Cell Coupling and Healing-Over in Cardiac Muscle

An integral sialoglycoprotein with Mr approximately 130,000 (Sgp 130) and highest expression in adult chicken gizzard smooth muscle has been recently identified as an excellent candidate for classification as a plasma membrane protein natively associated (directly or indirectly) with actin microfilaments (Rogalski, A.A., and S.J. Singer, 1985, J. Cell Biol., 101:785-801). In this study, the relative in situ distributions of the Sgp 130 integral species (a designation that also includes non-smooth muscle molecular forms) and the peripheral protein, vinculin, have been simultaneously revealed for the first time in selected cultured cells and tissues abundant in microfilament-membrane attachment sites, particularly, smooth and cardiac muscle. Specific antibody probes against Sgp 130 (mouse mAb 30B6) and vinculin (affinity-purified rabbit antibody) were used in double indirect immunofluorescent and immunoelectron microscopic experiments. In contrast to the widespread distributions of vinculin at microfilament-membrane attachment sites, Sgp 130 has been shown to exhibit striking site-specific variation in its abundancy levels in the plasma membrane. Sgp 130 and vinculin were found coincidentally concentrated at focal contact sites in cultured chick embryo fibroblasts and endothelial cells, membrane dense plaques of smooth muscle, and sarcolemma dense plaque sites overlying the Z line in cardiac muscle. However, at the fascia adherens junctional sites of cardiac muscle where vinculin is sharply confined, Sgp 130 was immunologically undetectable in both intact and EGTA-uncoupled tissue. This latter result was confirmed with immunoblotting experiments using isolated forms of the fascia adherens. The double immunolabeling studies of this report establish Sgp 130 as a major integral protein component of nonjunctional membrane dense plaque structures and raise the possibility that the 130-kD integral sialoglycoprotein (Sgp 130) and vinculin assume stable transmembrane associations at these particular microfilament-membrane attachment sites. Nonjunctional dense plaques are further suggested to be a molecularly distinct class of plasma membrane structures rather than a subgroup of adherens junctions. Our data also support a hypothesis that Sgp 130 is involved in plasma membrane force coupling events but not in junctional-related cell-cell coupling.

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Cell Coupling and Healing-Over in Cardiac Muscle

Physiology and Pathophysiology of the Heart - Developments in Cardiovascular Medicine ◽

10.1007/978-1-4757-1171-4_23 ◽

1984 ◽

pp. 493-501 ◽

Cited By ~ 1

Author(s):

Walmor C. De Mello

Keyword(s):

Cardiac Muscle ◽

Cell Coupling

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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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Calmodulin-mediated gating of lens gap junction channels in vesicles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110866 ◽

1984 ◽

Vol 42 ◽

pp. 134-137

Author(s):

Camillo Peracchia ◽

Stephen J. Girsch

Keyword(s):

Gap Junctions ◽

Freeze Fracture ◽

Orthogonal Arrays ◽

Eye Lens ◽

Lens Fiber ◽

Cell Coupling ◽

Particle Spacing ◽

Fiber Cells ◽

Gap Junction Channels ◽

Communicating Junctions

The fiber cells of eye lens communicate directly with each other by exchanging ions, dyes and metabolites. In most tissues this type of communication (cell coupling) is mediated by gap junctions. In the lens, the fiber cells are extensively interconnected by junctions. However, lens junctions, although morphologically similar to gap junctions, differ from them in a number of structural, biochemical and immunological features. Like gap junctions, lens junctions are regions of close cell-to-cell apposition. Unlike gap junctions, however, the extracellular gap is apparently absent in lens junctions, such that their thickness is approximately 2 nm smaller than that of typical gap junctions (Fig. 1,c). In freeze-fracture replicas, the particles of control lens junctions are more loosely packed than those of typical gap junctions (Fig. 1,a) and crystallize, when exposed to uncoupling agents such as Ca++, or H+, into pseudo-hexagonal, rhombic (Fig. 1,b) and orthogonal arrays with a particle-to-particle spacing of 6.5 nm. Because of these differences, questions have been raised about the interpretation of the lens junctions as communicating junctions, in spite of the fact that they are the only junctions interlinking lens fiber cells.

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Quantitative Freeze Fracture Studies of Gap Junctions in Somatic Cell Hybrids, Their Parents, and Revertants

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009107x ◽

1976 ◽

Vol 34 ◽

pp. 218-219

Author(s):

W. J. Larsen ◽

R. Azarnia ◽

W. R. Loewenstein

Keyword(s):

Gap Junctions ◽

Striated Muscle ◽

Freeze Fracture ◽

Cell Movement ◽

Dye Molecules ◽

Somatic Cell Hybrids ◽

Cell Coupling ◽

Normal Cells ◽

Mediate Cell ◽

Almost All

Although the physiological significance of the gap junction remains unspecified, these membrane specializations are now recognized as common to almost all normal cells (excluding adult striated muscle and some nerve cells) and are found in organisms ranging from the coelenterates to man. Since it appears likely that these structures mediate the cell-to-cell movement of ions and small dye molecules in some electrical tissues, we undertook this study with the objective of determining whether gap junctions in inexcitable tissues also mediate cell-to-cell coupling.To test this hypothesis, a coupling, human Lesh-Nyhan (LN) cell was fused with a non-coupling, mouse cl-1D cell, and the hybrids, revertants, and parental cells were analysed for coupling with respect both to ions and fluorescein and for membrane junctions with the freeze fracture technique.

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