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Sample records for radiation damage genomic

  1. DNA damage in cells exhibiting radiation-induced genomic instability

    DOE PAGESBeta

    Keszenman, Deborah J.; Kolodiuk, Lucia; Baulch, Janet E.

    2015-02-22

    Cells exhibiting radiation induced genomic instability exhibit varied spectra of genetic and chromosomal aberrations. Even so, oxidative stress remains a common theme in the initiation and/or perpetuation of this phenomenon. Isolated oxidatively modified bases, abasic sites, DNA single strand breaks and clustered DNA damage are induced in normal mammalian cultured cells and tissues due to endogenous reactive oxygen species generated during normal cellular metabolism in an aerobic environment. While sparse DNA damage may be easily repaired, clustered DNA damage may lead to persistent cytotoxic or mutagenic events that can lead to genomic instability. In this study, we tested the hypothesismore » that DNA damage signatures characterised by altered levels of endogenous, potentially mutagenic, types of DNA damage and chromosomal breakage are related to radiation-induced genomic instability and persistent oxidative stress phenotypes observed in the chromosomally unstable progeny of irradiated cells. The measurement of oxypurine, oxypyrimidine and abasic site endogenous DNA damage showed differences in non-double-strand breaks (DSB) clusters among the three of the four unstable clones evaluated as compared to genomically stable clones and the parental cell line. These three unstable clones also had increased levels of DSB clusters. The results of this study demonstrate that each unstable cell line has a unique spectrum of persistent damage and lead us to speculate that alterations in DNA damage signaling and repair may be related to the perpetuation of genomic instability.« less

  2. DNA damage in cells exhibiting radiation-induced genomic instability

    SciTech Connect

    Keszenman, Deborah J.; Kolodiuk, Lucia; Baulch, Janet E.

    2015-02-22

    Cells exhibiting radiation induced genomic instability exhibit varied spectra of genetic and chromosomal aberrations. Even so, oxidative stress remains a common theme in the initiation and/or perpetuation of this phenomenon. Isolated oxidatively modified bases, abasic sites, DNA single strand breaks and clustered DNA damage are induced in normal mammalian cultured cells and tissues due to endogenous reactive oxygen species generated during normal cellular metabolism in an aerobic environment. While sparse DNA damage may be easily repaired, clustered DNA damage may lead to persistent cytotoxic or mutagenic events that can lead to genomic instability. In this study, we tested the hypothesis that DNA damage signatures characterised by altered levels of endogenous, potentially mutagenic, types of DNA damage and chromosomal breakage are related to radiation-induced genomic instability and persistent oxidative stress phenotypes observed in the chromosomally unstable progeny of irradiated cells. The measurement of oxypurine, oxypyrimidine and abasic site endogenous DNA damage showed differences in non-double-strand breaks (DSB) clusters among the three of the four unstable clones evaluated as compared to genomically stable clones and the parental cell line. These three unstable clones also had increased levels of DSB clusters. The results of this study demonstrate that each unstable cell line has a unique spectrum of persistent damage and lead us to speculate that alterations in DNA damage signaling and repair may be related to the perpetuation of genomic instability.

  3. Chromatin Compaction Protects Genomic DNA from Radiation Damage

    PubMed Central

    Takata, Hideaki; Hanafusa, Tomo; Mori, Toshiaki; Shimura, Mari; Iida, Yutaka; Ishikawa, Kenichi; Yoshikawa, Kenichi; Yoshikawa, Yuko; Maeshima, Kazuhiro

    2013-01-01

    Genomic DNA is organized three-dimensionally in the nucleus, and is thought to form compact chromatin domains. Although chromatin compaction is known to be essential for mitosis, whether it confers other advantages, particularly in interphase cells, remains unknown. Here, we report that chromatin compaction protects genomic DNA from radiation damage. Using a newly developed solid-phase system, we found that the frequency of double-strand breaks (DSBs) in compact chromatin after ionizing irradiation was 5–50-fold lower than in decondensed chromatin. Since radical scavengers inhibited DSB induction in decondensed chromatin, condensed chromatin had a lower level of reactive radical generation after ionizing irradiation. We also found that chromatin compaction protects DNA from attack by chemical agents. Our findings suggest that genomic DNA compaction plays an important role in maintaining genomic integrity. PMID:24130727

  4. Mitochondria regulate DNA damage and genomic instability induced by high LET radiation

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Davidson, Mercy M.; Hei, Tom K.

    2014-04-01

    High linear energy transfer (LET) radiation including α particles and heavy ions is the major type of radiation found in space and is considered a potential health risk for astronauts. Even though the chance that these high LET particles traversing through the cytoplasm of cells is higher than that through the nuclei, the contribution of targeted cytoplasmic irradiation to the induction of genomic instability and other chromosomal damages induced by high LET radiation is not known. In the present study, we investigated whether mitochondria are the potential cytoplasmic target of high LET radiation in mediating cellular damage using a mitochondrial DNA (mtDNA) depleted (ρ0) human small airway epithelial (SAE) cell model and a precision charged particle microbeam with a beam width of merely one micron. Targeted cytoplasmic irradiation by high LET α particles induced DNA oxidative damage and double strand breaks in wild type ρ+ SAE cells. Furthermore, there was a significant increase in autophagy and micronuclei, which is an indication of genomic instability, together with the activation of nuclear factor kappa-B (NF-κB) and mitochondrial inducible nitric oxide synthase (iNOS) signaling pathways in ρ+ SAE cells. In contrast, ρ0 SAE cells exhibited a significantly lower response to these same endpoints examined after cytoplasmic irradiation with high LET α particles. The results indicate that mitochondria are essential in mediating cytoplasmic radiation induced genotoxic damage in mammalian cells. Furthermore, the findings may shed some light in the design of countermeasures for space radiation.

  5. Mitochondria regulate DNA damage and genomic instability induced by high LET radiation

    PubMed Central

    Zhang, Bo; Davidson, Mercy M.; Hei, Tom K.

    2014-01-01

    High linear energy transfer (LET) radiation including α particles and heavy ions is the major type of radiation find in space and is considered a potential health risk for astronauts. Even though the chance that these high LET particles traversing through the cytoplasm of cells is higher than that through the nuclei, the contribution of targeted cytoplasmic irradiation, to the induction of genomic instability and other chromosomal damages induced by high LET radiation is not known. In the present study, we investigated whether mitochondria are the potential cytoplasmic target of high LET radiation in mediating cellular damage using a mitochondrial DNA (mtDNA) depleted (ρ0) human small airway epithelial (SAE) cell model and a precision charged particle microbeam with a beam width of merely one micron. Targeted cytoplasmic irradiation by high LET α particles induced DNA oxidative damage and double strand breaks in wild type ρ+ SAE cells. Furthermore, there was a significant increase in autophagy, micronuclei, which is an indication of genomic instability, together with the activation of nuclear factor kappa-B (NF-κB) and mitochondrial inducible nitric oxide synthase (iNOS) signaling pathways in ρ+ SAE cells. In contrast, ρ0 SAE cells exhibited a significantly lower response to these same endpoints examined after cytoplasmic irradiation with high LET α particles. The results indicate that mitochondria are essential in mediating cytoplasmic radiation induced genotoxic damage in mammalian cells. Furthermore, the findings may shed some light in the design of countermeasures for space radiation. PMID:25072018

  6. How Magnetotactic Bacteria Respond to Radiation Induced Stress and Damage: Comparative Genomics Evidences for Evolutionary Adaptation

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Pan, Y.

    2015-12-01

    Solar radiation and galactic cosmic radiation is believed to be major restriction factors influencing survival and evolution of life. On planet earth, geomagnetic field along with atmosphere protect living beings from the harmful radiation. During a geomagnetic reversal or excursion, however, the efflux of charged particles on earth surface would increase as the shielding effect of magnetic field decrease. The stratospheric ozone can also be partially stripped away by solar wind when the strength of the field is weak, leading to an increasing ultraviolet radiation penetration to the earth surface. However, studies on the mechanism of radiation induced stress and damage are focused only on bacteria that have no response to magnetic field. This study was motivated by the need to fill the gap upon knowledge of that on magnetic field sensitive microorganism. Magnetotactic bacteria (MTB) are a group of microbes that are able to synthesis intracellular nano-sized magnetic particles (named magnetosomes). These chain-arranged magnetosomes help MTB sense and swim along the magnetic field to find their optimal living environment efficiently. In this paper, in silico prediction of stress and damage repair genes in response to different radiation were carried out on the complete genome of four nonmagnetotactic and four magnetotactic spirilla. In silico analyses of the genomes of magnetic field sensitive and non-sensitive spirilla revealed: 1) all strains contain genes for regulate responses superoxide and peroxide stress, DNA pyrimidine dimer and string breaks; 2) non-magnetotactic spirilla have more genes dealing with oxidative stress, while magnetotactic spirilla may benefit from magnetotaxis by swimming into oxic-anoxic zone away from oxidative stress and direct radiation damage; yet, the lipid hydroperoxide peroxidase gene in MTB may be responsible for possible ROS generated by the membrane enveloped magnetite magnetosome; 3) magnetotactic spirilla possess SOS rec

  7. DNA repair efficiency in germ cells and early mouse embryos and consequences for radiation-induced transgenerational genomic damage

    SciTech Connect

    Marchetti, Francesco; Wyrobek, Andrew J.

    2009-01-18

    Exposure to ionizing radiation and other environmental agents can affect the genomic integrity of germ cells and induce adverse health effects in the progeny. Efficient DNA repair during gametogenesis and the early embryonic cycles after fertilization is critical for preventing transmission of DNA damage to the progeny and relies on maternal factors stored in the egg before fertilization. The ability of the maternal repair machinery to repair DNA damage in both parental genomes in the fertilizing egg is especially crucial for the fertilizing male genome that has not experienced a DNA repair-competent cellular environment for several weeks prior to fertilization. During the DNA repair-deficient period of spermatogenesis, DNA lesions may accumulate in sperm and be carried into the egg where, if not properly repaired, could result in the formation of heritable chromosomal aberrations or mutations and associated birth defects. Studies with female mice deficient in specific DNA repair genes have shown that: (i) cell cycle checkpoints are activated in the fertilized egg by DNA damage carried by the sperm; and (ii) the maternal genotype plays a major role in determining the efficiency of repairing genomic lesions in the fertilizing sperm and directly affect the risk for abnormal reproductive outcomes. There is also growing evidence that implicates DNA damage carried by the fertilizing gamete as a mediator of postfertilization processes that contribute to genomic instability in subsequent generations. Transgenerational genomic instability most likely involves epigenetic mechanisms or error-prone DNA repair processes in the early embryo. Maternal and embryonic DNA repair processes during the early phases of mammalian embryonic development can have far reaching consequences for the genomic integrity and health of subsequent generations.

  8. [Radiation-induced damage of mitochondrial genome and its role in long-term effects of irradiation].

    PubMed

    Berogovskaia, N N; Savich, A V

    1994-01-01

    The role of mt-genome mutations in radiation-induced carcinogenesis has been hypothesized. The data on radiation chemistry of nucleic acids has been used to evaluate mutagenic effect of carcinogenic doses of ionizing radiation. The assumptions about the ways of biological augmentation of primary radiation-induced lesions in mt-genome has been given. PMID:8069366

  9. Modifying Radiation Damage

    PubMed Central

    Kim, Kwanghee; McBride, William H.

    2011-01-01

    Radiation leaves a fairly characteristic footprint in biological materials, but this is rapidly all but obliterated by the canonical biological responses to the radiation damage. The innate immune recognition systems that sense “danger” through direct radiation damage and through associated collateral damage set in motion a chain of events that, in a tissue compromised by radiation, often unwittingly result in oscillating waves of molecular and cellular responses as tissues attempt to heal. Understanding “nature’s whispers” that inform on these processes will lead to novel forms of intervention targeted more precisely towards modifying them in an appropriate and timely fashion so as to improve the healing process and prevent or mitigate the development of acute and late effects of normal tissue radiation damage, whether it be accidental, as a result of a terrorist incident, or of therapeutic treatment of cancer. Here we attempt to discuss some of the non-free radical scavenging mechanisms that modify radiation responses and comment on where we see them within a conceptual framework of an evolving radiation-induced lesion. PMID:20583981

  10. Protein damage, radiation sensitivity and aging.

    PubMed

    Radman, Miroslav

    2016-08-01

    This paper promotes a concept that protein damage determines radiation resistance and underlies aging and age-related diseases. The first bottleneck in cell recovery from radiation damage is functional (proteome) rather than informational (DNA), since prokaryotic and eukaryotic cell death correlates with incurred protein, but not DNA, damage. Proteome protection against oxidative damage determines survival after ionizing or UV irradiation, since sufficient residual proteome activity is required to turn on the DNA damage response activating DNA repair and protein renewal processes. Extreme radiation and desiccation resistance of rare bacterial and animal species is accounted for by exceptional constitutive proteome protection against oxidative damage. After excessive radiation their well-protected proteome faithfully reconstitutes a transcription-competent genome from hundreds of DNA fragments. The observation that oxidative damage targeted selectively to cellular proteins results in aging-like phenotypes suggests that aging and age-related diseases could be phenotypic consequences of proteome damage patterns progressing with age. PMID:27264559

  11. Radiation Damage Workshop

    NASA Technical Reports Server (NTRS)

    Stella, P. M.

    1984-01-01

    The availability of data regarding the radiation behavior of GaAs and silicon solar cells is discussed as well as efforts to provide sufficient information. Other materials are considered too immature for reasonable radiation evaluation. The lack of concern over the possible catastrophic radiation degradation in cascade cells is a potentially serious problem. Lithium counterdoping shows potential for removing damage in irradiated P-type material, although initial efficiencies are not comparable to current state of the art. The possibility of refining the lithium doping method to maintain high initial efficiencies and combining it with radiation tolerant structures such as thin BSF cells or vertical junction cells could provide a substantial improvement in EOL efficiencies. Laser annealing of junctions, either those formed ion implantation or diffusion, may not only improve initial cell performance but might also reduce the radiation degradation rate.

  12. Novel Synthetic (S,S) and (R,R)-Secoisolariciresinol Diglucosides (SDGs) Protect Naked Plasmid and Genomic DNA From Gamma Radiation Damage

    PubMed Central

    Mishra, Om P.; Pietrofesa, Ralph; Christofidou-Solomidou, Melpo

    2014-01-01

    Secoisolariciresinol diglucoside (SDG) is the major lignan in wholegrain flaxseed. However, extraction methods are complex and are associated with low yield and high costs. Using a novel synthetic pathway, our group succeeded in chemically synthesizing SDG (S,S and R,R enantiomers), which faithfully recapitulates the properties of their natural counterparts, possessing strong antioxidant and free radical scavenging properties. This study further extends initial findings by now investigating the DNA-radioprotective properties of the synthetic SDG enantiomers compared to the commercial SDG. DNA radioprotection was assessed by cell-free systems such as: (a) plasmid relaxation assay to determine the extent of the supercoiled (SC) converted to open-circular (OC) plasmid DNA (pBR322) after exposure of the plasmid to gamma radiation; and (b) determining the extent of genomic DNA fragmentation. Exposure of plasmid DNA to 25 Gy of γ radiation resulted in decreased supercoiled form and increased open-circular form, indicating radiation-induced DNA damage. Synthetic SDG (S,S) and SDG (R,R), and commercial SDG at concentrations of 25–250 μM significantly and equipotently reduced the radiation-induced supercoiled to open-circular plasmid DNA in a dose-dependent conversion. In addition, exposure of calf thymus DNA to 50 Gy of gamma radiation resulted in DNA fragments of low-molecular weight (<6,000 bps), which was prevented in a dose-dependence manner by all synthetic and natural SDG enantomers, at concentrations as low as 0.5 μM. These novel results demonstrated that synthetic SDG (S,S) and SDG (R,R) isomers and commercial SDG possess DNA-radioprotective properties. Such properties along with their antioxidant and free radical scavenging activity, reported earlier, suggest that SDGs are promising candidates for radioprotection for normal tissue damage as a result of accidental exposure during radiation therapy for cancer treatment. PMID:24945894

  13. DNA damage checkpoint, damage repair, and genome stability.

    PubMed

    Liu, Wei-Feng; Yu, Shan-Shan; Chen, Guan-Jun; Li, Yue-Zhong

    2006-05-01

    Genomic DNA is under constant attack from both endogenous and exogenous sources of DNA damaging agents. Without proper care, the ensuing DNA damages would lead to alteration of genomic structure thus affecting the faithful transmission of genetic information. During the process of evolution, organisms have acquired a series of mechanisms responding to and repairing DNA damage, thus assuring the maintenance of genome stability and faithful transmission of genetic information. DNA damage checkpoint is one such important mechanism by which, in the face of DNA damage, a cell can respond to amplified damage signals, either by actively halting the cell cycle until it ensures that critical processes such as DNA replication or mitosis are complete or by initiating apoptosis as a last resort. Over the last decade, complex hierarchical interactions between the key components like ATM/ATR in the checkpoint pathway and various other mediators, effectors including DNA damage repair proteins have begun to emerge. In the meantime, an intimate relationship between mechanisms of damage checkpoint pathway, DNA damage repair, and genome stability was also uncovered. Reviewed herein are the recent findings on both the mechanisms of activation of checkpoint pathways and their coordination with DNA damage repair machinery as well as their effect on genomic integrity. PMID:16722332

  14. Chemical Protection Against Radiation Damage

    ERIC Educational Resources Information Center

    Campaigne, Ernest

    1969-01-01

    Discusses potential war time and medical uses for chemical compounds giving protection against radiation damage. Describes compounds known to protect, research aimed at discovering such compounds, and problems of toxicity. (EB)

  15. Nuclear Radiation Damages Minds!

    ERIC Educational Resources Information Center

    Blai, Boris, Jr.

    Professors Ernest Sternglass (University of Pittsburgh) and Steven Bell (Berry College) have assembled cogent, conclusive evidence indicating that nuclear radiation is associated with impaired cognition. They suggest that Scholastic Aptitude Scores (SATs), which have declined steadily for 19 years, will begin to rise. Their prediction is based on…

  16. Radiation damage evolution in ceramics

    SciTech Connect

    Devanathan, Ramaswami

    2009-09-15

    A review is presented of recent results on radiation damage production, defect accumulation and dynamic annealing in a number of ceramics, such as silicon carbide, zircon and zirconia. Under energetic particle irradiation, ceramics can undergo amorphization by the accumulation of point defects and defect clusters (silicon carbide) or direct impact amorphization (zircon). Ceramics that resist radiation-induced amorphization have mechanisms to dissipate the primary knock-on atom energy, such as replacement collision sequences that leave the lattice undisturbed and low-energy cation site exchange. The presence of engineered mobile defects, such as structural vacancies in stabilized zirconia, can dynamically anneal radiation damage. Thus, defect engineering is a promising strategy to design radiation tolerance for applications such as nuclear waste disposal.

  17. Radiation Induced Genomic Instability

    SciTech Connect

    Morgan, William F.

    2011-03-01

    Radiation induced genomic instability can be observed in the progeny of irradiated cells multiple generations after irradiation of parental cells. The phenotype is well established both in vivo (Morgan 2003) and in vitro (Morgan 2003), and may be critical in radiation carcinogenesis (Little 2000, Huang et al. 2003). Instability can be induced by both the deposition of energy in irradiated cells as well as by signals transmitted by irradiated (targeted) cells to non-irradiated (non-targeted) cells (Kadhim et al. 1992, Lorimore et al. 1998). Thus both targeted and non-targeted cells can pass on the legacy of radiation to their progeny. However the radiation induced events and cellular processes that respond to both targeted and non-targeted radiation effects that lead to the unstable phenotype remain elusive. The cell system we have used to study radiation induced genomic instability utilizes human hamster GM10115 cells. These cells have a single copy of human chromosome 4 in a background of hamster chromosomes. Instability is evaluated in the clonal progeny of irradiated cells and a clone is considered unstable if it contains three or more metaphase sub-populations involving unique rearrangements of the human chromosome (Marder and Morgan 1993). Many of these unstable clones have been maintained in culture for many years and have been extensively characterized. As initially described by Clutton et al., (Clutton et al. 1996) many of our unstable clones exhibit persistently elevated levels of reactive oxygen species (Limoli et al. 2003), which appear to be due dysfunctional mitochondria (Kim et al. 2006, Kim et al. 2006). Interestingly, but perhaps not surprisingly, our unstable clones do not demonstrate a “mutator phenotype” (Limoli et al. 1997), but they do continue to rearrange their genomes for many years. The limiting factor with this system is the target – the human chromosome. While some clones demonstrate amplification of this chromosome and thus lend

  18. STS-118 Radiator Impact Damage

    NASA Technical Reports Server (NTRS)

    Lear, Dana M.; Hyde, J.; Christiansen, E.; Herrin, J.; Lyons, F.

    2008-01-01

    During the August 2007 STS-118 mission to the International Space Station, a micro-meteoroid or orbital debris (MMOD) particle impacted and completely penetrated one of shuttle Endeavour s radiator panels and the underlying thermal control system (TCS) blanket, leaving deposits on (but no damage to) the payload bay door. While it is not unusual for shuttle orbiters to be impacted by small MMOD particles, the damage from this impact is larger than any previously seen on the shuttle radiator panels. A close-up photograph of the radiator impact entry hole is shown in Figure 1, and the location of the impact on Endeavour s left-side aft-most radiator panel is shown in Figure 2. The aft radiator panel is 0.5-inches thick and consists of 0.011 inch thick aluminum facesheets on the front and back of an aluminum honeycomb core. The front facesheet is additionally covered by a 0.005 inch thick layer of silver-Teflon thermal tape. The entry hole in the silver-Teflon tape measured 8.1 mm by 6.4 mm (0.32 inches by 0.25 inches). The entry hole in the outer facesheet measured 7.4 mm by 5.3 mm (0.29 inches by 0.21 inches) (0.23 inches). The impactor also perforated an existing 0.012 inch doubler that had been bonded over the facesheet to repair previous impact damage (an example that lightning can strike the same place twice, even for MMOD impact). The peeled-back edge around the entry hole, or lip , is a characteristic of many hypervelocity impacts. High velocity impact with the front facesheet fragmented the impacting particle and caused it to spread out into a debris cloud. The debris cloud caused considerable damage to the internal honeycomb core with 23 honeycomb cells over a region of 28 mm by 26 mm (1.1 inches by 1.0 inches) having either been completely destroyed or partially damaged. Figure 3 is a view of the exit hole in the rear facesheet, and partially shows the extent of the honeycomb core damage and clearly shows the jagged petaled exit hole through the backside

  19. Radiation damage of germanium detectors

    NASA Technical Reports Server (NTRS)

    Pehl, R. H.

    1978-01-01

    Energetic particles can produce interstitial-vacancy pairs in a crystal by knocking the atoms from their normal positions. Detectors are unique among semiconductor devices in depending on very low concentrations of electrically active impurities, and also on efficient transport of holes and electrons over relatively large distances. Because the dense regions of damage produced by energetic particles may result in donors and/or acceptors, and also provide trapping sites for holes and electrons, detectors are very sensitive to radiation damage. In addition to these effects occurring within the detector, radiation may also change the characteristics of the exposed surfaces causing unpredictable effects on the detector leakage current. Radiation-induced surface degradation has rarely, if ever, been observed for germanium detectors. The possibility of minimizing hole trapping in charge collection by the use of a high-purity germanium coaxial detector configured with the p (+) contact on the coaxial periphery is discussed.

  20. Damage thresholds for terahertz radiation

    NASA Astrophysics Data System (ADS)

    Dalzell, Danielle R.; McQuade, Jill; Vincelette, Rebecca; Ibey, Bennet; Payne, Jason; Thomas, Robert; Roach, W. P.; Roth, Caleb L.; Wilmink, Gerald J.

    2010-02-01

    Several international organizations establish minimum safety standards to ensure that workers and the general population are protected against adverse health effects associated with electromagnetic radiation. Suitable standards are typically defined using published experimental data. To date, few experimental studies have been conducted at Terahertz (THz) frequencies, and as a result, current THz standards have been defined using extrapolated estimates from neighboring spectral regions. In this study, we used computational modeling and experimental approaches to determine tissue-damage thresholds at THz frequencies. For the computational modeling efforts, we used the Arrhenius damage integral to predict damage-thresholds. We determined thresholds experimentally for both long (minutes) and short (seconds) THz exposures. For the long exposure studies, we used an in-house molecular gas THz laser (υ= 1.89 THz, 189.92 mW/cm2, 10 minutes) and excised porcine skin. For the short exposure studies, we used the Free Electron Laser (FEL) at Jefferson Laboratory (υ= 0.1-1.0 THz, 2.0-14.0 mW/cm2, 2 seconds) and wet chamois cloths. Thresholds were determined using conventional damage score determination and probit analysis techniques, and tissue temperatures were measured using infrared thermographic techniques. We found that the FEL was ideal for tissue damage studies, while our in-house THz source was not suitable to determine tissue damage thresholds. Using experimental data, the tissue damage threshold (ED50) was determined to be 7.16 W/cm2. This value was in well agreement with that predicted using our computational models. We hope that knowledge of tissue-damage thresholds at THz frequencies helps to ensure the safe use of THz radiation.

  1. Radiation damage effects in zircon

    NASA Astrophysics Data System (ADS)

    Trachenko, Kostya; Dove, Martin; Salje, Ekhard

    2002-03-01

    Zircon, ZrSiO_4, is important for geology and geochronology, and has been proposed as a host material to immobilize highly radioactive materials from dismantled weapons and nuclear waste from power stations [1]. In these applications zircon is exposed to alpha-irradiation. Computer simulations have started to be employed to simulate radiation damage in zircon [2], but the origin and microscopic mechanisms of the most important structural changes in zircon - unit cell expansion and large macroscopic swelling at higher doses, strong shear deformation of the crystalline lattice, and polymerization of SiOn units [3], remain unknown. Here, we perform the molecular dynamics simulation of highly energetic recoils in zircon. Basing on the simulation results, we propose the simple picture of the density change in the damaged region that consists of the depleted and densified matter. We find that the experimentally observed structural changes originate from the interaction of the damaged region with the surrounding crystalline lattice: the shear of the lattice around the damaged region causes shear deformation and expansion of the unit cells. The polymers of connected SiOn polyhedra are most commonly present in the densified shell at the periphery of the damaged region. [1] R C Ewing et al, J. Mater. Res. 10, 243 (1995); W J Weber et al, B E Burakov et al, in Scientific Basis for Nuclear Waste Management XIX, 25-32 and 33-40 (Plenum, New York, 1996); R C Ewing, et al in Crystalline Ceramics: Waste Forms for the Disposal of Weapons Plutonium, NATO Workshop Proceedings 65 (Academic Publishers, Dordrecht, The Netherlands, 1996). [2] B Park et al, Phys. Rev. B, 64, 174108 (1-16) (2001); J P Crocombette and D Ghaleb, J. Nucl. Mater., 295, 167 (2001); K Trachenko et al, J. Appl. Phys., 87, 7702 (2000); K Trachenko et al, J. Phys.: Cond. Matt., 13, 1947 (2001). [3] T Murakami et al, Am. Min., 76, 1510 (1991); H D Holland and D Gottfried, Acta Cryst. 8, 291 (1955).; W J Weber, J. Am

  2. Radiation-induced genomic instability

    NASA Technical Reports Server (NTRS)

    Kronenberg, A.

    1994-01-01

    Quantitative assessment of the heritable somatic effects of ionizing radiation exposures has relied upon the assumption that radiation-induced lesions were 'fixed' in the DNA prior to the first postirradiation mitosis. Lesion conversion was thought to occur during the initial round of DNA replication or as a consequence of error-prone enzymatic processing of lesions. The standard experimental protocols for the assessment of a variety of radiation-induced endpoints (cell death, specific locus mutations, neoplastic transformation and chromosome aberrations) evaluate these various endpoints at a single snapshot in time. In contrast with the aforementioned approaches, some studies have specifically assessed radiation effects as a function of time following exposure. Evidence has accumulated in support of the hypothesis that radiation exposure induces a persistent destabilization of the genome. This instability has been observed as a delayed expression of lethal mutations, as an enhanced rate of accumulation of non-lethal heritable alterations, and as a progressive intraclonal chromosomal heterogeneity. The genetic controls and biochemical mechanisms underlying radiation-induced genomic instability have not yet been delineated. The aim is to integrate the accumulated evidence that suggests that radiation exposure has a persistent effect on the stability of the mammalian genome.

  3. Repair of radiation damage in mammalian cells

    SciTech Connect

    Setlow, R.B.

    1981-01-01

    The responses, such as survival, mutation, and carcinogenesis, of mammalian cells and tissues to radiation are dependent not only on the magnitude of the damage to macromolecular structures - DNA, RNA, protein, and membranes - but on the rates of macromolecular syntheses of cells relative to the half-lives of the damages. Cells possess a number of mechanisms for repairing damage to DNA. If the repair systems are rapid and error free, cells can tolerate much larger doses than if repair is slow or error prone. It is important to understand the effects of radiation and the repair of radiation damage because there exist reasonable amounts of epidemiological data that permits the construction of dose-response curves for humans. The shapes of such curves or the magnitude of the response will depend on repair. Radiation damage is emphasized because: (a) radiation dosimetry, with all its uncertainties for populations, is excellent compared to chemical dosimetry; (b) a number of cancer-prone diseases are known in which there are defects in DNA repair and radiation results in more chromosomal damage in cells from such individuals than in cells from normal individuals; (c) in some cases, specific radiation products in DNA have been correlated with biological effects, and (d) many chemical effects seem to mimic radiation effects. A further reason for emphasizing damage to DNA is the wealth of experimental evidence indicating that damages to DNA can be initiating events in carcinogenesis.

  4. Genome Damage in Oropharyngeal Cancer Patients Treated by Radiotherapy

    PubMed Central

    Gamulin, Marija; Kopjar, Nevenka; Grgić, Mislav; Ramić, Snježana; Bišof, Vesna; Garaj-Vrhovac, Vera

    2008-01-01

    Aim To estimate genome damage in oropharyngeal cancer patients before, during, and after radiotherapy and to measure the persistence of caused genome damage relevant in the evaluation of secondary cancer risk. Methods DNA damage was evaluated in peripheral blood lymphocytes of 10 oropharyngeal cancer patients using alkaline comet assay, analysis of structural chromosome aberrations, and micronucleus assay. Blood samples were taken 2 hours before irradiation on day 1 of the first radiotherapy cycle, 2 hours after the application of the first dose, in the middle of the radiotherapy cycle, within 2 hours after the last received radiotherapy dose, and after 6 and 12 months after radiotherapy. Results In most participants, the highest level of primary DNA damage was recorded in blood samples collected after the administration of first radiation dose (mean tail length 25.04 ± 6.23 μm). Most patients also had increased frequency of comets with long tail-nucleus (LTN comets) after the administration of the first radiation dose (mean, 10.50 ± 7.71 per 100 comets), which remained increased in the middle of radiotherapy (mean, 18.30 ± 27.62 per 100 comets). Later on, the levels of primary DNA damage as recorded by the comet assay, slightly diminished. The frequency of structural chromosome aberrations in lymphocytes gradually increased during the radiation cycle (26.50 ± 27.72 per 100 metaphases at the end of the therapy), as well as the frequency of micronuclei (mean total number of micronuclei 167.20 ± 35.69; per 1000 binuclear cells). Conclusion Oropharyngeal cancer patients had relatively high levels of primary DNA damage in their peripheral blood lymphocytes even before therapy. The frequency of complex structural chromosome aberrations and the frequency of micronuclei increased with the progression of the radiation cycle and the doses delivered. As the frequency of chromosomal aberrations a year after radiotherapy mostly did not return to pre

  5. Radiation damage in barium fluoride detector materials

    SciTech Connect

    Levey, P.W.; Kierstead, J.A.; Woody, C.L.

    1988-01-01

    To develop radiation hard detectors, particularly for high energy physics studies, radiation damage is being studied in BaF/sub 2/, both undoped and doped with La, Ce, Nd, Eu, Gd and Tm. Some dopants reduce radiation damage. In La doped BaF/sub 2/ they reduce the unwanted long lifetime luminescence which interferes with the short-lived fluorescence used to detect particles. Radiation induced coloring is being studied with facilities for making optical measurements before, during and after irradiation with /sup 60/C0 gamma rays. Doses of 10/sup 6/ rad, or less, create only ionization induced charge transfer effects since lattice atom displacement damage is negligible at these doses. All crystals studied exhibit color center formation, between approximately 200 and 800 nm, during irradiation and color center decay after irradiation. Thus only measurements made during irradiation show the total absorption present in a radiation field. Both undoped and La doped BaF/sub 2/ develop damage at minimum detectable levels in the UV---which is important for particle detectors. For particle detector applications these studies must be extended to high dose irradiations with particles energetic enough to cause lattice atom displacement damage. In principle, the reduction in damage provided by dopants could apply to other applications requiring radiation damage resistant materials.

  6. Gamma Radiation Damage in Silicon

    NASA Astrophysics Data System (ADS)

    Chang, Chensen

    A theory for interpreting carrier removal in terms of trap production has been derived from the carrier distribution function, which provides a relationship between the carrier removal rate and trap production rates due to the radiation damage. The carrier removal rate is a function of trap production as well as Fermi level position. Also, the carrier removal rate depends on many parameters, which are the density of states of the valance band as well as the conduction band, density of doping impurities, temperature, location of donor and acceptor energy levels and location of trap energy levels. P-type and n-type silicon Schottky diodes are irradiated by cobalt 60 gamma rays. The experimental results show that the carrier removal rate is dependent on the initial carrier concentration. Carrier concentrations are determined by room temperature C-V measurements while the trap production rates are determined by DLTS from measurements from 50 K to room temperature. A model presented by Williams, et al. for the carrier concentration vs. fluence, has been rederived from simple semiconductor carrier statistical mechanics. This model has then been extended to yield an expression for the initial carrier removal rate which depends on the production rate of each defect trap level in the band gap. We have tested these models thoroughly for the first time by measuring the trap production rates by DLTS, and then, using this information to calculate carrier removal rate and carrier concentration vs. fluence, we have verified that the results of the model can explain these same relationships obtained experimentally by C-V measurements. We believe that this is the first time that DLTS results have been linked directly to such simple and useful measurements as carrier removal rate and carrier concentration vs. fluence in a convincing manner. The success of this procedure also suggests that there are no "hidden" levels or traps which contribute to carrier removal rate but which do not

  7. Seismic Radiation from Material Damage During Explosions

    NASA Astrophysics Data System (ADS)

    Rodgers, A. J.; Ben-Zion, Y.

    2010-12-01

    Recent theoretical results on seismic representation from regions undergoing rapid material damage indicate that changes of elastic moduli can produce radiation that may be, in some cases, a significant portion of (or even larger than) the radiation from the standard moment source (Ben-Zion and Ampuero, 2009). The additional radiation is associated with a “damage-related source term” involving the product of the changes in the elasticity tensor and the total elastic strain tensor. The damage source term is non-zero in a certain volume where brittle damage occurs. The generated seismic motion can be computed, as for the classical moment source, by a convolution of the damage density in the affected volume with the spatial derivative of a Green’s functions for an earth model. Here we attempt to provide estimates of the amount and types (isotropic and deviatoric) of the damage related radiation for explosion scenarios. Using both analytic solutions and three-dimensional elastic finite difference calculations, we compute and compare the waves generated by the classical moment and damage related source terms in a full space. We assume a purely isotropic explosion of size corresponding to low-yield nuclear explosions, a granite (hard-rock) whole-space, and that the damage occurs instantaneously. Using a simple iterative approach, we adjust the strain ɛij where it exceeds the yield strength of the rock ɛij_c and reduce the local elastic moduli in proportion to the difference (ɛij - ɛij_c). The calculated adjustments to the strain and reduction of elastic moduli are used to estimate the additional moment contribution due to excess strain (ɛij - ɛij_c) and the associated damage source term in the yielding region. Finally, the seismic radiation from the brittle damage process is computed and compared to the radiation generated by the moment of the explosion source and the additional inelastic relaxation in the yielding region.

  8. DNA Damage Signals and Space Radiation Risk

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.

    2011-01-01

    Space radiation is comprised of high-energy and charge (HZE) nuclei and protons. The initial DNA damage from HZE nuclei is qualitatively different from X-rays or gamma rays due to the clustering of damage sites which increases their complexity. Clustering of DNA damage occurs on several scales. First there is clustering of single strand breaks (SSB), double strand breaks (DSB), and base damage within a few to several hundred base pairs (bp). A second form of damage clustering occurs on the scale of a few kbp where several DSB?s may be induced by single HZE nuclei. These forms of damage clusters do not occur at low to moderate doses of X-rays or gamma rays thus presenting new challenges to DNA repair systems. We review current knowledge of differences that occur in DNA repair pathways for different types of radiation and possible relationships to mutations, chromosomal aberrations and cancer risks.

  9. Spectrum of complex DNA damages depends on the incident radiation

    NASA Astrophysics Data System (ADS)

    Hada, M.; Sutherland, B.

    Ionizing radiation induces clustered DNA damages in DNA-two or more abasic sites oxidized bases and strand breaks on opposite DNA strands within a few helical turns Clustered damages are considered to be difficult to repair and therefore potentially lethal and mutagenic damages Although induction of single strand breaks and isolated lesions has been studied extensively little is known of factors affecting induction of clusters other than double strand breaks DSB The aim of the present study was to determine whether the type of incident radiation could affect yield or spectra of specific clusters Genomic T7 DNA a simple 40 kbp linear blunt-ended molecule was irradiated in non-scavenging buffer conditions with Fe 970 MeV n Ti 980 MeV n C 293 MeV n Si 586 MeV n ions or protons 1 GeV n at the NASA Space Radiation Laboratory or with 100 kVp X-rays Irradiated DNA was treated with homogeneous Fpg or Nfo proteins or without enzyme treatment for DSB quantitation then electrophoresed in neutral agarose gels DSB Fpg-OxyPurine clusters and Nfo-Abasic clusters were quantified by number average length analysis The results show that the yields of all these complex damages depend on the incident radiation Although LETs are similar protons induced twice as many DSBs than did X-rays Further the spectrum of damage also depends on the radiation The yield damage Mbp Gy of all damages decreased with increasing linear energy transfer LET of the radiation The relative frequencies of DSBs to Abasic- and OxyBase clusters were higher

  10. Endoplasmic Reticulum Stress, Genome Damage, and Cancer

    PubMed Central

    Dicks, Naomi; Gutierrez, Karina; Michalak, Marek; Bordignon, Vilceu; Agellon, Luis B.

    2015-01-01

    Endoplasmic reticulum (ER) stress has been linked to many diseases, including cancer. A large body of work has focused on the activation of the ER stress response in cancer cells to facilitate their survival and tumor growth; however, there are some studies suggesting that the ER stress response can also mitigate cancer progression. Despite these contradictions, it is clear that the ER stress response is closely associated with cancer biology. The ER stress response classically encompasses activation of three separate pathways, which are collectively categorized the unfolded protein response (UPR). The UPR has been extensively studied in various cancers and appears to confer a selective advantage to tumor cells to facilitate their enhanced growth and resistance to anti-cancer agents. It has also been shown that ER stress induces chromatin changes, which can also facilitate cell survival. Chromatin remodeling has been linked with many cancers through repression of tumor suppressor and apoptosis genes. Interplay between the classic UPR and genome damage repair mechanisms may have important implications in the transformation process of normal cells into cancer cells. PMID:25692096

  11. The expected radiation damage of CSNS target

    NASA Astrophysics Data System (ADS)

    Yin, W.; Yu, Q. Z.; Lu, Y. L.; Wang, S. L.; Tong, J. F.; Liang, T. J.

    2012-12-01

    The radiation damage to the tungsten target and its SS316 vessel for Chinese Spallation Neutron Source (CSNS) has been estimated with a Monte-Carlo simulation code MCNPX2.5.0. We compare the effects on the radiation damage due to two different proton beam profiles: a uniform distribution and a Gaussian distribution. We also discuss the dependence of the radiation damage estimation on different physics models. The results show the peak displacement productions in vessel and the fourth target plate are 2.5 and 5.5 dpa/y, respectively, under a Gaussian proton beam. The peak helium productions in the vessel and the fourth target are 305 and 353 appm/y, respectively, under the same proton beam. Based on these results and the allowable dpa values we have estimated the lifetime of the tungsten target and its vessel.

  12. Nanofoams Response to Radiation Damage

    SciTech Connect

    Fu, Engang; Serrano De Caro, Magdalena; Wang, Yongqiang; Nastasi, Michael; Zepeda-Ruiz, Luis; Bringa, Eduardo M.; Baldwin, Jon K.; Caro, Jose A.

    2012-07-30

    Conclusions of this presentation are: (1) np-Au foams were successfully synthesized by de-alloying process; (2) np-Au foams remain porous structure after Ne ion irradiation to 1 dpa; (3) SFTs were observed in irradiated np-Au foams with highest and intermediate flux, while no SFTs were observed with lowest flux; (4) SFTs were observed in irradiated np-Au foams at RT, whereas no SFTs were observed at LNT irradiation; (5) The diffusivity of vacancies in Au at RT is high enough so that the vacancies have enough time to agglomerate and thus collapse. As a result, SFTs were formed; (6) The high flux created much more damage/time, vacancies don't have enough time to diffuse or recombine. As a result, SFTs were formed.

  13. Radiation damage in MINP cells

    NASA Astrophysics Data System (ADS)

    Minahan, J. A.; Green, M. J.

    Experiments have been carried out to examine the effects of exposure to various fluence levels of 1 MeV electrons on 0.2 ohm-cm MINP silicon solar cell characteristics. Fluence levels ranged from 10 to the 14th e/sq cm to 3 x 10 to the 15th e/sq cm. Minority carrier diffusion lengths, Lbase, were derived from short circuit current calculations that included corrections for surface shadowing, reflection and emitter contribution to the short circuit current. From Lbase and fluences, a damage coefficient for diffusion length was calculated (1.4 x 10 to the -9th/electron) and compared with results obtained for other cell designs and base resistivities.

  14. Elastic softening of zircon by radiation damage

    SciTech Connect

    Salje, Ekhard K. H.

    2006-09-25

    The bulk modulus and the shear modulus of zircon soften by ca. 50% when zircon is amorphized by radiation damage. A theoretical description of the experimental findings is presented which shows that the elastic response on a zircon ceramics with radiation damage follows Hashin-Shtrikman [J. Mech. Phys. Solids 11, 127 (1963)] behavior with very narrow bounds. The elastic response depends, in good approximation, on the square of the volume fraction f{sub a} of the amorphized regions. In a slightly coarser approximation one finds an almost linear interpolation of the bulk and the shear modulus between those of the crystalline state and those of the fully amorphous state.

  15. Radiation damage effects in polarized deuterated ammonia

    SciTech Connect

    P.M. McKee

    2003-07-01

    Solid polarized targets utilizing deuterated ammonia, {sup 15}ND{sub 3}, offer an attractive combination of high polarization, high dilution factor and high resistance to polarization losses from radiation damage. Jefferson Laboratory Experiment E93-026 used {sup 15}ND{sub 3} as a target material in a five-month form factor measurement, allowing a detailed study of it's performance. The dependence of the deuteron polarization on received dose by the ammonia and the effectiveness of annealing the material to recover performance lost to radiation damage will be discussed.

  16. Probing Radiation Damage at the Molecular Level

    NASA Astrophysics Data System (ADS)

    Mason, N. J.; Smialek, M. A.; Moore, S. A.; Folkard, M.; Hoffmann, S. V.

    2006-12-01

    Radiation damage of DNA and other cellular components has traditionally been attributed to ionisation via direct impact of high-energy quanta or by complex radical chemistry. However recent research has shown that strand breaks in DNA may be initiated by secondary electrons and is strongly dependent upon the target DNA base identity. Such research provides the fascinating perspective that it is possible that radiation damage may be described and understood at an individual molecular level introducing new possibilites for therapy and perhaps providing an insight into the origins of life.

  17. Pluripotent stem cells and DNA damage response to ionizing radiations

    PubMed Central

    Mujoo, Kalpana; Butler, E. Brian; Pandita, Raj K.; Hunt, Clayton R.; Pandita, Tej K.

    2016-01-01

    Pluripotent stem cells (PSCs) hold great promise in regenerative medicine, disease modeling, functional genomics, toxicological studies and cell-based therapeutics due to their unique characteristics of self-renewal and pluripotency. Novel methods for generation of pluripotent stem cells and their differentiation to the specialized cell types such as neuronal cells, myocardial cells, hepatocytes, and beta cells of the pancreas and many other cells of the body are constantly being refined. Pluripotent stem cell derived differentiated cells, including neuronal cells or cardiac cells are ideal for stem cell transplantation as autologous or allogeneic cells from healthy donors due to their minimum risks of rejection. DNA damage induced by ionizing radiation (IR), ultraviolet (UV) light, genotoxic stress, and other intrinsic and extrinsic factors trigger a series of biochemical reactions termed as DNA damage response (DDR). In order to maintain genomic stability, and avoid transmission of mutations into progenitors cells, stem cells have robust DNA damage response signaling – a contrast to somatic cells. Stem cell transplantation may over come the late effects related to radiation. This review will particularly focus on differential DNA damage response between stem cells and derived differentiated cells and the possible pathways that determine such differences. PMID:27332952

  18. Pluripotent Stem Cells and DNA Damage Response to Ionizing Radiations.

    PubMed

    Mujoo, Kalpana; Butler, E Brian; Pandita, Raj K; Hunt, Clayton R; Pandita, Tej K

    2016-07-01

    Pluripotent stem cells (PSCs) hold great promise in regenerative medicine, disease modeling, functional genomics, toxicological studies and cell-based therapeutics due to their unique characteristics of self-renewal and pluripotency. Novel methods for generation of pluripotent stem cells and their differentiation to the specialized cell types such as neuronal cells, myocardial cells, hepatocytes and beta cells of the pancreas and many other cells of the body are constantly being refined. Pluripotent stem cell derived differentiated cells, including neuronal cells or cardiac cells, are ideal for stem cell transplantation as autologous or allogeneic cells from healthy donors due to their minimal risk of rejection. Radiation-induced DNA damage, ultraviolet light, genotoxic stress and other intrinsic and extrinsic factors triggers a series of biochemical reactions known as DNA damage response. To maintain genomic stability and avoid transmission of mutations into progenitors cells, stem cells have robust DNA damage response signaling, a contrast to somatic cells. Stem cell transplantation may protect against radiation-induced late effects. In particular, this review focuses on differential DNA damage response between stem cells and derived differentiated cells and the possible pathways that determine such differences. PMID:27332952

  19. 3D-DIP-Chip: a microarray-based method to measure genomic DNA damage

    PubMed Central

    Powell, James Rees; Bennett, Mark Richard; Evans, Katie Ellen; Yu, Shirong; Webster, Richard Michael; Waters, Raymond; Skinner, Nigel; Reed, Simon Huw

    2015-01-01

    Genotoxins cause DNA damage, which can result in genomic instability. The genetic changes induced have far-reaching consequences, often leading to diseases such as cancer. A wide range of genotoxins exists, including radiations and chemicals found naturally in the environment, and in man-made forms created by human activity across a variety of industries. Genomic technologies offer the possibility of unravelling the mechanisms of genotoxicity, including the repair of genetic damage, enhancing our ability to develop, test and safely use existing and novel materials. We have developed 3D-DIP-Chip, a microarray-based method to measure the prevalence of genomic genotoxin-induced DNA damage. We demonstrate the measurement of both physical and chemical induced DNA damage spectra, integrating the analysis of these with the associated changes in histone acetylation induced in the epigenome. We discuss the application of the method in the context of basic and translational sciences. PMID:25609656

  20. The Status of Radiation Damage Experiments

    SciTech Connect

    Strachan, Denis M.; Scheele, Randall D.; Icenhower, Jonathan P.; Kozelisky, Anne E.; Sell, Richard L.; Legore, Virginia L.; Schaef, Herbert T.; O'Hara, Matthew J.; Brown, Christopher F.; Buchmiller, William C.

    2001-11-20

    Experiments have been on-going for about two years to determine the effects that radiation damage have on the physical and chemical properties of candidate titanate ceramics for the immobilization of plutonium. We summarize the results of these experiments in this document.

  1. Undulator Radiation Damage Experience at LCLS

    SciTech Connect

    Nuhn, H. D.; Field, C.; Mao, S.; Levashov, Y.; Santana, M.; Welch, J. N.; Wolf, Z.

    2015-01-06

    The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checked for magnetic (50 ppm, rms) and mechanic (about 0.25 µm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate.

  2. Acoustic emission sensor radiation damage threshold experiment

    SciTech Connect

    Beeson, K.M.; Pepper, C.E.

    1994-09-01

    Determination of the threshold for damage to acoustic emission sensors exposed to radiation is important in their application to leak detection in radioactive waste transport and storage. Proper response to system leaks is necessary to ensure the safe operation of these systems. A radiation impaired sensor could provide ``false negative or false positive`` indication of acoustic signals from leaks within the system. Research was carried out in the Radiochemical Technology Division at Oak Ridge National Laboratory to determine the beta/gamma radiation damage threshold for acoustic emission sensor systems. The individual system consisted of an acoustic sensor mounted with a two part epoxy onto a stainless steel waveguide. The systems were placed in an irradiation fixture and exposed to a Cobalt-60 source. After each irradiation, the sensors were recalibrated by Physical Acoustics Corporation. The results were compared to the initial calibrations performed prior to irradiation and a control group, not exposed to radiation, was used to validate the results. This experiment determines the radiation damage threshold of each acoustic sensor system and verifies its life expectancy, usefulness and reliability for many applications in radioactive environments.

  3. Gallium arsenide solar cell radiation damage study

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Herbert, G. A.; Kinnison, J. D.; Meulenberg, A.

    1989-01-01

    A thorough analysis has been made of electron- and proton- damaged GaAs solar cells suitable for use in space. It is found that, although some electrical parametric data and spectral response data are quite similar, the type of damage due to the two types of radiation is different. An I-V analysis model shows that electrons damage the bulk of the cell and its currents relatively more, while protons damage the junction of the cell and its voltages more. It is suggested that multiple defects due to protons in a strong field region such as a p/n junction cause the greater degradation in cell voltage, whereas the individual point defects in the quasi-neutral minority-carrier-diffusion regions due to electrons cause the greater degradation in cell current and spectral response.

  4. Density Functional Theory Models for Radiation Damage

    NASA Astrophysics Data System (ADS)

    Dudarev, S. L.

    2013-07-01

    Density functional theory models developed over the past decade provide unique information about the structure of nanoscale defects produced by irradiation and about the nature of short-range interaction between radiation defects, clustering of defects, and their migration pathways. These ab initio models, involving no experimental input parameters, appear to be as quantitatively accurate and informative as the most advanced experimental techniques developed for the observation of radiation damage phenomena. Density functional theory models have effectively created a new paradigm for the scientific investigation and assessment of radiation damage effects, offering new insight into the origin of temperature- and dose-dependent response of materials to irradiation, a problem of pivotal significance for applications.

  5. Radiation-induced genomic instability: radiation quality and dose response

    NASA Technical Reports Server (NTRS)

    Smith, Leslie E.; Nagar, Shruti; Kim, Grace J.; Morgan, William F.

    2003-01-01

    Genomic instability is a term used to describe a phenomenon that results in the accumulation of multiple changes required to convert a stable genome of a normal cell to an unstable genome characteristic of a tumor. There has been considerable recent debate concerning the importance of genomic instability in human cancer and its temporal occurrence in the carcinogenic process. Radiation is capable of inducing genomic instability in mammalian cells and instability is thought to be the driving force responsible for radiation carcinogenesis. Genomic instability is characterized by a large collection of diverse endpoints that include large-scale chromosomal rearrangements and aberrations, amplification of genetic material, aneuploidy, micronucleus formation, microsatellite instability, and gene mutation. The capacity of radiation to induce genomic instability depends to a large extent on radiation quality or linear energy transfer (LET) and dose. There appears to be a low dose threshold effect with low LET, beyond which no additional genomic instability is induced. Low doses of both high and low LET radiation are capable of inducing this phenomenon. This report reviews data concerning dose rate effects of high and low LET radiation and their capacity to induce genomic instability assayed by chromosomal aberrations, delayed lethal mutations, micronuclei and apoptosis.

  6. Radiation damage in nanostructured metallic films

    NASA Astrophysics Data System (ADS)

    Yu, Kaiyuan

    High energy neutron and charged particle radiation cause microstructural and mechanical degradation in structural metals and alloys, such as phase segregation, void swelling, embrittlement and creep. Radiation induced damages typically limit nuclear materials to a lifetime of about 40 years. Next generation nuclear reactors require materials that can sustain over 60 - 80 years. Therefore it is of great significance to explore new materials with better radiation resistance, to design metals with favorable microstructures and to investigate their response to radiation. The goals of this thesis are to study the radiation responses of several nanostructured metallic thin film systems, including Ag/Ni multilayers, nanotwinned Ag and nanocrystalline Fe. Such systems obtain high volume fraction of boundaries, which are considered sinks to radiation induced defects. From the viewpoint of nanomechanics, it is of interest to investigate the plastic deformation mechanisms of nanostructured films, which typically show strong size dependence. By controlling the feature size (layer thickness, twin spacing and grain size), it is applicable to picture a deformation mechanism map which also provides prerequisite information for subsequent radiation hardening study. And from the viewpoint of radiation effects, it is of interest to explore the fundamentals of radiation response, to examine the microstructural and mechanical variations of irradiated nanometals and to enrich the design database. More importantly, with the assistance of in situ techniques, it is appealing to examine the defect generation, evolution, annihilation, absorption and interaction with internal interfaces (layer interfaces, twin boundaries and grain boundaries). Moreover, well-designed nanostructures can also verify the speculation that radiation induced defect density and hardening show clear size dependence. The focus of this thesis lies in the radiation response of Ag/Ni multilayers and nanotwinned Ag

  7. Nonuniform radiation damage in permanent magnet quadrupoles

    SciTech Connect

    Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.

    2014-08-15

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL’s pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.

  8. Nonuniform radiation damage in permanent magnet quadrupoles.

    PubMed

    Danly, C R; Merrill, F E; Barlow, D; Mariam, F G

    2014-08-01

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL's pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components. PMID:25173260

  9. Radiation damage in Luna 20 soil.

    NASA Technical Reports Server (NTRS)

    Phakey, P. P.; Price, P. B.

    1973-01-01

    As an extension of previous studies of radiation damage produced by heavy solar flare ions in lunar soils, high-voltage electron microscopy and electron diffraction procedures were used to rank a Luna 20 sample among the other soils returned by Soviet and American lunar missions. Micron-sized soil grains from the Luna 20 mission are the most lightly irradiated, in contrast to micron-sized grains from Luna 16 soil, which are the most heavily irradiated.

  10. Modulation of irinotecan-induced genomic DNA damage by theanine.

    PubMed

    Attia, Sabry

    2012-05-01

    The possible chemoprotective activity of theanine against irinotecan-induced genomic DNA damage towards mouse bone marrow cells was investigated. Chromosomal aberrations, DNA damage, micronuclei formation and mitotic activity were studied in the current study as markers of genomic damage. Oxidative DNA stress markers such as 8-hydroxydeoxyguanosine, lipid peroxidation, reduced and oxidized glutathione levels were assessed as a possible mechanism underlying this amelioration. Theanine was neither genotoxic nor cytotoxic in mice at doses equivalent to 30 or 60 mg/kg for 12 days. Pretreatment of mice with theanine significantly reduced irinotecan-induced genomic damage in the bone marrow cells and these effects were dose dependent. Irinotecan induced marked biochemical alterations characteristic of oxidative DNA stress, including increased 8-hydroxydeoxyguanosine, enhanced lipid peroxidation and reduction in the reduced/oxidized glutathione ratio. Prior administration of theanine ahead of irinotecan challenge ameliorated these oxidative DNA stress markers. Overall, this study provides for the first time that theanine has a protective role in the abatement of irinotecan-induced genomic damage in the bone marrow cells of mice that resides, at least in part, on its ability to modulate the cellular antioxidant levels and consequently protect bone marrow from irinotecan genotoxicity. PMID:22414655

  11. Follow-up studies on genome damage in children after Chernobyl nuclear power plant accident.

    PubMed

    Fucic, Aleksandra; Aghajanyan, Anna; Druzhinin, Vladimir; Minina, Varvara; Neronova, Elizaveta

    2016-09-01

    As children are more susceptible to ionizing radiation than adults, each nuclear accident demands special attention and care of this vulnerable population. The Chernobyl nuclear disaster occurred in a region populated with a large number of children, but despite all efforts and expertise of nuclear specialists, it was not possible to avoid casualties. As vast regions of Ukraine, Belarus and Russia were exposed to doses of ionizing radiation, which are known to be related with different diseases, shortly after the accident medical surveillance was launched, which also included analysis of genome damage. Child population affected by internal and external radiation consisted of subjects exposed prenatally, postnatally (both evacuated and non-evacuated), born by irradiated fathers who worked as liquidators, and parents exposed environmentally. In all groups of children during the last 30 years who were exposed to doses which were significantly higher than that recommended for general population of 1 mSv per year, increased genome damage was detected. Increased genome damage includes statistically higher frequency of dicentric and ring chromosomes, chromated and chromosome breaks, acentric fragments, translocations, and micronuclei. The presence of rogue cells confirmed internal contamination. Genome instability and radiosensitivity in children was detected both in evacuated and continuously exposed children. Today the population exposed to ionizing radiation in 1986 is in reproductive period of life and follow-up of this population and their offspring is of great importance. This review aims to give insight in results of studies, which reported genome damage in children in journals without language restrictions. PMID:27329326

  12. Impact of Genomic Methylation on Radiation Sensitivity of Colorectal Carcinoma

    SciTech Connect

    Hofstetter, Barbara; Niemierko, Andrzej; Forrer, Christian; Benhattar, Jean; Albertini, Veronica; Pruschy, Martn; Bosman, Fred T.; Catapano, Carlo V.; Ciernik, I. Frank

    2010-04-15

    Purpose: To investigate the influence of demethylation with 5-aza-cytidine (AZA) on radiation sensitivity and to define the intrinsic radiation sensitivity of methylation deficient colorectal carcinoma cells. Methods and Materials: Radiation sensitizing effects of AZA were investigated in four colorectal carcinoma cell lines (HCT116, SW480, L174 T, Co115), defining influence of AZA on proliferation, clonogenic survival, and cell cycling with or without ionizing radiation. The methylation status for cancer or DNA damage response-related genes silenced by promoter methylation was determined. The effect of deletion of the potential target genes (DNMT1, DNMT3b, and double mutants) on radiation sensitivity was analyzed. Results: AZA showed radiation sensitizing properties at >=1 {mu}mol/l, a concentration that does not interfere with the cell cycle by itself, in all four tested cell lines with a sensitivity-enhancing ratio (SER) of 1.6 to 2.1 (confidence interval [CI] 0.9-3.3). AZA successfully demethylated promoters of p16 and hMLH1, genes associated with ionizing radiation response. Prolonged exposure to low-dose AZA resulted in sustained radiosensitivity if associated with persistent genomic hypomethylation after recovery from AZA. Compared with maternal HCT116 cells, DNMT3b-defcient deficient cells were more sensitive to radiation with a SER of 2.0 (CI 0.9-2.1; p = 0.03), and DNMT3b/DNMT1-/- double-deficient cells showed a SER of 1.6 (CI 0.5-2.7; p = 0.09). Conclusions: AZA-induced genomic hypomethylation results in enhanced radiation sensitivity in colorectal carcinoma. The mediators leading to sensitization remain unknown. Defining the specific factors associated with radiation sensitization after genomic demethylation may open the way to better targeting for the purpose of radiation sensitization.

  13. Radiation damage calculations for the LANSCE degrader

    SciTech Connect

    Ferguson, P.D.; Sommer, W.F.; Dudziak, D.J.; Wechsler, M.S.; Barnett, M.H.; Corzine, R.K.

    1998-09-01

    The A-6 water degrader at the Los Alamos Neutron Science Center (LANSCE) linear proton accelerator has an outer shell of Inconel 718. The degrader was irradiated by 800-MeV protons during 1988--1993 to an exposure of 5.3 ampere-hours (A h). As described in Ref. 1, material from the Inconel is currently being cut into specimens for microhardness, three-point bending, ball punch, microscopy, and corrosion tests. This paper is devoted to calculations of radiation damage, particularly displacement and He production, sustained by the degrader Inconel.

  14. Radiation damage of transition metal carbides

    SciTech Connect

    Dixon, G.

    1991-01-01

    In this grant period we have investigated electrical properties of transition metal carbides and radiation-induced defects produced by low-temperature electron irradiation in them. Special attention has been given to the composition VC[sub 0.88] in which the vacancies on the carbon sublattice of this fcc crystal order to produce a V[sub 8]C[sub 7] superlattice. The existence of this superlattice structure was found to make the crystal somewhat resistant to radiation damage at low doses and/or at ambient temperature. At larger doses significant changes in the resistivity are produced. Annealing effects were observed which we believe to be connected with the reconstitution of the superlattice structure.

  15. Radiation damage in cubic-stabilized zirconia

    SciTech Connect

    Costantini, Jean-Marc; Beuneu, Francois; Weber, William J

    2013-01-01

    Cubic yttria-stabilized zirconia (YSZ) can be used for nuclear applications as an inert matrix for actinide immobilization or transmutation. Indeed, the large amount of native oxygen vacancies leads to a high radiation tolerance of this material owing to defect recombination occurring in the atomic displacements cascades induced by fast neutron irradiation or ion implantations, as showed by Molecular dynamics (MD) simulations. Amorphization cannot be obtained in YSZ either by nuclear-collision or electronic-excitation damage, just like in urania. A kind of polygonization structure with slightly disoriented crystalline domains is obtained in both cases. In the first steps of damage, specific isolated point defects (like F+-type color centers) and point-defect clusters are produced by nuclear collisions with charged particles or neutrons. Further increase of damage leads to dislocation-loop formation, then to collapse of the dislocation network into a polygonization structure. For swift heavy ion irradiations, a similar polygonization structure is obtained above a threshold stopping power value of about 20-30 keV nm-1.

  16. Radiation damage in zircon and monazite

    SciTech Connect

    Meldrum, A.; Boatner, L.A.; Weber, W.J.; Ewing, R.C.

    1998-07-01

    Monazite and zircon respond differently to ion irradiation and to thermal and irradiation-enhanced annealing. The damage process (i.e., elastic interactions leading to amorphization) in radioactive minerals (metamictization) is basically the same as for the ion-beam-irradiated samples with the exception of the dose rate which is much lower in the case of natural samples. The crystalline-to-metamict transition in natural samples with different degrees of damage, from almost fully crystalline to completely metamict, is compared to the sequence of microstructures observed for ion-beam-irradiated monazite and zircon. The damage accumulation process, representing the competing effects of radiation-induced structural disorder and subsequent annealing mechanisms (irradiation-enhanced and thermal) occurs at much higher temperatures for zircon than for monazite. The amorphization dose, expressed as displacements per atom, is considerably higher in the natural samples, and the atomic-scale process leading to metamictization appears to develop differently. Ion-beam-induced amorphization data were used to calculate the {alpha}-decay-event dose required for amorphization in terms of a critical radionuclide concentration, i.e., the concentration above which a sample of a given age will become metamict at a specific temperature. This equation was applied to estimate the reliability of U-Pb ages, to provide a qualitative estimate of the thermal history of high-U natural zircons, and to predict whether actinide-bearing zircon or monazite nuclear waste forms will become amorphous (metamict) over long timescales.

  17. Radiation induced genome instability: multiscale modelling and data analysis

    NASA Astrophysics Data System (ADS)

    Andreev, Sergey; Eidelman, Yuri

    2012-07-01

    Genome instability (GI) is thought to be an important step in cancer induction and progression. Radiation induced GI is usually defined as genome alterations in the progeny of irradiated cells. The aim of this report is to demonstrate an opportunity for integrative analysis of radiation induced GI on the basis of multiscale modelling. Integrative, systems level modelling is necessary to assess different pathways resulting in GI in which a variety of genetic and epigenetic processes are involved. The multilevel modelling includes the Monte Carlo based simulation of several key processes involved in GI: DNA double strand breaks (DSBs) generation in cells initially irradiated as well as in descendants of irradiated cells, damage transmission through mitosis. Taking the cell-cycle-dependent generation of DNA/chromosome breakage into account ensures an advantage in estimating the contribution of different DNA damage response pathways to GI, as to nonhomologous vs homologous recombination repair mechanisms, the role of DSBs at telomeres or interstitial chromosomal sites, etc. The preliminary estimates show that both telomeric and non-telomeric DSB interactions are involved in delayed effects of radiation although differentially for different cell types. The computational experiments provide the data on the wide spectrum of GI endpoints (dicentrics, micronuclei, nonclonal translocations, chromatid exchanges, chromosome fragments) similar to those obtained experimentally for various cell lines under various experimental conditions. The modelling based analysis of experimental data demonstrates that radiation induced GI may be viewed as processes of delayed DSB induction/interaction/transmission being a key for quantification of GI. On the other hand, this conclusion is not sufficient to understand GI as a whole because factors of DNA non-damaging origin can also induce GI. Additionally, new data on induced pluripotent stem cells reveal that GI is acquired in normal mature

  18. Correlation between thermoluminescence and radiation damage in bismuth germanate

    SciTech Connect

    Melcher, C.L.

    1985-02-01

    Thermoluminescence properties of bismuth germanate and their relationship to radiation damage characteristics have been investigated. Thermoluminescence and radiation damage in bismuth germanate display several similar properties including similar responses as a function of radiation dose, similar saturation levels, and similar decay times. Also a correlation was found between the thermoluminescence sensitivities and radiation damage sensitivities of four different crystals. The traps responsible for the radiation damage and those which store the thermoluminescence signal appear to be either closely related or actually the same traps. Four trapping centers can be seen in the thermoluminescence glow curves. The depth of the dominant trap is 1.1 eV. 10 references.

  19. Radiation Damage In Reactor Cavity Concrete

    SciTech Connect

    Field, Kevin G; Le Pape, Yann; Naus, Dan J; Remec, Igor; Busby, Jeremy T; Rosseel, Thomas M; Wall, Dr. James Joseph

    2015-01-01

    License renewal up to 60 years and the possibility of subsequent license renewal to 80 years has established a renewed focus on long-term aging of nuclear generating stations materials, and recently, on concrete. Large irreplaceable sections of most nuclear generating stations include concrete. The Expanded Materials Degradation Analysis (EMDA), jointly performed by the Department of Energy, the Nuclear Regulatory Commission and Industry, identified the urgent need to develop a consistent knowledge base on irradiation effects in concrete. Much of the historical mechanical performance data of irradiated concrete does not accurately reflect typical radiation conditions in NPPs or conditions out to 60 or 80 years of radiation exposure. To address these potential gaps in the knowledge base, The Electric Power Research Institute and Oak Ridge National Laboratory are working to disposition radiation damage as a degradation mechanism. This paper outlines the research program within this pathway including: (i) defining the upper bound of the neutron and gamma dose levels expected in the biological shield concrete for extended operation (80 years of operation and beyond), (ii) determining the effects of neutron and gamma irradiation as well as extended time at temperature on concrete, (iii) evaluating opportunities to irradiate prototypical concrete under accelerated neutron and gamma dose levels to establish a conservative bound and share data obtained from different flux, temperature, and fluence levels, (iv) evaluating opportunities to harvest and test irradiated concrete from international NPPs, (v) developing cooperative test programs to improve confidence in the results from the various concretes and research reactors, (vi) furthering the understanding of the effects of radiation on concrete (see companion paper) and (vii) establishing an international collaborative research and information exchange effort to leverage capabilities and knowledge.

  20. Synergistic damage by UVA radiation and pollutants.

    PubMed

    Burke, K E; Wei, H

    2009-01-01

    Not only is skin cancer by far the most common human cancer but also the incidence of skin cancer has been increasing at an alarming rate in recent decades. Fortunately, most people now realize that sun exposure causes unattractive photoaging and skin cancer, so they do apply sunscreens conscientiously. However, until recently, most sunscreens did not adequately protect against ultraviolet A (UVA) radiation. Although UVA is indeed less erythrogenic and less carcinogenic than UVB, UVA directly causes photoaging and enhances UVB-induced skin cancer. Furthermore, recent research demonstrates that UVA combined with environmental pollutants (including cigarette smoke) significantly increases the risk of skin cancer. Similarly, previous research demonstrated another synergy between environmental pollutants and UV: When ozone exposure precedes UV exposure, there is enhancement of UV-induced depletion of protective vitamin E from the skin's stratum corneum. This article reviews experimental evidence that environmental pollutants (such as benzo[a]pyrene (BaP), a commonly used index of environmental pollution) are photosensitizers that generate reactive oxygen species (ROS) when exposed to UVA radiation. This in turn causes oxidative and genetic damage, leading to unattractive photodamage and carcinogenesis. PMID:19651790

  1. The activation of DNA damage detection and repair responses in cleavage-stage rat embryos by a damaged paternal genome.

    PubMed

    Grenier, Lisanne; Robaire, Bernard; Hales, Barbara F

    2012-06-01

    Male germ cell DNA damage, after exposure to radiation, exogenous chemicals, or chemotherapeutic agents, is a major cause of male infertility. DNA-damaged spermatozoa can fertilize oocytes; this is of concern because there is limited information on the capacity of early embryos to repair a damaged male genome or on the fate of these embryos if repair is inadequate. We hypothesized that the early activation of DNA damage response in the early embryo is a critical determinant of its fate. The objective of this study was to assess the DNA damage response and mitochondrial function as a measure of the energy supply for DNA repair and general health in cleavage-stage embryos sired by males chronically exposed to an anticancer alkylating agent, cyclophosphamide. Male rats were treated with saline or cyclophosphamide (6 mg/kg/day) for 4 weeks and mated to naturally cycling females. Pronuclear two- and eight-cell embryos were collected for immunofluorescence analysis of mitochondrial function and biomarkers of the DNA damage response: γH2AX foci, 53BP1 reactivity, and poly(ADP-ribose) polymer formation. Mitochondrial activities did not differ between embryos sired by control- and cyclophosphamide-exposed males. At the two-cell stage, there was no treatment-related increase in DNA double-strand breaks; by the eight-cell stage, a significant increase was noted, as indicated by increased medium and large γH2AX foci. This was accompanied by a dampened DNA repair response, detected as a decrease in the nuclear intensity of poly(ADP-ribose) polymers. The micronuclei formed in cyclophosphamide-sired embryos contained large γH2AX foci and enhanced poly(ADP-ribose) polymer and 53BP1 reactivity compared with their nuclear counterparts. Thus, paternal cyclophosphamide exposure activated a DNA damage response in cleavage-stage embryos. Furthermore, this damage response may be useful in assessing embryo quality and developmental competence. PMID:22454429

  2. Clustered DNA damages induced in isolated DNA and in human cells by low doses of ionizing radiation

    NASA Technical Reports Server (NTRS)

    Sutherland, B. M.; Bennett, P. V.; Sidorkina, O.; Laval, J.; Lowenstein, D. I. (Principal Investigator)

    2000-01-01

    Clustered DNA damages-two or more closely spaced damages (strand breaks, abasic sites, or oxidized bases) on opposing strands-are suspects as critical lesions producing lethal and mutagenic effects of ionizing radiation. However, as a result of the lack of methods for measuring damage clusters induced by ionizing radiation in genomic DNA, neither the frequencies of their production by physiological doses of radiation, nor their repairability, nor their biological effects are known. On the basis of methods that we developed for quantitating damages in large DNAs, we have devised and validated a way of measuring ionizing radiation-induced clustered lesions in genomic DNA, including DNA from human cells. DNA is treated with an endonuclease that induces a single-strand cleavage at an oxidized base or abasic site. If there are two closely spaced damages on opposing strands, such cleavage will reduce the size of the DNA on a nondenaturing gel. We show that ionizing radiation does induce clustered DNA damages containing abasic sites, oxidized purines, or oxidized pyrimidines. Further, the frequency of each of these cluster classes is comparable to that of frank double-strand breaks; among all complex damages induced by ionizing radiation, double-strand breaks are only about 20%, with other clustered damage constituting some 80%. We also show that even low doses (0.1-1 Gy) of high linear energy transfer ionizing radiation induce clustered damages in human cells.

  3. Genomic instability and bystander effects: a paradigm shift in radiation biology?

    NASA Technical Reports Server (NTRS)

    Morgan, William F.

    2002-01-01

    A basic paradigm in radiobiology is that, following exposure to ionizing radiation, the deposition of energy in the cell nucleus and the resulting damage to DNA, the principal target, are responsible for the radiation's deleterious biological effects. Findings in two rapidly expanding fields of research--radiation-induced genomic instability and bystander effects--have caused us to reevaluate these central tenets. In this article, the potential influence of induced genomic instability and bystander effects on cellular injury after exposure to low-level radiation will be reviewed.

  4. Chemistry of radiation damage to wire chambers

    SciTech Connect

    Wise, J.

    1992-08-01

    Proportional counters are used to study aspects of radiation damage to wire chambers (wire aging). Principles of low-pressure, rf plasma chemistry are used to predict the plasma chemistry in electron avalanches (1 atm, dc). (1) Aging is studied in CF{sub 4}/iC{sub 4}H{sub 10} gas mixtures. Wire deposits are analyzed by Auger electron spectroscopy. An apparent cathode aging process resulting in loss of gain rather than in a self-sustained current is observed in CF{sub 4}-rich gases. A four-part model considering plasma polymerization of the hydrocarbon, etching of wire deposits by CF{sub 4}, acceleration of deposition processes in strongly etching environments, and reactivity of the wire surface is developed to understand anode wire aging in CF{sub 4}/iC{sub 4}H{sub 10} gases. Practical guidelines suggested by the model are discussed. (2) Data are presented to suggest that trace amounts of Freons do not affect aging rates in either dimethyl ether or Ar/C{sub 2}H{sub 6}. Apparent loss of gain is explained by attachment of primary electrons to a continuously increasing concentration of Freon 11 (CCl{sub 3}F) in the counter gas. An increase in the concentration of Freon 11 in dimethyl ether is caused by a distillation process in the gas supply bottle and is a natural consequence of the unequal volatilities of the two compounds.

  5. Non-randomized mtDNA damage after ionizing radiation via charge transport

    NASA Astrophysics Data System (ADS)

    Zhou, Xin; Liu, Xinguo; Zhang, Xin; Zhou, Rong; He, Yang; Li, Qiang; Wang, Zhenhua; Zhang, Hong

    2012-10-01

    Although it is well known that there are mutation hot spots in mtDNA, whether there are damage hot spots remain elusive. In this study, the regional DNA damage of mitochondrial genome after ionizing radiation was determined by real-time quantitative PCR. The mtDNA damage level was found to be dose-dependent and regional unequal. The control region was the most susceptible region to oxidative damage. GGG, as an typical hole trap during charge transport, was found to be disproportionally enriched in the control region. A total of 107 vertebrate mitochondrial genomes were then analyzed to testify whether the GGG enrichment in control region was evolutionary conserved. Surprisingly, the triple G enrichment can be observed in most of the homeothermal animals, while the majority of heterothermic animals showed no triple G enrichment. These results indicated that the triple G enrichment in control region was related to the mitochondrial metabolism during evolution.

  6. UV Radiation Damage and Bacterial DNA Repair Systems

    ERIC Educational Resources Information Center

    Zion, Michal; Guy, Daniel; Yarom, Ruth; Slesak, Michaela

    2006-01-01

    This paper reports on a simple hands-on laboratory procedure for high school students in studying both radiation damage and DNA repair systems in bacteria. The sensitivity to ultra-violet (UV) radiation of both "Escherichia coli" and "Serratia marcescens" is tested by radiating them for varying time periods. Two growth temperatures are used in…

  7. DNA damage and repair after high LET radiation

    NASA Astrophysics Data System (ADS)

    O'Neill, Peter; Cucinotta, Francis; Anderson, Jennifer

    Predictions from biophysical models of interactions of radiation tracks with cellular DNA indicate that clustered DNA damage sites, defined as two or more lesions formed within one or two helical turns of the DNA by passage of a single radiation track, are formed in mammalian cells. These complex DNA damage sites are regarded as a signature of ionizing radiation exposure particularly as the likelihood of clustered damage sites arising endogenously is low. For instance, it was predicted from biophysical modelling that 30-40% of low LET-induced double strand breaks (DSB), a form of clustered damage, are complex with the yield increasing to >90% for high LET radiation, consistent with the reduced reparability of DSB with increasing ionization density of the radiation. The question arises whether the increased biological effects such as mutagenesis, carcinogenesis and lethality is in part related to DNA damage complexity and/or spatial distribution of the damage sites, which may lead to small DNA fragments. With particle radiation it is also important to consider not only delta-rays which may cause clustered damaged sites and may be highly mutagenic but the non-random spatial distribution of DSB which may lead to deletions. In this overview I will concentrate on the molecular aspects of the variation of the complexity of DNA damage on radiation quality and the challenges this complexity presents the DNA damage repair pathways. I will draw on data from micro-irradiations which indicate that the repair of DSBs by non-homologous end joining is highly regulated with pathway choice and kinetics of repair dependent on the chemical complexity of the DSB. In summary the aim is to emphasis the link between the spatial distribution of energy deposition events related to the track, the molecular products formed and the consequence of damage complexity contributing to biological effects and to present some of the outstanding molecular challenges with particle radiation.

  8. Homologous recombination maintenance of genome integrity during DNA damage tolerance

    PubMed Central

    Prado, Félix

    2014-01-01

    The DNA strand exchange protein Rad51 provides a safe mechanism for the repair of DNA breaks using the information of a homologous DNA template. Homologous recombination (HR) also plays a key role in the response to DNA damage that impairs the advance of the replication forks by providing mechanisms to circumvent the lesion and fill in the tracks of single-stranded DNA that are generated during the process of lesion bypass. These activities postpone repair of the blocking lesion to ensure that DNA replication is completed in a timely manner. Experimental evidence generated over the last few years indicates that HR participates in this DNA damage tolerance response together with additional error-free (template switch) and error-prone (translesion synthesis) mechanisms through intricate connections, which are presented here. The choice between repair and tolerance, and the mechanism of tolerance, is critical to avoid increased mutagenesis and/or genome rearrangements, which are both hallmarks of cancer. PMID:27308329

  9. Radiation Damage to Artemia Cysts:Effects of Water Vapor.

    PubMed

    Snipes, W C; Gordy, W

    1963-10-25

    Water vapor altered the form and greatly increased the rate of decay of the electron-spin resonance pattern of long-lived free radicals obtained upon gamma irradiation of Artemia salina cysts ( brine shrimp eggs). These results, combined with data on radiation survival, indicate that the water vapor protects the cysts from radiation damage, or heals the damage. They also indicate that water protects the cysts from the effect of oxygen by neutralizing the radiation-induced free radicals before they can interact with oxygen to produce irreversible damage. PMID:17748168

  10. Protecting the heritable genome: DNA damage response mechanisms in spermatogonial stem cells.

    PubMed

    Rübe, Claudia E; Zhang, Sheng; Miebach, Nadine; Fricke, Andreas; Rübe, Christian

    2011-02-01

    Spermatogonial stem cells (SSCs) must maintain the integrity of their genome to prevent reproduction failure and limit the hereditary risk associated with transmission to the progeny. SSCs must therefore have robust response mechanisms to counteract the potentially deleterious effects of DNA damage, with DNA double-strand breaks (DSBs) representing the greatest threat to genomic integrity. Through in vivo analysis of the DNA damage response of SSCs within their physiological tissue context, we aimed to gain insights into the mechanisms by which SSCs preserve genome integrity. After whole-body irradiation of repair-proficient and repair-deficient (DNA-PK- and ATM-deficient) mice, the formation and rejoining of DSBs was analyzed in SSCs of testis compared with somatic cells of other tissues by enumerating γH2AX-, MDC1-, and 53BP1-foci. Caspase-3 and PARP-1 were used as markers for apoptotic cell death. Our results show that DNA damage response mechanisms in SSCs characterized by unique chromatin compositions are markedly different from those of somatic cells. In SSCs lacking compact heterochromatin, histone-associated signaling components of the DNA repair machinery are completely absent and radiation-induced DSBs are rejoined predominantly by DNA-PK-independent pathways, suggesting the existence of alternative repair mechanisms. As a complimentary mechanism characterized by low thresholds for ATM-dependent checkpoint activation, the differentiating progeny, but not the SSCs themselves, promote apoptosis in response to low levels of DNA damage. By evaluating SSCs within their stem cell niche, we show that DNA repair, cell-cycle checkpoints, and apoptosis function together to maintain the integrity of the heritable genome. PMID:21123119

  11. Influence of Detector Radiation Damage on CR Mammography Quality Control.

    PubMed

    Moriwaki, Atsumi; Ishii, Mie; Terazono, Shiho; Arao, Keiko; Ishii, Rie; Sanada, Taizo; Yoshida, Akira

    2016-05-01

    Recently, radiation damage to the detector apparatus employed in computed radiography (CR) mammography has become problematic. The CR system and the imaging plate (IP) applied to quality control (QC) program were also used in clinical mammography in our hospital, and the IP to which radiation damage has occurred was used for approximately 5 years (approximately 13,000 exposures). We considered using previously acquired QC image data, which is stored in a server, to investigate the influence of radiation damage to an IP. The mammography unit employed in this study was a phase contrast mammography (PCM) Mermaid (KONICA MINOLTA) system. The QC image was made newly, and it was output in the film, and thereafter the optical density of the step-phantom image was measured. An input (digital value)-output (optical density) conversion curve was plotted using the obtained data. The digital values were then converted to optical density values using a reference optical density vs. digital value curve. When a high radiation dose was applied directly, radiation damage occurred at a position on the IP where no object was present. Daily QC for mammography is conducted using an American College of Radiology (ACR) accreditation phantom and acrylic disc, and an environmental background density measurement is performed as one of the management indexes. In this study, the radiation damage sustained by the acrylic disc was shown to differ from that of the background. Thus, it was revealed that QC results are influenced by radiation damage. PMID:27211088

  12. Enhanced annealing of GaAs solar cell radiation damage

    NASA Technical Reports Server (NTRS)

    Loo, R.; Knechtli, R. C.; Kamath, G. S.

    1981-01-01

    Solar cells are degraded by radiation damage in space. Investigations have been conducted concerning possibilities for annealing this radiation damage in GaAs solar cells, taking into account the conditions favoring such annealing. It has been found that continuous annealing as well as the combination of injection annealing with thermal annealing can lead to recovery from radiation damage under particularly favorable conditions in GaAs solar cells. The damage caused by both electrons and protons in GaAs solar cells can be substantially reduced by annealing at temperatures as low as 150 C, under appropriate conditions. This possibility makes the GaAs solar cells especially attractive for long space missions, or for missions in severe radiation environments. Attention is given to results concerning periodic thermal annealing, continuous annealing, and injection annealing combined with thermal annealing.

  13. Computer simulation of radiation damage in gallium arsenide

    NASA Technical Reports Server (NTRS)

    Stith, John J.; Davenport, James C.; Copeland, Randolph L.

    1989-01-01

    A version of the binary-collision simulation code MARLOWE was used to study the spatial characteristics of radiation damage in proton and electron irradiated gallium arsenide. Comparisons made with the experimental results proved to be encouraging.

  14. Clustered DNA damages induced by high and low LET radiation, including heavy ions

    NASA Technical Reports Server (NTRS)

    Sutherland, B. M.; Bennett, P. V.; Schenk, H.; Sidorkina, O.; Laval, J.; Trunk, J.; Monteleone, D.; Sutherland, J.; Lowenstein, D. I. (Principal Investigator)

    2001-01-01

    Clustered DNA damages--here defined as two or more lesions (strand breaks, oxidized purines, oxidized pyrimidines or abasic sites) within a few helical turns--have been postulated as difficult to repair accurately, and thus highly significant biological lesions. Further, attempted repair of clusters may produce double strand breaks (DSBs). However, until recently, there was no way to measure ionizing radiation-induced clustered damages, except DSB. We recently described an approach for measuring classes of clustered damages (oxidized purine clusters, oxidized pyrimidine clusters, abasic clusters, along with DSB). We showed that ionizing radiation (gamma rays and Fe ions, 1 GeV/amu) does induce such clusters in genomic DNA in solution and in human cells. These studies also showed that each damage cluster results from one radiation hit (and its track), thus indicating that they can be induced by very low doses of radiation, i.e. two independent hits are not required for cluster induction. Further, among all complex damages, double strand breaks comprise--at most-- 20%, with the other clustered damages being at least 80%.

  15. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Garlick, G. F. J.

    1987-01-01

    High-efficiency gallium arsenide cells, made by the liquid epitaxy method (LPE), have been irradiated with 1-MeV electrons up to fluences of 10 to the 16th e/sq cm. Measurements have been made of cell spectral response and dark and light-excited current-voltage characteristics and analyzed using computer-based models to determine underlying parameters such as damage coefficients. It is possible to use spectral response to sort out damage effects in the different cell component layers. Damage coefficients are similar to other reported in the literature for the emitter and buffer (base). However, there is also a damage effect in the window layer and possibly at the window emitter interface similar to that found for proton-irradiated liquid-phase epitaxy-grown cells. Depletion layer recombination is found to be less than theoretically expected at high fluence.

  16. Radiation damage effects on solid state detectors

    NASA Technical Reports Server (NTRS)

    Trainor, J. H.

    1972-01-01

    Totally depleted silicon diodes are discussed which are used as nuclear particle detectors in investigations of galactic and solar cosmic radiation and trapped radiation. A study of radiation and chemical effects on the diodes was conducted. Work on electron and proton irradiation of surface barrier detectors with thicknesses up to 1 mm was completed, and work on lithium-drifted silicon devices with thicknesses of several millimeters was begun.

  17. Effects Of Dose Rates On Radiation Damage In CMOS Parts

    NASA Technical Reports Server (NTRS)

    Goben, Charles A.; Coss, James R.; Price, William E.

    1990-01-01

    Report describes measurements of effects of ionizing-radiation dose rate on consequent damage to complementary metal oxide/semiconductor (CMOS) electronic devices. Depending on irradiation time and degree of annealing, survivability of devices in outer space, or after explosion of nuclear weapons, enhanced. Annealing involving recovery beyond pre-irradiation conditions (rebound) detrimental. Damage more severe at lower dose rates.

  18. Adaptive radiations: From field to genomic studies

    PubMed Central

    Hodges, Scott A.; Derieg, Nathan J.

    2009-01-01

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  19. Adaptive radiations: from field to genomic studies.

    PubMed

    Hodges, Scott A; Derieg, Nathan J

    2009-06-16

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  20. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Joslin, D.; Garlick, J.; Lillington, D.; Gillanders, M.; Cavicchi, B.; Scott-Monck, J.; Kachare, R.; Anspaugh, B.

    1987-01-01

    High efficiency liquid phase epitaxy (LPE) gallium arsenide cells were irradiated with 1 Mev electrons up to fluences of 1 times 10 to the 16th power cm-2. Measurements of spectral response and dark and illuminated I-V data were made at each fluence and then, using computer codes, the experimental data was fitted to gallium arsenide cell models. In this way it was possible to determine the extent of the damage, and hence damage coefficients in both the emitter and base of the cell.

  1. Radiation damage in charge-coupled devices.

    PubMed

    Bassler, Niels

    2010-08-01

    Due to their high sensitivity and signal-to-noise ratio, charge-coupled devices (CCDs) have been the preferred optical photon detectors of astronomers for several decades. CCDs are flown in space as the main detection instrument on several well-known missions, such as the Hubble Space Telescope, XMM-Newton or the Cassini Probe. Also, CCDs are frequently used in satellite star trackers which provide attitude information to the satellite orientation system. However, one major drawback is their extreme vulnerability to radiation, which is readily abundant in space. Here, we shall give a brief overview of the radiation effects on CCDs, and mention ways how to mitigate the effects in other ways than merely increase shielding, such as cooling and annealing. As an example, we have investigated the radiation hardness of a particular CCD, the so-called CCD47-20 from Marconi Applied Technologies (now E2V), by exposing it to radiation fields representing the radiation environment found in a highly elliptic orbit crossing the Van-Allen radiation belts. Two engineering-grade CCDs were irradiated with proton beams and photons, and effects of increased bulk dark current, surface dark current and inversion threshold voltage shifts were observed and are quantified. PMID:20238121

  2. Electronic effects in high-energy radiation damage in tungsten

    DOE PAGESBeta

    Zarkadoula, Eva; Duffy, Dorothy M.; Nordlund, Kai; Seaton, M. A.; Todorov, I. T.; Weber, William J.; Trachenko, Kostya

    2015-01-01

    Even though the effects of the electronic excitations during high-energy radiation damage processes are not currently understood, it is shown that their role in the interaction of radiation with matter is important. We perform molecular dynamics simulations of high-energy collision cascades in bcc-tungsten using the coupled two-temperature molecular dynamics (2T-MD) model that incorporates both the effects of electronic stopping and electron–phonon interaction. We compare the combination of these effects on the induced damage with only the effect of electronic stopping, and conclude in several novel insights. In the 2T-MD model, the electron–phonon coupling results in less damage production in themore » molten region and in faster relaxation of the damage at short times. We show these two effects lead to a significantly smaller amount of the final damage at longer times.« less

  3. Electronic effects in high-energy radiation damage in tungsten

    SciTech Connect

    Zarkadoula, Eva; Duffy, Dorothy M.; Nordlund, Kai; Seaton, M. A.; Todorov, I. T.; Weber, William J.; Trachenko, Kostya

    2015-01-01

    Even though the effects of the electronic excitations during high-energy radiation damage processes are not currently understood, it is shown that their role in the interaction of radiation with matter is important. We perform molecular dynamics simulations of high-energy collision cascades in bcc-tungsten using the coupled two-temperature molecular dynamics (2T-MD) model that incorporates both the effects of electronic stopping and electron–phonon interaction. We compare the combination of these effects on the induced damage with only the effect of electronic stopping, and conclude in several novel insights. In the 2T-MD model, the electron–phonon coupling results in less damage production in the molten region and in faster relaxation of the damage at short times. We show these two effects lead to a significantly smaller amount of the final damage at longer times.

  4. Radiation damage to scintillator in the D0 luminosity monitor

    SciTech Connect

    Casey, Brendan; DeVaughan, Kayle; Enari, Yuji; Partridge, Richard; Yacoob, Sahal; /Northwestern U.

    2006-12-01

    We report the result of evaluating radiation damage to Bicron BC408 plastic scintillator used in the D0 Luminosity Monitor during Run IIa. The Luminosity Monitor provides pseudo-rapidity coverage over the range 2.7 < |{eta}| < 4.4, with the radiation dose in Run IIa estimated to be 0.5 MRad for the region closest to the beams. We find the light yield is degraded by 10-15% due to radiation damage by comparing new and old scintillator in four observables: (1) visual inspection, (2) optical transmittance, (3) response to the radioactive source of {sup 90}Sr and (4) light yield for cosmic rays.

  5. Radiation damage to nucleoprotein complexes in macromolecular crystallography

    PubMed Central

    Bury, Charles; Garman, Elspeth F.; Ginn, Helen Mary; Ravelli, Raimond B. G.; Carmichael, Ian; Kneale, Geoff; McGeehan, John E.

    2015-01-01

    Significant progress has been made in macromolecular crystallography over recent years in both the understanding and mitigation of X-ray induced radiation damage when collecting diffraction data from crystalline proteins. In contrast, despite the large field that is productively engaged in the study of radiation chemistry of nucleic acids, particularly of DNA, there are currently very few X-ray crystallographic studies on radiation damage mechanisms in nucleic acids. Quantitative comparison of damage to protein and DNA crystals separately is challenging, but many of the issues are circumvented by studying pre-formed biological nucleoprotein complexes where direct comparison of each component can be made under the same controlled conditions. Here a model protein–DNA complex C.Esp1396I is employed to investigate specific damage mechanisms for protein and DNA in a biologically relevant complex over a large dose range (2.07–44.63 MGy). In order to allow a quantitative analysis of radiation damage sites from a complex series of macromolecular diffraction data, a computational method has been developed that is generally applicable to the field. Typical specific damage was observed for both the protein on particular amino acids and for the DNA on, for example, the cleavage of base-sugar N1—C and sugar-phosphate C—O bonds. Strikingly the DNA component was determined to be far more resistant to specific damage than the protein for the investigated dose range. At low doses the protein was observed to be susceptible to radiation damage while the DNA was far more resistant, damage only being observed at significantly higher doses. PMID:25723923

  6. Space solar cells - High efficiency and radiation damage

    NASA Technical Reports Server (NTRS)

    Brandhorst, H. W., Jr.; Bernatowicz, D. T.

    1980-01-01

    The proceedings of the Third Solar Cell High Efficiency and Radiation Damage Meeting are outlined. The topics covered included high efficiency silicon solar cells, silicon solar cell radiation damage, GaAs solar cell performance, and 30 percent conversion devices. The study of radiation damage from a fundamental defect-centered basis is discussed and evaluated as a focus of future work. 18% AM0 efficiency and 0.7 V open-circuit voltages are designated as achievable goals for silicon solar cells, and the potential for 30% AM0 efficiencies from monolithic tandem cell designs without sunlight concentration is noted. In addition to its potential for 20% AM0 efficiencies, the GaAs cell offers the possibility of a radiation-insensitive power supply when operated at temperatures near 200 C.

  7. Radiation-induced DNA damage and chromatin structure

    NASA Technical Reports Server (NTRS)

    Rydberg, B.; Chatterjee, A. (Principal Investigator)

    2001-01-01

    DNA lesions induced by ionizing radiation in cells are clustered and not randomly distributed. For low linear energy transfer (LET) radiation this clustering occurs mainly on the small scales of DNA molecules and nucleosomes. For example, experimental evidence suggests that both strands of DNA on the nucleosomal surface can be damaged in single events and that this damage occurs with a 10-bp modulation because of protection by histones. For high LET radiation, clustering also occurs on a larger scale and depends on chromatin organization. A particularly significant clustering occurs when an ionizing particle traverses the 30 nm chromatin fiber with generation of heavily damaged DNA regions with an average size of about 2 kbp. On an even larger scale, high LET radiation can produce several DNA double-strand breaks in closer proximity than expected from randomness. It is suggested that this increases the probability of misrejoining of DNA ends and generation of lethal chromosome aberrations.

  8. Kinetic Modeling of Damage Repair, Genome Instability, and Neoplastic Transformation

    SciTech Connect

    Stewart, Robert D

    2007-03-17

    Inducible repair and pathway interactions may fundamentally alter the shape of dose-response curves because different mechanisms may be important under low- and high-dose exposure conditions. However, the significance of these phenomena for risk assessment purposes is an open question. This project developed new modeling tools to study the putative effects of DNA damage induction and repair on higher-level biological endpoints, including cell killing, neoplastic transformation and cancer. The project scope included (1) the development of new approaches to simulate the induction and base excision repair (BER) of DNA damage using Monte Carlo methods and (2) the integration of data from the Monte Carlo simulations with kinetic models for higher-level biological endpoints. Methods of calibrating and testing such multiscale biological simulations were developed. We also developed models to aid in the analysis and interpretation of data from experimental assays, such as the pulsed-field gel electrophoresis (PFGE) assay used to quantity the amount of DNA damage caused by ionizing radiation.

  9. Probing Radiation Damage in Plutonium Alloys with Multiple Measurement Techniques

    SciTech Connect

    McCall, S K; Fluss, M J; Chung, B W

    2010-04-21

    A material subjected to radiation damage will usually experience changes in its physical properties. Measuring these changes in the physical properties provides a basis to study radiation damage in a material which is important for a variety of real world applications from reactor materials to semiconducting devices. When investigating radiation damage, the relative sensitivity of any given property can vary considerably based on the concentration and type of damage present as well as external parameters such as the temperature and starting material composition. By measuring multiple physical properties, these differing sensitivities can be leveraged to provide greater insight into the different aspects of radiation damage accumulation, thereby providing a broader understanding of the mechanisms involved. In this report, self-damage from {alpha}-particle decay in Pu is investigated by measuring two different properties: magnetic susceptibility and resistivity. The results suggest that while the first annealing stage obeys second order chemical kinetics, the primary mechanism is not the recombination of vacancy-interstitial close pairs.

  10. Radiation-damaged tyrosinase molecules are inactive

    SciTech Connect

    Kempner, E.S.; Miller, J.H.

    1989-01-01

    Target analysis of radiation inactivation of mushroom tyrosinase yields different target sizes for diphenoloxidase and monophenoloxidase activities, which correspond to the subunits H and HL2 (or HL), respectively. After gel electrophoresis of irradiated samples, all diphenoloxidase activity is observed at the same position as seen in the original material. Radiolytic fragments contain no detectable activity, consistent with a fundamental assumption of target theory.

  11. Damage-tolerant nanotwinned metals with nanovoids under radiation environments.

    PubMed

    Chen, Y; Yu, K Y; Liu, Y; Shao, S; Wang, H; Kirk, M A; Wang, J; Zhang, X

    2015-01-01

    Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials. PMID:25906997

  12. Damage-tolerant nanotwinned metals with nanovoids under radiation environments

    PubMed Central

    Chen, Y.; Yu, K Y.; Liu, Y.; Shao, S.; Wang, H.; Kirk, M. A.; Wang, J.; Zhang, X.

    2015-01-01

    Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials. PMID:25906997

  13. Damage-tolerant nanotwinned metals with nanovoids under radiation environments

    DOE PAGESBeta

    Chen, Y.; Yu, K. Y.; Liu, Y.; Shao, S.; Wang, H.; Kirk, M. A.; Wang, J.; Zhang, X.

    2015-04-24

    Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from highmore » density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.« less

  14. Damage-tolerant nanotwinned metals with nanovoids under radiation environments

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Yu, K. Y.; Liu, Y.; Shao, S.; Wang, H.; Kirk, M. A.; Wang, J.; Zhang, X.

    2015-04-01

    Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.

  15. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D.W.; Bennett, B.L.; Cockroft, N.J.

    1998-09-08

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal. 5 figs.

  16. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D. Wayne; Bennett, Bryan L.; Cockroft, Nigel J.

    1998-01-01

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal.

  17. Opportunities for nutritional amelioration of radiation-induced cellular damage.

    PubMed

    Turner, Nancy D; Braby, Leslie A; Ford, John; Lupton, Joanne R

    2002-10-01

    The closed environment and limited evasive capabilities inherent in space flight cause astronauts to be exposed to many potential harmful agents (chemical contaminants in the environment and cosmic radiation exposure). Current power systems used to achieve space flight are prohibitively expensive for supporting the weight requirements to fully shield astronauts from cosmic radiation. Therefore, radiation poses a major, currently unresolvable risk for astronauts, especially for long-duration space flights. The major detrimental radiation effects that are of primary concern for long-duration space flights are damage to the lens of the eye, damage to the immune system, damage to the central nervous system, and cancer. In addition to the direct damage to biological molecules in cells, radiation exposure induces oxidative damage. Many natural antioxidants, whether consumed before or after radiation exposure, are able to confer some level of radioprotection. In addition to achieving beneficial effects from long-known antioxidants such as vitamins E and C and folic acid, some protection is conferred by several recently discovered antioxidant molecules, such as flavonoids, epigallocatechin, and other polyphenols. Somewhat counterintuitive is the protection provided by diets containing elevated levels of omega-3 polyunsaturated fatty acids, considering they are thought to be prone to peroxidation. Even with the information we have at our disposal, it will be difficult to predict the types of dietary modifications that can best reduce the risk of radiation exposure to astronauts, those living on Earth, or those enduring diagnostic or therapeutic radiation exposure. Much more work must be done in humans, whether on Earth or, preferably, in space, before we are able to make concrete recommendations. PMID:12361786

  18. Opportunities for nutritional amelioration of radiation-induced cellular damage

    NASA Technical Reports Server (NTRS)

    Turner, Nancy D.; Braby, Leslie A.; Ford, John; Lupton, Joanne R.

    2002-01-01

    The closed environment and limited evasive capabilities inherent in space flight cause astronauts to be exposed to many potential harmful agents (chemical contaminants in the environment and cosmic radiation exposure). Current power systems used to achieve space flight are prohibitively expensive for supporting the weight requirements to fully shield astronauts from cosmic radiation. Therefore, radiation poses a major, currently unresolvable risk for astronauts, especially for long-duration space flights. The major detrimental radiation effects that are of primary concern for long-duration space flights are damage to the lens of the eye, damage to the immune system, damage to the central nervous system, and cancer. In addition to the direct damage to biological molecules in cells, radiation exposure induces oxidative damage. Many natural antioxidants, whether consumed before or after radiation exposure, are able to confer some level of radioprotection. In addition to achieving beneficial effects from long-known antioxidants such as vitamins E and C and folic acid, some protection is conferred by several recently discovered antioxidant molecules, such as flavonoids, epigallocatechin, and other polyphenols. Somewhat counterintuitive is the protection provided by diets containing elevated levels of omega-3 polyunsaturated fatty acids, considering they are thought to be prone to peroxidation. Even with the information we have at our disposal, it will be difficult to predict the types of dietary modifications that can best reduce the risk of radiation exposure to astronauts, those living on Earth, or those enduring diagnostic or therapeutic radiation exposure. Much more work must be done in humans, whether on Earth or, preferably, in space, before we are able to make concrete recommendations.

  19. Prognostic value of genomic damage in non-small-cell lung cancer.

    PubMed Central

    de Juan, C.; Iniesta, P.; Vega, F. J.; Peinado, M. A.; Fernandez, C.; Caldés, T.; Massa, M. J.; López, J. A.; Sánchez, A.; Torres, A. J.; Balibrea, J. L.; Benito, M.

    1998-01-01

    Genomic alterations have been analysed in 65 non-small-cell lung cancer (NSCLC) tissue samples by using the arbitrarily primed polymerase chain reaction (AP-PCR), which is a PCR-based genomic fingerprinting. We have shown that AP-PCR may be applied as a useful and feasible practical method for detection of the genomic alterations that accompany malignancy in NSCLC. Genomic changes detected by us consisted of: allelic losses or gains in anonymous DNA sequences, homozygously deleted DNA sequences and polymorphic DNA sequences. According to these genomic changes, lung tumours evaluated in the present study have been scored into three groups: low, moderate and high genomic damage tumours. The aim of this study was to investigate the effect of genomic damage on patient survival. Survival analysis was carried out in 51 NSCLC patients. Our results revealed that high genomic damage patients showed a poorer prognosis than those with low or moderate genomic damage (P = 0.038). Multivariate Cox regression analysis showed that patients with higher genomic alterations displayed an adjusted-by-stage risk ratio 4.26 times higher than the remaining patients (95% CI = 1.03-17.54). We can conclude that genomic damage has an independent prognostic value of poor clinical evolution in NSCLC. Images Figure 1 Figure 2 PMID:9667677

  20. High-energy radiation damage in zirconia: Modeling results

    NASA Astrophysics Data System (ADS)

    Zarkadoula, E.; Devanathan, R.; Weber, W. J.; Seaton, M. A.; Todorov, I. T.; Nordlund, K.; Dove, M. T.; Trachenko, K.

    2014-02-01

    Zirconia is viewed as a material of exceptional resistance to amorphization by radiation damage, and consequently proposed as a candidate to immobilize nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1-0.5 MeV energies with account of electronic energy losses. We find that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely isolated from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution, and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  1. High-energy radiation damage in zirconia: modeling results

    SciTech Connect

    Zarkadoula, Evangelia; Devanathan, Ram; Weber, William J; Seaton, M; Todorov, I T; Nordlund, Kai; Dove, Martin T; Trachenko, Kostya

    2014-01-01

    Zirconia is viewed as a material of exceptional resistance to amorphization by radiation damage, and consequently proposed as a candidate to immobilize nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1-0.5 MeV energies with account of electronic energy losses. We nd that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely isolated from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  2. High-energy radiation damage in zirconia: modeling results

    SciTech Connect

    Zarkadoula, Eva; Devanathan, Ram; Weber, William J.; Seaton, Michael; Todorov, Ilian; Nordlund, Kai; Dove, Martin T.; Trachenko, Kostya

    2014-02-28

    Zirconia has been viewed as a material of exceptional resistance to amorphization by radiation damage, and was consequently proposed as a candidate to immobilize nuclear waste and serve as a nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1-0.5 MeV energies with the account of electronic energy losses. We find that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely disjoint from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  3. High-energy radiation damage in zirconia: Modeling results

    SciTech Connect

    Zarkadoula, E.; Devanathan, R.; Weber, W. J.; Seaton, M. A.; Todorov, I. T.; Nordlund, K.; Dove, M. T.; Trachenko, K.

    2014-02-28

    Zirconia is viewed as a material of exceptional resistance to amorphization by radiation damage, and consequently proposed as a candidate to immobilize nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1–0.5 MeV energies with account of electronic energy losses. We find that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely isolated from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution, and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  4. Studying Radiation Damage in Structural Materials by Using Ion Accelerators

    NASA Astrophysics Data System (ADS)

    Hosemann, Peter

    2011-02-01

    Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.

  5. Raman study of radiation-damaged zircon under hydrostatic compression

    NASA Astrophysics Data System (ADS)

    Nasdala, Lutz; Miletich, Ronald; Ruschel, Katja; Váczi, Tamás

    2008-12-01

    Pressure-induced changes of Raman band parameters of four natural, gem-quality zircon samples with different degrees of self-irradiation damage, and synthetic ZrSiO4 without radiation damage, have been studied under hydrostatic compression in a diamond anvil cell up to ~10 GPa. Radiation-damaged zircon shows similar up-shifts of internal SiO4 stretching modes at elevated pressures as non-damaged ZrSiO4. Only minor changes of band-widths were observed in all cases. This makes it possible to estimate the degree of radiation damage from the width of the ν3(SiO4) band of zircon inclusions in situ, almost independent from potential “fossilized pressures” or compressive strain acting on the inclusions. An application is the non-destructive analysis of gemstones such as corundum or spinel: broadened Raman bands are a reliable indicator of self-irradiation damage in zircon inclusions, whose presence allows one to exclude artificial color enhancement by high-temperature treatment of the specimen.

  6. ANL/WSU radiation damage studies

    SciTech Connect

    Jankowski, D.; Lopiano, D.; Proudfoot, J.; Underwood, D.; Miles, L.; Neidiger, J.; Tripard, G.

    1993-12-31

    We report preliminary results for the radiation hardness of (polystryrene) plastic scintillator stacks using a spectrum of energy hardened neutrons from a MARK-III TRIGA reactor. The total dose ranged from 100 KRad to 3MRad. The corresponding fluence was 3.8 {times} 10{sup 13} to 3.8 {times} 10{sup 14} (n/cm/cm) with the gamma contribution on the order 2--3% (of fluence). The measurements used Li-6, Li-7 Thermo-luminescence dosimeters. Radiochromic/GaF- Chromic film, and activated foils simultaneously allowing an inter-comparison of these various methods of dosimetry.

  7. Proton radiation damage in optical filter glass

    NASA Technical Reports Server (NTRS)

    Grillot, Patrick N.; Rosenberg, William J.

    1989-01-01

    Samples of Schott BG-39 and Hoya CM-500 blue-green filter glass were subjected to proton radiation to determine their acceptability for spaceflight. Initial testing done with 2.7 MeV protons showed negligible change in optical transmittance with doses as high as 5.2 x 10 to the 14th protons per sq cm. Irradiation with protons of energy up to 63 MeV caused a significant reduction in transmittance in the Schott samples at doses of 5.3 x 10 to the 12th protons per sq cm, while negligible change occurred in the Hoya samples.

  8. Multiscale approach to the physics of radiation damage with ions

    SciTech Connect

    Surdutovich, Eugene; Solov'yov, Andrey V.

    2013-04-19

    We review a multiscale approach to the physics of ion-beam cancer therapy, an approach suggested in order to understand the interplay of a large number of phenomena involved in radiation damage scenario occurring on a range of temporal, spatial, and energy scales. We briefly overview its history and present the current stage of its development. The differences of the multiscale approach from other methods of understanding and assessment of radiation damage are discussed as well as its relationship to other branches of physics, chemistry and biology.

  9. Computer simulation radiation damages in condensed matters

    NASA Astrophysics Data System (ADS)

    Kupchishin, A. I.; Kupchishin, A. A.; Voronova, N. A.; Kirdyashkin, V. I.; Gyngazov, V. A.

    2016-02-01

    As part of the cascade-probability method were calculated the energy spectra of primary knocked-out atoms and the concentration of radiation-induced defects in a number of metals irradiated by electrons. As follows from the formulas, the number of Frenkel pairs at a given depth depends on three variables having certain physical meaning: firstly, Cd (Ea h) is proportional to the average energy of the considered depth of the PKA (if it is higher, than the greater number of atoms it will displace); secondly is inversely proportional to the path length λ2 for the formation of the PKA (if λ1 is higher than is the smaller the probability of interaction) and thirdly is inversely proportional to Ed. In this case calculations are in satisfactory agreement with the experimental data (for example, copper and aluminum).

  10. Gallium Arsenide solar cell radiation damage experiment

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Kinnison, J. D.; Herbert, G. A.; Meulenberg, A.

    1991-01-01

    Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

  11. RNA protects a nucleoprotein complex against radiation damage.

    PubMed

    Bury, Charles S; McGeehan, John E; Antson, Alfred A; Carmichael, Ian; Gerstel, Markus; Shevtsov, Mikhail B; Garman, Elspeth F

    2016-05-01

    Radiation damage during macromolecular X-ray crystallographic data collection is still the main impediment for many macromolecular structure determinations. Even when an eventual model results from the crystallographic pipeline, the manifestations of radiation-induced structural and conformation changes, the so-called specific damage, within crystalline macromolecules can lead to false interpretations of biological mechanisms. Although this has been well characterized within protein crystals, far less is known about specific damage effects within the larger class of nucleoprotein complexes. Here, a methodology has been developed whereby per-atom density changes could be quantified with increasing dose over a wide (1.3-25.0 MGy) range and at higher resolution (1.98 Å) than the previous systematic specific damage study on a protein-DNA complex. Specific damage manifestations were determined within the large trp RNA-binding attenuation protein (TRAP) bound to a single-stranded RNA that forms a belt around the protein. Over a large dose range, the RNA was found to be far less susceptible to radiation-induced chemical changes than the protein. The availability of two TRAP molecules in the asymmetric unit, of which only one contained bound RNA, allowed a controlled investigation into the exact role of RNA binding in protein specific damage susceptibility. The 11-fold symmetry within each TRAP ring permitted statistically significant analysis of the Glu and Asp damage patterns, with RNA binding unexpectedly being observed to protect these otherwise highly sensitive residues within the 11 RNA-binding pockets distributed around the outside of the protein molecule. Additionally, the method enabled a quantification of the reduction in radiation-induced Lys and Phe disordering upon RNA binding directly from the electron density. PMID:27139628

  12. RNA protects a nucleoprotein complex against radiation damage

    PubMed Central

    Bury, Charles S.; McGeehan, John E.; Antson, Alfred A.; Carmichael, Ian; Gerstel, Markus; Shevtsov, Mikhail B.; Garman, Elspeth F.

    2016-01-01

    Radiation damage during macromolecular X-ray crystallographic data collection is still the main impediment for many macromolecular structure determinations. Even when an eventual model results from the crystallographic pipeline, the manifestations of radiation-induced structural and conformation changes, the so-called specific damage, within crystalline macromolecules can lead to false interpretations of biological mechanisms. Although this has been well characterized within protein crystals, far less is known about specific damage effects within the larger class of nucleoprotein complexes. Here, a methodology has been developed whereby per-atom density changes could be quantified with increasing dose over a wide (1.3–25.0 MGy) range and at higher resolution (1.98 Å) than the previous systematic specific damage study on a protein–DNA complex. Specific damage manifestations were determined within the large trp RNA-binding attenuation protein (TRAP) bound to a single-stranded RNA that forms a belt around the protein. Over a large dose range, the RNA was found to be far less susceptible to radiation-induced chemical changes than the protein. The availability of two TRAP molecules in the asymmetric unit, of which only one contained bound RNA, allowed a controlled investigation into the exact role of RNA binding in protein specific damage susceptibility. The 11-fold symmetry within each TRAP ring permitted statistically significant analysis of the Glu and Asp damage patterns, with RNA binding unexpectedly being observed to protect these otherwise highly sensitive residues within the 11 RNA-binding pockets distributed around the outside of the protein molecule. Additionally, the method enabled a quantification of the reduction in radiation-induced Lys and Phe disordering upon RNA binding directly from the electron density. PMID:27139628

  13. Radiation damage studies of silicon photomultipliers

    NASA Astrophysics Data System (ADS)

    Bohn, P.; Clough, A.; Hazen, E.; Heering, A.; Rohlf, J.; Freeman, J.; Los, S.; Cascio, E.; Kuleshov, S.; Musienko, Y.; Piemonte, C.

    2009-01-01

    We report on the measurement of the radiation hardness of silicon photomultipliers (SiPMs) manufactured by Fondazione Bruno Kessler in Italy (1 and 6.2 mm2), Center of Perspective Technology and Apparatus in Russia (1 and 4.4 mm2), and Hamamatsu Corporation in Japan (1 mm2). The SiPMs were irradiated using a beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences of up to 3×1010 protons per cm2 with the SiPMs at operating voltage. Leakage currents were read continuously during the irradiation. The delivery of the protons was paused periodically to record scope traces in response to calibrated light pulses to monitor the gains, photon detection efficiencies, and dark counts of the SiPMs. The leakage current and dark noise are found to increase with fluence. The leakage current is found to be proportional to the mean square deviation of the noise distribution, indicating the dark counts are due to increased random individual pixel activation, while SiPMs remain fully functional as photon detectors. The SiPMs are found to anneal at room temperature with a reduction in the leakage current by a factor of 2 in about 100 days.

  14. Radiation damage aspects of the chernobyl accident

    NASA Astrophysics Data System (ADS)

    Parmentier, N.; Nenot, J. C.

    During the night of 25 to 26 April 1986, the most severe nuclear accident occurred at the Chernobyl power station, about 150km north of Kiev, in the Ukraine. It resulted in the irradiation of 237 workers at dose levels justifying medical care. The most severe cases (115) were hospitalized in Moscow, with 20 patients with doses higher than 6 Gy. In most cases, the treatment was classical, based on transfusion of red cells and platelets, and heavy supportive therapy. For 19 patients with severe aplasia, transplantations of bone marrow (13) or foetal liver (6) were decided. Of these patients only one survived, which justifies the statement from U.S.S.R. physicians: after an accident the indications of grafting are limited and its risks may not justify its use. Most of the complications were related to radiation burns which involved 56 victims and resulted in fatal outcomes in at least 19 patients. The population was evacuated from a 30 km zone around the site; based on direct measurements and calculations, the collective dose was evaluated at 1.6 × 10 4 man Sv, with an individual average lower than 250 mSv. The European part of U.S.S.R. with 75 million persons is supposed to have received a collective dose likely to increase the natural mortality by less than 0.1%. The numbers with cancer in the Northern Hemisphere might increase by 0.004% over the next 50 years.

  15. Effect of Rosiglitazone on Radiation Damage in Bone Marrow Hemopoiesis

    NASA Astrophysics Data System (ADS)

    Benkő, Klára; Pintye, Éva; Szabó, Boglárka; Géresi, Krisztina; Megyeri, Attila; Benkő, Ilona

    2008-12-01

    To study radiobiological effects and drugs, which can modify radiation injury, has an importance if we would like to avoid harmful effects of radiation due to emergency situations or treat patients with malignant diseases by radiotherapy. During the long treatment schedules patients may be treated by not only anticancer but many other drugs because of accompanying diseases. These drugs may also modify radiobiological effects. Rosiglitazone pre-treatment proved to be myeloprotective and accelerated recovery of 5-fluorouracil-damaged bone marrow in our previous experiments. Our new studies are designed to evaluate whether rosiglitazone has similar beneficial effects in radiation-damaged hemopoiesis. Bone marrow damage was precipitated by total body irradiation (TBI) using single increasing doses (2-10 Gy) of γ—irradiation in groups of mice. Lethality was well correlated with damage in hemopoiesis measured by cellularity of bone marrow (LD50 values were 4.8 and 5.3 gray respectively). Rosiglitazone, an insulin-sensitizing drug, had no significant effect on bone marrow cellularity. Insulin resistance associated with obesity or diabetes mellitus type 2 is intensively growing among cancer patients requiring some kind of radiotherapy. Therefore it is important to know whether drugs used for their therapy can modify radiation effects.

  16. Neutron dosimetry and radiation damage calculations for HFBR

    SciTech Connect

    Greenwood, L.R.; Ratner, R.T.

    1998-03-01

    Neutron dosimetry measurements have been conducted for various positions of the High Flux Beam Reactor (HFBR) at Brookhaven National Laboratory (BNL) in order to measure the neutron flux and energy spectra. Neutron dosimetry results and radiation damage calculations are presented for positions V10, V14, and V15.

  17. On the Use of SRIM for Computing Radiation Damage Exposure

    SciTech Connect

    Stoller, Roger E.; Toloczko, Mychailo B.; Was, Gary S.; Certain, Alicia G.; Dwaraknath, S.; Garner, Frank A.

    2013-09-01

    The SRIM (formerly TRIM) Monte Carlo simulation code is widely used to compute a number of parameters relevant to ion beam implantation and ion beam processing of materials. It also has the capability to compute a common radiation damage exposure unit known as atomic displacements per atom (dpa). Since dpa is a standard measure of primary radiation damage production, most researchers who employ ion beams as a tool for inducing radiation damage in materials use SRIM to determine the dpa associated with their irradiations. The use of SRIM for this purpose has been evaluated and comparisons have been made with an internationally-recognized standard definition of dpa, as well as more detailed atomistic simulations of atomic displacement cascades. Differences between the standard and SRIM-based dpa are discussed and recommendations for future usage of SRIM in radiation damage studies are made. In particular, it is recommended that when direct comparisons between ion and neutron data are intended, the Kinchin-Pease option of SRIM should be selected.

  18. Effect of Rosiglitazone on Radiation Damage in Bone Marrow Hemopoiesis

    SciTech Connect

    Benko', Klara; Pintye, Eva; Szabo, Boglarka; Geresi, Krisztina; Megyeri, Attila; Benko, Ilona

    2008-12-08

    To study radiobiological effects and drugs, which can modify radiation injury, has an importance if we would like to avoid harmful effects of radiation due to emergency situations or treat patients with malignant diseases by radiotherapy. During the long treatment schedules patients may be treated by not only anticancer but many other drugs because of accompanying diseases. These drugs may also modify radiobiological effects. Rosiglitazone pre-treatment proved to be myeloprotective and accelerated recovery of 5-fluorouracil-damaged bone marrow in our previous experiments. Our new studies are designed to evaluate whether rosiglitazone has similar beneficial effects in radiation-damaged hemopoiesis. Bone marrow damage was precipitated by total body irradiation (TBI) using single increasing doses (2-10 Gy) of {gamma}--irradiation in groups of mice. Lethality was well correlated with damage in hemopoiesis measured by cellularity of bone marrow (LD{sub 50} values were 4.8 and 5.3 gray respectively). Rosiglitazone, an insulin-sensitizing drug, had no significant effect on bone marrow cellularity. Insulin resistance associated with obesity or diabetes mellitus type 2 is intensively growing among cancer patients requiring some kind of radiotherapy. Therefore it is important to know whether drugs used for their therapy can modify radiation effects.

  19. On the use of SRIM for computing radiation damage exposure

    NASA Astrophysics Data System (ADS)

    Stoller, R. E.; Toloczko, M. B.; Was, G. S.; Certain, A. G.; Dwaraknath, S.; Garner, F. A.

    2013-09-01

    The SRIM (formerly TRIM) Monte Carlo simulation code is widely used to compute a number of parameters relevant to ion beam implantation and ion beam processing of materials. It also has the capability to compute a common radiation damage exposure unit known as atomic displacements per atom (dpa). Since dpa is a standard measure of primary radiation damage production, most researchers who employ ion beams as a tool for inducing radiation damage in materials use SRIM to determine the dpa associated with their irradiations. The use of SRIM for this purpose has been evaluated and comparisons have been made with an internationally-recognized standard definition of dpa, as well as more detailed atomistic simulations of atomic displacement cascades. Differences between the standard and SRIM-based dpa are discussed and recommendations for future usage of SRIM in radiation damage studies are made. In particular, it is recommended that when direct comparisons between ion and neutron data are intended, the Kinchin-Pease option of SRIM should be selected.

  20. DNA damage tolerance: a double-edged sword guarding the genome

    PubMed Central

    Ghosal, Gargi; Chen, Junjie

    2013-01-01

    Preservation of genome integrity is an essential process for cell homeostasis. During the course of life of a single cell, the genome is constantly damaged by endogenous and exogenous agents. To ensure genome stability, cells use a global signaling network, namely the DNA damage response (DDR) to sense and repair DNA damage. DDR senses different types of DNA damage and coordinates a response that includes activation of transcription, cell cycle control, DNA repair pathways, apoptosis, senescence, and cell death. Despite several repair mechanisms that repair different types of DNA lesions, it is likely that the replication machinery would still encounter lesions that are mis-repaired or not repaired. Replication of damaged genome would result in high frequency of fork collapse and genome instability. In this scenario, the cells employ the DNA damage tolerance (DDT) pathway that recruits a specialized low fidelity translesion synthesis (TLS) polymerase to bypass the lesions for repair at a later time point. Thus, DDT is not a repair pathway per se, but provides a mechanism to tolerate DNA lesions during replication thereby increasing survival and preventing genome instability. Paradoxically, DDT process is also associated with increased mutagenesis, which can in turn drive the cell to cancer development. Thus, DDT process functions as a double-edged sword guarding the genome. In this review, we will discuss the replication stress induced DNA damage-signaling cascade, the stabilization and rescue of stalled replication forks by the DDT pathway and the effect of the DDT pathway on cancer. PMID:24058901

  1. Radiation damage effects in candidate titanates for Pu disposition: Pyrochlore

    NASA Astrophysics Data System (ADS)

    Strachan, D. M.; Scheele, R. D.; Buck, E. C.; Icenhower, J. P.; Kozelisky, A. E.; Sell, R. L.; Elovich, R. J.; Buchmiller, W. C.

    2005-10-01

    Laboratory experiments on titanate ceramics were performed to verify whether certain assumptions are valid regarding the swelling, chemical durability, and microcracking that might occur as 239Pu decays. Titanate ceramics are the material of choice for the immobilization of surplus weapons-grade Pu. The short-lived isotope 238Pu, was incorporated into the ceramic formulation to accelerate the effects of radiation-induced damage. We report on the effects of this damage on the density (volumetric swelling <6%), crystal structure of pyrochlore-bearing specimens (amorphous after about 2 × 1018 α/g), and dissolution (no change from the fully crystalline specimen). Even though the specimens became amorphous during the tests, there was no evidence for microcracking in the photomicrographs from the scanning electron microscope. Thus, although pyrochlore is susceptible to radiation-induced damage, the material remains chemically and physically viable as a material for immobilizing surplus weapons-grade Pu.

  2. Deoxyribonucleoprotein structure and radiation injury - Cellular radiosensitivity is determined by LET-infinity-dependent DNA damage in hydrated deoxyribonucleoproteins and the extent of its repair

    NASA Technical Reports Server (NTRS)

    Lett, J. T.; Peters, E. L.

    1992-01-01

    Until recently, OH radicals formed in bulk nuclear water were believed to be the major causes of DNA damage that results in cell death, especially for sparsely ionizing radiations. That hypothesis has now been challenged, if not refuted. Lethal genomic DNA damage is determined mainly by energy deposition in deoxyribonucleoproteins, and their hydration shells, and charge (energy) transfer processes within those structures.

  3. DNA Damage and Repair in Plants under Ultraviolet and Ionizing Radiations

    PubMed Central

    Gill, Sarvajeet S.; Gill, Ritu; Jha, Manoranjan; Tuteja, Narendra

    2015-01-01

    Being sessile, plants are continuously exposed to DNA-damaging agents present in the environment such as ultraviolet (UV) and ionizing radiations (IR). Sunlight acts as an energy source for photosynthetic plants; hence, avoidance of UV radiations (namely, UV-A, 315–400 nm; UV-B, 280–315 nm; and UV-C, <280 nm) is unpreventable. DNA in particular strongly absorbs UV-B; therefore, it is the most important target for UV-B induced damage. On the other hand, IR causes water radiolysis, which generates highly reactive hydroxyl radicals (OH•) and causes radiogenic damage to important cellular components. However, to maintain genomic integrity under UV/IR exposure, plants make use of several DNA repair mechanisms. In the light of recent breakthrough, the current minireview (a) introduces UV/IR and overviews UV/IR-mediated DNA damage products and (b) critically discusses the biochemistry and genetics of major pathways responsible for the repair of UV/IR-accrued DNA damage. The outcome of the discussion may be helpful in devising future research in the current context. PMID:25729769

  4. Early and Late Damages in Chromosome 3 of Human Lymphocytes After Radiation Exposure

    NASA Technical Reports Server (NTRS)

    Sunagawa, Mayumi; Mangala, Lingegowda; Zhang, Ye; Kahdim, Munira; Wilson, Bobby; Cucinotta, Francis A.; Wu, Honglu

    2011-01-01

    Tumor formation in humans or animals is a multi-step process. An early stage of cancer development is believed to be genomic instability (GI) which accelerates the mutation rate in the descendants of the cells surviving radiation exposure. GI is defined as elevated or persistent genetic damages occurring many generations after the cells are exposed. While early studies have demonstrated radiation-induced GI in several cell types as detected in endpoints such as mutation, apoptosis and damages in chromosomes, the dependence of GI on the quality of radiation remains uncertain. To investigate GI in human lymphocytes induced by both low- and high-LET radiation, we initially exposed white blood cells collected from healthy subjects to gamma rays in vitro, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis post irradiation and at several intervals during the culture period. Among a number of biological endpoints planned for the project, the multi-color banding fluorescent in situ hybridization (mBAND) allows identification of inversions that were expected to be stable. We present here early and late chromosome aberrations detected with mBAND in chromosome 3 after gamma exposure. Comparison of chromosome damages in between human lymphocytes and human epithelial cells is also discussed

  5. Contribution of radiation hybrids to genome mapping in domestic animals.

    PubMed

    Faraut, T; de Givry, S; Hitte, C; Lahbib-Mansais, Y; Morisson, M; Milan, D; Schiex, T; Servin, B; Vignal, A; Galibert, F; Yerle, M

    2009-01-01

    Radiation hybrid mapping has emerged in the end of the 1990 s as a successful and complementary approach to map genomes, essentially because of its ability to bridge the gaps between genetic and clone-based physical maps, but also using comparative mapping approaches, between 'gene-rich' and 'gene-poor' maps. Since its early development in human, radiation hybrid mapping played a pivotal role in the process of mapping animal genomes, especially mammalian ones. We review here all the different steps involved in radiation hybrid mapping from the constitution of panels to the construction of maps. A description of its contribution to whole genome maps with a special emphasis on domestic animals will also be presented. Finally, current applications of radiation hybrid mapping in the context of whole genome assemblies will be described. PMID:20016154

  6. Proton-induced radiation damage in germanium detectors

    NASA Technical Reports Server (NTRS)

    Brueckner, J.; Koerfer, M.; Waenke, H.; Schroeder, A. N. F.; Filges, D.; Dragovitsch, P.; Englert, P. A. J.; Starr, R.; Trombka, J. I.

    1991-01-01

    High-purity germanium (HPGe) detectors will be used in future space missions for gamma-ray measurements and will be subject to interactions with energetic particles. To simulate this process, several large-volume n-type HPGe detectors were incrementally exposed to a particle fluence of up to 10 to the 8th protons/sq cm (proton energy: 1.5 GeV) at different operating temperatures (90 to 120 K) to induce radiation damage. Basic scientific and engineering data on detector performance were collected. During the incremental irradiation, the peak shape produced by the detectors showed a significant change from a Gaussian shape to a broad complex structure. After the irradiation, all detectors were thoroughly characterized by measuring many parameters. To remove the accumulated radiation damage, the detectors were stepwise-annealed at temperatures below 110 C, while kept in their specially designed cryostats. This study shows that n-type HPGe detectors can be used in charged-particle environments as high-energy resolution devices until a certain level of radiation damage is accumulated and that the damage can be removed at moderate annealing temperatures and the detector returned to operating condition.

  7. Proton-induced radiation damage in germanium detectors

    SciTech Connect

    Bruckner, J.; Korfer, M.; Wanke, H. , Mainz ); Schroeder, A.N.F. ); Figes, D.; Dragovitsch, P. ); Englert, P.A.J. ); Starr, R.; Trombka, J.I. . Goddard Space Flight Center); Taylor, I. ); Drake, D.M.; Shunk, E.R. )

    1991-04-01

    High-purity germanium (HPGe) detectors will be used in future space missions for gamma-ray measurements and will be subject to interactions with energetic particles. To simulate this process several large-volume n-type HPGe detectors were incrementally exposed to a particle fluence of up to 10{sub 8} protons cm{sup {minus}2} (proton energy: 1.5 GeV) at different operating temperatures (90 to 120 K) to induce radiation damage. Basic scientific as well as engineering data on detector performance were collected. During the incremental irradiation, the peak shape produced by the detectors showed a significant change from a Gaussian shape to a broad complex structure. After the irradiation all detectors were thoroughly characterized by measuring many parameters. To remove the accumulated radiation damage the detectors were stepwise annealed at temperatures T {le} 110{degrees}C while staying specially designed cryostats. This paper shows that n-type HPGe detectors can be used in charged particles environments as high-energy resolution devices until a certain level of radiation damage is accumulated and that the damage can be removed at moderate annealing temperatures and the detector returned to operating condition.

  8. GUI to Facilitate Research on Biological Damage from Radiation

    NASA Technical Reports Server (NTRS)

    Cucinotta, Frances A.; Ponomarev, Artem Lvovich

    2010-01-01

    A graphical-user-interface (GUI) computer program has been developed to facilitate research on the damage caused by highly energetic particles and photons impinging on living organisms. The program brings together, into one computational workspace, computer codes that have been developed over the years, plus codes that will be developed during the foreseeable future, to address diverse aspects of radiation damage. These include codes that implement radiation-track models, codes for biophysical models of breakage of deoxyribonucleic acid (DNA) by radiation, pattern-recognition programs for extracting quantitative information from biological assays, and image-processing programs that aid visualization of DNA breaks. The radiation-track models are based on transport models of interactions of radiation with matter and solution of the Boltzmann transport equation by use of both theoretical and numerical models. The biophysical models of breakage of DNA by radiation include biopolymer coarse-grained and atomistic models of DNA, stochastic- process models of deposition of energy, and Markov-based probabilistic models of placement of double-strand breaks in DNA. The program is designed for use in the NT, 95, 98, 2000, ME, and XP variants of the Windows operating system.

  9. DNA damage induced by the direct effect of radiation

    NASA Astrophysics Data System (ADS)

    Yokoya, A.; Shikazono, N.; Fujii, K.; Urushibara, A.; Akamatsu, K.; Watanabe, R.

    2008-10-01

    We have studied the nature of DNA damage induced by the direct effect of radiation. The yields of single- (SSB) and double-strand breaks (DSB), base lesions and clustered damage were measured using the agarose gel electrophoresis method after exposing to various kinds of radiations to a simple model DNA molecule, fully hydrated closed-circular plasmid DNA (pUC18). The yield of SSB does not show significant dependence on linear energy transfer (LET) values. On the other hand, the yields of base lesions revealed by enzymatic probes, endonuclease III (Nth) and formamidopyrimidine DNA glycosylase (Fpg), which excise base lesions and leave a nick at the damage site, strongly depend on LET values. Soft X-ray photon (150 kVp) irradiation gives a maximum yield of the base lesions detected by the enzymatic probes as SSB and clustered damage, which is composed of one base lesion and proximate other base lesions or SSBs. The clustered damage is visualized as an enzymatically induced DSB. The yields of the enzymatically additional damages strikingly decrease with increasing levels of LET. These results suggest that in higher LET regions, the repair enzymes used as probes are compromised because of the dense damage clustering. The studies using simple plasmid DNA as a irradiation sample, however, have a technical difficulty to detect multiple SSBs in a plasmid DNA. To detect the additional SSBs induced in opposite strand of the first SSB, we have also developed a novel technique of DNA-denaturation assay. This allows us to detect multiply induced SSBs in both strand of DNA, but not induced DSB.

  10. Filia is an ESC-specific regulator of DNA damage response and safeguards genomic stability

    PubMed Central

    Zhao, Bo; Zhang, Wei-dao; Duan, Ying-liang; Lu, Yong-qing; Cun, Yi-xian; Li, Chao-hui; Guo, Kun; Nie, Wen-hui; Li, Lei; Zhang, Rugang; Zheng, Ping

    2015-01-01

    Summary Pluripotent stem cells (PSCs) hold great promise in cell-based therapy, but the genomic instability seen in culture hampers full application. Greater understanding of the factors that regulate genomic stability in PSCs could help address this issue. Here we describe the identification of Filia as a specific regulator of genomic stability in mouse embryonic stem cells (ESCs). Filia expression is induced by genotoxic stress. Filia promotes centrosome integrity and regulates DNA damage response (DDR) through multiple pathways, including DDR signaling, cell cycle checkpoints and damage repair, ESC differentiation and apoptosis. Filia depletion causes ESC genomic instability, induces resistance to apoptosis and promotes malignant transformation. As part of its role in the DDR, Filia interacts with PARP1 and stimulates its enzymatic activity. Filia also constitutively resides on centrosomes and translocates to DNA damage sites and mitochondria, consistent with its multifaceted roles in regulating centrosome integrity, damage repair and apoptosis. PMID:25936915

  11. Induced swelling in radiation damaged ZrSiO 4

    NASA Astrophysics Data System (ADS)

    Exarhos, G. J.

    1984-02-01

    A hydrothermal gelation method was used to prepare phase pure polycrystalline ZrSiO 4 which was sintered to 95% theoretical density. Actinide doped samples containing 10 wt% 238Pu were prepared by an analogous procedure and incurred bulk radiation damage through internal alpha-decay processes. Undoped samples were subjected to external irradiation from 5.5 MeV alpha sources, and from a 60Co gamma source. Actinide doped ZrSiO 4 exhibits dose dependent swelling caused by displacement processes leading to ingrowth of amorphous regions. Bulk density and XRD measurements, as a function of dose, showed first order exponential ingrowth behavior similar to that observed in other actinide doped materials. Results are compared with reported data for naturally damaged crystals subjected to significantly lower alpha decay rates. No significant dose rate dependence on damage ingrowth has been observed. Kinetic models for the observed dose dependent swelling are proposed and rate constants for damage ingrowth in synthetic and natural crystals are compared. To study localized damage induced by both external alpha and gamma irradiation, vibrational Raman measurements were obtained for several accumulated doses. Results indicate that the initial stage of damage ingrowth is confined to the silicate sublattice. Vibrational results will be discussed in terms of microstructural changes which result from irradiation.

  12. Damage-tolerant nanotwinned metals with nanovoids under radiation environments

    SciTech Connect

    Chen, Y.; Yu, K. Y.; Liu, Y.; Shao, S.; Wang, H.; Kirk, M. A.; Wang, J.; Zhang, X.

    2015-04-24

    Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.

  13. Extreme radiation damage in soil from Mare Fecunditatis.

    NASA Technical Reports Server (NTRS)

    Phakey, P. P.; Price, P. B.

    1972-01-01

    High-voltage electron microscopy has been used to compare radiation effects in micron-size soil grains from the Luna 16 site (Mare Fecunditatis) and the four Apollo landing sites. Radiation damage by heavy solar particles is strikingly greater in the Luna 16 sample than in the other four samples. It is suggested that less movement of the soil at Mare Fecunditatis has taken place, perhaps because of its proximity to the limb and consequent lower exposure to energetic electrons in the earth's magnetospheric tail, which would cause electrostatic agitation of fine particles.

  14. Proton induced radiation damage in fast crystal scintillators

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Zhang, Liyuan; Zhu, Ren-Yuan; Kapustinsky, Jon; Nelson, Ron; Wang, Zhehui

    2016-07-01

    This paper reports proton induced radiation damage in fast crystal scintillators. A 20 cm long LYSO crystal, a 15 cm long CeF3 crystal and four liquid scintillator based sealed quartz capillaries were irradiated by 800 MeV protons at Los Alamos up to 3.3 ×1014 p /cm2. Four 1.5 mm thick LYSO plates were irradiated by 24 GeV protons at CERN up to 6.9 ×1015 p /cm2. The results show an excellent radiation hardness of LYSO crystals against charged hadrons.

  15. Radiation damage studies of detector-compatible Si JFETs

    NASA Astrophysics Data System (ADS)

    Dalla Betta, Gian-Franco; Boscardin, Maurizio; Candelori, Andrea; Pancheri, Lucio; Piemonte, Claudio; Ratti, Lodovico; Zorzi, Nicola

    2007-03-01

    We have largely improved the performance of our detector-compatible Si JFETs by optimizing the fabrication technology. New devices feature thermal noise values close to the theoretical ones, and remarkably low 1/ f noise figures. In view of adopting these JFETs for X-ray imaging and HEP applications, bulk and surface radiation damage tests have been carried out by irradiating single transistors and test structures with neutrons and X-rays. Selected results from static and noise characterization of irradiated devices are discussed in this paper, and the impact of radiation effects on the performance of JFET-based circuits is addressed.

  16. A stochastic model of radiation-induced bone marrow damage

    SciTech Connect

    Cotlet, G.; Blue, T.E.

    2000-03-01

    A stochastic model, based on consensus principles from radiation biology, is used to estimate bone-marrow stem cell pool survival (CFU-S and stroma cells) after irradiation. The dose response model consists of three coupled first order linear differential equations which quantitatively describe time dependent cellular damage, repair, and killing of red bone marrow cells. This system of differential equations is solved analytically through the use of a matrix approach for continuous and fractionated irradiations. The analytic solutions are confirmed through the dynamical solution of the model equations using SIMULINK. Rate coefficients describing the cellular processes of radiation damage and repair, extrapolated to humans from animal data sets and adjusted for neutron-gamma mixed fields, are employed in a SIMULINK analysis of criticality accidents. The results show that, for the time structures which may occur in criticality accidents, cell survival is established mainly by the average dose and dose rate.

  17. Radiation damage in zircon by high-energy electron beams

    SciTech Connect

    Jiang Nan; Spence, John C. H.

    2009-06-15

    Radiation damage induced by high-energy (200 keV) electron irradiation in zircon has been studied thoroughly using imaging, diffraction, and electron energy-loss spectroscopy techniques in transmission electron microscopy. Both structural and compositional changes during the damage were measured using the above techniques in real time. It was found that the damage was mainly caused by the preferential sputtering of O. The loss of O occurred initially within small sporadic regions with dimension of several nanometers, resulting in the direct transformation of zircon into Zr{sub x}Si{sub y}. These isolated patches gradually connect each other and eventually cover the whole area of the electron beam. These differ from the previous observations either in the self-irradiated natural and synthetic zircon or in ion-beam irradiated thin zircon specimen.

  18. Multiscale approach to the physics of radiation damage with ions

    NASA Astrophysics Data System (ADS)

    Surdutovich, Eugene; Solov'yov, Andrey V.

    2014-11-01

    The multiscale approach to the assessment of biodamage resulting upon irradiation of biological media with ions is reviewed, explained and compared to other approaches. The processes of ion propagation in the medium concurrent with ionization and excitation of molecules, transport of secondary products, dynamics of the medium, and biological damage take place on a number of different temporal, spatial and energy scales. The multiscale approach, a physical phenomenon-based analysis of the scenario that leads to radiation damage, has been designed to consider all relevant effects on a variety of scales and develop an approach to the quantitative assessment of biological damage as a result of irradiation with ions. Presently, physical and chemical effects are included in the scenario while the biological effects such as DNA repair are only mentioned. This paper explains the scenario of radiation damage with ions, overviews its major parts, and applies the multiscale approach to different experimental conditions. On the basis of this experience, the recipe for application of the multiscale approach is formulated. The recipe leads to the calculation of relative biological effectiveness.

  19. Radiation damage effects in candidate titanates for Pu disposition: Zirconolite

    NASA Astrophysics Data System (ADS)

    Strachan, D. M.; Scheele, R. D.; Buck, E. C.; Kozelisky, A. E.; Sell, R. L.; Elovich, R. J.; Buchmiller, W. C.

    2008-01-01

    Results from studies of radiation-induced damage from the alpha decay of 238Pu on the density and crystal structure of a nominally phase-pure zirconolite and two other zirconolite-bearing ceramics are discussed. Macro and micro swelling were found to be temperature independent, whereas the density determined with He gas pycnometry was temperature dependent. Approximately 2.6 × 10 18 α/g were needed to render the specimens X-ray amorphous- more to saturate the swelling. Unlike pyrochlore-based ceramics, we did not observe any phase changes associated with storage temperature and damage ingrowth. The forward dissolution rate at a pH value of 2 for material containing essentially all zirconolite is 1.7(4) × 10 -3 g/(m 2 d) with very little pH dependence and no dependence on the amount of radiation-induced damage. Even after the radiation-induced swelling saturated, the specimens remained physically intact with no evidence for microcracking. Thus, the material remains physically a viable material for the disposition of surplus weapons-grade Pu.

  20. Ascorbic acid (AA) metabolism in protection against radiation damage

    SciTech Connect

    Rose, R.C.; Koch, M.J.

    1986-03-05

    The possibility is considered that AA protects tissues against radiation damage by scavenging free radicals that result from radiolysis of water. A physiologic buffer (pH 6.7) was incubated with /sup 14/C-AA and 1 mM thiourea (to slow spontaneous oxidation of AA). Aliquots were assayed by HPLC and scintillation spectrometry to identify the /sup 14/C-label. Samples exposed to Cobalt-60 radiation had a half time of AA decay of < 3 minutes compared with nonirradiated samples (t/sub 1/2/ > 30 minutes) indicating that AA scavenges radiation-induced free radicals and forms the ascorbate free radical (AFR). Pairs of /sup 14/C-AFR disproportionate, with the net effect of /sup 14/C-dehydroascorbic acid formation from /sup 14/C-AA. Having established that AFR result from ionizing radiation in an aqueous solution, the possibility was evaluated that a tissue factor reduces AFR. Cortical tissue from the kidneys of male rats was minced, homogenized in buffer and centrifuged at 8000 xg. The supernatant was found to slow the rate of radiation-induced AA degradation by > 90% when incubated at 23/sup 0/C in the presence of 15 ..mu..M /sup 14/C-AA. Samples of supernatant maintained at 100/sup 0/C for 10 minutes or precipitated with 5% PCA did not prevent radiation-induced AA degradation. AA may have a specific role in scavenging free radicals generated by ionizing radiation and thereby protect body tissues.

  1. Differential protection by nitroxides and hydroxylamines to radiation-induced and metal ion-catalyzed oxidative damage.

    PubMed

    Xavier, Sandhya; Yamada, Ken-ichi; Samuni, Ayelet M; Samuni, Amram; DeGraff, William; Krishna, Murali C; Mitchell, James B

    2002-11-14

    Modulation of radiation- and metal ion-catalyzed oxidative-induced damage using plasmid DNA, genomic DNA, and cell survival, by three nitroxides and their corresponding hydroxylamines, were examined. The antioxidant property of each compound was independently determined by reacting supercoiled DNA with copper II/1,10-phenanthroline complex fueled by the products of hypoxanthine/xanthine oxidase (HX/XO) and noting the protective effect as assessed by agarose gel electrophoresis. The nitroxides and their corresponding hydroxylamines protected approximately to the same degree (33-47% relaxed form) when compared to 76.7% relaxed form in the absence of protectors. Likewise, protection by both the nitroxide and corresponding hydroxylamine were observed for Chinese hamster V79 cells exposed to hydrogen peroxide. In contrast, when plasmid DNA damage was induced by ionizing radiation (100 Gy), only nitroxides (10 mM) provide protection (32.4-38.5% relaxed form) when compared to radiation alone or in the presence of hydroxylamines (10 mM) (79.8% relaxed form). Nitroxide protection was concentration dependent. Radiation cell survival studies and DNA double-strand break (DBS) assessment (pulse field electrophoresis) showed that only the nitroxide protected or prevented damage, respectively. Collectively, the results show that nitroxides and hydroxylamines protect equally against the damage mediated by oxidants generated by the metal ion-catalyzed Haber-Weiss reaction, but only nitroxides protect against radiation damage, suggesting that nitroxides may more readily react with intermediate radical species produced by radiation than hydroxylamines. PMID:12399020

  2. Radiation damage effects in CZT drift strip detectors

    NASA Astrophysics Data System (ADS)

    Kuvvetli, Irfan; Budtz-Joergensen, Carl; Korsbech, Uffe; Jensen, H. J.

    2003-03-01

    At DSRI, in collaboration with the cyclotron facility at Copenhagen University Hospital, we have performed a study of radiation effects exposing a 2.7 mm thick CZT drift strip detector to 30 MeV protons. The detector characteristics were evaluated after exposure to a number of dose loads in the range from 2*108 to 60*108 p+/cm2. Even for the highest dose loads, which had a dramatic effect on the spectroscopic performance, we were able to recover the detectors after an appropriate annealing procedure. The radiation damage was studied as function of depth inside the detector material. A numerical model that emulates the physical processes of the charge transport in the CZT detector was used to derive the charge trapping parameter , μτe (the product of charge mobility and trapping time) as function of dose. The analysis showed that the electron trapping increased proportional with the proton dose. The radiation contribution to the electron trapping was found to obey the following relation: (μτe)-1rad =(2.5±0.2)*10-7*Φ (V/cm2) with the proton fluence, Φ in p+/cm2. The trapping depth dependence, however, did not agree well the damage profile calculated using the standard Monte Carlo simulations, TRIM for the proton induced radiation effects. The present results suggest that proton induced nuclear reactions contribute significantly to the radiation damage. Further work will elaborate on these effects. The detector energy resolution was investigated as function of proton dose. It was found that the observed degradation is well explained by the decrease of μτe when the fluctuations of the electron path length are taken into account. The proton irradiation produced In meta stable isotopes in the CZT material. Their decay and production yield as function of depth were analyzed.

  3. Contribution of endogenous and exogenous damage to the total radiation-induced damage in the bacterial spore

    SciTech Connect

    Jacobs, G.P.; Samuni, A.; Czapski, G.

    1980-01-01

    Radical scavengers such as polyethylene glycol 4000 and bovine albumin have been used to define the contribution of exogenous and endogenous damage to the total radiation-induced damage in aqueous buffered suspensions of Bacillus pumilus spores. The results indicate that this damage in the bacterial spore is predominantly endogenous.

  4. PREFACE: Radiation Damage in Biomolecular Systems (RADAM07)

    NASA Astrophysics Data System (ADS)

    McGuigan, Kevin G.

    2008-03-01

    The annual meeting of the COST P9 Action `Radiation damage in biomolecular systems' took place from 19-22 June 2007 in the Royal College of Surgeons in Ireland, in Dublin. The conference was structured into 5 Working Group sessions: Electrons and biomolecular interactions Ions and biomolecular interactions Radiation in physiological environments Theoretical developments for radiation damage Track structure in cells Each of the five working groups presented two sessions of invited talks. Professor Ron Chesser of Texas Tech University, USA gave a riveting plenary talk on `Mechanisms of Adaptive Radiation Responses in Mammals at Chernobyl' and the implications his work has on the Linear-No Threshold model of radiation damage. In addition, this was the first RADAM meeting to take place after the Alexander Litvenenko affair and we were fortunate to have one of the leading scientists involved in the European response Professor Herwig Paretzke of GSF-Institut für Strahlenschutz, Neuherberg, Germany, available to speak. The remaining contributions were presented in the poster session. A total of 72 scientific contributions (32 oral, 40 poster), presented by 97 participants from 22 different countries, gave an overview on the current progress in the 5 different subfields. A 1-day pre-conference `Early Researcher Tutorial Workshop' on the same topic kicked off on 19 June attended by more than 40 postgrads, postdocs and senior researchers. Twenty papers, based on these reports, are included in this volume of Journal of Physics: Conference Series. All the contributions in this volume were fully refereed, and they represent a sample of the courses, invited talks and contributed talks presented during RADAM07. The interdisciplinary RADAM07 conference brought together researchers from a variety of different fields with a common interest in biomolecular radiation damage. This is reflected by the disparate backgrounds of the authors of the papers presented in these proceedings

  5. Molecular dynamics modelling of radiation damage in zircon

    NASA Astrophysics Data System (ADS)

    Grechanovsky, A. E.

    2009-04-01

    Zircon (ZrSiO4) is among actinide-bearing phases which has been proposed as a crystalline confinement matrix for nuclear waste management, especially for weapon-grade plutonium and UO2 spent fuel in the USA. Zircon is also widely used in geochronology. But, with accumulating α-decay damage, zircon undergoes a radiation induced transition to an amorphous (or metamict) state. So, in the present work molecular dynamics simulations (MD simulations) of zircon structure have been performed to study radiation damage in zircon. In this technique, one simulates the propagation of an energetic particle in a system of atoms interacting via model potentials, by integrating the Newton equations of motion. Author has used version 3.09 of the DL_POLY molecular simulation package. Zircon structure containing 181944 atoms (19x19x21 unit cells) was equilibrated at 300 K for 10 ps, and one Zr atom (usually called the primary knock-on atom, PKA) was given a velocity corresponding to an implantation energy of about 20 keV. MD simulations were performed in the microcanonical ensemble that is under conditions of constant particle number, volume and energy. Results of the MD simulations show that the number of interstitials is equal to 840 atoms. This is very close (4000-5000 atoms for 70 keV recoil atom 234Th) to what is measured in the diffuse x-ray scattering and NMR experiments on amorphous metamict samples (damaged by natural irradiation) of geological age. It has been shown that the damaged structure contains several depleted regions with characteristic sized up to 2,5 nm after single event and up to 4,5 nm after three overlapping events. Furthermore, these events produce channels of depleted matter between the overlapping damaged regions. These channels provide a high-diffusivity path for radiogenic Pb (percolation effect). Loss of radiogenic Pb may result in to incorrect dating of rocks.

  6. Biomolecular Damage Induced by Ionizing Radiation: The Direct and Indirect Effects of Low-Energy Electrons on DNA

    NASA Astrophysics Data System (ADS)

    Alizadeh, Elahe; Orlando, Thomas M.; Sanche, Léon

    2015-04-01

    Many experimental and theoretical advances have recently allowed the study of direct and indirect effects of low-energy electrons (LEEs) on DNA damage. In an effort to explain how LEEs damage the human genome, researchers have focused efforts on LEE interactions with bacterial plasmids, DNA bases, sugar analogs, phosphate groups, and longer DNA moieties. Here, we summarize the current understanding of the fundamental mechanisms involved in LEE-induced damage of DNA and complex biomolecule films. Results obtained by several laboratories on films prepared and analyzed by different methods and irradiated with different electron-beam current densities and fluencies are presented. Despite varied conditions (e.g., film thicknesses and morphologies, intrinsic water content, substrate interactions, and extrinsic atmospheric compositions), comparisons show a striking resemblance in the types of damage produced and their yield functions. The potential of controlling this damage using molecular and nanoparticle targets with high LEE yields in targeted radiation-based cancer therapies is also discussed.

  7. Radiation damage of the HEAO C-1 germanium detectors

    NASA Technical Reports Server (NTRS)

    Mahoney, W. A.; Ling, J. C.; Jacobson, A. S.

    1981-01-01

    The effects of radiation damage from proton bombardment of the four HEAO C-1 high purity germanium detectors have been measured and compared to predictions. Because of the presence of numerous gamma-ray lines in the detector background spectra and because of the relatively long exposure time of the HEAO 3 satellite to cosmic-ray and trapped protons, it has been possible to measure both the energy and time dependence of radiation damage. After 100 d in orbit, each of the four detectors has been exposed to approximately 3 x 10 to the 7th protons/sq cm, and the average energy resolution at 1460 keV had degraded from 3.2 keV fwhm to 8.6 keV fwhm. The lines were all broadened to the low energy side although the line profile was different for each of the four detectors. The damage-related contribution to the degradation in energy resolution was found to be linear in energy and proton influence.

  8. In Situ Measurement of Radiation Damage in Scintillating Fibers

    NASA Astrophysics Data System (ADS)

    Ziegler, Ar.; Holm, U.; Latuske, N.; Wick, K.; Zoufal, T.

    2002-11-01

    The radiation induced degradation of the optical transmission of the fibers SCSF-38M, SCSF-81M (Kuraray), BCF-60 and BCF-98 (Bicron) with polystyrene core (PS) was studied. During and after irradiation with a 100 kV X-ray source, a 137Cs source and a 60Co source the effects depend on the fiber type: (1) The permanent damage for BCF-98 (clear PS) is smaller than for the scintillators. (2) The BCF-60 is radiation harder than the other two scintillators but very light sensitive. Temperature treatments (up to 68°C) of SCSF-38M, without irradiation showed a transmission loss which clearly rises with the increasing temperature. This accelerated ageing phenomenon does not recover and the fiber is permanently damaged. In an additional experiment it was studied whether the transmission damage can be influenced by short illuminations with visible light during and after irradiation. For SCSF-38M a strong reduction of the permanent induced absorption remaining after the end of the recovery process was observed.

  9. Radiation damage in PVT (Polyvinyltoluene) induced by energetic ions

    NASA Astrophysics Data System (ADS)

    Torrisi, L.

    Polyvinyltoluene (PVT) is an organic polymer employed as base material for many plastic scintillators useful to detect charged particles. Radiation damage in PVT is investigated irradiating the polymer in vacuum with different ion beams (H+, He+, N+ and Ar+) as a function of their ion stopping power. The structural modifications indced in the polymer are deduced by monitoring in situ, during the ion irradiation, the molecular desorption from the polymer by a highly sensitive mass-quadrupole spectrometer. The desorbed molecules are detected in the mass range 1-100 amu and the chemical yields are measured with respect to the calibrated gas leaks. Main emitted species are H2, C2H2 and C3H5, the yields of which strongly depend on the ion stopping power. As will be discussed, the investigation of radiation damage in PVT permits to extend the results to the damage undergone by plastic scintillators during the detection of charged particles at high energy, such as protons of 10-100 MeV, an energy range useful in nuclear physics and in proton-therapy.

  10. Influence of radiation damage on xenon diffusion in silicon carbide

    NASA Astrophysics Data System (ADS)

    Friedland, E.; Gärtner, K.; Hlatshwayo, T. T.; van der Berg, N. G.; Thabethe, T. T.

    2014-08-01

    Diffusion of xenon in poly and single crystalline silicon carbide and the possible influence of radiation damage on it are investigated. For this purpose 360 keV xenon ions were implanted in commercial 6H-SiC and CVD-SiC wafers at room temperature, 350 °C and 600 °C. Width broadening of the implantation profiles and xenon retention during isochronal and isothermal annealing up to temperatures of 1500 °C was determined by RBS-analysis, whilst in the case of 6H-SiC damage profiles were simultaneously obtained by α-particle channelling. No diffusion or xenon loss was detected in the initially amorphized and eventually recrystallized surface layer of cold implanted 6H-SiC during annealing up to 1200 °C. Above that temperature serious erosion of the implanted surface occurred, which made any analysis impossible. No diffusion or xenon loss is detected in the hot implanted 6H-SiC samples during annealing up to 1400 °C. Radiation damage dependent grain boundary diffusion is observed at 1300 °C in CVD-SiC.

  11. Radiation-Induced Cytogenetic Damage as a Predictor of Cancer Risk for Protons and Fe Ions

    NASA Technical Reports Server (NTRS)

    Williams, Jerry R.

    1999-01-01

    We have successfully completed the series of experiments planned for year 1 and the first part of year 2 measuring the induction of chromosome aberrations induced in multiple cell types by three model space radiations: Fe-ions, protons and photons. Most of these data have now been compiled and a significant part subjected to detailed data analyses, although continuing data analysis is an important part of our current and future efforts. These analyses are directed toward defining the patterns of chromosomal damage induction by the three radiations and the extent to which such patterns are dependent on the type of cell irradiated. Our studies show significant differences, both quantitatively and qualitatively, between response of different cell types to these radiations however there is an overall pattern that characterizes each type of radiation in most cell lines. Thus our data identifies general dose-response patterns for each radiation for induction of multiple types of chromosomal aberrations but also identifies significant differences in response between some cell types. Specifically, we observe significant resistance for induction of aberrations in rat mammary epithelial cells when they are irradiated in vivo and assayed in vitro. Further, we have observed some remarkable differences in susceptibility to certain radiation-induced aberrations in cells whose genome has been modulated for two cancer- relevant genes, TP53 and CDKNIA. This data, if confirmed, may represent the first evidence of gene-specific differences in cellular metabolism of damage induced by densely-ionizing radiation that confers substantial sensitivity to protons compared to photons.

  12. A Role for Lsm1p in Response to Ultraviolet-Radiation Damage in Saccharomyces cerevisiae

    PubMed Central

    Spicakova, Tatiana; McCann, Kelly; Brown, J. Martin

    2008-01-01

    A genome-wide screen in Saccharomyces cerevisiae identified LSM1 as a new gene affecting sensitivity to ultraviolet (UV) radiation. Lsm1p is a member of a cytoplasmic complex composed of Lsm1p–7p that interacts with the yeast mRNA degradation machinery. To investigate the potential role of Lsm1p in response to UV radiation, we constructed double mutant strains in which LSM1 was deleted in combination with a representative gene from each of three known yeast DNA repair pathways. Our results show that lsm1Δ increases the UV-radiation sensitivity of the rad1Δ and rad51Δ mutants, but not the rad18Δ mutant, placing LSM1 within the post-replication repair/damage tolerance pathway (PRR). When combined with other deletions affecting PRR, lsm1Δ increases the UV-radiation sensitivity of the rev3Δ, rad30Δ and pol30-K164R mutants but not rad5Δ. Furthermore, the UV-radiation sensitivity phenotype of lsm1Δ is partially rescued by mutations in genes involved in 3′ to 5′ mRNA degradation, and mutations predicted to function in RNA interactions confer the most UV-radiation sensitivity. Together, these results suggest that Lsm1p may confer protection against UV-radiation damage by protecting the 3′ ends of mRNAs from exosome-dependent 3′ to 5′ degradation as part of a novel RAD5-mediated, PCNA-K164 ubiquitylation-independent subpathway of PRR. PMID:19024647

  13. Radiation damage and derivatization in macromolecular crystallography: a structure factor’s perspective

    PubMed Central

    Owen, Robin L.; Sherrell, Darren A.

    2016-01-01

    During, or even after, data collection the presence and effects of radiation damage in macromolecular crystallography may not always be immediately obvious. Despite this, radiation damage is almost always present, with site-specific damage occurring on very short time (dose) scales well before global damage becomes apparent. A result of both site-specific radiation damage and derivatization is a change in the relative intensity of reflections. The size and approximate rate of onset of X-ray-induced transformations is compared with the changes expected from derivatization, and strategies for minimizing radiation damage are discussed. PMID:26960125

  14. Recent Advances in Understanding Radiation Damage in Reactor Cavity Concrete

    SciTech Connect

    Rosseel, Thomas M; Field, Kevin G; Le Pape, Yann; Remec, Igor; Giorla, Alain B; Wall, Dr. James Joseph

    2015-01-01

    License renewal up to 60 years and the possibility of subsequent license renewal to 80 years has resulted in a renewed focus on long-term aging of materials at nuclear power plants (NPPs) including concrete. Large irreplaceable sections of most nuclear generating stations include concrete. The Expanded Materials Degradation Analysis, jointly performed by the Department of Energy, the Nuclear Regulatory Commission and Nuclear Industry, identified the urgent need to develop a consistent knowledge base on irradiation effects in concrete (Graves et al., (2014)). Much of the historical mechanical performance data of irradiated concrete (Hilsdorf et al., (1978)) does not accurately reflect typical radiation conditions in NPPs or conditions out to 60 or 80 years of radiation exposure (Kontani et al., (2011)). To address these potential gaps in the knowledge base, the Electric Power Research Institute and Oak Ridge National Laboratory, are working to better understand radiation damage as a degradation mechanism. This paper outlines recent progress toward: 1) assessing the radiation environment in concrete biological shields and defining the upper bound of the neutron and gamma dose levels expected in the biological shield for extended operation, and estimating adsorbed dose, 2) evaluating opportunities to harvest and test irradiated concrete from international NPPs, 3) evaluating opportunities to irradiate prototypical concrete and its components under accelerated neutron and gamma dose levels to establish conservative bounds and inform damage models, 4) developing improved models to enhance the understanding of the effects of radiation on concrete and 5) establishing an international collaborative research and information exchange effort to leverage capabilities and knowledge including developing cooperative test programs to improve confidence in data obtained from various concretes and from accelerated irradiation experiments.

  15. Torin2 Suppresses Ionizing Radiation-Induced DNA Damage Repair.

    PubMed

    Udayakumar, Durga; Pandita, Raj K; Horikoshi, Nobuo; Liu, Yan; Liu, Qingsong; Wong, Kwok-Kin; Hunt, Clayton R; Gray, Nathanael S; Minna, John D; Pandita, Tej K; Westover, Kenneth D

    2016-05-01

    Several classes of inhibitors of the mammalian target of rapamycin (mTOR) have been developed based on its central role in sensing growth factor and nutrient levels to regulate cellular metabolism. However, its ATP-binding site closely resembles other phosphatidylinositol 3-kinase-related kinase (PIKK) family members, resulting in reactivity with these targets that may also be therapeutically useful. The ATP-competitive mTOR inhibitor, Torin2, shows biochemical activity against the DNA repair-associated proteins ATM, ATR and DNA-PK, which raises the possibility that Torin2 and related compounds might radiosensitize cancerous tumors. In this study Torin2 was also found to enhance ionizing radiation-induced cell killing in conditions where ATM was dispensable, confirming the requirement for multiple PIKK targets. Moreover, Torin2 did not influence the initial appearance of γ-H2AX foci after irradiation but significantly delayed the disappearance of radiation-induced γ-H2AX foci, indicating a DNA repair defect. Torin2 increased the number of radiation-induced S-phase specific chromosome aberrations and reduced the frequency of radiation-induced CtIP and Rad51 foci formation, suggesting that Torin2 works by blocking homologous recombination (HR)-mediated DNA repair resulting in an S-phase specific DNA repair defect. Accordingly, Torin2 reduced HR-mediated repair of I-Sce1-induced DNA damage and contributed to replication fork stalling. We conclude that radiosensitization of tumor cells by Torin2 is associated with disrupting ATR- and ATM-dependent DNA damage responses. Our findings support the concept of developing combination cancer therapies that incorporate ionizing radiation therapy and Torin2 or compounds with similar properties. PMID:27135971

  16. Absolute Measurements of Radiation Damage in Nanometer Thick Films

    PubMed Central

    Alizadeh, Elahe; Sanche, Léon

    2013-01-01

    We address the problem of absolute measurements of radiation damage in films of nanometer thicknesses. Thin films of DNA (~ 2–160nm) are deposited onto glass substrates and irradiated with varying doses of 1.5 keV X-rays under dry N2 at atmospheric pressure and room temperature. For each different thickness, the damage is assessed by measuring the loss of the supercoiled configuration as a function of incident photon fluence. From the exposure curves, the G-values are deduced, assuming that X-ray photons interacting with DNA, deposit all of their energy in the film. The results show that the G-value (i.e., damage per unit of deposited energy) increases with film thickness and reaches a plateau at 30±5 nm. This thickness dependence provides a correction factor to estimate the actual G-value for films with thicknesses below 30nm thickness. Thus, the absolute values of damage can be compared with that of films of any thickness under different experimental conditions. PMID:22562941

  17. Unfermented grape juice reduce genomic damage on patients undergoing hemodialysis.

    PubMed

    Corredor, Zuray; Rodríguez-Ribera, Lara; Coll, Elisabeth; Montañés, Rosario; Diaz, Juan Manuel; Ballarin, José; Marcos, Ricard; Pastor, Susana

    2016-06-01

    Chronic kidney disease (CKD) patients in dialysis (HD) are considered to be submitted to a continuous oxidative stress. This stress can cause damage on DNA and, consequently, contribute to the high levels of DNA damage observed in these patients. Due to the well-known role of polyphenols as antioxidant agents we proposed its use to reduce the levels of genotoxicity present in HD-CKD patients. The objective of this study was to evaluate the antigenotoxic effects of unfermented grape juice (UGJ) on HD-CKD patients. The levels of DNA damage were analyzed using different biomarkers, such as breaks and oxidized DNA bases by the comet assay, chromosome damage by the micronucleus test. In addition, TEAC (Trolox equivalent antioxidant capacity) was also evaluated. Thirty-nine patients were followed for six months, of whom 25 were supplemented by UGJ and 14 were not supplemented. The obtained results showed a significant decrease in the underlying levels of oxidative DNA damage, in the supplemented group. Regarding the clinical parameters, LDL and cholesterol, were significantly reduced in the patients studied after the supplementation period, although cholesterol was also decreased in the non-supplemented patients. In conclusion, in our studied group the supplementation with UGJ reduced the levels of oxidative DNA damage of HD-CKD patients. PMID:27016493

  18. The role of nickel in radiation damage of ferritic alloys

    DOE PAGESBeta

    Osetskiy, Yury N.; Anento, Napoleon; Serra, Anna; Terentyev, Dmitry

    2014-11-26

    According to the modern theory damage evolution under neutron irradiation depends on the fraction of self interstitial atoms (SIAs) produced in the form of one-dimensionally (1-D) glissile clusters. These clusters, having a low interaction cross-section with other defects, sink mainly on grain boundaries and dislocations creating the so-called production bias. It is known empirically that addition of certain alloying elements affect many radiation effects, including swelling, however the mechanisms are unknown in many cases. In this paper we report the results of an extensive multi-technique atomistic level modeling of SIA clusters mobility in bcc Fe-Ni alloys with Ni content frommore » 0.8 to 10 at.%. We have found that Ni interacts strongly with periphery of clusters affecting their mobility. The total effect is defined by all Ni atoms interacting with the cluster at the same time and can be significant even in low-Ni alloys. Thus 1nm (37SIAs) cluster is practically immobile at T < 500K in the Fe-0.8at.% Ni alloy. Increasing cluster size and Ni content enhance cluster immobilization. Furthermore, this effect should have quite broad consequences in swelling rate, matrix damage accumulation, radiation induced hardening, etc. and the results obtained help in better understanding and prediction of radiation effects in Fe-Ni ferritic alloys.« less

  19. The evaluation of radiation damage parameter for CVD diamond

    NASA Astrophysics Data System (ADS)

    Grilj, V.; Skukan, N.; Jakšić, M.; Pomorski, M.; Kada, W.; Kamiya, T.; Ohshima, T.

    2016-04-01

    There are a few different phenomenological approaches that aim to track the dependence of signal height in irradiated solid state detectors on the fluence of damaging particles. However, none of them are capable to provide a unique radiation hardness parameter that would reflect solely the material capability to withstand high radiation environment. To extract such a parameter for chemical vapor deposited (CVD) diamond, two different diamond detectors were irradiated with proton beams in MeV energy range and subjected afterwards to ion beam induced charge (IBIC) analysis. The change in charge collection efficiency (CCE) due to defects produced was investigated in context of a theoretical model that was developed on the basis of the adjoint method for linearization of the continuity equations of electrons and holes. Detailed modeling of measured data resulted with the first known value of the kσ product for diamond, where k represents the number of charge carriers' traps created per one simulated primary lattice vacancy and σ represents the charge carriers' capture cross section. As discussed in the text, this product could be considered as a true radiation damage parameter.

  20. Radiation Damages in Aluminum Alloy SAV-1 under Neutron Irradiation

    NASA Astrophysics Data System (ADS)

    Salikhbaev, Umar; Akhmedzhanov, Farkhad; Alikulov, Sherali; Baytelesov, Sapar; Boltabaev, Azizbek

    2016-05-01

    The aim of this work was to study the effect of neutron irradiation on the kinetics of radiation damages in the SAV-1 alloy, which belongs to the group of aluminum alloys of the ternary system Al-Mg-Si. For fast-neutron irradiation by different doses up to fluence 1019 cm-2 the SAV-1 samples were placed in one of the vertical channels of the research WWR type reactor (Tashkent). The temperature dependence of the electrical resistance of the alloy samples was investigated in the range 290 - 490 K by the four-compensation method with an error about 0.1%. The experimental results were shown that at all the temperatures the dependence of the SAV-1 alloy resistivity on neutron fluence was nonlinear. With increasing neutron fluence the deviation from linearity and the growth rate of resistivity with temperature becomes more appreciable. The observed dependences are explained by means of martensitic transformations and the radiation damages in the studied alloy under neutron irradiation. The mechanisms of radiation modification of the SAV-1 alloy structure are discussed.

  1. A radiation damage repair model for normal tissues

    NASA Astrophysics Data System (ADS)

    Partridge, Mike

    2008-07-01

    A cellular Monte Carlo model describing radiation damage and repair in normal epithelial tissues is presented. The deliberately simplified model includes cell cycling, cell motility and radiation damage response (cell cycle arrest and cell death) only. Results demonstrate that the model produces a stable equilibrium system for mean cell cycle times in the range 24-96 h. Simulated irradiation of these stable equilibrium systems produced a range of responses that are shown to be consistent with experimental and clinical observation, including (i) re-epithelialization of radiation-induced lesions by a mixture of cell migration into the wound and repopulation at the periphery; (ii) observed radiosensitivity that is quantitatively consistent with both rate of induction of irreparable DNA lesions and, independently, with the observed acute oral and pharyngeal mucosal reactions to radiotherapy; (iii) an observed time between irradiation and maximum toxicity that is consistent with experimental data for skin; (iv) quantitatively accurate predictions of low-dose hyper-radiosensitivity; (v) Gomperzian repopulation for very small lesions (~2000 cells) and (vi) a linear rate of re-epithelialization of 5-10 µm h-1 for large lesions (>15 000 cells).

  2. The role of nickel in radiation damage of ferritic alloys

    SciTech Connect

    Osetskiy, Yury N.; Anento, Napoleon; Serra, Anna; Terentyev, Dmitry

    2014-11-26

    According to the modern theory damage evolution under neutron irradiation depends on the fraction of self interstitial atoms (SIAs) produced in the form of one-dimensionally (1-D) glissile clusters. These clusters, having a low interaction cross-section with other defects, sink mainly on grain boundaries and dislocations creating the so-called production bias. It is known empirically that addition of certain alloying elements affect many radiation effects, including swelling, however the mechanisms are unknown in many cases. In this paper we report the results of an extensive multi-technique atomistic level modeling of SIA clusters mobility in bcc Fe-Ni alloys with Ni content from 0.8 to 10 at.%. We have found that Ni interacts strongly with periphery of clusters affecting their mobility. The total effect is defined by all Ni atoms interacting with the cluster at the same time and can be significant even in low-Ni alloys. Thus 1nm (37SIAs) cluster is practically immobile at T < 500K in the Fe-0.8at.% Ni alloy. Increasing cluster size and Ni content enhance cluster immobilization. Furthermore, this effect should have quite broad consequences in swelling rate, matrix damage accumulation, radiation induced hardening, etc. and the results obtained help in better understanding and prediction of radiation effects in Fe-Ni ferritic alloys.

  3. Retinal damage from long-term exposure to laser radiation.

    PubMed

    Gibbons, W D; Allen, R G

    1977-06-01

    The maculae of rhesus monkeys were exposed to an argon-ion lazer operated in the TEM00 continuous wave mode at a wavelength of 514.5 nm. Both ophthalmoscopic and histopathologic evaluations of exposure sites were obtained. Threshold (ED50) values were obtained for 0.5, 5, 30, 120, and 1,000 sec. exposure times. Presence of minimum visible lesions was assessed ophthalmoscopically at both 1 hour and 24 hours after exposure. With increasing exposure times, a 24 hr. lesion-appearance criterion resulted in ED50 values too low to be consistent with a thermal damage mechanism. In contrast, exposure to neodymium laser radiation at a 1,060 nm. wavelength for 120 sec. produced only ED50 values consistent with those associated with thermal injury. These results suggest that the damage mechanisms for long-duration exposures to visible light may involve photochemical processes initiated by the interaction of visible light with the retinal photopigments. PMID:405344

  4. A Mathematical Model for Estimating Biological Damage Caused by Radiation

    NASA Astrophysics Data System (ADS)

    Manabe, Yuichiro; Ichikawa, Kento; Bando, Masako

    2012-10-01

    We propose a mathematical model for estimating biological damage caused by low-dose irradiation. We understand that the linear non threshold (LNT) hypothesis is realized only in the case of no recovery effects. In order to treat the realistic living objects, our model takes into account various types of recovery as well as proliferation mechanism, which may change the resultant damage, especially for the case of lower dose rate irradiation. It turns out that the lower the radiation dose rate, the safer the irradiated system of living object (which is called symbolically ``tissue'' hereafter) can have chances to survive, which can reproduce the so-called dose and dose-rate effectiveness factor (DDREF).

  5. Analytical modeling for gamma radiation damage on silicon photodiodes

    NASA Astrophysics Data System (ADS)

    Jafari, H.; Feghhi, S. A. H.

    2016-04-01

    Radiation-induced damage in PIN silicon photodiode induces degradation of the photodiode parameters. In this work, by presenting an analytical model, the effect of gamma dose on the dark current in a PIN photodiode array was investigated. Geant4 was used to obtain the damage constant as a result of primary incident particle fluence and NIEL distribution calculations. Experimental measurements as well as numerical simulation of the semiconductor with ATLAS were carried out to verify and parameterize the analytical model calculations. A reasonable agreement has been found between analytical results and experimental data for BPX65 silicon photodiodes irradiated by a Co-60 gamma source at total doses up to 500 krad under different reverse voltages. Moreover, the results showed that the dark current of each photodiode array pixel has considerably increased by gamma dose irradiation.

  6. Genome health nutrigenomics and nutrigenetics--diagnosis and nutritional treatment of genome damage on an individual basis.

    PubMed

    Fenech, Michael

    2008-04-01

    The term nutrigenomics refers to the effect of diet on gene expression. The term nutrigenetics refers to the impact of inherited traits on the response to a specific dietary pattern, functional food or supplement on a specific health outcome. The specific fields of genome health nutrigenomics and genome health nutrigenetics are emerging as important new research areas because it is becoming increasingly evident that (a) risk for developmental and degenerative disease increases with DNA damage which in turn is dependent on nutritional status and (b) optimal concentration of micronutrients for prevention of genome damage is also dependent on genetic polymorphisms that alter function of genes involved directly or indirectly in uptake and metabolism of micronutrients required for DNA repair and DNA replication. Development of dietary patterns, functional foods and supplements that are designed to improve genome health maintenance in humans with specific genetic backgrounds may provide an important contribution to a new optimum health strategy based on the diagnosis and individualised nutritional treatment of genome instability i.e. Genome Health Clinics. PMID:17693008

  7. Soft X-Ray Microscopy Radiation Damage On Fixed Cells Investigated With Synchrotron Radiation FTIR Microscopy

    NASA Astrophysics Data System (ADS)

    Gianoncelli, A.; Vaccari, L.; Kourousias, G.; Cassese, D.; Bedolla, D. E.; Kenig, S.; Storici, P.; Lazzarino, M.; Kiskinova, M.

    2015-05-01

    Radiation damage of biological samples remains a limiting factor in high resolution X-ray microscopy (XRM). Several studies have attempted to evaluate the extent and the effects of radiation damage, proposing strategies to minimise or prevent it. The present work aims to assess the impact of soft X-rays on formalin fixed cells on a systematic manner. The novelty of this approach resides on investigating the radiation damage not only with XRM, as often reported in relevant literature on the topic, but by coupling it with two additional independent non-destructive microscopy methods: Atomic Force Microscopy (AFM) and FTIR Microscopy (FTIRM). Human Embryonic Kidney 293 cells were exposed to different radiation doses at 1 keV. In order to reveal possible morphological and biochemical changes, the irradiated cells were systematically analysed with AFM and FTIRM before and after. Results reveal that while cell morphology is not substantially affected, cellular biochemical profile changes significantly and progressively when increasing dose, resulting in a severe breakdown of the covalent bonding network. This information impacts most soft XRM studies on fixed cells and adds an in-depth understanding of the radiation damage for developing better prevention strategies.

  8. Soft X-Ray Microscopy Radiation Damage On Fixed Cells Investigated With Synchrotron Radiation FTIR Microscopy

    PubMed Central

    Gianoncelli, A.; Vaccari, L.; Kourousias, G.; Cassese, D.; Bedolla, D. E.; Kenig, S.; Storici, P.; Lazzarino, M.; Kiskinova, M.

    2015-01-01

    Radiation damage of biological samples remains a limiting factor in high resolution X-ray microscopy (XRM). Several studies have attempted to evaluate the extent and the effects of radiation damage, proposing strategies to minimise or prevent it. The present work aims to assess the impact of soft X-rays on formalin fixed cells on a systematic manner. The novelty of this approach resides on investigating the radiation damage not only with XRM, as often reported in relevant literature on the topic, but by coupling it with two additional independent non-destructive microscopy methods: Atomic Force Microscopy (AFM) and FTIR Microscopy (FTIRM). Human Embryonic Kidney 293 cells were exposed to different radiation doses at 1 keV. In order to reveal possible morphological and biochemical changes, the irradiated cells were systematically analysed with AFM and FTIRM before and after. Results reveal that while cell morphology is not substantially affected, cellular biochemical profile changes significantly and progressively when increasing dose, resulting in a severe breakdown of the covalent bonding network. This information impacts most soft XRM studies on fixed cells and adds an in-depth understanding of the radiation damage for developing better prevention strategies. PMID:25974639

  9. Radiation damage and annealing of amorphous silicon solar cells

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Slemp, W. S.; Smith, B. T.; Buoncristiani, A. M.

    1984-01-01

    Amorphous silicon solar cells were irradiated with 1 MeV electrons at the Space Environmental Effects Laboratory of the NASA Langley Research Center. The cells accumulated a total fluence of 10 to the 14th, 10 to the 15th, and 10 to the 16th electrons per square centimeter and exhibited increasing degradation with each irradiation. This degradation was tracked by evaluating the I-V curves for AM0 illumination and the relative spectral response. The observed radiation damage was reversed following an anneal of the cells under vacuum at 200 C for 2 hours.

  10. Effects of radiation damage on the silicon lattice

    NASA Technical Reports Server (NTRS)

    Dumas, Katherine A.; Lowry, Lynn; Russo, O. Louis

    1987-01-01

    Silicon was irradiated with both proton and electron particle beams in order to investigate changes in the structural and optical properties of the lattice as a result of the radiation damage. Lattice expansions occurred when large strain fields (+0.34 percent) developed after 1- and 3-MeV proton bombardment. The strain was a factor of three less after 1-MeV electron irradiation. Average increases of approximately 22 meV in the 3.46-eV interband energy gap and 14 meV in the Lorentz broadening parameter were measured after the electron irradiation.

  11. A new mechanism for radiation damage processes in alkali halides

    NASA Astrophysics Data System (ADS)

    Dubinko, V. I.; Turkin, A. A.; Vainshtein, D. I.; den Hartog, H. W.

    1999-12-01

    We present a theory of radiation damage formation in alkali halides based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of H centers of dislocation lines. We consider the evolution of all experimentally observed extended defects: metal colloids, gas bubbles, and vacancy voids. Voids are shown to arise and grow large due to the reaction between F and VF centers at the surface of halogen bubbles. Voids can ignite a back reaction between the radiolytic products resulting in decomposition of the irradiated material.

  12. Protection of radiation detectors from fast neutron damage

    SciTech Connect

    Kronenberg, S.

    1984-01-30

    A circuit for biasing a solid state crystal used as a radiation detector in which the passage of the initial gamma ray pulse from the explosion of a nearby tactical nuclear weapon is utilized to temporarily remove the bias from said crystal for a time sufficient to permit the fast neutron pulse from the same explosion to pass by without permanently damaging the counter crystal. The circuit comprises an RC circuit between the bias supply and the crystal with a reverse biased diode across the capacitor.

  13. Simulation of neutron radiation damage in silicon semiconductor devices.

    SciTech Connect

    Shadid, John Nicolas; Hoekstra, Robert John; Hennigan, Gary Lee; Castro, Joseph Pete Jr.; Fixel, Deborah A.

    2007-10-01

    A code, Charon, is described which simulates the effects that neutron damage has on silicon semiconductor devices. The code uses a stabilized, finite-element discretization of the semiconductor drift-diffusion equations. The mathematical model used to simulate semiconductor devices in both normal and radiation environments will be described. Modeling of defect complexes is accomplished by adding an additional drift-diffusion equation for each of the defect species. Additionally, details are given describing how Charon can efficiently solve very large problems using modern parallel computers. Comparison between Charon and experiment will be given, as well as comparison with results from commercially-available TCAD codes.

  14. Multiscale physics of ion-induced radiation damage

    NASA Astrophysics Data System (ADS)

    Surdutovich, Eugene; Solov'yov, Andrey V.

    2013-06-01

    A multiscale approach to the physics of ion-beam cancer therapy, an approach suggested in order to understand the interplay of a large number of phenomena involved in radiation damage scenario occurring on a range of temporal, spatial, and energy scales, is being reviewed. The scenario is described along with a variety of effects that take place on different temporal, spatial, and energy scales and play major roles in the scenario of interaction of ions with tissue. The understanding of these effects leads to a quantitative assessment of relative biological effectiveness that relates the physical quantities, such as dose, to the biological values, such as the probability of cell survival.

  15. Genome of the Extremely Radiation-Resistant Bacterium Deinococcus radiodurans Viewed from the Perspective of Comparative Genomics

    PubMed Central

    Makarova, Kira S.; Aravind, L.; Wolf, Yuri I.; Tatusov, Roman L.; Minton, Kenneth W.; Koonin, Eugene V.; Daly, Michael J.

    2001-01-01

    The bacterium Deinococcus radiodurans shows remarkable resistance to a range of damage caused by ionizing radiation, desiccation, UV radiation, oxidizing agents, and electrophilic mutagens. D. radiodurans is best known for its extreme resistance to ionizing radiation; not only can it grow continuously in the presence of chronic radiation (6 kilorads/h), but also it can survive acute exposures to gamma radiation exceeding 1,500 kilorads without dying or undergoing induced mutation. These characteristics were the impetus for sequencing the genome of D. radiodurans and the ongoing development of its use for bioremediation of radioactive wastes. Although it is known that these multiple resistance phenotypes stem from efficient DNA repair processes, the mechanisms underlying these extraordinary repair capabilities remain poorly understood. In this work we present an extensive comparative sequence analysis of the Deinococcus genome. Deinococcus is the first representative with a completely sequenced genome from a distinct bacterial lineage of extremophiles, the Thermus-Deinococcus group. Phylogenetic tree analysis, combined with the identification of several synapomorphies between Thermus and Deinococcus, supports the hypothesis that it is an ancient group with no clear affinities to any of the other known bacterial lineages. Distinctive features of the Deinococcus genome as well as features shared with other free-living bacteria were revealed by comparison of its proteome to the collection of clusters of orthologous groups of proteins. Analysis of paralogs in Deinococcus has revealed several unique protein families. In addition, specific expansions of several other families including phosphatases, proteases, acyltransferases, and Nudix family pyrophosphohydrolases were detected. Genes that potentially affect DNA repair and recombination and stress responses were investigated in detail. Some proteins appear to have been horizontally transferred from eukaryotes and are

  16. The energy dependence of refractory metals and alloys radiation damageability

    NASA Astrophysics Data System (ADS)

    Mukashev, K. M.; Umarov, F. F.

    2015-04-01

    In this work the systematical investigation of the radiation defects distribution profile energy dependence in three different materials - tantalum, molybdenum and 10X18H10T-VD stainless steel irradiated by high energy protons has been performed. It has been shown that in stainless steel and tantalum, independently of proton energy, the vacancy complexes related by configuration appear which are described by the slightly expressed elastic channel. The defects are recovered in one annealing stage with different migration activation energy. At the same time the molybdenum radiation damageability is composed of two components in each of which its specified defects formation mechanism takes action. For high energy protons the inelastic channel of interaction is the basic and subcascades appearance is created by primary knocked-on atoms of considerable energies. For low energy protons the processes of elastic interaction with lattice atoms and atomic hydrogen in the end of run creation are major.

  17. Molecular dynamics simulation of radiation damage cascades in diamond

    SciTech Connect

    Buchan, J. T.; Robinson, M.; Christie, H. J.; Roach, D. L.; Ross, D. K.; Marks, N. A.

    2015-06-28

    Radiation damage cascades in diamond are studied by molecular dynamics simulations employing the Environment Dependent Interaction Potential for carbon. Primary knock-on atom (PKA) energies up to 2.5 keV are considered and a uniformly distributed set of 25 initial PKA directions provide robust statistics. The simulations reveal the atomistic origins of radiation-resistance in diamond and provide a comprehensive computational analysis of cascade evolution and dynamics. As for the case of graphite, the atomic trajectories are found to have a fractal-like character, thermal spikes are absent and only isolated point defects are generated. Quantitative analysis shows that the instantaneous maximum kinetic energy decays exponentially with time, and that the timescale of the ballistic phase has a power-law dependence on PKA energy. Defect recombination is efficient and independent of PKA energy, with only 50% of displacements resulting in defects, superior to graphite where the same quantity is nearly 75%.

  18. Medicinal protection with Chinese herb-compound against radiation damage

    SciTech Connect

    Zhang, R.J.; Qian, J.K.; Yang, G.H.; Wang, B.Z.; Wen, X.L. )

    1990-08-01

    Experiments were carried out on mice and the subjects irradiated for cancer therapy to evaluate the protective efficacy of a Chinese medicinal herb-compound (CMHC). The lethality and the degree of leucopenia caused by radiation in mice medicated with CMHC were significantly less in comparison with control mice (p less than 0.01 and p less than 0.001, respectively). CMHC significantly improved the WBC and the thrombocytes in irradiated workers (p less than 0.01 and p less than 0.001, respectively). The WBC count of 40 patients under radiotherapy while treated with CMHC recovered from 3450 +/- 77/c.mm to 5425 +/- 264/c.mm (p less than 0.001); whereas, in the control group, without any medication, the WBC count dropped significantly (p less than 0.001). Our results revealed the applicabilities of CMHC in protection against radiation damage in spaceflight and in other fields.

  19. Radiation-induced lung damage: dose-time-fractionation considerations.

    PubMed

    Van Dyk, J; Mah, K; Keane, T J

    1989-01-01

    The comparison of different dose-time-fractionation schedules requires the use of an isoeffect formula. In recent years, the NSD isoeffect formula has been heavily criticized. In this report, we consider an isoeffect formula which is specifically developed for radiation-induced lung damage. The formula is based on the linear-quadratic model and includes a factor for overall treatment time. The proposed procedures allow for the simultaneous derivation of an alpha/beta ratio and a gamma/beta time factor. From animal data in the literature, the derived alpha/beta and gamma/beta ratios for acute lung damage are 5.0 +/- 1.0 Gy and 2.7 +/- 1.4 Gy2/day respectively, while for late damage the suggested values are 2.0 Gy and 0.0 Gy2/day. Data from two clinical studies, one prospective and the other retrospective, were also analysed and corresponding alpha/beta and gamma/beta ratios were determined. For the prospective clinical study, with a limited range of doses per fraction, the resultant alpha/beta and gamma/beta ratios were 0.9 +/- 2.6 Gy and 2.6 +/- 2.5 Gy2/day. The combination of the retrospective and prospective data yielded alpha/beta and gamma/beta ratios of 3.3 +/- 1.5 Gy and 2.4 +/- 1.5 Gy2/day, respectively. One potential advantage of this isoeffect formalism is that it might possibly be applied to both acute and late lung damage. The results of this formulation for acute lung damage indicate that time-dependent effects such as slow repair or proliferation might be more important in determining isoeffect doses than previously predicted by the estimated single dose (ED) formula. Although we present this as an alternative approach, we would caution against its clinical use until its applicability has been confirmed by additional clinical data. PMID:2928557

  20. Role of Oxidative Damage in Radiation-Induced Bone Loss

    NASA Technical Reports Server (NTRS)

    Schreurs, Ann-Sofie; Alwood, Joshua S.; Limoli, Charles L.; Globus, Ruth K.

    2014-01-01

    During prolonged spaceflight, astronauts are exposed to both microgravity and space radiation, and are at risk for increased skeletal fragility due to bone loss. Evidence from rodent experiments demonstrates that both microgravity and ionizing radiation can cause bone loss due to increased bone-resorbing osteoclasts and decreased bone-forming osteoblasts, although the underlying molecular mechanisms for these changes are not fully understood. We hypothesized that excess reactive oxidative species (ROS), produced by conditions that simulate spaceflight, alter the tight balance between osteoclast and osteoblast activities, leading to accelerated skeletal remodeling and culminating in bone loss. To test this, we used the MCAT mouse model; these transgenic mice over-express the human catalase gene targeted to mitochondria, the major organelle contributing free radicals. Catalase is an anti-oxidant that converts reactive species, hydrogen peroxide into water and oxygen. This animal model was selected as it displays extended lifespan, reduced cardiovascular disease and reduced central nervous system radio-sensitivity, consistent with elevated anti-oxidant activity conferred by the transgene. We reasoned that mice overexpressing catalase in mitochondria of osteoblast and osteoclast lineage cells would be protected from the bone loss caused by simulated spaceflight. Over-expression of human catalase localized to mitochondria caused various skeletal phenotypic changes compared to WT mice; this includes greater bone length, decreased cortical bone area and moment of inertia, and indications of altered microarchitecture. These findings indicate mitochondrial ROS are important for normal bone-remodeling and skeletal integrity. Catalase over-expression did not fully protect skeletal tissue from structural decrements caused by simulated spaceflight; however there was significant protection in terms of cellular oxidative damage (MDA levels) to the skeletal tissue. Furthermore, we

  1. Identifying and quantifying radiation damage at the atomic level

    PubMed Central

    Gerstel, Markus; Deane, Charlotte M.; Garman, Elspeth F.

    2015-01-01

    Radiation damage impedes macromolecular diffraction experiments. Alongside the well known effects of global radiation damage, site-specific radiation damage affects data quality and the veracity of biological conclusions on protein mechanism and function. Site-specific radiation damage follows a relatively predetermined pattern, in that different structural motifs are affected at different dose regimes: in metal-free proteins, disulfide bonds tend to break first followed by the decarboxylation of aspartic and glutamic acids. Even within these damage motifs the decay does not progress uniformly at equal rates. Within the same protein, radiation-induced electron density decay of a particular chemical group is faster than for the same group elsewhere in the protein: an effect known as preferential specific damage. Here, B Damage, a new atomic metric, is defined and validated to recognize protein regions susceptible to specific damage and to quantify the damage at these sites. By applying B Damage to a large set of known protein structures in a statistical survey, correlations between the rates of damage and various physicochemical parameters were identified. Results indicate that specific radiation damage is independent of secondary protein structure. Different disulfide bond groups (spiral, hook, and staple) show dissimilar radiation damage susceptibility. There is a consistent positive correlation between specific damage and solvent accessibility. PMID:25723922

  2. Genetic damage in subjects exposed to radiofrequency radiation.

    PubMed

    Verschaeve, Luc

    2009-01-01

    Despite many research efforts and public debate there is still great concern about the possible adverse effects of radiofrequency (RF) radiation on human health. This is especially due to the enormous increase of wireless mobile telephones and other telecommunication devices throughout the world. The possible genetic effects of mobile phone radiation and other sources of radiofrequencies constitute one of the major points of concern. In the past several review papers were published on laboratory investigations that were devoted to in vitro and in vivo animal (cyto)genetic studies. However, it may be assumed that some of the most important observations are those obtained from studies with individuals that were exposed to relatively high levels of radiofrequency radiation, either as a result of their occupational activity or as frequent users of radiofrequency emitting tools. In this paper the cytogenetic biomonitoring studies of RF-exposed humans are reviewed. A majority of these studies do show that RF-exposed individuals have increased frequencies of genetic damage (e.g., chromosomal aberrations) in their lymphocytes or exfoliated buccal cells. However, most of the studies, if not all, have a number of shortcomings that actually prevents any firm conclusion. Radiation dosimetry was lacking in all papers, but some of the investigations were flawed by much more severe imperfections. Large well-coordinated multidisciplinary investigations are needed in order to reach any robust conclusion. PMID:19073278

  3. Radiation Damage Effects in Far Ultraviolet Filters and Substrates

    NASA Technical Reports Server (NTRS)

    Keffer, Charles E.; Torr, Marsha R.; Zukic, Muamer; Spann, James F.; Torr, Douglas G.; Kim, Jongmin

    1993-01-01

    New advances in VUV thin film filter technology have been made using filter designs with multilayers of materials such as Al2O3, BaF2, CaF2, HfO2, LaF3, MgF2, and SiO2. Our immediate application for these filters will be in an imaging system to be flown on a satellite where a 2 X 9 R(sub E) orbit will expose the instrument to approximately 275 krads of radiation. In view of the fact that no previous studies have been made on potential radiation damage of these materials in the thin film format, we report on such an assessment here. Transmittances and reflectances of BaF2, CaF2, HfO2, LaF3, MgF2, and SiO2 thin films on MgF2 substrates, Al2O3 thin films on fused silica substrates, uncoated fused silica and MgF2, and four multilayer filters made from these materials were measured from 120 nm to 180 nm before and after irradiation by 250 krads from a Co-60 gamma radiation source. No radiation-induced losses in transmittance or reflectance occurred in this wavelength range. Additional postradiation measurements from 160 nm to 300 nm indicated a 3 - 5% radiation-induced absorption near 260 nm in some of the samples with MgF2 substrates. From these measurements it is concluded that far ultraviolet filters made from the materials tested should experience less that 5% change from exposure to up to 250 krads of high energy radiation in space applications.

  4. Grad-Level Radiation Damage of SIO2 Detectors

    SciTech Connect

    Simos, N.; Atoian, G.; Ludewig, H; White, S; O'Conor, J; Mokhov, N.V.

    2009-05-04

    Radiation effects and levels to detectors. SiO{sub 2} quartz fibers of the LHC ATLAS Zero-degree Calorimeter (ZDC) anticipated to experience integrated doses of a few Grad at their closest position were exposed to 200 MeV protons and neutrons at the Brookhaven National Laboratory (BNL) Linac. Specifically, 1 mm- and 2mm-diameter quartz (GE 124) rods were exposed to direct 200 MeV protons during the first phase of exposure leading to peak integrated dose of {approx}28 Grad. Exposure to a primarily neutron flux of 1mm-diameter SiO{sub 2} fibers was also achieved with a special neutron source arrangement. In a post-irradiation analysis the quartz fiber transmittance was evaluated as a function of the absorbed dose. Dramatic degradation of the transmittance property was observed with increased radiation damage. In addition, detailed evaluation of the fibers under the microscope revealed interesting micro-structural damage features and irradiation-induced defects.

  5. Imperfection and radiation damage in protein crystals studied with coherent radiation

    PubMed Central

    Nave, Colin; Sutton, Geoff; Evans, Gwyndaf; Owen, Robin; Rau, Christoph; Robinson, Ian; Stuart, David Ian

    2016-01-01

    Fringes and speckles occur within diffraction spots when a crystal is illuminated with coherent radiation during X-ray diffraction. The additional information in these features provides insight into the imperfections in the crystal at the sub-micrometre scale. In addition, these features can provide more accurate intensity measurements (e.g. by model-based profile fitting), detwinning (by distinguishing the various components), phasing (by exploiting sampling of the molecular transform) and refinement (by distinguishing regions with different unit-cell parameters). In order to exploit these potential benefits, the features due to coherent diffraction have to be recorded and any change due to radiation damage properly modelled. Initial results from recording coherent diffraction at cryotemperatures from polyhedrin crystals of approximately 2 µm in size are described. These measurements allowed information about the type of crystal imperfections to be obtained at the sub-micrometre level, together with the changes due to radiation damage. PMID:26698068

  6. Positron annihilation lifetime study of radiation-damaged natural zircons

    NASA Astrophysics Data System (ADS)

    Roberts, J.; Gaugliardo, P.; Farnan, I.; Zhang, M.; Vance, E. R.; Davis, J.; Karatchevtseva, I.; Knott, R. B.; Mudie, S.; Buckman, S. J.; Sullivan, J. P.

    2016-04-01

    Zircons are a well-known candidate waste form for actinides and their radiation damage behaviour has been widely studied by a range of techniques. In this study, well-characterised natural single crystal zircons have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). In some, but not all, of the crystals that had incurred at least half of the alpha-event damage of ∼1019 α/g required to render them structurally amorphous, PALS spectra displayed long lifetimes corresponding to voids of ∼0.5 nm in diameter. The long lifetimes corresponded to expectations from published Small-Angle X-ray Scattering data on similar samples. However, the non-observation by PALS of such voids in some of the heavily damaged samples may reflect large size variations among the voids such that no singular size can be distinguished or. Characterisation of a range of samples was also performed using scanning electron microscopy, optical absorption spectroscopy, Raman scattering and X-ray scattering/diffraction, with the degree of alpha damage being inferred mainly from the Raman technique and X-ray diffraction. The observed void diameters and intensities of the long lifetime components were changed somewhat by annealing at 700 °C; annealing at 1200 °C removed the voids entirely. The voids themselves may derive from He gas bubbles or voids created by the inclusion of small quantities of organic and hydrous matter, notwithstanding the observation that no voidage was evidenced by PALS in two samples containing hydrous and organic matter.

  7. Maintaining Genome Stability in Defiance of Mitotic DNA Damage

    PubMed Central

    Ferrari, Stefano; Gentili, Christian

    2016-01-01

    The implementation of decisions affecting cell viability and proliferation is based on prompt detection of the issue to be addressed, formulation and transmission of a correct set of instructions and fidelity in the execution of orders. While the first and the last are purely mechanical processes relying on the faithful functioning of single proteins or macromolecular complexes (sensors and effectors), information is the real cue, with signal amplitude, duration, and frequency ultimately determining the type of response. The cellular response to DNA damage is no exception to the rule. In this review article we focus on DNA damage responses in G2 and Mitosis. First, we set the stage describing mitosis and the machineries in charge of assembling the apparatus responsible for chromosome alignment and segregation as well as the inputs that control its function (checkpoints). Next, we examine the type of issues that a cell approaching mitosis might face, presenting the impact of post-translational modifications (PTMs) on the correct and timely functioning of pathways correcting errors or damage before chromosome segregation. We conclude this essay with a perspective on the current status of mitotic signaling pathway inhibitors and their potential use in cancer therapy. PMID:27493659

  8. Radiation-induced Genomic Instability and Radiation Sensitivity

    SciTech Connect

    Varnum, Susan M.; Sowa, Marianne B.; Kim, Grace J.; Morgan, William F.

    2013-01-19

    The obvious relationships between reactive oxygen and nitrogen species, mitochondrial dysfunction, inflammatory type responses and reactive chemokines and cytokines suggests a general stress response induced by ionizing radiation most likely leads to the non-targeted effects described after radiation exposure. We argue that true bystander effects do not occur in the radiation therapy clinic. But there is no question that effects outside the target volume do occur. These “out of field effects” are considered very low dose effects in the context of therapy. So what are the implications of non-targeted effects on radiation sensitivity? The primary goal of therapy is to eradicate the tumor. Given the genetic diversity of the human population, lifestyle and environment factors it is likely some combination of these will influence patient outcome. Non-targeted effects may contribute to a greater or lesser extent. But consider the potential situation involving a partial body exposure due to a radiation accident or radiological terrorism. Non-targeted effects suggest that the tissue at risk for demonstrating possible detrimental effects of radiation exposure might be greater than the volume actually irradiated.

  9. Selective enrichment of damaged DNA molecules for ancient genome sequencing

    PubMed Central

    2014-01-01

    Contamination by present-day human and microbial DNA is one of the major hindrances for large-scale genomic studies using ancient biological material. We describe a new molecular method, U selection, which exploits one of the most distinctive features of ancient DNA—the presence of deoxyuracils—for selective enrichment of endogenous DNA against a complex background of contamination during DNA library preparation. By applying the method to Neanderthal DNA extracts that are heavily contaminated with present-day human DNA, we show that the fraction of useful sequence information increases ∼10-fold and that the resulting sequences are more efficiently depleted of human contamination than when using purely computational approaches. Furthermore, we show that U selection can lead to a four- to fivefold increase in the proportion of endogenous DNA sequences relative to those of microbial contaminants in some samples. U selection may thus help to lower the costs for ancient genome sequencing of nonhuman samples also. PMID:25081630

  10. Use of Displacement Damage Dose in an Engineering Model of GaAs Solar Cell Radiation Damage

    NASA Technical Reports Server (NTRS)

    Morton, T. L.; Chock, R.; Long, K. J.; Bailey, S.; Messenger, S. R.; Walters, R. J.; Summers, G. P.

    2005-01-01

    Current methods for calculating damage to solar cells are well documented in the GaAs Solar Cell Radiation Handbook (JPL 96-9). An alternative, the displacement damage dose (D(sub d)) method, has been developed by Summers, et al. This method is currently being implemented in the SAVANT computer program.

  11. Non-targeted and delayed effects of exposure to ionizing radiation: II. Radiation-induced genomic instability and bystander effects in vivo, clastogenic factors and transgenerational effects

    NASA Technical Reports Server (NTRS)

    Morgan, William F.

    2003-01-01

    The goal of this review is to summarize the evidence for non-targeted and delayed effects of exposure to ionizing radiation in vivo. Currently, human health risks associated with radiation exposures are based primarily on the assumption that the detrimental effects of radiation occur in irradiated cells. Over the years a number of non-targeted effects of radiation exposure in vivo have been described that challenge this concept. These include radiation-induced genomic instability, bystander effects, clastogenic factors produced in plasma from irradiated individuals that can cause chromosomal damage when cultured with nonirradiated cells, and transgenerational effects of parental irradiation that can manifest in the progeny. These effects pose new challenges to evaluating the risk(s) associated with radiation exposure and understanding radiation-induced carcinogenesis.

  12. Draft Genome Sequence of Kocuria rhizophila RF, a Radiation-Resistant Soil Isolate.

    PubMed

    Mehrabadi, Jalil Fallah; Mirzaie, Amir; Ahangar, Nahid; Rahimi, Arian; Rokni-Zadeh, Hassan

    2016-01-01

    Kocuria rhizophila RF, a soil isolate from Iran, is a radiation-resistant bacterium. Only a limited amount of genomic information for radiation-resistant bacteria is currently available. Here, we report the draft genome sequence of this bacterium, providing knowledge to aid in the discovery of the genomic basis of its resistance to radiation. PMID:26966202

  13. Draft Genome Sequence of Kocuria rhizophila RF, a Radiation-Resistant Soil Isolate

    PubMed Central

    Mehrabadi, Jalil Fallah; Mirzaie, Amir; Ahangar, Nahid; Rahimi, Arian

    2016-01-01

    Kocuria rhizophila RF, a soil isolate from Iran, is a radiation-resistant bacterium. Only a limited amount of genomic information for radiation-resistant bacteria is currently available. Here, we report the draft genome sequence of this bacterium, providing knowledge to aid in the discovery of the genomic basis of its resistance to radiation. PMID:26966202

  14. Weak-localization effect in superconductors from radiation damage

    NASA Astrophysics Data System (ADS)

    Park, Mi-Ae; Kim, Yong-Jihn

    2000-06-01

    Large reductions of the superconducting transition temperature Tc and the accompanying loss of the thermal electrical resistivity (electron-phonon interaction) due to radiation damage have been observed for several A15 compounds, Chevrel phase and ternary superconductors, and NbSe2 in the high-fluence regime. We examine these behaviors based on a recent theory of the weak localization effect in superconductors. We find a good fitting to the experimental data. In particular, the weak localization correction to the phonon-mediated interaction is derived from the density correlation function. It is shown that weak localization has a strong influence on both the phonon-mediated interaction and the electron-phonon interaction, which leads to the universal correlation of Tc and the resistance ratio.

  15. Radiation Damage on Multiple Length Scales in Uranium Dioxide

    NASA Astrophysics Data System (ADS)

    Gupta, Mahima

    Radiation damage in UO2 has been well studied but there exists little correlation between point defect accumulation, lattice structure changes and microstructure. This is partly because irradiated nuclear fuel is highly radioactive and its defect chemistry is extremely complicated resulting from fission of the material and consequent fission products being embedded in the fuel matrix [Olander1976]. To adequately study the evolution of defects from point defects through to microstructure features, the resulting defects have to be intentionally simplified for characterization. Ion accelerators have the unique capability of creating simple microstructure features using specific ions, without the added complication of fission and neutron activation from nuclear reactors. As an example, H+ ions have been used to create (only) a distribution of dislocations that were studied using various techniques. The ability to tune the energy or type of the ion to achieve desirable implantation depth and ideally simple microstructure renders it a lucrative instrument for this type of analysis. X-ray diffraction (XRD) studies and transmission electron microscopy (TEM) have been utilized to study extended structure changes and microstructure evolution. Ion beam irradiations create displacements and displacement networks, voids, surface fracturing, gas bubbles and several other microstructure changes to model nuclear reactor damage [Noris1972]. Using an ion accelerator, it has been possible to isolate these radiation induced defects and study their subsequent evolution with increasing dose. Insofar, since all of the phenomena caused by radiation damage originate from point defects, the elucidation of radiation effects on the atomic scale is crucial. This is rendered complicated due to aperiodic irradiation defects. This lack of periodicity renders standard approaches, such as TEM and XRD ineffective, as these methods probe average structure over tens of Angstroms. Therefore, techniques

  16. Development of resistant materials to beam impact and radiation damage

    NASA Astrophysics Data System (ADS)

    Kawai, Masayoshi; Kokawa, Hiroyuki; Okamura, Hiroshi; Kawasaki, Akira; Yamamura, Tsutomu; Hara, Nobuyoshi; Akao, Noboru; Futakawa, Masatoshi; Kikuchi, Kenji

    2006-09-01

    Materials that have strong resistance to both beam impact (or shock-wave) and radiation damage are required for the beam target of an intense accelerator and space applications. Recently, Futakawa et al. found in their experiments that Kolsterising specimens have a stronger resistance to pitting than SS316 CW. A similar effect can be expected for other hardening treatments, and new material development is hopeful. Accordingly, we have started the development of high-performance materials by organizing the project team from KEK, JAEA and universities. In this paper, the scope of the project is introduced. Recent topics involve the development of intergranular crack (IGC)-resistant austenitic stainless-steel, AlN-TiN ceramics and cladding techniques of thin tantalum or CrN film on a tungsten target by means of a molten-salt method and ion-beam-enhanced deposition. New observations on corrosion resistance are presented.

  17. Proton radiation damage in bulk n-GaAs

    NASA Technical Reports Server (NTRS)

    Liu, D. C.; Blue, J. W.; Flood, D. J.; Stanchina, W. E.

    1980-01-01

    Bulk samples of Te-doped n-type GaAs were irradiated using 10 MeV to 24 MeV protons to fluences between 2 x 10 to the 11th power protons/sq cm and 2 x 10 to the 14th power protons/sq cm. Majority carrier electrical effects were measured using the vanderPauw techniques and it was observed that radiation damage was minimal at the 10 to the 11th power proton/sq cm fluence. For the higher fluences, carrier removal was proportional to Delta E/Delta x for the protons indicating ionization interactions between the protons and atoms. Thermal annealing was observed at 155 C.

  18. Effects of Ionizing Radiation on Biological Molecules—Mechanisms of Damage and Emerging Methods of Detection

    PubMed Central

    Reisz, Julie A.; Bansal, Nidhi; Qian, Jiang; Zhao, Weiling

    2014-01-01

    Abstract Significance: The detrimental effects of ionizing radiation (IR) involve a highly orchestrated series of events that are amplified by endogenous signaling and culminating in oxidative damage to DNA, lipids, proteins, and many metabolites. Despite the global impact of IR, the molecular mechanisms underlying tissue damage reveal that many biomolecules are chemoselectively modified by IR. Recent Advances: The development of high-throughput “omics” technologies for mapping DNA and protein modifications have revolutionized the study of IR effects on biological systems. Studies in cells, tissues, and biological fluids are used to identify molecular features or biomarkers of IR exposure and response and the molecular mechanisms that regulate their expression or synthesis. Critical Issues: In this review, chemical mechanisms are described for IR-induced modifications of biomolecules along with methods for their detection. Included with the detection methods are crucial experimental considerations and caveats for their use. Additional factors critical to the cellular response to radiation, including alterations in protein expression, metabolomics, and epigenetic factors, are also discussed. Future Directions: Throughout the review, the synergy of combined “omics” technologies such as genomics and epigenomics, proteomics, and metabolomics is highlighted. These are anticipated to lead to new hypotheses to understand IR effects on biological systems and improve IR-based therapies. Antioxid. Redox Signal. 21: 260–292. PMID:24382094

  19. Dislocation dynamics modelling of radiation damage in thin films

    NASA Astrophysics Data System (ADS)

    Ferroni, Francesco; Tarleton, Edmund; Fitzgerald, Steven

    2014-06-01

    Transmission electron microscopy is a key tool for the extraction of information on radiation damage, the understanding of which is critical for materials development for nuclear fusion and fission reactors. Dislocations in TEM samples are subject to strong image forces, owing to the nanometric sample thicknesses, which may introduce artifacts in the damage analysis. Using dislocation dynamics, we elucidate the roles played by dislocation-surface interactions, dislocation-dislocation interactions and self-interactions due to climb for loop types observed in TEM. Comparisons with analytic solutions for a dislocation loop and an edge dislocation in a half-space are included, and the relationship between glide force and loop tilt examined. The parameters for convergence of the zero-traction boundary conditions are obtained, after which the evolution of dislocation structures in a thin film is studied. It is found that three main length scales govern the physical processes: the image force is governed by the distance of the loop from the surface and scales with the film thickness; the glide force is governed by the image stress as well as the loop-loop interaction stress which is in turn governed by the loop spacing L\\sim 1/\\sqrt{\\rho} , where ρ is the loop density; finally, the climb force depends on the loop size. The three forces compete and their relative magnitudes define the evolution pathway of the dislocation structure.

  20. Influence of radiation damage on krypton diffusion in silicon carbide

    NASA Astrophysics Data System (ADS)

    Friedland, E.; Hlatshwayo, T. T.; van der Berg, N. G.; Mabena, M. C.

    2015-07-01

    Diffusion of krypton in poly and single crystalline silicon carbide is investigated and compared with the previously obtained results for xenon, which pointed to a different diffusion mechanism than observed for chemically active elements. For this purpose 360 keV krypton ions were implanted in commercial 6H-SiC and CVD-SiC wafers at room temperature, 350 °C and 600 °C. Width broadening of the implantation profiles and krypton retention during isochronal and isothermal annealing up to temperatures of 1400 °C was determined by RBS-analysis, whilst in the case of 6H-SiC damage profiles were simultaneously obtained by α-particle channeling. Little diffusion and no krypton loss was detected in the initially amorphized and eventually recrystallized surface layer of cold implanted 6H-SiC during annealing up to 1200 °C. Above that temperature thermal etching of the implanted surface became increasingly important. No diffusion or krypton loss is detected in the hot implanted 6H-SiC samples during annealing up to 1400 °C. Radiation damage dependent grain boundary diffusion is observed at 1300 °C in CVD-SiC. The results seem to indicate, that the chemically inert noble gas atoms do not form defect-impurity complexes, which strongly influence the diffusion behavior of other diffusors in silicon carbide.

  1. Influence of XRCC1 Genetic Polymorphisms on Ionizing Radiation-Induced DNA Damage and Repair

    PubMed Central

    Sterpone, Silvia; Cozzi, Renata

    2010-01-01

    It is well known that ionizing radiation (IR) can damage DNA through a direct action, producing single- and double-strand breaks on DNA double helix, as well as an indirect effect by generating oxygen reactive species in the cells. Mammals have evolved several and distinct DNA repair pathways in order to maintain genomic stability and avoid tumour cell transformation. This review reports important data showing a huge interindividual variability on sensitivity to IR and in susceptibility to developing cancer; this variability is principally represented by genetic polymorphisms, that is, DNA repair gene polymorphisms. In particular we have focussed on single nucleotide polymorphisms (SNPs) of XRCC1, a gene that encodes for a scaffold protein involved basically in Base Excision Repair (BER). In this paper we have reported and presented recent studies that show an influence of XRCC1 variants on DNA repair capacity and susceptibility to breast cancer. PMID:20798883

  2. WIDE-CROSS WHOLE-GENOME RADIATION HYBIRD MAPPING OF THE COTTON (GOSSYPIUM BARBADENSE L.) GENOME

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Whole-genome radiation hybrid mapping has been applied extensively to human and certain animal species but little to plants. We recently demonstrated an alternative mapping approach in cotton (Gossypium hirsutum L.) based on segmentation by 5-krad gamma-irradiation and derivation of wild-cross whol...

  3. Altering genomic integrity: heavy metal exposure promotes trans-posable element-mediated damage

    PubMed Central

    Morales, Maria E.; Servant, Geraldine; Ade, Catherine; Roy-Enge, Astrid M.

    2015-01-01

    Maintenance of genomic integrity is critical for cellular homeostasis and survival. The active transposable elements (TEs) composed primarily of three mobile element lineages LINE-1, Alu, and SVA comprise approximately 30% of the mass of the human genome. For the past two decades, studies have shown that TEs significantly contribute to genetic instability and that TE-caused damages are associated with genetic diseases and cancer. Different environmental exposures, including several heavy metals, influence how TEs interact with its host genome increasing their negative impact. This mini-review provides some basic knowledge on TEs, their contribution to disease and an overview of the current knowledge on how heavy metals influence TE-mediated damage. PMID:25774044

  4. Mutational Strand Asymmetries in Cancer Genomes Reveal Mechanisms of DNA Damage and Repair.

    PubMed

    Haradhvala, Nicholas J; Polak, Paz; Stojanov, Petar; Covington, Kyle R; Shinbrot, Eve; Hess, Julian M; Rheinbay, Esther; Kim, Jaegil; Maruvka, Yosef E; Braunstein, Lior Z; Kamburov, Atanas; Hanawalt, Philip C; Wheeler, David A; Koren, Amnon; Lawrence, Michael S; Getz, Gad

    2016-01-28

    Mutational processes constantly shape the somatic genome, leading to immunity, aging, cancer, and other diseases. When cancer is the outcome, we are afforded a glimpse into these processes by the clonal expansion of the malignant cell. Here, we characterize a less explored layer of the mutational landscape of cancer: mutational asymmetries between the two DNA strands. Analyzing whole-genome sequences of 590 tumors from 14 different cancer types, we reveal widespread asymmetries across mutagenic processes, with transcriptional ("T-class") asymmetry dominating UV-, smoking-, and liver-cancer-associated mutations and replicative ("R-class") asymmetry dominating POLE-, APOBEC-, and MSI-associated mutations. We report a striking phenomenon of transcription-coupled damage (TCD) on the non-transcribed DNA strand and provide evidence that APOBEC mutagenesis occurs on the lagging-strand template during DNA replication. As more genomes are sequenced, studying and classifying their asymmetries will illuminate the underlying biological mechanisms of DNA damage and repair. PMID:26806129

  5. The genomic substrate for adaptive radiation in African cichlid fish

    PubMed Central

    Malinsky, Milan; Keller, Irene; Fan, Shaohua; Simakov, Oleg; Ng, Alvin Y.; Lim, Zhi Wei; Bezault, Etienne; Turner-Maier, Jason; Johnson, Jeremy; Alcazar, Rosa; Noh, Hyun Ji; Russell, Pamela; Aken, Bronwen; Alföldi, Jessica; Amemiya, Chris; Azzouzi, Naoual; Baroiller, Jean-François; Barloy-Hubler, Frederique; Berlin, Aaron; Bloomquist, Ryan; Carleton, Karen L.; Conte, Matthew A.; D'Cotta, Helena; Eshel, Orly; Gaffney, Leslie; Galibert, Francis; Gante, Hugo F.; Gnerre, Sante; Greuter, Lucie; Guyon, Richard; Haddad, Natalie S.; Haerty, Wilfried; Harris, Rayna M.; Hofmann, Hans A.; Hourlier, Thibaut; Hulata, Gideon; Jaffe, David B.; Lara, Marcia; Lee, Alison P.; MacCallum, Iain; Mwaiko, Salome; Nikaido, Masato; Nishihara, Hidenori; Ozouf-Costaz, Catherine; Penman, David J.; Przybylski, Dariusz; Rakotomanga, Michaelle; Renn, Suzy C. P.; Ribeiro, Filipe J.; Ron, Micha; Salzburger, Walter; Sanchez-Pulido, Luis; Santos, M. Emilia; Searle, Steve; Sharpe, Ted; Swofford, Ross; Tan, Frederick J.; Williams, Louise; Young, Sarah; Yin, Shuangye; Okada, Norihiro; Kocher, Thomas D.; Miska, Eric A.; Lander, Eric S.; Venkatesh, Byrappa; Fernald, Russell D.; Meyer, Axel; Ponting, Chris P.; Streelman, J. Todd; Lindblad-Toh, Kerstin; Seehausen, Ole; Di Palma, Federica

    2015-01-01

    Cichlid fishes are famous for large, diverse and replicated adaptive radiations in the Great Lakes of East Africa. To understand the molecular mechanisms underlying cichlid phenotypic diversity, we sequenced the genomes and transcriptomes of five lineages of African cichlids: the Nile tilapia (Oreochromis niloticus), an ancestral lineage with low diversity; and four members of the East African lineage: Neolamprologus brichardi/pulcher (older radiation, Lake Tanganyika), Metriaclima zebra (recent radiation, Lake Malawi), Pundamilia nyererei (very recent radiation, Lake Victoria), and Astatotilapia burtoni (riverine species around Lake Tanganyika). We found an excess of gene duplications in the East African lineage compared to tilapia and other teleosts, an abundance of non-coding element divergence, accelerated coding sequence evolution, expression divergence associated with transposable element insertions, and regulation by novel microRNAs. In addition, we analysed sequence data from sixty individuals representing six closely related species from Lake Victoria, and show genome-wide diversifying selection on coding and regulatory variants, some of which were recruited from ancient polymorphisms. We conclude that a number of molecular mechanisms shaped East African cichlid genomes, and that amassing of standing variation during periods of relaxed purifying selection may have been important in facilitating subsequent evolutionary diversification. PMID:25186727

  6. Assessment of genomic damage and repair on human lymphocytes by paint thinner in vitro.

    PubMed

    Londoño-Velasco, Elizabeth; Hidalgo-Cerón, Victor; Escobar-Hoyos, Luisa F; Hoyos-Giraldo, Luz Stella

    2014-05-01

    Paint thinners are organic-solvent complex mixtures frequently used by car painters around the world in industries and shops. Some studies have revealed the oxidative effect induced by thinner inhalation; however, its genotoxic effect is poorly studied. The aim of this study was to assess the cytotoxicity, genomic damage and DNA repair in vitro induced by commercial paint thinner 0.14 in human lymphocytes. Cytotoxicity was determined by cell-viability analysis with trypan blue after 4 h treatment with different thinner concentrations (0.025 to 1.2 µL/mL). Genomic damage was evaluated by means of the alkaline single-cell gel electrophoresis (SCGE; pH > 13) in treated cultures after 1 h with three low-cytotoxic thinner concentrations (0.05, 0.1 and 0.2 µL/mL). In order to evaluate the genomic DNA repair, one set of SCGE slides was prepared immediately after treatment, and another one was prepared after 4 h of liquid-holding recovery. A significant level of cytotoxicity was observed over the entire concentration range of paint thinner in lymphocytes (F = 175.98; p ≤ 0.001). In the SCGE % tail DNA assessment, a significant increase of lymphocyte genomic damage was evidenced (F = 72.32; p < 0.001). In addition, we found a significant decrease in the % tail DNA in thinner-treated cells after liquid-holding recovery period (all p < 0.05), demonstrating that DNA primary lesions induced by low-cytotoxic thinner concentrations are efficiently repaired. In conclusion, thinner components induce cytotoxicity and genomic damage in human lymphocytes under the study conditions, possibly by oxidative and alkylative DNA damage. PMID:24236478

  7. Effect of electron excitation on radiation damage in fce metals

    NASA Astrophysics Data System (ADS)

    Iwase, A.; Iwata, T.

    1994-05-01

    Defect production, radiation annealing and defect recovery are studied in several fcc metals (Al, Cu, Ni, Ag and Pt) irradiated with low-energy (˜ 1 MeV) and high-energy (˜ 100 MeV) ions. Irradiation of the metals with strong electron-lattice interaction (Al, Ni and Pt) by ˜ 100 MeV ions causes an anomalous reduction, or even a complete disappearance of stage-I recovery. This experimental result shows that the energy transferred from excited electrons to lattice atoms through the electron-lattice interaction contributes to the annihilation of single interstitials. This effect is also observed in Ni as a large cross section for radiation annealing, and a decrease of the damage efficiency. On the other hand, in Cu and Ag thin foils, we find that lattice defects are produced not only through elastic interactions, but also through a process strongly associated with electron excitation. In the latter process, the defect production cross section is proportional to Se1.7 in Cu and Se1.5 in Ag. The nearly quadratic dependence of the cross section on Se suggests that the mutual Coulomb repulsion of ions positively charged by electron excitation causes the defect production.

  8. Acute radiation-induced pulmonary damage: a clinical study on the response to fractionated radiation therapy.

    PubMed

    Mah, K; Van Dyk, J; Keane, T; Poon, P Y

    1987-02-01

    Acute radiation-induced pulmonary damage can be a significant cause of morbidity in radiation therapy of the thorax. A prospective, clinical study was conducted to obtain dose-response data on acute pulmonary damage caused by fractionated radiation therapy. The endpoint was a visible increase in lung density within the irradiated volume on a computed tomographic (CT) examination as observed independently by three diagnostic radiologists. Fifty-four patients with various malignancies of the thorax completed the study. CT chest scans were taken before and at preselected times following radiotherapy. To represent different fractionation schedules of equivalent biological effect, the estimated single dose (ED) model, ED = D X N-0.377 X T-0.058 was used in which D was the average lung dose within the high dose region in cGy, N was the number of fractions, and T was the overall treatment time in days. Patients were grouped according to ED and the percent incidence of pulmonary damage for each group was determined. Total average lung doses ranged from 29.8 Gy to 53.6 Gy given in 10 to 30 fractions over a range of 12 to 60 days. Five patient groups with incidence ranging from 30% (ED of 930) to 90% (ED of 1150) were obtained. The resulting dose-response curve predicted a 50% incidence level at an ED value (ED50) of 1000 +/- 40 ED units. This value represents fractionation schedules equivalent to a total average lung dose of 32.9 Gy given in 15 fractions over 19 days. Over the linear portion of the dose-response curve, a 5% increase in ED (or total dose if N and T remain constant), predicts a 12% increase in the incidence of acute radiation-induced pulmonary damage. PMID:3818385

  9. INVESTIGATION OF MICROSCOPIC RADIATION DAMAGE IN WASTE FORMS USING ODNMR AND AEM TECHNIQUES

    EPA Science Inventory

    The proposed project addresses DOE nuclear waste problems that are currently intractable without achieving a fundamental understanding of radiation effects on high level waste (HLW) forms. This project will investigate the microscopic effects of radiation damage in crystalline an...

  10. Rad9 interacts with Aft1 to facilitate genome surveillance in fragile genomic sites under non-DNA damage-inducing conditions in S. cerevisiae

    PubMed Central

    Andreadis, Christos; Nikolaou, Christoforos; Fragiadakis, George S.; Tsiliki, Georgia; Alexandraki, Despina

    2014-01-01

    DNA damage response and repair proteins are centrally involved in genome maintenance pathways. Yet, little is known about their functional role under non-DNA damage-inducing conditions. Here we show that Rad9 checkpoint protein, known to mediate the damage signal from upstream to downstream essential kinases, interacts with Aft1 transcription factor in the budding yeast. Aft1 regulates iron homeostasis and is also involved in genome integrity having additional iron-independent functions. Using genome-wide expression and chromatin immunoprecipitation approaches, we found Rad9 to be recruited to 16% of the yeast genes, often related to cellular growth and metabolism, while affecting the transcription of ∼2% of the coding genome in the absence of exogenously induced DNA damage. Importantly, Rad9 is recruited to fragile genomic regions (transcriptionally active, GC rich, centromeres, meiotic recombination hotspots and retrotransposons) non-randomly and in an Aft1-dependent manner. Further analyses revealed substantial genome-wide parallels between Rad9 binding patterns to the genome and major activating histone marks, such as H3K36me, H3K79me and H3K4me. Thus, our findings suggest that Rad9 functions together with Aft1 on DNA damage-prone chromatin to facilitate genome surveillance, thereby ensuring rapid and effective response to possible DNA damage events. PMID:25300486

  11. Complete genome sequence of Deinococcus actinosclerus BM2(T), a bacterium with Gamma-radiation resistance isolated from soil in South Korea.

    PubMed

    Kim, Myung Kyum; Kang, Myung Suk; Lee, Do Hee; Joo, Eun Sun; Kim, Eun Bit; Jeon, Seon Hwa; Jung, Hee-Young; Srinivasan, Sathiyaraj

    2016-04-20

    A Gram-positive, short-rod shaped and non-motile bacterium Deinococcus actinosclerus BM2(T), resistant to gamma and UV radiation, was isolated from a soil sample collected in South Korea. Strain BM2(T) showed high resistance to gamma radiation with D10 value of 9 kGy. The complete genome of D. actinosclerus BM2(T) consists of a single chromosome (3,264,334bp). The genome features showed the presence of intracellular proteases that help to eliminate radiation-induced ROS during recovery from ionizing radiation damage. PMID:26953742

  12. Dicarbonyl proteome and genome damage in metabolic and vascular disease.

    PubMed

    Rabbani, Naila; Thornalley, Paul J

    2014-04-01

    Methylglyoxal is a potent protein-glycating agent. It is an arginine-directed glycating agent and often modifies functionally important sites in proteins. Glycation forms mainly MG-H1 [Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine] residues. MG-H1 content of proteins is quantified by stable isotopic dilution analysis-MS/MS and also by immunoblotting with specific monoclonal antibodies. Methylglyoxal-modified proteins undergo cellular proteolysis and release MG-H1 free adduct for excretion. MG-H1 residues have been found in proteins of animals, plants, bacteria, fungi and protoctista. MG-H1 is often the major advanced glycation end-product in proteins of tissues and body fluids, increasing in diabetes and associated vascular complications, renal failure, cirrhosis, Alzheimer's disease, arthritis, Parkinson's disease and aging. Proteins susceptible to methylglyoxal modification with related functional impairment are called the DCP (dicarbonyl proteome). The DCP includes albumin, haemoglobin, transcription factors, mitochondrial proteins, extracellular matrix proteins, lens crystallins and others. DCP component proteins are linked to mitochondrial dysfunction in diabetes and aging, oxidative stress, dyslipidaemia, cell detachment and anoikis and apoptosis. Methylglyoxal also modifies DNA where deoxyguanosine residues are modified to imidazopurinone MGdG {3-(2'-deoxyribosyl)-6,7-dihydro-6,7-dihydroxy-6/7-methylimidazo-[2,3-b]purine-9(8)one} isomers. MGdG was the major quantitative adduct detected in vivo. It was linked to frequency of DNA strand breaks and increased markedly during apoptosis induced by a cell-permeant glyoxalase I inhibitor. Glyoxalase I metabolizes >99% methylglyoxal and thereby protects the proteome and genome. Gene deletion of GLO1 is embryonically lethal and GLO1 silencing increases methylglyoxal concentration, MG-H1 and MGdG, premature aging and disease. Studies of methylglyoxal glycation have importance for human health, longevity and

  13. Biophysical modelling of early and delayed radiation damage at chromosome level

    NASA Astrophysics Data System (ADS)

    Andreev, S.; Eidelman, Y.

    Exposure by ionising radiation increases cancer risk in human population Cancer is thought to originate from an altered expression of certain number of specific genes It is now widely recognised that chromosome aberrations CA are involved in stable change in expression of genes by gain or loss of their functions Thus CA can contribute to initiation or progression of cancer Therefore understanding mechanisms of CA formation in the course of cancer development might be valuable tool for quantification and prognosis of different stages of radiation carcinogenesis Early CA are defined as aberrations induced in first post-irradiation mitotic cycle The present work describes the original biophysical technique for early CA modelling It includes the following simulation steps the ionising particle track structure the structural organisation of all chromosomes in G 0 G 1 cell nucleus spatial distribution of radiation induced DNA double-strand breaks dsb within chromosomes dsb rejoining and misrejoining modelling cell cycle taking into account mitotic delay which results in complex time dependence of aberrant cells in first mitosis The results on prediction of dose-response curves for simple and complex CA measured in cells undergoing first division cycle are presented in comparison with recent experimental data There is increasing evidence that CA are also observed in descendents of irradiated cells many generations after direct DNA damage These delayed CA or chromosome instability CI are thought to be a manifestation of genome

  14. Higher-Density Culture in Human Embryonic Stem Cells Results in DNA Damage and Genome Instability.

    PubMed

    Jacobs, Kurt; Zambelli, Filippo; Mertzanidou, Afroditi; Smolders, Ilse; Geens, Mieke; Nguyen, Ha Thi; Barbé, Lise; Sermon, Karen; Spits, Claudia

    2016-03-01

    Human embryonic stem cells (hESC) show great promise for clinical and research applications, but their well-known proneness to genomic instability hampers the development to their full potential. Here, we demonstrate that medium acidification linked to culture density is the main cause of DNA damage and genomic alterations in hESC grown on feeder layers, and this even in the short time span of a single passage. In line with this, we show that increasing the frequency of the medium refreshments minimizes the levels of DNA damage and genetic instability. Also, we show that cells cultured on laminin-521 do not present this increase in DNA damage when grown at high density, although the (long-term) impact on their genomic stability remains to be elucidated. Our results explain the high levels of genome instability observed over the years by many laboratories worldwide, and show that the development of optimal culture conditions is key to solving this problem. PMID:26923824

  15. Higher-Density Culture in Human Embryonic Stem Cells Results in DNA Damage and Genome Instability

    PubMed Central

    Jacobs, Kurt; Zambelli, Filippo; Mertzanidou, Afroditi; Smolders, Ilse; Geens, Mieke; Nguyen, Ha Thi; Barbé, Lise; Sermon, Karen; Spits, Claudia

    2016-01-01

    Summary Human embryonic stem cells (hESC) show great promise for clinical and research applications, but their well-known proneness to genomic instability hampers the development to their full potential. Here, we demonstrate that medium acidification linked to culture density is the main cause of DNA damage and genomic alterations in hESC grown on feeder layers, and this even in the short time span of a single passage. In line with this, we show that increasing the frequency of the medium refreshments minimizes the levels of DNA damage and genetic instability. Also, we show that cells cultured on laminin-521 do not present this increase in DNA damage when grown at high density, although the (long-term) impact on their genomic stability remains to be elucidated. Our results explain the high levels of genome instability observed over the years by many laboratories worldwide, and show that the development of optimal culture conditions is key to solving this problem. PMID:26923824

  16. Lack of Genomic Instability in Bone Marrow Cells of SCID Mice Exposed Whole-Body to Low-Dose Radiation

    PubMed Central

    Rithidech, Kanokporn Noy; Udomtanakunchai, Chatchanok; Honikel, Louise; Whorton, Elbert

    2013-01-01

    It is clear that high-dose radiation is harmful. However, despite extensive research, assessment of potential health-risks associated with exposure to low-dose radiation (at doses below or equal to 0.1 Gy) is still challenging. Recently, we reported that 0.05 Gy of 137Cs gamma rays (the existing limit for radiation-exposure in the workplace) was incapable of inducing significant in vivo genomic instability (measured by the presence of late-occurring chromosomal damage at 6 months post-irradiation) in bone marrow (BM) cells of two mouse strains, one with constitutively high and one with intermediate levels of the repair enzyme DNA-dependent protein-kinase catalytic-subunit (DNA-PKcs). In this study, we present evidence for a lack of genomic instability in BM cells of the severely combined-immunodeficiency (SCID/J) mouse (which has an extremely low-level of DNA-PKcs activity) exposed whole-body to low-dose radiation (0.05 Gy). Together with our previous report, the data indicate that low-dose radiation (0.05 Gy) is incapable of inducing genomic instability in vivo (regardless of the levels of DNA-PKcs activity of the exposed mice), yet higher doses of radiation (0.1 and 1 Gy) do induce genomic instability in mice with intermediate and extremely low-levels of DNA-PKcs activity (indicating an important role of DNA-PKcs in DNA repair). PMID:23549227

  17. Genome-Wide Identification and 3D Modeling of Proteins involved in DNA Damage Recognition and Repair (Final Report)

    SciTech Connect

    Abagyan, Ruben; An, Jianghong

    2005-08-12

    DNA Damage Recognition and Repair (DDR&R) proteins play a critical role in cellular responses to low-dose radiation and are associated with cancer. We have performed a systematic, genome-wide computational analysis of genomic data for human genes involved in the DDR&R process. The significant achievements of this project include: 1) Construction of the computational pipeline for searching DDR&R genes, building and validation of 3D models of proteins involved in DDR&R; 2) Functional and structural annotation of the 3D models and generation of comprehensive lists of suggested knock-out mutations; and the development of a method to predict the effects of mutations. Large scale testing of technology to identify novel small binding pockets in protein structures leading to new DDRR inhibitor strategies 3) Improvements of macromolecular docking technology (see the CAPRI 1-3 and 4-5 results) 4) Development of a new algorithm for improved analysis of high-density oligonucleotide arrays for gene expression profiling; 5) Construction and maintenance of the DNA Damage Recognition and Repair Database; 6) Producing 15 research papers (12 published and 3 in preparation).

  18. Genome-Wide Identification and 3D Modeling of Proteins involved in DNA Damage Recognition and Repair (Final Report)

    SciTech Connect

    Ruben A. Abagyan, PhD

    2004-04-15

    OAK-B135 DNA Damage Recognition and Repair (DDR and R) proteins play a critical role in cellular responses to low-dose radiation and are associated with cancer. the authors have performed a systematic, genome-wide computational analysis of genomic data for human genes involved in the DDR and R process. The significant achievements of this project include: (1) Construction of the computational pipeline for searching DDR and R genes, building and validation of 3D models of proteins involved in DDR and R; (2) Functional and structural annotation of the 3D models and generation of comprehensive lists of suggested knock-out mutations; (3) Important improvement of macromolecular docking technology and its application to predict the DNA-Protein complex conformation; (4) Development of a new algorithm for improved analysis of high-density oligonucleotide arrays for gene expression profiling; (5) Construction and maintenance of the DNA Damage Recognition and Repair Database; and (6) Producing 14 research papers (10 published and 4 in preparation).

  19. A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE: INDUCED BY RADIATION, CHEMICALS AND ENZYMES

    EPA Science Inventory

    A simple and rapid assay to detect DNA damage is reported. This assay is based on the ability of certain dyes to fluoresce upon intercalation with dsDNA. Damage caused by ultraviolet (UV) radiation, chemicals or restriction enzymes is detected using this assay. UV radiation at...

  20. Deoxyribonucleoprotein structure and radiation injury: cellular radiosensitivity is determined by LET infinity -dependent DNA damage in hydrated deoxyribonucleoproteins and the extent of its repair.

    PubMed

    Lett, J T; Peters, E L

    1992-01-01

    For decades, theories of cellular radiosensitivity relied upon the initial patterns of energy deposition to explain radiation lethality. Such theories are unsound: cellular (DNA) repair also underlies cellular radiosensitivity. For the charged particles encountered in deep space, both the types of DNA damage caused in cellular deoxyribonucleoproteins and the efficacies of their repair are dependent on linear energy transfer (LET infinity), and repair efficiency is also influenced by cell and tissue type, i.e., the actual recovery processes involved. Therefore, quality factors derived from radiation quality alone are inadequate parameters for assessing the radiation risks of space flight. Until recently, OH radicals formed in bulk nuclear water were believed to be the major causes of DNA damage that results in cell death, especially for sparsely ionizing radiations. That hypothesis has now been challenged, if not refuted. Lethal genomic DNA damage is determined mainly by energy deposition in deoxyribonucleoproteins, and their hydration shells, and charge (energy) transfer processes within those structures. PMID:11537046

  1. Synergistic Effect of Triple Ion Beams on Radiation Damage in CLAM Steel

    NASA Astrophysics Data System (ADS)

    Yuan, Da-Qing; Zheng, Yong-Nan; Zuo, Yi; Fan, Ping; Zhou, Dong-Mei; Zhang, Qiao-Li; Ma, Xiao-Qiang; Cui, Bao-Qun; Chen, Li-Hua; Jiang, Wei-Sheng; Wu, Yi-Can; Huang, Qun-Ying; Peng, Lei; Cao, Xing-Zhong; Wang, Bao-Yi; Wei, Long; Zhu, Sheng-Yun

    2014-04-01

    The synergistic effect of triple ion beams is investigated by simultaneous and sequential irradiations of gold, hydrogen and helium ions on the low activation martensitic steel (CLAM) developed in China. The depth profile measurements of the positron annihilation Doppler broadening S parameter are carried out as a function of slow-positron beam energy to examine the produced radiation damage. The synergistic effect of displacement damage and hydrogen and helium on the formation of radiation damage is clearly observed. In the preset case, this effect suppresses the radiation damage in the CLAM steel due to the helium and/or hydrogen filling of vacancy clusters.

  2. Potential vascular damage from radiation in the space environment

    NASA Astrophysics Data System (ADS)

    Griem, M. L.; Robotewskyj, A.; Nagel, R. H.

    1994-10-01

    Cultured endothelial cells of blood vessels have a Do of 2 Gy for X-rays. A dose of 0.5 Gy of X-rays has an acute effect on vessel diameter. The vessels may show other acute effects such as change in permeability including a change in the blood brain barrier. Changes occurring from late effects of chronic exposure in vascular architecture include telangiectasia and decrease in vascular density. Changes in the perivascular connective tissue particularly collagen may play a role in these changes. After charged particle exposure of 15 and 30 Gy, radiation changes in the blood brain barrier and vascular changes are noted in the nervous system. These long term changes are recorded by PET, MRI, and CT imaging. Chronic exposure to alpha particles causes vascular damage in compact bone resulting in bone infarcts. Using tandem scanning confocal microscopy in-situ imaging of the capillaries and collagen of the papillary dermis provides a non-invasive method of serial recording of changes in irradiated microvasculature.

  3. UV radiation and freshwater zooplankton: damage, protection and recovery

    PubMed Central

    Rautio, Milla; Tartarotti, Barbara

    2011-01-01

    While many laboratory and field studies show that zooplankton are negatively affected when exposed to high intensities of ultraviolet radiation (UVR), most studies also indicate that zooplankton are well adapted to cope with large variations in their UVR exposure in the pelagic zone of lakes. The response mechanisms of zooplankton are diverse and efficient and may explain the success and richness of freshwater zooplankton in optically variable waters. While no single behavioural or physiological protection mechanism seems to be superior, and while several unexplained and contradictory patterns exist in zooplankton UVR ecology, recent increases in our understanding are consistent with UVR playing an important role for zooplankton. This review examines the variability in freshwater zooplankton responses to UVR, with a focus on crustacean zooplankton (Cladocera and Copepoda). We present an overview of UVR-induced damages, and the protection and recovery mechanisms freshwater zooplankton use when exposed to UVR. We review the current knowledge of UVR impact on freshwater zooplankton at species and community levels, and discuss briefly how global change over the last three decades has influenced the UVR milieu in lakes. PMID:21516254

  4. Radiation damage of BGO and CsI(Tl) crystals

    NASA Astrophysics Data System (ADS)

    Bieler, Ch.; Burkart, D.; Marks, J.; Riebesell, M.; Spitzer, H.; Wittenburg, K.; Winter, G.-G.

    1985-02-01

    We have measured the response of five 10-20 cm long BGO crystals from different manufacturers to irradiation with 137Cs γ-rays at doses of 40 and 85 rad. Immediately after irradiation the pulse height drops by 26-38% and recovers only partially with time. 110 d after irradiation the remaining damage is between 1 and 13%. A 10 cm long CsI (Tl) crystal shows pulse height reductions after irradiation which do not recover with time. The cumulative effect of a continuous irradiation on a BGO crystal (1 × 1× 15 cm 3) in a partially shielded position on the beam pipe of PETRA was measured over a period of 53 d. At an average daily dose of 1.9 rad the pulse height dropped continuously resulting in an overall pulse height loss of 9% in 7 weeks. This indicates that BGO when applied in long and narrow shapes is more sensitive to small radiation doses than previously assumed.

  5. Primary radiation damage of protein crystals by an intense synchrotron X-ray beam.

    PubMed

    Teng, T Y; Moffat, K

    2000-09-01

    X-ray radiation damage of a lysozyme single crystal by an intense monochromatic beam from a third-generation radiation source at the Advanced Photon Source has been studied. The results show that primary radiation damage is linearly dependent on the X-ray dose even when the crystal is at cryogenic temperatures. The existence of an upper limit for the primary radiation damage was observed. Above the threshold of approximately 1 x 10(7) Gy, excessive damage of the crystal develops which is interpreted as the onset of secondary and/or tertiary radiation damage. This upper limit of X-ray dose is compared with Henderson's limit [Henderson (1990). Proc. R. Soc. London, B241, 6-8], and its implication for the amount of useful X-ray diffraction data that can be obtained for crystals of a given scattering power is also discussed. PMID:16609214

  6. Clustered DNA damages induced in human hematopoietic cells by low doses of ionizing radiation

    NASA Technical Reports Server (NTRS)

    Sutherland, Betsy M.; Bennett, Paula V.; Cintron-Torres, Nela; Hada, Megumi; Trunk, John; Monteleone, Denise; Sutherland, John C.; Laval, Jacques; Stanislaus, Marisha; Gewirtz, Alan

    2002-01-01

    Ionizing radiation induces clusters of DNA damages--oxidized bases, abasic sites and strand breaks--on opposing strands within a few helical turns. Such damages have been postulated to be difficult to repair, as are double strand breaks (one type of cluster). We have shown that low doses of low and high linear energy transfer (LET) radiation induce such damage clusters in human cells. In human cells, DSB are about 30% of the total of complex damages, and the levels of DSBs and oxidized pyrimidine clusters are similar. The dose responses for cluster induction in cells can be described by a linear relationship, implying that even low doses of ionizing radiation can produce clustered damages. Studies are in progress to determine whether clusters can be produced by mechanisms other than ionizing radiation, as well as the levels of various cluster types formed by low and high LET radiation.

  7. Complete genome sequence of ionizing radiation-resistant Hymenobacter sp. strain PAMC26628 isolated from an Arctic lichen.

    PubMed

    Ahn, Do-Hwan; Han, So-Ra; Oh, Tae-Jin; Park, Hyun

    2016-04-10

    Ionizing radiation-resistant Hymenobacter sp. strain PAMC26628 was isolated from Stereocaulon sp., an Arctic lichen. Complete genome sequencing of Hymenobacter sp. PAMC26628 revealed one chromosome (5,277,381bp), one plasmid (89,596bp), and several genes involved in nucleotide excision repair, a DNA damage removal pathway. An analysis of the Hymenobacter sp. PAMC26628 genome will help us understand its evolution and provide novel insight into the adaptations that allow this organism to survive in the extreme cold of the Arctic. PMID:26924242

  8. Molecular mechanisms of radiation-induced genomic instability in human cells

    SciTech Connect

    Liber, Howard L.

    2003-02-13

    The overall strategy was to create a series of isogenic human cell lines that differ in key elements of cell cycle checkpoint, apoptosis, or DNA repair in response to radiation-induced damage. The goal then was to quantify the fractions of cells within a population that exhibit reduced telomere lengths and relate this to the genetic background of the cell, as well as to the response to ionizing radiation. Association between telomere length and degree of genomic instability in the population is being examined for seven closely related cell lines, that vary in p53 status, bcl-2 status, or ability to repair double strand breaks. Experiments utilize gamma rays at doses of 0, 10, and 200 cGy. During this time period the effort concentrated on generating data with two cell lines. Approximately one-third of the required clones were isolated, and analyses for mutagenesis and chromosome aberrations were undertaken.

  9. Regulation of homologous recombinational repair by lamin B1 in radiation-induced DNA damage.

    PubMed

    Liu, Ning-Ang; Sun, Jiying; Kono, Kazuteru; Horikoshi, Yasunori; Ikura, Tsuyoshi; Tong, Xing; Haraguchi, Tokuko; Tashiro, Satoshi

    2015-06-01

    DNA double-strand breaks (DSBs) are the major lethal lesion induced by ionizing radiation (IR). RAD51-dependent homologous recombination (HR) is one of the most important pathways in DSB repair and genome integrity maintenance. However, the mechanism of HR regulation by RAD51 remains unclear. To understand the mechanism of RAD51-dependent HR, we searched for interacting partners of RAD51 by a proteomics analysis and identified lamin B1 in human cells. Lamins are nuclear lamina proteins that play important roles in the structural organization of the nucleus and the regulation of chromosome functions. Immunoblotting analyses revealed that siRNA-mediated lamin B1 depletion repressed the DNA damage-dependent increase of RAD51 after IR. The repression was abolished by the proteasome inhibitor MG132, suggesting that lamin B1 stabilizes RAD51 by preventing proteasome-mediated degradation in cells with IR-induced DNA damage. We also showed that lamin B1 depletion repressed RAD51 focus formation and decreased the survival rates after IR. On the basis of these results, we propose that lamin B1 promotes DSB repair and cell survival by maintaining the RAD51 protein levels for HR upon DSB induction after IR. PMID:25733566

  10. Bystander effects, genomic instability, adaptive response, and cancer risk assessment for radiation and chemical exposures

    SciTech Connect

    Preston, R. Julian . E-mail: preston.julian@epa.gov

    2005-09-01

    There is an increased interest in utilizing mechanistic data in support of the cancer risk assessment process for ionizing radiation and environmental chemical exposures. In this regard, the use of biologically based dose-response models is particularly advocated. The aim is to provide an enhanced basis for describing the nature of the dose-response curve for induced tumors at low levels of exposure. Cellular responses that might influence the nature of the dose-response curve at low exposures are understandably receiving attention. These responses (bystander effects, genomic instability, and adaptive responses) have been studied most extensively for radiation exposures. The former two could result in an enhancement of the tumor response at low doses and the latter could lead to a reduced response compared to that predicted by a linear extrapolation from high dose responses. Bystander responses, whereby cells other than those directly traversed by radiation tracks are damaged, can alter the concept of target cell population per unit dose. Similarly, induced genomic instability can alter the concept of total response to an exposure. There appears to be a role for oxidative damage and cellular signaling in the etiology of these cellular responses. The adaptive response appears to be inducible at very low doses of radiation or of some chemicals and reduces the cellular response to a larger challenge dose. It is currently unclear how these cellular toxic responses might be involved in tumor formation, if indeed they are. In addition, it is not known how widespread they are as regards inducing agents. Thus, their impact on low dose cancer risk remains to be established.

  11. Micro-inhomogeneity effects and radiation damage in semi-insulating GaAs radiation detectors

    SciTech Connect

    Bates, R.; O`Shea, V.; Raine, C.; Smith, K.M.; Didziulis, R.; Kazukauskas, V.; Rinkevicius, V.; Storasta, J.; Vaitkus, J.

    1998-06-01

    Thermally-stimulated current (TSC) measurements and a detailed analysis of current-voltage (I-V) characteristics have been made on semi-insulating GaAs (SI-GaAs) Schottky diode particle detectors, fabricated on substrates from several supplies, before and after irradiation with 24 GeV protons and 300 MeV pions. The analysis of I-V characteristics allows the determination of the barrier height and bulk resistance in detectors. Changes observed in I-V characteristics and TSC spectra after irradiation are described and a dislocation-net model of radiation-damaged devices is proposed.

  12. Silymarin Protects Epidermal Keratinocytes from Ultraviolet Radiation-Induced Apoptosis and DNA Damage by Nucleotide Excision Repair Mechanism

    PubMed Central

    Katiyar, Santosh K.; Mantena, Sudheer K.; Meeran, Syed M.

    2011-01-01

    Solar ultraviolet (UV) radiation is a well recognized epidemiologic risk factor for melanoma and non-melanoma skin cancers. This observation has been linked to the accumulation of UVB radiation-induced DNA lesions in cells, and that finally lead to the development of skin cancers. Earlier, we have shown that topical treatment of skin with silymarin, a plant flavanoid from milk thistle (Silybum marianum), inhibits photocarcinogenesis in mice; however it is less understood whether chemopreventive effect of silymarin is mediated through the repair of DNA lesions in skin cells and that protect the cells from apoptosis. Here, we show that treatment of normal human epidermal keratinocytes (NHEK) with silymarin blocks UVB-induced apoptosis of NHEK in vitro. Silymarin reduces the amount of UVB radiation-induced DNA damage as demonstrated by reduced amounts of cyclobutane pyrimidine dimers (CPDs) and as measured by comet assay, and that ultimately may lead to reduced apoptosis of NHEK. The reduction of UV radiation-induced DNA damage by silymarin appears to be related with induction of nucleotide excision repair (NER) genes, because UV radiation-induced apoptosis was not blocked by silymarin in NER-deficient human fibroblasts. Cytostaining and dot-blot analysis revealed that silymarin repaired UV-induced CPDs in NER-proficient fibroblasts from a healthy individual but did not repair UV-induced CPD-positive cells in NER-deficient fibroblasts from patients suffering from xeroderma pigmentosum complementation-A disease. Similarly, immunohistochemical analysis revealed that silymarin did not reduce the number of UVB-induced sunburn/apoptotic cells in the skin of NER-deficient mice, but reduced the number of sunburn cells in their wild-type counterparts. Together, these results suggest that silymarin exert the capacity to reduce UV radiation-induced DNA damage and, thus, prevent the harmful effects of UV radiation on the genomic stability of epidermal cells. PMID:21731736

  13. Silymarin protects epidermal keratinocytes from ultraviolet radiation-induced apoptosis and DNA damage by nucleotide excision repair mechanism.

    PubMed

    Katiyar, Santosh K; Mantena, Sudheer K; Meeran, Syed M

    2011-01-01

    Solar ultraviolet (UV) radiation is a well recognized epidemiologic risk factor for melanoma and non-melanoma skin cancers. This observation has been linked to the accumulation of UVB radiation-induced DNA lesions in cells, and that finally lead to the development of skin cancers. Earlier, we have shown that topical treatment of skin with silymarin, a plant flavanoid from milk thistle (Silybum marianum), inhibits photocarcinogenesis in mice; however it is less understood whether chemopreventive effect of silymarin is mediated through the repair of DNA lesions in skin cells and that protect the cells from apoptosis. Here, we show that treatment of normal human epidermal keratinocytes (NHEK) with silymarin blocks UVB-induced apoptosis of NHEK in vitro. Silymarin reduces the amount of UVB radiation-induced DNA damage as demonstrated by reduced amounts of cyclobutane pyrimidine dimers (CPDs) and as measured by comet assay, and that ultimately may lead to reduced apoptosis of NHEK. The reduction of UV radiation-induced DNA damage by silymarin appears to be related with induction of nucleotide excision repair (NER) genes, because UV radiation-induced apoptosis was not blocked by silymarin in NER-deficient human fibroblasts. Cytostaining and dot-blot analysis revealed that silymarin repaired UV-induced CPDs in NER-proficient fibroblasts from a healthy individual but did not repair UV-induced CPD-positive cells in NER-deficient fibroblasts from patients suffering from xeroderma pigmentosum complementation-A disease. Similarly, immunohistochemical analysis revealed that silymarin did not reduce the number of UVB-induced sunburn/apoptotic cells in the skin of NER-deficient mice, but reduced the number of sunburn cells in their wild-type counterparts. Together, these results suggest that silymarin exert the capacity to reduce UV radiation-induced DNA damage and, thus, prevent the harmful effects of UV radiation on the genomic stability of epidermal cells. PMID:21731736

  14. Impact of DNA damaging agents on genome-wide transcriptional profiles in two marine Synechococcus species

    PubMed Central

    Tetu, Sasha G.; Johnson, Daniel A.; Varkey, Deepa; Phillippy, Katherine; Stuart, Rhona K.; Dupont, Chris L.; Hassan, Karl A.; Palenik, Brian; Paulsen, Ian T.

    2013-01-01

    Marine microorganisms, particularly those residing in coastal areas, may come in contact with any number of chemicals of environmental or xenobiotic origin. The sensitivity and response of marine cyanobacteria to such chemicals is, at present, poorly understood. We have looked at the transcriptional response of well characterized Synechococcus open ocean (WH8102) and coastal (CC9311) isolates to two DNA damaging agents, mitomycin C and ethidium bromide, using whole-genome expression microarrays. The coastal strain showed differential regulation of a larger proportion of its genome following “shock” treatment with each agent. Many of the orthologous genes in these strains, including those encoding sensor kinases, showed different transcriptional responses, with the CC9311 genes more likely to show significant changes in both treatments. While the overall response of each strain was considerably different, there were distinct transcriptional responses common to both strains observed for each DNA damaging agent, linked to the mode of action of each chemical. In both CC9311 and WH8102 there was evidence of SOS response induction under mitomycin C treatment, with genes recA, lexA and umuC significantly upregulated in this experiment but not under ethidium bromide treatment. Conversely, ethidium bromide treatment tended to result in upregulation of the DNA-directed RNA polymerase genes, not observed following mitomycin C treatment. Interestingly, a large number of genes residing on putative genomic island regions of each genome also showed significant upregulation under one or both chemical treatments. PMID:23966990

  15. Role of Pro-inflammatory Cytokines in Radiation-Induced Genomic Instability in Human Bronchial Epithelial Cells.

    PubMed

    Werner, Erica; Wang, Huichen; Doetsch, Paul W

    2015-12-01

    Inflammatory cytokines have been implicated in the regulation of radiation-induced genomic instability in the hematopoietic system and have also been shown to induce chronic DNA damage responses in radiation-induced senescence. We have previously shown that human bronchial epithelial cells (HBEC3-KT) have increased genomic instability and IL-8 production persisting at day 7 after exposure to high-LET (600 MeV/nucleon (56)Fe ions) compared to low-LET (320 keV X rays) radiation. Thus, we investigated whether IL-8 induction is part of a broader pro-inflammatory response produced by the epithelial cells in response to damage, which influences genomic instability measured by increased micronuclei and DNA repair foci frequencies. We found that exposure to radiation induced the release of multiple inflammatory cytokines into the media, including GM-CSF, GROα, IL-1α, IL-8 and the inflammation modulator, IL-1 receptor antagonist (IL-1RA). Our results suggest that this is an IL-1α-driven response, because an identical signature was induced by the addition of recombinant IL-1α to nonirradiated cells and functional interference with recombinant IL-1RA (Anakinra) or anti-IL-1α function-blocking antibody, decreased IL-8 production induced by radiation exposure. However, genomic instability was not influenced by this pathway as addition of recombinant IL-1α to naive or irradiated cells or the presence of IL-1 RA under the same conditions as those that interfered with the function of IL-8, did not affect micronuclei or DNA repair foci frequencies measured at day 7 after exposure. While dose-response studies revealed that genomic instability and IL-8 production are the consequences of targeted effects, experiments employing a co-culture transwell system revealed the propagation of pro-inflammatory responses but not genomic instability from irradiated to nonirradiated cells. Collectively, these results point to a cell-autonomous mechanism sustaining radiation-induced genomic

  16. Research progress in radiation detectors, pattern recognition programs, and radiation damage determination in DNA

    NASA Technical Reports Server (NTRS)

    Baily, N. A.

    1973-01-01

    The radiological implications of statistical variations in energy deposition by ionizing radiation were investigated in the conduct of the following experiments: (1) study of the production of secondary particles generated by the passage of the primary radiation through bone and muscle; (2) the study of the ratio of nonreparable to reparable damage in DNA as a function of different energy deposition patterns generated by X rays versus heavy fast charged particles; (3) the use of electronic radiography systems for direct fluoroscopic tomography and for the synthesis of multiple planes and; (4) the determination of the characteristics of systems response to split fields having different contrast levels, and of minimum detectable contrast levels between the halves under realistic clinical situations.

  17. Radiation damage studies related to nuclear waste forms

    SciTech Connect

    Gray, W.J.; Wald, J.W.; Turcotte, R.P.

    1981-12-01

    Much of the previously reported work on alpha radiation effects on crystalline phases of importance to nuclear waste forms has been derived from radiation effects studies of composite waste forms. In the present work, two single-phase crystalline materials, Gd/sub 2/Ti/sub 2/O/sub 7/ (pyrochlore) and CaZrTi/sub 2/O/sub 7/ (zirconolite), of relative importance to current waste forms were studied independently by doping with /sup 244/Cm at the 3 wt % level. Changes in the crystalline structure measured by x-ray diffraction as a function of dose show that damage ingrowth follows an expected exponential relationship of the form ..delta..V/V/sub 0/ = A(1-exp(-BD)). In both cases, the materials became x-ray amorphous before the estimated saturation value was reached. The predicted magnitudes of the unit cell volume changes at saturation are 5.4% and 3.5%, respectively, for Gd/sub 2/Ti/sub 2/O/sub 7/ and CaZrTi/sub 2/O/sub 7/. The later material exhibited anisotropic behavior in which the expansion of the monoclinic cell in the c/sub 0/ direction was over five times that of the a/sub 0/ direction. The effects of transmutations on the properties of high-level waste solids have not been studied until now because of the long half-lives of the important fission products. This problem was circumvented in the present study by preparing materials containing natural cesium and then irradiating them with neutrons to produce /sup 134/Cs, which has only a 2y half-life. The properties monitored at about one year intervals following irradiation have been density, leach rate and microstructure. A small amount of x-ray diffraction work has also been done. Small changes in density and leach rate have been observed for some of the materials, but they were not large enough to be of any consequence for the final disposal of high level wastes.

  18. DNA bending facilitates the error-free DNA damage tolerance pathway and upholds genome integrity

    PubMed Central

    Gonzalez-Huici, Victor; Szakal, Barnabas; Urulangodi, Madhusoodanan; Psakhye, Ivan; Castellucci, Federica; Menolfi, Demis; Rajakumara, Eerappa; Fumasoni, Marco; Bermejo, Rodrigo; Jentsch, Stefan; Branzei, Dana

    2014-01-01

    DNA replication is sensitive to damage in the template. To bypass lesions and complete replication, cells activate recombination-mediated (error-free) and translesion synthesis-mediated (error-prone) DNA damage tolerance pathways. Crucial for error-free DNA damage tolerance is template switching, which depends on the formation and resolution of damage-bypass intermediates consisting of sister chromatid junctions. Here we show that a chromatin architectural pathway involving the high mobility group box protein Hmo1 channels replication-associated lesions into the error-free DNA damage tolerance pathway mediated by Rad5 and PCNA polyubiquitylation, while preventing mutagenic bypass and toxic recombination. In the process of template switching, Hmo1 also promotes sister chromatid junction formation predominantly during replication. Its C-terminal tail, implicated in chromatin bending, facilitates the formation of catenations/hemicatenations and mediates the roles of Hmo1 in DNA damage tolerance pathway choice and sister chromatid junction formation. Together, the results suggest that replication-associated topological changes involving the molecular DNA bender, Hmo1, set the stage for dedicated repair reactions that limit errors during replication and impact on genome stability. PMID:24473148

  19. Recent radiation damage studies and developments of the Marlowe code

    NASA Astrophysics Data System (ADS)

    Ortiz, C. J.; Souidi, A.; Becquart, C. S.; Domain, C.; Hou, M.

    2014-07-01

    Radiation damage in materials relevant to applications evolves over time scales spanning from the femtosecond - the characteristic time for an atomic collision - to decades - the aging time expected for nuclear materials. The relevant kinetic energies of atoms span from thermal motion to the MeV range.The question motivating this contribution is to identify the relationship between elementary atomic displacements triggered by irradiation and the subsequent microstructural evolution of metals in the long term. The Marlowe code, based on the binary collision approximation (BCA) is used to simulate the sequences of atomic displacements generated by energetic primary recoils and the Object Kinetic Monte Carlo code LAKIMOCA, parameterized on a range of ab initio calculations, is used to predict the subsequent long-term evolution of point defect and clusters thereof. In agreement with full Molecular Dynamics, BCA displacement cascades in body-centered cubic (BCC) Fe and a face-centered cubic (FCC) Febond Nibond Cr alloy display recursive properties that are found useful for predictions in the long term.The case of defects evolution in W due to external irradiation with energetic H and He is also discussed. To this purpose, it was useful to extend the inelastic energy loss model available in Marlowe up to the Bethe regime. The last version of the Marlowe code (version 15) was delivered before message passing instructions softwares (such as MPI) were available but the structure of the code was designed in such a way to permit parallel executions within a distributed memory environment. This makes possible to obtain N different cascades simultaneously using N independent nodes without any communication between processors. The parallelization of the code using MPI was recently achieved by one author of this report (C.J.O.). Typically, the parallelized version of Marlowe allows simulating millions of displacement cascades using a limited number of processors (<64) within only

  20. Radiation damage calculations for the APT materials test program

    SciTech Connect

    Corzine, R.K.; Wechsler, M.S.; Dudziak, D.J.; Ferguson, P.D.; James, M.R.

    1999-09-01

    A materials irradiation was performed at the Los Alamos Neutron Science Center (LANSCE) in the fall of 1996 and spring of 1997 in support of the Accelerator Production of Tritium (APT) program. Testing of the irradiated materials is underway. In the proposed APT design, materials in the target and blanket are to be exposed to protons and neutrons over a wide range of energies. The irradiation and testing program was undertaken to enlarge the very limited direct knowledge presently available of the effects of medium-energy protons ({approximately}1 GeV) on the properties of engineering materials. APT candidate materials were placed in or near the LANSCE accelerator 800-MeV, 1-mA proton beam and received roughly the same proton current density in the center of the beam as would be the case for the APT facility. As a result, the proton fluences achieved in the irradiation were expected to approach the APT prototypic full-power-year values. To predict accurately the performance of materials in APT, radiation damage parameters for the materials experiment must be determined. By modeling the experiment, calculations for atomic displacement, helium and hydrogen cross sections and for proton and neutron fluences were done for representative samples in the 17A, 18A, and 18C areas. The LAHET code system (LCS) was used to model the irradiation program, LAHET 2.82 within LCS transports protons > 1 MeV, and neutrons >20 MeV. A modified version of MCNP for use in LCS, HMCNP 4A, was employed to tally neutrons of energies <20 MeV.

  1. Molecular responses of radiation-induced liver damage in rats

    PubMed Central

    CHENG, WEI; XIAO, LEI; AINIWAER, AIMUDULA; WANG, YUNLIAN; WU, GE; MAO, RUI; YANG, YING; BAO, YONGXING

    2015-01-01

    The aim of the present study was to investigate the molecular responses involved in radiation-induced liver damage (RILD). Sprague-Dawley rats (6-weeks-old) were irradiated once at a dose of 20 Gy to the right upper quadrant of the abdomen. The rats were then sacrificed 3 days and 1, 2, 4, 8 and 12 weeks after irradiation and rats, which were not exposed to irradiation were used as controls. Weight measurements and blood was obtained from the rats and liver tissues were collected for histological and apoptotic analysis. Immunohistochemistry, reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were performed to measure the expression levels of mRNAs and proteins, respectively. The serum levels of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase were increased significantly in the RILD rats. Histological investigation revealed the proliferation of collagen and the formation of fibrotic tissue 12 weeks after irradiation. Apoptotic cells were observed predominantly 2 and 4 weeks after irradiation. The immunohistochemistry, RT-qPCR and western blot analysis all revealed the same pattern of changes in the expression levels of the molecules assessed. The expression levels of transforming growth factor-β1 (TGF-β1), nuclear factor (NF)-κB65, mothers against decapentaplegic homolog 3 (Smad3) and Smad7 and connective tissue growth factor were increased during the recovery period following irradiation up to 12 weeks. The expression levels of tumor necrosis factor-α, Smad7 and Smad4 were only increased during the early phase (first 4 weeks) of recovery following irradiation. In the RILD rat model, the molecular responses indicated that the TGF-β1/Smads and NF-κB65 signaling pathways are involved in the mechanism of RILD recovery. PMID:25483171

  2. Protection of radiation detectors from fast neutron damage

    SciTech Connect

    Kronenberg, S.

    1986-09-02

    A device is described for measuring radiation emitted from a nuclear explosion, the radiation having a comparatively fast moving gamma ray component and a comparatively slower neutron component. The device consists of: a solid state crystal radiation detector; a voltage source applied to bias the detector; and means responsive to the gamma ray component for removing the bias voltage for a predetermined time period whereby the crystal radiation detector is rendered less sensitive to the passage of the neutron radiation component.

  3. Radiation-induced genomic instability and its implications for radiation carcinogenesis

    NASA Technical Reports Server (NTRS)

    Huang, Lei; Snyder, Andrew R.; Morgan, William F.

    2003-01-01

    Radiation-induced genomic instability is characterized by an increased rate of genetic alterations including cytogenetic rearrangements, mutations, gene amplifications, transformation and cell death in the progeny of irradiated cells multiple generations after the initial insult. Chromosomal rearrangements are the best-characterized end point of radiation-induced genomic instability, and many of the rearrangements described are similar to those found in human cancers. Chromosome breakage syndromes are defined by chromosome instability, and individuals with these diseases are cancer prone. Consequently, chromosomal instability as a phenotype may underlie some fraction of those changes leading to cancer. Here we attempt to relate current knowledge regarding radiation-induced chromosome instability with the emerging molecular information on the chromosome breakage syndromes. The goal is to understand how genetic and epigenetic factors might influence the onset of chromosome instability and the role of chromosomal instability in carcinogenesis.

  4. The contribution of co-transcriptional RNA:DNA hybrid structures to DNA damage and genome instability

    PubMed Central

    Hamperl, Stephan; Cimprich, Karlene A.

    2014-01-01

    Accurate DNA replication and DNA repair are crucial for the maintenance of genome stability, and it is generally accepted that failure of these processes is a major source of DNA damage in cells. Intriguingly, recent evidence suggests that DNA damage is more likely to occur at genomic loci with high transcriptional activity. Furthermore, loss of certain RNA processing factors in eukaryotic cells is associated with increased formation of co-transcriptional RNA:DNA hybrid structures known as R-loops, resulting in double-strand breaks (DSBs) and DNA damage. However, the molecular mechanisms by which R-loop structures ultimately lead to DNA breaks and genome instability is not well understood. In this review, we summarize the current knowledge about the formation, recognition and processing of RNA:DNA hybrids, and discuss possible mechanisms by which these structures contribute to DNA damage and genome instability in the cell. PMID:24746923

  5. Infrared A radiation promotes survival of human melanocytes carrying ultraviolet radiation-induced DNA damage.

    PubMed

    Kimeswenger, Susanne; Schwarz, Agatha; Födinger, Dagmar; Müller, Susanne; Pehamberger, Hubert; Schwarz, Thomas; Jantschitsch, Christian

    2016-06-01

    The link between solar radiation and melanoma is still elusive. Although infrared radiation (IR) accounts for over 50% of terrestrial solar energy, its influence on human skin is not well explored. There is increasing evidence that IR influences the expression patterns of several molecules independently of heat. A previous in vivo study revealed that pretreatment with IR might promote the development of UVR-induced non-epithelial skin cancer and possibly of melanoma in mice. To expand on this, the aim of the present study was to evaluate the impact of IR on UVR-induced apoptosis and DNA repair in normal human epidermal melanocytes. The balance between these two effects is a key factor of malignant transformation. Human melanocytes were exposed to physiologic doses of IR and UVR. Compared to cells irradiated with UVR only, simultaneous exposure to IR significantly reduced the apoptotic rate. However, IR did not influence the repair of UVR-induced DNA damage. IR partly reversed the pro-apoptotic effects of UVR via modification of the expression and activity of proteins mainly of the extrinsic apoptotic pathway. In conclusion, IR enhances the survival of melanocytes carrying UVR-induced DNA damage and thereby might contribute to melanomagenesis. PMID:26844814

  6. Radiation-Induced Liver Damage: Correlation of Histopathology with Hepatobiliary Magnetic Resonance Imaging, a Feasibility Study

    SciTech Connect

    Seidensticker, Max; Burak, Miroslaw; Kalinski, Thomas; Garlipp, Benjamin; Koelble, Konrad; Wust, Peter; Antweiler, Kai; Seidensticker, Ricarda; Mohnike, Konrad; Pech, Maciej; Ricke, Jens

    2015-02-15

    PurposeRadiotherapy of liver malignancies shows promising results (radioembolization, stereotactic irradiation, interstitial brachytherapy). Regardless of the route of application, a certain amount of nontumorous liver parenchyma will be collaterally damaged by radiation. The functional reserve may be significantly reduced with an impact on further treatment planning. Monitoring of radiation-induced liver damage by imaging is neither established nor validated. We performed an analysis to correlate the histopathological presence of radiation-induced liver damage with functional magnetic resonance imaging (MRI) utilizing hepatobiliary contrast media (Gd-BOPTA).MethodsPatients undergoing local high-dose-rate brachytherapy for whom a follow-up hepatobiliary MRI within 120 days after radiotherapy as well as an evaluable liver biopsy from radiation-exposed liver tissue within 7 days before MRI were retrospectively identified. Planning computed tomography (CT)/dosimetry was merged to the CT-documentation of the liver biopsy and to the MRI. Presence/absence of radiation-induced liver damage (histopathology) and Gd-BOPTA uptake (MRI) as well as the dose applied during brachytherapy at the site of tissue sampling was determined.ResultsFourteen biopsies from eight patients were evaluated. In all cases with histopathological evidence of radiation-induced liver damage (n = 11), no uptake of Gd-BOPTA was seen. In the remaining three, cases no radiation-induced liver damage but Gd-BOPTA uptake was seen. Presence of radiation-induced liver damage and absence of Gd-BOPTA uptake was correlated with a former high-dose exposition.ConclusionsAbsence of hepatobiliary MRI contrast media uptake in radiation-exposed liver parenchyma may indicate radiation-induced liver damage. Confirmatory studies are warranted.

  7. Radiation damage in protein serial femtosecond crystallography using an x-ray free-electron laser

    PubMed Central

    Lomb, Lukas; Barends, Thomas R. M.; Kassemeyer, Stephan; Aquila, Andrew; Epp, Sascha W.; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Shoeman, Robert L.; Andreasson, Jakob; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J.; Bostedt, Christoph; Bozek, John D.; Caleman, Carl; Coffee, Ryan; Coppola, Nicola; DePonte, Daniel P.; Doak, R. Bruce; Ekeberg, Tomas; Fleckenstein, Holger; Fromme, Petra; Gebhardt, Maike; Graafsma, Heinz; Gumprecht, Lars; Hampton, Christina Y.; Hartmann, Andreas; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M.; Hunter, Mark S.; Kabsch, Wolfgang; Kimmel, Nils; Kirian, Richard A.; Liang, Mengning; Maia, Filipe R. N. C.; Meinhart, Anton; Marchesini, Stefano; Martin, Andrew V.; Nass, Karol; Reich, Christian; Schulz, Joachim; Seibert, M. Marvin; Sierra, Raymond; Soltau, Heike; Spence, John C. H.; Steinbrener, Jan; Stellato, Francesco; Stern, Stephan; Timneanu, Nicusor; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; White, Thomas A.; Wunderer, Cornelia; Chapman, Henry N.; Ullrich, Joachim; Strüder, Lothar; Schlichting, Ilme

    2013-01-01

    X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects. PMID:24089594

  8. Radiation damage in protein crystals is reduced with a micron-sized X-ray beam

    PubMed Central

    Sanishvili, Ruslan; Yoder, Derek W.; Pothineni, Sudhir Babu; Rosenbaum, Gerd; Xu, Shenglan; Vogt, Stefan; Stepanov, Sergey; Makarov, Oleg A.; Corcoran, Stephen; Benn, Richard; Nagarajan, Venugopalan; Smith, Janet L.; Fischetti, Robert F.

    2011-01-01

    Radiation damage is a major limitation in crystallography of biological macromolecules, even for cryocooled samples, and is particularly acute in microdiffraction. For the X-ray energies most commonly used for protein crystallography at synchrotron sources, photoelectrons are the predominant source of radiation damage. If the beam size is small relative to the photoelectron path length, then the photoelectron may escape the beam footprint, resulting in less damage in the illuminated volume. Thus, it may be possible to exploit this phenomenon to reduce radiation-induced damage during data measurement for techniques such as diffraction, spectroscopy, and imaging that use X-rays to probe both crystalline and noncrystalline biological samples. In a systematic and direct experimental demonstration of reduced radiation damage in protein crystals with small beams, damage was measured as a function of micron-sized X-ray beams of decreasing dimensions. The damage rate normalized for dose was reduced by a factor of three from the largest (15.6 μm) to the smallest (0.84 μm) X-ray beam used. Radiation-induced damage to protein crystals was also mapped parallel and perpendicular to the polarization direction of an incident 1-μm X-ray beam. Damage was greatest at the beam center and decreased monotonically to zero at a distance of about 4 μm, establishing the range of photoelectrons. The observed damage is less anisotropic than photoelectron emission probability, consistent with photoelectron trajectory simulations. These experimental results provide the basis for data collection protocols to mitigate with micron-sized X-ray beams the effects of radiation damage. PMID:21444772

  9. Base excision repair of ionizing radiation-induced DNA damage in G1 and G2 cell cycle phases

    PubMed Central

    Chaudhry, M Ahmad

    2007-01-01

    Background Major genomic surveillance mechanisms regulated in response to DNA damage exist at the G1/S and G2/M checkpoints. It is presumed that these delays provide time for the repair of damaged DNA. Cells have developed multiple DNA repair pathways to protect themselves from different types of DNA damage. Oxidative DNA damage is processed by the base excision repair (BER) pathway. Little is known about the BER of ionizing radiation-induced DNA damage and putative heterogeneity of BER in the cell cycle context. We measured the activities of three BER enzymes throughout the cell cycle to investigate the cell cycle-specific repair of ionizing radiation-induced DNA damage. We further examined BER activities in G2 arrested human cells after exposure to ionizing radiation. Results Using an in vitro incision assay involving radiolabeled oligonucleotides with specific DNA lesions, we examined the activities of several BER enzymes in the whole cell extracts prepared from synchronized human HeLa cells irradiated in G1 and G2 phase of the cell cycle. The activities of human endonuclease III (hNTH1), a glycosylase/lyase that removes several damaged bases from DNA including dihydrouracil (DHU), 8-oxoguanine-DNA glycosylase (hOGG1) that recognizes 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxoG) lesion and apurinic/apyrimidinic endonuclease (hAPE1) that acts on abasic sites including synthetic analog furan were examined. Conclusion Overall the repair activities of hNTH1 and hAPE1 were higher in the G1 compared to G2 phase of the cell cycle. The percent cleavages of oligonucleotide substrate with furan were greater than substrate with DHU in both G1 and G2 phases. The irradiation of cells enhanced the cleavage of substrates with furan and DHU only in G1 phase. The activity of hOGG1 was much lower and did not vary within the cell cycle. These results demonstrate the cell cycle phase dependence on the BER of ionizing radiation-induced DNA damage. Interestingly no evidence of

  10. DNA Damage Response and Spindle Assembly Checkpoint Function throughout the Cell Cycle to Ensure Genomic Integrity

    PubMed Central

    Lawrence, Katherine S.; Chau, Thinh; Engebrecht, JoAnne

    2015-01-01

    Errors in replication or segregation lead to DNA damage, mutations, and aneuploidies. Consequently, cells monitor these events and delay progression through the cell cycle so repair precedes division. The DNA damage response (DDR), which monitors DNA integrity, and the spindle assembly checkpoint (SAC), which responds to defects in spindle attachment/tension during metaphase of mitosis and meiosis, are critical for preventing genome instability. Here we show that the DDR and SAC function together throughout the cell cycle to ensure genome integrity in C. elegans germ cells. Metaphase defects result in enrichment of SAC and DDR components to chromatin, and both SAC and DDR are required for metaphase delays. During persistent metaphase arrest following establishment of bi-oriented chromosomes, stability of the metaphase plate is compromised in the absence of DDR kinases ATR or CHK1 or SAC components, MAD1/MAD2, suggesting SAC functions in metaphase beyond its interactions with APC activator CDC20. In response to DNA damage, MAD2 and the histone variant CENPA become enriched at the nuclear periphery in a DDR-dependent manner. Further, depletion of either MAD1 or CENPA results in loss of peripherally associated damaged DNA. In contrast to a SAC-insensitive CDC20 mutant, germ cells deficient for SAC or CENPA cannot efficiently repair DNA damage, suggesting that SAC mediates DNA repair through CENPA interactions with the nuclear periphery. We also show that replication perturbations result in relocalization of MAD1/MAD2 in human cells, suggesting that the role of SAC in DNA repair is conserved. PMID:25898113

  11. Induction and persistence of radiation-induced DNA damage is more pronounced in young animals than in old animals

    PubMed Central

    Hudson, Darryl; Kovalchuk, Igor; Koturbash, Igor; Kolb, Bryan; Martin, Olga A.; Kovalchuk, Olga

    2011-01-01

    Younger individuals are more prone to develop cancer upon ionizing radiation (IR) exposure. Radiation-induced tumors are associated with inefficient repair of IR-induced DNA damage and genome instability. Phosphorylation of histone H2AX (γ-H2AX) is the initial event in repair of IR-induced DNA damage on the chromatin flanking the DNA strand breaks. This step is crucially important for the repair of DNA strand breaks and for the maintenance of genome stability. We studied the molecular underpinnings of the age-related IR effects using an animal model. By assaying for IR-induced γ-H2AX foci we analyzed the induction and repair of the DNA strand breaks in spleen, thymus, liver, lung, kidney, cerebellum, hippocampus, frontal cortex and olfactory bulb of 7, 14, 24, 30 and 45 days old male and female mice as a function of age. We demonstrate that tissues of younger animals are much more susceptible to IR-induced DNA damage. Younger animals exhibited higher levels of γ-H2AX formation which partially correlated with cellular proliferation and expression of DNA repair proteins. Induction and persistence of γ-H2AX foci was the highest in lymphoid organs (thymus and spleen) of 7 and 14 day old mice. The lowest focal induction was seen in lung and brain of young animals. The mechanisms of cell and tissue-specificity of in vivo IR responses need to be further dissected. This study provides a roadmap for the future analyses of DNA damage and repair induction in young individuals. PMID:21685513

  12. Archaeal Genome Guardians Give Insights into Eukaryotic DNA Replication and Damage Response Proteins

    PubMed Central

    Shin, David S.; Pratt, Ashley J.; Tainer, John A.

    2014-01-01

    As the third domain of life, archaea, like the eukarya and bacteria, must have robust DNA replication and repair complexes to ensure genome fidelity. Archaea moreover display a breadth of unique habitats and characteristics, and structural biologists increasingly appreciate these features. As archaea include extremophiles that can withstand diverse environmental stresses, they provide fundamental systems for understanding enzymes and pathways critical to genome integrity and stress responses. Such archaeal extremophiles provide critical data on the periodic table for life as well as on the biochemical, geochemical, and physical limitations to adaptive strategies allowing organisms to thrive under environmental stress relevant to determining the boundaries for life as we know it. Specifically, archaeal enzyme structures have informed the architecture and mechanisms of key DNA repair proteins and complexes. With added abilities to temperature-trap flexible complexes and reveal core domains of transient and dynamic complexes, these structures provide insights into mechanisms of maintaining genome integrity despite extreme environmental stress. The DNA damage response protein structures noted in this review therefore inform the basis for genome integrity in the face of environmental stress, with implications for all domains of life as well as for biomanufacturing, astrobiology, and medicine. PMID:24701133

  13. DNA damage checkpoint kinase ATM regulates germination and maintains genome stability in seeds.

    PubMed

    Waterworth, Wanda M; Footitt, Steven; Bray, Clifford M; Finch-Savage, William E; West, Christopher E

    2016-08-23

    Genome integrity is crucial for cellular survival and the faithful transmission of genetic information. The eukaryotic cellular response to DNA damage is orchestrated by the DNA damage checkpoint kinases ATAXIA TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR). Here we identify important physiological roles for these sensor kinases in control of seed germination. We demonstrate that double-strand breaks (DSBs) are rate-limiting for germination. We identify that desiccation tolerant seeds exhibit a striking transcriptional DSB damage response during germination, indicative of high levels of genotoxic stress, which is induced following maturation drying and quiescence. Mutant atr and atm seeds are highly resistant to aging, establishing ATM and ATR as determinants of seed viability. In response to aging, ATM delays germination, whereas atm mutant seeds germinate with extensive chromosomal abnormalities. This identifies ATM as a major factor that controls germination in aged seeds, integrating progression through germination with surveillance of genome integrity. Mechanistically, ATM functions through control of DNA replication in imbibing seeds. ATM signaling is mediated by transcriptional control of the cell cycle inhibitor SIAMESE-RELATED 5, an essential factor required for the aging-induced delay to germination. In the soil seed bank, seeds exhibit increased transcript levels of ATM and ATR, with changes in dormancy and germination potential modulated by environmental signals, including temperature and soil moisture. Collectively, our findings reveal physiological functions for these sensor kinases in linking genome integrity to germination, thereby influencing seed quality, crucial for plant survival in the natural environment and sustainable crop production. PMID:27503884

  14. DNA damage checkpoint kinase ATM regulates germination and maintains genome stability in seeds

    PubMed Central

    Waterworth, Wanda M.; Footitt, Steven; Bray, Clifford M.; Finch-Savage, William E.; West, Christopher E.

    2016-01-01

    Genome integrity is crucial for cellular survival and the faithful transmission of genetic information. The eukaryotic cellular response to DNA damage is orchestrated by the DNA damage checkpoint kinases ATAXIA TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR). Here we identify important physiological roles for these sensor kinases in control of seed germination. We demonstrate that double-strand breaks (DSBs) are rate-limiting for germination. We identify that desiccation tolerant seeds exhibit a striking transcriptional DSB damage response during germination, indicative of high levels of genotoxic stress, which is induced following maturation drying and quiescence. Mutant atr and atm seeds are highly resistant to aging, establishing ATM and ATR as determinants of seed viability. In response to aging, ATM delays germination, whereas atm mutant seeds germinate with extensive chromosomal abnormalities. This identifies ATM as a major factor that controls germination in aged seeds, integrating progression through germination with surveillance of genome integrity. Mechanistically, ATM functions through control of DNA replication in imbibing seeds. ATM signaling is mediated by transcriptional control of the cell cycle inhibitor SIAMESE-RELATED 5, an essential factor required for the aging-induced delay to germination. In the soil seed bank, seeds exhibit increased transcript levels of ATM and ATR, with changes in dormancy and germination potential modulated by environmental signals, including temperature and soil moisture. Collectively, our findings reveal physiological functions for these sensor kinases in linking genome integrity to germination, thereby influencing seed quality, crucial for plant survival in the natural environment and sustainable crop production. PMID:27503884

  15. The Radiation environment and damage in the CDF tracking volume

    SciTech Connect

    R. J. Tesarek et al.

    2003-12-16

    The authors present direct measurements of the spatial distribution of ionizing radiation and low energy neutrons (E{sub n} < 200 keV) inside the tracking volume of the collider detector at Fermilab (CDF). Using data from multiple exposures, the radiation field can be separated into components from beam losses and collisions and can be checked for consistency between the measurements. They compare the radiation measurements with an increase in the leakage currents of the CDF silicon detectors and find reasonable agreement.

  16. Radiation damage to tetramethlysilane and tetramethlygermanium ionization chambers

    NASA Astrophysics Data System (ADS)

    Hoshi, Y.; Higuchi, M.; Oyama, K.; Akaishi, H.; Yuta, H.; Abe, K.; Hasegawa, K.; Suekane, F.; Nagamine, T.; Kawamura, N.

    1994-08-01

    Two detector media suitable for a warm liquid, ionization chamber filled with tetramethylsilane(TMS) and tetramethylgermanium(TMG) were exposed to y radiation from a (sup 60)Co source up to dose 579Gray and 902Gray, respectively. The electron lifetimes and the free ion yields were measured as a function of accumulated radiation dose. A similar behavior of the electron lifetimes and the free ion yields with increasing radiation dose was observed between the TMS and TMG ionization chambers.

  17. Annealing radiation damaged silicon solar cells with a copper halide laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.

    1980-01-01

    The use of a multiply pulsed copper halide laser to significantly anneal out the damage to silicon solar cells caused by a simulated space radiation environment is investigated. Preliminary experiments demonstrate that the amount of damage can be decreased by 41% as measured by the maximum power generated.

  18. The Effects of Interfaces on Radiation Damage Production in Layered Metal Composites

    SciTech Connect

    Heinisch, Howard L.; Gao, Fei; Kurtz, Richard J.

    2003-12-07

    The objective of this research is to use molecular dynamics modeling to explore the effects of interfaces on cascade-producing radiation damage in nanolayered metal composites and to assess the resistance of these composites to damage by neutrons in fusion devices.

  19. Does iodinated contrast medium amplify DNA damage during exposure to radiation.

    PubMed

    Riley, Peter

    2015-01-01

    There is a recognized increased risk of cancer following exposure of humans to ionizing radiation; this is felt to be most likely due to damage to DNA strands during exposure. Damage to DNA strands can be demonstrated microscopically following exposure to X-rays, and new evidence is emerging that this effect may be compounded by administration of iodinated contrast agents. PMID:26234959

  20. Analysis of alcohol-induced DNA damage in Escherichia coli by visualizing single genomic DNA molecules.

    PubMed

    Kang, Yujin; Lee, Jinyong; Kim, Jisoo; Oh, Yeeun; Kim, Dogeun; Lee, Jungyun; Lim, Sangyong; Jo, Kyubong

    2016-07-21

    Consumption of alcohol injures DNA, and such damage is considered to be a primary cause for the development of cancer and many other diseases essentially due to reactive oxygen species generated from alcohol. To sensitively detect alcohol-induced DNA lesions in a biological system, we introduced a novel analytical platform for visualization of single genomic DNA molecules using E. coli. By fluorescently labelling the DNA lesions, our approach demonstrated, with the highest sensitivity, that we could count the number of DNA lesions induced by alcohol metabolism in a single bacterial cell. Moreover, our results showed a linear relationship between ethanol concentration and the number of DNA lesions: 0.88 lesions per 1% ethanol. Using this approach, we quantitatively analysed the DNA damage induced by exposure to alcoholic beverages such as beer (5% ethanol), rice wine (13%), soju (20%), and whisky (40%). PMID:27186604

  1. Complete genome sequence of Hymenobacter sp. strain PAMC26554, an ionizing radiation-resistant bacterium isolated from an Antarctic lichen.

    PubMed

    Oh, Tae-Jin; Han, So-Ra; Ahn, Do-Hwan; Park, Hyun; Kim, Augustine Yonghwi

    2016-06-10

    A Gram-negative, rod-shaped, red-pink in color, and UV radiation-resistant bacterium Hymenobacter sp. strain PAMC26554 was isolated from Usnea sp., an Antarctic lichen, and belongs to the class of Cytophagia and the phylum of Bacteroidetes. The complete genome of Hymenobacter sp. PAMC26554 consists of one chromosome (5,244,843bp) with two plasmids (199,990bp and 6421bp). The genomic sequence indicates that Hymenobacter sp. strain PAMC26554 possesses several genes involved in the nucleotide excision repair pathway that protects damaged DNA. This complete genome information will help us to understand its adaptation and novel survival strategy in the Antarctic extreme cold environment. PMID:27063139

  2. Past Exposure to Densely Ionizing Radiation Leaves a Unique Permanent Signature in the Genome

    PubMed Central

    Hande, M. Prakash; Azizova, Tamara V.; Geard, Charles R.; Burak, Ludmilla E.; Mitchell, Catherine R.; Khokhryakov, Valentin F.; Vasilenko, Evgeny K.; Brenner, David J.

    2003-01-01

    Speculation has long surrounded the question of whether past exposure to ionizing radiation leaves a unique permanent signature in the genome. Intrachromosomal rearrangements or deletions are produced much more efficiently by densely ionizing radiation than by chemical mutagens, x-rays, or endogenous aging processes. Until recently, such stable intrachromosomal aberrations have been very hard to detect, but a new chromosome band painting technique has made their detection practical. We report the detection and quantification of stable intrachromosomal aberrations in lymphocytes of healthy former nuclear-weapons workers who were exposed to plutonium many years ago. Even many years after occupational exposure, more than half the blood cells of the healthy plutonium workers contain large (>6 Mb) intrachromosomal rearrangements. The yield of these aberrations was highly correlated with plutonium dose to the bone marrow. The control groups contained very few such intrachromosomal aberrations. Quantification of this large-scale chromosomal damage in human populations exposed many years earlier will lead to new insights into the mechanisms and risks of cytogenetic damage. PMID:12679897

  3. Radiation Damage to the Nervous System: a delayed therapeutic hazard

    SciTech Connect

    Gilbert, H.A.; Kagan, A.R.

    1980-01-01

    This volume represents a good overview of an important issue - late effects of radiation on the nervous system, a topic of interest to everybody who deals with neurooncologic problems. The book is well edited and includes almost all relevant subjects ranging from diagnostic and dosimetric considerations to treatment of radiation brain necrosis.

  4. Cranial Radiation Therapy and Damage to Hippocampal Neurogenesis

    ERIC Educational Resources Information Center

    Monje, Michelle

    2008-01-01

    Cranial radiation therapy is associated with a progressive decline in cognitive function, prominently memory function. Impairment of hippocampal neurogenesis is thought to be an important mechanism underlying this cognitive decline. Recent work has elucidated the mechanisms of radiation-induced failure of neurogenesis. Potential therapeutic…

  5. Both Complexity and Location of DNA Damage Contribute to Cellular Senescence Induced by Ionizing Radiation

    PubMed Central

    Zhang, Xurui; Ye, Caiyong; Sun, Fang; Wei, Wenjun; Hu, Burong; Wang, Jufang

    2016-01-01

    Persistent DNA damage is considered as a main cause of cellular senescence induced by ionizing radiation. However, the molecular bases of the DNA damage and their contribution to cellular senescence are not completely clear. In this study, we found that both heavy ions and X-rays induced senescence in human uveal melanoma 92–1 cells. By measuring senescence associated-β-galactosidase and cell proliferation, we identified that heavy ions were more effective at inducing senescence than X-rays. We observed less efficient repair when DNA damage was induced by heavy ions compared with X-rays and most of the irreparable damage was complex of single strand breaks and double strand breaks, while DNA damage induced by X-rays was mostly repaired in 24 hours and the remained damage was preferentially associated with telomeric DNA. Our results suggest that DNA damage induced by heavy ion is often complex and difficult to repair, thus presents as persistent DNA damage and pushes the cell into senescence. In contrast, persistent DNA damage induced by X-rays is preferentially associated with telomeric DNA and the telomere-favored persistent DNA damage contributes to X-rays induced cellular senescence. These findings provide new insight into the understanding of high relative biological effectiveness of heavy ions relevant to cancer therapy and space radiation research. PMID:27187621

  6. Both Complexity and Location of DNA Damage Contribute to Cellular Senescence Induced by Ionizing Radiation.

    PubMed

    Zhang, Xurui; Ye, Caiyong; Sun, Fang; Wei, Wenjun; Hu, Burong; Wang, Jufang

    2016-01-01

    Persistent DNA damage is considered as a main cause of cellular senescence induced by ionizing radiation. However, the molecular bases of the DNA damage and their contribution to cellular senescence are not completely clear. In this study, we found that both heavy ions and X-rays induced senescence in human uveal melanoma 92-1 cells. By measuring senescence associated-β-galactosidase and cell proliferation, we identified that heavy ions were more effective at inducing senescence than X-rays. We observed less efficient repair when DNA damage was induced by heavy ions compared with X-rays and most of the irreparable damage was complex of single strand breaks and double strand breaks, while DNA damage induced by X-rays was mostly repaired in 24 hours and the remained damage was preferentially associated with telomeric DNA. Our results suggest that DNA damage induced by heavy ion is often complex and difficult to repair, thus presents as persistent DNA damage and pushes the cell into senescence. In contrast, persistent DNA damage induced by X-rays is preferentially associated with telomeric DNA and the telomere-favored persistent DNA damage contributes to X-rays induced cellular senescence. These findings provide new insight into the understanding of high relative biological effectiveness of heavy ions relevant to cancer therapy and space radiation research. PMID:27187621

  7. Iatrogenic Damage to the Periodontium Caused by Radiation and Radiotherapy

    PubMed Central

    Kassim, Najeeb; Sirajuddin, Syed; Biswas, Shriparna; Rafiuddin, Syed; Apine, Ashwini

    2015-01-01

    The radio-sensitivity of a tissue or organ is measured by its response to irradiation. Loss of moderate numbers of cells does not affect the function of most organs. However, with loss of large numbers of cells, all affected organisms display a clinical result. The severity of this change depends on the dosage and thus the extent of cell loss. Moderate doses to a localized area may lead to repairable damage. Comparable doses to a whole organism may result in death from damage to the most sensitive systems in the body. PMID:26312083

  8. Evidence of Dopant Type-Inversion and Other Radiation Damage Effects of the CDF Silicon Detectors

    SciTech Connect

    Martinez-Ballarin, Roberto

    2010-06-01

    The aim of this document is to study the effect of radiation damage on the silicon sensors. The reflection of the effect of radiation can be observed in two fundamental parameters of the detector: the bias current and the bias voltage. The leakage current directly affects the noise, while the bias voltage is required to collect the maximum signal deposited by the charged particle.

  9. DETECTION OF LOW DOSE RADIATION INDUCED DNA DAMAGE USING TEMPERATURE DIFFERENNTIAL FLUORESENCE ASSAY

    EPA Science Inventory

    A rapid and sensitive fluorescence assay for radiation-induced DNA damage is reported. Changes in temperature-induced strand separation in both calf thymus DNA and plasmid DNA (puc 19 plasmid from Escherichia coli) were measured after exposure to low doses of radiation. Exposures...

  10. DETECTION OF LOW DOSE RADIATION INDUCED DNA DAMAGE USING TEMPERATURE DIFFERENTIAL FLUORESCENCE ASSAY

    EPA Science Inventory

    A rapid and sensitive fluorescence assay for radiation-induced DNA damage is reported. Changes in temperature-induced strand separation in both calf thymus DNA and plasmid DNA (puc 19 plasmid from Escherichia coli) were measured after exposure to low doses of radiation. Exposur...

  11. [Molecular-genetic and epidemiologic examination of personnel subjected to occupational irradiation in Russian Federal Nuclear Center (Sarov). Report 1. Genome structural damage rate and radiosensitivity].

    PubMed

    Korzeneva, I B; Zaichkina, S I; Malinina, T V; Afanas'ev, K I; Dubrova, Iu E; Skorodumova, E N; Samsonova, V F; Volkova, I V; Shishova, R T; Shcherbakova, I L

    2008-01-01

    A comparative evaluation of the cytological and dosimetric examination of the cohort comprised by VNIEF personnel subjected chronically to gamma-neutron ionizing radiation, as well as non-irradiated cohort is given. The obtained data on the influence of the occupational and on X-ray irradiation, age and smoking on the rate of structural genome damage, as well as the activity of the human repair system activity are presented. The influence of the individual heterozygosis by 9 polymorphous loci: Hp, Tf, Gc; 6-PGD, EsD, ACP, PGM1, microsatellite lici SCF1PO and F13AO1 is shown. PMID:19004324

  12. Significance of the melanocortin 1 receptor in the DNA damage response of human melanocytes to ultraviolet radiation.

    PubMed

    Swope, Viki; Alexander, Christina; Starner, Renny; Schwemberger, Sandy; Babcock, George; Abdel-Malek, Zalfa A

    2014-07-01

    Activation of the melanocortin 1 receptor (MC1R) by α-melanocortin (α-MSH) stimulates eumelanin synthesis and enhances repair of ultraviolet radiation (UV)-induced DNA damage. We report on the DNA damage response (DDR) of human melanocytes to UV and its enhancement by α-MSH. α-MSH up-regulated the levels of XPC, the enzyme that recognizes DNA damage sites, enhanced the UV-induced phosphorylation of the DNA damage sensors ataxia telangiectasia and Rad3-related (ATR) and ataxia telangiectasia mutated (ATM) and their respect-ive substrates checkpoint kinases 1 and 2, and increased phosphorylated H2AX (γH2AX) formation. These effects required functional MC1R and were absent in melanocytes expressing loss of function (LOF) MC1R. The levels of wild-type p53-induced phosphatase 1 (Wip1), which dephosphorylates γH2AX, correlated inversely with γH2AX. We propose that α-MSH increases UV-induced γH2AX to facilitate formation of DNA repair complexes and repair of DNA photoproducts, and LOF of MC1R compromises the DDR and genomic stability of melanocytes. PMID:24730569

  13. The 2100MHz radiofrequency radiation of a 3G-mobile phone and the DNA oxidative damage in brain.

    PubMed

    Sahin, Duygu; Ozgur, Elcin; Guler, Goknur; Tomruk, Arın; Unlu, Ilhan; Sepici-Dinçel, Aylin; Seyhan, Nesrin

    2016-09-01

    We aimed to evaluate the effect of 2100MHz radiofrequency radiation emitted by a generator, simulating a 3G-mobile phone on the brain of rats during 10 and 40 days of exposure. The female rats were randomly divided into four groups. Group I; exposed to 3G modulated 2100MHz RFR signal for 6h/day, 5 consecutive days/wk for 2 weeks, group II; control 10 days, were kept in an inactive exposure set-up for 6h/day, 5 consecutive days/wk for 2 weeks, group III; exposed to 3G modulated 2100MHz RFR signal for 6h/day, 5 consecutive days/wk for 8 weeks and group IV; control 40 days, were kept in an inactive exposure set-up for 6h/day, 5 consecutive days/wk for 8 weeks. After the genomic DNA content of brain was extracted, oxidative DNA damage (8-hydroxy-2'deoxyguanosine, pg/mL) and malondialdehyde (MDA, nmoL/g tissue) levels were determined. Our main finding was the increased oxidative DNA damage to brain after 10 days of exposure with the decreased oxidative DNA damage following 40 days of exposure compared to their control groups. Besides decreased lipid peroxidation end product, MDA, was observed after 40 days of exposure. The measured decreased quantities of damage during the 40 days of exposure could be the means of adapted and increased DNA repair mechanisms. PMID:26775761

  14. Effect of radiation-induced damage on deuterium retention in tungsten, tungsten coatings and Eurofer

    NASA Astrophysics Data System (ADS)

    Ogorodnikova, O. V.; Sugiyama, K.

    2013-11-01

    An influence of radiation-induced damage on hydrogen isotope retention and transport in a bulk tungsten (W), dense nano-structured W coatings and Eurofer was investigated under well-defined laboratory conditions. Radiation-induced defects in W materials and Eurofer were created by irradiation with 20 MeV W ions. Following the damage production, samples were exposed to low-energy deuterium plasma. The deuterium (D) retention in each sample was subsequently measured by nuclear reaction analysis (NRA) for the depth profiling up to 6 μm. It was shown that the D retention at radiation-induced damage is almost equivalent for different W grades after irradiation at high enough fluence. The kinetic of D migration and trapping in damaged area as well as recovery of radiation-induced damage were investigated by loading at different temperatures. It was shown that deuterium retention in tungsten in fusion environment will be dominated by radiation-induced effect in a wide range of investigated temperatures, namely, from room temperature to 1100 K. Whereas displacement damage produced in Eurofer has less pronounced effect on the deuterium accumulation.

  15. Periodic annealing of radiation damage in GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Loo, R. Y.; Knechtli, R. C.; Kamath, G. S.

    1980-01-01

    Continuous annealing of GaAs solar cells is compared with periodic annealing to determine their relative effectiveness in minimizing proton radiation damage. It is concluded that continuous annealing of the cells in space at 150 C can effectively reduce the proton radiation damage to the GaAs solar cells. Periodic annealing is most effective if it can be initiated at relatively low fluences (approximating continuous annealing), especially if low temperatures of less than 200 C are to be used. If annealing is started only after the fluence of the damaging protons has accumulated to a high value 10 to the 11th power sq/pcm), effective annealing is still possible at relatively high temperatures. Finally, since electron radiation damage anneals even more easily than proton radiation damage, substantial improvements in GaAs solar cell life can be achieved by incorporating the proper annealing capabilities in solar panels for practical space missions where both electron and proton radiation damage have to be minimized.

  16. Prevent Eye Damage: Protect Yourself from UV Radiation

    MedlinePlus

    ... exposure to UV radiation from daily activities, including reflections off of snow, pavement, and other surfaces, can ... by a day at the beach without sunglasses; reflections off of snow, water, or concrete; or exposure ...

  17. Proton irradiation of stem cells: Radiation damage and chemical radioprotection

    NASA Technical Reports Server (NTRS)

    Riley, R. C.; Montour, J. L.; Gurney, C. W.

    1972-01-01

    Effects of high energy protons on erythropoietic stem cells and radioprotection by chemicals were investigated in NASA Space Radiation Effects Laboratory. The effects of a parallel beam of 600 MeV protons. The fluence, when converted to dose, were referenced to the synchrocyclotron beam monitors which were then used to administer radiation exposures. Mice were given graded doses to 300 rads to determine dose-response curve. Other mice received saline, AET, or 5-hydroxytryptamine 10 to 15 minutes before exposure.

  18. Dark progression reveals slow timescales for radiation damage between T = 180 and 240 K

    PubMed Central

    Warkentin, Matthew; Badeau, Ryan; Hopkins, Jesse; Thorne, Robert E.

    2011-01-01

    Can radiation damage to protein crystals be ‘outrun’ by collecting a structural data set before damage is manifested? Recent experiments using ultra-intense pulses from a free-electron laser show that the answer is yes. Here, evidence is presented that significant reductions in global damage at temperatures above 200 K may be possible using conventional X-ray sources and current or soon-to-be available detectors. Specifically, ‘dark progression’ (an increase in damage with time after the X-rays have been turned off) was observed at temperatures between 180 and 240 K and on timescales from 200 to 1200 s. This allowed estimation of the temperature-dependent timescale for damage. The rate of dark progression is consistent with an Arrhenius law with an activation energy of 14 kJ mol−1. This is comparable to the activation energy for the solvent-coupled diffusive damage processes responsible for the rapid increase in radiation sensitivity as crystals are warmed above the glass transition near 200 K. Analysis suggests that at T = 300 K data-collection times of the order of 1 s (and longer at lower temperatures) may allow significant reductions in global radiation damage, facilitating structure solution on crystals with liquid solvent. No dark progression was observed below T = 180 K, indicating that no important damage process is slowed through this timescale window in this temperature range. PMID:21904032

  19. Ionizing radiation, antioxidant response and oxidative damage: A meta-analysis.

    PubMed

    Einor, D; Bonisoli-Alquati, A; Costantini, D; Mousseau, T A; Møller, A P

    2016-04-01

    One mechanism proposed as a link between exposure to ionizing radiation and detrimental effects on organisms is oxidative damage. To test this hypothesis, we surveyed the scientific literature on the effects of chronic low-dose ionizing radiation (LDIR) on antioxidant responses and oxidative damage. We found 40 publications and 212 effect sizes for antioxidant responses and 288 effect sizes for effects of oxidative damage. We performed a meta-analysis of signed and unsigned effect sizes. We found large unsigned effects for both categories (0.918 for oxidative damage; 0.973 for antioxidant response). Mean signed effect size weighted by sample size was 0.276 for oxidative damage and -0.350 for antioxidant defenses, with significant heterogeneity among effects for both categories, implying that ionizing radiation caused small to intermediate increases in oxidative damage and small to intermediate decreases in antioxidant defenses. Our estimates are robust, as shown by very high fail-safe numbers. Species, biological matrix (tissue, blood, sperm) and age predicted the magnitude of effects for oxidative damage as well as antioxidant response. Meta-regression models showed that effect sizes for oxidative damage varied among species and age classes, while effect sizes for antioxidant responses varied among species and biological matrices. Our results are consistent with the description of mechanisms underlying pathological effects of chronic exposure to LDIR. Our results also highlight the importance of resistance to oxidative stress as one possible mechanism associated with variation in species responses to LDIR-contaminated areas. PMID:26851726

  20. Phytochemicals for prevention of solar ultraviolet radiation-induced damages.

    PubMed

    Adhami, Vaqar M; Syed, Deeba N; Khan, Naghma; Afaq, Farrukh

    2008-01-01

    While solar light is indispensable for sustenance of life, excessive exposure can cause several skin-related disorders. The UV part of solar radiation, in particular, is linked to disorders ranging from mild inflammatory effects of the skin to as serious as causing several different types of cancers. Changes in lifestyle together with depletion in the atmospheric ozone layer during the last few decades have led to an increase in the incidence of skin cancer. Skin cancers consisting of basal and squamous cell carcinomas are especially linked to the UVB part of solar radiation. Reducing excessive exposure to solar radiation is desirable; however, as this approach is unavoidable, it is suggested that other novel strategies be developed to reduce the effects of solar radiation to skin. One approach to reduce the harmful effects of solar radiation is through the use of phytochemicals, an approach that is popularly known as "Photochemoprotection." In recent years many phytochemicals with potential antioxidant properties have been identified and found to be photoprotective in nature. We describe here some of the most popular phytochemicals being studied that have the potential to reduce the harmful effects associated with solar UV radiation. PMID:18266816

  1. Comparative study of radiation damage accumulation in Cu and Fe

    NASA Astrophysics Data System (ADS)

    Caturla, M. J.; Soneda, N.; Alonso, E.; Wirth, B. D.; Díaz de la Rubia, T.; Perlado, J. M.

    2000-01-01

    Bcc and fcc metals exhibit significant differences in behavior when exposed to neutron or heavy ion irradiation. Transmission electron microscopy (TEM) observations reveal that damage in the form of stacking fault tetrahedra (SFT) is visible in copper irradiated to very low doses, but that no damage is visible in iron irradiated to the same total dose. In order to understand and quantify this difference in behavior, we have simulated damage production and accumulation in fcc Cu and bcc Fe. We use 20 keV primary knock-on atoms (PKAs) at a homologous temperature of 0.25 of the melting point. The primary damage state was calculated using molecular dynamics (MD) with empirical, embedded-atom interatomic potentials. Damage accumulation was modeled using a kinetic Monte Carlo (kMC) algorithm to follow the evolution of all defects produced in the cascades. The diffusivities and binding energies of defects are input data for this simulation and were either extracted from experiments, the literature, or calculated using MD. MD simulations reveal that vacancy clusters are produced within the cascade core in the case of copper. In iron, most of the vacancies do not cluster during cooling of the cascade core and are available for diffusion. In addition, self-interstitial atom (SIA) clusters are produced in copper cascades but those observed in iron are smaller in number and size. The combined MD/kMC simulations reveal that the visible cluster densities obtained as a function of dose are at least one order of magnitude lower in Fe than in Cu. We compare the results with experimental measurements of cluster density and find excellent agreement between the simulations and experiments when small interstitial clusters are considered to be mobile as suggested by recent MD simulations.

  2. The radiation damage of crystalline silicon PN diode in tritium beta-voltaic battery.

    PubMed

    Lei, Yisong; Yang, Yuqing; Liu, Yebing; Li, Hao; Wang, Guanquan; Hu, Rui; Xiong, Xiaoling; Luo, Shunzhong

    2014-08-01

    A tritium beta-voltaic battery using a crystalline silicon convertor composed of (100)Si/SiO2/Si3N4 film degrades remarkably with radiation from a high intensity titanium tritide film. Simulation and experiments were carried out to investigate the main factor causing the degradation. The radiation damages mainly comes from the x-ray emitted from the titanium tritide film and beta particle can relieve the damages. The x-ray radiation induced positive charges in the SiO2 film destroying the output property of the PN diode with the induction of an electric field. PMID:24751350

  3. A thermochemical model of radiation damage and annealing applied to GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Conway, E. J.; Walker, G. H.; Heinbockel, J. H.

    1981-01-01

    Calculations of the equilibrium conditions for continuous radiation damage and thermal annealing are reported. The calculations are based on a thermochemical model developed to analyze the incorporation of point imperfections in GaAs, and modified by introducing the radiation to produce native lattice defects rather than high-temperature and arsenic atmospheric pressure. The concentration of a set of defects, including vacancies, divacancies, and impurity vacancy complexes, are calculated as a function of temperature. Minority carrier lifetimes, short circuit current, and efficiency are deduced for a range of equilibrium temperatures. The results indicate that GaAs solar cells could have a mission life which is not greatly limited by radiation damage.

  4. Proton radiation damage in high-resistivity n-type silicon CCDs

    SciTech Connect

    Bebek, C.J.; Groom, D.E.; Holland, S.E.; Karcher, A.; Kolbe, W.F.; Lee, J.; Levi, M.E.; Palaio, N.P.; Turko, B.T.; Uslenghi, M.C.; Wagner, M.T.; Wang, G.

    2001-12-20

    A new type of p-channel CCD constructed on high-resistivity n-type silicon was exposed to 12 MeV protons at doses up to 1x1011 protons/cm2. The charge transfer efficiency was measured as a function of radiation dose and temperature. We previously reported that these CCDs are significantly more tolerant to radiation damage than conventional n-channel devices. In the work reported here, we used pocket pumping techniques and charge transfer efficiency measurements to determine the identity and concentrations of radiation induced traps present in the damaged devices.

  5. DNA Damage by Ionizing Radiation: Tandem Double Lesions by Charged Particles

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Chaban, Galina M.; Wang, Dunyou; Dateo, Christopher E.

    2005-01-01

    Oxidative damages by ionizing radiation are the source of radiation-induced carcinogenesis, damage to the central nervous system, lowering of the immune response, as well as other radiation-induced damages to human health. Monte Carlo track simulations and kinetic modeling of radiation damages to the DNA employ available molecular and cellular data to simulate the biological effect of high and low LET radiation io the DNA. While the simulations predict single and double strand breaks and base damages, so far all complex lesions are the result of stochastic coincidence from independent processes. Tandem double lesions have not yet been taken into account. Unlike the standard double lesions that are produced by two separate attacks by charged particles or radicals, tandem double lesions are produced by one single attack. The standard double lesions dominate at the high dosage regime. On the other hand, tandem double lesions do not depend on stochastic coincidences and become important at the low dosage regime of particular interest to NASA. Tandem double lesions by hydroxyl radical attack of guanine in isolated DNA have been reported at a dosage of radiation as low as 10 Gy. The formation of two tandem base lesions was found to be linear with the applied doses, a characteristic of tandem lesions. However, tandem double lesions from attack by a charged particle have not been reported.

  6. XPD localizes in mitochondria and protects the mitochondrial genome from oxidative DNA damage

    PubMed Central

    Liu, Jing; Fang, Hongbo; Chi, Zhenfen; Wu, Zan; Wei, Di; Mo, Dongliang; Niu, Kaifeng; Balajee, Adayabalam S.; Hei, Tom K.; Nie, Linghu; Zhao, Yongliang

    2015-01-01

    Xeroderma pigmentosum group D (XPD/ERCC2) encodes an ATP-dependent helicase that plays essential roles in both transcription and nucleotide excision repair of nuclear DNA, however, whether or not XPD exerts similar functions in mitochondria remains elusive. In this study, we provide the first evidence that XPD is localized in the inner membrane of mitochondria, and cells under oxidative stress showed an enhanced recruitment of XPD into mitochondrial compartment. Furthermore, mitochondrial reactive oxygen species production and levels of oxidative stress-induced mitochondrial DNA (mtDNA) common deletion were significantly elevated, whereas capacity for oxidative damage repair of mtDNA was markedly reduced in both XPD-suppressed human osteosarcoma (U2OS) cells and XPD-deficient human fibroblasts. Immunoprecipitation-mass spectrometry analysis was used to identify interacting factor(s) with XPD and TUFM, a mitochondrial Tu translation elongation factor was detected to be physically interacted with XPD. Similar to the findings in XPD-deficient cells, mitochondrial common deletion and oxidative damage repair capacity in U2OS cells were found to be significantly altered after TUFM knock-down. Our findings clearly demonstrate that XPD plays crucial role(s) in protecting mitochondrial genome stability by facilitating an efficient repair of oxidative DNA damage in mitochondria. PMID:25969448

  7. Evaluation of genome damage in subjects occupationally exposed to possible carcinogens.

    PubMed

    Zeljezic, Davor; Mladinic, Marin; Kopjar, Nevenka; Radulovic, Azra Hursidic

    2016-09-01

    In occupational exposures, populations are simultaneously exposed to a mixture of chemicals. We aimed to evaluate DNA damage due to possible carcinogen exposure (phenylhydrazine, ethylene oxide, dichloromethane, and 1,2-dichloroethane) in lymphocytes of pharmaceutical industry workers from the same production line. Population comprised 16 subjects (9 females and 7 males) who were exposed to multiple chemicals for 8 months. Genome damage was assessed using alkaline comet assay, micronucleus assay, and comet assay coupled with fluorescent in situ hybridization (comet-FISH). After 8 months of exposure, the issue of irregular use of all available personal protective equipment (PPE) came into light. To decrease the risk of exposure, strict use of PPE was enforced. After 8 months of strict PPE use, micronuclei frequency and comet assay parameters in lymphocytes of pharmaceutical workers significantly decreased compared with prior period of irregular PPE use. Comet-FISH results indicated a significant shift in distribution of signals for the TP 53 gene toward a more frequent occurrence in the comet tail. Prolonged exposure to possible carcinogens may hinder DNA repair mechanisms and affect structural integrity of TP 53 Two indicators of loss of TP 53 gene integrity have risen, namely, TP 53 fragmentation rate in lymphocytes with persistently elevated primary damage and incidence of TP 53 deletions in undamaged lymphocytes. PMID:25653038

  8. Experimental studies of radiation damage of silicon detectors. Internal report

    SciTech Connect

    Angelescu, T.; Ghete, V.M.; Ghiordanescu, N.; Lazanu, I.; Mihul, A.; Golutvin, I.; Lazanu, S.; Savin, I.; Vasilescu, A.; Biggeri, U.; Borchi, E.; Bruzzi, M. |; Li, Z.; Kraner, H.W.

    1994-02-01

    New particle physics experiments are correlated with high luminosity and/or high energy. The new generation of colliding beam machines which will be constructed will make an extrapolation of a factor of 100 in the center of mass energy and of 1000 in luminosity beyond present accelerators. The scientific community hopes that very exciting physics results could be achieved this way, from the solution to the problem of electroweak symmetry breaking to the possible discovery of new, unpredicted phenomena. The particles which compose the radiation field are: electrons, pions, neutrons, protons and photons. It has become evident that the problem of the radiation resistance of detectors in this severe environment is a crucial one. This situation is complicated more by the fact that detectors must work all the run time of the machine, and better all the time of the experiment, without replacement (part or whole). So, studies related to the investigation of the radiation hardness of all detector parts, are developing. The studies are in part material and device characterization after irradiation, and in part technological developments, made in order to find harder, cheaper technologies, for larger surfaces. Semiconductor detectors have proven to be a good choice for vertex and calorimeter. Both fixed target machines and colliders had utilized in the past silicon junction detectors as the whole or part of the detection system. Precision beam hodoscopes and sophisticated trigger devices with silicon are equally used. The associated electronics in located near the detectors, and is subjected to the same radiation fields. Studies of material and device radiation hardness are developing in parallel. Here the authors present results on the radiation hardness of silicon, both as a bulk material and as detectors, to neutron irradiation at high fluences.

  9. Radiation damage in proton irradiated indium phosphide solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Yamaguchi, Masafumi

    1986-01-01

    Indium phosphide solar cells exposed to 10 MeV proton irradiations were found to have significantly greater radiation resistance than either GaAs or Si. Performance predictions were obtained for two proton dominated orbits and one in which both protons and electrons were significant cell degradation factors. Array specific power was calculated using lightweight blanket technology, a SEP array structure, and projected cell efficiencies. Results indicate that arrays using fully developed InP cells should out-perform those using GaAs or Si in orbits where radiation is a significant cell degradation factor.

  10. Radiation damage in MOS integrated circuits, Part 1

    NASA Technical Reports Server (NTRS)

    Danchenko, V.

    1971-01-01

    Complementary and p-channel MOS integrated circuits made by four commercial manufacturers were investigated for sensitivity to radiation environment. The circuits were irradiated with 1.5 MeV electrons. The results are given for electrons and for the Co-60 gamma radiation equivalent. The data are presented in terms of shifts in the threshold potentials and changes in transconductances and leakages. Gate biases of -10V, +10V and zero volts were applied to individual MOS units during irradiation. It was found that, in most of circuits of complementary MOS technologies, noticable changes due to radiation appear first as increased leakage in n-channel MOSFETs somewhat before a total integrated dose 10 to the 12th power electrons/sg cm is reached. The inability of p-channel MOSFETs to turn on sets in at about 10 to the 13th power electrons/sq cm. Of the circuits tested, an RCA A-series circuit was the most radiation resistant sample.

  11. Thermal and radiation damage to SL/1 EREP films

    NASA Technical Reports Server (NTRS)

    Perry, L.

    1973-01-01

    Tests were conducted to determine the present sensitometric characteristics of the SL/1 EREP films stored in Skylab. These films underwent the high temperature environment at the beginning of the mission and have since been stored outside the film vault. As a result, the films will have received a radiation dose estimated at approximately 12 rads by the end of SL/3.

  12. Feasibility of OCT to detect radiation-induced esophageal damage in small animal models (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Jelvehgaran, Pouya; Alderliesten, Tanja; Salguero, Javier; Borst, Gerben; Song, Ji-Ying; van Leeuwen, Ton G.; de Boer, Johannes F.; de Bruin, Daniel M.; van Herk, Marcel B.

    2016-03-01

    Lung cancer survival is poor and radiotherapy patients often suffer serious treatment side effects. The esophagus is particularly sensitive leading to reduced food intake or even fistula formation. Only few direct techniques exist to measure radiation-induced esophageal damage, for which knowledge is needed to improve the balance between risk of tumor recurrence and complications. Optical coherence tomography (OCT) is a minimally-invasive imaging technique that obtains cross-sectional, high-resolution (1-10µm) images and is capable of scanning the esophageal wall up to 2-3mm depth. In this study we investigated the feasibility of OCT to detect esophageal radiation damage in mice. In total 30 mice were included in 4 study groups (1 main and 3 control groups). Mice underwent cone-beam CT imaging for initial setup assessment and dose planning followed by single-fraction dose delivery of 4, 10, 16, and 20Gy on 5mm spots, spaced 10mm apart. Mice were repeatedly imaged using OCT: pre-irradiation and up to 3 months post-irradiation. The control groups received either OCT only, irradiation only, or were sham-operated. We used histopathology as gold standard for radiation-induced damage diagnosis. The study showed edema in both the main and OCT-only groups. Furthermore, radiation-induced damage was primarily found in the highest dose region (distal esophagus). Based on the histopathology reports we were able to identify the radiation-induced damage in the OCT images as a change in tissue scattering related to the type of induced damage. This finding indicates the feasibility and thereby the potentially promising role of OCT in radiation-induced esophageal damage assessment.

  13. Analyses of the Secondary Particle Radiation and the DNA Damage it Causes to Human Keratinocytes

    SciTech Connect

    Lebel E. A.; Tafrov S.; Rusek, A.; Sivertz, M. B.; Yip, K.; Thompson, K. H.

    2011-11-01

    High-energy protons, and high mass and energy ions, along with the secondary particles they produce, are the main contributors to the radiation hazard during space explorations. Skin, particularly the epidermis, consisting mainly of keratinocytes with potential for proliferation and malignant transformation, absorbs the majority of the radiation dose. Therefore, we used normal human keratinocytes to investigate and quantify the DNA damage caused by secondary radiation. Its manifestation depends on the presence of retinol in the serum-free media, and is regulated by phosphatidylinositol 3-kinases. We simulated the generation of secondary radiation after the impact of protons and iron ions on an aluminum shield. We also measured the intensity and the type of the resulting secondary particles at two sample locations; our findings agreed well with our predictions. We showed that secondary particles inflict DNA damage to different extents, depending on the type of primary radiation. Low-energy protons produce fewer secondary particles and cause less DNA damage than do high-energy protons. However, both generate fewer secondary particles and inflict less DNA damage than do high mass and energy ions. The majority of cells repaired the initial damage, as denoted by the presence of 53BPI foci, within the first 24 hours after exposure, but some cells maintained the 53BP1 foci longer.

  14. Analyses of the secondary particle radiation and the DNA damage it causes to human keratinocytes

    SciTech Connect

    Lebel E.; Rusek A.; Sivertz, M.; Yip, K.; Thompson, K.; Tafrov, S.

    2011-11-22

    High-energy protons, and high mass and energy ions, along with the secondary particles they produce, are the main contributors to the radiation hazard during space explorations. Skin, particularly the epidermis, consisting mainly of keratinocytes with potential for proliferation and malignant transformation, absorbs the majority of the radiation dose. Therefore, we used normal human keratinocytes to investigate and quantify the DNA damage caused by secondary radiation. Its manifestation depends on the presence of retinol in the serum-free media, and is regulated by phosphatidylinositol 3-kinases. We simulated the generation of secondary radiation after the impact of protons and iron ions on an aluminum shield. We also measured the intensity and the type of the resulting secondary particles at two sample locations; our findings agreed well with our predictions. We showed that secondary particles inflict DNA damage to different extents, depending on the type of primary radiation. Low-energy protons produce fewer secondary particles and cause less DNA damage than do high-energy protons. However, both generate fewer secondary particles and inflict less DNA damage than do high mass and energy ions. The majority of cells repaired the initial damage, as denoted by the presence of 53BPI foci, within the first 24 hours after exposure, but some cells maintained the 53BP1 foci longer.

  15. Damage proneness induced by genomic DNA demethylation in mammalian cells cultivated in vitro.

    PubMed

    Perticone, P; Gensabella, G; Cozzi, R

    1997-07-01

    Variations in the genomic DNA methylation level have been shown to be an epigenetic inheritable modification affecting, among other targets, the sister chromatid exchange (SCE) rate in mammalian cells in vitro. The inheritable increase in SCE rate in affected cell populations appears as a puzzling phenomenon in view of the well established relation between SCE and both mutagenesis and carcinogenesis. In the present work we demonstrate that, in a treated cell population, demethylation could be responsible for the inheritable induction of damage proneness affecting both damage induction and repair. Normal and ethionine or azacytidine treated Chinese hamster ovary cells, subclone K1 (CHO-K1), were challenged with UV light (UV) or mitomycin-C (MMC) at different times from the demethylating treatment. The SCE rate was measured with two main objects in view: (i) the induction of synergism or additivity in combined treatments, where mutagen (UV or MMC) pulse is supplied from 0 to 48 h after the end of the demethylating treatment; and (ii) the pattern of damage extinction, for the duration of up to six cell cycles after the end of the combined (demethylating agent + mutagen) treatment. Results indicate both a synergism in SCE induction by mutagens in demethylated cells even if supplied up to four cell cycles after the end of the demethylation treatment and a delay in recovery of induced damage, compared with normally methylated cells. These data are discussed in the light of the supposed mechanism of SCE increase and of the possible biological significance in terms of mutagenesis and carcinogenesis. PMID:9237771

  16. Radiation damage in diagnostic window materials for the TFTR

    SciTech Connect

    Primak, W.

    1981-07-01

    The general problem of evaluating diagnostic window materials for the TFTR at the tank wall location is described. Specific evaluations are presented for several materials: vitreous silica, crystal quartz, sapphire, zinc selenide, and several fluorides: lithium fluoride, magnesium fluoride, and calcium fluoride; and seal glasses are discussed. The effects of the neutrons will be minimal. The major problems arise from the high flux of ionizing radiation, mainly the soft x rays which are absorbed near the surface of the materials. Additionally, this large energy deposition causes a significant thermal pulse with attendant thermal stresses. It is thus desirable to protect the windows with cover slips where this is feasible or to reduce the incident radiation by mounting the windows on long pipes. A more detailed summary is given at the end of this report.

  17. An Assessment of Radiation Damage Models and Methods

    SciTech Connect

    Stoller, Roger E; Mansur, Louis K

    2005-05-01

    The current state of development of the primary models used for investigating and simulating irradiation effects in structural alloys of interest to the U.S. DOE's Generation-IV reactor program are discussed. The underlying theory that supports model development is also described where appropriate. First, the key processes that underlie radiation-induced changes in material properties are summarized, and the types of radiation effects that subsequently arise are described. Future development work needed in order for theory, modeling, and computational materials science to support and add value to the Gen IV reactor materials program are then outlined. The expected specific outcomes and overall benefits of the required effort are: the knowledge to extrapolate material behavior to conditions for which there are no experimental data; systematic understanding of mechanisms and processes to enable confident interpolation between point-by-point experimental observations; acceleration of the development, selection, and qualification of materials for reactor service; and prediction of material response to real-world operating load histories which often involve a complicated superposition of time, temperature, radiation dose rate, and mechanical loading conditions. Opportunities for international collaboration to accelerate progress in all of the required research areas are briefly discussed, particularly in the context of two well coordinated, broad-based research projects on modeling and simulation of radiation effects on materials that are currently funded in Europe. In addition to providing the opportunity for substantial leveraging of the DOE-funded activities in this area, these projects may serve as models for future development within the Gen-IV program. The larger of these two projects, which involves 12 European research laboratories and 16 universities, is called PERFECT and is funded by the European Union. A smaller effort focusing on developing predictive

  18. Potential for radiation damage to carbon steel storage tanks for high level radioactive waste

    SciTech Connect

    Caskey, G.R. Jr.; Sindelar, R.L.; Thomas, J.K.

    1993-07-30

    A low intensity radiation field is generated by the high level waste that is stored within carbon steel lined tanks at the Savannah River Site (SRS). The highest level of radiation damage to the tank walls from gamma and spontaneous neutron emissions is estimated to be less than 1.0E-6 displacements per atom (DPA) for a 100 year exposure to fresh, ``high heat`` SRS waste assuming continuous replenishment of the radionuclides. This damage level is below the limit for measurable radiation damage to the mechanical properties of carbon steel. Structural assessment of tanks for storage of high level waste may be based on nominal or code values of the mechanical properties of the steels from which the tanks were constructed.

  19. Review of radiation damage in GaN-based materials and devices

    SciTech Connect

    Pearton, Stephen J.; Deist, Richard; Ren, Fan; Liu, Lu; Polyakov, Alexander Y.; Kim, Jihyun

    2013-09-15

    A review of the effects of proton, neutron, γ-ray, and electron irradiation on GaN materials and devices is presented. Neutron irradiation tends to create disordered regions in the GaN, while the damage from the other forms of radiation is more typically point defects. In all cases, the damaged region contains carrier traps that reduce the mobility and conductivity of the GaN and at high enough doses, a significant degradation of device performance. GaN is several orders of magnitude more resistant to radiation damage than GaAs of similar doping concentrations. In terms of heterostructures, preliminary data suggests that the radiation hardness decreases in the order AlN/GaN > AlGaN/GaN > InAlN/GaN, consistent with the average bond strengths in the Al-based materials.

  20. Modification of high LET radiation-induced damage and its repair in yeast by hypoxia.

    PubMed

    Subrahmanyam, P; Rao, B S; Reddy, N M; Murthy, M S; Madhvanath, U

    1979-11-01

    The lethal response of a diploid yeast strain BZ34 to densely ionizing radiations from the reaction 10B(n, alpha)7 Li was studied. The values for relative biological effectiveness (r.b.e.) and oxygen enhancement ratio (o.e.r.) for this radiation compare favourably with the data obtained with charged particles on the same strain of yeast. Recovery from potentially lethal damage was also studied by post-irradiation holding under non-nutrient conditions. In order to understand the role of oxygen in the recovery process, the investigation covered the following treatment regimens: (a) aerobic irradiation and aerobic holding (A-A), (b) aerobic irradiation and hypoxic holding (A-H), (c) hypoxic irradiation and hypoxic holding (H-H) and (d) hypoxic irradiation and aerobic holding (H-A). It has been found that the presence of oxygen is essential for recovery from the damage induced by both gamma rays and high linear energy transfer (LET) radiations. The extent of recovery was larger for gamma-induced damage than for damage induced by high LET radiation (alpha + 7Li) for the A-A condition. In the H-H condition, while only a slight recovery was seen for gamma-induced damage, it was totally absent for high LET damage. For the modality A-H, it was found that there is not recovery from the sparsely ionising gamma radiation-induced damage. The implications of these results for the treatment of malignant tumours by radiotherapy are briefly discussed. PMID:397200

  1. Nonlinear Ultrasonic Techniques to Monitor Radiation Damage in RPV and Internal Components

    SciTech Connect

    Jacobs, Laurence; Kim, Jin-Yeon; Qu, Jisnmin; Ramuhalli, Pradeep; Wall, Joe

    2015-11-02

    The objective of this research is to demonstrate that nonlinear ultrasonics (NLU) can be used to directly and quantitatively measure the remaining life in radiation damaged reactor pressure vessel (RPV) and internal components. Specific damage types to be monitored are irradiation embrittlement and irradiation assisted stress corrosion cracking (IASCC). Our vision is to develop a technique that allows operators to assess damage by making a limited number of NLU measurements in strategically selected critical reactor components during regularly scheduled outages. This measured data can then be used to determine the current condition of these key components, from which remaining useful life can be predicted. Methods to unambiguously characterize radiation related damage in reactor internals and RPVs remain elusive. NLU technology has demonstrated great potential to be used as a material sensor – a sensor that can continuously monitor a material’s damage state. The physical effect being monitored by NLU is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave. The degree of nonlinearity is quantified with the acoustic nonlinearity parameter, β, which is an absolute, measurable material constant. Recent research has demonstrated that nonlinear ultrasound can be used to characterize material state and changes in microscale characteristics such as internal stress states, precipitate formation and dislocation densities. Radiation damage reduces the fracture toughness of RPV steels and internals, and can leave them susceptible to IASCC, which may in turn limit the lifetimes of some operating reactors. The ability to characterize radiation damage in the RPV and internals will enable nuclear operators to set operation time thresholds for vessels and prescribe and schedule replacement activities for core internals. Such a capability will allow a more clear definition of reactor safety margins. The research consists of three tasks: (1

  2. Radiation Damage Study in Natural Zircon Using Neutrons Irradiation

    SciTech Connect

    Lwin, Maung Tin Moe; Amin, Yusoff Mohd.; Kassim, Hasan Abu; Mohamed, Abdul Aziz; Karim, Julia Abdul

    2011-03-30

    Changes of atomic displacements in crystalline structure of natural zircon (ZrSiO{sub 4}) can be studied by using neutron irradiation on the surface of zircon and compared the data from XRD measurements before and after irradiation. The results of neutron irradiation on natural zircon using Pneumatic Transfer System (PTS) at PUSPATI TRIGA Research Reactor in the Malaysian Nuclear Agency are discussed in this work. The reactor produces maximum thermal power output of 1 MWatt and the neutron flux of up to 1x10{sup 13} ncm{sup -2}s{sup -1}. From serial decay processes of uranium and thorium radionuclides in zircon crystalline structure, the emission of alpha particles can produce damage in terms of atomic displacements in zircon. Hence, zircon has been extensively studied as a possible candidate for immobilization of fission products and actinides.

  3. Radiation Damage Study in Natural Zircon Using Neutrons Irradiation

    NASA Astrophysics Data System (ADS)

    Lwin, Maung Tin Moe; Amin, Yusoff Mohd.; Kassim, Hasan Abu; Mohamed, Abdul Aziz; Karim, Julia Abdul

    2011-03-01

    Changes of atomic displacements in crystalline structure of natural zircon (ZrSiO4) can be studied by using neutron irradiation on the surface of zircon and compared the data from XRD measurements before and after irradiation. The results of neutron irradiation on natural zircon using Pneumatic Transfer System (PTS) at PUSPATI TRIGA Research Reactor in the Malaysian Nuclear Agency are discussed in this work. The reactor produces maximum thermal power output of 1 MWatt and the neutron flux of up to 1×1013 ncm-2s-1. From serial decay processes of uranium and thorium radionuclides in zircon crystalline structure, the emission of alpha particles can produce damage in terms of atomic displacements in zircon. Hence, zircon has been extensively studied as a possible candidate for immobilization of fission products and actinides.

  4. Repair of ionizing radiation DNA base damage in ataxia-telangiectasia cells

    SciTech Connect

    Fornace, A.J. Jr.; Kinsella, T.J.; Dobson, P.P.; Mitchell, J.B.

    1986-04-01

    Micrococcus luteus endonuclease sensitive sites were measured by alkaline elution in normal human and ataxia-telangiectasia (AT) fibroblasts after ionizing radiation. Due to the sensitivity of this assay, repair of base damage after 3 to 6 kilorads has been measured after oxic or hypoxic radiation. With 5.5 kilorads of oxic radiation, more than 50% of the base damage was removed after 1.5 h of repair incubation in all cells, including exr+ and exr- AT cells, and approximately 75% was removed by 4 h. After 3 or 4.5 kilorads of hypoxic X-irradiation, repair was equivalent in normal and exr- AT cells. This study included three exr- AT strains which have been reported to be deficient in the removal of gamma-ray base damage at higher doses. Since these strains repaired ionizing radiation base damage normally at lower doses, which are more relevant to survival, it is concluded that the X-ray hypersensitivity of AT cells is probably not related to the repair of base damage.

  5. Autophagy confers DNA damage repair pathways to protect the hematopoietic system from nuclear radiation injury

    PubMed Central

    Lin, Weiwei; Yuan, Na; Wang, Zhen; Cao, Yan; Fang, Yixuan; Li, Xin; Xu, Fei; Song, Lin; Wang, Jian; Zhang, Han; Yan, Lili; Xu, Li; Zhang, Xiaoying; Zhang, Suping; Wang, Jianrong

    2015-01-01

    Autophagy is essentially a metabolic process, but its in vivo role in nuclear radioprotection remains unexplored. We observed that ex vivo autophagy activation reversed the proliferation inhibition, apoptosis, and DNA damage in irradiated hematopoietic cells. In vivo autophagy activation improved bone marrow cellularity following nuclear radiation exposure. In contrast, defective autophagy in the hematopoietic conditional mouse model worsened the hematopoietic injury, reactive oxygen species (ROS) accumulation and DNA damage caused by nuclear radiation exposure. Strikingly, in vivo defective autophagy caused an absence or reduction in regulatory proteins critical to both homologous recombination (HR) and non-homologous end joining (NHEJ) DNA damage repair pathways, as well as a failure to induce these proteins in response to nuclear radiation. In contrast, in vivo autophagy activation increased most of these proteins in hematopoietic cells. DNA damage assays confirmed the role of in vivo autophagy in the resolution of double-stranded DNA breaks in total bone marrow cells as well as bone marrow stem and progenitor cells upon whole body irradiation. Hence, autophagy protects the hematopoietic system against nuclear radiation injury by conferring and intensifying the HR and NHEJ DNA damage repair pathways and by removing ROS and inhibiting apoptosis. PMID:26197097

  6. Bystander effects in radiation-induced genomic instability

    NASA Technical Reports Server (NTRS)

    Morgan, William F.; Hartmann, Andreas; Limoli, Charles L.; Nagar, Shruti; Ponnaiya, Brian

    2002-01-01

    Exposure of GM10115 hamster-human hybrid cells to X-rays can result in the induction of chromosomal instability in the progeny of surviving cells. This instability manifests as the dynamic production of novel sub-populations of cells with unique cytogenetic rearrangements involving the "marker" human chromosome. We have used the comet assay to investigate whether there was an elevated level of endogenous DNA breaks in chromosomally unstable clones that could provide a source for the chromosomal rearrangements and thus account for the persistent instability observed. Our results indicate no significant difference in comet tail measurement between non-irradiated and radiation-induced chromosomally unstable clones. Using two-color fluorescence in situ hybridization we also investigated whether recombinational events involving the interstitial telomere repeat-like sequences in GM10115 cells were involved at frequencies higher than random processes would otherwise predict. Nine of 11 clones demonstrated a significantly higher than expected involvement of these interstitial telomere repeat-like sequences at the recombination junction between the human and hamster chromosomes. Since elevated levels of endogenous breaks were not detected in unstable clones we propose that epigenetic or bystander effects (BSEs) lead to the activation of recombinational pathways that perpetuate the unstable phenotype. Specifically, we expand upon the hypothesis that radiation induces conditions and/or factors that stimulate the production of reactive oxygen species (ROS). These reactive intermediates then contribute to a chronic pro-oxidant environment that cycles over multiple generations, promoting chromosomal recombination and other phenotypes associated with genomic instability.

  7. Radiation damage studies for the SDC electromagnetic calorimeter

    NASA Astrophysics Data System (ADS)

    Fazely, A. R.; Gunasingha, R.; Imlay, R. L.; Khosravi, E. S.; Lim, Jit-Ning; Lyndon, C.; McMills, G.; McNeil, R. R.; Metcalf, W. J.; Courtney, J. C.; Tashakkori, R.; Vegara, B. J.

    1993-01-01

    We report the results from a year long study aimed at radiation resistance and optical performance of scintillator tile with green wave shifter fiber readout. A careful investigation of several rad-hard plastic scintillators from Bicron and Kuraray, studies indicate that for a specific rad-hard Bicron scintillator, it is possible to build a tile/fiber EM calorimeter that can operate in the design luminosity of SSC. This calorimeter with excellent optical response would only have a light loss of about 5% after being exposed to 1 Mrad.

  8. Central Role of Ubiquitination in Genome Maintenance: DNA Replication and Damage Repair

    PubMed Central

    Ghosh, Soma; Saha, Tapas

    2012-01-01

    Faithful transmission of genetic information through generations ensures genomic stability and integrity. However, genetic alterations occur every now and then during the course of genome duplication. In order to repair these genetic defects and lesions, nature has devised several repair pathways which function promptly to prevent the cell from accumulating permanent mutations. These repair mechanisms seem to be significantly impacted by posttranslational modifications of proteins like phosphorylation and ubiquitination. Protein ubiquitination is emerging as a critical regulatory mechanism of DNA damage response. Non-proteolytic, proteasome-independent functions of ubiquitin involving monoubiquitination and polyubiquitination of DNA repair proteins contribute significantly to the signaling of DNA repair pathways. In this paper, we will particularly highlight the work on ubiquitin-mediated signaling in the repair processes involving the Fanconi anemia pathway, translesional synthesis, nucleotide excision repair, and repair of double-strand breaks. We will also discuss the role of ubiquitin ligases in regulating checkpoint mechanisms, the role of deubiquitinating enzymes, and the growing possibilities of therapeutic intervention in this ubiquitin-conjugation system.

  9. Radiation damage of heavy crystalline detector materials by 24 GeV protons

    NASA Astrophysics Data System (ADS)

    Barysevich, A.; Dormenev, V.; Fedorov, A.; Glaser, M.; Kobayashi, M.; Korjik, M.; Maas, F.; Mechinski, V.; Rusack, R.; Singovski, A.; Zoueyski, R.

    2013-02-01

    Samples of three heavy crystalline materials: PbWO4, Bi4Si3O12, and PbF2 were irradiated in a high-intensity 24 GeV proton beam at the CERN PS to fluencies of 3.8×1013 protons/cm2. The optical transmission radiation damage was measured and all crystals show a shift of the cutoff in the transmission spectrum that is not observed when the crystals are irradiated with γ radiation. This shift of the cutoff under proton irradiation seems to be a general property of the heavy crystalline materials. A mechanism for this proton-induced transmission damage is discussed.

  10. Prediction and measurement of radiation damage to CMOS devices on board spacecraft

    NASA Technical Reports Server (NTRS)

    Cliff, R. A.; Danchenko, V.; Stassinopoulos, E. G.; Sing, M.; Brucker, G. J.; Ohanian, R. S.

    1976-01-01

    The initial results obtained from the Complementary Metal Oxide Semiconductors Radiation Effects Measurement experiment are presented. Predictions of radiation damage to C-MOS devices are based on standard environment models and computational techniques. A comparison of the shifts in CMOS threshold potentials, that is, those measured in space to those obtained from the on the ground simulation experiment with Co 60, indicated that the measured space damage is greater than predicted by a factor of two for shields thicker than 100 mils (2.54 mm), but agrees well with predictions for the thinner shields.

  11. Amelioration of radiation-induced liver damage in partially hepatectomized rats by hepatocyte transplantation.

    PubMed

    Guha, C; Sharma, A; Gupta, S; Alfieri, A; Gorla, G R; Gagandeep, S; Sokhi, R; Roy-Chowdhury, N; Tanaka, K E; Vikram, B; Roy-Chowdhury, J

    1999-12-01

    Hepatic tumors often recur in the liver after surgical resection. Postoperative radiotherapy (RT) could improve survival, but curative RT may induce delayed life-threatening radiation-induced liver damage. Because RT inhibits liver regeneration, we hypothesized that unirradiated, transplanted hepatocytes would proliferate preferentially in a partially resected and irradiated liver, providing metabolic support. We subjected F344 rats to hepatic RT and partial hepatectomy with/without a single intrasplenic, syngeneic hepatocyte transplantation. Hepatocyte transplantation ameliorated radiation-induced liver damage and improved survival of rats receiving RT after partial hepatectomy. We further demonstrated that transplanted hepatocytes extensively repopulate and function in a heavily irradiated rat liver. PMID:10606225

  12. Reference data file for neutron spectrum adjustment and related radiation damage calculations

    SciTech Connect

    Zsolnay, E.M. ); Nolthenius, H.J.; Greenwood, L.R.; Szondi, E.J. )

    1990-08-01

    The REAL-88 interlaboratory exercise organized by IAEA resulted in a neutron metrology file. (NMF-90) comprising problem dependent data for benchmark neutron fields, furthermore, nuclear data and computer programs for neutron spectrum adjustment and radiation damage parameter calculations for the service life assessment of nuclear facilities. Calculation results of some experienced laboratories are also present. This paper describes and analyses the content of the neutron metrology file and outlines the most important problems and tasks to be solved in the field of radiation damage parameter calculations. 14 refs., 2 figs., 1 tab.

  13. Exploiting Radiation Damage to Map Proteins in Nucleoprotein Complexes: The Internal Structure of Bacteriophage T7

    PubMed Central

    Cheng, Naiqian; Wu, Weimin; Watts, Norman R.; Steven, Alasdair C.

    2014-01-01

    In the final stage of radiation damage in cryo-electron microscopy of proteins, bubbles of hydrogen gas are generated. Proteins embedded in DNA bubble sooner than free-standing proteins and DNA does not bubble under the same conditions. These properties make it possible to distinguish protein from DNA. Here we explored the scope of this technique (“bubblegram imaging”) by applying it to bacteriophage T7, viewed as a partially defined model system. T7 has a thin-walled icosahedral capsid, 60 nm in diameter, with a barrel-shaped protein core under one of its twelve vertices (the portal vertex). The core is densely wrapped with DNA but details of their interaction and how their injection into a host bacterium is coordinated are lacking. With short (10 sec) intervals between exposures of 17 electrons/Å2 each, bubbling starts in the third exposure, with 1 – 4 bubbles nucleating in the core: in subsequent exposures, these bubbles grow and merge. A 3D reconstruction from fifth-exposure images depicts a bipartite cylindrical gas cloud in the core. In its portal-proximal half, the axial region is gaseous whereas in the portal-distal half, it is occupied by a 3 nm-wide dense rod. We propose that they respectively represent core protein and an end of the packaged genome, poised for injection into a host cell. Single bubbles at other sites may represent residual scaffolding protein. Thus, bubbling depends on dose rate, protein amount, and tightness of the DNA seal. PMID:24345345

  14. Radiation damage in silicon due to albedo neutrons emitted from hadronic beam dumps (Fe and U)

    SciTech Connect

    Gabriel, T.A.; Bishop, B.L.

    1987-01-01

    Calculations have been carried out to determine the level of radiation damage that can be expected from albedo neutrons when 1- and 5-GeV negative pions are incident on iron and uranium beam dumps. The calculated damage data are presented in several ways including neutron fluence above 0.111 MeV, 1 MeV equivalent neutron fluence, damage energy deposition, and DPA or displacements per atom. Details are presented as to the method of calculation. 14 refs., 1 fig., 1 tab.

  15. Modification of radiation-induced oxidative damage in liposomal and microsomal membrane by eugenol

    NASA Astrophysics Data System (ADS)

    Pandey, B. N.; Lathika, K. M.; Mishra, K. P.

    2006-03-01

    Radiation-induced membrane oxidative damage, and their modification by eugenol, a natural antioxidant, was investigated in liposomes and microsomes. Liposomes prepared with DPH showed decrease in fluorescence after γ-irradiation, which was prevented significantly by eugenol and correlated with magnitude of oxidation of phospholipids. Presence of eugenol resulted in substantial inhibition in MDA formation in irradiated liposomes/microsomes, which was less effective when added after irradiation. Similarly, the increase in phospholipase C activity observed after irradiation in microsomes was inhibited in samples pre-treated with eugenol. Results suggest association of radio- oxidative membrane damage with alterations in signaling molecules, and eugenol significantly prevented these membrane damaging events.

  16. Modification of radiation damage in rat spinal cord by mitotane

    SciTech Connect

    Glicksman, A.S.; Bliven, S.F.; Leith, J.T.

    1982-07-01

    Modification of the paralytic response in rats after 6-MV photon irradiation of the spinal cord with either single or split exposures (two equal fractions given in a 24-hour period) by mitotane was investigated. Mitotane was administered as a suspension in physiologic saline (300 mg/kg/day) for either 5 days prior to or 5 days after irradiation. For rats receiving split doses of 6-MV photons, either the last two doses of mitotane were given 2 hours prior to each radiation fraction or mitotane was begun 2 hours after the second fraction and continued for 5 days. The data to 6 months after irradiation indicate that, in rats given mitotane for 5 days prior to single-dose photon irradiation, the paralytic response (as defined by the dose needed to produce paralysis in 50% of the irradiated groups of rats) was enhanced by a dose-enhancement factor (DEF) of 1.40. The DEF in the group of rats given mitotane after single doses of 6-MV photons was 1.15. In the split-dose irradiation experiments, the DEF for the groups of rats given mitotane prior to each radiation fraction was 1.36; while the DEF for the group of rats receiving mitotane beginning after the second fraction was 1.18. These data indicate that mitotane can potentiate the effects of 6-MV photon irradiation to the central nervous system, with mitotane administered prior to irradiation being the most effective sequence.

  17. Radiation damage in high voltage silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Brandhorst, H., Jr.; Swartz, C. K.; Weizer, V. G.

    1980-01-01

    Three high open-circuit voltage cell designs based on 0.1 ohm-cm p-type silicon were irradiated with 1 MeV electrons and their performance determined to fluences as high as 10 to the 15th power/sq cm. Of the three cell designs, radiation induced degradation was greatest in the high-low emitter (HLE cell). The diffused and ion implanted cells degraded approximately equally but less than the HLE cell. Degradation was greatest in an HLE cell exposed to X-rays before electron irradiation. The cell regions controlling both short-circuit current and open-circuit voltage degradation were defined in all three cell types. An increase in front surface recombination velocity accompanied time dependent degradation of an HLE cell after X-irradiation. It was speculated that this was indirectly due to a decrease in positive charge at the silicon-oxide interface. Modifications aimed at reducing radiation induced degradation are proposed for all three cell types.

  18. Depletion layer recombination effects on the radiation damage hardness of gallium arsenide cells

    NASA Technical Reports Server (NTRS)

    Garlick, G. F. J.

    1985-01-01

    The significant effect of junction depletion layer recombination on the efficiency of windowed GaAs cells was demonstrated. The effect becomes more pronounced as radiation damage occurs. The depletion is considered for 1 MeV electron fluences up to 10 to the 16th power e/sq m. The cell modeling separates damage in emitter and base or buffer layers using different damage coefficients is reported. The lower coefficient for the emitter predicts less loss of performance at fluences greater than 10 to the 15th power e/sq cm. A method for obtaining information on junction recombination effects as damage proceeds is described; this enables a more complete diagnosis of damage to be made.

  19. A whole-genome, radiation hybrid map of wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Generating a reference sequence of bread wheat (Triticum aestivum L.) is a challenging task because of its large, highly repetitive and allopolyploid genome. Ordering of BAC- and NGS-based contigs in ongoing wheat genome-sequencing projects primarily uses recombination and comparative genomics-base...

  20. Opposite Roles for p38MAPK-Driven Responses and Reactive Oxygen Species in the Persistence and Resolution of Radiation-Induced Genomic Instability

    PubMed Central

    Werner, Erica; Wang, Huichen; Doetsch, Paul W.

    2014-01-01

    We report the functional and temporal relationship between cellular phenotypes such as oxidative stress, p38MAPK-dependent responses and genomic instability persisting in the progeny of cells exposed to sparsely ionizing low-Linear Energy Transfer (LET) radiation such as X-rays or high-charge and high-energy (HZE) particle high-LET radiation such as 56Fe ions. We found that exposure to low and high-LET radiation increased reactive oxygen species (ROS) levels as a threshold-like response induced independently of radiation quality and dose. This response was sustained for two weeks, which is the period of time when genomic instability is evidenced by increased micronucleus formation frequency and DNA damage associated foci. Indicators for another persisting response sharing phenotypes with stress-induced senescence, including beta galactosidase induction, increased nuclear size, p38MAPK activation and IL-8 production, were induced in the absence of cell proliferation arrest during the first, but not the second week following exposure to high-LET radiation. This response was driven by a p38MAPK-dependent mechanism and was affected by radiation quality and dose. This stress response and elevation of ROS affected genomic instability by distinct pathways. Through interference with p38MAPK activity, we show that radiation-induced stress phenotypes promote genomic instability. In contrast, exposure to physiologically relevant doses of hydrogen peroxide or increasing endogenous ROS levels with a catalase inhibitor reduced the level of genomic instability. Our results implicate persistently elevated ROS following exposure to radiation as a factor contributing to genome stabilization. PMID:25271419

  1. Terahertz Electromagnetic Fields (0.106 THz) Do Not Induce Manifest Genomic Damage In Vitro

    PubMed Central

    Hintzsche, Henning; Jastrow, Christian; Kleine-Ostmann, Thomas; Kärst, Uwe; Schrader, Thorsten; Stopper, Helga

    2012-01-01

    Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment. Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm2 to 2 mW/cm2, representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction. PMID:23029508

  2. The genomic response of the retinal pigment epithelium to light damage and retinal detachment

    PubMed Central

    Rattner, Amir; Toulabi, Leila; Williams, John; Yu, Huimin; Nathans, Jeremy

    2008-01-01

    The retinal pigment epithelium (RPE) plays an essential role in maintaining the health of the retina. The RPE is also the site of pathologic processes in a wide variety of retinal disorders including monogenic retinal dystrophies, age-related macular degeneration, and retinal detachment. Despite intense interest in the RPE, little is known about its molecular response to ocular damage or disease. We have conducted a comprehensive analysis of changes in transcript abundance (the “genomic response”) in the murine RPE following light damage. Several dozen transcripts, many related to cell-cell signaling, show significant increases in abundance in response to bright light; transcripts encoding visual cycle proteins show a decrease in abundance. Similar changes are induced by retinal detachment. Environmental and genetic perturbations that modulate the RPE response to bright light suggest that this response is controlled by the retina. In contrast to the response to bright light, the RPE response to retinal detachment over-rides these modulatory affects. PMID:18815272

  3. New Paradigms in the Repair of Oxidative Damage in Human Genome

    PubMed Central

    Dutta, Arijit; Yang, Chunying; Sengupta, Shiladitya; Mitra, Sankar; Hegde, Muralidhar L.

    2015-01-01

    Oxidized bases in the mammalian genome, which are invariably mutagenic due to their mis-pairing property, are continuously induced by endogenous reactive oxygen species (ROS) and more abundantly after oxidative stress. Unlike bulky base adducts induced by UV and other environmental mutagens in the genome that block replicative DNA polymerases, oxidatively damaged bases such as 5-hydoxyuracil (5-OHU), produced by oxidative deamination of cytosine in the template strand, do not block replicative polymerases and thus need to be repaired prior to replication in order to prevent mutation. Following up our earlier studies, which showed that the Nei endonuclease VIII like 1 (NEIL1) DNA glycosylase, one of five base excision repair (BER)-initiating enzymes in mammalian cells, has enhanced expression during the S-phase and higher affinity for replication fork-mimicking single-stranded (ss) DNA substrates, we recently provided direct experimental evidence for NEIL1’s role in replicating template-strand repair. The key requirement for this event, which we named as the ‘cow-catcher’ mechanism of pre-replicative BER, is NEIL1’s non-productive binding (substrate binding without product formation) to the lesion base in ss DNA template to stall DNA synthesis, causing fork regression. Repair of the lesion in re-annealed duplex is then carried out by NEIL1 in association with the DNA replication proteins. NEIL1 (and other BER-initiating enzymes) also interact with several accessory and non-canonical proteins including the heterogeneous nuclear ribonucleoprotein U (hnRNP-U) and Y-box-binding protein 1 (YB-1) as well as high mobility group box 1 protein (HMGB1), whose precise roles in BER are still obscure. In this review, we have discussed the recent advances in our understanding of oxidative genome damage repair pathways with particular focus on the pre-replicative template strand repair and the role of scaffold factors like X-ray repair cross-complementing protein 1 (XRCC1

  4. Regulation of zygotic genome activation and DNA damage checkpoint acquisition at the mid-blastula transition

    PubMed Central

    Zhang, Maomao; Kothari, Priyanka; Mullins, Mary; Lampson, Michael A.

    2014-01-01

    Following fertilization, oviparous embryos undergo rapid, mostly transcriptionally silent cleavage divisions until the mid-blastula transition (MBT), when large-scale developmental changes occur, including zygotic genome activation (ZGA) and cell cycle remodeling, via lengthening and checkpoint acquisition. Despite their concomitant appearance, whether these changes are co-regulated is unclear. Three models have been proposed to account for the timing of (ZGA). One model implicates a threshold nuclear to cytoplasmic (N:C) ratio, another stresses the importance cell cycle elongation, while the third model invokes a timer mechanism. We show that precocious Chk1 activity in pre-MBT zebrafish embryos elongates cleavage cycles, thereby slowing the increase in the N:C ratio. We find that cell cycle elongation does not lead to transcriptional activation. Rather, ZGA slows in parallel with the N:C ratio. We show further that the DNA damage checkpoint program is maternally supplied and independent of ZGA. Although pre-MBT embryos detect damage and activate Chk2 after induction of DNA double-strand breaks, the Chk1 arm of the DNA damage response is not activated, and the checkpoint is nonfunctional. Our results are consistent with the N:C ratio model for ZGA. Moreover, the ability of precocious Chk1 activity to delay pre-MBT cell cycles indicate that lack of Chk1 activity limits checkpoint function during cleavage cycles. We propose that Chk1 gain-of-function at the MBT underlies cell cycle remodeling, whereas ZGA is regulated independently by the N:C ratio. PMID:25558827

  5. Radiation-induced renal damage: the effects of hyperfractionation. [Mice

    SciTech Connect

    Stewart, F.A.; Soranson, J.A.; Alpen, E.L.; Williams, M.V.; Denekamp, J.

    1984-05-01

    The response of mouse kidneys to multifraction irradiation was assessed using three nondestructive functional end points. A series of schedules was investigated giving 1, 2, 4, 8, 16, 32, or 64 equal X-ray doses, using doses per fraction in the range of 0.9 to 16 Gy. The overall treatment time was kept constant at 3 weeks. Kidney function was assessed from 19 to 48 weeks after irradiation by measuring changes in isotope clearance, urine output, and hematocrit. All three assays yielded steep dose-effect curves from which the repair capacity of kidney could be estimated by comparing the isoeffective doses in different schedules. There was a marked influence of fractionation, with increasing dose being required to achieve the same level of damage for increasing fraction number, even between 32 and 64 fractions. The data are well fitted by a linear quadratic dose-response equation, and analysis of the data would suggest that hyperfractionation, using extremely small X-ray doses per fraction, would spare kidneys relative to tumors and acutely responding tissues.

  6. Radiation damage study using small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Rétfalvi, E.; Török, Gy; Rosta, L.

    2000-03-01

    Nuclear radiation provides important changes in the microstructure of metallic components of nuclear power plant and research reactors, influencing their mechanical properties. The investigation of this problem has primary interest for the safety and life-time of such nuclear installations. For the characterization of this kind of nanostructures small angle neutron scattering technique is a very useful tool. We have carried out experiments on samples of irradiated reactor vessel material and welded components of VVER-440-type reactors on the SANS instrument at the Budapest Research Reactor. In our measurements irradiated as well as non-irradiated samples were compared and magnetic field was applied for viewing the magnetic structure effects of the materials. A clear modification of the structure due to irradiation was obtained. Our data were analyzed by the ITP92 code, the inverse Fourier transform program of O. Glatter [1].

  7. Ion-counting nanodosimetry: a new method for assessing radiation damage to DNA

    NASA Astrophysics Data System (ADS)

    Shchemelinin, S.; Garty, G.; Breskin, A.; Chechik, R.; Schulte, R. W. M.

    2002-01-01

    A novel nanodosimeter is described, based on ion counting. It provides precise model-evaluation of radiation-induced ionization patterns in small condensed-matter volumes of nanometric size. The nanodosimeter consists of a millimetric, low-pressure, wall-less gas cell, serving as an expanded model of a nanometric condensed-matter volume. The method can also be employed for the assessment of radiation damage to advanced nanoelectronics.

  8. Human umbilical cord mesenchymal stem cells alleviate nasal mucosa radiation damage in a guinea pig model.

    PubMed

    Duan, Hong-Gang; Ji, Fang; Zheng, Chun-Quan; Wang, Chun-Hua; Li, Jing

    2015-02-01

    Nasal complications after radiotherapy severely affect the quality of life of nasopharyngeal carcinoma patients, and there is a compelling need to find novel therapies for nasal epithelial cell radiation damage. Therefore, we investigated the therapeutic effect of human umbilical cord mesenchymal stem cells (hUC-MSCs) in guinea pig model of nasal mucosa radiation damage and explored its therapeutic mechanism. Cultured hUC-MSCs were injected intravenously immediately after radiation in the nasal mucosa-radiation-damage guinea pig model. Migration of hUC-MSCs into the nasal mucosa and the potential for differentiation into nasal epithelial cells were evaluated by immunofluorescence. The therapeutic effects of hUC-MSCs were evaluated by mucus clearance time (MCT), degree of nasal mucosa edema, and the nasal mucosa cilia form and coverage ratio. Results indicate that the hUC-MSCs migrated to the nasal mucosa lamina propria and did not differentiate into nasal epithelial cells in this model. The MCT and degree of mucosal edema were improved at 1 week and 1 month after radiation, respectively, but no difference was found at 3 months and 6 months after radiation. The nasal mucosa cilia form and coverage ratio was not improved 6 months after radiation. Thus, hUC-MSCs can migrate to the nasal mucosa lamina propria and improve MCT and mucosa edema within a short time period, but these cells are unable to differentiate into nasal epithelial cells and improve nasal epithelial regeneration in the nasal mucosa radiation damage guinea pig model. PMID:25209829

  9. Spectromicroscopy of Polymers: Comparison of Radiation Damage with Electron and Photon Core Excitation Spectroscopy Techniques

    NASA Astrophysics Data System (ADS)

    Ade, H.; Smith, A. P.; Rightor, E. G.; Hitchcock, A. P.; Urquhart, S.; Leapman, R.

    1997-03-01

    Core excitation microspectroscopy has become a powerful tool for the characterization of polymeric materials due to its sensitivity to chemical functionality. However, the excitations utilized in electron energy loss spectroscopy performed in a scanning transmission electron microscope (TEM-EELS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy can introduce radiation damage and chemically modify the sample. In order to understand the radiation damage associated with TEM-EELS and NEXAFS spectroscopy we have studied the radiation damage of the common polymer poly(ethylene terephthalate) (PET) as exhibited by changes in the acquired C K-edge excitation spectra. By fitting gaussian functions to the spectral intensity changes as a function of dose, we have determined the critical radiation dose of PET for both NEXAFS spectroscopy and TEM-EELS under typical operating conditions. This critical radiation dose for TEM-EELS is found to be 1.7 ± 0.2 x 10^8 grey (1.7 ± 0.2 x 10^4 Mrad) compared to a critical radiation dose for NEXAFS spectroscopy of 1.4 ± 0.7 x 10^9 grey (1.4 ± 0.7 x 10^5 Mrad). By considering the G factors of the two techniques and the critical radiation dose, a rule of thumb was derived that indicates that with typical present operating conditions, NEXAFS spectroscopy can analyze areas 500 times smaller than TEM-EELS given the same amount of radiation damage. Work supported by: NSF Young Investigator Award (DMR-9458060) and Dow Chemical

  10. Concurrent Transient Activation of Wnt/{beta}-Catenin Pathway Prevents Radiation Damage to Salivary Glands

    SciTech Connect

    Hai Bo; Yang Zhenhua; Shangguan Lei; Zhao Yanqiu; Boyer, Arthur; Liu, Fei

    2012-05-01

    Purpose: Many head and neck cancer survivors treated with radiotherapy suffer from permanent impairment of their salivary gland function, for which few effective prevention or treatment options are available. This study explored the potential of transient activation of Wnt/{beta}-catenin signaling in preventing radiation damage to salivary glands in a preclinical model. Methods and Materials: Wnt reporter transgenic mice were exposed to 15 Gy single-dose radiation in the head and neck area to evaluate the effects of radiation on Wnt activity in salivary glands. Transient Wnt1 overexpression in basal epithelia was induced in inducible Wnt1 transgenic mice before together with, after, or without local radiation, and then saliva flow rate, histology, apoptosis, proliferation, stem cell activity, and mRNA expression were evaluated. Results: Radiation damage did not significantly affect activity of Wnt/{beta}-catenin pathway as physical damage did. Transient expression of Wnt1 in basal epithelia significantly activated the Wnt/{beta}-catenin pathway in submandibular glands of male mice but not in those of females. Concurrent transient activation of the Wnt pathway prevented chronic salivary gland dysfunction following radiation by suppressing apoptosis and preserving functional salivary stem/progenitor cells. In contrast, Wnt activation 3 days before or after irradiation did not show significant beneficial effects, mainly due to failure to inhibit acute apoptosis after radiation. Excessive Wnt activation before radiation failed to inhibit apoptosis, likely due to extensive induction of mitosis and up-regulation of proapoptosis gene PUMA while that after radiation might miss the critical treatment window. Conclusion: These results suggest that concurrent transient activation of the Wnt/{beta}-catenin pathway could prevent radiation-induced salivary gland dysfunction.

  11. A high-resolution radiation hybrid map of the human genome draft sequence.

    PubMed

    Olivier, M; Aggarwal, A; Allen, J; Almendras, A A; Bajorek, E S; Beasley, E M; Brady, S D; Bushard, J M; Bustos, V I; Chu, A; Chung, T R; De Witte, A; Denys, M E; Dominguez, R; Fang, N Y; Foster, B D; Freudenberg, R W; Hadley, D; Hamilton, L R; Jeffrey, T J; Kelly, L; Lazzeroni, L; Levy, M R; Lewis, S C; Liu, X; Lopez, F J; Louie, B; Marquis, J P; Martinez, R A; Matsuura, M K; Misherghi, N S; Norton, J A; Olshen, A; Perkins, S M; Perou, A J; Piercy, C; Piercy, M; Qin, F; Reif, T; Sheppard, K; Shokoohi, V; Smick, G A; Sun, W L; Stewart, E A; Fernando, J; Tejeda; Tran, N M; Trejo, T; Vo, N T; Yan, S C; Zierten, D L; Zhao, S; Sachidanandam, R; Trask, B J; Myers, R M; Cox, D R

    2001-02-16

    We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases. PMID:11181994

  12. Optimization of radiation damage to proteins using X-ray nanofocusing optics

    NASA Astrophysics Data System (ADS)

    Boularaoui, Selwa; Evans-Lutterodt, K.; Lee, S.; Isakovic, A. F.

    2013-03-01

    The need to understand protein structure and perform treatment lead to the use of X-ray and particle-based radiation. Since the use of such radiation has undesirable side effects, mostly through the damage to proteins, it is important to continuously work on decreasing radiation damage. We outline the proposal to use the kinoform refractive optics to focus X-rays on the nanoscale to minimize the radiation damage to protein crystals under study. These optics devices are nanofabricated from low-Z elements (silicon, diamond) and can be used at synchrotron X-ray radiation facilities. We discuss the automated setup that performs nanopositioning of the nanofocusing element, and collects the chemical and structural protein solution under study. We offer simple mathematical models in irradiation and in treatment that help optimize the radiation parameters. This work is supported in part by Khalifa University IRF-Level 1 Fund. The work at BNL-NSLS is supported through US DOE, Office of Basic Energy Sciences.

  13. Near infrared radiation damage mechanism in the lens

    NASA Astrophysics Data System (ADS)

    Söderberg, Per G.; Talebizadeh, Nooshin; Galichanin, Konstantin; Kronschläger, Martin; Schulmeister, Karl; Yu, Zhaohua

    2015-03-01

    The current data strongly indicates that there is no photochemical effect of in vivo exposure to 1090 nm near IRR radiation within the pupil. Four groups of 20 Sprague-Dawley rats were unilaterally exposed in vivo to 96 W·cm-2 centered inside the pupil for 10, 18, 33 and 60 min, respectively depending on group belonging. This resulted in radiant exposure doses of 57, 103, 198 and 344 kJ·cm-2. Temperature evolution at the limbus during the exposure and difference of intensity of forward light scattering between the exposed and the contralateral not exposed eye was measured at 1 week after exposure. The temperature at the limbus was found to increase exponentially towards an asymptote with an asymptote temperature of around 7 °C and a time constant (1/k) of around 15 s. No increase of light scattering was found despite that the cumulated radiant exposure dose was [80;250] times the threshold for photochemically induced cataract suggested by previous empirical data. It is concluded that at 1090 nm near IRR there is no photochemical effect.

  14. TEM study of radiation damage and annealing of neutron irradiated zirconolite

    SciTech Connect

    Lumpkin, G.R.; Smith, K.L.; Blake, R.G.

    1996-08-01

    Neutron irradiation was used to simulate alpha-decay damage in zirconolite, resulting in a transformation from the crystalline to the amorphous state at doses of 4--25 {times} 10{sup 19} n/cm{sup 2} (E {ge} 1 MeV). With increasing dose, the radiation damage microstructures resemble damage caused by: (1) alpha-decay of {sup 232}Th and {sup 238}U in natural zirconolites, (2) alpha-decay of {sup 238}Pu or {sup 244}Cm in synthetic samples, and (3) collision cascades in samples irradiated with heavy ions. Heavily damaged zirconolite recovers to a defect fluorite phase on annealing at temperatures up to 1,000 C. The main stage of structural recovery was found to occur at temperatures of 600--800 C. The microstructures after heating depend on the initial level of damage: zirconolite grains with low to moderate levels of damage anneal to imperfect single crystals, whereas heavily damaged grains recrystallize to a polycrystalline microstructure. Complications encountered in this work include the production of fission tracks (due to trace amounts of U) and a non-uniform distribution of damage at higher dose levels (possibly due to electron beam heating).

  15. Can radiation damage to protein crystals be reduced using small-molecule compounds?

    PubMed Central

    Kmetko, Jan; Warkentin, Matthew; Englich, Ulrich; Thorne, Robert E.

    2011-01-01

    Recent studies have defined a data-collection protocol and a metric that provide a robust measure of global radiation damage to protein crystals. Using this protocol and metric, 19 small-molecule compounds (introduced either by cocrystalliz­ation or soaking) were evaluated for their ability to protect lysozyme crystals from radiation damage. The compounds were selected based upon their ability to interact with radiolytic products (e.g. hydrated electrons, hydrogen, hydroxyl and perhydroxyl radicals) and/or their efficacy in protecting biological molecules from radiation damage in dilute aqueous solutions. At room temperature, 12 compounds had no effect and six had a sensitizing effect on global damage. Only one compound, sodium nitrate, appeared to extend crystal lifetimes, but not in all proteins and only by a factor of two or less. No compound provided protection at T = 100 K. Scavengers are ineffective in protecting protein crystals from global damage because a large fraction of primary X-ray-induced excitations are generated in and/or directly attack the protein and because the ratio of scavenger molecules to protein molecules is too small to provide appreciable competitive protection. The same reactivity that makes some scavengers effective radioprotectors in protein solutions may explain their sensitizing effect in the protein-dense environment of a crystal. A more productive focus for future efforts may be to identify and eliminate sensitizing compounds from crystallization solutions. PMID:21931220

  16. 3D imaging of radiation damage in silicon sensor and spatial mapping of charge collection efficiency

    NASA Astrophysics Data System (ADS)

    Jakubek, M.; Jakubek, J.; Zemlicka, J.; Platkevic, M.; Havranek, V.; Semian, V.

    2013-03-01

    Radiation damage in semiconductor sensors alters the response and degrades the performance of many devices ultimately limiting their stability and lifetime. In semiconductor radiation detectors the homogeneity of charge collection becomes distorted while decreasing the overall detection efficiency. Moreover the damage can significantly increase the detector noise and degrade other electrical properties such as leakage current. In this work we present a novel method for 3D mapping of the semiconductor radiation sensor volume allowing displaying the three dimensional distribution of detector properties such as charge collection efficiency and charge diffusion rate. This technique can visualize the spatially localized changes of local detector performance after radiation damage. Sensors used were 300 μm and 1000 μm thick silicon bump-bonded to a Timepix readout chip which serves as an imaging multichannel microprobe (256 × 256 square pixels with pitch of 55 μm, i.e. all together 65 thousand channels). Per pixel energy sensitivity of the Timepix chip allows to evaluate the local charge collection efficiency and also the charge diffusion rate. In this work we implement an X-ray line scanning technique for systematic evaluation of changes in the performance of a silicon sensor intentionally damaged by energetic protons.

  17. Variable-Temperature Cryostat For Radiation-Damage Testing Of Germanium Detectors

    NASA Technical Reports Server (NTRS)

    Floyd, Samuel R.; Puc, Bernard P.

    1992-01-01

    Variable-temperature cryostats developed to study radiation damage to, and annealing of, germanium gamma-ray detectors. Two styles: one accommodates large single detector and one accommodates two medium-sized detectors. New cryostats allow complete testing of large-volume germanium gamma-ray detectors without breaking cryostat vacuum and removing detectors for annealing.

  18. TGF-.beta. antagonists as mitigators of radiation-induced tissue damage

    DOEpatents

    Barcellos-Hoff, Mary H.

    1997-01-01

    A method for treating tissue damage caused by radiation is described by use of a TGF-.beta. antagonist, such as an anti-TGF-.beta. antibody or a TGF-.beta. latency associated protein. It is administered not more than a week after exposure, and is particularly useful in mitigating the side effects of breast cancer therapy.

  19. Geraniin down regulates gamma radiation-induced apoptosis by suppressing DNA damage.

    PubMed

    Bing, So Jin; Ha, Danbee; Kim, Min Ju; Park, Eunjin; Ahn, Ginnae; Kim, Dae Seung; Ko, Ryeo Kyeong; Park, Jae Woo; Lee, Nam Ho; Jee, Youngheun

    2013-07-01

    Gamma ray irradiation triggers DNA damage and apoptosis of proliferating stem cells and peripheral immune cells, resulting in the destruction of intestinal crypts and lymphoid system. Geraniin is a natural compound extracts from an aquatic plant Nymphaea tetragona and possesses good antioxidant property. In this study, we demonstrate that geraniin rescues radiosensitive splenocytes and jejunal crypt cells from radiation-induced DNA damage and apoptosis. Isolated splenocytes from C57BL/6 mice treated with geraniin were protected against radiation injury of 2 Gy irradiation through the enhancement of the proliferation and attenuation of DNA damage. Also, geraniin inhibited apoptosis in radiosensitive splenocytes by reducing the expression level and immunoreactivity of proapoptotic p53 and Bax and increasing those of anti-apoptotic Bcl-2. In mice exposed to radiation, geraniin treatment protected splenocytes and intestinal crypt cells from radiation-induced cell death. Our results suggest that geraniin presents radioprotective effects by regulating DNA damage on splenocytes, exerting immunostimulatory capacities and inhibiting apoptosis of radiosensitive immune cells and jejunal crypt cells. Therefore, geraniin can be a radioprotective agent against γ-irradiation exposure. PMID:23541438

  20. TGF-{beta} antagonists as mitigators of radiation-induced tissue damage

    DOEpatents

    Barcellos-Hoff, M.H.

    1997-04-01

    A method for treating tissue damage caused by radiation is described by use of a TGF-{beta} antagonist, such as an anti-TGF-{beta} antibody or a TGF-{beta} latency associated protein. It is administered not more than a week after exposure, and is particularly useful in mitigating the side effects of breast cancer therapy.

  1. Measurement of high-voltage and radiation-damage limitations to advanced solar array performance

    NASA Technical Reports Server (NTRS)

    Guidice, D. A.; Severance, P. S.; Keinhardt, K. C.

    1991-01-01

    A description is given of the reconfigured Photovoltaic Array Space Power (PASP) Plus experiment: its objectives, solar-array complement, and diagnostic sensors. Results from a successful spaceflight will lead to a better understanding of high-voltage and radiation-damage limitations in the operation of new-technology solar arrays.

  2. Ultraviolet radiation-specific DNA damage and embryonic viability in sea urchins from Kasitsna Bay, Alaska

    SciTech Connect

    Theodorakis, C.; Anderson, S.; Shugart, L.R.

    1995-12-31

    Ripe ova and sperm were obtained from Green Sea Urchins (Strongvlocentrotus drochbachiensis) collected from Kasitsna Bay, Alaska, and ova were fertilized in vitro. Embryos were immediately placed in plastic bags secured to floating racks deployed in the bay. The bags were suspended just below the surface of the water and at 1 and 2 meter depths for up to 120 hours. Bags were either left uncovered, covered with Mylar plastic (which blocks out UV-B but not UV-A radiations), or covered with dark plastic. The number of damaged DNA sites was determined by digesting the DNA with enzymes isolated from the bacterium Micrococcus luteus which cleave the DNA at damaged sites. It was found that DNA damage was present in a dose-dependent fashion with the amount of damage in embryos from the uncovered bags > Mylar covered bags > dark covered bags. No dimers were detected from embryos at 1 or 2 m. depths. Also, the number of damaged sites varied from day to day. Finally, the number of damaged sites was positively correlated with percent abnormal embryos in each bag. The results are discussed with relation to monitoring UV-B effects and ecological consequences of enhanced UV-B radiation.

  3. Determining the Radiation Damage Effect on Glovebox Glove Material.

    SciTech Connect

    Cournoyer, M. E.; Balkey, J. J.; Andrade, R.M.

    2005-01-01

    The Nuclear Material Technology (NMT) Division has the largest inventory of glove box gloves at Los Alamos National Laboratory. The minimization of unplanned breaches in the glovebox, e.g., glove failures, is a primary concern in the daily operations in NMT Division facilities, including the Plutonium Facility (PF-4) at TA-55 and Chemical and Metallurgy Research (CMR) Facility. Glovebox gloves in these facilities are exposed to elevated temperatures and exceptionally aggressive radiation environments (particulate {sup 239}Pu and {sup 238}Pu). Predictive models are needed to estimate glovebox glove service lifetimes, i.e. change-out intervals. Towards this aim aging studies have been initiated that correlate changes in mechanical (physical) properties with degradation chemistry. This present work derives glovebox glove change intervals based on previously reported mechanical data of thermally aged hypalon glove samples. Specifications for 30 mil tri-layered hypalon/lead glovebox gloves (TLH) and 15 mil hypalon gloves (HYP) have already been established. The relevant mechanical properties are shown on Table 1. Tensile strength is defined as the maximum load applied in breaking a tensile test piece divided by the original cross-sectional area of the test piece (Also termed maximum stress and ultimate tensile stress). Ultimate elongation is the elongation at time of rupture (Also termed maximum strain). The specification for the tensile test and ultimate elongation are the minimum acceptable values. In addition, the ultimate elongation must not vary 20% from the original value. In order to establish a service lifetimes for glovebox gloves in a thermal environment, the mechanical properties of glovebox glove materials were studied.

  4. Radiation-damage-induced phasing: a case study using UV irradiation with light-emitting diodes.

    PubMed

    de Sanctis, Daniele; Zubieta, Chloe; Felisaz, Franck; Caserotto, Hugo; Nanao, Max H

    2016-03-01

    Exposure to X-rays, high-intensity visible light or ultraviolet radiation results in alterations to protein structure such as the breakage of disulfide bonds, the loss of electron density at electron-rich centres and the movement of side chains. These specific changes can be exploited in order to obtain phase information. Here, a case study using insulin to illustrate each step of the radiation-damage-induced phasing (RIP) method is presented. Unlike a traditional X-ray-induced damage step, specific damage is introduced via ultraviolet light-emitting diodes (UV-LEDs). In contrast to UV lasers, UV-LEDs have the advantages of small size, low cost and relative ease of use. PMID:26960126

  5. Spontaneous perseverative turning in rats with radiation-induced hippocampal damage

    SciTech Connect

    Mickley, G.A.; Ferguson, J.L.; Nemeth, T.J.; Mulvihill, M.A.; Alderks, C.E. )

    1989-08-01

    This study found a new behavioral correlate of lesions specific to the dentate granule cell layer of the hippocampus: spontaneous perseverative turning. Irradiation of a portion of the neonatal rat cerebral hemispheres produced hypoplasia of the granule cell layer of the hippocampal dentate gyrus while sparing the rest of the brain. Radiation-induced damage to the hippocampal formation caused rats placed in bowls to spontaneously turn in long, slow bouts without reversals. Irradiated subjects also exhibited other behaviors characteristic of hippocampal damage (e.g., perseveration in spontaneous exploration of the arms of a T-maze, retarded acquisition of a passive avoidance task, and increased horizontal locomotion). These data extend previously reported behavioral correlates of fascia dentata lesions and suggest the usefulness of a bout analysis of spontaneous bowl turning as a measure of nondiscrete-trial spontaneous alternation and a sensitive additional indicator of radiation-induced hippocampal damage.

  6. Study of terahertz-radiation-induced DNA damage in human blood leukocytes

    SciTech Connect

    Angeluts, A A; Esaulkov, M N; Kosareva, O G; Solyankin, P M; Shkurinov, A P; Gapeyev, A B; Pashovkin, T N; Matyunin, S N; Nazarov, M M; Cherkasova, O P

    2014-03-28

    We have carried out the studies aimed at assessing the effect of terahertz radiation on DNA molecules in human blood leukocytes. Genotoxic testing of terahertz radiation was performed in three different oscillation regimes, the blood leukocytes from healthy donors being irradiated for 20 minutes with the mean intensity of 8 – 200 μW cm{sup -2} within the frequency range of 0.1 – 6.5 THz. Using the comet assay it is shown that in the selected regimes such radiation does not induce a direct DNA damage in viable human blood leukocytes. (biophotonics)

  7. Study of terahertz-radiation-induced DNA damage in human blood leukocytes

    NASA Astrophysics Data System (ADS)

    Angeluts, A. A.; Gapeyev, A. B.; Esaulkov, M. N.; Kosareva, O. G.; Matyunin, S. N.; Nazarov, M. M.; Pashovkin, T. N.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

    2014-03-01

    We have carried out the studies aimed at assessing the effect of terahertz radiation on DNA molecules in human blood leukocytes. Genotoxic testing of terahertz radiation was performed in three different oscillation regimes, the blood leukocytes from healthy donors being irradiated for 20 minutes with the mean intensity of 8 - 200 μW cm-2 within the frequency range of 0.1 - 6.5 THz. Using the comet assay it is shown that in the selected regimes such radiation does not induce a direct DNA damage in viable human blood leukocytes.

  8. Can radiation damage to protein crystals be reduced using small-molecule compounds?

    SciTech Connect

    Kmetko, Jan; Warkentin, Matthew; Englich, Ulrich; Thorne, Robert E.

    2011-10-01

    Free-radical scavengers that are known to be effective protectors of proteins in solution are found to increase global radiation damage to protein crystals. Protective mechanisms may become deleterious in the protein-dense environment of a crystal. Recent studies have defined a data-collection protocol and a metric that provide a robust measure of global radiation damage to protein crystals. Using this protocol and metric, 19 small-molecule compounds (introduced either by cocrystallization or soaking) were evaluated for their ability to protect lysozyme crystals from radiation damage. The compounds were selected based upon their ability to interact with radiolytic products (e.g. hydrated electrons, hydrogen, hydroxyl and perhydroxyl radicals) and/or their efficacy in protecting biological molecules from radiation damage in dilute aqueous solutions. At room temperature, 12 compounds had no effect and six had a sensitizing effect on global damage. Only one compound, sodium nitrate, appeared to extend crystal lifetimes, but not in all proteins and only by a factor of two or less. No compound provided protection at T = 100 K. Scavengers are ineffective in protecting protein crystals from global damage because a large fraction of primary X-ray-induced excitations are generated in and/or directly attack the protein and because the ratio of scavenger molecules to protein molecules is too small to provide appreciable competitive protection. The same reactivity that makes some scavengers effective radioprotectors in protein solutions may explain their sensitizing effect in the protein-dense environment of a crystal. A more productive focus for future efforts may be to identify and eliminate sensitizing compounds from crystallization solutions.

  9. Protecting the radiation-damaged skin from friction: a mini review

    SciTech Connect

    Herst, Patries M

    2014-06-15

    Radiation-induced skin reactions are an unavoidable side effect of external beam radiation therapy, particularly in areas prone to friction and excess moisture such as the axilla, head and neck region, perineum and skin folds. Clinical studies investigating interventions for preventing or managing these reactions have largely focussed on formulations with moisturising, anti-inflammatory, anti-microbial and wound healing properties. However, none of these interventions has emerged as a consistent candidate for best practice. Much less emphasis has been placed on evaluating ways to protect the radiation-damaged skin from friction and excess moisture. This mini review analyses the clinical evidence for barrier products that form a protective layer by adhering very closely to the skin folds and do not cause further trauma to the radiation-damaged skin upon removal. A database search identified only two types of barrier products that fitted these criteria and these were tested in two case series and six controlled clinical trials. Friction protection was most effective when the interventions were used from the start of treatment and continued for several weeks after completion of treatment. Soft silicone dressings (Mepilex Lite and Mepitel Film) and Cavilon No Sting Barrier Film, but not Cavilon Moisturizing Barrier Cream, decreased skin reaction severity, most likely due to differences in formulation and skin build-up properties. It seems that prophylactic use of friction protection of areas at risk could be a worthwhile addition to routine care of radiation-damaged skin.

  10. Recovery of Deinococcus radiodurans from radiation damage was enhanced under microgravity.

    PubMed

    Kobayashi, Y; Kikuchi, M; Nagaoka, S; Watanabe, H

    1996-09-01

    Effect of microgravity on recovery of bacterial cells from radiation damage was examined on the IML-2 mission in 1994 using extremely radioresistant bacterium Deinococcus radiodurans. The cells were lyophilized and exposed to 60Co gamma-rays with doses 2 to 12 kGy before the space flight. At the end of the mission, the cells were mixed on board with liquid nutrient medium to allow the cells to start recovery process from the radiation damage. Afterwards the cells were stored at 4 degrees C until landing. The influence of cosmic radiation was negligible, because total absorbed dose of space radiation measured during the mission was less than 2 mGy and this bacterium does not decrease its viability after both gamma-rays and high-LET heavy charged particles irradiation with doses up to 5 kGy. The survival of the cells incubated in space increased significantly compared with the ground controls, suggesting that the recovery of this bacterium from radiation damage was enhanced under microgravity. PMID:11785538

  11. Protecting the radiation-damaged skin from friction: a mini review

    PubMed Central

    Herst, Patries M

    2014-01-01

    Radiation-induced skin reactions are an unavoidable side effect of external beam radiation therapy, particularly in areas prone to friction and excess moisture such as the axilla, head and neck region, perineum and skin folds. Clinical studies investigating interventions for preventing or managing these reactions have largely focussed on formulations with moisturising, anti-inflammatory, anti-microbial and wound healing properties. However, none of these interventions has emerged as a consistent candidate for best practice. Much less emphasis has been placed on evaluating ways to protect the radiation-damaged skin from friction and excess moisture. This mini review analyses the clinical evidence for barrier products that form a protective layer by adhering very closely to the skin folds and do not cause further trauma to the radiation-damaged skin upon removal. A database search identified only two types of barrier products that fitted these criteria and these were tested in two case series and six controlled clinical trials. Friction protection was most effective when the interventions were used from the start of treatment and continued for several weeks after completion of treatment. Soft silicone dressings (Mepilex Lite and Mepitel Film) and Cavilon No Sting Barrier Film, but not Cavilon Moisturizing Barrier Cream, decreased skin reaction severity, most likely due to differences in formulation and skin build-up properties. It seems that prophylactic use of friction protection of areas at risk could be a worthwhile addition to routine care of radiation-damaged skin. PMID:26229646

  12. Protecting the radiation-damaged skin from friction: a mini review.

    PubMed

    Herst, Patries M

    2014-06-01

    Radiation-induced skin reactions are an unavoidable side effect of external beam radiation therapy, particularly in areas prone to friction and excess moisture such as the axilla, head and neck region, perineum and skin folds. Clinical studies investigating interventions for preventing or managing these reactions have largely focussed on formulations with moisturising, anti-inflammatory, anti-microbial and wound healing properties. However, none of these interventions has emerged as a consistent candidate for best practice. Much less emphasis has been placed on evaluating ways to protect the radiation-damaged skin from friction and excess moisture. This mini review analyses the clinical evidence for barrier products that form a protective layer by adhering very closely to the skin folds and do not cause further trauma to the radiation-damaged skin upon removal. A database search identified only two types of barrier products that fitted these criteria and these were tested in two case series and six controlled clinical trials. Friction protection was most effective when the interventions were used from the start of treatment and continued for several weeks after completion of treatment. Soft silicone dressings (Mepilex Lite and Mepitel Film) and Cavilon No Sting Barrier Film, but not Cavilon Moisturizing Barrier Cream, decreased skin reaction severity, most likely due to differences in formulation and skin build-up properties. It seems that prophylactic use of friction protection of areas at risk could be a worthwhile addition to routine care of radiation-damaged skin. PMID:26229646

  13. Image dissector photocathode solar damage test program. [solar radiation shielding using a fast optical lens

    NASA Technical Reports Server (NTRS)

    Smith, R. A.

    1977-01-01

    Image dissector sensors of the same type which will be used in the NASA shuttle star tracker were used in a series of tests directed towards obtaining solar radiation/time damage criteria. Data were evaluated to determine the predicted level of operability of the star tracker if tube damage became a reality. During the test series a technique for reducing the solar damage effect was conceived and verified. The damage concepts are outlined and the test methods and data obtained which were used for verification of the technique's feasibility are presented. The ability to operate an image dissector sensor with the solar image focussed on the photocathode by a fast optical lens under certain conditions is feasible and the elimination of a mechanical protection device is possible.

  14. Radiation damage in front and back illuminated high resistivity silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Goradia, C. P.; Swartz, C. K.; Brandhorst, H. W., Jr.

    1982-01-01

    Radiation induced degradation, in front and back illuminated 84 and 1250 ohm-cm n+pp+ silicon solar cells, was determined and cell performance interpreted using calculated optically injected charge distributions and cell voltage components. The 84 ohm-cm cell degraded less when illuminated from the front or n+ side compared to that when illuminated from the back or p+ side. On the other hand, the 1250 ohm-cm cell degraded less when back illuminated. It is concluded that, in addition to the usual mechanisms leading to decreased collection efficiencies, loss of conductivity modulation is a major cause of radiation damage in high resistivity silicon solar cells. These results suggest that radiation damage to high resistivity n+pp+ cells can be decreased by increasing cell collection efficiency and illuminating the cells from the p+ side.

  15. Prediction and measurement of radiation damage to CMOS devices on board spacecraft

    NASA Technical Reports Server (NTRS)

    Cliff, R. A.; Danchenko, V.; Stassinopoulos, E. G.; Sing, M.; Brucker, G. J.; Ohanian, R. S.

    1976-01-01

    The CMOS Radiation Effects Measurement (CREM) experiment is presently being flown on the Explorer-55. The purpose of the experiment is to evaluate device performance in the actual space radiation environment and to correlate the respective measurements to on-the-ground laboratory irradiation results. The experiment contains an assembly of C-MOS and P-MOS devices shielded in front by flat slabs of aluminum and by a practically infinite shield in the back. Predictions of radiation damage to C-MOS devices are based on standard environment models and computational techniques. A comparison of the shifts in CMOS threshold potentials, that is, those measured in space to those obtained from the on-the-ground simulation experiment with Co-60, indicates that the measured space damage is smaller than predicted by about a factor of 2-3 for thin shields, but agrees well with predictions for thicker shields.

  16. A simple model of space radiation damage in GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Stith, J. J.; Stock, L. V.

    1983-01-01

    A simple model is derived for the radiation damage of shallow junction gallium arsenide (GaAs) solar cells. Reasonable agreement is found between the model and specific experimental studies of radiation effects with electron and proton beams. In particular, the extreme sensitivity of the cell to protons stopping near the cell junction is predicted by the model. The equivalent fluence concept is of questionable validity for monoenergetic proton beams. Angular factors are quite important in establishing the cell sensitivity to incident particle types and energies. A fluence of isotropic incidence 1 MeV electrons (assuming infinite backing) is equivalent to four times the fluence of normal incidence 1 MeV electrons. Spectral factors common to the space radiations are considered, and cover glass thickness required to minimize the initial damage for a typical cell configuration is calculated. Rough equivalence between the geosynchronous environment and an equivalent 1 MeV electron fluence (normal incidence) is established.

  17. An Automated Method to Quantify Radiation Damage in Human Blood Cells

    SciTech Connect

    Gordon K. Livingston, Mark S. Jenkins and Akio A. Awa

    2006-07-10

    Cytogenetic analysis of blood lymphocytes is a well established method to assess the absorbed dose in persons exposed to ionizing radiation. Because mature lymphocytes circulate throughout the body, the dose to these cells is believed to represent the average whole body exposure. Cytogenetic methods measure the incidence of structural aberrations in chromosomes as a means to quantify DNA damage which occurs when ionizing radiation interacts with human tissue. Methods to quantify DNA damage at the chromosomal level vary in complexity and tend to be laborious and time consuming. In a mass casualty scenario involving radiological/nuclear materials, the ability to rapidly triage individuals according to radiation dose is critically important. For high-throughput screening for dicentric chromosomes, many of the data collection steps can be optimized with motorized microscopes coupled to automated slide scanning platforms.

  18. Atomic simulations of Fe/Ni multilayer nanocomposites on the radiation damage resistance

    NASA Astrophysics Data System (ADS)

    Chen, Feida; Tang, Xiaobin; Yang, Yahui; Huang, Hai; Liu, Jian; Li, Huan; Chen, Da

    2016-01-01

    We investigated the radiation damage resistance of the Fe/Ni multilayer nanocomposites by molecular dynamics. In the paper, two types of interface configuration with different orientation relationship were constructed. Their morphology evolution and number of final surviving defects induced by cascade collisions were discussed respectively. The interfaces of the two types of Fe/Ni multilayers kept distinct during the long-time relaxation before cascade. The comparison of surviving defects number produced by PKA with 5 keV at 100 K showed that the Fe/Ni multilayers have greater radiation tolerance than that of the bulk materials. However, the orientation relationship of the interface influences the defects self-healing capability greatly when the multilayers are irradiated by higher energy PKA or at high temperature. The radiation damage resistance of the Nishiyama - Wassermann type Fe/Ni multilayers which have larger lattice misfit is more stable than that of the Kurdjumov - Sachs type.

  19. The effect of space radiation on the induction of chromosome damage

    NASA Technical Reports Server (NTRS)

    George, K.; Wu, H.; Willingham, V.; Cucinotta, F. A.

    2001-01-01

    To obtain information on the cytogenetic damage caused by space radiation, chromosome exchanges in lymphocytes from crewmembers of long-term Mir missions, and a shorter duration shuttle mission, were examined using fluorescence in situ hybridization. A significant increase in chromosomal aberrations was observed after the long duration flights. The ratio of aberrations identified as complex was higher post-flight for some crewmembers, which is thought to be an indication of exposure to high-LET radiation. Ground-based studies have shown that the frequency of aberrations measured post-flight could be influenced by a mitotic delay in cells damaged by high-LET radiation and this effect could lower biological dose estimates. To counteract this effect, prematurely condensed chromosome (PCC) spreads were collected. Frequencies of aberrations in PCC were compared with those in metaphase spreads.

  20. Radiation induced apoptosis and initial DNA damage are inversely related in locally advanced breast cancer patients

    PubMed Central

    2010-01-01

    Background DNA-damage assays, quantifying the initial number of DNA double-strand breaks induced by radiation, have been proposed as a predictive test for radiation-induced toxicity. Determination of radiation-induced apoptosis in peripheral blood lymphocytes by flow cytometry analysis has also been proposed as an approach for predicting normal tissue responses following radiotherapy. The aim of the present study was to explore the association between initial DNA damage, estimated by the number of double-strand breaks induced by a given radiation dose, and the radio-induced apoptosis rates observed. Methods Peripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radio-induced apoptosis at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide. Results Radiation-induced apoptosis increased in order to radiation dose and data fitted to a semi logarithmic mathematical model. A positive correlation was found among radio-induced apoptosis values at different radiation doses: 1, 2 and 8 Gy (p < 0.0001 in all cases). Mean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). A statistically significant inverse correlation was found between initial damage to DNA and radio-induced apoptosis at 1 Gy (p = 0.034). A trend toward 2 Gy (p = 0.057) and 8 Gy (p = 0.067) was observed after 24 hours of incubation. Conclusions An inverse association was observed for the first time between these variables, both considered as predictive factors to radiation toxicity. PMID:20868468

  1. Reduction of arsenite-enhanced ultraviolet radiation-induced DNA damage by supplemental zinc

    SciTech Connect

    Cooper, Karen L.; King, Brenee S.; Sandoval, Monica M.; Liu, Ke Jian; Hudson, Laurie G.

    2013-06-01

    Arsenic is a recognized human carcinogen and there is evidence that arsenic augments the carcinogenicity of DNA damaging agents such as ultraviolet radiation (UVR) thereby acting as a co-carcinogen. Inhibition of DNA repair is one proposed mechanism to account for the co-carcinogenic actions of arsenic. We and others find that arsenite interferes with the function of certain zinc finger DNA repair proteins. Furthermore, we reported that zinc reverses the effects of arsenite in cultured cells and a DNA repair target protein, poly (ADP-ribose) polymerase-1. In order to determine whether zinc ameliorates the effects of arsenite on UVR-induced DNA damage in human keratinocytes and in an in vivo model, normal human epidermal keratinocytes and SKH-1 hairless mice were exposed to arsenite, zinc or both before solar-simulated (ss) UVR exposure. Poly (ADP-ribose) polymerase activity, DNA damage and mutation frequencies at the Hprt locus were measured in each treatment group in normal human keratinocytes. DNA damage was assessed in vivo by immunohistochemical staining of skin sections isolated from SKH-1 hairless mice. Cell-based findings demonstrate that ssUVR-induced DNA damage and mutagenesis are enhanced by arsenite, and supplemental zinc partially reverses the arsenite effect. In vivo studies confirm that zinc supplementation decreases arsenite-enhanced DNA damage in response to ssUVR exposure. From these data we can conclude that zinc offsets the impact of arsenic on ssUVR-stimulated DNA damage in cells and in vivo suggesting that zinc supplementation may provide a strategy to improve DNA repair capacity in arsenic exposed human populations. - Highlights: • Low levels of arsenite enhance UV-induced DNA damage in human keratinocytes. • UV-initiated HPRT mutation frequency is enhanced by arsenite. • Zinc supplementation offsets DNA damage and mutation frequency enhanced by arsenite. • Zinc-dependent reduction of arsenite enhanced DNA damage is confirmed in vivo.

  2. Genomic assay reveals tolerance of DNA damage by both translesion DNA synthesis and homology-dependent repair in mammalian cells.

    PubMed

    Izhar, Lior; Ziv, Omer; Cohen, Isadora S; Geacintov, Nicholas E; Livneh, Zvi

    2013-04-16

    DNA lesions can block replication forks and lead to the formation of single-stranded gaps. These replication complications are mitigated by DNA damage tolerance mechanisms, which prevent deleterious outcomes such as cell death, genomic instability, and carcinogenesis. The two main tolerance strategies are translesion DNA synthesis (TLS), in which low-fidelity DNA polymerases bypass the blocking lesion, and homology-dependent repair (HDR; postreplication repair), which is based on the homologous sister chromatid. Here we describe a unique high-resolution method for the simultaneous analysis of TLS and HDR across defined DNA lesions in mammalian genomes. The method is based on insertion of plasmids carrying defined site-specific DNA lesions into mammalian chromosomes, using phage integrase-mediated integration. Using this method we show that mammalian cells use HDR to tolerate DNA damage in their genome. Moreover, analysis of the tolerance of the UV light-induced 6-4 photoproduct, the tobacco smoke-induced benzo[a]pyrene-guanine adduct, and an artificial trimethylene insert shows that each of these three lesions is tolerated by both TLS and HDR. We also determined the specificity of nucleotide insertion opposite these lesions during TLS in human genomes. This unique method will be useful in elucidating the mechanism of DNA damage tolerance in mammalian chromosomes and their connection to pathological processes such as carcinogenesis. PMID:23530190

  3. Hsp90 induces increased genomic instability toward DNA-damaging agents by tuning down RAD53 transcription.

    PubMed

    Khurana, Nidhi; Laskar, Shyamasree; Bhattacharyya, Mrinal K; Bhattacharyya, Sunanda

    2016-08-01

    It is well documented that elevated body temperature causes tumors to regress upon radiotherapy. However, how hyperthermia induces DNA damage sensitivity is not clear. We show that a transient heat shock and particularly the concomitant induction of Hsp90 lead to increased genomic instability under DNA-damaging conditions. Using Saccharomyces cerevisiae as a model eukaryote, we demonstrate that elevated levels of Hsp90 attenuate efficient DNA damage signaling and dictate preferential use of the potentially mutagenic double-strand break repair pathway. We show that under normal physiological conditions, Hsp90 negatively regulates RAD53 transcription to suppress DNA damage checkpoint activation. However, under DNA damaging conditions, RAD53 is derepressed, and the increased level of Rad53p triggers an efficient DNA damage response. A higher abundance of Hsp90 causes increased transcriptional repression on RAD53 in a dose-dependent manner, which could not be fully derepressed even in the presence of DNA damage. Accordingly, cells behave like a rad53 loss-of-function mutant and show reduced NHEJ efficiency, with a drastic failure to up-regulate RAD51 expression and manifestly faster accumulation of CLN1 and CLN2 in DNA-damaged G1, cells leading to premature release from checkpoint arrest. We further demonstrate that Rad53 overexpression is able to rescue all of the aforementioned deleterious effects caused by Hsp90 overproduction. PMID:27307581

  4. Radiation hybrid maps of D-genome of Aegilops tauschii and their application in sequence assembly of large and complex plant genomes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The large and complex genome of bread wheat (Triticum aestivum L., ~17 Gb) requires high-resolution genome maps saturated with ordered markers to assist in anchoring and orienting BAC contigs/ sequence scaffolds for whole genome sequence assembly. Radiation hybrid (RH) mapping has proven to be an e...

  5. Inter- and intra-specific pan-genomes of Borrelia burgdorferi sensu lato: genome stability and adaptive radiation

    PubMed Central

    2013-01-01

    Background Lyme disease is caused by spirochete bacteria from the Borrelia burgdorferi sensu lato (B. burgdorferi s.l.) species complex. To reconstruct the evolution of B. burgdorferi s.l. and identify the genomic basis of its human virulence, we compared the genomes of 23 B. burgdorferi s.l. isolates from Europe and the United States, including B. burgdorferi sensu stricto (B. burgdorferi s.s., 14 isolates), B. afzelii (2), B. garinii (2), B. “bavariensis” (1), B. spielmanii (1), B. valaisiana (1), B. bissettii (1), and B. “finlandensis” (1). Results Robust B. burgdorferi s.s. and B. burgdorferi s.l. phylogenies were obtained using genome-wide single-nucleotide polymorphisms, despite recombination. Phylogeny-based pan-genome analysis showed that the rate of gene acquisition was higher between species than within species, suggesting adaptive speciation. Strong positive natural selection drives the sequence evolution of lipoproteins, including chromosomally-encoded genes 0102 and 0404, cp26-encoded ospC and b08, and lp54-encoded dbpA, a07, a22, a33, a53, a65. Computer simulations predicted rapid adaptive radiation of genomic groups as population size increases. Conclusions Intra- and inter-specific pan-genome sizes of B. burgdorferi s.l. expand linearly with phylogenetic diversity. Yet gene-acquisition rates in B. burgdorferi s.l. are among the lowest in bacterial pathogens, resulting in high genome stability and few lineage-specific genes. Genome adaptation of B. burgdorferi s.l. is driven predominantly by copy-number and sequence variations of lipoprotein genes. New genomic groups are likely to emerge if the current trend of B. burgdorferi s.l. population expansion continues. PMID:24112474

  6. Characterization of genomic alterations in radiation-associated breast cancer among childhood cancer survivors, using comparative genomic hybridization (CGH) arrays.

    PubMed

    Yang, Xiaohong R; Killian, J Keith; Hammond, Sue; Burke, Laura S; Bennett, Hunter; Wang, Yonghong; Davis, Sean R; Strong, Louise C; Neglia, Joseph; Stovall, Marilyn; Weathers, Rita E; Robison, Leslie L; Bhatia, Smita; Mabuchi, Kiyohiko; Inskip, Peter D; Meltzer, Paul

    2015-01-01

    Ionizing radiation is an established risk factor for breast cancer. Epidemiologic studies of radiation-exposed cohorts have been primarily descriptive; molecular events responsible for the development of radiation-associated breast cancer have not been elucidated. In this study, we used array comparative genomic hybridization (array-CGH) to characterize genome-wide copy number changes in breast tumors collected in the Childhood Cancer Survivor Study (CCSS). Array-CGH data were obtained from 32 cases who developed a second primary breast cancer following chest irradiation at early ages for the treatment of their first cancers, mostly Hodgkin lymphoma. The majority of these cases developed breast cancer before age 45 (91%, n = 29), had invasive ductal tumors (81%, n = 26), estrogen receptor (ER)-positive staining (68%, n = 19 out of 28), and high proliferation as indicated by high Ki-67 staining (77%, n = 17 out of 22). Genomic regions with low-copy number gains and losses and high-level amplifications were similar to what has been reported in sporadic breast tumors, however, the frequency of amplifications of the 17q12 region containing human epidermal growth factor receptor 2 (HER2) was much higher among CCSS cases (38%, n = 12). Our findings suggest that second primary breast cancers in CCSS were enriched for an "amplifier" genomic subgroup with highly proliferative breast tumors. Future investigation in a larger irradiated cohort will be needed to confirm our findings. PMID:25764003

  7. Sirtuin 7 promotes cellular survival following genomic stress by attenuation of DNA damage, SAPK activation and p53 response

    SciTech Connect

    Kiran, Shashi; Oddi, Vineesha; Ramakrishna, Gayatri

    2015-02-01

    Maintaining the genomic integrity is a constant challenge in proliferating cells. Amongst various proteins involved in this process, Sirtuins play a key role in DNA damage repair mechanisms in yeast as well as mammals. In the present work we report the role of one of the least explored Sirtuin viz., SIRT7, under conditions of genomic stress when treated with doxorubicin. Knockdown of SIRT7 sensitized osteosarcoma (U2OS) cells to DNA damage induced cell death by doxorubicin. SIRT7 overexpression in NIH3T3 delayed cell cycle progression by causing delay in G1 to S transition. SIRT7 overexpressing cells when treated with low dose of doxorubicin (0.25 µM) showed delayed onset of senescence, lesser accumulation of DNA damage marker γH2AX and lowered levels of growth arrest markers viz., p53 and p21 when compared to doxorubicin treated control GFP expressing cells. Resistance to DNA damage following SIRT7 overexpression was also evident by EdU incorporation studies where cellular growth arrest was significantly delayed. When treated with higher dose of doxorubicin (>1 µM), SIRT7 conferred resistance to apoptosis by attenuating stress activated kinases (SAPK viz., p38 and JNK) and p53 response thereby shifting the cellular fate towards senescence. Interestingly, relocalization of SIRT7 from nucleolus to nucleoplasm together with its co-localization with SAPK was an important feature associated with DNA damage. SIRT7 mediated resistance to doxorubicin induced apoptosis and senescence was lost when p53 level was restored by nutlin treatment. Overall, we propose SIRT7 attenuates DNA damage, SAPK activation and p53 response thereby promoting cellular survival under conditions of genomic stress. - Highlights: • Knockdown of SIRT7 sensitized cells to DNA damage induced apoptosis. • SIRT7 delayed onset of premature senescence by attenuating DNA damage response. • Overexpression of SIRT7 delayed cell cycle progression by delaying G1/S transition. • Upon DNA damage SIRT

  8. A high-resolution radiation hybrid map of the bovine genome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We are building high-resolution radiation hybrid maps of all 29 bovine autosomes and chromosome X, using a 58,000-marker genotyping assay, and a 12,000-rad whole-genome radiation hybrid (RH) panel. To accommodate the large number of markers, and to automate the map building procedure, a software pip...

  9. Nanocrystal Ghosting: Extensive radiation damage in MgO induced by low-energy electrons

    NASA Astrophysics Data System (ADS)

    Sawyer, William; Frankenfield, Zachery; Kane, Kenneth

    Radiation damage in magnesium oxide has been an ongoing source of investigation. Early work was motivated by its simple cubic structure and its excellent electrical insulating properties over a wide range of temperatures and mechanical conditions. The goal was to determine its suitability as an electrical insulator in radiation intense environments including nuclear reactors and proposed nuclear fusion devices. During this period experimental results for irradiation of MgO using electrons with energies less than 500 keV produced very limited damage. These results, supported by theoretical arguments, lead to the conclusion that MgO was relatively impervious to damage from electrons with energies below this threshold. More recently its excellent insulating properties and relative mechanical stability combined with an increased interest in nanomaterials applications have created renewed interest in MgO. In this paper direct evidence is presented for extensive radiation damage in MgO nanocrystals from intense irradiation by electrons (2 x 10 4electrons/nm2 sec) with beam energies between 120 keV and 60 keV.

  10. The interaction of melanin with ionizing and UVC radiations: Characterization of thymine damage

    SciTech Connect

    Huselton, C.A.

    1988-01-01

    These studies were undertaken to determine whether melanin could protect DNA against the harmful effects of ionizing or UVC radiations. A simple, in vitro, model system was developed to evaluate eumelanin (Sigma melanin) as a radioprotector of solutions of 0.1 mM thymine or thymidine exposed to 570Gy of ionizing radiation. Sigma melanin was compared to several amino acids, other biomolecules or to other forms of melanin. To investigate the role of melanin as a passive screen of UVC radiation, melanotic (I{sub 3}), amelanotic (AMEL) cells (both derived from a Cloudman S91 melanoma) and non-melanotic (EMT6) cells were labelled with radioactive dTHd and exposed to 0, 1, 5 or 10KJ/m{sup 2} of UVC. The DNA was extracted; the bases hydrolyzed with concentrated HCl. Thymine bases were separated by reverse phase HPLC. No difference in dimer content was observed between I{sub 3} and AMEL cells, but EMT6 cells had nearly twice the amount of dimer. Overall thymine degradation was more pronounced in I{sub 3} cells than in the other two cell lines, due to the production of non-dimer thymine damage. This damage was identified as thymine glycol by HPLC and mass spectrometry. Melanin, upon exposure to UVC, appears to enhance thymine damage by producing oxidative damage.

  11. Influence of ATM-Mediated DNA Damage Response on Genomic Variation in Human Induced Pluripotent Stem Cells.

    PubMed

    Lu, Junjie; Li, Hu; Baccei, Anna; Sasaki, Takayo; Gilbert, David M; Lerou, Paul H

    2016-05-01

    Genome instability is a potential limitation to the research and therapeutic application of induced pluripotent stem cells (iPSCs). Observed genomic variations reflect the combined activities of DNA damage, cellular DNA damage response (DDR), and selection pressure in culture. To understand the contribution of DDR on the distribution of copy number variations (CNVs) in iPSCs, we mapped CNVs of iPSCs with mutations in the central DDR gene ATM onto genome organization landscapes defined by genome-wide replication timing profiles. We show that following reprogramming the early and late replicating genome is differentially affected by CNVs in ATM-deficient iPSCs relative to wild-type iPSCs. Specifically, the early replicating regions had increased CNV losses during retroviral (RV) reprogramming. This differential CNV distribution was not present after later passage or after episomal reprogramming. Comparison of different reprogramming methods in the setting of defective DDR reveals unique vulnerability of early replicating open chromatin to RV vectors. PMID:26935587

  12. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

    DOE PAGESBeta

    Cheaito, Ramez; Gorham, Caroline S.; Carnegie Mellon Univ., Pittsburgh, PA; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

    2015-05-01

    The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacementmore » damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.« less

  13. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

    SciTech Connect

    Cheaito, Ramez; Gorham, Caroline S.; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

    2015-05-01

    The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacement damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.

  14. High and Low LET Radiation Differentially Induce Normal Tissue Damage Signals

    SciTech Connect

    Niemantsverdriet, Maarten; Goethem, Marc-Jan van; Bron, Reinier; Hogewerf, Wytse; Brandenburg, Sytze; Langendijk, Johannes A.; Luijk, Peter van; Coppes, Robert P.

    2012-07-15

    Purpose: Radiotherapy using high linear energy transfer (LET) radiation is aimed at efficiently killing tumor cells while minimizing dose (biological effective) to normal tissues to prevent toxicity. It is well established that high LET radiation results in lower cell survival per absorbed dose than low LET radiation. However, whether various mechanisms involved in the development of normal tissue damage may be regulated differentially is not known. Therefore the aim of this study was to investigate whether two actions related to normal tissue toxicity, p53-induced apoptosis and expression of the profibrotic gene PAI-1 (plasminogen activator inhibitor 1), are differentially induced by high and low LET radiation. Methods and Materials: Cells were irradiated with high LET carbon ions or low LET photons. Cell survival assays were performed, profibrotic PAI-1 expression was monitored by quantitative polymerase chain reaction, and apoptosis was assayed by annexin V staining. Activation of p53 by phosphorylation at serine 315 and serine 37 was monitored by Western blotting. Transfections of plasmids expressing p53 mutated at serines 315 and 37 were used to test the requirement of these residues for apoptosis and expression of PAI-1. Results: As expected, cell survival was lower and induction of apoptosis was higher in high -LET irradiated cells. Interestingly, induction of the profibrotic PAI-1 gene was similar with high and low LET radiation. In agreement with this finding, phosphorylation of p53 at serine 315 involved in PAI-1 expression was similar with high and low LET radiation, whereas phosphorylation of p53 at serine 37, involved in apoptosis induction, was much higher after high LET irradiation. Conclusions: Our results indicate that diverse mechanisms involved in the development of normal tissue damage may be differentially affected by high and low LET radiation. This may have consequences for the development and manifestation of normal tissue damage.

  15. Rapamycin‐induced autophagy sensitizes A549 cells to radiation associated with DNA damage repair inhibition

    PubMed Central

    Li, Yong; Liu, Fen; Wang, Yong; Li, Donghai; Guo, Fei; Xu, Liyao; Zeng, Zhengguo; Zhong, Xiaojun

    2016-01-01

    Abstract Background Autophagy has been reported to increase in cancer cells after radiation. However, it remains unknown whether increased autophagy as a result of radiation affects DNA damage repair and sensitizes cancer cells. In this study, the radiosensitization effect of rapamycin, a mammalian target of rapamycin inhibitor that induces autophagy, on human lung adenocarcinoma A549 cells was investigated. Methods A549 cells were treated with different concentrations of rapamycin. Cell viability was evaluated by methyl‐thiazolyl‐tetrazolium assay. Survival fraction values of A549 cells after radiotherapy were detected by colony formation assay. Autophagosome was observed by a transmission electron microscope. Furthermore, Western blot was employed to examine alterations in autophagy protein LC3 and p62, DNA damage protein γ–H2AX, and DNA damage repair proteins Rad51, Ku70, and Ku80. Rad51, Ku70, and Ku80 messenger ribonucleic acid (mRNA) expression levels were examined by real‐time polymerase chain reaction. Results Rapamycin suppressed A549 cell proliferation in dose and time‐dependent manners. An inhibitory concentration (IC) 10 dose of rapamycin could induce autophagy in A549 cells. Rapamycin combined with radiation significantly decreased the colony forming ability of cells, compared with rapamycin or radiation alone. Rapamycin and radiation combined increased γ–H2AX expression levels and decreased Rad51 and Ku80 expression levels, compared with single regimens. However, rapamycin treatment did not induce any change in Rad51, Ku70, and Ku80 mRNA levels, regardless of radiation. Conclusions These findings indicate that increasing autophagy sensitizes lung cancer cells to radiation. PMID:27385978

  16. Amelioration of radiation-induced hematopoietic and gastrointestinal damage by Ex-RAD® in mice

    PubMed Central

    Ghosh, Sanchita P.; Kulkarni, Shilpa; Perkins, Michael W.; Hieber, Kevin; Pessu, Roli L.; Gambles, Kristen; Maniar, Manoj; Kao, Tzu-Cheg; Seed, Thomas M.; Kumar, K. Sree

    2012-01-01

    The aim of the present study was to assess recovery from hematopoietic and gastrointestinal damage by Ex-RAD®, also known as ON01210.Na (4-carboxystyryl-4-chlorobenzylsulfone, sodium salt), after total body radiation. In our previous study, we reported that Ex-RAD, a small-molecule radioprotectant, enhances survival of mice exposed to gamma radiation, and prevents radiation-induced apoptosis as measured by the inhibition of radiation-induced protein 53 (p53) expression in cultured cells. We have expanded this study to determine best effective dose, dose-reduction factor (DRF), hematological and gastrointestinal protection, and in vivo inhibition of p53 signaling. A total of 500 mg/kg of Ex-RAD administered at 24 h and 15 min before radiation resulted in a DRF of 1.16. Ex-RAD ameliorated radiation-induced hematopoietic damage as monitored by the accelerated recovery of peripheral blood cells, and protection of granulocyte macrophage colony-forming units (GM-CFU) in bone marrow. Western blot analysis on spleen indicated that Ex-RAD treatment inhibited p53 phosphorylation. Ex-RAD treatment reduces terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay (TUNEL)-positive cells in jejunum compared with vehicle-treated mice after radiation injury. Finally, Ex-RAD preserved intestinal crypt cells compared with the vehicle control at 13 and 14 Gy. The results demonstrated that Ex-RAD ameliorates radiation-induced peripheral blood cell depletion, promotes bone marrow recovery, reduces p53 signaling in spleen and protects intestine from radiation injury. PMID:22843617

  17. From the Cover: Specific chemical and structural damage to proteins produced by synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Weik, Martin; Ravelli, Raimond B. G.; Kryger, Gitay; McSweeney, Sean; Raves, Maria L.; Harel, Michal; Gros, Piet; Silman, Israel; Kroon, Jan; Sussman, Joel L.

    2000-01-01

    Radiation damage is an inherent problem in x-ray crystallography. It usually is presumed to be nonspecific and manifested as a gradual decay in the overall quality of data obtained for a given crystal as data collection proceeds. Based on third-generation synchrotron x-ray data, collected at cryogenic temperatures, we show for the enzymes Torpedo californica acetylcholinesterase and hen egg white lysozyme that synchrotron radiation also can cause highly specific damage. Disulfide bridges break, and carboxyl groups of acidic residues lose their definition. Highly exposed carboxyls, and those in the active site of both enzymes, appear particularly susceptible. The catalytic triad residue, His-440, in acetylcholinesterase, also appears to be much more sensitive to radiation damage than other histidine residues. Our findings have direct practical implications for routine x-ray data collection at high-energy synchrotron sources. Furthermore, they provide a direct approach for studying the radiation chemistry of proteins and nucleic acids at a detailed, structural level and also may yield information concerning putative "weak links" in a given biological macromolecule, which may be of structural and functional significance.

  18. From electrons to stars : modelling and mitigation of radiation damage effects on astronomical CCDs

    NASA Astrophysics Data System (ADS)

    Prod'homme, Thibaut

    2011-11-01

    The work presented in this thesis is part of an on-going effort to understand and mitigate the effects of radiation damage in astronomical CCDs. My research was motivated by and took place in the challenging context of the European Space Agency's (ESA) astrometric mission, Gaia, for which radiation damage has been considered since its conception as one of the most important threats to its scientific performance. In this context my research focused primarily on the modelling of the effects of radiation-induced Charge Transfer Inefficiency (CTI) supported by the analysis of the experimental test data. I developed the most detailed model to date of CTI in CCDs that enables simulating the operation of irradiated devices (Chapter 2). Using this model I have been able to verify and enhance our current understanding of CTI as well as support the characterization of CCDs and the understanding of experimental results (Chapters 3 and 6). As part of this research I conducted the comprehensive re-assessment of the performance of Gaia taking into account radiation damage (Chapters 3 and 4). Finally I took part in the effort of countering CTI by elaborating, testing, and improving a forward modelling approach at the image processing level to mitigate the CTI effects on the Gaia easurements (Chapters 3 and 5), as well as test and explore the potential of a specific hardware mitigation tool (Chapter 6).

  19. New Modeling Approaches to Study DNA Damage by the Direct and Indirect Effects of Ionizing Radiation

    NASA Technical Reports Server (NTRS)

    Plante, Ianik; Cucinotta, Francis A.

    2012-01-01

    DNA is damaged both by the direct and indirect effects of radiation. In the direct effect, the DNA itself is ionized, whereas the indirect effect involves the radiolysis of the water molecules surrounding the DNA and the subsequent reaction of the DNA with radical products. While this problem has been studied for many years, many unknowns still exist. To study this problem, we have developed the computer code RITRACKS [1], which simulates the radiation track structure for heavy ions and electrons, calculating all energy deposition events and the coordinates of all species produced by the water radiolysis. In this work, we plan to simulate DNA damage by using the crystal structure of a nucleosome and calculations performed by RITRACKS. The energy deposition events are used to calculate the dose deposited in nanovolumes [2] and therefore can be used to simulate the direct effect of the radiation. Using the positions of the radiolytic species with a radiation chemistry code [3] it will be possible to simulate DNA damage by indirect effect. The simulation results can be compared with results from previous calculations such as the frequencies of simple and complex strand breaks [4] and with newer experimental data using surrogate markers of DNA double ]strand breaks such as . ]H2AX foci [5].

  20. [Use of vilosen in the treatment of radiation damage of the immune system].

    PubMed

    Tron'ko, M D; Sydorenko, D S; Bykova, L M; Goidash, M M; Boiko, M G; Synel'nikova, G L

    2001-01-01

    The possibility of vilosen usage for the immune system damage liquidation was studied. Rats obtained discrete rentgen irradiation during 1 month in the total dose of 4 Gr. Mice obtained internal 131I irradiation in a dose of 9.25 kBk/g. It was established that thymus and spleen masses, quantity of their cells, blood leukocytes and antibody production decreased by as external and internal irradiation. Irradiated animals treated with vilosen restored their immune system functional state partly or completely. The preparation was assumed to be used for the correction of immune system radiation damage. PMID:11296565

  1. Measuring DNA Damage and Repair in Mouse Splenocytes After Chronic In Vivo Exposure to Very Low Doses of Beta- and Gamma-Radiation.

    PubMed

    Flegal, Matthew; Blimkie, Melinda S; Wyatt, Heather; Bugden, Michelle; Surette, Joel; Klokov, Dmitry

    2015-01-01

    Low dose radiation exposure may produce a variety of biological effects that are different in quantity and quality from the effects produced by high radiation doses. Addressing questions related to environmental, occupational and public health safety in a proper and scientifically justified manner heavily relies on the ability to accurately measure the biological effects of low dose pollutants, such as ionizing radiation and chemical substances. DNA damage and repair are the most important early indicators of health risks due to their potential long term consequences, such as cancer. Here we describe a protocol to study the effect of chronic in vivo exposure to low doses of γ- and β-radiation on DNA damage and repair in mouse spleen cells. Using a commonly accepted marker of DNA double-strand breaks, phosphorylated histone H2AX called γH2AX, we demonstrate how it can be used to evaluate not only the levels of DNA damage, but also changes in the DNA repair capacity potentially produced by low dose in vivo exposures. Flow cytometry allows fast, accurate and reliable measurement of immunofluorescently labeled γH2AX in a large number of samples. DNA double-strand break repair can be evaluated by exposing extracted splenocytes to a challenging dose of 2 Gy to produce a sufficient number of DNA breaks to trigger repair and by measuring the induced (1 hr post-irradiation) and residual DNA damage (24 hrs post-irradiation). Residual DNA damage would be indicative of incomplete repair and the risk of long-term genomic instability and cancer. Combined with other assays and end-points that can easily be measured in such in vivo studies (e.g., chromosomal aberrations, micronuclei frequencies in bone marrow reticulocytes, gene expression, etc.), this approach allows an accurate and contextual evaluation of the biological effects of low level stressors. PMID:26168333

  2. Atomic and Molecular Data Needs for Radiation Damage Modeling: Multiscale Approach

    NASA Astrophysics Data System (ADS)

    Yakubovich, Alexander V.; Surdutovich, Eugene; Solov'yov, Andrey V.

    2011-05-01

    We present a brief overview of the multiscale approach towards understanding of the processes responsible for the radiation damage caused by energetic ions. This knowledge is very important, because it can be utilized in the ion-beam cancer therapy, which is one of the most advanced modern techniques to cure certain type of cancer. The central element of the multiscale approach is the theoretical evaluation and quantification of the DNA damage within cell environment. To achieve this goal one needs a significant amount of data on various atomic and molecular processes involved into the cascade of events starting with the ion entering and propagation in the biological medium and resulting in the DNA damage. The discussion of the follow up biological processes are beyond the scope of this brief overview. We consider different paths of the DNA damage and focus on the the illustration of the thermo-mechanical effects caused by the propagation of ions through the biological environment and in particular on the possibility of the creation of the shock waves in the vicinity of the ion tracks. We demonstrate that at the initial stages after ion's passage the shock wave is so strong that it can contribute to the DNA damage due to large pressure gradients developed at the distances of a few nanometers from the ionic tracks. This novel mechanism of the DNA damage provides an important contribution to the cumulative biodamage caused by low-energy secondary electrons, holes and free radicals.

  3. Atomic and Molecular Data Needs for Radiation Damage Modeling: Multiscale Approach

    SciTech Connect

    Yakubovich, Alexander V.; Solov'yov, Andrey V.; Surdutovich, Eugene

    2011-05-11

    We present a brief overview of the multiscale approach towards understanding of the processes responsible for the radiation damage caused by energetic ions. This knowledge is very important, because it can be utilized in the ion-beam cancer therapy, which is one of the most advanced modern techniques to cure certain type of cancer. The central element of the multiscale approach is the theoretical evaluation and quantification of the DNA damage within cell environment. To achieve this goal one needs a significant amount of data on various atomic and molecular processes involved into the cascade of events starting with the ion entering and propagation in the biological medium and resulting in the DNA damage. The discussion of the follow up biological processes are beyond the scope of this brief overview. We consider different paths of the DNA damage and focus on the the illustration of the thermo-mechanical effects caused by the propagation of ions through the biological environment and in particular on the possibility of the creation of the shock waves in the vicinity of the ion tracks. We demonstrate that at the initial stages after ion's passage the shock wave is so strong that it can contribute to the DNA damage due to large pressure gradients developed at the distances of a few nanometers from the ionic tracks. This novel mechanism of the DNA damage provides an important contribution to the cumulative biodamage caused by low-energy secondary electrons, holes and free radicals.

  4. Ideal sinks are not always ideal. Radiation damage accumulation in nanocomposites

    DOE PAGESBeta

    Uberuaga, Blas Pedro; Choudhury, Samrat; Caro, Alfredo

    2014-11-27

    Designing radiation tolerant materials is one of the primary challenges associated with advanced nuclear energy systems. One attractive route that has received much attention world-wide is to introduce a high density of sinks, often in the form of interfaces or secondary phases. Here, we develop a simple model of such nanocomposites and examine the ramifications of various factors on the overall radiation stability of the material. In particular, we determine how the distribution of secondary phases, the relative sink strength of those phases, and the irradiation temperature influence the radiation tolerance of the matrix. We find that the best scenariomore » is one in which the sinks have intermediate strength, transiently trapping defects before releasing them back into the matrix.This provides new insight into the optimal properties of nanocomposites for radiation damage environments.« less

  5. Mechanism for radiation damage resistance in yttrium oxide dispersion strengthened steels

    NASA Astrophysics Data System (ADS)

    Brodrick, J.; Hepburn, D. J.; Ackland, G. J.

    2014-02-01

    ODS steels based on yttrium oxide have been suggested as potential fusion reactor wall materials due to their observed radiation resistance properties. Presumably this radiation resistance can be related to the interaction of the particle with vacancies, self-interstitial atoms (SIAs) and other radiation damage debris. Density functional theory has been used to investigate this at the atomic scale. Four distinct interfaces, some based on HRTEM observations, between iron and yttrium oxide were investigated. It is been shown that the Y2O3-Fe interface acts as a strong trap with long-range attraction for both interstitial and vacancy defects, allowing recombination without altering the interface structure. The catalytic elimination of defects without change to the microstructure explains the improved behaviour of ODS steels with respect to radiation creep and swelling.

  6. Ideal sinks are not always ideal. Radiation damage accumulation in nanocomposites

    SciTech Connect

    Uberuaga, Blas Pedro; Choudhury, Samrat; Caro, Alfredo

    2014-11-27

    Designing radiation tolerant materials is one of the primary challenges associated with advanced nuclear energy systems. One attractive route that has received much attention world-wide is to introduce a high density of sinks, often in the form of interfaces or secondary phases. Here, we develop a simple model of such nanocomposites and examine the ramifications of various factors on the overall radiation stability of the material. In particular, we determine how the distribution of secondary phases, the relative sink strength of those phases, and the irradiation temperature influence the radiation tolerance of the matrix. We find that the best scenario is one in which the sinks have intermediate strength, transiently trapping defects before releasing them back into the matrix.This provides new insight into the optimal properties of nanocomposites for radiation damage environments.

  7. Radiation damage of PbWO 4 crystals due to irradiation by 60Co gamma rays

    NASA Astrophysics Data System (ADS)

    Kozma, Peter; Bajgar, Robert; Kozma, Petr

    2002-09-01

    Radiation resistivity of large tungstate crystals PbWO 4 from three suppliers has been studied for doses 10 4 Gy (10 6 rad) and 10 5 Gy (10 7 rad). Radiation resistivity was examined by the measurement of optical transmission through tungstate crystals before and after 60Co gamma-ray irradiations. The absolute degradation of transmission for 10 4 and 10 5 Gy doses at 480 nm wavelength of the peak emission of PbWO 4 doped with La 2+, was found to be lower than 12.3% and 14.2%, respectively. The results have been also compared with radiation hardness measurements for a large volume CeF 3 scintillation crystal. Complete recovery of radiation damage was observed between 10 and 15 days after irradiations.

  8. Nuclear radiation interference and damage effects in charged particle experiments for extended space missions.

    NASA Technical Reports Server (NTRS)

    Trainor, J. H.; Teegarden, B. J.

    1971-01-01

    Demonstration that meaningful galactic and solar cosmic radiation measurements can be carried out on deep space missions. The radioisotopic thermoelectric generators (RTGs) which must be used as a source of power and perhaps of heat are a problem, but with proper separation from the experiments, with orientation, and with some shielding the damage effects can be reduced to an acceptable level. The Pioneer spacecraft are crucial in that they are targeted at the heart of Jupiter's radiation belts, and should supply the details of those belts. The subsequent Grand Tour opportunities can be selected for those periods which result in larger distances of closest approach to Jupiter if necessary.

  9. Study of the effect of dose-rate on radiation-induced damage to human erythrocytes

    NASA Astrophysics Data System (ADS)

    Krokosz, Anita; Koziczak, Renata; Gonciarz, Marta; Szweda-Lewandowska, Zofia

    2006-01-01

    Human erythrocytes suspended in an isotonic Na-phosphate buffer, pH 7.4 (hematocrit of 2%) were irradiated with γ-rays at three dose-rates of 66.7, 36.7, 25 Gy min -1 in order to investigate the influence of the dose-rate on radiation-induced membrane damage, hemoglobin oxidation and loss of reduced glutathione. The obtained results showed that such processes as erythrocyte hemolysis, lipid and protein destruction depend on the radiation dose-rate. The parameter values describing these processes showed an inverse dose-rate effect.

  10. Radiation damage in undoped CsI and CsI(Tl)

    SciTech Connect

    Woody, C.L.; Kierstead, J.A.; Levy, P.W.; Stoll, S.

    1992-12-01

    Radiation damage has been studied in undoped CsI and CsI(TI) crystals using {sup 60}Co gamma radiation for doses up to {approximately} 4.2 {times} 10{sup 6}. Samples from various manufacturers were measured ranging in size from 2.54 cm long cylinders to a 30 cm long block. Measurements were made on the change in optical transmission and scintillation light output as a function of dose. Although some samples showed a small change in transmission, a significant change in light output was observed for all samples. Recovery from damage was also studied as a function of time and exposure to UV light. A short lived phosphorescence was observed in undoped CsI, similar to the phosphorescence seen in CsI(TI).

  11. Radiation damage in undoped CsI and CsI(Tl)

    SciTech Connect

    Woody, C.L.; Kierstead, J.A.; Levy, P.W.; Stoll, S.

    1992-01-01

    Radiation damage has been studied in undoped CsI and CsI(TI) crystals using [sup 60]Co gamma radiation for doses up to [approximately] 4.2 [times] 10[sup 6]. Samples from various manufacturers were measured ranging in size from 2.54 cm long cylinders to a 30 cm long block. Measurements were made on the change in optical transmission and scintillation light output as a function of dose. Although some samples showed a small change in transmission, a significant change in light output was observed for all samples. Recovery from damage was also studied as a function of time and exposure to UV light. A short lived phosphorescence was observed in undoped CsI, similar to the phosphorescence seen in CsI(TI).

  12. Exploring long-time response to radiation damage in MgO

    NASA Astrophysics Data System (ADS)

    Uberuaga, B. P.; Smith, R.; Cleave, A. R.; Henkelman, G.; Grimes, R. W.; Voter, A. F.; Sickafus, K. E.

    2005-01-01

    Using a variety of computational modeling and simulation methods, we examine the production and long-time evolution of damage created in irradiated MgO. We find that the damage produced in low energy (order 1 keV) collision cascades typically consists of point defects and small defect clusters. Over long times, interstitials annihilate with vacancies and aggregate with other interstitials, forming larger clusters that exhibit surprising behavior. For example, a six-atom interstitial cluster is found to have extremely high mobility. The implications of highly-mobile large clusters are explored via a rate theory model and comparison to other materials. We conclude that successful modeling of radiation damage evolution in MgO requires explicit treatment of large interstitial clusters.

  13. Low doses of ionizing radiation to mammalian cells may rather control than cause DNA damage

    SciTech Connect

    Feinendegen, L.E.; Bond, V.P.; Sondhaus, C.A.; Altman, K.I.

    1998-12-31

    This report examines the origin of tissue effects that may follow from different cellular responses to low-dose irradiation, using published data. Two principal categories of cellular responses are considered. One response category relates to the probability of radiation-induced DNA damage. The other category consists of low-dose induced metabolic changes that induce mechanisms of DNA damage mitigation, which do not operate at high levels of exposure. Modeled in this way, tissue is treated as a complex adaptive system. The interaction of the various cellular responses results in a net tissue dose-effect relation that is likely to deviate from linearity in the low-dose region. This suggests that the LNT hypothesis should be reexamined. This paper aims at demonstrating tissue effects as an expression of cellular responses, both damaging and defensive, in relation to the energy deposited in cell mass, by use of microdosimetric concepts.

  14. Topical vitamin C protects porcine skin from ultraviolet radiation-induced damage.

    PubMed

    Darr, D; Combs, S; Dunston, S; Manning, T; Pinnell, S

    1992-09-01

    Ultraviolet radiation damage to the skin is due, in part, to the generation of reactive oxygen species. Vitamin C (L-ascorbic acid) functions as a biological co-factor and antioxidant due to its reducing properties. Topical application of vitamin C has been shown to elevate significantly cutaneous levels of this vitamin in pigs, and this correlates with protection of the skin from UVB damage as measured by erythema and sunburn cell formation. This protection is biological and due to the reducing properties of the molecule. Further, we provide evidence that the vitamin C levels of the skin can be severely depleted after UV irradiation, which would lower this organ's innate protective mechanism as well as leaving it at risk of impaired healing after photoinduced damage. In addition, vitamin C protects porcine skin from UVA-mediated phototoxic reactions (PUVA) and therefore shows promise as a broad-spectrum photoprotectant. PMID:1390169

  15. The G2 checkpoint activated by DNA damage does not prevent genome instability in plant cells.

    PubMed

    Carballo, Jesús A; Pincheira, Juana; de la Torre, Consuelo

    2006-01-01

    Root growth, G2 length, and the frequency of aberrant mitoses and apoptotic nuclei were recorded after a single X-ray irradiation, ranging from 2.5 to 40 Gy, in Allium cepa L. root meristematic cells. After 72 h of recovery, root growth was reduced in a dose-dependent manner from 10 to 40 Gy, but not at 2.5 or 5 Gy doses. Flow cytometry plus TUNEL (TdT-mediated dUTP nick end labeling) showed that activation of apoptosis occurred only after 20 and 40 Gy of X-rays. Nevertheless, irrespective of the radiation dose, conventional flow cytometry showed that cells accumulated in G2 (4C DNA content). Simultaneously, the mitotic index fell, though a mitotic wave appeared later. Cell accumulation in G2 was transient and partially reversed by caffeine, thus it was checkpoint-dependent. Strikingly, the additional G2 time provided by this checkpoint was never long enough to complete DNA repair. Then, in all cases, some G2 cells with still-unrepaired DNA underwent checkpoint adaptation, i.e., they entered into the late mitotic wave with chromatid breaks. These cells and those produced by the breakage of chromosomal bridges in anaphase will reach the G1 of the next cell cycle unrepaired, ensuring the appearance of genome instability. PMID:16874408

  16. Measurement of DNA damage after exposure to 2450 MHz electromagnetic radiation.

    PubMed

    Malyapa, R S; Ahern, E W; Straube, W L; Moros, E G; Pickard, W F; Roti Roti, J L

    1997-12-01

    Recent reports suggest that exposure to 2450 MHz electromagnetic radiation causes DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) in cells of rat brain irradiated in vivo (Lai and Singh, Bioelectromagnetics 16, 207-210, 1995; Int. J. Radiat. Biol. 69, 513-521, 1996). Therefore, we endeavored to determine if exposure of cultured mammalian cells in vitro to 2450 MHz radiation causes DNA damage. The alkaline comet assay (single-cell gel electrophoresis), which is reportedly the most sensitive method to assay DNA damage in individual cells, was used to measure DNA damage after in vitro 2450 MHz irradiation. Exponentially growing U87MG and C3H 10T1/2 cells were exposed to 2450 MHz continuous-wave (CW) radiation in specially designed radial transmission lines (RTLs) that provided relatively uniform microwave exposure. Specific absorption rates (SARs) were calculated to be 0.7 and 1.9 W/kg. Temperatures in the RTLs were measured in real time and were maintained at 37 +/- 0.3 degrees C. Every experiment included sham exposure(s) in an RTL. Cells were irradiated for 2 h, 2 h followed by a 4-h incubation at 37 degrees C in an incubator, 4 h and 24 h. After these treatments samples were subjected to the alkaline comet assay as described by Olive et al. (Exp. Cell Res. 198, 259-267, 1992). Images of comets were digitized and analyzed using a PC-based image analysis system, and the "normalized comet moment" and "comet length" were determined. No significant differences were observed between the test group and the controls after exposure to 2450 MHz CW irradiation. Thus 2450 MHz irradiation does not appear to cause DNA damage in cultured mammalian cells under these exposure conditions as measured by this assay. PMID:9399707

  17. Neutron flux spectra and radiation damage parameters for the Russian Bor-60 and SM-2 reactors

    SciTech Connect

    Karasiov, A.V.; Greenwood, L.R.

    1995-04-01

    The objective is to compare neutron irradiation conditions in Russian reactors and similar US facilities. Neutron fluence and spectral information and calculated radiation damage parameters are presented for the BOR-60 (Fast Experimental Reactor - 60 MW) and SM-2 reactors in Russia. Their neutron exposure characteristics are comparable with those of the Experimental Breeder Reactor (ERB-II), the Fast Flux Test Facility (FFTF), and the High Flux Isotope Reactor (HFIR) in the United States.

  18. Space Photovoltaic Research and Technology 1983. High Efficiency, Radiation Damage, and Blanket Technology

    NASA Technical Reports Server (NTRS)

    1984-01-01

    This three day conference, sixth in a series that began in 1974, was held at the NASA Lewis Research Center on October 18-20, 1983. The conference provided a forum for the discussion of space photovoltaic systems, their research status, and program goals. Papers were presented and workshops were held in a variety of technology areas, including basic cell research, advanced blanket technology, and radiation damage.

  19. Performance characteristics and radiation damage results from the Fermilab E706 silicon microstrip detector system

    NASA Astrophysics Data System (ADS)

    Engels, E.; Mani, S.; Orris, D.; Shepard, P. F.; Weerasundara, P. D.; Choudhary, B. C.; Joshi, U.; Kapoor, V.; Shivpuri, R.; Baker, W.; Berg, D.; Carey, D.; Johnstone, C.; Nelson, C.; Bromberg, C.; Brown, D.; Huston, J.; Miller, R.; Nguyen, A.; Benson, R.; Lukens, P.; Ruddick, K.; Alverson, G.; Faissler, W.; Garelick, D.; Glaubman, M.; Kourbanis, I.; Lirakis, C.; Pothier, E.; Sinanidis, A.; Wu, G.-H.; Yasuda, T.; Yosef, C.; Easo, S.; Hartman, K.; Oh, B. Y.; Toothacker, W.; Whitmore, J.; Ballocchi, G.; Debarbaro, L.; Desoi, W.; Fanourakis, G.; Ferbel, T.; Ginther, G.; Gutierrez, P.; Lanaro, A.; Lobkowicz, F.; Mansour, J.; Pedeville, G.; Prebys, E.; Skow, D.; Slattery, P.; Varelas, N.; Zielinski, M.

    1989-07-01

    A charged particle spectrometer containing a 7120-channel silicon microstrip detector system, one component of Fermilab experiment E706 to study direct photon production in hadron-hadron collisions, was utilized in a run in which 6 million events were recorded. We describe the silicon system, provide early results of track and vertex reconstruction, and present data on the radiation damage to the silicon wafers resulting from the narrow high intensity beam.

  20. QUANTIFICATION OF ACTINIDE ALPHA-RADIATION DAMAGE IN MINERALS AND CERAMICS

    SciTech Connect

    Farnan, Ian E.; Cho, Herman M.; Weber, William J.

    2007-01-11

    There are large amounts of heavy alpha-emitters in nuclear waste and nuclear materials inventories stored in various sites around the world. These include plutonium and minor actinides such as americium and curium. In preparation for geological disposal there is a consensus that actinides that have been separated from spent nuclear fuel should be immobilised within mineral-based ceramics rather than glass. Over the long-term, the alpha-decay taking place in these ceramics will severely disrupt their crystalline structure and reduce their durability. A fundamental property in predicting cumulative radiation damage is the number of atoms permanently displaced per alpha–decay. Currently, this number is estimated as 1000-2000 atoms/alpha decay event. Here, we report nuclear magnetic resonance, spin-counting experiments that measure close to 5000 atoms/alpha decay event in radiation damaged natural zircons. New radiological NMR measurements on highly radioactive, 239Pu zircon show damage similar to that created by 238U and 232Th in mineral zircons at the same dose, indicating no significant effect of dose rate. Based on these measurements, the initially crystalline structure of a 10 wt% 239Pu zircon would be amorphous after only 1400 years in a geological repository. These measurements establish a basis for assessing the long-term structural durability of actinide-containing ceramics based on an atomistic understanding of the fundamental damage event.

  1. Recombinant Human Epidermal Growth Factor Accelerates Recovery of Mouse Small Intestinal Mucosa After Radiation Damage

    SciTech Connect

    Lee, Kang Kyoo; Jo, Hyang Jeong; Hong, Joon Pio; Lee, Sang-wook Sohn, Jung Sook; Moon, Soo Young; Yang, Sei Hoon; Shim, Hyeok; Lee, Sang Ho; Ryu, Seung-Hee; Moon, Sun Rock

    2008-07-15

    Purpose: To determine whether systemically administered recombinant human epidermal growth factor (rhEGF) accelerates the recovery of mouse small intestinal mucosa after irradiation. Methods and Materials: A mouse mucosal damage model was established by administering radiation to male BALB/c mice with a single dose of 15 Gy applied to the abdomen. After irradiation, rhEGF was administered subcutaneously at various doses (0.04, 0.2, 1.0, and 5.0 mg/kg/day) eight times at 2- to 3-day intervals. The evaluation methods included histologic changes of small intestinal mucosa, change in body weight, frequency of diarrhea, and survival rate. Results: The recovery of small intestinal mucosa after irradiation was significantly improved in the mice treated with a high dose of rhEGF. In the mice that underwent irradiation without rhEGF treatment, intestinal mucosal ulceration, mucosal layer damage, and severe inflammation occurred. The regeneration of villi was noticeable in mice treated with more than 0.2 mg/kg rhEGF, and the villi recovered fully in mice given more than 1 mg/kg rhEGF. The frequency of diarrhea persisting for more than 3 days was significantly greater in the radiation control group than in the rhEGF-treated groups. Conclusions: Systemic administration of rhEGF accelerates recovery from mucosal damage induced by irradiation. We suggest that rhEGF treatment shows promise for the reduction of small intestinal damage after irradiation.

  2. Assessment of Radiation Damage to the Structural Material of EAST Tokamak

    NASA Astrophysics Data System (ADS)

    Chen, Yixue; Wu, Yican

    2005-08-01

    Radiation damage to structural material of fusion facilities is of high concern for safety. The superconducting tokamak EAST will conduct D-D plasma experiments with the neutron production of 1015 neutrons per second. To evaluate the material radiation damage a programme system has been devised with the Monte Carlo transport code MCNP-4C, the inventory code FISPACT99, a specific interface, and the fusion evaluated nuclear data library FENDL-2. The key nuclear responses, i.e. fast neutron flux, displacement per atom, and the helium and hydrogen production, are calculated for the structural material SS-316L of the first wall, and the vacuum vessel, using this programme. The results demonstrate that the radiation damage to the structural material is so little that it will not lead to any significant change of material properties according to the reference design. This indicates that there is a large potential space for EAST to test advanced operation regime from the viewpoint of structural material safety.

  3. Summary of the radiation damage studies of the SDC dopants in polystyrene

    SciTech Connect

    Pla-Dalmau, A.; Foster, G.W.; Zhang, G.

    1993-12-22

    Approximately 80 commercially available fluorescent organic compounds were studied as dopants in a polystyrene matrix for possible use in wavelength shifting (WLS) fibers. The goal was to find a new green- emitting WLS fiber which would outperform in light yield and decay time the currently available fiber doped with K-27. Therefore the fluorescent compounds of interest should exhibit the following spectroscopic characteristics in polystyrene: {lambda}{sub abs} = 400--450 nm,{lambda}{sub em} = 450--550 nm, {tau} = 3--7 ns and quantum efficiency of minimum 0.7. Polystyrene samples doped with different fluorescent compounds were prepared and characterized. Of all the compounds tested, only a series of coumarins exhibited the spectroscopic characteristics of interest. Radiation damage studies had to be performed on these samples in order to condusively determine if they were better candidates than K-27 for green WLS fibers. AU samples except those showing opacity or deep coloration were irradiated. They were, however, separated in two sets. Radiation damage set No. 20 was mainly formed by the coumarin derivatives. Radiation damage set No. 22 was based on the remaining samples. The irradiations were performed at the Phoenix Memorial Laboratory using a {sup 60}Co source. Both sets were exposed to a total dose of 10 Mrad in air, at a dose rate of 1.8 Mrad/h. Transmittance measurements were recorded before and after irradiation, and after annealing. After irradiation, the samples were annealed in oxygen to accelerate the recovery process.

  4. Radiation damage and luminescence properties of gamma aluminum oxynitride transparent ceramic

    NASA Astrophysics Data System (ADS)

    Du, Xinhua; Yao, Shiyue; Jin, Xihai; Chen, Haohong; Li, Weifeng; Liang, Bo

    2015-09-01

    This paper reports on the radiation damage of gamma aluminum oxynitride (γ-AlON) transparent ceramic, which remarkably degrades UV-vis transparency and hence limits its applications in optoelectronic devices. The radiation-induced optical absorption of the as-sintered γ-AlON consists of at least two subbands: one is in the UV region with a peak at 270 nm and the other optical absorption band centers at 550 nm, covering the whole visible light spectrum, which makes the sample colored. Interestingly, all the radiation-induced color centers can be completely ‘bleached’ by low temperature annealing. In the thermoluminescence curve, we observed a broad luminescence in the range of 25-300 °C with the peak at 120 °C. Furthermore, the x-ray excited luminescence spectra revealed that there exist multiple emission centers in the γ-AlON. Based on this experimental fact, the radiation damage and luminescent mechanisms were studied. These optical properties of the γ-AlON are considered to be related to defect states. In the as-sintered γ-AlON, charge balancing is realized by the co-existence of \\text{V}\\text{Al}\\prime\\prime \\prime and \\text{O}\\text{N}\\bullet , and the predominant defect form is ≤ft[\\text{V}\\text{Al}\\prime\\prime \\prime-\\text{3O}\\text{N}\\bullet\\right] , which is optically inactive and no optical absorption occurs. However, isolated \\text{V}\\text{Al}\\prime\\prime \\prime and \\text{O}\\text{N}\\bullet can be formed by irradiation and it is these that are responsible for the radiation damage of γ-AlON transparent ceramic. In the end, the UV absorption and visible-light absorption in the irradiated sample were ascribed to VAl-related and ON-related intrinsic defects, respectively.

  5. Dissecting the molecular mechanism of ionizing radiation-induced tissue damage in the feather follicle.

    PubMed

    Chen, Xi; Liao, Chunyan; Chu, Qiqi; Zhou, Guixuan; Lin, Xiang; Li, Xiaobo; Lu, Haijie; Xu, Benhua; Yue, Zhicao

    2014-01-01

    Ionizing radiation (IR) is a common therapeutic agent in cancer therapy. It damages normal tissue and causes side effects including dermatitis and mucositis. Here we use the feather follicle as a model to investigate the mechanism of IR-induced tissue damage, because any perturbation of feather growth will be clearly recorded in its regular yet complex morphology. We find that IR induces defects in feather formation in a dose-dependent manner. No abnormality was observed at 5 Gy. A transient, reversible perturbation of feather growth was induced at 10 Gy, leading to defects in the feather structure. This perturbation became irreversible at 20 Gy. Molecular and cellular analysis revealed P53 activation, DNA damage and repair, cell cycle arrest and apoptosis in the pathobiology. IR also induces patterning defects in feather formation, with disrupted branching morphogenesis. This perturbation is mediated by cytokine production and Stat1 activation, as manipulation of cytokine levels or ectopic Stat1 over-expression also led to irregular feather branching. Furthermore, AG-490, a chemical inhibitor of Stat1 signaling, can partially rescue IR-induced tissue damage. Our results suggest that the feather follicle could serve as a useful model to address the in vivo impact of the many mechanisms of IR-induced tissue damage. PMID:24586618

  6. Inactivation of NADPH Oxidases NOX4 and NOX5 Protects Human Primary Fibroblasts from Ionizing Radiation-Induced DNA Damage

    PubMed Central

    Weyemi, Urbain; Redon, Christophe E.; Aziz, Towqir; Choudhuri, Rohini; Maeda, Daisuke; Parekh, Palak R.; Bonner, Michael Y.; Arbiser, Jack L.; Bonner, William M.

    2015-01-01

    Human exposure to ionizing radiation from medical procedures has increased sharply in the last three decades. Recent epidemiological studies suggest a direct relationship between exposure to ionizing radiation and health problems, including cancer incidence. Therefore, minimizing the impact of radiation exposure in patients has become a priority in the development of future clinical practices. Crucial players in radiation-induced DNA damage include reactive oxygen species (ROS), but the sources of these have remained elusive. To the best of our knowledge, we show here for the first time that two members of the ROS-generating NADPH oxidase family (NOXs), NOX4 and NOX5, are involved in radiation-induced DNA damage. Depleting these two NOXs in human primary fibroblasts resulted in reduced levels of DNA damage as measured by levels of radiation-induced foci, a marker of DNA double-strand breaks (DSBs) and the comet assay coupled with increased cell survival. NOX involvement was substantiated with fulvene-5, a NOXs-specific inhibitor. Moreover, fulvene-5 mitigated radiation-induced DNA damage in human peripheral blood mononuclear cells ex vivo. Our results provide evidence that the inactivation of NOXs protects cells from radiation-induced DNA damage and cell death. These findings suggest that NOXs inhibition may be considered as a future pharmacological target to help minimize the negative effects of radiation exposure for millions of patients each year. PMID:25706776

  7. Reduction of arsenite-enhanced ultraviolet radiation-induced DNA damage by supplemental zinc.

    PubMed

    Cooper, Karen L; King, Brenee S; Sandoval, Monica M; Liu, Ke Jian; Hudson, Laurie G

    2013-06-01

    Arsenic is a recognized human carcinogen and there is evidence that arsenic augments the carcinogenicity of DNA damaging agents such as ultraviolet radiation (UVR) thereby acting as a co-carcinogen. Inhibition of DNA repair is one proposed mechanism to account for the co-carcinogenic actions of arsenic. We and others find that arsenite interferes with the function of certain zinc finger DNA repair proteins. Furthermore, we reported that zinc reverses the effects of arsenite in cultured cells and a DNA repair target protein, poly (ADP-ribose) polymerase-1. In order to determine whether zinc ameliorates the effects of arsenite on UVR-induced DNA damage in human keratinocytes and in an in vivo model, normal human epidermal keratinocytes and SKH-1 hairless mice were exposed to arsenite, zinc or both before solar-simulated (ss) UVR exposure. Poly (ADP-ribose) polymerase activity, DNA damage and mutation frequencies at the Hprt locus were measured in each treatment group in normal human keratinocytes. DNA damage was assessed in vivo by immunohistochemical staining of skin sections isolated from SKH-1 hairless mice. Cell-based findings demonstrate that ssUVR-induced DNA damage and mutagenesis are enhanced by arsenite, and supplemental zinc partially reverses the arsenite effect. In vivo studies confirm that zinc supplementation decreases arsenite-enhanced DNA damage in response to ssUVR exposure. From these data we can conclude that zinc offsets the impact of arsenic on ssUVR-stimulated DNA damage in cells and in vivo suggesting that zinc supplementation may provide a strategy to improve DNA repair capacity in arsenic exposed human populations. PMID:23523584

  8. Radiation damage characterization in reactor pressure vessel steels with nonlinear ultrasound

    SciTech Connect

    Matlack, K. H.; Kim, J.-Y.; Wall, J. J.; Qu, J.; Jacobs, L. J.

    2014-02-18

    Nuclear generation currently accounts for roughly 20% of the US baseload power generation. Yet, many US nuclear plants are entering their first period of life extension and older plants are currently undergoing assessment of technical basis to operate beyond 60 years. This means that critical components, such as the reactor pressure vessel (RPV), will be exposed to higher levels of radiation than they were originally intended to withstand. Radiation damage in reactor pressure vessel steels causes microstructural changes such as vacancy clusters, precipitates, dislocations, and interstitial loops that leave the material in an embrittled state. The development of a nondestructive evaluation technique to characterize the effect of radiation exposure on the properties of the RPV would allow estimation of the remaining integrity of the RPV with time. Recent research has shown that nonlinear ultrasound is sensitive to radiation damage. The physical effect monitored by nonlinear ultrasonic techniques is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave, arising from the interaction of the ultrasonic wave with microstructural features such as dislocations, precipitates, and their combinations. Current findings relating the measured acoustic nonlinearity parameter to increasing levels of neutron fluence for different representative RPV materials are presented.

  9. Ionizing radiation-induced DNA injury and damage detection in patients with breast cancer

    PubMed Central

    Borrego-Soto, Gissela; Ortiz-López, Rocío; Rojas-Martínez, Augusto

    2015-01-01

    Abstract Breast cancer is the most common malignancy in women. Radiotherapy is frequently used in patients with breast cancer, but some patients may be more susceptible to ionizing radiation, and increased exposure to radiation sources may be associated to radiation adverse events. This susceptibility may be related to deficiencies in DNA repair mechanisms that are activated after cell-radiation, which causes DNA damage, particularly DNA double strand breaks. Some of these genetic susceptibilities in DNA-repair mechanisms are implicated in the etiology of hereditary breast/ovarian cancer (pathologic mutations in the BRCA 1 and 2 genes), but other less penetrant variants in genes involved in sporadic breast cancer have been described. These same genetic susceptibilities may be involved in negative radiotherapeutic outcomes. For these reasons, it is necessary to implement methods for detecting patients who are susceptible to radiotherapy-related adverse events. This review discusses mechanisms of DNA damage and repair, genes related to these functions, and the diagnosis methods designed and under research for detection of breast cancer patients with increased radiosensitivity. PMID:26692152

  10. Repair of clustered DNA damage caused by high LET radiation in human fibroblasts

    NASA Technical Reports Server (NTRS)

    Rydberg, B.; Lobrich, M.; Cooper, P. K.; Chatterjee, A. (Principal Investigator)

    1998-01-01

    It has recently been demonstrated experimentally that DNA damage induced by high LET radiation in mammalian cells is non-randomly distributed along the DNA molecule in the form of clusters of various sizes. The sizes of such clusters range from a few base-pairs to at least 200 kilobase-pairs. The high biological efficiency of high LET radiation for induction of relevant biological endpoints is probably a consequence of this clustering, although the exact mechanisms by which the clustering affects the biological outcome is not known. We discuss here results for induction and repair of base damage, single-strand breaks and double-strand breaks for low and high LET radiations. These results are discussed in the context of clustering. Of particular interest is to determine how clustering at different scales affects overall rejoining and fidelity of rejoining of DNA double-strand breaks. However, existing methods for measuring repair of DNA strand breaks are unable to resolve breaks that are close together in a cluster. This causes problems in interpretation of current results from high LET radiation and will require new methods to be developed.

  11. Protective Effects of Polysaccharides from Soybean Meal Against X-ray Radiation Induced Damage in Mouse Spleen Lymphocytes

    PubMed Central

    Yao, Lei; Wang, Zhenyu; Zhao, Haitian; Cheng, Cuilin; Fu, Xiaoyi; Liu, Jiaren; Yang, Xin

    2011-01-01

    The aim of this study was to investigate radioprotective effect of the polysaccharides from soybean meal (SMP) against X-ray radiation-induced damage in mouse spleen lymphocytes. MTT and comet assay were performed to evaluate SMP’s ability to prevent cell death and DNA damage induced by radiation. The results show that, X-ray radiation (30 KV, 10 mA, 8 min (4 Gy)) can significantly increase cell death and DNA fragmentation of mouse spleen lymphocytes. Pretreatment with SMP for 2 h before radiation could increase cell viability, moreover, the SMP can reduce X-ray radiation-induced DNA damage. The percentage of tail DNA and the tail moment of the SMP groups were significantly lower than those of the radiation alone group (p < 0.05). These results suggest SMP may be a good candidate as a radioprotective agent. PMID:22174652

  12. Oxidative Lung Damage Resulting from Repeated Exposure to Radiation and Hyperoxia Associated with Space Exploration

    PubMed Central

    Pietrofesa, Ralph A; Turowski, Jason B; Arguiri, Evguenia; Milovanova, Tatyana N; Solomides, Charalambos C; Thom, Stephen R; Christofidou-Solomidou, Melpo

    2013-01-01

    Background Spaceflight missions may require crewmembers to conduct Extravehicular Activities (EVA) for repair, maintenance or scientific purposes. Pre-breathe protocols in preparation for an EVA entail 100% hyperoxia exposure that may last for a few hours (5-8 hours), and may be repeated 2-3 times weekly. Each EVA is associated with additional challenges such as low levels of total body cosmic/galactic radiation exposure that may present a threat to crewmember health and therefore, pose a threat to the success of the mission. We have developed a murine model of combined, hyperoxia and radiation exposure (double-hit) in the context of evaluating countermeasures to oxidative lung damage associated with space flight. In the current study, our objective was to characterize the early and chronic effects of repeated single and double-hit challenge on lung tissue using a novel murine model of repeated exposure to low-level total body radiation and hyperoxia. This is the first study of its kind evaluating lung damage relevant to space exploration in a rodent model. Methods Mouse cohorts (n=5-15/group) were exposed to repeated: a) normoxia; b) >95% O2 (O2); c) 0.25Gy single fraction gamma radiation (IR); or d) a combination of O2 and IR (O2+IR) given 3 times per week for 4 weeks. Lungs were evaluated for oxidative damage, active TGFβ1 levels, cell apoptosis, inflammation, injury, and fibrosis at 1, 2, 4, 8, 12, 16, and 20 weeks post-initiation of exposure. Results Mouse cohorts exposed to all challenge conditions displayed decreased bodyweight compared to untreated controls at 4 and 8 weeks post-challenge initiation. Chronic oxidative lung damage to lipids (malondialdehyde levels), DNA (TUNEL, cleaved Caspase 3, cleaved PARP positivity) leading to apoptotic cell death and to proteins (nitrotyrosine levels) was elevated all treatment groups. Importantly, significant systemic oxidative stress was also noted at the late phase in mouse plasma, BAL fluid, and urine. Importantly

  13. Dose Rate Effects on Damage and Recovery of Radiation Hard Glass Under Gamma Irradiation

    NASA Astrophysics Data System (ADS)

    Menchini, Francesca; Baccaro, Stefania; Cemmi, Alessia; di Sarcina, Ilaria; Fiore, Salvatore; Piegari, Angela

    2014-06-01

    Optical systems employed in space missions are subjected to high fluxes of energetic particles. Their optical properties should be stable throughout the whole mission, to avoid a possible failure of the experiments. Radiation hard glasses are widely used as substrates or windows in high-energy applications, due to their resistance in hostile environments where energetic particles and γ rays are present. In this work we have irradiated radiation resistant glass windows by γ rays from a 60Co source at several doses, from 50 to 3×l05 Gy, and at two different dose rates. The optical properties of the samples have been monitored and the effects of radiations have been measured. Moreover, a partial recovery of the damage has been observed after the end of irradiation. The effects depend on the irradiation dose rate.

  14. An evaluation of radiation damage to solid state components flown in low earth orbit satellites.

    PubMed

    Shin, Myung-Won; Kim, Myung-Hyun

    2004-01-01

    The effects of total ionising radiation dose upon commercial off-the-shelf semiconductors fitted to satellites operating in low Earth orbit (LEO) conditions was evaluated. The evaluation was performed for the Korea Institute of Technology SATellite-1, (KITSAT-1) which was equipped with commercial solid state components. Two approximate calculation models for space radiation shielding were developed. Verification was performed by comparing the results with detailed three-dimensional calculations using the Monte-Carlo method and measured data from KITSAT-1. It was confirmed that the developed approximate models were reliable for satellite shielding calculations. It was also found that commercial semiconductor devices, which were not radiation hardened, could be damaged within their lifetime due to the total ionising dose they are subject to in the LEO environment. To conclude, an intensive shielding analysis should be considered when commercial devices are used. PMID:15103058

  15. Stability of Radiation Induced Chromosome Damage in Human Peripheral Blood Lymphocytes

    NASA Technical Reports Server (NTRS)

    Cucinotta, F. A.; George, K.; Willingham, V.

    2006-01-01

    Chromosome damage in an individual's peripheral blood lymphocytes can be an indicator of radiation exposure and this data can be used to evaluate dose after accidental or occupational exposure. Evidence suggests that the yield of chromosome damage in lymphocytes is also a relevant biomarker of cancer risk in humans that reflects individual cancer susceptibility. It follows that biomonitoring studies can be used to uncover subjects who are particularly susceptible to radiation damage and therefore at higher risk of cancer. Translocations and other stable aberrations are commonly believed to persist in peripheral blood cells for many years after exposure, and it has been suggested that translocations can be used for assessing retrospective radiation doses or chronic exposures. However, recent investigations suggest that translocations might not always persist indefinitely. We measured chromosome aberrations in the blood lymphocytes of six astronauts before their respective missions of approximately 3 to 6 months onboard the international space station, and again at various intervals up to 5 years after flight. In samples collected a few days after return to earth, the yield of chromosome translocations had significantly increased compared with preflight values, and results indicate that biodosimetry estimates lie within the range expected from physical dosimetry. However, for five of the astronauts, follow up analysis revealed a temporal decline in translocations with half-lives ranging from 10 to 58 months. The yield of exchanges remained unchanged for the sixth astronaut during an observation period of 5 months post-flight. These results may indicate complications with the use of stable aberrations for retrospective dose reconstruction and could affect cancer risk predictions that are estimated from yields of chromosome damage obtained shortly after exposure.

  16. Spatiotemporal characterization of ionizing radiation induced DNA damage foci and their relation to chromatin organization

    SciTech Connect

    Costes, Sylvain V; Chiolo, Irene; Pluth, Janice M.; Barcellos-Hoff, Mary Helen; Jakob, Burkhard

    2009-09-15

    DNA damage sensing proteins have been shown to localize to the sites of DSB within seconds to minutes following ionizing radiation (IR) exposure, resulting in the formation of microscopically visible nuclear domains referred to as radiation-induced foci (RIF). This review characterizes the spatio-temporal properties of RIF at physiological doses, minutes to hours following exposure to ionizing radiation, and it proposes a model describing RIF formation and resolution as a function of radiation quality and nuclear densities. Discussion is limited to RIF formed by three interrelated proteins ATM (Ataxia telangiectasia mutated), 53BP1 (p53 binding protein 1) and ?H2AX (phosphorylated variant histone H2AX). Early post-IR, we propose that RIF mark chromatin reorganization, leading to a local nuclear scaffold rigid enough to keep broken DNA from diffusing away, but open enough to allow the repair machinery. We review data indicating clear kinetic and physical differences between RIF emerging from dense and uncondensed regions of the nucleus. At later time post-IR, we propose that persistent RIF observed days following exposure to ionizing radiation are nuclear ?scars? marking permanent disruption of the chromatin architecture. When DNA damage is resolved, such chromatin modifications should not necessarily lead to growth arrest and it has been shown that persistent RIF can replicate during mitosis. Thus, heritable persistent RIF spanning over tens of Mbp may affect the transcriptome of a large progeny of cells. This opens the door for a non DNA mutation-based mechanism of radiation-induced phenotypes.

  17. Intermediate structures in radiation damaged titanite (CaTiSiO5): a Raman spectroscopic study.

    PubMed

    Zhang, Ming; Salje, Ekhard K H; Redfern, Simon A T; Bismayer, Ulrich; Groat, Lee A

    2013-03-20

    Effects of radiation damage and thermal annealing on the crystal structure of natural titanite (CaTiSiO(5)) were studied using Raman spectroscopy. The results show that well crystallized natural titanites generally have the P2(1)/a structure at the unit cell level, in contrast to the A2/a symmetry reported previously. Radiation caused by naturally incorporated impurities (such as U and Th) leads to structural damage and amorphization in titanite, as evidenced by a significant loss of band intensity, spectral broadening and frequency shifts. Additional bands (e.g. near 574 and 650 cm(-1)) occur in weakly or partially metamict titanite due to the formation of an intermediate phase (with the A2/a symmetry). Raman spectra of titanite thermal glasses showed features different from those of metamict titanite, especially in the Ti-O and Si-O stretching regions. The effect of thermal annealing is strongly affected by the initial degrees of damage that the sample experienced. Weakly damaged titanite samples showed that annealing leads to a structural recovery, and the spectral patterns of these recovered crystals are consistent with the P2(1)/a symmetry. Highly damaged titanite starts to recrystallize into an A2/a phase near 700-800 K, and additional structural modification occurs when annealed at 1300-1400 K, which involves significant change in broad Ti-O features. However, in terms of bandwidths, the metamict samples are far from fully recovered even on being annealed at 1300-1400 K. PMID:23407062

  18. Global radiation damage at 300 and 260 K with dose rates approaching 1 MGy s{sup −1}

    SciTech Connect

    Warkentin, Matthew; Badeau, Ryan; Hopkins, Jesse B.; Mulichak, Anne M.; Keefe, Lisa J.; Thorne, Robert E.

    2012-02-01

    Approximately half of global radiation damage to thaumatin crystals can be outrun at 260 K if data are collected in less than 1 s. Global radiation damage to 19 thaumatin crystals has been measured using dose rates from 3 to 680 kGy s{sup −1}. At room temperature damage per unit dose appears to be roughly independent of dose rate, suggesting that the timescales for important damage processes are less than ∼1 s. However, at T = 260 K approximately half of the global damage manifested at dose rates of ∼10 kGy s{sup −1} can be outrun by collecting data at 680 kGy s{sup −1}. Appreciable sample-to-sample variability in global radiation sensitivity at fixed dose rate is observed. This variability cannot be accounted for by errors in dose calculation, crystal slippage or the size of the data sets in the assay.

  19. a Study of Biophysical Mechanisms of Damage by Ionizing Radiation to Mammalian Cells in Vitro.

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Zhang

    Available from UMI in association with The British Library. An extensive survey made of published survival data of damage by ionizing radiation to mammalian cells in vitro has led to the new conclusion that the damage is determined by the specific ionization or the mean free path between ionizing events along the charged particle tracks. The optimum damage is observed when the mean free path is equivalent to the DNA double strand spacing of 1.8 nm. Therefore, the biological mechanism of ionizing radiation to mammalian cells in vitro is intra track dominant. A 100 keV electron accelerator has been constructed and commissioned to produce a broad beam irradiation field of greater than 1 cm diameter. The fluence rate may be adjusted from 10^8cm^ {-2}sec^{-1} downwards to enable further development as a chronic irradiation facility. Another new feature of the accelerator is that it incorporates a differential vacuum system which permits irradiation of the monolayer cell cultures to be carried out in normal pressure. Experiments of irradiation to Chinese hamster cells, by ^{241}Am alpha particles at low fluence rate, have supplied satisfactory data for testing a new DNA-rupture model which is under development. For V79 cells irradiated at a low fluence rate of 10^5cm^{ -2}min^{-1}, when survival data were fitted into the model, new biophysical parameters were extracted and a proposal was made that the repair phenomenon of cellular survival at very low doses is determined by three time factors: the irradiation time, the damage fixation time and the repair time. The values obtained were 3-4 hours for the mean repair time, and more than 10 hours for the damage to be considered permanent. Details of the monolayer cell culture technique developed and used in the present experiments are described. Consideration has been given to the significance of the results obtained from the study in radiation protection and in radiotherapy. In future studies it is recommended that more

  20. Study the radiation damage effects in Si microstrip detectors for future HEP experiments

    NASA Astrophysics Data System (ADS)

    Lalwani, Kavita; Jain, Geetika; Dalal, Ranjeet; Ranjan, Kirti; Bhardwaj, Ashutosh

    2016-07-01

    Silicon (Si) detectors are playing a key role in High Energy Physics (HEP) experiments due to their superior tracking capabilities. In future HEP experiments, like upgrade of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC), CERN, the silicon tracking detectors will be operated in a very intense radiation environment. This leads to both surface and bulk damage in Si detectors, which in turn will affect the operating performance of Si detectors. It is important to complement the measurements of the irradiated Si strip detectors with device simulation, which helps in understanding of both the device behavior and optimizing the design parameters needed for the future Si tracking system. An important ingredient of the device simulation is to develop a radiation damage model incorporating both bulk and surface damage. In this work, a simplified two-trap model is incorporated in device simulation to describe the type-inversion. Further, an extensive simulation of effective doping density as well as electric field profile is carried out at different temperatures for various fluences.

  1. Imaging of radiation damage using complementary field ion microscopy and atom probe tomography.

    PubMed

    Dagan, Michal; Hanna, Luke R; Xu, Alan; Roberts, Steve G; Smith, George D W; Gault, Baptiste; Edmondson, Philip D; Bagot, Paul A J; Moody, Michael P

    2015-12-01

    Radiation damage in tungsten and a tungsten-tantalum alloy, both of relevance to nuclear fusion research, has been characterized using a combination of field ion microscopy (FIM) imaging and atom probe tomography (APT). While APT provides 3D analytical imaging with sub-nanometer resolution, FIM is capable of imaging the arrangements of single atoms on a crystal lattice and has the potential to provide insights into radiation induced crystal damage, all the way down to its smallest manifestation--a single vacancy. This paper demonstrates the strength of combining these characterization techniques. In ion implanted tungsten, it was found that atomic scale lattice damage is best imaged using FIM. In certain cases, APT reveals an identifiable imprint in the data via the segregation of solute and impurities and trajectory aberrations. In a W-5at%Ta alloy, a combined APT-FIM study was able to determine the atomic distribution of tantalum inside the tungsten matrix. An indirect method was implemented to identify tantalum atoms inside the tungsten matrix in FIM images. By tracing irregularities in the evaporation sequence of atoms imaged with FIM, this method enables the benefit of FIM's atomic resolution in chemical distinction between the two species. PMID:25794822

  2. Energy Thresholds of DNA Damage Induced by UV Radiation: An XPS Study.

    PubMed

    Gomes, P J; Ferraria, A M; Botelho do Rego, A M; Hoffmann, S V; Ribeiro, P A; Raposo, M

    2015-04-30

    This work stresses on damage at the molecular level caused by ultraviolet radiation (UV) in the range from 3.5 to 8 eV, deoxyribonucleic acid (DNA) films observed by X-ray photoelectron spectroscopy (XPS). Detailed quantitative XPS analysis, in which all the amounts are relative to sodium-assumed not to be released from the samples, of the carbon, oxygen, and particularly, nitrogen components, reveals that irradiation leads to sugar degradation with CO-based compounds release for energies above 6.9 eV and decrease of nitrogen groups which are not involved in hydrogen bonding at energies above 4.2 eV. Also the phosphate groups are seen to decrease to energies above 4.2 eV. Analysis of XPS spectra allowed to conclude that the damage on bases peripheral nitrogen atoms are following the damage on phosphates. It suggests that very low kinetic energy photoelectrons are ejected from the DNA bases, as a result of UV light induced breaking of the phosphate ester groups which forms a transient anion with resonance formation and whereby most of the nitrogen DNA peripheral groups are removed. The degree of ionization of DNA was observed to increase with radiation energy, indicating that the ionized phosphate groups are kept unchanged. This result was interpreted by the shielding of phosphate groups caused by water molecules hydration near sodium atoms. PMID:25844940

  3. Molecular dynamics study of the bulk temperature effect on primary radiation damage in uranium dioxide

    NASA Astrophysics Data System (ADS)

    Martin, G.; Sabathier, C.; Wiktor, J.; Maillard, S.

    2015-06-01

    The effect of bulk temperature on the primary damage induced by a displacement cascade was investigated in uranium dioxide using classical molecular dynamics simulations. In this study, the Morelon potentials were used to model the middle-range interactions between the atoms that constitute the host matrix during the radiation events. Cascades were initiated by accelerating a uranium primary knock-on atom at 10keV inside a perfect UO2 lattice at a temperature between 700K and 1800K , a range which comprises in-pile temperatures of oxide fuels in light water reactors in standard operating conditions. Cascade overlap sequences were also simulated at 700K and 1400K in order to study the radiation damage accumulation in the oxide fuel. This study reveals the maximum damage level which the material can accommodate for decreases with the temperature. Furthermore the direct formation of vacancy clusters under irradiation is considerably slowed down above 1000K , notably during cascade overlap sequences.

  4. Prevention of UVB Radiation-induced Epidermal Damage by Expression of Heat Shock Protein 70*

    PubMed Central

    Matsuda, Minoru; Hoshino, Tatsuya; Yamashita, Yasuhiro; Tanaka, Ken-ichiro; Maji, Daisuke; Sato, Keizo; Adachi, Hiroaki; Sobue, Gen; Ihn, Hironobu; Funasaka, Yoko; Mizushima, Tohru

    2010-01-01

    Irradiation with UV light, especially UVB, causes epidermal damage via the induction of apoptosis, inflammatory responses, and DNA damage. Various stressors, including UV light, induce heat shock proteins (HSPs) and the induction, particularly that of HSP70, provides cellular resistance to such stressors. The anti-inflammatory activity of HSP70, such as its inhibition of nuclear factor kappa B (NF-κB), was recently revealed. These in vitro results suggest that HSP70 protects against UVB-induced epidermal damage. Here we tested this idea by using transgenic mice expressing HSP70 and cultured keratinocytes. Irradiation of wild-type mice with UVB caused epidermal damage such as induction of apoptosis, which was suppressed in transgenic mice expressing HSP70. UVB-induced apoptosis in cultured keratinocytes was suppressed by overexpression of HSP70. Irradiation of wild-type mice with UVB decreased the cutaneous level of IκB-α (an inhibitor of NF-κB) and increased the infiltration of leukocytes and levels of pro-inflammatory cytokines and chemokines in the epidermis. These inflammatory responses were suppressed in transgenic mice expressing HSP70. In vitro, the overexpression of HSP70 suppressed the expression of pro-inflammatory cytokines and chemokines and increased the level of IκB-α in keratinocytes irradiated with UVB. UVB induced an increase in cutaneous levels of cyclobutane pyrimidine dimers and 8-hydroxy-2′-deoxyguanosine, both of which were suppressed in transgenic mice expressing HSP70. This study provides genetic evidence that HSP70 protects the epidermis from UVB-induced radiation damage. The findings here also suggest that the protective action of HSP70 is mediated by anti-apoptotic, anti-inflammatory, and anti-DNA damage effects. PMID:20018843

  5. Persistence of Space Radiation Induced Cytogenetic Damage in the Blood Lymphocytes of Astronauts

    NASA Technical Reports Server (NTRS)

    George, Kerry; Cucinotta, Francis A.

    2008-01-01

    Cytogenetic damage in astronaut's peripheral blood lymphocytes is a useful in vivo marker of space radiation induced damage. Moreover, if radiation induced chromosome translocations persist in peripheral blood lymphocytes for many years, as has been assumed, they could potentially be used to measure retrospective doses or prolonged low dose rate exposures. However, as more data becomes available, evidence suggests that the yield of translocations may decline with time after exposure, at least in the case of space radiation exposures. We present our latest follow-up measurements of chromosome aberrations in astronauts blood lymphocytes assessed by FISH painting and collected a various times beginning directly after return from space to several years after flight. For most individuals the analysis of individual time-courses for translocations revealed a temporal decline of yields with different half-lives. Since the level of stable aberrations depends on the interplay between natural loss of circulating T-lymphocytes and replenishment from the stem or progenitor cells, the differences in the rates of decay could be explained by inter-individual variation in lymphocyte turn over. Biodosimetry estimates derived from cytogenetic analysis of samples collected a few days after return to earth lie within the range expected from physical dosimetry. However, a temporal decline in yields may indicate complications with the use of stable aberrations for retrospective dose reconstruction, and the differences in the decay time may reflect individual variability in risk from space radiation exposure. In addition, limited data on multiple flights show a lack of correlation between time in space and translocation yields. Data from one crewmember who has participated in two separate long-duration space missions and has been followed up for over 10 years provides limited information on the effect of repeat flights and show a possible adaptive response to space radiation exposure.

  6. Space Radiation Induced Cytogenetic Damage in the Blood Lymphocytes of Astronauts

    NASA Technical Reports Server (NTRS)

    George, K.; Cucinotta, F. A.

    2008-01-01

    Cytogenetic analysis of astronauts blood lymphocytes provides a direct in vivo measurement of space radiation damage, which takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. We present our latest analyses of chromosome damage in astronauts blood lymphocytes assessed by fluorescence in situ hybridization (FISH) chromosome painting and collected at various times beginning directly after return from space to several years after flight. Dose was derived from frequencies of chromosome exchanges using preflight calibration curves, and the Relative Biological Effect (RBE) was estimated by comparison with individually measured physically absorbed doses. Values for average RBE were compared to the average quality factor (Q), from direct measurements of the lineal energy spectra using a tissue-equivalent proportional counter (TEPC) and radiation transport codes. Results prove that cytogenetic biodosimetry analyses on blood collected within a week or two of return from space provides a reliable estimate of equivalent radiation dose and risk after protracted exposure to space radiation of a few months or more. However, data collected several months or years after flight suggests that the yield of chromosome translocations may decline with time after the mission, indicating that retrospective doses may be more difficult to estimate. In addition, limited data on multiple flights show a lack of correlation between time in space and translocation yields. Data from one crewmember, who has participated in two separate long-duration space missions and has been followed up for over 10 years, provide limited information on the effect of repeat flights and show a possible adaptive response to space radiation exposure.

  7. Influence of complex impurity centres on radiation damage in wide-gap metal oxides

    NASA Astrophysics Data System (ADS)

    Lushchik, A.; Lushchik, Ch.; Popov, A. I.; Schwartz, K.; Shablonin, E.; Vasil'chenko, E.

    2016-05-01

    Different mechanisms of radiation damage of wide-gap metal oxides as well as a dual influence of impurity ions on the efficiency of radiation damage have been considered on the example of binary ionic MgO and complex ionic-covalent Lu3Al5O12 single crystals. Particular emphasis has been placed on irradiation with ∼2 GeV heavy ions (197Au, 209Bi, 238U, fluence of 1012 ions/cm2) providing extremely high density of electronic excitations within ion tracks. Besides knock-out mechanism for Frenkel pair formation, the additional mechanism through the collapse of mobile discrete breathers at certain lattice places (e.g., complex impurity centres) leads to the creation of complex defects that involve a large number of host atoms. The experimental manifestations of the radiation creation of intrinsic and impurity antisite defects (Lu|Al or Ce|Al - a heavy ion in a wrong cation site) have been detected in LuAG and LuAG:Ce3+ single crystals. Light doping of LuAG causes a small enhancement of radiation resistance, while pair impurity centres (for instance, Ce|Lu-Ce|Al or Cr3+-Cr3+ in MgO) are formed with a rise of impurity concentration. These complex impurity centres as well as radiation-induced intrinsic antisite defects (Lu|Al strongly interacting with Lu in a regular site) tentatively serve as the places for breathers collapse, thus decreasing the material resistance against dense irradiation.

  8. Direct Radiation Damage to Crystalline DNA: What is the Source of Unaltered Base Release?

    PubMed Central

    Razskazovskiy, Yuriy; Debije, Michael G.; Bernhard, William A.

    2008-01-01

    The radiation chemical yields of unaltered base release have been measured in three crystalline double-stranded DNA oligomers after X irradiation at 4 K. The yields of released bases are between 10 and 20% of the total free radical yields measured at 4 K. Using these numbers, we estimate that the yield of DNA strand breaks due to the direct effect is about 0.1 μmol J−1. The damage responsible for base release is independent of the base type (C, G, A or T) and is not scavenged by anthracycline drugs intercalated in the DNA. For these reasons, reactions initiated by the hydroxyl radical have been ruled out as the source of base release. Since the intercalated anthracycline scavenges electrons and holes completely but does not inhibit base release, the possibility for damage transfer from the bases to the sugars can also be ruled out. The results are consistent with a model in which primary radical cations formed directly on the sugar-phosphate backbone react by two competing pathways: deprotonation, which localizes the damage on the sugar, and hole tunneling, which transfers the damage to the base stack. Quantitative estimates indicate that these two processes are approximately equally efficient. PMID:10761004

  9. Radiation damage of the PCO Pixelfly VGA CCD camera of the BES system on KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Náfrádi, Gábor; Kovácsik, Ákos; Pór, Gábor; Lampert, Máté; Un Nam, Yong; Zoletnik, Sándor

    2015-01-01

    A PCO Pixelfly VGA CCD camera which is part a of the Beam Emission Spectroscopy (BES) diagnostic system of the Korea Superconducting Tokamak Advanced Research (KSTAR) used for spatial calibrations, suffered from serious radiation damage, white pixel defects have been generated in it. The main goal of this work was to identify the origin of the radiation damage and to give solutions to avoid it. Monte Carlo N-Particle eXtended (MCNPX) model was built using Monte Carlo Modeling Interface Program (MCAM) and calculations were carried out to predict the neutron and gamma-ray fields in the camera position. Besides the MCNPX calculations pure gamma-ray irradiations of the CCD camera were carried out in the Training Reactor of BME. Before, during and after the irradiations numerous frames were taken with the camera with 5 s long exposure times. The evaluation of these frames showed that with the applied high gamma-ray dose (1.7 Gy) and dose rate levels (up to 2 Gy/h) the number of the white pixels did not increase. We have found that the origin of the white pixel generation was the neutron-induced thermal hopping of the electrons which means that in the future only neutron shielding is necessary around the CCD camera. Another solution could be to replace the CCD camera with a more radiation tolerant one for example with a suitable CMOS camera or apply both solutions simultaneously.

  10. [Induction of DNA damage in blood leucocytes and of cytogenetic injuries in bone marrow polychromatic erythrocytes in mice exposed to low-LET and high-LET radiation and in their progeny].

    PubMed

    Kuznetsova, E A; Zaichkina, S I; Sirota, N P; Abdullaev, S A; Rozanova, O M; Aptikaeva, G F; Sorokina, S S; Romanchenko, S P; Smirnova, E N

    2014-01-01

    The present work was aimed at studying the molecular and cellular levels of the response of the hematopoietic system in mice and their progeny to the action of low-LET and high-LET radiation at different times after exposure. The damage to the genome at the molecular level was assessed by the comet assay in peripheral blood leucocytes, whereas at the cellular level it was estimated by means of the micronuclear test in the marrow cells, after exposure of mice to X-radiation of 1, 3 and 5 Gy and to a high-LET low-intensity radiation at thedoses of 0.14 and 0.35 Gy, as well as to a combined effect of these types of radiation. When accessing the level of the DNA damage to individual cells by the comet assay, we also used, apart from a commonly accepted parameter %TDNA, additional characteristics: the proportions of leucocytes with an intact and highly fragmented DNA. Using these parameters, we detected the changes characterizing the dynamics of the leukocyte population in mouse blood at different times after the action of X-ray and high-LET radiation. It was found that: (1) the DNA damage increases with the dose of high-LET radiation; (2) the level of damage in the progeny of the animals exposed to high-LET radiation does not differ from that in unirradiated animals both at the molecular and cytogenetic levels; and (3) a decrease in the radiosensitivity of the progeny of the mice exposed to high-LET radiation at a dose of 0.35 Gy makes itself evident only at the molecular level, which may point to the possible transgeneration transmission of genomic lesions. PMID:25775822

  11. Trans-Differentiation of Neural Stem Cells: A Therapeutic Mechanism Against the Radiation Induced Brain Damage

    PubMed Central

    Kang, Bong Gu; Lee, Se Jeong; Kim, Kang Ho; Yang, Heekyoung; Lee, Young-Ae; Cho, Yu Jin; Im, Yong-Seok; Lee, Dong-Sup; Lim, Do-Hoon; Kim, Dong Hyun; Um, Hong-Duck; Lee, Sang-Hun; Lee, Jung-II; Nam, Do-Hyun

    2012-01-01

    Radiation therapy is an indispensable therapeutic modality for various brain diseases. Though endogenous neural stem cells (NSCs) would provide regenerative potential, many patients nevertheless suffer from radiation-induced brain damage. Accordingly, we tested beneficial effects of exogenous NSC supplementation using in vivo mouse models that received whole brain irradiation. Systemic supplementation of primarily cultured mouse fetal NSCs inhibited radiation-induced brain atrophy and thereby preserved brain functions such as short-term memory. Transplanted NSCs migrated to the irradiated brain and differentiated into neurons, astrocytes, or oligodendrocytes. In addition, neurotrophic factors such as NGF were significantly increased in the brain by NSCs, indicating that both paracrine and replacement effects could be the therapeutic mechanisms of NSCs. Interestingly, NSCs also differentiated into brain endothelial cells, which was accompanied by the restoration the cerebral blood flow that was reduced from the irradiation. Inhibition of the VEGF signaling reduced the migration and trans-differentiation of NSCs. Therefore, trans-differentiation of NSCs into brain endothelial cells by the VEGF signaling and the consequential restoration of the cerebral blood flow would also be one of the therapeutic mechanisms of NSCs. In summary, our data demonstrate that exogenous NSC supplementation could prevent radiation-induced functional loss of the brain. Therefore, successful combination of brain radiation therapy and NSC supplementation would provide a highly promising therapeutic option for patients with various brain diseases. PMID:22347993

  12. DNA base damage by reactive oxygen species, oxidizing agents, and UV radiation.

    PubMed

    Cadet, Jean; Wagner, J Richard

    2013-02-01

    Emphasis has been placed in this article dedicated to DNA damage on recent aspects of the formation and measurement of oxidatively generated damage in cellular DNA in order to provide a comprehensive and updated survey. This includes single pyrimidine and purine base lesions, intrastrand cross-links, purine 5',8-cyclonucleosides, DNA-protein adducts and interstrand cross-links formed by the reactions of either the nucleobases or the 2-deoxyribose moiety with the hydroxyl radical, one-electron oxidants, singlet oxygen, and hypochlorous acid. In addition, recent information concerning the mechanisms of formation, individual measurement, and repair-rate assessment of bipyrimidine photoproducts in isolated cells and human skin upon exposure to UVB radiation, UVA photons, or solar simulated light is critically reviewed. PMID:23378590

  13. DNA Base Damage by Reactive Oxygen Species, Oxidizing Agents, and UV Radiation

    PubMed Central

    Cadet, Jean; Wagner, J. Richard

    2013-01-01

    Emphasis has been placed in this article dedicated to DNA damage on recent aspects of the formation and measurement of oxidatively generated damage in cellular DNA in order to provide a comprehensive and updated survey. This includes single pyrimidine and purine base lesions, intrastrand cross-links, purine 5′,8-cyclonucleosides, DNA–protein adducts and interstrand cross-links formed by the reactions of either the nucleobases or the 2-deoxyribose moiety with the hydroxyl radical, one-electron oxidants, singlet oxygen, and hypochlorous acid. In addition, recent information concerning the mechanisms of formation, individual measurement, and repair-rate assessment of bipyrimidine photoproducts in isolated cells and human skin upon exposure to UVB radiation, UVA photons, or solar simulated light is critically reviewed. PMID:23378590

  14. Physical mapping resources for large plant genomes: radiation hybrids for wheat D-genome progenitor Aegilops tauschii

    PubMed Central

    2012-01-01

    Background Development of a high quality reference sequence is a daunting task in crops like wheat with large (~17Gb), highly repetitive (>80%) and polyploid genome. To achieve complete sequence assembly of such genomes, development of a high quality physical map is a necessary first step. However, due to the lack of recombination in certain regions of the chromosomes, genetic mapping, which uses recombination frequency to map marker loci, alone is not sufficient to develop high quality marker scaffolds for a sequence ready physical map. Radiation hybrid (RH) mapping, which uses radiation induced chromosomal breaks, has proven to be a successful approach for developing marker scaffolds for sequence assembly in animal systems. Here, the development and characterization of a RH panel for the mapping of D-genome of wheat progenitor Aegilops tauschii is reported. Results Radiation dosages of 350 and 450 Gy were optimized for seed irradiation of a synthetic hexaploid (AABBDD) wheat with the D-genome of Ae. tauschii accession AL8/78. The surviving plants after irradiation were crossed to durum wheat (AABB), to produce pentaploid RH1s (AABBD), which allows the simultaneous mapping of the whole D-genome. A panel of 1,510 RH1 plants was obtained, of which 592 plants were generated from the mature RH1 seeds, and 918 plants were rescued through embryo culture due to poor germination (<3%) of mature RH1 seeds. This panel showed a homogenous marker loss (2.1%) after screening with SSR markers uniformly covering all the D-genome chromosomes. Different marker systems mostly detected different lines with deletions. Using markers covering known distances, the mapping resolution of this RH panel was estimated to be <140kb. Analysis of only 16 RH lines carrying deletions on chromosome 2D resulted in a physical map with cM/cR ratio of 1:5.2 and 15 distinct bins. Additionally, with this small set of lines, almost all the tested ESTs could be mapped. A set of 399 most informative RH

  15. Electrode level Monte Carlo model of radiation damage effects on astronomical CCDs

    NASA Astrophysics Data System (ADS)

    Prod'homme, T.; Brown, A. G. A.; Lindegren, L.; Short, A. D. T.; Brown, S. W.

    2011-07-01

    Current optical space telescopes rely upon silicon charge-coupled devices (CCDs) to detect and image the incoming photons. The performance of a CCD detector depends on its ability to transfer electrons through the silicon efficiently, so that the signal from every pixel may be read out through a single amplifier. This process of electron transfer is highly susceptible to the effects of solar proton damage (or non-ionizing radiation damage). This is because charged particles passing through the CCD displace silicon atoms, introducing energy levels into the semiconductor band gap which act as localized electron traps. The reduction in charge transfer efficiency (CTE) leads to signal loss and image smearing. The European Space Agency's astrometric Gaia mission will make extensive use of CCDs to create the most complete and accurate stereoscopic map to date of the Milky Way. In the context of the Gaia mission CTE is referred to with the complementary quantity charge transfer inefficiency (CTI = 1-CTE). CTI is an extremely important issue that threatens Gaia's performances: the CCDs are very large so that the electrons need to be transferred a long way; the focal plane is also very large and difficult to shield; the mission will operate at second Lagrange point where the direct solar protons are highly energetic (penetrating) and the science requirements on image quality are very stringent. In order to tackle this issue, in depth experimental studies and modelling efforts are being conducted to explore the possible consequences and to mitigate the anticipated effects of radiation damage. We present here a detailed Monte Carlo model that has been developed to simulate the operation of a damaged CCD at the pixel electrode level. This model implements a new approach to both the charge density distribution within a pixel and the charge capture and release probabilities, which allows the reproduction of CTI effects on a variety of measurements for a large signal level range

  16. Quantification of actinide alpha-radiation damage in minerals and ceramics.

    PubMed

    Farnan, Ian; Cho, Herman; Weber, William J

    2007-01-11

    There are large amounts of heavy alpha-emitters in nuclear waste and nuclear materials inventories stored in various sites around the world. These include plutonium and minor actinides such as americium and curium. In preparation for geological disposal there is consensus that actinides that have been separated from spent nuclear fuel should be immobilized within mineral-based ceramics rather than glass because of their superior aqueous durability and lower risk of accidental criticality. However, in the long term, the alpha-decay taking place in these ceramics will severely disrupt their crystalline structure and reduce their durability. A fundamental property in predicting cumulative radiation damage is the number of atoms permanently displaced per alpha-decay. At present, this number is estimated to be 1,000-2,000 atoms/alpha in zircon. Here we report nuclear magnetic resonance, spin-counting experiments that measure close to 5,000 atoms/alpha in radiation-damaged natural zircons. New radiological nuclear magnetic resonance measurements on highly radioactive, 239Pu zircon show damage similar to that caused by 238U and 232Th in mineral zircons at the same dose, indicating no significant effect of half-life or loading levels (dose rate). On the basis of these measurements, the initially crystalline structure of a 10 weight per cent 239Pu zircon would be amorphous after only 1,400 years in a geological repository (desired immobilization timescales are of the order of 250,000 years). These measurements establish a basis for assessing the long-term structural durability of actinide-containing ceramics in terms of an atomistic understanding of the fundamental damage event. PMID:17215840

  17. Depletion of ATR selectively sensitizes ATM-deficient human mammary epithelial cells to ionizing radiation and DNA-damaging agents

    PubMed Central

    Cui, Yuxia; Palii, Stela S; Innes, Cynthia L; Paules, Richard S

    2014-01-01

    DNA damage response (DDR) to double strand breaks is coordinated by 3 phosphatidylinositol 3-kinase-related kinase (PIKK) family members: the ataxia-telangiectasia mutated kinase (ATM), the ATM and Rad3-related (ATR) kinase and the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs). ATM and ATR are central players in activating cell cycle checkpoints and function as an active barrier against genome instability and tumorigenesis in replicating cells. Loss of ATM function is frequently reported in various types of tumors, thus placing more reliance on ATR for checkpoint arrest and cell survival following DNA damage. To investigate the role of ATR in the G2/M checkpoint regulation in response to ionizing radiation (IR), particularly when ATM is deficient, cell lines deficient of ATM, ATR, or both were generated using a doxycycline-inducible lentiviral system. Our data suggests that while depletion of ATR or ATM alone in wild-type human mammary epithelial cell cultures (HME-CCs) has little effect on radiosensitivity or IR-induced G2/M checkpoint arrest, depletion of ATR in ATM-deficient cells causes synthetic lethality following IR, which correlates with severe G2/M checkpoint attenuation. ATR depletion also inhibits IR-induced autophagy, regardless of the ATM status, and enhances IR-induced apoptosis particularly when ATM is deficient. Collectively, our results clearly demonstrate that ATR function is required for the IR-induced G2/M checkpoint activation and subsequent survival of cells with ATM deficiency. The synthetic lethal interaction between ATM and ATR in response to IR supports ATR as a therapeutic target for improved anti-cancer regimens, especially in tumors with a dysfunctional ATM pathway. PMID:25483091

  18. Epigenetic dysregulation underlies radiation-induced transgenerational genome instability in vivo

    SciTech Connect

    Koturbash, Igor; Baker, Mike; Loree, Jonathan; Kutanzi, Kristy; Hudson, Darryl; Pogribny, Igor; Sedelnikova, Olga; Bonner, William; Kovalchuk, Olga . E-mail: olga.kovalchuk@uleth.ca

    2006-10-01

    Purpose: Although modern cancer radiation therapy has led to increased patient survival rates, the risk of radiation treatment-related complications is becoming a growing problem. Among various complications, radiation also poses a threat to the progeny of exposed parents. It causes transgenerational genome instability that is linked to transgenerational carcinogenesis. Although the occurrence of transgenerational genome instability, which manifests as elevated delayed and nontargeted mutation, has been well documented, the mechanisms by which it arises remain obscure. We hypothesized that epigenetic alterations may play a pivotal role in the molecular etiology of transgenerational genome instability. Methods and Materials: We studied the levels of cytosine DNA methylation in somatic tissues of unexposed offspring upon maternal, paternal, or combined parental exposure. Results: We observed a significant loss of global cytosine DNA methylation in the thymus tissue of the offspring upon combined parental exposure. The loss of DNA methylation was paralleled by a significant decrease in the levels of maintenance (DNMT1) and de novo methyltransferases DNMT3a and 3b and methyl-CpG-binding protein MeCP2. Along with profound changes in DNA methylation, we noted a significant accumulation of DNA strand breaks in thymus, which is a radiation carcinogenesis target organ. Conclusions: The observed changes were indicative of a profound epigenetic dysregulation in the offspring, which in turn could lead to genome destabilization and possibly could serve as precursor for transgenerational carcinogenesis. Future studies are clearly needed to address the cellular and carcinogenic repercussions of those changes.

  19. Exploiting radiation damage control on apatite (U Th)/He dates in cratonic regions

    NASA Astrophysics Data System (ADS)

    Flowers, Rebecca M.

    2009-01-01

    Apatites from four pairs of samples of Precambrian basement from the western Canadian shield were analyzed by (U-Th)/He thermochronometry to test for the influence of radiation damage on apatite (U-Th)/He dates in this cratonic region. Recent studies have demonstrated that the accumulation of radiation damage increases the apatite He retentivity, so that apatites with a span of effective U concentrations, eU, that experienced the same thermal history may be characterized by a range of closure temperatures. In this investigation, each sample pair consisted of a mafic dike cross-cutting felsic gneisses from a single outcrop or nearby outcrops that contained apatites with a span of eU. The apatites yielded (U-Th)/He dates from 846 to 123 Ma, and were positively correlated with eU within each sample pair. These results can be explained using a model that tracks the evolution of He mobility in response to the accumulation of radiation damage. When coupled with regional geological constraints, the data appear to require partial to complete He loss due to burial and reheating in Phanerozoic time. New apatite fission- track dates and length data were obtained for five of these samples. The apatite fission- track dates are Proterozoic regardless of apatite eU. Thermal history simulations indicate that the apatite fission-track data are compatible with the (U-Th)/He results, although the thermal histories are not identical in detail and the fission-track results alone do not require Phanerozoic heating. Together the data are consistent with burial of this region by ≥ 1 km of Phanerozoic strata that were subsequently denuded, thus pointing toward significant Phanerozoic deposition in the North American cratonic interior hundreds of kilometers east of where previously documented. The results suggest that exploiting radiation damage control on apatite (U-Th)/He dates through investigation of surface sample apatites with a span of closure temperatures can impose tighter

  20. Large-scale transient sensitivity analysis of a radiation damaged bipolar junction transistor.

    SciTech Connect

    Hoekstra, Robert John; Gay, David M.; Bartlett, Roscoe Ainsworth; Phipps, Eric Todd

    2007-11-01

    Automatic differentiation (AD) is useful in transient sensitivity analysis of a computational simulation of a bipolar junction transistor subject to radiation damage. We used forward-mode AD, implemented in a new Trilinos package called Sacado, to compute analytic derivatives for implicit time integration and forward sensitivity analysis. Sacado addresses element-based simulation codes written in C++ and works well with forward sensitivity analysis as implemented in the Trilinos time-integration package Rythmos. The forward sensitivity calculation is significantly more efficient and robust than finite differencing.

  1. Neutron Fluences and Radiation Damage Parameters for the HFIR-MFE-RB-17J Experiment

    SciTech Connect

    Greenwood, Lawrence R.; Glasgow, David C.; Baldwin, Charles A.

    2010-08-23

    The HFIR-MFE-RB-17J experiment was conducted in the removable beryllium (RB) position of HFIR with a Eu2O2 shield. The irradiation was conducted from April 27, 2004, to May 18, 2005. The total exposure was for 353.6 FPD (full power days). Reactor dosimetry capsules were analyzed and the activation data were used to provide the best estimates of the neutron fluences and radiation damage parameters as a function of height relative to midplane of the reactor.

  2. Molecular Mechanisms of Ultraviolet Radiation-Induced DNA Damage and Repair

    PubMed Central

    Rastogi, Rajesh P.; Richa; Kumar, Ashok; Tyagi, Madhu B.; Sinha, Rajeshwar P.

    2010-01-01

    DNA is one of the prime molecules, and its stability is of utmost importance for proper functioning and existence of all living systems. Genotoxic chemicals and radiations exert adverse effects on genome stability. Ultraviolet radiation (UVR) (mainly UV-B: 280–315 nm) is one of the powerful agents that can alter the normal state of life by inducing a variety of mutagenic and cytotoxic DNA lesions such as cyclobutane-pyrimidine dimers (CPDs), 6-4 photoproducts (6-4PPs), and their Dewar valence isomers as well as DNA strand breaks by interfering the genome integrity. To counteract these lesions, organisms have developed a number of highly conserved repair mechanisms such as photoreactivation, base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR). Additionally, double-strand break repair (by homologous recombination and nonhomologous end joining), SOS response, cell-cycle checkpoints, and programmed cell death (apoptosis) are also operative in various organisms with the expense of specific gene products. This review deals with UV-induced alterations in DNA and its maintenance by various repair mechanisms. PMID:21209706

  3. Radiation damage studies of cerium-doped radiation-resistant lead glass detectors

    NASA Astrophysics Data System (ADS)

    Adams, M. R.; Engelmann, R.; Grannis, P. D.; Horstkotte, J.; Godfrey, L.; Linn, S. L.; Marx, M. D.; Timms, J.; Tuts, P. M.; Willins, J.; Ahrens, L.; Aronson, S.; Levy, P. W.; Yamin, P.; Franzini, P.; Youssef, S.; Cutts, D.; Callas, J.

    1985-08-01

    Optical absorption measurements have been made on unirradiated and irradiated samples of cerium oxide doped lead silicate particle detector glasses. The addition of CeO 2 introduces one prominent and one weak absorption band near the ultraviolet transmission limit. However the CeO 2 greatly reduces the rate of formation of the radiation induced absorption. Detector size blocks of lead glass with 0.0, 0.25, and 1.2 weight percent CeO 2 were used to determine the energy resolution for 5 GeV electrons. The resolution deteriorates from 12 to 33% as the CeO 2 changes from 0.0 to 1.2%. At these CeO 2 levels, calculations indicate the yield of doped glass becomes superior to that of undoped glass for doses greater than 500 rad.

  4. Space Radiation Effects on Human Cells: Modeling DNA Breakage, DNA Damage Foci Distribution, Chromosomal Aberrations and Tissue Effects

    NASA Technical Reports Server (NTRS)

    Ponomarev, A. L.; Huff, J. L.; Cucinotta, F. A.

    2011-01-01

    Future long-tem space travel will face challenges from radiation concerns as the space environment poses health risk to humans in space from radiations with high biological efficiency and adverse post-flight long-term effects. Solar particles events may dramatically affect the crew performance, while Galactic Cosmic Rays will induce a chronic exposure to high-linear-energy-transfer (LET) particles. These types of radiation, not present on the ground level, can increase the probability of a fatal cancer later in astronaut life. No feasible shielding is possible from radiation in space, especially for the heavy ion component, as suggested solutions will require a dramatic increase in the mass of the mission. Our research group focuses on fundamental research and strategic analysis leading to better shielding design and to better understanding of the biological mechanisms of radiation damage. We present our recent effort to model DNA damage and tissue damage using computational models based on the physics of heavy ion radiation, DNA structure and DNA damage and repair in human cells. Our particular area of expertise include the clustered DNA damage from high-LET radiation, the visualization of DSBs (DNA double strand breaks) via DNA damage foci, image analysis and the statistics of the foci for different experimental situations, chromosomal aberration formation through DSB misrepair, the kinetics of DSB repair leading to a model-derived spectrum of chromosomal aberrations, and, finally, the simulation of human tissue and the pattern of apoptotic cell damage. This compendium of theoretical and experimental data sheds light on the complex nature of radiation interacting with human DNA, cells and tissues, which can lead to mutagenesis and carcinogenesis later in human life after the space mission.

  5. Radiation damage and annealing of lithium-doped silicon solar cells

    NASA Technical Reports Server (NTRS)

    Statler, R. L.

    1971-01-01

    Evidence has been presented that a lithium-diffused crucible-grown silicon solar cell can be made with better efficiency than the flight-quality n p 10 ohms-cm solar cell. When this lithium cell is exposed to a continuous radiation evironment at 60 C (electron spectrum from gamma rays) it has a higher power output than the N/P cell after a fluence equivalent to 1 MeV. A comparison of annealing of proton- and electron-damage in this lithium cell reveals a decidedly faster rate of recovery and higher level of recoverable power from the proton effects. Therefore, the lithium cell shows a good potential for many space missions where the proton flux is a significant fraction of the radiation field to be encountered.

  6. Ultraviolet radiation effects on the infrared damage rate of a thermal control coating

    NASA Technical Reports Server (NTRS)

    Bass, J. A.

    1972-01-01

    The effects of ultraviolet radiation on the infrared reflectance of ZnO silicone white thermal coatings were investigated. Narrow band ultraviolet radiation for wavelengths in the 2200A to 3500A range by a monochromator and a high pressure, 150-W Eimac xenon lamp. The sample was irradiated while in a vacuum of at least 0.000001 torr, and infrared reflectance was measured in situ with a spectroreflectometer at 19,500A. Reflectance degradation was studied as a function of wavelength, time, intensity, and dose. Damage was wavelength dependent at constant exposure, but no maximum was evident above the shortest wavelength investigated here. The degradation rate at constant intensity was an exponential function of time and varies with intensity.

  7. Infrared response measurements on radiation-damaged Si/Li/ detectors.

    NASA Technical Reports Server (NTRS)

    Sher, A. H.; Liu, Y. M.; Keery, W. J.

    1972-01-01

    The improved infrared response (IRR) technique has been used to qualitatively compare radiation effects on Si(Li) detectors with energy levels reported for silicon in the literature. Measurements have been made on five commercial silicon detectors and one fabricated in-house, both before and after irradiation with fast neutrons, 1.9-MeV protons, and 1.6-MeV electrons. Effects dependent upon the extent of radiation damage have been observed. It seems likely that the photo-EMF, or photo-voltage, effect is the basic mechanism for the observation of IRR in p-i-n diodes with a wide i-region. Experimental characteristics of the IRR measurement are in agreement with those of the photovoltage effect.

  8. Hypersensitivity to DNA damage in antephase as a safeguard for genome stability

    PubMed Central

    Feringa, Femke M.; Krenning, Lenno; Koch, André; van den Berg, Jeroen; van den Broek, Bram; Jalink, Kees; Medema, René H.

    2016-01-01

    Activation of the DNA-damage response can lead to the induction of an arrest at various stages in the cell cycle. These arrests are reversible in nature, unless the damage is too excessive. Here we find that checkpoint reversibility is lost in cells that are in very late G2, but not yet fully committed to enter mitosis (antephase). We show that antephase cells exit the cell cycle and enter senescence at levels of DNA damage that induce a reversible arrest in early G2. We show that checkpoint reversibility critically depends on the presence of the APC/C inhibitor Emi1, which is degraded just before mitosis. Importantly, ablation of the cell cycle withdrawal mechanism in antephase promotes cell division in the presence of broken chromosomes. Thus, our data uncover a novel, but irreversible, DNA-damage response in antephase that is required to prevent the propagation of DNA damage during cell division. PMID:27561326

  9. DETECTION OF LOW DOSE RADIATION-AND CHEMICALLY-INDUCED DNA DAMAGE USING TEMPERATURE DIFFERENTIAL FLUORESCENCE ASSAYS

    EPA Science Inventory

    Rapid, sensitive and simple assays for radiation- and chemically-induced DNA damage can be of significant benefit to a number of fields including radiation biology, clinical research, and environmental monitoring. Although temperature-induced DNA strand separation has been use...

  10. Role of interfaces i nthe design of ultra-high strength, radiation damage tolerant nanocomposites

    SciTech Connect

    Misra, Amit; Wang, Yongqiang; Nastasi, Michael A; Baldwin, Jon K; Wei, Qiangmin; Li, Nan; Mara, Nathan; Zhang, Xinghang; Fu, Engang; Anderoglu, Osman; Li, Hongqi; Bhattacharyya, Dhriti

    2010-12-09

    The combination of high strength and high radiation damage tolerance in nanolaminate composites can be achieved when the individual layers in these composites are only a few nanometers thick and contain special interfaces that act both as obstacles to slip, as well as sinks for radiation-induced defects. The morphological and phase stabilities and strength and ductility of these nano-composites under ion irradiation are explored as a function of layer thickness, temperature and interface structure. Magnetron sputtered metallic multilayers such as Cu-Nb and V-Ag with a range of individual layer thickness from approximately 2 nm to 50 nm and the corresponding 1000 nm thick single layer films were implanted with helium ions at room temperature. Cross-sectional Transmission Electron Microscopy (TEM) was used to measure the distribution of helium bubbles and correlated with the helium concentration profile measured vis ion beam analysis techniques to obtain the helium concentration at which bubbles are detected in TEM. It was found that in multilayers the minimum helium concentration to form bubbles (approximately I nm in size) that are easily resolved in through-focus TEM imaging was several atomic %, orders of magnitude higher than that in single layer metal films. This observation is consistent with an increased solubility of helium at interfaces that is predicted by atomistic modeling of the atomic structures of fcc-bcc interfaces. At helium concentrations as high as 7 at.%, a uniform distribution of I nm diameter bubbles results in negligible irradiation hardening and loss of deformability in multi layers with layer thicknesses of a few nanometers. The control of atomic structures of interfaces to produce high helium solubility at interfaces is crucial in the design of nano-composite materials that are radiation damage tolerant. Reduced radiation damage also leads to a reduction in the irradiation hardening, particularly at layer thickness of approximately 5 run

  11. Debris and radiation-induced damage effects on EUV nanolithography source collector mirror optics performance.

    SciTech Connect

    Allain, J. P.; Nieto, M.; Hendricks, M.; Harilal, S. S.; Hassanein, A.; Mathematics and Computer Science

    2007-01-01

    Exposure of collector mirrors facing the hot, dense pinch plasma in plasma-based EUV light sources to debris (fast ions, neutrals, off-band radiation, droplets) remains one of the highest critical issues of source component lifetime and commercial feasibility of nanolithography at 13.5-nm. Typical radiators used at 13.5-nm include Xe and Sn. Fast particles emerging from the pinch region of the lamp are known to induce serious damage to nearby collector mirrors. Candidate collector configurations include either multi-layer mirrors (MLM) or single-layer mirrors (SLM) used at grazing incidence. Studies at Argonne have focused on understanding the underlying mechanisms that hinder collector mirror performance at 13.5-nm under fast Sn or Xe exposure. This is possible by a new state-of-the-art in-situ EUV reflectometry system that measures real time relative EUV reflectivity (15-degree incidence and 13.5-nm) variation during fast particle exposure. Intense EUV light and off-band radiation is also known to contribute to mirror damage. For example offband radiation can couple to the mirror and induce heating affecting the mirror's surface properties. In addition, intense EUV light can partially photo-ionize background gas (e.g., Ar or He) used for mitigation in the source device. This can lead to local weakly ionized plasma creating a sheath and accelerating charged gas particles to the mirror surface and inducing sputtering. In this paper we study several aspects of debris and radiation-induced damage to candidate EUVL source collector optics materials. The first study concerns the use of IMD simulations to study the effect of surface roughness on EUV reflectivity. The second studies the effect of fast particles on MLM reflectivity at 13.5-nm. And lastly the third studies the effect of multiple energetic sources with thermal Sn on 13.5-nm reflectivity. These studies focus on conditions that simulate the EUVL source environment in a controlled way.

  12. The genomics of an adaptive radiation: insights across the Heliconius speciation continuum.

    PubMed

    Supple, Megan; Papa, Riccardo; Counterman, Brian; McMillan, W Owen

    2014-01-01

    Fueled by new technologies that allow rapid and inexpensive assessment of fine scale individual genomic variation, researchers are making transformational discoveries at the interface between genomes and biological complexity. Here we review genomic research in Heliconius butterflies - a radiation characterized by extraordinary phenotypic diversity in warningly colored wing patterns and composed of a continuum of taxa across the stages of speciation. These characteristics, coupled with a 50-year legacy of ecological and behavioral research, offer exceptional prospects for genomic studies into the nature of adaptive differences and the formation of new species. Research in Heliconius provides clear connections between genotype, phenotype, and fitness of wing color patterns shown to underlie adaptation and speciation. This research is challenging our perceptions about how speciation occurs in the presence of gene flow and the role of hybridization in generating adaptive novelty. With the release of the first Heliconius genome assembly, emerging genomic studies are painting a dynamic picture of the evolving species boundary. As the field of speciation genomics moves beyond describing patterns, towards a more integrated understanding of the process of speciation, groups such as Heliconius, where there is a clear speciation continuum and the traits underlying adaptation and speciation are known, will provide a roadmap for identifying variation crucial in the origins of biodiversity. PMID:24277304

  13. Pudendal Nerve and Internal Pudendal Artery Damage May Contribute to Radiation-Induced Erectile Dysfunction

    SciTech Connect

    Nolan, Michael W.; Marolf, Angela J.; Ehrhart, E.J.; Rao, Sangeeta; Kraft, Susan L.; Engel, Stephanie; Yoshikawa, Hiroto; Golden, Anne E.; Wasserman, Todd H.; LaRue, Susan M.

    2015-03-15

    Purpose/Objectives: Erectile dysfunction is common after radiation therapy for prostate cancer; yet, the etiopathology of radiation-induced erectile dysfunction (RI-ED) remains poorly understood. A novel animal model was developed to study RI-ED, wherein stereotactic body radiation therapy (SBRT) was used to irradiate the prostate, neurovascular bundles (NVB), and penile bulb (PB) of dogs. The purpose was to describe vascular and neurogenic injuries after the irradiation of only the NVB or the PB, and after irradiation of all 3 sites (prostate, NVB, and PB) with varying doses of radiation. Methods and Materials: Dogs were treated with 50, 40, or 30 Gy to the prostate, NVB, and PB, or 50 Gy to either the NVB or the PB, by 5-fraction SBRT. Electrophysiologic studies of the pudendal nerve and bulbospongiosus muscles and ultrasound studies of pelvic perfusion were performed before and after SBRT. The results of these bioassays were correlated with histopathologic changes. Results: SBRT caused slowing of the systolic rise time, which corresponded to decreased arterial patency. Alterations in the response of the internal pudendal artery to vasoactive drugs were observed, wherein SBRT caused a paradoxical response to papaverine, slowing the systolic rise time after 40 and 50 Gy; these changes appeared to have some dose dependency. The neurofilament content of penile nerves was also decreased at high doses and was more profound when the PB was irradiated than when the NVB was irradiated. These findings are coincident with slowing of motor nerve conduction velocities in the pudendal nerve after SBRT. Conclusions: This is the first report in which prostatic irradiation was shown to cause morphologic arterial damage that was coincident with altered internal pudendal arterial tone, and in which decreased motor function in the pudendal nerve was attributed to axonal degeneration and loss. Further investigation of the role played by damage to these structures in RI-ED is

  14. Involvement of inducible nitric oxide synthase in radiation-induced vascular endothelial damage.

    PubMed

    Hong, Chang-Won; Kim, Young-Mee; Pyo, Hongryull; Lee, Joon-Ho; Kim, Suwan; Lee, Sunyoung; Noh, Jae Myoung

    2013-11-01

    The use of radiation therapy has been linked to an increased risk of cardiovascular disease. To understand the mechanisms underlying radiation-induced vascular dysfunction, we employed two models. First, we examined the effect of X-ray irradiation on vasodilation in rabbit carotid arteries. Carotid arterial rings were irradiated with 8 or 16 Gy using in vivo and ex vivo methods. We measured the effect of acetylcholine-induced relaxation after phenylephrine-induced contraction on the rings. In irradiated carotid arteries, vasodilation was significantly attenuated by both irradiation methods. The relaxation response was completely blocked by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a potent inhibitor of soluble guanylate cyclase. Residual relaxation persisted after treatment with L-N(ω)-nitroarginine (L-NA), a non-specific inhibitor of nitric oxide synthase (NOS), but disappeared following the addition of aminoguanidine (AG), a selective inhibitor of inducible NOS (iNOS). The relaxation response was also affected by tetraethylammonium, an inhibitor of endothelium-derived hyperpolarizing factor activity. In the second model, we investigated the biochemical events of nitrosative stress in human umbilical-vein endothelial cells (HUVECs). We measured iNOS and nitrotyrosine expression in HUVECs exposed to a dose of 4 Gy. The expression of iNOS and nitrotyrosine was greater in irradiated HUVECs than in untreated controls. Pretreatment with AG, L-N(6)-(1-iminoethyl) lysine hydrochloride (a selective inhibitor of iNOS), and L-NA attenuated nitrosative stress. While a selective target of radiation-induced vascular endothelial damage was not definitely determined, these results suggest that NO generated from iNOS could contribute to vasorelaxation. These studies highlight a potential role of iNOS inhibitors in ameliorating radiation-induced vascular endothelial damage. PMID:23704776

  15. Anisotropic mechanical properties of zircon and the effect of radiation damage

    NASA Astrophysics Data System (ADS)

    Beirau, Tobias; Nix, William D.; Bismayer, Ulrich; Boatner, Lynn A.; Isaacson, Scott G.; Ewing, Rodney C.

    2016-06-01

    This study provides new insights into the relationship between radiation-dose-dependent structural damage due to natural U and Th impurities and the anisotropic mechanical properties (Poisson's ratio, elastic modulus and hardness) of zircon. Natural zircon samples from Sri Lanka (see Muarakami et al. in Am Mineral 76:1510-1532, 1991) and synthetic samples, covering a dose range of zero up to 6.8 × 1018 α-decays/g, have been studied by nanoindentation. Measurements along the [100] crystallographic direction and calculations, based on elastic stiffness constants determined by Özkan (J Appl Phys 47:4772-4779, 1976), revealed a general radiation-induced decrease in stiffness (~54 %) and hardness (~48 %) and an increase in the Poisson's ratio (~54 %) with increasing dose. Additional indentations on selected samples along the [001] allowed one to follow the amorphization process to the point that the mechanical properties are isotropic. This work shows that the radiation-dose-dependent changes of the mechanical properties of zircon can be directly correlated with the amorphous fraction as determined by previous investigations with local and global probes (Ríos et al. in J Phys Condens Matter 12:2401-2412, 2000a; Farnan and Salje in J Appl Phys 89:2084-2090, 2001; Zhang and Salje in J Phys Condens Matter 13:3057-3071, 2001). The excellent agreement, revealed by the different methods, indicates a large influence of structural and even local phenomena on the macroscopic mechanical properties. Therefore, this study indicates the importance of acquiring better knowledge about the mechanical long-term stability of radiation-damaged materials.

  16. Cell damage by UVA radiation of a mercury microscopy lamp probed by autofluorescence modifications, cloning assay, and comet assay

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Krasieva, Tatiana B.; Bauer, Eckhard; Fiedler, Ursula; Berns, Michael W.; Tromberg, Bruce J.; Greulich, Karl O.

    1996-04-01

    Cell damage by low-power 365-nm radiation of a 50-W high-pressure mercury microscopy lamp was studied. Exposure of Chinese hamster ovary cells to ultraviolet-A (UVA) radiation > 10 kJ/m2 resulted in significant modifications of nicotinamide adenine dinucleotide attributed autofluorescence and inhibition of cell division. Single-cell gel electrophoresis (comet assay) revealed UVA-induced single-strand DNA breaks. According to these results, UVA excitation radiation in fluorescence microscopy may damage cells. This has to be considered in vital cell microscopy, e.g., in calcium measurements.

  17. Scintillation mechanism and radiation damage in Ce{sub x}La{sub 1-x}F{sub 3} crystals

    SciTech Connect

    Wojtowicz, A.J.; Wisniewski, D. |; Lempicki, A.; Brecher, C.; Bartram, R.H.; Woody, C.; Levy, P.; Stoll, S.; Kierstead, J.; Pedrini, C.

    1994-08-01

    Recent spectroscopic and radiation damage experiments on a series of Ce{sub x}La{sub 1{minus}x}F{sub 3} crystals suggest that the scintillation light output is limited by an unusual quenching mechanism, which also plays a major role in minimizing radiation-induced damage. The intensity of the radiation-induced absorptions is a strong function of the Ce content x, reaching a maximum for x = 0.03 and a minimum for x = 1. This peculiar dependence appears to be due to the influence of deep-lying Ce levels on both scintillation mechanism and radiation damage. The authors suggest that various charge transfer processes can explain many aspects of the performance of Ce{sub x}La{sub 1{minus}x}F{sub 3} scintillators.

  18. Ultraviolet radiation, aging and the skin: prevention of damage by topical cAMP manipulation

    PubMed Central

    Amaro-Ortiz, Alexandra; Yan, Betty; D’Orazio, John A.

    2015-01-01

    Being the largest and most visible organ of the body and heavily influenced by environmental factors, skin is ideal to study long-term effects of aging. Throughout our lifetime, we accumulate damage generated by UV radiation. UV causes inflammation, immune changes, physical changes, impaired wound healing and DNA damage that promotes cellular senescence and carcinogenesis. Melanoma is the deadliest form of skin cancer and among the malignancies of highest increasing incidence over the last several decades. Melanoma incidence is directly related to age, with highest rates in individuals over the age of 55 years, making it a clear age-related disease. In this review, we will focus on UV-induced carcinogenesis and photo aging along with natural protective mechanisms that reduce amount of “realized” solar radiation dose and UV-induced injury. We will focus on the theoretical use of forskolin, a plant-derived pharmacologically active compound to protect the skin against UV injury and prevent aging symptoms by up-regulating melanin production. We will discuss its use as a topically-applied root-derived formulation of the Plectranthus barbatus (Coleus forskolii) plant that grows naturally in Asia and that has long been used in various Aryuvedic teas and therapeutic preparations. PMID:24838074

  19. Modelling electron distributions within ESA's Gaia satellite CCD pixels to mitigate radiation damage

    NASA Astrophysics Data System (ADS)

    Seabroke, G. M.; Holland, A. D.; Burt, D.; Robbins, M. S.

    2009-08-01

    The Gaia satellite is a high-precision astrometry, photometry and spectroscopic ESA cornerstone mission, currently scheduled for launch in 2012. Its primary science drivers are the composition, formation and evolution of the Galaxy. Gaia will achieve its unprecedented positional accuracy requirements with detailed calibration and correction for radiation damage. At L2, protons cause displacement damage in the silicon of CCDs. The resulting traps capture and emit electrons from passing charge packets in the CCD pixel, distorting the image PSF and biasing its centroid. Microscopic models of Gaia's CCDs are being developed to simulate this effect. The key to calculating the probability of an electron being captured by a trap is the 3D electron density within each CCD pixel. However, this has not been physically modelled for the Gaia CCD pixels. In Seabroke, Holland & Cropper (2008), the first paper of this series, we motivated the need for such specialised 3D device modelling and outlined how its future results will fit into Gaia's overall radiation calibration strategy. In this paper, the second of the series, we present our first results using Silvaco's physics-based, engineering software: the ATLAS device simulation framework. Inputting a doping profile, pixel geometry and materials into ATLAS and comparing the results to other simulations reveals that ATLAS has a free parameter, fixed oxide charge, that needs to be calibrated. ATLAS is successfully benchmarked against other simulations and measurements of a test device, identifying how to use it to model Gaia pixels and highlighting the affect of different doping approximations.

  20. The contribution made by lattice vacancies to the Wigner effect in radiation-damaged graphite.

    PubMed

    Latham, C D; Heggie, M I; Alatalo, M; Oberg, S; Briddon, P R

    2013-04-01

    Models for radiation damage in graphite are reviewed and compared, leading to a re-examination of the contribution made by vacancies to annealing processes. A method based on density functional theory, using large supercells with orthorhombic and hexagonal symmetry, is employed to calculate the properties and behaviour of lattice vacancies and displacement defects. It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K. The migration of isolated monovacancies is estimated to have an activation energy of E(a) ≈ 1.1 eV. Coalescence into divacancy defects occurs in several stages, with different barriers at each stage, depending on the path. The formation of pairs ultimately yields up to 8.9 eV energy, which is nearly 1.0 eV more than the formation energy for an isolated monovacancy. Processes resulting in vacancy coalescence and annihilation appear to be responsible for the main Wigner energy release peak in radiation-damaged graphite, occurring at about 475 K. PMID:23470497

  1. The contribution made by lattice vacancies to the Wigner effect in radiation-damaged graphite

    NASA Astrophysics Data System (ADS)

    Latham, C. D.; Heggie, M. I.; Alatalo, M.; Öberg, S.; Briddon, P. R.

    2013-04-01

    Models for radiation damage in graphite are reviewed and compared, leading to a re-examination of the contribution made by vacancies to annealing processes. A method based on density functional theory, using large supercells with orthorhombic and hexagonal symmetry, is employed to calculate the properties and behaviour of lattice vacancies and displacement defects. It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K. The migration of isolated monovacancies is estimated to have an activation energy of Ea ≈ 1.1 eV. Coalescence into divacancy defects occurs in several stages, with different barriers at each stage, depending on the path. The formation of pairs ultimately yields up to 8.9 eV energy, which is nearly 1.0 eV more than the formation energy for an isolated monovacancy. Processes resulting in vacancy coalescence and annihilation appear to be responsible for the main Wigner energy release peak in radiation-damaged graphite, occurring at about 475 K.

  2. High-energy proton radiation damage of high-purity germanium detectors

    NASA Technical Reports Server (NTRS)

    Pehl, R. H.; Varnell, L. S.; Metzger, A. E.

    1978-01-01

    Quantitative studies of radiation damage in high-purity germanium gamma-ray detectors due to high-energy charged particles have been carried out; two 1.0 cm thick planar detectors were irradiated by 6 GeV/c protons. Under proton bombardment, degradation in the energy resolution was found to begin below 7 x 10 to the 7th protons/sq cm and increased proportionately in both detectors until the experiment was terminated at a total flux of 5.7 x 10 to the 8th protons/sq cm, equivalent to about a six year exposure to cosmic-ray protons in space. At the end of the irradiation, the FWHM resolution measured at 1332 keV stood at 8.5 and 13.6 keV, with both detectors of only marginal utility as a spectrometer due to the severe tailing caused by charge trapping. Annealing these detectors after proton damage was found to be much easier than after neutron damage.

  3. Ozone depletion and UVB radiation: impact on plant DNA damage in southern South America.

    PubMed

    Rousseaux, M C; Ballaré, C L; Giordano, C V; Scopel, A L; Zima, A M; Szwarcberg-Bracchitta, M; Searles, P S; Caldwell, M M; Díaz, S B

    1999-12-21

    The primary motivation behind the considerable effort in studying stratospheric ozone depletion is the potential for biological consequences of increased solar UVB (280-315 nm) radiation. Yet, direct links between ozone depletion and biological impacts have been established only for organisms of Antarctic waters under the influence of the ozone "hole;" no direct evidence exists that ozone-related variations in UVB affect ecosystems of temperate latitudes. Indeed, calculations based on laboratory studies with plants suggest that the biological impact of ozone depletion (measured by the formation of cyclobutane pyrimidine dimers in DNA) is likely to be less marked than previously thought, because UVA quanta (315-400 nm) may also cause significant damage, and UVA is unaffected by ozone depletion. Herein, we show that the temperate ecosystems of southern South America have been subjected to increasingly high levels of ozone depletion during the last decade. We found that in the spring of 1997, despite frequent cloud cover, the passages of the ozone hole over Tierra del Fuego (55 degrees S) caused concomitant increases in solar UV and that the enhanced ground-level UV led to significant increases in DNA damage in the native plant Gunnera magellanica. The fluctuations in solar UV explained a large proportion of the variation in DNA damage (up to 68%), particularly when the solar UV was weighted for biological effectiveness according to action spectra that assume a sharp decline in quantum efficiency with increasing wavelength from the UVB into the UVA regions of the spectrum. PMID:10611381

  4. A 1-Mb resolution radiation hybrid map of the canine genome

    PubMed Central

    Guyon, Richard; Lorentzen, Travis D.; Hitte, Christophe; Kim, Lisa; Cadieu, Edouard; Parker, Heidi G.; Quignon, Pascale; Lowe, Jennifer K.; Renier, Corinne; Gelfenbeyn, Boris; Vignaux, Françoise; DeFrance, Hawkins B.; Gloux, Stephanie; Mahairas, Gregory G.; André, Catherine; Galibert, Francis; Ostrander, Elaine A.

    2003-01-01

    The purebred dog population consists of >300 partially inbred genetic isolates or breeds. Restriction of gene flow between breeds, together with strong selection for traits, has led to the establishment of a unique resource for dissecting the genetic basis of simple and complex mammalian traits. Toward this end, we present a comprehensive radiation hybrid map of the canine genome composed of 3,270 markers including 1,596 microsatellite-based markers, 900 cloned gene sequences and ESTs, 668 canine-specific bacterial artificial chromosome (BAC) ends, and 106 sequence-tagged sites. The map was constructed by using the RHDF5000-2 whole-genome radiation hybrid panel and computed by using multimap and tsp/concorde. The 3,270 markers map to 3,021 unique positions and define an average intermarker distance corresponding to 1 Mb. We also define a minimal screening set of 325 highly informative well spaced markers, to be used in the initiation of genome-wide scans. The well defined synteny between the dog and human genomes, established in part as a function of this work by the identification of 85 conserved fragments, will allow follow-up of initial findings of linkage by selection of candidate genes from the human genome sequence. This work continues to define the canine system as the method of choice in the pursuit of the genes causing mammalian variation and disease. PMID:12700351

  5. Distinguishing noise from signal in patterns of genomic divergence in a highly polymorphic avian radiation.

    PubMed

    Campagna, Leonardo; Gronau, Ilan; Silveira, Luís Fábio; Siepel, Adam; Lovette, Irby J

    2015-08-01

    Recently diverged taxa provide the opportunity to search for the genetic basis of the phenotypes that distinguish them. Genomic scans aim to identify loci that are diverged with respect to an otherwise weakly differentiated genetic background. These loci are candidates for being past targets of selection because they behave differently from the rest of the genome that has either not yet differentiated or that may cross species barriers through introgressive hybridization. Here we use a reduced-representation genomic approach to explore divergence among six species of southern capuchino seedeaters, a group of recently radiated sympatric passerine birds in the genus Sporophila. For the first time in these taxa, we discovered a small proportion of markers that appeared differentiated among species. However, when assessing the significance of these signatures of divergence, we found that similar patterns can also be recovered from random grouping of individuals representing different species. A detailed demographic inference indicates that genetic differences among Sporophila species could be the consequence of neutral processes, which include a very large ancestral effective population size that accentuates the effects of incomplete lineage sorting. As these neutral phenomena can generate genomic scan patterns that mimic those of markers involved in speciation and phenotypic differentiation, they highlight the need for caution when ascertaining and interpreting differentiated markers between species, especially when large numbers of markers are surveyed. Our study provides new insights into the demography of the southern capuchino radiation and proposes controls to distinguish signal from noise in similar genomic scans. PMID:26175196

  6. Antarctic Notothenioid Fishes: Genomic Resources and Strategies for Analyzing an Adaptive Radiation

    PubMed Central

    Detrich, H. W.; Amemiya, Chris T.

    2010-01-01

    The perciform suborder Notothenoidei provides a compelling opportunity to study the adaptive radiation of a marine species-flock in the cold Southern Ocean that surrounds Antarctica. To facilitate genome-level studies of the diversification of these fishes, we present estimates of the genome sizes of 11 Antarctic species and describe the production of high-quality bacterial artificial chromosome (BAC) libraries for two, the red-blooded notothen Notothenia coriiceps and the white-blooded icefish Chaenocephalus aceratus. Our results indicate that evolution of phylogenetically derived notothenioid families (e.g., the crown group Channichthyidae [icefishes]), was accompanied by genome expansion. Six species from the basal family Nototheniidae had C-values between 0.98 and 1.20 pg, a range that is consistent with the genome sizes of proposed outgroups (e.g., percids) of the notothenioid suborder. In contrast, four icefishes had C-values in the range 1.66–1.83 pg. The BAC libraries VMRC-19 (N. coriiceps) and VMRC-21 (C. aceratus) comprise 12× and 10× coverage of the respective genomes and have average insert sizes of 138 and 168 kb. Paired BAC-end reads representing ∼0.1% of each genome showed that the repetitive element landscapes of the two genomes (13.4% of the N. coriiceps genome and 14.5% for C. aceratus) were similar. The availability of these high-quality and well-characterized BAC libraries sets the stage for targeted genomic analyses of the unusual anatomical and physiological adaptations of the notothenioids, some of which mimic human diseases. Here we consider the evolution of secondary pelagicism by various taxa of the group and illustrate the utility of Antarctic icefishes as an evolutionary-mutant model of human osteopenia (low-mineral density of bones). PMID:21082069

  7. Caryocar brasiliense camb protects against genomic and oxidative damage in urethane-induced lung carcinogenesis

    PubMed Central

    Colombo, N.B.R.; Rangel, M.P.; Martins, V.; Hage, M.; Gelain, D.P.; Barbeiro, D.F.; Grisolia, C.K.; Parra, E.R.; Capelozzi, V.L.

    2015-01-01

    The antioxidant effects of Caryocar brasiliense Camb, commonly known as the pequi fruit, have not been evaluated to determine their protective effects against oxidative damage in lung carcinogenesis. In the present study, we evaluated the role of pequi fruit against urethane-induced DNA damage and oxidative stress in forty 8-12 week old male BALB/C mice. An in vivo comet assay was performed to assess DNA damage in lung tissues and changes in lipid peroxidation and redox cycle antioxidants were monitored for oxidative stress. Prior supplementation with pequi oil or its extract (15 µL, 60 days) significantly reduced urethane-induced oxidative stress. A protective effect against DNA damage was associated with the modulation of lipid peroxidation and low protein and gene expression of nitric oxide synthase. These findings suggest that the intake of pequi fruit might protect against in vivo genotoxicity and oxidative stress. PMID:26200231

  8. The damage repair role of He-Ne laser on plants exposed to different intensities of ultraviolet-B radiation.

    PubMed

    Qi, Zhi; Yue, Ming; Han, Rong; Wang, Xun-Ling

    2002-06-01

    Light-grown broad bean (Vicia faba L.) seedlings were subjected to different intensities of UV-B radiation (0, 0.05, 0.15, 0.45, 0.90, 1.45 and 1.98 W m(-2)) for 7 h under photosynthetically active radiation (70 micromol m(-2) s(-1)) and then exposed to He-Ne laser (632.8 nm, 5.43 mW mm(-2)) radiation for 5 min or red light radiation for 4 h without ambient light radiation. When He-Ne laser radiated leaves were treated using lower intensity UV-B, the activities of superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6) improved significantly. Moreover, the UV-B-injured plants treated with laser light recovered faster from UV-B treatment because the concentration of malondialdehyde and the rate of electrolyte leakage from leaf disks reached control levels (no UV-B or laser treatment) early compared with those exposed only to ambient light or in dark conditions. Laser treatment, however, had no repair effect on seedling damage induced by higher UV-B radiation (1.45 and 1.98 W m(-2)), even with higher laser flux rates and longer laser treatment. In addition, the red light treatment had no repair effect on UV-B-induced damage. Meanwhile, the long-term physiological effect of He-Ne laser treatment on UV-B damaged plants was presented and evaluated. The results showed that the laser had a long-term positive physiological effect on the growth of UV-B-damaged plants. With the exception of the severe damage caused by higher UV-B radiation, a laser with the proper flux rate and treatment time can repair UV-B-induced damage and shorten the recovery time. PMID:12081332

  9. Pharmaceutical drugs supporting regeneration of small-intestinal mucosa severely damaged by ionizing radiation in mice

    PubMed Central

    Ishihara, Hiroshi; Tanaka, Izumi; Yakumaru, Haruko; Tanaka, Mika; Yokochi, Kazuko; Akashi, Makoto

    2013-01-01

    Accidental exposure of the abdomen to high-dose radiation leads to severe consequences initiated by disruption of the mucosa in the small intestine. Therapeutic options are limited, even though various treatments have been investigated, particularly in the field of regenerative therapy. In order to identify readily available treatment methods, we included several current pharmaceutical drugs, for which the clinical trials have already been completed, in tests on mice that had undergone severe mucosal damage by radiation. The drugs were injected into mice 24 h after exposure to 15.7 Gy X-rays. The effects of the drugs on the damaged mucosa of the small intestine were evaluated using early regeneration indices [the expression of c-myb mRNA, and proliferation of epithelial cells in the form of microcolonies (MCs) by Days 4 and 5 post-irradiation] and the survival rate of the mice. Enhancement of mucosal regeneration at Day 4 (c-myb: P < 0.01, MC: P < 0.05) and improvement of the survival rate (P < 0.05) were observed when a clinical dose of gonadotropin, a stimulator of androgen, was injected. Similarly, a clinical dose of thiamazole (which prevents secretion of thyroid hormone) stimulated mucosal growth by Day 5 (c-myb: P < 0.01, MC: P < 0.05) and also improved the survival rate (P < 0.05). The nonclinical drugs histamine and high-dose octreotide (a growth hormone antagonist) also gave significant survival-enhancing benefits (P < 0.01 and P < 0.05, respectively). These results can be used to construct therapeutic programs and applied in various experimental studies to control the regeneration of damaged mucosa. PMID:23728323

  10. Diffusion of fission products and radiation damage in SiC

    NASA Astrophysics Data System (ADS)

    Malherbe, Johan B.

    2013-11-01

    A major problem with most of the present nuclear reactors is their safety in terms of the release of radioactivity into the environment during accidents. In some of the future nuclear reactor designs, i.e. Generation IV reactors, the fuel is in the form of coated spherical particles, i.e. TRISO (acronym for triple coated isotropic) particles. The main function of these coating layers is to act as diffusion barriers for radioactive fission products, thereby keeping these fission products within the fuel particles, even under accident conditions. The most important coating layer is composed of polycrystalline 3C-SiC. This paper reviews the diffusion of the important fission products (silver, caesium, iodine and strontium) in SiC. Because radiation damage can induce and enhance diffusion, the paper also briefly reviews damage created by energetic neutrons and ions at elevated temperatures, i.e. the temperatures at which the modern reactors will operate, and the annealing of the damage. The interaction between SiC and some fission products (such as Pd and I) is also briefly discussed. As shown, one of the key advantages of SiC is its radiation hardness at elevated temperatures, i.e. SiC is not amorphized by neutrons or bombardment at substrate temperatures above 350 °C. Based on the diffusion coefficients of the fission products considered, the review shows that at the normal operating temperatures of these new reactors (i.e. less than 950 °C) the SiC coating layer is a good diffusion barrier for these fission products. However, at higher temperatures the design of the coated particles needs to be adapted, possibly by adding a thin layer of ZrC.

  11. Accelerated radiation damage test facility using a 5 MV tandem ion accelerator

    NASA Astrophysics Data System (ADS)

    Wady, P. T.; Draude, A.; Shubeita, S. M.; Smith, A. D.; Mason, N.; Pimblott, S. M.; Jimenez-Melero, E.

    2016-01-01

    We have developed a new irradiation facility that allows to perform accelerated damage tests of nuclear reactor materials at temperatures up to 400 °C using the intense proton (<100 μA) and heavy ion (≈10 μA) beams produced by a 5 MV tandem ion accelerator. The dedicated beam line for radiation damage studies comprises: (1) beam diagnosis and focusing optical components, (2) a scanning and slit system that allows uniform irradiation of a sample area of 0.5-6 cm2, and (3) a sample stage designed to be able to monitor in-situ the sample temperature, current deposited on the sample, and the gamma spectrum of potential radio-active nuclides produced during the sample irradiation. The beam line capabilities have been tested by irradiating a 20Cr-25Ni-Nb stabilised stainless steel with a 3 MeV proton beam to a dose level of 3 dpa. The irradiation temperature was 356 °C, with a maximum range in temperature values of ±6 °C within the first 24 h of continuous irradiation. The sample stage is connected to ground through an electrometer to measure accurately the charge deposited on the sample. The charge can be integrated in hardware during irradiation, and this methodology removes uncertainties due to fluctuations in beam current. The measured gamma spectrum allowed the identification of the main radioactive nuclides produced during the proton bombardment from the lifetimes and gamma emissions. This dedicated radiation damage beam line is hosted by the Dalton Cumbrian Facility of the University of Manchester.

  12. Countering effects of a combination of podophyllotoxin, podophyllotoxin β-D-glucoside and rutin hydrate in minimizing radiation induced chromosomal damage, ROS and apoptosis in human blood lymphocytes.

    PubMed

    Dutta, Sangeeta; Yashavarddhan, M H; Srivastava, Nitya Nand; Ranjan, Rajiv; Bajaj, Sania; Kalita, Bhargab; Singh, Abhinav; Flora, Swaran J S; Gupta, Manju Lata

    2016-05-01

    The present study was conceptualized with the aim of developing a safe radioprotector for human application against radiation induced toxicity. For this study, a formulation (G-002M) prepared by combining three active principles isolated from rhizomes of Podophyllum hexandrum, was evaluated for its potential to protect genomic DNA of human blood cells exposed to different doses of radiation (5,7&10Gy). Blood samples were pretreated (-1hr to exposure) with G-002M. Parameters of Premature Chromosome Condensation (PCC) assay like PCC-index, PCC-rings and PCC-fragments were used to estimate radiation induced chromosomal aberrations. Radiation (7Gy) induce ROS generation and its modulation by G-002M was determined by flow-cytometry and fluorescent microscopy while apoptosis (0,2,24&48 hr) was analyzed using TUNEL assay. Effect on spindle organization in G2/M arrested cells by all the three compounds individually was studied using immunofluorescence microscopy. Irradiation caused dose dependent linear increase in PCC-rings and fragments, while decline in PCC index. G-002M pretreatment significantly decreased these chromosomal aberrations at all the radiation doses and assisted cell survival as indicated by increased PCC index compared with radiation only group. Significant decrease in radiation induced intracellular ROS (45 ± 3%) and apoptosis (49.9%) was also exhibited by the formulation. On podophyllotoxin treatment, most of the cells have shown blocked spindles however, depicted normal arrangement. G-002M also demonstrated a highly significant Dose Modifying Factor or DMF (PCC-rings: 2.27 and PCC-fragments: 1.60). Present study based on many parameters along with DMF study, strongly suggests that G-002M is an effective formulation with a potential to minimize chromosomal damage even at very high radiation doses. PMID:26993954

  13. DNA damage and repair in oncogenic transformation by heavy ion radiation

    NASA Astrophysics Data System (ADS)

    Yang, T. C.; Mei, M.; George, K. A.; Craise, L. M.

    Energetic heavy ions are present in galactic cosmic rays and solar particle events. One of the most important late effects in risk assessment is carcinogenesis. We have studied the carcinogenic effects of heavy ions at the cellular and molecular levels and have obtained quantitative data on dose-response curves and on the repair of oncogenic lesions for heavy particles with various charges and energies. Studies with repair inhibitors and restriction endonucleases indicated that for oncogenic transformation DNA is the primary target. Results from heavy ion experiments showed that the cross section increased with LET and reached a maximum value of about 0.02 mum^2 at about 500 keV/mum. This limited size of cross section suggests that only a fraction of cellular genomic DNA is important in radiogenic transformation. Free radical scavengers, such as DMSO, do not give any effect on induction of oncogenic transformation by 600 MeV/u iron particles, suggesting most oncogenic damage induced by high-LET heavy ions is through direct action. Repair studies with stationary phase cells showed that the amount of reparable oncogenic lesions decreased with an increase of LET and that heavy ions with LET greater than 200 keV/mum produced only irreparable oncogenic damage. An enhancement effect for oncogenic transformation was observed in cells irradiated by low-dose-rate argon ions (400 MeV/u; 120 keV/mum). Chromosomal aberrations, such as translocation and deletion, but not sister chromatid exchange, are essential for heavy-ion-induced oncogenic transformation. The basic mechanism(s) of misrepair of DNA damage, which form oncogenic lesions, is unknown.

  14. DNA damage and repair in oncogenic transformation by heavy ion radiation

    NASA Technical Reports Server (NTRS)

    Yang, T. C.; Mei, M.; George, K. A.; Craise, L. M.

    1996-01-01

    Energetic heavy ions are present in galactic cosmic rays and solar particle events. One of the most important late effects in risk assessment is carcinogenesis. We have studied the carcinogenic effects of heavy ions at the cellular and molecular levels and have obtained quantitative data on dose-response curves and on the repair of oncogenic lesions for heavy particles with various charges and energies. Studies with repair inhibitors and restriction endonucleases indicated that for oncogenic transformation DNA is the primary target. Results from heavy ion experiments showed that the cross section increased with LET and reached a maximum value of about 0.02 micrometer2 at about 500 keV/micrometer. This limited size of cross section suggests that only a fraction of cellular genomic DNA is important in radiogenic transformation. Free radical scavengers, such as DMSO, do not give any effect on induction of oncogenic transformation by 600 MeV/u iron particles, suggesting most oncogenic damage induced by high-LET heavy ions is through direct action. Repair studies with stationary phase cells showed that the amount of reparable oncogenic lesions decreased with an increase of LET and that heavy ions with LET greater than 200 keV/micrometer produced only irreparable oncogenic damage. An enhancement effect for oncogenic transformation was observed in cells irradiated by low-dose-rate argon ions (400 MeV/u; 120 keV/micrometer). Chromosomal aberrations, such as translocation and deletion, but not sister chromatid exchange, are essential for heavy-ion-induced oncogenic transformation. The basic mechanism(s) of misrepair of DNA damage, which form oncogenic lesions, is unknown.

  15. A mineral sunscreen affords genomic protection against ultraviolet (UV) B and UVA radiation: in vitro and in situ assays.

    PubMed

    Cayrol, C; Sarraute, J; Tarroux, R; Redoules, D; Charveron, M; Gall, Y

    1999-08-01

    Ultraviolet (UV) radiation has been shown to be responsible for different biological effects on human skin, including the initiation of photocarcinogenesis. Both UVB and UVA have been described as mutagenic, but the processes by which they alter the DNA are different. Although cells can repair DNA damage, some deleterious mutations nevertheless appear and can promote cancer. The risk of photocarcinogenesis is acknowledged and the frequency of photogenodermatosis is increasing. In order to evaluate the protection efficacy of a high sun protection factor (SPF) mineral sunscreen against UVB- and UVA-induced genomic alterations, we have followed two approaches. First, we have tested the sunscreen for its ability to decrease the unscheduled DNA synthesis response in vitro in human fibroblasts, as an indirect measure of UVB-induced lesions (0.005 and 0.01 J/cm2), and second, we have verified its ability to reduce the in situ end-labelling intensity in human skin as a direct measure of UVA-induced single-strand breaks (10 J/cm2). Microscopic analysis clearly demonstrated the protective effect of the sunscreen against UVB and UVA. A dose-dependent effect of mineral sunscreens was observed. There was also a relationship between the SPF and genomic protection. By limiting the accumulation of UV-induced lesions on DNA, this mineral sunscreen could limit the mutation frequency. PMID:10468796

  16. Integrated Molecular Analysis Indicates Undetectable Change in DNA Damage in Mice after Continuous Irradiation at ~ 400-fold Natural Background Radiation

    PubMed Central

    Olipitz, Werner; Wiktor-Brown, Dominika; Shuga, Joe; Pang, Bo; McFaline, Jose; Lonkar, Pallavi; Thomas, Aline; Mutamba, James T; Greenberger, Joel S; Samson, Leona D; Dedon, Peter C; Yanch, Jacquelyn C

    2012-01-01

    Background: In the event of a nuclear accident, people are exposed to elevated levels of continuous low dose-rate radiation. Nevertheless, most of the literature describes the biological effects of acute radiation. Objectives: DNA damage and mutations are well established for their carcinogenic effects. We assessed several key markers of DNA damage and DNA damage responses in mice exposed to low dose-rate radiation to reveal potential genotoxic effects associated with low dose-rate radiation. Methods: We studied low dose-rate radiation using a variable low dose-rate irradiator consisting of flood phantoms filled with 125Iodine-containing buffer. Mice were exposed to 0.0002 cGy/min (~ 400-fold background radiation) continuously over 5 weeks. We assessed base lesions, micronuclei, homologous recombination (HR; using fluorescent yellow direct repeat mice), and transcript levels for several radiation-sensitive genes. Results: We did not observe any changes in the levels of the DNA nucleobase damage products hypoxanthine, 8-oxo-7,8-dihydroguanine, 1,N6-ethenoadenine, or 3,N4-ethenocytosine above background levels under low dose-rate conditions. The micronucleus assay revealed no evidence that low dose-rate radiation induced DNA fragmentation, and there was no evidence of double strand break–induced HR. Furthermore, low dose-rate radiation did not induce Cdkn1a, Gadd45a, Mdm2, Atm, or Dbd2. Importantly, the same total dose, when delivered acutely, induced micronuclei and transcriptional responses. Conclusions: These results demonstrate in an in vivo animal model that lowering the dose-rate suppresses the potentially deleterious impact of radiation and calls attention to the need for a deeper understanding of the biological impact of low dose-rate radiation. PMID:22538203

  17. Genetic compensation of high dose radiation-induced damage in an anhydrobiotic insect

    NASA Astrophysics Data System (ADS)

    Gusev, Oleg; Nakahara, Yuichi; Sakashita, Tetsuya; Kikawada, Takahiro; Okuda, Takashi

    Anhydrobiotic larvae of African chironomid Polypedilum vanderplanki are known to show an extremely high tolerance against a range of stresses. The tolerance against various extreme environments exhibited by that insect might be due to being almost completely desiccated replacing water with trehalose, a state where little or no chemical reactions occur. From 2005 dried larvae of this insect are being used in a number of space experiments, both inside and outside of ISS as a model organism for estimation the limits of higher organisms' resistance to space environment stresses and long-term storage of the alive anhydrobiotic organisms during continues spaceflight. We have shown previously that both hydrated and dried larvae of Polypedilum vanderplanki have very higher tolerance against both highand low-linear energy transfer (LET), surviving after 7000Gy irradiation. It was suggested that the larvae would have effective DNA-reparation system in addition to artificial protection provided by glass-stage without water. In the present study we conducted analysis of stress-related gene expression in the larvae after 70-2000 Gy irradiations. Both DNA damage level and activity of DNA-reparation, anti-apoptotic and protein-damage related genes were analyzed. Direct visualization of DNA damage in the larvae fat body cells using Comet Assay showed that fragmented by radiation DNA is re-arranged within 76-98 hours after exposure. We found that massive overexpression of hsp and anti-oxidant genes occur in larvae entering anhydrobiosis , and provides refolding of proteins after rehydration. In the irradiated larvae overexpression of DNA-reparation enzymes anti-apoptotic genes was confirmed, suggesting that survival after high-dose irradiation is a result of combination of highly effective blocking of entering the apoptosis after severe DNA damage and DNA reparation.

  18. Theoretical versus Ex Vivo Assessment of Radiation Damage Repair: An Investigation in Normal Breast Tissue.

    PubMed

    Ebert, Martin A; Dhal, Bipina; Prunster, Janelle; McLaren, Sally; Zeps, Nikolajs; House, Michael; Reniers, Brigitte; Verhaegen, Frank; Corica, Tammy; Saunders, Christobel; Joseph, David J

    2016-04-01

    In vivo validation of models of DNA damage repair will enable their use for optimizing clinical radiotherapy. In this study, a theoretical assessment was made of DNA double-strand break (DSB) induction in normal breast tissue after intraoperative radiation therapy (IORT), which is now an accepted form of adjuvant radiotherapy for selected patients with early breast cancer. DSB rates and relative biological effectiveness (RBE) were calculated as a function of dose, radiation quality and dose rate, each varying based on the applicator size used during IORT. The spectra of primary electrons in breast tissue adjacent to each applicator were calculated using measured X-ray spectra and Monte Carlo methods, and were used to inform a Monte Carlo damage simulation code. In the absence of repair, asymptotic RBE values (relative to (60)Co) were approximately 1.5. Beam-quality changes led to only minor variations in RBE among applicators, though differences in dose rate and overall dose delivery time led to larger variations and a rapid decrease in RBE. An experimental assessment of DSB induction was performed ex vivo using pre- and postirradiation tissue samples from patients receiving breast intraoperative radiation therapy. Relative DSB rates were assessed via γ-H2AX immunohistochemistry using proportional staining. Maximum-likelihood parameter estimation yielded a DSB repair halftime of 25.9 min (95% CI, 21.5-30.4 min), although the resulting model was not statistically distinguishable from one where there was no change in DSB yield among patients. Although the model yielded an in vivo repair halftime of the order of previous estimates for in vitro repair halftimes, we cannot conclude that it is valid in this context. This study highlights some of the uncertainties inherent in population analysis of ex vivo samples, and of the quantitative limitations of immunohistochemistry for assessment of DSB repair. PMID:27023258

  19. HSPB1 polymorphisms might be associated with radiation-induced damage risk in lung cancer patients treated with radiotherapy.

    PubMed

    Li, Xiaofeng; Xu, Sheng; Cheng, Yu; Shu, Jun

    2016-05-01

    Several studies investigating the association between heat shock protein beta-1 (HSPB1) polymorphisms and radiation-induced damage in lung cancer patients administrated with radiotherapy have derived conflicting results. This meta-analysis aimed to assess the association between the HSPB1 genes' (rs2868370 and rs2868371) polymorphisms and the risk of radiation-induced damage in lung cancer patients. After an electronic literature search, four articles including six studies were found to be eligible for this meta-analysis. No association was observed between rs2868370 genotypes and radiation-induced damage risk. However, rs2868371 showed a statistically increased risk of radiation-induced damage under CC vs. CG/GG model (OR = 1.59, 95 % CI = 1.10-2.29). Subgroup analysis by ethnicity showed that the genotypes of rs2868371 were also associated with a significantly increased risk of radiation-induced damage in CC vs. CG/GG model (OR = 1.86, 95 % CI = 1.21-2.83) among mixed ethnicities which are mainly comprised of white people. When the data was stratified by organ-damaged, a significant association was only observed in the esophagus group (OR = 2.94, 95 % CI = 1.35-6.37, for CC vs. CG/GG model). In conclusion, the present study demonstrated that the rs2868371 genotypes of HSPB1 might be associated with radiation-induced esophagus damage risk, especially in Caucasians but not in the Asian population. PMID:26874728

  20. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    NASA Astrophysics Data System (ADS)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  1. Fundamental Processes of Coupled Radiation Damage and Mechanical Behavior in Nuclear Fuel Materials for High Temperature Reactors

    SciTech Connect

    Phillpot, Simon; Tulenko, James

    2011-09-08

    The objective of this work has been to elucidate the relationship among microstructure, radiation damage and mechanical properties for nuclear fuel materials. As representative nuclear materials, we have taken an hcp metal (Mg as a generic metal, and Ti alloys for fast reactors) and UO2 (representing fuel). The degradation of the thermo-mechanical behavior of nuclear fuels under irradiation, both the fissionable material itself and its cladding, is a longstanding issue of critical importance to the nuclear industry. There are experimental indications that nanocrystalline metals and ceramics may be more resistant to radiation damage than their coarse-grained counterparts. The objective of this project look at the effect of microstructure on radiation damage and mechanical behavior in these materials. The approach to be taken was state-of-the-art, large-scale atomic-level simulation. This systematic simulation program of the effects of irradiation on the structure and mechanical properties of polycrystalline Ti and UO2 identified radiation damage mechanisms. Moreover, it will provided important insights into behavior that can be expected in nanocrystalline microstructures and, by extension, nanocomposites. The fundamental insights from this work can be expected to help in the design microstructures that are less susceptible to radiation damage and thermomechanical degradation.

  2. The Trp53 delta proline (Trp53ΔP) mouse exhibits increased genome instability and susceptibility to radiation-induced, but not spontaneous, tumor development.

    PubMed

    Adams, Cassandra J; Yu, Jennifer S; Mao, Jian-Hua; Jen, Kuang-Yu; Costes, Sylvain V; Wade, Mark; Shoemake, Jocelyn; Aina, Olulanu H; Del Rosario, Reyno; Menchavez, Phuong Thuy; Cardiff, Robert D; Wahl, Geoffrey M; Balmain, Allan

    2016-09-01

    The tumor suppressor TP53 can initiate a plethora of anti-proliferative effects to maintain genomic integrity under conditions of genotoxic stress. The N-terminal proline-rich domain (PRD) of TP53 is important in the regulation of TP53 activity and stability. A common polymorphism at codon 72 in this region has been associated with altered cancer risk in humans. The Trp53ΔP mouse, which carries a germline homozygous deletion of a region of the PRD, does not develop spontaneous tumors in a mixed 129/Sv and C57BL/6 genetic background, but is highly susceptible to a broad range of tumor types following total body exposure to 4 Gy gamma (γ) radiation. This contrasts with the tumor spectrum in Trp53 null (-/-) mice, which mainly develop thymic lymphomas and osteosarcomas. Analysis of genomic instability in tissues and cells from Trp53ΔP mice demonstrated elevated basal levels of aneuploidy, but this is not sufficient to drive spontaneous tumorigenesis, which requires an additional DNA damage stimulus. Levels of genomic instability did not increase significantly in Trp53ΔP mice following irradiation exposure, suggesting that other radiation effects including tissue inflammation, altered metabolism or autophagy, may play an important role. The Trp53ΔP mouse is a novel model to dissect the mechanisms of tumor development induced by radiation exposure. © 2015 Wiley Periodicals, Inc. PMID:26310697

  3. Mechanism of Radiation Damage Reduction in Equiatomic Multicomponent Single Phase Alloys.

    PubMed

    Granberg, F; Nordlund, K; Ullah, Mohammad W; Jin, K; Lu, C; Bei, H; Wang, L M; Djurabekova, F; Weber, W J; Zhang, Y

    2016-04-01

    Recently a new class of metal alloys, of single-phase multicomponent composition at roughly equal atomic concentrations ("equiatomic"), have been shown to exhibit promising mechanical, magnetic, and corrosion resistance properties, in particular, at high temperatures. These features make them potential candidates for components of next-generation nuclear reactors and other high-radiation environments that will involve high temperatures combined with corrosive environments and extreme radiation exposure. In spite of a wide range of recent studies of many important properties of these alloys, their radiation tolerance at high doses remains unexplored. In this work, a combination of experimental and modeling efforts reveals a substantial reduction of damage accumulation under prolonged irradiation in single-phase NiFe and NiCoCr alloys compared to elemental Ni. This effect is explained by reduced dislocation mobility, which leads to slower growth of large dislocation structures. Moreover, there is no observable phase separation, ordering, or amorphization, pointing to a high phase stability of this class of alloys. PMID:27081990

  4. Mechanism of Radiation Damage Reduction in Equiatomic Multicomponent Single Phase Alloys

    NASA Astrophysics Data System (ADS)

    Granberg, F.; Nordlund, K.; Ullah, Mohammad W.; Jin, K.; Lu, C.; Bei, H.; Wang, L. M.; Djurabekova, F.; Weber, W. J.; Zhang, Y.

    2016-04-01

    Recently a new class of metal alloys, of single-phase multicomponent composition at roughly equal atomic concentrations ("equiatomic"), have been shown to exhibit promising mechanical, magnetic, and corrosion resistance properties, in particular, at high temperatures. These features make them potential candidates for components of next-generation nuclear reactors and other high-radiation environments that will involve high temperatures combined with corrosive environments and extreme radiation exposure. In spite of a wide range of recent studies of many important properties of these alloys, their radiation tolerance at high doses remains unexplored. In this work, a combination of experimental and modeling efforts reveals a substantial reduction of damage accumulation under prolonged irradiation in single-phase NiFe and NiCoCr alloys compared to elemental Ni. This effect is explained by reduced dislocation mobility, which leads to slower growth of large dislocation structures. Moreover, there is no observable phase separation, ordering, or amorphization, pointing to a high phase stability of this class of alloys.

  5. Anisotropic mechanical properties of zircon and the effect of radiation damage

    DOE PAGESBeta

    Beirau, Tobias; Nix, William D.; Bismayer, Ulrich; Boatner, Lynn A.; Isaacson, Scott G.; Ewing, Rodney C.

    2016-06-02

    Our study provides new insights into the relationship between radiation-dose-dependent structural damage, due to natural U and Th impurities, and the anisotropic mechanical properties (Poisson s ratio, elastic modulus and hardness) of zircon. Natural zircon samples from Sri Lanka (see Muarakami et al. 1991) and synthetic samples, covering a dose range of zero up to 6.8 x 1018 -decays/g, have been studied by nanoindentation. Measurements along the [100] crystallographic direction and calculations, based on elastic stiffness constants determined by zkan (1976), revealed a general radiation-induced decrease in stiffness (~ 54 %) and hardness (~ 48 %) and an increase ofmore » the Poisson s ratio (~ 54 %) with increasing dose. Additional indentations on selected samples along the [001] allowed one to follow the amorphization process to the point that the mechanical properties are isotropic. This work shows that the radiation-dose-dependent changes of the mechanical properties of zircon can be directly correlated with the amorphous fraction as determined by previous investigations with local and global probes (Rios et al. 2000a; Farnan and Salje 2001; Zhang and Salje 2001). This agreement, revealed by the different methods, indicates a huge influence of structural and even local phenomena on the macroscopic mechanical properties.« less

  6. Radiation damage studies on STAR250 CMOS sensor at 300 keV for electron microscopy

    NASA Astrophysics Data System (ADS)

    Faruqi, A. R.; Henderson, R.; Holmes, J.

    2006-09-01

    There is a pressing need for better electronic detectors to replace film for recording high-resolution images using electron cryomicroscopy. Our previous work has shown that direct electron detection in CMOS sensors is promising in terms of resolution and efficiency at 120 keV [A.R. Faruqi, R. Henderson, M. Prydderch, R. Turchetta, P. Allport, A. Evans, Nucl. Instr. and Meth. 546 (2005) 170], but in addition, the detectors must not be damaged by the electron irradiation. We now present new measurements on the radiation tolerance of a 25 μm pitch CMOS active-pixel sensor, the STAR250, which was designed by FillFactory using radiation-hard technology for space applications. Our tests on the STAR250 aimed to establish the imaging performance at 300 keV following irradiation. The residual contrast, measured on shadow images of a 300 mesh grid, was >80% after corrections for increased dark current, following irradiation with up to 5×10 7 electrons/pixel (equivalent to 80,000 electron/μm 2). A CMOS sensor with this degree of radiation tolerance would survive a year of normal usage for low-dose electron cryomicroscopy, which is a very useful advance.

  7. Collateral DNA damage produced by genome-editing drones: exception or rule?

    PubMed

    Canela, Andres; Stanlie, Andre; Nussenzweig, André

    2015-05-21

    In the recent issue of Nature Biotechnology, Frock et al. (2015) developed an elegant technique to capture translocation partners that can be utilized to determine off-target regions of genome-editing endonucleases as well as endogenous mutators at nucleotide resolution. PMID:26000841

  8. Differential Processing of Low and High LET Radiation Induced DNA Damage: Investigation of Switch from ATM to ATR Signaling

    NASA Technical Reports Server (NTRS)

    Saha, Janapriya; Wang, Minli; Hada, Megumi; Cucinotta, Francis A.

    2011-01-01

    The members of the phosphatidylinositol kinase-like kinase family of proteins namely ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) are directly responsible for the maintenance of genomic integrity by mounting DDR through signaling and facilitating the recruitment of repair factors at the sites of DNA damage along with coordinating the deployment of cell cycle checkpoints to permit repair by phosphorylating Checkpoint kinase Chk1, Chk2 and p53. High LET radiation from GCR (Galactic Cosmic Rays) consisting mainly of protons and high energy and charged (HZE) particles from SPE (Solar Particle Event) pose a major health risk for astronauts on their space flight missions. The determination of these risks and the design of potential safeguards require sound knowledge of the biological consequences of lesion induction and the capability of the cells to counter them. We here strive to determine the coordination of ATM and ATR kinases at the break sites directly affecting checkpoint signaling and DNA repair and whether differential processing of breaks induced by low and high LET radiation leads to possible augmentation of swap of these damage sensors at the sites of DNA damage. Exposure of cells to IR triggers rapid autophosphorylation of serine-1981 that causes dimer dissociation and initiates monomer formation of ATM. ATM kinase activity depends on the disruption of the dimer, which allows access and phosphorylation of downstream ATM substrates like Chk2. Evidence suggests that ATM is activated by the alterations in higher-order chromatin structure although direct binding of ATM to DSB ends may be a crucial step in its activation. On the other hand, in case of ATR, RPA (replication protein A)-coated ssDNA (single-stranded DNA) generated as a result of stalled DNA replication or during processing of chromosomal lesions is crucial for the localization of ATR to sites of DNA damage in association with ATR-interacting protein (ATRIP). Although the

  9. A whole-genome, radiation hybrid mapping resource of hexaploid wheat.

    PubMed

    Tiwari, Vijay K; Heesacker, Adam; Riera-Lizarazu, Oscar; Gunn, Hilary; Wang, Shichen; Wang, Yi; Gu, Young Q; Paux, Etienne; Koo, Dal-Hoe; Kumar, Ajay; Luo, Ming-Cheng; Lazo, Gerard; Zemetra, Robert; Akhunov, Eduard; Friebe, Bernd; Poland, Jesse; Gill, Bikram S; Kianian, Shahryar; Leonard, Jeffrey M

    2016-04-01

    Generating a contiguous, ordered reference sequence of a complex genome such as hexaploid wheat (2n = 6x = 42; approximately 17 GB) is a challenging task due to its large, highly repetitive, and allopolyploid genome. In wheat, ordering of whole-genome or hierarchical shotgun sequencing contigs is primarily based on recombination and comparative genomics-based approaches. However, comparative genomics approaches are limited to syntenic inference and recombination is suppressed within the pericentromeric regions of wheat chromosomes, thus, precise ordering of physical maps and sequenced contigs across the whole-genome using these approaches is nearly impossible. We developed a whole-genome radiation hybrid (WGRH) resource and tested it by genotyping a set of 115 randomly selected lines on a high-density single nucleotide polymorphism (SNP) array. At the whole-genome level, 26 299 SNP markers were mapped on the RH panel and provided an average mapping resolution of approximately 248 Kb/cR1500 with a total map length of 6866 cR1500 . The 7296 unique mapping bins provided a five- to eight-fold higher resolution than genetic maps used in similar studies. Most strikingly, the RH map had uniform bin resolution across the entire chromosome(s), including pericentromeric regions. Our research provides a valuable and low-cost resource for anchoring and ordering sequenced BAC and next generation sequencing (NGS) contigs. The WGRH developed for reference wheat line Chinese Spring (CS-WGRH), will be useful for anchoring and ordering sequenced BAC and NGS based contigs for assembling a high-quality, reference sequence of hexaploid wheat. Additionally, this study provides an excellent model for developing similar resources for other polyploid species. PMID:26945524

  10. Radiation damage to Kokchetav UHPM diamonds in zircon: Variations in Raman, photoluminescence, and cathodoluminescence spectra

    NASA Astrophysics Data System (ADS)

    Shimizu, Rentaro; Ogasawara, Yoshihide

    2014-10-01

    We conducted detailed in-situ Raman, photoluminescence (PL) and cathodoluminescence (CL) studies on microdiamonds in a tourmaline-rich quartzofeldspathic rock from the Kokchetav Massif, Kazakhstan. The microdiamonds occur as inclusions in the cores of K-tourmaline and in zoned zircons with varying U contents. The results of 2D Raman mapping of zircon showed that the U-rich parts were more metamictized than the U-poor parts. All the diamonds showed a strong Raman band at approximately 1332 cm- 1, however, the features of the Raman bands were distinctly different depending on the host minerals. On the one hand, diamonds in tourmaline had a sharp Raman band that is similar to that of kimberlite diamonds [full width at half maximum (FWHM): 2-3 cm- 1]. On the other hand, diamonds in zircon had a broad and downshifted band compared to those in tourmaline. In particular, diamonds in U-rich cores of zircons (up to 0.15 wt.% UO2) showed broader and more downshifted Raman bands (FWHMs and peak positions varied up to 9.3 cm- 1 and 1328 cm- 1, respectively), with additional small bands at approximately 1490 cm- 1 and 1630 cm- 1. A negative correlation was observed between the peak position and the FWHM of the principal Raman band of microdiamonds. Furthermore, the PL and CL spectra showed systematic variations. Diamonds in zircons with low to moderate U-concentrations had very strong PL and CL compared to diamonds in U-rich zircons and in tourmalines. Several characteristic peaks appeared in the PL and CL spectra, indicating the presence of irradiation and/or nitrogen-related point defects in the diamonds. PL and CL of microdiamonds in high-U zircon were weak, but still showed irradiation-related peaks. The relationship between the occurrence of microdiamonds (i.e., corresponding to the estimated total α-dose since crystallization) and the Raman, PL, and CL spectral characteristics of microdiamonds strongly suggests that radiation damage predominantly caused by

  11. REC-2006-A Fractionated Extract of Podophyllum hexandrum Protects Cellular DNA from Radiation-Induced Damage by Reducing the Initial Damage and Enhancing Its Repair In Vivo.

    PubMed

    Chaudhary, Pankaj; Shukla, Sandeep Kumar; Sharma, Rakesh Kumar

    2011-01-01

    Podophyllum hexandrum, a perennial herb commonly known as the Himalayan May Apple, is well known in Indian and Chinese traditional systems of medicine. P. hexandrum has been widely used for the treatment of venereal warts, skin infections, bacterial and viral infections, and different cancers of the brain, lung and bladder. This study aimed at elucidating the effect of REC-2006, a bioactive fractionated extract from the rhizome of P. hexandrum, on the kinetics of induction and repair of radiation-induced DNA damage in murine thymocytes in vivo. We evaluated its effect on non-specific radiation-induced DNA damage by the alkaline halo assay in terms of relative nuclear spreading factor (RNSF) and gene-specific radiation-induced DNA damage via semi-quantitative polymerase chain reaction. Whole body exposure of animals with gamma rays (10 Gy) caused a significant amount of DNA damage in thymocytes (RNSF values 17.7 ± 0.47, 12.96 ± 1.64 and 3.3 ± 0.014) and a reduction in the amplification of β-globin gene to 0, 28 and 43% at 0, 15 and 60 min, respectively. Administrating REC-2006 at a radioprotective concentration (15 mg kg(-1) body weight) 1 h before irradiation resulted in time-dependent reduction of DNA damage evident as a decrease in RNSF values 6.156 ± 0.576, 1.647 ± 0.534 and 0.496 ± 0.012, and an increase in β-globin gene amplification 36, 95 and 99%, at 0, 15 and 60 min, respectively. REC-2006 scavenged radiation-induced hydroxyl radicals in a dose-dependent manner stabilized DPPH free radicals and also inhibited superoxide anions. Various polyphenols and flavonoides present in REC-2006 might contribute to scavenging of radiation-induced free radicals, thereby preventing DNA damage and stimulating its repair. PMID:20008078

  12. Global radiation damage at 300 and 260 K with dose rates approaching 1 MGy s[superscript -1

    SciTech Connect

    Warkentin, Matthew; Badeau, Ryan; Hopkins, Jesse B.; Mulichak, Anne M.; Keefe, Lisa J.; Thorne, Robert E.

    2012-02-27

    Global radiation damage to 19 thaumatin crystals has been measured using dose rates from 3 to 680 kGy s{sup -1}. At room temperature damage per unit dose appears to be roughly independent of dose rate, suggesting that the timescales for important damage processes are less than {approx}1 s. However, at T = 260 K approximately half of the global damage manifested at dose rates of {approx}10 kGy s{sup -1} can be outrun by collecting data at 680 kGy s{sup -1}. Appreciable sample-to-sample variability in global radiation sensitivity at fixed dose rate is observed. This variability cannot be accounted for by errors in dose calculation, crystal slippage or the size of the data sets in the assay.

  13. Joint modeling of thermal creep and radiation damage interaction with gas permeability and release dynamics: The role of percolation

    NASA Astrophysics Data System (ADS)

    Ovaska, M.; Alava, M. J.

    2015-10-01

    Nuclear fuel material is an example of a sintered, porous ceramic material. We formulate a two-dimensional model which couples three physical mechanisms in the material: (scalar) damage accumulation by thermal creep and radiation effects, porosity changes due to the damage, and the time-dependent diffusion of (radiation-induced) gases in the pore system thus created. The most important effect in the dynamics arises from the process where the pore system is swept through the percolation transition. The main conclusions that can be drawn concern the fractional gas release and its dependence on the three effects present in the damage dynamics: creep, radiation-induced bubble formation, and recovery due to bubble closure. In the main, the model reproduces the experimentally observed quick gas release phenomenon qualitatively.

  14. Frozen human cells can record radiation damage accumulated during space flight: mutation induction and radioadaptation.

    PubMed

    Yatagai, Fumio; Honma, Masamitsu; Takahashi, Akihisa; Omori, Katsunori; Suzuki, Hiromi; Shimazu, Toru; Seki, Masaya; Hashizume, Toko; Ukai, Akiko; Sugasawa, Kaoru; Abe, Tomoko; Dohmae, Naoshi; Enomoto, Shuichi; Ohnishi, Takeo; Gordon, Alasdair; Ishioka, Noriaki

    2011-03-01

    To estimate the space-radiation effects separately from other space-environmental effects such as microgravity, frozen human lymphoblastoid TK6 cells were sent to the "Kibo" module of the International Space Station (ISS), preserved under frozen condition during the mission and finally recovered to Earth (after a total of 134 days flight, 72 mSv). Biological assays were performed on the cells recovered to Earth. We observed a tendency of increase (2.3-fold) in thymidine kinase deficient (TK(-)) mutations over the ground control. Loss of heterozygosity (LOH) analysis on the mutants also demonstrated a tendency of increase in proportion of the large deletion (beyond the TK locus) events, 6/41 in the in-flight samples and 1/17 in the ground control. Furthermore, in-flight samples exhibited 48% of the ground-control level in TK(-) mutation frequency upon exposure to a subsequent 2 Gy dose of X-rays, suggesting a tendency of radioadaptation when compared with the ground-control samples. The tendency of radioadaptation was also supported by the post-flight assays on DNA double-strand break repair: a 1.8- and 1.7-fold higher efficiency of in-flight samples compared to ground control via non-homologous end-joining and homologous recombination, respectively. These observations suggest that this system can be used as a biodosimeter, because DNA damage generated by space radiation is considered to be accumulated in the cells preserved frozen during the mission, Furthermore, this system is also suggested to be applicable for evaluating various cellular responses to low-dose space radiation, providing a better understanding of biological space-radiation effects as well as estimation of health influences of future space explores. PMID:21161544

  15. Radiation-induced genomic instability: Are epigenetic mechanisms the missing link?

    SciTech Connect

    Aypar, Umut; Morgan, William F.; Baulch, Janet E.

    2011-02-01

    Purpose: This review examines the evidence for the hypothesis that epigenetics are involved in the initiation and perpetuation of radiation-induced genomic instability (RIGI). Conclusion: In addition to the extensively studied targeted effects of radiation, it is now apparent that non-targeted delayed effects such as RIGI are also important post-irradiation outcomes. In RIGI, unirradiated progeny cells display phenotypic changes at delayed times after radiation of the parental cell. RIGI is thought to be important in the process of carcinogenesis, however, the mechanism by which this occurs remains to be elucidated. In the genomically unstable clones developed by Morgan and colleagues, radiation-induced mutations, double-strand breaks, or changes in mRNA levels alone could not account for the initiation or perpetuation of RIGI. Since changes in the DNA sequence could not fully explain the mechanism of RIGI, inherited epigenetic changes may be involved. Epigenetics are known to play an important role in many cellular processes and epigenetic aberrations can lead to carcinogenesis. Recent studies in the field of radiation biology suggest that the changes in methylation patterns may be involved in RIGI. Together these clues have led us to hypothesize that epigenetics may be the missing link in understanding the mechanism behind RIGI.

  16. Cell to Cell Variability of Radiation-Induced Foci: Relation between Observed Damage and Energy Deposition.

    PubMed

    Gruel, Gaëtan; Villagrasa, Carmen; Voisin, Pascale; Clairand, Isabelle; Benderitter, Marc; Bottollier-Depois, Jean-François; Barquinero, Joan Francesc

    2016-01-01

    Most studies that aim to understand the interactions between different types of photon radiation and cellular DNA assume homogeneous cell irradiation, with all cells receiving the same amount of energy. The level of DNA damage is therefore generally determined by averaging it over the entire population of exposed cells. However, evaluating the molecular consequences of a stochastic phenomenon such as energy deposition of ionizing radiation by measuring only an average effect may not be sufficient for understanding some aspects of the cellular response to this radiation. The variance among the cells associated with this average effect may also be important for the behaviour of irradiated tissue. In this study, we accurately estimated the distribution of the number of radiation-induced γH2AX foci (RIF) per cell nucleus in a large population of endothelial cells exposed to 3 macroscopic doses of gamma rays from 60Co. The number of RIF varied significantly and reproducibly from cell to cell, with its relative standard deviation ranging from 36% to 18% depending on the macroscopic dose delivered. Interestingly, this relative cell-to-cell variability increased as the dose decreased, contrary to the mean RIF count per cell. This result shows that the dose effect, in terms of the number of DNA lesions indicated by RIF is not as simple as a purely proportional relation in which relative SD is constant with dose. To analyse the origins of this observed variability, we calculated the spread of the specific energy distribution for the different target volumes and subvolumes in which RIF can be generated. Variances, standard deviations and relative standard deviations all changed similarly from dose to dose for biological and calculated microdosimetric values. This similarity is an important argument that supports the hypothesis of the conservation of the association between the number of RIF per nucleus and the specific energy per DNA molecule. This comparison allowed us to

  17. Cell to Cell Variability of Radiation-Induced Foci: Relation between Observed Damage and Energy Deposition

    PubMed Central

    Voisin, Pascale; Clairand, Isabelle; Benderitter, Marc; Bottollier-Depois, Jean-François; Barquinero, Joan Francesc

    2016-01-01

    Most studies that aim to understand the interactions between different types of photon radiation and cellular DNA assume homogeneous cell irradiation, with all cells receiving the same amount of energy. The level of DNA damage is therefore generally determined by averaging it over the entire population of exposed cells. However, evaluating the molecular consequences of a stochastic phenomenon such as energy deposition of ionizing radiation by measuring only an average effect may not be sufficient for understanding some aspects of the cellular response to this radiation. The variance among the cells associated with this average effect may also be important for the behaviour of irradiated tissue. In this study, we accurately estimated the distribution of the number of radiation-induced γH2AX foci (RIF) per cell nucleus in a large population of endothelial cells exposed to 3 macroscopic doses of gamma rays from 60Co. The number of RIF varied significantly and reproducibly from cell to cell, with its relative standard deviation ranging from 36% to 18% depending on the macroscopic dose delivered. Interestingly, this relative cell-to-cell variability increased as the dose decreased, contrary to the mean RIF count per cell. This result shows that the dose effect, in terms of the number of DNA lesions indicated by RIF is not as simple as a purely proportional relation in which relative SD is constant with dose. To analyse the origins of this observed variability, we calculated the spread of the specific energy distribution for the different target volumes and subvolumes in which RIF can be generated. Variances, standard deviations and relative standard deviations all changed similarly from dose to dose for biological and calculated microdosimetric values. This similarity is an important argument that supports the hypothesis of the conservation of the association between the number of RIF per nucleus and the specific energy per DNA molecule. This comparison allowed us to

  18. A computational investigation on radiation damage and activation of structural material for C-ADS

    NASA Astrophysics Data System (ADS)

    Liang, Tairan; Shen, Fei; Yin, Wen; Yu, Quanzhi; Liang, Tianjiao

    2015-11-01

    The C-ADS (China Accelerator-Driven Subcritical System) project, which aims at transmuting high-level radiotoxic waste (HLW) and power generation, is now in the research and development stage. In this paper, a simplified ADS model is set up based on the IAEA Th-ADS benchmark calculation model, then the radiation damage as well as the residual radioactivity of the structural material are estimated using the Monte Carlo simulation method. The peak displacement production rate, gas productions, activity and residual dose rate of the structural components like beam window and outer casing of subcritical reactor core are calculated. The calculation methods and the corresponding results provide the basic reference for making reasonable predictions for the lifetime and maintenance operations of the structural material of C-ADS.

  19. Radiation Damage in Nuclear Fuel for Advanced Burner Reactors: Modeling and Experimental Validation

    SciTech Connect

    Jensen, Niels Gronbech; Asta, Mark; Ozolins, Nigel Browning'Vidvuds; de Walle, Axel van; Wolverton, Christopher

    2011-12-29

    The consortium has completed its existence and we are here highlighting work and accomplishments. As outlined in the proposal, the objective of the work was to advance the theoretical understanding of advanced nuclear fuel materials (oxides) toward a comprehensive modeling strategy that incorporates the different relevant scales involved in radiation damage in oxide fuels. Approaching this we set out to investigate and develop a set of directions: 1) Fission fragment and ion trajectory studies through advanced molecular dynamics methods that allow for statistical multi-scale simulations. This work also includes an investigation of appropriate interatomic force fields useful for the energetic multi-scale phenomena of high energy collisions; 2) Studies of defect and gas bubble formation through electronic structure and Monte Carlo simulations; and 3) an experimental component for the characterization of materials such that comparisons can be obtained between theory and experiment.

  20. Radiation damage mechanisms for luminescence in Eu-doped GaN

    SciTech Connect

    Tringe, J. W.; Felter, T. E.; Talley, C. E.; Morse, J. D.; Stevens, C. G.; Castelaz, J. M.; Wetzel, C.

    2007-03-01

    Thin films of Eu-doped GaN were irradiated with 500 keV He{sup +} ions to understand radiation damage mechanisms and to quantify luminescence efficiency. The dependence of ion-beam-induced luminescence intensity on ion fluence was consistent with the simultaneous creation of nonradiative defects and the destruction of luminescent centers associated with 4f-4f core-level transitions in Eu{sup 3+}. This model contrasts with a previous description which takes into account only nonradiative defect generation in GaN:Eu. Based on light from a BaF{sub 2} scintillator standard, the luminescent energy generation efficiency of GaN:Eu films doped to {approx}3x10{sup 18} cm{sup -3} Eu is estimated to be {approx}0.1%.