Damage-repair studies of the DNA from X-irradiated Chinese hamster cells.
Sedimentation studies of the DNA-containing material released from Chinese hamster cells lysed on top of an alkaline sucrose gradient have shown these principal points: (1) After short lysis periods (e.g. approximately 60 min, approximately 25 degrees C), the DNA label from unirradiated cells sediments as a two-peaked pattern. The relative positions of these peaks are strongly dependent on centrifugal force. (2) With increasing lysis time, DNA lost from one peak (the "complex", the peak containing lipid) appears in the other (the "main peak"). (3) The same transition is effected, for a given lysis time, if prior to lysis cells are X-irradiated with small doses (from 100 to 700 rads). Since such doses are in the high survival range (approximately 80% to approximately 3%, respectively), an association between damage to the complex and survival is suggested. And (4) the cosedimentation of lipid and DNA in the complex is lost after doses that resolve the complex into main-peak DNA, while postirradiation incubation for repair results in a re-formation of the complex plus cosedimentation of lipid and DNA once again.
PubMed Abstracts
PubMed Abstracts