A.L. Blum

Immunization of BALB/c mice against Helicobacter felis infection with Helicobacter pylori urease

BACKGROUND/AIMS Because Helicobacter pylori is a potentially dangerous human pathogen, the protective potential of oral immunization with H. pylori urease and its subunits was evaluated in an animal model. METHODS Mice were orally immunized with H. pylori sonicate, urease, or recombinant enzymatically inactive urease subunits and then challenged with Helicobacter felis. Control mice were sham-immunized. RESULTS H. felis colonization was present 5 days after challenge in 9 of 10 sham-immunized, 6 of 9 sonicate-immunized, and 3 of 10 urease-immunized animals (P = 0.031 vs. sham-immunized). Twelve days after challenge, urease B-immunized mice had a weaker colonization than sham-immunized controls, whereas urease A had no effect. After 70 days, most urease A- and urease B-immunized mice had cleared the colonization (10/17: P = 0.0019; 16/20: P = 0.00002 vs. sham-immunized). In urease B-immunized animals, protection was often associated with corpus gastritis. CONCLUSIONS Oral immunization with H. pylori urease protects mice against H. felis infection. Enzymatically inactive urease A and B subunits contain protective epitopes. It is unclear whether protection depends on the development of a mononuclear inflammatory response in the gastric corpus. Our observations should encourage the development of a human vaccine.

Long-term ambulatory gastric pH monitoring: Validation of a new method and effect of H2-antagonists

A new ambulatory monitoring system was evaluated for long-term measurements of gastric acidity. A close correlation was observed between values indicated by the pH electrode of the system and the pH of simultaneously aspirated gastric juice, suggesting that the electrode signaled the pH of the gastric fluid content. When the pH electrode was passed via an endoscope, and its bulb was placed against the corpus mucosa, a higher acidity was recorded as compared with gastric juice. To test whether the electrodes measured mucosal pH during ordinary test conditions, the readings of pH probes with mechanically shielded bulbs that did not come into direct contact with the mucosa were compared with those of nonshielded probes in identical positions. Similar results were observed, supporting the hypothesis that nonshielded probes measured the pH of gastric contents rather than that of the mucosa. The importance of a standardized electrode position and a fixed meal schedule was demonstrated in simultaneous recordings of antral and fundic pH. Under fasting conditions, acidity was similar in both regions. After ingestion of a meal, gastric contents were more alkaline in the fundus than in the antrum. A wide range of 24-h acidity (19-83 mmol/L) was detected in 25 healthy subjects. The day-to-day reproducibility of the method as revealed in two consecutive 24-h tests was good. The effect of cimetidine and ranitidine on gastric acidity was evaluated in 9 subjects in a double-blind, double-dummy trial. Mean 24-h H+ activity was 37.4 +/- 4.6 mmol/L under placebo medication. It was lower with cimetidine, two doses of 400 mg (23.8 +/- 4.0); cimetidine, four doses of 400 mg (10.2 +/- 3.0); ranitidine, two doses of 150 mg (10.3 +/- 3.6), and two doses of 300 mg (10.0 +/- 3.5), respectively. In conclusion, ambulatory long-term pH monitoring is a suitable method to assess the physiologic pattern of gastric acidity and the effect of antisecretory drugs.

Monoclonal immunoglobulin a prevents adherence and invasion of polarized epithelial cell monolayers by Salmonella typhimurium

BACKGROUND/AIMS Invasion of the intestinal epithelium is considered a critical step in Salmonella pathogenesis. Infection by Salmonella of cultured monolayers of polarized Madin-Darby canine kidney (MDCK) cells has been established as a simple in vitro system that mimics the invasion of intestinal enterocytes in vivo. This study analyzes the protective role of secretory immunoglobulin (Ig) A antibodies against epithelial invasion. METHODS Salmonella typhimurium was applied to MDCK cell monolayers in the presence or absence of a monoclonal, polymeric IgA antibody (Sal4) directed against an antigenic determinant exposed on the surface of wild-type S. typhimurium. RESULTS In the presence of Sal4 IgA, confluent monolayers of MDCK cells were protected against apical invasion by wild-type S. typhimurium but not against a mutant strain that lacks the Sal4 epitope. Protection was Sal4-specific, dependent on the concentration of Sal4 in the apical medium, and occurred at IgA concentrations at which agglutination of IgA-bacterial complexes was observed. When MDCK cell monolayers were formaldehyde-fixed before incubation with Salmonella to prevent bacterial invasion, adhesion of Salmonella occurred in the absence of IgA and in the presence of control IgA but not in the presence of Sal4 IgA. CONCLUSIONS IgA alone can prevent bacterial adherence and invasion of epithelial cells in the absence of other immune or nonimmune protective mechanisms.

Does smoking interfere with the effect of histamine H2-receptor antagonists on intragastric acidity in man?

The interaction between smoking and the effect of histamine H2-antagonists on intragastric acidity was examined in a double blind double dummy placebo controlled study. Healthy volunteers, 11 smokers and 10 non-smokers, were given, on four separate days at least one week apart, either placebo or cimetidine 800 mg nocte or ranitidine 2 X 150 mg per day or ranitidine 300 mg nocte. Tablets were taken at 2115 and 0900 h. Smokers smoked a cigarette hourly from 0700 to 2300 h. Breakfast, lunch, and dinner were standardised. Intragastric acidity was measured with a combined intragastric glass electrode and a solid state recorder. The subjects were fully ambulatory. The three histamine H2-receptor antagonist regimens were less effective (p = 0.04) in smokers than in non-smokers, but the difference between acidity of smokers and non-smokers was small. Means of medians of pH during a 24-h period with placebo, cimetidine 800 mg, ranitidine 2 X 150 mg and ranitidine 300 mg were 1.6, 2.3, 3.1, and 2.7 in smokers and 1.5, 2.7, 3.2, and 3.1 in non-smokers, respectively. In a second part of the study seven chronic smokers were reexamined after acutely stopping smoking: inhibition of gastric acidity by histamine H2-receptor antagonists was similar before and after withdrawal. Smoking does not affect intragastric acidity in untreated volunteers and only slightly decreases the effectiveness of histamine H2-receptor antagonists on intragastric acidity. This effect best in part explains the unfavourable effect of smoking on healing of peptic ulcer in patients treated with these drugs.

Measurement of monoamines and their metabolites in the interstitial fluid of the gut

Bundles of hollow dialysis fibers were surgically implanted into the submucosa of the stomach and intestine allowing collection of an interstitial fluid (ISF) dialysate. Measurement of monoamines and their metabolites in ISF was performed using high-performance liquid chromatography with electrochemical detection. The local concentration of L-5-hydroxy-tryptophan (5-HTP) in ISF from the antrum was determined in conscious rats after intraperitoneal loading with 5-HTP. The metabolite was similarly evaluated after the administration of levodopa (L-DOPA). Validation of ISF dialysis as a method for determining changes of biogenic amine concentration in the extracellular fluid was determined for the antrum, duodenum, and colon in dogs after the oral or subcutaneous administration of 5-HTP as a precursor of serotonin and 5-hydroxyindole acetyl acetic acid. The proposed procedure provides a novel approach in pharmacologic studies, where a direct correlation between the distribution of a drug and its metabolites (pharmacokinetics) and their effects (pharmacodynamics) has to be measured.

Eradication of esophageal varices: Assessment by endosonography

Eradication of esophageal varices is usually assessed by endoscopy. The aim of this study was to evaluate by endosonography whether patients after apparent eradication of esophageal varices show residual vascular structures in the esophageal wall. Methods: Ten patients with liver cirrhosis were included in this study after confirmed eradication of esophageal varices by endoscopy. Three patients had Child-Pugs grade A, five had Child-Pugs grade B and two had Child-Pugs grade C. After routine endoscopy the proximal ten cm to the Z-line were investigated first by miniprobe endosonography (MP) (Olympus UM-3R, 20 MHz); this was performed by the investigator who had performed standard endoscopy. This was followed by routine endosonography (RES) (Olympus UM-20, 7.5 MHz) performed by an independent investigator unaware of MP findings. The number, the diameter and the length of vascular structures (VS) in the three inner sonngraphic layers of the esophageal wall were assessed by MP and RES. Results: In 9 patients, residual VS could be found by MP and in 8 patients with RES, The results are summarized in the following table; mean diameter and the length of VS are given in ram:

Sodium phosphate (NaP) and cisapride for precolonoscopy bowel cleansing: A prospective, randomized study

BackgroundA the quality of preparation (% of the mucosa visualised) was evaluated by endoscopists. Results: NaP was easier to take than PEG (mean score of overall facility 1.8; SD 1.0 vs 2.9; SD 1.3; p=0.0001); 88% of patients with NaP and 62% with PEG would repeat the same preparation (p=0.0001). Cisaprid did not have any effect on tolerability and on the quality of cleansing.