Change in the Number of Fibers and Nuclei in the Rat Soleus Muscle During Normal Development and Increased Work Load Exercise
Many orthodontists have desired to produce a permanent lengthening of a short upper lip. To produce a permanent increase in skeletal muscle mass, changes associated with hyperplasia would probably have to occur. If it would be possible to demonstrate in animals that skeletal muscle cells and corresponding deoxyribonucleic acid (DNA) increased with exercise, clinical studies on the upper lip would be in order. Male Sprague Dawley albino rats were used to study the effects of exercise and normal development. Increased work load exercise of the soleus muscle was induced by cutting the tendon of the synergestic gastrocnemius. Histological sections of the soleus were used in the studies. Changes of a 67% increase in muscle cell nuclei, a 74% increase in connective tissue cell nuclei with a 26% decrease in fiber number of the soleus found in normal development of rats taken at 24 and 80 days. In the rats with increased work load exercise a significant increase in DNA was found by a companion study using the same animals. It was concluded that increased DNA found in the exercised group may not necessarily indicate an increase in skeletal muscle nuclei, but more logically may represent an increase in DNA resulting from an unexpected pathological lesion.
Orthodontics and Orthodontology, Muscles; DNA
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