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Space Station Turns 2

Space Station Turns Two
Science: Bioastronautics

The International Space Station celebrated its second year of permanent habitation in 2002.

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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

IMAGE: Expedition Four and Five crews
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.

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

IMAGE: STS-108 spacewalker Linda Godwin
The Extravehicular Activity Radiation Monitoring experiment was the first to test astronauts' radiation exposure during spacewalks.

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

IMAGE: NASA ISS Science Officer Peggy Whitson works out
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.

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?

IMAGE: The Epstein-Barr virus as viewed under a microscope
The Epstein-Barr virus as viewed under a microscope.

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?"

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 12/16/2002
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