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  • 1
    Electronic Resource
    Electronic Resource
    Oscillations of intracellular Ca 2+ in mammalian cardiac muscle (1983)
    [s.l.] : Nature Publishing Group
    Nature 304 (1983), S. 735-738 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The experiments were performed on ferret papillary muscles which were microinjected with the photoprotein aequorin in order to measure [Ca2+]i. In most experiments between 30 and 100 cells were injected. The intensity of the light emitted by aequorin (a function of [Ca2+]i was measured with a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/304735a0
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    An improved apparatus for the optical recording of contraction of single heart cells (1988)
    Springer
    Pflügers Archiv 413 (1988), S. 197-205 
    Details
    ISSN: 1432-2013
    Keywords: Heart ; Cardiac muscle ; Cardiac myocytes ; Muscle contraction ; Apparatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An optical system for measuring changes in cell length during unloaded contractions of cardiac myocytes is described. A one-dimensional video “image” of a cell is obtained every 4 ms with a linear photodiode array, which is aligned with the longitudinal axis of the cell. The circuit used to process the image from the photodiode array has a variety of features to aid in the accurate determination of the distance between the ends of the cell, i.e. the cell length. First, the video image of the cell is divided into two “windows”, one encompassing the “front” edge of the cell, the other encompassing the “rear” edge. Other cells or debris beyond the cell edges are excluded. Changes in the general light level, for example as a result of debris floating above the cell, have little effect because within the windows the “background light level” is subtracted from the signals before they are processed further. To detect the cell edges, the system determines when the signals within the windows exceed (front edge) or drop below (rear edge) chosen threscholds, which are different for the front and rear edges. The system has “memory” and it identifies the rear edge of the cell as the last time the signal falls below the threshold; because of this “bright spots” within the cell are not mistaken for the end of the cell. The system has “hysteresis”, which enables it to ignore small fluctuations in brightness around the threshold. The system is easy to use, accurate, readily calibrated, and it has good spatial and time resolution (about 0.25 μm and 4 ms respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582531
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  • 3
    Electronic Resource
    Electronic Resource
    Acidosis alters the phosphorylation of Ser16 and Thr17 of phospholamban in rat cardiac muscle (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 475-483 
    Details
    ISSN: 1432-2013
    Keywords: Key words pH ; Isoprenaline ; Ca2+ ; Cardiac muscle ; Phospholamban
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effect of acidosis on the phosphorylation of Ser16 and Thr17 of phospholamban in rat cardiac muscle has been investigated using phosphorylation-site-specific antibodies to this protein. Ventricular myocytes were stimulated at 0.5 Hz for 5 min, in either control (pH 7.4) or acid (pH 6.5) physiological salt solution, in the absence or presence of isoprenaline. Site-specific phosphorylation of phospholamban was determined by Western blotting. Acidosis reduced phosphorylation of Ser16 in the absence of isoprenaline, but did not alter the isoprenaline-induced phosphorylation of Ser16. In contrast, acidosis increased Thr17 phosphorylation in the absence and presence of isoprenaline. Buffering intracellular Ca2+ ([Ca2+]i) with BAPTA inhibited the increase in Thr17 phosphorylation during acidosis but had no effect on Ser16 phosphorylation. We conclude that acidosis can alter the phosphorylation of Ser16 and Thr17 by inhibition of protein kinase A, and by an acidosis-induced increase in [Ca2+]i and the subsequent activation of a Ca2+/calmodulin-dependent protein kinase, respectively. The possible effect of these changes in phosphorylation on the activity of the Ca2+-ATPase of the cardiac sarcoplasmic reticulum during acidosis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050423
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of cytosolic Ca2+ on the Ca2+ content of the sarcoplasmic reticulum in saponin-permeabilized rat ventricular trabeculae (1998)
    Springer
    Pflügers Archiv 435 (1998), S. 555-563 
    Details
    ISSN: 1432-2013
    Keywords: Key words Heart muscle ; Extracellular [Ca2+] ; Intracellular [Ca2+] ; Sarcoplasmic reticulum ; Ca-uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rat ventricular trabeculae were mounted for isometric tension recording, and then permeabilized with saponin. The Ca2+ concentration ([Ca2+]) within the permeabilized preparation (cytosolic [Ca2+]) was monitored continuously using Indo-1 and the integrals of Ca2+ transients resulting from brief caffeine application used as an index of the sarcoplasmic reticulum (SR) Ca2+ content. The relationship between SR Ca2+ content and cytosolic [Ca2+] was studied within the reported physiological range (i.e. 50–250 nmol · l–1 Ca2+). Increasing cytosolic [Ca2+] from 50 nmol · l–1 to 250 nmol · l–1 increased the steady-state SR Ca2+ content about threefold. However, increasing [Ca2+] above 250 nmol · l–1 typically resulted in spontaneous SR Ca2+ release, with no further increase in SR Ca2+ content. The SR Ca2+ content increased only slowly when cytosolic [Ca2+] was increased; it was unchanged 20 s after a rapid increase in cytosolic [Ca2+], but increased progressively to a new steady-state level during the following 1–2 min. In a parallel series of experiments using intact papillary muscles, increasing extracellular [Ca2+] (from 0.5 to 5 mmol · l–1) significantly increased twitch tension within 20 s of the solution change. These results support previous suggestions that the SR Ca2+ content may increase when diastolic cytosolic [Ca2+] rises during inotropic interventions such as increased stimulus rate or extracellular [Ca2+]. However, the rate at which SR Ca2+ responds to changes in cytoplasmic [Ca2+] within the diastolic range does not appear rapid enough to explain the early potentiation of twitch tension in intact preparations after an increase in extracellular [Ca2+].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050552
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of the protein kinase A inhibitor H-89 on Ca2+ regulation in isolated ferret ventricular myocytes (1999)
    Springer
    Pflügers Archiv 437 (1999), S. 529-537 
    Details
    ISSN: 1432-2013
    Keywords: Key words Calcium ; Cardiac ; cAMP ; H-89 ; Protein kinase inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We investigated the effects of a protein kinase A (PKA) inhibitor, H-89 {N-[2-(p-bromocinnamylamino)ethyl]-5-iso-quinolinesulphonamide}, on Ca2+ regulation in Fura-2-loaded ferret myocytes. H-89 (10 µmol/l) decreased the amplitude of the Fura-2 transient to 28.2±4.3% (P〈0.001) of control and prolonged its duration, characterized by a decrease in the rate of decline of Ca2+ to diastolic levels: t 1/2 increased from 311±35 ms to 547±43 ms (P〈0.001, n=7). Reduced Ca2+ uptake by the sarcoplasmic reticulum (SR) in the presence of H-89 was also indicated by a decrease in the SR Ca2+ content, as assessed with caffeine. The apparent slowing of the SR Ca2+-ATPase was not caused by changes in phosphorylation of phospholamban (PLB). However, Ca2+ uptake in microsomal vesicles prepared from canine hearts and fast-twitch rat skeletal muscle (which lacks PLB) was decreased by 34.1 and 46.8% (n=3), respectively, suggesting that H-89 has a direct inhibitory effect on the SR Ca2+-ATPase. In electrophysiological experiments, 5.0 µmol/l H-89 decreased the L-type Ca2+ current (I Ca) by 39.5% (n=6) and slowed the upstroke of the action potential and, in some cases, caused loss of excitability without changes in the resting membrane potential. In summary, data show that [Ca2+ ]i regulation, and hence contraction, is sustained by PKA-mediated phosphorylation, even in the absence of β-agonists. However, the use of H-89 as a tool to study the role of this signalling pathway is limited by the non-specific effects of H-89 on the SR Ca2+-ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050814
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