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- Elmroth, Kerstin, 1970, et al.
(författare)
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Radiation-induced double-strand breaks in mammalian DNA: influence of temperature and DMSO
- 2000
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Ingår i: Int J Radiat Biol. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 76:11, s. 1501-8
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the effects of subphysiological irradiation temperature (2 28 degrees C) and the influence of the radical scavenger DMSO on the induction of double-strand breaks (DSB) in chromosomal DNA from a human breast cancer cell line (MCF-7) as well as in intact cells. The rejoining of DSB in cells irradiated at 2 degrees C or 37 degrees C was also investigated. MATERIALS AND METHODS: Agarose plugs with [14C]thymidine labelled MCF-7 cells were lysed in EDTA-NLS-proteinase-K buffer. The plugs containing chromosomal DNA were irradiated with X-rays under different temperatures and scavenging conditions. Intact MCF-7 cells were irradiated in Petri dishes and plugs were made. The cells were then lysed in EDTA-NLS-proteinase-K buffer. The induction of DSB was studied by constant field gel electrophoresis and expressed as DSB/100/Mbp, calculated from the fraction of activity released into the gel. RESULTS: The induction of DSB in chromosomal DNA was reduced by a decrease in temperature. This protective effect of low temperature was inhibited when the DNA was irradiated in the presence of DMSO. No difference was found when intact cells were irradiated at different temperatures. However, the rapid phase of rejoining was slower in cells irradiated at 37 degrees C than at 2 degrees C. CONCLUSIONS: The induction of DSB in naked DNA was reduced by hypothermic irradiation. The temperature had no influence on the induction of DSB in the presence of a high concentration of DMSO, indicating that the temperature effect is mediated via the indirect effects of ionizing radiation. Results are difficult to interpret in intact cells. Rejoining during irradiation at the higher temperature may counteract an increased induction. The difference in rejoining may be interpreted in terms of qualitative differences between breaks induced at the two temperatures.
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| 2. |
- Elmroth, Kerstin, 1970, et al.
(författare)
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Influence of temperature on radiation-induced inhibition of DNA supercoiling
- 1999
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Ingår i: Radiat Res. - 0033-7587. ; 152:2, s. 137-43
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Tidskriftsartikel (refereegranskat)abstract
- The influence of subnormal temperatures (2, 15 and 28 degrees C) on the effects of radiation in MCF-7 cell cultures was studied using the fluorescent (halo) nucleoid assay. Increasing the propidium iodide (PI) concentration (0.5-7.5 microgram/ml PI) resulted in relaxation, i.e. in increasing nucleoid area; higher concentrations up to 50 microgram/ml caused rewinding that resulted in nucleoid contraction. Rewinding was inhibited by X irradiation (2, 4 and 8 Gy) in a dose-dependent way. Incubation at subnormal temperature did not influence the nucleoid area but did reduce radiation-induced inhibition of rewinding after 4 Gy. The low temperature (2 degrees C) during rather than prior to irradiation appeared to protect from radiation-induced inhibition of nucleoid rewinding. Decreased temperature during irradiation may change the conditions so as to reduce DNA- matrix damage induced by radiation.
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| 3. |
- Elmroth, Kerstin, 1970, et al.
(författare)
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Radiation and hypothermia: changes in DNA supercoiling in human diploid fibroblasts
- 1999
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Ingår i: Anticancer Res. - 0250-7005 .- 1791-7530. ; 19:6B, s. 5307-11
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Tidskriftsartikel (refereegranskat)abstract
- The influence of hypothermia (2 degrees, 15 degrees and 28 degrees C) upon the effect of X-irradiation on chromatin from human diploid fibroblast cells (AG1518) was studied using the fluorescent halo assay. Rewinding of supercoils was inhibited in a dose-dependent manner when cells were irradiated with 4, 8 or 16 Gy. This inhibition of rewinding was reduced when cells were irradiated at subnormal temperatures compared with cells irradiated at 37 degrees C. One hour's preincubation at low temperature did not influence rewinding. When AG1518 cells were irradiated at 37 degrees C in the presence of the radical scavenger DMSO (0.5 M), the radiation-induced damage was reduced. No additional protection of DMSO in hypothermic cells (2 degrees C) was found, possibly indicating that OH-radical-mediated effects are more temperature dependent. These results are similar to those recently found for the malignant MCF-7 cell line.
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