The distribution of calsequestrin in rat myocardial sarcoplasmic reticulum

1984 ◽  
Vol 42 ◽  
pp. 712-713
Author(s):  
A. O. Jorgensen ◽  
A. C.-Y. Shen ◽  
K. P. Campbell ◽  
G. Denney
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Ventricular Muscle ◽  
Myocardial Cells ◽  
Transverse Tubules ◽  
Purkinje Fibers ◽  
Immunofluorescence Localization ◽  
Band Region ◽  
Junctional Sarcoplasmic Reticulum

We have previously identified and purified calsequestrin from canine ventricular muscle. Immunofluorescence localization suggested that cardiac calsequestrin is confined to the lumen of the interior and peripheral junctional sarcoplasmic reticulum (SR) in adult mammalian ventricular myocardial cells. Immunolocalization of calsequestrin in myocardial cells without transverse tubules (chicken ventricular myocardial cells and sheep Purkinje fibers) clearly showed that calsequestrin as predicted was present in the lumen of peripheral junctional SR but absent from the lumen of the network SR. However, in addition calsequestrin was also present in the lumen of the corbular SR, bulbous ends on the network SR mostly confined to the I band region of myocardial cells.

scholarly journals Evidence for the presence of calsequestrin in two structurally different regions of myocardial sarcoplasmic reticulum.

1984 ◽  
Vol 98 (4) ◽  
pp. 1597-1602 ◽  
Author(s):  
A O Jorgensen ◽  
K P Campbell
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Central Region ◽  
Protein A ◽  
Muscle Cells ◽  
Physiological Signals ◽  
Ventricular Muscle ◽  
Cardiac Muscle Cells ◽  
Band Region ◽  
Membrane Bound ◽  
Junctional Sarcoplasmic Reticulum

Localization of calsequestrin in chicken ventricular muscle cells was determined by indirect immunofluorescence and immuno-Protein A-colloidal gold labeling of cryostat and ultracryotomy sections, respectively. Calsequestrin was localized in the lumen of peripheral junctional sarcoplasmic reticulum, as well as in the lumen of membrane-bound structures present in the central region of the I-band, while being absent from the lumen of the sarcoplasmic reticulum in the A-band region of the cardiac muscle cells. Since chicken ventricular muscle cells lack transverse tubules, the presence of calsequestrin in membrane bound structures in the central region of the I-band suggests that these cells contain nonjunctional regions of sarcoplasmic reticulum that are involved in Ca2+ storage and possibly Ca2+ release. It is likely that the calsequestrin containing structures present throughout the I-band region of the muscle cells correspond to specialized regions of the free sarcoplasmic reticulum in the I-band called corbular sarcoplasmic reticulum. It will be of interest to determine whether Ca2+ storage and possibly Ca2+ release from junctional and nonjunctional regions of the sarcoplasmic reticulum in chicken ventricular muscle cells are regulated by the same or different physiological signals.

scholarly journals Immunoelectron microscopical localization of phospholamban in adult canine ventricular muscle.

1987 ◽  
Vol 104 (5) ◽  
pp. 1343-1352 ◽  
Author(s):  
A O Jorgensen ◽  
L R Jones
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Subcellular Distribution ◽  
Immunogold Labeling ◽  
Relative Distribution ◽  
Ventricular Muscle ◽  
Myocardial Cells ◽  
Microscopical Localization ◽  
Cytoplasmic Side ◽  
Junctional Sarcoplasmic Reticulum

The subcellular distribution of phospholamban in adult canine ventricular myocardial cells was determined by the indirect immunogold-labeling technique. The results presented suggest that phospholamban, like the Ca2+-ATPase, is uniformly distributed in the network sarcoplasmic reticulum but absent from the junctional portion of the junctional sarcoplasmic reticulum. Unlike the Ca2+-ATPase, but like cardiac calsequestrin, phospholamban also appears to be present in the corbular sarcoplasmic reticulum. Comparison of the relative distribution of phospholamban immunolabeling in the sarcoplasmic reticulum with that of the sarcolemma showed that the density of phospholamban in the network sarcoplasmic reticulum was approximately 35-fold higher than that of the cytoplasmic side of the sarcolemma, which in turn was found to be three- to fourfold higher than the density of the background labeling. However, a majority of the specific phospholamban labeling within 30 nm of the cytoplasmic side of the sarcolemma was clustered and present over the sarcoplasmic reticulum in the subsarcolemmal region of the myocardial cells, suggesting that phospholamban is confined to the junctional regions between the sarcolemma and the sarcoplasmic reticulum, but absent from the nonjunctional portion of the sarcolemma. Although the resolution of the immunogold-labeling technique used (60 nm) does not permit one to determine whether the specific labeling within 30 nm of the cytoplasmic side of the sarcolemma is associated with the sarcolemma and/or the junctional sarcoplasmic reticulum, it is likely that the low amount of labeling in this region represents phospholamban associated with sarcoplasmic reticulum. These results suggest that phospholamban is absent from the sarcolemma and confined to the sarcoplasmic reticulum in cardiac muscle.

scholarly journals SPHEROIDAL BODIES IN THE JUNCTIONAL SARCOPLASMIC RETICULUM OF LIZARD MYOCARDIAL CELLS

1974 ◽  
Vol 60 (3) ◽  
pp. 602-615 ◽  
Author(s):  
M. S. Forbes ◽  
N. Sperelakis
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Anolis Carolinensis ◽  
Myocardial Cells ◽  
En Face ◽  
Structural Details ◽  
Junctional Sarcoplasmic Reticulum

The sarcoplasmic reticulum (SR) of lizard (Anolis carolinensis) myocardial cells has been examined, with particular attention being paid to the structural details of the peripheral couplings (junctional SR). Spheroidal bodies are present within the opaque core of junctional SR; these can be seen both in sections made en face and in sections cut to show the apposition of the junctional SR with the sarcolemma. Opaque junctional processes extend between the sarcolemma and the peripheral junctional SR. The myocardial cells in addition contain some SR cisternae deep within the cells which also possess opaque cores composed of spheroids. Although the significance of the junctional SR spheroidal bodies is unknown, it is thought that they could act as a matrix on which enzymes such as calcium-specific ATPase may be located.

scholarly journals Localization of Ca2+ + Mg2+-ATPase of the sarcoplasmic reticulum in adult rat papillary muscle.

1982 ◽  
Vol 93 (3) ◽  
pp. 883-892 ◽  
Author(s):  
A O Jorgensen ◽  
A C Shen ◽  
P Daly ◽  
D H MacLennan
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Functional Role ◽  
Transverse Tubules ◽  
Contraction Coupling ◽  
Adult Rat ◽  
Sarcoplasmic Reticulum Membrane ◽  
Rat Papillary Muscle ◽  
Junctional Sarcoplasmic Reticulum

Localization of the Ca2+ + Mg2+-ATPase of the sarcoplasmic reticulum in rat papillary muscle was determined by indirect immunofluorescence and immunoferritin labeling of cryostat and ultracryotomy sections, respectively. The Ca2+ + Mg2+-ATPase was found to be rather uniformly distributed in the free sarcoplasmic reticulum membrane but to be absent from both peripheral and interior junctional sarcoplasmic reticulum membrane, transverse tubules, sarcolemma, and mitochondria. This suggests that the Ca2+ + Mg2+-ATPase of the sarcoplasmic reticulum is antigenically unrelated to the Ca2+ + Mg2+-ATPase of the sarcolemma. These results are in agreement with the idea that the sites of interior and peripheral coupling between sarcoplasmic reticulum membrane and transverse tubules and between sarcoplasmic reticulum and sarcolemmal membranes play the same functional role in the excitation-contraction coupling in cardiac muscle.

Avian Extended Junctional SR: 3-D Geometry Rendered in Stereo

1997 ◽  
Vol 3 (S2) ◽  
pp. 247-248
Author(s):  
J.R. Sommer ◽  
T. High ◽  
P. Ingram ◽  
D. Kopf ◽  
R. Nassar ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Muscle Contraction ◽  
Cardiac Myocytes ◽  
Ryanodine Receptor ◽  
Transverse Tubules ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Junctional Sarcoplasmic Reticulum ◽  
Invariant Differentiation

Extended junctional sarcoplasmic reticulum (EJSR) is an invariant differentiation of the sarcoplasmic reticulum (SR) in bird cardiac myocytes (CM) and central to excitation-contraction coupling (ECC). EJSR occurs as both continuous and discontinuous extensions of junctional sarcoplasmic reticulum (JSR), and surrounds and pervades the Z/I band as the “ EJSR Z-rete” whose geometry has mechanistic implications for the function of “couplings” in ECC, in general. “Peripheral coupling(s)” (PC) in birds, and the additional “interior coupling(s)” (IC) at transverse tubules (TT) in mammals, are formed by tight apposition to plasmalemma of JSR, a specialized calcium (Ca) store of the SR. Free SR (FSR; i.e. free of JSR/EJSR specializations) is the rest of the smooth, tubular SR network, which connects intercalated patches of EJSR forming the EJSR Z-retes and, elsewhere, displays both longitudinal and transverse geometries in surrounding the contractile material for the purpose of sequestering Ca after each muscle contraction. Except for EJSR having no plasmalemmal contact, morphologically, EJSR and JSR are homologues:1 both have similar sizes; are studded (approx. 32 nm center-to-center) with junctional processes (JP; ryanodine receptor (RyR)/-Ca-release channels);

Biochemical characteristics of free and junctional sarcoplasmic reticulum and of transverse tubules in human skeletal muscle

1989 ◽  
Vol 12 (4) ◽  
pp. 323-331 ◽  
Author(s):  
Ernesto Damiani ◽  
Alfredo Barillari ◽  
Gianantonio Tobaldin ◽  
Sandra Pierobon ◽  
Alfredo Margreth
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Human Skeletal Muscle ◽  
Transverse Tubules ◽  
Biochemical Characteristics ◽  
Junctional Sarcoplasmic Reticulum

Anchorfibers and the Topography of Junctional SR

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.

scholarly journals Spontaneous calcium release in tissue from the failing canine heart

2009 ◽  
Vol 297 (4) ◽  
pp. H1235-H1242 ◽  
Author(s):  
Gregory S. Hoeker ◽  
Rodolphe P. Katra ◽  
Lance D. Wilson ◽  
Bradley N. Plummer ◽  
Kenneth R. Laurita
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Tissue Level ◽  
Calcium Handling ◽  
Canine Heart ◽  
Myocardial Cells ◽  
Spontaneous Release ◽  
Adrenergic Stimulation ◽  
Electrical Instability ◽  
Delayed Afterdepolarization

Abnormalities in calcium handling have been implicated as a significant source of electrical instability in heart failure (HF). While these abnormalities have been investigated extensively in isolated myocytes, how they manifest at the tissue level and trigger arrhythmias is not clear. We hypothesize that in HF, triggered activity (TA) is due to spontaneous calcium release from the sarcoplasmic reticulum that occurs in an aggregate of myocardial cells (an SRC) and that peak SCR amplitude is what determines whether TA will occur. Calcium and voltage optical mapping was performed in ventricular wedge preparations from canines with and without tachycardia-induced HF. In HF, steady-state calcium transients have reduced amplitude [135 vs. 170 ratiometric units (RU), P < 0.05] and increased duration (252 vs. 229 s, P < 0.05) compared with those of normal. Under control conditions and during β-adrenergic stimulation, TA was more frequent in HF (53% and 93%, respectively) compared with normal (0% and 55%, respectively, P < 0.025). The mechanism of arrhythmias was SCRs, leading to delayed afterdepolarization-mediated triggered beats. Interestingly, the rate of SCR rise was greater for events that triggered a beat (0.41 RU/ms) compared with those that did not (0.18 RU/ms, P < 0.001). In contrast, there was no difference in SCR amplitude between the two groups. In conclusion, TA in HF tissue is associated with abnormal calcium regulation and mediated by the spontaneous release of calcium from the sarcoplasmic reticulum in aggregates of myocardial cells (i.e., an SCR), but importantly, it is the rate of SCR rise rather than amplitude that was associated with TA.

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