Mean Oxygen Consumption Rate Research Articles

Abstract P407: Decreased Peripheral Mitochondrial Respiration in Pre-Adolescent Hispanic Children With Hepatic Steatosis

Introduction: Mitochondria plays a significant role in the functioning of the liver. Its function and structure have been associated with diseases outside the organelle by producing reactive oxygen species (ROS), causing generalized oxidative stress, improper function to several metabolic pathways, and perpetuating a pro-inflammatory state in conditions like obesity, diabetes, and metabolic dysfunction associated steatotic liver disease (MASLD). These diseases are on the rise and increase future atherosclerotic cardiovascular disease. Little is known regarding the pathophysiology of the earliest stages of hepatic steatosis, although mitochondrial dysfunction has been shown in later stages. In young children with and without MASLD, we aimed to measure mitochondrial respiration and compare it to hepatic steatosis and other cardiometabolic parameters. The hypothesis of the sub-study was that children with MASLD will have a decreased mitochondrial function compared with healthy children. Methods: We report data on 9 subjects, (all Latino subjects, mean age of 8.1 years, mean BMIp of 78%) who participated in screening for an ongoing clinical trial (ClinicalTrials No. NCT05292352). After consent and assent, procedures included drawing whole blood and transferring it immediately to the lab. Monocyte isolation was performed using RosetteSep™ Cocktail and measurement of fatty acid oxidation and glycolysis using the Seahorse Bioscience XFp extracellular flux analyzer. We measured the Oxygen Consumption Rate (OCR) as a proxy for mitochondrial respiration. Association with the mitochondrial parameters was evaluated with the percentage of hepatic steatosis (Hepafat), levels of ALT, insulin, and BMI percentile (BMIp). Data were analyzed using the R software program version 4.2.3 Results: Mean hepatic steatosis (HS) was 5.97% with a low of 2.4% and a high of 13%. The mean OCR for the subjects without MASLD (n=4, HS ≤5% by MRI) was 404.64 and the mean for subjects with MASLD (n=5, HS ≥5% by MRI) was 349.88. The mean OCR of subjects with a normal, overweight, and obese BMIp was 441.58, 397.45, 309.08, respectively. We found peripheral mitochondrial respiration tends to decrease as hepatic steatosis, BMIp, ALT and insulin levels increase. Conclusion: Hepatic steatosis is associated with decreased mitochondrial respiration and perhaps perpetuates an inflammatory state at very young ages in this vulnerable population. More subjects from the NAFLD prevention study will increase the significance of the study in the future.

Four Weeks Of A Ketogenic Diet Increases Oxygen Consumption And Fat Oxidation During Moderate-intensity Walking

PURPOSE: Establish the time-course of changes in oxygen consumption, substrate metabolism, and heart rate during treadmill walking upon commencing a ketogenic diet. METHODS: In a randomized, parallel design, 53 men and women (mean ± SD, age: 35 ± 16 years, body mass index: 24 ± 3 kg/m2) were allocated to a moderate-sugar, moderate-carbohydrate diet [MODSUG; contribution of carbohydrate (of which sugars), fat and protein to total energy intake: 50% (15%), 35%, and 15%, respectively] a low-sugar, moderate-carbohydrate diet [LOWSUG; 50% (5%), 35%, and 15%, respectively] or a low-carbohydrate, ketogenic diet [LOWCHO; 8% (2%), 77%, and 15%, respectively] for 12 weeks. Oxygen consumption and substrate metabolism were determined by Douglas bags and heart rate using electrocardiography during submaximal walking at baseline, 4-weeks and 12-weeks of the dietary intervention. The submaximal treadmill test comprised 5-minute stages at 5.2 km/h with gradients of 0%, 3%, 6% and 9%. Data were analyzed by two-way (group x time) ANOVA with post-hoc test corrected for multiple comparisons by the Bonferroni method. RESULTS: Mean oxygen consumption rates displayed a group x time interaction (P = 0.016) whereby LOWCHO increased oxygen consumption from 17.8 ± 1.8 mL/kg/min at baseline to 18.4 ± 2.1 mL/kg/min by week 4 (P = 0.02), after which levels remained elevated at 18.4 ± 2.2 at week 12 (P > 0.05). Mean heart rate during all gradients increased with LOWCHO from 115 ± 12 beats/min at baseline to 121 ± 12 beats/min by week 4 (group x time interaction, P = 0.026; post-hoc comparison, P = 0.04), reaching 120 ± 14 beats/min at week 12 (P > 0.05). Peak fat oxidation rates increased with LOWCHO from 0.37 ± 0.18 g/min at baseline to 0.58 ± 0.25 g/min at week 4 with concomitant decreases in carbohydrate oxidation rates (group x time interaction, P < 0.001; post-hoc comparison, P < 0.001) with no further increases at week 12 (0.56 ± 0.27 g/min; P > 0.05). No such increases were observed with MODSUG or LOWSUG (all P > 0.05). CONCLUSIONS: Adaptations of oxygen consumption, heart rate and fat oxidation during walking plateau by 4 weeks of commencing a low-carbohydrate ketogenic diet, suggesting 4 weeks is sufficient to maximise metabolic adaptations to exercise with ketogenic diets. Supported by The Rank Prize Funds and Kenniscentrum Suiker & Voeding.

Influence of diet and feeding strategy on the performance of nitrifying trickling filter, oxygen consumption and ammonia excretion of gilthead sea bream (Sparus aurata) raised in recirculating aquaculture systems

Gilthead sea bream (Sparus aurata) was raised in six individual recirculating aquaculture systems (RAS) whose biofilters’ performance was analyzed. Fish were fed with three different diets (a control diet, a fishmeal-based diet (FM), and a plant meal-based diet (VM)) and with three different feeding strategies (manual feeding to apparent satiation, automatic feeding with restricted ration, and auto-demand feeding). For every combination of diet and feeding strategy, the mean oxygen consumption, ammonia excretion, and ammonia removal rate were determined. Fish fed with the VM diet consumed the most oxygen (20.06 ± 1.80 gO2 consumed kg−1 day−1). There were significant differences in ammonia excretion depending on the protein content and protein efficiency of the diet, as well as depending on feeding strategy, which in turn affected ammonia removal rates. Fish fed by auto-demand feeders led to the highest mean ammonia removal rate (0.10 gN-TAN removed m−2 biofiltration area day−1), while not leading to peaks of high ammonia concentration in water, which preserve fish welfare and growth.

Impact of Intertidal Distribution on the Physiological Performance of the Filter-Feeder Bivalve Perumytilus purpuratus (Bivalvia, Mytilidae) from Southern Chile

Intertidal animals experience reduced feeding times and differentiated respiratory capacity associated with aerial exposure, the duration of which depends on their location within the intertidal zone. Perumytilus purpuratus is a sessile mussel that forms dense mats in the rocky mid-intertidal in southern Chile. For this species, we documented the impact of different times of aerial exposure (3 and 6 h) on rates of oxygen consumption and feeding, according to their vertical location (upper and lower limits) within the intertidal zone. Mean oxygen consumption rates in air for individuals located in the upper intertidal zone were 52% higher than those of individuals located at the lower limits of their intertidal distribution. Additionally, individuals from the lower intertidal region always presented higher rates of oxygen consumption and particle clearance rates (58% higher and 18% higher, respectively) during immersion compared to individuals collected from the upper limit of their intertidal distribution, regardless of the duration of previous aerial exposure. Although we found no significant habitat-related differences in the relationship between shell length and gill surface area, individuals sampled from the lower intertidal zone were 8% heavier in dry tissue weight than individuals with the same shell lengths collected from of the upper limit of their intertidal distribution. Our results suggest that the individuals of this species near the upper limits of their intertidal distribution can probably compensate (e.g., higher absorption rate) for the reduced time that they have available for clearance, which might help them to avoid a major energetic disadvantage.

Resilience of Oxygen Consumption Rates in the Juvenile Blue Crab Callinectes sapidus to Future Predicted Increases in Environmental Temperature and pCo2 in the Mesohaline Chesapeake Bay

Quantifying the physiological impact of environmental stressors on living organisms is critical to predicting the response of any given species to future climate scenarios. Oxygen consumption rates (μmol/g/min) were measured to examine the physiological response of the juvenile blue crab Callinectes sapidus from the Chesapeake Bay (Patuxent River, Maryland) to elevated temperature and dissolved carbon dioxide in water (pCO2) reflective of projected future climate scenarios. Treatment levels were selected to represent current conditions in the Chesapeake Bay (26°C and 800 μatm) and conditions predicted to occur by the year 2100 (31°C and 8,000 μatm). Crabs were exposed in a factorial design to these conditions throughout two successive molts (approximately 30 days). At the end of the exposure, the oxygen consumption rates of individual crabs were determined over at least a 10-h period using a flow-through respiration chamber equipped with optical oxygen electrodes. No significant effect of temperature or pCO2 on oxygen consumption was observed, suggesting the absence of a respiratory impact of these two climate stressors on juvenile blue crabs. Oxygen consumption rates were also determined for crabs that experienced a rapid increase in temperature without prior acclimation. The oxygen consumption rate of crabs may have acclimated to increased temperature during the 30-day exposure period before respiratory measurement. This potential acclimation, combined with high individual variability, and a relatively small difference in temperature treatments are likely the cause for the lack of a statistically significant difference in mean oxygen consumption rates by temperature in the core experiment. The results of this study suggest that the blue crab may be quite resilient to future climate stressors and underscore the need for species-specific studies to quantify the effects of climate change on estuarine crustaceans.

Low-dose persistent organic pollutants and mitochondrial dysfunction in humans

TPS 634: Health effects of pops, voc and other chemicals, Johan Friso Foyer, Floor 1, August 27, 2019, 3:00 PM - 4:30 PM Background/Aim: Declining mitochondrial function, reflected by diminished electron transport chain activity, is related to many common chronic diseases. However, the risk factors of mitochondrial dysfunction are largely unknown. Recently, chronic exposure to low-dose environmental chemicals has been suspected to induce mitochondrial dysfunction in in vitro and in vivo settings. We evaluated the relationship between serum concentrations of lipophilic chemical mixtures and mitochondrial function in an apparently healthy population. Methods: Serum concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were measured in 248 Korean adults aged 30-64 years. Platelet oxygen consumption rates (OCRs), measured using the Seahorse XF Analyzer was used as a biomarker of mitochondrial function in 20-ml samples of fresh peripheral blood. Results: Mean OCR decreased significantly with increasing serum concentrations of OCPs. Across quartiles of summary measure of OCPs, mean OCRs were 12.4, 11.2, 9.0, and 8.5 (P trend<0.01). When the last quartile of summary measure of OCPs was further categorized according to 90%- and 95%-cutoff points, the linear association became stronger. Similarly, this linear relationship was observed in subgroups stratified according to age, sex, and body mass index. PCBs showed much weaker associations than OCPs. Conclusions: Considering the current human, in vitro, and in-vivo evidence, we suggest that mitochondrial dysfunction may be a key mechanism that links chronic exposure to low-dose chemical mixtures to common chronic diseases, such as diabetes or dementia. (□ Acknowledgement: This work was supported by the Korea Ministry of Environment (MOE) as the Environmental Health Action Program (2016001370002).)

In situ swimming behaviors and oxygen consumption rates of juvenile lemon sharks (Negaprion brevirostris)

Knowing how often animals engage in different behaviors and their energetic costs may explain why animals behave the way they do in the wild. This study sought to investigate the relationship between the frequency of various swimming behaviors and their associated energetic costs (oxygen consumption rates) in situ for juvenile lemon sharks (Negaprion brevirostris). Behaviors were identified for captive animals and remotely observed for animals in the wild with accelerometers, and oxygen consumption rates of behaviors were estimated using acceleration-calibrated relationships. Lemon sharks rested infrequently (4.3% of deployment), and the occurrence of active swimming behaviors was inversely related to their respective oxygen consumption rates. Furthermore, time of day and tide state influenced when lemon sharks exhibited active swimming behaviors – but not resting – such that sharks were most active during the day on flooding tides. Oxygen consumption rates also differed across and within different behaviors with time of day and tide state, although mean oxygen consumption rates were highest on daytime flooding tides and uniformly reduced across all other diel and tide combinations. Despite variation in oxygen consumption rates, however, lemon shark activity occurred at 32.3–35.6% of their aerobic metabolic scope. These data do not provide a clear oxygen consumption basis for swimming behaviors observed in situ, which may have been masked by potentially stronger ecological drivers (e.g., predator-prey dynamics). However, these data are relevant to linking behavioral modifications to changes in energy use that shows much promise for addressing conservation issues in fishes.

Abstract 833: Alginate hydrogels for three-dimensional culture and real-time monitoring of cancer cell metabolism and radiation response

Abstract The purpose of this study was to characterize a three-dimensional calcium alginate culture system for real-time monitoring of cancer cell metabolism and radiation response. HCT116 colorectal cancer cells were encapsulated in 2.5% calcium alginate using a custom electrostatic rig adapted from a previously published system. Bead diameter was a function of voltage and alginate concentration: 4 x 107 cells/mL encapsulated at 4 and 8 kV resulted in mean diameters of 880 and 584 µm, respectively. The distribution of bead radii for all voltages showed positive excess kurtosis (4 kV = 1.6, 8 kV = 3.0) and 72.9% of 4 kV and 77.2% of 8 kV bead diameters fell within one standard deviation of the mean. Encapsulated cell viability was assessed by staining with Trypan Blue and clonogenic survival assays (CSAs). The baseline viability of cells immediately after encapsulation was 93.2%, which decreased 2 days after a single 10 Gy dose (90.7%, p&amp;lt;0.05). After two weeks of continuous culturing, 84.1% of non-irradiated and 73.8% of irradiated encapsulated cells remained viable (p&amp;lt;0.003). Pimonidazole staining demonstrated the presence of hypoxic cores proportional to bead size. CSAs of 8 kV beads showed a dose modifying factor (DMF) of 1.06 relative to cells grown in a monolayer, while larger 4 kV beads showed a DMF of 1.58. Mean oxygen consumption rate rose with increasing number of 8 kV beads/well: 1 bead, 35.5; 2 beads, 97.4; 3 beads, 175.5; 4 beads, 209.9; 2.0 x 104 monolayer cells, 92.6 (all pmol/min, ~8.2 x103 cells/bead, p&amp;lt;0.005). Hyperpolarized 13C-NMR spectroscopy of 400 uL of 8 kV beads containing 1.2 x 108 cells/mL showed a detectable conversion of [1-13C]-pyruvate to [1-13C]-lactate; 1 hour after a single 10 Gy dose, the lactate:pyruvate ratio decreased by 25%. Unpaired 2-tailed Student’s t-tests were used to determine significance between and one-way ANOVA was used to determine significance among groups with α set at p≤0.05. These data demonstrate the versatility of alginate hydrogels for real-time metabolic and radiation response studies which are non-invasive, higher throughput, and lower cost compared to in vivo systems. Future directions include additional metabolic flux analysis and hyperpolarized 13C-NMR spectroscopy to further investigate the cancer cell metabolic response to drug and/or radiation therapy. Citation Format: Aparna H. Kesarwala, Jenna L. Carter, Graham H. Read, Natsuko Miura, Kazutoshi Yamamoto, James B. Mitchell, Murali C. Krishna. Alginate hydrogels for three-dimensional culture and real-time monitoring of cancer cell metabolism and radiation response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 833. doi:10.1158/1538-7445.AM2017-833

Field evaluation of oxygen consumption by two freshwater decapod morphotypes (Trichodactylidae and Aeglidae); the effect of different times of the day, body weight and sex

We report an analysis of the effect of two different times of day (noon and dusk), body weight and sex on the oxygen consumption rate (OCR) of the freshwater crabs Trichodactylus kensleyi (Trichodactylidae), Aegla singularis and A. platensis (Aeglidae) in their natural environment. Both families are sympatric in the studied locations, with a co-occurrence found between T. kensleyi and A. singularis or T. kensleyi and A. platensis. The mean OCR was highest in A. singularis and lowest in A. platensis. The OCR was higher in Aegla species at noon, and Trichodactylus consumed more oxygen at dusk. In aeglids, there was no difference in oxygen consumption between noon and dusk. T. kensleyi exhibited statistically significant differences in the OCR between noon and dusk. The oxygen uptake of all three species analysed was not influenced by the sex of the individual but varied according to the animals’ weight. The families evaluated share some biological and ecological characteristics, such as diet and habitats, but the strategies used in the regulation of gas exchange at different times of the day were different. Environmental factors may be influencing the oxygen consumption of each morphotype differently.

Self-selected speeds and metabolic cost of longboard skateboarding.

The purpose of this study was to determine self-selected speeds, metabolic rate, and gross metabolic cost during longboard skateboarding. We measured overground speed and metabolic rate while 15 experienced longboarders traveled at their self-selected slow, typical and fast speeds. Mean longboarding speeds were 3.7, 4.5 and 5.1 m s(-1), during slow, typical and fast trials, respectively. Mean rates of oxygen consumption were 24.1, 29.1 and 37.2 ml kg(-1) min(-1) and mean rates of energy expenditure were 33.5, 41.8 and 52.7 kJ min(-1) at the slow, typical and fast speeds, respectively. At typical speeds, average intensity was ~8.5 METs. There was a significant positive relationship between oxygen consumption and energy expenditure versus speed (R(2) = 0.69 (P < 0.001), and R(2) = 0.78 (P < 0.001), respectively). The gross metabolic cost was ~2.2 J kg(-1) m(-1) at the typical speed, greater than that reported for cycling and ~50% smaller than that of walking. These results suggest that longboarding is a novel form of physical activity that elicits vigorous intensity, yet is economical compared to walking.

Impact of short-term salinity stress on larval development of the marine gastropod Crepipatella fecunda (Calyptraeidae)

Shallow-water coastal environments suffer frequent reductions in salinity due to heavy rains. This creates stressful conditions for the organisms found there, particularly for the early stages of development, including pelagic larvae. Freshly hatched larvae of the gastropod Crepipatella fecunda were exposed to different levels of salinity stress (32 (control), 25, 20 and 15) for a single 6h period. Subsequently, all veligers were maintained at normal control salinity (32) through metamorphosis. Periodic measurements were made of mortality, larval growth, and larval behavior. In particular, we measured changes in velar surface area, swimming velocity, clearance rate, oxygen consumption rate, shell growth rate, larval mortality, time to metamorphosis, and size at metamorphosis. The short exposure to salinity stress decreased subsequent mean growth rates at normal salinity and mean size at metamorphosis, but increased the duration of the planktonic period and the extent of larval mortality. It also reduced the rate at which the velar surface area increased relative to shell growth, and reduced mean larval swimming velocity. Mean oxygen consumption rates and clearance rates were also significantly lower for larvae that had been stressed early in larval life, compared with values obtained for control individuals. Exposure to low salinity for even a short time early in larval life can clearly have a substantial impact on the rest of larval development.

Oxygen consumption rate of early pre-antral follicles from vitrified human ovarian cortical tissue.

The study of human ovarian tissue transplantation and cryopreservation has advanced significantly. Autotransplantation of human pre-antral follicles isolated from cryopreserved cortical tissue is a promising option for the preservation of fertility in young cancer patients. The purpose of the present study was to reveal the effect of vitrification after low-temperature transportation of human pre-antral follicles by using the oxygen consumption rate (OCR). Cortical tissues from 9 ovaries of female-to-male transsexuals were vitrified after transportation (6 or 18 h). The follicles were enzymatically isolated from nonvitrified tissue (group I, 18 h of transportation), vitrified-warmed tissue (group II, 6 and 18 h of transportation) and vitrified-warmed tissue that had been incubated for 24 h (group III, 6 and 18 h of transportation). OCR measurement and the LIVE/DEAD viability assay were performed. Despite the ischemic condition, the isolated pre-antral follicles in group I consumed oxygen, and the mean OCRs increased with developmental stage. Neither the transportation time nor patient age seemed to affect the OCR in this group. Meanwhile, the mean OCR was significantly lower (P < 0.05) in group II but was comparable to that of group I after 24 h of incubation. The integrity of vitrified-warmed primordial and primary follicles was clearly corroborated by the LIVE/DEAD viability assay. These results demonstrate that the OCR can be used to directly estimate the effect of vitrification on the viability of primordial and primary follicles and to select the viable primordial and primary follicles from vitrified-warmed follicles.

The Relationship between Climbing Ability and Physiological Responses to Rock Climbing

Aim. The aim of this study was to examine the relationship between submaximal and maximal physiological responses to rock climbing for climbers of differing abilities. Methods. Twenty-six male climbers performed a submaximal climbing test on a known circuit at 90° (vertical) and 105° (15° overhanging) inclination and speed 25 movements·min−1. A maximal test was undertaken on a similar circuit at the same speed with inclination increasing by 10° for each successive 3 min stage. Results. Mean oxygen consumption and heart rate (HR) increased with wall inclination and climbers reached a mean (±SD) peak of 40.3 ± 3.5 mL·kg−1 ·min−1 during the maximal test. Self-reported climbing ability was negatively correlated with and HR during the submaximal test at 90° (, r = −0.82; HR, and r = −0.66) and at 105° (, r = −0.84; HR, and r = −0.78) suggesting an increased exercise economy for climbers with a higher ability level. Conclusion. Findings from this study indicate that there is a relationship between wall inclination and the physiological demand of a climb. However, the increased technical ability and fitness of higher level climbers appears to an extent to offset the increased demand through improved exercise economy which in turn leads to an increased time to exhaustion and an improvement in performance.

138 FATTY ACID β-OXIDATION REGULATES BOVINE EMBRYO OXYGEN METABOLISM

Mammalian oocytes are rich in endogenous lipid, which provides a potential source of metabolic energy during oocyte maturation and early embryo development after fertilisation. Despite this, studies on early embryo metabolism have focussed on consumption of substrates from the culture medium, with comparatively little consideration for endogenous stores. Additionally, the interaction between fatty acid β-oxidation and oxygen consumption during pre-implantation development has not been investigated. This study has investigated the relationship between embryo fatty acid metabolism and oxygen consumption rate (OCR), a marker of overall oxidative metabolic activity. The amount of oxygen consumption by bovine blastocysts coupled to ATP synthesis was assessed by measuring embryo OCR following acute treatment with oligomycin, which inhibits ATP synthase. Bovine embryos were then produced in vitro and cultured from zygote to blastocyst stage (8 days) in the presence of β-mercaptoacetate (BMA), a competitive inhibitor of fatty acid β-oxidation, or L-carnitine, a cofactor that promotes β-oxidation. OCR of individual embryos was measured using a noninvasive, highly sensitive oxygen probe (Unisense), whereas OCR of embryos in groups was determined using the Oxygen Biosensor (OBS) fluorimetric assay (BD Biosciences, Erembodegem, Belgium). Mean OCR measured by each technique correlated well. Data are presented as means ± SEM. The effect of acute inhibition were compared by a paired t-test, with pre-treated embryos acting as their own control, whereas the effect of L-carnitine and BMA on OCR was compared across treatment groups using ANOVA with Dunn’s test for unequal groups post hoc, using Sigmaplot (Systat Software Inc., San Jose, CA, USA). Treatment with oligomycin caused blastocyst OCR to fall from 23.5 ± 3.3 to 7.9 ± 2.5 pmol/embryo/h (n = 3; P = 0.03). Inhibition of β-oxidation by BMA led to a modest, but consistent increased OCR in cleavage stage embryos: 4-cell: 14.8 ± 7.2 (n = 12) v. 8.9 ± 1.1 pmol/embryo/h (n = 3) control; 8-cell: 15.8 ± 2.2 (n = 6) v. 11.9 ± 2.3 pmol/embryo/h (n = 3) control. At the morula stage, BMA led to a significant rise in OCR (26.8 ± 3.6 (n = 7) v. 7.8 ± 1.7 pmol/embryo/h (n = 3) control; P = 0.003) and at the blastocyst stage, OCR was significantly elevated in the presence of BMA; 41.3 ± 2.6 (n = 19) v. 16.9 ± 1.3 pmol/embryo/h (n = 14) control (P = 0.01). By contrast, when groups of embryos were cultured in the presence of L-carnitine, blastocyst OCR was reduced by 45% from 24.7 ± 5.1 (group control) to 15.9 ± 3.7 pmol/embryo/h (n = 30; P &lt; 0.06). We report that 66.5% of oxygen consumption by bovine blastocysts is oligomycin sensitive, meaning that 33.5% of oxygen consumption is used for processes other than ATP synthesis. Surprisingly, inhibition of fatty acid β-oxidation caused total bovine embryo OCR to rise, although the reasons for this are unclear. It is possible that inhibiting β-oxidation leads to an accumulation of free fatty acids in the mitochondrion, which can disrupt the inner membrane and lead decoupling of ATP synthesis from oxygen consumption. Thus, manipulating fatty acid oxidation in the early embryo dysregulates oxidative metabolism; the implications of this are under further investigation.

Improving Oxygen Conditions in the Deeper Parts of Bornholm Sea by Pumped Injection of Winter Water

Vertical diffusivity and oxygen consumption in the basin water, the water below the sill level at about 59 m depth, have been estimated by applying budget methods to monitoring data from hydrographical stations BY4 and BY5 for periods without water renewal. From the vertical diffusivity, the mean rate of work against the buoyancy forces below 65 m depth is estimated to about 0.10 mW m−2. This is slightly higher than published values for East Gotland Sea. The horizontally averaged vertical diffusivity κ can be approximated by the expression κ = a 0 N −1 where N is the buoyancy frequency and a 0 ≈ 1.25 × 10−7 m2 s−2, which is similar to values for a 0 used for depths below the halocline in Baltic proper circulation models for long-term simulations. The contemporary mean rate of oxygen consumption in the basin water is about 75 g O2 m−2 year−1, which corresponds to an oxidation of 28 g C m−2 year−1. The oxygen consumption in the Bornholm Basin doubled from the 1970s to the 2000s, which qualitatively explains the observed increasing frequency and vertical extent of anoxia and hypoxia in the basin water in records from the end of the 1950s to present time. A horizontally averaged vertical advection–diffusion model of the basin water is used to calculate the effects on stratification and oxygen concentration by a forced pump-driven vertical convection. It is shown that the residence time of the basin water may be reduced by pumping down and mixing the so-called winter water into the deepwater. With the present rate of oxygen consumption, a pumped flux of about 25 km3 year−1 would be sufficient to keep the oxygen concentration in the deepwater above 2 mL O2 L−1.

Effect of low dissolved oxygen on the oxygen consumption rate and rhythm of the mudskipper Scartelaos gigas (Pisces, Gobiidae)

The mudskipper Scartelaos gigas is expected to experience repeated severe hypoxia in its environment. Hence, we conducted experiments on the oxygen consumption rate (OCR) and OCR rhythm of S. gigas at low graded dissolved oxygen (DO) levels, without access to atmospheric air, to estimate its tolerance to hypoxia. A dominant circadian OCR rhythm was observed at the control DO level of 6.96–7.78 mg O2/l. This rhythm was unchanged until 2.06 mg O2/l, even though the amplitude of the peak was somewhat diminished at 2.06–2.87 mg O2/l. The OCR rhythm amplitude was greatly diminished and the rhythm period was also greatly changed at 1.23–2.05 mg O2/l. Nevertheless, the mean OCR (0.11 ml O2/g WW/h) at 1.23–2.05 mg O2/l was similar to that of control (0.12 ml O2/g WW/h). Thus, the weakness and period change of the OCR rhythm kept the metabolic rate level similar to control. These results suggest that S. gigas does not have normal metabolic activity at 1.23–2.05 mg O2/l but barely manages to endure this DO level as a pre-emergency state. This species could be inhibited under a longer maintenance period at DO level of 1.23–2.05 mg O2/l or still lower. It can be concluded that S. gigas is quite tolerant to low DO environment and may have a specific strategy for such tolerance.

First respiration estimates of cold-seep vesicomyid bivalves from in situ total oxygen uptake measurements

Vesicomyid bivalves are one of the most abundant symbiont-bearing species inhabiting deep-sea reducing ecosystems. Nevertheless, except for the hydrothermal vent clam Calyptogena magnifica, their metabolic rates have not been documented, and only assessed with ex situ experiments. In this study, gathering benthic chamber measurements and biomass estimation, we give the first in situ assessment of the respiration rate of these bivalves. The giant pockmark Regab, located at 3160m depth along the Congo-Angola margin, is a cold-seep site characterised by dense assemblages of two species of vesicomyids: Christineconcha regab and Laubiericoncha chuni with high dominance of C. regab. Two sites with dense aggregates of vesicomyids were selected to measure total oxygen uptake (TOU), and methane fluxes using IFREMER's benthic chamber CALMAR deployed by the ROV Quest 4000 (MARUM). Photographs were taken and bivalves were sampled using blade corers to estimate density and biomass. Total oxygen uptake was higher at Site 2 compared to Site 1 (respectively 492mmol.m−2.d−1 and 332mmol.m−2.d−1). However, given vesicomyid densities and biomass, mean oxygen consumption rates were similar at both sites (1.9 to 2.5μmol.g total dry mass−1.h−1 at the Site 1 and 1.8 to 2.3μmol.g total dry mass−1.h−1 at Site 2). These respiration rates are higher than published ex situ estimates for cold-seep or hydrothermal vent bivalves. Although methane fluxes at the base of sulphide production were clearly higher at Site 2 (14.6mmol.m−2.d−1) than at Site 1 (0.3mmol.m−2.d−1), they do not seem to influence the respiration rates of these bivalves associated to sulphide-oxidizing symbionts.

Effects of Water Temperature Changes on the Oxygen Consumption Rhythm in the Japanese eel, Anguilla japonica

We investigated the effects of temperature changes on the oxygen consumption rhythm in Japanese eels, Anguilla japonica, using an automatic intermittent flow respirometer (AIFR). The endogenous rhythm of the oxygen consumption rate (OCR) in the eels (n = 18; 44-74 cm, 145-690 g), freshly collected by bag net from estuaries, was nearly synchronous with the tidal pattern of the estuarine collection site. The magnitude of mean OCR (mOCR) of eels showed variable range of 82.2 - 116.5 ml <TEX>$O_2\;kg^{-1}ww \;h^{-1}$</TEX> under constant conditions. In case of increasing temperature from 25 to <TEX>$38^{\circ}C$</TEX>, the OCR of eels exhibited a gradually increasing trend with a rhythmic pattern until <TEX>$36^{\circ}C$</TEX>. Above <TEX>$36^{\circ}C$</TEX> the rhythms of the OCR dampened and the OCR decreased rapidly at around <TEX>$36-37^{\circ}C$</TEX>. The OCR of the eels exhibited the maximum value at <TEX>$38^{\circ}C$</TEX>, and then it sharply decreased. The results suggested that the critical thermal maximum (CTM) regarding the endogenous rhythms of the eels was at around <TEX>$36-37^{\circ}C$</TEX> when water temperature increased at <TEX>$0.5^{\circ}C$</TEX>/14 h following the acclimation at <TEX>$25^{\circ}C$</TEX>. In case of decreasing temperature (<TEX>$0.5^{\circ}C$</TEX>/14 h) from 25 to <TEX>$0^{\circ}C$</TEX>, the OCR of the eels displayed a abrupt decrease up to <TEX>$23^{\circ}C$</TEX>, and between at 23 and <TEX>$20^{\circ}C$</TEX>, there was an agitation which showed a slight increase in the OCR with a duration of 1-2 days. Below <TEX>$9^{\circ}C$</TEX>, the OCR rhythm of the eels showed a constant state regardless of temperature decreasing. These results suggest that the Japanese eel has an upper incipient lethal temperature at <TEX>$36^{\circ}C$</TEX>, with a lower thermal limit at <TEX>$9^{\circ}C$</TEX>. The biochemical aspects of the eels influenced by water temperature need to be further studied.

대구 Gadus macrocephalus 치어의 산소 소비율에 미치는 수온과 광주기의 영향

A study was conducted to investigate the effect of water temperature and photoperiod on the oxygen consumption of the fasting juvenile Pacific cod Gadus macrocephalus (mean body weight 79.9±2.0 g) in order to quantify metabolic response of the species under given conditions. The oxygen consumption rate (OCR) of G. macrorephalus was measured under a combination of four different water temperatures (7, 10, 13 and 16℃) and three different photoperiods (24L:0D, 12L:12D and 0L:24D) with an interval of 5 minutes over a 24-hour period using a closed recirculating respirometer. Three replicates were set up in each treatment. OCRs increased with increased water temperatures under all photoperiod conditions (P＜0.001). Mean OCRs at 7, 10, 13 and 16℃ ranged from 793.7~1108.4, 1145.7~1570.3, 1352.8~1742.5 and 1458.2~1818.6 ㎎ O₂ ㎏?¹ h?¹, respectively. Under all water temperature conditions except 7℃ (P＜0.001), mean OCRs of G. macrorephalus were the highest in continuous light (24L:0D) followed by 12L:12D and 0L:24D photoperiods. Mean OCRs of fish exposed to the 12L:12D photoperiod were significantly higher during the light phase than during the dark phase under all temperature conditions (P＜0.001). Q₁? values ranged from 3.19~5.13 between 7 and 10℃, 1.41~1.74 between 10 and 13℃ and 1.15~1.35 between 13 and 16℃, respectively. Based on overall results, water temperature, photoperiod and their combinations exerted a significant influence on the metabolic rate of juvenile cod. This study provides empirical data for estimating the amount of oxygen demand and managing the culture of cod under the given water temperatures and photoperiods.

Rainbow trout Oncorhynchus mykiss energetic responsesto pulsed flows in the American River, California, assessed by electromyogram telemetry

Although rainbow trout Oncorhynchus mykiss within the American River, California, apparently exhibit minimal upstream or downstream movements in response to hydroelectric-power-generation-related pulsed flows, the associated energetic costs are unknown. We implanted rainbow trout (n = 9, ≥30 cm SL) with electromyogram (EMG)-sensor-equipped radio transmitters to assess the swimming behavior and associated energetic costs associated with their responses to pulsed flows. Using laboratory calibrations in a Brett-type swimming respirometer, the trouts’ swimming speeds and oxygen consumption rates were estimated for their in-river EMG data, through a complete hydroelectric power-generation river pulsed-flow sequence (pre-pulse, increasing flow, peak, and decreasing flow stages), on several (mean: 3.2) sampling dates. Using a mixed-linear model, we found that fish swimming speed estimates increased during the increasing flow stage, while the associated mean oxygen consumption rates also increased at this stage. At river flows near the usual peak (>44 m3s−1), swimming speeds and movement rates decreased, possibly due to the fish using the river’s habitat complexities as hydraulic cover. We conclude that rainbow trout incur increased swimming-related energetic costs during increasing flows and, potentially, decreased foraging opportunities at high flows.