查看完整版本: 《nature》February 21, 2008

《nature》February 21, 2008

英国著名杂志《自然》是世界上最早的国际性科技期刊，自从1869年创刊以来，始终如一地报道和评论全球科技领域里最重要的突破。
最新一期《nature》February 21, 2008
Editor's Summary
21 February 2008
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Water flow on Mars
Greener biofuels
Life class
Getting it together
Sun seekers
Self-mending rubber
Genetic baggage check
An organelle with history
Insulin resistance
Hydrogen at speed
A new angle on flight
The next new disease
Neural stem cells in learning
Countering ischaemia

Water flow on Mars

Editor's Summary
21 February 2008
Water flow on Mars
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Understanding how surface water flow could have produced the observed deltas and alluvial fans on the surface of Mars is fundamental to understanding the history of water on the planet. Flow duration in particular is an important factor, but to date, estimates for the longevity of martian hydrologic events have varied erratically, from decades to millions of years. Now, in a series of experiments here on Earth, in the Eurotank facility at Utrecht University, the characteristic morphology of martian stepped or terraced deltas has been recreated. The findings suggest that the stepped fans were formed by sudden release of water from subsurface storage, rather than by surface precipitation. In the conditions prevailing on Mars, this morphology is consistent with a single basin-filling event taking tens of years, and may have required an amount of water comparable to that discharged by a large terrestrial river about the size of the Mississippi. The cover image is a photo composite of a 4 mm-per-pixel digital terrain model of an experimentally formed crater from the Eurotank.
Letter
: Martian stepped-delta formation by rapid water release
Erin R. Kraal, Maurits van Dijk, George Postma & Maarten G. Kleinhans
doi:10.1038/nature06615
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了解表面水流是怎样形成火星表面所观测到的三角洲和冲积扇的，对于了解该星球上水的历史具有根本性的意义。水流的持续时间尤其是一个重要因素，但迄今为止，对火星水文事件持续时间的估计相差很大，从几十年到几百万年都有。现在，在地球上所做的一系列实验中（实验在荷兰乌得勒支大学的Eurotank实验室中进行），研究人员重建了火星上阶梯式三角洲的特征地形。他们获得的发现表明，火星上的阶梯式冲积扇是由地表下储存的水的突然释放形成的，而不是由表面降水形成的。在火星上的流行条件下，这种地形与需要几十年时间的单一盆地填充事件是一致的，所需的水量与跟密西西比河大小相仿的一个大型地表河流所排放的水量差不多。封面图片是一幅组合照片，是由Eurotank实验室通过实验形成的一个火山坑的每像素4毫米的数字化地形模型。

Greener biofuels

Editor's Summary
21 February 2008
Greener biofuels
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The honeymoon with biofuels is over. Environmentalists have been successful in spreading the message that fuels such as bioethanol are not so green after all, and rising food prices make the point dramatically. Can biotechnologists save the day with next-generations biofuels, such as ethanol produced by microbes? Jeff Tollefson asks the questions.
News feature
: Energy: Not your father's biofuels
If biofuels are to help the fight against climate change, they have to be made from more appropriate materials and in better ways. Jeff Tollefson asks what innovation can do to improve the outlook.
Jeff Tollefson
doi:10.1038/451880a
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叶绿体中含光合作用基因的一种藻类
Apicomplexans是动物的原生动物寄生虫，包括引起疟疾、弓形虫病和其他人类疾病的病原体。大多数apicomplexans都含有一个未染色的叶绿体残体——apicoplast，它是这种寄生虫生存所必需的。人们认为，光合作用基因在细胞器演化过程中丢失了，但 “光合作用apicomplexan”的后代却没有留下来，而已知有一个光合作用的质体。现在，从悉尼港的一个石珊瑚分离出的一种生物有可能填补这一空白。这种藻类与珊瑚一起生活，但也可以作为一种自由生活的生物来培养。从系统发育学上来讲，它与Apicomplexa是相关的，与甲藻不同，其叶绿体在遗传上有一个新奇之处——它们有光合作用基因，同时结合UGA密码子的使用来编码tryptophan，后者是apicoplasts的典型特征。

Insulin resistance

Editor's Summary
21 February 2008
Insulin resistance
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The modification of nuclear and cytoplasmic proteins by O-linked N-acetylglucosamine (O-GlcNAc) is emerging as a key regulator for many cellular processes. One suspected role is as a nutrient sensor, linked to glucose flux through the hexosamine biosynthetic pathway. A study of the role of O-GlcNAc in the response to glucose flux reveals a new type of lipid binding site on the enzyme O-GlcNAc transferase (OGT): on insulin stimulation, the lipid phosphatidylinositol 3,4,5-trisphosphate binds to OGT, recruiting it to the plasma membrane. OGT then decorates insulin signalling pathway proteins with sugars, impeding their activity and dampening the insulin response. Overexpression of OGT in the liver of mice causes insulin resistance and dyslipidaemia. Abnormal O-GlcNAc modification of insulin signalling may therefore contribute to insulin resistance, obesity and type-2 diabetes.
Article
: Phosphoinositide signalling links O-GlcNAc transferase to insulin resistance
Xiaoyong Yang, Pat P. Ongusaha, Philip D. Miles, Joyce C. Havstad, Fengxue Zhang, W. Venus So, Jeffrey E. Kudlow, Robert H. Michell, Jerrold M. Olefsky, Seth J. Field & Ronald M. Evans
doi:10.1038/nature06668
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O-GlcNAc在胰岛素抗性中所起作用
O-linked N-acetylglucosamine (O-GlcNAc)对核蛋白和胞质蛋白的修饰正在成为很多细胞过程的一个关键调控因子。人们怀疑，它们所扮演的一个角色是充当营养传感器，与通过氨基己糖生物合成通道的葡萄糖流量相关。对O-GlcNAc相应于葡萄糖流量所起作用所做的一项研究显示，在O-GlcNAc转移酶（OGT）上有一个新型类脂结合点：在胰岛素刺激下，名为“磷脂酰肌醇3,4,5, trisphsophate”的类脂与OGT结合，将其吸收进胞质膜中。然后，OGT用糖来“装饰”胰岛素信号通道蛋白，抑制它们的活性，阻滞胰岛素反应。OGT在小鼠肝脏中的过度表达引起胰岛素抗性和血脂异常。因此，胰岛素信号通道的异常O-GlcNAc修饰有助于胰岛素抗性、肥胖症和2-型糖尿病的形成。

Self-mending rubber

Editor's Summary
21 February 2008
Self-mending rubber
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When a rubber-band breaks, that's it: time to get another one. But a remarkable new material described in this issue behaves rather differently. Consisting of molecules containing three different functional groups that form multiple hydrogen bonds, the molecules associate to form a 'supramolecular rubber' containing both chains and cross-links. The system shows rubber-like behaviour, that is, recoverable extensibility when stretched to several times its original length. In contrast to conventional rubbers made of macromolecules, these systems when broken or cut can self-heal when the fractured surfaces are brought together at room temperature. The new material can be synthesized from simple ingredients — fatty acids and urea — and once synthesized it is readily reprocessed. In its current form supramolecular rubber has slow strain recovery and it 'creeps' under stress, but by adjusting the starting ingredients, a spectrum of properties is attainable.
News and Views
: Materials science: The gift of healing
Synthesis of a rubber-like material that can be recycled might not seem exciting. But one that can also repeatedly repair itself at room temperature, without adhesives, really stretches the imagination.
Justin L. Mynar & Takuzo Aida
doi:10.1038/451895a
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Letter
: Self-healing and thermoreversible rubber from supramolecular assembly
Philippe Cordier, François Tournilhac, Corinne Soulié-Ziakovic & Ludwik Leibler
doi:10.1038/nature06669
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一种“超分子橡胶”新材料
当一个橡胶带断裂后，我们的办法是换一个新的。但本期Nature上描述的一种引人瞩目的新材料的行为却很不相同。这种新材料由包含三种不同官能团的分子组成，三个官能团形成多个氢键，这些分子一起形成一种“超分子橡胶”，既包含链形结构，又包含交联结构。这个体系具有橡胶一样的行为，即当被拉长到其原始长度几倍的长度时，它们能够恢复到原始长度。与由大分子构成的传统橡胶相比，这种材料在断裂后，如将断面在室温下放到一起，它们还能自我愈合。这种新材料可以用简单的成分（脂肪酸和尿素）来合成，而一旦合成之后，再加工就比较容易了。按照其目前的形势，这种超分子橡胶在压力下恢复较慢，在应力作用下会发生“蠕变”，但通过调整起始组分，可以获得一系列不同性能。

[[i] 本帖最后由 kawapu007 于 2008-2-24 10:04 编辑 [/i]]

A new angle on flight

Editor's Summary
21 February 2008
A new angle on flight
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The quest to understand the origin of flight from the study of fossils and modern birds has spawned two distinct camps: those that think early birds took off from the ground, and those that think they started to fly by falling from trees or cliffs. The observation of birds in flight has not been very helpful, because wing movements vary so much depending on what the birds are doing. Now by filming chukars (a quail-like ground bird) in action, Dial et al. show that our confusion is a matter of perspective. If the line of the vertebral column is the reference frame, the wings appear to move according to particular behaviours. But if instead the angle that the wings make with the ground (gravity) is considered, it is found that this angle occupies a narrow range, irrespective of what the body is doing. Thus the flight stroke was a matter of learning to flap at a particular angle, irrespective of whether the protobird took off from the ground or jumped from a great height.
Letter
: A fundamental avian wing-stroke provides a new perspective on the evolution of flight
Kenneth P. Dial, Brandon E. Jackson & Paolo Segre
doi:10.1038/nature06517
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关于鸟类飞行起源的一个新观点
试图通过研究化石和现代鸟类来了解飞行起源的工作产生了两个截然不同的阵营：一个阵营认为，早期鸟类是从地面起飞的；另一个阵营认为，它们是通过从树上或崖壁上落下来起飞的。对飞翔中的鸟进行观测并不是很有帮助，因为翅膀的运动相差非常大，取决于鸟在干什么。现在，通过对飞翔中的chukars（一种在地面生活的像鹌鹑一样的鸟）进行摄像，Dial等人发现，我们的困惑实际上是一个视角问题。如果以脊柱线为参照系，那么我们可以看出它们的翅膀似乎是根据特定行为来动的。但如果考虑翅膀与地面（引力）所成角度，我们就会发现，这个角度很窄，与身体在做什么没有关系。所以，飞行的问题是一个学习以特定角度拍动翅膀的问题，与原始鸟类是从地面直接起飞的、还是通过从一定高度跳下来起飞的没有关系。

好东西，希望能多拿点这些出来跟大家分享[s:196]

太无敌了，有兴趣的碰哟翻译一下吧

Hydrogen at speed

Editor's Summary
21 February 2008
Hydrogen at speed
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The extrasolar planet HD 209458b is surrounded by a vast cloud of atomic hydrogen, covering a region larger than the stellar disk. A spectral line observed when the planet passed in front of its host star revealed the presence of high-velocity atomic hydrogen a great distance away from the planet, and this was interpreted as hydrogen atoms escaping from the planet's exosphere and being accelerated by stellar radiation pressure. Starting from the fact that energetic neutral atoms are seen in the Solar System wherever energetic ions from the solar wind encounter a neutral planetary atmosphere, Holmström et al. have developed an alternative model. In this, stellar wind particles pick up electrons from neutral hydrogen in the planet's exosphere to generate energetic neutral atoms.
Letter
: Energetic neutral atoms as the explanation for the high-velocity hydrogen around HD 209458b
M. Holmström, A. Ekenbäck, F. Selsis, T. Penz, H. Lammer & P. Wurz
doi:10.1038/nature06600

太阳系外行星HD 209458b周围原子氢的能量来源
太阳系外行星HD 209458b被一个由原子氢构成的巨大云团所包裹，覆盖一个比恒星盘还大的区域。当该行星从其宿主恒星前经过时所观测到的一条光谱线显示，在与该行星相距很远的距离处存在高速原子氢，这被解释为从该行星外逸层逃逸、被恒星辐射压力加速的氢原子。从在太阳系中来自太阳风的高能离子遇到一个中性的行星大气的所有地方都能看到高能中性原子的这个事实出发，Holmström等人建立了另外一个模型。按照这个模型，恒星风粒子从行星的外逸层中的中性氢获得电子，产生高能中性原子。

[[i] 本帖最后由 kawapu007 于 2008-2-24 06:55 编辑 [/i]]

Editor's Summary
21 February 2008
The next new disease
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Emerging infectious diseases are a major threat to health: AIDS, SARS, drug-resistant bacteria and Ebola virus are among the more recent examples. By identifying emerging disease 'hotspots', the thinking goes, it should be possible to spot health risks at an early stage and prepare containment strategies. An analysis of over 300 examples of disease emerging between 1940 and 2004 suggests that these hotspots can be accurately mapped based on socio-economic, environmental and ecological factors. The data show that the surveillance effort, and much current research spending, is concentrated in developed economies, yet the risk maps point to developing countries as the more likely source of new diseases.
News and Views
: Epidemiology: Emerging diseases go global
Novel human infections continue to appear all over the world, but the risk is higher in some regions than others. Identification of emerging-disease 'hotspots' will help target surveillance work.
Mark E. J. Woolhouse
doi:10.1038/451898a
Full Text | PDF (174K)
Letter
: Global trends in emerging infectious diseases
Kate E. Jones, Nikkita G. Patel, Marc A. Levy, Adam Storeygard, Deborah Balk, John L. Gittleman & Peter Daszak
doi:10.1038/nature06536
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新传染病的早期识别和遏制策略
新出现的传染病是对人类健康的一大威胁，艾滋病、SARS、抗药性细菌和埃博拉病毒是最近的一些例子。通过识别新出现的疾病热点，人们认为，应当有可能在早期阶段发现健康风险和制定遏制它们的策略。对在1940和2004年间出现的超过300例新出现的疾病所做的一项分析表明，这些热点可以根据社会-经济、环境和生态因素被准确描绘出来。该研究所获数据表明，疾病监测工作以及当前研究经费中的很大部分都集中在发达国家，而风险图则表明，新疾病更有可能出现在发展中国家。

Editor's Summary
21 February 2008
Genetic baggage check
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The analysis of genome-wide patterns of variation in human populations can provide genetic evidence of patterns of human migration and adaptation across the world. Two contrasting papers in this issue illustrate the power of the method. By combining a large number of datasets, Lohmueller et al. obtain precise estimates of the number of deleterious mutations carried by each of 15 African-Americans and 20 European-Americans, resequenced across 11,000 genes. They find that individuals with a European background have more potentially damaging mutations lurking in their genomes than those with an African background. This is interpreted as a genetic legacy from the 'out-of-Africa' bottleneck that accompanied the peopling of Europe. Jakobsson et al. take a broader snapshot of human variation by examining 29 populations in the Human Genome Diversity Project. They obtain genotype data for over 500,000 markers in the human genome. Echoing the study of Americans with African and European backgrounds, these data reveal increasing linkage disequilibrium with increasing geographic distance from Africa.
Letter
: Proportionally more deleterious genetic variation in European than in African populations
Kirk E. Lohmueller, Amit R. Indap, Steffen Schmidt, Adam R. Boyko, Ryan D. Hernandez, Melissa J. Hubisz, John J. Sninsky, Thomas J. White, Shamil R. Sunyaev, Rasmus Nielsen, Andrew G. Clark & Carlos D. Bustamante
doi:10.1038/nature06611
First paragraph | Full Text | PDF (302K) | Supplementary information
Letter
: Genotype, haplotype and copy-number variation in worldwide human populations
Mattias Jakobsson, Sonja W. Scholz, Paul Scheet, J. Raphael Gibbs, Jenna M. VanLiere, Hon-Chung Fung, Zachary A. Szpiech, James H. Degnan, Kai Wang, Rita Guerreiro, Jose M. Bras, Jennifer C. Schymick, Dena G. Hernandez, Bryan J. Traynor, Javier Simon-Sanchez, Mar Matarin, Angela Britton, Joyce van de Leemput, Ian Rafferty, Maja Bucan, Howard M. Cann, John A. Hardy, Noah A. Rosenberg & Andrew B. Singleton
doi:10.1038/nature06742
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通过基因组分析看人类的迁移史
对人类种群在整个基因组范围内的变化模式进行分析，可以为世界范围内的人类迁移和适应模式提供遗传证据。本期Nature上两篇形成对比的论文显示了这种方法的威力。通过将大量数据集结合起来，Lohmueller等人获得了对1/15的非洲裔美国人和1/20的欧洲裔美国人所携带的有害突变数量的精确估计（通过对11,000个基因重新测序获得）。他们发现，有欧洲背景的人与有非洲背景的人相比，其基因组中有潜在危害性的突变更多。这个现象可以被理解为伴随人类在欧洲定居而出现的“走出非洲”瓶颈事件所留下的一个遗传烙印。Jackobsson等人通过分析在“人类基因组多样化项目”中所涉及的29个种群，为我们提供了关于人类变化的一个更宽广的画面。他们获得了人类基因组中超过500,000个标记的基因型数据。与对有非洲背景和欧洲背景的美国人所做研究相呼应的是，这些数据表明，与非洲的地理距离越远，连锁不平衡（linkage disequilibrium）越大。

Editor's Summary
21 February 2008
Neural stem cells in learning
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The production of new neurons occurs in the adult brain, and appears to be influenced by external stimuli such as learning, exercise and stress. But it is not clear how the process is regulated or whether it is important for brain function. New work in knockout mice lacking the orphan nuclear receptor TLX, which is expressed in neural stem cells, suggests that adult neurogenesis plays a pivotal role in learning and memory. The mice had reduced stem-cell proliferation, and a marked decrease in spatial learning. But since other behaviours such as fear conditioning were unaffected, the new neurons appear to have a selective contribution to brain functions.
Letter
: A role for adult TLX-positive neural stem cells in learning and behaviour
Chun-Li Zhang, Yuhua Zou, Weimin He, Fred H. Gage & Ronald M. Evans
doi:10.1038/nature06562
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神经干细胞在学习和记忆中所起作用
新神经元的产生出现在成年脑中，似乎是受到如学习、锻炼和压力等外部刺激因素的刺激而出现的。但我们尚不清楚这个过程是怎样调控的，也不清楚它对脑功能是否重要。用缺失孤儿核受体TLX（在神经干细胞中表达）的基因剔除小鼠所做的新的研究工作表明，成年神经生成在学习和记忆中扮演一个至关重要的角色。实验中所用的小鼠干细胞繁殖减少，空间学习能力明显降低。但因为如恐惧条件反射等其他行为未受影响，所以这些新的神经元似乎对脑功能有一个选择性贡献。

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Editor's Summary
21 February 2008
Countering ischaemia
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The transcriptional regulator PGC-1 mediates many of the effects of exercise on skeletal muscle, including mitochondrial biogenesis and fibre-type switching. Now this protein has been found to activate a natural defence pathway that protects ischaemic tissues. PGC-1 is produced in response to hypoxia and nutrient deprivation, and it in turn induces VEGF to promote blood vessel formation. This pathway is separate from the hypoxia response pathway involving hypoxia inducible factor and may provide a novel therapeutic target for treating ischaemic diseases of the heart, brain and limbs.
Letter
: HIF-independent regulation of VEGF and angiogenesis by the transcriptional coactivator PGC-1
Zoltan Arany, Shi-Yin Foo, Yanhong Ma, Jorge L. Ruas, Archana Bommi-Reddy, Geoffrey Girnun, Marcus Cooper, Dina Laznik, Jessica Chinsomboon, Shamina M. Rangwala, Kwan Hyuck Baek, Anthony Rosenzweig & Bruce M. Spiegelman
doi:10.1038/nature06613
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转录调控因子PGC-1α的新功能
转录调控因子PGC-1α调控锻炼对骨骼肌的很多效应，包括线粒体生物生成和纤维型切换。现在，这种蛋白被发现能够激活一个自然防卫通道，该通道保护缺血组织。PGC-1α是响应于缺氧和营养缺乏而产生的，它反过来又会诱导VEGF去促进血管形成。这一通道与涉及缺氧诱导因子的缺氧反应通道是分开的，也许能够为治疗心、脑和肢体缺血疾病提供一个新的治疗目标。