Is Pattern of Fiber Types Modified in Des –/– Muscle?
After birth the first discernable effects of the lack of desmin were seen on the muscle fiber phenotype. These effects were mainly observed in the soleus and diaphragm muscles where modifications were accompanied by morphological and biochemical changes. These included variability in fiber diameter, the presence of central nuclei, crescent-shaped sarcolemnal masses, and decrease in the amount of type II MHC. Signs of degeneration with fibrosis, macrophage infiltration, and necrosis appear early in the same muscles. It is interesting to note that these effects were most prominent in the diaphragm and the soleus, which have a different morphogenetic pattern when compared to limb muscle (like the EDL). In the anlage of the diaphragm and soleus muscles, primary myotubes are juxtaposed to one another through the entire length and their membranes are extensively coupled by gap junctions; in the anlage of the EDL by contrast, primary myotubes are coupled only at the myotendinous junctions, bu
