Antiulcer activity of hypertonic solutions in the rat: possible role of prostaglandins.

The effects of hypertonic solutions on gastric acidity and on experimental gastric and duodenal ulcers as well as on gastric prostaglandins (PGs) were studied in the rat. The oral administration of a 10% NaCl solution resulted in complete absence of free acidity and very significant reductions in total acidity 24 h after pyloric ligation. The antiulcer effect of hypertonic saline was studied in three experimental models. In pyloric-ligated rats, both the incidence and the severity of gastric ulcers were remarkably reduced by hypertonic saline treatment. Indomethacin-induced gastric erosions were significantly reduced by hypertonic NaCl or sorbitol and completely prevented by hypertonic xylitol. Cysteamine-induced duodenal ulcers were also significantly reduced by hypertonic solutions of NaCl, xylitol or sorbitol. In the latter model, indomethacin potentiated the ulcerogenic effect of cysteamine and also reduced the efficacy of the hypertonic NaCl gavage. The possible contribution of PGs to these effects was further investigated by analysing PGE in the gastric mucosa and juice. Rats treated orally with hypertonic NaCl solutions had several-fold higher PGE contents in their gastric mucosa as well as higher PGE levels in the gastric juice. It is concluded that hypertonic solutions stimulate endogenous PGE biosynthesis and also exert profound antiulcer effects in the rat. A causal relationship between the two phenomena is suggested.     

Clinical and technical factors affecting pH and other biomarkers in exhaled breath condensate

Exhaled breath condensate (EBC) pH appears to be a robust measure of asthma. However, the association between EBC pH and clinical factors and airway inflammatory markers remains unclear. The objectives of this study were to investigate the factors determining EBC pH in asthmatic children, and the reproducibility and effects of collection devices on EBC pH in nine healthy, nonsmoking adults. EBC was collected once from asthmatic children using EcoScreen, and from adults over 3 consecutive days using both RTubes and EcoScreen. EBC pH was measured immediately in non-deaerated samples by microelectrode pH meter. Concentrations of 8-isoprostane, cysteinyl leukotrienes (cys-LT), and leukotriene B4 (LTB4) were measured using enzyme immunoassay. Exhaled nitric oxide concentration (FeNO) was measured by chemiluminescence. Fifty-eight asthmatics (16 intermittent, 12 mild persistent, and 30 moderate-to-severe persistent) were recruited. EBC pH was lower among patients with moderate-to-severe persistent than intermittent asthma (P = 0.046). This marker correlated inversely with disease severity score (rho = -0.276, P = 0.036), but not FeNO or other EBC biomarkers. Bland-Altman analyses found pH but not other EBC biomarkers to be reproducible, which were confirmed by its low coefficient of variation (2.7%; range, 0.4-5.2%). There was poor correlation between pH in EBC collected by RTube and EcoScreen (rho = 0.059, P = 0.784). Factor analysis selected four factors that explained 67.5% of the total variance, and EBC pH clustered with both cys-LT and LTB4. In conclusion, our results suggest that pH in non-deaerated EBC is influenced by asthma severity in children. EBC pH measurement is reproducible, but is dependent on the collection devices used.     

Lansoprazole in the treatment of gastrooesophageal reflux disease in childhood

BACKGROUND: Acid suppressive therapy is the mainstay of pharmacologic treatment of gastro-oesophageal reflux disease. Use of proton pump inhibitors in children is still limited and has only included omeprazole in a few controlled studies. AIM: To determine efficacy of lansoprazole, a relatively new proton pump inhibitor, on symptoms and oesophagitis in a group of children with gastro-oesophageal reflux disease refractory to H2 receptor antagonists. The required dose of the drug for inhibiting gastric acidity was also determined. PATIENTS AND METHODS: A series of 35 children (median age: 7.6 years, range: 3-15) with oesophagitis refractory to H2 receptor antagonists received a 12-week therapeutic course with lansoprazole. Prior to the study children underwent symptomatic and endoscopic assessment, oesophageal manometry and 24-hour intragastric and intra-oesophageal pH test. The latter was repeated after one week of therapy while patients were on treatment in order to monitor the degree of acid suppression and adjust the dose of the drug. Symptomatic assessment and endoscopy were repeated at the end of the trial RESULTS AND CONCLUSIONS: In 12 patients (group A), the initial dose of the drug was efficacious (1.3 to 1.5 mg/kg/day), whereas in 23 [group B) the initial dose (0.8 to 1.0 mg/kg/day) was increased by half because of insufficient inhibition of intragastric acidity (i.e., when the intra-gastric pH remained below 4.0 for more than 50% of the recording time). Nine patients in group A (75%) and 8 in group B (53.5%) healed (chi2: 3.6, p<0.05); 1 patient in group A [8.3%) and 7 in group B (30.5%) remained unchanged (chi2: 6.9, p<0.01); 2 patients in group A and 8 in group B improved and underwent a further month of therapy. The two groups did not differ as far as concerns baseline pH, endoscopic and clinical variables. In both groups, those patients failing to respond at the end of the trial showed a more impaired oesophageal motility than improved or healed patients. The drug was well tolerated and no significant laboratory abnormalities occurred. In children with gastro-oesophageal reflux disease refractory to H2 receptor antagonists, a 12-week course of lansoprazole is effective both in healing oesophagitis and improving symptoms. An initial dose of 1.5 mg/kg/day of the drug is suggested. However, if during treatment, patients remain symptomatic the dose should be increased and a prolonged intra-gastric and intra-oesophageal pH test performed to evaluate the acid suppression efficacy of the adjusted dose. A short course of lansoprazole appears to be safe and well tolerated in paediatric age.     

The Effect of Zeolite Features on the Dehydration Reaction of Methanol to Dimethyl Ether: Catalytic Behaviour and Kinetics

The synthesis of dimethyl ether (DME) is an important step in the production of chemical intermediate because it is possible to prepare it by direct hydrogenation of CO₂. This paper reports the effect of different zeolitic frameworks (such as: BEA, EUO, FER, MFI, MOR, MTW, TON) on methanol conversion, DME selectivity and catalyst deactivation. The effect of crystal size, Si/Al ratio and acidity of the investigated catalysts have been also studied. Finally, the kinetic parameters (such as: ∆H, ∆S and ∆G) have been evaluated together with pre-exponential factor and activation energy for catalysts with FER and MFI structure topology.     

Problems with the interpretation of gastric pH measurement

Summary The present study examines some of the assumptions underlying the use of intragastric pH-metry for assessing the degree of therapeutic gastric inhibition. Three separate studies were performed to determine the relationship between pH and titratable hydrogen ion concentration in gastric juice and to assess the relationship between the concentration of acid and the rate of gastric secretion. The concentration of acid derived from pH measurements tended to be lower than the titrated hydrogen ion concentration. The difference between the two readings — the buffered hydrogen ion concentration — was increased by the presence of food and was reduced during gastric secretory inhibition with ranitidine. The titrated hydrogen ion concentration reflected more accurately the amount of hydrochloric acid added to a container in vitro than pH measurement. However, in vivo even the measurement of titratable acidity was poorly correlated with the volume of secreted gastric juice so that measurement of gastric acid concentration does not permit inferences about the rate of gastric secretion. The results of the present study indicate that measurement of intragastric pH is unsatisfactory for assessing gastric secretion, particularly in response to a food stimulus, so that measurement of gastric acidity alone does not reflect the rate, or changes in the rate, of gastric acid secretion.     

Probing Microenvironmental Acidity in Lyophilized Protein and Vaccine Formulations Using Solid-state NMR Spectroscopy

Biophysical and biochemical instability of therapeutic proteins in the solution state may necessitate the development of products in the solid form, due to their enhanced stability. Lyophilization is a widely used method to ensure dry state stabilization of biological products. A commonly encountered issue is the pH shifts that can occur due to undesired crystallization of a buffer component, resulting in loss of protein activities. However, it is technically challenging to noninvasively investigate the physicochemical environment in the lyophile matrix. In this work, we demonstrate an approach based on solid-state NMR to investigate the microenvironmental acidity in lyophilized protein formulations, using histidine, a commonly used buffer agent, as a molecular probe. The solid-state acidity in the lyophilized matrix can be assessed by monitoring the chemical shift changes of histidine. The protonation and tautomeric states of histidine lyophilized at a range of pH values from 4.5 to 11.0 were identified from full ¹³C and ¹⁵N resonance assignments in one-dimensional and two-dimensional NMR experiments. The results demonstrated a pH-dependence of histidine chemical shift in the amorphous state. Moreover, we successfully applied this protocol to investigate the microenvironmental pH in lyophilized formulations of the HPV vaccine and lactate dehydrogenase protein.     

24小时胃内酸度监测评价多种抑酸剂静脉使用对十二指肠溃疡患者的抑酸效果

目的　对比各种常用抑酸剂对十二指肠溃疡出血患者胃酸的抑制效果。方法　运用随机、开放的方法分析５０ 例十二脂肠溃疡出血患者,分别使用奥美拉唑静脉滴注、法莫替丁静脉注射、雷尼替丁静脉注射、西咪替丁静脉注射或滴注。持续监测患者２４ 小时胃内ｐＨ 动态变化的情况、不同胃内ｐＨ值持续时间的百分率、２４ 小时平均胃内ｐＨ 和中位ｐＨ 值。结果　只有奥美拉唑８０ｍｇ／天组可达到胃内平均ｐＨ 和中位ｐＨ 均＞６ ,法莫替丁８０ｍｇ／天组可达到胃内平均ｐＨ 和中位ｐＨ 均＞ ４,其他治疗组均未达到ｐＨ＞ ４ 。２４ 小时胃内ｐＨ＜ ４ 、ｐＨ＜ ５、ｐＨ＜ ６ 时间所占百分比依次递增为：奥美拉唑８０ｍｇ／天组、法莫替丁８０ｍｇ／ 天组、雷尼替丁２００ｍｇ／天组、西咪替丁８００ｍｇ／天组。各Ｈ２ 受体拮抗剂组与奥美拉唑静脉滴注组比较,差异均有显著性。结论　静脉使用质子泵抑制剂的抑酸效果明显优于Ｈ２ 受体拮抗剂,尤其是奥美拉唑静脉滴注胃内ｐＨ 提高持续的时间较长。     

Silicoaluminates as “Support Activator” Systems in Olefin Polymerization Processes

In this work we report the polymerization behaviour of natural clays (montmorillonites, MMT) as activating supports. These materials have been modified by treatment with different aluminium compounds in order to obtain enriched aluminium clays and to modify the global Brönsted/Lewis acidity. As a consequence, the intrinsic structural properties of the starting materials have been changed. These changes were studied and these new materials used for ethylene polymerization using a zirconocene complex as catalyst. All the systems were shown to be active in ethylene polymerization. The catalyst activity and the dependence on acid strength and textural properties have been also studied. The behaviour of an artificial silica (SBA 15) modified with an aluminium compound to obtain a silicoaluminate has been studied, but no ethylene polymerization activity has been found yet.     

温度和酸度对田鼠型鼠疫耶尔森菌psa位点的转录调控研究

目的研究温度和酸度对田鼠型鼠疫耶尔森菌psa位点的转录调控作用。方法首先设计相关跨基因引物,用RT-PCR方法验证psa位点的相关操纵子结构。扩增操纵子首基因上游启动子区500 nt序列,并克隆入pRW50质粒β-半乳糖苷酶基因的上游,将重组质粒转入鼠疫菌中,通过测定β-半乳糖苷酶活性差异来判断不同温度（26和37℃）和酸度（pH 6.0和pH 8.0）对psaE和psaA的调控关系。最后提取鼠疫菌在上述不同温度和酸度条件下的总RNA,采用引物延伸实验进一步明确温度和酸度对psaA的调控关系。结果与结论 RT-PCR结果证实了田鼠型鼠疫菌的psa位点由操纵子psaEF和psaABC构成;半乳糖苷酶和引物延伸实验结果显示在37℃、pH 6.0培养条件下psaABC的转录水平最高,而psaEF的转录水平无明显变化,提示psaA的表达水平在37℃酸性条件下表达量最高,psaE则不受温度和酸度的调控。     

丹参口服液中总酚酸性成分的含量测定

目的控制丹参口服液的内在质量.方法采用比色法对其总酚酸性成分进行含量测定.结果回收率为(98.84±0.86)%,RSD为0.87%.结论该方法简便快速,准确度高,重现性好.