Relationship of transepithelial electrical potential to membrane potentials and conductance ratios in frog skin

1982 ◽  
Vol 69 (2) ◽  
pp. 125-136 ◽  
Author(s):  
Wolfram Nagel ◽  
Alvin Essig
Keyword(s):  
Frog Skin ◽  
Electrical Potential ◽  
Membrane Potentials ◽  
Relationship Of

scholarly journals Characterization of receptors mediating the actions of dopamine on an identified inhibitory motoneurone of the cockroach

1991 ◽  
Vol 155 (1) ◽  
pp. 203-217 ◽  
Author(s):  
J. P. Davis ◽  
R. M. Pitman
Keyword(s):  
Periplaneta Americana ◽  
Voltage Dependence ◽  
Negative Resistance ◽  
Membrane Potentials ◽  
Dopaminergic Agonists ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Ly 171555 ◽  
Relationship Of

1. The effects of a number of dopaminergic agonists and antagonists upon the soma of a prothoracic inhibitory motoneurone of the cockroach (Periplaneta americana) have been recorded under voltage-clamp conditions. 2. Dopamine generates inward currents that are extremely voltage-dependent: currents increase rapidly at membrane potentials more negative than about −120 to −150 mV and also show a peak at membrane potentials of approximately −20 mV. As a result of this voltage-dependence, dopamine induces a region of negative resistance in the current-voltage relationship of the neurone. 3. The dopaminergic agonists apomorphine, bromocriptine, ergometrine and A-6,7-DTN mimic the action of dopamine on this neurone, all having a similar voltage-dependence to that of dopamine. The selective D-1 receptor agonist SK&F82526 and the D-2 agonist LY 171555, however, were both inactive on the preparation. 4. Responses to dopamine were suppressed by a number of D-1 and D-2 receptor antagonists, indicating that the pharmacological profile of the dopamine-sensitive receptor in this insect preparation is different from that of vertebrate dopamine receptors.

Electrophysiology of the in situ contractile vacuole complex of Paramecium reveals its membrane dynamics and electrogenic site during osmoregulatory activity.

1998 ◽  
Vol 201 (3) ◽  
pp. 451-460 ◽  
Author(s):  
T Tominaga ◽  
R D Allen ◽  
Y Naitoh
Keyword(s):  
Proton Pump ◽  
Electrical Potential ◽  
Membrane Dynamics ◽  
Contractile Vacuole ◽  
Vacuole Membrane ◽  
Input Capacitance ◽  
Linear Current ◽  
Relationship Of ◽  
Voltage Relationship

In the freshwater protozoan Paramecium multomicronucleatum, excess cytosolic water, acquired osmotically, is segregated and expelled to the cell exterior through the activity of the contractile vacuole complex. This process keeps the cell volume constant. The electrophysiological parameters of the organelle were measured in situ using a fine-tipped microelectrode inserted into the contractile vacuole, the exocytotic vesicle of the organelle to which the segregated fluid is transported before being expelled to the exterior. The input capacitance decreased markedly immediately before fluid expulsion and regained its previous value when fluid filling resumed after fluid expulsion. This change in the capacitance proved that the contractile vacuole became disconnected from its radial arms, which project from the vacuole, before fluid expulsion occurred and then reconnected with the arms after fluid expulsion. A positive electrical potential was recorded from the contractile vacuole only when it was connected to the radial arms. This implies that the electrogenic mechanism resides exclusively in the radial arms and supports the idea that the decorated spongiomes, V-type proton-pump-covered terminal tubules of the radial arms that end blindly in the cytosol, are electrogenic. The linear current­voltage relationship of the contractile vacuole membrane also implies that few voltage-activated ion channels are present in the membrane. To explain the movement of water into the contractile vacuole complex, we favour the hypothesis that the potential generated across the decorated spongiome membrane can be used to drive counter-anions from the cytosol into the lumen of the complex. The anions could then act as an osmolite to pull cytosolic water into the lumen of the organelle.

Effect of furosemide on the electrical parameters of frog skin

1982 ◽  
Vol 243 (6) ◽  
pp. F581-F587 ◽  
Author(s):  
A. Corcia ◽  
S. R. Caplan
Keyword(s):  
Active Transport ◽  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Relative Increase ◽  
Electrical Potential Difference ◽  
Electrical Parameters ◽  
Active Conductance ◽  
Solution Bathing

When added to the mucosal solution bathing isolated frog skin at concentrations ranging from 5 X 10(-4) to 3 X 10(-3) M, the diuretic furosemide increased both the active transport of sodium and the electrical potential difference across the tissue in a dose-dependent way. The same effect was observed in chloride-free solutions. Mucosal furosemide also decreased the passive unidirectional fluxes of chloride. We believe that as far as electrical parameters are concerned mucosal furosemide has a double effect in frog skin: it increases the active conductance to sodium across the mucosal membrane, thus increasing active transport, and decreases the passive permeability to chloride, thus altering the passive conductance of the skin. The relative increase in short-circuit current was, however, invariably greater than the increase of the active conductance, suggesting the influence of yet a third effect. The effect of mucosal furosemide on active sodium transport was blocked by amiloride (5 X 1-(-5) M) and was independent of vasopressin. Qualitatively the effect was similar to the effect produced by triphenylmethylphosphonium ion.

scholarly journals Lithium-Induced Oscillations of Potential and Resistance in Isolated Frog Skin

1961 ◽  
Vol 44 (6) ◽  
pp. 1165-1176 ◽  
Author(s):  
Alan Finkelstein
Keyword(s):  
Hydrostatic Pressure ◽  
Phase Shift ◽  
Direct Current ◽  
Frog Skin ◽  
Water Movement ◽  
Electrical Potential ◽  
Lithium Ion ◽  
The Mean ◽  
The Waves ◽  
Hydrostatic Pressure Difference

The rhythmical variations of electrical potential and DC resistance resulting from the exposure of the anatomical outside of isolated frog skin to a concentration of lithium ion greater than 20 millinormal were reinvestigated. In general, the potential and resistance changes were in phase, although in some skins, a phase shift occurred after the first few waves. The mean level of the resistance declined during the exposure to lithium, returning to its former level upon reintroduction of sodium in place of lithium. The oscillations, with a period of from 3 to 15 minutes, could last for 2 hours or more before damping out; the amplitude of the waves could be altered during this time by the passage of direct current or by the introduction of a hydrostatic pressure difference across the skin. Even after the oscillations damped out, the system remained "excitable," responding to a step of direct current or hydrostatic pressure with an oscillatory train. The nature and magnitude of the response to current and pressure were dependent upon the "polarity" of the applied perturbation. Direct observation of the skin revealed no evidence of oscillatory water movement concomitant with the electrical events.

scholarly journals THE EFFECTS OF MAGNESIUM ON NUCLEOSIDE PHOSPHATASE ACTIVITY IN FROG SKIN

1967 ◽  
Vol 33 (2) ◽  
pp. 411-418 ◽  
Author(s):  
Rolf H. Dahl ◽  
James N. Pratley
Keyword(s):  
Cell Membrane ◽  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Spectrophotometric Analysis ◽  
Electrical Potential Difference ◽  
Ion Pump ◽  
Pump System ◽  
Nucleoside Triphosphatase

Histochemical tests, employing the Wachstein-Meisel medium, indicate that nucleoside triphosphatase activity is found predominantly in two areas of the frog skin epidermis: (1) in mitochondria, where activity is enhanced by dinitrophenol, Mg2+ dependent, but inhibited by fixation; and (2) apparently associated with cell membranes of the middle and outer portions of the epidermis, where activity is inhibited by Mg2+, unaffected by dinitrophenol, and only slightly reduced by fixation. Spectrophotometric analysis shows that Mg2+ in the medium does not increase spontaneous hydrolysis of ATP, thus obviating the possible explanation that changes in substrate concentrations in the medium lead to alterations in the "staining" distributions. It is postulated that perhaps the two enzymes differ in their requirements for substrate—one requiring the polyphosphate to be in complexed form with Mg2+, the other uncomplexed. Concentrations of Mg2+ required to inhibit cell membrane nucleoside triphosphatase activity also inhibit the electrical potential difference and short-circuit current of the frog skin. Although these observations might be taken as presumptive evidence of the cell membrane enzyme as a component of the ion pump system, because of certain dissimilarities with respect to the biochemists' "transport ATPase" and for other reasons discussed in the paper, any definite conclusions in this regard are premature.

scholarly journals The Effect Of Iodoacetate On The Electrical Potential And On The Oxygen Uptake Of Frog Skin

1938 ◽  
Vol 15 (1) ◽  
pp. 132-142
Author(s):  
W. L. FRANCIS ◽  
O. GATTY
Keyword(s):  
Oxygen Uptake ◽  
Frog Skin ◽  
Electrical Potential ◽  
Respiratory Inhibitor

The oxidative biochemistry of living frog skin in so far as it is concerned with the maintenance of the electrical potential across the skin has been investigated by the use of the respiratory inhibitor iodoacetate. It appears that internal supplies of carbohydrate and external supplies of dl-lactate, pyruvate, acetate, propionate, n-butyrate, iso-butyrate and possibly crotonate can all be oxidized to precursors of the potential. This is not so for external supplies of formate, glycollate, succinate, acrylate, malonate, dl-β-hydroxybutyrate, and acetoacetate.

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