Subcellular calcium signaling in cardiac cells revealed with fast two-dimensional confocal imaging

2002 ◽  
Author(s):  
Lothar A. Blatter ◽  
Katherine A. Sheehan ◽  
Jens Kockskaemper
Keyword(s):  
Calcium Signaling ◽  
Cardiac Cells ◽  
Confocal Imaging ◽  
Two Dimensional

Confocal imaging of calcium in intact ventricular muscle provides a new view of excitation-contraction coupling

1996 ◽  
Vol 54 ◽  
pp. 738-739
Author(s):  
W.G. Wier
Keyword(s):  
Local Control ◽  
Cardiac Tissue ◽  
Cell Function ◽  
Isolated Heart ◽  
Cardiac Cells ◽  
Confocal Imaging ◽  
Ion Concentration ◽  
Heart Cell ◽  
Free Calcium ◽  
Heart Cells

A fundamentally new understanding of cardiac excitation-contraction (E-C) coupling is being developed from recent experimental work using confocal microscopy of single isolated heart cells. In particular, the transient change in intracellular free calcium ion concentration ([Ca2+]i transient) that activates muscle contraction is now viewed as resulting from the spatial and temporal summation of small (∼ 8 μm3), subcellular, stereotyped ‘local [Ca2+]i-transients' or, as they have been called, ‘calcium sparks'. This new understanding may be called ‘local control of E-C coupling'. The relevance to normal heart cell function of ‘local control, theory and the recent confocal data on spontaneous Ca2+ ‘sparks', and on electrically evoked local [Ca2+]i-transients has been unknown however, because the previous studies were all conducted on slack, internally perfused, single, enzymatically dissociated cardiac cells, at room temperature, usually with Cs+ replacing K+, and often in the presence of Ca2-channel blockers. The present work was undertaken to establish whether or not the concepts derived from these studies are in fact relevant to normal cardiac tissue under physiological conditions, by attempting to record local [Ca2+]i-transients, sparks (and Ca2+ waves) in intact, multi-cellular cardiac tissue.

scholarly journals Transmural heterogeneity of repolarization and Ca2+ handling in a model of mouse ventricular tissue

2010 ◽  
Vol 299 (2) ◽  
pp. H454-H469 ◽  
Author(s):  
Vladimir E. Bondarenko ◽  
Randall L. Rasmusson
Keyword(s):  
Action Potentials ◽  
Cardiac Cells ◽  
Two Dimensional ◽  
Epicardial Cells ◽  
Irregular Structures ◽  
Ventricular Tissue ◽  
Intracellular Ca ◽  
Heterogeneous Tissue ◽  
Transmural Heterogeneity ◽  
Epicardial Myocytes

Mouse hearts have a diversity of action potentials (APs) generated by the cardiac myocytes from different regions. Recent evidence shows that cells from the epicardial and endocardial regions of the mouse ventricle have a diversity in Ca2+ handling properties as well as K+ current expression. To examine the mechanisms of AP generation, propagation, and stability in transmurally heterogeneous tissue, we developed a comprehensive model of the mouse cardiac cells from the epicardial and endocardial regions of the heart. Our computer model simulates the following differences between epicardial and endocardial myocytes: 1) AP duration is longer in endocardial and shorter in epicardial myocytes, 2) diastolic and systolic intracellular Ca2+ concentration and intracellular Ca2+ concentration transients are higher in paced endocardial and lower in epicardial myocytes, 3) Ca2+ release rate is about two times larger in endocardial than in epicardial myocytes, and 4) Na+/Ca2+ exchanger rate is greater in epicardial than in endocardial myocytes. Isolated epicardial cells showed a higher threshold for stability of AP generation but more complex patterns of AP duration at fast pacing rates. AP propagation velocities in the model of two-dimensional tissue are close to those measured experimentally. Simulations show that heterogeneity of repolarization and Ca2+ handling are sustained across the mouse ventricular wall. Stability analysis of AP propagation in the two-dimensional model showed the generation of Ca2+ alternans and more complex transmurally heterogeneous irregular structures of repolarization and intracellular Ca2+ transients at fast pacing rates.

A B56 regulatory subunit of protein phosphatase 2A localizes to nuclear speckles in cardiomyocytes

2005 ◽  
Vol 289 (1) ◽  
pp. H285-H294 ◽  
Author(s):  
Marisa S. Gigena ◽  
Akihiko Ito ◽  
Hiroshi Nojima ◽  
Terry B. Rogers
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Cardiac Cells ◽  
Confocal Imaging ◽  
Regulatory Subunit ◽  
Heart Cells ◽  
Nuclear Speckles ◽  
Gene Markers ◽  
Cell Extracts ◽  
Phosphatase 2A

Protein phosphatase 2A (PP2A) is widely distributed in heart tissues, yet its precise cellular functions are poorly understood. This study is based on the notion that PP2A action is governed by interactions of the core enzyme with B targeting/regulatory subunits. The subcellular localizations of two B subunits, B56α and B56γ1, were assessed using adenovirus-driven expression of epitope-tagged (hemagglutinin, HA) in cultured neonatal and adult rat ventricular myocytes. Confocal imaging revealed that HA-B56α was excluded from the nucleus and decorated striated structures, whereas HA-B56γ1 was principally found in the nucleus. Precise immunolabeling studies showed that B56γ1 was concentrated in intranuclear structures known as nuclear speckles, macromolecular structures that accumulate transcription and splicing factors. Western blot analyses revealed that overexpression of either B subunit had no effect on the levels of other PP2A subunits in cultured neonatal cardiac cells. However, overexpression of only B56γ1 increased whole cell PP2A activity by 40% when measured in cell extracts. Finally, B56γ1 did not alter global gene expression or expression of hypertrophic gene markers such as α-skeletal actin. However, morphometric analyses of confocal images revealed that B56γ1 alters the dynamic assembly/disassembly process of nuclear speckles in heart cells. These studies provide new insight into mechanisms of PP2A targeting in the subnuclear architecture in cardiomyocytes and into the role of this phosphatase in nuclear signaling.

scholarly journals The Synergistic Effect of Anabolic Steroid and Loading on Intercellular Calcium Signaling Via Gap Junctions in Human Supraspinatus Tendon Cells

2020 ◽  
pp. 1-8
Author(s):  
Ioannis K. Triantafyllopoulos ◽  
Ioannis K. Triantafyllopoulos ◽  
Natasa Dede
Keyword(s):  
Gap Junctions ◽  
Calcium Signaling ◽  
Anabolic Steroid ◽  
Connexin 43 ◽  
Supraspinatus Tendon ◽  
The Other ◽  
Two Dimensional ◽  
Nandrolone Decanoate ◽  
Steroid Administration ◽  
Tendon Cells

Objective: We hypothesized that anabolic steroid administration would act synergistically with substrate strain in two-dimensional cultures of human supraspinatus tendon cells, to upregulate the expression of connexin-43 and to increase the Ca2+ wave propagation through gap junctions. Methods: Supraspinatus tendon cells were isolated intra-operatively from human specimens during shoulder arthroscopy. Cells were plated in two-dimensional spot cultures and arranged into four experimental groups: 1) non-load, non-steroid (NLNS, n=12 wells); 2) non-load, steroid (NLS, n=12 wells); 3) load, non-steroid (LNS, n=12 wells); and 4) load, steroid (LS, n=12 wells) in order to produce bioartificial tendons (BATs). The load groups were stretched in culture plates and the steroid groups were given nandrolone decanoate. When BATs were macro- and microscopically mature, at five days, they were evaluated with immunocytochemistry for connexin-43 staining, fluorescence microscopy for calcium imaging and mechanical stimulation with a micropipette tip manipulation for calcium propagation. Dose response test was performed in order to establish any relation between nandrolone decanoate dose and calcium signaling response. ATP was applied to the spot culture cells from all groups and all patients to determine if the cells were sensitive to extracellular ATP. Results: Load-steroid group demonstrated the greatest density of cnx43 in comparison to all other groups. There were no significant differences between the groups considering the percentage of cells responding after mechanical stimulation (cell recruitment). The cells of load-steroid group showed a significantly greater mean peak [Ca2+]ic compared to the values of the other groups (p<0.05). The propagation time was significantly decreased in the LS group compared with the other groups (p<0.05). There were no significant differences between the groups considering the number of cells that were responding spontaneously prior to stimulation or the number of responding cells that were oscillating after the stimulation. Conclusion: Nandrolone decanoate and loading seem to have a synergistic effect on the upregulation of the gap junction protein cxn43 enhancing calcium signaling via gap junctions. Consecutively, anabolic steroid administration and load may enhance the formation of a better-organized cytoskeleton and particularly the actin stress monofilaments.

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