scholarly journals EFFECTS OF REDUCING THE EXTRACELLULAR CALCIUM CONCENTRATION ON THE RESTING POTENTIAL OF FROG'S SKELETAL MUSCLE FIBERS

1973 ◽  
Vol 23 (2) ◽  
pp. 183-197 ◽  
Author(s):  
G. B. FRANK ◽  
F. INOUE
Keyword(s):  
Skeletal Muscle ◽  
Calcium Concentration ◽  
Muscle Fibers ◽  
Extracellular Calcium ◽  
Resting Potential ◽  
Extracellular Calcium Concentration ◽  
Skeletal Muscle Fibers

Calcium Release and Spread Within the Sarcomere of Vertebrate Skeletal Muscle Fibers.

2000 ◽  
Vol 6 (S2) ◽  
pp. 94-95
Author(s):  
Stephen M. Baylor ◽  
Stephen Hollingworth
Keyword(s):  
Skeletal Muscle ◽  
Calcium Concentration ◽  
Calcium Release ◽  
Muscle Fibers ◽  
Time Derivative ◽  
Free Calcium ◽  
Time To Peak ◽  
Skeletal Muscle Fibers ◽  
Free Calcium Concentration ◽  
Vertebrate Skeletal Muscle

Experiments were carried out to investigate excitation-contraction coupling in vertebrate skeletal muscle fibers. Single-dissected twitch fibers of frog muscle were injected with flourescent calcium (Ca) indicators, and fluorescence intensity (F) and changes in intensity (ΔF) were recorded during various stimulation protocols (16-22 °C). In fibers activated by an action potential, the low-affinity indicator furaptra was used to estimate the spatially-averaged change in myoplasmic free calcium concentration (ΔC[a]; peak value, 15-20 μM; time to peak, 4-5 ms). Δ[Ca], in combination with a kinetic model, was used to calculate the change in concentration of calcium bound to the principal myoplasmic Ca buffers (ATP, troponin, parvalbumin). The rate of Ca release from the sarcoplasmic reticulum (SR) was obtained from the time derivative of the estimated change in total myoplasmic calcium concentration, Δ[CaT] (= Δ[Ca] + Δ[CaATP] + Δ[CaTroponin] + Δ[CaParvalbumin]).

The “KIMWIPE” Effect in Ultra-Thin Cryosections

1985 ◽  
Vol 43 ◽  
pp. 458-459
Author(s):  
I. Taylor ◽  
P. Ingram ◽  
J.R. Sommer
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Muscle Fibers ◽  
Ice Crystals ◽  
Crystal Formation ◽  
Ice Crystal ◽  
Thin Sections ◽  
Skeletal Muscle Fibers ◽  
Freeze Dried ◽  
Ice Crystal Formation

In studying quick-frozen single intact skeletal muscle fibers for structural and microchemical alterations that occur milliseconds, and fractions thereof, after electrical stimulation, we have developed a method to compare, directly, ice crystal formation in freeze-substituted thin sections adjacent to all, and beneath the last, freeze-dried cryosections. We have observed images in the cryosections that to our knowledge have not been published heretofore (Figs.1-4). The main features are that isolated, sometimes large regions of the sections appear hazy and have much less contrast than adjacent regions. Sometimes within the hazy regions there are smaller areas that appear crinkled and have much more contrast. We have also observed that while the hazy areas remain still, the regions of higher contrast visibly contract in the beam, often causing tears in the sections that are clearly not caused by ice crystals (Fig.3, arrows).

Effect of External Calcium and other Divalent Cations on K+ Contractures in Denervated Slow Skeletal Muscle Fibers of the Frog

2019 ◽  
Author(s):  
Leonardo Hernández
Keyword(s):  
Skeletal Muscle ◽  
Binding Capacity ◽  
Divalent Cations ◽  
Muscle Fibers ◽  
Free Calcium ◽  
Slow Skeletal Muscle ◽  
Skeletal Muscle Fibers ◽  
Free Calcium Concentration ◽  
Chronic Denervation ◽  
Denervated Muscles

The influence of Ca2+ and other divalent cations on contractile responses of slow skeletal muscle fibers of the frog (Rana pipiens) under conditions of chronic denervation was investigated.Isometric tension was recorded from slow bundles of normal and denervated cruralis muscle in normal solution and in solutions with free calcium concentration solution or in solutions where other divalent cations (Sr2+, Ni2+, Co2+ or Mn2+) substituted for calcium. In the second week after nerve section, in Ca2+-free solutions, we observed that contractures (evoked from 40 to 80 mM-K+) of non-denervated muscles showed significantly higher tensions (p<0.05), than those from denervated bundles. Likewise, in solutions where calcium was substituted by all divalent cations tested, with exception of Mn2+, the denervated bundles displayed lower tension than non-denervated, also in the second week of denervation. In this case, the Ca2+ substitution by Sr2+ caused the higher decrease in tension, followed by Co2+ and Ni2+, which were different to non-denervated bundles, as the lowest tension was developed by Mn2+, followed by Co2+, and then Ni2+ and Sr2+. After the third week, we observed a recovery in tension. These results suggest that denervation altering the binding capacity to divalent cations of the voltage sensor.

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