Posted on 03/10/2004 2:09:41 PM PST by neverdem
Challenging the bedrock verity of mammalian biology that a female's eggs, like private reserve wines, are made one time only, in limited numbers, and are apt to turn to vinegar if left on the shelf too long, researchers have found startling evidence that the ovaries may instead be replenished with new eggs throughout a female's reproductive career.
Dr. Jonathan Tilly and his colleagues at Harvard Medical School and the Massachusetts General Hospital report in today's issue of the journal Nature that they have discovered multiple signposts of germ-line stem cells in the ovaries of young and adult female mice: powerful and many-talented cells capable of generating a fresh batch of immature egg "seeds," as well as the nourishing ovarian infrastructure needed to bring these oocytes to fruition.
Moreover, the stem cells appear to be quite active, indicating that they are not a pool of insignificant holdovers from fetal development, but rather are busy creating new little egglets and their follicle housing on the surface of the adult ovary. Follicles are fluid-filled capsules in which oocytes (pronounced OH-oh-sites) ripen into fully formed eggs, capable of being fertilized.
If confirmed by other researchers, the results would upend a doctrine adhered to by reproductive biologists for the last 80 years: that a female mammal is born with all the oocytes and follicles she will ever have, and that her stock of eggs is steadily depleted until the procreation pantry is bare.
Males, by contrast, have long been known to possess germ-line stem cells in their testes that manufacture large batches of new sperm throughout adulthood.
And should the process of egg renewal prove to be at work in humans, the ramifications, reproductive biologists agree, are profound. "The mind boggles at the implications," said Dr. Roger G. Gosden, scientific director of the Jones Institute for Reproductive Medicine at Eastern Virginia Medical School in Norfolk. "The ability to make more eggs would be a revolution in women's health. In theory, it would allow you to have better control over the timing of menopause, to grow more eggs for one's own fertility treatment, to prevent premature menopause, to recover fertility after chemotherapy, and on and on."
Some results from the new study hint at the existence of egg stem cells in adult women, yet Dr. Gosden and others also caution that it is far too early to retire the familiar "no new eggs" doctrine.
"There is still a long march to go, and much strong evidence needs to be provided," said Dr. Ri-Cheng Chian, an expert in egg biology in the department of obstetrics and gynecology at McGill University in Montreal.
In fact, the new results are so dramatic that Dr. Tilly admits that at first he doubted them himself. "We had a six-month period of disbelief and trouble digesting the whole thing," he said. "The shock people may feel on seeing this paper, trust me, we went through it as well."
;-)
you bet it does, bub. I've put my time in and when these kids are grown that is IT. I'm gonna sit back and wait to spoil some grandchildren.
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