限制和修饰系统LlaBIII在构建抗噬菌体菌株中的作用

限制和修饰 (ｒｅｓｔｒｉｃｔｉｏｎａｎｄｍｏｄｉｆｉｃａｔｉｏｎ ,Ｒ Ｍ)系统是指由限制性内切酶和甲基化酶组成的单亚基或多亚基复合酶系统 ,两者通常成对出现 ,具有相同的ＤＮＡ识别位点 ,其作用相反。Ｒ Ｍ系统在原核生物中普遍存在 ,在保护细胞免遭外源病毒侵害方面具有重要作用[1] 。作为发酵剂的乳酸乳球菌在乳制品发酵中具有重要作用 ,但这类菌株极易遭受噬菌体感染 ,导致菌株产酸力降低 ,甚至发酵失败 ,造成严重的经济损失。所以在乳制品发酵过程中防止噬菌体感染就成为十分重要的问题。通过自然筛选或诱变处理等手段筛选噬菌…     

Rheological properties of polysaccharides produced by a Zoogloea sp.

A newly isolated marine bacterium, identified as Zoogloea sp., produced two different polysaccharides: one was water-soluble and the other was cell-bound. Both had non-Newtonian, pseudoplastic fluid behaviour and the solutions had low activation energies. The solutions of these polysaccharides showed rheological behaviour over a wide range of pH (2–12) and temperature (20–80 °C), and compatibility with NaCl.     

细胞凋亡机制的研究进展

以线虫和哺乳动物为实验材料,综述近年来对细胞凋亡机制的研究进展。     

Topoisomerase-I- and Alu-mediated genomic deletions of the APC gene in familial adenomatous polyposis

Germline mutation in the adenomatous polyposis coli (APC) gene results in familial adenomatous polyposis (FAP), a heritable form of colorectal cancer. We have previously reported two novel mutations that delete exons 11 and 14 of the APC gene, respectively, at the cDNA level without any splice junction defects at the genomic level. We describe here the precise breakpoints of the two mutations and the possible mechanisms leading to the genomic rearrangement. The first rearrangement is most likely a topoisomerase-I-mediated non-homologous recombination resulting in a 2-kb deletion that deletes exon 11 of the APC gene. Both 5' and 3' breakpoints have two topoisomerase I recognition sites and runs of pyrimidines within the 10-bp sequences in their vicinity. Further, the 3' breakpoint has an adenine-thymidine-rich region. This is probably the first report of a topoisomerase-I-mediated germline mutation in a tumor suppressor gene. The second rearrangement is most likely an Alu-Alu homologous recombination resulting in a 6-kb deletion encompassing exon 14. The Alu elements at the 5' and 3' breakpoints include the 26-bp core sequence thought to stimulate recombination. In both rearrangements, partial sequences from the long interspersed nuclear element family are in the vicinity of the breakpoints. Other than serving as markers for regions of DNA damage, their precise role in the recombination events, if any, is unclear. Both deletions result in truncated APC proteins missing the beta-catenin- and axin-binding domains, resulting in severe polyposis and cancer.     

中国林蛙卵人工孵化试验

中国林蛙 (Rana chinensis)是我国重要的经济蛙类之一。近年来 ,由于人们的生态经济意识不强 ,森林环境破坏严重 ,以及滥捕乱捉 ,使得中国林蛙种群数量急剧下降。但在一些地区 ,由于加强对中国林蛙的管护 ,大力发展林蛙人工养殖业 ,使之成为当地经济发展的一项重要支柱产业。由于林蛙人工饲养刚刚起步 ,饲养经验不完善 ,一些问题有待深入研究。如在自然条件下母蛙产卵时期 (4月上旬 )大致相同 ,但据以往观察 ,幼蛙出池时间却有很大差别 ,而出池时间的早晚表现在秋季回归时的体重差别较大 (约 1倍体重 )。因此缩短卵孵化时间 ,促使幼蛙提早…     

On the cicada genus Nipponosemia Kato,with description of one new species from China (Hemiptera,?Cicadidae)

The cicada genus Nipponosemia Kato is reviewed. Four species are illustrated, photographed and described, including three known species and one new species. A key to all species of this genusis presented, and information on the biology of Nipponosemia are provided. The systematic status of the tribe Cicadatrini and biogeography of Nipponosemia are discussed.