蓝藻的硫氧还蛋白

蓝藻(蓝细菌)是一种分布广泛,结构简单的原核生物。不象其它的光合细菌,蓝藻含有叶绿素a,并且象真核藻和高等植物一样,以分解水作为光合电子传递的电子源。有许多种蓝藻能够固氮。大多数丝状蓝藻具有营养胞和异形胞。异形胞是厌氧的固氮场所。       

循环包装回收技术在筛选肝癌细胞相关耐药基因中的应用

肝癌先天性多表达多药耐药基因,严重影响肝癌的化疗效果,筛选肝癌细胞中的耐药基因,研究其耐药机制有助于提高肝癌化疗效果,提高肝癌的治愈率。首先构建肝癌细胞逆转录病毒的cDNA文库,感染成纤维细胞,使得逆转录病毒基因整合进细胞,加药筛选,存活细胞中的基因再次包装成病毒,用于下一轮筛选。采用循环包装回收(Cyclical packaging rescue,CPR)技术进行肝癌细胞耐药基因的筛选即是通过病毒包装将基因从细胞中钓取出来,相比于常规筛选方法,仅通过一轮筛选可能会出现很多假阳性基因,采用CPR技术则是通过多轮筛选,很大程度减少了假阳性细胞的出现。通过该方法经过四轮筛选获得核糖体蛋白S11(RPS11)、核糖体蛋白L6(RPL6)、核糖体蛋白L11(RPL11)、核糖体蛋白L24(RPL24)等几种基因,经初步检测,增加了细胞的耐药性。     

ROC曲线分析在评价入侵物种分布模型中的应用

生态位模型（ecological niche models,ENMs）已广泛应用于物种潜在分布区预测,ENMs的应用也为外来入侵物种的风险分析提供了重要的定量化分析工具,但如何评价不同模型之间的预测效果成了当今研究的热点问题。本文介绍了受试者工作特征（ROC）曲线分析在评价不同生态位模型预测效果中的应用原理和分析方法,并以一种植物病原线虫-相似穿孔线虫（Radopholus similis）为例,应用ROC曲线分析法对其5种模型（BIOCLIM,CLIMEX,DOMAIN,GARP,MAXENT）的预测结果进行了比较分析。5种模型的ROC曲线下面积AUC（Area Under Curve）值分别为0.810,0.758,0.921,0.903和0.950,以MAXENT模型的AUC值最大,表明其预测效果最好;方差分析结果表明,除GARP与DOMAIN模型之间AUC值差异不显著外,其余各模型之间差异显著。     

Combinatorial signals of activin/nodal and bone morphogenic protein regulate the early lineage segregation of human embryonic stem cells

Cell fate commitment of pre-implantation blastocysts, to either the inner cell mass or trophoblast, is the first step in cell lineage segregation of the developing human embryo. However, the intercellular signals that control fate determination of these cells remain obscure. Human embryonic stem cells (hESCs) provide a unique model for studying human early embryonic development. We have previously shown that Activin/Nodal signaling contributes to maintaining pluripotency of hESCs, which are derivatives of the inner cell mass. Here we further demonstrate that the inhibition of Activin/Nodal signaling results in the loss of hESC pluripotency and trophoblast differentiation, similar to BMP4-induced trophoblast differentiation from hESCs. We also show that the trophoblast induction effect of BMP4 correlates with and depends on the inhibition of Activin/Nodal signaling. However, the activation of BMP signaling is still required for trophoblast differentiation when Activin/Nodal signaling is inhibited. These data reveal that the early lineage segregation of hESCs is determined by the combinatorial signals of Activin/Nodal and BMP.     

两种野生花卉的扦插繁殖研究

开展野生花卉车轮梅(Raphiolepis indica)和赤楠(Syzygium buxifolium)扦插试验,结果表明:车轮梅硬枝扦插需一定浓度的外源激素方能生根;对激素浓度大小不敏感;总体上NAA组合生根质量优于IBA组合。综合不同处理生根率、根数和不定根根长3个指标,以800 mg/L NAA或800 mg/L IBA作为车轮梅生产上扦插的激素种类和浓度。赤楠生根率较低,最高扦插率达66.7%,生根时间长,约需45 d始生根。综合生根率、不定根根数和不定根根长3个生根指标,试验的4种激素均能较好促进赤楠生根,200×根太阳在生根率和根数上效果最好,生产上可用200×根太阳浸泡2 h,也可用50-100 mg/L NAA或100-400 mg/L IBA浸泡2 h后进行扦插。     

Engineering imaging probes and molecular machines for nanomedicine

Nanomedicine is an emerging field that integrates nanotechnology, biomolecular engineering, life sciences and medicine; it is expected to produce major breakthroughs in medical diagnostics and therapeutics. Due to the size-compatibility of nano-scale structures and devices with proteins and nucleic acids, the design, synthesis and application of nanoprobes, nanocarriers and nanomachines provide unprecedented opportunities for achieving a better control of biological processes, and drastic improvements in disease detection, therapy, and prevention. Recent advances in nanomedicine include the development of functional nanoparticle based molecular imaging probes, nano-structured materials as drug/gene carriers for in vivo delivery, and engineered molecular machines for treating single-gene disorders. This review focuses on the development of molecular imaging probes and engineered nucleases for nanomedicine, including quantum dot bioconjugates, quantum dot-fluorescent protein FRET probes, molecular beacons, magnetic and gold nanoparticle based imaging contrast agents, and the design and validation of zinc finger nucleases (ZFNs) and TAL effector nucleases (TALENs) for gene targeting. The challenges in translating nanomedicine approaches to clinical applications are discussed.     

In vitro development and transfer of resistance to chlortetracycline in Bacillus subtilis

The present criteria and rules controlling the approval of the use of probiotics are limited to antibiotic resistance patterns and the presence of antibiotic resistance genes in bacteria. There is little information available in the literature regarding the risk of the usage of probiotics in the presence of antibiotic pressure. In this study we investigated the development and transfer of antibiotic resistance in Bacillus subtilis selected in vitro by chlortetracycline in a stepwise manner. Bacillus subtilis was exposed to increasing concentrations of chlortetracyclineto induce in vitro resistance to chlortetracycline, and the minimal inhibitory concentrations were determinedfor the mutants. Resistant B. subtilis were conjugated with Escherichia coli NK5449 and Enterococcus faecalis JH2-2 using the filter mating. Three B. subtilis tetracycline resistant mutants (namely, BS-1, BS-2, and BS-3) were derived in vitro. A tetracycline resistant gene, tet (K), was found in the plasmids of BS-1 and BS-2. Three conjugates (BS-1N, BS-2N, and BS-3N) were obtained when the resistant B. subtilis was conjugated with E. coli NK5449. The conjugation frequencies for the BS-1N, BS-2N, and BS-3N conjugates were 4.57×10^?7, 1.4×10^?7, and 1.3×10^?8, respectively. The tet(K) gene was found only in the plasmids of BS-1N. These results indicate that long-term use of probiotics under antibiotic selection pressure could cause antibiotic resistance, and the resistance gene could be transferred to other bacteria. The risk arising from the use of probiotics under antibiotic pressure should be considered in the criteria and rules for the safety assessment of probiotics.