Effect of denervation on pigeon slow skeletal muscle

Summary The slow anterior latissimus dorsi muscle (ALD) of the pigeon was denervated surgically and examined after varying post-operative intervals. Muscles were studied with respect to changes in weight, histological and ultrastructural alterations, and changes in size and number of fibers. The weights of the denervated muscles increased over the contralateral control, reaching a maximum hypertrophy in the first 18 days, but the hypertrophy persisted for several months. The fibers of the denervated muscle did not hypertrophy. They showed a gradation in size from the posterior to the anterior border, with the fibers in the anterior third of the muscle being the smallest. After measuring cross-sectional sizes from the anterior, middle, and posterior thirds of the muscle, the overall fiber change was one of atrophy.Morphologically, the fibers showed various signs of pathological changes, including nuclear proliferation, swelling and migration away from the sarcolemmal position, vacuolation, myofibril degeneration, connective-tissue infiltration and replacement of the fibers, and regenerative activities in the form of budding and myoblast formation. A condition termed a peripheral rim of degeneration is described. Although many abnormal conditions were found in these denervated muscles, much of the muscle appeared normal; the neurotrophic relationship of slow muscle is discussed.This investigation was supported in part by a Public Health Service Fellowship, 2 F 2 NB 35, 582, from the National Institute of Neurological Diseases and Stroke, and by an Ohio University Research Grant to R. Hikida; and a grant 5 RO 1 AN 10856 from the National Institute of Arthritis and Metabolic Diseases to W. Bock.The authors wish to acknowledge gratefully the skillful technical assistance of Mr. Lawrence Mezza and Miss Sally Mitchell.