The first suggestion that physical exercise results in free radical-mediated damage to tissues appeared in 1978, and the past three decades have resulted in a large growth of knowledge regarding exercise and oxidative stress. Although the sources of oxidant production during exercise continue to be debated, it is now well established that both resting and contracting skeletal muscles produce reactive oxygen species and reactive nitrogen species. Importantly, intense and prolonged exercise can result in oxidative damage to both proteins and lipids in the contracting myocytes. Furthermore, oxidants can modulate a number of cell signaling pathways and regulate the expression of multiple genes in eukaryotic cells. This oxidant-mediated change in gene expression involves changes at transcriptional, mRNA stability, and signal transduction levels. Furthermore, numerous products associated with oxidant-modulated genes have been identified and include antioxidant enzymes, stress proteins, DNA repair proteins, and mitochondrial electron transport proteins. Interestingly, low and physiological levels of reactive oxygen species are required for normal force production in skeletal muscle, but high levels of reactive oxygen species promote contractile dysfunction resulting in muscle weakness and fatigue. Ongoing research continues to probe the mechanisms by which oxidants influence skeletal muscle contractile properties and to explore interventions capable of protecting muscle from oxidant-mediated dysfunction.

Background: Dietary selenium intakes in many countries, including the United Kingdom, are lower than international recommendations. No functional consequences of these lower intakes have been recognized, although experimental studies suggest that they might contribute to reduced immune function, increased cancer incidence, and increased susceptibility to viral disease. Objective: The objective was to assess whether administration of small selenium supplements to otherwise healthy UK subjects leads to functional changes in immune status and the rates of clearance and mutation of a picornavirus: live attenuated polio vaccine. Design: Twenty-two adult UK subjects with relatively low plasma selenium concentrations (<1.2 μmol/L, ≈60% of those screened) received 50 or 100 μg Se (as sodium selenite) or placebo daily for 15 wk in a double-blind study. All subjects received an oral live attenuated poliomyelitis vaccine after 6 wk and enriched stable ⁷⁴Se intravenously 3 wk later. Results: Selenium supplementation increased plasma selenium concentrations, the body exchangeable selenium pool (measured by using ⁷⁴Se), and lymphocyte phospholipid and cytosolic glutathione peroxidase activities. Selenium supplements augmented the cellular immune response through an increased production of interferon γ and other cytokines, an earlier peak T cell proliferation, and an increase in T helper cells. Humoral immune responses were unaffected. Selenium-supplemented subjects also showed more rapid clearance of the poliovirus, and the poliovirus reverse transcriptase–polymerase chain reaction products recovered from the feces of the supplemented subjects contained a lower number of mutations. Conclusions: The data indicate that these subjects had a functional selenium deficit with suboptimal immune status and a deficit in viral handling. They also suggest that the additional 100 μg Se/d may be insufficient to support optimal function.

Background: We describe a method for subcellular fractionation of mouse skeletal muscle, myoblast and myotubes to obtain relatively pure fractions of nuclear, cytosolic and mitochondrial compartments. Fractionation allows the analysis of a protein of interest (or other cellular component) based on its subcellular compartmental distribution and can also generate molecular information about the state of a cell and/or tissue and how the distribution of a protein may differ between different cellular compartments, tissues or cell types, in response to treatments or ageing. Findings: The described method was specifically developed for skeletal muscle and proliferating/differentiated muscle cells. The purity of the different fractions, representing the cytoplasmic, mitochondrial and nuclear subcellular compartments was validated by western blot analysis of “house-keeper” marker proteins specific for each cellular compartment. Conclusion: This low cost method allowed the mitochondrial, cytoplasmic and nuclear subcellular compartments from the same starting muscle samples to be rapidly and simultaneously isolated with good purity and without the use of an ultracentrifuge. This method permits samples to be frozen at −80°C for future analysis and/or additional processing at a later date.