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This is Scientific American's 60-second Science, I'm Christopher Intagliata.
It sounds like a witches' recipe: gather the hearts of a fence lizard; a little brown bat; a naked-tailed armadillo; and dozens of others.
"So initially we tried to get them from zoos... but unfortunately that didn't work out very well.
We couldn't get any samples, even when the animal died, we couldn't get a heart."
Guo Huang, a developmental biologist at the University of California, San Francisco.
He says they had more success obtaining specimens from the jars of natural history museums.
The reason for this biological scavenger hunt?
Huang and his colleagues wanted to examine the number of chromosomes contained in heart cells across the animal kingdom.
Because there's a curious phenomenon in our hearts―which is that most of the human body's cells are diploid,
meaning two sets of chromosomes, one from each parent.
But the lion's share of our heart cells are actually polyploid, meaning two or more copies from mom, two or more copies from dad.
What Huang and his team found, looking at that collection of hearts,
is that the proportion of polyploid cells in a heart goes up as you go from fish to lizards to amphibians to transitional species like platypuses, to mammals.
The reason that finding might matter to us, is that recent studies in mice and zebrafish have shown that
hearts with more diploid cells―like a zebrafish's―are able to regenerate and heal themselves.
Hearts with more polyploid cells―like mice and humans―cannot.
So what makes a heart have more polyploid cells, and thus, less chance of regenerating?
这里是科学美国人――60秒科学系列,我是克里斯托弗・因塔格里塔。
收集篱蜥、小棕蝠、裸尾犰狳和几十种其它动物的心脏――这听起来像是女巫的药方。
“因此,一开始我们曾试图从动物园得到这些心脏样本……但不幸的是这不太可行。
我们无法得到任何样本,即使动物死亡,我们也拿不到心脏。”
加州大学旧金山分校的发育生物学家黄果说到。
他表示,他们从自然历史博物馆的罐子里成功获得了标本。
为何要进行这种生物寻宝游戏?
黄果及其同事想检查整个动物界心脏细胞中的染色体数量。
因为我们的心脏有种奇怪现象――人体细胞大多是二倍体细胞,
即人体内有两套分别来自父母的染色体。
但我们心脏细胞的大部分是多倍体,也就是说从父亲或母亲处遗传到两套或两套以上的染色体。
黄果及其团队通过观察这些心脏发现,
从鱼类到蜥蜴、两栖动物、鸭嘴兽等过渡物种,直至哺乳动物,心脏中多倍体细胞的比例逐渐增加。
这一发现或许对我们很重要的原因是,最近对老鼠和斑马鱼进行的研究表明,
像斑马鱼等拥有更多二倍体心脏细胞的动物,其心脏能再生和自我治愈。
而像老鼠和人类等拥有更多多倍体细胞的心脏,则不能再生和自愈。
为什么心脏拥有更多多倍体细胞,再生的几率反而减少了呢?
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