Impact of initial muscle length on force deficit following lengthening contractions in mammalian skeletal muscle

2002 ◽  
Vol 25 (6) ◽  
pp. 822-827 ◽  
Author(s):  
Luc E. Gosselin ◽  
Harold Burton
Keyword(s):  
Skeletal Muscle ◽  
Muscle Length ◽  
Mammalian Skeletal Muscle ◽  
Lengthening Contractions

Length-dependent potentiation and myosin light chain phosphorylation in rat gastrocnemius muscle

1997 ◽  
Vol 273 (1) ◽  
pp. C198-C204 ◽  
Author(s):  
D. E. Rassier ◽  
L. A. Tubman ◽  
B. R. MacIntosh
Keyword(s):  
Skeletal Muscle ◽  
Gastrocnemius Muscle ◽  
Average Rate ◽  
Muscle Length ◽  
Repetitive Stimulation ◽  
Mammalian Skeletal Muscle ◽  
Optimal Length ◽  
Regulatory Light Chains ◽  
Dependent Change

Changes in muscle length affect the degree of staircase potentiation in skeletal muscle, but the mechanism by which this occurs is unknown. In this study, we tested the hypothesis that length-dependent change in staircase is modulated by phosphorylation of the myosin regulatory light chains (RLC), since this is believed to be the main mechanism of potentiation. In situ isometric contractile responses of rat gastrocnemius muscle during 10 s of repetitive stimulation at 10 Hz were analyzed at optimal length (Lo), Lo - 10%, and Lo + 10%. The degree of enhancement of developed tension during 10 s of repetitive stimulation was observed to be length dependent, with increases of 118.5 +/- 7.8, 63.1 +/- 3.9, and 45.6 +/- 4.1% (means +/- SE) at Lo - 10%, Lo, and Lo + 10%, respectively. Staircase was accompanied by increases in the average rate of force development of 105.6 +/- 7.7, 55.6 +/- 4.1, and 37.2 +/- 4.4% for Lo - 10%, Lo, and Lo + 10%, respectively. RLC phosphorylation after 10 s of 10-Hz stimulation was higher than under resting conditions but not different among Lo - 10% (40 +/- 3.5%), Lo (35 +/- 3.5%), and Lo + 10% (41 +/- 3.5%). This study shows that there is a length dependence of staircase potentiation in mammalian skeletal muscle that may not be directly modulated by RLC phosphorylation. Interaction of RLC phosphorylation with length-dependent changes in Ca2+ release and intermyofilament spacing may explain these observations.

scholarly journals A myosin-based mechanism for stretch activation and its possible role revealed by varying phosphate concentration in fast and slow mouse skeletal muscle fibers

2019 ◽  
Vol 317 (6) ◽  
pp. C1143-C1152 ◽  
Author(s):  
Chad R. Straight ◽  
Kaylyn M. Bell ◽  
Jared N. Slosberg ◽  
Mark S. Miller ◽  
Douglas M. Swank
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Muscle Length ◽  
Power Stroke ◽  
Mammalian Skeletal Muscle ◽  
Stretch Activation ◽  
Force Ratio ◽  
Slow Twitch ◽  
Fast Twitch

Stretch activation (SA) is a delayed increase in force following a rapid muscle length increase. SA is best known for its role in asynchronous insect flight muscle, where it has replaced calcium’s typical role of modulating muscle force levels during a contraction cycle. SA also occurs in mammalian skeletal muscle but has previously been thought to be too low in magnitude, relative to calcium-activated (CA) force, to be a significant contributor to force generation during locomotion. To test this supposition, we compared SA and CA force at different Pi concentrations (0–16 mM) in skinned mouse soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscle fibers. CA isometric force decreased similarly in both muscles with increasing Pi, as expected. SA force decreased with Pi in EDL (40%), leaving the SA to CA force ratio relatively constant across Pi concentrations (17–25%). In contrast, SA force increased in soleus (42%), causing a quadrupling of the SA to CA force ratio, from 11% at 0 mM Pi to 43% at 16 mM Pi, showing that SA is a significant force modulator in slow-twitch mammalian fibers. This modulation would be most prominent during prolonged muscle use, which increases Pi concentration and impairs calcium cycling. Based upon our previous Drosophila myosin isoform studies and this work, we propose that in slow-twitch fibers a rapid stretch in the presence of Pi reverses myosin’s power stroke, enabling quick rebinding to actin and enhanced force production, while in fast-twitch fibers, stretch and Pi cause myosin to detach from actin.

Sarcomere length and capillary curvature of rat hindlimb muscles in vivo

1995 ◽  
Vol 78 (6) ◽  
pp. 2047-2051 ◽  
Author(s):  
M. A. Ledvina ◽  
S. S. Segal
Keyword(s):  
Skeletal Muscle ◽  
Sarcomere Length ◽  
Muscle Length ◽  
Physiological Saline ◽  
Mammalian Skeletal Muscle ◽  
Sprague Dawley ◽  
Hindlimb Muscles ◽  
Physiological Saline Solution ◽  
The Right

Mammalian skeletal muscle fibers have been reported to develop maximum force at a sarcomere length (Ls) of approximately 2.5 microns. However, the functional range of muscle length (Lm) and Ls encountered by skeletal muscle in vivo is not well defined. Changes in Ls markedly influence capillary geometry, but this effect has been shown only in fixed preparations. The purpose of this study was to evaluate the influence of limb position on Lm, Ls, and capillary geometry in living undisturbed hindlimb muscles. We tested the hypothesis that maximal excursion of the foot would have similar effects on Ls and capillary geometry of antagonistic soleus (Sol) and extensor digitorum longus (EDL) muscles in vivo. Female Sprague-Dawley rats (n = 9; 243 +/- 3 g) were anesthetized (pentobarbital sodium; 35 mg/kg). The right Sol and EDL muscles were exposed and irrigated with physiological saline solution (34 degrees C; pH 7.4). Sarcomeres and capillaries were observed with video microscopy (total magnification x 1,900; spatial resolution < 1 micron); sarcomeres were labeled with a fluorescent dye [4-(4-diethylaminostyryl)-N-methylpyridinium iodide]. As foot angle increased from 30 degrees (maximal dorsiflexion) to 170 degrees (maximal plantarflexion), Lm and Ls increased for EDL muscles (27.51 +/- 0.42 to 30.97 +/- 0.25 mm and 2.33 +/- 0.01 to 3.09 +/- 0.05 microns, respectively; P < 0.05) and decreased for Sol muscles (26.09 +/- 0.38 to 20.27 +/- 0.34 mm and 3.17 +/- 0.03 to 2.22 +/- 0.04 microns, respectively; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The Adaptive Potential of Skeletal Muscle Fibers

2002 ◽  
Vol 27 (4) ◽  
pp. 423-448 ◽  
Author(s):  
Dirk Pette
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Protein Isoforms ◽  
Mammalian Skeletal Muscle ◽  
Adaptive Potential ◽  
Hybrid Fibers ◽  
Neuromuscular Activity ◽  
Skeletal Muscle Fibers ◽  
Initial Location

Mammalian skeletal muscle fibers display a great adaptive potential. This potential results from the ability of muscle fibers to adjust their molecular, functional, and metabolic properties in response to altered functional demands, such as changes in neuromuscular activity or mechanical loading. Adaptive changes in the expression of myofibrillar and other protein isoforms result in fiber type transitions. These transitions occur in a sequential order and encompass a spectrum of pure and hybrid fibers. Depending on the quality, intensity, and duration of the alterations in functional demand, muscle fibers may undergo functional transitions in the direction of slow or fast, as well as metabolic transitions in the direction of aerobic-oxidative or glycotytic. The maximum range of possible transitions in either direction depends on the fiber phenotype and is determined by its initial location in the fiber spectrum. Key words: Ca-sequestering proteins, energy metabolism, fiber type transition, myofibrillar protein isofonns, myosin, neuromuscular activity

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