第三脑室注射组胺及其受体激动剂对五肽促胃液素诱导的大鼠胃酸分泌的影响

本文报道第三脑室注射组胺(0.25—2.0μg/5μl)对五肽促胃液素诱导的胃酸分泌的双重影响。雄性Wistar大鼠,重200—300g,戊巴比妥钠腹腔麻醉。用37℃生理盐水通过恒流泵进行连续胃灌流。在静脉恒速灌注五肽促胃液素(7.5μg/kg·h)的基础上,第三脑室注射组胺(0.25μg/5μl)或H_1受体激动剂2-Pyridylethylamine(PEA,10μg/5μl),10min后总酸排出量即开始减少,90min仍未恢复。组胺剂量增至1.0μg或2.0μg时,出现双重效应。部份动物(分别占73％或50％)胃酸分泌减少,另一部分动物(27％或50％)胃酸分泌增多。H_2受体激动剂dimaprit(10μg/5μl)或impromidine(0.1μg/5μl)对胃酸分泌无明显影响。苯海拉明(16μg/0.2ml或32μg/0.2ml,i.m.)预处理可分别取消组胺和PEA的抑胃酸效应。这些结果提示:脑内组胺可能参与胃酸分泌中枢调节。其抑制效应似通过H_1受体介导;双重效应的机制有待进一步研究。     

One- and two-dimensional NMR spectral analysis of the consequences of single amino acid replacements in proteins

The traditional approach of using homologous sequences to elucidate the role of specific amino acid residues in protein structure and function becomes more meaningful as the number of differences is minimized, with the limit being alteration of a single residue. For small proteins in solution, NMR spectroscopy offers a means of obtaining detailed information about each residue and its response to a given change in the protein sequence. Extraction of this information has been aided by recent progress in spectrometer technology (higher magnetic fields, more sensitive signal detection, more sophisticated computers) and experimental strategies (new NMR pulse sequences including multiple-quantum and two-dimensional NMR methods). The set of avian ovomucoid third domains, which consists of the third domain proper plus a short leader (connecting peptide) and has a maximum of 56 amino acid residues, offers an attractive system for developing experimental methods for investigating sequence-structure and structure-function relationships in proteins. Our NMR results provide examples of sequence effects on pKa' values, average conformation, and internal motion of amino acid side chains.     

Evaluation of nongenotoxic and genotoxic factors modulating the frequency of micronucleated erythrocytes in the peripheral blood of mice

The hematological micronucleus test is regarded as an indicator of the clastogenic effect of chemicals and acute cytogenetic damage. The test can be carried out in red blood cells of the bone marrow and of the spleen, as well as in peripheral erythrocytes. We have determined the precise background values of micronucleated red blood cells for the peripheral blood of BALB/c DBA/2, and NMRI mice. Bleeding, phenylhydrazine-induced hemolysis, and splenectomy generated an increase of micronucleated erythrocytes in the peripheral blood of mice. Our data thus demonstrate that such factors should be taken into consideration when the micronucleus test is used for screening the genotoxic potential of chemicals. Furthermore, the micronucleus-inducing effect of cyclophosphamide was studied in normal and splenectomized mice and, in addition, a comparison of the sensitivity of the micronucleus test was carried out in peripheral blood and bone marrow after cyclophosphamide treatment. Our data demonstrate that the kinetics of micronucleus formation were similar in normal and in splenectomized mice in which the micronucleus levels had returned to normal. The comparison of micronucleus formation in bone marrow and peripheral blood after cyclophosphamide treatment revealed the generation of similar quantities of micronucleated red blood cells in both tissues. The physiological mechanisms of micronucleus formation and removal and the potential role of chemically induced spleen damage during this process are discussed; the usefulness of the peripheral micronucleus test as a simple, rapid, and animal-saving modification of the standard bone marrow test is evaluated.Abbreviations CP cyclophosphamide - MN micronuclei - MNCE micronucleated normochromatic erythrocytes - MNPCE micronucleated polychromatic erythrocytes - MNRBC micronucleated red blood cells - NCE normochromatic erythrocytes - PCE polychromatic erythrocytes     

qSOFA评分、血乳酸及红细胞分布宽度与急性上消化道出血病情严重程度的关系及其预测患者预后的效能分析

摘要 目的：探讨快速序贯器官功能衰竭评估（qSOFA）评分、血乳酸（Lac）及红细胞分布宽度（RDW）与急性上消化道出血（AUGIB）病情严重程度的关系及其预测患者预后的效能。方法：选取2017年6月～2022年6月我院收治的230例AUGIB患者为研究对象,根据病情严重程度分为低危组44例、中危组140例、高危组36例、极高危组10例,且根据其入院28 d内生存情况分为死亡组（n=31）和存活组（n=199）。收集AUGIB患者临床资料,检测血Lac、RDW水平并计算qSOFA评分。采用多因素Logistic回归分析AUGIB患者预后不良的影响因素,受试者工作特征（ROC）曲线分析qSOFA评分和血Lac、RDW对AUGIB患者预后不良的预测价值。结果：低危组、中危组、高危组、极高危组qSOFA评分和血Lac、RDW水平依次升高（P＜0.05）。230例AUGIB患者入院28 d内死亡率为13.48％（31/230）。多因素Logistic回归分析显示,年龄增加、GBS评分≥6分及休克指数、qSOFA评分、血尿素氮、血Lac、RDW水平升高为AUGIB患者预后不良的独立危险因素（P＜0.05）。ROC曲线分析显示,qSOFA评分、血Lac及RDW联合预测AUGIB患者预后不良的曲线下面积大于qSOFA评分、血Lac及RDW单独预测。结论：AUGIB患者qSOFA评分、血Lac及RDW水平升高与病情加重和预后不良密切相关,qSOFA评分、血Lac及RDW联合预测AUGIB患者预后不良的效能较高。     

Water molecules participate in proteinase-inhibitor interactions: crystal structures of Leu18, Ala18, and Gly18 variants of turkey ovomucoid inhibitor third domain complexed with Streptomyces griseus proteinase B.

Crystal structures of the complexes of Streptomyces griseus proteinase B (SGPB) with three P1 variants of turkey ovomucoid inhibitor third domain (OMTKY3), Leu18, Ala18, and Gly18, have been determined and refined to high resolution. Comparisons among these structures and of each with native, uncomplexed SGPB reveal that each complex features a unique solvent structure in the S1 binding pocket. The number and relative positions of water molecules bound in the S1 binding pocket vary according to the size of the side chain of the P1 residue. Water molecules in the S1 binding pocket of SGPB are redistributed in response to the complex formation, probably to optimize hydrogen bonds between the enzyme and the inhibitor. There are extensive water-mediated hydrogen bonds in the interfaces of the complexes. In all complexes, Asn 36 of OMTKY3 participates in forming hydrogen bonds, via water molecules, with residues lining the S1 binding pocket of SGPB. For a homologous series of aliphatic straight side chains, Gly18, Ala18, Abu18, Ape18, and Ahp18 variants, the binding free energy is a linear function of the hydrophobic surface area buried in the interface of the corresponding complexes. The resulting constant of proportionality is 34.1 cal mol-1 A-2. These structures confirm that the binding of OMTKY3 to the preformed S1 pocket in SGPB involves no substantial structural disturbances that commonly occur in the site-directed mutagenesis studies of interior residues in other proteins, thus providing one of the most reliable assessments of the contribution of the hydrophobic effect to protein-complex stability.     

Gly-238-Ser substitution changes the substrate specificity of the SHV class A beta-lactamases

The SHV-type beta-lactamase SHV-2A is related to SHV-1 by a Gly-238-Ser replacement. Strains carrying SHV-2A are resistant to the third generation cephems cefotaxime and ceftizoxime, whereas those that carry SHV-1 are sensitive to these drugs. We present a kinetic analysis of a SHV-1 and SHV-2A enzymes, with the goal of gaining insight into the role of residue 238 in hydrolyzing cefotaxime and ceftizoxime. SHV-2A shows altered kinetic properties for a number of other cephems that also have heterocyclic side chains at the amino position of the 7-aminocephalosporanic acid nucleus (R1 side chain), including a significantly higher kcat/Km than does SHV-1 for cephaloridine, cephalothin, and cefotiam. Two cephems with straight chain R1 substitutions, cephalosporin C and cephacetrile, are not hydrolyzed more efficiently by SHV-2A. These results indicate that the Ser-238-Gly substitution increases the affinity toward cephems with a heterocyclic ring in the R1 side chain. In addition, the data for ampicillin and benzylpenicillin show that addition of a nitrogen to the second carbon of the R1 side chain of a penem results in a lower kcat/Km for SHV-2A relative to SHV-1. These data strongly suggest that the previously proposed hydrogen bond formation between Ser-238 and the second carbon nitrogen of cefotaxime is not an important factor in hydrolysis by SHV-2A. We propose that the Gly-238 to Ser-238 replacement in SHV-2A has altered the hydrophobic pocket so that it can better accommodate cephems with bulky R1 side chains.     

复方醋酸棉酚片联合独一味胶囊对大鼠无排卵型功能失调性子宫出血的改善作用及其作用机制

摘要 目的：探讨复方醋酸棉酚片联合独一味胶囊对大鼠无排卵型功能失调性子宫出血的改善作用及其作用机制。方法：将40只雌性SD大鼠随机均分成两组（空白组和模型组）,采用给大鼠连续21 d灌胃戊酸雌二醇的方法制备无排卵型功能失调性子宫大鼠模型。模型大鼠制备成功后,按随机法再均分成模型组、阳性组和治疗组,其中阳性组和治疗组分别灌胃给予相应的药物,空白组和模型组灌胃等体积的生理盐水,各组均连续灌胃7 d。计算各组大鼠的子宫系数,采用酶联免疫吸附法测定大鼠血清中雌二醇（estradiol, E₂）和孕酮（progestone,P）水平,采用免疫组化法测定大鼠子宫内膜组织中两个蛋白（matrix metalloproteinases-9,MMP-9和vascular endothelial growth factor ,VEGF）的表达量。结果：模型组大鼠血清中的P水平比空白组显著性减少（P<0.05）,子宫内膜组织中的MMP-9和VEGF表达量比空白组均显著性升高（P<0.05）。给药后,治疗组和阳性组大鼠血清中的P水平均显著高于模型组（P<0.05）,大鼠子宫内膜组织中的MMP-9和VEGF 表达量均显著低于模型组（P<0.05）,治疗组与阳性组之间无显著性差异（P >0.05）。结论：复方醋酸棉酚片联合独一味胶囊对无排卵型功能失调性子宫出血具有明显的改善作用,其机制可能与调控子宫内膜 MMP-9 和VEGF的表达量有关。     

巴中地区上消化道出血反复发作相关性因素分析

目的：了解巴中地区上消化道出血反复发作的原因,为治疗提供临床循证医学证据。方法：通过对2011年4月~2012年11月巴中地区1134例上消化道出血中132例反复发作的患者进行调查统计,分析这上消化道出血反复发作的132例患者的年龄、生理特征、生活饮食习惯、精神状态、生活压力等多种相关因素。结果：发现饮食不当、精神紧张、腹腔感染、腹腔内压增高、输液输血过速、过量等是造成病情反复发作的主要诱因。结论：通过消除疾病的诱发因素,认真做好健康教育指导,积极治疗原发病是预防反复发作的有效措施。     

The influence of PAMAM dendrimers surface groups on their interaction with porcine pepsin

In this study the ability of three polyamidoamine (PAMAM) dendrimers with different surface charge (positive, neutral and negative) to interact with a negatively charged protein (porcine pepsin) was examined. It was shown that the dendrimer with a positively charged surface (G4 PAMAM-NH₂), as well as the dendrimer with a neutral surface (G4 PAMAM-OH), were able to inhibit enzymatic activity of pepsin. It was also found that these dendrimers act as mixed partially non-competitive pepsin inhibitors. The negatively charged dendrimer (G3.5 PAMAM-COOH) was not able to inhibit the enzymatic activity of pepsin, probably due to the electrostatic repulsion between this dendrimer and the protein. No correlation between changes in enzymatic activity of pepsin and alterations in CD spectrum of the protein was observed. It indicates that the interactions between dendrimers and porcine pepsin are complex, multidirectional and not dependent only on disturbances of the secondary structure.