An automated respirometer system was used to measure VO2, protein catabolism as ammonia quotient and the energy budget to evaluate whether the crude protein content of a standard protein (SP) diet (42·5 %) or a high-protein (HP) diet (49·5 %) influences metabolism in rainbow trout under challenging intermittent, low dissolved oxygen concentrations. In total, three temperature phases (12, 16, 20°C) were tested sequentially, each of which were split into two oxygen periods with 5 d of unmanipulated oxygen levels (50–70 %), followed by a 5d manipulated oxygen period (16.00–08.00 hours) with low oxygen (40–50 %) levels. For both diets, catabolic protein usage was lowest at 16°C and was not altered under challenging oxygen conditions. Low night-time oxygen elevated mean daily VO2 by 3–14 % compared with the unmanipulated oxygen period for both diets at all temperatures. The relative change in VO2 and retained energy during the intermittent low oxygen period was smaller for the HP diet compared with the SP diet. However, in absolute terms, the SP diet was superior to the HP diet as the former demonstrated 30–40 % lower protein fuel use rates, higher retained energy (1–4 % digestible energy) and slightly lowered VO2 (0–8 %) over the range of conditions tested. The decrease in retained energy under low oxygen conditions suggests that there is scope to improve the performance of SP diets under challenging conditions; however, this study suggests that simply increasing the dietary protein content is not a remedy, and other strategies need to be explored.

Seed germination is responsive to diverse environmental, hormonal and chemical signals. Germination rates (i.e. speed and distribution in time) reveal information about timing, uniformity and extent of germination in seed populations and are sensitive indicators of seed vigour and stress tolerance. Population-based threshold (PBT) models have been applied to describe germination responses to temperature, water potential, hormones, ageing and oxygen. However, obtaining detailed data on germination rates of seed populations requires repeated observations at frequent times to construct germination time courses, which is labour intensive and often impractical. Recently, instruments have been developed to measure repeatedly the respiration (oxygen consumption) of individual seeds following imbibition, providing complete respiratory time courses for populations of individual seeds in an automated manner. In this study, we demonstrate a new approach that enables the use of single-seed respiratory data, rather than germination data, to characterize the responses of seed populations to diverse conditions. We applied PBT models to single-seed respiratory data and compared the results to similar analyses of germination time courses. We found consistent and quantitatively comparable relationships between seed respiratory and germination patterns in response to temperature, water potential, abscisic acid, gibberellin, respiratory inhibitors, ageing and priming. This close correspondence between seed respiration and germination time courses enables the use of semi-automated respiratory measurements to assess seed vigour and quality parameters. It also raises intriguing questions about the fundamental relationship between the respiratory capacities of seeds and the rates at which they proceed toward completion of germination.

Better understanding is needed regarding the effects of exercise alone, without any imposed dietary regimens, as a single tool for body-weight regulation. Thus, we evaluated the effects of an 8-week increase in activity energy expenditure (AEE) on ad libitum energy intake (EI), body mass and composition in healthy participants with baseline physical activity levels (PAL) in line with international recommendations. Forty-six male adults (BMI = 19·7–29·3 kg/m2) participated in an intervention group, and ten (BMI = 21·0–28·4 kg/m2) in a control group. Anthropometric measures, cardiorespiratory fitness, EI, AEE and exercise intensity were recorded at baseline and during the 1st, 5th and 8th intervention weeks, and movement was recorded throughout. Body composition was measured at the beginning and at the end of the study, and resting energy expenditure was measured after the study. The intervention group increased PAL from 1·74 (se 0·03) to 1·93 (se 0·03) (P < 0·0001) and cardiorespiratory fitness from 41·4 (se 0·9) to 45·7 (se 1·1) ml O2/kg per min (P = 0·001) while decreasing body mass (−1·36 (se 0·2) kg; P = 0·001) through adipose tissue mass loss (ATM) (−1·61 (se 0·2) kg; P = 0·0001) compared with baseline. The control group did not show any significant changes in activity, body mass or ATM. EI was unchanged in both groups. The results indicate that in normal-weight and overweight men, increasing PAL from 1·7 to 1·9 while keeping EI ad libitum over an 8-week period produces a prolonged negative energy balance. Replication using a longer period (and/or more intense increase in PAL) is needed to investigate if and at what body composition the increase in AEE is met by an equivalent increase in EI.

The Norway lobster, Nephrops norvegicus is a target fishery species in European waters. The stock assessment of N. norvegicus is complicated because it is caught in commercial gear only when it emerges from its burrow. Landings are lower in winter, and feeding limitations have been hypothesized as the cause. Wild large-sized male lobsters were sampled each season (winter, spring, summer and autumn), and two groups of animals were kept in captivity for 90 d (fed and food-deprived). The hepatopancreas and muscle were dissected, weighted, frozen for biochemical analyses (proximal analyses and DNA/RNA) and fixed in Bouin solution for microscopic observations. The oxygen consumption rates in the wild individuals caught in the spring and in the captive animals after the treatments were measured. Significant differences among the experimental groups were observed in the lipid concentration of the hepatopancreas and muscle, the water content in the hepatopancreas, and the numbers of vacuoles and pyknotic nuclei in the cells of the tubules of the hepatopancreas. The results showed that the wild Norway lobsters generally presented intermediate values between those observed in the food-deprived and the fed lobsters kept in captivity, but the values were closer to those obtained for the fed animals. This finding indicates that the wild animals exhibit a good nutritional condition throughout the year. Therefore, the wild males of N. norvegicus do not face food deprivation during winter as is suggested by the pattern of commercial catches, the flow of organic matter, and the moulting period/reproductive behaviour of the species.

Dietary fish oil modifies skeletal muscle membrane fatty acid composition and oxygen efficiency similar to changes in the myocardium. Oxygen efficiency is a key determinant of sustained force in mammalian skeletal muscle. Therefore, in the present study, we tested the effects of a fish-oil diet on skeletal muscle fatigue under the stress of contraction using the rat in vivo autologous perfused hindlimb model. For 8 weeks, male Wistar rats were fed a diet rich in saturated fat (SF), a diet rich in n-6 PUFA or a diet rich in long-chain (LC) n-3 PUFA DHA derived from fish oil. In anaesthetised, mechanically ventilated rats, with their hindlimbs perfused with arterial blood at a constant flow, the gastrocnemius–plantaris–soleus muscle bundle was stimulated via sciatic nerve (2 Hz, 6–12 V, 0·05 ms) to contract repetitively for 30 min. Rats fed the n-3 PUFA diet developed higher maximum twitch tension than those fed the SF and n-6 PUFA diets (P< 0·05) and sustained twitch tension through more repetitions before the tension declined to 50 % of the maximum twitch tension (P< 0·05). The n-3 PUFA group used less oxygen for tension developed and produced higher venous lactate concentrations with no difference in glycogen utilisation compared with the SF and n-6 PUFA groups. These results further support that incorporation of DHA into skeletal muscle membranes increases the efficiency of oxygen use over a range of contractile force and this is expressed as a higher sustained force and prolonged time to fatigue.

This study was designed to measure responses of four-year-old black-lip pearl oysters(Pinctada margaritifera) to different temperatures and foodconcentrations and to identify the energy requirements of each sex. Oysters were fed amonospecific microalgal diet of Isochrysis affinis galbana(T-iso). Measurements of oxygen consumption and ingestion rates were carried outat 24 °C and 27 °C and at two algal (T-iso) concentrations: 5000 and 30 000 cellml-1. Glycogen content in adductor muscle, absorption efficiency and scopefor growth were also estimated. Females and males responded differently to environmentalfactors, with food level being the most influential parameter. Oxygen consumption andabsorption efficiency were significantly higher in females than in males, but males hadsignificantly higher glycogen content than females. At high food concentration, glycogencontent, ingestion rate, oxygen consumption, and scope for growth were significantlyhigher than at the low food concentration. Only absorption efficiency was significantlyhigher at the low food concentration. Oxygen consumption was significantly higher at 27 °Cthan at 24 °C. These results indicate that females and males have different bioenergeticfunctioning and that energy demands for reproduction are higher in females.

Sessile animals that live on the foreshore undergo tidal cycles, and have to facevariations in physical and chemical parameters such as oxygen concentration. Duringemersion, availability of dissolved oxygen can be lowered for bivalves, which have only asmall reserve of seawater inside their closed shell. Differences in oxygen concentrationare thus expected to lead to modifications of the metabolism, including changes inmitochondrial activity. Previous studies investigated air exposure under extremeconditions, which do not always reflect environmental conditions these invertebrates haveto cope with. In this study, oxidative capacities of gill mitochondria of the oysterCrassostrea gigas were studied during a tidal cycle period, bycomparing oysters collected after emersion and immersion. Only minor differences werefound in state 3 (oxidative phosphorylation) or state 4 (non-phosphorylating oxygenconsumption) rates between the two conditions. Similarly, no difference was observed incytochrome c oxidase activity or in oxygen consumption related to maximalelectron flux through complexes I-IV, II-IV and IV. While capacities of substrateoxidation were maintained in both emersion and immersion conditions, capacity ofmitochondria to produce adenosine triphosphate (ATP) was significantly lower in oysterssampled during emersion. These results suggest that although C. gigascould maintain aerobic metabolism during emersion period within a tidal cycle inits environment, energy producing mechanisms are affected.

It has been hypothesised that, at non-limiting water oxygen conditions, voluntary feed intake (FI) in fish is limited by the maximal physiological capacity of oxygen use (i.e. an ‘oxystatic control of FI in fish’). This implies that fish will adjust FI when fed diets differing in oxygen demand, resulting in identical oxygen consumption. Therefore, FI, digestible energy (DE) intake, energy balance and oxygen consumption were monitored at non-limiting water oxygen conditions in Nile tilapia fed diets with contrasting macronutrient composition. Diets were formulated in a 2 × 2 factorial design in order to create contrasts in oxygen demand: two ratios of digestible protein (DP):DE (‘high’ v. ‘low’); and a contrast in the type of non-protein energy source (‘starch’ v. ‘fat’). Triplicate groups of tilapia were fed each diet twice daily to satiation for 48 d. FI (g DM/kg0·8 per d) was significantly lower (9·5 %) in tilapia fed the starch diets relative to the fat diets. The DP:DE ratio affected DE intakes (P < 0·05), being 11 % lower with ‘high’ than with ‘low’ DP:DE ratio diets, which was in line with the 11·9 % higher oxygen demand of these diets. Indeed, DE intakes of fish showed an inverse linear relationship with dietary oxygen demand (DOD; R2 0·81, P < 0·001). As hypothesised (‘oxystatic’ theory), oxygen consumption of fish was identical among three out of the four diets. Altogether, these results demonstrate the involvement of metabolic oxygen use and DOD in the control of FI in tilapia.

Dietary fish oil modulates skeletal muscle membrane fatty acid composition. Similar changes in heart membrane composition modulate myocardial oxygen consumption and enhance mechanical performance. The rat in vivo autologous perfused hindlimb was used to investigate the influence of membrane composition on skeletal muscle function. Male Wistar rats were fed either saturated fat (SF), n-6 PUFA (linoleic acid rich) or n-3 PUFA (fish oil) diets for 8 weeks. Hindlimb skeletal muscle perfused using the animal's own blood was stimulated via the sciatic nerve (1 Hz, 6-12 V, 0·05 ms) to contract in repeated 10 min bouts. The n-3 PUFA diet markedly increased 22 : 6n-3 DHA, total n-3 PUFA and decreased the n-6:n-3 PUFA ratio (P < 0·05) in red and white skeletal muscle membranes. There was no difference in initial twitch tension but the n-3 PUFA group maintained greater twitch tension within all contraction bouts and recovered better during rest to produce greater twitch tension throughout the final contraction bout (P < 0·05). Hindlimb oxygen consumption during contraction was significantly lower in the n-3 PUFA group compared with the SF group, producing a significantly higher O2 efficiency index compared with both SF and n-6 PUFA groups (P < 0·05). Resting oxygen consumption was increased in recovery in the SF group (P < 0·05) but did not change in the n-3 PUFA group. Membrane incorporation of n-3 PUFA DHA following fish oil feeding was associated with increased efficiency of muscle O2 consumption and promoted resistance to muscle fatigue.

The effect of haemoparasites on the physiology and behaviour traits of their hosts was examined using Haemogregarina sp., a parasite of the common lizard, Lacerta vivipara, from the south of France. Infection with haemogregarines was associated with a reduced haemoglobin concentration and an increased number of immature red blood cells. Parasitized individuals also showed a reduced oxygen consumption at rest and a lower locomotor speed. We also found that the multiplication rate of the parasite depended on the temperature at which the lizard was maintained. Between 21 and 28 °C the multiplication rate of the parasite was significantly lower than between 29 and 35 °C. This suggests that the parasites may suffer reproductive costs when hosts reduce their body temperature.

Mixed venous saturation of oxygen has for some time been used as a tool to assess the adequacy of systemic delivery of oxygen in intensive care. In the post-operative child with cardiac disease, it is increasingly being used to assess adequacy of cardiac output. In many of these patients, true sampling of mixed venous saturation of oxygen is not possible due to the infrequent use of pulmonary arterial catheters, or the presence of intra-cardiac left to right shunting leading to mixing of systemic and pulmonary venous blood. The use of saturation of oxygen in the central venous blood as a surrogate for mixed venous saturation of oxygen has been widely investigated in adults, but its use remains controversial. In this review, we discuss the theory behind the use of mixed venous saturation of oxygen in evaluating cardiac output, the problems pertinent to those patients with congenitally malformed hearts, and explore the evidence for central venous saturation of oxygen as a surrogate for mixed venous saturation of oxygen, and its use as a therapeutic target to improve outcomes in this population of patients.

In western Sweden, less than one-third of children born with complete transposition between 1964 and 1983 are long-time survivors. During bicycle ergometry, using a steady-state protocol with analyses of the expiratory gases and lactate, we investigated the exercise capacity in survivors of atrial redirection. There were 16 patients who had a Mustard procedure, now aged 16.9±3.6 years (12.0–22.0) and 15 patients who underwent a Senning correction aged 9.4±1.6 years (7.2–12.1). Nineteen percent of Mustard cases and 53% of Senning cases had minor or no sequels. Moderate sequels were found in 44% of post-Mustard cases, and 40% of post-Senning cases, including baffle complications, moderate systemic ventricular dysfunction, sinus node dysfunction and tracheal stenosis. Severe problems were encountered in 37% of post-Mustard cases and 7% of post-Senning cases, including pulmonary hypertension, pulmonary venous obstruction, atrioventricular block and hemiparesis. The maximal exercise capacity was low (p<0.0001); 71% had an oxygen uptake below −2 SD of predicted values, with severely impaired oxygen uptake in all except one of the cases with severe sequels, but no significant difference was found between patients having mild and moderate sequels. The maximally achieved heart rate was low (p<0.0001); 71% had values below −2 SD of predicted, including all cases with sinus nodal dysfunction, as well as 40% of cases without it. The maximal oxygen pulse was low (p<0.01), below −2 SD in 36%, but it was less affected than other exercise variables in 68% of the patients. Our study, therefore, presents exercise data in an epidemiologically-based population, relates the data to postoperative sequels and discusses some possible adaptive mechanisms.

Five previously untrained yearling sled dogs were evaluated for endurance training-induced changes in maximum oxygen consumption (VO2max) and submaximal blood lactate concentrations. Following 3 weeks of light training followed by 4 weeks of moderate training, VO2max increased by 10%, from 180.2 ± 9.9 to 198.7 ± 19.2 ml kg min− 1 (P = 0.046). Light training was not associated with any increase in VO2max. Blood lactate concentrations at the same absolute intensity decreased by 215%, from 9.2 ± 4.7 to 4.3 ± 2.4 mmol l− 1 (P = 0.022). Speeds associated with oxygen consumptions of 70% VO2max increased by 12%, from 4.8 ± 0.4 to 5.4 ± 0.5 m s− 1 (P = 0.008) and speeds associated with VO2max increased by 21%, from 6.7 ± 0.3 to 8.2 ± 0.7 m s− 1 (P = 0.012).

Summary

Background and objective: To determine the minimal oxygen delivery and pump flow that can maintain systemic oxygen uptake during normothermic (37°C) pulsatile and non-pulsatile cardiopulmonary bypass in dogs. Methods: Eighteen anaesthetized dogs were randomly assigned to receive either non-pulsatile (Group C; n = 9) or pulsatile bypass flow (Group P; n = 9). Oxygen delivery was reduced by a progressive decrease in pump flow, while arterial oxygen content was maintained constant. In each animal, critical oxygen delivery was determined from plots of oxygen uptake vs. oxygen delivery and from plots of blood lactate vs. oxygen delivery using a least sum of squares technique. Critical pump flow was determined from plots of lactate vs. pump flow. Results: At the critical point, oxygen delivery obtained from oxygen uptake was 7.7 ± 1.1 mL min−1 kg−1 in Group C and 6.8 ± 1.8 mL min−1 kg−1 in Group P (n.s.). These values were similar to those obtained from lactate measurements (Group C: 7.8 ± 1.6 mL min−1 kg−1; Group P: 7.6 ± 2.0 mL min−1 kg−1). Critical pump flows determined from lactate measurements were 55.6 ± 13.8 mL min−1 kg−1 in Group C and 60.8 ± 13.9 mL min−1 kg−1 in Group P (n.s.). Conclusions: Oxygen delivery values greater than 7–8 mL min−1 kg−1 were required to maintain oxygen uptake during normothermic cardiopulmonary bypass with either pulsatile or non-pulsatile blood flow. Elevation of blood lactate levels during bypass helps to identify inadequate tissue oxygen delivery related to insufficient pump flow.

The aim of the present study was to obtain serial values of O2 consumption (VO2), CO2 production (VCO2) and energy expenditure (EE) in healthy but extremely-low-birth-weight infants (birth weight <1000 g), during the first 5 weeks after birth. A total of seventeen spontaneously breathing and appropriate-for-gestational-age (birth weight and body length above the 10th and below the 90th percentile) preterm infants with gestational age 25–28 weeks and birth weight 590–990 g were enrolled in the study. Calorimetry was performed using an open-circuit calorimeter on days 6, 12, 18, 24, 30 and 36 of postnatal life. During the 5 weeks of observation, VO2 increased from 4·7 (SD 0·5) TO 9·1 (sd 1·0) ml/kg per min, VCO2 from 4·5 (sd 0·4) to 8·3 (SD 0·6) ml/kg per min and EE from 115 (sd 12) to 310 (sd 71) kJ/kg per d. The energy intake was always higher than EE, even at days 6 and 12. The RER decreased from 0·99 (sd 0·09) at day 12 to 0·91 (SD 0·05) at day 30. On all study days, there were highly significant positive correlations between energy intake and weight gain, EE and weight gain, and EE and energy intake (P<0·05). Multiple regression analysis showed that on most study days EE was more affected by energy intake than by weight gain. We conclude that in healthy preterm infants with birth weight <1000 g, EE increases by about 150 % in the first 5 weeks after birth, and that the EE values are related to energy intake and weight gain independent of postnatal age.

The effects of UV-A and UV-B (Cracow District, Poland, 50°04′N, 19°57′E; 220 m a.s.l.) on oxygen consumption were studied in common toad Bufo bufo (L.) tadpoles (Gosner stage 27). Ecologically relevant chronic doses of UV were simulated in the laboratory. Larvae separated for experiment were derived from UV-exposed or not exposed embryos. After hatching, tadpoles in stages 24–27 were treated with UV-A or UV-B. UV-A caused significant increases in oxygen consumption in larvae grown from untreated embryos, whereas no changes occurred in tadpoles irradiated with UV-A during embryonic and larval development. UV-B caused significant decreases in oxygen consumption in all exposed tadpoles. The changes were larger in larvae derived from eggs not exposed to UV-B than in tadpoles grown from UV-B-treated embryos. Our results suggest that ambient levels of UV-A and especially UV-B may affect the metabolic rate of common toad larvae living in shallow habitats. Affected respiration may retard development as well as increase the susceptibility of tadpoles to ecologically relevant pathogens. On the other hand, it seems that UV-irradiation induces some adaptive processes during embryonic development, which increase the resistance of the larval respiratory system to solar UV radiation.