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Nature Contents 10 August 2006 (Vol. 442 pp601-718)
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自然要览] （选自英国Nature杂志，2006年8月10日出版） 封面故事：5亿年前的动物胚胎化石？ Synchrotron X-ray tomographic microscopy of fossil embryos 保存非常好的、距今已有5亿年的动物胚胎化石（里面嵌入了磷酸钙，外面也包 裹了一层磷酸钙）引起人们很大兴趣，因为它们可能含有关于动物演化一个关键 阶段的发育过程的宝贵信息。 这些化石尺寸很小，这使得人们难以对它们进行 研究，但一种新开发的方法可以让科学家恢复以前无法接触到的结构细节。这种 新方法要用到利用一个同步加速器X-射线光源进行亚微米尺度的断层分析，它被 用来解决化石形成过程中的一些极端问题。关于已知最早的两侧对称动物胚胎 Markuelia 和 Pseudooides的微型化石的内部解剖结构的引人注目的数据，澄清 了关于前者发展史的某些疑问，并且显示了关于后者发育过程的一个以前未知的 模型。本期封面所示为一个Markuelia胚胎的一系列虚拟切片，它们既显示了这 种动物的胚胎特征，也显示了其死后特征。（Letter p. 680） 小鼠鼻子中的第二套嗅觉受体（Make scents of pheromones） A second class of chemosensory receptors in the olfactory epithelium 研究人员在小鼠鼻子中发现了第二套嗅觉受体，其中包括一些可能探测信息素、 因而也许与交配有关的嗅觉受体。这些受体的基因也存在于鱼类和人类中，这让 我们看到这样一个可能性：一种人类信息素受体可能很快将被发现。新发现的与 痕量胺相关的受体（TAAR）存在于鼻腔内层中一组独特的细胞表面上，与探测气 味的受体分子明显不同。 至少有三种不同的TAAR识别小鼠尿液中的不同化合 物，这说明它们在探测个体间微妙的化学信息中可能扮演一个角色。（Article p. 645; News and Views） Card9蛋白与先天免疫性的关系（A new line in immunity） Card9 controls a non-TLR signalling pathway for innate anti-fungal immunity 我们很不了解的Card9蛋白（在结构上与先天免疫系统中所涉及的Carma蛋白相 关）存在于包括血液淋巴细胞和脾脏在内的各种不同组织中。现在，Card9被发 现控制一种以前不知道的、具有抗菌活性的先天免疫通道。Card9与Dectin-1发 生相互作用，后者是哺乳动物先天免疫系统探测真菌的主要模式识别受体。该结 果表明，先天和适应性免疫系统在演化上截然不同的ITAM受体，都通过对上游适 应子的不同使用来选择性地结合保留下来的Bcl10/Malt1信号作用模块。 （Article p. 651） 关于古老恒星中锂数量的矛盾被解决（Cosmic lithium: out of sight） A probable stellar solution to the cosmological lithium discrepancy 对宇宙微波背景所做的精确测量，揭示了关于早期宇宙的性质及其膨胀过程的很 多信息。然而，有一个长期未能解决的矛盾：在最古老恒星上所观测到的锂的量 不到“大爆炸”中的核反应所产生的锂的一半。现在，Korn等人解决了这一矛 盾。他们发现，其他元素的丰度变化趋势可由扩散性涡动混合过程来解释，这个 过程将锂带到了恒星深层。（Letter p. 657; News and Views） 直径小于100米的海王星外天体（Solar System minnows） Occultation of X-rays from Scorpius X-1 by small trans-neptunian objects Scorpius X-1 (Sco X1)在天文学历史中具有重要地位，因为它曾经是 除太阳以 外第一个所探测到的宇宙X-射线源。现在，它有了一个新头衔：由“Rossi X-射 线定时探测器”卫星所获得的关于该天体X-射线光曲线中小而显著的下降，可能 代表着首次观测到的小型（直径小于100米）海王星外天体（TNO）。这些不规则 性出现在毫秒尺度上，几乎可以肯定是由微型TNO的隐藏造成的。自从奎波带天 体首次于1992年被发现以来， 迄今已经发现了超过1000个TNO。已经观测到的 TNO 直径在数百公里至几千公里之间，但预计还存在很多更小的天体。(Letter p. 660; News and Views) 声子-偏振子波及相关X-射线衍射技术（Many ions make light work） Tracking the motion of charges in a terahertz light field by femtosecond X-ray diffraction 通过空气传播的光的基本粒子是光子。但当光通过凝聚态物质传播时，它会与凝 聚态物质的晶格产生耦合，生成复杂的粒子，被称为偏振子。一项新的研究工 作，利用超快X-射线衍射来直接观测支持固体中这种光激发的原子位移。在这项 研究中，穿过铁电性钽酸锂（LiTaO3）传播的太赫辐射与晶格振动产生耦合，生 成声子-偏振子波。这种新的X-射线衍射技术使研究人员有可能去跟踪晶格中支 持这种波的传播的离子的绝对位移。（Letter p. 664） 火山岩浆从地幔流出的机制（Magma goes up in the world） The dynamics of melt and shear localization in partially molten aggregates 沿地球构造边界分布的火山的岩浆，是来自深层地幔中所产生的熔融物，但这些 熔融物是怎样从地幔到达火山的却仍然不清楚。受到最近一些发现部分熔融的岩 石中存在由应力驱动的分离现象的实验工作的启发，Katz等人提出了一个新理 论，来解释这一系统的行为。该理论预测，在正在发生变形的、部分熔融的团块 中，会自然出现成带状分布的集中的熔融物和剪切力。这说明，熔融的岩石从海 洋中部山脊下面的地幔中的快速流出，可能是通过一个具有高度渗透性的、由富 含熔融物的带状结构结成的网络发生的，而不是通过慢速流动的、统一分布的多 孔流发生的。（Letter p. 676） “刺胞动物”与两侧对称动物的Hox基因（Dividing line for Hox genes） Minimal ProtoHox cluster inferred from bilaterian and cnidarian Hox complements 从昆虫到人类的两侧对称动物的身体主轴，是在名为Hox的同一组基因的指示下 形成的。了解Hox基因的演化及相关的ParaHox基因，需要关于在更为古老的动物 类别中的Hox基因的互补基因的知识。Chourrout等人研究了这样两种动物中的 Hox基因，它们分别是“刺胞动物”Nematstella 和 Hydra， 是在距今6亿年前 出现的。虽然这些生物具有与两侧对称动物的前部Hox基因群相应的基因，但这 些Hox基因的其余部分却有独立起源的迹象。该研究还表明，假设中的ProtoHox 祖先基因群有一个简单的起源，即起源于仅仅两个基因。经过广泛的基因复制 后，“刺胞动物”和两侧对称动物的Hox基因群遵从了独立的演化轨迹，得到了 不同的结局。（Letter p. 684） IT皮质中的神经活动与物体识别相关（Making faces） Microstimulation of inferotemporal cortex influences face categorization 在灵长类动物大脑皮层中一个被称为下颞叶皮质(IT)的区域所进行的直接电生理 记录和fMRI扫描实验表明，该区域选择性地对高度复杂的视觉刺激（如面部特 征）做出响应，从而导致这样一个假设：大脑中这个区域与物体识别有关。现 在，研究人员获得了该假设的直接证据，因为他们发现了面部选择神经元与面部 识别之间的一个直接联系。 IT皮质中面部选择神经元的微弱电刺激，会导致猴 子关于面部类别的决定发生一个严重偏差。除了将 IT皮质中的神经活动与物体 识别联系起来外，这项研究工作还为今后进行关于物体形状的神经编码的研究搭 建了舞台。（Letter p. 692; News and Views） 可提高水稻抗涝性能的基因（Not taken at the flood） Sub1A is an ethylene-response-factor-like gene that confers submergence tolerance to rice 在很多亚洲国家，由于洪水损毁水稻作物而导致巨大的经济损失。大多数水稻栽 培品种会在完全浸在水中后一周内死亡，但也有一些品种能在水下生存几个星期 时间，这是由于它们有一个较大的定量特性基因位点，被称为Submergence 1 (Sub1)，其位置在第9号染色体的着丝点附近。现在，对 Sub1基因所做的一项详 细研究发现，其中的一个基因Sub1A是水稻抗浸没性能的主要决定因子。将Sub1A 引入一种在亚洲广泛栽培的水稻品种中，可提高其在洪水条件下的存活率，而不 需要以牺牲其高产量和其他优点为代价。（Letter p. 705; News and Views） |
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ningkeqing
木虫 (正式写手)
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---------------------- NEWS AND VIEWS ---------------------- Plant breeding: Rice in deep water Many otherwise productive cultivars of rice suffer badly if immersed in water for long. The identification of a gene variant that confers tolerance to this threat has practical potential. Takuji Sasaki 10.1038/442635a http://www.nature.com/nature/journal/v442/n7103/full/442635a.html Cosmology: Where all the lithium went For some years, astronomers have been trying to track down all the lithium predicted by standard cosmological models. Spectroscopic dissection of globular clusters reveals that the answer might lie in the stars. Corinne Charbonnel 10.1038/442636a http://www.nature.com/nature/journal/v442/n7103/full/442636a.html Neuroscience: An extra dimension to olfaction The sense of smell is triggered by receptors in the olfactory epithelium that lines the nose. In mice at least, that lining is also responsible for receiving chemosensory cues involved in mating and other social behaviours. John Ngai 10.1038/nature05001 http://www.nature.com/nature/jou ... ll/nature05001.html Materials science: Organosilica the conciliator Acidic and basic molecules are antagonistic, and keeping them in their place is no easy job -- unless, it seems, one unites them under the tutelage of ordered, nanoporous materials known as organosilicas. Mietek Jaroniec 10.1038/442638a http://www.nature.com/nature/journal/v442/n7103/full/442638a.html Solar System: Sifting through the debris A quadrillion previously unnoticed small bodies beyond Neptune have been spotted as they dimmed X-rays from a distant source. Models of the dynamics of debris in the Solar System's suburbs must now be reworked. Asantha Cooray 10.1038/442640a http://www.nature.com/nature/journal/v442/n7103/full/442640a.html Neurodegenerative disease: Cut to the chase A family of enzymes called caspases -- best known for their involvement in programmed cell death -- now seems to be pivotal in the progression of two neurodegenerative diseases. Lisa M. Ellerby and Harry T. Orr 10.1038/442641a http://www.nature.com/nature/journal/v442/n7103/full/442641a.html 50 & 100 years ago10.1038/442642a http://www.nature.com/nature/journal/v442/n7103/full/442642a.html Microscopy: Nanotomography comes of age The use of X-rays to construct three-dimensional tomographic images is well established in medicine. The same principle is being extended to the nanoscale, bringing us startlingly accurate pictures of tiny objects. David Attwood 10.1038/442642b http://www.nature.com/nature/journal/v442/n7103/full/442642b.html Neuroscience: Making faces in the brain Artificially activating the right neurons at the right time causes visual perception of a face. This new result shows that such neurons directly underlie the recognition of complex objects. James J. DiCarlo 10.1038/nature05000 http://www.nature.com/nature/jou ... ll/nature05000.html ---------------------- ARTICLES ---------------------- A second class of chemosensory receptors in the olfactory epithelium Stephen D. Liberles and Linda B. Buck 10.1038/nature05066 Abstract: http://www.nature.com/nature/jou ... bs/nature05066.html Article: http://www.nature.com/nature/jou ... ll/nature05066.html Card9 controls a non-TLR signalling pathway for innate anti-fungal immunity Olaf Gross et al. 10.1038/nature04926 Abstract: http://www.nature.com/nature/jou ... bs/nature04926.html Article: http://www.nature.com/nature/jou ... ll/nature04926.html ---------------------- LETTERS ---------------------- A probable stellar solution to the cosmological lithium discrepancy The predicted primordial lithium abundance is a factor of two to three times higher than the value measured in the atmospheres of old stars. This discrepancy is resolved by showing that trends in the abundances of other elements are explained by turbulent mixing, which takes the lithium deep into the stars and destroys it. A. J. Korn et al. 10.1038/nature05011 Abstract: http://www.nature.com/nature/jou ... bs/nature05011.html Article: http://www.nature.com/nature/jou ... ll/nature05011.html Occultation of X-rays from Scorpius X-1 by small trans-neptunian objects This paper reports the occultation of X-rays from Scorpius X-1 at millisecond timescales, which they attribute to a population of small trans-neptunian objects. Hsiang-Kuang Chang et al. 10.1038/nature04941 Abstract: http://www.nature.com/nature/jou ... bs/nature04941.html Article: http://www.nature.com/nature/jou ... ll/nature04941.html Tracking the motion of charges in a terahertz light field by femtosecond X-ray diffraction Terahertz radiation propagating through ferroelectric lithium tantalate (LiTa03) couples to lattice vibrations, resulting in phonon-polariton waves. The new X-ray diffraction technique makes it possible to follow directly the absolute displacements of ions in the lattice that underlie the propagation of these waves. A. Cavalleri et al. 10.1038/nature05041 Abstract: http://www.nature.com/nature/jou ... bs/nature05041.html Article: http://www.nature.com/nature/jou ... ll/nature05041.html Supercurrent reversal in quantum dots This paper reports a study of supercurrents through a quantum dot created in a semiconductor nanowire by local electrostatic gating. Owing to strong Coulomb interaction, electrons only tunnel one-by-one through the discrete energy levels of the quantum dot. This, nevertheless, can yield a supercurrent when subsequent tunnel events are coherent. Jorden A. van Dam et al. 10.1038/nature05018 Abstract: http://www.nature.com/nature/jou ... bs/nature05018.html Article: http://www.nature.com/nature/jou ... ll/nature05018.html Arctic hydrology during global warming at the Palaeocene/Eocene thermal maximum Mark Pagani et al. 10.1038/nature05043 Abstract: http://www.nature.com/nature/jou ... bs/nature05043.html Article: http://www.nature.com/nature/jou ... ll/nature05043.html The dynamics of melt and shear localization in partially molten aggregates Richard F. Katz, Marc Spiegelman and Benjamin Holtzman 10.1038/nature05039 Abstract: http://www.nature.com/nature/jou ... bs/nature05039.html Article: http://www.nature.com/nature/jou ... ll/nature05039.html Synchrotron X-ray tomographic microscopy of fossil embryos Philip C. J. Donoghue et al. 10.1038/nature04890 Abstract: http://www.nature.com/nature/jou ... bs/nature04890.html Article: http://www.nature.com/nature/jou ... ll/nature04890.html Minimal ProtoHox cluster inferred from bilaterian and cnidarian Hox complements Hox clusters in the cnidarians Nematostella vectensis and Hydra magnipapillata have genes that correspond to anterior-group Hox genes in Bilateria, but the remainder of the Hox genes shows signs of an independent origin. D. Chourrout et al. 10.1038/nature04863 Abstract: http://www.nature.com/nature/jou ... bs/nature04863.html Article: http://www.nature.com/nature/jou ... ll/nature04863.html Mesodermal Wnt2b signalling positively regulates liver specification This paper describes the identification of the only single gene that is known to exclusively regulate liver specification, and shows that liver formation is regulated by inductive Wnt signals and crosstalk between the endoderm and mesoderm along the gut tube. Elke A. Ober, Heather Verkade, Holly A. Field and Didier Y. R. Stainier 10.1038/nature04888 Abstract: http://www.nature.com/nature/jou ... bs/nature04888.html Article: http://www.nature.com/nature/jou ... ll/nature04888.html Microstimulation of inferotemporal cortex influences face categorization Seyed-Reza Afraz, Roozbeh Kiani and Hossein Esteky 10.1038/nature04982 Abstract: http://www.nature.com/nature/jou ... bs/nature04982.html Article: http://www.nature.com/nature/jou ... ll/nature04982.html Enzymatic activation of voltage-gated potassium channels Yajamana Ramu, Yanping Xu and Zhe Lu 10.1038/nature04880 Abstract: http://www.nature.com/nature/jou ... bs/nature04880.html Article: http://www.nature.com/nature/jou ... ll/nature04880.html An ARC/Mediator subunit required for SREBP control of cholesterol and lipid homeostasis A subunit of the ARC/Mediator co-activator complex is a key effector of the SREBP transcription factor during regulation of lipid homeostasis in human cells and Caenorhabditis elegans. The SREBP activation domain directly targets a KIX domain on ARC105/MED15 Fajun Yang et al. 10.1038/nature04942 Abstract: http://www.nature.com/nature/jou ... bs/nature04942.html Article: http://www.nature.com/nature/jou ... ll/nature04942.html Sub1A is an ethylene-response-factor-like gene that confers submergence tolerance to rice A gene that enables some strains of rice to survive under water for a period of time is identified. Furthermore, this gene confers its submergence tolerance when transferred into a strain of rice that normally dies when submerged under water. Kenong Xu et al. 10.1038/nature04920 Abstract: http://www.nature.com/nature/jou ... bs/nature04920.html Article: http://www.nature.com/nature/jou ... ll/nature04920.html Assembly dynamics of microtubules at molecular resolution A single-molecule approach was used to observe the growth dynamics of individual microtubules. Observations suggest that small tubulin oligomers can add directly to growing microtubules, and that the protein XMAP215 facilitates the addition of longer oligomers. Jacob W. J. Kerssemakers et al. 10.1038/nature04928 Abstract: http://www.nature.com/nature/jou ... bs/nature04928.html Article: http://www.nature.com/nature/jou ... ll/nature04928.html |
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