The first technique was described last month in the Journal of Clinical Investigation by two Columbia University researchers, Donald W. Landry and Howard A. Zucker, who spoke to the panel yesterday. They argued that a certain percentage of embryos created, frozen and later thawed for potential use in assisted-reproduction procedures are similar to brain-dead adults. The embryos no longer have the capacity for human life.
Cells have stopped dividing in those embryos, which in some cases account for about 60 percent of ones made in infertility treatments. Most such embryos die because of biological accidents that occur in the crucial first days after fertilization. The embryos cannot be put back on the path to normal development into a fetus and infant. They are, in Zucker and Landry's term, "organismically dead."
Young Chung, right, and researcher Joel Marh of Advanced Cell Technology in Worcester, Mass., examine mouse embryonic stem cells. The techniques described yesterday would require more refinement on animals before human cells could be used.
(Julia Malakie -- AP)
Studies have shown, however, that some of those "dead" embryos contain cells that are entirely normal and, if removed, capable of developing normally into stem cells. Removing them and using them, the scientists argued, would be like removing organs for transplantation from a brain-dead adult kept alive on a mechanical ventilator -- an act accepted by society.
"We would like to extend this idea to the developing human," Landry told the panel.
To do that, biologists would need to learn to identify with certainty which thawed embryos are "organismically dead." That will be done by observing many of them for days and determining whether there are biological "markers" -- something that can be tested for in a lab -- shared by all embryos that have stopped growing.
The second technique was described by William B. Hurlbut, a physician from Stanford University who is a member of the panel. Although he helped develop the concept, Hurlbut does not have the expertise to undertake the procedure himself or do research on it.
Hurlbut called his idea "altered nuclear transfer" -- a cloning procedure with one crucial alteration.
One or more genes essential for normal embryonic development would be temporarily canceled or inactivated at the start. The cluster of growing and dividing cells that would be produced would have no capacity ever to develop into a human fetus. Consequently, it would not have the status of a person by anyone's definition, he argued.
Agglomerations of cells such as this, known as teratomas, sometimes arise spontaneously as tumors from human egg or sperm cells. The teratomas contain partially or fully developed tissue, sometimes even teeth. But they are structurally disorganized and nonviable.
In Hurlbut's concept, the cells could be removed and then have their inactivated genes restored, making them functionally normal and presumably capable of developing into usable stem cells.
"If we could biologically mimic what goes on in teratomas, that would be what I'm after," he said.
Enthusiasm for the two ideas was not universal.
Paul R. McHugh, a psychiatrist from Johns Hopkins University, told Hurlbut: "What you propose, really, is to build a weird genetic hybrid. . . . Is that right?"
He added that he had not "finished my thoughts on this. But a few red flags come up."