http://www.msnbc.msn.com/id/18368186/site/newsweek?GT1=9951
part of the article
As recently as 1993, when Dr. Sherwin Nuland wrote the best seller
"How We Die," the conventional answer was that it was his cells
that had died. The patient couldn't be revived because the tissues
of his brain and heart had suffered irreversible damage from lack
of oxygen. This process was understood to begin after just four or
five minutes. If the patient doesn't receive cardiopulmonary
resuscitation within that time, and if his heart can't be restarted
soon thereafter, he is unlikely to recover. That dogma went
unquestioned until researchers actually looked at oxygen-starved
heart cells under a microscope. What they saw amazed them,
according to Dr. Lance Becker, an authority on emergency medicine
at the University of Pennsylvania. "After one hour," he says, "we
couldn't see evidence the cells had died. We thought we'd done
something wrong." In fact, cells cut off from their blood supply
died only hours later.
But if the cells are still alive, why can't doctors revive someone
who has been dead for an hour? Because once the cells have been
without oxygen for more than five minutes, they die when their
oxygen supply is resumed. It was that "astounding" discovery,
Becker says, that led him to his post as the director of Penn's
Center for Resuscitation Science, a newly created research
institute operating on one of medicine's newest frontiers: treating
the dead.
Biologists are still grappling with the implications of this new
view of cell death—not passive extinguishment, like a candle
flickering out when you cover it with a glass, but an active
biochemical event triggered by "reperfusion," the resumption of
oxygen supply. The research takes them deep into the machinery of
the cell, to the tiny membrane-enclosed structures known as
mitochondria where cellular fuel is oxidized to provide energy.
Mitochondria control the process known as apoptosis, the programmed
death of abnormal cells that is the body's primary defense against
cancer. "It looks to us," says Becker, "as if the cellular
surveillance mechanism cannot tell the difference between a cancer
cell and a cell being reperfused with oxygen. Something throws the
switch that makes the cell die."
