Search results for "Muscle fibers"
showing 10 items of 94 documents
Neural Activation During Submaximal Contractions Seems More Reflective of Neuromuscular Ageing than Maximal Voluntary Activation
2016
International audience; This study aimed at testing the hypothesis that differences in neural activation strategy during submaximal but not maximal plantarflexions exist between young and older men. Eleven young men (YM, 26 +/- 4 years) and thirteen old men (OM, 76 +/- 3 years) volunteered for the investigation. Maximal voluntary torque (MVT) was 38.2%, lower (p < 0.001) in OM than in YM, while voluntary activation was equivalent (similar to 97%). The relationship between the interpolated twitch torque and the voluntary torque (IT-VT relationship) was composite (curvilinear + exponential) for both age-groups. However, the OM showed accentuated concavity, as attested by the occurrence of the…
Universal spectral profile and dynamic evolution of muscle activation: A hallmark of muscle type and physiological state
2020
The skeletal muscle is an integrated multicomponent system with complex dynamics of continuous myoelectrical activation of various muscle types across time scales to facilitate muscle coordination among units and adaptation to physiological states. To understand the multiscale dynamics of neuromuscular activity, we investigated spectral characteristics of different muscle types across time scales and their evolution with physiological states. We hypothesized that each muscle type is characterized by a specific spectral profile, reflecting muscle composition and function, that remains invariant over time scales and is universal across subjects. Furthermore, we hypothesized that the myoelectr…
Effects of strength and endurance training on muscle fibrecharacteristics in elderly women
1997
The effects of 18 weeks' intensive strength and endurance training on fibre characteristics of the vastus lateralis muscle were studied in 76- to 78-year-old women. Type I and type IIa fibres constituted over 90% of the cell population and were almost equally represented. No changes were observed in the proportions of the different fibre types. When comparing the baseline and the 18-week measurements within the groups, the strength group showed a mean increase of 34% (P = 0.028) in mean type I fibre area. The frequency histograms showed an increased proportion of larger type I fibres after strength training and a decreased proportion of smaller type IIa fibres after endurance training. In t…
Reversible stress-induced lipid body formation in fast twitch rat myofibers
2012
We analyzed the existence of lipid bodies (LBs) in the fast twitch rat flexor digitorum brevis (FDB) myofibers and found that these structures were scarce. However, isolation procedure of the myofibers, heath shock, viral infection or the glycosylation inhibitor tunicamycin induced formation of the LBs, which were stationary structures flanking Z lines. We next infected FDB myofibers with recombinant Semliki Forest virus expressing caveolin 3-yellow fluorescent protein (cav3-YFP) since this chimeric protein was targeted to the LBs facilitating their further analysis. Photobleaching experiments showed that the LBs recovered cav 3-YFP extremely slowly, indicating that they were not continuous…
Protein targeting to the plasma membrane of adult skeletal muscle fiber: an organized mosaic of functional domains.
2001
The plasma membrane of differentiated skeletal muscle fibers comprises the sarcolemma, the transverse (T) tubule network, and the neuromuscular and muscle-tendon junctions. We analyzed the organization of these domains in relation to defined surface markers, beta-dystroglycan, dystrophin, and caveolin-3. These markers were shown to exhibit highly organized arrays along the length of the fiber. Caveolin-3 and beta-dystroglycan/dystrophin showed distinct, but to some extent overlapping, labeling patterns and both markers left transverse tubule openings clear. This labeling pattern revealed microdomains over the entire plasma membrane with the exception of the neuromuscular and muscle-tendon j…
Murine muscle engineered from dermal precursors: an in vitro model for skeletal muscle generation, degeneration and fatty infiltration.
2013
Skeletal muscle can be engineered by converting dermal precursors into muscle progenitors and differentiated myocytes. However, the efficiency of muscle development remains relatively low and it is currently unclear if this is due to poor characterization of the myogenic precursors, the protocols used for cell differentiation, or a combination of both. In this study, we characterized myogenic precursors present in murine dermospheres, and evaluated mature myotubes grown in a novel three-dimensional culture system. After 5-7 days of differentiation, we observed isolated, twitching myotubes followed by spontaneous contractions of the entire tissue-engineered muscle construct on an extracellul…
The muscleblind gene participates in the organization of Z-bands and epidermal attachments of Drosophila muscles and is regulated by Dmef2.
1998
We report the embryonic phenotype of muscleblind (mbl), a recently described Drosophila gene involved in terminal differentiation of adult ommatidia. mbl is a nuclear protein expressed late in the embryo in pharyngeal, visceral, and somatic muscles, the ventral nerve cord, and the larval photoreceptor system. All three mbl alleles studied exhibit a lethal phenotype and die as stage 17 embryos or first instar larvae. These larvae are partially paralyzed, show a characteristically contracted abdomen, and lack striation of muscles. Our analysis of the somatic musculature shows that the pattern of muscles is established correctly, and they form morphologically normal synapses. Ultrastructural a…
Regulation of type IV collagen gene expression and degradation in fast and slow muscles during dexamethasone treatment and exercise.
2003
Glucocorticoids have anti-anabolic effects on many tissues and can cause muscle atrophy. However, their effects on type IV collagen gene expression and degradation in skeletal muscle have not been studied previously. Rats were treated daily with dexamethasone or saline. Half the groups of experimental and control animals were also subjected to daily endurance or uphill running exercise to determine the possible preventive effects of exercise. After an experimental period of 3 or 10 days, the extensor digitorum longus, soleus and tibialis anterior muscles were studied. Dexamethasone treatment for 10 days reduced muscle weight and type IV collagen mRNA abundance in all muscles. Gene expressio…
Structural and functional features of human muscle-tendon unit.
2006
This paper reviews the architectural details and the in vivo behavior of the human muscle-tendon unit with the focus on the triceps surae and quadriceps femoris muscles. Recent advances in experimental techniques allow in vivo measurements of muscle-tendon architecture and function. In particular, the use of ultrasonography for measurement of tendon and muscle has expanded our knowledge in the last decade. Furthermore, the nuclear magnetic resonance imaging is opening up new insights not only for three-dimensional anatomical information but also for examining musculo-skeletal motion in vivo. While these two completely non-invasive methods provide kinematic data, in vivo force measurements s…
Diagnostic immunohistochemistry in neuromuscular disorders.
2005
Most neuromuscular disorders display only non-specific myopathological features in routine histological preparations. However, a number of proteins, including sarcolemmal, sarcomeric, and nuclear proteins as well as enzymes with defects responsible for neuromuscular disorders, have been identified during the past two decades, allowing a more specific and firm diagnosis of muscle diseases. Identification of protein defects relies predominantly on immunohistochemical preparations and on Western blot analysis. While immunohistochemistry is very useful in identifying abnormal expression of primary protein abnormalities in recessive conditions, it is less helpful in detecting primary defects in …