Matches in SemOpenAlex for { <https://semopenalex.org/work/W2087027656> ?p ?o ?g. }
Showing items 1 to 73 of
73
with 100 items per page.
- W2087027656 endingPage "41" @default.
- W2087027656 startingPage "35" @default.
- W2087027656 abstract "La myoglobine joue divers rôles qui sont fonction de ses caractéristiques physiques in vitro et des contraintes in vivo . Le rôle de réservoir en oxygène dévolu à l'oxymyoglobine est limité à environ 7 secondes chez l'homme. Cette protéine facilite le transfert de l'oxygène vers la mitochondrie par un mécanisme de diffusion facilitée. Le muscle humain se différencie du tissu musculaire du rat de par une concentration quasi double par rapport à l'animal. Les effets de l'entraînement, qui s'observent chez le rat, sont pratiquement inexistants chez l'homme. L'utilisation mitochondriale de l'oxygène dépend de la phosphorylation oxydative du NADH. De plus, la VO 2 max semble être en relation étroite avec l'évolution des rapports [ATP]/[ADP] [Pi] (faible) et [NADH]/[NAD + ] (élevé) au sein de la mitochondrie. La réoxydation du NADH cytosolique implique essentiellement le cycle malate-aspartate. De l'analyse des activités enzymatiques maximales, il apparaît nettement que l'enzyme limitante du potentiel oxydatif mitochondrial est l'α-cétoglutarate déshydrogénase. En nous basant sur son activité chez le sujet entraîné (2–3 μmoles min −1 g −1 de muscle frais), il ressort que la capacité d'oxydation mitochondriale in vitro se limite à 254–406 ml min −1 kg −1 , valeur enrobant les 350 ml d'O 2 min −1 kg −1 observés in vivo par Andersen et Saltin. Tout porte à croire que le transfert d'O 2 dans la fibre musculaire ne constitue pas un facteur limitant la consommation en oxygène mitochondrial. La limitation de la VO 2 max trouverait son origine principalement au sein de la machinerie enzymatique, tout au moins chez l'homme sain en normoxie. Myoglobin (Mb) promotes the release of oxygen (O 2 ) from the capillaries by increasing the transcapillary O 2 gradient. This Mb-facilitated diffusion permits intracellular O 2 transport at small concentration gradients knowing that the intracellular partial pression in O 2 is > 3 Torr. Although Mb diffuses at one twentieth the rate of free-oxygen diffusion, as the Mb concentration exceeds free-oxygen concentration in working muscles approximately 30 fold, the flux of oxy-Mb is expected to be of the same order. Mb acts as a short-term oxygen store (about 7 s) during exercise. However its concentration in skeletal muscles is different when one compares rat and human (Tables I, II). The latter almost doubles the amount of Mb in skeletal muscle as compared to the rodent. The rat does increase its Mb content in endurance training, while in most cases man does not present any adaptation to repeated exercises. Its seems that humans do have an adequate oxygen transport system to the mitochondria. Mb content of muscles is proportional to the cytochrome oxidase content. Mitochondrial oxygen uptake is irreversible and is related to the net rate of ATP formation. The driving force of O 2 consumption is constituted by a thermodynamic equation wich includes two ratio, ie [ATP]/[ADP] [Pi] (low) and [NADH]/[NAD + ] (high). At constant [ATP]/[ADP] [Pi] the respiratory rate is strongly dependant on [NADH]/[NAD + ]. In living muscles submitted to severe exercise, the NADH increases essentially in the mitochondria, stimulating the synthesis of ATP. It is suggested that the observed increases in NADH, ADP and Pi are metabolic adaptations wich serve to activate the aerobic ATP production. Endurance training induces a higher transfer of NADH into mitochondria mainly be the malate-aspartate shuttle, by increase in activity of the specific enzymes. The finely-tuned control mechanism of oxygen consumption depends on metabolic fluxes wich are under the influence of irreversible reactions of mitochondrial key enzymes (Tables III). The leading enzyme seems to be the 2-oxoglutarate dehydrogenase wich shows the lowest rate (2–3 μmoles.min −1 .g −1 wet weight) of activity of the citric acid cycle and the oxidative phosphorylation. If it is assumed that 1 μmol substrate utilizes 6 μmol O 2 to generate ATP, and that the lowest rate of the oxidative cycle enzymes leads the total chain reaction, it can be calculated that the maximal mitochondrial oxygen consumption is between 254 and 406 ml O 2 .min −1 .kg −1 of wet muscle. This value lays between the observed estimate of 350 ml O 2 .min −1 .kg −1 of wet muscle obtained in vivo by Andersen et al. (1985). Therefore, it seems most probable that the real limitation in VO 2 max is at the enzymatic mitochondrial site and that the transfer of intramuscular O 2 is not a limiting step in healthy humans exposed to normoxia." @default.
- W2087027656 created "2016-06-24" @default.
- W2087027656 creator A5032644552 @default.
- W2087027656 date "1994-01-01" @default.
- W2087027656 modified "2023-09-27" @default.
- W2087027656 title "L'utilisation périphérique de l'oxygène. de la diffusion musculaire facilitée à la consommation mitochondriale limitée" @default.
- W2087027656 cites W1567924553 @default.
- W2087027656 cites W1821184770 @default.
- W2087027656 cites W1862249865 @default.
- W2087027656 cites W1890789143 @default.
- W2087027656 cites W1931876014 @default.
- W2087027656 cites W1947047050 @default.
- W2087027656 cites W1960954627 @default.
- W2087027656 cites W1975643013 @default.
- W2087027656 cites W1976898345 @default.
- W2087027656 cites W1978354120 @default.
- W2087027656 cites W1978495288 @default.
- W2087027656 cites W1989085617 @default.
- W2087027656 cites W1995985173 @default.
- W2087027656 cites W2000225583 @default.
- W2087027656 cites W2008164791 @default.
- W2087027656 cites W2022229254 @default.
- W2087027656 cites W2037017787 @default.
- W2087027656 cites W2048040548 @default.
- W2087027656 cites W2049696812 @default.
- W2087027656 cites W2055586792 @default.
- W2087027656 cites W2061481869 @default.
- W2087027656 cites W2063277136 @default.
- W2087027656 cites W2068438914 @default.
- W2087027656 cites W2081941025 @default.
- W2087027656 cites W2085294263 @default.
- W2087027656 cites W2101756746 @default.
- W2087027656 cites W2104204697 @default.
- W2087027656 cites W2107621770 @default.
- W2087027656 cites W2115361179 @default.
- W2087027656 cites W2131862912 @default.
- W2087027656 cites W2157205323 @default.
- W2087027656 cites W2169524823 @default.
- W2087027656 cites W2174853803 @default.
- W2087027656 cites W2175875708 @default.
- W2087027656 cites W2175985062 @default.
- W2087027656 cites W2312579002 @default.
- W2087027656 cites W2335970670 @default.
- W2087027656 cites W2415604491 @default.
- W2087027656 cites W4205442313 @default.
- W2087027656 doi "https://doi.org/10.1016/s0765-1597(05)80022-x" @default.
- W2087027656 hasPublicationYear "1994" @default.
- W2087027656 type Work @default.
- W2087027656 sameAs 2087027656 @default.
- W2087027656 citedByCount "1" @default.
- W2087027656 crossrefType "journal-article" @default.
- W2087027656 hasAuthorship W2087027656A5032644552 @default.
- W2087027656 hasConcept C134018914 @default.
- W2087027656 hasConcept C153911025 @default.
- W2087027656 hasConcept C185592680 @default.
- W2087027656 hasConcept C2986317502 @default.
- W2087027656 hasConcept C86803240 @default.
- W2087027656 hasConceptScore W2087027656C134018914 @default.
- W2087027656 hasConceptScore W2087027656C153911025 @default.
- W2087027656 hasConceptScore W2087027656C185592680 @default.
- W2087027656 hasConceptScore W2087027656C2986317502 @default.
- W2087027656 hasConceptScore W2087027656C86803240 @default.
- W2087027656 hasIssue "1" @default.
- W2087027656 hasLocation W20870276561 @default.
- W2087027656 hasOpenAccess W2087027656 @default.
- W2087027656 hasPrimaryLocation W20870276561 @default.
- W2087027656 hasVolume "9" @default.
- W2087027656 isParatext "false" @default.
- W2087027656 isRetracted "false" @default.
- W2087027656 magId "2087027656" @default.
- W2087027656 workType "article" @default.