Effects of ranitidine bismuth citrate on Helicobacter pylori motility, morphology and survival.

AIM: The effects of the anti-ulcer agents ranitidine bismuth citrate (RBC), ranitidine hydrochloride (R) and colloidal bismuth citrate (BC), on Helicobacter pylori motility, morphology and survival were examined to determine whether the clinical effectiveness of RBC might be linked to a specific action that inhibits bacterial motility. METHODS: H. pylori from patients with duodenal ulcer or non-ulcer dyspepsia were exposed to RBC and BC at bismuth concentrations ranging from 12.5 to 50 microg/mL, and R at ranitidine concentrations ranging from 12.5 to 50 microg/mL for a brief period (< 15 min), 6 h and 24 h. Bacterial motility was assessed with a Hobson BacTracker, bacterial morphology by transmission electron microscopy, and growth inhibition by counting colony-forming units. RESULTS: H. pylori motility was diminished with RBC and BC but not R. However, the effect of RBC was markedly greater than that of BC at each bismuth concentration and time of exposure tested: (i) brief exposure to RBC/bismuth 50 microg/mL but not to BC, resulted in a significant loss of motility without loss of viability or change in cell morphology, and (ii) bacteria were immobilized, and lost viability after exposure to RBC/bismuth 50 microg/mL for 24 h but not to BC. Morphological destruction caused by RBC differed from that by BC: after 24 h exposure to the highest concentration tested, cell fragmentation and flagella detachment occurred more frequently with BC than RBC, but the latter produced greater disruption of intracellular structures. CONCLUSIONS: RBC suppresses growth of H. pylori, and has a specific inhibitory effect on the bacterial motor mechanism. These pharmacological actions are likely to contribute to the clinical effectiveness of the agent.

Some effects of tripotassium dicitrato bismuthate on gastric secretion and the mucus barrier.

The effect of tripotassium dicitrato bismuthate (De-Nol) on the breakdown of the gastric mucus barrier was investigated by measuring the output of mucus glycoprotein in pentagastrin-stimulated secretion from 13 patients before and after treatment for peptic ulcer, and by examining the accumulation of dialysable peptides and amino acids (DPAA) in stimulated secretion from ten of these patients. The accumulation of DPAA was significantly reduced after De-Nol (by 54%) and to a greater extent than was the output of mucus glycoprotein (by 27%). These observations are consistent with a decrease in the rate of breakdown of the mucus barrier as a result of De-Nol treatment. De-Nol significantly reduced pepsin output (by 32%) in the same group of patients. Comparison of the change in pepsin output with the change in accumulation of DPAA in stimulated juice indicated that De-Nol increases the resistance of the mucus barrier to acid-pepsin proteolysis and/or inhibits the secretion of amino acids and peptides from gastric mucosa.

Breakdown of gastric mucus in presence of Helicobacter pylori.

The potential of Helicobacter pylori to degrade gastric mucus was examined. Colonies of H pylori cultured from antral mucosal biopsy specimens of patients with non-autoimmune gastritis were washed with sterile saline, passed through a sterilisation filter, and the filtrate examined for urease, protease, and mucolytic activity. The filtrate failed to hydrolyse bovine serum albumin, or to degrade stable mucus glycoprotein structures of high particle weight that had been separated from human gastric mucus on Sepharose 2B. The high particle weight mucus glycoprotein was, however, extensively degraded when incubated with H pylori filtrate (which possessed urease activity) in the presence of 2 M urea, to release fragments of Mr approximately 2 X 10(6). The high particle weight mucus glycoprotein was also broken down to a comparable extent when incubated with Jack bean urease in the presence of 2 M urea, or 1 M ammonium carbonate, or 40 mM carbonate-bicarbonate buffer (pH 8.7), but not when treated with 4 M urea alone, or Jack bean urease alone. These results indicate that the loss of high particle weight mucus glycoprotein in gastric mucus from patients with gastritis and gastric ulcers is unlikely to be due to the mucolytic action of an extra-cellular protease produced by H pylori, but it may result from the destabilising effects of a carbonate-bicarbonate buffer, generated at the mucosal surface when H pylori urease hydrolyses transuded plasma urea.

Motility of Helicobacter pylori in a viscous environment.

BACKGROUND: Patients with gastroduodenal disease produce gastric mucus of higher viscosity, and mucins that are of a smaller size, than normal. We have modelled these changes to the mucus layer in solutions of methylcellulose, and measured bacterial motility in biopsied mucus, to assess how they might influence the movements of Helicobacter pylori. METHODS: Motilities of Helicobacter pylori were measured in solutions of methylcellulose with molecular mass of 14 and 41 kDa, and in biopsied mucus with a Hobson BacTracker. Four parameters of bacterial motility were quantified: curvilinear velocity (CLV), path length, track linearity and curvature rate. RESULTS: All H. pylori were motile in methylcellulose solutions, and had optimal motilities at a viscosity of 3 cp (CLV in methylcellulose of 41 kDa, for instance, was 33 +/- 1.4 microm/s (mean +/- SEM) and the path length in methylcellulose of 41 kDa was 22.4 +/- 2 microm). At higher viscosities, mean CLVs, path lengths and curvature rates decreased, and track linearities increased in direct proportion to the increase in methylcellulose viscosity. Bacteria become non-motile at a viscosity of 50 cp in methylcellulose of 14 kDa, and at 70 cp in methylcellulose of 41 kDa. Mean CLVs, path lengths and curvature rates (but not track linearities) were greater in methylcellulose of 41 kDa than in methylcellulose of 14 kDa at each viscosity tested. Motilities of H. pylori from patients with duodenal ulcer or non-ulcer dyspepsia in methylcellulose solutions were not significantly different. H. pylori had poor motility in biopsied mucus, but became highly motile when biopsied mucus was diluted with saline. CONCLUSIONS: The viscosity-motility profiles of H. pylori in methylcellulose and the motilities of H. pylori in biopsied mucus suggest (1) that H. pylori may have poor motility in mucus at the epithelial surface, but high motility at the luminal surface of the mucus layer, and (2) that the increased mucus viscosity and decreased mucin size in patients with gastroduodenal disease act in combination to decrease H. pylori motility in vivo.

Hypothesis: Helicobacter pylori, urease, mucus, and gastric ulcer.

Ammonia, released in the gastric mucosa by the action of Helicobacter pylori urease on transuded plasma urea, curtails the biosynthesis of mucus and/or causes the mucus to be disassembled at the mucosal surface. These changes facilitate colonisation by H pylori and may promote gastric ulcer formation.

The relationship between Helicobacter pylori motility, morphology and phase of growth: implications for gastric colonization and pathology.

To explore the relationship between Helicobacter pylori motility, morphology and phase of growth, bacteria were isolated from antral biopsies of patients with duodenal ulcer or non-ulcer dyspepsia, and grown in liquid medium in batch and continuous culture systems. Motilities and morphologies of H. pylori in different phases of growth were examined with a Hobson BackTracker and by transmission electron microscopy. Morphologies of bacteria grown in vitro were also compared with those of bacteria in antral biopsies from patients with non-autoimmune gastritis. H. pylori had poor motility in lag phase, became highly motile in mid-exponential phase and lost motility in the decline phase of growth. Motilities of bacteria in the same phase of growth from patients with duodenal ulcer or non-ulcer dyspepsia were not significantly different. In the mid/late-exponential phase of growth bacteria had helical morphologies and multiple polar flagella, typical of H. pylori in the gastric mucus layer. In the decline phase of growth bacteria shed flagella, and had precoccoidal or coccoidal morphologies. These findings support the view that helical and coccoidal H. pylori are in different phases of growth with different roles in gastric colonization, indicate that bacterial motility per se is unlikely to be a determinant of H. pylori pathology, and suggest that H. pylori in the antral mucus layer is in a state of continuous (exponential phase) growth.

Influence of blood group and secretor status on carbohydrate structures in human gastric mucins: implications for peptic ulcer.

1. The content and distribution of carbohydrate was examined in mucus glycopolypeptides from human antral mucosae. 2. The mean amount of carbohydrate per 1000 amino acid residues was found to be similar in glycopolypeptides with A, B or H activity. It was slightly, though significantly, less in glycopolypeptides lacking these determinants, because carbohydrate chains were of a shorter average length than in the A-, B- or H-active preparations. This difference was reflected in the sizes of oligosaccharide-alcohols released from representative glycopolypeptides with alkaline borohydride. 3. Differences between A-, B- or H-active and non-secretor glycopolypeptides in terms of the mean number of carbohydrate chains per 1000 amino acid residues were found to be small, and without significance. 4. The average number of peripheral monosaccharide units per 1000 amino acid residues was greater in A-active than in H-active, and least in non-secretor, glycopolypeptides. This order was reversed for monosaccharide units incorporated into skeletal (core plus backbone) structures. The difference in each case was statistically significant. 5. These findings suggest that the increased risk of peptic ulcer associated with blood group O and non-secretor status is unlikely to be attributable to an inherent deficiency in the protective mucus layer, linked to differences between mucins that are associated with A, B or H activity. Other hypotheses linked to infection with Helicobacter pylori are examined.

Changes to mucins in uninvolved mucosa and at the tumour site in gastric adenocarcinoma of intestinal type.

1. Mucin histochemistry is markedly altered in the stomach in intestinal-type adenocarcinoma. To increase understanding of these changes we have examined the content and distribution of carbohydrate in mucus glycopolypeptides isolated from non-malignant antrum, and from the uninvolved gastric mucosa and tumour site of patients with this disease. 2. The content of carbohydrate declined by 12.6% (P = 0.02) in mucus glycopolypeptides from uninvolved gastric mucosa when compared with those from non-malignant antrum, and by a further 25.4% (P < 0.001) in mucus glycopolypeptides from the tumour site. The first of these changes was accompanied by a significant decrease in the number of carbohydrate chains/1000 amino acid residues, and a significant increase in the number of monosaccharide units in each carbohydrate chain. The second of these changes was accompanied by significant decreases in both the number of carbohydrate chains/1000 amino acid residues, and in the number of monosaccharide units in each carbohydrate chain. 3. The number of sulphated monosaccharide units/100 carbohydrate chains increased from a mean of 7.2 in mucus glycopolypeptides from non-malignant antrum to a mean of 27.2 (P < 0.001) in preparations from uninvolved gastric mucosa and 22.7 (P < 0.001) in preparations from the tumour site. 4. Evidence is presented that these structural changes to mucus glycopolypeptides from the malignant stomach are due to an abnormal mucin biosynthesis by metaplastic goblet cells and/or immature gastric-type mucous cells within the uninvolved mucosa, and immature mucous cells at the tumour site.