Дисертації: "Radiation induced bystander effect"

1

Liu, Chang S. B. Massachusetts Institute of Technology. "Radiation-induced bystander fibroblasts both reduce and amplify micronuclei induction through the reciprocal bystander effect and the secondary bystander effect." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106695.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 25-27).
Aside from directly causing DNA damage, the traversal of radiation through cells also induces the bystander effect, which is the biological response of unirradiated cells that are neighboring or sharing medium with the irradiated cells. Although the mechanisms through which irradiated cells send signals to the bystander cells are not well understood, the bystander effect could potentially have clinical relevance or play a significant role in low dose radiation environments. The research in this thesis focuses on the ability of the bystander cells to influence the behavior of cells that share medium with them, which can be separated into three categories: unirradiated cells, irradiated cells, and the original irradiated cells that caused the bystander effect. These can be considered the "secondary bystanders." Human AG01522 fibroblasts were irradiated with 250 kVp X-rays and co-cultured with unirradiated fibroblasts to generate bystander cells, which were then cocultured with one of the three types of secondary bystander cells. The micronucleus assay was used to analyze the amount of chromosome aberrations present. In the unirradiated secondary bystander population, an increase in percentage of binucleated cells with micronuclei from the background level to approximately the level of the primary bystander cells was observed, indicating that bystander cells can send damaging signals. The data also showed that there was a lower frequency of micronuclei formation in the irradiated population with bystander inserts in comparison to irradiated populations without bystanders. However, there were no conclusive data on the effect of the bystander cells on other irradiated cells. Overall, the results suggest that bystander fibroblasts are capable of sending both detrimental and beneficial signals and can induce a range of behaviors in other cells.
by Chang Liu.
S.B.

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2

Koturbash, Igor, and University of Lethbridge Faculty of Arts and Science. "Molecular mechanisms of radiation-induced bystander effects in vivo." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2008, 2008. http://hdl.handle.net/10133/664.

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Ionizing radiation (IR), along with being an important diagnostic and treatment modality, is a potent tumor-causing agent, and the risk of secondary radiation treatment-related cancers is a growing clinical problem. Now some studies propose to link secondary radiation-induced cancers to an enigmatic phenomenon of bystander effects, whereby the exposed cells send signal damage and distress to their naïve neighbors and result in genome destabilization and carcinogenesis. Yet, no data existed on the bystander effects in an organ other than an exposed one. With this in mind, we focused on the analysis of existence and mechanisms of radiation-induced bystander effects in vivo. We have found that bystander effects occur in vivo in distant skin and spleen following half-body or cranial irradiation. These bystander effects resulted in elevated DNA damage, profound dysregulation of epigenetic machinery, and pronounced alterations in apoptosis, proliferation and gene expression. Bystander effects also exhibited persistency and sex specificity. The results obtained while using the animal model systems can potentially be extrapolated to different animals and humans.
xiii, 208 leaves : ill. ; 29 cm.

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3

Gonon, Géraldine. "Space radiation-induced bystander effect : kinetics of biologic responses, mechanisms, and significance of secondary radiations." Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-00987717.

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Widespread evidence indicates that exposure of cell cultures to α particles results in significant biological changes in both the irradiated and non-irradiated bystander cells in the population. The induction of non-targeted biological responses in cell cultures exposed to low fluences of high charge (Z) and high energy (E) particles is relevant to estimates of the health risks of space radiation and to radiotherapy. Here, we investigated the mechanisms underlying the induction of stressful effects in confluent normal human fibroblast cultures exposed to low fluences of 1000 MeV/u iron ions (linear energy transfer (LET) ~151 keV/µm), 600 MeV/u silicon ions (LET ~50 keV/µm) or 290 MeV/u carbon ions (LET ~13 keV/µm). We compared the results with those obtained in cell cultures exposed, in parallel, to low fluences of 0.92 MeV/u α particles (LET ~109 keV/µm).Induction of DNA damage, changes in gene expression, protein carbonylation and lipid peroxidation during 24 h after exposure of confluent cultures to mean doses as low as 0.2 cGy of iron or silicon ions strongly supported the propagation of stressful effects from irradiated to bystander cells. At a mean dose of 0.2 cGy, only ~1 and 3 % of the cells would be targeted through the nucleus by an iron or silicon ion, respectively. Within 24 h post-irradiation, immunoblot analyses revealed significant increases in the levels of phospho-TP53 (serine 15), p21Waf1 (also known as CDKN1A), HDM2, phospho-ERK1/2, protein carbonylation and lipid peroxidation. The magnitude of the responses suggested participation of non-targeted cells in the response. Furthermore, when the irradiated cell populations were subcultured in fresh medium shortly after irradiation, greater than expected increases in the levels of these markers were also observed during 24 h. Together, the results imply a rapidly propagated and persistent bystander effect. In situ analyses in confluent cultures showed 53BP1 foci formation, a marker of DNA damage, in more cells than expected based on the fraction of cells traversed through the nucleus by an iron or silicon ion. The effect was expressed as early as 15 min after exposure, peaked at 1 h and decreased by 24 h. A similar tendency occurred after exposure to a mean absorbed dose of 0.2 cGy of 3.7 MeV α particles, but not after 0.2 cGy of 290 MeV/u carbon ions.Analyses in dishes that incorporate a CR-39 solid state nuclear track detector bottom identified the cells irradiated with iron or silicon ions and further supported the participation of bystander cells in the stress response. Mechanistic studies indicated that gap junction intercellular communication, DNA repair, and oxidative metabolism participate in the propagation of the induced effects.We also considered the possible contribution of secondary particles produced along the primary particle tracks to the biological responses. Simulations with the FLUKA multi-particle transport code revealed that fragmentation products, other than electrons, in cells cultures exposed to HZE particles comprise <1 % of the absorbed dose. Further, the radial spread of dose due to secondary heavy ion fragments is confined to approximately 10-20 µm Thus, the latter are unlikely to significantly contribute to the stressful effects in cells not targeted by primary HZE particles.

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4

Whiteside, James Roy. "Persistent genomic instability and bystander effects induced by ultraviolet radiation." Thesis, Lancaster University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444640.

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5

Anzenberg, Vered. "LET dependence of radiation-induced bystander effects using human prostate tumor cells." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44795.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008.
"June 2008."
Includes bibliographical references (leaves 133-140).
In the past fifteen years, evidence provided by many independent research groups have indicated higher numbers of cells exhibiting damage than expected based on the number of cells traversed by the radiation. This phenomenon has been coined as the "bystander effect". The purpose of this study was to characterize the ability of irradiated tumor cells to induce bystander effects in co-cultured cells. Human DU-145 prostate carcinoma cells were grown on a 1.4 [mu]m-thick mylar membrane in specially constructed cell culture dishes for irradiation with alpha particles (average energy 3.14 MeV) from a 241Am source, or in 6-well plates for irradiation with 250 kVp x-rays at 25°C. In parallel experiments, the tumor cells were incubated at 4°C for one hour prior to irradiation and irradiated on ice to test the nature of the bystander signal. Bystander cells were placed into the medium above the irradiated DU-145 and were co-incubated for a length of time. The bystander effect endpoints measured in either DU-145 tumor cells or in normal primary AGO1522 fibroblasts were micronucleus (MN) formation, [gamma]-H2AX double strand break repair foci, and survival fraction. A 1.5-2.0-fold increase in MN formation was observed in both DU-145 and AG01522 bystander cells after either alpha particle or xray irradiation of the DU-145 target cells. A 1.5-fold [gamma]-H2AX bystander increase and a survival fraction reduction to 80% were only detected in AGO1522 cells, and only after xray irradiation of target DU-145 cells. Alpha particle irradiation of the target DU-145 cells produced neither [gamma]-H2AX foci nor survival fraction bystander effect in either cell line. Lowering the temperature to 4°C during the irradiation of the DU-145 tumor cells, with either x-rays or alpha particles, eliminated both the MN formation and the decreased survival fraction bystander effects in the co-cultured AG01522 fibroblasts.
(cont.) This study demonstrates that biochemical processes in the directly-irradiated tumor cells are required for initiation of the signaling process. Low temperature during the irradiation inhibited the initiation of a bystander signal. There are also LET-dependent differences in the signal released from DU-145 human prostate carcinoma cells; and that, for some endpoints, bystander AG01522 fibroblasts and bystander DU-145 prostate carcinoma cells respond differently to the same, medium-mediated signal.
by Vered Anzenberg.
Ph.D.

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6

Blyth, Benjamin John, and benjamin blyth@flinders edu au. "Development and use of an adoptive transfer method for detecting radiation-induced bystander effects in vivo." Flinders University. School of Medicine, 2009. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20091008.150317.

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Ionising radiation can cause damage to DNA that can result in gene mutations contributing to carcinogenesis. Radiation-protection policy currently estimates cancer risks from exposures to radiation in terms of excess risk per unit dose. At very low radiation dose-rates, where not all cells are absorbing radiation energy, this formula carries the inherent assumption that risk is limited to those cells receiving direct energy depositions. Numerous studies have now called this assumption into question. Such low dose-rates are in the relevant range that the public receives from natural background and man-made sources, and, if this fundamental assumption proves unfounded, current estimations of radiation-induced cancer risk at low doses will be incorrect. Accurate predictions of stochastic cancer risks from low-dose radiation exposures are crucial to evaluating the safety of radiation-based technologies for industry, power generation and the increasing use of radiation for medical diagnostic and screening purposes. This thesis explores phenomena known as radiation-induced bystander effects. The term bystander effects, as used here, describes biological responses to ionising radiation (hitherto observed in vitro) in cells not directly traversed by an ionising track, due to intercellular signals received from neighbouring cells that did receive energy depositions. This study aimed to determine whether radiation effects are communicated between irradiated and unirradiated cells in vivo, and if so, whether this effect alters current estimations of cancer risk following low-dose radiation exposures. In order to answer these questions, an in vivo experimental system for studying bystander effects in mice was developed. The method was based on the adoptive transfer of irradiated splenocytes into unirradiated hosts with simultaneous identification of irradiated donor cells, and biological endpoints in unirradiated bystander cells in situ using fluorescence microscopy and image analysis. Splenocytes from donor mice were radiolabelled with 3H-thymidine or received an acute X-ray dose. The irradiated donor cells, labelled with a fluorescent probe, were then adoptively transferred into unirradiated recipient mice via the tail vein, whilst control mice received sham-irradiated donor cells. A proportion of the cells lodged in the recipient mouse spleens where they remained for a period before the tissues were cryopreserved. The locations of donor cells were identified in frozen spleen sections by the fluorescent probe, and the levels of apoptosis and proliferation were simultaneously evaluated in situ in the surrounding unirradiated bystander cells using fluorescence-based assays. Transgenic pKZ1 recipient mice were also used to quantify chromosomal inversions in bystander cells. Since three-dimensional spatial relationships were preserved, responses could be measured in the local area surrounding irradiated cells as well as further afield. Following the development of the irradiated-cell adoptive transfer protocol and validation of the sensitivity and reproducibility of the biological assays in situ, a series of experiments was performed. In the initial experiments, 500,000 radiolabelled cells (0.33 mBq.cell-1) were injected into recipient mice and the spleen tissues were isolated 22 h later. No changes in apoptosis or proliferation were detected in local bystander spleen cells or throughout the spleen, compared to mice receiving sham-radiolabelled donor cells. In subsequent experiments, the effects of a number of experimental conditions were explored including the injection of tenfold more donor cells, analysis of spleen tissues after three days lodging in vivo, radiolabelling of donor cells with 100-fold higher 3H dose-rate and irradiation of donor cells ex vivo with 0.1 or 1 Gy X-rays. In each case, no changes in apoptosis or proliferation were observed. The in vivo method described here was designed to simulate the conditions of a bystander scenario from low dose-rate exposures relevant to public radiation protection. Contrary to the many reports of bystander effects in vitro, experiments using this sensitive method for examining the in vivo responses of unirradiated cells to neighbouring low-dose irradiated cells, have so far shown no changes in bystander cells in the spleen. This adoptive transfer method is the first in vivo method for examining the effects of known irradiated cells exposed to low radiation doses at low dose-rates, on neighbouring cells in situ that are truly unirradiated. Both the irradiated and bystander cells are normal, non-transformed primary spleen cells functioning in their natural environment. This in vivo experimental system allows the examination of tens of thousands of bystander cells and has shown a remarkable sensitivity, with statistical power to rule out changes in apoptosis <10% from the control. The relevance of in vitro bystander findings is unclear. Many reported bystander effects are more analogous to the systemic communication of abscopal effects from highly irradiated tissues. Disagreement between experimental systems and difficulty in reproducing key results between laboratories further complicate the translation of bystander data in vitro to human risk-estimation. The radiation protection community has expressed its need for in vivo validation of the bystander phenomenon before it can be included into the appraisal of carcinogenic risk. This adoptive transfer method is now available to study a range of bystander endpoints and potential signalling mechanisms in vivo, and provides a way to translate the wealth of data previously collected in vitro into findings directly relevant to human risk-estimation.

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7

Fullerton, Natasha Eileen. "Gene therapy and targeted radiotherapy applied to bladder and prostate cancer : examination of radiation-induced bystander effects in targeted radiotherapy." Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438687.

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8

Wordsworth, James William. "The senescent cell induced bystander effect." Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2536.

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The induction of senescence in response to persistent stress induces major phenotypic changes in senescent cells, including the secretion of a host of inflammatory factors and reactive oxygen species. Recent evidence has implicated senescent cells in the diseases of ageing and cancer; however, the mechanism by which this occurs is still unknown. This thesis uses a reporter cell line with cells expressing a fluorescent conjugate that allows real time live cell imaging of a sub set of cells within a co-culture, to provide the first evidence that senescent cells can induce a DNA damage response in healthy cells, and thus implicates a potential mechanism by which senescent cells could non-autonomously contribute to the ageing process. The use of specific inhibitors, stimulation, and targeted repression indicate that gap junctions, reactive oxygen species, p38, mTOR and NF-κB all play a key role in this observed bystander effect of senescent cells, and offer potential targets for therapies designed to reduce the damaging effects of senescent cells.

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9

Zemp, Franz Joseph, and University of Lethbridge Faculty of Arts and Science. "The bystander effect : animal and plant models." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2008, 2008. http://hdl.handle.net/10133/685.

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Bystander effects are traditionally known as a phenomenon whereby unexposed cells exhibit the molecular symptoms of stress exposure when adjacent or nearby cells are traversed by ionizing radiation. However, the realm of bystander effects can be expanded to include any systemic changes to cellular homeostasis in response to a number of biotic or abiotic stresses, in any molecular system. This thesis encompasses three independent experiments looking at bystander and bystander-like responses in both plant and animal models. In plants, an investigation into the regulation of small RNAs has given us some insights into the regulation of the plant hormone auxin in both stress-treated and systemic (bystander) leaves. Another plant model shows that a bystander-like plant-plant signal can be induced upon ionizing radiation to increase the genome instability of neighbouring unexposed (bystander) plants. In animals, it is shown that the microRNAome is largely affected in the bystander cells in a three-dimensional human tissue model. In silico and bioinfomatic analysis of this data provide us with clues as to the nature of bystander signalling in this human ‘in vivo’ model.
xiv, 141 p. : ill. ; 29 cm.

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10

Lumpkins, Sarah B. "Space radiation-induced bystander signaling in 2D and 3D skin tissue models." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70817.

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Thesis (Sc. D.)--Harvard-MIT Program in Health Sciences and Technology, 2012.
Page 157 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 145-156).
Space radiation poses a significant hazard to astronauts on long-duration missions, and the low fluences of charged particles characteristic of this field suggest that bystander effects, the phenomenon in which a greater number of cells exhibit damage than expected based on the number of cells traversed by radiation, could be significant contributors to overall cell damage. The purpose of this thesis was to investigate bystander effects due to signaling between different cell types cultured within 2D and 3D tissue architectures. 2D bystander signaling was investigated using a transwell insert system in which normal human fibroblasts (A) and keratinocytes (K) were irradiated with 1 GeV/n protons or iron ions at the NASA Space Radiation Laboratory using doses from either 2 Gy (protons) or 1 Gy (iron ions) down to spacerelevant low fluences. Medium-mediated bystander responses were investigated using three cell signaling combinations. Bystander signaling was also investigated in a 3D model by developing tissue constructs consisting of fibroblasts embedded in a collagen matrix with a keratinocyte epidermal layer. Bystander experiments were conducted by splitting each construct in half and exposing half to radiation then placing the other half in direct contact with the irradiated tissue on a transwell insert. Cell damage was evaluated primarily as formation of foci of the DNA repair-related protein 53BP1. In the 2D system, both protons and iron ions yielded a strong dose dependence for the induction of 53BP1 in irradiated cells, while the magnitudes and time courses of bystander responses were dependent on radiation quality. Furthermore, bystander effects were present in all three cell signaling combinations even at the low proton particle fluences used, suggesting the potential importance of including these effects in cancer risk models for low-dose space radiation exposures. Cells cultured in the 3D constructs exhibited a significant reduction in the percentages of both direct and bystander cells positive for 53BP1 foci, although the qualitative kinetics of DNA damage and repair were similar to those observed in 2D. These results provide evidence that the microenvironment significantly influences intercellular signaling and that cells may be more radioresistant in 3D compared to 2D systems.
by Sarah B. Lumpkins.
Sc.D.

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11

Nishiura, Hideki. "The bystander effect is a novel mechanism of UVA-induced melanogenesis." Kyoto University, 2012. http://hdl.handle.net/2433/157451.

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12

Diegeler, Sebastian [Verfasser]. "The role of nuclear factor kappa B in the radiation-induced bystander response / Sebastian Diegeler." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1219904465/34.

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13

MacPhail, Susan Helen. "Effect of intercellular contact on radiation-induced DNA damage." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27986.

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Chinese hamster V79-171B cells grown for about 24 hours in suspension culture display increased resistance to cell killing by ionizing radiation compared with cells grown as monolayers, an observation originally termed the "contact effect". More recently, development of that resistance was shown to be accompanied by changes in the conformation of the DNA which reduce its denaturation rate in high salt/weak alkali. These changes in DNA conformation, mediated by the cellular micro-environment, appear to be responsible for the contact effect. The conditions necessary for the development of the effect are not, however, completely understood. In particular, when cells grown as monolayers on petri plates are suspended in spinner culture flasks, their growth characteristics change in three distinct ways. First, cells in suspension no longer have a solid substrate, so they remain round. Second, after several hours, they begin to aggregate to form "spheroids", so that three-dimensional intercellular cell contact develops. Third, cells in the stirred suspension cultures are not subjected to high local concentrations of metabolic by-products or surrounded by a zone depleted of nutrients, as are cells in monolayer culture. The studies described here were designed to determine how each of these factors influence changes in DNA conformation, as assayed using the alkali unwinding technique. Our results indicated that a round shape may not be an essential requirement, since cells spread out on the surface of cytodex beads in suspension culture, and sparsely-seeded cells in monolayer culture demonstrated at least a partial contact effect. Three-dimensional intercellular contact does not always seem necessary for the development of the contact effect. Cells grown in a methyl cellulose matrix developed radioresistance, even though the cells formed only small clusters of less than five cells. Similarly, suspension culture cells which were prevented from aggregating by frequent exposure to trypsin, also developed the contact effect. There was no evidence that nutrient depletion plays a role in the failure of cells grown as monolayers to develop a contact effect. However, cells grown as spheroids in the presence of monolayer cells, or in monolayer cell-conditioned medium, did not display a full contact effect. This indicates a role for monolayer cell-produced factors (possibly extracellular matrix proteins) in preventing the development of the contact effect. We conclude that changes in DNA conformation and the increase in radiation resistance, seen in V79-171b cells grown as spheroids, are not the result of intercellular contact or round shape of the cells. This radioresistance appears to be the result of an absence of monolayer cell-produced factors which could control both cell shape and DNA conformation.
Medicine, Faculty of
Pathology and Laboratory Medicine, Department of
Graduate

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14

Barbara, Nabil Victor 1964. "Simulation of radiation-induced parametric degradation in electronic amplifiers." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277143.

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Many high performance amplifiers use power MOSFETs in their output stages, especially in operational amplifier applications whenever high current or power is needed. MOSFETs have advantages over bipolar transistors in amplifier output stage because MOSFETs are majority carrier devices. The result is wide frequency response, fast switching and better linearity than power bipolar transistors. But unlike bipolar circuits, which are relatively tolerant of ionizing radiation, MOSFETs may suffer severe parametric degradation at low total-dose levels. The effects of ionizing radiation on MOSFETs are discussed, and the performance of an amplifier circuit that uses a complementary MOSFET source follower in its output stage is simulated to examine the effect of MOSFET radiation damage on amplifier performance. An increase in power dissipation was the most significant degradation caused by ionizing radiation.

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15

Morabito, Brian Joseph. "Quantitating radiation induced DNA breaks by capillary electrophoresis." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/16339.

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16

Gladney, Dewey Clinton. "Simulating radiation-induced defects on semiconductor devices." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FGladney.pdf.

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17

Alvarado, Chacón Fresia. "Ion induced radiation damage on the molecular level." [S.l. : Groningen : s.n. ; University Library of Groningen] [Host], 2007. http://irs.ub.rug.nl/ppn/305192396.

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18

Tamminga, Jan, and University of Lethbridge Faculty of Arts and Science. "Radiation-induced epigenome deregulation in the male germline." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2008, 2008. http://hdl.handle.net/10133/746.

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Approximately 45% of men will develop cancer during their lifetime; some of which will be of reproductive age (Canadian Cancer Society, 2008). Current advances in treatment regimens such as radiotherapy have significantly lowered cancer-related mortality rates; however, one major quality-of-life issue in cancer survivors is the ability to produce healthy offspring. Exposure to ionizing radiation (IR) leads to genomic instability in the germline, and further to transgeneration genome instability in unexposed offspring of preconceptionally exposed parents. The results presented in this thesis define, in part, the molecular consequences of direct and indirect irradiation for the male germline. Direct exposure results in a significant accumulation of DNA damage, altered levels of global DNA methylation and microRNAome dysregulation of testis tissue. Localized cranial irradiation results in a significant accumulation of unrepaired DNA lesions and loss of global DNA methylation in the rodent (rat) germline. Biological consequences of the changes observed are discussed.
xii, 121 leaves : ill. ; 29 cm.

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19

Rafferty, Teresa S. "The effect of selenium on ultraviolet-B radiation-induced damage to the skin." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/22570.

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Selenium (Se) is a trace element found in many food sources, it is incorporated into specific selenoproteins. These include glutathione peroxidase and thioredoxin reductase which have strong antioxidant functions. In mice Se supplementation can reduce the number of skin tumours formed after UV irradiation. The purpose of the present thesis research was to characterise these protective mechanisms. To assess the effect of Se supplementation on UV irradiation of the skin, human skin cells were grown in vitro and supplemented with Se. Selenoprotein profiles were characterised by ⁷⁵Se labelling. It was shown that primary human fibroblasts, melanocytes and keratinocytes all express unique patterns of selenoproteins. Se reduced the amount of cell death induced by ultraviolet- B radiation(UVB), it also reduced apoptotic cell death. Following keratinocytes Se reduced the induction of mRNA for IL-8, IL-6 and TNFa, but not the protein. In mouse keratinocytes the levels of mRNA for TNFa and IL-10 were reduced and IL-10 protein level was reduced. The effect of Se on the UV induction of DNA damage was assessed by the comet assay. The formation and rate of repair of cyclobutane dimer sites was not affected by Se. However the formation of oxidative damage was reduced. P53 protein is also induced following UVB irradiation, Se did not affect the abundance of the protein, but it did reduce the activity of P53 as measured by reporter assay. Se also reduced the production of lipid peroxides in keratinocytes following UVB. Mouse studies were also carried out where mice were fed different levels of Se for six weeks, then exposed to MED UVB. It was found that the number of Langerhan cells was higher in the Se replete animals and remained higher even after UVB treatment.

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20

Safarjameh, Kourosh 1961. "Fast-neutron-induced resistivity change in power MOSFETs." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277011.

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Fast neutron irradiation tests were performed to determine the correlation of change of drain-source resistance and neutron fluence for power MOSFETs. The Objectives of the tests were: (1) to detect and measure the degradation of critical MOSFET device parameters as a function of neutron fluence (2) to compare the experimental results and the theoretical model. In general, the drain-source resistance increased from 1 Ohm to 100 Ohm after exposure to fast neutron fluence of 3 x 1014 neut/cm2, and decreased by a factor of five after high temperature annealing.

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21

Fengler, John Josef Paul. "Respiration induced oxygen gradients in cultured mammalian cells." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28381.

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Oxygen is known to sensitize X-irradiated cells to lethal radiation damage. At low ambient oxygen tensions, however, the molecular mechanisms of the sensitization process and the metabolic requirements of the cell may be forced to compete for the cellular oxygen supply. The effect of cell respiration on the availability of intracellular oxygen during irradiation was consequently investigated by comparing the radiosensitivities of respiring and non-respiring cells. Cultured mammalian cells were irradiated in single cell suspensions and thin film monolayers at respiration inhibiting (4°C) and at normal cell culturing (37°C) temperatures. Due to oxygen equilibration and radiolytic depletion problems, the results of the suspension culture experiments were inconclusive. By subsequently analyzing the diffusive mass transfer of oxygen in the suspension medium, the stirrer flask was determined to be an inappropriate culture vessel in which to irradiate cells at constant low oxygen concentrations. A thin film cell culture system in which the oxygen concentrations to which the cells were exposed during irradiation could be more accurately controlled was then developed. A comparison of the oxygen enhanced radiosensitivities of the respiring and non-respiring cells in thin film monolayers suggested that the metabolic depletion of oxygen at low oxygen tensions has a significant effect on the local and intracellular oxygen distribution. These effects are representative of those that would be produced if respiration induced oxygen gradients existed inside and immediately around respiring cells. The magnitude of the differential radiosensitivities was found to be dependent on cell shape and to have values that agreed very well with theoretical predictions based on the existence of such gradients.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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22

Coombs, Anne-Marie. "A study of near-ultraviolet radiation induced oxidative damage in Escherichia coli." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380929.

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23

Bryer, Bevan. "Protection unit for radiation induced errors in flash memory systems." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50070.

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Анотація:

Thesis (MScEng)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Flash memory and the errors induced in it by radiation were studied. A test board was then designed and developed as well as a radiation test program. The system was irradiated. This gave successful results, which confirmed aspects of the study and gave valuable insight into flash memory behaviour. To date, the board is still being used to test various flash devices for radiation-harsh environments. A memory protection unit (MPU) was conceptually designed and developed to morntor flash devices, increasing their reliability in radiation-harsh environments. This unit was designed for intended use onboard a micro-satellite. The chosen flash device for this study was the K9F1208XOA model from SAMSUNG. The MPU was designed to detect, maintain, mitigate and report radiation induced errors in this flash device. Most of the design was implemented in field programmable gate arrays and was realised using VHDL. Simulations were performed to verify the functionality of the design subsystems. These simulations showed that the various emulated errors were handled successfully by the MPU. A modular design methodology was followed, therefore allowing the chosen flash device to be replaced with any flash device, following a small reconfiguration. This also allows parts of the system to be duplicated to protect more than one device.
AFRIKAANSE OPSOMMING: 'n Studie is gemaak van" Flash" geheue en die foute daarop wat deur radiasie veroorsaak word. 'n Toetsbord is ontwerp en ontwikkel asook 'n radiasie toetsprogram waarna die stelsel bestraal is. Die resultate was suksesvol en het aspekte van die studie bevestig en belangrike insig gegee ten opsigte van "flash" komponente in radiasie intensiewe omgewmgs. 'n Geheue Beskermings Eenheid (GBE) is konseptueel ontwerp en ontwikkelom die "flash" komponente te monitor. Dit verhoog die betroubaarheid in radiasie intensiewe omgewings. Die eenheid was ontwerp met die oog om dit aan boord 'n mikro-satelliet te gebruik. Die gekose "flash" komponent vir die studie was die K9F1208XOA model van SAMSUNG. Die GBE is ontwerp om foute wat deur radiasie geïnduseer word in die "flash" komponent te identifiseer, herstel en reg te maak. Die grootste deel van die implementasie is gedoen in "field programmable gate arrays" and is gerealiseer deur gebruik te maak van VHDL. Simulasies is gedoen om die funksionaliteit van die ontwikkelde substelsels te verifieer. Hierdie simulasies het getoon dat die verskeie geëmuleerde foute suksesvol deur die GBE hanteer is. 'n Modulre ontwerpsmetodologie is gevolg sodat die gekose "flash" komponent deur enige ander flash komponent vervang kan word na gelang van 'n eenvoudige herkonfigurasie. Dit stelook dele van die sisteem in staat om gedupliseer te word om sodoende meer as een komponent te beskerm.

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24

Kovach, Matthew James. "Adaptive Advantages of Carotenoid Pigments in Alpine and Subalpine Copepod Responses to Polycyclic Aromatic Hydrocarbon Induced Phototoxicity." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc28444/.

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Alpine zooplankton are exposed to a variety of stressors in their natural environment including ultraviolet radiation. Physiological coping mechanisms such as the accumulation of photoprotective compounds provide these zooplankton protection from many of these stressors. Elevated levels of carotenoid compounds such as astaxanthin have been shown to help zooplankton survive longer when exposed to ultraviolet radiation presumably due to the strong antioxidant properties of carotenoid compounds. This antioxidant capacity is important because it may ameliorate natural and anthropogenic stressor-induced oxidative stress. While previous researchers have shown carotenoid compounds impart increased resistance to ultraviolet radiation in populations of zooplankton, little work has focused on the toxicological implications of PAH induced phototoxicity on zooplankton containing high levels of carotenoid compounds. This thesis discusses research studying the role that carotenoid compounds play in reducing PAH induced phototoxicity. By sampling different lakes at elevations ranging from 9,500' to 12,700' in the front range of the Colorado Rocky Mountains, copepod populations containing different levels of carotenoid compounds were obtained. These populations were then challenged with fluoranthene and ultraviolet radiation. Results discussed include differences in survival and levels of lipid peroxidation among populations exhibiting different levels of carotenoid compounds, and the toxicological and ecological implications of these results.

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25

Byrne, Shaun Edward. "An investigation into the processing of ionising radiation induced clustered DNA damage sites using mammalian cell extracts." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670082.

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26

Nilsson, Kenneth. "Radiation induced pneumonitis : clinical and experimental studies with special emphasis on the effect of smoking." Doctoral thesis, Umeå universitet, Onkologi, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100545.

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Bronchoalveolar lavage (BAL) is an established method providing diagnostic support and evaluation of disease activity in interstitial lung disease (ILD). The aims of the present investigation were 1) to study the inflammatory response in pneumonitis evoked by irradiation. 2) to evaluate how well lung tissue inflammation is reflected in BAL findings. 3) to study the effect of smoking on radiation-induced pneumonitis. BAL was performed in 21 patients (11 smokers, 10 non-smokers) who were treated for breast cancer, stage 1 (TjMaNq) by post-surgery irradiation to an accumulated target dose of 56 Gy. It was founa that irradiation induced an alveolitis in the non-smoking patient group while the smoking patients did not differ from their smoking controls. The alveolitis in non-smokers was characterized by an increase in lymphocytes, mast cells and elevated concentrations of hyaluronan (HA), and fibronectin (FN). Three of the non-smoking patients had chest X-ray infiltrates indicating the presence of pneumonitis. An animal experimental model for radiation-induced pneumonitis and fibrosis was established in rats, allowing comparative analysis of BAL fluid and morphology. In the rat model a divergence was noted between the differential cell counts in BAL and cells observed in the interstitial tissue, which was most notable for neutrophils (PMN) and mast cells whereas there was a good correlation between HA content in BAL and HA deposition in the lung tissue. A marked infiltration of intraseptally-located mast cells occurred during the pneumonitis-phase, and this increase was paralleled by a deposition of HA in the interstitial tissue. Histochemical fixation and staining properties of the mast cells revealed that the majority of these cells were of connective tissue mast cell type (CTMC). Compound 48/80, a mast cell secretagogue, significantly altered the HA content both in BAL and in lung tissue in the irradiated animals. Regular treatment throughout the whole experimental period induced depletion of mast cell granules and a decrease in HA deposition whereas 48/80 treatment during the pneumonitis phase enhanced HA deposition. A rat model with smoke exposure was developed, and the effect of cigarette smoke on radiation-induced inflammation was studied. Rats that smoked 3 weeks prior to irradiation and continued to smoke throughout the observation period (7 weeks) had a significantly reduced inflammatory response compared to irradiated non-smoking rats. The most prominent BAL findings in the smoke-exposed rats were a decrease in PMN, mast cells and a decrease in HA. In conclusion, irradiation induces an alveolitis characterized mainly by mononuclear cells. Mast cells seem to be of importance in the remodelling of the connective tissue in the radiation-induced inflammatory response. Hyaluronan is an important component in the early connective tissue response preceding later collagen deposition, and its interstitial deposition is very well reflected in BAL. Moreover, tobacco-smoke suppresses the radiation-induced inflammation with a decreased recruitment of effector cells including mast cells.

Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 5 uppsatser.

digitalisering@umu

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27

Lin, Jun. "Radiation-induced alterations in mesoporous silicas : The effect of electronic processes involving ions and electrons." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2022. http://theses.enscm.fr/ENSCM_2022_LIN.pdf.

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Les matériaux utilisés dans le nucléaire (combustible, matrice de conditionnement, matériaux de structure…) sont soumis à des contraintes importantes liées à la création de défauts qui modifient leurs propriétés. Plusieurs études ont montré que les interfaces peuvent agir comme un puits pour les défauts causés par l'irradiation, ce qui suggère que les nanomatériaux pourraient avoir une plus grande résistance à l'irradiation que les matériaux présentant une structure « micrométrique ». Par ailleurs, les silices mésoporeuses ont gagné en popularité ces dernières années et sont envisagées pour le traitement des effluents radioactifs (séparation, conditionnement…). Bien que de nombreuses études aient été réalisées sur le comportement de silices non poreuses sous irradiation, très peu de travaux s’intéressent à celui de la silice mésoporeuse en particulier lorsqu’elle est irradiée en régime d‘électronique.Le but de cette thèse est de comprendre et d'expliquer les modifications induites par irradiation dans les silices mésoporeuses en régime électronique. Ce travail a permis de quantifier l’évolution de propriétés physico-chimiques (polymérisation du réseau, création de défauts…) et structurales (volume poreux, diamètre et distribution des pores…) de la silice mésoporeuse irradiée par des faisceaux d'ions de haute énergie dans une gamme de pouvoirs d'arrêt variant entre 1 keV/nm et 12 keV/nm, ainsi que par des électrons (10 - 300 keV et 0.6 - 2.4 MeV). Des méthodes de caractérisation post-irradiation (réflectivité des rayons X, adsorption de gaz, SAXS et FTIR, etc.) ont été utilisées, ainsi que le suivi in situ de la structure des pores à l'aide de microscopie électronique. Les résultats expérimentaux ont indiqué que la structure des pores était sensible à l'irradiation conduisant dans certaines conditions à son effondrement, tandis que le réseau de silice lui-même évolue peu par rapport à la silice non poreuse. Parallèlement, un modèle TS3D (modèle de pointe thermique 3D) a été utilisé avec succès pour décrire et expliquer le comportement de contraction des pores observé en réponse à l'irradiation ionique. De plus, le mécanisme de contraction des pores sous irradiation par des électrons a été délimité en fonction du domaine des énergies incidentes des électrons et de la dose. Cette recherche a montré que par rapport à une silice non poreuse, la présence de pores nanométriques réduit l’accumulation des dommages causés par les irradiations. Conjointement à cet effet bénéfique, le pore se contracte jusqu’à disparaitre sous l’impact de l’irradiation. Par conséquent, d’un point de vue applicatif cette caractéristique pourrait être mise à profit pour imaginer de nouvelles voies de traitement des effluents radioactifs, par une stratégie de type « séparation/conditionnement » ou pour l'autoguérison des couches de gel poreux formées à la surface des colis de déchets vitrifiés dont l’exutoire envisagé est le stockage géologique profond
Materials used in nuclear energy (fuel, packaging matrix, structural materials...) are subject to significant stresses due to the creation of defects that modify their properties. Several studies have shown that interfaces can act as a sink for defects caused by irradiation, which suggests that nanomaterials could have a higher resistance to irradiation than materials with a "micrometric" structure. Simultaneously, mesoporous silica materials have grown in popularity in recent years and are becoming more involved in the domain related to radiation conditioning, such as the prospective use of conditioning for nuclear waste. While research has begun to focus on the behavior of non-porous silica materials when exposed to radiation, no extensive investigations have been conducted on the behavior of mesoporous silica when exposed to radiation, particularly at electronic irradiation regime.This thesis aims to comprehend and explain the radiation-induced changes in mesoporous silicas under electronic regimes. This work quantified the evolution of physical (pore volume, pore diameter and distribution...) and structural (polymerization of the network, creation of defects...) properties of mesoporous silica irradiated with high-energy ion beams with stopping powers ranging from 1 keV/nm to 12 keV/nm, and with electron beams (10 - 300 keV and 0.6 - 2.4 MeV). Post-irradiation characterization methods (X-ray reflectivity, gas adsorption, SAXS, FTIR, etc.) have been used, as well as in-situ pore structure monitoring using electron microscopes. The experimental findings indicated that pore structures were susceptible to a certain degree of irradiation-induced shrinking. In contrast, evidence shows that the silica network itself does not alter much in porous silica compared to non-porous silica. Meanwhile, a 3DTS (3D thermal spike) model has been successfully applied to describe and explain the observed pore contraction behavior in response to ionic irradiation. Additionally, the mechanism of pore contraction under electron irradiation has been delineated according to the domain of incident electron energies. When compared to non-porous silica, this research has demonstrated that the existence of nanoscale pores reduces the accumulation of damage induced by irradiation. In conjunction with this effect, the pore contracts until it completely disappears under the impact of irradiation. This characteristic could, from an applicative point of view, be of interest to practitioners in the context of new methods of treating radioactive effluents, such as through the use of a "separation/conditioning" strategy, or in the context of the self-healing of porous gel layers formed on the surface of vitrified waste packages whose final destination is deep geological disposal

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28

McRae, Dorothy A., and University of Lethbridge Faculty of Arts and Science. "Radiation induced epigenetic dysregulation in rat mammary gland tissue / Dorothy A. McRae." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, c2010, 2010. http://hdl.handle.net/10133/2615.

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Most breast cancer patients undergo radiation diagnostics and are also treated with radiotherapy. In addition to being an important treatment modality, ionizing radiation (IR) is a potent tumour-causing agent that has been linked to breast cancer development. However, the exact molecular etiology of IR-induced mammary gland carcinogenesis remains unknown. We set out to analyze the role of DNA methylation in mammary gland responses to low dose IR using a well-established rat model. We also studied low dose IR effects on global gene expression and microRNAome. We found that exposure to low, mammography-like dose of IR led to a significant loss of global DNA methylation in rat mammary gland tissue. Furthermore, low dose IR significantly affected rat mammary gland transcriptome and microRNAome. The datasets generated within the scope of this thesis may be used to identify novel predictive biomarkers for assessment of the magnitude of IR effects on mammary gland tissue.
xi, 120 leaves ; 29 cm

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29

Merrifield, Matthew, and University of Lethbridge Faculty of Arts and Science. "Radiation-induced deregulation of PiRNA pathway proteins : a possible molecular mechanism underlying transgenerational epigenomic instability." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Science, c2011, 2011. http://hdl.handle.net/10133/2617.

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PiRNAs and their Piwi family protein partners are part of a germline specific epigenetic regulatory mechanism essential for proper spermatogenesis, silencing of transposable elements, and maintaining germline genome integrity, yet their role in the response of the male germline to genotoxic stress is unknown. Ionizing radiation (IR) is known to cause transgenerational genome instability that is linked to carcinogenesis. Although the molecular etiology of IR-induced transgenerational genomic instability is not fully understood, it is believed to be an epigenetically mediated phenomenon. IR-induced alterations in the expression pattern of key regulatory proteins involved in the piRNA pathway essential for paternal germline genome stability may be directly involved in producing epigenetic alterations that can impact future generations. Here we show whole body and localized X-irradiation leads to significant altered expression of proteins that are necessary for, and intimately involved in, the proper functioning of the germline specific piRNA pathway in mice and rats. In addition we found that IR-induced alterations to piRNA pathway protein levels were time and dose dependent.
ix, 123 leaves : ill. (some col.) ; 29 cm

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30

Cai, Linghui, and 蔡凌辉. "Monte Carlo simulation of positron induced secondary electrons in thincarbon foils." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45460863.

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31

Barreiro, Fidalgo Alexandre. "Experimental studies of radiation-induced dissolution of UO2 : The effect of intrinsic solid phase properties and external factors." Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205605.

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Dissolution of the UO2 matrix is one of the potential routes for radionuclide release in a future deep geological repository for spent nuclear fuel. This doctoral thesis focuses on interfacial reactions of relevance in radiation-induced dissolution of UO2 and is divided in two parts: In the first part, we sought to explore the effects of solid phase composition: The impact of surface stoichiometry on the reactivity of UO2 towards aqueous radiolytic oxidants was studied. H2O2 reacts substantially faster with stoichiometric UO2 than with hyperstoichiometric UO2. In addition, the release of uranium from stoichiometric UO2 is lower than from hyperstoichiometric UO2. The behavior of stoichiometric powder changes with exposure to H2O2, approaching the behavior of hyperstoichiometric UO2 with the number of consecutive H2O2 additions. The impact of Gd-doping on the oxidative dissolution of UO2 in an aqueous system was investigated. A significant decrease in uranium dissolution and higher stability towards H2O2 for (U,Gd)O2 pellets compared to standard UO2 was found. In the second part, we sought to look at the effect of external factors: The surface reactivity of H2 and O2 was studied to understand the overall oxide surface reactivity of aqueous molecular radiolysis products. The results showed that hydrogen-abstracting radicals and H2O2 are formed in these systems. Identical experiments performed in aqueous systems containing UO2 powder showed that the simultaneous presence of H2 and O2 enhances the oxidative dissolution of UO2 compared to a system not containing H2. The effect of groundwater components such as bentonite and sulfide on the oxidative dissolution of UO2 was also explored. The presence of bentonite and sulfide in water could either delay or prevent in part the release of uranium to the environment. The Pd catalyzed H2 effect is more powerful than the sulfide effect. The poisoning of Pd catalyst is not observed under the conditions studied.

QC 20170421

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32

Martius, Gesa [Verfasser], Giuliano [Akademischer Betreuer] Ramadori, Wolfgang [Akademischer Betreuer] Engel та Wilfried [Akademischer Betreuer] Kramer. "Effect of radiation on hepatic fat metabolism in rat and mouse: A role of radiation-induced TNF-α in the regulation of FAT/CD36 / Gesa Martius. Gutachter: Wolfgang Engel ; Wilfried Kramer. Betreuer: Giuliano Ramadori". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1075372909/34.

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33

Medhat, Abdel Maksoud Dina. "Study of New Miniaturized Microwave Devices based on Ratchet Effect in an Environment of Asymmetric Nano-Scatterers." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0075/document.

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La nanotechnologie est un domaine en voie d'expansion qui a attiré l'attention de la recherche en raison de ses applications potentielles illimitées. La technologie des ondes millimétriques est un autre domaine intéressant qui joue un rôle de premier plan dans le développement des systèmes de communications sans fil. La combinaison de ces deux champs de recherche avancée, donne naissance à l'innovation du Dispositif Ratchet qui est une nouvelle application qui représente un vrai défi. Ce dispositif est de taille nanométrique et son concept d'opération consiste à générer une tension DC lorsque le dispositif, basé sur le gaz d'électron bidimensionnel, est rayonné par l'énergie des micro-ondes. L'objectif de cette thèse est d'essayer d'améliorer la réponse du dispositif, ce qui ouvre de nouvelles perspectives dans la fabrication des détecteurs de champ à haute fréquence et à l'échelle nanométrique. Malheureusement, les Dispositifs Ratchet actuels, basés sur des hétérostructures de semiconducteurs, réalisés jusqu'à présent fonctionnent à basse température pour assurer une grande mobilité électronique. Cette condition nécessite l'utilisation d'un setup expérimental complexe qui a un grand impact sur la tension induite et sur la reproductibilité du phénomène Ratchet observé. Dans ce contexte, le travail effectué dans le cadre de cette thèse a abordé ce problème en deux parties. La première partie concerne l'analyse électromagnétique du setup expérimental. Ceci a été réalisé par la mise en oeuvre des simulations électromagnétiques intenses. D'autre part, différentes solutions ont été proposées afin d'optimiser le setup et ainsi améliorer la tension Ratchet produite. Outre l'étude électromagnétique, certaines mesures de modulation ont été réalisées pour tester la faisabilité du Dispositif Ratchet comme un démodulateur d'amplitude. La deuxième partie de cette thèse traite l'étude de la matière qui compose le Dispositif Ratchet. Récemment, le graphène commence à envahir le monde scientifique et technologique avec ses fascinantes propriétés électroniques, tels que sa mobilité d'électrons élevée à température ambiante, où les matériaux conventionnels sont en train de confronter des obstacles. En conséquence, l'idée de fabriquer un Dispositif Ratchet à base de graphène au lieu des hétérojonctions de semiconducteurs, a été introduite. Plusieurs modèles de conception, caractérisation et mesures RF ont été accomplis en vue d'obtenir un Dispositif Ratchet fiable approprié pour de nombreuses applications pratiques à la température ambiante, dans la gamme de fréquences micro-ondes et pourraient s'étendre à la bande térahertz
Nanotechnology is a growing field that has attracted significant research attention due to its unlimited potential applications. Millimeter wave technology is another interesting field that plays a leading role in the development of wireless communications systems. Combining these two advanced research fields together, has given rise to the innovation of the Ratchet Device which is now a new challenging application. This device has a nanoscale size and its concept of operation consists of generating a DC voltage when radiating a two-dimensional electron gas based device with microwave energy. The aim of this thesis is in trying to improve the device response and hence opening new perspectives in the fabrication of high frequency field detectors on the nanoscale level. Unfortunately, the current Ratchet Devices, based on semiconductor heterostructures, realized till now, operate at low temperatures to ensure high electron mobility. This condition necessitates the use of a complex experimental setup that has a great impact on the induced voltage and on the reproducibility of the observed Ratchet phenomenon. In this context, the work performed within the framework of this thesis has addressed this problem in two parts. The first part concerns the electromagnetic analysis of the experimental setup behavior. This has been achieved by implementing intensive full wave electromagnetic simulations. Different solutions have been proposed to optimize the setup and thus enhance the Ratchet voltage produced. In addition to the electromagnetic study, some modulation measurements have been performed to test the feasibility of the Ratchet Device as an amplitude demodulator. The second part of this thesis deals with the study of the material composing the Ratchet Device. Recently, graphene has started to invade the scientific and the technological world with its fascinating electronic properties, such as its high electron mobility at room temperature, which distinguishes it from conventional materials that typically collide with obstacles. As a result, the idea of fabricating a Ratchet Device based on graphene instead of semiconductor heterojunctions has been introduced. Several design models, characterizations and RF measurements have been performed in order to obtain a reliable Ratchet Device suitable for many practical applications at room temperature. This has been done in the microwave frequency range and can also extend to the terahertz band

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34

Popel, Aleksej. "The effect of radiation damage by fission fragments on the structural stability and dissolution of the UO2 fuel matrix." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/265103.

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The aim of this work was to study the separate effect of fission fragment damage on the structural integrity and matrix dissolution of uranium dioxide in water. Radiation damage similar to fission damage was created by irradiating bulk undoped and doped ‘SIMFUEL’ disks of UO2, undoped bulk CeO2 and thin films of UO2 and CeO2 with high energy Xe and U ions. The UO2 thin films, with thicknesses in the range of 90 – 150 nm, were deposited onto (001), (110) and (111) orientations of single crystal LSAT (Al10La3O51Sr14Ta7) and YSZ (Yttria-Stabilised Zirconia) substrates. The CeO2 thin films were deposited onto single crystal silicon (001) substrates. Part of the bulk UO2 and CeO2 samples, the thin films of UO2 on the LSAT substrates and the thin films of CeO2 were irradiated with 92 MeV 129Xe23+ ions to a fluence of 4.8 × 1015 ions/cm2 to simulate the damage produced by fission fragments in uranium dioxide nuclear fuel. Part of the bulk UO2 and CeO2 samples and the thin films of UO2 on the YSZ substrates were irradiated with 110 MeV 238U31+ ions to a fluence of 5 × 1010, 5 × 1011 and 5 × 1012 ions/cm2 to study the accumulation of the damage induced. The irradiated and unirradiated samples were studied using scanning electron microscopy (SEM), focused ion beam (FIB), atomic force microscopy (AFM), energy dispersive X-ray (EDX) spectroscopy, electron probe microanalysis (EPMA), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) techniques to characterise the as-produced samples and assess the effects of the ion irradiations. Dissolution experiments were conducted to assess the effect of the Xe ion irradiation on the dissolution of the thin film UO2 samples on the LSAT substrates and the bulk and thin film CeO2 samples. The solutions obtained from the leaching of the irradiated and unirradiated samples were analysed using inductively coupled plasma mass spectrometry (ICP-MS). XRD studies of the bulk UO2 samples showed that the ion irradiations resulted in an increased lattice parameter, microstrain and decreased crystallite size, as expected. The irradiated UO2 thin films on the LSAT substrates underwent significant microstructural and crystallographic rearrangements. It was shown that by irradiating thin films of UO2 with high energy, high fluence ions, it is possible to produce a structure that is similar to a thin slice through the high burn-up structure. It is expected that the ion irradiation induced chemical mixing of the UO2 films with the substrate elements (La, Sr, Al, Ta). As a result, a material similar to a doped SIMFUEL with induced radiation damage was produced.

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35

Mansour, Nastaran. "Nonlinear Absorption Initiated Laser-Induced Damage in [Gamma]-Irradiated Fused Silica, Fluorozirconate Glass and Cubic Zirconia." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc331327/.

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The contributions of nonlinear absorption processes to laser-induced damage of three selected groups of transparent dielectrics were investigated. The studied materials were irradiated and non-irradiated fused silica, doped and undoped fluorozirconate glass and cubic zirconia stabilized with yttria. The laser-induced damage thresholds, prebreakdown transmission, and nonlinear absorption processes were studied for several specimens of each group. Experimental measurements were performed at wavelengths of 1064 nm and 532 nm using nanosecond and picosecond Nd:YAG laser pulses. In the irradiated fused silica and fluorozirconate glasses, we found that there is a correlation between the damage thresholds at wavelength λ and the linear absorption of the studied specimens at λ/2. In other words, the laser-induced breakdown is related to the probability of all possible two-photon transitions. The results are found to be in excellent agreement with a proposed two-photon-initiated electron avalanche breakdown model. In this model, the initial "seed" electrons for the formation of an avalanche are produced by two-photon excitations of E' centers and metallic impurity levels which are located within the bandgaps of irradiated Si02 and fluorozirconate glasses, respectively. Once the initial electrons are liberated in the conduction band, a highly absorbing plasma is formed by avalanche impact ionization. The resultant heating causes optical damage. In cubic zirconia, we present direct experimental evidence that significant energy is deposited in the samples at wavelength 532 nm prior to electron avalanche formation. The mechanism is found to be due to formation of color centers (F+ or F° centers) by the two-photon absorption process. The presence of these centers was directly shown by transmission measurements. The two-photon absorption (2PA) process was independently investigated and 2PA coefficients obtained. The accumulated effects of the induced centers on the nonlinear absorption measurements were also considered and the 2PA coefficients were measured using short pulses where this effect is negligible. At room temperature, the color centers slowly diffuse out of the irradiated region. The density of these centers was monitored as a function of time. The initial distribution of the centers was assumed to have a Gaussian profile. For this model the diffusion equation was solved exactly and the diffusion constant obtained.

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36

Jin, Xin. "Combining RBS/Channeling, X-ray diffraction and atomic-scale modelling to study irradiation-induced defects and microstructural changes." Thesis, Limoges, 2021. http://www.theses.fr/2021LIMO0017.

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Les particules énergétiques sont souvent impliquées dans les activités de la société moderne. Ils ont contribué à l'essor de l'industrie des semi-conducteurs et pourront à l'avenir jouer un rôle important dans la mise en forme des matériaux de manière contrôlée. Cependant, leur nature énergétique pose de grands défis. Ainsi, il est essentiel d'avoir une compréhension globale des mécanismes sous-jacents des défauts induits par l'irradiation et des changements microstructuraux associés. Expérimentalement, les effets induits par l'irradiation peuvent être suivis par des techniques de caractérisation telles que la rétrodiffusion de Rutherford en mode canalisé (RBS/C) et la diffraction des rayons X (XRD), pour ne citer que ces deux car elles sont extrêmement sensibles aux perturbations au sein des cristaux. Cependant, il n'est pas aisé d'établir un lien clair entre le résultat de la mesure et la quantité et la nature des défauts, et ce lien est généralement fait à partir de modèles phénoménologiques. Dans ce travail de thèse, afin de faire face à ce problème, nous avons couplé modélisations à l'échelle atomique et simulations de signaux de RBS/C et XRD. La première étape a consisté à améliorer un code de simulation RBS/C récemment développé qui peut générer des signaux à partir de structures atomiques. En modifiant les algorithmes décrivant les interactions ion-solide et en ajoutant de nouvelles fonctionnalités, nous avons amélioré la flexibilité du code et son applicabilité à différents types de matériaux. Par la suite, nous avons utilisé le code RBS/C amélioré avec un code pour la DRX, lui aussi utilisant les données de structures atomiques. Avec ces signaux, nous avons extraits des paramètres de désordre et de déformation élastique et nous avons déterminé les cinétiques d'évolution associées et ce, pour un matériau modèle, à savoir UO2. Les défauts d'irradiation ont été générés par dynamique moléculaire (MD) avec la technique de l'accumulation de paires de Frenkel. Les cinétiques issues des modélisations présentent un accord qualitativement étroit avec celles déterminées expérimentalement, indiquant la validité de la méthodologie utilisée. La décomposition des cinétiques modélisées a permis de décrire de façon quantitative l'évolution des différents de types de défauts. Enfin, nous avons calculé les signaux RBS/C et XRD à partir de cellules modèles de Fe produites par MD et contenant chacune un type de défauts à une concentration donnée, les deux informations étant connues. Une comparaison claire du désordre et de la déformation élastique induits par les différents types de défauts dans Fe a été faite. La relation entre le rendement RBS/C et l'énergie des ions sonde a également été étudiée et la dépendance en énergie, fonction de la nature des défauts, a été établie. L'approche globale utilisée dans ce travail doit désormais être étendue et testée dans d'autres matériaux
Energetic particles are involved in many activities of modern society. They constitute a significant aspect of the semiconductor industry and may play important role in shaping materials in a controllable way in the future. However, their energetic nature also poses grand challenges, especially in the nuclear industry. Thus, it is crucial to have a comprehensive understanding of the underlying mechanisms of irradiation-induced defects and the associated microstructural changes. Experimentally, irradiation-induced effects can be monitored by characterization techniques including, but not limited to, Rutherford backscattering spectrometry in channeling mode (RBS/C) and X-ray diffraction (XRD), because they are extremely sensitive to changes in the crystalline structure. However, it is not straightforward to establish a clear link between the characterization results and the defect quantity and nature, and this connection is usually made according to simple phenomenological models. In this thesis work, in order to cope with this problem, we performed RBS/C and XRD atomic-scale modelling. The first step was to improve a recently developed RBS/C simulation code that can generate RBS/C signals from arbitrary atomic structures. By modifying the algorithms describing ion-solid interactions and adding new features, we enhanced the flexibility of the code and its applicability to different types of materials. Subsequently, we employed the improved RBS/C code with a XRD program to compute disordering and elastic strain kinetics of a model material, namely UO2, as a function of irradiation fluence. Radiation defects in UO2 were simulated by molecular dynamics (MD) calculations. Both the strain and disordering kinetics exhibit qualitatively close agreement with those determined experimentally, indicating the validity of the used methodology. The decomposition of the kinetics was performed in order to study the effect of each defect separately, which enables a quantitative description of the disordering and strain build-up processes. Finally, we computed RBS/C and XRD signals from Fe MD cells, each of which contains one single type of defects. A clear comparison of disorder and elastic strain induced by different types of defects in Fe was made. The relation between RBS/C yield and He energy was also studied using the Fe MD cells, which shows dependency with defect types. The global approach used in this work has the hope to be extended and tested in more materials

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37

Filho, Rinaldo Gregório. "Condutividade induzida por radiação ionizante no Mylar (PET) e Kapton (polimiidia)." Universidade de São Paulo, 1986. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-10022010-144145/.

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Este trabalho apresenta uma extensiva série de resultados experimentais da condutividade induzida por radiação X contínua, durante e após a irradiação, em amostras de PET e Kapton. As medidas foram realizadas variando-se uma série de parâmetros, tais como: o campo elétrico aplicado, a taxa de exposição, a espessura da amostra, o tipo de eletrodo, a energia da radiação e as condições ambientes. Foram feitas ainda medidas da corrente termo-estimulada em amostras irradiadas e não irradiadas, que permitiram verificar a presença de armadilhas nos materiais. Medidas da corrente fotônica com diferentes eletrodos e espessuras das amostras, constataram a influência do eletrodo no valor dessa corrente. Finalmente um modelo teórico foi desenvolvido, baseado na teoria de balanço dos portadores generalizada, com a inclusão do efeito do campo elétrico na taxa de geração de portadores (efeito Onsager). O ajuste teórico-experimental permitiu a determinação numérica dos principais parâmetros de condução, tais como, mobilidade dos portadores, coeficiente de recombinação e densidade de armadilhas, para os dois materiais estudados.
In this work we present extensive results of measurements of the prompt and delayed radiation-induced conductivity of samples of PET and Kapton. Experimental parameters, such as the effective energy of the radiation, the exposure rate, the total dose, the value of the applied electric field, the nature of the electrodes, and the ambienta1 conditions were changed within wide limits. We also report measurement of thermally stimulated currents for non-irradiated and for irradiated samples which allowed us to investigate the trap-structure of the materials. Measurements of photo-Compton currents with different electrode materials and sample thicknesses gave information about the relation between the nature of the electrodes and the amplitudes of the currents. Based on the generalized rate theory of radiation-induced conduction we developed a theoretical model which includes the effect of the applied electric field on the carrier generation yield (geminate recombination, Onsager effect). Comparison of experimental and theoretical curves allowed us to determine the values of the main conduction parameters, such as carrier mobility, recombination coefficient, trap densities, for the materials under investigation.

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38

Sjostedt, Svetlana. "An in vitro investigation of the impact of radiation induced bystander effect on the therapeutic irradiation of a prostate cancer cell line." Thesis, 2013. http://hdl.handle.net/2440/81550.

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Introduction. The aim of radiotherapy, in general, is to deliver a high enough radiation dose to tumour cells to control (and stop) their growth without causing severe complications to surrounding healthy tissues. As a result, it is very important to define a precise irradiation target for radiotherapy treatment. For many years only DNA has been seen as the main target for radiation to cause cellular death in living tissues. In the last decade the fundamental dogma of radiobiology, known as the ‘target theory’, has been reviewed. The extensive experimental evidence demonstrates that not only cell nucleus but also cellular cytoplasm, membrane, and even neighbouring cells, located outside the radiation field, should be viewed as possible targets for therapeutic ionising radiation. Methodology. The research described in this thesis aims to investigate the impact of the non-targeted effects of 6MV x-rays during the radiotherapy. This thesis intends to analyse the published mathematical models which predict occurrence and magnitude of radiation induced bystander effects (RIBEs), with experimental validation of one of these models. The methodology undertaken involved: • Literature review and development of comprehensive understanding of general concepts of radiation induced bystander effects; • Establishment of a suitable experimental methodology to investigate these phenomena, in particular radiation induced additional killing, in the application to radiotherapy to PC3 human prostate epithelial adenocarcinoma cell line, including: • evaluation of biological characteristics such as population doubling time and plating efficiency; • evaluation of radiobiological characteristics such as the dose which kills half of clonogenes (D₅₀), which will be used subsequently as the prescribed dose in the dose cold spot experiment; (in the experiment investigating cell survival in the under-dosed region) • determination of suitable biological end-points (such as apoptotic cell death, reduced proliferation rate, clonogenic cell death) following radiation treatment; • design of a dose-cold spot experiment to investigate RIBE in a reduced dose region (ie receiving ~80% of the prescribed dose) in freely communicating cells and non-communicating cells; • Investigation of the extent of non-targeted effects on cell killing in a dose cold spot in human prostate PC3 cancer cell line; • Analysis of RIBE related models; • Validation of the published stochastic model that relates absorbed dose to the emission and processing of cell death signals by non-irradiated cells which included: • determination of magnitude of medium-borne signals (affecting non-targeted cells) dependence on the radiation doses received by donor cells • investigation of donor cell concentration impact on the emission of death signals predicted by the model. All cell irradiations were performed at the Royal Adelaide Hospital, Radiation Oncology Department using a 6 MV x-ray beam produced by a Varian linear accelerator (Varian, Palo Alto, CA,USA). A clinically applied nominal dose rate of 3 Gy/min was used. Each radiation treatment was performed at 100 cm from the beam focal spot with 20 x 20 cm² radiation field size. The culture dishes were placed on the top of 1.5 cm thick solid water build up sheets. To avoid irradiation through air gaps cells were treated posteriorly with gantry positioned at 180°. Custom made wax phantoms (for different flask sizes) were used in conjunction with 5 cm thick solid water slab to cover the flask to ensure full scatter conditions. Machine radiation output was routinely checked with Daily QA 3™ device (Sun Nuclear, USA) before each radiation treatment. The primary research objectives were investigated through a series of research papers. Results. The findings and results of the experiments designed and performed in the current work include: I. Biological characteristics of PC3 cell line such as plating efficiency and population doubling time were found to be 0.60, 48 hours respectively. II. The fraction of cells surviving the standard clinical daily dose of 2 Gy (SF2) typical of curative radiation protocols was found to be 0.586 (± 0.0279), while the dose that killed half of the clonogen population (D₅₀) was found to be 2.037Gy. III. Radiosensitivity of PC3 cells differs widely among laboratories - the maximum difference found was 131.58%. This cell line appeared to be very sensitive to the methods used therefore it was important to evaluate D₅₀ independently rather than relying on published data. IV. Apoptotic assay revealed no significant dose dependant early cell deaths until 96 hours after radiation exposure. Following this time the first sizable colonies can be detected by the clonogenic survival assessment. Hence cellular damage in a dose cold spot was assessed by long term survival data which includes all types of radiation induced damages. V. Cells exposed to a dose cold spot that are freely communicating versus non-communicating cells revealed significant decrease (16.2%) in cells survival presumably due to intercellular communication. Validation of the stochastic model predicting emission and processing of cell death signals in non-irradiated cells revealed significant decreases in cell survival (P<0.001) exposed to irradiated cell condition media (ICCM) derived from donor cells of various concentrations and irradiated with different doses. Dependency of the toxicity of ICCM on the cellular concentration of donor cells was fond to be significant (p<0.5) as well. Conclusion. For the given cell line under existing growing and treatment conditions the cell survival in the dose cold spot region was significantly lower when under-irradiated cells were in contact with the cells receiving 100% of the prescribed dose compared to the cellular survival obtained from the under-dosed cells, by the same amount of radiation, which were treated separately. Presumably these variations were mainly due to intercellular communication. Significant reduction in PC3 cell survival after receiving ICCM was observed. Data fitting revealed an exponential decrease in recipient cell survival with the dose received by the ICCM. However the current experiment was not able to identify the associated dose threshold for the reduction in survival from ICCM due to the saturation of the effect at the doses investigated. This can be attributed to either saturation in signal generation due to limited signal potency or saturation in recipient cell responses. It appeared that death signal emission may increase with increasing numbers of radiation hits to a certain target and with increasing number of targets able to emit death signals. However, the effect saturates when it reaches a specific value in a number of hits or in an amount of critical targets. The mechanisms behind radiation induced additional killing are not clear yet. Little is known about the types of DNA damage affecting bystander cells. The impact of RIBEs in application to novel radiotherapy treatment techniques, such as intensity modulated radiation therapy and tomotherapy, needs further investigation as they deliver highly conformal doses to tumours, but cover bigger volumes with the low doses where bystander responses are more pronounced. Incorporation of RIBEs into the research that underpins clinical radiotherapy will result in a shift beyond simple mechanistic models currently used towards a more systems-based approach. It is a difficult task to design a coherent research strategy to investigate the clinical impact of bystander phenomena, given the complex protean nature of it. Any consideration of bystander effects will challenge clinicians' preconceptions concerning the effects of radiation on tumours and normal tissues and therefore disease management.
Thesis (M.Sc.(Med.Phy.)) -- University of Adelaide, School of Chemistry and Physics, 2013

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Hou, Ya-Hsiue, and 侯雅雪. "Radiation-Induced Bystander Effect in Human Glioblastoma Cells and Functional Characterization of Lung Cancer Related Genes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/u6prap.

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碩士
中臺科技大學
放射科學研究所
96
Lung cancer, especially non-small cell lung cancer (NSCLC), is the most common cause of cancer related death worldwide. It is generally believed that lack of biomarkers of early detection or prognosis of NSCLC is the main reason that explains high mortality of this disease. In order to obtain such biomarkers, we have conducted a lung cancer cell line-based functional genomics screen, in which sox9 was a candidate biomarker. In the present study, in silico data mining and molecular biology emphasizing siRNA gene silencing technique was used to probe the functional roles of sox9 in NSCLC. Here we showed that the expression of sox9 is significantly higher in the tumor parts than in the normal parts of cells of NSCLC; mean while, its expression is also higher in patients with recurrent diseases than those without. Furthermore, silencing of sox9 expression can cause reduced viability of cells, affect the cell cycle progression through G1 or G2 phases, and change the invasion capability of cells. Microarray gene expression analysis and quantitative polymerase chain reaction (q-PCR) revealed that the genes affected by silencing of sox9 included MT2A、FTL、CASP4、FTH1、RPL35、AKAP5、JNK1 (up-regulated) and sox1、sox17、BBC3、IRS2、WNT6 (down-regulated). Many of the differentially expressed genes are involved in the signaling pathways of cell growth or proliferation. In summary, we concluded that sox9 plays important roles in the survival of NSCLC cells.

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Lo, Chia-Chien, and 羅佳茜. "Low dose radiation induces cellular senescence and bystander effect associated metastasis phenomenon by up-regulation of c-Myc and cofilin-1." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/50575683509244812863.

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碩士
國立陽明大學
生物醫學影像暨放射科學系
101
The low dose radiation may induce cellular senescence and promote secondary maligancy during radiotherapy. However, the molecular mechanisms are unclear. It has been reported that a variety of early response oncogenes can be up-regulated by the low dose radiation. Because oncogene-induced senescence (OIS) has been considered important for tumor development, we are interested in investigating whether the sublethal dose radiation also raises OIS to affect the malignancy. To this end, human diploid fibroblasts WI-38 cells and human non-small lung cancer H1299 cells were exposed to less than 2Gy of X-rays delivered by the RS2000 X-rays machine. Both cell types exhibited senescent phenotypes within a dose-dependent manner using the senescence-associated β-galactosidase (SA-β-gal) staining. Subsequently, we investigated the expression of c-Myc and k-Ras oncogenes, and the results showed that low dose radiation could induce c-Myc, but not k-Ras, in both transcriptional and translational levels. Additionally, up-regulated c-Myc exhibited transcriptional activity as demonstrated by the promoter-based reporter gene assys. Although the low dose radiation caused cellular senescence in exposed cells, the collected culture medium could increase the motility of non-irradiated H1299 cancer cells using the wound healing assay. Furthermore, the low dose radiation induced senescent phenotype was suppressed in cells treated with siRNA against c-Myc. Meanwhile, the motility of non-irradiated cells was not increased by the cultured medium obtained from irradiated c-Myc silenced cells. Taken together, the current data suggest that the low dose radiation causes c-Myc oncogene induced senescence, and this event may promote the bystander effects that influence the motility of non-irradiated cancer cells. In view of cMyc gene used some medicine to suppress the above phenomenon, and increased tumor control rate.

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Feng, Shaoyong. "C. Elegans and Microbeam Models in Bystander Effect Research." Thesis, 2013. http://hdl.handle.net/1969.1/151271.

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Radiation induced bystander effects have changed our understanding of the biological effects of ionizing radiations. The original assumption was that biological effects require direct damage to DNA. The bystander effect eliminated that requirement and has become one main stream in radiation research ever since first reported over 20 years ago. Most bystander studies to date have been carried out by using conventional single cell in vitro systems , 2D cell array and 3D tissue samples, which are useful tools to characterize basic cellular and molecular responses. But to reveal the complexity of radiation responses and cellular communication, live animal models have many advantages. In recent years, models such as C. elegans and Zebrafish have been utilized in bystander effects research. In the Loma Linda/TAMU experiment, a L1 larva C. elegans model was devloped to study the radiation bystander effects by irradiating single intestine cell nuclei with a microbeam of protons. Due to the stochastic nature of particle interactions with matter and changing stopping power when protons slow down, precise dosimetry in the target nucleus is a difficult problem. This research was undertaken to provide a detailed description of the energy deposition in the targeted and surrounding non-targeted cell nuclei, and to evaluate the probabilities of the non-targeted cell nucleus being irradiated. A low probability is required to exclude the possibility of radiation biological an effect in non-targeted cells is caused by scattered particles. Mathematical models of the microbeam system and the worm body were constructed in this research. Performing Monte Carlo simulations with computer code, Geant 4, this research provided dosimetry data in cell nuclei in different positions and Geant 4, this research provided dosimetry data in cell nuclei in different positions and probabilities of scattering to non-targeted cell nuclei in various microbeam collima- tor configurations. The data provided will be useful for future collimated microbeam design.

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42

Silva, Ana Manuela dos Santos. "The protective effect of regucalcin against radiation-induced testicular damage." Master's thesis, 2015. http://hdl.handle.net/10400.6/6061.

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Testicular cancer is the most common malignancy among young men, and radiation therapy is a generally used as treatment. However, the exposure to radiation has several adverse effects on male fertility. Considering the high survival rates and the age of incidence of this malignancy, it is mandatory to identify effective strategies protecting against radiation-induced testicular damage. Regucalcin (RGN) is a calcium (Ca2+)-binding protein that is broadly expressed in the male reproductive tract. Several studies have demonstrated RGN ability suppressing cell death in different cell types. Previously, our research group showed that RGN overexpression had beneficial effects on spermatogenesis by suppressing chemical-induced apoptosis. Moreover, RGN is upregulated in radioresistant cell lines, suggesting that it also can protect from radiation damage. The present work aimed to evaluate whether RGN may play a role in spermatogenesis recovery after radiation treatment. For this purpose, transgenic rats overexpressing RGN (Tg-RGN) and their wild-type (Wt) counterparts were exposed to X-rays. At ten weeks of recovery after irradiation, the testicular status and the epididymal sperm parameters were evaluated. The expression of RGN and several cell cycle and apoptosis regulators was also evaluated. In addition, the enzymatic activity of caspase-3 was measured. Upon radiation treatment and ten weeks of recovery, both the testicular status and sperm parameters seem to have been less affected by X-rays in Tg-RGN. We also found a diminished expression of p53 and p21, which may indicate the reinitiating of spermatogenesis. Moreover, the reduced activity of caspase-3 detected in Tg-RGN is in accordance with low levels of caspase-8 and increased Bcl-2/Bax ratio, suggesting that these animals are more resistant to testicular apoptosis in response to radiation. RGN expression was significantly enhanced in Wt rats after irradiation, supporting its involvement in the anti-apoptotic response. Altogether, the present findings point out a protective role for RGN overexpression against radiation-induced testicular damage.
O cancro testicular é a malignidade masculina mais frequente nos jovens, e a radioterapia é normalmente usada no seu tratamento. No entanto, a exposição à radiação tem vários efeitos secundários na fertilidade masculina, tornando-se necessária a identificação de estratégias efectivas para a proteger do dano testicular provocado pela radioterapia. A regucalcina (RGN) é uma proteína de ligação ao cálcio (Ca2+) que se encontra amplamente expressa no tracto reprodutor masculino. Vários estudos demonstraram a capacidade supressora da RGN na morte celular de diferentes tipos de células. Anteriormente, o nosso grupo de investigação mostrou que a sobre-expressão de RGN teve efeitos benéficos na espermatogénese por suprimir a apoptose induzida quimicamente. Para além disso, a RGN é regulada positivamente em linhas celulares radiorresistentes, sugerindo que esta pode proteger de danos causados pela radiação. O presente trabalho visa avaliar se a RGN desempenha um papel benéfico na recuperação da espermatogénese após radioterapia. Ratos, quer transgénicos que sobre-expressam a RGN (Tg-RGN) quer os seus homólogos selvagens (Wt), foram expostos a raios-X. Às dez semanas de recuperação após a radioterapia, o estado testicular e os parâmetros espermáticos foram avaliados. A expressão da RGN, bem como de vários reguladores do ciclo celular e da apoptose foi também avaliada. Para além disso, a actividade enzimática da caspase-3 foi determinada. Às dez semanas de recuperação após a radioterapia, tanto o estado testicular como os parâmetros espermáticos parecem ter sido menos afectados pelos raios-X nos Tg-RGN. Verificou-se ainda uma diminuição da expressão de p53 e de p21, o que pode indicar a reiniciação da espermatogénese. Para além disso, a reduzida actividade da caspase-3 detectada nos Tg-RGN está de acordo com os baixos níveis de caspase-8 e com o elevado rácio Bcl-2/Bax, sugerindo que os Tg-RGN são mais resistentes à apoptose testicular em resposta à radiação. A expressão de RGN aumentou significativamente nos ratos Wt, suportando o seu envolvimento na resposta anti-apoptótica. De forma geral, estes resultados indicam que a sobre-expressão da RGN desempenhou um papel protector relativamente ao dano testicular induzido pela radiação.

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Μαρτίνου, Μαρία. "Μελέτη των ακτινοβιολογικών φαινομένων που παρατηρούνται μετά από έκθεση καρκινικών κυττάρων σε ιοντίζουσα ακτινοβολία χαμηλής δόσης. Η σημασία τους στη [sic] κλινική πράξη". Thesis, 2014. http://hdl.handle.net/10889/8532.

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Τα αποτελέσματα ποικίλων δόσεων ακτινών Χ στην κυτταρική απόπτωση, τον πολλαπλασιασμό, την έκφραση του υποδοχέα του επιδερμικού αυξητικού παράγοντα (EGFR) και των μεταλλοπρωτεϊνασών-2 (MMP-2), μελετήθηκαν σε δύο κυτταρικές σειρές ανθρώπινου γλοιοβλαστώματος. Μέθοδος: Οι κυτταρικές σειρές LN18 και M059K ακτινοβολήθηκαν σε θερμοκρασία δωματίου με δόσεις κυμαινόμενες από 0,5 έως 15 Gy με τη χρήση πηγής 6 MV. Η απόπτωση μελετήθηκε με τη μέθοδο annexin V, ο πολλαπλασιασμός με τη μέθοδο MTT (methyl tetrazolium) και η έκκριση των MMP-2 με ζυμογράφημα. H καταγραφή των επιπέδων του φωσφοριωμένου EGFR έγινε με ELISA. Αποτελέσματα: Ο κυτταρικός πολλαπλασιασμός ανεστάλη με δόσο-εξαρτώμενο τρόπο ενώ η απόπτωση αυξήθηκε σημαντικά μετά την ακτινοβολία. Σε δόσεις μικρότερες των 2 Gy δεν καταγράφηκε καμία μεταβολή στην απόπτωση και τον κυτταρικό πολλαπλασιασμό. Τα επίπεδα των MMP-2 αυξήθηκαν 48 ώρες μετά την ακτινοβόληση με δόσο-εξαρτώμενο τρόπο. Αντιθέτως, η έκφραση του EGFR αυξήθηκε σημαντικά 15 λεπτά μετά την ακτινοβόληση και κατά δόσο-εξαρτώμενο τρόπο. Συμπέρασμα: Η ιοντίζουσα ακτινοβολία επάγει την έκφραση του EGFR και αυξάνει την έκκριση των MMP-2 γεγονός που αιτιολογεί την διηθητική και κακοήθη συμπεριφορά των γλοιωμάτων καθώς και την ανταπόκριση τους στην ιοντίζουσα ακτινοβολία.
The effect of different doses of X(-)rays on apoptosis, proliferation, epidermal growth factor receptor (EGFR) and matrix metalloproteinase (MMP-2) expression was investigated in a human glioblastoma cell line. Materials and Methods: The cell line LN18 was irradiated at room temperature with doses ranging from 0.5 to 15 Gy using 6 MV X(-)rays. Apoptosis was assessed using the annexin V binding assay, proliferation by the methyl tetrazolium (MTT) assay and MMP-2 secretion with zymography. The levels of phosphorylated (pEGFR) were estimated using a commercially available ELISA kit. Results: Cell proliferation decreased in a dose-dependent manner, while apoptosis was increased after radiation. Doses below 2 Gy did not affect proliferation or apoptosis. MMP-2 levels were increased 48 h after radiation in a dose-dependent manner. In contrast, EGFR signaling was significantly activated 15 min after radiation in a dose-dependent manner. Conclusion: Ionizing radiation activates EGFR signalling and enhances MMP-2 secretion, suggesting that the molecular pathways involved may contribute to the invasiveness and malignant behaviour of glioma cells and help to explain the response of gliomas to ionizing radiation.

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44

Yang, Pei-Yu, and 楊佩瑜. "Effect of Resistive Breathing Training on Radiation-Induced Diaphragm Contractile Dysfunction – Animal Study." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/51803517225513891078.

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Анотація:

碩士
國立臺灣大學
物理治療學研究所
102
Background: Radiotherapy (RT) had shown to induce acute diaphragm contractile dysfunction. Inspiratory muscle training (IMT) have proven to be effective in enhancing contractile function of the muscle; however, whether IMT prior to RT could ameliorate RT-related contractile dysfunction remains to be determined. Purposes: The purposes of this study were to investigate: 1) the effect of 1-week resistive breathing training on contractile function, antioxidant capacity and oxidative injury of the diaphragm; and 2) the effect of this training on RT-induced diaphragm contractile dysfunction and exploring the potential underlying mechanism in animal model. Methods: This study included two phases. In phase I, Sprague-Dawley (SD) rats were randomized into training (TG, n=7) or sham training (SG, n=6) group. TG received resistive breathing training using tracheal banding method for 1-week and SG received sham operation. Upon the completion of training, rats in both groups were sacrificed and the diaphragms were removed en bloc for contractile function assessment, antioxidant capacity and oxidative injury analysis. Antioxidant capacity analysis included total SOD activity, CuZnSOD and MnSOD mRNA expression. Oxidative injury was analyzed using protein carbonyl and 8-OHdG. In phase II, SD rats were randomized into training then RT (TR, n=6) or sham training then RT (SR, n=6) group. Training method was identical to that of phase I. After the completion of training, rats in both groups received one-shot 5 Gy RT to the diaphragm region. Twenty-four hours following RT, all rats were sacrificed and the diaphragms were removed for all the analyses as described in phase I. Generalized Estimated Equation and Generalized Linear Model were used to detect differences of variables between and within groups when suitable. Significant α level was set at 0.05. Results: Tracheal banding provided an average of 1.6 times increases in airway resistance. After 1-week of training, contractility (p<0.05), total SOD activity (p=0.004), and MnSOD mRNA expression (p=0.03) of the diaphragm were significantly higher in TG than those of SG. However, protein carbonyl level of the diaphragm were also increased after training (p<0.001). In phase II, contractility of the diaphragm were significantly higher (p<0.05), while fatigue index (p=0.002) and protein carbonyl level (p<0.001) were lower in TR than those of SR. Compared to SR, relative force-frequency curve showed significant downward shift between 30-50 Hz in TR. mRNA expression of CuZnSOD and MnSOD were significant higher in TR than those of SR (both p<0.05). Conclusions: This study showed that 1-week resistive breathing training could enhance diaphragm contractile function and thus reducing RT-induced its dysfunction through training related upregulation of antioxidant capacity of the diaphragm.

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45

Li, Chen-yu, та 李晨宇. "Inhibitory effect of microwave radiation on LPS-induced NFκB cytokine expression in the THP-1 monocytes". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/zaw97z.

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碩士
元培科技大學
醫學檢驗生物技術研究所
98
Microwave radiations, can be encountered regularly in daily lives. When World Health Organization (WHO) announced that microwave radiations as a kind of environmental energy which interferes with the physiological functions of human body, great concerns have been raised over the damage frequency can do to human physiology. The immunological performance and the activeness of cellular inflammatory factor NFκB have been closely related in monocyte. Due to the effect of phorbol 12-myristate 13-acetate (PMA) to THP-1 monocytes, THP-1 monocytes will divide into macrophages and will then react with lipopolysaccharides (LPS), and the amount of NFκB cytokine increases in THP-1 monocytes. Expression of cytokine will be affected when cells are exposed to frequency at 2450 MHz and are worked at 900W. Thus, from our experiments, an observation can be made when THP-1 monocytes are stimulated with PMA and LPS to differentiate into macrophage, the amount of NFκB cytokine in cells increases exponentially, and the level of expression is also restricted by the exposure of frequency. In conclusion, microwave radiations can inhibit the activity functions of THP-1 monocytes to be stimulated with PMA and LPS.

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46

Martius, Gesa. "Effect of radiation on hepatic fat metabolism in rat and mouse: A role of radiation-induced TNF-α in the regulation of FAT/CD36". Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0022-607A-4.

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47

Hubbard, Kenneth Roy. "Modelling induced fields in the human body exposed to electric fields from high voltage transmission lines designed to meet 10 kV/m at ground level." Thesis, 2017. http://hdl.handle.net/10539/23547.

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A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, February 2017
There has been increasing public concern regarding adverse health effects due to power frequency electric and magnetic fields. Safety guidelines/standards for electric and magnetic field exposures have been established by different public organizations. However, the link between low frequency (power frequency) electric and magnetic field exposure and adverse health effects is not yet well established. Limits on human exposure to low frequency electric and magnetic fields are fundamentally specified for in-situ fields in tissues/organs. These dosimetric limits are referred to as Basic Restrictions for protection against potentially adverse effects from electro-stimulation. In addition, secondary limits, the exposure Reference Levels in environmental electric and magnetic fields are also given for practical compliance purposes. These are generally derived from the Basic Restrictions based on uniform-fields with a provision that the Basic Restrictions must be observed for non-uniform cases. In practice, any structure influences the electric fields in High Voltage systems, and thus creates electric field non-uniformity. The human exposure of the general public to electric fields from Eskom’s 765 kV transmission network operating at 50 Hz, is addressed through physical measurements, theoretical predictions and 3-D human model dosimetry, which is presented in this dissertation.
MT 2017

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48

Ström, Petter. "Measurements of electric fields in a plasma by Stark mixing induced Lyman-α radiation". Thesis, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-206123.

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This paper treats a non-intrusive method of measuring electric fields in plasmas and other sensitive or hostile environments. The method is based on the use of an atomic hydrogen beam prepared in the metastable fine structure quantum state 2s1/2. Interaction with the field that is to be measured causes Stark mixing with the closely lying 2p1/2, whose spontaneous decay rate is much higher than that of 2s1/2. As a result, the total transition rate to the ground state and consequently the intensity of the Lyman-α line (121.6nm) is increased. Observations of emitted radiation from a region in which the interaction takes place are used to draw conclusions about the electric field, effectively providing a way to measure it. In the first section, the theory behind the method is described, using time dependent perturbation theory and taking into account both Lamb shift and hyperfine structure. A description of the set-up that we have used to test the theoretical predictions follows and practical aspects related to the operation of the experiment are briefly addressed. Measurements of the dependence of the Lyman-α intensity on both electric field frequency and amplitude are presented and shown to be in agreement with theory. These measurements have been performed in vacuum and in an argon plasma, both for static and RF fields. Two mechanisms, labeled oscillatory and geometrical saturation, that decrease the emitted intensity for strong fields are identified and described, and both are of importance for the future implementation of the studied diagnostic in a fusion device or other plasma experiment. Studies of the field profiles between a pair of electrically polarized plates have been carried out and algorithms for relating measured data to actual values of electric field strength have been developed. For static fields in vacuum, collected data is compensated for geometrical saturation and the resulting profiles are compared to those calculated with a finite element method. Good correspondence is seen in many cases, and where it is not, the discrepancies are explained. Static profile measurements in a plasma show the formation of a sheath whose thickness has been studied while varying discharge current, pressure and plasma frequency. The qualitative dependence of the sheath thickness on these parameters is in accordance with well established theory. When it comes to RF fields, a possible standing wave pattern is detected in the plasma despite problems with low signal to noise ratio. In order to optimize the working conditions of the set-up, effects of charge accumulation due to ions present in the hydrogen beam have been studied as well as errors due to residual particle fluxes during the off-phase when pulsing the beam. A conceptual design suggestion for implementing the method in the edge plasma of a tokamak or another similar device, based on the collected information, is also given.

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49

Wang, Hung-Yi, and 王宏禕. "The study of Vit D photoprotection effect on radiation induced skin DNA damage in kerationcytes and malenocytes co-cultured system." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/01752797027344599752.

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碩士
國防醫學院
生物及解剖學研究所
101
Ultraviolet B (UVB) could directly damage DNA through producing thymine dimmer and lead to cell mutations. Skin cancer has highly relationship with these mutations. In skin cells, UVB in addition to damage the DNA, also stimulate vitamin D synthesis, promote DNA repair and production of melanin. However, until now there are still not any reports about photoprotection effect by Vit D on radiation induced skin DNA damage in kerationcytes and malenocytes co-cultured system. In this study we compared the differences of UVB induced damage among mono-culture of keratinocytes, melanocytes and co-culture of keratinocytes and melanocytes with different concentration of Vit D treatment. First, through MTT assay to analysis the cell survival rate of differences treatment, we found keratinocytes which have higher cell survival rate in 70nM Vit D. Malenocytes and co-culture system had no difference. And then we used the immunocytochemistry analysis to observe the variation of thymine dimer expressed in keratinocytes and melanocytes after UVB irradiation. Thymine dimmer would decrease along with the culture time increasing after irradiated by UVB, but not difference in different concentration of Vit D. Through flow cytometry analyses quantifying the fluorescence intensity of thymine dimmer showed keratinocytes didn’t reduce fluorescence intensity of thymine dimmer in different concentration of Vit D. We also found that co-culture of keratinocytes and melanocytes would decrease the expression of thymine dimer in Vit D treatment. Finally, we observed that co-cultured system with Vit D pre treatment really protect cell against UVB damage and it was obviously deceased the fluorescence intensity of thymine dimmer of cells. Since higher concertration Vit D could inhibit keratinocytes proliferate and promote terminal differention, so the protection effect is not significant in cell survival rate.

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50

Enters, Dirk. "Aspect induced differences in vegetation and soil on north- and south-facing slopes in western Massachusetts /." 1999. https://scholarworks.umass.edu/theses/3476.

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Дисертації з теми "Radiation induced bystander effect"

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