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Petin V.G.,Medical Radiological Research Center | Evstratova E.S.,Medical Radiological Research Center | Kim J.K.,Advanced Radiation Technology Institute
Mutation Research - Genetic Toxicology and Environmental Mutagenesis | Year: 2014

Experimental results described earlier showed significantly larger relative biological effectiveness (RBE) values for wild-type diploid cells in comparison with radiosensitive mutants. This aspect was further studied in this paper. Diploid yeast cells were irradiated with gamma rays from 60Co and alpha particles from 239Pu in the stationary phase of cell growth. Survival curves and the kinetics of the liquid-holding recovery were measured. When the irradiated cells had completely recovered from potentially lethal damage, they were again exposed to radiation and allowed post-irradiation recovery. The procedure was repeated three times. By use of a quantitative approach - describing the process of recovery as a decrease in the effective radiation dose -, the probability of recovery per unit time and the proportion of irreversibly damaged cells were quantitatively estimated. It was shown that the irreversible fraction of cell injury was increased after repeated exposures to gamma rays, from 0.4 after the first irradiation to 0.7 after the third exposure. The effect was more clearly expressed after exposure to densely ionizing radiation, the corresponding values being 0.5 and 1.0. In contrast, the recovery constant did not depend on the number of repeated irradiations and only slightly depended on radiation quality. It is suggested that the process of recovery from potentially lethal radiation damage itself is not impaired after repeated exposures to both low- and high-LET radiations, and the decrease in the ability of the cell to recover from radiation damage is mainly explained by the increase in the proportion of irreversibly damaged cells. © 2014 Elsevier B.V. Source


Park S.,Chonnam National University | Park A.R.,Chonnam National University | Im S.,Chonnam National University | Han Y.-J.,Chonnam National University | And 4 more authors.
PLoS ONE | Year: 2014

Sesquiterpenoid capsidiol, exhibiting antifungal activity against pathogenic fungus, is accumulated in infected ripe pepper fruits. In this study, we found a negative relation between the capsidiol level and lesion size in fruits infected with Colletotrichum gloeosporioides, depending on the stage of ripening. To understand the developmental regulation of capsidiol biosynthesis, fungal-induced gene expressions in the isoprenoid biosynthetic pathways were examined in unripe and ripe pepper fruits. The sterol biosynthetic pathway was almost shut down in healthy ripe fruits, showing very low expression of hydroxymethyl glutaryl CoA reductase (HMGR) and squalene synthase (SS) genes. In contrast, genes in the carotenoid pathway were highly expressed in ripe fruits. In the sesquiterpene pathway, 5-epi-aristolochene synthase (EAS), belonging to a sesquiterpene cyclase (STC) family, was significantly induced in the ripe fruits upon fungal infection. Immunoblot and enzyme activity analyses showed that the STCs were induced both in the infected unripe and ripe fruits, while capsidiol was synthesized discriminatively in the ripe fruits, implying diverse enzymatic specificity of multiple STCs. Thereby, to divert sterol biosynthesis into sesquiterpene production, infected fruits were pretreated with an SS inhibitor, zaragozic acid (ZA), resulting in increased levels of capsidiol by more than 2-fold in the ripe fruits, with concurrent reduction of phytosterols. Taken together, the present results suggest that the enhanced expression and activity of EAS in the ripe fruits play an important role in capsidiol production, contributing to the incompatibility between the anthracnose fungus and the ripe pepper fruits. © 2014 Park et al. Source


Park B.-H.,Advanced Radiation Technology Institute | Sohn J.-Y.,Advanced Radiation Technology Institute | Yoon K.-S.,Chungnam National University | Shin J.,Advanced Radiation Technology Institute
Polymer (Korea) | Year: 2014

We prepared hydrophilic porous supporters for the reinforced composite fuel cell membrane by radiation grafting of acrylonitrile (AN) and hydrophilic sodium allylsulfonate (SAS) into a porous polytetrafluoroethylene (PTFE) supporter. The physicochemical properties of the supporters prepared under various reaction conditions such as molar ratio of SAS/AN, monomer concentration, and irradiation dose were evaluated. FTIR was utilized to confirm the successful introduction of SAS/AN copolymer chains into the porous PTFE. The pores of the porous PTFE film were found to be decreased with an increase in the degree of grafting by using FE-SEM and gurley number. Furthermore, by analyzing the degree of grafting, contact angle, and TBO (toluidine blue O) uptake, the hydrophilicity of the prepared supporters was found to increase with an increase in the degree of grafting. Source


Choi J.S.,Advanced Radiation Technology Institute | Baek G.Y.,Chungnam National University | Sohn J.-Y.,Advanced Radiation Technology Institute | Sohn J.-Y.,Hanyang University | Shin J.,Advanced Radiation Technology Institute
Polymer (Korea) | Year: 2015

In this study, poly(ethylene-alt-tetrafluoroethylene)-g-poly(vinylbenzyl sulfonic acid) (ETFE-g-PVBSA) membranes with various degrees of grafting were prepared by a radiation grafting and ETFE-g-PVBSA/ZrP membranes were then prepared by introducing zirconium phosphate (ZrP) nanoparticles into an ETFE-g-PVBSA membrane. The ZrP nanoparticle uptake of the grafted membranes was found to increase with an increase of degree of grafting (DOG). §EM- EDX was applied to observe the relative cross-sectional distribution of sulfur (S), zirconium (Zr), and phosphorus (P) meanwhile TEM was applied to observe the surface distribution in the ETFE-g-PVBSA/ZrP membrane. The effects of the introduced ZrP nanoparticles were evaluated by measuring the ion exchange capacity (IEC), water uptake, and TGA of the prepared membranes. It was confirmed that the cell performance of the ETFE-g-PVBSA/ZrP membrane was improved at a higher temperature and lower relative humidity condition by the introduction of ZrP nanoparticle. © 2015 The Polymer Society of Korea. All rights reserved. Source


Song B.-S.,Advanced Radiation Technology Institute | Song B.-S.,Seoul National University | Lee Y.,Advanced Radiation Technology Institute | Moon B.-G.,Advanced Radiation Technology Institute | And 6 more authors.
Radiation Physics and Chemistry | Year: 2016

This study was performed to verify the feasibility of 7.5 MeV X-rays for food pasteurization through a comparison of the bactericidal efficiency with those of other sources for selected bacterial pathogens. No significant differences were observed between the overall bactericidal efficiency for beef-inoculated pathogens based on the uncertainty of the absorbed dose and variations in bacterial counts. This result supported that all three irradiation sources were effective for inactivation of food-borne bacteria and that 7.5 MeV X-rays may be used for food pasteurization. © 2016 Elsevier Ltd. Source

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