Amiloride sensitivity of proton-conductive pathways in gastric and intestinal apical membrane vesicles

Summary Passive proton permeability of gastrointestinal apical membrane vesicles was determined. The nature of the pathways for proton permeation was investigated using amiloride. The rate of proton permeation (k _H ⁺ was determined by addition of vesicles (pH _i = 6.5) to a pH 8.0 solution containing acridine orange. The rate of recovery of acridine orange fluorescence after quenching by the acidic vesicles ranged from 4 × 10^–3 (gastric parietal cell stimulation-associated vesicles; SAV) and 5 × 10^–3 (duodenal brush-border membrane vesicles; dBBMV) to 11 × 10+^–3 sec^–1 (ileal BBMV; iBBMV). Amiloride, 0.03 and 0.1 mm, significantly reduced the rate of proton permeation in dBBMV and iBBMV, but not gastric SAV. The decreases in k _H ⁺ were proportionately greater in iBBMV as compared with dBBMV. The presence of Na⁺/H⁺ exchange was demonstrated in both dBBMV and iBBMV by proton-driven (pH _i < pH _o ) ²²Na⁺ uptake. Evidence was also sought for the conductive nature of pathways for proton permeation. Intravesicular acidification, again determined by quenching of acridine orange fluorescence, was observed during imposition of K⁺-diffusion potential ([K⁺] _i [K⁺ _o ). In dBBMV and iBBMV, intravesicular acidification was enhanced in the presence of the K⁺-ionophore valinomycin, indicating that the native K⁺ permeability is rate limiting. In the presence of valinomycin, the K⁺-diffusion potential drove BBMV intravesicular acidification to levels close to the electrochemical potential. In gastric SAV, acidification was not limited by the K⁺ permeability. Valinomycin was without effect, but the K⁺/H⁺ ionophore nigericin enhanced acidification in gastric SAV, illustrating the low proton permeability of these membranes. Amiloride, 0.03–1 mm, resulted in concentration-dependent reductions of K⁺-diffusion potential-driven acidification in dBBMV and iBBMV but not in gastric SAV. These data demonstrate that proton permeation in the three membrane types is rheogenic. The sensitivity of the proton-conductive pathways in intestinal BBMV to high concentrations of amiloride correlated with the presence of the Na⁺/H⁺ antiport and indicates that this transmembrane protein may represent a pathway for proton permeation.We thank Ruth Briggs for assistance with the Na/H exchange experiments. This work was supported by a grant from the Medical Research Council (G8418056CA).     

Effects of starvation on valine and alanine transport across the intestinal mucosal border in sea bass,Dicentrarchus labrax

Summary kinetics of intestinal transport of l-alanine and l-valine (substrates of the A-system and the L-system, respectively, in mammals) across the brush-border membrane in sea bass, Dicentrarchus labrax, were studied on intact mucosa using a short-term uptake technique. When fish were starved for 4–8 weeks, total influx (mucosa-to-cell) of valine fell owing to disappearance or modification of the diffusion component. The maximum influx rate of saturable component increased but its affinity (reflected by the Michaelis constant) decreased. Alanine transport by Na⁺-dependent and diffusion pathways was unchanged after starvation Fasting also induced an almost 20% decrease in the length of intestinal microvilli.Abbreviations K _d diffusional constant - K _m Michaelis constant - V _max maximum influx rate     

Trichinella spiralis: comparison of stages in host intestine with those of an Arctic Trichinella sp

The intestinal phase of Trichinella spiralis and of Trichinella sp. isolated in the Arctic were compared in experimental animals. Reproductive capacity, pathogenicity, distribution, and persistence of adults in the small intestine, morphological measurements, and release of newborn larvae in vitro were examined. Numerous passages of 40 days each for T. spiralis and the Trichinella sp. isolate in mice did not affect reproductive capacity, distribution of adults in the small intestine, and size of worms. Reproductive capacity index for T. spiralis, I = 151.27 ± 27.30 was significantly higher compared to the Trichinella sp. isolate index, I = 63.46 ± 19.34. The Trichinella sp. isolate was more pathogenic to mice and wild rodents compared to T. spiralis during the intestinal phase. Both parasites were located in the anterior part of the small intestine but the position of T. spiralis adults (P = 17.08) differed from position of the Trichinella sp. isolate adults (P = 23.46) in the small intestine. Intestinal phase of T. spiralis was longer (20 days) compared to the Trichinella sp. isolate (15 days) but sex ratios (:♂) were similar for both parasites. T. spiralis females released significantly higher numbers of larvae in vitro/24 hr compared to the Trichinella sp. isolate. Release of larvae was continuous during the intestinal phase and the average fecundity for T. spiralis was 335 larvae/female and for the Trichinella sp. isolate 114 larvae/female. Adults of T. spiralis and the Trichinella sp. isolate were morphologically indistinguishable and did not differ in size. A comparative index for the intestinal phase is proposed for comparison of any Trichinella spp. isolates and standard T. spiralis.     

The relation between cell proliferation,differentiation and ultrastructural development in rat intestinal epithelium

Summary The ultrastructural development of the principal cells in rat small intestine was studied by morphometric analyses in relation to the exact cell position along crypt and villus. From the bottom to the tip of the crypt, a gradual increase occurred in absolute size of the total cell, the cytoplasm, the terminal web and of nearly all cell organelles. Also, the relative size of the cytoplasm, mitochondria, microvilli and endoplasmic reticulum increased during crypt cell differentiation. No sudden changes in ultrastructure were observed in the so-called critical decision zone, normally located halfway up the crypt where the proliferative activity ceases. At the crypt-villous junction a 1.4–3 fold increase in cell size, cytoplasm, terminal web and of most organelles was noted. Expansion of the proliferative cell compartment over the total length of the crypt as occurs during recovery after a low X-irradiation dose (72 h after 400 R) does not affect the normal development of cellular ultrastructure. These findings are discussed in relation to biochemical and cell kinetic data.     

基于“心与小肠相表里”理论探讨肠道微生态与骨质疏松症的关系

近年来相关研究显示,肠道微生态在骨质疏松症的发生发展中起着重要作用。中医脏腑理论密切关注脏腑之间的生理病理关系,以中医经典《内经》“心与小肠相表里”理论为基础,探讨心、小肠、肠道微生态与骨质疏松症之间的关系。研究发现肠道微生态可能是心系疾病导致骨质疏松症的途径之一,这一发现可能为骨质疏松症的研究与防治提供一定的理论依据。     

胃底腺息肉与胃增生性息肉的临床、内镜特征分析

目的:分析胃底腺息肉与胃增生性息肉的临床、内镜下等特点。方法:回顾性搜集胃镜检出的经病理证实的胃底腺息肉和胃增生性息肉393例纳入分析,按年龄、性别、发生部位、大小、幽门螺杆菌(helicobacter pylori)感染状态、是否使用质子泵抑制剂(proton pump inhibitor)等因素进行分析比较。结果:393例增生性息肉与胃底腺息肉中,男178例,女215例,男女比例为1:1.2,年龄28~89岁。随着年龄的增高,胃息肉发生率越高,但各年龄段分布差异无统计学意义(P>0.05)。不同部位的增生性息肉与胃底腺性息肉大小相比差异有统计学意义(P<0.05)。两种胃息肉的性别分布差异有统计学意义(P<0.05)。增生性息肉H.pylori感染率较胃底腺性息肉高(P<0.05),而胃底腺息肉质子泵抑制剂使用率较胃增生性息肉高(P<0.05)。结论:增生性息肉与幽门螺旋杆菌感染有关,胃底腺息肉与质子泵抑制剂使用有关。对胃底腺息肉与胃增生性息肉的临床、内镜特点的分析有助于胃镜检查对胃息肉性质的初步判断,提高诊断的准确性。     

持续颅内压监测对大面积脑梗死外科治疗预后的应用价值

目的:探讨持续颅内压(ICP)监测对大面积脑梗死外科治疗预后的应用价值。方法:选取2013年3月至2018年3月期间在我院接受治疗的大面积脑梗死患者100例作为研究对象,所有患者经去骨瓣减压术后行ICP监测和生命体征监测,通过结果分为:低压组62例(2.70kPa≤ICP5.30kPa),高压组38例(ICP≥5.30 kPa)。记录患者ICP监测数值,接收者操作特征(ROC)曲线分析患者预后情况,对患者进行术后3个月内随访,了解患者平常活动能力进行判断预后的状况。观察ICP与预后的相关性。结果:两组患者性别、年龄、室速、室性早搏、糖尿病、高血压病、脑卒中、高脂血症、风心病、冠心病、扩张性心肌病、既往心肌梗死、肥厚性心肌病、甲亢性心脏病等资料比较差异无统计学意义(P0.05)。低压组患者中预后良好的ICP监测值显著低于预后不良者(P0.05),高压组中预后良好的ICP监测值显著低于预后不良者(P0.05)。ICP预测大面积脑梗死外科治疗预后的ROC曲线面积0.704,采用最大约等指数计算得出ICP预测大面积脑梗死外科治疗预后的最大AUC面积相应参数截止值为4.89,其中敏感度为0.435,特异性为0.896。结论:持续ICP监测结果显示ICP值越小,患者的预后就越好,ICP值越高,患者的预后越差。ICP监测对大面积脑梗死外科治疗的预后具有预测价值,对判断和改善预后能起到有效帮助,值得在临床推广应用。