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  3. The first step to defeat an enemy is to pin down his exact identity and how he operates. Hypertension — chronic, abnormally rais

The first step to defeat an enemy is to pin down his exact identity and how he operates. Hypertension — chronic, abnormally rais

admin2013-07-02  76
问题     The first step to defeat an enemy is to pin down his exact identity and how he operates. Hypertension — chronic, abnormally raised blood pressure — causes heart attacks, strokes and a multitude of other nasty conditions. Around a third of Americans and Britons suffer from it. It is thus a worthy enemy and nailing its cause is a priority. Until now, this has mostly seemed to lie in the kidneys. But Hidefumi Waki and Julian Paton of Bristol University think they have gathered some valuable new intelligence by studying the brain.

    In a previous experiment Dr Waki and Dr Paton had found that rodents(啮齿动物)with high blood pressure expressed some genes differently in an area of the brain, called the solitary nucleus(孤束核, which sets the body’s normal blood-pressure level. One of these genes was called "junctional adhesionmolecule-1" or JAM-1 for short. It is a molecule normally found in the walls of blood vessels that attracts clotting and immune cells — in other words, it causes inflammation(炎症). So the pair decided to look at JAM-1 in further depth.
    They found that in rats with high blood pressure JAM-1 levels were raised not only in the brain but also the kidney, lungs and skeletal muscle. To find out whether this was the cause or effect of high blood pressure, they then transferred the JAM-1 gene into the solitary nucleus of normal rats. After two weeks, these rats suffered from higher blood pressure than rats that had not received the gene.
    Previously, experts thought that high blood pressure was caused by the kidneys. The idea was that the kidneys failed to sense the blood pressure. This then caused the lungs to make a hormone that increases blood pressure, leading to a chain of events that raised pressure throughout the blood-vessel network. All blood-pressure-lowering drugs work by seeking to put this right. Yet blaming the kidneys cannot be the full explanation of what is going on, because only half the sufferers respond to blood-pressure-lowering drugs.
    Although these findings are preliminary, they have far-reaching implications. Variations in the JAM-1 gene and its expression may explain why high blood pressure tends to run in families, although it is also caused by a poor diet. The finding also shows that the brain could increase the activity of the sympathetic nerves, the part of the nervous system involved in stress response. Ultimately, the finding could hasten the development of drugs that would attack hypertension at its source, stopping its deadly consequences in their tracks.
The experiment of transferring JAM-1 into the normal rats is intended to prove the relationship between high blood pressure and______.
选项
答案the rise of JAM-1 levels
解析 由线索词transferring JAM-1定位至第三段第二句，文中说为了查明JAM-1水平增长和高血压的关系，他们就把JAM—l基因移植到正常老鼠的孤束核内。句中的this指上一句中的JAM—1 levels were raised。
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