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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  1
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.  
What can be inferred about completely normally fed mice from the text?
选项 A、They will not experience free radical production.
B、They will experience more genetic changes in their lifetime.
C、They have more liver genes to behave like young genes.
D、They are more likely to suffer from inflammation.
答案D
解析 推理判断题。根据normally fed mice定位到第二段。该段进一步阐明实验的具体过程和结果，其中讲到在正常喂养的老鼠中，有46例基因随年龄增长而变化，这些变化与炎症和自由基的产生有关，故可推断D项“它们更有可能得炎症”为正确选项。A项“不会产生自由基”这与文中意思相反；B项“它们在一生中会有更多的基因变化”、C项“它们有更多年轻肝脏基因”在文中并未提及，文章着重讲述的是一直减半喂食的老鼠以及生长到一定时期才开始减半喂食的老鼠。
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