Radiation Induced Bystander Responses In Vertebrates Given Low Doses Of In Vivo Radiation

Abstract

<p> The bystander response phenomenon shows that radiation induced changes in cells that have not been directly targeted, but are neighbors to or receive medium from directly hit cells. Our group has performed a range of single and serial, low dose irradiations (in vivo) on two strains of mice that have been documented to show genetic differences in their response to radiation. This thesis also explores the impact of environmental radiation contamination on female and male Mink frogs (Rana septentrionalis) sampled from contaminated and background (control) radiation sites. Bladder explants established from these vertebrates are incubated in culture medium, which is then used to measure apoptotic response (cell survival and calcium flux) in the keratinocyte reporter system. </p> <p> This study reveals that culture medium from acutely irradiated C57Bl6 mice, but not Balb/c mice, induces dose-dependant clonogenic death. The administration of a priming dose(s) to C57BL6, but not Balb/c mice, leads to stimulatory growth effects in reporters regardless of the time separation between the priming and challenge dose. Similarly, ITCM corresponding to male and female contaminated frogs results in a sexdependent decrease in reporter survival, but no reduction is induced from ITCM sampled from explants from female and male frogs from uncontaminated sites. When the ITCM is measured for its calcium inducing ability, results show abnormal calcium levels in both strains of mice only after the administration of a priming dose. However, chronic exposures to male and female frogs results in the production of ITCM that induces transient calcium flux in reporters. These results indicate that genetic predisposition in mice influences the type of bystander signal that is produced after exposure to low, acute doses of radiation. However, when mice are repeatedly exposed to radiation, the bystander signal is modified in a way that may be causing unregulated growth in reporter cells. </p>