Ovarian Modifications in Mice Exposed to Whole-Body Irradiation

This experiment was designed to determine the involvement of varying levels of whole-body irradiation on ovarian follicular and corpora luteal development in mice. Previous research has indicated reduced counts of ovarian follicles and corpora lutea in mice flown in space. These differences may be the result of microgravity, increased exposure to radiation, or some combination of both. Fifty-six mice were divided into three groups (apocynin-treated, nox2 knockout, and wild-type control) before exposure to 0 Gy, 0.5 Gy, or 2.0 Gy radiation. The tissues were harvested, preserved, run through the appropriate paraffin embedding procedures, serially sectioned, mounted on microscope slides, and stained using a standard H&E staining technique. Total and mean follicular and corpora luteal counts were accessed and compared across treatment groups. Mean ovarian weight, mean total reproductive weight, mean ovarian weight percentage of total body weight, mean total reproductive weight percentage of total body weight, and the apparent estrous phase of the animals were also compared. Radiation from 0.5-2.0 Gy had no significant effect on mean ovarian weight, mean total reproductive weight, mean ovarian weight percentage of total body weight, or mean total reproductive weight percentage of total body weight. Radiation from 0.5-2.0 Gy significantly increased mean early-stage follicular count in the wildtype group only. Radiation of 2.0 Gy increased late-stage follicular count across all groups after accounting for mean ovarian percent of total body weight. Radiation of 2.0 Gy significantly increased mean corpora lutea count in the wildtype group only. This result not only suggests that low-dose radiation accelerates oocyte development in the murine ovary, but also that the inaction of NADPH-oxidase (via apocynin inhibition or genetic knockout) may ameliorate some of these effects. Poole 4 INTRODUCTION Throughout its history on planet Earth, mankind has expanded its habitat to include the most extreme of environs, facing dramatic changes in temperature, molecular oxygen level, and illumination. Now man looks to conquer a new habitat, Mars and the space between, and the journey threatens to expose astronauts to the full spectrum of gravitational force. The challenges on Mars itself will resemble those most unforgiving habitats of Earth. Its surface is frozen, hypoxic, and unprotected from solar radiation. Investigation into such extreme conditions, and their combined effect upon human physiology, must be understood if spaceflight is to be a viable option for prolonging and protecting man’s future. The Space Studies Board and National Research Council convened in 1991 to address research goals for the new millennium, highlighting a need for spaceflight experimentation in the area of human viability in space. Possible reproductive pathologies associated with orbit were a primary concern. And although the recommendation by the council that spaceflight test animals remain in orbit for 2 life cycles has been largely abandoned in favor of cheaper, shorter experiments, the ongoing mission of the National Aeronautics and Space Agency (NASA) to increase spaceflight funding has been a successful one. Such progress is illustrated by the wealth of experiments that have been and are being done upon the recently constructed International Space Station (ISS). ISS is outfitted specifically for developmental biological studies. Organized by Professor Sally A. Moody of George Washington University and Dr. Catherine Golden of NASA, the International Space Life Sciences Working Group Developmental Biology Workshop aimed to further spaceflight research, specifically in reference to the processes of gametogenesis, Poole 5 fertilization, organogenesis, and vestibular system development (Moody and