title: Influence of thermal conditioning on the heat-induced radioresistance in primordial germ cells of the fish Oryzias latipes.
abstract: Heat treatment (41 degrees C, 30 min) given before gamma-irradiation results in an increase in radiation resistance of primordial germ cells (PGCs) in Oryzias latipes at a mitotically inactive stage. This may be attributed to the appearance of a shoulder region on the dose-response curve, indicating an increased capacity to tolerate radiation damage. The radiation response curve is biphasic and the conversion of a radiosensitive population to a less sensitive one as a result of heat treatment is suggested. When the PGCs were made thermotolerant by a 'priming' heat treatment (41 degrees C, 10 min) a second heat treatment (41 degrees C, 30 min) at 2 h interval did not induce resistance to radiation. A treatment of 41 degrees C for 30 min without 'priming' gave a thermal reduction ratio of 4.6, whereas with 'priming' the ratio was 1.0. Thus heat induces radiation resistance in PGCs but this induction is suppressed under thermotolerant conditions.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000528:radiation effects; D005399:Fishes / Q000196:embryology; D005720:Gamma Rays; D005854:Germ Cells / Q000166:cytology / Q000528:radiation effects*; D006358:Hot Temperature; D008940:Mitotic Index / Q000528:radiation effects; D011836:Radiation Tolerance; D013997:Time Factors