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1.
Huang J Juszkiewicz M de Jeu WH Cerda E Emrick T Menon N Russell TP 《Science (New York, N.Y.)》2007,317(5838):650-653
A freely floating polymer film, tens of nanometers in thickness, wrinkles under the capillary force exerted by a drop of water placed on its surface. The wrinkling pattern is characterized by the number and length of the wrinkles. The dependence of the number of wrinkles on the elastic properties of the film and on the capillary force exerted by the drop confirms recent theoretical predictions on the selection of a pattern with a well-defined length scale in the wrinkling instability. We combined scaling relations that were developed for the length of the wrinkles with those for the number of wrinkles to construct a metrology for measuring the elasticity and thickness of ultrathin films that relies on no more than a dish of fluid and a low-magnification microscope. We validated this method on polymer films modified by plasticizer. The relaxation of the wrinkles affords a simple method to study the viscoelastic response of ultrathin films. 相似文献
2.
Darwin's finches are a classic example of species diversification by natural selection. Their impressive variation in beak morphology is associated with the exploitation of a variety of ecological niches, but its developmental basis is unknown. We performed a comparative analysis of expression patterns of various growth factors in species comprising the genus Geospiza. We found that expression of Bmp4 in the mesenchyme of the upper beaks strongly correlated with deep and broad beak morphology. When misexpressed in chicken embryos, Bmp4 caused morphological transformations paralleling the beak morphology of the large ground finch G. magnirostris. 相似文献
3.
交叉喙是多基因控制的复杂性状，目前已在全球至少12个鸡种中报道，包括商业品种和地方品种。交叉喙鸡刚出壳时喙形正常，但在随后1~2个月内逐渐呈现上下喙交错、咬合不全的交叉状态。交叉喙严重影响个体采食和饮水、降低生产性能、损害动物福利。交叉喙以下喙偏离中线为主，原因是单侧下颌骨支发育缓慢，LOC426217、BMP4、FIGNL1基因和脂蛋白脂肪酶、清蛋白等与该性状的发生相关。综述了鸡交叉喙表型特征、遗传方式和分子调控机制等方面的研究进展，以期为深入解析该性状的遗传基础和降低发病率提供借鉴。 相似文献
4.
北太平洋柔鱼角质颚形态及生长年间差异 总被引：3，自引：3，他引：0
根据2010年、2015年和2016年在北太平洋海域所采集的柔鱼样本,分析其胴长、体质量及角质颚形态的年间差异和性别差异,并计算角质颚的月平均生长率,结合不同年份各月索饵场海表面温度(sea surface temperature,SST)和叶绿素a浓度(chlorophyll a,Chl.a)的分布,研究环境对角质颚形态和生长的影响。研究发现,3年的个体胴长和体质量均存在显著差异(P0.01),2016年的个体和角质颚的形态值最大,2015年的个体和角质颚形态值最小。不同年份间角质颚的各项参数均存在显著差异(P0.01)。分析角质颚形态值与胴长的关系发现,2010年生长参数b最大,2015年则最低。不同年份的角质颚月生长率中,2010年角质颚在8—9月有着较高的生长率,而2015年同期的生长率则最低。分析渔汛期索饵场SST和Chl.a的变化发现:2015年8—9月的SST相对其他年份较低,而2010年8—9月索饵场的Chl.a值较为分散,但高浓度(0.7 mg/m~3)所占比例较高;2016年由于适宜的SST和适宜的Chl.a,使得其个体有着形态较大的角质颚,同时个体也相对较大。不同年份间角质颚形态存在一定的差异,同时8—9月的SST和Chl.a的变化是影响该年度个体角质颚形态的主要因素之一。 相似文献
5.
Cellular and molecular mechanisms underlying differences in beak morphology likely involve interactions among multiple embryonic populations. We exchanged neural crest cells destined to participate in beak morphogenesis between two anatomically distinct species. Quail neural crest cells produced quail beaks in duck hosts and duck neural crest produced duck bills in quail hosts. These transformations involved morphological changes to non-neural crest host beak tissues. To achieve these changes, donor neural crest cells executed autonomous molecular programs and regulated gene expression in adjacent host tissues. Thus, neural crest cells are a source of molecular information that generates interspecific variation in beak morphology. 相似文献
6.
2007年4～11月通过样带和定点观察以及对当地保护站的保护人员调查发现,白琵鹭春季于4月初至4月末从南方越冬地迁到乌兰诺尔,成群营巢,营巢在有厚密芦苇、蒲草等植物和附近有灌丛或树木的水域及其附近地区,5月底至7月中为繁殖期,每窝产卵通常3～4枚。秋季于9月末至10月南迁。体大(84 cm)的白色琵鹭,长长的嘴灰色而呈琵琶形,头部裸出部位呈黄色。与冬季黑脸琵鹭相比,其体型较大,脸部黑色少,白色羽毛延伸过嘴基,嘴色较浅。喜泥泞水塘、湖泊或泥滩,在水中缓慢前进,嘴往两旁甩动以寻找食物。一般单独或成小群活动;部分夜行性。 相似文献
7.
茎柔鱼角质颚不仅表面存在色素沉积的梯度变化,从喙部到翼部黑色素逐渐变浅,其机械性能也存在显著的梯度变化,喙部具有很高的机械强度,从喙部到翼部机械强度逐渐变小,韧性逐渐增大。测定无水以及水合状态下茎柔鱼角质颚不同部位(喙部、侧壁、翼部)的机械强度(杨氏模量),以及主要化学成分、内部分子交联结构,并利用电子扫锚显微镜观察了其不同部位表面和断面上的物理结构,探究茎柔鱼角质颚机械强度梯度变化的主要原因。研究显示:无水茎柔鱼角质颚具有很高的杨氏模量,模量从喙部到翼部差异不显著(P0.01);而水合的角质颚杨氏模量明显减小,模量从喙部到翼部呈现显著梯度变化(P0.01)。茎柔鱼角质颚主要含有蛋白质、儿茶酚、壳聚糖和水,其机械强度随蛋白质、儿茶酚含量增加而增大,机械强度同时与内部分子交联反应形成的多巴-多交联多聚体以及与其表面和断面上物理结构有关,茎柔鱼喙部断面层状结构十分显著,生物体中分层越明显,其机械强度越大。 相似文献
8.
Pulmonary gas transport time: larynx to alveolus 总被引：1，自引：0，他引：1
The transport time of gas from the larynx to pulmonary alveolar capillary blood was directly measured by injecting a bolus of carbon monoxide into the inspired airstream of dogs and photoelectrically monitoring the formation of carboxyhemoglobin in the capillaries on the surface of the lung. The rapidity of transit (0.3 second) implies that gas transport during inspiration is facilitated by an interaction between bulk flow and diffusion. 相似文献
9.
【目的】中国地方鸡种如北京油鸡、清远麻鸡存在喙畸形现象,表现为上下喙咬合不全,呈交叉状。严重影响鸡饮水和采食,从而影响个体发育和生产性能的发挥,造成一定经济损失。笔者根据喙畸形个体的系谱记录,发现喙畸形的形成受到遗传因素的影响,但具体机制尚不明确。蛋白是行使各种生物学功能的最终形式之一,喙畸形个体的发生可能是由于核心蛋白或者相关调控蛋白代谢异常造成的。利用同位素标记相对和绝对定量（isobaric tags for relative and absolute quantitation,iTRAQ）技术以及生物信息学分析方法,筛选鸡畸形喙与正常喙中差异表达的蛋白,作为喙畸形相关的重要候选蛋白,为进一步研究北京油鸡喙畸形的遗传机制奠定基础。【方法】挑选3只120日龄喙畸形的公鸡作为试验组,编号为W1、W2、W3,同时,挑选与试验组个体为同胞关系（全同胞或半同胞）的喙正常公鸡作为对照组,编号为Z1、Z2、Z3。将喙畸形与其同胞正常个体作为一个比对组,iTRAQ试验具体包含3个比对组,即W1 vs Z1,W2 vs Z2,W3 vs Z3。屠宰个体后,剔除喙组织周围肌肉和筋膜,分离得到喙上颌骨和下颌骨,提取总蛋白样品,应用6个 iTRAQ标签标记各蛋白样品,经过色谱层析预分离,联合液相串联质谱分析,采用Mascot 2.3.02软件对蛋白进行鉴定和定量分析。试验组（W）与其同胞对照组(Z)样本比较（W1 vs Z1,W2 vs Z2,W3 vs Z3）,选择肽段数≥2,表达差异值＞1.2（上调）或＜0.83（下调）,且P＜0.05的蛋白作为差异表达蛋白。【结果】利用iTRAQ技术一共在喙组织中鉴定到3 372个蛋白,鉴定到的特异性肽段有12 769个。其中原鸡蛋白1 869个,分子质量主要分布在10-100 kD之间。3个比对组共鉴定出159个表达量有显著差异的蛋白质,其中包含70个表达上调的蛋白,89个表达下调的蛋白。统计各比对组蛋白表达差异值发现,表达量差异较大的上调蛋白质有LPL、MLC-2、CO9A1、MATN3、HSP90B1等,表达量差异较大的下调蛋白质有MBP、RLA1、PRVM、HAPLN1等。结合已经报道的这些蛋白的生物学功能,其中CO9A1、MATN3、HAPLN1与软骨合成和软骨骨化相关,CO9A1是带状软骨纤维的组成物质,MATN家族是非胶原性细胞外基质蛋白家族,HAPLN1是软骨细胞外基质的重要组成成分;PRVM是细胞内钙离子结合蛋白,参与调控Ca2+离子信号通路;LPL是多功能酶,主要在脂质代谢和转运过程中起作用,参与调控PPAR信号通路。初步筛选出CO9A1、MATN3、HAPLN1、PRVM、LPL作为与鸡喙畸形相关的候选蛋白。【结论】差异表达蛋白的发现为鸡喙畸形形态的发生提供蛋白质水平上的理论依据。 相似文献
10.
角质颚是研究头足类各种生物信息的重要组织，为实现头足类角质颚色素沉积的精确化测量，探究色素沉积在头足类角质颚判别分类中的作用，研究选取茎柔鱼、柔鱼以及翼柄柔鱼3种头足类生物的角质颚下颚为研究对象，以其侧视图像为基础，对其色素沉积按照等级Ⅰ：黑色、等级Ⅱ：灰色、等级Ⅲ：浅灰色、等级Ⅳ：透明四个等级进行可视化，分别计算出茎柔鱼、柔鱼以及翼柄柔鱼角质颚四种等级的色素沉积面积与头盖-翼部区域以及脊突-侧壁区域面积的比例关系，并且采用逐步判别分析法对3种头足类角质颚之间的色素沉积差异进行分析，结果显示等级Ⅰ、Ⅳ在脊突、侧壁区域各色素梯度占比对判定分类的结果具有显著意义，判别成功率为74.4%。研究认为，3种头足类的角质颚色素沉积情况存在一定差异，而这些差异有可能是由于3种头足类不同的生活特性和摄食习惯导致。研究实现了角质颚色素沉积的数值化和色素沉积等级的精确化划分，并按照划分的结果，将色素沉积情况作为全新的定量测量方法，为头足类生物角质颚色素沉积研究提供了新的思路。 相似文献
11.
利用常规气象资料和红外云图资料,对2013年7月14—16日呼伦贝尔市一次暴雨天气过程进行成因分析、,结果表明：此次降水的环流形势为典型的副热带高压与西风槽相互作用的暴雨天气形势．系统垂直发展旺盛且坡度陡直,使得中低层影响系统始终处于上升运动区：地面气旋的辐合作用和辐合线的抬升作用是这次暴雨产生的触发机制;中低空急流的耦合配置为对流发展创造了有利条件,同时低空急流为这次暴雨天气提供了源源不断的水汽输送：南北长达数千公里带状云系上的对流云团强盛发展与暴雨落区时应很好、 相似文献
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13.
The charge transport mechanism of a wire can be revealed by how its electrical resistance varies with length. We have measured the resistance and current-voltage characteristics of conjugated molecular wires ranging in length from 1 to 7 nanometers, connected between metal electrodes. We observe the theoretically predicted change in direct-current transport from tunneling to hopping as a function of systematically controlled wire length. We also demonstrate that site-specific disruption of conjugation in the wires greatly increases resistance in the hopping regime but has only a small effect in the tunneling regime. These nanoscale transport measurements elucidate the role of molecular length and bond architecture on molecular conductivity and open opportunities for greater understanding of electrical transport in conjugated polymer films. 相似文献
14.
Cheng RJ 《Science (New York, N.Y.)》1970,170(3965):1395-1396
The ejection of microdroplets from the surface of a freezing supercooled water drop has been observed and photographed. The fragmentation of a freezing drop in the forms of splintering, shattering, or bursting has been known for some time. This newly observed phenomenon of the ejection of numerous microdroplets, the duration of their ejection, and the electrical properties of these droplets suggest a possible mechanism of charge generation in thunderstorms. 相似文献
15.
How to make water run uphill 总被引：1，自引：0，他引：1
A surface having a spatial gradient in its surface free energy was capable of causing drops of water placed on it to move uphill. This motion was the result of an imbalance in the forces due to surface tension acting on the liquid-solid contact line on the two opposite sides ("uphill" or "downhill") of the drop. The required gradient in surface free energy was generated on the surface of a polished silicon wafer by exposing it to the diffusing front of a vapor of decyltrichlorosilane, Cl(3)Si(CH(2))(9)CH(3). The resulting surface displayed a gradient of hydrophobicity (with the contact angle of water changing from 97 degrees to 25 degrees ) over a distance of 1 centimeter. When the wafer was tilted from the horizontal plane by 15 degrees , with the hydrophobic end lower than the hydrophilic, and a drop of water (1 to 2 microliters) was placed at the hydrophobic end, the drop moved toward the hydrophilic end with an average velocity of approximately 1 to 2 millimeters per second. In order for the drop to move, the hysteresis in contact angle on the surface had to be low (相似文献
16.
Mechanism of membrane anchoring affects polarized expression of two proteins in MDCK cells 总被引：54，自引：0，他引：54
The signals that direct membrane proteins to the apical or basolateral plasma membrane domains of polarized epithelial cells are not known. Several of the class of proteins anchored in the membrane by glycosyl-phosphatidylinositol (GPI) are expressed on the apical surface of such cells. However, it is not known whether the mechanism of membrane anchorage or the polypeptide sequence provides the sorting information. The conversion of the normally basolateral vesicular stomatitis virus glycoprotein (VSV G) to a GPI-anchored protein led to its apical expression. Conversely, replacement of the GPI anchor of placental alkaline phosphatase with the transmembrane and cytoplasmic domains of VSV G shifted its expression from the apical to the basolateral surface. Thus, the mechanism of membrane anchorage can determine the sorting of proteins to the apical or basolateral surface, and the GPI anchor itself may provide an apical transport signal. 相似文献
17.
The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest. Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-L-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation. These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications. 相似文献
18.
哥斯达黎加海域茎柔鱼角质颚稳定同位素研究 总被引：1，自引：1，他引：0
头足类的角质颚具有结构单一和不易腐蚀的特性,其稳定同位素分析已成为头足类生态学研究的主要方法之一。根据2009年7-8月我国鱿钓船在哥斯达黎加外海捕捞的茎柔鱼样本,对其角质颚进行稳定同位素分析,探讨其与胴长、日龄、性腺成熟度等之间的关系。结果表明,茎柔鱼样本的胴长范围在25.6～35.8 cm之间,体重范围在447.6～1 122.3 g之间,为小型群体;上、下角质颚的δ13C和δ15 N有所差别,但无显著性差异（P〉0.05）;δ13C和δ15N值随着胴长和日龄的增大而增大,两者均符合线性关系;不同性成熟度的个体也有着不同的δ13C和δ15 N值,其中性成熟度为Ⅲ期个体的值最大。δ13C和δ15N值反应出茎柔鱼在生长过程中,其栖息环境从大陆架向大洋转变,活动范围也向着生产力更高的海域聚集,同时与性成熟和个体生长过程密切相关。建议今后应结合研究海域的浮游生物,对角质颚等不同硬组织及其不同部位稳定同位素进行深入分析,以便为了解和掌握茎柔鱼的生态学提供理论参考。 相似文献
19.
Clantin B Delattre AS Rucktooa P Saint N Méli AC Locht C Jacob-Dubuisson F Villeret V 《Science (New York, N.Y.)》2007,317(5840):957-961
In Gram-negative bacteria and eukaryotic organelles, beta-barrel proteins of the outer membrane protein 85-two-partner secretion B (Omp85-TpsB) superfamily are essential components of protein transport machineries. The TpsB transporter FhaC mediates the secretion of Bordetella pertussis filamentous hemagglutinin (FHA). We report the 3.15 A crystal structure of FhaC. The transporter comprises a 16-stranded beta barrel that is occluded by an N-terminal alpha helix and an extracellular loop and a periplasmic module composed of two aligned polypeptide-transport-associated (POTRA) domains. Functional data reveal that FHA binds to the POTRA 1 domain via its N-terminal domain and likely translocates the adhesin-repeated motifs in an extended hairpin conformation, with folding occurring at the cell surface. General features of the mechanism obtained here are likely to apply throughout the superfamily. 相似文献