Space Shuttle Experiment Shows Frogs Can Reproduce In Space
WASHINGTON (AP) _ A giant leap for frogdom _ and maybe people too?
A space shuttle experiment that shows frogs can reproduce in orbit has proven that embryo development common to all vertebrates, including humans, can take place in the absence of gravity, said Steven D. Black, an embryologist at Reed College in Portland, Ore.
``These frogs showed that embryos can go through the early landmark stages of development okay,″ Black said Monday. ``Humans go through these same stages.″
Kenneth A. Souza of NASA’s Ames Research Center in Moffett Field, Calif.,
said the study supports the idea that one day humans will be able to reproduce in orbit. But he cautioned that much more study is needed before that could ever be attempted.
``We don’t see any reason to suspect that fetal development could not be accomplished normally in the absence of gravity,″ said Souza. ``That includes humans.″
Black, Souza and Richard J. Wassersug of Dalhousie University, Halifax, Nova Scotia, are co-authors of the frog study, which was being published Tuesday in the Proceedings of the National Academy of Sciences.
In the study, four female African clawed frogs were launched aboard space shuttle Endeavour in September 1992. Once in orbit, the frogs were injected with a hormone that caused egg production.
Also on board were the testes from male African clawed frogs. Black said the testes were crushed by the astronauts and the resulting fluid was injected onto the frogs’ eggs. Many of the eggs became fertilized. They were then transferred to a container filled with water.
Four days later, the eggs hatched into tadpoles that appeared to be normal.
``They seemed to be okay,″ said Black. ``There was no problem with navigation even in microgravity. They swam in a straight line.″
The space shuttle landed three days later and the tadpoles were transferred to aquariums and compared with tadpoles that were hatched on Earth at the same time.
Black said the only difference was that the space-born tads had smaller lungs, a factor related to their inability to get a lung full of air inside their closed water cell in space. Once the tadpole astronauts were able to get breaths, he said their lungs expanded to normal.
Since that mission, the tadpoles have grown up and reproduced, and Black said their offspring also are normal.
The important finding from the frog experiment, said Black, is that it proved embryos can successfully go through a vertebrate stage of development called gastrulation. This is when surface cells of an embryo are brought inside and start changing into cells that form the spine, central nervous system and internal organs.
``Everybody does this, including humans,″ said Black. ``There was concern that embryos could not do it in the absence of gravity.″
Souza said that an earlier experiment, in which rats in midpregnancy were flown on the space shuttle, have shown that fetal develop can proceed normally in weightlessness. Now, he said, the frog experiment has verified that embryos can grow normally also.
But he cautioned there is a great leap between what is known now and the possibility of human reproduction in space.
``The difference between a frog and a human egg is the incubator,″ said Souza. People in orbit, including pregnant women, would undergo physical changes in weightlessness that could affect the fetus. These changes include the loss of calcium and alterations in blood and fluid flow patterns, he said.
The next major step is to put mice or rats through a full reproductive cycle in space. That may not happen until 2010 aboard the planned space station, said Souza.
It has already been tried. The Russians took male and female mice into orbit but ``there were no evidence that breeding ever occurred.″
Floating around in weightlessness, said Souza, apparently spoiled any rodent romance.