-
(单词翻译:双击或拖选)
This is Scientific American's 60-second Science, I'm Christopher Intagliata.
It sounds like a witches' recipe: gather the hearts of a fence lizard1; a little brown bat; a naked-tailed armadillo; and dozens of others. "So initially2 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 specimens3 from the jars of natural history museums. The reason for this biological scavenger4 hunt? Huang and his colleagues wanted to examine the number of chromosomes5 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 lizards6 to amphibians7 to transitional species like platypuses8, 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 regenerate9 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 regenerating10? "That's actually the million-dollar question." But one answer Huang's team found, is that thyroid hormone11—the same hormone that regulates metabolism12 and makes us warm-blooded creatures—might be to blame. Because when they added extra thyroid hormone to zebrafish's tanks, their tiny hearts were no longer able to regenerate. And, conversely, when they engineered mice to have hearts that were insensitive to thyroid hormone, the mouse hearts could regenerate back after injury.
"When we look at the heart function which is mainly measured by contract ability of the heart, we can see heart function improve over time after injury, while control mice cannot improve."
The results are in the journal Science.
As for fixing human hearts? Perhaps manipulating thyroid hormone levels could be a start. "We know regulating thyroid hormone probably alone is not sufficient to cure heart disease, at least for promoting heart regeneration completely. If we can figure out other major regulators of this process, we might be in a better shape."
Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.
![收听单词发音](/images/play.gif)
1
lizard
![]() |
|
n.蜥蜴,壁虎 | |
参考例句: |
|
|
2
initially
![]() |
|
adv.最初,开始 | |
参考例句: |
|
|
3
specimens
![]() |
|
n.样品( specimen的名词复数 );范例;(化验的)抽样;某种类型的人 | |
参考例句: |
|
|
4
scavenger
![]() |
|
n.以腐尸为食的动物,清扫工 | |
参考例句: |
|
|
5
chromosomes
![]() |
|
n.染色体( chromosome的名词复数 ) | |
参考例句: |
|
|
6
lizards
![]() |
|
n.蜥蜴( lizard的名词复数 ) | |
参考例句: |
|
|
7
amphibians
![]() |
|
两栖动物( amphibian的名词复数 ); 水陆两用车; 水旱两生植物; 水陆两用飞行器 | |
参考例句: |
|
|
8
platypuses
![]() |
|
n.鸭嘴兽( platypus的名词复数 ) | |
参考例句: |
|
|
9
regenerate
![]() |
|
vt.使恢复,使新生;vi.恢复,再生;adj.恢复的 | |
参考例句: |
|
|
10
regenerating
![]() |
|
v.新生,再生( regenerate的现在分词 );正反馈 | |
参考例句: |
|
|
11
hormone
![]() |
|
n.荷尔蒙,激素,内分泌 | |
参考例句: |
|
|
12
metabolism
![]() |
|
n.新陈代谢 | |
参考例句: |
|
|