Regulation of Muscle Satellite Cell Activation and Cycles Consequent to Various Forms of Training
Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse in The Routledge Handbook on Biochemistry of Exercise, 2020
Skeletal muscle is a highly dynamic and metabolically active tissue responsible for a variety of bodily functions. Although skeletal muscle is highly adaptable, the post-mitotic nature of skeletal muscle requires the primary muscle progenitor, SCs, to contribute new nuclei to existing muscle fibres in response to appropriate stimuli. Importantly, SCs are highly responsive to various forms of exercise and, in humans, are believed to play in important role in skeletal muscle hypertrophy following resistance exercise training and may play a role in mediating non-hypertrophic adaptations observed following aerobic training. In recent years, much research has aimed at determining optimal exercise interventions to maximize the SC response, specifically in populations where muscle mass may be compromised (i.e., aging). However, more research is required to determine the mechanisms supporting SC function and how exercise and potentially nutritional interventions may result in optimal SC function to support the maintenance of muscle health throughout the lifespan.
Dietary Protein and Physical Training Effects on Body Composition and Performance
Henry C. Lukaski in Body Composition, 2017
Skeletal muscle is a vital tissue supporting locomotion and performance for both athletic and functional tasks. Skeletal muscle health can be optimized through performance of both resistance and aerobic exercise and consumption of adequate amounts of protein. When performed regularly, the combination of activity and protein consumption can enhance both athletic and functional performance across the lifespan. Skeletal muscle mass increases in the early years of life and plateaus thereafter, but begins to decline in the fourth or fifth decade of life at a rate of ∼0.8% per year (Goodpaster et al. 2006). Furthermore, states of energy restriction for weight loss can also induce a reduction in skeletal muscle mass (Krieger et al. 2006). Declines in muscle mass can negatively impact muscle strength as well as athletic and functional performance both in young and older adults and thus strategies to offset these declines are advantageous. In this chapter, we discuss the role protein and exercise (both aerobic and resistance) play in the optimization of muscle mass and performance under normal conditions (i.e., young, healthy individuals) as well as during periods of acute (i.e., weight loss) and chronic (i.e., aging) muscle catabolism.
The heart
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
There are also important differences between skeletal muscle and cardiac muscle. Skeletal muscle cells are elongated and run the length of the entire muscle. Furthermore, there is no electrical communication between these cells. Cardiac muscle cells, on the other hand, are considerably shorter than skeletal muscle fibers, and they branch and interconnect with each other. Intercellular junctions found where adjoining cells meet end-to-end are referred to as intercalated discs. There are two types of cell-to-cell junctions within these discs. Desmosomes hold the muscle cells together and provide the structural support needed when the heart beats and exerts a mechanical stress that would tend to pull the cells apart. Gap junctions are areas of very low electrical resistance (1/400 the resistance of the outside membrane) that allow free diffusion of ions. It is through the gap junctions that the electrical impulse, or heartbeat, spreads rapidly from one cell to another and forms the myocardium into a syncytium, where the initiation of a heartbeat in one region of the heart results in the stimulation and contraction of all the cardiac muscle cells at essentially the same time. The heart is composed of two syncytiums: the atrial syncytium and the ventricular syncytium. In each case, but particularly in the ventricles, the simultaneous stimulation of all the muscle cells results in a more powerful contraction, facilitating the pumping of the blood.
Bidirectional regulation of genistein on the proliferation and differentiation of C2C12 myoblasts
Published in Xenobiotica, 2020
Mailin Gan, Dongli Yang, Yuan Fan, Jingjing Du, Linyuan Shen, Qiang Li, Yanzhi Jiang, Guoqing Tang, Mingzhou Li, Jinyong Wang, Xuewei Li, Shunhua Zhang, Li Zhu
Skeletal muscle is an important tissue in animals, and it accounts for 30–40% of total body weight (Shen et al., 2016). Skeletal muscle cells of vertebrates are contractile, multinucleated cells that undergo a complex differentiation process during their development. The majority of myocytes are derived from the paraxial mesodermal somites. These mesodermal progenitor cells proliferate and subsequently withdraw from the cell cycle. They then differentiate into myotubes and myofibers; this maturation is driven by the muscle-specific factors (Sabourin & Rudnicki, 2000). Under the control of neural regulation, skeletal muscle and bones constitute the motor system, and skeletal muscle also a main metabolic organ and endocrine organ (Abe et al., 2016; Schnyder & Handschin, 2015). Skeletal muscle participates in glucose utilization, muscle glycogen synthesis, and fatty acid oxidation. It also synthesizes and secretes many active factors in the regulation of cell biological processes. The function of skeletal muscle is closely related to many diseases, including dyskinesia, muscle atrophy, insulin resistance, and obesity (Reynolds et al., 2016; Wu & Ballantyne, 2017).
Ultrastructural changes of extraocular muscles in strabismus patients
Published in Ultrastructural Pathology, 2019
Yahya Al-Falki, Mubarak Al-Shraim, Nasser A. Alsabaani, Refaat A. Eid, Khaled Radad
Normal EOMs showed skeletal muscle fibers (cells) with intact basal membrane and sarcolemma, tightly aligned myofibrils with well-arranged sarcomeres, Z line and H zone, and normally distributed mitochondria. Skeletal muscle fibers were separated with a normal amount of extracellular matrix. Satellite cells were seen in some areas in between basal lamina and sarcolemma (Figure 2a). TEM examination of EOMs from different strabismus patients showed varied ultrastructural changes including vacuolation, accumulation of lipid droplets, presence of subsarcolemmal inclusions and muscle fiber degeneration (Figure 2b,c). Clustering of mitochondria in between myofibrils is one of the most prominent features in strabismus specimens (Figure 3a,b). Some mitochondria were seen enclosed by autophagic vacuoles (Figure 3b). In some situations, mitochondria appeared atrophied and elongated (Figure 3c).
A Phase 2, Double-Blind, Randomized, Dose-Ranging Trial Of Reldesemtiv In Patients With ALS
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2021
Jeremy M. Shefner, Jinsy A. Andrews, Angela Genge, Carlayne Jackson, Noah Lechtzin, Timothy M. Miller, Bettina M. Cockroft, Lisa Meng, Jenny Wei, Andrew A. Wolff, Fady I. Malik, Cynthia Bodkin, Benjamin R. Brooks, James Caress, Annie Dionne, Dominic Fee, Stephen A. Goutman, Namita A. Goyal, Orla Hardiman, Ghazala Hayat, Terry Heiman-Patterson, Daragh Heitzman, Robert D. Henderson, Wendy Johnston, Chafic Karam, Matthew C. Kiernan, Stephen J. Kolb, Lawrence Korngut, Shafeeq Ladha, Genevieve Matte, Jesus S. Mora, Merrilee Needham, Bjorn Oskarsson, Gary L. Pattee, Erik P. Pioro, Michael Pulley, Dianna Quan, Kourosh Rezania, Kerri L. Schellenberg, David Schultz, Christen Shoesmith, Zachary Simmons, Jeffrey Statland, Shumaila Sultan, Andrea Swenson, Leonard H. Van Den Berg, Tuan Vu, Steve Vucic, Michael Weiss, Ashley Whyte-Rayson, James Wymer, Lorne Zinman, Stacy A. Rudnicki
Fast skeletal muscle troponin activators (FSTAs) sensitize the sarcomere to calcium and increase muscle force. This mechanism is of potential relevance in amyotrophic lateral sclerosis (ALS) and other neuromuscular disorders that cause weakness and muscle fatigue. A first-generation FSTA, tirasemtiv, showed promise in phase 2a studies in ALS (1–3) and myasthenia gravis (4). Additionally, a large phase 2b study of tirasemtiv in ALS suggested efficacy by slowing the rates of decline of slow vital capacity (SVC) and isometric muscle strength (5). Dizziness was the most common adverse event (AE) of tirasemtiv, which often resulted in dropout from the study. A subsequent phase 3 trial was designed to reduce the incidence of early termination. The trial failed to show a statistically significant effect on any endpoint; however, large numbers of dose-dependent, early terminations due to poor tolerability still occurred and confounded the interpretation of the trial results (6).
Related Knowledge Centers
- Bone
- Muscle
- Sarcomere
- Skeleton
- Somatic Nervous System
- Striated Muscle Tissue
- Tendon
- Cardiac Muscle
- Muscle Cell
- Muscular System