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American Journal of Physiology. Heart... Jan 2019Peripheral artery disease (PAD) in the lower extremities often leads to intermittent claudication. In the present study, we proposed a low-dose DCE MRI protocol for...
Peripheral artery disease (PAD) in the lower extremities often leads to intermittent claudication. In the present study, we proposed a low-dose DCE MRI protocol for quantifying calf muscle perfusion stimulated with plantar flexion and multiple new metrics for interpreting perfusion maps, including the ratio of gastrocnemius over soleus perfusion (G/S; for assessing the vascular redistribution between the two muscles) and muscle perfusion normalized by whole body perfusion (for quantifying the muscle's active hyperemia). Twenty-eight human subjects participated in this Institutional Review Board-approved study, with 10 healthy subjects ( group A) for assessing interday reproducibility and 8 healthy subjects ( group B) for exploring the relationship between plantar-flexion load and induced muscle perfusion. In a pilot group of five elderly healthy subjects and five patients with PAD ( group C), we proposed a protocol that measured perfusion for a low-intensity exercise and for an exhaustion exercise in a single MRI session. In group A, perfusion estimates for calf muscles were highly reproducible, with correlation coefficients of 0.90-0.93. In group B, gastrocnemius perfusion increased linearly with the exercise workload ( P < 0.05). With the low-intensity exercise, patients with PAD in group C showed substantially lower gastrocnemius perfusion compared with elderly healthy subjects [43.4 (SD 23.5) vs. 106.7 (SD 73.2) ml·min·100 g]. With exhaustion exercise, G/S [1.0 (SD 0.4)] for patients with PAD was lower than both its low-intensity level [1.9 (SD 1.3)] and the level in elderly healthy subjects [2.7 (SD 2.1)]. In conclusion, the proposed MRI protocol and the new metrics are feasible for quantifying exercise-induced muscle hyperemia, a promising functional test of PAD. NEW & NOTEWORTHY To quantitatively map exercise-induced hyperemia in calf muscles, we proposed a high-resolution MRI method shown to be highly reproducible and sensitive to exercise load. With the use of low contrast, it is feasible to measure calf muscle hyperemia for both low-intensity and exhaustion exercises in a single MRI session. The newly proposed metrics for interpreting perfusion maps are promising for quantifying intermuscle vascular redistribution or a muscle's active hyperemia.
Topics: Adult; Ankle; Exercise; Female; Humans; Hyperemia; Magnetic Resonance Imaging; Male; Middle Aged; Muscle, Skeletal; Peripheral Arterial Disease
PubMed: 30388024
DOI: 10.1152/ajpheart.00537.2018 -
The Biochemical Journal May 1985
Review
Topics: Animals; Cations, Divalent; Cell Fusion; Cell Membrane; Cells, Cultured; Humans; Kinetics; Lipid Metabolism; Muscle Proteins; Muscles; Muscular Diseases; Rats
PubMed: 3890835
DOI: 10.1042/bj2280001 -
Journal of Anatomy Dec 2021Quantitative functional anatomy of amniote thoracic and abdominal regions is crucial to understanding constraints on and adaptations for facilitating simultaneous...
Quantitative functional anatomy of amniote thoracic and abdominal regions is crucial to understanding constraints on and adaptations for facilitating simultaneous breathing and locomotion. Crocodilians have diverse locomotor modes and variable breathing mechanics facilitated by basal and derived (accessory) muscles. However, the inherent flexibility of these systems is not well studied, and the functional specialisation of the crocodilian trunk is yet to be investigated. Increases in body size and trunk stiffness would be expected to cause a disproportionate increase in muscle force demands and therefore constrain the basal costal aspiration mechanism, necessitating changes in respiratory mechanics. Here, we describe the anatomy of the trunk muscles, their properties that determine muscle performance (mass, length and physiological cross-sectional area [PCSA]) and investigate their scaling in juvenile Alligator mississippiensis spanning an order of magnitude in body mass (359 g-5.5 kg). Comparatively, the expiratory muscles (transversus abdominis, rectus abdominis, iliocostalis), which compress the trunk, have greater relative PCSA being specialised for greater force-generating capacity, while the inspiratory muscles (diaphragmaticus, truncocaudalis ischiotruncus, ischiopubis), which create negative internal pressure, have greater relative fascicle lengths, being adapted for greater working range and contraction velocity. Fascicle lengths of the accessory diaphragmaticus scaled with positive allometry in the alligators examined, enhancing contractile capacity, in line with this muscle's ability to modulate both tidal volume and breathing frequency in response to energetic demand during terrestrial locomotion. The iliocostalis, an accessory expiratory muscle, also demonstrated positive allometry in fascicle lengths and mass. All accessory muscles of the infrapubic abdominal wall demonstrated positive allometry in PCSA, which would enhance their force-generating capacity. Conversely, the basal tetrapod expiratory pump (transversus abdominis) scaled isometrically, which may indicate a decreased reliance on this muscle with ontogeny. Collectively, these findings would support existing anecdotal evidence that crocodilians shift their breathing mechanics as they increase in size. Furthermore, the functional specialisation of the diaphragmaticus and compliance of the body wall in the lumbar region against which it works may contribute to low-cost breathing in crocodilians.
Topics: Abdomen; Alligators and Crocodiles; Animals; Locomotion; Muscle, Skeletal; Respiration
PubMed: 34302302
DOI: 10.1111/joa.13523 -
The Journal of Physiology May 2023Skeletal muscle's isometric contractile properties are one of the classic structure-function relationships in all of biology allowing for extrapolation of single fibre...
Skeletal muscle's isometric contractile properties are one of the classic structure-function relationships in all of biology allowing for extrapolation of single fibre mechanical properties to whole muscle properties based on the muscle's optimal fibre length and physiological cross-sectional area (PCSA). However, this relationship has only been validated in small animals and then extrapolated to human muscles, which are much larger in terms of length and PCSA. The present study aimed to measure directly the in situ properties and function of the human gracilis muscle to validate this relationship. We leveraged a unique surgical technique in which a human gracilis muscle is transferred from the thigh to the arm, restoring elbow flexion after brachial plexus injury. During this surgery, we directly measured subject specific gracilis muscle force-length relationship in situ and properties ex vivo. Each subject's optimal fibre length was calculated from their muscle's length-tension properties. Each subject's PCSA was calculated from their muscle volume and optimal fibre length. From these experimental data, we established a human muscle fibre-specific tension of 171 kPa. We also determined that average gracilis optimal fibre length is 12.9 cm. Using this subject-specific fibre length, we observed an excellent fit between experimental and theorical active length-tension curves. However, these fibre lengths were about half of the previously reported optimal fascicle lengths of 23 cm. Thus, the long gracilis muscle appears to be composed of relatively short fibres acting in parallel that may not have been appreciated based on traditional anatomical methods. KEY POINTS: Skeletal muscle's isometric contractile properties represent one of the classic structure-function relationships in all of biology and allow scaling single fibre mechanical properties to whole muscle properties based on the muscle's architecture. This physiological relationship has only been validated in small animals but is often extrapolated to human muscles, which are orders of magnitude larger. We leverage a unique surgical technique in which a human gracilis muscle is transplanted from the thigh to the arm to restore elbow flexion after brachial plexus injury, aiming to directly measure muscles properties in situ and test directly the architectural scaling predictions. Using these direct measurements, we establish human muscle fibre-specific tension of ∼170 kPa. Furthermore, we show that the gracilis muscle actually functions as a muscle with relatively short fibres acting in parallel vs. long fibres as previously assumed based on traditional anatomical models.
Topics: Humans; Animals; Muscle Fibers, Skeletal; Isometric Contraction; Elbow; Biomechanical Phenomena; Muscle, Skeletal
PubMed: 36905200
DOI: 10.1113/JP284092 -
Neurourology and Urodynamics Nov 2015The levator ani muscle (LA) injury associated with vaginal birth occurs in a characteristic site of injury on the inner surface of the pubic bone to the pubovisceral...
AIMS
The levator ani muscle (LA) injury associated with vaginal birth occurs in a characteristic site of injury on the inner surface of the pubic bone to the pubovisceral portion of the levator ani muscle's origin. This study investigated the gross and microscopic anatomy of the pubic origin of the LA in this region.
METHODS
Pubic origin of the levator ani muscle was examined in situ then harvested from nine female cadavers (35-98 years). A combination of targeted feature sampling and sequential sampling was used where each specimen was cut sequentially in approximately 5 mm thick slices apart in the area of known LA injury. Histological sections were stained with Masson's trichrome.
RESULTS
The pubovisceral origin is transparent and thin as it attaches tangentially to the pubic periosteum, with its morphology changing from medial to lateral regions. Medially, fibers of the thick muscle belly coalesce toward multiple narrow points of bony attachment for individual fascicles. In the central portion there is an aponeurosis and the distance between muscle and periosteum is wider (∼3 mm) than in the medial region. Laterally, the LA fibers attach to the levator arch where the transition from pubovisceral muscle to the iliococcygeal muscle occurs.
CONCLUSIONS
The morphology of the levator ani origin varies from the medial to lateral margin. The medial origin is a rather direct attachment of the muscle, while lateral origin is made through the levator arch.
Topics: Adult; Aged; Aged, 80 and over; Female; Humans; Middle Aged; Muscle, Skeletal; Muscle, Smooth; Pelvic Floor; Pubic Bone
PubMed: 25156808
DOI: 10.1002/nau.22649 -
Anatomical Record (Hoboken, N.J. : 2007) Sep 2014
Topics: Animals; Humans; Muscle Proteins; Muscle, Skeletal; Muscles; Myofibrils
PubMed: 25125166
DOI: 10.1002/ar.22982 -
Journal of the Mechanical Behavior of... Feb 2020In this paper, the interstitial fluid flow in skeletal muscle endomysium was examined using an in-situ indentation testing in combination with theoretical modelling. The...
In this paper, the interstitial fluid flow in skeletal muscle endomysium was examined using an in-situ indentation testing in combination with theoretical modelling. The objective was to understand the transport properties of the three-dimensional and highly hierarchical muscular interstitial matrices, which play important roles in muscle-bone cross-talk and signaling during musculoskeletal development and maintenance. Gastrocnemius muscles from four 3-month old calves were harvested and subjected to a creeping test using a custom-designed device. The experiments, in combination with an anatomy-based theoretical model, were used to capture the spatial-temporal response of the skeletal muscle to external impacts. For the first time, the detailed load-induced interstitial fluid pressurization in the muscle endomyseal space was obtained. The relative contribution from the solid muscle fibers and the interstitial fluid to the temporal loading response was captured. The paper presented herein provides important information regarding the mechanical environment within the muscle tissue, which could help the future study of muscle's response to forces and its subsequent signaling to surrounding tissues in vivo.
Topics: Animals; Bone and Bones; Cattle; Extracellular Fluid; Muscle Fibers, Skeletal; Muscle, Skeletal; Physical Phenomena
PubMed: 31670258
DOI: 10.1016/j.jmbbm.2019.103504 -
Theranostics 2019Complete re-innervation after a traumatic injury severing a muscle's peripheral nerve may take years. During this time, the denervated muscle atrophies and loses...
Complete re-innervation after a traumatic injury severing a muscle's peripheral nerve may take years. During this time, the denervated muscle atrophies and loses acetylcholine receptors, a vital component of the neuromuscular junction, limiting functional recovery. One common clinical treatment for atrophy is electrical stimulation; however, epimysial electrodes currently used are bulky and often fail due to an excessive inflammatory response. Additionally, there remains a need for a device providing monitoring of neuromuscular regeneration and the maintenance of acetylcholine receptors. Here, an implantable, flexible microelectrode array (MEA) was developed that provides surface neuromuscular stimulation and recording during long-term denervation. The MEA uses a flexible polyimide elastomer and an array of gold-based microelectrodes featuring Peano curve motifs, which together maintain electrode flexibility. The devices were implanted along the denervated gastrocnemius muscles of 5 rats. These rats underwent therapeutic stimulation using the MEA daily beginning on post-operative day 2. Another 5 rats underwent tibial nerve resection without implantation of MEA. Tissues were harvested on post-operative day 14 and evaluated for quantification of acetylcholine receptors and muscle fiber area using immunofluorescence and histological staining. The Young's modulus was 1.67 GPa, which is comparable to native tendon and muscle. The devices successfully recorded electromyogram data when implanted in rats. When compared to untreated denervated muscles, MEA therapy attenuated atrophy by maintaining larger muscle fiber cross-sectional areas (p < 0.05). Furthermore, the acetylcholine receptor areas were markedly larger with MEA treatment (p < 0.05). This proof-of-concept work successfully demonstrates the ability to combine conformability, tensile strength-enhancing metal micropatterning, electrical stimulation and recording into a functional implant for both epimysial stimulation and recording.
Topics: Animals; Elastic Modulus; Electric Stimulation Therapy; Electromyography; Female; Humans; Muscle Fibers, Skeletal; Muscle, Skeletal; Peripheral Nerve Injuries; Rats; Rats, Inbred Lew; Receptors, Cholinergic
PubMed: 31660089
DOI: 10.7150/thno.35436 -
The Journal of Experimental Biology May 2017Hill-type models are ubiquitous in the field of biomechanics, providing estimates of a muscle's force as a function of its activation state and its assumed force-length... (Comparative Study)
Comparative Study
Hill-type models are ubiquitous in the field of biomechanics, providing estimates of a muscle's force as a function of its activation state and its assumed force-length and force-velocity properties. However, despite their routine use, the accuracy with which Hill-type models predict the forces generated by muscles during submaximal, dynamic tasks remains largely unknown. This study compared human gastrocnemius forces predicted by Hill-type models with the forces estimated from ultrasound-based measures of tendon length changes and stiffness during cycling, over a range of loads and cadences. We tested both a traditional model, with one contractile element, and a differential model, with two contractile elements that accounted for independent contributions of slow and fast muscle fibres. Both models were driven by subject-specific, ultrasound-based measures of fascicle lengths, velocities and pennation angles and by activation patterns of slow and fast muscle fibres derived from surface electromyographic recordings. The models predicted, on average, 54% of the time-varying gastrocnemius forces estimated from the ultrasound-based methods. However, differences between predicted and estimated forces were smaller under low speed-high activation conditions, with models able to predict nearly 80% of the gastrocnemius force over a complete pedal cycle. Additionally, the predictions from the Hill-type muscle models tested here showed that a similar pattern of force production could be achieved for most conditions with and without accounting for the independent contributions of different muscle fibre types.
Topics: Adult; Bicycling; Biomechanical Phenomena; Female; Humans; Male; Middle Aged; Models, Biological; Muscle Contraction; Muscle, Skeletal; Ultrasonography
PubMed: 28202584
DOI: 10.1242/jeb.154807 -
Poultry Science Feb 2021It is generally held that the content of several free amino acids and dipeptides is closely related to the energy-supplying metabolism of skeletal muscles. Metabolic...
It is generally held that the content of several free amino acids and dipeptides is closely related to the energy-supplying metabolism of skeletal muscles. Metabolic characteristics of muscles are involved in the variability of meat quality due to their ability to influence the patterns of energy metabolism not only in living animal but also during postmortem time. Within this context, this study aimed at establishing whether the concentration of histidine dipeptides can affect muscle postmortem metabolism, examining the glycolytic pathway of 3 chicken muscles (pectoralis major, extensor iliotibialis lateralis, and gastrocnemius internus as glycolytic, intermediate, and oxidative-type, respectively) selected based on their histidine dipeptides content and ultimate pH. Thus, a total of 8 carcasses were obtained from the same flock of broiler chickens (Ross 308 strain, females, 49 d of age, 2.8 kg body weight at slaughter) and selected immediately after evisceration from the line of a commercial processing plant. Meat samples of about 1 cm were excised from bone-in muscles at 15, 60, 120, and 1,440 min postmortem, instantly frozen in liquid nitrogen and used for the determination of pH, glycolytic metabolites, buffering capacity as well as histidine dipeptides content through H-NMR. Overall results suggest that glycolysis in leg muscles ceased already after 2 h postmortem, whereas in breast muscle continued until 24 h, when it exhibited significantly lower pH values (P < 0.05). However, considering its remarkable glycolytic potential, pectoralis major muscle should have exhibited a greater and faster acidification, suggesting that its higher (P < 0.05) histidine dipeptides' content might have prevented a potentially stronger acidification process. Accordingly, breast muscle also showed greater (P < 0.05) buffering ability in the pH range 6.0-7.0. Therefore, anserine and carnosine, being highly positively correlated with muscle's buffering capacity (P < 0.001), might play a role in regulating postmortem pH decline, thus exerting an effect on muscle metabolism during prerigor phase and the quality of the forthcoming meat. Overall results also suggest that total histidine dipeptides content along with muscular ultimate pH represent good indicators for the energy-supplying metabolism of chicken muscles.
Topics: Animals; Chickens; Dipeptides; Energy Metabolism; Female; Glycolysis; Histidine; Hydrogen-Ion Concentration; Meat; Muscle, Skeletal; Pectoralis Muscles; Postmortem Changes
PubMed: 33518087
DOI: 10.1016/j.psj.2020.11.032