Analysis of thermopile records from contracting isolated cardiac muscle

1990 ◽  
Vol 259 (5) ◽  
pp. H1601-H1605 ◽  
Author(s):  
F. Mast ◽  
R. C. Woledge ◽  
G. Elzinga
Keyword(s):  
Steady State ◽  
Cardiac Muscle ◽  
Time Constant ◽  
Papillary Muscle ◽  
Heat Production ◽  
Heart Muscle ◽  
Stimulus Frequency ◽  
Recovery Process ◽  
Total Heat ◽  
Rabbit Papillary Muscle

Recovery heat production after contraction in rabbit papillary muscle at 20 degrees C occurs at an exponentially declining rate. The time constant describing this decline is 25 s; it is not different when 10 twitches or when a steady-state twitch train is studied, and it is unaltered by changing stimulus frequency from 0.125 to 0.2 Hz. The same value has previously been found after single twitches. If it is assumed that phosphocreatine (PCr) resynthesis is the cause of recovery heat production and that it occurs also during contractions at a rate proportional to the amount of PCr depletion, it is possible to divide the total heat production for any period of stimulation into that caused by this recovery process (R) and that caused by initial (I) processes (presumed to be PCr splitting). The value of R/I obtained by using this method is 1.10 +/- 0.04 (means +/- SE, n = 27 muscles), close to the theoretical value of 1.13. The correspondence between the measured and the predicted ratio supports the assumptions underlying the measurement. Thus in heart muscle the heat produced during and after contraction can be explained by PCr splitting and reformation. The older Bugnard method of analysis applied to the same data gives an R/I value of 1.5; the reasons for the discrepancy are described.

scholarly journals The relation between initial and recovery heat production in frog's nerve

1933 ◽  
Vol 113 (784) ◽  
pp. 369-386 ◽  
Keyword(s):  
Steady State ◽  
Heat Production ◽  
Short Interval ◽  
Preceding Paper ◽  
Heat Rate ◽  
Recovery Process ◽  
Quantitative Relation ◽  
Rate Of Recovery ◽  
Initial Heat

The latest and best determination of the quantitative relation of the two chief phases of heat production in frog's nerve is that of Bronk (1931) who found the average ratio of total to initial heat to be 11. More recently Hill (1932) has given reason to believe that even Bronk's ratio is probably too low, and in the same paper (p. 148) has suggested an alternative method of estimating it based on the principle of the steady state. the present work arose from this suggestion and has led to the discovery of the profound effect of steady activity on the “efficiency” of the recovery process. The steady state of nerve activity during continual stimulation has been discussed in a preceding paper. Its nature is such that the rate of recovery heat production at any moment corresponds to the rate of initial heat production at that moment. the total heat rate can easily be measured. The initial heat rate can be determined by omitting the stimulus for a short interval, when an analysis of the resulting defection allows an estimate of the heat which immediately drops out as a result of omitting the stimulus, i. e ., of the initial heat.

scholarly journals Cat Heart Muscle in Vitro

1965 ◽  
Vol 48 (5) ◽  
pp. 933-948 ◽  
Author(s):  
Jon Goerke ◽  
Ernest Page
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Papillary Muscle ◽  
Heart Muscle ◽  
Volume Ratio ◽  
K Concentration ◽  
Linear Manner ◽  
Cat Heart ◽  
External K

The exchange of cell K with K42, JK, has been measured in cat right ventricular papillary muscle under conditions of a steady state with respect to intracellular K concentration. Within the limits of the measurement, all of cell K exchanged at a single rate. Cells from small cats are smaller and have larger surface/volume ratios than cells from large cats. The larger surface/volume ratio results in larger flux values. JK increases in an approximately linear manner as the external K concentration is increased twentyfold, from 2.5 to 50 mM, at constant intracellular K concentration. The permeability for K ions, PK, calculated from the influx and membrane potential, remains very nearly constant over this range of external K concentrations. JK is not affected by replacement of O2 by N2, or by stimulated contractions at 60 per minute, but K influx decreases markedly in 10-5 M and 10-8 M ouabain.

Time course of mechanical efficiency during afterloaded contractions in isolated cardiac muscle

1991 ◽  
Vol 261 (4) ◽  
pp. 27-29
Author(s):  
Jon N. Peterson ◽  
Norman R. Alpert
Keyword(s):  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Time Course ◽  
Mechanical Efficiency ◽  
Constant Load ◽  
Maximum Length ◽  
Rabbit Papillary Muscle ◽  
Muscle Work ◽  
Initial Heat

The time course of mechanical efficiency during working contractions in rabbit papillary muscle is presented. Efficiency is found to remain relatively constant during the working portion of the twitch, when the muscle is contracting against a constant load. As afterload was decreased, efficiency increased to 65 ± 11% (mean ± SE, n = 3) at 10% developed force at maximum length. This is in contrast to muscle work, which reached a peak of 3.0 ± 0.3 ( n = 6) mJ/g at 50% developed force at maximum length. heart; initial heat; rabbit; working contractions

Estimated time course of Ca2+ bound to troponin C during relaxation in isolated cardiac muscle

1991 ◽  
Vol 260 (3) ◽  
pp. H1013-H1024 ◽  
Author(s):  
J. N. Peterson ◽  
W. C. Hunter ◽  
M. R. Berman
Keyword(s):  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Time Course ◽  
Initial Rate ◽  
Troponin C ◽  
Rabbit Papillary Muscle ◽  
Rabbit Myocardium ◽  
Cross Bridges

We present a mechanical assay for estimating the time course of Ca2+ bound to low-affinity sites on troponin C (TnC) in twitching rabbit papillary muscle. The assay is based on a theoretical correlation between the rate of force redevelopment after detachment of all cross-bridges and the amount of Ca2+ bound to TnC. Experimentally, we applied length impulses at different times to detach all cross-bridges; the initial rate of force redevelopment after each impulse was taken as an index of bound Ca2+ at that time. Under control conditions, the magnitude of this index decreased to 10% of its maximum during early relaxation, when force had declined only slightly 78 +/- 12% of its peak isometric value. The time course of this index was examined after addition of either isoproterenol or ryanodine, which are known to shorten and prolong, respectively, the intracellular free Ca2+ transient. As expected, changes previously reported in the free Ca2+ time course were qualitatively reflected in the time course of the bound Ca2+ index. We conclude that this index constitutes a reasonable method for estimating the time course of bound Ca2+ and that bound Ca2+ declines well ahead of force in isometrically contracting rabbit myocardium at 24 degrees C.

ATP formation and energy demand in anoxic heart muscle of the rabbit

1992 ◽  
Vol 263 (2) ◽  
pp. H526-H532 ◽  
Author(s):  
D. L. Dietrich ◽  
G. Elzinga
Keyword(s):  
Oxidative Phosphorylation ◽  
Papillary Muscle ◽  
Heart Muscle ◽  
Energy Demand ◽  
Stimulus Frequency ◽  
Main Determinant ◽  
Atp Formation ◽  
Threefold Increase ◽  
Lactate Formation ◽  
Glycolytic Rate

In quiescent rabbit papillary muscle at 20 degrees C, the formation of ATP in nitrogen, estimated from the production of lactate, is 21% of that in oxygen. Stimulating the anoxic muscles at 0.2 Hz causes a threefold increase in ATP formation. In this study we want to determine 1) whether glycolytic ATP formation can be increased to a rate that would meet the aerobic ATP demand at rest and 2) what the maximum glycolytic rate attainable through stimulation is. Glycolytic rate is estimated from the amount of lactate produced at various times over 40 min of anoxia. Nucleotides and creatine compounds are also determined. Lactate formation at the onset of anoxia is proportional to stimulus frequency. The amount of lactate formed is correlated to the breakdown of glycogen; glucose is not used. Therefore the amount of glycogen present in the muscle at the onset of anoxia is the main determinant of the amount of ATP formed when oxidative phosphorylation is inhibited. The rate of lactate formation at the onset of anoxia increases from 1.22 mumol.g dry wt-1.min-1 in resting muscles to 18.5 mumol.g dry wt-1.min-1 in 1-Hz-stimulated muscles. This implies that in anoxic myocardium, glycolysis can provide ATP at more than three times the rate found in the muscle at rest in ample oxygen.

Time course of mechanical efficiency during afterloaded contractions in isolated cardiac muscle

1991 ◽  
Vol 261 (4) ◽  
pp. L27-L29
Author(s):  
Jon N. Peterson ◽  
Norman R. Alpert
Keyword(s):  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Time Course ◽  
Mechanical Efficiency ◽  
Constant Load ◽  
Maximum Length ◽  
Rabbit Papillary Muscle ◽  
Muscle Work ◽  
Initial Heat

The time course of mechanical efficiency during working contractions in rabbit papillary muscle is presented. Efficiency is found to remain relatively constant during the working portion of the twitch, when the muscle is contracting against a constant load. As afterload was decreased, efficiency increased to 65 ± 11% (mean ± SE, n = 3) at 10% developed force at maximum length. This is in contrast to muscle work, which reached a peak of 3.0 ± 0.3 (n = 6) mJ/g at 50% developed force at maximum length. heart; initial heat; rabbit; working contractions

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