From: Alejandro Dubrovsky (email@example.com)
Date: Fri Jan 18 2002 - 00:06:14 MST
how does this make sense?
By Merritt McKinney
NEW YORK (Reuters Health) - Stem cells, the immature cells that can give
rise to a variety of specialized cells, are essential in early
development, but new research suggests that, in worms at least, one type
of stem cell may play a role later in life as well.
Germ-line stem cells, which differentiate to form cells of the
reproductive system, seem to be involved in regulating life span in
nematode worms, according to a team led by Dr. Cynthia Kenyon at the
University of California, San Francisco.
``We knew already that the germ line of these animals had an impact on
life span,'' Dr. Nuno Arantes-Oliveira, the study's first author, told
Reuters Health in an interview.
``We've defined which cells produce that effect and when they act,'' he
The stem cells kick off the development of the reproductive system, but
they also seem to regulate the system that speeds aging, the researchers
report in the January 18th issue of the journal Science.
``We found that the effect is still present in the adult animal,''
The investigators previously found that killing certain germ-line
precursor cells that form from stem cells extends the life span of
Although earlier research has shown that reproduction can reduce life
span, this did not seem to explain the life-extending effects of killing
germ-line precursor cells. The researchers found that removing the
entire reproductive system from the worms did not have any effect on how
long they lived.
In a series of experiments, the researchers tried to find out which
parts of the reproductive system were involved in regulating life span.
They were able to rule out several types of cells, including sperm and
eggs, since removing them did not make worms live longer.
But killing germ-line stem cells did extend the worms' lives.
The next step, according to Arantes-Oliveira, will be to learn how these
stem cells influence longevity.
``The big thing will be to find out what signals these tissues are
producing,'' he said. One possibility, according to the California
researcher, is that some kind of hormone is producing the effect. Once
the mechanism is revealed, it may be possible to see whether it is
present in other species, such as humans, he said.
The researchers point out in the report that fruit flies live longer
when their precursor germ-line cells are killed, suggesting that the
role of early germ-line cells in aging may be conserved in several
In the interview, Arantes-Oliveira said that the evidence that a similar
process occurs in fruit flies is ``very suggestive.'' But, he cautioned,
``We don't know whether the effect is the same or not.''
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