Regenerated rat skeletal muscle after periodic contusions.
In the present study we evaluated the morphological aspect and changes in the area and incidence of muscle fiber types of long-term regenerated rat tibialis anterior (TA) muscle previously submitted to periodic contusions. Animals received eight consecutive traumas: one trauma per week, for eight weeks, and were evaluated one (N = 8) and four (N = 9) months after the last contusion. Serial cross-sections were evaluated by toluidine blue staining, acid phosphatase and myosin ATPase reactions. The weight of injured muscles was decreased compared to the contralateral intact one (one month: 0.77 +/- 0.15 vs 0.91 +/- 0.09 g, P = 0.03; four months: 0.79 +/- 0.14 vs 1.02 +/- 0.07 g, P = 0.0007, respectively) and showed abundant presence of split fibers and fibers with centralized nuclei, mainly in the deep portion. Damaged muscles presented a higher incidence of undifferentiated fibers when compared to the intact one (one month: 3.4 +/- 2.1 vs 0.5 +/- 0.3%, P = 0.006; four months: 2.3 +/- 1.6 vs 0.3 +/- 0.3%, P = 0.007, respectively). Injured TA evaluated one month later showed a decreased area of muscle fibers when compared to the intact one (P = 0.003). Thus, we conclude that: a) muscle fibers were damaged mainly in the deep portion, probably because they were compressed against the tibia; b) periodic contusions in the TA muscle did not change the percentage of type I and II muscle fibers; c) periodically injured TA muscles took four months to reach a muscle fiber area similar to that of the intact muscle.
Minamoto
V B
VB
Laboratório de Neurociências, Unidade de Plasticidade Muscular, Departamento de Fisioterapia, Universidade Federal de São Carlos, 13565-905 São Carlos, SP, Brazil.
Bunho
S R
SR
Salvini
T F
TF
D000818:Animals; D003288:Contusions / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000473:pathology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000293:injuries* / Q000473:pathology / Q000502:physiology / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration; D013997:Time Factors