《微生物学》：二苯脲类化合物或能治疗肺结核

英国研究人员日前报告说,有些化合物可以通过抑制结核杆菌中一种酶的功能来杀死这种细菌,这是一种对付结核杆菌的新方法,将有助于研发治疗肺结核的新药物。     

科研快讯

《微生物学》:二苯脲类化合物或能治疗肺结核英国研究人员日前报告说,有些化合物可以通过抑制结核杆菌中一种酶的功能来杀死这种细菌,这是一种对付结核杆菌的新方法,将有助于研发治疗肺结核的新药物。     

采用微生物-生物技术途径降解芳香烃化合物

芳香烃化合物指的是分子结构中含有苯环的化合物,实际上是苯的衍生物。其分子结构稳定,废弃后在自然环境中难以被降解。据统计,这类毒性强的物质有1100种,其中有些化合物排放到环境中造成污染,人体吸收后具有很高的毒性作用,可致癌、致畸、致突变。引发这“三致”的物质(芳烃化合物)已引起世界科研工作的重视。传统方法深埋、     

植物次生代谢产物的应用

世界上有形形色色的植物,在它们的新陈代谢过程中产生了各种各样的化学物质,其中有些化合物是维持植物生命活动所必须的,通常称之为初生代谢产物,如糖、氨基酸、多肽、蛋白质等。而在新陈代谢过程中产生的绝大多数化合物对植物本身的生命活动似乎无关紧要,如生物碱、黄酮、香豆素、木脂素、挥发油、蒽醌、皂甙、强心甙等成分,这些化合物通常被称为次     

以智取胜的植物

植物还会“智胜”动物。有的植物为了使自己免受动物侵害,就分泌出某些化学物质来对付动物。如昆虫吃了植物的茎叶之后,就会消化分解植物体内的多糖。昆虫胃里有糖苷酶,它能促使多糖水解成单糖,在昆虫体内产生能量维持生命。有些植物根据这一情况,制造出一类带羟基的吡咯烷化合物,其化学结构跟果糖相似,能成功欺骗糖苷酶,使它误把这种化合物当作果糖结合,但一结合就再难水解,从而破坏了糖苷酶的催化水解反应,昆虫吃     

植物细胞大量培养与次生物质代谢研究的一点意见

植物是人类生活需要的天然产物的重要来源,如药物、香料、色素、调味剂等。本世纪末,地球上人口爆增、耕地减少、环境污染、资源亏缺,靠采集野生资源或人工种植的方法来获得原料,已远不能满足需要。由于有机化学的发展,可用人工合成的方法来获得某些产品,但结构复杂的化合物,合成困难,且有些合成产品对人体健康存在不利的影响。五、六十年代兴起的植物细胞培养与次生物质代谢研究,因具有不受环境条件限制,不受病虫害侵     

培养时间相关的中国被毛孢代谢产物初步分析

采用偏最小二乘判别分析法(PLS‐DA)分析不同培养时间中国被毛孢代谢产物的变化。结果表明,在不同培养时间内,供试菌株菌丝的次级代谢产物差异显著。根据代谢组差异可将中国被毛孢培养时间分为前期(19d前)、中期(19–26d)、后期(26d后)3个阶段。3个培养阶段共出现43种显著差异化合物,其中仅在培养前期出现的差异化合物有3种,大部分差异代谢物出现在前期后段及中期,包括8种抗生素及多种具有独特生物活性的物质,在培养后期有3种抗生素没有检测到。在整个培养过程中,有些代谢物可能是受反馈调节机制控制,其含量呈波动变化;有些是持续合成的稳定的代谢终产物,其含量持续增加;有些由于合成速度逐渐减慢,或分解速度逐渐加快而出现含量持续下降。从代谢物的利用角度来说,人工培养菌丝适宜在培养中期采收,因为此阶段生物活性代谢物最多,但对于含量持续下降的化合物的利用应在培养前期采收;对于含量持续增加的化合物的利用宜在培养后期采收。     

天然醛类化合物的存在类型和共存关系

带有醛基的天然化合物,具有苯丙素、萜类、皂苷类、生物碱、香豆素和蒽醌等多个存在的类型。一些植物中存在的多个醛类化合物,往往是带有醛基的母核部分相同,而取代基不同。而在有些植物中,还可以见到一些母核部分相同,而仅仅是醛基的碳呈不同氧化状态的系列化合物,表现为甲基(-CH3)、羟甲基(-CH2OH)、醛基(-CHO)、羧酸基(-COOH)和酯基(-COOR)。     

污染物的生物降解

水体及各种类型土壤中分布着种类繁多的人工合成化合物。其中,有些是有毒的或可能在自然生态系统中被转变为有害物质。环境学家、生物学家、化学家已经密切关注着自然生境中此类有机化合物的行为模式及其最终归宿;司题。近年统计表明,数目庞大的化合物被生产应用。许多化合物被随意地排入水体和土壤中。值得注意的是,这些化合物中许多都是生物学家和化学家研究的空白点。排入陆生或水生生态系统中的有机化合物可能会与环境因子发生非酶促或酶促反应。几种典型的化学反应机制,比如：水生环境中的光化学反应已为大家所了解。目前的研究结…     

Ames法和SCE法检测正定霉素和甲氨基喋吟钠盐的诱变性研究

据估计,目前全世界人工合成的化合物其 总数已超过七千万种。每年还有近千种新的化 合物进人人类环境。这些化合物包括农药、药 物、食品添加物、化工产品、工业三废等。其中 有些能改变人体细胞里DNA的结构,从而诱 发肿瘤或导致畸胎和提高遗传病的发病率。因 此,检测化合物的诱变性和潜在致癌性是关系 到人类健康的大事。当前,我国化学品的生产 和使用正日益扩大,随着四个现代化的进展,检 Al工作的重要性将更加突出。     

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.