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221.
Molecular evolution of connective tissue growth factor in Cyprinidae (Teleostei: Cypriniformes) 总被引:1,自引:0,他引:1
Connective tissue growth factor (CTGF) plays an important role in regulation of cell growth, differentiation, apoptosis and individual development in animals. The study of sequences variation and molecular evolution of CTGF gene across various species of the cyprinid could be helpful for understanding of speciation and gene divergence in this kind of fish. In this study, 19 novel sequences of CTGF gene were obtained from the representative species of the family Cyprinidae using PCR amplification, cloning and sequencing. Phylogenetic relationships of Cyprinidae were reconstructed by neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) and Bayesian method. Oryzias latipes from the family Cyprinodontidae was assigned to be the outgroup taxon. Leuciscini and Barbini were clustered into the monophyletic lineages, respectively, with the high nodal supports. The estimation of the ratio of non-synonymous to synonymous substitution (dN/dS) for the various branches indicated that there stood the different evolution rates between the Leuciscini and the Barbini. With the ratio of dN/dS of the Leuciscini being lower than that of the Barbini, species within the Barbini were demonstrated to be subjected to the relatively less selection pressure and under the relaxable evolution background. A 6 bp indel (insertion/deletion) was found at the 5' end of CTGF gene of Cyprinidae, and this 6 bp deletion only appeared in the Leuciscini, which is a typical characteristic of the Leuciscini and provides evidence for the monophylogeny of the Leuciscini. For the amino acid sequences of CTGF protein, the most variations and indels were distributed in the signal region and IGFBP region of this protein, implying that these variations were correlated with the regulation of the CTGF gene expression and protein activity. 相似文献
222.
D Reich N Patterson D Campbell A Tandon S Mazieres N Ray MV Parra W Rojas C Duque N Mesa LF García O Triana S Blair A Maestre JC Dib CM Bravi G Bailliet D Corach T Hünemeier MC Bortolini FM Salzano ML Petzl-Erler V Acuña-Alonzo C Aguilar-Salinas S Canizales-Quinteros T Tusié-Luna L Riba M Rodríguez-Cruz M Lopez-Alarcón R Coral-Vazquez T Canto-Cetina I Silva-Zolezzi JC Fernandez-Lopez AV Contreras G Jimenez-Sanchez MJ Gómez-Vázquez J Molina A Carracedo A Salas C Gallo G Poletti DB Witonsky 《Nature》2012,488(7411):370-374
The peopling of the Americas has been the subject of extensive genetic, archaeological and linguistic research; however, central questions remain unresolved. One contentious issue is whether the settlement occurred by means of a single migration or multiple streams of migration from Siberia. The pattern of dispersals within the Americas is also poorly understood. To address these questions at a higher resolution than was previously possible, we assembled data from 52 Native American and 17 Siberian groups genotyped at 364,470 single nucleotide polymorphisms. Here we show that Native Americans descend from at least three streams of Asian gene flow. Most descend entirely from a single ancestral population that we call 'First American'. However, speakers of Eskimo-Aleut languages from the Arctic inherit almost half their ancestry from a second stream of Asian gene flow, and the Na-Dene-speaking Chipewyan from Canada inherit roughly one-tenth of their ancestry from a third stream. We show that the initial peopling followed a southward expansion facilitated by the coast, with sequential population splits and little gene flow after divergence, especially in South America. A major exception is in Chibchan speakers on both sides of the Panama isthmus, who have ancestry from both North and South America. 相似文献
223.
Notch activity acts as a sensor for extracellular calcium during vertebrate left-right determination
Raya A Kawakami Y Rodríguez-Esteban C Ibañes M Rasskin-Gutman D Rodríguez-León J Büscher D Feijó JA Izpisúa Belmonte JC 《Nature》2004,427(6970):121-128
During vertebrate embryo development, the breaking of the initial bilateral symmetry is translated into asymmetric gene expression around the node and/or in the lateral plate mesoderm. The earliest conserved feature of this asymmetric gene expression cascade is the left-sided expression of Nodal, which depends on the activity of the Notch signalling pathway. Here we present a mathematical model describing the dynamics of the Notch signalling pathway during chick embryo gastrulation, which reveals a complex and highly robust genetic network that locally activates Notch on the left side of Hensen's node. We identify the source of the asymmetric activation of Notch as a transient accumulation of extracellular calcium, which in turn depends on left-right differences in H+/K+-ATPase activity. Our results uncover a mechanism by which the Notch signalling pathway translates asymmetry in epigenetic factors into asymmetric gene expression around the node. 相似文献
224.
225.
A transition between the supersonic solar wind and the subsonic heliosheath was observed by Voyager 1, but the expected termination shock was not seen owing to a gap in the telemetry. Here we report observations of the magnetic field structure and dynamics of the termination shock, made by Voyager 2 on 31 August-1 September 2007 at a distance of 83.7 au from the Sun (1 au is the Earth-Sun distance). A single crossing of the shock was expected, with a boundary that was stable on a timescale of several days. But the data reveal a complex, rippled, quasi-perpendicular supercritical magnetohydrodynamic shock of moderate strength undergoing reformation on a scale of a few hours. The observed structure suggests the importance of ionized interstellar atoms ('pickup protons') at the shock. 相似文献
226.
杨咏秋a 《西昌学院学报(自然科学版)》2024,38(2):79-86
以四川省邛崃市冉义镇为研究对象,以2012、2015、2018年3期高分辨率遥感影像图为基础数据,运用目视解译法结合ArcGIS软件绘制冉义镇3期土地利用类型现状图并建立土地利用转移矩阵;运用Fragstats景观指数计算软件得出冉义镇景观格局指数变化。结果表明:(1)冉义镇耕地面积增加并且聚集程度提高,耕地景观更加紧凑与规模化;(2)城市建设用地面积优势度不断上升,宅基地优势度及破碎化程度均降低;(3)2012—2018年冉义镇景观格局的丰富度和均衡度均在降低;(4)产业结构变化、生态文明建设、土地综合整治是冉义镇土地利用景观格局变化的主要影响因素。 相似文献
227.
大学计算机基础课程是一门重要的基础课程,但因当前高等院校存在生源复杂、学生水平参差不齐等问题,实际教学效果不尽如人意。分析了当前大学计算机基础课程改革面临的新挑战,探讨了基于翻转课堂的教学新模式,使学生在通过自主学习完成对知识的深度掌握。通过问卷调查和对比研究,证明该模式在一定程度上提高了学生学习兴趣,有利于知识的吸收,提高了教学质量,获得了较好的教学效果。 相似文献
228.
E. Hahne U. Gross G. BarthauInstitut für Thermodynamik und Warmetechnik Universitat Stuttgart Pfaffenwaldring D Stuttgart Germany E mail: pm@itw.uni stuttgart.de TU Bergakademie Freiberg Institut für Technische Th 《清华大学学报》2002,7(2)
IntroductionWell- known optical phenomena in fluids in thethermodynamic critical state are the disappearanceof the meniscus between liquid and vapour phaseand the existence of a“critical opalescence”. This opalescence is observed as bluish inreflected… 相似文献
229.
230.
Early Paleozoic granite in Nujiang River of northwest Yunnan in southwestern China and its tectonic implications 总被引:8,自引:0,他引:8
The Nujiang region along the China-Burma border in the western Yunnan has received a great deal of attention has been considered to be the important channel of southeastward escape of the Tibetan Plateau-.…… 《科学通报(英文版)》2007,52(17):2402-2406
The Nujiang region along the China-Burma border in the western Yunnan has received a great deal of attention and has been considered to be the important channel of southeastward escape of the Tibetan Plateau[1-4]. This channel is bordered by the Red River-Ailao Mountain left-literal strick-slip fault in the east and Gaoligong- Sagaing right-literal strick-slip fault in the west[5-7]. Within this channel, it is still not clear to which tectonic 相似文献