Hand Grip Strength and Myocardial Oxygen Consumption Index among Coronary Artery Bypass Grafting Patients

BACKGROUND

Hand grip strength (HGS) is a reliable indicator of peripheral muscle strength. Although, numerous studies have investigated the strength of hand grip; little attention has been given to coronary artery disease (CAD) patients, exploring the relationship between HGS and myocardial oxygen consumption (MVO2) index. The current study aimed to evaluate the interaction between HGS and MVO2 index findings before and after cardiac surgery.

METHODS

Twenty-seven patients with CAD had HGS were assessed using handheld dynamometer. HGS for each hand were documented. MVO2 index was assessed using rate pressure product (RPP), which is the product of the heart rate (HR) and systolic blood pressure (SBP). Repeated measures MANOVA were carried out to estimate the interaction between both hands HGS and MVO2 index before and after surgery.

RESULTS

There was significant interactions (P<0.001) for both HGS dominant and non-dominant with large effect sizes (HGS dominant×MVO2 index: hp (2)=0.44; HGS dominant×RPP: hp (2)=0.49). This signifies that peripheral muscle strength of the upper limb (HGS dominant and non-dominant) had different effects on MVO2 index before and after surgery. The interaction graph shows that the increase in MVO2 index after surgery was significantly greater for peripheral muscle strength of the dominant hand when compared to non-dominant.

CONCLUSION

Patients with CAD had interactions between HGS and oxygen consumption before and after surgery. Hence, HGS might be used as a predictor to assess oxygen consumption among cardiac patients.

Influence of the temperature and oxygen exposure in red Port wine: A kinetic approach

Although phenolics are recognized to be related with health benefits by limiting lipid oxidation, in wine, they are the primary substrates for oxidation resulting in the quinone by-products with the participation of transition metal ions. Nevertheless, high quality Port wines require a period of aging in either bottle or barrels. During this time, a modification of sensory properties of wines such as the decrease of astringency or the stabilization of color is recognized to phenolic compounds, mainly attributed to anthocyanins and derived pigments. The present work aims to illustrate the oxidation of red Port wine based on its phenolic composition by the effect of both thermal and oxygen exposures. A kinetic approach toanthocyanins degradation was also achieved. For this purpose a forced red Port wine aging protocol was performed at four different storage temperatures, respectively, 20, 30, 35 and 40°C, and two adjusted oxygen saturation levels, no oxygen addition (treatment I), and oxygen addition (treatment II). Three hydroxycinnamic esters, three hydroxycinnamic acids, three hydroxybenzoic acids, two flavan-3-ols, and six anthocyanins were quantitated weekly during 63days, along with oxygen consumption. The most relevant phenolic oxidation markers were anthocyanins and catechin-type flavonoids, which had the highest decreases during the thermal and oxidative red Port wine process. Both temperature and oxygen treatments affected the rate of phenolic degradation. In addition, temperature seems to influence mostly the phenolics kinetic degradation.

Technological, environmental and biological factors: referent variance values for infrared imaging of the bovine

Background

Despite its variety of potential applications, the wide implementation of infrared technology in cattle production faces technical, environmental and biological challenges similar to other indicators of metabolic state. Nine trials, divided into three classes (technological, environmental and biological factors) were conducted to illustrate the influence of these factors on body surface temperature assessed through infrared imaging.

Results

Evaluation of technological factors indicated the following: measurements of body temperatures were strongly repeatable when taken within 10 s; appropriateness of differing infrared camera technologies was influenced by distance to the target; and results were consistent when analysis of thermographs was compared between judges. Evaluation of environmental factors illustrated that wind and debris caused decreases in body surface temperatures without affecting metabolic rate; additionally, body surface temperature increased due to sunlight but returned to baseline values within minutes of shade exposure. Examination/investigation/exploration of animal factors demonstrated that exercise caused an increase in body surface temperature and metabolic rate. Administration of sedative and anti-sedative caused changes on body surface temperature and metabolic rate, and during late pregnancy a foetal thermal imprint was visible through abdominal infrared imaging.

Conclusion

The above factors should be considered in order to standardize operational procedures for taking thermographs, thereby optimizing the use of such technology in cattle operations.

Analysis of hypoxia-induced metabolic reprogramming. Methods Enzymol. 2014;542:425-455. [PMID: 24862279 DOI: 10.1016/B978-0-12-416618-9.00022-4]

Hypoxia is a common finding in advanced human tumors and is often associated with metastatic dissemination and poor prognosis. Cancer cells adapt to hypoxia by utilizing physiological adaptation pathways that promote a switch from oxidative to glycolytic metabolism. This promotes the conversion of glucose into lactate while limiting its transformation into acetyl coenzyme A (acetyl-CoA). The uptake of glucose and the glycolytic flux are increased under hypoxic conditions, mostly owing to the upregulation of genes encoding glucose transporters and glycolytic enzymes, a process that depends on hypoxia-inducible factor 1 (HIF-1). The reduced delivery of acetyl-CoA to the tricarboxylic acid cycle leads to a switch from glucose to glutamine as the major substrate for fatty acid synthesis in hypoxic cells. In addition, hypoxia induces (1) the HIF-1-dependent expression of BCL2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3) and BNIP3-like (BNIP3L), which trigger mitochondrial autophagy, thereby decreasing the oxidative metabolism of both fatty acids and glucose, and (2) the expression of the sodium-hydrogen exchanger NHE1, which maintains an alkaline intracellular pH. Here, we present a compendium of methods to study hypoxia-induced metabolic alterations.

Differential impacts of elevated CO2 and acidosis on the energy budget of gill and liver cells from Atlantic cod, Gadus morhua

Ocean acidification impacts fish and other marine species through increased seawater PCO2 levels (hypercapnia). Knowledge of the physiological mechanisms mediating effects in various tissues of fish is incomplete. Here we tested the effects of extracellular hypercapnia and acidosis on energy metabolism of gill and liver cells of Atlantic cod. Exposure media mimicked blood conditions in vivo, either during normo- or hypercapnia and at control or acidic extracellular pH (pHe). We determined metabolic rate and energy expenditure for protein biosynthesis, Na(+)/K(+)-ATPase and H(+)-ATPase and considered nutrition status by measurements of metabolic rate and protein biosynthesis in media with and without free amino acids (FAA). Addition of FAA stimulated hepatic but not branchial oxygen consumption. Normo- and hypercapnic acidosis as well as hypercapnia at control pHe depressed metabolic stimulation of hepatocytes. In gill cells, acidosis depressed respiration independent of PCO2 and FAA levels. For both cell types, depressed respiration was not correlated with the same reduction in energy allocated to protein biosynthesis or Na(+)/K(+)-ATPase. Hepatic energy expenditure for protein synthesis and Na(+)/K(+)-ATPase was even elevated at acidic compared to control pHe suggesting increased costs for ion regulation and cellular reorganization. Hypercapnia at control pHe strongly reduced oxygen demand of branchial Na(+)/K(+)-ATPase with a similar trend for H(+)-ATPase. We conclude that extracellular acidosis triggers metabolic depression in gill and metabolically stimulated liver cells. Additionally, hypercapnia itself seems to limit capacities for metabolic usage of amino acids in liver cells while it decreases the use and costs of ion regulatory ATPases in gill cells.

Persistent reduced oxygen requirement following blood transfusion during recovery from hemorrhagic shock

Our study intended to determine the effects on oxygen uptake (VO2) of restoring a normal rate of O2 delivery following blood transfusion (BT) after a severe hemorrhage (H). Spontaneously breathing urethane anesthetized rats were bled by removing 20 ml/kg of blood over 30 min. Rats were then infused with their own shed blood 15 min after the end of H. At mid-perfusion, half of the rats received a unique infusion of the decoupling agent 2,4-dinitrophenol (DNP, 6 mg/kg). VO2 and arterial blood pressure (ABP) were continuously measured throughout the study, along with serial determination of blood lactate concentration [La]. Animals were euthanized 45 min after the end of reperfusion; liver and lungs were further analyzed for early expression of oxidative stress gene using RT-PCR. Our bleeding protocol induced a significant decrease in ABP and increase in [La], while VO2 dropped by half. The O2 deficit progressively accumulated during the period of bleeding reached -114 ± 53 ml/kg, just before blood transfusion. Despite the transfusion of blood, a significant O2 deficit persisted (-82 ± 59 ml/kg) 45 min after reperfusion. This slow recovery of VO2 was sped up by DNP injection, leading to a fast recovery of O2 deficit after reperfusion, becoming positive (+460 ± 132 ml/kg) by the end of the protocol, supporting the view that O2 supply is not the main controller of VO2 dynamics after BT. Of note is that DNP also enhanced oxidative stress gene expression (up-regulation of NADPH oxidase 4 in the lung for instance). The mechanism of slow recovery of O2 requirement/demand following BT and the resulting effects on tissues exposed to relatively high O2 partial pressure are discussed.

Vocal performance affects metabolic rate in dolphins: implications for animals communicating in noisy environments

Many animals produce louder, longer or more repetitious vocalizations to compensate for increases in environmental noise. Biological costs of increased vocal effort in response to noise, including energetic costs, remain empirically undefined in many taxa, particularly in marine mammals that rely on sound for fundamental biological functions in increasingly noisy habitats. For this investigation, we tested the hypothesis that an increase in vocal effort would result in an energetic cost to the signaler by experimentally measuring oxygen consumption during rest and a 2 min vocal period in dolphins that were trained to vary vocal loudness across trials. Vocal effort was quantified as the total acoustic energy of sounds produced. Metabolic rates during the vocal period were, on average, 1.2 and 1.5 times resting metabolic rate (RMR) in dolphin A and B, respectively. As vocal effort increased, we found that there was a significant increase in metabolic rate over RMR during the 2 min following sound production in both dolphins, and in total oxygen consumption (metabolic cost of sound production plus recovery costs) in the dolphin that showed a wider range of vocal effort across trials. Increases in vocal effort, as a consequence of increases in vocal amplitude, repetition rate and/or duration, are consistent with behavioral responses to noise in free-ranging animals. Here, we empirically demonstrate for the first time in a marine mammal, that these vocal modifications can have an energetic impact at the individual level and, importantly, these data provide a mechanistic foundation for evaluating biological consequences of vocal modification in noise-polluted habitats.

Exercise intensity criteria for routine rehabilitation therapy for stroke patients

[Purpose] The aim of this study was to observe the relationships among heart rate, rate of perceived exertion, and oxygen consumption in stroke patients and the effectiveness of improving aerobic capacity during routine rehabilitation therapy. [Subjects and Methods] Thirty-six stroke patients participated in the study. A K4b² pulmonary function device was used to record heart rate (beats per minute), oxygen consumption (Equation Section (Next)ml·min⁻¹·kg⁻¹), and rate of perceived exertion. Results were recorded after completing the following activities continuously: (1) silent sitting, (2) sit-to-stand transfers, (3) hip extension while standing against a wall, (4) weight loading on the affected leg, (5) upward and downward leg movements on a stall bar, (6) walking up and down a flight of stairs, and (7) a 60-meter walk. Correlation analyses were performed to demonstrate the relationship of oxygen consumption with HR and RPE. [Results] Moderate correlation was found between HR and oxygen consumption, and low correlation was found between rate of perceived exertion and oxygen consumption. The routine rehabilitation therapy could reduce the accumulation of lactate. [Conclusion] HR is a better index than rate of perceived exertion in evaluating exercise intensity in stroke patients. The routine rehabilitation therapy can improve the aerobic capacity of stroke patients.

Pregnancy limits lung function during exercise and depresses metabolic rate in the skink Tiliqua nigrolutea

High gestational loads have been associated with a range of ecological costs, such as decreased locomotor ability; however, the physiological mechanisms that underpin these changes are poorly understood. In this study, breathing patterns, metabolic rates, lung volume and lung diffusing capacity were measured at rest and during exercise in the pregnant skink Tiliqua nigrolutea. Breathing patterns were largely unaffected by gestation; however, decreases in metabolic rate (rate of oxygen consumption) in the late stages of pregnancy induced a relative hyperventilation. The reductions in metabolic rate during late pregnancy prevent the calculation of the maintenance cost of pregnancy based on post-partum and neonatal metabolic rates. Despite the high relative litter mass of 38.9±5.3%, lung diffusing capacity was maintained during all stages of pregnancy, suggesting that alterations in diffusion at the alveolar capillary membrane were not responsible for the relative hyperventilation. Lung volume was increased during pregnancy compared with non-pregnant females, but lung volume was significantly lower during pregnancy compared with post-partum lung volume. Pregnant females were unable to produce the same metabolic and ventilatory changes induced by exercise in non-pregnant females. This lack of ability to respond to increased respiratory drive during exercise may underpin the locomotor impairment measured during gestation in previous studies.

Effect of regular exercise on cardiopulmonary fitness in males with spinal cord injury

Objective

To evaluate the cardiopulmonary endurance of subjects with spinal cord injury by measuring the maximal oxygen consumption with varying degrees of spinal cord injury level, age, and regular exercise.

Methods

We instructed the subjects to perform exercises using arm ergometer on healthy adults at 20 years of age or older with spinal cord injury, and their maximal oxygen consumption (VO₂max) was measured with a metabolic measurement system. The exercise proceeded stepwise according to the exercise protocol and was stopped when the subject was exhausted or when VO₂ reached an equilibriu

Results

Among the 40 subjects, there were 10 subjects with cervical cord injury, 27 with thoracic cord injury, and 3 with lumbar cord injury. Twenty-five subjects who were exercised regularly showed statistically higher results of VO₂max than those who did not exercise regularly. Subjects with cervical injury showed statistically lower VO₂max than the subjects with thoracic or lumbar injury out of the 40 subjects with neurologic injury. In addition, higher age showed a statistically lower VO₂max. Lastly, the regularly exercising paraplegic group showed higher VO₂max than the non-exercising paraplegic group.

Conclusion

There are differences in VO₂max of subjects with spinal cord injury according to the degree of neurologic injury, age, and whether the subject participates in regular exercise. We found that regular exercise increased the VO₂max in individuals with spinal cord injury.

Phloretin ameliorates arsenic trioxide induced mitochondrial dysfunction in H9c2 cardiomyoblasts mediated via alterations in membrane permeability and ETC complexes

Arsenic trioxide (ATO), though a very effective drug for the treatment of acute promyelocytic leukemia, leads to cardiotoxicity. As mitochondria are the center of attention of cardiac cell׳s general metabolic status, it is primarily important to see the interaction of ATO with mitochondria. Studies related exclusively to the alterations in mitochondria and its associated functions caused by ATO are very limited. The present investigation aims to explore the effect of ATO on various components of electron transport chain, oxygen consumption, ATP production, mitochondrial superoxide generation, transmembrane potential, permeability pore opening, calcium homeostasis and apoptosis. Attempts were also made to see the efficacy of phloretin, a potent antioxidant flavonoid found majorly in apple peel on cardiotoxicity. The H9c2 cells exposed to ATO (5µM) exhibited increased oxidative stress with reduced innate antioxidant status, mitochondrial dysfunctions and apoptosis. It increased the intracellular calcium content, caused alterations in the activity of transcription factor Nrf2, xanthine oxidase, aconitase and caspase 3 compared to the control group. Phloretin at 2.5 and 5µM concentrations were able to protect the cells from ATO toxicity via protecting mitochondria through its antioxidant potential. The present investigation based on mitochondria reveals the probability of cardioprotective potential of phloretin for the cancer patients on ATO chemotherapy.

Reverse electron transport effects on NADH formation and metmyoglobin reduction

The objective was to determine if NADH generated via reverse electron flow in beef mitochondria can be used for electron transport-mediated reduction and metmyoglobin reductase pathways. Beef mitochondria were isolated from bovine hearts (n=5) and reacted with combinations of succinate, NAD, and mitochondrial inhibitors to measure oxygen consumption and NADH formation. Mitochondria and metmyoglobin were reacted with succinate, NAD, and mitochondrial inhibitors to measure electron transport-mediated metmyoglobin reduction and metmyoglobin reductase activity. Addition of succinate and NAD increased oxygen consumption, NADH formation, electron transport-mediated metmyoglobin reduction, and reductase activity (p<0.05). Addition of antimycin A prevented electron flow beyond complex III, therefore, decreasing oxygen consumption and electron transport-mediated metmyoglobin reduction. Addition of rotenone prevented reverse electron flow, increased oxygen consumption, increased electron transport-mediated metmyoglobin reduction, and decreased NADH formation. Succinate and NAD can generate NADH in bovine tissue postmortem via reverse electron flow and this NADH can be used by both electron transport-mediated and metmyoglobin reductase pathways.

Mechanism involved in Danshen-induced fluid secretion in salivary glands

AIM: Danshen’s capability to induce salivary fluid secretion and its mechanisms were studied to determine if it could improve xerostomia.

METHODS: Submandibular glands were isolated from male Wistar rats under systemic anesthesia with pentobarbital sodium. The artery was cannulated and vascularly perfused at a constant rate. The excretory duct was also cannulated and the secreted saliva was weighed in a cup on an electronic balance. The weight of the accumulated saliva was measured every 3 s and the salivary flow rate was calculated. In addition, the arterio-venous difference in the partial oxygen pressure was measured as an indicator of oxygen consumption. In order to assess the mechanism involved in Danshen-induced fluid secretion, either ouabain (an inhibitor of Na⁺/K⁺ ATPase) or bumetanide (an inhibitor of NKCC1) was additionally applied during the Danshen stimulation. In order to examine the involvement of the main membrane receptors, atropine was added to block the M₃ muscarinic receptors, or phentolamine was added to block the α₁ adrenergic receptors. In order to examine the requirement for extracellular Ca²⁺, Danshen was applied during the perfusion with nominal Ca²⁺ free solution.

RESULTS: Although Danshen induced salivary fluid secretion, 88.7 ± 12.8 μL/g-min, n = 9, (the highest value around 20 min from start of DS perfusion was significantly high vs 32.5 ± 5.3 μL/g-min by carbamylcholine, P = 0.00093 by t-test) in the submandibular glands, the time course of that secretion differed from that induced by carbamylcholine. There was a latency associated with the fluid secretion induced by Danshen, followed by a gradual increase in the secretion to its highest value, which was in turn followed by a slow decline to a near zero level. The application of either ouabain or bumetanide inhibited the fluid secretion by 85% or 93%, and suppressed the oxygen consumption by 49% or 66%, respectively. These results indicated that Danshen activates Na⁺/K⁺ ATPase and NKCC1 to maintain Cl^- release and K⁺ release for fluid secretion. Neither atropine or phentolamine inhibited the fluid secretion induced by Danshen (263% ± 63% vs 309% ± 45%, 227% ± 63% vs 309% ± 45%, P = 0.899, 0.626 > 0.05 respectively, by ANOVA). Accordingly, Danshen does not bind with M₃ or α₁ receptors. These characteristics suggested that the mechanism involved in DS-induced salivary fluid secretion could be different from that induced by carbamylcholine. Carbamylcholine activates the M₃ receptor to release inositol trisphosphate (IP₃) and quickly releases Ca²⁺ from the calcium stores. The elevation of [Ca²⁺]_i induces chloride release and quick osmosis, resulting in an onset of fluid secretion. An increase in [Ca²⁺]_i is essential for the activation of the luminal Cl^- and basolateral K⁺ channels. The nominal removal of extracellular Ca²⁺ totally abolished the fluid secretion induced by Danshen (1.8 ± 0.8 μL/g-min vs 101.9 ± 17.2 μL/g-min, P = 0.00023 < 0.01, by t-test), suggesting the involvement of Ca²⁺ in the activation of these channels. Therefore, IP₃-store Ca²⁺ release signalling may not be involved in the secretion induced by Danshen, but rather, there may be a distinct signalling process.

CONCLUSION: The present findings suggest that Danshen can be used in the treatment of xerostomia, to avoid the systemic side effects associated with muscarinic drugs.

Which type of cane is the most efficient, based on oxygen consumption and balance capacity, in chronic stroke patients?

Canes are widely prescribed as walking aids, but little is known about the effects of canes on the physiological cost of walking. The purpose of this study was to investigate the differences in oxygen consumption associated with the gaits of hemiplegic patients in terms of balance capacity according to the type of cane used. Twenty-nine patients with chronic stroke were divided into poor-balance (n=15) and relatively-better-balance groups (n=14) based on a cutoff score of 49 on the Berg balance scale (BBS). Each patient completed three consecutive days of walking with a randomly assigned singlepoint cane, quad cane, or hemi-walker. We measured the oxygen expenditure and oxygen cost using a portable gas analyzer and heart rate during a 6-min walk test (6MWT) and a 10-m walk test (10MWT). The oxygen expenditure, gait endurance, and gait velocity were higher with the single-point cane (p<0.01) than with any of the other cane types, and the oxygen costs were lower (p<0.01) with the single-point cane among the patients with relatively better balance. The oxygen cost for the quad cane was lower (p<0.01) than that found for any the other cane types among the patients with relatively poor balance. Our study revealed that single-point canes require less oxygen use at a given speed and permits greater speed at the same oxygen consumption for hemiplegic patients with good balance. Walking aids with a greater base support may be more suitable than those with a smaller base support for patients with relatively poor balance. However, our conclusions are only preliminary because of the small sample size (KCT0001076).

A repeated measures, randomised cross-over trial, comparing the acute exercise response between passive and active sitting in critically ill patients

BACKGROUND

Early mobilisation of critically ill patients is safe and beneficial, but the metabolic cost of exercise remains unquantified. This study compared the acute exercise response in critically ill participants during passive and active sitting.

METHOD

We conducted a prospective, randomised, cross-over study, in ventilated patients receiving rehabilitative physiotherapy. Ten participants completed a passive chair transfer, or a sit on the edge of the bed, followed by the alternate exercise activity on the consecutive day. The primary outcome measure was oxygen consumption.

RESULTS

In comparison to resting supine, a passive chair transfer elicited no change in oxygen consumption, carbon dioxide production or minute ventilation; but mean arterial pressure (91.86 mmHg (95% CI 84.61 to 99.10) to 101.23 mmHg (95% CI 93.35 to 109.11) (p = 0.002)) and heart rate (89.13 bpm (95% CI 77.14 to 101.13) to 97.21 bpm (95% CI 81.22 to 113.20) (p = 0.008)) increased. Sitting on the edge of the bed resulted in significant increases in oxygen consumption (262.33 ml/min (95% CI 201.97 to 322.70) to 353.02 ml/min (95% CI 303.50 to 402.55), p = 0.002), carbon dioxide production (171.93 ml/min (95% CI 131.87 to 211.98) to 206.23 ml/min (95% CI 151.03 to 261.43), p = 0.026), minute ventilation (9.97 l/min (95% CI 7.30 to 12.65) to 12.82 l/min (95% CI 10.29 to 15.36), p < 0.001), mean arterial pressure (86.81 mmHg (95% CI 77.48 to 96.14) to 95.59 mmHg (95% CI 88.62 to 102.56), p = 0.034) and heart rate (87.60 bpm (95% CI 73.64 to 101.56) to 94.91 bpm (95% CI 79.57 to 110.25), p = 0.007). When comparing the 2 activities, sitting on the edge of the bed elicited a significantly larger increase in oxygen consumption (90.69 ml/min (95% CI 44.04 to 137.34) vs 14.43 ml/min (95% CI -27.28 to 56.14), p = 0.007) and minute ventilation (2.85 l/min (95% CI 1.70 to 3.99) vs 0.74 l/min (95% CI -0.92 to 1.56), p = 0.012).

CONCLUSION

Sitting on the edge of the bed is a more metabolically demanding activity than a passive chair transfer in critically ill patients.

Energy expenditure at work in physical education teachers

The objective of this study was to quantify work energy expenditure (EE) in physical education (PE) teachers. Sixty-four (64) physical educators (49 men, 15 women) had their individualized linear function between heart rate (HR) and oxygen consumption measured by laboratory testing. HR was then recorded on 2 different days at work to estimate EE, correlated with a diary of daily tasks. Average absolute EE was low-to-moderate (2.7 ± 1.4 to 4.6 ± 2.5 kcal·min(-1)) and low when expressed in relative values (15.3 ± 6.1% to 24.8 ± 7.6% of VO2max). However, these physical educators often reached very high intensities (from 7.5 ± 7.9% to 23.8 ± 22.3% of work time at 100 bpm and more). PE teaching requires a light-to-moderate EE with more intense periods of physical activity. The variety of tasks performed (office work, supervision and monitoring, mixed participation and active participation) significantly influenced EE.

Development of a model to determine oxygen consumption when crawling

During a mine disaster or emergency, underground air can quickly become contaminated. In these circumstances, all underground mine workers are taught to don breathable air supply units at the first sign of an emergency. However, no contemporary oxygen consumption data is available for the purposes of designing breathing air supply equipment specifically for mine escape. Further, it would be useful to quantify the oxygen requirements of breathing air supply users for various escape scenarios. To address this need, 14 participants crawled a distance of 305 m each while their breath-by-breath oxygen consumption measurements were taken. Using these data, linear regression models were developed to determine peak and average oxygen consumption rates as well as total oxygen consumption. These models can be used by manufacturers of breathing air supply equipment to aid in the design of devices that would be capable of producing sufficient on-demand oxygen to allow miners to perform self-escape.

Reliability of peak O2 uptake and O2 uptake kinetics in step exercise tests in healthy subjects

To date little is known about the reliability of peak oxygen consumption (V˙O2PEAK) in incremental metronome paced step tests (IST) and the reliability of on-kinetics V˙O2 has never been studied. We aimed to study the reliability of both tests. Eleven healthy subjects performed two ISTs until exhaustion. On two different days two duplicate 4min constant metronome paced step tests (CST) were performed. V˙O2PEAK, mean response time (MRT) and phase II time constant (τ) were tested for reproducibility using the paired t-tests, in addition to the limits of agreement (LOA) and within subject coefficient of variation (COV). With a 95% LOA of 0.38 to 0.26Lmin(-1), -8.7 to 9.1s and -9.9 to 10.5s they exhibit a COV of 3%, 4.5% and 6.9% for V˙O2PEAK, MRT and τ respectively. ST are sufficiently reliable for maximal and submaximal aerobic power assessments in healthy subjects and new studies of oxygen uptake kinetics in selected patient groups are warranted.

Normobaric hyperoxia alters the microcirculation in healthy volunteers

The use of high concentrations of inhaled oxygen has been associated with adverse effects but recent data suggest a potential therapeutic role of normobaric hyperoxia (NH) in sepsis and cerebral ischemia. Hyperoxia may induce vasoconstriction and alter endothelial function, so we evaluated its effects on the microcirculation in 40 healthy adult volunteers using side-stream dark field (SDF) video-microscopy on the sublingual area and near-infrared spectroscopy (NIRS) on the thenar eminence. In a first group of volunteers (n=18), measurements were taken every 30 min: at baseline in air, during NH (close to 100% oxygen via a non-rebreathing mask) and during recovery in air. In a second group (n=22), NIRS measurements were taken in NH or ambient air on two separate days to prevent any potential influence of repeated NIRS measurements. NH significantly decreased the proportion of perfused vessels (PPV) from 92% to 66%, perfused vessel density (PVD) from 11.0 to 7.3 vessels/mm, perfused small vessel density (PSVD) from 9.0 to 5.8 vessels/mm and microvascular flow index (MFI) from 2.8 to 2.0, and increased PPV heterogeneity from 7.5% to 30.4%. Thirty minutes after return to air, PPV, PVD, PSVD and MFI remained partially altered. During NH, NIRS descending slope and NIRS muscle oxygen consumption (VO2) decreased from 8.5 to 7.9%/s and 127 to 103 units, respectively, in the first group and from 10.7 to 9.4%/s and 150 to 115 units in the second group. NH, therefore, alters the microcirculation in healthy subjects, decreasing capillary perfusion and VO2 and increasing the heterogeneity of the perfusion.

Docosahexaenoic and arachidonic acid peroxidation: It's a within molecule cascade

Peroxidation is a well-known natural phenomenon associated with both health and disease. We compared the peroxidation kinetics of phosphatidylcholine (PC) molecules with different fatty acid compositions (i.e. 18:0, 18:1n-9, 18:2n-6, 20:4n-6 and 22:6n-3 at the sn-2 and 16:0 at sn-1 position) either as molecules free in solution or formed into liposomes. Fatty acid levels, oxygen consumption plus lipid hydroperoxide and malondialdehyde production were measured from the same incubations, at the same time during maximal elicitable peroxidation. PCs with highly peroxidizable fatty acids (i.e. 20:4n-6 and 22:6n-3) in the same incubation were found to be either fully peroxidized or intact. Rates of peroxidation of PCs with multiple bisallylic groups (i.e. 20:4n-6 and 22:6n-3) peroxidized at 2-3 times the rate per bisallylic bond than the same phospholipid with 18:2n-6. The results suggest that propagation of peroxidation (H-atom transfer) is firstly an intramolecular process that is several-fold faster than intermolecular peroxidation. PCs in solution peroxidized twice as fast as those in liposomes suggesting that only half of the phospholipids in liposomes were available to peroxidize i.e. the outer leaflet. Experiments on liposomes suggest that even after heavy peroxidation of the outer leaflet the inner leaflet is unaffected, indicating how cells may protect themselves from external peroxidation and maintain control over internal peroxidation. Intramolecular peroxidation may produce highly concentrated, localized sites of peroxidation product that together with internal control of peroxidation of the inner leaflet of membranes provide new insights into how cells control peroxidation at the membrane level.

Multidimensional outcome measure of selective dorsal rhizotomy in spastic cerebral palsy

BACKGROUND

One of the treatment option to reduce spasticity in cerebral palsy children is selective dorsal rhizotomy. Several studies have demonstrated short and long term improvements in gait and other activities after rhizotomy but this surgery still remains a controversial procedure and patient outcome indicators measures are not uniform.

AIMS

To describe our assessment and outcome evaluation protocol and to verify by this protocol short term results of rhizotomy.

METHODS

We recruited 9 cerebral palsy children (mean age 7.9 years ± 3.2) affected by mild to moderate spastic diplegia and operated by rhizotomy. Patients were studied preoperatively and at 12 months after surgery by the following clinical and instrumental measures correlated to the International Classification of Functioning: modified Ashworth Scale, passive Range of Motion, Medical Research Council Scale, Selective Motor Control Scale, 3D-motion analysis and energy cost of locomotion measurements (indicators of "body functions"); Gross Motor Functional Measure and Motor Functional Independence Measure (indicators of "activities and participation").

RESULTS

Our data showed, after rhizotomy, reduction of spasticity specially in plantarflexors muscles (p < 0.01), increase of strength of knee flexors/extensors and foot plantar/dorsiflexion muscles (p < 0.01), improvement of selective motor control (p < 0.05), more similar spatio-temporal parameters of gait analysis to healthy subjects, reduced equinus foot and knees hyperflexion as energy cost.

CONCLUSION

The complementary use of multiple indicators may improve the evaluation of the results of dorsal rhizotomy. A beneficial outcome measured by these indicators has been found in our spastic diplegic children one year after rhizotomy.

Estimating oxygen consumption from heart rate using adaptive neuro-fuzzy inference system and analytical approaches

In new approaches based on adaptive neuro-fuzzy systems (ANFIS) and analytical method, heart rate (HR) measurements were used to estimate oxygen consumption (VO2). Thirty-five participants performed Meyer and Flenghi's step-test (eight of which performed regeneration release work), during which heart rate and oxygen consumption were measured. Two individualized models and a General ANFIS model that does not require individual calibration were developed. Results indicated the superior precision achieved with individualized ANFIS modelling (RMSE = 1.0 and 2.8 ml/kg min in laboratory and field, respectively). The analytical model outperformed the traditional linear calibration and Flex-HR methods with field data. The General ANFIS model's estimates of VO2 were not significantly different from actual field VO2 measurements (RMSE = 3.5 ml/kg min). With its ease of use and low implementation cost, the General ANFIS model shows potential to replace any of the traditional individualized methods for VO2 estimation from HR data collected in the field.

Temporary forced oral breathing affects neonates oxygen consumption, carbon dioxide elimination, diaphragm muscles structure and physiological parameters

OBJECTIVES

We studied adaptation of diaphragm, oxygen consumption and carbon dioxide elimination to forced oral breathing (lasting for only 4 days) following reversible bilateral nasal obstruction performed on day 8 post-natal male rats.

METHODS

Diaphragm myosin heavy chain (MHC) composition, oxygen consumption, carbon dioxide elimination and hormones level were analysed during nasal obstruction period.

RESULTS

Diaphragm muscle showed significant increases in adult isoforms (MHC 1, 2a) in oral breathing group versus control. Reversible nasal obstruction was associated with a decrease of oxygen consumption and carbon dioxide elimination. Nasal obstruction period was associated with reduced growth of the olfactory bulbs and an initial decrease in lung growth. One day after implementing nasal obstruction, basal corticosterone levels had increased (by over 1000). Oral breathing was also associated with a lower level of thyroid hormone.

CONCLUSIONS

We conclude that a 4 day nasal obstruction period in young rats leads to hormonal changes and to Diaphragm myosin heavy chain structural adaptation.

Comparing the physiological and perceptual responses of construction workers (bar benders and bar fixers) in a hot environment

This study aimed to (1) quantify the respective physical workloads of bar bending and fixing; and (2) compare the physiological and perceptual responses between bar benders and bar fixers. Field studies were conducted during the summer in Hong Kong from July 2011 to August 2011 over six construction sites. Synchronized physiological, perceptual, and environmental parameters were measured from construction rebar workers. The average duration of the 39 field measurements was 151.1 ± 22.4 min under hot environment (WBGT = 31.4 ± 2.2 °C), during which physiological, perceptual and environmental parameters were synchronized. Energy expenditure of overall rebar work, bar bending, and bar fixing were 2.57, 2.26 and 2.67 Kcal/min (179, 158 and 186 W), respectively. Bar fixing induced significantly higher physiological responses in heart rate (113.6 vs. 102.3 beat/min, p < 0.05), oxygen consumption (9.53 vs. 7.14 ml/min/kg, p < 0.05), and energy expenditure (2.67 vs. 2.26 Kcal/min, p < 0.05) (186 vs. 158 W, p < 0.05) as compared to bar bending. Perceptual response was higher in bar fixing but such difference was not statistically significant. Findings of this study enable the calculation of daily energy expenditure of rebar work.

Vasodilating prostaglandin E1 does not reproduce interleukin-1β-induced oxygen metabolism abnormalities in rabbits

Background

We have reported that administration of recombinant human interleukin (IL)-1β induced circulatory shock in rabbits by causing overproduction of vasodilating prostaglandin(s) and simultaneously impaired oxygen metabolism by causing an abnormal dependence of oxygen consumption (VO₂) on oxygen delivery (DO₂). The present study was carried out to compare the effect of administration of exogenous PGE₁ with that of IL-1β on oxygen metabolism.

Methods

Sixteen rabbits were assigned to one of three groups and given a single injection of 10 μg/kg IL-1β (IL-1β group, n = 5), continuous infusion of 1 μg/kg/min PGE₁ (PGE₁ group, n = 6), or saline (control group, n = 5). All rabbits were subjected to stepwise cardiac tamponade to decrease DO₂ by inflating a balloon placed into the pericardial sac. The VO₂/DO₂ relation was analyzed by the dual-line method.

Results

Both IL-1β and PGE₁ decreased the baseline value of mean arterial pressure by approximately 25% without inducing significant alteration of the cardiac index. With respect to the VO₂/DO₂ relation, the slope of the supply-independent line was significantly increased in the IL-1β group (y = 0.13x + 6.4), but not in the PGE₁ group (y = 0.01x + 10.0) compared to that in the control group (y = 0.05x + 8.7).

Conclusion

These results indicate that simple vasodilation and hypotension induced by administration of PGE₁ are insufficient to account for the abnormal oxygen metabolism induced by IL-1β.

Acute effects of physical exercise in type 2 diabetes: A review

The literature has shown the efficiency of exercise in the control of type 2 diabetes (T2D), being suggested as one of the best kinds of non-pharmacological treatments for its population. Thus, the scientific production related to this phenomenon has growing exponentially. However, despite its advances, still there is a lack of studies that have carried out a review on the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in individuals with T2D, not to mention that in a related way, these themes have been very little studied today. Therefore, the aim of this study was to organize and analyze the current scientific production about the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in T2D individuals. For such, a research with the following keywords was performed: -exercise; diabetes and post-exercise hypotension; diabetes and excess post-exercise oxygen consumption; diabetes and acute effects in PUBMED, SCIELO and HIGHWIRE databases. From the analyzed studies, it is possible to conclude that, a single exercise session can promote an increase in the bioavailability of nitric oxide and elicit decreases in postexercise blood pressure. Furthermore, the metabolic stress from physical exercise can increase the oxidation of carbohydrate during the exercise and keep it, in high levels, the post exercise consumption of O_², this phenomenon increases the rate of fat oxidation during recovery periods after exercise, improves glucose tolerance and insulin sensitivity and reduces glycemia between 2-72 h, which seems to be dependent on the exercise intensity and duration of the effort.

Functional relevance of mitochondrial abnormalities in sporadic inclusion body myositis

Cytochrome c oxidase (COX)-deficient fibers and multiple mitochondrial DNA (mtDNA) deletions are frequent findings in sporadic inclusion body myositis (s-IBM). However, the functional impact of these defects is not known. We investigated oxygen desaturation during exercise using the forearm exercise test, accumulation of lactate during exercise using a cycle ergometry test and mitochondrial changes (COX-deficient fibers, biochemical activities of respiratory chain complexes, multiple mtDNA deletions by long-range polymerase chain reaction) in 10 patients with s-IBM and compared the findings with age and sex-matched normal and diseased controls (without mitochondrial disorders) as well as patients with mitochondrial disorder due to nuclear gene defects resulting in multiple mtDNA deletions (MITO group). The mean age of the s-IBM patients was 68.2 ± 5.7 years (range: 56-75). Patients with s-IBM had statistically significantly reduced oxygen desaturation (ΔsO2) during the handgrip exercise (p<0.05) and elevated peak serum lactate levels during cycle ergometry compared to normal controls (p<0.05). The percentage of COX-deficient fibers in s-IBM and MITO patients was significantly increased compared to normal controls (p<0.01). Five out of nine s-IBM patients had multiple mtDNA deletions. Thirty-three percent of s-IBM patients showed an increased citrate synthase content and decreased activities of complex IV (COX). The biochemical pattern of respiratory chain complexes in patients with s-IBM and MITO was similar. Histopathological analysis showed similar changes in s-IBM and MITO due to nuclear gene defects. Functional tests reflecting mitochondrial impairment suggest a contribution of mitochondrial defects to disease-related symptoms such as fatigue and exertion-induced symptoms.

Activity of a novel strobilurin fungicide benzothiostrobin against Sclerotinia sclerotiorum

Benzothiostrobin is a novel strobilurin fungicide. In this study, baseline sensitivity of Sclerotinia sclerotiorum (Lib.) de Bary to benzothiostrobin was determined using 100 strains collected during 2012 and 2013 from different geographical regions in Jiangsu Province of China, and the average EC50 value was 0.0218 (± 0.0111)μg/mL for mycelial growth. After benzothiostrobin treatment, hyphae were contorted with offshoot of top increasing and cell membrane permeability increased markedly, while sclerotial production and oxalic acid content significantly decreased. Benzothiostrobin strongly inhibited mycelial respiration within 12h and the oxygen consumption of the mycelia could not be inhibited after 24h. On detached rapeseed leaves, the protective and curative activity test of benzothiostrobin suggested that benzothiostrobin had good control efficiency against S. sclerotiorum, and protective activity was better than curative activity. These results will contribute to us evaluating the potential of the new strobilurin fungicide benzothiostrobin for management of diseases caused by S. sclerotiorum and understanding the mode of action of benzothiostrobin against S. sclerotiorum.

Critical windows in embryonic development: Shifting incubation temperatures alter heart rate and oxygen consumption of Lake Whitefish (Coregonus clupeaformis) embryos and hatchlings

Critical windows are periods of developmental susceptibility when the phenotype of an embryonic, juvenile or adult animal may be vulnerable to environmental fluctuations. Temperature has pervasive effects on poikilotherm physiology, and embryos are especially vulnerable to temperature shifts. To identify critical windows, we incubated whitefish embryos at control temperatures of 2°C, 5°C, or 8°C, and shifted treatments among temperatures at the end of gastrulation or organogenesis. Heart rate (fH) and oxygen consumption ( [Formula: see text] ) were measured across embryonic development, and [Formula: see text] was measured in 1-day old hatchlings. Thermal shifts, up or down, from initial incubation temperatures caused persistent changes in fH and [Formula: see text] compared to control embryos measured at the same temperature (2°C, 5°C, or 8°C). Most prominently, when embryos were measured at organogenesis, shifting incubation temperature after gastrulation significantly lowered [Formula: see text] or fH. Incubation at 2°C or 5°C through gastrulation significantly lowered [Formula: see text] (42% decrease) and fH (20% decrease) at 8°C, incubation at 2°C significantly lowered [Formula: see text] (40% decrease) and fH (30% decrease) at 5°C, and incubation at 5°C and 8°C significantly lowered [Formula: see text] at 2°C (27% decrease). Through the latter half of development, [Formula: see text] and fH in embryos were not different from control values for thermally shifted treatments. However, in hatchlings measured at 2°C, [Formula: see text] was higher in groups incubated at 5°C or 8°C through organogenesis, compared to 2°C controls (43 or 65% increase, respectively). Collectively, these data suggest that embryonic development through organogenesis represents a critical window of embryonic and hatchling phenotypic plasticity. This study presents an experimental design that identified thermally sensitive periods for fish embryos.

Increased physiologic intensity during walking and running on a non-motorized, curved treadmill

OBJECTIVE

To determine whether exercise performed on a non-motorized, curved treadmill (NMCT) provides greater physiologic stimulus compared to a standard motorized treadmill (SMT).

STUDY DESIGN

Crossover.

SETTING

Clinical research laboratory.

PARTICIPANTS

10 healthy athletic adults.

MAIN OUTCOME MEASURES

Participants walked (1.34 m s(-1)) for 3 min and ran (2.24 m s(-1)) for 4 min on NMCT and SMT (randomized order) while metabolic data and rating of perceived exertion (RPE) were collected. Participants then identified preferred easy and moderate intensity training paces on each treadmill while blinded to speed. Repeated-measures ANOVA and Wilcoxon Signed-Rank tests were used to compare responses between treadmills.

RESULTS

Intensity was significantly greater (P < 0.001) for NMCT than SMT [mean (95% confidence interval): Walking = 5.9(5.3,6.4) vs. 3.4(3.0,3.7) METs; Running = 10.7(9,6,11.7) vs. 7.3(6.8,7.8) METs]. Overall RPE was significantly greater (P < 0.01) on NMCT than SMT for walking [median (inter-quartile range): 7(1) vs. 6(0.8)] and running [11.5(3) vs. 8(2.5)]. Preferred speed was significantly slower on NMCT than SMT for easy [2.5(2.3,2.7) vs. 2.8(2.5,3.1) m s(-1)] and moderate [3.2(3.0,3.4) vs. 3.5(3.1,3.9) m s(-1)] intensities.

CONCLUSIONS

NMCT elicits greater physiological stimulus than SMT with small, though statistically significant, changes in RPE at matched speeds. Clinicians must be aware of differences in intensity and RPE when prescribing exercise on NMCT.

Measuring dissolved oxygen to track erythroid differentiation of hematopoietic progenitor cells in culture

As stem cell technologies move from the developmental to the commercial stage strategies must be developed to monitor culture operations. These will ensure consistency of differentiation programs and maintenance of optimum cell viability during production runs. Due to the sensitivity of stem cells to their environment, and their variability in response to external stimuli, accurate monitoring of in vitro conditions will be crucial for effective large-scale culturing of therapeutic stem cells. Here we describe a simple method to monitor the expansion and maturation of adult human haematopoietic stem/progenitor cells into red blood cells in vitro by measuring the oxygen consumption rate of cultures. Cell cultures followed a characteristic pattern of oxygen consumption that is reflective of in vivo erythroid maturation. This method could be easily developed as an online system to map erythroid differentiation and maturation of cultured cells as effectively as the more time consuming process of flow cytometric analysis of surface marker expression patterns.

Extended lifespan, reduced body size and leg skeletal muscle mass, and decreased mitochondrial function in clk-1 transgenic mice

Mutational inactivation of clk-1, which encodes an enzyme necessary for the biosynthesis of coenzyme Q (CoQ), extends the lifespan of Caenorhabditis elegans. However, whether mammalian clk-1 regulates the lifespan of mice is not known because clk-1-deficiencies are embryonic lethal. Here, we investigated the lifespan of clk-1 transgenic mice (Tg96/I), which were rescued from embryonic lethality via the transgenic expression of mouse clk-1. Tg96/I mice lived longer and had smaller bodies than wild-type mice, but Tg96/I mice had CoQ levels equivalent to wild-type mice. The small-sized Tg96/I mice exhibited reduced whole-body oxygen consumption (VO2) during the dark period, and lean leg skeletal muscles with reduced mitochondrial VO2 and ATP content compared with wild-type mice. These findings indicate a close relationship between lifespan extension and decreased mitochondrial function, which was induced by the transgenic expression of clk-1, in leg skeletal muscles that exhibit high metabolic activity.

Hemodynamic effects of Ivabradine in addition to dobutamine in patients with severe systolic dysfunction

BACKGROUND

Dobutamine induced tachycardia increases myocardial oxygen consumption and impairs ventricular filling. We hypothesized that Ivabradine may be efficient to control dobutamine induced tachycardia.

METHODS

We assessed the effects of Ivabradine in addition to dobutamine in stable heart failure (HF) patients (LVEF < 35%, n = 22, test population) and validated its effects in refractory cardiogenic shock patients (n = 9, validation population) with contraindication to cardiac assistance or transplant. In the test population (62 ± 17 years, LVEF = 24 ± 8%), systolic and diastolic function were assessed at rest and under dobutamine [10 γ/min], before and after Ivabradine [5mg per os]. In the validation population (54 ± 11 years, LVEF = 22 ± 7%), Ivabradine [5mg twice a day] was added to the dobutamine infusion.

RESULTS

In the test population, Ivabradine decreased heart rate [HR] at rest and during dobutamine echocardiography (-9 ± 8 bpm, P = 0.0004). The decrease in HR was associated with a decrease in cardiac power output and an increase in diastolic duration at rest (+ 74 ± 67 ms, P = 0.0002), and during dobutamine infusion (+ 75 ± 67 ms, P < 0.0001). Change in LVEF during dobutamine was greater after Ivabradine treatment than before (+ 7.2 ± 4.7% vs. + 3.6 ± 4.2%, P = 0.002). In the validation population, Ivabradine decreased HR (-18 ± 11 bpm, P = 0.008) and improved diastolic filling time (+ 67 ± 42 ms, P = 0.012) without decreasing cardiac output. At 24h, Ivabradine improved systolic blood pressure (+ 9 ± 5 mmHg, P = 0.007), daily urine output (+ 0.7 ± 0.5L, P = 0.008), oxygen balance (ΔScv02 = + 13 ± 15%, P = 0.010), and NT-pro BNP (-2270 ± 1912 pg/mL, P = 0.017). Finally, only 2/9 (22%) patients died whereas expected mortality determined from a historical cohort was 78% (P = 0.017).

CONCLUSION

This pilot study demonstrates the safety and potential benefit of a HR lowering agent in cardiogenic shock.

Inhibition of cytoplasmic p53 differentially modulates Ca(2+) signaling and cellular viability in young and aged striata

The p53 protein, a transcription factor with many gene targets, can also trigger apoptosis in the cytoplasm. The disruption of cell homeostasis, such as Ca(2+) signaling and mitochondrial respiration, contributes to the loss of viability and ultimately leads to cell death. However, the link between Ca(2+) signaling and p53 signaling remains unclear. During aging, there are alterations in cell physiology that are commonly associated with a reduced adaptive stress response, thus increasing cell vulnerability. In this work, we examined the effects of a cytoplasmic p53 inhibitor (pifithrin μ) in the striatum of young and aged rats by evaluating Ca(2+) signaling, mitochondrial respiration, apoptotic protein expression, and tissue viability. Our results showed that pifithrin μ differentially modulated cytoplasmic and mitochondrial Ca(2+) in young and aged rats. Cytoplasmic p53 inhibition appeared to reduce the mitochondrial respiration rate in both groups. In addition, p53 phosphorylation and Bax protein levels were elevated upon cytoplasmic p53 inhibition and could contribute to the reduction of tissue viability. Following glutamate challenge, pifithrin μ improved cell viability in aged tissue, reduced reactive oxygen species (ROS) generation, and reduced mitochondrial membrane potential (ΔΨm). Taken together, these results indicate that cytoplasmic p53 may have a special role in cell viability by influencing cellular Ca(2+) homeostasis and respiration and may produce differential effects in the striatum of young and aged rats.

Applying the cost of generating force hypothesis to uphill running

Historically, several different approaches have been applied to explain the metabolic cost of uphill human running. Most of these approaches result in unrealistically high values for the efficiency of performing vertical work during running uphill, or are only valid for running up steep inclines. The purpose of this study was to reexamine the metabolic cost of uphill running, based upon our understanding of level running energetics and ground reaction forces during uphill running. In contrast to the vertical efficiency approach, we propose that during incline running at a certain velocity, the forces (and hence metabolic energy) required for braking and propelling the body mass parallel to the running surface are less than during level running. Based on this idea, we propose that the metabolic rate during uphill running can be predicted by a model, which posits that (1) the metabolic cost of perpendicular bouncing remains the same as during level running, (2) the metabolic cost of running parallel to the running surface decreases with incline, (3) the delta efficiency of producing mechanical power to lift the COM vertically is constant, independent of incline and running velocity, and (4) the costs of leg and arm swing do not change with incline. To test this approach, we collected ground reaction force (GRF) data for eight runners who ran thirty 30-second trials (velocity: 2.0–3.0 m/s; incline: 0–9°). We also measured the metabolic rates of eight different runners for 17, 7-minute trials (velocity: 2.0–3.0 m/s; incline: 0–8°). During uphill running, parallel braking GRF approached zero for the 9° incline trials. Thus, we modeled the metabolic cost of parallel running as exponentially decreasing with incline. With that assumption, best-fit parameters for the metabolic rate data indicate that the efficiency of producing mechanical power to lift the center of mass vertically was independent of incline and running velocity, with a value of ∼29%. The metabolic cost of uphill running is not simply equal to the sum of the cost of level running and the cost of performing work to lift the body mass against gravity. Rather, it reflects a constant cost of perpendicular bouncing, decreased costs of parallel braking and propulsion and of course the cost of lifting body mass against gravity.

Inhibition of mitochondrial glycerol-3-phosphate dehydrogenase by α-tocopheryl succinate

α-Tocopheryl succinate (TOS), a redox-silent analogue of vitamin E, suppresses cell growth in a number of clinical and experimental cancers, inhibits mitochondrial succinate dehydrogenase (SDH) and activates reactive oxygen species (ROS) generation. The aim of this study was to test whether TOS also inhibits glycerol-3-phosphate dehydrogenase (mGPDH), another flavoprotein-dependent enzyme of the mitochondrial respiratory chain because there are differences between electron transfer pathway from SDH and mGPDH to coenzyme Q pool. For our experiments brown adipose tissue mitochondria with high expression of mGPDH were used. Our data showed that inhibition of glycerol-3-phosphate (GP)-dependent oxygen consumption by TOS was more pronounced than the succinate (SUC)-dependent one (50% inhibition was reached at 10 μmol/l TOS vs. 80 μmol/l TOS, respectively). A comparison of the inhibitory effect of TOS on GP-oxidase, GP-cytochrome c oxidoreductase and GP-dehydrogenase activities showed that TOS directly interacts with the dehydrogenase. After TOS application the GP-dependent generation of ROS was highly depressed. It may thus be concluded that TOS-induced inhibition of mGPDH is more pronounced than TOS-induced inhibition of SDH and that the inhibitory effect of TOS for both substrates is exerted at different locations of the particular dehydrogenases. Our data indicate that the inhibition of mGPDH activity could also play a role in TOS-induced growth suppression in neoplastic cells.

Oxidation of hydrogen sulfide by human liver mitochondria

Hydrogen sulfide (H2S) is the third gasotransmitter discovered. Sulfide shares with the two others (NO and CO) the same inhibiting properties towards mitochondrial respiration. However, in contrast with NO or CO, sulfide at concentrations lower than the toxic (μM) level is an hydrogen donor and a substrate for mitochondrial respiration. This is due to the activity of a sulfide quinone reductase found in a large majority of mitochondria. An ongoing study of the metabolic state of liver in obese patients allowed us to evaluate the sulfide oxidation capacity with twelve preparations of human liver mitochondria. The results indicate relatively high rates of sulfide oxidation with a large variability between individuals. These observations made with isolated mitochondria appear in agreement with the main characteristics of sulfide oxidation as established before with the help of cellular models.

Brain perfusion and oxygenation

Maintenance of brain perfusion and oxygenation is of paramount importance to patient outcome with various types of brain injuries (traumatic, ischemic, and hemorrhagic). Historically, monitoring of intracranial pressure and cerebral perfusion pressure has been the mainstay of neuromonitoring techniques used at the critical care bedside to monitor brain perfusion and oxygenation. This article describes the bedside neuromonitoring techniques that have emerged for use with these patients in the critical care area. To give the reader an understanding of the functionality of these neuromonitoring techniques, the article first summarizes the physiology of brain perfusion and oxygenation.

The influence of active and passive smoking on the cardiorespiratory fitness of adults

BACKGROUND

The aim of this study was to analyze the influence of active and passive smoking on cardiorespiratory responses in asymptomatic adults during a sub-maximal-exertion incremental test.

METHODS

The participants (n = 43) were divided into three different groups: active smokers (n = 14; aged 36.5 ± 8 years), passive smokers (n = 14; aged 34.6 ± 11.9 years) and non-smokers (n = 15; aged 30 ± 8.1 years). They all answered the Test for Nicotine Dependence and underwent anthropometric evaluation, spirometry and ergospirometry according to the Bruce Treadmill Protocol.

RESULTS

VO2max differed statistically between active and non-smokers groups (p < 0.001) and between non-smokers and passive group (p=0.022). However, there was no difference between the passive and active smokers groups (p=0.053). Negative and significant correlations occurred between VO2max and age (r = - 0.401, p = 0.044), percentage of body fat (r = - 0.429, p = 0.011), and waist circumference (WC) (r = - 0.382, p = 0.025).

CONCLUSION

VO2max was significantly higher in non-smokers compared to active smokers and passive smokers. However, the VO2max of passive smokers did not differ from active smokers.

PHA-induced inflammation is not energetically costly in the subterranean rodent Ctenomys talarum (tuco-tucos)

Immune activity has been proposed to be associated with substantial costs, due to trade-offs with other functions or activities that share common resources and contribute to an animal's fitness. However, direct estimates of the cost of mounting an immune response are few and have been performed mainly in birds. Thus, further work is needed to clarify the relative costs of different components of the immune system and the role of environmental and life-history traits in modulating the costs of resistance. Within the components of immunity, inflammation is considered to be associated with a larger energetic expenditure. Here, we evaluated the energetic cost of the inflammatory response to phytohemagglutinin (PHA) in a wild population of a subterranean rodent, Ctenomys talarum, and the trade-offs between immune activity and reproduction. C. talarum develops an inflammatory response to PHA, but contrary to our predictions, this response was not associated with an increase in oxygen consumption regardless of reproductive status or sex. Our study shows that an immune challenge may not always result in a detectable energetic cost. We discuss the possibility that other currencies could be underlying the cost, such as micro-or macronutrients requirements, autoimmunity or oxidative stress.

Influence of inhalation injury on energy expenditure in severely burned children

OBJECTIVE

Determine the effect of inhalation injury on burn-induced hypermetabolism in children.

DESIGN

Prospective study comparing hypermetabolism (i.e., resting energy expenditure and oxygen consumption) in burned children with and without inhalation injury during acute hospitalization.

SETTING

Single pediatric burn center.

PATIENTS

Eighty-six children (1-18 years) with ≥40% total body surface area burns were stratified to two groups: no inhalation injury and inhalation injury.

INTERVENTIONS

None.

MAIN MEASUREMENTS AND RESULTS

Inhalation injury was diagnosed based on bronchoscopic evaluation. At admission, PaO2:FiO2 ratios (an index of respiratory distress) were significantly higher in patients with no inhalation injury than in patients with inhalation injury. No differences were detected in resting energy expenditure or percent of the predicted basal metabolic rate between groups. Additionally, oxygen consumption did not significantly differ between groups.

CONCLUSIONS

Inhalation injury does not augment the burn-induced hypermetabolic stress response in children, as reflected by resting energy expenditure and oxygen consumption.

Acute effects of cadmium and copper on survival, oxygen consumption, ammonia-N excretion, and metal accumulation in juvenile Exopalaemon carinicauda

Ridgetail white prawn (Exopalaemon carinicauda), a commercially important species in China, is a potential candidate for evaluating impairments caused by environmental pollutants in coastal and estuarine areas. The main purpose of the present study was to investigate the acute effects of cadmium (Cd) and copper (Cu) on survival, oxygen consumption, ammonia-N excretion, and metal accumulation in E. carinicauda. The feasibility of using this species for pollution monitoring was also evaluated. Results showed that the median lethal concentrations (LC50) for 24h, 48h, 72h, and 96h were 0.66mg/L, 0.379mg/L, 0.343mg/L, and 0.258mg/L for Cd, and 0.932mg/L, 0.748mg/L, 0.725mg/L, and 0.712mg/L for Cu. Cd exposure (0.66mg/L) caused an inhibition in oxygen consumption of 21.1 percent and an increase in ammonia-N excretion of 47.1 percent, thereby decreasing the atomic ratio of oxygen consumed to nitrogen consumed (O:N ratio) of 46.32 percent relative to the control. Cu exposure (0.932mg/L) also resulted in an inhibition in oxygen consumption of 34.8 percent and a decrease in the O:N ratio of 23.9 percent in relation to the control, but the ammonia-N excretion was not influenced by the Cu exposure. Concentration-depended accumulation was observed in the experimental animals, which a maximum of 244.8 folds and 1.1 folds increase of mental concentration was measured upon exposure to 24h LC50 of Cd and Cu for 24h, respectively. The change in O:N ratio indicated an alteration in energy utilization. Based on its sensitivity to heavy metals and its availability all year round, E. carinicauda can be used as a test organism to monitor for metal pollution.

The effect of foot orthoses and in-shoe wedges during cycling: a systematic review

Background

The use of foot orthoses and in-shoe wedges in cycling are largely based on theoretical benefits and anecdotal evidence. This review aimed to systematically collect all published research on this topic, critically evaluate the methods and summarise the findings.

Methods

Study inclusion criteria were: all empirical studies that evaluated the effects of foot orthoses or in-shoe wedges on cycling; outcome measures that investigated physiological parameters, kinematics and kinetics of the lower limb, and power; and, published in English. Studies were located by data-base searching (Medline, CINAHL, Embase and SPORTDiscus) and hand-searching in February 2014. Selected studies were assessed for methodological quality using a modified Quality Index. Data were synthesised descriptively. Meta-analysis was not performed as the included studies were not sufficiently homogeneous to provide a meaningful summary.

Results

Six studies were identified as meeting the eligibility criteria. All studies were laboratory-based and used a repeated measures design. The quality of the studies varied, with Quality Index scores ranging from 7 to 10 out of 14. Five studies investigated foot orthoses and one studied in-shoe wedges. Foot orthoses were found to increase contact area in the midfoot, peak pressures under the hallux and were perceived to provide better arch support, compared to a control. With respect to physiological parameters, contrasting findings have been reported regarding the effect foot orthoses have on oxygen consumption. Further, foot orthoses have been shown to not provide effects on lower limb kinematics and perceived comfort. Both foot orthoses and in-shoe wedges have been shown to provide no effect on power.

Conclusion

In general, there is limited high-quality research on the effects foot orthoses and in-shoe wedges provide during cycling. At present, there is some evidence that during cycling foot orthoses: increase contact area under the foot and increase plantar pressures under the hallux, but provide no gains in power. Based on available evidence, no definitive conclusions can be made about the effects foot orthoses have on lower limb kinematics and oxygen consumption, and the effect in-shoe wedges have on power during cycling. Future well-designed studies on this topic are warranted.

The effects of respiratory muscle training on respiratory mechanics and energy cost

Resistance respiratory muscle training (RRMT) increases respiratory muscle strength and can increase swimming endurance time by as much as 85%. The purpose of this study was to examine potential mechanisms by which RRMT improves exercise endurance. Eight healthy adult male scuba divers underwent experiments in a hyperbaric chamber at sea level (1 atmosphere absolute (ATA)), 2.7 ATA and 4.6 ATA, both dry and fully submersed. Subjects rested, exercised, and rested while mimicking their own exercise breathing (ISEV). Airway resistance (R(aw)), exhaled nitric oxide output (V˙(NO)), and respiratory duty cycle (T(I)/T(Tot)) were determined before and after four weeks of RRMT. RRMT decreased T(I)/T(Tot) (-10% at rest at 1 ATA), V˙(O2) (-17% at 2.7 ATA during submersed exercise), V˙(E) (-6% at 2.7 ATA during submersed exercise), and R(aw) (-34% inspiratory at 4.6 ATA submersed, -38% expiratory at 2.7 ATA dry), independent of changes in V˙(NO). Most importantly, respiratory muscle efficiency increased (+83% at 2.7 ATA submersed).

Effects of chitosan and oligochitosan on development and mitochondrial function of Rhizopus stolonifer

The antifungal activities of chitosan and oligochitosan have been used to control postharvest decay of the fruits. The effect of chitosan and oligochitosan on mycelium growth, spore germination, and mitochondrial function of Rhizopus stolonifer was evaluated in order to establish a connection between fungus development and the main organelle in charge to provide energy to the cell. The mycelium growth of R. stolonifer was significantly reduced on minimum media amended with chitosan or oligochitosan. The highest antifungal indexes were obtained on media containing chitosan or oligochitosan at 2.0 mg ml(-1). Microscopic observation showed that chitosan and oligochitosan affected the spore germination and hyphae morphology. Both polymers increased oxygen consumption of R. stolonifer. Respiratory activity was restored with NADH in permeabilized treated and untreated cells, and was inhibited with rotenone and flavones. Complex III and IV were inhibited by antimycin A and cyanide, respectively, in treated and untreated cells. Chitosan and oligochitosan increased NADH dehydrogenase activity in isolated mitochondria. However, there were not changes in the cytochrome c oxidase and ATPase activities by effect of these polymers. These results suggest that both chitosan and oligochitosan affect the development of R. stolonifer and might be implicated in the mitochondrial dysfunction.

Huntingtin protein is essential for mitochondrial metabolism, bioenergetics and structure in murine embryonic stem cells

Mutations in the Huntington locus (htt) have devastating consequences. Gain-of-poly-Q repeats in Htt protein causes Huntington's disease (HD), while htt(-/-) mutants display early embryonic lethality. Despite its importance, the function of Htt remains elusive. To address this, we compared more than 3700 compounds in three syngeneic mouse embryonic stem cell (mESC) lines: htt(-/-), extended poly-Q (Htt-Q140/7), and wild-type mESCs (Htt-Q7/7) using untargeted metabolite profiling. While Htt-Q140/7 cells did not show major differences in cellular bioenergetics, we find extensive metabolic aberrations in htt(-/-) mESCs, including (i) complete failure of ATP production despite preservation of the mitochondrial membrane potential; (ii) near-maximal glycolysis, with little or no glycolytic reserve; (iii) marked ketogenesis; (iv) depletion of intracellular NTPs; (v) accelerated purine biosynthesis and salvage; and (vi) loss of mitochondrial structural integrity. Together, our findings reveal that Htt is necessary for mitochondrial structure and function from the earliest stages of embryogenesis, providing a molecular explanation for htt(-/-) early embryonic lethality.

Whole body oxygen uptake and evoked torque during subtetanic isometric electrical stimulation of the quadriceps muscles in a single 30-minute session

OBJECTIVE

To evaluate the time course of fatigue in torque output and oxygen uptake during isometric subtetanic neuromuscular electrical stimulation (NMES) to facilitate the design of NMES-based rehabilitation protocols that can accumulate a defined aerobic exercise volume within a given time period.

DESIGN

Single-arm intervention study with within-subject comparisons.

SETTING

University research laboratory.

PARTICIPANTS

Volunteer sample of healthy men (N=11; mean age, 34.2 ± 11.5 y; range, 19-53 y; body mass, 79.1 ± 11.7 kg; range, 58-100 kg).

INTERVENTION

A single 30-minute session of continuous bilateral isometric quadriceps NMES at 4 Hz evoking a mean twitch amplitude of 12% of the maximum voluntary contraction.

MAIN OUTCOME MEASURES

Whole body oxygen consumption rate (V˙o2), and evoked torque were measured simultaneously throughout.

RESULTS

Mean increment in V˙o2 was 596 ± 238 mL/min, and average exercise intensity during the session was 3 ±.47 metabolic equivalents. The V˙o2 and torque declined slowly at a rate of -.54%±.31% and -.47%±.57% per minute, respectively.

CONCLUSIONS

Despite having a higher incremental V˙o2, the observed fatigue rate was considerably less than that previously reported during intermittent isometric tetanic stimulation, suggesting that subtetanic isometric NMES is more sustainable for exercise interventions aimed at accumulating a therapeutic aerobic exercise volume.

Comparison of metabolic cost and cardiovascular response to stair ascending and descending with walkers and canes in older adults

OBJECTIVE

To compare oxygen cost (mL·kg(-1)·m(-1)) and cardiovascular response (beats/m) and oxygen consumption (mL·kg(-1)·min(-1)) and heart rate (beats/min) to stair ascending and descending with walkers, with canes, and without assistive devices (ADs) in older adults.

DESIGN

Descriptive, repeated measures.

SETTING

Indoor stairway.

PARTICIPANTS

Convenience sample of able-bodied volunteers, non-AD users (N=14; mean age, 63.71 ± 11.7 y; mean body mass, 72.7 ± 14.1 kg; mean height, 165.7 ± 9.2 cm).

INTERVENTIONS

Participants performed 4 randomized trials of stair ascending and descending at their own self-selected speed with 3 ADs: single-point cane, standard walker (SW), and wheeled walker (WW). They also performed unassisted stair ascending and descending. Each trial consisted of a 5-minute steady-state session followed by a 2-minute data collection period. Steady-state expired ventilations were collected in Douglas bags for metabolic analysis.

MAIN OUTCOME MEASURES

Oxygen cost (mL·kg(-1)·m(-1)), heart rate (HR) response (beats/m), oxygen consumption (mL·kg(-1)·min(-1)), and HR (beats/min) were compared for each trial of stair ascending and descending using analysis of variance repeated measures (P<.05).

RESULTS

Greater oxygen cost (per meter) was found for stair ascending and descending using the single-point cane (121%), SW (217%), and WW (232%) compared with unassisted stair ascending and descending (P<.05). Increased HR response (per meter) was found for stair ascending and descending using the single-point cane (116%), SW (126%), and WW (147%) compared with unassisted stair ascending and descending (P<.05). However, oxygen consumption (per minute) and HR (per minute) were not significantly increased during stair ascending and descending with the ADs compared with unassisted stair ascending and descending. Participants stair ascended and descended at significantly (P<.05) reduced speeds during trials with the ADs.

CONCLUSIONS

This research should aid clinicians by providing evidence to base recommendations on regarding AD usage when encountering stairs during home and community ambulation.