Duchenne muscular dystrophy is due to genetic abnormalities in the dystrophin gene and represents one of the most frequent genetic childhood diseases. In the X-linked muscular dystrophy (mdx) mouse model of dystrophinopathy, different subtypes of skeletal muscles are affected to a varying degree albeit the same single base substitution within exon 23 of the dystrophin gene. Thus, to determine p...

It has been shown that lipid peroxidation product levels in the soleus muscles of rats fed palm olein were lower than in the soleus muscles of rats fed soya bean oil. A study was carried out to test our hypothesis that the lower level of lipid peroxidation products in the soleus muscle of palm olein-fed rats is due, at least partly, to the higher amount of vitamin E in their soleus muscles. Exp...

This study examined the effects of an elevation of the gravity factor (hypergravity--2 g) on the molecular and functional characteristics of rat soleus and plantaris muscles. Long Evans rats were conceived, born and reared (CBR) continuously in hypergravity conditions until the age of 100 days. Whole muscle morphological parameters, Ca2+ activation characteristics from single skinned fibers, tr...

We examined whether the protein level and/or activity of glycogenin, the protein core upon which glycogen is synthesized, is limiting for maximal attainable glycogen levels in rat skeletal muscle. Glycogenin activity was 27.5 +/- 1.4, 34.7 +/- 1.7, and 39.7 +/- 1.3 mU/mg protein in white gastrocnemius, red gastrocnemius, and soleus muscles, respectively. A similar fiber type dependency of glyco...

The intracellular signals that mediate skeletal muscle protein loss and functional deficits due to muscular disuse are just beginning to be elucidated. Previously we showed that the activity of an NF-kappaB-dependent reporter gene was markedly increased in unloaded muscles, and p50 and Bcl-3 proteins were implicated in this induction. In the present study, mice with a knockout of the p105/p50 (...

The rapid atrophy of skeletal muscles upon fasting or denervation is due largely to an increased rate of protein breakdown. Blocking the lysosomal or the Ca(2+)-dependent pathways did not prevent increased proteolysis in muscles from fasted animals or following denervation. In contrast, upon food deprivation, the nonlysosomal ATP-dependent process increased by 150-350%. After refeeding, this pr...

Tumor necrosis factor-alpha (TNF-alpha) has been associated with cachexia and is known to regulate multiple inflammatory cell (neutrophil and macrophage) responses. We tested the hypothesis that neutrophils and macrophages accumulate in the extensor digitorum longus (EDL) and soleus muscles of mice after chronic TNF-alpha administration. Murine recombinant TNF-alpha (approximately 100 microg x ...

The hindlimb-unloading model was used to study the ability of muscle injured in a weightless environment to recover after reloading. Satellite cell mitotic activity and DNA unit size were determined in injured and intact soleus muscles from hindlimb-unloaded and age-matched weight-bearing rats at the conclusion of 28 days of hindlimb unloading, 2 wk after reloading, and 9 wk after reloading. Th...

Male skeletal muscles are generally faster and have higher maximum power output than female muscles. Conversely, during repeated contractions, female muscles are generally more fatigue resistant and recover faster. We studied the role of estrogen receptor-beta (ERbeta) in this gender difference by comparing contractile function of soleus (mainly slow-twitch) and extensor digitorum longus (fast-...

Beitzel F, Sillence MN, Lynch GS. -Adrenoceptor signaling in regenerating skeletal muscle after -agonist administration. Am J Physiol Endocrinol Metab 293: E932–E940, 2007. First published July 10, 2007; doi:10.1152/ajpendo.00175.2007.—Stimulating the -adrenoceptor ( -AR) signaling pathway can enhance the functional repair of skeletal muscle after injury, but long-term use of -AR agonists cause...