Appearance of complex branched fibers following repetitive muscle trauma in normal rat skeletal muscle

Abstract

These findings suggest that the formation of an anastomosing syncytial reticulum is one of the adaptation mechanisms of normal skeletal muscle rather than a specific event in mdx mutant mice, and long-term repeated trauma of the same fiber is necessary for this formation. Adaptive changes in the muscles with the three different types of muscle trauma are discussed.

Characteristics of compensatory hypertrophied muscle in the rat: I. Electron microscopic and immunohistochemical studies

“…However, branched fibers observed under normal physiological conditions showed simple shapes of the letters X and Y (Tamaki et al, 1992a1, and complex branched fibers were rarely observed. We also reported that increased number of branched fibers occurred in the muscles of mdx mouse (Tamaki et al, 1993), and in muscles subjected to repetitive trauma (Tamaki and Akatsuka, 1994). In these cases, the shape of the branched fibers appeared more complex and ASR pattern was common.…”

“…The particular fibers of the branched fibers were selected for further three-dimensional analysis (Tamaki et al, 1992a(Tamaki et al, , 1993Tamaki and Akatsuka, 1994). To remove surface connective tissue surrounding the muscle fibers, isolated branched fibers were transferred to glass sample tubes containing 0.01 M PBS and placed in a hot ultrasonic wave bath at 45-50°C for 1-3 min.…”

“…Recently, we have established a method of three-dimensional analysis of individual muscle fibers using scanning electron microscopy (Tamaki et al, 1992a(Tamaki et al, , 1993Tamaki and Akatsuka, 1994). Using this method, we found that the muscle of a myopathic animal (mdx mutant mice) contained numerous complex branched fibers resembling "anastomosing syncytial reticulum" (ASR) evident in histological sections (Tamaki et al, 1993).…”

“…Using this method, we found that the muscle of a myopathic animal (mdx mutant mice) contained numerous complex branched fibers resembling "anastomosing syncytial reticulum" (ASR) evident in histological sections (Tamaki et al, 1993). However, the formation of ASR is not specific to the mdx mouse since it was also demonstrated in the normal rat skeletal muscle following repetitive degeneration-regeneration state of the same muscle in response to repeated injections of bupivacaine hydrochloride, an agent known to cause selective massive fiber necrosis (Tamaki and Akatsuka, 1994).…”

A gene for speed: contractile properties of isolated whole EDL muscle from an α-actinin-3 knockout mouse

“…A feature of repetitive muscle damage is the development of muscle fibers which are branched, or split (16). Branched fibers are found in processes involving continuous degeneration and regeneration of muscle, such as in the X-linked recessive condition of Duchenne muscular dystrophy.…”