Transcriptional profile of GTP-mediated differentiation of C2C12 skeletal muscle cells.

Several purine receptors have been localised on skeletal muscle membranes. Previous data support the hypothesis that extracellular guanosine 5'-triphosphate (GTP) is an important regulatory factor in the development and function of muscle tissue. We have previously described specific extracellular binding sites for GTP on the plasma membrane of mouse skeletal muscle (C2C12) cells. Extracellular GTP induces an increase in intracellular Ca(2+) concentrations that results in membrane hyperpolarisation through Ca(2+)-activated K(+) channels, as has been demonstrated by patch-clamp experiments. This GTP-evoked increase in intracellular Ca(2+) is due to release of Ca(2+) from intracellular inositol-1,4,5-trisphosphate-sensitive stores. This enhances the expression of the myosin heavy chain in these C2C12 myoblasts and commits them to fuse into multinucleated myotubes, probably via a phosphoinositide-3-kinase-dependent signal-transduction mechanism. To define the signalling of extracellular GTP as an enhancer or modulator of myogenesis, we investigated whether the gene-expression profile of differentiated C2C12 cells (4 and 24 h in culture) is affected by extracellular GTP. To investigate the nuclear activity and target genes modulated by GTP, transcriptional profile analysis and real-time PCR were used. We demonstrate that in the early stages of differentiation, GTP up-regulates genes involved in different pathways associated with myogenic processes, including cytoskeleton structure, the respiratory chain, myogenesis, chromatin reorganisation, cell adhesion, and the Jak/Stat pathway, and down-regulates the mitogen-activated protein kinase pathway. GTP also increases the expression of three genes involved in myogenesis, Pp3ca, Gsk3b, and Pax7. Our data suggests that in the myogenic C2C12 cell line, extracellular GTP acts as a differentiative factor in the induction and sustaining of myogenesis.

Effects of hypoxia on nocturnal erection quality: a case report from the Manaslu expedition.

INTRODUCTION: High altitude environment represents a fine model to study physiological and pathophysiological effects of oxygen availability on sleep-related erections (SREs). AIM: To describe altitude-dependent effects on quality of SREs in order to estimate the role of hypoxia in erection physiology. METHODS: A healthy 37-year-old male mountain climber underwent a chronic high altitude-related hypoxia experience during the 43 days of the Manaslu expedition (Nepal). SREs were recorded by RigiScan (Timm Medical Technologies, Inc., Eden Prairie, MN, USA) at altitudes ranging from 0 to 5,800 m above sea level. The erection-related parameters assessed were: number, duration, event duration (% of session), event rigidity %, time rigidity %, tumescence and rigidity activated unit, and event tum % > bline (%). MAIN OUTCOMES MEASURES: SREs were recorded by RigiScan at altitudes ranging from 0 to 5,800 m above sea level. RESULTS: Erectile parameters showed an altitude-related reduction during the hypoxic exposure, although all functional alterations were reverted by the return to sea level. CONCLUSIONS: Our case report supports the hypothesis that oxygen availability and delivery could play an important role in the regulation of local penile erection-related mechanisms and that low oxygen levels might be considered an etiological cofactor in erectile dysfunction.

Tiny percutaneous needle biopsy: An efficient method for studying cellular and molecular aspects of skeletal muscle in humans.

Needle biopsy is widely used to obtain specimens for physiological, anatomical and biochemical studies of skeletal muscle (SM). We optimized a procedure which we termed tiny percutaneous needle biopsy (TPNB), to efficiently gather good numbers of human satellite cells and single dissociated fibers for the functional study of skeletal muscle; these samples permit isolation of high-quality RNA and sufficient amounts of proteins to allow molecular analysis. Moreover, TPNB showed a clear advantage in that the technique was easier than other procedures used on healthy volunteers in human trials. TPNB is a very safe minor surgical procedure. It is less traumatic than needle aspiration biopsy, and significant complications are improbable. TPNB should become established as an important tool in the investigation of SM and may be employed to study various physiological aspects of SM in human subjects. We suggest that TPNB should also be used in the study of muscle diseases and disorders including muscular dystrophy, congenital myopathy, and metabolic defects.

Acute and cumulative effects of focused high-frequency vibrations on the endocrine system and muscle strength.

The purpose of this study was to evaluate the acute and long-term effects of local high-intensity vibration (HLV, f = 300 Hz) on muscle performance and blood hormone concentrations in healthy young men. Totally 18 subjects (cV group) were studied in two sessions, either without (control) or with HLV treatment. The protocol was the same on both control and test days, except that, in the second session, subjects underwent HLV treatment. Counter-movement jumping (CMJ), maximal isometric voluntary contraction (MVC) test, and hormonal levels were measured before the procedure, immediately thereafter, and 1 h later. To assess the long-term effects of HLV, the cV group was subjected to HLV on the leg muscles for 4 weeks, and a second group (cR group, n = 18) embarked upon a resistance training program. All subjects underwent an MVC test and an isokinetic (100 deg/s) test before training, 4 weeks after training, and 2 months after the end of training. The HLV protocol significantly increased the serum level of growth hormone (GH, P < 0.05) and creatine phosphokinase (CPK, P < 0.05), and decreased the level of cortisol (P < 0.05). None of GH, CPK or testosterone levels were altered in controls. There was a significant improvement in MVC (P < 0.05). After 4 weeks, both the cV and cR groups demonstrated significant improvement in MVC and isokinetic tests (P < 0.05). This increase persisted for at least 2 months. Our results indicate that HLV influences the levels of particular hormones and improves neuromuscular performance. Our results indicate that HLV has a long-term beneficial effect comparable to that of resistance training.

Oxidative stress in the denervated muscle.

Following experimental hind limb denervation in rats, this study demonstrates that oxidative stress occurs and advances an hypothesis about its origin. In fact: (i) ROS are formed; (ii) membrane lipids are oxidized; (iii) oxidized ion channels and pumps may lead to increased [Ca(2+)](i); all the above mentioned events increase with denervation time. In the denervated muscle, (iv) mRNA abundance of cytoprotective and anti-oxidant proteins (Hsp70, Hsp27, Sod1, Catalase, Gpx1, Gpx4, Gstm1), as well as (v) SOD1 enzymatic activity and HSP70i protein increase; (vi) an unbalance in mitochondrial OXPHOS enzymes occurs, presumably leading to excess mitochondrial ROS production; (vii) increased cPLA2alpha expression (mRNA) and activation (increased [Ca(2+)](i)) may lead to increased hydroperoxides release. Since anti-oxidant defences appear inadequate to counterbalance increased ROS production with increased denervation time, an anti-oxidant therapeutic strategy seems to be advisable in the many medical conditions where the nerve-muscle connection is impaired.

Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation.

Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation in scuba divers was evaluated. Six volunteers participated in four diving protocols, with 2 wk of recovery between dives. On dive 1, before diving, all divers breathed normally for 20 min at the surface of the sea (Air). On dive 2, before diving, all divers breathed 100% oxygen for 20 min at the surface of the sea [normobaric oxygenation (NBO)]. On dive 3, before diving, all divers breathed 100% O2 for 20 min at 6 m of seawater [msw; hyperbaric oxygenation (HBO) 1.6 atmospheres absolute (ATA)]. On dive 4, before diving, all divers breathed 100% O2 for 20 min at 12 msw (HBO 2.2 ATA). Then they dove to 30 msw (4 ATA) for 20 min breathing air from scuba. After each dive, blood samples were collected as soon as the divers surfaced. Bubbles were measured at 20 and 50 min after decompression and converted to bubble count estimate (BCE) and numeric bubble grade (NBG). BCE and NBG were significantly lower in NBO than in Air [0.142+/-0.034 vs. 0.191+/-0.066 (P<0.05) and 1.61+/-0.25 vs. 1.89+/-0.31 (P<0.05), respectively] at 20 min, but not at 50 min. HBO at 1.6 ATA and 2.2 ATA has a similar significant effect of reducing BCE and NBG. BCE was 0.067+/-0.026 and 0.040+/-0.018 at 20 min and 0.030+/-0.022 and 0.020+/-0.020 at 50 min. NBG was 1.11+/-0.17 and 0.92+/-0.16 at 20 min and 0.83+/-0.18 and 0.75+/-0.16 at 50 min. Prebreathing NBO and HBO significantly alleviated decompression-induced platelet activation. Activation of CD62p was 3.0+/-0.4, 13.5+/-1.3, 10.7+/-0.9, 4.5+/-0.7, and 7.6+/-0.8% for baseline, Air, NBO, HBO at 1.6 ATA, and HBO at 2.2 ATA, respectively. The data show that prebreathing oxygen, more effective with HBO than NBO, decreases air bubbles and platelet activation and, therefore, may be beneficial in reducing the development of decompression sickness.

Oxidative stress and muscle homeostasis.

PURPOSE OF REVIEW: The term oxidative stress is often used to indicate a condition in which the accumulation of reactive oxygen species is considered just damaging. We will discuss both the physiological and pathological role of oxidative stress on skeletal muscle homeostasis and function, and how oxidative stress can activates opposite signaling molecule to regulate gene and protein expression to guarantee muscle adaptation and to trigger a pathological condition. RECENT FINDINGS: Emerging evidences have assigned a critical role to oxidative stress in muscle homeostasis and in the physiopathology of skeletal muscle, suggesting that reactive oxygen species are not merely damaging agent inflicting random destruction to the cell structure and function, but useful signaling molecules to regulate growth, proliferation, differentiation, and adaptation, at least within physiological concentration. SUMMARY: The role of oxidative stress on muscle homeostasis is quite complex. It is clear that transiently increased levels of oxidative stress might reflect a potentially health promoting process, whereas an uncontrolled accumulation of oxidative stress might have pathological implication. Additional work is, therefore, necessary to understand and define precisely whether the manipulation of the redox balance represents a useful approach in the design of therapeutic strategies for muscle diseases.

Effects of acute and chronic low frequency electromagnetic field exposure on PC12 cells during neuronal differentiation.

BACKGROUND/AIMS: The purpose of this study was to provide information about the in vitro neuritogenesis during cell exposure to extremely low frequency electromagnetic fields (ELF-EMFs) of different intensities and durations using pheochromocytoma-derived cell line (PC12 cells) as neuronal model. METHODS: Proliferative rates and neuritogenesis were tested by colorimetric assay and morphological analysis, respectively; reactive oxygen species (ROS) levels and intracellular Ca(2+) variations monitored using single cell videomicroscopy. RESULTS: The long-lasting ELF-EMF exposure (0.1-1.0 mT) did not appear to significantly affect the biological response (proliferation and neuritogenesis). However, during the acute ELF-EMF exposure (30 min), in undifferentiated PC12 cells, there were increased ROS levels and decreased catalase activity, that, conversely, resulted increased after chronic exposure (7 days) at 1.0 mT. Acute exposure (0.1-1.0 mT) affected the spontaneous intracellular Ca(2+) variations in undifferentiated cells, in which basal intracellular Ca(2+) resulted increased after chronic exposure. In addition acute exposure affected cell response to a depolarizing agent, while basal membrane potential was not changed. CONCLUSION: Even if further studies remain necessary to identify the ROS/intracellular Ca(2+)cross-talking pathway activated by ELF-EMF exposure, we support the hypothesis that ROS and Ca(2+) could be the cellular "primum movens" of the ELF-EMF induced effects on biological systems.

Modulation of redox status and calcium handling by extremely low frequency electromagnetic fields in C2C12 muscle cells: A real-time, single-cell approach.

The biological effects of electric and magnetic fields, which are ubiquitous in modern society, remain poorly understood. Here, we applied a single-cell approach to study the effects of short-term exposure to extremely low frequency electromagnetic fields (ELF-EMFs) on muscle cell differentiation and function using C2C12 cells as an in vitro model of the skeletal muscle phenotype. Our focus was on markers of oxidative stress and calcium (Ca(2+)) handling, two interrelated cellular processes previously shown to be affected by such radiation in other cell models. Collectively, our data reveal that ELF-EMFs (1) induced reactive oxygen species production in myoblasts and myotubes with a concomitant decrease in mitochondrial membrane potential; (2) activated the cellular detoxification system, increasing catalase and glutathione peroxidase activities; and (3) altered intracellular Ca(2+)homeostasis, increasing the spontaneous activity of myotubes and enhancing cellular reactivity to a depolarizing agent (KCl) or an agonist (caffeine) of intracellular store Ca(2+)channels. In conclusion, our data support a possible link between exposure to ELF-EMFs and modification of the cellular redox state, which could, in turn, increase the level of intracellular Ca(2+)and thus modulate the metabolic activity of C2C12 cells.

A subpopulation of rat muscle fibers maintains an assessable excitation-contraction coupling mechanism after long-standing denervation despite lost contractility.

To define the time course and potential effects of electrical stimulation on permanently denervated muscle, we evaluated excitation-contraction coupling (ECC) of rat leg muscles during progression to long-term denervation by ultrastructural analysis, specific binding to dihydropyridine receptors, ryanodine receptor 1 (RYR-1), Ca channels and extrusion Ca pumps, gene transcription and translation of Ca-handling proteins, and in vitro mechanical properties and electrophysiological analyses of sarcolemmal passive properties and L-type Ca current (ICa) parameters. We found that in response to long-term denervation: 1) isolated muscle that is unable to twitch in vitro by electrical stimulation has very small myofibers but may show a slow caffeine contracture; 2) only roughly half of the muscle fibers with "voltage-dependent Ca channel activity" are able to contract; 3) the ECC mechanisms are still present and, in part, functional; 4)ECC-related gene expression is upregulated; and 5) at any time point, there are muscle fibers that are more resistant than others to denervation atrophy and disorganization of the ECC apparatus. These results support the hypothesis that prolonged "resting" [Ca] may drive progression of muscle atrophy to degeneration and that electrical stimulation-induced [Ca] modulation may mimic the lost nerve influence, playing a key role in modifying the gene expression of denervated muscle. Hence, these data provide a potential molecular explanation for the muscle recovery that occurs in response to rehabilitation strategies developed based on empirical clinical observations.

Effects of local vibrations on skeletal muscle trophism in elderly people: mechanical, cellular, and molecular events.

Several studies have examined the effects of vibrations on muscle mass and performance in young healthy people. We studied the effects of vibrations on muscles of elderly male and female volunteers (65-85 years of age) diagnosed with sarcopenia. We applied mechanical vibrations locally (local vibrational training) to the thigh muscles at 300 Hz for a period of 12 weeks, starting with a session of 15 min stimulation once a week and increasing to three sessions of 15 min per week. Treated muscles displayed enhanced maximal isometric strength and increased content of fast MyHC-2X myosin. Single muscle fiber analysis did not show any change in cross-sectional area or in specific tension. Analysis of transcriptional profiles by microarray revealed changes in gene expression after 12 weeks of local vibrational training. In particular, pathways related with energy metabolism, sarcomeric protein balance and oxidative stress response were affected. We conclude that vibration treatment is effective in counteracting the loss of muscular strength associated with sarcopenia and the mode of action of vibration is based on cellular and molecular changes which do not include increase in fiber or muscle size.

Energetics of karate (kata and kumite techniques) in top-level athletes.

Breath-by-breath O(2) uptake (VO2, L min(-1)) and blood lactate concentration were measured before, during exercise, and recovery in six kata and six kumite karate Word Champions performing a simulated competition. VO2max, maximal anaerobic alactic, and lactic power were also assessed. The total energy cost (VO2TOT mL kg(-1) above resting) of each simulated competition was calculated and subdivided into aerobic, lactic, and alactic fractions. Results showed that (a) no differences between kata and kumite groups in VO2max, height of vertical jump, and Wingate test were found; (b) VO2TOT were 87.8 +/- 6.6 and 82.3 +/- 12.3 mL kg(-1) in kata male and female with a performance time of 138 +/- 4 and 158 +/- 14 s, respectively; 189.0 +/- 14.6 mL kg(-1) in kumite male and 155.8 +/- 38.4 mL kg(-1) in kumite female with a predetermined performance time of 240 +/- 0 and 180 +/- 0 s, respectively; (c) the metabolic power was significantly higher in kumite than in kata athletes (p < or = 0.05 in both gender); (d) aerobic and anaerobic alactic sources, in percentage of the total, were significantly different between gender and disciplines (p < 0.05), while the lactic source was similar; (e) HR ranged between 174 and 187 b min(-1) during simulated competition. In conclusion, kumite appears to require a much higher metabolic power than kata, being the energy source with the aerobic contribution predominant.

Molecular basis of the myogenic profile of aged human skeletal muscle satellite cells during differentiation.

Sarcopenia is the age-related loss of muscle mass, strength and function. Human muscle proteins are synthesized at a slower rate in the elderly than in young adults, leading to atrophy and muscle mass loss with a decline in the functional capability. Additionally, aging is accompanied by a decrease in the ability of muscle tissue to regenerate following injury or overuse due to the impairment of intervening satellite cells, in which we previously reported oxidative damage evidences. The aim of the present study was to determine the effects of aging on myoblasts and myotubes obtained from human skeletal muscle, and characterize the transcriptional profile as molecular expression patterns in relation to age-dependent modifications in their regenerative capacity. Our data show that the failure to differentiate does not depend on reduced myogenic cell number, but difficulty to complete the differentiation program. Data reported here suggested the following findings: (i) oxidative damage accumulation in molecular substrates, probably due to impaired antioxidant activity and insufficient repair capability, (ii) limited capability of elderly myoblasts to execute a complete differentiation program; restricted fusion, possibly due to altered cytoskeleton turnover and extracellular matrix degradation and (iii) activation of atrophy mechanism by activation of a specific FOXO-dependent program.

Oxidative-induced membrane damage in diabetes lymphocytes: effects on intracellular Ca(2 +) homeostasis.

Oxidative stress is linked to several human diseases, including diabetes. However, the intracellular signal transduction pathways regulated by reactive oxygen species (ROS) remain to be established. Deleterious effects of ROS stem from interactions with various ion transport proteins such as ion channels and pumps, primarily altering Ca(2 +) homeostasis and inducing cell dysfunction. This study characterized the Ca(2 +) transport system in lymphocytes of patients with type-2 diabetes, evaluating the possible correlation between cell modifications and the existence of specific oxidative stress damage. Lymphocytes from type-2 diabetes patients displayed oxidative stress features (accumulation of some ROS species, membrane peroxidation, increase in protein carbonyls, increase in SOD and Catalase activity) and Ca(2 +) dyshomeostasis (modified voltage-dependent and inositol 1,4,5-triphosphate-mediated Ca(2 +) channel activities, decrease in Ca(2 +) pumps activity). The data support a correlation between oxidative damage and alterations in intracellular Ca(2 +) homeostasis, possibly due to modification of the ionic control in lymphocytes of type-2 diabetes patients.

Skeletal muscle is a primary target of SOD1G93A-mediated toxicity.

The antioxidant enzyme superoxide dismutase 1 (SOD1) is a critical player of the antioxidative defense whose activity is altered in several chronic diseases, including amyotrophic lateral sclerosis. However, how oxidative insult affects muscle homeostasis remains unclear. This study addresses the role of oxidative stress on muscle homeostasis and function by the generation of a transgenic mouse model expressing a mutant SOD1 gene (SOD1(G93A)) selectively in skeletal muscle. Transgenic mice developed progressive muscle atrophy, associated with a significant reduction in muscle strength, alterations in the contractile apparatus, and mitochondrial dysfunction. The analysis of molecular pathways associated with muscle atrophy revealed that accumulation of oxidative stress served as signaling molecules to initiate autophagy, one of the major intracellular degradation mechanisms. These data demonstrate that skeletal muscle is a primary target of SOD1(G93A) -mediated toxicity and disclose the molecular mechanism whereby oxidative stress triggers muscle atrophy.

IgIII (270-280)-fragment-like H2N-DDSDEEN-COOH peptide modulates N-CAM expression via Ca2+-dependent ERK signaling during "in vitro neurogenesis".

The two major isoforms (180 kDa and 140 kDa) of the neural cell adhesion molecule (N-CAM) are crucially involved in neurogenesis and brain repair via activation of the mitogen-activated protein kinase (MAPK) cascade. Modification by glycosylation, and homophilic and heterophilic interactions regulate the function of N-CAM, but little is known about the interplay of these processes. In the neuron-like PC12 cell line, extracellular small acidic peptides have been shown to modulate the expression of N-CAM mRNA and protein and regulate its translocation to the plasma membrane. Among these peptides, a synthetic Ig-III-like short sequence (H2N-DDSDEEN-COOH), designated sSP, was particularly potent. In this study, we analyzed the cross-talk between nerve growth factor (NGF) and extracellular sSP in native and N-CAM-transfected PC12 cells to determine if these systems interact to modulate transduction pathways and regulate early steps of neurogenesis in vitro. Our results indicate that sSP accelerated the phosphorylation of extracellular regulated kinase-1 (ERK1) and -2 (ERK2) and promoted plasma membrane translocation of 180 kDa N-CAM. By stabilizing cell-cell contacts and promoting cell cluster formation, these events, which were mediated via a significant increase in intracellular Ca2+, regulated some of the early stages of the NGF-induced differentiation process.

Specific correlations between muscle oxidative stress and chronic fatigue syndrome: a working hypothesis.

Chronic fatigue syndrome (CFS) is a relatively common disorder defined as a status of severe persistent disabling fatigue and subjective unwellness. While the biological basis of the pathology of this disease has recently been confirmed, its pathophysiology remains to be elucidated. Moreover, since the causes of CFS have not been identified, treatment programs are directed at symptom relief, with the ultimate goal of the patient regaining some level of pre-existing function and well-being. Several studies have examined whether CFS is associated with: (i) a range of infectious agents and or immune disturbance; (ii) specific changes of activity in the central or peripheral nervous systems; and (iii) elevated stress periods, which may be associated with the pathology via genetic mechanisms. The role of oxidative stress in CFS is an emerging focus of research due to evidence of its association with some pathological features of this syndrome. New data collectively support the presence of specific critical points in the muscle that are affected by free radicals and in view of these considerations, the possible role of skeletal muscle oxidative imbalance in the genesis of CFS is discussed.

Progressive disorganization of the excitation-contraction coupling apparatus in aging human skeletal muscle as revealed by electron microscopy: a possible role in the decline of muscle performance.

An impairment of the mechanisms controlling the release of calcium from internal stores (excitation-contraction [EC] coupling) has been proposed to contribute to the age-related decline of muscle performance that accompanies aging (EC uncoupling theory). EC coupling in muscle fibers occurs at the junctions between sarcoplasmic reticulum and transverse tubules, in structures called calcium release units (CRUs). We studied the frequency, cellular localization, and ultrastructure of CRUs in human muscle biopsies from male and female participants with ages ranging from 28 to 83 years. Our results show significant alterations in the CRUs' morphology and cellular disposition, and a significant decrease in their frequency between control and aged samples: 24.4/100 microm(2) (n = 2) versus 11.6/100 microm(2) (n = 7). These data indicate that in aging humans the EC coupling apparatus undergoes a partial disarrangement and a spatial reorganization that could interfere with an efficient delivery of Ca(2+) ions to the contractile proteins.

Extracellular guanosine-5'-triphosphate modulates myogenesis via intermediate Ca(2+)-activated K+ currents in C2C12 mouse cells.

In this study we investigated the role of extracellular 5'-guanosine-triphosphate (GTP) on early phases of skeletal muscle differentiation using the widely used C2C12 mouse cells as a myogenic model. We show that extracellular GTP binding to specific sites activates a metabotropic cascade that leads to a transient intracellular Ca2+ mobilization, consequent activation of the intermediate Ca(2+)-activated K+ channels (IK(Ca)), and hyperpolarization of the plasma membrane. We further show that in differentiating C2C12 myoblasts GTP induces a proliferative boost, and increases the number of cells positive for the myosin heavy chain (MyHC) proteins. These effects were shown to be mediated by the IK(Ca) channel-dependent hyperpolarization, as evidenced by their disappearance when myoblasts were incubated with the IK(Ca) channel inhibitor charybdotoxin. These data give new insights into nucleotide purinergic signalling pathways, and address the role of the GTP-dependent IK(Ca) channel activation and hyperpolarization in myogenesis.

Age-dependent imbalance of the antioxidative system in human satellite cells.

The mature myofibres of human skeletal muscle are surrounded by a type of adult stem cell, known as the satellite cell, which lies outside the sarcolemma but within the basal lamina. These cells remain quiescent until external stimuli trigger their re-entry into the cell cycle. In humans, ageing is characterised by a progressive loss of muscle mass and strength (sarcopenia) associated with a decline in functional ability. One of the possible causes of this decline in muscle performance is a decrease in the antioxidative capacity of skeletal muscle, resulting in an abnormal accumulation of the reactive oxygen species (ROS) critical for cell life. The present study shows that: (i) the antioxidant activity of Catalase and Gluthatione transferase in satellite cells derived from the elderly is drastically reduced compared to that in cells isolated from young individuals; (ii) cell membrane fluidity is considerably different between the two age groups; and (iii) basal [Ca(2+)](i) levels in satellite cells increase significantly in an age-dependent manner. In view of the data obtained, we hypothesise that the destabilising oxidative damage that occurs during ageing in skeletal muscle also affects quiescent satellite cells, which spend their life in close anatomic and functional contact with adult fibres. This status is derived from a decrease in the antioxidative capacity, and may negatively affect the ageing satellite cells ability to repair muscle.