Cardiac Muscle

Sommer, J.; Johnson, Edward A.

doi:10.1083/jcb.36.3.497

Cited by 323 publications

(92 citation statements)

References 60 publications

(84 reference statements)

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“…These low values for cardiac muscle are no doubt attributable to the fact that the actual area of membrane per unit length of preparation was much greater than that calculated for a right circular cylinder equal in diameter to that of the preparation. This assumption is obviously at variance with histological fact in the case of ungulate Purkinje strands (15,38) for which many of the earlier estimates of R,, were made (see Discussion).…”

Section: Membrane Resistancementioning

confidence: 56%

“…In addition to the problems associated with ion accumulation and depletion in these clefts (e.g. 53), the individual bundles have been shown to split into daughter bundles (15).…”

Section: Discussionmentioning

confidence: 99%

“…The morphology mayin fact be more complex, as in dog (15), or simpler in a given cross section, as in goat (15). However, the bundles of Purkinje cells are tightly packed together, higgledy-piggledy in the dog, more orderly in the goat (15), effectively separating the membrane capacitance into two components, one on the surface and one in series with an appreciable resistance in the form of the narrow clefts of extracellular space between fibers (3,4). In addition to the problems associated with ion accumulation and depletion in these clefts (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Our idea is that we might thereby separate those aspects of the results which arise from inhomogeneities of membrane potential control from those which originate from membrane properties. Our inability to find a naturally occurring preparation satisfying our criteria of simplicity (15,16) drove us to explore the feasibility of growing in tissue culture an artificial preparation of cardiac muscle which would conform to a desired geometry, e.g. a single column of cells.…”

Section: Introductionmentioning

confidence: 99%

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A synthetic strand of cardiac muscle: its passive electrical properties.

Lieberman¹,

Sawanobori²,

Kootsey³

et al. 1975

The Journal of General Physiology

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A B S T R n O T The passive electrical properties of synthetic strands of cardiac muscle, grown in tissue culture, were studied using two intraeeUular microelectrodes: one to inject a rectangular pulse of current and the other to record the resultant displacement of membrane potential at various distances from the current source. In all preparations, the potential displacement, instead of approaching a steady value as would be expected for a cell with constant electrical properties, increased slowly with time throughout the current step. In such circumstances, the specific electrical constants for the membrane and cytoplasm must not be obtained by applying the usual methods, which are based on the analytical solution of the partial differential equation describing a one-dimensional cell with constant electrical properties. A satisfactory fit of the potential waveforms was, however, obtained with numerical solutions of a modified form of this equation in which the membrane resistance increased linearly with time. Best fits of the waveforms from 12 preparations gave the foUowing values for the membrane resistance times unit length, membrane capacitance per unit length, and for the myoplasmic resistance: 1.22 4-0.13 X 10 ~ f~cm, 0.224 4-0.023 # F . c m -x, and 1.37 -4-0.13 X 107 ~crn -t, respectively. The value of membrane capacitance per unit length was close to that obtained from the time constant of the foot of the action potential and was in keeping with the generally satisfactory fit of the recorded waveforms with solutions of the cable equation in which the membrane impedance is that of a single capacitor and resistor in parallel. The area of membrane per unit length and the cross-sectional area of myoplasm at any given length of the preparation were determined from light and composite electron micrographs, and these were used to calculate the foUowing values for the specific electrical membrane resistance, membrane capacitance, and the resistivity of the cytoplasm: 20.5 + 3.0 )< 103 ftcm z, 1.54 4-0.24 #F.cm-", and 180 -4-34 ~cm, respectively. I N T R O D U C T I O NIn cardiac muscle, as in other excitable cells, the passive electrical properties of the cell m e m b r a n e a n d cytoplasm must be d e t e r m i n e d from observations of

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Section: Membrane Resistancementioning

confidence: 56%

“…In addition to the problems associated with ion accumulation and depletion in these clefts (e.g. 53), the individual bundles have been shown to split into daughter bundles (15).…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A synthetic strand of cardiac muscle: its passive electrical properties.

Lieberman¹,

Sawanobori²,

Kootsey³

et al. 1975

The Journal of General Physiology

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“…However, there was no clear-cut separation between areas showing fiber type predominance, the various fiber types being often intermingled and closely associated . Fiber type heterogeneity was also seen in small bundles of muscle fibers crossing the ventricular cavity (trabeculae carneae), which appear to correspond to the "Purkinje strands" described by Sommer and Johnson (30) .…”

Section: Rabbit Heartmentioning

confidence: 92%

Myosin types and fiber types in cardiac muscle. I. Ventricular myocardium.

Sartore¹,

Gorza²,

Bormioli³

et al. 1981

The Journal of Cell Biology

130

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Antisera against bovine atrial myosin were raised in rabbits, purified by affinity chromatography, and absorbed with insolubilized ventricular myosin. Specific anti-bovine atrial myosin (anti-bAm) antibodies reacted selectively with atrial myosin heavy chains, as determined by enzyme immunoassay combined with SDS-gel electrophoresis. In direct and indirect immunofluorescence assay, anti-bAm was found to stain all atrial muscle fibers and a minor proportion of ventricular muscle fibers in the right ventricle of the bovine heart. In contrast, almost all muscle fibers in the left ventricle were unreactive. Purkinje fibers showed variable reactivity. In the rabbit heart, all atrial muscle fibers were stained by anti-bAm, whereas ventricular fibers showed a variable response in both the right and left ventricle, with a tendency for reactive fibers to be more numerous in the right ventricle and in subepicardial regions. Diversification of fiber types with respect to anti-bAm reactivity was found to occur during late stages of postnatal development in the rabbit heart and to be influenced by thyroid hormone. All ventricular muscle fibers became strongly reactive after thyroxine treatment, whereas they became unreactive or poorly reactive after propylthiouracil treatment. These findings are consistent with the existence of different ventricular isomyosins whose relative proportions can vary according to the thyroid state. Variations in ventricular isomyosin composition can account for the changes in myosin Ca2+-activated ATPase activity previously observed in cardiac muscle from hyper- and hypothyroid animals and may be responsible for the changes in the velocity of contraction of ventricular myocardium that occur under these conditions. The differential distribution of ventricular isomyosins in the normal heart suggests that fiber types with different contractile properties may coexist in the ventricular myocardium.

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Electron‐dense material within sarcoplasmic reticulum apposed to transverse tubules and to the sarcolemma in dog papillary muscle fibers

1970

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The space between the sarcoplasmic reticulum (SR) apposed to the transverse ( T ) tubules and the sarcolemma in dog papillary muscle fibers is traversed by structures of varying densities. The distance between apposed membranes is about 70 A at the level of densities and about 100 A at the level of less dense areas that alternate with the densities. The apposed SR shows a marked increase in electrondense material when comparison is made with the SR not apposed. The electron-dense material is located in a dense layer parallel to and about midway between the membranes of the apposed SR and in numerous projections from the inside surface of the membranes. With appropriate staining procedures the central dense layer and the projections are as thick as membranes and they frequently show paired densities separated by a distance about equal to the distance between the outer dense layers of trilaminar membranes. The paired densities in the central dense layer and in the projections indicate that the electron-dense material within apposed SR has structure. The projections are frequently in register with scallops or serrations in the SR membranes and they also appear to contribute to a waviness in the central dense layer. The senations and waviness are interpreted as evidence that the projections exert a holding force because they project &om the SR membranes and connect with the central dense layer.Veratti's ('02) elegant observations on reticular structures in skeletal muscles of invertebrates and vertebrates have been clarified by electron microscope examinations showing that the sarcoplasmic reticulum (SR) encircled each fibril and formed a close association with Z lines in fowl breast muscle (Bennett and Porter, '53) and that tubules of the SR formed a network in rat sartorius and cardiac muscle fibers (Porter and Palade, '57). Segments of the SR tubules were found in apposition with what appeared to be vesicles. The apposition was seen near the A-I junction in sartorius muscle and near the Z line in cardiac muscle. Serial sections of mouse leg muscle indicated that the structures between terminal segments of the network were also tubules transversely oriented across the fiber (hdersson-Cedergren, '59). A space about 100 A wide was observed between apposed membranes of transverse tubules (T tubules) and terminal segments of the network of tubules. Continuity of the T tubules with the sarco-AM. J. ANAT., 128: 33-44. lemma has been demonstrated near the Z line in mammalian cardiac fibers (Lindner, '57; Simpson and Oertelis, '61), in fish and tadpole tail muscle fibers (Franzini-Armstrong and Porter, '64) and near the A-I junction in rat gastrocnemius muscle fibers (Walker and Schrodt, '65a). Tubules of the sarcoplasmic reticulum are continuous with SR apposed to the sarcolemma of rabbit cardiac muscle fibers (Johnson and Sommer, '67) and skeletal muscle fibers of fetal and newborn rats (Walker et al., '69). The network of SR tubules extends without interruption throughout successive sarcomeres in mammalian car...

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Cardiac Muscle

Cited by 323 publications

References 60 publications

A synthetic strand of cardiac muscle: its passive electrical properties.

A synthetic strand of cardiac muscle: its passive electrical properties.

Myosin types and fiber types in cardiac muscle. I. Ventricular myocardium.

Electron‐dense material within sarcoplasmic reticulum apposed to transverse tubules and to the sarcolemma in dog papillary muscle fibers

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