WASHINGTON -- A team of French researchers may have uncovered a clue to why space travel affects the human body.
Studies of astronauts have shown that periods of weightlessness reduce the body's bone mass, depress the immune system and lead to changes usually associated with aging. The causes are not fully understood but are thought to originate at the cellular level.
The new French study reports that gravity is necessary for microtubules in developing cells to become organized. These tiny tubes form a structure called the cytoskeleton, which helps cells retain their shape by organizing in either parallel or circular patterns.
The new study, published in Tuesday's issue of Proceedings of the National Academy of Science, found that cells that began to develop in the weightlessness of space did not organize the microtubules even after return to Earth.
Organization was normal, however, in companion sets of cells sent up in the European Space Agency rocket that were spun in a centrifuge during their first 13 minutes of development.
"Gravity can thus intervene in a fundamental cellular process and will indirectly affect other cellular processes that in their turn depend on microtubule self-organization," reported the team, led by Cyril Papaseit of the Department of Molecular and Structural Biology of the French Atomic Energy Commission.
"The gravity direction ... leads to the emergence of form and pattern," the researchers said. "Such processes may have played a role in the development of life on Earth."