-
Journal of Nutritional Science and... 2022We examined the effects of dietary vitamin D deficiency on markers of mitochondrial biogenesis and dynamics in rat soleus muscle. Male Wistar rats were fed a chow with...
We examined the effects of dietary vitamin D deficiency on markers of mitochondrial biogenesis and dynamics in rat soleus muscle. Male Wistar rats were fed a chow with no vitamin D (No-D; 0 IU/kg) or a moderate dose (Mod-D; 2,000 IU/kg) of vitamin D chow for 8 wk. Compared to the Mod-D group, at 8 wk the No-D group showed significantly lower serum 25(OH)D levels. Although vitamin D deficiency had no effect on body composition, the No-D rats showed significantly decreased levels of PGC-1α, a marker of skeletal muscle mitochondrial biogenesis, and DRP1, a marker of skeletal muscle mitochondrial fission. The change in the PGC-1α protein expression and the serum 25(OH)D concentrations were significantly correlated. The change in DRP1 protein expression and the serum 25(OH)D concentrations tended to be correlated. There was no significant between-group difference in markers of mitochondrial fusion (MFN2 and OPA1) and mitophagy (PARKIN) in soleus muscle, and no relationship with serum 25(OH)D concentrations. Collectively our findings suggest that dietary vitamin D deficiency decreased PGC-1α and DRP1 protein expression in rat soleus muscle.
Topics: Animals; Male; Mitochondrial Dynamics; Muscle, Skeletal; Organelle Biogenesis; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Rats; Rats, Wistar; Vitamin D Deficiency
PubMed: 36047095
DOI: 10.3177/jnsv.68.243 -
The Journal of Experimental Biology Jun 2013The lengths and velocities of muscle fibers have a dramatic effect on muscle force generation. It is unknown, however, whether the lengths and velocities of lower limb...
The lengths and velocities of muscle fibers have a dramatic effect on muscle force generation. It is unknown, however, whether the lengths and velocities of lower limb muscle fibers substantially affect the ability of muscles to generate force during walking and running. We examined this issue by developing simulations of muscle-tendon dynamics to calculate the lengths and velocities of muscle fibers from electromyographic recordings of 11 lower limb muscles and kinematic measurements of the hip, knee and ankle made as five subjects walked at speeds of 1.0-1.75 m s(-1) and ran at speeds of 2.0-5.0 m s(-1). We analyzed the simulated fiber lengths, fiber velocities and forces to evaluate the influence of force-length and force-velocity properties on force generation at different walking and running speeds. The simulations revealed that force generation ability (i.e. the force generated per unit of activation) of eight of the 11 muscles was significantly affected by walking or running speed. Soleus force generation ability decreased with increasing walking speed, but the transition from walking to running increased the force generation ability by reducing fiber velocities. Our results demonstrate the influence of soleus muscle architecture on the walk-to-run transition and the effects of muscle-tendon compliance on the plantarflexors' ability to generate ankle moment and power. The study presents data that permit lower limb muscles to be studied in unprecedented detail by relating muscle fiber dynamics and force generation to the mechanical demands of walking and running.
Topics: Biomechanical Phenomena; Computer Simulation; Humans; Male; Models, Biological; Muscle Fibers, Skeletal; Muscle, Skeletal; Running; Tendons; Walking
PubMed: 23470656
DOI: 10.1242/jeb.075697 -
Journal of Applied Biomechanics Jun 2019The triceps surae muscle-tendon units are important in governing walking performance, acting to regulate mechanical behavior of the ankle through interaction between...
The triceps surae muscle-tendon units are important in governing walking performance, acting to regulate mechanical behavior of the ankle through interaction between active muscle and passive elastic structures. Ankle joint quasi-stiffness (the slope of the relation between ankle moment and ankle rotation, k) is a useful aggregate measure of this mechanical behavior. However, the role of muscle activation and length-tension behavior in augmenting k remains unclear. In this study, 10 subjects completed eccentric isokinetic contractions at rest and at 2 soleus activation levels (25% and 75% isometric voluntary contraction) prescribed using electromyographic biofeedback. Ultrasound imaging quantified activation-dependent modulation of soleus muscle length-tension behavior and its role in augmenting k. The authors found that soleus muscle stiffness (k) and k exhibit nonlinear relations with muscle activation and both were more sensitive to the onset of activation than to subsequent increases in activation. Our findings also suggest that k can be modulated via activation through changes in soleus muscle length-tension behavior. However, this modulation is more complex than previously appreciated-reflecting interaction between active muscle and passive elastic tissues. Our findings may have implications for understanding normal and pathological ankle joint function and the design of impedance-based prostheses.
Topics: Ankle Joint; Biomechanical Phenomena; Electromyography; Female; Humans; Isometric Contraction; Male; Muscle Contraction; Muscle, Skeletal; Ultrasonography; Young Adult
PubMed: 30676171
DOI: 10.1123/jab.2018-0297 -
International Journal of Molecular... Feb 2023Disuse muscle atrophy is usually accompanied by changes in skeletal muscle structure, signaling, and contractile potential. Different models of muscle unloading can...
Disuse muscle atrophy is usually accompanied by changes in skeletal muscle structure, signaling, and contractile potential. Different models of muscle unloading can provide valuable information, but the protocols of experiments with complete immobilization are not physiologically representative of a sedentary lifestyle, which is highly prevalent among humans now. In the current study, we investigated the potential effects of restricted activity on the mechanical characteristics of rat postural (soleus) and locomotor (extensor digitorum longus, EDL) muscles. The restricted-activity rats were kept in small Plexiglas cages (17.0 × 9.6 × 13.0 cm) for 7 and 21 days. After this, soleus and EDL muscles were collected for ex vivo mechanical measurements and biochemical analysis. We demonstrated that while a 21-day movement restriction affected the weight of both muscles, in soleus muscle we observed a greater decrease. The maximum isometric force and passive tension in both muscles also significantly changed after 21 days of movement restriction, along with a decrease in the level of collagen 1 and 3 mRNA expression. Furthermore, the collagen content itself changed only in soleus after 7 and 21 days of movement restriction. With regard to cytoskeletal proteins, in our experiment we observed a significant decrease in telethonin in soleus, and a similar decrease in desmin and telethonin in EDL. We also observed a shift towards fast-type myosin heavy chain expression in soleus, but not in EDL. In summary, in this study we showed that movement restriction leads to profound specific changes in the mechanical properties of fast and slow skeletal muscles. Future studies may include evaluation of signaling mechanisms regulating the synthesis, degradation, and mRNA expression of the extracellular matrix and scaffold proteins of myofibers.
Topics: Animals; Rats; Muscle Contraction; Muscle, Skeletal; Myosin Heavy Chains; RNA, Messenger; Sedentary Behavior
PubMed: 36835551
DOI: 10.3390/ijms24044141 -
The Journal of Physiological Sciences :... Sep 2019The effects of a combination of the antioxidant astaxanthin (AX) and electrical stimulation (ES) on muscle mass and mitochondrial oxidative capacity were investigated in...
The effects of a combination of the antioxidant astaxanthin (AX) and electrical stimulation (ES) on muscle mass and mitochondrial oxidative capacity were investigated in the soleus muscle of hindlimb unloaded rats. Five groups of male Sprague-Dawley rats were used; control, 1-week hindlimb unloading (HU), HU + AX, HU + ES, and HU + AX + ES. Respective rats in the AX groups received 50-mg/kg AX twice daily during HU. Calf muscles of rats in the ES groups were electrically stimulated for 240 s/day during HU. One-week HU decreased muscle mass along with decreased FoxO3a phosphorylation and increased ubiquitinated proteins expressions, decreased oxidative enzymatic activity accompanied with decline in PGC-1α protein expression, and increased reactive oxygen species production. However, the combination treatment could synergistically attenuate/suppress all HU-related changes, suggesting protective effects on muscle atrophy and decreased muscle oxidative capacity due to chronic neuromuscular inactivity.
Topics: Animals; Antioxidants; Dietary Supplements; Electric Stimulation; Hindlimb; Hindlimb Suspension; Male; Muscle, Skeletal; Muscular Atrophy; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Xanthophylls
PubMed: 31273678
DOI: 10.1007/s12576-019-00692-7 -
Revista Brasileira de Fisioterapia (Sao... Jun 2012Evidence of self-sustained muscle activation following a brief electrical stimulation has been reported in the literature for certain muscles.
BACKGROUND
Evidence of self-sustained muscle activation following a brief electrical stimulation has been reported in the literature for certain muscles.
OBJECTIVES
This report shows that the foot muscle (Flexor Digitorum Brevis - FDB) shows a self-sustained increase in muscle activity during upright stance in some subjects following a train of stimuli to the tibial nerve.
METHODS
Healthy subjects were requested to stand upright and surface EMG electrodes were placed on the FDB, Soleus and Tibialis Anterior muscles. After background muscle activity (BGA) acquisition, a 50 Hz train of stimuli was applied to the tibial nerve at the popliteal fossa. The root mean square values (RMS) of the BGA and the post-stimulus muscle activation were computed.
RESULTS
There was a 13.8% average increase in the FDB muscle EMG amplitude with respect to BGA after the stimulation was turned off. The corresponding post-stimulus Soleus EMG activity decreased by an average of 9.2%. We hypothesize that the sustained contraction observed in the FDB following stimulus may be evidence of persistent inward currents (PIC) generated in FDB spinal motoneurons. The post-stimulus decrease in soleus activity may have occurred due to the action of inhibitory interneurons caused by the PICs, which were triggered by the stimulus train.
CONCLUSIONS
These sustained post-stimulation changes in postural muscle activity, found in different levels in different subjects, may be part of a set of possible responses that contribute to overall postural control.
Topics: Electric Stimulation; Foot; Humans; Muscle, Skeletal; Posture; Tibial Nerve
PubMed: 22641561
DOI: 10.1590/s1413-35552012005000024 -
The Journal of Physiology Sep 19961. In order to study fusimotor control in reduced preparations, soleus muscle spindle afferents were recorded in premammillary decerebrate cats (n = 15) during crossed...
1. In order to study fusimotor control in reduced preparations, soleus muscle spindle afferents were recorded in premammillary decerebrate cats (n = 15) during crossed extensor reflexes and, after spinalization, during locomotion produced by either clonidine or L-beta-3,4-dihydroxyphenylalanine (L-DOPA). The soleus muscle was oscillated sinusoidally (0.25 mm, 4 Hz) and the afferent mean firing rate and modulation were calculated. An increase in firing rate was assumed to arise from activity in dynamic gamma-motoneurones (dynamic gamma-drive) when associated with an increase in modulation to stretching, and in static gamma-motoneurones (static gamma-drive) when modulation decreased. 2. At rest in all preparations the firing rate and modulation in primary muscle spindle afferents were generally much higher than after de-efferentation (ventral root section), suggesting a predominant dynamic gamma-drive. Clonidine decreased and even eliminated this presumed resting gamma-drive in many afferents, both in the decerebrate (7 of 8) and the spinal (6 of 18) state. This effect on gamma-drive may account, at least in part, for its suppressive effect on spasticity in humans. 3. When locomotion commenced in clonidine-treated spinal cats, primary afferents generally fired with much higher mean rates (+121%) and lower sensitivities (-32%), suggesting a large increase in static gamma-drive (possibly accompanied by a small decrease in dynamic gamma-drive). These high rates were usually maintained tonically throughout the step cycle. However, a third of the afferents were silenced during locomotor contractions, and de-efferentation had no significant effect on their firing rates. Thus, for some spindles alpha-activity can occur without significant gamma-drive. 4. During locomotion in L-DOPA-treated spinal cats the inferred static gamma-drive only occurred phasically, coactivated with the EMG, though it could precede the EMG by 100-500 ms. In the flexion phase both the afferent rate and modulation were lower than before locomotion, suggesting a lack of effective gamma-drive. 5. Crossed extensor reflexes in decerebrate cats also produced a substantial increase in primary afferent firing rate (+187%) and decrease in sensitivity (-37%), again suggesting increased static gamma-drive (n = 18). This gamma-drive was largely independent of EMG activity and often occurred without alpha-activity. The mean firing rate of secondary muscle spindle afferents increased significantly during locomotion (with L-DOPA) and crossed extensor reflexes, again indicating increased static gamma-drive. Clonidine reduced or eliminated the gamma-drive in seven of eight afferents during crossed extensor reflexes. 6. In conclusion, although there are some common features, such as a predominant static gamma-drive in all walking preparations, the pattern of static and dynamic gamma-drive is not closely linked to alpha-activity under the conditions studied. As well as gamma-drive without alpha-activity, we have shown for the first time that alpha-motoneurones can be activated without significant gamma-drive to many spindles during behavioural tasks.
Topics: Action Potentials; Afferent Pathways; Animals; Cats; Clonidine; Decerebrate State; Electrophysiology; Levodopa; Motor Activity; Motor Neurons, Gamma; Muscle Contraction; Muscle, Skeletal; Posture; Sympatholytics
PubMed: 8887786
DOI: 10.1113/jphysiol.1996.sp021636 -
American Journal of Physiology.... Dec 2012Persons with Down syndrome (DS) exhibit low muscle strength that significantly impairs their physical functioning. The Ts65Dn mouse model of DS also exhibits muscle...
Persons with Down syndrome (DS) exhibit low muscle strength that significantly impairs their physical functioning. The Ts65Dn mouse model of DS also exhibits muscle weakness in vivo and may be a useful model to examine DS-associated muscle dysfunction. Therefore, the purpose of this experiment was to directly assess skeletal muscle function in the Ts65Dn mouse and to reveal potential mechanisms of DS-associated muscle weakness. Soleus muscles were harvested from anesthetized male Ts65Dn and wild-type (WT) colony controls. In vitro muscle contractile experiments revealed normal force generation of nonfatigued Ts65Dn soleus, but a 12% reduction in force was observed during recovery from fatiguing contractions compared with WT muscle (P < 0.05). Indicators of oxidative stress and mitochondrial oxidative capacity were assessed to reveal potential mechanisms of DS-associated muscle weakness. Protein expression of copper-zinc superoxide dismutase (SOD1), a triplicated gene in persons with DS and Ts65Dn mice, was increased 25% (P < 0.05) in Ts65Dn soleus. Nontriplicated antioxidant protein expression was similar between groups. Lipid peroxidation was unaltered in Ts65Dn animals, but protein oxidation was 20% greater compared with controls (P < 0.05). Cytochrome-c oxidase expression was 22% lower in Ts65Dn muscle (P < 0.05), while expression of citrate synthase was similar between groups. Microarray analysis revealed alteration of numerous pathways in Ts65Dn muscle, including proteolysis, glucose and fat metabolism, neuromuscular transmission, and ATP biosynthesis. In summary, despite biochemical and gene expression differences in soleus muscle of Ts65Dn animals, the functional properties of skeletal muscle likely contribute a minor part to the in vivo muscle weakness.
Topics: Animals; Disease Models, Animal; Down Syndrome; Electron Transport Complex IV; In Vitro Techniques; Lipid Peroxidation; Male; Mice; Mice, Mutant Strains; Muscle Contraction; Muscle Fatigue; Muscle Weakness; Muscle, Skeletal; Oxidative Stress; Superoxide Dismutase
PubMed: 23115123
DOI: 10.1152/ajpregu.00312.2012 -
American Journal of Physiology.... Jul 2007During chronic obstructive pulmonary disease (COPD) diaphragm and peripheral muscle weakness occur. Muscle remodeling and wasting may be a result of apoptosis and...
During chronic obstructive pulmonary disease (COPD) diaphragm and peripheral muscle weakness occur. Muscle remodeling and wasting may be a result of apoptosis and changes in muscle-specific transcription factors, such as MyoD, altering muscle-specific gene transcription and muscle regenerative capacity. To investigate this, we instilled under ketamine/xylazine anesthesia porcine elastase in the lungs of hamsters to induce emphysema. The emphysematous hamster is an accepted model for COPD. In the diaphragm and peripheral muscles we assessed the occurrence of apoptosis, and in the diaphragm and soleus also the expression of MyoD and inhibitor of differentiation protein 2 (Id2). There was no significant muscle atrophy in emphysematous hamsters. The mRNA levels of TNF-alpha and markers of apoptosis were significantly elevated in the diaphragm and soleus muscles during emphysema. This was accompanied by an increased presence of nucleosomes in the cytosol. Caspase 3 activity and the DNA-binding activity of the p65 subunit of NF-kappaB, however, were unaltered in all muscles. The protein expression of MyoD and Id2 were decreased and increased in the diaphragm and the soleus muscle, respectively. Thus, despite the absence of muscle atrophy in emphysematous hamsters, there was evidence of increased TNF-alpha expression, apoptosis, and altered muscle-specific transcriptional regulation as reflected by decreased MyoD and elevated Id2 levels at least in the soleus and diaphragm muscle. These alterations may impair the regenerative capacity of skeletal muscles and ultimately contribute to muscle wasting.
Topics: Animals; Apoptosis; Caspase 3; Cell Nucleus; Cricetinae; Cytosol; DNA Fragmentation; Diaphragm; Emphysema; Inhibitor of Differentiation Protein 2; Male; Mesocricetus; Muscle Fibers, Skeletal; Muscle, Skeletal; MyoD Protein; Myosin Heavy Chains; NF-kappa B; Pulmonary Disease, Chronic Obstructive; RNA, Messenger; Reverse Transcriptase Polymerase Chain Reaction; Tumor Necrosis Factor-alpha
PubMed: 17395785
DOI: 10.1152/ajpregu.00046.2007 -
Acta Neurobiologiae Experimentalis 1996Influences exerted by tactile stimuli on the muscle activity were investigated with two methods: (1) analysis of kinematics and electromyographic (EMG) activity of eight... (Review)
Review
Influences exerted by tactile stimuli on the muscle activity were investigated with two methods: (1) analysis of kinematics and electromyographic (EMG) activity of eight forelimb muscles during contact placing (CP) reactions elicited by tactile stimuli applied to the dorsal, medial or lateral sides of the paw in cats, and (2) the Hoffmann (H)-reflex technique to quantify the effects of the tactile stimuli on the excitability of the alpha motoneurones of the soleus muscle in awake rats. The first group of the data showed that the tactile stimuli applied to dorsal, medial or lateral aspects of the paw led to different strategies of the forelimb movements during CP reactions. These differences arose from various patterns of activation of the elbow flexor and extensor muscles at the beginning of CP reactions and a various involvement of the medio-lateral components of movements, depending on the site of the tactile stimulus application. With the H-reflex technique it was found that the tactile stimulus diminished the excitability of alpha motoneurones of the soleus muscle when applied to the skin overlying the lateral side of the ankle joint. This effect was in line with the observation that the tactile stimulus applied to the lateral side of the paw activated the elbow flexor muscles but not their antagonists to initiate CP reaction.
Topics: Animals; Electromyography; Forelimb; Humans; Movement; Muscle, Skeletal; Physical Stimulation
PubMed: 8787204
DOI: 10.55782/ane-1996-1146