scholarly journals Preliminary Observations on Skeletal Muscle Adaptation and Plasticity in Homer 2-/- Mice

Metabolites ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 642
Author(s):  
Paola Lorenzon ◽  
Sandra Furlan ◽  
Barbara Ravara ◽  
Alessandra Bosutti ◽  
Gabriele Massaria ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Ring Finger ◽  
Muscle Adaptation ◽  
Rt Pcr ◽  
Cross Sectional ◽  
Longus Muscle ◽  
Confocal Immunofluorescence ◽  
Electrophysiological Measurements ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

Homer represents a diversified family of scaffold and transduction proteins made up of several isoforms. Here, we present preliminary observations on skeletal muscle adaptation and plasticity in a transgenic model of Homer 2-/- mouse using a multifaceted approach entailing morphometry, quantitative RT-PCR, confocal immunofluorescence, and electrophysiology. Morphometry shows that Soleus muscle (SOL), at variance with Extensor digitorum longus muscle (EDL) and Flexor digitorum brevis muscle (FDB), displays sizable reduction of fibre cross-sectional area compared to the WT counterparts. In SOL of Homer 2-/- mice, quantitative RT-PCR indicated the upregulation of Atrogin-1 and Muscle ring finger protein 1 (MuRF1) genes, and confocal immunofluorescence showed the decrease of neuromuscular junction (NMJ) Homer content. Electrophysiological measurements of isolated FDB fibres from Homer 2-/- mice detected the exclusive presence of the adult ε-nAChR isoform excluding denervation. As for NMJ morphology, data were not conclusive, and further work is needed to ascertain whether the null Homer 2 phenotype induces any endplate remodelling. Within the context of adaptation and plasticity, the present data show that Homer 2 is a co-regulator of the normotrophic status in a muscle specific fashion.

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 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.

Effect of electrical stimulation on intracellular triacylglycerol in isolated skeletal muscle

1990 ◽  
Vol 68 (1) ◽  
pp. 348-354 ◽  
Author(s):  
J. F. Hopp ◽  
W. K. Palmer
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Glucose Control ◽  
Muscle Preparation ◽  
Bicarbonate Buffer ◽  
Intermittent Stimulation ◽  
Flexor Digitorum Brevis ◽  
Muscle Groups ◽  
Flexor Digitorum

The contribution of intracellular triacylglycerol (TG) as a substrate for skeletal muscle during electrical stimulation is equivocal. Therefore, the purpose of this study was to investigate the effect of electrical stimulation on the TG content in the isolated intact rat flexor digitorum brevis skeletal muscle preparation by use of two different stimulation protocols. Muscles were electrically stimulated for 1 h either continuously at 1 Hz or intermittently (30 s on, 60 s off) at 5 Hz while incubated in 21 degrees C Krebs bicarbonate buffer (pH 7.4) that contained 11 mM glucose. Control muscles were either frozen immediately after excision or incubated for 1 h. TG content was significantly decreased (P less than 0.05) compared with control concentrations in both stimulated muscle groups, with the greatest reduction (60%) occurring after 5-Hz intermittent stimulation. These data indicate that intramuscular TG is hydrolyzed in response to electrical stimulation in the isolated flexor digitorum brevis muscle preparation. In addition, the type of stimulation (higher frequency intermittent vs. lower frequency continuous) employed influences the amount of intracellular TG hydrolyzed.

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.

scholarly journals Sarcolipin overexpression improves muscle energetics and reduces fatigue

2015 ◽  
Vol 118 (8) ◽  
pp. 1050-1058 ◽  
Author(s):  
Danesh H. Sopariwala ◽  
Meghna Pant ◽  
Sana A. Shaikh ◽  
Sanjeewa A. Goonasekera ◽  
Jeffery D. Molkentin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Performance ◽  
Force Frequency ◽  
Frequency Curve ◽  
Muscle Energetics ◽  
Store Operated Calcium Entry ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Muscle Contractile ◽  
Frequency Curves

Sarcolipin (SLN) is a regulator of sarcoendoplasmic reticulum calcium ATPase in skeletal muscle. Recent studies using SLN-null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression ( Sln OE) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/fatigue, and metabolic rate in whole animals and isolated muscle. We found that Sln OE mice are more resistant to fatigue and can run significantly longer distances than wild-type (WT). Studies with isolated extensor digitorum longus (EDL) muscles showed that Sln OE EDL produced higher twitch force than WT. The force-frequency curves were not different between WT and Sln OE EDLs, but at lower frequencies the pyruvate-induced potentiation of force was significantly higher in Sln OE EDL. SLN overexpression did not alter the twitch and force-frequency curve in isolated soleus muscle. However, during a 10-min fatigue protocol, both EDL and soleus from Sln OE mice fatigued significantly less than WT muscles. Interestingly, Sln OE muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in Sln OE EDL, suggesting increased glycolytic capacity. We also found an increase in store-operated calcium entry (SOCE) in isolated flexor digitorum brevis fibers of Sln OE compared with WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity by increasing SOCE and muscle energetics.

Influence of electrical stimulation on a fast-twitch muscle in aging rats

1991 ◽  
Vol 71 (5) ◽  
pp. 1921-1928 ◽  
Author(s):  
T. J. Walters ◽  
H. L. Sweeney ◽  
R. P. Farrar
Keyword(s):  
Electrical Stimulation ◽  
Fiber Type ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Flexor Digitorum Longus ◽  
Cross Sectional ◽  
Fischer 344 ◽  
Longus Muscle ◽  
Flexor Digitorum ◽  
Fast Twitch

Recently we observed that the flexor digitorum longus muscle of the Fischer 344 rat, which is comprised primarily of type IIb muscle, does not change in size, fiber type, or physiological characteristics during senescence [Am. J. Physiol. 258 (Cell Physiol. 27): C1031-C1035, 1990]. This muscle was utilized to determine whether a predominantly fast-twitch glycolytic muscle would respond to tonic electrical stimulation (ES) with the same degree of fiber-type transformation in aging and young rats. The extent of transformation was quantified by measuring the contractile and metabolic properties, as well as the fiber-type composition, of the flexor digitorum longus muscle after ES (10 Hz, 8 h/day) imposed on the tibial nerve for periods of 0–90 days in young adult (YG; 6–8 mo), middle-aged (MA; 16–18 mo), and senescent (SN; 26–28 mo) male Fischer 344 rats. Although ES induced a IIb-to-IIa fiber-type shift in all groups, in the SN rats the shift was significantly less pronounced at the intermediate time points and remained incomplete after 90 days, compared with YG and MA rats. ES resulted in a reduction in tetanic tension (Po), which in the YG and MA rats was due to a reduction in muscle cross-sectional area. In the SN rats the reduced Po was due to a combined loss of cross-sectional area and specific tension (Po, N/cm2). Contraction and half-relaxation times were largely unaffected by ES, and maximal velocity of unloaded shortening declined throughout ES in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Intramedular transfer of the flexor digitorum brevis tendon for the correction of clawtoe/hammertoe deformity: A cross-sectional study

2021 ◽  
Vol 234 ◽  
pp. 151646
Author(s):  
Julia Cosín-Matamoros ◽  
Ricardo Becerro-de-Bengoa-Vallejo ◽  
Marta Elena Losa-Iglesias ◽  
Israel Casado-Hernández ◽  
María Benito-de-Pedro ◽  
...  
Keyword(s):  
Cross Sectional Study ◽  
Sectional Study ◽  
Cross Sectional ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

scholarly journals Characterization and utilization of the flexor digitorum brevis for assessing skeletal muscle function

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Michael D. Tarpey ◽  
Adam J. Amorese ◽  
Nicholas P. Balestrieri ◽  
Terence E. Ryan ◽  
Cameron A. Schmidt ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Function ◽  
Skeletal Muscle Function ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

Ouabain stimulates unidirectional and net potassium efflux in resting mammalian skeletal muscle

2001 ◽  
Vol 79 (11) ◽  
pp. 932-941 ◽  
Author(s):  
Thomas J Hawke ◽  
Sarah Lessard ◽  
Lisa Vickery ◽  
Shonda L Lipskie ◽  
Michael I Lindinger
Keyword(s):  
Skeletal Muscle ◽  
Mammalian Skeletal Muscle ◽  
Potassium Efflux ◽  
Hindlimb Muscle ◽  
Flexor Digitorum Brevis ◽  
Baseline Values ◽  
Flexor Digitorum ◽  
Subsequent Addition

The present study compared ouabain-sensitive unidirectional K+ flux into (JinK) and out of (JoutK) perfused rat hindlimb skeletal muscle in situ and mouse flexor digitorum brevis (FDB) in vitro. In situ, 5 mM ouabain inhibited 54 ± 4% of the total JinK in 28 ± 1 min, and increased the net and unidirectional efflux of K+ within 4 min. In contrast, 1.8 mM ouabain inhibited 40 ± 8% of the total JinK in 38 ± 2 min, but did not significantly affect JoutK. In vitro, 1.8 and 0.2 mM ouabain decreased JinK to a greater extent (83 ± 5%) than in situ, but did not significantly affect 42K loss rate compared with controls. The increase in unidirectional K+ efflux (JoutK) with 5 mM ouabain in situ was attributed to increased K+ efflux through cation channels, since addition of barium (1 mM) to ouabain-perfused muscles returned JoutK to baseline values within 12 min. Perfusion with 5 mM ouabain plus 2 mM tetracaine for 30 min decreased JinK 46 ± 9% (0.30 ± 0.03 to 0.16 ± 0.02 µmol·min–1·g–1), however tetracaine was unable to abolish the ouabain-induced increase in unidirectional K+ efflux. In both rat hindlimb and mouse FDB, tetracaine had no effect on JoutK. Perfusion of hindlimb muscle with 0.1 mM tetrodotoxin (TTX, a Na+ channel blocker) decreased JinK by 15 ± 1%, but had no effect on JoutK; subsequent addition of ouabain (5 mM) decreased JinK a further 32 ± 2%. The ouabain-induced increase in unidirectional K+ efflux did not occur when TTX was perfused prior to and during perfusion with 5 mM ouabain. We conclude that 5 mM ouabain increases the unidirectional efflux of K+ from skeletal muscle through a barium and TTX-sensitive pathway, suggestive of voltage sensitive Na+ channels, in addition to inhibiting Na+/K+-ATPase activity.Key words: cardiac glycoside, Na,K pump, K+ channels, Na+ channels, perfused rat hindlimb, flexor digitorum brevis, TTX, barium, tetracaine.

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