Evaluation of renal tubular function by multiparametric functional MRI in early diabetes

Purpose To evaluate the tubular function in an alloxan-induced type 1 diabetes mellitus (DM) rabbit model measured by renal oxygenation (R2*), oxygen extraction fraction (OEF), and renal blood flow (RBF) using blood oxygenation level dependent, asymmetric spin echo, and arterial spin labeling MRI. Methods Twenty-six rabbits were randomized into the 3-day DM group (n = 13) and the 7-day DM group (n = 13). We performed pairs of multiparametric MRIs (before and after furosemide injection) at baseline and 3/7 days post-DM, and scored pathological kidney injury. We performed statistical analyses using non-parametric, chi-square, and Spearman correlation tests. Results At baseline, medullary R2* significantly decreased by 24.97% and 16.74% in the outer and inner stripes of the outer medulla (OS and IS, p = 0.006 and 0.003, respectively) after furosemide administration. While the corresponding OEF decreased by 15.91% for OS and 16.67% for IS (both p = 0.003), and no significant change in medullary RBF was observed (p > 0.05). In the 3-day DM group, the decrease of medullary R2* and OEF post-furosemide became unremarkable, suggesting tubular dysfunction. We noticed similar changes in the 7-day DM group. Correlation analysis showed pathological tubular injury score significantly correlated with medullary ∆R2* (post-furosemide - pre-furosemide difference, r = 0.82 for OS and 0.82 for IS) and ∆OEF (r = 0.82 for OS and 0.82 for IS) (p < 0.001, respectively). Conclusion: The combination of medullary OEF and R2* in response to furosemide could detect renal tubular dysfunction in early DM.

Developmental energetics in the oviparous corn snake, Pantherophis guttatus, confirms a conservative evolutionary pattern in snakes

Eggs of oviparous reptiles are ideal models for studying evolutionary patterns of embryonic metabolism since they allow tracking of energy allocation during development. Analyzing oxygen consumption of whole eggs throughout development indicates three patterns among reptiles. Embryos initially grow and consume oxygen exponentially, but oxygen consumption slows, or drops before hatching in some species. Turtles, crocodilians, and most lizards follow curves with initial exponential increases followed by declines, whereas embryonic snakes that have been studied exhibit a consistently exponential pattern. This study measured oxygen consumption of corn snake, Pantherophis guttatus, embryos to determine if this species also exhibits an exponential increase in oxygen consumption. Individual eggs, sampled weekly from oviposition to hatching, were placed in respirometry chambers for 24-h during which oxygen consumption was recorded. Embryos were staged and carcasses and yolk were weighed separately. Results indicate steady inclines in oxygen consumption during early stages of development, with a rapid increase prior to hatching. The findings support the hypothesis that embryonic oxygen consumption of snakes differs from most other non-avian reptiles. Total energy required for development was determined based on calorimetry of initial yolk compared to hatchlings and residual yolk and by integration of the area under the curve plotting oxygen consumption versus age of embryos. The cost of development estimates based on these two methods were 6.4 and 10.0 kJ, respectively. Our results emphasize the unique physiological aspects of snake embryogenesis and illustrate how the study of physiological characteristics can contribute to the broader understanding of reptilian evolution.

Hypoxic adaptation of mitochondria and its impact on tumor cell function

Mitochondria are the major sink for oxygen in the cell, consuming it during ATP production. Therefore, when environmental oxygen levels drop in the tumor, significant adaptation is required. Mitochondrial activity is also a major producer of biosynthetic precursors and a regulator of cellular oxidative and reductive balance. Because of the complex biochemistry, mitochondrial adaptation to hypoxia occurs through multiple mechanisms and has significant impact on other cellular processes such as macromolecule synthesis and gene regulation. In tumor hypoxia, mitochondria shift their location in the cell and accelerate the fission and quality control pathways. Hypoxic mitochondria also undergo significant changes to fundamental metabolic pathways of carbon metabolism and electron transport. These metabolic changes further impact the nuclear epigenome because mitochondrial metabolites are used as enzymatic substrates for modifying chromatin. This coordinated response delivers physiological flexibility and increased tumor cell robustness during the environmental stress of low oxygen.

Metabolic load during morning care and active bed exercises in critically ill patients: An explorative study

BACKGROUND

To avoid overexertion in critically ill patients, information on the physical demand, i.e., metabolic load, of daily care and active exercises is warranted.

OBJECTIVE

The objective of this study was toassess the metabolic load during morning care activities and active bed exercises in mechanically ventilated critically ill patients.

METHODS

This study incorporated an explorative observational study executed in a university hospital intensive care unit. Oxygen consumption (VO2) was measured in mechanically ventilated (≥48 h) critically ill patients during rest, routine morning care, and active bed exercises. We aimed to describe and compare VO2 in terms of absolute VO2 (mL) defined as the VO2 attributable to the activity and relative VO2 in mL per kilogram bodyweight, per minute (mL/kg/min). Additional outcomes achieved during the activity were perceived exertion, respiratory variables, and the highest VO2 values. Changes in VO2 and activity duration were tested using paired tests.

RESULTS

Twenty-one patients were included with a mean (standard deviation) age of 59 y (12). Median (interquartile range [IQR]) durations of morning care and active bed exercises were 26 min (21-29) and 7 min (5-12), respectively. Absolute VO2 of morning care was significantly higher than that of active bed exercises (p = 0,009). Median (IQR) relative VO2 was 2.9 (2.6-3.8) mL/kg/min during rest; 3.1 (2.8-3.7) mL/kg/min during morning care; and 3.2 (2.7-4) mL/kg/min during active bed exercises. The highest VO2 value was 4.9 (4.2-5.7) mL/kg/min during morning care and 3.7 (3.2-5.3) mL/kg/min during active bed exercises. Median (IQR) perceived exertion on the 6-20 Borg scale was 12 (10.3-14.5) during morning care (n = 8) and 13.5 (11-15) during active bed exercises (n = 6).

CONCLUSION

Absolute VO2 in mechanically ventilated patients may be higher during morning care than during active bed exercises due to the longer duration of the activity. Intensive care unit clinicians should be aware that daily-care activities may cause intervals of high metabolic load and high ratings of perceived exertion.

The troglitazone derivative EP13 disrupts energy metabolism through respiratory chain complex I inhibition in breast cancer cells and potentiates the antiproliferative effect of glycolysis inhibitntriors

BACKGROUND

The metabolism of cancer cells generally differs from that of normal cells. Indeed, most cancer cells have a high rate of glycolysis, even at normal oxygen concentrations. These metabolic properties can potentially be exploited for therapeutic intervention. In this context, we have developed troglitazone derivatives to treat hormone-sensitive and triple-negative breast cancers, which currently lack therapeutic targets, have an aggressive phenotype, and often have a worse prognosis than other subtypes. Here, we studied the metabolic impact of the EP13 compound, a desulfured derivative of Δ2-troglitazone that we synthetized and is more potent than its parent compounds.

METHODS

EP13 was tested on two triple-negative breast cancer cell lines, MDA-MB-231 and Hs578T, and on the luminal cell line MCF-7. The oxygen consumption rate (OCR) of the treated cell lines, Hs578T mammospheres and isolated mitochondria was measured using the XFe24 Seahorse analyser. ROS production was quantified using the MitoSOX fluorescent probe. Glycolytic activity was evaluated through measurement of the extracellular acidification rate (ECAR), glucose consumption and lactate production in extracellular medium. The synergistic effect of EP13 with glycolysis inhibitors (oxamate and 2-deoxyglucose) on cell cytotoxicity was established using the Chou-Talalay method.

RESULTS

After exposure to EP13, we observed a decrease in the mitochondrial oxygen consumption rate in MCF7, MDA-MB-231 and Hs578T cells. EP13 also modified the maximal OCR of Hs578T spheroids. EP13 reduced the OCR through inhibition of respiratory chain complex I. After 24 h, ATP levels in EP13-treated cells were not altered compared with those in untreated cells, suggesting compensation by glycolysis activity, as shown by the increase in ECAR, the glucose consumption and lactate production. Finally, we performed co-treatments with EP13 and glycolysis inhibitors (oxamate and 2-DG) and observed that EP13 potentiated their cytotoxic effects.

CONCLUSION

This study demonstrates that EP13 inhibits OXPHOS in breast cancer cells and potentiates the effect of glycolysis inhibitors.

High carbohydrate is preferable to high lipid parenteral nutrition in healthy dogs undergoing prolonged sedation

Parenteral nutrition (PN) is commonly used in intensive care units (ICUs) and is associated with earlier hospital outcome. However, there is scarcity of information about the metabolic effects of PN caloric distribution for dogs. Considering the high tolerance of dogs to lipids and, also, that hospitalized animals usually present insulin resistance, PN formulation with high fat instead high glucose can provide metabolic benefits in this specie. This study evaluated two PN protocols, based on high lipid or high carbohydrate in 12 healthy dogs under sedation/ventilation during 24 h. For baseline data, blood samples were collected 24 h before the study beginning. After fasting, the dogs were anesthetized and put under mechanical ventilation without energy support for 12 h to obtain: daily energy expenditure (DEE), respiratory quotient (RQ), oxygen consumption (VO2), carbon dioxide production (VCO2), lactate, glucose, cholesterol, and triglycerides concentrations. After, the dogs were allocated into two groups: lipid-based energy group (LEG) and carbohydrate-based energy group (CEG). Both groups received the PN infusions at a rate of 3 mL/kg/h for 12 h. Blood tests were performed 12, 24, and 48 h after infusion's completion. VO2 increased after PN in LEG, increasing energy expenditure compared to CEG. RQ remained close to 1 in CEG, indicating carbohydrate preferential consumption. Triglycerides increased in both groups after propofol infusion, remaining higher in LEG until the end of the evaluation. Glycaemia increased in CEG compared to baseline. In conclusion, both PN protocols can be used in healthy animals undergoing prolonged sedation protocols. However, high lipid PN had higher VO2 and DEE, and resulted in higher triglycerides concentrations and lower glycaemia indexes than carbohydrate, making high carbohydrate PN preferable to high lipid PN. Therefore, for use in critically ill patients, the data obtained in this study should be extrapolated, taking into consideration the specificity of each case.

Low respiratory quotient correlates with high mortality in patients undergoing mechanical ventilation

OBJECTIVE

Oxygen consumption (VO2), carbon dioxide generation (VCO2), and respiratory quotient (RQ), which is the ratio of VO2 to VCO2, are critical indicators of human metabolism. To seek a link between the patient's metabolism and pathophysiology of critical illness, we investigated the correlation of these values with mortality in critical care patients.

METHODS

This was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Age 18 years or older healthy volunteers and patients who underwent mechanical ventilation were enrolled. A high-fidelity automation device, which accuracy is equivalent to the gold standard Douglas Bag technique, was used to measure VO2, VCO2, and RQ at a wide range of fraction of inspired oxygen (FIO2).

RESULTS

We included a total of 21 subjects including 8 post-cardiothoracic surgery patients, 7 intensive care patients, 3 patients from the emergency room, and 3 healthy volunteers. This study included 10 critical care patients, whose metabolic measurements were performed in the ER and ICU, and 6 died. VO2, VCO2, and RQ of survivors were 282 +/- 95 mL/min, 202 +/- 81 mL/min, and 0.70 +/- 0.10, and those of non-survivors were 240 +/- 87 mL/min, 140 +/- 66 mL/min, and 0.57 +/- 0.08 (p = 0.34, p = 0.10, and p < 0.01), respectively. The difference of RQ was statistically significant (p < 0.01) and it remained significant when the subjects with FIO2 < 0.5 were excluded (p < 0.05).

CONCLUSIONS

Low RQ correlated with high mortality, which may potentially indicate a decompensation of the oxygen metabolism in critically ill patients.

A practical and robust method to evaluate metabolic fluxes in primary pancreatic islets

OBJECTIVE

Evaluation of mitochondrial oxygen consumption and ATP production is important to investigate pancreatic islet pathophysiology. Most studies use cell lines due to difficulties in measuring primary islet respiration, which requires specific equipment and consumables, is expensive and poorly reproducible. Our aim was to establish a practical method to assess primary islet metabolic fluxes using standard commercial consumables.

METHODS

Pancreatic islets were isolated from mice/rats, dispersed with trypsin, and adhered to pre-coated standard Seahorse or Resipher microplates. Oxygen consumption was evaluated using a Seahorse Extracellular Flux Analyzer or a Resipher Real-time Cell Analyzer.

RESULTS

We provide a detailed protocol with all steps to optimize islet isolation with high yield and functionality. Our method requires a few islets per replicate; both rat and mouse islets present robust basal respiration and proper response to mitochondrial modulators and glucose. The technique was validated by other functional assays, which show these cells present conserved calcium influx and insulin secretion in response to glucose. We also show that our dispersed islets maintain robust basal respiration levels, in addition to maintaining up to 89% viability after five days in dispersed cultures. Furthermore, OCRs can be measured in Seahorse analyzers and in other plate respirometry systems, using standard materials.

CONCLUSIONS

Overall, we established a practical and robust method to assess islet metabolic fluxes and oxidative phosphorylation, a valuable tool to uncover basic β-cell metabolic mechanisms as well as for translational investigations, such as pharmacological candidate discovery and islet transplantation protocols.

Exploring the Metabolic Response of Pseudomonas putida to L-arginine

Beyond their role as protein-building units, amino acids are modulators of multiple behaviours in different microorganisms. In the root-colonizing beneficial bacterium Pseudomonas putida (recently proposed to be reclassified as alloputida) KT2440, current evidence suggests that arginine functions both as a metabolic indicator and as an environmental signal molecule, modulating processes such as chemotactic responses, siderophore-mediated iron uptake or the levels of the intracellular second messenger cyclic diguanylate (c-di-GMP). Using microcalorimetry and extracellular flux analysis, in this work we have studied the metabolic adaptation of P. putida KT2440 to the presence of L-arginine in the growth medium, and the influence of mutations related to arginine metabolism. Arginine causes rapid changes in the respiratory activity of P. putida, particularly magnified in a mutant lacking the transcriptional regulator ArgR. The metabolic activity of mutants affected in arginine transport and metabolism is also altered during biofilm formation in the presence of the amino acid. The results obtained here further support the role of arginine as a metabolic signal in P. putida and the relevance of ArgR in the adaptation to the amino acid. They also serve as proof of concept on the use of calorimetric and extracellular flux techniques to analyse metabolic responses in bacteria and the impact of different mutant backgrounds on such responses.

Postprandial energy metabolism is modulated in response to a low-intensity walking exercise in fasted healthy individuals

Postprandial metabolism is a relevant indicator of overall metabolic health, which can be influenced by a single bout of exercise before food consumption. The present study examined the effects of an acute, fasted, low-intensity exercise on postprandial metabolism and appetite sensations. We hypothesized that exercise would induce an increase in postprandial fat oxidation, associated with better satiety responses. Twenty-two healthy adults (16 females) attended the laboratory twice separated by a minimum of 3 days to perform 2 conditions: (1) a control condition and (2) an exercise condition (EX) with a 30-minute low-intensity walking exercise performed before the breakfast (500-kcal fixed meal). Subjective appetite sensations were assessed before and up to 60 minutes after the meal in regular intervals. Energy expenditure and substrate oxidation were measured until 2 hours after the meal. Energy expenditure and carbohydrate oxidation were higher in the EX condition (condition effect: P < .01). There was no effect of exercise on appetite sensations and overall fat oxidation, but a higher increase in relative and absolute fat oxidation was observed from 15- to 45-minutes postmeal in EX compared with control (time × condition interaction effect: P < .05). In the EX condition only, postprandial satiety was associated positively with postprandial fat oxidation and negatively with carbohydrate oxidation. To conclude, a fasted low-intensity exercise induced an enhancement of postprandial metabolic flexibility through the modulation of fat oxidation. Substrate oxidation appeared to be related to satiety only after exercise, suggesting a specific regulation of appetite induced by exercise.

The striking differences in the bioenergetics of brain and liver mitochondria are enhanced in mitochondrial disease

Mitochondrial disorders are hallmarked by the dysfunction of oxidative phosphorylation (OXPHOS) yet are highly heterogeneous at the clinical and genetic levels. Striking tissue-specific pathological manifestations are a poorly understood feature of these conditions, even if the disease-causing genes are ubiquitously expressed. To investigate the functional basis of this phenomenon, we analyzed several OXPHOS-related bioenergetic parameters, including oxygen consumption rates, electron transfer system (ETS)-related coenzyme Q (mtCoQ) redox state and production of reactive oxygen species (ROS) in mouse brain and liver mitochondria fueled by different substrates. In addition, we determined how these functional parameters are affected by ETS impairment in a tissue-specific manner using pathologically relevant mouse models lacking either Ndufs4 or Ttc19, leading to Complex I (CI) or Complex III (CIII) deficiency, respectively. Detailed OXPHOS analysis revealed striking differences between brain and liver mitochondria in the capacity of the different metabolic substrates to fuel the ETS, reduce the ETS-related mtCoQ, and to induce ROS production. In addition, ETS deficiency due to either CI or CIII dysfunction had a much greater impact on the intrinsic bioenergetic parameters of brain compared with liver mitochondria. These findings are discussed in terms of the still rather mysterious tissue-specific manifestations of mitochondrial disease.

Paraspinal muscle oxygenation and mechanical efficiency are reduced in individuals with chronic low back pain

This study aimed to compare the systemic and local metabolic responses during a 5-min trunk extension exercise in individuals with chronic low back pain (CLBP) and in healthy individuals. Thirteen active participants with CLBP paired with 13 healthy participants performed a standardised 5-min trunk extension exercise on an isokinetic dynamometer set in continuous passive motion mode. During exercise, we used near-infrared spectroscopy to measure tissue oxygenation (TOI) and total haemoglobin-myoglobin (THb). We used a gas exchange analyser to measure breath-by-breath oxygen consumption (V̇O2) and carbon dioxide produced (V̇CO2). We also calculated mechanical efficiency. We assessed the intensity of low back pain sensation before and after exercise by using a visual analogue scale. In participants with CLBP, low back pain increased following exercise (+ 1.5 units; p < 0.001) and THb decreased during exercise (- 4.0 units; p = 0.043). Paraspinal muscle oxygenation (65.0 and 71.0%, respectively; p = 0.009) and mechanical efficiency (4.7 and 5.3%, respectively; p = 0.034) were both lower in participants with CLBP compared with healthy participants. The increase in pain sensation was related to the decrease in tissue oxygenation (R2 = - 0.420; p = 0.036). Decreases in total haemoglobin-myoglobin and mechanical efficiency could involve fatigability in exercise-soliciting paraspinal muscles and, therefore, exacerbate inabilities in daily life. Given the positive correlation between tissue oxygenation and exercise-induced pain exacerbation, muscle oxygenation may be related to persisting and crippling low back pain.

Alternative blood transfusion triggers: a narrative review

BACKGROUND

Anemia, characterized by low hemoglobin levels, is a global public health concern. Anemia is an independent factor worsening outcomes in various patient groups. Blood transfusion has been the traditional treatment for anemia; its triggers, primarily based on hemoglobin levels; however, hemoglobin level is not always an ideal trigger for blood transfusion. Additionally, blood transfusion worsens clinical outcomes in certain patient groups. This narrative review explores alternative triggers for red blood cell transfusion and their physiological basis.

MAIN TEXT

The review delves into the physiology of oxygen transport and highlights the limitations of using hemoglobin levels alone as transfusion trigger. The main aim of blood transfusion is to optimize oxygen delivery, necessitating an individualized approach based on clinical signs of anemia and the balance between oxygen delivery and consumption, reflected by the oxygen extraction rate. The narrative review covers different alternative triggers. It presents insights into their diagnostic value and clinical applications, emphasizing the need for personalized transfusion strategies.

CONCLUSION

Anemia and blood transfusion are significant factors affecting patient outcomes. While restrictive transfusion strategies are widely recommended, they may not account for the nuances of specific patient populations. The search for alternative transfusion triggers is essential to tailor transfusion therapy effectively, especially in patients with comorbidities or unique clinical profiles. Investigating alternative triggers not only enhances patient care by identifying more precise indicators but also minimizes transfusion-related risks, optimizes blood product utilization, and ensures availability when needed. Personalized transfusion strategies based on alternative triggers hold the potential to improve outcomes in various clinical scenarios, addressing anemia's complex challenges in healthcare. Further research and evidence are needed to refine these alternative triggers and guide their implementation in clinical practice.

Continuous cardiac output estimation using a new modified Fick method during off-pump coronary artery bypass graft surgery: a retrospective observational study

PURPOSE

Several technical aspects of the Fick method limit its use intraoperatively. A data-driven modification of the Fick method may enable its use in intraoperative settings.

METHODS

This two-center retrospective observational study included 57 (28 and 29 in each center) patients who underwent off-pump coronary artery bypass graft (OPCAB) surgery. Intraoperative recordings of physiological data were obtained and divided into training and test datasets. The Fick equation was used to calculate cardiac output (CO-Fick) using ventilator-determined variables, intraoperative hemoglobin level, and SvO2, with continuous thermodilution cardiac output (CCO) used as a reference. A modification CO-Fick was derived and validated: CO-Fick-AD, which adjusts the denominator of the original equation.

RESULTS

Increased deviation between CO-Fick and CCO was observed when oxygen extraction was low. The root mean square error of CO-Fick was decreased from 6.07 L/min to 0.70 L/min after the modification. CO-Fick-AD showed a mean bias of 0.17 (95% CI 0.00-0.34) L/min, with a 36.4% (95% CI 30.6-44.4%) error. The concordance rates of CO-Fick-AD ranged from 73.3 to 87.1% depending on the time interval and exclusion zone.

CONCLUSIONS

The original Fick method is not reliable when oxygen extraction is low, but a modification using data-driven approach could enable continuous estimation of cardiac output during the dynamic intraoperative period with minimal bias. However, further improvements in precision and trending ability are needed.

Synergistic effects of microplastic and lead trigger physiological and biochemical impairment in a mangrove crab

Microplastics (MP) are vectors for other environmental contaminants, such as metals, being a considerable problem, especially in the aquatic ecosystem. To investigate the combined effects of MP (high density polyethylene) with lead (Pb), we exposed the mangrove fiddler crab Minuca vocator to Pb (50 mg L-1), and MP (25 mg L-1) alone and in mixture, for 5 days. We aimed to determine Pb and MP bioaccumulation, as well as physiological (oxygen consumption and hemolymph osmolality) and biochemical (superoxide dismutase, catalase, glutathione peroxidase, and lipid peroxidation) traits effects. Co-exposure of MP and Pb significantly increased the bioaccumulation of Pb, but reduced MP tissue accumulation. Regarding the physiological traits, increasing osmolality and oxygen consumption rates compared to the control were observed, particularly in the combined Pb and MP exposure. As to biochemical traits, the combination of Pb and MP induced the most significant responses in the enzymatic profile antioxidant enzyme activity. The catalase (CAT), glutathione peroxidase (GPx), and dismutase superoxide (SOD) decreased compared to individual exposure effects; the combination of MP and Pb had a synergistic effect on promoting lipid peroxidation (LPO). The co-exposure of MP and Pb acted synergistically when compared to the effects of the isolated compounds. Due to the increasing MP contamination in mangroves, more severe physiological and biochemical effects can be expected on mangrove crabs exposed to metal contamination.

Bromine indirubin FLIM/PLIM sensors to measure oxygen in normoxic and hypoxic PDT conditions

BACKGROUND

The induction of phototoxicity during photodynamic therapy (PDT) is dependent on oxygen availability. For this reason, the development of sensors to measure oxygen and oxygen consumption is extremely important.

APPROACH

In this project we have used Fluorescence Lifetime imaging (FLIM) and Phosphorescence Lifetime Imaging/ delayed Fluorescence Lifetime Imaging (PLIM/dFLIM) to investigate the ability of bromine indirubin derivatives as oxygen sensors.

RESULTS

The oxygen sensitivity of bromine indirubins was detected through PLIM/dFLIM. Moreover, we have observed, by measuring nicotinamide adenine dinucleotide (NADH) FLIM, that bromine indirubin has a significant impact on cellular metabolism by shifting the SCC-4 Cells metabolism from oxidative phosphorylation (OXPHOS) to glycolysis.

CONCLUSIONS

In conclusion, this study successfully achieves its goals and provides important insights into the use of indirubin as a potential oxygen consumption sensor with the capability to identify and differentiate between normoxic and hypoxic regions within the cells.

The electrocardiographic manifestations of pectus excavatum before and after surgical correction

BACKGROUND

Pectus excavatum (PEx) can cause cardiopulmonary limitations due to cardiac compression and displacement. There is limited data on electrocardiogram (ECG) alterations before and after PEx surgical repair, and ECG findings suggesting cardiopulmonary limitations have not been reported. The aim of this study is to explore ECG manifestations of PEx before and after surgery including associations with exercise capacity.

METHODS

A retrospective review of PEx patients who underwent primary repair was performed. ECGs before and after surgical correction were evaluated and the associations between preoperative ECG abnormalities and cardiopulmonary function were investigated.

RESULTS

In total, 310 patients were included (mean age 35.1 ± 11.6 years). Preoperative ECG findings included a predominant negative P wave morphology in V1, and this abnormal pattern significantly decreased from 86.9% to 57.4% (p < 0.001) postoperatively. The presence of abnormal P wave amplitude in lead II (>2.5 mm) significantly decreased from 7.1% to 1.6% postoperatively (p < 0.001). Right bundle branch block (RBBB) (9.4% versus 3.9%, p < 0.001), rsr' patterns (40.6% versus 12.9%, p < 0.001), and T wave inversion in leads V1-V3 (62.3% vs 37.7%, p < 0.001) were observed less frequently after surgery. Preoperative presence of RBBB (OR = 4.8; 95%CI 1.1-21.6) and T wave inversion in leads V1-3 (OR = 2.3; 95%CI 1.3-4.2) were associated with abnormal results in cardiopulmonary exercise testings.

CONCLUSION

Electrocardiographic abnormalities in PEx are frequent and can revert to normal following surgery. Preoperative RBBB and T wave inversion in leads V1-3 suggested a reduction in exercise capacity, serving as a marker for the need for further cardiovascular evaluation of these patients.

Short-term effects of sacubitril/valsartan therapy on myocardial oxygen consumption and energetic efficiency of cardiac work in heart failure with reduced ejection fraction: A randomized controlled study

AIMS

We sought to evaluate the mechanism of angiotensin receptor-neprilysin inhibitor (ARNI) sacubitril/valsartan therapy and compare it with a valsartan-only control group in patients with heart failure with reduced ejection fraction (HFrEF).

METHODS AND RESULTS

The study was a phase IV, prospective, randomized, double-blind, parallel-group study in patients with New York Heart Association class II-III heart failure and left ventricular ejection fraction (LVEF) ≤35%. During a 6-week run-in period, all patients received valsartan therapy, which was up-titrated to the highest tolerated dose level (80 mg bid or 160 mg bid) and then randomized to either valsartan or sacubitril/valsartan. Myocardial oxygen consumption, energetic efficiency of cardiac work, cardiac and systemic haemodynamics were quantified using echocardiography and 11 C-acetate positron emission tomography before and after 6 weeks of therapy (on stable dose) in 55 patients (ARNI group: n = 27, mean age 63 ± 10 years, LVEF 29.2 ± 10.4%; and valsartan-only control group: n = 28, mean age 64 ± 8 years, LVEF 29.0 ± 7.3%; all p = NS). The energetic efficiency of cardiac work remained unchanged in both treatment arms. However, both diastolic (-4.5 mmHg; p = 0.026) and systolic blood pressure (-9.8 mmHg; p = 0.0007), myocardial perfusion (-0.054 ml/g/min; p = 0.045), and left ventricular mechanical work (-296; p = 0.038) decreased significantly in the ARNI group compared to the control group. Although myocardial oxygen consumption decreased in the ARNI group (-5.4%) compared with the run-in period and remained unchanged in the control group (+0.5%), the between-treatment group difference was not significant (p = 0.088).

CONCLUSIONS

We found no differences in the energetic efficiency of cardiac work between ARNI and valsartan-only groups in HFrEF patients. However, ARNI appears to have haemodynamic and cardiac mechanical effects over valsartan in heart failure patients.

Evaluation of Oxygen Consumption Rates In Situ

An analysis of the mitochondrial respiration function represented by the oxygen consumption rate is necessary to assess mitochondrial bioenergetics and redox function. This protocol describes two alternative techniques to evaluate mitochondrial respiration function in situ: (1) measure oxygen consumption rates via an electrode; (2) measure oxygen consumption rates via a seahorse instrument. These in situ approaches provide more physiological access to mitochondria to evaluate mitochondrial respiration function in a relatively integrated cellular system.

Effects of pulmonary rehabilitation in hematopoietic stem cell transplantation recipients: a randomized controlled study

PURPOSE

During hematopoietic stem cell transplantation (HSCT), patients' exercise capacity and quality of life (QOL) are impaired. Exercise training is recommended to preserve cardiorespiratory fitness during the compelling HSCT period. However, studies investigating the effects of pulmonary rehabilitation (PR) in HSCT recipients are limited. Therefore, this study aimed to investigate the effects of two different PR programs on maximal exercise capacity, respiratory muscle strength and endurance, pulmonary function, and QOL.

METHODS

This is a prospective, randomized, controlled, triple-blinded study. Thirty hospitalized patients undergoing HSCT were randomized to the pulmonary rehabilitation plus inspiratory muscle training (PR + IMT) group and the PR group. PR group performed upper extremity aerobic exercise training (AET) and progressive resistance exercise training (PRET), PR + IMT group performed IMT in addition to the upper extremity AET and PRET. Maximal exercise capacity (cardiopulmonary exercise testing), respiratory muscle strength (mouth pressure device, (MIP and MEP)) and respiratory muscle endurance (threshold loading test), pulmonary function (spirometry), and QOL (European Organization for Research and Treatment of Cancer (EORTC QLQ-C30) were evaluated before HSCT and after discharge.

RESULTS

Changes in pulmonary function, respiratory muscle strength and endurance, and QOL were similar within groups (p > 0.05). The MEP, peak oxygen consumption, and oxygen pulse significantly decreased in both groups (p < 0.05).

CONCLUSION

Pulmonary function, inspiratory muscle strength and endurance, and QOL preserved after HSCT. Expiratory muscle strength and maximal exercise capacity decreased even though PR during HSCT. Breathing reserve and restriction improved in the PR + IMT group. In addition, minute ventilation and dyspnea were preserved in the PR + IMT group, while these values were worsened during two structured PR programs. Therefore, PR should be applied in accordance with the patient's current clinical and hematologic status to patients undergoing HSCT.

CLINICALTRIALS

gov (19/07/2018, NCT03625063).

Hypoxic loss of consciousness in air diving: two cases of mixtures made hypoxic by oxidation of the scuba diving cylinder

Without an adequate supply of oxygen from the scuba apparatus, humans would not be able to dive. The air normally contained in a scuba tank is dry and free of toxic gases. The presence of liquid in the tank can cause corrosion and change the composition of the gas mixture. Various chemical reactions consume oxygen, making the mixture hypoxic. We report two cases of internal corrosion of a scuba cylinder rendering the respired gas profoundly hypoxic and causing immediate hypoxic loss of consciousness in divers.

Effects of temperature on metabolic rate during metamorphosis in the alfalfa leafcutting bee

Spring conditions, especially in temperate regions, may fluctuate abruptly and drastically. Environmental variability can expose organisms to temperatures outside of their optimal thermal ranges. For ectotherms, sudden changes in temperature may cause short- and long-term physiological effects, including changes in respiration, morphology, and reproduction. Exposure to variable temperatures during active development, which is likely to occur for insects developing in spring, can cause detrimental effects. Using the alfalfa leafcutting bee, Megachile rotundata, we aimed to determine if oxygen consumption could be measured using a new system and to test the hypothesis that female and male M. rotundata have a thermal performance curve with a wide optimal range. Oxygen consumption of M. rotundata pupae was measured across a large range of temperatures (6-48°C) using an optical oxygen sensor in a closed respirometry system. Absolute and mass-specific metabolic rates were calculated and compared between bees that were extracted from their brood cells and those remaining in the brood cell to determine whether pupae could be accurately measured inside their brood cells. The metabolic response to temperature was non-linear, which is an assumption of a thermal performance curve; however, the predicted negative slope at higher temperatures was not observed. Despite sexual dimorphism in body mass, sex differences only occurred in mass-specific metabolic rates. Higher metabolic rates in males may be attributed to faster development times, which could explain why there were no differences in absolute metabolic rate measurements. Understanding the physiological and ecological effects of thermal environmental variability on M. rotundata will help to better predict their response to climate change.

Energetic responses of head-out water immersion at different temperatures during post-exercise recovery and its consequence on anaerobic mechanical power

PURPOSE

While exercise recovery may be beneficial from a physiological point of view, it may be detrimental to subsequent anaerobic performance. To investigate the energetic responses of water immersion at different temperatures during post-exercise recovery and its consequences on subsequent anaerobic performance, a randomized and controlled crossover experimental design was performed with 21 trained cyclists.

METHOD

Participants were assigned to receive three passive recovery strategies during 10 min after a Wingate Anaerobic Test (WAnT): control (CON: non-immersed condition), cold water immersion (CWI: 20 ℃), and hot water immersion (HWI: 40 ℃). Blood lactate, cardiorespiratory, and mechanical outcomes were measured during the WAnT and its recovery. Time constant (τ), asymptotic value, and area under the curve (AUC) were quantified for each physiologic parameter during recovery. After that, a second WAnT test and 10-min recovery were realized in the same session.

RESULTS

Regardless the water immersion temperature, water immersion increased [Formula: see text] (+ 18%), asymptote ([Formula: see text]+ 16%, [Formula: see text] + 13%, [Formula: see text] + 17%, HR + 16%) and AUC ([Formula: see text]+ 27%, [Formula: see text] + 18%, [Formula: see text] + 20%, HR + 25%), while decreased [Formula: see text] (- 33%). There was no influence of water immersion on blood lactate parameters. HWI improved the mean power output during the second WAnT (2.2%), while the CWI decreased 2.4% (P < 0.01).

CONCLUSION

Independent of temperature, water immersion enhanced aerobic energy recovery without modifying blood lactate recovery. However, subsequent anaerobic performance was increased only during HWI and decreased during CWI. Despite higher than in other studies, 20 °C effectively triggered physiological and performance responses. Water immersion-induced physiological changes did not predict subsequent anaerobic performance.

Critical temperatures and aerobic metabolism in post-larvae of Pacific white shrimp Litopenaeus vannamei (Boone, 1931)

Increasing water temperature because of climate change decreases the oxygen concentration while increasing the oxygen requirement of species in aquatic environments. Temperature is one of the most important environmental factors affecting the physiological functions of organisms, especially poikilothermic animals, such as shrimp at all levels. In intensive shrimp culture, it is of great importance to know the tolerable temperature range of cultured species and their metabolism since this affects the physiological condition. In this study, critical temperatures (CTM: CTmin and CTmax) of Pacific white shrimp, Litopenaeus vannamei, post-larvae (PL), were determined at different acclimation temperatures of 15, 20, 25, and 30 °C. Lower and upper incipient lethal temperatures (ILT: LILT and UILT) were also calculated for the PL. The thermal windows of the PL were developed using the CTM and ILT values. The standard metabolic rate (SMR) of the PL was determined based on the oxygen consumption rate (OCR) at the different acclimation temperatures mentioned above. The acclimation temperature had a subsequent effect on the thermal tolerance and SMR of the PL (P < 0.01). The PLs of Pacific white shrimp have high thermal tolerance and can survive at extreme temperatures (CTmin and CTmax: 8.2-43.8 °C) with their large dynamic and static thermal window areas of 1128 and 931 °C2, respectively. The optimal temperature range for Pacific white shrimp PLs is the 25-30 °C range, where a decrease in SMR is determined with increasing temperature. The result of this study reveals that a range of 25-30 °C is optimal for effective PL culture of Pacific white shrimp.

The effect of pH and aging on mitochondrial reduction of bovine myoglobin's affinity for oxygen

In skeletal muscles, mitochondria have been shown to decrease the oxygen affinity of myoglobin. In this study, we investigated whether the mitochondrial function of decreasing myoglobin affinity for oxygen persists and operates at the final pH of postmortem bovine skeletal muscle. The oxygen affinity and myoglobin consumption in the presence of mitochondria obtained from fresh and wet-aged beef were evaluated and compared at pH 5.1, 5.6, and 5.7. The results showed that mitochondria obtained from fresh beef preserved myoglobin oxygen consumption and affinity interference, whereas those obtained from wet-aged beef did not. Oxygen consumption and affinity interference were mostly absent at pH 5.1 and were higher at pH 5.7 than those at pH 5.6. Our findings suggest that mitochondria contribute both to an increase in the oxygen affinity of myoglobin in aged meat and a decrease in the oxygen affinity of myoglobin in high-pH meat, such as dark-cutting beef.

Discussion on key issues of carbon footprint accounting for bast fiber textiles

Bast fiber textiles have become increasingly popular as a sustainable alternative in recent years. Although the carbon emissions of bast fiber textiles have been studied using life cycle assessment method, there is a lack of comprehensive literature analyzing and summarizing the results. This study reviews the current state of research on the carbon emissions of bast fiber textiles. Compared to other plant fibers, there are fewer studies on the carbon footprint or life cycle assessment of bast fiber textiles, and these studies lack a comprehensive "cradle to grave" or "gate to grave" analysis. In addition, inconsistencies exist in the allocation methods used for carbon footprint assessments. This study suggests a combination of physical and economic allocation to conduct a more accurate environmental impact assessment of bast fiber textiles. On the basis of the above review, this study modularizes the process of the entire life cycle of textiles and analyzes the carbon sequestration and emission characteristics to determine the main considerations for carbon footprint assessment. The carbon sequestration effect of bast fiber textiles should be analyzed at the raw material extraction stage and at the end-of-life stage. Oxygen release and consumption are also considered as additional factors to be quantified and analyzed in this study. In the future, the modular method should be used for all carbon footprint evaluation reports for bast fiber textiles. This method helps to comprehensively quantify and evaluate the carbon footprint of bast fiber textiles throughout their entire life cycle. It can provide recommendations for green design, green production and sustainable consumption.

Prediction of pseudoprogression in post-treatment glioblastoma using dynamic susceptibility contrast-derived oxygenation and microvascular transit time heterogeneity measures

OBJECTIVES

To evaluate the added value of MR dynamic susceptibility contrast (DSC)-perfusion-weighted imaging (PWI)-derived tumour microvascular and oxygenation information with cerebral blood volume (CBV) to distinguish pseudoprogression from true progression (TP) in post-treatment glioblastoma.

METHODS

This retrospective single-institution study included patients with isocitrate dehydrogenase (IDH) wild-type glioblastoma and a newly developed or enlarging measurable contrast-enhancing mass within 12 weeks after concurrent chemoradiotherapy. CBV, capillary transit time heterogeneity (CTH), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) were obtained from DSC-PWI. Predictors were selected using univariable logistic regression, and performance was measured with adjusted diagnostic odds with tumour volume and area under the curve (AUC) of receiver operating characteristics analysis.

RESULTS

A total of 103 patients were included (mean age, 59.6 years; 59 women), with 67 cases of TP and 36 cases of pseudoprogression. Pseudoprogression exhibited higher CTH (4.0 vs. 3.4, p = .019) and higher OEF (12.7 vs. 10.7, p = .014) than TP, but a similar CBV (1.48 vs. 1.53, p = .13) and CMRO2 (7.7 vs. 7.3s, p = .598). Independent of tumour volume, both high CTH (adjusted odds ratio [OR] 1.52; 95% confidence interval [CI]: 1.11-2.09, p = .009) and high OEF (adjusted OR 1.17; 95% CI:1.03-1.33, p = .016) were predictors of pseudoprogression. The combination of CTH, OEF, and CBV yielded higher diagnostic performance (AUC 0.71) than CBV alone (AUC 0.65).

CONCLUSION

High intratumoural capillary transit heterogeneity and high oxygen extraction fraction derived from DSC-PWI have enhanced the diagnostic value of CBV in pseudoprogression of post-treatment IDH-wild type glioblastoma.

CLINICAL RELEVANCE STATEMENT

In the early post-treatment stage of glioblastoma, pseudoprogression exhibited both high oxygen extraction fraction and high capillary transit heterogeneity and these dynamic susceptibility contrast-perfusion weighted imaging derived parameters have added value in cerebral blood volume-based noninvasive differentiation of pseudoprogression from true progression.

KEY POINTS

• Capillary transit time heterogeneity and oxygen extraction fraction can be measured noninvasively through processing of dynamic susceptibility contrast imaging. • Pseudoprogression exhibited higher capillary transit time heterogeneity and higher oxygen extraction fraction than true progression. • A combination of cerebral blood volume, capillary transit time heterogeneity, and oxygen extraction fraction yielded the highest diagnostic performance (area under the curve 0.71).

Continuous and repeat metabolic measurements compared between post-cardiothoracic surgery and critical care patients

OBJECTIVE

Using a system, which accuracy is equivalent to the gold standard Douglas Bag (DB) technique for measuring oxygen consumption (VO2), carbon dioxide generation (VCO2), and respiratory quotient (RQ), we aimed to continuously measure these metabolic indicators and compare the values between post-cardiothoracic surgery and critical care patients.

METHODS

This was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Age 18 years or older patients who underwent mechanical ventilation were enrolled.

RESULTS

We included 4 post-surgery and 6 critical care patients. Of those, 3 critical care patients died. The longest measurement reached to 12 h and 15 min and 50 cycles of repeat measurements were performed. VO2 of the post-surgery patients were 234 ± 14, 262 ± 27, 212 ± 16, and 192 ± 20 mL/min, and those of critical care patients were 122 ± 20, 189 ± 9, 191 ± 7, 191 ± 24, 212 ± 12, and 135 ± 21 mL/min, respectively. The value of VO2 was more variable in the post-surgery patients and the range of each patient was 44, 126, 71, and 67, respectively. SOFA scores were higher in non-survivors and there were negative correlations of RQ with SOFA.

CONCLUSIONS

We developed an accurate system that enables continuous and repeat measurements of VO2, VCO2, and RQ. Critical care patients may have less activity in metabolism represented by less variable values of VO2 and VCO2 over time as compared to those of post-cardiothoracic surgery patients. Additionally, an alteration of these values may mean a systemic distinction of the metabolism of critically ill patients.

Exercise in hypoxia: a model from laboratory to on-field studies

Clinical outcome and quality of life of patients with chronic heart failure (HF) have greatly improved over the last two decades. These results and the availability of modern lifts allow many cardiac patients to spend leisure time at altitude. Heart failure per se does not impede a safe stay at altitude, but exercise at both simulated and real altitudes is associated with a reduction in performance, which is inversely proportional to HF severity. For example, in normal subjects, the reduction in functional capacity is ∼2% every 1000 m altitude increase, whereas it is 4 and 10% in HF patients with normal or slightly diminished exercise capacity and in HF patients with markedly diminished exercise capacity, respectively. Also, the on-field experience with HF patients at altitude confirms safety and shows overall similar data to that reported at simulated altitude. Even 'optimal' HF treatment in patients spending time at altitude or at hypoxic conditions is likely different from optimal treatment at sea level, particularly with regard to the selectivity of β-blockers. Furthermore, high altitude, both simulated and on-field, represents a stimulating model of hypoxia in HF patients and healthy subjects. Our data suggest that spending time at altitude (<3500 m) can be safe even for HF patients, provided that subjects are free from comorbidities that may directly interfere with the adaptation to altitude and are stable. However, HF patients experience a reduction of exercise capacity directly proportional to HF severity and altitude. Finally, HF patients should be tested for functional capacity and must undergo a specific 'hypoxic-tailored treatment' to avoid pharmacological interference with altitude adaptation mechanisms, particularly with regard to the selectivity of β-blockers.

Aquaporin 3 inhibition suppresses the mitochondrial respiration rate and viability of multiple myeloma cells

Aquaporin 3 (AQP3) is a member of the aquaporin water channel family expressed by numerous cell types, including some cancer cells. Accumulating evidence suggests that AQP3 inhibition may impede cancer progression, but drugs targeting AQP3 are still in the early pre-clinical stage of development. Here, we examined the effect of AQP3 inhibition on multiple myeloma (MM), an incurable plasma cell malignancy. Four MM cell lines were cultured in the presence of an anti-AQP3 monoclonal antibody (mAb), the AQP3 inhibitor DFP00173, or corresponding controls, and the effects on cell viability, proliferation, apoptosis, and mitochondrial respiration capacity were compared. Both anti-AQP3 mAb and DFP00173 reduced cell growth, mitochondrial respiration rate, and electron transport chain complex I activity. Both agents also potentiated the antiproliferative efficacy of the anticancer drug venetoclax. Administration of the anti-AQP3 mAb to immunodeficient mice inoculated with RPMI8226 or KMS-11 MM cells significantly suppressed tumor growth. These data provide evidence that AQP3 blockade can suppress MM cell growth in vitro and tumor growth in mice. Thus, AQP3 inhibition may be an effective therapeutic strategy for MM.

Chronic supplementation of noni in diabetic type 1-STZ rats: effects on glycemic levels, kidney toxicity and exercise performance

Noni is a fruit with potential medicinal use preventing elevated blood glucose levels in diabetes mellitus. Its effects have been attributed to an antioxidant property in several other diseases. However, the effects of noni-chronic supplementation on exercise performance in the presence of diabetes conditions are not known. Thirty-two male Wistar rats were used to verify the effects of chronic noni (Morinda citrifolia L) juice administration on glycemia, triglyceride levels, and its relation to physical performance. In addition, it was verified if chronic noni supplementation is safe for clinical use through kidney morphology analysis. In half of the rats, diabetes mellitus (DM) was induced with STZ. All rats were submitted to an incremental workload running test (IWT) until fatigued so that oxygen consumption and performance indexes (exercise time to fatigue and workload) could be analyzed before noni administration. Then, the control and DM groups received a placebo (saline solution) or noni juice (dilution 2:1) at a dose of 2 mL/kg once a day for 60 days. The result was four groups: control + placebo (CP), control + noni (CN), DM + placebo (DMP), and DM + noni (DMN). Our dose was based on in previous study by Nayak et al. (2011) that observed a significant reduction in glycemia with 2 ml/kg of the noni juice without any toxicity effect cited. Groups were then given a third IWT to verify the effect of the noni juice on exercise performance (exercise time to fatigue, workload, maximal oxygen consumption) and glycemia. Twenty-four hours after the third test, all animals were euthanized and blood and kidneys were removed for posterior analysis. The DM induction with STZ impaired the performance by 39%. Noni administration improved the time to fatigue and workload in DM rats beyond reducing hyperglycemia. These results could be associated with an improved energy efficiency promoted by noni ingestion, since the oxygen consumption was not different between the groups, although the exercise was longer in animals with noni ingestion. Our results provided evidence that chronic noni administration causes kidney damage since increased Bowman's space area in the control rats, suggesting glomerular hyperfiltration at the same magnitude as the non-treated DM group.In conclusion, chronic noni ingestion promoted glycemic control and improved the performance in DM rats but caused kidney toxicity.

Comparison of ventilatory and oxygen consumption measurements of yearling Thoroughbred colts and fillies exercising unridden on an all-weather track

Sex effects on ventilatory and oxygen consumption (V̇O2) measurements during exercise have been identified in humans. This study's aim was to evaluate the hypothesis that there are sex effects on ventilatory and V̇O2 measurements in exercising, untrained yearling Thoroughbreds (Tb). Forty-one Tbs (16 colts, 25 fillies; 19.8 ± 1.4 months old) were recruited. Physiological, ventilatory and exercise data were gathered from horses exercising unridden at high intensity on an all-weather track from a global positioning-heart rate unit and a portable ergospirometry system. Data were analysed with an unpaired Student's t-test and the Benjamini-Hochberg correction for multiple testing (P ≤ 0.05 significant). Mean bodyweight (BW, P = 0.002) and wither height (P = 0.04) were greater for colts than fillies. There were no differences in physiological and exercise data and absolute peak V̇O2 between groups. However, fillies had a higher mass specific peak V̇O2 (P = 0.03) than colts (121.5 ± 21.6 mL/kg.min vs. 111.9 ± 27.4 mL/kg.min). The peak breathing frequency was greater for fillies (P < 0.001) while the peak inspiratory (P < 0.001) and expiratory air flow (P < 0.001), peak expiratory tidal volume (VTE; P < 0.001) and peak minute ventilation (V̇E; P = 0.01) were greater for colts; there were no differences for peak VTE and V̇E when adjusted for BW. Differences in BW explain the differences in mass specific peak V̇O2 between groups. Given their morphological differences, it is likely that lung volumes and airway diameters are smaller for fillies, resulting in greater resistance and lower air flows and volumes. Further research is required to investigate the ventilatory differences and how they may change with maturation and impact performance.

The effects of SLICE®- and ivermectin-contaminated sediment on avoidance behaviour and oxygen consumption in marine benthic invertebrates

Pest management strategies to reduce sea lice infestations in the salmon aquaculture industry include in-feed treatments with ivermectin (IVM) and SLICE® (active ingredient [AI] emamectin benzoate [EMB]), which can result in local contamination of the environment. These compounds partition to sediments, have moderate persistence, and may pose a risk to non-target benthic organisms. The sub-lethal effects of EMB, IVM and a combination of both (EMB/IVM) on the benthic amphipod Eohaustorius estuarius and polychaete Nereis virens at environmentally relevant sediment concentrations were examined in subchronic exposures (28-30-d). E. estuarius avoided sediment containing >50 μg/kg IVM alone and in combination with EMB. N. virens avoided sediment with >50 μg/kg IVM and >0.5 μg/kg EMB/IVM and exhibited impaired burrowing and locomotory behaviour with both treatments. Oxygen consumption was significantly decreased in E. estuarius (up to 50% compared to controls) and increased in N. virens (by ∼ 200%) when exposed to EMB, IVM and EMB/IVM at concentrations <5 μg/kg. IVM, SLICE® and combination exposures at environmentally relevant concentrations caused adverse effects in E. estuarius and N. virens which could significantly alter organism fitness near salmon aquaculture operations.

Oxygen consumption and formation of recalcitrant organic carbon from the decomposition of free-floating macrophyte leachates

Aquatic macrophytes contain high levels of hydrosoluble compounds. These compounds disproportionately support microbial breakdown and affect biological oxygen demand in eutrophic waters. In this study, we investigated the fate of leachates from free-floating macrophytes (Pistia stratiotes and Eichhornia crassipes) usually present in eutrophic tropical lacustrine environments. After extraction, the leachates were fractioned into high and low molecular weight compounds and incubated under aerobic conditions, in the dark and at 20.0 ± 1.3 °C. The concentrations of dissolved oxygen and the total, dissolved, and particulate organic carbon (TOC, DOC, and POC) were determined during 60 days. The selected leachates supported the detritus trophic chain of the Barra Bonita Reservoir. High rates of carbon transfer were measured, which were ascribed to the temperature selected (20 °C), nutrient availability, and labile fractions of the leachates. Decomposition occurred mainly through catabolic pathways (mineralization), with the formation of POC (immobilization) being only minor. In the early stages of P. stratiotes and E. crassipes decomposition, the mineralization of leachates (mainly the low molecular weight) led to declines in dissolved oxygen. Owing to the low rates of mass loss, the recalcitrant fractions of these leachates should constitute the main forms of organic carbon exported from the reservoir.

Analysis of electrical stimulation and voluntary muscle contraction on skeletal muscle oxygen uptake and mitochondrial recovery using near-infrared spectroscopy

PURPOSE

This investigation was to compare differences in skeletal muscle oxygen consumption ([Formula: see text]) and mitochondrial recovery between voluntary (VOL) and electrically stimulated (ES) plantarflexion contractions.

METHODS

Twelve men and women (26 ± 4.0 years; 171.8 ± 5.1 cm; 74.0 ± 13.7 kg) were seated in a chair with their right knee fully extended and right foot secured to a force transducer. ES electrodes and a near-infrared spectroscopy device were placed on the gastrocnemius. Participants performed ES plantarflexion contractions across a range of stimulation intensities at frequencies of 1 and 2 Hz and similar VOL contractions. Cuff occlusion occurred immediately following each series of contractions to measure [Formula: see text]. A standardized mitochondrial function assessment protocol was also performed to calculate K-constants between work-matched ES and VOL contractions.

RESULTS

For mitochondrial assessments, there were no significant differences between ES and VOL rate constants (2.03 ± 0.98 vs. 1.25 ± 1.35 min-1, p = 0.266). ES resulted in a significantly greater workrate-[Formula: see text] slope at 1 Hz (0.007 ± 0.007 vs. 0.001 ± 0.002% [Formula: see text]/s/N, p = 0.014) and 2 Hz (0.010 ± 0.010 vs. 0.001 ± 0.001% [Formula: see text]/s/N, p = 0.012), as well as a significantly greater workrate-[Formula: see text] Y-intercept at 2 Hz (1.603 ± 1.513 vs. 0.556 ± 0.564% [Formula: see text]/s, p = 0.035) but not 1 Hz (0.579 ± 0.448 vs. 0.442 ± 0.357% mV̇O2/s, p = 0.535) when compared to VOL.

CONCLUSION

ES results in a significantly greater [Formula: see text] at similar work rates compared to VOL, however, the mitochondrial recovery rate constants were similar. The greater mVO2 with ES may partially contribute to the increased rate of fatigue during ES exercise in individuals with muscle paralysis.

Three weeks of mental training changes physiological outcomes during a time trial to exhaustion

Mental training (MT) can increase endurance performance. The purpose of this study was to examine the minimum dose of mental training needed to increase performance and elucidate the physiological mechanisms underlying this improvement. In a randomized between groups pre-test-post-test design, 33 participants visited the lab on 6 separate days. A VO2peak with ventilatory threshold (VT) was performed on day 1. The subsequent visits consisted of time trials to exhaustion (TTE) performed at 10% above VT. Between visit 3 and 6, the MT group (n = 16) watched a video for 10-15 min each day for 3 weeks, while the control group (CON; n = 17) did no mental training. Heart rate (HR), rate of perceived exertion (RPE), VAS scores for pain and fatigue, electromyography, and metabolic and neuromuscular data were collected and recorded during the time trials. The GRIT-S and CD-RISC 10 surveys were completed before study days 3 and 6. TTE increased significantly for MT beginning after 2 weeks (10.0 ± 13.1%) with no further change after 3 weeks (10.4 ± 13.2). TTE also significantly decreased during the last TTE for CON (-10.3 ± 12.7). VO2, ventilation, and frequency of breathing were significantly reduced in the latter stages of the TTE for MT. EMG was also significantly decreased for MT as compared for CON throughout the trial. Three weeks of mental training improves performance by reducing EMG, decreasing activation of the muscle and reducing metabolic factors during the latter stages of exercise.

The role of pyruvate-induced enhancement of oxygen metabolism in extracellular purinergic signaling in the post-cardiac arrest rat model

Purine nucleotide adenosine triphosphate (ATP) is a source of intracellular energy maintained by mitochondrial oxidative phosphorylation. However, when released from ischemic cells into the extracellular space, they act as death-signaling molecules (eATP). Despite there being potential benefit in using pyruvate to enhance mitochondria by inducing a highly oxidative metabolic state, its association with eATP levels is still poorly understood. Therefore, while we hypothesized that pyruvate could beneficially increase intracellular ATP with the enhancement of mitochondrial function after cardiac arrest (CA), our main focus was whether a proportion of the raised intracellular ATP would detrimentally leak out into the extracellular space. As indicated by the increased levels in systemic oxygen consumption, intravenous administrations of bolus (500 mg/kg) and continuous infusion (1000 mg/kg/h) of pyruvate successfully increased oxygen metabolism in post 10-min CA rats. Plasma ATP levels increased significantly from 67 ± 11 nM before CA to 227 ± 103 nM 2 h after the resuscitation; however, pyruvate administration did not affect post-CA ATP levels. Notably, pyruvate improved post-CA cardiac contraction and acidemia (low pH). We also found that pyruvate increased systemic CO₂ production post-CA. These data support that pyruvate has therapeutic potential for improving CA outcomes by enhancing oxygen and energy metabolism in the brain and heart and attenuating intracellular hydrogen ion disorders, but does not exacerbate the death-signaling of eATP in the blood.

The metabolic cost of inspiratory muscle training in mechanically ventilated patients in critical care

BACKGROUND

Diaphragmatic dysfunction is well documented in patients receiving mechanical ventilation. Inspiratory muscle training (IMT) has been used to facilitate weaning by strengthening the inspiratory muscles, yet the optimal approach remains uncertain. Whilst some data on the metabolic response to whole body exercise in critical care exist, the metabolic response to IMT in critical care is yet to be investigated. This study aimed to quantify the metabolic response to IMT in critical care and its relationship to physiological variables.

METHODS

We conducted a prospective observational study on mechanically ventilated patients ventilated for ≥ 72 h and able to participate in IMT in a medical, surgical, and cardiothoracic intensive care unit. 76 measurements were taken on 26 patients performing IMT using an inspiratory threshold loading device at 4 cmH₂O, and at 30, 50 and 80% of their negative inspiratory force (NIF). Oxygen consumption (VO₂) was measured continuously using indirect calorimetry.

RESULTS

First session mean (SD) VO₂ was 276 (86) ml/min at baseline, significantly increasing to 321 (93) ml/min, 333 (92) ml/min, 351(101) ml/min and 388 (98) ml/min after IMT at 4 cmH₂O and 30, 50 and 80% NIF, respectively (p = 0.003). Post hoc comparisons revealed significant differences in VO₂ between baseline and 50% NIF and baseline and 80% NIF (p = 0.048 and p = 0.001, respectively). VO₂ increased by 9.3 ml/min for every 1 cmH₂O increase in inspiratory load from IMT. Every increase in P/F ratio of 1 decreased the intercept VO₂ by 0.41 ml/min (CI - 0.58 to - 0.24 p < 0.001). NIF had a significant effect on the intercept and slope, with every 1 cmH₂O increase in NIF increasing intercept VO₂ by 3.28 ml/min (CI 1.98-4.59 p < 0.001) and decreasing the dose-response slope by 0.15 ml/min/cmH₂O (CI - 0.24 to - 0.05 p = 0.002).

CONCLUSIONS

IMT causes a significant load-dependent increase in VO₂. P/F ratio and NIF impact baseline VO₂. The dose-response relationship of the applied respiratory load during IMT is modulated by respiratory strength. These data may offer a novel approach to prescription of IMT.

TAKE HOME MESSAGE

The optimal approach to IMT in ICU is uncertain; we measured VO₂ at different applied respiratory loads to assess whether VO₂ increased proportionally with load and found VO₂ increased by 9.3 ml/min for every 1 cmH₂O increase in inspiratory load from IMT. Baseline NIF has a significant effect on the intercept and slope, participants with a higher baseline NIF have a higher resting VO₂ but a less pronounced increase in VO₂ as the inspiratory load increases; this may offer a novel approach to IMT prescription. Trial registration ClinicalTrials.gov, registration number: NCT05101850. Registered on 28 September 2021, https://clinicaltrials.gov/ct2/show/NCT05101850.

A new reservoir-based CPAP with low oxygen consumption: the Bag-CPAP

BACKGROUND

Several noninvasive ventilatory supports rely in their design on high oxygen consumption which may precipitate oxygen shortage, as experienced during the COVID-19 pandemic. In this bench-to-bedside study, we assessed the performance of a new continuous positive airway pressure (CPAP) device integrating a large reservoir ("Bag-CPAP") designed to minimize oxygen consumption, and compared it with other CPAP devices.

METHODS

First, a bench study compared the performances of Bag-CPAP and four CPAP devices with an intensive care unit ventilator. Two FiO₂ targets (40-60% and 80-100%) at a predefined positive end expiratory pressure (PEEP) level between 5 and 10 cm H₂O were tested and fraction of inspired oxygen (FiO₂) and oxygen consumption were measured. Device-imposed work of breathing (WOB) was also evaluated. Second, an observational clinical study evaluated the new CPAP in 20 adult patients with acute respiratory failure in two hospitals in France. Actual FiO₂, PEEP, peripheral oxygen saturation, respiratory rate, and dyspnea score were assessed.

RESULTS

All six systems tested in the bench study reached the minimal FiO₂ target of 40% and four reached at least 80% FiO₂ while maintaining PEEP in the predefined range. Device-delivered FiO₂/consumed oxygen ratio was the highest with the new reservoir-based CPAP irrespective of FiO₂ target. WOB induced by the device was higher with Bag-CPAP. In the clinical study, Bag-CPAP was well tolerated and could reach high (> 90%) and moderate (> 50%) FiO₂ with an oxygen flow rate of 15 [15-16] and 8 [7-9] L/min, respectively. Dyspnea score improved significantly after introduction of Bag-CPAP, and SpO₂ increased.

CONCLUSIONS

In vitro, Bag-CPAP exhibited the highest oxygen saving properties albeit had increased WOB. It was well accepted clinically and reduced dyspnea. Bag-CPAP may be useful to treat patients with acute respiratory failure in the field, especially when facing constraints in oxygen delivery.

Moderate intensity active recovery improves performance in a second wingate test in cyclists

Background

The aim of the present study was to compare the effects of active (AR) vs. passive recovery (PR) between two Wingate Anaerobic Tests (WAnT) on power output, blood lactate (BLa) and oxygen consumption (VO₂) in a second WAnT.

Methods

Twelve well-trained cyclists underwent three experimental sessions. In the first session, they completed an incremental test for maximum oxygen consumption (V O₂max) and lactate threshold determination. In the second and third sessions, cyclists completed, in random order, two WAnT tests separated by 30-min recovery intervals, during which they performed an AR at 70% of the V O₂ at lactate threshold (V O₂LT) or a PR. The cardiorespiratory, metabolic, and mechanical responses in the two recovery conditions were compared.

Results

No differences were found in the VO₂-on kinetics between WAnT tests (p > 0.05). As expected, blood lactate kinetics showed a greater clearance (from the 7th to the 31st min, p < 0.001) during AR; however, no differences were found in peak BLa between conditions (p > 0.05). Mean and peak power, and total work were significantly higher in the second WAnT after AR (p < 0.001), while the power decline was also lower in this condition (p < 0.05).

Conclusion

The submaximal active recovery strategy used in the present study can induce an improvement in mechanical power and total work during a second WAnT. This suggests that AR of submaximal intensity can induce a post-activation performance enhancement when used during the recovery phase between maximal anaerobic efforts.

Development and validation of equation for cardiorespiratory fitness in patients with heart failure with preserved ejection fraction

Background/Aims

Cardiorespiratory fitness (CRF), as measured by maximal oxygen consumption (VO2max), is an important independent predictive factor of cardiovascular outcomes in patients with heart failure (HF). However, it is unclear whether conventional equations for estimating CRF are applicable to patients with HF with preserved ejection fraction (HFpEF).

Methods

This study included 521 patients with HFpEF (EF ≥ 50%) whose CRF was directly measured by cardiopulmonary exercise test using a treadmill. We developed a new equation (Kor-HFpEF) for half of the patients in the HFpEF cohort (group A, n = 253) and validated it for the remaining half (group B, n = 268). The accuracy of the Kor-HFpEF equation was compared to that of the other equations in the validation group.

Results

In the total HFpEF cohort, the directly measured VO2max was significantly overestimated by the FRIEND and ACSM equations (p < 0.001) and underestimated by the FRIEND-HF equation (p <0.001) (direct 21.2 ± 5.9 mL/kg/min; FRIEND 29.1 ± 11.8 mL/kg/min; ACSM 32.5 ± 13.4 mL/kg/min; FRIEND-HF 14.1 ± 4.9 mL/kg/min). However, the VO2max estimated by the Kor-HFpEF equation (21.3 ± 4.6 mL/kg/min) was similar to the directly measured VO2max (21.7 ± 5.9 mL/kg/min, p = 0.124), whereas the VO2max estimated by the other three equations was still significantly different from the directly measured VO2max in group B (all p < 0.001).

Conclusions

Traditional equations used to estimate VO2max were not applicable to patients with HFpEF. We developed and validated a new Kor-HFpEF equation for these patients, which had a high accuracy.

Cholic and deoxycholic acids induce mitochondrial dysfunction, impaired biogenesis and autophagic flux in skeletal muscle cells

BACKGROUND

Skeletal muscle is sensitive to bile acids (BA) because it expresses the TGR5 receptor for BA. Cholic (CA) and deoxycholic (DCA) acids induce a sarcopenia-like phenotype through TGR5-dependent mechanisms. Besides, a mouse model of cholestasis-induced sarcopenia was characterised by increased levels of serum BA and muscle weakness, alterations that are dependent on TGR5 expression. Mitochondrial alterations, such as decreased mitochondrial potential and oxygen consumption rate (OCR), increased mitochondrial reactive oxygen species (mtROS) and unbalanced biogenesis and mitophagy, have not been studied in BA-induced sarcopenia.

METHODS

We evaluated the effects of DCA and CA on mitochondrial alterations in C₂C₁₂ myotubes and a mouse model of cholestasis-induced sarcopenia. We measured mitochondrial mass by TOM20 levels and mitochondrial DNA; ultrastructural alterations by transmission electronic microscopy; mitochondrial biogenesis by PGC-1α plasmid reporter activity and protein levels by western blot analysis; mitophagy by the co-localisation of the MitoTracker and LysoTracker fluorescent probes; mitochondrial potential by detecting the TMRE probe signal; protein levels of OXPHOS complexes and LC3B by western blot analysis; OCR by Seahorse measures; and mtROS by MitoSOX probe signals.

RESULTS

DCA and CA caused a reduction in mitochondrial mass and decreased mitochondrial biogenesis. Interestingly, DCA and CA increased LC3II/LC3I ratio and decreased autophagic flux concordant with raised mitophagosome-like structures. In addition, DCA and CA decreased mitochondrial potential and reduced protein levels in OXPHOS complexes I and II. The results also demonstrated that DCA and CA decreased basal, ATP-linked, FCCP-induced maximal respiration and spare OCR. DCA and CA also reduced the number of cristae. In addition, DCA and CA increased the mtROS. In mice with cholestasis-induced sarcopenia, TOM20, OXPHOS complexes I, II and III, and OCR were diminished. Interestingly, the OCR and OXPHOS complexes were correlated with muscle strength and bile acid levels.

CONCLUSION

Our results showed that DCA and CA decreased mitochondrial mass, possibly by reducing mitochondrial biogenesis, which affects mitochondrial function, thereby altering potential OCR and mtROS generation. Some mitochondrial alterations were also observed in a mouse model of cholestasis-induced sarcopenia characterised by increased levels of BA, such as DCA and CA.

The Effects of Incorporating Dry-land Short Intervals to Long Aerobic-dominant In-Water Swimming Training on Physiological Parameters, Hormonal Factors, and Performance: A Randomized-Controlled Intervention Study

This study investigated the impact of a 4-week dry-land short sprint interval program (sSIT) on a swim ergometer, when incorporated into long aerobic-dominant in-water swimming training, on the physiological parameters, hormonal factors, and swimming performance of well-trained swimmers. Sixteen participants (age = 25 ± 6 years, height = 183 ± 6 cm, weight 78 ± 6 kg, body fat = 10.6 ± 3.1%) were randomized to either a long aerobic-dominant in-pool training plus three sessions/week of sSIT or a control group (CON) who didn't engage in SIT. sSIT consisted of 3 sets of 10 × 4 s, 10 × 6 s, and 10 × 8 s all-out sprints interspersed by 15, 60, and 40 s recovery between each sprint, respectively. Pre- and post-training assessments included peak oxygen uptake (V̇O₂peak), O₂pulse (V̇O₂/HR), ventilation at V̇O₂peak (V̇_E@V̇O₂peak), peak and average power output, and freestyle swim performance at 50, 100, and 200-m distances, stroke rate, as well as testosterone and cortisol. sSIT resulted in significant improvements in V̇O₂peak (5.8%), O₂pulse (4.7%), V̇_E@V̇O₂peak (7.1%), peak and average power output (6.7% and 13.8%, respectively), total testosterone (20%), testosterone to cortisol ratio (16.1%), and 50, 100, and 200-m freestyle swimming performance (-2.2%, -1.2%, and -1.1%, respectively). Furthermore, the observed alterations in the physiological, biochemical, and performance adaptations were significantly more substantial in the sSIT group than the CON group (p ≤ 0.05), demonstrating no modifications during the 4-week long aerobic-dominant in-water swimming without sSIT. The current research effectively established that supplementing standard long aerobic-dominant in-water swim training with three weekly dry-land sSIT sessions triggers adaptive mechanisms that foster enhancements in the aerobic and anaerobic capacity and swimming performance in well-trained swimmers.

The mitochondrial respiratory chain

We present a brief review of the mitochondrial respiratory chain with emphasis on complexes I, III and IV, which contribute to the generation of protonmotive force across the inner mitochondrial membrane, and drive the synthesis of ATP by the process called oxidative phosphorylation. The basic structural and functional details of these complexes are discussed. In addition, we briefly review the information on the so-called supercomplexes, aggregates of complexes I-IV, and summarize basic physiological aspects of cell respiration.

A novel automated method for the simultaneous detection of breathing frequency and amplitude in zebrafish (Danio rerio) embryos and larvae

Stress responses of fish to disruption of oxygen homeostasis include adjusted oxygen consumption rate (MO₂) as well as the hyperventilation consisting of changes in breathing frequency (f_v) and amplitude (f_ampl). However, studying the HVR in very small organisms such as zebrafish (Danio rerio) embryos and larvae is challenging, and breathing movements (i.e., f_v) are usually manually counted, which is time- and human resource-intense, error-prone and does not provide information on the amplitude of breathing movements of the response, the breathing amplitude (f_ampl). Hence, in the present study, a new automated method was developed to simultaneously measure f_v and f_ampl in small zebrafish embryos and larvae with the computer software DanioScope™. To compare HVR strategies at different life-stages of zebrafish and the physiologically linked MO₂, hatched 4 d old embryos and early gill-breathing 12 d old larvae were treated with the HVR-inducing neurotoxic compound lindane (γ-hexachlorocyclohexane; γ-HCH) as a model substance. Comparison of manually counted f_v with f_v data measured by DanioScope™ at both life-stages showed high to moderate agreement between the two methods with respect to f_v in control fish and in fish treated with lower lindane concentrations (3 - 18% deviation at 25 µg/L γ-HCH). With increasing lindane concentrations (100 and 400 µg/L γ-HCH), however, manual counts showed an average underestimation of f_v by up to 30%, mainly due to very fast, rapidly successive, and indistinct movements of the fish, which cannot be properly detected by manual counts. Automated measurement thus proved significantly more sensitive, although several pre- and post-processing steps are needed. The improved automated detection of f_v and the first reliable estimation of f_ampl in small fish embryos and larvae, as well as the inclusion of MO₂, may provide new insights into different respiratory strategies and may, thus, represent a tool to lower the detection limit for reactions of different life-stages of fish to environmental stressors. In the present study, this became evident, as early gill-breathing 12 d old zebrafish larvae showed symptoms of respiratory failure (i.e., increase in f_v, f_ampl and MO₂, followed by subsequent lethargy) after exposure to lindane, whereas skin-breathing in 4 d old embryos proved mainly insensitive to the paralytic effects of lindane.

Comparison of resting energy expenditure measured with metabolic cart and calculated with predictive formulas in critically ill patients on mechanical ventilation

INTRODUCTION

The purpose was to compare the resting energy expenditure (REE) measured with the Q-NRG™+ metabolic-cart (MREE) with REE predicted by equations (the Harris-Benedict formula and an equation developed in ward, REE-HB and REE-W, respectively). We also aimed to assess the agreement of the measurements of oxygen consumption (V̇O₂) and carbon dioxide production (V̇CO₂) at different inspired fractions of oxygen (FiO₂).

METHODS

27 mechanically ventilated ICU patients were enrolled. V̇O₂ and V̇CO₂ were measured by Q-NRG™+ during breathing 40% and 60% FiO₂. MREE was compared with REE-W and REE-HB normalized for body weight.

RESULTS

V̇O₂ was 233.0 (95.2) ml/min and 217.5 (89.8) ml/min at FiO₂ 40% and 60%, respectively (NS). V̇CO₂ was 199.0 (91.7) ml/min at FiO₂ 40%, and 197.5 (85.5) ml/min at FiO₂ 60% (NS). The REE estimated from the equations was significantly different from the MREE. The best agreement was found for the Harris-Benedict equation without correction for stress-factors. Harris-Benedict equation corrected overestimates REE.

CONCLUSIONS

This new metabolic cart Q-NRG™+ provides a concordance of values for V̇O₂ and V̇CO₂ when measured at different FiO₂, and is a reliable tool for estimating energy expenditure and assessing the nutritional needs of the patient. This study demonstrates that the estimation of REE using predictive formulas does not allow accurate calculation of metabolic demands in ventilated intensive care patient. However, predictive equations allow for a rapid assessment of REE and calculation of the amount of energy derived from different substrates.

Embryonic encapsulated development of the gastropod Acanthina monodon is impacted by future environmental changes of temperature and pCO2

Egg capsules of the gastropod Acanthina monodon were maintained during the entire period of encapsulated development at three temperatures (10, 15, 20 °C) and two pCO₂ levels (400, 1200 μatm). Embryos per capsule, size at hatching, time to hatching, embryonic metabolic rates, and the resistance of juveniles to shell breakage were quantified. No embryos maintained at 20 °C developed to hatching. The combination of temperature and pCO₂ levels had synergistic effects on hatching time and developmental success, antagonistic effects on number of hatchlings per capsule, resistance to juvenile shell cracking and metabolism, and additive effect on hatching size. Juveniles hatched significantly sooner at 15 °C, independent of the pCO₂ level that they had been exposed to, while individuals hatched at significantly smaller sizes if they had been held under 15 °C/1200 μatm rather than at 10 °C/low pCO₂. Embryos held at the higher pCO₂ had a significantly greater percentage of abnormalities. For capsules maintained at low pCO₂ and 15 °C, emerging juveniles had less resistance to shell breakage. Embryonic metabolism was significantly higher at 15 °C than at 10 °C, independent of pCO₂ level. The lower metabolism occurred in embryos maintained at the higher pCO₂ level. Thus, in this study, temperature was the factor that had the greatest effect on the encapsulated development of A. monodon, increasing the metabolism of the embryos and consequently accelerating development, which was expressed in a shorter intracapsular development time, but with smaller individuals at hatching and a lower resistance of their shells to breakage. On the other hand, the high pCO₂ level suppressed metabolism, prolonged intracapsular development, and promoted more incomplete development of the embryos. However, the combination of the two factors can mitigate--to some extent--the adverse effects of both incomplete development and lower resistance to shell breakage.

Oxygen consumption and gait dynamics in transfemoral bone-anchored prosthesis users compared to socket-prosthesis users: A cross-sectional study

BACKGROUND

A transfemoral bone-anchored prosthesis (BAP) is an alternative for the conventional socket-suspended prosthesis (SSP) in persons suffering from socket-related problems. In these persons, it has been demonstrated to reduce oxygen consumption during walking, which could be related to centre of mass (CoM) and trunk dynamics. However, it remains uncertain whether the same comparative findings are found in SSP-users without any socket-related problems.

RESEARCH QUESTION

Do oxygen consumption, CoM and trunk dynamics during walking differ between satisfied transfemoral SSP- and BAP-users and able-bodied individuals (AB); and are CoM and trunk dynamics and pistoning potential determinants of oxygen consumption?

METHODS

Oxygen consumption was measured while participants walked on a treadmill at preferred speed, 30 % slower, and 30 % faster. At preferred speed, we also evaluated CoM deviation, root-mean-square values (RMS) of mediolateral (ML) CoM and trunk excursions, and pistoning. In the prosthetic users, we evaluated whether oxygen consumption, CoM and trunk dynamics, and pistoning were associated.

RESULTS

We included BAP-users (n = 10), SSP-users (n = 10), and AB (n = 10). SSP-users demonstrated higher oxygen consumption, CoM and trunk RMS ML in comparison to AB during walking. BAP-users showed intermediate results between SSP-users and AB, yet not significantly different from either group. Greater CoM and trunk excursions were associated with higher oxygen consumption; in the SSP-users a greater degree of pistoning, in turn, was found to associate with larger trunk RMS ML.

SIGNIFICANCE

Our results indicate that satisfied SSP-users have increased oxygen consumption compared to AB subjects and use compensatory movements during walking. An assessment of CoM and trunk dynamics, and pistoning during walking may be considered for evaluating whether an individual SSP-user could possibly benefit from a BAP, in addition to the currently used functional tests for evaluating eligibility. This might lead to a larger group of persons with a transfemoral SSP benefiting from this technology.

Regional Cerebral Oxygen Saturation and Estimated Oxygen Extraction Ratio as Predictive Markers of Major Adverse Events in Infants with Congenital Heart Disease

Regional cerebral oxygen saturation (ScO₂) determined by near-infrared spectroscopy, monitoring both arterial and venous blood oxygenation of the brain, could reflect the balance between oxygen delivery and consumption. The aim of this study was to determine the predictabilities of ScO₂ and estimated oxygen extraction ratio (eO₂ER) with outcomes in infants with congenital heart disease (CHD). This study was a two-center, retrospective study of patients at 12 months of age or younger with CHD who underwent cardiac surgery. The primary outcome was a composite of one or more major adverse events (MAEs) after surgery: death from any cause, circulatory collapse that needed cardiopulmonary resuscitation, and requirement for extracorporeal membrane oxygenation. Based on the assumptions of arterial to venous blood ratio, eO₂ER was calculated. A total of 647 cases were included in this study. MAEs occurred in 16 patients (2.5%). There were significant differences in post-bypass ScO₂ [46.61 (40.90, 52.05) vs. 58.52 (51.52, 66.08), p < 0.001] and post-bypass eO₂ER [0.66 (0.60, 0.78) vs. 0.52 (0.43, 0.61), p < 0.001] between patients with MAEs and patients without MAEs. Area under the receiver operating curve (AUROC) of post-bypass ScO₂ was 0.818 (95% confidence interval: 0.747-0.889), AUROC of post-bypass eO₂ER was 0.783 (0.697-0.870) and AUROC of post-bypass maximum serum lactate level was 0.635 (0.525-0.746). Both ScO₂ and eO₂ER, especially after weaning off bypass, are acceptable predictive markers for predicting MAEs after cardiac surgery in infants.(227 words).

Acute physiological responses to steady-state arm cycling ergometry with and without blood flow restriction

PURPOSE

To compare heart rate (HR), oxygen consumption (VO₂), blood lactate (BL), and ratings of perceived exertion (RPE) during arm cycling with and without a blood flow restriction (BFR).

METHODS

Twelve healthy males (age: 23.9 ± 3.75 years) completed four, randomized, 15-min arm cycling conditions: high-workload (HW: 60% maximal power output), low-workload (LW: 30% maximal power output), low-workload with BFR (LW-BFR), and BFR with no exercise (BFR-only). In the BFR conditions, cuff pressure to the proximal biceps brachii was set to 70% of occlusion pressure. HR, VO₂, and RPE were recorded throughout the exercise, and BL was measured before, immediately after, and five minutes post-exercise. Within-subject repeated-measures ANOVA was used to evaluate condition-by-time interactions.

RESULTS

HW elicited the greatest responses in HR (91% of peak; 163.3 ± 15.8 bpm), VO₂ (71% of peak; 24.0 ± 3.7 ml kg^-1 min^-1), BL (7.7 ± 2.5 mmol L^-1), and RPE (14 ± 1.7) and was significantly different from the other conditions (p < 0.01). The LW and LW-BFR conditions did not differ from each other in HR, VO₂, BL, and RPE mean of conditions: ~ 68%, 41%, 3.5 ± 1.6 mmol L^-1, 10.4 ± 1.6, respectively; p > 0.05). During the BFR-only condition, HR increased from baseline by ~ 15% (on average) (p < 0.01) without any changes in VO₂, BL, and RPE (p > 0.05).

CONCLUSIONS

HW arm cycling elicited the largest and most persistent physiological responses compared to LW arm cycling with and without a BFR. As such, practitioners who prescribe arm cycling for their clients should be advised to augment the demands of exercise via increases in exercise intensity (i.e., power output), rather than by adding BFR.