Liftoff to Learning: All Systems Go! .
Although the data analysis-from the SLS-1 mission is continuing, researchers have pieced together some of the changes that take place in living organisms and living cells during exposure to microgravity. Human, plant, and animal cells exposed to the microgravity of space for only a few days show changes in function and structure. The data suggest that alterations in cell metabolism, immune cell function, cell division, and cell attachment have occurred in space. Scientists have reported that after nine days in space, human immune cells failed to differentiate into mature effector cells. The results of investigations into how the stress of space flight can alter normal metabolic activities and important aspects of immune cell function may indicate the body's inability to produce mature and fully differentiated cells in space. This may lead to health problems on long-term spaceflights, including impaired healing abilities and increased risk of infection.
Studies on rat bone cells revealed a significant number of floating, dead bone forming cells. Bone cells die if they are unsuccessful in attaching themselves to something. This finding could be significant since many biological processes, both in single cells and in multi-celled organisms, depend on cell attachment and the recognition processes. The finding suggests that gravity clues may be required to show the cells where to attach themselves. Furthermore, studies of rat bone cells also revealed that healthy cells showed no signs of producing minerals. It may be that bone cells do not need to produce minerals to support themselves in a microgravity environment.
Similar studies of mouse bone cells developed in space and of those developed on the ground revealed similar changes in attachment properties in microgravity. Microscopic examination of the surfaces of flight cells revealed that they were smoother than cells used in the ground-based control experiment. This finding indicated that matrix production or secretion is altered in microgravity. Matrix forms the basic structure of bone.
Plant cell studies also revealed unusual responses to microgravity. Data collected indicated that cells in the roots of plants subjected to spaceflight undergo major changes in their cell division profile, even after as few as four days in space. One plant studied, Haplopappus gracilis, has only four chromosomes. Overall root production in this plant was significantly faster under spaceflight conditions than in ground control studies. Furthermore, changes in chromosomes were found in up to one-third of the cells that flew in space.
Scientists have reported dramatic changes associated with space travel in some of the human body systems, with a resiliency in others, all of which may affect long stays in space and medical research on Earth. These results point to the need for a long term laboratory in space to complement Earth-based laboratory research. Key findings from the SLS-1 mission for three of the major body systems studied (cardiovascular, musculoskeletal, and neurovestibular) revealed important changes that take place in the human body in microgravity.
Space travel presents a drastic change in working conditions to the heart and lungs. Often, astronauts who have just returned from space have difficulty maintaining normal blood pressure and blood flow when standing. One SLS-1 experiment used a catheter inserted preflight into an arm vein of an astronaut and later moved nearer to the heart. This catheter had a sensor attached which measured the blood pressure closest to the heart. The experiment showed that the astronaut experienced a much more rapid fall in central venous 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. A closely-fitting neck collar (similar to a whip-lash collar) was used on astronauts during the SLS-1 mission to test and 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. The changes that developed were large, statistically significant, and occurred in all astronauts studied. These results validated findings obtained on Earth by studying subjects after prolonged bed rest. This validation can lead to important studies in clinical medicine and provide insights into medical problems here on Earth.
The results of another SLS-1 experiment show 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 increases during spaceflight, but the size of these structures does not increase. Therefore, these systems should be able to adapt to the differing gravitational environments of space, the Moon, and Mars. 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.
During spaceflight,there is a significant and dramatic reduction in the size of all muscles needed for standing and moving. Furthermore, it seems that there is a reduced capacity of muscles to burn fat for energy production. Studies have also verified that muscles that support the body when we walk 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 spaceflight.
As researchers continue to analyze the data collected through the experiments of the Spacelab Life Sciences-1 mission, reports of the findings will be made public through professional journals. Refer to the reference list for sources of additional information.
The following hands-on activities can be used to demonstrate some of the concepts presented in this videotape.
Pencil or masking tape tab (to mark height against a wall)
Demonstrate one of the changes that takes place in the human body in microgravity by having students measure their height immediately after rising in the morning and just before going to bed at night. People are measurably taller in the morning than they are in the evening. During bed rest, the disks that separate the vertebrae in the spinal column expand slightly. This increases the total body height by a centimeter or more. By evening, the disks have been compacted, producing a shorter body height. During exposure to microgravity, the spine expands and doesn't contract until to return to Earth.
Upper Body Fluid Shift
Washable (non-toxic) marker pen
Wood blocks (cut from 2 x 4s)
Measure the circumference of the mid-calf of several volunteer students while they are standing. Carefully mark the placement of the tape measure with the marker pen. Record the measurement. Lay each student down on the table in turn and elevate one end of the table by placing the legs on the wood blocks. The student should be in a head-down position. Ask the student to describe the sensations felt, especially in the head and upper body. After five minutes of "bed rest," measure the circumference of the calf again in the exact place as before. Record the measurement. Is there a difference in the two measurements? What might cause these differences?
Note: While standing on Earth, gravity tries to pull blood and other body fluids to the feet. Without the pumping action of the legs during movement, humans standing still for long periods tend to black out. In Earth orbit, the local effects of gravity are counteracted, but the pumping actions of the legs continue. This leads to an upper body fluid shift that creates a puffy look in the face and neck and a thinning of the calf ("chicken legs"). Bed rest can simulate this effect.
Cardiac Output and Exercise
Stopwatch or watch with a second hand
Wood blocks (made from 2x4s)
Measure the pulse rate (in beats per minute) of a volunteer student standing at rest. Record the rate. Give the volunteer the hand weights and have the student exercise vigorously with them for two to four minutes. Again, measure and record the heart rate. When the heart rate has returned to the rate at rest, place the student on the table. Elevate the end of the table under the student's feet. After five minutes of "bed rest" with the feet elevated, measure the volunteer's heart rate. Again, give the student the hand weights and have the student exercise vigorously for two to four minutes while still lying down. Measure and record the heart rate after exercise. Calculate the cardiac output for each measure. The cardiac output in milliliters per minute equals the stroke volume (ml/beat) times the heart rate (beats per minute).
Cardiac Output = Stroke Volume x Heart Rate
Assume that the standing stroke volume is about 75 ml/beat. During bed rest and in microgravity, the stroke volume increases to about 95 ml/beat. Was there a difference in cardiac output before and after exercise while standing? During bed rest? Compare standing cardiac output with bed rest (microgravity) output. Is there a difference? Why or why not?
Note: This activity and the proceeding one can be combined into a single study.
STS-40 Crew Roster
Commander: Bryan D. O'Connor (Col.,USMC)
Pilot: Sidney M. Gutierrez (Lt.Col.,USAF)
Mission Specialist: James P. Bagian (M.D.)
Mission Specialist: Tamara E. Jernigan (Ph.D.)
Mission Specialist: Magaret Rhea Seddon (M.D.)
Payload Specialist: F.Andrew(Drew) Gaffney (M.D.)
Payload Specialist: Millie Hughes-Fulford (Ph.D.)
To obtain biographic information, click on highlighted names