- BOSTON - No one can live
forever. Or can they?
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- Scientists have found a way to create human embyonic
stem cells in a lab. The stem cells, which can form every kind of human
tissue, normally exist only for a few days at the beginning of life. "As
a human race," says scientist Michael West, "we may see our final
frontier as conquering death itself."
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- West's company, Advanced Cell Technology, is dedicated
to the astonishing possibility. West himself, an anti-aging specialist
and biotech entrepreneur, is quite confident that science has the potential
to make humans immortal.
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- "I would not underestimate the power of science
and medicine," says West, "to unlock the mechanisms of aging
and give human beings the choice of whether they want to have a life span
of 100 years, a life span of 500 years, or an indefinite life span."
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- Creating Human Embryonic Cells
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- One possible way to get there is with human embryonic
stem cells -- cells that can form every kind of human tissue.
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- Normally, these cells only exist for a few days at the
very beginning of life. Now, human embryonic stem cells can be created
in the lab.
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- "The concept here is to take a cell from your body,"
explains West, "and put it back into an egg cell, [as] sort of a time
machine, taking it back in time to the beginning of life, where we can
make all these powerful cells that can become any cell or tissue type for
you."
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- Finding the way to turn those embryonic stem cells into
human organs -- in particular, the parts that break down with age, such
as a heart or a liver -- is the next big step.
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- There are already promising results in animals.
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- Making Nerve Cells in Mice
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- At Washington University School of Medicine in St. Louis,
neurobiologist David Gottlieb has learned how to stimulate the embryonic
stem cells of a mouse to make nerve cells.
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- "I predict," says Gottlieb, "the ability
to direct human embryonic stem cells along different path ways will come
and match what we can now do in the mouse."
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- "I think the exciting point of where we're at today
is the hardest step of all: making the clock run in reverse; taking an
old cell, making it young again," says West. "I think that's
the most difficult step, and that step we've accomplished."
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- A step into a remarkable new technology that may alter
the end of life by using cells from our very beginning.
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- An Enzyme, Telomerase, Can Make Cells Grow Again
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- Recent discoveries make it more likely that future generations
can have greater control over the aging process.
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- From the day we are born we start to age. But scientists
are making discoveries that have some hoping that soon we will be able
to slow down the aging process. Is immortality attainable?
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- "Could we live to be 200? I don't see why not,"
says biologist Cynthia Kenyon. "And could we not just live to be 200
but could we stay young? Could a 100-year-old person look like a 50 year-old?"
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- Kenyon is unlocking the secrets of aging with her research
on microscopic worms at the University of California.
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- Normally these worms live for 14 days. By day three,
the worm slows down. It is already old. But when just one gene is altered,
the worms live twice as long and remain lively for most of their lives.
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- "I think that the worm has given us a very powerful
new concept, which is that aging does not have to be fixed in stone,"
says Kenyon. "It doesn't have to be going at the rate it is. So we're
animals, you know, why not us too?"
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- An Immortality Switch
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- At the biotech company Geron, chief scientist Calvin
Harley has made a stunning discovery about human aging. He located a gene
that contains an immortality switch.
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- The switch is an enzyme called telomerase. Normally,
telomerase switches off in most human cells as we age. And when the cells
stop dividing and break down, humans become prone to immune disorders,
heart disease, arthritis - the ills of old age.
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- Harley's research shows how old cells can be treated
in the lab with telomorase to get them growing again, to becoming young
again.
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- It is the first sold proof that telomerase plays some
role in human aging. Of course, no one knows yet how this experiment in
a lab dish will play out in a complex human body.
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- But for the next generation, the fountain of youth is
all the more imaginable.
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- New Brain Cells Grown From Stem Cells
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- 2-25-00
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- "They said that by destroying certain brain cells
in zebra finches, they prompted the generation of new cells. Writing in
the journal Neuron, they said they believed that neural stem cells must
have been the source of the new neurons. This is, we believe, the first
example where it has been demonstrated that one can induce the birth of
new neurons and that they actually contribute to a complex behavior,"
Jeffrey Macklis, a neuroscientist at Bostons Childrens Hospital, said
in a statement. It is a step toward attempting the same in mammals.
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- Adult stem cells are a kind of nursery or progenitor
cell that exist throughout the body. They include cells that are used to
regenerate bone marrow after cancer chemotherapy, and are different from
the embryonic stem cells that scientists want to use for tissue transplants,
to grow new organs, and for other research.
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- Scientists are trying to find ways to use either adult
or embryonic stem cells, or both, to regenerate various forms of tissue,
including brain cells of patients with disease such as Alzheimers or Parkinsons.
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- The cells are hard to isolate and grow. They can be taken
from aborted fetuses or from embryos left over from IVF (test-tube) fertilization
efforts, but these sources can be controversial.
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- Working with colleagues at New Yorks Rockefeller University,
Macklis decided to see if they could be prompted into growing in place,
in the body.
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- They chose zebra finches because of an interesting variation
in bird biology. Canaries stop singing every autumn when a population of
song-generating neurons in a part of their brains called the high vocal
center dies off.
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- Over the winter, a whole new population of neurons grows
back and in the spring the canaries learn their songs all over again.
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- But zebra finches small birds favored by bird-fanciers
lack this seasonal cycle. Instead, their brains generate a constant, tiny
trickle of new neurons.
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- Songbirds devote a great deal of brain space to singing,
but the way the zebra finchs brain works more resembles the way the brains
of mammals, including humans, operate.
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- Until recently scientists believed brain cells did not
regenerate at all, but they now know new cells grow to a limited degree,
especially in the olfactory bulb and the hippocampus.
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- One theory holds that when certain neurons die, they
somehow signal stem cells and prompt the production of replacements.
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- Mackliss team selectively killed one kind of song-related
neuron in their zebra finches. The birds, as predicted, partly lost their
songs. But three months later they were singing as normal.
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- When the researchers looked at their brains, they saw
that the neurons had grown back, in much the same way that canary neurons
come back.
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- They said they were doing more experiments to see just
where the new cells came from.
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