Isotropic Components of Antipyrylazo III Signals from Frog Skeletal Muscle Fibers

Baylor, Stephen M.; Quinta‐Ferreira, Mário; Hui, Chiu Shuen

doi:10.1007/978-1-4613-2377-8_38

Cited by 15 publications

(37 citation statements)

References 21 publications

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“…1 A and has a very different wavelength dependence. These traces are similar to those obtained from intact fibers (Baylor et al, 1982b(Baylor et al, , 1985.…”

Section: Methodssupporting

confidence: 84%

“…The wavelength dependence of the slowly recovering component of the absorbance change matches approximately the cuvette difference spectra for increases in either pH or free [Mg] (Fig. 1 B; Baylor et al, 1982bBaylor et al, , 1985, which are similar but not identical. The amplitude of the slowly recovering signal, however, is relatively small, at least after a single action potential, so Column 1 gives fiber reference and column 2 gives the time that elapsed from saponin treatment of the endpool segments to the time of the measurements used for columns 3-9.…”

Section: Comparison Of the Time Courses Of The Antipyrylazo III Aa(59mentioning

confidence: 52%

“…At this time, the 590-nm signal has reached its peak value (see Fig. 1 A for cut fiber results and Baylor et al, 1982bBaylor et al, , 1983bBaylor et al, , 1985 for intact fiber results). Thereafter, it recovers slowly over the next few seconds (Fig.…”

Section: Comparison Of the Time Courses Of The Antipyrylazo III Aa(59mentioning

confidence: 88%

“…It seems likely that most of the observed increase in myoplasmic free [Mg] is due to Mg leaving parvalbumin (Baylor et al, 1983a(Baylor et al, , 1985, a Ca and Mg binding protein found in brain (Gosselin-Rey et al, 1978) and fast twitch skeletal muscle (for example, Gosselin-Rey and Gerday, 1977), which is thought to play a role in muscle relaxation (Gerday and Gillis, 1976).…”

Section: The Origin Of the Myoplasmic Mg Transientmentioning

confidence: 99%

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Simultaneous monitoring of changes in magnesium and calcium concentrations in frog cut twitch fibers containing antipyrylazo III.

Irving

Maylie

Sizto

et al. 1989

The Journal of General Physiology

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Antipyrylazo III was introduced into frog cut twitch fibers (17-19~ by diffusion. After action potential stimulation, the change in indicator absorbance could be resolved into two components that had different time courses and wavelength dependences. The first component was early and transient and due to an increase in myoplasmic free [Ca] (Maylie, J., M. Irving, N.L. Sizto, and W. [C Chandler, 1987,Journal of General Physiology, 89:83-143). The second component, usually measured at 590 nm (near the isosbestic wavelength for Ca), developed later than the Ca transient and returned towards baseline about 100 times more slowly. Although the wavelength dependence of this component is consistent with an increase in either free [Mg] or pH, its time course is clearly different from that of the signals obtained with the pH indicators phenol red and 4',5'-dimethyl-5-(and -6-) carboxyfluorescein, suggesting that it is mainly due to an increase in free [Mg]. After a single action potential in freshly prepared cut fibers that contained 0.3 mM antipyrylazo III, the mean peak amplitude of &A(590) would correspond to an increase in free [Mg] of 47 #M if all the signal were due to a change in [Mg] and all the intracellular indicator reacted with Mg as in cuvette calibrations. With either repetitive action potential stimulation or voltage-clamp depolarization, the AA(590) signal continued to develop throughout the period when free [Ca] was elevated and then recovered to within 40-90% of the prestimulus baseline with an average rate constant between 0.5 and 1.0 s -1. With prolonged voltage-clamp depolarization, both the amplitude and rate of development of the &A(590) signal increased with the amplitude of the depolarization and appeared to saturate at levels corresponding to an increase in free [Mg] of 0.8-1.4 mM and a maximum rate constant of 3-4 s -1, respectively. These results are consistent with the idea Address reprint requests to Dr.

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“…1 A and has a very different wavelength dependence. These traces are similar to those obtained from intact fibers (Baylor et al, 1982b(Baylor et al, , 1985.…”

Section: Methodssupporting

confidence: 84%

Section: Comparison Of the Time Courses Of The Antipyrylazo III Aa(59mentioning

confidence: 52%

Section: Comparison Of the Time Courses Of The Antipyrylazo III Aa(59mentioning

confidence: 88%

Section: The Origin Of the Myoplasmic Mg Transientmentioning

confidence: 99%

See 2 more Smart Citations

Simultaneous monitoring of changes in magnesium and calcium concentrations in frog cut twitch fibers containing antipyrylazo III.

Irving

Maylie

Sizto

et al. 1989

The Journal of General Physiology

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“…When the records were taken, ApIII concentrations, measured in the central (working) segment of the fibre, were between 600 and 1100 ìÒ, with fluo-3 they were 600-900 ìÒ, and with Calcium Green-1 they were 300-600 ìÒ. Ca¥ transients were derived using methods described by , using as kinetic parameters of ApIII, koff = 700 s¢ (Baylor, Quinta-Ferreira & Hui, 1985) and kon = 0·025 s¢ ìÒ¦Â (Kovacs, R úos & Schneider, 1983). Ca¥ release flux was derived from Ca¥ transients by the removal method of Melzer et al (1987, updated by Brum et al 1988 In some cases (specified in text and figure legends), the release flux caused significant depletion of sarcoplasmic reticulum (SR) calcium (shown by a slow decrement in flux following the initial fast decay phase).…”

Section: Methodsmentioning

confidence: 99%

‘Quantal’ calcium release operated by membrane voltage in frog skeletal muscle

Pizarro

Shirokova

Tsugorka

et al. 1997

The Journal of Physiology

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Ca2+ transients and Ca2+ release flux were determined optically in cut skeletal muscle fibres under voltage clamp. ‘Decay’ of release during a depolarizing pulse was defined as the difference between the peak value of release and the much lower steady level reached after about 100 ms of depolarization. Using a double‐pulse protocol, the inactivating effect of release was measured by ‘suppression’, the difference between the peak values of release in the test pulse, in the absence and presence of a conditioning pulse that closely preceded the test pulse. The relationship between decay and suppression was found to follow two simple arithmetic rules. Whenever the conditioning depolarization was less than or equal to the test depolarization, decay in the conditioning release was approximately equal to suppression of the test release. Whenever the conditioning depolarization was greater than that of the test, suppression was complete, i.e. test release was reduced to a function that increased monotonically to a steady level. The steady level was the same with or without conditioning. These arithmetic rules suggest that inactivation of Ca2+ release channels is strictly and fatally linked to their activation. More than a strict linkage, however, is required to explain the arithmetic properties. The arithmetic rules of inactivation result in three other properties that are inexplicable with classical models of channel gating: constant suppression, incremental inactivation and increment detection. These properties were first demonstrated for inositol trisphosphate (IP3)‐sensitive channels and used to define IP3‐induced release as quantal. In this sense, it can now be stated that skeletal muscle Ca2+ release is activated by membrane voltage in a quantal manner. For both classes of intracellular Ca2+ channels, one explanation of the observations is the existence of subsets of channels with different sensitivities (to voltage or agonist dose). In an alternative explanation, channels are identical, but have a complex repertoire of voltage‐ or dose‐dependent responses.

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Calcium indicators and calcium signalling in skeletal muscle fibres during excitation–contraction coupling

Baylor

Hollingworth

2011

Progress in Biophysics and Molecular Biology

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During excitation-contraction coupling in skeletal muscle, calcium ions are released into the myoplasm by the sarcoplasmic reticulum (SR) in response to depolarization of the fibre's exterior membranes. Ca 2+ then diffuses to the thin filaments, where Ca 2+ binds to the Ca 2+ regulatory sites on troponin to activate muscle contraction. Quantitative studies of these events in intact muscle preparations have relied heavily on Ca 2+ -indicator dyes to measure the change in the spatiallyaveraged myoplasmic free Ca 2+ concentration (Δ[Ca 2+ ]) that results from the release of SR Ca 2+ . In normal fibres stimulated by an action potential, Δ[Ca 2+ ] is large and brief, requiring that an accurate measurement of Δ[Ca 2+ ] be made with a low-affinity rapidly-responding indicator. Some low-affinity Ca 2+ indicators monitor Δ[Ca 2+ ] much more accurately than others, however, as reviewed here in measurements in frog twitch fibres with sixteen low-affinity indicators. This article also examines measurements and simulations of Δ[Ca 2+ ] in mouse fast-twitch fibres. The simulations use a multi-compartment model of the sarcomere that takes into account Ca 2+ 's release from the SR, its diffusion and binding within the myoplasm, and its re-sequestration by the SR Ca 2+ pump. The simulations are quantitatively consistent with the measurements and appear to provide a satisfactory picture of the underlying Ca 2+ movements.

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Isotropic Components of Antipyrylazo III Signals from Frog Skeletal Muscle Fibers

Cited by 15 publications

References 21 publications

Simultaneous monitoring of changes in magnesium and calcium concentrations in frog cut twitch fibers containing antipyrylazo III.

Simultaneous monitoring of changes in magnesium and calcium concentrations in frog cut twitch fibers containing antipyrylazo III.

‘Quantal’ calcium release operated by membrane voltage in frog skeletal muscle

Calcium indicators and calcium signalling in skeletal muscle fibres during excitation–contraction coupling

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