The cells of the rat gastric groove and cardia. An ultrastructural and carbohydrate histochemical study, with special reference to the fibrillovesicular cells.

The distal wall of the groove between the rat forestomach and glandular stomach is lined with a special type of columnar cells (CCGG) and with fibrillovesicular cells (FVC). The cardiac glands contain cardiac mucosa (CMC) and serous cells (CSC). The CCGG contain small mucous granules and special vesicles and tubules. The CMC are filled with large mucous granules and resemble mucous neck cells. The CSC are filled with large proteinaceous granules. The FVC are characterized by long microvilli, apical bundles of microfilaments and a complex "tubulovesicular system". The pattern of 3H-thymidine incorporation and the presence of immature and transitional forms indicate a possible origin of all the cell types concerned from a common undifferentiated precursor. The membranes of the tubulovesicular system of FVC as well as the apical cell membrane were reactive to Thiéry's carbohydrate stain. However, lanthanum tracing of the extracellular space and ultrastructural stereoscopy did not reveal a permanent continuity between both membrane systems. The absence of 3H-thymidine label showed that FVC were not proliferative. The structural characteristics of FVC do not account for a secretory, resorptive or receptive function. The special arrangement of microfilaments and the tubulovesicular system suggests an ability to fast changes in surface area.

Ultrastructural and carbohydrate histochemical studies on the differentiation and renewal of mucous cells in the rat gastric fundus.

Gastric surface mucous cells (SMC), mucous neck cells (MNC) and their undifferentiated and immature precursors were studied by light and electron microscopic histochemistry. The secretory granules of SMC were smaller, more electron dense and more reactive to PAS and its analogues than those of MNC. Alcian blue demonstrated that the mucus of SMC was acidic and that of MNC was neutral. The periodic acid-thiocarbohydrazide-silver proteinate method revealed the pressence of carbohydrates in the golgi apparatus, condensing vacuoles, secretory granules, apical vesicles and tubules and cell coat. Maturation of SMC during their migration towards the free surface was reflected by an increase in size and number of secretory granules, an increase of RER and microfilaments, and a decrease of microvilli and apical vesicles and tubules. The secretory granules of older SMC were less acidic and possessed a proteinaceous core. Most MNC were fully differentiated, but some immature MNC containing only a few granules were found. Furthermore, undifferentiated cells and intermediates between SMC and MNC were also observed. The presence of both transitional and intermediate forms indicates that both SMC, and MNC arise from the same population of undifferentiated cells. Incorporation of 3H-thymidine revealed that undifferentiated cells, use isthmic SMC, MNC and intermediate cells are proliferative. No proliferative activity was found in foveolar SMC, parietal, chief, fibrillovesicular or endocrine cells.

Renewal of mouse gastric mucous cells following fast neutron irradiation. An ultrastructural and carbohydrate histochemical study.

Mouse gastric mucosa was studied ultrastructurally and histochemically after exposure to fast neutron irradiation, the number of cells per gastric gland was decreased and the glands were shorter. At day 9, several glands showed a dilated lumen lined by flattened cells. Between days 9 and 16, some of the glands disappeared. Parietal and chief cells disappeared from the remaining glands. At the same time, restoration of the mucosa started. At day 6, proliferative cells were scattered along the isthmus. As in controls, the isthmus contained a few undifferentiated cells many differentiating surface mucous cells (SMC) with developing rough endoplasmic reticulum and silver proteinate-reactive Golgi elements and small secretory granules. At day 9, numerous proliferative cells were clustered in foci. Almost all these cells contained silver proteinate-reactive Golgi elements, granules and vesicles. Most of them were SMC, others mucous neck cells (MNC) or intermediates. At day 16, proliferative foci were larger and consisted of differentiated mucous cells. Regenerated foveolae and glands consisted of large SMC and MNC and a few fibrillovesicular cells. In conclusion, proliferative activity is confined to undifferentiated cells and differentiating mucous cells, which identifies them as the progenitors of the other gastric cell types.

Glycoprotein synthesis in the mucous cells of the vascularly perfused rat stomach. II. Differentiating mucous cells.

Labeled leucine, serine, galactose, glucosamine and sulphate were administered to rat stomachs in a perfusion system. Sections of the gastric fundus were studied by light microscopic autoradiography. Five categories of mucous cells were distinguished and their glycoprotein synthetic activity was measured in autoradiographs by counting silver grains over each category. During their differentiation, while migrating from the isthmus of the fundic glands to the free luminal surface, the surface mucous cells (SMC) showed an increase in incorporation of all precursors used. Differences between the incorporation patterns of the various precursors, in cells of different ages, suggest that structural development runs ahead of functional activity, and that the latter continues up to the very moment the cell is shed from the surface. Sulphate was incorporated at a considerably lower rate by the SMC of the free surface than by the foveolar SMC, in which by cytochemical staining strongly acidic glycoproteins were shown. Since the mucous neck cells incorporated all precursors at a low rate, these cells apparently do not play an important role in gastric mucus synthesis. They did not incorporate sulphate, which is consistent with histochemical observations.