ISSN:0012-2823    

DOI:10.1159/000201002

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

It has become apparent recently that a variety of small GTPases (small GTP-binding proteins or smgs), related to the oncogene ras, are involved in many cellular functions, especially membrane traffic and cytoskeleton regulation. This review will summarize some of the major themes that are emerging, focusing on the presence and possible functions of these smgs in the gastrointestinal tract. In addition, new cellular locations and functions for heterotri-meric G-proteins, previously believed to be solely associated with plasma membrane receptors, are becoming evident and will be discussed here.

ISSN:0012-2823    

DOI:10.1159/000201003

出版商:S. Karger AG    

年代:1993

数据来源: Karger

ISSN:0012-2823    

DOI:10.1159/000201067

出版商:S. Karger AG    

年代:1993

数据来源: Karger

ISSN:0012-2823    

DOI:10.1159/000201004

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Somatostatin is widely distributed throughout the human gastrointestinal system. There it is found in neurons and fibers of both the submucosal and the myenteric plexus and the pancreas as well as in the D cells of the stomach, gut and pancreatic islets. Whereas in the intestinal nervous system, in the duodenum and the pancreas, somatostatin-14 appears to be the predominant molecular form, the endocrine-type D cells of the intestine primarily contain somatostatin-28. Somatostatin peptides may act very differently at different sites, as hormones, as paracrine substances or neurotransmitters. Because of this complexity of action, very little is known about the physiological effects of somatostatin in the gastrointestinal tract. In contrast, the pharmacological actions of natural synthetic somatostatin have been thoroughly studied and have given rise to many therapeutic applications. Octreotide, an analogue with a longer half-life and higher potency, has greatly facilitated the clinical application of somatostatin. This review deals with the pharmacological effects of octreotide on different gastrointestinal functions. The somatostatin analogue exerts a long-lasting inhibitory action on gastric acid, pancreatic enzyme and bicarbonate secretion as well as on bile flow. It is also able to inhibit stimulated intestinal secretion, the release of neuropeptides from the gut and the pancreas. It can also prolong orocecum transit time and prevent gallbladder contraction. It inhibits absorption of nutrients and exerts inhibitory effects on splanchnic hemodynamics. It is because of these actions that somatostatin has attracted so much attention in the treatment of different gastrointestinal disorders.

ISSN:0012-2823    

DOI:10.1159/000201070

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The effect of intravenous omeprazole (40 and 80 mg) on the gastric and duodenal potential difference (PD) and pH was investigated in 9 healthy volunteers. Gastric PD and pH increased significantly (p < 0.05) following omeprazole, and the increases were equal following the two doses. No changes were found in duodenal PD or pH. It has been claimed that gastric PD changes following acid secretion inhibition with cimetidine and glucagon might be due to changes in the parietal cell surface area. Omeprazole causes no changes in the parietal cell structure, and the changes in gastric PD following omeprazole might therefore be ascribed to changes in mucosal electrophysiologic transport or resistance.

ISSN:0012-2823    

DOI:10.1159/000201005

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

In the present study, the effect of graded intravenous infusions of human epidermal growth factor (hEGF) 0.005, 0.05 and 0.25 μg/ml, with or without 4 mg/kg i.p. indomethacin pretreatment, on rat duodenal bicarbonate secretion was investigated. Perfused duodenal loops were prepared in rats which were given intravenous infusions of hEGF with or without indomethacin. Duodenal pH and pCO2 were measured at 5-min intervals for 45 min, and bicarbonate secretion was calculated. Compared to control, each dose of hEGF caused a significant dose/response rise of duodenal bicarbonate secretion. Prostaglandin release was abolished by indomethacin pretreatment. Indomethacin-pretreated rats had a significant reduction of bicarbonate secretion which was still higher than in controls. These results provide evidence that duodenal bicarbonate secretion induced by hEGF is only partly accounted for by a prostaglandin-dependent mechanism

ISSN:0012-2823    

DOI:10.1159/000201006

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Somatostatin and its analogue, octreotide, produce dramatic decreases in splanchnic arterial blood flow and portal venous pressure while preserving cardiac output and systemic blood pressure. A limited number of prospective randomized clinical trials of somatostatin and octreotide have noted superiority to placebo and equivalence to vasopressin in control of variceal hemorrhage. Moreover, several studies (Saari et al., Kravetz et al, McKee et al.) have reported a significant decrease in morbid side effects when somatostatin or octreotide is used to control variceal bleed. In addition, McKee et al. noted a significant reduction in mortality when octreotide was compared to balloon tamponade therapy for variceal hemorrhage. Somatostatin and octreotide are particularly advantageous in controlling vigorous variceal hemorrhage in hemodynamically unstable patients. This control often enables other effective therapy, endoscopic sclerotherapy and surgical (or radiologic) shunting, to be safely performed.

ISSN:0012-2823    

DOI:10.1159/000201071

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Capsaicin and papaverine are potent vasorelaxants with strong gastroprotective activity against damage induced by absolute ethanol. This protection was originally attributed to the increase in gastric mucosal blood flow (GBF) and the present study was designed to determine the possible role of nitric oxide (NO) and prostaglandins (PG) in the protective and hyperemic effects of capsaicin and papaverine on rat gastric mucosa. We found that the pretreatment with capsaicin (0.1-0.5 mg/kg i.g.) or papaverine (0.1-2 mg/kg i.g.) reduced dose dependently the area of ethanol-induced lesions, the ED50 being 0.3 and 1 mg/kg, respectively. This protection was accompanied by a gradual increase in the GBF. Intravenous injection of Nω-nitro-L-arginine (L -NNA; 1.2-5 mg/kg), a selective blocker of NO synthase, which by itself caused only a small increase in ethanol lesions, reversed dose dependently the protective and hyperemic effects of capsaicin and papaverine against ethanol-induced damage and attenuated the increase in GBF induced by each of these agents alone. This deleterious effect of L -NNA on the gastric mucosa and the GBF was fully antagonized by L -arginine (200 mg/kg i.v.) but not by D-arginine. L -arginine partly restored the decrease in GBF induced by L -NNA. Pretreatment with indomethacin (5 mg/kg i.p.), which suppressed the generation of PG by 85%, slightly enhanced the mucosal lesions induced by ethanol but failed to affect the fall in GBF induced by this irritant. Gastroprotective and hyperemic effects of capsaicin and papaverine were partly reversed by indomethacin suggesting that endogenous PG are also implicated in these effects. Addition of L -NNA to indomethacin completely eliminated both the protective and hyperemic effects of capsaicin and papaverine. We conclude that both NO and PG contribute to the gastroprotective and hyperemic effects of capsaicin and papaverine on the gastric mucosa

ISSN:0012-2823    

DOI:10.1159/000201007

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

This communication deals with the emergency control of variceal bleeding rather than the prevention of rebleeding. The current main options of oesophageal tamponade, emergency sclerotherapy and drug therapy are discussed, with particular reference to the use of somatostatin. Sandostatin (Sandoz, Basel), a synthetic long-acting somatostatin analogue, was found to reduce transhepatic venous gradient by 30% with no effect on systemic haemodynamics in a study of 16 stable cirrhotic patients. In a trial comparing intravenous infusion of Sandostatin (SMS) to oesophageal tamponade (OT) in active variceal bleeding, 18 of 20 bleeds in the SMS group and 19 of 20 bleeds in the OT group were controlled at 4 h. Ten in the SMS group and 14 in the OT group had no further bleeding during the 48-hour study period. Thus SMS may be useful in the temporary control of active variceal bleeding.

ISSN:0012-2823    

DOI:10.1159/000201072

出版商:S. Karger AG    

年代:1993

数据来源: Karger