Aerobic and anaerobic metabolism for the zebrafish, Danio rerio, reared under normoxic and hypoxic conditions and exposed to acute hypoxia during development / Metabolismo aeróbico e anaeróbico do paulistinha Danio rerio, mantidos sob normóxia e hipóxia moderada e expostos a hipóxia aguda durante diferentes estágios de desenvolvimento

In order to verify the influence of chronic and acute ambient oxygen levels from egg to adult stage of the zebrafish, in vivo oxygen consumption (MO2), critical tensions of oxygen (Pcrit), heart rate (fH) and total body lactate concentration (Lc) were determined for Danio rerio (Hamilton, 1822) raised at 28 °C under normoxic (7.5 mgO2.L-1 or 80 mm.Hg-1) and hypoxic conditions (4.3 mgO2.L-1) and exposed to acute hypoxia during different developmental stages. Our findings confirmed that very early stages do not respond effectively to ambient acute hypoxia. However, after the stage corresponding to the age of 30 days, D. rerio was able to respond to acute hypoxia through effective physiological mechanisms involving aerobic and anaerobic metabolism. Such responses were more efficient for the fishes reared under hypoxia which showed that D. rerio survival capability increased during acclimation to mild hypoxia. Measurements of body mass and length showed that moderate hypoxia did not affect growth significantly until the fish reached the stage of 60 days. Moreover, a growth delay was verified for the hypoxic-reared animals. Also, the D. rerio eggs-to-larvae survival varied from 87.7 to 62.4 percent in animals reared under normoxia and mild hypoxia, respectively. However, the surviving animals raised under moderated hypoxia showed a better aptitude to regulate aerobic and anaerobic capacities when exposed to acute hypoxia.

A influência de diferentes níveis de oxigênio no desenvolvimento (ovos a adulto) do peixe paulistinha Danio rerio (Hamilton, 1822) foi verificada por meio de medidas experimentais de consumo de oxigênio (MO2), tensões críticas de oxigênio (Pcrit), taxa de batimentos cardíacos (fH) e concentração total de lactato nos tecidos (Lc), para os animais mantidos a 28 ºC sob níveis normóxicos de oxigênio (7.5 mgO2.L-1 ou 80 mmHg) e hipóxicos (4.3 mgO2.L-1) e submetidos a hipóxia ambiental aguda, em diferentes estágios de desenvolvimento. Os resultados obtidos indicam que os peixes em estágios iniciais do desenvolvimento não variam suas respostas fisiológicas em função das oscilações ambientais nos níveis de oxigênio, visto que tais respostas iniciaram-se somente no estágio de 30 dias de vida. A partir deste estágio D. rerio apresentou capacidade em responder à hipóxia aguda por meio de mecanismos fisiológicos efetivos envolvendo metabolismo aeróbico e anaeróbico. Tais respostas foram mais efetivas para os peixes mantidos sob hipóxia, o que mostrou que a capacidade de sobrevivência de D. rerio aumentou durante o período de aclimatação à hipóxia moderada. As medidas de massa e comprimento corpóreos mostraram que a permanência dos peixes em hipóxia durante o desenvolvimento não afetou esses parâmetro até os peixes atingirem o estágio de 60 dias. A partir deste estágio foi observado ligeiro atraso no crescimento dos espécimes mantidos sob hipóxia. A taxa de sobrevivência de D.rerio variou de 87,7 a 62,4 por cento para os animais mantidos respectivamente sob níveis normóxicos e hipóxicos. No entanto, os animais mantidos sob hipóxia moderada, que sobreviveram, mostraram maior capacidade em regular seu metabolismo aeróbico e anaeróbico quando expostos à hipóxia ambiental aguda.

Heart rate & blood lactate response in amateur competitive boxing.

The heart rate (HR) and blood lactate response were studied on 26 senior national level boxers in competitive bouts to explore the aerobic-anaerobic metabolism as well as the training status of the players. The aerobic capacity (VO2 max) of the players were determined using graded running protocol on a treadmill. Heart rate and blood lactate concentration were measured during warm up and boxing rounds. The mean relative VO2 max of the heavy weight category boxers was lower (P < 0.05) than the other two weight categories. No interweight category as well as inter-round differences were observed in the heart rate and blood lactate concentration of the boxers, excepting in the 48-57 kg category, the mean lactate levels in the second and third rounds were higher (P < 0.05) than in the first round. When all weight categories were pooled the mean HR and blood lactate levels were 178 beats/min and 8.24 mMol/l respectively. The study highlights that in amateur boxing, irrespective of the weight category and aerobic capacity, the anaerobic adaptability of the boxers was the same. The training requirements of the boxers demand that they should be also to tolerate a high blood lactate level (approx. 9.0 mMol/l) and a high HR (approx. 180 beats/min) over a total duration of one bout.