The history of spaceflight has from the earliest days depended upon the understanding of the charged-particle radiation field encountered in space. First discovered aboard Victor Hess’ high altitude balloons in 1911, charged particles emanating from space were further characterized by experiments aboard James Van Allen’s sub-orbital rockets, their detection was the principle experiment aboard the first American satellite, Explorer 1, and were one of the primary sources of astronaut health concern during the Apollo missions. As NASA prepares for the first manned mission to Mars, the threat posed by the charged particle environment in the interplanetary space is more pressing than ever, as astronauts are estimated to be exposed for approximately three years, with no feasible shielding at this time. Due to cost and impracticalities, experiments aiming to understand the effects of charged-particle radiation on normal tissues must be performed on ground-based particle accelerators, which are capable of accelerating particles at realistic energies and dosages encountered in deep space. We exposed mice of astronaut-equivalent ages to mission-relevant doses of charged particles at NASA’s space radiation laboratory. Due to the importance of the central nervous system to critical astronaut tasks, specifically memory, we tested mice at various time points following irradiation to determine acute and late risks. The processes of memory formation, consolidation and retrieval are considered hippocampus-dependent tasks. We therefore tested mice for hippocampus-dependent memory behaviors, and following sacrifice, brains were collected and analyzed for changes in hippocampal morphology, and expression of genes associated with inflammation and excitatory signaling in the hippocampus. Our experiments indicate that acute exposures to charged-particle radiation resulted in memory deficits at various time points after exposure, which appear to be particle-, dose-, and sex-dependent. Post-mortem analyses revealed severe modulation of dendritic branching, and reductions in dendritic spine stability across various hippocampal subregions after irradiation. These changes appear to be related to inflammatory processes, though future studies should confirm this relationship. Overall, data accrued from various experiments suggest that charged-particle radiation poses a significant risk to the central nervous system of astronauts on a mission to mars.
|Commitee:||Boerma, Marjan, Price, Elvin T., Aykin-Burns, Nukhet, Hayar, Abdallah|
|School:||University of Arkansas for Medical Sciences|
|School Location:||United States -- Arkansas|
|Source:||DAI-B 81/2(E), Dissertation Abstracts International|
|Subjects:||Neurosciences, Immunology, Behavioral psychology|
|Keywords:||Astronaut, Brain, Charged-particle, Hippocampus, Mars, Radiation|
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