The radiation environment in space is complex in terms of both the variety of charged particles and their dose rates. Simulation of such an environment for experimental studies is technically very difficult. However, with the variety of beams available at the National Space Research Laboratory (NSRL) at Brookhaven National Laboratory (BNL) it is possible to ask questions about potential interactions of these radiations. In this study, the end point examined was transformation in vitro from a preneoplastic to a neoplastic phenotype. The effects of 1 GeV/n iron ions and 1 GeV/n protons alone provided strong evidence for suppression of transformation at doses ≤5 cGy. These ions were also studied in combination in so-called mixed-beam experiments. The specific protocols were a low dose (10 cGy) of protons followed after either 5–15 min (immediate) or 16–24 h (delayed) by 1 Gy of iron ions and a low dose (10 cGy) of iron ions followed after either 5–15 min or 16–24 h by 1 Gy of protons. Within experimental error the results indicated an additive interaction under all conditions with no evidence of an adaptive response, with the one possible exception of 10 cGy iron ions followed immediately by 1 Gy protons. A similar challenge dose protocol was also used in single-beam studies to test for adaptive responses induced by 232 MeV/n protons and 137Cs γ radiation and, contrary to expectations, none were observed. However, subsequent tests of 10 cGy of 137Cs γ radiation followed after either 5–15 min or 8 h by 1 Gy of 137Cs γ radiation did demonstrate an adaptive response at 8 h, pointing out the importance of the interval between adapting and challenge dose. Furthermore, the dose–response data for each ion alone indicate that the initial adapting dose of 10 cGy used in the mixed-beam setting may have been too high to see any potential adaptive response.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 176 • No. 3