The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Yoshihisa Kurachi - One of the best experts on this subject based on the ideXlab platform.
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How is the highly positive endocochlear Potential formed? The specific architecture of the stria vascularis and the roles of the ion-transport apparatus
Pflügers Archiv - European Journal of Physiology, 2010Co-Authors: Hiroshi Hibino, Chizuru Tsuzuki, Yoshihisa KurachiAbstract:Cochlear endolymph, an extracellular solution containing 150 mM K^+, exhibits a positive Potential of +80 mV. This is called the endocochlear Potential (EP) and is essential for audition. The mechanism responsible for formation of the EP has been an enigma for the half century since its first measurement. A key element is the stria vascularis, which displays a characteristic tissue structure and expresses multiple ion-transport apparatus. The stria comprises two epithelial layers: a layer of marginal cells and one composed of intermediate and basal cells. Between the two layers lies an extracellular space termed the intrastrial space (IS), which is thus surrounded by the apical membranes of intermediate cells and the basolateral membranes of marginal cells. The fluid in the IS exhibits a low concentration of K^+ and a positive Potential similar to the EP. We have demonstrated that the IS is electrically isolated from the neighboring extracellular fluids, perilymph, and endolymph, which allows the IS to sustain its positive Potential. This IS Potential is generated by K^+ Diffusion across the apical membranes of intermediate cells, where inwardly rectifying Kir4.1 channels are localized. The low K^+ concentration in the IS, which is mandatory for the large K^+-Diffusion Potential, is maintained by Na^+,K^+-ATPases and Na^+,K^+,2Cl^−-cotransporters expressed at the basolateral membranes of marginal cells. An additional K^+-Diffusion Potential formed by KCNQ1/KCNE1-K^+ channels at the apical membranes of marginal cells also contributes to the EP. Therefore, the EP depends on an electrically isolated space and two K^+-Diffusion Potentials in the stria vascularis.
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the endocochlear Potential depends on two k Diffusion Potentials and an electrical barrier in the stria vascularis of the inner ear
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Hiroshi Hibino, Toshihiro Suzuki, Yasuo Hisa, Yoshihisa KurachiAbstract:An endocochlear Potential (EP) of +80 mV is essential for audition. Although the regulation of K+ concentration ([K+]) in various compartments of the cochlear stria vascularis seems crucial for the formation of the EP, the mechanism remains uncertain. We have used multibarreled electrodes to measure the Potential, [K+], and input resistance in each compartment of the stria vascularis. The stria faces two fluids, perilymph and endolymph, and contains an extracelluar compartment, the intrastrial space (IS), surrounded by two epithelial layers, the marginal cell (MC) layer and that composed of intermediate and basal cells. Fluid in the IS exhibits a low [K+] and a positive Potential, called the intrastrial Potential (ISP). We found that the input resistance of the IS was high, indicating this space is electrically isolated from the neighboring extracellular fluids. This arrangement is indispensable for maintaining positive ISP. Inhibiting the K+ transporters of the stria by anoxia, ouabain, or bumetanide caused the [K+] of the IS to increase and the intracellular [K+] of MCs to decrease, reducing both the ISP and the EP. Calculations indicate that the ISP represents the K+ Diffusion Potential across the apical membranes of intermediate cells through Ba2+-sensitive K+ channels. The K+ Diffusion Potential across the apical membranes of MCs also contributes to the EP. Because the EP depends on two K+ Diffusion Potentials and an electrical barrier in the stria vascularis, interference with any of these elements can interrupt hearing.
Hiroshi Hibino - One of the best experts on this subject based on the ideXlab platform.
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How is the highly positive endocochlear Potential formed? The specific architecture of the stria vascularis and the roles of the ion-transport apparatus
Pflügers Archiv - European Journal of Physiology, 2010Co-Authors: Hiroshi Hibino, Chizuru Tsuzuki, Yoshihisa KurachiAbstract:Cochlear endolymph, an extracellular solution containing 150 mM K^+, exhibits a positive Potential of +80 mV. This is called the endocochlear Potential (EP) and is essential for audition. The mechanism responsible for formation of the EP has been an enigma for the half century since its first measurement. A key element is the stria vascularis, which displays a characteristic tissue structure and expresses multiple ion-transport apparatus. The stria comprises two epithelial layers: a layer of marginal cells and one composed of intermediate and basal cells. Between the two layers lies an extracellular space termed the intrastrial space (IS), which is thus surrounded by the apical membranes of intermediate cells and the basolateral membranes of marginal cells. The fluid in the IS exhibits a low concentration of K^+ and a positive Potential similar to the EP. We have demonstrated that the IS is electrically isolated from the neighboring extracellular fluids, perilymph, and endolymph, which allows the IS to sustain its positive Potential. This IS Potential is generated by K^+ Diffusion across the apical membranes of intermediate cells, where inwardly rectifying Kir4.1 channels are localized. The low K^+ concentration in the IS, which is mandatory for the large K^+-Diffusion Potential, is maintained by Na^+,K^+-ATPases and Na^+,K^+,2Cl^−-cotransporters expressed at the basolateral membranes of marginal cells. An additional K^+-Diffusion Potential formed by KCNQ1/KCNE1-K^+ channels at the apical membranes of marginal cells also contributes to the EP. Therefore, the EP depends on an electrically isolated space and two K^+-Diffusion Potentials in the stria vascularis.
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the endocochlear Potential depends on two k Diffusion Potentials and an electrical barrier in the stria vascularis of the inner ear
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Hiroshi Hibino, Toshihiro Suzuki, Yasuo Hisa, Yoshihisa KurachiAbstract:An endocochlear Potential (EP) of +80 mV is essential for audition. Although the regulation of K+ concentration ([K+]) in various compartments of the cochlear stria vascularis seems crucial for the formation of the EP, the mechanism remains uncertain. We have used multibarreled electrodes to measure the Potential, [K+], and input resistance in each compartment of the stria vascularis. The stria faces two fluids, perilymph and endolymph, and contains an extracelluar compartment, the intrastrial space (IS), surrounded by two epithelial layers, the marginal cell (MC) layer and that composed of intermediate and basal cells. Fluid in the IS exhibits a low [K+] and a positive Potential, called the intrastrial Potential (ISP). We found that the input resistance of the IS was high, indicating this space is electrically isolated from the neighboring extracellular fluids. This arrangement is indispensable for maintaining positive ISP. Inhibiting the K+ transporters of the stria by anoxia, ouabain, or bumetanide caused the [K+] of the IS to increase and the intracellular [K+] of MCs to decrease, reducing both the ISP and the EP. Calculations indicate that the ISP represents the K+ Diffusion Potential across the apical membranes of intermediate cells through Ba2+-sensitive K+ channels. The K+ Diffusion Potential across the apical membranes of MCs also contributes to the EP. Because the EP depends on two K+ Diffusion Potentials and an electrical barrier in the stria vascularis, interference with any of these elements can interrupt hearing.
Peter Smigaň - One of the best experts on this subject based on the ideXlab platform.
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isolation and characterization of an amiloride resistant mutant of methanothermobacter thermautotrophicus possessing a defective na h antiport
Fems Microbiology Letters, 2007Co-Authors: Stanislav Surin, Alan Majernik, James P J Chong, Lubomira Cuboňova, Paul Mcdermott, Peter SmigaňAbstract:A spontaneous mutant of Methanothermobacter thermautotrophicus resistant to the Na+/H+ antiporter inhibitor amiloride was isolated. The Na+/H+ exchanger activity in the mutant cells was remarkably decreased in comparison with wild-type cells. Methanogenesis rates in the mutant strain were higher than wild-type cells and resistant to the inhibitory effect of 2 mM amiloride. In contrast, methanogenesis in wild-type cells was completely inhibited by the same amiloride concentration. ATP synthesis driven by methanogenic electron transport or by an electrogenic potassium efflux in the presence of sodium ions was significantly enhanced in the mutant cells. ATP synthesis driven by potassium Diffusion Potential was profoundly inhibited in wild-type cells by the presence of uncoupler 3,3′,4′,5- tetrachlorosalicylanilide and sodium ions, whereas c. 50% inhibition was observed in the mutant cells under the same conditions.
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isolation and characterization of an uncoupler resistant mutant of methanothermobacter thermautotrophicus
Fems Microbiology Letters, 2004Co-Authors: Lubomira Cuboňova, Stanislav Surin, Alan Majernik, Peter SmigaňAbstract:A spontaneous mutant of Methanothermobacter thermautotrophicus resistant to the protonophorous uncoupler TCS was isolated. The mutant strain exhibited increased CH4 formation and elevated level of ATPase activity under non-growing conditions. ATP synthesis driven by methanogenic electron transport as well as by potassium Diffusion Potential in the presence of either H+ or Na+ ions was markedly diminished in the mutant strain. An abundant membrane-associated protein complex with molecular mass approximately 670 kDa was detected in the mutant strain after native PAGE. The results indicate that TCS resistance in this mutant has arisen as a consequence of mutation(s) that affects a specific locus coding for an uncoupler binding protein(s) and/or modulate the activity of unidentified ATPase.
Jeong-o Lee - One of the best experts on this subject based on the ideXlab platform.
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Temperature dependence of the current-voltage characteristics of a carbon-nanotube heterojunction
Physical Review B - Condensed Matter and Materials Physics, 2001Co-Authors: Hwangyou Oh, Kyung-hwa Yoo, Ju Jin Kim, Jinhee Kim, Jeong-o LeeAbstract:Electrical transport properties of a heterojunction consisting of two multi-wall carbon nanotubes were studied. The current-voltage characteristics of the junction exhibited reproducible rectifying behavior which could be explained well by the Schottky barrier junction model in the intermediate temperature region. The barrier height and the Diffusion Potential were determined by fitting the current-voltage characteristics to the generalized diode equation. Noticeable deviations from the ideal behavior were observed both in high and low-temperature regions. © 2001 The American Physical Society.
Toshihiro Suzuki - One of the best experts on this subject based on the ideXlab platform.
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the endocochlear Potential depends on two k Diffusion Potentials and an electrical barrier in the stria vascularis of the inner ear
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Hiroshi Hibino, Toshihiro Suzuki, Yasuo Hisa, Yoshihisa KurachiAbstract:An endocochlear Potential (EP) of +80 mV is essential for audition. Although the regulation of K+ concentration ([K+]) in various compartments of the cochlear stria vascularis seems crucial for the formation of the EP, the mechanism remains uncertain. We have used multibarreled electrodes to measure the Potential, [K+], and input resistance in each compartment of the stria vascularis. The stria faces two fluids, perilymph and endolymph, and contains an extracelluar compartment, the intrastrial space (IS), surrounded by two epithelial layers, the marginal cell (MC) layer and that composed of intermediate and basal cells. Fluid in the IS exhibits a low [K+] and a positive Potential, called the intrastrial Potential (ISP). We found that the input resistance of the IS was high, indicating this space is electrically isolated from the neighboring extracellular fluids. This arrangement is indispensable for maintaining positive ISP. Inhibiting the K+ transporters of the stria by anoxia, ouabain, or bumetanide caused the [K+] of the IS to increase and the intracellular [K+] of MCs to decrease, reducing both the ISP and the EP. Calculations indicate that the ISP represents the K+ Diffusion Potential across the apical membranes of intermediate cells through Ba2+-sensitive K+ channels. The K+ Diffusion Potential across the apical membranes of MCs also contributes to the EP. Because the EP depends on two K+ Diffusion Potentials and an electrical barrier in the stria vascularis, interference with any of these elements can interrupt hearing.