scholarly journals High Time Resolution Analysis of Voltage-Dependent and Voltage-Independent Calcium Sparks in Frog Skeletal Muscle Fibers

2020 ◽  
Vol 11 ◽  
Author(s):  
Henrietta Cserne Szappanos ◽  
János Vincze ◽  
Dóra Bodnár ◽  
Beatrix Dienes ◽  
Martin F. Schneider ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Time Resolution ◽  
Ryanodine Receptors ◽  
High Time ◽  
Fiber Axis ◽  
High Time Resolution ◽  
Frog Skeletal Muscle ◽  
Calcium Sparks ◽  
Caffeine Treatment ◽  
Voltage Dependent

In amphibian skeletal muscle calcium (Ca2+) sparks occur both as voltage-dependent and voltage-independent ligand-activated release events. However, whether their properties and their origin show similarities are still in debate. Elevated K+, constant Cl– content solutions were used to initiate small depolarizations of the resting membrane potential to activate dihydropyridine receptors (DHPR) and caffeine to open ryanodine receptors (RyR) on intact fibers. The properties of Ca2+ sparks observed under control conditions were compared to those measured on depolarized cells and those after caffeine treatment. Calcium sparks were recorded on intact frog skeletal muscle fibers using high time resolution confocal microscopy (x-y scan: 30 Hz). Sparks were elicited by 1 mmol/l caffeine or subthreshold depolarization to different membrane potentials. Both treatments increased the frequency of sparks and altered their morphology. Images were analyzed by custom-made computer programs. Both the amplitude (in ΔF/F0; 0.259 ± 0.001 vs. 0.164 ± 0.001; n = 24942 and 43326, respectively; mean ± SE, p < 0.001) and the full width at half maximum (FWHM, in μm; parallel with fiber axis: 2.34 ± 0.01 vs. 1.92 ± 0.01, p < 0.001; perpendicular to fiber axis: 2.08 ± 0.01 vs. 1.68 ± 0.01, p < 0.001) of sparks was significantly greater after caffeine treatment than on depolarized cells. 9.8% of the sparks detected on depolarized fibers and about one third of the caffeine activated sparks (29.7%) overlapped with another one on the previous frame on x-y scans. Centre of overlapping sparks travelled significantly longer distances between consecutive frames after caffeine treatment then after depolarization (in μm; 1.66 ± 0.01 vs. 0.95 ± 0.01, p < 0.001). Our results suggest that the two types of ryanodine receptors, the junctional RyRs controlled by DHPRs and the parajunctional RyRs are activated independently, using alternate ways, with the possibility of cooperation between neighboring release channels.

scholarly journals Time Course of Individual Ca2+ Sparks in Frog Skeletal Muscle Recorded at High Time Resolution

1999 ◽  
Vol 113 (2) ◽  
pp. 187-198 ◽  
Author(s):  
Alain Lacampagne ◽  
Christopher W. Ward ◽  
Michael G. Klein ◽  
Martin F. Schneider
Keyword(s):  
Skeletal Muscle ◽  
Time Resolution ◽  
Rise Time ◽  
Laser Scanning ◽  
Time Course ◽  
High Time ◽  
High Time Resolution ◽  
Frog Skeletal Muscle ◽  
Resolution System ◽  
Constant Rate

Discrete Ca2+ release events (Ca2+ “sparks”) were recorded in cut segments of single frog skeletal muscle fibers using a video-rate laser-scanning confocal microscope operating in line-scan mode (63 μs per line). Fibers loaded with the Ca2+ indicator fluo-3 were voltage clamped at a holding potential of 0 mV, briefly reprimed at −90 mV, and then strongly depolarized with a large test pulse to activate any reprimed voltage sensors. Using this high time resolution system, it was possible to record individual Ca2+ sparks at ∼30-fold higher time resolution than previously attained. The resulting new experimental data provides a means of characterizing the time course of fluorescence during the brief (a few milliseconds) rising phase of a spark, which was not possible with the previously used 1.5–2 ms per line confocal systems. Analysis of the time course of individual identified events indicates that fluorescence begins to rise rather abruptly at the start of the spark, continues to rise at a slightly decreasing rate to a relatively sharp peak, and then declines along a quasi-exponential time course. The mean rise time of 198 sparks was 4.7 ± 0.1 ms, and there was no correlation between rise time and peak amplitude. Average sparks constructed by temporally and spatially superimposing and summing groups of individual sparks having similar rise times gave a lower noise representation of the sparks, consistent with the time course of individual events. In theory, the rising phase of a spark provides a lower bound estimation of the time that Ca2+ ions are being released by the sarcoplasmic reticulum Ca2+ channel(s) generating the spark. The observed time course of fluorescence suggests that the Ca2+ release underlying a spark could continue at a fairly constant rate throughout the rising phase of the spark, and then stop rather abruptly at the time of the peak.

Open-state substructure of single chloride channels from Torpedo electroplax

1982 ◽  
Vol 299 (1097) ◽  
pp. 401-411 ◽  
Keyword(s):  
Time Resolution ◽  
Chloride Channels ◽  
Open Channel ◽  
Single Channel ◽  
High Time ◽  
High Time Resolution ◽  
Phospholipid Membranes ◽  
Voltage Dependent ◽  
Single Channel Currents ◽  
Channel Currents

Chloride channels from Torpedo californica electroplax were inserted into planar phospholipid membranes, and single-channel currents were studied at high time-resolution. The open channel fluctuates rapidly between three substates, with conductances of 18.5, 9.4 and 0 pS in 150 mM Cl- . Under various ionic conditions the three substates are always equally spaced in conductance; at various voltages leading to different probabilities of observing the three substates, the substate frequencies are always Dinomially distributed. The conclusion emerges that the conducting unit of this Cl-channel is composed of two identical Cl- diffusion pathways, each with a voltage-dependent gate.

Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak

1994 ◽  
Vol 144 ◽  
pp. 431-434
Author(s):  
M. Minarovjech ◽  
M. Rybanský
Keyword(s):  
Solar Corona ◽  
Time Resolution ◽  
Active Regions ◽  
High Time ◽  
High Time Resolution ◽  
List Type ◽  
Type Number ◽  
Coronal Line ◽  
Global Cycle

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.

Discovery of the fast optical variability of GRB 080319B and the prospects for wide-field optical monitoring with high time resolution

2010 ◽  
Vol 180 (4) ◽  
pp. 424 ◽  
Author(s):  
G.M. Beskin ◽  
S.V. Karpov ◽  
S.F. Bondar ◽  
V.L. Plokhotnichenko ◽  
A. Guarnieri ◽  
...  
Keyword(s):  
Time Resolution ◽  
High Time ◽  
High Time Resolution ◽  
Optical Variability ◽  
Wide Field ◽  
Optical Monitoring

scholarly journals Detecting telecom single photons with 99.5−2.07+0.5% system detection efficiency and high time resolution

APL Photonics ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 036114
Author(s):  
J. Chang ◽  
J. W. N. Los ◽  
J. O. Tenorio-Pearl ◽  
N. Noordzij ◽  
R. Gourgues ◽  
...  
Keyword(s):  
Time Resolution ◽  
Detection Efficiency ◽  
High Time ◽  
High Time Resolution ◽  
Single Photons

High-time-resolution PM2.5 source apportionment based on multi-model with organic tracers in Beijing during haze episodes

2021 ◽  
Vol 772 ◽  
pp. 144766
Author(s):  
Lingling Lv ◽  
Yingjun Chen ◽  
Yong Han ◽  
Min Cui ◽  
Peng Wei ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Time Resolution ◽  
High Time ◽  
High Time Resolution
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