Generating color-coded anatomic muscle maps for correlation of quantitative magnetic resonance imaging analysis with clinical examination in neuromuscular disorders

Duchenne and Becker muscular dystrophy: Cellular mechanisms, image analysis, and computational models: A review

The muscle is the principal tissue that is capable to transform potential energy into kinetic energy. This process is due to the transformation of chemical energy into mechanical energy to enhance the movements and all the daily activities. However, muscular tissues can be affected by some pathologies associated with genetic alterations that affect the expression of proteins. As the muscle is a highly organized structure in which most of the signaling pathways and proteins are related to one another, pathologies may overlap. Duchenne muscular dystrophy (DMD) is one of the most severe muscle pathologies triggering degeneration and muscle necrosis. Several mathematical models have been developed to predict muscle response to different scenarios and pathologies. The aim of this review is to describe DMD and Becker muscular dystrophy in terms of cellular behavior and molecular disorders and to present an overview of the computational models implemented to understand muscle behavior with the aim of improving regenerative therapy.

Micro- and nano-tomography analysis of mouse soleus muscle using radiation

In this study, we analyze radiation images of muscle structure of mice soleus muscles using radiation source-based microtomography and nanotomography. Soleus muscle samples were collected for analysis from 8-week-old male Institute of Cancer Research mice. First, phase-contrast X-ray microtomography was employed in these experiments. Then to obtain images with excellent contrast, imaging was performed using monochromatic light with excellent transmission power. To analyze additional muscle structures in higher magnification images than these images, nanotomography was performed, which facilitated obtaining high-magnification and high-resolution images. Muscle tissue microstructures were confirmed through three-dimensional images obtained from phase-contrast X-ray microtomography. Thus, the muscle tissue's overall shape at microscopic level can be captured. Additionally, a single muscle fiber was examined using hard X-ray nano-imaging, through which we could observe the alignment of countless myofibrils, that is, actin and myosin filaments in the muscle fibers. Thus, the methodology adopted here proved to be advantageous in analyzing the muscle tissue's overall structure with microtomography and in observing the myofibrils in detail using nanotomography.

Protein and amino acids for skeletal muscle health in aging

Proteins and its building blocks, amino acids, have many physiological roles in the body. While some amino acids can be synthesized endogenously, exogenous protein and amino acids are necessary to maintain homeostasis. Because skeletal muscle contains a large portion of endogenous protein and plays important roles in movement, regulation, and metabolism, imbalanced protein and amino acid availability may result in clinical conditions including skeletal muscle atrophy, impaired muscle growth or regrowth, and functional decline. Aging is associated with changes in protein metabolism and multiple physiological and functional alterations in the skeletal muscle that are accentuated by decreased dietary protein intake and impaired anabolic responses to stimuli. Inactivity and chronically elevated inflammation of the skeletal muscle can initiate and/or augment pathological remodeling of the tissue (i.e., increase of fat and fibrotic tissues and atrophy of the muscle). Defining an adequate amount of dietary protein that is appropriate to maintain the availability of amino acids for biological needs is necessary but is still widely debated for older adults. This chapter will provide (i) an overview of dietary protein and amino acids and their role in skeletal muscle health; (ii) an overview of skeletal muscle structure and function and the deterioration of muscle that occurs with advancing age; (iii) a discussion of the relationship between protein/amino acid metabolism and skeletal muscle decline with aging; and (iv) a brief discussion of optimal protein intakes for older adults to maintain skeletal muscle health in aging.

Skeletal muscle: a brief review of structure and function

Skeletal muscle is one of the most dynamic and plastic tissues of the human body. In humans, skeletal muscle comprises approximately 40% of total body weight and contains 50-75% of all body proteins. In general, muscle mass depends on the balance between protein synthesis and degradation and both processes are sensitive to factors such as nutritional status, hormonal balance, physical activity/exercise, and injury or disease, among others. In this review, we discuss the various domains of muscle structure and function including its cytoskeletal architecture, excitation-contraction coupling, energy metabolism, and force and power generation. We will limit the discussion to human skeletal muscle and emphasize recent scientific literature on single muscle fibers.