The structure of the unliganded extracellular domain of the interleukin-6 signal transducer gp130 in solution

Interleukin-6 (IL-6) plays an important role in immune responses and signals via two different pathways. When IL-6 binds to its non-signalling membrane-bound receptor (IL-6R), a non-covalent dimer of the ubiquitous interleukin-6 signal transducer gp130 is recruited to initiate intracellular signalling cascades. This so-called classical signalling pathway is restricted to cells expressing the membrane-bound IL-6R, such as hepatocytes and certain leukocytes. In addition, an alternative trans-signalling pathway uses soluble forms of IL-6R (sIL-6R) in complex with IL-6 to activate cells expressing gp130, but not membrane-bound IL-6R. In both cases, a tetrameric or hexameric signalling complex consisting of two gp130 molecules and one or two molecules each of IL-6 and (s)IL-6R is formed. The structure of the hexameric complex of the ligand-binding domains of gp130 (D1-D3) with IL-6 and sIL-6R has been solved by X-ray crystallography as well as the full-length extracellular part of gp130 (D1-D6) as a monomer. Since gp130 exists as a preformed dimer on the cell surface, we used a sgp130Fc fusion protein - consisting of two extracellular gp130 regions (D1-D6) dimerised by an IgG1-Fc part - to study the structure of unliganded gp130 extracellular domains in solution by small-angle X-ray scattering (SAXS). The SAXS data indicated that sgp130Fc forms a rigid molecule in solution. The low resolution structural model reveals an elongated assembly with an Fc base and two gp130 arms, whereby the orientation of the ligand-binding domains D1-D3 with respect to the membrane-proximal domains D4-D6 differs from that in the crystallographic monomer. Functional implications of these findings are discussed.     

盐碱池塘围隔生态系统浮游原生动物种群增长和生产量

1998年 5～ 9月用原位测定法研究了盐碱池塘无鱼和单养鲢围隔生态系统浮游原生动物的种群增长和生产量。结果表明 ,原生动物主要优势种团焰毛虫、瓜形膜袋虫、旋回侠盗虫、绿色前管虫和拟急游虫的世代时间分别为 6 93～ 2 3 10、 6 30～ 18 73、 9 90、 9 90～ 14 75和 7 6 2hr,其种群增长率分别为 0 0 30～ 0 10 0、0 0 37～ 0 110、 0 0 70、 0 0 47～ 0 0 70和 0 0 91/hr。 5～ 8月份无鱼和有鱼围隔原位试验瓶中原生动物累积日均产量分别为 10 70 2 5和 944 2 5mg/m3 ·d ,而相同时间两围隔中原生动物按月计算的日均生产量分别为 1 79和9 72mg/m3 ·d ,日P/B系数分别为 2 5 0和 2 0 3。无鱼围隔原生动物生物量和生产量均比有鱼围隔的低。     

细胞共培养技术在骨组织生物学中的应用

骨组织不同细胞相互交织构成了复杂的网络结构,通过旁分泌和间隙连接途径相互传递信号,调节了个体发育的骨重塑和成体的骨重建过程。细胞共培养技术是研究细胞间相互作用的重要手段,目前主要有接触式和非接触式两种。就骨组织而言,由于骨细胞(osteocyte)在力学感知及调节骨重塑/重建平衡中的中心枢纽作用,建立适宜于骨细胞与骨组织其他细胞间的共培养技术,对于骨组织基础生物学的研究具有重要意义。该文就当前应用于骨组织生物学中的细胞共培养技术进行综述。     

动物的模仿和玩耍学习行为

简要介绍了模仿和玩耍两种学习类型的基本概念、特点、类型和适应意义,提供了两张图片和大量实例。     

有效抽提乙醇中螨标本的核DNA

对如何有效地从乙醇保存的叶螨中抽提核基因组DNA作了探讨。70％乙醇保存的叶螨标本,经过干燥,TEN洗涤,蛋白酶K消化,酚—氯仿抽提,2倍体积无水乙醇沉淀等步骤,得到叶螨核基因组DNA沉淀,再用TE或无菌水溶解后,以其为模板,进行随机引物PCR扩增。结果显示.该方法抽提的DNA无Taq酶抑制物,且其纯度达到进行PCR反应对模板要求的程度。这为采用AP-PCR技术研究螨的系统分类提供了便利。     

Fructose uptake in Bifidobacterium longum NCC2705 is mediated by an ATP-binding cassette transporter

Recently, a putative ATP-binding cassette (ABC) transport system was identified in Bifidobacterium longum NCC2705 that is highly up-regulated during growth on fructose as the sole carbon source. Cloning and expression of the corresponding ORFs (bl0033-0036) result in efficient fructose uptake by bacteria. Sequence analysis reveals high similarity to typical ABC transport systems and suggests that these genes are organized as an operon. Expression of FruE is induced by fructose, ribose, or xylose and is able to bind these sugars with fructose as the preferred substrate. Our data suggest that BL0033-0036 constitute a high affinity fructose-specific ABC transporter of B. longum NCC2705. We thus suggest to rename the coding genes to fruEKFG and the corresponding proteins to FruE (sugar-binding protein), FruK (ATPase subunit), FruF, and FruG (membrane permeases). Furthermore, protein-protein interactions between the components of the transporter complex were determined by GST pulldown and Western blot analysis. This revealed interactions between the membrane subunits FruF and FruG with FruE, which in vivo is located on the external side of the membrane, and with the cytoplasmatic ATPase FruK. This is in line with the proposed model for bacterial ABC sugar transporters.     

乳酸左氧氟沙星对豚鼠心肌细胞电生理的影响

目的了解乳酸左氧氟沙星(LVFX)对豚鼠心室肌细胞电生理的影响.方法经腹腔注射不同剂量的LVFX,记录并分析注药后5～360 min豚鼠Ⅱ导联心电图的QT间期,以及校正的QT间期(QTc).采用全细胞膜片钳技术,记录不同浓度LVFX对体外单个心室肌细胞的延迟整流钾电流(IK)的作用.结果①LVFX给药量为200 mg/kg时,心电图QT间期延长19.38%±3.15%(P＜0.05);在50 mg/kg和100 mg/kg等较低剂量时,QT间期延长不明显(P＞0.05).②LVFX抑制IK电流,且抑制作用呈现电压依赖性和浓度依赖性.结论LVFX可能通过抑制心肌细胞IK电流引起心脏QT间期延长,临床应谨慎使用.     

九连小蘖悬浮培养细胞生理生化研究 Ⅰ.细胞生长与培养液的电导率和过氧化物酶活性的变化

本文报道了九连小蘖细胞悬浮培养过程中,细胞生长与培养液的电导率、pH值、可溶性糖含量及过氨化物酶活性的变化。实验表明细胞生长曲线与培养液的电导率、可溶性糖含量变化的曲线恰成镜像关系。而细胞生长曲线与培养液的过氨化物酶活性变化的曲线相互平行。从而,可以通过监测培养液的电导率和过氧化物酶活性的变化来了解细胞生长状况,并可作为植物细胞培养过程中生物量增长的参考指标。     

在板栗疫病菌线粒体中检出低毒病毒编码蛋白p29

p29蛋白是低毒病毒基因组编码的一个木瓜蛋白酶样蛋白。前人研究发现,在宿主板栗疫病菌(Cryphonectria parasitica)体内表达p29,会引起真菌毒力降低,色素产生减少,丧失产生无性孢子的能力。除已知p29与源于高尔基体的膜结构共分离之外,p29在细胞内的其它分布形式未明。本研究在成功制备p29特异抗体和高效分离板栗疫病菌线粒体的基础上,尝试用p29抗体检测线粒体中是否存在p29蛋白。Western印迹结果表明,受CHV1-EP713感染的EP713菌株线粒体中存在与p29抗体特异作用的病毒蛋白。本研究结果暗示,低毒病毒蛋白p29可能参与调控宿主线粒体功能。     

大豆诱导型启动子驱动类受体蛋白激酶GmSARK转基因植物分析

植物LRR型类受体蛋白激酶在植物生命活动中发挥着重要作用。前期研究发现,大豆（Glycine max）LRR型类受体蛋白激酶基因GmSARK可能参与调控大豆叶片的衰老过程。利用CaMV35S启动子驱动组成型过表达GmSARK基因可导致转基因植株出现致死表型,据此构建了可诱导型启动子GVG驱动GmSARK基因过表达的双元表达载体,转化野生型拟南芥（Arabidopsis thaliana）并获得了多株转基因植株。研究结果表明,外源施加诱导物地塞米松可引起GmSARK基因在转基因植株中过表达,并导致转基因植株出现叶片变黄下卷和生长受抑制等表型;外源细胞分裂素处理可以抑制GmSARK的表达,但是不能逆转GmSARK过表达所引起的上述变化。