雅思备考规划
扫码添加助教免费咨询雅思备考规划
扫码关注回复雅思获取最新雅思口语题库和备考资料
新东方在线雅思网特为大家准备了雅思阅读模拟练习题:配对题(33)。雅思模拟试题在雅思备考过程中所起的作用不可小觑,通过模拟练习题,我们可以很直接地了解到自己的备考状况,从而可以更有针对性地进行之后的复习。希望以下内容能够对大家的雅思备考有所帮助!更多雅思报名官网的最新消息,最新、最专业的雅思备考资料,新东方在线雅思网将第一时间为大家发布。
The Search for the Anti-aging Pill
In government laboratories and elsewhere, scientists are seeking a drug able to prolong life and youthful vigor. Studies of caloric restriction are showing the way
As researchers on aging noted recently, no treatment on the market today has been proved to slow human aging - the build-up of molecular and cellular damage that increases vulnerability to infirmity as we grow older. But one intervention, consumption of a low-calorie*yet nutritionally balanced diet, works incredibly well in a broad range of animals, increasing longevity and prolonging good health. Those findings suggest that caloric restriction could delay aging and increase longevity in humans, too.
*calorie: a measure of the energy value of food
Unfortunately, for maximum benefit, people would probably have to reduce their caloric intake by roughly thirty per cent, equivalent to dropping from 2,500 calories a day to 1,750. Few mortals could stick to that harsh a regimen, especially for years on end. But what if someone could create a pill that mimicked the physiological effects of eating less without actually forcing people to eat less? Could such a 'caloric-restriction mimetic', as we call it, enable people to stay healthy longer, postponing age-related disorders (such as diabetes, arteriosclerosis, heart disease and cancer) until very late in life? Scientists first posed this question in the mid-1990s, after researchers came upon a chemical agent that in rodents seemed to reproduce many of caloric restriction's benefits. No compound that would safely achieve the same feat in people has been found yet, but the search has been informative and has fanned hope that caloric-restriction (CR) mimetics can indeed be developed eventually.
The benefits of caloric restriction
The hunt for CR mimetics grew out of a desire to better understand caloric restriction's many effects on the body. Scientists first recognized the value of the practice more than 60 years ago, when they found that rats fed a low-calorie diet lived longer on average than free-feeding rats and also had a reduced incidence of conditions that become increasingly common in old age. What is more, some of the treated animals survived longer than the oldest-living animals in the control group, which means that the maximum lifespan (the oldest attainable age), not merely the normal lifespan, increased. Various interventions, such as infection-fighting drugs, can increase a population's average survival time, but only approaches that slow the body's rate of aging will increase the maximum lifespan.
The rat findings have been replicated many times and extended to creatures ranging from yeast to fruit flies, worms, fish, spiders, mice and hamsters. Until fairly recently, the studies were limited to short-lived creatures genetically distant from humans. But caloric-restriction projects underway in two species more closely related to humans - rhesus and squirrel monkeys - have made scientists optimistic that CR mimetics could help people.
The monkey projects demonstrate that, compared with control animals that eat normally, caloric-restricted monkeys have lower body temperatures and levels of the pancreatic hormone insulin, and they retain more youthful levels of certain hormones that tend to fall with age.
The caloric-restricted animals also look better on indicators of risk for age-related diseases. For example, they have lower blood pressure and triglyceride levels (signifying a decreased likelihood of heart disease), and they have more normal blood glucose levels (pointing to a reduced risk for diabetes, which is marked by unusually high blood glucose levels). Further, it has recently been shown that rhesus monkeys kept on caloric-restricted diets for an extended time (nearly 15 years) have less chronic disease. They and the other monkeys must be followed still longer, however, to know whether low-calorie intake can increase both average and maximum life spans in monkeys. Unlike the multitude of elixirs being touted as the latest anti-aging cure, CR mimetics would alter fundamental processes that underlie aging. We aim to develop compounds that fool cells into activating maintenance and repair.
How a prototype caloric-restriction mimetic works
The best-studied candidate for a caloric-restriction mimetic, 2DG (2-deoxy-D-glucose), works by interfering with the way cells process glucose. It has proved toxic at some doses in animals and so cannot be used in humans. But it has demonstrated that chemicals can replicate the effects of caloric restriction; the trick is finding the right one.
Cells use the glucose from food to generate ATP (adenosine triphosphate), the molecule that powers many activities in the body. By limiting food intake, caloric restriction minimizes the amount of glucose entering cells and decreases ATP generation. When 2DG is administered to animals that eat normally, glucose reaches cells in abundance but the drug prevents most of it from being processed and thus reduces ATP synthesis. Researchers have proposed several explanations for why interruption of glucose processing and ATP production might retard aging. One possibility relates to the ATP-making machinery's emission of free radicals, which are thought to contribute to aging and to such age-related diseases as cancer by damaging cells. Reduced operation of the machinery should limit their production and thereby constrain the damage. Another hypothesis suggests that decreased processing of glucose could indicate to cells that food is scarce (even if it isn't) and induce them to shift into an anti-aging mode that emphasizes preservation of the organism over such 'luxuries' as growth and reproduction.
本文关键字: 雅思阅读模拟练习题:配对题(33)
资料下载
雅思写作高频词汇PDF下载
发布时间:2023-08-26添加新东方在线雅思助教号
回复【200】获取
590组雅思阅读写作必背短语PDF版下载
发布时间:2023-08-09添加新东方在线雅思助教号
回复【590】获取
雅思学术词汇搭配表PDF版下载
发布时间:2023-08-04添加新东方在线雅思助教号
回复【ACL】获取
雅思口语part3结构策略PDF版下载
发布时间:2023-08-04添加新东方在线雅思助教号
回复【Part3】获取
雅思听力高频场景词PDF版下载
发布时间:2023-08-09添加新东方在线雅思助教号
回复【高频词】获取
雅思口语Part2答案示范15篇PDF下载
发布时间:2023-07-26添加新东方在线雅思助教号
回复【P2】获取
雅思小作文35组必备表达PDF下载
发布时间:2023-07-26添加新东方在线雅思助教号
回复【35】获取
雅思阅读高频短语PDF下载
发布时间:2023-07-20添加新东方在线雅思助教号
回复【短语】获取
200组雅思写作高频词汇PDF下载
发布时间:2023-07-20添加新东方在线雅思助教号
回复【200】获取
雅思写作话题词汇PDF下载
发布时间:2023-07-16添加新东方在线雅思助教号
回复【话题】获取
50组雅思口语同义替换词PDF下载
发布时间:2023-07-10添加新东方在线雅思助教号
回复【替换】获取
雅思写作大作文精选题目101PDF下载
发布时间:2023-07-09添加新东方在线雅思助教号
回复【101】获取
雅思口语核心300词PDF下载
发布时间:2023-06-23添加新东方在线雅思助教号
回复【300】获取
雅思阅读分类词汇PDF下载
发布时间:2023-06-17添加新东方在线雅思助教号
回复【分类词】获取
雅思口语必备习语PDF下载
发布时间:2023-06-17添加新东方在线雅思助教号
回复【习语】获取
雅思小作文常用词汇66词PDF下载
发布时间:2023-06-16添加新东方在线雅思助教号
回复【66】获取
雅思口语常见功能结构109句PDF下载
发布时间:2023-06-08添加新东方在线雅思助教号
回复【109】获取
10年雅思写作题库PDF下载
发布时间:2023-06-08添加新东方在线雅思助教号
回复【写作话题】获取
雅思图表作文精选套句50句PDF下载
发布时间:2023-05-28添加新东方在线雅思助教号
回复【50】获取
雅思写作99组高频词汇PDF资料
发布时间:2023-05-28添加新东方在线雅思助教号
回复【99】获取
2023年5月雅思口语新题题库PDF版本
发布时间:2023-05-14添加新东方在线雅思助教号
回复【新题】获取
2023年5-8月雅思口语新题题库与解析PDF版本
发布时间:2023-05-06关注新东方在线考雅课程中心服务号
回复【新题】获取
雅思听力考点词汇PDF资料
发布时间:2023-04-27添加新东方在线雅思助教号
回复【考点词】获取
雅思听力机经词汇PDF资料
发布时间:2023-04-24添加新东方在线雅思助教号
回复【TL】获取
雅思口语Part1常见话题语料库PDF资料
发布时间:2023-04-20添加新东方在线雅思助教号
回复【Part1】获取
剑桥雅思阅读长难句50句PDF资料
发布时间:2023-04-19添加新东方在线雅思助教号
回复【长难句】获取
雅思阅读核心学术词汇表PDF资料
发布时间:2023-04-07关注新东方在线考雅课程中心服务号
回复【核心】获取
100个雅思写作观点词和替换词表达PDF资料
发布时间:2023-03-24关注新东方在线考雅课程中心服务号
回复【100】获取
雅思阅读分类词汇PDF资料
发布时间:2023-03-22关注新东方在线考雅课程中心服务号
回复【分类词】获取
雅思阅读短语PDF资料
发布时间:2023-03-08关注新东方在线考雅课程中心服务号
回复【短语】获取
添加新东方在线雅思助教,
回复【口语】获取雅思口语资料大礼包
推荐阅读
更多>>大家在备考雅思考试的过程中可以多做雅思模拟题,了解自己的雅思水平,分析自己的薄弱项,新东方在线雅思在本文为大家带来的是雅思阅读模拟题:Texting the Television,大家可以练习练习。
大家在备考雅思考试的过程中可以多做雅思模拟题,了解自己的雅思水平,分析自己的薄弱项,新东方在线雅思在本文为大家带来的是雅思阅读模拟题:Sand Dunes,大家可以练习练习。
大家在备考雅思考试的过程中可以多做雅思模拟题,了解自己的雅思水平,分析自己的薄弱项,新东方在线雅思在本文为大家带来的是雅思阅读模拟题:The Concept of Childhood in the Western Countries,大家可以练习练习。
大家在备考雅思考试的过程中可以多做雅思模拟题,了解自己的雅思水平,分析自己的薄弱项,新东方在线雅思在本文为大家带来的是雅思阅读模拟题:Robert Louis Stevenson,大家可以练习练习。
大家在备考雅思考试的过程中可以多做雅思模拟题,了解自己的雅思水平,分析自己的薄弱项,新东方在线雅思在本文为大家带来的是雅思阅读模拟题:Revolutions in Mapping,大家可以练习练习。
资料下载
更多>>添加新东方在线雅思助教号
回复【200】获取
添加新东方在线雅思助教号
回复【590】获取
添加新东方在线雅思助教号
回复【ACL】获取
添加新东方在线雅思助教号
回复【Part3】获取
添加新东方在线雅思助教号
回复【高频词】获取
添加新东方在线雅思助教号
回复【P2】获取
添加新东方在线雅思助教号
回复【35】获取
添加新东方在线雅思助教号
回复【短语】获取
添加新东方在线雅思助教号
回复【200】获取
添加新东方在线雅思助教号
回复【话题】获取
添加新东方在线雅思助教号
回复【替换】获取
添加新东方在线雅思助教号
回复【101】获取
添加新东方在线雅思助教号
回复【300】获取
添加新东方在线雅思助教号
回复【分类词】获取
添加新东方在线雅思助教号
回复【习语】获取
添加新东方在线雅思助教号
回复【66】获取
添加新东方在线雅思助教号
回复【109】获取
添加新东方在线雅思助教号
回复【写作话题】获取
添加新东方在线雅思助教号
回复【50】获取
添加新东方在线雅思助教号
回复【99】获取
添加新东方在线雅思助教号
回复【新题】获取
关注新东方在线考雅课程中心服务号
回复【新题】获取
添加新东方在线雅思助教号
回复【考点词】获取
添加新东方在线雅思助教号
回复【TL】获取
添加新东方在线雅思助教号
回复【Part1】获取
添加新东方在线雅思助教号
回复【长难句】获取
关注新东方在线考雅课程中心服务号
回复【核心】获取
关注新东方在线考雅课程中心服务号
回复【100】获取
关注新东方在线考雅课程中心服务号
回复【分类词】获取
关注新东方在线考雅课程中心服务号
回复【短语】获取
编辑推荐
雅思新题
阅读排行榜
相关内容