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 bom with or if they could be renewed." he said.

　　The process of renewing these cells 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.

　　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 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 tumover in diseased hearts is the same remains unknown.

　　1. The human heart stops producing cardiac cells

　　A. when a person becomes old

　　B. as soon as a person gets sick

　　C. immediately after a person is born

　　D. once a person dies

　　2. 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 disease

　　D. the study of longstanding mysteries

　　3. In people in their mid-70s, only 0. 45 percent of cardiomyocytes _ .

　　A. are still functional

　　B. are reduced each year

　　C. are replaced each year

　　D. are damaged each year
　4. Chronic heart failure is attributed to

　　A. the dying heart cells

　　B. the effect of pharmceutical

　　C. the weight of a patient

　　D. the life span of a person

　　5. It is not known yet if the rate of cell turnover in diseased hearts

　　A. is high enough to replace cells faster than they're dying off

　　B. is of any use to researchers

　　C. is the same as that in healthy hearts

　　D. changes over time

　　參考譯文及答案：

人類(lèi)心臟可以制造新的細(xì)胞

　　科學(xué)家發(fā)現(xiàn)在人的整個(gè)生命進(jìn)程中，心臟會(huì)持續(xù)產(chǎn)生新的心肌細(xì)胞，盡管新細(xì)胞產(chǎn)生的速度會(huì)隨著年齡的增長(zhǎng)而降低，這一發(fā)現(xiàn)解決了很長(zhǎng)時(shí)間以來(lái)的一個(gè)謎團(tuán)。

　　這一研究成果發(fā)表于《科學(xué)》雜志四月三號(hào)那一期，專(zhuān)家稱，這一研究成果將為心臟�。ɡ�如心臟衰竭和心臟病發(fā)作）的醫(yī)治開(kāi)拓新的途徑。

　　研究負(fù)責(zé)人Jonas Frisen博士是瑞典斯德哥爾摩卡羅琳斯卡研究院研究干細(xì)胞的教授。

　　他說(shuō)："我們發(fā)現(xiàn)心臟中的心肌細(xì)胞會(huì)被更替。在此之前我們不知道我們生來(lái)就擁有的心肌細(xì)胞是固定的還是可以更新。"

　　Frisen補(bǔ)充說(shuō)，這些細(xì)胞的更替過(guò)程會(huì)隨著時(shí)間而變化。一個(gè)人20歲時(shí)，其每年被更替的心肌細(xì)胞大約為1%，隨著年齡的增長(zhǎng)，該更替率不斷下降，等到75歲時(shí)，只有0. 45%。

　　Frisen說(shuō)："如果我們知道新的心肌細(xì)胞產(chǎn)生的規(guī)律，也許就有可能研發(fā)出在心臟病發(fā)后能促進(jìn)細(xì)胞生成的藥物。"

　　那將有助于受損心臟恢復(fù)。

　　該研究論文的合著者Ratan Bhardwaj博士說(shuō)："很多人都在忍受慢性心衰的折磨。"

　　Ratan Bhardwaj也是來(lái)自于卡羅琳斯卡研究院，他說(shuō)："慢性心衰是由心肌細(xì)胞死亡引發(fā)的。"

　　有了這一發(fā)現(xiàn)，"科學(xué)家即將開(kāi)啟一扇通往自愈潛在療法的大門(mén)"，Bhardwaj說(shuō)："也許我們可以設(shè)計(jì)出一種藥物制劑使心臟細(xì)胞生成出更多更新的細(xì)胞來(lái)克服它們面臨的問(wèn)題。"

　　不過(guò)障礙依然存在。根據(jù)Bhardwaj的觀點(diǎn)，科學(xué)家還不知道如何才能使心臟細(xì)胞產(chǎn)生的速度超過(guò)其死亡的速度，尤其是對(duì)于患有心臟病的老年人。此外，心臟產(chǎn)生的新細(xì)胞的數(shù)量是按照健康心臟計(jì)算的，而有心臟病的細(xì)胞更替率能否與健康心臟相同還不得而知。

　　1.D [解析]根據(jù)是第一段中：…the human heart continues to generate new cardiac cells throughout the life span。在人的整個(gè)生命進(jìn)程中，其心臟不時(shí)產(chǎn)生新的心肌細(xì)胞。言外之意，這個(gè)過(guò)程直到人死才會(huì)停止。

　　2.C [解析]根據(jù)是第二段中：The finding，…，could open a new path for the treatment of heart diseases 這一研究成果將為心臟病的醫(yī)治開(kāi)拓新的途徑。

　　3.C[解析]第四段說(shuō)，一個(gè)人20歲時(shí)，其每年被更替的心肌細(xì)胞為1%，隨著年齡的增長(zhǎng)，該更替率( turnover rate)不斷下降，等到75歲時(shí)，只有0.45%。

　　4.A [解析]倒數(shù)第三段說(shuō)：Chronic heart failure arises from heart cells dying。慢性心衰是由心肌細(xì)胞死亡導(dǎo)致的。

　　5.C[解析]最后一句說(shuō)：心臟產(chǎn)生的新細(xì)胞的數(shù)量是按照健康心臟計(jì)算的，而有心臟病的細(xì)胞更替率是否與健康心臟相同還不得而知。