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Physiology (Bethesda, Md.) Apr 2009Metazoan organisms are dependent on a continuous supply of O(2) for survival. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that regulates oxygen... (Review)
Review
Metazoan organisms are dependent on a continuous supply of O(2) for survival. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that regulates oxygen homeostasis and plays key roles in development, physiology, and disease. HIF-1 activity is induced in response to continuous hypoxia, intermittent hypoxia, growth factor stimulation, and Ca(2+) signaling. HIF-1 mediates adaptive responses to hypoxia, including erythropoiesis, angiogenesis, and metabolic reprogramming. In each case, HIF-1 regulates the expression of multiple genes encoding key components of the response pathway. HIF-1 also mediates maladaptive responses to chronic continuous and intermittent hypoxia, which underlie the development of pulmonary and systemic hypertension, respectively.
Topics: Animals; HIV-1; Homeostasis; Humans; Hypoxia; Oxygen Consumption; Signal Transduction
PubMed: 19364912
DOI: 10.1152/physiol.00045.2008 -
Endocrinology Aug 2009Thyroid hormone plays a critical role in mitochondrial biogenesis in two areas of the developing brain, the cerebral cortex and the striatum. Here we analyzed, in the...
Thyroid hormone plays a critical role in mitochondrial biogenesis in two areas of the developing brain, the cerebral cortex and the striatum. Here we analyzed, in the cerebral cortex of neonatal rats, the effect of hypothyroidism on the biogenesis in free and synaptosomal mitochondria by analyzing, in isolated mitochondria, the activity of respiratory complex I, oxidative phosphorylation, oxygen consumption, and the expression of mitochondrial genome. In addition, we studied the effect of thyroid hormone in oxygen consumption in vivo by determining metabolic flow through (13)C nuclear magnetic resonance spectroscopy. Our results clearly show that in vivo, hypothyroidism markedly reduces oxygen consumption in the neural population of the cerebral cortex. This effect correlates with decreased free mitochondria biogenesis. In contrast, no effect was observed in the biogenesis in synaptosomal mitochondria. The parameters analyzed were markedly improved after T(3) administration. These results suggest that a reduced biogenesis and the subsequent reduction of respiratory capacity in free mitochondria could be the underlying cause of decreased oxygen consumption in the neurons of the cerebral cortex of hypothyroid neonates.
Topics: Animals; Cerebral Cortex; Congenital Hypothyroidism; Female; Hypothyroidism; Magnetic Resonance Spectroscopy; Male; Methimazole; Mitochondria; Mitochondrial Proteins; Oxidative Phosphorylation; Oxygen Consumption; Rats; Rats, Wistar
PubMed: 19389834
DOI: 10.1210/en.2008-1755 -
Critical Care (London, England) Mar 2013Perioperative hemodynamic optimization, or goal-directed therapy (GDT), has been show to significantly decrease complications and risk of death in high-risk patients... (Review)
Review
Perioperative hemodynamic optimization, or goal-directed therapy (GDT), has been show to significantly decrease complications and risk of death in high-risk patients undergoing noncardiac surgery. An important aim of GDT is to prevent an imbalance between oxygen delivery and oxygen consumption in order to avoid the development of multiple organ dysfunction. The utilization of cardiac output monitoring in the perioperative period has been shown to improve outcomes if integrated into a GDT strategy. GDT guided by dynamic predictors of fluid responsiveness or functional hemodynamics with minimally invasive cardiac output monitoring is suitable for the majority of patients undergoing major surgery with expected significant volume shifts due to bleeding or other significant intravascular volume losses. For patients at higher risk of complications and death, such as those with advanced age and limited cardiorespiratory reserve, the addition of dobutamine or dopexamine to the treatment algorithm, to maximize oxygen delivery, is associated with better outcomes.
Topics: Cardiovascular Diseases; Hemodynamics; Humans; Oxygen Consumption; Patient Care Planning; Perioperative Care; Postoperative Complications
PubMed: 23672840
DOI: 10.1186/cc11861 -
International Journal of Molecular... Dec 2022Dissolved oxygen (DO) is deeply involved in preserving the life of cellular tissues and human beings due to its key role in cellular metabolism: its alterations may... (Review)
Review
Dissolved oxygen (DO) is deeply involved in preserving the life of cellular tissues and human beings due to its key role in cellular metabolism: its alterations may reflect important pathophysiological conditions. DO levels are measured to identify pathological conditions, explain pathophysiological mechanisms, and monitor the efficacy of therapeutic approaches. This is particularly relevant when the measurements are performed in vivo but also in contexts where a variety of biological and synthetic media are used, such as ex vivo organ perfusion. A reliable measurement of medium oxygenation ensures a high-quality process. It is crucial to provide a high-accuracy, real-time method for DO quantification, which could be robust towards different medium compositions and temperatures. In fact, biological fluids and synthetic clinical fluids represent a challenging environment where DO interacts with various compounds and can change continuously and dynamically, and further precaution is needed to obtain reliable results. This study aims to present and discuss the main oxygen detection and quantification methods, focusing on the technical needs for their translation to clinical practice. Firstly, we resumed all the main methodologies and advancements concerning dissolved oxygen determination. After identifying the main groups of all the available techniques for DO sensing based on their mechanisms and applicability, we focused on transferring the most promising approaches to a clinical in vivo/ex vivo setting.
Topics: Humans; Oxygen; Oxygen Consumption
PubMed: 36555613
DOI: 10.3390/ijms232415971 -
Medicine and Science in Sports and... Jul 2022This study aimed to investigate the effects of aerodynamic drag and drafting on propulsive force (FPROP), drag area (CDA), oxygen cost (V˙O2), metabolic rate (E˙), and...
PURPOSE
This study aimed to investigate the effects of aerodynamic drag and drafting on propulsive force (FPROP), drag area (CDA), oxygen cost (V˙O2), metabolic rate (E˙), and heart rate (HR) during roller skiing on a treadmill in a wind tunnel using the double poling technique. A secondary aim was to investigate the effects of wind versus no-wind test conditions on the same physiological parameters.
METHODS
Ten subjects of each gender participated in the experiments. One pair of skiers of the same gender roller skied simultaneously in line with the air flow; the distance between the skiers was ~2.05 m. Each pair was tested as follows: I) with wind, leading; II) with wind, drafting; and III) without wind. The treadmill inclination was 0° throughout the tests. For the wind conditions, the air velocity was similar to the treadmill belt speed: 3 to 7 m·s-1 for men and 3 to 6 m·s-1 for women.
RESULTS
Drafting resulted in significantly (P < 0.05) lower FPROP,CDA, V˙O2, and E˙, compared with leading, for both genders at racing speed but not at lower speeds, whereas HR was only affected for the male skiers at racing speed. The test without wind resulted in significantly lower FPROP, V˙O2, and E˙ at all tested speeds compared with the tests with wind present, whereas HR was lower only at higher speeds.
CONCLUSIONS
At racing speed, but not at lower speeds, the positive effects of drafting behind a skier during double poling were obvious and resulted in a lower FPROP, CDA, V˙O2, E˙, and HR. Tests without wind present put even lower demands on the skiers' physiology, which was also evident at lower speeds.
Topics: Biomechanical Phenomena; Exercise Test; Female; Heart Rate; Humans; Male; Oxygen Consumption; Skiing
PubMed: 35142710
DOI: 10.1249/MSS.0000000000002885 -
Anaesthesia Aug 2009This study reviews the predictive value of maximum oxygen consumption (VO2max) and anaerobic threshold, obtained through cardiopulmonary exercise testing, in calculating... (Review)
Review
This study reviews the predictive value of maximum oxygen consumption (VO2max) and anaerobic threshold, obtained through cardiopulmonary exercise testing, in calculating peri-operative morbidity and mortality in non-cardiopulmonary thoraco-abdominal surgery. A literature review provided nine studies that investigated either one or both of these two variables across a wide range of surgical procedures. Six of the seven studies that reported sufficiently detailed results on peak oxygen consumption and four of the six studies that reported sufficiently detailed results on anaerobic threshold found them to be significant predictors. We conclude that peak oxygen consumption and possibly anaerobic threshold are valid predictors of peri-operative morbidity and mortality in non-cardiopulmonary thoraco-abdominal surgery. These indicators could potentially provide a means of allocating increased care to high-risk patients.
Topics: Anaerobic Threshold; Exercise Test; Health Status Indicators; Humans; Oxygen Consumption; Postoperative Complications; Preoperative Care; Prognosis; Risk Assessment
PubMed: 19604193
DOI: 10.1111/j.1365-2044.2009.05983.x -
American Journal of Physiology. Renal... Jun 2015The objective of this study was to investigate how physiological, pharmacological, and pathological conditions that alter sodium reabsorption (TNa) in the proximal...
The objective of this study was to investigate how physiological, pharmacological, and pathological conditions that alter sodium reabsorption (TNa) in the proximal tubule affect oxygen consumption (QO2 ) and Na(+) transport efficiency (TNa/QO2 ). To do so, we expanded a mathematical model of solute transport in the proximal tubule of the rat kidney. The model represents compliant S1, S2, and S3 segments and accounts for their specific apical and basolateral transporters. Sodium is reabsorbed transcellularly, via apical Na(+)/H(+) exchangers (NHE) and Na(+)-glucose (SGLT) cotransporters, and paracellularly. Our results suggest that TNa/QO2 is 80% higher in S3 than in S1-S2 segments, due to the greater contribution of the passive paracellular pathway to TNa in the former segment. Inhibition of NHE or Na-K-ATPase reduced TNa and QO2 , as well as Na(+) transport efficiency. SGLT2 inhibition also reduced proximal tubular TNa but increased QO2 ; these effects were relatively more pronounced in the S3 vs. the S1-S2 segments. Diabetes increased TNa and QO2 and reduced TNa/QO2 , owing mostly to hyperfiltration. Since SGLT2 inhibition lowers diabetic hyperfiltration, the net effect on TNa, QO2 , and Na(+) transport efficiency in the proximal tubule will largely depend on the individual extent to which glomerular filtration rate is lowered.
Topics: Animals; Biological Transport; Diabetes Mellitus; Glomerular Filtration Rate; Hypoglycemic Agents; Kidney Tubules, Proximal; Oxygen Consumption; Rats; Sodium; Sodium-Glucose Transporter 2; Sodium-Glucose Transporter 2 Inhibitors; Sodium-Hydrogen Exchangers
PubMed: 25855513
DOI: 10.1152/ajprenal.00007.2015 -
Developmental Cognitive Neuroscience Jul 2011BOLD fMRI (blood oxygenation level dependent functional magnetic resonance imaging) is increasingly used to detect developmental changes of human brain function that are... (Review)
Review
BOLD fMRI (blood oxygenation level dependent functional magnetic resonance imaging) is increasingly used to detect developmental changes of human brain function that are hypothesized to underlie the maturation of cognitive processes. BOLD signals depend on neuronal activity increasing cerebral blood flow, and are reduced by neural oxygen consumption. Thus, developmental changes of BOLD signals may not reflect altered information processing if there are concomitant changes in neurovascular coupling (the mechanism by which neuronal activity increases blood flow) or neural energy use (and hence oxygen consumption). We review how BOLD signals are generated, and explain the signalling pathways which convert neuronal activity into increased blood flow. We then summarize in broad terms the developmental changes that the brain's neural circuitry undergoes during growth from childhood through adolescence to adulthood, and present the changes in neurovascular coupling mechanisms and energy use which occur over the same period. This information provides a framework for assessing whether the BOLD changes observed during human development reflect altered cognitive processing or changes in neurovascular coupling and energy use.
Topics: Animals; Brain; Cerebrovascular Circulation; Humans; Magnetic Resonance Imaging; Neuronal Plasticity; Oxygen Consumption; Signal Processing, Computer-Assisted
PubMed: 22436508
DOI: 10.1016/j.dcn.2011.04.001 -
Critical Care (London, England) 2009A small group of patients account for the majority of peri-operative morbidity and mortality. These 'high-risk' patients have a poor outcome due to their inability to... (Review)
Review
A small group of patients account for the majority of peri-operative morbidity and mortality. These 'high-risk' patients have a poor outcome due to their inability to meet the oxygen transport demands imposed on them by the nature of the surgical response during the peri-operative period. It has been shown that by targeting specific haemodynamic and oxygen transport goals at any point during the peri-operative period, the outcomes of these patients can be improved. This goal directed therapy includes the use of fluid loading and inotropes, in order to optimize the preload, contractility and afterload of the heart whilst maintaining an adequate coronary perfusion pressure. Despite the benefits seen, it remains a challenge to implement this management due to difficulties in identifying these patients, scepticism and lack of critical care resources.
Topics: General Surgery; Goals; Hemodynamics; Humans; Oxygen Consumption; Perioperative Care; Postoperative Complications
PubMed: 19863764
DOI: 10.1186/cc8039 -
The Journal of Physiology Jan 2008The evolution of biological complexity beyond single-celled organisms was linked temporally with the development of an oxygen atmosphere. Functionally, this linkage can... (Review)
Review
The evolution of biological complexity beyond single-celled organisms was linked temporally with the development of an oxygen atmosphere. Functionally, this linkage can be attributed to oxygen ranking high in both abundance and electronegativity amongst the stable elements of the universe. That is, reduction of oxygen provides for close to the largest possible transfer of energy for each electron transfer reaction. This suggests the general hypothesis that the steep thermodynamic gradient of an oxygen environment was permissive for the development of multicellular complexity. A corollary of this hypothesis is that aerobic metabolism underwrites complex biological function mechanistically at all levels of organization. The strong contemporary functional association of aerobic metabolism with both physical capacity and health is presumably a product of the integral role of oxygen in our evolutionary history. Here we provide arguments from thermodynamics, evolution, metabolic network analysis, clinical observations and animal models that are in accord with the centrality of oxygen in biology.
Topics: Animals; Biological Evolution; Energy Metabolism; Humans; Models, Animal; Motor Activity; Oxygen; Oxygen Consumption; Thermodynamics
PubMed: 17947307
DOI: 10.1113/jphysiol.2007.144709