The forward pulling tension exerted by individual mice was measured nearly isometrically in a simple apparatus designed to determine whole body tension (WBT). WBT determinations on control (C57Bl10/SnJ) and experimental (C57Bl10-mdx) mice indicate a muscle weakness which lasts throughout the lifespan of mdx mice. Direct muscle stimulation experiments in vivo also showed significant decreases in peak twitch and tetanic tensions in adult mdx muscle with no obvious alterations in twitch time course or in twitch: tetanus ratios. We suggest that the noninvasive WBT procedure may be used to partially assess various therapies on this murine model of Duchenne muscular dystrophy.
Further studies are reported which examines the influence of fixed negative sites on anion distribution in the interstitium of mouse gastrocnemius muscle. For this purpose, the 35S-sulfate distribution in in vitro muscles was examined in the absence and presence of a number of cations which are thought to bind to the interstitial fixed negative sites. Each of the cation treated muscles gave sulfate space measurements which were statistically greater than the control muscles. Ferritin, spermidine and ruthenium red treatment resulted in muscle sulfate spaces similar to the true morphometric ECV. This study suggests that the fixed negative sites in the interstitium of mouse gastrocnemius muscle exists in sufficient density to influence the distribution of anions in these tissue.
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