From: Howard Rothenburg (hrothenb@mail.bcpl.lib.md.us)
Date: Mon Jan 19 1998 - 22:29:42 MST
Several people have posted questions about the recent cow cloning
experiments. I think this is one of the original articles:
___________
Human cloning could now develop faster
By Linda Carroll
MSNBC
Using egg “shells” from cows, scientists have created embryos from DNA
gathered from a variety of other animals, including primates. The new
research may allow human cloning to develop at a much faster rate,
experts say.
NBC's Robert Hager reports Monday on recent breakthroughs in cloning
procedures.
THE NEW RESEARCH takes the cloning experiment that produced Dolly the
sheep in a new direction. Now scientists are learning that it may not
matter where the egg “shell” used to produce a cloned animal comes from.
Rather, they suggest that a mammal egg “shell” contains only the
machinery needed to spark life, not the information that determines what
species will develop. If the work pans out, it may allow scientists to
use eggs of one species as a “universal recipient” for the genes from
another species — including humans, researchers from the University of
Wisconsin said. The new research has medical ethicists worried. “Cloning
experts have been saying we had some lead time before we had to worry
about cloning human beings,” said David Magnus, an ethicist and
researcher at the Center for Bioethics at the University of Pennsylvania
in Philadelphia. One of the major factors limiting the development of
cloning was the inefficiency of the process, Magnus said. It took more
than 270 tries before Dolly’s makers were able to create an embryo that
matured into a sheep. Since it would be very difficult and extremely
expensive to gather up that many human eggs, experts have predicted that
cloning of a human being would be far in the future, Magnus said. But
because cow eggs can be harvested cheaply and easily, one crucial
barrier to human cloning may have fallen, the Philadelphia ethicist
said.
CREATING THE EMBRYOS The studies, which were described Monday at a
meeting in Boston, come several days after Chicago physicist Richard
Seed announced to the world his plans to clone humans. Maverick cattle
cloner Neal L. First of the University of Wisconsin in Madison. While no
successful pregnancies have been achieved using the technique developed
in the laboratory of cloning pioneer Neal L. First, the eggs with the
foreign genes did develop into viable preimplantation-stage embryos. To
develop their experimental embryos, the Wisconsin researchers collected
unfertilized eggs from cows. Under a microscope, the researchers
inserted a fine glass needle into each cow egg and sucked out its
nucleus, explained Tanja Dominko, now a staff scientist at the Oregon
Regional Primate Research Center in Beaverton, Ore. After performing a
similar procedure on cells from the ears of mature sheep, monkeys and
pigs, Dominko and her colleagues replaced each cow egg nucleus with DNA
from another species. Then, the researchers zapped the cow eggs with a
small electric current.
The electricity serves two purposes, Dominko explained. It fuses the two
separate units — the DNA and the shell — into one egg. And sometimes,
the electric shock is enough to jump start the development of the egg
with its new nucleus into an embryo. Dominko and her colleagues have
watched their cow-egg embryos growing in the test tube. When the embryos
were seven to nine days old and about 100 cells large, the researchers
transferred them to the uteruses of potential surrogate animal mothers.
So far, none of the embryos appears to have implanted, Dominko admits.
“We really don’t know why,” she said. “We have to go back and check the
embryos to see if they have the right number of chromosomes, to see if
they have any chromosomal abnormalities.” At this stage, “this is really
just dreaming,” Dominko said. “I don’t know if it will ever go any
further.” If the research does progress, it might provide a way to
protect endangered species, Dominko said. The new research suggests that
the molecular machinery responsible for programming genes within the
egg’s “shell” may be similar or identical in all mammals. Not everyone
thinks that the new research will lead to human cloning. The Wisconsin
group still hasn’t produced a live animal with its technique, said Dr.
Jamie Griffo, director of the division of reproductive endocrinology at
the New York University Medical Center. “We have tons of good looking
embryos in our in vitro fertilization lab and very few of them make
babies,” Griffo said. “ I don’t think this is the next big breakthrough
that will allow us to clone human beings.” Griffo himself is trying to
find a way to use the egg “shells” from younger women to house the DNA
of older women who have no viable eggs left. The New York Fertility
expert worries that a media furor over the Wisconsin research will
result in laws that limit experimentation with eggs and embryos. “The
big losers in this could be infertility patients who want to be genetic
parents,” he said.
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