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控制生物钟延长生育期已不是梦想
http://www.100md.com 2001年7月26日 家庭医生医疗保健网
     妇女在做生育计划时都面对一个时间问题,因为妇女的一生中仅仅在某一个时期可以怀孕生孩子。近年革命性的不育治疗已经正在改变着人体生物钟。通过延长正常卵子的有效期,如冷冻年轻妇女的卵子,留待以后再解冻,可以让妇女在相当高龄的时候仍能顺利怀孕产子。

    理论上,妇女的绝经期也可以从50岁延长到60岁。目前,美国麻省总医院文森特生殖生物中心主任约翰·蒂里已经在老鼠身上停止了更年期。蒂里发现了引起卵巢成长、衰老和卵子死亡的一种基因。 被繁殖的不带这种基因的老鼠在生长到相当于妇女100岁的年龄时,卵巢仍能发挥正常功能。

    女性卵巢在出生时就已携带了所有卵子。到了青春期,95%的卵子已经衰亡;三、四十岁的时候卵子数迅速地减少。到了五十岁,实际上有活力的卵子已经基本上没有了。研究人员认为,如果能够把这个时间改变一下,比如说,用药物停止排卵,停药后又能恢复排卵,那么,我们下一代的女性就再也不会被高龄生育问题困扰了。

, 百拇医药     研究人员,认为卵子从卵巢上的逸出是推动更年期到来的机制。如果能搞清楚什么引起卵子逸出,什么引发卵子死亡,就有可能阻止它并延长卵巢发挥作用的时间。

    可以说,是患者的需要推动了技术进步,促使科学研究去探讨那些听起来不可想象的事情。但正是这种需要成为科研的动力:“当你怀抱婴儿的时候,就会觉得一切都是值得的。”

    Beating the Biological Clock with Research

    Revolutionary fertility treatments may allow women to give birth to healthy babies later and later in life by extending the shelf life of healthy eggs.

, 百拇医药     Millions of women plan their lives based on something of a deadline. And there‘s only a certain window of time when they can safely give birth. Allison Carlson wonders if she waited too long to have a baby. She started trying to get pregnant at 42.

    "We just hoped that everything would be fine and the statistics didn‘t apply to us," says Carlson.

    Carlson soon turned to in-vitro fertilization. She got pregnant but quickly miscarried, as almost half of women over 40 usually do.
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    "It rocks your world," says Carlson. And rocks the family budget: She has spent $60,000 on fertility treatments.

    "We‘d rather spend our money on a baby than cars and [an] apartment," she insists.

    Now at age 45, she‘s not giving up. "You want to feel you did everything that you could to have a reasonable chance to have a baby," she says.

    The next generation of women in their 40s may have a better chance. Researchers have succeeded in freezing the eggs of a younger woman and thawing them later. It is one promising area of research, while another is pushing back menopause.
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    Extending Shelf Life of Healthy Eggs

    Women are born with all the eggs they will ever have. By puberty, 95 percent of them are gone. The rest dwindle quickly through the 30s and 40s. By the age of 50, a woman‘s eggs are virtually gone.

    But what if the timing were altered? What if there was a pill to stop the release of a woman‘s eggs that would resume when she stopped taking the pill?

    That‘s exactly what Roger Gosden, the an infertility researcher at McGill University in Montreal is currently researching and finds "it might also delay menopause, instead of 50 then 60, that‘s the theory."
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    At Massachusetts General Hospital, John Tilly, the director of the Vincent Center for Reproductive Biology, has stopped menopause in mice. Tilly discovered a gene that causes ovaries to grow old and eggs to die.

    The idea was that egg loss from the ovaries is the mechanism that drives menopause. "And if we could understand what causes egg loss, what triggers the death of the eggs," he explains, "then we could maybe one day stop it from occurring and extend how long the ovaries are functioning."
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    When he bred mice without that gene, "we had mice that were roughly the equivalent of 100-year-old women. And their ovaries were still functioning normally."

    Research for women is years away, but revolutionary fertility treatments are already changing the biological clock.

    "It‘s the patients who drive the techniques," says Dr. Jamie Grifo of New York University. "And that‘s what makes us do what sound like crazy things, but it‘s really to help people have healthy babies."

    It‘s why Carlsen keeps trying: "It seems to be worth it when you have a baby in your arms.", 百拇医药