Genetic trail leads to new HIV research
Aids researchers have discovered a key genetic factor that determines how likely people are to be infected with HIV and how fast the disease progresses after infection. The finding may lead to a screening test that identifies people with a higher or lower susceptibility to HIV/Aids enabling clinicians to adapt treatments, vaccine trials and other studies accordingly.
The research is a collaboration between the US National Institute of Allergy and Infectious Diseases (NIAID) and the US military, whose scientists have been following a racially diverse group of people with HIV over 20 years.
The study, published yesterday in the online edition of Science, shows that people with more copies of a gene called CCL3L1 are better at resisting HIV/Aids. Although we have two copies of most genes (one from each parent) the human genome has extra copies of some genes such as CCL3L1; these are often connected to the immune system and may be an evolutionary response to viral infection.
“This important study identifies genetic factors of particular groups that either mitigate or enhance one's susceptibility to infection and disease onset,” says Anthony Fauci, NIAID director. “In a broader sense, it also suggests how the immune systems of individuals with different geographical ancestries might have evolved in response to microbial stresses and how these differences in the immune system might result in medical approaches to thwart HIV/Aids or other infections that vary among groups.”
CCL3L1 makes a potent HIV-blocking protein that interacts with CCR5, a “receptor” that HIV uses as a doorway to enter and infect cells.
The researchers analysed CCL3L1 genes in 4,300 Americans with and without HIV. They found that on average people with African ancestry had four copies of the gene, those with Hispanic backgrounds had three and west European ancestry just two.
Surprisingly, this does not mean that Europeans in general are more susceptible to Aids than Africans. What matters to an individual is how many CCL3L1 copies he or she has in relation to other people with the same ethnic or racial background. Much more research will be needed to work out the complicated interplay between individual and population genetics in the immune system.
www.niaid.nih.gov The black hole that cannot stop eatingAstronomers have recorded the most powerful eruption of energy yet observed in the universe. It comes from a gigantic black hole, a billion times more massive than our sun, which is swallowing vast amounts of material from its surrounding galaxy.
The eruption was discovered with the Chandra X-ray observatory operated by Nasa, the US space agency, and is reported in the journal Nature. Brian McNamara of Ohio University, the study leader, said he had previously observed vast cosmic bubbles of hot gas extending outward from “supermassive” black holes in distant galaxies, but “what literally almost knocked me off my chair was the scale, the magnitude of this one”.
It is not yet clear where all the matter required to sustain the eruption is coming from, nor how the black hole can digest it. “It's like a 300lb pound person eating 100lb pounds of meat in one sitting,” says Prof McNamara.
Co-author Paul Nulsen of the Harvard-Smithsonian Centre for Astrophysics uses a similar analogy. “This new result is as surprising as it is exciting,” he says. “This black hole is feasting when it should be fasting.” The new study supports recent theories that supermassive black holes have a big impact on the structure of the universe. The black hole occupies a volume of space about the same size as our solar system but it affects a volume of space about 600 times the size of the whole Milky Way galaxy. “From this tiny region of space, the energy is spread out over enormous distances,” Prof McNamara says.
chandra.harvard.edu
Giant raptors flew over New ZealandGiant eagles with a wing span of 3 metres dominated the ecosystem of New Zealand before human settlement 700 years ago. Haast's eagles would swoop down on flightless moa birds, which weighed up to 200kg each, and kill them with a single blow.
Researchers from Oxford (UK), McMaster (Canada) and Canterbury (NZ) universities publish their discoveries about the outsize birds that thrived in New Zealand before Maori settlers wiped them out in the online journal PLoS Biology this week. They say Haast's eagle, at 10kg-14kg, was about 40 per cent heavier than the largest living bird of prey, the South American harpy eagle, and close to the upper weight limit of powered flight.
Folk memories of the eagle, which became extinct about 500 years ago, are preserved in Maori oral history and rock art. The species may also remind fans of the Lord of the Rings film filmed in New Zealand of the giant eagles that swooped down to rescue Sam and Frodo.
DNA extracted from fossilised bones at Oxford's Ancient Biomolecules Centre showed that Haast's eagle had an unexpected ancestry. The scientists expected to find that it was closely related to the large Australian wedge-tailed eagle, says Michael Bunce of McMaster University.
“The DNA results were so radical that, at first, we questioned their authenticity,” he says. The results showed that the New Zealand giant was in fact related to one of the world's smallest eagles, the Little Eagle of Australia and New Guinea, which typically weighs under 1kg.
“Even more striking was how closely related genetically the two species were,” Dr Bunce adds. “We estimate that their common ancestor lived less than a million years ago. It means that an eagle arrived in New Zealand and increased in weight by 10 to 15 times over this period. Such rapid size change is unprecedented in birds and animals.”
最新科学研究三则 艾滋病研究新发现: 遗传因子
艾滋病研究人员已发现一个关键的遗传因子，它决定人们染上艾滋病病毒的可能性有多大，以及染上后艾滋病的发展速度。这一发现可能导致一种筛选检测法，以辨别对艾滋病/艾滋病病毒的易感性较高或较低的人，使得临床医生能据此采用合适的疗法、疫苗试验并进行其它研究。
这项研究由美国国家免疫与传染病研究所(NIAID)和美国军方合作进行，20年来，它们的科学家一直在跟踪一组不同人种的艾滋病患者。
昨天在网络版《科学》杂志上发表的这一研究报告显示，拥有一种名为CCL3L1的基因副本越多的人，他们越能抵御艾滋病/艾滋病病毒。尽管我们拥有大多数基因的两个副本（双亲各提供一个），但在人体染色体中，还有CCL3L1等一些基因的额外副本，这些基因副本同免疫系统相联，并可能是针对病毒感染的进化反应。
“这一重要研究识别了特殊人群的遗传因子，这些因子能减轻或提高人们对感染和疾病发生的易感性，”美国国家免疫与传染病研究所主任安东尼?福奇(Anthony Fauci)表示，“从更广泛的意义上说，该研究也表明，对于有着不同地域血统的个体而言，他们的免疫系统可能对微生物压力做出反应并进化了，以及由于免疫系统存在这些差异，可能导致对抗艾滋病/艾滋病病毒或其它感染病的医疗手段因不同人群而异。”
CCL3L1生成一种有效的艾滋病病毒阻断蛋白质，这种蛋白质与CCR5互相作用，后者是一种“受体”，艾滋病病毒用它作为进入和感染细胞的入口。
研究人员分析了4300名美国人的CCL3L1基因，他们中有些有艾滋病病毒，有些没有。研究人员发现，有非洲血统的人平均有4个CCL3L1基因副本，西班牙背景的人有3个，而西欧血统的人只有2个。
令人惊讶的是，这并不意味着欧洲人普遍比非洲人更容易感染艾滋病。对于个体来说，关键是要看，与其他有相同种族或人种背景的人相比，他/她有多少个CCL3L1基因副本。要了解在免疫系统方面个体和群体遗传学之间复杂的相互作用，还需要进行更多的研究。
700年前新西兰上空的猛禽
在700年前新西兰有人类定居前，翅膀长达3米的巨鹰在当地生态系统中占据统治地位。哈斯特鹰(Haast’s eagles)会向不能飞的新西兰恐鸟(moa bird)俯冲过去，一下就能杀死这种重达200公斤的猎物。
这种巨型鸟类在新西兰曾经很繁盛，直到去那里定居的毛利人将它们消灭。来自牛津大学(英国)、麦克马斯特大学(加拿大)和坎特伯雷大学(新西兰)的研究人员上周在电子杂志《生物公共图书馆杂志》(PLoS Biology)上发表了对这种鸟的研究结果。他们表示，哈斯特鹰重10至14公斤，大约比南美洲角雕重40%，而且接近动力飞行的重量上限。南美洲角雕是目前世上最大的猛禽。
哈斯特鹰大约在500年前灭绝，关于这种鸟的民间传说至今在毛利人口中流传，并保留在他们的岩刻艺术中。这种鸟类或许会让《指环王》(Lord of the Rings)的影迷们想起那头扑下去营救萨姆(Sam)和弗洛多(Frodo)的巨鹰。《指环王》一片就是在新西兰拍摄的。
牛津古代生物分子中心(Ancient Biomolecules Centre)保存着哈斯特鹰的骨化石。从中提取的DNA表明，哈斯特鹰有个令人意外的祖先。麦克马斯特大学的迈克尔?邦斯(Michael Bunce)说，预计科学家们会发现，它与澳大利亚的大型契尾鹰有着密切关系。
“DNA研究结果如此激进，以至于我们起初曾怀疑其真实性，”他说。结果表明，这种新西兰巨鹰其实与世界上最小的一种鹰有亲缘关系，那就是澳大利亚和新几内亚小鹰，其体重通常不到1公斤。
“更令人吃惊的是，这两个物种的基因有着如此密切的关联，”邦斯博士补充说，“我们估计，它们的共同祖先生活在不到100万年前。这就意味着，在这段时间内，一种鹰来到新西兰，然后体重增加了10至15倍。如此快速的体型变化在鸟类和动物中是前所未有的。”
黑洞不停地吞噬
天文学家记录到了迄今在宇宙中观测到的最强大的能量爆发。它来自一个巨大的黑洞，这个黑洞比太阳还要大10亿倍，正在吞噬它周围星系中的大量物质。
这次爆发是钱德拉X射线天文台观测到的。该天文台由美国太空机构美国国家航空航天局(NASA)管理。《自然》杂志报导了这次爆发。俄亥俄大学的布赖恩#麦克纳马拉(Brian McNamara)是这项研究的负责人。他表示，他此前也曾观察到，宇宙中有巨大的炽热气泡从遥远星系中一些“特大质量的”黑洞中冒出来，但“真让我差点从椅子上摔下来的，是这次爆发的巨大规模。”
维持此次爆发所需的物质来自何方尚不清楚，也不清楚这个黑洞如何能吞噬这些物质。“这就像一个300磅的人一次就吃下100磅的肉，”麦克纳马拉教授说。
该研究报告的共同作者、哈佛史密松天体物理学中心的保罗#纳尔森(Paul Nulsen)使用了类似的类比。“这一新结果既令人惊讶又令人兴奋，”他说，“这个黑洞在它应该斋戒时却大开盛宴。”近期一些理论称，特大质量的黑洞对宇宙的结构有很大影响，新研究支持了这些理论。这一黑洞在宇宙中所占空间与我们太阳系所占空间几乎一样大，但它所影响的空间大约相当于整个银河系规模的600倍。“从宇宙这一微小区域爆发的能量扩散距离非常大，”麦克纳马拉教授说。
