"I was stunned," said Francis Collins, the director of the National Institutes of Health, which sets the rules for stemcell research funded by the federal government.

"This decision has the potential to do serious damage to one of the more promising areas of biomedical research and just at a time when we were gaining momentum," he told reporters in a conference call.

Calling the consequences of the ruling "dramatic and far reaching," Collin said 50 grant proposals that were awaiting peer review have been pulled, and as much as 74 million dollars in grant monies for other projects has been frozen.

"If this decision stands, very promising research on human diseases for which we need new insights and new options will not get done," he said.

"It's back to the future," said Kurt Civin, director of the University of Maryland's Center for Stem Cell Biology and Regenerative Medicine.

Civin said institutions around the country are now scrambling to understand the implications of the ruling and determine how their research projects might be affected.

"It seems that we will have to put a lot of research in the freezer right now," he told AFP.

William Caldwell, CEO of Advanced Cell Technology in Worcester, Massachusetts, said not all such research would stop because there were still state and private sources of funding.

"I do believe there is a strong, positive sentiment in Congress, actually on both the Republican and the Democratic side, to support embryonic stem cell development in this country," he said.

Researchers believe that stem cells, so-called because they are the foundation for all human cells, provide two promising avenues for scientists.

First, they can be used for research that cannot be performed inside the body. But scientists believe they can also coax the foundational cells into cardiac, pancreatic or brain cells to replace damaged or infected cells and allow tissue or organs to reconstitute themselves.

There are three types of stem cells currently being examined for their potential medical research value.

Embryonic stem cells, which are extracted from human embryos; adult stem cells, which are taken from the body or from elements discarded after birth, such the umbilical cord; and induced pluripotent stem cells -- adult stem cells that have been genetically modified to resemble embryonic stem cells.

Source-AFP