- On a farm about six miles outside this gambling town,
Jason Chamberlain looks over a flock of about 50 smelly sheep, many of
them possessing partially human livers, hearts, brains and other
organs.
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- The University of Nevada-Reno researcher talks
matter-of-factly
about his plans to euthanize one of the pregnant sheep in a nearby lab.
He can't wait to examine the effects of the human cells he had injected
into the fetus' brain about two months ago.
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- "It's mice on a large scale," Chamberlain says
with a shrug.
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- As strange as his work may sound, it falls firmly within
the new ethics guidelines the influential National Academies issued this
past week for stem cell research.
-
- In fact, the Academies' report endorses research that
co-mingles human and animal tissue as vital to ensuring that experimental
drugs and new tissue replacement therapies are safe for people.
-
- Doctors have transplanted pig valves into human hearts
for years, and scientists have injected human cells into lab animals for
even longer.
-
- But the biological co-mingling of animal and human is
now evolving into even more exotic and unsettling mixes of species, evoking
the Greek myth of the monstrous chimera, which was part lion, part goat
and part serpent.
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- In the past two years, scientists have created pigs with
human blood, fused rabbit eggs with human DNA and injected human stem cells
to make paralyzed mice walk.
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- Particularly worrisome to some scientists are the
nightmare
scenarios that could arise from the mixing of brain cells: What if a human
mind somehow got trapped inside a sheep's head?
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- The "idea that human neuronal cells might
participate
in 'higher order' brain functions in a nonhuman animal, however unlikely
that may be, raises concerns that need to be considered," the
academies
report warned.
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- In January, an informal ethics committee at Stanford
University endorsed a proposal to create mice with brains nearly completely
made of human brain cells. Stem cell scientist Irving Weissman said his
experiment could provide unparalleled insight into how the human brain
develops and how degenerative brain diseases like Parkinson's
progress.
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- Stanford law professor Hank Greely, who chaired the
ethics
committee, said the board was satisfied that the size and shape of the
mouse brain would prevent the human cells from creating any traits of
humanity.
Just in case, Greely said, the committee recommended closely monitoring
the mice's behavior and immediately killing any that display human-like
behavior.
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- The Academies' report recommends that each institution
involved in stem cell research create a formal, standing committee to
specifically
oversee the work, including experiments that mix human and animal
cells.
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- Weissman, who has already created mice with 1 percent
human brain cells, said he has no immediate plans to make mostly human
mouse brains, but wanted to get ethical clearance in any case. A formal
Stanford committee that oversees research at the university would also
need to authorize the experiment.
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- Few human-animal hybrids are as advanced as the sheep
created by another stem cell scientist, Esmail Zanjani, and his team at
the University of Nevada-Reno. They want to one day turn sheep into living
factories for human organs and tissues and along the way create
cutting-edge
lab animals to more effectively test experimental drugs.
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- Zanjani is most optimistic about the sheep that grow
partially human livers after human stem cells are injected into them while
they are still in the womb. Most of the adult sheep in his experiment
contain
about 10 percent human liver cells, though a few have as much as 40
percent,
Zanjani said.
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- Because the human liver regenerates, the research raises
the possibility of transplanting partial organs into people whose livers
are failing.
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- Zanjani must first ensure no animal diseases would be
passed on to patients. He also must find an efficient way to completely
separate the human and sheep cells, a tough task because the human cells
aren't clumped together but are rather spread throughout the sheep's
liver.
-
- Zanjani and other stem cell scientists defend their
research
and insist they aren't creating monsters - or anything remotely
human.
-
- "We haven't seen them act as anything but
sheep,"
Zanjani said.
-
- Zanjani's goals are many years from being
realized.
-
- He's also had trouble raising funds, and the U.S.
Department
of Agriculture is investigating the university over allegations made by
another researcher that the school mishandled its research sheep. Zanjani
declined to comment on that matter, and university officials have stood
by their practices.
-
- Allegations about the proper treatment of lab animals
may take on strange new meanings as scientists work their way up the
evolutionary
chart. First, human stem cells were injected into bacteria, then mice and
now sheep. Such research blurs biological divisions between species that
couldn't until now be breached.
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- Drawing ethical boundaries that no research appears to
have crossed yet, the Academies recommend a prohibition on mixing human
stem cells with embryos from monkeys and other primates. But even that
policy recommendation isn't tough enough for some researchers.
-
- "The boundary is going to push further into larger
animals," New York Medical College professor Stuart Newman said.
"That's
just asking for trouble."
-
- Newman and anti-biotechnology activist Jeremy Rifkin
have been tracking this issue for the last decade and were behind a rather
creative assault on both interspecies mixing and the government's policy
of patenting individual human genes and other living matter.
-
- Years ago, the two applied for a patent for what they
called a "humanzee," a hypothetical - but very possible -
creation
that was half human and chimp.
-
- The U.S. Patent and Trademark Office finally denied their
application this year, ruling that the proposed invention was too human:
Constitutional prohibitions against slavery prevents the patenting of
people.
-
- Newman and Rifkin were delighted, since they never
intended
to create the creature and instead wanted to use their application to
protest
what they see as science and commerce turning people into
commodities.
-
- And that's a point, Newman warns, that stem scientists
are edging closer to every day: "Once you are on the slope, you tend
to move down it."
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- ___
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- On the Net:
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- NAS: http://www.nas.edu
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- Zanjani's Web site:
- http://www.unr.edu/cmbprog/ezanjani-new.htm
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- Copyright © 2005 The Associated Press. All rights
reserved.
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