Showing papers in "Radiation Research in 2006"
TL;DR: The estimated α terms of the liner-quadratic model with a fixed β value reproduced the experimental results for cell irradiation for ion beams with LETs of less than 450 keV/μm, except in the region near the distal peak.
Abstract: Kase, Y., Kanai, T., Matsumoto, Y., Furusawa, Y., Okamoto, H., Asaba, T., Sakama, M. and Shinoda, H. Microdosimetric Measurements and Estimation of Human Cell Survival for Heavy-Ion Beams. Radiat. Res. 166, 629–638 (2006). The microdosimetric spectra for high-energy beams of photons and proton, helium, carbon, neon, silicon and iron ions (LET = 0.5–880 keV/μm) were measured with a spherical-walled tissue-equivalent proportional counter at various depths in a plastic phantom. Survival curves for human tumor cells were also obtained under the same conditions. Then the survival curves were compared with those estimated by a microdosimetric model based on the spectra and the biological parameters for each cell line. The estimated α terms of the liner-quadratic model with a fixed β value reproduced the experimental results for cell irradiation for ion beams with LETs of less than 450 keV/μm, except in the region near the distal peak.
250 citations
TL;DR: It is proposed that LTGF-β1 contains a redox switch centered at methionine 253, which allows it to act uniquely as an extracellular sensor of oxidative stress in tissues and suggest that ROS-induced oxidation in LAP-β 1 triggers a conformational change that releases TGF- β1.
Abstract: The three mammalian transforming growth factor beta (TGF-beta) isoforms are each secreted in a latent complex in which TGF-beta homodimers are non-covalently associated with homodimers of their respective pro-peptide called the latency-associated peptide (LAP). Release of TGF-beta from its LAP, called activation, is required for binding of TGF-beta to cellular receptors, making extracellular activation a critical regulatory point for TGF-beta bioavailability. Our previous work demonstrated that latent TGF-beta1 (LTGF-beta1) is efficiently activated by ionizing radiation in vivo and by reactive oxygen species (ROS) generated by Fenton chemistry in vitro. In the current study, we determined the specific ROS and protein target that render LTGF-beta1 redox sensitive. First, we compared LTGF-beta1, LTGF-beta2 and LTGF-beta3 to determine the generality of this mechanism of activation and found that redox-mediated activation is restricted to the LTGF-beta1 isoform. Next, we used scavengers to determine that ROS activation was a function of OH(.) availability, confirming oxidation as the primary mechanism. To identify which partner of the LTGF-beta1 complex was functionally modified, each was exposed to ROS and tested for the ability to form a latent complex. Exposure of TGF-beta1 did not alter its ability to associate with LAP, but exposing LAP-beta1 to ROS prohibited this phenomenon, while treatment of ROS-exposed LAP-beta1 with a mild reducing agent restored its ability to neutralize TGF-beta1 activity. Taken together, these results suggest that ROS-induced oxidation in LAP-beta1 triggers a conformational change that releases TGF-beta1. Using site-specific mutation, we identified a methionine residue at amino acid position 253 unique to LAP-beta1 as critical to ROS-mediated activation. We propose that LTGF-beta1 contains a redox switch centered at methionine 253, which allows LTGF-beta1 to act uniquely as an extracellular sensor of oxidative stress in tissues.
241 citations
TL;DR: Methods developed specifically for reconstructing individual organ- and tissue-absorbed dose of radiation from past exposures from medical treatments and procedures for use in epidemiological studies are described and compared.
Abstract: This paper describes methods developed specifically for reconstructing individual organ- and tissue-absorbed dose of radiation from past exposures from medical treatments and procedures for use in epidemiological studies. These methods have evolved over the past three decades and have been applied to a variety of medical exposures including external-beam radiation therapy and brachytherapy for malignant and benign diseases as well as diagnostic examinations. The methods used for estimating absorbed dose to organs in and outside the defined treatment volume generally require archival data collection, abstraction and review, and phantom measurements to simulate past exposure conditions. Three techniques are used to estimate doses from radiation therapy: (1) calculation in three-dimensional mathematical computer models using an extensive database of out-of-beam doses measured in tissue-equivalent materials, (2) measurement in anthropomorphic phantoms constructed of tissue-equivalent material, and (3) calculation using a three-dimensional treatment-planning computer. For diagnostic exposures, doses are estimated from published data and software based on Monte Carlo techniques. We describe and compare these methods of dose estimation and discuss uncertainties in estimated organ doses and potential for future improvement. Seven epidemiological studies are discussed to illustrate the methods.
219 citations
TL;DR: Investigation of MAPK signaling pathways in bystander cells exposed to irradiated cell conditioned medium found reactive oxygen species, such as superoxide and hydrogen peroxide, and calcium signaling were found to be important modulators of bystander responses.
Abstract: Much evidence now exists regarding radiation-induced bystander effects, but the mechanisms involved in the transduction of the signal are still unclear. The mitogen-activated protein kinase (MAPK) pathways have been linked to growth factor-mediated regulation of cellular events such as proliferation, senescence, differentiation and apoptosis. Activation of multiple MAPK pathways such as the ERK, JNK and p38 pathways have been shown to occur after exposure of cells to radiation and a variety of other toxic stresses. Previous studies have shown oxidative stress and calcium signaling to be important in radiation-induced bystander effects. The aim of the present study was to investigate MAPK signaling pathways in bystander cells exposed to irradiated cell conditioned medium (ICCM) and the role of oxidative metabolism and calcium signaling in the induction of bystander responses. Human keratinocytes (HPV-G cell line) were irradiated (0.005-5 Gy) using a cobalt-60 teletherapy unit. The medium was harvested 1 h postirradiation and transferred to recipient HPV-G cells. Phosphorylated forms of p38, JNK and ERK were studied by immunofluorescence 30 min-24 h after exposure to ICCM. Inhibitors of the ERK pathway (PD98059 and U0126), the JNK pathway (SP600125), and the p38 pathway (SB203580) were used to investigate whether bystander-induced cell death could be blocked. Cells were also incubated with ICCM in the presence of superoxide dismutase, catalase, EGTA, verapamil, nifedipine and thapsigargin to investigate whether bystander effects could be inhibited because of the known effects on calcium homeostasis. Activated forms of JNK and ERK proteins were observed after exposure to ICCM. Inhibition of the ERK pathway appeared to increase bystander-induced apoptosis, while inhibition of the JNK pathway appeared to decrease apoptosis. In addition, reactive oxygen species, such as superoxide and hydrogen peroxide, and calcium signaling were found to be important modulators of bystander responses. Further investigations of these signaling pathways may aid in the identification of novel therapeutic targets.
202 citations
TL;DR: The cohorts and the history and evolution of dose estimation from early efforts through the newest system, DS02, emphasizing the technical development and use of DS02 are described, and current efforts and plans for further improvements are described.
Abstract: Cullings, H. M., Fujita, S., Funamoto, S., Grant, E. J., Kerr, G. D. and Preston, D. L. Dose Estimation for Atomic Bomb Survivor Studies: Its Evolution and Present Status. Radiat. Res. 166, 219–254 (2006). In the decade after the bombings of Hiroshima and Nagasaki, several large cohorts of survivors were organized for studies of radiation health effects. The U.S. Atomic Bomb Casualty Commission (ABCC) and its U.S./Japan successor, the Radiation Effects Research Foundation (RERF), have performed continuous studies since then, with extensive efforts to collect data on survivor locations and shielding and to create systems to estimate individual doses from the bombs' neutrons and γ rays. Several successive systems have been developed by extramural working groups and collaboratively implemented by ABCC and RERF investigators. We describe the cohorts and the history and evolution of dose estimation from early efforts through the newest system, DS02, emphasizing the technical development and use of DS0...
162 citations
TL;DR: The work shows that the size and frequency of radiation-induced foci vary as a function of radiation quality, dose, time and protein target, and the dynamic nature of both contradicts their accepted equivalence for low doses of different radiation qualities.
Abstract: Costes, S. V., Boissiere, A., Ravani, S., Romano, R., Parvin, B. and Barcellos-Hoff, M. H. Imaging Features that Discriminate between Foci Induced by High- and Low-LET Radiation in Human Fibroblasts. Radiat. Res. 165, 505–515 (2006). In this study, we investigated the formation of radiation-induced foci in normal human fibroblasts exposed to X rays or 130 keV/μm nitrogen ions using antibodies to phosphorylated protein kinase ataxia telangiectasia mutated (ATMp) and histone H2AX (γ-H2AX). High-content automatic image analysis was used to quantify the immunofluorescence of radiation-induced foci. The size of radiation-induced foci increased for both proteins over a 2-h period after nitrogen-ion irradiation, while the size of radiation-induced foci did not change after exposure to low-LET radiation. The number of radiation-induced ATMp foci showed a more rapid rise and greater frequency after X-ray exposure and was resolved more rapidly such that the frequency of radiation-induced foci decreased by ...
159 citations
TL;DR: A clinically relevant regimen of fractionated whole-brain irradiation led to significant impairments in spatial learning and reference memory and alterations in the relative levels of subunits of the NMDA, but not the AMPA, receptors in hippocampal CA1, suggesting for the first time that radiation-induced cognitive impairments may be associated with alterations in glutamate receptor composition.
Abstract: Shi, L., Adams, M. M., Long, A., Carter, C. C., Bennett, C., Sonntag, W. E., Nicolle, M. M., Robbins, M., D'Agostino, R., Jr. and Brunso-Bechtold, J. K. Spatial Learning and Memory Deficits after Whole-Brain Irradiation are Associated with Changes in NMDA Receptor Subunits in the Hippocampus. Radiat. Res. 166, 892–899 (2006). Whole-brain irradiation is used for the treatment of brain tumors, but can it also induce neural changes, with progressive dementia occurring in 20–50% of long-term survivors. The present study investigated whether 45 Gy of whole-brain irradiation delivered to 12-month-old Fischer 344 × Brown Norway rats as nine fractions over 4.5 weeks leads to impaired Morris water maze (MWM) performance 12 months later. Compared to sham-irradiated rats, the irradiated rats demonstrated impaired MWM performance. The relative levels of the NR1 and NR2A but not the NR2B subunits of the NMDA receptor were significantly higher in hippocampal CA1 of irradiated rats compared to control rats. No ...
156 citations
TL;DR: The results indicate that high-LET radiation induces complex DNA damage that is not easily repaired or is not repaired by NHEJ even at low radiation doses such as 2 Gy, and this phase is likely to result from a defective N HEJ protein.
Abstract: Okayasu, R., Okada, M., Okabe, A., Noguchi, M., Takakura, K. and Takahashi, S. Repair of DNA Damage Induced by Accelerated Heavy Ions in Mammalian Cells Proficient and Deficient in the Non-homologous End-Joining Pathway. Radiat. Res. 165, 59–67 (2006). Human and rodent cells proficient and deficient in non-homologous end joining (NHEJ) were irradiated with X rays, 70 keV/μm carbon ions, and 200 keV/μm iron ions, and the biological effects on these cells were compared. For wild-type CHO and normal human fibroblast (HFL III) cells, exposure to iron ions yielded the lowest cell survival, followed by carbon ions and then X rays. NHEJ-deficient xrs6 (a Ku80 mutant of CHO) and 180BR human fibroblast (DNA ligase IV mutant) cells showed similar cell survival for X and carbon-ion irradiation (RBE = ∼1.0). This phenotype is likely to result from a defective NHEJ protein because xrs6-hamKu80 cells (xrs6 cells corrected with the wild-type KU80 gene) exhibited the wild-type response. At doses higher than 1 Gy...
150 citations
TL;DR: The yields (damages/Mbp Gy−1) of all damages decreased with increasing linear energy transfer (LET) of the radiation, and the relative frequencies of DSBs compared to abasic and oxybase clusters were higher for the charged particles—including the high-energy, low-LET protons—than for the ionizing photons.
Abstract: Hada, M. and Sutherland, B. M. Spectrum of Complex DNA Damages Depends on the Incident Radiation. Radiat. Res. 165, 223–230 (2006). Ionizing radiation induces bistranded clustered damages— two or more abasic sites, oxidized bases and strand breaks on opposite DNA strands within a few helical turns. Since clusters are refractory to repair and are potential sources of double-strand breaks (DSBs), they are potentially lethal and mutagenic. Although induction of single-strand breaks (SSBs) and isolated lesions has been studied extensively, little is known about the factors affecting induction of clusters other than DSBs. To determine whether the type of incident radiation could affect the yields or spectra of specific clusters, we irradiated genomic T7 DNA, a simple 40-kbp linear, blunt-ended molecule, with ion beams [iron (970 MeV/nucleon), carbon (293 MeV/nucleon), titanium (980 MeV/nucleon), silicon (586 MeV/nucleon), protons (1 GeV/nucleon)] or 100 kVp X rays and then quantified DSBs, Fpg-oxypuri...
148 citations
TL;DR: The large differences seen in glial progenitor survival seen 1 week after irradiation were also maintained during the 4–5-month latent period before the development of radiation myelopathy, due to selective white matter necrosis, after irradiated with doses that would produce a high incidence of radiationMyelopathy.
Abstract: Selective irradiation of the vasculature of the rat spinal cord was used in this study, which was designed specifically to address the question as to whether it is the endothelial cell or the glial progenitor cell that is the target responsible for late white matter necrosis in the CNS. Selective irradiation of the vascular endothelium was achieved by the intraperitoneal (ip) administration of a boron compound known as BSH (Na(2)B(12)H(11)SH), followed by local irradiation with thermal neutrons. The blood-brain barrier is known to exclude BSH from the CNS parenchyma. Thirty minutes after the ip injection of BSH, the boron concentration in blood was 100 microg (10)B/ g, while that in the CNS parenchyma was below the detection limit of the boron analysis system, <1 microg (10)B/g. An ex vivo clonogenic assay of the O2A (oligodendrocyte-type 2 astrocyte) glial progenitor cell survival was performed 1 week after irradiation and at various times during the latent period before white matter necrosis in the spinal cord resulted in myelopathy. One week after 4.5 Gy of thermal neutron irradiation alone (approximately one-third of the dose required to produce a 50% incidence of radiation myelopathy), the average glial progenitor cell surviving fraction was 0.03. The surviving fraction of glial progenitor cells after a thermal neutron irradiation with BSH for a comparable effect was 0.46. The high level of glial progenitor cell survival after irradiation in the presence of BSH clearly reflects the lower dose delivered to the parenchyma due to the complete exclusion of BSH by the blood-brain barrier. The intermediate response of glial progenitor cells after irradiation with thermal neutrons in the presence of a boron compound known as BPA (p-dihydroxyboryl-phenylalanine), again for a dose that represents one-third the ED(50) for radiation-induced myelopathy, reflects the differential partition of boron-10 between blood and CNS parenchyma for this compound, which crosses the blood-brain barrier, at the time of irradiation. The large differences in glial progenitor survival seen 1 week after irradiation were also maintained during the 4-5-month latent period before the development of radiation myelopathy, due to selective white matter necrosis, after irradiation with doses that would produce a high incidence of radiation myelopathy. Glial progenitor survival was similar to control values at 100 days after irradiation with a dose of thermal neutrons in the presence of BSH, significantly greater than the ED(100), shortly before the normal time of onset of myelopathy. In contrast, glial progenitor survival was less than 1% of control levels after irradiation with 15 Gy of thermal neutrons alone. This dose of thermal neutrons represents the approximate ED(90-100) for myelopathy. The response to irradiation with an equivalent dose of X rays (ED(90): 23 Gy) was intermediate between these extremes as it was to thermal neutrons in the presence of BPA at a slightly lower dose equivalent to the approximate ED(60) for radiation myelopathy. The conclusions from these studies, performed at dose levels approximately iso-effective for radiation-induced myelopathy as a consequence of white matter necrosis, were that the large differences observed in glial progenitor survival were directly related to the dose distribution in the parenchyma. These observations clearly indicate the relative importance of the dose to the vascular endothelium as the primary event leading to white matter necrosis.
144 citations
TL;DR: Evidence is shown for a dose threshold around 2 mGy for the human skin cell line used with a suggestion of increased survival below that dose, which may have implications for understanding the role of bystander effects at low doses.
Abstract: Liu, Z., Mothersill, C. E., McNeill, F. E., Lyng, F. M., Byun, S. H., Seymour, C. B. and Prestwich, W. V. A Dose Threshold for a Medium Transfer Bystander Effect for a Human Skin Cell Line. Radiat. Res. 166, 19–23 (2006). The existence of radiation-induced bystander effects mediated by diffusible factors is now accepted, but the mechanisms and precise behavior at low doses remain unclear. We exposed cells to γ-ray doses in the range 0.04 mGy–5 Gy, harvested the culture medium, and transferred it to unirradiated reporter cells. Calcium fluxes and clonogenic survival were measured in the recipients. We show evidence for a dose threshold around 2 mGy for the human skin cell line used with a suggestion of increased survival below that dose. Similar experiments using direct γ irradiation showed no reduction in survival until the dose exceeded 7 mGy. Preliminary data for neutrons where the γ-ray dose was kept below the bystander threshold do not show a significant bystander effect in the dose range 1–3...
TL;DR: This work proposes analytical functions that can predict the cosmic-ray neutron spectra for any location in the atmosphere at altitudes below 20 km, considering the influences of local geometries such as ground and aircraft on the spectra.
Abstract: Sato, T and Niita, K Analytical Functions to Predict Cosmic-Ray Neutron Spectra in the Atmosphere Radiat Res 166, 544–555 (2006) Estimation of cosmic-ray neutron spectra in the atmosphere has been an essential issue in the evaluation of the aircrew doses and the soft-error rates of semiconductor devices We therefore performed Monte Carlo simulations for estimating neutron spectra using the PHITS code in adopting the nuclear data library JENDL-High-Energy file Excellent agreements were observed between the calculated and measured spectra for a wide altitude range even at the ground level Based on a comprehensive analysis of the simulation results, we propose analytical functions that can predict the cosmic-ray neutron spectra for any location in the atmosphere at altitudes below 20 km, considering the influences of local geometries such as ground and aircraft on the spectra The accuracy of the analytical functions was well verified by various experimental data
TL;DR: Investigating the role of changes in calcium levels in bystander responses leading to chromosomal damage in nonirradiated T98G glioma cells and AG01522 fibroblasts indicates that calcium signaling may be an early response in radiation-induced bystander effects leading to chromosome damage.
Abstract: Shao, C., Lyng, F. M., Folkard, M. and Prise, K. M. Calcium Fluxes Modulate the Radiation-Induced Bystander Responses in Targeted Glioma and Fibroblast Cells. Radiat. Res. 166, 479–487 (2006). Bystander responses have been reported to be a major determinant of the response of cells to radiation exposure at low doses, including those of relevance to therapy. This study investigated the role of changes in calcium levels in bystander responses leading to chromosomal damage in nonirradiated T98G glioma cells and AG01522 fibroblasts that had been either exposed to conditioned medium from irradiated cells or co-cultured with a population where a fraction of cells were individually targeted through the nucleus or cytoplasm with a precise number of microbeam helium-3 particles. After the recipient cells were treated with conditioned medium from T98G or AG01522 cells that had been irradiated through either nucleus or cytoplasm, rapid calcium fluxes were monitored in the nonirradiated recipient cells. Thei...
TL;DR: Both EAR and ERR were higher in the Belarusian settlements than in the Ukrainian settlements, and in contrast to ERR, EAR increases with time after exposure, while ERR decreased strongly with age at exposure.
Abstract: The purpose of the present study was to analyze the thyroid cancer incidence risk after the Chernobyl accident and its degree of dependence on time and age. Data were analyzed for 1034 settlements in Ukraine and Belarus, in which more than 10 measurements of the 131 I content in human thyroids had been performed in May/June 1986. Thyroid doses due to the Chernobyl accident were assessed for the birth years 1968‐ 1985 and related to thyroid cancers that were surgically removed during the period 1990‐2001. The central estimate for the linear coefficient of the EAR dose response was 2.66 (95% CI: 2.19; 3.13) cases per 10 4 PY-Gy; for the quadratic coefficient, it was20.145 (95% CI: 20.171; 20.119) cases per 10 4 PY-Gy 2 . The EAR was found to be higher for females than for males by a factor of 1.4. It decreased with age at exposure and increased with age attained. The central estimate for the linear coefficient of the ERR dose response was 18.9 (95% CI: 11.1; 26.7) Gy 21 ; for the quadratic coefficient, it was 21.03 (95% CI: 21.46; 20.60) Gy 22 . The ERR was found to be smaller for females than for males by a factor of 3.8 and decreased strongly with age at exposure. Both EAR and ERR were higher in the Belarusian settlements than in the Ukrainian settlements. In contrast to ERR, EAR increases with time after exposure. At the end of the observation period, excess risk estimates were found to be close to those observed in a major pooled analysis of seven studies of childhood thyroid cancer after external exposures. q 2006 by Radiation Research Society
United States Department of Health and Human Services1, National Institutes of Health2, University of Texas MD Anderson Cancer Center3, University of Minnesota4, Fred Hutchinson Cancer Research Center5, Ohio State University6, Stanford University7, University of Pennsylvania8, Memorial Sloan Kettering Cancer Center9
TL;DR: Models derived from radiobiology were applied to describe the radiation dose–response curve for thyroid cancer in an epidemiological study and convincing evidence for a downturn in risk at high doses was found.
Abstract: Radiation exposure at a young age is a strong risk factor for thyroid cancer. We conducted a nested case-control study of 69 thyroid cancer cases and 265 controls from a cohort of 14,054 childhood cancer survivors to evaluate the shape of the radiation dose-response relationship, in particular at high doses, and to assess modification of the radiation effects by patient and treatment characteristics. We considered several types of statistical models to estimate the excess relative risk (ERR), mainly guided by radiobiological models. A two-parameter model with a term linear in dose and a negative exponential in dose squared provided the best parsimonious description with an ERR of 1.3 per gray (95% confidence interval 0.4-4.1) at doses below 6 Gy and a relative decrease in ERR of 0.2% per unit dose squared with increasing dose, that is, decreases in the ERR/Gy of 53% at 20 Gy and 95% at 40 Gy. Further analyses using spline models suggested that the significant nonlinearity at high doses was characterized most appropriately as a true downturn rather than a flattening of the dose-response curve. We found no statistically significant modification of the dose-response relationship by patient characteristics; however, the linear parameter (i.e., the ERR/ Gy at doses less than 6 Gy) did decrease consistently and linearly with increasing age at childhood cancer diagnosis, from 4.45 for 0-1-year-olds to 0.48 for 15-20-year-olds. In summary, we applied models derived from radiobiology to describe the radiation dose-response curve for thyroid cancer in an epidemiological study and found convincing evidence for a downturn in risk at high doses.
TL;DR: Personal computer-based algorithms are developed and described, operating as utilities on available software, that allow an objective and quantitative analysis of foci from confocal images and can be employed to evaluate colocalization between foci formed by different proteins.
Abstract: Observation and counting of gamma-H2AX foci in untreated cells as well as in cells exposed to cytotoxic agents is a widely used method for documenting the presence of double-strand breaks (DSBs) in the DNA and for analysis of their repair. Similar methods are employed to analyze formation of foci by a variety of proteins implicated in the cellular responses to DNA damage. Despite the wide application of the approach, the manual counting that is frequently used is prone to inaccuracies and investigator-related biases and artifacts. To alleviate this limitation, we developed and describe here personal computer-based algorithms, operating as utilities on available software, that allow an objective and quantitative analysis of foci from confocal images. The algorithms allow focus counting as well as size definition and correct for focus coincidence due to the overlap normally occurring with an increasing number of foci per nucleus. Furthermore, the software allows measurement of the integrated optical density (IOD) of each individual focus, which enables analysis of properties of foci as a function of time. Finally, the information generated by the above analysis algorithms can be employed to evaluate colocalization between foci formed by different proteins. A validation of the software is presented for radiation-induced gamma-H2AX foci in three widely used human cell lines and colocalization tested with RAD51 and gamma-H2AX foci. The computational methods presented extend to images generated by digital cameras.
TL;DR: The results indicate that guanosine and inosine, natural antioxidants, prevent oxidative damage to DNA, decrease the generation of ROS, and protect mice against γ-radiation-induced death.
Abstract: Gudkov, S. V., Shtarkman, I. N., Smirnova, V. S., Chernikov, A. V. and Bruskov, V. I. Guanosine and Inosine Display Antioxidant Activity, Protect DNA In Vitro from Oxidative Damage Induced by Reactive Oxygen Species, and Serve as Radioprotectors in Mice. Radiat. Res. 165, 538–545 (2006). The effect of ribonucleosides on 8-oxoguanine formation in salmon sperm DNA dissolved in 1 mM phosphate buffer, pH 6.8, upon exposure to γ rays was examined by ELISA using monoclonal antibodies against 8-oxoguanine. Nucleosides (1 mM) decreased the radiation-induced yield of 8-oxoguanine in the order Guo > Ino > Ado > Thd > Urd > Cyd. Guanosine and inosine considerably reduced deamination of cytosine in the DNA solutions upon heating for 24 h at 80°C. The action of nucleosides on the heat-induced generation of reactive oxygen species in the phosphate buffer was studied. The concentration of hydrogen peroxide was measured by enhanced chemiluminescence in a peroxidase–luminol–p-iodophenol system; the hydroxyl radic...
TL;DR: DeToledo et al. as mentioned in this paper investigated low-dose/low-dose-rate effects of low-linear energy transfer (LET) ionizing radiation, they used γ-irradiated cells adapted to grow in a three-dimensional architecture that mimics cell growth in vivo.
Abstract: de Toledo, S. M., Asaad, N., Venkatachalam, P., Li, L., Howell, R. W., Spitz, D. R. and Azzam, E. I. Adaptive Responses to Low-Dose/Low-Dose-Rate γ Rays in Normal Human Fibroblasts: The Role of Growth Architecture and Oxidative Metabolism. Radiat. Res. 166, 849–857 (2006). To investigate low-dose/low-dose-rate effects of low-linear energy transfer (LET) ionizing radiation, we used γ-irradiated cells adapted to grow in a three-dimensional architecture that mimics cell growth in vivo. We determined the cellular, molecular and biochemical changes in these cells. Quiescent normal human fibroblasts were irradiated with single acute or chronic doses (1–10 cGy) of 137Cs γ rays. Whereas exposure to an acute dose of 10 cGy increased micronucleus formation, protraction of the dose over 48 h reduced micronucleus frequency to a level similar to or lower than what occurs spontaneously. The protracted treatment also up-regulated the cellular content of the antioxidant glutathione. These changes correlated with...
TL;DR: Panajojovic et al. as discussed by the authors determined effective cross sections for production of singlestrand breaks in plasmid DNA [pGEM 3Zf(-)] by electrons of 10 eV and energies between 0.1 and 4.7 eV.
Abstract: Panajotovic, R., Martin, F., Cloutier, P., Hunting, D. and Sanche, L. Effective Cross Sections for Production of Single-Strand Breaks in Plasmid DNA by 0.1 to 4.7 eV Electrons. Radiat. Res. 165, 452–459 (2006). We determined effective cross sections for production of single-strand breaks (SSBs) in plasmid DNA [pGEM 3Zf(-)] by electrons of 10 eV and energies between 0.1 and 4.7 eV. After purification and lyophilization on a chemically clean tantalum foil, dry plasmid DNA samples were transferred into a high-vacuum chamber and bombarded by a monoenergetic electron beam. The amount of the circular relaxed DNA in the samples was separated from undamaged molecules and quantified using agarose gel electrophoresis. The effective cross sections were derived from the slope of the yield as a function of exposure and had values in the range of 10−15– 10−14 cm2, giving an effective cross section of the order of 10−18 cm2 per nucleotide. Their strong variation with incident electron energy and the resonant en...
TL;DR: This work discusses phenotypes of current mouse models and altered polymerase functions and the relationship of DNA polymerase gene mutations to human cell phenotypes, and discusses the putative functional consequences of single nucleotide polymorphisms (SNPs) in relation to human disease.
Abstract: DNA polymerases function in DNA replication, repair, recombination and translesion synthesis. Currently, 15 DNA polymerase genes have been identified in human cells, belonging to four distinct families. In this review, we briefly describe the biochemical activities and known cellular roles of each DNA polymerase. Our major focus is on the phenotypic consequences of mutation or ablation of individual DNA polymerase genes. We discuss phenotypes of current mouse models and altered polymerase functions and the relationship of DNA polymerase gene mutations to human cell phenotypes. Interestingly, over 120 single nucleotide polymorphisms (SNPs) have been identified in human populations that are predicted to result in nonsynonymous amino acid substitutions of DNA polymerases. We discuss the putative functional consequences of these SNPs in relation to human disease.
TL;DR: Results suggested that an enhancement of the antioxidative capacities played an important role in the reduction of initial DNA damage by low-dose-rate radiation.
Abstract: Otsuka, K., Koana, T., Tauchi, H. and Sakai, K. Activation of Antioxidative Enzymes Induced by Low-Dose-Rate Whole-Body γ Irradiation: Adaptive Response in Terms of Initial DNA Damage. Radiat. Res. 166, 474–478 (2006). An adaptive response induced by long-term low-dose-rate irradiation in mice was evaluated in terms of the amount of DNA damage in the spleen analyzed by a comet assay. C57BL/ 6N female mice were irradiated with 0.5 Gy of 137Cs γ rays at 1.2 mGy/h; thereafter, a challenge dose (0.4, 0.8 or 1.6 Gy) at a high dose rate was given. Less DNA damage was observed in the spleen cells of preirradiated mice than in those of mice that received the challenge dose only; an adaptive response in terms of DNA damage was induced by long-term low-dose-rate irradiation in mice. The gene expression of catalase and Mn-SOD was significantly increased in the spleen after 23 days of the low-dose-rate radiation (0.5 Gy). In addition, the enzymatic activity of catalase corresponded to the gene expression lev...
TL;DR: The ability of the microprobe to reliably hit randomly positioned etched nuclear tracks in CR-39 with single ions as well as the ability to visualize the ion hits using immunofluorescence staining for 53BP1 as a marker of DNA damage in the targeted cell nuclei are described.
Abstract: Heis, M., Fischer, B. E., Jakob, B., Fournier, C., Becker, G. and Taucher-Scholz, G. Targeted Irradiation of Mammalian Cells Using a Heavy-Ion Microprobe. Radiat. Res. 165, 231–239 (2006). The existing focusing heavy-ion microprobe at the Gesellschaft fur Schwerionenforschung in Darmstadt (Germany) has been modified to enable the targeted irradiation of single, selected cells with a defined number of ions. With this setup, ions in the range from helium to uranium with linear energy transfers (LETs) up to ∼15,000 keV/μm can be positioned with a precision of a few micrometers in the nuclei of single cells that are growing in culture on a thin polypropylene film. To achieve this accuracy, the microbeam traverses a thin vacuum window with minimal scattering. Electron emission from that window is used for particle detection. The cells are kept in a specially designed dish that is mounted directly behind the vacuum window in a setup allowing the precise movement and the imaging of the sample with micro...
TL;DR: It is suggested that IL1B plays a critical role in radiation-induced fibrosis and that the increased MMPs fail to block the IL1-related collagen accumulation.
Abstract: Liu, W., Ding, I., Chen, K., Olschowka, J., Xu, J., Hu, D., Morrow, G. and Okunieff, P. Interleukin 1β (IL1B) Signaling is a Critical Component of Radiation-Induced Skin Fibrosis. Radiat. Res. 165, 181–191 (2006). Interleukin 1 beta (IL1B), a potent pro-inflammatory cytokine, is directly up-regulated by radiation and is known to regulate other inflammation-related molecules, such as the matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs). However, the nature of the interaction of IL1B with MMPs and TIMPs in radiation-induced skin fibrosis is unknown. We examined the response of primary dermal keratinocytes, fibroblasts and endothelial cells to single-fraction radiation (10 Gy) and compared the results to a temporal sequence of histology from irradiated C57BL/6 and IL1R1 knockout mice. These studies showed that keratinocytes are the major IL1-producing cells in vitro and that radiation induces an immediate and chronic elevation in the expression of IL1B mRNA in the skin of C57...
ENEA1
TL;DR: Investigating whether 24 h exposure to radiofrequency electromagnetic fields similar to those emitted by mobile phones induces genotoxic effects and/or effects on cell cycle kinetics in cultured human peripheral blood lymphocytes provided no evidence for the existence ofgenotoxic or cytotoxiceffects in the range of SARs investigated.
Abstract: The objective of this study was to investigate whether 24 h exposure to radiofrequency electromagnetic fields similar to those emitted by mobile phones induces genotoxic effects and/or effects on cell cycle kinetics in cultured human peripheral blood lymphocytes. The effect of 900 MHz exposure (GSM signal) was evaluated at four specific absorption rates (SARs, 0, 1, 5 and 10 W/kg peak values). The exposures were carried out in wire patch cells under strictly controlled conditions of both temperature and dosimetry, and the induction of genotoxic effects was evaluated in lymphocyte cultures from 10 healthy donors by applying the cytokinesis-block micronucleus assay. Positive controls were provided by using mitomycin C. Two research groups were involved in the study, one at ENEA, Rome, and the other at CNR-IREA, Naples. Each laboratory tested five donors, and the resulting slides were scored by both laboratories. Following this experimental scheme, it was also possible to compare the results obtained by cross-scoring of slides. The results obtained provided no evidence for the existence of genotoxic or cytotoxic effects in the range of SARs investigated. These findings were confirmed in the two groups of five donors examined in the two laboratories and when the same slides were scored by two operators.
TL;DR: The formation of phosphorylated ataxia telangiectasia mutated (ATM) foci in exponentially growing normal human diploid cells exposed to low doses of X rays showed a linear dose–response relationship with doses ranging for 10 mGy to 1 Gy, and the average number of foci per gray was approximately 50.
Abstract: Suzuki, K., Okada, H., Yamauchi, M., Oka, Y., Kodama, S. and Watanabe, M. Qualitative and Quantitative Analysis of Phosphorylated ATM Foci Induced by Low-Dose Ionizing Radiation. Radiat. Res. 165, 499–504 (2006). We examined the formation of phosphorylated ataxia telangiectasia mutated (ATM) foci in exponentially growing normal human diploid cells exposed to low doses of X rays. Phosphorylated ATM foci were detected immediately after irradiation, and the number of foci decreased as the time after irradiation increased. The kinetics of phosphorylated ATM foci was comparable to that of phosphorylated histone H2AX. We found that there were fewer spontaneous phosphorylated ATM foci than that phosphorylated histone H2AX foci. Notably, significant numbers of phosphorylated histone H2AX foci, but not phosphorylated ATM foci, were detected in the S-phase cells. The induction of foci showed a linear dose–response relationship with doses ranging for 10 mGy to 1 Gy, and the average number of phosphorylated ...
TL;DR: The models and predictions presented here, while continuing to be modified and improved, represent one of the most comprehensive dose reconstructions undertaken to date for a large cohort of medical radiation workers.
Abstract: Simon, S. L., Weinstock, R. M., Doody, M. M., Neton, J., Wenzel, T., Stewart, P., Mohan, A. K., Yoder, C., Freedman, M., Hauptmann, M., Bouville, A., Cardarelli, J., Feng, H. A. and Linet, M. Estimating Historical Radiation Doses to a Cohort of U.S. Radiologic Technologists. Radiat. Res. 166, 174– 192 (2006). Data have been collected and physical and statistical models have been constructed to estimate unknown occupational radiation doses among 90,000 members of the U.S. Radiologic Technologists cohort who responded to a baseline questionnaire during the mid-1980s. Since the availability of radiation dose data differed by calendar period, different models were developed and applied for years worked before 1960, 1960– 1976 and 1977–1984. The dose estimation used available film-badge measurements (approximately 350,000) for individual cohort members, information provided by the technologists on their work history and protection practices, and measurement and other data derived from the literature. ...
TL;DR: The singlet oxygen-induced lesion was isolated from a short synthetic oligomer after exposure to UVA radiation in the presence of methylene blue and could be enzymatically excised from the oligomer in the form of a modified dinucleoside monophosphate.
Abstract: Singlet oxygen, hydrogen peroxide, hydroxyl radical and hydrogen peroxide are the reactive oxygen species (ROS) considered most responsible for producing oxidative stress in cells and organisms. Singlet oxygen interacts preferentially with guanine to produce 8-oxo-7,8-dihydroguanine and spiroiminodihydantoin. DNA damage due to the latter lesion has not been detected directly in the DNA of cells exposed to singlet oxygen. In this study, the singlet oxygen-induced lesion was isolated from a short synthetic oligomer after exposure to UVA radiation in the presence of methylene blue. The lesion could be enzymatically excised from the oligomer in the form of a modified dinucleoside monophosphate. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), the singlet oxygen lesion was detected in the form of modified dinucleoside monophosphates in double-stranded DNA and in the DNA of HeLa cells exposed to singlet oxygen. Pentamer containing the singlet oxygen-induced lesion and an isotopic label was synthesized as an internal standard for quantifying the lesion and served as well as for correcting for losses of product during sample preparation.
TL;DR: The results indicate that phosphorylated histone H2AX foci persist if DNA breaks are rejoined, and it is suggested that “residual” foci indicate an aberrant chromatin structure by illegitimate rejoining but not a DNA double-strand break itself.
Abstract: Suzuki, M., Suzuki, K., Kodama, S. and Watanabe M. Phosphorylated Histone H2AX Foci Persist on Rejoined Mitotic Chromosomes in Normal Human Diploid Cells Exposed to Ionizing Radiation. Radiat. Res. 165, 269–276 (2006). Histone H2AX is phosphorylated and forms foci in response to exposure to ionizing radiation. It has been thought that phosphorylated histone H2AX foci reflect unrepaired DNA double-strand breaks; however, we report here the localization of phosphorylated histone H2AX foci at the site of rejoined DNA double-strand breaks. We observed that phosphorylated histone H2AX foci remained even 96 h after exposure to X rays in interphase cells. To clarify the localization of residual phosphorylated histone H2AX foci, we examined localization of focus formation on mitotic chromosomes irradiated with X rays. We found that phosphorylated histone H2AX foci were located not only on chromosomal fragments but also on intact metaphase chromosomes without fragments. In anaphase cells, chromosomal brid...
TL;DR: Investigation of the relationship between the recognition of radiation-induced DNA double-strand breaks as defined by γ-H2AX staining and the incidence of HRS in three pairs of isogenic cell lines with known differences in radiosensitivity and DNA repair functionality suggests that the persistence of γ, H2AX foci could be adopted as a surrogate assay of cellular radiosensitivity to predict clinical radiation responsiveness.
Abstract: Wykes, S. M., Piasentin, E., Joiner, M. C., Wilson, G. D. and Marples, B. Low-Dose Hyper-radiosensitivity is not Caused by a Failure to Recognize DNA Double-Strand Breaks. Radiat. Res. 165, 516–524 (2006). One of the earliest cellular responses to radiation-induced DNA damage is the phosphorylation of the histone variant H2AX (γ-H2AX). γ-H2AX facilitates the local concentration and focus formation of numerous repair-related proteins within the vicinity of DNA DSBs. Previously, we have shown that low-dose hyper-radiosensitivity (HRS), the excessive sensitivity of mammalian cells to very low doses of ionizing radiation, is a response specific to G2-phase cells and is attributed to evasion of an ATM-dependent G2-phase cell cycle checkpoint. To further define the mechanism of low-dose hyper-radiosensitivity, we investigated the relationship between the recognition of radiation-induced DNA double-strand breaks as defined by γ-H2AX staining and the incidence of HRS in three pairs of isogenic cell lines...
TL;DR: The involvement of heat-shock proteins as a possible inhibitor of free radical production was investigated and the HSP70 expression level after different RF EMF exposures; no significant effects were detected.
Abstract: Lantow, M., Schuderer, J., Hartwig, C. and Simko, M. Free Radical Release and HSP70 Expression in Two Human Immune-Relevant Cell Lines after Exposure to 1800 MHz Radiofrequency Radiation. Radiat. Res. 165, 88–94 (2006). The goal of this study was to investigate whether radiofrequency (RF) electromagnetic-field (EMF) exposure at 1800 MHz causes production of free radicals and/or expression of heat-shock proteins (HSP70) in human immune-relevant cell systems. Human Mono Mac 6 and K562 cells were used to examine free radical release after exposure to incubator control, sham, RF EMFs, PMA, LPS, heat (40°C) or co-exposure conditions. Several signals were used: continuous-wave, several typical modulations of the Global System for Mobile Communications (GSM): GSM-non DTX (speaking only), GSM-DTX (hearing only), GSM-Talk (34% speaking and 66% hearing) at specific absorption rates (SARs) of 0.5, 1.0, 1.5 and 2.0 W/kg. Heat and PMA treatment induced a significant increase in superoxide radical anions and i...