Abstract
Histologic, chemical, and physiologic studies have been undertaken in various types of experimentally produced muscle atrophies in young Macacus rhesus monkeys. In a series of 6 animals, simple disuse atrophy was produced in the right leg of each animal by immobilizing it in a plaster cast. The left leg was used as the control in each case. The gastrocnemius and soleus muscles were completely removed by careful dissection from their proximal and distal attachments while the animals were under light ether anesthesia. The excised muscles (6 atrophied and 6 controls) were then weighed and split longitudinally, one-half being used in the preparation of histologic sections and the other used for chemical studies. The half used for chemical analyses was weighed immediately, sliced into several pieces, and desiccated over sulphuric acid under reduced vapor pressure (20-30 mm. Hg.) until a constant weight was obtained. Nitrogen was then determined quantitatively by the Kjeldahl method, duplicate determinations being made for each of the 12 specimens, and the protein content calculated.
The loss in muscle weight varied from 4.9% in the one-week atrophy to 32.5% in the 10-week atrophy. Despite the decrease of muscle bulk in the atrophied muscle as compared with the respective controls, the relative proportions of water and protein remained substantially the same as in normal muscle. In the 10-week atrophy, for example, the variation in protein content between the control and the atrophied leg was but 0.3% and the difference in water content negligible.
Histologically the chief finding was a uniform shrinkage of the muscle cells. The muscle fibers were narrower but the characteristic appearance of the transverse striations remained unaltered. There was no increase in sarcolemmal or muscle nuclei nor in the connective tissue. The intramuscular blood vessels, nerves, and nerve endings were likewise unaltered.
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