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31.
MicroRNA Mirn140 modulates Pdgf signaling during palatogenesis 总被引:2,自引:0,他引:2
Eberhart JK He X Swartz ME Yan YL Song H Boling TC Kunerth AK Walker MB Kimmel CB Postlethwait JH 《Nature genetics》2008,40(3):290-298
Disruption of signaling pathways such as those mediated by sonic hedgehog (Shh) or platelet-derived growth factor (Pdgf) causes craniofacial abnormalities, including cleft palate. The role that microRNAs play in modulating palatogenesis, however, is completely unknown. We show that, in zebrafish, the microRNA Mirn140 negatively regulates Pdgf signaling during palatal development, and we provide a mechanism for how disruption of Pdgf signaling causes palatal clefting. The pdgf receptor alpha (pdgfra) 3' UTR contained a Mirn140 binding site functioning in the negative regulation of Pdgfra protein levels in vivo. pdgfra mutants and Mirn140-injected embryos shared a range of facial defects, including clefting of the crest-derived cartilages that develop in the roof of the larval mouth. Concomitantly, the oral ectoderm beneath where these cartilages develop lost pitx2 and shha expression. Mirn140 modulated Pdgf-mediated attraction of cranial neural crest cells to the oral ectoderm, where crest-derived signals were necessary for oral ectodermal gene expression. Mirn140 loss of function elevated Pdgfra protein levels, altered palatal shape and caused neural crest cells to accumulate around the optic stalk, a source of the ligand Pdgfaa. These results suggest that the conserved regulatory interactions of mirn140 and pdgfra define an ancient mechanism of palatogenesis, and they provide candidate genes for cleft palate. 相似文献
32.
Wright FA Strug LJ Doshi VK Commander CW Blackman SM Sun L Berthiaume Y Cutler D Cojocaru A Collaco JM Corey M Dorfman R Goddard K Green D Kent JW Lange EM Lee S Li W Luo J Mayhew GM Naughton KM Pace RG Paré P Rommens JM Sandford A Stonebraker JR Sun W Taylor C Vanscoy LL Zou F Blangero J Zielenski J O'Neal WK Drumm ML Durie PR Knowles MR Cutting GR 《Nature genetics》2011,43(6):539-546
A combined genome-wide association and linkage study was used to identify loci causing variation in cystic fibrosis lung disease severity. We identified a significant association (P = 3.34 × 10(-8)) near EHF and APIP (chr11p13) in p.Phe508del homozygotes (n = 1,978). The association replicated in p.Phe508del homozygotes (P = 0.006) from a separate family based study (n = 557), with P = 1.49 × 10(-9) for the three-study joint meta-analysis. Linkage analysis of 486 sibling pairs from the family based study identified a significant quantitative trait locus on chromosome 20q13.2 (log(10) odds = 5.03). Our findings provide insight into the causes of variation in lung disease severity in cystic fibrosis and suggest new therapeutic targets for this life-limiting disorder. 相似文献
33.
The male epiprocts of 2 closely related western Nearctic species, Sweltsa fidelis (Banks) and S. revelstoka (Jewett), were examined using SEM. The males of these 2 species have been historically distinguished by epiproct measurements. The ratio of the length of the base to greatest width versus total epiproct length ranges from 0.49 μm to 0.67 μm ( ̄ x = 0.56) in S. fidelis and 0.55 μm to 0.69 μm ( ̄ x = 0.60) in S. revelstoka . Similarities in measurement suggest that the location of the greatest epiproct width is not a reliable and consistent character for distinguishing males of these 2 species. 相似文献
34.
Yannian Lou Chaojie Zhang Xiaojun Jin Zhonghe Jin 《系统工程与电子技术(英文版)》2014,(6):949-958
In a system based on the phase lock loop(PLL), a trade-off must be made between the tracking precision and the dynamic performance if constant parameters are adopted. To overcome this drawback, a new method called no phase slipping adaptive bandwidth(NPS-AB) is proposed, which can adjust the loop bandwidth adaptively for different working conditions. As a result, both the tracking precision and the dynamic performance can be achieved concurrently. NPS-AB has two features to keep the loop stable: one is the capability of quick response to dynamics; the other is a series of additional constraints when the bandwidth is switched. Compared with other methods, there is no phase slipping during the adjustment process for NPS-AB. The phase integer ambiguity can be avoided and the phase value is kept valid. It is meaningful for carrier ranging systems. Simulation results show that NPS-AB can deal with sudden dynamics and keep the pseudo-range value stable in the entire dynamic process. 相似文献
35.
The state transfer under control fields is analyzed based on the Bloch sphere representation of a single qubit. In order to
achieve the target from an arbitrary initial state to a target state, the conditions that parameters should satisfy are deduced
separately in two different requirements: One is in the case of the rotation angle around the x-axis being fixed and another is in the situation with a given evolution time. Several typical states trajectories are demonstrated
by numerical simulations on the Bloch sphere. The relations between parameters and the trajectories are analyzed. 相似文献
36.
娄必伟 《贵州工业大学学报(自然科学版)》1991,(4)
本文讨论了一类三次Kolmogorov系统(Ⅰ),在第一象限得到了可行平衡点的全局稳定性,正平衡点的全局稳定性以及围绕正平衡点极限环的存在性与唯一性。推广了[2]、[3]、[4]中的结论,并对所得结论给予了生物解释。 相似文献
37.
本文采用单边缺口板状试样研究了四种含碳量的CrNiMo钢缺口根部的疲劳裂纹萌生寿命及其萌生机制。裂纹萌生可能有四种方式—沿驻留滑移带压入挤出、微孔聚集型切变、准解理和沿晶机制。文中论述了钢的含碳量、热处理规范及外加应力水平对裂纹形核机制的影响。研究表明:在双对数坐标中,表观循环应力范围和萌生寿命的关系可用两段不同斜率的直线来描述,两段萌生线的分界点随钢的强度水平提高而迅速向低周次范围推移,但两段的裂纹萌生均仍属于应力疲劳范畴。文中分析了微观塑性变形对缺口根部实际循环应力范围和应力循环比的影响,给出了对它们进行修正估算的方法。修正后的实际循环应力范围和萌生寿命的关系可用一条直线反映出来。在此基础上,提出了一种用光滑试样应力疲劳曲线估算缺口根部裂纹萌生寿命的新方法。 相似文献
38.
在材料的断裂与疲劳问题的研究中,裂纹尖端的闭合行为一直是人们十分关注的课题,它是深入研究材料断裂和疲劳机理的重要基础,然而精确地检测裂纹闭合行为的重要参数——裂纹张开载荷P_(op)仍是一个研究课题。高精度裂纹闭合测试仪的研制成功,则提供了有效的研究手段。本文重点介绍仪器的设计原理,电路的设计及其应用实例。 相似文献
39.
碳还原锆英石分离SiO2和ZrO2 总被引:1,自引:0,他引:1
进行了配碳量,温度,时间和颗粒大小及试样形式对碳还原锆英石中SiO2的实验研究,得到相应脱硅率的影响规律,理论上,脱硅率的极大值可达到97.22%,碳还原锆石的表现反应活化能,在1600~2000℃温度范围内为282.04kj/mol。锆英石被碳还原的限制环节是锆英石的热分解,而不是它裂解成SiO2之后再与碳的反应。 相似文献
40.
十种(株)杜氏藻β-胡萝卜素的提取及含量比较 总被引:5,自引:2,他引:5
建立了从杜氏藻鲜藻中直接提取、纯化β-胡萝卜素及快速检测其含量的新方法,发现在十种(株)杜氏藻Dunaliellabardauil中生成β-胡萝卜素的量最高,达藻干重的4.19%,在最佳条件下可达13%,经动物急性毒性实验测得小鼠对杜氏藻β-胡萝卜素的最大耐受量>240mg·kg ̄(-1). 相似文献