4 resultados para myosin VI

em Brock University, Canada


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ABSTRACT The myosm regulatory light chain (RLC) of type II fibres is phosphorylated by Ca2+ -calmodulin dependent myosin light chain kinase (skMLCK) during muscular activation. The purpose of this study was to explore the effect of skMLCK gene ablation on the fatigability of mouse skeletal muscles during repetitive stimulation. The absence of myosin RLC phosphorylation in skMLCK knockout muscles attenuated contractile performance without a significant metabolic cost. Twitch force was potentiated to a greater extent in wildtype muscles until peak force had diminished to ~60% of baseline (37.2 ± 0.05% vs. 14.3 ± 0.02%). Despite no difference in peak force (Po) and shortening velocity (Vo), rate of force development (+dP/dt) and shortening-induced deactivation (SID) were almost two-fold greater in WT muscles. The present results demonstrate that myosin RLC phosphorylation may improve contractile performance during fatigue; providing a contractile advantage to working muscles and protecting against progressive fatigue.

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The Weekly Register, also known as Niles Weekly Register, was a weekly periodical edited by Hezekiah Niles (1777-1839) and published in Baltimore Maryland. Volumes of interest were published between 1811 (Vol. 1, No. 1, September 7, 1811) to 1814 (Vol. 5, No. 26, February 26, 1814). These volumes focus primarily on 19th century politics and government in the United States of America. Niles edited and published the Weekly Register until 1836, making it one of the most widely-circulated magazines in the United States. The popularity also made Niles into one of the most influential journalists of his day. Devoted primarily to politics, Niles' Weekly Register is considered an important source for the history of the period. The Register also recorded current economics, technology, science, medicine, geography, archaeology, the weather, and stories of human interest. This issue is part of a bound book titled the Weekly Register 1812-1814. Pages are divided as follows: November 14, 1812- Pages 161-174 January 22, 1814- Pages 337-352 July 30, 1814- Pages 361-376 Look for other issues of the Weekly Register within the website.

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This letter authorizes William Hamilton of Portmollart to repair to Edinburgh notwithstanding the acts discharging the Hamiltons from being within six miles of the King’s person. James VI and James I (June 19, 1566 – March 27, 1625) was King of Scots as James VI from July 24th, 1567 and King of England and Ireland as James I from the union of the English and Scottish crowns on March 24, 1603 after the passing of Elizabeth I.

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Activated by elevations in myoplasmic calcium concentration, myosin light chain kinase (skMLCK) phosphorylates the regulatory light chains (RLCs) of fast muscle myosin. This covalent modification potentiates force production, but requires an investment of ATP. Our objective was to investigate the effect of RLC phosphorylation on the contractile economy (mechanical output:metabolic input) of fast twitch skeletal muscle. Extensor digitorum longus muscles isolated from Wildtype and skMLCK-/- mice mounted in vitro (25°C) were subjected to repetitive low-frequency stimulation (10Hz,15s) known to cause activation of skMLCK, and staircase potentiation of force. With a 3-fold increase in RLC phosphate content, Wildtype generated 44% more force than skMLCK-/- muscles over the stimulation period (P = .002), without an accompanied increase in energy cost (P = .449). Overall, the contractile economy of Wildtype muscles, with an intact RLC phosphorylation mechanism, was 73% greater than skMLCK /- muscles (P = .043), demonstrating an important physiological function of skMLCK during repetitive contractile activity.