These sheep exhibit clinical features and morphological changes at the muscle tissue level that are similar to those shown by humans with the disease (Tan et al., 1997).
In this animal model, regeneration of muscle fibers after necrosis induced by notexin injection reduced glycogen storage in regenerating muscle fibers, which showed re-expression of non-muscle (liver and brain) isoforms of GP, thereby indicating the need to investigate the potential functional benefit of inducing at the muscle tissue level these normally latent isoforms (Howell et al., 2014).
The results of a recent study performed in a McArdle sheep model showed that enteral and intramuscular injection of VPA increased muscle expression of GP, although glycogen deposits and the expression of specific GP isoforms at the muscle tissue level were not analyzed (Howell et al., 2015).
In cancer cachexia, where there is extensive and specific loss of skeletal muscle, tissue levels of mRNA for ubiquitin, 20S proteasome α and β subunits and the ubiquitin-conjugating enzyme, E214k, have been found to be increased in mouse (Lorite et al, 1998), rat (Temparis et al, 1994) and humans (Williams et al, 1999).
With regard to the level of PrPSc detected in muscle tissue, the level estimated from the amplification factor in PMCA was lower than that found in a brain homogenate diluted to 10−6 because no PrPSc signal was detected in the first round of amplification.
Sair et al. also recently reported that skeletal muscle tissue pO2 levels are higher than normal in patients with severe sepsis [ 14].
With maximal effort intensities, specific skeletal muscle tissue adaptations (molecular level) may arise through the oxygen-sensing pathway (ie, capillary-to-fibre ratio, fibre cross-sectional area, myoglobin content and oxidative enzyme activity such as citrate synthase) that either do not occur in normoxic conditions or, if they do, they do so to a lesser degree.
Compounding the problem is the finding that while normal muscle tissue makes low levels of HMGCR, regenerating muscle cells make very high levels of HMGCR.
Both the inflamed and noninflamed muscle tissue had equivalent levels of CXCL12 transcripts, but inflamed muscle contained more transcripts of the CXCL12 receptor CXCR4.
In muscle tissue, MSTN mRNA levels were elevated in C57BL/6 in response to high-fat diet, as well as in SWR mice following 9 and 12 wk of high-fat diet intake.
An attempt was also made to relate any observed differences between myocardial and skeletal muscle tissue to localised levels of the two cytokines, tumor necrosis factor-alpha (TNFα) and interleukin-6 (IL-6), as they have, in part, been implicated in eliciting reductions in muscle protein content [19], [20].
