第三篇
Eat More, Weigh Less, Live Longer
Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, US, and his colleagues have been able to extend the lifespan (寿命) of mice by 18 per cent by blocking the rodent's (啮齿动物) increase of fat in specific cells. This suggests that thinness——and not necessarily diet——promotes long life in "calorie (热量卡) restricted" animals.
"It's very cool work," says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It's like heaven."
Calorie restriction dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown partly because few people are willing to submit to such a strict diet:
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But Kahn's team wondered whether the animals simply benefit by becoming thin.
To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice——but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn's modified mice had up to 70 per cent less body fat than normal control mice, despite the fact that they ate 55 per cent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging.
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting."
41 Ronald Kahn and his colleagues can make mice live longer by
A offering them less food.
B giving them a balanced diet.
C disrupting the specific genes in their fat cells.
D preventing them growing larger.
42 According to the passage, we do not know whether humans will benefit from taking in fewer calories partly because
A humans, worms and rodents are different.
B most people are not willing to be put on a strict diet.
C the effect is not known.
D genetic changes in tissues can not be performed on humans.
43 What does the last sentence in the third paragraph imply?
A People like to lose weight, but they do not like to eat less.
B People want to go to heaven, but they do not want to die.
C Mice will go to heaven if they lose weight.
D Mice enjoy losing weight.
44 The average modified mouse lived
A 3 years.
B 753 days.
C More than 3 years.
D 887 days.
45 What can be inferred from the passage about the route to long life?
A It remains to be studied.
B It has already been discovered.
C Eating more leads to long life.
D Eating less leads to long life.
31. A 32. B 33. C 34. D 35. D
36. C 37. D 38. D 39. B 40. A
41. C 42. B 43. A 44. D 45. A
31. A 文章的第一段第一句说在把基本研究成果成功的应用到工业领域方面,几乎没有那个国家能和德国相提并论。还可以结合第一段最后一句话理解可知答案选A, 德国的繁荣主要是把科学技术应用到了工业领域
32. B 根据文章第三段第三句话,可知答案选B。
33. C 文章最后一段第一句话提供了答案。
34. D 同上,从文章最后一段第一句话可找到答案。
35. D 文中说科学领域源源不断的新思想和“expertise”, 所以它的意思应该与新思想是同类的东西。而且“experts”是指专家,能手; “scientists”是指科学家;“scholars”是指学者,奖学金获得者。所以答案选D。
36. C 根据第二段最后一句话可知俄国和加拿大两个国家的选手都获得了冠军。
37. D 根据文章第三段可轻易得知答案选D
38. D 第四段Jerry Bingham说我仍然需要进一步确信,所以他是持怀疑态度的。
39. B 根据第四段第一句话可知英国对他们提出的新规则是持保留态度的。
40. A 文中倒数第三段中,Jeff Cook说如果去掉一个最高分,去掉一个最低分,留取中间值,可以得到一个比较合理的平均值。这在各种水下运动中是行得通的。可以很快的选出答案A。 但是这个题要注意题干里的“NOT”。
41. C 根据第二段的第一句话以及第六段的第一句话可知答案为C。
42. B 答案可从第四段的最后一句话中找出。
43. A 文中说这些老鼠随便想吃什么就吃什么,还能减肥,活的更长,就像在天堂一样。这是带着幽默意味的一句话,暗含的意思是人们对这样的老鼠有点“嫉妒”,人们也想减肥,也不想节食,但是人却不能像这些老鼠一样。
44. D 从倒数第三段第一句话可得到答案。
45. A Guarente 说的话用了两个“might”, 说明还只是一种不确定的猜测,还需进一步研究。
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