OBJECTIVE In order to provide the scientific basis to find out a practical and effective method to evaluate the degree of muscle atrophy and a better method of prevention and treatment of skeletal muscle atrophy. METHODS Forty-two adult Spray-Dawley rats were used and the model of denervated gastrocnemius muscle was established by cutting off the tibial nerve. The muscle wet weight, diameter and cross section area of myocyte were measured. The motor end-plate, fibrillation potential amplitude and frequency of denervated skeletal muscle were observed. RESULTS The muscle wet weight rapidly reduced within 4 weeks. Afterwards, it maintained about 30 per cent of normal value, and the diameter and cross section area of myocyte progressively reduced. The motor end-plate slightly changed within 4 weeks, but its degeneration accelerated in 6 weeks and disappeared after 16 weeks. The fibrillation potential amplitude was maximum at 2 weeks and it progressively reduced after 12 weeks of muscle denervation. The changes of amplitude and frequency were consistent with the degeneration of end-plate. CONCLUSION The muscle wet weight, diameter and cross section area of myocyte, fibrillation potential amplitude and frequency could be considered as the morphological and electrophysiological indexes of muscle atrophy degree. It’s suggested that the repairing operation of peripheral nerve should be performed before the disappearance of motor end-plate.
OBJECTIVE To explore the regularity of the change of S-100 protein in degenerative nerve after different pathological brachial plexus injuries. METHODS Eighty SD rats were randomly divided into two groups, right C5, C6 preganglionic injury, and postganglionic injury. The distribution and content of S-100 protein in distal degenerative nerve were detected after 1, 2, 3 and 6 months of injury by immunohistochemical methods. RESULTS The S-100 protein was mainly distributed along the axons. The S-100 protein positive axons of each time interval decreased after operation, with significant difference from normal nerves (P lt; 0.01). There was no statistically significant difference among 1, 2, 3 and 6 months group (P gt; 0.05). The S-100 protein stain of postganglionic group was negative. CONCLUSION In preganglionic injury, the functional expression of Schwann’s cells in the distal stump keeps at a certain level and for a certain period. Since Schwann’s cell has inductive effect on nerve regeneration, it suggests that the distal nerve stump in preganglionic injury can be used as nerve grafts.