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Search Results: 1 - 10 of 1998 matches for " Junsung Woo "
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Columnar distribution of activity dependent gabaergic depolarization in sensorimotor cortical neurons
Lee Jaekwang,Woo Junsung,Favorov Oleg V,Tommerdahl Mark
Molecular Brain , 2012, DOI: 10.1186/1756-6606-5-33
Abstract: Background GABA, the major inhibitory neurotransmitter in CNS, has been demonstrated to paradoxically produce excitation even in mature brain. However activity-dependent form of GABA excitation in cortical neurons has not been observed. Here we report that after an intense electrical stimulation adult cortical neurons displayed a transient GABA excitation that lasted for about 30s. Results Whole-cell patch recordings were performed to evaluate the effects of briefly applied GABA on pyramidal neurons in adult rodent sensorimotor cortical slice before and after 1 s, 20 Hz suprathreshold electrical stimulation of the junction between layer 6 and the underlying white matter (L6/WM stimulation). Immediately after L6/WM stimulation, GABA puffs produced neuronal depolarization in the center of the column-shaped region. However, both prior to or 30s after stimulation GABA puffs produced hyperpolarization of neurons. 2-photon imaging in neurons infected with adenovirus carrying a chloride sensor Clomeleon revealed that GABA induced depolarization is due to an increase in [Cl-]i after stimulation. To reveal the spatial extent of excitatory action of GABA, isoguvacine, a GABAA receptors agonist, was applied right after stimulation while monitoring the intracellular Ca2+ concentration in pyramidal neurons. Isoguvacine induced an increase in [Ca2+]i in pyramidal neurons especially in the center of the column but not in the peripheral regions of the column. The global pattern of the Ca2+ signal showed a column-shaped distribution along the stimulation site. Conclusion These results demonstrate that the well-known inhibitory transmitter GABA rapidly switches from hyperpolarization to depolarization upon synaptic activity in adult somatosensory cortical neurons.
Channel-mediated astrocytic glutamate release via Bestrophin-1 targets synaptic NMDARs
Han Kyung-Seok,Woo Junsung,Park Hyungju,Yoon Bong-June
Molecular Brain , 2013, DOI: 10.1186/1756-6606-6-4
Abstract: Background Astrocytes regulate neuronal excitability and synaptic activity by releasing gliotransmitters such as glutamate. Our recent study demonstrated that astrocytes release glutamate upon GPCR activation via Ca2+ activated anion channel, Bestrophin-1 (Best1). The target of Best1-mediated astrocytic glutamate has been shown to be the neuronal NMDA receptors (NMDAR). However, whether it targets synaptically or extra-synaptically localized NMDAR is not known. Findings We recorded spontaneous miniature excitatory postsynaptic currents (mEPSCs) from CA1 pyramidal cells to test whether Best1-mediated astrocytic glutamate targets synaptic NMDAR. An agonist of protease activated receptor 1 (PAR1) was used to induce astrocytic Ca2+ increase and glutamate release. Firstly, we found that activation of PAR1 and subsequent release of glutamate from astrocyte does not alone increase the frequency of mEPSCs. Secondly, we found that mEPSC rise time is variable depending on the different electrotonic distances from the somatic recording site to the synaptic region where each mEPSC occurs. Two subgroups of mEPSC from CA1 pyramidal neuron by rise time were selected and analyzed. One group is fast rising mEPSCs with a rise time of 1 ~ 5 ms, representing synaptic activities arising from proximal dendrites. The other group is slowly rising mEPSCs with a rise time of 5 ~ 10 ms, representing synaptic events arising from glutamate release at synapses located in the distal dendrites. We used cell-type specific Best1 gene silencing system by Cre-loxP cleavage to dissociate the effect of neuronal and astrocytic Best1. Astrocytic Best1-mediated glutamate release by PAR1 activation did not affect decay kinetics, frequency, and amplitude of fast rising mEPSC. In contrast, PAR1 activation resulted in an NMDA receptor component to be present on slowly rising mEPSC, but did not alter frequency or amplitude. Conclusions Our results indicate that astrocytic glutamate via Best1 channel targets and activates synaptic NMDARs.
Development operators on 4D moving object databases
重庆邮电大学学报(自然科学版) , 2004,
The amount of astrocytic GABA positively correlates with the degree of tonic inhibition in hippocampal CA1 and cerebellum
Bo-Eun Yoon, Seonmi Jo, Junsung Woo, Jae-Hoon Lee, Taekeun Kim, Daesoo Kim, C Justin Lee
Molecular Brain , 2011, DOI: 10.1186/1756-6606-4-42
Abstract: Tonic inhibition originates from the sustained activation of high affinity gamma-aminobutyric acid (GABA) receptors by ambient GABA [1]. Tonic current is typically seen during electrophysiological recordings as a continuous current, which is blocked by the GABAA receptor blockers such as GABAzine, picrotoxin and bicuculline. Because of its persistent increase in input conductance, tonic inhibition dominates over the conventional (phasic) synaptic inhibition in controlling neuronal excitability [1]. Thus, tonic inhibition plays an important role in neuronal information processing [2], and it has been implicated in epilepsy, absence seizure, sleep, memory, cognition and motor impairment [3-6].Tonic inhibition was first identified in the cerebellum, where it is particularly prominent [7]. Recently, more studies on tonic inhibition have been performed in various regions including hippocampus and thalamus [8-11]. So far, tonic inhibition has been demonstrated in dentate granule cells [9,11], thalamocortical neurons in thalamus [5], pyramidal neurons in neocortex [12] and neurons of motor cortex [13].Unlike those brain regions, Tonic inhibition in hippocampal CA1 region is somewhat controversial. It is reported to be absent in the pyramidal neurons of hippocampal CA1 and could be detected only in early development or in specific circumstances [10]. Other investigators reported tonic inhibition currents in pyramidal neuron after pre-incubating with GABA-transaminase inhibitor or GABA [3,14] to artificially enhance the ambient GABA level. These studies indicated that pyramidal neurons express high affinity extrasynaptic GABA receptors, ready to sense tonic GABA release. Similarly, Semyanov et al. could not observe tonic inhibition in pyramidal neurons both in stratum oriens and stratum radiatum unless the extracellular GABA concentration was elevated experimentally [15-17]. However, significant tonic inhibition was found in the interneurons of hippocampal CA1 region [16]. T
Imiquimod enhances excitability of dorsal root ganglion neurons by inhibiting background (K2P) and voltage-gated (Kv1.1 and Kv1.2) potassium channels
Jaekwang Lee, Taekeun Kim, Jinpyo Hong, Junsung Woo, Hyunjung Min, Eunmi Hwang, Sung Lee, C Justin Lee
Molecular Pain , 2012, DOI: 10.1186/1744-8069-8-2
Abstract: When IQ was applied to DRG neurons, we observed an increase in action potential (AP) duration and membrane resistance both in wild type and TLR7-deficient mice. Based on these results, we tested whether the treatment of IQ has an effect on the activity of K+ channels, Kv1.1 and Kv1.2 (voltage-gated K+ channels) and TREK1 and TRAAK (K2P channels). IQ effectively reduced the currents mediated by both K+ channels in a dose-dependent manner, acting as an antagonist at TREK1 and TRAAK and as a partial antagonist at Kv1.1 and Kv1.2.Our results demonstrate that IQ blocks the voltage-gated K+ channels to increase AP duration and K2P channels to increase membrane resistance, which are critical for the membrane excitability of DRG neurons. Therefore, we propose that IQ enhances the excitability of DRG neurons by blocking multiple potassium channels and causing pruritus.Imiquimod (IQ) is widely used to treat various skin diseases such as molluscum contagiosum, basal cell carcinoma, and Bowen's disease [1]. Topical application of the compound is currently approved for treatment of genital warts, a highly contagious sexually transmitted disease caused by human papillomavirus [1-5]. It is believed that IQ modulates immune responses via Toll-like receptor 7 (TLR7) releasing IFN-α/β and proinflammatory cytokines [6]. Nevertheless, the exact mechanism of how IQ activates the immune system is not fully understood. Despite its clinical importance, the most prominent side effect of IQ is pruritus, e.g. itching sensation [7,8]. The mechanism of how IQ causes itching sensation has remained unknown.Recently we and others reported that IQ-induced depolarization in dorsal root ganglion (DRG) neurons leads to itching behavior [7,8]. Even though these two studies agreed upon IQ's action on the cellular and behavioral level, there was a profound discrepancy on the molecular target of IQ. The study by Liu et al. reported that membrane depolarization caused by IQ required TLR7 to generate action
Reliability Design of Ice-Maker System Subjected to Repetitive Loading  [PDF]
Seong-Woo Woo
Engineering (ENG) , 2016, DOI: 10.4236/eng.2016.89056
Abstract: Parametric Accelerated Life Testing (ALT) was used to improve the reliability of ice-maker system with a fractured helix upper dispenser in field. By using bond graphs and state equations, a variety of mechanical loads in the assembly were analyzed. The acceleration factor was derived from a generalized life-stress failure model with a new load concept. To reproduce the failure modes and mechanisms causing the fracture, new sample size equation was derived. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly reproduce early failure in field. Consequently, the failure modes and mechanisms found were identical with those of the failed sample. The design of this testing should help an engineer uncover the design parameters affecting the reliability of fractured helix upper dispenser in field. By eliminating the design flaws, gaps and weldline, the B1 life of the redesign of helix upper dispenser is now guaranteed to be over 10 years with a yearly failure rate of 0.1% that is the reliability quantitative test specifications (RQ).
Effect of On-Line Hemodiafiltration on Dry Weight Adjustment in Intradialytic Hypotension-Prone Patients: Comparative Study of Conventional Hemodialysis and On-Line Hemodiafiltration  [PDF]
Sun Woo Kang
Open Journal of Nephrology (OJNeph) , 2014, DOI: 10.4236/ojneph.2014.41001

Introduction: Correct adjustment of dry weight after hemodialysis (HD) with no signs of hypervolemia is important. Intradialytic hypotension (IDH) is the most common complication during HD. IDH occurs in 15% to 30% and possibly in up to 50% of dialysis sessions. IDH augments mortality essentially due to chronic overhydration and the inability to reach the proper dry weight. On-line hemodiafiltration (ol-HDF) has been reported to reduce the frequency of IDH. The aim of this study was to assess the effect of ol-HDF on hemodynamic stability and dry weight adjustment compared with low-flux HD. Methods: IDH-prone HD patients at our center were enrolled. This study was designed as a crossover trial with two phases (A arm: low-flux HD for 8 weeks followed by ol-HDF for 8 weeks vs. B arm: ol-HDF for 8 weeks followed by low-flux HD for 8 weeks) and two treatment arms (ol-HDF vs. low-flux HD), each phase lasting 8 weeks. We measured the proportion of body water using a body composition monitor (BCM). Results: In a comparison of the systolic blood pressure (SBP) and diastolic blood pressure (DBP) reductions from the baseline blood pressure between the HD and ol-HDF groups, statistically significant differences were observed only in the SBP of the B arm (SBP: HD vs. HDF, -9.83 ± 6.64 vs. -4.62 ± 1.61 mmHg, p = 0.036; DBP: HD vs. HDF, -3.29 ± 4.05 vs. -1.86 ± 1.49 mmHg, p = 0.261). Neither the mean of the interdialytic body weight gains nor the frequency of IDH was different between the A and B arms (p = 0.817 and p = 0.562, respectively). In terms of dialysis modality, there were no significant differences in the amount of overhydration between the conventional

One-wave optical phase conjugation mirror by actively coupling arbitrary light fields into a single-mode reflector
KyeoReh Lee,Junsung Lee,Jung-Hoon Park,Ji-Ho Park,YongKeun Park
Physics , 2015, DOI: 10.1103/PhysRevLett.115.153902
Abstract: Rewinding the arrow of time via phase conjugation is an intriguing phenomena made possible by the wave property of light. To exploit this phenomenon, diverse research fields have pursed the realization of an ideal phase conjugation mirror, but an optical system that requires a single-input and a single-output beam, like natural conventional mirrors has never been demonstrated. Here, we demonstrate the realization of a one-wave optical phase conjugation mirror using a spatial light modulator. An adaptable single-mode filter is created, and a phase-conjugate beam is then prepared by reverse propagation through this filter. Our method is simple, alignment free, and fast while allowing high power throughput in the time reversed wave, which have not been simultaneously demonstrated before. Using our method, we demonstrate high throughput full-field light delivery through highly scattering biological tissue and multimode fibers, even for quantum dot fluorescence.
Improving the Reliability of a Domestic Refrigerator Compressor Subjected to Repetitive Loading  [PDF]
Seong-Woo Woo, Dennis L. O’Neal
Engineering (ENG) , 2016, DOI: 10.4236/eng.2016.83012
Abstract: As a reliability quantitative specification, parametric accelerated life testing was used to assess the reliability of a newly designed compressor of a commercial refrigerator subjected to repetitive stresses. A generalized life-stress failure model and new sample size equation with a new load concept were derived starting with the basic refrigeration cycle. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly evaluate the expected lifetime. The design of this testing should help an engineer uncover the design parameters affecting reliability during the design process of the compressor system. Consequently, it should help companies improve product reliability and avoid recalls due to the product failures in the field. A newly designed compressor in a commercial refrigerator was used as a test case.
Forest decline of the world: A linkage with air pollution and global warming
SY Woo
African Journal of Biotechnology , 2009,
Abstract: Various forest declines and forest health conditions have been described for forest ecosystems throughout the world. The connection to global warming and air pollution is clear in some area, but not in others. In this study, some evidences that support or contradict air pollution and global warming being causal factors in reported cases of decline in Eastern North America, Central Europe and Republic of Korea. Many studies suggested that forest decline phenomenon seems to be strongly associated to air pollution and global warming.
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