病原菌逃避宿主细胞防御的策略

病原菌对宿主致病是病原菌与宿主复杂相互作用的结果。病原菌与宿主相互作用可造成宿主在细胞、组织及器官不同水平的损伤。病原菌对宿主的致病性及毒力,一方面在于病原菌,另一方面在于宿主因素以及宿主与病原菌的相互作用。病原菌-宿主在细胞水平的相互作用是病原菌感染致病的重要环节。结合本课题组对猪链球菌的研究,从黏附与定殖、侵袭、逃避与扩散等方面概述病原菌逃避宿主细胞防御的机制。     

卷叶黄精对植物病原菌的抗菌活性研究

采用菌丝生长速率法研究了卷叶黄精根提取物对植物病原菌的抗菌活性。结果表明:卷叶黄精对所选10种植物病原菌中的7种呈现不同程度的抗菌活性,而且各萃取物的抑菌菌种各不相同,其中正丁醇萃取物对4种病原菌、乙酸乙酯萃取物对3种病原菌有明显的抑菌活性,水浓缩物仅对1种病原菌有抗菌活性,而石油醚萃取物对供试植物病原菌没有抗菌活性;正丁醇萃取物对苹果褐腐病、玉米大斑病、棉黄萎病病原菌抑制作用较强,EC50分别为261.26、376.03和430.05μg.mL-1;乙酸乙酯萃取物对苹果腐烂病、番茄黑霉病病原菌抑制作用较强,EC50分别为386.00和865.75μg.mL-1,各样品对植物病原菌的毒力随着浓度的增高而增强;卷叶黄精对植物病原菌的抑菌活性随着作用时间的延长,均呈现不同的下降趋势。     

肠杆菌电动学研究

细菌的带电现象与其生长环境选择、染色反应、凝集反应、抑菌和杀菌作用有密切关系。通常认为,生理情况下机体肠道内正常菌群具有阻止病原菌侵袭肠粘膜及抑制病原菌生长和繁殖的屏障作用。我们曾发现某些病原菌和非病原菌具有不同的带电现象,此可能同病原菌的致病性及     

肠道微生物屏障功能与病原菌毒力作用

人类肠道内存在大量共生菌,其可以抵抗病原菌入侵,对维持人体健康起重要保护作用,被称为肠道微生物屏障。肠道共生菌这种抵抗病原菌入侵保护宿主的作用称为定植抗力。一旦肠道菌群出现紊乱,定植抗力遭到破坏,机体获得感染的机率将明显升高。本综述就共生菌如何限制病原菌生长、抑制病原菌毒力以及反过来病原菌如何躲避竞争、促进菌群紊乱进行了综述。     

病原菌负反馈作用促进物种共存的研究进展

植物病原菌包括真菌、细菌、病毒等,广泛存在于自然界中,可以引起各种植物病害。病原菌对植物的负反馈作用,即植物个体附近的土壤病原菌,可能反过来侵害其自身或同种个体,致死或影响生长植物的现象。植物病原菌对群落中优势种的更新有强烈的抑制作用,从而促进物种的共存。植物病原菌的负反馈作用在植物种群动态和群落演替中起着重要的调控作用。     

7种消毒剂对鲟4种病原菌体外抑菌效果

为了筛选高效的消毒剂用于防治鲟细菌性疾病,采用二倍稀释法测定了7种消毒剂对鲟4种病原菌的最小抑菌浓度(MIC)和最小杀菌质量浓度(MBC)。结果显示,高铁酸钾对鲟4种病原菌抑菌效果最好,MIC为8 mg/L,MBC为8¹6 mg/L,戊二醛、甲醛、苯扎溴铵、过氧化氢及季铵盐络合碘5种消毒剂抑菌效果中等,聚维酮碘对鲟4种病原菌抑菌效果最差,聚维酮碘对鲟4种病原菌的MBC最大值为2048 mg/L。根据上述研究结果,选择抑菌效果好的消毒剂高铁酸钾进一步研究了鲟4种病原菌随时间和高铁酸钾浓度变化的生长趋势,显示消毒液浓度为5 mg/L、9 mg/L的消毒液在短时间能抑制病原菌生长繁殖,病原菌数量同样能在短时间内繁殖恢复到原来的水平,浓度为13 mg/L、17 mg/L的高铁酸钾消毒液能快速杀灭病原菌,病原菌在较长时间维持在较低水平,甚至病原菌全部被杀死。研究对于使用高铁酸钾防治鲟养殖实践中的疾病具有重要的指导意义。     

呼吸机相关肺炎病原菌分布和耐药性监测

目的 探讨呼吸机相关肺炎(VAP)的病原菌分布及耐药性特征.方法 从235例使用呼吸机引发肺炎患者的呼吸道标本中分离出126株病原菌,采用K-B纸片扩散法进行敏感试验,对病原菌分布及耐药性进行分析.结果 早发性VAP组病原菌主要来源于呼吸道定植的病原体如肺炎链球菌、金黄色葡萄球菌等;而迟发性VAP组病原菌常由肠杆菌科病原菌等所致;病原菌以革兰阴性菌为主,占69.2％、革兰阳性菌17.9％、真菌l2.8％;细菌的耐药率普遍较高,耐甲氧西林金黄色葡萄球菌(MRSA)占40.0％,耐甲氧西林表皮葡萄球菌(MRSE)占85.7％;肺炎克雷伯菌、大肠埃希菌、阴沟肠杆菌中ESBLs阳性菌检出率分别为33.3％和37.5％和16.7％.结论 早发性VAP病原菌和迟发性VAP病原菌分布差异较大,呼吸机相关肺炎主要病原菌对常用抗菌药物大多耐药,加强其病原菌分布及耐药性监测,对指导临床合理用药具有重要意义.     

草莓拟盘多毛孢叶斑病的病原菌

于2013年在北京市房山区发现了一种新的草莓叶部病害,为明确引起该病害的病原菌种类,采用组织分离法对病叶进行了病原菌的分离,经纯化得到一株病原菌CMF4。通过室内人工接种对该菌株的致病性和寄主范围进行测定,发现该菌株可以导致草莓叶片坏死和果实腐烂,可引起有伤供试植物牡丹、海棠、芍药、杏、樱桃、桃和月季发病,但不能无伤侵入,对人工接种发病的植株进行病原菌再分离可得到原接种病原菌。采用rDNA-ITS序列分析方法并结合该病原菌的形态特征进行鉴定,发现引起该病害的病原菌为棒孢拟盘多毛孢Pestalotiopsis clavispora。这是棒孢拟盘多毛孢所致草莓叶斑病在国内的首次报道。     

3种木醋液化学成分与抑菌活性研究

用GC-MS联用技术分析玉米芯木醋液(Y)、松塔木醋液(S)和核桃枝木醋液(Z)的化学成分,并对木醋液的体外抑菌活性进行研究.结果表明,3种木醋液主要由酸类、酚类、酮类和醛类物质组成,醇类和酯类等含量较少.其共有化合物有38种,占各木醋液总化合物种类60%左右,且共有化合物的相对含量之和占各木醋液总含量的80%左右.3种木醋液对20种供试植物病原菌都有不同程度的抑菌作用.除柿子炭疽病原菌、棉花枯萎病原菌、葡萄炭疽病原菌和白菜黑斑病原菌外,对其他植物病原菌的抑菌活性依次为:Y>S>Z.Y和S对黄瓜炭疽病原菌和柿子炭疽病原菌抑制作用最强,抑制率分别为77.04%和71.61%.     

创面分泌物病原菌的分布及危险因素分析

目的分析烧伤外科患者创面分泌物病原菌的分布及感染危险因素,为临床防控提供理论依据。方法采用回顾性分析方法,收集2012年至2014年期间本院烧伤外科住院患者的临床细菌学资料,分析创面病原菌的分布。根据创面分泌物细菌培养结果分为病原菌阴性组和阳性组,对比两组患者临床资料,分析创面分泌物病原菌阳性的相关危险因素,并采用非条件Logistic回归法分析独立危险因素。结果创面分泌物培养401次,阳性结果302次(75.31%)。分离出315株病原菌,其中革兰阳性菌148株(46.98%),革兰阴性菌167株(53.02%)。常见病原菌为:金黄色葡萄球菌(37.46%)、铜绿假单胞菌(23.81%)、大肠埃希菌(8.89%)、粪肠球菌(5.08%)、肺炎克雷伯杆菌(5.08%)。255例患者纳入研究,其中创面分泌物病原菌阴性组92例(36.08%),阳性组163例(63.92%)。单因素分析显示:住院史、危重症、创面深度、难愈性创面、血红蛋白、近期导管植入、近期输液、近期手术、近期抗菌药物治疗是创面分泌物病原菌阳性的相关危险因素(P0.05)。多因素Logistic回归分析显示:难愈性创面和近期抗菌药物治疗是创面分泌物病原菌阳性的独立危险因素(P0.05)。结论创面分泌物病原菌分布广泛,金黄色葡萄球菌和铜绿假单胞菌是常见菌。难愈性创面和近期抗菌药物治疗与创面分泌物病原菌阳性有关。     

Formation of gamma-aminobutyric acid from glutamate and putrescine in rat hypothalamic and hippocampal synaptosomes and regulation of these processes by glucocorticoids]

It has been shown that single or multiple hydrocortisone and ACTH administrations to intact rats increased GABA content and its synthesis from glutamate and putrescine in synaptosomes of hypothalamus. The letter content was increased by single hormonal administration while multiple hormonal administration and adrenalectomy decreased it. Ornithine decarboxylase activity was increased by single hydrocortisone administration to intact animals, following adrenalectomy, and it was decreased by single hormonal administration to adrenalectomized rats. GABA synthesis in synaptosomes of hippocampus from putrescine was increased by single hydrocortisone and multiple hormonal administrations. GABA content was increased by multiple administration of both hormones and was decreased by adrenalectomy. Putrescine level was decreased by multiple hydrocortisone administration to intact and single administration to adrenalectomized rats; ornithine decarboxylase activity was decreased by multiple administration of both hormones.     

The role of nitric oxide and cGMP in platelet adhesion to vascular endothelium

The inhibition of platelet adhesion by nitric oxide (NO) and prostacyclin and their mechanism of action was studied. Platelet adhesion to collagen fibrils and endothelial cell matrix was inhibited completely by NO but only partially by prostacyclin. Adhesion of platelets to endothelial cell monolayers was inhibited by bradykinin. This effect of bradykinin was unaffected by aspirin, and was accounted for by the amounts of NO released by the endothelial cells. Inhibition of platelet adhesion by NO and prostacyclin was potentiated by selective inhibitors of cGMP phosphodiesterase, but not of cAMP phosphodiesterase, indicating that elevation of cGMP regulates platelet adhesion.     

Sulfur metabolism in Beggiatoa alba

The metabolism of sulfide, sulfur, and acetate by Beggiatoa alba was investigated under oxic and anoxic conditions. B. alba oxidized acetate to carbon dioxide with the stoichiometric reduction of oxygen to water. In vivo acetate oxidation was suppressed by sulfide and by several classic respiratory inhibitors, including dibromothymoquinone, an inhibitor specific for ubiquinones. B. alba also carried out an oxygen-dependent conversion of sulfide to sulfur, a reaction that was inhibited by several electron transport inhibitors but not by dibromothymoquinone, indicating that the electrons released from sulfide oxidation were shuttled to oxygen without the involvement of ubiquinones. Intracellular sulfur stored by B. alba was not oxidized to sulfate or converted to an external soluble form under aerobic conditions. On the other hand, sulfur stored by filaments of Thiothrix nivea was oxidized to extracellular soluble oxidation products, including sulfate. Sulfur stored by filaments of B. alba, however, was reduced to sulfide under short-term anoxic conditions. This anaerobic reduction of sulfur was linked to the endogenous oxidation of stored carbon and to hydrogen oxidation.     

Inhibition of microsomal lipid peroxidation by cytosolic protein in presence of ADP and high concentration of Fe2+

Microsomal lipid peroxidation induced by NADPH, but not by ascorbate, was found to be inhibited by liver cytosol. This inhibition was not dependent on glutathione and was enhanced by ADP in presence of Fe2+ at a concentration of 50 microM or higher. ATP was also effective, but not AMP or cyclic AMP. The cytosolic factor appeared to be a protein as it was heat-labile (greater than 70 degrees C), was non-dialyzable and was precipitated by ammonium sulfate and acetone. It was stable for several months in frozen state and also when heated at 50 degrees C for 10 min. The inhibition by the cytosolic protein was obtained by producing a lag in the activity of lipid peroxidation and was reversed by ceruloplasmin but not by catalase, cytochrome c, hemoglobin or superoxide dismutase. This inhibitory effect by cytosol was limited to formation of lipid peroxides whereas oxygen uptake and NADPH oxidation remained unaffected. Regulation of lipid peroxidation by nucleotide-Fe complexes and cytosolic proteins is indicated by these studies.     

NADH- and NADPH-dependent lipid peroxidation in bovine heart submitochondrial particles. Dependence on the rate of electron flow in the respiratory chain and an antioxidant role of ubiquinol.

Malondialdehyde formations by bovine heart submitochondrial particles supported by NADH or NADPH in the presence of ADP and FeCl3 was studied. The NADH-dependent reaction was maximal at very low rate of electron input from NADH to the respiratory chain and it decreased when the rate became high. The reaction was stimulated by rotenone and inhibited by antimycin A when the input was fast, whereas it was not affected by the inhibitors when the input was slow. The input rate of the electrons from NADPH was also so low that the reaction supported by NADPH was not affected by the inhibitors. Most of the endogenous ubiquinone in the particles treated with antimycin A was reduced by NADH even in the presence of ADP-Fe3+ chelate, but uniquinone was not reduced by NADPH when ADP-Fe3+ was present. Succinate strongly inhibited both NADH- and NADPH-dependent lipid peroxidation. The inhibition was abolished when uniquinone was removed from the particles, and it appeared again when uniquinone was reincorporated into the particles. Reduced uniquinone-2 also inhibited the peroxidation, but duroquinol, which reduces cytochrome b without reducing endogenous uniquinone, did not. Thus the malondialdehyde formation appeared to be inversely related to the extent of the reduction of endogenous uniquinone. These observations suggest that both NADH- and NADPH-dependent liquid-peroxidation reactions are closely related to the respiratory chain and that the peroxidation is controlled by the concentration of reduced ubiquinone.     

Glutamine synthetase and glutamate synthase activities during growth and sporulation in Bacillus subtilis.

Glutamine synthetase in Bacillus subtilis 168 was repressed to a greater extent by L-glutamine or L-arginine than by ammonia when each was used as sole nitrogen source. It was derepressed when either L-glutamate or nitrate was used as nitrogen source. Glutamate synthase was repressed by L-glutamate or L-arginine and, to a lesser extent, by L-glutamine but was derepressed during growth with ammonia or nitrate. Glutamine synthetase activity was unaltered during the onset of sporulation. Glutamate synthase activity, however, underwent a small and apparently transient increase in bacteria induced to sporulate by nitrogen limitation.     

Immune opsonin-independent phagocytosis by pulmonary macrophages

The uptake of albumin-coated latex particles by hamster pulmonary macrophages (PM) in vitro was investigated by using a new technique that combined flow cytometry and fluorescence microscopy to differentiate and quantitate bound vs ingested particles. In the absence of serum, PM avidly bound and ingested particles, whereas phagocytosis by hamster polymorphonuclear leukocytes (PMN) was less marked. In the presence of serum, phagocytosis by PM was slightly depressed, whereas phagocytosis by PMN was stimulated more than 10-fold. The binding of particles to PM in the absence of serum was pH, temperature, and trypsin sensitive and was dependent on the presence of extracellular Ca++ but not Mg++. The ingestion of particles by this immune opsonin-independent pathway was also temperature sensitive but was not affected by either pH or extracellular Ca++. Particle ingestion, but not binding, was inhibited by cytochalasin D and the divalent cation ionophore A23187.     

Further investigation of the antiovulatory effects of the antiprogestational steroid RMI 12,936 in the rat.

Inhibition of ovulation by RMI 12,936 was associated with suppression of the pro-oestrous peak of hypothalamic dopamine. The antiovulatory effect was not reversed by administration of oestrogen, was partly reversed by progesterone and was fully reversed by oestrogen and progesterone. Hypophysial sensitivity to LH-RH, known to be reduced by RMI 12,936, remained low when ovulation was restored by steroid treatment. Administration of oestrogen did not restore the pro-oestrous peak of hypothalamic dopamine and ovulation was not induced following administration of L-DOPA in RMI 12,936-treated animals. It was concluded that RMI 12,936 is antioestrogenic as well as antiprogestational, that oestrogen is necessary for induction of full hypothalamic-hypophysial responsiveness to progesterone and that a hypothalamic dopaminergic pathway may have a non-essential role in the control of ovulation possibly associated with increasing hypophysial sensitivity to LH-RH.     

Inhibition of Ca2+-induced cytosolic enzyme efflux from skeletal muscle by vitamin E and related compounds.

1. Efflux of an intracellular enzyme (creatine kinase) from normal rat skeletal muscles was induced by treatment with the Ca2+ ionophore A23187. Addition of alpha-tocopherol (230 microM) to the incubation medium was found to significantly diminish this efflux, and this effect was mimicked by alpha-tocopherol acetate, phytol and isophytol, but not by Trolox C (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid). 2. Analysis of muscle cation content has shown that these protective effects of alpha-tocopherol etc. are not due to an inhibition of the Ca2+ accumulating effects of the ionophore. 3. Non-enzymic lipid peroxidation of skeletal-muscle homogenates was found to be inhibited by alpha-tocopherol and Trolox C, partially inhibited by phytol and isophytol, but unaffected by alpha-tocopherol acetate. 4. The activity of lipoxygenase enzymes was partially inhibited by alpha-tocopherol, phytol and isophytol, but not by alpha-tocopherol acetate or Trolox C. 5. Prostaglandin E2 efflux from isolated skeletal muscles was stimulated by treatment with the Ca2+ ionophore, but this was unaffected by alpha-tocopherol treatment.