scholarly journals An oscillatory component of propagated fluctuation electric potential in lupine shoot

2014 ◽  
Vol 55 (1) ◽  
pp. 53-66 ◽  
Author(s):  
Zygmunt Hejnowicz ◽  
Andrzej Pijanowski ◽  
Krzysztof Głębicki
Keyword(s):  
Action Potential ◽  
Electric Potential ◽  
Volume Conductor ◽  
Excitable Cells ◽  
Oscillatory Component ◽  
Band Pass ◽  
Cut Surface

Application of a drop of auxin solution to a cut surface on the petiole in lupine shoot elicits a travelling pulse of electric potential decrease. This pulse was simultaneously recorded by means of a DC amplifier and band-pass amplifier 0.1-100 Hz, both connected to the same exploring AgCl electrode driven into the stem. The DC record shows a pulse 20-80 mV in height of about 30 s duration at its height with smooth slopes. The band-pass amplifier shows one to a few pairs of spikes (negative and positive) whose amplitude is at least of an order lower than that of the DC pulse. These spikes are interpreted as the action potential of certain excitable cells recorded in a "volume conductor". The pulse is interpreted as a wave of cooperative depolarization of excitable and a mass of inexcitable cells.

scholarly journals The effect of dipole housing and feeding wires in physical phantoms for EEG

2019 ◽  
Vol 5 (1) ◽  
pp. 85-88
Author(s):  
René Machts ◽  
Alexander Hunold ◽  
Jens Haueisen
Keyword(s):  
Electric Potential ◽  
Volume Conductor ◽  
Constant Current ◽  
Twisted Pair ◽  
Eeg Data ◽  
Phantom Measurements ◽  
Average Change ◽  
Electric Potentials ◽  
The Difference ◽  
Signal Sources

AbstractCurrent dipoles are well established models in the localization of neuronal activity to electroencephalography (EEG) data. In physical phantoms, current dipoles can be used as signal sources. Current dipoles are often powered by constant current sources connected via twisted pair wires mostly consisting of copper. The poles are typically formed by platinum wires. These wires as well as the dipole housing might disturb the electric potential distributions in physical phantom measurements. We aimed to quantify this distortion by comparing simulation setups with and without the wires and the housing. The electric potential distributions were simulated using finite element method (FEM). We chose a homogenous volume conductor surrounding the dipoles, which was 100 times larger than the size of the dipoles. We calculated the difference of the electric potential at the surface of the volume conductor between the simulations with and without the connecting wires and the housing. Comparing simulations neglecting all connecting wires and the housing rod to simulations considering them, the electric potential at the surface of the volume conductor differed on average by 2.85 %. Both platinum and twisted pair copper wires had a smaller effect on the electric potentials with a maximum average change of 6.38 ppm. Consequently, source localization of measurements in physical head phantoms should consider these rods in the forward model.

Epithelial Conduction in Salps: I. Properties of the Outer Skin Pulse System of the Stolon

1979 ◽  
Vol 80 (1) ◽  
pp. 231-239
Author(s):  
PETER A. V. ANDERSON
Keyword(s):  
Action Potential ◽  
Tight Junctions ◽  
Action Potentials ◽  
Calcium Influx ◽  
Sodium Current ◽  
Pulse System ◽  
Excitable Cells ◽  
Outer Skin ◽  
Embryonic Tissues

1. The Outer Skin Pulse (OSP) system of the stolon of Salpa fusiformis was studied histologically and electrophysiologically. 2. The cells of the conducting epithelium are cuboidal, 4–10 μm in diameter and are connected by gap and tight junctions (Fig. 1). They have resting potentials of - 75 to - 96 mV. 3. Outer Skin Pulses are conducted as overshooting action potentials 84–104 mV in amplitude which are characterized by the absence of a hyperpolarizing undershoot during the repolarizing phase (Fig. 2 A). When OSPs are evoked at frequencies in excess of 2 s−1 a pronounced plateau appears in the repolarizing phase (Fig. 2C). 4. Tetrodotoxin blocks OSPs in a manner which suggests that a sodium current is responsible for activation of the action potential. 5. Addition of 15 mM manganese to the bath blocks OSPs. This effect was initially accompanied by a reduction in OSP amplitude and an increase in duration (Fig. 5). This observation was interpreted as indicating the presence of a calcium influx during the action potential. 6. The results are compared with those obtained from epithelial conduction systems in other organisms, other embryonic tissues and excitable cells in other non-vertebrate chordates.

scholarly journals Action potentials in Xenopus oocytes triggered by blue light

2020 ◽  
Vol 152 (5) ◽  
Author(s):  
Florian Walther ◽  
Dominic Feind ◽  
Christian vom Dahl ◽  
Christoph Emanuel Müller ◽  
Taulant Kukaj ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Blue Light ◽  
Action Potentials ◽  
Xenopus Oocytes ◽  
Na Channel ◽  
Xenopus Laevis Oocytes ◽  
Na Channels ◽  
Excitable Cells ◽  
Voltage Gated

Voltage-gated sodium (Na+) channels are responsible for the fast upstroke of the action potential of excitable cells. The different α subunits of Na+ channels respond to brief membrane depolarizations above a threshold level by undergoing conformational changes that result in the opening of the pore and a subsequent inward flux of Na+. Physiologically, these initial membrane depolarizations are caused by other ion channels that are activated by a variety of stimuli such as mechanical stretch, temperature changes, and various ligands. In the present study, we developed an optogenetic approach to activate Na+ channels and elicit action potentials in Xenopus laevis oocytes. All recordings were performed by the two-microelectrode technique. We first coupled channelrhodopsin-2 (ChR2), a light-sensitive ion channel of the green alga Chlamydomonas reinhardtii, to the auxiliary β1 subunit of voltage-gated Na+ channels. The resulting fusion construct, β1-ChR2, retained the ability to modulate Na+ channel kinetics and generate photosensitive inward currents. Stimulation of Xenopus oocytes coexpressing the skeletal muscle Na+ channel Nav1.4 and β1-ChR2 with 25-ms lasting blue-light pulses resulted in rapid alterations of the membrane potential strongly resembling typical action potentials of excitable cells. Blocking Nav1.4 with tetrodotoxin prevented the fast upstroke and the reversal of the membrane potential. Coexpression of the voltage-gated K+ channel Kv2.1 facilitated action potential repolarization considerably. Light-induced action potentials were also obtained by coexpressing β1-ChR2 with either the neuronal Na+ channel Nav1.2 or the cardiac-specific isoform Nav1.5. Potential applications of this novel optogenetic tool are discussed.

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