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Advances in Physiology Education Dec 2022The interchange among the energy-providing phosphagen, glycolytic, and aerobic systems during exercise is often poorly understood by beginning students in exercise...
The interchange among the energy-providing phosphagen, glycolytic, and aerobic systems during exercise is often poorly understood by beginning students in exercise physiology. Exercise is oftentimes thought of as being aerobic or anaerobic, with the body progressing sequentially from one system to the next, although the energy systems work synergistically to produce energy from the onset of exercise, and all ultimately use oxygen. Traditional methods of teaching these concepts using only indirect calorimetry and a metabolic cart can be misleading. Relatively inexpensive noninvasive monitors of muscle oxygenation levels ([Formula: see text]) provide a useful tool to help students better understand the contribution and timing of these three systems of ATP generation and convey the concept that ultimately all energy production in the human body is oxygen dependent. In this laboratory, students use near-infrared spectroscopy (NIRS) to visualize oxygen utilization by skeletal muscle during exercise by devising three exercise unique protocols, with each designed to stress a different energy system. Students then perform their protocols while using NIRS to measure and analyze [Formula: see text]. Students generate graphs with collected data, allowing them to visualize and appreciate oxygen consumption during all three protocols as well as elevated oxygen consumption after exercise. The students learn that any exercise is really all about oxygen. Traditional methods of teaching bioenergetics using indirect calorimetry and a metabolic cart may be misleading. Recent advances in technology have made near-infrared spectroscopy (NIRS) a relatively inexpensive, noninvasive means of monitoring muscle oxygen levels during exercise. In this laboratory activity, NIRS devices are used for hands-on exploration of the synergistic nature of the energy systems, allowing students to appreciate the synergistic nature of the energy systems and how all exercise is really all about oxygen.
Topics: Humans; Spectroscopy, Near-Infrared; Oxygen; Oxygen Consumption; Energy Metabolism; Muscle, Skeletal
PubMed: 36201307
DOI: 10.1152/advan.00106.2022 -
The Journal of Physiology Jan 2004Fetal growth depends on the transplacental nutrient supply, which, in turn, is determined partially by the consumption and production of nutrients by the uteroplacental... (Comparative Study)
Comparative Study
Fetal growth depends on the transplacental nutrient supply, which, in turn, is determined partially by the consumption and production of nutrients by the uteroplacental tissues. In fetal sheep, the rates of growth and umbilical glucose uptake decline coincidently towards term in parallel with the normal prepartum rise in plasma cortisol. While cortisol is known to reduce growth in fetal sheep, its effects on the uteroplacental handling and delivery of nutrients remain unknown. Hence, this study, quantified the rates of umbilical uptake and uteroplacental consumption of nutrients in preterm fetuses infused with cortisol for 5 days to mimic the prepartum cortisol surge. Umbilical uptakes of glucose and lactate, but not oxygen, were significantly lower in cortisol- than saline-infused fetuses, irrespective of whether values were expressed as absolute or weight-specific rates. The rate of uteroplacental consumption of glucose, but not oxygen, was significantly higher in cortisol- than saline-infused animals. Absolute rates of uteroplacental lactate production were lower in cortisol-infused animals. When all data were combined, fetal plasma cortisol levels were positively correlated to uteroplacental glucose consumption and inversely related to umbilical glucose uptake. Cortisol treatment had no apparent effect on placental mRNA expression for the glucose transporters, GLUT-1 and GLUT-3. The results demonstrate that cortisol is physiological regulator of uteroplacental metabolism and nutrient delivery to the sheep fetus. These observations have important implications for fetal growth both in late gestation and during adverse intrauterine conditions, which raise fetal cortisol levels earlier in gestation.
Topics: Animals; Dose-Response Relationship, Drug; Female; Glucose; Hydrocortisone; Lactic Acid; Maternal-Fetal Exchange; Oxygen Consumption; Placental Circulation; Pregnancy; Sheep
PubMed: 14594988
DOI: 10.1113/jphysiol.2003.054577 -
Critical Care (London, England) 2005This review examines experimental evidence that the microvascular dysfunction that occurs early in sepsis is the critical first stage in tissue hypoxia and organ... (Review)
Review
This review examines experimental evidence that the microvascular dysfunction that occurs early in sepsis is the critical first stage in tissue hypoxia and organ failure. A functional microvasculature maintains tissue oxygenation despite limitations on oxygen delivery from blood to tissue imposed by diffusion; the density of perfused (functional) capillaries is high enough to ensure appropriate diffusion distances, and arterioles regulate the distribution of oxygen within the organ precisely to where it is needed. Key components of this regulatory system are the endothelium, which communicates and integrates signals along the microvascular network, and the erythrocytes, which directly monitor and regulate oxygen delivery. During hypovolemic shock, a functional microvasculature responds to diminish the impact of a decrease in oxygen supply on tissue perfusion. However, within hours of the onset of sepsis, a dysfunctional microcirculation is, due to a loss of functional capillary density and impaired regulation of oxygen delivery, unable to maintain capillary oxygen saturation levels and prevent the rapid onset of tissue hypoxia despite adequate oxygen supply to the organ. The mechanism(s) responsible for this dysfunctional microvasculature must be understood in order to develop appropriate management strategies for sepsis.
Topics: Animals; Erythrocytes; Humans; Microcirculation; Models, Cardiovascular; Oxygen Consumption; Sepsis
PubMed: 16168072
DOI: 10.1186/cc3751 -
Molecular Metabolism Oct 2022Alterations in mitochondrial function play an important role in the development of various diseases, such as obesity, insulin resistance, steatohepatitis,...
OBJECTIVE
Alterations in mitochondrial function play an important role in the development of various diseases, such as obesity, insulin resistance, steatohepatitis, atherosclerosis and cancer. However, accurate assessment of mitochondrial respiration ex vivo is limited and remains highly challenging. Using our novel method, we measured mitochondrial oxygen consumption (OCR) and extracellular acidification rate (ECAR) of metabolically relevant tissues ex vivo to investigate the impact of different metabolic stressors on mitochondrial function.
METHODS
Comparative analyses of OCR and ECAR were performed in tissue biopsies of young mice fed 12 weeks standard-control (STD), high-fat (HFD), high-sucrose (HSD), or western diet (WD), matured mice with HFD, and 2year-old mice aged on STD with and without fasting.
RESULTS
While diets had only marginal effects on mitochondrial respiration, respiratory chain complexes II and IV were reduced in adipose tissue (AT). Moreover, matured HFD-fed mice showed a decreased hepatic metabolic flexibility and prolonged aging increased OCR in brown AT. Interestingly, fasting boosted pancreatic and hepatic OCR while decreasing weight of those organs. Furthermore, ECAR measurements in AT could indicate its lipolytic capacity.
CONCLUSION
Using ex vivo tissue measurements, we could extensively analyze mitochondrial function of liver, AT, pancreas and heart revealing effects of metabolic stress, especially aging.
Topics: Animals; Mice; Adipose Tissue, Brown; Aging; Diet, High-Fat; Fasting; Oxygen Consumption; Stress, Physiological
PubMed: 35944898
DOI: 10.1016/j.molmet.2022.101563 -
BMC Anesthesiology Jun 2023Body temperature (BT) is thought to have associations with oxygen consumption (VO). However, there have been few studies in which the association between systemic VO and...
BACKGROUND
Body temperature (BT) is thought to have associations with oxygen consumption (VO). However, there have been few studies in which the association between systemic VO and BT in humans was investigated in a wide range of BTs. The aims of this study were 1) to determine the association between VO and age and 2) to determine the association between VO and BT.
METHODS
This study was a retrospective study of patients who underwent surgery under general anesthesia at a tertiary teaching hospital. VO was measured by the Dräger Perseus A500 anesthesia workstation (Dräger Medical, Lubeck, Germany). The associations of VO with age and BT were examined using spline regression and multivariable regression analysis with a random effect.
RESULTS
A total of 7,567 cases were included in this study. A linear spline with one knot shows that VO was reduced by 2.1 ml/kg/min with one year of age (p < 0.001) among patients less than 18 years of age and that there was no significant change in VO among patients 18 years of age or older (estimate: 0.014 ml/kg/min, p = 0.08). VO in all bands of BT < 36.0 °C was not significantly different from VO in BT > = 36 °C and < 36.5 °C. Multivariable linear regression analysis showed that compared with VO in BT > = 36 °C and < 36.5 °C as a reference, VO levels were significantly higher by 0.57 ml/kg/min in BT > = 36.5 °C and < 37 °C (p < 0.001), by 1.8 ml/kg/min in BT > = 37 °C and < 37.5 °C (p < 0.001), by 3.6 ml/kg/min in BT > = 37.5 °C and < 38 °C (p < 0.001), by 4.9 ml/kg/min in BT > = 38 °C and < 38.5 °C (p < 0.001), and by 5.7 ml/kg/min in BT > = 38.5 °C (p < 0.001). The associations between VO and BT were significantly different among categorized age groups (p = 0.03).
CONCLUSIONS
VO increases in parallel with increase in body temperature in a hyperthermic state but remains constant in a hypothermic state. Neonates and infants, who have high VO, may have a large systemic organ response in VO to change in BT.
Topics: Infant; Infant, Newborn; Humans; Adolescent; Adult; Child, Preschool; Body Temperature; Retrospective Studies; Anesthesia, General; Fever; Oxygen Consumption; Oxygen
PubMed: 37340340
DOI: 10.1186/s12871-023-02182-1 -
Journal of Optometry 2022The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the...
The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the last 20 years to model the physiology of the human cornea during contact lens wear. Unfortunately, some of these models, based on a constant corneal oxygen consumption rate, produce areas on the cornea where the oxygen tension is negative, which has no physical sense. In order to avoid such inconsistency, different researchers have developed alternative models of oxygen consumption, which predict the likely oxygen metrics available at the interface cornea/post lens tear film by determination of oxygen flux, oxygen consumption, and oxygen tension through the different layers (endothelium, stroma, and epithelium). Although oxygen deficiency produces corneal edema, corneal swelling, hypoxia, acidosis, and other abnormalities, the estimation of the oxygen distribution below the impact of a contact lens wear is interesting to know which lens transmissibility was adequate to maintain the cornea and avoid epithelial and stromal anoxia. The estimation of minimum transmissibility for a lens for extended wear applications will be very useful for both clinicians and manufacturers. The aim of this work is to present a complete discussion based on Monod kinetics model that permits give an estimation of oxygen partial pressure distribution, the profile distribution of corneal flux and oxygen consumption rate, and finally the estimation of the relaxation mechanism of the cornea depending on the oxygen tension at the interface cornea/post lens tear film. Relaxation time in this context can quantify the capability of the corneal tissue to adapt to increasing concentrations of oxygen. It is proposed this parameter as a biological meaningful indicator of the interaction between contact lens polymers and living tissues such as the corneal cellular layer.
Topics: Contact Lenses, Hydrophilic; Cornea; Humans; Oxygen; Oxygen Consumption; Tears
PubMed: 33589396
DOI: 10.1016/j.optom.2020.12.002 -
International Journal of Environmental... Sep 2022Uphill running induces a higher physiological demand than level conditions. Although many studies have investigated this locomotion from a psychological point of view,...
Uphill running induces a higher physiological demand than level conditions. Although many studies have investigated this locomotion from a psychological point of view, there is no clear position on the effects of the slope on the physiological variables during an incremental running test performed on a slope condition. The existing studies have heterogeneous designs with different populations or slopes and have reported unclear results. Some studies observed an increase in oxygen consumption, whereas it remained unaffected in others. The aim of this study is to investigate the effect of a slope on the oxygen consumption, breathing frequency, ventilation and heart rate during an incremental test performed on 0, 15, 25 and 40% gradient slopes by specialist trail runners. The values are compared at the first and second ventilatory threshold and exhaustion. A one-way repeated measures ANOVA, with a Bonferroni post-hoc analysis, was used to determine the effects of a slope gradient (0, 15, 25 and 40%) on the physiological variables. Our study shows that all the variables are not affected in same way by the slopes during the incremental test. The heart rate and breathing frequency did not differ from the level condition and all the slope gradients at the ventilatory thresholds or exhaustion. At the same time, the ventilation and oxygen consumption increased concomitantly with the slope ( < 0.001) in all positions. The post-hoc analysis highlighted that the ventilation significantly increased between each successive gradient (0 to 15%, 15% to 25% and 25% to 40%), while the oxygen consumption stopped increasing at the 25% gradient. Our results show that the 25 and 40% gradient slopes allow the specialist trail runners to reach the highest oxygen consumption level.
Topics: Exercise Test; Heart Rate; Oxygen Consumption; Respiration; Running
PubMed: 36231513
DOI: 10.3390/ijerph191912210 -
Frontiers in Bioscience (Landmark... Jul 2022This report aims to detail the use of the phosphorescence oxygen analyzer for investigation of thymic responses to pharmaceutical agents, in particular...
BACKGROUND
This report aims to detail the use of the phosphorescence oxygen analyzer for investigation of thymic responses to pharmaceutical agents, in particular immunosuppressants and immunomodulators. Sirolimus (a highly specific inhibitor of the 'molecular target of rapamycin', mTOR) and ozanimod (an agonist of the sphingosine 1-phosphate receptor, recently approved for treatment of multiple sclerosis and ulcerative colitis) are used for this purpose.
METHODS
Thymic fragments from mice were placed in glass vials containing phosphate-buffered saline, bovine albumin, and Pd(II) meso-tetra (sulfophenyl) tetrabenzoporphyrin. The vials were sealed from air, and the cellular oxygen consumption was monitored as function of time.
RESULTS
The decline of dissolved oxygen concentration with time (d[O2]/d) was linear; thus, its rate (thymocyte respiration) was expressed as μM O2 min-1. Cyanide inhibited respiration, confirming the oxygen consumption was in cytochrome oxidase. In age-matched mice, the rate of thymocyte respiration (mean ± SD, in μM O2 min-1 mg-1) was 0.046 ± 0.011 (median = 0.043, range = 0.028 to 0.062, n = 10). In thymic fragments from littermates, this rate was inhibited in the presence of sirolimus (16% lower) or ozanimod (29% lower).
CONCLUSIONS
Thymocyte respiration can serve as a surrogate biomarker for studying the mode-of-action and the cytotoxicity of immunotoxins and immunosuppressants.
Topics: Animals; Cattle; Cell Respiration; Immunosuppressive Agents; Mice; Oxygen; Oxygen Consumption; Sirolimus
PubMed: 36042174
DOI: 10.31083/j.fbl2708230 -
Frontiers in Bioscience (Scholar... Jan 2011Low temperatures provoke increased production of heat accompanied by increased respiration, oxygen consumption and the production of partially reduced oxygen species... (Review)
Review
Low temperatures provoke increased production of heat accompanied by increased respiration, oxygen consumption and the production of partially reduced oxygen species called ROS. ROS induce different forms of cellular oxidative damage, disturb the redox state and can change the activity of several metabolic enzymes. Organisms have developed a functionally connected set of anti-oxidant enzymes and low molecular mass compounds (together termed the ADS) that metabolise primary ROS. If ROS production within cells overwhelms the ADS, oxidative damage arises and oxidative stress can occur. Short-term cold exposure in endotherms leads to oxidative stress. As cold exposure persists organisms develop adaptive changes toward reducing ROS production and increasing the ADS. In contrast, heterotherms and ectotherms as a normal part of their over-wintering strategy slow down metabolism, oxygen consumption and subsequently cause ROS production. Increased baseline activity of key anti-oxidant enzymes as well as 'secondary' enzymatic defence and/or glutathione levels in preparation for a putative oxidative stressful situation arising from tissue re-oxygenation seems to be the preferred evolutionary adaptation of such animals exposed to low environmental temperatures.
Topics: Acclimatization; Cold Temperature; Humans; Models, Biological; Oxidation-Reduction; Oxidative Stress; Oxygen Consumption; Reactive Oxygen Species; Thermogenesis
PubMed: 21196386
DOI: 10.2741/s161 -
The Journal of Physiology Aug 2019Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity...
KEY POINTS
Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity impact physiology is unknown. Using human haemoglobin variants, we demonstrate that the affinity of haemoglobin for oxygen is highly correlated with haemoglobin concentration. Using the Fick equation, we model how altered haemoglobin affinity and the associated haemoglobin concentration influences oxygen consumption at rest and during exercise via alterations in cardiac output and mixed-venous . The combination of low oxygen affinity haemoglobin and reduced haemoglobin concentration seen in vivo may be unable to support oxygen uptake during moderate or heavy exercise.
ABSTRACT
The physiological implications, with regard to exercise, of altered haemoglobin affinity for oxygen are not fully understood. Data from the Mayo Clinic Laboratories database of rare human haemoglobin variants reveal a strong inverse correlation (r = -0.82) between blood haemoglobin concentration and P , an index of oxygen affinity [Hb = -0.3135(P ) + 23.636]. In the present study, observed P values for high, normal and low oxygen-affinity haemoglobin variants (13, 26 and 39 mmHg) and corresponding haemoglobin concentrations (19.5, 15.5 and 11.4 g dL respectively) are used to model oxygen consumption as a fraction of delivery at rest ( = 0.25 L min , cardiac output = 5.70 L min ) and during exercise ( = 2.75 L min , cardiac output = 18.9 l min ). With high-affinity haemoglobin, the model shows that normal levels of oxygen consumption can be achieved at rest and during exercise at the assumed cardiac output levels, with reduced oxygen extraction both at rest (16.8% high affinity vs. 21.7% normal) and during exercise (55.8% high affinity vs. 72.2% normal). With low-affinity haemoglobin, which predicts low haemoglobin concentration, oxygen consumption at rest can be sustained with the assumed cardiac output, with increased oxygen extraction (31.1% low affinity vs. 21.7% normal). However, exercise at 2.75 l min cannot be achieved with the assumed cardiac output, even with 100% oxygen extraction. In conclusion, the model indicates chronic alterations in P associate directly with Hb concentration, highlighting that human Hb variants can serve as 'experiments of nature' to address fundamental hypotheses on oxygen transport and exercise.
Topics: Hemoglobins; Humans; Models, Biological; Oxygen; Oxygen Consumption
PubMed: 31290158
DOI: 10.1113/JP277591