您当前的位置:随你译 > 翻译资讯 > 英语翻译 > “返祖现象”是怎么回事


时间:2011-01-27 06:56    点击:
TAGS:回事,怎么,现象,the,of,and 翻译



Four-year-old Jiaxue, of China, was born with hairy black moles covering parts of her back, chest, neck and face. The media reported her condition as an atavism.
Perhaps you've heard of the world's hairiest man. The media loves to show his picture. Newspapers call conditions like this and others atavisms(返祖现象). Is the world's hairiest man really a throwback to our simian(猿) ancestors Not quite. Ape faces are clear of hair, as Michael Le Page notes in his New Scientist article on atavisms. So hypertrichosis(多毛症), a condition in which excessive amounts of hair cover the body, isn't an atavism -- unless our ancestors were werewolves(狼人). If it is an avatism, it's not from the animals we point to when we talk about evolution, like chimps.

What's the difference between atavisms and vestigial(发育不全的,退化器官的) structures They're actually pretty close. Vestigial structures are body parts that survive as degenerate, imperfect versions of what they should be. Think of the ostrich: It has wings, but it can't fly. Ostriches use their wings for other purposes, like balance, but their wings can't function as wings. Their wings are vestigial -- they're used for a purpose, but not the purpose for which they were designed.

Atavisms are traits of distant ancestors that reappear in the modern day. In order for the trait to be an atavism, an organism's parents can't have the trait, and neither can recent ancestors. The atavism you've probably heard of most often The human tail. It's not just a gag to pull in a Farrelly brothers movie -- it really happens. There are two kinds of human tails, however: the pseudo-tail and the much rarer, true human tail. The pseudo-tail doesn't have any bones or cartilage(软骨) -- it's skin and fat. But the true human tail has nerves and muscles and sometimes even cartilage or vertebrae(椎骨), although there seems to be some scientific debate about this last point. All vertebrates have the ability to make a tail, and guess what Humans are vertebrates. Way back when, maybe we all had tails, and they provided some important function for us, perhaps to help us balance.

So how do these traits crop up One idea is that instead of genes being lost during evolution, they're merely silent - they're still there, they're just not doing anything. But maybe these genes can be turned back on. Studies have shown species that lose and regain wings millions of years afterward. Are these species just evolving once again Or did a silent gene labeled "grow wings" suddenly switch back on

Scientists aren't sure how atavisms work -- not yet. They point to embryos to help decipher the answer. Embryos develop characteristics in the womb that later disappear. Whale embryos do grow buds where their legs would be, but they lose them as they develop. When you were a fetus, you had a little bud where a tail would be, but it disappeared before you were born. But on rare occasions, they don't disappear, and a baby whale is born with leg-like appendages or a human baby is born with a tail, which is usually amputated.

So why do atavisms happen What place do they have in evolution We don't know the answer. Often when people think of genetic information, they think about cloning, designer children and other controversial topics. But as scientists delve more deeply into our genetic information, this could be one of the most exciting areas of research -- finally figuring out where we came from and how we got to where we are.




一种新型高效的免疫抑制剂。是链霉菌属丝状菌(Streptomyces hygro scopicus)发酵产生的一种具有抗真菌作用的大环内脂类抗生素。1975年Vezina和Sehgal从加拿大Rapa Nui岛的土壤中分离出来而得名。1977年Martel等报告其具有免疫抑制作用。1989年Morris等率先将Rapa用于抗移植排斥反应。
Rapa通过抑制细胞周期的G0期和G1期,阻断G1进入S期而发挥其作用机制:⑴抑制T和B淋巴细胞的增殖;⑵抑制IL-1、IL-2、IL-6和γ-IFN诱导的淋巴细胞增殖作用;⑶抑制IgG和供者特异性抗体(细胞毒抗体)的产生;⑷抑制单核细胞的增殖。动物实验表明Rapa能预防和逆转急性排斥反应,抑制加速性排斥反应,并能预防慢性排斥反应所致的移植物血管病变,还可有效防止小肠移植后的GVHD,延长异种移植物的 存活以及诱导供体特异性移植耐受。目前已进入临床试用阶段。

FK506是日本藤泽制药公司于1982年从土壤真菌(Streptomyces tsukub-aensis)的肉汤培养基中提取的一种大环内酯类抗生素,发现其有极强的免疫抑制作用,是继CsA以后发现的又一种新的强效免疫抑制剂。1989年试用于临床以来取得了良好的效果。

联系我们 - 快捷支付 - 招聘信息 -  服务条款 - 友情链接 - 网站地图 - TAG 点击这里给我发消息
京ICP备09008907号 Powered by suiniyi.com Copyright 2010