• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.122-129
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• 2007

The purpose of this study was to evaluate the effects of a various light curing time on the residual monomers released from light-cured dental sealant, and to examine the effectiveness of surface treatment in reducing the oxygen-inhibited layer of light-cured dental sealant($Helioseal^{(R)}$ F, Vivadent, Liechtenstein). Specimens were cured with a halogen light curing unit(XL 3000, 3M, USA) for 20, 40, 60s. Surface treatment of a light-cured dental sealant included no treatment(control group), a 10-seconds exposure to distilled water(Group I), 10-seconds manual application using a cotton pellet wetted with 75% alcohol(Group II), and 10-seconds application of a water/pumice slurry using a rubber cup on a slow-speed handpiece The specimens were eluted in distilled water for 10 minutes. All elutes were analyzed by HPLC for identification and quantitive analysis of monomers. The results of this study can be summarized as follows. 1. None of the chromatograms of the tested sealant displayed peaks with the same retention time as that of the standard solution, except for TEGDMA. 2. The release of TEGDMA decreased with increasing curing time in conventional halogen light. 3. All surface treatment group had a decrease of monomer release in comparison with no treatment group. 4. Treatment that Group III eliminated the greatest amount of any type of residual monomers. 5. The elution of unreacted monomers from curing with halogen curing unit for 60s and Group III was less than other groups.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.32 no.2 s.57
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• pp.75-79
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• 2006

In this study. we evaluated anti-aging activity of medical plants that protect the skin cell damage induced by UV irradiation. We have investigated diverse biological activities of Selaginella tamariscina as an anti-aging ingredient of cosmetics. S. tamariscina was found to show scavenging activities of radicals and reactive oxygen species (ROS) with the $IC_{50}$ values of $65.1{\mu}g/mL$ against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and $40.9 {\mu}g/mL$ against superoxide radicals in the xanthine/xanthine oxidase system, respectively. For testing intracellular ROS scavenging activity, the cultured human dermal fibroblasts were analyzed by increase in dichlorofluorescein (DCF) fluorescence upon exposure to UVB $20 mJ/cm^2$ after treatment of S. tamariscina. UVA-induced MMP-1 protein and mRNA expression in human dermal fibroblasts were reduced in a dose-dependent manner by S. tamariscina. Moreover, S. tamariscina inhibited MMP-2 (gelatinase) activity in UVA-irradiated human dermal fibroblasts assayed by zymography and semi-quantitative RT-PCR. Taken together, these results suggest that S. tamariscina may act as an anti-aging agent by Increasing collagen and preventing the skin cell damage induced by UV irradiation, and imply that S. tamariscina nay be useful as a new ingredient for anti-aging cosmetics.

• Korean Journal of Veterinary Research
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• v.44 no.3
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• pp.379-387
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• 2004

When an organism is exposed to various toxicants chronically, reactive oxygen species(ROS) are accumulated and eventually result in several biological effects from gene expression to cell death. In the present study we investigated the oxidative damage of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin(TCDD) and/or benzo(a)pyrene (B(a)P) in C100 cells. C100 cells treated with TCDD(30 nM) and B(a)P($3{\mu}M$) underwent diverse oxidative stress as determined through thiobarbituric acid-reactive substances(TBARS) formation, DNA fragmentation, DNA single strand break(SSB) assay, immunohistochemical staining of 8-hydroxy-2'-deoxyguanosine(8-OHdG), and mRNA expressions of antioxidant enzymatic genes such as Cu/Zn-SOD gene, GPx(glutathione peroxidase 5) gene, and catalase gene. Lipid peroxidation in C100 cells was determined through measuing the formation of TBARS. For theat, the cells were pretreated with TCDD(30 nM) and/or B(a)P($3{\mu}M$) for 0.5, 1, 2 and 4 days. TBARS formation was increased in TCDD(30 nM) and B(a)P($3{\mu}M$) and mixture($30nM\;TCDD+3{\mu}M\;B(a)P$) and positive control treatment groups comparing to the controls. Mixture treatment induced more DNA fragmentation than the single treatment group at day 6. Also, SSB in all treatment groups was clearly observed when compared with the negative control group. As with the expression of antioxidant enzyme, GPx 5mRNA, B(a)P alone and mixture($30nM\;TCDD+3{\mu}M\;B(a)P$) treatment were higher comparing to those of the negative control and TCDD treatment groups. Our results suggest that exposure of C100 cells to mixture of TCDD and B(a)P leads to significant oxidative damage comparing to the exposures to the individual chemicals. Mechanisms of action are discussed. Additional studies are needed to elucidate the detailed mechanism of mixture-induced toxicity.

• Journal of Life Science
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• v.23 no.10
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• pp.1223-1229
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• 2013

Ursolic acid (UA) a bio-active ingredient found in a variety of fruits and vegetables, and it has potent antioxidant activity. However, the role of UA in mouse embryonic stem (ES) cells is poorly understood. This study investigated the functional role of UA in regulating the development of mouse ES cells under hypoxia. Hypoxia did not exert a significant effect on the undifferentiated state of mouse ES cells. However, it induced reactive oxygen species (ROS) generation and increased the level of lactate dehydrogenase (LDH) production at 48 h of hypoxic exposure. Conversely, oxidative stress induced by hypoxia was significantly inhibited by UA ($30{\mu}M$) pretreatment. Hypoxia significantly decreased cell survival and the level of [$^3H$] thymidine incorporation, both of which recovered following pretreatment of UA. In addition, UA decreased the apoptotic effect of hypoxia by attenuating caspase-3 cleavage or by recovering cellular inhibition of the apoptotic protein (cIAP)-2 and Bcl-2 expression. We further found that UA decreased senescence-associated beta-galactosidase activity. We suggest that UA is a natural antioxidant and one of the functional modulators of hypoxia-induced survival, apoptosis, proliferation, and aging in mouse ES cells.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.33-39
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• 2010

The electrolytic reduction of a spent oxide fuel involves a liberation of the oxygen in a molten LiCl electrolyte, which results in a chemically aggressive environment that is too corrosive for typical structural materials. Accordingly, it is essential to choose the optimum material for the processing equipment that handles the high molten salt. In this study, hot corrosion studies were performed on bare as well as coated superalloy specimens after exposure to lithium molten salt at $675^{\circ}C$ for 216 h under an oxidizing atmosphere. The IN713LC superalloy specimens were sprayed with an aluminized NiCrAlY bond coat and then with an $Y_2O_3$ top coat. The bare superalloy reveals an obvious weight loss due to spalling of the scale by the rapid scale growth and thermal stress. The chemical and thermal stability of the top coat has been found to be beneficial for increasing to the corrosion resistance of the structural materials for handling high temperature lithium molten salts.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.1
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• pp.70-76
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• 2006

The aim of this study was comparison of effectiveness of surface treatment methods in reducing the oxygen-inhibited layer of a commercially available freshly polymerized, light cured dental sealant($concise^{TM}$, 3M, St Paul, USA). Surface treatment groups were consisted of no treatment(negative control group) and 3 experimental groups according to surface treatment of light-cured sealant. Experimental group I was 10 seconds' exposure to distilled water syringe, group II was 10 seconds' manual application using a cotton pellet wetted with 75% alcohol and group III was 10 seconds' prophylaxis with pumice/water slurry using rubber cup on a slow-speed handpiece. All specimens were immersed in 5ml distilled water and stored at 37c water bath for 10 minutes. All eluates were analyzed by HLPC for identification and quantitive analysis of monomers. The results of this study can be summarized as follows. 1. None of the chromatograms of the tested sealant displayed peaks with the same retention time as that of the standard solution, except for TEGDMA. 2. All surface treatment group had a statistically significant decrease of monomer release in comparison with no treatment group. 3. Removal effects of unreacted monomer in group III was statistically significant in comparison with group I and group II. These results revealed that mechanical method using pumice and rubber cup is the most effective in removing residual monomer and may be valuable to be used effectively in clinic.

• Korean Journal of Food Science and Technology
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• v.36 no.2
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• pp.283-287
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• 2004

Persimmons suffer from such physiological disorders as flesh softening, peel blackening, and flesh browning, which occur rapidly particularly when exposed to ambient temperature after storage at low temperature, In this study causes of these disorders were examined in terms of respiration and ethylene production of the fruits. Jelly-like flesh softening, considered as symptom of chilling injury, rapidly developed within 3 days of exposure to ambient temperature without modified atmosphere (MA) packaging after low temperature storage. Disorder development was more suppressed at $30^{\circ}C$ than at $20^{\circ}C$; such temperature dependence is closely connected to ethylene production rate of fruits at both temperatures. Inhibition of ethylene production through MA packaging effectively reduced disorder development, which indicates ethylene production is closely related to jelly-like flesh softening disorder. Development of black-staining on peels occurs in fruits exposed directly to ambient temperature, but not in those packaged with thick PE-film. Flesh browning developed only under anaerobic respiration condition of high temperature and MA packaging with thick PE film, and occurred at quick reduction of available oxygen inside MA package at high temperature.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.1
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• pp.63-71
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• 2012

As nanotechnology is a key industry, there is growing concern relating to the potential risk of nanoparticles. They are known to be released into the environment via various exposure routes. When nanoparticles are present in water environments, they are supposed to be illuminated by ultraviolet light, and the ecotoxicity of photoactive nanoparticles may be changed. In this study, a review of the ecotoxicity of photoactive nanoparticles, including the mechanisms of phototoxicity, are presented. In order to address this issue, studies on the ecotoxicity to soil and water organisms exposed to photoactive nanoparticles were investigated. The photoactive nanoparticles chosen for this study were zinc oxide, titanium dioxide and fullerene. Microorganisms, nematode, earthworm, algae and fish, etc., were chosen to assess the toxicity of nanoparticles using diverse methods. However, studies on the phototoxicity potentially induced by nanoparticles on UV illumination have been reviewed in only 8 studies. From a few studies, photoactive nanoparticles have shown high dissolution rates under UV conditions, with the released ions observed to profoundly influence test organisms. In addition, NPs exposed to UV produced reactive oxygen species (ROS). These ROS can induce oxidative stress in exposed organisms. Evidence of phototoxicity by nanoparticles were found based on previous studies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.295-306
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• 2004

Spatial patterns in the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike and environmental variables were examined in August 2001, In total, 156 macrobenthic species(123 intertidal species and 90 subtidal species) were recorded during this study, predominately polychaetes $(40{\%})$, bivalves $(22{\%})$, and crustaceans $(22{\%})$. Polychaetes made up less than $40{\%}$ of the intertidal communitr, but more than $50{\%}$ of the subtidal community. The mean density during this study was $1,456ind./m^{2}.$ Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among four regions: near the Iwon dike (B1), the high and middle intertidal zone (B2), low intertidal zone (Al), and subtidal zone (A2). The number of species, total density, and diversity (H') varied significantly among the four regions. The distribution of macrobenthic community was affected by environmental variables, such as ${\%}$ silt/clay content, total sulfide, lose of ignition, and chemical oxygen demand. These environmental variables were negatively correlated with the dominant species (Nephtys polybranchia, Umbonium thomasi, and Scoloplos armiger) in the intertidal area, but positively correlated with the dominant species (Lumbrineris cruzensis, Notomastus latericeus, and Moerella sp.) in the subtidal area. Environmental variables $({\%}\;silt/clay content and total sulfide)$ were positively correlated with the dominant species (Heteromastus filiformis) in region Bl, but negatively correlated with the dominant species (Umbonium thomasi and Scoloplos koreanus) in region B2. Amphipods Urothoe spp. and Monoculodes koreanus were the dominant species in region Al. Umbonium thomasi, the dominant species in region B2, was not found in regions Bl or Al. We suggest that the inter-specific competition for territory and exposure to seawater may be important factors controlling the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike.

• Journal of Life Science
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• v.23 no.11
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• pp.1342-1350
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• 2013

We examined the effect of hydrogen sulfide ($H_2S$) in chemical hypoxia-induced injury in mouse hepatocytes. Cell viability was significantly decreased by cobalt chloride ($CoCl_2$), a well-known hypoxia mimetic agent in a time- and dose- dependent manner. Sodium hydrosulfide (NaHS, a donor of $H_2S$) pretreatment before exposure to $CoCl_2$ significantly attenuated the $CoCl_2$-induced decrease of cell viability. $CoCl_2$ treatment resulted in an increase of intracellular ROS generation, which is inhibited by NaHS or N-acetyl-cysteine (NAC, a ROS scavenger), and p38 MAPK phosphorylation, which is also blocked by NaHS or NAC. The $CoCl_2$-induced increase of the Bax/Bcl-2 ratio was attenuated by NaHS, NAC, and SB 203580 (p38 MAPK inhibitor). The $CoCl_2$-induced decrease of cell viability was also attenuated by NaHS, NAC, and SB 203580 pretreatment. Additionally, NaHS inhibited the $CoCl_2$-induced COX-2. Similar to the effect of NaHS, NAC blocked $CoCl_2$-induced COX-2 expression. Furthermore, NS-398 (a selective COX-2 inhibitor) attenuated not only the $CoCl_2$-induced increase of the Bax/Bcl-2 ratio, it also decreased cell viability. Taken together, $H_2S$ protects primary cultured mouse hepatocytes against $CoCl_2$-induced cell injury through inhibition of the ROS-activated p38 MAPK cascade and the COX-2 pathway.