scholarly journals Causes of fatigue in slow-twitch rat skeletal muscle during dynamic activity

2009 ◽  
Vol 297 (3) ◽  
pp. R900-R910 ◽  
Author(s):  
Morten Munkvik ◽  
Per Kristian Lunde ◽  
Ole M. Sejersted
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Force Production ◽  
Maximum Force ◽  
Stimulation Protocol ◽  
Shortening Velocity ◽  
Dynamic Activity ◽  
Initial Values ◽  
Isotonic Shortening

Skeletal muscle fatigue is most often studied in vitro at room temperature and is classically defined as a decline in maximum force production or power output, exclusively linked to repeated isometric contractions. However, most muscles shorten during normal use, and we propose that both the functional correlate of fatigue, as well as the fatigue mechanism, will be different during dynamic contractions compared with static contractions. Under isoflurane anesthesia, fatigue was induced in rat soleus muscles in situ by isotonic shortening contractions at 37°C. Muscles were stimulated repeatedly for 1 s at 30 Hz every 2 s for a total of 15 min. The muscles were allowed to shorten isotonically against a load corresponding to one-third of maximal isometric force. Maximal unloaded shortening velocity (V0), maximum force production (Fmax), and isometric relaxation rate (−dF/d t) was reduced after 100 s but returned to almost initial values at the end of the stimulation protocol. Likewise, ATP and creatine phosphate (CrP) were reduced after 100 s, but the level of CrP was partially restored to initial values after 15 min. The rate of isometric force development, the velocity of shortening, and isotonic shortening were also reduced at 100 s, but in striking contrast, did not recover during the remainder of the stimulation protocol. The regulatory myosin light chain (MLC2s) was dephosphorylated after 100 s and did not recover. Although metabolic changes may account for the changes of Fmax, −dF/d t, and V0, dephosphorylation of MLC2s may be involved in the fatigue seen as sustained slower contraction velocities and decreased muscle shortening.

Injury to skeletal muscle fibers of mice following lengthening contractions

1985 ◽  
Vol 59 (1) ◽  
pp. 119-126 ◽  
Author(s):  
K. K. McCully ◽  
J. A. Faulkner
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Lengthening Contractions ◽  
Control Value ◽  
Skeletal Muscle Fibers ◽  
Maximum Isometric Force ◽  
Distal Tendon ◽  
Shortening Contractions

We tested the hypothesis that lengthening contractions result in greater injury to skeletal muscle fibers than isometric or shortening contractions. Mice were anesthetized with pentobarbital sodium and secured to a platform maintained at 37 degrees C. The distal tendon of the extensor digitorum longus muscle was attached to a servomotor. A protocol consisting of isometric, shortening, or lengthening contractions was performed. After the contraction protocol the distal tendon was reattached, incisions were closed, and the mice were allowed to recover. The muscles were removed after 1–30 days, and maximum isometric force (Po) was measured in vitro at 37 degrees C. Three days after isometric and shortening contractions and sham operations, histological appearance was not different from control and Po was 80% of the control value. Three days after lengthening contractions, histological sections showed that 37 +/- 4% of muscle fibers degenerated and Po was 22 +/- 3% of the control value. Muscle regeneration, first seen at 4 days, was nearly complete by 30 days, when Po was 84 +/- 3% of the control value. We conclude that, with the protocol used, lengthening, but not isometric or shortening contractions, caused significant injury to muscle fibers.

Abstract 958: Cardiac MyBP-C Modulates Actomyosin Interactions: Evidence From Cardiac MyBP-c−/ − Mice

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Yves Lecarpentier ◽  
Nicolas Vignier ◽  
Patricia Oliviero ◽  
Miguel Cortes-Morichetti ◽  
Lucie Carrier ◽  
...  
Keyword(s):  
Thin Filament ◽  
Isometric Force ◽  
Binding Protein ◽  
Critical Role ◽  
Cardiac Contractility ◽  
Left Ventricular ◽  
Actin Binding ◽  
Power Stroke ◽  
Shortening Velocity

The precise role of cardiac myosin binding protein C (cMyBP-C) on actomyosin interaction (AMI) remains unknown. We hypothesized that the lack of cMyBP-C impaired cardiac AMI. Experiments were performed on 16 weeks old cMyBP-C −/− (KO) and age-matched wild-type (WT) mice (n=20/group). In vitro mechanical and energetics properties were performed on left ventricular (LV) papillary muscles and Huxley’s equations were used to characterize AMI. In vitro motility assays were performed using myosin purified from LV. Myosin-based sliding velocities of actin filaments were analyzed at baseline, after pretreatment of the myosin solution with 10 umol of the catalytic subunit of PKA and/or in the presence of increasing amount of α-actinin, an actin-binding protein that acts as an internal load thereby providing an index of relative isometric force. Western-blot analysis was used to quantify cMyBP-C and phosphorylated cMyBP-C in myosin solutions. Compared to WT, both total tension and maximum shortening velocity were lower in KO (p<0.001). The probability for myosin to be weakly bound to actin was higher in KO than in WT (8.6±0.3 vs. 5.4±0.2%, p<0.05), whereas the number of strongly bound, high-force generated state cross-bridges was lower in KO (6.4±0.9 vs. 11.6±1.0 10 9 /mm 2 , p<0.001). The unitary force per AMI was lower in KO than in WT (p<0.01). At baseline, myosin-based velocities of actin were slower in KO than in WT (1.65±0.01 vs. 1.98±0.01 um/s, p<0.01). The minimum amount of α-actinin needed to completely arrest the thin filament motility was significantly higher in WT than in KO (73.3±1.1 vs 29.1±0.1 ug/l, p<0.001). As expected, cMyBP-C was present in WT myosin solution whereas cMyBP-C was not detected in KO. In WT, PKA induced a 1.6-fold increased in cMyBP-C phosphorylation (p<0.01) associated with a 53±1% increase in the amount of α-actinin required to arrest thin filament motility (p<0.001). PKA did not modify sliding velocity in WT. In KO, PKA had no effect on myosin sliding. We conclude that cMyBP-C regulates AMI by limiting inefficient cross-bridge formation and by enhancing the power stroke step. Phosphorylation status of cMyBP-C appears to play a critical role on cardiac contractility through a direct effect on the myosin molecular motor.

In vivo and in vitro correlation of trachealis muscle contraction in dogs

1992 ◽  
Vol 73 (4) ◽  
pp. 1486-1493 ◽  
Author(s):  
M. Okazawa ◽  
K. Ishida ◽  
J. Road ◽  
R. R. Schellenberg ◽  
P. D. Pare
Keyword(s):  
Isometric Force ◽  
Optimal Length ◽  
Linear Elastic ◽  
Elastic Load ◽  
Muscle Shortening ◽  
Anesthetized Dogs ◽  
Trachealis Muscle ◽  
Isotonic Shortening

Maximal trachealis muscle shortening in vivo was compared with that in vitro in seven anesthetized dogs. In addition, the effect of graded elastic loads on the muscle was evaluated in vitro. In vivo trachealis muscle shortening, as measured using sonomicrometry, revealed maximal active shortening to be 28.8 +/- 11.7% (SD) of initial length. Trachealis muscle preparations from the same animals were studied in vitro to evaluate isometric force generation, isotonic shortening, and the effect of applying linear elastic loads to the trachealis muscle during contraction from optimal length. Maximal isotonic shortening was 66.8 +/- 8.4% of optimal length in vitro. Increasing elastic loads decreased active shortening and velocity of shortening in vitro in a hyperbolic manner. The elastic load required to decrease in vitro shortening to the extent of the shortening observed in vivo was similar to the estimated load provided by the tracheal cartilage. We conclude that decreased active shortening in vivo is primarily due to the elastic afterload provided by cartilage.

Age-related increases in diaphragmatic maximal shortening velocity

1996 ◽  
Vol 80 (2) ◽  
pp. 445-451 ◽  
Author(s):  
S. K. Powers ◽  
D. Criswell ◽  
R. A. Herb ◽  
H. Demirel ◽  
S. Dodd
Keyword(s):  
Force Production ◽  
Specific Force ◽  
Fischer 344 Rats ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Fischer 344 ◽  
Age Related ◽  
Highly Correlated ◽  
Related Increase

Recent evidence demonstrates that aging results in an increase in fast (type IIB) myosin heavy chain (MHC) in the rat diaphragm. It is unknown whether this age-related change in fast MHC influences the diaphragmatic maximal shortening velocity (Vmax). Therefore, we tested the hypothesis that aging is associated with an increase in the diaphragmatic Vmax and that the increase in the Vmax is highly correlated with the percentage of type IIb MHC. In vitro contractile properties were measured with costal diaphragm strips obtained from young (4 mo old; n = 8) and (old 24 mo old; n = 8) male Fischer-344 rats. Diaphragmatic maximal tetanic specific force production was 14.5% lower in the old compared with the young animals (23.0 +/- 0.4 vs. 19.7 +/- 0.8 N/cm2; P < 0.05). In contrast, the diaphragmatic Vmax was significantly higher in the old compared with the young animals (5.5 +/- 0.1 vs. 4.4 +/- 0.3 lengths/s; P < 0.05). Although the percent type IIb MHC was significantly higher (approximately +14%; P < 0.05) in the old compared with the young animals, the correlation between Vmax and percent type IIb MHC was relatively low (r = 0.50; P = 0.05). These data support the hypothesis that an age-related increase in diaphragmatic Vmax occurs; however, factors in addition to type IIb MHC are involved in regulating diaphragmatic Vmax. Interestingly, although aging resulted in a decrease in diaphragmatic maximal specific force production, power output at all muscle loads was maintained in the old animals due to the increase in diaphragmatic shortening velocity.

Effect of airway inflammation on smooth muscle shortening and contractility in guinea pig trachealis

1993 ◽  
Vol 265 (6) ◽  
pp. L549-L554 ◽  
Author(s):  
R. W. Mitchell ◽  
I. M. Ndukwu ◽  
K. Arbetter ◽  
J. Solway ◽  
A. R. Leff
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Neurogenic Inflammation ◽  
Isometric Force ◽  
Electrical Field Stimulation ◽  
Shortening Velocity ◽  
Lever System ◽  
Force Velocity

We studied the effect of either 1) immunogenic inflammation caused by aerosolized ovalbumin or 2) neurogenic inflammation caused by aerosolized capsaicin in vivo on guinea pig tracheal smooth muscle (TSM) contractility in vitro. Force-velocity relationships were determined for nine epithelium-intact TSM strips from ovalbumin-sensitized (OAS) vs. seven sham-sensitized controls and TSM strips for seven animals treated with capsaicin aerosol (Cap-Aer) vs. eight sham controls. Muscle strips were tethered to an electromagnetic lever system, which allowed isotonic shortening when load clamps [from 0 to maximal isometric force (Po)] were applied at specific times after onset of contraction. Contractions were elicited by supramaximal electrical field stimulation (60 Hz, 10-s duration, 18 V). Optimal length for each muscle was determined during equilibration. Maximal shortening velocity (Vmax) was increased in TSM from OAS (1.72 +/- 0.46 mm/s) compared with sham-sensitized animals (0.90 +/- 0.15 mm/s, P < 0.05); Vmax for TSM from Cap-Aer (0.88 +/- 0.11 mm/s) was not different from control TSM (1.13 +/- 0.08 mm/s, P = NS). Similarly, maximal shortening (delta max) was augmented in TSM from OAS (1.01 +/- 0.15 mm) compared with sham-sensitized animals (0.72 +/- 0.14 mm, P < 0.05); delta max for TSM from Cap-Aer animals (0.65 +/- 0.11 mm) was not different from saline aerosol controls (0.71 +/- 0.15 mm, P = NS). We demonstrate Vmax and delta max are augmented in TSM after ovalbumin sensitization; in contrast, neurogenic inflammation caused by capsaicin has no effect on isolated TSM contractility in vitro. These data suggest that airway hyperresponsiveness in vivo that occurs in association with immunogenic or neurogenic inflammation may result from different effects of these types of inflammation on airway smooth muscle.

Absence of myofibrillar creatine kinase and diaphragm isometric function during repetitive activation

1998 ◽  
Vol 84 (4) ◽  
pp. 1166-1173 ◽  
Author(s):  
John J. Labella ◽  
Monica J. Daood ◽  
A. P. Koretsky ◽  
Brian B. Roman ◽  
Gary C. Sieck ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Creatine Kinase ◽  
Muscle Function ◽  
Isometric Force ◽  
Force Generation ◽  
Fatigue Properties ◽  
Specific Force ◽  
Null Mutant ◽  
Isometric Muscle

Creatine kinase (CK) provides ATP buffering in skeletal muscle and is expressed as 1) cytosolic myofibrillar CK (M-CK) and 2) sarcomeric mitochondrial CK (ScCKmit) isoforms that differ in their subcellular localization. We compared the isometric contractile and fatigue properties of 1) control CK-sufficient (Ctl), 2) M-CK-deficient (M-CK[−/−]), and 3) combined M-CK/ScCKmit-deficient null mutant (CK[−/−]) diaphragm (Dia) to determine the effect of the absence of M-CK activity on Dia performance in vitro. Baseline contractile properties were comparable across groups except for specific force, which was ∼16% lower in CK[−/−] Dia compared with M-CK[−/−] and Ctl Dia. During repetitive activation (40 Hz, [Formula: see text] duty cycle), force declined in all three groups. This decline was significantly greater in CK[−/−] Dia compared with Ctl and M-CK[−/−] Dia. The pattern of force decline did not differ between M-CK[−/−] and Ctl Dia. We conclude that Dia isometric muscle function is not absolutely dependent on the presence of M-CK, whereas the complete absence of CK acutely impairs isometric force generation during repetitive activation.

Effects of pH on the length-dependent twitch potentiation in skeletal muscle

2002 ◽  
Vol 92 (3) ◽  
pp. 1293-1299 ◽  
Author(s):  
Dilson E. Rassier ◽  
Walter Herzog
Keyword(s):  
Skeletal Muscle ◽  
Force Production ◽  
Optimal Length ◽  
Twitch Potentiation ◽  
Length Dependence ◽  
Charge Potential ◽  
Before And After ◽  
Effects Of Ph ◽  
Isometric Twitch

When muscle is elongated, there is a length dependence of twitch potentiation and an increased Ca2+ sensitivity of the myofilaments. Changes in the charge potential of myofilaments, induced by a decrease in pH, are known to abolish the length dependence of Ca2+ sensitivity. This study was aimed at testing the hypothesis that a decrease in pH, and the concomitant loss of length dependence of Ca2+sensitivity, depresses the length dependence of staircase potentiation. In vitro, isometric twitch contractions of fiber bundles dissected from the mouse extensor digitorum longus, performed before and after 10 s of 10-Hz stimulation (i.e., the staircase potentiation protocol) were analyzed at five different lengths, ranging from optimal length for maximal force production ( L o; = 12 ± 0.7 mm) to L o + 1.2 mm ( L o + 10%). These measurements were made at an extracellular pH of 6.6, 7.4, and 7.8 (pH changes induced by altering the CO2 concentration of the bath solution). At pH 7.4 and 7.8, the degree of potentiation after 10-Hz stimulation showed a linear decrease with increased fiber bundle length ( r 2 = 0.95 and r 2 = 0.99, respectively). At pH 6.6, the length dependence of potentiation was abolished, and the slope of the length-potentiation relationship was not different from zero ( r 2 = 0.05). The results of this study indicate that length dependence of potentiation in intact skeletal muscle is abolished by lowering the pH. Because decreasing the pH decreases Ca2+ sensitivity and changes the charge potential of the filaments, the mechanism of length-dependent potentiation may be closely related to the length dependence of Ca2+sensitivity, and changes in the charge potential of the myofilaments may be important in regulating this relationship.

scholarly journals Slowing of velocity during isotonic shortening in single isolated smooth muscle cells. Evidence for an internal load.

1990 ◽  
Vol 96 (3) ◽  
pp. 581-601 ◽  
Author(s):  
D E Harris ◽  
D M Warshaw
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Isometric Force ◽  
Muscle Cells ◽  
Force Transducer ◽  
Cell Stiffness ◽  
Shortening Velocity ◽  
Internal Load ◽  
Isolated Smooth Muscle Cells ◽  
Isotonic Shortening

In single smooth muscle cells, shortening velocity slows continuously during the course of an isotonic (fixed force) contraction (Warshaw, D.M. 1987. J. Gen. Physiol. 89:771-789). To distinguish among several possible explanations for this slowing, single smooth muscle cells were isolated from the gastric muscularis of the toad (Bufo marinus) and attached to an ultrasensitive force transducer and a length displacement device. Cells were stimulated electrically and produced maximum stress of 144 mN/mm2. Cell force was then reduced to and maintained at preset fractions of maximum, and cell shortening was allowed to occur. Cell stiffness, a measure of relative numbers of attached crossbridges, was measured during isotonic shortening by imposing 50-Hz sinusoidal force oscillations. Continuous slowing of shortening velocity was observed during isotonic shortening at all force levels. This slowing was not related to the time after the onset of stimulation or due to reduced isometric force generating capacity. Stiffness did not change significantly over the course of an isotonic shortening response, suggesting that the observed slowing was not the result of reduced numbers of cycling crossbridges. Furthermore, isotonic shortening velocity was better described as a function of the extent of shortening than as a function of the time after the onset of the release. Therefore, we propose that slowing during isotonic shortening in single isolated smooth muscle cells is the result of an internal load that opposes shortening and increases as cell length decreases.

scholarly journals Role of TRPC1 channel in skeletal muscle function

2010 ◽  
Vol 298 (1) ◽  
pp. C149-C162 ◽  
Author(s):  
Nadège Zanou ◽  
Georges Shapovalov ◽  
Magali Louis ◽  
Nicolas Tajeddine ◽  
Chiara Gallo ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Function ◽  
Transient Receptor Potential ◽  
Force Production ◽  
Receptor Potential ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Skeletal Muscle Function ◽  
Cross Sectional

Skeletal muscle contraction is reputed not to depend on extracellular Ca2+. Indeed, stricto sensu , excitation-contraction coupling does not necessitate entry of Ca2+. However, we previously observed that, during sustained activity (repeated contractions), entry of Ca2+is needed to maintain force production. In the present study, we evaluated the possible involvement of the canonical transient receptor potential (TRPC)1 ion channel in this entry of Ca2+and investigated its possible role in muscle function. Patch-clamp experiments reveal the presence of a small-conductance channel (13 pS) that is completely lost in adult fibers from TRPC1−/−mice. The influx of Ca2+through TRPC1 channels represents a minor part of the entry of Ca2+into muscle fibers at rest, and the activity of the channel is not store dependent. The lack of TRPC1 does not affect intracellular Ca2+concentration ([Ca2+]i) transients reached during a single isometric contraction. However, the involvement of TRPC1-related Ca2+entry is clearly emphasized in muscle fatigue. Indeed, muscles from TRPC1−/−mice stimulated repeatedly progressively display lower [Ca2+]itransients than those observed in TRPC1+/+fibers, and they also present an accentuated progressive loss of force. Interestingly, muscles from TRPC1−/−mice display a smaller fiber cross-sectional area, generate less force per cross-sectional area, and contain less myofibrillar proteins than their controls. They do not present other signs of myopathy. In agreement with in vitro experiments, TRPC1−/−mice present an important decrease of endurance of physical activity. We conclude that TRPC1 ion channels modulate the entry of Ca2+during repeated contractions and help muscles to maintain their force during sustained repeated contractions.

In Vitro Effects of Eltanolone on Rat Myocardium

1995 ◽  
Vol 83 (4) ◽  
pp. 792-798. ◽  
Author(s):  
Bruno Riou ◽  
Patrick Ruel ◽  
Jean-Luc Hanouz ◽  
Olivier Langeron ◽  
Yves Lecarpentier ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Isometric Force ◽  
Left Ventricular ◽  
Inotropic Effect ◽  
Induction Agent ◽  
Dependent Manner ◽  
Rat Myocardium ◽  
Shortening Velocity

Background Eltanolone is a new short-acting intravenous induction agent. However, its effects on intrinsic myocardial contractility remain unknown. Methods The effects of eltanolone and its solvent (soya bean emulsion) on the intrinsic contractility of rat left ventricular papillary muscles were investigated in vitro (Krebs-Henseleit solution, 29 degrees C, pH 7.40, Ca2+ 0.5 mM, stimulation frequency 12 pulses/min). We studied contraction; relaxation; contraction-relaxation coupling under high and low loads; and postrest potentiation. Results Eltanolone (0.1, 0.3, 1, 3, and 10 micrograms.ml-1) induced no significant inotropic effect, as shown by the lack of changes in maximum unloaded shortening velocity and active isometric force. Eltanolone did not significantly modify the contraction-relaxation coupling under low load, suggesting that it did not modify calcium uptake by the sarcoplasmic reticulum. Eltanolone did not significantly modify the contraction-relaxation coupling under high load, suggesting that it did not modify calcium myofilament sensitivity. Eltanolone decreased the postrest potentiation in a concentration-dependent manner (from 150 +/- 14% to 118 +/- 9% at 10 micrograms.ml-1, P &lt; 0.001), suggesting a decrease in the maximum capacity of calcium release by the sarcoplasmic reticulum, whereas its solvent did not. However, eltanolone did not slow postrest potentiation recovery, as shown by the absence of significant changes in the recovery slope, tau (4.5 +/- 1.4 vs. 3.8 +/- 1.0 beats; difference not statistically significant). Conclusions Eltanolone induced no significant inotropic effect on rat myocardium. It induced a decrease in the calcium release function of the sarcoplasmic reticulum, but this effect was not sufficiently important to modify the inotropic properties.

Sign in / Sign up

Export Citation Format

Share Document