An energy budget for Porites porites (Scleractinia), growing in a stressed environment

An energy budget was determined for the coral Porites porites living in a stressed environment for comparison of the energy inputs and expenditure with those of the same species living in an adjacent clear water fore reef environment. The stressed site was characterised by higher sedimentation and lower irradiances than at the fore reef site. Zooplankton ingestion was found to be an insignificant component of the energy intake: the coral is fully autotrophic under stress conditions. The integrated 24 h rate of photosynthetic energy production on a clear sunny day was 20% higher for stressed corals compared to fore reef corals. This was largely the result of photoadaptation which resulted in increased values for and decreased values for I_k in the hyperbolic tangent function equation for the photosynthesis versus irradiance curve. The energy investment in growth of animal tissue was lower in stressed corals. The percentage translocation of photosynthase to the animal tissue remained at about 78%, but the respiration rate of the animal tissue was reduced by 3 fold. These data combined with the high rate of photosynthetic production predict a net daily energy surplus of 67% in stressed corals compared with the 45% surplus in unstressed corals. Scope for growth is reduced under stress conditions.     

Energy allocation rules inDaphnia magna: clonal and age differences in the effects of food limitation

Summary The allocation of energy to carapace formation, respiration, growth, and reproduction were examined in two parthenogenetic clones ofDaphnia magna (Cladocera) cultured at two levels of food (Chlorella) concentration. Clonal differences in energy allocation were more apparent at high ration (1.5 g C mL^-1) than at low ration (0.3 g C mL^-1). These differences included respiratory and molting costs, and the timing of energy allocation to growth and reproduction. A comparison of active vs. anesthetized animals revealed that the interclonal difference in respiration rate was the result of a difference in activity level. In both clones mass-specific rates of respiration, growth, and brood production all decreased at low vs. high ration levels, whereas mass-specific molt-loss rate increased. Lowered food concentration decreased the relative allocation of energy to growth and reproduction, but increased allocation to maintenance (respiration and carapace formation). These allocation responses to food limitation indicated that for both clones the highest energy priority was carapace formation. However, the relative priority of respiration, growth and reproduction varied with age and clone. In juveniles (instars 1–4) the priority ranking of growth was essentially equal to that of respiration, whereas respiration always had higher priority in adults (instars 5–9). All three possibilities for the relative ranking of growth and reproduction (i.e., growth>reproduction, growth=reproduction, and reproduction>growth), as specified by different models in the literature, were observed depending on age and clone. The energy allocation rules were also shown to vary between other daphniid species. Furthermore, metabolic responses to chronic food limitation may be different from responses to acute food deprivation. In this study, one clone showed a greater decrease in respiration rate as a result of lifetime food limitation than did the other, but the opposite was true when these clones were exposed to 48 h of starvation. These differences in allocation rules and in acute vs. chronic responses may have to be considered when using physiological data to modelDaphnia populations.     

Human skeletal muscle mitochondrial uncoupling is associated with cold induced adaptive thermogenesis

Background

Mild cold exposure and overfeeding are known to elevate energy expenditure in mammals, including humans. This process is called adaptive thermogenesis. In small animals, adaptive thermogenesis is mainly caused by mitochondrial uncoupling in brown adipose tissue and regulated via the sympathetic nervous system. In humans, skeletal muscle is a candidate tissue, known to account for a large part of the epinephrine-induced increase in energy expenditure. However, mitochondrial uncoupling in skeletal muscle has not extensively been studied in relation to adaptive thermogenesis in humans. Therefore we hypothesized that cold-induced adaptive thermogenesis in humans is accompanied by an increase in mitochondrial uncoupling in skeletal muscle.

Methodology/Principal Findings

The metabolic response to mild cold exposure in 11 lean, male subjects was measured in a respiration chamber at baseline and mild cold exposure. Skeletal muscle mitochondrial uncoupling (state 4) was measured in muscle biopsies taken at the end of the respiration chamber stays. Mild cold exposure caused a significant increase in 24h energy expenditure of 2.8% (0.32 MJ/day, range of −0.21 to 1.66 MJ/day, p<0.05). The individual increases in energy expenditure correlated to state 4 respiration (p<0.02, R² = 0.50).

Conclusions/Significance

This study for the first time shows that in humans, skeletal muscle has the intrinsic capacity for cold induced adaptive thermogenesis via mitochondrial uncoupling under physiological conditions. This opens possibilities for mitochondrial uncoupling as an alternative therapeutic target in the treatment of obesity.     

Daily energy expenditure and the cost of activity in a free-living mammal

Summary Antelope ground squirrels (Ammospermophilus leucurus, 80–100 g) began surface activity 1.0–1.5 h after sunrise and ended it 0.5–1.25 h before sunset throughout the year near Barstow, California. Daily energy expenditure (DEE) of free-living animals measured with doubly labeled water (H³H¹⁸O) decreased from 1,340 kJ kg^-1 d^-1 in April to 970 in October. Resting metabolic rates (RMR) of freshly-captured, fed, ground squirrels varied through the year (22.1 J g^-1 h^-1 in August, 19.1 in January) but most of the change in DEE could be explained by differences in thermoregulatory costs between seasons. The ground squirrels had lower rates of resting metabolism at night (15.3J g^-1 H^-1) than during the day.The cost of activity (calculated by subtracting 24 h resting costs from total DEE during August and October, periods when thermoregulatory costs were negligible) was 550 kJ kg^-1 d^-1 in August and October. Thus, activity accounted for about 50% of the total DEE. The mean rate of energy expenditure during the activity period, calculated as activity cost (kJ d^-1) divided by activity time (h d^-1), then plus RMR, was about 3xRMR. This multiplication factor may be useful as an estimator of foraging costs or in estimating DEE from time budgets.     

Meeting the energy demands of reproduction in female koalas,<Emphasis Type="Italic"> Phascolarctos cinereus</Emphasis>: evidence for energetic compensation

Koalas are generally considered to be limited by their ability to acquire energy from their diet of Eucalyptus foliage and have the lowest mass-specific peak lactational energy output measured in any mammal to date. This study considered the energetics and sources of energy utilised for reproduction in free-ranging female koalas. Energy requirements and foliage intake were greater in both lactating and non-lactating females in winter than summer, presumably due to demands of thermoregulation. Koalas met the peak energy requirements of lactation primarily by a 36% increase in their intake of foliage. Metabolic energy expenditure (field metabolic rate, 1778 kJ.day^–1 for a 6.25-kg female at the time of peak lactation) was not elevated during lactation. This was due to compensation for part of their lactational demands by reduction of another, non-reproductive, component of their energy budget. The observed energetic compensation was probably due primarily to substitution of the waste heat from the metabolic costs of milk production and increased heat increment of feeding for thermoregulatory energy expenditure. There may also have been energetic compensation by reduction of some aspect of maintenance metabolism. Such energetic compensation, together with the strategy of spreading lactation over a long period, minimises the magnitude of lactational energy demands on koalas, and thus the increase in daily food intake required during lactation. As the nutritional requirements of females at peak lactation are the highest of any members of the population, low reproductive requirements effectively increase the types and amount of habitat able to support koala populations.Abbreviations FMR field metabolic rate - HIF heat increment of feeding - RMR resting metabolic rate - _O2 rate of oxygen consumptionCommunicated by I.D. Hume     

Sympathetic support of energy expenditure and sympathetic nervous system activity after gastric bypass surgery

Objective:

This study was designed to determine how gastric bypass affects the sympathetically‐mediated component of resting energy expenditure (REE) and muscle sympathetic nerve activity (MSNA).

Design and Methods:

We measured REE before and after beta‐blockade in seventeen female subjects approximately three years post‐gastric bypass surgery and in nineteen female obese individuals for comparison. We also measured MSNA in a subset of these subjects.

Results:

The gastric bypass subjects had no change in REE after systemic beta‐blockade, reflecting a lack of sympathetic support of REE, in contrast to obese subjects where REE was reduced by beta‐blockade by approximately 5% (P < 0.05). The gastric bypass subjects, while still overweight (BMI = 29.3 vs 38.0 kg·m^?2 for obese subjects, P < 0.05), also had significantly lower MSNA compared to obese subjects (10.9 ± 2.3 vs. 21.9 ± 4.1 bursts·min^?1, P < 0.05). The reasons for low MSNA and a lack of sympathetically mediated support of REE after gastric bypass are likely multifactorial and may be related to changes in insulin sensitivity, body composition, and leptin, among other factors.

Conclusions:

These findings may have important consequences for the maintenance of weight loss after gastric bypass. Longitudinal studies are needed to further explore the changes in sympathetic support of REE and if changes in MSNA or tissue responsiveness are related to the sympathetic support of REE.

     

Nematode numbers,biomass and respiratory metabolism in a beech woodland—Wytham Woods,Oxford

Summary The mean annual population density of nematodes in the litter and upper 6 cm of soil was found to be 368,000 m^-2. Mean individual live weight biomass approximated 0.2 g and mean biomass was calculated to be 74.6 mg live weight m^-2. No evidence of seasonal vertical migration between the litter, 0–3 cm and 3–6 cm strata was found and on average these strata contained 21.9, 46.2 and 31.9% respectively of the total number of nematodes recovered. The equivalent biomass values were 26.14, 56.57, and 17.29%. Total numbers revealed a general picture of low densities in spring and high ones in early winter, whereas biomass m^-2 was low in late summer — autumn and high in winter. The annual oxygen consumption of the extracted nematodes was calculated to approximate 0.211 m^-2 (4.0 kJ m^-2) but when corrected for the effect of individual biomass (weight specific oxygen uptake) was equivalent to an energy expenditure 6.0 kJ m^-2 which in its turn, because of the efficiencies of extraction, probably accounts for only 87% of the total energy expenditure by the nematode fauna. The nematodes were estimated to be responsible for a minimum of 0.11% to a maximum of 0.13% of the total soil respiration. A production/biomass ratio of 5.16 was estimated as was a net population production efficiency of 36.63%.     

Mass-transfer-limited nitrate uptake on a coral reef flat,Warraber Island,Torres Strait,Australia

Previous research has identified a relationship between the rate of dissipation of turbulent kinetic energy, , and the mass-transfer-limited rate of uptake by a surface, herein called the ^1/4 law, and suggests this law may be applicable to nutrient uptake on coral reefs. To test this suggestion, nitrate uptake rate and gravitational potential energy loss have been measured for a section of Warraber Island reef flat, Torres Strait, northern Australia. The reef flat section is 3 km long, with a 3 m tidal range, and on the days measured, subject to 6 m s^–1 tradewinds. The measured nitrate uptake coefficient, S , on two consecutive days during the rising tide was 1.23±0.28 and 1.42±0.52×10^–4 m s^–1. The measured loss of gravitational potential energy across the reef flat, GPE , on the same rising tides over a 178 m section was 208±24 and 161±20 kg m^–1 s^–2. Assuming the GPE is dissipated as turbulent kinetic energy in the water column, and using the ^1/4 law, the mass-transfer-limited nitrate uptake coefficient, S_MTL , on the two days was 1.57±0.03 and 1.45±0.04×10^–4 m s^–1. Nitrate uptake on Warraber Island reef flat is close to the mass-transfer limit, and is determined by oceanographic nitrate concentrations and energy climate.Communicated by B.C. Hatcher     

Metabolic costs of the predation strategy of the spider Pardosa amentata (Clerck) (Lycosidae)

Summary Pardosa amentata adopts a sit-and-wait predation strategy with periodic changes of site. The metabolic costs of this strategy were evaluated using a Gilson respirometer. The respirometer was run at the mean temperatures prevailing month by month in the litter layer from which the experimental animals were collected and equations relating standard respiration rate to spider weight were established for each temperature. The mean value of b, the exponent relating weight to respiration rate, was 0.8011. Active respiration rate was determined at each temperature by using larger experimental flasks containing small glass beads which, in conjunction with the shaker mechanism on the respirometer, ensured that the spiders in the respirometer flasks maintained a fairly consistent level of locomotory activity. It was found that the measured active respiration rate was on average 3.17 times the standard rate. The two respiration rates were combined in the appropriate proportions to calculate the daily energy expenditure of an adult spider exhibiting its normal pattern of activity at different temperatures. It is shown that as locomotory activity is very limited in duration in P. amentata, the associated active respiration rate accounts for only a small proportion of daily respiratory energy losses, 0.36% at 5°C, 0.69% at 10°C, and 1.01% at 15°C.     

基于Ecopath模型的崂山湾人工鱼礁区生态系统结构和功能研究

基于2014—2016年青岛崂山湾人工鱼礁区的生物资源调查数据,利用Ecopath with Ecosim(EwE)软件构建崂山湾人工鱼礁区生态系统生态通道模型(Ecopath),系统分析了崂山湾人工鱼礁区生态系统的能量流动规律和结构特征,估算了栉孔扇贝的养殖容量。该模型由17个功能组组成,基本涵盖了崂山湾人工鱼礁区生态系统能量流动的主要过程。生态网络分析表明,生态系统各功能组的营养级范围为1.0—4.255,星康吉鳗占据了营养级的最高层。能量流动主要有5级,各营养级平均能量传递效率为10.8%,其中来自初级生产者的能量效率为9.8%,来自碎屑的传递效率为10.9%;系统总流量为14256.510 t km~(-2) a~(-1),其中68%的能量来自碎屑供给;系统的总初级生产量/总呼吸量为1.127,系统联结指数为0.293,杂食指数为0.333,表明崂山湾人工鱼礁区生态系统成熟度较高,食物网结构较复杂,系统内部稳定性较高。关键种指数分析结果显示,许氏平鲉具有较高的关键指数和相对总影响,表明其可能在当前生态系统中扮演重要的生态角色。吊笼养殖栉孔扇贝生态容纳量为189.679 t/km~2,在维持生态系统平衡和稳定的前提下,当前现存量最大可增加18.55%。     

Energy costs of reproduction in the djungarian hamster Phodopus sungorus under laboratory and seminatural conditions

Summary The aim of this study was to obtain ecologically relevant data on the rates and efficiencies of energy allocation to reproduction and to determine how laboratory data compare with data obtained under seminatural conditions. Using the tritiated water (HTO) method we measured average daily metabolic rates (ADMRs) in Phodopus sungorus reproducing females over the whole period of pregnancy and lactation and in nonreproducing ones, under both laboratory and seminatural conditions.Taking the difference in total energy expenditure between reproducing and nonreproducing females as the additional energy requirement for reproduction, it was found that the absolute energy expenditure for reproduction was independent of the experimental conditions used. For the production and nursing of one litter, Djungarian hamsters metabolized an additional 20.9 MJ kg^-1 in the laboratory, i.e. a 37% increase over normal maintenance expenditure, and 22.6 MJ kg^-1 under seminatural conditions, i.e. a 24% increase. The efficiency of litter production was estimated as 18.3% in the laboratory and as 16.4% under seminatural conditions. The differences between the two experimental conditions were not significant.     

Vagus Nerve Stimulation Increases Energy Expenditure: Relation to Brown Adipose Tissue Activity

Background

Human brown adipose tissue (BAT) activity is inversely related to obesity and positively related to energy expenditure. BAT is highly innervated and it is suggested the vagus nerve mediates peripheral signals to the central nervous system, there connecting to sympathetic nerves that innervate BAT. Vagus nerve stimulation (VNS) is used for refractory epilepsy, but is also reported to generate weight loss. We hypothesize VNS increases energy expenditure by activating BAT.

Methods and Findings

Fifteen patients with stable VNS therapy (age: 45±10yrs; body mass index; 25.2±3.5 kg/m²) were included between January 2011 and June 2012. Ten subjects were measured twice, once with active and once with inactivated VNS. Five other subjects were measured twice, once with active VNS at room temperature and once with active VNS under cold exposure in order to determine maximal cold-induced BAT activity. BAT activity was assessed by 18-Fluoro-Deoxy-Glucose-Positron-Emission-Tomography-and-Computed-Tomography. Basal metabolic rate (BMR) was significantly higher when VNS was turned on (mean change; +2.2%). Mean BAT activity was not significantly different between active VNS and inactive VNS (BAT SUV^Mean; 0.55±0.25 versus 0.67±0.46, P = 0.619). However, the change in energy expenditure upon VNS intervention (On-Off) was significantly correlated to the change in BAT activity (r = 0.935, P<0.001).

Conclusions

VNS significantly increases energy expenditure. The observed change in energy expenditure was significantly related to the change in BAT activity. This suggests a role for BAT in the VNS increase in energy expenditure. Chronic VNS may have a beneficial effect on the human energy balance that has potential application for weight management therapy.

Trial Registration

The study was registered in the Clinical Trial Register under the ClinicalTrials.gov Identifier {"type":"clinical-trial","attrs":{"text":"NCT01491282","term_id":"NCT01491282"}}NCT01491282.     

Coral Skeletons Defend against Ultraviolet Radiation

Background

Many coral reef organisms are photosynthetic or have evolved in tight symbiosis with photosynthetic symbionts. As such, the tissues of reef organisms are often exposed to intense solar radiation in clear tropical waters and have adapted to trap and harness photosynthetically active radiation (PAR). High levels of ultraviolet radiation (UVR) associated with sunlight, however, represent a potential problem in terms of tissue damage.

Methodology/Principal Findings

By measuring UVR and PAR reflectance from intact and ground bare coral skeletons we show that the property of calcium carbonate skeletons to absorb downwelling UVR to a significant extent, while reflecting PAR back to the overlying tissue, has biological advantages. We placed cnidarians on top of bare skeletons and a UVR reflective substrate and showed that under ambient UVR levels, UVR transmitted through the tissues of cnidarians placed on top of bare skeletons were four times lower compared to their counterparts placed on a UVR reflective white substrate. In accordance with the lower levels of UVR measured in cnidarians on top of coral skeletons, a similar drop in UVR damage to their DNA was detected. The skeletons emitted absorbed UVR as yellow fluorescence, which allows for safe dissipation of the otherwise harmful radiation.

Conclusions/Significance

Our study presents a novel defensive role for coral skeletons and reveals that the strong UVR absorbance by the skeleton can contribute to the ability of corals, and potentially other calcifiers, to thrive under UVR levels that are detrimental to most marine life.     

Induction by glucose of an antimycin-insensitive,azide-sensitive respiration in the yeast Kluyveromyces lactis

Increasing the glucose concentration from 0.1 to 10% in exponentially growing cultures of Kluyveromyces lactis CBS 2359 does not repress the antimycin-sensitive respiration (Q_{O 2} of 80 l O₂·h^-1·mg^-1 dry weight) but raises the antimycin-insensitive respiration from 3 to 12 l O₂·h^-1·mg^-1 dry weight. Antimycin A inhibits the growth of K. lactis on a variety of substrates with the exception of glucose at concentrations equal to or higher than 1% where substantial antimycin-insensitive respiratory rates are induced. It can be concluded that a minimal antimycin-insensitive Q_{O 2} is necessary for cellular growth when the normal respiratory pathway is not functional.The antimycin-insensitive respiration elicited by growth in high glucose concentrations is poorly inhibited by hydroxamate and is inhibited by 50% by 90 m azide or 1mm cyanide. These concentrations are much higher than those necessary to inhibit cytochrome c oxidase which is not involved in the antimycin-insensitive respiration as was demonstrated by spectral measurements. A pigment absorbing at 555 nm is specifically reduced after addition of glucose to antimycin-inhibited cells. The same pigment is reoxidized by further addition of high concentrations of sodium azide indicating its participation in the antimycin-insensitive, azide-sensitive respiration.     

The energetics of starvation and growth after refeeding in juveniles of three cyprinid species

Synopsis Experiments were conducted to monitor changes in body mass and metabolic energy expenditure before, during, and after periods of starvation in juveniles of three species of cyprinids: Leuciscus cephalus, Chalcalburnus chalcoides mento, and Scardinius erythrophthalmus. During the starvation period all fish lost weight at about the same rate and the total amount of oxygen consumed during an experimental period of 20 h was about 40% lower in the starved than in the fed groups. Upon refeeding, both mass specific maintenance; and routine rates of metabolism as well as relative growth rates increased rapidly, the peaks of these increases being directly proportional to the length of the starvation period. Maximum compensatory growth was observed after four weeks of starvation in C. chalcoides and S. erythrophthalmus, with relative growth rates reaching 30% d^-1 during the first measuring interval after refeeding. The pattern of time-dependent compensatory growth displayed by these fish is similar to the responses of a colonial hydroid in which the rate of catch-up growth increased with the amount of stress to which the animals had been exposed. The exact cost of compensatory growth cannot be calculated because oxygen consumption and growth were not measured simultaneously. However, on the basis of data and calculations reported by Wieser & Medgyesy (1990) it appears that compensatory growth, if fuelled by the metabolic power indicated by our measurements of oxygen consumption, would have to be about twice as efficient as normal growth in the related species Rutilus rutilus.     

Scaling of heat production by thermogenic flowers: limits to floral size and maximum rate of respiration

Effect of size of inflorescences, flowers and cones on maximum rate of heat production is analysed allometrically in 23 species of thermogenic plants having diverse structures and ranging between 1.8 and 600 g. Total respiration rate (, µmol s^?1) varies with spadix mass (M, g) according to in 15 species of Araceae. Thermal conductance (C, mW °C^?1) for spadices scales according to C = 18.5M^0.73. Mass does not significantly affect the difference between floral and air temperature. Aroids with exposed appendices with high surface area have high thermal conductance, consistent with the need to vaporize attractive scents. True flowers have significantly lower heat production and thermal conductance, because closed petals retain heat that benefits resident insects. The florets on aroid spadices, either within a floral chamber or spathe, have intermediate thermal conductance, consistent with mixed roles. Mass‐specific rates of respiration are variable between species, but reach 900 nmol s^?1 g^?1 in aroid male florets, exceeding rates of all other plants and even most animals. Maximum mass‐specific respiration appears to be limited by oxygen delivery through individual cells. Reducing mass‐specific respiration may be one selective influence on the evolution of large size of thermogenic flowers.     

16O2/18O2 analysis of oxygen exchange in Dunaliella tertiolecta. Evidence for the inhibition of mitochondrial respiration in the light

A mass spectrometric ¹⁶O₂/¹⁸O₂-isotope technique was used to analyse the rates of gross O₂ evolution, net O₂ evolution and gross O₂ uptake in relation to photon fluence rate by Dunaliella tertiolecta adapted to 0.5, 1.0, 1.5, 2.0 and 2.5 M NaCl at 25°C and pH 7.0.At concentrations of dissolved inorganic carbon saturating for photosynthesis (200 M) gross O₂ evolution and net O₂ evolution increased with increasing salinity as well as with photon fluence rate. Light compensation was also enhanced with increased salinities. Light saturation of net O₂ evolution was reached at about 1000 mol m^-2s^-1 for all salt concentrations tested. Gross O₂ uptake in the light was increased in relation to the NaCl concentration but it was decreased with increasing photon fluence rate for almost all salinities, although an enhanced flow of light generated electrons was simultaneously observed. In addition, a comparison between gross O₂ uptake at 1000 mol photons m^-2s^-1, dark respiration before illumination and immediately after darkening of each experiment showed that gross O₂ uptake in the light paralleled but was lower than mitochondrial O₂ consumption in the dark.From these results it is suggested that O₂ uptake by Dunaliella tertiolecta in the light is mainly influenced by mitochondrial O₂ uptake. Therefore, it appears that the light dependent inhibition of gross O₂ uptake is caused by a reduction in mitochondrial O₂ consumption by light.Abbreviations DCMU 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea - DHAP dihydroxy-acetonephosphate - DIC dissolved inorganic carbon - DR_a rate of dark respiration immediately after illumination - DR_b rate of dark respiration before illumination - E₀ rate of gross oxygen evolution in the light - NET rate of net oxygen evolution in the light - PFR photon fluence rate - RubP rubulose-1,5-bisphosphate - SHAM salicyl hydroxamic acid - U₀ rate of gross oxygen uptake in the light     

Acute Effects of Capsaicin on Energy Expenditure and Fat Oxidation in Negative Energy Balance

Background

Addition of capsaicin (CAPS) to the diet has been shown to increase energy expenditure; therefore capsaicin is an interesting target for anti-obesity therapy.

Aim

We investigated the 24 h effects of CAPS on energy expenditure, substrate oxidation and blood pressure during 25% negative energy balance.

Methods

Subjects underwent four 36 h sessions in a respiration chamber for measurements of energy expenditure, substrate oxidation and blood pressure. They received 100% or 75% of their daily energy requirements in the conditions ‘100%CAPS’, ‘100%Control’, ‘75%CAPS’ and ‘75%Control’. CAPS was given at a dose of 2.56 mg (1.03 g of red chili pepper, 39,050 Scoville heat units (SHU)) with every meal.

Results

An induced negative energy balance of 25% was effectively a 20.5% negative energy balance due to adapting mechanisms. Diet-induced thermogenesis (DIT) and resting energy expenditure (REE) at 75%CAPS did not differ from DIT and REE at 100%Control, while at 75%Control these tended to be or were lower than at 100%Control (p = 0.05 and p = 0.02 respectively). Sleeping metabolic rate (SMR) at 75%CAPS did not differ from SMR at 100%CAPS, while SMR at 75%Control was lower than at 100%CAPS (p = 0.04). Fat oxidation at 75%CAPS was higher than at 100%Control (p = 0.03), while with 75%Control it did not differ from 100%Control. Respiratory quotient (RQ) was more decreased at 75%CAPS (p = 0.04) than at 75%Control (p = 0.05) when compared with 100%Control. Blood pressure did not differ between the four conditions.

Conclusion

In an effectively 20.5% negative energy balance, consumption of 2.56 mg capsaicin per meal supports negative energy balance by counteracting the unfavorable negative energy balance effect of decrease in components of energy expenditure. Moreover, consumption of 2.56 mg capsaicin per meal promotes fat oxidation in negative energy balance and does not increase blood pressure significantly.

Trial Registration

Nederlands Trial Register; registration number NTR2944     

Cardiorespiratory reflexes and aquatic surface respiration in the neotropical fish tambaqui (<Emphasis Type="Italic">Colossoma macropomum</Emphasis>): acute responses to hypercarbia

We examined the cardiorespiratory responses to 6 h of acute hypercarbia (1, 2.5, and 5% CO₂) in intact and gill-denervated (bilateral denervation of branchial branches of cranial nerves IX and X) tambaqui, Colossoma macropomum. Intact fish exposed to 1 and 2.5% CO₂ increased respiratory frequency (f_R) and ventilation amplitude (V_AMP) slowly over a 1- to 3-h period. Denervated fish did not show this response, suggesting that tambaqui possess receptors in the gills that will produce excitatory responses to low levels of hypercarbia (1 and 2.5% CO₂) if the exposure is prolonged. The cardiac response to stimulation of these receptors with this level of CO₂ was a tachycardia and not a bradycardia. During exposure to 5% CO₂, intact fish increased f_R and V_AMP, and showed a pronounced bradycardia after 1 h. After 2 h, the heart rate (f_H) started to increase, but returned to control values after 6 h. In denervated fish, the increase in f_R was abolished. The slow increase in V_AMP and the bradycardia were not abolished, suggesting that these changes arose from extra-branchial receptors. Neither intact nor denervated fish developed the swelling of the lower lip or performed aquatic surface respiration, even after 6 h, suggesting that these are unique responses to hypoxia and not hypercarbia.Abbreviations ASR aquatic surface respiration - f_H heart frequency - f_R respiratory frequency - V_AMP ventilation amplitude - _TOT total ventilation     

Exploring Metrics to Express Energy Expenditure of Physical Activity in Youth

Background

Several approaches have been used to express energy expenditure in youth, but no consensus exists as to which best normalizes data for the wide range of ages and body sizes across a range of physical activities. This study examined several common metrics for expressing energy expenditure to determine whether one metric can be used for all healthy children. Such a metric could improve our ability to further advance the Compendium of Physical Activities for Youth.

Methods

A secondary analysis of oxygen uptake (VO₂) data obtained from five sites was completed, that included 947 children ages 5 to 18 years, who engaged in 14 different activities. Resting metabolic rate (RMR) was computed based on Schofield Equations [Hum Nutr Clin Nut. 39(Suppl 1), 1985]. Absolute oxygen uptake (ml.min^-1), oxygen uptake per kilogram body mass (VO₂ in ml.kg^-1.min^-1), net oxygen uptake (VO₂ – resting metabolic rate), allometric scaled oxygen uptake (VO₂ in ml.kg^-0.75.min^-1) and YOUTH-MET (VO₂.[resting VO₂] ^-1) were calculated. These metrics were regressed with age, sex, height, and body mass.

Results

Net and allometric-scaled VO₂, and YOUTH-MET were least associated with age, sex and physical characteristics. For moderate-to-vigorous intensity activities, allometric scaling was least related to age and sex. For sedentary and low-intensity activities, YOUTH-MET was least related to age and sex.

Conclusions

No energy expenditure metric completely eliminated the influence of age, physical characteristics, and sex. The Adult MET consistently overestimated EE. YOUTH-MET was better for expressing energy expenditure for sedentary and light activities, whereas allometric scaling was better for moderate and vigorous intensity activities. From a practical perspective, The YOUTH-MET may be the more feasible metric for improving of the Compendium of Physical Activities for Youth.