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Search Results: 1 - 10 of 6962 matches for " Myoung-Hwan Chi "
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Oxygen and an Extracellular Phase Transition Independently Control Central Regulatory Genes and Conidiogenesis in Aspergillus fumigatus
Myoung-Hwan Chi, Kelly D. Craven
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0074805
Abstract: Conidiogenesis is the primary process for asexual reproduction in filamentous fungi. As the conidia resulting from the conidiogenesis process are primarily disseminated via air currents and/or water, an outstanding question has been how fungi recognize aerial environments suitable for conidial development. In this study, we documented the somewhat complex development of the conidia-bearing structures, termed conidiophores, from several Aspergillus species in a subsurface (gel-phase) layer of solid media. A subset of the isolates studied was able to develop conidiophores in a gel-phase environment, but exposure to the aeriform environment was required for the terminal developmental transition from phialide cells to conidia. The remaining Aspergilli could not initiate the conidiogenesis process until they were exposed to the aeriform environment. Our observations of conidiophore development in high or low oxygen conditions in both aeriform and gel-phase environments revealed that oxygen and the aeriform state are positive environmental factors for inducing conidiogenesis in most of the aspergilli tested in this study. Transcriptional analysis using A. fumigatus strain AF293 confined to either the aeriform or gel-phase environments revealed that expression of a key regulatory gene for conidiophore development (AfubrlA) is facilitated by oxygen while expression of another regulatory gene controlling conidia formation from phialides (AfuabaA) was repressed regardless of oxygen levels in the gel-embedded environment. Furthermore, by comparing the developmental behavior of conidiation-defective mutants lacking genes controlling various regulatory checkpoints throughout the conidiogenesis pathway, we propose that this aerial response by the fungus requires both oxygen and the phase transition (solid to aeriform), with these environmental signals integrating into the upstream regulatory pathway and central regulatory pathway of conidiogenesis, respectively. Our findings provide not only novel insight into how fungi respond to an aerial environment to trigger development for airborne conidia production but also the relationship between environmental factors and conidiogenesis regulation in aspergilli.
A Novel Pathogenicity Gene Is Required in the Rice Blast Fungus to Suppress the Basal Defenses of the Host
Myoung-Hwan Chi,Sook-Young Park,Soonok Kim,Yong-Hwan Lee
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000401
Abstract: For successful colonization and further reproduction in host plants, pathogens need to overcome the innate defenses of the plant. We demonstrate that a novel pathogenicity gene, DES1, in Magnaporthe oryzae regulates counter-defenses against host basal resistance. The DES1 gene was identified by screening for pathogenicity-defective mutants in a T-DNA insertional mutant library. Bioinformatic analysis revealed that this gene encodes a serine-rich protein that has unknown biochemical properties, and its homologs are strictly conserved in filamentous Ascomycetes. Targeted gene deletion of DES1 had no apparent effect on developmental morphogenesis, including vegetative growth, conidial germination, appressorium formation, and appressorium-mediated penetration. Conidial size of the mutant became smaller than that of the wild type, but the mutant displayed no defects on cell wall integrity. The Δdes1 mutant was hypersensitive to exogenous oxidative stress and the activity and transcription level of extracellular enzymes including peroxidases and laccases were severely decreased in the mutant. In addition, ferrous ion leakage was observed in the Δdes1 mutant. In the interaction with a susceptible rice cultivar, rice cells inoculated with the Δdes1 mutant exhibited strong defense responses accompanied by brown granules in primary infected cells, the accumulation of reactive oxygen species (ROS), the generation of autofluorescent materials, and PR gene induction in neighboring tissues. The Δdes1 mutant displayed a significant reduction in infectious hyphal extension, which caused a decrease in pathogenicity. Notably, the suppression of ROS generation by treatment with diphenyleneiodonium (DPI), an inhibitor of NADPH oxidases, resulted in a significant reduction in the defense responses in plant tissues challenged with the Δdes1 mutant. Furthermore, the Δdes1 mutant recovered its normal infectious growth in DPI-treated plant tissues. These results suggest that DES1 functions as a novel pathogenicity gene that regulates the activity of fungal proteins, compromising ROS-mediated plant defense.
Homeobox Transcription Factors Are Required for Conidiation and Appressorium Development in the Rice Blast Fungus Magnaporthe oryzae
Seryun Kim,Sook-Young Park,Kyoung Su Kim,Hee-Sool Rho,Myoung-Hwan Chi,Jaehyuk Choi,Jongsun Park,Sunghyung Kong,Jaejin Park,Jaeduk Goh,Yong-Hwan Lee
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000757
Abstract: The appropriate development of conidia and appressoria is critical in the disease cycle of many fungal pathogens, including Magnaporthe oryzae. A total of eight genes (MoHOX1 to MoHOX8) encoding putative homeobox transcription factors (TFs) were identified from the M. oryzae genome. Knockout mutants for each MoHOX gene were obtained via homology-dependent gene replacement. Two mutants, ΔMohox3 and ΔMohox5, exhibited no difference to wild-type in growth, conidiation, conidium size, conidial germination, appressorium formation, and pathogenicity. However, the ΔMohox1 showed a dramatic reduction in hyphal growth and increase in melanin pigmentation, compared to those in wild-type. ΔMohox4 and ΔMohox6 showed significantly reduced conidium size and hyphal growth, respectively. ΔMohox8 formed normal appressoria, but failed in pathogenicity, probably due to defects in the development of penetration peg and invasive growth. It is most notable that asexual reproduction was completely abolished in ΔMohox2, in which no conidia formed. ΔMohox2 was still pathogenic through hypha-driven appressoria in a manner similar to that of the wild-type. However, ΔMohox7 was unable to form appressoria either on conidial germ tubes, or at hyphal tips, being non-pathogenic. These factors indicate that M. oryzae is able to cause foliar disease via hyphal appressorium-mediated penetration, and MoHOX7 is mutually required to drive appressorium formation from hyphae and germ tubes. Transcriptional analyses suggest that the functioning of M. oryzae homeobox TFs is mediated through the regulation of gene expression and is affected by cAMP and Ca2+ signaling and/or MAPK pathways. The divergent roles of this gene set may help reveal how the genome and regulatory pathways evolved within the rice blast pathogen and close relatives.
A New Algorithm for Sea Fog/Stratus Detection Using GMS-5 IR Data
A New Algorithm for Sea Fog/Stratus Detection Using GMS-5 IR Data

Myoung-Hwan AHN,Eun-Ha SOHN,Byong-Jun HWANG,
Myoung-Hwan AHN
,Eun-Ha SOHN,Byong-Jun HWANG

大气科学进展 , 2003,
Abstract: A new algorithm for the detection of fog/stratus over the ocean from the GMS-5 infrared (IR) channel data is presented. The new algorithm uses a clear-sky radiance composite map (CSCM) to compare the hourly observations of the IR radiance. The feasibility of the simple comparison is justified by the theoretical simulations of the fog effect on the measured radiance using a radiative transfer model. The simulation results show that the presence of fog can be detected provided the visibility is worse than 1 k...
Operational Implementation of the ATOVS Processing Procedure in KMA and Its Validation
Myoung-Hwan AHN,Mee-Ja KIM,Chu-Yong CHUNG,Ae-Sook SUH,
Myoung-Hwan AHN
,Mee-Ja KIM,Chu-Yong CHUNG,Ae-Sook SUH

大气科学进展 , 2003,
Abstract: The Korea Meteorological Administration (KMA) has processed the data from the advanced TOVS (ATOVS) onboard NOAA-16 satellite since May 2001. The operational production utilizes the AAPP (ATOVS and AVHRR Processing Package) of EUMETSAT and IAPP (International ATOVS Processing Package) of the University of Wisconsin. For the initial guess profiles, the predicted fields (usually 6 to 12 hour forecasted fields) from the global aviation model of NOAA/NCEP are used. The average number of profiles retrieved from the ATOVS data is about 1,300 for each morning and afternoon orbit at about 18 and 06 UTC, respectively. The retrieved temperature and dew point temperatures are provided to forecasters in real time and used for initialization of prediction models. With the advanced microwave sensor (AMSU; Advanced Microwave Sounding Unit), accuracy of the ATOVS products is expected to be better than that of the TOVS products, especially in cloudy conditions. Indeed, the preliminary results from a validation study with the collocated radiosonde data during a 8-month period, from May to December 2001, for the East Asia region show an improved accuracy of the ATOVS products for cloudy skies versus the TOVS, especially for higher altitudes. The RMS (Root Mean Square) difference between the ATOVS products and radiosonde data is about 1.3°C for both clear and cloudy conditions, except for near the ground and at higher altitudes, at around 200 hPa. There is no significant temporal variation of the error statistics at all pressure levels. In case of the water vapor mixing ratio, the largest difference is shown at lower altitudes, while the accuracy is much better for the clear sky cases than the cloudy sky cases. The bias and RMSE at lower altitudes is about 0.557 g kg 1 and 2.5 g kg 1 and decrease significantly with increasing altitude.
Derivation of Regression Coefficients for Sea Surface Temperature Retrieval over East Asia
Myoung-Hwan AHN,Eun-Ha SOHN,Byong-Jun HWANG,Chu-Yong CHUNG,Xiangqian WU,
Myoung-Hwan AHN
,Eun-Ha SOHN,Byong-Jun HWANG,Chu-Yong CHUNG,Xiangqian WU

大气科学进展 , 2006,
Abstract: Among the regression-based algorithms for deriving SST from satellite measurements, regionally optimized algorithms normally perform better than the corresponding global algorithm. In this paper, three algorithms are considered for SST retrieval over the East Asia region (15°–55°N, 105°–170°E), including the multi-channel algorithm (MCSST), the quadratic algorithm (QSST), and the Pathfinder algorithm (PFSST). All algorithms are derived and validated using collocated buoy and Geostationary Meteorological Satellite (GMS-5) observations from 1997 to 2001. An important part of the derivation and validation of the algorithms is the quality control procedure for the buoy SST data and an improved cloud screening method for the satellite brightness temperature measurements. The regionally optimized MCSST algorithm shows an overall improvement over the global algorithm, removing the bias of about 0.13°C and reducing the root-mean-square difference (rmsd) from 1.36°C to 1.26°C. The QSST is only slightly better than the MCSST. For both algorithms, a seasonal dependence of the remaining error statistics is still evident. The Pathfinder approach for deriving a season-specific set of coefficients, one for August to October and one for the rest of the year, provides the smallest rmsd overall that is also stable over time.
Regulated RalBP1 Binding to RalA and PSD-95 Controls AMPA Receptor Endocytosis and LTD
Kihoon Han,Myoung-Hwan Kim,Daniel Seeburg,Jinsoo Seo,Chiara Verpelli,Seungnam Han,Hye Sun Chung,Jaewon Ko,Hyun Woo Lee,Karam Kim,Won Do Heo,Tobias Meyer,Hyun Kim,Carlo Sala,Se-Young Choi,Morgan Sheng,Eunjoon Kim
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000187
Abstract: Long-term depression (LTD) is a long-lasting activity-dependent decrease in synaptic strength. NMDA receptor (NMDAR)–dependent LTD, an extensively studied form of LTD, involves the endocytosis of AMPA receptors (AMPARs) via protein dephosphorylation, but the underlying mechanism has remained unclear. We show here that a regulated interaction of the endocytic adaptor RalBP1 with two synaptic proteins, the small GTPase RalA and the postsynaptic scaffolding protein PSD-95, controls NMDAR-dependent AMPAR endocytosis during LTD. NMDAR activation stimulates RalA, which binds and translocates widespread RalBP1 to synapses. In addition, NMDAR activation dephosphorylates RalBP1, promoting the interaction of RalBP1 with PSD-95. These two regulated interactions are required for NMDAR-dependent AMPAR endocytosis and LTD and are sufficient to induce AMPAR endocytosis in the absence of NMDAR activation. RalA in the basal state, however, maintains surface AMPARs. We propose that NMDAR activation brings RalBP1 close to PSD-95 to promote the interaction of RalBP1-associated endocytic proteins with PSD-95-associated AMPARs. This suggests that scaffolding proteins at specialized cellular junctions can switch their function from maintenance to endocytosis of interacting membrane proteins in a regulated manner.
Regulated RalBP1 Binding to RalA and PSD-95 Controls AMPA Receptor Endocytosis and LTD
Kihoon Han equal contributor,Myoung-Hwan Kim equal contributor,Daniel Seeburg,Jinsoo Seo,Chiara Verpelli,Seungnam Han,Hye Sun Chung,Jaewon Ko,Hyun Woo Lee,Karam Kim,Won Do Heo,Tobias Meyer,Hyun Kim,Carlo Sala,Se-Young Choi,Morgan Sheng,Eunjoon Kim
PLOS Biology , 2009, DOI: 10.1371/journal.pbio.1000187
Abstract: Long-term depression (LTD) is a long-lasting activity-dependent decrease in synaptic strength. NMDA receptor (NMDAR)–dependent LTD, an extensively studied form of LTD, involves the endocytosis of AMPA receptors (AMPARs) via protein dephosphorylation, but the underlying mechanism has remained unclear. We show here that a regulated interaction of the endocytic adaptor RalBP1 with two synaptic proteins, the small GTPase RalA and the postsynaptic scaffolding protein PSD-95, controls NMDAR-dependent AMPAR endocytosis during LTD. NMDAR activation stimulates RalA, which binds and translocates widespread RalBP1 to synapses. In addition, NMDAR activation dephosphorylates RalBP1, promoting the interaction of RalBP1 with PSD-95. These two regulated interactions are required for NMDAR-dependent AMPAR endocytosis and LTD and are sufficient to induce AMPAR endocytosis in the absence of NMDAR activation. RalA in the basal state, however, maintains surface AMPARs. We propose that NMDAR activation brings RalBP1 close to PSD-95 to promote the interaction of RalBP1-associated endocytic proteins with PSD-95-associated AMPARs. This suggests that scaffolding proteins at specialized cellular junctions can switch their function from maintenance to endocytosis of interacting membrane proteins in a regulated manner.
Topical Application of Cudrania tricuspidata Stem Extract Inhibits Atopic Dermatitis-Like Skin Lesions in an NC/Nga Mouse Model: An Experimental Animal Study  [PDF]
Yoo-Sin Park, Shin-Hee Kim, Sang-Yeon Kim, Gae-Myoung Koh, Ju-Hwan Suh, Ju-Seop Kang
Pharmacology & Pharmacy (PP) , 2016, DOI: 10.4236/pp.2016.78044
Abstract:
Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by elevated immunoglobulin E (IgE), mast cell infiltration and skin lesions including pruritus, erythema and eczema. Cudrania tricuspidata extracts have been clinically administered for a long time in the East Asia including Korean and China as a home-remedy to diminish the inflammation of gastritis and hepatitis. To examine whether it works on AD or not, an AD-like animal model was experimented in this study. AD was induced by applying Dermatophagoides farinae (D. farinae) extract to the backs of 9-week old NC/Nga mice for 21 days. Following this, an ethanol extract of C. tricuspidata stems (EECT) was applied topically for 14 days to the sensitized skin, while distilled water was used as a control (EECT0 mice). Anti-AD effects of EECT were evaluated using scores for AD-like skin lesions, serum IgE levels and mast cell counts in the skin dermal layers to assess inflammation. Topically applied ethanol extract of Cudrania tricuspidata stems (EECT 7.5, 25 and 75 mg/mL) markedly reduced AD-like skin lesions after 4 days (by 30.1%, 31.4% and 38.5%, respectively) and also after 14 days (by 63.6%, 66.1% and 49.6%, respectively), while distilled water improved AD by 17.8% and 38.7%, respectively (p < 0.05). Serum IgE production was reduced in the EECT7.5, EECT25 and EECT75 groups after 4 days (by 57.6%, 65.9% and 59.3%, respectively) and after 14 days of the treatment (by 82.0%, 79.6% and 75.3%, respectively), while distilled water decreased it by 38.8% and 62.3% (p = 0.0001 and p = 0.0001, respectively). Mast cell counts increased after sensitization by D. farinae extract (p =
Spontaneous Symmetry Breaking of Population between Two Dynamic Attractors in a Driven Atomic Trap: Ising-class Phase Transition
Kihwan Kim,Myoung-Sun Heo,Ki-Hwan Lee,Kiyoub Jang,Heung-Ryoul Noh,Doochul Kim,Wonho Jhe
Physics , 2005, DOI: 10.1103/PhysRevLett.96.150601
Abstract: We have observed spontaneous symmetry breaking of atomic populations in the dynamic phase-space double-potential system, which is produced in the parametrically driven magneto-optical trap of atoms. We find that the system exhibits similar characteristics of the Ising-class phase transition and the critical value of the control parameter, which is the total atomic number, can be calculated. In particular, the collective effect of the laser shadow becomes dominant at large atomic number, which is responsible for the population asymmetry of the dynamic two-state system. This study may be useful for investigation of dynamic phase transition and temporal behaviour of critical phenomena.
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