• Toxicological Research
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• v.27 no.2
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• pp.61-70
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• 2011

Brominated flame retardants (BFRs) are present in many consumer products ranging from fabrics to plastics and electronics. Wide use of flame retardants can pose an environmental hazard, which makes it important to determine the mechanism of their toxicity. In the present study, dose-dependent toxicity of tetrabromobisphenol A (TBBPA), a flame retardant, was examined in male prepubertal rats (postnatal day 18) treated orally with TBBPA at 0, 125, 250 or 500 mg/kg for 30 days. There were no differences in body weight gain between the control and TBBPA-treated groups. However, absolute and relative liver weights were significantly increased in high dose of TBBPA-treated groups. TBBPA treatment led to significant induction of CYP2B1 and constitutive androstane receptor (CAR) expression in the liver. In addition, serum thyroxin (T4) concentration was significantly reduced in the TBBPA treated group. These results indicate that repeated exposure to TBBPA induces drug-metabolising enzymes in rats through the CAR signaling pathway. In particular, TBBPA efficiently produced reactive oxygen species (ROS) through CYP2B1 induction in rats. We measured 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of DNA oxidative damage, in the kidney, liver and testes of rats following TBBPA treatment. As expected, TBBPA strongly induced the production of 8-OHdG in the testis and kidney. These observations suggest that TBBPA-induced target organ toxicity may be due to ROS produced by metabolism of TBBPA in Sprague-Dawley rats.

• Journal of Applied Biological Chemistry
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• v.60 no.4
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• pp.357-362
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• 2017

The purpose of this study was to investigate the antiaging effect in the fibroblasts by using the extracts and fractions of Nymphoides peltata for the development of new functional cosmetic materials. The anti-aging effects of the extracts and fractions of N. peltata were measured using CCD-986sk cells. Ethyl aceate (EA) fraction inhibited UVB-induced reactive oxygen species expression by more than 50%, and n-butyl alcohol (BuOH) fraction increased expression of pro-collagen mRNA by more than 50% at $25{\mu}g/mL$. In addition, EA and BuOH fractions inhibited MMP-1 protein and mRNA expression in a concentration-dependent manner, BuOH fraction inhibited MMP-1 mRNA expression by more than 40% at $10{\mu}g/mL$. Especially, the high efficacy of EA and BuOH of the N. peltata was confirmed. Therefore, the EA and BuOH of N. peltata are expected to be useful as anti-aging materials in cosmetics field.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.656-669
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• 1998

Hydrogen peroxide at high concentration during walking bleaching may cause damage to the tooth structure and to the surrounding periodontal tissues and may develop external root resorption. Clinically, It is so important to find a method of prevention or minimization of these complications. The efficacy of various chamber-irrigating agents to eliminate residual hydrogen peroxide after walking bleaching was examined and compared with water rinse in this study. Extracted human 46 premolars without any cementoenamel junction defects were treated endodontically and based with IRM to 1 mm below CEJ and totally bleached 3 times for each tooth with 30% hydrogen peroxide and sodium perborate. Upon completion of the 3rd walking bleaching procedure, the cervical portion and pulp chamber of each group of teeth were irrigated with catalase, 70% ethylalcohol, acetone, and distilled water. And then, a radicular hydrogen peroxide penetration was measured with spectrophotometer immediately after each bleaching and following treatment with each chamber-irrigating agents, and the significance of their eliminating efficacy of residual hydrogen peroxide was analyzed by Kruskal-Wallis test. The results were obtained as follows. 1. Cervical root penetration of hydrogen peroxide was increased as the bleaching procedure was repeated(P<.01). 2. The most effective irrigant that removed residual hydrogen peroxide was the catalase, and the least effective one was water rinsing (P<.01).; there was no significant difference between the acetone and ethanol group. 3. The Irrigation with antioxidant enzyme or water-displacement solutions can eliminate residual oxygen radicals from the pulp chamber effectively after walking bleaching. So, these agents can reduce adverse effects such as cervical external resorption and periapical inflammation and prevent residual $O_2$ from impeding composite resin polymerization, thus increase the bonding strength of composite resin. This, in turn reduces microleakage and discoloration of the esthetic restoration, extending its service-life.

• Korean Journal of Microbiology
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• v.46 no.2
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• pp.169-176
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• 2010

A pilot-scale wastewater treatment plant combined with rotating biological contactor and tapered aeration reactors was operated with the wastewater discharged from a food factory for 5 months. The bacterial communities of this plant were investigated by terminal restriction fragment length polymorphism (T-RFLP) and phylogenetic analysis of 16S rRNA genes. In spite of high concentration of nitrogen and phosphorus as well as organic carbon, removal efficiency of chemical oxygen demand, total nitrogen, and total phosphorus was 98%, 93%, and 95%, respectively. Bacterial community at the initial operation stage was clearly distinguished from that of the stable operation stage. The most predominant phylum in the sample of stable stage was Bacteroidetes. Major population of operation period was Haliscomenobacter, Sphaerotilus, and candidate division TM7, which were classified as filamentous bacteria. However, sludge bulking caused by these bacteria was not observed. The population that has a close relationship with Haliscomenobacter increased during the stable operation stage, emerging as the most predominant group. These results suggest that the filamentous bacteria participated in nutrient removal when using rotating biological contactor and tapered aeration reactor.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.8
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• pp.1151-1156
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• 2005

The comparison on antioxidative activity of 13 kinds of vegetables that showed efficient oxygen radical absorbance capacity was carried out under in uitro and cellular model using LLC-$ PK_{1}$ renal epithelial cell, and also the total Phenol contents were analyzed. Beets, eggplant, and kale exerted the strong 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect and also these vegetables showed high contents of total phenol, indicating the positive relationship between DPPH radical scavenging effect and total phenol content. In addition, the treatment of 1 mM 2,2'-azobis (2-amidinopropane) dihydrochloride for 24 hrs to LLC-$PK_{1}$ cell susceptible to oxidative stress led to the decline of cell viability to 68.1$\%$, whereas the cellular oxidative damage was ameliorated by vegetables, especially eggplant and cauliflower, resulting in the elevation of cell viability to higher than 90$\%$ at the concentration of 5 $\mu$g/mL. This study suggests that 13 kinds of vegetables exert antioxidative activity under in uitro and cellular oxidative damage model, in particular among them eggplant showed the most effective antioxidative activity with higher total phenol content.

• Korean Journal of Plant Resources
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• v.24 no.4
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• pp.456-460
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• 2011

The objective of this study was to investigate the antioxidative capacity of Rhododendron brachycarpum 95% ethanol extracts. Total antioxidant status was examined by total antioxidant capacity against ABTS radical reactions. Total antioxidant capacities of R. brachycarpum extract at the concentrations of 0.2 and 1 mg/mL were 0.33 and 2.26 mM Trolox equivalents, respectively. Superoxide scavenging activities of R. brachycarpum extract at the concentrations of 0.2 and 1 mg/mL were 45.0 and 77.0%, respectively. Oxygen radical absorbance capacities of R. brachycarpum extract at the concentrations of 5 and 100 ${\mu}g/mL$ were 40.88 and 131.00 ${\mu}M$ Trolox equivalents, respectively. Total phenolic contents of R. brachycarpum extract at the concentrations of 0.2 and 1 mg/mL were 0.37 and 1.25 mM gallic acid equivalents, respectively. R. brachycarpum extract at the concentration of 0.1 mg/mL inhibited 0.2 mM and 0.5 mM tert-butyl hydroperoxide induced cyototoxicity by 52.1 and 30.3%, respectively, in HepG2 cell culture system. Thus, strong antioxidant and cytotoxicity-inhibiting effects of R. brachycarpum extract seem to be due to, at least in part, the prevention from free radicals-induced oxidation as well as high levels in total phenolic contents.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.105-112
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• 2018

To compare the denitrification efficiency, this study used molasses and methanol were used as external carbon sources. Specific experimental conditions were classified according to C/N ratio conditions. The batch test showed that the denitrification efficiency increased as C/N ratios of molasses and methanol rose. The most suitable C/N ratio of molasses turned out 4:1 considering the concentration of the residue chemical oxygen demand (COD) and the denitrification efficiency, which was 91.4%. Specific denitrification rate (SDNR) drawn as a kinetic factor demonstrated that molasses and methanol showed similar SDNR values as C/N ratios of molasses and methanol increased. Under the condition of C/N ratio 4:1, 0.0292 g $NO_3{^-}-N$ removal/g mixed liquor volatile suspended solid (MLVSS)/day (molasses), 0.0299 g $NO_3{^-}-N$ removal/g MLVSS/day (methanol) were found. Sludge adapted to molasses showed that Bacterium Pseudomonas sp. and Bergeylla sp. dominated through an analysis of microbial community. In addition, some bacteria were high convergences than the variety of microbial community. Accordingly, it was assumed that molasses focus on growing microorganisms specialized in denitrification and applied as a replaceable external carbon source that can enhance denitrification performance.

• Journal of Sensor Science and Technology
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• v.7 no.4
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• pp.254-262
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• 1998

Multilayer Langmuir-Blodgett (LB) films coated on quartz crystal microbalance (QCM) of octa-substituted metallophhtalocyanines ($MPc(OEH)_8$, M = Cu, Co, and Sn) and dihydrogen phthalocyanines ($H_2Pc(OEH)_8$) were used to quantify $NO_2$ concentrations. They were exposed to various concentrations of $NO_2$ in dry $N_2$. Among the four phthalocyanines we tested, the metal-free $H_2Pc(OEH)_8$ was observed to be most sensitive to $NO_2$. However, its LB film showed a partially irreversible behavior, that is part of the frequency change due to $NO_2$ adsorption could not be recovered even after purging with pure $N_2$ gas for an extended period. Examining the spectra of NMR and FTIR revealed fact that the irreversible portion of frequency change was due to ether groups in the linkage between side chains and the Pc unit. In order to remove the effect of such initial deactivation, on $NO_2$ quantification experiment, a freshly fabricated LB film was treated at a high concentration of $NO_2$ so that the ether sites were saturated. A pretreated LB film showed a reproducible performance for repeated uses. The $CuPc(OEH)_8$ LB film showed a satisfactory sensing performance down to as low as 4 ppm. For the $H_2Pc(OEH)_8$ LB film, the lower detection limit was found to be 35ppb of $NO_2$. In order to make the experimental condition more realistic, the carrier gas, dry nitrogen, was replaced by air. It was observed that the presence of oxygen, a weak electron acceptor, reduced the sensitivity and thus increased the sensing limit to hundreds of ppb. Results of experiments with moisture added showed that the interference of moisture was quite severe.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.564-570
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• 2007

This study investigated the treatment of liquid waste containing highly concentrated iron(III)-ethylenediaminetetraaceticacid (Fe(III)-EDTA) of 70,000 mg/L by an underwater electrical discharge process using low voltage and high current. When AC voltage is applied to the discharging electrode with the other electrode grounded, the temperature of the liquid waste around the discharging electrode rapidly increases, and at the same time, hydrogen and oxygen gases are formed at the electrode as a result of electrochemical reactions. Ultimately, gases formed by vaporization of water and electrochemical reactions cover the electrode. Since the liquid waste is electrically conductive, it elongates the ground electrode up to the border of the gas layer, where electrical discharge occurs. Without hydrogen peroxide, electrical discharge was able to remove about 50% of Fe(III)-EDTA. As the concentration of hydrogen peroxide added increased, the removal efficiency of Fe(III)-EDTA increased. When the molar ratio of hydrogen peroxide to the initial Fe(III)-EDTA was higher than 24.7, more than 80 g of Fe(III)-EDTA was removed with an energy of 1 kWh. A comparison between tungsten and steel electrodes showed that electrode material did not affect the Fe(III)-EDTA removal. In the present underwater electrical discharge process, the removal of Fe(III)-EDTA was completed within 30 min at molar ratios of hydrogen peroxide to the initial Fe(III)-EDTA higher than 24.7.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.3
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• pp.311-319
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• 2018

Mitochondrial calcium overload is a crucial event in determining the fate of neuronal cell survival and death, implicated in pathogenesis of neurodegenerative diseases. One of the driving forces of calcium influx into mitochondria is mitochondria membrane potential (${\Delta}{\psi}_m$). Therefore, pharmacological manipulation of ${\Delta}{\psi}_m$ can be a promising strategy to prevent neuronal cell death against brain insults. Based on these issues, we investigated here whether nobiletin, a Citrus polymethoxylated flavone, prevents neurotoxic neuronal calcium overload and cell death via regulating basal ${\Delta}{\psi}_m$ against neuronal insult in primary cortical neurons and pure brain mitochondria isolated from rat cortices. Results demonstrated that nobiletin treatment significantly increased cell viability against glutamate toxicity ($100{\mu}M$, 20 min) in primary cortical neurons. Real-time imaging-based fluorometry data reveal that nobiletin evokes partial mitochondrial depolarization in these neurons. Nobiletin markedly attenuated mitochondrial calcium overload and reactive oxygen species (ROS) generation in glutamate ($100{\mu}M$)-stimulated cortical neurons and isolated pure mitochondria exposed to high concentration of $Ca^{2+}$ ($5{\mu}M$). Nobiletin-induced partial mitochondrial depolarization in intact neurons was confirmed in isolated brain mitochondria using a fluorescence microplate reader. Nobiletin effects on basal ${\Delta}{\psi}_m$ were completely abolished in $K^+-free$ medium on pure isolated mitochondria. Taken together, results demonstrate that $K^+$ influx into mitochondria is critically involved in partial mitochondrial depolarization-related neuroprotective effect of nobiletin. Nobiletin-induced mitochondrial $K^+$ influx is probably mediated, at least in part, by activation of mitochondrial $K^+$ channels. However, further detailed studies should be conducted to determine exact molecular targets of nobiletin in mitochondria.