• Korean Journal of Materials Research
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• v.12 no.1
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• pp.48-53
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• 2002

$Al_2O_3-SiC$ and $Al_2O_3-SiC$-TiC composite powders were prepared by SHS process using $SiO_2,\;TiO_2$, Al and C as raw materials. Aluminum powder was used as reducing agent of $SiO_2,\;TiO_2$ and activated charcoal was used as carbon source. In the preparations of $Al_2O_3-SiC$, the effect of the molar ratio in raw materials, compaction pressure, preheating temperature and atmosphere were investigated. The most important variable affecting the synthesis of $Al_2O_3-SiC$ was the molar ratio of carbon. Unreactants remained in the product among all conditions without compaction. The optimum condition in this reaction was $SiO_2$: Al: C=3: 5: 5.5, 80MPa compaction pressure under Preheating of $400^{\circ}C$ with Ar atmosphere. However there remains cabon in the optimum condition. The effect of $TiO_2$ as additive was investigated in the preparations of $Al_2O_3-SiC$. As a result of $TiO_2$ addition, $Al_2O_3-SiC$-TiC composite powder was prepared. The $Al_2O_3$ powder showed an angular type with 8 to $15{\mu}m$, and the particle size of SiC powder were 5~$10{\mu}m$ and TiC powder were 2 to $5{\mu}m$.

• Journal of Microbiology and Biotechnology
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• v.29 no.10
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• pp.1656-1664
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• 2019

Isoprene has the potential to replace some petroleum-based chemicals and can be produced through biological systems using renewable carbon sources. Ralstonia eutropha can produce value-added compounds, including intracellular polyhydroxyalkanoate (PHA) through fatty acid and lipid metabolism. In the present study, we engineered strains of R. eutropha H16 and examined the strains for isoprene production. We optimized codons of all the genes involved in isoprene synthesis by the mevalonate pathway and manipulated the promoter regions using pLac and pJ5 elements. Our results showed that isoprene productivity was higher using the J5 promoter ($1.9{\pm}0.24{\mu}g/l$) than when using the lac promoter ($1.5{\pm}0.2{\mu}g/l$). Additionally, the use of three J5 promoters was more efficient ($3.8{\pm}0.18{\mu}g/l$) for isoprene production than a one-promoter system, and could be scaled up to a 5-L batch-cultivation from a T-flask culture. Although the isoprene yield obtained in our study was insufficient to meet industrial demands, our study, for the first time, shows that R. eutropha can be modified for efficient isoprene production and lays the foundation for further optimization of the fermentation process.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.495-500
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• 2011

Separation of naphthalene from pyrolyzed fuel oil, by product of Naphta cracking process (NCC) process, has been accomplished by the solvent extraction, distillation and purification process. The residual pyrolyzed fuel oil (PFO), called precursor of carbon materials, has been calcined at $300{\sim}800^{\circ}C$ in nitrogen gas to raw pitch. After the treatment of PFO by hexane and methanol, either a flake phased carbon at $350^{\circ}C$ or a carbon sphere at above $400^{\circ}C$ forms. As the calcination temperature increases, the shape of raw pitch changes from the flake phase to the sphere one, and the size of them decreases to several ${\mu}m$. Based on the BET and XRD spectrum, the carbon sphere is classified to a mesophase amorphous carbon with a cubic phase.

• Food Science and Preservation
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• v.19 no.3
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• pp.393-399
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• 2012

In this study, the antioxidant and anti-wrinkling effects of extracts from Aruncus diocius var. kamtschaticus (ADV) were investigated. According to the results, the ethanol extract has better antioxidant and anti-wrinkling effects than the water extract. The amounts of total polyphenol and flavonoid compounds in the ethanol extract were 122 and 36 mg/g, respectively, while those in the water extract were 87 and 26 mg/g. The antioxidant activities of the ethanol and water extracts were 395 and 4,682 ${\mu}g/mL$ as the $RC_{50}$ values for the DPPH radical scavenging activity, and 227 and 366 ${\mu}g/mL$ for the $ABTS^+$ radical scavenging activity, respectively. The reducing power of the ethanol extract (1.58 at 2 mg/mL) was higher than that of the water extract (0.88 at 2 mg/mL). The astringent activities of the ethanol and water extracts were 91.27 and 16.35% at 10 mg/mL, respectively. Furthermore, the ADV ethanol extract treatment of the fibroblast cell after UV irradiation resulted in increased cell viability (10% at 100 ${\mu}g/mL$) and collagen biosynthesis (33% at 100 ${\mu}g/mL$), with a lowering in the MMP-1 expression level (16.8 % at 100 ${\mu}g/mL$). These results demonstrate that AVD provides a remarkable and significant tensor and anti-wrinkling effect on the skin, which could be of a great use in anti-aging skin care products.

• Tuberculosis and Respiratory Diseases
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• v.47 no.2
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• pp.172-183
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• 1999

Background: Nitric oxide is a short-lived effector molecule derived from L-arginine by the nitric oxide synthase(NOS). Nitric oxide plays a role in a number of physiologic and pathophysiologic functions including host defense, edema formation, and regulation of smooth muscle tone. Some kinds of cells including macrophage are known to produce large quantities of nitric oxide in response to inflammatory stimuli such as interleukin-$1\beta$(IL-$1\beta$), tumor necrosis factor-$\alpha$(TNF-$\alpha$), interferon-$\gamma$(IFN-$\gamma$) and lipopolysaccharide(LPS). Reactive oxygen species are also known to be important in the pathogenesis of acute cell and tissue injury such as acute lung injury model Methods: Using the RA W264.7 cells, we have examined the ability of oxidant hydrogen peroxide($H_2O_2$) to stimulate nitric oxide production and inducible NOS mRNA expression. Also, we have examined the effects of NOS inhibitors and antioxidants on $H_2O_2$ induced nitric oxide production. Results: Stimulation of RAW264.7 cells with combinations of 100 ng/ml IL-$1\beta$, 100 ng/ml TNF-$\alpha$, and 100 U/ml IFN-$\gamma$ or 100 U/ml IFN-$\gamma$ and $1{\mu}g/ml$ LPS induced the synthesis of nitric oxide as measured by the oxidation products nitrite($NO_2^-$) and nitrate($NO_3^-$). Addition of $250 {\mu}M-2$ mM $H_2O_2$ to the cytokines significantly augmented the synthesis of $NO_2^-$ and $NO_3^-$(p<0.05). When cells were incubated with increasing concentrations of $H_2O_2$ in the presence of IL-$1\beta$, TNF-$\alpha$ and IFN-$\gamma$ at constant level, the synthesis of $NO_2^-$ and $NO_3^-$ was dose-dependently increased(p<0.05). $N^G$-nitro-L-arginine methyl ester(L-NAME), dose dependently, significantly inhibited the formation of $NO_2^-$ and $NO_3^-$ in cells stimulated with LPS, IFN-$\gamma$ and $H_2O_2$ at constant level(p<0.05). Catalase significantly inhibited the $H_2O_2$-induced augmentation of cytokine-induced $NO_2^-$ and $NO_3^-$ formation(p<0.05). But, boiled catalase did not produce a significant inhibition in comparison with the native enzyme. Another antioxidant 2-mercaptoethanol and orthophenanthroline dose-dependently suppressed $NO_2^-$ and $NO_3^-$ synthesis(p<0.05). Northern blotting demonstrated that H:02 synergistically stimulated the cytokine-induced iNOS mRNA expression in RA W264.7. Conclusion: These results suggest that $H_2O_2$ contributes to inflammatory process by augmenting the iNOS expression and nitric oxide synthesis induced by cytokines.

• The Korean Journal of Nuclear Medicine
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• v.35 no.5
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• pp.334-341
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• 2001

Purpose: Ascorbic acid us known to act as an antioxidant. Therefore, it can be used in increasing the efficiency of radiochemical labeling of Technetium-99m setamibi by inhibition of oxidation of $Sn^{2+}$ at low concentration. We intended to estimate the efficiency of radiochemical labeling and the stability of the newly formed formulation when ascorbic acid was added to a commercial kit. Materials and Methods: Synthesis of sestamibi was performed according to Dong-A's patent procedure (No.10-2001-0012877). First, we undertook a study to evaluate the efficiency of radiochemical labeling of sestamibi containing ascorbic acid. The stability of the vials was assessed using either $7.5{\mu}g\;or\;75{\mu}g$ of ascorbic acid, added to commercial vials under the accelerated condition(Temp : $40^{\circ}C{\pm}2^{\circ}C$, Relative humidity : $75{\pm}5%$). Results: Sestamibi was synthesized in overall 35-40% yield over 5 steps from a commercially available methallyl chloride as a starling material. When ascorbic acid was added, the efficiency of radiochemical labeling was maintained compared to the vial with no ascorbic acid. The accelerated test showed that the addition of ascorbic acid inhibited the oxidation of $Sn^{2+}$ ion by antioxidation mechanism. Also, the efficiency of radiochemical labeling of this vial after 9 months was nearly the same as the starting point. Therefore, the storage period of the kit is likely to be extended. Taken together, it suggests that the addition of ascorbic acid as a stabilizer is desirable. Conclusion: To increase the stability of a sestamibi cold kit, it is desirable to add ascorbic acid as a stabilizer to the commercial formulation.

• The Korean Journal of Food And Nutrition
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• v.29 no.3
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• pp.301-306
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• 2016

Vitamin K (phylloquinone) is an essential cofactor in the synthesis of active blood-clotting factors II, VII, IX and X. Deficiency of vitamin K leads to inadequate activity of these factors, resulting in bleeding. In this study, we investigated vitamin $K_1$ content of agricultural products that are widely and specifically grown in Korea including 9 leaves and vegetables, 16 fruits, and 11 cereals and specialty crops. Vitamin $K_1$ analysis of the agro-samples was by a validated, modified, reversed phase-HPLC method with fluorescence detection after post-column derivatization. The vitamin $K_1$ content ranged from 1.83 to $682.73{\mu}g$/100 g in leaves and vegetables, 0.17 to $28.22{\mu}g$/100 g in fruits, and ND to $279{\mu}g$/100 g in cereals and specialty crops. Among the 36 samples, high content of vitamin $K_1$ were found in Gugija (Lycium chinense Miller) leaves (average $682.73{\mu}g$/100 g) and Hansan ramie leaves (average $423.12{\mu}g$/100 g); however, mushroom, amaranth and Chinese artichoke showed no detectable levels. The results of ourstudy provide reliable vitamin $K_1$ content of Korean grown agricultural products that expand nutritional information and food composition database.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.3
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• pp.219-226
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• 2000

In order to elucidate the role of platelet activating factor (PAF) in the acute lung injury induced by endotoxin (ETX), activities of phospholipase A2, lyso PAF acetyltransferase and oxidative stress by neutrophilic respiratory burst were probed in the present study. To induce acute lung injury, $100\;{\mu}g$ of E.coli ETX (type 0127; B8) was instilled directly into the tracheae of Sprague-Dawley rats. Five hours after the ETX instillation, induction of acute lung injury was confirmed by lung leak index and protein contents in the bronchoalveolar lavage (BAL) fluid. At the same time, lung phospholipase A2 (PLA2) activity and expression of group I and II secretory type PLA2 were examined. In these acutely injured rats, ketotifen fumarate, known as lyso PAF acetyltransferase inhibitor and mepacrine were administered to examine the role of PAF in the pathogenesis of the acute lung injury. To know the effect of the ETX in the synthesis of the PAF in the lungs, lyso PAF acetyltransferase activity and PAF content in the lungs were measured after treatments of ETX, ketotifen fumarate and mepacrine. In addition, the role of neutrophils causing the oxidative stress after ETX was examined by measuring lung myeloperoxidase (MPO) and enumerating neutrophils in the BAL fluid. To confirm the oxidative stress in the lungs, pulmonary contents of malondialdehyde (MDA) were measured. After instillation of the ETX in the lungs, lung leak index increased dramatically (p＜0.001), whereas mepacrine and ketotifen decreased the lung leak index significantly (p＜0.001). Lung PLA2 activity also increased (p＜0.001) after ETX treatment compared with control, which was reversed by mepacrine and ketotifen (p＜0.001). In the examination of expression of group I and II secretory PLA2, mRNA synthesis of the group II PLA2 was enhanced by ETX treatment, whereas ketotifen and WEB 2086, the PAF receptor antagonist, decreased the expression. The activity of the lysoPAF acetyltransferase increased (p＜0.001) after treatment of ETX, which implies the increased synthesis of PAF by the remodelling of lysoPAF in the lungs. Consequently, the contents of the PAF in the lungs were increased by ETX compared with control (p＜0.001), while mepacrine (p＜0.001) and ketotifen (p＜0.01) decreased the synthesis of the PAF in the lungs of ETX treated rats. The infiltration of the neutrophils was confirmed by measuring and enumerating lung MPO and the neutrophils in the BAL fluid respectively. Compared with control, ETX increased lung MPO and number of neutrophils in BAL significantly (p＜0.001) whereas mepacrine and ketotifen decrerased number of neutrophils (p＜0.001) and MPO (p＜0.05, p＜0.001, respectively). The lung MDA contents were also increased (p＜0.001) by ETX treatment, but treatment with mepacrine (p＜0.001) and ketotifen (p＜0.01) decreased the lung MDA contents. Collectively, we conclude that ETX increases PLA2 activity, and that the subsequently increased production of PAF was ensued by the remodelling of the lyso PAF resulting in tissue injury by means of oxidative stress in the lungs.

• Journal of Periodontal and Implant Science
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• v.26 no.2
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• pp.491-510
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• 1996

This study was performed to evaluate the effects of platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) on the characteristics of beagle dog's periodontal ligament (BPD) cells and bone marrow (BBM) cells which have the important role on the early stage of periodontal tissue regeneration in vitro. In control group, the cells ($1.5{\times}10^5$cells/ml) were cultured alone with Dulbecco's Modified Eagle's Medium contained with 10% fetal bovine serum, $50{\mu]g/ml$ ascorbic acid, and 10mM/ml ${\beta}-glycerophosphate$. In experimental groups, growth factors, PDGF or EGF(10ng/ml), were added into the above culture condition. And then each group was characterized by examining the cell proliferation rate, amount of total protein synthesis, alkaline phosphatase activity at 1, 5, 9, 13, 17th day after seeding of cells into the culture wells. The results were as follows: 1. Both BPD and BBM cells in PDGF-treated group proliferated more rapidly than non-treated cells. This finding also was observed in EGF-treated group but it was not as prominent as that of PDGF-treated group. The proliferation rates of both cells showed the time-dependent pattern during experimental periods in all three groups. 2. Amount of total protein synthesis was more increased in PDGF-treated group than in control group. But no significant difference between EGF-treated group and control group was observed throughout experimental periods even though the tendency of amount of protein synthesis was time-dependent pattern. 3. Alkaline phosphatase activity also more increased in PDGF-treated group than control group. But slight decrease tendency was seen in both cells of EGF-treated group. From the above results, PDGF appeared to enhance the proliferation and cellular activities including amount of total protein synthesis and alkaline phosphatase activity of BPD and BBM cell, but EGF did not show notable effects. The optimal application of these growth factors was thought to be useful as the adjunctive means in periodontal regeneration procedures.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.4 s.54
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• pp.349-357
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• 2005

New antioxidative substances for cosmeceuticals were screened from natural resources such as microbial metabolites, mushrooms, and medicinal plants. Four antioxidants were isolated from the fungal metabolite of Eupenicillium shearii and their structures were determined to be new phenolic compounds. The compounds were designated as melanocins A, B, C, and D. Melanocins $A{\sim}D$ exhibited free radical scavenging activity on DPPH and superoxide with $EC_{50}$ values of $21{\sim}94\;and\;7{\sim}84{\mu}M$, respectively, which were stronger activity than those of ${\alpha}-tocopherol$ and BHA. Melanocin A showed anti-wrinkle effects on the UV-irrated hairless mouse skin. A novel hispidin antioxidative compound designated as inoscavin A was isolated from the fruiting body of the mushroom, Inonotus xeranticus. Inoscavin A scavenged superoxide radical with $EC_{50}$ values of $0.03{\mu}g/mL$, and inhibited rat liver microsomal lipid peroxidation with $EC_{50}$ values of $0.3{\mu}g/mL$. Benzastatins $A{\sim}G$, the novel antioxidants isolated from the culture of Streptomyces nitrosporeus showed potent lipid peroxidation inhibitory activity with $EC_{50}$ values of $3{\sim}30{\mu}M$. A cyclopentene compound with strong hypopigmentary effect was isolated from the fungal metabolite of Penicillium sp. and identifed as terrein. Terrein significantly reduced melanin levels in a melanomacyte cell line, Mel-Ab. It showed 10 times stronger activity than kojic acid, but exhibited no cytotoxic effect even in $100{\mu}M$. It was suggested that terrein reduced melanin synthesis by reducing tyrosinase production by MITF down-regulation.