Effect of rearing system intensiveness on biological features, culture performance and larval quality of meagre (Argyrosomus regius Asso, 1801) larvae

[EN]Meagre, Argyrosomus regius A., is a new species for aquaculture in south Atlantic and Mediterranean regions, that can reach a mean fresh weight of 8.02±2.51g. at 95dah. However, hatchery techniques must be improved to optimize culture performance and larval quality. Eggs of meagre were cultured under intensive (75 indv.l-1 in 2m3 tanks) and semi-intensive system (7.5 indv.l-1 in 40m3 tanks) to evaluate the effect of the intensification on biological features, stress resistance and skeletal deformities. At 30dah, despite in semi-intensive system reared larvae a higher total length (19.08± 2.3mm vs 16.00±1.54mm), dry body weight (13.09± 2.43mg vs 6.46±0.52mg), and survival after the activity test (75.0± 13.8% vs 53.3±11.5%) was found, the use of intensive systems were also very suitable and cost-effective for larval rearing of this species

The ergogenic effect of recombinant human erythropoietin on VO2max depends on the severity of arterial hypoxemia

Treatment with recombinant human erythropoietin (rhEpo) induces a rise in blood oxygen-carrying capacity (CaO(2)) that unequivocally enhances maximal oxygen uptake (VO(2)max) during exercise in normoxia, but not when exercise is carried out in severe acute hypoxia. This implies that there should be a threshold altitude at which VO(2)max is less dependent on CaO(2). To ascertain which are the mechanisms explaining the interactions between hypoxia, CaO(2) and VO(2)max we measured systemic and leg O(2) transport and utilization during incremental exercise to exhaustion in normoxia and with different degrees of acute hypoxia in eight rhEpo-treated subjects. Following prolonged rhEpo treatment, the gain in systemic VO(2)max observed in normoxia (6-7%) persisted during mild hypoxia (8% at inspired O(2) fraction (F(I)O(2)) of 0.173) and was even larger during moderate hypoxia (14-17% at F(I)O(2) = 0.153-0.134). When hypoxia was further augmented to F(I)O(2) = 0.115, there was no rhEpo-induced enhancement of systemic VO(2)max or peak leg VO(2). The mechanism highlighted by our data is that besides its strong influence on CaO(2), rhEpo was found to enhance leg VO(2)max in normoxia through a preferential redistribution of cardiac output toward the exercising legs, whereas this advantageous effect disappeared during severe hypoxia, leaving augmented CaO(2) alone insufficient for improving peak leg O(2) delivery and VO(2). Finally, that VO(2)max was largely dependent on CaO(2) during moderate hypoxia but became abruptly CaO(2)-independent by slightly increasing the severity of hypoxia could be an indirect evidence of the appearance of central fatigue.

Effect of blood haemoglobin concentration on V(O2,max) and cardiovascular function in lowlanders acclimatised to 5260 m

[EN] The principal aim of this investigation was to determine the influence of blood haemoglobin concentration ([Hb]) on maximal exercise capacity and maximal O(2) consumption (V(O(2),max)) in healthy subjects acclimatised to high altitude. Secondarily, we examined the effects of [Hb] on the regulation of cardiac output (CO), blood pressure and muscular blood flow (LBF) during exercise. Eight Danish lowlanders (three females and five males; 24 +/- 0.6 years, mean +/- S.E.M.) performed submaximal and maximal exercise on a cycle ergometer after 9 weeks at an altitude of 5260 m (Mt Chacaltaya, Bolivia). This was done first with the high [Hb] resulting from acclimatisation and again 2-4 days later, 1 h after isovolaemic haemodilution with Dextran 70 to near sea level [Hb]. After measurements at maximal exercise while breathing air at each [Hb], subjects were switched to hyperoxia (55 % O(2) in N(2)) and the measurements were repeated, increasing the work rate as tolerated. Hyperoxia increased maximal power output and leg V(O(2),max), showing that breathing ambient air at 5260 m, V(O(2),max) is limited by the availability of O(2) rather than by muscular oxidative capacity. Altitude increased [Hb] by 36 % from 136 +/- 5 to 185 +/- 5 g l(-1) (P < 0.001), while haemodilution (replacing 1 l of blood with 1 l of 6 % Dextran) lowered [Hb] by 24 % to 142 +/- 6 g l(-1) (P < 0.001). Haemodilution had no effect on maximal pulmonary or leg V(O(2),max), or power output. Despite higher LBF, leg O(2) delivery was reduced and maximal V(O(2)) was thus maintained by higher O(2) extraction. While CO increased linearly with work rate irrespective of [Hb] or inspired oxygen fraction (F(I,O(2))), both LBF and leg vascular conductance were systematically higher when [Hb] was low. Close and significant relationships were seen between LBF (and CO) and both plasma noradrenaline and K(+) concentrations, independently of [Hb] and F(I,O(2)). In summary, under conditions where O(2) supply limits maximal exercise, the increase in [Hb] with altitude acclimatisation does not improve maximal exercise capacity or V(O(2),max), and does not alter peak CO. However, LBF and vascular conductance are higher at altitude when [Hb] is lowered to sea level values, with both relating closely to catecholamine and potassium concentrations. This suggests that the lack of effect of [Hb] on V(O(2),max) may involve reciprocal changes in LBF via local metabolic control of the muscle vasculature.