The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform
Douglas R Ferguson - One of the best experts on this subject based on the ideXlab platform.
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regulation of na channel density at the apical surface of rabbit urinary Bladder Epithelium
European Journal of Pharmacology, 2002Co-Authors: Timothy J Burton, Michael J Edwardson, Jamie Ingham, Heidi V Tempest, Douglas R FergusonAbstract:Abstract We have investigated the effects of various manipulations on Na+ transport across the rabbit urinary Bladder Epithelium. After Bladders were mounted in Ussing chambers there was a spontaneous and significant (>4-fold) increase in amiloride-sensitive short-circuit current (equivalent to net Na+ transport) over a 6-h period. The increase in current was almost abolished by brefeldin A, an inhibitor of anterograde vesicular transport, and reduced after a 3-h delay by cycloheximide, an inhibitor of protein synthesis. The spontaneous increase in short-circuit current was potentiated by treatment of Bladders with either forskolin, which causes an elevation in cAMP levels, or aldosterone. Acting together, these two agents produced a significant synergistic effect on short-circuit current. The short-circuit current recovered rapidly after reduction in intracellular Na+ levels, achieved either by lowering the extracellular Na+ concentration or blockade of epithelial Na+ channels with the sulphydryl modifying reagent p-chloromercuribenzenesulphonic acid (PCMBS). Recovery after PCMBS treatment was partially sensitive to brefeldin A. Short-circuit current saturated as the extracellular Na+ concentration was increased (EC50=51 mM). Saturation occurred over a range of Na+ concentrations in which single channel permeability is known to remain constant, indicating that it depends on a reduction in epithelial Na+ channel density at the apical plasma membrane. Exposure of Bladders to a high Na+ concentration caused an increase in endocytotic activity, detected through an increase in the uptake of the fluid-phase marker fluorescein isothiocyanate (FITC)–dextran into vesicles located beneath the apical plasma membrane. We conclude that the urinary Bladder Epithelium is able to respond rapidly and efficiently to changes in its environment by regulating the density of epithelial Na+ channels in its apical surface.
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Regulation of Na+ channel density at the apical surface of rabbit urinary Bladder Epithelium.
European journal of pharmacology, 2002Co-Authors: Timothy J Burton, Jamie Ingham, Heidi V Tempest, J Michael Edwardson, Douglas R FergusonAbstract:We have investigated the effects of various manipulations on Na(+) transport across the rabbit urinary Bladder Epithelium. After Bladders were mounted in Ussing chambers there was a spontaneous and significant (>4-fold) increase in amiloride-sensitive short-circuit current (equivalent to net Na(+) transport) over a 6-h period. The increase in current was almost abolished by brefeldin A, an inhibitor of anterograde vesicular transport, and reduced after a 3-h delay by cycloheximide, an inhibitor of protein synthesis. The spontaneous increase in short-circuit current was potentiated by treatment of Bladders with either forskolin, which causes an elevation in cAMP levels, or aldosterone. Acting together, these two agents produced a significant synergistic effect on short-circuit current. The short-circuit current recovered rapidly after reduction in intracellular Na(+) levels, achieved either by lowering the extracellular Na(+) concentration or blockade of epithelial Na(+) channels with the sulphydryl modifying reagent p-chloromercuribenzenesulphonic acid (PCMBS). Recovery after PCMBS treatment was partially sensitive to brefeldin A. Short-circuit current saturated as the extracellular Na(+) concentration was increased (EC(50) = 51 mM). Saturation occurred over a range of Na(+) concentrations in which single channel permeability is known to remain constant, indicating that it depends on a reduction in epithelial Na(+) channel density at the apical plasma membrane. Exposure of Bladders to a high Na(+) concentration caused an increase in endocytotic activity, detected through an increase in the uptake of the fluid-phase marker fluorescein isothiocyanate (FITC)-dextran into vesicles located beneath the apical plasma membrane. We conclude that the urinary Bladder Epithelium is able to respond rapidly and efficiently to changes in its environment by regulating the density of epithelial Na(+) channels in its apical surface.
John W Hanrahan - One of the best experts on this subject based on the ideXlab platform.
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physiological approaches for studying mammalian urinary Bladder Epithelium
Methods in Enzymology, 1990Co-Authors: Simon A Lewis, John W HanrahanAbstract:Publisher Summary This chapter describes the methods used to measure the physiological properties of the mammalian urinary Bladder Epithelium in vitro . This involves the selection of a bathing solution similar in composition to plasma, development of a method to remove the muscle layers from the Epithelium with minimal traumatization of the tissue, design of an in vitro chamber into which the Epithelium is mounted with minimal damage, and choice of an electrical recording system to assess the transepithelial properties of the tissues in a nonintrusive manner. This chapter also discusses methods that were used during this work, emphasizing modifications that are unique to this particular tissue. The mammalian urinary Bladder offers many advantages over other Na + -transporting epithelia that are widely used as model preparations. The apical cell layer seems not to be coupled to the lower two germinal cell layers, and this apical layer is composed of only one cell type.
Timothy J Burton - One of the best experts on this subject based on the ideXlab platform.
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regulation of na channel density at the apical surface of rabbit urinary Bladder Epithelium
European Journal of Pharmacology, 2002Co-Authors: Timothy J Burton, Michael J Edwardson, Jamie Ingham, Heidi V Tempest, Douglas R FergusonAbstract:Abstract We have investigated the effects of various manipulations on Na+ transport across the rabbit urinary Bladder Epithelium. After Bladders were mounted in Ussing chambers there was a spontaneous and significant (>4-fold) increase in amiloride-sensitive short-circuit current (equivalent to net Na+ transport) over a 6-h period. The increase in current was almost abolished by brefeldin A, an inhibitor of anterograde vesicular transport, and reduced after a 3-h delay by cycloheximide, an inhibitor of protein synthesis. The spontaneous increase in short-circuit current was potentiated by treatment of Bladders with either forskolin, which causes an elevation in cAMP levels, or aldosterone. Acting together, these two agents produced a significant synergistic effect on short-circuit current. The short-circuit current recovered rapidly after reduction in intracellular Na+ levels, achieved either by lowering the extracellular Na+ concentration or blockade of epithelial Na+ channels with the sulphydryl modifying reagent p-chloromercuribenzenesulphonic acid (PCMBS). Recovery after PCMBS treatment was partially sensitive to brefeldin A. Short-circuit current saturated as the extracellular Na+ concentration was increased (EC50=51 mM). Saturation occurred over a range of Na+ concentrations in which single channel permeability is known to remain constant, indicating that it depends on a reduction in epithelial Na+ channel density at the apical plasma membrane. Exposure of Bladders to a high Na+ concentration caused an increase in endocytotic activity, detected through an increase in the uptake of the fluid-phase marker fluorescein isothiocyanate (FITC)–dextran into vesicles located beneath the apical plasma membrane. We conclude that the urinary Bladder Epithelium is able to respond rapidly and efficiently to changes in its environment by regulating the density of epithelial Na+ channels in its apical surface.
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Regulation of Na+ channel density at the apical surface of rabbit urinary Bladder Epithelium.
European journal of pharmacology, 2002Co-Authors: Timothy J Burton, Jamie Ingham, Heidi V Tempest, J Michael Edwardson, Douglas R FergusonAbstract:We have investigated the effects of various manipulations on Na(+) transport across the rabbit urinary Bladder Epithelium. After Bladders were mounted in Ussing chambers there was a spontaneous and significant (>4-fold) increase in amiloride-sensitive short-circuit current (equivalent to net Na(+) transport) over a 6-h period. The increase in current was almost abolished by brefeldin A, an inhibitor of anterograde vesicular transport, and reduced after a 3-h delay by cycloheximide, an inhibitor of protein synthesis. The spontaneous increase in short-circuit current was potentiated by treatment of Bladders with either forskolin, which causes an elevation in cAMP levels, or aldosterone. Acting together, these two agents produced a significant synergistic effect on short-circuit current. The short-circuit current recovered rapidly after reduction in intracellular Na(+) levels, achieved either by lowering the extracellular Na(+) concentration or blockade of epithelial Na(+) channels with the sulphydryl modifying reagent p-chloromercuribenzenesulphonic acid (PCMBS). Recovery after PCMBS treatment was partially sensitive to brefeldin A. Short-circuit current saturated as the extracellular Na(+) concentration was increased (EC(50) = 51 mM). Saturation occurred over a range of Na(+) concentrations in which single channel permeability is known to remain constant, indicating that it depends on a reduction in epithelial Na(+) channel density at the apical plasma membrane. Exposure of Bladders to a high Na(+) concentration caused an increase in endocytotic activity, detected through an increase in the uptake of the fluid-phase marker fluorescein isothiocyanate (FITC)-dextran into vesicles located beneath the apical plasma membrane. We conclude that the urinary Bladder Epithelium is able to respond rapidly and efficiently to changes in its environment by regulating the density of epithelial Na(+) channels in its apical surface.
Simon A Lewis - One of the best experts on this subject based on the ideXlab platform.
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Eosinophil major basic protein increases membrane permeability in mammalian urinary Bladder Epithelium
American Journal of Physiology-cell Physiology, 1998Co-Authors: Teri J. Kleine, Gerald J. Gleich, Simon A LewisAbstract:The eosinophil granule protein major basic protein (MBP) is toxic to a wide variety of cell types, by a poorly understood mechanism. To determine whether the action of MBP involves an alteration in membrane permeability, we tested purified MBP on rabbit urinary Bladder Epithelium using transepithelial voltage-clamp techniques. Addition of nanomolar concentrations of MBP to the mucosal solution caused an increase in apical membrane conductance only when the voltage across the apical membrane was cell interior negative. The magnitude of the MBP-induced conductance was a function of MBP concentration, and the rate of the initial increase in conductance was a function of the transepithelial voltage. The MBP-induced conductance was nonselective for K+ and Cl−. Mucosal Ca2+ reversed the induced conductance, whereas mucosal Mg2+partially blocked the induced conductance and slowed the rate of the increase in conductance. The induced conductance was partially reversed by changing the voltage gradient across the ap...
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physiological approaches for studying mammalian urinary Bladder Epithelium
Methods in Enzymology, 1990Co-Authors: Simon A Lewis, John W HanrahanAbstract:Publisher Summary This chapter describes the methods used to measure the physiological properties of the mammalian urinary Bladder Epithelium in vitro . This involves the selection of a bathing solution similar in composition to plasma, development of a method to remove the muscle layers from the Epithelium with minimal traumatization of the tissue, design of an in vitro chamber into which the Epithelium is mounted with minimal damage, and choice of an electrical recording system to assess the transepithelial properties of the tissues in a nonintrusive manner. This chapter also discusses methods that were used during this work, emphasizing modifications that are unique to this particular tissue. The mammalian urinary Bladder offers many advantages over other Na + -transporting epithelia that are widely used as model preparations. The apical cell layer seems not to be coupled to the lower two germinal cell layers, and this apical layer is composed of only one cell type.
Mark L Zeidel - One of the best experts on this subject based on the ideXlab platform.
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permeability properties of the intact mammalian Bladder Epithelium
American Journal of Physiology-renal Physiology, 1996Co-Authors: Hilmer Negrete, John P Lavelle, J Berg, S A Lewis, Mark L ZeidelAbstract:Because the mammalian Bladder must store urine of composition which differs markedly from that of plasma for prolonged periods, the Bladder permeability barrier must maintain extremely low permeabilities to substances which normally cross membranes relatively rapidly, such as water, protons, and small nonelectrolytes like urea and ammonia. In the present studies, permeabilities of the apical membrane of dissected rabbit Bladder Epithelium to water, urea, ammonia, and protons were measured in Ussing chambers and averaged (in cm/s) for water, 5.15 +/- 0.43 x 10(-5); for urea, 4.51 +/- 0.67 x 10(-6); for ammonia, 5.14 +/- 0.62 x 10(-4); and for protons, 2.98 +/- 1.87 x 10(-3), respectively. These permeability values are exceptionally low and are expected to result in minimal to no leakage of these normally permeable substances across the Epithelium. Water permeabilities in intact whole rabbit Bladders were indistinguishable from those obtained in the dissected epithelial preparation. Moreover, addition of ny...
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Permeability properties of the intact mammalian Bladder Epithelium.
The American journal of physiology, 1996Co-Authors: Hilmer Negrete, John P Lavelle, J Berg, S A Lewis, Mark L ZeidelAbstract:Because the mammalian Bladder must store urine of composition which differs markedly from that of plasma for prolonged periods, the Bladder permeability barrier must maintain extremely low permeabilities to substances which normally cross membranes relatively rapidly, such as water, protons, and small nonelectrolytes like urea and ammonia. In the present studies, permeabilities of the apical membrane of dissected rabbit Bladder Epithelium to water, urea, ammonia, and protons were measured in Ussing chambers and averaged (in cm/s) for water, 5.15 +/- 0.43 x 10(-5); for urea, 4.51 +/- 0.67 x 10(-6); for ammonia, 5.14 +/- 0.62 x 10(-4); and for protons, 2.98 +/- 1.87 x 10(-3), respectively. These permeability values are exceptionally low and are expected to result in minimal to no leakage of these normally permeable substances across the Epithelium. Water permeabilities in intact whole rabbit Bladders were indistinguishable from those obtained in the dissected epithelial preparation. Moreover, addition of nystatin to the apical solution of dissected epithelia rapidly increased water permeability in conjunction with loss of epithelial resistance. These results confirm that the apical membrane of the Bladder epithelial cells represents the Bladder permeability barrier. In addition, they establish a model system that will permit examination of how membrane structure reduces permeability and how epithelial injury compromises barrier function.
