There is evidence that the usual variety of high blood pressure is, in part, a familial disease. Since families have similar genes as well as similar environments, familial diseases could be due to shared genetic influences, to shared environmental factors, or to both. For some years, the role of one
environment factor commonly shared by families, namely dietary salt (i.e., sodium chloride), has been studied at Brookhaven National Laboratory. These studies suggest that long excess salt intake can lead to high blood pressure in man and animals. Some individuals, however, and some rats consume large amounts of salt without developing high blood pressure. No matter how strictly all environmental factors were controlled in these experiments, some salt-fed animals never developed hypertension whereas a few rapidly developed very severe hypertension followed by early death. These marked variations were interpreted to result from differences in genetic constitution.
By mating long successive generations of those animals that failed to develop hypertension from salt intake, a resistant strain (the R strain) has been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly. In contrast, by mating only animals that quickly develop hypertension from salt, sensitive strain (the S strain) has also been developed.
The availability of these two strains permits investigations possible. They provide a plausible laboratory model on which to investigate some clinical aspects of the human hypertension. More important, there might be the possibility of developing methods by which genetic susceptibility (敏感性) of human beings to high blood pressure can be defined without waiting for its appearance. Radioactive sodium 22 was an important tool in working out the characteristics of the sodium chloride metabolism.
21. The study of the effects of salt on high blood pressure was carried out_______.
A. as members of the same family tend to use similar amounts of salt
B. to explore the long-term use of a sodium based substance
C. because it was proven that salt caused high blood pressure
D. because of the availability of chemically pure salt and its derivatives
22. The main difference between S and R rats is their_______.
A. need for sodium 22 B. rate of mating
C. reaction to salt D. type of blood
23. We can infer from the article that sodium 22 can be used to_______.
A. control high blood pressure
B. cure high blood pressure caused by salt
C. tell the S rats from the R rats
D. determine what a sodium chloride metabolism is like
24. The most beneficial results of the research might be_______.
A. development of diets free of salt
B. an early cure for high blood pressure
C. control of genetic agents that cause high blood pressure
D. the early identification of potential high blood pressure victims
25. Which of the statements best relates the main idea of this article?
A. When salt is added rats and human beings react similarly.
B. The near future will see a cure for high blood pressure.
C. The medical field is desperately in need of research.
D. A tendency toward high blood pressure may be a hereditary factor.
参考答案:21. A 22. C 23. D 24. D 25. D
以上就是查字典大学网为同学们带来的“2016年12月英语四级考试仔细阅读练习及答案(8)”内容了,希望看完能够带给大家一些力量,对同学的生活有所启示,更多内容在这里,请继续关注我们。
办公室恋情恶果VS好处
90后求职女生吴丽春:“相信勇敢之后必有春天”
中国的社会保障改革亟须顶层设计
职场为人处世三大准则:爱岗敬业 不卑不亢 自信坦然
创业,会给职业生涯加分多少?
中国IT城市满意度排名
15个细节助你走向美好的职业生涯
中国国际形象最佳城市排名 上海居首
大学生利用过年前短短的十几天兼职
大学生如何弥补自身的求职劣势
彩虹族成职场白领新宠
高校“求职达人” 毕业即获50万年薪 做好职业规划
别把职业规划当成口头禅
2010全球城市排名中国七城市上榜 北京排名十五
新兴职业发展遇瓶颈 或"无地用武"或"有市无人"
大一小伙骑单车37天到拉萨 全程2166公里
关于主动性的三个小故事
职场白领热门电影推荐