分枝杆菌噬菌体 D29的生物学特性研究及其抗耐药结核潜力的探讨

目的研究分枝杆菌噬菌体 D29的生物学特性,为 D29抗耐药结核治疗奠定基础.方法观察噬菌体电镜结构和噬菌斑形态;测定 D29最佳感染复数(MOI);一步生长实验;检测 pH值对 D29活力的影响;斑点法测定裂解谱;中和实验检测抗原性.结果 D29噬菌斑圆形透明,边界清楚;D29尾长129nm,最佳 MOI为10-4;D29感染宿主菌的潜伏期约为50min,裂解量为10;pH值对 D29存活率影响大,酸性环境不影响 D29裂解能力;D29能裂解分枝杆菌临床耐药株;D29K值为1069.50.结论 D29属于长尾噬菌体科(siphoviridae),裂解谱广,抗原性较高,具有抗耐药结核潜力     

噬菌体在癌症治疗研究中的应用

噬菌体作为一类特殊病毒能影响癌症进程.最新研究发现部分噬菌体通过活化免疫应答,影响细胞因子的分泌,调节肿瘤微环境,有益于癌症治疗.噬菌体还可作为筛选具有诱导抗肿瘤效应的外源肽的平台.本文综述噬菌体在癌症治疗研究中的应用,寻找攻克恶性肿瘤新途径.     

腹腔感染早期腹膜淋巴孔变化及淋巴引流的研究

目的研究腹腔感染早期腹膜淋巴孔孔径及分布密度的变化,探讨腹腔内毒素的淋巴转归及其机制。方法将40只WISTA大鼠(200~250 g),随机分为正常组(10只)、假手术组(10只)和腹腔感染组(20只)。应用扫描电镜观察各组大鼠腹膜淋巴孔孔径大小及分布密度,利用显色基质鲎试剂检测门静脉血及胸导管淋巴内毒素的浓度,同时利用一氧化氮硝酸还原法测定腹膜组织中一氧化氮(NO)的含量。结果 1与正常组相比,腹腔感染组淋巴孔的孔径(P0.01)和密度显著增加(P0.01),且感染时间越长,腹膜淋巴孔径增加越显著(P0.01),但分布密度无明显增加(P0.05)。2腹腔感染组大鼠胸导管淋巴液中内毒素的含量显著高于正常组(P0.01),且感染时间越长,内毒素的含量越高(P0.01),而各组大鼠门静脉血中内毒素的含量无显著差异(P0.05)。3腹腔感染组大鼠腹膜组织中NO的含量显著高于正常组(P0.01)。结论腹腔感染早期,腹膜淋巴孔孔径增大,分布密度增多,细菌内毒素主要通过变大、增多的腹膜淋巴孔进入淋巴回流系统,而非门静脉血流循环。体内NO是调控腹膜淋巴孔开闭的一个重要调节因子。     

粘弹性表面活性剂在油气藏增产改造领域的研究进展

粘弹性表面活性剂(VES)由两亲分子组成,在地层条件下具有独特的物理化学性质,被广泛应用于油气藏增产改造领域。本文在简要介绍粘弹性表面活性剂胶束结构和胶束特性、作用机理的基础上,重点对VES压裂液和VES自转向酸两部分所涉及理论基础、技术进展及井场应用情况进行综述:VES压裂液具有携砂能力强、滤失低、压裂效能高、返排能力强、地层伤害小等优势;VES自转向酸具有配制简单、破胶容易、对地层伤害小、缓速、滤失少等优点。最后,指出粘弹性表面活性剂在现阶段研究存在的问题和需要克服的难点,以期推动粘弹性表面活性剂在油气藏增产改造领域的进一步应用。     

分子生物学与基因工程引发的思考

扼要地介绍了分子生物学与基因工程的基本内容和发展趋势。论述了基因工程在推动人类社会文明与进步中的巨大作用，特别是在解决当今全球性问题方面的巨大。探讨了分子生物学诞生的诱因及其为新世纪的科技创新活动提供的宝贵启示。     

我国农作物生物技术的成就与展望

自1983年人类首次获得转基因烟草、马铃薯以来,植物基因工程技术在世界范围内取得了飞速的发展,转基因植物的研究和开发取得了一系列令人瞩目的进展,已培育成功一批抗虫、抗病、耐除草剂和高产优质的农作物新品种.与此同时,农作物基因工程产业化的步伐在各国政府的大力参与下正在加快,预计在下个世纪初期将成为经济的支柱产业之一.近几年,美国、欧洲、日本等发达国家为加强基因工程的研究和开发,相继制订了一些利于其发展的新政策,如美国的"面向21世纪的生物技术",欧洲的"尤里卡计划",日本的"官、产、学一体化推进21世纪的生物技术计划",都把农业生物技术列为优先发展领域.农作物基因工程由于应用体外重组DNA技术将动物、植物、微生物的基因相互转移,打破了物种之间基因交流的天然屏障,因此无论在基础研究还是在应用开发方面都取得了相当的成就,其研究成果正在越来越多地应用于农业生产,深刻影响着农业的生产方式和效益,并日益显示出其解决人类所面临的环境恶化、资源匮乏、效益衰减等问题的巨大作用.     

环肽的分析方法与研究

环肽是一种较线性多肽更为稳定的具有多种生理功能和医药价值的环状多肽,在形成荷尔蒙、抗生素、离子载体系统、抗真菌素、癌制剂以及毒素等方面展现出丰富多样的生物活性,具有重大的应用价值。近年来随着生物技术以及生物学与化学领域的交叉发展,不断有新的环肽被分离并鉴定出来。本文综述了自然界存在的一些环肽及环肽的分离纯化、分析方法,并且对环肽的生物合成机制和化学合成进行了概述。     

常用全身麻醉药对炎性细胞因子的影响

在手术、创伤、应激等因素所致的炎症中,细胞因子起着重要作用。炎性细胞因子产生和释放过多,破坏了致炎因子和抗炎因子的平衡,从而引起炎症反应。适当的炎症反应可以起到抵抗损伤和修复创伤等防御作用;过度的炎症可致手术后感染、组织修复不良甚至诱发机体感染性休克和多器官功能障碍综合征（MODS）。常用全麻药对细胞因子具有一定的影响和潜在的调节作用,越来越受到麻醉医生的重视。本文就近几年的研究现状作一综述。     

活性毁伤材料及其应用技术研究进展

活性毁伤体制弹药战斗部技术,是武器毁伤领域近二十年发展起来的颠覆性前沿技术方向,为大幅度提升弹药战斗部威力开辟了新途径,成为支撑和引领高效毁伤技术发展的关键核心技术.本文首先从现役弹药战斗部威力形成方式着手,分析大幅提升威力面临的技术瓶颈,阐述活性毁伤体制弹药战斗部技术特点及优势.在此基础上,重点阐述活性毁伤材料技术、终点效应表征技术和武器化应用技术三方面研究进展.在活性毁伤材料技术方面,重点阐述材料体系、制备方法及力热化耦合响应等研究进展.在终点效应表征技术方面,重点阐述动能侵彻效应、化学能释放效应、结构毁伤增强效应、引燃和引爆增强效应等研究进展.在武器化应用技术方面,重点阐述活性毁伤材料在杀爆类、聚能类和侵彻类等弹药战斗部上应用研究进展,并讨论发展方向.     

从主要指标看中国科技创新发展态势——基于历年统计数据的分析

本文试图通过将创新资源投入、科技活动产出、创新绩效等方面的指标与世界主要国家进行对比,剖析中国科技创新的优势与劣势,并对中国创新能力做出宏观判断。结果表明,与发达国家相比,中国的规模和速度指标具有明显优势,而在反映质量、效率的结构指标和相对指标等方面相对不足。中国科技创新能力要得到大幅提升,仍需依靠持续积累和长期投入。     

Platelets in defense against bacterial pathogens

Platelets interact with bacterial pathogens through a wide array of cellular and molecular mechanisms. The consequences of this interaction may significantly influence the balance between infection and immunity. On the one hand, recent data indicate that certain bacteria may be capable of exploiting these interactions to gain a virulence advantage. Indeed, certain bacterial pathogens appear to have evolved specific ways in which to subvert activated platelets. Hence, it is conceivable that some bacterial pathogens exploit platelet responses. On the other hand, platelets are now known to possess unambiguous structures and functions of host defense effector cells. Recent discoveries emphasize critical features enabling such functions, including expression of toll-like receptors that detect hallmark signals of bacterial infection, an array of microbicidal peptides, as well as other host defense molecules and functions. These concepts are consistent with increased risk and severity of bacterial infection as correlates of clinical abnormalities in platelet quantity and quality. In these respects, the molecular and cellular roles of platelets in host defense against bacterial pathogens are explored with attention on advances in platelet immunobiology.     

Preliminary observations of a bacteriophage infecting Xenorhabdus luminescens (Enterobacteriaceae)

A bacteriophage infective to Xenorhabdus luminescens, a bacterial symbiont of heterorhabditid nematodes, was recovered from insects that supported poor nematode development. Plaque tests showed the phage particles to be infective only to primary and not secondary colonies of X. luminescens. The phage was not infective to X. nematophilus primaries or secondaries. The bacteriophage particles ranged 80-90 nm in length, with the head ranging from 40 to 50 nm in diameter. Restriction analysis was performed on isolated bacteriophage DNA. This first report of a bacteriophage from Xenorhabdus species has practical implications since it could be detrimental to cultures of Heterorhabditis nematodes that are being produced throughout the world for the biological control of insects.     

Mobile genetic elements of Staphylococcus aureus

Bacteria such as Staphylococcus aureus are successful as commensal organisms or pathogens in part because they adapt rapidly to selective pressures imparted by the human host. Mobile genetic elements (MGEs) play a central role in this adaptation process and are a means to transfer genetic information (DNA) among and within bacterial species. Importantly, MGEs encode putative virulence factors and molecules that confer resistance to antibiotics, including the gene that confers resistance to beta-lactam antibiotics in methicillin-resistant S. aureus (MRSA). Inasmuch as MRSA infections are a significant problem worldwide and continue to emerge in epidemic waves, there has been significant effort to improve diagnostic assays and to develop new antimicrobial agents for treatment of disease. Our understanding of S. aureus MGEs and the molecules they encode has played an important role toward these ends and has provided detailed insight into the evolution of antimicrobial resistance mechanisms and virulence.     

Influence of bacteria on epigenetic gene control

Cellular information is inherited by daughter cells through epigenetic routes in addition to genetic routes. Epigenetics, which is primarily mediated by inheritable DNA methylation and histone post-translational modifications, involves changes in the chromatin structure important for regulating gene expression. It is widely known that epigenetic control of gene expression plays an essential role in cell differentiation processes in vertebrates. Furthermore, because epigenetic changes can occur reversibly depending on environmental factors in differentiated cells, they have recently attracted considerable attention as targets for disease prevention and treatment. These environmental factors include diet, exposure to bacteria or viruses, and air pollution, of which this review focuses on the influence of bacteria on epigenetic gene control in a host. Host-bacterial interactions not only occur upon pathogenic bacterial infection but also continuously exist between commensal bacteria and the host. These bacterial stimuli play an essential role in various biological responses involving external stimuli and in maintaining physiological homeostasis by altering epigenetic markers and machinery.     

T-cell signal transduction and the role of protein kinase C

The T lymphocyte has a vital part to play in maintaining the host response to bacterial and viral infection and also appears to play a key pathological role in autoimmune diseases such as rheumatoid arthritis. In this review, we summarize the signalling pathways which trigger antigen-driven T-cell proliferation and examine the evidence which suggests that protein kinase C (PKC) is fundamental to this process. Finally, we discuss the therapeutic potential that PKC inhibitors may have in the treatment of autoimmune disease. Received 31 March 1998; received after revision 19 May 1998; accepted 19 May 1998     

Preliminary observations of a bacteriophage infectingXenorhabdus luminescens (Enterobacteriaceae)

A bacteriophage infective toXenorhabdus luminescens, a bacterial symbiont of heterorhabditid nematodes, was recovered from insects that supported poor nematode development. Plaque tests showed the phage particles to be infective only to primary and not secondary colonies ofX. luminescens. The phage was not infective toX. nenatophilus primaries or secondaries. The bacteriophage particles ranged 80–90 nm in length, with the head ranging from 40 to 50 nm in diameter. Restriction analysis was performed on isolated bacteriophage DNA. This first report of a bacteriophage fromXenorhabdus species has pratical implications since it could be detrimental to cultures ofHeterorhabditis nematodes that are being produced throughout the world for the biological control of insects.     

Bacterial laccases: promising biological green tools for industrial applications

Multicopper oxidases (MCOs) are a pervasive family of enzymes that oxidize a wide range of phenolic and nonphenolic aromatic substrates, concomitantly with the reduction of dioxygen to water. MCOs are usually divided into two functional classes: metalloxidases and laccases. Given their broad substrate specificity and eco-friendliness (molecular oxygen from air as is used as the final electron acceptor and they only release water as byproduct), laccases are regarded as promising biological green tools for an array of applications. Among these laccases, those of bacterial origin have attracted research attention because of their notable advantages, including broad substrate spectrum, wide pH range, high thermostability, and tolerance to alkaline environments. This review aims to summarize the significant research efforts on the properties, mechanisms and structures, laccase-mediator systems, genetic engineering, immobilization, and biotechnological applications of the bacteria-source laccases and laccase-like enzymes, which principally include Bacillus laccases, actinomycetic laccases and some other species of bacterial laccases. In addition, these enzymes may offer tremendous potential for environmental and industrial applications.     

Multifunctional cationic host defence peptides and their clinical applications

With the rapid rise in the emergence of bacterial strains resistant to multiple classes of antimicrobial agents, there is an urgent need to develop novel antimicrobial therapies to combat these pathogens. Cationic host defence peptides (HDPs) and synthetic derivatives termed innate defence regulators (IDRs) represent a promising alternative approach in the treatment of microbial-related diseases. Cationic HDPs (also termed antimicrobial peptides) have emerged from their origins as nature’s antibiotics and are widely distributed in organisms from insects to plants to mammals and non-mammalian vertebrates. Although their original and primary function was proposed to be direct antimicrobial activity against bacteria, fungi, parasites and/or viruses, cationic HDPs are becoming increasingly recognized as multifunctional mediators, with both antimicrobial activity and diverse immunomodulatory properties. Here we provide an overview of the antimicrobial and immunomodulatory activities of cationic HDPs, and discuss their potential application as beneficial therapeutics in overcoming infectious diseases.     

Bacterial antibiotic efflux systems of medical importance

Multidrug efflux systems endow on bacterial cells the ability to limit the access of antimicrobial agents to their targets. By actively pumping out antibiotic molecules, these systems prevent the intracellular accumulation necessary for antibiotics to exert their lethal activity. Drug efflux appears to be one of the most widespread antibiotic resistance mechanisms among microorganisms, since it has been demonstrated to occur in many Gram-positive and Gram-negative bacteria including medically important species like staphylococci, streptococci, enterobacteria and opportunistic pathogens like Pseudomonas aeruginosa. Efflux pumps can be specific for only one substrate or accommodate a more or less wide range of noxious products. Export of structurally unrelated compounds confers a multidrug-resistance phenotype on bacterial cells. Therapeutically critical levels of resistance can be achieved by overexpression of efflux systems, especially in those species such as P. aeruginosa which possess a low outer membrane permeability. It is suspected that the dual physiological function of active efflux systems is both the secretion of intracellular metabolites and the protection against a variety of harmful substances that the microorganism may encounter in its natural environment.