Lee D.,Pohang University of Science and Technology |
Lee S.-G.,Seoul Science High School |
Kim S.,Pohang University of Science and Technology
European Physical Journal B | Year: 2012
The transmission of a signal through an axon is studied using a compartment model of a non-uniform axon. We find that the transmission efficiency in these axons has nonlinear mode-locking structure that depends on the relative ion channel density. The refractory period of the soma is found to be longer than that of its axon and this structure appears by it. Our study suggets that non-uniform axons can actively participate in information processing. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012.
PubMed | Amore Pacific, Seoul Science High School, Collge of Pharmacy. and Seoul National University
Type: Journal Article | Journal: Biomolecules & therapeutics | Year: 2015
Endocannabinoids can affect multiple cellular targets, such as cannabinoid (CB) receptors, transient receptor potential cation channel, subfamily V, member 1 (TRPV1) and peroxisome proliferator-activated receptor (PPAR). The stimuli to induce adipocyte differentiation in hBM-MSCs increase the gene transcription of the CB1 receptor, TRPV1 and PPAR. In this study, the effects of three endocannabinoids, N-arachidonoyl ethanolamine (AEA), N-arachidonoyl dopamine (NADA) and 2-arachidonoyl glycerol (2-AG), on adipogenesis in hBM-MSCs were evaluated. The adipocyte differentiation was promoted by AEA whereas inhibited by NADA. No change was observed by the treatment of non-cytotoxic concentrations of 2-AG. The difference between AEA and NADA in the regulation of adipogenesis is associated with their effects on PPAR transactivation. AEA can directly activate PPAR. The effect of AEA on PPAR in hBM-MSCs may prevail over that on the CB1 receptor mediated signal transduction, giving rise to the AEA-induced promotion of adipogenesis. In contrast, NADA had no effect on the PPAR activity in the PPAR transactivation assay. The inhibitory effect of NADA on adipogenesis in hBM-MSCs was reversed not by capsazepine, a TRPV1 antagonist, but by rimonabant, a CB1 antagonist/inverse agonist. Rimonabant by itself promoted adipogenesis in hBM-MSCs, which may be interpreted as the result of the inverse agonism of the CB1 receptor. This result suggests that the constantly active CB1 receptor may contribute to suppress the adipocyte differentiation of hBM-MSCs. Therefore, the selective CB1 agonists that are unable to affect cellular PPAR activity inhibit adipogenesis in hBM-MSCs.
Kim H.-R.,Ewha Womans University |
Lee S.-M.,Ewha Womans University |
Won J.-W.,Seoul Science High School |
Lim W.,Ewha Womans University |
And 3 more authors.
Immunology | Year: 2013
Regulatory T (Treg) cells are important in the regulation of immune response, but the exact regulation of Treg-cell function in vivo is still not well known. In the present study, we investigated the functional activity of CD4+ CD25+ Treg cells as well as the frequency and number of CD4+ CD25+ FoxP3+ Treg cells in the spleens of experimentally infected mice with a tissue-migrating parasite, sparganum (plerocercoid of Spirometra mansoni) for 3 weeks. The results demonstrated fluctuations in the Treg-cell function during the parasite infection, being up-regulated at day 3, down-regulated until day 14, and thereafter up-regulated again at day 21. We also investigated the cytokine-producing capability of the splenocytes to study the pattern of immune response of the mice to the parasite. The results showed decreased capabilities of interleukin-2 (IL-2), interferon-γ (IFN-γ) and IL-17α production, whereas IL-4-producing and IL-10-producing capabilities were increased along with the parasitic infection. Meanwhile, IL-6-producing capability was increased to reach a peak at week 2, and thereafter was decreased to the baseline level. As a regulatory mechanism, we found that Treg-cell function was attenuated in the presence of the crude extracts of sparganum, but was enhanced in the presence of the excretory-secretory products, suggesting that sparganum products were involved in the triggering and regulation of immune response in the acute and chronic phases, respectively. Results show that Treg cells are central in the immune homeostasis in vivo that is maintained by host-parasite interactions during the parasitic infection. © 2012 Blackwell Publishing Ltd.
Li Y.,Yonsei University |
Lee D.,Korea University |
Lee C.,Korea University |
Lee J.,Seoul Science High School |
And 4 more authors.
Computer Vision and Image Understanding | Year: 2014
In this paper, we present a novel fast and accurate numerical method for the surface embedding narrow volume reconstruction from unorganized points in R3. Though the level set method prevails in the image processing, it requires a redistancing procedure to maintain a desired shape of the level set function. On the other hand, our method is based on the Allen-Cahn equation, which has been applied in image segmentation due to its motion by mean curvature property. We modify the original Allen-Cahn equation by multiplying a control function to restrict the evolution within a narrow band around the given surface data set. To improve the numerical stability of our proposed model, we split the governing equation into linear and nonlinear terms and use an operator splitting technique. The linear equation is solved by the multigrid method which is a fast solver and the nonlinear equation is solved analytically. The unconditional stability of the proposed scheme is also proved. Various numerical results are presented to demonstrate the robustness and accuracy of the proposed method. © 2014 Elsevier Ltd. All rights reserved.
Lee S.H.,Konkuk University |
Lee Y.-S.,Suncheon Health Service Center |
Lee I.Y.,Yonsei University |
Lim J.W.,National Institute of Biological Resources |
And 3 more authors.
Korean Journal of Parasitology | Year: 2012
Monthly surveys were conducted to investigate the occurrence of chigger mites and seroprevalence of scrub typhus among small mammals in Jeollanam-do, the southwestern part of Korea, from November 2006 through October 2007. Fifty-eight small mammals, including 57 Apodemus agrarius (98.3%) and 1 Crocidura lasiura (1.7%), were captured, and a total of 4,675 chigger mites representing 4 genera and 8 species were collected from them. The chigger infestation rate among small mammals was 69.0%. The most predominant species in A. agrarius was Leptotrombidium scutellare (54.0%), followed by Leptotrombidium pallidum (39.4%), Leptotrombidium orientale (4.4%), Leptotrombidium palpale (1.1%), Neotrombicula tamiyai (0.6%), Eushoengastia koreaensis (0.3%), Neotrombicula gardellai (0.3%), and Cheladonta ikaoensis (<0.1%). The chigger index of A. agrarius was the highest in October (740.0), followed by November (242.0), September (134.6), March (98.3), February (38.2), January (35.3), December (34.5), April (30.8), and May (1.7). The average antibody positive rate of scrub typhus in wild rodents was 50.0%. The seropositive rates were high in October (100.0%) and November (83.3%), whereas those in other months were relatively low (28.6-57.1%). The chigger index of L. scutel-lare rapidly increased in September to form an acuminate peak in October, followed by a gradual decline. These results suggest that the outbreak of scrub typhus in the southwestern part of Korean peninsula is mostly due to L. scutellare. © 2012, Korean Society for Parasitology and Tropical Medicine.
Hahn C.,Hanyang University |
Oh C.-H.,Hanyang University |
Wang H.,Seoul Science High School
Journal of the Korean Physical Society | Year: 2011
A photonic crystal structure was fabricated by using a flow-controlled vertical deposition (FCVD) method. We simplified the fabrication setup by replacing the peristaltic pump with just an open hole at the bottom of beaker. The optimum surface drop velocity of the polystyrene suspension for a photonic crystal structure with uniform surface and thickness was experimentally determined to be 0.35 μm/s. The photonic band-gap behavior of the fabricated photonic crystal structure was analyzed by using the transmission spectrum. The measured transmission spectrum was compared with a theoretical calculation, and we learned that the particle size contracted during the selfassembly process.
Jung K.,Seoul Science High School |
Cho W.,Wonkwang University
Analytical Chemistry | Year: 2013
Glycan-targeting affinity chromatography systems are becoming increasingly important as tools in the purification, enrichment, and identification of glycoproteins. The great advantage of this strategy is that immobilized lectin and antibody selectors allow specific glycan structures to be matched with a particular protein. It is also possible to show that a glycan seen at one site in a glycoprotein may not be present at another glycosylation site in the same glycoprotein. A problem with single-column affinity chromatography is how to obtain information on glycan diversity within the oligosaccharide portions of captured glycoproteins. Although all the glycoprotein species bearing a particular glycan feature will be captured by an affinity column, there is no way of knowing whether the ligand being targeted appears alone or coresides with a series of other glycan features in the same oligosaccharide conjugate. The work being described here examines the utility of serial affinity columns in determining whether individual glycan structures appear alone or together with other glycans in specific proteins. Four different types of affinity columns were examined in two series; the LEL → HPA → anti-LexAb → anti-sLexAb series and the anti-sLexAb → anti-LexAb → HPA → LEL series. Patterns in protein capture from these two series were very different. Thus, serial affinity chromatography (SAC) can be a valuable tool in recognizing diversity in protein glycosylation, especially when the order of columns in the SAC series is varied. Two clear types of diversity were recognized. One is the independent occurrence of different affinity-targetable glycan features in the same glycoprotein. The other is that multiple targetable glycan features were coresident in the same glycoprotein. The great advantage of this method is that it couples easily with current methods used in glycoproteomics. © 2013 American Chemical Society.
Lee S.H.,Seoul Science High School |
Lee S.,Seoul Science High School
Journal of the Korean Astronomical Society | Year: 2012
We present a mathematical model that predicts the variation of illuminance during a solar eclipse, considering continuous effects of limb darkening. We assume that (1) the Sun and the Moon constitute perfect spheres, (2) the Moon crosses the Sun with a constant apparent velocity, and (3) sunspots, prominences, and coronae can be neglected. We compare predictions of this model with actual measurements made by M̈ollmann & Vollmer (2006) during a total solar eclipse in Turkey, and with predictions of existing models. The new model is shown to describe the actual phenomenon more accurately than existing models. © 2012 The Korean Astronomical Society. All rights reserved.
PubMed | Korea University and Seoul Science High School
Type: | Journal: Journal of molecular graphics & modelling | Year: 2016
Amyloid proteins are known to be the main cause of numerous degenerative and neurodegenerative diseases. In general, amyloids are misfolded from monomers and they tend to have -strand formations. These misfolded monomers are then transformed into oligomers, fibrils, and plaques. It is important to understand the forming mechanism of amyloids in order to prevent degenerative diseases to occur. A protein is a highly noticeable protein which causes Alzheimers disease. It is reported that solvents affect the forming mechanism of A amyloids. In this research, A1-42 was analyzed using an all-atom MD simulation with the consideration of effects induced by two disparate solvents: water and DMSO. As a result, two different conformation changes of A1-42 were exhibited in each solvent. It was found that salt-bridge of Asp23 and Lys28 in A1-42 was the key for amyloid folding based on the various analysis including hydrogen bond, electrostatic interaction energy and salt-bridge distance. Since this salt-bridge region plays a crucial role in initiating the misfolding of A1-42, this research may shed a light for studies related in amyloid folding and misfolding.
PubMed | Korea University and Seoul Science High School
Type: | Journal: Biophysical chemistry | Year: 2015
Amyloid proteins are misfolded, denatured proteins that are responsible for causing several degenerative and neuro-degenerative diseases. Determining the mechanical stability of these amyloids is crucial for understanding the disease mechanisms, which will guide us in treatment. Furthermore, many research groups recognized amyloid proteins as functional biological materials that can be used in nanosensors, bacterial biofilms, coatings, etc. Many in vitro studies have been carried out to determine the characteristics of amyloid proteins via force spectroscopy methods, atomic force microscopy, and optical tweezers. However, computational methods (e.g. molecular dynamics and elastic network model) not only reveal the mechanical properties of the amyloid proteins, but also provide more in-depth information about the amyloids by presenting a visualization of their conformational changes. In this study, we evaluated the various material properties and behaviors of four different polymorphic structures of human islet amyloid polypeptide (hIAPP) by using steered molecular dynamics (SMD) simulations under tensile conditions. From our results, we examined how these mechanical properties may differ with respect to the structural formation of amyloid proteins.