Heat production in quiescent cardiac muscle is length‐, velocity‐, and muscle‐dependent: Implications for active heat measurement

It has been suggested that there is a shortening-heat component that is an extra liberation of heat on shortening above that due to the external work, which contributes to the total energy expenditure of the beating heart. The presence of a shortening heat component was studied in isolated papillary muscles from the right ventricle of rabbits killed by cervical dislocation. At the onset of a contraction, muscles were shortened from various initial lengths through fixed distances at near maximum velocity before being allowed to develop force at the new length; the heat production accompanying such contractions was measured. The measured heat was compared with heat values predicted from previously established heat-stress curves obtained by using either preshortening or latency release methods. There was no shortening-related increment in heat output per contraction when comparison was made to a control heat-stress curve, obtained using the latency release method. An increase in heat production of 10% was observed with long shortening distances when comparison was made to a control heat-stress curve obtained by preshortening the muscles; however, this difference is most likely due to an underestimate of the magnitude of the activation heat component in these control heat-stress curves. An increase in isometric heat production due to maintained stretch per se was observed. The present data indicate that it is unlikely that there is a significant shortening heat component when cardiac muscle shortens. The absence of such a metabolic component may account for the rapid fall off in total enthalpy output in isotonic contractions at low to medium afterloads when compared with the skeletal muscle data.

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Analysis of thermopile records from contracting isolated cardiac muscle

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.259.5.h1601 ◽

1990 ◽

Vol 259 (5) ◽

pp. H1601-H1605 ◽

Cited By ~ 3

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.

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Thermodynamic phenomena exhibited in a shortening or lengthening muscle

Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character ◽

10.1098/rspb.1924.0031 ◽

1924 ◽

Vol 96 (677) ◽

pp. 338-348 ◽

Cited By ~ 14

Keyword(s):

Heat Production ◽

Quantitative Relation ◽

Sartorius Muscle ◽

Heat Measurement

Recently Fenn (1) (2) has investigated the quantitative relation between the energy liberated and the work performed by the isolated sartorius muscle of the frog. He has advanced a qualitative statement of the effect of shortening and lengthening of the muscle on its heat-production, viz., shortening during contraction or lengthening during relaxation produces more heat than the contraction allowed to proceed isometrically, while lengthening during contraction or shortening during relaxation gives out less heat. The present paper deals with a further investigation of this relation. Apparatus and methods. A pair of sartorius muscles of the frog was mounted in the combined thermopile and muscle chamber made by Fenn (1). The method of heat measurement and calibration was essentially the same as that of Hartree and Hill (3); some modification, however, was necessary.

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Anchorfibers and the Topography of Junctional SR

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100080341 ◽

1977 ◽

Vol 35 ◽

pp. 582-583

Author(s):

James Junker ◽

Joachim R. Sommer

Keyword(s):

Sarcoplasmic Reticulum ◽

Cardiac Muscle ◽

Single Filament ◽

Relaxation Cycle ◽

10 Nm Filaments ◽

Junctional Sarcoplasmic Reticulum

Junctional sarcoplasmic reticulum (JSR) in all its forms (extended JSR, JSR of couplings, corbular SR) in both skeletal and cardiac muscle is always located at the Z - I regions of the sarcomeres. The Z tubule is a tubule of the free SR (non-specialized SR) which is consistently located at the Z lines in cardiac muscle (1). Short connections between JSR and Z lines have been described (2), and bundles of filaments at Z lines have been seen in skeletal (3) and cardiac (4) muscle. In opossum cardiac muscle, we have seen bundles of 10 nm filaments stretching across interfibrillary spaces and adjacent myofibrils with extensions to the plasma- lemma in longitudinal (Fig. 1) and transverse (Fig. 2) sections. Only an occasional single filament is seen elsewhere along a sarcomere. We propose that these filaments represent anchor fibers that maintain the observed invariant topography of the free SR and JSR throughout the contraction-relaxation cycle.

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Neuronal and Extraneuronal Uptake of 3H-Norepinephrine in the Heart of the Active Bat: An Electron Microscopic Radioautographic Study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100073052 ◽

1973 ◽

Vol 31 ◽

pp. 522-523

Author(s):

Martin Hagopian ◽

Michael D. Gershon ◽

Eladio A. Nunez

Keyword(s):

Smooth Muscle ◽

Monoamine Oxidase ◽

Vascular Smooth Muscle ◽

Cardiac Muscle ◽

Maximum Rate ◽

External Medium ◽

Extraneuronal Uptake ◽

Electron Microscopic ◽

Cardiac Tissues ◽

High Affinity

The ability of cardiac tissues to take up norepinephrine from an external medium is well known. Two mechanisms, called Uptake and Uptake respectively by Iversen have been differentiated. Uptake is a high affinity system associated with adrenergic neuronal elements. Uptake is a low affinity system, with a higher maximum rate than that of Uptake. Uptake has been associated with extraneuronal tissues such as cardiac muscle, fibroblasts or vascular smooth muscle. At low perfusion concentrations of norepinephrine most of the amine taken up by Uptake is metabolized. In order to study the localization of sites of norepinephrine storage following its uptake in the active bat heart, tritiated norepinephrine (2.5 mCi; 0.064 mg) was given intravenously to 2 bats. Monoamine oxidase had been inhibited with pheniprazine (10 mg/kg) one hour previously to decrease metabolism of norepinephrine.

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Morphological Basis of the Disparity Between Muscle Length and Sarcomere Length in the Myocardium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072551 ◽

1973 ◽

Vol 31 ◽

pp. 422-423

Author(s):

G.E. Adomian ◽

L. Chuck ◽

W.W. Pannley

Keyword(s):

Cardiac Muscle ◽

Sarcomere Length ◽

Muscle Length ◽

Contractile Force ◽

Direct Function ◽

Morphological Basis ◽

Tension Curve

Sonnenblick, et al, have shown that sarcomeres change length as a function of cardiac muscle length along the ascending portion of the length-tension curve. This allows the contractile force to be expressed as a direct function of sarcomere length. Below L max, muscle length is directly related to sarcomere length at lengths greater than 85% of optimum. However, beyond the apex of the tension-length curve, i.e. L max, a disparity occurs between cardiac muscle length and sarcomere length. To account for this disproportionate increase in muscle length as sarcomere length remains relatively stable, the concept of fiber slippage was suggested as a plausible explanation. These observations have subsequently been extended to the intact ventricle.

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High Resolution Stereography of Complementary Freeze-Fracture Replicas Reveals the Presence of Depressions Opposite Membrane Associated Particles of Split Membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066267 ◽

1971 ◽

Vol 29 ◽

pp. 442-443

Author(s):

Russell L. Steere

Keyword(s):

High Resolution ◽

Cardiac Muscle ◽

Electron Micrographs ◽

Chromic Acid ◽

Freeze Fracture ◽

Distilled Water ◽

Fine Scale ◽

Acid Cleaning ◽

Cleaning Solution

Complementary replicas have revealed the fact that the two common faces observed in electron micrographs of freeze-fracture and freeze-etch specimens are complementary to each other and are thus the new faces of a split membrane rather than the original inner and outer surfaces (1, 2 and personal observations). The big question raised by published electron micrographs is why do we not see depressions in the complementary face opposite membrane-associated particles? Reports have appeared indicating that some depressions do appear but complementarity on such a fine scale has yet to be shown.Dog cardiac muscle was perfused with glutaraldehyde, washed in distilled water, then transferred to 30% glycerol (material furnished by Dr. Joaquim Sommer, Duke Univ., and VA Hospital, Durham, N.C.). Small strips were freeze-fractured in a Denton Vacuum DFE-2 Freeze-Etch Unit with complementary replica tooling. Replicas were cleaned in chromic acid cleaning solution, then washed in 4 changes of distilled water and mounted on opposite sides of the center wire of a Formvar-coated grid.

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