Locomotor Muscle Research Articles

Restricted Activity and Protein Synthesis in Postural and Locomotor Muscles

Restricted Activity and Protein Synthesis in Postural and Locomotor Muscles

A Fast‐Start Pacing Strategy Does Not Improve Locomotor Fatigue Dynamics But Does Improve Supra‐Critical Power Work Capacity

Tolerance for high-intensity constant power exercise is dictated by the hyperbolic relationship between power and duration. This relationship is defined by two parameters: the asymptote, termed critical power, and the curvature constant (W′). Critical power distinguishes predictable tolerance to high-intensity work from power outputs resulting in unpredictable exercise tolerance. The amount of work that can be completed above critical power is W′. Interestingly, the pacing strategy for which the participant expends W' affects exercise tolerance in short bouts. However, these improvements seem not to persist during exercise bouts 6 min or longer. Purported mechanisms for this modulation in tolerance are speeding/slowing of oxidative metabolism. One result of speeded kinetics of metabolism could be the preservation of voluntary locomotor power. Objective To measure locomotor muscle fatigue dynamics and exercise tolerance during a fast-start pacing strategy compared to a constant power task. Methods Volunteers (N=15, 27±4yr, 176±7cm, 77±12kg) completed constant and fast-start exercise tasks to the limit of tolerance above critical power. Maximal isokinetic power was measured throughout as an index of locomotor fatigue. Results Compared to constant power pacing, a fast-start pacing strategy resulted in augmented tolerance to supra-critical power exercise of (CI95 23, 79 s). Tolerance to constant power exercise was reproducible and was not different before and after the fast-start strategy bout. The decline in maximal isokinetic power was not different during constant power and fast-start pacing strategies, nor was there an interaction of pacing strategy and time (F[5, 168]=0.5, p=0.75). Maximal isokinetic power was lower during the fast-start strategy vs constant power when the data were normalized to baseline isokinetic power (F[1,168]=6.2, p=0.01). However, no interaction of pacing strategy and time was present (F[5,168]=0.39, p=0.85). Conclusions While fast-start pacing improved exercise tolerance and augmented the supra-critical power work tolerance, the dynamics of locomotor fatigue were not different between conditions. Interestingly, our data argue against a fixed volume of work (W') above critical power and lend more evidence that W' is a result of a complex conflation of fatigue-related processes rather than a simple work capacity.

Acute and chronic tirasemtiv treatment improves in vivo and in vitro muscle performance in actin-based nemaline myopathy mice.

Nemaline myopathy, a disease of the actin-based thin filament, is one of the most frequent congenital myopathies. To date, no specific therapy is available to treat muscle weakness in nemaline myopathy. We tested the ability of tirasemtiv, a fast skeletal troponin activator that targets the thin filament, to augment muscle force—both in vivo and in vitro—in a nemaline myopathy mouse model with a mutation (H40Y) in Acta1. In Acta1H40Y mice, treatment with tirasemtiv increased the force response of muscles to submaximal stimulation frequencies. This resulted in a reduced energetic cost of force generation, which increases the force production during a fatigue protocol. The inotropic effects of tirasemtiv were present in locomotor muscles and, albeit to a lesser extent, in respiratory muscles, and they persisted during chronic treatment, an important finding as respiratory failure is the main cause of death in patients with congenital myopathy. Finally, translational studies on permeabilized muscle fibers isolated from a biopsy of a patient with the ACTA1H40Y mutation revealed that at physiological Ca2+ concentrations, tirasemtiv increased force generation to values that were close to those generated in muscle fibers of healthy subjects. These findings indicate the therapeutic potential of fast skeletal muscle troponin activators to improve muscle function in nemaline myopathy due to the ACTA1H40Y mutation, and future studies should assess their merit for other forms of nemaline myopathy and for other congenital myopathies.

SDH Subunit C Regulates Muscle Oxygen Consumption and Fatigability in an Animal Model of Pulmonary Emphysema.

Patients with pulmonary emphysema often develop locomotor muscle dysfunction, which is independently associated with disability and higher mortality in that population. Muscle dysfunction entails reduced force generation capacity, which partially depends on fibers' oxidative potential, yet very little mechanistic research has focused on muscle respiration in pulmonary emphysema. Using a recently established animal model of pulmonary emphysema-driven skeletal muscle dysfunction, we found downregulation of SDHC (succinate dehydrogenase subunitC) in association with lower oxygen consumption and fatigue tolerance in locomotor muscles. Reduced SDH activity has been previously observed in muscles from patients with pulmonary emphysema, and we found that SDHC is required to support respiration in cultured muscle cells. Moreover, invivo gain of SDH function in emphysema animals' muscles resulted in better oxygen consumption rate and fatigue tolerance. These changes correlated with a larger number of relatively more oxidative type 2-A and 2X fibers and a reduced amount of 2B fibers. Our data suggest that SDHC is a key regulator of respiration and fatigability in pulmonary emphysema-driven skeletal muscles, which could be impactful in developing strategies aimed at attenuating this comorbidity.

Exercise Training-Induced Extracellular Matrix Protein Adaptation in Locomotor Muscles: A Systematic Review

Exercise training promotes muscle adaptation and remodelling by balancing the processes of anabolism and catabolism; however, the mechanisms by which exercise delays accelerated muscle wasting are not fully understood. Intramuscular extracellular matrix (ECM) proteins are essential to tissue structure and function, as they create a responsive environment for the survival and repair of the muscle fibres. However, their role in muscle adaptation is underappreciated and underinvestigated. The PubMed, COCHRANE, Scopus and CIHNAL databases were systematically searched from inception until February 2021. The inclusion criteria were on ECM adaptation after exercise training in healthy adult population. Evidence from 21 studies on 402 participants demonstrates that exercise training induces muscle remodelling, and this is accompanied by ECM adaptation. All types of exercise interventions promoted a widespread increase in collagens, glycoproteins and proteoglycans ECM transcriptomes in younger and older participants. The ECM controlling mechanisms highlighted here were concerned with myogenic and angiogenic processes during muscle adaptation and remodelling. Further research identifying the mechanisms underlying the link between ECMs and muscle adaptation will support the discovery of novel therapeutic targets and the development of personalised exercise training medicine.

The evolution of pelvic limb muscle moment arms in bird-line archosaurs.

Bipedal locomotion evolved along the archosaurian lineage to birds, shifting from "hip-based" to "knee-based" mechanisms. However, the roles of individual muscles in these changes and their evolutionary timings remain obscure. Using 13 three-dimensional musculoskeletal models of the hindlimbs of bird-line archosaurs, we quantify how the moment arms (i.e., leverages) of 35 locomotor muscles evolved. Our results support two hypotheses: From early theropod dinosaurs to birds, knee flexors' moment arms decreased relative to knee extensors', and medial long-axis rotator moment arms for the hip increased (trading off with decreased hip abductor moment arms). Our results reveal how, from the Triassic Period, bipedal theropod dinosaurs gradually modified their hindlimb form and function, shifting more from hip-based to knee-based locomotion and hip-abductor to hip-rotator balancing mechanisms inherited by birds. Yet, we also discover unexpected ancestral specializations in larger Jurassic theropods, lost later in the bird-line, complicating the paradigm of gradual transformation.

A Comparison of the Effect of Strength Training on Cycling Performance between Men and Women.

During the last decade numerous review articles have been published on how concurrent strength and endurance training affect cycling performance. However, none of these have reviewed if there are any sex differences in the effects of concurrent training on cycling performance, and most research in this area has been performed with male cyclists. Thus, the aim of the current paper is to review the scientific literature on the effect of concurrent training on cycling performance in male and female cyclists with a special emphasis on potential sex differences. The results indicate that both male and female cyclists experience a similar beneficial effect from concurrent training on cycling performance and its physiological determinants compared to normal endurance training only. Some data indicate that women have a larger effect on cycling economy, but more studies are needed to explore this further. Furthermore, the adaptations to strength training thought to be responsible for the beneficial effects on cycling performance seem to be very similar between men and women. Interestingly, increased muscle cross-sectional area in the main locomotor muscles seems to be an important adaptation for improved performance, and, contrary to popular belief, cyclists should aim for increased muscle cross-sectional area when adding strength training to their normal training. We conclude that both male and female cyclists can improve their cycling performance by adding strength training to their normal training.

Maniraptoran pelvic musculature highlights evolutionary patterns in theropod locomotion on the line to birds.

Locomotion is a fundamental aspect of palaeobiology and often investigated by comparing osteological structures and proportions. Previous studies document a stepwise accumulation of avian-like features in theropod dinosaurs that accelerates in the clade Maniraptora. However, the soft tissues that influenced the skeleton offer another perspective on locomotory adaptations. Examination of the pelvis for osteological correlates of hind limb and tail musculature allowed reconstruction of primary locomotory muscles across theropods and their closest extant relatives. Additionally, the areas of pelvic muscle origins were quantified to measure relative differences within and between taxa, to compare morphological features associated with cursoriality, and offer insight into the evolution of locomotor modules. Locomotory inferences based on myology often corroborate those based on osteology, although they occasionally conflict and indicate greater complexity than previously appreciated. Maniraptoran pelvic musculature underscores previous studies noting the multifaceted nature of cursoriality and suggests that a more punctuated step in caudal decoupling occurred at or near the base of Maniraptora.

Mechanisms of adaptation of motor «fast» and «slow» locomotor muscles in mice under conditions of allergic reorganization of the body

The state of the contractile function of transversely striated locomotor muscles under conditions of allergic reorganization remains relevant for modern sports medicine. In particular, it is known that the mandatory vaccination of athletes before the competition leads to changes in the state of the muscular system. The mechanisms of these changes are not fully understood. In the presented work, the following research methods were used: the registration of: a) the contractile function of various locomotor «fast» and «slow» muscles of the mouse in vitro on humoral initiators of contraction — carbacholine (CCh) and potassium chloride (KCI); b) indicators of the systems of pro- and antioxidant balance in the blood and in the tissues of these muscles and the determination of the level of malondialdehyde (MDA) in them. The differences in the ratios of the dynamics of the contraction force and the MDA level in both muscles demonstrate the degree of their resistance to oxidative stress, which determines the differences in the mechanisms of their adaptation to allergic reorganization. The materials of the article can be used to correct the function of locomotor muscles during vaccination, as well as to determine the strategy of therapeutic action, taking into account their fiber composition. The purpose of the article is to determine the mechanisms of adaptation of skeletal muscles (SM) of the mouse («fast» (m.EDL) and «slow» (m.Soleus)) during allergic reorganization.

ANTIOXIDANT, SEDATIVE AND HYPNOTIC POTENTIAL OF MILK EXTRACT OF MYRISTICA FRAGRANS: A COMPLIMENTARY MEDICINE FOR THE MANAGEMENT OF INSOMNIA

The Myristica fragrans (MF) is well known in Ayurveda for many therapeutic uses. The present research work was carried out to investigate the antioxidant (in vitro), sedative and hypnotic effects of the MFmilk extracts in Wistar rats. The extraction was carried out by hot percolation and cold maceration methods. The phytochemical, HPLC and pharmacological evaluations were done. The overall sedative and hypnotic effects of the different extracts were evaluated using the parameters locomotor activity, muscle strength and thiopental induced sleeping time. The milk extracts shown the presence of quercetin. It was confirmed using HPLC analysis, which might be responsible for its in-vitro antioxidant activity. The extract also showed the significant (P<0.05) sedative and hypnotic effect at 50 mg/kg, 100 mg/kg and 200 mg/kg on oral administration. Consequently, the treated groups have shown a significant increase in thiopental induced sleeping time. The study concluded that the milk extracts possess antioxidant, sedative and hypnotic activity. further research is needed to develop suitable formulation and to establish the mechanism of action of milk extract of MF.

The impact of interrupting enzyme replacement therapy in late-onset Pompe disease

BackgroundLate-onset Pompe disease (LOPD) is a rare autosomal recessive disorder caused by mutations in the GAA gene, leading to progressive weakness of locomotor and respiratory muscles. Enzyme replacement therapy (ERT), administered every second week, has been proven to slow down disease progression and stabilize pulmonary function. Due to the COVID-19 pandemic in Germany, ERT was interrupted at our centre for 29 days. As reports on ERT discontinuation in LOPD are rare, our study aimed to analyse the impact of ERT interruption on the change in clinical outcome.MethodsWe performed a prospective cohort study in 12 LOPD patients. Clinical assessments were performed after ERT interruption and after the next three consecutive infusions. We assessed motor function by muscle strength testing, a 6-minute-walk-test, pulmonary function tests, and adverse events. For statistical analysis, an estimated baseline was calculated based on the individual yearly decline.ResultsThe mean time of ERT interruption was 49.42 days (SD ± 12.54). During ERT interruption, seven patients reported 14 adverse events and two of them were severe. Frequent symptoms were reduced muscle endurance/increased muscle fatigability and shortness of breath/worsening of breathing impairment. After ERT interruption, significant deterioration was found for MIP%pred (p = 0.026) and MRC%pred, as well as a trend to clinical deterioration in FVC%pred and the 6MWT%pred.ConclusionInterruption of ERT was associated with a deterioration in the core clinical outcome measures. Therefore, an interruption of ERT should be kept as short as possible.

Myoglobin Concentration and Oxygen Stores in Different Functional Muscle Groups from Three Small Cetacean Species.

Simple SummaryMarine mammals display several physiological adaptations to their marine environment. Higher myoglobin concentrations in their muscles compared to terrestrial mammals allow them to increase their onboard oxygen stores, enhancing the time available to dive. Most previous studies have calculated cetaceans’ onboard oxygen stores by assuming the myoglobin concentration of a single muscle to be representative of all the muscles in the body. In this study, we analyzed this assumption by comparing it to a more precise method that weighs all body muscles and measures myoglobin concentration in different functional groups.Compared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g−1 muscle), enhancing their onboard oxygen (O2) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O2 stores have been often determined by measuring Mb concentration from a single muscle sample (longissimus dorsi) and multiplying that value by the animal’s locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O2 stores calculations. For that, body muscles from three delphinid species: Delphinus delphis, Stenella coeruleoalba, and Stenella frontalis, were dissected and weighed. Mb concentration was calculated from six muscles/muscle groups (epaxial, hypaxial and rectus abdominis; mastohumeralis; sternohyoideus; and dorsal scalenus), each representative of different functional groups (locomotion powering swimming, pectoral fin movement, feeding and respiration, respectively). Results demonstrated that the Mb concentration was heterogeneously distributed, being significantly higher in locomotor muscles. Locomotor muscles were the major contributors to total muscle O2 stores (mean 92.8%) due to their high Mb concentration and large muscle masses. Compared to this method, previous studies assuming homogenous Mb concentration distribution likely underestimated total muscle O2 stores by 10% when only considering locomotor muscles and overestimated them by 13% when total muscle mass was considered.

Effects of aerobic exercise training on muscle plasticity in a mouse model of cervical spinal cord injury

Cervical spinal cord injury (SCI) results in permanent life-altering motor and respiratory deficits. Other than mechanical ventilation for respiratory insufficiency secondary to cervical SCI, effective treatments are lacking and the development of animal models to explore new therapeutic strategies are needed. The aim of this work was to demonstrate the feasibility of using a mouse model of partial cervical spinal hemisection at the second cervical metameric segment (C2) to investigate the impact of 6 weeks training on forced exercise wheel system on locomotor/respiratory plasticity muscles. To measure run capacity locomotor and respiratory functions, incremental exercise tests and diaphragmatic electromyography were done. In addition, muscle fiber type composition and capillary distribution were assessed at 51 days following chronic C2 injury in diaphragm, extensor digitorum communis (EDC), tibialis anterior (TA) and soleus (SOL) muscles. Six-week exercise training increased the running capacity of trained SCI mice. Fiber type composition in EDC, TA and SOL muscles was not modified by our protocol of exercise. The vascularization was increased in all muscle limbs in SCI trained group. No increase in diaphragmatic electromyography amplitude of the diaphragm muscle on the side of SCI was observed, while the contraction duration was significantly decreased in sedentary group compared to trained group. Cross-sectional area of type IIa myofiber in the contralateral diaphragm side of SCI was smaller in trained group. Fiber type distribution between contralateral and ipsilateral diaphragm in SCI sedentary group was affected, while no difference was observed in trained group. In addition, the vascularization of the diaphragm side contralateral to SCI was increased in trained group. All these results suggest an increase in fatigue resistance and a contribution to the running capacity in SCI trained group. Our exercise protocol could be a promising non-invasive strategy to sustain locomotor and respiratory muscle plasticity following SCI.

Abnormal skeletal muscle blood flow, contractile mechanics and fibre morphology in a rat model of obese-HFpEF.

Key points Heart failure is characterised by limb and respiratory muscle impairments that limit functional capacity and quality of life. However, compared with heart failure with reduced ejection fraction (HFrEF), skeletal muscle alterations induced by heart failure with preserved ejection fraction (HFpEF) remain poorly explored.Here we report that obese‐HFpEF induces multiple skeletal muscle alterations in the rat hindlimb, including impaired muscle mechanics related to shortening velocity, fibre atrophy, capillary loss, and an impaired blood flow response to contractions that implies a perfusive oxygen delivery limitation.We also demonstrate that obese‐HFpEF is characterised by diaphragmatic alterations similar to those caused by denervation – atrophy in Type IIb/IIx (fast/glycolytic) fibres and hypertrophy in Type I (slow/oxidative) fibres.These findings extend current knowledge in HFpEF skeletal muscle physiology, potentially underlying exercise intolerance, which may facilitate future therapeutic approaches. Peripheral skeletal muscle and vascular alterations induced by heart failure with preserved ejection fraction (HFpEF) remain poorly identified, with limited therapeutic targets. This study used a cardiometabolic obese‐HFpEF rat model to comprehensively phenotype skeletal muscle mechanics, blood flow, microvasculature and fibre atrophy. Lean (n = 8) and obese‐HFpEF (n = 8) ZSF1 rats were compared. Skeletal muscles (soleus and diaphragm) were assessed for in vitro contractility (isometric and isotonic properties) alongside indices of fibre‐type cross‐sectional area, myosin isoform, and capillarity, and estimated muscle PO2. In situ extensor digitorum longus (EDL) contractility and femoral blood flow were assessed. HFpEF soleus demonstrated lower absolute maximal force by 22%, fibre atrophy by 24%, a fibre‐type shift from I to IIa, and a 17% lower capillary‐to‐fibre ratio despite increased capillary density (all P < 0.05) with preserved muscle PO2 (P = 0.115) and isometric specific force (P > 0.05). Soleus isotonic properties (shortening velocity and power) were impaired by up to 17 and 22%, respectively (P < 0.05), while the magnitude of the exercise hyperaemia was attenuated by 73% (P = 0.012) in line with higher muscle fatigue by 26% (P = 0.079). Diaphragm alterations (P < 0.05) included Type IIx fibre atrophy despite Type I/IIa fibre hypertrophy, with increased indices of capillarity alongside preserved contractile properties during isometric, isotonic, and cyclical contractions. In conclusion, obese‐HFpEF rats demonstrated blunted skeletal muscle blood flow during contractions in parallel to microvascular structural remodelling, fibre atrophy, and isotonic contractile dysfunction in the locomotor muscles. In contrast, diaphragm phenotype remained well preserved. This study identifies numerous muscle‐specific impairments that could exacerbate exercise intolerance in obese‐HFpEF.

Jump control of a robot with a redundant musculoskeletal system including biarticular muscles

Understanding the functions of a coordinated drive of biarticular and monoarticular muscles in locomotion is fundamental to establishing a control strategy of a musculoskeletal robot. However, our current understanding is inadequate due to the complexity of the musculoskeletal structure. To tackle this issue, in this study, we developed a monopod robot with a musculoskeletal system including three biarticular muscles. We investigated the relationship between the height of a jump and the drive timing of two muscles: the gastrocnemius and soleus. As a result, we found that the relationship of the drive timing determined the height of a jump. We found that driving the gastrocnemius muscle earlier than the soleus muscle improved the jump height compared to the case where it was not. We also confirmed that the robot could jump three times consecutively with the parameters achieving the highest jump in this study.

Ограничение двигательной активности и синтез белка в постуральных и локомоторных мышцах

With urbanization, automation and mechanization of labor, a difficult epidemiological situation and self-isolation, the level of daily physical activity in a modern person decreases. The aim of the study was to study the effect of restricted activity on protein synthesis in postural and locomotor muscles. An experiment with restricted activity for 21 days was carried out on Wistar rats. The intensity of protein synthesis and anabolic signaling pathways were studied in the soleus muscle (m. soleus), which mainly consists of slow fibers, and the long extensor digitorum of the fingers (m. EDL), mainly consists of fast fibers. The mass of m. soleus and m. EDL was reduced, and a significant decrease in protein synthesis was observed only in m. EDL. There was also a decrease in the phosphorylation of S6 ribosomal protein only in the fast muscle. At the same time, а GSK3β phosphorylation was decreased in m. soleus, in contrast to m. EDL. Markers of proteolysis have been studied. In the experiment, a decrease in the MuRF-1 expression in m. soleus and Atrogin-1/MAFbx expression in m. EDL was observed, as well as an increase in the expression of calpains in m. soleus. Thus, atrophic processes are associated with restricted activity in fast and slow muscle by different signaling mechanisms.

The modulatory effect of Hydrocotyle sibthorpioides in attenuating the aluminium chloride induced neurotoxicity in rat brain

Hydrocotyle sibthorpioides Lam. (Family: Araliaceae) is used widely in the preparation of food in different cuisines of the world. The study was designed to explore the protective effect of different standardised extracts of H. sibthorpioides on the AlCl3 induced neurotoxicity in Alzheimeric rats. When AlCl3 at a dose of 100 mg/kg body weight was administered i.p. for 60 days showed a significant increase in aluminium (Al) level, acetylcholinesterase (AChE) level and protein expressions of amyloid precursor proteins, β and γ secretase, and β-amyloid (Aβ1–42) in the cortex and hippocampus comparing to the control. Moreover, there was a significant reduction in locomotor activity, muscle coordination and cognition and memory. On the other hand, animals treated with chloroform and methanolic extracts of H. sibthorpiodes given at 200 and 100 mg/kg body weight orally with AlCl3 altered the behavioural impairment caused by Al and Al concentration, activity of AChE, synthesis molecules of Aβ generation. The report of histological studies in hippocampus and cortex supported the neuroprotective role of chloroform and a methanolic extract of H. sibthorpioides, which conserved a normal histoarchitecture pattern of cortex and hippocampus. Finally, it can be concluded that chloroform and methanolic extract of H sibthorpioides can alter memory loss induced by aluminum toxicity by enhancing AChE activity and by its involvement in amyloidogenic pathway.

Hypercapnic Respiratory Failure-Driven Skeletal Muscle Dysfunction: It Is Time for Animal Model-Based Mechanistic Research.

Dysfunction of locomotor muscles is frequent in chronic pulmonary diseases and strongly associated with worse outcomes including higher mortality. Although these associations have been corroborated over the last decades, there is poor mechanistic understanding of the process, in part due to the lack of adequate animal models to investigate this process. Most of the mechanistic research has so far been accomplished using relevant individual stimuli such as low oxygen or high CO2 delivered to otherwise healthy animals as surrogates of the phenomena occurring in the clinical setting. This review advocates for the development of a syndromic model in which skeletal muscle dysfunction is investigated as a comorbidity of a well-validated pulmonary disease model, which could potentially allow discovering meaningful mechanisms and pathways and lead to more substantial progress to treat this devastating condition.

Neuroprotective activity of Garcinia morella desr against monosodium glutamate-induced neurotoxicity in rats

The aim of the present study is to evaluate the neuroprotective effect of methanol extract of Garcinia morella Desr leaves in monosodium glutamate (MSG) induced neurotoxicity in rats. The MSG 2 g/kg, i.p. was used to induce the neurotoxicity. The rats were administrated with methanol extract of Garcinia morella Desr leaves (MEGM) 200 and 400 mg/kg, p.o. and Dextromethorphan 30 mg/kg, p.o. after 1 h injection of MSG. The animals were evaluated for its behavioural factors such as muscle grip and locomotor activity. At the end of the study, the antioxidant enzymes levels, neurotransmitter levels, TNFα, ß-amyloid and mineral levels were estimated in brain homogenate. The MEGM treated group shows significant improvement of behavioural and locomotor activity and muscle strength against MSG induced neurotoxicity. The glutathione, SOD, catalase and total protein levels were significantly increased in MEGM treated group. However, significant reduction within the level of varied neurotransmitters like AChE, Dopamine, TNFα, ß-amyloid were observed on treatment with MEGM extract. Further, MEGM also significantly decrease the MSG induced toxicity through declined levels of Ca+2 and Na+ with increased levels of K+. In conclusion, the present study suggests that the MEGM has significant neuroprotective activity against MSG induced neurotoxic rats.

Oxygen uptake, heart rate and activities of locomotor muscles during a critical swimming speed protocol in the gilthead sea bream Sparus aurata.

Oxygen uptake, heart rate and contraction frequencies of slow oxidative (SO) and fast glycolytic (FG) muscle were measured simultaneously in gilthead seabream Sparus aurata submitted to stepwise increases in current speed in a swimming respirometer. Variation in oxygen uptake was closely related to variation in heart rate, over initial steps these rose in concert with an increase in contraction frequency of SO muscle. There was an asymptote in oxygen uptake and heart rate at high speeds that reflected a transition from exclusive use of aerobic SO muscle to a combination of SO and anaerobic FG muscle, and which preceded fatigue.