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Search Results: 1 - 10 of 351807 matches for " Hong J. Lee "
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An update of blood donor recruitment and retention in Hong Kong
Lee C,Hong J,Hung ATF
Asian Journal of Transfusion Science , 2008,
Abstract: A healthy blood donor pool has to be well maintained in order to achieve self sufficiency in blood supply. Not only should new and young donors should be attracted and recruited into the pool so as to compensate the loss from drop out and deferred donors. At the same time, previous donors should be also actively retained to ensure they can come regularly. The status of donor recruitment and retention in Hong Kong is reviewed here to highlight the current difficulties in coping with increasing blood demand from an ageing population, stringent donor eligibility criteria and quality requirement in the blood collection. With a systemic analysis of the donation pattern, proposal is put forward to tackle the challenging problems.
Subtle cytotoxicity and genotoxicity differences in superparamagnetic iron oxide nanoparticles coated with various functional groups
Hong SC,Lee JH,Lee J,Kim HY
International Journal of Nanomedicine , 2011,
Abstract: Seong Cheol Hong1,*, Jong Ho Lee1,*, Jaewook Lee1, Hyeon Yong Kim1, Jung Youn Park2, Johann Cho3, Jaebeom Lee1, Dong-Wook Han11Department of Nanomedical Engineering, BK21 Nano Fusion Technology Division, College of Nanoscience and Nanotechnology, Pusan National University, 2Department of Biotechnology Research, National Fisheries Research and Development Institute, Busan, 3Electronic Materials Lab, Samsung Corning Precision Materials Co, Ltd, Gumi City, Gyeongsangbukdo, Korea*These authors contributed equally to this workAbstract: Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely utilized for the diagnosis and therapy of specific diseases, as magnetic resonance imaging (MRI) contrast agents and drug-delivery carriers, due to their easy transportation to targeted areas by an external magnetic field. For such biomedical applications, SPIONs must have multifunctional characteristics, including optimized size and modified surface. However, the biofunctionality and biocompatibility of SPIONs with various surface functional groups of different sizes have yet to be elucidated clearly. Therefore, it is important to carefully monitor the cytotoxicity and genotoxicity of SPIONs that are surfaced-modified with various functional groups of different sizes. In this study, we evaluated SPIONs with diameters of approximately 10 nm and 100~150 nm, containing different surface functional groups. SPIONs were covered with –O-groups, so-called bare SPIONs. Following this, they were modified with three different functional groups – hydroxyl (–OH), carboxylic (–COOH), and amine (–NH2) groups – by coating their surfaces with tetraethyl orthosilicate (TEOS), (3-aminopropyl)trimethoxysilane (APTMS), TEOS-APTMS, or citrate, which imparted different surface charges and sizes to the particles. The effects of SPIONs coated with these functional groups on mitochondrial activity, intracellular accumulation of reactive oxygen species, membrane integrity, and DNA stability in L-929 fibroblasts were determined by water-soluble tetrazolium, 2',7'-dichlorodihydrofluorescein, lactate dehydrogenase, and comet assays, respectively. Our toxicological observations suggest that the functional groups and sizes of SPIONs are critical determinants of cellular responses, degrees of cytotoxicity and genotoxicity, and potential mechanisms of toxicity. Nanoparticles with various surface modifications and of different sizes induced slight, but possibly meaningful, changes in cell cytotoxicity and genotoxicity, which would be significantly valuable in further studies of bioconjugation
Higher dimensional cosmological model with a phantom field
S. T. Hong,J. Lee,T. H. Lee,P. OH
Physics , 2008, DOI: 10.1103/PhysRevD.78.047503
Abstract: We consider a higher dimensional gravity theory with a negative kinetic energy scalar field and a cosmological constant. We find that the theory admits an exact cosmological solution for the scale factor of our universe. It has the feature that the universe undergoes a continuous transition from deceleration to acceleration at some finite time. This transition time can be interpreted as that of recent acceleration of our universe.
Subtle cytotoxicity and genotoxicity differences in superparamagnetic iron oxide nanoparticles coated with various functional groups
Hong SC, Lee JH, Lee J, Kim HY, Park JY, Cho J, Lee J, Han DW
International Journal of Nanomedicine , 2011, DOI: http://dx.doi.org/10.2147/IJN.S26355
Abstract: btle cytotoxicity and genotoxicity differences in superparamagnetic iron oxide nanoparticles coated with various functional groups Original Research (4218) Total Article Views Authors: Hong SC, Lee JH, Lee J, Kim HY, Park JY, Cho J, Lee J, Han DW Published Date December 2011 Volume 2011:6 Pages 3219 - 3231 DOI: http://dx.doi.org/10.2147/IJN.S26355 Seong Cheol Hong1,*, Jong Ho Lee1,*, Jaewook Lee1, Hyeon Yong Kim1, Jung Youn Park2, Johann Cho3, Jaebeom Lee1, Dong-Wook Han1 1Department of Nanomedical Engineering, BK21 Nano Fusion Technology Division, College of Nanoscience and Nanotechnology, Pusan National University, 2Department of Biotechnology Research, National Fisheries Research and Development Institute, Busan, 3Electronic Materials Lab, Samsung Corning Precision Materials Co, Ltd, Gumi City, Gyeongsangbukdo, Korea *These authors contributed equally to this work Abstract: Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely utilized for the diagnosis and therapy of specific diseases, as magnetic resonance imaging (MRI) contrast agents and drug-delivery carriers, due to their easy transportation to targeted areas by an external magnetic field. For such biomedical applications, SPIONs must have multifunctional characteristics, including optimized size and modified surface. However, the biofunctionality and biocompatibility of SPIONs with various surface functional groups of different sizes have yet to be elucidated clearly. Therefore, it is important to carefully monitor the cytotoxicity and genotoxicity of SPIONs that are surfaced-modified with various functional groups of different sizes. In this study, we evaluated SPIONs with diameters of approximately 10 nm and 100~150 nm, containing different surface functional groups. SPIONs were covered with –O-groups, so-called bare SPIONs. Following this, they were modified with three different functional groups – hydroxyl (–OH), carboxylic (–COOH), and amine (–NH2) groups – by coating their surfaces with tetraethyl orthosilicate (TEOS), (3-aminopropyl)trimethoxysilane (APTMS), TEOS-APTMS, or citrate, which imparted different surface charges and sizes to the particles. The effects of SPIONs coated with these functional groups on mitochondrial activity, intracellular accumulation of reactive oxygen species, membrane integrity, and DNA stability in L-929 fibroblasts were determined by water-soluble tetrazolium, 2',7'-dichlorodihydrofluorescein, lactate dehydrogenase, and comet assays, respectively. Our toxicological observations suggest that the functional groups and sizes of SPIONs are critical determinants of cellular responses, degrees of cytotoxicity and genotoxicity, and potential mechanisms of toxicity. Nanoparticles with various surface modifications and of different sizes induced slight, but possibly meaningful, changes in cell cytotoxicity and genotoxicity, which would be significantly valuable in further studies of bioconjugation and cell interaction for drug delivery, cell cu
Altered Neural and Behavioral Dynamics in Huntington's Disease: An Entropy Conservation Approach
S. Lee Hong, Scott J. Barton, George V. Rebec
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030879
Abstract: Background Huntington's disease (HD) is an inherited condition that results in neurodegeneration of the striatum, the forebrain structure that processes cortical information for behavioral output. In the R6/2 transgenic mouse model of HD, striatal neurons exhibit aberrant firing patterns that are coupled with reduced flexibility in the motor system. The aim of this study was to test the patterns of unpredictability in brain and behavior in wild-type (WT) and R6/2 mice. Methodology/Principal Findings Striatal local field potentials (LFP) were recorded from 18 WT and 17 R6/2 mice (aged 8–11 weeks) while the mice were exploring a plus-shaped maze. We targeted LFP activity for up to 2 s before and 2 s after each choice-point entry. Approximate Entropy (ApEn) was calculated for LFPs and Shannon Entropy was used to measure the probability of arm choice, as well as the likelihood of making consecutive 90-degree turns in the maze. We found that although the total number of choice-point crossings and entropy of arm-choice probability was similar in both groups, R6/2 mice had more predictable behavioral responses (i.e., were less likely to make 90-degree turns and perform them in alternation with running straight down the same arm), while exhibiting more unpredictable striatal activity, as indicated by higher ApEn values. In both WT and R6/2 mice, however, behavioral unpredictability was negatively correlated with LFP ApEn. Conclusions/Significance HD results in a perseverative exploration of the environment, occurring in concert with more unpredictable brain activity. Our results support the entropy conservation hypothesis in which unpredictable behavioral patterns are coupled with more predictable brain activation patterns, suggesting that this may be a fundamental process unaffected by HD.
Synthesis and Biological Analysis of Thiotetra(ethylene glycol) monomethyl Ether-Functionalized Porphyrazines: Cellular Uptake and Toxicity Studies
Sangwan Lee,Benjamin J. Vesper,Hong Zong,Neal D. Hammer
Metal-Based Drugs , 2007, DOI: 10.1155/2008/391418
Abstract: The porphyrazines (pzs), a class of porphyrin analogues, are being investigated for their potential use as tumor imaging/therapeutic agents. We here examine six peripherally-functionalized M[pz(AnB4-n)] pzs with n=4, 3, or 2 (in a trans conformation) and M = H2 or Zn, where A is an [S((CH2)2O)4Me]2 unit and B is a fused 2, 2 ¢ € 2-diisopropyloxybenzo group. Cell viability/proliferation assays and fluorescence microscopy were carried out in both tumor and normal cells. Dark toxicity studies disclosed that four of the compounds exhibited toxicity in both normal and tumor cells; one was nontoxic in both normal and tumor cells, and one was selectively toxic to normal cells. Additionally, three of the pzs showed enhanced photo-induced toxicity with these effects in some cases being observed at treatment concentrations of up to ten-fold lower than that needed for a response in Photofrin. All six compounds were preferentially absorbed by tumor cells, suggesting that they have potential as in vitro diagnostic agents and as aids in the isolation and purification of aberrant cells from pathological specimens. In particular, two promising diagnostic candidates have been identified as part of this work.
Unsupervised Video Shot Detection Using Clustering Ensemble with a Color Global Scale-Invariant Feature Transform Descriptor
Yuchou Chang,D. J. Lee,Yi Hong,James Archibald
EURASIP Journal on Image and Video Processing , 2008, DOI: 10.1155/2008/860743
Abstract: Scale-invariant feature transform (SIFT) transforms a grayscale image into scale-invariant coordinates of local features that are invariant to image scale, rotation, and changing viewpoints. Because of its scale-invariant properties, SIFT has been successfully used for object recognition and content-based image retrieval. The biggest drawback of SIFT is that it uses only grayscale information and misses important visual information regarding color. In this paper, we present the development of a novel color feature extraction algorithm that addresses this problem, and we also propose a new clustering strategy using clustering ensembles for video shot detection. Based on Fibonacci lattice-quantization, we develop a novel color global scale-invariant feature transform (CGSIFT) for better description of color contents in video frames for video shot detection. CGSIFT first quantizes a color image, representing it with a small number of color indices, and then uses SIFT to extract features from the quantized color index image. We also develop a new space description method using small image regions to represent global color features as the second step of CGSIFT. Clustering ensembles focusing on knowledge reuse are then applied to obtain better clustering results than using single clustering methods for video shot detection. Evaluation of the proposed feature extraction algorithm and the new clustering strategy using clustering ensembles reveals very promising results for video shot detection.
Electron focusing, mode spectroscopy and mass enhancement in small GaAs/AlGaAs rings
J Liu,K Ismail,KY Lee,JM Hong,S Washburn
Physics , 1992, DOI: 10.1103/PhysRevB.47.13039
Abstract: A new electron focusing effect has been discovered in small single and coupled GaAs/AlGaAs rings. The focusing in the single ring is attributed solely to internal orbits. The focusing effect allows the ring to be used as a small mass spectrometer. The focusing causes peaks in the magnetoresistance at low fields, and the peak positions were used to study the dispersion relation of the one-dimensional magnetoelectric subbands. The electron effective mass increases with the applied magnetic field by a factor of $50$, at a magnetic field of $0.5T$. This is the first time this increase has been measured directly. General agreement obtains between the experiment and the subband calculations for straight channels.
Midkine, heparin-binding growth factor, blocks kainic acid-induced seizure and neuronal cell death in mouse hippocampus
Yun B Kim, Jae K Ryu, Hong J Lee, In J Lim, Dongsun Park, Min C Lee, Seung U Kim
BMC Neuroscience , 2010, DOI: 10.1186/1471-2202-11-42
Abstract: Increased expression of MK was found in hippocampus of mouse following seizures induced by intracerebroventricular injection of KA, and MK expression was found in glial fibrillary acidic protein (GFAP)-positive astrocytes. Concurrent injection of MK and KA attenuated KA-induced seizure activity and cell death of hippocampal neurons including pyramidal cells and glutamic acid decarboxylase 67 (GAD67)-positive GABAergic interneurons in the CA3 and hilar area.The results of the present study indicate that MK functions as an anticonvulsant and neuroprotective agent in hippocampus during KA-induced seizures.Temporal lobe epilepsy (TLE) is pathologically characterized by extensive neuronal loss in the CA1, CA3 and hilar regions of hippocampus [1,2]. Previous studies have demonstrated that the animal models of TLE generated by intracerebroventricular injection of kainic acid (KA) faithfully reproduce clinical and pathological features found in human TLE [3-7].Previous studies have reported the possible involvement of neurotrophic factors in epilepsy as suggested by the gene expression of neurotrophic factors such as NGF, BDNF and NT-3 in hippocampus in human TLE as well as in TLE animal models [8,9]. Midkine (MK), one of such neurotrophic factors, has emerged as an important neuromodulator in the central nervous system (CNS). MK, a member of the heparin-binding growth factor family, which includes MK and pleiotrophin, is known to possess neurotrophic and neuroprotective properties [10,11]. MK was originally isolated as the product of retinoic acid-responsive gene that functions primarily in inducing cell differentiation in mouse teratocarcinoma cells [12], and has the ability to influence a variety of neuronal functions including neurite extension [13], neuronal differentiation [14,15] and neuronal survival following injury or damage in the CNS [15,16]. During the fetal development of the CNS, MK expression was demonstrated in neuroepithelial/neural progenitor cells follow
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.
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