title: Cytoplasm-to-myonucleus ratios and succinate dehydrogenase activities in adult rat slow and fast muscle fibers.
abstract: The relationship between myonuclear number, cellular size, succinate dehydrogenase activity, and myosin type was examined in single fiber segments (n = 54; 9 +/- 3 mm long) mechanically dissected from soleus and plantaris muscles of adult rats. One end of each fiber segment was stained for DNA before quantitative photometric analysis of succinate dehydrogenase activity; the other end was double immunolabeled with fast and slow myosin heavy chain monoclonal antibodies. Mean +/- S.D. cytoplasmic volume/myonucleus ratio was higher in fast and slow plantaris fibers (112 +/- 69 vs. 34 +/- 21 x 10(3) microns3) than fast and slow soleus fibers (40 +/- 20 vs. 30 +/- 14 x 10(3) microns3), respectively. Slow fibers always had small volumes/myonucleus, regardless of fiber diameter, succinate dehydrogenase activity, or muscle of origin. In contrast, smaller diameter (< 70 microns) fast soleus and plantaris fibers with high succinate dehydrogenase activity appeared to have low volumes/myonucleus while larger diameter (> 70 microns) fast fibers with low succinate dehydrogenase activity always had large volume/myonucleus. Slow soleus fibers had significantly greater numbers of myonuclei/mm than did either fast soleus or fast plantaris fibers (116 +/- 51 vs. 55 +/- 22 and 44 +/- 23), respectively. These data suggest that the myonuclear domain is more limited in slow than fast fibers and in the fibers with a high, compared to a low, oxidative metabolic capability.
authors.affiliation: School of Nursing, Los Angeles, CA 90024-6918.
authors.forename: B S
authors.initials: BS
authors.lastname: Tseng
authors.forename: C E
authors.initials: CE
authors.lastname: Kasper
authors.forename: V R
authors.initials: VR
authors.lastname: Edgerton
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002467:Cell Nucleus / Q000201:enzymology / Q000648:ultrastructure*; D048429:Cell Size; D003593:Cytoplasm / Q000201:enzymology / Q000648:ultrastructure*; D004247:DNA / Q000032:analysis; D005260:Female; D009124:Muscle Proteins / Q000032:analysis*; D009132:Muscles / Q000201:enzymology / Q000648:ultrastructure*; D009218:Myosins / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013385:Succinate Dehydrogenase / Q000032:analysis*
chemical_list: D000911:Antibodies, Monoclonal; D009124:Muscle Proteins; D004247:DNA; D013385:Succinate Dehydrogenase; D009218:Myosins