scholarly journals NUCLEOSIDE PHOSPHATASE ACTIVITIES IN RAT CARDIAC MUSCLE

1965 ◽  
Vol 25 (2) ◽  
pp. 201-215 ◽  
Author(s):  
Edward Essner ◽  
Alex B. Novikoff ◽  
Nelson Quintana
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Capillary Endothelium ◽  
Frozen Sections ◽  
Phosphatase Activities ◽  
Intercalated Discs ◽  
Capillary Endothelial Cells ◽  
Contraction And Relaxation ◽  
Terminal Cisternae ◽  
T System

Localizations of aldehyde-resistant nucleoside phosphatase activities in frozen sections of rat cardiac muscle have been studied by electron microscopy. Activities are higher after fixation with formaldehyde than with glutaraldehyde. After incubation with adenosine triphosphate or inosine diphosphate at pH 7.2, reaction product is found in the "terminal cisternae" or "transverse sacs" of the sarcoplasmic reticulum, which, together with the "intermediary vesicles" (T system), constitute the "dyads" or "triads". Reaction product is also present at the membranes of micropinocytotic vacuoles which apparently form from the plasma membrane of capillary endothelial cells and from the sarcolemma. In certain regions of the intercalated discs, reaction product is found within the narrow spaces between sarcolemmas of adjacent cells and within micropinocytotic vacuoles that seem to form from the sarcolemma. With inosine diphosphate, reaction product is also found in other parts of the sarcoplasmic reticulum. After incubation with cytidine monophosphate at pH 5, reaction product is present in the transverse sacs of sarcoplasmic reticulum, in micropinocytotic vacuoles in capillary endothelium, and in lysosomes of muscle fibers and capillaries. The possible significance of the sarcoplasmic reticulum phosphatases is discussed in relation to the role the reticulum probably plays in moving calcium ions and thereby controlling contraction and relaxation of the muscle fiber.

scholarly journals Ultrastructural localization of the Ca2+ + Mg2+-dependent ATPase of sarcoplasmic reticulum in rat skeletal muscle by immunoferritin labeling of ultrathin frozen sections.

1982 ◽  
Vol 92 (2) ◽  
pp. 409-416 ◽  
Author(s):  
A O Jorgensen ◽  
A C Shen ◽  
D H MacLennan ◽  
K T Tokuyasu
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Plasma Membranes ◽  
Ultrastructural Localization ◽  
Published Data ◽  
Frozen Sections ◽  
Dependent Atpase ◽  
Sarcoplasmic Reticulum Membrane ◽  
Ultrathin Frozen Sections ◽  
Terminal Cisternae ◽  
Simultaneous Visualization

The ultrastructural localization of the Ca2+ + Mg2+-dependent ATPase of sarcoplasmic reticulum in rat gracilis muscle was determined by indirect immunoferritin labeling of ultrathin frozen sections. Simultaneous visualization of ferritin particles and of adsorption-stained cellular membranes showed that the Ca2+ + Mg2+-ATPase was concentrated in the longitudinal sarcoplasmic reticulum and in the nonjunctional regions of the terminal cisternae membrane but was virtually absent from mitochondria, plasma membranes, transverse tubules, and junctional sarcoplasmic reticulum. Ferritin particles were found preponderantly on the cytoplasmic surface of the membrane, in agreement with published data showing an asymmetry of the Ca2+ + Mg2+-ATPase within the sarcoplasmic reticulum membrane. Comparison of the density of ferritin particles in fast and slow myofibers suggested that the density of the Ca2+ + Mg2+-ATPase in the sarcoplasmic reticulum membrane in a fast myofiber is approximately two times higher than in a slow myofiber.

scholarly journals The sarcoplasmic reticulum plays a major role in isometric contraction in atrial muscle of yellowfin tuna

1999 ◽  
Vol 202 (7) ◽  
pp. 881-890 ◽  
Author(s):  
H.A. Shiels ◽  
E.V. Freund ◽  
A.P. Farrell ◽  
B.A. Block
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Isometric Contraction ◽  
Yellowfin Tuna ◽  
Thunnus Albacares ◽  
Force Of Contraction ◽  
Muscle Preparation ◽  
Force Development ◽  
Contraction And Relaxation ◽  
Isometric Muscle

We used an isometric muscle preparation to test the hypothesis that yellowfin tuna Thunnus albacares utilize the intracellular Ca2+ storage sites of the sarcoplasmic reticulum (SR) during routine contractions. Ryanodine (a blocker of SR Ca2+ release) reduced the force of contraction by approximately 50 % and the rates of contraction and relaxation by 60 % in yellowfin tuna atrium. High levels of adrenaline were unable to ameliorate the effects of ryanodine. We conclude that the SR is active in contributing Ca2+ to force development at physiological contraction frequencies. Further, we suggest that, by using intracellular Ca2+ cycling, the yellowfin tuna is able to increase the maximum contraction frequency of its cardiac muscle beyond that of most other fishes.

scholarly journals Electrical models of excitation-contraction coupling and charge movement in skeletal muscle.

1980 ◽  
Vol 76 (1) ◽  
pp. 1-31 ◽  
Author(s):  
R T Mathias ◽  
R A Levis ◽  
R S Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Ionic Current ◽  
Charge Movement ◽  
Transient Currents ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Intramembrane Charge Movement ◽  
Terminal Cisternae ◽  
T System

The consequences of ionic current flow from the T system to the sarcoplasmic reticulum (SR) of skeletal muscle are examined. The Appendix analyzes a simple model in which the conductance gx, linking T system and SR, is in series with a parallel resistor and capacitor having fixed values. The conductance gx is supposed to increase rapidly with depolarization and to decrease slowly with repolarization. Nonlinear transient currents computed from this model have some of the properties of gating currents produced by intramembrane charge movement. In particular, the integral of the transient current upon depolarization approximates that upon repolarization. Thus, equality of nonlinear charge movement can occur without intramembrane charge movement. A more complicated model is used in the text to fit the structure of skeletal muscle and other properties of its charge movement. Rectification is introduced into gx and the membrane conductance of the terminal cisternae to give asymmetry in the time-course of the transient currents and saturation in the curve relating charge movement to depolarization, respectively. The more complex model fits experimental data quite well if the longitudinal tubules of the sarcoplasmic reticulum are isolated from the terminal cisternae by a substantial resistance and if calcium release from the terminal cisternae is, for the most part, electrically silent. Specific experimental tests of the model are proposed, and the implications for excitation-contraction coupling are discussed.

scholarly journals CARDIAC MUSCLE

1971 ◽  
Vol 49 (1) ◽  
pp. 50-65 ◽  
Author(s):  
Paul H. Jewett ◽  
J. R. Sommer ◽  
E. A. Johnson
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Muscle Fibers ◽  
Cardiac Cells ◽  
Transverse Tubules ◽  
Heart Rates ◽  
Intercalated Discs ◽  
Cardiac Muscle Fibers ◽  
Morphological Differences

Cardiac muscle fibers of the hummingbird and finch have no transverse tubules and are smaller in diameter than those of mammalian hearts. The fibers are connected by intercalated discs which are composed of desmosomes and f. adherentes; small nexuses are often interspersed. As in cardiac muscle of several other animals, the junctional SR of the couplings is highly structured in these two birds but, in addition, and after having lost sarcolemmal contact, the junctional SR continues beyond the coupling to extend deep into the interior of the cells and to form belts around the Z-I regions of the sarcomeres. This portion of the sarcoplasmic reticulum, which we have named "extended junctional SR," and which is so prominent and invariant a feature of cardiac cells of hummingbirds and finches, has not been observed in chicken cardiac cells. The morphological differences between these species of birds may be related to respective differences in heart rates characteristic for these birds.

scholarly journals Ultrastructural localization of calsequestrin in rat skeletal muscle by immunoferritin labeling of ultrathin frozen sections.

1983 ◽  
Vol 97 (5) ◽  
pp. 1573-1581 ◽  
Author(s):  
A O Jorgensen ◽  
A C Shen ◽  
K P Campbell ◽  
D H MacLennan
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Central Region ◽  
Ultrastructural Localization ◽  
Frozen Sections ◽  
Rat Skeletal Muscle ◽  
Major Site ◽  
Ultrathin Frozen Sections ◽  
Terminal Cisternae

The ultrastructural localization of calsequestrin in rat skeletal muscle (gracilis) was determined by indirect immunoferritin labeling of ultrathin frozen sections. Calsequestrin was found in the lumen of transversely and longitudinally oriented terminal cisternae but was absent from most of the longitudinal sarcotubules and the fenestrated sarcoplasmic reticulum. Calsequestrin was occasionally observed in vesicular structures found in the central region of the I band. Since calsequestrin is believed to provide the major site of Ca2+ sequestration in the sarcoplasmic reticulum, the present results support the view that Ca2+, transported to the lumen of the sarcoplasmic reticulum, is preferentially sequestered in the terminal cisternae, but they also suggest that additional Ca2+ sequestration may occur near the center of the I band.

The transverse tubular (T) system of rat cardiac muscle fibers as demonstrated by tannic acid mordanting

1978 ◽  
Vol 56 (9) ◽  
pp. 1906-1916 ◽  
Author(s):  
T. S. Leeson
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Tannic Acid ◽  
Extracellular Space ◽  
Inverse Relationship ◽  
Muscle Fibres ◽  
Fiber Size ◽  
T Tubules ◽  
Cardiac Muscle Fibers ◽  
T System

T-tubules and subsarcolemmal caveolae in rat cardiac muscle fibres have been studied using the tannic acid mordanting technique. While T-tubules form an extensive and relatively regular meshwork with triads at Z-lines in ventricular fibers, in atrial fibers the tubules are often absent, or very sparse and with an irregular distribution. There appears to be a relation to fiber size, the meshwork being more extensive in fibers of larger diameter, and an inverse relationship to the number of couplings found between sarcoplasmic reticulum and plasmalemma. In larger atrial fibers, while the T-tubule meshwork was extensive, it did not show the regularity of distribution found in ventricular fibers. T-tubule continuity with the extracellular space was visualized clearly, both directly and indirectly via subsarcolemmal caveolae.

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.

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