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2024-12-27 04:03 本頁(yè)面
【正文】 titute in Stockholm, Sweden. It has previously not been known whether we were limited to the cardiomyocytes we are born with or if they could be renewed, he said. The process of renewing these cells changes over time, Frisen added. In a 20yearold, about 1 percent of cardiomyocytes are exchanged each year, but the turnover(更替 ) rate decreases with age to only percent by age 75. If we can understand how the generation of new cardiomyocytes is regulated, it may be potentially possible to develop pharmaceuticals that promote this process to stimulate regeneration after, for example, a heart attack, Frisen said. That could lead to treatment that helps restore damaged hearts. A lot of people suffer from chronic heart failure, noted coauthor Dr. Ratan Bhardwaj, also from the Karolinska Institute. Chronic heart failure arises from heart cells dying, he said. With this finding, scientists are opening the door to potential therapies to having ourselves heal ourselves, Bhardwaj said. Maybe one could devise a pharmaceutical(藥物 ) agent that would make heart cells make new and more cells to overe the problem they are facing. But barriers remain. According to Bhardwaj, scientists do not yet know how to increase heart cell production to a rate that would replace cells faster than they are dying off, especially in older patients with heart failure. In addition, the number of new cells the heart produces was estimated using healthy hearts — whether the rate of cell turnover in diseased hearts is the same remains unknown. 31. The human heart stops producing cardiac cells A when a person bees old. B as soon as a person gets sick. C immediately after a person is born. D once a person dies. √ 32. The finding could prove to be useful to A the analysis of cardiac cells. B the prevention of chronic diseases. C the treatment of heart diseases. √ D the study of longstanding mysteries. 33. In people who39。re in their mid70 s, only percent of cardiomyocytes A are still functional. B are reduced each year. C are replaced each year. √ D are damaged each year. 34. Chronic heart failure is attributed to A the dying heart cells. √ B the effects of pharmaceuticals. C the weight of the patient. D the life span of a person. 35. It remains unknown whether the rate of cell turnover in diseased hearts D changes over time. B is of any use to researchers C is the same as that in healthy hearts. √ A is high enough to replace cells faster than they39。re dying off. 第二篇 The Ice man On a September day in 1991, two Germans were climbing the mountain between Austria and Italy. High up on a mountain pass, they found the body of a man lying on the ice. At that height(10,499 feet, or 3,200 meters), the ice is usually permanent, but 1991 had been an especially warm year. The mountain ice had melted more than just usual and so the body had e to the surface. It was lying face downward. The skeleton(骨架 ) was in perfect condition, except for a wound in the head. There was still skin on the bones and the remains of some clothes. The hands were still holding the wooden handle of an ax and on the feet there were very simple leather and cloth boots. Nearby was a pair of gloves made of tree bark(樹(shù)皮 ) and a holder for arrows. Who was the man? How and when had he died? Everybody had a different answer to these questions. Some people thought that it was from this century, perhaps the body of a soldier who died in World WarⅠ , since several soldiers had already been found in the area. A Swiss woman who believed it might be her father, who had died in those mountains twenty years before and whose body had never been found. The scientists who rushed to look at the body thought it was probably much older, maybe even a thousand years old. With modern dating techniques, the scientists soon learned that the iceman was about 5,300 years old. Born in about 3300 ., he lived during the Bronze Age in Europe. At first scientists thought he was probably a hunter who had died from an accident in the high mountains. More recent evidence, how
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