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The ultrastructure of rat parietal cells of the gastric mucosa was investigated during the twenty-four hours of a day. Male rats were housed at ad libitum feeding under normal light conditions with dark night. The animals were sacrificed at 6.00 h, 12.00 h, 18.00 h and 24.00 h respectively, in groups of 5 animals after standard 24 hours of starvation. From this material the electronograms of 356 parietal cells (19% in 6.00 h, 26% in 12.00 h, 21% in 18.00 h and 34% in 24.00 h samples) were evaluated. Based on literary data, the parietal cells were specified as secreting parietal cells (S, 38% of the total), secreting parietal cells returning to resting state (SR, 18% of the total), resting parietal cells (R, 35% of the total) and resting parietal cells tending to early secreting state (RS, 9% of the total). Some types of parietal cells are statistically highly significantly (x2 = 130.9, p less than 0.001) unequally distributed during the circadian rhythm: S are less numerous at 6.00 h (2% of the total) and 12.00 h (4% of the total) than expected (7 and 10% respectively), and more numerous at 18.00 h (11% of the total) and 24.00 h (21% of the total) than expected (8 and 13% respectively). Conversely, R are more numerous in the morning (13 and 15% instead of 7 and 9% respectively) and less in evening samples (4 and 3% instead of 7 and 12% respectively). Distribution differences were proved statistically (x2-test) for all cell-cell and hour-hour combinations expect the combinations S-RS and 6.00 h to 12.00 h. The maximal differences in distribution were found to be between the amounts of S and R at 6.00 h and 24.00 h (x2 = 77.3, p less than 0.001) and at 12.00 h and 24.00 h (x2 = 69.3, p less than 0.001). Thus, a distinct circadian rhythm of parietal cells, especially as to their fine cell structures involved in acid production was demonstrated. The results render further evidence of the rhythmicity of gastric acid production in rats.

Summary The effect of distension of the stomach by air ( in vitro ) upon the ultrastructural picture of gastric endocrine cells in rats starved for 72 hours was investigated. Distension of the stomach by air in vitro , lasting for 5,10, 15 and 20 minutes, resulted in massive dissolution of gastrin granules that had accumulated in the course of starvation. In AL, D1, EC and ECL cells distension of the stomach by air failed to induce dissolution of granular content or release of granules by any other mechanism. In AL and D1 cells accumulation of secretory granules caused by starvation was observed, the ultrastructure of EC and ECL cells remained unchanged both under the effect of starvation and distension. Dilatation of endoplasmic reticulum profiles as well as other changes on some cell organelles observ-ved on endocrine cells after distension of the stomach by air in vitro are due to the effect of autolysis.

Summary The histology and ultrastructure of the rat gastric mucosa were investigated during 168 hoursof starvation. An increased desquamation of individual foveolar cells was found. In the preserved cells of the foveolae, the content of the PAS positive mucosubstances did not change during starvation, and no changes took place in the appearance and in the amount of the mucous granules at the electron microscopic investigation. The number of lipid droplets increased in the mucous foveolar cells within 24 and 48 hours. During starvation the mitochondria (mainly in the parietal cells) were enlarged and contained rare mitochondrial cristae. Some mitochondria were distintegrated and removed by lysosomes. The number of lysosomes (mainly cytosegresomes) was markedly increased in parietal cells. A collapse of the intracellular canaliculi occurred as well as a narrowing in the tubulovesicular profiles. In chief cells the profiles of the granular endoplasmic reticulum and Golgi apparatus were reduced. It was shown that the ultrastructural changes induced by starvation can be interpreted functionally in changed histochemical parameters of the gastric mucosa.

Summary The ultrastructure of the human antral G cells was examined in gastrobiopsies of 7 healthy volunteersfasting 24 to 240 hours. In contrast to the animal gastric C cells during fasting, the dissolution of the substance of gastrin granules (but not emiocytosis of granules) was observed in the human antral G cells during long fasting. The authors consider the possibility of artificially inducing the dissolution of the substance of the granules only the technique of gastrobiopsy itself.