VOA标准英语2011--Pythons Unlock Human Heart Health Secrets

Pythons Unlock Human Heart Health Secrets

Studying snakes might seem like an unlikely way to help people with heart disease, but a python’s remarkable¹ ability to quickly enlarge its heart during digestion² has Colorado medical researchers looking toward surprising new therapies to treat human heart conditions.

Young Burmese pythons coil in plastic boxes at a science lab at the University of Colorado in Boulder³. Each one is well over a meter long, but they can grow to seven meters.

The snakes' “extreme” physiology⁴ is why molecular⁵ biologist Leslie Leinwand studies them. For instance, she says, even a big python never needs a mid-day dinner or even a weekly meal.

“They can go for months and months without eating anything, and nothing terrible happens to them.”

When these giant serpents do finally show up for supper, they prefer rats, pigs or even a deer. And, unlike people, pythons never nibble⁶. They swallow their prey⁷ whole, in one gulp⁸. After that, Leinwand says, things get even stranger.

“Right after they eat a meal, the bulk of their organs in the body get bigger.”

To speed digestion after that monstrous⁹ meal, the python’s heart also gets bigger - 40 percent larger than normal - and it can take two weeks for a python to finish digesting its dinner. After that, the heart and digestive organs gradually return to their normal size.

Dramatic changes

The key to this unusual process appears to be the python’s blood. When scientists filter out the red blood cells of a resting python, the remaining plasma¹⁰ is clear, like human plasma. However, python plasma changes dramatically during the first days of digestion.

“Their blood is actually milky¹¹ white, and that milkiness¹², what’s making it white, is actually the fat in the blood,” CU student Ryan Doptis explains.

That fat gives the python energy to digest its meal, says Leinwand, just as blood fats fuel our bodies. However, she says, the strange, milky blood coursing through a python’s body during the digestion process contains 50 times more fat than normal. In people, high blood fat can increase the risk of heart attack, but that's not the case for these snakes.

“In the python, it isn’t toxic¹³ at all. What happens is the pythons have evolved a way of burning that fat, that’s in the blood, very efficiently¹⁴ and without harmful byproducts," says Leinwand. "There’s what we would call cardio-protection or heart protection that the python has.”

Heart protection

She adds that people, too, sometimes need cardio-protection. When someone suffers from high blood pressure or has a heart attack, heart cells can die. Over time, the weakened heart may grow flabbier in a way that increases damage. While exercise can strengthen some hearts, Leinwand warns it’s not for everyone.

“Some people with such severe heart disease can’t exercise enough to get that benefit, so our idea is that we could use what we’ve learned in the python perhaps to treat heart disease.”

According to Leinwand, when the python’s heart grows to help the snake digest its meal, it’s doing something that also happens, to a much lesser¹⁵ extent, to a human athlete’s heart. Each individual heart cell is getting larger and stronger.

Impact on mammals

Post-graduate student, lead researcher Cecilia Riquelme, wondered if the fatty snake blood could produce similar changes to a mammal’s heart. So she followed a hunch¹⁶.

“There has to be a factor in the blood that was inducing all the organs to grow in a concerted manner. So how can we prove that?" Riquelme says. "I decided¹⁷ maybe I can just try the python blood on cardiac cells in the laboratory.”

So Riquelme bathed heart cells from a rat in python plasma. The cells grew bigger and stronger.

The results, published online in Science, astonished Leinwand. “That was the first eureka moment of this project. Because, it still would be of academic interest if this was something specific to snakes. But when she showed that you could promote this type of cellular¹⁸ growth in the heart cells of a mammal, that motivated us to really push on this project.”

Heart drug for humans?

The researchers zeroed in on three key fatty acids in the python’s milky blood, fats which are also found in foods such as coconut¹⁹ oil, animal fat and butter.

“So it’s myristic, palmitic and palmitoleic," Leinwand says. "I want to emphasize it needs to be those three and in a particular combination that’s found in the python.”

These fatty acids are only a fraction of the many fats in a python’s blood. Still, in the right proportions, even small amounts of them have proven powerful at strengthening the heart of a healthy, live mouse.

If further testing shows that these fatty acids can also strengthen a sick mammalian heart - possibly a diseased human heart, Leinwand envisions a new drug for treating heart disease.

“Those three fatty acids would be the drug,” she says.

1 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

2 digestion   

n.消化，吸收

参考例句：

• This kind of tea acts as an aid to digestion.这种茶可助消化。
• This food is easy of digestion.这食物容易消化。

3 boulder   

n.巨砾；卵石，圆石

参考例句：

• We all heaved together and removed the boulder.大家一齐用劲，把大石头搬开了。
• He stepped clear of the boulder.他从大石头后面走了出来。

4 physiology   

n.生理学，生理机能

参考例句：

• He bought a book about physiology.他买了一本生理学方面的书。
• He was awarded the Nobel Prize for achievements in physiology.他因生理学方面的建树而被授予诺贝尔奖。

5 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

6 nibble   

n.轻咬，啃；v.一点点地咬，慢慢啃，吹毛求疵

参考例句：

• Inflation began to nibble away at their savings.通货膨胀开始蚕食他们的存款。
• The birds cling to the wall and nibble at the brickwork.鸟儿们紧贴在墙上，啄着砖缝。

7 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

8 gulp   

vt.吞咽，大口地吸（气）；vi.哽住；n.吞咽

参考例句：

• She took down the tablets in one gulp.她把那些药片一口吞了下去。
• Don't gulp your food,chew it before you swallow it.吃东西不要狼吞虎咽，要嚼碎了再咽下去。

9 monstrous   

adj.巨大的；恐怖的；可耻的，丢脸的

参考例句：

• The smoke began to whirl and grew into a monstrous column.浓烟开始盘旋上升，形成了一个巨大的烟柱。
• Your behaviour in class is monstrous!你在课堂上的行为真是丢人！

10 plasma   

n.血浆，细胞质，乳清

参考例句：

• Keep some blood plasma back for the serious cases.留一些血浆给重病号。
• The plasma is the liquid portion of blood that is free of cells .血浆是血液的液体部分，不包含各种细胞。

11 milky   

adj.牛奶的，多奶的；乳白色的

参考例句：

• Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。

12 milkiness   

乳状； 乳白色； 浑浊； 软弱

参考例句：

• Through calcareous milkiness liquid deposition, optimum reaction conditions were selected. 通过采用灰乳沉淀法，选取最佳反应条件。

13 toxic   

adj.有毒的，因中毒引起的

参考例句：

• The factory had accidentally released a quantity of toxic waste into the sea.这家工厂意外泄漏大量有毒废物到海中。
• There is a risk that toxic chemicals might be blasted into the atmosphere.爆炸后有毒化学物质可能会进入大气层。

14 efficiently   

adv.高效率地，有能力地

参考例句：

• The worker oils the machine to operate it more efficiently.工人给机器上油以使机器运转更有效。
• Local authorities have to learn to allocate resources efficiently.地方政府必须学会有效地分配资源。

15 lesser   

adj.次要的，较小的；adv.较小地，较少地

参考例句：

• Kept some of the lesser players out.不让那些次要的球员参加联赛。
• She has also been affected,but to a lesser degree.她也受到波及，但程度较轻。

16 hunch   

n.预感，直觉

参考例句：

• I have a hunch that he didn't really want to go.我有这么一种感觉，他并不真正想去。
• I had a hunch that Susan and I would work well together.我有预感和苏珊共事会很融洽。

17 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

18 cellular   

adj.移动的；细胞的，由细胞组成的

参考例句：

• She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
• Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。

19 coconut   

n.椰子

参考例句：

• The husk of this coconut is particularly strong.椰子的外壳很明显非常坚固。
• The falling coconut gave him a terrific bang on the head.那只掉下的椰子砰地击中他的脑袋。