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时间:2019年10月14日 20:59:51

Science and technology科学技术Stem-cell therapies干细胞治疗Prometheus unbound普罗米修斯自由了Researchers have yet to realise the old dream of regenerating organs. But they are getting closer亘古以来,器官再生便是人类的夙愿。如今研究人员虽然还未真正实现,但成功的脚步已经越来越近PROMETHEUS, a Titan bound to a rock by Zeus, endured the daily torture of an eagle feasting on his liver, only to have the organ regrow each night.在希腊神话之中,提坦普罗米修斯被宙斯束缚在一块巨石之上,白天忍受着老鹰啄食他的肝脏,夜晚他的肝脏却又总会再次生长。Compared with this spectacle, a on the website of Nature this week seems decidedly dull.与生动的故事情节相比,本周《自然》网站上的一段视频就显得如此枯燥。It shows a collection of pink dots consolidating into a darker central glob.这段视频向世人展示了无数粉红色的小点向中心聚拢,成为一个颜色更深的团状物的过程。But something titanic is indeed happening.但这正是普罗米修斯自由的曙光。The pink dots are stem cells, and the shows the development of a liver bud, something which can go on to look and act like a liver.那些粉红色的小点就是干细胞,而视频显示的正是肝芽生长的过程,并且这个肝芽可以进一步发育为,无论是外表还是功能都与肝脏类似的组织。Takanori Takebe and Hideki Taniguchi of Yokohama City University, in Japan, who made the , have created working human-liver tissue.日本横滨市立大学的武部孝则和谷口英机拍摄了这段视频,这次他们培养出了具有功能性的人类肝脏组织。Researchers have long dreamed that stem cells might be used to repair or replace damaged tissue, an aspiration known as regenerative medicine.研究人员长期以来都设想干细胞能够用来修复或替换受损组织,该研究领域则被冠名为再生医学。Embryonic stem cells, in particular, are pluripotent, meaning they are able to become any other type of cell.多能的胚胎干细胞被再生医学家们寄予厚望,所谓多能就意味着这些干细胞可以分化出多种其他类型的细胞。And it is now possible to induce pluripotency in cells that have not come from embryos, thus circumventing the ethical minefield previously associated with obtaining them.现在的技术已经可以在非胚胎细胞中诱导细胞的多能性,这样就可以绕过之前直接使用胚胎细胞时所引发的伦理争议。Last year Shinya Yamanaka of Kyoto University won a Nobel prize for the invention of induced pluripotency.日本京都大学的山中伸弥由于成功诱导细胞的多能性而于去年荣获诺贝尔奖。He had shown how four signal proteins can reprogram adult cells into a pluripotent state.他公开发表了借助四种信号蛋白,重组成人细胞并使其具有多能性的实验过程。Beside dealing with the ethical problems of embryonic cells, Dr Yamanakas induced pluripotent stem cells allow—at least in theory—a treatment to be created from a patients own body.除了成功躲开了胚胎细胞的伦理问题,山中士发明的诱导多能干细胞,使得再生医学可以从患者体内提取细胞进行再生治疗。This would have his own genetic make up and would thus not attract the attention of his immune system.这样就可以取得患者自身的基因组合,避免了患者免疫系统的排异反应。Realising such treatments has been fiendishly difficult.要真正实现这种干细胞治疗仍然困难重重,But Dr Takebes paper in Nature is one of several signs that the Promethean dream is slowly coming to life.但是武部士发表于《自然》的论文则是人类又一次向解放普罗米修斯迈出了坚实的一步。Budding hope星星之火Clinical trials of pluripotent cells are aly happening, though they hark back to the days when only cells derived from embryos were available.多能细胞的临床试验其实早已开始进行,只是这种多能细胞还是由胚胎干细胞所培养。An American firm called Advanced Cell Technology is using them to treat macular degeneration, a cause of blindness.美国先进细胞技术公司正运用多能细胞治疗可能致盲的黄斑变性。Last year it reported promising results in two patients and Gary Rabin, the firms boss, says tests continue.去年该公司报告了两例有望好转的临床病患,公司老总加里·拉宾也表示,试验仍会继续。Even if this specific approach works, though, it is likely to be overtaken by iPS technology.不过,即使这一临床试验终获成功,也有可能会被iPS技术所取代。The Japanese, not surprisingly, are in the lead.日本在iPS技术方面无疑领先于世界其他各国。Soon, the countrys health ministry is expected to approve the first clinical trial of iPS cells, also for macular degeneration.该国卫生部应该不久便会批准iPS细胞的第一例临床试验,同样也是治疗黄斑变性。But ACT is not far behind.然而ACT也并未脱离战队,It hopes to begin a trial of platelets made from iPS cells.该公司希望开始一项iPS细胞培养血小板的试验。And other firms want to treat everything from Parkinsons disease to glaucoma to multiple sclerosis.还有些公司则希望透过iPS技术治疗其他疾病,包括帕金森病、青光眼、多发性硬化等。Academia is pushing ahead as well.学术界则正在进一步地研究iPS技术。Inspired by Dr Yamanakas work, people are looking for other shortcuts to pluripotency.受到山中教授研究成果的启发,人们纷纷开始探究诱导细胞多能性更为便捷的其他途径。Marius Wernig of Stanford University, for instance, has worked out how to use three proteins to turn connective-tissue cells into neurons.斯坦福大学的马吕斯·维米格就发现了使用三种蛋白质,将结缔组织细胞转化为神经细胞的方法。Deepak Srivastava of the University of California, San Francisco, meanwhile, has shown how to convert connective tissue into heart cells.加州大学旧金山分校的迪帕克·司里瓦斯德瓦则发表了将结缔组织转化为心肌细胞的过程。Other research is going beyond simple cell cultures.还有一些研究就没有局限于简单的细胞培养领域。左使良树任职于神户的理化研究所发育生物学中心。In 2011 Yoshiki Sasai of the RIKEN Centre for Developmental Biology, in Kobe, showed how mouse embryonic stem cells, if mixed with a few appropriate growth factors, quickly form a three-dimensional cluster made of the precursor cells to neurons.他于2011年发表论文,阐述了老鼠胚胎干细胞在给予一些适当的生长因子后,快速形成一个三维立体簇集物的过程。This cluster then turns into something resembling the back of an eye.而这种簇集物由多种细胞构成,并进而发育成一种类似于眼底结构的组织。Last year Dr Sasai repeated the trick with human cells.去年左使士使用人类细胞再次重复了这一实验过程。The dream is to make a complex organ from scratch.人们的梦想就是从无到有地创造出一个复杂的器官。With this in mind researchers at Wake Forest University in North Carolina have used a three-dimensional printer to produce an artificial kidney using immature kidney cells.为了实现这个梦想,北卡罗来纳州维克森林大学的研究员们使用三维打印技术,用不成熟的肾脏细胞做出了一个人造肾脏。But if such organs are to work in people, they will need blood vessels to deliver oxygen and nutrients.不过要让这样的肾脏在人体内正常工作,其中还是缺少了用于输送氧气和营养物质的血管。The way to do that might, paradoxically, be for scientists to do less. Instead of making the whole organ in a laboratory, they might create a less-developed form, as Dr Sasai did with his proto-retina, and then leave the rest of the work to the body.如果真要实现这个梦想,科学家可能用不着在肾脏中再造血管—这听起来可能有些自相矛盾—他们其实不必在实验室中造出完整的人体器官。科学家可以先造出还没发育完全的器官试样,然后在活体体内完成剩下的研究工作。This is what Dr Takebe has done with his liver buds.武部士的肝芽生长研究正是遵照这样的器官再造思路而完成的。He coaxed some iPS cells into becoming liver endodermal cells.他小心地将一些iPS细胞导入合适的肝脏内胚层细胞。He then cultured them with two other cell types: endothelial cells, which make up the inner linings of blood vessels, that were derived from umbilical cord; and mesenchymal stem cells, derived from bone marrow, which can differentiate into several kinds of cells, though not as many as pluripotent cells.然后将这些肝脏内胚层细胞与其他两种细胞一起培养。一种是取自脐带的内皮细胞,这种细胞构成了血管内层;另一种细胞是取自骨髓的间充质干细胞,这种细胞可以分化成多种细胞类型。Cultures without mesenchymal stem cells failed to form a cluster.实验明,如果培养过程中缺少间充质干细胞,就不会形成簇集物;Those without endothelial cells failed to create a network of blood vessels.而如果没有内皮细胞,就无法形成血管网络。But together, the three types of cell, with little additional prodding, formed a bud within two days.只有将肝脏内胚层细胞与这两者结合,并配合少量的其他刺激,才最终能在两天内形成肝芽。At six days this bud was expressing genes known to be early markers of the liver.到了第六天,肝芽开始表达一些在肝脏早期形成阶段具有标志性的基因。And when Dr Takebe implanted such buds into the brains of mice whose immune systems had been disabled to prevent rejection, he observed that they connected with the mouses blood system within two days.随后,武部士将这些肝芽结构植入一些丧失免疫能力的老鼠的脑中,这样老鼠就不会对肝芽组织形成排斥反应。武部士发现,两天内肝芽结构就与这些老鼠脑中的血液循环系统相互融合了。After two months the buds not only looked like liver, they acted like it.两个月后,肝芽结构除了看上去像肝脏外,也具有了肝脏的生理功能—他们产生出了肝脏独有的蛋白质。They produced liver-specific proteins. And if Dr Takebe transplanted them to their hosts abdominal cavity, having first caused the animals real liver to fail, they often kept the mouse alive when an animal without the transplant would have died.然后武部士又将这些肝芽结构移植到了相应老鼠的腹腔中,起初肝芽结构会破坏老鼠体内自身的肝脏,但是接着很多老鼠并没有死亡。Translating this work into a way of growing new livers for people whose old ones have stopped working will take time.诚然,要将这个过程在人类身上临床试验仍需时日。But it is a big step forward.但在老鼠体内的实验已是继往开来的重要一步。After years of promise, regenerative medicine may be coming close to delivering.在人们年复一年的期盼中,再生医疗终会有实现梦想的那一天。 /201310/262804

It sounds like something from a fairy tale. 这听起来就像是个童话故事。If you look at the horizon at sunset–exactly as the last sliver of sun disappears–you might see a flash of brilliant green blaze across the sky. 日落的时候如果你看看地平线,尤其是在太阳的最后一缕银光消失的时候,你可能会看到一束耀眼的火焰划过天空。Indeed, an old Scottish proverb maintains that whoever sees this flash will always be lucky in love. 的确,有一句古老的苏格兰谚语这么说,看见这道光焰的人总是会在爱情上交好运。While we cant confirm the lucky-in-love part of this, there is a scientific explanation for the flash of green light. 尽管我们无法实会有桃花运,但对于这束绿光倒有一个科学的解释。As sunlight enters our atmosphere, it bends slightly.当阳光进入大气层,光线会发生轻微的弯曲。 This is due to refraction, the same thing that makes a pencil look slightly askew when you stick it half way into a glass of water. 这是折射的作用,就象把铅笔的一半插入一玻璃杯水中,铅笔会看起来有点倾斜。The atmospheric bending of light rays is greatest when the sun is right along the horizon, at sunrise or sunset. 日出日落时分,太阳恰好贴着地平线的时候就是光线折射作用最强的时候。How does bending sunlight create a green flash? 但弯折的太阳光又是怎样产生绿光的呢?When sunlight is bent by refraction, it separates into different colors, just like light through a prism. 当日光由于折射而弯曲时,光线就会分解成不同的颜色,就像通过棱镜发射不同的光一样。While a prism can make a dramatic rainbow, atmospheric refraction isnt that strong. 然而三棱镜可以折射出漂亮的七色虹,而大气的折射作用却没有那么强。It doesnt turn the sun into a rainbow, but it makes the lowest part of the sun seem a bit more red, and the top of the sun seem greenish blue. 它不会将太阳光折射成虹,但是它可以使最底部的光变得更红一些,而最顶部的光看上去像蓝绿色。The effect is so subtle, youd never notice it. 这个变化非常微妙,你可能从来都未曾注意。Except, of course, at sunset or sunrise. 当然,除了在日出或日落的时候。For a split second, when most of the suns globe is below the horizon, the only part showing is that blue-green sliver along the top. 只有那么一瞬间,当太阳的大部分轮廓低于水平线,仅有的露出来的部分就是顶部的蓝绿色长条。Blue light is scattered by the atmosphere, so whats left is a brief flash of green, the only illumintion in the sky! 蓝光被大气层分散,剩下的就是一缕缕的绿光,天空唯一的光亮处。Please remember, this happens immediately after a sunset. Never look directly at the setting sun. 请记住,这种现象只在日落后的一瞬间发生。要记着可别一直盯着落日看。 201308/251825


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