Fine structural aspects on the renewal and development of surface mucous cells and glandular cells of the gastric body of the adult golden hamster.

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Abstract
By light microscopic and EM autoradiography using 3H-thymidine, the renewal and development of surface mucous cells and glandular cells in the gastric body were studied in normal young adult golden hamsters. The isthmus and neck regions of the gastric gland are composed of immature surface mucous cells, immature parietal cells, young parietal cells and mucous neck cells. It is presumed that the stem cell having the potency of differentiating into various kinds of cells is not present in the gastric mucosa of the adult golden hamster. Immature surface mucous cells, located in the isthmus region and capable of synthesizing DNA, contain abundant free ribosomes and a small number of secretory granules. The secretory granules increase in number as the cells ascend towards the gastric surface, forming a thick granule zone in the cell apex. The cells further contain small electron lucent vesicles which are likely involved in the formation of glycocalyx. The immature parietal cells in a low differentiated state, possessing the DNA synthesizing ability, are rarely found in the isthmus. They show collapsed intracellular canaliculi with long microvilli and contain numerous free ribosomes, but smooth tubular elements are difficult to recognize. Some of the mucous neck cells located in the isthmus to neck region and capable of synthesizing DNA, are characterized by abundant free ribosomes, a few elements of rough endoplasmic reticulum relatively well developed Golgi apparatus and a few dense secretory granules. Mature surface mucous cells contain abundant secretory granules filling an apical granule zone. They are fated to be degenerated and extruded into the gastric lumen. This is considered to be a holocrine process. The middle and basal regions of the gland consist mainly of chief cells, parietal cells and endocrine cells. A few of the chief cells in the middle part of the gastric gland also have the activity of synthesizing DNA. Some of the immature cells in the isthmus region and mature glandular cells in the bottom of the gland are degenerated and phagocytosed by neighboring epithelial cells. The occurrence of smooth muscle fibers in the lamina propria, extending from the muscularis mucosae to the basal part of the degenerated surface epithelium was also recorded.