Electrical and transport characteristics of skin of larval Rana catesbeiana

1979 ◽  
Vol 237 (1) ◽  
pp. R74-R79 ◽  
Author(s):  
T. C. Cox ◽  
R. H. Alvarado
Keyword(s):  
Rana Catesbeiana ◽  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Open Circuit ◽  
Shunt Resistance ◽  
Ion Substitution ◽  
Adult Skin

Carefully dissected, mounted, and bathed with Ringer solution, the larval bullfrog skin has a resistance of about 9,000 omega.cm2 and a stable transepithelial electrical potential of about 20 mV (inside +). A short-circuit current of about 2 microA.cm-2 is generated that is comparable in magnitude to the net inward flux of Na+. At open circuit the flux ratio equation for Na+ is not satisfied. Larval skin is less sensitive to ouabain, amiloride, and ADH than adult skin. The current-voltage (C-V) relationship across the preparation is not linear; there are distinct breaks in both the hyperpolarizing and hypopolarizing regions. The former break, at about +130 mV, corresponds with a break observed in adult skin that corresponds with ENa. The shunt resistance (RS) and active pathway resistance (RA) were estimated by C-V curve analysis and by ion substitution. The two methods yielded comparable values with RS about 11 k omega.cm2 and RA about 62 k omega.cm2. It is suggested that transport is limited by the number of entry sites for sodium at the apical border of transport cells.

Nystatin studies of the skin of larval Rana catesbeiana

1983 ◽  
Vol 244 (1) ◽  
pp. R58-R65
Author(s):  
T. C. Cox ◽  
R. H. Alvarado
Keyword(s):  
Rana Catesbeiana ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Electrical Characteristics ◽  
Shunt Resistance ◽  
Selective Permeability ◽  
Ion Substitution

Transport and electrical characteristics of the isolated skin of larval Rana catesbeiana were analyzed using ion substitution and nystatin. When the inner (IBS) and outer (OBS) bathing solutions contained Na Ringer solution the electrical potential (TEP), short-circuit current (SCC), and resistance (R2) were 23.5 +/- 7.0 mV, 2.8 +/- 0.7 microA . cm-2, and 8.00 +/- 0.74 k omega. cm2, respectively (n = 4). When K was substituted for Na in the OBS these values were not changed significantly. When nystatin (120 U.cm-3), a drug that increases the permeability of membranes to small cations, was added to the OBS (Na Ringer) there was a striking increase in the TEP to 52.8 +/- 3.1 mV, SCC to 14.8 +/- 2.0 microA . cm-2, and drop in R2 to 3.75 +/- 0.52 k omega . cm2. The response to nystatin was similar with Na or K Ringer solution in the OBS (Na Ringer in the IBS). With Na Ringer in the OBS and IBS, the increase in SCC induced by low doses of nystatin equaled net Na flux measured isotopically. Plots of transepithelial conductance against SCC after nystatin were linear and provided estimates of shunt resistance (R*sh = 14.6 +/- 1.3 k omega . cm2) and electromotive driving force for ions (E*A = 76 +/- 3 mV). Similar curves were obtained with K Ringer in the OBS. In the presence of nystatin, characteristics of the basolateral membrane were evaluated. It displayed selective permeability to K relative to Na or Tris.

Determination of the ENa of from skin from studies of its current-voltage relationship

1975 ◽  
Vol 229 (4) ◽  
pp. 947-951 ◽  
Author(s):  
SI Helman ◽  
RG O'Neil ◽  
RS Fisher
Keyword(s):  
Frog Skin ◽  
Short Circuit ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Shunt Resistance ◽  
Transport Pathways ◽  
Current Voltage ◽  
Current Voltage Relationship ◽  
Voltage Relationship

Studies were done to test the idea that the emf of the sodium pump (ENa) of isolated frog skin could be estimated directly from studies of its current-voltage relationship. ENa was estimated in two ways: a) from the bidirectional sodium flux ratio according to Ussing and Zerahn, and b) from the values of open-circuit voltage, short-circuit current, and the shunt resistance estimated when the [Na] of the outer solution was reduced to zero. When the values of ENa were compared with the values of E1 obtained from the current-voltage relationships, they were found to be the same despite considerable variability in the values of ENa between skins (77-168 mV). In general, the values of ENa were considerably higher when the skins were bathed with sulfate-Ringer as compared with chloride-Ringer solution. These data are compatible with the idea that in nonedge-damaged frog skin, the unidirectional sodium fluxes were confined primarily to active transport pathways alone, and, accordingly, they may be excluded from parallel-shunt pathways.

Further Observations on the Physiology of Salinity Adaptation in the Crab-Eating Frog (Rana Cancrivora)

1968 ◽  
Vol 49 (1) ◽  
pp. 185-193
Author(s):  
MALCOLM S. GORDON ◽  
VANCE A. TUCKER
Keyword(s):  
Sea Water ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Osmotic Concentration ◽  
Green Toad ◽  
The Face ◽  
Solution Bathing ◽  
Toad Bufo

1. Total rates of urea loss from adult euryhaline crab-eating frogs (Rana cancrivora) adapted to various environmental salinities between fresh water and 80 % sea water increase as salinity increases above 40% sea water. Oxygen consumption is constant in rate in all salinities studied. 2. The presence of urea in the Ringer solution bathing isolated pieces of skin of frogs adapted to 60% sea water increases both the electrical potential and the inwardly directed short-circuit current across the skin. 3. In skeletal muscle cells addition of intracellular solutes maintains tissue hydration in the face of large increases in plasma osmotic concentration in high-salinity media. Changes in the intracellular urea and free amino acid concentrations are primarily responsible for increases in intracellular osmotic concentration. 4. Some implications of these observations are discussed and comparisons made with the euryhaline green toad, Bufo viridis.

Acidification stimulates chloride and fluid absorption across frog retinal pigment epithelium

1994 ◽  
Vol 266 (4) ◽  
pp. C946-C956 ◽  
Author(s):  
J. L. Edelman ◽  
H. Lin ◽  
S. S. Miller
Keyword(s):  
Retinal Pigment Epithelium ◽  
Short Circuit ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Open Circuit ◽  
Disulfonic Acid ◽  
Fluid Absorption

Radioactive tracers and a modified capacitance-probe technique were used to characterize the mechanisms that mediate Cl and fluid absorption across the bullfrog retinal pigment epithelium (RPE)-choroid. In control (HCO3/CO2) Ringer solution, 36Cl was actively absorbed (retina to choroid) at a mean rate of 0.34 mu eq.cm-2.h-1 (n = 34) and accounted for approximately 25% of the short-circuit current. Apical bumetanide (100 microM) or basal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS; 1 mM) inhibited active Cl transport by 70 and 62%, respectively. Active Cl absorption was doubled, either by removing HCO3 from the bathing media or by elevating CO2 from 5 to 13%, and the increased flux was inhibited by apical bumetanide or basal DIDS. Open-circuit measurements of fluid absorption rate (Jv) and the net fluxes of 36Cl, 22Na, and 86Rb (K substitute) indicated that CO2-induced acidification stimulated NaCl and fluid absorption across the RPE. During acidification, bumetanide produced a twofold larger inhibition of Jv compared with control. Stimulation of net Cl absorption was most likely caused by inhibition of the the basolateral membrane intracellular pH-dependent Cl-HCO3 exchanger.

scholarly journals Electrical and photoelectric properties of MoN/p-CdTe and MoN/n-CdTe heterojunctions

2021 ◽  
pp. 33-38
Author(s):  
T. T. Kovaliuk ◽  
M. N. Solovan ◽  
P. D. Maryanchuk
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Current Transfer ◽  
Vapor Pressures ◽  
Bridgman Technique ◽  
Shunt Resistance ◽  
Recombination Mechanism ◽  
Type Conductivity ◽  
Photoelectric Properties

Due to the physical properties of MoN and ITO thin films, it was decided to create MoN/p-CdTe and MoN/n-CdTe heterostructures and investigate their electrical and photoelectric properties. The method of reactive magnetron sputtering was used to create thin MoN and ITO films on single crystal CdTe substrates with different conductivity types. To manufacture test heterostructures, the following CdTe crystal substrates were used: 1) p-type conductivity, grown by Bridgman technique at low cadmium vapor pressures; 2) n-type conductivity, grown by Bridgman technique at high cadmium vapor pressures. During the deposition process, the argon pressure in the vacuum chamber was 0.4 Pa. The power of the magnetron was 30 W, the sputtering process continued 5 min at a substrate temperature of 150°C. I-V characteristics of the heterostructures at different temperatures were measured, the height of the potential barrier, the values of the series and shunt resistance were determined. Electrical and photoelectric properties of the heterostructures were studied, and the dominant mechanisms of current transfer at forward displacements was established. The tunnel-recombination mechanism was found to be the dominant mechanism of current transfer in the MoN/p-CdTe and MoN/n-CdTe heterostructures. It was shown that the photoelectric parameters for the MoN/p-CdTe heterostructure are higher than those for MoN/n-CdTe. MoN/p-CdTe heterojunctions have the following photoelectric parameters: open-circuit voltage Voc = 0.4 V, short-circuit current Isc = 24.6 mA/cm2 at an illumination intensity of 80 mW/cm2. This makes them a promising material for the manufacture of detectors of various radiation types.

In vitro studies of sodium transport across the lower intestine of a desert parrot

1980 ◽  
Vol 239 (3) ◽  
pp. R285-R290
Author(s):  
E. Skadhauge ◽  
T. J. Dawson
Keyword(s):  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Na Transport ◽  
Salt Loading ◽  
Ussing Chambers ◽  
Lower Intestine

The lower intestine (coprodeum and colon) of the Australian parrot, the galah, was mounted in Ussing chambers. Short-circuit current (SCC), electrical potential difference (PD), and unidirectional fluxes of Na and Cl were measured in birds that were fed mixed seeds or were NaCl loaded. The net Na transport of both coprodeum and colon was nearly equal to the SCC, and the flux ratio for Cl was unity. In birds which received mixed seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but increased colonic Na transport. The coprodeal and colonic SCC and NA transport of birds receiving mixed seeds were inhibited by amiloride on the mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by amiloride (by 17%), but stimulated by amino acids (by 18%).

scholarly journals Modélisation et commande d’un panneau photovoltaïque dans l’environnement PSIM

2019 ◽  
Author(s):  
Saad Motahhir ◽  
Abdelaziz El Ghzizal ◽  
Aziz Derouich
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Maximum Power ◽  
Physical Parameters ◽  
Maximum Power Point ◽  
Shunt Resistance ◽  
Photovoltaic Panel ◽  
Current Voltage ◽  
Power Point

The objective of this work is to make a model of photovoltaic cells (PV) dedicated to teaching renewable energy using PSIM software. This model is based on ratings provided by the manufacturer as: open circuit voltage, short circuit current, voltage and current corresponding to the maximum power point. So the resulting model has a better approach and takes into account the influence of different physical parameters including temperature, irradiation, series resistance, shunt resistance and saturation current of the diode. After a general presentation of the photovoltaic conversion chain, the article details, at first, the modeling of a photovoltaic panel. Secondly, we focus on the implementation of a MPPT command for controlling the DC / DC to operate the PV array at maximum power (MPP).

scholarly journals Photovoltaic Cell and Module I-V Characteristic Approximation Using Bézier Curves

2018 ◽  
Author(s):  
Roland Szabo ◽  
Aurel Gontean
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Photovoltaic Cell ◽  
Open Circuit ◽  
Maximum Power ◽  
Shunt Resistance ◽  
First Case ◽  
Novel Approach ◽  
Pv Cell ◽  
Different Temperatures

The aim of this work is to introduce new ways to model the I-V characteristic of a PV cell or PV module using straight lines and Bézier curves. This is a complete novel approach, Bézier curves being previously used mainly for computer graphics. The I-V characteristic is divided in three sections, modeled with lines and a quadratic Bézier curve in the first case and with three cubic Bézier curves in the second case. The result proves to be accurate and relies on the fundamental points usually present in the PV cell datasheets: Voc (the open circuit voltage), Isc (the short circuit current), Vmp (the maximum power corresponding voltage) and Imp (the maximum power corresponding current) and the parasitic resistances Rsh0 (shunt resistance at Isc) and Rs0 (series resistance at Voc). The proposed algorithm completely defines all the implied control points and the error is analyzed. The proposed method is validated for different temperatures and irradiances. The model is finally compared and validated using the least squares fitting method.

Role of active potassium transport by integumentary epithelium in secretion of larval-pupal moulting fluid during silkmoth development

1975 ◽  
Vol 62 (2) ◽  
pp. 357-366
Author(s):  
A. M. Jungreis ◽  
W. R. Harvey
Keyword(s):  
Short Circuit ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Potassium Transport ◽  
Open Circuit ◽  
Ratio Test ◽  
Potassium Flux

1. The exuvial side of the pharate pupal integument is usually positive to the haemolymph-side, both in vivo and in vitro, during the period when the moulting fluid is being secreted. 2. The ratio of potassium flux toward the exuvial space is higher than that toward the haemolymph, under both open-circuit conditions and short-circuit conditions, demonstrating by the Flux Ratio test that potassium is actively transported across the isolated integument during this secretion period. 3. Just prior to ecdysis, while moulting fluid is being reabsorbed, the potassium flux ratios become unity, suggesting that active potassium transport has ceased, but the short-circuit current that remains suggests that some other ion is actively transported at this time. 4. We argue that the potassium salt solution, formed in the exuvial space (as water presumably follows the actively transported potassium), has three functions (1) to accomplish the gel--sol transformation, (2) to activate the gel enzymes and (3) to buffer the enzyme solution at a pH favourable to the activity of the gel enzymes.

scholarly journals Na Transport across Frog Skin at Low External Na Concentrations

1966 ◽  
Vol 49 (6) ◽  
pp. 1161-1176 ◽  
Author(s):  
THOMAS U. L. BIBER ◽  
RONALD A. CHEZ ◽  
PETER F. CURRAN
Keyword(s):  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Potential Profile ◽  
Na Transport ◽  
Ringer’S Solution ◽  
Electrical Potentials ◽  
Single Compartment

Isolated frog skin was bathed with a dilute solution containing 1 mm NaCl on the outside and with normal Ringer’s solution on the inner surface. Net Na flux was determined by simultaneous measurement of unidirectional fluxes with Na22 and Na24 and intracellular electrical potentials were examined with microelectrodes. There was a net inward transport of Na under both open-circuit and short-circuit conditions. The short-circuit current was approximately 15% greater than the net Na flux; the discrepancy could be accounted for by a small outward flux of Cl. The electrical potential profile did not differ greatly from that observed in skins bathed on the outside with normal Ringer’s solution. Under open-circuit conditions, there were usually several potential steps and under short-circuit conditions the cells were negative relative to the bathing solutions. Estimates of epithelial Na concentrations utilizing radioactive Na suggested that if all epithelial Na were in a single compartment, an active entry step would be necessary to allow a net inward Na transport. The results could also be explained by a series arrangement of Na compartments without necessarily postulating an active Na entry. The behavior of the potential profile suggested that this latter alternative was more likely.

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