Excess Oxygen Consumption Research Articles

Pulsed SILAC-based proteomic analysis unveils hypoxia- and serum starvation-induced de novo protein synthesis with PHD finger protein 14 (PHF14) as a hypoxia sensitive epigenetic regulator in cell cycle progression.

Hypoxia is an environmental cue that is associated with multiple tumorigenic processes such as immunosuppression, angiogenesis, cancer invasion, metastasis, drug resistance, and poor clinical outcomes. When facing hypoxic stress, cells initiate several adaptive responses such as cell cycle arrest to reduce excessive oxygen consumption and co-activation of oncogenic factors. In order to identify the critical novel proteins for hypoxia responses, we used pulsed-SILAC method to trace the active cellular translation events in A431 cells. Proteomic discovery data and biochemical assays showed that cancer cells selectively activate key glycolytic enzymes and novel ER-stress markers, while protein synthesis is severely suppressed. Interestingly, deprivation of oxygen affected the expression of various epigenetic regulators such as histone demethylases and NuRD (nucleosome remodeling and deacetylase) complex in A431 cells. In addition, we identified PHF14 (the plant homeodomain finger-14) as a novel hypoxia-sensitive epigenetic regulator that plays a key role in cell cycle progress and protein synthesis. Hypoxia-mediated inhibition of PHF14 was associated with increase of key cell cycle inhibitors, p14ARF, p15INK4b, and p16INK4a, which are responsible for G1-S phase transition and decrease of AKT-mTOR-4E-BP1/pS6K signaling pathway, a master regulator of protein synthesis, in response to environmental cues. Analysis of TCGA colon cancer (n=461) and skin cancer (n=470) datasets revealed a positive correlation between PHF14 expression and protein translation initiation factors, eIF4E, eIF4B, and RPS6. Significance of PHF14 gene was further demonstrated by in vivo mouse xenograft model using PHF14 KD cell lines.

Multispectral imaging of cortical vascular and hemodynamic responses to a shock wave: observation of spreading depolarization and oxygen supply-demand mismatch.

.Blast-induced traumatic brain injury has been a recent major concern in neurotraumatology. However, its pathophysiology and mechanism are not understood partly due to insufficient information on the brain pathophysiology during/immediately after shock wave exposure. We transcranially applied a laser-induced shock wave (LISW, ) to the left frontal region in a rat and performed multispectral imaging of the ipsilateral cortex through a cranial window (). For the spectral data obtained, we conducted multiple regression analysis aided by Monte Carlo simulation to evaluate vascular diameters, regional hemoglobin concentration (), tissue oxygen saturation (), oxygen extraction fraction, and light-scattering signals as a signature of cortical spreading depolarization (CSD). Immediately after LISW exposure, and were significantly decreased with distinct venular constriction. CSD was then generated and was accompanied by distinct hyperemia/hyperoxemia. This was followed by oligemia with arteriolar constriction, but it soon recovered (within ). However, severe hypoxemia was persistently observed during the post-CSD period (). These observations indicate that inadequate oxygen supply and/or excessive oxygen consumption continued even after blood supply was restored in the cortex. Such a hypoxemic state and/or a hypermetabolic state might be associated with brain damage caused by a shock wave.

Assessment of surface water quality using water quality index and multivariate statistical analyses in Saraydüzü Dam Lake, Turkey.

In this study, observations were carried out in the surface waters of Saraydüzü Dam Lake within Sinop provincial borders for 1year to determine water quality. The basic 28 variables used to determine water quality were measured monthly at six stations. Taking into account the World Health Organization's drinking water standards, the water quality index (WQI) and Turkey's Ministry of Forestry and Water Affairs Surface Water Quality Regulations (SWQR) were used in determining the water quality. In addition, irrigation water quality was examined. For this, sodium absorption rates (SAR), sodium percentage and residual sodium carbonate (RSC) values were calculated. WQI values in the lake were found to be between 17.62 and 29.88. Water quality parameters did not exceed the recommended limit values in all months and at all stations. According to these values, the Saraydüzü Dam Lake water belongs to the 'very good' class in terms of drinking water quality. The results obtained showed that there were no nitrogen or phosphate inputs that could harm the ecosystem in the lake and that there were no low/insufficient ambient oxygen conditions resulting from excessive oxygen consumption during the degradation process of organic matter. All water quality parametres are well below the permissible limits except some heavy metals according to SWQR. Cu, Zn and Fe were found to exceed the limit values. The water quality of irrigation water was found to be good in terms of SAR and sodium percentage, whereas RSC was observed to have varying qualities during the year and not be suitable for irrigation in some months. According to results of factor analysis (FA), pH, temperature, electrical conductivity, suspended solid matter (SSM), biological oxygen demand (BOD), total hardness (TH),total alkalinity (TA), calcium, nitrate, ammonium, mercury and dissolved oxygen are the main variables responsible for the processes in the ecosystem.

Decreases in Oral Tissue Blood Flow Induced by Remifentanil Are Not Accompanied by Deterioration of Oral Tissue Oxygen Tension in Rabbits

The purpose of this study was to investigate the effects of remifentanil infusion on tissue blood flow and tissue oxygen tension in the mandibular bone marrow and masseter muscle in rabbits. In addition, changes in tissue oxygen consumption in those tissues during remifentanil infusion were investigated. Sixteen male tracheotomized Japanese White rabbits were anesthetized with sevoflurane under mechanical ventilation. Under oxygen and air inhalation, fraction of inspiratory oxygen was set at 0.4 and remifentanil was infused at a rate of 0.4μg ∙ kg-1 ∙ min-1. Measurements were performed before remifentanil infusion, 20minutes after the start of remifentanil infusion, and 20 and 60minutes after the completion of remifentanil infusion (n=8). The observed variables included heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO2), and masseter muscle tissue oxygen tension (PmO2). Another 8 rabbits were observed for arterial pH, lactate, base excess (BE), and tissue oxygen consumption in the region from which the retromandibular vein received venous blood. Measurements were performed before remifentanil infusion and 20minutes after the start of remifentanil infusion. HR, SBP, DBP, MAP, BBF, and MBF decreased during remifentanil infusion. PbO2 increased 20minutes after remifentanil infusion and returned to almost the baseline value 60minutes after remifentanil infusion. PmO2 did not change throughout the experiment. The difference between the arterial oxygen content of the femoral artery and the venous oxygen content of the retromandibular vein decreased during remifentanil infusion. Arterial pH, lactate, and BE did not change during remifentanil infusion. Remifentanil decreased BBF and MBF but did not decrease PbO2 and PmO2. It is suggested that tissue oxygen consumption decreased during remifentanil infusion.

Water Quality Improvement of Non-Powered Water Circulation System for Shallow Reservoirs

A large number of reservoirs in Korea have experienced eutrophication and deterioration of water quality including the occurrence of algal blooms, anaerobic state near the bottom due to excessive oxygen consumption, and the elution of nutrients from the sediment. Non-powered water circulation system inducing downward flow from wind-driven current has been developed for domestic reservoirs with shallow water depth. One of the functions of the system is to improve water quality by breaking thermal stratification and prohibiting anaerobic condition near the bottom. The monitoring results of the test-bed, which have been observed for 1 year, showed clearly that the circulation system could maintain DO (dissolved oxygen) concentration higher than 5 mg/L in deep layer (hypolimnion) and also mitigate DO supersaturation about 17% in surface layer (epilimnion). Key words: DO Improvement, Eutrophication, Stratification, Water Circulation, Water Quality Improvement

Influence of the ACTN3 Genotype and the Exercise Intensity on the Respiratory Exchange Ratio and Excess Oxygen Consumption After Exercise.

de L. Corrêa, H, Ribeiro, HS, Maya, ÁTD, Neves, RP, de Moraes, MR, Lima, RM, Nóbrega, OT, and Ferreira, AP. Influence of the ACTN3 genotype and the exercise intensity on the respiratory exchange ratio and excess oxygen consumption after exercise. J Strength Cond Res 35(5): 1380-1388, 2021-This study aimed to assess the respiratory exchange ratio (RER) and excess postexercise oxygen consumption (EPOC) after high-intensity interval training and continuous moderate-intensity aerobic training in accordance with the ACTN3 genotype. A cross-sectional study with 30 physically active individuals who participated in 3 experimental sessions, as follows: a high-intensity interval aerobic exercise, for 3 minutes at 115% anaerobic threshold, with 90 seconds of passive recovery; a continuous moderate-intensity aerobic exercise at 85% anaerobic threshold; and a control session. Respiratory exchange ratio and V̇o2 were obtained through an indirect, calorimetry-based gas analysis method, using a breath-by-breath approach, assessed at baseline, during the trials, and at 1, 2, 3, and 4 hours after exercise. We found that lower postexercise RER values were observed only in subjects with the X allele, in both the high- and the moderate-intensity training protocols. Homozygous RR subjects showed no differences in postexercise RER compared with the scores at the control day. After both sessions of exercise, EPOC levels were higher compared with scores at the control day for 2 hours among X allele carriers, and only in the first hour among RR homozygous. Thus, the RER and EPOC presented different responses after moderate and intense exercise according to the ACTN3 genotype. Moreover, individuals with the X allele of the ACTN3 gene show a higher oxidation of fats in the postexercise period.

The Effects Of Pre-exercise Protein Vs. Carbohydrate Consumption On Energy Expenditure After High-volume Resistance Exercise

During the recovery period following a bout of resistance exercise, oxygen consumption remains elevated for a variable timeframe, reflecting an acute enhancement in resting energy expenditure. What remains uncertain is whether pre-exercise nutrient consumption further promotes these acute metabolic responses to a bout of resistance exercise and if the type of nutrient influences these effects. PURPOSE: Therefore, the objective of this study was to determine, in college-age, resistance trained male subjects, the extent by which pre-exercise supplementation of whey protein or carbohydrate modulates metabolic and substrate oxidation rates following a bout of high-volume, total body resistance exercise. METHODS: In a randomized, placebo controlled, cross-over study, healthy, resistance trained male (n=10) subjects initially underwent baseline testing for resting energy expenditure and maximum strength. Subjects were familiarized with the resistance exercise protocol during the subsequent visit. Afterwards, across 3 separate subsequent visits, subjects consumed whey protein (PRO), carbohydrate (CHO), or no nutrients (CON) prior to a bout of high-volume resistance exercise. After exercise, subjects were tested for energy expenditure (EE), oxygen consumption (VO2), respiratory exchange ratio (RER), and heart rate (HR). RESULTS: PRO (+23.5%; p=0.003), CHO (+12.8%; p=0.001), and CON (+9.5%; p=0.005) increased EE from resting baseline with concomitant changes to VO2, RER, and HR. PRO (p=0.019) and CHO (p=0.003) demonstrated equivalently greater post-exercise EE than CON. Post-exercise VO2 was significantly greater in PRO vs. CON (p=0.034) while CHO did not differ from PRO or CON. CONCLUSION: Overall, nutrient consumption prior to resistance exercise may augment the post-exercise elevation in EE. Consumption of whey protein pre-exercise may enhance excess post-resistance exercise oxygen consumption (i.e EPOC) to a greater extent than carbohydrate intake.

PTP1B controls non-mitochondrial oxygen consumption by regulating RNF213 to promote tumour survival during hypoxia.

Tumours exist in a hypoxic microenvironment and must limit excessive oxygen consumption. Hypoxia-inducible factor controls mitochondrial oxygen consumption, but how/if tumours regulate non-mitochondrial oxygen consumption (NMOC) is unknown. Protein-Tyrosine Phosphatase-1B (PTP1B) is required for Her2/Neu-driven breast cancer (BC) in mice, though the underlying mechanism and human relevance remain unclear. We found that PTP1B-deficient HER2+ xenografts have increased hypoxia, necrosis and impaired growth. In vitro, PTP1B deficiency sensitizes HER2+ BC lines to hypoxia by increasing NMOC by α-KG-dependent dioxygenases (α-KGDDs). The Moyamoya disease gene product RNF213 , an E3 ligase, is negatively regulated by PTP1B in HER2+ BC cells. RNF213 knockdown reverses the effects of PTP1B-deficiency on α-KGDDs, NMOC and hypoxia-induced death of HER2+ BC cells, and partially restores tumourigenicity. We conclude that PTP1B acts via RNF213 to suppress α-KGDD activity and NMOC. This PTP1B/RNF213/α-KGDD pathway is critical for survival of HER2+ BC, and possibly other malignancies, in the hypoxic tumour microenvironment.

Oxygen uptake and heart rate kinetics after different types of resistance exercise.

Oxygen uptake (VO2) and heart rate (HR) kinetics after exercise are important indicators of fitness and cardiovascular health. However, these variables have been little investigated in resistance exercise (RE). The current study compared post-exercise kinetics of VO2 and the HR among different types of REs. The study included 14 males (age: 26.5±5.4 years, body mass: 80.1±11.4 kg, body height: 1.77±0.07 m, fat content: 11.3±4.6%) with RE experience. Dynamic muscle strength was measured using one repetition maximum (1RM) with regard to the half-squat, bench press, pull-down, and triceps pushdown exercises. The participants performed a maximum number of repetitions at 80% of 1RM for each exercise, separated by a recovery period of 60 minutes. VO2 was measured using ergospirometry. VO2 and HR kinetics were assessed using the time constant of the recovery curves, and excess oxygen consumption (EPOC) was calculated afterward. Significant differences were not observed across the exercises with regard to VO2 kinetics. However, the half-squat exercise elicited a greater EPOC than the bench press and triceps pushdown exercises (p<.05). HR kinetics was slower for the half-squat exercise than for the other exercises (p<.05). These findings confirm that the type of RE influences both the cardiac autonomic response post-exercise and EPOC, but not VO2 kinetics.

Hyaluronan peroxidation is required for normal synovial function: An hypothesis

Despite widespread use of antioxidants, reactive oxygen species have important functions in normal tissues. Herein, we present an example of a physiological role for free radicals, and in particular, reactive oxygen species, that are suppressed by anti-oxidants. Free radicals catalyze the degradation of hyaluronan in synovial fluid, a tissue in which hyaluronidase activity is barely detectable. Articular cartilage requires a low oxygen environment. The process of hyaluronan peroxidation consumes significant amounts of molecular oxygen, thus keeping the tension of oxygen in the joint at a low but physiologically critical level. One concern is the change in physical activity between day and night, with periods of joint hyperemia and ischemia, respectively. Increased oxygen and the resulting oxidative stress would lead to chondrocyte dysfunction and cartilage damage. A mechanism for keeping oxygen levels low is required. We postulate that a mechanism indeed exists for the removal of excess oxygen. High-molar-mass hyaluronan turnover in synovial fluid utilizes peroxidative degradation, during which oxygen is massively consumed. The peroxidation itself may be initiated by hydrogen peroxide, which is produced by chondrocyte mitochondria, that can diffuse into the synovial fluid. The resulting decrease in available oxygen down-regulates hyaluronan peroxidation. This in turn prevents excessive oxygen consumption. It appears that free radicals and reactive oxygen species may be components of normal physiology, particularly in the synovial fluid of joints and articular cartilage. It is suggested therefore that indiscriminate use of anti-oxidants, vigorously promoted currently by health professionals and the health industry, be approached with caution.

Outer Segments of Retinal Photoreceptors – A Review in the Light of Novel Findings

Aims: Recent studies have demonstrated that all molecules of the respiratory chain are present in the photoreceptor outer segment (see Calzia et al., Biol Cell 2013). Furthermore, our group (Roehlecke et al., PLoS One 2013) could show that, after blue light stress of the retina, the outer segments are significant sources of reactive oxygen species (ROS) ‐ even more so than the mitochondria in the inner segment. These two new findings have also important implications for degenerative diseases of the retina. Methodology: In this respect we revisited the literature regarding the photoreceptor reactions after blue light and radical stress. Furthermore, we refer to the common features of mitochondria and outer segments. Results: In the light of the recent findings many unique features of the photoreceptors get understandable: they are characterized by excessive oxygen consumption - even higher than that of other neuronal cells. Photoreceptors possess, in addition to their mitochondria ‐ rich neuronal component an outer segment packed with stacks of membrane discs harbouring the photo pigments, respiratory enzymes and enzymes of the visual cycle. Therapeutic use of red and near infrared light is often explained by ameliorating the

Clinical Implications

HomeHypertensionVol. 62, No. 5Clinical Implications Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBClinical Implications Originally published1 Nov 2013https://doi.org/10.1161/01.hyp.0000436210.57019.2eHypertension. 2013;62:809HT/PET-MPs (Gestational Hypertension and Preeclampsia/Toxemia-Microparticles) Affect Trophoblast and Endothelial Function (page 893)Hypertensive disorders of pregnancy are common vascular pathologies having severe implications for maternal and fetal health. Unraveling the complex pathogenesis of gestational vascular complications is crucial for their prevention and improved management.Previously, microvesicles (MVs) were shown to affect coagulation and inflammation in pregnancy. Our study demonstrates that MVs obtained from women with gestational hypertension and preeclampsia present higher levels of antiangiogenic proteins and proinflammatory cytokines. The present study shows that in contrast to MVs of healthy pregnant women, gestational vascular complication MVs do not induce early stage trophoblast migration (Figure S5), inhibit endothelial tube formation, and cause massive apoptosis in term trophoblasts. This indicates the involvement of MVs in placental development at early gestational ages and in placental health at late stages of pregnancy.Recent studies suggested that LMWH (low molecular weight heparin) could improve the outcome of women with gestational vascular complications. The mechanisms through which LMWH exert its effect are multifaceted, involving maternal and placental anticoagulation, as well as anti-inflammatory and complement pathway activity. The findings of the current study highlight that MVs are a new critical player participating in physiological mechanisms of placental development and in the pathology of hypertensive disease in pregnancy. Furthermore, these data could foster our understanding of LMWH effects in this challenging clinical setting.Download figureDownload PowerPointAmyloid-β Peptides (page 966)Alzheimer disease (AD) is the most common form of dementia with 27 million known cases worldwide. Its incidence is rapidly increasing, and there are no effective treatments. The cause is essentially unknown. Initially, defective cholinergic signaling was implicated. Subsequently, the role of amyloid deposits and the amyloid precursor protein was added to the picture. Amyloid-β (Aβ) is a peptide of 36 to 43 amino acids that is processed from amyloid precursor protein. A specific isoform of apolipoprotein, APOE4, is a major genetic risk factor for AD. Apolipoproteins enhance the breakdown of Aβ, but APOE4 is not very effective, leading to an excess amyloid buildup in the brain. Tau proteins stabilize microtubules. They are abundant in neurons of the central nervous system. Hyperphosphorylated tau pairs with other threads of tau eventually forming neurofibrillary tangles inside nerve cell bodies. Viruses, prions, oxidative stress, biometal biology, and numerous other factors are also implicated in AD including small-vessel vascular disease. Could AD be in part a vascular disorder? Indeed, amyloid can cause abnormal vascular reactivity. We found that Aβ induced vasoconstriction of coronary arteries in Langendorff-perfused rat hearts. Aβ bound to the α1 adrenoreceptor, thereby inducing a signal-transduction cascade with cytosolic calcium and extracellular-related kinase phosphorylation in vascular smooth muscle cells. Thus, Aβ itself could be a vascular signaling molecule. Aβ induced vasoconstriction, decreased coronary blood flow, and exhibited α1 adrenoreceptor–mediated signaling. Nonetheless, an in vivo model is necessary to pursue translation of our findings. The implications from our work are that successful therapies directed at AD will probably contain a component addressing the participation of blood vessels. The α1 adrenoreceptor has appeal as a target because the compounds are clinically in use. Furthermore, our notion could be investigated epidemiologically.Download figureDownload PowerPointHypoxia and Development of Nephropathy (page 914)It is well established that kidney hypoxia is present in diseases closely associated with development of nephropathy, such as diabetes mellitus and hypertension. The hypothesis that chronic kidney hypoxia results in the development of nephropathy was originally proposed in 1998 and has since gained increasing support. However, the specific contribution of kidney hypoxia for the development of nephropathy is difficult to determine because of the presence of confounding factors, such as hyperglycemia, hypertension, and oxidative stress. To identify the specific role of kidney hypoxia, Friederich-Persson et al treated normoglycemic control rats with dinitrophenol, a mitochondrial uncoupler, which increases the mitochondrial oxygen consumption. Consequently, treatment with dinitrophenol increased total kidney oxygen consumption and resulted in kidney hypoxia. Interestingly, this resulted in nephropathy evidenced as increased protein excretion and tubulointerstitial damage. Importantly, there was no hyperglycemia, hypertension, or increased oxidative stress levels after dinitrophenol treatment. Thus, the main conclusion was that kidney tissue hypoxia is an independent pathway for the development of nephropathy. Being able to detect and target early alterations in intrarenal oxygen metabolism may be important for patients at risk of developing nephropathy. As such, interventions to prevent excessive kidney oxygen consumption or to restore kidney tissue oxygen availability may prove beneficial in preventing nephropathy in patients.Download figureDownload PowerPoint Previous Back to top Next FiguresReferencesRelatedDetails November 2013Vol 62, Issue 5 Advertisement Article InformationMetrics © 2013 American Heart Association, Inc.https://doi.org/10.1161/01.hyp.0000436210.57019.2e Originally publishedNovember 1, 2013 PDF download Advertisement

Effect of long-term orthotic treatment on gait biomechanics in adolescent idiopathic scoliosis

Background contextA previous study showed subtle biomechanical changes in the gait of unbraced adolescent idiopathic scoliosis (AIS) patients such as a reduction of pelvic, hip, knee, and ankle displacements. However, lumbopelvic muscles' timing activity was bilaterally increased during gait and correlated to excessive oxygen consumption as compared with healthy subjects. Usually, a brace, when indicated, is worn strictly for 22 hours every day in skeletally immature idiopathic scoliotic girls. To our knowledge, no study has assessed the long-term brace effect (6 months) on functional activities such as level walking. PurposeTo assess the stiffening effects of 6 months' brace wearing on instrumented gait analysis in girls with thoracolumbar/lumbar adolescent idiopathic scoliosis. Study design/settingClinical prospective study. Patient sampleThirteen girls diagnosed as progressive adolescent idiopathic scoliosis with left thoracolumbar/lumbar curves (curves ranging 25°–40°). Outcome measuresAll patients underwent a radiographic and instrumented gait analysis, including assessment of kinematics, mechanics, electromyography (EMG), and energetics of walking. MethodsThe scoliotic girls were prospectively studied at S1 (before bracing) and 6 months later at S2 (out-brace: treatment effect). The gait parameters were compared with those of 13 matched healthy girls. A t paired test was conducted to evaluate the effect of the 6-month orthotic treatment in AIS girls. Student t test was performed to compare the scoliotic group at S2 and the healthy subjects to identify if the observed changes in gait parameters meant improvement or worsening of gait. ResultsAfter 6 months of orthotic treatment in AIS, thoracolumbar/lumbar curves and apical rotation remained reduced by 25% and 61%, respectively. During gait, frontal pelvis and hip motions were significantly increased. Muscular mechanical work increased becoming closer but still different as compared with healthy subjects. Bilateral lumbopelvic muscles were almost 40% more active in AIS at S1 compared with healthy subjects and did not change at S2 except for the erector spinae muscles EMG activity, which decreased significantly. Energy cost exceeded by 30% in AIS at S1 compared with healthy subjects and did not change at 6 months' follow-up. ConclusionsAfter 6 months of orthotic treatment, in an out-brace situation, the main structural thoracolumbar/lumbar curve remained partly corrected. Frontal pelvis and hip motion increased, contributing to an improvement of muscular mechanical work during walking. EMG activity duration of lumbopelvic muscles did not change except for the erector spinae muscles, which was decreased but without any beneficial change in the energy cost of walking. In summary, brace treatment, after 6 months, did not significantly influence the gait variables in AIS girls deleteriously, but did not reduce the excessive energy cost, which was 30% above the values of normal adolescents.

Excess post‐hypoxic oxygen consumption in Atlantic cod Gadus morhua

Atlantic cod Gadus morhua experienced oxygen deficit ( D O 2 ) when exposed to oxygen levels below their critical level (c. 73% of pcrit ) and subsequent excess post-hypoxic oxygen consumption (CEPHO ) upon return to normoxic conditions, indicative of an oxygen debt. The mean ± s.e. CEPHO : D O 2 was 6·9 ± 1·5, suggesting that resorting to anaerobic energy production in severe hypoxia is energetically expensive.

Very short-term effect of brace wearing on gait in adolescent idiopathic scoliosis girls

Adolescent idiopathic scoliotic (AIS) deformity induces excessive oxygen consumption correlated to a bilateral increase of lumbo-pelvic muscles timing activity (EMG) during gait. Wearing a brace, the usual treatment for AIS, by supporting the spine and the pelvis, would generate lumbo-pelvic muscular relaxation and consequently reduce excessive oxygen consumption. The purpose of this study was to evaluate the short-term effect of bracing on gait biomechanics in scoliotic spine when compared with normal braced spine. Thirteen healthy volunteers were compared to 13 AIS girls. In both samples, gait analysis was assessed using a three-dimensional motion analysis, including synchronous kinematic, electromyographic, mechanical and energy measurements, first without brace, then wearing a brace. For scoliotic patients, comparison of in-brace and out-brace situations revealed a significant decrease of frontal pelvis (p < 0.001), hip (p < 0.001) and shoulder (p = 0.004) motion in brace associated with a significant reduction of pelvis rotation (p = 0.003). However, the brace did not change significantly the lumbo-pelvic muscle activity duration (EMG) or the mechanical and energetic parameters. Transversal pelvis motion was reduced by 39% (p = 0.04), frontal hip and shoulder motions by 23% (p = 0.004) and 30% (p = 0.01) respectively, and energy cost of walking remained increased by 37% in braced AIS girls relatively to braced healthy subjects. Mechanical and electromyographic variables were not significantly different between the two braced populations during gait except for the gluteus medius muscle that showed bilaterally an increase of duration of electrical activity in healthy subjects and contrarily a decrease in AIS patients (healthy: -3.5 ± 9.6% of gait cycle vs. scoliotic: 3.7 ± 7.7% of gait cycle; p = 0.04). Bracing changed neither the oxygen consumption nor the timing of the lumbo-pelvic muscles activity in both groups during gait. However, in brace the timing activity of bilateral gluteus medius muscles tended to decrease in AIS patients and increase in healthy subjects. Moreover, braced AIS patients had more restricted frontal hips and shoulder motion as well as pelvis rotation than braced healthy subjects.

Excess post-hypoxic oxygen consumption is independent from lactate accumulation in two cyprinid fishes

Carassius carassius responds to hypoxic conditions by conversion of lactate into ethanol, which is excreted over the gills. However, a closely related species, Cyprinus carpio, does not possess the ability to produce ethanol and would be expected to accumulate lactate during hypoxic exposure. While the increase in oxygen consumption in fish required following strenuous exercise or low environmental oxygen availability has been frequently considered, the primary contributing mechanism remains unknown. This study utilized the close relationship but strongly divergent physiology between C. carpio and C. carassius to examine the possible correlation between excess post-hypoxic oxygen consumption (EPHOC) and lactate accumulation. No difference in the EPHOC:O2 deficit ratio was observed between the two species after 2.5h anoxia, with ratios of 2.0±0.6 (C. carpio) and 1.3±0.3 (C. carassius). As predicted, lactate accumulation dynamics did significantly differ between the species in both plasma and white muscle following anoxic exposure. Significant lactate accumulation was seen in both plasma and muscle in C. carpio, but there was no accumulation of lactate in white muscle tissue of C. carassius. These findings indicate that lactate accumulated as a consequence of 2.5h anoxic exposure is not a major determinant of the resulting EPHOC.

Rethinking Heart Failure

An increasing body of clinical observations and experimental evidence suggests that cardiac dysfunction results from autonomic dysregulation of the contractile output of the heart. Excessive activation of the sympathetic nervous system and a decrease in parasympathetic tone are associated with increased mortality. Elevated levels of circulating catecholamines closely correlate with the severity and poor prognosis in heart failure. Sympathetic over-stimulation causes increased levels of catecholamines, which induce excessive aerobic metabolism leading to excessive cardiac oxygen consumption. Resulting impaired mitochondrial function causes acidosis, which results in reduction in blood flow by impairment of contractility. To the extent that the excessive aerobic metabolism resulting from adrenergic stimulation comes to a halt the energy deficit has to be compensated for by anaerobic metabolism. Glucose and glycogen become the essential nutrients. Beta-adrenergic blockade is used successfully to decrease hyperadrenergic drive. Neurohumoral antagonists block adrenergic over-stimulation but do not provide the heart with fuel for compensatory anaerobic metabolism. The endogenous hormone ouabain reduces catecholamine levels in healthy volunteers, promotes the secretion of insulin, induces release of acetylcholine from synaptosomes and potentiates the stimulation of glucose metabolism by insulin and acetylcholine. Ouabain stimulates glycogen synthesis and increases lactate utilisation by the myocardium. Decades of clinical experience with ouabain confirm the cardioprotective effects of this endogenous hormone. The so far neglected sympatholytic and vagotonic effects of ouabain on myocardial metabolism clearly make a clinical re-evaluation of this endogenous hormone necessary. Clinical studies with ouabain that correspond to current standards are warranted. Cardiol Res. 2012;3(6):243-257 doi: https://doi.org/10.4021/cr228w

Excess posthypoxic oxygen consumption in rainbow trout (Oncorhynchus mykiss): recovery in normoxia and hypoxia

Under certain conditions, a number of fish species may perform brief excursions into severe hypoxia and return to water with a higher oxygen content. The term severe hypoxia describes oxygen conditions that are below the critical oxygen saturation (Scrit), defined here as the oxygen threshold at which the standard metabolic rate becomes dependent upon the ambient oxygen content. Using rainbow trout ( Oncorhynchus mykiss (Walbaum, 1792), this study quantified the excess posthypoxic oxygen consumption (EPHOC) occurring after exposure to oxygen availability below Scrit. Tests showed that Scritwas 13.5% air saturation (O2sat). Fish were exposed to 10% O2satfor 0.97 h, and the EPHOC was quantified in normoxia (≥95% O2sat) and hypoxia (30% O2sat) to test the hypothesis that reduced oxygen availability would decrease the peak metabolic rate (MO2peak) and prolong the duration of the metabolic recovery. Results showed that MO2peakduring the recovery was reduced from 253 to 127 mg O2·kg–1·h–1in hypoxia compared with normoxia. Metabolic recovery lasted 5.2 h in normoxia and 9.8 h in hypoxia. The EPHOC, however, did not differ between the two treatments. Impeded metabolic recovery in hypoxia may have implications for fish recovering from exposure to oxygen availability below Scrit.

Rethinking Heart Failure.

An increasing body of clinical observations and experimental evidence suggests that cardiac dysfunction results from autonomic dysregulation of the contractile output of the heart. Excessive activation of the sympathetic nervous system and a decrease in parasympathetic tone are associated with increased mortality. Elevated levels of circulating catecholamines closely correlate with the severity and poor prognosis in heart failure. Sympathetic over-stimulation causes increased levels of catecholamines, which induce excessive aerobic metabolism leading to excessive cardiac oxygen consumption. Resulting impaired mitochondrial function causes acidosis, which results in reduction in blood flow by impairment of contractility. To the extent that the excessive aerobic metabolism resulting from adrenergic stimulation comes to a halt the energy deficit has to be compensated for by anaerobic metabolism. Glucose and glycogen become the essential nutrients. Beta-adrenergic blockade is used successfully to decrease hyperadrenergic drive. Neurohumoral antagonists block adrenergic over-stimulation but do not provide the heart with fuel for compensatory anaerobic metabolism. The endogenous hormone ouabain reduces catecholamine levels in healthy volunteers, promotes the secretion of insulin, induces release of acetylcholine from synaptosomes and potentiates the stimulation of glucose metabolism by insulin and acetylcholine. Ouabain stimulates glycogen synthesis and increases lactate utilisation by the myocardium. Decades of clinical experience with ouabain confirm the cardioprotective effects of this endogenous hormone. The so far neglected sympatholytic and vagotonic effects of ouabain on myocardial metabolism clearly make a clinical re-evaluation of this endogenous hormone necessary. Clinical studies with ouabain that correspond to current standards are warranted.

Predictability of Crude Oil In-Situ Combustion by the Isoconversional Kinetic Approach

Summary One method to access unconventional heavy-crude-oil resources as well as residual oil after conventional recovery operations is to apply in-situ combustion (ISC) enhanced oil recovery. ISC oxidizes in place a small fraction of the hydrocarbon, thereby providing heat to reduce oil viscosity and increase reservoir pressure. Both effects serve to enhance recovery. The complex nature of petroleum as a multicomponent mixture and the multistep character of combustion reactions substantially complicate analysis of crude-oil oxidation and the identification of settings where ISC could be successful. In this study, isoconversional analysis of ramped temperature-oxidation (RTO) kinetic data was applied to eight different crude-oil samples. In addition, combustion-tube runs that explore ignition and combustion-front propagation were carried out. By using experimentally determined combustion kinetics of eight crude-oil samples along with combustion-tube results, we show that isoconversional analysis of RTO data is useful to predict combustion-front propagation. Isoconversional analysis also provides new insight into the nature of the reactions occurring during ISC. Additionally, five of the 10 crude-oil/rock systems studied employed a carbonate rock. No system displayed excessive oxygen consumption resulting from carbonate decomposition at combustion temperatures. This result is encouraging as it contributes to widening of the applicability of ISC.