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To: PROLIFE who wrote (397563)	4/23/2003 4:51:11 PM
From: DuckTapeSunroof	Read Replies (2) \| Respond to of 769670

"Virgin Births" look like a promising source of embryonic stem cells: 'Virgin birth' method promises ethical stem cells newscientist.com 19:00 23 April 03 Sylvia Pagán Westphal, Boston The phenomenon that leads to "virgin births" in some species looks like a promising source of embryonic stem cells. Researchers are on the brink of obtaining human stem cells this way for the first time, and animal experiments suggest such cells are indistinguishable from normal stem cells. In parthenogenesis, an unfertilised egg keeps two sets of chromosomes and begins developing as if it had been fertilised. Some insects and reptiles can reproduce this way but even though an electric or chemical stimulus can induce parthenogenesis in mammals, the resulting embryos die after a few days. And that, according to its proponents, is the beauty of the technique as far as stem cells are concerned: it produces embryos that could never become human beings. So destroying these embryos to obtain stem cells would avoid the ethical concerns that have led to restrictions or bans on embryonic stem cell research in many countries. However, while the technique works in mice and monkeys (New Scientist print edition, 26 October 2001), attempts with human eggs have not got far. Until now, that is. A team led by fertility specialist David Wininger at biotech firm Stemron of Maryland has grown parthenogenetic human embryos to the blastocyst stage, at which stem cells can be obtained. Cells taken from one of the embryos survived for a few days (Stem Cells, vol 21, p 152). "It's the first time I know of parthenogenetic cells in humans," says Kent Vrana of Wake Forest University School of Medicine in North Carolina, whose team pioneered the work in monkeys. Indefinite growth The next step is to get the cells to grow in culture indefinitely: that is, to obtain a stem cell line. In monkeys, such a cell line has been growing for over two years, and it makes the human experiments all the more relevant. According to Vrana, extensive analysis of the monkey cells suggests that they are indistinguishable from normal embryonic stem cells. "They are identical to ESCs by every known criterion we have tested," he says, adding that details will soon be published in a peer-reviewed journal. A lot of work still has to be done to ensure any tissues made from parthenogenetic stem cells are absolutely normal, says Jerry Hall of the Institute for Reproductive Medicine and Genetics in Los Angeles. But he is optimistic. "Patients are so interested in this procedure, and we are confident enough in its feasibility, that we have been willing to store eggs for use as soon as safety and effectiveness is shown," he says. Since eggs are needed to make parthenogenetic stem cells, one potential problem is that the technique could not be used to make matching stem cells for men or for women after menopause. Therapeutic cloning, by contrast, could provide matching stem cells for any individual. However, because cells made by parthenogenesis have two identical sets of chromosomes, rather than one set each from the father and the mother, they have less variation in the surface proteins on cells that can trigger immune reactions. Wininger thinks it will possible to establish a bank of parthenogenetic stem cells that could provide cells to suit most individuals. And such banks would be much cheaper than creating stem cells from scratch for each individual. 19:00 23 April 03 © Copyright Reed Business Information Ltd.

To: PROLIFE who wrote (397563)	4/23/2003 4:55:23 PM
From: DuckTapeSunroof	Read Replies (1) \| Respond to of 769670

Baby teeth revealed as source of stem cells --------------------------------- Produce stem cells intermediate in usefulness between fetal stem cells and adult stem cells. --------------------------------- 22:00 21 April 03 Catherine Zandonella newscientist.com The tooth fairy could soon face competition for baby teeth from scientists who have discovered the teeth are a source of stem cells. The cells could help repair damaged teeth and perhaps even treat neural injuries or degenerative diseases. Currently, researchers can isolate two types of stem cells. Embryonic stem cells can develop into any cell in the body, but their harvesting requires the destruction of embryos, which pro-life groups oppose. Adult stem cells avoid this problem, but have more limited abilities. Now it appears that the stem cells from children's lost teeth could provide an intermediate and easily accessible source. "These stem cells seem to grow faster and have more potential to differentiate into other cell types than adult stem cells," says Songtao Shi, a pediatric dentist at the US National Institutes of Health in Bethesda, Maryland. Shi and his colleagues found the baby teeth cells can differentiate into tooth-forming cells called ondontoblasts, and also neural cells and fat cells. Baby teeth, also called milk teeth or deciduous teeth, appear from the age of about six months and then fall out when children are between six and 13 years old. Daughter cells Previous work by Shi in 2000 had already shown that extracted adult wisdom teeth contain stem cells in the pulp at the centre of the tooth (PNAS, vol 97, p 13625). So when his six-year old daughter and her friends started losing their baby teeth, he decided to see if they also contained stem cells. Whenever a tooth fell out, instead of putting it under the pillow, the parents stored the tooth in a glass of milk in the refrigerator overnight. To isolate the stem cells, Shi extracted the pulp and cultured the cells for several days, then tested the survivors for markers of stem cell activity. About 12 to 20 cells from a typical incisor tooth turn out to be stem cells. By culturing the cells in various growth factors, Shi could differentiate the cells into tooth-forming cells, fat cells or neural cells. The differentiated cells survived when implanted under the skin and in the brain of immunocompromised mice. Shi also found that the cells promote the growth of bone. He suspects the stem cells may play a role in preparing the way for adult teeth. "We don't have evidence at the moment, but we think these stem cells do have a reason to be there." The discovery of stem cells in baby teeth could give a big boost to oral surgery, says oral biologist Bjorn Reino Olsen, at Harvard Medical School. The cells, once differentiated into odontoblasts, could secrete dentine. This bone-like material could then replace the less biocompatible metal posts that are currently used to anchor implants to the jaw. Journal reference:Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0937635100) 22:00 21 April 03 © Copyright Reed Business Information Ltd.