非正交修正型平面蜗杆传动的研究

本文简要地介绍了利用微机绘图对非正交修正型平面蜗轮副的几何和啮合特性进行的一些研究结果。文中给出了一组理论公式,初步研究结果表明:该类(即第Ⅱ类)的“基型”传动在防止小速比时蜗杆边齿顶厚易变尖等主要特性皆不低于SG-71型(即第Ⅰ类)平面蜗轮副。     

接种S180肉瘤的小鼠肿瘤组织和器官中组蛋白与正常小鼠的比较研究

采用酸抽提法分别提取接种S180肉瘤的小鼠肿瘤组织以及肝、脾、肾等器官的组蛋白和正常小鼠相应组织和器官的组蛋白，并采用SDS-PAGE方法进行检测．结果表明，正常小鼠的肝、脾、肾等器官提取的组蛋白在检测中可以看到组蛋白H1的亚带，而接种了S180肉瘤的小鼠的肿瘤组织以及肝、脾、肾等器官的组蛋白在检测中基本无明显的条带．这说明发生在小鼠身上的S180肿瘤组织对小鼠的肝、脾、肾组织中的组蛋白产生一定影响．     

组蛋白H2A与染色质的动态结合

在真核细胞中,核小体的核心结构组蛋白被DNA紧密缠绕,但是这种紧密的结合有时也可能变得松散,以利于其他蛋白与DNA的结合。将组蛋白H2A与绿色荧光蛋白的融合表达载体和核仁纤维蛋白(fibrillarin)与红色荧光蛋白的融合表达载体共转染COS7细胞,利用荧光漂白恢复(FRAP)技术研究了H2A在细胞核内的动态变化。结果显示,在少数间期细胞的核仁区有组蛋白聚集现象,且此区域内H2A的运动速度显著地高于非核仁区的H2A,推测该现象仅出现于细胞周期的某个时期。     

Crucial function of histone lysine methylation in plant reproduction

Unlike animals, plants do not set aside germ cells early in development. In angiosperm species, reproduction occurs in the adult plant upon flowering. The multicellular male and female gametophytes differentiate from meiotic products within reproductive floral organs. Double fertilization is another remarkable feature of most angiosperm species. The zygote derived from fertilization of the egg cell by one of the sperm cells and the endosperm from fertilization of the central cell by the second sperm cell develop in a coordinated manner together and enclosed in the sporophytic maternal integuments, forming the seed. Understanding plant reproduction is biologically pertinent and agronomically and ecologically important. Here, we describe the known functions of histone lysine methylations in various steps of reproduction in the reference plant Arabidopsis thaliana. It is emerging that histone lysine methylation is key for understanding epigenetic regulation networks of genome function.     

The histones ofDictyostelium discoideum

Summary The histones of the cellular slime mouldDictyostelium discoideum have been separated by electrophoresis using both acid urea and sodium dodecyl sulphate systems, and the gel pattern compared with that of histones fromPhysarum polycephalum and calf thymus.Dictyostelium is found to possess a full complement of H1, H2A, H2B, H3 and H4.     

表观遗传学研究进展

 概述了表观遗传调节模式、表观遗传调节的效应、植物表观遗传学的研究进展等。在每种细胞中,都会发生一部分特异基因激活、另一部分基因抑制的现象,形成多种基因表达模式。表观遗传指DNA序列不发生变化,而基因表达发生可遗传改变的现象。表观遗传学改变包括DNA甲基化、组蛋白修饰、非编码RNA作用等,产生基因组印记、母性影响、基因沉默、核仁显性、休眠转座子激活等效应。表观遗传变异是环境因素和细胞内遗传物质间交互作用的结果,其效应通过调节基因表达,控制生物学表型来实现。正是因为表观修饰对于维持生物体内环境和各器官系统功能的重要性,表观遗传的异常会引发疾病,这也成为药物和治疗方案设计的着眼点。     

青霉菌组蛋白去乙酰化酶基因的敲除及其次级代谢产物变化

丝状真菌尤其是青霉菌Penicillium代谢的各类次级产物日趋成为研制新药的重要来源,很多药物如抗癌药物、抗生素、免疫抑制剂等均来源于真菌。然而真菌次级代谢受多因素的影响,其中表观遗传修饰起到重要的调控作用。组蛋白乙酰化表观遗传修饰常与转录激活相关,从而促进次级代谢产物的合成。以青霉属真菌Penicillium christenseniae SD-193.84为研究对象,利用生物信息学手段确定其组蛋白去乙酰化酶（HDAC）基因,建立该菌中同源重组基因敲除技术,对该基因进行敲除,并比较了基因敲除前后次级代谢产物的变化,发现HDAC影响了多种次级代谢产物的合成。本研究为青霉菌分子遗传操作及次级代谢调控提供了参考。     

Modulation by polyamines of apoptotic pathways triggered by procyanidins in human metastatic SW620 cells

We showed previously that inhibition of polyamine catabolism with the polyamine oxidase inhibitor MDL 72527 (MDL) potentiates the apoptotic effects of apple procyanidins (Pcy) in SW620 cells. Here we report that Pcy caused an activation of the intrinsic apoptotic pathway through enhanced polyamine catabolism and mitochondrial membrane depolarization. MDL in the presence of Pcy caused a profound intracellular depletion of polyamines and exerted a protective effect on mitochondrial functions. MDL potentiation of Pcy-triggered apoptosis was reversed by addition of exogenous polyamines. In addition, MDL in combination with Pcy activated the extrinsic apoptotic pathway through enhanced TRAIL-death receptor (DR4/DR5) expression. Potentiation of Pcy-triggered apoptosis by MDL was inhibited when cells were exposed to specific inhibitors of DR4/DR5. These data indicate that the depletion of intracellular polyamines by MDL in the presence of Pcy caused a switch from intrinsic to extrinsic apoptotic pathways in human colon cancer-derived metastatic cells. Received 15 January 2008; received after revision 19 February 2008; accepted 7 March 2008