The effect of pH on H. pylori urease activity in its ecological niche was studied in gastric antral biopsy specimens. Specimens were incubated in 10 mmol/liter urea solutions at pH range 3.3-8.2. Activity of urease was studied by measuring production of ammonia and change in pH of the solutions. Urease activity was reduced at pH 8.2 (1424 +/- 218 mumol/liter) but decreasing initial pH to neutral and acidic values resulted in significant maximal 6.5-fold increase in ammonia production (9491 +/- 1073 mumol/liter, P < 0.0005), which considerably raised the pH of the test solutions. Peak urease activity was between pH 5.0 and 7.0. In contrast to specimens incubated initially at pH 8.0, reincubation of washed specimens from solutions with initial pH 7.0 showed eightfold decreased urease activity. It is concluded that urease activity is markedly pH dependent with pH optima below the physiological mucosal surface pH. Furthermore, availability of urease is limited. Thus, an impaired gastric mucosal integrity allowing back diffusion of hydrogen ions may release urease activity, which might further weaken the mucus barrier and damage the gastric epithelium.
Pathological alterations of the ductal system found during ERCP in 1082 examinations were due to pancreatic carcinoma in 54 patients. The diagnosis was confirmed by laparotomy or autopsy. Predominant findings in 42 patients were stenoses, prestenotic dilatation, caliber variation, stop of contrast medium and ductal displacement in pancreatography. In 28 cholangiograms stenoses were most common which were localized in one third of the cases in the proximal common bile duct. Four types may be differentiated: a stenosing type, an obstructed type, a tapering type and a cavernous type. The stenosing type can be divided in a form with and without interruption of the contrast medium column. A precise differential diagnosis between pancreatic carcinoma and chronic pancreatitis is not possible but a long stenosis with or without stop of the contrast medium speaks in favour of a tumorous process.
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