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  3. A meager diet may give you health and long life, but it’s not much fun—and it might not even be necessary. We may be able to han

A meager diet may give you health and long life, but it’s not much fun—and it might not even be necessary. We may be able to han

admin2015-12-23  6
问题     A meager diet may give you health and long life, but it’s not much fun—and it might not even be necessary. We may be able to hang on to most of that youthful vigor even if we don’t start to diet until old age. Stephen Spindler and his colleagues from the University of California at Riverside have found that some of an elderly mouse’s liver genes can be made to behave as they did when the mouse was young simply by limiting its food for four weeks. The genetic rejuvenation won’t reverse other damage caused by time for the mouse, but could help its liver metabolize drugs or get rid of toxins.
    Spindler’s team fed three mice a normal diet for their whole lives, and fed another three on half-rations. Three more mice were switched from the formal diet to half-feed for a month when they were 34 months old— equivalent to about 70 human years. The researchers checked the activity of 11,000 genes from the mouse livers, and found that 46 changed with age in the normally fed mice. The changes were associated with things like inflammation and free radical production—probably bad news for mouse health. In the mice that had dieted all their lives, 27 of those 46 genes continued, to behave like young genes. But the most surprising finding was that the mice that only started dieting in old age also benefited from 70 percent of these gene changes. "This is the first indication that these effects kick in pretty quickly," says Huber Warner from the National Institute on Aging near Washington, D.C.
    No one yet knows if calorie restriction works in people as it does in mice, but Spindler is hopeful. "There’s attracting and tempting evidence out there that it will work," he says. If it does work in people, there might be good reasons for rejuvenating the liver. As we get older, our bodies are less efficient at metabolizing drugs, for example. A brief period of time of dieting, says Spindler, could be enough to make sure a drug is effective.
    But Spindler isn’t sure the trade-off is worth it. "The mice get less disease, they live longer, but they’re hungry," he says. "Even seeing what a diet ddis, it’s still hard to go to a restaurant and say: ’I can only eat half of that’." Spindler hopes we soon won’t need to diet at all. His company, Life Span Genetics in California, is looking for drugs that have the effects of calorie restriction.  
An elderly mouse is mentioned to
选项 A、describe the influence of old age on mice.
B、illustrate the effect of a meager diet on mice.
C、tell us how mice’s liver genes behave.
D、inform us of the process of metabolizing drugs.
答案B
解析 推理判断题。第一段第一句提及减少进食可能会使个体健康长寿，随后用elderly mice为例，目的应在于举例证明，即B项。A项“描述年老对老鼠的影响”，文中仅提到高龄鼠肝脏基因的变化，并未提到年老对老鼠的影响；文中指出“一些老鼠的肝脏基因可以恢复到年轻时的状态，可以帮助其肝脏代谢药物”，故C项“介绍老鼠肝脏基因是如何工作的”、D项“介绍代谢药物的过程”都属过度推断。
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