Ionizing Radiation Research Papers - Academia.edu (original) (raw)

Exposure of human tumor cell lines to different chemotherapeutic drugs, ionizing radiation, and differentiating agents induced morphological, enzymatic, and ploidy changes resembling replicative senescence of normal cells. Moderate doses... more

Exposure of human tumor cell lines to different chemotherapeutic drugs, ionizing radiation, and differentiating agents induced morphological, enzymatic, and ploidy changes resembling replicative senescence of normal cells. Moderate doses of doxorubicin induced this senescence-like phenotype (SLP) in 11 of 14 tested cell lines derived from different types of human solid tumors, including all of the lines with wild-type p53 and half of p53-mutated cell lines. SLP induction seemed to be independent from mitotic cell death, the other major effect of drug treatment. Among cells that survived drug exposure, SLP markers distinguished those cells that became terminally growth-arrested within a small number of cell divisions from the cells that recovered and resumed proliferation. SLP induction in breast carcinoma cells treated with retinoids in vitro or in vivo was found to correlate with permanent growth inhibition under the conditions of minimal cytotoxicity, suggesting that this response may be particularly important for the antiproliferative effect of differentiating agents. The senescence-like program of terminal proliferation arrest may provide an important determinant of treatment outcome and a target for augmentation in cancer therapy.

V. A. KUDRYAVTSEV, V. A. KUZNETSOV, AND O. G. RYAZHKAYA Institute.for Nuclear Research of the Academy of Sciences of the USSR, Moscow We study the self-arline properties of intensity fluctuations of underground muons generated by primary... more

V. A. KUDRYAVTSEV, V. A. KUZNETSOV, AND O. G. RYAZHKAYA Institute.for Nuclear Research of the Academy of Sciences of the USSR, Moscow We study the self-arline properties of intensity fluctuations of underground muons generated by primary cosmic rays of rigidity > 1600 GV. The muon time series were recorded at a vertical depth of 570 Hg/cm 2 during the years 1981-1983. This time interval includes a period of intense solar activity in the summer of 1982 which was characterized by the creation of large solar wind shocks and associated production of major interplanetary disturbances. The purpose of our analysis is to obtain from the behavior of the muon intensity some insight into the large-scale behavior of interplanetary magnetic field fluctuations and their effects on the propagation of high-rigidity galactic cosmic rays. The results give good evidence for fractal behavior of large-scale muon fluctuations in the range from a few hours to more than 10 days, w,•th the scaling exponent H varying according to the time interval analyzed. We find that the large time scale muon fluctuations evolve from a preshock condition in late 1981 to early 1982 characterized by a scaling exponent H = 0.28 and power spectrum f-x.6 to a condition with H = 0.07 and anj '-•'• power spectrum during the most intense solar activity in 1982, followed by a slow return in 1983 to the original preshock conditions (H = 0.14, f-•.3).

Data are limited on the role of chronic exposure to lowdose ionizing radiation in the etiology of cancer. In a nationwide cohort of 146,022 U.S. radiologic technologists (73% female), we evaluated mortality risks in relation to work... more

Data are limited on the role of chronic exposure to lowdose ionizing radiation in the etiology of cancer. In a nationwide cohort of 146,022 U.S. radiologic technologists (73% female), we evaluated mortality risks in relation to work characteristics. Standardized mortality ratios (SMRs) were computed to compare mortality in the total cohort vs. the general population of the United States. Mortality risks were low for all causes (SMR ‫؍‬ 0.76) and for all cancers (SMR ‫؍‬ 0.82) among the radiologic technologists. We also calculated relative risks (RR) for the 90,305 technologists who responded to a baseline mailed questionnaire, using Poisson regression models, adjusted for known risk factors. Risks were higher for all cancers (RR ‫؍‬ 1.28, 95% confidence interval [CI] ‫؍‬ 0.93-1.69) and breast cancer (RR ‫؍‬ 2.92, 95% CI ‫؍‬ 1.22-7.00) among radiologic technologists first employed prior to 1940 compared to those first employed in 1960 or later, and risks declined with more recent calendar year of first employment (p-trend ‫؍‬ 0.04 and 0.002, respectively), irrespective of employment duration. Risk for the combined category of acute lymphocytic, acute myeloid and chronic myeloid leukemias was increased among those first employed prior to 1950 (RR ‫؍‬ 1.64, 95% CI ‫؍‬ 0.42-6.31) compared to those first employed in 1950 or later. Risks rose for breast cancer (p-trend ‫؍‬ 0.018) and for acute lymphocytic, acute myeloid and chronic myeloid leukemias (p-trend ‫؍‬ 0.05) with increasing duration of employment as a radiologic technologist prior to 1950. The elevated mortality risks for breast cancer and for the combined group of acute lymphocytic, acute myeloid and chronic myeloid leukemias are consistent with a radiation etiology given greater occupational exposures to ionizing radiation prior to 1950 than in more recent times.

The normal anatomy and many pathologies of the pediatric genitourinary system can be assessed with different imaging modalities. Most of them are based on the use of ionizing radiation and/or invasive techniques. The contribution of... more

The normal anatomy and many pathologies of the pediatric genitourinary system can be assessed with different imaging modalities. Most of them are based on the use of ionizing radiation and/or invasive techniques. The contribution of magnetic resonance imaging in this regard has opened new ways of approaching pathological conditions in this patient group. The addition of the newly developed rapid techniques has enhanced the superiority of MRI, and both morphological and functional evaluation of the genitourinary system can be achieved. There are different factors on which rely the optimization and the efficiency of magnetic resonance urography (MRU). Of importance is adequate patient immobilization and the use of optimal imaging sequences. The rapid technical development, including the advent of the post-processing respiratory navigator, allows acquisition of high-quality images independent of the patient's respiratory rate. In the future, it is expected that MRU, due to its non-use of ionizing radiation, will become the most important tool in the diagnostic work-up of genitourinary pathologies in infants and small children.

We report first results of laboratory tests of Si:As blocked-impurity-band (BIB) mid-infrared (4 to 28 µm) detectors developed by IMEC. These prototypes feature 88 pixels hybridized on an integrated cryogenic readout electronics (CRE).... more

We report first results of laboratory tests of Si:As blocked-impurity-band (BIB) mid-infrared (4 to 28 µm) detectors developed by IMEC. These prototypes feature 88 pixels hybridized on an integrated cryogenic readout electronics (CRE). They were developed as part of a technology demonstration program for the future Darwin mission. In order to be able to separate detector and readout effects, a custom build TIA circuitry was used to characterize additional single pixel detectors. We used a newly designed test setup at the MPIA to determine the relative spectral response, the quantum efficiency, and the dark current. All these properties were measured as a function of operating temperature and detector bias. In addition the effects of ionizing radiation on the detector were studied. For determining the relative spectral response we used a dualgrating monochromator and a bolometer with known response that was operated in parallel to the Si:As detectors. The quantum efficiency was measured by using a custom-build high-precision vacuum black body together with cold (T ∼ 4 K) filters of known (measured) transmission.

Medulloblastoma (MB) is the most common brain malignancy in children. Whole neural axis irradiation is the treatment of choice, but it often results in long-term neurocognitive and developmental impairment. Only insights into MB biology... more

Medulloblastoma (MB) is the most common brain malignancy in children. Whole neural axis irradiation is the treatment of choice, but it often results in long-term neurocognitive and developmental impairment. Only insights into MB biology will lead to improved therapeutic outcome. Wingless (WNT) signalling deregulation occurs in up to 25% of sporadic tumors, but the specific role of nuclear b-catenin and its involvement in the radioresponse remains unsettled. Therefore we studied the c-radiation response of two MB cell lines from cellular and molecular points of view. Our data show that the p53 wild-type cell line is more sensitive to ionizing radiations (IR) than the p53 mutated line, but apoptosis is also induced in p53mutated cells, suggesting an alternative p53-independent mechanism. In addition, this study is the first to demonstrate that c-rays trigger the WNT system in our in vitro models. Further studies are required to test if this could explain the radiosensitivity of MB and the favorable prognostic value of nuclear b-catenin in this tumor.

With 5-7 month long duration missions at 51.6°inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the... more

With 5-7 month long duration missions at 51.6°inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the ''as low as reasonably achievable'' (ALARA) precept requires that radiological risks be minimized when possible through a dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (C n H n ) is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in equivalent dose to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry.

This is a preprint or i paper intended for publication in a journal or proceedings. Since changes may he made before publication, this preprint is made available with the un derstanding that it will not be cited or reproduced without the... more

This is a preprint or i paper intended for publication in a journal or proceedings. Since changes may he made before publication, this preprint is made available with the un derstanding that it will not be cited or reproduced without the permission of the author.

Nuclear medicine workers are occupationally exposed to chronic ionizing radiation. It is known that ionizing radiation may have damaging effects on chromosomes. In the present study, we investigated the genotoxic effects of ionizing... more

Nuclear medicine workers are occupationally exposed to chronic ionizing radiation. It is known that ionizing radiation may have damaging effects on chromosomes. In the present study, we investigated the genotoxic effects of ionizing radiation on nuclear medicine workers. We used two different indicators of genotoxicity methods: sister chromatid exchange (SCE) and micronucleus (MN).

Glassy polymeric carbon (GPC), which is made from phenolic resins, has a high chemical inertness and is used as high temperature and radiation resistant coatings, as high temperature heat-exchangers, as well as a biomaterial in medicine... more

Glassy polymeric carbon (GPC), which is made from phenolic resins, has a high chemical inertness and is used as high temperature and radiation resistant coatings, as high temperature heat-exchangers, as well as a biomaterial in medicine for the manufacture of heart valves and prosthetic devices [G.M. Jenkins, D. Ila, H. Maleki, Mater. Res. Soc. Symp. Proc. 394 ]. GPC is also used for the harsh environment of space, as well as for protective coating against extreme environments such as high temperature, highly ionizing radiation, as well as corrosive environments.

A nuclear imaging of heart is a noninvasive procedure that reveals the cardiac structure and physiology enabling evaluation of cardiac function. According to the regulations published by the Polish Government and the Polish Ministry of... more

A nuclear imaging of heart is a noninvasive procedure that reveals the cardiac structure and physiology enabling evaluation of cardiac function. According to the regulations published by the Polish Government and the Polish Ministry of Health, the nuclear medicine departments must follow the new legislation which has imposed quality assurance (QA) and quality control (QC) of equipment and medical testing procedures as compulsory.

Calf thymus DNA Ethidium bromide (EB) Ni(II)-DHA (nickel complex of 1, 2-dihydroxy-910-anthraquinone) Fe(III)-DHA (iron complex of 1, 2-dihydroxy-910-anthraquinone) a b s t r a c t Ionizing radiation when allowed to fall upon cells or... more

Calf thymus DNA Ethidium bromide (EB) Ni(II)-DHA (nickel complex of 1, 2-dihydroxy-910-anthraquinone) Fe(III)-DHA (iron complex of 1, 2-dihydroxy-910-anthraquinone) a b s t r a c t Ionizing radiation when allowed to fall upon cells or DNA, the radicals produced modify the base-pair region of the double strands. Radiation-induced double-strand modifications in calf thymus DNA were detected using Ni(II) and Fe(III) complexes of 1,2 dihydroxy 9,10 anthraquinone (DHA). 60 Co was used as the source for g-radiation and ethidium bromide (EB) as the fluorescent dye for detecting double-strand modifications caused in DNA. Results show that the Fe(III)-DHA complex is more efficient in modifying the base-pair region in double-stranded DNA in comparison to DHA or the Ni(II)-DHA complex.

Purpose: To investigate if there is a statistically significant difference in cancer cell survival using a high dose per pulse flattening filter-free (FFF) beam compared to a standard flattened beam. Material and methods: To validate the... more

Purpose: To investigate if there is a statistically significant difference in cancer cell survival using a high dose per pulse flattening filter-free (FFF) beam compared to a standard flattened beam. Material and methods: To validate the radiobiological effect of the flattened and FFF beam, two glioblastoma cell lines were treated with either 5 or 10 Gy using different dose rates. Dose verification was performed and colony formation assays were carried out. To compare the predictability of our data, radiobiological models were included. Results: The results presented here demonstrate that irradiation of glioblastoma cell lines using the FFF beam is more efficient in reducing clonogenic cell survival than the standard flattened beam, an effect which becomes more significant the higher the single dose. Interestingly, in our experimental setting, the radiobiological effect of the FFF beam is dependent on dose per pulse rather than on delivery time. The used radiobiological models are able to describe the observed dose rate dependency between 6 and 24 Gy/min. Conclusion: The results presented here show that dose per pulse might become a crucial factor which influences cancer cell survival. Using high dose rates, currently used radiobiological models as well as molecular mechanisms involved urgently need to be re-examined.

Optical absorption in Si02-Core/Si02:F-Clad fibers was investigated in situ during 6oCo 7 irradiation. Bands at 610 and c400 nm were first created, then permanently erased by exposures > 1 MGy(Si) in the presence of injected visible light... more

Optical absorption in Si02-Core/Si02:F-Clad fibers was investigated in situ during 6oCo 7 irradiation. Bands at 610 and c400 nm were first created, then permanently erased by exposures > 1 MGy(Si) in the presence of injected visible light ( -5 pW).

The biological effects of high-dose total body ionizing irradiation [(thereafter, irradiation (IR)] are attributed to primary oxidative breakage of biomolecule targets, mitotic, apoptotic and necrotic cell death in the dose-limiting... more

The biological effects of high-dose total body ionizing irradiation [(thereafter, irradiation (IR)] are attributed to primary oxidative breakage of biomolecule targets, mitotic, apoptotic and necrotic cell death in the dose-limiting tissues, clastogenic and epigenetic effects, and cascades of functional and reactive responses leading to radiation sickness defined as the acute radiation syndrome (ARS). The range of remaining and protracted injuries at any given radiation dose as well as the dynamics of post-IR alterations is tissue-specific. Therefore, functional integrity of the homeostatic tissue barriers may decline gradually within weeks in the post-IR period culminating with sepsis and failure of organs and systems. Multiple organ failure (MOF) leading to moribundity is a common sequela of the hemotapoietic form of ARS (hARS). Onset of MOF in hARS can be presented as "two-hit phenomenon" where the "first hit" is the underlying consequences of the IR-induced radiolysis in cells and biofluids, non-septic inflammation, metabolic up-regulation of pro-oxidative metabolic reactions, suppression of the radiosensitive hematopoietic and lymphoid tissues and the damage to gut mucosa and vascular endothelium. While the "second hit" derives from bacterial translocation and spread of the bacterial pathogens and inflammagens through the vascular system leading to septic inflammatory, metabolic responses and a cascade of redox pro-oxidative and adaptive reactions. This sequence of events can create a ground for development of prolonged metabolic, inflammatory, oxidative, nitrative, and carbonyl, electrophilic stress in crucial tissues and thus exacerbate the hARS outcomes. With this perspective, the redox mechanisms, which can mediate the IR-induced protracted oxidative post-translational

In the hierarchy of cellular targets damaged by ionizing radiation (IR), classical models of radiation toxicity place DNA at the top. Yet, many prokaryotes are killed by doses of IR that cause little DNA damage. Here we have probed the... more

In the hierarchy of cellular targets damaged by ionizing radiation (IR), classical models of radiation toxicity place DNA at the top. Yet, many prokaryotes are killed by doses of IR that cause little DNA damage. Here we have probed the nature of Mn-facilitated IR resistance in Deinococcus radiodurans, which together with other extremely IR-resistant bacteria have high intracellular Mn/Fe concentration ratios compared to IR-sensitive bacteria. For in vitro and in vivo irradiation, we demonstrate a mechanistic link between Mn(II) ions and protection of proteins from oxidative modifications that introduce carbonyl groups. Conditions that inhibited Mn accumulation or Mn redox cycling rendered D. radiodurans radiation sensitive and highly susceptible to protein oxidation. X-ray fluorescence microprobe analysis showed that Mn is globally distributed in D. radiodurans, but Fe is sequestered in a region between dividing cells. For a group of phylogenetically diverse IR-resistant and IR-sensitive wild-type bacteria, our findings support the idea that the degree of resistance is determined by the level of oxidative protein damage caused during irradiation. We present the case that protein, rather than DNA, is the principal target of the biological action of IR in sensitive bacteria, and extreme resistance in Mn-accumulating bacteria is based on protein protection. Citation: Daly MJ, Gaidamakova EK, Matrosova VY, Vasilenko A, Zhai M, et al. (2007) Protein oxidation implicated as the primary determinant of bacterial radioresistance. PLoS Biol 5(4): e92.

Este articulo presenta una revision de los fundamentos de la tomografia computarizada, empezando por un recuento de los inicios y progresos de esta tecnica a traves del tiempo, y continuando con una descripcion de los principios fisicos... more

Este articulo presenta una revision de los fundamentos de la tomografia computarizada, empezando por un recuento de los inicios y progresos de esta tecnica a traves del tiempo, y continuando con una descripcion de los principios fisicos que rigen la produccion de los rayos X. El articulo tambien discute las bases matematicas para la reconstruccion de las imagenes a partir de proyecciones utilizando metodos analiticos o iterativos. En una seccion independiente, se revisan los conceptos mas importantes relacionados con los riesgos de la radiacion ionizante y se discuten investigaciones recientes, algunas polemicas, acerca de los beneficios y riesgos asociados con la tomografia computarizada y como estos afectan los protocolos de adquisicion de las imagenes. Finalmente, con base en los avances cientificos y tendencias mas recientes, el articulo propone las areas que, presumiblemente, continuaran siendo el centro de atencion de la tomografia computarizada de rayos X en los proximos anos.

This paper describes the design and the performance characteristics of an X-ray preionized discharge pumped XeCl laser system operated at very high repetition rate frequency and high average power (200 W). The laser system is mainly... more

This paper describes the design and the performance characteristics of an X-ray preionized discharge pumped XeCl laser system operated at very high repetition rate frequency and high average power (200 W). The laser system is mainly composed of a fast flow subsonic closed cycle wind tunnel, a laser head, a high average power electrical excitation system, and an X-ray preionization source. The laser head design and the dumping of acoustic waves induced by fast electrical energy deposition of 50 J / L bar allow this device to be operated at repetition rate frequencies of up to = 1700 Hz.

We study the reionisation of the Universe by stellar sources using a numerical approach that combines fast 3D radiative transfer calculations with high resolution hydrodynamical simulations. By supplementing a one-step radiative transfer... more

We study the reionisation of the Universe by stellar sources using a numerical approach that combines fast 3D radiative transfer calculations with high resolution hydrodynamical simulations. By supplementing a one-step radiative transfer code specifically designed for following ionisation processes with an adaptive ray-tracing algorithm, we are able to significantly speed up the calculations to the point where handling a vast number of sources becomes technically feasible. This allows us to study how dim low-mass sources, excluded in previous investigations owing to computational limitations, affect the morphological evolution of the reionisation process.

Oxidative stress is a cellular or physiological condition of elevated concentrations of reactive oxygen species that cause molecular damage to vital structures and functions. Several factors influence the susceptibility to oxidative... more

Oxidative stress is a cellular or physiological condition of elevated concentrations of reactive oxygen species that cause molecular damage to vital structures and functions. Several factors influence the susceptibility to oxidative stress by affecting the antioxidant status or free oxygen radical generation. Here, we review the effect of alcohol, air pollution, cigarette smoke, diet, exercise, non-ionizing radiation (UV and microwaves) and psychological stress on the development of oxidative stress. Regular exercise and carbohydrate-rich diets seem to increase the resistance against oxidative stress. Air pollution, alcohol, cigarette smoke, non-ionizing radiation and psychological stress seem to increase oxidative stress. Alcohol in lower doses may act as an antioxidant on low density lipoproteins and thereby have an anti-atherosclerotic property.

The aim of this study is to develop the application of irradiation technology to chicken eggs in order to get a product free of pathogenic microorganisms. Bioburden values of eggs from chickens of different ages (n ¼ 150) were found to... more

The aim of this study is to develop the application of irradiation technology to chicken eggs in order to get a product free of pathogenic microorganisms. Bioburden values of eggs from chickens of different ages (n ¼ 150) were found to not be significantly different (po0:05) and an average value of (2.070.3). 10 5 cfu/egg was obtained for the shell. Two major microbial groups were characterized in the egg's natural microbiota, no Salmonella or Campylobacter were detected. HACCP studies indicated the feed as a critical point. Dosimetry studies were carried out in a g facility to find the best geometry and dose rate for irradiation. Whole eggs were artificially contaminated with reference strains of Salmonella typhimurium, Salmonella enteritidis, Campylobacter coli and Campylobacter jejuni and irradiated in the g facility at sub-lethal doses (0.2-1 kGy) with a dose rate of 1.0 kGy/h. D value varied between 0.31-0.26 kGy and 0.20-0.19 kGy in S. typhimurium and S. enteritidis, and between 0.21-0.18 kGy and 0.07-0.09 in C. coli and C. jejuni, for shell and yolk+white. Using sub-lethal doses up to 5 kGy, the D value of natural microbiota in whole eggs was 1.29 kGy. Results show that low irradiation doses could guarantee egg sanitation. r

Chest ultrasonography is a useful tool for assessing disease activity in the peripheral lung parenchyma, pleura, chest wall, diaphragm, and mediastinum. Ultrasound imaging also provides highly useful guidance in invasive diagnostic and... more

Chest ultrasonography is a useful tool for assessing disease activity in the peripheral lung parenchyma, pleura, chest wall, diaphragm, and mediastinum. Ultrasound imaging also provides highly useful guidance in invasive diagnostic and therapeutic procedures. The main advantages of this imaging technology are the absence of ionizing radiation and the possibility of real-time bedside applications. The chief indications and limitations of chest ultrasonography and the principal sonographic signs are reviewed.

d n a r e p a i r 6 ( 2 0 0 7 ) 505-516 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / d n a r e p a i r Uracil in DNA Uracil-DNA glycosylase... more

d n a r e p a i r 6 ( 2 0 0 7 ) 505-516 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / d n a r e p a i r Uracil in DNA Uracil-DNA glycosylase Somatic hypermutation Class switch recombination B cell lymphoma a b s t r a c t Deamination of cytosine in DNA results in mutagenic U:G mispairs, whereas incorporation of dUMP leads to U:A pairs that may be genotoxic directly or indirectly. In both cases, uracil is mainly removed by a uracil-DNA glycosylase (UDG) that initiates the base excision repair pathway. The major UDGs are mitochondrial UNG1 and nuclear UNG2 encoded by the UNGgene, and nuclear SMUG1. TDG and MBD4 remove uracil from special sequence contexts, but their roles remain poorly understood. UNG2 is cell cycle regulated and has a major role in post-replicative removal of incorporated uracils. UNG2 and SMUG1 are both important for prevention of mutations caused by cytosine deamination, and their functions are nonredundant. In addition, SMUG1 has a major role in removal of hydroxymethyl uracil from oxidized thymines. Furthermore, UNG-proteins and SMUG1 may have important functions in removal of oxidized cytosines, e.g. isodialuric acid, alloxan and 5-hydroxyuracil after exposure to ionizing radiation. UNG2 is also essential in the acquired immune response, including somatic hypermutation (SHM) required for antibody affinity maturation and class switch recombination (CSR) mediating new effector functions, e.g. from IgM to IgG. Upon antigen exposure B-lymphocytes express activation induced cytosine deaminase that generates U:G mispairs at the Ig locus. These result in GC to AT transition mutations upon DNA replication and apparently other mutations as well. Some of these may result from the generation of abasic sites and translesion bypass synthesis across such sites. SMUG1 can not complement UNG2 deficiency, probably because it works very inefficiently on singlestranded DNA and is down-regulated in B cells. In humans, UNG-deficiency results in the hyper IgM syndrome characterized by recurrent infections, lymphoid hyperplasia, extremely low IgG, IgA and IgE and elevated IgM. Ung −/− mice have a similar phenotype, but in addition display dysregulated cytokine production and develop B cell lymphomas late in life.

The development of radioprotective agents has been the subject of intense research in view of their potential for use within a radiation environment, such as space exploration, radiotherapy and even nuclear war. However, no ideal, safe... more

The development of radioprotective agents has been the subject of intense research in view of their potential for use within a radiation environment, such as space exploration, radiotherapy and even nuclear war. However, no ideal, safe synthetic radioprotectors are available to date, so the search for alternative sources, including plants, has been on going for several decades. In Ayurveda, the traditional Indian system of medicine, several plants have been used to treat free radical-mediated ailments and, therefore, it is logical to expect that such plants may also render some protection against radiation damage. A systematic screening approach can provide leads to identifying potential new candidate drugs from plant sources, for mitigation of radiation injury. This article reviews some of the most promising plants, and their bioactive principles, that are widely used in traditional systems of medicine, and which have rendered significant radioprotection in both in vitro and in vivo model systems. Plants and their constituents with pharmacological activities that may be relevant to amelioration of radiation-mediated damage, including antiemetic, antiinflammatory, antioxidant, cell proliferative, wound healing and haemopoietic stimulatories are also discussed.

Phosphors are key components of x-ray framing cameras. On implosion experiments at the National Ignition Facility, the x-ray framing cameras must operate in a harsh neutron induced ionizing radiation. One promising approach of neutron... more

Phosphors are key components of x-ray framing cameras. On implosion experiments at the National Ignition Facility, the x-ray framing cameras must operate in a harsh neutron induced ionizing radiation. One promising approach of neutron induced background reduction is separation of the neutron background with using difference of x-ray and neutron time-of-flight. To complete x-ray imaging before arrival of the neutron induced radiation to the detector, it is crucial to find a phosphor which has high efficiency and fast decay time. We tested various phosphor materials to optimize design of framing cameras for implosion experiments.

The effect of gamma radiation (doses: 5, 10 and 30 kGy) on mechanical properties, gas and water vapour permeability and overall migration values into distilled water, 3% aqueous acetic acid and iso-octane was studied for a series of... more

The effect of gamma radiation (doses: 5, 10 and 30 kGy) on mechanical properties, gas and water vapour permeability and overall migration values into distilled water, 3% aqueous acetic acid and iso-octane was studied for a series of commercial multilayer flexible packaging materials based on coextruded polypropylene (PP), ethylene vinyl alcohol (EVOH), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyamide (PA) and Ionomer. The results showed that radiation doses of 5 and 10 kGy induced no statistically significant differences (p > 0:05) in all polymer properties examined. A dose of 30 kGy induced differences (po0:05) in the mechanical properties of PA/LDPE, LDPE/EVOH/LDPE and LDPE/PA/Ionomer films. In addition, the same dose induced differences (po0:05) in the overall migration from Ionomer/EVOH/LDPE and LDPE/PA/Ionomer films into 3% acetic acid and iso-octane and in the overall migration from PP/EVOH/LDPE-LLDPE into iso-octane. Differences recorded, are discussed in relation to food irradiation applications of respective packaging materials. r

and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in... more

and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Allelic loss is an important mutational mechanism in human carcinogenesis. Loss of heterozygosity (LOH) at an autosomal locus is one outcome of the repair of DNA double-strand breaks (DSBs) and can occur by deletion or by mitotic... more

Allelic loss is an important mutational mechanism in human carcinogenesis. Loss of heterozygosity (LOH) at an autosomal locus is one outcome of the repair of DNA double-strand breaks (DSBs) and can occur by deletion or by mitotic recombination. We report that mitotic recombination between homologous chromosomes occurred in human lymphoid cells exposed to densely ionizing radiation. We used cells derived from the same donor that express either normal TP53 (TK6 cells) or homozygous mutant TP53 (WTK1 cells) to assess the influence of TP53 on radiation-induced mutagenesis. Expression of mutant TP53 (Met 237 Ile) was associated with a small increase in mutation frequencies at the hemizygous HPRT (hypoxanthine phosphoribosyl transferase) locus, but the mutation spectra were unaffected at this locus. In contrast, WTK1 cells (mutant TP53) were 30-fold more susceptible than TK6 cells (wild-type TP53) to radiation-induced mutagenesis at the TK1 (thymidine kinase) locus. Gene dosage analysis c...

Human population throughout the world is surrounded by an invisible continuously increasing web of radiation, originating from both natural and non-natural sources. Radiation is of two types: ionizing and non-ionizing depending upon their... more

Human population throughout the world is surrounded by an invisible continuously increasing web of radiation, originating from both natural and non-natural sources. Radiation is of two types: ionizing and non-ionizing depending upon their energy. The exposure to radiation has increased many folds in the recent years with the invention and launch of many electromagnetic devices. Exposure to ionizing radiations has been found to cause severe abnormalities in human beings such as DNA damage, cancer, infertility, electro-hypersensitivity, etc. which however is of different intensity depending upon the age group of human beings, with children and fetus being the maximum sufferers because of immature immune system and also various other cells in their body are still at the stage of division and differentiation. Present study has been aimed to investigate a generalized preliminary idea of various health related complications caused by ionizing radiations to human beings with special emphasis to fetus and children.

The tremendous variability of the inferior epigastric arterial system makes accurate imaging of the vasculature of the anterior abdominal wall an essential component of optimal perforator selection. Preoperative imaging of the abdominal... more

The tremendous variability of the inferior epigastric arterial system makes accurate imaging of the vasculature of the anterior abdominal wall an essential component of optimal perforator selection. Preoperative imaging of the abdominal vasculature allows for preoperative perforator selection, resulting in improved operative efficiency and flap design. Abdominal wall perforators of 1-mm diameter can be reliably visualized without exposing patients to ionizing radiation or iodinated intravenous contrast through advances in magnetic resonance imaging angiography (MRA). In this study, MRA imaging was performed on 31 patients who underwent 50 abdominal flaps. For each flap, the location, relative to the umbilicus, of the three largest perforators on both the left and right sides of the abdomen was determined with MRA. Vessel diameter and anatomic course were also evaluated. Postoperatively, a survey was completed by the surgeon to assess the accuracy of the MRA with respect to the intraoperative findings. All perforators visualized on MRA were found at surgery (0% false-positive). In 2 of 50 flaps, the surgeon transferred a flap based upon a vessel not visualized on the MRA (4% false-negative). This article details our experience with MRA as a reliable preoperative imaging technique for abdominal perforator flap breast reconstruction.

Here we have used an intrachromosomal substrate to monitor the end joining of distant ends, which leads to DNA rearrangements in mammalian cells. We show that silencing Mre11 reduces the efficiency of nonhomologous end joining (NHEJ),... more

Here we have used an intrachromosomal substrate to monitor the end joining of distant ends, which leads to DNA rearrangements in mammalian cells. We show that silencing Mre11 reduces the efficiency of nonhomologous end joining (NHEJ), affecting both the canonical and alternative pathways, partly in a manner that is independent of the ataxia-telangiectasia mutated kinase (ATM). Silencing of Rad50 or CtIP decreases end-joining efficiency in the same pathway as Mre11. In cells defective for Xrcc4, the MRE11-RAD50-NBS1 (MRN) complex inhibitor MIRIN decreases end-joining frequencies, demonstrating a role for MRN in alternative NHEJ. Consistently, MIRIN sensitizes both complemented and NHEJ-defective cells to ionizing radiation. Conversely, overexpression of Mre11 stimulates the resection of single-stranded DNA and increases alternative end joining, through a mechanism that requires Mre11's nuclease activity, but in an ATM-independent manner. These data demonstrate that, in addition to its role in ATM activation, Mre11 can favor alternative NHEJ through its nuclease activity.

The ENEA fast neutron dosemeter is based on a planar PADC (Poly Allyl Diglicol Carbonate) placed in a polyethylene holder. The present paper reports the results of a preliminary experimental comparison of a CR-39 Ò material with the... more

The ENEA fast neutron dosemeter is based on a planar PADC (Poly Allyl Diglicol Carbonate) placed in a polyethylene holder. The present paper reports the results of a preliminary experimental comparison of a CR-39 Ò material with the addition of 0.1% of DOP (Dioctylphthalate), produced by the Italian company Intercast Europe S.p.A., and TASTRAK material produced by the British company TASL (UK).

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and... more

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

Imaging plays a major role in the diagnostic work-up of children with hepatobiliary or pancreatic diseases. It consists mainly of US, CT and MRI, with US and MRI being the preferred imaging modalities because of the lack of ionizing... more

Imaging plays a major role in the diagnostic work-up of children with hepatobiliary or pancreatic diseases. It consists mainly of US, CT and MRI, with US and MRI being the preferred imaging modalities because of the lack of ionizing radiation. In this review the technique of US, CT and MRI in children will be addressed, followed by a comprehensive overview of the imaging characteristics of several hepatobiliary and pancreatic disease entities most common in the paediatric age group.

Page 1. 1484 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 40, NO. 6, DECEMBER 1993 Altitude and Latitude Variations in Avionics SEU and Atmospheric Neutron Flux E. Normand and T. J. Baker Boeing Defense & Space Group, Seattle, WA... more

Page 1. 1484 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 40, NO. 6, DECEMBER 1993 Altitude and Latitude Variations in Avionics SEU and Atmospheric Neutron Flux E. Normand and T. J. Baker Boeing Defense & Space Group, Seattle, WA 98124-2499 Abstract ...

In order to explore the Moon and Mars it is necessary to investigate the hazards due to the space environment and especially ionizing radiation. According to previous papers, much information has been presented in radiation analysis... more

In order to explore the Moon and Mars it is necessary to investigate the hazards due to the space environment and especially ionizing radiation. According to previous papers, much information has been presented in radiation analysis inside the Earth's magnetosphere, but much of this work was not directly relevant to the interplanetary medium. This work intends to explore the effect of radiation on humans inside structures such as the ISS and provide a detailed analysis of galactic cosmic rays (GCRs) and solar proton events (SPEs) using SPENVIS (Space Environment Effects and Information System) and CREME96 data files for particle flux outside the Earth's magnetosphere. The simulation was conducted using GRAS, a European Space Agency (ESA) software based on GEANT4. Dose and equivalent dose have been calculated as well as secondary particle effects and GCR energy spectrum. The calculated total dose effects and equivalent dose indicate the risk and effects that space radiation could have on the crew, these values are calculated using two different types of structures, the ISS and the TransHab modules. Final results indicate the amounts of radiation expected to be absorbed by the astronauts during long duration interplanetary flights; this denotes importance of radiation shielding and the use of proper materials to reduce the effects.

Spondylolysis is an osseous defect of the pars interarticularis, thought to be a developmental or acquired stress fracture secondary to chronic low-grade trauma. It is encountered most frequently in adolescents, most commonly involving... more

Spondylolysis is an osseous defect of the pars interarticularis, thought to be a developmental or acquired stress fracture secondary to chronic low-grade trauma. It is encountered most frequently in adolescents, most commonly involving the lower lumbar spine, with particularly high prevalence among athletes involved in certain sports or activities. Spondylolysis can be asymptomatic or can be a cause of spine instability, back pain, and radiculopathy. The biomechanics and pathophysiology of spondylolysis are complex and debated. Imaging is utilized to detect spondylolysis, distinguish acute and active lesions from chronic inactive non-union, help establish prognosis, guide treatment, and to assess bony healing. Radiography with satisfactory technical quality can often demonstrate a pars defect. Multislice CT with multiplanar reformats is the most accurate modality for detecting the bony defect and may also be used for assessment of osseous healing; however, as with radiographs, it is not sensitive for detection of the early edematous stress response without a fracture line and exposes the patient to ionizing radiation. Magnetic resonance (MR) imaging should be used as the primary investigation for adolescents with back pain and suspected stress reactions of the lumbar pars interarticularis. Several imaging pitfalls render MR imaging less sensitive than CT for directly visualizing the pars defects (regional degenerative changes and sclerosis). Nevertheless, the presence of bone marrow edema on fluid-sensitive images is an important early finding that may suggest stress response without a visible fracture line. Moreover, MR is the imaging modality of choice for identifying associated nerve root compression. Single-photon emission computed tomography (SPECT) use is limited by a high rate of false-positive and false-negative results and by considerable ionizing radiation exposure. In this article, we provide a review of the current concepts regarding spondylolysis, its epidemiology, pathogenesis, and general treatment guidelines, as well as a detailed review and discussion of the imaging principles for the diagnosis and follow-up of this condition.

Management of solid waste is an important problem, which is becoming progressively worse as a byproduct of continuing economic growth and development. Polymeric materials (plastics and rubbers) comprise a steadily increasing proportion of... more

Management of solid waste is an important problem, which is becoming progressively worse as a byproduct of continuing economic growth and development. Polymeric materials (plastics and rubbers) comprise a steadily increasing proportion of the municipal and industrial waste going into landfill. Development of technologies for reducing polymeric waste, which are acceptable from the environmental standpoint, and which are cost-effective, has proven to be a difficult challenge due to complexities inherent in the reuse of polymers. Establishing optimal processes for the reuse/recycling of polymeric materials thus remains a worldwide challenge as we enter the new century.