Pseudomonas biofilm formation and antibiotic resistance are linked to phenotypic variation

Colonization of the lungs of cystic fibrosis (CF) patients by the opportunistic bacterial pathogen Pseudomonas aeruginosa is the principal cause of mortality in CF populations. Pseudomonas aeruginosa infections generally persist despite the use of long-term antibiotic therapy. This has been explained by postulating that P. aeruginosa forms an antibiotic-resistant biofilm consisting of bacterial communities embedded in an exopolysaccharide matrix. Alternatively, it has been proposed that resistant P. aeruginosa variants may be selected in the CF respiratory tract by antimicrobial therapy itself. Here we report that both explanations are correct, and are interrelated. We found that antibiotic-resistant phenotypic variants of P. aeruginosa with enhanced ability to form biofilms arise at high frequency both in vitro and in the lungs of CF patients. We also identified a regulatory protein (PvrR) that controls the conversion between antibiotic-resistant and antibiotic-susceptible forms. Compounds that affect PvrR function could have an important role in the treatment of CF infections.     

Several alleles of the multidrug-resistance gene are closely linked to chloroquine resistance in Plasmodium falciparum

The lethal form of human malaria caused by Plasmodium falciparum is virtually uncontrollable in many areas because of the development of drug resistance, in particular chloroquine resistance (CQR). CQR is biologically similar to the multiple drug resistance phenotype (MDR) of mammalian tumour cells, as both involve expulsion of drug from the cell and both can be reversed by calcium channel antagonists. A homologue (pfmdr1) of the mammalian multidrug resistance gene has been implicated in CQR because it is amplified in some CQR isolates of P. falciparum as is an mdr gene in MDR tumour cells. We show here that the complete sequences of pfmdr1 genes from 2 CQ sensitive (CQS) P. falciparum isolates are identical. In 5 CQR isolates, 1-4 key nucleotide differences resulted in amino acid substitutions. On the basis of these substitutions, we have correctly predicted the CQS/CQR status of a further 34 out of 36 isolates. This is a paradox as CQR arises much less frequently than would be predicted if single point mutations were sufficient. We conclude that a mutated pfmdr1 gene is one of at least two mutated genes required for CQR.     

对十七大报告中关于效率和公平关系的思考

社会主义和谐社会的和谐点应该是效率与公平的均衡点。中国革命和建设的历程，就是不断追求效率与公平均衡统一的历史，不能忘记历史经验的警示：重视公平时压抑了效率，追求效率时又忽视公平；改革开放以来，我国在效率快速提高，GDP和人均收入普遍增加时，公平正义却遇到了空前的挑战，不公平的负效应是严重的，应引起我们的高度重视!当前在继续强调发展，提高效率的同时，必须更加突出公平，倍加关注社会弱势群体；通过深化改革，从制度、体制、政策等方面，切实保障弱势群体的合法权益。     

Relative efficiency of marker assisted selection when marker and QTL are incompletely linked

The relative superiority in selection response of two basic marker-assisted selection strategies, marker-assisted BLUP (MBLUP) and two-stage selection, in comparison to standard BLUP was investigated using stochastic simulation of a closed nucleus herd. In marker-assisted BLUP the marker information and the phenotypic information were utilized simultaneously for selecting parental animals, whereas in two-stage selection they were utilized separately in two stages. Different heritabilities and QTL sizes were considered in the simulation. The QTL was assumed to be referred only via flanking markers, which were incompletely linked to the QTL. It was shown that both MBLUP and two-stage selection increased the QTL response but decreased the polygenic response. When the heritability was low or the QTL effect was large MBLUP was superior to standard BLUP by up to 5% with respect to total genetic response. While the two-stage selection did not show any superiority although it gave extremely large increase in QTL response due to a rapid increase in favorable QTL allele frequency. The relative responses of MAS were stark associated with the generations of selection. The superiority or inferiority of MAS was large in the early generations and became small or vanished in the later generations.     

必须重视文化的重要作用

在当前国际、国内的背景下，文化的作用越来越突出。文章分析了文化对提升人的素质，整合社会资源，保持社会稳定等方面的作用。     

滚切齿数大于100的质数斜齿圆柱齿轮

介绍了滚切齿数大于１００的质数斜齿圆柱齿轮的调整公式,并介绍了挂轮累加计算法。实践证明,使用这种计算方法能准确地确定挂轮齿数,提高传动链的传动精度。     

滚切齿数大于100的质数斜齿圆柱齿轮

介绍了滚切齿数大于100的质数斜齿圆柱齿轮的调整公式,并介绍了挂轮累加计算法.实践证明,使用这种计算方法能准确地确定挂轮齿数,提高传动链的传动精度.     

Molecular markers linked to Rsa resistant to soybean mosaic virus

Soybean mosaic virus (SMV) is a severe disease in worldwide soybean production. A cross was made between Kefeng No. 1 with broad spectrum resistance to SMV and Nannong 1138–2, a susceptible cultivar. The inheritance of resistance to SMV strain Sa prevailing in southern China was analyzed. Results of x² test from inoculation experiment on parents F1, F2 and F3 lines showed that the resistance to strain Sa was controlled by a single dominant gene Rsa. BSA method was adopted and 900 random 10-mer primers were used to amplify total DNA from resistant pool and susceptible pool in order to obtain polymorphic bands in two bulks. 16 primers could generate polymorphic bands, of which OPW-05 and OPAS-06 could generate the most stable RAPD patterns. RAPD markers OPW-05₆₆₀ and OPAS-06₁₈₀₀ were found to be linked to Rsa. Their order and genetic distance were OPAS-06₁₈₀₀22.2cM Rsa10.1 cM OPW-05₆₆₀. Southern blotting showed that both OPAS-06₁₈₀₀ and 0PW-05₆₆₀ were low copy DNA in genomic DNA. 0PW-05₆₆₀ has been converted into an RFLP marker successfully. Additionally, pK644H, an RFLP marker, has been identified to be linked to 0PW-05₆₆₀, and their genetic distance was 37.4 cM.     

英语泛读课教学刍议

泛读课是英语专业的一门主课 ,所以如何更有效地上好泛读课具有重要的现实意义。文章从阅读法的介绍、课堂气氛的营造以及作业的设计三方面对此进行了探讨 ,以其找到更有效的泛读教学法。     

把寻求新发展的目光更多地投向服务业

提出这个观点的背景由以下三方面构成：首先是理论界开拓的崭新视野。自国内一些经济发达城市的人均GDP超过3000美元后，理论界对服务业的研究更加深入，这标志着对服务业的认识将达到一个新的高度。其次是服务业地位飙升的客观态势。当人均GDP达到3000—10000美元时，将进入经济总量持续增长、经济结构优化升级、经济运行质量明显改善的阶段。期间。“服务业经济”将成为国民经济的主体。这标志