负载型丝光沸石催化剂的催化性能研究

运用二元碱氮置换吸附红外光谱法、分子筛孔径分布测定技术、XPS技术,考察了丝光沸石表面酸性与孔结构的相互关系、钯在丝光沸石上分布情况和价态及其与沸石的相互作用。结果表明,随着丝光沸石脱铝程度的增加,表面出现大量不规整晶格,存在较多的次级孔道。强质子酸中心主要分布在它的“外表面”。钯在其表面富集,并与“外表面”上的质子酸中心协同作用,促进了轻质烷烃异构化反应。     

Acid and Hyperosmolal Solutions in the Upper Intestine of Chronic Gastric Fistula Rats Inhibit Gastric Acid Secretion by Different Mechanisms

In chronic gastric fistula rats 0.20 M HC1 and 1200 mOsm × kg^-1 solution of polyethylene glycol (PEG) infused into a duodenal loop anastomosed to the jejunum (Roux-en-Y) produced maximal inhibition of pentagastrin-stimulated acid secretion, which amounted to 60% and 50%, respectively. In the present study in Roux-en-Y rats with gastric fistula, perfusion of the loop with hyperosmolal (1200 mOsm × kg^-1 of PEG solution) 0.20 M HC1 produced a greater reduction of the maximal response to pentagastrin (91% inhibition) than perfusion with 0.20 M HC1 (64%), suggesting that HC1 and hyperosmolal solution inhibit secretion by different mechanisms. The maximal acid response to histamine was more resistant to inhibition than that to pentagastrin; 0.20 M HC1 inhibited secretion by 43%, 1200 mOsm × kg^-1 of PEG solution by 42%, and hyperosmolal 0.20 M HC1 by 60%. The results suggest that HC1 and hyperosmolal solution also inhibit histamine-stimulated secretion by different mechanisms. The anatomical sites of the mechanisms remain to be established.     

Pathophysiology of gastric acid secretion in patients with chronic renal failure: influence of Helicobacter pylori infection

OBJECTIVES: The incidence of gastroduodenal diseases is high in patients with chronic renal failure (CRF). However, gastric acidity in CRF has been reported to range in level from low to high. Moreover, it remains unknown whether Helicobacter pylori infection influences gastric acidity in such patients. Thus, we aimed to clarify the pathophysiological perturbation in gastric acidity and to determine the influence of H. pylori infection in CRF. DESIGN: Case-control study. SETTING: A university hospital. SUBJECTS: Twenty-seven patients with CRF and 24 control patients, presenting with either gastrointestinal symptoms, positive faecal occult blood, or anaemia (haemoglobin <10 g dL(-1)). MEASURES: The patients underwent gastroduodenal endoscopy with simultaneous determination of H. pylori infection. Gastric ammonium concentration, serum pepsinogen I and II, and basal gastrin level were measured. Thereafter, gastric acid secretion was monitored by 24-h intragastric acidity measurement with calculation of pH-3 holding time (%) (hours showing pH>3/24 h). RESULTS: In the CRF group, pH-3 holding time of H. pylori (+) subgroup was significantly greater than that of H. pylori (-) subgroup (71.2 +/- 32.4% vs. 32.8 +/- 30.0%, mean +/- SD; P=0.03). Pepsinogen I/II ratio was inversely correlated with pH-3 holding time in the control and CRF groups. Gastric ammonium concentration in CRF/H. pylori (+) subgroup (14.1 +/- 9.2 mmol L(-1)) was significantly higher than in CRF/H. pylori (-) (2.5 +/- 2.7 mmol L(-1); P=0.002) and control/H. pylori (+) subgroups (6.1 +/- 4.2 mmol L(-1); P=0.01). Serum gastrin level was significantly higher in the CRF group than in the control group (297 +/-343 pg mL(-1) vs. 116 +/- 69 pg mL(-1); P=0.02) as a whole. However, there was no significant correlation between serum creatinine and gastrin levels in the CRF group. Gastrin level in CRF/H. pylori (+) subgroup was significantly higher than in CRF/H. pylori (-), control/H. pylori (+), and control/H. pylori (-) subgroups (423 +/-398 pg mL(-1) vs. 113 +/- 79, 124 +/- 78, and 96 +/-43 pg mL(-1), respectively; P=0.01-0.03). Significant positive correlations amongst pH-3 holding time, ammonium and gastrin concentrations were found in the CRF group, but not in the control group. CONCLUSIONS: CRF without H. pylori infection primarily shows a tendency for high gastric acidity, but without hypergastrinaemia. Persistent H. pylori infection in CRF leads to decreased acidity and, consequently, to fasting hypergastrinaemia via a feedback mechanism. The hypoacidity in CRF with H. pylori infection appears to result from neutralization of acid by ammonia as well as from gastric atrophy. Thus, H. pylori infection status critically determines perturbation in gastric acidity and fasting gastrin level in CRF.     

The effect of omeprazole on 24 h intragastric pH and fasting plasma gastrin during low dosage (10 mg) in the morning or the evening

Abstract The effect of a low dose of omeprazole on intragastric acidity and fasting plasma gastrin concentration was measured in eight subjects with duodenal ulcer in remission. Intragastric acidity was measured during a baseline 24 h period. This was then repeated after 14 days of dosage with 10 mg of omeprazole administered daily, either in the morning or the evening, using a randomized, double-blind cross-over design. The median 24 h pH level rose significantly from a baseline of 1.6, to 3.1 and 3.5 during morning and evening dosages, respectively. However, variability in the response to this dose was substantial: three subjects exhibited no discernible change in 24 h median acidity on two occasions, while in others it was reduced by greater than 99%. Fasting plasma gastrin concentrations were not significantly altered by the administration of 10 mg of omeprazole daily for 2 weeks.     

Early effects of lafutidine or rabeprazole on intragastric acidity: which drug is more suitable for on-demand use?

Background Medication for the relief of heartburn should have the rapid onset of action required for on-demand use. We studied the inhibition of gastric acid secretion by lafutidine and rabeprazole, given in single doses to fasting and postprandial subjects.Methods A total of 22 healthy male, Helicobacter pylori-negative volunteers participated in this randomized, two-way crossover study. They were randomly assigned to receive a single oral dose of 10mg lafutidine or 20mg rabeprazole after fasting overnight (12 subjects, fasting study) or after eating a test meal (noodles, 364kcal; protein, 10.1g; fat, 16g; carbohydrates, 44.9g; NaCl, 1.1g; 10 subjects, postprandial study). Intragastric pH was monitored continuously for 6h after treatment. The other drug was given after a washout period of at least 7 days, and intragastric pH was similarly monitored.Results In the fasting study, lafutidine sustained pH at >3 and >4 during the second, third, fourth, fifth, and sixth hours of the study for significantly longer than rabeprazole. During the first 6h after treatment, lafutidine sustained pH at more than 2, 3, 3.5, 4, 5, 6, and 7 longer than rabeprazole. In the postprandial study, lafutidine sustained pH >3 and >4 for longer periods than rabeprazole during the third, fourth, fifth, and sixth hours of the study. During the first 6h after treatment, lafutidine sustained pH at more than 2, 3, 3.5, 4, 5, 6, and 7 longer than rabeprazole.Conclusions Lafutidine 10mg produces a prompter rise in intragastric pH than rabeprazole 20mg in fasting and postprandial Helicobacter pylori-negative male subjects.     

Validation of the Blood Quininium Resin Test for Assessing Gastric Hypochlorhydria

Although gastric hypochlorhydria is a risk factor for gastroenteritis and for gastric cancer, no reliable, inexpensive, noninvasive test exists for screening or epidemiologic studies. We aimed to evaluate the sensitivity and specificity of the blood quininium resin test (bQRT) for hypochlorhydria, against pH monitoring. Twelve fasting adult volunteers—seven with and five without H. pylori infection—ingested 80 mg/kg of quininium resin twice, once with and once without acid suppression. Gastric pH was monitored for 75 minutes; serum samples were obtained at times 0 and 75 minutes. The bQRT levels were compared to gastric pH, controlling for omeprazole use and H. pylori infection. Subjects with a median recorded pH ≥3.5 were considered hypochlorhydric. Using a bQRT level of 10 as a cutoff for hypochlorhydria, the sensitivity and specificity of the bQRT were 100% and 37.5%, respectively. The bQRT predicted omeprazole use more accurately than pH monitoring. In conclusions, The bQRT has a high sensitivity for hypochlorhydria, making it potentially useful in populations with a high prevalence of hypochlorhydria. In its current formulation, the bQRT's low specificity makes it less useful in low-risk population. Supported in part by NIH grant 5 M01 RR000070 from the National Center for Research Resources, and in part by NIH grant RO1 DK53689.     

Single Gastric Biopsy in Subjects with Low Acid Secretion after Maximal Histamine Stimulation

Examinations of 83 patients and 13 healthy subjects with the augmented histamine test and gastric biopsy show that a maximal acid secretion lower than 10 mEq HCl/hour signifies a diffuse gastritic lesion, the type of which can be verified by a single gastric biopsy. Detailed investigations of the nature and clinical course of gastritis, however, require repeated tests of gastric function and multiple gastric biopsies.     

Screening for Atrophic Gastritis: Comparison of the Results of Azure-A Test and Uropepsin Determination with Gastric Biopsy in a Rural Population

A ‘high risk group’ consisting of 32 persons was selected from 1046 inhabitants of a Finnish rural commune by means of the Azure-A test and uropepsin determination. Gastric biopsy was performed in 24 persons, and the results were compared with those of a representative series of 142 persons ‘selected at random’ from the same population. Significantly more atrophic gastritis was found in the ‘high risk group’ than in the ‘group selected at random’. During two years 2 cases of pernicious anaemia and 2 cases of gastric carcinoma were found in the ‘high risk group’ while in the control group consisting of 1014 persons no case was found.     

Peptic Ulceration and Obstructive Disease

Augmented histamine, gastric biopsy, and barium meal studies were made of 44 patients with respiratory insufficiency. Despite the fact that 80% evidenced atrophic gastritis, 27% had peptic ulcers and high acid secretion. More comprehensive studies of total acid production and of multiple gastric biopsies arc desirable.     

Pentapeptide Infusion Test

Pentapeptide infused intravenously in graded doses provoked at a dose of 1.5 μg per kg per hour a peak HCl output, which was significantly higher than the HCl secretion induced by intravenous histamine in a dose of 40 μg per kg per hour in five healthy subjects. Pentapeptide infusion test at a dose of 1.5 μg per kg per hour appears to be a very reproducible and safe mode of gastric stimulation, giving a sustained and high level of gastric secretion in 20 subjects, including 10 healthy men and 10 duodenal ulcer patients. Infusion test with pentapeptide has some advantage over histamine stimulation in so far as it is safe, and almost completely free of side-effects. No difference in the response curves to pentapeptide and histamine was found between the normal subjects and duodenal ulcer patients.