Adaptive response of the chicken embryo to low doses of x-irradiation.
Chicken embryos were x-irradiated in ovo with 5-30 cGy (=priming dose) at the 13th-15th day of development. After 3-48 h, brain- and liver-cell suspensions were x-irradiated in vitro with (challenge) doses of 4-32 Gy. Significantly less radiation damage was observed when the radiation response was measured by scheduled DNA synthesis, nucleoid sedimentation and viscosity of alkaline cell lysates 12-36 h after the priming exposure. In vivo, pre-irradiation with 10 cGy enhanced regeneration as evidenced by the DNA content of chicken embryo brain and liver 24 h following a challenge dose of 4 Gy. From nucleoid sedimentation analyses in brain and liver cells immediately after irradiation with 16 Gy and after a 30-min repair period in the presence of aphidicolin, dideoxythymidine and 3-aminobenzamide or in the absence of these DNA repair inhibitors, it is concluded that a reduction of the initial radiation damage is the dominant mechanism of the "radio-adaptive" response of the chicken embryo. Sedimentation of nucleoids from ethidium bromide (EB) (0.75-400 micrograms/ml)-treated cells suggests a higher tendency of "radio-adapted" cells to undergo positive DNA supercoiling in the presence of high EB concentrations.
D000818:Animals; D001921:Brain / Q000196:embryology / Q000528:radiation effects; D002467:Cell Nucleus / Q000187:drug effects / Q000528:radiation effects; D002642:Chick Embryo / Q000528:radiation effects*; D004247:DNA / Q000096:biosynthesis / Q000528:radiation effects; D004261:DNA Replication / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004996:Ethidium / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000196:embryology / Q000528:radiation effects; D012038:Regeneration / Q000528:radiation effects; D014965:X-Rays
D004247:DNA; D004996:Ethidium