Table II.
MMg Transgene Causes Fast Fiber Cross Sectional Area to Decrease
| Genotype | Metabolic fiber type | MyHC fiber type | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AllArea |
Glycolytic | Oxidative | Type 2BArea |
|||||||||
| Area | Number | Area | Number | |||||||||
| μm2 ± SEM (n) | μm2 ± SEM | % ± SD | μm2 ± SEM | % ± SD | μm2 ± SEM (n) | |||||||
| wt | 1,119 ± 130 (3) | 1,553 ± 151 | 40 ± 6 | 827 ± 86 | 60 ± 6 | 1,330 ± 101 (3) | ||||||
| MMg | 823 ± 114 (3) | NA | ‡0 | 823 ± 114 | ‡100 | ‡705 ± 19 (4) | ||||||
| MMg + MId | 728 ± 84 (4) | *840 ± 116 | *28 ± 2 | 678 ± 73 | *72 ± 2 | ND | ||||||
| MId | 662 (1) | 727 | 56 | 578 | 44 | ND | ||||||
EDL muscles of animals of each genotype were cryosectioned and reacted for NADH tetrazolium reductase or 2B MyHC. The cross sectional area of each of >200 fibers from the midregion of each muscle was quantified, and the mean area and number of fibers for each category were determined. The means were then averaged to produce the values shown. A statistically robust unbalanced ANOVA determined whether fiber populations varied in size depending on fiber type, individual animal, and genotype. Significant differences were found between animals of the same genotype. After accounting for individual variation, significant differences from wild-type at the genotype level are represented by
(P < 0.05),
(P < 0.001). Distinct metabolic fiber types differed significantly (P < 0.01) in fiber size in wild-type and MId, but not in MMg or MMg + MId.