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The formation of acute gastric lesions depends upon the balance between the aggressive factors promoting mucosal damage and the natural defense mechanisms. Previous studies have shown that melatonin inhibits gastric acid secretion, enhances the release of gastrin, augments gastric blood flow (GBF), increases the cyclooxygenase-2 (COX-2)–prostaglandin (PG) system and scavenges free radicals, resulting in the prevention of stress-induced gastric lesions. Besides the pineal gland, melatonin is also generated in large amounts in the gastrointestinal tract and due to its antioxidant and anti-inflammatory properties; this indole might serve as local protective endogen preventing the development of acute gastric damage. The results of the present study indicate that stress-induced gastric lesions show circadian variations with an increase in the day time and a decline at night. These changes are inversely related to plasma melatonin levels. Following pinealectomy, stress-induced gastric mucosal lesions were more pronounced both during the day and at night, and were accompanied by markedly reduced plasma melatonin levels with a pronounced reduction in mucosal generation of prostaglandin E2 (PGE2), GBF and increased free radical formation and by small rise in plasma melatonin during the dark phase. We conclude that stress-induced gastric ulcerations exhibit a circadian variation with an increase in the day and attenuation at night and that these fluctuations of gastric stress ulcerogenesis occur also after pinealectomy, depending upon the interaction of COX–PG and free radicals, probably mediated by the changes in local gastric melatonin. [ABSTRACT FROM AUTHOR]

Background: The members of the family of heat shock factors coordinate the inducible transcription of heat shock genes in response to diverse stimuli. Any disturbances in signal transduction may lead to the attenuation of heat shock proteins synthesis and to cell death due to apoptosis. It has been shown by others that different nuclear factors, such as nuclear factor interleukine 6 or signal transducer and activator of transcription 3, co-operate with heat shock factors, mostly enhancing their activator effect on heat shock proteins genes expression. Therefore, we sought to determine whether apoptosis induced in the gastric epithelium exposed to live Helicobacter pylori might occur due to the elimination of HSP70 expression and deregulation of the heat shock response of the cell. Materials and Methods: Experiments were performed on KATO III gastric epithelial cells exposed to live cagA, vacA expressing Hp over different periods of time. Total cellular RNA, cytoplasmic and nuclear proteins were isolated for polimerase chain reaction, western-blot, electrophoretic mobility shift assay, decoy and co-immunoprecipitation studies. Results: We found that in human gastric epithelium exposed to Helicobacter pylori, heat shock factor 1 is bound and restrained in complexes by phosphorylated signal transducer and activator of transcription 3 protein. In consequence, heat shock factor 1 bound up with phosphorylated signal transducer and activator of transcription 3 protein is unable to activate HSP70 protein synthesis in KATO III cells under stress conditions. Helicobacter pylori also causes changes in bax/bcl-2 cellular equilibrium, leading to the induction of apoptosis. Conclusions: The observed phenomenon might be the mechanism whereby gastric epithelium adapts to the infection of Helicobacter pylori, eliminating cells which are damaged or altered by bacterial cytotoxic products from the tissue. [ABSTRACT FROM AUTHOR]

Conclusion. Stimulation of pancreatic sensory nerves by capsaicin produced secretory effects probably caused, at least in part, by the release of CGRP. Background. In the pancreas calcitonin gene-related peptide (CGRP) has been localized in the sensory nerves, but its physiological role is unknown. This study was undertaken to compare the changes of pancreatic enzyme secretion produced by CGRP and by stimulation or destruction of sensory nerves. Methods. To stimulate sensory nerves, low doses of capsaicin (0.25-0.5 mg/kg) were given intraduodenally to the conscious rats with chronic pancreatic fistula. To inactivate sensory nerves high doses of capsaicin (100 mg/kg) were given subcutaneously 10 d before tests. For the in vitro experiments pancreatic slices and isolated pancreatic acini were prepared from intact and capsaicin-denervated rats. Results. In conscious rats, CGRP given subcutaneously (5-10 ~tg/kg) and low doses of capsaicin given intraduodenally reduced basal pancreatic secretion. In isolated pancreatic acini, CGRP (10-10 -10-6 M), but not capsaicin, increased basal or secretagog-stimulated amylase release. In pancreatic slices (containing nerve fibers) capsaicin (10-10 10-6 M) increased enzyme secretion, and this secretion was abolished by previous inactivation of sensory nerves by this neurotoxin. Capsaicin deactivation did not affect the secretory response of pancreatic acini to CGRP, cerulein, or urecholine. Sensory denervation by capsaicin did not change basal protein secretion, but reduced that produced by feeding or diversion of pancreatic juice to the exterior during first 2 h of the tests. [ABSTRACT FROM AUTHOR]

The inhibitory effects of intravenous secretion on the gastric acid responses to a meal and to pentagastrin were studied in seven duodenal ulcer patients. A test meal of 10% peptone adjusted to pH 5·0 was introduced into the stomach and the Fordtran and Walsh method was used to measure the gastric acid output by monitoring the rate at which a solution of 0·3 M sodium bicarbonate had to be added to keep the pH of the gastric content constant at the value of 5·0. A constant dose of secretin (1 U/kg-hr) significantly depressed the serum gastrin response to a meal and produced an inhibition of acid secretion by about 70% of the control level. Secretin inhibited the acid response induced by pentagastrin by about 60% and simultaneously provoked a pancreatic bicarbonate output sufficient to neutralize about 60% of the gastric acid output to pentagastrin. We conclude that secretin is a strong inhibitor of gastric secretion in duodenal ulcer patients induced by a meal and by pentagastrin. [ABSTRACT FROM PUBLISHER]