The Experts below are selected from a list of 3483 Experts worldwide ranked by ideXlab platform
Peggy L Olive - One of the best experts on this subject based on the ideXlab platform.
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overnight lysis improves the efficiency of detection of dna damage in the alkaline comet assay
Radiation Research, 2001Co-Authors: Judit P Banath, Andrew Kim, Peggy L OliveAbstract:Abstract Banath, J. P., Kim, A. and Olive, P. L. Overnight Lysis Improves the Efficiency of Detection of DNA Damage in the Alkaline Comet Assay. The ability to detect DNA damage using the alkaline comet assay depends on pH, lysis time and temperature during lysis. However, it is not known whether different lysis conditions identify different types of DNA damage or simply measure the same damage with different efficiencies. Results support the latter interpretation for radiation, but not for the alkylating agent MNNG. For X-ray-induced damage, cells showed the same amount of damage, regardless of lysis pH (12.3 compared to >13). However, increasing the duRation of lysis at 5°C from 1 h to more than 6 h increased the amount of DNA damage detected by almost twofold. Another twofold increase in apparent damage was observed by conducting lysis at room temperature (22°C) for 6 h, but at the expense of a higher background level of DNA damage. The Oxygen Enhancement Ratio and the rate of rejoining of single-stran...
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radiation induced dna base damage detected in individual aerobic and hypoxic cells with endonuclease iii and formamidopyrimidine glycosylase
Radiation Research, 1999Co-Authors: Judit P Banath, Susan S Wallace, Jennifer Thompson, Peggy L OliveAbstract:X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the Oxygen Enhancement Ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4°C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37°C) was readily apparent after treatment with low concentRations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentRations. We conclude that: (1) the OER for base damage is 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.
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radiation induced dna base damage detected in individual aerobic and hypoxic cells with endonuclease iii and formamidopyrimidine glycosylase
Radiation Research, 1999Co-Authors: Judit P Banath, Susan S Wallace, Jennifer Thompson, Peggy L OliveAbstract:: X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the Oxygen Enhancement Ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4 degrees C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37 degrees C) was readily apparent after treatment with low concentRations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentRations. We conclude that: (1) the OER for base damage is approximately 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.
Judit P Banath - One of the best experts on this subject based on the ideXlab platform.
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overnight lysis improves the efficiency of detection of dna damage in the alkaline comet assay
Radiation Research, 2001Co-Authors: Judit P Banath, Andrew Kim, Peggy L OliveAbstract:Abstract Banath, J. P., Kim, A. and Olive, P. L. Overnight Lysis Improves the Efficiency of Detection of DNA Damage in the Alkaline Comet Assay. The ability to detect DNA damage using the alkaline comet assay depends on pH, lysis time and temperature during lysis. However, it is not known whether different lysis conditions identify different types of DNA damage or simply measure the same damage with different efficiencies. Results support the latter interpretation for radiation, but not for the alkylating agent MNNG. For X-ray-induced damage, cells showed the same amount of damage, regardless of lysis pH (12.3 compared to >13). However, increasing the duRation of lysis at 5°C from 1 h to more than 6 h increased the amount of DNA damage detected by almost twofold. Another twofold increase in apparent damage was observed by conducting lysis at room temperature (22°C) for 6 h, but at the expense of a higher background level of DNA damage. The Oxygen Enhancement Ratio and the rate of rejoining of single-stran...
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radiation induced dna base damage detected in individual aerobic and hypoxic cells with endonuclease iii and formamidopyrimidine glycosylase
Radiation Research, 1999Co-Authors: Judit P Banath, Susan S Wallace, Jennifer Thompson, Peggy L OliveAbstract:X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the Oxygen Enhancement Ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4°C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37°C) was readily apparent after treatment with low concentRations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentRations. We conclude that: (1) the OER for base damage is 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.
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radiation induced dna base damage detected in individual aerobic and hypoxic cells with endonuclease iii and formamidopyrimidine glycosylase
Radiation Research, 1999Co-Authors: Judit P Banath, Susan S Wallace, Jennifer Thompson, Peggy L OliveAbstract:: X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the Oxygen Enhancement Ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4 degrees C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37 degrees C) was readily apparent after treatment with low concentRations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentRations. We conclude that: (1) the OER for base damage is approximately 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.
E Scifoni - One of the best experts on this subject based on the ideXlab platform.
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kill painting of hypoxic tumours in charged particle therapy
Scientific Reports, 2015Co-Authors: Walter Tinganelli, Marco Durante, Andreas Maier, Ryoichi Hirayama, Michael R Kramer, Wilma Kraftweyrather, Yoshiya Furusawa, Thomas Friedrich, E ScifoniAbstract:Solid tumours often present regions with severe Oxygen deprivation (hypoxia), which are resistant to both chemotherapy and radiotherapy. Increased radiosensitivity as a function of the Oxygen concentRation is well described for X-rays. It has also been demonstrated that radioresistance in anoxia is reduced using high-LET radiation rather than conventional X-rays. However, the dependence of the Oxygen Enhancement Ratio (OER) on radiation quality in the regions of intermediate Oxygen concentRations, those normally found in tumours, had never been measured and biophysical models were based on extrapolations. Here we present a complete survival dataset of mammalian cells exposed to different ions in Oxygen concentRation ranging from normoxia (21%) to anoxia (0%). The data were used to generate a model of the dependence of the OER on Oxygen concentRation and particle energy. The model was implemented in the ion beam treatment planning system to prescribe uniform cell killing across volumes with heterogeneous radiosensitivity. The adaptive treatment plans have been validated in two different accelerator facilities, using a biological phantom where cells can be irradiated simultaneously at three different Oxygen concentRations. We thus realized a hypoxia-adapted treatment plan, which will be used for painting by voxel of hypoxic tumours visualized by functional imaging.
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let painting increases tumour control probability in hypoxic tumours
Acta Oncologica, 2014Co-Authors: Niels Bassler, E Scifoni, Michael R Kramer, J Toftegaard, Armin Luhr, Brita Singers Sorensen, Oliver Jakel, Lise Sakso Mortensen, Jens Overgaard, J B B PetersenAbstract:LET-painting was suggested as a method to overcome tumour hypoxia. In vitro experiments have demonstrated a well-established relationship between the Oxygen Enhancement Ratio (OER) and linear energy transfer (LET), where OER approaches unity for high-LET values. However, high-LET radiation also increases the risk for side effects in normal tissue. LET-painting attempts to restrict high-LET radiation to compartments that are found to be hypoxic, while applying lower LET radiation to normoxic tissues. Methods. Carbon-12 and Oxygen-16 ion treatment plans with four fields and with homogeneous dose in the target volume, are applied on an oropharyngeal cancer case with an identified hypoxic entity within the tumour. The target dose is optimised to achieve a tumour control probability (TCP) of 95% when assuming a fully normoxic tissue. Using the same primary particle energy fluence needed for this plan, TCP is recalculated for three cases assuming hypoxia: first, redistributing LET to match the hypoxic structure (LET-painting). Second, plans are recalculated for varying hypoxic tumour volume in order to investigate the threshold volume where TCP can be established. Finally, a slight dose boost (5-20%) is additionally allowed in the hypoxic subvolume to assess its impact on TCP. Results. LET-painting with carbon-12 ions can only achieve tumour control for hypoxic subvolumes smaller than 0.5 cm(3). Using Oxygen-16 ions, tumour control can be achieved for tumours with hypoxic subvolumes of up to 1 or 2 cm(3). Tumour control can be achieved for tumours with even larger hypoxic subvolumes, if a slight dose boost is allowed in combination with LET-painting. Conclusion. Our findings clearly indicate that a substantial increase in tumour control can be achieved when applying the LET-painting concept using Oxygen-16 ions on hypoxic tumours, ideally with a slight dose boost.
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including Oxygen Enhancement Ratio in ion beam treatment planning model implementation and experimental verification
Physics in Medicine and Biology, 2013Co-Authors: E Scifoni, Walter Tinganelli, W K Weyrather, Marco Durante, Andreas Maier, M KramerAbstract:We present a method for adapting a biologically optimized treatment planning for particle beams to a spatially inhomogeneous tumor sensitivity due to hypoxia, and detected e.g., by PET functional imaging. The TRiP98 code, established treatment planning system for particles, has been extended for including explicitly the Oxygen Enhancement Ratio (OER) in the biological effect calculation, providing the first set up of a dedicated ion beam treatment planning approach directed to hypoxic tumors, TRiP-OER, here reported together with experimental tests. A simple semi-empirical model for calculating the OER as a function of Oxygen concentRation and dose averaged linear energy transfer, generating input tables for the program is introduced. The code is then extended in order to import such tables coming from the present or alternative models, accordingly and to perform forward and inverse planning, i.e., predicting the survival response of differently Oxygenated areas as well as optimizing the required dose for restoring a uniform survival effect in the whole irradiated target. The multiple field optimization results show how the program selects the best beam components for treating the hypoxic regions. The calculations performed for different ions, provide indications for the possible clinical advantages of a multi-ion treatment. Finally the predictivity of the code is tested through dedicated cell culture experiments on extended targets irradiation using specially designed hypoxic chambers, providing a qualitative agreement, despite some limits in full survival calculations arising from the RBE assessment. The comparison of the predictions resulting by using different model tables are also reported.
Daniel S Kapp - One of the best experts on this subject based on the ideXlab platform.
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a computational model of radiolytic Oxygen depletion during flash irradiation and its effect on the Oxygen Enhancement Ratio
Physics in Medicine and Biology, 2019Co-Authors: Guillem Pratx, Daniel S KappAbstract:Recent results from animal irradiation studies have demonstrated the potential of ultra-high dose rate irradiation (also known as FLASH) for reducing radiation toxicity in normal tissues. However, despite mounting evidence of a "FLASH effect", a mechanism has yet to be elucidated. This article hypothesizes that the radioprotecting effect of FLASH irradiation could be due to the specific sparing of hypoxic stem cell niches, which have been identified in several organs including the bone marrow and the brain. To explore this hypothesis, a new computational model is presented that frames transient radiolytic Oxygen depletion (ROD) during FLASH irradiation in terms of its effect on the Oxygen Enhancement Ratio (OER). The model takes into consideRation Oxygen diffusion through the tissue, its consumption by metabolic cells, and its radiolytic depletion to estimate the relative decrease in radiosensitivity of cells receiving FLASH irradiation. Based on this model and the following parameters (Oxygen diffusion constant Dalt;subagt;O2alt;/subagt; = 210alt;supagt;5alt;/supagt; cmalt;supagt;2alt;/supagt; salt;supagt;-1alt;/supagt;, Oxygen metabolic rate m = 3 mmHg salt;supagt;-1alt;/supagt;, ROD rate alt;Iagt;Lalt;/iagt;alt;subagt;RODalt;/subagt; = 0.42 mmHg Gyalt;supagt;-1alt;/supagt;, prescribed dose Dp = 10 Gy, and capillary Oxygen tension palt;subagt;0alt;/subagt; = 40 mmHg), several predictions are made that could be tested in future experiments: (1) the FLASH effect should gradually disappear as the radiation pulse duRation is increased from alt;1 s to 10 s; (2) dose should be deposited using the smallest number of radiation pulses to achieve the greatest FLASH effect; (3) a FLASH effect should only be observed in cells that are already hypoxic at the time of irradiation; and (4) changes in capillary Oxygen tension (increase or decrease) should diminish the FLASH effect.
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a computational model of radiolytic Oxygen depletion during flash irradiation and its effect on the Oxygen Enhancement Ratio
arXiv: Medical Physics, 2019Co-Authors: Guillem Pratx, Daniel S KappAbstract:Recent results from animal irradiation studies have rekindled interest in the potential of ultra-high dose rate irradiation (also known as FLASH) for reducing normal tissue toxicity. However, despite mounting evidence of a "FLASH effect", a mechanism has yet to be elucidated. This article hypothesizes that the radioprotecting effect of FLASH irradiation could be due to the specific sparing of hypoxic stem cell niches, which have been identified in several organs including the bone marrow and the brain. To explore this hypothesis, a new computational model is presented that frames transient radiolytic Oxygen depletion (ROD) during FLASH irradiation in terms of its effect on the Oxygen Enhancement Ratio (OER). The model takes into consideRation Oxygen diffusion through the tissue, its consumption by metabolic cells, and its radiolytic depletion to estimate the relative decrease in radiosensitivity of cells receiving FLASH irradiation. Based on this model, several predictions are made that could be tested in future experiments: (1) the FLASH effect should gradually disappear as the radiation pulse duRation is increased from <1s to 10 s; (2) dose should be deposited using the smallest number of radiation pulses to achieve the greatest FLASH effect; (3) a FLASH effect should only be observed in cells that are already hypoxic at the time of irradiation; and (4) changes in capillary Oxygen tension (increase or decrease) should diminish the FLASH effect.
Jennifer Thompson - One of the best experts on this subject based on the ideXlab platform.
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radiation induced dna base damage detected in individual aerobic and hypoxic cells with endonuclease iii and formamidopyrimidine glycosylase
Radiation Research, 1999Co-Authors: Judit P Banath, Susan S Wallace, Jennifer Thompson, Peggy L OliveAbstract:X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the Oxygen Enhancement Ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4°C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37°C) was readily apparent after treatment with low concentRations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentRations. We conclude that: (1) the OER for base damage is 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.
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radiation induced dna base damage detected in individual aerobic and hypoxic cells with endonuclease iii and formamidopyrimidine glycosylase
Radiation Research, 1999Co-Authors: Judit P Banath, Susan S Wallace, Jennifer Thompson, Peggy L OliveAbstract:: X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the Oxygen Enhancement Ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4 degrees C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37 degrees C) was readily apparent after treatment with low concentRations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentRations. We conclude that: (1) the OER for base damage is approximately 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.
