大肠杆菌O157:H7的毒力岛与毒力因子的研究进展

大肠杆菌O157:H7是肠出血性大肠埃希菌的主要血清型,能引起人的出血性肠炎和溶血性尿路综合征。大肠杆菌O157:H7致病机制与其毒力岛编码的毒力因子有关,这些毒力岛包括染色体上的LEE岛、前噬菌体上的slt基因、大质粒上的hly、ka tP、espP、toxB、stcE基因。大肠杆菌O157:H7致病机理不是由单一毒力因子所决定,而是多种毒力因子共同作用的结果。     

副溶血弧菌耐热性溶血素的肠毒性及细胞毒性

副溶血弧菌是在世界范围内因食用海产品而致胃肠炎的主要病原体.耐热性溶血素(TDH)是该菌分泌的一种主要的致病因子,TDH以细胞毒性作用引起肠液分泌的增加.     

禽致病性大肠杆菌IMT5155 疑似毒力基因在人源及动物源大肠杆菌中的分布

[目的]检测禽致病性大肠杆菌IMT5155自分泌黏附素基因等具有代表性的疑似毒力基因在不同来源大肠杆菌中的分布,为进一步研究其致病机理提供依据.[方法]采用PCR和Dot blot,检测疑似毒力基因在不同地区(101株大肠杆菌中国分离株和121株大肠杆菌德国分离株)、不同来源(人源、禽源及猪源)大肠杆菌中的分布,并分析其和大肠杆菌系统进化分群的关系.[结果]自分泌黏附素基因B11等11个疑似毒力基因在禽致病性大肠杆菌中分布率较高,阳性率分别为:A1 36.4%(32/88)、A8 53.4%(47/88)、A1063.6%(56/88)、B1137.5%(33/88)、F3 59.1%(52/88)等,且疑似毒力基因主要存在于大肠杆菌B2进化群中.值得注意的是,D1、E9和F11基因片段在新生儿脑膜炎大肠杆菌中有较高的分布率,分别为60%(6/10)、80%(8/10)和90%(9/10),而在新生儿脑膜炎大肠杆菌中未检测到B11基因.[结论]自分泌黏附素B11等疑似毒力基因与禽致病性大肠杆菌关系密切,但疑似毒力基因D1、E9和F11与新生儿脑膜炎大肠杆菌密切相关,提示禽致病性大肠杆菌可能是新生儿脑膜炎大肠杆菌的毒力基因储库.     

肠出血性大肠杆菌O157:H7紧密黏附素与受体的研究进展

肠出血性大肠杆菌O157∶H7能引起出血性结肠炎、溶血性尿毒综合征、血小板减少性紫癜等。大肠杆菌O157∶H7的主要毒力因子紧密黏附素由其毒力岛LEE岛上的eae基因编码,C末端的280个氨基酸是受体结合位点。目前发现紧密黏附素受体有紧密黏附素转位受体(Tir)、核仁素和β1整合素。紧密黏附素主要与受体Tir结合,通过Ⅲ型分泌系统转位到宿主细胞,在Tir-细胞骨架偶联蛋白(Tccp)的参与下,与N-Wiskott aldrich综合征蛋白、肌动蛋白-相关蛋白2/3相互作用产生信号级联放大,导致宿主大肠黏膜上产生黏附-抹去损伤。     

引起无症状性菌尿的大肠埃希菌的毒力特征

大肠埃希菌(简称大肠杆菌)是引起无并发症尿路感染(UTI)最常见的细菌。具有尿路致病性的大肠杆菌可产生多种参与其致病过程的毒力因子,包括P-菌毛、溶血素、aembactin和细胞毒性坏死因子-1。然而尿液中细菌的繁殖通常在没有临床症状的情况下发生,即无症状性菌尿(ABU)。ABU不一定需要治疗,而且良性细菌的无症状繁殖还可有助于     

大肠杆蓖O157：H7致病因子及其保护性免疫研究现状

大肠杆菌O157：H7是肠出因型大肠杆菌（EHEC）的主要病原血清型,它可产生特殊的粘附因子粘附靶细胞,产生Vero毒素和肠溶血素毒力因子。近几年对大肠杆菌O157：H7的毒力因子有了深入的了解,对致病机理作了一些探讨,用实验动物对保护性免疫进行了研究。本文对近几年来O157：H7大肠杆菌的致病因子及其主要的保护性免疫的研究作一简要综述。     

大肠杆菌O157:H7致病因子及其保护性免疫研究现状

大肠杆菌O157:H7是肠出血型大肠杆菌(EHEC)的主要病原血清型,它可产生特殊的粘附因子粘附靶细胞,产生Vero毒素和肠溶血素毒力因子.近几年对大肠杆菌O157:H7的毒力因子有了深入的了解,对致病机理作了一些探讨,用实验动物对保护性免疫进行了研究.本文对近几年来0157:H7大肠杆菌的致病因子及其主要的保护性免疫的研究作一简要综述.     

奇异变形杆菌毒力因子的研究进展

奇异变形杆菌是革兰阴性细菌,在自然界中广泛存在,具有特殊的群集运动能力,与临床关系密切,可在膀胱和肾脏中形成结石,在尿道留置管外表面、内腔中形成结晶生物膜,是引起复杂尿路感染的主要病原体,主要的毒力因子包括菌毛、黏附素、尿素酶、溶血素、金属摄取和免疫逃避等。综述了近年来有关奇异变形杆菌毒力因子的研究,为相关研究提供参考。     

白念珠菌侵袭宿主毒力因子研究进展

白念珠菌是一种寄生于人类黏膜表面的条件致病菌,是导致免疫功能低下人群侵袭性真菌感染的主要病原菌。白念珠菌形成侵袭性感染的过程主要分为黏附、侵袭、播散、形成感染灶等步骤,其中黏附和侵袭过程最为关键。黏附是白念珠菌入侵宿主的前提,该过程主要依赖于细胞壁表面的黏附素。侵袭阶段主要与菌丝形成、细胞壁表面毒力蛋白表达和蛋白水解酶分泌增加有关。形成菌丝是白念珠菌侵袭宿主的关键因素,主要由细胞内cAMP/PKA和MAPK等信号通路调控;侵袭素主要位于白念珠菌细胞壁表面,可以协助其穿刺宿主上皮细胞、诱导内吞作用;白念珠菌还可分泌多种蛋白水解酶,它能够破坏宿主组织细胞,协助白念珠菌形成感染灶。该文主要对白念珠菌黏附和侵袭宿主过程中关键的毒力因子进行综述,为理解白念珠菌致病机制以及选择潜在的药物靶点提供参考。     

鳗弧菌毒力相关基因的研究进展

鳗弧菌是引起多种海水鱼类出血性败血症的病原菌。其致病机理与各个毒力基因的协同作用密切相关。文中综述了鳗弧菌的主要毒力基因,包括编码外毒素、粘附因子、侵袭因子、细胞表面成分以及铁吸收系统的基因和部分检测方法。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.