The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform
Hikaru Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Intercellular electrical communication among smooth muscle and endothelial cells in guinea-pig mesenteric arterioles.
The Journal of Physiology, 2001Co-Authors: Yoshimichi Yamamoto, Megan F Klemm, F. R. Edwards, Hikaru SuzukiAbstract:1. Current clamp studies using two patch electrodes and morphological observations have been performed in guinea-pig mesenteric arterioles to evaluate intercellular electrical couplings. 2. In electron micrographs, preparations were found to have a single layer of smooth muscle cells. Typical gap junctions were readily observed between endothelial cells only. 3. While immunoreactivity to connexin 40 was strongly expressed on the membranes of endothelial cells only, that to connexin 43 was expressed on both smooth muscle and endothelial cell membranes. 4. Neurobiotin injected into a smooth muscle cell diffused into several neighbouring smooth muscle cells while that injected into an endothelial cell diffused into many endothelial cells. 5. Acetylcholine-induced hyperpolarizations were conducted from endothelial cells to smooth muscle cells with a relative amplitude of 80.1 %. Ba(2+)-induced action Potentials were conducted in the opposite direction with a relative amplitude of 92.4 %. 6. An Electrotonic Potential produced in a smooth muscle cell by current injection diminished steeply with distance as it spread along the muscle layer, plateauing at distances beyond 25 microm. An Electrotonic Potential produced in an endothelial cell spread within the intima with virtually no reduction. Electrotonic Potentials could conduct through myoendothelial couplings, which seemed to behave as ohmic resistors without rectification. 7. The coupling resistance between adjacent smooth muscle cells was estimated to be at least 90 MOhms and that between a smooth muscle cell and the whole endothelial layer to be 0.9 GOhms. 8. The results indicate that although the resistance of myoendothelial couplings is appreciable, the endothelium may be important as a low resistance path connecting many smooth muscle cells.
Yoshimichi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Intercellular electrical communication among smooth muscle and endothelial cells in guinea-pig mesenteric arterioles.
The Journal of Physiology, 2001Co-Authors: Yoshimichi Yamamoto, Megan F Klemm, F. R. Edwards, Hikaru SuzukiAbstract:1. Current clamp studies using two patch electrodes and morphological observations have been performed in guinea-pig mesenteric arterioles to evaluate intercellular electrical couplings. 2. In electron micrographs, preparations were found to have a single layer of smooth muscle cells. Typical gap junctions were readily observed between endothelial cells only. 3. While immunoreactivity to connexin 40 was strongly expressed on the membranes of endothelial cells only, that to connexin 43 was expressed on both smooth muscle and endothelial cell membranes. 4. Neurobiotin injected into a smooth muscle cell diffused into several neighbouring smooth muscle cells while that injected into an endothelial cell diffused into many endothelial cells. 5. Acetylcholine-induced hyperpolarizations were conducted from endothelial cells to smooth muscle cells with a relative amplitude of 80.1 %. Ba(2+)-induced action Potentials were conducted in the opposite direction with a relative amplitude of 92.4 %. 6. An Electrotonic Potential produced in a smooth muscle cell by current injection diminished steeply with distance as it spread along the muscle layer, plateauing at distances beyond 25 microm. An Electrotonic Potential produced in an endothelial cell spread within the intima with virtually no reduction. Electrotonic Potentials could conduct through myoendothelial couplings, which seemed to behave as ohmic resistors without rectification. 7. The coupling resistance between adjacent smooth muscle cells was estimated to be at least 90 MOhms and that between a smooth muscle cell and the whole endothelial layer to be 0.9 GOhms. 8. The results indicate that although the resistance of myoendothelial couplings is appreciable, the endothelium may be important as a low resistance path connecting many smooth muscle cells.
Tadao Tomita - One of the best experts on this subject based on the ideXlab platform.
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Consequences of metabolic inhibition in smooth muscle isolated from guinea-pig stomach
The Journal of Physiology, 1997Co-Authors: Shinsuke Nakayama, T. Horrachi, Shingo Chihara, Joseph F. Clark, S M Huang, Tadao TomitaAbstract:1In smooth muscle isolated from the guinea-pig stomach, cyanide (CN) and iodoacetic acid (IAA) were applied to block oxidative phosphorylation and glycolysis, respectively. Effects of IAA on generation of spontaneous mechanical and electrical activities were systematically investigated by comparing those of CN. Spontaneous activity ceased in 10–20 min during applications of 1 mm IAA. On the other hand, application of 1 mm CN also reduced the spontaneous activity, but never terminated it. In the presence of CN the negativity of the resting membrane Potential was slightly reduced. 2When spontaneous activity ceased with IAA, the resting membrane Potential was not significantly affected. Also, before ceasing, the amplitude and duration of the spontaneous electrical activity were significantly reduced. The amplitude of the Electrotonic Potential was, however, not changed by IAA. Further, glibenclamide did not prevent the effects of IAA. These results suggest that, unlike cardiac muscle, activation of metabolism-dependent K+ channels in stomach smooth muscle does not seem to play a major role in reducing and terminating spontaneous activity during metabolic inhibition. 3Carbachol-induced contraction transiently increased, and subsequently decreased gradually during application of IAA. 4After 50 min application of IAA, when there was no spontaneous activity, the concentrations of phosphocreatine (PCr) and ATP measured with 31P nuclear magnetic resonance decreased to 60 and 80% of the control, respectively, while inorganic phosphate (Pi) concentration paradoxically fell to below detectable levels. During subsequent prolonged application of IAA, high-energy phosphates steadily decreased. On the other hand, after 50 min CN application, [PCr] and [ATP] decreased to approximately 30 and 80% of the control, respectively, while [Pi] increased by 2.6-fold. 5In the presence of either CN or IAA, spontaneous mechanical and electrical activities were reduced or eliminated, although amounts of high-energy phosphates sufficient to contract smooth muscle remained. It can be postulated that some mechanism(s) related to energy metabolism, but not including ATP-sensitive K+ channels, plays an important role in generating spontaneous activity in guinea-pig stomach smooth muscle. During metabolic inhibition the energy metabolism-dependent mechanism(s) would preserve high-energy phosphates, and consequently cell viability, by stopping spontaneous activity.
R. Veteikis - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Evaluation of Space Constants of Electrotonic Decay in
Elektronika Ir Elektrotechnika, 2009Co-Authors: R. VeteikisAbstract:Computer programs have been developed to calculate the distribution of Electrotonic Potential in a two-dimensional anisotropic medium when the source of current is point-shaped, circle-shaped and disk-shaped. Families of curves have been obtained to demonstrate the dependence of the normalized experimental space constants of Electrotonic decay on anisotropy, distance between the Electrotonic Potential recording site and the source of current, the size of the source of current. Ill. 7, bibl. 17 (in English; summaries in English, Russian and Lithuanian).
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Theoretical Evaluation of Space Constants of Electrotronic Decay in Resistive Anisotropic Media: Common Equation
Elektronika Ir Elektrotechnika, 2008Co-Authors: R. VeteikisAbstract:A mathematical model of the Electrotonic Potential distribution in a three-dimensional bidomain anisotropic resistive-capacitive medium (myocardium) is devised for the case when the source of current is point-, circle- disc- or cylinder-shaped. Using the superposition principle, the current electrode is approximated by point sources, arranging them on the perimeter of the circle-shaped electrode in two ways such that: a) the distances between them are identical in the metric system of coordinates; b) the distances between the point sources are identical in a normalized system of coordinates. The disk-shaped and cylinder-shaped current sources are approximated by point sources, evenly arranging them on the surface. Ill. 2, bibl. 23 (in English; summaries in English, Russian and Lithuanian).
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Mathematical Modeling of the Distribution of Electrotonic Potential in Three-Dimensional Anisotropic RC Media
Elektronika Ir Elektrotechnika, 2000Co-Authors: A. Grigaliunas, R. VeteikisAbstract:Myocardium is a complex three-dimensional anisotropic syncytial structure formed of separate cells connected in between by intercellular contacts. As the passive electric properties of myocardium cannot be measured directly, for the purpose the mathematical models of anisotropic ohmic-capacitive (RC) media have been developed. The analysis of simplified cases with a point-shaped source of current made it possible to discover one of regularities of the distribution of Electrotonic Potential in the one- and two-dimensional RC media: time T1/2 during which Electrotonic Potential reaches half of its stationary amplitude is in linear dependence on the distance R between the point-shaped source of current and the Electrotonic Potential recording site: T1/2=R/2+const. It has been found by mathematical modeling that in the three-dimensional anisotropic RC medium of finite thickness (D) the dependence T1/2=f(R,D) is not linear in close proximity to the source of current of finite size.
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Modelling of the Electrotonic Potential Distribution in Two-Dimensional Anisotropic Ohmic Me-dia
Elektronika Ir Elektrotechnika, 1998Co-Authors: A. Grigaliunas, R. VeteikisAbstract:As the myocardium is a complex three-dimensional anisotropic syncytial tissue, the parameters of myocardium as an electric medium cannot be measured directly. The experimental values of space constants of Electrotonic decay lxe and lye are estimated and, by using mathematical models, their actual values lx and ly are found from which the values of the myocardial electric parameters are derived. During the experimental measurement, the current is delivered to the intracellular tissue through a circle-shaped suction-electrode. The present study includes theoretical simulation of the dependence of the values of space constants lxe and lye upon the size of the current source, the degree of Electrotonic anisotropy and the distance between the current source and the measurement site of Electrotonic Potential. Evaluation of the correlation between the measured and actual Electrotonic anisotropy is presented.
Megan F Klemm - One of the best experts on this subject based on the ideXlab platform.
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Intercellular electrical communication among smooth muscle and endothelial cells in guinea-pig mesenteric arterioles.
The Journal of Physiology, 2001Co-Authors: Yoshimichi Yamamoto, Megan F Klemm, F. R. Edwards, Hikaru SuzukiAbstract:1. Current clamp studies using two patch electrodes and morphological observations have been performed in guinea-pig mesenteric arterioles to evaluate intercellular electrical couplings. 2. In electron micrographs, preparations were found to have a single layer of smooth muscle cells. Typical gap junctions were readily observed between endothelial cells only. 3. While immunoreactivity to connexin 40 was strongly expressed on the membranes of endothelial cells only, that to connexin 43 was expressed on both smooth muscle and endothelial cell membranes. 4. Neurobiotin injected into a smooth muscle cell diffused into several neighbouring smooth muscle cells while that injected into an endothelial cell diffused into many endothelial cells. 5. Acetylcholine-induced hyperpolarizations were conducted from endothelial cells to smooth muscle cells with a relative amplitude of 80.1 %. Ba(2+)-induced action Potentials were conducted in the opposite direction with a relative amplitude of 92.4 %. 6. An Electrotonic Potential produced in a smooth muscle cell by current injection diminished steeply with distance as it spread along the muscle layer, plateauing at distances beyond 25 microm. An Electrotonic Potential produced in an endothelial cell spread within the intima with virtually no reduction. Electrotonic Potentials could conduct through myoendothelial couplings, which seemed to behave as ohmic resistors without rectification. 7. The coupling resistance between adjacent smooth muscle cells was estimated to be at least 90 MOhms and that between a smooth muscle cell and the whole endothelial layer to be 0.9 GOhms. 8. The results indicate that although the resistance of myoendothelial couplings is appreciable, the endothelium may be important as a low resistance path connecting many smooth muscle cells.