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Michigan State University, East Lansing 48824 and Massey University, Palmerston North, New Zealand
Abstract
Muscle growth of male obese (ob/ob) and lean mice at 2, 3, 5 and 8 wk were analyzed on the basis of weights of gastrocnemius, plantaris and soleus muscles from each hind leg. The carcasses (prepared by removing skin, viscera, head, feet and tail) were analyzed for fat content so that the effect of phenotype on the relationship between muscle weight and fat-free carcass weight could be assessed. For each age group the obese mice had less muscle relative to fat-free carcass weight than lean mice, with the difference being significant at 3 wk (P<.05) and 8 wk (P<.025). The proliferative activity of muscle satellite cells in 2- and 3-wk-old obese and lean mice was measured on isolated muscle fibers by autoradiography. Muscle fiber diameter and number of nuclei/unit length were unaffected by phenotype, but the proportion of muscle nuclei showing proliferative activity was lower (P<.01) in obese than in lean mice at 2 wk (1.05 vs 1.93%, respectively) and 3 wk of age (.23 vs .59%, respectively). These results are consistent with the suggestion that muscle growth is limited by satellite-cell proliferative activity, although direct evidence for a cause and effect relationship is not provided.
1 Supported in part by NIH AM 15847, Michigan Agr. Exp. Sta. No. 10962.
2 Dept. of Anim. Sci., Massey Univ.
3 Dept. of Food Sci. and Human Nutr., Michigan State Univ.
4 Dept. of Anim. Sci., Univ. of Arizona, Tucson 85721.
5 Dept. of Anim. Sci., Michigan State Univ.
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