永生的涡虫体细胞可对抗衰老

sunsong7

Immortal Worms Defy Aging3 `: u9 z+ e* p" Q5 ^" {' {
ScienceDaily (Feb. 27, 2012) — Researchers from The University of Nottingham have demonstrated how a species of flatworm overcomes the aging process to be potentially immortal.' v* S' y, x& o7 O

' t( @. w5 G, s. iA Schmidtea mediterranea planarian in laboratory culture. (Credit: Image courtesy of University of Nottingham)
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The discovery, published in the Proceedings of the National Academy of Sciences, is part of a project funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and Medical Research Council (MRC) and may shed light on the possibilities of alleviating aging and age-related characteristics in human cells. Planarian worms have amazed scientists with their apparently limitless ability to regenerate. Researchers have been studying their ability to replace aged or damaged tissues and cells in a bid to understand the mechanisms underlying their longevity.
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* ]0 J9 k5 s- P) X* UDr Aziz Aboobaker from the University's School of Biology, said: "We've been studying two types of planarian worms; those that reproduce sexually, like us, and those that reproduce asexually, simply dividing in two. Both appear to regenerate indefinitely by growing new muscles, skin, guts and even entire brains over and over again.
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"Usually when stem cells divide -- to heal wounds, or during reproduction or for growth -- they start to show signs of aging. This means that the stem cells are no longer able to divide and so become less able to replace exhausted specialised cells in the tissues of our bodies. Our aging skin is perhaps the most visible example of this effect. Planarian worms and their stem cells are somehow able to avoid the aging process and to keep their cells dividing."
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1 e4 s  W  D8 S$ v* I9 ?One of the events associated with aging cells is related to telomere length. In order to grow and function normally, cells in our bodies must keep dividing to replace cells that are worn out or damaged. During this division process, copies of the genetic material must pass on to the next generation of cells. The genetic information inside cells is arranged in twisted strands of DNA called chromosomes. At the end of these strands is a protective 'cap' called a telomere. Telomeres have been likened to the protective end of a shoelace which stops strands from fraying or sticking to other strands.
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Each time a cell divides the protective telomere 'cap' gets shorter. When they get too short, the cell loses its ability to renew and divide. In an immortal animal we would therefore expect cells to be able to maintain telomere length indefinitely so that they can continue to replicate. Dr Aboobaker predicted that planarian worms actively maintain the ends of their chromosomes in adult stem cells, leading to theoretical immortality.7 N/ A: n; r8 ?8 G3 {% ~1 D
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Dr Thomas Tan made some exciting discoveries for this paper as part of his PhD. He performed a series of challenging experiments to explain the worm's immortality. In collaboration with the rest of the team, he also went some way to understanding the clever molecular trick that enabled cells to go on dividing indefinitely without suffering from shortened chromosome ends.# {( R9 |6 l/ n! T+ b& i

  u7 g  {' Y2 Q2 s: FPrevious work, leading to the award of the 2009 Nobel Prize for Physiology or Medicine, had shown that telomeres could be maintained by the activity of an enzyme called telomerase. In most sexually reproducing organisms the enzyme is most active only during early development. So as we age, telomeres start to reduce in length.8 [; u1 ~8 F2 \6 x* l' c
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This project identified a possible planarian version of the gene coding for this enzyme and turned down its activity. This resulted in reduced telomere length and proved it was the right gene. They were then able to confidently measure its activity and resulting telomere length and found that asexual worms dramatically increase the activity of this gene when they regenerate, allowing stem cells to maintain their telomeres as they divide to replace missing tissues.5 T# W- J5 z3 }2 D+ a  Y% {
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Dr Tan pointed out the importance of the interdisciplinary expertise: "It was serendipitous to be sandwiched between Professor Edward Louis's yeast genetics lab and the Children's Brain Tumour Research Centre, both University of Nottingham research centres with expertise in telomere biology. Aziz and Ed kept demanding clearer proof and I feel we have been able to give a very satisfying answer."
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! R" N2 A/ O) j  ]& k2 THowever, what puzzled the team is that sexually reproducing planarian worms do not appear to maintain telomere length in the same way. The difference they observed between asexual and sexual animals was surprising, given that they both appear to have an indefinite regenerative capacity. The team believe that sexually reproductive worms will eventually show effects of telomere shortening, or that they are able to use another mechanism to maintain telomeres that would not involve the telomerase enzyme.# J% J1 ^2 z; {! y0 I) w) U
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Dr Aboobaker concluded: "Asexual planarian worms demonstrate the potential to maintain telomere length during regeneration. Our data satisfy one of the predictions about what it would take for an animal to be potentially immortal and that it is possible for this scenario to evolve. The next goals for us are to understand the mechanisms in more detail and to understand more about how you evolve an immortal animal."2 s! R- q5 Y4 x

5 u0 e' G6 g; k1 e! q* ^Professor Douglas Kell, BBSRC Chief Executive, said: "This exciting research contributes significantly to our fundamental understanding of some of the processes involved in aging, and builds strong foundations for improving health and potentially longevity in other organisms, including humans."' B0 b1 }0 |$ _4 b
http://www.sciencedaily.com/releases/2012/02/120227152612.htm) X/ n5 t, t: v* L8 ^/ Y

sunsong7

科学家发现“长生不老”蠕虫 大脑可无限复制

来源：腾讯网 日期: 2012年03月01日

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6 K6 F+ z# q7 i! N  ^0 z( v* m据国外媒体报道，近日，美国国家科学家刊登了一项研究成果，发现蠕虫具有惊人的无限重生能力，揭示人类细胞延缓衰老的可能性以及与年龄有关的特征。研究人员一直在探索它们替换衰老或者损坏的组织和细胞的能力，以了解长寿背后的机制。据生物学博士阿齐兹阿布贝克尔（Aziz Aboobaker）介绍：我们一直在研究两种类型的蠕虫，有些是具有有性生殖能力，就像我们人类这样，而另一些是无性生殖。但两者均出现无限再生的特征，可生长出新的肌肉、皮肤、内脏甚至是整个大脑。  H3 a, s3 l7 X3 A
通常干细胞发生分裂于伤口的愈合过程中、复制期间或者繁殖的进程中，并开始显示出衰老的迹象。这就意味着我们身体中的干细胞不能再发生分裂，而逐渐丧失更新细胞的能力，最明显的例子便是我们皮肤表现出衰老的特征。蠕虫和它们身体中的干细胞在某种程度上却能避免衰老的进程发生，并保持细胞的分裂能力。( o# E/ O2 r6 W% l
细胞老化被认为与端粒的长度有关联，为了保持正常的生长和机体运作，我们身体中的细胞必须不断分裂，替代衰老或者受损的细胞。在分裂过程中，遗传物质还必须复制到下一代细胞中，这些遗传信息集中在扭曲的DNA分子链上，称为染色体。而在其末端具有保护性机制的序列被称为端粒，当DNA每进行一次复制时，端粒的长度就会缩短，至少它被完全消耗殆尽。只要当端粒长度过短，细胞就失去了重新复制分裂的能力，而“长生不老”的动物就应该有能力保持端粒的长度，使之无限复制生长。
' S4 o9 R/ G$ M8 h因此，阿布贝克尔推测蠕虫应该非常积极地保持其成熟干细胞内端粒的长度，这样在理论上它们可以长生不老。托马斯（Thomas Tan）博士也提出了一些令人兴奋的发现，进行了一系列的具有挑战性的实验来解释蠕虫长生不老之谜。他与其他研究团队合作，通过一些分子途径使细胞在没有遭受端粒长度缩短的情况下无限分裂。! V  i* d  q5 U
这些研究工作使他获得了2009年的诺贝尔生理学与医学奖，旨在探究染色体端粒在一种被称为端粒酶的作用下保持活性。在大多数与有性生殖有关的生物酶中，只有在最初的发展阶段才具有最活跃的特征，所以随着我们年龄增长，端粒的长度就开始变短。此研究项目同时也确定了蠕虫的生物酶的基因编码，并筛选出可导致端粒长度减少的基因，但进一步的结果发现当细胞进行复制时，无性蠕虫可戏剧性地提升该基因的活性，允许干细胞维持端粒的长度以分裂并替代缺失的组织。
+ i. E" v$ t9 j; P2 W托马斯博士指出本项研究所涉及的跨学科专业知识的重要性，分别是爱德华·路易斯教授的酵母遗传学实验室与儿童脑肿瘤研究中心，它们为诺丁汉大学两个具有专业端粒生物学的研究中心。科学家将进一步探索蠕虫长生不老的秘诀，其结果应该会是一个非常令人满意的答案。然而，使研究小组困惑的是有性生殖的蠕虫并不会以同样的方式保持端粒长度的稳定，当他们观察到有性生殖与无性生殖之间存在不同之处时感到非常惊讶，因为这两者似乎都有无限再生的能力，但机制却不同。研究小组认为有性生殖蠕虫的端粒将最终出现缩短，或者它们有另一种机制来保护端粒的长度，但并不涉及到端粒酶。8 }8 J+ C5 _( {5 G4 [
阿布贝克尔最后得出的结论为：无性生殖的蠕虫在复制过程中展现了保持端粒长度的能力，我们的研究证明了生物具有长生不老的潜力，这样的剧本在进化过程中是可能发生的。下一步的目标是了解更详细的机制，并发现通过何种途径可以长生不老。格拉斯·凯尔（Douglas Kell）教授认为这个研究是令人兴奋的，有利于理解衰老进程中的问题，为其他生命体（包括人类）保持健康和增加寿命建立基础。
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（发布：王楠）

lzy198

与搞涡虫的同学的研究不同