Significant Change In Oxygen Consumption Research Articles

The Impact of Exercise-Induced Muscle Damage on Various Cycling Performance Metrics: A Systematic Review and Meta-Analysis.

Devantier-Thomas, B, Deakin, GB, Crowther, F, Schumann, M, and Doma, K. The impact of exercise-induced muscle damage on various cycling performance metrics: a systematic review and meta-analysis. J Strength Cond Res 38(1): 196-212, 2024-This systematic review and meta-analysis examined the impact of exercise-induced muscle damage (EIMD) on cycling performance. The primary outcome measure was cycling performance, whereas secondary outcome measures included creatine kinase (CK), delayed-onset muscle soreness (DOMS), and muscular contractions. Data were extracted and quantified through forest plots to report on the standardized mean difference and p values. The meta-analysis showed no significant change in oxygen consumption at 24-48 hours (p > 0.05) after the muscle damage protocol, although ventilation and rating of perceived exertion significantly increased (p < 0.05) during submaximal cycling protocols. Peak power output during both sprint and incremental cycling performance was significantly reduced (p < 0.05), but time-trial and distance-trial performance showed no change (p > 0.05). Measures of CK and DOMS were significantly increased (p < 0.05), whereas muscular force was significantly reduced following the muscle-damaging protocols (p < 0.05), confirming that cycling performance was assessed during periods of EIMD. This systematic review showed that EIMD affected both maximal and submaximal cycling performance. Therefore, coaches should consider the effect of EIMD on cycling performance when implementing unaccustomed exercise into a cycling program. Careful consideration should be taken to ensure that additional training does not impair performance and endurance adaptation.

Loss of the large conductance calcium-activated potassium channel causes an increase in mitochondrial reactive oxygen species in glioblastoma cells.

Mitochondrial potassium (mitoK) channels play an important role in cellular physiology. These channels are expressed in healthy tissues and cancer cells. Activation of mitoK channels can protect neurons and cardiac tissue against injury induced by ischemia-reperfusion. In cancer cells, inhibition of mitoK channels leads to an increase in mitochondrial reactive oxygen species, which leads to cell death. In glioma cell activity of the mitochondrial, large conductance calcium-activated potassium (mitoBKCa) channel is regulated by the mitochondrial respiratory chain. In our project, we used CRISPR/Cas9 technology in human glioblastoma U-87 MG cells to generate knockout cell lines lacking the α-subunit of the BKCa channel encoded by the KCNMA1 gene, which also encodes cardiac mitoBKCa. Mitochondrial patch-clamp experiments showed the absence of an active mitoBKCa channel in knockout cells. Additionally, the absence of this channel resulted in increased levels of mitochondrial reactive oxygen species. However, analysis of the mitochondrial respiration rate did not show significant changes in oxygen consumption in the cell lines lacking BKCa channels compared to the wild-type U-87 MG cell line. These observations were reflected in the expression levels of selected mitochondrial genes, organization of the respiratory chain, and mitochondrial morphology, which did not show significant differences between the analyzed cell lines. In conclusion, we show that in U-87 MG cells, the pore-forming subunit of the mitoBKCa channel is encoded by the KCNMA1 gene. Additionally, the presence of this channel is important for the regulation of reactive oxygen species levels in mitochondria.

High doses of sodium nitrate prior to exhaustive exercise increases plasma peroxynitrite levels in well-trained subjects: randomized, double-blinded, crossover study.

The aim of this study was to investigate the effect of different doses of pre-workout sodium nitrate supplementation on nitric oxide, peroxynitrite levels, and performance parameters. Ten well-trained male subjects participated in a randomized, double-blinded, crossover study. They ingested 8, 16, and 24 mmol sodium nitrate or placebo (NaCl) dissolved in water at 2.5 h before an incremental exercise test. Respiratory gases (oxygen consumption, carbon dioxide production, respiratory exchange ratio) were measured throughout the exercise trials and 3 blood samples (pre-ingestion, 2.5 h post-ingestion and postexercise) were taken to analyze nitrate/nitrite (NOx) and peroxynitrite levels. Data were analyzed using repeated-measures ANOVA at significance level of P < 0.05. NOx levels significantly increased following sodium nitrate ingestion compared with placebo (placebo: 40.86 ± 10.7 μmol/L, 8 mmol: 203.69 ± 25.1 μmol/L, 16 mmol: 289.41 ± 30.1 μmol/L, and 24 mmol: 300.95 ± 42.4 μmol/L, respectively) (P = 0.0001). However, this did not induce any significant change in oxygen consumption (P = 0.351), blood lactate concentration (P = 0.245), and time-to-exhaustion (P = 0.147). Peroxynitrite levels were similar compared with placebo when participants ingested 8 and 16 mmol of inorganic nitrate but a significant increase was observed after exercise at maximal intensity when participants were supplemented with 24 mmol (mean = 14.60 ± 1.3 μmol/L, P = 0.001). Pre-workout ingestion of high dose of sodium nitrate (24 mmol) induced peroxynitrate formation, a marker of oxidative stress. Caution must be taken regarding administration of higher doses before benefits or adverse effects are established in this population.

Wntless represses brown adipose tissue differentiation and energy expenditure

Objective To explore the effect of Wntless (Wls)-mediated Wnt signaling on the development and energy metabolism of brown adipose tissue (BAT). Methods BAT-specific Wls knockout (WlsMyf5Δ/Δ) mice were generated by Cre-loxP system. The differentiations of BAT in WlsMyf5Δ/Δ knockout mice and Wlsfl/fl control mice were analyzed by histological morphology, immunohistochemistry, real-time PCR, and Western blot. After stromal vascular fraction (SVF) cells in BAT were induced to differentiate, oil red O staining, real-time PCR, and cell respiration experiments were performed for analyzing in-vitro cell differentiation and oxygen consumption. The energy metabolism of mice was monitored by rectal temperature, oxygen consumption rate in BAT, and energy expenditure. The adiposity of mice was evaluated by NMR while the glucose metabolism was analyzed by the glucose and insulin tolerance tests. Results The WlsMyf5Δ/Δ knockout mice appeared smaller body size, lower weight, higher percentage of lean fat, lower size of BAT, with higher body temperature on the back as compared to Wlsfl/fl control mice. The differentiation and thermogenesis of BAT in Wls-deficient mice were relatively augmented, along with an increase in Ucp1 mRNA and protein expressions. SVF cells from BAT in WlsMyf5Δ/Δ knockout mice revealed enhanced brown differentiation. Adiposity was decreased and glucose metabolic capacity was enhanced in the WlsMyf5Δ/Δ knockout mice, without significant change in oxygen consumption of the whole body. Conclusion Wls-mediated Wnt signaling decreases the thermogenesis and glucose metabolism of BAT by suppressing its differentiation. Key words: Wnt signaling pathway; Wntless gene; Brown adipose tissue

Efficacy of intermittent hypoxic training on hemodynamic function and exercise performance in competitive swimmers

[Purpose]Hemodynamic function is a parameter indicating oxygen delivery and utilization capacity and is an important determinant of exercise performance. The present study aimed to determine whether intermittent hypoxic training (IHT) ameliorates hemodynamic function and exercise performance in competitive swimmers.[Methods]Twenty competitive swimmers (10 men, 10 women) volunteered to participate in the study. Participants were divided into the normoxic training (NT) group and the hypoxic training (HT) group and were subjected to training in a simulated altitude of 3000 m. We evaluated hemodynamic function profiles over 30 min of submaximal exercise on a bicycle and exercise performance before and after 6 weeks of training, which involved continuous exercise at 80% maximal heart rate (HRmax) for 30 min and interval exercise at 90% of HRmax measured before training for 30 min (ten rounds comprising 2 min of exercise followed by 1 min of rest each round).[Results]Significant changes in oxygen consumption (decrease) and end-diastolic volume (increase) were observed only in the HT group. Heart rate (HR), cardiac output (CO), and ejection fraction (EF) were significantly reduced in both groups, but the reduction rates of HR and CO were greater in the HT group than in the NT group. Exercise performance measures, including maximal oxygen consumption and 400-m time trial, were significantly increased only in the HT group.[Conclusion]Our findings suggested that 6 weeks of IHT, which involved high-intensity continuous and interval exercise, can effectively improve exercise performance by enhancing hemodynamic function in competitive swimmers.

Effect of a respiratory muscle training program on lung function, respiratory muscle strength and resting oxygen consumption in sedentary young people

Introduction: Physical inactivity is a risk factor for developing noncommnunicable diseases, as well as respiratory and cardiovascular disorders. To counter this, different types of interventions have been proposed, including respiratory muscle training (RMT).Objective: To determine the effect of a respiratory muscle training program on respiratory muscle strength, lung function and resting oxygen consumption in sedentary subjects.Materials and methods: Pretest-posttest experimental study conducted in sedentary students. Lifestyle and the level of physical activity was determined using the International Physical Activity Questionnaire (IPAQ) and the FANTASTIC questionnaire, while respiratory muscle strength was established by means of expiratory and inspiratory pressure using a Dwyer Series 477 meter, and lung function and oxygen consumption was determined by spirometry and indirect calorimetry whit Vmax Encore 29C® calorimeter. Respiratory muscle training was performed for eight weeks with Threshold IMT system. R software, version 3.1.2, was used for statistical analysis.Results: Clinically and statistically significant improvements were found in maximal inspiratory pressure (MIP) (pre: 81.23±22.00/post: 96.44±24.54 cmH2O; p&lt;0.001); maximal expiratory pressure (MEP) (pre: 94.84±21.63/post: 107.39±29.15 cmH2O; p&lt;0.05); pulmonary function FEV1 [(pre: 3.33±0.88/post: 3.54±0.90L) (p&lt;0.05)]; and FEV1/FVC ratio [(pre: 87.78±7.67/post: 93.20±6.02% (p&lt;0.01)].Conclusion: The respiratory muscle training protocol implemented for eight weeks using the Threshold IMT system improved strength and FEV1. There were no significant changes in oxygen consumption.

Short- and long-term consequences of developmental saline stress: impacts on anuran respiration and behaviour.

Secondary salinization has been identified as a major stressor to amphibians. Exposure to elevated salinity necessitates physiological adjustments and biochemical changes that may be energetically demanding. As such, exposure to non-lethal levels of salinity during development could potentially alter anuran metabolic rates and individual performance in both pre- and post-metamorphic life stages. We investigated the effects of non-lethal levels of salinity on metamorphic traits (time to reach metamorphosis and metamorphic mass), tadpole oxygen consumption, escape response behaviour (pre- and post-metamorphosis) and foraging ability post-metamorphosis in two native Australian frog species, the southern brown tree frog (Litoria ewingii) and the striped marsh frog (Limnodynastes peronii). We found that both Lit. ewingii and Lim. peronii exhibited differences in metamorphic traits in response to elevated salinity. Neither species showed significant change in oxygen consumption during development in response to salinity, relative to freshwater controls. Both species displayed impaired escape response behaviours in response to salinity during larval development, but flow-on effects to adult escape response behaviours and foraging performance were species-specific. Our results show that the influence of stressors during development can have consequences for anuran physiology and behaviour at multiple life stages, and emphasize the need for studies that examine the energetics of anuran responses in order to better understand the responses of biota to stressful environments.

Effect of rocker shoe radius on oxygen consumption rate in young able-bodied persons

We studied oxygen consumption rate of eleven young able-bodied persons walking at self-selected speed with five different pairs of shoes: one regular pair without rocker soles (REG) and four pairs with uniform hardness (35–40 shore A durometer) rocker soles of different radii (25% of leg length (LL) (R25), 40% LL (R40), 55% LL (R55), and infinite radius (FLAT)). Rocker soled shoes in the study were developed to provide similar vertical lift (three inches higher than the REG shoes condition). Oxygen consumption rate was significantly affected by the use of the different shoes (p<0.001) and pairwise comparisons indicated that persons consumed significantly less oxygen (per minute per kilogram of body mass) when walking on the R40 shoes when compared with both the FLAT (p<0.001) and REG (p=0.021) shoe conditions. Oxygen consumption was also significantly less for the R25 shoes compared with the FLAT shoes (p=0.005) and for the R55 shoes compared with FLAT shoes (p=0.027). The three-inch lift on the FLAT shoe did not cause a significant change in oxygen consumption compared to the shoe without the lift (REG).

Oxygen consumption by Daphnia magna straus as a marker of chemical stress in the aquatic environment

Oxygen consumption by Daphnia magna Straus was investigated as a bioindicator for the presence of 11 common aquatic pollutants: Benzo[b]fluoranthene (BbF), mercury(II) chloride (HgCl(2)), 2-dimethoxyphosphinothioylthio-N-methylacetamide (dimethoate), hexachlorocyclohexane (lindane), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), 4-chloro-o-tolyloxyacetic acid, bis(tributyltin) oxide (TBTO), carbon tetrachloride (CCl4), tetramethylthiuram disulfide (thiram), 2,4,6-trichlorophenol, and arsenic trioxide (As(2)O(3)). The measurement of oxygen consumption by D. magna was carried out after 15 and 210 min of exposure to the toxicants under controlled laboratory conditions. The technique applied in the present study was found to be useful for the detection of significant changes in oxygen consumption for most toxicants, with the exception of BbF, dimethoate, and CCl4. Significant differences in oxygen consumption were noted, relative to the control treatments, for six of the compounds after only 15 min of exposure. For thiram and TBTO, statistically significant changes in oxygen consumption were recorded after 210 min of exposure. The present results suggest that the measurement of oxygen consumption by D. magna is a useful biomarker and could possibly be used as a biological early warning system for detecting pollutants in the aquatic environment.

Extremes of metabolic strategy in Antarctic Bryozoa

The physiology of many organisms in many places varies with seasonality of environment characteristics. Polar marine environments are amongst the least and most seasonal. For example, sea temperature varies by <3°C while light climate and primary productivity vary more than elsewhere. Polar nearshore invertebrates generally live life at a slow pace with recorded metabolic rates of 22–454 μg O2/g ash-free dry-mass/h. We measured oxygen uptake by three Antarctic cheilostomatid bryozoan species during summer and winter months. Our data suggest that, in many ways, bryozoans differ from other animals. They have enormous metabolic flexibility; more within the order Cheilostomatida than in all other polar marine animals measured to date. One species alone, Kymella polaris, had both the lowest (16.8) and highest (574.9 μg O2/g ash-free dry-mass/h levels recorded. Furthermore, Camptoplites bicornis showed no significant change in oxygen consumption with season whereas the final species, Isoseculiflustra tenuis, showed the highest winter to summer metabolic rise (ratio =3.45) reported for a polar species. They may not have a resting state analogous to other animals, but exhibit either full activity or ‘dormancy’ in which most organic tissues are reabsorbed. The concept of resting metabolism in this taxon may be inappropriate.

Mood and energy regulation in seasonal and non-seasonal depression before and after midday treatment with physical exercise or bright light

The effects of two non-drug treatments (physical exercise and bright light) on mood, body weight and oxygen consumption were compared in age-matched groups of female subjects with winter depression, non-seasonal depression or without depression. It was found that oxygen consumption in the pre-treatment condition was similar in non-depressed subjects ( n=18) and depressed non-seasonals ( n=18), while comparatively lower values were obtained in winter depression ( n=27). Neither mood nor metabolic parameters changed significantly in the group of nine untreated winter depressives. One week of physical exercise (1-h pedaling on a bicycle ergometer between 13.00 and 14.00 h) increased oxygen consumption in the group of nine winter depressives and lowered oxygen consumption in nine-subject groups of depressed and non-depressed non-seasonals. One week of bright light treatment (2-h exposure to 2500 lux between 14.00 and 16.00 h) increased oxygen consumption in nine winter depressives and nine non-depressed subjects, while no significant change in oxygen consumption was found in nine subjects with non-seasonal depression. Weight loss was observed in the groups treated with physical exercise and in the group of light-treated winter depressives. Winter depression responded equally well to exercising and light, while a significant therapeutic difference in favor of exercising was found in non-seasonal depression. Overall, the results of the study suggest that energy-regulating systems are implicated in the antidepressant action of the non-drug treatments.

Energy cost of walking: Comparison of “intelligent prosthesis” with conventional mechanism

Objective: To determine physiological energy cost with Blatchford's “Intelligent Prosthesis” (IP) compared to energy cost with a conventional pnuematic swing phase control (PSPC) mechanism. Design: Before-After trial: subjects fitted with IP walked on programmable treadmill at speeds: 6min slow, 6min fast, 8min while speed changed, between slow, normal, and fast, every minute, and 6min normal. Breath-by-breath analysis of subject's expired air determined average Vo 2 (L/min) within each period. Procedure repeated after 1-week interval using PSPC prosthesis. Testing sessions supervised by experienced prosthetist. Setting: Rehabilitation centre. Subjects: Volunteer sample. Three men, unilateral transfemoral traumatic amputee patients, ages 39 to 59 years. Normally used ischial containment socket, Blatchford Endolite Stabilised Stance Flex knee with PSPC and Multiflex foot and ankle. Interventions: Fitting, programming, and alignment of IP (own socket) by Bioengineering Unit's resident prosthetist. IP's microprocessor programmed to facilitate five walking speeds. Main Outcome Measure: Physiological energy cost (Vo 2), of using IP compared to using PSPC mechanism. Results: Two subjects displayed reduced Vo 2 of between 5.6% and 9.0% using IP compared to PSPC prosthesis at a pace either faster or slower than their normal pace. Third subject showed no significant change in oxygen consumption despite IP unit being heavier. All subjects displayed reduced Vo 2 (averaging 4.1%) using IP for period of variable speed walking. Conclusions: Although differences were small, they tend to indicate that use of the heavier IP unit lowered the energy cost of walking at speeds other than the amputee's normal pace.

Metabolic depression during environmental stress: the role of extracellular versus intracellular pH in Sipunculus nudus

Environmental stresses such as hypoxia or hypercapnia are known to cause acid-base disturbances and in several organisms they lead to metabolic depression. The present study was undertaken to quantify the influence of these changes in acid&shyp;base parameters on metabolic rate. We determined the rate of oxygen consumption in a non-perfused preparation of the body wall musculature of the marine worm Sipunculus nudus at various levels of extra- and intracellular pH (pHe and pHi, respectively), PCO2 and [HCO3-]. The acid&shyp;base status of the tissue was modified and clamped by long-term exposure to media set to specific values of extracellular pH, PCO2 and [HCO3-]. At a pHe of 7.90, which is equivalent to the normoxic normocapnic in vivo extracellular pH, and an ambient PCO2 of 0.03 kPa (control conditions), pHi was 7.26&plusmn;0.02 (mean &plusmn; s.d., N=5). A reduction of extracellular pH from 7.90 to 7.20 resulted in a significant decrease of pHi to 7.17&plusmn;0.05 at 0.03 kPa PCO2 (normocapnia) and to 7.20&plusmn;0.02 at 1.01 kPa PCO2 (hypercapnia). At the same time, the rate of oxygen consumption of the tissue was significantly depressed by 18.7&plusmn;4.7 % and 17.7&plusmn;3.0 %, respectively. A significant depression of oxygen consumption by 13.7&plusmn;4.7 % also occurred under hypercapnia at pHe 7.55 when pHi was elevated above control values (7.32&plusmn;0.01). No significant changes in oxygen consumption were observed when pHe was either drastically elevated to 8.70 under normocapnia (pHi 7.36&plusmn;0.05) or maintained at 7.90 during hypercapnia (pHi 7.37&plusmn;0.03). ATP and phospho-l-arginine concentrations, as well as the Gibbs free energy change of ATP hydrolysis (dG/dATP), were maintained at high levels during all treatments, indicating an equilibrium between energy supply and demand. We conclude that the depression of aerobic energy turnover in isolated body wall musculature of S. nudus is induced by low extracellular pH. A model is proposed which could explain a reduced ATP cost of pHi regulation during extracellular acidosis, thus contributing to metabolic depression.

Central Limits to Sustainable Metabolic Rate Have No Role in Cold Acclimation of the Short-Tailed Field Vole (Microtus agrestis)

We investigated the extent to which the changes in basal metabolic rate (BMR), gut morphology, andfood intake (FI) that typically occur during cold acclima­ tion in small mammals can be explained by the concept ofalimentary-mediated limits to sustainable metabolic energy expenditure. Adult short-tailedfield voles (Microtus agrestis) were cold stressed by continuous exposure to 5°C. Exposure for 10, 20, 50, and 100 d (n = 6 in all cases) produced significant changes in oxygen consumption ([102 ) , mass, FI, and the dry weight ofa variety ofmorpho­ logical parameters when compared with voles that were not cold exposed (n = 8). At 10°, 20°, and 25°C, V02 (mL· min-I) increased significantly with the duration ofcold exposure. After 100 d cold exposure, VOz had increased by more than 50% at each test temperature. Food intake (g. d- I) increased significantly by 106% after 10 d cold exposure but did not increase further with increased ex­ posure time. The ratio ofFI (j. h- I) to BMR (j. h- I) was 1.2 in controls and in­ creased to 2. 7 after 10 d cold exposure. Thereafter the ratio decreased, and after 100 d cold exposure FI:BMR was not significantly differentfrom control levels. The mass ofcold-exposed voles increased significantly with duration ojexposure. Masses ofthe following morphologicalparameters increased with increasing du­ ration ofcold exposure; whole body mass, carcass, skeleton, pelage, subcutaneous fat, liver, kidney, lung, and interscapular brown fat (BAT). There was no signifi­ cant relationship between duration ofcold exposure and the masses ofmuscle, large intestine, heart.and brain. Using stepwise multiple regression analysis we showed that variation in BMR was linked mostly to changes in skeletal mass. However, when skeletal mass was removed as an independent variable from the analysis, BAT, muscle, and gut mass entered as Significantpredictors, together explaining 55.5% ofthe uariatiori in BMR. Although FJ increased during cold ex­ posure, the increase (106%) was apparently insufficient to precipitate a hyper­ trophic response in the gut. Nevertheless BMR did increase as duration ofcold ex­ posure increased, probably linked to an increase in BAT mass and thus thermogenic capacity. We cannot support the hypothesis that the changes that typ

The effects of rate responsive pacing on exercise performance in the postoperative univentricular heart.

Following the Fontan operation for definitive palliation of the univentricular heart, sinus node dysfunction, and/or atrioventricular block requiring pacemaker therapy is common. In previous studies ventricular rate responsive pacing (VVI,R) resulted in improved exercise performance over VVI pacing in anatomically normal hearts with either sinus node disease or atrioventricular block. In this study, the usefulness of both VVI,R and DDD,R pacing are evaluated in the postoperative univentricular heart following the Fontan operation. Eight postoperative Fontan patients with sinus node disease or atrioventricular block underwent exercise testing using a treadmill protocol. Six patients had single chamber ventricular pacemakers and two patients had dual chambered rate responsive pacemakers. Median age at exercise testing was 14 years. Patients were tested in the VVI, VVI,R, and DDD,R modes acting as their own controls. Heart rate, work rate, oxygen consumption, and respiratory exchange ratio were monitored continuously. Heart rate was significantly increased in the rate responsive modes compared to the VVI mode. In spite of the significant increase in heart rate, there was no change in maximal work rate or oxygen consumption. There was also no significant change in oxygen consumption at ventilatory anaerobic threshold. From these data we would conclude that VVI,R pacing in postoperative univentricular hearts does not result in improved exercise performance and that further study with DDD,R pacing is needed to determine its usefulness in this group of patients.

The relationship of blood lactate concentrations, oxygen delivery and oxygen consumption in septic shock and the adult respiratory distress syndrome.

Tissue hypoxia is thought to be pivotal to the development of multiple organ failure, but cannot be measured directly in clinical practice. We assessed the relationship between initial arterial blood lactate concentrations and the presence of the phenomenon of delivery-dependent oxygen consumption, both of which may indicate tissue hypoxia. Twenty-three critically ill patients with septic shock and adult respiratory distress syndrome were studied prospectively and allocated to one of two groups according to blood lactate concentrations. In group 1, blood lactate concentration was less than the level widely accepted as significant (2 mmol.l-1); in group 2, the concentration exceeded 2 mmol.l-1. In both groups, resuscitation with colloid, blood and vasoactive drugs resulted in significant increases in oxygen delivery; in group 1 (n = 13), mean (SEM) oxygen delivery increased from 484 (36) to 730 (44) ml.min-1.m-2 (p < 0.005) and in group 2 (n = 10) from 550 (54) to 780 (54) ml.min-1.m-2 (p < 0.05). In neither group was there a significant change in oxygen consumption. However, there were individuals in both groups who exhibited pathological delivery dependence. This suggests that the absence of hyperlactataemia does not preclude delivery dependence of oxygen consumption with the attendant potential for tissue hypoxia.

The relationship between water velocity, energetic costs, and microhabitat use in four North American stream fishes

We employed field and laboratory data to test the hypothesis that microhabitat use by rainbow trout (Oncorhynchus mykiss), rosyside dace (Clinostomus funduloides), longnose dace (Rhinichthys cataractae) and mottled sculpin (Cottus bairdi) was affected by energetic constraints. Both rainbow trout and rosyside dace occupied water-column microhabitats in Coweeta Creek, North Carolina, U.S.A. These species were over-represented at velocities requiring lower rates of oxygen consumption, as predicted by an energetic cost hypothesis. Morphological and behavioral adaptations of the two benthic species (mottled sculpin and longnose dace) enabled them to hold position over a wide range of velocities without significant changes in oxygen consumption. Focal point velocities of longnose dace were not significantly different from those available, suggesting a lack of velocity preference. Mottled sculpin, however, consistently were over-represented at low velocities, even though oxygen consumption data showed that energetic costs were not decreased by occupying these microhabitats. Our results indicate that microhabitat use by rainbow trout and rosyside dace is consistent with predictions of an energetic cost hypothesis, whereas the morphological adaptations of longnose dace and mottled sculpin minimize the constraints of energetic costs in microhabitat selection.

Adrenaline in treatment of septic shock: Effects on haemodynamics and oxygen transport

The effects of adrenaline on haemodynamics and oxygen transport were studied in 13 patients with septic shock persisting after optimal fluid loading. Adrenaline was administered by intravenous infusion at an increasing dose until no further benefit was seen. There were significant increases in mean arterial pressure, cardiac index, left ventricular stroke work index and oxygen delivery index. There was no significant change in oxygen consumption although the trend was towards an increase. There was a significant reduction in oxygen extraction ratio, but no change in shunt fraction. Adrenaline would appear to have beneficial haemodynamic effects in septic shock.

The Effect of a Warm Environment on Respiratory Water Loss in Fullterm Newborn Infants on Their First Day after Birth

Continuous measurements of respiratory water loss (RWL), oxygen consumption and carbon dioxide production were made in 21 fullterm infants on their first day after birth. The infants were first studied in incubators with a temperature of 32.5 degrees C and an ambient humidity of 50%. After an interval with stable conditions the incubator temperature was raised to 36.5 degrees C while the water vapour pressure was kept constant. When the rectal temperature had increased to 37.8 degrees C or when the infant had started to sweat, the relative humidity in the incubator was increased to 50%. At the start of the measurements mean RWL was 4.9 mg/kg min. On the average, RWL increased to a maximal value of 7.0 mg/kg min in the warm environment. Mean oxygen consumption only increased from 5.3 to 5.8 ml/kg min. This meant that when nursed in this warm environment the infants were able to increase their respiratory water loss by nearly 50% without a significant change in oxygen consumption.

The Metabolic Cost of Maintaining Position for Four North American Stream Fishes: Effects of Season and Velocity

We used a swimming respirometer to measure oxygen consumption (i. e., metabolic cost) of four species of stream fishes while they held position at diferent velocities. We tested naturally acclimatized individuals during spring, summer, fall, and winter at seasonal temperatures and photoperiods. Rosyside dace (Clinostomus funduloides), longnose dace (Rhinichthys cataractae), mottled sculpin (Cottus bairdi), and juvenile rainbow trout (Oncorhynchus mykiss) all showed seasonal changes in oxygen consumption. Seasonal changes in standard metabolic rates seemed to be influenced by changes in reproductive condition as well as ambient temperature. The metabolic cost of maintaining position for rainbow trout and rosyside dace generally increased with velocity. At velocities below eight body lengths per second, longnose dace did not exhibit a significant change in oxygen consumption, because they held position without swimming. At higher velocities, however, long-nose dace swam to maintain their position and oxygen consumption increased rapidly. Mottled sculpin held position without swimming and therefore showed little or no change in energy use with changing current velocity.