Effects of Ultraviolet Radiation on the Plasma Membranes of Chara corallina. II* The Action Potential

1976 ◽  
Vol 3 (5) ◽  
pp. 687
Author(s):  
C.J Doughty ◽  
A.B Hope
Keyword(s):  
Action Potential ◽  
Ultraviolet Radiation ◽  
Membrane Permeability ◽  
Ultraviolet Light ◽  
Plasma Membranes ◽  
Peak Height ◽  
Chara Corallina ◽  
Membrane Properties ◽  
Resting Potential ◽  
Gating Mechanisms

When cells of C. corallina were irradiated with 254 nm ultraviolet light, the action potential across the plasmalemma was unaffected in its peak height, but its duration (measured at half-peak height) was increased, more so as the dose was varied between 1500 and 6000 J m-2. The action potential across the tonoplast was reduced in peak height and increased in duration by U.V. The effects were slowly reversible. The effect of 285 nm u.v., effective in depolarizing the resting potential difference, was to decrease the peak of the plasmalemma action potential while leaving the duration virtually unaffected. The results are interpreted as revealing differential effects on gating mechanisms determining the duration, and on transient membrane permeability to chloride (and possibly potassium) determining the peak, of the action potential. Because of the differential wavelength effects, these two membrane properties are postulated to be mediated by molecules which act as distinctive targets to the two wavelengths.

Effects of Ultraviolet Radiation on the Plasma Membranes of Chara corallina. I The Hyperpolarized State

1976 ◽  
Vol 3 (5) ◽  
pp. 677
Author(s):  
C.J Doughty ◽  
A.B Hope
Keyword(s):  
Membrane Potential ◽  
Ultraviolet Radiation ◽  
Ultraviolet Irradiation ◽  
Plasma Membranes ◽  
Membrane Conductance ◽  
Chara Corallina ◽  
Potential Difference ◽  
Electrogenic Pump ◽  
Chloride Permeability ◽  
Membrane Potential Difference

Effects of 254 nm ultraviolet irradiation on the plasmalemma potential difference and conductance in C, corallina have been further analysed. Following an increase in passive chloride permeability, revealed from previous studies, and which is manifested as a depolarization of membrane potential difference and an increase in membrane conductance, a secondary depolarization was prominent at pH 7 and is attributed to u.v.-induced inhibition of an electrogenic pump. The secondary depolarization was usually accompanied by a decrease in membrane conductance. For doses of u.v. of 1400 J m-2, these effects were almost reversible within about 1 h

scholarly journals Changes in Membrane Properties of Chick Embryonic Hearts during Development

1972 ◽  
Vol 60 (4) ◽  
pp. 430-453 ◽  
Author(s):  
Nick Sperelakis ◽  
K. Shigenobu
Keyword(s):  
Action Potential ◽  
Input Resistance ◽  
Membrane Properties ◽  
Resting Potential ◽  
Lower Sensitivity ◽  
Na Channels ◽  
Electrophysiological Properties ◽  
Ventricular Cells ◽  
High K ◽  
Pacemaker Potentials

The electrophysiological properties of embryonic chick hearts (ventricles) change during development; the largest changes occur between days 2 and 8. Resting potential (Em) and peak overshoot potential (+Emax) increase, respectively, from -35 mv and +11 mv at day 2 to -70 mv and +28 mv at days 12–21. Action potential duration does not change significantly. Maximum rate of rise of the action potential (+Vmax) increases from about 20 v/sec at days 2–3 to 150 v/sec at days 18–21; + Vmax of young cells is not greatly increased by applied hyperpolarizing current pulses. In resting Em vs. log [K+]o curves, the slope at high K+ is lower in young hearts (e.g. 30 mv/decade) than the 50–60 mv/decade obtained in old hearts, but the extrapolated [K+]i values (125–140 mM) are almost as high. Input resistance is much higher in young hearts (13 MΩ at day 2 vs. 4.5 MΩ at days 8–21), suggesting that the membrane resistivity (Rm) is higher. The ratio of permeabilities, PNa/PK, is high (about 0.2) in young hearts, due to a low PK, and decreases during ontogeny (to about 0.05). The low K+ conductance (gK) in young hearts accounts for the greater incidence of hyperpolarizing afterpotentials and pacemaker potentials, the lower sensitivity (with respect to loss of excitability) to elevation of [K+]o, and the higher chronaxie. Acetylcholine does not increase gK of young or old ventricular cells. The increase in (Na+, K+)-adenosine triphosphatase (ATPase) activity during development tends to compensate for the increase in gK. +Emax and + Vmax are dependent on [Na+]o in both young and old hearts. However, the Na+ channels in young hearts (2–4 days) are slow, tetrodotoxin (TTX)-insensitive, and activated-inactivated at lower Em. In contrast, the Na+ channels of cells in older hearts (> 8 days) are fast and TTX-sensitive, but they revert back to slow channels when placed in culture.

Die Wasser- und Ionen-Permeabilität der Zellmembran von Protozoen unter Einwirkung von ultraviolettem Licht / The Permeability of the Protozoan Cell Membrane to Water and Ions under the Action of Ultraviolet Light

1972 ◽  
Vol 27 (10) ◽  
pp. 1243-1257 ◽  
Author(s):  
Eilo Hildebrand ◽  
Hennig Stieve
Keyword(s):  
Membrane Potential ◽  
Membrane Permeability ◽  
Ultraviolet Light ◽  
Spectral Sensitivity ◽  
Morphological Changes ◽  
Membrane Resistance ◽  
Membrane Properties ◽  
Osmotic Gradient ◽  
Sensitivity Curve ◽  
Spectral Sensitivity Curve

The action of ultraviolet light on certain membrane properties of protozoa was investigated in Paramecium, Euplotes, and Opalina using the following methods: observation of morphological changes of the animals, recording of the osmoregulatory organelle (Paramecium), and measurement of membrane potential and resistance by means of intracellularly inserted microelectrodes.This paper presents only slow effects which occur within some minutes after uv irradiation and does not directly concern excitability of protozoa.Due to large uv doses swelling was observed both in Paramecium and Opalina; in Euplotes a liquid-filled vacuole was formed.Small uv doses cause an increase in the frequency of the contractile vacuole of Paramecium; larger doses diminish the frequency reversibly (Fig. 4), and even larger doses lead to an irreversible inactivation of this organelle.Membrane potential and membrane resistance in Opalina are shown to change in different ways under continuous irradiation (Fig. 13): After a transient decrease the membrane potential increases to about the initial value and after this it decreases to zero, whereas the membrane resistance decreases from the beginning of irradiation.The spectral sensitivity curve (Fig. 9) obtained from a standard decrease of the membrane potential shows a maximum at about 280 nm and a rise from 250 nm towards shorter wavelengths.The results indicate an influx of water following the osmotic gradient and an increase of the membrane permeability to cations. With respect to the different behavior of membrane potential and conductivity the mechanism of uv action is discussed. The most probable assumption is that the permeability increases unspecifically but gradually in succession for water, chloride, potassium, and sodium. The possibility of disruption of disulfide links is discussed with respect to the spectral sensitivity curve. It is suggested that the altered permeability is based on photochemically induced changes of the structure of proteins which are either part of the membrane or have an important function in the regulation of the membrane permeability.

Membrane properties and electrogenesis in the distal axons of small dorsal root ganglion neurons in vitro

2012 ◽  
Vol 108 (3) ◽  
pp. 729-740 ◽  
Author(s):  
Dmytro V. Vasylyev ◽  
Stephen G. Waxman
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Dorsal Root ◽  
Small Diameter ◽  
Dorsal Root Ganglion Neurons ◽  
Membrane Properties ◽  
Resting Potential ◽  
Drg Neurons ◽  
Ganglion Neurons

Although it is generally thought that sensory transduction occurs at or close to peripheral nerve endings, with action potentials subsequently propagating along the axons of dorsal root ganglia (DRG) neurons toward the central nervous system, the small diameter of nociceptive axons and their endings have made it difficult to estimate their membrane properties and electrogenic characteristics. Even the resting potentials of nociceptive axons are unknown. In this study, we developed the capability to record directly with patch-clamp electrodes from the small-diameter distal axons of DRG neurons in vitro. We showed using current-clamp recordings that 1) these sensory axons have a resting potential of −60.2 ± 1 mV; 2) both tetrodotoxin (TTX)-sensitive (TTX-S) and TTX-resistant (TTX-R) Na+ channels are present and available for activation at resting potential, at densities that can support action potential electrogenesis in these axons; 3) TTX-sensitive channels contribute to the amplification of small depolarizations that are subthreshold with respect to the action potential in these axons; 4) TTX-R channels can support the production of action potentials in these axons; and 5) these TTX-R channels can produce repetitive firing, even at depolarized membrane potentials where TTX-S channels are inactivated. Finally, using voltage-clamp recordings with an action potential as the command, we confirmed the presence of both TTX-S and TTX-R channels, which are activated sequentially during action potential in these axons. These results provide direct evidence for the presence of TTX-S and TTX-R Na+ channels that are functionally available at resting potential and contribute to electrogenesis in small-diameter afferent axons.

scholarly journals Effects of Varied Culturing and Experimental Temperature on Electrical Membrane Properties in Paramecium

1984 ◽  
Vol 108 (1) ◽  
pp. 179-194
Author(s):  
BORIS MARTINAC ◽  
HANS MACHEMER
Keyword(s):  
Action Potential ◽  
Voltage Clamp ◽  
Input Resistance ◽  
Membrane Properties ◽  
Resting Potential ◽  
Constant Current ◽  
Temperature Changes ◽  
Stimulus Response ◽  
Time To Peak ◽  
Relationship Of

Effects of temperature on the electrical properties of the Paramecium membrane were investigated under constant current and voltage-clamp stimulation. With cells cultured at 18°C, the resting potential was largely stable with experimental temperatures varied over the range of 10–25°C, whereas action potential amplitude and membrane input resistance were inversely related to temperature increases. During voltage clamp, the early calcium current was increased, the time-to-peak decreased, and the early conductance increased with temperature. Similar modifications of the culturing temperature did not affect the resting potential, input resistance and stimulus-response relationship of the action potential, but the early conductance was reduced with increase in temperature. Possible effects of long- and short-term temperature changes upon intraciliary calcium concentration are discussed.

scholarly journals A classic experiment revisited: membrane permeability changes during the action potential

2021 ◽  
Vol 45 (1) ◽  
pp. 178-181
Author(s):  
Carolyn L. Powell ◽  
Angus M. Brown
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Membrane Permeability ◽  
Reversal Potential ◽  
Resting Potential ◽  
Membrane Excitability ◽  
Permeability Changes ◽  
The Relationship ◽  
Potential Peak ◽  
Three Phases

The ability to understand the relationship between the reversal potential and the membrane potential is a fundamental skill that must be mastered by students studying membrane excitability. To clarify this relationship, we have reframed a classic experiment carried out by Hodgkin and Katz, where we compare graphically the membrane potential at three phases of the action potential (resting potential, action potential peak, and afterhyperpolarization) to reversal potential for K+ ( EK), reversal potential for Na ( ENa), and membrane potential ( Em) (calculated by the Goldman Hodgkin Katz equation) to illustrate that the membrane potential approaches the reversal potential of the ion to which it is most permeable at that instant.

Subthreshold frequency selectivity in avian auditory thalamus

1994 ◽  
Vol 71 (4) ◽  
pp. 1361-1372 ◽  
Author(s):  
B. Strohmann ◽  
D. W. Schwarz ◽  
E. Puil
Keyword(s):  
Frequency Selectivity ◽  
Membrane Properties ◽  
Resting Potential ◽  
Resonant Peak ◽  
Auditory Signal ◽  
Voltage Response ◽  
Potential Range ◽  
Na Current ◽  
Frequency Responses ◽  
Low Threshold

1. We studied the frequency responses of neurons in the nucleus ovoidalis (OV), the principal thalamic auditory relay nucleus of the chicken, in the subthreshold range of membrane potentials. The frequency response is the impedance amplitude profile evident in the voltage response to a broadband stimulus. The stimulus was a deterministic periodic current input of small amplitude, sweeping through a specified frequency range. We used whole-cell, tight-seal recording techniques in slices to study the voltage responses and membrane properties in current and voltage clamp. 2. Generally, low-frequency resonant humps with peak impedances of approximately 6 Hz characterized the frequency responses of OV neurons. This resonance was the principal determinant for frequency selectivity in the majority of OV neurons expressing only a tonic mode of firing. 3. The 6-Hz resonance was voltage dependent and most distinct where the activation ranges of a hyperpolarization activated inward current (IH) and a persistent Na+ current tend to overlap. The potential range for optimal resonance often included the resting potential. 4. Application of the Na+ current antagonist, tetrodotoxin, blocked the persistent Na+ current and most of the resonant hump at depolarized levels but did not affect the resonant peak along the frequency axis. Thus the persistent Na+ current may serve to amplify the resonance. 5. Extracellular application of Cs+, but not Ba2+, blocked a voltage sag during pulsed hyperpolarization as well as the IH current. Application of Cs+ also eliminated the 6-Hz resonance. An IH seems, therefore, instrumental for the resonance. 6. A minority of neurons that expressed low-threshold Ca2+ spikes and burst firing at hyperpolarized states displayed voltage oscillations at 2-4 Hz, spontaneously or in response to pulsatile stimuli. Application of Ni2+ blocked the oscillations and the low-threshold spikes, presumably produced by a T-type Ca2+ current. The resonance at 6 Hz, however, was only slightly affected by Ni2+. A T-type current, therefore, is critical for the 2- to 4-Hz oscillations. 7. Membrane resonance may dominate the power spectrum of subthreshold potential fluctuations. The resonance demonstrated in vitro may be stabilized by experimental procedures; its frequency may be different and more variable in vivo. Resonances in thalamic neurons may play a role in auditory signal processing in birds.

Properties of visceral primary afferent neurons in the nodose ganglion of the rabbit

1985 ◽  
Vol 54 (2) ◽  
pp. 245-260 ◽  
Author(s):  
C. E. Stansfeld ◽  
D. I. Wallis
Keyword(s):  
Action Potentials ◽  
Input Resistance ◽  
Nodose Ganglion ◽  
Time Dependent ◽  
Membrane Properties ◽  
Resting Potential ◽  
Inward Rectification ◽  
C Cells ◽  
Axonal Conduction ◽  
A Cells

The active and passive membrane properties of rabbit nodose ganglion cells and their responsiveness to depolarizing agents have been examined in vitro. Neurons with an axonal conduction velocity of less than 3 m/s were classified as C-cells and the remainder as A-cells. Mean axonal conduction velocities of A- and C-cells were 16.4 m/s and 0.99 m/s, respectively. A-cells had action potentials of brief duration (1.16 ms), high rate of rise (385 V/s), an overshoot of 23 mV, and relatively high spike following frequency (SFF). C-cells typically had action potentials with a "humped" configuration (duration 2.51 ms), lower rate of rise (255 V/s), an overshoot of 28.6 mV, an after potential of longer duration than A-cells, and relatively low SFF. Eight of 15 A-cells whose axons conducted at less than 10 m/s had action potentials of longer duration with a humped configuration; these were termed Ah-cells. They formed about 10% of cells whose axons conducted above 2.5 m/s. The soma action potential of A-cells was blocked by tetrodotoxin (TTX), but that of 6/11 C-cells was unaffected by TTX. Typically, A-cells showed strong delayed (outward) rectification on passage of depolarizing current through the soma membrane and time-dependent (inward) rectification on inward current passage. Input resistance was thus highly sensitive to membrane potential close to rest. In C-cells, delayed rectification was not marked, and slight time-dependent rectification occurred in only 3 of 25 cells; I/V curves were normally linear over the range: resting potential to 40 mV more negative. Data on Ah-cells were incomplete, but in our sample of eight cells time-dependent rectification was absent or mild. C-cells had a higher input resistance and a higher neuronal capacitance than A-cells. In a proportion of A-cells, RN was low at resting potential (5 M omega) but increased as the membrane was hyperpolarized by a few millivolts. A-cells were depolarized by GABA but were normally unaffected by 5-HT or DMPP. C-cells were depolarized by GABA in a similar manner to A-cells but also responded strongly to 5-HT; 53/66 gave a depolarizing response, and 3/66, a hyperpolarizing response. Of C-cells, 75% gave a depolarizing response to DMPP.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C402-C408 ◽  
Author(s):  
E. P. Burke ◽  
K. M. Sanders
Keyword(s):  
Membrane Potential ◽  
Potential Gradient ◽  
Circular Muscle ◽  
Input Resistance ◽  
Pump Current ◽  
Muscle Layer ◽  
Membrane Properties ◽  
Resting Potential ◽  
Voltage Dependent ◽  
In Cells

Previous studies have suggested that the membrane potential gradient across the circular muscle layer of the canine proximal colon is due to a gradient in the contribution of the Na(+)-K(+)-ATPase. Cells at the submucosal border generate approximately 35 mV of pump potential, whereas at the myenteric border the pump contributes very little to resting potential. Results from experiments in intact muscles in which the pump is blocked are somewhat difficult to interpret because of possible effects of pump inhibitors on membrane conductances. Therefore, we studied isolated colonic myocytes to test the effects of ouabain on passive membrane properties and voltage-dependent currents. Ouabain (10(-5) M) depolarized cells and decreased input resistance from 0.487 +/- 0.060 to 0.292 +/- 0.040 G omega. The decrease in resistance was attributed to an increase in K+ conductance. Studies were also performed to measure the ouabain-dependent current. At 37 degrees C, in cells dialyzed with 19 mM intracellular Na+ concentration [( Na+]i), ouabain caused an inward current averaging 71.06 +/- 7.49 pA, which was attributed to blockade of pump current. At 24 degrees C or in cells dialyzed with low [Na+]i (11 mM), ouabain caused little change in holding current. With the input resistance of colonic cells, pump current appears capable of generating at least 35 mV. Thus an electrogenic Na+ pump could contribute significantly to membrane potential.

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