&lt;b&gt;Effect of denervation on phosphorylation of the myosin light chain in rat extensor digitorum longus &lt;/b&gt;&lt;b&gt;muscles &lt;/b&gt;

Matsushita, Shigeki; Takeda, Shin‐ichi; Shoji, Shin’ichi; Yanagisawa, Nobuo

doi:10.2220/biomedres.8.211

Cited by 4 publications

(3 citation statements)

References 13 publications

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“…Spinal cord hemisection resulted in decreased mobility and substantially less use of the gastrocnemius muscle. This would be expected to cause muscle atrophy, but not to the same extent as that observed during complete muscle disuse due to denervation14 or tetrodotoxin administration 22, 24. We were not able to quantify the magnitude of atrophy in this study, because muscles were clamp‐frozen to permit measurements of RLC phosphorylation.…”

Section: Discussionmentioning

confidence: 95%

Staircase but not posttetanic potentiation in rat muscle after spinal cord hemisection

2008

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Spinal cord hemisection (SCH) results in atrophy of skeletal muscle and altered contractile properties. In this study our purpose was to assess staircase and posttetanic potentiation in the rat gastrocnemius muscle in situ, 1 week after SCH. Tetanic force was reduced by SCH, but twitch amplitude was not. The time course and magnitude of staircase during stimulation at 5 HZ (for 21 s) was similar in the control, sham-operated, and SCH groups. However, posttetanic potentiation observed after 100-, 500-, and 1000-ms tetanic (200 HZ) contractions was absent or drastically reduced after SCH. Twitch force increased 44+/-8.7%, 47+/-7.4%, and 15+/-2.8% for the control, sham, and SCH groups, respectively, after the 1000-ms tetanic contraction. After the 1000-ms tetanic contraction, twitch active force decreased in all groups and was significantly reduced at 5 min relative to pretetanic twitch. In the control and sham groups, but not SCH, the active force recovered to the pretetanic level by 15 min. Resting regulatory light chain (RLC) phosphorylation was 15.4+/-2.5% and 10.97+/-3.3% for the control and SCH groups, respectively. After the 1-s tetanic contraction, values were 41.6+/-2.8% and 9.3+/-2.9%, respectively. The potentiation observed in the SCH animals with 1000-ms contraction apparently occurred without increases in RLC phosphorylation. One week after SCH there were clear changes in the contractile properties typically associated with prior activation. It is concluded that activity-dependent potentiation can occur by a mechanism that is independent of RLC phosphorylation, and accelerated fatigue can mask the potentiating effects of prior activity.

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Section: Discussionmentioning

confidence: 95%

Staircase but not posttetanic potentiation in rat muscle after spinal cord hemisection

2008

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“…A length dependence of phosphorylation could be an alternative explanation for the different levels of post-tetanic twitch potentiation at different muscle lengths. However, it has been shown that the amount of phosphorylated light chain is not dependent on the length at which the phosphorylating contraction is elicited [24].…”

Section: Discussionmentioning

confidence: 99%

“…Notably, studies on atrophied rat skeletal muscles have shown attenuation of phosphorylation of the light chains [24,39] and consequently no twitch potentiation during repetitive low frequency activation (staircase potentiation) [39]. Extrapolation of this result to muscle after adaptation to spinal cord injuries would make potentiation unlikely.…”

Section: Discussionmentioning

confidence: 99%

The influence of stimulation frequency and ankle joint angle on the moment exerted by human dorsiflexor muscles

Mela

Veltink

Huijing

2001

Journal of Electromyography and Kinesiology

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Absence of myosin light chain phosphorylation and twitch potentiation in atrophied skeletal muscle

Tubman¹,

Rassier²,

MacIntosh³

1996

Can. J. Physiol. Pharmacol.

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Staircase potentiation does not occur in atrophied rat gastrocnemius muscle subjected to repetitive stimulation. Since twitch potentiation is strongly correlated with phosphorylation of the regulatory light chains (R-LC) of myosin, our purpose was to determine if R-LC phosphorylation with repetitive stimulation is also diminished in atrophied gastrocnemius muscle. Following 2 weeks of disuse, induced by delivery of tetrodotoxin (TTX) to the sciatic nerve, phosphorylation and twitch developed tension were measured at 10 s of 10-Hz stimulation in situ in control, sham, and TTX-treated rats. Phosphorylation was significantly diminished in TTX-treated animals (9.3 +/- 3.7%), compared with control (57.0 +/- 3.4%) and sham-treated (45.5 +/- 5.6%) animals. Concomitantly, at 10 s of 10-Hz stimulation, potentiation was absent in atrophied muscles (74.4 +/- 9.4% of initial twitch), whereas control (188.4 +/- 10.3%) and sham-treated (151.7 +/- 10.3%) muscles demonstrated a great deal of potentiation. The twitch contraction of the atrophied muscles had a decreased rate of tension development and peak rate of relaxation, and an increased contraction time and half-relaxation time. The observation that the light chains are present, but not phosphorylated, suggests that the process of phosphorylation is impaired. The association of diminished phosphorylation with the absence of staircase supports the theory that R-LC phosphorylation may be the principal mechanism for twitch potentiation but does not rule out other contributing factors.

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<b>Effect of denervation on phosphorylation of the myosin light chain in rat extensor digitorum longus </b><b>muscles </b>

Cited by 4 publications

References 13 publications

Staircase but not posttetanic potentiation in rat muscle after spinal cord hemisection

Staircase but not posttetanic potentiation in rat muscle after spinal cord hemisection

The influence of stimulation frequency and ankle joint angle on the moment exerted by human dorsiflexor muscles

Absence of myosin light chain phosphorylation and twitch potentiation in atrophied skeletal muscle

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