## 3 Results
### Transmission Electron Microscopy
These myofibers show myofibrillar degeneration (**A–C**), hydropic degeneration (**D–F**), and necrosis (**G–I**). (**A–C**) Narrowed and split myofibrils (white #) with preserved sarcomere structure, glycogen accumulation (G), dark elongated mitochondria (M), and displaced triads (circle) in widened intermyofibrillar spaces. The myofibers show Z-line smearing (black arrow), “zig-zag” appearance of the Z-line (white arrow), focal disorganization, and disruption of sarcomeric myofilaments and Z-line material over multiple sarcomere lengths is visible in B. (**D–F**) The myofibers show myosin loss (black *) and glycogen accumulation (G) in widened edematous intermyofibrillar spaces containing vacuoles (V), swollen vacuolar mitochondria (M), and displaced triads with swollen terminal cisternae (TC). (**G–H**) Electron-dense necrotic myofibers with hypercontraction of myofibrils (white *), amorphous granular material (black #), numerous vacuolized mitochondria (M), autophagic vacuoles (V), lysosomes (Ly), and lipid droplets (Li). Extrusion of the nucleus and surrounding sarcoplasm is visible in H. (**I**) Electron-lucent necrotic myofiber with fragmented nucleus (N), extensive myosin loss with preserved but misoriented Z-line material, and related actin filaments (rectangle). Figure 4: Electron micrographs of two longitudinally-sectioned degenerative myofib. (**A**) The cytoplasm of an active macrophage (Ma) is in intimate contact with the nucleus (N2) of the necrotic fiber on the right. The nucleus of the macrophage (N4) is in contact with another nucleus of the necrotic myofiber (N3). Note the satellite cell (SC) at the periphery of the myofiber on the left, from which the nucleus is indicated by N1. Endomysium (E). (**B,C**) Higher magnifications of the degenerative muscle fiber with areas of myofibrillar and hydrop degeneration, with myofilament loss (white *) and narrowed myofibrils (white #). The sarcoplasm of the widened intermyofibrillar spaces contains vacuolar mitochondria (M), lipid droplets (Li), accumulations of glycogen (G1), and displaced triads (T). In some triads the central T-tubule is flanked by swollen terminal cisternae (circle). Accumulations of glycogen are also present subsarcolemmal (G2). Nucleus N5 is located in a large membrane bleb (white arrow), has several indentations (black arrow), and is surrounded by perinuclear glycogen accumulation (G3). Several sarcolemmal folds (F) are projecting into the extracellular space. The satellite cell (SC) is located within the basal lamina (small black arrows) of the muscle fiber, tightly associated with the sarcolemma. The nucleus of the necrotic fiber is indicated by N2. (**D**) Higher magnification of the necrotic fiber characterized by local hypercontraction of myofibrils (black *) and places where the myofilament structure is replaced by an amorphous granular material (black #). Figure 5: Electron micrograph of three myofibers, showing different degrees of degenerative changes. (**A**) Myofibers show different degrees of degenerative changes, from mild degeneration (white *), to moderate degeneration (black #), and towards necrosis (white #). Two myofibers have fragmented nuclei (N1 and N2; N3 and N4) located in a large membrane bleb that is oriented towards a neighboring capillary (C). The pyknotic nucleus (N5) of the third myofiber is centrally located. (**B**) Higher magnification of the mild degenerative myofiber, showing widened intermyofibellar spaces with accumulated glycogen (G1) and swollen mitochondria (M). Lipid droplets (Li). Vacuoles (V). Subsarcolemmal accumulations of glycogen (G2). (**C**) Higher magnification of the moderate degenerative myofiber, showing myofibrillar disorganization and widened intermyofibrillar spaces with accumulated glycogen (G1). “Zig-zag” appearance of the Z-line (white arrow). Subsarcolemmal accumulations of glycogen (G2).