Type-specific changes in fibre size and satellite cell activation following muscle denervation in two strains of turkey (Meleagris gallopavo).

Morphological features and the chronology of muscle changes after denervation were studied over a 21 d period in 2 heavy (HW) and light-weight (LW) strains of 6-wk-old male turkeys. The atrophy of tibialis cranialis, gastrocnemius lateralis and plantaris muscles was apparent at d 3 after denervation. By d 21 the weight of these muscles had reached 45-60% of that of nondenervated contralateral muscle. Cellular lesions, such as irregularities in mitochondrial distribution or coagulative necrosis with fragmentation and lysis associated with moderate infiltration of inflammatory cells, were similar in both strains. Ten days after denervation, immunolabelling of a proliferating cell nuclear antigen (PCNA) expressed during the G1 and S phase of the cell cycle revealed satellite cell activation in denervated muscles. The number of satellite cells activated at d 21 was markedly greater in the HW than LW strain. Morphometric analysis revealed that fast twitch (type II) fibres were atrophied after denervation, whereas slow-twitch (type I) and slow tonic (type III) fibres were hypertrophied from d 10. Hypertrophy occurred more rapidly in the LW than HW strain.