scholarly journals Impairment of Ca2+ release in single Xenopusmuscle fibers fatigued at varied extracellular P O 2

2000 ◽  
Vol 88 (5) ◽  
pp. 1743-1748 ◽  
Author(s):  
Creed M. Stary ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Rapid Onset ◽  
Skeletal Muscle Fibers ◽  
Significant Difference ◽  
Force Recovery ◽  
Series Of Experiments ◽  
Initial Peak ◽  
Time Point ◽  
Text Condition

We tested the hypothesis that the mechanisms involved in the more rapid onset of fatigue when O2 availability is reduced in contracting skeletal muscle are similar to those when O2 availability is more sufficient. Two series of experiments were performed in isolated, single skeletal muscle fibers from Xenopus laevis. First, relative force and free cytosolic Ca2+concentrations ([Ca2+]c) were measured simultaneously in single fibers ( n = 6) stimulated at increasing frequencies (0.25, 0.33, 0.5, and 1 Hz) at an extracellular[Formula: see text] of either 22 or 159 Torr. Muscle fatigue (force = 50% of initial peak tension) occurred significantly sooner ( P < 0.05) during the low- (237 ± 40 s) vs. high-[Formula: see text]treatments (280 ± 38 s). Relative [Ca2+]c was significantly decreased from maximal values at the fatigue time point during both the high- (72 ± 4%) and low-[Formula: see text] conditions (78 ± 4%), but no significant difference was observed between the treatments. In the second series of experiments, using the same stimulation regime as the first, fibers ( n = 6) exposed to 5 mM caffeine immediately after fatigue demonstrated an immediate but incomplete relative force recovery during both the low- (89 ± 4%) and high-[Formula: see text] treatments (82 ± 3%), with no significant difference between treatments. Additionally, there was no significant difference in relative [Ca2+]c between the high- (100 ± 12% of prefatigue values) and low-[Formula: see text] treatments (108 ± 12%) on application of caffeine. These results suggest that in isolated, single skeletal muscle fibers, the earlier onset of fatigue that occurred during the low-extracellular[Formula: see text] condition was modulated through similar pathways as the fatigue process during the high and involved a decrease in relative peak [Ca2+]c.

Effect of varied extracellular P O 2 on muscle performance inXenopus single skeletal muscle fibers

1999 ◽  
Vol 86 (6) ◽  
pp. 1812-1816 ◽  
Author(s):  
Creed M. Stary ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Mitochondrial Respiration ◽  
Muscle Fibers ◽  
Muscle Performance ◽  
Tetanic Force ◽  
Skeletal Muscle Fibers ◽  
Rate Limiting ◽  
Single Living ◽  
Initial Peak ◽  
Text Condition

The purpose of this study was to examine the development of fatigue in isolated, single skeletal muscle fibers when O2 availability was reduced but not to levels considered rate limiting to mitochondrial respiration. Tetanic force was measured in single living muscle fibers ( n = 6) from Xenopus laevis while being stimulated at increasing contraction rates (0.25, 0.33, 0.5, and 1 Hz) in a sequential manner, with each stimulation frequency lasting 2 min. Muscle fatigue (determined as 75% of initial maximum force) was measured during three separate work bouts (with 45 min of rest between) as the perfusate [Formula: see text] was switched between values of 30 ± 1.9, 76 ± 3.0, or 159 Torr in a blocked-order design. No significant differences were found in the initial peak tensions between the high-, intermediate-, and low-[Formula: see text] treatments (323 ± 22, 298 ± 27, and 331 ± 24 kPa, respectively). The time to fatigue was reached significantly sooner ( P < 0.05) during the 30-Torr treatment (233 ± 39 s) compared with the 76- (385 ± 62 s) or 159-Torr (416 ± 65 s) treatments. The calculated critical extracellular [Formula: see text]necessary to develop an anoxic core within these fibers was 13 ± 1 Torr, indicating that the extracellular[Formula: see text] of 30 Torr should not have been rate limiting to mitochondrial respiration. The magnitude of an unstirred layer (243 ± 64 μm) or an intracellular O2 diffusion coefficient (0.45 ± 0.04 × 10−5cm2/s) necessary to develop an anoxic core under the conditions of the study was unlikely. The earlier initiation of fatigue during the lowest extracellular[Formula: see text] condition, at physiologically high intracellular [Formula: see text] levels, suggests that muscle performance may be O2 dependent even when mitochondrial respiration is not necessarily compromised.

Intracellular pH during sequential, fatiguing contractile periods in isolated single Xenopus skeletal muscle fibers

2005 ◽  
Vol 99 (1) ◽  
pp. 308-312 ◽  
Author(s):  
C. M. Stary ◽  
M. C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Ph ◽  
Recovery Period ◽  
Muscle Fibers ◽  
Force Development ◽  
Skeletal Muscle Fibers ◽  
Significant Difference ◽  
Lumbrical Muscle ◽  
Initial Force ◽  
Time Point

The purpose of the present study was to test the hypothesis that a preceding contractile period in isolated single skeletal muscle fibers would attenuate the decrease in pH during an identical, subsequent contractile period, thereby reducing the rate of fatigue. Intact single skeletal muscle fibers ( n = 9) were isolated from Xenopus lumbrical muscle and incubated with the fluorescent cytosolic H+ indicator 2′,7′-bis-(2-carboxyethyl)-5( 6 )-carboxyfluorescein (BCECF) AM for 30 min. Two identical contractile periods were performed in each fiber, separated by a 1-h recovery period. Force and intracellular pH (pHi) fluorescence were measured simultaneously while fibers were stimulated (tetanic contractions of 350-ms trains with 70-Hz stimuli at 9 V) at progressively increasing frequencies (0.25, 0.33, 0.5, and 1 contraction/s) until the development of fatigue (to 60% initial force). No significant difference ( P < 0.05) was observed between the first and second contractile periods in initial force development, resting pHi, or time to fatigue (5.3 ± 0.5 vs. 5.1 ± 0.6 min). However, the relative decrease in the BCECF fluorescence ratio (and therefore pHi) from rest to the fatigue time point was significantly greater ( P < 0.05) during the first contractile period (to 65 ± 4% of initial resting values) compared with the second (77 ± 4%). The results of the present study demonstrated that, when preceded by an initial fatiguing contractile period, the rise in cytosolic H+ concentration in contracting single skeletal muscle fibers during a second contractile period was significantly reduced but did not attenuate the fatigue process in the second contractile period. These results suggest that intracellular factors other than H+ accumulation contribute to the fall in force development under these conditions.

scholarly journals Steady State Relation between Cytoplasmic Free Ca2+ Concentration and Force in Intact Frog Skeletal Muscle Fibers

1998 ◽  
Vol 111 (4) ◽  
pp. 505-519 ◽  
Author(s):  
Masato Konishi ◽  
Masaru Watanabe
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Skinned Fibers ◽  
Hill Coefficient ◽  
Experimental Conditions ◽  
Skeletal Muscle Fibers ◽  
Force Relation ◽  
Series Of Experiments

The steady state relation between cytoplasmic Ca2+ concentration ([Ca2+]i) and force was studied in intact skeletal muscle fibers of frogs. Intact twitch fibers were injected with the dextran-conjugated Ca2+ indicator, fura dextran, and the fluorescence signals of fura dextran were converted to [Ca2+]i using calibration parameters previously estimated in permeabilized muscle fibers (Konishi and Watanabe. 1995. J. Gen. Physiol. 106:1123–1150). In the first series of experiments, [Ca2+]i and isometric force were simultaneously measured during high K+ depolarization. Slow changes in [Ca2+]i and force induced by 15–30 mM K+ appeared to be in equilibrium, as instantaneous [Ca2+]i versus force plot tracked the common path in the rising and relaxation phases of K+ contractures. In the second series of experiments, 2,5-di-tert-butylhydroquinone (TBQ), an inhibitor of the sarcoplasmic reticulum Ca2+ pump, was used to decrease the rate of decline of [Ca2+]i after tetanic stimulation. The decay time courses of both [Ca2+]i and force were dose-dependently slowed by TBQ up to 5 μM; the instantaneous [Ca2+]i– force relations were nearly identical at ≥1 μM TBQ, suggesting that the change in [Ca2+]i was slow enough to reach equilibrium with force. The [Ca2+]i–force data obtained from the two types of experiments were consistent with the Hill curve using a Hill coefficient of 3.2–3.9 and [Ca2+]i for half activation (Ca50) of 1.5–1.7 μM. However, if fura dextran reacts with Ca2+ with a 2.5-fold greater Kd as previously estimated from the kinetic fitting (Konishi and Watanabe. 1995. J. Gen. Physiol. 106:1123–1150), Ca50 would be 3.7–4.2 μM. We also studied the [Ca2+]–force relation in skinned fibers under similar experimental conditions. The average Hill coefficient and Ca50 were estimated to be 3.3 and 1.8 μM, respectively. Although uncertainties remain about the precise levels of [Ca2+]i, we conclude that the steady state force is a 3rd to 4th power function of [Ca2+]i, and Ca50 is in the low micromolar range in intact frog muscle fibers, which is in reasonable agreement with results obtained from skinned fibers.

scholarly journals Age affects myosin relaxation states in skeletal muscle fibers of female but not male mice

2018 ◽  
Author(s):  
Lien A. Phung ◽  
Sira M. Karvinen ◽  
Brett A. Colson ◽  
David D. Thomas ◽  
Dawn A. Lowe
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Natural Aging ◽  
Psoas Muscle ◽  
Male Mice ◽  
Skeletal Muscle Fibers ◽  
Significant Difference ◽  
Potential Contributor ◽  
Aging Muscle ◽  
Kinetics Of

AbstractThe recent discovery that myosin has two distinct states in relaxed muscle – disordered relaxed (DRX) and super-relaxed (SRX) – provides another factor to consider in our fundamental understanding of the aging mechanism in skeletal muscle, since myosin is thought to be a potential contributor to dynapenia. The primary goal of this study was to determine the effects of age on DRX and SRX states and to examine their sex specificity. We have used quantitative fluorescence microscopy of the fluorescent nucleotide analog 2′/3′-O-(N-methylanthraniloyl) ATP (mantATP) to measure single-nucleotide turnover kinetics of myosin in skinned skeletal muscle fibers under relaxing conditions. We examined changes in DRX and SRX in response to the natural aging process by measuring the turnover of mantATP in skinned fibers isolated from psoas muscle of adult young (3-4 months old) and aged (26-28 months old) C57BL/6 female and male mice. Fluorescence decays were fitted to a multi-exponential decay function to determine both the time constants and mole fractions of fast and slow turnover populations, and significance was analyzed by a t-test. We found that in females, both the DRX and SRX lifetimes of myosin ATP turnover at steady state were shorter in aged muscle fibers compared to young muscle fibers (p≤0.033). However, there was no significant difference in relaxation lifetime of either DRX (p=0.202) or SRX (p=0.804) between young and aged male mice. No significant effects were measured on the mole fractions (populations) of these states, as a function of sex or age (females, p=0.100; males, p=0.929). The effect of age on the order of myosin heads at rest and their ATPase function is sex specific, affecting only females. These findings provide new insight into the molecular factors and mechanisms that contribute to aging muscle dysfunction in a sex-specific manner.

Quantitative elemental x-ray imaging of timed calcium displacement from stores (JSR) in isolated single frog skeletal muscle fibers: Its efficacy in quantitation

1989 ◽  
Vol 47 ◽  
pp. 240-241 ◽  
Author(s):  
R. Nassar ◽  
P. Ingram ◽  
T. High ◽  
J.R. Sommer
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Muscle Fibers ◽  
X Ray ◽  
Statistical Confidence ◽  
Scanning Time ◽  
Skeletal Muscle Fibers ◽  
X Ray Imaging ◽  
Series Of Experiments ◽  
Spatial Displacements

We are performing a continuing series of experiments to describe the time course of fast physiological events in terms of morphology and microtopochemistry, using electron probe x-ray microanalysis in both the static probe (STP) and quantitative digital imaging (QDI) modes. As a model, we are using timed spatial displacements of elements (e.g. the release of calcium from JSR) during the process of excitation-contraction coupling in single, intact skeletal muscle fibers quick-frozen at known time intervals following electrical stimulation. There is considerable variance in the total calcium concentration ([Ca]t) among JSRs, which increases the requirement for widespread sampling to increase statistical confidence. Even at a low number of pixels/raster chosen for time economy, QDI seems well suited to deal with this variance because it covers a large number of JSRs in a reasonably short scanning time (64x64 pixels: ∽3 h; 128×128 pixels: ∽9 h). Here, we report on the efficacy of QDI in our experiments and compare the results with those obtained from STP.

scholarly journals Phosphorylating pathways and fatigue development in contracting Xenopus single skeletal muscle fibers

2000 ◽  
Vol 278 (3) ◽  
pp. R587-R591 ◽  
Author(s):  
Creed M. Stary ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Oxidative Phosphorylation ◽  
Muscle Fibers ◽  
Force Production ◽  
Single Type ◽  
Substrate Level Phosphorylation ◽  
Fatigue Development ◽  
Significant Difference ◽  
Substrate Level ◽  
Text Condition

To investigate the differential contribution of oxidative and substrate-level phosphorylation to force production during repetitive, maximal tetanic contractions, single skeletal muscle fiber performance was examined under conditions of high-oxygen availability and anoxia. Tetanic force development (P) was measured in isolated, single type-1 muscle fibers (fast twitch; n = 6) dissected from Xenopus lumbrical muscle while being stimulated at increasing frequencies (0.25, 0.33, and 0.5 Hz), with each frequency lasting 2 min. Two separate work bouts were conducted, with the perfusate [Formula: see text]being either 0 or 159 mmHg. No significant ( P < 0.05) difference was found in the initial peak tensions (P0) between the high (334 ± 57 kPa) and the low (325 ± 41 kPa) [Formula: see text]treatment. No significant difference in P was observed between the treatments during the first 50 s. However, a significant difference in force production was observed between the high (P/P0 = 0.96 ± 0.02) and the low [Formula: see text] condition (P/P0 = 0.92 ± 0.02) by 60 s of work. After 60 s, steady-state force production was maintained during the high compared with the low [Formula: see text] condition until stimulation frequency was increased, at which point developed tension during the high [Formula: see text] condition began to decline. Time to fatigue (P/P0 = 0.3) was reached significantly sooner during the low (250 ± 16 s) than the high[Formula: see text] condition (367 ± 28 s). These results demonstrate that during the first 50 s of 0.25-Hz contractions, substrate-level phosphorylation has the capacity to maintain force and ATP hydrolysis when oxidative phosphorylation is absent. This period was followed by an oxygen-dependent phase in which force generation was maintained during the high [Formula: see text]condition (but not during the low [Formula: see text]condition) until the onset of a final fatiguing phase, at which a calculated maximal rate of oxidative phosphorylation was reached.

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.

scholarly journals Development of a human neuromuscular tissue-on-a-chip model on a 24-well-plate-format compartmentalized microfluidic device

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Kazuki Yamamoto ◽  
Nao Yamaoka ◽  
Yu Imaizumi ◽  
Takunori Nagashima ◽  
Taiki Furutani ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Microfluidic Device ◽  
Motor Neurons ◽  
Muscle Fibers ◽  
Three Dimensional ◽  
Tissue Model ◽  
Skeletal Muscle Fibers

A three-dimensional human neuromuscular tissue model that mimics the physically separated structures of motor neurons and skeletal muscle fibers is presented.

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