Phenotypic characterization of pore mutants of the Vibrio cholerae porin OmpU

General-diffusion porins form large β-barrel channels that control the permeability of the outer membrane of gram-negative bacteria to nutrients, some antibiotics, and external signals. Here, we have analyzed the effects of mutations in the OmpU porin of Vibrio cholerae at conserved residues that are known to affect pore properties in the Escherichia coli porins OmpF and OmpC. Various phenotypes were investigated, including sensitivity to β-lactam antibiotics, growth on large sugars, and sensitivity to and biofilm induction by sodium deoxycholate, a major bile component that acts as an external signal for multiple cellular responses of this intestinal pathogen. Overall, our results indicate that specific residues play different roles in controlling the passage of various compounds. Mutations of barrel wall arginine residues that protrude in the pore affect pore size and growth in the presence of large sugars or sodium deoxycholate. Sensitivity to large cephalosporins is mostly affected by D116, located on the L3 loop, whose homolog in E. coli, OmpF, is a known binding determinant for these drugs. L3 loop residues also affect biofilm induction. The results are interpreted in terms of a homology model based on the structures of E. coli porins.     

How does cholecystokinin stimulate exocrine pancreatic secretion? From birds, rodents, to humans

The field of cholecystokinin (CCK) stimulation of exocrine pancreatic secretion has experienced major changes in the recent past. This review attempts to summarize the present status of the field. CCK production in the intestinal I cells, the molecular forms of CCK produced and subsequently circulated in the blood, the presence or absence of CCK receptors on the isolated pancreatic acinar cells and the associated signaling for acinar cell secretion, and the actual circuits and sites of action for CCK regulation of exocrine pancreatic secretion in vivo are reviewed in different animal species with an emphasis on birds, rodents, and humans. Clear differences in the relative importance of neural and direct modes of CCK action on pancreatic acinar cells were identified. Rodents seem to be endowed with both modes of action, whereas in humans the neural mode may predominate. In birds, such as duck, the direct mode needs further assistance from pituitary adenylate cyclase-activating peptide/VIP receptors. However, much further work needs to be directed to the neural mode to map out all sites of CCK action and details of the full circuits, and we foresee a major revival for this field of research in the near future.     

Transendothelial flow inhibits neutrophil transmigration through a nitric oxide-dependent mechanism: potential role for cleft shear stress

Endothelial cells in vivo are well known to respond to parallel shear stress induced by luminal blood flow. In addition, fluid filtration across endothelium (transendothelial flow) may trigger nitric oxide (NO) production, presumably via shear stress within intercellular clefts. Since NO regulates neutrophil-endothelial interactions, we determined whether transendothelial flow regulates neutrophil transmigration. Interleukin-1beta-treated human umbilical vein endothelial cell (HUVEC) monolayers cultured on a polycarbonate filter were placed in a custom chamber with or without a modest hydrostatic pressure gradient (DeltaP, 10 cm H(2)O) to induce transendothelial flow. In other experiments, cells were studied in a parallel plate flow chamber at various transendothelial flows (DeltaP = 0, 5, and 10 cm H(2)O) and luminal flows (shear stress of 0, 1, and 2 dyn/cm(2)). In the absence of luminal flow, transendothelial flow reduced transmigration of freshly isolated human neutrophils from 57% to 14% (P < 0.05) and induced an increase in NO detected with a fluorescent assay (DAF-2DA). The NO synthase inhibitor L-NAME prevented the effects of transendothelial flow on neutrophil transmigration, while a NO donor (DETA/NO, 1 mM) inhibited neutrophil transmigration. Finally, in the presence of luminal flow (1 and 2 dyn/cm(2)), transendothelial flow also inhibited transmigration. On the basis of HUVEC morphometry and measured transendothelial volume flow, we estimated cleft shear stress to range from 49 to 198 dyn/cm(2). These shear stress estimates, while substantial, are of similar magnitude to those reported by others with similar analyses. These data are consistent with the hypothesis that endothelial cleft shear stress inhibits neutrophil transmigration via a NO-dependent mechanism.     

Oxidative stress reversibly inactivates myocardial enzymes during cardiac arrest

Oxidative stress during cardiac arrest may inactivate myocardial enzymes and thereby exacerbate ischemic derangements of myocardial metabolism. This study examined the impact of cardiac arrest on left ventricular enzymes. Beagles were subjected to 5 min of cardiac arrest and 5 min of open-chest cardiac compressions (OCCC) before epicardial direct current countershocks were applied to restore sinus rhythm. Glutathione/glutathione disulfide redox state (GSH/GSSG) and a panel of enzyme activities were measured in snap-frozen left ventricle. To test whether oxidative stress during arrest inactivated the enzymes, metabolic (pyruvate) or pharmacological (N-acetyl-l-cysteine) antioxidants were infused intravenously for 30 min before arrest. During cardiac arrest, activities of phosphofructokinase, citrate synthase, aconitase, malate dehydrogenase, creatine kinase, glucose-6-phosphate dehydrogenase, and glutathione reductase fell by 56, 81, 55, 34, 42, 55, and 45%, respectively, coincident with 50% decline in GSH/GSSG. OCCC effected full recovery of glutathione reductase and partial recovery of citrate synthase and aconitase, in parallel with GSH/GSSG. Phosphofructokinase, malate dehydrogenase, creatine kinase, and glucose-6-phosphate dehydrogenase recovered only after cardioversion. Antioxidant pretreatments augmented phosphofructokinase, aconitase, and malate dehydrogenase activities before arrest and enhanced these activities, as well as those of citrate synthase and glucose-6-phosphate dehydrogenase, during arrest. In conclusion, cardiac arrest reversibly inactivates several important myocardial metabolic enzymes. Antioxidant protection of these enzymes implicates oxidative stress as a principal mechanism of enzyme inactivation during arrest.     

孕鼠被动吸烟对子鼠学习记忆能力和海马LTP的影响

目的:探讨小鼠孕期被动吸烟对其子代小鼠学习记忆能力和神经机制长时程增强(LTP)效应的影响,及采用不同抗氧化剂的干预效应。方法:孕鼠给予被动吸烟染毒,并采用槲皮素和维生素E(VE)进行干预,待产子后研究子鼠水迷宫和LTP的变化。结果:被动吸烟使子鼠空间学习记忆能力下降。槲皮素组LTP与对照组相比增强显著(P<0.05);吸烟组LTP增强受到抑制(P<0.05);VE及与槲皮素协同干预组子鼠LTP较吸烟组增强显著(P<0.05)。结论:胚胎期被动吸烟使小鼠学习记忆功能下降,通过抗氧化剂干预可能得到改善。     

上海市人群Echo30病毒性脑膜炎隐性感染调查

为了了解上海市不同年龄组人群的Echo30病毒隐性感染情况及IgG抗体阳性率分布。采集上海市412份不同年龄组人群血清,用间接酶联免疫吸附试验(ELISA)检测血清中的Echo30IgG抗体。发现受检普通人群血清中Echo30IgG抗体阳性率为25.8%。其中1岁以下婴幼儿中未见抗体阳性者,15岁以下儿童抗体阳性率较低(10%～16.7%),15岁以上人群抗体阳性率水平明显升高(45.0%～46.7%)。孕妇与普通人群抗体阳性率无显著性差异。研究结果提示上海市人群中存在隐性感染者,人群通过自然感染获得免疫保护,15岁以下儿童为Echo30感染及发病的高危人群,母体传递给婴幼儿的抗体水平较低,不能为婴幼儿提供先天性免疫保护。     

HPLC法测定烟草不同部位、不同提取方法茄尼醇的含量

为了建立烟草不同部位、不同烟草原料中茄尼醇的含量测定方法,本文取烟草不同部位经甲醇超声提取及烟草不同提取方法的提取物,分别用高效液相色谱法测定茄尼醇的含量。结果显示,烟草茎及叶柄中茄尼醇含量极低,烤烟中的茄尼醇的含量：中部烟〉上部烟〉下部烟,烟叶档次越高茄尼醇含量越高。提取溶媒为石油醚〉丙酮〉乙醇。     

瑞香狼毒根提取物对山楂叶螨的生物活性

采用不同的生物活性测定方法比较了瑞香狼毒(Stellera chamaejasme L.)根部4种不同溶剂提取物的杀螨活性。结果表明,瑞香狼毒根提取物对山楂叶螨(Tetranychus viennensis Zacher)有很好的触杀和内吸活性。在触杀活性测试中,石油醚提取物和氯仿提取物的杀螨活性最高;在内吸作用中,乙醇、氯仿和石油醚提取物的杀螨活性均较高,杀螨效果显著。在对石油醚提取物的不同溶剂萃取物进行生物活性追踪测定中发现,石油醚萃取物和氯仿萃取物具有较高的生物活性,浓度为0.6 g.L-1,山楂叶螨的24 h校正死亡率分别达到93.22%和79.66%。     

Synthesis, biological evaluation and structural determination of beta-aminoacyl-containing cyclic hydrazine derivatives as dipeptidyl peptidase IV (DPP-IV) inhibitors

Inhibitors of dipeptidyl peptidase IV (DPP-IV) have been shown to be effective treatments for type 2 diabetes. A series of beta-aminoacyl-containing cyclic hydrazine derivatives were synthesized and evaluated as DPP-IV inhibitors. One member of this series, (R)-3-amino-1-(2-benzoyl-1,2-diazepan-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one (10f), showed potent in vitro activity, good selectivity and in vivo efficacy in mouse models. Also, the binding mode of compound 10f was determined by X-ray crystallography.