Faciogenital dysplasia protein (FGD1) and Vav, two related proteins required for normal embryonic development, are upstream regulators of Rho GTPases

BACKGROUND: Dbl, a guanine nucleotide exchange factor (GEF) for members of the Rho family of small GTPases, is the prototype of a family of 15 related proteins. The majority of proteins that contain a DH (Dbl homology) domain were isolated as oncogenes in transfection assays, but two members of the DH family, FGD1 (the product of the faciogenital dysplasia or Aarskog-Scott syndrome locus) and Vav, have been shown to be essential for normal embryonic development. Mutations to the FGD1 gene result in a human developmental disorder affecting specific skeletal structures, including elements of the face, cervical vertebrae and distal extremities. Homozygous Vav-/- knockout mice embryos are not viable past the blastocyst stage, indicating an essential role of Vav in embryonic implantation. RESULTS: Here, we show that the microinjection of FGD1 and Vav into Swiss 3T3 fibroblasts induces the polymerization of actin and the assembly of clustered integrin complexes. FGD1 activates Cdc42, whereas Vav activates Rho, Rac and Cdc42. In addition, FGD1 and Vav stimulate the mitogen activated protein kinase cascade that leads to activation of the c-Jun kinase SAPK/JNK1. CONCLUSIONS: We conclude that FGD1 and Vav are regulators of the Rho GTPase family. Along with their target proteins Cdc42, Rac and Rho, FGD1 and Vav control essential signals required during embryonic development.     

Age changes in cells in Streptococcus diacetilactis cultures

The activity of metabolism changed in the cultures of Streptococcus diacetilactis, strain Bogdan, with aging. The number of viable cells decreased as well as the ability to evolve oxygen, to produce C-4 compounds, and to react to pH changes by liberating acids upon alkalifying or neutral products upon acidifying. After the culture had been grown during 72 hours, 2,3-butyleneglycol was found in the cultural broth, and the number of viable cells was low. As was revealed by electron microscopy, the cells were intact during 48 hours; they started to disintegrate by 72 hours. After 120 hours all cells were disintegrated. First, the cells produced no more mesosomes, became less electron dense; then the cell wall was decomposed and the contents of the cell poured through disruptions in the cytoplasmic membrane.     

甲醛在nano-Pt/GC电极上的电催化氧化研究

应用循环伏安法制备了nano-Pt/GC电极,并用SEM和电极在H2SO4中的循环伏安曲线对其进行了表征。结果表明,该方法制备的电极表面铂粒子分布较为均匀,粒径大小约为140nm,电极具有较大比表面积。电化学实验表明,该电极对甲醛电氧化的催化活性明显好于铂片电极。修饰电极的催化活性与铂粒子的沉积条件有关,铂微粒在电极表面的最佳沉积条件为循环次数100次和沉积速度5mV/s。     

心桥无止甘肃省天水市大滩村无止桥建设与实践

文章介绍了甘肃省天水市大滩村无止桥的设计及建设过程。项目在扶助贫困的同时,运用生态可持续技术为发扬地方传统文化做出有益的尝试,并藉此措建起联系内地和香港两地的“心桥”。     

低噪声沥青路面吸声特性研究

通过混响室法测试了低噪声沥青路面的吸声系数,研究了低噪声沥青路面的噪声特征,并与驻波管法测试结果进行了比较.引用圆管模型对吸卢系数的影响因素进行了解释.结果表明,低噪声沥青路面降噪系数为0.45,比普通混凝土路面理论降噪6.79 dB.混响室法测得吸声系数在中高频段要稍高于驻波管法所得结果.     

新工艺制备矿渣微晶玻璃初探

目前制备矿渣微晶玻璃的方法主要有压延法、浇注法和烧结法,在充分吸收浇注法和烧结法优点的基础上,提出一种制备矿渣微晶玻璃的新工艺.并以钽铌尾矿为主要原料,基础玻璃组成选择在CaO-Al2O3-SiO2系统的玻璃形成区内,利用DTA、XRD和SEM等测试办法研究了热处理工艺制度对晶化过程、晶相组成、显微结构的影响.结果表明,采用新工艺制备微晶玻璃在实验室是可行的,热处理工艺制度的变化会影响玻璃的析晶转变过程和微晶玻璃的微观结构.     

环氧丙烯酸树脂的合成及其改性

采用丙烯酸(AA)对环氧树脂(EP)进行光活性改性制备环氧丙烯酸树脂(EA),通过单因素试验法优选出制备EA的最佳反应条件。结果表明:制备EA的最佳反应条件是以N′N-二甲基苯胺为催化剂,w(催化剂)=2.5%(相对于反应物总质量而言);以对苯二酚为阻聚剂,w(阻聚剂)=0.1%(相对于反应物总质量而言);反应温度为90℃,反应时间为2.0～3.5h。当w(引发剂)=1.0%时,EA的固化性能较好。采用多元醇先对EP进行改性,然后再进行光活性改性,可明显降低产物的黏度。     

大型储罐单盘浮顶施工工艺

大型单盘浮顶的钢板薄、焊缝密度高、焊接工作量大、焊缝交叉点较多．很难控制焊接变形．不仅影响浮顶单盘焊后的外观质量．而且影响浮顶单盘的排水能力。结合大型储罐单盘浮顶的施工．分析了施工工艺的特点与不足．创新性地总结出了大型储罐单盘浮顶施工的新工艺。新工艺采用CO2气体保护焊＋手工焊焊接方法、更利于均匀释放焊接应力的焊接顺序以及更合理的浮顶临时架台搭设方法等,能有效节约施工成本,缩短工期,解决单盘浮顶焊接变形等问题。文章对该工艺的施工特点、适用范围、工艺原理、工艺流程及操作要点等进行了详细的介绍。