Ca ²⁺ Entry is Required for Mechanical Stimulation-induced ATP Release from Astrocyte

Lee, Jaekwang,Chun, Ye-Eun,Han, Kyung-Seok,Lee, Jungmoo,Woo, Dong Ho,Lee, C. Justin The Korean Society for Brain and Neural Science 2015 Experimental Neurobiology Vol.24 No.1

<P>Astrocytes and neurons are inseparable partners in the brain. Neurotransmitters released from neurons activate corresponding G protein-coupled receptors (GPCR) expressed in astrocytes, resulting in release of gliotransmitters such as glutamate, D-serine, and ATP. These gliotransmitters in turn influence neuronal excitability and synaptic activities. Among these gliotransmitters, ATP regulates the level of network excitability and is critically involved in sleep homeostasis and astrocytic Ca<SUP>2+</SUP> oscillations. ATP is known to be released from astrocytes by Ca<SUP>2+</SUP>-dependent manner. However, the precise source of Ca<SUP>2+</SUP>, whether it is Ca<SUP>2+</SUP> entry from outside of cell or from the intracellular store, is still not clear yet. Here, we performed sniffer patch to detect ATP release from astrocyte by using various stimulation. We found that ATP was not released from astrocyte when Ca<SUP>2+</SUP> was released from intracellular stores by activation of Gα<SUB>q</SUB>-coupled GPCR including PAR1, P2YR, and B2R. More importantly, mechanical stimulation (MS)-induced ATP release from astrocyte was eliminated when external Ca<SUP>2+</SUP> was omitted. Our results suggest that Ca<SUP>2+</SUP> entry, but not release from intracellular Ca<SUP>2+</SUP> store, is critical for MS-induced ATP release from astrocyte.</P>

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

Lee, Hyeon Jun,Guo, Er-Jia,Min, Taewon,Hwang, Seung Hyun,Lee, Su Yong,Dorr, Kathrin,Lee, Jaekwang,Jo, Ji Young Tsinghua Press, co-published with Springer-Verlag 2018 NANO RESEARCH Vol.11 No.7

<P>Atomic movement under application of external stimuli (i.e., electric field or mechanical stress) in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscopy, time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO3 film, the hysteresis loop of the reflected X-ray intensity was found to result from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-field-induced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. The effect of external stress on the BiFeO3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.</P>

Study of Food/Nutrition-Based Hearing Protection

Jaekwang Lee 한국식품영양과학회 2022 한국식품영양과학회 학술대회발표집 Vol.2022 No.10

Attenuated Glial K ⁺ Clearance Contributes to Long-Term Synaptic Potentiation Via Depolarizing GABA in Dorsal Horn Neurons of Rat Spinal Cord

Lee, Jaekwang,Favorov, Oleg V,Tommerdahl, Mark,Lee, C. Justin,Whitsel, Barry L. The Korean Society for Brain and Neural Science 2014 Experimental Neurobiology Vol.23 No.1

<P>It has been reported that long-term enhancement of superficial dorsal horn (DH<SUB>s</SUB>) excitatory synaptic transmission underlies central sensitization, secondary hyperalgesia, and persistent pain. We tested whether impaired clearance of K<SUP>+</SUP> and glutamate by glia in DH<SUB>s</SUB> may contribute to initiation and maintenance of the CNS pain circuit and sensorimotor abnormalities. Transient exposure of the spinal cord slice to fluorocitrate (FC) is shown to be accompanied by a protracted <I>decrease</I> of the DH<SUB>s</SUB> optical response to repetitive electrical stimulation of the ipsilateral dorsal root, and by a similarly protracted <I>increase</I> in the postsynaptic response of the DH<SUB>s</SUB> like LTP. It also is shown that LTP<SUB>FC</SUB><I>does not</I> occur in the presence of APV, and becomes progressively <I>smaller</I> as [K<SUP>+</SUP>]<SUB>o</SUB> in the perfusion solution decreased from 3.0 mM to 0.0 mM. Interestingly LTP<SUB>FC</SUB> is <I>reduced</I> by bath application of Bic. Whole-cell patch recordings were carried out to evaluate the effects of FC on the response of DH<SUB>s</SUB> neurons to puffer-applied GABA. The observations reveal that transient exposure to FC is reliably accompanied by a prolonged (>1 hr) depolarizing shift of the equilibrium potential for the DH<SUB>s</SUB> neuron transmembrane ionic currents evoked by GABA. Considered collectively, the findings demonstrate that LTP<SUB>FC</SUB> involves (1) elevation of [K<SUP>+</SUP>]<SUB>o</SUB> in the DH<SUB>s</SUB>, (2) NMDAR activation, and (3) conversion of the effect of GABA on DH<SUB>s</SUB> neurons from inhibition to excitation. It is proposed that a transient impairment of astrocyte energy production can trigger the cascade of dorsal horn mechanisms that underlies hyperalgesia and persistent pain.</P>

Reduction of Epitaxial MoO2 to Mo by High-temperature Hydrogen Annealing

Lee Joonhyuck,Kim Hyun Jung,Ahn Eunyoung,Lee Jaekwang,Seo Ambrose,Jeen Hyoungjeen 한국물리학회 2023 새물리 Vol.73 No.2

The molybdenum oxide (MoO2) reduction process using hydrogen gas at elevated temperatures is commonly used to purify Mo metal. We report a methodology to reduce epitaxial MoO2 films using diluted hydrogen gas comprising 3% hydrogen and 97% argon. Under the reaction temperature that is similar to the reduction process of bulk MoO2, it is remarkable that oxygen-free epitaxial Mo metal films are created according to structural characterizations and spectroscopic studies. The result of this study helps in understanding the reduction process of epitaxial binary oxides.

IoT Analysis and Processing System using Sensed Data for Laboratory Safety Management

HyunSeong Lee,SeoungHyeon Lee,JaeKwang Lee 대한전자공학회 2019 IEIE Transactions on Smart Processing & Computing Vol.8 No.4

This study proposes and implements a real-time message analysis processing system using sensed data for safety management of a laboratory composed of Internet of Things (IoT) sensor devices. Existing IoT systems have difficulty storing data in a relational database system due to the different data formats between sensor devices, and they also have preprocessing overhead due to nonstandard communications protocols. Furthermore, they are centralized systems with unstable service continuity, and it is difficult to add new functions or extend the system because of the complex connections among sensor devices and services. Studies on real-time analysis and processing of large volumes of sensor data are also insufficient. To address these problems, the proposed system uses IoT sensor devices, based on standard communications protocols, and message queue brokers based on standard messaging protocols. The message queue brokers can facilitate adding sensor devices or services by delivering the sensor data from the gateway and central server to the services. Services can continue, even in the event of network trouble, because the services that had been provided from the central server are now provided through smart gateways. The central server can provide risk analysis and prevention services for laboratory safety management through Apache Spark, a real-time big data analysis and processing platform. Through the experiments in this study, the proposed real-time message analysis processing system for laboratory safety management was implemented. The message queue brokers between the standard Message Queuing Telemetry Transport (MQTT) protocol and the smart gateway receiving the data were built into sensor devices equipped with network and sensor modules. Exchange routing keys are also specified by topic and service for each sensor device in line with the laboratory safety management environment. Data transmission processing is handled by a federated connection of the gateway brokers and the central server brokers.

Acute Liver Failure Secondary to Hepatic Infiltration of Malignant Melanoma

Yujin Lee,Jaekwang Lee,Hyunsoo Kim,Changkeun Park,Jaekwon Jung,Daejin Kim,Yun Jin Chung,Hanjun Ryu 대한소화기내시경학회 2022 Clinical Endoscopy Vol.55 No.2

Acute liver failure due to malignant melanoma is uncommon. We presents a case of acute liver failure secondary to hepatic infiltrationof a malignant melanoma. An 86-year-old man was admitted with elevated liver enzymes and an increased lactate dehydrogenaselevel. His condition progressed to acute liver failure, but the etiology of liver failure was unclear. Esophagogastroduodenoscopy wasperformed to evaluate dyspepsia, which showed signs indicative of malignant melanoma. Based on the endoscopy findings andelevated liver enzyme levels, liver biopsy was performed to confirm the presence of malignant melanoma. Hepatic infiltration ofmalignant melanoma was observed histologically. However, massive and diffuse liver metastasis is very rare and difficult to identifyon imaging studies. If the etiology of liver failure is unclear, diffuse metastatic melanoma infiltration should be considered asdifferential diagnosis. Early liver biopsy can help to clarify the diagnosis.

자기 위치 결정을 위한 SIFT 기반의 특징 지도 갱신 알고리즘

이재광(Jaekwang Lee),허욱열(Ukyoul Huh),김학일(Hakil Kim) 대한전기학회 2004 정보 및 제어 심포지엄 논문집 Vol.2004 No.1

Web Page Evaluation based on Implicit User Reactions and Neural Networks

Donghoon Lee,Jaekwang Kim,Jee-Hyong Lee 한국지능시스템학회 2012 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.12 No.2

This paper proposes a method for evaluating web pages by considering implicit user reaction on web pages. Usually users spend more time and make more reactions, such as clicking, dragging and scrolling, while reading interesting pages. Based on this observation, a web page evaluation method by observing implicit user reaction is proposed. The system is designed with Ajax for observing user reactions, and neural networks for learning correlation between user reactions and usefulness of pages. The amounts of each type of user reactions are inputted to neural networks. Also the numbers of characters and images of pages are used as inputs because the amount of users’ behaviors has a tendency to increase as the length of pages increase. The experiment is conducted with 113 people and 74 pages. Each page is ranked by users with a questionnaire. The proposed method shows more close ranking results to the user ranks than Google. That is, our system evaluates web pages more closely to users’ viewpoint than Google. Although our experiment is limited, our result shows powerful potential of new element for web page evaluation. Some approaches evaluate web pages with their contents and some evaluate web pages with structural attributes, particularly links, of pages. Web page evaluation is for users, so the best evaluation can be done by users themselves. So, user feedback is one of the most important factors for web page evaluation. This paper proposes a new method which reflects user feedbacks on web pages.

청각 기능 보호 개선 식의약 소재 개발 현황

이재광(Jaekwang Lee) 한국식품영양과학회 2020 식품산업과 영양 Vol.25 No.2