• The Korean Journal of Physiology and Pharmacology
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• 제21권6호
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• pp.591-598
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• 2017

Propofol is known to cause vasorelaxation of several systemic vascular beds. However, its effect on the pulmonary vasculature remains controversial. In the present study, we investigated the effects of propofol on human pulmonary arteries obtained from patients who had undergone surgery. Arterial rings were mounted in a Multi-Myograph system for measurement of isometric forces. U46619 was used to induce sustained contraction of the intrapulmonary arteries, and propofol was then applied (in increments from $10-300{\mu}m$). Arteries denuded of endothelium, preincubated or not with indomethacin, were used to investigate the effects of propofol on isolated arteries. Propofol exhibited a bifunctional effect on isolated human pulmonary arteries contracted by U46619, evoking constriction at low concentrations ($10-100{\mu}m$) followed by secondary relaxation (at $100-300{\mu}m$). The extent of constriction induced by propofol was higher in an endothelium-denuded group than in an endothelium-intact group. Preincubation with indomethacin abolished constriction and potentiated relaxation. The maximal relaxation was greater in the endothelium-intact than the endothelium-denuded group. Propofol also suppressed $CaCl_2$-induced constriction in the 60 mM $K^+$-containing $Ca^{2+}$-free solution in a dose-dependent manner. Fluorescent imaging of $Ca^{2+}$ using fluo-4 showed that a 10 min incubation with propofol ($10-300{\mu}m$) inhibited the $Ca^{2+}$ influx into human pulmonary arterial smooth muscle cells induced by a 60 mM $K^+$-containing $Ca^{2+}$-free solution. In conclusion, propofol-induced arterial constriction appears to involve prostaglandin production by cyclooxygenase in pulmonary artery smooth muscle cells and the relaxation depends in part on endothelial function, principally on the inhibition of calcium influx through L-type voltage-operated calcium channels.

• 한국인터넷방송통신학회논문지
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• 제15권3호
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• pp.169-173
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• 2015

이 논문은 사용한지 13년 지난 운전 중 22 kV 케이블시스템을, 7년 동안 절연저항을 측정하여 그 결과를 연구한 논문이다. 우리는 발전소에서 설치 운전 중인 고전압 케이블이 시간에 따라 성능이 악화되는 현상의 추세를 결정하는 수명지수를 파악하였다. 위한 논문이다. 케이블 시스템은 시간에 따라 절연 저항이 감소한다. 초기 케이블 시스템은 아레니우스 열화 곡선을 따른다. 초기에는 수명 지수 n값이 9로 설계하였고, 이후 n값을 상향하여 16으로 결정하였다. 이유는 고전압에서 케이블이 동작할 경우, n값이 클 때 파괴특성이 높지 않고, n값이 낮은 값에서 파괴특성이 높았기 때문이다. 그러나 전압열화에 의하여 와이블 프롯을 따른 v-t 특성에 의하여 n값은 10~11의 값을 갖는 것을 확인하였다. 과거 케이블 설계 시 정한 n=9의 이론적 근거와 n=16 으로 높아진 원인을 파악함으로써 누설 전류 및 절연 저항의 선형적인 변화를 확인하였다. 단기적으로는 운전 중 케이블 시스템의 진단 평가에 활용되며, 장기적으로는 발전소 부하에서 동작 중인케이블 시스템의 설치 및 운영에 있어서 원가를 절감하기 위한 노력에 기여하고자 한다.

• The Korean Journal of Physiology
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• 제20권1호
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• pp.31-41
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• 1986

The sufficient myoplasmic $Ca^{++}$ to react with the contractile proteins is necessary to induce contraction of a cardiac muscle. These $Ca^{++}$ for the production of muscle contraction are supplied from the three recognized $Ca^{++}$ sources; internal $Ca^{++}$ release via the sarcoplasmic reticulum(SR), $Ca^{++}$ influx through a gated Ca-channel in the membrane as a Isi, and $Ca^{++}$ transport by the mechanism of Na/ca exchange. However, it is still controversial which $Ca^{++}$ sources act as a main contributor for myoplasmic $Ca^{++}$, Therefore, this study was undertaken in order to examine the $Ca^{++}$ sources for the contraction of frog ventricle. There is evidence that the SR is sparse in frog ventricular fibers, and that T-tubules are absent. Isolated ventricular strips of frog, Rana nigromaculata, were used in this experiment. Isometric tension was recorded by force transducer, and membrane potentials of ventricular muscles were measured through the intracellular glass microelectrodes, which were filled with 3M KCI and had resistance of $30{\pm}50M{\Omega}$. All experiments were performed at room temperature in a tris·buffered Ringer solution which was aerated with 100% $O_2$. Isotonic high K, low Na solution was used to induce K-contracture, K-contracture appeared at the concentration of 20 to 30mM-KCI and was potentiated in parallel with the increase in KCI concentration. The contracture had two components: an initial rapid phasic and a subsequent slow tonic contractile responses. Membrane Potentials measured at normal Ringer solution(2.5mM KCI) was -90 to -100 mV, and decreased linearly as the KCI concentration increased; -55mV at 20mM.KCI, -45mV at 30 mM.KCI, -30 mY at 50 mM.KCI, and -12 mV at 100 mM.KCI. K-contracture was evoked firstly at the membrane potential of -45 mV. The contracture was potentiated by the increase of bathing extracellular $Ca^{++}$ concentration. However, in the absence of $Ca^{++}$ the contracture was almost not induced by 50 mM.KCI solution. Caffeine(20mM) in normal Ringer solution, which is known to release $Ca^{++}$ from SR without substantial effects on the $Ca^{++}$ fluxes across the surface membrane, did not affect membrane potential and also not initiate contracture, but the caffeine in 20 mM-KCI Ringer solution produced a contracture. Above results suggest that the main $Ca^{++}$ source for the K·contracture of frog ventricle is $Ca^{++}$ influx through the voltage-dependent Ca-channel, and that in the K-contracture at the concentration of 100 mM-KCI, the mechanism of Na/ca exchange also partly contributs, in addition to the $Ca^{++}$ influx.

• The Korean Journal of Physiology and Pharmacology
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• 제2권3호
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• pp.297-305
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• 1998

This study used in vivo intracellular recording in rat hippocampus to evaluate the effect of lidocaine and MK-801 on the membrane properties and the synaptic responses of individual neurons to electrical stimulation of the commissural pathway. Cells in control group typically fired in a tonic discharge mode with an average firing frequency of $2.4{\pm}0.9$ Hz. Neuron in MK-801 treated group (0.2 mg/kg, i.p.) had an average input resistance of $3.28{\pm}5.7\;M{\Omega}$ and a membrane time constant of $7.4{\pm}1.8$ ms. These neurons exhibited $2.4{\pm}0.2$ ms spike durations, which were similar to the average spike duration recorded in the neurons of the control group. Slightly less than half of these neurons were firing spontaneously with an average discharge rate of $2.4{\pm}1.1$ Hz. The average peak amplitude of the AHP following the spikes in these groups was $7.4{\pm}0.6$ mV with respect to the resting membrane potential. Cells in MK-801 and lidocaine treated group (5 mg/kg, i.c.v.) had an average input resistance of $3.45{\pm}6.0\;M{\Omega}$ and an average time constant of $8.0{\pm}1.4$ ms. The cells were firing spontaneously at an average discharge rate of $0.6{\pm}0.4$ Hz. Upon depolarization of the membrane by 0.8 nA for 400 ms, all of the tested cells exhibited accommodation of spike discharge. The most common synaptic response contained an EPSP followed by early-IPSP and late-IPSP. Analysis of the voltage dependence revealed that the early-IPSP and late-IPSP were putative $Cl^--and\;K^+-dependent$, respectively. Systemic injection of the NMDA receptor blocker, MK-801, did not block synaptic responses to the stimulation of the commissural pathway. No significant modifications of EPSP, early-IPSP, or late-IPSP components were detected in the MK-801 and/or lidocaine treated group. These results suggest that MK-801 and lidocaine manifest their CNS effects through firing pattern of hippocampal pyramidal cells and neural network pattern by changing the synaptic efficacy and cellular membrane properties.

• The Korean Journal of Physiology and Pharmacology
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• 제24권6호
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• pp.555-561
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• 2020

TWIK-related two-pore domain K⁺ channel-2 (TREK-2) has voltage-independent activity and shows additional activation by acidic intracellular pH (pH_i) via neutralizing the E³³² in the cytoplasmic C terminal (Ct). We reported opposite regulations of TREK-2 by phosphatidylinositol 4,5-bisphosphate (PIP₂) via the alkaline K³³⁰ and triple Arg residues (R^355-357); inhibition and activation, respectively. The G³³⁴ between them appeared critical because its mutation (G³³⁴A) endowed hTREK-2 with tonic activity, similar to the mutation of the inhibitory K³³⁰ (K³³⁰A). To further elucidate the role of putative bent conformation at G³³⁴, we compared the dual mutation forms, K³³⁰A/G³³⁴A and G³³⁴A/R^355-7A, showing higher and lower basal activity, respectively. The results suggested that the tonic activity of G³³⁴A owes to a dominant influence from R^355-7. Since there are additional triple Arg residues (R^377-9) distal to R^355-7, we also examined the triple mutant (G³³⁴A/R^355-7A/R^377-9A) that showed tonic inhibition same with G³³⁴A/R^355-7A. Despite the state of tonic inhibition, the activation by acidic pH_i was preserved in both G³³⁴A/R^355-7A and G³³⁴A/R^355-7A/R^377-9A, similar to the R^355-7A. Also, the inhibitory effect of ATP could be commonly demonstrated under the activation by acidic pH_i in R^355-7A, G³³⁴A/R^355-7A, and G³³⁴A/R^355-7A/R^377-9A. These results suggest that the putative bent conformation at G³³⁴ is important to set the tug-of-war between K³³⁰ and R^355-7 in the PIP₂-dependent regulation of TREK-2.

• 대한화학회지
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• 제36권4호
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• pp.552-557
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• 1992

Chloramphenicol에 대한 미분 펄스 폴라로그래피 분석법을 연구하였다. Chloramphenicol은 Ag/AgCl(포화 KCl) 기준전극에 대하여 0.00∼-1.50 Volt 영역에서 pH 의존성을 갖는 하나의 환원 피이크를 나타내었다. 실온(20$^{\circ}C$)에서 측정한 피이크 전위(Ep)를 Chloramphenicol 용액의 pH에 대하여 조시하였을 때 직선적인 관계를 보여주었으며 pH 8.9에서 기울기(Ep/pH) 변화를 나타내었다. 기울기는 pH 2.7∼8.9 사이에서 -59.7mV/pH이었고 pH 8.9∼11.2 사이에서는 -24.3mV/pH이었다. pH 8.0 암모늄완충용액을 지지전해질로 사용하여 4.8 ${\times}$ 10$^{-7}$ M and 6.2 ${\times}$ 10$^{-5}$ M (0.16 ppm∼20 ppm), Chloramphenicol 용액의 피이크 전류(ip)를 농도에 대하여 도시하였을 때 직선성을 나타내었다. Chlormaphenicol에 대한 미분 펄스 폴라로그래피법과 공정서 방법인 278nm에서의 자외선 흡수분광분석법 사이에 상관계수는 0.996으로서 우수한 상관관계를 나타내었다. Chloramphenicol을 약알칼리성(pH 8.0) 용액에서 장기간 보관시 분해 생성물의 검출은 미분펄스 폴라로그래피법이 분광분석법보다 용이하였다.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 2002년도 학술대회지
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• pp.392-400
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• 2002

We have previously found that the saponins but not other components in the ginseng reduce the secretion of catecholamines (CAs) from bovine adrenal chromaffin cells, a model of sympathetic nerves, evoked by acetylcholine (ACh) due to the blockade of $Na^+$ influx through nicotinic ACh receptor-operated cation channels, and it has been concluded that the inhibitory effect may be associated with the anti-stress action of ginseng. However, the saponins, which showed the great reduction of the CA secretion, were mainly the protopanaxiatriols. The protopanaxadiol and oleanolic acid saponins had a little or little such effect. Recent studies demonstrated that the oligosaccharides connected to the hydroxyl groups of the aglycones of the saponins are in turn hydrolyzed by gastric acid and enzymes in the intestinal bacteria when the ginseng is orally administrated. In this study, the effects of their major 6 kinds of metabolites on the secretion of CAs were investigated. All metabolites (M1, 2, 3 and 5 derived from the protopanaxadiols, and M4 and 11 from the protopanaxiatriols) reduced the ACh-evoked secretion from the cells. In the metabolites, the M4 inhibition was the most potent ($IC_{50}({\mu}M):M4(9)$ < M2 (18) < M3 (19) < M1l (22) < M5 (36) < MI (38)). Although M4 also reduced the CA secretion induced by high $K^+$, a stimulation activating voltage-sensitive $Ca^{2+}$ channels, the inhibitory effect was much less than that on the ACh-evoked secretion. M4 inhibited the ACh-induced $Na^+$ influx into the cells in a concentration-dependent manner similar to that of the inhibition of the ACh-evoked secretion. When the cells were washed by the incubation buffer after the preincubation of the cells with M4 and then incubated without M4 in the presence of ACh, the M4 inhibition was not completely abolished. On the other hand, its inhibition was maintained even by increasing the external ACh concentration. These results indicate that the saponins are metabolized to the more active substances in the digestive tract and the metabolites attenuate the secretion of CAs from bovine adrenal chromaffin cells stimulated by ACh due to the noncompetitive blockade of the ACh-induced $Na^+$ influx into the cells. These findings may further explain the anti-stress action of ginseng.

• 한국자기학회지
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• 제18권4호
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• pp.142-146
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• 2008

마그네트론 스퍼터링방법으로 제작한 다층박막 $[Pt/Co]_N-IrMn$에 측정자기장이 박막면에 수직한 방향에서 면방향으로 각도 $\theta$방향으로 인가될때, 교환결합바이어스($H_{ex}$)와 보자력($H_c$)의 각도의존성이 측정되었다. 자기이력곡선은 인가 자기장축 뿐 아니라 자화축에 대하여도 그 원점이 이동하여 비대칭을 나타내었다. $H__{ex}$와 $H_c$는 각도$\theta$에 대하여 각각 $1/cos{\theta}$과 $1/|cos{\theta}|$ 의존성을 나타내며, 이와 같은 각도의존특성은 자기장냉각(박막면에 수직방향)을 통하여 생긴 강한 수직자기이방성에 기인하는 것을 알 수 있다.

• 한국결정성장학회지
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• 제29권4호
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• pp.179-186
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• 2019

본 연구에서는 $Ga_2O_3$ 박막의 구조적 특성과 Ti/Au 전극을 증착하여 제작된 metal-semiconductor-metal (MSM) photodetector 소자의 광학적, 전기적 특성에 대해 연구하였다. 유기 금속 화학 증착법(metal organic chemical vapor deposition, MOCVD)을 이용해 서로 다른 온도에서 $Ga_2O_3$ 박막을 성장하였다. 성장온도에 따라 $Ga_2O_3$의 결정상이 ${\varepsilon}$-상에서 ${\beta}$-상으로 변화하는 것을 확인할 수 있었다. X-선 회절 분석(X-ray diffraction, XRD) 결과로 ${\varepsilon}-Ga_2O_3$의 결정구조를 확인하였고, 주사 전자 현미경(scanning electron microscopy, SEM) 이미지로 결정구조의 형성 메커니즘에 대해 논의하였다. 음극선 발광(Cathode luminescence, CL) 측정으로 $Ga_2O_3$의 발광성 천이에 관여하는 에너지 준위의 형성 원인에 대해 논의하였다. 제작된 MSM photodetector 소자의 외부 광에 대한 전류-전압 특성과 시간 의존성 on/off 광 응답 특성을 통해 ${\varepsilon}-Ga_2O_3$로 제작한 photodetector는 가시광보다 266 nm UV 파장 영역에서 훨씬 뛰어난 광전류 특성을 보이는 것을 확인하였다.

• 한국정보통신학회논문지
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• 제25권11호
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• pp.1627-1634
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• 2021

본 논문은 저전력 뉴럴 네트워크 가속기 SOC를 위한 아날로그 Convolution Filter용 저전력 초소형 ADC 회로 및 칩 설계 기술을 소개한다. 대부분의 딥러닝의 학습과 추론을 할 수 있는 Convolution neural network accelerator는 디지털회로로 구현되고 있다. 이들은 수많은 곱셈기 및 덧셈기를 병렬 구조로 구현하며, 기존의 복잡한 곱셉기와 덧셈기의 디지털 구현 방식은 높은 전력소모와 큰 면적을 요구하는 문제점을 가지고 있다. 이 한계점을 극복하고자 본 연구는 디지털 Convolution filter circuit을 Analog multiplier와 Accumulator, ADC로 구성된 Analog Convolution Filter로 대체한다. 본 논문에서는 최소의 칩면적와 전력소모로 Analog Accumulator의 아날로그 결과 신호를 디지털 Feature 데이터로 변환하는 8-bit SAR ADC를 제안한다. 제안하는 ADC는 Capacitor Array의 모든 Capacitor branch에 Split capacitor를 삽입하여 모든 branch의 Capacitor 크기가 균등하게 Unit capacitor가 되도록 설계하여 칩면적을 최소화 한다. 또한 초소형 unit capacitor의 Voltage-dependent capacitance variation 문제점을 제거하기 Flipped Dual-Capacitor 회로를 제안한다. 제안하는 ADC를 TSMC CMOS 65nm 공정을 이용하여 설계하였으며, 전체 chip size는 1355.7㎛², Power consumption은 2.6㎼, SNDR은 44.19dB, ENOB는 7.04bit의 성능을 달성하였다.