WASHINGTON -- The therapeutic applications of adult stem cells from bone marrow, once promoted as potentially limitless, are not as affective as scientists once believed, according to a U.S. study published Thursday.

Hematopoietic stem cells in bone marrow produce many kinds of blood cells. To determine if the multi-talented cells could perform in a foreign environment, researchers grafted some of these cells from healthy mice onto mice whose bone marrow had been destroyed by radiation.

The transplanted cells, outlined with a fluorescent markers so that scientists could follow them, produced blood cells but failed to help tissue cell formation such as brain, kidney, intestines, liver or muscle cells, according to study-head Amy Wagers, a professor at the University of Stanford Medical School.

Although almost all of the transplanted cells did little else than produce blood cells, the researchers noted that a small portion-- one out of every 70,000-- did succeed in producing liver cells.

But this was not a high enough rate to be an effective therapy, according to the study posted on Scienexpress, the Internet site of **** Science **** magazine.

"It's not to say that nobody should think about adult stem cell plasticity-- of course people should look into it-- but it's not as robust as it is claimed to be," AFP quoted Wagers as saying.

"I hope it tempers the enthusiasm for adult stem cell plasticity. Maybe it's not the answer that it appeared to be," she said.

This study may aid those in favor of embryonic stem cell research, which is controversial but proven to have therapeutic value.

One of the principal arguments against extracting stem cells from human embryos was that adult stem cells could produce the same therapeutic results.