scholarly journals Characterization of the basolateral membrane conductance of Necturus urinary bladder.

1987 ◽  
Vol 89 (4) ◽  
pp. 541-562 ◽  
Author(s):  
J R Demarest ◽  
A L Finn
Keyword(s):  
Electrical Properties ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Transference Numbers ◽  
Sudden Increase ◽  
Membrane Selectivity ◽  
Rapid Changes ◽  
K Concentration ◽  
Passive Electrical Properties

Necturus urinary bladders stripped of serosal muscle and connective tissue were impaled through their basolateral membranes with microelectrodes in experiments that permitted rapid changes in the ion composition of the serosal solution. The transepithelial electrical properties exhibited a marked seasonal variation that could be attributed to variations in the conductance of the shunt pathway, apical membrane selectivity, and basolateral Na+ transport. In contrast, the passive electrical properties of the basolateral membrane remained constant throughout the year. The apparent transference numbers (Ti) of the basolateral membrane for K+ and Cl- were determined from the effect on the basolateral membrane equivalent electromotive force of a sudden increase in the serosal K+ concentration from 2.5 to 50 mM/liter or a decrease in the Cl- concentration from 101 to 10 mM/liter. TK and TCl were 0.71 +/- 0.05 and 0.04 +/- 0.01, respectively. The basolateral K+ conductance could be blocked by Ba2+ (0.5 mM), Cs+ (10 mM), or Rb+ (10 mM), but was unaffected by 3,4-diaminopyridine (100 microM), decamethonium (100 microM), or tetraethylammonium (10 mM). We conclude that a highly selective K+ conductance dominates the electrical properties of the basolateral membrane and that this conductance is different from those found in nerve and muscle membranes.

Characterization of the apical membrane ionic permeability of the rabbit proximal convoluted tubule

1986 ◽  
Vol 250 (2) ◽  
pp. F339-F347
Author(s):  
J. Y. Lapointe ◽  
R. Laprade ◽  
J. Cardinal
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Transference Number ◽  
Membrane Resistance ◽  
Transference Numbers ◽  
Vitro Analysis ◽  
Convoluted Tubules

Basolateral membrane potential (psi BL), transepithelial potential (psi T), and the ratio of apical to basolateral membrane resistance (RA/RBL) were measured in rabbit proximal convoluted tubules (PCT) perfused in vitro. Analysis of RA/RBL changes using several luminal perfusates indicates that the cotransport of Na with glucose and alanine would represent 19% of the apical conductance in normal conditions; the cotransport of Na with acetate, citrate, sulfate, and phosphate would represent 7%, whereas Na, K, and Cl diffusion would represent 10, 4, and 0% of this apical conductance, respectively. On the other hand, psi BL values can also be analyzed using the equivalent circuit of the epithelium to obtain the apical membrane equivalent electromotive force (EA) in the presence of each perfusate. These values, as well as the preceding values obtained from RA/RBL measurements, indicate that in the absence of cotransported solutes the transference number for Na diffusion is several times larger than for K diffusion. Among the conductance pathways studied, the transference number sequence would be as follows: Na cotransport with alanine and glucose greater than Na cotransport with anions greater than Na diffusion greater than K diffusion greater than Cl diffusion. This study also suggests the presence of another important but unidentified apical ionic permeation pathway, since the total of the transference numbers obtained from RA/RBL analysis represents only 40% of the total apical membrane conductance and the absolute values of EA are difficult to account for using only the tested apical membrane permeation pathways.

Electrophysiological characterization of upper portion of descending limb of long-looped nephron

1991 ◽  
Vol 260 (3) ◽  
pp. F311-F316 ◽  
Author(s):  
K. Yoshitomi ◽  
M. Imai
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
High Water ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Major Pathway ◽  
K Concentration ◽  
Electrophysiological Characterization

The upper portion of the descending limb of long-looped nephron (LDLu) of the hamster is characterized by high water and ion permeabilities. Although the paracellular route is considered to be the major pathway representing cation permselectivity of this segment, ion transport mechanisms through the transcellular pathway are unknown. To study this issue; we applied cable analysis and conventional microelectrode technique to the hamster LDLu perfused in vitro. The transmural voltage (VT) was not different from zero, and transmural resistance (RT) was very low, 18.3 +/- 2.0 omega.cm2 (n = 12). The basolateral membrane voltage was -80 +/- 2 mV (n = 55), and fractional apical membrane resistance was 0.92 +/- 0.23 (n = 5). Ouabain (0.1 mM) in the bath decreased basolateral membrane voltage (VB) by 23 +/- 3 mV (n = 6, P less than 0.001). Increase in K+ concentration in bath and in lumen from 5 to 50 mM decreased VB by 39 +/- 2 (n = 7, P less than 0.01) and apical membrane voltage (VA) by 10 +/- 1 mV (n = 7, P less than 0.001), respectively. Addition of 2 mM Ba2+ to bath and to lumen decreased VB by -47 +/- 2 (n = 11, P less than 0.001) and decreased VA by 8 +/- 1 mV, respectively. Reduction of HCO3- in bath from 25 to 2.5 mM decreased VB by 4 +/- 1 mV (n = 7, P less than 0.005). Reduction of bath Cl- did not cause any rapid deflection of VB. No appreciable Na+ conductance was detected in the apical membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Electrophysiology of flounder intestinal mucosa. I. Conductance properties of the cellular and paracellular pathways.

1985 ◽  
Vol 85 (6) ◽  
pp. 843-864 ◽  
Author(s):  
D R Halm ◽  
E J Krasny ◽  
R A Frizzell
Keyword(s):  
Membrane Potential ◽  
Apical Membrane ◽  
Driving Forces ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Membrane Conductance ◽  
Equivalent Circuit Analysis ◽  
K Secretion ◽  
Paracellular Pathways ◽  
K Concentration

We evaluated the conductances for ion flow across the cellular and paracellular pathways of flounder intestine using microelectrode techniques and ion-replacement studies. Apical membrane conductance properties are dominated by the presence of Ba-sensitive K channels. An elevated mucosal solution K concentration, [K]m, depolarized the apical membrane potential (psi a) and, at [K]m less than 40 mM, the K dependence of psi a was abolished by 1-2 mM mucosal Ba. The basolateral membrane displayed Cl conductance behavior, as evidenced by depolarization of the basolateral membrane potential (psi b) with reduced serosal Cl concentrations, [Cl]s. psi b was unaffected by changes in [K]s or [Na]s. From the effect of mucosal Ba on transepithelial K selectivity, we estimated that paracellular conductance (Gp) normally accounts for 96% of transepithelial conductance (Gt). The high Gp attenuates the contribution of the cellular pathway to psi t while permitting the apical K and basolateral Cl conductances to influence the electrical potential differences across both membranes. Thus, psi a and psi b (approximately 60 mV, inside negative) lie between the equilibrium potentials for K (76 mV) and Cl (40 mV), thereby establishing driving forces for K secretion across the apical membrane and Cl absorption across the basolateral membrane. Equivalent circuit analysis suggests that apical conductance (Ga approximately equal to 5 mS/cm2) is sufficient to account for the observed rate of K secretion, but that basolateral conductance (Gb approximately equal to 1.5 mS/cm2) would account for only 50% of net Cl absorption. This, together with our failure to detect a basolateral K conductance, suggests that Cl absorption across this barrier involves KCl co-transport.

scholarly journals Cation Transport in Escherichia coli

1965 ◽  
Vol 49 (2) ◽  
pp. 221-234 ◽  
Author(s):  
Wolfgang Epstein ◽  
Stanley G. Schultz
Keyword(s):  
Escherichia Coli ◽  
Growth Medium ◽  
Cation Transport ◽  
Major Determinant ◽  
Sudden Increase ◽  
Rapid Loss ◽  
Rapid Changes ◽  
K Concentration

Measurement of cellular K and Na concentrations in growing Escherichia coli indicates that the osmololity of the medium is a major determinant of the cell K concentration. In contrast, the cell Na concentration is independent of the medium osmolality and is largely dependent on the Na concentration of the medium. Sudden changes in the osmolality of the medium lead to rapid changes in K content. Washing the cells with solutions of lower osmolality results in a very rapid loss of K, which is greater in more dilute and in cold solutions. A sudden increase in the osmolality of the growth medium produces a rapid uptake of K by a mechanism whose rate is a saturable function of the K concentration of the medium and which appears to involve an exchange of K for cellular H.

Characterization of potassium permeability of cochlear duct by perilymphatic perfusion of barium

1984 ◽  
Vol 247 (3) ◽  
pp. C240-C246 ◽  
Author(s):  
D. C. Marcus
Keyword(s):  
Basolateral Membrane ◽  
Electrical Potential ◽  
Organ Of Corti ◽  
Sensory Cells ◽  
Cochlear Duct ◽  
Cellular Origin ◽  
Cell Tissue ◽  
Rapid Changes ◽  
Junctional Complexes

The relative transepithelial "permeabilities" of the cochlear duct to K, Na, and Cl were investigated so as to identify the K-selective tissues and to determine the cellular origin of this selectivity. Single-ion substitutions were made for K, Na, and Cl with the impermeant species N-methyl-D-glucamine (NMDG) for K and Na and gluconate or sulfate for Cl in perilymph. Transepithelial potential changes were relatively slow and small for Na and Cl substitutions. However, either K for Na or K for NMDG substitutions demonstrated a pronounced K selectivity (rapid changes of electrical potential) of only the sensory-cell tissue (organ of Corti). The response to the K for Na substitution was most clearly seen after electrogenic K transport was inhibited by ischemia while the sensory cells were metabolically sustained via perilymphatic perfusion. Under this condition, perfusion of a medium containing 154 mM K gluconate reduced the negative potential (typically -25 to -40 mV) to within a few millivolts of zero. In a control medium, perilymphatic barium (0.5-5 mM) produced qualitatively similar effects, suggesting that this K selectivity is localized primarily at the basolateral membrane of the sensory cells rather than at the junctional complexes.

Effect of the structure of cellulose acetate membranes on their permeability, electrical conductivity and rejection

1990 ◽  
Vol 55 (12) ◽  
pp. 2933-2939 ◽  
Author(s):  
Hans-Hartmut Schwarz ◽  
Vlastimil Kůdela ◽  
Klaus Richau
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Cellulose Acetate ◽  
Reverse Osmosis ◽  
Water Flux ◽  
Cellulose Acetate Membrane ◽  
Structure Parameters ◽  
Dc Electrical Conductivity ◽  
Cellulose Acetate Membranes

Ultrafiltration cellulose acetate membrane can be transformed by annealing into reverse osmosis membranes (RO type). Annealing brings about changes in structural properties of the membranes, accompanied by changes in their permeability behaviour and electrical properties. Correlations between structure parameters and electrochemical properties are shown for the temperature range 20-90 °C. Relations have been derived which explain the role played by the dc electrical conductivity in the characterization of rejection ability of the membranes in the reverse osmosis, i.e. rRO = (1 + exp (A-B))-1, where exp A and exp B are statistically significant correlation functions of electrical conductivity and salt permeation, or of electrical conductivity and water flux through the membrane, respectively.

Electrical Characterization of the Graphene-SiC Heterojunction

2012 ◽  
Vol 717-720 ◽  
pp. 641-644
Author(s):  
Travis J. Anderson ◽  
Karl D. Hobart ◽  
Luke O. Nyakiti ◽  
Virginia D. Wheeler ◽  
Rachael L. Myers-Ward ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Charge Carrier ◽  
Graphene Sheet ◽  
Carrier Transport ◽  
Electrical Characterization ◽  
Epitaxial Graphene ◽  
Charge Carrier Transport ◽  
Semiconductor System ◽  
Significant Research

Graphene, a 2D material, has motivated significant research in the study of its in-plane charge carrier transport in order to understand and exploit its unique physical and electrical properties. The vertical graphene-semiconductor system, however, also presents opportunities for unique devices, yet there have been few attempts to understand the properties of carrier transport through the graphene sheet into an underlying substrate. In this work, we investigate the epitaxial graphene/4H-SiC system, studying both p and n-type SiC substrates with varying doping levels in order to better understand this vertical heterojunction.

Reversal of glibenclamide and voltage block of an epithelial KATP channel

1996 ◽  
Vol 271 (4) ◽  
pp. C1122-C1130 ◽  
Author(s):  
O. Mayorga-Wark ◽  
W. P. Dubinsky ◽  
S. G. Schultz
Keyword(s):  
Hydrophobic Interactions ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Voltage Gating ◽  
Electrical Potential Difference ◽  
Outer Solution ◽  
Channel Inhibition ◽  
K Concentration ◽  
Voltage Gate

K+ channels present in basolateral membrane vesicles isolated from Necturus maculosa small intestinal cells and reconstituted into planar phospholipid bilayers are inhibited by MgATP and sulfonylurea derivatives, such as tolbutamide and glibenclamide, when these agents are added to the solution bathing the inner mouth of the channel. In addition, these channels possess an intrinsic "voltage gate" and are blocked when the electrical potential difference across the channel is oriented so that the inner solution is electrically positive with respect to the outer solution. We now show that increasing the concentration of permeant ions such as K+ or Rb+ in the outer solution reverses channel inhibition resulting from the addition of 50 microM glibenclamide to the inner solution and also inhibits intrinsic voltage gating; these effects are not elicited by increasing the concentrations of the relatively impermeant ions, Na+ or choline, in the outer solution. Furthermore, increasing the K+ concentration in the outer solution in the absence of glibenclamide inhibits voltage gating, and, under these conditions, the subsequent addition of glibenclamide to the inner solution is ineffective. These results are consistent with a model in which the voltage gate is an open-channel blocker whose action is directly reversed by elevating the external concentration of relatively permeant cations and where the action of glibenclamide is to stabilize the inactivated state of the channel, possibly through hydrophobic interactions.

scholarly journals Characterization of the Muscle Electrical Properties in Low Back Pain Patients by Electrical Impedance Myography

PLoS ONE ◽  
2013 ◽  
Vol 8 (4) ◽  
pp. e61639 ◽  
Author(s):  
Congo Tak-Shing Ching ◽  
Yueh-Chi Chen ◽  
Li-Hua Lu ◽  
Peiyuan F. Hsieh ◽  
Chin-Sung Hsiao ◽  
...  
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Electrical Properties ◽  
Electrical Impedance ◽  
Low Back ◽  
Pain Patients
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