Dose-rate effects on cycling and noncycling C3H 10T 1/2 cells exposed to gamma rays
Plateau-phase cultures of density inhibited C3H 10T 1/2 mouse cells were used to obtain populations of noncycling cells. In plateau-phase these contact inhibited cultures are comprised of a nearly pure G1 population. The medium overlying confluent monolayers was changed at five day intervals to keep the cells viable. For unirradiated cultures approximately 15 to 30% of the cells were triggered to enter S-phase over a two day period following each medium change. Continuous irradiation with cesium-137 gamma rays at all dose rates studied dramatically reduced or eliminated the progression of cells into S-phase following each medium change due to a radiation induced G1 block. For noncycling cells a dose-rate effect was clearly evident when the dose-rate was reduced from 55.6 to 2.4 Gy/h, from 2.4 to 0.49 Gy/h, and from 0.49 to 0.29 Gy/h. Survival curves at 0.29, 0.17, and 0.06 Gy/h were not significantly different and the average D/sub 0/ for these curves was 7.32 Gy. Since repair alone was responsible for the dose-rate effect, all repairable damage was repaired under these conditions, leaving only non-repairable damage leading to cell reproductive death at dose rates of 0.29, 0.17, and 0.06 Gy/h. Also since these curves were not significantly different from a linear exponential function of dose, they should represent an accurate measurement of the initial non-zero slope of the acute dose survival curve, /sub 1/D/sub 0/. Dose-rate effects on log-phase cultures of cycling C3H 10T 1/2 cells were also studied. A dose-rate effect was clearly evident at dose rates of 1.42, 0.49, and 0.29 Gy/h. Factors besides repair identified as influencing the dose-rate effect were cell cycle redistribution into more radiosensitive phases of the cell cycle and cell division occurring during the exposure periods.
- Research Organization:
- Colorado State Univ., Fort Collins (USA)
- OSTI ID:
- 5017110
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALI METAL ISOTOPES
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CELL CULTURES
CELL CYCLE
CELL DIVISION
CELL KILLING
CESIUM 137
CESIUM ISOTOPES
DATA
DOSE RATES
DOSE-RESPONSE RELATIONSHIPS
DOSES
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
GAMMA RADIATION
INFORMATION
IONIZING RADIATIONS
ISOTOPES
MAMMALS
MICE
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
RADIATION DOSES
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
RECOVERY
REPAIR
RODENTS
SURVIVAL CURVES
VERTEBRATES
YEARS LIVING RADIOISOTOPES