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Effects of dextrorotatory morphinans on brain Na<sup>+</sup> channels expressed in Xenopus oocytes
Lee, J.H.,Shin, E.J.,Jeong, S.M.,Lee, B.H.,Yoon, I.S.,Lee, J.H.,Choi, S.H.,Kim, Y.H.,Pyo, M.K.,Lee, S.M.,Chae, J.S.,Rhim, H.,Oh, J.W.,Kim, H.C.,Nah, S.Y. North-Holland ; Elsevier Science Ltd 2007 european journal of pharmacology Vol.564 No.1
We previously demonstrated that dextromethorphan (DM; 3-methoxy-17-methylmorphinan) analogs have neuroprotective effects. Here, we investigated the effects of DM, three of its analogs (DF, 3-methyl-17-methylmorphinan; AM, 3-allyloxy-17-methoxymorphian; and CM, 3-cyclopropyl-17-methoxymorphinan) and one of its metabolites (HM; 3-methoxymorphinan), on Na<SUP>+</SUP> channel activity. We used the two-microelectrode voltage-clamp technique to test the effects of DM, DF, AM, CM and HM on Na<SUP>+</SUP> currents (I<SUB>Na</SUB>) in Xenopus oocytes expressing cRNAs encoding rat brain Nav1.2 α and β1 or β2 subunits. In oocytes expressing Na<SUP>+</SUP> channels, DM, DF, AM and CM, but not HM, induced tonic and use-dependent inhibitions of peak I<SUB>Na</SUB> following low- and high-frequency stimulations. The order of potency for the inhibition of peak I<SUB>Na</SUB> was AM-CM > DM=DF. The DM, DF, AM and CM-induced tonic inhibitions of peak I<SUB>Na</SUB> were voltage-dependent, dose-dependent and reversible. The IC<SUB>50</SUB> values for DM, DF, AM and CM were 116.7+/-14.9, 175.8+/-16.9, 38.6+/-15.5, and 42.5+/-8.5 μM, respectively. DM and its analogs did not affect the steady-state activation and inactivation voltages. AM and CM, but not DM and DF, inhibited the plateau I<SUB>Na</SUB> more effectively than the peak I<SUB>Na</SUB> in oocytes expressing inactivation-deficient I1485Q-F1486Q-M1487Q (IFMQ3) mutant channels; the IC<SUB>50</SUB> values for AM and CM in this system were 8.4+/-1.3 and 8.7+/-1.3 μM, respectively, for the plateau I<SUB>Na</SUB> and 43.7+/-5.9 and 32.6+/-7.8 μM, respectively, for the peak I<SUB>Na</SUB>. These results collectively indicate that DM and its analogs could be novel Na<SUP>+</SUP> channel blockers acting on the resting and open states of brain Na<SUP>+</SUP> channels.
Shin, J.M.,Kim, J.,Kim, H.E.,Lee, M.J.,Lee, K.I.,Gyong Yoo, E.,Joo Jeon, Y.,Chae, D.W.K.J.I.,Chung, H.M. Elsevier 2011 Stem cell research Vol.7 No.3
Hypoxia is one way of inducing differentiation due to the activation of the key regulatory factor, Hypoxia-inducible factor 1 alpha (HIF-1α). However, the action of HIF-1α on the differentiation of hESCs was unclear until now. To investigate the effect of hypoxia on the differentiation of hESCs, we compared the differentiation efficacy into vascular lineage cells under normoxic and hypoxic conditions. We observed HIF-1α expression and the related expression of pro-angiogenic factors VEGF, bFGF, Ang-1 and PDGF in hEBs cultured under hypoxic conditions. Along with this, differentiation efficacy into vascular lineage cells was improved under hypoxic conditions. When HIF-1α was blocked by echinomycin, both angiogenic factors and the differentiation efficacy were down-regulated, suggesting that the enhancement of differentiation efficacy was caused by intrinsic up-regulation of HIF-1α and these pro-angiogenic factors under hypoxic condition. This response might be primarily regulated by the HIF-1α signal pathway, and hypoxia might be the key to improving the differentiation of hESCs into vascular lineage cells. Therefore, this study demonstrated that microenvironmental changes (i.e., hypoxia) can improve differentiation efficacy of hESCs into a vascular lineage without exogenous factors via cell-intrinsic up-regulation of angiogenic factors. These facts will contribute to the regulation of stem cell fate.
Abnormal Temperature Dependence of Tunneling Magnetoresistance for Magnetic Tunnel Junctions
K. I. Lee,J. H. Lee,W. Y. Lee,K. Rhie,B. C. Lee,K.-H. Shin 한국자기학회 2002 Journal of Magnetics Vol.7 No.2
Magnetic tunnel junctions (MTJs) were fabricated with high bias for plasma oxidation and the effects of annealing on the temperature dependence of tunneling magnetoresistance (TMR) were investigated experimentally. As-grown, TMR increases, peaks around 160 K, and decreases with increasing temperature from 80 K to 300 K. When MTJs are annealed, Tmax, the temperature at which maximum TMR is obtained, decreases as annealing temperature increases to the optimal point. In order to explain this abnormal temperature dependence of TMR, the difference of conductance between parallel and antiparallel alignments of magnetizations as a function of temperature is also analyzed. The shifts of Tmax due to annealing process are described phenomenologically with spin-dependent transfer rates of electrons tunnel through the barrier.
Effects of Rapid Thermal Anneal on the Magnetoresistive Properties of Magnetic Tunnel Junction
K. I. Lee,J. H. Lee,W. Y. Lee,K. Rhie,J. G. Ha,K.-H. Shin 한국자기학회 2001 Journal of Magnetics Vol.6 No.4
The effect of rapid thermal anneal (RTA) has been investigated on the properties of an FeMn exchange-biased magnetic tunnel junction (MTJ) using magnetoresistance and I-V measurements and transmission electron microscopy (TEM). The tunneling magnetoresistance (TMR) in an as-grown MTJ is found to be ~27%, while the TMR in MTJs annealed by RTA increases with annealing temperature up to 300℃, reaching ~46%. A TEM image reveals a structural change in the interface of Al₂O₃ layer for the MTJ annealed by RTA at 300℃. The oxide barrier parameters are found to vary abruptly with annealing time within a few ten seconds. Our results demonstrate that the present RTA enhances the magnetoresistive properties of MTJs.
USING ORBITAL EFFECTS TO BREAK THE CLOSE/WIDE DEGENERACY IN BINARY-LENS MICROLENSING EVENTS
Shin, I.-G.,Sumi, T.,Udalski, A.,Choi, J. Y.,Han, C.,Gould, A.,Abe, F.,Bennett, D. P.,Bond, I. A.,Botzler, C. S.,Chote, P.,Freeman, M.,Fukui, A.,Furusawa, K.,Harris, P.,Itow, Y.,Ling, C. H.,Masuda, K. IOP Publishing 2013 The Astrophysical journal Vol.764 No.1
<P>Microlensing can provide an important tool to study binaries, especially those composed of faint or dark objects. However, accurate analysis of binary-lens light curves is often hampered by the well-known degeneracy between close (s < 1) and wide (s > 1) binaries, which can be very severe due to an intrinsic symmetry in the lens equation. Here, s is the normalized projected binary separation. In this paper, we propose a method that can resolve the close/wide degeneracy using the effect of a lens orbital motion on lensing light curves. The method is based on the fact that the orbital effect tends to be important for close binaries while it is negligible for wide binaries. We demonstrate the usefulness of the method by applying it to an actually observed binary-lens event MOA-2011-BLG-040/OGLE-2011-BLG-0001, which suffers from severe close/wide degeneracy. From this, we are able to uniquely specify that the lens is composed of K- and M-type dwarfs located similar to 3.5 kpc from the Earth.</P>
수정된 화학전이 NMR 영상법에 의한 수분과 지질의 비율 측정에 관한 연구
신용진,장차익,홍광준,유상하,이관교,양경승,백창현,김남수,정준우 조선대학교 기초과학연구소 1996 自然科學硏究 Vol.19 No.1
다양한 화학종(化學種)의 선택적인 핵자기공명(nuclear magnetic resonance, NMR) 영상(imaging)을 얻기 위한 몇몇 기술들이 가장 일반적인 Dixon's, CHESS, SECSI 등 3가지 방법들과 함께 발전해 왔다. 모든 화학전이 영상법(chemical shift imaging method)에 있어서 가장 큰 문제점은 정자기장의 균일성과 RF(radiofrequency) 코일에 대전된 시료가 인가되었을 때 나타나는 자기장의 찌그러짐이다. 만약 자기장의 shimming이 없다면, 약 3.5ppm으로 분리된 수분(water)과 지질(fat)의 선택적 양성자 영상을 얻는데 위 세 가지 방법들은 이용될 수 없다. 2.5ppm에서 3.5ppm의 선폭(linewidth)을 가진 시료(phantom)를 이용한 실험으로 위의 세 가지 기술과 새로운 화학전이 영상기술을 정량적으로 분석할 수 있었다. 본 연구에서는 선택적인 포화(saturation)와 재집중(refocusing) pulse가 포함된 새로운 화학전이 영상기술(modified CHESS+SECSI technique)이 다양한 시료에서 수분과 지질의 정량적 비율을 측정하는데 이용될 수 있도록 개발되었다. There are several methods developed to achieve selective NMR image of differing chemical species with the three most popular being Dixon's, CHESS, and SECSI, A major problem common to all chemical shift imaging methods is the uniformity of the static magnetic field and distortions introduced when RF coils are loaded with a conducting specimen. Without magnetic field shimming, these methods cannot be used to selectively image protons in fat and water which are separated by approximately 3.5ppm. Experiments with a phantom, with linewidths of 2.5 to 3.5ppm, were quantitatively evaluated for the above three methods and a new chemical shift imaging method. In this study the new chemical shift imaging method (modified CHESS+SECSI technique) which included a selective saturation and refocusing pulse, was developed to determine the ratio of water and fat in different samples.