Medicines from Space : Part 2

by Food and Drug Administration (FDA)

(Page 2 of 3)

Slowing Down

Other phenomena occur more slowly in space than on Earth. One example is the growth of protein crystals from biological cells, which are important in the development of treatments for cancer, AIDS and diabetes. The microgravity environment of a spacecraft allows production of crystals that are better because they form more slowly.

A crystal forming rapidly on Earth may become as irregular as a brick barrier hastily thrown up, like the Berlin Wall. A wall built slowly and carefully will assume the precise shape the builder desires. But protein crystals growing slowly in space will exhibit a greater regularity, allowing researchers to design drugs with a more precise "fit."

Working from these well-formed protein crystals, scientists can design exact antidotes to disease-causing organisms, rendering them ineffective.

Some protein crystals produced in space are larger and more symmetrical than their equivalents produced on Earth, and consequently more useful to scientists. Scientists at the University of Alabama's Center for Macromolecular Crystallography hope that longer flights, or even an orbiting space station, will produce larger and even better-formed crystals. Thus, the microgravity effects that slow some biological processes can be as useful to scientists as those which speed others up. The same is true of those that are just different.

Differing Processes

Human adaptation to the extraordinary stresses of long space voyages, even for limited periods, demands intensive medical investigation.

This research, usually done on Earth, has yielded information helpful to treating patients with certain diseases. For example, one process that is different in space, the radical shifts of bodily fluids that can incapacitate astronauts during takeoff or atmosphere reentry, has implications for patients with circulatory problems.

Claire Lathers, Ph.D., former FDA pharmacologist and consultant to NASA, has been working on the problem of orthostatic intolerance — the body's difficulty in accommodating sudden footward fluid shifts, particularly after prolonged weightlessness. A common result of orthostatic intolerance is that astronauts may faint or become lightheaded from the decreased blood flow to the head when they attempt to stand after their spacecraft reenters Earth's gravity.

Realizing that astronauts' muscular and cardiovascular systems atrophy in ways comparable to those of bedridden long-term hospital patients, Lathers and her associates studied healthy volunteers during periods of prolonged bed rest. "Experimental procedures and equipment are first tested on Earth," Lathers states, adding that in time this research may well directly benefit future hospital patients as much as astronauts.

From volunteers resting in bed for as long as 17 weeks, experiments progressed to NASA's KC-135 aircraft, a plane designed to give brief periods of weightlessness. Finally, astronauts apply the findings in space flight.

Lathers and her associates used a technique, lower body negative pressure (LBNP), common in hospital clinical pharmacology units, to study patients with circulatory problems. LBNP counteracts the tendency of blood and other fluids to pool in the head during takeoff and then rush toward the feet during landing, causing astronauts to exhibit orthostatic intolerance and/or to faint. The researchers conducted numerous bed-rest studies using the cumbersome metal vacuum chambers, similar in design to the old "iron lung," used on the long-term Skylab missions.

Subsequently, the personnel in NASA's Johnson Space Center Cardiovascular Laboratory, directed by John B. Charles, Ph.D., contributed to the development of a new, compact, collapsible LBNP device. It looks like a duffel bag designed for astronauts to stand in, and it is used on the space shuttle. The LBNP device is sealed around the waist. A vacuum draws fluids to the lower body.

In addition to using the LBNP device, Lathers and Charles have considered the effects of various drugs to stabilize blood pressure to prevent orthostatic intolerance. Finally, they have pondered the use of both pharmaceuticals and LBNP devices in combination.

As their work progresses, the goal of keeping humans in space long enough to perform significant medical research moves closer to reality. Their experiments could have important benefits for patients on Earth who experience circulatory problems, including serious high- and low-blood pressure conditions. If researchers can learn to control distribution of bodily fluids in space, they can, in time, do so on Earth. An enhanced understanding of the entire cardiovascular system could result.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.