| Paula Cleggett-Haleim
Headquarters, Washington, D.C.
RELEASE: 92-125
Scientists report dramatic changes from space travel in some of the
body's systems, with a resiliency in others -- all of which affect long stays
in space and medical research on Earth. These results are from the Spacelab
Life Sciences-1 (SLS-1) mission, flown aboard Space Shuttle Columbia in June
1991.
"Taken together, these results show the need for a laboratory in space
to complement the traditional laboratory on Earth. This is vital in
understanding how the human body works, whether it is in space or on Earth,"
says Dr. Ronald White, chief scientist of NASA's Life Sciences Division.
Four principal investigators from the SLS-1 mission report key findings
in the areas of cardiovascular (heart and lungs), musculoskeletal (muscles and
bones) and neurovestibular (inner ear/brain) physiology.
CARDIOVASCULA
Space travel presents a drastic change in working conditions to the
heart and lungs, according to Dr. C. Gunnar Blomqvist, a cardiologist from the
University of Texas Health Science Center in Dallas.
Often astronauts just returning from space have difficulty maintaining
normal blood pressure and blood flow when standing. One SLS-1 experiment using
a catheter inserted preflight into an arm vein of an astronaut and later moved
nearer to the heart shows the astronaut experienced much more rapid fall in
central blood pressure than was predicted.
In another area of cardiovascular research, it was found that exposure
to space impairs an astronaut's pressure regulating reflexes, called
baroreflexes, according to Dr. Dwain L. Eckberg of the Hunter Holmes McGurie
Department of Veterans Affairs Medical Center and the Medical College of
Virginia,.
A closely fitting neck collar (similar to a whip-lash collar) was used
on astronauts during the SLS-1 mission to record two blood pressure sensing
areas located in the neck.
By the eighth day of flight, astronauts had significantly faster
resting heart rates, less maximum change of heart rate per unit of neck
pressure change and a smaller range of heart rate responses. These changes
occurred in all astronauts studied. The changes that developed were large and
statistically significant.
These results validated findings obtained on Earth. They were based on
predictions that Dr. Eckberg made by studying subjects after prolonged bedrest.
This validation can lead to important studies in clinical medicine
because studying astronauts before and after flight or by studying healthy
people before and after bedrest, provide insights into medical problems here on
Earth.
Nervous System
In another SLS-1 experiment, there is clear evidence that the number of
structures (synapses) used to communicate between the cells of the inner ear's
gravity detecting organ and the central nervous system increase greatly during
space flight, but not in size. Therefore, these systems should be able to
adapt to the differing gravitational environments of space, the moon and Mars,
according to Dr. Muriel D. Ross, a neuroanatomist from NASA's Ames Research
Center, Moffett Field, Calif.
Further research in this area should also shed light on the broader
topics of memory and learning in neural tissue and on clinical diseases of the
inner ear.
Muscles
Following space flight, there is a significant and dramatic reduction
in the size of all muscles needed for standing and moving, according to Dr.
Kenneth M. Baldwin, an exercise and muscle physiologist from the College of
Medicine at the University of California, Irvine.
"Also, there is a reduced capacity of muscles to burn fat for energy
production," says Dr. Baldwin. "In addition, this experiment has verified that
muscles that suport the body when we walk around on Earth change their nature
in space because they are not needed."
Taken together, these findings suggest that properties of the skeletal
muscle system, the largest organ system of the body, are greatly altered during
space flight.
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| Paula Cleggett-Haleim
Headquarters, Washington, D.C. July 24, 1992
Jane Hutchison
Ames Research Center, Moffett Field, Calif.
RELEASE: 92-124
Human, plant and animal cells exposed to the microgravity of space for
only a few days show changes in function and structure, according to NASA
scientists.
Although preliminary, the results of the recent life sciences research
on the space shuttle suggest alterations in metabolism, immune cell function,
cell division and cell attachment.
"This type of research is important not only in helping us understand
how life adapts to the weightlessness of space, but also in increasing our
knowledge of basic cell function and thus contribute to the well-being of life
on Earth," said Dr. Thora Halstead, Manager of NASA's Space Biology Program.
Dr. Gerald Sonnenfeld of the University of Louisville, Kentucky,
reports that after nine days in space, human immune cells failed to
differentiate into mature effector cells. The results of his investigation
into how the stress of space flight affects immune system cells suggest that
the stress of space flight can alter normal metabolic activities and important
aspects of immune cell function.
"The failure of the body to produce mature, fully differentiated cells
in space may lead to health problems, including impaired healing abilities and
increased risk of infection," he said.
"Bone-forming cells exposed to microgravity also show changes," said
Dr. Emily Morey-Holton of NASA's Ames Research Center, Moffett Field, Calif.
Her study of how exposure to microgravity changes the size, shape and cellular
components of rat bone cells revealed a significant number of floating, dead
bone-forming cells.
"Bone cells die if they can't attach to something," Morey-Holton said.
"That we found so many unattached, dead cells may indicate that gravity is
required to show the cells where to attach. This finding could be significant
since many biological processes, both in single cells and in multicelled
organisms, depend on cell attachment and recognition processes."
She added that the attached bone cells, although healthy, showed no
signs of producing mineral. "It may be that bone cells don't need to form
mineral to support themselves in microgravity," she said.
Morey-Holton and Sonnenfeld both used a novel computerized cell culture
incubator (the Space Tissue Loss Module) to keep their cultures alive. The
module, developed by Dr. William Weismann of the Walter Reed Army Institute of
Research in Washington, D.C., was designed specifically for studying the
metabolic activities of cells in space.
"The successful operation of the STL Module signified a landmark
technological achievement in our ability to study cell functions during space
flight," Halstead said.
Plant cells also respond to microgravity, according to Dr. Abraham
Krikorian of the State University of New York at Stony Brook. "There is
increasing evidence that cells in the roots of plants subjected to space flight
undergo major changes in their cell division profile, even after as few as four
days in space," he said.
"One particularly important consideration is that cells be able to
divide efficiently and to partition their genetic information with high
fidelity," he said. "In short, they have to get their signals straight and to
process them accurately."
He noted that in one plant (Haplopappus gracilis) that has only four
chromosomes, overall root production was significantly faster under space
flight conditions. He also said that changes in chromosomes were found in up
to one-third of the cells that flew in space.
Dr. Pauline J. Duke of the University of Texas Health Science Center
in Houston also found differences between mouse bone cells developed in space
and on the ground. She said the cells in microgravity showed changes in
attachment.
"The surfaces of flight cells were smoother than those of ground- based
controls, indicating that matrix production or secretion is altered during
space flight, probably as a direct result of microgravity exposure," she said.
"Matrix forms the basic structure of bone."
Dukes experiment, the first culture of skeletal cells in space, was
designed to determine whether cells sensitive to gravitational changes in the
whole animal and in organ culture retained that sensitivity in cell culture.
Although Halstead is pleased with the results of these studies, she
said there is still much to learn. "We are just beginning to understand how
cells function in space," she said.
"A more thorough understanding will come only after much more research.
We are looking to Space Station Freedom to give us the opportunities to conduct
the long-term studies that ultimately may hold the key to this basic component
of life," she said.
The results of these studies will be reported Monday, July 27, 1992, at
a workshop on Cellular Response to Microgravity as part of the Fifth
International Congress on Cell Biology in Madrid, Spain.
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