| 2005年01月13日 Nature中文摘要 | | 点击： 作者： 来源： 时间： 2006-11-11 本站论坛 |
|  | Volume 433 Number 7022 pp91-178
封面故事：Wnt蛋白家族在动物界的演化起源
Wnt蛋白家族是在演化过程中保留程度很高的信号分子，它们控制胚胎形成过程中细胞的命运，并且与包括癌症在内的人类疾病有关。现在，研究表明，Wnt家族在动物界的演化根源之深出乎意料。海葵（Nematostella vectensis，见本期封面照片）是刺丝胞动物门（Cnidaria）的一个成员，这个门的动物包括水母和珊瑚，它们的起源在两侧对称动物的演化之前。研究人员过去并未想到低等动物海葵有很复杂的结构，但现在却在这种海葵的胚胎中发现了近乎完整的一套Wnt基因，它们在执行复杂的任务。因此，这一古老的成模式体系可能为被称为“寒武纪爆炸”的身体构造的分化提供了一个跳板。
能制造工具的乌鸦
新卡里多尼亚乌鸦在野外制造很多不同的工具。例如，它们会从嫩枝上摘下树叶，折下侧枝，并将其用作工具来收集食物。新的实验表明，人工养育的幼年新卡里多尼亚乌鸦能在不与成年乌鸦有任何接触、或以前没有接受过人类任何演示的条件下制造和使用工具。这说明，人们在野生成年乌鸦身上所观察到的高水平的技能不是通过社会交往获得的。社会的影响在传播特殊技术和工具形状方面可能是重要的，但在本实验中的年轻乌鸦却非常注意由养育它们的人所做的关于如何使用工具的演示。新卡里多尼亚乌鸦也许可作为一个模型，来研究在它们的工具技术的发展过程中遗传特性与个体和社会学习之间的相互作用，它们也将有助于了解人类文化是怎样出现的。
“雪球地球”假说的证据
“雪球地球”假说是一个有争议的假说，即假设在新原生纪期间，地球至少有两次几乎完全被冰覆盖，冰川延伸到热带地区。大约6.35亿年前，这些冰川中的一个消失了，如此多的冰的迅速融化很可能引起了海平面的大幅度上升。现在，研究发现，这一海平面上升时期所形成的碳酸盐沉积物保留了巨大波浪的证据。这些海床结构只可能在由高速风产生的、时间非常长的表面引力波的作用下才能形成。这说明，冰川消失是与极大的风和波浪条件相关联的。不管当时地球是否是雪球，那肯定是一个气候恶劣的时期。
关于蛋白动态的新发现
蛋白的动态性质对其功能来说非常重要，但其动态经常是与蛋白结构分开考虑的。一种确定结构的新方法将NMR光谱方法与分子动态模拟结合起来，显示出一系列可相互转换的构形，它们构成一个蛋白在细胞中的原始状态。研究人员将这一方法应用于人类“泛素”，发现传统的结构确定方法严重低估这种原始状态的可变性。尤其是该蛋白的侧链，它们具有高度可变性，甚至在骨干原子动态范围更为有限的憎水核中也是如此。
恒星研究：b-Pictoris
绕恒星b-Pictoris运转的著名碎片盘的多波长图像，以前所未有的精度显示了盘物质的分布。该中心盘的不寻常之处是，其一翼比另一翼亮得多。新的图像表明，亮的区域是由一团粒子引起的，这团粒子与该盘中其他地方的粒子大小不同，很可能是由被束缚在该盘中的微行星之间的碰撞形成的，或是由一颗微行星的激变分裂形成的。
宇宙中碳-12核合成反应的速度
1953年，Fred Hoyle预测，在恒星中心的极端条件下，三个阿尔法粒子（氦核）可结合，形成一个激发态的碳-12。现在这种类型的恒星核合成被认为是宇宙中重元素的来源。令人吃惊的是，关于产生碳-12的反应的性质仍然有相当大的不确定性。现在，Fynbo等人对合成碳-12的反应速度进行了更准确的测定，准确度远远超过以前的测定，其方法是间接测定该反应之逆反应的速度。在年轻恒星上的温度下，新的反应速度大致是以前数值的两倍，但在超新星上10亿K的温度下，核合成比以前所想的速度慢得多。
吃恐龙的哺乳动物
生活在恐龙阴影中的哺乳动物通常被设想为东躲西藏，惟恐被巨大的恐龙吃掉或踩死。它们很小，跟今天的鼩鼱或老鼠差不多大，以昆虫为食，夜间出来活动。对当时的哺乳动物的这种认识正在发生变化。5年前发现的已经灭绝的哺乳动物Repenomamus robustus改变了人们的固有印象：它的体形要大得多，跟佛吉尼亚负鼠差不多。现在，Repenomamus属的另一成员已被发现，约是獾或豺的一半大。而且，还发现了一个R. robustus标本，它的胃中还保留着其最后一餐所吃的东西，即小恐龙的骨头。这些肉食性哺乳动物在开始“走出阴影”。
胚胎发育并不很复杂
控制多细胞动物胚胎发育的程序被认为是复杂的。但这是什么意思呢？这种复杂性能否量化？Azevedo等人从发育程序与电脑程序之间的相似性出发对这一问题进行了研究。通过研究细胞系能够精确认定的动物如蛔虫等的胚胎发育，他们发现，发育过程没有人们所想的那么复杂。事实上，由于需要将精确数量的细胞放在发育中的胚胎中的特定位置，这些细胞系已经简单得不能再简单了。演化过程选择了降低的复杂性。
基因组与遗传变异
“一个基因组，一个生物”听起来似乎是一个合理的经验规则，但对“丛枝菌根真菌”（AMF）来说，情况可能不是这样。这些真菌是共生在大多数植物根部的，在那里，它们能够促进植物生长。它们已经存在了4亿年而没有变化，没有有性繁殖。这些真菌单一个体内有高度的遗传变异，但对这一现象的解释却是一个有争议的话题。一种假设是，在一个细胞内的变异是由于在遗传上不同的细胞核。该假设将向演化遗传学中的一些基本假设提出挑战。但一项新的研究得出结论认为，这一基因的遗传变异不能由多倍体或高拷贝数来解释（人们通常是用它们来解释的），这种遗传变异肯定是在细胞核之间分割的。（Letters, p. 160）这一话题还是Brief Communications中一场辩论的主题，该辩论本周将在网上直播（见本期121页的辩论组成员名单）。
利用基因删除方法制备疟疾活疫苗
本期发表的一项研究工作表明，从一种活的疟疾寄生虫获得的一种疫苗能够在一种啮齿动物疟疾模型中防止感染。这一成果使得大规模生产一种有效疟疾疫苗的前景更近了一步。当一只被感染的疟蚊咬一个人时，疟原虫可进入血液。用在成功的活疫苗中的疟原虫是经过基因改造的，除掉了uis 3基因，该基因是疟原虫在肝脏中进入其生命周期的下一阶段所需要的。注射了这些弱化的寄生虫的小鼠对正常的感染性疟原虫有了免疫力。采用这一基因删除方法来制备人类疫苗将需要满足很高的安全标准，所以离我们仍有一段距离，但能证明这样做行得通也是一个重要进展。
本期目录：
Editorials
Dangerous state of denial p91
Despite the warning shots of SARS and last year's Asian outbreak of avian flu, governments are still not doing enough to monitor and prepare for the next viral pandemic. This inaction is scandalous.
doi: 10.1038/433091a
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Rockets in Russia's back yard p91
Users of the Baikonur rocket base should care more about the health of local people
doi: 10.1038/433091b
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Top of pageNews
Forces gather behind proposal for a natural-disaster agency p93
Asian tsunami prompts political support for new international body.
Jim Giles and Emma Marris
doi: 10.1038/433093a
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Agencies fear global crises will lose out to tsunami donations p94
AIDS, malaria among the issues that may face funding shortfall.
Declan Butler
doi: 10.1038/433094a
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Scientists seek action to fix Asia's ravaged ecosystems p94
Environmental concerns will be key to repairing communities.
Helen Pearson
doi: 10.1038/433094b
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Study links sickness to Russian launch site p95
Baikonur Cosmodrome may cause disease in Siberia.
Jim Giles
doi: 10.1038/433095a
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European research framework set to expand p96
Seventh funding programme set to be twice as big as the sixth.
Alison Abbott
doi: 10.1038/433096a
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Health rules may hamper Japanese import of lab mice p96
New regulations to stem disease may make research harder.
Ichiko Fuyuno
doi: 10.1038/433096b
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Science's next generation finds its own way p97
Young researchers meet in Marrakech for World Academy.
Quirin Schiermeier
doi: 10.1038/433097a
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news in brief p98
doi: 10.1038/433098a
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Top of pageNews Features
Historical monuments: The film crew p100
Cave paintings and catacomb walls around Europe are decaying under microbial attack. Are nightclub lights and designer chemicals the answer? Federica Castellani finds out.
doi: 10.1038/433100a
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Infectious disease: Vietnam's war on flu p102
Having suffered heavily from avian influenza in 2004, Vietnam might now be brewing the next human flu pandemic. Yet, as Peter Aldhous discovers, local researchers don't have the resources to investigate the risk properly.
doi: 10.1038/433102a
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Top of pageCorrespondence
Oceans need protection from scientists too p105
Unregulated research poses a serious threat to some unique marine environments.
Magnus Johnson
doi: 10.1038/433105a
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Oceans: fisheries not to blame for damage p105
Kjartan Hoydal
doi: 10.1038/433105b
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No political interference in US agricultural grants p105
Anne Vidaver
doi: 10.1038/433105c
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Top of pageBooks and Arts
Science lessons p107
Japan must learn from its mistakes in the human genome project.
doi: 10.1038/433107a
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Museum collection: A taste of their own medicines p108
doi: 10.1038/433108a
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Positive thinking p108
doi: 10.1038/433108b
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Stemming the tide of turtle extinction p109
doi: 10.1038/433109a
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Top of pageEssay
Concept
Body doubles p111
Cryptic species: as we discover more examples of species that are morphologically indistinguishable, we need to ask why and how they exist.
Alberto G. Sáez and Encarnación Lozano
doi: 10.1038/433111a
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Top of pageNews and Views
Medicine: Knockout malaria vaccine? p113
An effective vaccine against malaria remains elusive. But the finding that a genetically manipulated malaria parasite can protect its host lends fresh appeal to the idea of vaccines involving live attenuated parasites.
Robert Ménard
doi: 10.1038/433113a
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Planetary science: Construction-site inspection p114
How do you build a planetary system? Astronomers are tackling the question by peering back in time at the gas and dust surrounding stars younger than our Sun.
Alycia J. Weinberger
doi: 10.1038/433114a
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Palaeoclimate: Ripples of stormy weather p115
Heike Langenberg
doi: 10.1038/433115a
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100 and 50 years ago p116
doi: 10.1038/433116a
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Mammalian palaeobiology: Living large in the Cretaceous p116
Discoveries of large, carnivorous mammals from the Cretaceous challenge the long-held view that primitive mammals were small and uninteresting. Have palaeontologists been asking the wrong questions?
Anne Weil
doi: 10.1038/433116b
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Astrophysics: The process of carbon creation p117
In the Universe, the element carbon is created only in stars, in a remarkable reaction called the triple- process. Fresh insights into the reaction now come from the latest experiments carried out on Earth.
Mounib El Eid
doi: 10.1038/433117a
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Conservation biology: Parasite rattles diversity's cage p119
Grazing and mechanical mowing can increase plant diversity in grassland, probably by weakening dominant species and so allowing others to thrive. A partially parasitic flower can, it seems, have a similar effect.
Peter D. Moore
doi: 10.1038/433119a
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Top of pageBrief Communications
Behavioural ecology: Tool manufacture by naive juvenile crows p121
The use of twigs by these birds to coax out hidden food seems to be an instinctive skill.
Ben Kenward, Alex A. S. Weir, Christian Rutz and Alex Kacelnik
doi: 10.1038/433121a
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Top of pageBrief Communications Arising
Arbuscular mycorrhizal fungi: Hyphal fusion and multigenomic structure pE3
James D. Bever and Mei Wang
doi: 10.1038/nature03294
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Arbuscular mycorrhizal fungi: Hyphal fusion and multigenomic structure (reply) pE4
Teresa E. Pawlowska and John W. Taylor
doi: 10.1038/nature03295
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Top of pageArticles
Extreme winds and waves in the aftermath of a Neoproterozoic glaciation p123
Philip A. Allen and Paul F. Hoffman
doi: 10.1038/nature03176
Abstract | Full Text | PDF (382K)
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Simultaneous determination of protein structure and dynamics p128
Kresten Lindorff-Larsen, Robert B. Best, Mark A. DePristo, Christopher M. Dobson and Michele Vendruscolo
doi: 10.1038/nature03199
Abstract | Full Text | PDF (294K) | Supplementary information
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Top of pageLetters to Nature
Mid-infrared images of Pictoris and the possible role of planetesimal collisions in the central disk p133
Charles M. Telesco, R. Scott Fisher, Mark C. Wyatt, Stanley F. Dermott, Thomas J. J. Kehoe, Steven Novotny, Naibi Mari?as, James T. Radomski, Christopher Packham, James De Buizer and Thomas L. Hayward
doi: 10.1038/nature03255
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Revised rates for the stellar triple- process from measurement of 12C nuclear resonances p136
Hans O. U. Fynbo, Christian Aa. Diget, Uffe C. Bergmann, Maria J. G. Borge, Joakim Cederk?ll, Peter Dendooven, Luis M. Fraile, Serge Franchoo, Valentin N. Fedosseev, Brian R. Fulton, Wenxue Huang, Jussi Huikari, Henrik B. Jeppesen, Ari S. Jokinen, Peter Jones, Bj?rn Jonson, Ulli K?ster, Karlheinz Langanke, Mikael Meister, Thomas Nilsson, G?ran Nyman, Yolanda Prezado, Karsten Riisager, Sami Rinta-Antila, Olof Tengblad, Manuela Turrion, Youbao Wang, Leonid Weissman, Katarina Wilhelmsen, Juha ?yst? and The ISOLDE Collaboration
doi: 10.1038/nature03219
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Systematic design of chemical oscillators using complexation and precipitation equilibria p139
Krisztina Kurin-Cs?rgei, Irving R. Epstein and Miklós Orbán
doi: 10.1038/nature03214
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Efficient export of carbon to the deep ocean through dissolved organic matter p142
Charles S. Hopkinson, Jr and Joseph J. Vallino
doi: 10.1038/nature03191
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Magma-assisted rifting in Ethiopia p146
J.-M. Kendall, G. W. Stuart, C. J. Ebinger, I. D. Bastow and D. Keir
doi: 10.1038/nature03161
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Large Mesozoic mammals fed on young dinosaurs p149
Yaoming Hu, Jin Meng, Yuanqing Wang and Chuankui Li
doi: 10.1038/nature03102
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The simplicity of metazoan cell lineages p152
Ricardo B. R. Azevedo, Rolf Lohaus, Volker Braun, Markus Gumbel, Muralikrishna Umamaheshwar, Paul-Michael Agapow, Wouter Houthoofd, Ute Platzer, Ga?tan Borgonie, Hans-Peter Meinzer and Armand M. Leroi
doi: 10.1038/nature03178
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Unexpected complexity of the Wnt gene family in a sea anemone p156
Arne Kusserow, Kevin Pang, Carsten Sturm, Martina Hrouda, Jan Lentfer, Heiko A. Schmidt, Ulrich Technau, Arndt von Haeseler, Bert Hobmayer, Mark Q. Martindale and Thomas W. Holstein
doi: 10.1038/nature03158
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Low gene copy number shows that arbuscular mycorrhizal fungi inherit genetically different nuclei p160
Mohamed Hijri and Ian R. Sanders
doi: 10.1038/nature03069
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Genetically modified Plasmodium parasites as a protective experimental malaria vaccine p164
Ann-Kristin Mueller, Mehdi Labaied, Stefan H. I. Kappe and Kai Matuschewski
doi: 10.1038/nature03188
First paragraph | Full Text | PDF (240K)
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Binding of brassinosteroids to the extracellular domain of plant receptor kinase BRI1 p167
Toshinori Kinoshita, Ana Ca?o-Delgado, Hideharu Seto, Sayoko Hiranuma, Shozo Fujioka, Shigeo Yoshida and Joanne Chory
doi: 10.1038/nature03227
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Stabilization of microtubule dynamics at anaphase onset promotes chromosome segregation p171
Toru Higuchi and Frank Uhlmann
doi: 10.1038/nature03240
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Top of pageNaturejobs
Scientific personalities p177
Paul Smaglik
doi: 10.1038/nj7022-177a
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Graduate Journal: Over-specialization? p178
Anne Margaret Lee
doi: 10.1038/nj7022-178a
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Scientists & Societies p178
Darlene Zellers
doi: 10.1038/nj7022-178b
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Movers p178
doi: 10.1038/nj7022-178c
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