title: Radiation killing of E. coli K1060: role of membrane fluidity, hypothermia and local anaesthetics.
abstract: The enhancement of killing by gamma-irradiation, which is seen when E. coli K1060 are cooled below the transition temperature of their membrane lipids, is blocked by procaine-HCl. These data are consistent with the hypothesis that increased killing associated with irradiation at 0 degree C is the result of membrane microviscosity increases, since procaine is known to fluidize membranes. A cooling enhancement ratio (c.e.r.) is defined as the ratio of radiation D0 at 22 degrees C to its value at 0 degree C. The c.e.r. for oxygen-bubbled cells is 1.5 and for nitrogen-bubbled cells is 2.1. In the presence of 25 mM procaine the respective c.e.r. values are 1.08 and 1.29. The oxygen enhancement ratio (o.e.r.) at 22 degree C is 3.43 and at 0 degree C is 2.45. The addition of procaine does not change the o.e.r. Thus, the temperature effect on o.e.r. does not appear to be related to membrane fluidity.
mesh_terms: D002462:Cell Membrane / Q000528:radiation effects; D003080:Cold Temperature; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D005720:Gamma Rays; D008560:Membrane Fluidity; D009154:Mutation; D009584:Nitrogen; D009829:Oleic Acids / Q000494:pharmacology; D010100:Oxygen; D011343:Procaine / Q000494:pharmacology; D011829:Radiation Dosage
chemical_list: D009829:Oleic Acids; D011343:Procaine; D009584:Nitrogen; D010100:Oxygen