Editing Radiation hormesis (section)

=== Cultures ===

Studies in cell cultures can be useful for finding mechanisms for biological processes, but they also can be criticized for not effectively capturing the whole of the living organism.

A study by E. I. Azzam suggested that pre-exposure to radiation causes cells to turn on protection mechanisms.<ref>{{cite journal| author=Azzam, E. I. |journal=Radiation Research |year=1994 |volume=138 |pmid=8146320 |pages=S28–S31 |doi=10.2307/3578755 |title=Radiation-Induced Adaptive Response for Protection against Micronucleus Formation and Neoplastic Transformation in C3H 10T1/2 Mouse Embryo Cells |last2=Raaphorst |first2=G. P. |last3=Mitchel |first3=R. E. J. |issue=1 |jstor=3578755 |bibcode=1994RadR..138S..28A}}</ref> A different study by de Toledo and collaborators has shown that irradiation with gamma rays increases the concentration of glutathione, an antioxidant found in cells.<ref>{{cite journal |doi=10.1667/RR0640.1 |title=Adaptive Responses to Low-Dose/Low-Dose-Rate γ Rays in Normal Human Fibroblasts: The Role of Growth Architecture and Oxidative Metabolism |year=2006 |last1=De Toledo |first1=Sonia M. |last2=Asaad |first2=Nesrin |last3=Venkatachalam |first3=Perumal |last4=Li |first4=Ling |last5=Howell |first5=Roger W. |last6=Spitz |first6=Douglas R. |last7=Azzam |first7=Edouard I. |journal=Radiation Research |volume=166 |issue=6 |pages=849–857 |pmid=17149977|bibcode=2006RadR..166..849D |s2cid=31148344 }}</ref>

In 2011, an ''in vitro'' study led by S. V. Costes showed in time-lapse images a strongly non-linear response of certain cellular repair mechanisms called radiation-induced foci (RIF). The study found that low doses of radiation prompted higher rates of RIF formation than high doses, and that after low-dose exposure RIF continued to form after the radiation had ended. Measured rates of RIF formation were 15&nbsp;RIF/[[Gray (unit)|Gy]] at 2&nbsp;Gy, and 64&nbsp;RIF/Gy at 0.1&nbsp;Gy.<ref name="Neumaier2011" /> These results suggest that low dose levels of [[ionizing radiation]] may not increase cancer risk directly proportional to dose and thus contradict the linear-no-threshold standard model.<ref name=HC24865 >{{Cite web |url=http://www.healthcanal.com/public-health-safety/24865-New-Take-Impacts-Low-Dose-Radiation.html |title = New Take on Impacts of Low Dose Radiation |date = 20 December 2011}}</ref> [[Mina Bissell]], a world-renowned breast-cancer researcher and collaborator in this study stated: "Our data show that at lower doses of ionizing radiation, DNA repair mechanisms work much better than at higher doses. This non-linear DNA damage response casts doubt on the general assumption that any amount of ionizing radiation is harmful and additive."<ref name=HC24865/>