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Aboard the
International Space Station, Expedition Four and Five crewmembers
performed a total of 12 bioastronautics investigations. Here
are some highlights from their research.
 How
does prolonged weightlessness affect the lungs?
One of the
bioastronautics experiments was a study by John West of the University of California at San Diego on the effects of spacewalks and long-term
exposure to microgravity on the function of human lungs. This
investigation is measuring pulmonary function and the effects
of long-term exposure to gases and particles present in the atmosphere
of the station, as well as the effects of spacewalks, which require
the use of spacesuits with low atmospheric pressures.
Results
from previous studies show that the lungs are affected by being
in space. Gravity causes blood to move primarily through the bottom
portion of the lungs and the weight of the rib cage affects the
shape of the lungs. Without the pull of gravity, the lungs reshape
slightly and blood flows through them differently.
Getting
Along in Space
 | | The
Expedition Four crew bottom row) and the Expedition
Five crew (top row) shared a few days on the International
Space Station. Flight Engineer Dan
Bursch (lower left) and NASA ISS Science Officer
Peggy
Whitson (upper right) wrote about living and working
with crewmates. |
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Nick Kanas
of the Veterans' Affairs Medical Center in San Francisco, Calif.,
investigated the interactions between station crewmembers and
ground support staff during Expeditions Two through Five. His
objective was to measure the impact of cultural and language differences
and to characterize changes over time in interpersonal factors,
such as tension, cohesion, the leadership role and the relationships
between orbiting crews and personnel on Earth.
Preventing
Kidney Stones
Expedition
Five NASA ISS Science Officer Peggy Whitson is performing a 40-month
assessment of renal stone risk and the use of potassium citrate
as a possible countermeasure. Alterations in kidney function,
fluid redistribution, bone loss and muscle atrophy all contribute
to alterations in the urinary system and to potential renal stone
formation during and immediately after flight.
Studying
Radiation Effects on the Body
 | | The
Extravehicular Activity Radiation Monitoring experiment
was the first to test astronauts' radiation exposure
during spacewalks. |
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Five radiation
investigations have been conducted on the ISS. During Expeditions
Four and Five, Ian Thomson from Ottawa, Canada, monitored the
radiation environment that astronauts experience during spacewalks.
He measured doses to skin, eyes and blood-forming organs, using
a relatively new type of electronic radiation dosimeter -- the
metal oxide semiconductor field effect transistor, or MOSFET.
Determining
which parts of the human body are exposed to the highest radiation
levels will allow future measurements to focus on the appropriate
parts of the human body. In addition, the study benefits future
spacesuit designs, since it characterizes the radiation field
inside the astronaut's suit.
Measuring
Bone Loss
Bone loss
resulting from long-duration space flight continues to be a serious
issue and will become more so when humans begin to explore beyond
low-Earth orbit. Thomas Lang from the University of California
in San Francisco is performing an assessment of bone loss in the
axial skeleton through Expedition Six. He uses 3-D images of the
bones of 15 astronauts and cosmonauts before flight, immediately
after flight and one year after flight. These data are compared
to understand bone loss in the spine and hip and the recovery
rate and percent of bone mass following flight.
How
Microgravity Affects Blood Flow
During Expeditions
Three, Four and Five, Anders Gabrielson of the National University
Hospital in Copenhagen, Denmark, studied the effects of microgravity
on blood flow through the body. Generally, blood is evenly distributed
throughout the body, but, after flight, the astronaut's blood
pressure when standing is too low to pump sufficient amounts of
blood above the level of the heart. Blood collects in the lower
part of the body, temporarily depriving the brain, which can lead
to fainting.
Complementary
to this experiment is one by the Johnson Space Center's Janice Meck. She tested midodrine -- a drug that constricts blood vessels
and in turn increases blood pressure -- as a countermeasure against
postflight lightheadedness or fainting.
Muscle
Loss in Microgravity
 | | To
prevent muscle loss in microgravity, Expedition Five
NASA ISS Science Officer Peggy Whitson exercised vigorously.
She maintained an exercise log throughout her mission
for researchers to use in studying her case. |
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During the
preflight and postflight activities of Expedition Five, Robert
Fitts from Marquette University in Milwaukee, Wis., biopsied astronaut
calf muscles to study the effect of prolonged space flight on
human skeletal muscle. Past studies show that weightlessness causes
deterioration of muscle strength and size; this investigation
examined changes at the cellular level. The experiment investigators
tested the astronauts' muscles before and after the mission, and
the subjects kept records of their exercise while in space. This
experiment is being repeated on Expedition Six and again in 2003during
Expeditions Seven and Eight.
Testing
the Human Nervous System
Douglas Watt
of McGill University in Montreal, Canada, studied the effects
of altered gravity on spinal cord excitability during Expeditions
Two, Three and Four. This test was the first neurological experiment
to test spinal cord excitability using Hoffmann Reflex (H-Reflex)
testing. H-Reflex method was chosen rather than tendon tap response
because the electrical stimulus is better controlled, the response
can be measured more precisely and changes in muscle stretch receptor
sensitivity do not affect the results.
An experiment
performed by Johnson Space Center's Jacob Bloomberg examined an inflight training regimen that might mitigate locomotor dysfunction
after flight. Astronauts returning from a microgravity environment
often experience difficulty walking, as the brain reprograms body
movements in a gravity environment. Studies have shown that the
central nervous system requires a rich and varied sensorimotor
environment to maintain its normal structure and function.
Does
the Stress of Space Flight Activate the Epstein-Barr Virus?
 | | The
Epstein-Barr virus as viewed under a microscope. |
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Raymond Stowe
of the University of Texas Medical Branch in Galveston, Texas,
studied how space flight affects the Epstein-Barr virus, or EBV.
There are viruses contracted in childhood that can remain latent
or inactive in our bodies throughout our lives. Since astronauts
are known to experience unique stresses caused by space flight
and stress can cause changes in the immune system, Dr. Stowe compared
the differences between pre- and postflight levels of EBV. He
then inferred that a particular astronaut's immune system was
affected by their long-duration space flight. Eventually, he hopes
to answer the question: "When you throw in the factors of stress,
decreased immune functions and added radiation, will this cause
lymphomas or cancers on these longer missions?"
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