearance. In mucous neck cells, both immunoreactivities were found exclusively on the same electron-dense core located eccentrically in the mucous granule showing light or moderate electron density. In transitional mucous neck/chief cells, electron-dense cores became larger in size and some granules were occupied by the electron-dense core without a halo between the core and the limiting membrane. Both immunoreactivities were found uniformly over the electron-dense core. The granules having no halo in the transitional cells could not be distinguished from the typical zymogen granules in the chief cells.

Cellular and subcellular localization of progastricsin in calf fundic mucosa : colocalization with pepsinogen and prochymosin

The presence of gastricsin in bovine abomasal juice has been reported previously, but its exact site of origin has not yet been established. Specific polyclonal antibodies were used in the peroxidase-antiperoxidase method or the protein A/gold technique to label cells producing progastricsin. This immunocytolocalization was correlated with that of pepsinogen and prochymosin using specific polyclonal antibodies against those zymogens. The present study clearly established that progastricsin was located exclusively in chief, mucous neck, transitional mucous neck/chief, foveolar epithelial and surface epithelial cells of the calf fundic mucosa. Furthermore, progastricsin was found to be colocalized with pepsinogen and prochymosin in the same secretory granules of these cells. Progastricsin was not observed in parietal, gastric endocrine and undifferentiated neck cells.

Morphological Study of the Surface Structure of the Omasal Laminae in Cattle, Sheep and Goats

The mucosal relief of the omasum in cattle, sheep and goats was examined by the naked eye, stereoscopic microscope and scanning electron microscope. The mucosal relief of the omasum showed wide variations both between and within these species. Omasal papillae on the laminae varied highly in shape, i. e. conical, rounded, claw‐like, wart‐like, finger‐like etc. They decreased gradually in size from the oral to the aboral region of the omasal lamina. Ridge‐like structures and linear arrangements of the papillae were also seen on the omasal laminae of cattle and sheep. Many grooves and folds were found on the lateral surface of the omasal papillae in adult cattle and on the inter‐papillar surface of the laminae of all three species. The mucosal relief of the omasum in cattle seemed to be more well‐developed than those of sheep and goats. Dietary effects on the omasal mucosa were also discussed.

Muscular architecture in the omasal laminae of cattle and sheep.

The muscular architecture of the bovine omasal laminae was examined. The omasal laminae had three thin smooth muscle layers which consisted of an intermediate layer and two lateral layers. The muscle bundles of the intermediate layers ran radially in the laminae and those of the two lateral layers ran parallel to the free border of the laminae. At the free border, three types of the muscular architecture were observed. In a histological study, the muscle bundles of the intermediate layer penetrated into the connective tissue around the smooth muscle fasciculi of the inner layer of the tunica muscularis of the omasal wall and attached to the bundles of both the inner layer and of the outer layer of the tunica muscularis. These results indicate that a re-evaluation of the muscular architecture in the omasal laminae is required to facilitate better understanding of the omasal morphology and physiology.

Three-Dimensional Architecture of the Subepithelial Connective Tissue in the Omasal Laminae of Sheep and Cattle

The three-dimensional architecture of the subepithelial connective tissue in the omasal laminae of sheep and cattle was studied by scanning electron microscopy after treatment with 2 N NaOH solution. The omasal laminae were equipped with highly undulated subepithelial connective tissue showing various projections or ridges. In the sheep, the subepithelial connective tissue in the omasal papillae formed flat papillary projections in the oral and middle regions of the laminae. Ridges were arranged in cellular or rosette-like form in the aboral region. In the interpapillary space, the subepithelial connective tissue formed papillary projections in the oral region, parallel ridges with dentate projections in the middle region and smooth low ridges in the aboral region. In the cattle, the projections of the subepithelial connective tissue were more developed than in the sheep. The reticular or cellular ridges were uniformly arranged. The omasal papillae with horny tips located near the reticulo-omasal orifice showed various shapes of papillary projections. In the interpapillary space, round-edged and complex folded ridges with high undulations and deep grooves were observed. These findings may indicate regional and interspecies diversities in the function of the omasal mucosa.