Does Hze Radiation-induced Dna Damage Differ from Low-energy High Let Radiation Damage?

METHODS We have used 1 GeV/u and 600 MeV/u iron ions at NSRL, 300 kVp X-rays and 25 MeV/u nitrogen ions from the 88” cyclotron at Lawrence Berkeley National Laboratory. For measurements of DNA double-strand breaks we are using pulsed-field gel electrophoresis (PFGE) with a dual label technique that includes control samples in each lane and the use of the most sensitive part of the FAR vs dose curve. This methodology allows us to use the same low doses for DSB measurements (0.2 – 2 Gy) as is used for the PCC damage measurements and micronuclei formation. Immuno-staining and counting of g-H2AX foci is used as an alternative method to score DSBs. PCC is induced by calyculin-A, and scored in coded slides. Chromatid and iso-chromatid breaks in PCC samples are scored in G2/M cells. Bystander effects are measured in cells that receive medium from irradiated cultures (medium transfer technique).