5.5亿年前地球氧气含量迅速增加
文章来源:未知 文章作者:meng 发布时间:2010-12-20 02:29 字体: [ ]  进入论坛
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Researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) at the University of Oxford1 have uncovered a clue that may help to explain why the earliest evidence of complex multicellular animal life appears around 550 million years ago, when atmospheric2 oxygen levels on the planet rose sharply from 3% to their modern day level of 21%. The team, led by Professor Chris Schofield, has found that humans share a method of sensing oxygen with the world's simplest known living animal - Trichoplax adhaerens(丝盘虫) - suggesting the method has been around since the first animals emerged around 550 million years ago.

This discovery, published today (17 December) in the January 2011 edition of EMBO Reports, throws light on how humans sense oxygen and how oxygen levels drove the very earliest stages of animal evolution.

Professor Schofield said "It's absolutely necessary for any multicellular organism to have a sufficient supply of oxygen to almost every cell and so the atmospheric rise in oxygen made it possible for multicellular organisms to exist.

"But there was still a very different physiological3 challenge for these organisms than for the more evolutionarily ancient single-celled organisms such as bacteria. Being multicelluar means oxygen has to get to cells not on the surface of the organism. We think this is what drove the ancesters of Trichoplax adhaerens to develop a system to sense a lack of oxygen in any cell and then do something about it."

The oxygen sensing process enables animals to survive better at low oxygen levels, or 'hypoxia'. In humans this system responds to hypoxia, such as is caused by high altitudes or physical exertion4, and is very important for the prevention of stroke and heart attacks as well as some types of cancer.

Trichoplax adhaerens is a tiny seawater organism that lacks any organs and has only five types of cells, giving it the appearance of an amoeba(变形虫) . By analysing how Trichoplax reacts to a lack of oxygen, Oxford researcher Dr Christoph Loenarz found that it uses the same mechanism5 as humans - in fact, when the key enzyme6 from Trichoplax was put it in a human cell, it worked just as well as the human enzyme usually would.

They also looked at the genomes of several other species and found that this mechanism is present in multi-cellular animals, but not in the single-celled organisms that were the precursors7 of animals, suggesting that the mechanism evolved at the same time as the earliest multicellular animals

Defects in the most important human oxygen sensing enzyme can cause polycythemia(红血球增多症) - an increase in red blood cells. The work published today could also open up new approaches to develop therapies for this disorder8.

Professor Douglas Kell, Chief Executive, BBSRC said "Understanding how animals - and ultimately humans - evolved is essential to our ability to pick apart the workings of our cells. Knowledge of normal biological processes underpins9 new developments that can improve quality of life for everyone. The more skilful10 we become in studying the evolution of some of our most essential cell biology, the better our chances of ensuring long term health and well being to match the increase in average lifespan in the UK and beyond."



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1 Oxford Wmmz0a     
n.牛津(英国城市)
参考例句:
  • At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
  • This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。
2 atmospheric 6eayR     
adj.大气的,空气的;大气层的;大气所引起的
参考例句:
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
3 physiological aAvyK     
adj.生理学的,生理学上的
参考例句:
  • He bought a physiological book.他买了一本生理学方面的书。
  • Every individual has a physiological requirement for each nutrient.每个人对每种营养成分都有一种生理上的需要。
4 exertion F7Fyi     
n.尽力,努力
参考例句:
  • We were sweating profusely from the exertion of moving the furniture.我们搬动家具大费气力,累得大汗淋漓。
  • She was hot and breathless from the exertion of cycling uphill.由于用力骑车爬坡,她浑身发热。
5 mechanism zCWxr     
n.机械装置;机构,结构
参考例句:
  • The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
  • The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。
6 enzyme cPozF     
n.酵素,酶
参考例句:
  • Above a certain temperature,the enzyme molecule will become unfolded.超过一定温度,酶分子将会展开。
  • An enzyme that dissolves the fibrin of blood clots.能溶解血凝块中的纤维的酶。
7 precursors 5e19fce64ab14f5a4b5c8687640c2593     
n.先驱( precursor的名词复数 );先行者;先兆;初期形式
参考例句:
  • Phenyl (or polyphenyl) substituted epoxides serve as excellent precursors to phenyl (or diphenyl) carbenes. 某些苯代(或多苯)环氧乙烷是制取带苯环(或二苯)碳烯的极好原料。 来自辞典例句
  • Note the presence of megakaryocytes, erythroid islands, and granulocytic precursors. 可见巨核细胞,红细胞岛和粒细胞前体细胞。 来自互联网
8 disorder Et1x4     
n.紊乱,混乱;骚动,骚乱;疾病,失调
参考例句:
  • When returning back,he discovered the room to be in disorder.回家后,他发现屋子里乱七八糟。
  • It contained a vast number of letters in great disorder.里面七零八落地装着许多信件。
9 underpins 998953e540e369bb5f54bfcdaf83d62f     
n.基础材料( underpin的名词复数 );基础结构;(学说、理论等的)基础;(人的)腿v.用砖石结构等从下面支撑(墙等)( underpin的第三人称单数 );加固(墙等)的基础;为(论据、主张等)打下基础;加强
参考例句:
  • A powerful sense of mission underpins everything he does. 一种强烈的使命感支撑他所做的一切。 来自《简明英汉词典》
  • His presence at the crime underpins the case against him. 案子发生时他在场对他更不利。 来自辞典例句
10 skilful 8i2zDY     
(=skillful)adj.灵巧的,熟练的
参考例句:
  • The more you practise,the more skilful you'll become.练习的次数越多,熟练的程度越高。
  • He's not very skilful with his chopsticks.他用筷子不大熟练。
TAG标签: life research oxygen
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