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161.
162.
Sung LY Gao S Shen H Yu H Song Y Smith SL Chang CC Inoue K Kuo L Lian J Li A Tian XC Tuck DP Weissman SM Yang X Cheng T 《Nature genetics》2006,38(11):1323-1328
Since the creation of Dolly via somatic cell nuclear transfer (SCNT), more than a dozen species of mammals have been cloned using this technology. One hypothesis for the limited success of cloning via SCNT (1%-5%) is that the clones are likely to be derived from adult stem cells. Support for this hypothesis comes from the findings that the reproductive cloning efficiency for embryonic stem cells is five to ten times higher than that for somatic cells as donors and that cloned pups cannot be produced directly from cloned embryos derived from differentiated B and T cells or neuronal cells. The question remains as to whether SCNT-derived animal clones can be derived from truly differentiated somatic cells. We tested this hypothesis with mouse hematopoietic cells at different differentiation stages: hematopoietic stem cells, progenitor cells and granulocytes. We found that cloning efficiency increases over the differentiation hierarchy, and terminally differentiated postmitotic granulocytes yield cloned pups with the greatest cloning efficiency. 相似文献
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164.
DNA methylation profiling of human chromosomes 6, 20 and 22 总被引:24,自引:0,他引:24
165.
Common variation in three genes, including a noncoding variant in CFH, strongly influences risk of age-related macular degeneration 总被引:12,自引:0,他引:12
Maller J George S Purcell S Fagerness J Altshuler D Daly MJ Seddon JM 《Nature genetics》2006,38(9):1055-1059
Age-related macular degeneration (AMD) is a common, late-onset disease with seemingly typical complexity: recurrence ratios for siblings of an affected individual are three- to sixfold higher than in the general population, and family-based analysis has resulted in only modestly significant evidence for linkage. In a case-control study drawn from a US-based population of European descent, we have identified a previously unrecognized common, noncoding variant in CFH, the gene encoding complement factor H, that substantially increases the influence of this locus on AMD, and we have strongly replicated the associations of four other previously reported common alleles in three genes (P values ranging from 10(-6) to 10(-70)). Despite excellent power to detect epistasis, we observed purely additive accumulation of risk from alleles at these genes. We found no differences in association of these loci with major phenotypic categories of advanced AMD. Genotypes at these five common SNPs define a broad spectrum of interindividual disease risk and explain about half of the classical sibling risk of AMD in our study population. 相似文献
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167.
<正> Stock loans are business contracts between borrowers and lenders in which the borroweruses shares of stock as collateral for the loan.Since the value of the collateral is subject to wide andfrequent price swings,valuing such a transaction behaves more like an option pricing problem thana debt valuation problem.This paper will list,prove,and analyze formulas for stock loan valuationwith finite horizon under various stock models,including classical geometric Brownian motion,meanreverting,and two-state regime-switching with both mean-reverting and geometric Brownian motionstates.Numerical examples are reported to illustrate the results. 相似文献
168.
David Nofre 《Annals of science》2014,71(3):410-431
The spread of the modern computer is assumed to have been a smooth process of technology transfer. This view relies on an assessment of the open circulation of knowledge ensured by the US and British governments in the early post-war years. This article presents new historical evidence that question this view. At the centre of the article lies the ill-fated establishment of the UNESCO International Computation Centre. The project was initially conceived in 1946 to provide advanced computation capabilities to scientists of all nations. It soon became a prize sought by Western European countries like the Netherlands and Italy seeking to speed up their own national research programs. Nonetheless, as the article explains, the US government's limitations on the research function of the future centre resulted in the withdrawal of European support for the project. These limitations illustrate the extent to which US foreign science policy could operate as (stealth) industrial policy to secure a competitive technological advantage and the prospects of US manufacturers in a future European market. 相似文献
169.
DU LiNa YANG JunXing RINTELEN Thomas von CHEN XiaoYong ALDRIDGE David 《科学通报(英文版)》2013,58(18):2154-2162
We investigated the phylogeny of the viviparid genus Margarya,endemic to Yunnan,China,using two mitochondrial gene fragments(COI and 16S rRNA).The molecular phylogeny based on the combined dataset indicates that Margarya is polyphyletic,as two of the three well-supported clades containing species of Margarya also comprise species from other viviparid genera.In one clade,sequences of four species of Margarya even cluster indiscriminately with those of two species of Cipangopaludina,indicating that the current state of Asian viviparid taxonomy needs to be revised.Additionally,these data suggest that shell evolution in viviparids is complex,as even the large and strongly sculptured shells of Margarya,which are outstanding among Asian viviparids,can apparently be easily converted to simple smooth shells.The molecular data also indicate that the species status of the six extant species of Margarya should be re-assessed. 相似文献
170.
D. Kendall Brown Anthony A. Echelle David L. Propst James E. Brooks William L. Fisher 《西北部美国博物学家》2011,61(2)
We used the computer program RAMAS to explore the sensitivity of an extinction-risk model for the Gila trout ( Oncorhynchus gilae ) to management of wildfires and number of populations of the species. The Gila trout is an endangered salmonid presently restricted to very few headwaters of the Gila and San Francisco river tributaries in southwestern New Mexico. Life history data for 10 extant populations were used to examine sensitivity of the species viability to changes in a variety of factors including population size, fecundity, life stage structure, number of populations, severity and probability of forest fires, and a regulated fishery. The probability and severity of forest fires and number of populations had the greatest effect on viability. Results indicate that successful conservation of Gila trout requires establishment of additional populations and reduction of the severity of forest fires through a program incorporating more frequent, but less severe, fires. 相似文献