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Flegal M.,Radiological Protection Research and Instrumentation | Blimkie M.S.,Radiological Protection Research and Instrumentation | Wyatt H.,Radiological Protection Research and Instrumentation | Bugden M.,Radiological Protection Research and Instrumentation | And 2 more authors.
Journal of Visualized Experiments | Year: 2015

Low dose radiation exposure may produce a variety of biological effects that are different in quantity and quality from the effects produced byhigh radiation doses. Addressing questions related to environmental, occupational and public health safety in a proper and scientifically justifiedmanner heavily relies on the ability to accurately measure the biological effects of low dose pollutants, such as ionizing radiation and chemicalsubstances. DNA damage and repair are the most important early indicators of health risks due to their potential long term consequences, suchas cancer. Here we describe a protocol to study the effect of chronic in vivo exposure to low doses of γ- and β-radiation on DNA damage andrepair in mouse spleen cells. Using a commonly accepted marker of DNA double-strand breaks, phosphorylated histone H2AX called γH2AX,we demonstrate how it can be used to evaluate not only the levels of DNA damage, but also changes in the DNA repair capacity potentiallyproduced by low dose in vivo exposures. Flow cytometry allows fast, accurate and reliable measurement of immunofluorescently labeled γH2AXin a large number of samples. DNA double-strand break repair can be evaluated by exposing extracted splenocytes to a challenging dose of 2Gy to produce a sufficient number of DNA breaks to trigger repair and by measuring the induced (1 hr post-irradiation) and residual DNA damage(24 hrs post-irradiation). Residual DNA damage would be indicative of incomplete repair and the risk of long-term genomic instability and cancer.Combined with other assays and end-points that can easily be measured in such in vivo studies (e.g., chromosomal aberrations, micronucleifrequencies in bone marrow reticulocytes, gene expression, etc.), this approach allows an accurate and contextual evaluation of the biologicaleffects of low level stressors. © 2015 Journal of Visualized Experiments.

El-Jaby S.,Radiological Protection Research and Instrumentation
Life Sciences in Space Research | Year: 2016

A recent paper published in Life Sciences in Space Research (El-Jaby and Richardson, 2015) presented estimates of the secondary neutron ambient and effective dose equivalent rates, in air, from surface altitudes up to suborbital altitudes and low Earth orbit. These estimates were based on MCNPX (LANL, 2011) (Monte Carlo N-Particle eXtended) radiation transport simulations of galactic cosmic radiation passing through Earth's atmosphere. During a recent review of the input decks used for these simulations, a systematic error was discovered that is addressed here. After reassessment, the neutron ambient and effective dose equivalent rates estimated are found to be 10 to 15% different, though, the essence of the conclusions drawn remains unchanged. © 2016.

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