• The Korean Journal of Physiology and Pharmacology
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• 제23권6호
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• pp.483-491
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• 2019

Cordycepin exerts neuroprotective effects against excitotoxic neuronal death. However, its direct electrophysiological evidence in Alzheimer's disease (AD) remains unclear. This study aimed to explore the electrophysiological mechanisms underlying the protective effect of cordycepin against the excitotoxic neuronal insult in AD using whole-cell patch clamp techniques. ${\beta}$-Amyloid ($A{\beta}$) and ibotenic acid (IBO)-induced injury model in cultured hippocampal neurons was used for the purpose. The results revealed that cordycepin significantly delayed $A{\beta}$ + IBO-induced excessive neuronal membrane depolarization. It increased the onset time/latency, extended the duration, and reduced the slope in both slow and rapid depolarization. Additionally, cordycepin reversed the neuronal hyperactivity in $A{\beta}$ + IBO-induced evoked action potential (AP) firing, including increase in repetitive firing frequency, shortening of evoked AP latency, decrease in the amplitude of fast afterhyperpolarization, and increase in membrane depolarization. Further, the suppressive effect of cordycepin against $A{\beta}$ + IBO-induced excessive neuronal membrane depolarization and neuronal hyperactivity was blocked by DPCPX (8-cyclopentyl-1,3-dipropylxanthine, an adenosine $A_1$ receptor-specific blocker). Collectively, these results revealed the suppressive effect of cordycepin against the $A{\beta}$ + IBO-induced excitotoxic neuronal insult by attenuating excessive neuronal activity and membrane depolarization, and the mechanism through the activation of $A_1R$ is strongly recommended, thus highlighting the therapeutic potential of cordycepin in AD.

• 한국세라믹학회지
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• 제46권2호
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• pp.155-160
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• 2009

The reliability could be one of the essential properties for multilayer ceramic capacitor (MLCC) using in various electronic devices and the concentration and mobility of oxygen vacancy would play important role in the reliability. To investigate the migration behavior of oxygen vacancies, thermally stimulated depolarization current (TSDC) is adopted. In dielectric material of X5R MLCC, the TSD-Current peak observed around 150$^{\circ}C$ and 200$^{\circ}C$ which represented the migration of oxygen vacancy. Substituting Yttrium for Dysprosium in X5R MLCC showed higher migration activation energy and lower TSD current density.

• Journal of the Optical Society of Korea
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• 제18권2호
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• pp.184-187
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• 2014

This study examined the effects of particle size on the light scattering of a nano-sized color filter pigment used to obtain a range of colors in liquid crystal displays. The contrast ratio is one of the most important characteristics of liquid crystal displays. When a color filter is located between two crossed polarizers, the size of the pigment can give rise to a decrease in the contrast ratio due to Rayleigh scattering by the nanoparticles in the filter. The size effect of the color filter pigment on the contrast ratio was investigated in terms of the depolarization parameter. As an experimental result, the depolarization parameter increased with decreasing pigment size. Therefore, a smaller pigment size can reduce light leakage caused by light scattering in the color filter between two crossed polarizers. The depolarization function was also proposed as a useful function for predicting the decrease in the contrast ratio of the color filter.

• Corrosion Science and Technology
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• 제11권6호
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• pp.242-246
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• 2012

This measurement represents the effectiveness of sacrificial anode cathodic protection (SACP) system in a coastal bridge structure. To verify the cathodic protection (CP) effect, the monitoring sensor (DMS-100) that could measure potential, corrosion rate, current, concrete resistivity, and temperature was embedded. The measurement conducted for three years after CP system was installed. Specifically, due to the fact that fresh water and sea water was repeated in the bridge structure, this bridge structure presented special CP behavior. Measurement factors were CP potential, CP current, concrete resistivity, and depolarization potential. In addition, visual inspection was also carried out. As a result of current and depolarization measurement, CP system was well activated in most piers.

• 대한원격탐사학회지
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• 제28권1호
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• pp.1-9
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• 2012

대기중의 꽃가루를 원격 탐사 기술을 이용하여 실시간 연속적으로 수행한 연구는 현재까지 전무하다. 본 연구는 지상 라이다 원격 탐사 기술을 이용하여 꽃가루 대기 분포의 일변화를 실시간 연속적으로 모니터링 하였다. 지상 라이다를 이용한 관측은 5월 4일부터 6월 2일까지 광주과학기술원에서 지속적으로 수행되었다. 라이다 데이터의 소산계수 분석을 통하여 대기 에어러솔의 분포를 확인하고 편광소멸도를 이용하여 입자의 비구형성을 확인하였다. 관측 기간 중 5월 4일부터 9일까지 일출 이후 09시경부터 편광소멸도 값이 0.08에서 0.14로 높은 값이 지표면 가까이부터 관측되기 시작하여 정오경에 1.5 - 2.0 km까지 고도가 증가하다 이후 감소하기 시작하여 일출시간(18시 이후)에 사라지는 현상이 관측되었다. 이 때 일별 꽃가루 농도는 $1,000m^{-3}$ 이상의 높은 농도를 보여 편광소멸도의 증가가 꽃가루로부터 유발된 것임을 알 수 있었다. 라이다 편광소멸도 관측과 기상 자료와의 비교분석을 통하여 수목류가 방출한 꽃가루는 지표면 기온이 상승하고 대기 중 상대습도가 낮아지는 낮 시간 동안 대기경계층 고도까지 상승하지만 시간이 지남에 따라 기온의 하강과 상대습도의 증가, 그리고 풍속이 감소하면서 꽃가루의 관측 고도는 낮아져 늦은 오후 시간대부터는 꽃가루가 대기 중에서 사라지는 일정한 일변화 형태를 보임을 파악할 수 있었다.

• 대한한의학방제학회지
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• 제31권1호
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• pp.11-19
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• 2023

Objectives : The purpose of this study was to examine the effects of herbal medicines on pacemaker potentials of large intestinal interstitial Cells of Cajal (ICC) in mice. Methods : We made the ICC culture in large intestine in mice and used the electrophysiological method to record pacemaker potentials. Also we used MTT assay to check cell viability and examined the ICC protein expression by western blot. Results : 1.Glycyrrhiza uralensis Fischer (GF) (50-150 ㎍/ml) induced pacemaker depolarization and decreased frequency with concentration-dependent manners. EC₅₀ is 58.95 ㎍/ml. Angelica gigas (AG) (50-200 ㎍/ml) induced pacemaker depolarization and decreased frequency with concentration-dependent manners. EC₅₀ is 77.22 ㎍/ml. Poncirus fructus (PF) (10-100 ㎍/ml) induced pacemaker depolarization and decreased frequency with concentration-dependent manners. EC₅₀ is 13.39 ㎍/ml. Citrus unshiu S. Marcov. (CU) (10-500 ㎍/ml) induced pacemaker depolarization and decreased frequency with concentration-dependent manners. EC₅₀ is 139.80 ㎍/ml. Gardenia jasminoides J. Ellis (GJ) (100-500 ㎍/ml) induced pacemaker depolarization and decreased frequency with concentration-dependent manners. EC₅₀ is 78.70 ㎍/ml. Coptis chinensis (CC) (100-1000 ㎍/ml) induced pacemaker depolarization and decreased frequency with concentration-dependent manners. EC₅₀ is 138.10 ㎍/ml. Scutellaria baicalensis (SB) (10-100 ㎍/ml) had no effects on pacemaker potentials and decreased frequency with concentration-dependent manners. IC₅₀ is 18.34 ㎍/ml. Atractylodes macrocephala koidzumi (AM) (10-100 ㎍/ml) induced pacemaker hyperpolarizations and decreased frequency with concentration-dependent manners. IC₅₀ is 18.54 ㎍/ml. 2. PF, SB and AM had no effects on cell death in large ICC. 3. PF increased the ANO1 and c-kit protein expression and SB and AM increased the c-kit protein expression in large ICC. Conclusions : These results suggest that PF, SB, and AM are likely to be the optimal combination of herbal medicines that can be used to treat diseases such as gastrointestinal motility disorders such as irritable bowel syndrome.

• 대한전기학회논문지
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• 제39권4호
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• pp.357-363
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• 1990

A thermally stimulated current measurement using a temperature gradient (TG-TSC) has been applied to the study of dipolar depolarization in polymers. It has been clarified that theoretical analysis of TG-TSC in the initial rise region corresponds with the experimental results. We conclude that the experimental results on a cross-linked polyethy-lene (XLPE) film can be explained using the above relation and that the charasteristics obtained from the above theoretical analysis can be used for ascertaining the presence of a constant temperature gradient in a film.

• The Korean Journal of Physiology and Pharmacology
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• 제21권4호
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• pp.371-376
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• 2017

The caudal subnucleus of the spinal trigeminal nucleus (medullary dorsal horn; MDH) receives direct inputs from small diameter primary afferent fibers that predominantly transmit nociceptive information in the orofacial region. Recent studies indicate that reactive oxygen species (ROS) is involved in persistent pain, primarily through spinal mechanisms. In this study, we aimed to investigate the role of xanthine/xanthine oxidase (X/XO) system, a known generator of superoxide anion ($O_2{^-}$), on membrane excitability in the rat MDH neurons. For this, we used patch clamp recording and confocal imaging. An application of X/XO ($300{\mu}M/30mU$) induced membrane depolarization and inward currents. When slices were pretreated with ROS scavengers, such as phenyl N-tert-butylnitrone (PBN), superoxide dismutase (SOD), and catalase, X/XO-induced responses decreased. Fluorescence intensity in the DCF-DA and DHE-loaded MDH cells increased on the application of X/XO. An anion channel blocker, 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS), significantly decreased X/XO-induced depolarization. X/XO elicited an inward current associated with a linear current-voltage relationship that reversed near -40 mV. X/XO-induced depolarization reduced in the presence of $La^{3+}$, a nonselective cation channel (NSCC) blocker, and by lowering the external sodium concentration, indicating that membrane depolarization and inward current are induced by influx of $Na^+$ ions. In conclusion, X/XO-induced ROS modulate the membrane excitability of MDH neurons, which was related to the activation of NSCC.

• KSBB Journal
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• 제30권6호
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• pp.313-318
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• 2015

${\delta}$-Aminolevulinic acid (ALA) is an endogenous metabolite formed in the mitochondria from succinyl-CoA and glycine, and plays a key role in the living body as an intermediate of the compound in the porphyrin biosynthesis pathway. ALA has been commonly used in photodynamic therapy for several years, because ALA is of interest as a biodegradable mediator, a growth regulator, and an effective agent used in dermatology. Here, we determined which ALA derivatives were the most effective for the inhibition of the cell proliferation and growth of human fibroblast. As a result, we found that the treatment of ALA derivatives including ALA, ALAP (ALA phosphate salt), MAL (Methyl 5-aminolevulinate hydrochloride salt), PBGL (phophobilinogen lactam) and PBGH (phophobilinogen-HCl) could attenuate cell proliferation of human fibroblast cells. Among them, PBGH was the most effective derivative. In addition, PBGH treatment could induce mitochondrial membrane depolarization, leading to cell death of human fibroblast. These results suggest that mitochondrial membrane depolarization induced by ALA and PBGH treatment might be responsible for inhibition of cell proliferation and death. Taken together, our results propose the possibility that PBGH can be used as one of the effective drugs in human skin disease, psoriasis.

• International Journal of Oral Biology
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• 제38권1호
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• pp.5-12
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• 2013

Recent studies indicate that reactive oxygen species (ROS) can act as modulators of neuronal activity, and are critically involved in persistent pain primarily through spinal mechanisms. In this study, we investigated the effects of NaOCl, a ROS donor, on neuronal excitability and the intracellular calcium concentration ($[Ca^{2+}]_i$) in spinal substantia gelatinosa (SG) neurons. In current clamp conditions, the application of NaOCl caused a membrane depolarization, which was inhibited by pretreatment with phenyl-N-tert-buthylnitrone (PBN), a ROS scavenger. The NaOCl-induced depolarization was not blocked however by pretreatment with dithiothreitol, a sulfhydryl-reducing agent. Confocal scanning laser microscopy was used to confirm whether NaOCl increases the intracellular ROS level. ROS-induced fluorescence intensity was found to be increased during perfusion of NaOCl after the loading of 2',7'-dichlorofluorescin diacetate ($H_2DCF$-DA). NaOCl-induced depolarization was not blocked by pretreatment with external $Ca^{2+}$ free solution or by the addition of nifedifine. However, when slices were pretreated with the $Ca^{2+}$ ATPase inhibitor thapsigargin, NaOCl failed to induce membrane depolarization. In a calcium imaging technique using the $Ca^{2+}$-sensitive fluorescence dye fura-2, the $[Ca^{2+}]_i$ was found to be increased by NaOCl. These results indicate that NaOCl activates the excitability of SG neurons via the modulation of the intracellular calcium concentration, and suggest that ROS induces nociception through a central sensitization.