Reproduction and growth of mice and rats under conditions of simulated increased gravity.

OYAMA, JIRO, AND WILLTAM T. PLATT. Reproduction and growth of mice and rats under condz’tions of simulated increased gravity. Am. J* Physiol. ZIQ(I): 164-166. q67.-Mating studies were performed on rats and mice subjected to chronic centrifugation at various g loads. Rats conceived and delivered viable pups at 2.5 and 3.6 g but not at 4.7 g. Newborn pups, however, survived only when they were removed intermittently from the centrifuge during the first several weeks of exposure. Newborn mice, in contrast, exposed continuously to 2.5 g from birth were able to survive and grow. Growth rates of animals born and reared on the centrifuge were lower than those of controls. Measurements were made of changes in food and water consumption and body mass of rats born at and adapted to 23 g when shifted to 3.6 g or returned to normal gravity. A transient increase in food and water consumption of animals returned to normal gravity was the only significant change observed. Results of this study show that rats and mice can reproduce under conditions of simulated increased gravity. Compared to rats, newborn mice are better able to tolerate increased gravity. Animals born and reared in an increased gravitational environment appear normal in all respects except for a relatively smaller body mass,