Exercise Dose Equalization in High-Intensity Interval Training: A Scoping Review.

Based on comparisons to moderate continuous exercise (MICT), high-intensity interval training (HIIT) is becoming a worldwide trend in physical exercise. This raises methodological questions related to equalization of exercise dose when comparing protocols. The present scoping review aims to identify in the literature the evidence for protocol equalization and the soundness of methods used for it.

Case Studies in Physiology: Maximal oxygen consumption and performance in a centenarian cyclist.

The purpose of this study was to examine the physiological characteristics of an elite centenarian cyclist who, at 101 yr old, established the 1-h cycling record for individuals ≥100 yr old (24.25 km) and to determine the physiological factors associated with his performance improvement 2 yr later at 103 yr old (26.92 km; +11%).

Erythropoietin and the use of a transgenic model of erythropoietin-deficient mice.

Despite its well-known role in red blood cell production, it is now accepted that erythropoietin (Epo) has other physiological functions. Epo and its receptors are expressed in many tissues, such as the brain and heart. The presence of Epo/Epo receptors in these organs suggests other roles than those usually assigned to this protein.

Regulation of myogenesis by environmental hypoxia.

In aerobic organisms, oxygen is a critical factor for tissue and organ morphogenesis from embryonic development throughout the adult life. It regulates various intracellular pathways involved in cellular metabolism, proliferation, cell survival and fate. Organisms or tissues rapidly respond to changes in oxygen availability by activating complex signalling networks, which culminate in the control of mRNA translation and/or gene expression.

Oxygen modulates the glutathione peroxidase activity during the L6 myoblast early differentiation process.

Aim: This work aims to study the regulation of the glutathione peroxidase and catalase activities in myoblasts from the L6 line exposed to 21%, 5% and 1% O2 during the cell differentiation.

Material And Methods: Rat L6 myoblasts were grown in 1%, 5% or 21% O2 in the presence or absence of N-acetyl cysteine. The cell proliferation was evaluated by determining the doubling time and kinetics of cultures by counting cells.

Epo is relevant neither for microvascular formation nor for the new formation and maintenance of mice skeletal muscle fibres in both normoxia and hypoxia.

Erythropoietin (Epo) and vascular growth factor (VEGF) are known to be involved in the regulation of cellular activity when oxygen transport is reduced as in anaemia or hypoxic conditions. Because it has been suggested that Epo could play a role in skeletal muscle development, regeneration, and angiogenesis, we aimed to assess Epo deficiency in both normoxia and hypoxia by using an Epo-deficient transgenic mouse model (Epo-TAg(h)). Histoimmunology, ELISA and real time RT-PCR did not show any muscle fiber atrophy or accumulation of active HIF-1alpha but an improvement of microvessel network and an upregulation of VEGFR2 mRNA in Epo-deficient gastrocnemius compared with Wild-Type one.

Skeletal muscle intrinsic functional properties are preserved in a model of erythropoietin deficient mice exposed to hypoxia.

Erythropoietin (Epo)-induced polycythemia is the main factor of adaptation to hypoxia. In this study, we analysed the effects of Epo deficiency on intrinsic functional properties of slow and fast twitch muscles in a model of erythropoietin deficient mice (Epo-TAg(h)) exposed to hypoxia. We hypothesised that Epo deficiency would be deleterious for skeletal muscle structure and phenotype, which could change its functional properties and alters the adaptive response to ambient hypoxia.

Cerebral adaptations to chronic anemia in a model of erythropoietin-deficient mice exposed to hypoxia.

Anemia and hypoxia in rats result in an increase in factors potentially involved in cerebral angiogenesis. Therefore, the aim of this study was to assess the effect of chronic anemia and/or chronic hypoxia on cerebral cellular responses and angiogenesis in wild-type and anemic transgenic mice. These studies were done in erythropoietin-deficient mice (Epo-TAg(h)) in normoxia and following acute (one day) and chronic (14 days, barometric pressure = 420 mmHg) hypoxia.

Prevotella timonensis sp. nov., isolated from a human breast abscess.

Gram-negative anaerobic rods were isolated from a human breast abscess. Based on genotypic and phenotypic characteristics, the novel strain belonged to the genus Prevotella. Phylogenetic analysis based on 16S rRNA gene sequence comparisons showed that it was closely related to Prevotella buccalis (94 % 16S rRNA gene sequence similarity), Prevotella salivae (90 %) and Prevotella oris (89.

Expression of slow myosin heavy chain during muscle regeneration is not always dependent on muscle innervation and calcineurin phosphatase activity.

In the literature, there is an ambiguity as to the respective roles played by calcineurin phosphatase activity (CPA) and muscle innervation in the reestablishment of the slow-twitch muscle phenotype after muscle regeneration in different species. In this study, we wanted to determine the role of calcineurin and muscle innervation on the appearance and maintenance of the slow phenotype during mouse muscle regeneration. The pattern of myosin expression and CPA was analyzed in adult (n=15), regenerating (n=45) and denervated-regenerating (n=32) slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles.

FGF6 regulates muscle differentiation through a calcineurin-dependent pathway in regenerating soleus of adult mice.

Important functions in myogenesis have been proposed for FGF6, a member of the fibroblast growth factor family accumulating almost exclusively in the myogenic lineage, but its precise role in vivo remains mostly unclear. Here, using FGF6 (-/-) mice and rescue experiments by injection of recombinant FGF6, we dissected the functional role of FGF6 during in vivo myogenesis. We found that the appearance of myotubes was accelerated during regeneration of the soleus of FGF6 (-/-) mice versus wild type mice.

IGF-II is up-regulated and myofibres are hypertrophied in regenerating soleus of mice lacking FGF6.

Important functions in myogenesis have been proposed for FGF6, a member of the fibroblast growth factor family accumulating almost exclusively in the myogenic lineage. However, the use of FGF6(-/-) mutant mice gave contradictory results and the role of FGF6 during myogenesis remains largely unclear. Using FGF6(-/-) mice, we first analysed the morphology of the regenerated soleus following cardiotoxin injection and showed hypertrophied myofibres in soleus of the mutant mice as compared to wild-type mice.

Injection of FGF6 accelerates regeneration of the soleus muscle in adult mice.

FGF6, a member of the fibroblast growth factor (FGF) family, accumulated almost exclusively in the myogenic lineage, supporting the finding that FGF6 could specifically regulate myogenesis. Using FGF6 (-/-) mutant mice, important functions in muscle regeneration have been proposed for FGF6 but remain largely controversial. Here, we examined the effect of a single injection of recombinant FGF6 (rhFGF6) on the regeneration of mouse soleus subjected to cardiotoxin injection, specifically looking for molecular and morphological phenotypes.

Expression of MRF4 protein in adult and in regenerating muscles in Xenopus.

In Xenopus, previous studies showed that the transcripts of the myogenic regulatory factor (MRF) MRF4 accumulate during skeletal muscle differentiation, but nothing is known about the accumulation of XMRF4 protein during myogenesis. In this report, an affinity-purified polyclonal antibody against Xenopus MRF4 was developed and used to describe the pattern of expression of this myogenic factor in the adult and in regenerating muscles. From young forming myotubes, XMRF4 protein persistently accumulated in nuclei during the regeneration process and was strongly expressed in nuclei of adult muscles.

Specific activation of the acetylcholine receptor subunit genes by MyoD family proteins.

Whether the myogenic regulatory factors (MRFs) of the MyoD family can discriminate among the muscle gene targets for the proper and reproducible formation of skeletal muscle is a recurrent question. We have previously shown that, in Xenopus laevis, myogenin specifically transactivated muscle structural genes in vivo. In the present study, we used the Xenopus model to examine the role of XMyoD, XMyf5, and XMRF4 for the transactivation of the (nicotinic acetylcholine receptor) nAChR genes in vivo.

Expression and neural control of follistatin versus myostatin genes during regeneration of mouse soleus.

Follistatin and myostatin are two secreted proteins involved in the control of muscle mass during development. These two proteins have opposite effects on muscle growth, as documented by genetic models. The aims of this work were to analyze in mouse, by using in situ hybridization, the spatial and temporal expression patterns of follistatin and myostatin mRNAs during soleus regeneration after cardiotoxin injury, and to investigate the influence of innervation on the accumulation of these two transcripts.

Two myogenin-related genes are differentially expressed in Xenopus laevis myogenesis and differ in their ability to transactivate muscle structural genes.

Among the myogenic regulatory factors, myogenin is a transcriptional activator situated at a crucial position for terminal differentiation in muscle development. It is unclear at present whether myogenin exhibits unique specificities to transactivate late muscular markers. During Xenopus development, the accumulation of myogenin mRNA is restricted to secondary myogenesis, at the onset of the appearance of adult isoforms of beta-tropomyosin and myosin heavy chain.