Hajime Kuwayama

Effects of Water Immersion Restraint Stress and Chronic Indomethacin Ingestion on Gastric Antral and Fundic Epithelial Proliferation

We studied the effects on gastric fundic and antral epithelial proliferation of acute water immersion restraint stress in rats and of chronic indomethacin ingestion in rats and humans using autoradiographic methods. Acute stress appeared to inhibit fundic epithelial proliferation but had no effect on antral proliferation in rats. We conjecture that this inhibition of fundic epithelial proliferation may help explain the development of stress-related mucosal lesions, which are more likely to occur in fundic mucosa. Chronic indomethacin ingestion stimulated fundic epithelial proliferation but had no effect on antral proliferation in both rats and humans. From these observations we conjecture that the failure of antral epithelial proliferation to respond to indomethacin may account in part for the ulcerogenic action of this drug.

Effects of parenteral hydrocortisone sodium succinate on epithelial renewal in hamster gastric mucosa.

The aim of this study was to determine whether parenteral administration of steroids affects epithelial renewal in hamster stomach. Male golden hamsters received either hydrocortisone sodium succinate or saline intraperitoneally for three days. In the first experiment, hamsters were sacrificed 1 hr after injection of tritiated thymidine ([3]HTdR) to label proliferating cells. In the second experiment, hamsters were sacrificed hourly after a single [3H]TdR injection up to 48 hr in order to determine cell cycle time by the method of fraction of labeled mitoses. In the third experiment, hamsters were sacrificed 1, 24, and 72 hr after [3H]TdR injection for the study of epithelial migration and cell turnover time. Sections of fundic and antral mucosae were prepared for light autoradiography. Steroid treatment caused no gross or microscopic injury to gastric mucosa, but the number of [3H]TdR-labeled cells as well as the thickness of the proliferative zone were reduced significantly in fundic mucosa, but not in antral mucosa. The study of the fraction labeled mitoses indicated that steroid treatment lengthened the cell cycle time in fundic mucosa, which was due primarily to prolonged G1 and DNA synthesis phases. Furthermore, epithelial migration was significantly slower in fundic mucosa after steroid treatment, which was associated with a prolonged cell turnover time. Thus, parenteral steroids depress the entire process of epithelial renewal in hamster fundic mucosa.

Endoscopic local injection of early gastric carcinoma with 5-fluorouracil

We treated four patients who had early gastric carcinoma with weekly endoscopic local injections of 5-fluorouracil (5FU). In all four patients the lesions disappeared by endoscopic and biopsy examination within 12–18 weeks of treatment. None of the patients experienced side effects which are usually associated with oral or intravenous administration of 5FU. Two patients eventually underwent surgery. In one, a small focus of carcinoma was identified within the resected stomach; no evidence of carcinoma was found in the other. The remaining two patients have not submitted to surgery and are free of carcinoma by endoscopy for over 1 1/2 years. In this uncontrolled study, endoscopic local injection of 5FU appeared to be effective in treating early gastric carcinoma as assessed by endoscopic and histological criteria. Surgery remains the treatment of choice for early gastric carcinoma. However, further studies of endoscopic injection therapy are needed to determine whether this treatment is appropriate for patients with early gastric carcinoma who are not surgical candidates.

Proliferative Response of Rabbit and Rat Gastric Epithelial Cells to Human Epidermal Growth Factor

The effect of human epidermal growth factor (hEGF) on gastric epithelial proliferation was studied in vitro and in vivo. In the first study, subconfluent gastric epithelial cells derived from fetal rabbit stomach were incubated with hEGF at doses of 0, 1, 10, 50, 100, 500 ng/ml and tritiated thymidine incorporation into DNA was determined. In the second study, fasted rats were given intraperitoneal injections of 100 micrograms/kg hEGF and ornithine decarboxylase activity was quantitated. In the third study, hEGF at doses of 0, 5, 10, 25, 50 micrograms/kg was administered perorally 3 times a day for 7 days. During the experiment, rats were allowed ad libitum intake of food and water. After 7 days, all rats were injected with tritiated thymidine 1 microCi/g body weight and sacrificed 1 h later. Sections from fundic and antral mucosae were processed for autoradiography. While hEGF stimulated tritiated thymidine incorporation into DNA by gastric epithelial cells in vitro, neither parenteral nor peroral administration of hEGF affected the proliferative measurements as assessed by ornithine decarboxylase activity or autoradiography in adult rat gastric fundic and antral mucosae in vivo. These results indicate that although hEGF has a direct proliferative effect on fetal rabbit gastric epithelial cells, exogenously administered hEGF has little effect on adult rat gastric mucosal steady state cell proliferation under physiological conditions.

Light and electron microscopic and autoradiographic studies on N-methyl-N-amylnitrosamine-induced rat esophageal carcinogenesis

The purpose of this study was to investigate the histogenesis of experimental tumors in the rat esophagus. Thirty rats received 0.0015% N-methyl-N-amylnitrosamine (MNAN) in the drinking water for 12 weeks. Another 30 rats received tap water. All rats then received tap water until sacrifice. Rats from each group were sacrificed immediately after MNAN administration, four weeks after, and eight weeks after. One hour before sacrifice, [3H]TdR was injected by tail vein to label proliferating cells. The entire esophagus and stomach were removed and processed for light and electron microscopy and autoradiography. The overall frequency of esophageal tumors after MNAN was 83% and did not differ significantly among the three experimental groups. Tumors were primarily papillomas and squamous cell carcinomas and occurred with equal frequency in the upper, middle, and lower thirds of the esophagus. No tumors were found in the squamous-lined forestomach. Electron microscopy revealed abundant tonofilaments, free ribosomes, and mitochondria accompanied by vacuoles. By autoradiography, esophageal epithelial proliferation was markedly stimulated in nontumorous mucosa from all three experimental groups. We conclude that MNAN ingestion for 12 weeks reliably produces papillomas and squamous cell carcinomas throughout the rat esophagus, but not in the squamouslined forestomach, and that MNAN stimulated marked epithelial proliferation which is accompanied by thickening of the epithelium in nontumorus esophageal mucosa.

Gastroduodenal Mucosal Injury by Nonsteroidal Anti-Inflammatory Drugs

SummaryNonsteroidal anti-inflammatory drugs (NSAIDs) cause gastric mucosal injury through multiple pharmacological effects (local and systemic) on mucosal defence. Although many factors contribute to mucosal defence, the most consistent and well studied effect of NSAIDs on the mechanisms of mucosal defence is the inhibition of prostaglandin generation. It is known that normal gastric mucosa has the ability to adapt to repeated administration of NSAIDs despite distinct evidence of mucosal injury after single administration. Nevertheless, the high incidence of mucosal injury in patients who are on long term NSAID therapy should not be overlooked, since gastroduodenal injury by long term use is associated with bleeding or perforation, both of which are serious complications. Among several factors responsible for mucosal defence, the role of epithelial renewal is discussed.

Effect of long-term sucralfate ingestion on antral and fundic epithelial proliferation in the rat

Sucralfate accelerates the healing of chronic gastric ulcers, but its mechanism is not well understood. We studied the effect of long-term administration of sucralfate on gastric epithelial proliferation in the rat by means of tritiated thymidine autoradiography. Rats were treated perorally with 500 mg/kg sucralfate once a day. After 28 days, rats were injected with tritiated thymidine 1µCi/g body weight and sacrificed 1 hr later. Autoradiographs from antral and fundic mucosae were prepared and a number of proliferative measurements were made. Long-term sucralfate administration produced an increase in tritiated thymidine labeling of epithelial cells and expansion of the proliferative zone in antral mucosa. These results indicate that long-term sucralfate ingestion stimulates gastric antral epithelial proliferation in the rat. In light of the fact that chronic gastric ulcers are usually located in the antral region in humans, this enhanced epithelial proliferation may contribute to the beneficial effect of sucralfate in accelerating the healing of gastric ulcers.

Effects of prostaglandins on ornithine decarboxylase activity in rat small intestine

Role of prostaglandins on feeding-associated induction of ornithine decarboxylase in small intestine was studied. Rats received intraperitoneal injection of either saline, or 16,16-dimethyl prostaglandin E2, or TRY-200 (a stable prostaglandin I2 analog), or refeeding, after a 44 hr-fast. Four hours later, mucosae from duodenum, jejunum, and ileum were scraped for subsequent measurements of enzyme activity of ornithine decarboxylase by a radiometric technique. Refeeding resulted in a profound induction of enzyme activity throughout the small intestine. Parenteral administration of prostaglandin I2 also led to a significant induction with the level similar to refeeding. The stimulatory effect of prostaglandin I2 was completely abolished by a specific and irreversible enzyme inhibitor, difluoromethylornithine. Prostaglandin E2 had a similar but lesser effect than prostaglandin I2 on the induction of the enzyme activity. Pretreatment with indomethacin, a cyclooxygenase inhibitor had no effect on feeding-associated enzyme induction. These results indicate that although exogenous prostaglandin I2 appears to be a potent stimulant for ornithine decarboxylase activity in rat small intestine, endogenous prostaglandins seem to play little or no role in feeding-associated induction of ornithine decarboxylase.

Abstracts of selected papers presented at the 29th annual meeting of the japanese society of gastroenterology

S OF SELECTED PAPERS PRESENTED AT THE 29TH A N N U A L MEETING OF THE JAPANESE SOCIETY OF GASTROENTEROLOGY K0fu, Japan, November 5--7, 1987 Chairman: Katsuhiko SUGAHARA, M.D.