In a rare appearance last month, former first lady Nancy Reagan spoke at an event to raise money for embryo stem cell research. She hoped, she said, that others would benefit from research on such diseases as Alzheimer's, which had afflicted her husband, Ronald.

"Ronnie's long journey has finally taken him to a distant place where I can no longer reach him," she said. "Because of this, I'm determined to do whatever I can to save other families from this pain."

Reagan, 82, who was married to the nation's 40th president for 52 years, had been by the ailing president's side, particularly as the family publicly acknowledged his bout with the disease 10 years ago. Reagan's recent public support of stem cell research, however, has put her at odds with other Republicans, including President George W. Bush, who opposes the research.

Still, Reagan, whose support carries much clout, is doing what she says she has to do. "I just don't see how we can turn our back on this," she said at the fund-raiser.

Although the first human embryonic stem cell line was created in the United States, the majority of new embryonic cell lines - colonies of potent cells with the ability to create any type of tissue in the human body - are now being created overseas, a concrete sign that American science is losing its pre-eminence in a key field of 21st-century research. Nearly three years ago, the Bush administration prohibited the use of federal funds to work with any embryonic cell lines created after Aug. 9, 2001, because of moral concerns over the destruction of human embryos. At the time, the president said there would be more than 60 lines of these cells available. But today there are only 19 usable lines created before that date, and that number is never likely to rise above 23, according to the National Institutes of Health.

However, the number of cell lines available to the world's researchers, but off-limits to U.S. government-funded researchers, is now much higher: at least 51. It could rise to more than 100 over the coming year. There are three new lines in Dvorak's lab, with four more in progress. And there are also new lines in Sweden, Israel, Finland, and South Korea. Last week, the world's first public bank of embryonic stem
cells opened in Britain, a country where there are at least five new lines and more on the way.

"Science is like a stream of water, because it finds its way," said Susan Fisher, a stem-cell researcher at the University of California at San Francisco. "And now it has found its way outside the United States."