Morphometric properties and innervation of muscle compartments in rat medial gastrocnemius

Taborowska, M.; Bukowska, D; Drzymała‐Celichowska, Hanna; Mierzejewska-Krzyzowska, B; Celichowski, Jan

doi:10.1080/08990220.2016.1254609

Cited by 7 publications

(7 citation statements)

References 52 publications

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“…The transitory force decrease needs longer trains of high-frequency stimuli, which supports disturbances in the force transmission as a possible mechanism. This suggestion is supported by the observation that transitory force decrease occurs most frequently in FR MUs, distributed in the proximal compartment of the medial gastrocnemius [12] and covering only 40% of the muscle length [26], indicating that force must be transmitted to the tendon by long intramuscular collagen structures.…”

Section: Discussionmentioning

confidence: 74%

“…A previous study suggested that the transitory force decrease probably has a biomechanical background, involving processes of the force transmission by collagen within the muscle, because the phenomenon was found for only one-half of studied MUs, most frequently fast-resistant (FR) ones [16]. These units in the studied medial gastrocnemius muscle were found to be distributed predominantly within the proximal compartment [27], corresponding to only 40% of the muscle length [26], which indicates that their force is transmitted by collagen structures in the distal compartment.…”

Section: Introductionmentioning

confidence: 99%

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Biomechanical conditioning of the motor unit transitory force decrease following a reduction in stimulation rate

Rakoczy¹,

Kryściak²,

Drzymała‐Celichowska³

et al. 2020

BMC Sports Sci Med Rehabil

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Background The biomechanical background of the transitory force decrease following a sudden reduction in the stimulation frequency under selected experimental conditions was studied on fast resistant motor units (MUs) of rat medial gastrocnemius in order to better understand the mechanisms of changes in force transmission. Methods Firstly, MUs were stimulated with three-phase trains of stimuli (low–high–low frequency pattern) to identify patterns when the strongest force decrease (3–36.5%) following the middle high frequency stimulation was observed. Then, in the second part of experiments, the MUs which presented the largest force decrease in the last low-frequency phase were alternatively tested under one of five conditions to analyse the influence of biomechanical factors of the force decrease: (1) determine the influence of muscle stretch on amplitude of the force decrease, (2) determine the numbers of interpulse intervals necessary to evoke the studied phenomenon, (3) study the influence of coactivation of other MUs on the studied force decrease, (4) test the presence of the transitory force decrease at progressive changes in stimulation frequency, (5) and perform mathematical analysis of changes in twitch-shape responses to individual stimuli within a tetanus phase with the studied force decrease. Results Results indicated that (1) the force decrease was highest when the muscle passive stretch was optimal for the MU twitch (100 mN); (2) the middle high-frequency burst of stimuli composed of at least several pulses was able to evoke the force decrease; (3) the force decrease was eliminated by a coactivation of 10% or more MUs in the examined muscle; (4) the transitory force decrease occured also at the progressive decrease in stimulation frequency; and (5) a mathematical decomposition of contractions with the transitory force decrease into twitch-shape responses to individual stimuli revealed that the force decrease in question results from the decrease of twitch forces and a shortening in contraction time whereas further force restitution is related to the prolongation of relaxation. Conclusions High sensitivity to biomechanical conditioning indicates that the transitory force decrease is dependent on disturbances in the force transmission predominantly by collagen surrounding active muscle fibres.

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Section: Discussionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Biomechanical conditioning of the motor unit transitory force decrease following a reduction in stimulation rate

Rakoczy¹,

Kryściak²,

Drzymała‐Celichowska³

et al. 2020

BMC Sports Sci Med Rehabil

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“…The above reported by us functional changes in MUs properties, observed predominantly in FR MUs as early as after 2 weeks of training, such as an increase in resistance to fatigue, were accompanied by a transient significant increase in the expression of slow myosin heavy chain mRNA and Ca 2+ ATPase 2 mRNA in MGS ( Fig 6A and 6B ). These results show that fast-to-slow transition at mRNA level occurs at the early stage of training and takes place in the slow part of the muscle (MGS, Fig 6A and 6B ) with higher content of fatigue resistant MUs [ 39 , 41 ]. No effect of training on the parvalbumin expression both in the fast and slow parts of gastrocnemius has been observed (Figs 5C and 6C ).…”

Section: Discussionmentioning

confidence: 85%

“…The red (slow, MGS) and white (fast, MGF) portions of the MG muscle were carefully separated and immediately frozen. The MGF is a part located distally, predominantly corresponding to the distal compartment of the muscle [ 39 ] which consists of fast-twitch glycolytic fibres (20% type IIX and 80% IIB muscle fibres). The MGS is a deep and proximal part, corresponding to the proximal compartment.…”

Section: Methodsmentioning

confidence: 99%

Adaptation of motor unit contractile properties in rat medial gastrocnemius to treadmill endurance training: Relationship to muscle mitochondrial biogenesis

Kryściak¹,

Majerczak

Kryściak³

et al. 2018

PLoS ONE

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This study aimed at investigating the effects of 2, 4 and 8 weeks of endurance training on the contractile properties of slow (S), fast fatigue resistant (FR) and fast fatigable (FF) motor units (MUs) in rat medial gastrocnemius (MG) in relation to the changes in muscle mitochondrial biogenesis. The properties of functionally isolated MUs were examined in vivo. Mitochondrial biogenesis was judged based on the changes in mitochondrial DNA copy number (mtDNA), the content of the electron transport chain (ETC) proteins and PGC-1α in the MG. Moreover, the markers of mitochondria remodeling mitofusins (Mfn1, Mfn2) and dynamin-like protein (Opa1) were studied using qPCR. A proportion of FR MUs increased from 37.9% to 50.8% and a proportion of FF units decreased from 44.7% to 26.6% after 8 weeks of training. The increased fatigue resistance, shortened twitch duration, and increased ability to potentiate force were found as early as after 2 weeks of endurance training, predominantly in FR MUs. Moreover, just after 2 weeks of the training an enhancement of the mitochondrial network remodeling was present as judged by an increase in expression of Mfn1, Opa1 and an increase in PGC-1α in the slow part of MG. Interestingly, no signs of intensification of mitochondrial biogenesis assessed by ETC proteins content and mtDNA in slow and fast parts of gastrocnemius were found at this stage of the training. Nevertheless, after 8 weeks of training an increase in the ETC protein content was observed, but mainly in the slow part of gastrocnemius. Concluding, the functional changes in MUs’ contractile properties leading to the enhancement of muscle performance accompanied by an activation of signalling that controls the muscle mitochondrial network reorganisation and mitochondrial biogenesis belong to an early muscle adaptive responses that precede an increase in mitochondrial ETC protein content.

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“…The proximal segment of the SH muscle belly receives efferent fibers from C1-3 in addition to branches from XII, which also innervates the distal segment (Müntener et al 1980). There is also evidence of distinct sciatic motor efferents supplying the distal versus proximal and mid-belly compartments of the rat MG (De Ruiter et al 1995a, 1995bRijkelijkhuizen et al 2003;Prodanov et al 2005;Taborowska et al 2016). Differing fiber-type compositions also exist within these compartments of the rat MG, with the proximal compartment having a higher oxidative capacity than that of the distal compartment (De Ruiter et al 1995b;Furrer et al 2013).…”

Section: Segment Strain Heterogeneitymentioning

confidence: 99%

Different Segments within Vertebrate Muscles Can Operate on Different Regions of Their Force–Length Relationships

Ahn

Konow

Tijs

et al. 2018

Integrative and Comparative Biology

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To relate in vivo behavior of fascicle segments within a muscle to their in vitro force-length relationships, we examined the strain behavior of paired segments within each of three vertebrate muscles. After determining in vivo muscle activity patterns and length changes of in-series segments within the semimembranosus muscle (SM) in the American Toad (Bufo americanus) during hopping and within the sternohyoid (SH) muscle in the rat (Rattus rattus) during swallowing, and of spatially separated fascicles within the medial gastrocnemius (MG) muscle in the rat during trotting, we measured their corresponding in vitro (toad) or in situ (rat) force-length relationships (FLRs). For all three muscles, in vivo strain heterogeneity lasted for about 36-57% of the behavior cycle, during which one segment or fascicle shortened while the other segment or fascicle simultaneously lengthened. In the toad SM, the proximal segment shortened from the descending limb across the plateau of its FLR from 1.12 to 0.91 of its optimal length (Lo), while the distal segment lengthened (by 0.04 ± 0.04 Lo) before shortening down the ascending limb from 0.94 to 0.83 Lo. In the rat SH muscle, the proximal segment tended to shorten on its ascending limb from 0.90 to 0.85 Lo while the distal segment tended to lengthen across Lo (0.96-1.12 Lo). In the rat MG muscle, in vivo strains of proximal fascicles ranged from 0.72 to 1.02 Lo, while the distal fascicles ranged from 0.88 to 1.11 Lo. Even though the timing of muscle activation patterns were similar between segments, the heterogeneous strain patterns of fascicle segments measured in vivo coincided with different operating ranges across their FLRs simultaneously, implying differences in force-velocity behavior as well. The three vertebrate skeletal muscles represent a diversity of fiber architectures and functions and suggest that patterns of in vivo contractile strain and the operating range over the FLR in one muscle region does not necessarily represent other regions within the same muscle.

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Morphometric properties and innervation of muscle compartments in rat medial gastrocnemius

Cited by 7 publications

References 52 publications

Biomechanical conditioning of the motor unit transitory force decrease following a reduction in stimulation rate

Biomechanical conditioning of the motor unit transitory force decrease following a reduction in stimulation rate

Adaptation of motor unit contractile properties in rat medial gastrocnemius to treadmill endurance training: Relationship to muscle mitochondrial biogenesis

Different Segments within Vertebrate Muscles Can Operate on Different Regions of Their Force–Length Relationships

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