温度对中型指环虫产卵和孵化的影响

指环虫病是严重影响鱼类养殖的寄生虫病.为了有效控制指环虫病,实验研究了寄生在金鱼(Carassius auratus)鳃部的中型指环虫(Dactylogyrus intermedius)卵、纤毛幼虫的形态,以及在离体条件下温度对其产卵和孵化的影响.成熟的中型指环虫虫卵大部分为梨形,长30 μm左右,后端有一个卵柄.纤毛幼虫呈圆筒状,两端稍尖,眼点两对;后吸盘具有若干对小锚钩;在前部、中部和尾部分别具有一圈纤毛.实验研究了4℃、10℃、22℃、30℃和35℃条件下中型指环虫的产卵和孵化情况,在4℃条件下,中型指环虫基本不产卵也不孵化;在其他4个温度条件下,产卵量随着温度的升高而增加,其平均产卵量分别为3.30、4.10、4.13和4.24枚/虫.统计结果显示:在35℃条件下的产卵量明显高于10℃(P＜0.05),其他温度条件下的平均产卵量没有显著性差异.中型指环虫的产卵速率随着温度的升高而加快,产卵维持的时间分别为4d、23h、15h和llh.孵化率在22℃时最高,为72.7％,在30℃和35℃的孵化率为50％左右,卡方检验显示:4种温度下的孵化率之间没有显著性差异p＞0.05);随着温度的升高,孵化速率逐渐加快,而孵化时间和纤毛幼虫的存活时间则缩短,平均孵化时间分别为24d、3d、42h和26h,纤毛幼虫的最长存活时间分别为4d、3d、56h和34h.结果显示,当水温为22℃时,中型指环虫的产卵数量和纤毛幼虫的存活时间都比较高,且孵化率最高,表明该温度条件较适合中型指环虫的种群增长.     

我国分离的肠道病毒71型(SHZH03病毒株)全基因组核苷酸序列分析

对肠道病毒71型(enterovirus 71,EV71)中国(深圳)分离株SHZH03进行了全基因组(未包括多聚腺苷尾)7406个碱基的核苷酸序列测定.结果表明,SHZH03株与其它肠道病毒71型毒株相比,在编码区没有核苷酸的缺失和插入,其5′UTR和3′UTR区的长度和序列有一定的差异.核苷酸同源性比较结果表明,在P1区SHZH03株与SHZH98株、中国台湾流行株(TW2086、TW2272)的同源性较高(分别为92.5%,90.1%和87.9%),与新加坡流行株SIN5666、SIN5865及标准株MS、BrCr的同源性则在81%左右,而与Coxsackievirus A16(Cox.A16)的同源性最低(63.6%).氨基酸同源性比较结果表明,在P1区SHZH03株与Cox. A16的同源性最低,但在P2和P3区SHZH03株与Cox.A16的同源性最高.P1区的遗传进化分析表明,SHZH03株和中国台湾1998年流行的EV71毒株的亲缘关系较近,属于同一型(genogroup),而与标准株BrCr和MS的亲缘关系较远.上述结果有助于肠道病毒71型的基础研究和中国对于EV71所致疾病的预防.     

Discovery of antibacterial cyclic peptides that inhibit the ClpXP protease

A method to rapidly screen libraries of cyclic peptides in vivo for molecules with biological activity has been developed and used to isolate cyclic peptide inhibitors of the ClpXP protease. Fluorescence activated cell sorting was used in conjunction with a fluorescent reporter to isolate cyclic peptides that inhibit the proteolysis of tmRNA-tagged proteins in Escherichia coli. Inhibitors shared little sequence similarity and interfered with unexpected steps in the ClpXP mechanism in vitro. One cyclic peptide, IXP1, inhibited the degradation of unrelated ClpXP substrates and has bactericidal activity when added to growing cultures of Caulobacter crescentus, a model organism that requires ClpXP activity for viability. The screen used here could be adapted to identify cyclic peptide inhibitors of any enzyme that can be expressed in E. coli in conjunction with a fluorescent reporter.     

ARHGAP18, a GTPase-activating protein for RhoA, controls cell shape, spreading, and motility

Rho GTPases are molecular switches that transmit biochemical signals in response to extracellular stimuli to elicit changes in the actin cytoskeleton. Rho GTPases cycle between an active, GTP-bound state and an inactive, GDP-bound state. These states are regulated by two distinct families of proteins-guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We studied the role of a previously uncharacterized GAP, ARHGAP18 (MacGAP). Overexpression of ARHGAP18 suppressed the activity of RhoA and disrupted stress fiber formation. Conversely, silencing of ARHGAP18 by small interfering RNA transfection-enhanced stress fiber formation and induced rounding of cells. We examined the role of ARHGAP18 in cell spreading and migration. Immunofluorescence analysis revealed that ARHGAP18 was localized to the leading edge during cell spreading and migration. ARHGAP18-knockdown cells showed impaired spreading, premature formation of stress fibers, and sustained activation of RhoA upon cell attachment. In addition, knockdown and overexpression of ARHGAP18 resulted in the inhibition and promotion of cell migration, respectively. Furthermore, ARHGAP18 was required for the polarization of cells for migration. Our results define ARHGAP18 as one of the crucial factors for the regulation of RhoA for the control of cell shape, spreading, and migration.     

二氮嗪对自发性高血压大鼠心功能及心肌ERK和JNK表达的影响

目的:探讨二氮嗪对离体自发性高血压大鼠心脏缺血/再灌注心功能及心肌组织ERK和JNK表达的影响及可能机制。方法:雄性自发性高血压大鼠取心行Langendorff灌流。实验分为5组(n=6/组):对照组(Con)在平衡后继续灌流40min,全心缺血25min,复灌30min。其余各组除全心缺血前处理不同外,余均同对照组。缺血预处理组(IP)2次给予5min缺血+10min复灌,二氮嗪预处理组(DP)给予2次含50μmol·L-1二氮嗪的K-H液10min后给不含二氮嗪的K-H液5min,5-HD、5-HD+DP组则在平衡后给予10min150μmol·L-1线粒体KATP阻断剂5-HD,余同Con及DP组。结果:IP组及DP组复灌末左室发展压、+dP/dtmax和-dP/dtmax的恢复率均高于Con组(P<0.01),但两组左室舒张末期压恢复率低于Con组(P<0.01);5-HD能拮抗二氮嗪引起的心功能指标的改善。复灌末IP、DP及5-HD+DP组ERK表达增加。IP组及DP组心肌的JNK表达低于Con组(P<0.05),5-HD+DP组JNK表达显著高于DP组。结论:二氮嗪预处理对离体自发性高血压大鼠心肌缺血/再灌注损伤有保护作用,此保护作用可能与ERK的表达增加及JNK表达减少有关。     

Enhanced immunodetection of cell-free synthesized erythropoietin under denaturing conditions

A monoclonal antibody produced by hydridoma cell line, ATCC HB8209, was used to detect and purify erythropoietin synthesized in a cell-free system. The antibody was raised against the N-terminal 20 residues of erythropoietin. It retained anti-erythropoietin activity in 6 M urea in which most of the cell-free synthesized erythropoietin became soluble and gave an enhanced activity of the antibody.     

非线性接触率和种群动力学对SI传染病模型的影响

本文研究了具有一般非线性接触率和易感类中具有Logistic增长的SI传染病模型的正不变集、平衡位置以及平衡位置的稳定性．