• Title, Summary, Keyword: AH Tau

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PERIOD CHANCE OF THE CONTACT BINARY AH Tauri (접촉쌍성 AH Tauri의 공전주기 변화)

  • Lee, Dong-Joo;Lee, Chung-Uk;Lee, Jae-Woo;Kim, Seung-Lee;Oh, Kyu-Dong;Kim, Chun-Hwey
    • Journal of Astronomy and Space Sciences
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    • v.21 no.4
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    • pp.283-294
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    • 2004
  • New BV RI photometric observations of the contact binary AH Tau were performed with the 61 cm reflector and a 2K CCD camera at the Sobaeksan Optical Astronomy Observatory during seven nights from September to December, 2001. A total of 144 times of minima observed up to date, including three times of minima obtained from our observation, were analyzed. It is found that the orbital period of AH Tau has varied in a cyclic way superposed on a secular period decrease. The rate of the secular period decrease is calculated to be $1^s$ .04 per century, implying that a mass of about $3.8{\times}10^{-8}M{\odot}/yr$ from the more massive primary flows into the secondary if a conservative mass transfer is assumed. Assuming that the sinusoidal period variation is produced by a light-time effect due to an unseen third body, the resultant semi-amplitude, period, and eccentricity for the deduced light-time orbit are obtained as 35.4 years, 0.014 day and 0.52, respectively. The mass of the third-body is calculated as a tout $0.24M{\odot}$ when the third body is assumed to be coplanar with AH Tau system.

NOTES ON CRITICAL ALMOST HERMITIAN STRUCTURES

  • Lee, Jung-Chan;Park, Jeong-Hyeong;Sekigawa, Kouei
    • Bulletin of the Korean Mathematical Society
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    • v.47 no.1
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    • pp.167-178
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    • 2010
  • We discuss the critical points of the functional $F_{\lambda,\mu}(J,g)=\int_M(\lambda\tau+\mu\tau^*)d\upsilon_g$ on the spaces of all almost Hermitian structures AH(M) with $(\lambda,\mu){\in}R^2-(0,0)$, where $\tau$ and $\tau^*$ being the scalar curvature and the *-scalar curvature of (J, g), respectively. We shall give several characterizations of Kahler structure for some special classes of almost Hermitian manifolds, in terms of the critical points of the functionals $F_{\lambda,\mu}(J,g)$ on AH(M). Further, we provide the almost Hermitian analogy of the Hilbert's result.

Tau mis-splicing in the pathogenesis of neurodegenerative disorders

  • Park, Sun Ah;Ahn, Sang Il;Gallo, Jean-Marc
    • BMB Reports
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    • v.49 no.8
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    • pp.405-413
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    • 2016
  • Tau proteins, which stabilize the structure and regulate the dynamics of microtubules, also play important roles in axonal transport and signal transduction. Tau proteins are missorted, aggregated, and found as tau inclusions under many pathological conditions associated with neurodegenerative disorders, which are collectively known as tauopathies. In the adult human brain, tau protein can be expressed in six isoforms due to alternative splicing. The aberrant splicing of tau pre-mRNA has been consistently identified in a variety of tauopathies but is not restricted to these types of disorders as it is also present in patients with non-tau proteinopathies and RNAopathies. Tau mis-splicing results in isoform-specific impairments in normal physiological function and enhanced recruitment of excessive tau isoforms into the pathological process. A variety of factors are involved in the complex set of mechanisms underlying tau mis-splicing, but variation in the cis-element, methylation of the MAPT gene, genetic polymorphisms, the quantity and activity of spliceosomal proteins, and the patency of other RNA-binding proteins, are related to aberrant splicing. Currently, there is a lack of appropriate therapeutic strategies aimed at correcting the tau mis-splicing process in patients with neurodegenerative disorders. Thus, a more comprehensive understanding of the relationship between tau mis-splicing and neurodegenerative disorders will aid in the development of efficient therapeutic strategies for patients with a tauopathy or other, related neurodegenerative disorders.

Docosahexaenoic acid-mediated protein aggregates may reduce proteasome activity and delay myotube degradation during muscle atrophy in vitro

  • Shin, Seung Kyun;Kim, Ji Hyeon;Lee, Jung Hoon;Son, Young Hoon;Lee, Min Wook;Kim, Hak Joong;Noh, Sue Ah;Kim, Kwang Pyo;Kim, In-Gyu;Lee, Min Jae
    • Experimental and Molecular Medicine
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    • v.49 no.1
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    • pp.6.1-6.11
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    • 2017
  • Proteasomes are the primary degradation machinery for oxidatively damaged proteins that compose a class of misfolded protein substrates. Cellular levels of reactive oxygen species increase with age and this cellular propensity is particularly harmful when combined with the age-associated development of various human disorders including cancer, neurodegenerative disease and muscle atrophy. Proteasome activity is reportedly downregulated in these disease conditions. Herein, we report that docosahexaenoic acid (DHA), a major dietary omega-3 polyunsaturated fatty acid, mediates intermolecular protein cross-linkages through oxidation, and the resulting protein aggregates potently reduce proteasomal activity both in vitro and in cultured cells. Cellular models overexpressing aggregation-prone proteins such as tau showed significantly elevated levels of tau aggregates and total ubiquitin conjugates in the presence of DHA, thereby reflecting suppressed proteasome activity. Strong synergetic cytotoxicity was observed when the cells overexpressing tau were simultaneously treated with DHA. Antioxidant N-acetyl cysteine significantly desensitized the cells to DHA-induced oxidative stress. DHA significantly delayed the proteasomal degradation of muscle proteins in a cellular atrophy model. Thus, the results of our study identified DHA as a potent inducer of cellular protein aggregates that inhibit proteasome activity and potentially delay systemic muscle protein degradation in certain pathologic conditions.

Absolute Dimensions of Fifteen High Mass Main Sequence Eclipsing Binaries

  • Surina, Farung;Kang, Young-Woon
    • Bulletin of the Korean Space Science Society
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    • pp.23.2-23.2
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    • 2008
  • We presented the accurate absolute dimensions and distances of fifteen main sequence eclipsing binaries. The photometric and spectroscopic solutions of the binary systems were determined by analyzing light curves and radial velocity curves collected from the literature using the Wilson-Devinney computer code. The fifteen double-line spectroscopic binaries consist of nine detached systems; QX Car, AH Cep, CW Cep, ZZ Cep, XY Cet, RX Her, V451 Oph, VV Pyx and V760 Sco, six semi-detached systems; LY Aur, IU Aur, AO Cas, DM Per, V Pup and HU Tau. The temperatures of the binary systems were determined from their colors using the color-temperature calibrations. Then the temperature of each component star were determined using the temperature ratio which was adjusted from the light curves. We estimated the possible Z values and ages for the detached systems by adopting the Y2 (Yonsei-Yale) stellar evolutionary tracks. The derived distances are in good agreement of the Hipparcos distances whose error of parallax is within 10 %. Finally these well-investigated systems will be used as the standard eclipsing binaries.

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Antioxidant Activities of Gynura procumbens Extracts (명월초 추출물의 항산화 활성)

  • Kim, Kyeong Jin;Gim, Ah Hyun;Kim, Ji Hyun;Kim, Do Hee;Lee, Seo Rin;Park, Jee Hyun;Lim, Ji Won;Ha, Ji Hoon;Park, Soo Nam
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.41 no.2
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    • pp.181-187
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    • 2015
  • In this study, the methanol fraction and aglycone fraction were made from Gynura procumbens (G. procumbens) extracts and their antioxidative effects were investigated. The free radical scavenging activity (1,1-diphenyl-2-picrylhydrazyl, DPPH), total antioxidant capacity by luminol-dependent chemiluminescence assay, and the protective effects against reactive oxygen species (ROS) in erythrocytes were measured to evaluate the antioxidative activities of the extracts. Free radical scavenging activities ($FSC_{50}$) of the methanol fraction and aglycone fraction were 90.25 and $81.38{\mu}g/mL$, respectively. Total antioxidant capacities ($OSC_{50}$) of the methanol fraction and aglycone fraction were 16.96 and $12.30{\mu}g/mL$, respectively. The free radical scavenging activity and total antioxidant capacity of the aglycone fraction were greater than those of methanol fraction. The cellular protective effect on the $^1O_2$-induced cellular damage of human erythrocytes was confirmed by ${\tau}_{50}$ value. The ${\tau}_{50}$ value of the methanol fraction and aglycone fraction were 36.7 min and 76.1 min, respectively in $5{\mu}g/mL$, and the aglycone fraction showed about 2 times higher cellular protecive effect than (+)-${\alpha}$-tocopherol (35.4 min). These results indicate that the aglycone fraction of G. procumbens extracts has application possibility as antioxidant ingredient of cosmetic.

Radical Scavenging Effect and Neuroprotective Activity from Oxidative Stress of Engelhardtia chrysolepis Leaf (Engelhardtia chrysolepis의 라디칼 소거능 및 신경세포의 산화 스트레스 보호효과)

  • Kim, Eun Jung;Lee, Ah Young;Choi, Soo Yeon;Seo, Hye Rin;Lee, Young A;Cho, Eun Ju
    • Korean Journal of Pharmacognosy
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    • v.47 no.3
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    • pp.251-257
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    • 2016
  • In this study, the radical scavenging activity and protective effect of ethanol extract from leaf of Engelhardtia chrysolepis HANCE (ECE) against oxidative stress were investigated under in vitro and cellular system. ECE showed strong radical scavenging activities in 1,1-diphenyl-2-picrylhydrazyl, hydroxyl(${\cdot}OH$) and nitric oxide(NO) radical as a concentration-dependent manner. Particularly, strong scavenging activity against the ${\cdot}OH$ and NO radical were observed with the $IC_{50}$ value of $1.30{\mu}g/ml$ and $12.61{\mu}g/ml$, respectively. Furthermore, the cellular oxidative stress was induced by amyloid beta($A{\beta}_{25-35}$) in C6 glial cells. The treatment of $A{\beta}_{25-35}$ to C6 glial cells generated high levels of reactive oxygen species(ROS) and declined cell viability. However, production of ROS was decreased by the treatment of ECE. In addition, the cell viability was significantly increased at each concentration(10, 25, $50{\mu}g/ml$) as dose-dependent manner. The Alzheimer's disease-related protein expressions in $A{\beta}_{25-35}$-treated C6 glial cells were analyzed. The ECE treatment inhibited expression of amyloid precursor protein(APP), C-terminal fragment-${\beta}(CTF-{\beta})$, ${\beta}$-site APP cleaving enzyme(BACE), phosphorylated tau(p-tau) proteins in C6 glial cells induced by $A{\beta}_{25-35}$. The present study indicated that ECE has strong radical scavenging activity and neuroprotective effect through attenuating oxidative stress.

Reproducibility of Adenosine Tc-99m sestaMIBI SPECT for the Diagnosis of Coronary Artery Disease (관동맥질환의 진단을 위한 아데노신 Tc-99m sestaMIBI SPECT의 재현성)

  • Lee, Duk-Young;Bae, Jin-Ho;Lee, Sang-Woo;Chun, Kyung-Ah;Yoo, Jeong-Soo;Ahn, Byeong-Cheol;Ha, Jeoung-Hee;Chae, Shung-Chull;Lee, Kyu-Bo;Lee, Jae-Tae
    • The Korean Journal of Nuclear Medicine
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    • v.39 no.6
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    • pp.473-480
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    • 2005
  • Purpose: Adenosine myocardial perfusion SPECT has proven to be useful in the detection of coronary artery disease, in the follow up the success of various therapeutic regimens and in assessing the prognosis of coronary artery disease. The purpose of this study is to define the reproducibility of myocardial perfusion SPECT using adenosine stress testing between two consecutive Tc-99m sestaMIBI (MIBI) SPECT studies in the same subjects. Methods: Thirty patients suspected of coronary artery disease in stable condition underwent sequential Tc-99m MIBI SPECT studies using intravenous adenosine. Gamma camera, acquisition and processing protocols used for the two tests were identical and no invasive procedures were performed between two tests. Mean interval between two tests were 4.1 days (range: 2-11 days). The left ventricular wall was divided into na segments and the degree of myocardial tracer uptake was graded with four-point scoring system by visual analysis. Images were interpretated by two independent nuclear medicine physicians and consensus was taken for final decision, if segmental score was not agreeable. Results: Hemodynamic responses to adenosine were not different between two consecutive studies. There were no serious side effects to stop infusion of adenosine and side effects profile was not different. When myocardial uptake was divided into normal and abnormal uptake, 481 of 540 segments were concordant (agreement rate 89%, Kappa index 0.74). With four-grade storing system, exact agreement was 81.3% (439 of 540 segments, tau b=0.73). One and two-grade differences were observed in 97 segments (18%) and 4 segments (0.7%) respectively, but three-grade difference was not observed in any segment. Extent and severity scores were not different between two studios. The extent and severity scores of the perfusion defect revealed excellent positive correlation between two test (r value for percentage extent and severity score is 0.982 and 0.965, p<0.001) Conclusion: Hemodynamic responses and side effects profile were not different between two consecutive adenosine stress tests in the same subjects. Adenosine Tc-99m sestaMIBI SPECT is highly reproducible, and could be used to assess temporal changes in myocardial perfusion in individual patients.

Antioxidative Effect and Tyrosinase Inhibitory Activity of Rheum undulatum L. Extracts (대황의 항산화 효과 및 타이로시네이즈 저해 활성)

  • Kim, Jung-Eun;Park, Chan-Ha;Oh, Dae-Seok;Lee, Seung-Yeon;Jang, Se-Hun;Hong, Jee-Yeon;Min, Hye-Jin;Park, Su-Ah;Won, Doo-Hyun;Park, Soo-Nam
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.37 no.4
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    • pp.357-363
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    • 2011
  • In this study, the antioxidative effects and inhibitory activities on tyrosinase of Rheum undulatum (R.undulatum) L. extracts were investigated. 50 % ethanol extract, ethyl acetate and aglycone fractions of R. undulatum L. were used in experiments. The DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activities ($FSC_{50}$) of R. undulatum L. extracts was lower than (+)-${\alpha}$-tocopherol, known as a typical antioxidant. Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) of aglycone fraction on ROS generated in $Fe^{3+}$-EDTA/$H_2O_2$ system using the luminol-dependent chemiluminescence assay showed the most prominent effect at a concentration of $0.265\;{\mu}g/mL$. The cellular protective effects of extract/fractions of R. undulatum L. on the rose-bengal sensitized photohemolysis of human erythrocytes were increased in a concentration dependent manner ($1{\sim}50\;{\mu}g/mL$). Especially, aglycone fraction in $10\;{\mu}g/mL$ concentration showed the most protective effect among extracts (${\tau}_{50}$, 757.0 min). The inhibitory effects ($IC_{50}$, $11.20\;{\mu}g/mL$) on tyrosinase of aglycone fraction was much higher than arbutin ($226.88\;{\mu}g/mL$), known as a whitening agent. These results indicate that R. undulatum L. extracts can be used as antioxidant. Particularly, aglycone fraction of R. undulatum L. showed superior antioxdative activity and high inhibitory effect on tyrosinase. Therefore, aglycone fraction of R. undulatum L. could be applicable to new functional cosmetics.