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Gamma Radiation (gamma + radiation)
Selected AbstractsLong-term Changes in Postnatal Susceptibility to Pilocarpine-induced Seizures in Rats Exposed to Gamma Radiation at Different Stages of Prenatal DevelopmentEPILEPSIA, Issue 10 2003Zuzanna Setkowicz Summary:,Purpose: To determine whether brains irradiated at different stages of prenatal development also have different postnatal susceptibility to seizures evoked by pilocarpine. Methods: Pregnant Wistar rats were exposed to a single 1.0-Gy dose of gamma rays on gestation days 13, 15, 17, or 19 (E13, E15, E17, and E19, respectively). On postnatal day 60, their offspring received i.p. pilocarpine injections to evoke status epilepticus. Behavior of the animals was observed continuously for 6 h after the injection, and motor manifestations of seizure activity were rated, and survival times recorded. After 7-day survival, the animals were killed, and their brains were weighed. Results: The average brain weight of animals exposed to irradiation at earlier prenatal stages (E13 or E15) was significantly lower than that after irradiation on E17 or E19. However, effects of the irradiation on the susceptibility to pilocarpine-induced seizures were quite opposite. The intensity of status epilepticus evoked in rats irradiated on E13 or E15 was significantly lower than that in nonirradiated controls or in those irradiated on E17 or E19. Moreover, after irradiation on E13 or E15, survival of the animals was significantly higher in relation not only to other irradiated groups but also to the controls. Conclusions: The results suggest than the extent of neuronal deficit, even if relatively greater, cannot always lead to higher susceptibility of the dysplastic brain to seizures. Functional consequences of the deficit, even if its magnitude is relatively smaller but involving specific brain areas, appear to be critical for the epileptogenesis. [source] Gamma radiation induced graft copolymerization of acrylamide onto EPDM blended with PEPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2002E. M. El-Nesr Abstract Gamma radiation induced grafting of acrylamide (AAm) onto vulcanized strips of EPDM and EPDM/PE blends has been carried out. The effects of different parameters on the graft yield have been investigated. These parameters include: radiation dose, monomer concentration, diluent composition and types of inhibitors. It has been found that water is the most appropriate solvent. The preswelling of crosslinked rubber samples in cyclohexane prior to grafting enhances the grafting and the addition of methanol to water as binary diluent in the ratio (1,:,1) decreases the graft yield. The presence of Mohr's salt and copper sulfate in the reaction mixture in the molar ratio (2.1,:,0.5) markedly increases the graft yield. Evidence of grafting have been conducted using thermal analysis as well as swelling measurements in water. Also, it has been found that the mechanical properties of the blends decrease at graft yield 13%. Copyright © 2002 John Wiley & Sons, Ltd. [source] Induction of V(D)J-mediated recombination of an extrachromosomal substrate following exposure to DNA-damaging agentsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 6 2007Robert L. Pinsonneault Abstract V(D)J recombinase normally mediates recombination signal sequence (RSS) directed rearrangements of variable (V), diversity (D), and joining (J) germline gene segments that lead to the generation of diversified T cell receptor or immunoglobulin proteins in lymphoid cells. Of significant clinical importance is that V(D)J-recombinase-mediated rearrangements at immune RSS and nonimmune cryptic RSS (cRSS) have been implicated in the genomic alterations observed in lymphoid malignancies. There is growing evidence that exposure to DNA-damaging agents can increase the frequency of V(D)J-recombinase-mediated rearrangements in vivo in humans. In this study, we investigated the frequency of V(D)J-recombinase-mediated rearrangements of an extrachromosomal V(D)J plasmid substrate following exposure to alkylating agents and ionizing radiation. We observed significant dose- and time-dependent increases in V(D)J recombination frequency (V(D)J RF) following exposure to ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS) but not a nonreactive analogue, methylsulfone (MeSulf). We also observed a dose-dependent increase in V(D)J RF when cells were exposed to gamma radiation. The induction of V(D)J rearrangements following exposure to DNA-damaging agents was not associated with an increase in the expression of RAG 1/2 mRNA compared to unexposed controls or an increase in expression of the DNA repair Ku70, Ku80 or Artemis proteins of the nonhomologous end joining pathway. These studies demonstrate that genotoxic alkylating agents and ionizing radiation can induce V(D)J rearrangements through a cellular response that appears to be independent of differential expression of proteins involved with V(D)J recombination. Environ. Mol. Mutagen., 2007. © 2007 Wiley-Liss, Inc. [source] Hormetic effects of gamma radiation on the stress axis of natural populations of meadow voles (Microtus pennsylvanicus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2005Rudy Boonstra Abstract We tested the hypothesis that low doses of gamma radiation have beneficial, hormetic effects on the stress axis (the hypothalamic-pituitary-adrenocortical axis) of free-ranging meadow vole populations (Microtus pennsylvanicus). Voles were exposed to chronic gamma radiation from a 137Cs field irradiator. In isolated populations, voles received one of three treatments over a four-year period: Controls (0.19,0.42 ,Gy/h , levels that were 2,5X above background levels [0.1 ,Gy/h] and live-trapped in all years , 1982,1985), low doses (22.6 ,Gy/h , 50,200X background, live-trapped from November 1982,April 1985), or high doses (3,840 ,Gy/h , 40,000X background, live-trapped from November 1983,April 1985). Voles exposed to a low dose had levels of free and total corticosterone that were significantly higher than those in the control or high-dose groups. Differences in response to radiation between the sexes were apparent for maximum corticosterone-binding capacity, with females exposed to low doses having higher binding capacity than control or high-dose females, whereas males exposed to low doses had lower binding capacity than control or high-dose males. Low-dose voles had higher counts of neutrophils than either the controls or high-dose voles; hematocrit was greater in the controls than in irradiated voles. These results indicate that voles display a hormetic response to radiation, wherein low doses of an otherwise harmful agent produce a beneficial effect. The stimulation of the stress axis resulting in the increased secretion of glucocorticoids, which may protect against the excessive actions of the immune and inflammatory responses, may be a key mechanism producing this effect. [source] Complex chromosome aberrations persist in individuals many years after occupational exposure to densely ionizing radiation: An mFISH studyGENES, CHROMOSOMES AND CANCER, Issue 1 2005M. Prakash Hande Long-lived, sensitive, and specific biomarkers of particular mutagenic agents are much sought after and potentially have broad applications in the fields of cancer biology, epidemiology, and prevention. Many clastogens induce a spectrum of chromosome aberrations, and some of them can be exploited as biomarkers of exposure. Densely ionizing radiation, for example, alpha particle radiation (from radon or plutonium) and neutron radiation, preferentially induces complex chromosome aberrations, which can be detected by the 24-color multifluor fluorescence in situ hybridization (mFISH) technique. We report the detection and quantification of stable complex chromosome aberrations in lymphocytes of healthy former nuclear-weapons workers, who were exposed many years ago to plutonium, gamma rays, or both, at the Mayak weapons complex in Russia. We analyzed peripheral-blood lymphocytes from these individuals for the presence of persistent complex chromosome aberrations. A significantly elevated frequency of complex chromosome translocations was detected in the highly exposed plutonium workers but not in the group exposed only to high doses of gamma radiation. No such differences were found for simple chromosomal aberrations. The results suggest that stable complex chromosomal translocations represent a long-lived, quantitative, low-background biomarker of densely ionizing radiation for human populations exposed many years ago. © 2005 Wiley-Liss, Inc. [source] Dialyzer reactions in a patient switching from peritoneal dialysis to hemodialysisHEMODIALYSIS INTERNATIONAL, Issue 2 2005Robert C. Yang Many terms have been used to describe the collection of signs and symptoms triggered by the initial use of dialyzers. These reactions can be divided into Type A (hypersensitivity reactions, with the incidence of 4/100,000) and Type B (nonspecific reactions, incidence 3,5/100). Many different mechanisms have been postulated, including complement activation, pulmonary leukostasis, hypersensitivity to ethylene oxide, interaction between the AN69 membrane and angiotensin-converting enzyme inhibitors, and dialysate contamination. An unusual case of dialyzer reactions is presented here, involving a patient who had to discontinue peritoneal dialysis when she was admitted with fungal peritonitis. Upon initiation of hemodialysis, she experienced dyspnea and burning sensation and demonstrated significant leukopenia, thrombocytopenia, and oxygen desaturation. These reactions persisted despite double-rinsing of the dialyzers and the use of several different dialyzers with synthetic membranes (polysulfone and AN69), and a variety of sterilization methods (electron beam and gamma radiation). In the end, a simple measure was found to be effective in preventing further dialyzer reactions in this fascinating case. [source] NUTRITIONAL QUALITY OF IRRADIATED ORANGE JUICE,JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2002XUETONG FAN Single-strength orange juice was exposed to 0, 0.89, 2.24, 4.23 and 8.71 kGy gamma radiation at 5C, and then stored at 23C for 6 days and 7C for 21 days. Conversion of ascorbic acid (AA) to dehydroascorbic acid (DHA), and loss of AA, total AA (TAA = AA plus DHA) and total antioxidants increased with radiation dose. Rate of TAA loss due to irradiation was much less than that of AA loss. Compared to nonirradiated juice (0 kGy), juice irradiated at 2.24 kGy or less had similar rates of AA and TAA loss during storage while juice irradiated at 4.23 and 8.71 kGy had higher rates of AA and TAA loss. Loss of total antioxidants in irradiated orange juice appeared to result from loss of AA. [source] Effectiveness of Radiation Processing for Elimination of Salmonella Typhimurium from Minimally Processed Pineapple (Ananas comosus Merr.)JOURNAL OF FOOD SCIENCE, Issue 3 2007Ravindranath Shashidhar ABSTRACT:, The microbiological quality of market samples of minimally processed (MP) pineapple was examined. The effectiveness of radiation treatment in eliminating Salmonella Typhimurium from laboratory inoculated ready-to-eat pineapple slices was also studied. Microbiological quality of minimally processed pineapple samples from Mumbai market was poor; 8.8% of the samples were positive for Salmonella. D10 (the radiation dose required to reduce bacterial population by 90%) value for S. Typhimurium inoculated in pineapple was 0.242 kGy. Inoculated pack studies in minimally processed pineapple showed that the treatment with a 2-kGy dose of gamma radiation could eliminate 5 log CFU/g of S. Typhimurium. The pathogen was not detected from radiation-processed samples up to 12 d during storage at 4 and 10 °C. The processing of market samples with 1 and 2 kGy was effective in improving the microbiological quality of these products. [source] Development of Shelf-stable Intermediate-moisture Meat Products Using Active Edible ChitosanCoating and IrradiationJOURNAL OF FOOD SCIENCE, Issue 7 2005M. Shobita Rao ABSTRACT Shelf-stable intermediate-moisture (IM) meat products were developed using a combination of hurdles such as reduced aw, active edible coating of chitosan, and irradiation. Chitosan prepared from chitin had a viscosity of 16 c P, molecular weight of 17.54 kDa, and a degree of deacetylation (DD) of 74%. The nitrogen content of the chitosan was estimated to be 7.56%. The antioxidant activity of chitosan increased upon irradiation without significantly affecting its antimicrobial property. The effect of irradiated chitosan coating in terms of its antimicrobial and antioxidant properties in IM meat products immediately after irradiation and during storage was assessed. The aw of meat products such as mutton sheek kababs and streaky bacon was first reduced to 0.85 ± 0.02. The products were then coated with chitosan and irradiated (4 kGy). No viable bacteria or fungi were detected in chitosan-coated, irradiated products. In contrast, IM meat products that were not subjected to gamma radiation showed visible fungal growth within 2 wk. The chitosan-coated products showed lower thiobarbituric acid-reactive substances (TBARS) than the noncoated samples for up to 4 wk of storage at ambient temperature. The studies thus clearly indicated the potential use of chitosan coating for the preparation of safe and stable meat products. [source] Basic Rules of Dosimetry in Endovascular BrachytherapyJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 6 2000PHILIPPE A. COUCKE M.D. Endovascular brachytherapy after percutaneous coronary intervention (PCI), is becoming a standard approach for the treatment and prevention of restenosis. A variety of technical approaches are currently available to deliver ionizing irradiation to the vascular target. Basically two kinds of radioactive isotopes are available that emit gamma radiation (photons) or beta radiation (electrons). The pitfalls and solutions for the optimization of dosimetry are discussed. As might be expected, the inhomogeneous dose distribution across the target volume results in recurrence by underdosage or in complications because of overdosage. Moreover, uniformization of the target definition and reporting of the dose distribution in endovascular brachytherapy is a prerequisite for comparison between the results of the various clinical trials and is absolutely necessary to improve the therapeutic efficacy of this new approach in the prevention of restenosis after coronary angioplasty with or without stenting. [source] Evaluation of the radioprotective effect of Ageratum conyzoides Linn. extract in mice exposed to different doses of gamma radiationJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2003Ganesh Chandra Jagetia The effect of various doses (0, 25, 50, 75, 100, 125, 150, 300, 600 and 900 mg kg,1) of the alcoholic extract of the plant Ageratum conyzoides Linn. (ACE), on the alteration of radiation-induced mortality in mice exposed to 10 Gy of gamma radiation was studied. The acute toxicity studies showed that the drug was non-toxic up to a dose of 3000 mg kg,1, the highest dose that could be tested for acute toxicity. Administration of ACE resulted in a dose-dependent decline in radiation-induced mortality up to a dose of 75 mg kg,1, the dose at which the highest number of survivors (70.83%) was observed. Thereafter, the number of survivors declined with increasing doses of ACE and a nadir was reached at 900 mg kg,1 ACE. Since the number of survivors was highest for 75 mg kg,1 ACE, this was considered the optimum dose for radioprotection and used in further studies in which mice were treated with 75 mg kg,1 ACE before exposure to 6, 7, 8, 9, 10 and 11 Gy of gamma radiation. The treatment of mice with 75 mg kg,1 ACE reduced the severity of symptoms of radiation sickness and mortality at all exposure doses, and a significant increase in survival was observed compared with the non-treated irradiated group. The ACE treatment effectively protected mice against the gastrointestinal as well as bone marrow related death, as revealed by the increased number of survivors at all irradiation doses. The dose reduction factor was found to be 1.3. To understand the mechanism of action, various doses of ACE were evaluated for their in-vitro scavenging action on 1,1-diphenyl-2-picrylhydrazyl (DPPH), a chemically stable free radical. ACE was found to scavenge DPPH radicals in a concentration-dependent manner, indicating that the radioprotection afforded by ACE may be in part due to the scavenging of reactive oxygen species induced by ionizing radiation. [source] The effect of gamma irradiation on the microbial load, mineral concentration and sensory characteristics of liquorice (Glycyrrhiza glabra L)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2003Mahfouz Al-Bachir Abstract Ground liquorice roots were exposed to various doses (0, 5, 10, 15 and 20,kGy) of gamma radiation from a 60Co source. Irradiated and non-irradiated samples were stored at room temperature. Microbial population, viscosity, concentrations of some minerals and the sensory properties of the extracts were evaluated after 0 and 12 months of storage. Tests carried out immediately after irradiation showed that the microbial count had been reduced and that the dose required to reduce the count by 1 log cycle (D10) was about 2,kGy. No effect was observed on the total dissolved solids in extracts of liquorice roots. Glycyrrhizinic acid concentration in the extracts and the viscosities of suspensions produced from irradiated roots were lower than those from non-irradiated ones. Sensory evaluation indicated that there were no significant differences (P,<,0.05) in colour, taste or flavour between extracts produced from irradiated and non-irradiated roots. However, after 12 months of storage, some mineral ion (Na+, Ca2+ and K+) concentrations in extracts produced from irradiated roots were lower than in those from non-irradiated ones; no significant differences (P,<,0.05) in viscosity were found between suspensions of irradiated and non-irradiated roots. © 2002 Society of Chemical Industry [source] Effect of environmental stresses on the sensitivity of Enterobacter sakazakii in powdered infant milk formula to gamma radiationLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2008T. Osaili Abstract Aim:, To evaluate the effect of starvation, heat, cold, acid, alkaline, chlorine and ethanol stresses on the resistance of Enterobacter sakazakii in powdered infant milk formula (PIMF) towards gamma radiation. Methods and Results:, Stressed cells of E. sakazakii ATCC 51329 and four other food isolate strains were mixed individually with PIMF, kept overnight at room temperature, and then exposed to gamma radiation up to 7·5 kGy. The D10 -values were determined using linear regression and for the stressed E. sakazakii strains these values ranged from 0·82 to 1·95 kGy. Conclusions:, Environmental stresses did not significantly change the sensitivity of most E. sakazakii strains to ionizing radiation. Significance and Impact of the Study:, Data obtained established that most forms of environmental stress are unlikely to significantly enhance the resistance of E. sakazakii strains to lethal, low dose irradiation treatment. [source] Effects of Combined Photodynamic Therapy and Ionizing Radiationon Human Glioma Spheroids,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2002Steen J. Madsen ABSTRACT The effects of combined photodynamic therapy (PDT) and ionizing radiation are studied in a human glioma spheroid model. The degree of interaction between the two modalities depends in a complex manner on factors such as PDT irradiation fluence, fluence rate and dose of ionizing radiation. It is shown that gamma radiation and PDT interact in a synergistic manner only if both light fluence and gamma radiation dose exceed approximately 25 J cm,2 and 8 Gy, respectively. Synergistic interactions are observed only for the lower fluence rate (25 mW cm,2) investigated. The degree of interaction appears to be independent of both sequence and the PDT or ionizing radiation time intervals investigated (1 and 24 h). Terminal deoxynucleotidyl transferase,mediated deoxyuridine triphosphate nick-end labeling assays show that low-fluence rate PDT is very efficient at inducing apoptotic cell death, whereas neither high-fluence rate PDT nor ionizing radiation produces significant apoptosis. Although the mechanisms remain to be elucidated, the data imply that the observed synergism is likely not due to gamma-induced cell cycle arrest or to PDT-induced inhibition of DNA repair. [source] The O,(Al2) centre in topaz and its relation to the blue colourPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005D. N. da Silva Abstract Colour-enhanced blue topaz is one of the most traded gemstones. Naturally very rare, mostly topaz is irradiated by neutrons, electrons, gamma radiation and combinations of them. The colour centre is still not identified. It was speculated that it is related to a Si dangling bond defect occupied by two electrons with spin S = 0. We investigated natural blue as well as colourless topaz from different regions in Brazil by electron paramagnetic resonance (EPR), optical absorption and Raman spectroscopy. The results are compared with neutron and gamma-irradiated blue topaz. By EPR two paramagnetic defects are identified in all samples: (i) the peroxy radical (O2,) measured at room temperature and (ii) an (O,) hole centre interacting with two equivalent Al neighbours measured at low temperature. Blue samples show an absorption band centred at 620 nm which is responsible for the blue colour. From our investigation we find that the O,(Al2) hole centre has nearly the same thermal stability as the optical absorption band. However, we cannot say whether it is responsible for the absorption band and the blue colour. We suggest that at least it plays a dominant role in the stabilization of the blue colour. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mint oil (Mentha spicata Linn.) offers behavioral radioprotection: a radiation-induced conditioned taste aversion studyPHYTOTHERAPY RESEARCH, Issue 2 2009A. Haksar Abstract Mentha spicata Linn. (mint), a herb well known for its gastroprotective properties in the traditional system of medicine has been shown to protect against radiation-induced lethality, and recently its constituents have been found to possess calcium channel antagonizing properties. The present study examined the behavioral radioprotective efficacy of mint oil (obtained from Mentha spicata), particularly in mitigating radiation-induced conditioned taste aversion (CTA), which has been proposed as a behavioral endpoint that is mediated by the toxic effects of gamma radiation on peripheral systems, primarily the gastrointestinal system in the Sprague-Dawley rat model. Intraperitoneal administration of Mentha spicata oil 10% (v/v), 1 h before 2 Gy gamma radiation, was found to render significant radioprotection against CTA (p < 0.05), by blocking the saccharin avoidance response within 5 post-treatment observational days, with the highest saccharin intake being observed on day 5. This finding clearly demonstrates that gastroprotective and calcium channel antagonizing properties of Mentha spicata can be effectively utilized in preventing radiation-induced behavioral changes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Radiation Response Genotype and Risk of Differentiated Thyroid Cancer: A Case-Control Analysis,THE LARYNGOSCOPE, Issue 6 2005Erich M. Sturgis MD Abstract Background: Radiation is the only clear etiologic agent for differentiated thyroid cancer (DTC). Understanding the factors affecting sensitivity to gamma radiation and susceptibility to DTC will be critical to early detection and prevention of DTC. Hypothesis: Germline variants of double-strand break repair genes are markers of DTC risk. Objective: Determine the frequency of common single nucleotide polymorphisms of genes of the double-strand break repair pathway in patients with DTC and cancer-free controls. Study Design: Case-control study. Methods: This study included 134 patients with DTC, 79 patients with benign thyroid lesions, and 166 cancer-free control subjects. To avoid ethnic confounding, all subjects were non-Hispanic whites. Genotype analyses were performed on DNA isolated from peripheral blood lymphocytes. Multivariate logistic regression analyses were performed to estimate the risk of DTC associated with each variant genotype. Results: The XRCC3 18067T polymorphic allele was found significantly more commonly among the DTC cases than for the control subjects (P = .006). After multivariate adjustment, having the XRCC3 18067T allele was associated with an increased risk of DTC (adjusted odds ratio [OR] = 2.1; 95% confidence interval [CI] = 1.3 to 3.4; P = .004). In addition, there was a suggestion that the XRCC3 18067T polymorphic allele was more common among the patients with benign thyroid disease (P = .054), and the homozygous polymorphic genotype was associated with risk for benign thyroid disease (adjusted OR = 2.1; 95% CI = 0.9,4.9; P = .078). Conclusions: In this case-control analysis, the XRCC3 18067T polymorphism is associated with DTC risk. However, such work needs confirmation in larger studies. [source] Influence of gamma radiation on the electrical properties of MnO and MnO/TeO2 thin filmsANNALEN DER PHYSIK, Issue 1-2 2004K. Arshak Abstract The pure and mixed oxide materials, such as manganese oxide (MnO) and tellurium dioxide (TeO2), in the form of thermally deposited thin films were studied in terms of their susceptibility to gamma radiation exposure. Radiation-induced changes in their electrical properties indicated the level of radiation damage. These thin film devices showed increase in values of current by the increase in the radiation dose. The dose response was found to be composition- and thickness-dependant. [source] | |||||||||||||||||||