The
trabecular bone-low-density bone is latticelike material
in these photomicrographs that is especially vulnerable
to osteoporosis.Here the images is, the femur of a sheep
treated 20 mins a day for a year (A) shows a 3rd more
bone growth than an untreated sheeps (B).
Weightlessness sure looks like a lot of fun, but prolonged
exposure to zero-G in space can have some negative side
effects -- like the weakening of human bones.
Everybody knows space is dangerous. Some of the perils
are obvious: hard vacuum, extreme cold, and unpredictable
blasts of radiation from the Sun. Other perils are less
conspicuous. The effects of prolonged weightlessness
on the human body, for example, can be slow and subtle
-- yet no less dangerous if astronauts fail to take
proper precautions. Weakening of the bones due to the
progressive loss of bone mass is a particularly serious
effect of extended spaceflight.Studies
of cosmonauts and astronauts who spent many months on
space station Mir revealed that space travelers can
lose 1 to 2 percent of bone mass each month -- a loss
doctors don't yet know how to prevent. "The magnitude
of this [effect] has led NASA to consider bone loss
an inherent risk of extended space flights," says Dr.
Jay Shapiro, team leader for bone studies at the National
Space Biomedical Research Institute.
Space travelers aren't the only ones who worry about
bone loss. At least 10 million people suffer from bone
loss in the U.S. and untold numbers worldwide -- it's
called osteoporosis. Postmenopausal women are especially
prone to osteoporosis, but most of us contract the disease
as we age, including men. Researchers hope that solving
the riddle of bone loss in space will reveal important
clues about what causes osteoporosis right here on Earth.
Spacefarers typically experience bone loss in the lower
halves of their bodies, particularly in the lumbar vertebrae
and the leg bones. Diminishing bone mass also triggers
a rise in calcium levels in the blood, which increases
the risk of kidney stones.
|
The
loss of bone mass that many people experience in space
weakens the bone, which can present problems when the
person returns to a weight-bearing environment, such
as the Earth or Mars. |
