Effects of Environmental Oxygen Content and Dissolved Oxygen on the Surface Tension and Viscosity of Liquid Nickel

NASA Astrophysics Data System (ADS)

SanSoucie, M. P.; Rogers, J. R.; Kumar, V.; Rodriguez, J.; Xiao, X.; Matson, D. M.

2016-07-01

The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately 10^{-28} {to} 10^{-9} bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.

Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.; Gowda, Vijaya Kumar Malahalli Shankare; Rodriguez, Justin; Matson, Douglas M.

2015-01-01

The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has been recently upgraded with an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, theoretically in the range from 10-36 to 100 bar. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte, which is yttria-stabilized zirconia. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, PID-based current loop, and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects of oxygen partial pressure on the surface tension of undercooled liquid nickel will be analyzed, and the results will be presented. The surface tension will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension will be measured using the oscillating drop method. While undercooled, each sample will be oscillated several times consecutively to investigate how the surface tension behaves with time while at a particular oxygen partial pressure.

Direct Regularized Estimation of Retinal Vascular Oxygen Tension Based on an Experimental Model

PubMed Central

Yildirim, Isa; Ansari, Rashid; Yetik, I. Samil; Shahidi, Mahnaz

2014-01-01

Phosphorescence lifetime imaging is commonly used to generate oxygen tension maps of retinal blood vessels by classical least squares (LS) estimation method. A spatial regularization method was later proposed and provided improved results. However, both methods obtain oxygen tension values from the estimates of intermediate variables, and do not yield an optimum estimate of oxygen tension values, due to their nonlinear dependence on the ratio of intermediate variables. In this paper, we provide an improved solution by devising a regularized direct least squares (RDLS) method that exploits available knowledge in studies that provide models of oxygen tension in retinal arteries and veins, unlike the earlier regularized LS approach where knowledge about intermediate variables is limited. The performance of the proposed RDLS method is evaluated by investigating and comparing the bias, variance, oxygen tension maps, 1-D profiles of arterial oxygen tension, and mean absolute error with those of earlier methods, and its superior performance both quantitatively and qualitatively is demonstrated. PMID:23732915

Measurement of oxygen tension within mesenchymal stem cell spheroids.

PubMed

Murphy, Kaitlin C; Hung, Ben P; Browne-Bourne, Stephen; Zhou, Dejie; Yeung, Jessica; Genetos, Damian C; Leach, J Kent

2017-02-01

Spheroids formed of mesenchymal stem cells (MSCs) exhibit increased cell survival and trophic factor secretion compared with dissociated MSCs, making them therapeutically advantageous for cell therapy. Presently, there is no consensus for the mechanism of action. Many hypothesize that spheroid formation potentiates cell function by generating a hypoxic core within spheroids of sufficiently large diameters. The purpose of this study was to experimentally determine whether a hypoxic core is generated in MSC spheroids by measuring oxygen tension in aggregates of increasing diameter and correlating oxygen tension values with cell function. MSC spheroids were formed with 15 000, 30 000 or 60 000 cells per spheroid, resulting in radii of 176 ± 8 µm, 251 ± 12 µm and 353 ± 18 µm, respectively. Oxygen tension values coupled with mathematical modelling revealed a gradient that varied less than 10% from the outer diameter within the largest spheroids. Despite the modest radial variance in oxygen tension, cellular metabolism from spheroids significantly decreased as the number of cells and resultant spheroid size increased. This may be due to adaptive reductions in matrix deposition and packing density with increases in spheroid diameter, enabling spheroids to avoid the formation of a hypoxic core. Overall, these data provide evidence that the enhanced function of MSC spheroids is not oxygen mediated. © 2017 The Author(s).

New technique for servo-control of arterial oxygen tension in preterm infants.

PubMed Central

Beddis, I R; Collins, P; Levy, N M; Godfrey, S; Silverman, M

1979-01-01

Equipment has been developed for the servo-control of arterial oxygen tension in sick, newborn babies. Using an indwelling umbilical arterial oxygen electrode as sensor, the equipment successfully regulated the administration of oxygen to 12 newborn babies with respiratory distress syndrome, significantly improving the stability of arterial oxygen tension and lessening the duration of episodes of hypoxia and hyperoxia. PMID:453911

Measurement of oxygen tension in the ischemic myocardium using encased polargraphic oxygen electrodes.

PubMed

Barrett, J A; Lynch, V D; Balkon, J; Wolf, P S

1986-06-01

The ability to continuously monitor the delicate balance between blood flow and oxygen consumption would be a great asset in the study of myocardial ischemia. The present study was performed, in anesthetized dogs, to validate the use of encased polargraphic oxygen electrodes in the study of myocardial ischemia. Polargraphic oxygen electrodes were placed in the area to be rendered ischemic at fixed tissue depths of 3 mm (epicardium) and 9 mm (endocardium). Endocardial and epicardial oxygen tensions as well as the ratio of endocardial to epicardial oxygen tension and left circumflex coronary flow were monitored. Ischemia was induced by decreasing left circumflex coronary flow by 50%. Upon completion of a 20-min poststenotic period, endocardial pO2, endocardial/epicardial ratio, and coronary flow were significantly decreased (59 +/- 7, 52 +/- 7, and 55 +/- 4%, respectively) whereas epicardial pO2 was slightly decreased. Nitroglycerin (10 micrograms/kg, i.v.) markedly increased endocardial pO2 and endocardial/epicardial ratio above poststenotic control (13 +/- 5 mmHg and 64 +/- 10%, respectively) whereas epicardial pO2 was not significantly decreased. The increases in endocardial pO2 occurred at a point where coronary flow and mean arterial pressure were not significantly changed. Conversely, dipyridamole (125 micrograms/kg, i.v.) significantly increased coronary flow (26 +/- 2 ml/min/100 g) although it did not appreciably alter endocardial or epicardial pO2. It is concluded that encased polargraphic oxygen electrodes provide a quantitative method for determination of oxygen tension in the ischemic myocardium.

Oxygen Tension Within the Neurogenic Niche Regulates Dopaminergic Neurogenesis in the Developing Midbrain

PubMed Central

Wagenführ, Lisa; Meyer, Anne Karen; Marrone, Lara

2016-01-01

Oxygen tension is an important factor controlling stem cell proliferation and maintenance in various stem cell populations with a particular relevance in midbrain dopaminergic progenitors. Further studies have shown that the oxygen-dependent transcription factor hypoxia-inducible factor 1α (HIF-1α) is involved in these processes. However, all available studies on oxygen effects in dopaminergic neuroprogenitors were performed in vitro and thus it remains unclear whether tissue oxygen tension in the embryonic midbrain is also relevant for the regulation of dopaminergic neurogenesis in vivo. We thus dissect here the effects of oxygen tension in combination with HIF-1α conditional knockout on dopaminergic neurogenesis by using a novel experimental design allowing for the control of oxygen tension within the microenvironment of the neurogenic niche of the murine fetal midbrain in vivo. The microenvironment of the midbrain dopaminergic neurogenic niche was detected as hypoxic with oxygen tensions below 1.1%. Maternal oxygen treatment of 10%, 21%, and 75% atmospheric oxygen tension for 48 h translates into robust changes in fetal midbrain oxygenation. Fetal midbrain hypoxia hampered the generation of dopaminergic neurons and is accompanied with restricted fetal midbrain development. In contrast, induced hyperoxia stimulated proliferation and differentiation of dopaminergic progenitors during early and late embryogenesis. Oxygen effects were not directly mediated through HIF-1α signaling. These data—in agreement with in vitro data—indicate that oxygen is a crucial regulator of developmental dopaminergic neurogenesis. Our study provides the initial framework for future studies on molecular mechanisms mediating oxygen regulation of dopaminergic neurogenesis within the fetal midbrain as its natural environment. PMID:26577812

Effect of body position and oxygen tension on foramen ovale recruitment.

PubMed

Moses, Kayla L; Beshish, Arij G; Heinowski, Nicole; Baker, Kim R; Pegelow, David F; Eldridge, Marlowe W; Bates, Melissa L

2015-01-01

While there is an increased prevalence of stroke at altitude in individuals who are considered to be low risk for thrombotic events, it is uncertain how venous thrombi reach the brain. The patent foramen ovale (PFO) is a recruitable intracardiac shunt between the right and left atrium. We aimed to determine whether body position and oxygen tension affect blood flow through the PFO in healthy adults. We hypothesized that hypoxia and body positions that promote right atrial filling would independently recruit the PFO. Subjects with a PFO (n = 11) performed 11 trials, combining four different fractions of inhaled oxygen (FiO₂) (1.0, 0.21, 0.15, and 0.10) and three positions (upright, supine, and 45° head down), with the exception of FiO₂ = 0.10, while 45° head down. After 5 min in each position, breathing the prescribed oxygen tension, saline bubbles were injected into an antecubital vein and a four-chamber echocardiogram was obtained to evaluate PFO recruitment. We observed a high incidence of PFO recruitment in all conditions, with increased recruitment in response to severe hypoxia and some contribution of body position at moderate levels of hypoxia. We suspect that increased pulmonary vascular pressure, secondary to hypoxia-induced pulmonary vasoconstriction, increased right atrial pressure enough to recruit the PFO. Additionally, we hypothesize that the minor increase in breathing resistance that was added by the mouthpiece, used during experimental trials, affected intrathoracic pressure and venous return sufficiently to recruit the PFO. Copyright © 2015 the American Physiological Society.

Skin oxygen tension is improved by immersion in oxygen-enriched water.

PubMed

Reading, S A; Yeomans, M; Levesque, C

2013-12-01

The perceived health and physiologic functioning of skin depends on adequate oxygen availability. Economical and easily used therapeutic approaches to increase skin oxygenation could improve the subjective appearance of the skin as well as support the management of some cutaneous conditions related to chronic hypoxic ischaemia (e.g. ulcerative wounds). We have tested the hypothesis that the O2 partial pressure of skin (PskO2 ) increases during immersion in water enriched with high levels of dissolved oxygen. A commercially available device was used to produce water containing 45 to 65 mg L(-1) of dissolved O2 . Young adults (YA; n = 7), older adults (OA; n = 13) and older adults with diabetes (OAD; n = 11) completed different experiments that required them to immerse their feet in tap water (<2 mg L(-1) of O2 ; control) or O2 -enriched water (O2 -H2 O; experimental) for 30 min. Transcutaneous oximetry was used to measure PskO2 for 20 min pre- and post-immersion. Pre-immersion mean (standard deviation) PskO2 on the plantar surface of the big toe was 75 (10), 67 (10) and 65 (10) mmHg in YA, OA and OAD, respectively. Post-immersion PskO2 was 244 (25), 193 (28) and 205 (28) mmHg for the same groups. We also show that post-immersion PskO2 varies by location and with advancing age. Water is an effective vehicle for transporting dissolved O2 across the skin surface and could be used as a basis for development of economical therapeutic approaches that improve skin oxygen tension to support skin health and function. © 2013 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Low oxygen tension enhances endothelial fate of human pluripotent stem cells.

PubMed

Kusuma, Sravanti; Peijnenburg, Elizabeth; Patel, Parth; Gerecht, Sharon

2014-04-01

A critical regulator of the developing or regenerating vasculature is low oxygen tension. Precise elucidation of the role of low oxygen environments on endothelial commitment from human pluripotent stem cells necessitates controlled in vitro differentiation environments. We used a feeder-free, 2-dimensional differentiation system in which we could monitor accurately dissolved oxygen levels during human pluripotent stem cell differentiation toward early vascular cells (EVCs). We found that oxygen uptake rate of differentiating human pluripotent stem cells is lower in 5% O2 compared with atmospheric conditions. EVCs differentiated in 5% O2 had an increased vascular endothelial cadherin expression with clusters of vascular endothelial cadherin+ cells surrounded by platelet-derived growth factor β+ cells. When we assessed the temporal effects of low oxygen differentiation environments, we determined that low oxygen environments during the early stages of EVC differentiation enhance endothelial lineage commitment. EVCs differentiated in 5% O2 exhibited an increased expression of vascular endothelial cadherin and CD31 along with their localization to the membrane, enhanced lectin binding and acetylated low-density lipoprotein uptake, rapid cord-like structure formation, and increased expression of arterial endothelial cell markers. Inhibition of reactive oxygen species generation during the early stages of differentiation abrogated the endothelial inductive effects of the low oxygen environments. Low oxygen tension during early stages of EVC derivation induces endothelial commitment and maturation through the accumulation of reactive oxygen species, highlighting the importance of regulating oxygen tensions during human pluripotent stem cell-vascular differentiation.

The levels and kinetics of oxygen tension detectable at the surface of human dermal fibroblast cultures.

PubMed

Tokuda, Y; Crane, S; Yamaguchi, Y; Zhou, L; Falanga, V

2000-03-01

Low oxygen tension has recently been shown to stimulate cell growth and clonal expansion, as well as synthesis and transcription of certain growth factors and extracellular matrix components. These results have been obtained by exposing cell cultures to a hypoxic environment. Using an oxygen probe, we have now studied how experimental conditions affect the oxygen tension detectable at the cell surface. Dissolved oxygen tension was directly related to the height of the medium above the cell surface (r = 0.8793, P = 0.021), but was constant when no cells were present in the flask (r = -0. 9732, P = 0.001). In both human dermal fibroblasts and NIH/3T3 cultures, oxygen tension decreased linearly as cell density increased (r = -0.835, P < 0.0001; r = -0.916, P < 0.0001, respectively). When human dermal fibroblasts were exposed to 2% O(2), maximum hypoxic levels (0 mmHg) were achieved within approximately 15 min, and the recovery time was within a similar time frame. The addition of rotenone, an inhibitor of cellular respiration, blocked this decrease in oxygen tension at the cell surface, suggesting that cellular consumption of oxygen is responsible for the decline. Finally, we examined the cell-surface oxygen tension in control and acutely wounded human skin equivalents (HSE), consisting of a keratinocyte layer over a type I collagen matrix containing fibroblasts. We found that oxygen tension dropped significantly (P < 0.0001) in acutely wounded areas of HSE as compared to unwounded areas of HSE and that this drop was prevented by the addition of mitomycin C. These results indicate that cell-surface oxygen tension is indirectly related to cell density, and that the amount of detectable oxygen at the cell surface is a function of cell density, the oxygen tension in the incubator, and increased cellular activity, as occurs after injury. Copyright 2000 Wiley-Liss, Inc.

Intracellular oxygen tension limits muscle contraction-induced change in muscle oxygen consumption under hypoxic conditions during Hb-free perfusion.

PubMed

Takakura, Hisashi; Ojino, Minoru; Jue, Thomas; Yamada, Tatsuya; Furuichi, Yasuro; Hashimoto, Takeshi; Iwase, Satoshi; Masuda, Kazumi

2017-01-01

Under acute hypoxic conditions, the muscle oxygen uptake (mV˙O 2 ) during exercise is reduced by the restriction in oxygen-supplied volume to the mitochondria within the peripheral tissue. This suggests the existence of a factor restricting the mV˙O 2 under hypoxic conditions at the peripheral tissue level. Therefore, this study set out to test the hypothesis that the restriction in mV˙O 2 is regulated by the net decrease in intracellular oxygen tension equilibrated with myoglobin oxygen saturation (∆P mb O 2 ) during muscle contraction under hypoxic conditions. The hindlimb of male Wistar rats (8 weeks old, n = 5) was perfused with hemoglobin-free Krebs-Henseleit buffer equilibrated with three different fractions of O 2 gas: 95.0%O 2 , 71.3%O 2 , and 47.5%O 2 The deoxygenated myoglobin (Mb) kinetics during muscle contraction were measured under each oxygen condition with a near-infrared spectroscopy. The ∆[deoxy-Mb] kinetics were converted to oxygen saturation of myoglobin (S mb O 2 ), and the P mb O 2 was then calculated based on the S mb O 2 and the O 2 dissociation curve of the Mb. The S mb O 2 and P mb O 2 at rest decreased with the decrease in O 2 supply, and the muscle contraction caused a further decrease in S mb O 2 and P mb O 2 under all O 2 conditions. The net increase in mV˙O 2 from the muscle contraction (∆mV˙O 2 ) gradually decreased as the ∆P mb O 2 decreased during muscle contraction. The results of this study suggest that ΔP mb O 2 is a key determinant of the ΔmV˙O 2 . © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Low oxygen tension increased fibronectin fragment induced catabolic activities--response prevented with biomechanical signals.

PubMed

Parker, Eleanor; Vessillier, Sandrine; Pingguan-Murphy, Belinda; Abas, Wan; Bader, Dan L; Chowdhury, Tina T

2013-10-25

The inherent low oxygen tension in normal cartilage has implications on inflammatory conditions associated with osteoarthritis (OA). Biomechanical signals will additionally contribute to changes in tissue remodelling and influence the inflammatory response. In this study, we investigated the combined effects of oxygen tension and fibronectin fragment (FN-f) on the inflammatory response of chondrocytes subjected to biomechanical signals. Chondrocytes were cultured under free-swelling conditions at 1%, 5% and 21% oxygen tension or subjected to dynamic compression in an ex vivo 3D/bioreactor model with 29 kDa FN-f, interleukin-1beta (IL-1β) and/or the nitric oxide synthase (NOS) inhibitor for 6 and 48 hours. Markers for catabolic activity (NO, PGE2), tissue remodelling (GAG, MMPs) and cytokines (IL-1β, IL-6 and TNFα) were quantified by biochemical assay. Aggrecan, collagen type II, iNOS and COX-2 gene expression were examined by real-time quantitative PCR. Two-way ANOVA and a post hoc Bonferroni-corrected t-test were used to analyse data. Both FN-fs and IL-1β increased NO, PGE2 and MMP production (all P< 0.001). FN-f was more active than IL-1β with greater levels of NO observed at 5% than 1% or 21% oxygen tension (P < 0.001). Whilst FN-f reduced GAG synthesis at all oxygen tension, the effect of IL-1β was significant at 1% oxygen tension. In unstrained constructs, treatment with FN-f or IL-1β increased iNOS and COX-2 expression and reduced aggrecan and collagen type II (all P < 0.001). In unstrained constructs, FN-f was more effective than IL-1β at 5% oxygen tension and increased production of NO, PGE2, MMP, IL-1β, IL-6 and TNFα. At 5% and 21% oxygen tension, co-stimulation with compression and the NOS inhibitor abolished fragment or cytokine-induced catabolic activities and restored anabolic response. The present findings revealed that FN-fs are more potent than IL-1β in exerting catabolic effects dependent on oxygen tension via iNOS and COX-2 upregulation

The effect of oxygen tension on human articular chondrocyte matrix synthesis: Integration of experimental and computational approaches

PubMed Central

Li, S; Oreffo, ROC; Sengers, BG; Tare, RS

2014-01-01

Significant oxygen gradients occur within tissue engineered cartilaginous constructs. Although oxygen tension is an important limiting parameter in the development of new cartilage matrix, its precise role in matrix formation by chondrocytes remains controversial, primarily due to discrepancies in the experimental setup applied in different studies. In this study, the specific effects of oxygen tension on the synthesis of cartilaginous matrix by human articular chondrocytes were studied using a combined experimental-computational approach in a “scaffold-free” 3D pellet culture model. Key parameters including cellular oxygen uptake rate were determined experimentally and used in conjunction with a mathematical model to estimate oxygen tension profiles in 21-day cartilaginous pellets. A threshold oxygen tension (pO2 ≈ 8% atmospheric pressure) for human articular chondrocytes was estimated from these inferred oxygen profiles and histological analysis of pellet sections. Human articular chondrocytes that experienced oxygen tension below this threshold demonstrated enhanced proteoglycan deposition. Conversely, oxygen tension higher than the threshold favored collagen synthesis. This study has demonstrated a close relationship between oxygen tension and matrix synthesis by human articular chondrocytes in a “scaffold-free” 3D pellet culture model, providing valuable insight into the understanding and optimization of cartilage bioengineering approaches. Biotechnol. Bioeng. 2014;111: 1876–1885. PMID:24668194

Influence of Oxygen Tension on Dopaminergic Differentiation of Human Fetal Stem Cells of Midbrain and Forebrain Origin

PubMed Central

Krabbe, Christina; Bak, Sara Thornby; Jensen, Pia; von Linstow, Christian; Martínez Serrano, Alberto; Hansen, Claus; Meyer, Morten

2014-01-01

Neural stem cells (NSCs) constitute a promising source of cells for transplantation in Parkinson's disease (PD), but protocols for controlled dopaminergic differentiation are not yet available. Here we investigated the influence of oxygen on dopaminergic differentiation of human fetal NSCs derived from the midbrain and forebrain. Cells were differentiated for 10 days in vitro at low, physiological (3%) versus high, atmospheric (20%) oxygen tension. Low oxygen resulted in upregulation of vascular endothelial growth factor and increased the proportion of tyrosine hydroxylase-immunoreactive (TH-ir) cells in both types of cultures (midbrain: 9.1±0.5 and 17.1±0.4 (P<0.001); forebrain: 1.9±0.4 and 3.9±0.6 (P<0.01) percent of total cells). Regardless of oxygen levels, the content of TH-ir cells with mature neuronal morphologies was higher for midbrain as compared to forebrain cultures. Proliferative Ki67-ir cells were found in both types of cultures, but the relative proportion of these cells was significantly higher for forebrain NSCs cultured at low, as compared to high, oxygen tension. No such difference was detected for midbrain-derived cells. Western blot analysis revealed that low oxygen enhanced β-tubulin III and GFAP expression in both cultures. Up-regulation of β-tubulin III was most pronounced for midbrain cells, whereas GFAP expression was higher in forebrain as compared to midbrain cells. NSCs from both brain regions displayed less cell death when cultured at low oxygen tension. Following mictrotransplantation into mouse striatal slice cultures predifferentiated midbrain NSCs were found to proliferate and differentiate into substantial numbers of TH-ir neurons with mature neuronal morphologies, particularly at low oxygen. In contrast, predifferentiated forebrain NSCs microtransplanted using identical conditions displayed little proliferation and contained few TH-ir cells, all of which had an immature appearance. Our data may reflect differences in

Hemodynamic parameters change earlier than tissue oxygen tension in hemorrhage.

PubMed

Pestel, Gunther J; Fukui, Kimiko; Kimberger, Oliver; Hager, Helmut; Kurz, Andrea; Hiltebrand, Luzius B

2010-05-15

Untreated hypovolemia results in impaired outcome. This study tests our hypothesis whether general hemodynamic parameters detect acute blood loss earlier than monitoring parameters of regional tissue beds. Eight pigs (23-25 kg) were anesthetized and mechanically ventilated. A pulmonary artery catheter and an arterial catheter were inserted. Tissue oxygen tension was measured with Clark-type electrodes in the jejunal and colonic wall, in the liver, and subcutaneously. Jejunal microcirculation was assessed by laser Doppler flowmetry (LDF). Intravascular volume was optimized using difference in pulse pressure (dPP) to keep dPP below 13%. Sixty minutes after preparation, baseline measurements were taken. At first, 5% of total blood volume was withdrawn, followed by another 5% increment, and then in 10% increments until death. After withdrawal of 5% of estimated blood volume, dPP increased from 6.1% +/- 3.0% to 20.8% +/- 2.7% (P < 0.01). Mean arterial pressure (MAP), mean pulmonary artery pressure (PAP) and pulmonary artery occlusion pressure (PAOP) decreased with a blood loss of 10% (P < 0.01). Cardiac output (CO) changed after a blood loss of 20% (P < 0.05). Tissue oxygen tension in central organs, and blood flow in the jejunal muscularis decreased (P < 0.05) after a blood loss of 20%. Tissue oxygen tension in the skin, and jejunal mucosa blood flow decreased (P < 0.05) after a blood loss of 40% and 50%, respectively. In this hemorrhagic pig model systemic hemodynamic parameters were more sensitive to detect acute hypovolemia than tissue oxygen tension measurements or jejunal LDF measurements. Acute blood loss was detected first by dPP. Copyright (c) 2010 Elsevier Inc. All rights reserved.

Mimicking physiological O2 tension in the female reproductive tract improves Assisted Reproduction outcomes in pig.

PubMed

García-Martínez, S; Sánchez-Hurtado, M A; Gutiérrez, H; Sánchez-Margallo, F M; Romar, R; Latorre, R; Coy, P; López-Albors, O

2018-02-27

48hpi, cleavage was evaluated under the stereomicroscope. Finally, at 180hpi, development to the blastocyst stage was quantified, blastocyst morphology was assessed, and embryos were fixed and stained to count the mean cell number per blastocyst. The mean O2 content within the pig oviduct and uterus was always lower than in ambient air. The average O2 percentage was higher in gilts (10.0%) than in sows (7.6%) (p < 0.0001). The cleavage rate of porcine in vitro fertilized embryos maintained under 7% O2 during IVF and EC was significantly higher (60.0 ± 2.3) compared with those cultured under 20% O2 (32.0 ± 2.2) (p < 0.05). An increase in the number of cells in embryos cultured under the low O2 concentration (88.9 ± 5.9) was observed compared to those cultured under 20% O2 (59.0 ± 5.0) (p < 0.05). None. Although minimally invasive surgery was used the effect of anaesthesia and manipulations on O2 tension within the organs are unknown. Using physiological oxygen concentrations in IVF/EC could improve ART outcomes. This study was funded by Spanish Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER). Grants AGL2012-40180-C03-01 and AGL2015-66341-R. The authors declare no conflict of interest.

Transcutaneous oxygen tension monitoring in critically ill patients receiving packed red blood cells.

PubMed

Schlager, Oliver; Gschwandtner, Michael E; Willfort-Ehringer, Andrea; Kurz, Martin; Mueller, Markus; Koppensteiner, Renate; Heinz, Gottfried

2014-12-01

Whether transfusions of packed red blood cells (PRBCs) affect tissue oxygenation in stable critically ill patients is still matter of discussion. The microvascular capacity for tissue oxygenation can be determined noninvasively by measuring transcutaneous oxygen tension (tcpO2). The aim of this study was to assess tissue oxygenation by measuring tcpO2 in stable critically ill patients receiving PRBC transfusions. Nineteen stable critically ill patients, who received 2 units of PRBC, were prospectively included into this pilot study. Transcutaneous oxygen tension was measured continuously during PRBC transfusions using Clark's electrodes. In addition, whole blood viscosity and global hemodynamics were determined. Reliable measurement signals during continuous tcpO2 monitoring were observed in 17 of 19 included patients. Transcutaneous oxygen tension was related to the global oxygen consumption (r=-0.78; P=.003), the arterio-venous oxygen content difference (r=-0.65; P=.005), and the extraction rate (r=-0.71; P=.02). The transfusion-induced increase of the hemoglobin concentration was paralleled by an increase of the whole blood viscosity (P<.001). Microvascular tissue oxygenation by means of tcpO2 was not affected by PRBC transfusions (P=.46). Packed red blood cell transfusions resulted in an increase of global oxygen delivery (P=.02) and central venous oxygen saturation (P=.01), whereas oxygen consumption remained unchanged (P=.72). In stable critically ill patients, microvascular tissue oxygenation can be continuously monitored by Clark's tcpO2 electrodes. According to continuous tcpO2 measurements, the microvascular tissue oxygenation is not affected by PRBC transfusions. Copyright © 2014 Elsevier Inc. All rights reserved.

Mixed-venous oxygen tension by nitrogen rebreathing - A critical, theoretical analysis.

NASA Technical Reports Server (NTRS)

Kelman, G. R.

1972-01-01

There is dispute about the validity of the nitrogen rebreathing technique for determination of mixed-venous oxygen tension. This theoretical analysis examines the circumstances under which the technique is likely to be applicable. When the plateau method is used the probable error in mixed-venous oxygen tension is plus or minus 2.5 mm Hg at rest, and of the order of plus or minus 1 mm Hg during exercise. Provided, that the rebreathing bag size is reasonably chosen, Denison's (1967) extrapolation technique gives results at least as accurate as those obtained by the plateau method. At rest, however, extrapolation should be to 30 rather than to 20 sec.

Oxygen diffusion and consumption in extracellular matrix gels: implications for designing three-dimensional cultures.

PubMed

Colom, Adai; Galgoczy, Roland; Almendros, Isaac; Xaubet, Antonio; Farré, Ramon; Alcaraz, Jordi

2014-08-01

Three-dimensional (3D) cultures are increasingly used as tissue surrogates to study many physiopathological processes. However, to what extent current 3D culture protocols provide physiologic oxygen tension conditions remains ill defined. To address this limitation, oxygen tension was measured in a panel of acellular or cellularized extracellular matrix (ECM) gels with A549 cells, and analyzed in terms of oxygen diffusion and consumption. Gels included reconstituted basement membrane, fibrin and collagen. Oxygen diffusivity in acellular gels was up to 40% smaller than that of water, and the lower values were observed in the denser gels. In 3D cultures, physiologic oxygen tension was achieved after 2 days in dense (≥3 mg/mL) but not sparse gels, revealing that the latter gels are not suitable tissue surrogates in terms of oxygen distribution. In dense gels, we observed a dominant effect of ECM composition over density in oxygen consumption. All diffusion and consumption data were used in a simple model to estimate ranges for gel thickness, seeding density and time-window that may support physiologic oxygen tension. Thus, we identified critical variables for oxygen tension in ECM gels, and introduced a model to assess initial values of these variables, which may short-cut the optimization step of 3D culture studies. © 2013 Wiley Periodicals, Inc.

Influence of oxygen partial pressure on surface tension and its temperature coefficient of molten iron

NASA Astrophysics Data System (ADS)

Ozawa, S.; Suzuki, S.; Hibiya, T.; Fukuyama, H.

2011-01-01

Influences of oxygen partial pressure, PO2, of ambient atmosphere and temperature on surface tension and its temperature coefficient for molten iron were experimentally investigated by an oscillating droplet method using an electromagnetic levitation furnace. We successfully measured the surface tension of molten iron over a very wide temperature range of 780 K including undercooling condition in a well controlled PO2 atmosphere. When PO2 is fixed at 10-2 Pa at the inlet of the chamber, a "boomerang shape" temperature dependence of surface tension was experimentally observed; surface tension increased and then decreased with increasing temperature. The pure surface tension of molten iron was deduced from the negative temperature coefficient in the boomerang shape temperature dependence. When the surface tension was measured under the H2-containing gas atmosphere, surface tension did not show a linear relationship against temperature. The temperature dependence of the surface tension shows anomalous kink at around 1850 K due to competition between the temperature dependence of PO2 and that of the equilibrium constant of oxygen adsorption.

The effect of bladder outlet obstruction on tissue oxygen tension and blood flow in the pig bladder.

PubMed

Greenland, J E; Hvistendahl, J J; Andersen, H; Jörgensen, T M; McMurray, G; Cortina-Borja, M; Brading, A F; Frøkiaer, J

2000-06-01

To investigate the effect of partial bladder outlet obstruction on detrusor blood flow and oxygen tension (PdetO2) in female pigs. Detrusor-layer oxygen tension and blood flow were measured using oxygen-sensitive electrode and radiolabelled microsphere techniques in five female Large White pigs with a partial urethral obstruction and in five sham-operated controls. The effects of chronic outlet obstruction on bladder weight, and cholinergic nerve density and distribution, are also described. In the obstructed bladders, blood flow and oxygen tension were, respectively, 54.9% and 74.3% of control values at low bladder volume, and 47.5% and 42.5% at cystometric capacity. Detrusor blood flow declined by 27.8% and 37.5% in the control and obstructed bladders, respectively, as a result of bladder filling, whilst PdetO2 did not decrease in the controls, but fell by 42.7% in the obstructed bladders. Bladder weight increased whilst cholinergic nerve density decreased in the obstructed animals. In pigs with chronic bladder outlet obstruction, blood flow and oxygen tension in the detrusor layer were lower than in control animals. In addition, increasing detrusor pressure during filling caused significantly greater decreases in blood flow and oxygen tension in the obstructed than in the control bladders.

Impact of low oxygen tension on stemness, proliferation and differentiation potential of human adipose-derived stem cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Jane Ru; Pingguan-Murphy, Belinda; Wan Abas, Wan Abu Bakar

2014-05-30

Highlights: • Hypoxia maintains the stemness of adipose-derived stem cells (ASCs). • ASCs show an increased proliferation rate under low oxygen tension. • Oxygen level as low as 2% enhances the chondrogenic differentiation potential of ASCs. • HIF-1α may regulate the proliferation and differentiation activities of ASCs under hypoxia. - Abstract: Adipose-derived stem cells (ASCs) have been found adapted to a specific niche with low oxygen tension (hypoxia) in the body. As an important component of this niche, oxygen tension has been known to play a critical role in the maintenance of stem cell characteristics. However, the effect of O{submore » 2} tension on their functional properties has not been well determined. In this study, we investigated the effects of O{sub 2} tension on ASCs stemness, differentiation and proliferation ability. Human ASCs were cultured under normoxia (21% O{sub 2}) and hypoxia (2% O{sub 2}). We found that hypoxia increased ASC stemness marker expression and proliferation rate without altering their morphology and surface markers. Low oxygen tension further enhances the chondrogenic differentiation ability, but reduces both adipogenic and osteogenic differentiation potential. These results might be correlated with the increased expression of HIF-1α under hypoxia. Taken together, we suggest that growing ASCs under 2% O{sub 2} tension may be important in expanding ASCs effectively while maintaining their functional properties for clinical therapy, particularly for the treatment of cartilage defects.« less

[Long-term expansion of multipotent mesenchymal stromal cells under reduced oxygen tension].

PubMed

Rylova, Iu V; Buravkova, L B

2013-01-01

We have shown that the decrease in oxygen tension in the culture medium of multipotent mesenchymal stromal cells (MMSCs) results in a short-term reduction in the proportion of CD73(+)-cells in the population, without effecting the number of cells expressing other constitutive surface markers (CD90 and CD105). In this case, the heterogeneity of the cell population declined: large spread cells disappeared. The proliferative activity of MMSCs significantly increased and remained stable in conditions in which the oxygen content was close to the tissue oxygen levels (5% O2). At lower oxygen concentration, proliferative activity of the cells gradually reduced from passages 3-4. The increase in proliferative activity was not accompanied by increased expression of telomerase gene indicateding the alsance of cell transformation. However, genome-wide analysis of MMSC gene expression level revealed changes in expression of cyclins (CCND2 and PCNA), regulatory subunit cyclin-dependent kinase (CKS2) and an inhibitor of cyclin-dependent kinase (CDKN2C), regulating the cell cycle, which is obviously facilitated the increase in the proliferative capacity of cells at lower oxygen tension.

Renal transplantation induces mitochondrial uncoupling, increased kidney oxygen consumption, and decreased kidney oxygen tension.

PubMed

Papazova, Diana A; Friederich-Persson, Malou; Joles, Jaap A; Verhaar, Marianne C

2015-01-01

Hypoxia is an acknowledged pathway to renal injury and ischemia-reperfusion (I/R) and is known to reduce renal oxygen tension (Po2). We hypothesized that renal I/R increases oxidative damage and induces mitochondrial uncoupling, resulting in increased oxygen consumption and hence kidney hypoxia. Lewis rats underwent syngenic renal transplantation (TX) and contralateral nephrectomy. Controls were uninephrectomized (1K-CON) or left untreated (2K-CON). After 7 days, urinary excretion of protein and thiobarbituric acid-reactive substances were measured, and after 14 days glomerular filtration rate (GFR), renal blood flow, whole kidney Qo2, cortical Po2, kidney cortex mitochondrial uncoupling, renal oxidative damage, and tubulointerstitial injury were assessed. TX, compared with 1K-CON, resulted in mitochondrial uncoupling mediated via uncoupling protein-2 (16 ± 3.3 vs. 0.9 ± 0.4 pmol O2 · s(-1)· mg protein(-1), P < 0.05) and increased whole kidney Qo2 (55 ± 16 vs. 33 ± 10 μmol O2/min, P < 0.05). Corticomedullary Po2 was lower in TX compared with 1K-CON (30 ± 13 vs. 47 ± 4 μM, P < 0.05) whereas no significant difference was observed between 2K-CON and 1K-CON rats. Proteinuria, oxidative damage, and the tubulointerstitial injury score were not significantly different in 1K-CON and TX. Treatment of donors for 5 days with mito-TEMPO reduced mitochondrial uncoupling but did not affect renal hemodynamics, Qo2, Po2, or injury. Collectively, our results demonstrate increased mitochondrial uncoupling as an early event after experimental renal transplantation associated with increased oxygen consumption and kidney hypoxia in the absence of increases in markers of damage. Copyright © 2015 the American Physiological Society.

Exogenous and endogenous angiotensin-II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow.

PubMed

Emans, Tonja W; Janssen, Ben J; Pinkham, Maximilian I; Ow, Connie P C; Evans, Roger G; Joles, Jaap A; Malpas, Simon C; Krediet, C T Paul; Koeners, Maarten P

2016-11-01

Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary. We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats. This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation. Exogenous angiotensin-II reduced renal cortical tissue PO2 more than equi-pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine. Activation of the endogenous renin-angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin-II receptor type 1 antagonist. Angiotensin-II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease. We hypothesised that both exogenous and endogenous angiotensin-II (AngII) can decrease the partial pressure of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn contribute to the progression of chronic kidney disease. Rats were instrumented with telemeters equipped with a carbon paste electrode for continuous measurement of renal cortical tissue PO2. The method reproducibly detected acute changes in cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious rats, renal cortical PO2 was dose-dependently reduced by intravenous AngII. Reductions in PO2 were significantly greater than those induced by equi-pressor doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not affected, and filtration fraction was increased only in the AngII infused animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood flow (RBF) fell by 3.3 ml min -1 . Equi-pressor infusion of

Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

PubMed Central

Sgouralis, Ioannis; Kett, Michelle M.; Ow, Connie P. C.; Abdelkader, Amany; Layton, Anita T.; Gardiner, Bruce S.; Smith, David W.; Lankadeva, Yugeesh R.

2016-01-01

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2. Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2. Both intravenous infusion of [Phe2,Ile3,Orn8]-vasopressin and infusion of NG-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8–17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r2 = 0.87–0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2. Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1–0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10–50% of the change in pelvic urine/medullary Po2. Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury. PMID:27385734

Oxygen tension affects histone remodeling of in vitro-produced embryos in a bovine model.

PubMed

Gaspar, Roberta C; Arnold, Daniel R; Corrêa, Carolina A P; da Rocha, Carlos V; Penteado, João C T; Del Collado, Maite; Vantini, Roberta; Garcia, Joaquim M; Lopes, Flavia L

2015-06-01

In vitro production of bovine embryos is a biotechnology of great economic impact. Epigenetic processes, such as histone remodeling, control gene expression and are essential for proper embryo development. Given the importance of IVP as a reproductive biotechnology, the role of epigenetic processes during embryo development, and the important correlation between culture conditions and epigenetic patterns, the present study was designed as a 2 × 2 factorial to investigate the influence of varying oxygen tensions (O2; 5% and 20%) and concentrations of fetal bovine serum (0% and 2.5%), during IVC, in the epigenetic remodeling of H3K9me2 (repressive) and H3K4me2 (permissive) in bovine embryos. Bovine oocytes were used for IVP of embryos, cleavage and blastocyst rates were evaluated, and expanded blastocysts were used for evaluation of the histone marks H3K9me2 and H3K4me2. Morulae and expanded blastocysts were also used to evaluate the expression of remodeling enzymes, specific to the aforementioned marks, by real-time polymerase chain reaction. Embryos produced in the presence of fetal bovine serum (2.5%) had a 10% higher rate of blastocyst formation. Global staining for the residues H3K9me2 and H3K4me2 was not affected significantly by the presence of serum. Notwithstanding, the main effect of oxygen tension was significant for both histone marks, with both repressive and permissive marks being higher in embryos cultured at the higher oxygen tension; however, expression of the remodeling enzymes did not differ in morulae or blastocysts in response to the varying oxygen tension. These results suggest that the use of serum during IVC of embryos increases blastocyst rate without affecting the evaluated histone marks and that oxygen tension has an important effect on the histone marks H3K9me2 and H3K4me2 in bovine blastocysts. Copyright © 2015 Elsevier Inc. All rights reserved.

Oxygen demand of perfused heart preparations: how electromechanical function and inadequate oxygenation affect physiology and optical measurements.

PubMed

Kuzmiak-Glancy, Sarah; Jaimes, Rafael; Wengrowski, Anastasia M; Kay, Matthew W

2015-06-01

What is the topic of this review? This review discusses how the function and electrophysiology of isolated perfused hearts are affected by oxygenation and energy utilization. The impact of oxygenation on fluorescence measurements in perfused hearts is also discussed. What advances does it highlight? Recent studies have illuminated the inherent differences in electromechanical function, energy utilization rate and oxygen requirements between the primary types of excised heart preparations. A summary and analysis of how these variables affect experimental results are necessary to elevate the physiological relevance of these approaches in order to advance the field of whole-heart research. The ex vivo perfused heart recreates important aspects of in vivo conditions to provide insight into whole-organ function. In this review we discuss multiple types of ex vivo heart preparations, explain how closely each mimic in vivo function, and discuss how changes in electromechanical function and inadequate oxygenation of ex vivo perfused hearts may affect measurements of physiology. Hearts that perform physiological work have high oxygen demand and are likely to experience hypoxia when perfused with a crystalloid perfusate. Adequate myocardial oxygenation is critically important for obtaining physiologically relevant measurements, so when designing experiments the type of ex vivo preparation and the capacity of perfusate to deliver oxygen must be carefully considered. When workload is low, such as during interventions that inhibit contraction, oxygen demand is also low, which could dramatically alter a physiological response to experimental variables. Changes in oxygenation also alter the optical properties of cardiac tissue, an effect that may influence optical signals measured from both endogenous and exogenous fluorophores. Careful consideration of oxygen supply, working condition, and wavelengths used to acquire optical signals is critical for obtaining physiologically

Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Pia; Department of Neurosurgery, University of Bern, CH-3010 Bern; Gramsbergen, Jan-Bert

Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than in high oxygen cultures. Low oxygen during FGF2-mediated expansion resulted also in a significant increase in tyrosine hydroxylase-immunoreactivemore » (TH-ir) dopaminergic neurons as compared to high oxygen tension, but no corresponding effect was observed for dopamine release into the culture medium. However, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells.« less

Brain oxygen tension controls the expansion of outer subventricular zone-like basal progenitors in the developing mouse brain.

PubMed

Wagenführ, Lisa; Meyer, Anne K; Braunschweig, Lena; Marrone, Lara; Storch, Alexander

2015-09-01

The mammalian neocortex shows a conserved six-layered structure that differs between species in the total number of cortical neurons produced owing to differences in the relative abundance of distinct progenitor populations. Recent studies have identified a new class of proliferative neurogenic cells in the outer subventricular zone (OSVZ) in gyrencephalic species such as primates and ferrets. Lissencephalic brains of mice possess fewer OSVZ-like progenitor cells and these do not constitute a distinct layer. Most in vitro and in vivo studies have shown that oxygen regulates the maintenance, proliferation and differentiation of neural progenitor cells. Here we dissect the effects of fetal brain oxygen tension on neural progenitor cell activity using a novel mouse model that allows oxygen tension to be controlled within the hypoxic microenvironment in the neurogenic niche of the fetal brain in vivo. Indeed, maternal oxygen treatment of 10%, 21% and 75% atmospheric oxygen tension for 48 h translates into robust changes in fetal brain oxygenation. Increased oxygen tension in fetal mouse forebrain in vivo leads to a marked expansion of a distinct proliferative cell population, basal to the SVZ. These cells constitute a novel neurogenic cell layer, similar to the OSVZ, and contribute to corticogenesis by heading for deeper cortical layers as a part of the cortical plate. © 2015. Published by The Company of Biologists Ltd.

Regional myocardial oxygen tension: 19F MRI of sequestered perfluorocarbon.

PubMed

Shukla, H P; Mason, R P; Bansal, N; Antich, P P

1996-06-01

A novel noninvasive method of measuring local myocardial oxygen tension (pO2) in the perfused rat heart using 19F MRI is demonstrated. Tissue pO2 was determined on the basis of the 19F spin-lattice relaxation rate (R1) of perflubron (perfluorooctyl bromide) sequestered in the heart after IV infusion of an emulsion. Spectroscopic measurement of R1 was previously used to measure a global weighted average of oxygen status. 19F MRI now provides 3D spatial resolution indicating local cardiac pO2 under normally perfused, globally ischemic, and regionally ischemic conditions.

Contrasted Reactivity to Oxygen Tensions in Frankia sp. Strain CcI3 throughout Nitrogen Fixation and Assimilation

PubMed Central

Ghodhbane-Gtari, Faten; Hezbri, Karima; Ktari, Amir; Sbissi, Imed; Beauchemin, Nicholas; Gtari, Maher; Tisa, Louis S.

2014-01-01

Reconciling the irreconcilable is a primary struggle in aerobic nitrogen-fixing bacteria. Although nitrogenase is oxygen and reactive oxygen species-labile, oxygen tension is required to sustain respiration. In the nitrogen-fixing Frankia, various strategies have been developed through evolution to control the respiration and nitrogen-fixation balance. Here, we assessed the effect of different oxygen tensions on Frankia sp. strain CcI3 growth, vesicle production, and gene expression under different oxygen tensions. Both biomass and vesicle production were correlated with elevated oxygen levels under both nitrogen-replete and nitrogen-deficient conditions. The mRNA levels for the nitrogenase structural genes (nifHDK) were high under hypoxic and hyperoxic conditions compared to oxic conditions. The mRNA level for the hopanoid biosynthesis genes (sqhC and hpnC) was also elevated under hyperoxic conditions suggesting an increase in the vesicle envelope. Under nitrogen-deficient conditions, the hup2 mRNA levels increased with hyperoxic environment, while hup1 mRNA levels remained relatively constant. Taken together, these results indicate that Frankia protects nitrogenase by the use of multiple mechanisms including the vesicle-hopanoid barrier and increased respiratory protection. PMID:24987692

Cerebral interstitial tissue oxygen tension, pH, HCO3, CO2.

PubMed

Charbel, F T; Hoffman, W E; Misra, M; Hannigan, K; Ausman, J I

1997-10-01

There are many techniques for monitoring the injured brain following trauma, subarachnoid hemorrhage, or surgery. It is thought that the major determinants for recovery of injured cerebral tissue are oxygen, glucose delivery, and the clearance of metabolites. These factors, at optimal levels, are probably responsible for the regaining of neuronal functions. These parameters are in turn dependent on the tissue's blood flow and metabolism. We have been using a single, compact, polyethylene sensor, the Paratrend 7 for the measurement of cerebral oxygen tension, CO2, pH, and temperature. This sensor is designed for continuous blood gas analysis to aid in monitoring neurosurgical patients, both during surgery and in the intensive care unit. Using the Paratrend 7 sensor, we found the normal range of values to be: PO2 33 +/- 11 mm Hg; PCO2 48 +/- 7 mm Hg; pH 7.19 +/- 0.11. Critical measurements are considered to be tissue PO2 < 10 mm Hg; PCO2 > 60 mm Hg, and pH < 6.8. We have had no complications with this device; the risks are similar to those of placing a parenchymal intracranial pressure monitor. We believe that assessment of interstitial cerebral oxygen saturation can be of great value both intraoperatively and postoperatively. In our experience, the Paratrend 7 system is an effective method of measuring tissue cerebral oxygen tension, along with carbon dioxide levels, pH, and temperature.

Co-regulation of primary mouse hepatocyte viability and function by oxygen and matrix.

PubMed

Buck, Lorenna D; Inman, S Walker; Rusyn, Ivan; Griffith, Linda G

2014-05-01

Although oxygen and extracellular matrix cues both influence differentiation state and metabolic function of primary rat and human hepatocytes, relatively little is known about how these factors together regulate behaviors of primary mouse hepatocytes in culture. To determine the effects of pericellular oxygen tension on hepatocellular function, we employed two methods of altering oxygen concentration in the local cellular microenvironment of cells cultured in the presence or absence of an extracellular matrix (Matrigel) supplement. By systematically altering medium depth and gas phase oxygen tension, we created multiple oxygen regimes (hypoxic, normoxic, and hyperoxic) and measured the local oxygen concentrations in the pericellular environment using custom-designed oxygen microprobes. From these measurements of oxygen concentrations, we derived values of oxygen consumption rates under a spectrum of environmental contexts, thus providing the first reported estimates of these values for primary mouse hepatocytes. Oxygen tension and matrix microenvironment were found to synergistically regulate hepatocellular survival and function as assessed using quantitative image analysis for cells stained with vital dyes, and assessment of secretion of albumin. Hepatocellular viability was affected only at strongly hypoxic conditions. Surprisingly, albumin secretion rates were greatest at a moderately supra-physiological oxygen concentration, and this effect was mitigated at still greater supra-physiological concentrations. Matrigel enhanced the effects of oxygen on retention of function. This study underscores the importance of carefully controlling cell density, medium depth, and gas phase oxygen, as the effects of these parameters on local pericellular oxygen tension and subsequent hepatocellular function are profound. © 2014 Wiley Periodicals, Inc.

Co-regulation of Primary Mouse Hepatocyte Viability and Function by Oxygen and Matrix

PubMed Central

Buck, Lorenna D.; Inman, S. Walker; Rusyn, Ivan; Griffith, Linda G.

2014-01-01

Although oxygen and extracellular matrix cues both influence differentiation state and metabolic function of primary rat and human hepatocytes, relatively little is known about how these factors together regulate behaviors of primary mouse hepatocytes in culture. To determine the effects of pericellular oxygen tension on hepatocellular function, we employed 2 methods of altering oxygen concentration in the local cellular microenvironment of cells cultured in the presence or absence of an extracellular matrix (Matrigel) supplement. By systematically altering medium depth and gas phase oxygen tension, we created multiple oxygen regimes (hypoxic, normoxic, and hyperoxic) and measured the local oxygen concentrations in the pericellular environment using custom-designed oxygen microprobes. From these measurements of oxygen concentrations, we derived values of oxygen consumption rates under a spectrum of environmental contexts, thus providing the first reported estimates of these values for primary mouse hepatocytes. Oxygen tension and matrix microenvironment were found to synergistically regulate hepatocellular survival and function as assessed using quantitative image analysis for cells stained with vital dyes, and assessment of secretion of albumin. Hepatocellular viability was affected only at strongly hypoxic conditions. Surprisingly, albumin secretion rates were greatest at a moderately supra-physiological oxygen concentration, and this effect was mitigated at still greater supra-physiological concentrations. Matrigel enhanced the effects of oxygen on retention of function. This study underscores the importance of carefully controlling cell density, medium depth and gas phase oxygen, as the effects of these parameters on local pericellular oxygen tension and subsequent hepatocellular function are profound. PMID:24222008

Synoviocyte Derived-Extracellular Matrix Enhances Human Articular Chondrocyte Proliferation and Maintains Re-Differentiation Capacity at Both Low and Atmospheric Oxygen Tensions

PubMed Central

Kean, Thomas J.; Dennis, James E.

2015-01-01

Background Current tissue engineering methods are insufficient for total joint resurfacing, and chondrocytes undergo de-differentiation when expanded on tissue culture plastic. De-differentiated chondrocytes show poor re-differentiation in culture, giving reduced glycosaminoglycan (GAG) and collagen matrix accumulation. To address this, porcine synoviocyte-derived extracellular matrix and low (5%) oxygen tension were assessed for their ability to enhance human articular chondrocyte expansion and maintain re-differentiation potential. Methods Porcine synoviocyte matrices were devitalized using 3 non-detergent methods. These devitalized synoviocyte matrices were compared against tissue culture plastic for their ability to support human chondrocyte expansion. Expansion was further compared at both low (5%), and atmospheric (20%) oxygen tension on all surfaces. Expanded cells then underwent chondrogenic re-differentiation in aggregate culture at both low and atmospheric oxygen tension. Aggregates were assessed for their GAG and collagen content both biochemically and histologically. Results Human chondrocytes expanded twice as fast on devitalized synoviocyte matrix vs. tissue culture plastic, and cells retained their re-differentiation capacity for twice the number of population doublings. There was no significant difference in growth rate between low and atmospheric oxygen tension. There was significantly less collagen type I, collagen type II, aggrecan and more MMP13 expression in cells expanded on synoviocyte matrix vs. tissue culture plastic. There were also significant effects due to oxygen tension on gene expression, wherein there was greater collagen type I, collagen type II, SOX9 and less MMP13 expression on tissue culture plastic compared to synoviocyte matrix. There was a significant increase in GAG, but not collagen, accumulation in chondrocyte aggregates re-differentiated at low oxygen tension over that achieved in atmospheric oxygen conditions. Conclusions

Physiological effects of positive pressure breathing with pure oxygen and a low oxygen gas mixture.

PubMed

Liu, Xiaopeng; Xiao, Huajun; Shi, Weiru; Wen, Dongqing; Yu, Lihua; Chen, Jianzhang

2015-01-01

Positive pressure breathing (PPB) can cause circulatory dysfunction due to peripheral pooling of blood. This study explored a better way at ground level to simulate pure oxygen PPB at 59,055 ft (18,000 m) by comparing the physiological changes during PPB with pure oxygen and low oxygen at ground level. Six subjects were exposed to 3 min of 69-mmHg PPB and 3 min of 59-mmHg PPB with pure oxygen and low oxygen while wearing the thoracic counterpressure jerkin inflated to 1× breathing pressure and G-suit inflated to 3 and 4× breathing pressure. Stroke volume (SV), cardiac output (CO), heart rate (HR), and peripheral oxygen saturation (Spo2) were measured. Subjects completed a simulating flying task (SFT) during 3-min PPB and scores were recorded. HR and SV responses differed significantly between breathing pure oxygen and low oxygen. CO response was not significantly different for pure oxygen and low oxygen, the two levels of PPB, and the two levels of G-suit pressure. Spo2 declined as a linear function of time during low-oxygen PPB and there was a significant difference in Spo2 response for the two levels of PPB. The average score of SFT during pure oxygen PPB was 3970.5 ± 1050.4, which was significantly higher than 2708.0 ± 702.7 with low oxygen PPB. Hypoxia and PPB have a synergistic negative effect on both the cardiovascular system and SFT performance. PPB with low oxygen was more appropriate at ground level to investigate physiological responses during PPB and evaluate the protective performance of garments. Liu X, Xiao H, Shi W, Wen D, Yu L, Chen J. Physiological effects of positive pressure breathing with pure oxygen and a low oxygen gas mixture.

Physiologically Low Oxygen Enhances Biomolecule Production and Stemness of Mesenchymal Stem Cell Spheroids

PubMed Central

Shearier, Emily; Xing, Qi; Qian, Zichen

2016-01-01

Multicellular human mesenchymal stem cell (hMSC) spheroids have been demonstrated to be valuable in a variety of applications, including cartilage regeneration, wound healing, and neoangiogenesis. Physiological relevant low oxygen culture can significantly improve in vitro hMSC expansion by preventing cell differentiation. We hypothesize that hypoxia-cultured hMSC spheroids can better maintain the regenerative properties of hMSCs. In this study, hMSC spheroids were fabricated using hanging drop method and cultured under 2% O2 and 20% O2 for up to 96 h. Spheroid diameter and viability were examined, as well as extracellular matrix (ECM) components and growth factor levels between the two oxygen tensions at different time points. Stemness was measured among the spheroid culture conditions and compared to two-dimensional cell cultures. Spheroid viability and structural integrity were studied using different needle gauges to ensure no damage would occur when implemented in vivo. Spheroid attachment and integration within a tissue substitute were also demonstrated. The results showed that a three-dimensional hMSC spheroid cultured at low oxygen conditions can enhance the production of ECM proteins and growth factors, while maintaining the spheroids' stemness and ability to be injected, attached, and potentially be integrated within a tissue. PMID:26830500

Oxygen Tension Regulates Human Mesenchymal Stem Cell Paracrine Functions

PubMed Central

Deschepper, Mickael; Moya, Adrien; Logeart-Avramoglou, Delphine; Boisson-Vidal, Catherine; Petite, Hervé

2015-01-01

Mesenchymal stem cells (MSCs) have captured the attention and research endeavors of the scientific world because of their differentiation potential. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly due to the multitude of bioactive mediators secreted by these cells. Because the paracrine potential of MSCs is closely related to their microenvironment, the present study investigated and characterized select aspects of the human MSC (hMSC) secretome and assessed its in vitro and in vivo bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. In contrast to supernatant conditioned media (CM) obtained from hMSCs cultured at either 5% or 21% of O2, CM from hMSCs cultured under near anoxia exhibited significantly (p < .05) enhanced chemotactic and proangiogenic properties and a significant (p < .05) decrease in the inflammatory mediator content. An analysis of the hMSC secretome revealed a specific profile under near anoxia: hMSCs increase their paracrine expression of the angiogenic mediators vascular endothelial growth factor (VEGF)-A, VEGF-C, interleukin-8, RANTES, and monocyte chemoattractant protein 1 but significantly decrease expression of several inflammatory/immunomodulatory mediators. These findings provide new evidence that elucidates aspects of great importance for the use of MSCs in regenerative medicine and could contribute to improving the efficacy of such therapies. Significance The present study investigated and characterized select aspects of the human mesenchymal stem cell (hMSC) secretome and assessed its in vitro and in vivo biological bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. The present study

Oxygen Tension Regulates Human Mesenchymal Stem Cell Paracrine Functions.

PubMed

Paquet, Joseph; Deschepper, Mickael; Moya, Adrien; Logeart-Avramoglou, Delphine; Boisson-Vidal, Catherine; Petite, Hervé

2015-07-01

: Mesenchymal stem cells (MSCs) have captured the attention and research endeavors of the scientific world because of their differentiation potential. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly due to the multitude of bioactive mediators secreted by these cells. Because the paracrine potential of MSCs is closely related to their microenvironment, the present study investigated and characterized select aspects of the human MSC (hMSC) secretome and assessed its in vitro and in vivo bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. In contrast to supernatant conditioned media (CM) obtained from hMSCs cultured at either 5% or 21% of O2, CM from hMSCs cultured under near anoxia exhibited significantly (p < .05) enhanced chemotactic and proangiogenic properties and a significant (p < .05) decrease in the inflammatory mediator content. An analysis of the hMSC secretome revealed a specific profile under near anoxia: hMSCs increase their paracrine expression of the angiogenic mediators vascular endothelial growth factor (VEGF)-A, VEGF-C, interleukin-8, RANTES, and monocyte chemoattractant protein 1 but significantly decrease expression of several inflammatory/immunomodulatory mediators. These findings provide new evidence that elucidates aspects of great importance for the use of MSCs in regenerative medicine and could contribute to improving the efficacy of such therapies. The present study investigated and characterized select aspects of the human mesenchymal stem cell (hMSC) secretome and assessed its in vitro and in vivo biological bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. The present study provided

Microcomputer-based system for registration of oxygen tension in peripheral muscle.

PubMed

Odman, S; Bratt, H; Erlandsson, I; Sjögren, L

1986-01-01

For registration of oxygen tension fields in peripheral muscle a microcomputer based system was designed on the M6800 microprocessor. The system was designed to record the signals from a multiwire oxygen electrode, MDO, which is a multiwire electrode for measuring oxygen on the surface of an organ. The system contained patient safety isolation unit built on optocopplers and the upper frequency limit was 0.64 Hz. Collected data were corrected for drift and temperature changes during the measurement by using pre- and after calibrations and a linear compensation technique. Measure drift of the electrodes were proved to be linear and thus the drift could be compensated for. The system was tested in an experiment on pig. To study the distribution of oxygen statistically mean, standard deviation, skewness and curtosis were calculated. To see changes or differences between histograms a Kolmogorv-Smirnov test was used.

Some responses of the electric ray (Torpedo marmorata) to low ambient oxygen tensions.

PubMed

Hughes, G M; Johnston, I A

1978-04-01

I. Blood samples were taken during prolonged hypoxia experiments in which the inspired water oxygen tension was less than 10 mmHg. The oxygen tension of the post-branchial blood was about 5 mmHg and its pH shows a significant lowering from normoxic levels. 2. The decrease in blood pH is correlated with increases in levels of lactate and pyruvate. The lactate/pyruvate ratio increases during hypoxia. 3. An increase in blood succinate was also found, and strongly suggests the accumulation of multiple anaerobic end-products within the tissues. 4. Recovery of normoxic levels of succinate takes place almost immediately following the restart of ventilation whereas the decrease in lactate concentration is slower. 5. It is concluded that these adaptations may be related to the habitat of the fish at low tide in pools where the Po2 may fall very markedly.

Effect of hemoglobin polymerization on oxygen transport in hemoglobin solutions.

PubMed

Budhiraja, Vikas; Hellums, J David

2002-09-01

The effect of hemoglobin (Hb) polymerization on facilitated transport of oxygen in a bovine hemoglobin-based oxygen carrier was studied using a diffusion cell. In high oxygen tension gradient experiments (HOTG) at 37 degrees C the diffusion of dissolved oxygen in polymerized Hb samples was similar to that in unpolymerized Hb solutions during oxygen uptake. However, in the oxygen release experiments, the transport by diffusion of dissolved oxygen was augmented by diffusion of oxyhemoglobin over a range of oxygen saturations. The augmentation was up to 30% in the case of polymerized Hb and up to 100% in the case of unpolymerized Hb solution. In experiments performed at constant, low oxygen tension gradients in the range of physiological significance, the augmentation effect was less than that in the HOTG experiments. Oxygen transport in polymerized Hb samples was approximately the same as that in unpolymerized samples over a wide range of oxygen tensions. However, at oxygen tensions lower than 30 mm Hg, there were more significant augmentation effects in unpolymerized bovine Hb samples than in polymerized Hb. The results presented here are the first accurate, quantitative measurements of effective diffusion coefficients for oxygen transport in hemoglobin-based oxygen carriers of the type being evaluated to replace red cells in transfusions. In all cases the oxygen carrier was found to have higher effective oxygen diffusion coefficients than blood.

Near-simultaneous hemoglobin saturation and oxygen tension maps in mouse brain using an AOTF microscope.

PubMed

Shonat, R D; Wachman, E S; Niu, W; Koretsky, A P; Farkas, D L

1997-09-01

A newly developed microscope using acousto-optic tunable filters (AOTFs) was used to generate in vivo hemoglobin saturation (SO2) and oxygen tension (PO2) maps in the cerebral cortex of mice. SO2 maps were generated from the spectral analysis of reflected absorbance images collected at different wavelengths, and PO2 maps were generated from the phosphorescence lifetimes of an injected palladium-porphyrin compound using a frequency-domain measurement. As the inspiratory O2 was stepped from hypoxia (10% O2), through normoxia (21% O2), to hyperoxia (60% O2), measured SO2 and PO2 levels rose accordingly and predictably throughout. A plot of SO2 versus PO2 in different arterial and venous regions of the pial vessels conformed to the sigmoidal shape of the oxygen-hemoglobin dissociation curve, providing further validation of the two mapping procedures. The study demonstrates the versatility of the AOTF microscope for in vivo physiologic investigation, allowing for the generation of nearly simultaneous SO2 and PO2 maps in the cerebral cortex, and the frequency-domain detection of phosphorescence lifetimes. This class of study opens up exciting new possibilities for investigating the dynamics of hemoglobin and O2 binding during functional activation of neuronal tissues.

Differential expression of survival proteins during decreased intracellular oxygen tension in brain endothelial cells of grey mullets.

PubMed

Ekambaram, Padmini; Narayanan, Meenakshi; Parasuraman, Parimala

2017-02-15

The brain requires constant oxygen supply to perform its biological functions essential for survival. Because of low oxygen capacity and poor oxygen diffusibility of water, many fish species have evolved various adaptive mechanisms to cope with depleted oxygen. Endothelial cells (EC) are the primary components responsible for controlled environment of brain. Brain homeostasis largely depends on integrity of the EC. To elucidate their adaptive strategy, EC were isolated from the fish brain of Kovalam-control site and Ennore estuary-test/field hypoxic site and were subjected to low oxygen tension in laboratory. Cell viability, 4-hydroxynonenal (4HNE) and total antioxidant capacity (TAC) were analyzed to ascertain stress. Hypoxic insult, cytoprotective role of HSPs and apoptotic effect were analyzed by assessing hypoxia-inducible-factor-α (HIF1α), heat-shock-protein-70 (HSP70), heme-oxygenase 1 (HO-1), and apoptosis signal regulating kinase-1 (ASK1). This study evidenced that HSP70 and HO-1 are the key stress proteins, confer high tolerance to decreased oxygen tension mediated stress. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxygen tension regulates the osteogenic, chondrogenic and endochondral phenotype of bone marrow derived mesenchymal stem cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehy, Eamon J.; Buckley, Conor T.; Kelly, Daniel J., E-mail: kellyd9@tcd.ie

2012-01-06

Highlights: Black-Right-Pointing-Pointer Expansion in low oxygen enhances MSC proliferation and osteogenesis. Black-Right-Pointing-Pointer Differentiation in low oxygen enhances chondrogenesis and suppresses hypertrophy. Black-Right-Pointing-Pointer Oxygen can regulate the MSC phenotype for use in tissue engineering applications. -- Abstract: The local oxygen tension is a key regulator of the fate of mesenchymal stem cells (MSCs). The objective of this study was to investigate the effect of a low oxygen tension during expansion and differentiation on the proliferation kinetics as well as the subsequent osteogenic and chondrogenic potential of MSCs. We first hypothesised that expansion in a low oxygen tension (5% pO{sub 2}) wouldmore » improve both the subsequent osteogenic and chondrogenic potential of MSCs compared to expansion in a normoxic environment (20% pO{sub 2}). Furthermore, we hypothesised that chondrogenic differentiation in a low oxygen environment would suppress hypertrophy of MSCs cultured in both pellets and hydrogels used in tissue engineering strategies. MSCs expanded at 5% pO{sub 2} proliferated faster forming larger colonies, resulting in higher cell yields. Expansion at 5% pO{sub 2} also enhanced subsequent osteogenesis of MSCs, whereas differentiation at 5% pO{sub 2} was found to be a more potent promoter of chondrogenesis than expansion at 5% pO{sub 2}. Greater collagen accumulation, and more intense staining for collagen types I and X, was observed in pellets maintained at 20% pO{sub 2} compared to 5% pO{sub 2}. Both pellets and hydrogels stained more intensely for type II collagen when undergoing chondrogenesis in a low oxygen environment. Differentiation at 5% pO{sub 2} also appeared to inhibit hypertrophy in both pellets and hydrogels, as demonstrated by reduced collagen type X and Alizarin Red staining and alkaline phosphatase activity. This study demonstrates that the local oxygen environment can be manipulated in vitro to either

Nitrite produced by Mycobacterium tuberculosis in human macrophages in physiologic oxygen impacts bacterial ATP consumption and gene expression

PubMed Central

Cunningham-Bussel, Amy; Zhang, Tuo; Nathan, Carl F.

2013-01-01

In high enough concentrations, such as produced by inducible nitric oxide synthase (iNOS), reactive nitrogen species (RNS) can kill Mycobacterium tuberculosis (Mtb). Lesional macrophages in macaques and humans with tuberculosis express iNOS, and mice need iNOS to avoid succumbing rapidly to tuberculosis. However, Mtb’s own ability to produce RNS is rarely considered, perhaps because nitrate reduction to nitrite is only prominent in axenic Mtb cultures at oxygen tensions ≤1%. Here we found that cultures of Mtb-infected human macrophages cultured at physiologic oxygen tensions produced copious nitrite. Surprisingly, the nitrite arose from the Mtb, not the macrophages. Mtb responded to nitrite by ceasing growth; elevating levels of ATP through reduced consumption; and altering the expression of 120 genes associated with adaptation to acid, hypoxia, nitric oxide, oxidative stress, and iron deprivation. The transcriptomic effect of endogenous nitrite was distinct from that of nitric oxide. Thus, whether or not Mtb is hypoxic, the host expresses iNOS, or hypoxia impairs the action of iNOS, Mtb in vivo is likely to encounter RNS by producing nitrite. Endogenous nitrite may slow Mtb’s growth and prepare it to resist host stresses while the pathogen waits for immunopathology to promote its transmission. PMID:24145454

Methyl sterol and cyclopropane fatty acid composition of Methylococcus capsulatus grown at low oxygen tensions

NASA Technical Reports Server (NTRS)

Jahnke, L. L.; Nichols, P. D.

1986-01-01

The sterol and fatty acid concentrations for M. capsulatus grown in fed-batch cultures over a wide range of oxygen tensions (0.1-10.6 percent) and at a constant methane level are evaluated. The analyses reveal that the biomass decreases as oxygen levels are lowered; the sterol concentration increases when the oxygen range is between 0.5-1.1 percent and decreases when the oxygen range is below 0.5 percent; and the amount of monounsaturated C16 decreases and the concentration of cyclopropane fatty acids increases after oxygen is reduced. It is noted that growth and membrane synthesis occur at low oxygen concentrations and that the synthesis of membrane lipids responds to growth conditions.

Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes.

PubMed

Buckley, C T; Vinardell, T; Kelly, D J

2010-10-01

For current tissue engineering or regenerative medicine strategies, chondrocyte (CC)- or mesenchymal stem cell (MSC)-seeded constructs are typically cultured in normoxic conditions (20% oxygen). However, within the knee joint capsule a lower oxygen tension exists. The objective of this study was to investigate how CCs and infrapatellar fad pad derived MSCs will respond to a low oxygen (5%) environment in 3D agarose culture. Our hypothesis was that culture in a low oxygen environment (5%) will enhance the functional properties of cartilaginous tissues engineered using both cell sources. Cell-encapsulated agarose hydrogel constructs (seeded with CCs or infrapatellar fat pad (IFP) derived MSCs) were prepared and cultured in a chemically defined serum-free medium in the presence (CCs and MSCs) or absence (CCs only) of transforming growth factor-beta3 (TGF-β3) in normoxic (20%) or low oxygen (5%) conditions for 42 days. Constructs were assessed at days 0, 21 and 42 in terms of mechanical properties, biochemical content and histologically. Low oxygen tension (5%) was observed to promote extracellular matrix (ECM) production by CCs cultured in the absence of TGF-β3, but was inhibitory in the presence of TGF-β3. In contrast, a low oxygen tension enhanced chondrogenesis of IFP constructs in the presence of TGF-β3, leading to superior mechanical functionality compared to CCs cultured in identical conditions. Extrapolating the results of this study to the in vivo setting, it would appear that joint fat pad derived MSCs may possess a superior potential to generate a functional repair tissue in low oxygen tensions. However, in the context of in vitro cartilage tissue engineering, CCs maintained in normoxic conditions in the presence of TGF-β3 generate the most mechanically functional tissue. Copyright © 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

[Effect of different oxygen tension on the cytoskeleton remodeling of goat temporomandibular joint disc cells].

PubMed

Xiaolan, He; Guangjie, Bao; Linglu, Sun; Xue, Zhang; Shanying, Bao; Hong, Kang

2017-08-01

Objective The effect of different oxygen tensions on the cytoskeleton remodeling of goat temporomandibular joint (TMJ) disc cells were investigated. Methods Goat TMJ disc cells were cultured under normoxia (21% O₂) and hypoxia (2%, 4%, and 8% O₂). Toluidine blue, picrosirius red, and type Ⅰ collagen immunocytochemical staining were performed to observe the changes in cell phenotype under different oxygen levels. Immunofluorescent staining and real-time reverse transcription-polymerase chain reaction analysis were then performed to identify actin, tubulin, and vimentin in the cultured disc cells. Results TMJ disc cells still displayed fibroblast characteristics under different oxygen levels and their cytoskeletons had regular arrangement. The fluorescence intensities of actin and vimentin were lowest at 4% O₂(P<0.05), whereas that of tubulin was highest at 2% O₂ (P<0.05). No significant difference among the other groups was observed (P>0.05). Actin mRNA levels were considerably decreased at 2% O₂ and 4% O₂ in hypoxic conditions, while actin mRNA expression was highest in 21% O₂. Tubulin mRNA levels considerably increased at 2% O₂, while tubulin mRNA expression was lowest in 8% O₂ (P<0.05). Vimentin mRNA expression was lowest at 4% O₂ and highest at 21% O₂, and significant differences were observed between vimentin mRNA expression levels among these oxygen levels (P<0.05). Conclusion Cytoskeletons were reconstructed in different oxygen tensions, and 2% O₂ may be the optimal oxygen level required to proliferate TMJ disc cells.

Near-simultaneous hemoglobin saturation and oxygen tension maps in mouse brain using an AOTF microscope.

PubMed Central

Shonat, R D; Wachman, E S; Niu, W; Koretsky, A P; Farkas, D L

1997-01-01

A newly developed microscope using acousto-optic tunable filters (AOTFs) was used to generate in vivo hemoglobin saturation (SO2) and oxygen tension (PO2) maps in the cerebral cortex of mice. SO2 maps were generated from the spectral analysis of reflected absorbance images collected at different wavelengths, and PO2 maps were generated from the phosphorescence lifetimes of an injected palladium-porphyrin compound using a frequency-domain measurement. As the inspiratory O2 was stepped from hypoxia (10% O2), through normoxia (21% O2), to hyperoxia (60% O2), measured SO2 and PO2 levels rose accordingly and predictably throughout. A plot of SO2 versus PO2 in different arterial and venous regions of the pial vessels conformed to the sigmoidal shape of the oxygen-hemoglobin dissociation curve, providing further validation of the two mapping procedures. The study demonstrates the versatility of the AOTF microscope for in vivo physiologic investigation, allowing for the generation of nearly simultaneous SO2 and PO2 maps in the cerebral cortex, and the frequency-domain detection of phosphorescence lifetimes. This class of study opens up exciting new possibilities for investigating the dynamics of hemoglobin and O2 binding during functional activation of neuronal tissues. Images FIGURE 1 FIGURE 3 FIGURE 4 FIGURE 6 PMID:9284290

Evolution and physiology of neural oxygen sensing

PubMed Central

Costa, Kauê M.; Accorsi-Mendonça, Daniela; Moraes, Davi J. A.; Machado, Benedito H.

2014-01-01

Major evolutionary trends in animal physiology have been heavily influenced by atmospheric O2 levels. Amongst other important factors, the increase in atmospheric O2 which occurred in the Pre-Cambrian and the development of aerobic respiration beckoned the evolution of animal organ systems that were dedicated to the absorption and transportation of O2, e.g., the respiratory and cardiovascular systems of vertebrates. Global variations of O2 levels in post-Cambrian periods have also been correlated with evolutionary changes in animal physiology, especially cardiorespiratory function. Oxygen transportation systems are, in our view, ultimately controlled by the brain related mechanisms, which senses changes in O2 availability and regulates autonomic and respiratory responses that ensure the survival of the organism in the face of hypoxic challenges. In vertebrates, the major sensorial system for oxygen sensing and responding to hypoxia is the peripheral chemoreflex neuronal pathways, which includes the oxygen chemosensitive glomus cells and several brainstem regions involved in the autonomic regulation of the cardiovascular system and respiratory control. In this review we discuss the concept that regulating O2 homeostasis was one of the primordial roles of the nervous system. We also review the physiology of the peripheral chemoreflex, focusing on the integrative repercussions of chemoreflex activation and the evolutionary importance of this system, which is essential for the survival of complex organisms such as vertebrates. The contribution of hypoxia and peripheral chemoreflex for the development of diseases associated to the cardiovascular and respiratory systems is also discussed in an evolutionary context. PMID:25161625

Oxygen Exposure Resulting in Arterial Oxygen Tensions Above the Protocol Goal Was Associated With Worse Clinical Outcomes in Acute Respiratory Distress Syndrome.

PubMed

Aggarwal, Neil R; Brower, Roy G; Hager, David N; Thompson, B Taylor; Netzer, Giora; Shanholtz, Carl; Lagakos, Adrian; Checkley, William

2018-04-01

High fractions of inspired oxygen may augment lung damage to exacerbate lung injury in patients with acute respiratory distress syndrome. Participants enrolled in Acute Respiratory Distress Syndrome Network trials had a goal partial pressure of oxygen in arterial blood range of 55-80 mm Hg, yet the effect of oxygen exposure above this arterial oxygen tension range on clinical outcomes is unknown. We sought to determine if oxygen exposure that resulted in a partial pressure of oxygen in arterial blood above goal (> 80 mm Hg) was associated with worse outcomes in patients with acute respiratory distress syndrome. Longitudinal analysis of data collected in these trials. Ten clinical trials conducted at Acute Respiratory Distress Syndrome Network hospitals between 1996 and 2013. Critically ill patients with acute respiratory distress syndrome. None. We defined above goal oxygen exposure as the difference between the fraction of inspired oxygen and 0.5 whenever the fraction of inspired oxygen was above 0.5 and when the partial pressure of oxygen in arterial blood was above 80 mm Hg. We then summed above goal oxygen exposures in the first five days to calculate a cumulative above goal oxygen exposure. We determined the effect of a cumulative 5-day above goal oxygen exposure on mortality prior to discharge home at 90 days. Among 2,994 participants (mean age, 51.3 yr; 54% male) with a study-entry partial pressure of oxygen in arterial blood/fraction of inspired oxygen that met acute respiratory distress syndrome criteria, average cumulative above goal oxygen exposure was 0.24 fraction of inspired oxygen-days (interquartile range, 0-0.38). Participants with above goal oxygen exposure were more likely to die (adjusted interquartile range odds ratio, 1.20; 95% CI, 1.11-1.31) and have lower ventilator-free days (adjusted interquartile range mean difference of -0.83; 95% CI, -1.18 to -0.48) and lower hospital-free days (adjusted interquartile range mean difference of -1.38; 95

Effect of oxygen levels on the physiology of dendritic cells: implications for adoptive cell therapy.

PubMed

Futalan, Diahnn; Huang, Chien-Tze; Schmidt-Wolf, Ingo G H; Larsson, Marie; Messmer, Davorka

2011-01-01

Dendritic cell (DC)-based adoptive tumor immunotherapy approaches have shown promising results, but the incidence of tumor regression is low and there is an evident call for identifying culture conditions that produce DCs with a more potent Th1 potential. Routinely, DCs are differentiated in CO(2) incubators under atmospheric oxygen conditions (21% O(2)), which differ from physiological oxygen levels of only 3-5% in tissue, where most DCs reside. We investigated whether differentiation and maturation of DCs under physiological oxygen levels could produce more potent T-cell stimulatory DCs for use in adoptive immunotherapy. We found that immature DCs differentiated under physiological oxygen levels showed a small but significant reduction in their endocytic capacity. The different oxygen levels did not influence their stimuli-induced upregulation of cluster of differentiation 54 (CD54), CD40, CD83, CD86, C-C chemokine receptor type 7 (CCR7), C-X-C chemokine receptor type 4 (CXCR4) and human leukocyte antigen (HLA)-DR or the secretion of interleukin (IL)-6, tumor necrosis factor (TNF)-α and IL-10 in response to lipopolysaccharide (LPS) or a cytokine cocktail. However, DCs differentiated under physiological oxygen level secreted higher levels of IL-12(p70) after exposure to LPS or CD40 ligand. Immature DCs differentiated at physiological oxygen levels caused increased T-cell proliferation, but no differences were observed for mature DCs with regard to T-cell activation. In conclusion, we show that although DCs generated under atmospheric or physiological oxygen conditions are mostly similar in function and phenotype, DCs differentiated under physiological oxygen secrete larger amounts of IL-12(p70). This result could have implications for the use of ex vivo-generated DCs for clinical studies, since DCs differentiated at physiological oxygen could induce increased Th1 responses in vivo.

Clinical, Biomechanical, and Physiological Translational Interpretations of Human Resting Myofascial Tone or Tension

PubMed Central

Masi, Alfonse T.; Nair, Kalyani; Evans, Tyler; Ghandour, Yousef

2010-01-01

Background Myofascial tissues generate integrated webs and networks of passive and active tensional forces that provide stabilizing support and that control movement in the body. Passive [central nervous system (CNS)–independent] resting myofascial tension is present in the body and provides a low-level stabilizing component to help maintain balanced postures. This property was recently called “human resting myofascial tone” (HRMT). The HRMT model evolved from electromyography (EMG) research in the 1950s that showed lumbar muscles usually to be EMG-silent in relaxed gravity-neutral upright postures. Methods Biomechanical, clinical, and physiological studies were reviewed to interpret the passive stiffness properties of HRMT that help to stabilize various relaxed functions such as quiet balanced standing. Biomechanical analyses and experimental studies of the lumbar multifidus were reviewed to interpret its passive stiffness properties. The lumbar multifidus was illustrated as the major core stabilizing muscle of the spine, serving an important passive biomechanical role in the body. Results Research into muscle physiology suggests that passive resting tension (CNS-independent) is generated in sarcomeres by the molecular elasticity of low-level cycling cross-bridges between the actomyosin filaments. In turn, tension is complexly transmitted to intimately enveloping fascial matrix fibrils and other molecular elements in connective tissue, which, collectively, constitute the myofascial unit. Postural myofascial tonus varies with age and sex. Also, individuals in the population are proposed to vary in a polymorphism of postural HRMT. A few people are expected to have outlier degrees of innate postural hypotonicity or hypertonicity. Such biomechanical variations likely predispose to greater risk of related musculoskeletal disorders, a situation that deserves greater attention in clinical practice and research. Axial myofascial hypertonicity was hypothesized to

Multibreath alveolar oxygen tension imaging.

PubMed

Clapp, Justin; Hamedani, Hooman; Kadlecek, Stephen; Xin, Yi; Shaghaghi, Hoora; Siddiqui, Sarmad; Rossman, Milton D; Rizi, Rahim R

2016-10-01

This study tested the ability of a multibreath hyperpolarized HP (3) He MRI protocol to increase the accuracy of regional alveolar oxygen tension (PA O2 ) measurements by lessening the influence of gas-flow artifacts. Conventional single-breath PA O2 measurement has been susceptible to error induced by intervoxel gas flow, particularly when used to study subjects with moderate-to-severe chronic obstructive pulmonary disease (COPD). Both single-breath and multibreath PA O2 imaging schemes were implemented in seven human subjects (one healthy, three asymptomatic smokers, and three COPD). The number and location of voxels with nonphysiologic PA O2 values generated by intervoxel gas flow were compared between the two protocols. The multibreath scheme resulted in a significantly lower total percentage of nonphysiologic PA O2 values (6.0%) than the single-breath scheme (13.7%) (P = 0.006). PA O2 maps showed several patterns of gas-flow artifacts that were present in the single-breath protocol but mitigated by the multibreath approach. Multibreath imaging also allowed for the analysis of slow-filling areas that presented no signal after a single breath. A multibreath approach enhances the accuracy and completeness of noninvasive PA O2 measurement by significantly lessening the proportion of nonphysiologic values generated by intervoxel gas flow. Magn Reson Med 76:1092-1101, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Sub-physiological oxygen levels optimal for growth and survival of human atrial cardiac stem cells.

PubMed

RajendranNair, Deepthi Sreerengam; Karunakaran, Jayakumar; Nair, Renuka R

2017-08-01

Cardiac stem cells reside in niches where the oxygen levels are close to 3%. For cytotherapy, cells are conventionally expanded in ambient oxygen (21% O 2 ) which represents hyperoxia compared to the oxygen tension of niches. Cardiosphere-derived cells (CDCs) are then transplanted to host tissue with lower-O 2 levels. The high-O 2 gradient can reduce the efficacy of cultured cells. Based on the assumption that minimizing injury due to O 2 gradients will enhance the yield of functionally efficient cells, CDCs were cultured in 3% O 2 and compared with cells maintained in ambient O 2 . CDCs were isolated from human right atrial explants and expanded in parallel in 21 and 3% oxygen and compared with regard to survival, proliferation, and retention of stemness. Increased cell viability even in the tenth passage and enhanced cardiosphere formation was observed in cells expanded in 3% O 2 . The cell yield from seven passages was fourfold higher for cells cultured in 3% O 2 . Preservation of stemness in hypoxic environment was evident from the proportion of c-kit-positive cells and reduced myogenic differentiation. Hypoxia promoted angiogenesis and reduced the tendency to differentiate to noncardiac lineages (adipocytes and osteocytes). Mimicking the microenvironment at transplantation, when shifted to 5% O 2 , viability and proliferation rate were significantly higher for CDCs expanded in 3% O 2 . Expansion of CDCs, from atria in sub-physiological oxygen, helps in obtaining a higher yield of healthy cells with better preservation of stem cell characteristics. The cells so cultured are expected to improve engraftment and facilitate myocardial regeneration.

Matrix forming characteristics of inner and outer human meniscus cells on 3D collagen scaffolds under normal and low oxygen tensions.

PubMed

Croutze, Roger; Jomha, Nadr; Uludag, Hasan; Adesida, Adetola

2013-12-13

Limited intrinsic healing potential of the meniscus and a strong correlation between meniscal injury and osteoarthritis have prompted investigation of surgical repair options, including the implantation of functional bioengineered constructs. Cell-based constructs appear promising, however the generation of meniscal constructs is complicated by the presence of diverse cell populations within this heterogeneous tissue and gaps in the information concerning their response to manipulation of oxygen tension during cell culture. Four human lateral menisci were harvested from patients undergoing total knee replacement. Inner and outer meniscal fibrochondrocytes (MFCs) were expanded to passage 3 in growth medium supplemented with basic fibroblast growth factor (FGF-2), then embedded in porous collagen type I scaffolds and chondrogenically stimulated with transforming growth factor β3 (TGF-β3) under 21% (normal or normoxic) or 3% (hypoxic) oxygen tension for 21 days. Following scaffold culture, constructs were analyzed biochemically for glycosaminoglycan production, histologically for deposition of extracellular matrix (ECM), as well as at the molecular level for expression of characteristic mRNA transcripts. Constructs cultured under normal oxygen tension expressed higher levels of collagen type II (p = 0.05), aggrecan (p < 0.05) and cartilage oligomeric matrix protein, (COMP) (p < 0.05) compared to hypoxic expanded and cultured constructs. Accumulation of ECM rich in collagen type II and sulfated proteoglycan was evident in normoxic cultured scaffolds compared to those under low oxygen tension. There was no significant difference in expression of these genes between scaffolds seeded with MFCs isolated from inner or outer regions of the tissue following 21 days chondrogenic stimulation (p > 0.05). Cells isolated from inner and outer regions of the human meniscus demonstrated equivalent differentiation potential toward chondrogenic phenotype and ECM production. Oxygen

Effect of low oxygen tension on the biological characteristics of human bone marrow mesenchymal stem cells.

PubMed

Kim, Dae Seong; Ko, Young Jong; Lee, Myoung Woo; Park, Hyun Jin; Park, Yoo Jin; Kim, Dong-Ik; Sung, Ki Woong; Koo, Hong Hoe; Yoo, Keon Hee

2016-11-01

Culture of mesenchymal stem cells (MSCs) under ambient conditions does not replicate the low oxygen environment of normal physiological or pathological states and can result in cellular impairment during culture. To overcome these limitations, we explored the effect of hypoxia (1 % O 2 ) on the biological characteristics of MSCs over the course of different culture periods. The following biological characteristics were examined in human bone marrow-derived MSCs cultured under hypoxia for 8 weeks: proliferation rate, morphology, cell size, senescence, immunophenotypic characteristics, and the expression levels of stemness-associated factors and cytokine and chemokine genes. MSCs cultured under hypoxia for approximately 2 weeks showed increased proliferation and viability. During long-term culture, hypoxia delayed phenotypic changes in MSCs, such as increased cell volume, altered morphology, and the expression of senescence-associated-β-gal, without altering their characteristic immunophenotypic characteristics. Furthermore, hypoxia increased the expression of stemness and chemokine-related genes, including OCT4 and CXCR7, and did not decrease the expression of KLF4, C-MYC, CCL2, CXCL9, CXCL10, and CXCR4 compared with levels in cells cultured under normoxia. In conclusion, low oxygen tension improved the biological characteristics of MSCs during ex vivo expansion. These data suggest that hypoxic culture could be a useful method for increasing the efficacy of MSC cell therapies.

Determination of oxygen tension in the subcutaneous tissue of cosmonauts during the Salyut-6 mission

NASA Technical Reports Server (NTRS)

Baranski, S.; Bloszczynski, R.; Hermaszewski, M.; Kubiczkowa, J.; Piorko, A.; Saganiak, R.; Sarol, Z.; Skibniewsky, F.; Stendera, J.; Walichnowski, W.

1982-01-01

A polarographic technique was used to measure the oxygen tension in subcutaneous tissue of the forearm of a cosmonaut prior to, after, and on the fourth day of a space mission performed by Salut-6. A drop in the oxygen exchange rate in the peripheral tissues during weightlessness was observed. The mechanisms of this change are studied, taking into consideration the blood distribution in the organism and microcirculation disorders reflected by a decreased blood flow rate in arterial-venous junctions.

Physiological Equivalence of Normobaric and Hypobaric Exposures of Humans to 25,000 Feet

DTIC Science & Technology

2010-12-01

alveolar oxygen tension (PAO2), alveolar carbon dioxide tension (PACO2), and respiratory quotient (RQ) differed significantly between the chamber and...the U.S. Navy (1) and Air force (2) physiological training programs have instituted ground-level hypoxia training. Respiratory physiologists have been...gas composition and respiratory quotients (RQ) under hypobaric and normobaric condi- tions will be quite different at the same level of ventilatory

Hypoxic Niche-Mediated Regeneration of Hematopoiesis in the Engraftment Window Is Dominantly Affected by Oxygen Tension in the Milieu

PubMed Central

Moirangthem, Ranjita Devi; Singh, Shweta; Adsul, Ashwini; Jalnapurkar, Sapana; Limaye, Lalita

2015-01-01

The bone marrow (BM) microenvironment or the hematopoietic stem cell (HSC) niche is normally hypoxic, which maintains HSC quiescence. Paradoxically, transplanted HSCs rapidly proliferate in this niche. Pretransplant myelosuppression results in a substantial rise in oxygen levels in the marrow microenvironment due to reduced cellularity and consequent low oxygen consumption. Therefore, it may be construed that the rapid proliferation of the engrafted HSCs in the BM niche is facilitated by the transiently elevated oxygen tension in this milieu during the “engraftment window.” To determine whether oxygen tension dominantly affects the regeneration of hematopoiesis in the BM niche, we created an “oxygen-independent hypoxic niche” by treating BM-derived mesenchymal stromal cells (BMSCs) with a hypoxia-mimetic compound, cobalt chloride (CoCl2) and cocultured them with BM-derived HSC-enriched cells under normoxic conditions (HSCs; CoCl2-cocultures). Cocultures with untreated BMSCs incubated under normoxia (control- cocultures) or hypoxia (1% O2; hypoxic-cocultures) were used as comparators. Biochemical analyses showed that though, both CoCl2 and hypoxia evoked comparable signals in the BMSCs, the regeneration of hematopoiesis in their respective cocultures was radically different. The CoCl2-BMSCs supported robust hematopoiesis, while the hypoxic-BMSCs exerted strong inhibition. The hematopoiesis-supportive ability of CoCl2-BMSCs was abrogated if the CoCl2-cocultures were incubated under hypoxia, demonstrating that the prevalent oxygen tension in the milieu dominantly affects the outcome of the HSC-BM niche interactions. Our data suggest that pharmacologically delaying the reestablishment of hypoxia in the BM may boost post-transplant regeneration of hematopoiesis. PMID:26107807

In Vivo Mitochondrial Oxygen Tension Measured by a Delayed Fluorescence Lifetime Technique

PubMed Central

Mik, Egbert G.; Johannes, Tanja; Zuurbier, Coert J.; Heinen, Andre; Houben-Weerts, Judith H. P. M.; Balestra, Gianmarco M.; Stap, Jan; Beek, Johan F.; Ince, Can

2008-01-01

Mitochondrial oxygen tension (mitoPO2) is a key parameter for cellular function, which is considered to be affected under various pathophysiological circumstances. Although many techniques for assessing in vivo oxygenation are available, no technique for measuring mitoPO2 in vivo exists. Here we report in vivo measurement of mitoPO2 and the recovery of mitoPO2 histograms in rat liver by a novel optical technique under normal and pathological circumstances. The technique is based on oxygen-dependent quenching of the delayed fluorescence lifetime of protoporphyrin IX. Application of 5-aminolevulinic acid enhanced mitochondrial protoporphyrin IX levels and induced oxygen-dependent delayed fluorescence in various tissues, without affecting mitochondrial respiration. Using fluorescence microscopy, we demonstrate in isolated hepatocytes that the signal is of mitochondrial origin. The delayed fluorescence lifetime was calibrated in isolated hepatocytes and isolated perfused livers. Ultimately, the technique was applied to measure mitoPO2 in rat liver in vivo. The results demonstrate mitoPO2 values of ∼30–40 mmHg. mitoPO2 was highly sensitive to small changes in inspired oxygen concentration around atmospheric oxygen level. Ischemia-reperfusion interventions showed altered mitoPO2 distribution, which flattened overall compared to baseline conditions. The reported technology is scalable from microscopic to macroscopic applications, and its reliance on an endogenous compound greatly enhances its potential field of applications. PMID:18641065

Oxygen Modulates Human Decidual Natural Killer Cell Surface Receptor Expression and Interactions with Trophoblasts1

PubMed Central

Wallace, Alison E.; Goulwara, Sonu S.; Whitley, Guy S.; Cartwright, Judith E.

2014-01-01

Decidual natural killer (dNK) cells have been shown to both promote and inhibit trophoblast behavior important for decidual remodeling in pregnancy and have a distinct phenotype compared to peripheral blood NK cells. We investigated whether different levels of oxygen tension, mimicking the physiological conditions of the decidua in early pregnancy, altered cell surface receptor expression and activity of dNK cells and their interactions with trophoblast. dNK cells were isolated from terminated first-trimester pregnancies and cultured in oxygen tensions of 3%, 10%, and 21% for 24 h. Cell surface receptor expression was examined by flow cytometry, and the effects of secreted factors in conditioned medium (CM) on the trophoblast cell line SGHPL-4 were assessed in vitro. SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 10% were significantly more invasive (P < 0.05) and formed endothelial-like networks to a greater extent (P < 0.05) than SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 3% or 21%. After 24 h, a lower percentage of dNK cells expressed CD56 at 21% oxygen (P < 0.05), and an increased percentage of dNK cells expressed NKG2D at 10% oxygen (P < 0.05) compared to other oxygen tensions, with large patient variation. This study demonstrates dNK cell phenotype and secreted factors are modulated by oxygen tension, which induces changes in trophoblast invasion and endovascular-like differentiation. Alterations in dNK cell surface receptor expression and secreted factors at different oxygen tensions may represent regulation of function within the decidua during the first trimester of pregnancy. PMID:25232021

Measuring oxygen tension modulation, induced by a new pre-radiotherapy therapeutic, in a mammary window chamber mouse model

NASA Astrophysics Data System (ADS)

Schafer, Rachel; Gmitro, Arthur F.

2015-03-01

Tumor regions under hypoxic or low oxygen conditions respond less effectively to many treatment strategies, including radiation therapy. A novel investigational therapeutic, NVX-108 (NuvOx Pharma), has been developed to increase delivery of oxygen through the use of a nano-emulsion of dodecofluoropentane. By raising pO2 levels prior to delivering radiation, treatment efficacy may be improved. To aid in evaluating the novel drug, oxygen tension was quantitatively measured, spatially and temporally, to record the effect of administrating NVX-108 in an orthotopic mammary window chamber mouse model of breast cancer. The oxygen tension was measured through the use of an oxygen-sensitive coating, comprised of phosphorescent platinum porphyrin dye embedded in a polystyrene matrix. The coating, applied to the surface of the coverslip of the window chamber through spin coating, is placed in contact with the mammary fat pad to record the oxygenation status of the surface tissue layer. Prior to implantation of the window chamber, a tumor is grown in the SCID mouse model by injection of MCF-7 cells into the mammary fat pad. Two-dimensional spatial distributions of the pO2 levels were obtained through conversion of measured maps of phosphorescent lifetime. The resulting information on the spatial and temporal variation of the induced oxygen modulation could provide valuable insight into the optimal timing between administration of NVX-108 and radiation treatment to provide the most effective treatment outcome.

The importance of controlling in vitro oxygen tension to accurately model in vivo neurophysiology.

PubMed

Bordt, Evan A

2018-05-01

The majority of in vitro studies modeling in vivo conditions are performed on the lab bench in atmospheric air. However, the oxygen tension (pO 2 ) present in atmospheric air (160mm Hg, ∼21% O 2 ) is in great excess to the pO 2 that permeates tissues within the brain (5-45mm Hg, ∼1-6% O 2 ). This review will discuss the differentiation between pO 2 in the in vivo environment and the pO 2 commonly used during in vitro experiments, and how this could affect assay outcomes. Also highlighted are studies linking changes in pO 2 to changes in cellular function, particularly the role of pO 2 in mitochondrial function, reactive oxygen species production, and cellular growth and differentiation. The role of hypoxia inducible factor 1 and oxygen sensing is also presented. Finally, emerging literature exploring sex differences in tissue oxygenation is discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

The importance of hypoxia and extra physiologic oxygen shock/stress for collection and processing of stem and progenitor cells to understand true physiology/pathology of these cells ex vivo.

PubMed

Broxmeyer, Hal E; O'Leary, Heather A; Huang, Xinxin; Mantel, Charlie

2015-07-01

Hematopoietic stem (HSCs) and progenitor (HPCs) cells reside in a hypoxic (lowered oxygen tension) environment, in vivo. We review literature on growth of HSCs and HPCs under hypoxic and normoxic (ambient air) conditions with a focus on our recent work demonstrating the detrimental effects of collecting and processing cells in ambient air through a phenomenon termed extra physiologic oxygen shock/stress (EPHOSS), and we describe means to counteract EPHOSS for enhanced collection of HSCs. Collection and processing of bone marrow and cord blood cells in ambient air cause rapid differentiation and loss of HSCs, with increases in HPCs. This apparently irreversible EPHOSS phenomenon results from increased mitochondrial reactive oxygen species, mediated by a p53-cyclophilin D-mitochondrial permeability transition pore axis, and involves hypoxia inducing factor-1α and micro-RNA 210. EPHOSS can be mitigated by collecting and processing cells in lowered (3%) oxygen, or in ambient air in the presence of, cyclosporine A which effects the mitochondrial permeability transition pore, resulting in increased HSC collections. Our recent findings may be advantageous for HSC collection for hematopoietic cell transplantation, and likely for enhanced collection of other stem cell types. EPHOSS should be considered when ex-vivo cell analysis is utilized for personalized medicine, as metabolism of cells and their response to targeted drug treatment ex vivo may not mimic what occurs in vivo.

Physiological oxygen concentration alters glioma cell malignancy and responsiveness to photodynamic therapy in vitro.

PubMed

Albert, Ina; Hefti, Martin; Luginbuehl, Vera

2014-11-01

The partial pressure of oxygen (pO2) in brain tumors ranges from 5 to 15%. Nevertheless, the majority of in vitro experiments with glioblastoma multiforme (GBM) cell lines are carried out under an atmospheric pO2 of 19 to 21%. Recently, 5-aminolevulinic acid (5-ALA), a precursor of protoporphyrin IX (PpIX), has been introduced to neurosurgery to allow for photodynamic diagnosis and photodynamic therapy (PDT) in high-grade gliomas. Here, we investigate whether low pO2 affects GBM cell physiology, PpIX accumulation, or PDT efficacy. GBM cell lines (U-87 MG and U-251 MG) were cultured under atmospheric (pO2  =  19%) and physiological (pO2  =  9%) oxygen concentrations. PpIX accumulation and localization were investigated, and cell survival and cell death were observed following in vitro PDT. A physiological pO2 of 9% stimulated GBM cell migration, increased hypoxia-inducible factor (HIF)-1 alpha levels, and elevated resistance to camptothecin in U-87 MG cells compared to cultivation at a pO2 of 19%. This oxygen reduction did not alter 5-ALA-induced intracellular PpIX accumulation. However, physiological pO2 changed the responsiveness of U-87 MG but not of U-251 MG cells to in vitro PDT. Around 20% more irradiation light was required to kill U-87 MG cells at physiological pO2, resulting in reduced lactate dehydrogenase (LDH) release (one- to two-fold) and inhibition of caspase 3 activation. Reduction of oxygen concentration from atmospheric to a more physiological level can influence the malignant behavior and survival of GBM cell lines after in vitro PDT. Therefore, precise oxygen concentration control should be considered when designing and performing experiments with GBM cells.

Oxygen transport by hemoglobin.

PubMed

Mairbäurl, Heimo; Weber, Roy E

2012-04-01

Hemoglobin (Hb) constitutes a vital link between ambient O2 availability and aerobic metabolism by transporting oxygen (O2) from the respiratory surfaces of the lungs or gills to the O2-consuming tissues. The amount of O2 available to tissues depends on the blood-perfusion rate, as well as the arterio-venous difference in blood O2 contents, which is determined by the respective loading and unloading O2 tensions and Hb-O2-affinity. Short-term adjustments in tissue oxygen delivery in response to decreased O2 supply or increased O2 demand (under exercise, hypoxia at high altitude, cardiovascular disease, and ischemia) are mediated by metabolically induced changes in the red cell levels of allosteric effectors such as protons (H(+)), carbon dioxide (CO2), organic phosphates, and chloride (Cl(-)) that modulate Hb-O2 affinity. The long-term, genetically coded adaptations in oxygen transport encountered in animals that permanently are subjected to low environmental O2 tensions commonly result from changes in the molecular structure of Hb, notably amino acid exchanges that alter Hb's intrinsic O2 affinity or its sensitivity to allosteric effectors. Structure-function studies of animal Hbs and human Hb mutants illustrate the different strategies for adjusting Hb-O2 affinity and optimizing tissue oxygen supply. © 2012 American Physiological Society. Compr Physiol 2:1491-1539, 2012.

Effect of supplemental oxygen versus dobutamine administration on liver oxygen tension in dPP-guided normovolemic pigs.

PubMed

Pestel, G; Fukui, K; Hager, H; Kurz, A; Hiltebrand, L

2009-01-01

Difference in pulse pressure (dPP) confirms adequate intravascular filling as a prerequisite for tissue perfusion. We hypothesized that both oxygen and dobutamine increase liver tissue oxygen tension (ptO(2)). Eight anesthetized pigs received dPP-guided fluid management. Hepatic pO(2) was measured with Clark-type electrodes placed subcapsularly, and on the liver surface. Pigs received: (1) supplemental oxygen (F(i)O(2) 1.0); (2) dobutamine 2.5 microg/kg/min, and (3) dobutamine 5 microg/kg/min. Data were analyzed using repeated-measures ANOVA followed by a Tukey post-test for multiple comparisons. ptO(2 )measured subcapsularly and at the liver surface were compared using the Bland-Altman plot. Variation in F(i)O(2) changed local hepatic tissue ptO(2) [subcapsular measurement: 39 +/- 12 (F(i)O(2) 0.3), 89 +/- 35 mm Hg (F(i)O(2) 1.0, p = 0.01 vs. F(i)O(2) 0.3), 44 +/- 10 mm Hg (F(i)O(2) 0.3, p = 0.05 vs. F(i)O(2) 1.0); surface measurement: 52 +/- 35 (F(i)O(2) 0.3), 112 +/- 24 mm Hg (F(i)O(2) 1.0, p = 0.001 vs. F(i)O(2) 0.3), 54 +/- 24 mm Hg (F(i)O(2) 0.3, p = 0.001 vs. F(i)O(2) 1.0)]. Surface measurements were widely scattered compared to subcapsular measurements (bias: -15 mm Hg, precision: 76.3 mm Hg). Dobutamine did not affect hepatic oxygenation. Supplemental oxygen increased hepatic tissue pO(2) while dobutamine did not. Although less invasive, the use of surface measurements is discouraged. Copyright 2009 S. Karger AG, Basel.

Investigation of arterial bloodgases at altitude using constant-flow oxygen masks.

PubMed

Hodgson, W R; Wright, R C; Nelson, G C; Letchford, T

1978-06-01

Arterial blood oxygen tensions up to 6700 m altitude (FL220) were measured polarographically while subjects breathed from various masks with constant-flow oxygen. The Sierra and Aro masks used for emergency decompression descent in commercial passenger aircraft, gave mean PaO2's of 130 +/- 7.6 and 130 +/- 12.1 torr at 6700 m (FL220) and 90 +/- 3.8 and 77 +/- 3.35 torr at 4260 m (FL140), respectively, when supplied with oxygen flows corresponding to those available in the Boeing 747. These oxygen tensions during descent are acceptable for normal physiological function in a heterogeneous population of air travellers whereas breathing ambient air during return to base at 4260 m (FL 140) (PaO2 of 48 or less) is not acceptable. The valveless Hudson 1007 and Puritan 114011 masks, used for air ambulance service, gave mean PaO2's of 110 +/- 2.7 and 98 +/- 4.5 torr at 6700 m and 80 +/- 3.0 and 77 +/- 2.5 torr at 4260 m under the same condition--significantly less than the Sierra mask.

Vertical Gradients in Regional Alveolar Oxygen Tension in Supine Human Lung Imaged by Hyperpolarized 3He MRI

PubMed Central

Hamedani, Hooman; Shaghaghi, Hoora; Kadlecek, Stephen J.; Xin, Yi; Han, Biao; Siddiqui, Sarmad; Rajaei, Jennia; Ishii, Masaru; Rossman, Milton; Rizi, Rahim R.

2015-01-01

Purpose To evaluate whether regional alveolar oxygen tension (PAO2) vertical gradients imaged with hyperpolarized 3He can identify smoking-induced pulmonary alterations. To compare these gradients with common clinical measurements including pulmonary function tests, the six minute walk test, and the St. George’s Respiratory Questionnaire. Materials and Methods 8 healthy nonsmokers, 12 asymptomatic smokers, and 7 symptomatic subjects with chronic obstructive pulmonary disease (COPD) underwent two sets of back-to-back PAO2 imaging acquisitions in supine position with two opposite directions (top to bottom and bottom to top), followed by clinically standard pulmonary tests. The whole-lung mean, standard deviation (DPAO2) and vertical gradients of PAO2 along the slices were extracted, and the results were compared with clinically derived metrics. Statistical tests were performed to analyze the differences between cohorts. Results The anterior-posterior vertical gradients and DPAO2 effectively differentiated all three cohorts (p<0.05). The average vertical gradient PAO2 in healthy subjects was −1.03 ± 0.51 Torr/cm toward lower values in the posterior/dependent regions. The directional gradient was absent in smokers (0.36 ± 1.22 Torr/cm) and was in the opposite direction in COPD subjects (2.18 ± 1.54 Torr/cm). The vertical gradients correlated with Smoking History (p=0.004); BMI (p=0.037), PFT metrics (FEV1, p=0.025; and %RV/TLC, p=0.033) and with distance walked in six minutes (p=0.009). Discussion Regional PAO2 data indicate that cigarette smoke induces physiological alterations that are not being detected by the most widely used physiologic tests. PMID:25395184

Effectiveness of Spiritist "passe" (Spiritual healing) for anxiety levels, depression, pain, muscle tension, well-being, and physiological parameters in cardiovascular inpatients: A randomized controlled trial.

PubMed

Carneiro, Élida Mara; Barbosa, Luana Pereira; Marson, Jorge Marcelo; Terra, Juverson Alves; Martins, Claudio Jacinto Pereira; Modesto, Danielle; Resende, Luiz Antônio Pertili Rodrigues de; Borges, Maria de Fátima

2017-02-01

Biofield therapies, such as laying on of hands, are used in association with Conventional Medicine as Spiritist "passe", among others. The aim of this study was to evaluate anxiety, depression, pain, muscle tension and well-being, as well as physiological parameters in cardiovascular inpatients submitted to the Spiritist "passe", sham, and no intervention. In the total, 41 cardiovascular inpatients submitted to the Spiritist "passe", sham, and no intervention during a 10-min period on 3 consecutive days. They were evaluated through anxiety and depression level, pain, the perceptions of muscle tension and well-being and physiological parameters, before and after interventions. A significant reduction (p=0.001) in anxiety scores and muscle tension (p=0.011), improvement of well-being (p=0.003) and a significant increase in peripheral oxyhemoglobin saturation scores (p=0.028) were observed in Spiritist "passe" patients, and a significant reduction (p=0.028) of muscle tension and improvement of well-being (p=0.045) in sham patients. However, muscle tension reduction (p=0.003) and improvement of well-being (p=0.003) were more accentuated in the Spiritist "passe" compared to sham and no intervention. Results suggest that the Spiritist "passe" appeared to be effective, reducing anxiety level and the perception of muscle tension, consequently improving peripheral oxyhemoglobin saturation and the sensation of well-being compared to sham and no intervention in cardiovascular inpatients. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Online monitoring of dissolved oxygen tension in microtiter plates based on infrared fluorescent oxygen-sensitive nanoparticles.

PubMed

Ladner, Tobias; Flitsch, David; Schlepütz, Tino; Büchs, Jochen

2015-10-09

During the past years, new high-throughput screening systems with capabilities of online monitoring turned out to be powerful tools for the characterization of microbial cell cultures. These systems are often easy to use, offer economic advantages compared to larger systems and allow to determine many important process parameters within short time. Fluorescent protein tags tremendously simplified the tracking and observation of cellular activity in vivo. Unfortunately, interferences between established fluorescence based dissolved oxygen tension (DOT) measurement techniques and fluorescence-based protein tags appeared. Therefore, the applicability of new oxygen-sensitive nanoparticles operated within the more suitable infrared wavelength region are introduced and validated for DOT measurement. The biocompatibility of the used dispersed oxygen-sensitive nanoparticles was proven via RAMOS cultivations for Hansenula polymorpha, Gluconobacter oxydans, and Escherichia coli. The applicability of the introduced DOT measurement technique for online monitoring of cultivations was demonstrated and successfully validated. The nanoparticles showed no disturbing effect on the online measurement of the fluorescence intensities of the proteins GFP, mCherry and YFP measured by a BioLector prototype. Additionally, the DOT measurement was not influenced by changing concentrations of these proteins. The kLa values for the applied cultivation conditions were successfully determined based on the measured DOT. The introduced technique appeared to be practically as well as economically advantageous for DOT online measuring in microtiter plates. The disadvantage of limited availability of microtiter plates with immobilized sensor spots (optodes) does not apply for this introduced technique. Due to the infrared wavelength range, used for the DOT measurement, no interferences with biogenic fluorescence or with expressed fluorescent proteins (e.g. YFP, GFP or mCherry) occur.

Assessment of Renal Hemodynamics and Oxygenation by Simultaneous Magnetic Resonance Imaging (MRI) and Quantitative Invasive Physiological Measurements.

PubMed

Cantow, Kathleen; Arakelyan, Karen; Seeliger, Erdmann; Niendorf, Thoralf; Pohlmann, Andreas

2016-01-01

In vivo assessment of renal perfusion and oxygenation under (patho)physiological conditions by means of noninvasive diagnostic imaging is conceptually appealing. Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) and quantitative parametric mapping of the magnetic resonance (MR) relaxation times T 2* and T 2 are thought to provide surrogates of renal tissue oxygenation. The validity and efficacy of this technique for quantitative characterization of local tissue oxygenation and its changes under different functional conditions have not been systematically examined yet and remain to be established. For this purpose, the development of an integrative multimodality approaches is essential. Here we describe an integrated hybrid approach (MR-PHYSIOL) that combines established quantitative physiological measurements with T 2* (T 2) mapping and MR-based kidney size measurements. Standardized reversible (patho)physiologically relevant interventions, such as brief periods of aortic occlusion, hypoxia, and hyperoxia, are used for detailing the relation between the MR-PHYSIOL parameters, in particular between renal T 2* and tissue oxygenation.

Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration.

PubMed

Sheard, Michael A; Ghent, Matthew V; Cabral, Daniel J; Lee, Joanne C; Khankaldyyan, Vazgen; Ji, Lingyun; Wu, Samuel Q; Kang, Min H; Sposto, Richard; Asgharzadeh, Shahab; Reynolds, C Patrick

2015-05-15

Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival, expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. Copyright © 2015. Published by Elsevier Inc.

The relationship between alveolar oxygen tension and the single-breath carbon monoxide diffusing capacity.

PubMed

Kanner, R E; Crapo, R O

1986-04-01

The effects of alveolar oxygen tension (PAO2) on the single-breath carbon monoxide diffusing capacity (DLCO) were quantified and a factor was derived to accommodate for differences in PAO2 over commonly encountered altitudes and/or varying concentrations of oxygen in the test gas mixture (FIO2) We performed duplicate measurements of DLCO in 7 normal subjects with 6 different oxygen fractions (0.176, 0.196, 0.211, 0.22, 0.25, and 0.27). The PAO2 for each test was measured as the PO2 in the alveolar gas sample bag. DLCO varied inversely with PAO2 and changed by 0.35% for each mmHg change in PAO2 (r = -0.62, p less than 0.001). At an FIO2 of 0.25, PAO2 varied between subjects and was highly correlated with each subject's residual volume to total lung capacity ratio (r = -0.84, p less than 0.001). We suggest that laboratories can adjust the measured DLCO when PAO2 is not congruent to 120 mmHg by the following formula: DLCO (corrected = DLCO (measured) x [1.0 + 0.0035 (PAO2 - 120)].

Nitric oxide inhibits succinate dehydrogenase-driven oxygen consumption in potato tuber mitochondria in an oxygen tension-independent manner.

PubMed

Simonin, Vagner; Galina, Antonio

2013-01-01

NO (nitric oxide) is described as an inhibitor of plant and mammalian respiratory chains owing to its high affinity for COX (cytochrome c oxidase), which hinders the reduction of oxygen to water. In the present study we show that in plant mitochondria NO may interfere with other respiratory complexes as well. We analysed oxygen consumption supported by complex I and/or complex II and/or external NADH dehydrogenase in Percoll-isolated potato tuber (Solanum tuberosum) mitochondria. When mitochondrial respiration was stimulated by succinate, adding the NO donors SNAP (S-nitroso-N-acetyl-DL-penicillamine) or DETA-NONOate caused a 70% reduction in oxygen consumption rate in state 3 (stimulated with 1 mM of ADP). This inhibition was followed by a significant increase in the Km value of SDH (succinate dehydrogenase) for succinate (Km of 0.77±0.19 to 34.3±5.9 mM, in the presence of NO). When mitochondrial respiration was stimulated by external NADH dehydrogenase or complex I, NO had no effect on respiration. NO itself and DETA-NONOate had similar effects to SNAP. No significant inhibition of respiration was observed in the absence of ADP. More importantly, SNAP inhibited PTM (potato tuber mitochondria) respiration independently of oxygen tensions, indicating a different kinetic mechanism from that observed in mammalian mitochondria. We also observed, in an FAD reduction assay, that SNAP blocked the intrinsic SDH electron flow in much the same way as TTFA (thenoyltrifluoroacetone), a non-competitive SDH inhibitor. We suggest that NO inhibits SDH in its ubiquinone site or its Fe-S centres. These data indicate that SDH has an alternative site of NO action in plant mitochondria.

Acute hypoxia in a simulated high-altitude airdrop scenario due to oxygen system failure.

PubMed

Ottestad, William; Hansen, Tor Are; Pradhan, Gaurav; Stepanek, Jan; Høiseth, Lars Øivind; Kåsin, Jan Ivar

2017-12-01

High-Altitude High Opening (HAHO) is a military operational procedure in which parachute jumps are performed at high altitude requiring supplemental oxygen, putting personnel at risk of acute hypoxia in the event of oxygen equipment failure. This study was initiated by the Norwegian Army to evaluate potential outcomes during failure of oxygen supply, and to explore physiology during acute severe hypobaric hypoxia. A simulated HAHO without supplemental oxygen was carried out in a hypobaric chamber with decompression to 30,000 ft (9,144 m) and then recompression to ground level with a descent rate of 1,000 ft/min (305 m/min). Nine subjects were studied. Repeated arterial blood gas samples were drawn throughout the entire hypoxic exposure. Additionally, pulse oximetry, cerebral oximetry, and hemodynamic variables were monitored. Desaturation evolved rapidly and the arterial oxygen tensions are among the lowest ever reported in volunteers during acute hypoxia. Pa O 2 decreased from baseline 18.4 (17.3-19.1) kPa, 138.0 (133.5-143.3) mmHg, to a minimum value of 3.3 (2.9-3.7) kPa, 24.8 (21.6-27.8) mmHg, after 180 (60-210) s, [median (range)], N = 9. Hyperventilation with ensuing hypocapnia was associated with both increased arterial oxygen saturation and cerebral oximetry values, and potentially improved tolerance to severe hypoxia. One subject had a sharp drop in heart rate and cardiac index and lost consciousness 4 min into the hypoxic exposure. A simulated high-altitude airdrop scenario without supplemental oxygen results in extreme hypoxemia and may result in loss of consciousness in some individuals. NEW & NOTEWORTHY This is the first study to investigate physiology and clinical outcome of oxygen system failure in a simulated HAHO scenario. The acquired knowledge is of great value to make valid risk-benefit analyses during HAHO training or operations. The arterial oxygen tensions reported in this hypobaric chamber study are among the lowest ever reported during acute

The new Licox combined brain tissue oxygen and brain temperature monitor: assessment of in vitro accuracy and clinical experience in severe traumatic brain injury.

PubMed

Stewart, Campbell; Haitsma, Iain; Zador, Zsolt; Hemphill, J Claude; Morabito, Diane; Manley, Geoffrey; Rosenthal, Guy

2008-12-01

Monitoring of brain tissue oxygen tension is increasingly being used to monitor patients after severe traumatic brain injury and to guide therapies aimed at maintaining brain tissue oxygen tension above threshold levels. The new Licox PMO combined oxygen and temperature catheter (Integra LifeSciences, Plainsboro, NJ) combines measurements of oxygen tension and temperature in a single probe inserted through a bolt mechanism. In this study, we sought to evaluate the accuracy of the new Licox PMO probe under controlled laboratory conditions and to assess the accuracy of oxygen tension and temperature measurements and the new automated card calibration system. We also describe our clinical experience with the Licox PMO probe. Oxygen tension was measured in a 2-chambered apparatus at different oxygen tensions and temperatures. The new card calibration system was compared with a manually calibrated system. Rates of hematoma, infection, and dislodgement in our clinical experience were recorded. The new Licox PMO probe accurately measures oxygen tension over a wide range of oxygen concentrations and physiological temperatures, but it does have a small tendency to underestimate oxygen tension (mean error, -3.8 +/- 3.5%) that is more pronounced between the temperatures of 33 and 39 degrees C. The thermistor of the PMO probe also has a tendency to underestimate temperature when compared with a resistance thermometer (mean error, -0.67 +/- 0.22 degrees C). The card calibration system was also found to introduce some variability in measurements of oxygen tension when compared with a manually calibrated system. Clinical experience with the new probe indicates good placement within the white matter using the improved bolt system and low rates of hematoma (2.9%), infection (0%), and dislodgement (5.9%). The new Licox PMO probe is accurate but has a small, consistent tendency to under-read oxygen tension that is more pronounced at higher temperatures. The probe tends to under

Towards a quantitative understanding of oxygen tension and cell density evolution in fibrin hydrogels.

PubMed

Demol, Jan; Lambrechts, Dennis; Geris, Liesbet; Schrooten, Jan; Van Oosterwyck, Hans

2011-01-01

The in vitro culture of hydrogel-based constructs above a critical size is accompanied by problems of unequal cell distribution when diffusion is the primary mode of oxygen transfer. In this study, an experimentally-informed mathematical model was developed to relate cell proliferation and death inside fibrin hydrogels to the local oxygen tension in a quantitative manner. The predictive capacity of the resulting model was tested by comparing its outcomes to the density, distribution and viability of human periosteum derived cells (hPDCs) that were cultured inside fibrin hydrogels in vitro. The model was able to reproduce important experimental findings, such as the formation of a multilayered cell sheet at the hydrogel periphery and the occurrence of a cell density gradient throughout the hydrogel. In addition, the model demonstrated that cell culture in fibrin hydrogels can lead to complete anoxia in the centre of the hydrogel for realistic values of oxygen diffusion and consumption. A sensitivity analysis also identified these two parameters, together with the proliferation parameters of the encapsulated cells, as the governing parameters for the occurrence of anoxia. In conclusion, this study indicates that mathematical models can help to better understand oxygen transport limitations and its influence on cell behaviour during the in vitro culture of cell-seeded hydrogels. Copyright © 2010 Elsevier Ltd. All rights reserved.

Obesity Decreases Perioperative Tissue Oxygenation

PubMed Central

Kabon, Barbara; Nagele, Angelika; Reddy, Dayakar; Eagon, Chris; Fleshman, James W.; Sessler, Daniel I.; Kurz, Andrea

2005-01-01

Background: Obesity is an important risk factor for surgical site infections. The incidence of surgical wound infections is directly related to tissue perfusion and oxygenation. Fat tissue mass expands without a concomitant increase in blood flow per cell, which might result in a relative hypoperfusion with decreased tissue oxygenation. Consequently, we tested the hypotheses that perioperative tissue oxygen tension is reduced in obese surgical patients. Furthermore, we compared the effect of supplemental oxygen administration on tissue oxygenation in obese and non-obese patients. Methods: Forty-six patients undergoing major abdominal surgery were assigned to one of two groups according to their body mass index (BMI): BMI < 30 kg/m2 (non-obese) and BMI ≥ 30 kg/m2 (obese). Intraoperative oxygen administration was adjusted to arterial oxygen tensions of ≈150 mmHg and ≈300 mmHg in random order. Anesthesia technique and perioperative fluid management were standardized. Subcutaneous tissue oxygen tension was measured with a polarographic electrode positioned within a subcutaneous tonometer in the lateral upper arm during surgery, in the recovery room, and on the first postoperative day. Postoperative tissue oxygen was also measured adjacent to the wound. Data were compared with unpaired two tailed t-tests and Wilcoxon rank-sum tests; P < 0.05 was considered statistically significant. Results: Intraoperative subcutaneous tissue oxygen tension was significantly less in the obese patients at baseline (36 vs. 57 mmHg, P = 0.002) and with supplemental oxygen administration (47 vs. 76 mmHg, P = 0.014). Immediate postoperative tissue oxygen tension was also significantly less in subcutaneous tissue of the upper arm (43 vs. 54 mmHg, P = 0.011) as well as near the incision (42 vs. 62 mmHg, P = 0.012) in obese patients. In contrast, tissue oxygen tension was comparable in each group on the first postoperative morning. Conclusion: Wound and tissue hypoxia were common in obese

Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheard, Michael A., E-mail: msheard@chla.usc.edu; Ghent, Matthew V., E-mail: mattghent@gmail.com; Cabral, Daniel J., E-mail: dcabral14@gmail.com

2015-05-15

Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival,more » expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. - Highlights: • Establishing new ALL cell lines in 5% oxygen resulted in higher glycolytic expression and function. • Establishing new ALL cell lines in 5% oxygen resulted in higher proliferation and lower cell death. • The divergent metabolic phenotypes selected in 5% and 20% oxygen are semi-permanent.« less

Optimizing the Calculation of DM,CO and VC via the Single Breath Single Oxygen Tension DLCO/NO Method

PubMed Central

Coffman, Kirsten E.; Taylor, Bryan J.; Carlson, Alex R.; Wentz, Robert J.; Johnson, Bruce D.

2015-01-01

Alveolar-capillary membrane conductance (DM,CO) and pulmonary-capillary blood volume (VC) are calculated via lung diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO) using the single breath, single oxygen tension (single-FiO2) method. However, two calculation parameters, the reaction rate of carbon monoxide with blood (θCO) and the DM,NO/DM,CO ratio (α-ratio), are controversial. This study systematically determined optimal θCO and α-ratio values to be used in the single-FiO2 method that yielded the most similar DM,CO and VC values compared to the ‘gold-standard’ multiple-FiO2 method. Eleven healthy subjects performed single breath DLCO/DLNO maneuvers at rest and during exercise. DM,CO and VC were calculated via the single-FiO2 and multiple-FiO2 methods by implementing seven θCO equations and a range of previously reported α-ratios. The RP θCO equation (Reeves and Park, Respiration physiology 88:1–21, 1992.) and an α-ratio of 4.0–4.4 yielded DM,CO and VC values that were most similar between methods. The RP θCO equation and an experimental α-ratio should be used in future studies. PMID:26521031

Cognitive Imagery and Physiological Feedback Relaxation Protocols Applied to Clinically Tense Young Adults: A Comparison of State, Trait, and Physiological Effects.

ERIC Educational Resources Information Center

Schandler, Steven L.; Dana, Edward R.

1983-01-01

Examined changes in tension behaviors and reductions in physiological tension associated with cognitive imagery and electromyographic biofeedback relaxation procedures in 45 college students. Results showed: imagery significantly reduced state anxiety. Self-rest was less effective; biofeedback greatly reduced physiological tension, but not state…

Physiological (antioxidant) responses of estuarine fishes to variability in dissolved oxygen.

PubMed

Ross, S W; Dalton, D A; Kramer, S; Christensen, B L

2001-11-01

Cycles of dissolved oxygen (DO) in estuaries can range from anoxia to various levels of supersaturation (200-300%) over short time periods. Aerobic metabolism causes formation of damaging reactive oxygen species (ROS), a process exacerbated by high or low DO. Fish can generate physiological defenses (e.g. antioxidant enzymes) against ROS, however, there are little data tying this to environmental conditions. We investigated physiological defenses generated by estuarine fishes in response to high DO and various DO cycles. We hypothesized that chemical defenses and/or oxidative damage are related to patterns of DO supersaturation. Specific activities of antioxidants in fish tissues should be positively correlated with increasing levels of DO, if high DO levels are physiologically stressful. We caged common benthic fishes (longjaw mudsucker, Gillichthys mirabilis, and staghorn sculpin, Leptocottus armatus, in CA and spot, Leiostomus xanthurus and pinfish, Lagodon rhomboides, in NC) during summer 1998 in two estuarine sites in southern North Carolina and two in central California. At each site a water quality meter measured bottom DO, salinity, temperature, depth, pH and turbidity at 30 min intervals throughout the study. These sites exhibited a wide variety of dissolved oxygen patterns. After 2 weeks in the cages, fish gills and livers were analyzed for antioxidant enzymes (glutathione peroxidase, catalase and superoxide dismutase) and the metabolite glutathione. All fish exhibited antioxidant enzyme activity. There was a significant site-dependent effect on all enzyme activities at the NC sites, with the most activity at the site with the highest DO cycling and the most DO supersaturation. There was a trend towards higher enzyme activities under high DO levels at the CA sites.

Non-invasive measurement of the mean alveolar O(2) tension from the oxygen uptake versus tidal volume curve.

PubMed

Jordanoglou, J; Latsi, P; Chroneou, A; Koulouris, N G

2007-10-01

The classical equations for measuring the mean and the ideal alveolar O(2) tension are based on assumptions, which are shown to be invalid. So we thought to develop a new, non-invasive method for measuring the mean alveolar P,O(2) within the volume domain (PA,O(2(Bohr))). This method is based on the oxygen uptake vs. tidal volume curve (VO(2) vs. VT) obtained during tidal breathing of room air and/or air enriched with oxygen. PA,O(2(Bohr)) and the ideal alveolar PO(2) (PA,O(2(ideal))) were simultaneously measured in 10 healthy subjects and 34 patients suffering from chronic obstructive pulmonary disease (COPD) breathing tidally room air at rest. Additionally, 10 subjects (three healthy subjects and seven COPD patients) were studied while breathing initially room air and subsequently air enriched with oxygen. According to the results, PA,O(2(Bohr)) considerably differed from PA,O(2(ideal)) (P = 0.004). The cause of the difference, at the individual's R, is: (1) the difference between the arterial and Bohr's alveolar CO(2) tension, mainly in COPD patients, and (2) the inequality between Bohr's alveolar part of the tidal volume for CO(2) and O(2). Furthermore, end-tidal gas tension (PET,CO(2) and PET,O(2)) differed from Pa,CO(2) and PA,O(2(Bohr)) respectively. The deviation of PA,O(2(Bohr)) from PA,O(2(ideal)) has a definite impact on Bohr's dead space ratio for O(2) and CO(2), and on the alveolar-arterial O(2) difference. The difference (PA,O(2(Bohr)) - PA,O(2(ideal))) is not related to the pathology of the disease. So, gas exchange within the lungs should be assessed at the subject's R from PA,O(2(Bohr)) and PA,CO(2(Bohr)) but not from PA,O(2(ideal)) nor Pa,CO(2).

Modeling Variable Phanerozoic Oxygen Effects on Physiology and Evolution.

PubMed

Graham, Jeffrey B; Jew, Corey J; Wegner, Nicholas C

2016-01-01

Geochemical approximation of Earth's atmospheric O2 level over geologic time prompts hypotheses linking hyper- and hypoxic atmospheres to transformative events in the evolutionary history of the biosphere. Such correlations, however, remain problematic due to the relative imprecision of the timing and scope of oxygen change and the looseness of its overlay on the chronology of key biotic events such as radiations, evolutionary innovation, and extinctions. There are nevertheless general attributions of atmospheric oxygen concentration to key evolutionary changes among groups having a primary dependence upon oxygen diffusion for respiration. These include the occurrence of Devonian hypoxia and the accentuation of air-breathing dependence leading to the origin of vertebrate terrestriality, the occurrence of Carboniferous-Permian hyperoxia and the major radiation of early tetrapods and the origins of insect flight and gigantism, and the Mid-Late Permian oxygen decline accompanying the Permian extinction. However, because of variability between and error within different atmospheric models, there is little basis for postulating correlations outside the Late Paleozoic. Other problems arising in the correlation of paleo-oxygen with significant biological events include tendencies to ignore the role of blood pigment affinity modulation in maintaining homeostasis, the slow rates of O2 change that would have allowed for adaptation, and significant respiratory and circulatory modifications that can and do occur without changes in atmospheric oxygen. The purpose of this paper is thus to refocus thinking about basic questions central to the biological and physiological implications of O2 change over geological time.

The importance of physiological oxygen concentrations in the sandwich cultures of rat hepatocytes on gas-permeable membranes.

PubMed

Xiao, Wenjin; Shinohara, Marie; Komori, Kikuo; Sakai, Yasuyuki; Matsui, Hitoshi; Osada, Tomoharu

2014-01-01

Oxygen supply is a critical issue in the optimization of in vitro hepatocyte microenvironments. Although several strategies have been developed to balance complex oxygen requirements, these techniques are not able to accurately meet the cellular oxygen demand. Indeed, neither the actual oxygen concentration encountered by cells nor the cellular oxygen consumption rates (OCR) was assessed. The aim of this study is to define appropriate oxygen conditions at the cell level that could accurately match the OCR and allow hepatocytes to maintain liver specific functions in a normoxic environment. Matrigel overlaid rat hepatocytes were cultured on the polydimethylsiloxane (PDMS) membranes under either atmospheric oxygen concentration [20%-O2 (+)] or physiological oxygen concentrations [10%-O2 (+), 5%-O2 (+)], respectively, to investigate the effects of various oxygen concentrations on the efficient functioning of hepatocytes. In parallel, the gas-impermeable cultures (polystyrene) with PDMS membrane inserts were used as the control groups [PS-O2 (-)]. The results indicated that the hepatocytes under 10%-O2 (+) exhibited improved survival and maintenance of metabolic activities and functional polarization. The dramatic elevation of cellular OCR up to the in vivo liver rate proposed a normoxic environment for hepatocytes, especially when comparing with PS-O2 (-) cultures, in which the cells generally tolerated hypoxia. Additionally, the expression levels of 84 drug-metabolism genes were the closest to physiological levels. In conclusion, this study clearly shows the benefit of long-term culture of hepatocytes at physiological oxygen concentration, and indicates on an oxygen-permeable membrane system to provide a simple method for in vitro studies. © 2014 American Institute of Chemical Engineers.

Cerebral oxygenation in traumatic brain injury; Can a non-invasive frequency domain near-infrared spectroscopy device detect changes in brain tissue oxygen tension as well as the established invasive monitor?

PubMed

Davies, David James; Clancy, Michael; Dehghani, Hamid; Lucas, Samuel John Edwin; Forcione, Mario; Yakoub, Kamal Makram; Belli, Antonio

2018-06-07

The cost and highly invasive nature of brain monitoring modality in traumatic brain injury patients currently restrict its utility to specialist neurological intensive care settings. We aim to test the abilities of a frequency domain near-infrared spectroscopy (FD-NIRS) device in predicting changes in invasively measured brain tissue oxygen tension. Individuals admitted to a United Kingdom specialist major trauma centre were contemporaneously monitored with an FD-NIRS device and invasively measured brain tissue oxygen tension probe. Area under the curve receiver operating characteristic (AUROC) statistical analysis was utilised to assess the predictive power of FD-NIRS in detecting both moderate and severe hypoxia (20 and 10 mmHg, respectively), as measured invasively. 16 individuals were prospectively recruited to the investigation. Severe hypoxic episodes were detected in 9 of these individuals, with the NIRS demonstrating a broad range of predictive abilities (AUROC 0.68-0.88) from relatively poor to good. Moderate hypoxic episodes were detected in seven individuals with similar predictive performance (AUROC 0.576 - 0.905). A variable performance in the predictive powers of this FD-NIRS device to detect changes in brain tissue oxygen was demonstrated. Consequently, this enhanced NIRS technology has not demonstrated sufficient ability to replace the established invasive measurement.

Physiological Gut Oxygenation Alters GLP-1 Secretion from the Enteroendocrine Cell Line STC-1.

PubMed

Kondrashina, Alina; Papkovsky, Dmitri; Giblin, Linda

2018-02-01

Enteroendocrine cell lines are routinely assayed in simple buffers at ≈20% oxygen to screen foods for bioactives that boost satiety hormone levels. However, in vivo, enteroendocrine cells are exposed to different phases of food digestion and function at low oxygen concentration, ranging from 7.5% in the stomach to 0.5% in the colon-rectal junction. The objective of this study is to investigate the effect of physiologically relevant O 2 concentrations of the gut on the production and secretion of the satiety hormone, glucagon-like peptide 1 (GLP-1), from the murine enteroendocrine cell line, secretin tumor cell line (STC-1), in response to dairy macronutrients as they transit the gut. GLP-1 exocytosis from STC-1 cells is influenced by both oxygen concentration and by individual macronutrients. At low oxygen, STC-1 cell viability is significantly improved for all macronutrient stimulations and cyclic adenosine monophosphate levels are dampened. GLP-1 secretion from STC-1 cells is influenced by both the phase of yogurt digestion and corresponding O 2 concentration. Atmospheric oxygen at 4.5% combined with upper gastric digesta, which simulates ileum conditions, yields the highest GLP-1 response. This demonstrates the importance of considering physiological oxygen levels and food digestion along gastrointestinal tract for reliable in vitro analysis of gut hormone secretion. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous sampling of tissue oxygenation and oxygen consumption in skeletal muscle.

PubMed

Nugent, William H; Song, Bjorn K; Pittman, Roland N; Golub, Aleksander S

2016-05-01

Under physiologic conditions, microvascular oxygen delivery appears to be well matched to oxygen consumption in respiring tissues. We present a technique to measure interstitial oxygen tension (PISFO2) and oxygen consumption (VO2) under steady-state conditions, as well as during the transitions from rest to activity and back. Phosphorescence Quenching Microscopy (PQM) was employed with pneumatic compression cycling to achieve 1 to 10 Hz sampling rates of interstitial PO2 and simultaneous recurrent sampling of VO2 (3/min) in the exteriorized rat spinotrapezius muscle. The compression pressure was optimized to 120-130 mmHg without adverse effect on the tissue preparation. A cycle of 5s compression followed by 15s recovery yielded a resting VO2 of 0.98 ± 0.03 ml O2/100 cm(3)min while preserving microvascular oxygen delivery. The measurement system was then used to assess VO2 dependence on PISFO2 at rest and further tested under conditions of isometric muscle contraction to demonstrate a robust ability to monitor the on-kinetics of tissue respiration and the compensatory changes in PISFO2 during contraction and recovery. The temporal and spatial resolution of this approach is well suited to studies seeking to characterize microvascular oxygen supply and demand in thin tissues. Copyright © 2015 Elsevier Inc. All rights reserved.

Spatial Variations in Vitreous Oxygen Consumption.

PubMed

Murali, Karthik; Kang, Dongyang; Nazari, Hossein; Scianmarello, Nicholas; Cadenas, Enrique; Tai, Yu-Chong; Kashani, Amir; Humayun, Mark

2016-01-01

We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M(-1) s(-1) ± 0.708 M(-1) s(-1) (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration.

Spatial Variations in Vitreous Oxygen Consumption

PubMed Central

Murali, Karthik; Kang, Dongyang; Nazari, Hossein; Scianmarello, Nicholas; Cadenas, Enrique; Tai, Yu-Chong; Kashani, Amir; Humayun, Mark

2016-01-01

We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M-1s-1 ± 0.708 M-1s-1 (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration. PMID:26930281

Diffusion capacity and CT measures of emphysema and airway wall thickness - relation to arterial oxygen tension in COPD patients.

PubMed

Saure, Eirunn Waatevik; Bakke, Per Sigvald; Lind Eagan, Tomas Mikal; Aanerud, Marianne; Jensen, Robert Leroy; Grydeland, Thomas Blix; Johannessen, Ane; Nilsen, Roy Miodini; Thorsen, Einar; Hardie, Jon Andrew

2016-01-01

Decreased diffusing capacity of the lung for carbon monoxide (DLCO) is associated with emphysema. DLCO is also related to decreased arterial oxygen tension (PaO2), but there are limited data on associations between PaO2 and computed tomography (CT) derived measures of emphysema and airway wall thickness. To examine whether CT measures of emphysema and airway wall thickness are associated with level of arterial oxygen tension beyond that provided by measurements of diffusion capacity and spirometry. The study sample consisted of 271 smoking or ex-smoking COPD patients from the Bergen COPD Cohort Study examined in 2007-2008. Emphysema was assessed as percent of low-attenuation areas<-950 Hounsfield units (%LAA), and airway wall thickness as standardised measure at an internal perimeter of 10 mm (AWT-Pi10). Multiple linear regression models were fitted with PaO2 as the outcome variable, and %LAA, AWT-Pi10, DLCO and carbon monoxide transfer coefficient (KCO) as main explanatory variables. The models were adjusted for sex, age, smoking status, and haemoglobin concentration, as well as forced expiratory volume in one second (FEV1). Sixty two per cent of the subjects were men, mean (SD) age was 64 (7) years, mean (SD) FEV1 in percent predicted was 50 (15)%, and mean PaO2 (SD) was 9.3 (1.1) kPa. The adjusted regression coefficient (CI) for PaO2 was -0.32 (-0.04-(-0.019)) per 10% increase in %LAA (p<0.01). When diffusion capacity and FEV1 were added to the model, respectively, the association lost its statistical significance. No relationship between airway wall thickness and PaO2 was found. CT assessment of airway wall thickness is not associated with arterial oxygen tension in COPD patients. Emphysema score measured by chest CT, is related to decreased PaO2, but cannot replace measurements of diffusion capacity in the clinical evaluation of hypoxaemia.

The Risk of Oxygen during Cardiac Surgery (ROCS) trial: study protocol for a randomized clinical trial.

PubMed

Lopez, Marcos G; Pretorius, Mias; Shotwell, Matthew S; Deegan, Robert; Eagle, Susan S; Bennett, Jeremy M; Sileshi, Bantayehu; Liang, Yafen; Gelfand, Brian J; Kingeter, Adam J; Siegrist, Kara K; Lombard, Frederick W; Richburg, Tiffany M; Fornero, Dane A; Shaw, Andrew D; Hernandez, Antonio; Billings, Frederic T

2017-06-26

Anesthesiologists administer excess supplemental oxygen (hyper-oxygenation) to patients during surgery to avoid hypoxia. Hyper-oxygenation, however, may increase the generation of reactive oxygen species and cause oxidative damage. In cardiac surgery, increased oxidative damage has been associated with postoperative kidney and brain injury. We hypothesize that maintenance of normoxia during cardiac surgery (physiologic oxygenation) decreases kidney injury and oxidative damage compared to hyper-oxygenation. The Risk of Oxygen during Cardiac Surgery (ROCS) trial will randomly assign 200 cardiac surgery patients to receive physiologic oxygenation, defined as the lowest fraction of inspired oxygen (FIO 2 ) necessary to maintain an arterial hemoglobin saturation of 95 to 97%, or hyper-oxygenation (FIO 2  = 1.0) during surgery. The primary clinical endpoint is serum creatinine change from baseline to postoperative day 2, and the primary mechanism endpoint is change in plasma concentrations of F 2 -isoprostanes and isofurans. Secondary endpoints include superoxide production, clinical delirium, myocardial injury, and length of stay. An endothelial function substudy will examine the effects of oxygen treatment and oxidative stress on endothelial function, measured using flow mediated dilation, peripheral arterial tonometry, and wire tension myography of epicardial fat arterioles. The ROCS trial will test the hypothesis that intraoperative physiologic oxygenation decreases oxidative damage and organ injury compared to hyper-oxygenation in patients undergoing cardiac surgery. ClinicalTrials.gov, ID: NCT02361944 . Registered on the 30th of January 2015.

Influence of low oxygen tensions and sorption to sediment black carbon on biodegradation of pyrene.

PubMed

Ortega-Calvo, José-Julio; Gschwend, Philip M

2010-07-01

Sorption to sediment black carbon (BC) may limit the aerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) in resuspension events and intact sediment beds. We examined this hypothesis experimentally under conditions that were realistic in terms of oxygen concentrations and BC content. A new method, based on synchronous fluorescence observations of (14)C-pyrene, was developed for continuously measuring the uptake of dissolved pyrene by Mycobacterium gilvum VM552, a representative degrader of PAHs. The effect of oxygen and pyrene concentrations on pyrene uptake followed Michaelis-Menten kinetics, resulting in a dissolved oxygen half-saturation constant (K(om)) of 14.1 microM and a dissolved pyrene half-saturation constant (K(pm)) of 6 nM. The fluorescence of (14)C-pyrene in air-saturated suspensions of sediments and induced cells followed time courses that reflected simultaneous desorption and biodegradation of pyrene, ultimately causing a quasi-steady-state concentration of dissolved pyrene balancing desorptive inputs and biodegradation removals. The increasing concentrations of (14)CO(2) in these suspensions, as determined with liquid scintillation, evidenced the strong impact of sorption to BC-rich sediments on the biodegradation rate. Using the best-fit parameter values, we integrated oxygen and sorption effects and showed that oxygen tensions far below saturation levels in water are sufficient to enable significant decreases in the steady-state concentrations of aqueous-phase pyrene. These findings may be relevant for bioaccumulation scenarios that consider the effect of sediment resuspension events on exposure to water column and sediment pore water, as well as the direct uptake of PAHs from sediments.

Optimizing the calculation of DM,CO and VC via the single breath single oxygen tension DLCO/NO method.

PubMed

Coffman, Kirsten E; Taylor, Bryan J; Carlson, Alex R; Wentz, Robert J; Johnson, Bruce D

2016-01-15

Alveolar-capillary membrane conductance (D(M,CO)) and pulmonary-capillary blood volume (V(C)) are calculated via lung diffusing capacity for carbon monoxide (DL(CO)) and nitric oxide (DL(NO)) using the single breath, single oxygen tension (single-FiO2) method. However, two calculation parameters, the reaction rate of carbon monoxide with blood (θ(CO)) and the D(M,NO)/D(M,CO) ratio (α-ratio), are controversial. This study systematically determined optimal θ(CO) and α-ratio values to be used in the single-FiO2 method that yielded the most similar D(M,CO) and V(C) values compared to the 'gold-standard' multiple-FiO2 method. Eleven healthy subjects performed single breath DL(CO)/DL(NO) maneuvers at rest and during exercise. D(M,CO) and V(C) were calculated via the single-FiO2 and multiple-FiO2 methods by implementing seven θ(CO) equations and a range of previously reported α-ratios. The RP θ(CO) equation (Reeves, R.B., Park, H.K., 1992. Respiration Physiology 88 1-21) and an α-ratio of 4.0-4.4 yielded DM,CO and VC values that were most similar between methods. The RP θ(CO) equation and an experimental α-ratio should be used in future studies. Copyright © 2015 Elsevier B.V. All rights reserved.

The role of reduced oxygen in the developmental physiology of growth and metamorphosis initiation in Drosophila

USDA-ARS?s Scientific Manuscript database

Rearing oxygen level is known to affect final body size in a variety of insects, but the physiological mechanisms by which oxygen affects size are incompletely understood. In Manduca and Drosophila, the larval size at which metamorphosis is initiated largely determines adult size, and metamorphosis ...

Modeling Corneal Oxygen with Scleral Gas Permeable Lens Wear.

PubMed

Compañ, Vicente; Aguilella-Arzo, Marcel; Edrington, Timothy B; Weissman, Barry A

2016-11-01

The main goal of this current work is to use an updated calculation paradigm, and updated boundary conditions, to provide theoretical guidelines to assist the clinician whose goal is to improve his or her scleral gas permeable (GP) contact lens wearing patients' anterior corneal oxygen supply. Our model uses a variable value of corneal oxygen consumption developed through Monod equations that disallows negative oxygen tensions within the stroma to predict oxygen tension at the anterior corneal surface of scleral GP contact lens wearing eyes, and to describe oxygen tension and flux profiles, for various boundary conditions, through the lens, tears, and cornea. We use several updated tissue and boundary parameters in our model. Tear exchange with GP scleral lenses is considered nonexistent in this model. The majority of current scleral GP contact lenses should produce some levels of corneal hypoxia under open eye conditions. Only lenses producing the thinnest of tear vaults should result in anterior corneal surface oxygen tensions greater than a presumed critical oxygen tension of 100 mmHg. We also find that corneal oxygen tension and flux are each more sensitive to modification in tear vault than to changes in lens oxygen permeability, within the ranges of current clinical manipulation. Our study suggests that clinicians would be prudent to prescribe scleral GP lenses manufactured from higher oxygen permeability materials and especially to fit without excessive corneal clearance.

Physiological closed-loop control in intelligent oxygen therapy: A review.

PubMed

Sanchez-Morillo, Daniel; Olaby, Osama; Fernandez-Granero, Miguel Angel; Leon-Jimenez, Antonio

2017-07-01

Oxygen therapy has become a standard care for the treatment of patients with chronic obstructive pulmonary disease and other hypoxemic chronic lung diseases. In current systems, manually continuous adjustment of O 2 flow rate is a time-consuming task, often unsuccessful, that requires experienced staff. The primary aim of this systematic review is to collate and report on the principles, algorithms and accuracy of autonomous physiological close-loop controlled oxygen devices as well to present recommendations for future research and studies in this area. A literature search was performed on medical database MEDLINE, engineering database IEEE-Xplore and wide-raging scientific databases Scopus and Web of Science. A narrative synthesis of the results was carried out. A summary of the findings of this review suggests that when compared to the conventional manual practice, the closed-loop controllers maintain higher saturation levels, spend less time below the target saturation, and save oxygen resources. Nonetheless, despite of their potential, autonomous oxygen therapy devices are scarce in real clinical applications. Robustness of control algorithms, fail-safe mechanisms, limited reliability of sensors, usability issues and the need for standardized evaluating methods of assessing risks can be among the reasons for this lack of matureness and need to be addressed before the wide spreading of a new generation of automatic oxygen devices. Copyright © 2017 Elsevier B.V. All rights reserved.

The Tension Literature.

ERIC Educational Resources Information Center

Frederick, A. B.

This is a bibliography of literature on the subject of tension. Books, films, and periodicals with a bearing on stress, relaxation, anxiety, and/or methods of controlling stress are listed from the fields of physiology, psychology, and philosophy. New methods such as transcendental meditation and biofeedback are analyzed briefly and criteria are…

Comparison of Preterm and Term Wharton's Jelly-Derived Mesenchymal Stem Cell Properties in Different Oxygen Tensions.

PubMed

Balgi-Agarwal, Saloni; Winter, Caitlyn; Corral, Alexis; Mustafa, Shamimunisa B; Hornsby, Peter; Moreira, Alvaro

2018-06-27

Mesenchymal stem cells (MSCs) have shown promise as therapeutic agents in treating morbidities associated with premature birth. MSCs derived from the human umbilical cord are easy to isolate and have low immunogenicity and a robust ability to secrete paracrine factors. To date, there are no studies evaluating preterm versus term umbilical cord tissue-derived MSCs. Therefore, our aim was twofold: (1) to compare stem cell properties in preterm versus term MSCs and (2) to examine the impact of oxygen tension on stem cell behavior. Umbilical cord tissue was obtained from 5 preterm and 5 term neonates. The cells were isolated and characterized as MSCs in accordance with the International Society for Cellular Therapy. We exposed MSCs to different oxygen tensions to examine the impact of environmental factors on cell performance. We studied the following stem cell properties: (i) motility, (ii) proliferation, (iii) senescence, (iv) cell viability, (v) colony-forming unit efficiency, and (vi) inflammatory cytokine expression. Under normoxia (21% O2), cells from preterm and term infants had similar properties. Under hypoxic conditions (1% O2), term MSCs had better cell proliferation; however, cells exposed to hyperoxia (90% O2) had the slowest motility and lowest cell viability (p < 0.05). There was no difference in the expression of senescence or cytokine expression between the groups. The term cells demonstrated more colony-forming efficiency than the preterm cells. In sum, our preliminary findings suggest that MSCs derived from term and preterm umbilical cords have similar characteristics, offering the potential of future autologous/allogeneic MSC transplants in neonates. © 2018 S. Karger AG, Basel.

Erythrocytes Are Oxygen-Sensing Regulators of the Cerebral Microcirculation.

PubMed

Wei, Helen Shinru; Kang, Hongyi; Rasheed, Izad-Yar Daniel; Zhou, Sitong; Lou, Nanhong; Gershteyn, Anna; McConnell, Evan Daniel; Wang, Yixuan; Richardson, Kristopher Emil; Palmer, Andre Francis; Xu, Chris; Wan, Jiandi; Nedergaard, Maiken

2016-08-17

Energy production in the brain depends almost exclusively on oxidative metabolism. Neurons have small energy reserves and require a continuous supply of oxygen (O2). It is therefore not surprising that one of the hallmarks of normal brain function is the tight coupling between cerebral blood flow and neuronal activity. Since capillaries are embedded in the O2-consuming neuropil, we have here examined whether activity-dependent dips in O2 tension drive capillary hyperemia. In vivo analyses showed that transient dips in tissue O2 tension elicit capillary hyperemia. Ex vivo experiments revealed that red blood cells (RBCs) themselves act as O2 sensors that autonomously regulate their own deformability and thereby flow velocity through capillaries in response to physiological decreases in O2 tension. This observation has broad implications for understanding how local changes in blood flow are coupled to synaptic transmission. Copyright © 2016 Elsevier Inc. All rights reserved.

Seed birth to death: dual functions of reactive oxygen species in seed physiology.

PubMed

Jeevan Kumar, S P; Rajendra Prasad, S; Banerjee, Rintu; Thammineni, Chakradhar

2015-09-01

Reactive oxygen species (ROS) are considered to be detrimental to seed viability. However, recent studies have demonstrated that ROS have key roles in seed germination particularly in the release of seed dormancy and embryogenesis, as well as in protection from pathogens. This review considers the functions of ROS in seed physiology. ROS are present in all cells and at all phases of the seed life cycle. ROS accumulation is important in breaking seed dormancy, and stimulating seed germination and protection from pathogens. However, excessive ROS accumulation can be detrimental. Therefore, knowledge of the mechanisms by which ROS influence seed physiology will provide insights that may not only allow the development of seed quality markers but also help us understand how dormancy can be broken in several recalcitrant species. Reactive oxygen species have a dual role in seed physiology. Understanding the relative importance of beneficial and detrimental effects of ROS provides great scope for the improvement and maintenance of seed vigour and quality, factors that may ultimately increase crop yields. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Tear Oxygen Under Hydrogel and Silicone Hydrogel Contact Lenses in Humans

PubMed Central

Bonanno, Joseph A.; Clark, Christopher; Pruitt, John; Alvord, Larry

2011-01-01

Purpose To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects. Methods Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure. Results Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies. Conclusions The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea. PMID:19609230

Tear oxygen under hydrogel and silicone hydrogel contact lenses in humans.

PubMed

Bonanno, Joseph A; Clark, Christopher; Pruitt, John; Alvord, Larry

2009-08-01

To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects. Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure. Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies. The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea.

Ultrasound Findings in Tension Pneumothorax: A Case Report.

PubMed

Inocencio, Maxine; Childs, Jeannine; Chilstrom, Mikaela L; Berona, Kristin

2017-06-01

Delayed recognition of tension pneumothorax can lead to a mortality of 31% to 91%. However, the classic physical examination findings of tracheal deviation and distended neck veins are poorly sensitive in the diagnosis of tension pneumothorax. Point-of-care ultrasound is accurate in identifying the presence of pneumothorax, but sonographic findings of tension pneumothorax are less well described. We report the case of a 21-year-old man with sudden-onset left-sided chest pain. He was clinically stable without hypoxia or hypotension, and the initial chest x-ray study showed a large pneumothorax without mediastinal shift. While the patient was awaiting tube thoracostomy, a point-of-care ultrasound demonstrated findings of mediastinal shift and a dilated inferior vena cava (IVC) concerning for tension physiology, even though the patient remained hemodynamically stable. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case demonstrates a unique clinical scenario of ultrasound evidence of tension physiology in a clinically stable patient. Although this patient was well appearing without hypotension, respiratory distress, tracheal deviation, or distended neck veins, point-of-care ultrasound revealed mediastinal shift and a plethoric IVC. Given that the classic clinical signs of tension pneumothorax are not uniformly present, this case shows how point-of-care ultrasound may diagnose tension pneumothorax before clinical decompensation. Published by Elsevier Inc.

The Role of Oxygen Sensors, Hydroxylases, and HIF in Cardiac Function and Disease.

PubMed

Townley-Tilson, W H Davin; Pi, Xinchun; Xie, Liang

2015-01-01

Ischemic heart disease is the leading cause of death worldwide. Oxygen-sensing proteins are critical components of the physiological response to hypoxia and reperfusion injury, but the role of oxygen and oxygen-mediated effects is complex in that they can be cardioprotective or deleterious to the cardiac tissue. Over 200 oxygen-sensing proteins mediate the effects of oxygen tension and use oxygen as a substrate for posttranslational modification of other proteins. Hydroxylases are an essential component of these oxygen-sensing proteins. While a major role of hydroxylases is regulating the transcription factor HIF, we investigate the increasing scope of hydroxylase substrates. This review discusses the importance of oxygen-mediated effects in the heart as well as how the field of oxygen-sensing proteins is expanding, providing a more complete picture into how these enzymes play a multifaceted role in cardiac function and disease. We also review how oxygen-sensing proteins and hydroxylase function could prove to be invaluable in drug design and therapeutic targets for heart disease.

Effect of Oxygen Tension and Medium Components on Monomer Distribution of Alginate.

PubMed

Kıvılcımdan Moral, Çiğdem; Doğan, Özdemir; Sanin, Faika Dilek

2015-06-01

Alginate is a natural biopolymer composed of mannuronic and guluronic acid monomers. It is produced by algae and some species of Azotobacter and Pseudomonas. This study aims to investigate the effect of dissolved oxygen tension (DOT) and growth medium substrate and calcium concentrations on the monomeric composition of alginate produced by Azotobacter vinelandii ATCC® 9046 in a fermenter. Results showed that alginate production increased with increasing DOT from 1 to 5 %. The highest alginate production was obtained as 4.51 g/L under 20 g/L of sucrose and 50 mg/L of calcium at 5 % DOT. At these conditions, alginate was rich in mannuronic acid (up to 61 %) and it was particularly high at low calcium concentration. On the other hand, at extreme conditions such as high DOT level (10 % DOT) and low sucrose concentration (10 g/L), guluronic acid was dominant (ranging between 65 and 100 %).

Improvement in production and quality of gellan gum by Sphingomonas paucimobilis under high dissolved oxygen tension levels.

PubMed

Banik, R M; Santhiagu, A

2006-09-01

The effect of agitation rate and dissolved oxygen tension (DOT) on growth and gellan production by Sphingomonas paucimobilis was studied. Higher cell growth of 5.4 g l(-1) was obtained at 700 rpm but maximum gellan (15 g l(-1)) was produced at 500 rpm. DOT levels above 20% had no effect on cell growth but gellan yield was increased to 23 g l(-1 )with increase in DOT level to 100%. Higher DOT levels improved the viscosity and molecular weight of the polymer with change in acetate and glycerate content of the polymer.

Flickering analysis of erythrocyte mechanical properties: dependence on oxygenation level, cell shape, and hydration level.

PubMed

Yoon, Young-Zoon; Hong, Ha; Brown, Aidan; Kim, Dong Chung; Kang, Dae Joon; Lew, Virgilio L; Cicuta, Pietro

2009-09-16

Erythrocytes (red blood cells) play an essential role in the respiratory functions of vertebrates, carrying oxygen from lungs to tissues and CO(2) from tissues to lungs. They are mechanically very soft, enabling circulation through small capillaries. The small thermally induced displacements of the membrane provide an important tool in the investigation of the mechanics of the cell membrane. However, despite numerous studies, uncertainties in the interpretation of the data, and in the values derived for the main parameters of cell mechanics, have rendered past conclusions from the fluctuation approach somewhat controversial. Here we revisit the experimental method and theoretical analysis of fluctuations, to adapt them to the case of cell contour fluctuations, which are readily observable experimentally. This enables direct measurements of membrane tension, of bending modulus, and of the viscosity of the cell cytoplasm. Of the various factors that influence the mechanical properties of the cell, we focus here on: 1), the level of oxygenation, as monitored by Raman spectrometry; 2), cell shape; and 3), the concentration of hemoglobin. The results show that, contrary to previous reports, there is no significant difference in cell tension and bending modulus between oxygenated and deoxygenated states, in line with the softness requirement for optimal circulatory flow in both states. On the other hand, tension and bending moduli of discocyte- and spherocyte-shaped cells differ markedly, in both the oxygenated and deoxygenated states. The tension in spherocytes is much higher, consistent with recent theoretical models that describe the transitions between red blood cell shapes as a function of membrane tension. Cell cytoplasmic viscosity is strongly influenced by the hydration state. The implications of these results to circulatory flow dynamics in physiological and pathological conditions are discussed.

Molecular dynamics simulations of the surface tension of oxygen-supersaturated water

NASA Astrophysics Data System (ADS)

Jain, S.; Qiao, L.

2017-04-01

In this work, non-reactive molecular dynamic simulations were conducted to determine the surface tension of water as a function of the concentration of the dissolved gaseous molecules (O2), which would in turn help to predict the pressure inside the nanobubbles under supersaturation conditions. Knowing the bubble pressure is a prerequisite for understanding the mechanisms behind the spontaneous combustion of the H2/O2 gases inside the nanobubbles. First, the surface tension of pure water was determined using the planar interface method and the Irving and Kirkwood formula. Next, the surface tension of water containing four different supersaturation concentrations (S) of O2 gas molecules was computed considering the curved interface of a nanobubble. The surface tension of water was found to decrease with an increase in the supersaturation ratio or the concentration of the dissolved O2 gas molecules.

Preventing and Treating Hypoxia: Using a Physiology Simulator to Demonstrate the Value of Pre-Oxygenation and the Futility of Hyperventilation.

PubMed

Lerant, Anna A; Hester, Robert L; Coleman, Thomas G; Phillips, William J; Orledge, Jeffrey D; Murray, W Bosseau

2015-01-01

Insufficient pre-oxygenation before emergency intubation, and hyperventilation after intubation are mistakes that are frequently observed in and outside the operating room, in clinical practice and in simulation exercises. Physiological parameters, as appearing on standard patient monitors, do not alert to the deleterious effects of low oxygen saturation on coronary perfusion, or that of low carbon dioxide concentrations on cerebral perfusion. We suggest the use of HumMod, a computer-based human physiology simulator, to demonstrate beneficial physiological responses to pre-oxygenation and the futility of excessive minute ventilation after intubation. We programmed HumMod, to A.) compare varying times (0-7 minutes) of pre-oxygenation on oxygen saturation (SpO2) during subsequent apnoea; B.) simulate hyperventilation after apnoea. We compared the effect of different minute ventilation rates on SpO2, acid-base status, cerebral perfusion and other haemodynamic parameters. A.) With no pre-oxygenation, starting SpO2 dropped from 98% to 90% in 52 seconds with apnoea. At the other extreme, following full pre-oxygenation with 100% O2 for 3 minutes or more, the SpO2 remained 100% for 7.75 minutes during apnoea, and dropped to 90% after another 75 seconds. B.) Hyperventilation, did not result in more rapid normalization of SpO2, irrespective of the level of minute ventilation. However, hyperventilation did cause significant decreases in cerebral blood flow (CBF). HumMod accurately simulates the physiological responses compared to published human studies of pre-oxygenation and varying post intubation minute ventilations, and it can be used over wider ranges of parameters than available in human studies and therefore available in the literature.

Preventing and Treating Hypoxia: Using a Physiology Simulator to Demonstrate the Value of Pre-Oxygenation and the Futility of Hyperventilation

PubMed Central

Lerant, Anna A.; Hester, Robert L.; Coleman, Thomas G.; Phillips, William J.; Orledge, Jeffrey D.; Murray, W. Bosseau

2015-01-01

Introduction: Insufficient pre-oxygenation before emergency intubation, and hyperventilation after intubation are mistakes that are frequently observed in and outside the operating room, in clinical practice and in simulation exercises. Physiological parameters, as appearing on standard patient monitors, do not alert to the deleterious effects of low oxygen saturation on coronary perfusion, or that of low carbon dioxide concentrations on cerebral perfusion. We suggest the use of HumMod, a computer-based human physiology simulator, to demonstrate beneficial physiological responses to pre-oxygenation and the futility of excessive minute ventilation after intubation. Methods: We programmed HumMod, to A.) compare varying times (0-7 minutes) of pre-oxygenation on oxygen saturation (SpO2) during subsequent apnoea; B.) simulate hyperventilation after apnoea. We compared the effect of different minute ventilation rates on SpO2, acid-base status, cerebral perfusion and other haemodynamic parameters. Results: A.) With no pre-oxygenation, starting SpO2 dropped from 98% to 90% in 52 seconds with apnoea. At the other extreme, following full pre-oxygenation with 100% O2 for 3 minutes or more, the SpO2 remained 100% for 7.75 minutes during apnoea, and dropped to 90% after another 75 seconds. B.) Hyperventilation, did not result in more rapid normalization of SpO2, irrespective of the level of minute ventilation. However, hyperventilation did cause significant decreases in cerebral blood flow (CBF). Conclusions: HumMod accurately simulates the physiological responses compared to published human studies of pre-oxygenation and varying post intubation minute ventilations, and it can be used over wider ranges of parameters than available in human studies and therefore available in the literature. PMID:26283881

Comparative In Vivo Effects of Hemoglobin-Based Oxygen Carriers (HBOC) with Varying Prooxidant and Physiological Reactivity.

PubMed

Toma, Vlad Al; Farcaș, Anca D; Roman, Ioana; Sevastre, Bogdan; Hathazi, Denisa; Scurtu, Florina; Damian, Grigore; Silaghi-Dumitrescu, Radu

2016-01-01

A series of hemoglobin-based oxygen carrier candidates (HBOC), previously noted for their differences in prooxidative and physiological reactivity, were compared in terms of the negative effects displayed upon injection in Wistar rats. At the concentrations tested, antioxidant strategies based on albumin as well as based on rubrerythrin appear to offer observable physiological advantages.

Numerical study of oxygen transport in a carotid bifurcation

NASA Astrophysics Data System (ADS)

Tada, Shigeru

2010-07-01

This study investigates the oxygen mass transport in the region around the human carotid bifurcation, particularly addressing the effects of bifurcation geometry and pulsatile blood flow on the oxygen transport between the blood flow and artery wall tissue, coupled with the metabolic oxygen consumption and oxygen diffusion in the artery wall tissue. The temporal variations and spatial distributions of the oxygen tension are predicted quantitatively using a geometric model of the human carotid bifurcation and realistic blood flow waveforms. Results reveal that the flow separation at the outside wall of the sinus of the internal carotid artery (ICA) can markedly alter the flow pattern, oxygen tension and the oxygen wall flux. Results also clarify that the flow unsteadiness has a secondary effect on the oxygen tension inside the wall. The non-dimensional oxygen flux, the Sherwood number Sh, at the outside wall of the ICA sinus, takes markedly lower values of about 45 than at other sites because the rates of oxygen transport by the convective flow are reduced at the outside wall of the ICA sinus. The transverse distributions of the oxygen tension inside the artery wall show parabolic profiles having minima in the middle of the wall thickness, with the lowest value of 35 mmHg. These predicted distributions of the oxygen tension inside the wall closely resemble those obtained from experiments. The results demonstrate that hypoxic zones appear inside the artery walls at locations where atherosclerotic lesions are prone to develop.

Box-modeling of bone and tooth phosphate oxygen isotope compositions as a function of environmental and physiological parameters.

PubMed

Langlois, C; Simon, L; Lécuyer, Ch

2003-12-01

A time-dependent box model is developed to calculate oxygen isotope compositions of bone phosphate as a function of environmental and physiological parameters. Input and output oxygen fluxes related to body water and bone reservoirs are scaled to the body mass. The oxygen fluxes are evaluated by stoichiometric scaling to the calcium accretion and resorption rates, assuming a pure hydroxylapatite composition for the bone and tooth mineral. The model shows how the diet composition, body mass, ambient relative humidity and temperature may control the oxygen isotope composition of bone phosphate. The model also computes how bones and teeth record short-term variations in relative humidity, air temperature and delta18O of drinking water, depending on body mass. The documented diversity of oxygen isotope fractionation equations for vertebrates is accounted for by our model when for each specimen the physiological and diet parameters are adjusted in the living range of environmental conditions.

Temperature and oxygenation during organ preservation: friends or foes?

PubMed

Gilbo, Nicholas; Monbaliu, Diethard

2017-06-01

The liberalization of donor selection criteria in organ transplantation, with the increased use of suboptimal grafts, has stimulated interest in ischemia-reperfusion injury prevention and graft reconditioning. Organ preservation technologies are changing considerably, mostly through the reintroduction of dynamic machine preservation. Here, we review the current evidence on the role of temperature and oxygenation during dynamic machine preservation. A large but complex body of evidence exists and comparative studies are few. Oxygenation seems to support an advantageous effect in hypothermic machine preservation and is mandatory in normothermic machine preservation, although in the latter, supraphysiological oxygen tensions should be avoided. High-risk grafts, such as suboptimal organs, may optimally benefit from oxygenated perfusion conditions that support metabolism and activate mechanisms of repair such as subnormothermic machine preservation, controlled oxygenated rewarming, and normothermic machine preservation. For lower risk grafts, oxygenation during hypothermic machine preservation may sufficiently reduce injuries and recharge the cellular energy to secure functional recovery after transplantation. The relationship between temperature and oxygenation in organ preservation is more complex than physiological laws would suggest. Rather than one default perfusion temperature/oxygenation standard, perfusion protocols should be tailored for specific needs of grafts of different quality.

Development of sensors for monitoring oxygen and free radicals in plant physiology

NASA Astrophysics Data System (ADS)

Chaturvedi, Prachee

Oxygen plays a critical role in the physiology of photosynthetic organisms, including bioenergetics, metabolism, development, and stress response. Oxygen levels affect photosynthesis, respiration, and alternative oxidase pathways. Likewise, the metabolic rate of spatially distinct plant cells (and therefore oxygen flux) is known to be affected by biotic stress (e.g., herbivory) and environmental stress (e.g., salt/nutrient stress). During aerobic metabolism, cells produce reactive oxygen species (ROS) as a by product. Plants also produce ROS during adaptation to stress (e.g., abscisic acid (ABA) mediated stress responses). If stress conditions are prolonged, ROS levels surpass the capacity of detoxifying mechanisms within the cell, resulting in oxidative damage. While stress response pathways such as ABA-mediated mechanisms have been well characterized (e.g., water stress, inhibited shoot growth, synthesis of storage proteins in seeds), the connection between ROS production, oxygen metabolism and stress response remains unknown. In part, this is because details of oxygen transport at the interface of cell(s) and the surrounding microenvironment remains nebulous. The overall goal of this research was to develop oxygen and Free radical sensors for studying stress signaling in plants. Recent developments in nanomaterials and data acquisition systems were integrated to develop real-time, non-invasive oxygen and Free radical sensors. The availability of these sensors for plant physiologists is an exciting opportunity to probe the functional realm of cells and tissues in ways that were not previously possible.

Developing a Customized Perfusion Bioreactor Prototype with Controlled Positional Variability in Oxygen Partial Pressure for Bone and Cartilage Tissue Engineering.

PubMed

Lee, Poh Soo; Eckert, Hagen; Hess, Ricarda; Gelinsky, Michael; Rancourt, Derrick; Krawetz, Roman; Cuniberti, Gianaurelio; Scharnweber, Dieter

2017-05-01

Skeletal development is a multistep process that involves the complex interplay of multiple cell types at different stages of development. Besides biochemical and physical cues, oxygen tension also plays a pivotal role in influencing cell fate during skeletal development. At physiological conditions, bone cells generally reside in a relatively oxygenated environment whereas chondrocytes reside in a hypoxic environment. However, it is technically challenging to achieve such defined, yet diverse oxygen distribution on traditional in vitro cultivation platforms. Instead, engineered osteochondral constructs are commonly cultivated in a homogeneous, stable environment. In this study, we describe a customized perfusion bioreactor having stable positional variability in oxygen tension at defined regions. Further, engineered collagen constructs were coaxed into adopting the shape and dimensions of defined cultivation platforms that were precasted in 1.5% agarose bedding. After cultivating murine embryonic stem cells that were embedded in collagen constructs for 50 days, mineralized constructs of specific dimensions and a stable structural integrity were achieved. The end-products, specifically constructs cultivated without chondroitin sulfate A (CSA), showed a significant increase in mechanical stiffness compared with their initial gel-like constructs. More importantly, the localization of osteochondral cell types was specific and corresponded to the oxygen tension gradient generated in the bioreactor. In addition, CSA in complementary with low oxygen tension was also found to be a potent inducer of chondrogenesis in this system. In summary, we have demonstrated a customized perfusion bioreactor prototype that is capable of generating a more dynamic, yet specific cultivation environment that could support propagation of multiple osteochondral lineages within a single engineered construct in vitro. Our system opens up new possibilities for in vitro research on human

Localized increase of tissue oxygen tension by magnetic targeted drug delivery

NASA Astrophysics Data System (ADS)

Liong, Celine; Ortiz, Daniel; Ao-ieong, Eilleen; Navati, Mahantesh S.; Friedman, Joel M.; Cabrales, Pedro

2014-07-01

Hypoxia is the major hindrance to successful radiation therapy of tumors. Attempts to increase the oxygen (O2) tension (PO2) of tissue by delivering more O2 have been clinically disappointing, largely due to the way O2 is transported and released by the hemoglobin (Hb) within the red blood cells (RBCs). Systemic manipulation of O2 transport increases vascular resistance due to metabolic autoregulation of blood flow to prevent over oxygenation. This study investigates a new technology to increase O2 delivery to a target tissue by decreasing the Hb-O2 affinity of the blood circulating within the targeted tissue. As the Hb-O2 affinity decreases, the tissue PO2 to satisfy tissue O2 metabolic needs increases without increasing O2 delivery or extraction. Paramagnetic nanoparticles (PMNPs), synthetized using gadolinium oxide, were coated with the cell permeable Hb allosteric effector L35 (3,5-trichlorophenylureido-phenoxy-methylpropionic acid). L35 decreases Hb affinity for O2 and favors the release of O2. The L35-coated PMNPs (L35-PMNPs) were intravenously infused (10 mg kg-1) to hamsters instrumented with the dorsal window chamber model. A magnetic field of 3 mT was applied to localize the effects of the L35-PMNPs to the window chamber. Systemic O2 transport characteristics and microvascular tissue oxygenation were measured after administration of L35-PMNPs with and without magnetic field. The tissue PO2 in untreated control animals was 25.2 mmHg. L35-PMNPs without magnetic field decreased tissue PO2 to 23.4 mmHg, increased blood pressure, and reduced blood flow, largely due to systemic modification of Hb-O2 affinity. L35-PMNPs with magnetic field increased tissue PO2 to 27.9 mmHg, without systemic or microhemodynamic changes. These results indicate that localized modification of Hb-O2 affinity can increase PO2 of target tissue without affecting systemic O2 delivery or triggering O2 autoregulation mechanisms. This technology can be used to treat local hypoxia and to

Modeling spatial distribution of oxygen in 3d culture of islet beta-cells.

PubMed

McReynolds, John; Wen, Yu; Li, Xiaofei; Guan, Jianjun; Jin, Sha

2017-01-01

Three-dimensional (3D) scaffold culture of pancreatic β-cell has been proven to be able to better mimic physiological conditions in the body. However, one critical issue with culturing pancreatic β-cells is that β-cells consume large amounts of oxygen, and hence insufficient oxygen supply in the culture leads to loss of β-cell mass and functions. This becomes more significant when cells are cultured in a 3D scaffold. In this study, in order to understand the effect of oxygen tension inside a cell-laden collagen culture on β-cell proliferation, a culture model with encapsulation of an oxygen-generator was established. The oxygen-generator was made by embedding hydrogen peroxide into nontoxic polydimethylsiloxane to avoid the toxicity of a chemical reaction in the β-cell culture. To examine the effectiveness of the oxygenation enabled 3D culture, the spatial-temporal distribution of oxygen tension inside a scaffold was evaluated by a mathematical modeling approach. Our simulation results indicated that an oxygenation-aided 3D culture would augment the oxygen supply required for the β-cells. Furthermore, we identified that cell seeding density and the capacity of the oxygenator are two critical parameters in the optimization of the culture. Notably, cell-laden scaffold cultures with an in situ oxygen supply significantly improved the β-cells' biological function. These β-cells possess high insulin secretion capacity. The results obtained in this work would provide valuable information for optimizing and encouraging functional β-cell cultures. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:221-228, 2017. © 2016 American Institute of Chemical Engineers.

Quasi-continuous parallel online scattered light, fluorescence and dissolved oxygen tension measurement combined with monitoring of the oxygen transfer rate in each well of a shaken microtiter plate.

PubMed

Ladner, Tobias; Held, Markus; Flitsch, David; Beckers, Mario; Büchs, Jochen

2016-12-03

Microtiter plates (MTP) are often applied as culture vessels in high-throughput screening programs. If online measuring techniques are available, MTPs can also be applied in the first steps of process development. For such small-scale bioreactors dipping probes are usually too large; therefore, optical measurements are often used. For example, the BioLector technology allows for the online monitoring of scattered light and fluorescence in each well of a continuously orbitally shaken MTP. Although this system provides valuable data, these measurements are mainly of a semi-quantitative nature. Therefore, signal calibration is required to obtain absolute values. With the µRAMOS technology it became possible for the first time to quantify the oxygen transfer rate (OTR) separately in each well of an MTP. In this work, a device is presented that combines both techniques, to provide a hitherto unparalleled high amount of information from each single well. Because both systems (BioLector and µRAMOS) are based on optical measurements, the measurements need to be synchronized to avoid interferences with the optical signals. The new experimental setup was applied for online monitoring in cultures of Escherichia coli and Hansenula polymorpha. It has been demonstrated that the well-to-well reproducibility is very high, and that the monitored signals provide reliable and valuable information about the process. With varying filling volumes, different maximum oxygen transfer capacities (OTR max ) were adjusted in oxygen-limited cultures. The different degrees of stress during the culture due to oxygen limitation affected microbial growth and also impacted reproducibility from culture to culture. Furthermore, it was demonstrated that this new device significantly simplifies the experimental efforts: instead of parallel cultures in a shake flask and MTP, just one single experiment in MTP needs to be conducted to measure the OTR, dissolved oxygen tension (DOT), scattered light and

Air-breathing fishes in aquaculture. What can we learn from physiology?

PubMed

Lefevre, S; Wang, T; Jensen, A; Cong, N V; Huong, D T T; Phuong, N T; Bayley, M

2014-03-01

During the past decade, the culture of air-breathing fish species has increased dramatically and is now a significant global source of protein for human consumption. This development has generated a need for specific information on how to maximize growth and minimize the environmental effect of culture systems. Here, the existing data on metabolism in air-breathing fishes are reviewed, with the aim of shedding new light on the oxygen requirements of air-breathing fishes in aquaculture, reaching the conclusion that aquatic oxygenation is much more important than previously assumed. In addition, the possible effects on growth of the recurrent exposure to deep hypoxia and associated elevated concentrations of carbon dioxide, ammonia and nitrite, that occurs in the culture ponds used for air-breathing fishes, are discussed. Where data on air-breathing fishes are simply lacking, data for a few water-breathing species will be reviewed, to put the physiological effects into a growth perspective. It is argued that an understanding of air-breathing fishes' respiratory physiology, including metabolic rate, partitioning of oxygen uptake from air and water in facultative air breathers, the critical oxygen tension, can provide important input for the optimization of culture practices. Given the growing importance of air breathers in aquaculture production, there is an urgent need for further data on these issues. © 2014 The Fisheries Society of the British Isles.

Prostaglandins, oxygen tension and smooth muscle tone

PubMed Central

Eckenfels, A.; Vane, J. R.

1972-01-01

1. By using indomethacin to inhibit their intramural synthesis, we have investigated the contribution of prostaglandins to the maintenance of (a) the intrinsic tone of isolated smooth muscle preparations and (b) contractions produced by drugs or high oxygen concentration. 2. When treated with indomethacin, the rat stomach strip and chick rectum preparation slowly relaxed, whether they were bathed in Krebs solution or blood. Although their sensitivity to added prostaglandin was somewhat enhanced, they became insensitive to changes in oxygen or glucose concentration. However, another smooth muscle preparation, the rat colon, was neither relaxed by indomethacin nor contracted by high oxygen concentration. 3. These results support the hypothesis that intramural generation of prostaglandin maintains the tone of some smooth muscle preparations. 4. Contractions of the guinea-pig isolated colon were induced by histamine. These contractions were normally well maintained but in Krebs solution lacking either oxygen or glucose, only the initial spike contraction remained. In the presence of indomethacin the histamine contraction was also poorly sustained, but maintenance was restored by a low concentration of prostaglandin E2. 5. Thus, the effects on smooth muscle of oxygen or glucose lack may also be mediated by reduction in the synthesis or effects of an intramural prostaglandin. Extension of this hypothesis to intestinal and vascular smooth muscle in vivo is discussed. PMID:5072227

Estimation of changes in alveolar-arterial oxygen gradient induced by hypoxia.

PubMed

Hoffstein, V; Duguid, N; Zamel, N; Rebuck, A S

1984-11-01

The alveolar-arterial oxygen tension difference provides a useful clinical indication of ventilation-blood flow mismatching in the lungs. In some clinical situations involving alveolar hypoxia (e.g., patients with chronic obstructive lung disease flying in commercial aircraft or normal humans at high altitudes) it would be useful to know this tension difference to predict the likely arterial PO2 under such potentially stressful conditions. Such estimates would require multiple arterial punctures performed under a variety of trying circumstances, conditions usually far distant from a suitable analytic facility. Consequently, we induced controlled hypoxia in 23 healthy humans and calculated changes in the alveolar-arterial oxygen tension difference during the hypoxic challenge test. We plotted this difference as a function of the alveolar oxygen tension over a range from 35 to 110 mm Hg. In addition to a series of control studies in which multiple arterial blood samples were obtained, we calculated arterial PO2 by converting the arterial oxyhemoglobin saturation (measured with an ear oximeter) into partial pressure of oxygen. During hypoxic procedures in which levels of oxygenation fell on the steep section of the oxyhemoglobin dissociation curve, fixing PCO2 at constant predetermined levels allowed accurate predictions of arterial PO2. We were able to demonstrate that the alveolar-arterial oxygen tension difference narrowed with decreasing alveolar oxygen tension, and that measurement with an ear oximeter provided data that allowed a reasonable estimate of the tension difference during hypoxic conditions.

The Oxygen Dissociation Curve of Hemoglobin: Bridging the Gap between Biochemistry and Physiology

NASA Astrophysics Data System (ADS)

Gómez-Cambronero, Julian

2001-06-01

Cooperativity is a very difficult concept for biochemistry students in the health sciences. An analogy between breaking salt bonds and tearing apart a block of four stamps has been proposed for hemoglobin (Hb). However, since tearing is equated to binding of molecules, two intrinsically contradictory terms, students still have difficulty. I apply the pictorial analogy to the releasing of oxygen instead of the binding, thus bridging biochemistry (cooperativity) with physiology (oxygen dissociation). I embark on an imaginary journey from the lungs (saturation at 100 mmHg) to the oxygen-starved tissues. The stamps represent fully loaded Hb. By making two cuts the first "oxygen" is released. For the second, only one cut is needed. With one final cut, the last two stamps are separated. This means that less energy is needed to unload oxygen: just small drops in partial pressure do the trick in the right place (tissues) but not in the wrong one (lungs). In doing this, I use the three main models of learning: association, discovery and mentoring. Additionally, by guiding students to discover the truth by themselves, I can use hemoglobin as a wonderful excuse to apply the "Socratic method" in the classroom.

Physiology, intervention, and outcome: three critical questions about cerebral tissue oxygen saturation monitoring.

PubMed

Meng, Lingzhong; Gruenbaum, Shaun E; Dai, Feng; Wang, Tianlong

2018-05-01

The balance between cerebral tissue oxygen consumption and supply can be continuously assessed by cerebral tissue oxygen saturation (SctO2) monitor. A construct consisting of three sequential questions, targeting the physiology monitored, the intervention implemented, and the outcomes affected, is proposed to critically appraise this monitor. The impact of the SctO2-guided care on patient outcome was examined through a systematic literature search and meta-analysis. We concluded that the physiology monitored by SctO2 is robust and dynamic, fragile (prone to derangement), and adversely consequential when deranged. The inter-individual variability of SctO2 measurement advocates for an intervention threshold based on a relative, not absolute, change. The intra-individual variability has multiple determinants which is the foundation of intervention. A variety of therapeutic options are available; however, none are 100% efficacious in treating cerebral dys-oxygenation. The therapeutic efficacy likely depends on both an appropriate differential diagnosis and the functional status of the regulatory mechanisms of cerebral blood flow. Meta-analysis based on five randomized controlled trials suggested a reduced incidence of early postoperative cognitive decline after major surgeries (RR= 0.53; 95% CI: 0.33-0.87; I2 =82%; P=0.01). However, its effects on other neurocognitive outcomes remain unclear. These results need to be interpreted with caution due to the high risks of bias. Quality RCTs based on improved intervention protocols and standardized outcome assessment are warranted in the future.

Augmented Oxygen-Dependent Killing of Leishmania.

DTIC Science & Technology

1992-06-30

reduction-oxidation cycling drugs: amphotericin B, menadione , and phenazine methosulfate. Promastigotes were exposed to the above drugs under...P02 = 2]..1 kPa) or hyperoxic conditions(P02 - 91.7 kPa). High oxygen tensions did not alter the lethal effects of either menadione or phenazine...effects of high oxygen tensions on the lethal effects of three reduction-oxidation cycling drugs: amphotericin B, menadione , and phenazine

Oxygen tension regulates the miRNA profile and bioactivity of exosomes released from extravillous trophoblast cells – Liquid biopsies for monitoring complications of pregnancy

PubMed Central

Truong, Grace; Guanzon, Dominic; Kinhal, Vyjayanthi; Elfeky, Omar; Lai, Andrew; Longo, Sherri; Nuzhat, Zarin; Palma, Carlos; Scholz-Romero, Katherin; Menon, Ramkumar; Mol, Ben W.; Rice, Gregory E.; Salomon, Carlos

2017-01-01

Our understanding of how cells communicate has undergone a paradigm shift since the recent recognition of the role of exosomes in intercellular signaling. In this study, we investigated whether oxygen tension alters the exosome release and miRNA profile from extravillous trophoblast (EVT) cells, modifying their bioactivity on endothelial cells (EC). Furthermore, we have established the exosomal miRNA profile at early gestation in women who develop pre-eclampsia (PE) and spontaneous preterm birth (SPTB). HTR-8/SVneo cells were used as an EVT model. The effect of oxygen tension (i.e. 8% and 1% oxygen) on exosome release was quantified using nanocrystals (Qdot®) coupled to CD63 by fluorescence NTA. A real-time, live-cell imaging system (Incucyte™) was used to establish the effect of exosomes on EC. Plasma samples were obtained at early gestation (<18 weeks) and classified according to pregnancy outcomes. An Illumina TrueSeq Small RNA kit was used to construct a small RNA library from exosomal RNA obtained from EVT and plasma samples. The number of exosomes was significantly higher in EVT cultured under 1% compared to 8% oxygen. In total, 741 miRNA were identified in exosomes from EVT. Bioinformatic analysis revealed that these miRNA were associated with cell migration and cytokine production. Interestingly, exosomes isolated from EVT cultured at 8% oxygen increased EC migration, whilst exosomes cultured at 1% oxygen decreased EC migration. These changes were inversely proportional to TNF-α released from EC. Finally, we have identified a set of unique miRNAs in exosomes from EVT cultured at 1% oxygen and exosomes isolated from the circulation of mothers at early gestation, who later developed PE and SPTB. We suggest that aberrant exosomal signalling by placental cells is a common aetiological factor in pregnancy complications characterised by incomplete SpA remodeling and is therefore a clinically relevant biomarker of pregnancy complications. PMID:28350871

Oxygen uptake in Pacific salmon Oncorhynchus spp.: when ecology and physiology meet.

PubMed

Eliason, E J; Farrell, A P

2016-01-01

Over the past several decades, a substantial amount of research has examined how cardiorespiratory physiology supports the diverse activities performed throughout the life cycle of Pacific salmon, genus Oncorhynchus. Pioneering experiments emphasized the importance of aerobic scope in setting the functional thermal tolerance for activity in fishes. Variation in routine metabolism can have important performance and fitness consequences as it is related to dominance, aggression, boldness, territoriality, growth rate, postprandial oxygen consumption, life history, season, time of day, availability of shelter and social interactions. Wild fishes must perform many activities simultaneously (e.g. swim, obtain prey, avoid predators, compete, digest and reproduce) and oxygen delivery is allocated among competing organ systems according to the capacity of the heart to deliver blood. For example, salmonids that are simultaneously swimming and digesting trade-off maximum swimming performance in order to support the oxygen demands of digestion. As adult Pacific salmonids cease feeding in the ocean prior to their home migration, endogenous energy reserves and cardiac capacity are primarily partitioned among the demands for swimming upriver, sexual maturation and spawning behaviours. Furthermore, the upriver spawning migration is under strong selection pressure, given that Pacific salmonids are semelparous (single opportunity to spawn). Consequently, these fishes optimize energy expenditures in a number of ways: strong homing, precise migration timing, choosing forward-assist current paths and exploiting the boundary layer to avoid the strong currents in the middle of the river, using energetically efficient swimming speeds, and recovering rapidly from anaerobic swimming. Upon arrival at the spawning ground, remaining energy can be strategically allocated to the various spawning behaviours. Strong fidelity to natal streams has resulted in reproductively isolated populations that

Application of Oxygen-Enriched Aeration in the Production of Bacitracin by Bacillus licheniformis

PubMed Central

Flickinger, M. C.; Perlman, D.

1979-01-01

The physiological effects of controlling the dissolved oxygen tension at 0.01, 0.02, and 0.05 atm by the use of oxygen-enriched aeration were investigated during growth and bacitracin production by Bacillus licheniformis ATCC 10716. Up to a 2.35-fold increase in the final antibiotic yield and a 4-fold increase in the rate of bacitracin synthesis were observed in response to O2-enriched aeration. The increase in antibiotic production was accompanied by increased respiratory activity and an increase in the specific productivity of the culture from 1.3 to 3.6 g of antibiotic per g of cell mass produced. Oxygen enrichment of the aeration decreased medium carbohydrate uptake and the maximum specific growth rate of B. licheniformis from 0.6 h−1 to as low as 0.15 h−1, depending upon the level of enrichment and the conditions of oxygen transfer rate (impeller speed). The response of this culture to O2 enrichment suggests that this method of controlling the dissolved oxygen tension for antibiotic-producing cultures may simulate conditions that would occur if the carbon source were fed slowly, as is often employed to optimize antibiotic production. Analysis of the biologically active bacitracins produced by B. licheniformis ATCC 10716 suggested that the ratio of biologically active peptides was not changed by O2 enrichment, nor were any new biologically active compounds formed. Images PMID:34361

Numerical simulation of oxygen delivery to muscle tissue in the presence of hemoglobin-based oxygen carriers.

PubMed

Patton, Jaqunda N; Palmer, Andre F

2006-01-01

This work represents a culmination of research on oxygen transport to muscle tissue, which takes into account oxygen transport due to convection, diffusion, and the kinetics of simultaneous reactions between oxygen and hemoglobin and myoglobin. The effect of adding hemoglobin-based oxygen carriers (HBOCs) to the plasma layer of blood in a single capillary surrounded by muscle tissue based on the geometry of the Krogh tissue cylinder is examined for a range of HBOC oxygen affinity, HBOC concentration, capillary inlet oxygen tension (pO(2)), and hematocrit. The full capillary length of the hamster retractor muscle was modeled under resting (V(max) = 1.57 x 10(-4) mLO(2) mL(-1) s(-1), cell velocity (v(c)) = 0.015 cm/s) and working (V(max) = 1.57 x 10(-3) mLO(2) mL(-1) s(-1), v(c) = 0.075 cm/s) conditions. Two spacings between the red blood cell (RBC) and the capillary wall were examined, corresponding to a capillary with and without an endothelial surface layer. Simulations led to the following conclusions, which lend physiological insight into oxygen transport to muscle tissue in the presence of HBOCs: (1) The reaction kinetics between oxygen and myoglobin in the tissue region, oxygen and HBOCs in the plasma, and oxygen and RBCs in the capillary lumen should not be neglected. (2) Simulation results yielded new insight into possible mechanisms of oxygen transport in the presence of HBOCs. (3) HBOCs may act as a source or sink for oxygen in the capillary and may compete with RBCs for oxygen. (4) HBOCs return oxygen delivery to muscle tissue to normal for varying degrees of hypoxia (inlet capillary pO(2) < 30 mmHg) and anemia (hematocrit < 46%) for the hamster model.

Membrane culture and reduced oxygen tension enhances cartilage matrix formation from equine cord blood mesenchymal stromal cells in vitro.

PubMed

Co, C; Vickaryous, M K; Koch, T G

2014-03-01

Ongoing research is aimed at increasing cartilage tissue yield and quality from multipotent mesenchymal stromal cells (MSC) for the purpose of treating cartilage damage in horses. Low oxygen culture has been shown to enhance chondrogenesis, and novel membrane culture has been proposed to increase tissue yield and homogeneity. The objective of this study was to evaluate and compare the effect of reduced oxygen and membrane culture during in vitro chondrogenesis of equine cord blood (CB) MSC. CB-MSC (n = 5 foals) were expanded at 21% oxygen prior to 3-week differentiation in membrane or pellet culture at 5% and 21% oxygen. Assessment included histological examination (H&E, toluidine Blue, immunohistochemistry (IHC) for collagen type I and II), protein quantification by hydroxyproline assay and dimethylmethylene assay, and mRNA analysis for collagen IA1, collagen IIA1, collagen XA1, HIF1α and Sox9. Among treatment groups, 5% membrane culture produced neocartilage most closely resembling hyaline cartilage. Membrane culture resulted in increased wet mass, homogenous matrix morphology and an increase in total collagen content, while 5% oxygen culture resulted in higher GAG and type II collagen content. No significant differences were observed for mRNA analysis. Membrane culture at 5% oxygen produces a comparatively larger amount of higher quality neocartilage. Matrix homogeneity is attributed to a uniform diffusion gradient and reduced surface tension. Membrane culture holds promise for scale-up for therapeutic purposes, for cellular preconditioning prior to cytotherapeutic applications, and for modeling system for gas-dependent chondrogenic differentiation studies. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Cyclic mechanical loading enables solute transport and oxygen supply in bone healing: an in vitro investigation.

PubMed

Witt, Florian; Duda, Georg N; Bergmann, Camilla; Petersen, Ansgar

2014-02-01

Bone healing is a complex process with an increased metabolic activity and consequently high demand for oxygen. In the hematoma phase, inflammatory cells and mesenchymal stromal cells (MSCs) are initially cut off from direct nutritional supply via blood vessels. Cyclic mechanical loading that occurs, for example, during walking is expected to have an impact on the biophysical environment of the cells but meaningful quantitative experimental data are still missing. In this study, the hypothesis that cyclic mechanical loading within a physiological range significantly contributes to oxygen transport into the fracture hematoma was investigated by an in vitro approach. MSCs were embedded in a fibrin matrix to mimic the hematoma phase during bone healing. Construct geometry, culture conditions, and parameters of mechanical loading in a bioreactor system were chosen to resemble the in vivo situation based on data from human studies and a well-characterized large animal model. Oxygen tension was measured before and after mechanical loading intervals by a chemical optical microsensor. The increase in oxygen tension at the center of the constructs was significant and depended on loading time with maximal values of 9.9%±5.1%, 14.8%±4.9%, and 25.3%±7.2% of normal atmospheric oxygen tension for 5, 15, and 30 min of cyclic loading respectively. Histological staining of hypoxic cells after 48 h of incubation confirmed sensor measurements by showing an increased number of normoxic cells with intermittent cyclic compression compared with unloaded controls. The present study demonstrates that moderate cyclic mechanical loading leads to an increased oxygen transport and thus to substantially enhanced supply conditions for cells entrapped in the hematoma. This link between mechanical conditions and nutrition supply in the early regenerative phases could be employed to improve the environmental conditions for cell metabolism and consequently prevent necrosis.

Differential responses of choroidal melanocytes and uveal melanoma cells to low oxygen conditions

PubMed Central

Weidmann, Cindy; Pomerleau, Jade; Trudel-Vandal, Laurence

2017-01-01

Purpose Tissue culture is traditionally performed at atmospheric oxygen concentration (21%), which induces hyperoxic stress, as endogenous physiologic oxygen tension found in tissues varies between 2% and 9%. This discrepancy may lead to misinterpretation of results and may explain why effects observed in vitro cannot always be reproduced in vivo and vice versa. Only a few studies have been conducted in low physiologic oxygen conditions to understand the development and differentiation of cells from the eye. Methods The aim of this study was to investigate the growth and gene expression profile of melanocytes from the choroid permanently exposed to 21% (hyperoxic) or 3% (physiologic) oxygen with proliferation assays and DNA microarray. The cellular behavior of the melanocytes was then compared to that of cancer cells. Results The gross morphology and melanin content of choroidal melanocytes changed slightly when they were exposed to 3% O2, and the doubling time was statistically significantly faster. There was an increase in the percentage of choroidal melanocytes in the active phases of the cell cycle as observed by using the proliferation marker Ki67. The caveolin-1 senescence marker was not increased in choroidal melanocytes or uveal melanoma cells grown in hyperoxia. In comparison, the morphology of the uveal melanoma cells was similar between the two oxygen levels, and the doubling time was slower at 3% O2. Surprisingly, gene expression profiling of the choroidal melanocytes did not reveal a large list of transcripts considerably dysregulated between the two oxygen concentrations; only the lactate transporter monocarboxylate transporter (MCT4) was statistically significantly upregulated at 3% O2. Conclusions This study showed that the oxygen concentration must be tightly controlled in experimental settings, because it influences the subsequent cellular behavior of human choroidal melanocytes. PMID:28356703

AUTOGENIC THERAPY IN TENSION HEADACHE

PubMed Central

Amruthraj, Brunda; Mishra, H.; Kumaraiah, V.

1987-01-01

SUMMARY Ten subjects diagnosed as Psychalgia were taken for study. A multiple baseline design was adapted and clients were subjected to 30 sessions of autogenic training. They were assessed using physiological (EMG and thermal change) and behavioural measures (Visual analogue scale and behavioural symptom checklist). Findings revealed autogenic therapy to be effective in reducing tension headache. PMID:21927245

Effect of aerobic fitness on the physiological stress responses at work.

PubMed

Ritvanen, Tiina; Louhevaara, Veikko; Helin, Pertti; Halonen, Toivo; Hänninen, Osmo

2007-01-01

The aim of the present study was to examine the effects of aerobic fitness on physiological stress responses experienced by teachers during working hours. Twenty-six healthy female and male teachers aged 33-62 years participated in the study. The ratings of perceived stress visual analogue scale (VAS), and the measurement of physiological responses (norepinephrine, epinephrine, cortisol, diastolic and systolic blood pressure, heart rate (HR), and trapezius muscle activity by electromyography (EMG), were determined. Predicted maximal oxygen uptake (VO(2)max) was measured using the submaximal bicycle ergometer test. The predicted VO(2)max was standardized for age using residuals of linear regression analyses. Static EMG activity, HR and VAS were associated with aerobic fitness in teachers. The results suggest that a higher level of aerobic fitness may reduce muscle tension, HR and perceived work stress in teachers.

Transient changes in oxygen tension inhibit osteogenic differentiation and Runx2 expression in osteoblasts.

PubMed

Salim, Ali; Nacamuli, Randall P; Morgan, Elise F; Giaccia, Amato J; Longaker, Michael T

2004-09-17

Vascular disruption following bony injury results in a hypoxic gradient within the wound microenvironment. Nevertheless, the effects of low oxygen tension on osteogenic precursors remain to be fully elucidated. In the present study, we investigated in vitro osteoblast and mesenchymal stem cell differentiation following exposure to 21% O(2) (ambient oxygen), 2% O(2) (hypoxia), and <0.02% O(2) (anoxia). Hypoxia had little effect on osteogenic differentiation. In contrast, short-term anoxic treatment of primary osteoblasts and mesenchymal precursors inhibited in vitro bone nodule formation and extracellular calcium deposition. Cell viability assays revealed that this effect was not caused by immediate or delayed cell death. Microarray profiling implicated down-regulation of the key osteogenic transcription factor Runx2 as a potential mechanism for the anoxic inhibition of differentiation. Subsequent analysis revealed not only a short-term differential regulation of Runx2 and its targets by anoxia and hypoxia, but a long-term inhibition of Runx2 transcriptional and protein levels after only 12-24 h of anoxic insult. Furthermore, we present evidence that Runx2 inhibition may, at least in part, be because of anoxic repression of BMP2, and that restoring Runx2 levels during anoxia by pretreatment with recombinant BMP2 rescued the anoxic inhibition of differentiation. Taken together, our findings indicate that brief exposure to anoxia (but not 2% hypoxia) down-regulated BMP2 and Runx2 expression, thus inhibiting critical steps in the osteogenic differentiation of pluripotent mesenchymal precursors and committed osteoblasts.

Exercise capacity in the Bidirectional Glenn physiology: Coupling cardiac index, ventricular function and oxygen extraction ratio.

PubMed

Vallecilla, Carolina; Khiabani, Reza H; Trusty, Phillip; Sandoval, Néstor; Fogel, Mark; Briceño, Juan Carlos; Yoganathan, Ajit P

2015-07-16

In Bi-directional Glenn (BDG) physiology, the superior systemic circulation and pulmonary circulation are in series. Consequently, only blood from the superior vena cava is oxygenated in the lungs. Oxygenated blood then travels to the ventricle where it is mixed with blood returning from the lower body. Therefore, incremental changes in oxygen extraction ratio (OER) could compromise exercise tolerance. In this study, the effect of exercise on the hemodynamic and ventricular performance of BDG physiology was investigated using clinical patient data as inputs for a lumped parameter model coupled with oxygenation equations. Changes in cardiac index, Qp/Qs, systemic pressure, oxygen extraction ratio and ventricular/vascular coupling ratio were calculated for three different exercise levels. The patient cohort (n=29) was sub-grouped by age and pulmonary vascular resistance (PVR) at rest. It was observed that the changes in exercise tolerance are significant in both comparisons, but most significant when sub-grouped by PVR at rest. Results showed that patients over 2 years old with high PVR are above or close to the upper tolerable limit of OER (0.32) at baseline. Patients with high PVR at rest had very poor exercise tolerance while patients with low PVR at rest could tolerate low exercise conditions. In general, ventricular function of SV patients is too poor to increase CI and fulfill exercise requirements. The presented mathematical model provides a framework to estimate the hemodynamic performance of BDG patients at different exercise levels according to patient specific data. Published by Elsevier Ltd.

Community-level physiological profiling performed with an oxygen-sensitive fluorophore in a microtiter plate

NASA Technical Reports Server (NTRS)

Garland, Jay L.; Roberts, Michael S.; Levine, Lanfang H.; Mills, Aaron L.

2003-01-01

Community-level physiological profiling based upon fluorometric detection of oxygen consumption was performed on hydroponic rhizosphere and salt marsh litter samples by using substrate levels as low as 50 ppm with incubation times between 5 and 24 h. The rate and extent of response were increased in samples acclimated to specific substrates and were reduced by limiting nitrogen availability in the wells.

Preflight studies on tolerance of pocket mice to oxygen and heat. I - Physiological studies

NASA Technical Reports Server (NTRS)

Leon, H. A.; Suri, K.; Mctigue, M.; Smith, J.; Cooper, W.; Miquel, J.; Ashley, W. W.; Behnke, A. R., Jr.; Saunders, J. F.

1975-01-01

Tests were carried out on pocket mice to ascertain their tolerance to elevated oxygen pressures alone and to a combination of hyperoxia and heat in excess of that expected during the flight of the mice on Apollo XVII. The mice withstood oxygen partial pressures up to 12 psi at normal room temperature (24 C, 75 F) over a period of 7 days. A few mice previously exposed to increased PO2 died in the course of exposure to an oxygen pressure of 10 psi or 12 psi (517 mm or 620 mm Hg) for 13 d in ambient heat of 32 C (90 F). Supplemental vitamin E and physiological saline loading given prior to exposure had no apparent protective effect. The overall conclusion was that the pocket mice which were to go on Apollo XVII could readily survive the ambient atmosphere to which they would be exposed.

Impact of physiological noise correction on detecting blood oxygenation level-dependent contrast in the breast

NASA Astrophysics Data System (ADS)

Wallace, Tess E.; Manavaki, Roido; Graves, Martin J.; Patterson, Andrew J.; Gilbert, Fiona J.

2017-01-01

Physiological fluctuations are expected to be a dominant source of noise in blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) experiments to assess tumour oxygenation and angiogenesis. This work investigates the impact of various physiological noise regressors: retrospective image correction (RETROICOR), heart rate (HR) and respiratory volume per unit time (RVT), on signal variance and the detection of BOLD contrast in the breast in response to a modulated respiratory stimulus. BOLD MRI was performed at 3 T in ten volunteers at rest and during cycles of oxygen and carbogen gas breathing. RETROICOR was optimized using F-tests to determine which cardiac and respiratory phase terms accounted for a significant amount of signal variance. A nested regression analysis was performed to assess the effect of RETROICOR, HR and RVT on the model fit residuals, temporal signal-to-noise ratio, and BOLD activation parameters. The optimized RETROICOR model accounted for the largest amount of signal variance ( Δ R\\text{adj}2   =  3.3  ±  2.1%) and improved the detection of BOLD activation (P  =  0.002). Inclusion of HR and RVT regressors explained additional signal variance, but had a negative impact on activation parameter estimation (P  <  0.001). Fluctuations in HR and RVT appeared to be correlated with the stimulus and may contribute to apparent BOLD signal reactivity.

Simultaneous Monitoring of Vascular Oxygenation and Tissue Oxygen Tension of Breast Tumors Under Hyperbaric Oxygen Exposure

DTIC Science & Technology

2008-04-01

28. Alagoz, T., R. Buller, B. Anderson, K. Terrell , R...and oxygenation Ann . New Acad. Sci. 838 29–45 Chapman J D, Stobbe C C, Arnfield M R, Santus R, Lee J and McPhee M S 1991 Oxygen dependency of tumor

Aberrant patterns of X chromosome inactivation in a new line of human embryonic stem cells established in physiological oxygen concentrations.

PubMed

de Oliveira Georges, Juliana Andrea; Vergani, Naja; Fonseca, Simone Aparecida Siqueira; Fraga, Ana Maria; de Mello, Joana Carvalho Moreira; Albuquerque, Maria Cecília R Maciel; Fujihara, Litsuko Shimabukuro; Pereira, Lygia Veiga

2014-08-01

One of the differences between murine and human embryonic stem cells (ESCs) is the epigenetic state of the X chromosomes in female lines. Murine ESCs (mESCs) present two transcriptionally active Xs that will undergo the dosage compensation process of XCI upon differentiation, whereas most human ESCs (hESCs) spontaneously inactivate one X while keeping their pluripotency. Whether this reflects differences in embryonic development of mice and humans, or distinct culture requirements for the two kinds of pluripotent cells is not known. Recently it has been shown that hESCs established in physiological oxygen levels are in a stable pre-XCI state equivalent to that of mESCs, suggesting that culture in low oxygen concentration is enough to preserve that epigenetic state of the X chromosomes. Here we describe the establishment of two new lines of hESCs under physiological oxygen level and the characterization of the XCI state in the 46,XX line BR-5. We show that a fraction of undifferentiated cells present XIST RNA accumulation and single H3K27me foci, characteristic of the inactive X. Moreover, analysis of allele specific gene expression suggests that pluripotent BR-5 cells present completely skewed XCI. Our data indicate that physiological levels of oxygen are not sufficient for the stabilization of the pre-XCI state in hESCs.

Oxygen delivery using engineered microparticles

PubMed Central

Seekell, Raymond P.; Lock, Andrew T.; Peng, Yifeng; Cole, Alexis R.; Perry, Dorothy A.; Kheir, John N.; Polizzotti, Brian D.

2016-01-01

A continuous supply of oxygen to tissues is vital to life and interruptions in its delivery are poorly tolerated. The treatment of low-blood oxygen tensions requires restoration of functional airways and lungs. Unfortunately, severe oxygen deprivation carries a high mortality rate and can make otherwise-survivable illnesses unsurvivable. Thus, an effective and rapid treatment for hypoxemia would be revolutionary. The i.v. injection of oxygen bubbles has recently emerged as a potential strategy to rapidly raise arterial oxygen tensions. In this report, we describe the fabrication of a polymer-based intravascular oxygen delivery agent. Polymer hollow microparticles (PHMs) are thin-walled, hollow polymer microcapsules with tunable nanoporous shells. We show that PHMs are easily charged with oxygen gas and that they release their oxygen payload only when exposed to desaturated blood. We demonstrate that oxygen release from PHMs is diffusion-controlled, that they deliver approximately five times more oxygen gas than human red blood cells (per gram), and that they are safe and effective when injected in vivo. Finally, we show that PHMs can be stored at room temperature under dry ambient conditions for at least 2 mo without any effect on particle size distribution or gas carrying capacity. PMID:27791101

High Oxygen Concentrations Adversely Affect the Performance of Pulmonary Surfactant.

PubMed

Smallwood, Craig D; Boloori-Zadeh, Parnian; Silva, Maricris R; Gouldstone, Andrew

2017-08-01

Although effective in the neonatal population, exogenous pulmonary surfactant has not demonstrated a benefit in pediatric and adult subjects with hypoxic lung injury despite a sound physiologic rationale. Importantly, neonatal surfactant replacement therapy is administered in conjunction with low fractional F IO 2 while pediatric/adult therapy is administered with high F IO 2 . We suspected a connection between F IO 2 and surfactant performance. Therefore, we sought to assess a possible mechanism by which the activity of pulmonary surfactant is adversely affected by direct oxygen exposure in in vitro experiments. The mechanical performance of pulmonary surfactant was evaluated using 2 methods. First, Langmuir-Wilhelmy balance was utilized to study the reduction in surface area (δA) of surfactant to achieve a low bound value of surface tension after repeated compression and expansion cycles. Second, dynamic light scattering was utilized to measure the size of pulmonary surfactant particles in aqueous suspension. For both experiments, comparisons were made between surfactant exposed to 21% and 100% oxygen. The δA of surfactant was 21.1 ± 2.0% and 35.8 ± 2.0% during exposure to 21% and 100% oxygen, respectively ( P = .02). Furthermore, dynamic light-scattering experiments revealed a micelle diameter of 336.0 ± 12.5 μm and 280.2 ± 11.0 μm in 21% and 100% oxygen, respectively ( P < .001), corresponding to a ∼16% decrease in micelle diameter following exposure to 100% oxygen. The characteristics of pulmonary surfactant were adversely affected by short-term exposure to oxygen. Specifically, surface tension studies revealed that short-term exposure of surfactant film to high concentrations of oxygen expedited the frangibility of pulmonary surfactant, as shown with the δA. This suggests that reductions in pulmonary compliance and associated adverse effects could begin to take effect in a very short period of time. If these findings can be demonstrated in vivo, a

Case Studies in Physiology: Maximal oxygen consumption and performance in a centenarian cyclist.

PubMed

Billat, Véronique; Dhonneur, Gilles; Mille-Hamard, Laurence; Le Moyec, Laurence; Momken, Iman; Launay, Thierry; Koralsztein, Jean Pierre; Besse, Sophie

2017-03-01

The purpose of this study was to examine the physiological characteristics of an elite centenarian cyclist who, at 101 yr old, established the 1-h cycling record for individuals ≥100 yr old (24.25 km) and to determine the physiological factors associated with his performance improvement 2 yr later at 103 yr old (26.92 km; +11%). Before each record, he performed an incremental test on a cycling ergometer. For 2 yr, he trained 5,000 km/yr with a polarized training that involved cycling 80% of mileage at "light" rate of perceived exertion (RPE) ≤12 and 20% at "hard" RPE ≥15 at a cadence between 50 and 70 rpm. His body weight and lean body mass did not change, while his maximal oxygen consumption (V̇o 2max ) increased (31-35 ml·kg -1 ·min -1 ; +13%). Peak power output increased from 90 to 125 W (+39%), mainly because of increasing the maximal pedaling frequency (69-90 rpm; +30%). Maximal heart rate did not change (134-137 beats/min) in contrast to the maximal ventilation (57-70 l/min, +23%), increasing with both the respiratory frequency (38-41 cycles/min; +8%) and the tidal volume (1.5-1.7 liters; +13%). Respiratory exchange ratio increased (1.03-1.14) to the same extent as tolerance to V̇co 2 In conclusion, it is possible to increase performance and V̇o 2max with polarized training focusing on a high pedaling cadence even after turning 100 yr old. NEW & NOTEWORTHY This study shows, for the first time, that maximal oxygen consumption (+13%) and performance (+11%) can still be increased between 101 and 103 yr old with 2 yr of training and that a centenarian is able, at 103 yr old, to cover 26.9 km/h in 1 h. Copyright © 2017 the American Physiological Society.

The Culture-Repopulating Ability Assays and Incubation in Low Oxygen: A Simple Way to Test Drugs on Leukaemia Stem or Progenitor Cells

PubMed Central

Cipolleschi, Maria Grazia; Rovida, Elisabetta; Sbarba, Persio Dello

2013-01-01

The Culture-Repopulating Ability (CRA) assays is a method to measure in vitro the bone marrow-repopulating potential of haematopoietic cells. The method was developed in our laboratory in the course of studies based on the use of growth factor-supplemented liquid cultures to study haematopoietic stem/progenitor cell resistance to, and selection at, low oxygen tensions in the incubation atmosphere. These studies led us to put forward the first hypothesis of the existence in vivo of haematopoietic stem cell niches where oxygen tension is physiologically lower than in other bone marrow areas. The CRA assays and incubation in low oxygen were later adapted to the study of leukaemias. Stabilized leukaemia cell lines, ensuring genetically homogeneous cells and enhancing repeatability of results, were found nevertheless phenotypically heterogeneous, comprising cell subsets exhibiting functional phenotypes of stem or progenitor cells. These subsets can be assayed separately, provided an experimental system capable to select one from another (such as different criteria for incubation in low oxygen) is established. On this basis, a two-step procedure was designed, including a primary culture of leukaemia cells in low oxygen for different times, where drug treatment is applied, followed by the transfer of residual cell population (CRA assay) to a drug-free secondary culture incubated at standard oxygen tension, where the expansion of population is allowed. The CRA assays, applied to cell lines first and then to primary cells, represent a simple and relatively rapid, yet accurate and reliable, method for the pre-screening of drugs potentially active on leukaemias which in our opinion could be adopted systematically before they are tested in vivo. PMID:23394087

Correlated oxygen-sensing PLIM, cell metabolism FLIM and applications

NASA Astrophysics Data System (ADS)

Rück, A. C.; Kalinina, S.; Schäfer, P.; von Einem, B.; von Arnim, C.

2017-02-01

Correlated imaging of phosphorescence and fluorescence lifetime parameters of metabolic markers is a challenge for direct investigating mechanisms related to cell metabolism and oxygen tension. A large variety of clinical phenotypes is associated with mitochondrial defects accomplished with changes in cell metabolism. In many cases the hypoxic microenvironment of cancer cells shifts metabolism from oxidative phosphorylation (OXPHOS) to anaerobic or aerobic glycolysis, a process known as "Warburg" effect. Also during stem cell differentiation a switch in cell metabolism is observed. Mitochondrial dysfunction associated with hypoxia has been invoked in many complex disorders such as type 2 diabetes, Alzheimeŕs disease, cardiac ischemia/reperfusion injury, tissue inflammation and cancer. Cellular responses to oxygen tension have been studied extensively, optical imaging techniques based on time correlated single photon counting (TCSPC) to detect oxygen concentration and distribution are therefore of prominent interest. Moreover, they offer the possibility by inspecting fluorescence decay characteristics of intrinsic coenzymes to directly image metabolic pathways, whereas oxygen tension can be determined by considering the phosphorescence lifetime of a phosphorescent probe. The combination of both fluorescence lifetime imaging (FLIM) of coenzymes like NAD(P)H and FAD and phosphorescence lifetime (PLIM) of phosphorescent dyes could provide valuable information about correlation of metabolic pathways and oxygen tension.

Oxygen-sensitive potassium channels in chemoreceptor cell physiology: making a virtue of necessity.

PubMed

Gonzalez, Constancio; Vaquero, Luis M; López-López, José Ramón; Pérez-García, M Teresa

2009-10-01

The characterization of the molecular mechanisms involved in low-oxygen chemotransduction has been an active field of research since the first description of an oxygen-sensitive K(+) channel in rabbit carotid body (CB) chemoreceptor cells. As a result, a large number of components of the transduction cascade, from O(2) sensors to O(2)-sensitive ion channels, have been found. Although the endpoints of the process are analogous, the heterogeneity of the elements involved in the different chemoreceptor tissues precludes a unifying theory of hypoxic signaling, and it has been a source of controversy. However, when these molecular constituents of the hypoxic cascade are brought back to their physiological context, it becomes clear that the diversity of mechanisms is necessary to build up an integrated cellular response that demands the concerted action of several O(2) sensors and several effectors.

Nasal high-flow oxygen therapy improves arterial oxygenation during one-lung ventilation in non-intubated thoracoscopic surgery.

PubMed

Wang, Man-Ling; Hung, Ming-Hui; Chen, Jin-Shing; Hsu, Hsao-Hsun; Cheng, Ya-Jung

2018-05-01

Intraoperative hypoxaemia during one-lung ventilation (OLV) remains a major concern in thoracic surgery. Non-intubated video-assisted thoracic surgery (VATS) involves a greater risk of consequent emergent conversion to endotracheal intubation. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) has recently been reported to be beneficial for higher oxygen reserves during difficult intubations and for enhancing postoperative recovery after thoracic surgery. However, the effects of THRIVE on oxygenation and carbon dioxide elimination before and during OLV in non-intubated VATS have not been investigated. Between September 2016 and October 2016, 30 patients underwent non-intubated VATS for lung tumour and were maintained with THRIVE at a flow of 20 l/min. These patients were compared with a historical control group comprising 30 patients who were maintained with oxygen masks at an oxygen flow of 10 l/min using a propensity score matching algorithm between September 2015 and July 2016. The preoperative arterial oxygen tension was significantly higher in patients maintained with THRIVE than it was in patients maintained with oxygen masks (mean 416.0 vs 265.9 mmHg, P < 0.01). During OLV, arterial oxygen tension remained significantly higher in the THRIVE group than in the oxygen mask group (mean 207.0 vs 127.8 mmHg, P = 0.01). The arterial carbon dioxide tension was comparable before and during OLV. The results indicated that THRIVE effectively increases the oxygen reserve both during OLV and after anaesthesia. Furthermore, non-intubated VATS is safer if THRIVE with flow adjustment is incorporated into a minimally invasive surgical approach, although carbon dioxide elimination is not facilitated.

Temperature dependence of surface tension of molten iron under reducing gas atmosphere

NASA Astrophysics Data System (ADS)

Ozawa, S.; Takahashi, S.; Fukuyama, H.; Watanabe, M.

2011-12-01

Surface tension of molten iron was measured under Ar-He-5vol.%H2 gas by oscillating droplet method using electromagnetic levitation furnace in consideration of the temperature dependence of oxygen partial pressure, Po2, of the gas. For comparison, the measurement was carried under Ar-He atmosphere to fix the Po2 of the inlet gas at 10-2Pa. The surface tension was successfully measured over a wide temperature range of about 780K including undercooling condition. When Po2 is fixed at 10-2 Pa, the surface tension increased and then decreased with increasing temperature like a boomerang shape. When the measurement was carried out under the H2-containing gas atmosphere, the temperature dependence of the surface tension shows unique kink at around 1810K instead of liner relationship due to competition between the temperature dependence of the Po2 and that of the equilibrium constant of oxygen adsorption reaction. The relationship between the calculated lnKad with respect to inverse temperature using Szyszkowski model was different between the atmospheric gases.

Modeling tensional homeostasis in multicellular clusters.

PubMed

Tam, Sze Nok; Smith, Michael L; Stamenović, Dimitrije

2017-03-01

Homeostasis of mechanical stress in cells, or tensional homeostasis, is essential for normal physiological function of tissues and organs and is protective against disease progression, including atherosclerosis and cancer. Recent experimental studies have shown that isolated cells are not capable of maintaining tensional homeostasis, whereas multicellular clusters are, with stability increasing with the size of the clusters. Here, we proposed simple mathematical models to interpret experimental results and to obtain insight into factors that determine homeostasis. Multicellular clusters were modeled as one-dimensional arrays of linearly elastic blocks that were either jointed or disjointed. Fluctuating forces that mimicked experimentally measured cell-substrate tractions were obtained from Monte Carlo simulations. These forces were applied to the cluster models, and the corresponding stress field in the cluster was calculated by solving the equilibrium equation. It was found that temporal fluctuations of the cluster stress field became attenuated with increasing cluster size, indicating that the cluster approached tensional homeostasis. These results were consistent with previously reported experimental data. Furthermore, the models revealed that key determinants of tensional homeostasis in multicellular clusters included the cluster size, the distribution of traction forces, and mechanical coupling between adjacent cells. Based on these findings, we concluded that tensional homeostasis was a multicellular phenomenon. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The differential effects of 2% oxygen preconditioning on the subsequent differentiation of mouse and human pluripotent stem cells.

PubMed

Fynes, Kate; Tostoes, Rui; Ruban, Ludmila; Weil, Ben; Mason, Christopher; Veraitch, Farlan S

2014-08-15

A major challenge facing the development of effective cell therapies is the efficient differentiation of pluripotent stem cells (PSCs) into pure populations. Lowering oxygen tension to physiological levels can affect both the expansion and differentiation stages. However, to date, there are no studies investigating the knock-on effect of culturing PSCs under low oxygen conditions on subsequent lineage commitment at ambient oxygen levels. PSCs were passaged three times at 2% O2 before allowing cells to spontaneously differentiate as embryoid bodies (EBs) in high oxygen (20% O2) conditions. Maintenance of mouse PSCs in low oxygen was associated with a significant increase in the expression of early differentiation markers FGF5 and Eomes, while conversely we observed decreased expression of these genes in human PSCs. Low oxygen preconditioning primed mouse PSCs for their subsequent differentiation into mesodermal and endodermal lineages, as confirmed by increased gene expression of Eomes, Goosecoid, Brachyury, AFP, Sox17, FoxA2, and protein expression of Brachyury, Eomes, Sox17, FoxA2, relative to high oxygen cultures. The effects extended to the subsequent formation of more mature mesodermal lineages. We observed significant upregulation of cardiomyocyte marker Nkx2.5, and critically a decrease in the number of contaminant pluripotent cells after 12 days using a directed cardiomyocyte protocol. However, the impact of low oxygen preconditioning was to prime human cells for ectodermal lineage commitment during subsequent EB differentiation, with significant upregulation of Nestin and β3-tubulin. Our research demonstrates the importance of oxygen tension control during cell maintenance on the subsequent differentiation of both mouse and human PSCs, and highlights the differential effects.

Tension bulla: a cause of reversible pulmonary hypertension.

PubMed

Waxman, Michael J; Waxman, Jacob D; Forman, John M

2015-01-01

A tension pneumothorax represents a medical emergency warranting urgent diagnosis and treatment. A rapidly expanding bulla may resemble the same clinical presentation but requires an entirely different treatment. A 53-year-old woman presented with increasing shortness of breath and her physical examination and chest x-ray were interpreted as showing a tension pneumothorax. A chest tube was placed which did not resolve the process. Placement of a second chest tube was likewise unsuccessful. A chest CT was then performed and was interpreted as showing an unresolved tension pneumothorax, despite seemingly adequate placement of the 2 chest tubes. Further review of the CT showed the border of a giant bulla and a tentative diagnosis was made of a rapidly expanding bulla with tension physiology. Echocardiogram revealed significant pulmonary hypertension. The bulla was surgically excised, the patient had marked improvement in her clinical symptoms and signs, and echocardiographic follow-up showed complete resolution of the pulmonary hypertension.

Oxygen and Oxygen Toxicity: The Birth of Concepts

PubMed Central

Zhu, Hong; Traore, Kassim; Santo, Arben; Trush, Michael A.; Li, Y. Robert

2018-01-01

Molecular dioxygen (O2) is an essential element of aerobic life, yet incomplete reduction or excitation of O2 during aerobic metabolisms generates diverse oxygen-containing reactive species, commonly known as reactive oxygen species (ROS). On the one hand, ROS pose a serious threat to aerobic organisms via inducing oxidative damage to cellular constituents. On the other hand, these reactive species, when their generation is under homeostatic control, also play important physiological roles (e.g., constituting an important component of immunity and participating in redox signaling). This article defines oxygen and the key facts about oxygen, and discusses the relationship between oxygen and the emergence of early animals on Earth. The article then describes the discovery of oxygen by three historical figures and examines the birth of the concepts of oxygen toxicity and the underlying free radical mechanisms. The article ends with a brief introduction to the emerging field of ROS-mediated redox signaling and physiological responses. PMID:29707642

Oxygen and differentiation status modulate the effect of X-ray irradiation on physiology and mitochondrial proteome of human neuroblastoma cells.

PubMed

Džinić, Tamara; Hartwig, Sonja; Lehr, Stefan; Dencher, Norbert A

2016-12-01

Cytotoxic effects, including oxidative stress, of low linear energy transfer (LET)-ionizing radiation are often underestimated and studies of their mechanisms using cell culture models are widely conducted with cells cultivated at atmospheric oxygen that does not match its physiological levels in body tissues. Also, cell differentiation status plays a role in the outcome of experiments. We compared effects of 2 Gy X-ray irradiation on the physiology and mitochondrial proteome of nondifferentiated and human neuroblastoma (SH-SY5Y) cells treated with retinoic acid cultivated at 21% and 5% O 2 . Irradiation did not affect the amount of subunits of OxPhos complexes and other non-OxPhos mitochondrial proteins, except for heat shock protein 70, which was increased depending on oxygen level and differentiation status. These two factors were proven to modulate mitochondrial membrane potential and the bioenergetic status of cells. We suggest, moreover, that oxygen plays a role in the differentiation of human SH-SY5Y cells.

The physiology of endothelial xanthine oxidase: from urate catabolism to reperfusion injury to inflammatory signal transduction.

PubMed

Meneshian, Avedis; Bulkley, Gregory B

2002-07-01

Xanthine oxidoreductase (XOR) is a ubiquitous metalloflavoprotein that appears in two interconvertible yet functionally distinct forms: xanthine dehydrogenase (XD), which is constitutively expressed in vivo; and xanthine oxidase (XO), which is generated by the posttranslational modification of XD, either through the reversible, incremental thiol oxidation of sulfhydryl residues on XD or the irreversible proteolytic cleavage of a segment of XD, which occurs at low oxygen tension and in the presence of several proinflammatory mediators. Functionally, both XD and XO catalyze the oxidation of purines to urate. However, whereas XD requires NAD+ as an electron acceptor for these redox reactions, thereby generating the stable product NADH, XO is unable to use NAD+ as an electron acceptor, requiring instead the reduction of molecular oxygen for this purine oxidation and generating the highly reactive superoxide free radical. Nearly 100 years of study has documented the physiologic role of XD in urate catabolism. However, the rapid, posttranslational conversion of XD to the oxidant-generating form XO provides a possible physiologic mechanism for rapid, posttranslational, oxidant-mediated signaling. XO-generated reactive oxygen species (ROS) have been implicated in various clinicopathologic entities, including ischemia/reperfusion injury and multisystem organ failure. More recently, the concept of physiologic signal transduction mediated by ROS has been proposed, and the possibility of XD to XO conversion, with subsequent ROS generation, serving as the trigger of the microvascular inflammatory response in vivo has been hypothesized. This review presents the evidence and basis for this hypothesis.

Low Oxygen Modulates Multiple Signaling Pathways, Increasing Self-Renewal, While Decreasing Differentiation, Senescence, and Apoptosis in Stromal MIAMI Cells

PubMed Central

Rios, Carmen; D'Ippolito, Gianluca; Curtis, Kevin M.; Delcroix, Gaëtan J.-R.; Gomez, Lourdes A.; El Hokayem, Jimmy; Rieger, Megan; Parrondo, Ricardo; de las Pozas, Alicia; Perez-Stable, Carlos; Howard, Guy A.

2016-01-01

Human bone marrow multipotent mesenchymal stromal cell (hMSC) number decreases with aging. Subpopulations of hMSCs can differentiate into cells found in bone, vasculature, cartilage, gut, and other tissues and participate in their repair. Maintaining throughout adult life such cell subpopulations should help prevent or delay the onset of age-related degenerative conditions. Low oxygen tension, the physiological environment in progenitor cell-rich regions of the bone marrow microarchitecture, stimulates the self-renewal of marrow-isolated adult multilineage inducible (MIAMI) cells and expression of Sox2, Nanog, Oct4a nuclear accumulation, Notch intracellular domain, notch target genes, neuronal transcriptional repressor element 1 (RE1)-silencing transcription factor (REST), and hypoxia-inducible factor-1 alpha (HIF-1α), and additionally, by decreasing the expression of (i) the proapoptotic proteins, apoptosis-inducing factor (AIF) and Bak, and (ii) senescence-associated p53 expression and β-galactosidase activity. Furthermore, low oxygen increases canonical Wnt pathway signaling coreceptor Lrp5 expression, and PI3K/Akt pathway activation. Lrp5 inhibition decreases self-renewal marker Sox2 mRNA, Oct4a nuclear accumulation, and cell numbers. Wortmannin-mediated PI3K/Akt pathway inhibition leads to increased osteoblastic differentiation at both low and high oxygen tension. We demonstrate that low oxygen stimulates a complex signaling network involving PI3K/Akt, Notch, and canonical Wnt pathways, which mediate the observed increase in nuclear Oct4a and REST, with simultaneous decrease in p53, AIF, and Bak. Collectively, these pathway activations contribute to increased self-renewal with concomitant decreased differentiation, cell cycle arrest, apoptosis, and/or senescence in MIAMI cells. Importantly, the PI3K/Akt pathway plays a central mechanistic role in the oxygen tension-regulated self-renewal versus osteoblastic differentiation of progenitor cells. PMID:27059084

Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology

NASA Technical Reports Server (NTRS)

Megaridis, Constantine M.; Bellizia, Giulio; McNallan, Michael; Wallace, David B.

2003-01-01

Surface tension forces play a critical role in fluid dynamic phenomena that are important in materials processing. The surface tension of liquid metals has been shown to be very susceptible to small amounts of adsorbed oxygen. Consequently, the kinetics of oxygen adsorption can influence the capillary breakup of liquid-metal jets targeted for use in electronics assembly applications, where low-melting-point metals (such as tin-containing solders) are utilized as an attachment material for mounting of electronic components to substrates. By interpreting values of surface tension measured at various surface ages, adsorption and diffusion rates of oxygen on the surface of the melt can be estimated. This research program investigates the adsorption kinetics of oxygen on the surface of an atomizing molten-metal jet. A novel oscillating capillary jet method has been developed for the measurement of dynamic surface tension of liquids, and in particular, metal melts which are susceptible to rapid surface degradation caused by oxygen adsorption. The experimental technique captures the evolution of jet swells and necks continuously along the jet propagation axis and is used in conjunction with an existing linear, axisymmetric, constant-property model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated so far focus on a time window of 2-4ms from the jet orifice. The surface properties of the eutectic 63%Sn-37%Pb solder alloy have been investigated in terms of their variation due to O2 adsorption from a N2 atmosphere containing controlled amounts of oxygen (from 8 ppm to 1000 ppm). The method performed well for situations where the oxygen adsorption was low in that time window. The value of surface tension for the 63Sn-37Pb solder in pure nitrogen was found to be 0.49 N/m, in good agreement with previously published work. A characteristic

Quantifying oxygen in paper-based cell cultures with luminescent thin film sensors.

PubMed

Boyce, Matthew W; Kenney, Rachael M; Truong, Andrew S; Lockett, Matthew R

2016-04-01

Paper-based scaffolds are an attractive material for generating 3D tissue-like cultures because paper is readily available and does not require specialized equipment to pattern, cut, or use. By controlling the exchange of fresh culture medium with the paper-based scaffolds, we can engineer diffusion-dominated environments similar to those found in spheroids or solid tumors. Oxygen tension directly regulates cellular phenotype and invasiveness through hypoxia-inducible transcription factors and also has chemotactic properties. To date, gradients of oxygen generated in the paper-based cultures have relied on cellular response-based readouts. In this work, we prepared a luminescent thin film capable of quantifying oxygen tensions in apposed cell-containing paper-based scaffolds. The oxygen sensors, which are polystyrene films containing a Pd(II) tetrakis(pentafluorophenyl)porphyrin dye, are photostable, stable in culture conditions, and not cytotoxic. They have a linear response for oxygen tensions ranging from 0 to 160 mmHg O2, and a Stern-Volmer constant (K sv) of 0.239 ± 0.003 mmHg O2 (-1). We used these oxygen-sensing films to measure the spatial and temporal changes in oxygen tension for paper-based cultures containing a breast cancer line that was engineered to constitutively express a fluorescent protein. By acquiring images of the oxygen-sensing film and the fluorescently labeled cells, we were able to approximate the oxygen consumption rates of the cells in our cultures.

The Steady-State Transport of Oxygen through Hemoglobin Solutions

PubMed Central

Keller, K. H.; Friedlander, S. K.

1966-01-01

The steady-state transport of oxygen through hemoglobin solutions was studied to identify the mechanism of the diffusion augmentation observed at low oxygen tensions. A novel technique employing a platinum-silver oxygen electrode was developed to measure the effective diffusion coefficient of oxygen in steady-state transport. The measurements were made over a wider range of hemoglobin and oxygen concentrations than previously reported. Values of the Brownian motion diffusion coefficient of oxygen in hemoglobin solution were obtained as well as measurements of facilitated transport at low oxygen tensions. Transport rates up to ten times greater than ordinary diffusion rates were found. Predictions of oxygen flux were made assuming that the oxyhemoglobin transport coefficient was equal to the Brownian motion diffusivity which was measured in a separate set of experiments. The close correlation between prediction and experiment indicates that the diffusion of oxyhemoglobin is the mechanism by which steady-state oxygen transport is facilitated. PMID:5943608

The anatomy of microbial cell state transitions in response to oxygen.

PubMed

Schmid, Amy K; Reiss, David J; Kaur, Amardeep; Pan, Min; King, Nichole; Van, Phu T; Hohmann, Laura; Martin, Daniel B; Baliga, Nitin S

2007-10-01

Adjustment of physiology in response to changes in oxygen availability is critical for the survival of all organisms. However, the chronology of events and the regulatory processes that determine how and when changes in environmental oxygen tension result in an appropriate cellular response is not well understood at a systems level. Therefore, transcriptome, proteome, ATP, and growth changes were analyzed in a halophilic archaeon to generate a temporal model that describes the cellular events that drive the transition between the organism's two opposing cell states of anoxic quiescence and aerobic growth. According to this model, upon oxygen influx, an initial burst of protein synthesis precedes ATP and transcription induction, rapidly driving the cell out of anoxic quiescence, culminating in the resumption of growth. This model also suggests that quiescent cells appear to remain actively poised for energy production from a variety of different sources. Dynamic temporal analysis of relationships between transcription and translation of key genes suggests several important mechanisms for cellular sustenance under anoxia as well as specific instances of post-transcriptional regulation.

The anatomy of microbial cell state transitions in response to oxygen

PubMed Central

Schmid, Amy K.; Reiss, David J.; Kaur, Amardeep; Pan, Min; King, Nichole; Van, Phu T.; Hohmann, Laura; Martin, Daniel B.; Baliga, Nitin S.

2007-01-01

Adjustment of physiology in response to changes in oxygen availability is critical for the survival of all organisms. However, the chronology of events and the regulatory processes that determine how and when changes in environmental oxygen tension result in an appropriate cellular response is not well understood at a systems level. Therefore, transcriptome, proteome, ATP, and growth changes were analyzed in a halophilic archaeon to generate a temporal model that describes the cellular events that drive the transition between the organism’s two opposing cell states of anoxic quiescence and aerobic growth. According to this model, upon oxygen influx, an initial burst of protein synthesis precedes ATP and transcription induction, rapidly driving the cell out of anoxic quiescence, culminating in the resumption of growth. This model also suggests that quiescent cells appear to remain actively poised for energy production from a variety of different sources. Dynamic temporal analysis of relationships between transcription and translation of key genes suggests several important mechanisms for cellular sustenance under anoxia as well as specific instances of post-transcriptional regulation. PMID:17785531

Supplemental Oxygen and Carbon Dioxide Each Increase Subcutaneous and Intestinal Intramural Oxygenation

PubMed Central

Ratnaraj, Jebadurai; Kabon, Barbara; Talcott, Michael R.; Sessler, Daniel I.

2005-01-01

Oxidative killing by neutrophils, a primary defense against surgical pathogens, is directly related to tissue oxygenation. We tested the hypothesis that supplemental inspired oxygen or mild hypercapnia (end-tidal PCO2 of 50 mmHg) improves intestinal oxygenation. Pigs (25±2.5 kg) were used in two studies in random order: 1) Oxygen Study — 30% vs. 100% inspired oxygen concentration at an end-tidal PCO2 of 40 mmHg, and 2) Carbon Dioxide Study — end-tidal PCO2 of 30 mmHg vs. 50 mmHg with 30% oxygen. Within each study, treatment order was randomized. Treatments were maintained for 1.5 hours; measurements were averaged over the final hour. A tonometer inserted in the subcutaneous tissue of the left upper foreleg measured subcutaneous oxygen tension. Tonometers inserted into the intestinal wall measured intestinal intramural oxygen tension from the small and large intestines. 100% oxygen administration doubled subcutaneous oxygen partial pressure (PO2) (57±10 to 107±48 mmHg, P=0.006) and large intestine intramural PO2 (53±14 to 118±72 mmHg, P=0.014); intramural PO2increased 40% in the small intestine (37±10 to 52±25 mmHg, P=0.004). An end-tidal PCO2 of 50 mmHg increased large intestinal PO2 approximately 16% (49±10 to 57±12 mmHg, P=0.039), while intramural PO2 increased by 45% in the small intestine (31±12 to 44±16 mmHg, P=0.002). Supplemental oxygen and mild hypercapnia each increased subcutaneous and intramural tissue PO2, with supplemental oxygen being most effective. PMID:15281531

Oxygen flux as an indicator of physiological stress in aquatic organisms: a real-time biomonitoring system of water quality

NASA Astrophysics Data System (ADS)

Sanchez, Brian C.; Yale, Gowri; Chatni, Rameez; Ochoa-Acuña, Hugo G.; Porterfield, D. Marshall; Mclamore, Eric S.; Sepúlveda, María S.

2009-05-01

The detection of harmful chemicals and biological agents in real time is a critical need for protecting water quality. We studied the real-time effects of five environmental contaminants with differing modes of action (atrazine, pentachlorophenol, cadmium chloride, malathion, and potassium cyanide) on respiratory oxygen consumption in 2-day post-fertilization fathead minnow (Pimephales promelas) eggs. Our objective was to assess the sensitivity of fathead minnow eggs using the self-referencing micro-optrode technique to detect instantaneous changes in oxygen consumption after brief exposures to low concentrations of contaminants. Oxygen consumption data indicated that the technique is indeed sensitive enough to reliably detect physiological alterations induced by all contaminants. After 2 h of exposure, we identified significant increases in oxygen consumption upon exposure to pentachlorophenol (100 and 1000 μg/L), cadmium chloride (0.0002 and 0.002 μg/L), and atrazine (150 μg/L). In contrast, we observed a significant decrease in oxygen flux after exposures to potassium cyanide (5.2, 22, and 44 μg/L) and atrazine (1500 μg/L). No effects were detected after exposures to malathion (200 and 340 μg/L). We have also tested the sensitivity of Daphnia magna embryos as another animal model for real-time environmental biomonitoring. Our results are so far encouraging and support further development of this technology as a physiologically coupled biomonitoring tool for the detection of environmental toxicants.

SOIL GAS OXYGEN TENSION AND PENTACHLOROPHENOL BIODEGRADATION

EPA Science Inventory

Laboratory tests were conducted to determine the effect of soil gas oxygen concentration on the degradation and mineralization of spiked 14C-pentachlorophenol and nonlabeled pentachlorophenol (PCP) present in soil taken from a prepared-bed land treatment unit at the Champion Inte...

Physiologic oxygen concentration enhances the stem-like properties of CD133+ human glioblastoma cells in vitro.

PubMed

McCord, Amy M; Jamal, Muhammad; Shankavaram, Uma T; Shankavarum, Uma T; Lang, Frederick F; Camphausen, Kevin; Tofilon, Philip J

2009-04-01

In vitro investigations of tumor stem-like cells (TSC) isolated from human glioblastoma (GB) surgical specimens have been done primarily at an atmospheric oxygen level of 20%. To determine whether an oxygen level more consistent with in situ conditions affects their stem cell-like characteristics, we compared GB TSCs grown under conditions of 20% and 7% oxygen. Growing CD133(+) cells sorted from three GB neurosphere cultures at 7% O(2) reduced their doubling time and increased the self-renewal potential as reflected by clonogenicity. Furthermore, at 7% oxygen, the cultures exhibited an enhanced capacity to differentiate along both the glial and neuronal pathways. As compared with 20%, growth at 7% oxygen resulted in an increase in the expression levels of the neural stem cell markers CD133 and nestin as well as the stem cell markers Oct4 and Sox2. In addition, whereas hypoxia inducible factor 1alpha was not affected in CD133(+) TSCs grown at 7% O(2), hypoxia-inducible factor 2alpha was expressed at higher levels as compared with 20% oxygen. Gene expression profiles generated by microarray analysis revealed that reducing oxygen level to 7% resulted in the up-regulation and down-regulation of a significant number of genes, with more than 140 being commonly affected among the three CD133(+) cultures. Furthermore, Gene Ontology categories up-regulated at 7% oxygen included those associated with stem cells or GB TSCs. Thus, the data presented indicate that growth at the more physiologically relevant oxygen level of 7% enhances the stem cell-like phenotype of CD133(+) GB cells.

Oxygen-controlled automated neural differentiation of mouse embryonic stem cells.

PubMed

Mondragon-Teran, Paul; Tostoes, Rui; Mason, Chris; Lye, Gary J; Veraitch, Farlan S

2013-03-01

Automation and oxygen tension control are two tools that provide significant improvements to the reproducibility and efficiency of stem cell production processes. the aim of this study was to establish a novel automation platform capable of controlling oxygen tension during both the cell-culture and liquid-handling steps of neural differentiation processes. We built a bespoke automation platform, which enclosed a liquid-handling platform in a sterile, oxygen-controlled environment. An airtight connection was used to transfer cell culture plates to and from an automated oxygen-controlled incubator. Our results demonstrate that our system yielded comparable cell numbers, viabilities, metabolism profiles and differentiation efficiencies when compared with traditional manual processes. Interestingly, eliminating exposure to ambient conditions during the liquid-handling stage resulted in significant improvements in the yield of MAP2-positive neural cells, indicating that this level of control can improve differentiation processes. This article describes, for the first time, an automation platform capable of maintaining oxygen tension control during both the cell-culture and liquid-handling stages of a 2D embryonic stem cell differentiation process.

Tissue Oxygenation in Obese and Non-obese Patients During Laparoscopy

PubMed Central

Fleischmann, Edith; Kurz, Andrea; Niedermayr, Monika; Schebesta, Karl; Kimberger, Oliver; Prager, Gerhard; Sessler, Daniel I.; Kabon, Barbara

2005-01-01

Background: Wound infection risk is inversely related to subcutaneous oxygenation, which is reduced in obese patients and may be reduced even more during laparoscopic procedures. Methods: We evaluated subcutaneous tissue oxygenation (PsqO2) in 20 patients with a body mass index (BMI) ≥40 kg·m–2 (obese) and 15 patients with BMI <30 kg·m-2 (non-obese) undergoing laparoscopic surgery with standardised anaesthesia technique and fluid administration. Arterial oxygen tension was maintained near 150 mmHg. PsqO2 was measured from a surrogate wound on the upper arm. Data were analyzed with unpaired two-tailed t or Wilcoxon rank-sum tests; P < 0.05 was statistically significant. Data are given as mean (SD). Results: An FIO2 of 51% (13%) was required in obese patients to reach an arterial oxygen tension of 150 mmHg; however, an FIO2 of only 40% (7%) was required to reach the same oxygen tension in non-obese patients (P=0.007). PsqO2 was significantly less in obese patients: 41 (10) vs. 57 (15) mmHg (P<0.001). Conclusion: Obesity reduces the amount of inspired oxygen required to obtain a given arterial partial pressure and tissue oxygenation. Both factors probably contribute to high infection risk in obese patients. PMID:15978153

Oxygen matters: tissue culture oxygen levels affect mitochondrial function and structure as well as responses to HIV viroproteins.

PubMed

Tiede, L M; Cook, E A; Morsey, B; Fox, H S

2011-12-22

Mitochondrial dysfunction is implicated in a majority of neurodegenerative disorders and much study of neurodegenerative disease is done on cultured neurons. In traditional tissue culture, the oxygen level that cells experience is dramatically higher (21%) than in vivo conditions (1-11%). These differences can alter experimental results, especially, pertaining to mitochondria and oxidative metabolism. Our results show that primary neurons cultured at physiological oxygen levels found in the brain showed higher polarization, lower rates of ROS production, larger mitochondrial networks, greater cytoplasmic fractions of mitochondria and larger mitochondrial perimeters than those cultured at higher oxygen levels. Although neurons cultured in either physiological oxygen or atmospheric oxygen exhibit significant increases in mitochondrial reactive oxygen species (ROS) production when treated with the human immunodeficiency virus (HIV) virotoxin trans-activator of transcription, mitochondria of neurons cultured at physiological oxygen underwent depolarization with dramatically increased cell death, whereas those cultured at atmospheric oxygen became hyperpolarized with no increase in cell death. Studies with a second HIV virotoxin, negative regulation factor (Nef), revealed that Nef treatment also increased mitochondrial ROS production for both the oxygen conditions, but resulted in mitochondrial depolarization and increased death only in neurons cultured in physiological oxygen. These results indicate a role for oxidative metabolism in a mechanism of neurotoxicity during HIV infection and demonstrate the importance of choosing the correct, physiological, culture oxygen in mitochondrial studies performed in neurons.

The impact of physiological oxygen during culture, and vitrification for cryopreservation, on the outcome of extended culture in human IVF.

PubMed

Gardner, David K

2016-02-01

Extended culture has facilitated the move to single blastocyst transfer, resulting in significant increases in implantation and live birth rate, while concomitantly reducing fetal loss during pregnancy. However, concerns have been raised regarding subsequent neo-natal outcomes following extended culture. Analysis of the literature reveals differences in outcomes according to geographical region and between individual clinics. A common factor amongst reports of potentially adverse outcomes following blastocyst transfer appears to be that atmospheric (~20%) oxygen was typically employed for embryo culture. Clinics and countries utilizing physiological concentrations of oxygen (~5%) have not reported adverse perinatal outcomes with blastocyst transfer. Atmospheric oxygen imposes significant negative effects upon the embryo's molecular and cellular physiology, and further it increases the sensitivity of the preimplantation embryo to other stressors in the laboratory. With the recent adoption of vitrification for blastocyst cryopreservation, cumulative pregnancy rates per cycle with extended culture will increase significantly. Consequently, rather than perceiving extended culture as a potentially negative procedure, it is concluded that neo-natal data need to be interpreted in light of the conditions used to culture and cryopreserve blastocysts, and that furthermore a policy of embryo culture using 20% oxygen can no longer be justified. Copyright © 2015 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

[Case of tension pneumothorax associated with asthma attack during general anesthesia].

PubMed

Komasawa, Nobuyasu; Ueki, Ryusuke; Kusuyama, Kazuki; Okano, Yukari; Tatara, Tsuneo; Tashiro, Chikara

2010-05-01

We report a case of tension pneumothorax associated with asthma attack during general anesthesia. An 86-year-old woman with dementia underwent cataract surgery under general anesthesia. At 70 min after the start of operation, airway pressure suddenly increased from 19 to 28 cm HO2O. In spite of bag ventilation with 100% oxygen, Sp(O2) decreased to 81%. Chest-Xp showed typical image of tension pneumothorax. Chest drainage was immediately performed, after which Pa(O2) recovered soon. She was extubated on postoperative day 1 without any neurological disorder. Hyperinflation of fragile alveoli by mechanical ventilation was likely a cause of tension pneumothorax.

Influence of tissue metabolism and capillary oxygen supply on arteriolar oxygen transport: a computational model.

PubMed

Moschandreou, T E; Ellis, C G; Goldman, D

2011-07-01

We present a theoretical model for steady-state radial and longitudinal oxygen transport in arterioles containing flowing blood (plasma and red blood cells) and surrounded by living tissue. This model combines a detailed description of convective and diffusive oxygen transport inside the arteriole with a novel boundary condition at the arteriolar lumen surface, and the results provide new mass transfer coefficients for computing arteriolar O(2) losses based on far-field tissue O(2) tension and in the presence of spatially distributed capillaries. A numerical procedure is introduced for calculating O(2) diffusion from an arteriole to a continuous capillary-tissue matrix immediately adjacent to the arteriole. The tissue O(2) consumption rate is assumed to be constant and capillaries act as either O(2) sources or sinks depending on the local O(2) environment. Using the model, O(2) saturation (SO(2)) and tension (PO(2)) are determined for the intraluminal region of the arteriole, as well as for the extraluminal region in the neighbouring tissue. Our model gives results that are consistent with available experimental data and previous intraluminal transport models, including appreciable radial decreases in intraluminal PO(2) for all vessel diameters considered (12-100 μm) and slower longitudinal decreases in PO(2) for larger vessels than for smaller ones, and predicts substantially less diffusion of O(2) from arteriolar blood than do models with PO(2) specified at the edge of the lumen. The dependence of the new mass transfer coefficients on vessel diameter, SO(2) and far-field PO(2) is calculated allowing their application to a wide range of physiological situations. This novel arteriolar O(2) transport model will be a vital component of future integrated models of microvascular regulation of O(2) supply to capillary beds and the tissue regions they support. Copyright © 2011 Elsevier Inc. All rights reserved.

Protein-mediated looping of DNA under tension requires supercoiling

PubMed Central

Yan, Yan; Leng, Fenfei; Finzi, Laura; Dunlap, David

2018-01-01

Abstract Protein-mediated DNA looping is ubiquitous in chromatin organization and gene regulation, but to what extent supercoiling or nucleoid associated proteins promote looping is poorly understood. Using the lac repressor (LacI), a paradigmatic loop-mediating protein, we measured LacI-induced looping as a function of either supercoiling or the concentration of the HU protein, an abundant nucleoid protein in Escherichia coli. Negative supercoiling to physiological levels with magnetic tweezers easily drove the looping probability from 0 to 100% in single DNA molecules under slight tension that likely exists in vivo. In contrast, even saturating (micromolar) concentrations of HU could not raise the looping probability above 30% in similarly stretched DNA or 80% in DNA without tension. Negative supercoiling is required to induce significant looping of DNA under any appreciable tension. PMID:29365152

Interplay of tumor vascular oxygenation and pO2 in tumors using NIRS and needle electrode

NASA Astrophysics Data System (ADS)

Kim, Jae Gwan; Song, Yulin; Zhao, Dawen; Constantinescu, Anca; Mason, Ralph P.; Liu, Hanli

2001-06-01

The effective measurement of dynamic changes of blood and tissue oxygenation of tumors could be valuable for optimizing tumor treatment plans. For this study, a near- infrared spectroscopy system and pO2 needle electrode were used to measure simultaneously changes in total hemoglobin concentration ([Hb]total), oxygenated hemoglobin concentration ([HbO2[) and local oxygen tension (pO2) in the vascular bed of prostate tumors implanted in rats in response to respiratory challenge. The inhaled gas was alternated between air and carbogen (95% oxygen, 5% CO2). Significant changes in tumor vascular oxygenation were observed with an apparent threshold for variation in [HbO2]/[HbO2]max. For comparison, a phantom study was undertaken with 1% intralipid solution and blood. The slope of [HbO2]/[HbO2[max vs. pO2 in the phantom was ten times larger than in the tumor indicating that tumor cells are relatively resistant to oxygenation. This study demonstrates that the NIR technology can provide an efficient, real-time, non-invasive approach to monitoring tumor physiology and is compatible with additional techniques.

Effect of oxygen tension and serum during IVM on developmental competence of bovine oocytes.

PubMed

Pereira, Michele M; Machado, Marco A; Costa, Fernanda Q; Serapiao, Raquel V; Viana, Joao H M; Camargo, Luiz S A

2010-01-01

With an aim to improve the in vitro production of bovine embryos, the present study investigated the effect of serum and oxygen tension during IVM on oocyte developmental competence. Four experimental groups were evaluated: G1, 10% oestrus cow serum (OCS) with 20% O(2); G2, 0.1% polyvinyl alcohol (PVA) with 20% O(2); G3, 10% OCS with 5% O(2); and G4, 0.1% PVA with 5% O(2). The proportion of MII oocytes, blastocyst rates and total cell number were not affected (P > 0.05) when the OCS was replaced with PVA under 5% O(2), whereas a higher (P < 0.05) blastocyst rate and total cell number were found with OCS compared with PVA under 20% O(2). The apoptosis index was lower in blastocysts from oocytes matured with PVA under 5% O(2) (G4) compared with other groups (G1, G2 and G3), but no differences (P > 0.05) were found in maturation and blastocyst rates. Significant differences were found in the amount of specific transcripts in oocytes matured under different conditions. In conclusion maturation with PVA and 5% O(2) provides an efficient in vitro culture condition for the maturation of bovine oocytes.

Oxygen flux as an indicator of physiological stress in fathead minnow (Pimephales promelas) embryos: a real-time biomonitoring system of water quality.

PubMed

Sanchez, Brian C; Ochoa-Acuña, Hugo; Porterfield, D Marshall; Sepúlveda, María S

2008-09-15

The detection of harmful chemicals and biological agents in real time is a critical need for protecting freshwater ecosystems. We studied the real-time effects of five environmental contaminants with differing modes of action (atrazine, cadmium chloride, pentachlorophenol, malathion, and potassium cyanide) on respiratory oxygen consumption in 2-day postfertilization fathead minnow (Pimephales promelas) eggs. Our objective was to assess the sensitivity of fathead minnow eggs using the self-referencing micro-optrode technique to detect instantaneous changes in oxygen consumption after brief exposures to low concentrations of contaminants. Oxygen consumption data indicated that the technique is indeed sensitive enough to reliably detect physiological alterations induced by four of the five contaminants. After 2 h of exposure, we identified significant increases in oxygen consumption upon exposure to pentachlorophenol (100 and 1000 microg/L), cadmium chloride (0.0002 and 0.002 microg/L), and atrazine (150 microg/L). In contrast, we observed a significant decrease in oxygen flux after exposuresto potassium cyanide (44 and 66 microg/L) and atrazine (1500 microg/L). No effects were detected after exposures to malathion (200 and 340 microg/L). Our work is the first step in development of a new technique for physiologically coupled biomonitoring as a sensitive and reliable tool for the detection of environmental toxicants.

Oxygen matters: tissue culture oxygen levels affect mitochondrial function and structure as well as responses to HIV viroproteins

PubMed Central

Tiede, L M; Cook, E A; Morsey, B; Fox, H S

2011-01-01

Mitochondrial dysfunction is implicated in a majority of neurodegenerative disorders and much study of neurodegenerative disease is done on cultured neurons. In traditional tissue culture, the oxygen level that cells experience is dramatically higher (21%) than in vivo conditions (1–11%). These differences can alter experimental results, especially, pertaining to mitochondria and oxidative metabolism. Our results show that primary neurons cultured at physiological oxygen levels found in the brain showed higher polarization, lower rates of ROS production, larger mitochondrial networks, greater cytoplasmic fractions of mitochondria and larger mitochondrial perimeters than those cultured at higher oxygen levels. Although neurons cultured in either physiological oxygen or atmospheric oxygen exhibit significant increases in mitochondrial reactive oxygen species (ROS) production when treated with the human immunodeficiency virus (HIV) virotoxin trans-activator of transcription, mitochondria of neurons cultured at physiological oxygen underwent depolarization with dramatically increased cell death, whereas those cultured at atmospheric oxygen became hyperpolarized with no increase in cell death. Studies with a second HIV virotoxin, negative regulation factor (Nef), revealed that Nef treatment also increased mitochondrial ROS production for both the oxygen conditions, but resulted in mitochondrial depolarization and increased death only in neurons cultured in physiological oxygen. These results indicate a role for oxidative metabolism in a mechanism of neurotoxicity during HIV infection and demonstrate the importance of choosing the correct, physiological, culture oxygen in mitochondrial studies performed in neurons. PMID:22190005

Oxygen cost and physiological responses of recreational badminton match play.

PubMed

Deka, Pallav; Berg, Kris; Harder, Jeanette; Batelaan, Herman; McGRATH, Melanie

2017-06-01

Badminton, as an Olympic sport, is popular worldwide. However, the benefits of recreational badminton match play are not well known. The purpose of the study was to determine the oxygen cost of recreational badminton match play. Heart rate (HR), blood lactate (BL), rating of perceived exertion (RPE), step count and energy expenditure were also assessed. Fourteen male recreational badminton players aged 35.9±6.62 years participated in test sessions to assess oxygen uptake (VO2) and the related physiological responses of match play. During the match play sessions, participants played singles badminton matches for 30 min while wearing a portable metabolic system. VO2 and HR were continuously recorded while blood lactate and RPE were determined following warm-up, at 15 minutes and 30 minutes of match play. Step count was recorded at 15 minutes and 30 minutes of play. VO2 over 30 minutes was 34.4±5.8 mL/kg/min which was 76.1% of maximal oxygen uptake. Across three 10-minute periods of play, VO2 was not significantly different while HR was higher in the third 10-minute period than the first and second 10-minute periods (P=0.001). Mean HR over 30 minutes was 167.9±9.4 bpm. BL was significantly higher at 15 and 30 minutes than following warm-up while RPE of 17.57±1.91 after 30 minutes was significantly higher (P=0.009) than RPE of 15.79±1.63 at 15 minutes. Step count did not vary between the two 15-minute periods of play with a total of 2404±360 steps while energy expenditure over 30 minutes of play was 391.7±66 kcal. Recreational badminton match play can be categorized as vigorous intensity suggesting that it can be a viable means of achieving recommended physical activity and improving aerobic fitness.

Mitochondrial stress controls the radiosensitivity of the oxygen effect: Implications for radiotherapy.

PubMed

Richardson, Richard B; Harper, Mary-Ellen

2016-04-19

It has been more than 60 years since the discovery of the oxygen effect that empirically demonstrates the direct association between cell radiosensitivity and oxygen tension, important parameters in radiotherapy. Yet the mechanisms underlying this principal tenet of radiobiology are poorly understood. Better understanding of the oxygen effect may explain difficulty in eliminating hypoxic tumor cells, a major cause of regrowth after therapy. Our analysis utilizes the Howard-Flanders and Alper formula, which describes the relationship of radiosensitivity with oxygen tension. Here, we assign and qualitatively assess the relative contributions of two important mechanisms. The first mechanism involves the emission of reactive oxygen species from the mitochondrial electron transport chain, which increases with oxygen tension. The second mechanism is related to an energy and repair deficit, which increases with hypoxia. Following a radiation exposure, the uncoupling of the oxidative phosphorylation system (proton leak) in mitochondria lowers the emission of reactive oxygen species which has implications for fractionated radiotherapy, particularly of hypoxic tumors. Our analysis shows that, in oxygenated tumor and normal cells, mitochondria, rather than the nucleus, are the primary loci of radiotherapy effects, especially for low linear energy transfer radiation. Therefore, the oxygen effect can be explained by radiation-induced effects in mitochondria that generate reactive oxygen species, which in turn indirectly target nuclear DNA.

Normal-tension glaucoma (Low-tension glaucoma)

PubMed Central

Anderson, Douglas R

2011-01-01

Glaucoma is now considered an abnormal physiology in the optic nerve head that interacts with the level of intraocular pressure (IOP), with the degree and rate of damage depending on the IOP and presumably the degree of abnormal physiology. Diagnosis of normal-tension glaucoma (NTG), defined as glaucoma without a clearly abnormal IOP, depends on recognizing symptoms and signs associated with optic nerve vulnerability, in addition to absence of other explanations for disc abnormality and visual field loss. Among the findings are a halo or crescent of absence of retinal pigment epithelium around the disc, bilateral pre-chiasmal visual field defects, splinter hemorrhages at the disc margin, vascular dysregulation (low blood pressure, cold hands and feet, migraine headache with aura, and the like), or a family history of glaucoma. Possibly relevant, is a history of hemodynamic crisis, arterial obstructive disease, or sleep apnea. Neurological evaluation with imaging is needed only for atypical cases or ones that progress unexpectedly. Management follows the same principle of other chronic glaucomas, to lower the IOP by a substantial amount, enough to prevent disabling visual loss. However, many NTG cases are non-progressive. Therefore, it may often be wisein mild cases to determine whether the case is progressive and the rate of progression before deciding on how aggressivene to be with therapy. Efforts at neuroprotection and improvement in blood flow have not yet been shown effective. PMID:21150042

Bilateral tension pneumothorax related to acupuncture.

PubMed

Tagami, Rumi; Moriya, Takashi; Kinoshita, Kosaku; Tanjoh, Katsuhisa

2013-06-01

We report on a patient with a rare case of bilateral tension pneumothorax that occurred after acupuncture. A 69-year-old large-bodied man, who otherwise had no risk factors for spontaneous pneumothorax, presented with chest pressure, cold sweats and shortness of breath. Immediately after bilateral pneumothorax had been identified on a chest radiograph in the emergency room, his blood pressure and percutaneous oxygen saturation suddenly decreased to 78 mm Hg and 86%, respectively. We confirmed deterioration in his cardiopulmonary status and diagnosed bilateral tension pneumothorax. We punctured his chest bilaterally and inserted chest tubes for drainage. His vital signs promptly recovered. After the bilateral puncture and drainage, we learnt that he had been treated with acupuncture on his upper back. We finally diagnosed a bilateral tension pneumothorax based on the symptoms that appeared 8 h after the acupuncture. Because the patient had no risk factors for spontaneous pneumothorax, no alternative diagnosis was proposed. We recommend that patients receiving acupuncture around the chest wall must be adequately informed of the possibility of complications and expected symptoms, as a definitive diagnosis can be difficult without complete information.

Accounting for oxygen in the renal cortex: a computational study of factors that predispose the cortex to hypoxia.

PubMed

Lee, Chang-Joon; Gardiner, Bruce S; Ngo, Jennifer P; Kar, Saptarshi; Evans, Roger G; Smith, David W

2017-08-01

We develop a pseudo-three-dimensional model of oxygen transport for the renal cortex of the rat, incorporating both the axial and radial geometry of the preglomerular circulation and quantitative information regarding the surface areas and transport from the vasculature and renal corpuscles. The computational model was validated by simulating four sets of published experimental studies of renal oxygenation in rats. Under the control conditions, the predicted cortical tissue oxygen tension ([Formula: see text]) or microvascular oxygen tension (µPo 2 ) were within ±1 SE of the mean value observed experimentally. The predicted [Formula: see text] or µPo 2 in response to ischemia-reperfusion injury, acute hemodilution, blockade of nitric oxide synthase, or uncoupling mitochondrial respiration, were within ±2 SE observed experimentally. We performed a sensitivity analysis of the key model parameters to assess their individual or combined impact on the predicted [Formula: see text] and µPo 2 The model parameters analyzed were as follows: 1 ) the major determinants of renal oxygen delivery ([Formula: see text]) (arterial blood Po 2 , hemoglobin concentration, and renal blood flow); 2 ) the major determinants of renal oxygen consumption (V̇o 2 ) [glomerular filtration rate (GFR) and the efficiency of oxygen utilization for sodium reabsorption (β)]; and 3) peritubular capillary surface area (PCSA). Reductions in PCSA by 50% were found to profoundly increase the sensitivity of [Formula: see text] and µPo 2 to the major the determinants of [Formula: see text] and V̇o 2 The increasing likelihood of hypoxia with decreasing PCSA provides a potential explanation for the increased risk of acute kidney injury in some experimental animals and for patients with chronic kidney disease. Copyright © 2017 the American Physiological Society.

Oxygen-sensing PHDs regulate bone homeostasis through the modulation of osteoprotegerin

PubMed Central

Wu, Colleen; Rankin, Erinn B.; Castellini, Laura; Fernandez-Alcudia, Javier; LaGory, Edward L.; Andersen, Rebecca; Rhodes, Steven D.; Wilson, Tremika L.S.; Mohammad, Khalid S.; Castillo, Alesha B.; Guise, Theresa A.; Schipani, Ernestina

2015-01-01

The bone microenvironment is composed of niches that house cells across variable oxygen tensions. However, the contribution of oxygen gradients in regulating bone and blood homeostasis remains unknown. Here, we generated mice with either single or combined genetic inactivation of the critical oxygen-sensing prolyl hydroxylase (PHD) enzymes (PHD1–3) in osteoprogenitors. Hypoxia-inducible factor (HIF) activation associated with Phd2 and Phd3 inactivation drove bone accumulation by modulating osteoblastic/osteoclastic cross-talk through the direct regulation of osteoprotegerin (OPG). In contrast, combined inactivation of Phd1, Phd2, and Phd3 resulted in extreme HIF signaling, leading to polycythemia and excessive bone accumulation by overstimulating angiogenic–osteogenic coupling. We also demonstrate that genetic ablation of Phd2 and Phd3 was sufficient to protect ovariectomized mice against bone loss without disrupting hematopoietic homeostasis. Importantly, we identify OPG as a HIF target gene capable of directing osteoblast-mediated osteoclastogenesis to regulate bone homeostasis. Here, we show that coordinated activation of specific PHD isoforms fine-tunes the osteoblastic response to hypoxia, thereby directing two important aspects of bone physiology: cross-talk between osteoblasts and osteoclasts and angiogenic–osteogenic coupling. PMID:25846796

Mixomics analysis of Bacillus subtilis: effect of oxygen availability on riboflavin production.

PubMed

Hu, Junlang; Lei, Pan; Mohsin, Ali; Liu, Xiaoyun; Huang, Mingzhi; Li, Liang; Hu, Jianhua; Hang, Haifeng; Zhuang, Yingping; Guo, Meijin

2017-09-12

Riboflavin, an intermediate of primary metabolism, is one kind of important food additive with high economic value. The microbial cell factory Bacillus subtilis has already been proven to possess significant importance for the food industry and have become one of the most widely used riboflavin-producing strains. In the practical fermentation processes, a sharp decrease in riboflavin production is encountered along with a decrease in the dissolved oxygen (DO) tension. Influence of this oxygen availability on riboflavin biosynthesis through carbon central metabolic pathways in B. subtilis is unknown so far. Therefore the unveiled effective metabolic pathways were still an unaccomplished task till present research work. In this paper, the microscopic regulation mechanisms of B. subtilis grown under different dissolved oxygen tensions were studied by integrating 13 C metabolic flux analysis, metabolomics and transcriptomics. It was revealed that the glucose metabolic flux through pentose phosphate (PP) pathway was lower as being confirmed by smaller pool sizes of metabolites in PP pathway and lower expression amount of ykgB at transcriptional level. The latter encodes 6-phosphogluconolactonase (6-PGL) under low DO tension. In response to low DO tension in broth, the glucose metabolic flux through Embden-Meyerhof-Parnas (EMP) pathway was higher and the gene, alsS, encoding for acetolactate synthase was significantly activated that may result due to lower ATP concentration and higher NADH/NAD + ratio. Moreover, ResE, a membrane-anchored protein that is capable of oxygen regulated phosphorylase activity, and ResD, a regulatory protein that can be phosphorylated and dephosphorylated by ResE, were considered as DO tension sensor and transcriptional regulator respectively. This study shows that integration of transcriptomics, 13 C metabolic flux analysis and metabolomics analysis provides a comprehensive understanding of biosynthesized riboflavin's regulatory mechanisms in

Regulation of nitrite transport in red blood cells by hemoglobin oxygen fractional saturation.

PubMed

Vitturi, Dario A; Teng, Xinjun; Toledo, José C; Matalon, Sadis; Lancaster, Jack R; Patel, Rakesh P

2009-05-01

Allosteric regulation of nitrite reduction by deoxyhemoglobin has been proposed to mediate nitric oxide (NO) formation during hypoxia. Nitrite is predominantly an anion at physiological pH, raising questions about the mechanism by which it enters the red blood cell (RBC) and whether this is regulated and coupled to deoxyhemoglobin-mediated reduction. We tested the hypothesis that nitrite transport by RBCs is regulated by fractional saturation. Using human RBCs, nitrite consumption was faster at lower fractional saturations, consistent with faster reactions with deoxyheme. A membrane-based regulation was suggested by slower nitrite consumption with intact versus lysed RBCs. Interestingly, upon nitrite addition, intracellular nitrite concentrations attained a steady state that, despite increased rates of consumption, did not change with decreasing oxygen tensions, suggesting a deoxygenation-sensitive step that either increases nitrite import or decreases the rate of nitrite export. A role for anion exchanger (AE)-1 in the control of nitrite export was suggested by increased intracellular nitrite concentrations in RBCs treated with DIDS. Moreover, deoxygenation decreased steady-state levels of intracellular nitrite in AE-1-inhibited RBCs. Based on these data, we propose a model in which deoxyhemoglobin binding to AE-1 inhibits nitrite export under low oxygen tensions allowing for the coupling between deoxygenation and nitrite reduction to NO along the arterial-to-venous gradient.

Biophysical and physiological origins of blood oxygenation level-dependent fMRI signals.

PubMed

Kim, Seong-Gi; Ogawa, Seiji

2012-07-01

After its discovery in 1990, blood oxygenation level-dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) has been widely used to map brain activation in humans and animals. Since fMRI relies on signal changes induced by neural activity, its signal source can be complex and is also dependent on imaging parameters and techniques. In this review, we identify and describe the origins of BOLD fMRI signals, including the topics of (1) effects of spin density, volume fraction, inflow, perfusion, and susceptibility as potential contributors to BOLD fMRI, (2) intravascular and extravascular contributions to conventional gradient-echo and spin-echo BOLD fMRI, (3) spatial specificity of hemodynamic-based fMRI related to vascular architecture and intrinsic hemodynamic responses, (4) BOLD signal contributions from functional changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of O(2) utilization (CMRO(2)), (5) dynamic responses of BOLD, CBF, CMRO(2), and arterial and venous CBV, (6) potential sources of initial BOLD dips, poststimulus BOLD undershoots, and prolonged negative BOLD fMRI signals, (7) dependence of stimulus-evoked BOLD signals on baseline physiology, and (8) basis of resting-state BOLD fluctuations. These discussions are highly relevant to interpreting BOLD fMRI signals as physiological means.

Biophysical and physiological origins of blood oxygenation level-dependent fMRI signals

PubMed Central

Kim, Seong-Gi; Ogawa, Seiji

2012-01-01

After its discovery in 1990, blood oxygenation level-dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) has been widely used to map brain activation in humans and animals. Since fMRI relies on signal changes induced by neural activity, its signal source can be complex and is also dependent on imaging parameters and techniques. In this review, we identify and describe the origins of BOLD fMRI signals, including the topics of (1) effects of spin density, volume fraction, inflow, perfusion, and susceptibility as potential contributors to BOLD fMRI, (2) intravascular and extravascular contributions to conventional gradient-echo and spin-echo BOLD fMRI, (3) spatial specificity of hemodynamic-based fMRI related to vascular architecture and intrinsic hemodynamic responses, (4) BOLD signal contributions from functional changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of O2 utilization (CMRO2), (5) dynamic responses of BOLD, CBF, CMRO2, and arterial and venous CBV, (6) potential sources of initial BOLD dips, poststimulus BOLD undershoots, and prolonged negative BOLD fMRI signals, (7) dependence of stimulus-evoked BOLD signals on baseline physiology, and (8) basis of resting-state BOLD fluctuations. These discussions are highly relevant to interpreting BOLD fMRI signals as physiological means. PMID:22395207

Physiological complexity of acute traumatic brain injury in patients treated with a brain oxygen protocol: utility of symbolic regression in predictive modeling of a dynamical system.

PubMed

Narotam, Pradeep K; Morrison, John F; Schmidt, Michael D; Nathoo, Narendra

2014-04-01

Predictive modeling of emergent behavior, inherent to complex physiological systems, requires the analysis of large complex clinical data streams currently being generated in the intensive care unit. Brain tissue oxygen protocols have yielded outcome benefits in traumatic brain injury (TBI), but the critical physiological thresholds for low brain oxygen have not been established for a dynamical patho-physiological system. High frequency, multi-modal clinical data sets from 29 patients with severe TBI who underwent multi-modality neuro-clinical care monitoring and treatment with a brain oxygen protocol were analyzed. The inter-relationship between acute physiological parameters was determined using symbolic regression (SR) as the computational framework. The mean patient age was 44.4±15 with a mean admission GCS of 6.6±3.9. Sixty-three percent sustained motor vehicle accidents and the most common pathology was intra-cerebral hemorrhage (50%). Hospital discharge mortality was 21%, poor outcome occurred in 24% of patients, and good outcome occurred in 56% of patients. Criticality for low brain oxygen was intracranial pressure (ICP) ≥22.8 mm Hg, for mortality at ICP≥37.1 mm Hg. The upper therapeutic threshold for cerebral perfusion pressure (CPP) was 75 mm Hg. Eubaric hyperoxia significantly impacted partial pressure of oxygen in brain tissue (PbtO2) at all ICP levels. Optimal brain temperature (Tbr) was 34-35°C, with an adverse effect when Tbr≥38°C. Survivors clustered at [Formula: see text] Hg vs. non-survivors [Formula: see text] 18 mm Hg. There were two mortality clusters for ICP: High ICP/low PbtO2 and low ICP/low PbtO2. Survivors maintained PbtO2 at all ranges of mean arterial pressure in contrast to non-survivors. The final SR equation for cerebral oxygenation is: [Formula: see text]. The SR-model of acute TBI advances new physiological thresholds or boundary conditions for acute TBI management: PbtO2≥25 mmHg; ICP≤22 mmHg; CPP≈60-75�

A PP2A-mediated feedback mechanism controls Ca2+-dependent NO synthesis under physiological oxygen.

PubMed

Keeley, Thomas P; Siow, Richard C M; Jacob, Ron; Mann, Giovanni E

2017-12-01

Intracellular O 2 is a key regulator of NO signaling, yet most in vitro studies are conducted in atmospheric O 2 levels, hyperoxic with respect to the physiologic milieu. We investigated NO signaling in endothelial cells cultured in physiologic (5%) O 2 and stimulated with histamine or shear stress. Culture of cells in 5% O 2 (>5 d) decreased histamine- but not shear stress-stimulated endothelial (e)NOS activity. Unlike cells adapted to a hypoxic environment (1% O 2 ), those cultured in 5% O 2 still mobilized sufficient Ca 2+ to activate AMPK. Enhanced expression and membrane targeting of PP2A-C was observed in 5% O 2 , resulting in greater interaction with eNOS in response to histamine. Moreover, increased dephosphorylation of eNOS in 5% O 2 was Ca 2+ -sensitive and reversed by okadaic acid or PP2A-C siRNA. The present findings establish that Ca 2+ mobilization stimulates both NO synthesis and PP2A-mediated eNOS dephosphorylation, thus constituting a novel negative feedback mechanism regulating eNOS activity not present in response to shear stress. This, coupled with enhanced NO bioavailability, underpins differences in NO signaling induced by inflammatory and physiologic stimuli that are apparent only in physiologic O 2 levels. Furthermore, an explicit delineation between physiologic normoxia and genuine hypoxia is defined here, with implications for our understanding of pathophysiological hypoxia.-Keeley, T. P., Siow, R. C. M., Jacob, R., Mann, G. E. A PP2A-mediated feedback mechanism controls Ca 2+ -dependent NO synthesis under physiological oxygen. © The Author(s).

Pericellular oxygen concentration of cultured primary human trophoblasts

PubMed Central

Chen, Baosheng; Longtine, Mark S.; Nelson, D. Michael

2012-01-01

Introduction Oxygen is pivotal in placental development and function. In vitro culture of human trophoblasts provides a useful model to study this phenomenon, but a hotly debated issue is whether or not the oxygen tension of the culture conditions mimics in vivo conditions. We tested the hypothesis that ambient oxygen tensions in culture reflect the pericellular oxygen levels. Methods We used a microelectrode oxygen sensor to measure the concentration of dissolved oxygen in the culture medium equilibrated with 21%, 8% or <0.5% oxygen. Results The concentration of oxygen in medium without cells resembled that in the ambient atmosphere. The oxygen concentration present in medium bathing trophoblasts was remarkably dependent on the depth within the medium where sampling occurred, and the oxygen concentration within the overlying atmosphere was not reflected in medium immediately adjacent to the cells. Indeed, the pericellular oxygen concentration was in a range that most would consider severe hypoxia, at ≤ 0.6% oxygen or about 4.6 mm Hg, when the overlying atmosphere was 21% oxygen. Conclusions We conclude that culture conditions of 21% oxygen are unable to replicate the pO2 of 40–60 mm Hg commonly attributed to the maternal blood in the intervillous space in the second and third trimesters of pregnancy. We further surmise that oxygen atmospheres in culture conditions between 0.5% and 21% provide different oxygen fluxes in the immediate pericellular environment yet can still yield insights into the responses of human trophoblast to different oxygen conditions. PMID:23211472

The role of size in synchronous air breathing of Hoplosternum littorale.

PubMed

Sloman, Katherine A; Sloman, Richard D; De Boeck, Gudrun; Scott, Graham R; Iftikar, Fathima I; Wood, Chris M; Almeida-Val, Vera M F; Val, Adalberto L

2009-01-01

Synchronized air breathing may have evolved as a way of minimizing the predation risk known to be associated with air breathing in fish. Little is known about how the size of individuals affects synchronized air breathing and whether some individuals are required to surface earlier than necessary in support of conspecifics, while others delay air intake. Here, the air-breathing behavior of Hoplosternum littorale held in groups or in isolation was investigated in relation to body mass, oxygen tensions, and a variety of other physiological parameters (plasma lactate, hepatic glycogen, hematocrit, hemoglobin, and size of heart, branchial basket, liver, and air-breathing organ [ABO]). A mass-specific relationship with oxygen tension of first surfacing was seen when fish were held in isolation; smaller individuals surfaced at higher oxygen tensions. However, this relationship was lost when the same individuals were held in social groups of four, where synchronous air breathing was observed. In isolation, 62% of fish first surfaced at an oxygen tension lower than the calculated P(crit) (8.13 kPa), but in the group environment this was reduced to 38% of individuals. Higher oxygen tensions at first surfacing in the group environment were related to higher levels of activity rather than any of the physiological parameters measured. In fish held in isolation but denied access to the water surface for 12 h before behavioral testing, there was no mass-specific relationship with oxygen tension at first surfacing. Larger individuals with a greater capacity to store air in their ABOs may, therefore, remain in hypoxic waters for longer periods than smaller individuals when held in isolation unless prior access to the air is prevented. This study highlights how social interaction can affect air-breathing behaviors and the importance of considering both behavioral and physiological responses of fish to hypoxia to understand the survival mechanisms they employ.

Oxygen and carbon isotope disequilibria in Galapagos corals: isotopic thermometry and calcification physiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConnaughey, T.A.

1986-01-01

Biological carbonate skeletons are built largely from carbon dioxide, which reacts to form carbonate ion within thin extracellular solutions. The light isotopes of carbon and oxygen react faster than the heavy isotopes, depleting the resulting carbonate ions in /sup 13/C and /sup 18/O. Calcium carbonate precipitation occurs sufficiently fast that the skeleton remains out of isotopic equilibrium with surrounding fluids. This explanation for isotopic disequilibrium in biological carbonates was partially simulated in vitro, producing results similar to those seen in non-photosynthetic corals. Photosynthetic corals have higher /sup 13/C//sup 12/C ratios due to the preferential removal of /sup 12/C (as organicmore » carbon) from the reservoir of dissolved inorganic carbon. The oxygen isotopic variations in corals can be used to reconstruct past sea surface temperatures to an accuracy of about 0.5/sup 0/C. The carbon isotopic content of photosynthetic corals provides an indication of cloudiness. Using isotopic data from Galapagos corals, it was possible to construct proxy histories of the El Nino phenomenon. The physiology of skeletogenesis appears to be surprisingly similar in calcium carbonate, calcium phosphate, and silica precipitating systems.« less

Membrane development in purple photosynthetic bacteria in response to alterations in light intensity and oxygen tension.

PubMed

Niederman, Robert A

2013-10-01

Studies on membrane development in purple bacteria during adaptation to alterations in light intensity and oxygen tension are reviewed. Anoxygenic phototrophic such as the purple α-proteobacterium Rhodobacter sphaeroides have served as simple, dynamic, and experimentally accessible model organisms for studies of the photosynthetic apparatus. A major landmark in photosynthesis research, which dramatically illustrates this point, was provided by the determination of the X-ray structure of the reaction center (RC) in Blastochloris viridis (Deisenhofer and Michel, EMBO J 8:2149-2170, 1989), once it was realized that this represented the general structure for the photosystem II RC present in all oxygenic phototrophs. This seminal advance, together with a considerable body of subsequent research on the light-harvesting (LH) and electron transfer components of the photosynthetic apparatus has provided a firm basis for the current understanding of how phototrophs acclimate to alterations in light intensity and quality. Oxygenic phototrophs adapt to these changes by extensive thylakoid membrane remodeling, which results in a dramatic supramolecular reordering to assure that an appropriate flow of quinone redox species occurs within the membrane bilayer for efficient and rapid electron transfer. Despite the high level of photosynthetic unit organization in Rba. sphaeroides as observed by atomic force microscopy (AFM), fluorescence induction/relaxation measurements have demonstrated that the addition of the peripheral LH2 antenna complex in cells adapting to low-intensity illumination results in a slowing of the rate of electron transfer turnover by the RC of up to an order of magnitude. This is ascribed to constraints in quinone redox species diffusion between the RC and cytochrome bc1 complexes arising from the increased packing density as the intracytoplasmic membrane (ICM) bilayer becomes crowded with LH2 rings. In addition to downshifts in light intensity as a paradigm

Effect of diatrizoate meglumine (Hypaque) on the perilymphatic oxygen tension.

PubMed

Nagahara, K; Fisch, U

1982-12-01

The effect of diatrizoate meglumine (Hypaque) upon the perilymphatic oxygenation has been investigated using the polarographic method in cats submitted to various conditions such as normoxia, apnea, hypercapnia and chronically reduced vascularization. The minimal changes of the perilymphatic PO2 recorded after the injection of Hypaque permit to conclude that this drug has no practical effect upon the oxygenation of the perilymph.

Air-breathing behavior and physiological responses to hypoxia and air exposure in the air-breathing loricariid fish, Pterygoplichthys anisitsi.

PubMed

da Cruz, André Luis; da Silva, Hugo Ribeiro; Lundstedt, Lícia Maria; Schwantes, Arno Rudi; Moraes, Gilberto; Klein, Wilfried; Fernandes, Marisa Narciso

2013-04-01

Hypoxic water and episodic air exposure are potentially life-threatening conditions that fish in tropical regions can face during the dry season. This study investigated the air-breathing behavior, oxygen consumption, and respiratory responses of the air-breathing (AB) armored catfish Pterygoplichthys anisitsi. The hematological parameters and oxygen-binding characteristics of whole blood and stripped hemoglobin and the intermediate metabolism of selected tissue in normoxia, different hypoxic conditions, and after air exposure were also examined. In normoxia, this species exhibited high activity at night and AB behavior (2-5 AB h(-1)). The exposure to acute severe hypoxia elicited the AB behavior (4 AB h(-1)) during the day. Under progressive hypoxia without access to the water surface, the fish were oxyregulators with a critical O2 tension, calculated as the inspired water O2 pressure, as 47 ± 2 mmHg. At water O2 tensions lower than 40 mmHg, the fish exhibited continuous apnea behavior. The blood exhibited high capacity for transporting O2, having a cathodic hemoglobin component with a high Hb-O2 affinity. Under severe hypoxia, the fish used anaerobic metabolism to maintain metabolic rate. Air exposure revealed physiological and biochemical traits similar to those observed under normoxic conditions.

Physiological and hypoxic oxygen concentration differentially regulates human c-Kit+ cardiac stem cell proliferation and migration.

PubMed

Bellio, Michael A; Rodrigues, Claudia O; Landin, Ana Marie; Hatzistergos, Konstantinos E; Kuznetsov, Jeffim; Florea, Victoria; Valasaki, Krystalenia; Khan, Aisha; Hare, Joshua M; Schulman, Ivonne Hernandez

2016-12-01

Cardiac stem cells (CSCs) are being evaluated for their efficacy in the treatment of heart failure. However, numerous factors impair the exogenously delivered cells' regenerative capabilities. Hypoxia is one stress that contributes to inadequate tissue repair. Here, we tested the hypothesis that hypoxia impairs cell proliferation, survival, and migration of human CSCs relative to physiological and room air oxygen concentrations. Human endomyocardial biopsy-derived CSCs were isolated, selected for c-Kit expression, and expanded in vitro at room air (21% O 2 ). To assess the effect on proliferation, survival, and migration, CSCs were transferred to physiological (5%) or hypoxic (0.5%) O 2 concentrations. Physiological O 2 levels increased proliferation (P < 0.05) but did not affect survival of CSCs. Although similar growth rates were observed in room air and hypoxia, a significant reduction of β-galactosidase activity (-4,203 fluorescent units, P < 0.05), p16 protein expression (0.58-fold, P < 0.001), and mitochondrial content (0.18-fold, P < 0.001) in hypoxia suggests that transition from high (21%) to low (0.5%) O 2 reduces senescence and promotes quiescence. Furthermore, physiological O 2 levels increased migration (P < 0.05) compared with room air and hypoxia, and treatment with mesenchymal stem cell-conditioned media rescued CSC migration under hypoxia to levels comparable to physiological O 2 migration (2-fold, P < 0.05 relative to CSC media control). Our finding that physiological O 2 concentration is optimal for in vitro parameters of CSC biology suggests that standard room air may diminish cell regenerative potential. This study provides novel insights into the modulatory effects of O 2 concentration on CSC biology and has important implications for refining stem cell therapies. Copyright © 2016 the American Physiological Society.

Prediction of inspired oxygen fraction for targeted arterial oxygen tension following open heart surgery in non-smoking and smoking patients.

PubMed

Bou-Khalil, Pierre; Zeineldine, Salah; Chatburn, Robert; Ayyoub, Chakib; Elkhatib, Farouk; Bou-Akl, Imad; El-Khatib, Mohamad

2017-10-01

Simple and accurate expressions describing the P a O 2 -F i O 2 relationship in mechanically ventilated patients are lacking. The current study aims to validate a novel mathematical expression for accurate prediction of the fraction of inspired oxygen that will result in a targeted arterial oxygen tension in non-smoking and smoking patients receiving mechanical ventilation following open heart surgeries. One hundred P a O 2 -F i O 2 data pairs were obtained from 25 non-smoking patients mechanically ventilated following open heart surgeries. One data pair was collected at each of F i O 2 of 40, 60, 80, and 100% while maintaining same mechanical ventilation support settings. Similarly, another 100 hundred P a O 2 -F i O 2 data pairs were obtained from 25 smoking patients mechanically ventilated following open heart surgeries. The utility of the new mathematical expression in accurately describing the P a O 2 -F i O 2 relationship in these patients was assessed by the regression and Bland-Altman analyses. Significant correlations were seen between the true and estimated F i O 2 values in non-smoking (r 2  = 0.9424; p < 0.05) and smoking (r 2  = 0.9466; p < 0.05) patients. Tight biases between the true and estimated F i O 2 values for non-smoking (3.1%) and smoking (4.1%) patients were observed. Also, significant correlations were seen between the true and estimated P a O 2 /F i O 2 ratios in non-smoking (r 2  = 0.9530; p < 0.05) and smoking (r 2  = 0.9675; p < 0.05) patients. Tight biases between the true and estimated P a O 2 /F i O 2 ratios for non-smoking (-18 mmHg) and smoking (-16 mmHg) patients were also observed. The new mathematical expression for the description of the P a O 2 -F i O 2 relationship is valid and accurate in non-smoking and smoking patients who are receiving mechanical ventilation for post cardiac surgery.

Physiologically Relevant Prosthetic Limb Movement Feedback for Upper and Lower Extremity Amputees

DTIC Science & Technology

2016-10-01

upper arm (elbow movement), Upper leg (knee movement) and lower leg ( ankle movement) to provide a physiologically relevant sense of limb movement...Additionally a BOA cable tensioning system is passed through these plates and anchored to the external surface of the socket. When tension is applied the

A novel technique for monitoring of fast variations in brain oxygen tension using an uncoated fluorescence quenching probe (Foxy AL-300).

PubMed

Klein, Klaus Ulrich; Boehme, Stefan; Hartmann, Erik Kristopher; Szczyrba, Marc; David, Matthias; Markstaller, Klaus; Engelhard, Kristin

2011-10-01

A novel uncoated fluorescence quenching probe allows fast measurement of oxygen tension in vessels and tissue. The present study reports the first use of the technology for dual measurements of arterial (paO(2)) and brain tissue oxygen tension (ptiO(2)) during hypoxic challenge in a pig model. Eight pigs were anesthetized using fentanyl and propofol. Fluorescence quenching pO(2) probes (Foxy AL-300, Ocean Optics, Dunedin, FL) were placed in the ascending aorta (Foxy-paO(2)) and subcortically at 14 mm in brain tissue (Foxy-ptiO(2)). As reference, a clark-type electrode probe (Licox-ptiO(2)) was placed into brain tissue close to the Foxy probe (Licox, Integra Neurosciences, Plainsboro, NJ). Measurements were taken at baseline (FiO(2) 1.0), during episodes of apnea, and during recovery (FiO(2) 1.0). descriptive results. Individual Foxy-paO(2), Foxy-ptiO(2), and Licox-ptiO(2) courses were related to episodes of apnea. The response time of the Foxy measurements was 10 Hz. Baseline values at FiO(2) 1.0 were Foxy-paO(2) 520±120 mm Hg, Foxy-ptiO(2) 62±24 mm Hg, and Licox-ptiO(2) 55±29 mm Hg; apnea values were Foxy-paO(2) 64±10 mm Hg, Foxy-ptiO(2) 37±12 mm Hg, and Licox-ptiO(2) 31±16 mm Hg; recovery values at FiO(2) 1.0 were Foxy-paO(2) 478±98 mm Hg, Foxy-ptiO(2) 78±26 mm Hg, and Licox-ptiO(2) 62±32 mm Hg. The present study demonstrates the feasibility of pO(2) measurements in macrocirculation and cerebral microcirculation using a novel uncoated fluorescence quenching probe. The technology allows for real-time investigation of pO(2) changes at a temporal resolution of 0.05 to 10 Hz.

Cable tensioned membrane solar collector module with variable tension control

DOEpatents

Murphy, Lawrence M.

1985-01-01

Disclosed is a solar collector comprising a membrane for concentrating sunlight, a plurality of elongated structural members for suspending the membrane member thereon, and a plurality of control members for adjustably tensioning the membrane member, as well as for controlling a focus produced by the membrane members. Each control member is disposed at a different corresponding one of the plurality of structural members. The collector also comprises an elongated flexible tensioning member, which serves to stretch the membrane member and to thereafter hold it in tension, and a plurality of sleeve members, which serve to provide the membrane member with a desired surface contour during tensioning of the membrane member. The tensioning member is coupled to the structural members such that the tensioning member is adjustably tensioned through the structural members. The tensioning member is also coupled to the membrane member through the sleeve members such that the sleeve members uniformly and symmetrically stretch the membrane member upon applying tension to the tensioning member with the control members.

Cable tensioned membrane solar collector module with variable tension control

DOEpatents

Murphy, L.M.

1984-01-09

Disclosed is a solar collector comprising a membrane member for concentrating sunlight, a plurality of elongated structural members for suspending the membrane member thereon, and a plurality of control members for adjustably tensioning the membrane member, as well as for controlling a focus produced by the membrane members. Each control member is disposed at a different corresponding one of the plurality of structural members. The collector also comprises an elongated flexible tensioning member, which serves to stretch the membrane member and to thereafter hold it in tension, and a plurality of sleeve members which serve to provide the membrane member with a desired surface contour during tensioning of the membrane member. The tensioning member is coupled to the structural members such that the tensioning member is adjustably tensioned through the structural members. The tensioning member is also coupled to the membrane member through the sleeve members such that the sleeve members uniformly and symmetrically stretch the membrane member upon applying tension to the tensioning member with the control members.

Regional cell density distribution and oxygen consumption rates in porcine TMJ discs: an explant study.

PubMed

Kuo, J; Shi, C; Cisewski, S; Zhang, L; Kern, M J; Yao, H

2011-07-01

To determine the regional cell density distribution and basal oxygen consumption rates (based on tissue volume and cell number) of temporomandibular joint (TMJ) discs and further examine the impact of oxygen tension on these rates. TMJ discs from pigs aged 6-8 months were divided into five regions: anterior, intermediate, posterior, lateral and medial. The cell density was determined using confocal laser scanning microscopy. The change in oxygen tension was recorded while TMJ disc explants were cultured in sealed metabolism chambers. The volume based oxygen consumption rate of explants was determined by theoretical curve-fitting of the recorded oxygen tension data with the Michaelis-Menten equation. The rate on a per-cell basis was calculated based on the cell density measurements and volume based rate measured in another group of discs. The overall cell density [mean, 95% confidence interval (CI)] was 51.3 (21.3-81.3) × 10(6) cells/mL wet tissue. Along the anteroposterior axis, the anterior band had 25.5% higher cell density than the intermediate zone (P<0.02) and 29.1% higher than the posterior band (P<0.008). Along the mediolateral axes, the medial region had 26.2% higher cell density than the intermediate zone (P<0.04) and 25.4% higher than the lateral region (P<0.045). The overall volume and cell based maximum oxygen consumption rates were 1.44 (0.44-2.44) μmol/mL wet tissue/h and 28.7 (12.2-45.2)nmol/10(6)cells/h, respectively. The central regions (intermediate, lateral, and medial) had significantly higher volume based (P<0.02) and cell based (P<0.005) oxygen consumption rates than the anterior and posterior bands. At high oxygen tension, the oxygen consumption rate remained constant, but dropped as oxygen tension fell below 5%. The TMJ disc had higher cell density and oxygen consumption rates than articular cartilage reported in the literature. These results suggest that a steeper oxygen gradient may exist in the TMJ disc and may be vulnerable to

Regional Cell Density Distribution and Oxygen Consumption Rates in Porcine TMJ Discs: An Explant Study

PubMed Central

Kuo, Jonathan; Shi, Changcheng; Cisewski, Sarah; Zhang, Lixia; Kern, Michael J.; Yao, Hai

2011-01-01

Objective To determine the regional cell density distribution and basal oxygen consumption rates (based on tissue volume and cell number) of temporomandibular joint (TMJ) discs and further examine the impact of oxygen tension on these rates. Design TMJ discs from pigs aged 6–8 months were divided into five regions: anterior, intermediate, posterior, lateral and medial. The cell density was determined using confocal laser scanning microscopy. The change in oxygen tension was recorded while TMJ disc explants were cultured in sealed metabolism chambers. The volume based oxygen consumption rate of explants was determined by theoretical curve fitting of the recoded oxygen tension data with the Michaelis-Menten equation. The rate on a per-cell basis was calculated based on the cell density measurements and volume based rate measured in another group of discs. Results The overall cell density (mean, 95% CI) was 51.3(21.3–81.3)×106cells/mL wet tissue. Along the anteroposterior axis, the anterior band had 25.5% higher cell density than the intermediate zone (p<0.02) and 29.1% higher than the posterior band (p<0.008). Along the mediolateral axes, the medial region had 26.2% higher cell density than the intermediate zone (p<0.04) and 25.4% higher than the lateral region (p<0.045). The overall volume and cell based maximum oxygen consumption rates were 1.44(0.44–2.44) μmol/mL wet tissue/hr and 28.7(12.2–45.2) nmol/106 cells/hr, respectively. The central regions (intermediate, lateral, and medial) had significantly higher volume based (p<0.02) and cell based (p<0.005) oxygen consumption rates than the anterior and posterior bands. At high oxygen tension, the oxygen consumption rate remained constant, but dropped as oxygen tension fell below 5%. Conclusions The TMJ disc had higher cell density and oxygen consumption rates than articular cartilage reported in the literature. These results suggest that a steeper oxygen gradient may exist in the TMJ disc and may be

The effect of deep inspiration breath-hold on tumour oxygenation.

PubMed

Aquino-Parsons, C; Ries, C R; Minchinton, A I; D'yachkova, Y

2003-10-01

To investigate the influence of deep inspiration breath-hold on the oxygen tension of in-vivo tumours measured using an Eppendorf pO2 histograph. Patients with accessible primary or metastatic tumours > or = 2 cm diameter were entered into a protocol measuring tumour oxygenation with an Eppendorf pO2 histograph during normal breathing (NB) and deep inspiration breath-hold (DIBH). Change in oxygen tension was assessed using the Wilcoxon Signed Ranks test. Thirty patients were entered in to this protocol. The median maximum tumour dimension was 4 cm. The median of the median pO2 of these tumours was 18 mmHg. Tumours were assessed during NB and DIBH. Oxygen tension measurements along 1-3 pairs of tracks per tumour (median of 2) were obtained. The median number of measurements per track was 30 for NB and 29 for DIBH (range 17-59). In six tumours, the values during NB were significantly higher than during DIBH, whereas, for six other tumours, the relationship was the opposite; for the remaining 18 patients, no significant difference was observed. These data show heterogeneity of tumour oxygenation seen with in-situ tumours both at baseline and as a result of DIBH. No systematic change in the Eppendorf pO2 measurements was seen as a result of DIBH; however, the individual tumour responses to DIBH varied dramatically.

The influence of oxygen and hydrostatic pressure on articular chondrocytes and adherent bone marrow cells in vitro.

PubMed

Scherer, Katrin; Schünke, Michael; Sellckau, Roland; Hassenpflug, Joachim; Kurz, Bodo

2004-01-01

Tissue engineering of articular cartilage from chondrocytes or stem cells is considered to be a potential aspect in the treatment of cartilage defects. In order to optimize culture conditions the influence of low oxygen tension (5%) - single or in combination with intermittent hydrostatic pressure (HP: 30/2 min on/off loading; 0.2 MPa) - on the biosynthetic activity (sulfate and proline incorporation) of human osteoarthritic chondrocytes cultured on collagen I/III membranes was investigated. Additionally, chondrogenesis from high density or monolayer cultures of bovine adherent bone marrow cells (aBMC) with and without chondrogenic medium supplements (CM) was analyzed by RT-PCR (mRNA expression of aggrecan and collagen type II). We could show that low oxygen tension increases significantly the biosynthesis of collagen I/III membrane-associated chondrocytes and even higher under co-stimulation with HP. While there is no chondrogenesis in monolayer cultures, CM induces expression of cartilage matrix molecules in high density cultures of aBMC which is even increased under the influence of low oxygen tension. Both, low oxygen tension and HP without CM are alone not sufficient stimuli for chondrogenesis. It can be concluded that low oxygen tension and HP might be useful tools in cartilage tissue engineering and that these physico-chemical factors promote but do not induce chondrogenesis under the given conditions.

Biological oxygen apparent transmissibility of hydrogel contact lenses with and without organosilicon moieties.

PubMed

Compañ, V; López-Alemany, A; Riande, E; Refojo, M F

2004-01-01

The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed- and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact lenses with oxygen transmissibility higher than 100 Dk/t units [1 Dk/t unit=10(-9) [cm(3) O(2) (STp) cm(-2)s(-1)(mmHg)(-1)] posses a large oxygen tension at the lens-cornea interface that substantially reduces the oxygen flux onto the cornea. Lenses whose oxygen transmissibility is lower than 50 Dk/t units allow a rather small oxygen flux onto the cornea under closed eyelids condition that prevent their use for extended wear.

Critical oxygen levels and metabolic suppression in oceanic oxygen minimum zones.

PubMed

Seibel, Brad A

2011-01-15

The survival of oceanic organisms in oxygen minimum zones (OMZs) depends on their total oxygen demand and the capacities for oxygen extraction and transport, anaerobic ATP production and metabolic suppression. Anaerobic metabolism and metabolic suppression are required for daytime forays into the most extreme OMZs. Critical oxygen partial pressures are, within a range, evolved to match the minimum oxygen level to which a species is exposed. This fact demands that low oxygen habitats be defined by the biological response to low oxygen rather than by some arbitrary oxygen concentration. A broad comparative analysis of oxygen tolerance facilitates the identification of two oxygen thresholds that may prove useful for policy makers as OMZs expand due to climate change. Between these thresholds, specific physiological adaptations to low oxygen are required of virtually all species. The lower threshold represents a limit to evolved oxygen extraction capacity. Climate change that pushes oxygen concentrations below the lower threshold (~0.8 kPa) will certainly result in a transition from an ecosystem dominated by a diverse midwater fauna to one dominated by diel migrant biota that must return to surface waters at night. Animal physiology and, in particular, the response of animals to expanding hypoxia, is a critical, but understudied, component of biogeochemical cycles and oceanic ecology. Here, I discuss the definition of hypoxia and critical oxygen levels, review adaptations of animals to OMZs and discuss the capacity for, and prevalence of, metabolic suppression as a response to temporary residence in OMZs and the possible consequences of climate change on OMZ ecology.

Measurement and Control of Oxygen Partial Pressure in an Electrostatic Levitator

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.

2014-01-01

Recently the NASA Marshall Space Flight Center electrostatic levitation (ESL) laboratory has been upgraded to include an oxygen control system. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, at elevated temperatures, theoretically in the range from 10(exp -36) to 10(exp 0) bar. The role of active surface agents in liquid metals is fairly well known; however, published surface tension data typically has large scatter, which has been hypothesized to be caused by the presence of oxygen. The surface tension of metals is affected by even a small amount of adsorption of oxygen. It has even been shown that oxygen partial pressures may need to be as low as 10(exp -24) bar to avoid oxidation. While electrostatic levitation is done under high vacuum, oxide films or dissolved oxygen may have significant effects on materials properties, such as surface tension and viscosity. Therefore, the ability to measure and control the oxygen partial pressure within the chamber is highly desirable. The oxygen control system installed at MSFC contains a potentiometric sensor, which measures the oxygen partial pressure, and an oxygen ion pump. In the pump, a pulse-width modulated electric current is applied to yttrium-stabilized zirconia, resulting in oxygen transfer into or out of the system. Also part of the system is a control unit, which consists of temperature controllers for the sensor and pump, PID-based current loop for the ion pump, and a control algorithm. This system can be used to study the effects of oxygen on the thermophysical properties of metals, ceramics, glasses, and alloys. It can also be used to provide more accurate measurements by processing the samples at very low oxygen partial pressures. The oxygen control system will be explained in more detail and an overview of its use and limitations in an electrostatic levitator will be described. Some preliminary measurements have been made, and the results to date will

Heterogeneity of renal cortical oxygenation: seeing is believing.

PubMed

Evans, Roger G; Ow, Connie P C

2018-06-01

The limited spatial and temporal resolution of available methods for quantifying renal tissue oxygen tension is a major impediment to identification of the roles of renal hypoxia in kidney diseases. Intravital phosphorescence lifetime imaging microscopy allows cellular oxygen tension in the renal cortex of live animals to be resolved to the level of individual tubular cross-sections. This paves the way for future investigations of the spatial relationships between cellular hypoxia and pathophysiological events in kidney disease. Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen.

PubMed

Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten; Lauritzen, Martin

2013-02-01

Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus loading with OGB-1/AM and SR101. We report that the occurrence of spontaneous waves is 20 times more frequent in the cerebellar cortex of aging as compared with adult mice, which correlated with a reduction in resting brain oxygen tension. In adult mice, spontaneous glial wave activity increased on reducing resting brain oxygen tension, and ATP-evoked glial waves reduced the tissue O(2) tension. Finally, although spontaneous Purkinje cell (PC) activity was not associated with increased glia wave activity, spontaneous glial waves did affect intracellular Ca(2+) activity in PCs. The increased wave activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.

Analysis of constant tension-induced rupture of lipid membranes using activation energy.

PubMed

Karal, Mohammad Abu Sayem; Levadnyy, Victor; Yamazaki, Masahito

2016-05-11

The stretching of biomembranes and lipid membranes plays important roles in various physiological and physicochemical phenomena. Here we analyzed the rate constant kp of constant tension-induced rupture of giant unilamellar vesicles (GUVs) as a function of tension σ using their activation energy Ua. To determine the values of kp, we applied constant tension to a GUV membrane using the micropipette aspiration method and observed the rupture of GUVs, and then analyzed these data statistically. First, we investigated the temperature dependence of kp for GUVs of charged lipid membranes composed of negatively charged dioleoylphosphatidylglycerol (DOPG) and electrically neutral dioleoylphosphatidylcholine (DOPC). By analyzing this result, the values of Ua of tension-induced rupture of DOPG/DOPC-GUVs were obtained. Ua decreased with an increase in σ, supporting the classical theory of tension-induced pore formation. The analysis of the relationship between Ua and σ using the theory on the electrostatic interaction effects on the tension-induced rupture of GUVs provided the equation of Ua including electrostatic interaction effects, which well fits the experimental data of the tension dependence of Ua. A constant which does not depend on tension, U0, was also found to contribute significantly to Ua. The Arrhenius equations for kp using the equation of Ua and the parameters determined by the above analysis fit well to the experimental data of the tension dependence of kp for DOPG/DOPC-GUVs as well as for DOPC-GUVs. On the basis of these results, we discussed the possible elementary processes underlying the tension-induced rupture of GUVs of lipid membranes. These results indicate that the Arrhenius equation using the experimentally determined Ua is useful in the analysis of tension-induced rupture of GUVs.

Oxygen Sensing and Homeostasis

PubMed Central

Semenza, Gregg L.

2015-01-01

The discovery of carotid bodies as sensory receptors for detecting arterial blood oxygen levels, and the identification and elucidation of the roles of hypoxia-inducible factors (HIFs) in oxygen homeostasis have propelled the field of oxygen biology. This review highlights the gas-messenger signaling mechanisms associated with oxygen sensing, as well as transcriptional and non-transcriptional mechanisms underlying the maintenance of oxygen homeostasis by HIFs and their relevance to physiology and pathology. PMID:26328879

The oxygen status algorithm: a computer program for calculating and displaying pH and blood gas data.

PubMed

Siggaard-Andersen, O; Siggaard-Andersen, M

1990-01-01

Input parameters for the program are the arterial pH, pCO2, and pO2 (measured by a blood gas analyzer), oxygen saturation, carboxy-, met-, and total hemoglobin (measured by a multi-wavelength spectrometer), supplemented by patient age, sex, temperature, inspired oxygen fraction, fraction of fetal hemoglobin, and ambient pressure. Output parameters are the inspired and alveolar oxygen partial pressures, pH,pCO2 and pO2 referring to the actual patient temperature, estimated shunt fraction, half-saturation tension, estimated 2,3-diphosphoglycerate concentration, oxygen content and oxygen capacity, extracellular base excess, and plasma bicarbonate concentration. Three parameters related to the blood oxygen availability are calculated: the oxygen extraction tension, concentration of extractable oxygen, and oxygen compensation factor. Calculations of the 'reverse' type may also be performed so that the effect of therapeutic measures on the oxygen status or the acid-base status can be predicted. The user may choose among several different units of measurement and two different conventions for symbols. The results are presented in a data display screen comprising all quantities together with age, sex, and temperature adjusted reference values. The program generates a 'laboratory diagnosis' of the oxygen status and the acid-base status and three graphs illustrating the oxygen status and the acid-base status of the patient: the oxygen graph, the acid-base chart and the blood gas map. A printed summary in one A4 page including a graphical display can be produced with an Epson or HP Laser compatible printer. The program is primarily intended for routine laboratories with a blood gas analyzer combined with a multi-wavelength spectrometer. Calculating the derived quantities may enhance the usefulness of the analyzers and improve patient care. The program may also be used as a teaching aid in acid-base and respiratory physiology. The program requires an IBM PC, XT, AT or similar

Oxygen Generating Biomaterials Preserve Skeletal Muscle Homeostasis under Hypoxic and Ischemic Conditions

PubMed Central

Ward, Catherine L.; Corona, Benjamin T.; Yoo, James J.; Harrison, Benjamin S.; Christ, George J.

2013-01-01

Provision of supplemental oxygen to maintain soft tissue viability acutely following trauma in which vascularization has been compromised would be beneficial for limb and tissue salvage. For this application, an oxygen generating biomaterial that may be injected directly into the soft tissue could provide an unprecedented treatment in the acute trauma setting. The purpose of the current investigation was to determine if sodium percarbonate (SPO), an oxygen generating biomaterial, is capable of maintaining resting skeletal muscle homeostasis under otherwise hypoxic conditions. In the current studies, a biologically and physiologically compatible range of SPO (1–2 mg/mL) was shown to: 1) improve the maintenance of contractility and attenuate the accumulation of HIF1α, depletion of intramuscular glycogen, and oxidative stress (lipid peroxidation) that occurred following ∼30 minutes of hypoxia in primarily resting (duty cycle = 0.2 s train/120 s contraction interval <0.002) rat extensor digitorum longus (EDL) muscles in vitro (95% N2–5% CO2, 37°C); 2) attenuate elevations of rat EDL muscle resting tension that occurred during contractile fatigue testing (3 bouts of 25 100 Hz tetanic contractions; duty cycle = 0.2 s/2 s = 0.1) under oxygenated conditions in vitro (95% O2–5% CO2, 37°C); and 3) improve the maintenance of contractility (in vivo) and prevent glycogen depletion in rat tibialis anterior (TA) muscle in a hindlimb ischemia model (i.e., ligation of the iliac artery). Additionally, injection of a commercially available lipid oxygen-carrying compound or the components (sodium bicarbonate and hydrogen peroxide) of 1 mg/mL SPO did not improve EDL muscle contractility under hypoxic conditions in vitro. Collectively, these findings demonstrate that a biological and physiological concentration of SPO (1–2 mg/mL) injected directly into rat skeletal muscle (EDL or TA muscles) can partially preserve resting skeletal muscle homeostasis under

Nitroxyl (HNO) Reacts with Molecular Oxygen and Forms Peroxynitrite at Physiological pH

PubMed Central

Smulik, Renata; Dębski, Dawid; Zielonka, Jacek; Michałowski, Bartosz; Adamus, Jan; Marcinek, Andrzej; Kalyanaraman, Balaraman; Sikora, Adam

2014-01-01

Nitroxyl (HNO), the protonated one-electron reduction product of NO, remains an enigmatic reactive nitrogen species. Its chemical reactivity and biological activity are still not completely understood. HNO donors show biological effects different from NO donors. Although HNO reactivity with molecular oxygen is described in the literature, the product of this reaction has not yet been unambiguously identified. Here we report that the decomposition of HNO donors under aerobic conditions in aqueous solutions at physiological pH leads to the formation of peroxynitrite (ONOO−) as a major intermediate. We have specifically detected and quantified ONOO− with the aid of boronate probes, e.g. coumarin-7-boronic acid or 4-boronobenzyl derivative of fluorescein methyl ester. In addition to the major phenolic products, peroxynitrite-specific minor products of oxidation of boronate probes were detected under these conditions. Using the competition kinetics method and a set of HNO scavengers, the value of the second order rate constant of the HNO reaction with oxygen (k = 1.8 × 104 m−1 s−1) was determined. The rate constant (k = 2 × 104 m−1 s−1) was also determined using kinetic simulations. The kinetic parameters of the reactions of HNO with selected thiols, including cysteine, dithiothreitol, N-acetylcysteine, captopril, bovine and human serum albumins, and hydrogen sulfide, are reported. Biological and cardiovascular implications of nitroxyl reactions are discussed. PMID:25378389

[Several indicators of tissue oxygen during modeling of extravehicular activity of man].

PubMed

Lan'shina, O E; Loginov, V A; Akinfiev, A V; Kovalenko, E A

1995-01-01

Investigations of tissue oxygen indices during simulation of extravehicular activity (EVA) of cosmonauts demonstrated that breathing pure oxygen at approximately 280 mmHg elevates oxygen tension in capillary blood, and capillary-tissue gradient during physical work. Physical work alone stimulates tissue oxygenation due to, apparently, intensification of the processes of oxidative phosphorylation. The observed shifts in oxygen status reverse significantly within the first 5 min after completion of the experiment.

Surface tension in human pathophysiology and its application as a medical diagnostic tool

PubMed Central

Fathi-Azarbayjani, Anahita; Jouyban, Abolghasem

2015-01-01

Introduction: Pathological features of disease appear to be quite different. Despite this diversity, the common feature of various disorders underlies physicochemical and biochemical factors such as surface tension. Human biological fluids comprise various proteins and phospholipids which are capable of adsorption at fluid interfaces and play a vital role in the physiological function of human organs. Surface tension of body fluids correlates directly to the development of pathological states. Methods: In this review, the variety of human diseases mediated by the surface tension changes of biological phenomena and the failure of biological fluids to remain in their native state are discussed. Results: Dynamic surface tension measurements of human biological fluids depend on various parameters such as sex, age and changes during pregnancy or certain disease. It is expected that studies of surface tension behavior of human biological fluids will provide additional information and might become useful in medical practice. Theoretical background on surface tension measurement and surface tension values of reference fluids obtained from healthy and sick patients are depicted. Conclusion: It is well accepted that no single biomarker will be effective in clinical diagnosis. The surface tension measurement combined with routine lab tests may be a novel non-invasive method which can not only facilitate the discovery of diagnostic models for various diseases and its severity, but also be a useful tool for monitoring treatment efficacy. We therefore expect that studies of surface tension behavior of human biological fluids will provide additional useful information in medical practice. PMID:25901295

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen

PubMed Central

Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten; Lauritzen, Martin

2013-01-01

Glial calcium (Ca2+) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca2+ waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus loading with OGB-1/AM and SR101. We report that the occurrence of spontaneous waves is 20 times more frequent in the cerebellar cortex of aging as compared with adult mice, which correlated with a reduction in resting brain oxygen tension. In adult mice, spontaneous glial wave activity increased on reducing resting brain oxygen tension, and ATP-evoked glial waves reduced the tissue O2 tension. Finally, although spontaneous Purkinje cell (PC) activity was not associated with increased glia wave activity, spontaneous glial waves did affect intracellular Ca2+ activity in PCs. The increased wave activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology. PMID:23211964

Optoacoustic Monitoring of Physiologic Variables

PubMed Central

Esenaliev, Rinat O.

2017-01-01

Optoacoustic (photoacoustic) technique is a novel diagnostic platform that can be used for noninvasive measurements of physiologic variables, functional imaging, and hemodynamic monitoring. This technique is based on generation and time-resolved detection of optoacoustic (thermoelastic) waves generated in tissue by short optical pulses. This provides probing of tissues and individual blood vessels with high optical contrast and ultrasound spatial resolution. Because the optoacoustic waves carry information on tissue optical and thermophysical properties, detection, and analysis of the optoacoustic waves allow for measurements of physiologic variables with high accuracy and specificity. We proposed to use the optoacoustic technique for monitoring of a number of important physiologic variables including temperature, thermal coagulation, freezing, concentration of molecular dyes, nanoparticles, oxygenation, and hemoglobin concentration. In this review we present origin of contrast and high spatial resolution in these measurements performed with optoacoustic systems developed and built by our group. We summarize data obtained in vitro, in experimental animals, and in humans on monitoring of these physiologic variables. Our data indicate that the optoacoustic technology may be used for monitoring of cerebral blood oxygenation in patients with traumatic brain injury and in neonatal patients, central venous oxygenation monitoring, total hemoglobin concentration monitoring, hematoma detection and characterization, monitoring of temperature, and coagulation and freezing boundaries during thermotherapy. PMID:29311964

Optoacoustic Monitoring of Physiologic Variables.

PubMed

Esenaliev, Rinat O

2017-01-01

Optoacoustic (photoacoustic) technique is a novel diagnostic platform that can be used for noninvasive measurements of physiologic variables, functional imaging, and hemodynamic monitoring. This technique is based on generation and time-resolved detection of optoacoustic (thermoelastic) waves generated in tissue by short optical pulses. This provides probing of tissues and individual blood vessels with high optical contrast and ultrasound spatial resolution. Because the optoacoustic waves carry information on tissue optical and thermophysical properties, detection, and analysis of the optoacoustic waves allow for measurements of physiologic variables with high accuracy and specificity. We proposed to use the optoacoustic technique for monitoring of a number of important physiologic variables including temperature, thermal coagulation, freezing, concentration of molecular dyes, nanoparticles, oxygenation, and hemoglobin concentration. In this review we present origin of contrast and high spatial resolution in these measurements performed with optoacoustic systems developed and built by our group. We summarize data obtained in vitro , in experimental animals, and in humans on monitoring of these physiologic variables. Our data indicate that the optoacoustic technology may be used for monitoring of cerebral blood oxygenation in patients with traumatic brain injury and in neonatal patients, central venous oxygenation monitoring, total hemoglobin concentration monitoring, hematoma detection and characterization, monitoring of temperature, and coagulation and freezing boundaries during thermotherapy.

The Secretion of Oxygen into the Swim-bladder of Fish

PubMed Central

Wittenberg, Jonathan B.; Wittenberg, Beatrice A.

1961-01-01

Toadfish, Opsanus tau, L., were maintained in sea water equilibrated with gas mixtures containing a fixed proportion of oxygen and varying proportions of carbon monoxide. The swim-bladder was emptied by puncture, and, after an interval of 24 or 48 hours, the newly secreted gases were withdrawn and analyzed. Both carbon monoxide and oxygen are accumulated in the swim-bladder at tensions greater than ambient. The ratio of concentrations, carbon monoxide (secreted): carbon monoxide (administered) bears a constant relation to the ratio, oxygen (secreted): oxygen (administered). The value of the partition coefficient describing this relation is (α = 5.44). The two gases are considered to compete for a common intracellular carrier mediating their active transport. The suggestion is advanced that the intracellular oxygen carrier is a hemoglobin. Comparison of the proportions of carboxy- and oxyhemoglobin in the blood with the composition of the secreted gas proves that the secreted gases are not evolved directly from combination with blood hemoglobin. The suggestion is advanced that cellular oxygen secretion occurs in the rete mirabile: the rete may build up large oxygen tensions in the gas gland capillaries. It is suggested that the gas gland acts as a valve impeding back diffusion of gases from the swim-bladder. PMID:13786093

Oxygen and the spatial structure of microbial communities.

PubMed

Fenchel, Tom; Finlay, Bland

2008-11-01

Oxygen has two faces. On one side it is the terminal electron acceptor of aerobic respiration - the most efficient engine of energy metabolism. On the other hand, oxygen is toxic because the reduction of molecular O2 creates reactive oxygen species such as the superoxide anion, peroxide, and the hydroxyl radical. Probably most prokaryotes, and virtually all eukaryotes, depend on oxygen respiration, and we show that the ambiguous relation to oxygen is both an evolutionary force and a dominating factor driving functional interactions and the spatial structure of microbial communities.We focus on microbial communities that are specialised for life in concentration gradients of oxygen, where they acquire the full panoply of specific requirements from limited ranges of PO2, which also support the spatial organisation of microbial communities. Marine and lake sediments provide examples of steep O2 gradients, which arise because consumption or production of oxygen exceeds transport rates of molecular diffusion. Deep lakes undergo thermal stratification in warm waters, resulting in seasonal anaerobiosis below the thermocline, and lakes with a permanent pycnocline often have permanent anoxic deep water. The oxycline is here biologically similar to sediments, and it harbours similar microbial biota, the main difference being the spatial scale. In sediments, transport is dominated by molecular diffusion, and in the water column, turbulent mixing dominates vertical transport. Cell size determines the minimum requirement of aerobic organisms. For bacteria (and mitochondria), the half-saturation constant for oxygen uptake ranges within 0.05-0.1% atmospheric saturation; for the amoeba Acanthamoeba castellanii it is 0.2%, and for two ciliate species measuring around 150 microm, it is 1-2 % atmospheric saturation. Protection against O2 toxicity has an energetic cost that increases with increasing ambient O2 tension. Oxygen sensing seems universal in aquatic organisms. Many aspects

The effects of capillary transit time heterogeneity (CTH) on brain oxygenation

PubMed Central

Angleys, Hugo; Østergaard, Leif; Jespersen, Sune N

2015-01-01

We recently extended the classic flow–diffusion equation, which relates blood flow to tissue oxygenation, to take capillary transit time heterogeneity (CTH) into account. Realizing that cerebral oxygen availability depends on both cerebral blood flow (CBF) and capillary flow patterns, we have speculated that CTH may be actively regulated and that changes in the capillary morphology and function, as well as in blood rheology, may be involved in the pathogenesis of conditions such as dementia and ischemia-reperfusion injury. The first extended flow–diffusion equation involved simplifying assumptions which may not hold in tissue. Here, we explicitly incorporate the effects of oxygen metabolism on tissue oxygen tension and extraction efficacy, and assess the extent to which the type of capillary transit time distribution affects the overall effects of CTH on flow–metabolism coupling reported earlier. After incorporating tissue oxygen metabolism, our model predicts changes in oxygen consumption and tissue oxygen tension during functional activation in accordance with literature reports. We find that, for large CTH values, a blood flow increase fails to cause significant improvements in oxygen delivery, and can even decrease it; a condition of malignant CTH. These results are found to be largely insensitive to the choice of the transit time distribution. PMID:25669911

Benefits of 21% Oxygen Compared with 100% Oxygen for Delivery of Isoflurane to Mice (Mus musculus) and Rats (Rattus norvegicus)

PubMed Central

Wilding, Laura A; Hampel, Joe A; Khoury, Basma M; Kang, Stacey; Machado‑Aranda, David; Raghavendran, Krishnan; Nemzek, Jean A

2017-01-01

At research institutions, isoflurane delivered by precision vaporizer to a face mask is the standard for rodent surgery and for procedures with durations that exceed a few minutes. Pure oxygen is often used as the carrier gas for isoflurane anesthesia, despite documented complications from long-term 100% oxygen use in humans and known occupational safety risks. We therefore examined the effect of anesthetic delivery gas on physiologic variables in mice and rats. Rodents were anesthetized for 60 min with isoflurane delivered in either 21% or 100% oxygen by means of a nose cone. We noted no difference between carrier gasses in physiologic variables in mice, including body temperature, respiratory rate, mean arterial pressure, surgical recovery time, pH, or PaCO2.However, blood gas analysis revealed evidence of a ventilation–perfusion mismatch in the 100% oxygen group. Pressure–volume hysteresis and histomorphometric analyses confirmed the presence of increased atelectasis in mice that received 100% oxygen. Unlike mice, rats that received isoflurane in 100% oxygen had acute respiratory acidosis and elevated mean arterial pressure, but atelectasis was similar between carrier gasses. Our data suggest that both 100% and 21% oxygen are acceptable for the delivery of isoflurane to mice. However, mice anesthetized for studies focused on lung physiology or architecture would benefit from the delivery of isoflurane in 21% oxygen to reduce absorption atelectasis and the potential associated downstream inflammatory effects. For rats, delivery of isoflurane in 21% and 100% oxygen both caused perturbations in physiologic variables, and choosing a carrier gas is not straightforward. PMID:28315643

Long-term and acute effects of temperature and oxygen on metabolism, food intake, growth and heat tolerance in a freshwater gastropod.

PubMed

Hoefnagel, K Natan; Verberk, Wilco C E P

2017-08-01

Temperature affects the physiology and life-history of ectothermic animals, often increasing metabolic rate and decreasing body size. Oxygen limitation has been put forward as a mechanism to explain thermal responses of body size and the ability to survive stress. However the time-scales involved in growth performance and heat tolerance differ radically. In order to increase our understanding of oxygen and temperature effects on body size and heat tolerance and the time scale involved, we reared Lymnaea stagnalis under six combinations of temperature and oxygen tension from hatching up to an age of 300 days and recorded shell length during this whole period. At the end of this period, we determined scope for growth by measuring food intake rate, assimilation efficiency, respiration rate and ammonium excretion rate at two different temperatures. We also measured the snails' ability to survive heat stress (CTmax), both at normoxia and hypoxia. We found that scope for growth and long term growth performance were much more affected by interactions of chronic oxygen and temperature conditions during rearing than by acute conditions during testing. Furthermore, our study shows that individual variation in growth performance can be traced back to individual differences in rates of food and oxygen consumption. Developmental acclimation also gave rise to differences in CTmax, but these were relatively small and were only expressed when CTmax was tested under hypoxia. The large effects of rearing oxygen conditions on growth and other physiological rates compared to modest effects of test oxygen conditions on CTmax suggest that small effects of hypoxia on the short term (e.g. heat tolerance) may nevertheless have large repercussions on the long term (e.g. growth and reproduction), even in a pulmonate snail that can compensate for hypoxia to some extent by aerial respiration. Copyright © 2016 Elsevier Ltd. All rights reserved.

Review: correlations between oxygen affinity and sequence classifications of plant hemoglobins.

PubMed

Smagghe, Benoit J; Hoy, Julie A; Percifield, Ryan; Kundu, Suman; Hargrove, Mark S; Sarath, Gautam; Hilbert, Jean-Louis; Watts, Richard A; Dennis, Elizabeth S; Peacock, W James; Dewilde, Sylvia; Moens, Luc; Blouin, George C; Olson, John S; Appleby, Cyril A

2009-12-01

Plants express three phylogenetic classes of hemoglobins (Hb) based on sequence analyses. Class 1 and 2 Hbs are full-length globins with the classical eight helix Mb-like fold, whereas Class 3 plant Hbs resemble the truncated globins found in bacteria. With the exception of the specialized leghemoglobins, the physiological functions of these plant hemoglobins remain unknown. We have reviewed and, in some cases, measured new oxygen binding properties of a large number of Class 1 and 2 plant nonsymbiotic Hbs and leghemoglobins. We found that sequence classification correlates with distinct extents of hexacoordination with the distal histidine and markedly different overall oxygen affinities and association and dissociation rate constants. These results suggest strong selective pressure for the evolution of distinct physiological functions. The leghemoglobins evolved from the Class 2 globins and show no hexacoordination, very high rates of O(2) binding ( approximately 250 muM(-1) s(-1)), moderately high rates of O(2) dissociation ( approximately 5-15 s(-1)), and high oxygen affinity (K(d) or P(50) approximately 50 nM). These properties both facilitate O(2) diffusion to respiring N(2) fixing bacteria and reduce O(2) tension in the root nodules of legumes. The Class 1 plant Hbs show weak hexacoordination (K(HisE7) approximately 2), moderate rates of O(2) binding ( approximately 25 muM(-1) s(-1)), very small rates of O(2) dissociation ( approximately 0.16 s(-1)), and remarkably high O(2) affinities (P(50) approximately 2 nM), suggesting a function involving O(2) and nitric oxide (NO) scavenging. The Class 2 Hbs exhibit strong hexacoordination (K(HisE7) approximately 100), low rates of O(2) binding ( approximately 1 muM(-1) s(-1)), moderately low O(2) dissociation rate constants ( approximately 1 s(-1)), and moderate, Mb-like O(2) affinities (P(50) approximately 340 nM), perhaps suggesting a sensing role for sustained low, micromolar levels of oxygen.

A Threshold in Phanerozoic Oxygen Concentrations: Evidence from Carbonate Sediment Color and Physiological Requirements of Marine Fauna

NASA Astrophysics Data System (ADS)

Sugla, R.; Norris, R. D.; Lyakov, J.

2017-12-01

In his book The Nature of the Stratigraphical Record, Derek Ager made the remarkable observation that the geologic eras of the Phanerozoic could be identified by coloration patterns of carbonate sediments in outcrops. This observation, however, was never quantified nor explained by Ager. Here, we present a record of spectral reflectance of carbonate sediments collected from sections worldwide. While sediment color is governed by many factors, global and abrupt shifts in sediment color across depositional envrionments observed here may represent a shift towards rising oxygen concentrations. Such a shift would explain changes in redox state of iron or organic matter concentrations, both factors which influence sediment color. This record is combined with a simple model of physiological requirements of marine fauna in order to infer a minimum pO2 in the atmosphere to support life. Results indicate a strong threshold change in the Earth system near the Triassic-Jurassic boundary, potentially reflecting rising atmospheric oxygen concentrations not previously recorded.

Modified Veress needle decompression of tension pneumothorax: a randomized crossover animal study.

PubMed

Lubin, Dafney; Tang, Andrew L; Friese, Randall S; Martin, Matthew; Green, D J; Jones, Trevor; Means, Russell R; Ginwalla, Rashna; O'Keeffe, Terence S; Joseph, Bellal A; Wynne, Julie L; Kulvatunyou, Narong; Vercruysse, Gary; Gries, Lynn; Rhee, Peter

2013-12-01

The current prehospital standard of care using a large bore intravenous catheter for tension pneumothorax (tPTX) decompression is associated with a high failure rate. We developed a modified Veress needle (mVN) for this condition. The purpose of this study was to evaluate the effectiveness and safety of the mVN as compared with a 14-gauge needle thoracostomy (NT) in a swine tPTX model. tPTX was created in 16 adult swine via thoracic CO2 insufflation to 15 mm Hg. After tension physiology was achieved, defined as a 50% reduction of cardiac output, the swine were randomized to undergo either mVN or NT decompression. Failure to restore 80% baseline systolic blood pressure within 5 minutes resulted in crossover to the alternate device. The success rate of each device, death, and need for crossover were analyzed using χ. Forty-three tension events were created in 16 swine (24 mVN, 19 NT) at 15 mm Hg of intrathoracic pressure with a mean CO2 volume of 3.8 L. tPTX resulted in a 48% decline of systolic blood pressure from baseline and 73% decline of cardiac output, and 42% had equalization of central venous pressure with pulmonary capillary wedge pressure. All tension events randomized to mVN were successfully rescued within a mean (SD) of 70 (86) seconds. NT resulted in four successful decompressions (21%) within a mean (SD) of 157 (96) seconds. Four swine (21%) died within 5 minutes of NT decompression. The persistent tension events where the swine survived past 5 minutes (11 of 19 NTs) underwent crossover mVN decompression, yielding 100% rescue. Neither the mVN nor the NT was associated with inadvertent injuries to the viscera. Thoracic insufflation produced a reliable and highly reproducible model of tPTX. The mVN is vastly superior to NT for effective and safe tPTX decompression and physiologic recovery. Further research should be invested in the mVN for device refinement and replacement of NT in the field.

Coulomb string tension, asymptotic string tension, and the gluon chain

DOE PAGES

Greensite, Jeff; Szczepaniak, Adam P.

2015-02-01

We compute, via numerical simulations, the non-perturbative Coulomb potential and position-space ghost propagator in pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

Functional importance of blood flow dynamics and partial oxygen pressure in the anterior pituitary.

PubMed

Schaeffer, Marie; Hodson, David J; Lafont, Chrystel; Mollard, Patrice

2010-12-01

The pulsatile release of hormone is obligatory for the control of a range of important body homeostatic functions. To generate these pulses, endocrine organs have developed finely regulated mechanisms to modulate blood flow both to meet the metabolic demand associated with intense endocrine cell activity and to ensure the temporally precise uptake of secreted hormone into the bloodstream. With a particular focus on the pituitary gland as a model system, we review here the importance of the interplay between blood flow regulation and oxygen tensions in the functioning of endocrine systems, and the known regulatory signals involved in the modification of flow patterns under both normal physiological and pathological conditions. © 2010 The Authors. European Journal of Neuroscience © 2010 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Biofeedback for Developing Self-Control of Tension and Stress in One's Hierarchy of Psychological States.

ERIC Educational Resources Information Center

Cassel, Russell

1985-01-01

Describes six stage hierarchial patterns in the development of self-control through biofeedback. The stages include Skeletal and Striated Muscle Tension; Visceral Involvement-Anxiety Neuroses; Chronic Physiological Dysfunctioning; Decision Making Competency; Twilight Learning-Permissive Concentration; and Autogenic Feedback Training. (BL)

Breast tumor oxygenation in response to carbogen intervention assessed simultaneously by three oxygen-sensitive parameters

NASA Astrophysics Data System (ADS)

Gu, Yueqing; Bourke, Vincent; Kim, Jae Gwan; Xia, Mengna; Constantinescu, Anca; Mason, Ralph P.; Liu, Hanli

2003-07-01

Three oxygen-sensitive parameters (arterial hemoglobin oxygen saturation SaO2, tumor vascular oxygenated hemoglobin concentration [HbO2], and tumor oxygen tension pO2) were measured simultaneously by three different optical techniques (pulse oximeter, near infrared spectroscopy, and FOXY) to evaluate dynamic responses of breast tumors to carbogen (5% CO2 and 95% O2) intervention. All three parameters displayed similar trends in dynamic response to carbogen challenge, but with different response times. These response times were quantified by the time constants of the exponential fitting curves, revealing the immediate and the fastest response from the arterial SaO2, followed by changes in global tumor vascular [HbO2], and delayed responses for pO2. The consistency of the three oxygen-sensitive parameters demonstrated the ability of NIRS to monitor therapeutic interventions for rat breast tumors in-vivo in real time.

Unintended inhalation of nitric oxide by contamination of compressed air: physiologic effects and interference with intended nitric oxide inhalation in acute lung injury.

PubMed

Benzing, A; Loop, T; Mols, G; Geiger, K

1999-10-01

Compressed air from a hospital's central gas supply may contain nitric oxide as a result of air pollution. Inhaled nitric oxide may increase arterial oxygen tension and decrease pulmonary vascular resistance in patients with acute lung injury and acute respiratory distress syndrome. Therefore, the authors wanted to determine whether unintentional nitric oxide inhalation by contamination of compressed air influences arterial oxygen tension and pulmonary vascular resistance and interferes with the therapeutic use of nitric oxide. Nitric oxide concentrations in the compressed air of a university hospital were measured continuously by chemiluminescence during two periods (4 and 2 weeks). The effects of unintended nitric oxide inhalation on arterial oxygen tension (n = 15) and on pulmonary vascular resistance (n = 9) were measured in patients with acute lung injury and acute respiratory distress syndrome by changing the source of compressed air of the ventilator from the hospital's central gas supply to a nitric oxide-free gas tank containing compressed air. In five of these patients, the effects of an additional inhalation of 5 ppm nitric oxide were evaluated. During working days, compressed air of the hospital's central gas supply contained clinically effective nitric oxide concentrations (> 80 parts per billion) during 40% of the time. Change to gas tank-supplied nitric oxide-free compressed air decreased the arterial oxygen tension by 10% and increased pulmonary vascular resistance by 13%. The addition of 5 ppm nitric oxide had a minimal effect on arterial oxygen tension and pulmonary vascular resistance when added to hospital-supplied compressed air but improved both when added to tank-supplied compressed air. Unintended inhalation of nitric oxide increases arterial oxygen tension and decreases pulmonary vascular resistance in patients with acute lung injury and acute respiratory distress syndrome. The unintended nitric oxide inhalation interferes with the

Safety, reliability, and validity of a physiologic definition of bronchopulmonary dysplasia.

PubMed

Walsh, Michele C; Wilson-Costello, Deanna; Zadell, Arlene; Newman, Nancy; Fanaroff, Avroy

2003-09-01

Bronchopulmonary dysplasia (BPD) is the focus of many intervention trials, yet the outcome measure when based solely on oxygen administration may be confounded by differing criteria for oxygen administration between physicians. Thus, we wished to define BPD by a standardized oxygen saturation monitoring at 36 weeks corrected age, and compare this physiologic definition with the standard clinical definition of BPD based solely on oxygen administration. A total of 199 consecutive very low birthweight infants (VLBW, 501 to 1500 g birthweight) were assessed prospectively at 36+/-1 weeks corrected age. Neonates on positive pressure support or receiving >30% supplemental oxygen were assigned the outcome BPD. Those receiving < or =30% oxygen underwent a stepwise 2% reduction in supplemental oxygen to room air while under continuous observation and oxygen saturation monitoring. Outcomes of the test were "no BPD" (saturations > or =88% for 60 minutes) or "BPD" (saturation < 88%). At the conclusion of the test, all infants were returned to their baseline oxygen. Safety (apnea, bradycardia, increased oxygen use), inter-rater reliability, test-retest reliability, and validity of the physiologic definition vs the clinical definition were assessed. A total of 199 VLBW were assessed, of whom 45 (36%) were diagnosed with BPD by the clinical definition of oxygen use at 36 weeks corrected age. The physiologic definition identified 15 infants treated with oxygen who successfully passed the saturation monitoring test in room air. The physiologic definition diagnosed BPD in 30 (24%) of the cohort. All infants were safely studied. The test was highly reliable (inter-rater reliability, kappa=1.0; test-retest reliability, kappa=0.83) and highly correlated with discharge home in oxygen, length of hospital stay, and hospital readmissions in the first year of life. The physiologic definition of BPD is safe, feasible, reliable, and valid and improves the precision of the diagnosis of BPD

Macrophages Under Low Oxygen Culture Conditions Respond to Ion Parametric Resonance Magnetic Fields

EPA Science Inventory

Macrophages, when entering inflamed tissue, encounter low oxygen tension due to the impairment of blood supply and/or the massive infiltration of cells that consume oxygen. Previously, we showed that such macrophages release more bacteriotoxic hydrogen peroxide (H202) when expose...

Macrophages Under Low Oxygen Culture ConditionsRespond to Ion Parametric Resonance Magnetic Fields

EPA Science Inventory

Macrophages, when entering inflamed tissue, encounter low oxygen tension due to the impairment of blood supply and/or the massive infiltration of cells that consume oxygen. Previously, we showed that such macrophages release more bacteriotoxic hydrogen peroxide (H202) when expose...

OXYGEN DISSOCIATION OF WHOLE BLOOD STUDIED POLAROGRAPHICALLY

PubMed Central

Markus, Gabor; Baumberger, J. Percy

1952-01-01

The polarographic current of whole blood is in excess of that given by plasma at the same oxygen tension. The magnitude of this difference depends on (a) the oxygen content of the sample and thus is determined by the red blood cell content and by the state of oxygen saturation of hemoglobin, and (b) on the rate of dissociation of oxyhemoglobin and therefore is influenced by changes in pH, pCO2, and temperature. The total current at 37°C. is proportional to the oxygen content of the sample and can be used to determine the latter. The theoretical basis of the studied phenomena is discussed in detail. PMID:13011281

An integrated physiology model to study regional lung damage effects and the physiologic response

PubMed Central

2014-01-01

Background This work expands upon a previously developed exercise dynamic physiology model (DPM) with the addition of an anatomic pulmonary system in order to quantify the impact of lung damage on oxygen transport and physical performance decrement. Methods A pulmonary model is derived with an anatomic structure based on morphometric measurements, accounting for heterogeneous ventilation and perfusion observed experimentally. The model is incorporated into an existing exercise physiology model; the combined system is validated using human exercise data. Pulmonary damage from blast, blunt trauma, and chemical injury is quantified in the model based on lung fluid infiltration (edema) which reduces oxygen delivery to the blood. The pulmonary damage component is derived and calibrated based on published animal experiments; scaling laws are used to predict the human response to lung injury in terms of physical performance decrement. Results The augmented dynamic physiology model (DPM) accurately predicted the human response to hypoxia, altitude, and exercise observed experimentally. The pulmonary damage parameters (shunt and diffusing capacity reduction) were fit to experimental animal data obtained in blast, blunt trauma, and chemical damage studies which link lung damage to lung weight change; the model is able to predict the reduced oxygen delivery in damage conditions. The model accurately estimates physical performance reduction with pulmonary damage. Conclusions We have developed a physiologically-based mathematical model to predict performance decrement endpoints in the presence of thoracic damage; simulations can be extended to estimate human performance and escape in extreme situations. PMID:25044032

Intravenous oxygen: a novel method of oxygen delivery in hypoxemic respiratory failure?

PubMed

Gehlbach, Jonathan A; Rehder, Kyle J; Gentile, Michael A; Turner, David A; Grady, Daniel J; Cheifetz, Ira M

2017-01-01

Hypoxemic respiratory failure is a common problem in critical care. Current management strategies, including mechanical ventilation and extracorporeal membranous oxygenation, can be efficacious but these therapies put patients at risk for toxicities associated with invasive forms of support. Areas covered: In this manuscript, we discuss intravenous oxygen (IVO 2 ), a novel method to improve oxygen delivery that involves intravenous administration of a physiologic solution containing dissolved oxygen at hyperbaric concentrations. After a brief review of the physiology behind supersaturated fluids, we summarize the current evidence surrounding IVO 2 . Expert commentary: Although not yet at the stage of clinical testing in the United States and Europe, IVO 2 has been used safely in Asia. Furthermore, preliminary laboratory data have been encouraging, suggesting that IVO 2 may play a role in the management of patients with hypoxemic respiratory failure in years to come. However, significantly more work needs to be done, including definitive evidence that such a therapy is safe, before it can be included in an intensivist's arsenal for hypoxemic respiratory failure.

Losartan does not decrease renal oxygenation and norepinephrine effects in rats after resuscitated haemorrhage.

PubMed

Jönsson, Sofia; Melville, Jacqueline M; Becirovic-Agic, Mediha; Hultström, Michael

2018-04-18

Renin-angiotensin-system blockers are thought to increase the risk of acute kidney injury after surgery and haemorrhage. We found that Losartan does not cause renal cortical hypoxia after haemorrhage in rats because of decreased renal vascular resistance, but did not evaluate resuscitation. Study Losartan´s effect on renal cortical and medullary oxygenation, and norepinephrine´s vasopressor effect in a model of resuscitated haemorrhage. After seven days Losartan (60 mg/kg/day) or control treatment, male Wistar rats were haemorrhaged 20 % of the blood volume and resuscitated with Ringer's Acetate. Mean arterial pressure, renal blood flow, and kidney tissue oxygenation was measured at baseline and after resuscitation. Finally, the effect of norepinephrine on mean arterial pressure and renal blood flow was investigated. As expected, Losartan lowered mean arterial pressure but not renal blood flow. Losartan did not affect renal oxygen consumption and oxygen tension. Mean arterial pressure and renal blood flow were lower after resuscitated haemorrhage. Smaller increase of renal vascular resistance in Losartan group translated to smaller decrease in cortical oxygen tension, but no significant difference seen in medullary oxygen tension either between groups or after haemorrhage. The effect of norepinephrine on mean arterial pressure and renal blood flow was similar in controls and Losartan treated rats. Losartan does not decrease renal oxygenation after resuscitated haemorrhage because of a smaller increase in renal vascular resistance. Further, Losartan does not decrease the efficiency of norepinephrine as a vasopressor indicating that blood pressure may be managed effectively during Losartan treatment.

Oxygen environment and islet size are the primary limiting factors of isolated pancreatic islet survival

PubMed Central

Komatsu, Hirotake; Cook, Colin; Wang, Chia-Hao; Medrano, Leonard; Lin, Henry; Kandeel, Fouad; Tai, Yu-Chong; Mullen, Yoko

2017-01-01

Background Type 1 diabetes is an autoimmune disease that destroys insulin-producing beta cells in the pancreas. Pancreatic islet transplantation could be an effective treatment option for type 1 diabetes once several issues are resolved, including donor shortage, prevention of islet necrosis and loss in pre- and post-transplantation, and optimization of immunosuppression. This study seeks to determine the cause of necrotic loss of isolated islets to improve transplant efficiency. Methodology The oxygen tension inside isolated human islets of different sizes was simulated under varying oxygen environments using a computational in silico model. In vitro human islet viability was also assessed after culturing in different oxygen conditions. Correlation between simulation data and experimentally measured islet viability was examined. Using these in vitro viability data of human islets, the effect of islet diameter and oxygen tension of the culture environment on islet viability was also analyzed using a logistic regression model. Principal findings Computational simulation clearly revealed the oxygen gradient inside the islet structure. We found that oxygen tension in the islet core was greatly lower (hypoxic) than that on the islet surface due to the oxygen consumption by the cells. The hypoxic core was expanded in the larger islets or in lower oxygen cultures. These findings were consistent with results from in vitro islet viability assays that measured central necrosis in the islet core, indicating that hypoxia is one of the major causes of central necrosis. The logistic regression analysis revealed a negative effect of large islet and low oxygen culture on islet survival. Conclusions/Significance Hypoxic core conditions, induced by the oxygen gradient inside islets, contribute to the development of central necrosis of human isolated islets. Supplying sufficient oxygen during culture could be an effective and reasonable method to maintain isolated islets viable

Evolution of air breathing: oxygen homeostasis and the transitions from water to land and sky.

PubMed

Hsia, Connie C W; Schmitz, Anke; Lambertz, Markus; Perry, Steven F; Maina, John N

2013-04-01

Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems for acquiring oxygen from the environment. Ambient oxygen tension (PO2) fluctuated through the ages in correlation with biodiversity and body size, enabling organisms to migrate from water to land and air and sometimes in the opposite direction. Habitat expansion compels the use of different gas exchangers, for example, skin, gills, tracheae, lungs, and their intermediate stages, that may coexist within the same species; coexistence may be temporally disjunct (e.g., larval gills vs. adult lungs) or simultaneous (e.g., skin, gills, and lungs in some salamanders). Disparate systems exhibit similar directions of adaptation: toward larger diffusion interfaces, thinner barriers, finer dynamic regulation, and reduced cost of breathing. Efficient respiratory gas exchange, coupled to downstream convective and diffusive resistances, comprise the "oxygen cascade"-step-down of PO2 that balances supply against toxicity. Here, we review the origin of oxygen homeostasis, a primal selection factor for all respiratory systems, which in turn function as gatekeepers of the cascade. Within an organism's lifespan, the respiratory apparatus adapts in various ways to upregulate oxygen uptake in hypoxia and restrict uptake in hyperoxia. In an evolutionary context, certain species also become adapted to environmental conditions or habitual organismic demands. We, therefore, survey the comparative anatomy and physiology of respiratory systems from invertebrates to vertebrates, water to air breathers, and terrestrial to aerial inhabitants. Through the evolutionary directions and variety of gas exchangers, their shared features and individual compromises may be appreciated.

Evolution of Air Breathing: Oxygen Homeostasis and the Transitions from Water to Land and Sky

PubMed Central

Hsia, Connie C. W.; Schmitz, Anke; Lambertz, Markus; Perry, Steven F.; Maina, John N.

2014-01-01

Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems for acquiring oxygen from the environment. Ambient oxygen tension (PO2) fluctuated through the ages in correlation with biodiversity and body size, enabling organisms to migrate from water to land and air and sometimes in the opposite direction. Habitat expansion compels the use of different gas exchangers, for example, skin, gills, tracheae, lungs, and their intermediate stages, that may coexist within the same species; coexistence may be temporally disjunct (e.g., larval gills vs. adult lungs) or simultaneous (e.g., skin, gills, and lungs in some salamanders). Disparate systems exhibit similar directions of adaptation: toward larger diffusion interfaces, thinner barriers, finer dynamic regulation, and reduced cost of breathing. Efficient respiratory gas exchange, coupled to downstream convective and diffusive resistances, comprise the “oxygen cascade”—step-down of PO2 that balances supply against toxicity. Here, we review the origin of oxygen homeostasis, a primal selection factor for all respiratory systems, which in turn function as gatekeepers of the cascade. Within an organism's lifespan, the respiratory apparatus adapts in various ways to upregulate oxygen uptake in hypoxia and restrict uptake in hyperoxia. In an evolutionary context, certain species also become adapted to environmental conditions or habitual organismic demands. We, therefore, survey the comparative anatomy and physiology of respiratory systems from invertebrates to vertebrates, water to air breathers, and terrestrial to aerial inhabitants. Through the evolutionary directions and variety of gas exchangers, their shared features and individual compromises may be appreciated. PMID:23720333

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

PubMed

A Abdel-Rahman, Engy; Mahmoud, Ali M; Khalifa, Abdulrahman M; Ali, Sameh S

2016-08-15

Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Relative stability of tension band versus two-cortex screw fixation for treating fifth metatarsal base avulsion fractures.

PubMed

Husain, Z S; DeFronzo, D J

2000-01-01

This study assesses the strength of fixating avulsion fractures of the fifth metatarsal base with a 4.0-mm partially threaded cancellous screw crossing two cortices as compared to tension banding. Our data showed statistically significant fixation strength improvement over tension banding for avulsion fractures (p < 0.02) in both polystyrene foam models and fresh, nonpreserved frozen cadaveric samples. In cadavers, the screw fixations were able to withstand more than three times the load sustained by the tension band fixations. The study utilized the Instron 8500 tensiometer to apply physiologic loads to test the constructs until failure. The displacement and load data at failure show the limitations of both fixations. By increasing the load resistance while maintaining compression, the bicortical cancellous screw fixation created greater stability at the avulsion fracture of the fifth metatarsal base as compared to tension band stabilization.

Human Cells Cultured under Physiological Oxygen Utilize Two Cap-binding Proteins to recruit Distinct mRNAs for Translation*

PubMed Central

Timpano, Sara; Uniacke, James

2016-01-01

Translation initiation is a focal point of translational control and requires the binding of eIF4E to the 5′ cap of mRNA. Under conditions of extreme oxygen depletion (hypoxia), human cells repress eIF4E and switch to an alternative cap-dependent translation mediated by a homolog of eIF4E, eIF4E2. This homolog forms a complex with the oxygen-regulated hypoxia-inducible factor 2α and can escape translation repression. This complex mediates cap-dependent translation under cell culture conditions of 1% oxygen (to mimic tumor microenvironments), whereas eIF4E mediates cap-dependent translation at 21% oxygen (ambient air). However, emerging evidence suggests that culturing cells in ambient air, or “normoxia,” is far from physiological or “normal.” In fact, oxygen in human tissues ranges from 1–11% or “physioxia.” Here we show that two distinct modes of cap-dependent translation initiation are active during physioxia and act on separate pools of mRNAs. The oxygen-dependent activities of eIF4E and eIF4E2 are elucidated by observing their polysome association and the status of mammalian target of rapamycin complex 1 (eIF4E-dependent) or hypoxia-inducible factor 2α expression (eIF4E2-dependent). We have identified oxygen conditions where eIF4E is the dominant cap-binding protein (21% normoxia or standard cell culture conditions), where eIF4E2 is the dominant cap-binding protein (1% hypoxia or ischemic diseases and cancerous tumors), and where both cap-binding proteins act simultaneously to initiate the translation of distinct mRNAs (1–11% physioxia or during development and stem cell differentiation). These data suggest that the physioxic proteome is generated by initiating translation of mRNAs via two distinct but complementary cap-binding proteins. PMID:27002144

Effects of Cyanate and 2,3-Diphosphoglycerate on Sickling RELATIONSHIP TO OXYGENATION

PubMed Central

Jensen, Michael; Bunn, H. Franklin; Halikas, George; Kan, Yuet Wai; Nathan, David G.

1973-01-01

Cyanate and 2,3-diphosphoglycerate (2,3-DPG) both influence the oxygen affinity of hemoglobin. The studies presented here concern the effects of these compounds on the sickling phenomenon. The inhibitory effect of cyanate on sickling is largely due to the fact that it increases the percentage of oxyhemoglobin S at a given oxygen tension. In addition, cyanate inhibits sickling by a mechanism that is independent of oxygenation. In this paper, we have demonstrated that the viscosity of carbamylated sickle blood was lower than that of non-carbamylated controls at the same oxygen saturation. Furthermore, carbamylation resulted in an increase in the minimum concentration of deoxy-sickle hemoglobin required for gelation. Like cyanate, 2,3-DPG affected sickling of intact erythrocytes by two mechanisms. Since 2,3-DPG decreases the percentage of oxyhemoglobin S at a given oxygen tension, sickling is enhanced. In addition, 2,3-DPG had a direct effect. When the intracellular 2,3-DPG concentration was increased in vitro, a greater percentage of cells were sickled at a given oxygen saturation. Conversely, sickling was inhibited in cells in which 2,3-DPG was artificially lowered. These data indicate that the enhancement of sickling by 2,3-DPG is in part independent of its influence on oxygen affinity. PMID:4729047

Metabolic physiology of the Humboldt squid, Dosidicus gigas: Implications for vertical migration in a pronounced oxygen minimum zone

NASA Astrophysics Data System (ADS)

Rosa, Rui; Seibel, Brad A.

2010-07-01

The Humboldt (or jumbo) squid, Dosidicus gigas, is an active predator endemic to the Eastern Pacific that undergoes diel vertical migrations into a pronounced oxygen minimum layer (OML). Here, we investigate the physiological mechanisms that facilitate these migrations and assess the associated costs and benefits. Exposure to hypoxic conditions equivalent to those found in the OML (∼10 μM O 2 at 10 °C) led to a significant reduction in the squid’s routine metabolic rate (RMR), from 8.9 to 1.6 μmol O 2 g -1 h -1 ( p < 0.05), and a concomitant increase in mantle muscle octopine levels (from 0.50 to 5.24 μmol g -1 tissue, p < 0.05). Enhanced glycolitic ATP production accounted for only 7.0% and 2.8% at 10 °C and 20 °C, respectively, of the energy deficit that resulted from the decline in aerobic respiration. The observed metabolic suppression presumably extends survival time in the OML by conserving the finite stores of fermentable substrate and avoiding the accumulation of the deleterious anaerobic end products in the tissues. RMR increased significantly with temperature ( p < 0.05), from 8.9 (at 10 °C) to 49.85 μmol O 2 g -1 h -1 (at 25 °C) which yielded a Q10 of 2.0 between 10 and 20 °C and 7.9 between 20 and 25 °C ( p < 0.05). These results suggest that 25 °C, although within the normal surface temperature range in the Gulf of California, is outside this species’ normal temperature range. By following the scattering layer into oxygen-enriched shallow water at night, D. gigas may repay any oxygen debt accumulated during the daytime. The dive to deeper water may minimize exposure to stressful surface temperatures when most prey have migrated to depth during the daytime. The physiological and ecological strategies demonstrated here may have facilitated the recent range expansion of this species into northern waters where expanding hypoxic zones prohibit competing top predators.

Physiology of Oxygen Breathing in Pilots: A Brief Review

DTIC Science & Technology

2018-03-23

brief review Abstract This non-exhaustive survey presents literature describing some effects of breathing oxygen partial pressures between...CG, J Butler, AB DuBois (1959). Some effects of restriction of chest cage expansion on pulmonary function in man: an experimental study. J Clin...Effects of Submerged Breathing of Air or Oxygen. Navy Experimental Diving Unit TR 02-14, Panama City, FL. http://archive.rubicon- foundation.org/3483

Surface tension phenomena in the xylem sap of three diffuse porous temperate tree species

Treesearch

K. K. Christensen-Dalsgaard; M. T. Tyree; P. G. Mussone

2011-01-01

In plant physiology models involving bubble nucleation, expansion or elimination, it is typically assumed that the surface tension of xylem sap is equal to that of pure water, though this has never been tested. In this study we collected xylem sap from branches of the tree species Populus tremuloides, Betula papyrifera and Sorbus...

Impacts of nitric oxide and superoxide on renal medullary oxygen transport and urine concentration.

PubMed

Fry, Brendan C; Edwards, Aurélie; Layton, Anita T

2015-05-01

The goal of this study was to investigate the reciprocal interactions among oxygen (O2), nitric oxide (NO), and superoxide (O2 (-)) and their effects on medullary oxygenation and urinary output. To accomplish that goal, we developed a detailed mathematical model of solute transport in the renal medulla of the rat kidney. The model represents the radial organization of the renal tubules and vessels, which centers around the vascular bundles in the outer medulla and around clusters of collecting ducts in the inner medulla. Model simulations yield significant radial gradients in interstitial fluid oxygen tension (Po2) and NO and O2 (-) concentration in the OM and upper IM. In the deep inner medulla, interstitial fluid concentrations become much more homogeneous, as the radial organization of tubules and vessels is not distinguishable. The model further predicts that due to the nonlinear interactions among O2, NO, and O2 (-), the effects of NO and O2 (-) on sodium transport, osmolality, and medullary oxygenation cannot be gleaned by considering each solute's effect in isolation. An additional simulation suggests that a sufficiently large reduction in tubular transport efficiency may be the key contributing factor, more so than oxidative stress alone, to hypertension-induced medullary hypoxia. Moreover, model predictions suggest that urine Po2 could serve as a biomarker for medullary hypoxia and a predictor of the risk for hospital-acquired acute kidney injury. Copyright © 2015 the American Physiological Society.

Coaction of intercellular adhesion and cortical tension specifies tissue surface tension

PubMed Central

Manning, M. Lisa; Foty, Ramsey A.; Steinberg, Malcolm S.; Schoetz, Eva-Maria

2010-01-01

In the course of animal morphogenesis, large-scale cell movements occur, which involve the rearrangement, mutual spreading, and compartmentalization of cell populations in specific configurations. Morphogenetic cell rearrangements such as cell sorting and mutual tissue spreading have been compared with the behaviors of immiscible liquids, which they closely resemble. Based on this similarity, it has been proposed that tissues behave as liquids and possess a characteristic surface tension, which arises as a collective, macroscopic property of groups of mobile, cohering cells. But how are tissue surface tensions generated? Different theories have been proposed to explain how mesoscopic cell properties such as cell–cell adhesion and contractility of cell interfaces may underlie tissue surface tensions. Although recent work suggests that both may be contributors, an explicit model for the dependence of tissue surface tension on these mesoscopic parameters has been missing. Here we show explicitly that the ratio of adhesion to cortical tension determines tissue surface tension. Our minimal model successfully explains the available experimental data and makes predictions, based on the feedback between mechanical energy and geometry, about the shapes of aggregate surface cells, which we verify experimentally. This model indicates that there is a crossover from adhesion dominated to cortical-tension dominated behavior as a function of the ratio between these two quantities. PMID:20616053

Bolt-Tension Sensor

NASA Technical Reports Server (NTRS)

Goldie, James H.; Bushko, Dariusz A.; Gerver, Michael J.

1995-01-01

In technique for measuring tensile force of bolt, specially fabricated magnetostrictive washer used as force transducer. Compact, portable inductive electronic sensor placed against washer to measure tension force. New system provides accurate, economical, and convenient way to measure bolt tension in field. Measurements on test assembly shows that tension can be measured to accuracy of about plus or minus 1 percent of load capacity of typical bolt.

Tension pneumothorax accompanied by type A aortic dissection.

PubMed

Hifumi, Toru; Kiriu, Nobuaki; Inoue, Junichi; Koido, Yuichi

2012-11-09

A 51-year-old man was brought to the emergency room because of a sudden onset of severe dysponea. On presentation, his blood pressure was 94/55 mm Hg. Oxygen saturation was 86% while he was receiving 10 l/min oxygen through a non-rebreather mask. On physical examination, no jugular venous distention was noted, but breath sounds over the left lung were diminished. A bedside chest radiograph showed left tension pneumothorax, for which urgent needle decompression followed by chest thoracostomy was performed. Ventricular tachycardia developed, but a biphasic shock at 120 J immediately restored normal sinus rhythm. His vital signs, however, did not improve. A CT scan of the chest showed type A aortic dissection with bullae in the upper lobe of the left lung. He had an emergency operation for distal aortic arch displacement and was discharged on the 37th day of hospitalisation.

Permanent tensions in organization.

PubMed

Jansson, Noora

2015-01-01

The purpose of this paper is to investigate the relationship between permanent tensions and organizational change. This study used paradox theory and a case study. The case organization is a public university hospital in Finland involving several stakeholders. The analysis suggests that the relationship between permanent tensions and organizational change is a paradox that is part of organizational reality. As an organization learns to live with its permanent tensions, the renewal paradox settles into equilibrium. When tensions are provoked, the paradox is disturbed until it finds a new balance. This flexible nature of the paradox is the force that keeps the different stakeholders simultaneously empowered to maintain their unique missions and cohesive in order to benefit from the larger synergy. This research suggests that identification and evaluation of each permanent tension within an organization is important when executing organizational change. The fact that certain tensions are permanent and cannot be solved may have an influence on how planned change initiatives are executed. The results show that permanent tensions may be harnessed for the benefit of an organizational change. This research demonstrates originality by offering an alternative view of tensions, a view which emphasizes not only their permanent and plural nature but their importance for enabling the organization to change at its own, non-disruptive pace. The research also proposes a new concept, the "renewal paradox", to enhance understanding of the relationship between permanent tensions and organizational change.

Fatigue life of additively manufactured Ti6Al4V scaffolds under tension-tension, tension-compression and compression-compression fatigue load.

PubMed

Lietaert, Karel; Cutolo, Antonio; Boey, Dries; Van Hooreweder, Brecht

2018-03-21

Mechanical performance of additively manufactured (AM) Ti6Al4V scaffolds has mostly been studied in uniaxial compression. However, in real-life applications, more complex load conditions occur. To address this, a novel sample geometry was designed, tested and analyzed in this work. The new scaffold geometry, with porosity gradient between the solid ends and scaffold middle, was successfully used for quasi-static tension, tension-tension (R = 0.1), tension-compression (R = -1) and compression-compression (R = 10) fatigue tests. Results show that global loading in tension-tension leads to a decreased fatigue performance compared to global loading in compression-compression. This difference in fatigue life can be understood fairly well by approximating the local tensile stress amplitudes in the struts near the nodes. Local stress based Haigh diagrams were constructed to provide more insight in the fatigue behavior. When fatigue life is interpreted in terms of local stresses, the behavior of single struts is shown to be qualitatively the same as bulk Ti6Al4V. Compression-compression and tension-tension fatigue regimes lead to a shorter fatigue life than fully reversed loading due to the presence of a mean local tensile stress. Fractographic analysis showed that most fracture sites were located close to the nodes, where the highest tensile stresses are located.

In vivo oxygen transport in the normal rabbit femoral arterial wall.

PubMed Central

Crawford, D W; Back, L H; Cole, M A

1980-01-01

In vivo measurements of tissue oxygen tension were made at 10-micrometer intervals through functioning in situ rabbit femoral arterial walls, using inhalation anesthesia and recessed microcathodes with approximately 4-micrometer external diameters. External environment was controlled with a superfusion well at 30 torr PO2, 35 torr PCO2. Blood pressure, gas tension levels, and blood pH were held within the normal range. Radial PO2 measurements closely fit a mathematical model for unidimensional diffusion into a thick-walled artery with uniform oxygen consumption, and the distances traversed fit measured dimensions of quick-frozen in vivo sections. Using standard values of diffusion and solubility coefficients, mean calculated medial oxygen consumption was 99 nl0/ml-s. Mural oxygen consumption appeared to be related linearly to mean tangential wall stress. Differences in experimental design and technique were compared with previous in vivo and in vitro measurements of wall oxygenation, and largely account for the varying results obtained. Control of environment external to the artery, and maintenance of normally flowing blood in the lumen in vivo appeared critical to an understanding of mural oxygenation in life. If the conditions of this experiment prevailed in arteries with thicker avascular layers, PO2 could have been 20 torr at approximately 156 micrometer and 10 torr at 168 micrometer from blood (average values). Images PMID:7410554

Endurance exercise performance: the physiology of champions

PubMed Central

Joyner, Michael J; Coyle, Edward F

2008-01-01

Efforts to understand human physiology through the study of champion athletes and record performances have been ongoing for about a century. For endurance sports three main factors – maximal oxygen consumption , the so-called ‘lactate threshold’ and efficiency (i.e. the oxygen cost to generate a give running speed or cycling power output) – appear to play key roles in endurance performance. and lactate threshold interact to determine the ‘performance ‘ which is the oxygen consumption that can be sustained for a given period of time. Efficiency interacts with the performance to establish the speed or power that can be generated at this oxygen consumption. This review focuses on what is currently known about how these factors interact, their utility as predictors of elite performance, and areas where there is relatively less information to guide current thinking. In this context, definitive ideas about the physiological determinants of running and cycling efficiency is relatively lacking in comparison with and the lactate threshold, and there is surprisingly limited and clear information about the genetic factors that might pre-dispose for elite performance. It should also be cautioned that complex motivational and sociological factors also play important roles in who does or does not become a champion and these factors go far beyond simple physiological explanations. Therefore, the performance of elite athletes is likely to defy the types of easy explanations sought by scientific reductionism and remain an important puzzle for those interested in physiological integration well into the future. PMID:17901124

Approaching the evolutionary advantage of ancillary types of haemoglobin in Daphnia magna by simulation of oxygen supply.

PubMed

Moenickes, S; Richter, O; Pirow, R

2010-02-01

The planktonic crustacean Daphnia magna synthesizes haemoglobin (Hb) macromolecules of variant subunit composition and oxygen affinity. This is one of the strategies by which the animals cope with variations in environmental conditions such as ambient oxygen tension. The enrichment of high-affinity Hb molecules in the haemolymph of hypoxia-exposed animals is thought to reduce Hb synthesis costs due to an enhanced transport efficiency of these molecules in comparison to the low-affinity Hb molecules. How great this economic advantage is, and under which conditions this benefit disappears, is still not fully understood. Here we implemented a rigorously simplified model of the daphnid body and described the transport of oxygen from the environment via the haemolymph to the tissues in terms of the convection-diffusion-reaction equation. The model was validated by comparing various model predictions with experimental data. A sensitivity analysis was used to evaluate the influence of parameter uncertainties on the model predictions. Cost-benefit analysis revealed in which way at the system's level the increase in Hb oxygen affinity improves the oxygen loading at the respiratory surfaces and impairs the release of oxygen to the tissues. The benefit arising from the improved oxygen loading exceeds the disadvantage of impaired unloading only under conditions where the ambient oxygen tension is critically low and the Hb concentration is high. The low-affinity Hb, on the other hand, provides an advantage given that the Hb concentration is low and the ambient oxygen tension is well above the critical level. Computer-aided modelling and simulation therefore provide valuable mechanistic insights into the driving forces that could have shaped the evolution of globin genes in daphnids.

Effects of increased inspired oxygen concentration on tissue oxygenation: theoretical considerations.

PubMed

Lumb, Andrew B; Nair, Sindhu

2010-03-01

Breathing increased fractional oxygen concentration (FiO2) is recommended for the treatment of tissue ischaemia. The theoretical benefits of increasing FiO2 on tissue oxygenation were evaluated using standard physiological equations. Assuming constant oxygen consumption by tissues throughout the length of a capillary, the oxygen content at 20 arbitrary points along a capillary was calculated. Using mathematical representations of the haemoglobin dissociation curve and an iterative approach to include the dissolved oxygen component of oxygen content, the oxygen partial pressure (PO2) profile along a capillary was estimated. High FiO2 concentrations cause large increases in PO2 at the arteriolar end of capillaries but these large PO2 values, caused by the extra dissolved oxygen, rapidly decline along the capillary. At the venular end of the capillary (the area of tissue most likely to be hypoxic), breathing oxygen causes only a modest improvement in PO2. Increasing FiO2 to treat tissue hypoxia has clear benefits, but a multimodal approach to management is required.

An in silico analysis of oxygen uptake of a mild COPD patient during rest and exercise using a portable oxygen concentrator

PubMed Central

Katz, Ira; Pichelin, Marine; Montesantos, Spyridon; Kang, Min-Yeong; Sapoval, Bernard; Zhu, Kaixian; Thevenin, Charles-Philippe; McCoy, Robert; Martin, Andrew R; Caillibotte, Georges

2016-01-01

Oxygen treatment based on intermittent-flow devices with pulse delivery modes available from portable oxygen concentrators (POCs) depends on the characteristics of the delivered pulse such as volume, pulse width (the time of the pulse to be delivered), and pulse delay (the time for the pulse to be initiated from the start of inhalation) as well as a patient’s breathing characteristics, disease state, and respiratory morphology. This article presents a physiological-based analysis of the performance, in terms of blood oxygenation, of a commercial POC at different settings using an in silico model of a COPD patient at rest and during exercise. The analysis encompasses experimental measurements of pulse volume, width, and time delay of the POC at three different settings and two breathing rates related to rest and exercise. These experimental data of device performance are inputs to a physiological-based model of oxygen uptake that takes into account the real dynamic nature of gas exchange to illustrate how device- and patient-specific factors can affect patient oxygenation. This type of physiological analysis that considers the true effectiveness of oxygen transfer to the blood, as opposed to delivery to the nose (or mouth), can be instructive in applying therapies and designing new devices. PMID:27729783

Physiological oxygen prevents frequent silencing of the DLK1-DIO3 cluster during human embryonic stem cells culture.

PubMed

Xie, Pingyuan; Sun, Yi; Ouyang, Qi; Hu, Liang; Tan, Yueqiu; Zhou, Xiaoying; Xiong, Bo; Zhang, Qianjun; Yuan, Ding; Pan, Yi; Liu, Tiancheng; Liang, Ping; Lu, Guangxiu; Lin, Ge

2014-02-01

Genetic and epigenetic alterations are observed in long-term culture (>30 passages) of human embryonic stem cells (hESCs); however, little information is available in early cultures. Through a large-scale gene expression analysis between initial-passage hESCs (ihESCs, <10 passages) and early-passage hESCs (ehESCs, 20-30 passages) of 12 hESC lines, we found that the DLK1-DIO3 gene cluster was normally expressed and showed normal methylation pattern in ihESC, but was frequently silenced after 20 passages. Both the DLK1-DIO3 active status in ihESCs and the inactive status in ehESCs were inheritable during differentiation. Silencing of the DLK1-DIO3 cluster did not seem to compromise the multilineage differentiation ability of hESCs, but was associated with reduced DNA damage-induced apoptosis in ehESCs and their differentiated hepatocyte-like cell derivatives, possibly through attenuation of the expression and phosphorylation of p53. Furthermore, we demonstrated that 5% oxygen, instead of the commonly used 20% oxygen, is required for preserving the expression of the DLK1-DIO3 cluster. Overall, the data suggest that active expression of the DLK1-DIO3 cluster represents a new biomarker for epigenetic stability of hESCs and indicates the importance of using a proper physiological oxygen level during the derivation and culture of hESCs. © AlphaMed Press.

Dissolved oxygen concentration in the medium during cell culture: Defects and improvements.

PubMed

Zhang, Kuan; Zhao, Tong; Huang, Xin; He, Yunlin; Zhou, Yanzhao; Wu, Liying; Wu, Kuiwu; Fan, Ming; Zhu, Lingling

2016-03-01

In vitro cell culture has provided a useful model to study the effects of oxygen on cellular behavior. However, it remains unknown whether the in vitro operations themselves affect the medium oxygen levels and the living states of cells. In addition, a prevailing controversy is whether reactive oxygen species (ROS) production is induced by continuous hypoxia or reoxygenation. In this study, we have measured the effects of different types of cell culture containers and the oxygen environment where medium replacement takes place on the actual oxygen tension in the medium. We found that the deviations of oxygen concentrations in the medium are much greater in 25-cm(2) flasks than in 24-well plates and 35-mm dishes. The dissolved oxygen concentrations in the medium were increased after medium replacement in normoxia, but remained unchanged in glove boxes in which the oxygen tension remained at a low level (11.4, 5.7, and 0.5% O2 ). We also found that medium replacement in normoxia increased the number of ROS-positive cells and reduced the cell viability; meanwhile, medium replacement in a glove box did not produce the above effects. Therefore, we conclude that the use of 25-cm(2) flasks should be avoided and demonstrate that continuous hypoxia does not produce ROS, whereas the reoxygenation that occurs during the harvesting of cells leads to ROS and induces cell death. © 2015 International Federation for Cell Biology.

Prompt meningeal reconstruction mediated by oxygen-sensitive AKAP12 scaffolding protein after central nervous system injury

PubMed Central

Cha, Jong-Ho; Wee, Hee-Jun; Seo, Ji Hae; Ahn, Bum Ju; Park, Ji-Hyeon; Yang, Jun-Mo; Lee, Sae-Won; Lee, Ok-Hee; Lee, Hyo-Jong; Gelman, Irwin H.; Arai, Ken; Lo, Eng H.; Kim, Kyu-Won

2015-01-01

The meninges forms a critical epithelial barrier, which protects the central nervous system (CNS), and therefore its prompt reconstruction after CNS injury is essential for reducing neuronal damage. Meningeal cells migrate into the lesion site after undergoing an epithelial-mesenchymal transition (EMT) and repair the impaired meninges. However, the molecular mechanisms of meningeal EMT remain largely undefined. Here we show that TGF-β1 and retinoic acid (RA) released from the meninges, together with oxygen tension, could constitute the mechanism for rapid meningeal reconstruction. AKAP12 is an effector of this mechanism, and its expression in meningeal cells is regulated by integrated upstream signals composed of TGF-β1, RA and oxygen tension. Functionally, AKAP12 modulates meningeal EMT by regulating the TGF-β1-non-Smad-SNAI1 signalling pathway. Collectively, TGF-β1, RA and oxygen tension can modulate the dynamic change in AKAP12 expression, causing prompt meningeal reconstruction after CNS injury by regulating the transition between the epithelial and mesenchymal states of meningeal cells. PMID:25229625

Human physiological responses to wooden indoor environment.

PubMed

Zhang, Xi; Lian, Zhiwei; Wu, Yong

2017-05-15

Previous studies are mainly focused on non-wooden environments, whereas few are concerned with wooden ones. How wooden indoor environments impact the physiology of the occupants is still unclear. The purpose of this study was to explore the distinct physiological responses to wooden and non-wooden indoor environments, assessed by physiological parameters tests including blood pressure, electrocardiogram measurements, electro-dermal activity, oxyhemoglobin saturation, skin temperature, and near distance vision. Twenty healthy adults participated in this experiment, and their physiological responses were evaluated in a 90minute investigation. The results illustrated that; less tension and fatigue were generated in the wooden rooms than in the non-wooden rooms when the participants did their work. In addition, the study also found that the wooden environments benefit the autonomic nervous system, respiratory system, and visual system. Moreover, wooden rooms play a valuable role in physiological regulation and ease function especially after a consecutive period of work. These results provide an experimental basis to support that wooden environment is beneficial to indoor occupants than the non-wooden indoor environment. Copyright © 2017 Elsevier Inc. All rights reserved.

Reduced-Gravity Measurements of the Effect of Oxygen on Properties of Zirconium

NASA Technical Reports Server (NTRS)

Zhao, J.; Lee, J.; Wunderlich, R.; Fecht, H.-J.; Schneider, S.; SanSoucie, M.; Rogers, J.; Hyers, R.

2016-01-01

The influence of oxygen on the thermophysical properties of zirconium is being investigated using MSL-EML (Material Science Laboratory - Electromagnetic Levitator) on ISS (International Space Station) in collaboration with NASA, ESA (European Space Agency), and DLR (German Aerospace Center). Zirconium samples with different oxygen concentrations will be put into multiple melt cycles, during which the density, viscosity, surface tension, heat capacity, and electric conductivity will be measured at various undercooled temperatures. The facility check-up of MSL-EML and the first set of melting experiments have been successfully performed in 2015. The first zirconium sample will be tested near the end of 2015. As part of ground support activities, the thermophysical properties of zirconium and ZrO were measured using a ground-based electrostatic levitator located at the NASA Marshall Space Flight Center. The influence of oxygen on the measured surface tension was evaluated. The results of this research will serve as reference data for those measured in ISS.

Case-Based Learning of Blood Oxygen Transport

ERIC Educational Resources Information Center

Cliff, William H.

2006-01-01

A case study about carbon monoxide poisoning was used help students gain a greater understanding of the physiology of oxygen transport by the blood. A review of student answers to the case questions showed that students can use the oxygen-hemoglobin dissociation curve to make meaningful determinations of oxygen uptake and delivery. However, the…

Renal Medullary and Urinary Oxygen Tension during Cardiopulmonary Bypass in the Rat

PubMed Central

Sgouralis, Ioannis; Evans, Roger G.; Layton, Anita T.

2017-01-01

Renal hypoxia could result from a mismatch in renal oxygen supply and demand, particularly in the renal medulla. Medullary hypoxic damage is believed to give rise to acute kidney injury, which is a prevalent complication of cardiac surgery performed on cardiopulmonary bypass (CPB). To determine the mechanisms that could lead to medullary hypoxia during CPB in the rat kidney, we developed a mathematical model which incorporates (i) autoregulation of renal blood flow and glomerular filtration rate, (ii) detailed oxygen transport and utilization in the renal medulla, and (iii) oxygen transport along the ureter. Within the outer medulla, the lowest interstitial tissue PO2, which is an indicator of renal hypoxia, is predicted near the thick ascending limbs. Interstitial tissue PO2 exhibits a general decrease along the inner medullary axis, but urine PO2 increases significantly along the ureter. Thus, bladder urinary PO2 is predicted to be substantially higher than medullary PO2. The model is used to identify the phase of cardiac surgery performed on CPB that is associated with the highest risk for hypoxic kidney injury. Simulation results indicate that the outer medulla’s vulnerability to hypoxic injury depends, in part, on the extent to which medullary blood flow is autoregulated. With imperfect medullary blood flow autoregulation, the model predicts that the rewarming phase of CPB, in which medullary blood flow is low but medullary oxygen consumption remains high, is the phase in which the kidney is most likely to suffer hypoxic injury. PMID:27281792

Effects of Changes in Arterial Carbon Dioxide and Oxygen Partial Pressures on Cerebral Oximeter Performance.

PubMed

Schober, Andrew; Feiner, John R; Bickler, Philip E; Rollins, Mark D

2018-01-01

Cerebral oximetry (cerebral oxygen saturation; ScO2) is used to noninvasively monitor cerebral oxygenation. ScO2 readings are based on the fraction of reduced and oxidized hemoglobin as an indirect estimate of brain tissue oxygenation and assume a static ratio of arterial to venous intracranial blood. Conditions that alter cerebral blood flow, such as acute changes in PaCO2, may decrease accuracy. We assessed the performance of two commercial cerebral oximeters across a range of oxygen concentrations during normocapnia and hypocapnia. Casmed FORE-SIGHT Elite (CAS Medical Systems, Inc., USA) and Covidien INVOS 5100C (Covidien, USA) oximeter sensors were placed on 12 healthy volunteers. The fractional inspired oxygen tension was varied to achieve seven steady-state levels including hypoxic and hyperoxic PaO2 values. ScO2 and simultaneous arterial and jugular venous blood gas measurements were obtained with both normocapnia and hypocapnia. Oximeter bias was calculated as the difference between the ScO2 and reference saturation using manufacturer-specified weighting ratios from the arterial and venous samples. FORE-SIGHT Elite bias was greater during hypocapnia as compared with normocapnia (4 ± 9% vs. 0 ± 6%; P < 0.001). The INVOS 5100C bias was also lower during normocapnia (5 ± 15% vs. 3 ± 12%; P = 0.01). Hypocapnia resulted in a significant decrease in mixed venous oxygen saturation and mixed venous oxygen tension, as well as increased oxygen extraction across fractional inspired oxygen tension levels (P < 0.0001). Bias increased significantly with increasing oxygen extraction (P < 0.0001). Changes in PaCO2 affect cerebral oximeter accuracy, and increased bias occurs with hypocapnia. Decreased accuracy may represent an incorrect assumption of a static arterial-venous blood fraction. Understanding cerebral oximetry limitations is especially important in patients at risk for hypoxia-induced brain injury, where PaCO2 may be purposefully altered.

A continuous physiological data collector

NASA Technical Reports Server (NTRS)

Bush, J. C.

1972-01-01

COP-DAC system utilizes oxygen and carbon dioxide analyzers, gas-flow meter, gas breathe-through system, analog computer, and data storage system to provide actual rather than average measurements of physiological and metabolic functions.

Reactive Oxygen Species in Cardiovascular Disease

PubMed Central

Sugamura, Koichi; Keaney, John F.

2011-01-01

Based on the ‘free-radical theory’ of disease, researchers have been trying to elucidate the role of oxidative stress from free radicals in cardiovascular disease. Considerable data indicate that ROS and oxidative stress are important features of cardiovascular diseases including atherosclerosis, hypertension, and congestive heart failure. However, blanket strategies with antioxidants to ameliorate cardiovascular disease have not generally yielded favorable results. However, our understanding or reactive oxygen species has evolved to the point that we now realize these species have important roles in physiology as well as pathophysiology. Thus, it is overly simplistic to assume a general antioxidant strategy will yield specific effects on cardiovascular disease. Indeed, there are several sources of reactive oxygen species that are known to be active in the cardiovascular system. This review will address our understanding of reactive oxygen species sources in cardiovascular disease and both animal and human data defining how reactive oxygen species contribute to physiology and pathology. PMID:21627987

Managing tension headaches at home

MedlinePlus

Tension-type headache - self-care; Muscle contraction headache - self-care; Headache - benign - self-care; Headache - tension- self-care; Chronic headaches - tension - self-care; Rebound headaches - ...

Responses to altered oxygen tension are distinct between human stem cells of high and low chondrogenic capacity.

PubMed

Anderson, Devon E; Markway, Brandon D; Bond, Derek; McCarthy, Helen E; Johnstone, Brian

2016-10-20

Lowering oxygen from atmospheric level (hyperoxia) to the physiological level (physioxia) of articular cartilage promotes mesenchymal stem cell (MSC) chondrogenesis. However, the literature is equivocal regarding the benefits of physioxic culture on preventing hypertrophy of MSC-derived chondrocytes. Articular cartilage progenitors (ACPs) undergo chondrogenic differentiation with reduced hypertrophy marker expression in hyperoxia but have not been studied in physioxia. This study sought to delineate the effects of physioxic culture on both cell types undergoing chondrogenesis. MSCs were isolated from human bone marrow aspirates and ACP clones were isolated from healthy human cartilage. Cells were differentiated in pellet culture in physioxia (2 % oxygen) or hyperoxia (20 % oxygen) over 14 days. Chondrogenesis was characterized by biochemical assays and gene and protein expression analysis. MSC preparations and ACP clones of high intrinsic chondrogenicity (termed high-GAG) produced abundant matrix in hyperoxia and physioxia. Poorly chondrogenic cells (low-GAG) demonstrated a significant fold-change matrix increase in physioxia. Both high-GAG and low-GAG groups of MSCs and ACPs significantly upregulated chondrogenic genes; however, only high-GAG groups had a concomitant decrease in hypertrophy-related genes. High-GAG MSCs upregulated many common hypoxia-responsive genes in physioxia while low-GAG cells downregulated most of these genes. In physioxia, high-GAG MSCs and ACPs produced comparable type II collagen but less type I collagen than those in hyperoxia. Type X collagen was detectable in some ACP pellets in hyperoxia but reduced or absent in physioxia. In contrast, type X collagen was detectable in all MSC preparations in hyperoxia and physioxia. MSC preparations and ACP clones had a wide range of chondrogenicity between donors. Physioxia significantly enhanced the chondrogenic potential of both ACPs and MSCs compared with hyperoxia, but the magnitude of

Endothelial cell respiration is affected by the oxygen tension during shear exposure: role of mitochondrial peroxynitrite.

PubMed

Jones, Charles I; Han, Zhaosheng; Presley, Tennille; Varadharaj, Saradhadevi; Zweier, Jay L; Ilangovan, Govindasamy; Alevriadou, B Rita

2008-07-01

Cultured vascular endothelial cell (EC) exposure to steady laminar shear stress results in peroxynitrite (ONOO(-)) formation intramitochondrially and inactivation of the electron transport chain. We examined whether the "hyperoxic state" of 21% O(2), compared with more physiological O(2) tensions (Po(2)), increases the shear-induced nitric oxide (NO) synthesis and mitochondrial superoxide (O(2)(*-)) generation leading to ONOO(-) formation and suppression of respiration. Electron paramagnetic resonance oximetry was used to measure O(2) consumption rates of bovine aortic ECs sheared (10 dyn/cm(2), 30 min) at 5%, 10%, or 21% O(2) or left static at 5% or 21% O(2). Respiration was inhibited to a greater extent when ECs were sheared at 21% O(2) than at lower Po(2) or left static at different Po(2). Flow in the presence of an endothelial NO synthase (eNOS) inhibitor or a ONOO(-) scavenger abolished the inhibitory effect. EC transfection with an adenovirus that expresses manganese superoxide dismutase in mitochondria, and not a control virus, blocked the inhibitory effect. Intracellular and mitochondrial O(2)(*-) production was higher in ECs sheared at 21% than at 5% O(2), as determined by dihydroethidium and MitoSOX red fluorescence, respectively, and the latter was, at least in part, NO-dependent. Accumulation of NO metabolites in media of ECs sheared at 21% O(2) was modestly increased compared with ECs sheared at lower Po(2), suggesting that eNOS activity may be higher at 21% O(2). Hence, the hyperoxia of in vitro EC flow studies, via increased NO and mitochondrial O(2)(*-) production, leads to enhanced ONOO(-) formation intramitochondrially and suppression of respiration.

Relationship between locking-bolt torque and load pre-tension in the Ilizarov frame.

PubMed

Osei, N A; Bradley, B M; Culpan, P; Mitchell, J B; Barry, M; Tanner, K E

2006-10-01

The wire-bolt interface in an Ilizarov frame has been mechanically tested. The optimal torque to be applied to the frame locking-bolts during physiological loading has been defined. The set-up configuration was as is used clinically except a copper tube was used to simulate bone. The force-displacement curves of the Ilizarov wires are not altered by locking-bolt torque. The force in the bone model at which pre-tension is lost increases as the locking-bolts are tightened to 14 Nm torque, but decreases if torque exceeds 14 Nm. Thus, 14 Nm is the optimal locking-bolt torque in frame. The relationship between pre-tension versus load for different locking-bolt torques arises because at low and high clamping torques poor wire holding and plastic deformation respectively occur. Wire damage was seen under light and electron microscopy. Clinically, over or under-tightening locking-bolts will cause loss of pre-tension, reduction in frame stiffness and excessive movement at the fracture site, which may be associated with delayed union.

Matrix stiffness reverses the effect of actomyosin tension on cell proliferation.

PubMed

Mih, Justin D; Marinkovic, Aleksandar; Liu, Fei; Sharif, Asma S; Tschumperlin, Daniel J

2012-12-15

The stiffness of the extracellular matrix exerts powerful effects on cell proliferation and differentiation, but the mechanisms transducing matrix stiffness into cellular fate decisions remain poorly understood. Two widely reported responses to matrix stiffening are increases in actomyosin contractility and cell proliferation. To delineate their relationship, we modulated cytoskeletal tension in cells grown across a physiological range of matrix stiffnesses. On both synthetic and naturally derived soft matrices, and across a panel of cell types, we observed a striking reversal of the effect of inhibiting actomyosin contractility, switching from the attenuation of proliferation on rigid substrates to the robust promotion of proliferation on soft matrices. Inhibiting contractility on soft matrices decoupled proliferation from cytoskeletal tension and focal adhesion organization, but not from cell spread area. Our results demonstrate that matrix stiffness and actomyosin contractility converge on cell spreading in an unexpected fashion to control a key aspect of cell fate.

Oxygenates from Electrochemical Reduction of CO2.

PubMed

Feng, Guanghui; Chen, Wei; Wang, Baiyin; Song, Yanfang; Li, Guihua; Fang, Jianhui; Wei, Wei; Sun, Yuhan

2018-05-29

Electrochemical reduction of carbon dioxide (CO2) driven by renewable electricity to chemicals and fuels is considered as an ideal approach that can alleviate both carbon emission and energy tension stresses. High-value chemicals such as oxygenates can be effectively produced from CO2 electroreduction, which is highly attractive for the great promotion of the economy and applicability of CO2 utilization. This review focuses the recent advancements on the CO2 electrochemical reduction to formic acid, methanol, ethanol, acetic acid, and other oxygenates. The related principles, influence factors, and typical catalysts are summarized. On the basis of the aforementioned discussions, we present the future prospects for further development of CO2 electroreduction to oxygenates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation on maternal physiological and psychological factors of cheilopalatognathus.

PubMed

Ma, J; Zhao, W; Ma, R M; Li, X J; Wen, Z H; Liu, X F; Hu, W D; Zhang, C B

2013-01-01

Case-control study on mothers of cheilopalatognathus children was conducted, to investigate the maternal physiological and psychological factors for occurrence of cheilopalatognathus. One hundred ten mothers of cheilopalatognathus children who were scheduled for one-stage surgery were selected as a research group, and 110 mothers of normal children served as a normal control group at the same time. Trait Anxiety Inventory (T-AI), Life Events Scale (LES), Trait Coping Style Questionnaire (TCSQ), Type C Behavior Scale (CBS), adult Eysenck Personality Questionnaire (EPQ), and homemade general questionnaire survey were employed for the investigation. Compared with the control group, the scores for negative event tension value, anxiety, and depressive factors were higher in the study group (p < 0.05); while the scores for positive event tension value, intellect, optimism, and social support factors were lower (p < 0.05). Regression analysis found that physiological factors included were five: education, changes in body weight during pregnancy, the intake amount of milk and beans, and intake of healthcare products, and supplementary folic acid taken or not, while the psychological factors included were four: positive event stimulation, negative event stimulation, the amount of social support, as well as introvert and extrovert personalities. The study results suggest that pregnant women's physiological and psychological factors can cause changes in cheilopalatognathus incidence, which is expected to be guidance for healthcare during pregnancy, to prevent the occurrence of cheilopalatognathus.

A miniature tension sensor to measure surgical suture tension of deformable musculoskeletal tissues during joint motion.

PubMed

Kiriyama, Yoshimori; Matsumoto, Hideo; Toyama, Yoshiaki; Nagura, Takeo

2014-02-01

The aim of this study was to develop a new suture tension sensor for musculoskeletal soft tissue that shows deformation or movements. The suture tension sensor was 10 mm in size, which was small enough to avoid conflicting with the adjacent sensor. Furthermore, the sensor had good linearity up to a tension of 50 N, which is equivalent to the breaking strength of a size 1 absorbable suture defined by the United States Pharmacopeia. The design and mechanism were analyzed using a finite element model prior to developing the actual sensor. Based on the analysis, adequate material was selected, and the output linearity was confirmed and compared with the simulated result. To evaluate practical application, the incision of the skin and capsule were sutured during simulated total knee arthroplasty. When conventional surgery and minimally invasive surgery were performed, suture tensions were compared. In minimally invasive surgery, the distal portion of the knee was dissected, and the proximal portion of the knee was dissected additionally in conventional surgery. In the skin suturing, the maximum tension was 4.4 N, and this tension was independent of the sensor location. In contrast, the sensor suturing the capsule in the distal portion had a tension of 4.4 N in minimally invasive surgery, while the proximal sensor had a tension of 44 N in conventional surgery. The suture tensions increased nonlinearly and were dependent on the knee flexion angle. Furthermore, the tension changes showed hysteresis. This miniature tension sensor may help establish the optimal suturing method with adequate tension to ensure wound healing and early recovery.

Aspects on the Physiological and Biochemical Foundations of Neurocritical Care

PubMed Central

Nordström, Carl-Henrik; Koskinen, Lars-Owe; Olivecrona, Magnus

2017-01-01

Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood–brain barrier (BBB) and the regulation of CBF. Brain volume is strictly controlled as the BBB permeability to crystalloids is very low restricting net transport of water across the capillary wall. Cerebral pressure autoregulation prevents changes in intracranial blood volume and intracapillary hydrostatic pressure at variations in arterial blood pressure. Information regarding cerebral oxidative metabolism is obtained from measurements of brain tissue oxygen tension (PbtO2) and biochemical data obtained from intracerebral microdialysis. As interstitial lactate/pyruvate (LP) ratio instantaneously reflects shifts in intracellular cytoplasmatic redox state, it is an important indicator of compromised cerebral oxidative metabolism. The combined information obtained from PbtO2, LP ratio, and the pattern of biochemical variables reveals whether impaired oxidative metabolism is due to insufficient perfusion (ischemia) or mitochondrial dysfunction. Intracerebral microdialysis and PbtO2 give information from a very small volume of tissue. Accordingly, clinical interpretation of the data must be based on information of the probe location in relation to focal brain damage. Attempts to evaluate global cerebral energy state from microdialysis of intraventricular fluid and from the LP ratio of the draining venous blood have recently been presented. To be of clinical relevance, the

Impact of renal medullary three-dimensional architecture on oxygen transport.

PubMed

Fry, Brendan C; Edwards, Aurélie; Sgouralis, Ioannis; Layton, Anita T

2014-08-01

We have developed a highly detailed mathematical model of solute transport in the renal medulla of the rat kidney to study the impact of the structured organization of nephrons and vessels revealed in anatomic studies. The model represents the arrangement of tubules around a vascular bundle in the outer medulla and around a collecting duct cluster in the upper inner medulla. Model simulations yield marked gradients in intrabundle and interbundle interstitial fluid oxygen tension (PO2), NaCl concentration, and osmolality in the outer medulla, owing to the vigorous active reabsorption of NaCl by the thick ascending limbs. In the inner medulla, where the thin ascending limbs do not mediate significant active NaCl transport, interstitial fluid composition becomes much more homogeneous with respect to NaCl, urea, and osmolality. Nonetheless, a substantial PO2 gradient remains, owing to the relatively high oxygen demand of the inner medullary collecting ducts. Perhaps more importantly, the model predicts that in the absence of the three-dimensional medullary architecture, oxygen delivery to the inner medulla would drastically decrease, with the terminal inner medulla nearly completely deprived of oxygen. Thus model results suggest that the functional role of the three-dimensional medullary architecture may be to preserve oxygen delivery to the papilla. Additionally, a simulation that represents low medullary blood flow suggests that the separation of thick limbs from the vascular bundles substantially increases the risk of the segments to hypoxic injury. When nephrons and vessels are more homogeneously distributed, luminal PO2 in the thick ascending limb of superficial nephrons increases by 66% in the inner stripe. Furthermore, simulations predict that owing to the Bohr effect, the presumed greater acidity of blood in the interbundle regions, where thick ascending limbs are located, relative to that in the vascular bundles, facilitates the delivery of O2 to support the

Sensing the Tension

NASA Technical Reports Server (NTRS)

2003-01-01

Spanning over 4 decades, NASA's bolt tension monitoring technology has benefited automakers, airplane builders, and other major manufacturers that rely on the devices to evaluate the performance of computerized torque wrenches and other assembly line mechanisms. In recent years, the advancement of ultrasonic sensors has drastically eased this process for users, ensuring that proper tension and torque are being applied to bolts and fasteners, with less time needed for data analysis. Langley Research Center s Nondestructive Evaluation Branch is one of the latest NASA programs to incorporate ultrasonic sensors within a bolt tension measurement instrument. As a multi-disciplined research group focused on spacecraft and aerospace transportation safety, one of the branch s many commitments includes transferring problem solutions to industry. In 1998, the branch carried out this obligation in a licensing agreement with Micro Control, Inc., of West Bloomfield, Michigan. Micro Control, an automotive inspection company, obtained the licenses to two Langley patents to provide an improved-but-inexpensive means of ultrasonic tension measurement.

Effect of Membrane Tension on the Electric Field and Dipole Potential of Lipid Bilayer Membrane

PubMed Central

Warshaviak, Dora Toledo; Muellner, Michael J.; Chachisvilis, Mirianas

2011-01-01

The dipole potential of lipid bilayer membrane controls the difference in permeability of the membrane to oppositely charged ions. We have combined molecular dynamics (MD) simulations and experimental studies to determine changes in electric field and electrostatic potential of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid bilayer in response to applied membrane tension. MD simulations based on CHARMM36 force field showed that electrostatic potential of DOPC bilayer decreases by ~45 mV in the physiologically relevant range of membrane tension values (0 to 15 dyn/cm). The electrostatic field exhibits a peak (~0.8×109 V/m) near the water/lipid interface which shifts by 0.9 Å towards the bilayer center at 15 dyn/cm. Maximum membrane tension of 15 dyn/cm caused 6.4% increase in area per lipid, 4.7% decrease in bilayer thickness and 1.4% increase in the volume of the bilayer. Dipole-potential sensitive fluorescent probes were used to detect membrane tension induced changes in DOPC vesicles exposed to osmotic stress. Experiments confirmed that dipole potential of DOPC bilayer decreases at higher membrane tensions. These results are suggestive of a potentially new mechanosensing mechanism by which mechanically induced structural changes in the lipid bilayer membrane could modulate the function of membrane proteins by altering electrostatic interactions and energetics of protein conformational states. PMID:21722624

Pericellular oxygen monitoring with integrated sensor chips for reproducible cell culture experiments.

PubMed

Kieninger, J; Aravindalochanan, K; Sandvik, J A; Pettersen, E O; Urban, G A

2014-04-01

Here we present an application, in two tumour cell lines, based on the Sensing Cell Culture Flask system as a cell culture monitoring tool for pericellular oxygen sensing. T-47D (human breast cancer) and T98G (human brain cancer) cells were cultured either in atmospheric air or in a glove-box set at 4% oxygen, in both cases with 5% CO2 in the gas phase. Pericellular oxygen tension was measured with the help of an integrated sensor chip comprising oxygen sensor arrays. Obtained results illustrate variation of pericellular oxygen tension in attached cells covered by stagnant medium. Independent of incubation conditions, low pericellular oxygen concentration levels, usually associated with hypoxia, were found in dense cell cultures. Respiration alone brought pericellular oxygen concentration down to levels which could activate hypoxia-sensing regulatory processes in cultures believed to be aerobic. Cells in culture believed to experience conditions of mild hypoxia may, in reality, experience severe hypoxia. This would lead to incorrect assumptions and suggests that pericellular oxygen concentration readings are of great importance to obtain reproducible results when dealing with hypoxic and normoxic (aerobic) incubation conditions. The Sensing Cell Culture Flask system allows continuous monitoring of pericellular oxygen concentration with outstanding long-term stability and no need for recalibration during cell culture experiments. The sensor is integrated into the flask bottom, thus in direct contact with attached cells. No additional equipment needs to be inserted into the flask during culturing. Transparency of the electrochemical sensor chip allows optical inspection of cells attached on top of the sensor. © 2014 John Wiley & Sons Ltd.

The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox

PubMed Central

Kot, Jacek; Sicko, Zdzislaw

2015-01-01

Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window—also called inherent unsaturation or partial pressure vacancy—but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of

Dependence of nitrite oxidation on nitrite and oxygen in low-oxygen seawater

NASA Astrophysics Data System (ADS)

Sun, Xin; Ji, Qixing; Jayakumar, Amal; Ward, Bess B.

2017-08-01

Nitrite oxidation is an essential step in transformations of fixed nitrogen. The physiology of nitrite oxidizing bacteria (NOB) implies that the rates of nitrite oxidation should be controlled by concentration of their substrate, nitrite, and the terminal electron acceptor, oxygen. The sensitivities of nitrite oxidation to oxygen and nitrite concentrations were investigated using 15N tracer incubations in the Eastern Tropical North Pacific. Nitrite stimulated nitrite oxidation under low in situ nitrite conditions, following Michaelis-Menten kinetics, indicating that nitrite was the limiting substrate. The nitrite half-saturation constant (Ks = 0.254 ± 0.161 μM) was 1-3 orders of magnitude lower than in cultivated NOB, indicating higher affinity of marine NOB for nitrite. The highest rates of nitrite oxidation were measured in the oxygen depleted zone (ODZ), and were partially inhibited by additions of oxygen. This oxygen sensitivity suggests that ODZ specialist NOB, adapted to low-oxygen conditions, are responsible for apparently anaerobic nitrite oxidation.

Changes in passive tension of muscle in humans and animals after eccentric exercise

PubMed Central

Whitehead, N P; Weerakkody, N S; Gregory, J E; Morgan, D L; Proske, U

2001-01-01

This is a report of experiments on ankle extensor muscles of human subjects and a parallel series on the medial gastrocnemius of the anaesthetised cat, investigating the origin of the rise in passive tension after a period of eccentric exercise. Subjects exercised their triceps surae of one leg eccentrically by walking backwards on an inclined, forward-moving treadmill. Concentric exercise required walking forwards on a backwards-moving treadmill. For all subjects the other leg acted as a control. Immediately after both eccentric and concentric exercise there was a significant drop in peak active torque, but only after eccentric exercise was this accompanied by a shift in optimum angle for torque generation and a rise in passive torque. In the eccentrically exercised group some swelling and soreness developed but not until 24 h post-exercise. In the animal experiments the contracting muscle was stretched by 6 mm at 50 mm s−1 over a length range symmetrical about the optimum length for tension generation. Measurements of passive tension were made before and after the eccentric contractions, using small stretches to a range of muscle lengths, or with large stretches covering the full physiological range. After 150 eccentric contractions, passive tension was significantly elevated over most of the range of lengths. Measurements of work absorption during stretch-release cycles showed significant increases after the contractions. It is suggested that the rise in passive tension in both human and animal muscles after eccentric contractions is the result of development of injury contractures in damaged muscle fibres. PMID:11389215

[Functional state of various physiological systems of the human body during respiration of neon-oxygen mixture at depth up to 400 meters].

PubMed

Poleshuk, I P; Genin, A M; Unku, R D; Mikhnenko, A E; Sementsov, V N; Suvorov, A V

1991-01-01

Hyperbaric neon-oxygen mixture has been studied for the effect of its high density under pressure of 41 ata on basic physiological functions of human organism. Typical changes of the cardiorespiratory system and tissue respiration parameters are revealed. Changes in physical working capacity are shown. Exposure to gaseous medium of high pressure and density is accompanied by the development of some compensatory-adaptive reactions. The possibility to perform mid-hard physical work is attained with overstrain of respiration and circulation function.

Matrix stiffness reverses the effect of actomyosin tension on cell proliferation

PubMed Central

Mih, Justin D.; Marinkovic, Aleksandar; Liu, Fei; Sharif, Asma S.; Tschumperlin, Daniel J.

2012-01-01

Summary The stiffness of the extracellular matrix exerts powerful effects on cell proliferation and differentiation, but the mechanisms transducing matrix stiffness into cellular fate decisions remain poorly understood. Two widely reported responses to matrix stiffening are increases in actomyosin contractility and cell proliferation. To delineate their relationship, we modulated cytoskeletal tension in cells grown across a physiological range of matrix stiffnesses. On both synthetic and naturally derived soft matrices, and across a panel of cell types, we observed a striking reversal of the effect of inhibiting actomyosin contractility, switching from the attenuation of proliferation on rigid substrates to the robust promotion of proliferation on soft matrices. Inhibiting contractility on soft matrices decoupled proliferation from cytoskeletal tension and focal adhesion organization, but not from cell spread area. Our results demonstrate that matrix stiffness and actomyosin contractility converge on cell spreading in an unexpected fashion to control a key aspect of cell fate. PMID:23097048

Oxygen and Early Animal Evolution

NASA Astrophysics Data System (ADS)

Xiao, S.

2012-12-01

It is often hypothesized that the rise of animals was triggered by an increase in O2 levels in the atmosphere and oceans. However, this hypothesis is remarkably difficult to test, because the timing of animal divergences is poorly resolved, the physiology of early animals is often unknown, estimates of past pO2 levels come with large error bars, and causal relationships between oxygenation and animal evolution are difficult to establish. Nonetheless, existing phylogenetic, paleontological, and geochemical data indicate that the evolution of macroscopic animals and motile macrometazoans with energetically expensive lifestyles may be temporally coupled with ocean oxygenation events in the Ediacaran Period. Thus, it is plausible that ocean oxygenation may have been a limiting factor in the early evolution of macroscopic, complex, and metabolically aggressive animals (particularly bilaterian animals). However, ocean oxygenation and animal evolution were likely engaged in two-way interactions: Ediacaran oxygenation may have initially lifted a physiological barrier for the evolution of animal size, motility, and active lifestyles, but subsequent animal diversification in the Paleozoic may have also changed oceanic redox structures. Viewed in a broader context, the early evolutionary history of animals was contingent upon a series of events, including genetic preparation (developmental genetics), environmental facilitation (oceanic oxygenation), and ecological escalation (Cambrian explosion), but the rise of animals to ecological importance also had important geobiological impacts on oceanic redox structures, sedimentary fabrics, and global geochemical cycles.

Thick-Filament Strain and Interfilament Spacing in Passive Muscle: Effect of Titin-Based Passive Tension

PubMed Central

Irving, Thomas; Wu, Yiming; Bekyarova, Tanya; Farman, Gerrie P.; Fukuda, Norio; Granzier, Henk

2011-01-01

We studied the effect of titin-based passive tension on sarcomere structure by simultaneously measuring passive tension and low-angle x-ray diffraction patterns on passive fiber bundles from rabbit skinned psoas muscle. We used a stretch-hold-release protocol with measurement of x-ray diffraction patterns at various passive tension levels during the hold phase before and after passive stress relaxation. Measurements were performed in relaxing solution without and with dextran T-500 to compress the lattice toward physiological levels. The myofilament lattice spacing was measured in the A-band (d1,0) and Z-disk (dZ) regions of the sarcomere. The axial spacing of the thick-filament backbone was determined from the sixth myosin meridional reflection (M6) and the equilibrium positions of myosin heads from the fourth myosin layer line peak position and the I1,1/I1,0 intensity ratio. Total passive tension was measured during the x-ray experiments, and a differential extraction technique was used to determine the relations between collagen- and titin-based passive tension and sarcomere length. Within the employed range of sarcomere lengths (∼2.2–3.4 μm), titin accounted for >80% of passive tension. X-ray results indicate that titin compresses both the A-band and Z-disk lattice spacing with viscoelastic behavior when fibers are swollen after skinning, and elastic behavior when the lattice is reduced with dextran. Titin also increases the axial thick-filament spacing, M6, in an elastic manner in both the presence and absence of dextran. No changes were detected in either I1,1/I1,0 or the position of peaks on the fourth myosin layer line during passive stress relaxation. Passive tension and M6 measurements were converted to thick-filament compliance, yielding a value of ∼85 m/N, which is several-fold larger than the thick-filament compliance determined by others during the tetanic tension plateau of activated intact muscle. This difference can be explained by the fact

A sigh of relief or a sigh to relieve: The psychological and physiological relief effect of deep breaths.

PubMed

Vlemincx, Elke; Van Diest, Ilse; Van den Bergh, Omer

2016-10-15

Both animal and human research have revealed important associations between sighs and relief. Previously we argued to conceive of sighs as resetters which temporarily induce relief. The present study aimed to investigate the psychological and physiological relief effect of sighs by instructed deep breaths and spontaneous sighs compared to a control breathing maneuver. Participants completed three blocks of 40 trials during which uncertainty cues were followed by either safety cues followed by a positive picture, or danger cues followed by a negative picture. One block was presented without breathing instructions, two subsequent blocks with breathing instructions. During the presentation of the safety and danger cues, an instruction was given to either 'take a deep breath' or 'postpone the next inhalation for 2 s (breath hold). Continuously, participants rated relief and Frontalis electromyography was recorded. Trait anxiety sensitivity was assessed by the Anxiety Sensitivity Index. Self-reported relief and physiological tension were compared 5s before and after instructed deep breaths and breath holds, and before and after spontaneous deep breaths and breath holds in the respective blocks. Results show that self-reported relief following an instructed deep breath was higher than before. Physiological tension decreased following a spontaneous sigh in high anxiety sensitive persons and following a spontaneous breath hold in low anxiety sensitive persons. These results are the first to show that a deep breath relieves and, in anxiety sensitive persons, reduces physiological tension. These findings support the hypothesis that sighs are psychological and physiological resetters. Copyright © 2016 Elsevier Inc. All rights reserved.

Physiology of Angina and Its Alleviation With Nitroglycerin

PubMed Central

Williams, Rupert; Lockie, Timothy; Khawaja, Muhammed Z.; De Silva, Kalpa; Lumley, Matthew; Patterson, Tiffany; Arri, Satpal; Ihsan, Sana; Ellis, Howard; Guilcher, Antoine; Clapp, Brian; Chowienczyk, Philip J.; Plein, Sven; Perera, Divaka; Marber, Michael S.; Redwood, Simon R.

2017-01-01

Background: The mechanisms governing exercise-induced angina and its alleviation by the most commonly used antianginal drug, nitroglycerin, are incompletely understood. The purpose of this study was to develop a method by which the effects of antianginal drugs could be evaluated invasively during physiological exercise to gain further understanding of the clinical impact of angina and nitroglycerin. Methods: Forty patients (mean age, 65.2±7.6 years) with exertional angina and coronary artery disease underwent cardiac catheterization via radial access and performed incremental exercise using a supine cycle ergometer. As they developed limiting angina, sublingual nitroglycerin was administered to half the patients, and all patients continued to exercise for 2 minutes at the same workload. Throughout exercise, distal coronary pressure and flow velocity and central aortic pressure were recorded with sensor wires. Results: Patients continued to exercise after nitroglycerin administration with less ST-segment depression (P=0.003) and therefore myocardial ischemia. Significant reductions in afterload (aortic pressure, P=0.030) and myocardial oxygen demand were seen (tension-time index, P=0.024; rate-pressure product, P=0.046), as well as an increase in myocardial oxygen supply (Buckberg index, P=0.017). Exercise reduced peripheral arterial wave reflection (P<0.05), which was not further augmented by the administration of nitroglycerin (P=0.648). The observed increases in coronary pressure gradient, stenosis resistance, and flow velocity did not reach statistical significance; however, the diastolic velocity–pressure gradient relation was consistent with a significant increase in relative stenosis severity (k coefficient, P<0.0001), in keeping with exercise-induced vasoconstriction of stenosed epicardial segments and dilatation of normal segments, with trends toward reversal with nitroglycerin. Conclusions: The catheterization laboratory protocol provides a model to

Enhancement of C2C12 differentiation by perfluorocarbon-mediated oxygen delivery.

PubMed

Fujita, Hideaki; Shimizu, Kazunori; Morioka, Yuki; Nagamori, Eiji

2010-09-01

We have studied the effect of enhanced oxygen delivery by perfluorocarbons on the differentiation of C2C12 cells. The extent of differentiation was assessed by means of phase contrast/fluorescence microscopy, active tension measurement and the glucose consumption/lactate production rates. We found that enhanced oxygen delivery is suitable for full differentiation of C2C12 cells. Copyright 2010 The Society for Biotechnology, Japan. All rights reserved.

The prefrontal oxygenation and ventilatory responses at start of one-legged cycling exercise have relation to central command.

PubMed

Asahara, Ryota; Matsukawa, Kanji; Ishii, Kei; Liang, Nan; Endo, Kana

2016-11-01

When performing exercise arbitrarily, activation of central command should start before the onset of exercise, but when exercise is forced to start with cue, activation of central command should be delayed. We examined whether the in-advance activation of central command influenced the ventilatory response and reflected in the prefrontal oxygenation, by comparing the responses during exercise with arbitrary and cued start. The breath-by-breath respiratory variables and the prefrontal oxygenated-hemoglobin concentration (Oxy-Hb) were measured during one-legged cycling. Minute ventilation (V̇e) at the onset of arbitrary one-legged cycling was augmented to a greater extent than cued cycling, while end-tidal carbon dioxide tension (ETco 2 ) decreased irrespective of arbitrary or cued start. Symmetric increase in the bilateral prefrontal Oxy-Hb occurred before and at the onset of arbitrary one-legged cycling, whereas such an increase was absent with cued start. The time course and magnitude of the increased prefrontal oxygenation were not influenced by the extent of subjective rating of perceived exertion and were the same as those of the prefrontal oxygenation during two-legged cycling previously reported. Mental imagery or passive performance of the one-legged cycling increased V̇e and decreased ETco 2 Neither intervention, however, augmented the prefrontal Oxy-Hb. The changes in ETco 2 could not explain the prefrontal oxygenation response during voluntary or passive one-legged cycling. Taken together, it is likely that the in-advance activation of central command influenced the ventilatory response by enhancing minute ventilation at the onset of one-legged cycling exercise and reflected in the preexercise increase in the prefrontal oxygenation. Copyright © 2016 the American Physiological Society.

Activation of Cu,Zn-superoxide dismutase in the absence of oxygen and the copper chaperone CCS.

PubMed

Leitch, Jeffry M; Jensen, Laran T; Bouldin, Samantha D; Outten, Caryn E; Hart, P John; Culotta, Valeria C

2009-08-14

Eukaryotic Cu,Zn-superoxide dismutases (SOD1s) are generally thought to acquire the essential copper cofactor and intramolecular disulfide bond through the action of the CCS copper chaperone. However, several metazoan SOD1s have been shown to acquire activity in vivo in the absence of CCS, and the Cu,Zn-SOD from Caenorhabditis elegans has evolved complete independence from CCS. To investigate SOD1 activation in the absence of CCS, we compared and contrasted the CCS-independent activation of C. elegans and human SOD1 to the strict CCS-dependent activation of Saccharomyces cerevisiae SOD1. Using a yeast expression system, both pathways were seen to acquire copper derived from cell surface transporters and compete for the same intracellular pool of copper. Like CCS, CCS-independent activation occurs rapidly with a preexisting pool of apo-SOD1 without the need for new protein synthesis. The two pathways, however, strongly diverge when assayed for the SOD1 disulfide. SOD1 molecules that are activated without CCS exhibit disulfide oxidation in vivo without oxygen and under copper-depleted conditions. The strict requirement for copper, oxygen, and CCS in disulfide bond oxidation appears exclusive to yeast SOD1, and we find that a unique proline at position 144 in yeast SOD1 is responsible for this disulfide effect. CCS-dependent and -independent pathways also exhibit differential requirements for molecular oxygen. CCS activation of SOD1 requires oxygen, whereas the CCS-independent pathway is able to activate SOD1s even under anaerobic conditions. In this manner, Cu,Zn-SOD from metazoans may retain activity over a wide range of physiological oxygen tensions.

Interfacial Tension and Surface Pressure of High Density Lipoprotein, Low Density Lipoprotein, and Related Lipid Droplets

PubMed Central

Ollila, O. H. Samuli; Lamberg, Antti; Lehtivaara, Maria; Koivuniemi, Artturi; Vattulainen, Ilpo

2012-01-01

Lipid droplets play a central role in energy storage and metabolism on a cellular scale. Their core is comprised of hydrophobic lipids covered by a surface region consisting of amphiphilic lipids and proteins. For example, high and low density lipoproteins (HDL and LDL, respectively) are essentially lipid droplets surrounded by specific proteins, their main function being to transport cholesterol. Interfacial tension and surface pressure of these particles are of great interest because they are related to the shape and the stability of the droplets and to protein adsorption at the interface. Here we use coarse-grained molecular-dynamics simulations to consider a number of related issues by calculating the interfacial tension in protein-free lipid droplets, and in HDL and LDL particles mimicking physiological conditions. First, our results suggest that the curvature dependence of interfacial tension becomes significant for particles with a radius of ∼5 nm, when the area per molecule in the surface region is <1.4 nm2. Further, interfacial tensions in the used HDL and LDL models are essentially unaffected by single apo-proteins at the surface. Finally, interfacial tensions of lipoproteins are higher than in thermodynamically stable droplets, suggesting that HDL and LDL are kinetically trapped into a metastable state. PMID:22995496

Effects of the kinematic viscosity and surface tension on the bubble take-off period in a catalase-hydrogen peroxide system.

PubMed

Sasaki, Satoshi; Iida, Yoshinori

2009-06-01

The effect of kinematic viscosity and surface tension of the solution was investigated by adding catalase, glucose oxidase, or glucose on the bubble movement in a catalase-hydrogen peroxide system. The kinematic viscosity was measured using a Cannon-Fenske kinematic viscometer. The surface tension of the solution was measured by the Wilhelmy method using a self-made apparatus. The effects of the hole diameter/cell wall thickness, catalase concentration, glucose concentration, and glucose oxidase concentration on the kinematic viscosity, surface tension, and bubble take-off period were investigated. With our system, the effects of the changes in the solution materiality on the bubble take-off period were proven to be very small in comparison to the change in the oxygen-producing rate.

Effect of simulated commercial flight on oxygenation in patients with interstitial lung disease and chronic obstructive pulmonary disease

PubMed Central

Seccombe, L; Kelly, P; Wong, C; Rogers, P; Lim, S; Peters, M

2004-01-01

Background: Commercial aircraft cabins provide a hostile environment for patients with underlying respiratory disease. Although there are algorithms and guidelines for predicting in-flight hypoxaemia, these relate to chronic obstructive pulmonary disease (COPD) and data for interstitial lung disease (ILD) are lacking. The purpose of this study was to evaluate the effect of simulated cabin altitude on subjects with ILD at rest and during a limited walking task. Methods: Fifteen subjects with ILD and 10 subjects with COPD were recruited. All subjects had resting arterial oxygen pressure (PaO2) of >9.3 kPa. Subjects breathed a hypoxic gas mixture containing 15% oxygen with balance nitrogen for 20 minutes at rest followed by a 50 metre walking task. Pulse oximetry (SpO2) was monitored continuously with testing terminated if levels fell below 80%. Arterial blood gas tensions were taken on room air at rest and after the resting and exercise phases of breathing the gas mixture. Results: In both groups there was a statistically significant decrease in arterial oxygen saturation (SaO2) and PaO2 from room air to 15% oxygen at rest and from 15% oxygen at rest to the completion of the walking task. The ILD group differed significantly from the COPD group in resting 15% oxygen SaO2, PaO2, and room air pH. Means for both groups fell below recommended levels at both resting and when walking on 15% oxygen. Conclusion: Even in the presence of acceptable arterial blood gas tensions at sea level, subjects with both ILD and COPD fall below recommended levels of oxygenation when cabin altitude is simulated. This is exacerbated by minimal exercise. Resting sea level arterial blood gas tensions are similarly poor in both COPD and ILD for predicting the response to simulated cabin altitude. PMID:15516473

Adaptation to oxygen: role of terminal oxidases in photosynthesis initiation in the purple photosynthetic bacterium, Rubrivivax gelatinosus.

PubMed

Hassani, Bahia Khalfaoui; Steunou, Anne-Soisig; Liotenberg, Sylviane; Reiss-Husson, Françoise; Astier, Chantal; Ouchane, Soufian

2010-06-25

The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb(3), bd, and caa(3)) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb(3)(-)/bd(-) double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O(2) tension is reduced. The cbb(3) and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O(2) pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb(3)(-) mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O(2)-detoxifying action of terminal oxidases.

Ambient Oxygen Promotes Tumorigenesis

PubMed Central

Starost, Matthew F.; Lago, Cory U.; Lim, Philip K.; Sack, Michael N.; Kang, Ju-Gyeong; Wang, Ping-yuan; Hwang, Paul M.

2011-01-01

Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ∼50% increase in the median tumor-free survival time of p53−/− mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53−/− mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo. PMID:21589870

Structural design significance of tension-tension fatigue data on composites

NASA Technical Reports Server (NTRS)

Grimes, G. C.

1977-01-01

Constant cycle tension-tension fatigue and related static tension data have been generated on six single composite material/orientation combinations and twenty-one hybrid composite material/orientation combinations. Anomalies are related to the temperature rise and stopped interval creep, whereas endurance limit stresses (runouts) are associated with static proportional limit values, when they occur, and internal damage. The significance of these room temperature-dry data on the design allowables and weight of aerodynamic structueres is discussed. Such structures are helicopter rotor blades and wing and horizontal stabilizer lower surfaces. Typical criteria for turning these data into preliminary allowables are shown, as are examples of such allowables developed from the data. These values are then compared to those that might be used if the structures were made of metal.

Laser Doppler flowmetry, transcutaneous oxygen tension measurements and Doppler pressure compared in patients undergoing amputation.

PubMed

Lantsberg, L; Goldman, M

1991-04-01

The level of amputation continues to present a challenge for surgeons. In view of this, 24 patients who required an amputation of their ischaemic leg were studied prospectively using Laser Doppler flowmetry (LDF), TcpO2 measurements and Doppler ultrasound to assess the best level for amputation. In all patients gangrene of the leg and rest pain were the indication for an amputation. Skin oxygen tension (TcpO2) and skin blood flow (LDF) measurements were obtained the day before surgery on the proposed anterior and posterior skin flaps for below knee amputation and the maximum Doppler systolic pressure was measured. The level of amputation was chosen at surgery by clinical judgement without reference to the measurements mentioned above. A below knee amputation was performed in 17 patients and an above knee in seven. All amputations healed by primary intention. Doppler pressures showed poor discrimination with a median value of 10 mmHg (0-25) in AK patients and 35 mmHg (0-85) in the BK group (p greater than 0.05). In contrast TcpO2 showed a trend. In the BK group the median value was 20 mmHg (4-50) on the anterior and 22 mmHg (2-60) on the posterior flap compared to above knee amputees with median values of 6 mmHg (2-11) and 8 mmHg (3-38), respectively (p greater than 0.05). Laser Doppler seemed more useful. In BK patients the median LDF values were 36 mV (20-85) on the anterior and 34 mV (20-80) on the posterior flap with median LDF values of 10 mV (10-18) on the anterior and 11 mV (8-38) on the posterior flap in the above knee group (p less than 0.01). Laser Doppler flowmetry is a simple objective test, which is a better discriminator of skin flap perfusion than either TcpO2 or Doppler ankle pressures.

Oxygen-coupled redox regulation of the skeletal muscle ryanodine receptor-Ca2+ release channel by NADPH oxidase 4

PubMed Central

Sun, Qi-An; Hess, Douglas T.; Nogueira, Leonardo; Yong, Sandro; Bowles, Dawn E.; Eu, Jerry; Laurita, Kenneth R.; Meissner, Gerhard; Stamler, Jonathan S.

2011-01-01

Physiological sensing of O2 tension (partial O2 pressure, pO2) plays an important role in some mammalian cellular systems, but striated muscle generally is not considered to be among them. Here we describe a molecular mechanism in skeletal muscle that acutely couples changes in pO2 to altered calcium release through the ryanodine receptor–Ca2+-release channel (RyR1). Reactive oxygen species are generated in proportion to pO2 by NADPH oxidase 4 (Nox4) in the sarcoplasmic reticulum, and the consequent oxidation of a small set of RyR1 cysteine thiols results in increased RyR1 activity and Ca2+ release in isolated sarcoplasmic reticulum and in cultured myofibers and enhanced contractility of intact muscle. Thus, Nox4 is an O2 sensor in skeletal muscle, and O2-coupled hydrogen peroxide production by Nox4 governs the redox state of regulatory RyR1 thiols and thereby governs muscle performance. These findings reveal a molecular mechanism for O2-based signaling by an NADPH oxidase and demonstrate a physiological role for oxidative modification of RyR1. PMID:21896730

Surface Tension Mediated Under-Water Adhesion of Rigid Spheres on Soft, Charged Surfaces

NASA Astrophysics Data System (ADS)

Sinha, Shayandev; Das, Siddhartha

2015-11-01

Understanding the phenomenon of surface-tension-mediated under-water adhesion is necessary for studying a plethora of physiological and technical phenomena, such as the uptake of bacteria or nanoparticle by cells, attachment of virus on bacterial surfaces, biofouling on large ocean vessels and marine devices, etc. This adhesion phenomenon becomes highly non-trivial in case the soft surface where the adhesion occurs is also charged. Here we propose a theory for analyzing such an under-water adhesion of a rigid sphere on a soft, charged surface, represented by a grafted polyelectrolyte layer (PEL). We develop a model based on the minimization of free energy that, in addition to considering the elastic and the surface-tension-mediated adhesion energies, also accounts for the PEL electric double layer (EDL) induced electrostatic energies. We show that in the presence of surface charges, adhesion gets enhanced. This can be explained by the fact that the increase in the elastic energy is better balanced by the lowering of the EDL energy associated with the adhesion process. The entire behaviour is further dictated by the surface tension components that govern the adhesion energy.

Retinal Vessel Oxygen Saturation during 100% Oxygen Breathing in Healthy Individuals

PubMed Central

Olafsdottir, Olof Birna; Eliasdottir, Thorunn Scheving; Kristjansdottir, Jona Valgerdur; Hardarson, Sveinn Hakon; Stefánsson, Einar

2015-01-01

Purpose To detect how systemic hyperoxia affects oxygen saturation in retinal arterioles and venules in healthy individuals. Methods Retinal vessel oxygen saturation was measured in 30 healthy individuals with a spectrophotometric retinal oximeter (Oxymap T1). Oximetry was performed during breathing of room air, 100% oxygen (10 minutes, 6L/min) and then again room air (10 minutes recovery). Results Mean oxygen saturation rises modestly in retinal arterioles during 100% oxygen breathing (94.5%±3.8 vs. 92.0%±3.7% at baseline, p<0.0001) and dramatically in retinal venules (76.2%±8.0% vs. 51.3%±5.6%, p<0.0001). The arteriovenous difference decreased during 100% oxygen breathing (18.3%±9.0% vs. 40.7%±5.7%, p<0.0001). The mean diameter of arterioles decreased during 100% oxygen breathing compared to baseline (9.7±1.4 pixels vs. 10.3±1.3 pixels, p<0.0001) and the same applies to the mean venular diameter (11.4±1.2 pixels vs. 13.3±1.5 pixels, p<0.0001). Conclusions Breathing 100% oxygen increases oxygen saturation in retinal arterioles and more so in venules and constricts them compared to baseline levels. The dramatic increase in oxygen saturation in venules reflects oxygen flow from the choroid and the unusual vascular anatomy and oxygen physiology of the eye. PMID:26042732

Blood oxygenation level-dependent MRI for assessment of renal oxygenation

PubMed Central

Neugarten, Joel; Golestaneh, Ladan

2014-01-01

Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently emerged as an important noninvasive technique to assess intrarenal oxygenation under physiologic and pathophysiologic conditions. Although this tool represents a major addition to our armamentarium of methodologies to investigate the role of hypoxia in the pathogenesis of acute kidney injury and progressive chronic kidney disease, numerous technical limitations confound interpretation of data derived from this approach. BOLD MRI has been utilized to assess intrarenal oxygenation in numerous experimental models of kidney disease and in human subjects with diabetic and nondiabetic chronic kidney disease, acute kidney injury, renal allograft rejection, contrast-associated nephropathy, and obstructive uropathy. However, confidence in conclusions based on data derived from BOLD MRI measurements will require continuing advances and technical refinements in the use of this technique. PMID:25473304

Thermodynamic approach to oxygen delivery in vivo by natural and artificial oxygen carriers.

PubMed

Bucci, Enrico

2009-06-01

Oxygen is a toxic gas, still indispensable to aerobic life. This paper explores how normal physiology uses the physico-chemical and thermodynamic characteristics of oxygen for transforming a toxic gas into a non toxic indispensable metabolite. Plasma oxygen concentration is in the range of 10(-5) M, insufficient to sustain metabolism. Oxygen carriers, present in blood, release oxygen into plasma, thereby replacing consumed oxygen and buffering PO(2) near their P(50). They are the natural cell-bound carriers, like hemoglobin inside red cells, myoglobin inside myocytes, and artificial cell-free hemoglobin-based oxygen carriers (HBOC) dissolved in plasma. Metabolic oxygen replacement can be defined as cell-bound and cell-free delivery. Cell-bound delivery is retarded by the slow diffusion of oxygen in plasma and interstitial fluids. The 40% hematocrit of normal blood compensates for the delay, coping with the fast oxygen consumption by mitochondria. Facilitated oxygen diffusion by HBOCs corrects for the slow diffusion, making cell-free delivery relatively independent from P(50). At all oxygen affinities, HBOCs produce hyperoxygenations that are compensated by vasoconstrictions. There is a strict direct correlation between the rate of oxygen replacement and hemoglobin content of blood. The free energy loss of the gradient adds a relevant regulation of tissues oxygenation. Oxygen is retained intravascularly by the limited permeability to gases of vessel walls.

Influence of oxygen availability on the activities of ammonia-oxidizing archaea.

PubMed

Qin, Wei; Meinhardt, Kelley A; Moffett, James W; Devol, Allan H; Virginia Armbrust, E; Ingalls, Anitra E; Stahl, David A

2017-06-01

Recent studies point to the importance of oxygen (O 2 ) in controlling the distribution and activity of marine ammonia-oxidizing archaea (AOA), one of the most abundant prokaryotes in the ocean. The AOA are associated with regions of low O 2 tension in oceanic oxygen minimum zones (OMZs), and O 2 availability is suggested to influence their production of the ozone-depleting greenhouse gas nitrous oxide (N 2 O). We show that marine AOA available in pure culture sustain high ammonia oxidation activity at low μM O 2 concentrations, characteristic of suboxic regions of OMZs (<10 µM O 2 ), and that atmospheric concentrations of O 2 may inhibit the growth of some environmental populations. We quantify the increasing N 2 O production by marine AOA with decreasing O 2 tensions, consistent with the plausibility of an AOA contribution to the accumulation of N 2 O at the oxic-anoxic redox boundaries of OMZs. Variable sensitivity to peroxide also suggests that endogenous or exogenous reactive oxygen species are of importance in determining the environmental distribution of some populations. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Vented chest seals for prevention of tension pneumothorax in a communicating pneumothorax.

PubMed

Kotora, Joseph G; Henao, Jose; Littlejohn, Lanny F; Kircher, Sara

2013-11-01

Tension pneumothorax accounts for 3%-4% of combat casualties and 10% of civilian chest trauma. Air entering a wound via a communicating pneumothorax rather than by the trachea can result in respiratory arrest and death. In such cases, the Committee on Tactical Combat Casualty Care advocates the use of unvented chest seals to prevent respiratory compromise. A comparison of three commercially available vented chest seals was undertaken to evaluate the efficacy of tension pneumothorax prevention after seal application. A surgical thoracostomy was created and sealed by placing a shortened 10-mL syringe barrel (with plunger in place) into the wound. Tension pneumothorax was achieved via air introduction through a Cordis to a maximum volume of 50 mL/kg. A 20% drop in mean arterial pressure or a 20% increase in heart rate confirmed hemodynamic compromise. After evacuation, one of three vented chest seals (HyFin(®), n = 8; Sentinel(®), n = 8, SAM(®), n = 8) was applied. Air was injected to a maximum of 50 mL/kg twice, followed by a 10% autologous blood infusion, and finally, a third 50 mL/kg air bolus. Survivors completed all three interventions, and a 15-min recovery period. The introduction of 29.0 (±11.5) mL/kg of air resulted in tension physiology. All three seals effectively evacuated air and blood. Hemodynamic compromise failed to develop with a chest seal in place. HyFin(®), SAM(®), and Sentinel(®) vented chest seals are equally effective in evacuating blood and air in a communicating pneumothorax model. All three prevented tension pneumothorax formation after penetrating thoracic trauma. Published by Elsevier Inc.

Transcriptional and metabolic response of recombinant Escherichia coli to spatial dissolved oxygen tension gradients simulated in a scale-down system.

PubMed

Lara, Alvaro R; Leal, Lidia; Flores, Noemí; Gosset, Guillermo; Bolívar, Francisco; Ramírez, Octavio T

2006-02-05

Escherichia coli, expressing recombinant green fluorescent protein (GFP), was subjected to dissolved oxygen tension (DOT) oscillations in a two-compartment system for simulating gradients that can occur in large-scale bioreactors. Cells were continuously circulated between the anaerobic (0% DOT) and aerobic (10% DOT) vessels of the scale-down system to mimic an overall circulation time of 50 s, and a mean residence time in the anaerobic and aerobic compartments of 33 and 17 s, respectively. Transcription levels of mixed acid fermentation genes (ldhA, poxB, frdD, ackA, adhE, pflD, and fdhF), measured by quantitative RT-PCR, increased between 1.5- to over 6-fold under oscillatory DOT compared to aerobic cultures (constant 10% DOT). In addition, the transcription level of fumB increased whereas it decreased for sucA and sucB, suggesting that the tricarboxylic acid cycle was functioning as two open branches. Gene transcription levels revealed that cytrochrome bd, which has higher affinity to oxygen but lower energy efficiency, was preferred over cytochrome bO3 in oscillatory DOT cultures. Post-transcriptional processing limited heterologous protein production in the scale-down system, as inferred from similar gfp transcription but 19% lower GFP concentration compared to aerobic cultures. Simulated DOT gradients also affected the transcription of genes of the glyoxylate shunt (aceA), of global regulators of aerobic and anaerobic metabolism (fnr, arcA, and arcB), and other relevant genes (luxS, sodA, fumA, and sdhB). Transcriptional changes explained the observed alterations in overall stoichiometric and kinetic parameters, and production of ethanol and organic acids. Differences in transcription levels between aerobic and anaerobic compartments were also observed, indicating that E. coli can respond very fast to intermittent DOT conditions. The transcriptional responses of E. coli to DOT gradients reported here are useful for establishing rational scale-up criteria and

External post-tensioning anchorage.

DOT National Transportation Integrated Search

2011-05-01

Post-tensioning tendons in segmental bridge construction are often only anchored within the deviator and pier segments. The effectiveness of the post-tensioning (PT) system is therefore dependent on proper functioning of the anchorages. On August 28,...

Maximal Oxygen Intake and Maximal Work Performance of Active College Women.

ERIC Educational Resources Information Center

Higgs, Susanne L.

Maximal oxygen intake and associated physiological variables were measured during strenuous exercise on women subjects (N=20 physical education majors). Following assessment of maximal oxygen intake, all subjects underwent a performance test at the work level which had elicited their maximal oxygen intake. Mean maximal oxygen intake was 41.32…

Impact of Missing Physiologic Data on Performance of the Simplified Acute Physiology Score 3 Risk-Prediction Model.

PubMed

Engerström, Lars; Nolin, Thomas; Mårdh, Caroline; Sjöberg, Folke; Karlström, Göran; Fredrikson, Mats; Walther, Sten M

2017-12-01

The Simplified Acute Physiology 3 outcome prediction model has a narrow time window for recording physiologic measurements. Our objective was to examine the prevalence and impact of missing physiologic data on the Simplified Acute Physiology 3 model's performance. Retrospective analysis of prospectively collected data. Sixty-three ICUs in the Swedish Intensive Care Registry. Patients admitted during 2011-2014 (n = 107,310). None. Model performance was analyzed using the area under the receiver operating curve, scaled Brier's score, and standardized mortality rate. We used a recalibrated Simplified Acute Physiology 3 model and examined model performance in the original dataset and in a dataset of complete records where missing data were generated (simulated dataset). One or more data were missing in 40.9% of the admissions, more common in survivors and low-risk admissions than in nonsurvivors and high-risk admissions. Discrimination did not decrease with one to two missing variables, but accuracy was highest with no missing data. Calibration was best in the original dataset with a mix of full records and records with some missing values (area under the receiver operating curve was 0.85, scaled Brier 27%, and standardized mortality rate 0.99). With zero, one, and two data missing, the scaled Brier was 31%, 26%, and 21%; area under the receiver operating curve was 0.84, 0.87, and 0.89; and standardized mortality rate was 0.92, 1.05 and 1.10, respectively. Datasets where the missing data were simulated for oxygenation or oxygenation and hydrogen ion concentration together performed worse than datasets with these data originally missing. There is a coupling between missing physiologic data, admission type, low risk, and survival. Increased loss of physiologic data reduced model performance and will deflate mortality risk, resulting in falsely high standardized mortality rates.

The influence of systemic hemodynamics and oxygen transport on cerebral oxygen saturation in neonates after the Norwood procedure.

PubMed

Li, Jia; Zhang, Gencheng; Holtby, Helen; Guerguerian, Anne-Marie; Cai, Sally; Humpl, Tilman; Caldarone, Christopher A; Redington, Andrew N; Van Arsdell, Glen S

2008-01-01

Ischemic brain injury is an important morbidity in neonates after the Norwood procedure. Its relationship to systemic hemodynamic oxygen transport is poorly understood. Sixteen neonates undergoing the Norwood procedure were studied. Continuous cerebral oxygen saturation was measured by near-infrared spectroscopy. Continuous oxygen consumption was measured by respiratory mass spectrometry. Pulmonary and systemic blood flow, systemic vascular resistance, oxygen delivery, and oxygen extraction ratio were derived with measurements of arterial, and superior vena cava and pulmonary venous gases and pressures at 2- to 4-hour intervals during the first 72 hours in the intensive care unit. Mean cerebral oxygen saturation was 66% +/- 12% before the operation, reduced to 51% +/- 13% on arrival in the intensive care unit, and remained low during the first 8 hours; it increased to 56% +/- 9% at 72 hours, still significantly lower than the preoperative level (P < .05). Postoperatively, cerebral oxygen saturation was closely and positively correlated with systemic arterial pressure, arterial oxygen saturation, and arterial oxygen tension and negatively with oxygen extraction ratio (P < .0001 for all). Cerebral oxygen saturation was moderately and positively correlated with systemic blood flow and oxygen delivery (P < .0001 for both). It was weakly and positively correlated with pulmonary blood flow (P = .001) and hemoglobin (P = .02) and negatively correlated with systemic vascular resistance (P = .003). It was not correlated with oxygen consumption (P > .05). Cerebral oxygen saturation decreased significantly in neonates during the early postoperative period after the Norwood procedure and was significantly influenced by systemic hemodynamic and metabolic events. As such, hemodynamic interventions to modify systemic oxygen transport may provide further opportunities to reduce the risk of cerebral ischemia and improve neurodevelopmental outcomes.

Causal Structure of Brain Physiology after Brain Injury from Subarachnoid Hemorrhage.

PubMed

Claassen, Jan; Rahman, Shah Atiqur; Huang, Yuxiao; Frey, Hans-Peter; Schmidt, J Michael; Albers, David; Falo, Cristina Maria; Park, Soojin; Agarwal, Sachin; Connolly, E Sander; Kleinberg, Samantha

2016-01-01

High frequency physiologic data are routinely generated for intensive care patients. While massive amounts of data make it difficult for clinicians to extract meaningful signals, these data could provide insight into the state of critically ill patients and guide interventions. We develop uniquely customized computational methods to uncover the causal structure within systemic and brain physiologic measures recorded in a neurological intensive care unit after subarachnoid hemorrhage. While the data have many missing values, poor signal-to-noise ratio, and are composed from a heterogeneous patient population, our advanced imputation and causal inference techniques enable physiologic models to be learned for individuals. Our analyses confirm that complex physiologic relationships including demand and supply of oxygen underlie brain oxygen measurements and that mechanisms for brain swelling early after injury may differ from those that develop in a delayed fashion. These inference methods will enable wider use of ICU data to understand patient physiology.

Do low oxygen environments facilitate marine invasions? Relative tolerance of native and invasive species to low oxygen conditions.

PubMed

Lagos, Marcelo E; Barneche, Diego R; White, Craig R; Marshall, Dustin J

2017-06-01

Biological invasions are one of the biggest threats to global biodiversity. Marine artificial structures are proliferating worldwide and provide a haven for marine invasive species. Such structures disrupt local hydrodynamics, which can lead to the formation of oxygen-depleted microsites. The extent to which native fauna can cope with such low oxygen conditions, and whether invasive species, long associated with artificial structures in flow-restricted habitats, have adapted to these conditions remains unclear. We measured water flow and oxygen availability in marinas and piers at the scales relevant to sessile marine invertebrates (mm). We then measured the capacity of invasive and native marine invertebrates to maintain metabolic rates under decreasing levels of oxygen using standard laboratory assays. We found that marinas reduce water flow relative to piers, and that local oxygen levels can be zero in low flow conditions. We also found that for species with erect growth forms, invasive species can tolerate much lower levels of oxygen relative to native species. Integrating the field and laboratory data showed that up to 30% of available microhabitats within low flow environments are physiologically stressful for native species, while only 18% of the same habitat is physiologically stressful for invasive species. These results suggest that invasive species have adapted to low oxygen habitats associated with manmade habitats, and artificial structures may be creating niche opportunities for invasive species. © 2017 John Wiley & Sons Ltd.

Encouraging effects of a short-term, adapted Nordic diet intervention on skin microvascular function and skin oxygen tension in younger and older adults.

PubMed

Rogerson, David; McNeill, Scott; Könönen, Heidi; Klonizakis, Markos

2018-05-01

The microvascular benefits of regional diets appear in the literature; however, little is known about Nordic-type diets. We investigated the effects of a short-term, adapted, Nordic diet on microvascular function in younger and older individuals at rest and during activity. Thirteen young (mean age: 28 y; standard deviation: 5 y) and 15 older (mean age: 68 y; standard deviation: 6 y) participants consumed a modified Nordic diet for 4 wk. Laser Doppler flowmetry and transcutaneous oxygen monitoring were used to assess cutaneous microvascular function and oxygen tension pre- and postintervention; blood pressure, body mass, body fat percentage, ratings of perceived exertion, and peak heart rate during activity were examined concurrently. Axon-mediated vasodilation improved in older participants (1.17 [0.30] to 1.30 [0.30]; P < 0.05). Improvements in endothelium-dependent vasodilation were noted in both young (1.67 [0.50] to 2.03 [0.62]; P < 0.05) and older participants (1.49 [0.37] to 1.63 [0.39]; P < 0.05). Reduced peak heart rate during activity was noted in older participants only (36.5 [8.9] to 35.3 [8.5]; P < 0.05) and reduced body fat percentage in young participants only (young = 27.2 [8.3] to 25.2 [8.8]; P < 0.05). No other variables reached statistical significance; however, trends were observed. We observed statistically significant improvements in microvascular function, peak heart rate, and body composition. An adapted Nordic diet might improve microvascular health. Copyright © 2017 Elsevier Inc. All rights reserved.

CPAP and High-Flow Nasal Cannula Oxygen in Bronchiolitis.

PubMed

Sinha, Ian P; McBride, Antonia K S; Smith, Rachel; Fernandes, Ricardo M

2015-09-01

Severe respiratory failure develops in some infants with bronchiolitis because of a complex pathophysiologic process involving increased airways resistance, alveolar atelectasis, muscle fatigue, and hypoxemia due to mismatch between ventilation and perfusion. Nasal CPAP and high-flow nasal cannula (HFNC) oxygen may improve the work of breathing and oxygenation. Although the mechanisms behind these noninvasive modalities of respiratory support are not well understood, they may help infants by way of distending pressure and delivery of high concentrations of warmed and humidified oxygen. Observational studies of varying quality have suggested that CPAP and HFNC may confer direct physiologic benefits to infants with bronchiolitis and that their use has reduced the need for intubation. No trials to our knowledge, however, have compared CPAP with HFNC in bronchiolitis. Two randomized trials compared CPAP with oxygen delivered by low-flow nasal cannula or face mask and found some improvements in blood gas results and some physiologic parameters, but these trials were unable to demonstrate a reduction in the need for intubation. Two trials evaluated HFNC in bronchiolitis (one comparing it with headbox oxygen, the other with nebulized hypertonic saline), with the results not seeming to suggest important clinical or physiologic benefits. In this article, we review the pathophysiology of respiratory failure in bronchiolitis, discuss these trials in detail, and consider how future research studies may be designed to best evaluate CPAP and HFNC in bronchiolitis.

Jumonji Domain Containing Protein 6: A Novel Oxygen Sensor in the Human Placenta.

PubMed

Alahari, Sruthi; Post, Martin; Caniggia, Isabella

2015-08-01

Persistent low oxygen is implicated in the pathogenesis of placental-associated pathologies such as preeclampsia, a serious disorder of pregnancy. Emerging evidence implicates a novel family of Jumonji C catalytic domain proteins as mediators of hypoxic gene expression. Here, we investigated the regulatory relationship between Jumonji C domain containing protein 6 (JMJD6) and hypoxia-inducible factor (HIF)1A in the human placenta at physiological and pathological conditions. JMJD6 expression inversely correlated with changes in oxygen tension during early placental development, ie, high at 7-9 weeks when-partial pressure of O2 is low and declining afterwards when-partial pressure of O2 increases. Moreover, JMJD6 protein was significantly elevated in early-onset preeclamptic placentae, localizing to the syncytiotrophoblast layer and syncytial knots. Exposure of primary isolated trophoblast cells, human villous explants, and JEG3 choriocarcinoma cells to low oxygen (3%) and sodium nitroprusside (inducer of oxidative stress) also resulted in elevated JMJD6 levels, which was abrogated by HIF1A knockdown. In normoxia, knockdown of JMJD6 in JEG3 cells stabilized HIF1A with a concomitant decrease in von Hippel-Lindau (VHL) tumor suppressor protein, a negative regulator of HIF1A stability. In contrast, overexpression of JMJD6 enhanced VHL expression and destabilized HIF1A. JMJD6 regulation of VHL stability did not involve the ubiquitin-proteasome system but likely occurred through lysyl hydroxylation and small ubiquitin-like modifier 1-dependent small ubiquitin-like modifierylation. In summary, our data signify a novel role for JMJD6 as an oxygen sensor in the human placenta, and alterations in the JMJD6-VHL-HIF1A feedback loop may indirectly contribute to elevated HIF1A found in preeclampsia.

Neonatal pulmonary physiology.

PubMed

Davis, Ryan P; Mychaliska, George B

2013-11-01

Managing pulmonary issues faced by both term and preterm infants remains a challenge to the practicing pediatric surgeon. An understanding of normal fetal and neonatal pulmonary development and physiology is the cornerstone for understanding the pathophysiology and treatment of many congenital and acquired problems in the neonate. Progression through the phases of lung development and the transition to postnatal life requires a symphony of complex and overlapping events to work in concert for smooth and successful transition to occur. Pulmonary physiology and oxygen transport in the neonate are similar to older children; however, there are critical differences that are important to take into consideration when treating the youngest of patients. Our understanding of fetal and neonatal pulmonary physiology continues to evolve as the molecular and cellular events governing these processes are better understood. This deeper understanding has helped to facilitate groundbreaking research, leading to improved technology and treatment of term and preterm infants. As therapeutics and research continue to advance, a review of neonatal pulmonary physiology is essential to assist the clinician with his/her management of the wide variety of challenging congenital and acquired pulmonary disease. © 2013 Published by Elsevier Inc.

Mitochondria and Reactive Oxygen Species: Physiology and Pathophysiology

PubMed Central

Bolisetty, Subhashini; Jaimes, Edgar A.

2013-01-01

The air that we breathe contains nearly 21% oxygen, most of which is utilized by mitochondria during respiration. While we cannot live without it, it was perceived as a bane to aerobic organisms due to the generation of reactive oxygen and nitrogen metabolites by mitochondria and other cellular compartments. However, this dogma was challenged when these species were demonstrated to modulate cellular responses through altering signaling pathways. In fact, since this discovery of a dichotomous role of reactive species in immune function and signal transduction, research in this field grew at an exponential pace and the pursuit for mechanisms involved began. Due to a significant number of review articles present on the reactive species mediated cell death, we have focused on emerging novel pathways such as autophagy, signaling and maintenance of the mitochondrial network. Despite its role in several processes, increased reactive species generation has been associated with the origin and pathogenesis of a plethora of diseases. While it is tempting to speculate that anti-oxidant therapy would protect against these disorders, growing evidence suggests that this may not be true. This further supports our belief that these reactive species play a fundamental role in maintenance of cellular and tissue homeostasis. PMID:23528859

Soft-tissue tension total knee arthroplasty.

PubMed

Asano, Hiroshi; Hoshino, Akiho; Wilton, Tim J

2004-08-01

It is far from clear how best to define the proper strength of soft-tissue tensioning in total knee arthroplasty (TKA). We attached a torque driver to the Monogram balancer/tensor device and measured soft-tissue tension in full extension and 90 degrees flexion during TKA. In our surgical procedure, when we felt proper soft-tissue tension was being applied, the mean distraction force was noted to be 126N in extension and 121N in flexion. There was no significant correlation between soft-tissue tension and the postoperative flexion angle finally achieved. To the best of our knowledge, this is the first study to assess the actual distraction forces in relation to soft-tissue tension in TKA. Further study may reveal the most appropriate forces to achieve proper soft-tissue tension in the wide variety of circumstances presenting at knee arthroplasty.

Cutaneous respirometry by dynamic measurement of mitochondrial oxygen tension for monitoring mitochondrial function in vivo.

PubMed

Harms, Floor A; Voorbeijtel, Wilhelmina J; Bodmer, Sander I A; Raat, Nicolaas J H; Mik, Egbert G

2013-09-01

Progress in diagnosis and treatment of mitochondrial dysfunction in chronic and acute disease could greatly benefit from techniques for monitoring of mitochondrial function in vivo. In this study we demonstrate the feasibility of in vivo respirometry in skin. Mitochondrial oxygen measurements by means of oxygen-dependent delayed fluorescence of protoporphyrin IX are shown to provide a robust basis for measurement of local oxygen disappearance rate (ODR). The fundamental principles behind the technology are described, together with an analysis method for retrievel of respirometry data. The feasibility and reproducibility of this clinically useful approach are demonstrated in a series of rats. Copyright © 2012 Elsevier B.V. All rights reserved.

Mathematical modeling of human brain physiological data

NASA Astrophysics Data System (ADS)

Böhm, Matthias; Faltermeier, Rupert; Brawanski, Alexander; Lang, Elmar W.

2013-12-01

Recently, a mathematical model of the basic physiological processes regulating the cerebral perfusion and oxygen supply was introduced [Jung , J. Math. Biol.JMBLAJ0303-681210.1007/s00285-005-0343-5 51, 491 (2005)]. Although this model correctly describes the interdependence of arterial blood pressure (ABP) and intracranial pressure (ICP), it fails badly when it comes to explaining certain abnormal correlations seen in about 80% of the recordings of ABP together with ICP and the partial oxygen pressure (TiPO2) of the neuronal tissue, taken at an intensive care unit during neuromonitoring of patients with a severe brain trauma. Such recordings occasionally show segments, where the mean arterial blood pressure is correlated with the partial oxygen pressure in tissue but anticorrelated with the intracranial pressure. The origin of such abnormal correlations has not been fully understood yet. Here, two extensions to the previous approach are proposed which can reproduce such abnormal correlations in simulations quantitatively. Furthermore, as the simulations are based on a mathematical model, additional insight into the physiological mechanisms from which such abnormal correlations originate can be gained.

Leadership Tensions and Dilemmas

ERIC Educational Resources Information Center

Edmunds, Bill; Mulford, Bill; Kendall, Diana; Kendall, Lawrie

2008-01-01

Results from the Tasmanian Successful School Principal Project (SSPP) survey concur with the four major leadership tensions and dilemmas identified in a background literature review. These tensions and dilemmas relate to internal/external control, ethic of care/responsibility, and an emphasis on professional/personal as well as…

[Oxygen diffusion through the venule walls in the rat cerebral cortex during breathing with pure oxygen].

PubMed

Vovenko, E P; Sokolova, I B; Loshchagin, O V

2002-03-01

Using oxygen microelectrodes, distribution of oxygen tension (pO2) has been studied in venules of the rat brain cortex at normobaric hyperoxia (spontaneous breathing with pure oxygen). It has been shown that inhalation of oxygen results in sharp increase of pO2 in majority of the venules under study. The pO2 distribution along the length of venous microvessels of 7-280 microns in diameter is best approximated by equation: pO2 = 76.44 e-0.0008D, n = 407. The pO2 distribution was characterised by extremely high pO2 values (180-240 mm Hg) in some minute venules. Heterogeneity of pO2 distribution in venous microvessels at hyperoxia was shown to be significantly increased. Profiles of pO2 between neighbouring arterioles and venules were for the first time measured. The data clearly evidenced that O2 diffusional shunting took place between cortical arterioles and venules, provided they were distanced from each other for not over 80-100 microns. Distribution of pO2 in venules has been shown to be dependent on the blood flow in the brain cortical microvessels.

A hybrid multibreath wash-in wash-out lung function quantification scheme in human subjects using hyperpolarized 3 He MRI for simultaneous assessment of specific ventilation, alveolar oxygen tension, oxygen uptake, and air trapping.

PubMed

Hamedani, Hooman; Kadlecek, Stephen; Xin, Yi; Siddiqui, Sarmad; Gatens, Heather; Naji, Joseph; Ishii, Masaru; Cereda, Maurizio; Rossman, Milton; Rizi, Rahim

2017-08-01

To present a method for simultaneous acquisition of alveolar oxygen tension (P A O 2 ), specific ventilation (SV), and apparent diffusion coefficient (ADC) of hyperpolarized (HP) gas in the human lung, allowing reinterpretation of the P A O 2 and SV maps to produce a map of oxygen uptake (R). An imaging scheme was designed with a series of identical normoxic HP gas wash-in breaths to measure ADC, SV, P A O 2 , and R in less than 2 min. Signal dynamics were fit to an iterative recursive model that regionally solved for these parameters. This measurement was successfully performed in 12 subjects classified in three healthy, smoker, and chronic obstructive pulmonary disease (COPD) cohorts. The overall whole lung ADC, SV, P A O 2 , and R in healthy, smoker, and COPD subjects was 0.20 ± 0.03 cm 2 /s, 0.39 ± 0.06,113 ± 2 Torr, and 1.55 ± 0.35 Torr/s, respectively, in healthy subjects; 0.21 ± 0.03 cm 2 /s, 0.33 ± 0.06, 115.9 ± 4 Torr, and 0.97 ± 0.2 Torr/s, respectively, in smokers; and 0.25 ± 0.06 cm 2 /s, 0.23 ± 0.08, 114.8 ± 6.0Torr, and 0.94 ± 0.12 Torr/s, respectively, in subjects with COPD. Hetrogeneity of SV, P A O 2 , and R were indicators of both smoking-related changes and disease, and the severity of the disease correlated with the degree of this heterogeneity. Subjects with symptoms showed reduced oxygen uptake and specific ventilation. High-resolution, nearly coregistered and quantitative measures of lung function and structure were obtained with less than 1 L of HP gas. This hybrid multibreath technique produced measures of lung function that revealed clear differences among the cohorts and subjects and were confirmed by correlations with global lung measurements. Magn Reson Med 78:611-624, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

A Comparison of Exercise and Meditation in Reducing Physiological Response to Stress.

ERIC Educational Resources Information Center

Sime, Wesley E.

The purpose of this investigation was to compare the effects of brief treadmill exercise and meditation with a placebo-control treatment for reduction in several physiological and psychological measures of stress, anxiety, and tension before and after a written final examination in 48 high-test anxiety subjects. The subjects, 24 men and 24 women,…

Metabolic Prosthesis for Oxygenation of Ischemic Tissue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenbaum, Elias

2009-01-01

This communication discloses new ideas and preliminary results on the development of a "metabolic prosthesis" for local oxygenation of ischemic tissue under physiological neutral conditions. We report for the first time the selective electrolysis of physiological saline by repetitively pulsed charge-limited electrolysis for the production of oxygen and suppression of free chlorine. For example, using 800 A amplitude current pulses and <200 sec pulse durations, we demonstrated prompt oxygen production and delayed chlorine production at the surface of a shiny 0.85 mm diameter spherical platinum electrode. The data, interpreted in terms of the ionic structure of the electric double layer,more » suggest a strategy for in situ production of metabolic oxygen via a new class of "smart" prosthetic implants for dealing with ischemic disease such as diabetic retinopathy. We also present data indicating that drift of the local pH of the oxygenated environment can be held constant using a feedback-controlled three electrode electrolysis system that chooses anode and cathode pair based on pH data provided by local microsensors. The work is discussed in the context of diabetic retinopathy since surgical techniques for multielectrode prosthetic implants aimed at retinal degenerative diseases have been developed.« less

Physiological responses to environmental factors related to space flight

NASA Technical Reports Server (NTRS)

Pace, N.; Grunbaum, B. W.; Kodama, A. M.; Mains, R. C.; Rahlmann, D. F.

1975-01-01

Physiological procedures and instrumentation developed for the measurement of hemodynamic and metabolic parameters during prolonged periods of weightlessness are described along with the physiological response of monkeys to weightlessness. Specific areas examined include: cardiovascular studies; thyroid function; blood oxygen transport; growth and reproduction; excreta analysis for metabolic balance studies; and electrophoretic separation of creatine phosphokinase isoenzymes in human blood.

Diabetes-Induced Decrease in Renal Oxygen Tension: Effects of an Altered Metabolism

NASA Astrophysics Data System (ADS)

Palm, Fredrik; Carlsson, Per-Ola; Fasching, Angelica; Hansell, Peter; Liss, Per

During conditions with experimental diabetes mellitus, it is evident that several alterations in renal oxygen metabolism occur, including increased mitochondrial respiration and increased lactate accumulation in the renal tissue. Consequently, these alterations will contribute to decrease the interstitial pO2, preferentially in the renal medulla of animals with sustained long-term hyperglycemia.

Tensions in Distributed Leadership

ERIC Educational Resources Information Center

Ho, Jeanne; Ng, David

2017-01-01

Purpose: This article proposes the utility of using activity theory as an analytical lens to examine the theoretical construct of distributed leadership, specifically to illuminate tensions encountered by leaders and how they resolved these tensions. Research Method: The study adopted the naturalistic inquiry approach of a case study of an…

Initial tension loss in cerclage cables.

PubMed

Ménard, Jérémie; Émard, Maxime; Canet, Fanny; Brailovski, Vladimir; Petit, Yvan; Laflamme, George Y

2013-10-01

Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure tension during insertion. Significant tension loss was observed with crimping for all cables (P<0.05). Removing the tensioner led to an additional unexpected tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent tension loss. Copyright © 2013 Elsevier Inc. All rights reserved.

Effect of epidural tramadol and lignocaine on physiological and behavioural changes in goats subjected to castration with a high tension band.

PubMed

Ajadi, R A; Owanikin, A O; Martins, M M; Gazal, O S

2012-11-01

To compare the effect of a single epidural injection of either lignocaine or tramadol on behavioural changes, anaesthetic indices, leucocyte parameters, erythrocyte sedimentation rates and concentration of cortisol in plasma in goats subjected to castration by high tension band. Ten male goats weighing 14.4 (SD 0.7) kg were randomly allocated to anaesthesia with epidural injections of tramadol (3 mg/kg), or lignocaine (4 mg/kg). Following anaesthesia, a rubber ring was applied and tensioned to the scrotal neck of each goat. Behavioural changes were noted as they occurred, and the onset of drug action (time between epidural injection and loss of pedal reflex) and duration of antinociception (time interval between disappearance and reappearance of pedal withdrawal reflex) were determined. Hearts rates, respiratory rates and rectal temperatures were determined every 15 minutes for a 90-minute period, while blood was obtained for determination of white cell counts, erythrocyte sedimentation rates and concentrations of cortisol. Anaesthetic indices were compared using Student's t-test, while physiological parameters were compared using an ANOVA for repeated measurements. Goats treated with epidural tramadol were not recumbent and continued rumination while goats treated with epidural lignocaine were recumbent and did not continue rumination. The onset of analgesia was longer (p=0.01) in goats treated with epidural tramadol (5.0 minutes; SD 1.2) than goats treated with epidural lignocaine (3.0 minutes; SD 1.1), while duration of analgesia was shorter (p=0.003) in goats treated with epidural tramadol (47.2 minutes; SD 13.1) than goats treated with epidural lignocaine (89.8 minutes; SD 23.1). There was no significant difference in heart rates, respiratory rates and erythrocyte sedimentation rates, while the concentration of cortisol in plasma differed (p<0.05) between goats treated with epidural tramadol and lignocaine. Epidural lignocaine injection produced longer

A review of calibrated blood oxygenation level-dependent (BOLD) methods for the measurement of task-induced changes in brain oxygen metabolism

PubMed Central

Blockley, Nicholas P.; Griffeth, Valerie E. M.; Simon, Aaron B.; Buxton, Richard B.

2013-01-01

The dynamics of the blood oxygenation level-dependent (BOLD) response are dependent on changes in cerebral blood flow, cerebral blood volume and the cerebral metabolic rate of oxygen consumption. Furthermore, the amplitude of the response is dependent on the baseline physiological state, defined by the haematocrit, oxygen extraction fraction and cerebral blood volume. As a result of this complex dependence, the accurate interpretation of BOLD data and robust intersubject comparisons when the baseline physiology is varied are difficult. The calibrated BOLD technique was developed to address these issues. However, the methodology is complex and its full promise has not yet been realised. In this review, the theoretical underpinnings of calibrated BOLD, and issues regarding this theory that are still to be resolved, are discussed. Important aspects of practical implementation are reviewed and reported applications of this methodology are presented. PMID:22945365

Atomic Oxygen Durability Testing of an International Space Station Solar Array Validation Coupon

NASA Technical Reports Server (NTRS)

Forkapa, Mark J.; Stidham, Curtis; Banks, Bruce A.; Rutledge, Sharon K.; Ma, David H.; Sechkar, Edward A.

1996-01-01

An International Space Station solar array validation coupon was exposed in a directed atomic oxygen beam for space environment durability testing at the NASA Lewis Research Center. Exposure to atomic oxygen and intermittent tensioning of the solar array were conducted to verify the solar array#s durability to low Earth orbital atomic oxygen and to the docking threat of plume loading both of which are anticipated over its expected mission life of fifteen years. The validation coupon was mounted on a specially designed rotisserie. The rotisserie mounting enabled the solar and anti-solar facing side of the array to be exposed to directed atomic oxygen in a sweeping arrival process replicating space exposure. The rotisserie mounting also enabled tensioning, in order to examine the durability of the array and its hinge to simulated plume loads. Flash testing to verify electrical performance of the solar array was performed with a solar simulator before and after the exposure to atomic oxygen and tensile loading. Results of the flash testing indicated little or no degradation in the solar array#s performance. Photographs were also taken of the array before and after the durability testing and are included along with comparisons and discussions in this report. The amount of atomic oxygen damage appeared minor with the exception of a very few isolated defects. There were also no indications that the simulated plume loadings had weakened or damaged the array, even though there was some erosion of Kapton due to atomic oxygen attack. Based on the results of this testing, it is apparent that the International Space Station#s solar arrays should survive the low Earth orbital atomic oxygen environment and docking threats which are anticipated over its expected mission life.

Effects of in vitro low oxygen tension preconditioning of adipose stromal cells on their in vivo chondrogenic potential: application in cartilage tissue repair.

PubMed

Portron, Sophie; Merceron, Christophe; Gauthier, Olivier; Lesoeur, Julie; Sourice, Sophie; Masson, Martial; Fellah, Borhane Hakim; Geffroy, Olivier; Lallemand, Elodie; Weiss, Pierre; Guicheux, Jérôme; Vinatier, Claire

2013-01-01

Multipotent stromal cell (MSC)-based regenerative strategy has shown promise for the repair of cartilage, an avascular tissue in which cells experience hypoxia. Hypoxia is known to promote the early chondrogenic differentiation of MSC. The aim of our study was therefore to determine whether low oxygen tension could be used to enhance the regenerative potential of MSC for cartilage repair. MSC from rabbit or human adipose stromal cells (ASC) were preconditioned in vitro in control or chondrogenic (ITS and TGF-β) medium and in 21 or 5% O2. Chondrogenic commitment was monitored by measuring COL2A1 and ACAN expression (real-time PCR). Preconditioned rabbit and human ASC were then incorporated into an Si-HPMC hydrogel and injected (i) into rabbit articular cartilage defects for 18 weeks or (ii) subcutaneously into nude mice for five weeks. The newly formed tissue was qualitatively and quantitatively evaluated by cartilage-specific immunohistological staining and scoring. The phenotype of ASC cultured in a monolayer or within Si-HPMC in control or chondrogenic medium and in 21 or 5% O2 was finally evaluated using real-time PCR. 5% O2 increased the in vitro expression of chondrogenic markers in ASC cultured in induction medium. Cells implanted within Si-HPMC hydrogel and preconditioned in chondrogenic medium formed a cartilaginous tissue, regardless of the level of oxygen. In addition, the 3D in vitro culture of ASC within Si-HPMC hydrogel was found to reinforce the pro-chondrogenic effects of the induction medium and 5% O2. These data together indicate that although 5% O2 enhances the in vitro chondrogenic differentiation of ASC, it does not enhance their in vivo chondrogenesis. These results also highlight the in vivo chondrogenic potential of ASC and their potential value in cartilage repair.

Physiological effects of intermittent hypoxia.

PubMed

Powell, F L; Garcia, N

2000-01-01

Intermittent hypoxia (IH), or periodic exposure to hypoxia interrupted by return to normoxia or less hypoxic conditions, occurs in many circumstances. In high altitude mountaineering, IH is used to optimize acclimatization although laboratory studies have not generally revealed physiologically significant benefits. IH enhances athletic performance at sea level if blood oxygen capacity increases and the usual level of training is not decreased significantly. IH for high altitude workers who commute from low altitude homes is of considerable practical interest and the ideal commuting schedule for physical and mental performance is being studied. The effect of oxygen enrichment at altitude (i.e., intermittent normoxia on a background of chronic hypoxia) on human performance is under study also. Physiological mechanisms of IH, and specifically the differences between effects of IH and acute or chronic continuous hypoxia remains to be determined. Biomedical researchers are defining the molecular and cellular mechanisms for effects of hypoxia on the body in health and disease. A comparative approach may provide additional insight about the biological significance of these effects.

Core vs. Bulk Samples in Soil-Moisture Tension Analyses

Treesearch

Walter M. Broadfoot

1954-01-01

The usual laboratory procedure in determining soil-moisture tension values is to use "undisturbed" soil cores for tensions up to 60 cm. of water and bulk soil samples for higher tensions. Low tensions are usually obtained with a tension table and the higher tensions by use of pressure plate apparatus. In tension analysis at the Vicksburg Infiltration Project...

Physiology of vitreous surgery.

PubMed

Stefánsson, Einar

2009-02-01

Vitreous surgery has various physiological and clinical consequences, both beneficial and harmful. Vitrectomy reduces the risk of retinal neovascularization, while increasing the risk of iris neovascularization, reduces macular edema and stimulates cataract formation. These clinical consequences may be understood with the help of classical laws of physics and physiology. The laws of Fick, Stokes-Einstein and Hagen-Poiseuille state that molecular transport by diffusion or convection is inversely related to the viscosity of the medium. When the vitreous gel is replaced with less viscous saline, the transport of all molecules, including oxygen and cytokines, is facilitated. Oxygen transport to ischemic retinal areas is improved, as is clearance of VEGF and other cytokines from these areas, thus reducing edema and neovascularization. At the same time, oxygen is transported faster down a concentration gradient from the anterior to the posterior segment, while VEGF moves in the opposite direction, making the anterior segment less oxygenated and with more VEGF, stimulating iris neovascularization. Silicone oil is the exception that proves the rule: it is more viscous than vitreous humour, re-establishes the transport barrier to oxygen and VEGF, and reduces the risk for iris neovascularization in the vitrectomized-lentectomized eye. Modern vitreous surgery involves a variety of treatment options in addition to vitrectomy itself, such as photocoagulation, anti-VEGF drugs, intravitreal steroids and release of vitreoretinal traction. A full understanding of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and improves retinal hemodynamics. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and the permeability effect of VEGF reduced with corticosteroids

Professional Identity Tensions of Beginning Teachers

ERIC Educational Resources Information Center

Pillen, Marieke; Beijaard, Douwe; den Brok, Perry

2013-01-01

This study reports on interviews with 24 beginning teachers about tensions they experienced regarding their professional identity. The interviewees reported a total of 59 tensions of tension that fell into three themes: (1) the change in role from student to teacher; (2) conflicts between desired and actual support given to students; and (3)…

Girdin/GIV is upregulated by cyclic tension, propagates mechanical signal transduction, and is required for the cellular proliferation and migration of MG-63 cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Jiang-Tian; Li, Yan; Yu, Bing

2015-08-21

To explore how Girdin/GIV is regulated by cyclic tension and propagates downstream signals to affect cell proliferation and migration. Human osteoblast-like MG-63 cells were exposed to cyclic tension force at 4000 μstrain and 0.5 Hz for 6 h, produced by a four-point bending system. Cyclic tension force upregulated Girdin and Akt expression and phosphorylation in cultured MG-63 cells. Girdin and Akt each promoted the phosphorylation of the other under stimulated tension. In vitro MTT and transwell assays showed that Girdin and Akt are required for cell proliferation and migration during cellular quiescence. Moreover, STAT3 was determined to be essential for Girdin expression undermore » stimulated tension force in the physiological condition, as well as for osteoblast proliferation and migration during quiescence. These findings suggest that the STAT3/Girdin/Akt pathway activates in osteoblasts in response to mechanical stimulation and may play a significant role in triggering osteoblast proliferation and migration during orthodontic treatment. - Highlights: • Tension force upregulates Girdin and Akt expression and phosphorylation. • Girdin and Akt promotes the phosphorylation of each other under tension stimulation. • Girdin and Akt are required for MG-63 cell proliferation and migration. • STAT3 is essential for Girdin expression after application of the tension forces.« less

Blood Vessel Tension Tester

NASA Technical Reports Server (NTRS)

1978-01-01

In the photo, a medical researcher is using a specially designed laboratory apparatus for measuring blood vessel tension. It was designed by Langley Research Center as a service to researchers of Norfolk General Hospital and Eastern Virginia Medical School, Norfolk, Virginia. The investigators are studying how vascular smooth muscle-muscle in the walls of blood vessels-reacts to various stimulants, such as coffee, tea, alcohol or drugs. They sought help from Langley Research Center in devising a method of measuring the tension in blood vessel segments subjected to various stimuli. The task was complicated by the extremely small size of the specimens to be tested, blood vessel "loops" resembling small rubber bands, some only half a millimeter in diameter. Langley's Instrumentation Development Section responded with a miniaturized system whose key components are a "micropositioner" for stretching a length of blood vessel and a strain gage for measuring the smooth muscle tension developed. The micropositioner is a two-pronged holder. The loop of Mood vessel is hooked over the prongs and it is stretched by increasing the distance between the prongs in minute increments, fractions of a millimeter. At each increase, the tension developed is carefully measured. In some experiments, the holder and specimen are lowered into the test tubes shown, which contain a saline solution simulating body fluid; the effect of the compound on developed tension is then measured. The device has functioned well and the investigators say it has saved several months research time.

Shape accuracy optimization for cable-rib tension deployable antenna structure with tensioned cables

NASA Astrophysics Data System (ADS)

Liu, Ruiwei; Guo, Hongwei; Liu, Rongqiang; Wang, Hongxiang; Tang, Dewei; Song, Xiaoke

2017-11-01

Shape accuracy is of substantial importance in deployable structures as the demand for large-scale deployable structures in various fields, especially in aerospace engineering, increases. The main purpose of this paper is to present a shape accuracy optimization method to find the optimal pretensions for the desired shape of cable-rib tension deployable antenna structure with tensioned cables. First, an analysis model of the deployable structure is established by using finite element method. In this model, geometrical nonlinearity is considered for the cable element and beam element. Flexible deformations of the deployable structure under the action of cable network and tensioned cables are subsequently analyzed separately. Moreover, the influence of pretension of tensioned cables on natural frequencies is studied. Based on the results, a genetic algorithm is used to find a set of reasonable pretension and thus minimize structural deformation under the first natural frequency constraint. Finally, numerical simulations are presented to analyze the deployable structure under two kinds of constraints. Results show that the shape accuracy and natural frequencies of deployable structure can be effectively improved by pretension optimization.

Spontaneous tension haemopneumothorax.

PubMed

Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey

2008-10-31

We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported.Aetiology and current approach to spontaneous haemothorax are discussed briefly.

Is oxygen availability a limiting factor for in vitro folliculogenesis?

PubMed Central

Sudhakaran, Sam; Barbato, Vincenza; Merolla, Anna; Braun, Sabrina; Di Nardo, Maddalena; Costanzo, Valentina; Ferraro, Raffaele; Iannantuoni, Nicola

2018-01-01

Transplantation of ovarian tissue for the preservation of fertility in oncological patients is becoming an accepted clinical practice. However, the risk of re-introducing tumour cells at transplantation has stirred an increased interest for complete in vitro folliculogenesis. This has not yet been achieved in humans possibly for the lack of knowledge on the environmental milieu that orchestrates folliculogenesis in vivo. The main aim of this study was to investigate the effect of oxygen availability on follicle health and growth during in vitro culture of ovarian tissue strips. To this end, a model was developed to predict the dissolved oxygen concentration in tissue under varying culture conditions. Ovarian cortical strips of bovine, adopted as an animal model, and human tissue were cultured in conventional (CD) and gas permeable (PD) dishes under different media column heights and gaseous oxygen tensions for 3, 6 and 9 days. Follicle quality, activation of primordial follicles to the primary stage, and progression to the secondary stage were analysed through histology. Follicle viability was assessed through a live-dead assay at the confocal scanning laser microscope. Findings showed a higher follicle quality and viability after culture of bovine ovarian strips in PD in adequate medium height and oxygen tensions. The best culture conditions found in the bovine were adopted for human ovarian strip culture and promoted a higher follicle quality, viability and progression. Overall, data demonstrated that modulation of oxygen availability in tissue plays a key role in maintaining follicles’ health and their ability to survive and progress to the secondary stage during ovarian tissue in vitro culture. Such culture conditions could increase the yield of healthy secondary follicles for subsequent dissection and individual culture to obtain competent oocytes. PMID:29425251

Membrane tension regulates clathrin-coated pit dynamics

NASA Astrophysics Data System (ADS)

Liu, Allen

2014-03-01

Intracellular organization depends on close communication between the extracellular environment and a network of cytoskeleton filaments. The interactions between cytoskeletal filaments and the plasma membrane lead to changes in membrane tension that in turns help regulate biological processes. Endocytosis is thought to be stimulated by low membrane tension and the removal of membrane increases membrane tension. While it is appreciated that the opposing effects of exocytosis and endocytosis have on keeping plasma membrane tension to a set point, it is not clear how membrane tension affects the dynamics of clathrin-coated pits (CCPs), the individual functional units of clathrin-mediated endocytosis. Furthermore, although it was recently shown that actin dynamics counteracts membrane tension during CCP formation, it is not clear what roles plasma membrane tension plays during CCP initiation. Based on the notion that plasma membrane tension is increased when the membrane area increases during cell spreading, we designed micro-patterned surfaces of different sizes to control the cell spreading sizes. Total internal reflection fluorescence microscopy of living cells and high content image analysis were used to quantify the dynamics of CCPs. We found that there is an increased proportion of CCPs with short (<20s) lifetime for cells on larger patterns. Interestingly, cells on larger patterns have higher CCP initiation density, an effect unexpected based on the conventional view of decreasing endocytosis with increasing membrane tension. Furthermore, by analyzing the intensity profiles of CCPs that were longer-lived, we found CCP intensity decreases with increasing cell size, indicating that the CCPs are smaller with increasing membrane tension. Finally, disruption of actin dynamics significantly increased the number of short-lived CCPs, but also decreased CCP initiation rate. Together, our study reveals new mechanistic insights into how plasma membrane tension regulates

UHMS position statement: topical oxygen for chronic wounds.

PubMed

Feldmeier, J J; Hopf, H W; Warriner, R A; Fife, C E; Gesell, L B; Bennett, M

2005-01-01

A small body of literature has been published reporting the application of topical oxygen for chronic non-healing wounds . Frequently, and erroneously, this form of oxygen administration has been referred to as "topical hyperbaric oxygen therapy" or even more erroneously "hyperbaric oxygen therapy." The advocates of topical oxygen claim several advantages over systemic hyperbaric oxygen including decreased cost, increased safety, decreased complications and putative physiologic effects including decreased free radical formation and more efficient delivery of oxygen to the wound surface. With topical oxygen an airtight chamber or polyethylene bag is sealed around a limb or the trunk by either a constriction/tourniquet device or by tape and high flow (usually 10 liters per minute) oxygen is introduced into the bag and over the wound. Pressures just over 1.0 atmospheres absolute (atm abs) (typically 1.004 to 1.013 atm abs) are recommended because higher pressures could decrease arterial/capillary inflow. The premise for topical oxygen, the diffusion of oxygen into the wound adequate to enhance healing, is attractive (though not proven) and its delivery is certainly less complex and expensive than hyperbaric oxygen. When discussing the physiology of topical oxygen, its proponents frequently reference studies of systemic hyperbaric oxygen suggesting that mechanisms are equally applicable to both topical and systemic high pressure oxygen delivery. In fact, however, the two are very different. To date, mechanisms of action whereby topical oxygen might be effective have not been defined or substantiated. Conversely, cellular toxicities due to extended courses of topical oxygen have been reported, although, again these data are not conclusive, and no mechanism for toxicity has been examined scientifically. Generally, collagen production and fibroblast proliferation are considered evidence of improved healing, and these are both enhanced by hyperbaric oxygen therapy

Tensioning device for a stretched membrane collector

DOEpatents

Murphy, Lawrence M.

1984-01-01

Disclosed is a solar concentrating collector comprising an elastic membrane member for concentrating sunlight, a frame for holding the membrane member in plane and in tension, and a tensioning means for varying the tension of the membrane member. The tensioning means is disposed at the frame and is adapted to releasably attach the membrane member thereto. The tensioning means is also adapted to uniformly and symmetrically subject the membrane member to stretching forces such that membrane stresses produced thereby are distributed uniformly over a thickness of the membrane member and reciprocal twisting moments are substantially prevented from acting about said frame.

Tensioning device for a stretched membrane collector

DOEpatents

Murphy, L.M.

1984-01-01

Disclosed is a solar concentrating collector comprising an elestic membrane member for concentrating sunlight, a frame for holding the membrane member in plane and in tension, and a tensioning means for varying the tension of the membrane member. The tensioning means is disposed at the frame and is adapted to releasably attach the membrane member thereto. The tensioning means is also adapted to uniformly and symmetrically subject the membrane member to stretching forces such that membrane stresses produced thereby are distributed uniformly over a thickness of the membrane member and reciprocal twisting moments are substantially prevented from acting about said frame.

Reduced oxygen utilization in septic shock: disorder or adaptation?

PubMed

Steiner, Alexandre A

2015-01-01

A fall in oxygen utilization during septic or endotoxic shock is thought to reflect circulatory hypoxia or mitochondrial dysfunction, but these pathology-oriented hypotheses do not explain all clinical observations. Here we discuss an alternative hypothesis of how oxygen utilization could fall as the result of a physiological thermometabolic adaptation.

A pseudo-three-dimensional model for quantification of oxygen diffusion from preglomerular arteries to renal tissue and renal venous blood.

PubMed

Lee, Chang-Joon; Ngo, Jennifer P; Kar, Saptarshi; Gardiner, Bruce S; Evans, Roger G; Smith, David W

2017-08-01

To assess the physiological significance of arterial-to-venous (AV) oxygen shunting, we generated a new pseudo-three-dimensional computational model of oxygen diffusion from intrarenal arteries to cortical tissue and veins. The model combines the 11 branching levels (known as "Strahler" orders) of the preglomerular renal vasculature in the rat, with an analysis of an extensive data set obtained using light microscopy to estimate oxygen mass transfer coefficients for each Strahler order. Furthermore, the AV shunting model is now set within a global oxygen transport model that includes transport from arteries, glomeruli, peritubular capillaries, and veins to tissue. While a number of lines of evidence suggest AV shunting is significant, most importantly, our AV oxygen shunting model predicts AV shunting is small under normal physiological conditions (~0.9% of total renal oxygen delivery; range 0.4-1.4%), but increases during renal ischemia, glomerular hyperfiltration (~2.1% of total renal oxygen delivery; range 0.84-3.36%), and some cardiovascular disease states (~3.0% of total renal oxygen delivery; range 1.2-4.8%). Under normal physiological conditions, blood Po 2 is predicted to fall by ~16 mmHg from the root of the renal artery to glomerular entry, with AV oxygen shunting contributing ~40% and oxygen diffusion from arteries to tissue contributing ~60% of this decline. Arterial Po 2 is predicted to fall most rapidly from Strahler order 4 , under normal physiological conditions. We conclude that AV oxygen shunting normally has only a small impact on renal oxygenation, but may exacerbate renal hypoxia during renal ischemia, hyperfiltration, and some cardiovascular disease states. Copyright © 2017 the American Physiological Society.

Performance, physiological, and oculometer evaluation of VTOL landing displays

NASA Technical Reports Server (NTRS)

North, R. A.; Stackhouse, S. P.; Graffunder, K.

1979-01-01

A methodological approach to measuring workload was investigated for evaluation of new concepts in VTOL aircraft displays. Physiological, visual response, and conventional flight performance measures were recorded for landing approaches performed in the NASA Visual Motion Simulator (VMS). Three displays (two computer graphic and a conventional flight director), three crosswind amplitudes, and two motion base conditions (fixed vs. moving base) were tested in a factorial design. Multivariate discriminant functions were formed from flight performance and/or visual response variables. The flight performance variable discriminant showed maximum differentation between crosswind conditions. The visual response measure discriminant maximized differences between fixed vs. motion base conditions and experimental displays. Physiological variables were used to attempt to predict the discriminant function values for each subject/condition trial. The weights of the physiological variables in these equations showed agreement with previous studies. High muscle tension, light but irregular breathing patterns, and higher heart rate with low amplitude all produced higher scores on this scale and thus represent higher workload levels.

POLYCYCLIC AROMATIC HYDROCARBON BIODEGRADATION AS A FUNCTION OF OXYGEN TENSION IN CONTAMINATED SOIL

EPA Science Inventory

Laboratory tests were conducted to determine the effect of soil gas oxygen concentration on the degradation and mineralization of spiked 14C-pyrene and nonspiked 16 priority pollutant polycyclic aromatic hydrocarbons (PAH) present in the soil. The soil used for the evaluation was...

Toward a general psychological model of tension and suspense.

PubMed

Lehne, Moritz; Koelsch, Stefan

2015-01-01

Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena.

Toward a general psychological model of tension and suspense

PubMed Central

Lehne, Moritz; Koelsch, Stefan

2015-01-01

Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309

Oximetry: A Reflective Tool for the Detection of Physiological Expression of Emotions in a Science Education Classroom

ERIC Educational Resources Information Center

Calderón, Olga

2016-01-01

The pulse oximeter is a device that measures the oxygen concentration (or oxygen saturation--SpO[subscript 2]); heart rate, and heartbeat of a person at any given time. This instrument is commonly used in medical and aerospace fields to monitor physiological outputs of a patient according to health conditions or physiological yields of a flying…

A product of its environment: the epaulette shark (Hemiscyllium ocellatum) exhibits physiological tolerance to elevated environmental CO2

PubMed Central

Heinrich, Dennis D. U.; Rummer, Jodie L.; Morash, Andrea J.; Watson, Sue-Ann; Simpfendorfer, Colin A.; Heupel, Michelle R.; Munday, Philip L.

2014-01-01

Ocean acidification, resulting from increasing anthropogenic CO2 emissions, is predicted to affect the physiological performance of many marine species. Recent studies have shown substantial reductions in aerobic performance in some teleost fish species, but no change or even enhanced performance in others. Notably lacking, however, are studies on the effects of near-future CO2 conditions on larger meso and apex predators, such as elasmobranchs. The epaulette shark (Hemiscyllium ocellatum) lives on shallow coral reef flats and in lagoons, where it may frequently encounter short-term periods of environmental hypoxia and elevated CO2, especially during nocturnal low tides. Indeed, H. ocellatum is remarkably tolerant to short periods (hours) of hypoxia, and possibly hypercapnia, but nothing is known about its response to prolonged exposure. We exposed H. ocellatum individuals to control (390 µatm) or one of two near-future CO2 treatments (600 or 880 µatm) for a minimum of 60 days and then measured key aspects of their respiratory physiology, namely the resting oxygen consumption rate, which is used to estimate resting metabolic rate, and critical oxygen tension, a proxy for hypoxia sensitivity. Neither of these respiratory attributes was affected by the long-term exposure to elevated CO2. Furthermore, there was no change in citrate synthase activity, a cellular indicator of aerobic energy production. Plasma bicarbonate concentrations were significantly elevated in sharks exposed to 600 and 880 µatm CO2 treatments, indicating that acidosis was probably prevented by regulatory changes in acid–base relevant ions. Epaulette sharks may therefore possess adaptations that confer tolerance to CO2 levels projected to occur in the ocean by the end of this century. It remains uncertain whether other elasmobranchs, especially pelagic species that do not experience such diurnal fluctuations in their environment, will be equally tolerant. PMID:27293668

Air breathing in the Arctic: influence of temperature, hypoxia, activity and restricted air access on respiratory physiology of the Alaska blackfish Dallia pectoralis

PubMed Central

Lefevre, Sjannie; Damsgaard, Christian; Pascale, Desirae R.; Nilsson, Göran E.; Stecyk, Jonathan A. W.

2014-01-01

The Alaska blackfish (Dallia pectoralis) is an air-breathing fish native to Alaska and the Bering Sea islands, where it inhabits lakes that are ice-covered in the winter, but enters warm and hypoxic waters in the summer to forage and reproduce. To understand the respiratory physiology of this species under these conditions and the selective pressures that maintain the ability to breathe air, we acclimated fish to 5°C and 15°C and used respirometry to measure: standard oxygen uptake () in normoxia (19.8 kPa PO2) and hypoxia (2.5 kPa), with and without access to air; partitioning of standard in normoxia and hypoxia; maximum and partitioning after exercise; and critical oxygen tension (Pcrit). Additionally, the effects of temperature acclimation on haematocrit, haemoglobin oxygen affinity and gill morphology were assessed. Standard was higher, but air breathing was not increased, at 15°C or after exercise at both temperatures. Fish acclimated to 5°C or 15°C increased air breathing to compensate and fully maintain standard in hypoxia. Fish were able to maintain through aquatic respiration when air was denied in normoxia, but when air was denied in hypoxia, standard was reduced by ∼30–50%. Pcrit was relatively high (5 kPa) and there were no differences in Pcrit, gill morphology, haematocrit or haemoglobin oxygen affinity at the two temperatures. Therefore, Alaska blackfish depends on air breathing in hypoxia and additional mechanisms must thus be utilised to survive hypoxic submergence during the winter, such as hypoxia-induced enhancement in the capacities for carrying and binding blood oxygen, behavioural avoidance of hypoxia and suppression of metabolic rate. PMID:25394628

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing

PubMed Central

A. Abdel‐Rahman, Engy; Mahmoud, Ali M.; Khalifa, Abdulrahman M.

2016-01-01

Abstract Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site‐directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. PMID:26801204

The impact of including spatially longitudinal heterogeneities of vessel oxygen content and vascular fraction in 3D tumor oxygenation models on predicted radiation sensitivity.

PubMed

Lagerlöf, Jakob H; Kindblom, Jon; Bernhardt, Peter

2014-04-01

Oxygen distribution models have been used to analyze the influences of oxygen tensions on tissue response after radiotherapy. These distributions are often generated assuming constant oxygen tension in the blood vessels. However, as red blood cells progress through the vessels, oxygen is continuously released into the plasma and the surrounding tissue, resulting in longitudinally varying oxygen levels in the blood vessels. In the present study, the authors investigated whether a tumor oxygenation model that incorporated longitudinally varying oxygen levels would provide different predictions of necrotic fractions and radiosensitivity compared to commonly used models with a constant oxygen pressure. Our models simulated oxygen diffusion based on a Green's function approach and oxygen consumption according to the Michaelis-Menten equation. The authors constructed tumor models with different vascular fractions (VFs), from which they generated depth oxygenation curves and a look-up table of oxygen pressure gradients. The authors evaluated models of spherical tumors of various sizes, from 1 to 10(4) mg. The authors compared the results from a model with constant vessel oxygen (CVO) pressure to those from models with longitudinal variations in oxygen saturation and either a constant VF (CVF) or variable VF (VVF) within the tumor tissue. The authors monitored the necrotic fractions, defined as tumor regions with an oxygen pressure below 1 mmHg. Tumor radiation sensitivity was expressed as D99, the homogeneous radiation dose required for a tumor control probability of 0.99. In the CVO saturation model, no necrosis was observed, and decreasing the VF could only decrease the D99 by up to 10%. Furthermore, the D99 vs VF dependence was similar for different tumor masses. Compared to the CVO model, the extended CVF and VVF models provided clearly different results, including pronounced effects of VF and tumor size on the necrotic fraction and D99, necrotic fractions ranging