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The flexor digitorum brevis muscle is located in the foot. Its precise location is within the sole of the foot, directly above the plantar aponeurosis, which supports the arch of the foot.
Although EMG normalization influences the distribution of simulated muscle force, we are confident that our normalization method did not compromise the results of this study. We normalized subjects filtered EMG to the maximum value observed for each muscle over all gait speeds. This normalization method will cause the estimated excitation to be over-estimated if the muscle was not maximally excited during any of the trials. The impact of such an error on the muscle fiber length and velocity depends on muscle-tendon compliance. In muscles where the ratio of tendon slack length to optimal fiber length is less than two (vastus lateralis, vastus medialis, semitendinosus, gluteus maximus and gluteus medius), fiber lengths and velocities are not sensitive to excitation level [see figs 4 and 6 of Arnold and Delp (Arnold and Delp, 2011)]. Gastrocnemius medialis, gastrocnemius lateralis and soleus have the highest muscle-tendon compliance in our study; however, it is reasonable to expect that soleus and ...
The nuclear export of Foxo can be inhibited by LMB (Fig. 11), which binds to and thus removes the availability of CRM1 for nuclear export. In the presence of a fully blocking concentration of LMB, any Foxo that enters the nucleus is unable to leave and becomes trapped in the nucleus. Inhibition of nuclear export via LMB thus provides a powerful tool for measuring the rate of unidirectional nuclear influx and for calculating its rate constant of cytoplasmic efflux. The change in the rate constant for unidirectional efflux out of the cytoplasm due to treatment with phosphorylation modulators demonstrates the importance of cytoplasmic phosphorylation/dephosphorylation of Foxo1 in regulation of its rate of cytoplasmic efflux (Figs. 6, 9, and 10). Furthermore, the increase in the rate of nuclear influx that resulted from staurosporine addition in the presence of LMB (Fig. 9A) indicates that the nuclear import machinery is not saturated at the level of expression of Foxo1-GFP employed under our ...
Model 1 differs in several ways from most previously published spark models. The differences include: (a) the value assumed for [Ca2+]R; (b) the particular reaction chosen for the SR Ca2+ pump; (c) the inclusion of ATP as an endogenous Ca2+ buffer; and (d) the inclusion of a binding reaction between fluo-3 and myoplasmic protein. To evaluate the effect of these differences, the parameters of the model were modified as described in the following paragraphs. In each case, the amplitude of the Ca2+ flux at the source was readjusted so that the mean amplitude of the larger simulated noisy sparks matched that of the measurements. Table IV, columns 4-7 give the morphological parameters obtained in the simulations after these modifications.. The first modification was to increase the value of [Ca2+]R from 50 to 100 nM. The main effect of this change is to increase resting fluorescence (F) by the factor 1.73. The fractional increase in F is smaller than that in [Ca2+]R because the fluorescence of ...
When the contractile properties of single muscle fibres are studied, force is typically normalized by fibre cross-sectional area and expressed as specific force. We studied a set of 2725 chemically skinned human single muscle fibres from 119 healthy adults to determine whether specific force is the optimal way to express the relationship between single-fibre force and size. A linear mixed effects model was used to estimate the slope and slope variability among individuals of log-log plots of force and diameter. For type I fibres, the slope estimate was 0.99 (95% confidence interval 0.36-1.62), and for type IIa fibres it was 0.94 (95% confidence interval 0.77-1.11), indicating that force is proportional to fibre diameter, rather than to cross-sectional area. If force were proportional to cross-sectional area, the slope estimate would be 2.0. In future studies using the chemically skinned single fibre preparation, force may be normalized to fibre diameter rather than cross-sectional area. We ...
We tested the proposition that muscle cell types have different contents of phosphocreatine (PCr), ATP, and Pi by 31P NMR spectroscopy and HPLC analyses of adult rat and mouse muscles containing various volume fractions of different fiber types. There was a 2-fold difference in the PCr content between muscles with a high volume fraction of fiber types 1 and 2x versus those with fast-twitch (types 2a and 2b) fiber types. Pi content was low, and PCr and ATP contents were high in muscles with large contents of type 2b and 2a fibers; the reverse was true in muscles with a large volume fraction of type 1 and 2x fibers. There is a large range in the Pi/PCr ratios in normal resting muscles, from less than 0.05 in type 2 to 0.51 in type 1 fibers, depending upon the distribution of their component fiber types. In all muscles, the peak area resulting from the beta phosphate of ATP constituted approximately 13% of the sum of all peak areas observable in the 31P spectrum. Fiber types 2a and 2b were not ...
Mutungi, GM and Ranatunga, KW (1998) Effects of reducing sarcomere length on twitch contraction in mammalian (rat) muscle fibres. The Journal of Physiology, 511.P. pp. 155-156. ISSN 1469-7793 Full text not available from this repository. (Request a copy ...
C2 skeletal muscle cells (myotubes) developing in culture, coloured scanning electron micrograph (SEM). Myogenesis is the formation of muscular tissue, especially in embryonic development. Muscle fibres form from the fusion of myoblasts into multi-nucleated fibres called myotubes. In the early development of an embryo these myoblasts will undergo multiple divisions. The second stage involves the alignment of the myoblasts into the myotubes. The third stage is the actual cell fusion of myotubes in to muscle fibres. Magnification: x240 when shortest axis printed at 25 millimetres. - Stock Image C032/0169
It is unclear whether accumulation of lactate in skeletal muscle fibers during intense activity contributes to muscle fatigue. Using mechanically skinned fibers from rat and toad muscle, we were able to examine the effect of l(+)-lactate on excitation-contraction coupling independently of other metabolic changes. We investigated the effects of lactate on the contractile apparatus, caffeine-induced ...
Synonyms for muscle fiber in Free Thesaurus. Antonyms for muscle fiber. 2 synonyms for muscle fiber: muscle cell, muscle fibre. What are synonyms for muscle fiber?
Main objective of this article is to define and discuss on Muscle Fibres. Here explain different muscle Muscle Fibres. Type I Muscle Fibres are those that are called the slow twitch or the sluggish oxidative fibers, which contain lots of myoglobin, mitochondria, and naturally, blood capillaries. These fibers have a
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The mean fibre area of the semitendinosus, diaphragm and pectoralis transversus muscles in differing types of horse and dog.: The mean fibre areas of samples fr
Initiated by neural impulses and subsequent calcium release, skeletal muscle fibers contract (actively generate force) as a result of repetitive power strokes of acto-myosin cross-bridges. The energy required for performing these cross-bridge cycles is provided by the hydrolysis of adenosine triphosphate (ATP). The reaction products, adenosine diphosphate (ADP) and inorganic phosphate (Pi), are then used-among other reactants, such as creatine phosphate-to refuel the ATP energy storage. However, similar to yeasts that perish at the hands of their own waste, the hydrolysis reaction products diminish the chemical potential of ATP and thus inhibit the muscles force generation as their concentration rises. We suggest to use the term
D. Rotator Cuff. V Exercise. A. aerobic. 1. increased endurance. B. resistance or isometric (vs. isotonic). 1. increased muscle size. a. cause of increased size When you finish this unit, you should be able to: - explain the basic characteristics of all muscle tissue. - define acetylcholine, motor end plate, neuromuscular junction. - draw a neuromuscular junction and explain the sequence of events occurring there. - explain how a skeletal muscle fiber knows when to contract. - draw the structure of a skeletal muscle fiber labeling myofibril, sarcomere, myofilament, actin, myosin, A-band, I-band, Z-line. - explain HOW a single muscle fiber manages to shorten its length. - explain the Sliding Filament Theory of Contraction - describe the structure of a whole skeletal muscle (the organ) including the connective tissue wrappings. - list the steps between exciting a muscle fiber and the muscle moving a bone. - explain how one muscle can perform different strengths of contraction - list the causes ...
An interactive quiz about the general anatomy of skeletal muscle fibers, featuring illustrations-based multiple choice questions. Click and start learning now!
Collection of computational implementations and examples for the numerical construction of skeletal muscle fiber maps based on a Laplacian field approach.
Bajusz, E, "red Skeletal muscle fibers. Relative independence of neural control." (1964). Subject Strain Bibliography 1964. 52 ...
Muscle fibers With HIT training we are specifically trying to stimulate a certain type of muscle fiber. We have different muscle fibers in the body
After you have stopped exercising for just a few weeks, your muscles are smaller and weaker and cannot remove as much sugar from your bloodstream when blood sugar levels rise too high. To regain your muscle size and strength, you need to exercise intensely enough to damage the muscle fibers so they will be stronger when they heal. When you use your muscles, you contract the muscle and shorten its fibers. However, you do not contract a muscle fiber equally throughout its length. Muscle fibers are made up of blocks, called sarcomeres, touching end to end to form the long stringy muscle fiber. Each block touches the next block at a point called the Z-line. You have to damage the Z-line to make a muscle grow larger and stronger. If you pedal a bicycle with great pressure or run very fast, you can damage the muscle fibers at the Z-lines, but most people do not run or cycle hard enough to do this. Adding weight training to the recovery program will help to regain the lost strength and muscle size. See ...
A major finding from this study was the shift to higher EMG frequencies at the faster muscle fascicle strain rates for the MG (figure 7). Many studies quantify EMG frequencies by the mean or median frequency of the EMG power spectra (Roy et al. 1986; Solomonow et al. 1990; Kupa et al. 1995; De Luca 1997). However, in the current study, the shift in frequency does not merely represent an increase in the mean frequency of the EMG-intensity spectrum but more specifically occurs as a decrease in the low-frequency (less than 100 Hz) components and an increase in the high-frequency (greater than 100 Hz) components of the spectra (Wakeling & Rozitis 2004). Furthermore, the results showed that shifts in frequency occurred even when the total EMG-intensity remained the same and the statistical analysis showed that the strain rate-dependent shifts in frequency occurred independently from changes in the locomotor load, measured as crank torque and the muscle fascicle strain.. There are many factors that ...
They are also self-healing(more later)! The mouse muscle fiber grew from progenitor satellite cells which exist in mature living muscle. The trick, according to the Duke researchers, required finding "the perfect environment for muscle growth" for the satellite cells. Specifically they needed "well-developed contractile muscle fibers" included in the mix with the immature cells. Once the cells grew into mature fibers themselves, they were grafted into mice where the new muscle adapted function and strength. As for self-healing, an ex vivo study in which new-grown fibers were damaged by toxin, they recovered contractile function after being re-exposed to the milieu of immature cells.. ...
Health,A protein can change easily worn muscle fibres into energy-producing m...There are two types of muscle fibre. Type II is the easily-fatigue...The research isnt meant for a quick-fix to replace a commitment t......,Protein,can,change,worn,muscle,fibres,medicine,medical news today,latest medical news,medical newsletters,current medical news,latest medicine news
As you know, movement is controlled by the brain. The first step towards muscular contraction is a signal sent by the brain to your muscles telling them to contract. You might say that the Mind-Muscle Connection (MMC) occurs at something called the "neuromuscular junction". This is where the mind meets the body. The brain releases a chemical neurotransmitter called Acetylcholine to communicate with muscles in the body.. The more you can improve this communication, the more muscle fibers you will recruit. A single muscle head is made up of many individual muscle fibers. By improving your MMC you are actually increasing the number of muscle fibers being recruited when you perform a lift. This results in a better quality muscle contraction and better workout.. When youre in the middle of a set, whats going through your mind? Are you simply trying to force out as many reps as you can? If this is you, Ive got some tips below to help you develop your MMC and maximize your gains.. You should be ...
For a physiologically realistic joint range of motion and therefore range of muscle fiber lengths, only part of the whole muscle force-length curve can be used in vivo; that is, only a section of the force-length curve is ...
The current study explored whether the marked hypertrophic response noted with a short-term unilateral concurrent exercise paradigm was associated with more prominent changes in myonuclei accretion, ribosome biogenesis and capillarization compared to resistance exercise alone (RE). Ten men (age 25±4yr) performed aerobic and resistance exercise (AE+RE) for one leg, while the other leg did RE. Muscle biopsies were obtained before and after 5 weeks of training and subjected to fiber-type specific immunohistochemical analysis, and quantification of total RNA content and mRNA/rRNA transcript abundance. Type-II fiber cross-sectional area (CSA) increased with both AE+RE (22%) and RE (16%), while type-I fiber CSA increased mainly with AE+RE (16%). The change-score tended to differ between legs for type-I CSA (P=0.099), and the increase in smallest fiber diameter was greater in AE+RE than RE (P=0.029). The number of nuclei per fiber increased after AE+RE in both fiber types, and this increase was ...
We all have our reasons for going to the gym. And muscle hypertrophy, or growth, is one of the main ones. To build lean, dense muscle, you must progressively overload your muscles to enhance muscle fiber recruitment. How do you do that?
Even though the absolute poundage is greater on a machine, the actual overload on the muscle is greater with free weights because youre responsible for balancing and stabilizing all the weight yourself. This, along with an increased range of motion, is why free weights are better for more muscle fiber recruitment and maximum stimulation ...
Hello, I was hopeful you could provide assistance with my analysis. At the bottom of this description, you will find a link to the two images discussed below. The first image is a cross-section of muscle fibers w…
Overall strength is about a lot more than just muscle size and makeup. It is mostly about muscle recruitment. All of us have the opportunity to be about 5 times stronger than we think we are, because our brains randomly fire about 20% or less of our available muscle fibers. They do this to limit joint damage and leverage and maximize resources of glucose and creatine in the muscle fiber and potassium and calcium in the blood that fuel the nerve processes. The super human strength shown sometimes is a result of fight or flight overriding the normal random firing. Old grandmas are stronger than young bodybuilders when they fire 100% of their fibers, but they also risk grave injury ...
Martin, H. Newell The Human Body: A Text-book of Anatomy, Physiology and Hygiene (New York: Henry Holt and Company, 1900) 62. ...
Rebounding improves coordination between the propreoceptors in the joints, the transmission of nerve impulses to and from the brain, transmission of nerve impulses and responsiveness of the muscle fibers. ...
This study assessed age and sex effects on muscle fibre adaptations to heavy-resistance strength training (ST). Twenty-two young men and women (20-30 years old) and 18 older men and women (65-75 years old) completed 9 weeks of heavy-resistance knee extension exercises with the dominant leg 3 days week−1; the non-dominant leg served as a within-subject, untrained control. Bilateral vastus lateralis muscle biopsies were obtained before and after ST for analysis of type I, IIa and IIx muscle fibre cross-sectional area (CSA) and fibre type distribution. One-repetition maximum (1-RM) strength was also assessed before and after ST. ST resulted in increased CSA of type I, IIa and IIx muscle fibres in the trained leg of young men, type I and IIa fibres in young women, type IIa fibres in older men, and type IIx fibres in older women (all P , 0.05). Analysis of fibre type distribution revealed a significant increase in the percentage of type I fibres (P , 0.05) along with a decrease in type IIx fibres ...
Muscle, motor unit and muscle fibre type-specific differences in force-generating capacity have been investigated for many years, but there is still no consensus regarding specific differences between slow- and fast-twitch muscles, motor units or muscle fibres. This is probably related to a number of different confounding factors disguising the function of the molecular motor protein myosin. We have therefore studied the force-generating capacity of specific myosin isoforms or combination of isoforms extracted from short single human muscle fibre segments in a modified single fibre myosin in vitro motility assay, in which an internal load (actin-binding protein) was added in different concentrations to evaluate the force-generating capacity. The force indices were the x-axis intercept and the slope of the relationship between the fraction of moving filaments and the α-actinin concentration. The force-generating capacity of the β/slow myosin isoform (type I) was weaker (P , 0.05) than the fast ...
TY - JOUR. T1 - Human skeletal muscle fibre contractile properties and proteomic profile. T2 - Adaptations to 3 weeks of unilateral lower limb suspension and active recovery. AU - Brocca, Lorenza. AU - Longa, Emanuela. AU - Cannavino, Jessica. AU - Seynnes, Olivier. AU - de Vito, Giuseppe. AU - Mcphee, Jamie. AU - Narici, Marco. AU - Pellegrino, Maria Antonietta. AU - Bottinelli, Roberto. PY - 2015/12/15. Y1 - 2015/12/15. N2 - Following disuse, muscle fibre function goes through adaptations such as a loss of specific force (PO/CSA) and an increase in unloaded shortening velocity, which could be a result of both quantitative changes (i.e. atrophy) and qualitative changes in protein pattern. The underlying mechanisms remain to be clarified. In addition, little is known about the recovery of muscle mass and strength following disuse. In the present study, we report an extensive dataset describing, in detail,the functional and protein content adaptations of skeletal muscle in response to both disuse ...
Current beef production has to meet the growing consumers demands for high quality beef, while concurrently increasing the resource efficiency. Meat quality is influenced by several factors. Milićević et al [1] found that the fatty acid profiles could affect the overall acceptability of meat; as well as influence several meat quality parameters, such as softness, hardness, oxidation stability, color and flavor. In addition, muscle fiber development is also known to have an important impact on the meat quality. Although the total number of skeletal muscle fibers is fixed in animals before birth [2], the composition of muscle fiber types varies during the life of an animal to adapt to different physiological requirements [3]. The contractile properties depend primarily on myosin heavy-chain isoforms (MyHCs) present within the thick filaments. In most mature mammalian skeletal striated muscles, four types of MyHC are expressed: I, IIa, IIx, and IIb [4]. The muscle fiber composition could ...
Skeletal muscle mass and strength are crucial determinants of health. Muscle mass loss is associated with weakness, fatigue, and insulin resistance. In fact, it is predicted that controlling muscle atrophy can reduce morbidity and mortality associated with diseases such as cancer cachexia and sarcopenia. We analyzed gene expression data from muscle of mice or human patients with diverse muscle pathologies and identified LMCD1 as a gene strongly associated with skeletal muscle function. We transiently expressed or silenced LMCD1 in mouse gastrocnemius muscle or in mouse primary muscle cells and determined muscle/cell size, targeted gene expression, kinase activity with kinase arrays, protein immunoblotting, and protein synthesis levels. To evaluate force, calcium handling, and fatigue, we transduced the flexor digitorum brevis muscle with a LMCD1-expressing adenovirus and measured specific force and sarcoplasmic reticulum Ca2+ release in individual fibers. Finally, to explore the relationship between
TY - JOUR. T1 - Effects of intermittent pressure imitating rolling manipulation on calcium ion homeostasis in human skeletal muscle cells. AU - Zhang, Hong. AU - Liu, Howe. AU - Lin, Qing. AU - Zhang, Guohui. AU - Mason, David C.. PY - 2016/8/26. Y1 - 2016/8/26. N2 - Background: Homeostasis imbalance of intracellular Ca2+ is one of the key pathophysiological factors in skeletal muscle injuries. Such imbalance can cause significant change in the metabolism of Ca2+-related biomarkers in skeletal muscle, such as superoxide dismutase (SOD), malondialdehyde (MDA) and creatine kinase (CK). Measurements of these biomarkers can be used to evaluate the degree of damage to human skeletal muscle cells (HSKMCs) injury. Rolling manipulation is the most popular myofascial release technique in Traditional Chinese Medicine. The mechanism of how this technique works in ameliorating muscle injury is unknown. This study aimed to investigate the possible Ca2+ mediated effects of intermittent pressure imitating ...
In skeletal muscle, an accumulation of lipid droplets (LDs) in the subsarcolemmal space is associated with insulin resistance, but the underlying mechanism is not clear. We aimed to investigate how the size, number and location of LDs are associated with insulin sensitivity and muscle fiber types, and are regulated by aerobic training and treatment with an erythropoiesis-stimulating agent (ESA) in healthy young untrained males. LD analyses were performed by quantitative transmission electron microscopy and insulin sensitivity was assessed by a hyperinsulinemic euglycemic clamp. At baseline, we found that only the diameter (and not the number) of individual subsarcolemmal LDs was negatively associated with insulin sensitivity (R2 = 0.20, P = 0.03, n = 29). Despite 34% (P = 0.004) fewer LDs, the diameter of individual subsarcolemmal LDs was 20% (P = 0.0004) larger in type 2 fibers than in type 1 fibers. Furthermore, aerobic training decreased the size of subsarcolemmal LDs in the type 2fibers, and ...
In skeletal muscle, an accumulation of lipid droplets (LDs) in the subsarcolemmal space is associated with insulin resistance, but the underlying mechanism is not clear. We aimed to investigate how the size, number and location of LDs are associated with insulin sensitivity and muscle fiber types, and are regulated by aerobic training and treatment with an erythropoiesis-stimulating agent (ESA) in healthy young untrained males. LD analyses were performed by quantitative transmission electron microscopy and insulin sensitivity was assessed by a hyperinsulinemic euglycemic clamp. At baseline, we found that only the diameter (and not the number) of individual subsarcolemmal LDs was negatively associated with insulin sensitivity (R2 = 0.20, P = 0.03, n = 29). Despite 34% (P = 0.004) fewer LDs, the diameter of individual subsarcolemmal LDs was 20% (P = 0.0004) larger in type 2 fibers than in type 1 fibers. Furthermore, aerobic training decreased the size of subsarcolemmal LDs in the type 2fibers, and ...
This is, to our knowledge, the first report describing active canonical Wnt together with YAP/Taz/TEAD signaling in adult skeletal muscle fibers. Using Axin2-lacZ reporter mice, we identified active canonical Wnt signaling in type II myofibers (Fig. 2) (Lustig et al., 2002). This mouse model is well established for tracing active canonical Wnt signaling since Axin2 is a direct target of β-catenin-mediated gene expression (Barolo, 2006). In fact, heterozygous Axin2-lacZ mice, without any known signs of haploinsufficiency, express muscular β-gal in type II muscle fibers, suggesting that active canonical Wnt signaling is present physiologically in adult muscle fibers (Fig. 2). In homozygous Axin2-lacZ mice, not only is the doubled lacZ gene dosage responsible for elevated Axin2-lacZ reporter expression, but also the derepression of canonical Wnt signaling, since Axin2 itself is a negative regulator and target of canonical Wnt signaling and therefore participates in a negative-feedback loop. In ...
Read "Sodium Channel NaV1.5 Expression is Enhanced in Cultured Adult Rat Skeletal Muscle Fibers, The Journal of Membrane Biology" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
The endurance exercise-training program induced substantial improvements in peak exercise capacity and work capacity in the study population at 3 and 12 months of training compared with control patients. The hypothesis that older patients condition predominantly by noncardiac adaptations is supported by the fact that the increases in peak aerobic exercise capacity were mediated primarily by an increase in peak exercise AVo2 Diff with no measurable increase in peak exercise cardiac output. The increase in peak AVo2 Diff was associated with adaptations of skeletal muscle fiber size, capillarity, and SDH activity with only subtle alterations in cardiac performance and no discernible alterations of peripheral arterial blood flow. The skeletal muscle adaptations consisted of an increased oxidative enzyme activity and an increased capillary density after 3 months of conditioning and an increased muscle fiber cross-sectional area after 12 months of conditioning. However, although directional changes of ...
TY - JOUR. T1 - The membrane potential of rat diaphragm muscle fibres and the effect of denerevation. AU - Bray, JJ. AU - Hawken, Michael. AU - Hubbard, JI. AU - Pockett, S. AU - Wilson, L. PY - 1976. Y1 - 1976. M3 - Article. VL - 255. SP - 651. EP - 667. JO - Journal of Physiology. JF - Journal of Physiology. SN - 0022-3751. ER - ...
Individual fibres were mounted between a force transducer and servomotor, and exposed to activating calcium solutions, as described previously [9]. Maximal tension (i.e. maximal force normalised to muscle fibre cross-sectional area (CSA)) was significantly lower in fast-twitch muscle fibres of PAH patients (Npatients=11, nfibres=112) than in control subjects (Npatients=8, nfibres=62) (mean±sem 192±5 versus 226±8 mN·mm−2, p,0.005; fig. 1b). Based on our permeabilised muscle fibre measurements, we observed no significant difference in fast-twitch muscle fibre CSA between groups (PAH versus control: 3387±280 versus 3307±242 µm2; p=0.84).. In muscle fibres, force is generated by the cyclic interaction between myosin-based cross-bridges and actin. Thus, to determine the underlying cause of the reduction in maximal tension, we studied cross-bridge cycling kinetics. In permeabilised muscle fibres, active force generation is determined by: 1) the fraction of strongly bound cross-bridges; 2) the ...
The expression of receptors and the mitogenic response to PDGF by C2 myoblasts, derived from adult mouse skeletal muscle, was investigated. Employing 125I-PDGF binding assays, we showed that the cells exhibit high level binding of PDGF-BB (approximately 165 x 10(3) molecules/cell at saturation) and much lower binding of the PDGF-AA and PDGF-AB (6-12 x 10(3) molecules/cell at saturation). This indicates that the C2 myoblasts express high levels of PDGF receptor beta-subunits and low levels of alpha-subunits. PDGF-BB enhances the proliferation of C2 cells maintained in 2% FCS by about fivefold. PDGF-AB had a moderate effect on cell proliferation (less than twofold) and PDGF-AA had no effect. Inverse effects of PDGF isoforms on the frequency of differentiated myoblasts were observed; the frequency of myosin-positive cells was reduced in the presence of PDGF-BB while PDGF-AA and PDGF-AB had no effect. PDGF may thus act to increase the number of myoblasts that participate in muscle regeneration ...
Acetylcholine receptors (AChRs) are highly concentrated in the postsynaptic membrane at the neuromuscular junction. To investigate mechanisms that lead to the formation or maintenance of this synaptic specialization, we generated transgenic mice in which regulatory elements from the AChR alpha or epsilon-subunit genes are linked to a gene for a reporter protein that is targeted to the nucleus (nlacZ). Both transgenes were selectively expressed and developmentally regulated in muscle; nuclei in both extrafusal (ordinary) and intrafusal (spindle) muscle fibers were labeled. Within individual muscle fibers from epsilon-nlacZ mice, nuclei near synaptic sites were nlacZ-positive, whereas extrasynaptic nuclei were nlacZ-negative. In contrast, nlacZ was expressed in both synaptic and extrasynaptic nuclei when under the control of regulatory elements from the AChR alpha-subunit gene; however, synaptic nuclei were somewhat more intensely stained than extrasynaptic nuclei in a minority of muscle fibers ...
Our results highlight the importance of using subject-specific data for accurate modelling and demonstrate the value of conducting comprehensive sensitivity analyses to assess the effects of uncertainties and errors in the choice of input variables.. The degree to which the model predictions match experimental data is highly dependent on how the muscles are represented. Our sensitivity analyses show that changing pennation angles has a much smaller effect on predicted bite force magnitudes than does changing muscle fibre length or intrinsic strength (figure 5a-c). This is to be expected because the latter variables directly impact on maximum muscle force. Altering the orientation of the modelled muscle strands, and thus the muscle force vectors also affects predicted bite force magnitudes (figure 5d). In our model, muscle wrapping has a greater effect than extreme values of pennation angle but this is less than the effect of using extreme values of muscle fibre length.. Bite force predictions ...
Regenerative coordination and remodeling of the intramuscular motoneuron network and neuromuscular connections are critical for restoring skeletal muscle function and physiological properties. The regulatory mechanisms of such coordination remain unclear, although both attractive and repulsive axon guidance molecules may be involved in the signaling pathway. Here we show that expression of a neural secreted chemorepellent semaphorin 3A (Sema3A) is remarkably upregulated in satellite cells of resident myogenic stem cells that are positioned beneath the basal lamina of mature muscle fibers, when treated with hepatocyte growth factor (HGF), established as an essential cue in muscle fiber growth and regeneration. When satellite cells were treated with HGF in primary cultures of cells or muscle fibers, Sema3A message and protein were upregulated as revealed by reverse transcription-polymerase chain reaction and immunochemical studies. Other growth factors had no inductive effect except for a slight ...