Fast fibres in a large animal: fibre types, contractile properties and myosin expression in pig skeletal muscles

Fibre types in the iliofibularis muscle of the freshwater terrapin Pseudemys scripta elegans have been characterized on the basis of their histochemical characteristics, nerve endings and contractile properties. Three types of focally innervated fibres are present, corresponding to the fast glycolytic (Fg), fast oxidative glycolytic (FOG) and slow oxidative (SO) fibre types of other vertebrates. Single fibres or small bundles of fibres representing each histochemical type were identified on the basis of their light scattering properties under dark-field illumination. Fibres were detergent-skinned using Brij 58, and their maximum isometric tension (P0) and unloaded contraction velocity (V0) were determined by the slack test method. At 15 degrees C, fast glycolytic fibres generated maximum isometric tensions of 184 +/− 5 kNm-2 and V0 values of 5.5 +/− 0.3 muscle lengths per second (L0s-1). Slow oxidative fibres produced tensions of 70.6 +/− 3 kNm-2 and had V0 values of 1.3 L0s-1. Tensions and V0 values of fast oxidative glycolytic fibres were between those of Fg and SO fibres. The force-velocity (P-V) characteristics of slow oxidative fibres were studied at 5 degrees and 15 degrees C. Points below 0.6 P0 on the curves could be fitted by a linear form of Hill's equation. Maximum contraction velocities (Vmax) extrapolated from the P-V relationship were 0.62 L0s-1 at 5 degrees C and 0.91 L0s-1 at 15 degrees C. The curvature of the P-V relationship was relatively independent of temperature over the range 5 to 15 degrees C. Values for Hill's constant a/P0 were 0.29 and 0.33 at 5 degrees C and 15 degrees C, respectively. The temperature dependence of P0 and contraction velocity at near zero load (Vi) were studied at constant pH, and under conditions designed to simulate the changes in intracellular pH which occur with temperature in vivo (delta pH/delta T = −0.0186). Changes in pH in the range 6.6 to 7.8 had no effect on either tension or Vi at temperatures between 0 degrees and 20 degrees C. However, below and above this pH range, both tension and Vi were depressed. It is concluded that pH changes within the normal physiological range (6.7-7.8) have no effect on the temperature dependence of P0 and Vi.

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Contractile properties of slow and fast skeletal muscles from protease activated receptor-1 null mice

Muscle & Nerve ◽

10.1002/mus.24256 ◽

2014 ◽

Vol 50 (6) ◽

pp. 991-998 ◽

Cited By ~ 3

Author(s):

Paran K. Sitparan ◽

Charles N. Pagel ◽

Gavin J. Pinniger ◽

H.J. Yoo ◽

Eleanor J. Mackie ◽

...

Keyword(s):

Skeletal Muscles ◽

Contractile Properties ◽

Protease Activated Receptor 1

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Effect of L-carnitine on diabetes-induced changes of skeletal muscles in rats

Journal of Basic and Clinical Physiology and Pharmacology ◽

10.1515/jbcpp-2016-0185 ◽

2018 ◽

Vol 29 (1) ◽

pp. 47-59 ◽

Cited By ~ 6

Author(s):

Shereen M. Samir ◽

Amr M. Abbas ◽

Sally M. Safwat ◽

Hanaa G. Elserougy

Keyword(s):

Skeletal Muscles ◽

Gastrocnemius Muscle ◽

Ring Finger ◽

Diabetic Rats ◽

Contractile Properties ◽

Sensitivity Index ◽

Haemoglobin A1c ◽

Protective Effects ◽

Sprague Dawley ◽

Histopathological Studies

AbstractBackground:Patients with diabetes mellitus (DM) are at risk of experiencing chronic complications such as retinopathy, nephropathy and myopathy. We aimed to evaluate the effects of L-carnitine on type II DM (T2DM)-induced biochemical, contractile and pathological changes in skeletal muscles of rats.Methods:Thirty-two male Sprague Dawley rats were divided into the control, control+L-carnitine, T2DM and T2DM+L-carnitine groups. Plasma levels of glucose, insulin, malondialdehyde and antioxidants such as reduced glutathione, catalase and superoxide dismutase, haemoglobin A1c (HbA1c), insulin sensitivity index (ISI) as well as the contractile properties of the gastrocnemius muscle were measured. Also, histopathological studies and immunohistochemical examination of the gastrocnemius muscle using the MuRF1 (muscle RING-finger protein-1) marker were performed.Results:In diabetic rats, malondialdehyde, glucose, insulin, HbA1c and MuRF1 were increased, whereas ISI and antioxidants were decreased and the contractile properties deteriorated. L-carnitine decreased malondialdehyde, glucose, insulin, HbA1c and MuRF1 and increased ISI and antioxidants. Also, L-carnitine improves the contractile properties in diabetic rats. Histopathological studies confirm our data.Conclusions:We conclude that L-carnitine exhibits protective effects on skeletal muscles of T2DM rats through its hypoglycemic and antioxidant actions as well as its inhibitory effect on protein degradation.

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