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Search Results: 1 - 10 of 39345 matches for " Seung U. Kim "
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Live Fibular Graft for the Treatment of Long Bone Tumors in Children  [PDF]
Seung-Koo Rhee, Mohammed Einayet Abdelhameed, Chi-Hoon Ahn, Cheol-U Kim
Journal of Cancer Therapy (JCT) , 2017, DOI: 10.4236/jct.2017.83019
Abstract: Purposes: We would like to inform the characteristics of recurred osteo-fibrous dysplasia (OFD), and also the possible use of vascularized composite autograft and allografts (VCA) combined with live fibular graft (LFG) for the treatment of aggressive benign bone tumor and osteogenic sarcomas in children. Materials and Methods: We reviewed one boy with recurred OFD after LFG, and other four children with osteogenic sarcoma in long bone which was treated with LFG and VCA, and followed them for average 9 years (3 - 14 years). Survival of the LFG and VCA was estimated by the ISOLS Functional Radiologic Scoring System, but not with Kaplans-Meier’s scoring system because of a small series of case reports. Results: All succeed after surgeries initially, but the cause of recurrence of OFD was still unclear, and one girl with osteogenic sarcoma on distal femur died with skip and lung metastasis, 4 years after surgeries. Conclusions: The causes of recurred OFD are not found thru pathologic studies of our patient, but we believe the multifocal origin of tumor cells even on the adjacent soft tissues in OFD is one of the causes. The excised long bone tumor is recycled by pasteurization or autoclaving, or allograft, then LFG, and neo-adjuvant chemotherapy would be one of elective surgery for the treatment of malignant long bone tumors in children. The LFG into recycled autograft or allograft bone is difficult to perform simultaneously, but very effective to increase more earlier regenerative vascularities and also the stabilities of the dead bones in children.
Human Neural Stem Cells Genetically Modified to Overexpress Akt1 Provide Neuroprotection and Functional Improvement in Mouse Stroke Model
Hong J. Lee, Mi K. Kim, Hee J. Kim, Seung U. Kim
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005586
Abstract: In a previous study, we have shown that human neural stem cells (hNSCs) transplanted in brain of mouse intracerebral hemorrhage (ICH) stroke model selectively migrate to the ICH lesion and induce behavioral recovery. However, low survival rate of grafted hNSCs in the brain precludes long-term therapeutic effect. We hypothesized that hNSCs overexpressing Akt1 transplanted into the lesion site could provide long-term improved survival of hNSCs, and behavioral recovery in mouse ICH model. F3 hNSC was genetically modified with a mouse Akt1 gene using a retroviral vector. F3 hNSCs expressing Akt1 were found to be highly resistant to H2O2-induced cytotoxicity in vitro. Following transplantation in ICH mouse brain, F3.Akt1 hNSCs induced behavioral improvement and significantly increased cell survival (50–100% increase) at 2 and 8 weeks post-transplantation as compared to parental F3 hNSCs. Brain transplantation of hNSCs overexpressing Akt1 in ICH animals provided functional recovery, and survival and differentiation of grafted hNSCs. These results indicate that the F3.Akt1 human NSCs should be a great value as a cellular source for the cellular therapy in animal models of human neurological disorders including ICH.
Ex Vivo VEGF Delivery by Neural Stem Cells Enhances Proliferation of Glial Progenitors, Angiogenesis, and Tissue Sparing after Spinal Cord Injury
Hyuk Min Kim, Dong Hoon Hwang, Jong Eun Lee, Seung U. Kim, Byung G. Kim
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004987
Abstract: The present study was undertaken to examine multifaceted therapeutic effects of vascular endothelial growth factor (VEGF) in a rat spinal cord injury (SCI) model, focusing on its capability to stimulate proliferation of endogenous glial progenitor cells. Neural stem cells (NSCs) can be genetically modified to efficiently transfer therapeutic genes to diseased CNS. We adopted an ex vivo approach using immortalized human NSC line (F3 cells) to achieve stable and robust expression of VEGF in the injured spinal cord. Transplantation of NSCs retrovirally transduced to overexpress VEGF (F3.VEGF cells) at 7 days after contusive SCI markedly elevated the amount of VEGF in the injured spinal cord tissue compared to injection of PBS or F3 cells without VEGF. Concomitantly, phosphorylation of VEGF receptor flk-1 increased in F3.VEGF group. Stereological counting of BrdU+ cells revealed that transplantation of F3.VEGF significantly enhanced cellular proliferation at 2 weeks after SCI. The number of proliferating NG2+ glial progenitor cells (NG2+/BrdU+) was also increased by F3.VEGF. Furthermore, transplantation of F3.VEGF increased the number of early proliferating cells that differentiated into mature oligodendrocytes, but not astrocytes, at 6 weeks after SCI. F3.VEGF treatment also increased the density of blood vessels in the injured spinal cord and enhanced tissue sparing. These anatomical results were accompanied by improved BBB locomotor scores. The multifaceted effects of VEGF on endogenous gliogenesis, angiogenesis, and tissue sparing could be utilized to improve functional outcomes following SCI.
Computer Simulation Study of Biopolymer Betanova  [PDF]
Seung-Yeon Kim
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.312002

Betanova is a monomeric, three-stranded antiparallel beta-sheet protein with twenty residues. The pathways between the folded native structure and unfolded conformations of betanova are studied using UNRES force field and the most popular computer simulation method, Metropolis Monte Carlo algorithm. At a fixed temperature, 100 Monte Carlo simulations are performed, starting from the folded native structure, and the pathways are obtained at two different temperatures.

Folding and Unfolding Simulations of a Three-Stranded Beta-Sheet Protein  [PDF]
Seung-Yeon Kim
Journal of Materials Science and Chemical Engineering (MSCE) , 2016, DOI: 10.4236/msce.2016.41003

Understanding the folding processes of a protein into its three-dimensional native structure only with its amino-acid sequence information is a long-standing challenge in modern science. Two- hundred independent folding simulations (starting from non-native conformations) and two- hundred independent unfolding simulations (starting from the folded native structure) are performed using the united-residue force field and Metropolis Monte Carlo algorithm for betanova (three-stranded antiparallel beta-sheet protein). From these extensive computer simulations, two representative folding pathways and two representative unfolding pathways are obtained in the reaction coordinates such as the fraction of native contacts, the radius of gyration, and the root- mean-square deviation. The folding pathways and the unfolding pathways are similar each other. The largest deviation between the folding pathways and the unfolding pathways results from the root-mean-square deviation near the folded native structure. In general, unfolding computer simulations could capture the essentials of folding simulations.

Human Neural Stem Cells Over-Expressing VEGF Provide Neuroprotection, Angiogenesis and Functional Recovery in Mouse Stroke Model
Hong J. Lee, Kwang S. Kim, In H. Park, Seung U. Kim
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000156
Abstract: Background Intracerebral hemorrhage (ICH) is a lethal stroke type. As mortality approaches 50%, and current medical therapy against ICH shows only limited effectiveness, an alternative approach is required, such as stem cell-based cell therapy. Previously we have shown that intravenously transplanted human neural stem cells (NSCs) selectively migrate to the brain and induce behavioral recovery in rat ICH model, and that combined administration of NSCs and vascular endothelial growth factor (VEGF) results in improved structural and functional outcome from cerebral ischemia. Methods and Findings We postulated that human NSCs overexpressing VEGF transplanted into cerebral cortex overlying ICH lesion could provide improved survival of grafted NSCs, increased angiogenesis and behavioral recovery in mouse ICH model. ICH was induced in adult mice by unilateral injection of bacterial collagenase into striatum. HB1.F3.VEGF human NSC line produced an amount of VEGF four times higher than parental F3 cell line in vitro, and induced behavioral improvement and 2–3 fold increase in cell survival at two weeks and eight weeks post-transplantation. Conclusions Brain transplantation of F3 human NSCs over-expressing VEGF near ICH lesion sites provided differentiation and survival of grafted human NSCs and renewed angiogenesis of host brain and functional recovery of ICH animals. These results suggest a possible application of the human neural stem cell line, which is genetically modified to over-express VEGF, as a therapeutic agent for ICH-stroke.
Human Motor Neurons Generated from Neural Stem Cells Delay Clinical Onset and Prolong Life in ALS Mouse Model
Hong J. Lee, Kwang S. Kim, Jin Ahn, Hye M. Bae, Inja Lim, Seung U. Kim
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0097518
Abstract: Amyotrophic lateral sclerosis (ALS) is the most common adult onset motor neuron disease. The etiology and pathogenic mechanisms of the disease remain unknown, and there is no effective treatment. Here we show that intrathecal transplantation of human motor neurons derived from neural stem cells (NSCs) in spinal cord of the SOD1G93A mouse ALS model delayed disease onset and extended life span of the animals. When HB1.F3.Olig2 (F3.Olig2) cells, stable immortalized human NSCs encoding the human Olig2 gene, were treated with sonic hedgehog (Shh) protein for 5–7 days, the cells expressed motor neuron cell type-specific phenotypes Hb9, Isl-1 and choline acetyltransferase (ChAT). These F3.Olig2-Shh human motor neurons were transplanted intrathecally in L5–L6 spinal cord of SOD1G93A mice, and at 4 weeks post-transplantation, transplanted F3.Olig2-Shh motor neurons expressing the neuronal phenotype markers NF, MAP2, Hb9, and ChAT were found in the ventral horn of the spinal cord. Onset of clinical signs in ALS mice with F3.Olig2-Shh motor neuron implants was delayed for 7 days and life span of animals was significantly extended by 20 days. Our results indicate that this treatment modality of intrathecal transplantation of human motor neurons derived from NSCs might be of value in the treatment of ALS patients without significant adverse effects.
Transplantation of human neural stem cells transduced with Olig2 transcription factor improves locomotor recovery and enhances myelination in the white matter of rat spinal cord following contusive injury
Dong H Hwang, Byung G Kim, Eun J Kim, Seung I Lee, In S Joo, Haeyoung Suh-Kim, Seonghyang Sohn, Seung U Kim
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-117
Abstract: HB1.F3 (F3) immortalized human NSC line was transduced with a retroviral vector encoding Olig2, an essential regulator of oligodendrocyte development. Overexpression of Olig2 in human NSCs (F3.Olig2) induced activation of NKX2.2 and directed differentiation of NSCs into oligodendrocyte lineage cells in vitro. Introduction of Olig2 conferred higher proliferative activity, and a much larger number of F3.Olig2 NSCs were detected by 7 weeks after transplantation into contused spinal cord than that of parental F3 NSCs. F3.Olig2 NSCs exhibited frequent migration towards the white matter, whereas F3 NSCs were mostly confined to the gray matter or around the lesion cavities. Most of F3.Olig2 NSCs occupying the spared white matter differentiated into mature oligodendrocytes. Transplantation of F3.Olig2 NSCs increased the volume of spared white matter and reduced the cavity volume. Moreover, F3.Olig2 grafts significantly increased the thickness of myelin sheath around the axons in the spared white matter. Finally, animals with F3.Olig2 grafts showed an improvement in the quality of hindlimbs locomotion.Transplantation of NSCs genetically modified to differentiate into an oligodendrocytic lineage may be an effective strategy to improve functional outcomes following spinal cord trauma. The present study suggests that molecular factors governing cell fate decisions can be manipulated to enhance reparative potential of the cell-based therapy.Traumatic spinal cord injury (SCI) results in severe and permanent neurological deficits. However, there is no single effective therapeutic option to improve functional outcomes. Intense research efforts, employing a rodent model of contusive injury which closely mimics human SCI, have identified that the pathology in the white matter incurred by injury is closely associated with the degree of functional deficits [1-3]. One of the important pathological processes in the white matter is a chronic and progressive demyelination of the spared axo
Human Microglia Transplanted in Rat Focal Ischemia Brain Induce Neuroprotection and Behavioral Improvement
Dashdemberel Narantuya,Atsushi Nagai,Abdullah Md. Sheikh,Junichi Masuda,Shotai Kobayashi,Shuhei Yamaguchi,Seung U. Kim
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011746
Abstract: Microglia are resident immunocompenent and phagocytic cells of central nervous system (CNS), which produce various cytokines and growth factors in response to injury and thereby regulate disease pathology. The purpose of this study is to investigate the effects of microglial transplantation on focal cerebral ischemia model in rat.
Simultaneous Second Harmonic Generation of Multiple Wavelength Laser Outputs for Medical Sensing
Seung Nam Son,Jae-Jin Song,Jin U. Kang,Chang-Seok Kim
Sensors , 2011, DOI: 10.3390/s110606125
Abstract: Multiple wavelength light sources in the medical spectral window region are useful for various medical sensing applications in tissue by distinguishing the absorption and scattering coefficients optically. We propose a simultaneous second harmonic generation of multiple wavelength fiber laser output using parallel channels of periodically-poled lithium niobate (PPLN) waveguides. High intensity dual wavelength lasing output is experimentally realized with two tunable fiber Bragg gratings of 1,547.20 nm and 1,554.48 nm for the efficient conversion to the half wavelengths, 773.60 nm and 777.24 nm, by using two parallel PPLN channels. Compared with a conventional dual second harmonic generation (SHG) configuration based on two different input wavelengths from each independent light source, this method has a relatively higher efficiency to align the input light beam into the adjacent parallel PPLN channels simultaneously. The use of fiber lasers offers several advantages since they are relatively inexpensive, provide high power in excess of tens of watts, are widely tunable, and can produce pulses from milliseconds to femtoseconds.
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