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Electrophysiological Analysis of GABA and Glycine Action on Neurons of the Catfish Retina
Bai, Sun-Ho,Jung, Chang-Sub,Lee, Sung-Jong The Korean Physiological Society 1993 대한생리학회지 Vol.27 No.2
Vertebrate retinal neurons, like brain tracts farm complex synaptic relations in the enter and inner plexiform layers which ape equivalent to the central nervous system nuclei. The effects of $\gamma-aminobutyric$ acid(GABA) and glycine on retinal neurons were explored to discern the mechanisms of action of neurotransmitters. Experiments were performed in the superfused retina-eyecup preparation of the channel catfish, Ictalurus punctatus, using intracellular electrophysiological techniques. The roles of GABA and glycine as inhibitory neurotransmitters are well established in the vertebrate retina. But, we found that the depolarizing action of GABA and glycine on third-order neurons in the catfish retina. GABA and glycine appeared to act on retinal ueurons based on the observations that (1) effects on photoreceptors were not observed, (2) horizontal cells were either hyperpolarized $({\sim}33%)$ or depolarized $({\sim}67%)$, (3) bipolar cells were all hyperpolarized (4) amacrine and ganglion cells were either hyperpolarized $({\sim}37%)$ or depolarized $({\sim}63%)$, (5) GABA and glycine may be working to suppress presynaptic inhibition. The results suggest that depolarization of third-order neurons by GABA and glycine is due to at least two mechanisms; a direct postsynaptic effect and an indirect effect. Therefore, in the catfish retina, a mechanism of presynaptic inhibition or disinhibition including the direct postsynaptic effect may exist in the third-order neurons.
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배선호(Bai, Sun-Ho),김철(Kim, Chul) 대한생리학회 1975 대한생리학회지 Vol.9 No.1
뇌 해마가 전기충격에 의한 내력(tolerance)에 미치는 영향을 구명하기 위하여, 두정 후두 경계 부위의 대뇌피질을 양측성으로 둥글게 떼어내고, 이를 거쳐 해마를 평균 97%가량 떼어버린 흰쥐(해마군) 14마리와 해마를 덮는 대뇌피질 부분만을 떼어버린 흰쥐(대뇌피질 대조군) 17마리 및 두개골을 노출하는데 그치고 뇌에 손상을 주지 않은 흰쥐(정상 대조군) 17마리를 사용하여 다음과 같은 실험을 실시하였다. 24시간 동안 먹이 없이 물만으로 지나게 한 다음 구금판에 세 무리를 구금하고 24시간 동안 매회 1.5초 동안씩 계속되는 4mA의 교류전류에 의한 충격을 1분 간격으로 반복하여 폐사하는 동물의 수효를 세어 다음과 같은 결과를 얻었다. 1. 전기충격을 가하는 동안 폐사한 동물의 수효에서 해마군의 값은 두 대조군의 값에 비하여 유의하게 적었으나, 두 대조군 사이에는 이렇다 할 차가 없었다. 2. 전기충격으로 인하여 폐사한 예에서 전기충격의 시작부터 폐사할 때까지의 시간은 해마군의 값이 두 대조군의 값에 비하여 연장된 경향을 보여 주었다. 이상의 결과로 미루어 뇌 해마는 전기충격에 대한 내력(耐力)에 억제적 영향을 끼친다고 추리된다. A study was designed to clarify the influence of the hippocampus upon tolerance by electric shock. Forty-eight male rats were used, of which 14 rats had their hippocampal tissue on both sides removed through an opening in the parieto-occipital cortex (hippocampal group), 17 rats received damage to the parieto-occipital cortex only (cortical control group), and 17 rats served as normal control animals. After 24 hours fasting with water ad libitum, each animal was restrained on a plate with added electric shock (4 mA A.C., 1.5 sec in a duration, and once per minute in average) to the tail for the last 24 hours without food and water. The mortality in each animal group and the mean survival time of the dead animal during the repitition of electric shock were calculated. Results obtained were as follows: 1. The mortality was lower significantly in the hippocampal group than in the two control groups. 2. The mean survival time of the dead animal was longer insignificantly in the hippocampal group than in the two control groups. The inference from the above results is that the hippocampus exerts a inhibitory influence upon tolerance by electric shock.
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Two Types of Voltage-activated Calcium Currents in Goldfish Horizontal Cells
Sun-Sook Paik,Sun-Ho Bai,Chang-Sub Jung 대한생리학회-대한약리학회 2005 The Korean Journal of Physiology & Pharmacology Vol.9 No.5
In horizontal cells (HCs) that were freshly dissociated from goldfish retina, two types of voltage- dependent calcium currents (I<SUB>Ca</SUB>) were recorded using a patch-clamping configuration: a transient type current and a sustained type current. The cell was held at 40 mV, and the prepulse step of 90 mV was applied before command pulse between 65 and 55 mV. The transient Ca<SUP>2</SUP> current was activated by depolarization to around 50 mV from a prepulse voltage of 90 mV lasting at least 400 ms and reached a maximal value near 25 mV. On the other hand, the sustained Ca<SUP>2</SUP> current was induced by pre-inactivation for less than 10 ms duration. Its activation started near 10 mV and peaked at 20 mV. Co<SUP>2</SUP> (2 mM) suppressed both of these two components, but nifedipine (20μM), L-type Ca<SUP>2</SUP> channel antagonist, blocked only the sustained current. Based on the activation voltage and the pharmacological specificity, the sustained current appears to be similar to L-type I<SUB>Ca</SUB> and the transient type to T-type I<SUB>Ca</SUB>. This study is the first to confirm that transient type I<SUB>Ca</SUB> together with the sustained one is present in HCs dissociated from goldfish retina.
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Bai, Meng-Meng,Shi, Wei,Tian, Jun-Mian,Lei, Ming,Kim, Jang Hoon,Sun, Ya Nan,Kim, Young Ho,Gao, Jin-Ming American Chemical Society 2015 Journal of agricultural and food chemistry Vol.63 No.8
<P><I>Eucommia ulmoides</I> leaves have been used as a functional food and drink in China. The purpose of this study was to identify the bioactive constituents with soluble epoxide hydrolase (sEH) inhibitory activity and anti-inflammatory properties. Twenty-seven known compounds (<B>1</B>–<B>27</B>) were isolated from the leaves of <I>E. ulmoides</I> Oliver, and their structures were identified by NMR and ESIMS analysis; three of these, 2,5-dimethoxy-3-glucopyranosyl cinnamic alcohol (<B>11</B>), foliasalacioside E<SUB>2</SUB> (<B>26</B>), and icariside F<SUB>2</SUB> (<B>27</B>), were obtained from this plant for the first time. Compounds <B>1</B>–<B>7</B> exhibited soluble epoxide hydrolase (sEH) inhibitory activity at 100 μM; among them, quercetin (<B>1</B>) and kaempferol (<B>5</B>) displayed potential activities with IC<SUB>50</SUB> values of 22.5 ± 0.9 and 31.3 ± 2.6 μM, respectively, with noncompetitive inhibition mode. Nuclear factor kappa B (NF-κB) inhibitory activity of the isolated compounds was evaluated by the NF-κB liciferase assay in HepG2 cells. Compounds <B>1</B>, <B>9</B>, <B>20</B>, and <B>27</B> displayed potent NF-κB inhibitory effects, with IC<SUB>50</SUB> values of 15.14 ± 2.29, 15.23 ± 2.34, 16.88 ± 2.17, and 16.25 ± 2.19 μM, respectively, whereas other compounds showed weak inhibition of NF-κB transcriptional activity ranging from 17.54 to 92.6 μM. A structure–activity relationship of flavonoids <B>1</B>–<B>9</B> was also discussed. The results obtained in this work might contribute to the understanding of pharmacological activities of <I>E. ulmoides</I> leaves and further investigation on its potential application values for food and drug.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2015/jafcau.2015.63.issue-8/acs.jafc.5b00055/production/images/medium/jf-2015-00055j_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jf5b00055'>ACS Electronic Supporting Info</A></P>
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Ultra-fast Adaptive Frequency-controlled Hysteretic Buck Converter for Portable Devices
Kwang-Ho Kim,Bai-Sun Kong 대한전자공학회 2016 Journal of semiconductor technology and science Vol.16 No.5
The paper describes a hysteretic buck converter including a differentiator and an adaptive hysteresis window controller. Differentiating the feedback signal achieves ultra-fast switching of the buck converter. The adaptive hysteresis window control allows a monotonous operation with predictable noise spectrum, and gives way to efficient design for variable supply and output voltages. The measurement results in a 0.13-μm CMOS process indicated that the switching frequency became double times higher, and the voltage ripple was reduced by up to 69%. They also indicated that the normalized switching frequency variation was reduced by 74% with variable VDD and by 63% with variable VOUT. The power efficiency was improved by 3.5% depending on loading condition.
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Two Types of Voltage-activated Calcium Currents in Goldfish Horizontal Cells
Paik, Sun-Sook,Bai, Sun-Ho,Jung, Chang-Sub The Korean Society of Pharmacology 2005 The Korean Journal of Physiology & Pharmacology Vol.9 No.5
In horizontal cells (HCs) that were freshly dissociated from goldfish retina, two types of voltagedependent calcium currents ($I_{Ca}$) were recorded using a patch-clamping configuration: a transient type current and a sustained type current. The cell was held at -40 mV, and the prepulse step of -90 mV was applied before command pulse between -65 and +55 mV. The transient $Ca^{2+}$ current was activated by depolarization to around -50 mV from a prepulse voltage of -90 mV lasting at least 400 ms and reached a maximal value near -25 mV. On the other hand, the sustained $Ca^{2+}$ current was induced by pre-inactivation for less than 10 ms duration. Its activation started near -10 mV and peaked at +20 mV. $Co^{2+}$ (2 mM) suppressed both of these two components, but nifedipine ($20{\mu}M$), L-type $Ca^{2+}$ channel antagonist, blocked only the sustained current. Based on the activation voltage and the pharmacolog$I_{Ca}$l specificity, the sustained current appears to be similar to L-type $I_{Ca}$ and the transient type to T-type $I_{Ca}$. This study is the first to confirm that transient type $I_{Ca}$ together with the sustained one is present in HCs dissociated from goldfish retina.
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