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Single muscle fiber

Boudewijn T H M Sleutjes, Judith Drenthen, Ernest Boskovic, Leonard J van Schelven, Maria O Kovalchuk, Paul G E Lumens, Leonard H van den Berg, Hessel Franssen
OBJECTIVE: To study excitability of single motor units (MUs) using high-density surface-EMG. METHODS: Motor unit action potentials (MUAPs) were evoked by submaximal stimulation of the median nerve at the wrist and recorded with a 9 × 14 electrode grid on the skin overlying the thenar muscles. For excitability tests of single MUs, the most optimal specific single-channel surface-EMG signal was selected based on the spatiotemporal profile of single MUs. RESULTS: Axonal excitability measures were successfully obtained from 14 single MUs derived from ten healthy subjects...
June 1, 2018: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
Robert Rockenfeller, Michael Günther
The maximum of a muscle fiber's force-length curve (FLC) shifts to shorter lengths as muscle activation increases. State-of-the-art muscle models cannot explain the mechanistic basis for this shift, which is therefore either omitted or added ad hoc in a descriptive manner. A more theoretical approach developed by H. Hatze, who had particularly modeled the process of muscle activation, does predict this shift but can be shown to consist of multiple mathematical attempts that are all inconsistent with their common assertion: to represent local volume constancy...
June 11, 2018: Journal of Theoretical Biology
Hiroyuki Iwamoto
X-ray fiber diffraction is a powerful tool used for investigating the molecular structure of muscle and its dynamics during contraction. This technique has been successfully applied not only to skeletal and cardiac muscles of vertebrates but also to insect flight muscle. Generally, insect flight muscle has a highly ordered structure and is often capable of high-frequency oscillations. The X-ray diffraction studies on muscle have been accelerated by the advent of 3rd-generation synchrotron radiation facilities, which can generate brilliant and highly oriented X-ray beams...
June 13, 2018: International Journal of Molecular Sciences
Tim Snijders, Kirsten E Bell, Joshua P Nederveen, Nelson I Saddler, Nicole Mazara, Dinesh A Kumbhare, Stuart M Phillips, Gianni Parise
Background: Nutritional supplementation can have beneficial effects on body composition, strength, and function in older adults. However, whether the response of satellite cells can be altered by nutritional supplementation in older adults remains unknown. Objective: We assessed whether a multi-ingredient protein-based supplement taken over a prolonged period of time could alter the muscle satellite cell response after exercise in older men. Methods: Twenty-seven older men [mean ± SD age: 73 ± 1 y; mean ± SD body mass index (kg/m2): 28 ± 1] participated in a randomized double-blind experiment...
June 1, 2018: Journal of Nutrition
Hyun Young Koo, Lamis M F El-Baz, Stacey L House, Sarah N Cilvik, Samuel J Dorry, Nahla M Shoukry, Mohamed L Salem, Hani S Hafez, Nickolai O Dulin, David M Ornitz, Robert D Guzy
Fibroblast growth factor (FGF) signaling has been implicated in the pathogenesis of pulmonary fibrosis. Mice lacking FGF2 have increased mortality and impaired epithelial recovery after bleomycin exposure, supporting a protective or reparative function following lung injury. To determine whether FGF2 overexpression reduces bleomycin-induced injury, we developed an inducible genetic system to express FGF2 in type II pneumocytes. Double-transgenic (DTG) mice with doxycycline-inducible overexpression of human FGF2 (SPC-rtTA; TRE-hFGF2) or single-transgenic controls were administered intratracheal bleomycin and fed doxycycline chow, starting at either day 0 or 7...
June 6, 2018: Journal of Pathology
Ryan L Wood, Keaton S Karlinsey, Austin D Thompson, Mark N Rigby, Greggory D Boatright, William G Pitt, Beverly L Roeder, Scott C Steffensen, Alonzo D Cook
Schwann cells play a major role in helping heal injured nerves. They help clear debris, produce neurotrophins, upregulate neurotrophin receptors, and form bands of Büngner to guide the healing nerve. But nerves do not always produce enough neurotrophins and neurotrophin receptors to repair themselves. Nerve growth factor (NGF) is an important neurotrophin for promoting nerve healing and lysophosphatidylcholine (LPC) has been shown to stimulate NGF receptors (NGFR). This study tested the administration of a single intraneural injection of LPC (1 mg/mL for single LPC injection and 10 mg/mL for multiple LPC injections) at day 0 and one (day 7), two (days 5 and 7), or three (days 5, 7, and 9) injections of NGF (160 ng/mL for single injections and 80 ng/mL for multiple injections) to determine baseline effects on crushed sciatic nerves in rats...
May 2018: Neural Regeneration Research
Jung-Hoon Lee, Hyun-Su Choi
BACKGROUND: Although cross tape has recently been used by clinicians for various musculoskeletal conditions, scientific studies on the direction of cross tape application are lacking. METHODS: The present study aimed to investigate whether the direction of cross tape application affected the outcomes of the modified O-ring test and maximal pinch strength using a pinch gauge and the conformity between these 2 tests when cross tape was applied to the forearm muscles of individuals with no upper extremity pain and no restriction of joint range of motion...
June 2018: Medicine (Baltimore)
Christopher A Wolff, Adam R Konopka, Miranda K Suer, Todd A Trappe, Leonard A Kaminsky, Matthew P Harber
BACKGROUND: It is unclear to what extent an improved skeletal muscle phenotype influences maximal aerobic capacity (VO2max) when changes in cardiopulmonary function are limited. Thus, to primarily target skeletal muscle adaptations, we employed an alternating single-leg knee extension exercise training protocol and evaluated the impact on skeletal muscle morphology and whole body exercise capacity. METHODS: Eight sedentary volunteers (20±1 y; VO2max: 38.4±2.6 mL...
May 29, 2018: Journal of Sports Medicine and Physical Fitness
François Chauvigné, Janmejay Parhi, Carla Ducat, Judith Ollé, Roderick Nigel Finn, Joan Cerdà
Aquaporin-mediated fluid transport in the mammalian efferent duct and epididymis is believed to play a role in sperm maturation and concentration. In fish, such as the marine teleost gilthead seabream (Sparus aurata), the control of fluid homeostasis in the spermatic duct seems also to be crucial for male fertility, but no information exists on the expression and distribution of aquaporins. In this study, reverse transcriptase-polymerase chain reaction and immunoblotting analyses, employing available and newly raised paralog-specific antibodies for seabream aquaporins, indicate that up to nine functional aquaporins, Aqp0a, -1aa, -1ab, -3a, -4a, -7, -8bb, -9b and -10b, are expressed in the spermatic duct...
May 27, 2018: Journal of Anatomy
Jonathan J Stone, Kimberly K Amrami, Jodi M Carter, Robert J Spinner
Neuromuscular choristoma (NMC) is a rare congenital nerve lesion that is classified by the presence of heterotopic muscle fibers intercalated within nerve fascicles.1 The presence of NMC typically causes progressive neuropathy and bony/soft tissue undergrowth, often leading to a shortened atrophic limb.2,3 The typical appearance of NMC on magnetic resonance imaging is an enlarged fusiform nerve that exhibits minimal gadolinium enhancement.4 While there is increasing documentation of pathognomonic clinical and radiographic features for various diffuse fusiform peripheral nerve lesions, nerve biopsy is still occasionally required for some patients given the rarity of these diseases and progressive neuropathic features...
May 24, 2018: Operative Neurosurgery (Hagerstown, Md.)
Xiangyu Gao, Jigang Yang, Xiaojie Zhang, Ping Wang, Hongwei Li
RATIONALE: Hypertrophic cardiomyopathy (HCM) is a disease that is characterized by inappropriate left ventricular and/or right ventricular hypertrophy and hypercontractility that is often asymmetrical and associated with microscopic evidence of myocardial fiber disarray. The aim of this study was to present a previously under-recognized subset of HCM patients with left ventricular (LV) apical aneurysms. PATIENTS CONCERNS: A 33-year-old man who presented with chest discomfort for 10 days...
May 2018: Medicine (Baltimore)
Sara R Piva, Samannaaz S Khoja, Frederico G S Toledo, Mary Chester Wasko, G Kelley Fitzgerald, Bret H Goodpaster, Clair N Smith, Anthony Delitto
OBJECTIVES: To compare the feasibility and effectiveness of Neuromuscular Electrical Stimulation (NMES) with high-intensity volitional resistance training in improving muscle structure and function, and physical function in patients with rheumatoid arthritis (RA). We also described pre- and post-intervention values of myocyte characteristics. METHODS: Two-group single-blinded pilot randomized study in adults with RA. Participants were assigned to 36 sessions over 16 weeks of NMES (n=31) or volitional training (n=28)...
May 21, 2018: Arthritis Care & Research
Aliaa A Tawfeek, Amani M Nawito, Radwa M Azmy, Amr Hassan, Lamia M Afifi, Saly H Elkholy
Background: Conventional motor nerve conduction studies are usually normal in early and mild carpal tunnel syndrome (CTS). Single-fiber electromyography (SFEMG) measures the mean consecutive difference (MCD) as an expression of the variability in impulse transmission over the motor endplates and along the nerve fibers distally to the last branching point and along the muscle fibers.Application of concentric needle SFEMG in a group of CTS patients who showed pure sensory abnormalities in nerve conduction studies to examine for subclinical motor involvement...
2018: The Egyptian journal of neurology, psychiatry and neurosurgery
Marissa A Ruehle, Hazel Y Stevens, Aaron M Beedle, Robert E Guldberg, Jarrod A Call
Duchenne muscular dystrophy (DMD) is a severe muscle wasting disease due to the absence of the dystrophin protein from the muscle cell membrane which renders the muscle susceptible to continuous damage. In DMD patients, muscle weakness, together with cycles of degeneration/regeneration and replacement with non-contractile tissue, limit mobility and lifespan. Since the loss of dystrophin result in loss of polarity and a reduction in the number of self-renewing satellite cells, it is postulated that these patients could achieve an improved quality of life if delivered cells could restore satellite cell function...
May 18, 2018: Journal of Tissue Engineering and Regenerative Medicine
Stefano Schiaffino
Different forms of myosin heavy chains (MyHCs), coded by a large family of sarcomeric MYH genes, are expressed in striated muscles. The generation of specific anti-MyHC antibodies has provided a powerful tool to define the fiber types present in skeletal muscles, their functional properties, their response to conditions that affect muscle plasticity and their changes in muscle disorders. Cardiomyocyte heterogeneity has been revealed by the serendipitous observation that different MyHCs are present in atrial and ventricular myocardium and in heart conduction tissue...
May 14, 2018: FEBS Journal
Christopher K Thompson, Francesco Negro, Michael D Johnson, Matthew R Holmes, Laura Miller McPherson, Randall K Powers, Dario Farina, Charles J Heckman
KEY POINTS SUMMARY: The spinal alpha motoneuron is the only cell in the human CNS whose discharge can be routinely recorded in humans. We have reengineered motor unit collection and decomposition approaches, originally developed in humans, to measure the neural drive to muscle and estimate muscle force generation in the decerebrate cat model. Experimental, computational, and predictive approaches are used to demonstrate the validity of this approach across a wide range of modes to activate the motor pool...
May 3, 2018: Journal of Physiology
Sobiya Mahnaz Ayesha, A K Meena, Navatha Vangala, Liza Rajasekhar, Subhash Kaul, Rupam Borgahain, Megha S Uppin
Background: Idiopathic inflammatory myopathies (IIMs) are a group of chronic, autoimmune disorders which include a new entity, necrotizing autoimmune myopathy (NAM). NAM lacks inflammation and presents with markedly elevated creatinine phosphokinase (CPK) levels. It is associated with connective tissue diseases (CTDs), statin use, malignancies, and most cases are idiopathic. Objectives: The objectives of this study are to describe the clinicopathologic features in muscle biopsy-proven cases of NAM...
January 2018: Annals of Indian Academy of Neurology
Naoto Fujita, Saki Aono, Kohei Karasaki, Fumi Sera, Tomoyuki Kurose, Hidemi Fujino, Susumu Urakawa
Although exercise is effective in improving obesity and hyperinsulinemia, the exact influence of exercise on the capillary density of skeletal muscles remains unknown. The aim of this study was to investigate the effects of low-intensity exercise training on metabolism in obesity with hyperinsulinemia, focusing specifically on the capillary density within the skeletal muscle. Otsuka Long-Evans Tokushima fatty (OLETF) rats were used as animal models of obesity with hyperinsulinemia, whereas Long-Evans Tokushima Otsuka (LETO) rats served as controls (no obesity, no hyperinsulinemia)...
2018: PloS One
Massimo Venturelli, Carlo Reggiani, Russell S Richardson, Federico Schena
Although skeletal muscle function is diminished with advanced age, single muscle fiber function appears to be preserved. Therefore, this review examines the hypothesis that the skeletal muscle fiber, per se, is not the predominant factor responsible for the reduction in force generating capacity in the oldest-old, but, rather, is attributable to a combination of factors external to the muscle fibers.
April 17, 2018: Exercise and Sport Sciences Reviews
Lisa D Glass, Arthur J Cheng, Brian R MacIntosh
Fatigue of single mouse fibers during repeated high-frequency stimulation results initially from decreased Ca2+ sensitivity while free myoplasmic calcium concentration ([Ca2+ ]m ) increases, followed by decreasing [Ca2+ ]m . Recovery of active force with low-frequency stimulation is slow and persistent fatigue results from low [Ca2+ ]m . However, the consequences of intermittent submaximal contractions are not known. The aim of the present study was to investigate the changes in [Ca2+ ]m and active force during intermittent submaximal contractions and subsequent recovery...
April 18, 2018: Pflügers Archiv: European Journal of Physiology
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