*第十八篇 Human Heart Can Make New Cells
Solving a longstanding mystery, scientists have found that the human heart continues to generate new cardiac cells throughout the life span, although the rate of new cell production slows with age.
The finding, published in the April 3 issue of Science, could open a new path for the treatment of heart diseases such as heart failure and heart attack,experts say.
"We find that the beating cells in the heart, cardiomyocytes, are renewed,"said lead researcher Dr. Jonas Frisen, a professor of stem cell research at the Karolinska Institute 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 renewed1," he said.
The process of renewing these ceils changes over time, Frisen added. In a 20-year-old, about 1 percent of cardiomyocytes are exchanged each year, but the turnover rate decreases with age to only 0.45 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 co-author Dr.
Ratan Bhardwaj, also from the Karolinska Institute. "Chronic heart failure arises from heart cells dying2," he said. from www.yingyukaoshi.com
With this finding, scientists are "opening the door to potential therapies to having ourselves3," heal ourselves Bhardwaj said. "Maybe one could devise a pharmaceutical agent that would make heart cells make new and more cells to overcome 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.
词汇 Longstanding adj. 为时甚久的turnover n. 更替率
Cardiac adj. 心脏的pharmaceutical n. 药物
cardiomyocyte n. 心肌细胞therapy n. 疗法、治疗
注释 1. It has previously not been known whether we were limited to the cardiomyocytes we are born with or if they could be renewed: 早前并不清楚人们是否局限于出生时所具有的细胞还是说这些细胞可以被更新。
2. Chronic heart failure arises from heart cells dying: 慢性心衰是由心肌细胞死亡导致的。
3. With this finding, scientists are "opening the door to potential therapies to having ourselves heal ourselves": 有了这一发现，科学家们正在打开让我们自愈的潜在疗法的大门。
练习： 1. The human heart stops producing cardiac cells
A when a person is born.
B when a person becomes old.
C when a person gets sick.
D when a person dies.
2. The finding could prove to be helpful to
A the study of longstanding mysteries.
B the analysis of cardiac cells.
C the prevention of chronic diseases.
D the treatment of heart disease.
3. The people who're in their mid-70s, only 0.45 percent of cardiomyocytes
A are still functional
B are replaced each year.
C are lost each year.
D are damaged each year.
4. Chronic heart failure is associated with
A the death of heart cells.
B the life span of a person.
C the effects of pharmaceuticals.
D the weight of the patient.
5. It remains unknown whether the rate of cell turnover in diseased hearts
A changes over time.
B can be monitored.
C is the same as that in healthy hearts.
D is high enough to replace cells faster than they're dying off.
答案与解析 1. D 短文的第一段说，科学家们发现，在人的整个生命过程中，其心脏不断产生新的心肌细胞。言外之意，这个过程直到人死才会停止。
2. D 短文的第二段说，这一发现将为心脏病的治疗开辟新的途径。
3. B 短文的第四段说，一个人20 岁时，其每年被更替的心肌细胞为1%，随着年龄的增长，该更替率不断下降，等到75 岁时，只有0.45%。
4. A 短文的倒数第三段说，慢性心衰是由心肌细胞死亡导致的。
5. C 短文的最后一段说，心脏产生的新细胞的数量是按着健康心脏计算的，而有病心脏的细胞更替率是否与健康心脏相同还不得而知。
责任编辑：sealion1986
