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. 1997 Oct 6;139(1):129–144. doi: 10.1083/jcb.139.1.129

Figure 4.

Figure 4

MHC isoforms and ATPase activity in 4- and 12-wk-old mice. (A) Electrophoretic separation of MHC isoforms of muscles from soleus, diaphragm, and gastrocnemius. Four major isoforms (IIX/D, IIA, IIB, and I) can be identified. When we compared the desmin +/+, +/−, and −/− mice, similar patterns were found at 4 wk. However, the yield of MHC per mg of tissue was always much less in the Des −/− mice. Note the decreased amount of IIA and IIX MHC in the soleus, and IIB in the diaphragm (at 12 wk). (B) Quantification of the number of slow and fast fibers present in three muscles by ATPase activity at 4 and 12 wk. Slow fibers, such as type I (black), exhibit a high activity, whereas fast fibers, such as type II (white), display a low ATPase activity after acid preincubation. Percentage of fast and slow fibers was measured in the soleus, diaphragm, and gastrocnemius of Des +/+ and −/− mice. In the soleus of Des −/− at 12 wk, note a decrease of fast fibers (white bar) corresponding to the disappearance of the type IIA and X MHC. A relative increase in the percentage of slow fibers (black) was found.