Polarographic Oxygen Sensor Research Articles

Mitochondrial respiratory capacity in patients with acute episodes of bipolar disorder compared with clinical remission

IntroductionBipolar disorder (BD) is a chronic and recurrent disease characterized by acute mood episodes alternated with periods of euthymia. The available literature postulates that a biphasic dysregulation of mitochondrial bioenergetics might be observed in BD.ObjectivesWe aimed to explore differences in in vivo mitochondrial respiration (1) intra-individually: longitudinally within patients during an acute mood episode of BD and after clinical remission, and (2) inter-individually: between patients with BD on depressive or manic episodes and healthy controls (HC).MethodsPatients admitted to our acute psychiatric ward with a manic episode or bipolar depression were recruited. Different mitochondrial oxygen consumption rates (OCRs) were assessed during the acute episode (T0) and after clinical remission (T1) in one million of peripheral blood mononuclear cells (PBMC): Routine, Leak, ETC and Rox. They were measured as picomoles of oxygen per million cells (pmol O2/million). This experiment was also conducted in HC. High-resolution respirometry was performed at 37°C by polarographic oxygen sensors in a two-chamber Oxygraph-2k system. Manic and depressive symptoms were assessed using standardized psychometric scales. Oxygen consumption capacity was compared (1) intra-individually, during acute episodes and after clinical remission, and (2) inter-individually, during acute manic and depressive episodes, and in HC. Statistical analyses were performed with SPSS, GraphPad and R Statistics.Results20 patients with BD (15 manic, 5 depressed) and 10 HC were included. A significant increase in the maximal oxygen consumption capacity (ETC) was observed in clinical remission (27.4 ± 17.4) compared to the acute episodes (21.1 ± 11.7, p = 0.001), which remained significant after subtracting Rox from the other rates (p = 0.001). At T1, patients admitted with a manic episode tended to show higher mean ETC (31.2 ± 18.7) compared with T0 (24.1 ± 12.0, p = 0.074); the tendency persisted after Rox subtraction (p = 0.076). Patients admitted with a depressive episode also showed higher ETC means in T1 (16.3 ± 3.8) compared to T0 (12.1 ± 3.4), but there were not significant differences (p = 0.231). When HC, manic and depressive patients at T0 were compared between them, significant differences were observed in ETC (H =8.5; p =0.014) and Rox (H =13.8; p = 0.001). After Rox deduction, differences in ETC remained (H =11.7; p = 0.003). Individuals with bipolar depression showed lower ETC rates (12.1 ± 3.4) than those with a manic episode (24.1 ± 12.0; t = -3.5, p = 0.003), which was also found after Rox deduction (p = 0.001).ConclusionsIn both manic and depressive episodes in BD, mitochondrial respiration might be reduced and increase after clinical remission. Further studies with larger samples will allow to confirm these results and also to identify potential mitochondrial state-dependent biomarkers.Disclosure of InterestA. Giménez-Palomo Grant / Research support from: AGP is supported by a Rio Hortega 2021 grant (CM21/00094) from the Spanish Ministry of Health financed by ISCIII and cofinanced by Fondo Social Europeo Plus (FSE+)., M. Guitart-Mampel: None Declared, A. Meseguer: None Declared, M. Valentí: None Declared, L. Bracco: None Declared, H. Andreu: None Declared, E. Vieta: None Declared, G. Garrabou: None Declared, I. Pacchiarotti: None Declared

Reduced mitochondrial respiratory capacity in patients with acute episodes of bipolar disorder: Could bipolar disorder be a state-dependent mitochondrial disease?

Bipolar disorder (BD) is a chronic and recurrent disease characterized by acute mood episodes and periods of euthymia. The available literature postulates that a biphasic dysregulation of mitochondrial bioenergetics might underpin the neurobiology of BD. However, most studies focused on inter-subject differences rather than intra-subject variations between different mood states. To test this hypothesis, in this preliminary proof-of-concept study, we measured in vivo mitochondrial respiration in patients with BD during a mood episode and investigated differences compared to healthy controls (HC) and to the same patients upon clinical remission. This longitudinal study recruited 20 patients with BD admitted to our acute psychiatric ward with a manic (n = 15) or depressive (n = 5) episode, and 10 matched HC. We assessed manic and depressive symptoms using standardized psychometric scales. Different mitochondrial oxygen consumption rates (OCRs: Routine, Leak, electron transport chain [ETC], Rox) were assessed during the acute episode (T0) and after clinical remission (T1) using high-resolution respirometry at 37°C by polarographic oxygen sensors in a two-chamber Oxygraph-2k system in one million of peripheral blood mononuclear cells (PMBC). Specific OCRs were expressed as mean ± SD in picomoles of oxygen per million cells. Significant results were adjusted for age, sex, and body mass index. The longitudinal analysis showed a significant increase in the maximal oxygen consumption capacity (ETC) in clinical remission (25.7 ± 16.7) compared to the acute episodes (19.1 ± 11.8, p = 0.025), and was observed separately for patients admitted with a manic episode (29.2 ± 18.9 in T1, 22.3 ± 11.9 in T0, p = 0.076), and at a trend-level for patients admitted with a depressive episode (15.4 ± 3.9 in T1 compared to 9.4 ± 3.2 in T0, p = 0.107). Compared to HC, significant differences were observed in ETC in patients with a bipolar mood episode (H = 11.7; p = 0.003). Individuals with bipolar depression showed lower ETC than those with a manic episode (t = -3.7, p = 0.001). Also, significant differences were observed in ETC rates between HC and bipolar depression (Z = 1.000, p = 0.005). Bioenergetic and mitochondrial dysregulation could be present in both manic and depressive phases in BD and, importantly, they may restore after clinical remission. These preliminary results suggest that mitochondrial respiratory capacity could be a biomarker of illness activity and clinical response in BD. Further studies with larger samples and similar approaches are needed to confirm these results and identify potential biomarkers in different phases of the disease.

Radiochemical Oxygen Depletion Depends on Chemical Environment and Dose-Rate: Implications for FLASH Effect

FLASH (dose rates > 40 Gy/s) radiotherapy (RT) protects normal tissues from radiation damage, compared with conventional RT (∼Gy/min). Radiation-chemical oxygen depletion (ROD) has been the leading and most-studied mechanism to explain FLASH. Previous studies have reported low ROD values of ∼0.35 µM/Gy, however, they do not accurately model (utilizing water or oxidized substrates such as albumin) the intracellular environment. It has been proposed that the intracellular environment may support higher ROD values due to its specific chemical makeup. As chemical reducing agents, which play a critical role in the cell, may promote ROD, we measured ROD for several well-known cellular reducing agents. Precision polarographic oxygen sensors were used to measure ROD over a ∼100-0 µM oxygen concentration range in solutions containing various types of intracellular reducing agents, either alone or combined with glycerol (1M; to simulate the intracellular hydroxyl-radical-scavenging capacity). A Cs irradiator and a research proton beamline were used for radiation beam generation over a 10,000-fold (0.0085 to 100 Gy/s) dose rate range. Reagents were grouped generally into primary free-radical scavengers (glycerol & lysozyme) and reducing agents (cysteamine, cysteine, glutathione, dextrin-conjugated linoleic acid, NAD(P)H, ascorbate and uric acid). Reducing agents at 1 mM significantly altered ROD values. ROD, at 0.1 Gy/s varied from greater than 1 µM/Gy for NADPH to less than 0.1 µM/Gy for uric acid. Even higher RODs were found at lower dose rates and/or higher reducing agent concentrations. Although most greatly increased ROD, ascorbate and uric acid decreased ROD and additionally imposed an oxygen dependence of ROD at low oxygen concentrations. Interestingly, all agents having high rates of ROD at low dose rates show a decrease at FLASH dose rates and this seems to be a proportional response (i.e., the greater the ROD at low dose rate, the greater the inhibition by FLASH). At FLASH dose rates our data for a simple mixture of glycerol and glutathione showed the same trend as recent studies that, in general, FLASH had ∼25% lower ROD rates than conventional demonstrating agreement between polarographic sensors and optical phosphorescence decay methods. ROD was greatly augmented by some intracellular reducing agents but others effectively reversed this effect. Ascorbate had its greatest impact at low oxygen concentrations. ROD decreased with increasing dose rate and in all cases was less than 1 µM/Gy at 100 Gy/s, potentially posing a fundamental limit of max ROD for FLASH.

Bioenergetic changes and mitochondrial dysfunction in mania versus euthymia in bipolar disorder type I

IntroductionCurrent evidence has hypothesized the involvement of mitochondrial dysfunction during the acute episodes of BD compared to symptomatic remission. So far, no studies have compared mitochondrial and bioenergetic functions both in-vivo (respiratory parameters) and ex-vivo (cellular respiration) in different phases of the disease in the same individuals.ObjectivesThis multidisciplinary pilot study aims at assessing bioenergetic and mitochondrial intra-individual differences between manic and euthymic states.MethodsFour patients with a manic episode admitted to our acute psychiatric ward were recruited. Bioenergetic parameters were measured at admission (T0) and after symptomatic remission (T1).At admission (T0) and before discharge (T1), HAMD and YMRS total scores were obtained. For the assessment of cellular respiration, polymorphonuclear cells were obtained by a Ficoll density gradient centrifugation procedure. To determine oxygen consumption (at T0 and T1), a million of living peripheral blood mononuclear cells (PBMC) were used. High-resolution respirometry was performed at 37°C by polarographic oxygen sensors in a two-chamber Oxygraph-2k system.Specific oxygen uptakes (Routine: basal oxygen consumption; Proton Leak: oxygen consumption not coupled to ATP synthesis; and ETC: maximal capacity of the electron transport chain) rates were obtained using mitochondrial chain inhibitors and uncouplers. Oxygen consumption was normalized for protein concentration. Results are expressed as picomoles of oxygen per millilitre (pmol O2/s*μg prot).Also, a constant work rate exercise test was performed on a cycle ergometer and basal and effort respiratory variables were measured.Statistical analysis was performed with the SPSS v. 25.0 and GraphPad. Results were expressed as means and SD. Nonparametric tests (Mann–Whitney, Pearson) were used to determine differences (significant at p value <0.05).ResultsOne patient was a man and three patients were women, with a mean age of 28 years old. HAMD initial and final mean scores were 11.0 and 7.0, and mean YMRS scores were 21.5 and 7.0 respectively.Results from mitochondrial oxygen consumption revealed that mean basal oxygen consumption tended to be higher in T1 (0.98±0.45) than in T0, and maximal respiratory capacity was significantly increased in T1 (2.26±0.33; p=0.028) compared to T0.Mean lactate levels and pH levels were similar in T0 and T1. Scales scores were not correlated to different pH or lactate changes after the effort task. Higher initial oxygen consumption was significantly correlated to higher maximal capacity (p<0.05) in T0 and T1.Image:ConclusionsOur preliminary results suggest that mania could imply lower oxygen consumption capacity, which should be confirmed in future studies. A bigger study is planned to determine changes in bioenergetic patterns and capacity for aerobic response in manic and depressive episodes.Disclosure of InterestNone Declared

Energetic cost derived of short-term starvation on marine crustacean Palaemon elegans

Event Abstract Back to Event Energetic cost derived of short-term starvation on marine crustacean Palaemon elegans Ico Martinez1*, Alicia Herrera1, Inmaculada Herrera1, Daniel R. Bondyale-Juez1, Vanesa Romero-Kutzner1, Mayte Tames-Espinosa1, Theodore T. Packard1 and May Gómez Cabrera1 1 University of Las Palmas de Gran Canaria, Spain Starvation has a major impact on physiological processes in marine plankton and these processes have a major impact on the energy transfer through marine ecosystems. However, quantifying and understanding how starvation changes different aspects of the energy transfer has been retarded because planktologists have largely relied on biomass fractionation to shed light on it. Here, we experiment with the cellular energy allocation approach (CEA index), the respiratory electron transport system activity (ETS), and organic analysis of lipids (Lip), carbohydrates (Carb) and proteins (Prot) to help further our understanding of the energy transfer in the caridean shrimp, Palaemon elegans. We analyzed the effect of 72 hours of starvation using the CEA index that is calculated as the ratio between energy available to energy consumption. It allows us to evaluate the net energy budget (Verslycke and Janssen, 2002). The energy available (Ea) was determined from Lip, Carb, and Prot content, where Ea = Lip + Carb + Prot. Energy consumption (Ec) was calculated from the activity of ETS. All the parameters were transformed into energy equivalents using their respective energy of combustion (Gnaiger, 1983). Proteins were the main energy source (1450.8±355.7 mJ•mgWW-1), followed by lipids (727.2±124.4 mJ•mgWW-1) and carbohydrates (82.1±17.9 mJ•mgWW-1). After 24 hours of starvation, the carbohydrates dropped by 38.2%, a significant decrease. After 48 hours, the proteins had decreased by 36.0%. The lipids were the last to decrease. After 72 hours they had dropped by 42.3%. Adding these organic constituents to calculate the Ea revealed a significant decreasing trend of 34.42% at 72 hours (from 2260.1±485.5 to 1482.3±120.9 mJ•mgWW-1). In contrast, the Ec, as ETS activity, showed a significant increase at 24 hours (from 85.2±16.6 to 158.0±40.4 mJ•h-1•mgWW-1) that stabilized after 72 hours. Overall, the energy balance (Ea/Ec) showed that the energy available was higher than the energy consumption during the experiment. Ea/Ec ratio decreased for the first 24 hours, then remained stable for the next 48 hours. This portrait of energy regulation shows a rapid shift mechanism of P. elegans under sudden adverse conditions. References Gnaiger, E. (1983). ‘Calculation of energetic and biochemical equivalents of respiratory oxygen consumption’, in Polarographic oxygen sensors (Springer), 337–345. Verslycke, T., and Janssen, C. R. (2002). Effects of a changing abiotic environment on the energy metabolism in the estuarine mysid shrimp Neomysis integer (Crustacea: Mysidacea). J. Exp. Mar. Bio. Ecol. 279, 61–72. Keywords: CEA index, Energy available, energy consumption, Palaemon elegans, Starvation Conference: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019. Presentation Type: Poster Presentation Topic: Ecology, Biodiversity and Vulnerable Ecosystems Citation: Martinez I, Herrera A, Herrera I, Bondyale-Juez DR, Romero-Kutzner V, Tames-Espinosa M, Packard TT and Gómez Cabrera M (2019). Energetic cost derived of short-term starvation on marine crustacean Palaemon elegans. Front. Mar. Sci. Conference Abstract: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) . doi: 10.3389/conf.fmars.2019.08.00191 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 14 May 2019; Published Online: 27 Sep 2019. * Correspondence: Mrs. Ico Martinez, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain, ico.martinez@ulpgc.es Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ico Martinez Alicia Herrera Inmaculada Herrera Daniel R Bondyale-Juez Vanesa Romero-Kutzner Mayte Tames-Espinosa Theodore T Packard May Gómez Cabrera Google Ico Martinez Alicia Herrera Inmaculada Herrera Daniel R Bondyale-Juez Vanesa Romero-Kutzner Mayte Tames-Espinosa Theodore T Packard May Gómez Cabrera Google Scholar Ico Martinez Alicia Herrera Inmaculada Herrera Daniel R Bondyale-Juez Vanesa Romero-Kutzner Mayte Tames-Espinosa Theodore T Packard May Gómez Cabrera PubMed Ico Martinez Alicia Herrera Inmaculada Herrera Daniel R Bondyale-Juez Vanesa Romero-Kutzner Mayte Tames-Espinosa Theodore T Packard May Gómez Cabrera Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

High-Resolution FluoRespirometry and OXPHOS Protocols for Human Cells, Permeabilized Fibers from Small Biopsies of Muscle, and Isolated Mitochondria.

Protocols for High-Resolution FluoRespirometry of intact cells, permeabilized cells, permeabilized muscle fibers, isolated mitochondria, and tissue homogenates offer sensitive diagnostic tests of integrated mitochondrial function using standard cell culture techniques, small needle biopsies of muscle, and mitochondrial preparation methods. Multiple substrate-uncoupler-inhibitor titration (SUIT) protocols for analysis of oxidative phosphorylation (OXPHOS) improve our understanding of mitochondrial respiratory control and the pathophysiology of mitochondrial diseases. Respiratory states are defined in functional terms to account for the network of metabolic interactions in complex SUIT protocols with stepwise modulation of coupling control and electron transfer pathway states. A regulated degree of intrinsic uncoupling is a hallmark of oxidative phosphorylation, whereas pathological and toxicological dyscoupling is evaluated as a mitochondrial defect. The noncoupled state of maximum respiration is experimentally induced by titration of established uncouplers (CCCP, FCCP, DNP) to collapse the protonmotive force across the mitochondrial inner membrane and measure the electron transfer (ET) capacity (open-circuit operation of respiration). Intrinsic uncoupling and dyscoupling are evaluated as the flux control ratio between non-phosphorylating LEAK respiration (electron flow coupled to proton pumping to compensate for proton leaks) and ET capacity. If OXPHOS capacity (maximally ADP-stimulated O2 flux) is less than ET capacity, the phosphorylation pathway contributes to flux control. Physiological substrate combinations supporting the NADH and succinate pathway are required to reconstitute tricarboxylic acid cycle function. This supports maximum ET and OXPHOS capacities, due to the additive effect of multiple electron supply pathways converging at the Q-junction. ET pathways with electron entry separately through NADH (pyruvate and malate or glutamate and malate) or succinate (succinate and rotenone) restrict ET capacity and artificially enhance flux control upstream of the Q-cycle, providing diagnostic information on specific ET-pathway branches. O2 concentration is maintained above air saturation in protocols with permeabilized muscle fibers to avoid experimental O2 limitation of respiration. Standardized two-point calibration of the polarographic oxygen sensor (static sensor calibration), calibration of the sensor response time (dynamic sensor calibration), and evaluation of instrumental background O2 flux (systemic flux compensation) provide the unique experimental basis for high accuracy of quantitative results and quality control in High-Resolution FluoRespirometry.

High-resolution Respirometry to Assess Mitochondrial Function in Permeabilized and Intact Cells.

A high-resolution oxygraph is a device for measuring cellular oxygen consumption in a closed-chamber system with very high resolution and sensitivity in biological samples (intact and permeabilized cells, tissues or isolated mitochondria). The high-resolution oxygraph device is equipped with two chambers and uses polarographic oxygen sensors to measure oxygen concentration and calculate oxygen consumption within each chamber. Oxygen consumption rates are calculated using software and expressed as picomoles per second per number of cells. Each high-resolution oxygraph chamber contains a stopper with injection ports, which makes it ideal for substrate-uncoupler-inhibitor titrations or detergent titration protocols for determining effective and optimum concentrations for plasma membrane permeabilization. The technique can be applied to measure respiration in a wide range of cell types and also provides information on mitochondrial quality and integrity, and maximal mitochondrial respiratory electron transport system capacity.

The effects of stirring, population levels and a potential anti-nematodal product on the respiration of second-stage juveniles of Meloidogyne incognita measured with different technology

The oxygen consumption rate (OCR) ofMeloidogyne incognitasecond-stage juveniles (J2) was measured using polarographic oxygen sensor (POS) and fibre-optic oxygen sensor (FOS) technology. The effect of stirring speed on the OCR of J2 suspended in tap water was determined using POS. Next, the OCR of different J2 numbers was measured using FOS. Also, the OCR of J2 in tap water using POS and FOS was recorded, and also the effect of SoilBioMuti (SBM) on J2 OCR using FOS. Stirring speed had no pronounced effect on the OCR of J2. FOS recorded the OCR of as few as five J2. The OCR of J2 in sterile tap water was significantly lower for POS than FOS. Using FOS, non-filtered (NF) SBM without J2 had the highest OCR, being 42% higher than that of NF SBM with J2. The two filtered SBM (with and without J2) treatments had the lowest OCR values.

PENENTUAN KADAR OKSIGEN TERLARUT MENGGUNAKAN SENSOR POLAROGRAFI BERMEMBRAN PLASTIK (Determination of dissolved oxygen with polarographic oxygen sensor plastic membrane probe)

Plastic membrane sensor for polarographic oxygen measurement has been investigated. The Probe was constructed of: Pt as a working electrode; Ag- AgCl as a reference electrode and an auxiliary electrode; solution of KCl as an electrolyte solution; plastic wrap (thickness 72.7  m) as a membrane; and polyester polymer as a body of sensor. It was found that the polarographic oxygen sensor plastic membrane probe was suited for determination of dissolved oxygen with an optimum operating characteristics at applied voltage of –0.65 V and solution KCl 30% as an electrolyte. The probe showed that reduction current achieved steady state after 75 seconds. The standard calibration curve (concentration – current) showed that the linear relationships were achieved for dissolved oxygen in the range of 1.0 – 30.6 ppm. The analytical performance characteristics of the probe were: precision 0.87% – 30.0 %; calibration sensitivity 0.17 ppm/  A; analytical sensitivity 0.56 – 0.84 ppm/  A; and detection limit 0.8 ppm. The t- test and F-test at 95% confidence level showed that there was no significant difference between the determinations of dissolved oxygen by polarographic oxygen sensor membrane plastic and by Winkler method. Key words: membrane plastic, polarographic, steady state, Winkler method.

다전극 산소 센서를 이용한 고분자 막의 산소 투과도 측정 장치 연구

The existing permeability measurements based on pressure differential between the polymer membrane that is permeable to measure the amount of oxygen used, but these methods must be kept in a vacuum, and the measurement of the membrane with low permeability in the membrane is too time consuming. In recent years by using electrochemical method polymer membrane currents caused by the amount of oxygen is a measure of how much is used. In this study, apparatus consisting of one anode and six cathodes for multi-oxygen permeability tester used the same number of membranes produced by electrochemical oxygen permeation characteristics. In this study, one silver/silver chloride anode electrochemical method with a hexagonal sensor to put various kinds of polymer membranes with the six oxygen permeability for simultaneous measurement in real-time systems. Six cathodes (Pt), and one of the coil-shaped anode (Ag/AgCl) to form a hexagonal one of the polarographic oxygen sensor in a single measurement system by six sensors. Each sensor for making hexagonal specificity of the sensor to compensate for the conditions obtained in a pure nitrogen gas and pure oxygen gas conditions. With this study, self-developed hexagonal sensor capable of measuring sensors and oxygen permeability tester, for a multi-six different oxygen permeability characteristics of the membrane measured at the same time.

392 AN ASSESSMENT OF HYPOXIA IN HUMAN RENAL TUMOURS USING DIRECT OXYGEN PROBE MEASUREMENTS

You have accessJournal of UrologyKidney Cancer: Basic Research1 Apr 2011392 AN ASSESSMENT OF HYPOXIA IN HUMAN RENAL TUMOURS USING DIRECT OXYGEN PROBE MEASUREMENTS Nathan Lawrentschuk, Aurora Poon, Lydia Johns-Putra, Carmel Murone, Ian Davis, Damien Bolton, and Andrew Scott Nathan LawrentschukNathan Lawrentschuk Heidelberg, Australia More articles by this author , Aurora PoonAurora Poon Heidelberg, Australia More articles by this author , Lydia Johns-PutraLydia Johns-Putra Heidelberg, Australia More articles by this author , Carmel MuroneCarmel Murone Heidelberg, Australia More articles by this author , Ian DavisIan Davis Heidelberg, Australia More articles by this author , Damien BoltonDamien Bolton Heidelberg, Australia More articles by this author , and Andrew ScottAndrew Scott Heidelberg, Australia More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.480AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Renal Cell Carcinoma (RCC) is yet to have its oxygen status formally investigated. This is despite an improved understanding of the genetic basis of RCC at a sub-cellular level (e.g. the von-Hippel Lindau axis with hypoxia-inducible factor) and the development of targeted therapies that exploit such pathways. Our aim is to measure the oxygen levels within normal kidney and RCC using direct invasive measurements. METHODS The gold standard' of oxygen tension measurement being the Polarographic Oxygen Sensor (POS) was utilized in normal and RCC tissue in patients undergoing open nephrectomy in a prospective ethically-approved study. The mean pO2Tas well as the hypoxic fraction or percentage of measurements below 5 and 10mmHg (HP5 and HP10) were recorded. Immunohistochemistry was also undertaken to analyse expression of hypoxia-related antigens. RESULTS Eleven patients successfully had POS measurements completed. Normal tissue mean pO2 was 44.95b26.06 (mmHg ±95% C.I, range 10.9–113.3) whilst tumours had a mean pO2 11.17±5.81 (0–24.9). The and also differed between Normal tissue had lower hypoxic fractions of HP10 at 21.55±12.60 (mean ±95% C.I) and HP5 16.99±11.24 compared to tumour tissue at 53.36±23.39 and 47.44±22.67 respectively (Figure 1). CONCLUSIONS Invasive POS measurements have demonstrated hypoxia in RCC consistent with that found in other solid tumours which is generally defined to occur at an oxygen tension <10mmHg (Figure 2). This in formation is imperative if we are to develop hypoxic imaging, targeted therapies and ultimately improved survival for patients with RCC. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e158-e159 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Nathan Lawrentschuk Heidelberg, Australia More articles by this author Aurora Poon Heidelberg, Australia More articles by this author Lydia Johns-Putra Heidelberg, Australia More articles by this author Carmel Murone Heidelberg, Australia More articles by this author Ian Davis Heidelberg, Australia More articles by this author Damien Bolton Heidelberg, Australia More articles by this author Andrew Scott Heidelberg, Australia More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Characterizing Spatial and Temporal Variability of Dissolved Gases in Aquatic Environments with in situ Mass Spectrometry

The TETHYS mass spectrometer is intended for long-term in situ observation of dissolved gases and volatile organic compounds in aquatic environments. Its design maintains excellent low mass range sensitivity and stability during long-term operations, enabling characterization of low-frequency variability in many trace dissolved gases. Results are presented from laboratory trials and a 300-h in situ trial in a shallow marine embayment in Massachusetts, U.S.A. This time series consists of over 15000 sample measurements and represents the longest continuous record made by an in situ mass spectrometer in an aquatic environment. These measurements possess sufficient sampling density and duration to apply frequency analysis techniques for study of temporal variability in dissolved gases. Results reveal correlations with specific environmental periodicities. Numerical methods are presented for converting mass spectrometer ion peak ratios to absolute-scale dissolved gas concentrations across wide temperature regimes irrespective of ambient pressure, during vertical water column profiles in a hypoxic deep marine basin off the coast of California, U.S.A. Dissolved oxygen concentration values obtained with the TETHYS instrument indicate close correlation with polarographic oxygen sensor data across the entire depth range. These methods and technology enable observation of aquatic environmental chemical distributions and dynamics at appropriate scales of resolution.

Development of a Biomimetic Root Oxygen Bioavailability Sensor

Low oxygen availability in soil can impair root function, thereby decreasing agronomic productivity. Without oxygen to support mitochondrial respiration, energy levels in roots may limit mineral nutrient (N, P, K) transport. Traditional methods for measuring soil oxygenation include the use of redox electrodes and polarographic oxygen sensors. These approaches are limited to measuring oxygen concentrations at specific locations and cannot determine the bio-availability of that oxygen to a growing root. An innovative approach has been developed for direct measurement of oxygen bioavailability. Instead of building the sensor to measure oxygen concentrations, it is possible to construct an electrochemical system in a manner that makes it sensitive to changes in oxygen transport and availability in the soil. Furthermore, it is even possible to construct the sensor to match the oxygen consumption characteristics of a specific root tip, which is important because most metabolism and nutrient uptake occurs here. This is accomplished by using a conductive-gel membrane system that allows sensor profiles to be engineered to match the metabolic profiles of specific species. If constructed to these standards, the sensor will biomimetically replicate biophysical oxygen depletion profiles that are analogous to those found in the rhizosphere of a growing root tip. The biomimetic root oxygen bio-availability (ROB) sensor integrates all biotic and abiotic factors in the soil that limit oxygen transport to the root, while providing real-time sensing. This new sensor technology could be used as a research tool or as a closed-loop control system for field and greenhouse irrigation.

In Vitro Assessment of Pancreatic Islet Vitality by Oxymetry

In order to assess the quality of freshly isolated and cultivated pancreatic islets designed for experimental transplantation in rats we combined the vitality staining test, in vitro measurement of insulin secretion capacity, and assessment of islet respiration. Oxygen consumption was measured using the respirometer Oxygraph 2K equipped with polarographic oxygen sensors. The results of oxymetry demonstrated a linear correlation between islet number and oxygen consumption. Respiration per unit of viable islet tissue was constant. Oxygen consumption tests were in good correlation with the results of insulin release assays, with a correlation coefficient of 0.82. We found no significant differences in all three vitality-testing methods performed with fresh and 24-hour cultivated islets ( P > .05). We conclude that polarographic oxymetry provides a fast and easy evaluation test of islet quality. After appropriate standardization, the oxymetric technique can be used for routine clinical pretransplant islet quality testing. In addition, cell membrane integrity and mitochondrial function could be assessed after addition of specific respiration inhibitors or stimulators.

Assessing regional hypoxia in human renal tumours using 18F‐fluoromisonidazole positron emission tomography

To assess renal tumours for hypoxic regions using 18F-fluoromisonidazole (18F-FMISO) positron emission tomography (PET), a recognized noninvasive method for detecting hypoxia in tumours, as renal cell carcinoma (RCC) can be potentially cured with nephrectomy but recurrence develops in most patients, who then respond poorly to treatments such as chemotherapy, and hypoxia is known to confer resistance to radiotherapy and chemotherapy in many solid tumours. In all, 17 patients had 18F-FMISO PET scans before nephrectomy for presumed RCC. Specimens were examined histologically, and immunohistochemistry was used to compare the microvessel density (MVD) as an indicator of angiogenesis in the tumour and normal parenchyma, in 15 patients. Tumour oxygenation was measured invasively in three patients using a polarographic oxygen sensor probe. Of the 15 patients with histological results, 11 had RCC and four had other tumours. Although there was a trend there was no statistically significant (P = 0.14) difference in the maximum standardized uptake value (SUV(max)) when comparing the region of the kidney involved with RCC; the mean (95% confidence interval) SUV(max) in the tumours was 1.3 (0.15), whilst that in the normal contralateral kidney was 1.1 (0.22). The MVD was greater in RCC, at 13.7 (3.1) mean vessels per high-power field than in normal tissue, at 6.9 (1.9). Hypoxia as measured polarographically was detected in three RCCs (median pO2 9.6 mmHg) compared to normal parenchyma at 37.6 mmHg. Although 18F-FMISO scans showed significant uptake in other solid tumours, there was only mild 18F-FMISO uptake in the present RCCs. The invasive measurements indicated that there was hypoxia in RCC, but the median pO2 did not fall below 9.5 mmHg. Further direct studies of renal tumour oxygenation combined with therapies directed towards hypoxia may allow a better understanding of the relationship between 18F-FMISO results and the biological significance of hypoxia in RCC.

The relationship between temporal variation of hypoxia, polarographic measurements and predictions of tumour response to radiation

The polarographic oxygen sensor is one of the most used devices for in vivo measurements of oxygen and many other measurement techniques for measuring tumour hypoxia are correlated with electrode measurements. Little is known however about the relationship between electrode measurements and the real tissue oxygenation. This paper investigates the influence of the temporal change of the hypoxic pattern on the electrode measurements and the tumour response.Electrode measurements and tumour response were simulated using a computer program that allows both the calculation of the tissue oxygenation with respect to the two types of hypoxia that might arise in tumours and the virtual insertion of the electrode into the tissue. It was therefore possible to control the amount of each type of hypoxia in order to investigate their influence on the measurement results. Tissues with several vascular architectures ranging from well oxygenated to poorly oxygenated were taken into consideration as might be seen in practice. The influence of the electrode measurements on the treatment outcome was estimated by calculating the tumour control probability for the tumours characterized either by the real or by the measured tumour oxygenation.We have simulated electrode oxygen measurements in different types of tissues, covering a wide range of tumour oxygenations. The results of the simulations showed that the measured distribution depends on the details of the vascular network and not on the type of hypoxia. We have also simulated the effects of the temporal change of the acute hypoxic pattern due to the opening and the closure of different blood vessels during a full fractionated treatment. The results of this simulation suggested that the temporal variation of the hypoxic pattern does not lead to significantly different results for the electrode measurements or the predicted tumour control probabilities.In conclusion, it was found that the averaging effect of the electrode leads to a systematic deviation between the actual oxygen distribution and the measured distribution. However, as the electrode reflects the general trends of the tissue oxygenation it has the potential of being used for the general characterization of tumour hypoxia even if the actual type of hypoxia measured by the electrode cannot be determined. Indeed, the change in time of the acute hypoxic region does not compensate for the lack of oxygenation at a specific moment and therefore does not influence the polarographic oxygen measurements.

The dynamic response of optical oxygen sensors and voltammetric electrodes to temporal changes in dissolved oxygen concentrations

Accurately measuring dissolved oxygen concentrations in fresh and salt water environments has long been an interdisciplinary priority. Many methodologies exist, including two very promising new ones, optical fluorescence quenching optrodes (or optodes) and solid-state voltammetric electrodes. In this study we compare the responsiveness of these two techniques to dynamic changes in dissolved oxygen concentrations, using traditional methods of polarographic oxygen sensors and Winkler’s chemical titrations to corroborate the measurements. Advantages of the optrode system include simplicity of operation and high sensitivity when changes in oxygen concentrations are small (<Δ10 μM O 2 min −1). Advantages of voltammetry include equally high sensitivity, independent of rate of change of oxygen concentration, and the capability of simultaneously measuring other chemical species. Both systems have the capability of producing high-resolution, continuous oxygen profiles by collecting and reporting real-time data. Kinetic estimates of the binding and dissociation constants for the ruthenium–oxygen complex in the optrode revealed a relatively long half-life of the Ru 2+–O 2 complex for dissociation ( t 1/2 of 43.2 s to equilibrate from a 100 to 0% O 2 saturation change). In contrast, the Ru 2+–O 2 association constant was 5.0 times faster ( t 1/2 of 8.6 s to equilibrate from a 0 to 100% O 2 saturation change). Therefore, because of these differential kinetics, researchers should take care when using a ruthenium-based optrode to measure real-time dissolved oxygen concentrations undergoing temporal variability.

Oxygen solubilities of media used in electrochemical respiration measurements

Solubility data are presented as equations from which the oxygen concentration of arbitrary media may be calculated with an accuracy of about 1%. These equations, covering the range 5–40 °C, are based on measurements with a modification of the physical method of St. Helen and Fatt (I. Fatt, Polarographic Oxygen Sensors, CRC Press, Cleveland (1976)). Solutions of the following compounds were measured: EDTA (ethylenediaminetetraacetic acid), EGTA (ethyleneglycol-bis(2-aminoethylether)tetraacetic acid), glucose, Hepes ( N-2-hydroxyethylpiperazine- N ′-2-ethanesulfonic acid), lactobionic acid (galactosylgluconic acid), magnesium chloride, mannitol, Mes (2-( N-morpholino)ethanesulfonic acid), potassium chloride, potassium phosphate, sodium chloride, sucrose, taurine, and Tris (tris(hydroxymethyl)aminomethane). The present data are compared with solubility data obtained with the method involving oxidation of calibrated amounts of reduced nicotinamide adenine dinucleotide (e.g., R.W. Estabrook, Methods Enzymol. 10 (1967) 41–47) and with the kinetic method of Reynafarje et al. (Anal. Biochem. 145 (1985) 406–418). It is concluded that the former method produces reliable results provided that some simple precautions are taken. The kinetic method, however, appears to have produced calibration errors up to about 5%.

A method for accurate measurements of the respiration rates of marine invertebrate embryos and larvae

Measurements of respiration rates are essential to quantify the energy requirements of embryos and larvae. Here we describe a ')_rBOD' method that employs small (~1 ml) Biological Oxygen Demand (BOD) glass vials in which embryos and larvae are incubated. A decrease in oxygen concen- tration is measured by injecting seawater from each vial into the measurement chamber of a standard polarographic oxygen sensor. This pBOD method was used to measure respiration rates of larvae of the sea urchin Strongylocentrotus purpuratus (at 15°C) and embryos and larvae of 2 Antarctic echino- derms, the sea urchin Sterecbinus neumayeri and the seastar Odontasfer valiclus (both at -1SC). For validation, a comparison of different methods was performed with embryos and larvae of S. neumayeri. The nBOD method gave results for respiration rates during development that were equivalent to those obtained with either coulometric capacitance respirometry or standard Winkler's titrations of large (300 ml) BOD bottles. Currently, the most common method for measuring respiration rates of inverte- brate embryos and larvae is to place them in small respiration chambers and continuously monitor oxygen tension with a polarographic oxygen sensor (POS). However, respiration rates for embryos and larvae of S. neumayeri were underestimated when standard POS measurements were compared to the measurements made with either pBOD, Winkler's titrations or coulometric capacitance respirometry. A comparison of the pBOD and POS methods during early development in S. neumayeri resulted in different estimates of 920 and 343 pJ, respectively, for the total energetic cost of embryogenesis to gastrulation, illustrating that the POS error can be as great as 63 %. The yBOD method is accurate for micro-respiration measurements of invertebrate embryos and larvae as well as being simple to operate and appropriate for field work.

Non-photosynthetic oxygen production and non-respiratory oxygen uptake in the dark: a theory of oxygen dynamics in plankton communities

Plankton respiration is commonly measured in terms of oxygen uptake, usually employing the Winkler method, much less commonly the polarographic method. Both methods produce results that can be misinterpreted when H2O2 production and decomposition are ignored. This paper: (1) presents experimental evidence of significant H2O2 involvement during plankton incubation in dark bottles, (2) explains how results differ between the Winkler and polarographic methods in the presence of H2O2, (3) discusses how this difference is clouded by side issues of variability inherent in the Winkler technique and the use of different bottle sizes, and (4) shows that unexpected and variable results of light-/dark-bottle incubations can all be explained by a theory of H2O2 production and decomposition. During an initial period in the dark, when plankton respiration has been poisoned by mercuric chloride or chloroform, O2 increase can be measured with a polarographic oxy‐gen sensor (POS). The trend in O2 changes is linear for several days when only respiration is occurring, but curvilinear when there is concurrent O2 production. O2 production in the dark and H2O2 decomposition are one and the same process. Measurement of oxygen by Winkler analysis and POS produce different results when H2O2 is present because the former method measures oxidizing equivalent while a POS measures O2 pressure. A real difference in results between the two methods is prima facie evidence that H2O2 is involved. The synthesis of this new empirical evidence with diverse knowledge from various fields shows that the common practice of estimating gross community primary production from oxygen changes in light and dark bottles is based on untenable assumptions.