A Stem Cell Glossary click here

Few would have predicted a year ago that the most trying decision of the opening months of the new presidency would involve stem-cell research.

But for President Bush, that has been precisely the case. Last night, after intense lobbying from both proponents and foes, Mr. Bush finally explained his decision: to allow limited federal government funding for embryonic stem-cell research, restricting it to work that already is underway using cells previously extracted from embryos.

By then, though, the subject had gone from a footnote in the 2000 presidential campaign debate to an emotional subject that split members of Mr. Bush's own party -even his own administration- and brought intense pressure on the White House from the Catholic Church, abortion foes, research scientists and the medical industry.

The issue has mushroomed quickly, for it was only in 1998 that scientists at the University of Wisconsin successfully isolated stem cells from embryos. The cells' potentially spectacular properties have been widely reported. The question facing Mr. Bush was whether to lend the work vital help in the form of government funding; privately funded research is unfettered.

The debate has grown so heated, so fast that some details of the issue remain elusive for many Americans not directly involved in the political give and take. So here are some questions and answers about the science and the policy at stake in the decision.

What are embryonic-stem cells good for?
They can transform themselves into any type of human tissue, and they can keep dividing and multiplying indefinitely in the laboratory. Therefore, they could revolutionize transplant medicine by providing unlimited supplies of replacement tissue, such as insulin-making pancreas cells to help diabetics, cancer, heart failure, Lou Gehrig's disease, Parkinson's disease and spinal-cord injuries are among the other conditions that could benefit from such a supply of new tissue. The cells also are a boon to scientists interested in studying human development.

Where do the cells come from?
They have been extracted from human embryos that are created and grown in the laboratory until they are about five days old. At this stage, an embryo is called a blastocyst and consists of a hollow ball of about 100 cells. These embryos generally are left from in vitro fertility treatments, in which many extra embryos are created.

Why are the embryonic cells so controversial?
Many are concerned that funding re- search would condone the destruction of the human embryos from which the cells are de- rived. Antiabortion groups believe destroying embryos is tantamount to killing the youngest and most vulnerable members of the human race.

Do all those opposed to abortion oppose stem-cell research, and vice versa?
No. Utah Sen. Orrin Hatch and Tennessee Sen. Bill Frist oppose abortion, but in a huge blow to research opponents they announced their support for government funding of embryonic stem-cell research this summer. The senators argued that a true "pro life" position allows medical research to go forward to help people afflicted with devastating diseases. Conversely, at least one group that supports abortion rights, the United Methodist Church, opposes embryonic cell research as unethical.

What are the effects of limiting government funding for this work in the U.S.?
Most biomedical research in universities in the U.S. is paid for by the National Institutes of Health in Bethesda, Md. The president decided to limit the federally funded research to about 60 "lines" of stem cells that already have been established and can be re- produced, which is more than some thought existed but fewer than many scientists would like to have available. Privately funded efforts at a limited number of universities and companies could move ahead without restrictions-but also without the involvement of many top scientists and outside normal peer review that comes with government oversight.

Which researchers and companies are likely to feel the most impact from the Bush decision?
Government-funded scientists and the biotechnology industry both are heavily affected. Probably no company stands to gain so much from federal support for stem-cell research as Geron Corp., of Menlo Park, Calif., which has funded much of the early work in the field and has patents and licenses effectively giving it exclusive rights to most products that could be developed from stem cells.

Other companies working with embryonic stem-cell technology also could benefit from an increased research effort, including closely held Advanced Cell Technology in Worcester, Mass., and Infigen Inc. of Madison, Wis. Companies seeking to develop treatments from adult stem cells Include StemCells Inc. of Palo Alto, Calif., and Aastroll Biosciences Inc. of Ann Arbor, Mich.
Such companies' stocks soared on expectations of some kind of compromise decision. At 4 p.m. in NASDAQ Stock Market trading, shares of Geron were up $2.04, or 16%, to $14.94; StemCells shares were up $1.72, or 36%, to $6.45; Aastrom Biosciences shares were up 46 cents, or 26%, to $2.25.

What did Mr. Bush say about the issue during the campaign?
Last Aug. 23, when the National Institutes of Health issued guidelines for funding the research, Mr. Bush said through a spokesman that he opposed using government funds for the work. He has repeated the view since then. Recently, the American Life League ran newspaper ads highlighting his campaign promise, and warned that if Mr. Bush doesn't stick to it, his political base will abandon him in the next election. They likened it to the decision by the first President Bush to break his no-new-taxes pledge. Mr. Bush's compromise won't entirely please his most-conservative supporters, though last night they mostly ex- pressed gratitude he hadn't approved the much broader funding approach some had advocated.

What happens now that President Bush has made his decision?
The decision sets the administration's policy on federal funding. But Congress has the ultimate power to appropriate money for any government program, and it could choose to accept, reject or modify the Bush plan. If Congress chooses a different course, the president can veto the legislation to try to enforce his vision. Meanwhile, both opponents and proponents of federal funding have filed lawsuits to try to get the government to do what they want, so the courts could playa role as well.

How does using stem cells relate to cloning?
This is a confusing issue, especially for legislators. Last week, the House of Representatives voted to ban all forms of human cloning. But some scientists say cloning technology can create customized stem cells. In a controversial procedure called "therapeutic cloning," scientists hope to create an embryo-stage clone of a living patient, harvest its stem cells and transplant them back into the patient. Since both patient and embryo share the same DNA, there is no rejection problem. The embryo is destroyed in the process.

Can adult stem cells work in place of embryonic stem cells?
Adult stem cells are found in mature tissue-such as bone or brain-and serve naturally as "spare parts" to replace worn-out cells. But because adult stem cells are more specialized than embryo cells, they are harder to manipulate in a lab. Groups opposed to embryo research argue that adult stem cells are a viable alternative, but many scientists disagree.

What laws govern embryonic stem-cell research elsewhere?
Rules vary widely overseas, where countries face two issues. First, is it legal to extract stem cells from embryos? And, is it permissible to study embryonic stem cells created in this way and imported from abroad?

Most European countries are struggling with these questions and will closely study the Bush administration's decision. Britain, however, passed a law in January permitting stem-cell research on human embryos, including embryos created in a lab though cloning. Germany, haunted by its history of Nazi medical experiments, has the toughest rules and bars virtually all embryo research.