| 1. |
|
|
| 2. |
- Ahnström, G., et al.
(författare)
-
The effect of dimethyl sulphoxide on the induction and repair of double-strand breaks in human cells after irradiation with γ-rays and accelerated ions : Rapid or slow repair may depend on accessibility of breaks in chromatin of different compactness
- 2000
-
Ingår i: International Journal of Radiation Biology. - 0955-3002 .- 1362-3095. ; 76:4, s. 533-538
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: The repair of double-strand breaks (dsb) in mammalian cells is characterized by a rapid phase with a half-life of less than half an hour and a slower phase that lasts for many hours. The proportion of slow repair increase with LET and it has been suggested that the slow repair component consists of more complex damage and is more deleterious to the cells. To see if removal of OH radicals could remove part of the damage in complex dsb and make them easier to repair, human cells were irradiated in the presence of dimethyl sulphoxide (DMSO). Methods: Induction and repair of dsb were studied by neutral elution in human VH10 cells exposed to γ-rays, helium ions (mean LET 40 keV/μm) and 80 and 125 keV/μm monoenergetic nitrogen ions in the presence and absence of 2 M DMSO. Results: Incubation of cells exposed to γ-rays, 40 keV/μm helium and 80 keV/μm N ions demonstrated that scavenging of OH radicals by DMSO removed most of the rapid repair component. The response to DMSO was less marked after 125 keV/μm nitrogen ions, where about half of the repair was resistant to DMSO. Conclusions: It is unlikely that the complexity of dsb is responsible for the slow repair because the removal of OH radicals did not make the breaks easier to repair. Instead, it is suggested that rapid and slow repair can be explained on the basis of how different parts of the chromatin are accessible to repair enzymes.
|
|
| 3. |
- Brzozowska, Kinga, et al.
(författare)
-
Effect of temperature during irradiation on the level of micronuclei in human peripheral blood lymphocytes exposed to X-rays and neutrons.
- 2009
-
Ingår i: International Journal of Radiation Biology. - 0955-3002 .- 1362-3095. ; , s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: It has been reported that the level of cytogenetic damage in human peripheral blood lymphocytes (PBL) is higher following irradiation at 37 degrees C than at 0-4 degrees C. The mechanisms of this cytogenetic temperature effect are not fully known. The aim of our study was to check whether the effect was related to the indirect or direct action of radiation. Materials and methods: PBL were kept at 37 degrees C and 0 degrees C for 20 min and exposed to 2 Gy of X-rays. In some experiments PBL were isolated and 0.5 M dimethyl sulfoxide (DMSO) was added for 5 min before exposure. PBL were also irradiated at 37 degrees C and 0 degrees C with 1 Gy of 6 MeV neutrons. Micronuclei were scored as the endpoint. Following exposure to X-rays the level of initial DNA damage was also measured by the alkaline and neutral comet assay. Results: The frequency of micronuclei in cells exposed at 37 degrees C to X-rays or neutrons was higher than that after exposure at 0 degrees C. No effect of temperature was seen when PBL were exposed to X-rays in the presence of DMSO. No effect of temperature was observed on the level of DNA damage measured with the alkaline or neutral comet assay. Conclusions: The results of experiments with DMSO indicate that the temperature effect is due to the indirect action of radiation, i.e., via reactive oxygen species. However, this is not supported by the results with neutrons and the comet assay. Possible reasons for the discrepancies are discussed.
|
|
| 4. |
|
|
| 5. |
- Elmroth, Kerstin, 1970, et al.
(författare)
-
Chromatin- and temperature-dependent modulation of radiation-induced double-strand breaks
- 2003
-
Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 79:10, s. 809-816
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the influence of chromatin organization and scavenging capacity in relation to irradiation temperature on the induction of double-strand breaks (DSB) in structures derived from human diploid fibroblasts. Materials and methods: Agarose plugs with different chromatin structures (intact cells±wortmannin, permeabilized cells with condensed chromatin, nucleoids and DNA) were prepared and irradiated with X-rays at 2 or 37°C and lysed using two different lysis protocols (new ice-cold lysis or standard lysis at 37°C). Induction of DSB was determined by constant-field gel electrophoresis. Results: The dose-modifying factor (DMFtemp) for irradiation at 37 compared with 2°C was 0.92 in intact cells (i.e. more DSB induced at 2°C), but gradually increased to 1.5 in permeabilized cells, 2.2 in nucleoids and 2.6 in naked DNA, suggesting a role of chromatin organization for temperature modulation of DNA damage. In addition, DMFtemp was influenced by the presence of 0.1 M DMSO or 30 mM glutathione, but not by post-irradiation temperature. Conclusion: The protective effect of low temperature was correlated to the indirect effects of ionizing radiation and was not dependent on post-irradiation temperature. Reasons for a dose modifying factor <1 in intact cells are discussed.
|
|
| 6. |
- Elmroth, Kerstin, 1970, et al.
(författare)
-
Radiation-induced double-strand breaks in mammalian DNA: influence of temperature and DMSO
- 2000
-
Ingår i: Int J Radiat Biol. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 76:11, s. 1501-8
-
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.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
