Cell and Tissue Research

, Volume 302, Issue 2, pp 235–241

Nuclear DNA fragmentation and morphological alterations in adult rabbit skeletal muscle after short-term immobilization

Authors

  • Heather K. Smith
    • Department of Sport and Exercise Science, University of Auckland, Private Bag 92019, Auckland, New Zealand
  • Linda Maxwell
    • Department of Pathology, University of Auckland, Auckland, New Zealand
  • Julie A. Martyn
    • AgResearch, Ruakura, New Zealand
  • John J. Bass
    • AgResearch, Ruakura, New Zealand
Regular Article

DOI: 10.1007/s004410000280

Cite this article as:
Smith, H., Maxwell, L., Martyn, J. et al. Cell Tissue Res (2000) 302: 235. doi:10.1007/s004410000280

Abstract.

Nuclear DNA fragmentation and ultrastructural changes, indicative of myonuclear apoptosis, were examined in adult skeletal muscle in response to short-term immobilization. Adult rabbits were allocated to 2 days (n=5) or 6 days (n=5) of unilateral casting of the ankle in full plantar flexion or were used as untreated controls (n=2). Atrophy of the soleus muscle was apparent by significant reductions in wet mass of 15% and 26% after 2 days and 6 days of casting (P≤0.05), respectively. Mean fibre cross-sectional area and myonuclear number per section were also lower (17% and 9.1%, respectively) after 6 days of casting, in comparison with contralateral control muscles (P≤0.05). Electron-microscopic examination showed condensed chromatin and irregularly shaped myonuclei in muscles immobilized for either 2 days or 6 days. Myofibrillar disruption and abnormalities of the subsarcolemmal mitochondria were also apparent in the absence of inflammation or plasma membrane alterations in cast muscles. Longitudinal and transverse sections showed abundant in situ end-labelling of DNA strand breaks (TUNEL) after 2 days, with less after 6 days, of immobilization. Positive labelling corresponded to myonuclear locations within fibres, yet the number of TUNEL-positive nuclei indicated DNA fragmentation in additional cell types such as capillary endothelial cells or fibroblasts. The data indicate that the immobilization of slow-twitch skeletal muscle in a shortened position rapidly induces morphological alterations consistent with mitochondrial injury and apoptotic myonuclear elimination.

Apoptosis Atrophy Inflammation Myonuclei Necrosis Rabbit

Copyright information

© Springer-Verlag 2000