Adaptive and nonadaptive responses to voluntary wheel running by mdx mice

Abstract

The purpose of this study was to determine the extent to which hindlimb muscles of mdx mice adapt to a voluntary endurance type of exercise. mdx and C57BL mice engaged in 8 weeks of wheel running or maintained normal cage activities. Beneficial adaptations that occurred in mdx mice included changes in muscle mass, fiber size, and fiber types based on myosin heavy chain (MHC) isoform expression. These adaptations occurred without increases in fiber central nuclei and embryonic MHC expression. An undesirable outcome, however, was that muscle mitochondrial enzyme activities did not improve with exercise in mdx mice as they did in C57BL mice. Cellular remodeling of dystrophic muscle following exercise has not been studied adequately. In this study we found that some, but not all, of the expected adaptations occurred in mdx mouse muscle. We must better understand these (non)adaptations in order to inform individuals with DMD about the benefits of exercise.

Adaptive strength gains in dystrophic muscle exposed to repeated bouts of eccentric contraction

“…The voltage was adjusted from 3.0 to 9.0 V until maximal isometric torque (fused tetanus) was achieved. Torque as a function of stimulation frequency was then measured during nine isometric contractions at varying stimulation frequencies (20,40,60,80,100,125,150,200, and 250 Hz) using a 0.1-ms pulse duration. Next, the anterior crural muscles were injured by performing 10 or 100 eccentric contractions.…”

“…Individual fiber cross-sectional areas were measured (20), and fibers with centralized nuclei were counted from 300 fibers within each muscle.…”

Skeletal muscle contractile function and neuromuscular performance in Zmpste24 −/− mice, a murine model of human progeria

“…Cross-sectional area of~200 fibers per soleus, and EDL muscle were measured from hematoxylin and eosin-stained sections (Landisch et al 2008). Capillarity of those muscles were assessed by the periodic acid-Schiff reaction (Josephson 1993).…”

“…Capillarity of those muscles were assessed by the periodic acid-Schiff reaction (Josephson 1993). The next three sections of each muscle were analyzed for fiber type via myosin heavy chain isoform I, IIa, or IIb (Landisch et al 2008). If a fiber did not react to either the myosin heavy chain I, IIa, or IIb antibody, it was classified as a IIx fiber.…”

“…The final serial sections were used to assess the abundance of nuclei in relationship to the~200 fibers analyzed. For this, nuclei were labeled using DAPI and a dystrophin antibody (1:20 dilution of NCL-DYS1; Novocastra Laboratories, Newcastle upon Tyne) was used to define the sarcolemma; nuclei were counted as myonuclei per fiber, central nuclei per fiber, or extracellular-related nuclei per total area (Landisch et al 2008;Moran et al 2005). Care was taken not to count nuclei if they appeared to be in a vessel.…”