It's not quite the Fountain of Youth, but scientists have found a way to induce some of our cells to live forever.

The purpose isn't to make people immortal, but rather to create therapies that might one day treat or delay the onset of disease, such as progressive eye disease, gastrointestinal disorders and cancer.

The research is focused on so-called telomeres, small bits of DNA that serve as protective coverings at the end of our chromosomes. These caps keep our chromosomes from unraveling, much like the plastic tips at the ends of shoelaces. When our telomeres are healthy, our cells remain healthy. But each time the cells divide, telomeres get shorter. When they reach a critically short length, as they do with age or the onset of certain diseases, cells lose the ability to divide and eventually die.

Three Americans discovered telomeres and the enzyme that makes them, called telomerase, in the 1980s, work for which they recently won the Nobel Prize in medicine. Since then, a growing number of researchers have been seeking to understand how telomeres work.

One feat researchers have achieved in the lab is using telomerase to 'immortalize' human cells. Scientists from the University of Texas Southwestern Medical Center at Dallas and others have shown they can keep certain cells living forever, including those from the breast, skin, retina and, recently, the colon, by adding telomerase to keep telomeres intact or repair those that are too short. Researchers are studying how telomerase therapies could help repair damaged cells and play an major role in cancerresearch. 'What our goal should be isn't increasing life span, but healthy life span,' says Jerry Shay who, with his UT Southwestern colleague Woodring Wright, first figured out how to use telomerase to immortalize cells in the late 1990s. 'Is there some way we can intervene and slow down some of the problems?'

Telomeres aren't the only reason we age, likely accounting for 10% or less of the aging process, biologists say. But if cells can be kept healthier longer, diseases that might have caused serious illness at 65 years old could be delayed until, say, 75.

Compressing disease into a smaller window later in life could significantly improve individuals' quality of life, helping them live independently for longer, says Dr. Shay, professor of cell biology and associatedirector of the Simmons Cancer Center at UT Southwestern. 'Potentially we can keep you from getting too frail,' he says.

A limit to telomerase is that it benefits only cells that divide -- and most neurons, the dominant type of cell in the brain, don't divide. If scientists could figure out a way to get telomerase even to the small portion of brain cells that do divide, there could be some brain benefit, according to Dr. Shay.

A related concern is the possibility of inadvertently creating or accelerating cancer if telomerase were administered throughout the body, including to cancerous or pre-cancerous cells. Somehow, cancer cells have telomeres that are just the right length and don't shorten -- a perfection of the division process that allows cells to keep dividing, Dr. Shay says.

But if a telomerase-based therapy could be given to specific cells temporarily, say for a week or two, it could be a therapeutic 'home run,' repairing telomeres and allowing cells to keep dividing, Dr. Shay says. Such a therapy -- which would occur on a patients' own cells grown in a lab dish -- could help people with conditions where cells have been injured and have used up their allotment of telomeres, such as anemia or skin sores or conditions involving inflammation. Many cancerresearchers are trying to figure out how to turn off telomerase and potentially treat cancer.

Shirley S. Wang

• fountain [´fauntin] n.泉水；源泉；根源 (初中英语单词)
• immortal [i´mɔ:təl] a.不死的n.不朽的人物 (初中英语单词)
• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• healthy [´helθi] a.健康的 (初中英语单词)
• ability [ə´biliti] n.(办事)能力；才干 (初中英语单词)
• medical [´medikəl] a.医学的；医疗的 (初中英语单词)
• repair [ri´peə] v.&n.修理，修补 (初中英语单词)
• cancer [´kænsə] n.癌；毒瘤 (初中英语单词)
• illness [´ilnis] n.生病，不健康，疾病 (初中英语单词)
• associate [ə´səuʃieit] v.联合a.同伴的n.伙伴 (初中英语单词)
• director [di´rektə] n.指导者；....长；导演 (初中英语单词)
• portion [´pɔ:ʃən] n.嫁妆；命运 vt.分配 (初中英语单词)
• possibility [,pɔsə´biliti] n.可能(性)；希望；前途 (初中英语单词)
• progressive [prə´gresiv] a.进步的；前进的 (高中英语单词)
• so-called [´sou ´kɔ:ld] a.所谓的，号称的 (高中英语单词)
• intervene [,intə´vi:n] vi.干涉；插进 (高中英语单词)
• related [ri´leitid] a.叙述的；有联系的 (高中英语单词)
• perfection [pə´fekʃən] n.完美；极致；熟练 (高中英语单词)
• specific [spi´sifik] a.具体的；特有的 (高中英语单词)
• protective [prə´tektiv] a.防护的；保护贸易的 (英语四级单词)
• eventually [i´ventʃuəli] ad.最后，终于 (英语四级单词)
• dallas [´dæləs] n.达拉斯 (英语四级单词)
• colleague [´kɔli:g] n.同事，同僚 (英语四级单词)
• biology [bai´ɔlədʒi] n.生物学，生态学 (英语四级单词)
• dominant [´dɔminənt] a.统治的；占优势的 (英语四级单词)
• shorten [´ʃɔ:tn] v.缩短，变短 (英语四级单词)
• temporarily [´tempərərili] ad.暂时地 (英语四级单词)
• trying [´traiiŋ] a.难堪的；费劲的 (英语四级单词)
• southwestern [,sauθ´westən] a.西南的 (英语六级单词)
• intact [in´tækt] a.未动过的，完整的 (英语六级单词)
• independently [,indi´pendəntli] ad.独立地；自由地 (英语六级单词)