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Blinks L. R. - One of the best experts on this subject based on the ideXlab platform.
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THE ELECTRICAL CAPACITY OF VALONIA : DIRECT CURRENT MEASUREMENTS
The Rockefeller University Press, 2024Co-Authors: Blinks L. R., Skow R. K.Abstract:Impaled cells of Valonia were balanced in a Wheatstone bridge against a simple series-parallel circuit of two resistances and a capacity, the transient charge and discharge curves at make and break of direct current being recorded with a String Galvanometer. With the resistances properly balanced, a series of characteristic deflections resulted when the balancing capacity was varied. With many cells, no complete capacity balance was ever attained over the entire transient time course; but instead either a monophasic or diphasic residual deflection always remained. This behavior is comparable to that of a polarizing electrode in D.C., although not so clearly marked; and it is concluded that Valonia usually has an appreciable polarization component, probably in parallel with a static capacity. However, some cells can be balanced almost completely against a mica condenser of proper value, which indicates that they display a nearly pure static capacity under some conditions. This static state could be produced experimentally by exposure to weak acids (acetic, carbonic, etc.) and by metabolic agents probably inducing internal acidity (low oxygen tension, long exposure to cold, narcotics, etc.). Conversely, penetrating weak bases, such as ammonia, abolished the static capacity, or even any regular polarization. Light acts something like ammonia, after an initial "acid gush" anomaly. Most of these agents likewise affect the P.D. and its response to external ionic alterations, and it seems likely that the change in capacity type reflects altered ionic permeabilities and relative mobilities
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THE EFFECTS OF CURRENT FLOW ON BIOELECTRIC POTENTIAL : III. NITELLA
The Rockefeller University Press, 2024Co-Authors: Blinks L. R.Abstract:String Galvanometer records show the effect of current flow upon the bioelectric potential of Nitella cells. Three classes of effects are distinguished. 1. Counter E.M.F'S, due either to static or polarization capacity, probably the latter. These account for the high effective resistance of the cells. They record as symmetrical charge and discharge curves, which are similar for currents passing inward or outward across the protoplasm, and increase in magnitude with increasing current density. The normal positive bioelectric potential may be increased by inward currents some 100 or 200 mv., or to a total of 300 to 400 mv. The regular decrease with outward current flow is much less (40 to 50 mv.) since larger outward currents produce the next characteristic effect. 2. Stimulation. This occurs with outward currents of a density which varies somewhat from cell to cell, but is often between 1 and 2 µa/cm.2 of cell surface. At this threshold a regular counter E.M.F. starts to develop but passes over with an inflection into a rapid decrease or even disappearance of positive P.D., in a sigmoid curve with a cusp near its apex. If the current is stopped early in the curve regular depolarization occurs, but if continued a little longer beyond the first inflection, stimulation goes on to completion even though the current is then stopped. This is the "action current" or negative variation which is self propagated down the cell. During the most profound depression of P.D. in stimulation, current flow produces little or no counter E.M.F., the resistance of the cell being purely ohmic and very low. Then as the P.D. begins to recover, after a second or two, counter E.M.F. also reappears, both becoming nearly normal in 10 or 15 seconds. The threshold for further stimulation remains enhanced for some time, successively larger current densities being needed to stimulate after each action current. The recovery process is also powerful enough to occur even though the original stimulating outward current continues to flow during the entire negative variation; recovery is slightly slower in this case however. Stimulation may be produced at the break of large inward currents, doubtless by discharge of the enhanced positive P.D. (polarization). 3. Restorative Effects.—The flow of inward current during a negative variation somewhat speeds up recovery. This effect is still more strikingly shown in cells exposed to KCl solutions, which may be regarded as causing "permanent stimulation" by inhibiting recovery from a negative variation. Small currents in either direction now produce no counter E.M.F., so that the effective resistance of the cells is very low. With inward currents at a threshold density of some 10 to 20 µa/cm.2, however, there is a counter E.M.F. produced, which builds up in a sigmoid curve to some 100 to 200 mv. positive P.D. This usually shows a marked cusp and then fluctuates irregularly during current flow, falling off abruptly when the current is stopped. Further increases of current density produce this P.D. more rapidly, while decreased densities again cease to be effective below a certain threshold. The effects in Nitella are compared with those in Valonia and Halicystis, which display many of the same phenomena under proper conditions. It is suggested that the regular counter E.M.F.'S (polarizations) are due to the presence of an intact surface film or other structure offering differential hindrance to ionic passage. Small currents do not affect this structure, but it is possibly altered or destroyed by large outward currents, restored by large inward currents. Mechanisms which might accomplish the destruction and restoration are discussed. These include changes of acidity by differential migration of H ion (membrane "electrolysis"); movement of inorganic ions such as potassium; movement of organic ions, (such as Osterhout's substance R), or the radicals (such as fatty acid) of the surface film itself. Although no decision can be yet made between these, much evidence indicates that inward currents increase acidity in some critical part of the protoplasm, while outward ones decrease acidity
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THE EFFECTS OF CURRENT FLOW ON BIOELECTRIC POTENTIAL : I. VALONIA
The Rockefeller University Press, 2024Co-Authors: Blinks L. R.Abstract:The effect of direct current flow upon the potential difference across the protoplasm of impaled Valonia cells was studied. Current density and direction were controlled in a bridge which balanced the ohmic resistances, leaving the changes (increase, decrease, or reversal) of the small, normally negative, bioelectric potential to be recorded continuously, before, during, and after current flow, with a String Galvanometer connected into a vacuum tube detector circuit. Two chief states of response were distinguished: State A.—Regular polarization, which begins to build up the instant current starts to flow, the counter E.M.F. increasing most rapidly at that moment, then more and more slowly, and finally reaching a constant value within 1 second or less. The magnitude of counter E.M.F. is proportional to the current density with small currents flowing in either direction across the protoplasm, but falls off at higher density, giving a cusp with recession to lower values; this recession occurs with slightly lower currents outward than inward. Otherwise the curves are much the same for inward and outward currents, for different densities, for charge and discharge, and for successive current flows. There is a slight tendency for the bioelectric potential to become temporarily positive following these current flows. Records in the regular state (State A) show very little effect of increased series resistance on the time constant of counter E.M.F. This seems to indicate that a polarization rather than a static capacity is involved. State B.—Delayed and non-proportional polarization, in which there is no counter E.M.F. developed with small currents in either direction across the protoplasm, nor with very large outward currents. But with inward currents a threshold density is reached at which a counter E.M.F. rather suddenly develops, with a sigmoid curve rising to high positive values (200 mv. or more). There is sometimes a cusp, after which the P.D. remains strongly positive as long as the current flows. It falls off again to negative values on cessation of current flow, more rapidly after short flows, more slowly after longer ones. The curves of charge are usually quite different in shape from those of discharge. Successive current flows of threshold density in rapid succession produce quicker and quicker polarizations, the inflection of the curve often becoming smoothed away. After long interruptions, however, the sigmoid curve reappears. Larger inward currents produce relatively little additional positive P.D.; smaller ones on the other hand, if following soon after, have a greatly increased effectiveness, the threshold for polarization falling considerably. The effect dies away, however, with very small inward currents, even as they continue to flow. Over a medium range of densities, small increments or decrements of continuing inward current produce almost as regular polarizations as in State A. Temporary polarization occurs with outward currents following soon after the threshold inward currents, but the very flow of outward current tends to destroy this, and to decondition the protoplasm, again raising the threshold, for succeeding inward flows. State A is characteristic of a few freshly gathered cells and of most of those which have recovered from injuries of collecting, cleaning, and separating. It persists a short time after such cells are impaled, but usually changes over to State B for a considerable period thereafter. Eventually there is a reappearance of regular polarization; in the transition there is a marked tendency for positive P.D. to be produced after current flow, and during this the polarizations to outward currents may become much larger than those to inward currents. In this it resembles the effects of acidified sea water, and of certain phenolic compounds, e.g. p-cresol, which produce State A in cells previously in State B. Ammonia on the other hand counteracts these effects, producing delayed polarization to an exaggerated extent. Large polarizations persist when the cells are exposed to potassium-rich solutions, showing it is not the motion of potassium ions (e.g. from the sap) which accounts for the loss or restoration of polarization. It is suggested that inward currents restore a protoplasmic surface responsible for polarization by increasing acidity, while outward currents alter it by increasing alkalinity. Possibly this is by esterification or saponification respectively of a fatty film. For comparison, records of delayed polarization in silver-silver chloride electrodes are included
Charles Fisch - One of the best experts on this subject based on the ideXlab platform.
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centennial of the String Galvanometer and the electrocardiogram
Journal of the American College of Cardiology, 2000Co-Authors: Charles FischAbstract:This article is a review of the history of the String Galvanometer and of the electrocardiogram (ECG) on the occasion of the centennial of the instrument. Einthoven most likely developed the String Galvanometer prior to 1901, the date of the first publication. The Galvanometer made electrocardiography practical creating a new branch of medicine and even a new industry. In 1791 Galvani, in 1842 Mateucci and in 1855 Kolliker and Muller recorded, using the nerve muscle preparation, contraction of injured muscle, contraction of muscle when laid across a beating heart, and occasionally two contractions. In 1872 Lippmann introduced the capillary manometer. Using the capillary manometer Waller recorded for the first time from body surface voltage changes generated by the heart. Einthoven and Lewis dominated the early years of electrocardiography. The former made his contributions by 1913 while Lewis continued the studies of arrhythmias until 1920. The period following 1920 was influenced largely by Wilson. None did as much to advance ECG knowledge as did Wilson. The interest shifted to the theory of the ECG, abnormalities of wave form and of ECG leads. A major contribution of the ECG is in evaluation of ischemic heart disease and cardiac arrhythmias. Issues facing electrocardiography in the year 2000 include a shortage of experienced electrocardiographers, the advent of new noninvasive procedures and, paradoxically, wide acceptance of the ECG by the medical profession. The role of the computer in analysis of the clinical ECG is limited. The technique, while reasonably reliable for analysis of the normal tracing and some ECG waveforms, has serious limitations when applied to arrhythmias. The early hopes for "stand-alone" programs are yet to be realized.
Ganxin Yan - One of the best experts on this subject based on the ideXlab platform.
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is there a significant transmural gradient in repolarization time in the intact heart cellular basis of the t wave a century of controversy
Circulation-arrhythmia and Electrophysiology, 2009Co-Authors: Chinmay Patel, James F Burke, Harsh Patel, Prasad Gupta, Peter R Kowey, Charles Antzelevitch, Ganxin YanAbstract:The ECG is one of the oldest and most versatile noninvasive cardiac diagnostic tests. It has remained in use essentially in its original form despite dramatic advances in cardiac electrophysiology. In May 1887, Augustus Desire Waller recorded the first human Electrogram using a primitive instrument called a Libbmann capillary electrometer. It had 2 deflections corresponding to ventricular depolarization and repolarization.1 In 1903, Willem Einthoven invented the String Galvanometer—a more sophisticated voltage recording instrument and recorded an Elektrokardiogramm with 5 deflections that he named PQRST.2 Response by Opthof et al p 80 Since its initial invention, the body surface ECG has become a commonly used and extremely valuable test for the diagnosis of a variety of cardiac conditions. Despite a century of prolific use and intensive investigation, the cellular basis of ECG waveforms, particularly the T wave, remains a matter of debate. The saga of the T wave began in 1856, when 2 German physiologists Kolliker and Muller attempted to explore the electric activity of the heart using frog sciatic nerve attached to gastroenemius muscle as a voltage recording instrument and observed 2 contractions (see review by Noble and Cohen3). In retrospect, the second “contraction” probably reflected a voltage gradient related to the T wave of Einthoven. In 1883, Burdon-Sanderson and Page4 were the first to demonstrate that in the frog’s heart, the wave of excitation spreads from the base to the apex of the ventricle. The record was diphasic, with the first positive (R) wave followed by a negative (T) wave. They also demonstrated that the T wave corresponds to repolarization of the ventricle. Similar series of experiments by Bayliss and Starling in 18925 in the canine heart showed that the T waves are usually upright in mammals. This was followed by Mines6 on …
Chinmay Patel - One of the best experts on this subject based on the ideXlab platform.
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is there a significant transmural gradient in repolarization time in the intact heart cellular basis of the t wave a century of controversy
Circulation-arrhythmia and Electrophysiology, 2009Co-Authors: Chinmay Patel, James F Burke, Harsh Patel, Prasad Gupta, Peter R Kowey, Charles Antzelevitch, Ganxin YanAbstract:The ECG is one of the oldest and most versatile noninvasive cardiac diagnostic tests. It has remained in use essentially in its original form despite dramatic advances in cardiac electrophysiology. In May 1887, Augustus Desire Waller recorded the first human Electrogram using a primitive instrument called a Libbmann capillary electrometer. It had 2 deflections corresponding to ventricular depolarization and repolarization.1 In 1903, Willem Einthoven invented the String Galvanometer—a more sophisticated voltage recording instrument and recorded an Elektrokardiogramm with 5 deflections that he named PQRST.2 Response by Opthof et al p 80 Since its initial invention, the body surface ECG has become a commonly used and extremely valuable test for the diagnosis of a variety of cardiac conditions. Despite a century of prolific use and intensive investigation, the cellular basis of ECG waveforms, particularly the T wave, remains a matter of debate. The saga of the T wave began in 1856, when 2 German physiologists Kolliker and Muller attempted to explore the electric activity of the heart using frog sciatic nerve attached to gastroenemius muscle as a voltage recording instrument and observed 2 contractions (see review by Noble and Cohen3). In retrospect, the second “contraction” probably reflected a voltage gradient related to the T wave of Einthoven. In 1883, Burdon-Sanderson and Page4 were the first to demonstrate that in the frog’s heart, the wave of excitation spreads from the base to the apex of the ventricle. The record was diphasic, with the first positive (R) wave followed by a negative (T) wave. They also demonstrated that the T wave corresponds to repolarization of the ventricle. Similar series of experiments by Bayliss and Starling in 18925 in the canine heart showed that the T waves are usually upright in mammals. This was followed by Mines6 on …
P J Wyers - One of the best experts on this subject based on the ideXlab platform.
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adaptation of einthoven s String Galvanometer for electrocardiography in the netherlands
Nederlands Tijdschrift voor Geneeskunde, 2001Co-Authors: P J WyersAbstract:After the Dutch physiologist Willem Einthoven (1860-1927) published the construction of his String Galvanometer in 1901, the development of electrocardiography in the Netherlands was slow. During the next twenty years only a few String Galvanometers were in use in the Netherlands, mostly in physiology laboratories. Publications concerning electrocardiographic tests on patients were scarce. In 1924, Einthoven was awarded the Nobel Prize for Physiology and Medicine for discovering the mechanism of the electrocardiogram. From that moment onwards, electrocardiography developed rapidly in the Netherlands and during the following 30 years particular use was made of the French String Galvanometer designed by Boulitte.
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the String of einthoven s String Galvanometer
Gewina, 1996Co-Authors: P J WyersAbstract:The Dutch physiologist Willem Einthoven (1860-1927) published in 1901 his construction of a String Galvanometer. With this apparatus he opened the era for electrocardiography. As the quality of his instrument largely depended on the String of the String Galvanometer it is surprising to note that in his publications Einthoven never mentioned the exact way of producing the String. However, Einthoven's hand written laboratory notes are preserved at the Museum Boerhaave in Leiden. From these notes it comes clear what problems Einthoven had with the String. To get a very thin thread of quarts he first used the method of shooting the thread as was described by Boys (1887), later the blowing method of Nichols (1894). The silvering of the thread was done first chemically, later by cathode spray. In all cases premature breaking of the thread was a nuisance. Because of these failures Einthoven might have decided not to publish any details.
