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Snails fly for San Antonio researchers (3/9/98)

The ultimate aim of a research partnership between German and American scientists, including Michael L. Wiederhold, PhD, professor of otolaryngology - head and neck surgery at The University of Texas Health Science Center at San Antonio, is to determine how weightlessness affects the formation of an embryo born in space.

Earth's gravity extends far into space, yet astronauts and objects orbiting the earth react as if they are weightless. Why?

When an object falls due to gravity, it is nearly weightless. And when a spacecraft is orbiting the earth, it is really falling around the earth; the craft's speed and altitude keep it from crashing to earth or from going off into the far reaches of outer space. In this environment, scientists have an opportunity to study the effects of weightlessness.

The National Aeronautics and Space Administration (NASA) and the European Space Agency have been conducting experiments with plants and animals. Dr. Wiederhold and his group work with Dr. Volker Bluem and his co-workers from Ruhr-University of Bochum, Germany. The German scientists have constructed a big fish and snail hatchery at the Kennedy Space Center, where thousands of animals are bred for ground and space experiments. They also have developed and constructed a sealed aquarium in which to send plants and animals into space.

The tank contains rootless water plants called hornweed, which transforms light energy into chemical energy through photosynthesis, and converts water and carbon dioxide into carbohydrates and oxygen, used by swordtail fish, water snails and microorganisms to breathe. The animals exhale carbon dioxide, essential for plant photosynthesis, then excrete ammonia ions which go through a process that serves as a nitrogen source for plants.

Eventually, systems could be developed in which the implementation of plant-eating fish would produce plant and animal biomass for human consumption. Another possible result of these experiments is valuable information that could be used to treat human diseases such as osteoporosis and kidney stones.

The spaceshuttle Endeavour, launched in January, contained a sealed aquarium with swordtail fish and 25 adult pond snails as well as hornweed (ceratophyllum) plants. Dr. Wiederhold journeyed to Kennedy Space Center to meet the spacecraft when it landed in early February after docking with the Russian space station, Mir. The word Mir means peace in Russian.

In 1994, Russia and the United States signed an agreement that will end in 2003. In exchange for installing equipment on Mir and having an American astronaut onboard the Russian station to conduct experiments, NASA provided funds to help add another science module to Mir. The NASA/Mir microgravity program will include nine dockings of the shuttle with Mir, to carry experiments and crew to and from the station.

"My main interest is in what happens to the gravity-sensing part of the inner ear in zero gravity during the critical developmental period," says Dr. Wiederhold. "We now know how the parameters change for adult animals and people during the time they are in space. It takes from two to five days to adapt to zero gravity once they are in orbit, and about the same length of time to readapt to earth's gravity after they land.

"The adult fish (xiphophorus) were put in the aquarium pregnant," Dr. Wiederhold continued. "The experiment was timed so we could remove a mature embryo and larvae, and measure the otolith - the stones in the inner ear on which gravity pulls. In earlier experiments on the Japanese newt, we found that more stones formed in embryos developed in space than in those developed on earth. We will now compare the findings in snails and fish from this flight with those of the earlier flight."

Dr. Wiederhold was in the hatchery at the Kennedy Space Center located down the hall from the astronauts medical testing room, removing animals from the aquarium so tests could be completed, when two of the astronauts who had been on the flight came into the laboratory to see how the snails were doing.

"Although all they did for us during the space flight was to change the videotapes, they found if they looked into an air vent they could watch the fish," Dr. Wiederhold says, "and they became interested in our experiments. This will make a big difference in the future because their interest will help if anything goes wrong on the flight."

Back in the laboratory at the Health Science Center, Hugo Pedrozo, PhD, Dr. Wiederhold's postdoctoral fellow, reared both snail embryos and larvae on a centrifuge at 1, 2, 3 and 5x Gs. He removed the statocysts and found that at higher Gs, the number and size of the stones were smaller than normal.

"On earth, the snails prefer to crawl downward, hop off the side of the tank and float back to the top," Dr. Wiederhold says. "In our first experiment, conducted about four hours after the spacecraft landed, we used immature snails who had been born in space. They crawled in a completely random pattern. Then we tested the adults; they crawled downward as they normally do. Thereafter, the immature snails also crawled downward.

"We aren't sure why," Dr. Wiederhold says. "We are doing more behavorial studies on the Neurolab flight. The findings should be interesting."

In the flight due to be launched in April, 1998, the spacecraft will carry the same aquarium containing fish and snails. Scientists will then determine how vertebrates function, and measure their self-sustaining abilities in space. This laboratory will be flown under identical experimental conditions and be operative for a minimum of 16-18 days; the February flight lasted only nine days.

Dr. Wiederhold, who received both his bachelors and masters in electrical engineering as well as his PhD in communications biophysics from the Massachusetts Institute of Technology, has been continuously funded by NASA for the past 13 years.

Contact: Jan Elkins (210) 567-2570