ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

This review of the past year's literature focuses on progress in the elucidation of the pathways and mechanisms controlling gastric acid secretion at the central, peripheral, and intracellular levels. Injection of thyrotropin-releasing peptide and neuropeptide Y into the central nervous system stimulates acid secretion; the effects are mediated via the vagus nerve. Elevated intracranial pressure and increasing age also stimulate acid secretion, whereas γ-aminobutyric acid, tachykinins, and prostaglandins act centrally to inhibit acid secretion. The stimulatory effect of gastrin and acetylcholine on acid secretion may be mediated via release of histamine, possibly from enterochromaffin-like cells. Histamine stimulation of the parietal cell is accompanied by increasing cellular levels of cyclic AMP and dephosphorylation of type II cyclic AMP-dependent protein kinase. Besides releasing histamine, muscarinic agonists appear to stimulate the parietal cell directly via the M3-receptor subtype. This subtype is also coupled to release of intracellular calcium and influx of extracellular calcium. Glucagon-like peptide, low concentrations of ethanol, cigarettes, and coffee stimulate acid secretion whereas neurotensin, oxyntomodulin, serotonin, interleukins, and high concentrations of ethanol inhibit acid secretion. Vasoactive intestinal polypeptide exerts dual stimulatory and inhibitory actions on acid secretion; the inhibitory effect is mediated by release of somatostatin. Candidate enterogastrones include secretin, cholecystokinin, somatostatin, and possibly peptide YY.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

This article reviews advances over the past year in our understanding of the regulation of gastric pepsinogen secretion. These advances are placed in the context of previous observations regarding signal transduction in chief cells. The actions of stimulatory agents,ie, cholinergic agonists, cholecystokinin, secretin, vasoactive intestinal polypeptide and so on are described. Advances in understanding interactions between signaling pathways and the actions of inhibitory peptides, like peptide YY and neuropeptide Y, are also considered. The review concludes with an analysis of where investigation in this field appears to be directed at present.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

This paper reviews the major advances made during the past year in understanding the ability of the gastroduodenal mucosa to resist injury. In particular, advances have been made in our understanding of the neural pathways and chemical messengers that mediate the hyperemic response to superficial injury; the regulation of gastric and duodenal bicarbonate secretion; the importance of mucus in mucosal defense and the physical properties that contribute to this role; the endogenous enzymes that prevent or reduce oxidant-induced injury; and the contribution of growth factors, polyamines, and prostaglandins to adaptive responses to injury.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Helicobacter pyloriis causally related to inflammation and ulceration of the stomach and is a risk factor for the development of gastric carcinoma. The mechanisms by which this organism induces cell injury are currently not well understood. Detailed histologic examination of the gastric mucosa support a “leaking roof” model of ulcerogenesis, with progressive focal cellular destruction and exposure of the lamina propria. The cellular damage may result from direct action of soluble factors produced byHelicobacter, such as ammonia and cytotoxin, or indirect stimulation of the inflammatory cascade by activation and degranulation of leukocytes. The immune response againstHelicobactermay damage the gastric mucosa by producing antibodies that cross-react with gastric epithelium. The inflammatory process results in aberrant HLA-DR expression on the epithelial cells.Helicobacteralso increases acid and pepsin secretion by stimulating gastrin and pepsinogen production, which could exacerbate any cellular damage caused by cytotoxins or inflammatory mediators, leading to focal necrosis and ulceration.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Growth factors regulate mucosal growth and adaptation to mucosal injury and intestinal resection. A number of peptide growth factors have been identified, including epidermal growth factor, transforming growth factor-α, insulinlike growth factor-l, and fibroblast growth factors. A series of articles are reviewed which emphasize that a number of peptide growth factors promote epithelial cell proliferation in response to injury. These studies provide some initial insights into mechanisms involved in ulcer healing. Understanding of physiologic events in the gastric and intestinal phases of gastric acid secretion have been aided by specific peptide receptor antagonists and monoclonal antibodies capable of neutralizing circulating peptide hormones. Application of these techniques has revealed that gastrin is a principal mediator of meal-stimulated acid secretion. Furthermore, somatostatin and cholecystokinin have been shown to inhibit gastric acid secretion when acid and fat, respectively, are introduced into the intestine. The concept of nonadrenergic noncholinergic inhibitory neural mechanisms has been reconfigured with the demonstration that nitric oxide is capable of inhibiting gastrointestinal smooth muscle and acting as a mediator of vasodilatation. It is clear that nitric oxide is an important inhibitory neurotransmitter and cell-derived mediator within the gastrointestinal tract.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The past year's literature on the treatment of peptic ulcer disease can be conveniently divided into four categories: 1) comparison of traditional antisecretory and topical agent therapy, which ranges from antacids to potent agents like omeprazole, 2)Helicobacter pyloritreatment, 3) treatment options for recalcitrant ulcers or ulcers due to nonsteroidal anti-inflammatory drugs, and 4) some safety information.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Recent advances in the pathophysiology of peptic ulcer indicate that 1) a defect in angiogenesis factor is important and that basic fibroblast growth factor leads to rapid ulcer healing, 2) peptic ulcer may be an infectious disease and the addition of 2 weeks of antibiotics to conventional ulcer therapy reduces recurrence from 95% to 12%, and 3) nonsteroidal anti-inflammatory drugs are increasingly more important in precipitating ulcer complications. Proximal gastric vagotomy, the elective treatment of choice for duodenal ulcer, is exceedingly safe but is associated with a 15% ulcer recurrence rate. A new operation, pylorus and anteroseromuscular flap-preserving gastrectomy, is designed to reduce the recurrence rate without increasing complications. Several prospective randomized trials have established that in perforated duodenal ulcer, proximal gastric vagotomy significantly reduces postoperative ulcer recurrence and the need for subsequent operation. With respect to gastric carcinoma, a significant increase in the percentage of early gastric cancers and a significant reduction in operative mortality rates have been reported.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

This review highlights points of interest in the year's literature on upper gastrointestinal hemorrhage. Clinical studies of upper gastrointestinal hemorrhage in patients with acquired immunodeficiency virus, or recovering from cardiac surgery, or who are taking corticosteroids are reported. There has been little progress in diagnostic aspects: clinical features cannot reliably predict high-risk endoscopic findings and red cell scanning is unhelpful in localizing the site of upper gastrointestinal bleeding. The diagnostic and therapeutic contributions of angiography are reviewed. General management measures include recognizing the safety of early refeeding in patients who have no high-risk features. Likewise, early discharge from the hospital may be possible; hospital admission may even be avoided altogether if appropriate criteria are met. Drug therapy continues to have no major role in the management of bleeding ulcers. This year, therapeutic endoscopy is again the major area of interest. Studies have continued to show benefit from the simple maneuver of injecting 1:10,000 adrenaline around the ulcer; more sophisticated measures probably do not produce better results. The place of surgery is being reevaluated in the light of therapeutic endoscopy, but when surgery is required, a conventional operation (vagotomy and pyloroplasty, partial gastrectomy) may be better than minimal surgery (underrunning or excising the ulcer).

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Disorders involving the motility of the stomach and small intestine are significant medical problems. We have selected articles in four areas where exciting new advances have been made toward understanding these neuromuscular diseases. First, a recent paper has shown that in women gastrointestinal symptoms often wax and wane with the menstrual cycle, increasing at the midluteal phase, peaking at the onset of menstruation, and then rapidly decreasing until the next cycle. In our experience, this pattern has been strikingly apparent in these disorders. Second, we readdress the importance of the hypothalamus and its contribution to the overall expression of these neuromuscular disorders. Releasing factors that regulate pituitary function are emerging as important chemical modulators of systemic endocrine function in addition to their neuroendocrine effect on the gastrointestinal tract. Analogues of one of these releasing factors and an analogue of a neuropeptide are becoming priceless pharmacologic agents as well as important biologic probes for understanding pathophysiology. Third, the possible action of viruses as agents that cause these disorders, and the relationship of these disorders with chronic fatigue syndrome, are also discussed. Finally, we review an interesting paper regarding one of the mechanisms of diarrhea. These are exciting times in gastroenterology; we are at the frontiers of medical therapy and progress.

ISSN:0267-1379    

出版商:OVID    

年代:1992

数据来源: OVID