Average Oxygen Consumption Research Articles

Oxygen Consumption Characteristics in 3D Constructs Depend on Cell Density.

Oxygen is not only crucial for cell survival but also a determinant for cell fate and function. However, the supply of oxygen and other nutrients as well as the removal of toxic waste products often limit cell viability in 3-dimensional (3D) engineered tissues. The aim of this study was to determine the oxygen consumption characteristics of 3D constructs as a function of their cell density. The oxygen concentration was measured at the base of hepatocyte laden constructs and a tightly controlled experimental and analytical framework was used to reduce the system geometry to a single coordinate and enable the precise identification of initial and boundary conditions. Then dynamic process modeling was used to fit the measured oxygen vs. time profiles to a reaction and diffusion model. We show that oxygen consumption rates are well-described by Michaelis-Menten kinetics. However, the reaction parameters are not literature constants but depend on the cell density. Moreover, the average cellular oxygen consumption rate (or OCR) also varies with density. We discuss why the OCR of cells is often misinterpreted and erroneously reported, particularly in the case of 3D tissues and scaffolds.

Sorbitol/methanol mixed induction reduces process impurities and improves centrifugal dewatering in Pichia pastoris culture

This study investigates how sorbitol/methanol mixed induction affects fermentation performance, dewatering characteristics of cells during harvesting and the profile of host cell proteins (HCP) in the process fluid when producing the target recombinant protein aprotinin. Compared to standard methanol induction, sorbitol/methanol (1:1, C-mol/C-mol) mixed induction improved cellular viability from 92.8 ± 0.3% to 97.7 ± 0.1% although resulted in a reduced product yield from 1.65 ± 0.03 g L−1 to 1.12 ± 0.07 g L−1. On the other hand, average oxygen consumption rate (OUR) dropped from 241.4 ± 21.3 mmol L−1 h−1 to 145.5 ± 6.7 mmol L−1 h−1. Cell diameter decreased over time in the mixed induction, resulting in a D50 value of 3.14 μm at harvest compared to 3.85 μm with methanol. The reduction in cell size enhanced the maximum dewatering efficiency from 78.1 ± 3.9% to 84.5 ± 3.3% as evaluated by using an established ultra scale-down methodology that models pilot and industrial scale disc stack centrifugation. Seventy host cell proteins (HCPs) were identified in clarified supernatant when using sorbitol/methanol mixed induction regimen. The total number of HCPs identified with standard methanol induction was nearly one hundred. The downstream process advantage of the mixed induction lies in improved product purity by reducing both cell mortality and level of released whole cell proteins. This needs to be balanced and optimised against the observed reduction in product yield during fermentation.

Experimental study on the characteristics of oxidation kinetics and heat transfer for coal-field fires under axial compression

Coal-field fire results in much loss of resource and severe harm for human beings. In order to investigate the oxidation and heat transfer characteristics of coal-field fire under axial compression, the coal samples were heated and loaded by stress within axial compression equipped with a temperature-programmed device. Considering the heat generating rates over temperature in temperature-programmed (TP) device, both the critical temperatures Tc and Tg were obtained to divide the process of TP under axial compression into three stages. (Here, Tc is the critical temperature, it indicates that the coal begins to undergo an intense oxidation reaction. Tg represents the burnout temperature, as the temperature reaches Tg, the oxygen supplied to the furnace is almost exhausted and then fuel molecule of coal reacts with oxygen slowly again.) Stage I (less than Tc) represents the process as the temperature of coal increases slowly, Stage II (Tc ~ Tg) the temperature of coal rises rapidly, and Stage III (more than Tg) the temperature of coal combusts steadily. In Stage I, the smaller the apparent activation energy of coal, the lower the critical temperature Tc. The apparent activation energy of coal is the smallest as the axial compression reaches the critical axial compression (4 MPa), and the thermal conductivity of coal decreases with the increasing temperature. In Stage II, the smaller the apparent activation energy of coal, the lower the Tg, and the thermal conductivity of coal goes up and down as 2, 4, 6 and 8 MPa were loaded in turn. Generally, the results show that the average oxygen consumption rate of coal increases as the porosity increases, while the average porosity of coal increases linearly with the decreasing axial compression. Furthermore, the thermal conductivity changes as a cubic function with the increasing axial compression. The results would be meaningful to explain the spread of coal-field fires and provide guidance for the on-site prevention and control for coal-field fires.

Disruption of por1 gene in Candida utilis improves co-production of S-adenosylmethionine and glutathione

The por1 gene encoding one of the mitochondrial porin channels in C. utilis CCTCC M 209298 was disrupted using a homologous recombination method. The co-production of S-adenosylmethionine (SAM) and glutathione (GSH) in the mutant C. utilis Δpor1 increased by 34.9% and 25.1%, respectively, during batch and fed-batch fermentation, relative to the parental strain. The average oxygen consumption rate, activities of key enzymes involved in SAM and GSH biosynthesis, levels of intracellular cofactors such as NADH and ATP, and carbon fluxes of key metabolites were compared between the parental strain and the Δpor1 mutant. The disruption of por1 gene increased the rate of mitochondrial respiration, increased the activities of both methionine adenosyltransferase and γ-glutamylcysteine synthetase, and enhanced the supply of energy and substrates for SAM and GSH biosynthesis, all of which favored the overproduction of SAM and GSH in the Δpor1 mutant.

PO-136 Cycling Incremental test using Breath-by-breath Metabolic Cart to Predict VO2 max

Objective Maximal oxygen uptake (VO2 max) is a key indicator to assess health as well as sports performance. In heterogeneous, athletic populations, VO2 max is one of the most frequently measured variables in exercise physiology laboratories. The purpose of this study was to investigate the relationship between Maximal oxygen uptake with other metabolism parameters during one high-intensity activity, and provide simple solution for VO2 max prediction.
 Methods A total of 27 young athletes were selected. The incremental test was performed on a cycle ergometer (Monark 874 E, Sweden). Participants warmed up for 5 min at 50 watts (W); thereafter, the power output was increased 125 W every 3 min until exhaustion, which was defined as the incapacity to maintain a pedal cadence above 60 revolution per minute (rpm). Oxygen uptake (V̇O2), carbon dioxide production (V̇CO2) and other metabolism indexes were obtained breath-by-breath throughout the test using a metabolic cart (Quark b2, COSMED, Italy). Heart rate (HR) was measured throughout the test using a HR monitor (Polar Vantage NV, Finland). The main method in the VO2 prediction is the use of a mixed effects regression model. The potential explanatory variables include VO2kg (functional data with information on oxygen consumption per kg weight during the test), HR (functional data with heart rate information during the test), MHR (maximum heart rate of the athlete), VO2kgmean (average oxygen consumption during the test), VO2kgmax (maximum oxygen consumption value during the test), VCO2 (carbon dioxide emissions per minute during the test), HRmean (heart rate average), HRmax (maximum heart rate value during the test), age, height, weight. The model statistical analyses were implemented in R platform (version 3.3.3).
 Results (1) regression model results revealed MHR did not have stronger effects on VO2 max prediction. (2) Parameters of VO2kg, HR, HRmean, height, weight showed relative higher r2 values and lower RMSE values indicating the possible indexes for VO2 max prediction. (3) the interaction effects occurred between indicators which increase the complexity of the model.
 Conclusions In this study, a simple methodology for the prediction of maximum oxygen consumption has been presented. It combines a relatively simple level of base metabolism parameters. Despite the easy test and low level of exercise required the test provides an rational prediction of VO2 max, which could provide necessary information when it applied as a simple way.

Effects of multiwalled carbon nanotubes and carbofuran on metabolism in Astyanax ribeirae, a native species.

The study of the toxic effect of carbofuran and multiwalled carbon nanotubes (MWCNTs) on Astyanax ribeirae metabolism is of paramount importance due to the increasing use of this pesticide in agriculture and in the production of nanotubes within the material industry. This study aimed to evaluate the effects of carbofuran, MWCNT, and the combination of these compounds on specific oxygen consumption and excretion of ammonia in A. ribeirae. Therefore, 65 fish were divided into three groups of treatments at varying concentrations: carbofuran (0.01, 0.05, 0.1, and 0.5mg/L), MWCNT (0.1, 0.25, 0.5, and 1.0mg/L), and 0.5mg/L of MWCNT added to carbofuran concentrations (0.01, 0.05, 0.1, and 0.5mg/L). The average specific oxygen consumption in the groups exposed to carbofuran, compared to the control, increased 73.49% at the 0.01mg/L concentration and decreased 63.86% and 91.57% with treatments of 0.1 and 0.5mg/L, respectively. For groups exposed to the MWCNT, there was an 83.91% drop with the 1.0mg/L treatment, and the carbofuran + MWCNT groups recorded a decrease of 71.09%, 92.77%, and 93.98% at concentrations of 0.05, 0.1, and 0.5mg/L, respectively. In relation to specific ammonia excretion, in groups exposed to carbofuran compared to the control, there was an increase of 134.37% and 200% with the 0.1 and 0.5mg/L treatments, respectively. The group exposed to carbofuran + MWCNT experienced a decrease of 60% and 80% with treatments of 0.1mg/L carbofuran + 0.5mg/L MWCNT and 0.5mg/L carbofuran + 0.5mg/L MWCNT, respectively. Therefore, it was concluded that carbofuran + MWCNT interact, increasing the effects in Astyanax sp.

The Effect of Match Schedule on Accelerometry-Derived Exercise Dose during Training Sessions throughout a Competitive Basketball Season.

Accelerometry-derived exercise dose (intensity × duration) was assessed throughout a competitive basketball season. Nine elite basketballers wore accelerometers during a Yo-Yo intermittent recovery test (Yo-Yo-IR1) and during three two-week blocks of training that represented phases of the season defined as easy, medium, and hard based on difficulty of match schedule. Exercise dose was determined using accumulated impulse (accelerometry-derived average net force × duration). Relative exercise intensity was quantified using linear relationships between average net force and oxygen consumption during the Yo-Yo-IR1. Time spent in different intensity zones was computed. Influences of match schedule difficulty and playing position were evaluated. Exercise dose reduced for recovery and pre-match tapering sessions during the medium match schedule. Exercise dose did not vary during the hard match schedule. Exercise dose was not different between playing positions. The majority of activity during training was spent performing sedentary behaviour or very light intensity activity (64.3 ± 6.1%). Front-court players performed a greater proportion of very light intensity activity (mean difference: 6.8 ± 2.8%), whereas back-court players performed more supramaximal intensity activity (mean difference: 4.5 ± 1.0%). No positional differences existed in the proportion of time in all other intensity zones. Objective evaluation of exercise dose might allow coaches to better prescribe and monitor the demands of basketball training.

Is ventilatory therapy combined with exercise training effective in patients with heart failure and sleep-disordered breathing? Results of a randomized trial during a cardiac rehabilitation programme (SATELIT-HF)

Sleep-related disordered breathing is common in patients with chronic heart failure. To assess the efficacy of short-term nocturnal ventilatory therapy combined with exercise training (V+ET) compared with exercise training alone (ET) in patients with chronic heart failure with sleep-disordered breathing. Patients in New York Heart Association functional class II-IIIb, with an apnoea-hypopnoea index (AHI)>15/h, and enrolled in a cardiac rehabilitation programme, were centrally randomized to V+ET or ET. Subjects were classified as having obstructive sleep apnoea (OSA) (n=49) or central sleep apnoea (CSA)/mixed (n=69). The primary outcome was the change in the 10-second average oxygen consumption at maximum exercise (VO2peak) at the end of the cardiac rehabilitation programme. Fifty-eight patients were randomized to V+ET and 60 patients to ET. The median increase in VO2peak was 15% [interquartile range 6-36%] in the V+ET group and 16% [0-31%] in the ET group (P=0.34). AHI decreased in both groups, but significantly more in the V+ET group (P=0.006). The decrease in the ventilatory efficiency (VE/VCO2) slope was not statistically different between the two-randomization groups (P=0.10). In subjects with CSA, the VE/VCO2 slope decreased significantly more in the V+ET group (P=0.03), while there was no difference between the two-randomization groups in subjects with OSA (P=0.75). Six cardiovascular events occurred in patients with OSA (all randomized to the ET group); in subjects with CSA, two events occurred in the V+ET group and three in the ET group. Short-term nocturnal ventilation combined with exercise training does not increase the exercise capacity of patients with chronic heart failure.

Evolution of Sangiovese Wines With Varied Tannin and Anthocyanin Ratios During Oxidative Aging.

Changes in phenolic compounds, chromatic characteristics, acetaldehyde, and protein-reactive tannins associated with oxidative aging were studied in Sangiovese wines with varied tannin T/anthocyanin A ratios. For this purpose, three Sangiovese vineyards located in Tuscany were considered in the 2016 vintage. To obtain wines with different T/A ratios, two red wines were produced from each vinification batch: a free run juice with a lower T/A ratio and a marc pressed wine with a higher T/A ratio. An overall of six wines with T/A ratios ranging between 5 and 23 were produced. An oxidation treatment (four saturation cycles) was applied to each wine. Average and initial oxygen consumption rates (OCR) were positively correlated to VRF/mA (vanilline reactive flavans/monomeric anthocyanins) and T/A ratios while OCRs were negatively related to the wine content in monomeric and total anthocyanins. The higher the A content was, the greater the loss of total and free anthocyanins. A significant lower production of polymeric pigments was detected in all pressed wines with respect to the correspondant free run one. A gradual decrease of tannin reactivity toward saliva proteins after the application of oxygen saturation cycles was detected. The results obtained in this experiment indicate that VRF/mA and T/A ratios are among the fundamental parameters to evaluate before choosing the antioxidant protection to be used and the right oxidation level to apply for a longer shelf-life of red wine.

Acute intensity and motivation to play: comparison of structured and unstructured active video games - a pilot study

Objective: To compare intensity (heart rate, oxygen consumption, and perceived exertion) and motivation to play between AVG types (unstructured, UNS-AVG and structured, S-AVG). Methods: A Pre-test-Post-test experimental study with randomized counterbalanced groups (UNS- and S-AVG type) was performed at the laboratory. Eight male young adults [Mean (SD), age: 19(1) years, body mass index: 23.1(2.4) kg/m²] volunteered to participate in this study. Participants underwent a diagnostic evaluation for health status, anthropometric, cardiovascular and metabolic measures. After this, they were paired according to oxygen consumption levels and randomly assigned to each group and performed a 30-min AVG session (UNS-AVG: Kinect Sports Boxing game or S-AVG: Nike Kinect Training game). Heart rate (HR) was recorded during all AVG session. At the end of the session, motivation to play and rating of perceived exertion (RPE) were self-reported. Oxygen consumption estimated for the AVG session was obtained by linear regression line from HR reached during the game and maximal HR during the test session. Unpaired t-test was used to compare game type groups (P<0.05). Moreover, effect size (ES) was calculated using Cohen’s d statistic. Results: Average HR (%Δ=7.1, P=0.025, ES=0.76) and oxygen consumption estimated (%Δ=69.5, P=0.002, ES=3.63) during the sessions were greater for S-AVG compared to UNS-AVG. Motivation to play was similar between groups (%Δ=18.2, P=0.685, ES=0.72). RPE was greater for S-AVG compared to UNS-AVG group (%Δ=20.6, P=0.045, ES=1.85). Conclusion: S-AVG type requires more physical exertion than UNS-AVG; however, these AVG types can be used interchangeably if the goal is motivation. Due to the strong correlation between the HR and oxygen consumption for both AVG types, this data suggests that S-AVG may be a better tool to exercise and probably contribute to reducing sedentary lifestyle more than UNS-AVG in young adults.

Oxygen Consumption (V\u2019O2) and physical Strainas measured by the occupational activity of cleaning personnel

BackgroundThe aim of the study was to determine the physical effort and energy expenditure needed over a working period of 45–60 min, specifically for the occupational activity of cleaning. The effort was demonstrated in absolute terms (V’O2), in relation to the involved person’s maximum physical capacity (peak V’O2) and in relation to the individual aerobic-anaerobic threshold (V’O2 at VT1, the point when lactate starts to accumulate but can be cleared). In addition to this, the aim was to verify the suitability of portable ergospirometry in determining the occupational workload in a real-life setting.MethodsThirty-five cleaners performed a bicycle ergospirometry to determine their maximum physical capacity (peak V’O2 = L/min) and their aerobic-anaerobic threshold (V’O2 at the Ventilatory Threshold 1 [VT1]). This was followed by portable ergospirometry lasting 45–60 min while pursuing regular cleaning activities.ResultsPerformance V’O2 (the average oxygen consumption over 45–60 min of work- time) was 1.06 L/min or 4.4 METs. This was scarcely lower than the individual V’O2 at VT1 and approached 45% of the maximum physical capacity (peak V’O2). In addition, there was positive feedback regarding the wearability of the portable device. The dropout rate was low.ConclusionThe occupational activity of cleaning was defined as a “committed activity”, performed close to the upper limit of the continuous physical capacity (approaching V’O2 at VT1). The positive feedback and a low dropout rate proved good acceptance of portable ergospirometry in this field of work over a 45–60 min period.

Oxygen transfer dynamics and nitrification in a novel rotational sponge reactor

The nitrification process demands higher oxygen supply, which is fulfilled through external aeration in wastewater treatment. To perform nitrification without external aeration, this study developed a novel rotating sponge (RS) reactor and estimated its oxygen transfer capability. The reactor obtained an oxygen transfer coefficient (KLa) value of over 100d−1 at 40 rounds per hour (rph), which is one-eighth of the rotational speed of conventional rotational biological contactors. Within 53days of operation, reactor achieved 97% nitrification efficiency with an effluent NH4+-N concentration of 1mgL−1. On the other hand, the volumetric oxygen transfer rate in the reactor was 245mg-O2L−1d−1 at 10rph during the experimental period. However, the average volumetric oxygen consumption rate during nitrification was 187mg-O2L−1d−1, which was below the oxygen transfer rate. Microbial community analysis revealed high relative abundance of bacteria such as Nitrosomonas, Nitrospira, and Nitrobacter in the RS reactor, which contributed to nitrification.

Effect of exoskeletal joint constraint and passive resistance on metabolic energy expenditure: Implications for walking in paraplegia.

An important consideration in the design of a practical system to restore walking in individuals with spinal cord injury is to minimize metabolic energy demand on the user. In this study, the effects of exoskeletal constraints on metabolic energy expenditure were evaluated in able-bodied volunteers to gain insight into the demands of walking with a hybrid neuroprosthesis after paralysis. The exoskeleton had a hydraulic mechanism to reciprocally couple hip flexion and extension, unlocked hydraulic stance controlled knee mechanisms, and ankles fixed at neutral by ankle-foot orthoses. These mechanisms added passive resistance to the hip (15 Nm) and knee (6 Nm) joints while the exoskeleton constrained joint motion to the sagittal plane. The average oxygen consumption when walking with the exoskeleton was 22.5 ± 3.4 ml O2/min/kg as compared to 11.7 ± 2.0 ml O2/min/kg when walking without the exoskeleton at a comparable speed. The heart rate and physiological cost index with the exoskeleton were at least 30% and 4.3 times higher, respectively, than walking without it. The maximum average speed achieved with the exoskeleton was 1.2 ± 0.2 m/s, at a cadence of 104 ± 11 steps/min, and step length of 70 ± 7 cm. Average peak hip joint angles (25 ± 7°) were within normal range, while average peak knee joint angles (40 ± 8°) were less than normal. Both hip and knee angular velocities were reduced with the exoskeleton as compared to normal. While the walking speed achieved with the exoskeleton could be sufficient for community ambulation, metabolic energy expenditure was significantly increased and unsustainable for such activities. This suggests that passive resistance, constraining leg motion to the sagittal plane, reciprocally coupling the hip joints, and weight of exoskeleton place considerable limitations on the utility of the device and need to be minimized in future designs of practical hybrid neuroprostheses for walking after paraplegia.

Catalytic effect of in-situ preparation of copper oxide nanoparticles on the heavy oil low-temperature oxidation process in air injection recovery

ABSTRACTIn situ prepared hydrophobic CuO nanoparticles, about 84.3 nm in mean diameter, was synthesized and used to catalyze heavy oil low-temperature oxidation (LTO) reaction. Experimental results showed the average oxygen consumption rate with CuO nanoparticles addition increased by 1.4 times, and the residue oxygen content in tail gas in autoclave was decreased from 8.76% to 3.9% compared to the blank experiment (without CuO nanoparticles). In addition, the CuO nanoparticles could facilitate the cleavage reaction during LTO. This study can provide guidelines to improve effectively the safety of air flooding technology in the heavy oil.

Crouch severity is a poor predictor of elevated oxygen consumption in cerebral palsy

Children with cerebral palsy (CP) expend more energy to walk compared to typically-developing peers. One of the most prevalent gait patterns among children with CP, crouch gait, is often singled out as especially exhausting. The dynamics of crouch gait increase external flexion moments and the demand on extensor muscles. This elevated demand is thought to dramatically increase energy expenditure. However, the impact of crouch severity on energy expenditure has not been investigated among children with CP. We evaluated oxygen consumption and gait kinematics for 573 children with bilateral CP. The average net nondimensional oxygen consumption during gait of the children with CP (0.18±0.06) was 2.9 times that of speed-matched typically-developing peers. Crouch severity was only modestly related to oxygen consumption, with measures of knee flexion angle during gait explaining only 5–20% of the variability in oxygen consumption. While knee moment and muscle activity were moderately to strongly correlated with crouch severity (r2=0.13–0.73), these variables were only weakly correlated with oxygen consumption (r2=0.02–0.04). Thus, although the dynamics of crouch gait increased muscle demand, these effects did not directly result in elevated energy expenditure. In clinical gait analysis, assumptions about an individual’s energy expenditure should not be based upon kinematics or kinetics alone. Identifying patient-specific factors that contribute to increased energy expenditure may provide new pathways to improve gait for children with CP.

Ex Situ Perfusion of Human Limb Allografts for 24 Hours.

Vascularized composite allografts, particularly hand and forearm, have limited ischemic tolerance after procurement. In bilateral hand transplantations, this demands a 2 team approach and expedited transfer of the allograft, limiting the recovery to a small geographic area. Ex situ perfusion may be an alternative allograft preservation method to extend allograft survival time. This is a short report of 5 human limbs maintained for 24 hours with ex situ perfusion. Upper limbs were procured from brain-dead organ donors. Following recovery, the brachial artery was cannulated and flushed with 10 000 U of heparin. The limb was then attached to a custom-made, near-normothermic (30-33°C) ex situ perfusion system composed of a pump, reservoir, and oxygenator. Perfusate was plasma-based with a hemoglobin concentration of 4 to 6 g/dL. Average warm ischemia time was 76 minutes. Perfusion was maintained at an average systolic pressure of 93 ± 2 mm Hg, flow 310 ± 20 mL/min, and vascular resistance 153 ± 16 mm Hg/L per minute. Average oxygen consumption was 1.1 ± 0.2 mL/kg per minute. Neuromuscular electrical stimulation continually displayed contraction until the end of perfusion, and histology showed no myocyte injury. Human limb allografts appeared viable after 24 hours of near-normothermic ex situ perfusion. Although these results are early and need validation with transplantation, this technology has promise for extending allograft storage times.

Relationship between aerobic capacity and pelvic floor muscles function: a cross-sectional study.

The objective of this study was to evaluate the relationship between aerobic capacity and pelvic floor muscles (PFM) function in adult women. Women aged 18 or over and without urinary dysfunction or other chronic diseases were eligible to participate. They completed the habitual physical activity (HPA) questionnaire, underwent a PFM functional evaluation by palpation and perineometry, and performed a submaximal (between 75 and 85% of maximum heart rate) cardiopulmonary exercise (CPX) test to determine the ventilatory anaerobic threshold (VAT). Forty-one women were included (35±16 years, 75% physically active, 17% very active, and 8% sedentary and 17% presented grade 1 PFM contraction, 31.8% grade 2, 26.8% grade 3, and 24.4% grade 4, according to the modified Oxford Scale). The average PFM contraction pressure obtained by perineometer was 53±26 cmH2O and the average oxygen consumption at VAT (VO2VAT) obtained from CPX was 14±2 mL·kg-1·min-1. Significant correlations were found between PFM contraction pressure and VO2VAT (r=0.55; P<0.001); between PFM contraction pressure and HPA score (r=0.38; P=0.02); between age and VO2VAT (r=-0.25; P=0.049); and between VO2VAT and HPA score (r=0.36; P=0.02). An age-adjusted multiple linear regression equation (R2=0.32) was derived to estimate VO2VAT from the contraction value obtained by perineometer, so that the PFM contraction pressure was able to predict VO2VAT. The equation was validated using data from another group of 20 healthy women (33±12 years; PFM contraction: 49±23 cmH2O) and no significant difference was found between actual VO2VAT and predicted VO2VAT (13.1±1.9 vs 13.8±2.0 mL·kg-1·min-1). In conclusion, PFM function is associated with aerobic capacity in healthy women and PFM contraction pressure may be used to estimate VO2VAT in this population.

A bioenergetics assay for studying the effects of environmental stressors on mitochondrial function in vivo in zebrafish larvae

Mitochondria, an integral component of cellular energy metabolism and other key functions, are extremely vulnerable to damage by environmental stressors. Although methods to measure mitochondrial function in vitro exist, sensitive, medium- to high-throughput assays that assess respiration within physiologically-relevant whole organisms are needed to identify drugs and/or chemicals that disrupt mitochondrial function, particularly at sensitive early developmental stages. Consequently, we have developed and optimized an assay to measure mitochondrial bioenergetics in zebrafish larvae using the XFe24 Extracellular Flux Analyzer. To prevent larval movement from confounding oxygen consumption measurements, we relied on MS-222-based anesthetization. We obtained stable measurement values in the absence of effects on average oxygen consumption rate and subsequently optimized the use of pharmacological agents for metabolic partitioning. To confirm assay reproducibility we demonstrated that triclosan, a positive control, significantly decreased spare respiratory capacity. We then exposed zebrafish from 5 hours post-fertilization (hpf) to 6days post-fertilization (dpf) to three polycyclic aromatic hydrocarbons (PAHs) – benzo(a)pyrene (BaP), phenanthrene (Phe), and fluoranthene (FL) – and measured various fundamental parameters of mitochondrial respiratory chain function, including maximal respiration, spare respiratory capacity, mitochondrial and non-mitochondrial respiration. Exposure to all three PAHs decreased spare respiratory capacity and maximal respiration. Additionally, Phe exposure increased non-mitochondrial respiration and FL exposure decreased mitochondrial respiration and increased non-mitochondrial respiration. Overall, this whole organism-based assay provides a platform for examining mitochondrial dysfunction in vivo at critical developmental stages. It has important implications in biomedical sciences, toxicology and ecophysiology, particularly to examine the effects of environmental chemicals and/or drugs on mitochondrial bioenergetics.

Poor embryo development in post-ovulatoryin vivo-aged mouse oocytes is associated with mitochondrial dysfunction, but mitochondrial transfer from somatic cells is not sufficient for rejuvenation

Does in vivo aging of mouse oocytes affect mitochondrial function? Mitochondrial function was impaired in post-ovulatory in vivo-aged mouse oocytes and microinjection of somatic cell mitochondria did not rescue poor fertilization and embryonic development rates. The mechanisms underlying the decline in oocyte quality associated with oocyte aging remain unknown, although studies have suggested that the decline is regulated by mitochondrial dysfunction. However, only a limited number of studies have provided direct evidence implicating mitochondrial dysfunction in oocyte quality during the aging of oocytes. We used post-ovulatory, in vivo-aged mouse oocytes as a model for studying low-quality oocytes in oocyte aging. Superovulated oocytes released from the oviduct at 14 h and 20-24 h post-hCG injection were designated as 'fresh' and 'aged' oocytes, respectively. Membrane potentials and oxygen consumption in single oocytes were evaluated as measures of mitochondrial function in fresh and aged oocytes. Mitochondrial transcriptional factor A (TFAM) expression levels were examined by western blotting, and colocalization of mitochondria and TFAM was analyzed by measuring immunofluorescence in fresh and aged oocytes. IVF and blastocyst formation rates were calculated after oocyte microinjection with mitochondria derived from liver cells. The average mitochondrial membrane potential in fresh oocytes was significantly higher than that in aged oocytes (P<0.05). The average oxygen consumption rate in aged oocytes was significantly lower than that in fresh oocytes (P<0.05). Although total TFAM expression was unchanged, its colocalization with mitochondria decreased in aged oocytes. IVF and blastocyst formation rates for mitochondrion-injected aged oocytes were not significantly different from those for buffer-injected aged oocytes. Not applicable. A limitation of this study is that we did not examine the effects of microinjecting mitochondria from other somatic cell types into aged oocytes on their fertilization and embryonic development rates. The results from the present study showed that poor embryonic development was associated with impairment of mitochondrial functions in in vivo-aged oocytes. However, the microinjection of mitochondria from liver cells did not improve the low fertilization and embryonic development rates of aged oocytes. It remains to be demonstrated whether oocyte quality can be rescued by the transfer of cytosolic factors or cellular organelles, such as the endoplasmic reticulum or mitochondria, from specific cell types. This study was supported by Grants-in-Aid for General Science Research to Toshifumi Takahashi (No. 25462550) and Hideki Igarashi (No. 26462474). The funding source played no role in study design in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. The authors have no conflict of interest to disclose.

Analysis of the application of the generalized monod kinetics model to describe the human corneal oxygen-consumption rate during soft contact lens wear.

This work is an analysis of the application of the generalized Monod kinetics model describing human corneal oxygen consumption during soft contact lens wear to models previously used by Chhabra et al. (J Biomed Mater Res B Appl Biomater, 2009a;90:202-209, Optom Vis Sci 2009b;86:454-466) and Larrea and Büchler (Invest Ophthalmol Vis Sci 2009;50:1076-1080). We use oxygen tension from in vivo estimations provided by Bonanno [Bonanno et al., Invest Ophthalmol Vis Sci 2002;43:371-376, and Bonanno et al 2009]. We consider four hydrogel and six silicone hydrogel lenses. The cornea is considered a single homogeneous layer, with constant oxygen permeability regardless of the type of lens worn. Our calculations yield different values for the maximum oxygen consumption rate Qc,max , whith differents oxygen tensions (high and low pc ) at the cornea-tears interface. Surprisingly, for both models, we observe an increase in oxygen consumption near an oxygen tension of 105 mmHg until a maximum is reached, then decreasing for higher levels of oxygen pressure. That is, when lowering the pressure of oxygen, the parameter Qc,max initially increases depending on the intensity of the change in pressure. Which, it could be related with the variation of the pH. Furthermore, it is also noted that to greater reductions in pressure, this parameter decreases, possibly due to changes in the concentration of glucose related to the anaerobic respiration. The averaged in vivo human corneal oxygen consumption rate of 1.47 × 10-4 cm3 of O2 /cm3 tissue s, with Monod kinetics model, considering all the lenses studied, is smaller than the average oxygen consumption rate value obtained using the Larrea and Büchler model. The impact that these calculations have on the oxygen partial pressure available at different depths in the corneal tissue is presented and discussed, taking into consideration previous models used in this study. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2269-2281, 2017.