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        검색결과 519

        221.
        2012.06 구독 인증기관·개인회원 무료
        Polycystic ovarian syndrome (PCOS) is a heterogeneous syndrome associated with follicle growth arrest, dysregulated sex hormone profile, hyperthecosis and insulin resistance. Chemerin, a novel adipokine, is associated with obesity and metabolic syndrome. Although obese women and in PCOS subjects have elevated plasma chemerin levels, whether and how chemerin is involved in the regulation of follicular growth/steroidogenesis and pathogenesis of PCOS is unknown. Our objective is to better understand the complex regulatory mechanisms involved in the control of these processes and gain insights in their dysregulation in the pathogenesis of PCOS. We hypothesize that: (a) hyperandrogenism induces small and medium antral follicle growth arrest and ovarian structural changes, resulting from granulosa cell and oocyte apoptosis and theca cell survival, and (b) chemerin regulates follicular growth and steroidogenesis and contributes to the pathogenesis of PCOS. Using immature rats (day 13~15 for follicle culture and day 21~24 for granulosa cells culture) and a chronically androgenized rat model [dihydrotestosterone (DHT); 83 μg daily, day 21~105] which recapitulates the reproductive and metabolic phenotypes of human PCOS, we have examined the granulosa cell expression patterns of chemerin and its receptor CMKLR1 and their steroidogenic and follicle growth capability. DHT treatment resulted in decreased follicle numbers in preantral to preovulatory stages and absence of corpus luteum, but increased numbers of condensed atypical follicles. Atypical follicles, constituted predominantly of theca cells, exhibited high expression of calpain and down‐regulation of the cytoskeletal protein substrates vimentin, fodrin and β‐tubulin. Granulosa cell aromatase expression was significantly down‐regulated, a response accompanied by increased activated caspase‐3 content and DNA fragmentation. While PTEN levels were considerably higher in granulosa cells in the PCOS rats than controls, phospho‐Akt (Ser473) content was lower. In addition, DHT also activated granulosa cell caspase‐3, decreased XIAP, PARP and phospho‐Akt contents and induced apoptosis in vitro, responses that could be attenuated by forced expression of XIAP. These findings are consistent with our hypothesis that dysregulated follicular growth in PCOS is associated with changes in follicular growth dynamics and follicle cell fate, a consequence of dysregulated interactions of pro‐survival (p‐Akt, XIAP, PARP) and proapoptotic (calpain, PTEN, caspase‐3) modulators in a cell‐specific manner. Chemerin and CMKLR1 were expressed in granulosa cells and negatively regulated by gonadotropin in vivo and in vitro. Serum and ovarian chemerin levels in DHT‐treated rats were elevated, and associated with arrested early antral follicular growth, remodeling of the follicle wall and decreased expression of p450 side‐chain cleavage enzyme (p450- scc), aromatase and hydroxysteroid dehydrogenases. Recombinant chemerin inhibited FSH ‐ induced estradiol secretion in granulosa cells from DHT‐treated rats in vitro. Chemerin also suppressed basal and FSH‐ and GDF9‐induced follicle growth and estradiol/ progesterone production in preantral follicle cultures. Moreover, chemerin suppressed FSH‐induced p450scc/aromatase expression and progesterone/estradiol secretion in immature rat granulosa cells in vitro. These studies demonstrate that chemerin is a novel negative regulator in FSH‐induced follicular growth and steroidogenesis and support the notion that the dysregulation of chemerin expression and function contributes to pathogenesis of PCOS. Our observations also suggest that this chronically androgenized rat model may be useful not only for studies on the long term effects of androgen on folliculogenesis, but also on the pathophysiology of PCOS. * This work was supported by grants from the Canadian Institutes of Health Research (CIHR; MOP‐119381) and the World Class University (WCU) program through the Ministry of Education, Science and Technology funded by the National Research Foundation of Korea (R31‐10056).
        222.
        2012.05 구독 인증기관·개인회원 무료
        In the process of revising the tachinid subgenus Linnaemya Robineau-Desvoidy of South Korea, three species are recognized as new to the country: Linnaemya pallidohirta Chao, L. scutellaris (Malloch) and L. lateralis (Townsend). They belong to the oralis species group of the subgenus. L. scutellaris (Malloch) and L. lateralis very closely resemble each other so that they need to be identified with caution. We here provide detailed redescriptions and illustrations with their diagnostic characters indicated.
        225.
        2011.12 구독 인증기관 무료, 개인회원 유료
        The objective of this study was to determine the effect of macrophages on growth of human colon cancer cells. The results showed that co-culture of colon cancer cells with macrophages inhibited the growth of colon cancer cells (HCT116 and SW620) depending on the number of macrophages, RAW 264.7 cells, and activated THP-1 cells accompanied by down regulation of pSTAT3 in cancer cells. We also found that expression and release of cancer cell growth inhibitory cytokines, IL-1 receptor antagonist (IL-1ra) and IL-10, was increased in macrophages. Blocking of the STAT3 pathway with specific inhibitor and siRNA of STAT3 abolished the growth of colon cancer cells and expression of IL-1ra and IL-10. In addition, neutralization of IL-1ra and IL-10 with antibodies resulted in reversal of macrophage-induced inhibition of cancer cell growth. These data showed that IL-1ra and IL-10 released from macrophages inhibit growth of colon cancer cells through inhibition of the STAT3 pathway.
        4,500원
        230.
        2011.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        To perform imaging observations of optically red objects such as high redshift quasars and brown dwarfs, the Center for the Exploration of the Origin of the Universe (CEOU) recently developed an optical CCD camera, Camera for QUasars in EArly uNiverse (CQUEAN), which is sensitive at 0.7-1.1 μm. To enable observations with long exposures, we develop an auto-guiding system for CQUEAN. This system consists of an off-axis mirror, a baffle, a CCD camera, a motor and a differential decelerator. To increase the number of available guiding stars, we design a rotating mechanism for the off-axis guiding camera. The guiding field can be scanned along the 10 arcmin ring offset from the optical axis of the telescope. Combined with the auto-guiding software of the McDonald Observatory, we confirm that a stable image can be obtained with an exposure time as long as 1200 seconds.
        4,000원
        231.
        2011.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present results of two-color VR photometry of the intermediate polar RXS J1803. The data were aquired using the Korean 1-m telescope located at Mt. Lemmon, USA. Different "high" and "low" luminosity states, similar to other intermediate polars, were discovered. No statistically significant variability of the color index with varying luminosity was detected. The orbital variability was found to be not statistically significant. Spin maxima timings were determined, as well as the photometric ephemeris for the time interval of our observations. The spin period variations, caused by interaction of the accretion structure with the rotating magnetic white dwarf, were also detected. These variations are of complicated character, and their study requires further observations. We determine the color transformation coefficients for our photometric systems, and improve on the secondary photometric standards.
        4,000원
        232.
        2011.06 구독 인증기관 무료, 개인회원 유료
        In all living organisms, respiration may lead to oxidative stress, a state where increased formation of reactive oxygen species overwhelms host protection and subsequently induces DNA damage, lipid peroxidation, and protein denaturation. As a phenolic acid, chlorogenic acid occurs ubiquitously in food. It has been proven to have a number of biological effects in vitro and in vivo, including antioxidant, anti-inflammatory, and anticarcinogenic properties. Therefore, to some extent, chlorogenic acid can promote human health, and hopefully provide new methods for treatment of chronic disease. Recent studies have focused on the antioxidant properties of dietary polyphenols. The in vitro data often conflict with results obtained from in vivo studies on the antioxidant capacity of plasma or the resistance of plasma and lipoproteins to oxidation ex vivo after consumption of polyphenol-rich foods by human subjects. These inconsistencies are likely explained by the limited bioavailability of dietary polyphenols and their extensive metabolism in humans. Polyphenols exert multifaceted actions, and any clinical application using these substances should be based on a precise understanding of the physiologically relevant mechanisms.
        4,000원
        233.
        2011.06 구독 인증기관 무료, 개인회원 유료
        The dissemination process of agricultural research and development (R&D) results has somewhat different characteristics from that of typical R&D results. However, these characteristics are not adequately considered on the basis of an examination of the current performance system, the resulting management plans, and strategies for the application and dissemination of the results of agricultural R&D in Korea. The performance evaluation indicator exposed the problem of the inadequate consideration of the characteristics of each of these areas, particularly the lack of unified R&D-related institutions and the inadequacy of the system to monitor outcomes. To address these shortcomings in the agricultural R&D programs in Korea, the policies pertaining to agricultural R&D performance, results management, and dissemination in the U.S. and Japan were examined. Based on these investigations, we proposed strategies to improve the agricultural R&D policies in Korea.
        6,900원
        234.
        2011.06 구독 인증기관 무료, 개인회원 유료
        This study describes the development of a web-based system that collects all data generated in the research conducted to set pre-harvest residue limits (PHRLs) for agricultural product safety control. These data, including concentrations of pesticide residues, limit of detection, limit of quantitation, recoveries, weather charts, and growth rates, are incorporated into a database, a regression analysis of the data is performed using statistical techniques, and the PHRL for an agricultural product is automatically computed. The development and establishment of this system increased the efficiency and improved the reliability of the research in this area by standardizing the data and maintaining its accuracy without temporal or spatial limitations. The system permits automatic computation of the PHRL and a quick review of the goodness of fit of the regression model. By building and analyzing a database, it also allows data accumulated over the last 10 years to be utilized.
        6,600원
        237.
        2011.05 구독 인증기관·개인회원 무료
        In the process of revising the tachinid genus Linnaemya Robineau-Desvoidy in Korea, we have discovered two species for the first time in Korea. They closely resemble each other and need to be identified with caution. We here provide detailed redescriptions and illustrations with their diagnostic characters indicated. L. atriventris can be distinguished from L. hirtipennis by the combination of the following characteristics: 1) abdomen black in ground color; 2) wing vein R1 without setulose; 3) hypandrium without secondary posterior lobe; 4) male with antero-basal 1/3 of flagellomere I distinctly swollen; and 5) postgonite very weakly curved dorsally.
        239.
        2011.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study experimentally investigated dicyclohexylammonium 2-cyanoacrylate (CA) as a potential comonomer for polyacrylonitrile (PAN) based carbon fiber precursors. The P(AN-CA) copolymers with different CA contents (0.19-0.78 mol% in the feed) were polymerized using solution polymerization with 2,2-azobis(isobutyronitrile) as an initiator. The chemical structure and composition of P(AN-CA) copolymers were determined by proton nuclear magnetic resonance and elemental analysis, and the copolymer composition was similar to the feeding ratio of the monomers. The effects of CA comonomer on the thermal properties of its copolymers were characterized differential scanning calorimetry (DSC) in nitrogen and air atmospheres. The DSC curves of P(AN-CA) under nitrogen atmosphere indicated that the initiation temperature for cyclization of nitrile groups was reduced to around 235℃. The heat release and the activation energy for cyclization reactions were decreased in comparison with those of PAN homopolymers. On the other hand, under air atmosphere, the P(AN-CA) with 0.78 mol% CA content showed that the initiation temperature of cyclization was significantly lowered to 160.1℃. The activation energy value showed 116 kJ/mol, that was smaller than that of the copolymers with 0.82 mol% of itaconic acids. The thermal stability of P(AN-CA), evidenced by thermogravimetric analyses in air atmosphere, was found higher than PAN homopolymer and similar to P(AN-IA) copolymers. Therefore, this study successfully demonstrated the great potential of P(AN-CA) copolymers as carbon fiber precursors, taking advantages of the temperature-lowering effects of CA comonomers and higher thermal stability of the CA copolymers for the stabilizing processes.
        4,000원
        240.
        2011.03 구독 인증기관 무료, 개인회원 유료
        Sepsis is a clinical syndrome defined as a systemic inflammatory response to infection. Eritoran is a synthetic lipid A derivative that competes with lipopolysaccharide in binding to the identical site of myeloid differentiation-2/toll-like receptor 4 complex. Eritoran is effective in decreasing the septic mortality of Gram-negative bacteria-infected animals. Eritoran has been highlighted as a candidate drug for treatment of endotoxemia in phase I clinical studies with healthy human volunteers. A phase II trial of eritoran has been conducted in patients with severe sepsis. Intravenous infusion of eritoran reduced the mortality rate, as compared with the placebo group, in sepsis patients at a high risk of mortality according to acute physiology and chronic health evaluation-II scores. A phase III study of eritoran was completed in 2011. The results appear to be disappointing as no statistically significant difference in all-cause mortality was observed between the eritoran treatment group and the placebo group on day 28 in sepsis patients with a high risk of death. In this review, we focus on the rationale for the use of eritoran in treatment of sepsis as well as its clinical applications.
        4,000원