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51.
The evolutionary interaction between influenza A virus and the human immune system, manifest as 'antigenic drift' of the viral haemagglutinin, is one of the best described patterns in molecular evolution. However, little is known about the genome-scale evolutionary dynamics of this pathogen. Similarly, how genomic processes relate to global influenza epidemiology, in which the A/H3N2 and A/H1N1 subtypes co-circulate, is poorly understood. Here through an analysis of 1,302 complete viral genomes sampled from temperate populations in both hemispheres, we show that the genomic evolution of influenza A virus is characterized by a complex interplay between frequent reassortment and periodic selective sweeps. The A/H3N2 and A/H1N1 subtypes exhibit different evolutionary dynamics, with diverse lineages circulating in A/H1N1, indicative of weaker antigenic drift. These results suggest a sink-source model of viral ecology in which new lineages are seeded from a persistent influenza reservoir, which we hypothesize to be located in the tropics, to sink populations in temperate regions. 相似文献
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Suppression of phage nonsense and temperature-sensitive mutants by an suA mutant E. coli 总被引:1,自引:0,他引:1
G E Holmes 《Nature》1974,250(461):73-75
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The increasing preponderance of opinion that some natural phenomena can be explained mathematically has inspired a search for a viable account of distinctively mathematical explanation. Among the desiderata for an adequate account is that it should solve the problem of directionality —the reversals of distinctively mathematical explanations should not count as members among the explanatory fold but any solution must also avoid the exclusion of genuine explanations. In what follows, I introduce and defend what I refer to as a quasi-erotetic solution which provides a remedy to the problem in the form of an additional necessary condition on explanation. 相似文献
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高校图书馆功能拓展的理论研究与实践探索 总被引:1,自引:0,他引:1
以拓展高校图书馆功能的缘由为切入点,在比较几种高校图书馆功能拓展理论分析方法的基础上,总结了高校图书馆功能拓展的一些实践探索,指出当前研究中存在的问题,并对未来的研究进行了展望。 相似文献
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Holmes Rolston III 《西北部美国博物学家》2011,61(3)
Yellowstone National Parks mission and policy can be clarified by analysis of the natural and the unnatural. Nature is a comprehensive word, in some uses excluding nothing; more useful is a contrast distinguishing nature and culture . Specifying ""wild nature"" denotes spontaneous nature absent human influence. Critics claim that the meaning of wild nature, especially of wilderness, is a foil of culture. Pristine nature, often romanticized, is contrasted with a technological and industrial culture. By this account, wilderness is a social construction. Nevertheless, wild nature successfully denotes, outside culture, an evolutionary and ecological natural history, which remains present on the Yellowstone landscape, jeopardized by numerous human influences, including the invasions of exotic species. Natural processes have returned in the past, as when Native Americans left the landscape. Natural processes can be preserved today, because of, rather than in spite of, park management. Over much of the North American landscape nature is managed and at an end. Yellowstone provides an opportunity to encounter and to conserve ""untrammeled"" nature as an end in itself, past, present, and future. 相似文献
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Yusa K Rashid ST Strick-Marchand H Varela I Liu PQ Paschon DE Miranda E Ordóñez A Hannan NR Rouhani FJ Darche S Alexander G Marciniak SJ Fusaki N Hasegawa M Holmes MC Di Santo JP Lomas DA Bradley A Vallier L 《Nature》2011,478(7369):391-394
Human induced pluripotent stem cells (iPSCs) represent a unique opportunity for regenerative medicine because they offer the prospect of generating unlimited quantities of cells for autologous transplantation, with potential application in treatments for a broad range of disorders. However, the use of human iPSCs in the context of genetically inherited human disease will require the correction of disease-causing mutations in a manner that is fully compatible with clinical applications. The methods currently available, such as homologous recombination, lack the necessary efficiency and also leave residual sequences in the targeted genome. Therefore, the development of new approaches to edit the mammalian genome is a prerequisite to delivering the clinical promise of human iPSCs. Here we show that a combination of zinc finger nucleases (ZFNs) and piggyBac technology in human iPSCs can achieve biallelic correction of a point mutation (Glu342Lys) in the α(1)-antitrypsin (A1AT, also known as SERPINA1) gene that is responsible for α(1)-antitrypsin deficiency. Genetic correction of human iPSCs restored the structure and function of A1AT in subsequently derived liver cells in vitro and in vivo. This approach is significantly more efficient than any other gene-targeting technology that is currently available and crucially prevents contamination of the host genome with residual non-human sequences. Our results provide the first proof of principle, to our knowledge, for the potential of combining human iPSCs with genetic correction to generate clinically relevant cells for autologous cell-based therapies. 相似文献
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