RESUMO
The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen conssumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85 per cent of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation.
Assuntos
Animais , Masculino , Pesos e Medidas Corporais , Cordados não Vertebrados/fisiologia , Consumo de Oxigênio/fisiologia , Nível de Oxigênio , Análise de VariânciaRESUMO
The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen consumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85% of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation.
Assuntos
Peso Corporal , Cordados não Vertebrados/fisiologia , Consumo de Oxigênio/fisiologia , Análise de Variância , Animais , MasculinoRESUMO
Actomyosin ATPase is the dominant ATP sink during muscle work. Its catalytic capacities in fast-twitch oxidative glycolytic fibers have long been known to exceed by about 3-fold those of slow-twitch oxidative fibers, but the relative contributions to control of metabolic rates during exercise have never been closely examined. We compared fast-twitch oxidative glycolytic and slow-twitch oxidative fibers that displayed similar mitochondrial abundance (similar activities of mitochondrial marker enzymes). During short-term, but near maximum, aerobic exercise, fast-twitch oxidative glycolytic fibers displayed ATP turnover rates that were 2-4 times higher than for slow-twitch oxidative fibers (despite similar mitochondrial metabolic capacities), implying a large ATPase contribution to control of maximum metabolic rate. Fluxes through the ATP in equilibrium ADP + Pi cycle were extremely well regulated; at the lower limit, the forward flux exceeded the backward flux by only 0.06%, whereas at the upper limit, ATPase rates exceeded ATP synthesis rates by 0.12%. This very high precision of energy coupling could not be easily explained by standard metabolic regulation models.
