Biomedical subjects
S F Moss
Publications and source records attributed to S F Moss.
Induction of gastric epithelial apoptosis by Helicobacter pylori.
BACKGROUND: Helicobacter pylori may promote gastric carcinogenesis through increasing gastric epithelial cell proliferation. How H pylori does so is unknown. Programmed, non-necrotic, cell death (apoptosis) occurs throughout the gut and is linked to proliferation. It was hypothesised that H pylori may induce hyper-proliferation through increasing apoptosis. AIM: To measure the effect of H pylori infection on gastric epithelial apoptosis in situ. PATIENTS: Patients with duodenal ulcers treated to eradicate H pylori and patients with H pylori negative non-ulcer dyspepsia. METHODS: Retrospective quantification of apoptotic epithelial cells in situ from formalin fixed biopsy specimens, counted after staining by terminal uridine deoxynucleotidyl nick end-labelling. RESULTS: In the uninfected stomach, apoptotic cells were rare and situated in the most superficial portion of gastric glands (mean 2.9% of epithelial cells). In H pylori infection, they were more numerous and were located throughout the depth of gastric glands, comprising 16.8% of epithelial cells, falling to 3.1% after H pylori eradication, p = 0.017. Apoptotic cell number did not correlate with the degree of histological gastritis. CONCLUSIONS: These results suggest that H pylori induces epithelial apoptosis in vivo. Increased apoptosis may be the stimulus for a compensatory hyperproliferative and potentially preneoplastic response in chronic H pylori infection.
Increased small intestinal apoptosis in coeliac disease.
BACKGROUND: Coeliac disease (CD) mucosa is flattened despite epithelial hyperproliferation. AIMS: To establish mechanisms of cell loss in CD. PATIENTS: 14 controls, 17 active CD patients, and 16 maintained with gluten free diet. METHODS: Programmed cell death was examined in small intestinal biopsy specimens by staining fragmented DNA using terminal uridine deoxynucleotidyl nick end labelling (TUNEL), in comparison with haematoxylin and eosin stained adjacent sections. Double staining with anti-CD45 antibodies determined the origin of apoptotic cells. Apoptosis was graded from 1-3 (< 5, 5-20, > 20% respectively). Proliferating cells, immunostained by Ki-67 (MIB-1) antibody, were counted. RESULTS: Apoptotic cells were seen rarely by haematoxylin and eosin but more readily by TUNEL. In controls, 1.4 +/- 0.2% of epithelial cells were apoptotic (mean grade 1.1), mainly located in the upper villus. In active CD, frequent apoptotic cells were distributed throughout the crypt-villus unit (mean grade 2.4), decreasing after treatment to 1.1 (p < 0.001) even when still histologically abnormal. CD45 antibodies rarely stained apoptotic cells in active CD. The number of TUNEL positive cells correlated with proliferating cell number (p < 0.001). CONCLUSION: Enterocyte apoptosis is greatly increased in untreated CD, correlates with proliferation, and falls to normal with a gluten free diet, before histological improvement. Increased apoptosis may be responsible for villous atrophy in CD.
Novel C-2 substituted carbapenem derivatives. Part II. Synthesis and structure-activity relationships of isoxazolin-2-yl, isoxazolidin-2-yl and 2-pyrazolin-2-yl carbapenems generated using 1,3-dipolar cycloaddition chemistry.
A series of carbapenems containing novel C-2 semisaturated heterocyclic substituents were synthesised by 1,3 dipolar cycloaddition reactions of nitrile oxides, nitrile imines and a nitrone to 2-vinylcarbapenem. The isoxazoline and isoxazolidine compounds showed potent antibacterial activity but moderate stability to human dehydropeptidase 1 (DHP-1). Stability to DHP-1 was improved by methyl substitution in the isoxazoline ring, but at the expense of antibacterial activity. The pyrazolines exhibited excellent stability to DHP-1, but reduced potency against Gram-negative organisms.
Fecal and rectal mucosal diacylglycerol concentrations and epithelial proliferative kinetics.
Fecal diacylglycerol (DAG) concentrations have been suggested as biomarkers for colonic neoplasia because of their potential to be absorbed in the colon and to stimulate epithelial cell proliferation. The interrelationships among nutrient intake, fecal and mucosal DAG, and colonic proliferative markers have not previously been studied. We designed a pilot study to evaluate the feasibility of evaluating these interrelationships in 12 volunteers who had a history of colonic adenomatous polyposis. Total mucosal DAG concentrations were not related to fecal DAG concentrations, but mucosal DAG correlated inversely with the whole crypt labeling index. Dietary intake did not alter fecal DAG concentrations. However, the percentage of calories from dietary fat correlated positively with the whole crypt labeling index. Fiber and calcium intake showed a positive correlation with the labeling index in the upper 40% of the crypt. The present pilot study failed to demonstrate a correlation between dietary components and fecal and total mucosal DAG. Additional studies relating fecal DAG with mucosal proliferation will require the evaluation of DAG concentrations in subcellular compartments of mucosal cells and/or measurement of fecal DAG fatty acid composition.
Helicobacter pylori seroprevalence and colorectal neoplasia: evidence against an association.
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Reciprocal changes in antral gastrin and somatostatin mRNA in pernicious anemia.
Somatostatin is involved in the regulation of gastrin by intragastric pH in animal models. To investigate whether this is so in man, we measured gastrin and somatostatin mRNA in endoscopic biopsies from six patients with hypergastrinemia and achlorhydria due to pernicious anemia and 12 age- and sex-matched controls. The pernicious anemia patients had significantly higher fasting plasma gastrin concentrations with a median (range) of 640 (420-3500) pmol/liter compared with 5 (2-58) pmol/liter, P < 0.001. The median gastrin mRNA/rRNA ratio was 10.4 (3.7-38.0) in the pernicious anemia patients compared with 1.7 (0.7-8.3) in the controls (P < 0.02), and it correlated strongly with the plasma gastrin concentration, r = 0.93, P < 0.0001. In contrast, the median somatostatin mRNA/rRNA ratio was lower in the pernicious anemia patients 0.84 (0.58-2.32) versus 2.04 (0.05-6.47) in the controls, P < 0.05. These findings suggest that in pernicious anemia gastric neutralization leads to hypergastrinemia through the modulation of antral gastrin synthesis by somatostatin.
Cytokine gene expression in Helicobacter pylori associated antral gastritis.
Infection of the gastric antrum by Helicobacter pylori is characterised by a cellular inflammatory infiltrate. Whether cytokines are involved in the pathogenesis of this gastritis has been investigated by studying the effect of eradicating H pylori on the expression of genes encoding the cytokines interleukin 8 (IL-8) and tumour necrosis factor alpha (TNF-alpha) in the antral mucosa. Gastric antral biopsy specimens were taken from nine patients with duodenal ulcers and cytokine transcripts were identified and quantified by northern blotting. After H pylori had been eradicated the chronic inflammatory infiltrate decreased in all the patients and the polymorphonuclear infiltrate virtually disappeared. Expression of genes also decreased. After eradication, the median TNF-alpha mRNA/rRNA fell to 48% (p = 0.02) and the median IL-8 mRNA/rRNA fell to 5% (p = 0.004) of initial values. These results support the role of increased synthesis of these cytokines in the pathogenesis of the gastritis.
Acid hypersecretion in duodenal ulcer patients.
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Use of endoscopic biopsies and microelectrodes to study human gastric acid secretion in vitro.
We have investigated the possibility of measuring acid secretion from human gastric mucosa in vitro as a potential pharmacological preparation. We used open-ended 10 microns-tip, lix-based glass microelectrodes to measure the pH of the mucus layer of gastric biopsies superfused with a HEPES buffered solution in an organ bath. With no drugs added the pH of the mucus layer of biopsies from the body of the stomach stayed constant but the pH of antral biopsies fell slightly by a median of 0.12 pH units over 80 min (P < 0.05). Stimulation of the biopsies with 1-100 microM histamine produced a dose-dependent decrease in pH which was significantly greater in biopsies from the gastric body than from the antrum. 500 pM pentagastrin produced a median fall in pH of 1.20 (P < 0.01) which was prevented by the prior addition of 100 microM omeprazole or 10 microM ranitidine. Omeprazole or ranitidine alone produced slight rises in the median pH of 0.47 (P < 0.05) and 0.26 (P < 0.05) units respectively. Those biopsies which were infected with Helicobacter pylori had a slightly elevated initial pH of about 0.2 of a pH unit (P < 0.05). This novel system provides a means to study human gastric acid secretion in vitro and may be valuable in the testing of new drugs on the stomach.
Metronidazole uptake by sensitive and resistant isolates of Helicobacter pylori.
The development of metronidazole resistance in Helicobacter pylori has become an important factor in the clinical use of this drug in the treatment of gastritis and peptic ulcers. The mechanism for the development of resistance is not known but may involve factors which influence metronidazole uptake and metabolism. In this study, a simple and reliable HPLC assay for metronidazole was developed and the uptake of the drug from broth cultures of both resistant and sensitive strains of H. pylori was investigated. Resistance to metronidazole was determined by the E test as well as plate and broth assays. In the presence of the antibiotic (approximately 10 mg/L), metronidazole-sensitive strains were killed within 24 h and there was a concomitant fall in the concentration of metronidazole in the broth. In contrast, the killing of resistant strains of H. pylori was associated with < 10% loss of antibiotic from broth. These differences in metronidazole uptake are ascribed to alterations in the mechanisms of action of the drug in sensitive and resistant strains.
Acid secretion and sensitivity to gastrin in patients with duodenal ulcer: effect of eradication of Helicobacter pylori.
The effect of ulcer healing with eradication of Helicobacter pylori (H pylori) on gastric function was investigated in nine patients with duodenal ulcer disease. One month after eradication there were significant reductions in both basal plasma gastrin concentration, from a median (range) of 19 (1-22) to 6 (2-15) pmol/l (p < 0.05), and of basal acid secretion from 8.3 (2.4-24) to 2.6 (1.4-8.1) mM H+/h, (p < 0.01). The peak acid secretion rate was unchanged from 37 (16-59) to 37 (21-59) mM H+/h. After treatment there was no change in the parietal cell sensitivity to stepped infusions of gastrin heptadecapeptide: the median concentration of gastrin required for 50% of maximal acid secretion (EC50) was 41 (14.8-126) before and 33 (23-125) pmol/l after eradication of H pylori. The metabolic clearance rate of gastrin was also unaffected by the eradication of H pylori. Thus eradication of H pylori infection from patients with active duodenal ulcers is accompanied by falls in both basal gastrin release and basal acid secretion without a change in the parietal cell sensitivity to gastrin. Cyclical changes in H pylori infection may cause the variations in basal acid secretion that are seen in duodenal ulcer disease.
Pleural involvement in the carcinoid syndrome.
Tissue fibrosis is a recognized complication of the carcinoid syndrome but pleural changes have not been described. Prompted by the finding of severe pleural thickening in two patients with the metastatic carcinoid syndrome but no thoracic metastases or previous pleural disease we reviewed the chest radiographs and CT scans in 50 patients with the carcinoid syndrome investigated from 1981 to 1990. Pleural abnormality was noted in 14 of the 50 patients (28%), five of whom had other possible causes for pleural disease. However, nine (18%) patients had 'idiopathic' pleural thickening. Pleural disease had developed within 2 years of the diagnosis in all cases, and seven of the nine patients had fibrosis elsewhere (heart valves, skin or mesentery). There were no features to suggest a more rapid disease progression in the patients with pleural disease. We suggest that the pleural abnormality is a complication of metastatic carcinoid disease.
Effect of Helicobacter pylori on gastric somatostatin in duodenal ulcer disease.
Infection of the gastric antrum by Helicobacter pylori is associated with recurrent duodenal ulcer disease but the mechanism of ulcerogenesis is unclear. Since pathways inhibiting gastric secretion are defective in patients with duodenal ulcers, we investigated whether H pylori interferes with the normal gastric inhibition that is mediated by somatostatin. We studied 28 patients with active duodenal ulcers in whom H pylori was eradicated successfully. In 18 patients, we measured the density of antral somatostatin-immunoreactive cells and in a further 10 subjects, the amount of somatostatin mRNA before and after eradication of H pylori was determined. After eradication, the median density of somatostatin-immunoreactive cells increased significantly from 9 (range 3-47) to 19 (6-57) cells per mm muscularis mucosa (p = 0.025). The median somatostatin mRNA/rRNA ratio increased from 50 (25-160) to 95 (40-180) (p = 0.01). The number of gastrin cells and quantity of gastrin mRNA did not change significantly. Our results suggest that in duodenal ulcer disease, gastric secretory function is disinhibited through the suppression of mucosal somatostatin.
Sucralfate diminishes basal acid output without affecting gastrin, H. pylori or gastritis in duodenal ulcer patients.
Twelve patients with active duodenal ulcer disease and Helicobacter pylori infection were treated with 1 g sucralfate q.d.s. for 1 month. Ulcers healed in 8 of the 12 patients without an alteration in the H. pylori-associated antral gastritis. Sucralfate produced a significant fall in basal acid output in all the patients, from a median of 4.8 (range 2.1-12.1) to 1.6 (0.4-8) mmol/h, P less than 0.01, whereas peak acid output was unchanged from 41 (21-59) before to 38 (24-55) mmol/h after treatment. Basal plasma gastrin concentrations and the meal-stimulated integrated gastrin response were not altered significantly by sucralfate: 8 (2-17) pmol/L and 732 (188-1045) pmol. min/L pre-treatment and 6 (2-17) pmol/L and 600 (140-1302) pmol. min/L post-treatment, respectively. The fall in basal acid output observed may contribute to prolonged duodenal ulcer remission after treatment with sucralfate.
Intestinal lymphangiectasia associated with angiofollicular lymph node hyperplasia (Castleman's disease).
A patient presenting with predominantly gastrointestinal symptoms and a history of myocardial infarction was found to have ascites, hepatosplenomegaly, para-aortic lymphadenopathy, thrombocytosis, and a paraproteinaemia. A jejunal biopsy specimen showed lymphangiectasia and histology of the spleen and lymph nodes showed angiofollicular hyperplasia or Castleman's disease of the hyaline vascular type. This association has not previously been described and, moreover, systemic symptoms are unusual in this variant of Castleman's disease.
Gastric antral vascular ectasia: maintenance treatment with oestrogen-progesterone.
Gastric antral vascular ectasia ('watermelon stomach') is a rare cause of chronic gastrointestinal bleeding and various medical and surgical treatments have been described. We report a patient in whom an oestrogen-progesterone preparation successfully controlled recurrent blood loss.
pH-dependent secretion of gastrin in duodenal ulcer disease: effect of suppressing Helicobacter pylori.
Patients with duodenal ulcers and Helicobacter pylori infection have elevated plasma gastrin concentrations which fall after suppression of the organism. This may be due to H. pylori elevating the pH of the antral mucous layer, therefore preventing luminal acid from inhibiting gastrin release. To test this idea, we measured the plasma gastrin concentrations under basal conditions and in response to 4% peptone when the gastric lumen was maintained at pH 2.5 and at pH 5.5 by gastric perfusion. We studied 11 duodenal ulcer patients before and after suppression of H. pylori. Gastrin concentrations were significantly higher before suppression of H. pylori than after treatment in all three states; basal gastrin (pmol/l) fell from 9.2 (3.7-23, median and range) to 5.1 (1.7-15) after treatment; from 11.3 (3.8-29) to 5.9 (5.7-6.1) at pH 2.5 and from 15.2 (3.9-32) to 7.15 (6.1-14) at pH 5.5. The ratio of peptone-stimulated gastrin at pH 2.5/pH 5.5 was similar before (0.8; 0.5-1.7) and after (0.8; 0.5-1.1) suppression of H. pylori. These results indicate that infection with H. pylori increases basal and peptone-stimulated plasma gastrin concentrations, and that this response is independent of luminal pH.