Structural changes in mammalian cell DNA induced by low-dose x-ray damage and subsequent postirradiation incubation in the presence and absence of caffeine
DNA damage and postirradiation incubation effects from X-ray doses of 30-2000 rad delivered to rat 9L cells in vitro were detemined by viscoelastic analysis of neutral (pH 7) cell lysates. Damage studies showed first an increase in the principal viscoelastic retardation time, T, with increasing dose, followed by a decrease, with the maximum retardation time occurring at 1000 rad. Also, the variation of retardation time with increasing postirradiation incubation time at 37/sup 0/C was determined. At doses greater than 50 rad, this variation was quite complicated; e.g., following 100 rad, the retardation time showed a minimum followed by a maximum as a function of incubation time. All doses showed an initial return of T to close to control values at early times. Following 50 rad, control viscoelastic behavior was recovered in 1 hr. For doses of 100 rad and higher, 5 hr or more were required for complete return to control behavior has determined by both the value of T and the viscoelastic response to a probe dose of 200 rad immediately prior to lysis. These results are analyzed in terms of the dependence of the principal retardation time T on DNA molecular weight and conformation. Evidence is discussed indicating that the observed changes in T during postirradiation incubation reflect repair of DNA damage. Postirradiation incubation in the presence of 0.5 mM caffeine appeared to result in an inhibition of repair. In this case, both 30- and 50-rad doses required 5 hr for complete recovery of control behavior and showed the minimum and maximum in the T vs incubation time curve observed for incubation in the absence of caffeine following a dose of 100 rad.
- Research Organization:
- Univ., of California, San Francisco
- OSTI ID:
- 5174278
- Journal Information:
- Radiat. Res.; (United States), Vol. 90:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BIOLOGICAL REPAIR
INHIBITION
CAFFEINE
RADIOSENSITIVITY EFFECTS
DNA
BIOLOGICAL RADIATION EFFECTS
VISCOSITY
ANIMAL CELLS
DOSE-RESPONSE RELATIONSHIPS
IN VITRO
LOW DOSE IRRADIATION
PH VALUE
RATS
TUMOR CELLS
X RADIATION
ANALEPTICS
ANIMALS
BIOLOGICAL EFFECTS
BIOLOGICAL RECOVERY
CENTRAL NERVOUS SYSTEM AGENTS
DRUGS
ELECTROMAGNETIC RADIATION
HETEROCYCLIC COMPOUNDS
IONIZING RADIATIONS
IRRADIATION
MAMMALS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PURINES
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
RODENTS
VERTEBRATES
XANTHINES
560121* - Radiation Effects on Cells- External Source- (-1987)