Electrical events

Kostyuk, P. G. Electrical events during active transport of ions through biological membranes, in Topic in Bioelectrochemistry and Bioenergetics, Vol. 2, (ed.) Milazzo, G., New York, Wiley 1978... 

Excitation-contraction coupling (EC coupling) is the mechanism underlying transformation of the electrical event (action potential) in the sarcolemma into the mechanical event (muscle contraction) which happens all over the muscle. In other words, it is the mechanism governing the way in which the action potential induces the increase in the cytoplasmic Ca2+ which enables the activation of myofibrils. 

Stimulation of the motoneuron releases acetylcholine onto the muscle endplate and results in contraction of the muscle fiber. Contraction and associated electrical events can be produced by intra-arterial injection of ACh close to the muscle. Since skeletal muscle does not possess inherent myogenic tone, the tone of apparently resting muscle is maintained by spontaneous and intermittent release of ACh. The consequences of spontaneous release at the motor endplate of skeletal muscle are small depolarizations from the quantized release of ACh, termed miniature endplate potentials (MEPPs) [15] (seeCh. 10). Decay times for the MEPPs range between l and 2 ms, a duration similar to the mean channel open time seen with ACh stimulation of individual receptor molecules. Stimulation of the motoneuron results in the release of several hundred quanta of ACh. The summation of MEPPs gives rise to a postsynaptic excitatory potential (PSEP),... 

If severe symptoms are present, synchronized DCC should be instituted immediately to restore sinus rhythm. Precipitating factors should be corrected if possible. If VT is an isolated electrical event associated with a transient initiating factor (e.g., acute myocardial ischemia, digitalis toxicity), there is no need for long-term antiarrhythmic therapy after precipitating factors are corrected. 

Fig. 6.4. Statistical confidence level associated with the electric events synchronized with the laser pulses during a thunderstorm. The color scale is transparent below 98% (i.e., for error risks above 2%), leaving the topographical background uncovered. Arrowhead location of the laser-induced plasma channel Arrow tail laser emitter. Topographic background courtesy of US Geological Survey [31]...

Because the laser is fired independently from the electric activity in the clouds, and because natural electric activity in clouds is a random process, temporal correlations between the electric events detected by the LMA and the laser operation were used as an evidence for an effect of the laser. At each location, the events synchronized (within 2 ms) with the laser have been identified. The probability async that these events may have been obtained by chance among random events, rather than being due to an effect of the laser, was estimated. async can be understood as the risk of error when concluding that the observed pulses are related with the laser pulses. This corresponding confidence level is therefore 1 — async-... 

Similar results have been obtained during the second thunderstorm [31]. In contrast, no effect was observed when the electric field was low or negative. Therefore, these results suggest that a small fraction (0.24% of the laser pulses, i.e., d event/minute) of the plasma filaments have initiated electric events in a strong positive (upward pointing) electric field [31]. 

Plasma filaments generated in the atmosphere by ultrashort laser pulses therefore appear to be able to trigger electric events in thunderclouds under high positive electric field. This result constitutes a first step towards laser-controlled lightning. 

She is symptomatic and may benefit from a short course of high-intensity intravenous therapy with a cAMP-elevating agent (e.g., dobutamine, milrinone, amrinone). This may be a reversible event or part of the inevitable decline of the disease process. Approximately 45% of CHE patients die suddenly of a presumed electrical event (e.g., ventricular tachycardia, asystole). The others die slowly of progressive deterioration. Many patients at the end stages of CHE prefer to try repeated outpatient inotropic (cAMP elevating) therapy for symptomatic... 

Historically and romantically, the heartbeat is recognized as the quintessential hallmark of life. Normally, the heart beats at 60-100 beats per minute (bpm), with each beat yielding a ventricular contraction that ejects blood out to the body. Each heartbeat is an electrical event that originates from a collection of electrically excitable cells within the heart called the sinoatrial node (SA), anatomically located at the upper pole of the heart. The sinoatrial node is the primary pacemaker of the heart. The electrical impulse generated in the sinoatrial node spreads rapidly downward from the atria chambers of the heart and reaches the atrioventricular node (AV), a collection of electrically excitable cells that constitutes the electrical interface between the atria and ventricles of the heart. Erom the AV node, the impulse propagates throughout the ventricles via an electrical conduction system referred to as the His-Purkinje system. The electrical transmission... 

Calcium also forms a link between the electrical events in the membrane and contractile proteins. Digitalis makes more calcium available for excitation-contraction coupling and increasing cardiac contractility. 

Electrical sensors offer many benefits due to their versatility and ease of use. Another important factor relates to the ease by which an electrical event may be monitored, using simpler and therefore less expensive approaches than those required for following an optical event. Much of this work on electronic sensors has been previously reviewed [11]. 

A serious deleterious outcome associated to date primarily with myoblasts (and with thawed BM in chemotherapy patients) (50) is the incidence of cardiac electrical instability for a presumed transient period after cell delivery. These early reports of electrical instability in patients after the receipt of autologous skeletal myoblasts have led to doubts about the safety of these cells as a treatment in the injured heart. Patients who received myoblasts in the earliest clinical studies (33,38) were extremely ill patients with an expected high potential for negative electrical events. In fact, many of the patients who were included in the early trials met the Multicenter Automatic Defibrillator Implantation Trial MADIT-II criteria, which were presented after those trials began, and suggested that all patients who met those criteria be treated with AlCDs. As a result, in more recent clinical studies, many investigators have only enrolled patients who receive AlCDs... 

In spite of the lack of a detailed correlation between the photochemical events as monitored spectroscopically and the electrical events in the retina, it is generally believed that the transmitter release and the subsequent LRP are initiated by protein conformational change occurring in the MI478 + MIl3gQ transition (337,338). The evidence in this respect comes from the observation that the preceding thermal processes, BAT543 - ... 

The question remains how can interference effects be produced in the brain One can imagine that when nerve impulses arrive at synapses (the junction between two nerve cells), they produce electrical events on the other side of the synapse that take the form of momentary standing wave fronts. Typically the junctions made by a nerve fiber number in the dozens, if not hundreds. 

Cardiac muscle contraction is an electrical event initiated at the sinoatrial node. Each cardiac muscle cell fires an action potential as a result of excitation propagated from the sinoatrial node, which produces muscle cell contraction. A wave of action potentials spreads across the organ to produce coordinated contraction of the heart and efficient ejection of blood to the body. Excitation and the subsequent return of a cardiac muscle cell to rest (repolarization) during the action potential is dictated by the flow of ions across the cell membrane. Membrane repolarization is produced by the flow of potassium ions through various types of potassium channels. 

Fig. 19. Plots of the decay time of the 515-nm field-indicating absorption change (A) and the rate of ATP formation (B) in chloroplasts as a function of gramicidin concentration the corresponding gramicidin-to-chlorophyll ratios are indicated in the top scaie sampie chioro-phyll concentration=2x10 M. GMCD stands for gramicidin. Figure source Boeck and Witt (1972) Correlation between electrical events and ATP-generation in the functional membrane of photosynthesis. In G Forti, M Avron and A Melandri (eds) Proc II. Intern Congr of Photosynthesis Research, Stresa (1971) p 910.

M Boeck and FIT Witt (1971) Correlation between electrical events andATP-generation in the functional membrane of photosynthesis. In G Forti, M Avron and A Melandri (eds) Proc II. Intern Congr of Photosynthesis Research, Stresa. pp 903-911... 

GABA Receptor-Mediated Electrical Events In Vivo Properties... 

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