Ultradian rhythms of gastric acidity

Underlying mechanism of the cyclic migrating motor complex in Suncus murinus: a change in gastrointestinal pH is the key regulator

In the fasted gastrointestinal (GI) tract, a characteristic cyclical rhythmic migrating motor complex (MMC) occurs in an ultradian rhythm, at 90–120 min time intervals, in many species. However, the underlying mechanism directing this ultradian rhythmic MMC pattern is yet to be completely elucidated. Therefore, this study aimed to identify the possible causes or factors that involve in the occurrence of the fasting gastric contractions by using Suncus murinus a small model animal featuring almost the same rhythmic MMC as that found in humans and dogs. We observed that either intraduodenal infusion of saline at pH 8 evoked the strong gastric contraction or continuously lowering duodenal pH to 3‐evoked gastric phase II‐like and phase III‐like contractions, and both strong contractions were essentially abolished by the intravenous administration of MA 2029 (motilin receptor antagonist) and D‐Lys3‐GHRP6 (ghrelin receptor antagonist) in a vagus‐independent manner. Moreover, we observed that the prostaglandin E2‐alpha (PGE2_‐α) and serotonin type 4 (5HT4) receptors play important roles as intermediate molecules in changes in GI pH and motilin release. These results suggest a clear insight mechanism that change in the duodenal pH to alkaline condition is an essential factor for stimulating the endogenous release of motilin and governs the fasting MMC in a vagus‐independent manner. Finally, we believe that the changes in duodenal pH triggered by flowing gastric acid and the release of duodenal bicarbonate through the involvement of PGE2_‐α and 5HT4 receptor are the key events in the occurrence of the MMC.

Campylobacter pylori isolated from the stomach of the monkey, Macaca nemestrina

Campylobacter pylori was isolated from the gastric mucosa in 6 of 24 pigtailed macaques (Macaca nemestrina) examined by gastric biopsy and culture; 3 isolates were recovered during gastroendoscopy, and 3 were recovered at necropsy. The isolates were morphologically and biochemically similar to the human type strain NCTC 11638, differing only in colony diameter, pigmentation, and rate of growth. Identity of the isolates was confirmed by whole-genomic DNA-DNA hybridization with the type strain. Colonization of the monkey stomachs was associated with hypochlorhydria and histologic features resembling type B chronic gastritis in humans. Host animals exhibited no morbid clinical effects of colonization, although endoscopy revealed inflammation, erythema, and friable tissue in some animals. The discovery of C. pylori occurring spontaneously in M. nemestrina extends the known range of the hosts of the organism and offers the possibility of a natural or experimental model of the infection in monkeys.

Chronobiologic factors in experimental stress ulcer

The available literature on chronobiologic factors in experimental stress ulcer is extremely small and thematically limited. It focuses almost exclusively on circadian rhythms and, within that, on rhythms related to light-dark cycles, activity and body temperature. Among these, only differences in ulcer induction related to circadian activity patterns have been adequately demonstrated. Other circadian patterns and other temporal phase relationships might be profitably explored, including those related to postnatal development. It is also likely that the important relationships between biorhythms and stress ulcer are not limited to ulcer induction. Future studies should address chronobiologic factors in predisposition, severity of illness, the probability of recovery and response to various therapeutic interventions.