| 1. |
- Ainsbury, Elizabeth A., et al.
(författare)
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Uncertainty of fast biological radiation dose assessment for emergency response scenarios
- 2017
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 93:1, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Reliable dose estimation is an important factor in appropriate dosimetric triage categorization of exposed individuals to support radiation emergency response. Materials and methods: Following work done under the EU FP7 MULTIBIODOSE and RENEB projects, formal methods for defining uncertainties on biological dose estimates are compared using simulated and real data from recent exercises. Results: The results demonstrate that a Bayesian method of uncertainty assessment is the most appropriate, even in the absence of detailed prior information. The relative accuracy and relevance of techniques for calculating uncertainty and combining assay results to produce single dose and uncertainty estimates is further discussed. Conclusions: Finally, it is demonstrated that whatever uncertainty estimation method is employed, ignoring the uncertainty on fast dose assessments can have an important impact on rapid biodosimetric categorization.
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| 2. |
- Akuwudike, Pamela, 1987-, et al.
(författare)
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Mechanistic insights from high resolution DNA damage analysis to understand mixed radiation exposure
- 2023
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Ingår i: DNA Repair. - 1568-7864 .- 1568-7856. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- Cells exposed to densely ionising high and scattered low linear energy transfer (LET) radiation (50 % dose of each) react more strongly than to the same dose of each separately. The relationship between DNA double strand break location inside the nucleus and chromatin structure was evaluated, using high-resolution transmission electron microscopy (TEM) in breast cancer MDA-MB-231 cells at 30 min post 5 Gy. Additionally, response to high and/or low LET radiation was assessed using single (1 ×1.5 Gy) versus fractionated dose delivery (5 ×0.3 Gy). By TEM analysis, the highest total number of γH2AX nanobeads were found in cells irradiated with alpha radiation just prior to gamma radiation (called mixed beam), followed by alpha, then gamma radiation. γH2AX foci induced by mixed beam radiation tended to be surrounded by open chromatin (lighter TEM regions), yet foci containing the highest number of beads, i.e. larger foci representing complex damage, remained in the heterochromatic areas. The γH2AX large focus area was also greater in mixed beam-treated cells when analysed by immunofluorescence. Fractionated mixed beams given daily induced the strongest reduction in cell viability and colony formation in MDA-MB-231 and osteosarcoma U2OS cells compared to the other radiation qualities, as well as versus acute exposure. This may partially be explained by recurring low LET oxidative DNA damage by every fraction together with a delay in recompaction of chromatin after high LET, demonstrated by low levels of heterochromatin marker H3K9me3 at 2 h after the last mixed beam fraction in MDA-MB-231. In conclusion, early differences in response to complex DNA damage may lead to a stronger cell kill induced by fractionated exposure, which suggest a therapeutic potential of combined high and low LET irradiation.
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| 3. |
- Blomgren, August, et al.
(författare)
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Home-made low-cost dosemeter for photon dose measurements in radiobiological experiments and for education in the field of radiation sciences
- 2024
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Ingår i: Radiation and Environmental Biophysics. - 0301-634X .- 1432-2099. ; 63, s. 395-404
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Tidskriftsartikel (refereegranskat)abstract
- Reliable dosimetry systems are crucial for radiobiological experiments either to quantify the biological consequences of ionizing radiation or to reproduce results by other laboratories. Also, they are essential for didactic purposes in the field of radiation research. Professional dosemeters are expensive and difficult to use in exposure facilities with closed exposure chambers. Consequently, a simple, inexpensive, battery-driven dosemeter was developed that can be easily built using readily available components. Measurements were performed to validate its readout with photons of different energy and dose rate and to demonstrate the applicability of the dosemeter. It turned out that the accuracy of the dose measurements using the developed dosemeter was better than 10%, which is satisfactory for radiobiological experiments. It is concluded that this dosemeter can be used both for determining the dose rates of an exposure facility and for educational purposes.
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| 4. |
- Brzozowska, Beata, et al.
(författare)
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Freeware tool for analysing numbers and sizes of cell colonies
- 2019
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Ingår i: Radiation and Environmental Biophysics. - : Springer Science and Business Media LLC. - 0301-634X .- 1432-2099. ; 58:1, s. 109-117
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Tidskriftsartikel (refereegranskat)abstract
- The clonogenic cell survival assay is a basic method to study the cytotoxic effect of radiation and chemical toxins. In large experimental setups, counting of colonies by eye is tiresome and prone to bias. Moreover, it is often interesting to quantify the size of individual colonies. Such analyses are largely facilitated by computerised image analysis systems. Although a number of such systems exist, they all focus on enumerating colonies and not on analysing the colony size. We have developed a new software package for both counting colonies and plotting their size distributions. The software called count and Plot HIstograms of Colony Size(countPHICS) consists of two parts: (1) a macro written for ImageJ which analyses computerised images of cell culture dishes or 6-well plates, counts colonies, estimates their size and saves the results in a text file; (2) a program written with QT Creator which reads the text file, plots histograms of colony size distribution and fits the best function. The full program is freely available at: http://www.fuw.edu.pl/similar to bbrzozow/FizMed/countPHICS.html. In conclusion, our new publically available software will facilitate colony counting and provide additional information on the colony growth rate, which is relevant especially for radiosensitisation studies.
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| 5. |
- Brzozowska, Beata, et al.
(författare)
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Monte Carlo Modeling of DNA Lesions and Chromosomal Aberrations Induced by Mixed Beams of Alpha Particles and X-Rays
- 2020
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Ingår i: Frontiers in Physics. - : Frontiers Media SA. - 2296-424X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Prediction of health risks associated with exposure to mixed beams of high- and low-linear energy transfer ionizing radiation is based on the assumption that the biological effect caused by mixed radiation equals the sum of effects resulting from the action of individual beam components. Experimental studies have demonstrated that the cellular effects in cells exposed to mixed radiations are higher than that calculated based on the assumption of additivity. The present work contains a comparative analysis of published results on chromosomal aberrations in human peripheral blood lymphocytes exposed to mixed beams of alpha particles and X-rays with computer simulations using the PARTRAC program based on Monte Carlo methods. PARTRAC was used to calculate the levels of DNA single-strand breaks (SSB) and double-strand breaks (DSB—both complex and simple) and the level of chromosomal aberrations. SSB and DSB yields were found to be additive. A synergistic effect was obtained at the level of chromosomal aberrations, being in good agreement with the experimental results. This result demonstrates that the synergistic action of mixed beams results from processing of SSB and DSB and not from their initial frequencies. The level of synergy was dependent on the composition of the mixed beam, with highest level at 50:50 ratio of alpha particles and X-rays.
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| 6. |
- Brzozowska, Beata, et al.
(författare)
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RENEB accident simulation exercise
- 2017
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 93:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The RENEB accident exercise was carried out in order to train the RENEB participants in coordinating and managing potentially large data sets that would be generated in case of a major radiological event. Materials and methods: Each participant was offered the possibility to activate the network by sending an alerting email about a simulated radiation emergency. The same participant had to collect, compile and report capacity, triage categorization and exposure scenario results obtained from all other participants. The exercise was performed over 27 weeks and involved the network consisting of 28 institutes: 21 RENEB members, four candidates and three non-RENEB partners. Results: The duration of a single exercise never exceeded 10 days, while the response from the assisting laboratories never came later than within half a day. During each week of the exercise, around 4500 samples were reported by all service laboratories (SL) to be examined and 54 scenarios were coherently estimated by all laboratories (the standard deviation from the mean of all SL answers for a given scenario category and a set of data was not larger than 3 patient codes). Conclusions: Each participant received training in both the role of a reference laboratory (activating the network) and of a service laboratory (responding to an activation request). The procedures in the case of radiological event were successfully established and tested.
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| 7. |
- Cheng, Lei, et al.
(författare)
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Comet assay reveals an interaction of DNA lesions and impairment of DNA repair in peripheral blood lymphocytes simultaneously exposed to alpha particles and X-rays
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The biological effectiveness of ionising radiation is related to the ionisation density which is defined by the linear energy transfer LET. Radiation quality factors are applied to calculate the equivalent dose in the field of radiation protection and the biologically effective dose in the field of radiotherapy. Additivity is assumed in exposure scenarios where radiations of different qualities are mixed. We have carried out a series of studies on the cytogenetic effect of exposing human peripheral blood lymphocytes to a mixed beam of the high LET alpha radiation and low LET X-rays and could demonstrate that both radiations interact in producing more chromosomal aberrations than expected based on additivity. The aim of the present investigation was to look at the mechanism of the interaction, especially with respect to the question if it is due to an augmented level of initial damage or impaired DNA repair. The level of DNA damage and the kinetics of damage repair was quantified by the alkaline comet assay. The levels of phosphorylated, key DNA damage response (DDR) proteins were also measured by Western blotting. The results revealed that alpha particles and X-rays interact in inducing DNA damage above the level predicted by assuming additivity and that the repair of damage occurs with a delay. Moreover, the activation levels of the key DDR proteins ATM, p53 and DNA PK were highest in cells exposed to mixed beams substantiating the idea exposure to mixed beams presents a challenge to the cellular DNA damage response system.
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| 8. |
- Cheng, Lei, et al.
(författare)
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Impact of ATM and DNA-PK Inhibition on Gene Expression and Individual Response of Human Lymphocytes to Mixed Beams of Alpha Particles and X-Rays
- 2019
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Ingår i: Cancers. - : MDPI AG. - 2072-6694. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Accumulating evidence suggests a synergistic effect in cells simultaneously exposed to different types of clustered and dispersed DNA damage. We aimed to analyse the effect of mixed beams of alpha particles and X-rays (1:1 dose of each) on DNA damage response genes in human peripheral blood lymphocytes isolated from four donors. Two donors were compared upon inhibition of ATM or DNA-PK and at different sampling times. qPCR was used to measure mRNA levels of FDXR, GADD45A, BBC3, MDM2, CDKN1A, and XPC 24 h following exposure. Generally, alpha particles and mixed beams were stronger inducers of gene expression compared to X-rays, displaying saturated versus linear dose-response curves, respectively. Three out of four donors responded synergistically to mixed beams. When two donors were sampled again one year later, the former additive effect in one donor was now synergistic and no significant difference in intrinsic radiosensitivity was displayed, as determined by gamma-radiation-induced micronuclei. ATM, but not DNA-PK inhibition, reduced the radiation-induced gene expression, but differently for alpha radiation between the two donors. In conclusion, synergy was present for all donors, but the results suggest individual variability in the response to mixed beams, most likely due to lifestyle changes.
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| 9. |
- Cheng, Lei, et al.
(författare)
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Simultaneous induction of dispersed and clustered DNA lesions compromises DNA damage response in human peripheral blood lymphocytes
- 2018
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- Due to its ability to induce DNA damage in a space and time controlled manner, ionising radiation is a unique tool for studying the mechanisms of DNA repair. The biological effectiveness of ionising radiation is related to the ionisation density which is defined by the linear energy transfer (LET). Alpha particles are characterised by high LET, while X-rays by low LET values. An interesting question is how cells react when exposed to a mixed beam of high and low LET radiation. In an earlier study carried out with human peripheral blood lymphocytes (PBL) we could demonstrate that alpha radiation X-rays interact in producing more chromosomal aberrations than expected based on additivity. The aim of the present investigation was to look at the mechanism of the interaction, especially with respect to the question if it is due to an augmented level of initial damage or impaired DNA repair. PBL were exposed to various doses of alpha particles, X-rays and mixed beams. DNA damage and the kinetics of damage repair was quantified by the alkaline comet assay. The levels of phosphorylated, key DNA damage response (DDR) proteins ATM, p53 and DNA-PK were measured by Western blotting and mRNA levels of 6 damage-responsive genes were measured by qPCR. Alpha particles and X-rays interact in inducing DNA damage above the level predicted by assuming additivity and that the repair of damage occurs with a delay. The activation levels of DDR proteins and mRNA levels of the studied genes were highest in cells exposed to mixed beams. The results substantiate the idea that exposure to mixed beams presents a challenge for the cellular DDR system.
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| 10. |
- Eriksson, Mina, et al.
(författare)
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Analysis of Chromatin Opening in Heterochromatic Non-Small Cell Lung Cancer Tumor-Initiating Cells in Relation to DNA-Damaging Antitumor Treatment
- 2018
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier BV. - 0360-3016 .- 1879-355X. ; 100:1, s. 174-187
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: We previously reported that sphere-forming non-small cell lung cancer (NSCLC) tumor-initiating cells (TICs) have an altered activation of DNA damage response-and repair proteins and are refractory to DNA-damaging treatments. We analyzed whether chromatin organization plays a role in the observed refractoriness.Methods and Materials: Bulk cells and TICs from the NSCLC H23 and H1299 cell lines were examined using cell viability, clonogenic survival, Western blot, short interfering RNA analysis, and micronucleus assay.Results: NSCLC TICs displayed elevated heterochromatin markers trimethylated lysine 9 of histone H3 and heterochromatin protein 1 gamma relative to bulk cells and reduced cell viability upon histone deacetylase inhibition (HDACi). Vorinostat and trichostatin A increased the euchromatin markers acetylated lysine 9/14 of histone H3 and lysine 8 of histone H4, and HDACi pretreatment increased the phosphorylation of the DNA damage response proteins ataxia telangiectasia mutated and DNA-dependent protein kinase, catalytic subunit, upon irradiation in TICs. HDACi sensitized TICs to cisplatin and to some extent to ionizing irradiation. The protectiveness of a dense chromatin structure was indicated by an enhanced frequency of micronuclei in TICs following irradiation, after knockdown of heterochromatin protein 1 gamma.Conclusions: Although confirmatory studies in additional NSCLC model systems and with respect to analyses of other DNA damage response proteins are needed, our data point toward a heterochromatic structure of NSCLC TICs, such that HDACi can sensitize TICs to DNA damage.
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