scholarly journals Caracterização do exercício voluntário em discos de corrida e resposta adaptativa do músculo flexor digitorum brevis em camundongos

2019 ◽  
Author(s):  
Gustavo Manzanares ◽  
Paulo Guimaraes Gandra ◽  
Guilherme Brito da Silva
Keyword(s):  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

O exercício físico melhora a patofisiologia de doenças crônicas e promove o envelhecimento saudável. Um modelo muito utilizado para o estudo dos efeitos do exercício em camundongos é a corrida voluntária, que pode ser realizada em rodas de corrida verticais ou discos de corrida. O músculo flexor digitorum brevis (FDB) é pequeno e superficial, o que facilita a transfecção in vivo e preparações com fibras isoladas. Como não é claro se o FDB responde à corrida voluntária, o seu uso em estudos sobre as respostas ao exercício ainda é muito limitado. Portanto, os objetivos deste projeto são: 1) desenvolver um sistema de discos de corrida e caracterizar os parâmetros de corrida em camundongos; 2) definir se o músculo FDB apresenta respostas adaptativas à corrida voluntária.

scholarly journals Consequences of SUR2[A478V] Mutation in Skeletal Muscle of Murine Model of Cantu Syndrome

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1791
Author(s):  
Rosa Scala ◽  
Fatima Maqoud ◽  
Nicola Zizzo ◽  
Giuseppe Passantino ◽  
Antonietta Mele ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Katp Channel ◽  
Ex Vivo ◽  
Channel Modulation ◽  
Flexor Digitorum Brevis ◽  
Inflammatory Edema ◽  
Flexor Digitorum ◽  
Channel Currents

(1) Background: Cantu syndrome (CS) arises from gain-of-function (GOF) mutations in the ABCC9 and KCNJ8 genes, which encode ATP-sensitive K+ (KATP) channel subunits SUR2 and Kir6.1, respectively. Most CS patients have mutations in SUR2, the major component of skeletal muscle KATP, but the consequences of SUR2 GOF in skeletal muscle are unknown. (2) Methods: We performed in vivo and ex vivo characterization of skeletal muscle in heterozygous SUR2[A478V] (SUR2wt/AV) and homozygous SUR2[A478V] (SUR2AV/AV) CS mice. (3) Results: In SUR2wt/AV and SUR2AV/AV mice, forelimb strength and diaphragm amplitude movement were reduced; muscle echodensity was enhanced. KATP channel currents recorded in Flexor digitorum brevis fibers showed reduced MgATP-sensitivity in SUR2wt/AV, dramatically so in SUR2AV/AV mice; IC50 for MgATP inhibition of KATP currents were 1.9 ± 0.5 × 10−5 M in SUR2wt/AV and 8.6 ± 0.4 × 10−6 M in WT mice and was not measurable in SUR2AV/AV. A slight rightward shift of sensitivity to inhibition by glibenclamide was detected in SUR2AV/AV mice. Histopathological and qPCR analysis revealed atrophy of soleus and tibialis anterior muscles and up-regulation of atrogin-1 and MuRF1 mRNA in CS mice. (4) Conclusions: SUR2[A478V] “knock-in” mutation in mice impairs KATP channel modulation by MgATP, markedly so in SUR2AV/AV, with atrophy and non-inflammatory edema in different skeletal muscle phenotypes.

scholarly journals Effects of myofiber isolation technique on sarcolemma biomechanics

BioTechniques ◽  
2020 ◽  
Vol 69 (5) ◽  
pp. 388-391
Author(s):  
Karla P Garcia-Pelagio ◽  
Stephen JP Pratt ◽  
Richard M Lovering
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Sarcomere Length ◽  
Biomechanical Properties ◽  
Isolation Technique ◽  
Enzymatic Dissociation ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Biomechanical Measurements

Isolated myofibers are commonly used to understand the function of skeletal muscle in vivo. This can involve single isolated myofibers obtained from dissection or from enzymatic dissociation. Isolation via dissection allows control of sarcomere length and preserves tendon attachment but is labor-intensive, time-consuming and yields few viable myofibers. In contrast, enzymatic dissociation is fast and facile, produces hundreds of myofibers, and more importantly reduces the number of muscles/animals needed for studies. Biomechanical properties of the sarcolemma have been studied using myofibers from the extensor digitorum longus, but this has been limited to dissected myofibers, making data collection slow and difficult. We have modified this tool to perform biomechanical measurements of the sarcolemma in dissociated myofibers from the flexor digitorum brevis.

Calsequestrin (CASQ1) rescues function and structure of calcium release units in skeletal muscles of CASQ1-null mice

2012 ◽  
Vol 302 (3) ◽  
pp. C575-C586 ◽  
Author(s):  
Mirta Tomasi ◽  
Marta Canato ◽  
Cecilia Paolini ◽  
Marco Dainese ◽  
Carlo Reggiani ◽  
...  
Keyword(s):  
Skeletal Muscles ◽  
Calcium Release ◽  
Fluorescent Protein ◽  
Adaptive Mechanisms ◽  
Flexor Digitorum Brevis ◽  
Green Fluorescent ◽  
Flexor Digitorum ◽  
Fast Twitch ◽  
Terminal Cisternae

Amplitude of Ca2+ transients, ultrastructure of Ca2+ release units, and molecular composition of sarcoplasmic reticulum (SR) are altered in fast-twitch skeletal muscles of calsequestrin-1 (CASQ1)-null mice. To determine whether such changes are directly caused by CASQ1 ablation or are instead the result of adaptive mechanisms, here we assessed ability of CASQ1 in rescuing the null phenotype. In vivo reintroduction of CASQ1 was carried out by cDNA electro transfer in flexor digitorum brevis muscle of the mouse. Exogenous CASQ1 was found to be correctly targeted to the junctional SR (jSR), as judged by immunofluorescence and confocal microscopy; terminal cisternae (TC) lumen was filled with electron dense material and its width was significantly increased, as judged by electron microscopy; peak amplitude of Ca2+ transients was significantly increased compared with null muscle fibers transfected only with green fluorescent protein (control); and finally, transfected fibers were able to sustain cytosolic Ca2+ concentration during prolonged tetanic stimulation. Only the expression of TC proteins, such as calsequestrin 2, sarcalumenin, and triadin, was not rescued as judged by Western blot. Thus our results support the view that CASQ1 plays a key role in both Ca2+ homeostasis and TC structure.

scholarly journals Moderately elevated extracellular [K+] potentiates submaximal force and power in skeletal muscle via increased [Ca2+]i during contractions

2019 ◽  
Vol 317 (5) ◽  
pp. C900-C909 ◽  
Author(s):  
Katja K. Pedersen ◽  
Arthur J. Cheng ◽  
Håkan Westerblad ◽  
Jonas H. Olesen ◽  
Kristian Overgaard
Keyword(s):  
Skeletal Muscle ◽  
Peak Power ◽  
Extensor Digitorum Longus ◽  
Isometric Force ◽  
Flexor Digitorum Brevis ◽  
Muscle Types ◽  
Flexor Digitorum ◽  
Moderate Elevation ◽  
Different Levels

The extracellular K+ concentration ([K+]o) increases during physical exercise. We here studied whether moderately elevated [K+]o may increase force and power output during contractions at in vivo-like subtetanic frequencies and whether such potentiation was associated with increased cytosolic free Ca2+ concentration ([Ca2+]i) during contractions. Isolated whole soleus and extensor digitorum longus (EDL) rat muscles were incubated at different levels of [K+]o, and isometric and dynamic contractility were tested at various stimulation frequencies. Furthermore, [Ca2+]i at rest and during contraction was measured along with isometric force in single mouse flexor digitorum brevis (FDB) fibers exposed to elevated [K+]o. Elevating [K+]o from 4 mM up to 8 mM (soleus) and 11 mM (EDL) increased isometric force at subtetanic frequencies, 2–15 Hz in soleus and up to 50 Hz in EDL, while inhibition was seen at tetanic frequency in both muscle types. Elevating [K+]o also increased peak power of dynamic subtetanic contractions, with potentiation being more pronounced in EDL than in soleus muscles. The force-potentiating effect of elevated [K+]o was transient in FDB single fibers, reaching peak after ~4 and 2.5 min in 9 and 11 mM [K+]o, respectively. At the time of peak potentiation, force and [Ca2+]i during 15-Hz contractions were significantly increased, whereas force was slightly decreased and [Ca2+]i unchanged during 50-Hz contractions. Moderate elevation of [K+]o can transiently potentiate force and power during contractions at subtetanic frequencies, which can be explained by a higher [Ca2+]i during contractions.

scholarly journals Percutaneous flexor digitorum brevis tenotomy: An anatomical study

2021 ◽  
Author(s):  
Paulo Carvalho ◽  
Miki Dalmau-Pastor ◽  
Caroline Lozi ◽  
Matheus Souza ◽  
Julien Lucas-Y-Hernandez ◽  
...  
Keyword(s):  
Anatomical Study ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

Intramuscular Hemangioma of Flexor Digitorum Brevis Muscle

2012 ◽  
Vol 91 (10) ◽  
pp. 910 ◽  
Author(s):  
Mustafa Ozsahin ◽  
Mustafa Uslu ◽  
Erkan Inanmaz ◽  
Ramazan Buyukkaya ◽  
Havva Erdem
Keyword(s):  
Flexor Digitorum Brevis ◽  
Intramuscular Hemangioma ◽  
Flexor Digitorum

scholarly journals Differential impact of mitochondrial positioning on mitochondrial Ca2+ uptake and Ca2+ spark suppression in skeletal muscle

2011 ◽  
Vol 301 (5) ◽  
pp. C1128-C1139 ◽  
Author(s):  
Ann E. Rossi ◽  
Simona Boncompagni ◽  
Lan Wei ◽  
Feliciano Protasi ◽  
Robert T. Dirksen
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Osmotic Shock ◽  
Progressive Increase ◽  
Tetanic Stimulation ◽  
Differential Impact ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Activity Dependent ◽  
Old Mice

Muscle contraction requires ATP and Ca2+ and, thus, is under direct control of mitochondria and the sarcoplasmic reticulum. During postnatal skeletal muscle maturation, the mitochondrial network exhibits a shift from a longitudinal (“longitudinal mitochondria”) to a mostly transversal orientation as a result of a progressive increase in mitochondrial association with Ca2+ release units (CRUs) or triads (“triadic mitochondria”). To determine the physiological implications of this shift in mitochondrial disposition, we used confocal microscopy to monitor activity-dependent changes in myoplasmic (fluo 4) and mitochondrial (rhod 2) Ca2+ in single flexor digitorum brevis (FDB) fibers from 1- to 4-mo-old mice. A robust and sustained Ca2+ accumulation in triadic mitochondria was triggered by repetitive tetanic stimulation (500 ms, 100 Hz, every 2.5 s) in FDB fibers from 4-mo-old mice. Specifically, mitochondrial rhod 2 fluorescence increased 272 ± 39% after a single tetanus and 412 ± 45% after five tetani and decayed slowly over 10 min following the final tetanus. Similar results were observed in fibers expressing mitochondrial pericam, a mitochondrial-targeted ratiometric Ca2+ indicator. Interestingly, sustained mitochondrial Ca2+ uptake following repetitive tetanic stimulation was similar for triadic and longitudinal mitochondria in FDB fibers from 1-mo-old mice, and both mitochondrial populations were found by electron microscopy to be continuous and structurally tethered to the sarcoplasmic reticulum. Conversely, the frequency of osmotic shock-induced Ca2+ sparks per CRU density decreased threefold (from 3.6 ± 0.2 to 1.2 ± 0.1 events·CRU−1·min−1·100 μm−2) during postnatal development in direct linear correspondence ( r2 = 0.95) to an increase in mitochondrion-CRU pairing. Together, these results indicate that mitochondrion-CRU association promotes Ca2+ spark suppression but does not significantly impact mitochondrial Ca2+ uptake.

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