Voltage clamping induces resistance and current-voltage plot changes in frog gastric mucosa

1984 ◽  
Vol 246 (5) ◽  
pp. G574-G579
Author(s):  
G. W. Kidder ◽  
M. G. Elrod
Keyword(s):  
Gastric Mucosa ◽  
Membrane Resistance ◽  
Previous Model ◽  
Half Time ◽  
Ion Content ◽  
Zero Current ◽  
Current Voltage ◽  
Measured Resistance ◽  
Voltage Clamping ◽  
Voltage Transients

Changing the potential across the isolated frog gastric mucosa by voltage clamping changes the measured resistance of the tissue in two ways. An immediate change in resistance results from changing the measuring position on the nonlinear current-voltage (I-V) plot. Subsequent to this, the resistance changes slowly with a half-time of about 3 min, a change that is not predicted by a previous model for voltage transients and that implies slow changes in membrane resistance following changes in intracellular ion content. The I-V plot over the range examined shows three breakpoints; changing clamp voltage alters the position of two of these breakpoints as well as the slope of the connecting resistances. The central breakpoint agrees with the potential at zero current and varies with it as the clamp potential is changed, as predicted from a diode model for breakpoint generation.

Characterization of dogfish gastric mucosa under hyperbaric conditions

1983 ◽  
Vol 245 (2) ◽  
pp. G236-G241
Author(s):  
G. W. Kidder
Keyword(s):  
Gastric Mucosa ◽  
Transient Response ◽  
Partial Pressure Of Oxygen ◽  
Urea Content ◽  
Current Voltage ◽  
Current Passage ◽  
Long Time ◽  
Voltage Clamping ◽  
Hyperbaric Conditions

Using hyperbaric conditions previously shown to give improved oxygen delivery to the chambered dogfish gastric mucosa, experiments were performed to further characterize this tissue under these conditions. Removal of Cl- depressed but did not abolish acid secretion, raised the transepithelial resistance, and caused the potential to become more negative with reference to the mucosal surface. Voltage clamping to -60 mV inhibited secretion significantly; voltage clamping to +60 mV sometimes gave a stimulation. There was no long time-constant transient response to current passage. Under hyperbaric conditions, addition of the normal 350 mM urea content of elasmobranch plasma stimulated secretion. A further increase in partial pressure of oxygen (PO2) above 1.9 atm had no effect on secretion. The current-voltage plot showed two breakpoints, one about -23 mV and a second (not always detectable) at +50 mV; the negative breakpoint was stable as PO2 changed from 0.9 to 1.9 atm. Many of these observations are different from those reported for normabaric tissue and closely resemble those in the isolated frog gastric mucosa.

Point Contact Current Voltage Measurements of 4H-SiC Samples with Different Doping Profiles

2017 ◽  
Vol 897 ◽  
pp. 287-290 ◽  
Author(s):  
Matthias Kocher ◽  
Michael Niebauer ◽  
Mathias Rommel ◽  
Volker Haeublein ◽  
Anton J. Bauer
Keyword(s):  
Epitaxial Layer ◽  
Depth Profile ◽  
Point Contact ◽  
Surface Preparation ◽  
Epitaxial Layers ◽  
Depth Profiles ◽  
Current Voltage ◽  
Measured Resistance ◽  
Doping Profiles ◽  
Good Agreement

Point contact current voltage (PCIV) measurements were performed on 4H-SiC samples, both for n- an p-doped epitaxial layers as well as samples with rather shallow doping profiles realized by N- or Al-implantation in a range from 1016 cm-3 to 1019 cm-3. Surface preparation and measurement parameters were investigated in order to determine their influence on the measured resistance profiles. Furthermore depth profile measurements were performed on both an epitaxial layer as well as on implanted samples. These depth profiles could be measured reproducibly and showed good agreement with expected profiles for Al-implanted samples as well as for epitaxial layer whereas for N-implanted samples deviations between measured and expected profiles could be observed. It could be proven that PCIV profiling technique is a promising method for characterizing doped profiles in 4H-SiC, especially on Al-implanted samples.

Structure and electrical properties of eye muscles in cave- and surface-dwelling crayfishes

1980 ◽  
Vol 84 (1) ◽  
pp. 187-199
Author(s):  
D. Mellon ◽  
G. Lnenicka
Keyword(s):  
Input Resistance ◽  
Selective Advantage ◽  
Oculomotor System ◽  
Membrane Resistance ◽  
Muscle Fibres ◽  
Cross Sectional ◽  
Eye Muscles ◽  
Current Voltage ◽  
The Difference ◽  
Cave Dweller

The morphologies and passive electrical parameters of fibres in two eye muscles of a surface- and a cave-dwelling crayfish were compared. In the cave-dwelling form the muscles contained fewer fibres, of less diameter, and hence had a smaller cross-sectional area. Current-voltage relationships were similar in both species. Input resistance was higher in the cave-dweller, but the difference was not as great as would be expected on the basis of geometry alone. Accordingly, the specific membrane resistance of muscle fibres in the cave-dweller is 50–60% smaller than that in the surface-dweller. This may account partially for the observation that identified excitatory junctional potentials in muscles of cave- and surface dwellers have similar amplitudes. We conclude that a functional oculomotor system is maintained in cave-dwelling crayfish, and that this system confers some positive selective advantage.

Segregation of gastric Na and Cl transport: a vibrating probe and microelectrode study

1986 ◽  
Vol 251 (4) ◽  
pp. C643-C648 ◽  
Author(s):  
J. R. Demarest ◽  
C. Scheffey ◽  
T. E. Machen
Keyword(s):  
Gastric Mucosa ◽  
Cell Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Cell Types ◽  
Open Circuit ◽  
Membrane Potentials ◽  
Vibrating Probe ◽  
Zero Current ◽  
Mucosal Side

The short-circuit current (Isc) of resting Necturus gastric mucosa (approximately 20 microA/cm2) can be attributed to the algebraic sum of the net Cl- secretion and amiloride-inhibitable net Na+ absorption. We have attempted to identify the cell types [surface epithelial cells (SCs) or oxyntic cells (OCs)] responsible for the transport of these ions in Necturus gastric mucosa using microelectrodes (ME) and a vibrating probe (VP). Mucosae were mounted horizontally in an open-topped Plexiglas chamber either serosal side up for basolateral ME impalements of OCs or mucosal side up for apical impalements of SCs and VP measurements. Cell impalements were made under open-circuit conditions, and VP measurements were performed under short-circuit conditions. Impalements of OCs indicate that neither the ratio of their apical to basolateral cell membrane resistances (Ra/Rb = 1.3 +/- 0.2) nor their cell membrane potentials were affected by 10(-6) M mucosal amiloride. In contrast, impalements of SCs indicate that amiloride increased their Ra/Rb from 3.5 +/- 0.2 to 15.6 +/- 1.8 and hyperpolarized both cell membrane potentials by greater than 20 mV. VP measurements showed that the amiloride-induced change in the current from SCs (5.6 microA/cm2) accounted for the amiloride-induced change in the Isc (5.5 microA/cm2). A non-zero current (4.4 +/- 1.0 microA/cm2) measured over SCs in the presence of amiloride was due to contamination from current arising from the gastric crypts that contain the OCs.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals DC GAS BREAKDOWN AND TOWNSEND DISCHARGE IN CO2

2020 ◽  
pp. 154-158
Author(s):  
V.A. Lisovskiy ◽  
S.V. Dudin ◽  
P.P. Platonov ◽  
V.D. Yegorenkov
Keyword(s):  
Carbon Dioxide ◽  
Breakdown Voltage ◽  
Electrode Distance ◽  
Zero Current ◽  
Dc Discharge ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Gas Breakdown ◽  
Townsend Discharge ◽  
Maximum Voltage

We report the breakdown curves and current-voltage characteristics (CVC) of the Townsend mode DC discharge we have measured in carbon dioxide. We compare the breakdown curves measured with two different techniques. With the first technique we regard as breakdown voltage the maximum voltage which we can apply across the electrodes without igniting the discharge with fixed values of the inter-electrode distance and the gas pressure. With the second technique we register the CVC of the Townsend mode in the μA-mA range and then extrapolate them to zero current. We reveal that in the nA-μA range the CVCs of the Townsend mode may have a complicated behavior due to the formation of the space charge. Therefore the second technique furnishes incorrect values of the breakdown voltage.

Effect of inhibitors of gastric secretion on polarization of gastric potential by voltage clamping

1993 ◽  
Vol 264 (4) ◽  
pp. G630-G636
Author(s):  
G. Carrasquer ◽  
J. Y. Zhang ◽  
X. Wu ◽  
W. S. Rehm ◽  
M. Schwartz
Keyword(s):  
Plasma Membrane ◽  
Gastric Mucosa ◽  
Gastric Secretion ◽  
Proton Pump ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Luminal Membrane ◽  
Voltage Clamping ◽  
K Concentration ◽  
Effect Of Inhibitors

Voltage clamping across the frog gastric mucosa, nutrient positive to secretory, results in an increase in the open-circuit potential difference (OCPD). The increase in OCPD, or polarization, induced by voltage clamping could be caused by a redistribution of ions across the plasma membrane or by a polarization of pump electromotive forces, such as the Na(+)-K(+)-adenosinetriphosphatase (ATPase) located in the nutrient (serosal) membrane or the proton pump located in the secretory (luminal) membrane. The polarization induced by voltage clamping was not affected by removing Cl- and Na+ or by increasing the K+ concentration to 79 mM but was markedly reduced by placing in the nutrient solution 10(-3) M famotidine or 10(-4) M omeprazole. These data suggest that there is a strong contribution of the proton pump to the polarization induced by voltage clamping with some contribution of ion redistribution and/or the Na(+)-K(+)-ATPase. The data support the electrogenicity of the proton pump.

Sodium-potassium-ATPase electrogenicity in cerebral precapillary arterioles

2000 ◽  
Vol 279 (1) ◽  
pp. H351-H360 ◽  
Author(s):  
K. Quinn ◽  
C. Guibert ◽  
D. J. Beech
Keyword(s):  
Pump Current ◽  
Membrane Resistance ◽  
Inward Rectifier ◽  
Resting Potential ◽  
Patch Clamp Recording ◽  
High Background ◽  
Channel Current ◽  
Zero Current ◽  
Negative Membrane Potential ◽  
Rabbit Cerebral Cortex

Electrogenicity of the Na+/K+ pump has the capability to generate a large negative membrane potential independently of ion-channel current. The high background membrane resistance of arterioles may make them susceptible to such an effect. Pump current was detected by patch-clamp recording from smooth muscle cells in fragments of arterioles (diameter 24–58 μm) isolated from pial membrane of rabbit cerebral cortex. The current was 20 pA at −60 mV, and the extrapolated zero current potential was −160 mV. Two methods of estimating the effect of pump electrogenicity on resting potential indicated an average contribution of −35 mV. In 20% of the recordings, block of inward rectifier K+ channels by 10–100 μM Ba2+ led to a small depolarization, but hyperpolarization was a more common response. Ba2+ also inhibited depolarization evoked by 20 mM K+. In arterioles within intact pial membrane, Ba2+ failed to evoke constriction but inhibited K+-induced constriction. The data suggest that cerebral arterioles are vulnerable to the hyperpolarizing effect of the Na+/K+pump, excessive effects of which are prevented by depolarizing inward rectifier K+ current

scholarly journals Identification and functional assay of an extracellular calcium-sensing receptor in Necturusgastric mucosa

1997 ◽  
Vol 273 (5) ◽  
pp. G1051-G1060 ◽  
Author(s):  
Robert R. Cima ◽  
Ivan Cheng ◽  
Mary E. Klingensmith ◽  
Naibedya Chattopadhyay ◽  
Olga Kifor ◽  
...  
Keyword(s):  
Gastric Mucosa ◽  
Rat Kidney ◽  
Basolateral Membrane ◽  
Basal Membrane ◽  
Membrane Resistance ◽  
Immunohistochemical Localization ◽  
Functional Assay ◽  
Antral Mucosa ◽  
Electrical Potentials ◽  
Necturus Maculosus

In mammals and amphibians, increases in extracellular Ca2+ can activate bicarbonate secretion and other protective functions of gastric mucosa. We hypothesized that the recently cloned extracellular Ca2+-sensing receptor (CaR) is functioning in the gastric mucosa. In Necturus maculosus gastric mucosa, reverse transcription-polymerase chain reaction using primers based on previously cloned CaR sequences amplified a 326-bp DNA fragment that had 84% nucleotide sequence identity with the rat kidney CaR. Immunohistochemical localization of the CaR using specific anti-CaR antiserum revealed its presence on the basal aspect of gastric epithelial cells. In microelectrode studies of Necturus antral mucosa, exposure to elevated Ca2+ (4.8 mM) and the CaR agonists NPS-467 and neomycin sulfate resulted in significant hyperpolarizations of basal membrane electrical potentials and increases in apical-to-basal membrane resistance ratios. Circuit analysis revealed that these changes reflected specific decreases in basolateral membrane resistance. Inhibition of prostaglandin synthesis using indomethacin significantly attenuated these effects. We conclude that the CaR is present and functioning in Necturus gastric antrum.

Effect of potassium on secretion and potential of frog's gastric mucosa in Cl–-free solutions

1963 ◽  
Vol 205 (5) ◽  
pp. 873-877 ◽  
Author(s):  
T. L. Davis ◽  
J. R. Rutledge ◽  
W. S. Rehm
Keyword(s):  
Gastric Mucosa ◽  
Potential Difference ◽  
Secretory Rate ◽  
Voltage Clamping ◽  
Bathing Fluid

In previous work it was shown that the potential difference of the secreting mucosa bathed in Cl–-free solutions (SO4– replacing Cl–) is negative (nutrient side negative). In the present work it was found that an increase of the K+ concentration (K+ substituted for Na+) of the bathing fluid on the secretory side produced an increase in H+ secretory rate. The effect of voltage-clamping at zero and at +100 mv on the H+ rate, with various K+ concentrations in the bathing fluids, yielded results predicted by the electrogenic H+ theory, but not by a forced exchange concept.

scholarly journals Analysis of Depolarizing and Hyperpolarizing Inactivation Responses in Gymnotid Electroplaques

1966 ◽  
Vol 50 (1) ◽  
pp. 141-169 ◽  
Author(s):  
Michael V. L. Bennett ◽  
Harry Grundfest
Keyword(s):  
Outward Current ◽  
High Resistance State ◽  
Membrane Resistance ◽  
Negative Resistance ◽  
Resting Potential ◽  
High K ◽  
Current Voltage ◽  
Resistance State ◽  
Time Courses ◽  
In Cells

In electroplaques of several gymnotid fishes hyperpolarizing or depolarizing currents can evoke all-or-none responses that are due to increase in membrane resistance as much as 10- to 12-fold. During a response the emf of the membrane shifts little, if at all, when the cell either is at its normal resting potential, or is depolarized by increasing external K, and in the case of depolarizing responses when either Cl or an impermeant anion is present. Thus, the increase in resistance is due mainly, or perhaps entirely, to decrease in K permeability, termed depolarizing or hyperpolarizing K inactivation, respectively. In voltage clamp measurements the current-voltage relation shows a negative resistance region. This characteristic accounts for the all-or-none initiation and termination of the responses demonstrable in current clamp experiments. Depolarizing inactivation is initiated and reversed too rapidly to measure with present techniques in cells in high K. Both time courses are slowed in cells studied in normal Ringer's. Once established, the high resistance state is maintained as long as an outward current is applied. Hyperpolarizing inactivation occurs in normal Ringer's or with moderate excess K. Its onset is more rapid with stronger stimuli. During prolonged currents it is not maintained; i.e., there is a secondary increase in conductance. Hyperpolarizing inactivation responses exhibit a long refractory period, presumably because of persistence of this secondary increase in conductance.

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