This is the VOA Special English Health Report, from http://voaspecialenglish.com | http://facebook.com/voalearningenglish
New
research could raise hope for women who are having trouble getting pregnant. For
years, the thinking has been that women are born with all the eggs their bodies
will ever produce. In fact, this has been the thinking not just about humans but
all mammals. Then, in two thousand four, a researcher at Massachusetts General
Hospital reported that adult female mice could produce new eggs. Now, Jonathan
Tilly has extended his work and reported another discovery -- this time about
human females. "We've isolated, essentially, the female equivalent of the stem
cells that we know exist in men that actively make new sperm." He says having
these cells now isolated opens up a lot of opportunities to consider. Stem cells
are special kinds of cells. Starting in embryos just a few days old, they
produce the many different cell types and tissues that form the body. In some
adult tissues, stem cells produce replacements for damaged or worn out cells. In
his new study, Jonathan Tilly and other researchers removed cells from ovaries.
Ovaries are the female reproductive organs that produce eggs. The scientists did
laboratory tests to make sure they had the right cells that they were looking
for. Then they used what are known as culturing methods to grow the cells so
they would divide and produce more cells. "And we could start with perhaps one
hundred cells, and over several months' time take those one hundred cells and
make hundreds of thousands of cells. And, interestingly, we noticed that these
cells would spontaneously generate immature eggs, all on their own, in these
cultures." The researchers then placed some of the cells into human ovary tissue
and implanted the tissue under the skin of mice. The studies found that these
human cells were -- in Jonathan Tilly's words -- "more than happy to create
brand-new human egg cells." He says growing eggs in the lab could improve the
chances for women who are having the process known as in vitro fertilization.
With IVF, an egg is fertilized with sperm in a laboratory, then placed in the
woman's uterus to develop. Jonathan Tilly says his work could also lead to
fertility treatments that might improve the chances for more traditional
fertilization methods. The journal Nature Medicine published the findings. Some
experts raised questions about his earlier work with mice. Some are not so sure
about this study either, until other researchers can reproduce the findings. For
VOA Special English, I'm Mario Ritter.
(Adapted from a radio program
broadcast 29Feb2012)
원문출처 : http://www.youtube.com/watch?v=5do1MBBCHPU&feature=youtube_gdata
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