Variability in energy cost of running at the end of a triathlon and a marathon

International audienceThe aim of this study was to investigate the increase in energy cost of running occurring at the end of a triathlon and a marathon event and to link them to the metabolic and hormonal changes, as well as to variations in stride length. Seven subjects took part in 3 experimental situations: a 2 h 15 min triathlon (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 min marathon (MR) were the fast 45 min were run at the same speed as the triathlon run (TR), and a 45 min isolated run (IR) done at triathlon speed. The results show that energy cost during MR was higher than during TR (p < 0.01) (+ 8.9 %). Similar observations were made for pulmonary ventilation (+ 7.9 %) and heart rate (+ 6.3 %). Moreover, the values were significantly greater than the values obtained during the IR. TR and MR lead to greater weight loss (p < 0.01) (2.4±0.3 kg) than IR (1 ± 0.2 kg). The triathlon and the marathon produced a large decrease in plasma volume (respectively 19.6 ± 1.4 % and 12.9 ± 1.1 %) compared to IR (2 ± 0.4 %). Plasma renin activity was higher for the triathlon and the marathon than for the IR (p < 0.01). MR produces a significantly greater increase in plasma free fatty acids (F.F.A.) than TR (p < 0.05) and IR (p < 0.01). In addition, the F.F.A. at the end of TR were significantly higher than IR (p < 0.05). At the end of the trial the mean stride lengths for TR and IR were greater (+ 15 %) (p <0.01) than for MR. This study, carried out with subjects running overground, confirms the decrease in running efficiency previously shown at the end of a laboratory triathlon, and demonstrates that this decrease is lower than that occurring during a marathon

Mutants in the Mouse NuRD/Mi2 Component P66α Are Embryonic Lethal

The NuRD/Mi2 chromatin complex is involved in histone modifications and contains a large number of subunits, including the p66 protein. There are two mouse and human p66 paralogs, p66alpha and p66beta. The functions of these genes are not clear, in part because there are no mutants available, except in invertebrate model systems.We made loss of function mutants in the mouse p66alpha gene (mp66alpha, official name Gatad2a, MGI:2384585). We found that mp66alpha is essential for development, as mutant embryos die around day 10 of embryogenesis. The gene is not required for normal blastocyst development or for implantation. The phenotype of mutant embryos and the pattern of gene expression in mutants are consistent with a role of mp66alpha in gene silencing.mp66alpha is an essential gene, required for early mouse development. The lethal phenotype supports a role in execution of methylated DNA silencing

Stress-Induced PARP Activation Mediates Recruitment of Drosophila Mi-2 to Promote Heat Shock Gene Expression

Eukaryotic cells respond to genomic and environmental stresses, such as DNA damage and heat shock (HS), with the synthesis of poly-[ADP-ribose] (PAR) at specific chromatin regions, such as DNA breaks or HS genes, by PAR polymerases (PARP). Little is known about the role of this modification during cellular stress responses. We show here that the nucleosome remodeler dMi-2 is recruited to active HS genes in a PARP–dependent manner. dMi-2 binds PAR suggesting that this physical interaction is important for recruitment. Indeed, a dMi-2 mutant unable to bind PAR does not localise to active HS loci in vivo. We have identified several dMi-2 regions which bind PAR independently in vitro, including the chromodomains and regions near the N-terminus containing motifs rich in K and R residues. Moreover, upon HS gene activation, dMi-2 associates with nascent HS gene transcripts, and its catalytic activity is required for efficient transcription and co-transcriptional RNA processing. RNA and PAR compete for dMi-2 binding in vitro, suggesting a two step process for dMi-2 association with active HS genes: initial recruitment to the locus via PAR interaction, followed by binding to nascent RNA transcripts. We suggest that stress-induced chromatin PARylation serves to rapidly attract factors that are required for an efficient and timely transcriptional response

SS18 Together with Animal-Specific Factors Defines Human BAF-Type SWI/SNF Complexes

Contains fulltext : 94049.pdf (publisher's version ) (Open Access

DNA methylation and methyl-CpG binding proteins: developmental requirements and function

DNA methylation is a major epigenetic modification in the genomes of higher eukaryotes. In vertebrates, DNA methylation occurs predominantly on the CpG dinucleotide, and approximately 60% to 90% of these dinucleotides are modified. Distinct DNA methylation patterns, which can vary between different tissues and developmental stages, exist on specific loci. Sites of DNA methylation are occupied by various proteins, including methyl-CpG binding domain (MBD) proteins which recruit the enzymatic machinery to establish silent chromatin. Mutations in the MBD family member MeCP2 are the cause of Rett syndrome, a severe neurodevelopmental disorder, whereas other MBDs are known to bind sites of hypermethylation in human cancer cell lines. Here, we review the advances in our understanding of the function of DNA methylation, DNA methyltransferases, and methyl-CpG binding proteins in vertebrate embryonic development. MBDs function in transcriptional repression and long-range interactions in chromatin and also appear to play a role in genomic stability, neural signaling, and transcriptional activation. DNA methylation makes an essential and versatile epigenetic contribution to genome integrity and function

Sodium citrate ingestion and muscle performance in acute hypobaric hypoxia

International audienc

Modélisation de l'enchaînement natation-cyclisme d'un triathlon en laboratoire. Influence sur la cinétique de la lactatémie

International audienceThis study, which simulates the swimming-cycling transition of a triathlon, compares the kinetics of blood lactate and aerobic capacity during one exercise that only involves lower limbs (similar to cycling) and during one exercise that involves first upper limbs, then lower limbs (similar to swimming and cycling). Male competitor triathletes performed two groups of exercises (fig 1): the first consisted in incremental bicycle exercises to maximal intensity, with (T2) or without (T1) prior upper limb exercise; the second consisted in bicycle exercises at a constant intensity at approximately 80% VO2 max, with (R2) or without (R1) prior upper limb exercise. The results show enhanced lactic acid clearance produced by a lower limb exercise, when it occurs after an upper limb exercise (p < 0.05). This reduction may be due either to an increase in lactate oxidation or a participation in the intramuscular glyconeogenesis in the upper limbs partially depleted in glycogen. The free fatty acid concentration increased after upper limb exercise (T2: 0.51 ± 0.12 mM vs 0.17t 0.03 mM; R2: 0.37 ± 0.04 mM vs 0.13 ± 0.02 mM). Moreover, the respiratory exchange ratios calculated at 60%, 85% and 100% V02 max are significantly lower during T2 exercise thon during T1 exercise (p < 0.05). These results suggest that the use of lipid substrates, stimulated by upper limb exercise does not affect performance during lower limb exercise (maximal aerobic power and maximal oxygen uptake: VO2 max).Cette étude, en modélisant l'enchaînement natation-cyclisme d'un triathlon, vise à apprécier les modifications de la cinétique de la lactatémie et de l'aptitude aérobie chez des sujets réalisant d'une part un exercice des membres inférieurs seuls (de type cyclisme) et d'autre part un exercice impliquant successivement membres supérieurs puis membres inférieurs (de type natation + cyclisme). Les sujets, masculins, triathlètes compétiteurs, sont soumis à deux groupes d'épreuves : le premier est constitué d'exercices d'intensité croissante par palier sur les membres inférieurs (exercices triangulaires précédés (T2) ou non (T1) d'un exercice au niveau des membres supérieurs), le deuxième étant constitué d'exercices d'intensité constante (80% de VO2max) sur les membres inférieurs (exercices rectangulaires précédés (R2) ou non (R1) d'un exercice au niveau des membres supérieurs). Les résultats montrent que la lactatémie mesurée au cours et après un exercice réalisé avec les membres inférieurs est plus basse quand celui-ci a été précédé d'un exercice des membres supérieurs (p < 0,05). Cette diminution peut être due aussi bien à une augmentation de l'oxydation du lactate qu'à une participation de celui-ci à la néoglucogenèse intramusculaire au niveau des membres supérieurs partiellement déplétés en glycogène. La concentration plasmatique des acides gras libres a augmenté après l'exercice de pédalage des membres supérieurs (T2 : 0,51 ± 0,12 mM vs 0,17 ± 0,03 mM ; R2 : 0,37 ± 0,04 mM vs 0,13 ± 0,02 mM). Par ailleurs, les quotients respiratoires calculés au cours des paliers correspondant à 60%, 85% et 100% de VO2 max de l'épreuve T2 sont significativement plus bas que ceux calculés au cours de l'épreuve T1 (p < 0,05). Ces résultats permettent de suggérer que l'utilisation de substrats lipidiques, stimulée par l'exercice des membres supérieurs, ne pénalise pas les performances réalisées au cours de l'exercice intéressant les membres inférieurs en termes de puissance maximale aérobie (PMA) et de consommation maximale d'oxygène (VO2max)

Modélisation de l'enchaînement natation-cyclisme d'un triathlon en laboratoire. Influence sur la cinétique de la lactatémie

International audienceThis study, which simulates the swimming-cycling transition of a triathlon, compares the kinetics of blood lactate and aerobic capacity during one exercise that only involves lower limbs (similar to cycling) and during one exercise that involves first upper limbs, then lower limbs (similar to swimming and cycling). Male competitor triathletes performed two groups of exercises (fig 1): the first consisted in incremental bicycle exercises to maximal intensity, with (T2) or without (T1) prior upper limb exercise; the second consisted in bicycle exercises at a constant intensity at approximately 80% VO2 max, with (R2) or without (R1) prior upper limb exercise. The results show enhanced lactic acid clearance produced by a lower limb exercise, when it occurs after an upper limb exercise (p < 0.05). This reduction may be due either to an increase in lactate oxidation or a participation in the intramuscular glyconeogenesis in the upper limbs partially depleted in glycogen. The free fatty acid concentration increased after upper limb exercise (T2: 0.51 ± 0.12 mM vs 0.17t 0.03 mM; R2: 0.37 ± 0.04 mM vs 0.13 ± 0.02 mM). Moreover, the respiratory exchange ratios calculated at 60%, 85% and 100% V02 max are significantly lower during T2 exercise thon during T1 exercise (p < 0.05). These results suggest that the use of lipid substrates, stimulated by upper limb exercise does not affect performance during lower limb exercise (maximal aerobic power and maximal oxygen uptake: VO2 max).Cette étude, en modélisant l'enchaînement natation-cyclisme d'un triathlon, vise à apprécier les modifications de la cinétique de la lactatémie et de l'aptitude aérobie chez des sujets réalisant d'une part un exercice des membres inférieurs seuls (de type cyclisme) et d'autre part un exercice impliquant successivement membres supérieurs puis membres inférieurs (de type natation + cyclisme). Les sujets, masculins, triathlètes compétiteurs, sont soumis à deux groupes d'épreuves : le premier est constitué d'exercices d'intensité croissante par palier sur les membres inférieurs (exercices triangulaires précédés (T2) ou non (T1) d'un exercice au niveau des membres supérieurs), le deuxième étant constitué d'exercices d'intensité constante (80% de VO2max) sur les membres inférieurs (exercices rectangulaires précédés (R2) ou non (R1) d'un exercice au niveau des membres supérieurs). Les résultats montrent que la lactatémie mesurée au cours et après un exercice réalisé avec les membres inférieurs est plus basse quand celui-ci a été précédé d'un exercice des membres supérieurs (p < 0,05). Cette diminution peut être due aussi bien à une augmentation de l'oxydation du lactate qu'à une participation de celui-ci à la néoglucogenèse intramusculaire au niveau des membres supérieurs partiellement déplétés en glycogène. La concentration plasmatique des acides gras libres a augmenté après l'exercice de pédalage des membres supérieurs (T2 : 0,51 ± 0,12 mM vs 0,17 ± 0,03 mM ; R2 : 0,37 ± 0,04 mM vs 0,13 ± 0,02 mM). Par ailleurs, les quotients respiratoires calculés au cours des paliers correspondant à 60%, 85% et 100% de VO2 max de l'épreuve T2 sont significativement plus bas que ceux calculés au cours de l'épreuve T1 (p < 0,05). Ces résultats permettent de suggérer que l'utilisation de substrats lipidiques, stimulée par l'exercice des membres supérieurs, ne pénalise pas les performances réalisées au cours de l'exercice intéressant les membres inférieurs en termes de puissance maximale aérobie (PMA) et de consommation maximale d'oxygène (VO2max)