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Search Results: 1 - 10 of 27101 matches for " Kwang-Woo Lee "
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A mutation of HEXB gene in Sandhoff disease presenting as motor neuron disease
Ahn Suk-Won,Kim Su-Hyun,Hong Yoon-Ho,Lee Kwang-Woo
Neurology India , 2010,
Capnography for Assessing Nocturnal Hypoventilation and Predicting Compliance with Subsequent Noninvasive Ventilation in Patients with ALS
Sung-Min Kim,Kyung Seok Park,Hyunwoo Nam,Suk-Won Ahn,Suhyun Kim,Jung-Joon Sung,Kwang-Woo Lee
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017893
Abstract: Patients with amyotrophic lateral sclerosis (ALS) suffer from hypoventilation, which can easily worsen during sleep. This study evaluated the efficacy of capnography monitoring in patients with ALS for assessing nocturnal hypoventilation and predicting good compliance with subsequent noninvasive ventilation (NIV) treatment.
Amyotrophic Lateral Sclerosis Is Associated with Hypolipidemia at the Presymptomatic Stage in Mice
Sung-Min Kim,Heejaung Kim,Jee-Eun Kim,Kyung Seok Park,Jung-Joon Sung,Seung Hyun Kim,Kwang-Woo Lee
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017985
Abstract: To demonstrate that hypolipidemia is a typical feature of the mouse model of amyotrophic lateral sclerosis (ALS) and to assess the association between hypolipidemia and disease stage, dietary intake, and sex.
Factors Associated With the Time to Next Attack in Neuromyelitis Optica: Accelerated Failure Time Models With Random Effects
Sung-Min Kim, Junwoo Park, Sun Hee Kim, Su-Yeon Park, Jee Young Kim, Jung-Joon Sung, Kyung Seok Park, Kwang-Woo Lee
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082325
Abstract: Background and Objective Neuromyelitis optica (NMO) is an inflammatory demyelinating disorder of the central nervous system with a relapsing and remitting course. We aimed to identify factors associated with the time to next attack, including the effect of the natural disease course and the diverse treatment regimens, by applying a longitudinal statistical analysis to the individual attacks of each patient. Methods In total, 184 acute attacks among 58 patients with either NMO or NMO spectrum disorder with anti-aquaporin-4 antibody were assessed retrospectively. Patient demographics, clinical characteristics at each attack, and type of treatment during inter-attack periods were assessed. The dependent variable was defined as the time from each attack to the next attack (inter-attack interval). An exponential accelerated failure time model with shared gamma frailty was adapted for statistical analysis. Results A multivariable analysis revealed that the time from each attack to the next attack in NMO increased independently by 1.31 times (95% confidence interval (CI), 1.02–1.67; p = 0.035) with each additional cumulative attack experienced, by 5.34 times (95% CI, 1.57–18.13; p = 0.007) with combined azathioprine treatment and continued oral prednisolone, and by 4.26 times (95% CI, 1.09–16.61; p = 0.037) with rituximab treatment. Conclusion The time to next attack in NMO can increase naturally in the later stages of the disease as the number of cumulative attacks increases. Nevertheless, both combined azathioprine treatment with continued oral prednisolone and rituximab treatment were also associated with a longer time to next attack, independently of the natural disease course of NMO.
Nocturnal Hypoxia in ALS Is Related to Cognitive Dysfunction and Can Occur as Clusters of Desaturations
Su-Yeon Park, Sung-Min Kim, Jung-Joon Sung, Kyung-Min Lee, Kyung-Seok Park, Sang-Yun Kim, Hyun-woo Nam, Kwang-Woo Lee
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075324
Abstract: Background Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that leads to progressive weakness of the respiratory and limb muscles. Consequently, most patients with ALS exhibit progressive hypoventilation, which worsens during sleep. The aim of this study was to evaluate the relationship between nocturnal hypoxia and cognitive dysfunction and to assess the pattern of nocturnal hypoxia in patients with ALS. Method Twenty-five patients with definite or probable ALS underwent neuropsychologic testing, nocturnal pulse oximetry, and capnography. Patients were grouped according to the presence of nocturnal hypoxia (SpO2<95% for ≥10% of the night) and their clinical characteristics and cognitive function were compared. Results Compared to patients without nocturnal hypoxia, those with nocturnal hypoxia (n = 10, 40%) had poor memory retention (p = 0.039) and retrieval efficiency (p = 0.045). A cluster-of-desaturation pattern was identified in 7 patients (70%) in the Hypoxia Group. Conclusions These results suggest that nocturnal hypoxia can be related to cognitive dysfunction in ALS. In addition, a considerable number of patients with ALS may be exposed to repeated episodes of deoxygenation–reoxygenation (a cluster-of-desaturation pattern) during sleep, which could be associated with the generation of reactive oxygen species. Further studies are required to define the exact causal relationships between these phenomena, the exact manifestations of nocturnal cluster-of-desaturation patterns, and the effect of clusters of desaturation on ALS progression.
Intermittent Hypoxia Can Aggravate Motor Neuronal Loss and Cognitive Dysfunction in ALS Mice
Sung-Min Kim, Heejaung Kim, Jeong-Seon Lee, Kyung Seok Park, Gye Sun Jeon, Jeeheun Shon, Suk-Won Ahn, Seung Hyun Kim, Kyung Min Lee, Jung-Joon Sung, Kwang-Woo Lee
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081808
Abstract: Background Patients with ALS may be exposed to variable degrees of chronic intermittent hypoxia. However, all previous experimental studies on the effects of hypoxia in ALS have only used a sustained hypoxia model and it is possible that chronic intermittent hypoxia exerts effects via a different molecular mechanism from that of sustained hypoxia. No study has yet shown that hypoxia (either chronic intermittent or sustained) can affect the loss of motor neurons or cognitive function in an in vivo model of ALS. Objective To evaluate the effects of chronic intermittent hypoxia on motor and cognitive function in ALS mice. Methods Sixteen ALS mice and 16 wild-type mice were divided into 2 groups and subjected to either chronic intermittent hypoxia or normoxia for 2 weeks. The effects of chronic intermittent hypoxia on ALS mice were evaluated using the rotarod, Y-maze, and wire-hanging tests. In addition, numbers of motor neurons in the ventral horn of the spinal cord were counted and western blot analyses were performed for markers of oxidative stress and inflammatory pathway activation. Results Compared to ALS mice kept in normoxic conditions, ALS mice that experienced chronic intermittent hypoxia had poorer motor learning on the rotarod test, poorer spatial memory on the Y-maze test, shorter wire hanging time, and fewer motor neurons in the ventral spinal cord. Compared to ALS-normoxic and wild-type mice, ALS mice that experienced chronic intermittent hypoxia had higher levels of oxidative stress and inflammation. Conclusions Chronic intermittent hypoxia can aggravate motor neuronal death, neuromuscular weakness, and probably cognitive dysfunction in ALS mice. The generation of oxidative stress with activation of inflammatory pathways may be associated with this mechanism. Our study will provide insight into the association of hypoxia with disease progression, and in turn, the rationale for an early non-invasive ventilation treatment in patients with ALS.
Essential Roles of the Kar2/BiP Molecular Chaperone Downstream of the UPR Pathway in Cryptococcus neoformans
Kwang-Woo Jung, Hyun Ah Kang, Yong-Sun Bahn
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0058956
Abstract: The endoplasmic reticulum (ER) is a central hub where secreted or membrane-bound proteins are maturated and folded properly in eukaryotes. Maintenance of ER homeostasis is particularly important for human fungal pathogens, such as Cryptococcus neoformans, which encounter a plethora of host-mediated stresses during infection. Our previous study demonstrated that the unfolded protein response (UPR) pathway, composed of the evolutionarily conserved Ire1 kinase and the unique Hxl1 transcription factor, has pleiotropic roles in ER stress response, thermotolerance, antifungal drug resistance, and virulence in C. neoformans. Here, we functionally characterized an ER-resident molecular chaperone, Kar2/BiP, in C. neoformans. Conditional expression of KAR2 by the copper-regulated promoter revealed that Kar2 is essential for the viability of C. neoformans. Constitutive expression of KAR2 by the strong histone H3 promoter partially restores resistance to ER stress, cell wall stress, thermotolerance, and genotoxic stress in ire1Δ and hxl1Δ mutants, suggesting that Kar2 mainly functions downstream of the UPR pathway. Furthermore, Kar2 appears to control azole resistance in C. neoformans downstream of the UPR pathway without regulation of ERG11 or ERG3. Interestingly, we discovered that azole treatment is sensed as ER-stress and subsequently activates the Ire1-dependent Hxl1 splicing event and induction of KAR2 by the UPR pathway. In contrast, the constitutive expression of Kar2 is not sufficient to restore the Ire1-mediated regulation of capsule production in C. neoformans UPR mutants. In conclusion, this study demonstrates that Kar2 is not only essential for vegetative growth but also required for response and adaptation to the environmental stresses and antifungal drugs downstream of the UPR pathway in C. neoformans.
Hrk1 Plays Both Hog1-Dependent and -Independent Roles in Controlling Stress Response and Antifungal Drug Resistance in Cryptococcus neoformans
Seo-Young Kim,Young-Joon Ko,Kwang-Woo Jung,Anna Strain,Kirsten Nielsen,Yong-Sun Bahn
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018769
Abstract: The HOG (High Osmolarity Glycerol response) pathway plays a central role in controlling stress response, ergosterol biosynthesis, virulence factor production, and differentiation of Cryptococcus neoformans, which causes fatal fungal meningoencephalitis. Recent transcriptome analysis of the HOG pathway discovered a Hog1-regulated gene (CNAG_00130.2), encoding a putative protein kinase orthologous to Rck1/2 in Saccharomyces cerevisiae and Srk1 in Schizosaccharomyces pombe. Its function is not known in C. neoformans. The present study functionally characterized the role of Hrk1 in C. neoformans. Northern blot analysis confirmed that HRK1 expression depends on the Hog1 MAPK. Similar to the hog1Δ mutant, the hrk1Δ mutant exhibited almost complete resistance to fludioxonil, which triggers glycerol biosynthesis via the HOG pathway. Supporting this, the hrk1Δ mutant showed reduced intracellular glycerol accumulation and swollen cell morphology in response to fludioxonil, further suggesting that Hrk1 works downstream of the HOG pathway. However, Hrk1 also appeared to have Hog1-independent functions. Mutation of HRK1 not only further increased osmosensitivity of the hog1Δ mutant, but also suppressed increased azole-resistance of the hog1Δ mutant in an Erg11-independent manner. Furthermore, unlike the hog1Δ mutant, Hrk1 was not involved in capsule biosynthesis. Hrk1 was slightly involved in melanin production but dispensable for virulence of C. neoformans. These findings suggest that Hrk1 plays both Hog1-dependent and –independent roles in stress and antifungal drug susceptibility and virulence factor production in C. neoformans. Particularly, the finding that inhibition of Hrk1 substantially increases azole drug susceptibility provides a novel strategy for combination antifungal therapy.
Unique Evolution of the UPR Pathway with a Novel bZIP Transcription Factor, Hxl1, for Controlling Pathogenicity of Cryptococcus neoformans
Seon Ah Cheon equal contributor,Kwang-Woo Jung equal contributor,Ying-Lien Chen,Joseph Heitman,Yong-Sun Bahn ,Hyun Ah Kang
PLOS Pathogens , 2011, DOI: 10.1371/journal.ppat.1002177
Abstract: In eukaryotic cells, the unfolded protein response (UPR) pathway plays a crucial role in cellular homeostasis of the endoplasmic reticulum (ER) during exposure to diverse environmental conditions that cause ER stress. Here we report that the human fungal pathogen Cryptococcus neoformans has evolved a unique UPR pathway composed of an evolutionarily conserved Ire1 protein kinase and a novel bZIP transcription factor encoded by HXL1 (HAC1 and XBP1-Like gene 1). C. neoformans HXL1 encodes a protein lacking sequence homology to any known fungal or mammalian Hac1/Xbp1 protein yet undergoes the UPR-induced unconventional splicing in an Ire1-dependent manner upon exposure to various stresses. The structural organization of HXL1 and its unconventional splicing is widely conserved in C. neoformans strains of divergent serotypes. Notably, both C. neoformans ire1 and hxl1 mutants exhibited extreme growth defects at 37°C and hypersensitivity to ER stress and cell wall destabilization. All of the growth defects of the ire1 mutant were suppressed by the spliced active form of Hxl1, supporting that HXL1 mRNA is a downstream target of Ire1. Interestingly, however, the ire1 and hxl1 mutants showed differences in thermosensitivity, expression patterns for a subset of genes, and capsule synthesis, indicating that Ire1 has both Hxl1-dependent and -independent functions in C. neoformans. Finally, Ire1 and Hxl1 were shown to be critical for virulence of C. neoformans, suggesting UPR signaling as a novel antifungal therapeutic target.
Integrated Testing Environment of Instructor Station for SMART Simulator  [PDF]
Joon Ku Lee, Geun Ok Park, Keung Koo Kim, Woo Seok Huh, Kwang Young Sohn
Open Journal of Modelling and Simulation (OJMSi) , 2015, DOI: 10.4236/ojmsi.2015.32004
Abstract: SMART is the reactor that has been researched for many years by KAERI in order to provide the small-mid scale of power for typically seawater desalination. Now Korea Atomic Energy Research Institute (KAERI) has issued Standard Safety Analysis Report (SSAR) and acquired Standard Design Approval (SDA) for SMART. In order to conduct the design verification and validation for license, the integrated simulation test environment that is composed of 1) the system specific simulation codes formerly developed in the name of Nuclear Plant Analyzer (NPA) including NSSS and BOP simulation, 2) Instructor Station (IS), 3) Supervisory Control and Data Acquisition (SCADA), 4) operator and instructor Human Machine Interface (HMI), and 5) soft-controller has been considered as an important area for operator training and system validation. These sub-components has been designed and implemented for verifying and validating the SMART design and training of operators and for generating the backup data for licensing. This paper introduces the structure of integrated simulation test environment for SMART, explains the efforts to assist system-specific simulation code interface, and also addresses the effort for implementing and optimizing the test environment by maintaining its own simulation functionality and performance in order to review the simulation results efficiently.
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