The initial heat production in garfish olfactory nerve fibres

1979 ◽  
Vol 205 (1160) ◽  
pp. 347-367 ◽  
Keyword(s):  
Action Potential ◽  
Heat Production ◽  
Time Course ◽  
Olfactory Nerve ◽  
Effect Of Temperature ◽  
Temperature Changes ◽  
Membrane Capacity ◽  
Voltage Change ◽  
True Time ◽  
Initial Heat

A study has been made of the temperature changes associated with the passage of a single impulse in the non-myelinated fibres of the garfish olfactory nerve: and the time course of these temperature changes has been compared with the time course of the electrical events during the action potential. As in other non-myelinated nerves studied the observed temperature changes result from a biphasic initial heat production con­sisting of a transient evolution of heat (the positive heat) followed by a a rapid heat reabsorption (referred to as the negative heat). There is no evidence of any additional phases of initial heat production. At 0 °C the measured positive initial heat is 224 μcal/g impulse (937 μJ/g impulse); and the corresponding negative initial heat is 230 μcal/g impulse (962 μJ/g impulse). The residual initial heat is very small, being about ─6 μcal/g impulse (─25 μJ/g impulse). In the range 0─ 10 °C there is no significant effect of temperature on the magnitude of either the positive or the negative phases of heat production. The experimental thermal records were analysed to determine the true time course of the tem­perature changes in the nerve undistorted by the recording system. The time course of the temperature changes does not fit with that of the transmembrane voltage change as represented by the monophasic com­pound action potential recorded externally from the same point on the nerve. A better fit is obtained if the temperature changes are compared with the square of the voltage change in accordance with the view that the heat derives almost wholly from free energy changes and entropy changes in the membrane capacity. The best fit is obtained if it is assumed that the membrane potential does not discharge to zero during the action potential but that at the peak of the action potential the charge (and hence the p. d.) across the membrane capacity retains about 24% of its resting value.

scholarly journals Temperature changes accompanying signal propagation in axons

2019 ◽  
Vol 44 (3) ◽  
pp. 277-284 ◽  
Author(s):  
Kert Tamm ◽  
Jüri Engelbrecht ◽  
Tanel Peets
Keyword(s):  
Differential Equations ◽  
Action Potential ◽  
Mathematical Models ◽  
Heat Production ◽  
Mathematical Description ◽  
Signal Propagation ◽  
Nerve Fibers ◽  
The Novel ◽  
Temperature Changes ◽  
Whole Process

Abstract In this paper mathematical models are formulated in order to simulate heat production and corresponding temperature changes which accompany the propagation of an action potential. Based on earlier experimental results, several models are proposed. Together with the earlier system of coupled differential equations derived by the authors for describing the electrical and mechanical components of signaling in nerve fibers, the novel results permit to cast the whole process of signaling into one system. The emphasis is on the mathematical description of coupling forces. The numerical results are qualitatively similar to experiments.

scholarly journals Methods of analysing the heat production of muscle

1937 ◽  
Vol 124 (835) ◽  
pp. 114-136 ◽  
Keyword(s):  
Cross Section ◽  
Heat Production ◽  
Time Course ◽  
Short Interval ◽  
Uniform Heating ◽  
Satisfactory Method ◽  
Uniform Cross Section ◽  
Muscle Heat Production ◽  
Initial Heat

The initial heat production of muscle (as distinguished from the delayed heat production) occurs so rapidly that the determination of its distribution in time, particularly in relation to contraction, relaxation and the performance of mechanical work, requires special methods of analysis (see e.g. Hartree 1933). The only means hitherto found satisfactory of measuring muscle heat production has employed a thermopile and galvanometer. For the rise of temperature involved the e.m.f. developed by the thermopile is only a few microvolts, and it has not been possible to devise any really satisfactory method of amplification: the current has had to be read directly by the galvanometer. Since the current was small the galvanometer had to be sensitive, and therefore comparatively slow. This introduced the first element of delay in the measurement of the heat, that due to the galvanometer. The second was due to the thermopile, for all thermopiles hitherto employed have been rather slow in reaching the temperature of the muscle. Moreover, their heat capacity has been so large that the sensitivity of the system has been considerably less than that calculated simply from the constants of the apparatus. For all these reasons the analysis and the calibration have been performed by heating the muscle electrically during a known short interval, or “instantaneously”, and finding numerically what distribution of such heat-pulses would give the same deflexion, in time and amplitude, as the heat produced by the stimulated muscle. The method is laborious and there are various objections to it, particularly (i) the requirement that the muscle must be of uniform cross-section if it is to be uniformly heated (see Hill 19316, p. 144, Appendix II), (ii) the need of very good electrical insulation, in order to avoid leaks, and (iii) the danger of non-uniform heating in the immediate neighbourhood of the electrodes leading current to the muscle. Within limits, however, the method has fulfilled its purpose, and all significant results on the time-course of the heat production of muscle (and nerve) have been obtained with it.

Influence of argon laser stapedotomy on inner ear function and temperature

1983 ◽  
Vol 91 (5) ◽  
pp. 521-526 ◽  
Author(s):  
Michael Vollrath ◽  
Christoph Schreiner
Keyword(s):  
Action Potential ◽  
Inner Ear ◽  
Guinea Pigs ◽  
Time Course ◽  
Argon Laser ◽  
Compound Action Potential ◽  
Clinical Use ◽  
Cochlear Microphonics ◽  
Temperature Changes ◽  
Compound Action

The influence of argon laser stapedotomy on inner ear function was investigated in guinea pigs. The cochlear microphonics (CM) and the compound action potential (CAP) served as parameters for the functional status of the cochlear. Transitory depression of both potentials was found during and after laser stapedotomy. The time course of CM and CAP depression and recovery is compared to endocochlear temperature changes. Possible implications for clinical use are discussed.

Consideration of the temperature factor of atmospheric air when determining standard consumption of fuel and energy resources for train traction

2018 ◽  
Vol 77 (6) ◽  
pp. 375-381
Author(s):  
K. M. Popov
Keyword(s):  
Statistical Processing ◽  
Specific Consumption ◽  
Energy Resources ◽  
Effect Of Temperature ◽  
Influence Coefficient ◽  
Specific Work ◽  
Specific Flow ◽  
Temperature Changes ◽  
Work Area ◽  
Physical Laws

Abstract. Influence of air temperature on the consumption of fuel and energy resources (FER) on train traction is due to a number of physical laws. The extent of this effect is specified in the Rules for Traction Settlement (RTS). At the same time, when rationing FER consumption for train traction, a specialized methodical base is used, which involves a different approach to accounting for the effect of temperature on FER consumption for train traction. At the same time in different documents of this base, the effects of low temperature on the absolute and specific consumption of fuel and energy resources on train traction are taken into account in a different way, which is due to the lack of consensus among specialists on the way this factor is taken into account. Specialists of JSC “VNIIZhT” carried out an analysis of a significant amount of driver’s routes data, results of which showed that the dependence of the specific flow rate on temperature, on the basis of which the corresponding influence coefficient is determined, needs to be periodically updated. In addition, when technically standardizing the consumption of fuel and energy resources (for the locomotive crew work site), the temperature effect coefficients need to be calculated for a specific work area and direction of motion on it, while using the average network coefficient values will lead to errors. When calculating additional flow of fuel and energy from the effect of temperature for electric multiple units (EMU), the equations of regression dependencies should be used, obtained by statistical processing of data on temperature changes and specific consumption of fuel and energy resources for EMU and determined for each series of EMU when working on a particular suburban area.

scholarly journals Canine Myocytes Represent a Good Model for Human Ventricular Cells Regarding Their Electrophysiological Properties

2021 ◽  
Vol 14 (8) ◽  
pp. 748
Author(s):  
Péter P. Nánási ◽  
Balázs Horváth ◽  
Fábián Tar ◽  
János Almássy ◽  
Norbert Szentandrássy ◽  
...  
Keyword(s):  
Action Potential ◽  
Time Course ◽  
Laboratory Animals ◽  
Delayed Rectifier ◽  
Ion Currents ◽  
Human Cardiomyocytes ◽  
Ventricular Cells ◽  
Repolarization Reserve ◽  
Electrophysiological Studies ◽  
K Current

Due to the limited availability of healthy human ventricular tissues, the most suitable animal model has to be applied for electrophysiological and pharmacological studies. This can be best identified by studying the properties of ion currents shaping the action potential in the frequently used laboratory animals, such as dogs, rabbits, guinea pigs, or rats, and comparing them to those of human cardiomyocytes. The authors of this article with the experience of three decades of electrophysiological studies, performed in mammalian and human ventricular tissues and isolated cardiomyocytes, summarize their results obtained regarding the major canine and human cardiac ion currents. Accordingly, L-type Ca2+ current (ICa), late Na+ current (INa-late), rapid and slow components of the delayed rectifier K+ current (IKr and IKs, respectively), inward rectifier K+ current (IK1), transient outward K+ current (Ito1), and Na+/Ca2+ exchange current (INCX) were characterized and compared. Importantly, many of these measurements were performed using the action potential voltage clamp technique allowing for visualization of the actual current profiles flowing during the ventricular action potential. Densities and shapes of these ion currents, as well as the action potential configuration, were similar in human and canine ventricular cells, except for the density of IK1 and the recovery kinetics of Ito. IK1 displayed a largely four-fold larger density in canine than human myocytes, and Ito recovery from inactivation displayed a somewhat different time course in the two species. On the basis of these results, it is concluded that canine ventricular cells represent a reasonably good model for human myocytes for electrophysiological studies, however, it must be borne in mind that due to their stronger IK1, the repolarization reserve is more pronounced in canine cells, and moderate differences in the frequency-dependent repolarization patterns can also be anticipated.

Calcium Dynamics and Compartmentalization in Leech Neurons

2005 ◽  
Vol 94 (6) ◽  
pp. 4430-4440 ◽  
Author(s):  
Sofija Andjelic ◽  
Vincent Torre
Keyword(s):  
Information Processing ◽  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Ccd Camera ◽  
Calcium Dynamics ◽  
Single Action ◽  
Single Action Potential ◽  
Calcium Indicator ◽  
Mechanosensory Neurons

Calcium dynamics in leech neurons were studied using a fast CCD camera. Fluorescence changes (Δ F/ F) of the membrane impermeable calcium indicator Oregon Green were measured. The dye was pressure injected into the soma of neurons under investigation. Δ F/ F caused by a single action potential (AP) in mechanosensory neurons had approximately the same amplitude and time course in the soma and in distal processes. By contrast, in other neurons such as the Anterior Pagoda neuron, the Annulus Erector motoneuron, the L motoneuron, and other motoneurons, APs evoked by passing depolarizing current in the soma produced much larger fluorescence changes in distal processes than in the soma. When APs were evoked by stimulating one distal axon through the root, Δ F/ F was large in all distal processes but very small in the soma. Our results show a clear compartmentalization of calcium dynamics in most leech neurons in which the soma does not give propagating action potentials. In such cells, the soma, while not excitable, can affect information processing by modulating the sites of origin and conduction of AP propagation in distal excitable processes.

Flow Behaviors of High Acyl Gellan Aqueous Solutions as Affected by Temperature, and Calcium and Gellan Concentrations

2008 ◽  
Vol 4 (5) ◽  
Author(s):  
Yiqun Huang ◽  
Pawan Singh Takhar ◽  
Juming Tang ◽  
Barry G Swanson
Keyword(s):  
Shear Rate ◽  
Aqueous Solutions ◽  
Apparent Viscosity ◽  
Flow Resistance ◽  
Effect Of Temperature ◽  
Temperature Changes ◽  
Influence Of Temperature ◽  
Rheological Behaviors ◽  
Low Concentrations ◽  
Influence Of Temperature On

Rheological behaviors of high acyl (HA) gellan are not well understood partially because of its relatively late commercialization compared to low acyl gellan. The objective of this study was to investigate the effect of temperature (5-30 °C), calcium (0, 1 and 10 mM) and gellan concentrations (0.0044-0.1000% w/v) on the flow behaviors of high acyl gellan aqueous solutions using rheological tests. Gellan solutions with 0 or 1 mM added Ca++ exhibited shear thinning behavior at gellan concentrations above 0.0125%. The influence of temperature on apparent viscosity (shear rate, 100 s-1) of gellan solutions can be described with an Arrhenius relationship. The apparent viscosity of gellan solution at low concentrations was more sensitive to temperature changes. The addition of Ca++ led to a decrease in flow resistance for a dilute gellan solution (<0.0125%), but an increased resistance for a relatively concentrated gellan solution (>0.0125%).

Scientific contributions of A. V. Hill: exercise physiology pioneer

2002 ◽  
Vol 93 (5) ◽  
pp. 1567-1582 ◽  
Author(s):  
David R. Bassett
Keyword(s):  
World War Ii ◽  
Heat Production ◽  
Time Course ◽  
Exercise Physiology ◽  
Frog Muscle ◽  
World War ◽  
Academic Assistance ◽  
Physiological Adaptations ◽  
Velocity Equation ◽  
Force Velocity

Beginning in 1910, A. V. Hill performed careful experiments on the time course of heat production in isolated frog muscle. His research paralleled that of the German biochemist Otto Meyerhof, who measured the changes in muscle glycogen and lactate during contractions and recovery. For their work in discovering the distinction between aerobic and anaerobic metabolism, Hill and Meyerhof were jointly awarded the 1922 Nobel Prize for Physiology or Medicine. Because of Hill's interest in athletics, he sought to apply the concepts discovered in isolated frog muscle to the exercising human. Hill and his colleagues made measurements of O2 consumption on themselves and other subjects running around an 85-m grass track. In the process of this work, they defined the terms “maximum O2 intake,” “O2requirement,” and “steady state of exercise.” Other contributions of Hill include his discoveries of heat production in nerve, the series elastic component, and the force-velocity equation in muscle. Around the time of World War II, Hill was a leading figure in the Academic Assistance Council, which helped Jewish scientists fleeing Nazi Germany to relocate in the West. He served as a member of the British Parliament from 1940 to 1945 and as a scientific advisor to India. Hill's vision and enthusiasm attracted many scientists to the field of exercise physiology, and he pointed the way toward many of the physiological adaptations that occur with physical training.

Abstract 5316: hERG 1b as a Potential Target for Inherited and Acquired Long QT Syndrome

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Gail A Robertson ◽  
Harinath Sale ◽  
David Tester ◽  
Thomas J O’Hara ◽  
Pallavi Phartiyal ◽  
...  
Keyword(s):  
Action Potential ◽  
Long Qt Syndrome ◽  
Time Course ◽  
Drug Sensitivity ◽  
Long Qt ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
Acquired Long Qt Syndrome ◽  
293 Cells ◽  
Qt Syndrome

Cardiac I Kr is a critical repolarizing current in the heart and a target for inherited and acquired long QT syndrome. Biochemical studies show that native I Kr channels are heteromers composed of both hERG 1a and 1b subunits, yet our current understanding of I Kr functional properties derives primarily from studies of homo-oligomers of the original hERG 1a isolate. The hERG 1a and 1b subunits are identical except at the amino (NH2) terminus, which in hERG 1b is much shorter and has a unique primary sequence. We compared the biophysical properties of currents produced by hERG 1a and 1a/1b channels expressed in HEK-293 cells at near-physiological temperatures. We found that heteromeric hERG 1a/1b currents are much larger than hERG 1a currents and conduct 80% more charge during an action potential. This surprising difference corresponds to a two-fold increase in the apparent rates of activation and recovery from inactivation, which reduces rectification and facilitates current rebound during repolarization. Kinetic modeling shows these gating differences account quantitatively for the differences in current amplitude between the two channel types. Depending on the action potential model used, loss of 1b predicts an increase in action potential duration of 27 ms (7%) or 41 ms (17%), respectively. Drug sensitivity was also different. Compared to homomeric 1a channels, heteromeric 1a/1b channels were inhibited by E-4031 with a slower time course and a corresponding four-fold positive shift in the IC 50 . Differences in current kinetics and drug sensitivity were modeled by “NH2 mode” gating with conformational states bound by the amino terminus in hERG 1a homomers but not 1a/1b heteromers. The importance of hERG 1b in vivo is supported by the identification of a 1b-specific A8V missense mutation in 1/269 unrelated genotype-negative LQTS patients and absent in 400 control alleles. Mutant 1bA8V expressed alone or with hERG 1a in HEK-293 cells nearly eliminated 1b protein. Thus, mutations specifically disrupting hERG 1b function are expected to reduce cardiac I Kr , prolong QT interval and enhance drug sensitivity, thus representing a potential mechanism underlying inherited or acquired LQTS.

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