Fifty-eight senators are asking President Bush (search) to relax federal restrictions on stem cell research, and several said Monday that the late President Reagan's (search) Alzheimer's disease underscored a need to expand the research using human embryos.

The senators' letter to Bush was sent Friday, before Reagan died after a long struggle with Alzheimer's (search).

But Sen. Dianne Feinstein, D-Calif., said: "This issue is especially poignant given President Reagan's passing. Embryonic stem cell research (search) might hold the key to a cure for Alzheimer's and other terrible diseases."

Last month, Nancy Reagan appeared at a fund-raising dinner in Los Angeles to promote stem cell research.

"We would very much like to work with you to modify the current embryonic stem cell policy so that it provides this area of research the greatest opportunity to lead to the treatments and cures for which we are all hoping," the senators wrote Bush.

The letter was signed by 43 Democrats, the Senate's one independent and 14 Republicans, among them conservatives who oppose abortion. In April, 206 House members sent a similar letter to Bush.

Stem cells typically are taken from days-old human embryos and then grown in a laboratory into lines or colonies. Because the embryos are destroyed when the cells are extracted, the process is opposed by some conservatives who link it to abortion.

Bush signed an executive order in August 2001 limiting federal research funding for stem cell research to 78 embryonic stem cell lines then in existence.

But the letter complains that only 19 of those lines are now available to researchers and those available are contaminated with mouse feeder cells which makes their use for humans uncertain.

Signers include Democratic Sens. John Kerry and Ted Kennedy of Massachusetts, Hillary Rodham Clinton of New York and Tom Harkin of Iowa, and Republicans Arlen Specter of Pennsylvania, Orrin Hatch of Utah and Lamar Alexander of Tennessee.

"Maybe one of the small blessings that will come from (Reagan's) passing will be a greater opportunity for Nancy to work on this issue, which of course means so much to her," Hatch said. "I believe that it's going to be pretty tough for anybody not to have empathy for her feelings on this issue."

White House spokesman Ken Lisaius said Bush stood by his stem cell policy.

"The president remains committed to exploring the promise of stem cell research but at the same time continues to believe strongly that we should not cross a fundamental moral line by funding or encouraging the destruction of human embryos," Lisaius said.

"The president does not believe that life should be created for the sole purpose of destroying it. He does believe we can explore the promise and potential of stem cell research using the existing lines of stem cells."

Because stem cells develop into the various types of cells that make up the human body, scientists believe they could be grown into replacement organs and tissues to treat a wide range of diseases, including Parkinson's, diabetes, cancer and Alzheimer's.