Measurement Of Oxygen Concentration Research Articles

Direct measurement of local oxygen concentration in the bone marrow of live animals

Characterizing how the microenvironment, or niche, regulates stem cell activity is central to understanding stem cell biology and to developing strategies for therapeutic manipulation of stem cells1. Low oxygen tension (hypoxia) is commonly thought to be a shared niche characteristic in maintaining quiescence in multiple stem cell types2–4. However, support for the existence of a hypoxic niche has largely come from indirect evidence such as proteomic analysis5, expression of HIF-1 and related genes6, and staining with surrogate hypoxic markers (e.g. pimonidazole)6–8. Here we perform direct in vivo measurements of local oxygen tension (pO2) in the bone marrow (BM) of live mice. Using two-photon phosphorescence lifetime microscopy (2PLM), we determined the absolute pO2 of the BM to be quite low (<32 mmHg) despite very high vascular density. We further uncovered heterogeneities in local pO2, with the lowest pO2 (~9.9 mmHg, or 1.3%) found in deeper peri-sinusoidal regions. The endosteal region, by contrast, is less hypoxic as it is perfused with small arteries that are often positive for the marker nestin. These pO2 values change dramatically after radiation and chemotherapy, pointing to the role of stress in altering the stem cell metabolic microenvironment.

Aquatic Respiration Rate Measurements at Low Oxygen Concentrations

Despite its huge ecological importance, microbial oxygen respiration in pelagic waters is little studied, primarily due to methodological difficulties. Respiration measurements are challenging because of the required high resolution of oxygen concentration measurements. Recent improvements in oxygen sensing techniques bear great potential to overcome these limitations. Here we compare 3 different methods to measure oxygen consumption rates at low oxygen concentrations, utilizing amperometric Clark type sensors (STOX), optical sensors (optodes), and mass spectrometry in combination with 18-18O2 labeling. Oxygen concentrations and consumption rates agreed well between the different methods when applied in the same experimental setting. Oxygen consumption rates between 30 and 400 nmol L−1 h−1 were measured with high precision and relative standard errors of less than 3%. Rate detection limits in the range of 1 nmol L−1 h−1 were suitable for rate determinations in open ocean water and were lowest at the lowest applied O2 concentration.

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

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.

Development of a prototype malaxer to investigate the influence of oxygen on extra-virgin olive oil quality and yield, to define a new design of machine

The malaxation has been a focus of extra-virgin olive oil (EVOO) research for many years. A system that supplied gas and measured oxygen concentration was implemented on a prototype malaxer that was used as a control tool to investigate the influence of oxygen concentration on the final quality and extraction yield of EVOO. The oxygen content in the headspace and olive paste was measured and the balance between these contents was assessed; a high correlation between the oxygen consumed in the headspace and the oxygen consumed by the olive paste was found. The optimal amount of oxygen per kilogram of dough over 40 min of kneading was identified to be in the range 55.4–77.9 mg [O2] kg−1 [olive paste]. This oxygen content facilitates the acquisition of the best qualitative and quantitative performance during the malaxation process. These data allowed us to define new basic parameters for the malaxer design and to optimise the extraction performance, thus ensuring the production of high-quality olive oil.

Preliminary results of a miniaturized respiratory sensor system used under hypergravity conditions up to 9 gz

Respiratory gas analyses are used to explore the influence of increased gravity on the physiology of breathing. Due to the mass, size and intricacy of standard measurement systems, previous studies were limited to a maximum acceleration of + 5 gz (head-to-foot direction). Furthermore, no in situ mainstream measurements of oxygen and carbon dioxide concentration were possible under hypergravity conditions so far. This paper shows a first study which demonstrates a respiratory sensor system developed at the Institute for Aerospace Engineering at TU Dresden. This system is suitable for an in situ measurement of respiratory changes up to + 9 gz (maximum acceleration of jet pilots) and therefore provides a possibility for detailed physiological analyses in future. Three jet pilots were equipped with this system and accelerated under a defined profile up to 7, 8 and + 9 gz. The breathing air flow, oxygen and carbon dioxide concentration were recorded with our miniaturized solid state electrolyte gas sensors, which are also described in this paper. The analysed data show significant changes of the measured respiratory parameters depending on the G-level, the acceleration rate (G-rate of onset [g s−1]) and the examination time.

Validation of wavelength modulation spectroscopy techniques for oxygen concentration measurement

Tunable Diode Laser Absorption Spectroscopy (TDLAS) based gas sensing technology, has widespread applications, ranging from use in biomedical industry to aerospace applications. An experimental set-up was established to measure concentration of oxygen gas in the range 0–100% using TDLAS technique. The oxygen absorption at 760.241nm was scanned with a tunable DFB laser, and wavelength modulation spectroscopy was used to obtain the harmonics (1f, 2f, 3f & 4f) of the oxygen absorption signal. The modulation parameters such as the modulation voltage, modulation frequency, reference phase, time constant of lock in amplifier, the tuning voltage, and the tuning frequency were optimized to obtain the harmonics of high amplitude and narrow half width. Keeping the experimental parameters constant, the oxygen concentration measurements were obtained by the following three methodologies, viz, (i) using only the 2nd harmonic, (ii) using the 2nd and 4th harmonics and, (iii) using the 1st and 2nd harmonics. The results of these measurements were compared and the merits and drawbacks of these methods are discussed.

Increased root zone oxygen by a capillary barrier is beneficial to bell pepper irrigated with brackish water in an arid region

Limitations to growth and biomass production are expected under high (>30°C) soil temperatures due to low soil oxygen levels and insufficient oxygen transport to roots. These limitations will be exacerbated when irrigation with brackish water dictates large amounts of water application for leaching salts. We hypothesized that the introduction of an artificial capillary barrier (CB), in the form of a gravel layer at the lower root-zone boundary, can increase yields of irrigated horticultural crops due to better soil aeration and improved oxygen supply to roots. The specific objectives of the study were (1) to isolate scenarios where insufficient oxygen concentrations may limit pepper plant growth, (2) to measure oxygen concentrations in media under varied scenarios of CB placement below the active root zone and (3) to understand the environmental factors leading to sub-optimum oxygen concentrations in horticultural soils in a desert environment where supra-optimal soil temperatures are prevalent. At high root-zone temperatures oxygen flux to the roots was lower than the potential uptake rate and therefore soil oxygen concentrations were sub-optimal. These conditions led to reduced plant biomass and fruit yield. Fruit yield was found to decrease by 1% for every soil oxygen concentration decrease of 700ppm. In a fine textured Reg soil, allowing roots to penetrate into the capillary barrier gravel layer increased oxygen concentration in the root zone by 5% and improved biomass and fruit yield by 16% and 18%, respectively.

Isolation, Identification and Characterization of an Electrogenic Microalgae Strain

Extracellular electron transfer involving microbes is important as it closely reflects the ability of cells to communicate with the environment. However, there are few reports on electron transfer mechanisms of pure microalgae and a lack of any model alga to study the transfer processes. In the present study, nine green microalgae species were isolated from wastewater and characterized in terms of their ability to transfer electrons between cells and an electrode. One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen. The microalga was identified as Desmodesmus sp. based on phylogenetic analysis and electron microscopy. Electrochemical tests demonstrated that Desmodesmus sp. was able to act as a cathodic microorganism. Stable current densities of −0.24, 35.54 and 170 mA m−2 were achieved at potentials of +0.2, −0.2 and −0.4 V, respectively, under illumination. Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L−1 in light decreasing to 4.29 mg L−1 in the dark. This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.

Boron-oxygen defect imaging in p-type Czochralski silicon

In this work, we demonstrate an accurate method for determining the effective boron-oxygen (BO) related defect density on Czochralski-grown silicon wafers using photoluminescence imaging. Furthermore, by combining a recently developed dopant density imaging technique and microscopic Fourier transform infrared spectroscopy measurements of the local interstitial oxygen concentration [Oi], the BO-related defect density, [Oi], and the boron dopant density from the same wafer were determined, all with a spatial resolution of 160 μm. The results clearly confirm the established dependencies of the BO-related defect density on [Oi] and the boron dopant density and demonstrate a powerful technique for studying this important defect.

Measurement of non-condensable gas in a PWR small-break LOCA simulation test with LSTF for OECD/NEA ROSA Project and RELAP5 post-test analysis

An OECD/NEA ROSA Project experiment with the large scale test facility was conducted simulating a PWR 0.5% cold leg small-break loss-of-coolant accident with steam generator (SG) secondary-side depressurization as an accident management measure to clarify such complex phenomena as non-uniform flow among the SG U-tubes under natural circulation (NC) with non-condensable gas. Non-condensable gas inflow to the primary system from accumulator tanks was simulated with air. The gas concentration was measured at the SG outlet plenum by using a gas measurement device to measure oxygen concentration in steam–gas mixture that is developed employing a Zirconia sensor. Non-uniform flow behaviors were observed in the SG U-tubes with non-condensable gas ingress depending probably on gas accumulation rate as well as asymmetric NC between two loops. Air concentration in steam–gas mixture was estimated to be about 40-50% at the SG outlet plena after the U-tube downflow side became empty of liquid, which was a bit larger than the estimated value based on the gas phase temperature. Post-test analysis by JAEA-modified RELAP5/MOD3.2.1.2 code revealed that the code underpredicts the primary pressure a bit after the gas inflow with some discrepancies in the SG U-tube liquid level and the NC mass flow rate.

Action of La3+ on the systems providing contractility of vertebrate myocardium

The inotropic action of La3+ on frog myocardium was studied with taking into account of its effect on mitochondria of cardiomyocytes (CM). It has been established that in the range of studied concentrations (0.2-6 mM), La3+ decreases dose-dependently the strength of cardiac contractions (by 3.3-92.2 %). In parallel experiments on isolated rat heart mitochondria (RHM), La3+ at a concentration of 25 microM has been shown to cause swelling of non-energized and energized mitochondria in isotonic medium with 125 mM NH4NO3 and in hypotonic medium with 25 mM CH3COOK. The study of oxidative processes in mitochondria with aid of polarographic method of measurement of oxygen concentration has shown that La3+ at concentrations of 50 and 100 microM increases the oxygen consumption rate by mitochondria in the state 2. However, La3+ does not decrease the respiration rate of isolated mitochondria in the state 3, as this takes place in the case of use of Cd2+ or at the Ca(2+)-overloading of mitochondria. The rate of endogenous respiration of isolated mitochondria in the medium with La3+ was higher than in control, which implies its effect on ion permeability of the inner membrane. The data obtained in this work indicate that the La(3+)-produced decrease of the contractility of cardiac muscle is not only due to the direct blocking effect on the potential-controlled Ca2+ channels, but is also mediated by its unspecific action on the CM mitochondria. This action is manifested in acceleration of the energy-dependent K+ transport in matrix and in an increase of ion permeability of the inner mitochondrial membrane (IMM).

An Eulerian–Lagrangian method for the simulation of the oxygen concentration dissolved by a two-phase turbulent jet system

Multiphase jet systems are used in environmental engineering to mix and provide oxygen in activated sludge plants for the aerobic digestion of degradable substrates.Here a laboratory experiment, based on a lab-scale model where mixing is obtained by a turbulent multiphase jet of tap water and pure oxygen, is used to validate a multiscale numerical model of the oxygen concentration evolution based on a “one-way coupling” approach.The velocity field inside the lab-model, measured by means of a 3D Acoustic Doppler Velocimeter, allows to check the data provided by a finite-volume RANS numerical model of the flow, where turbulent effects are taken into account by a RNG k–ε turbulence model. The obtained numerical velocity field is then used as input for an Eulerian–Lagrangian numerical model for the dissolved oxygen balance equation, where diffusion effects are computed by a random walk model based on the turbulent kinetic energy field. The bubble size distribution of the jet, determined by a photographic technique, is taken into account in the numerical model in order to calculate the mass transfer from the bubbles to the liquid. Several mass transfer models are implemented and tested in order to perform a sensitivity analysis. The obtained numerical results are compared with experimental measurements of dissolved oxygen concentration inside the lab-scale model during a transient. Results show that the developed numerical technique yields an accurate reproduction of the measured oxygen concentration in time and can be applied to analyse the behaviour of jet systems for oxygenation and mixing in activated sludge plants.

Oxygen control technology in applications of liquid lead and lead–bismuth systems for mitigating materials corrosion

Oxygen control technology has been successfully applied in liquid lead and lead–bismuth coolant systems for mitigating materials corrosion. In the present study, the development of the oxygen control technology is reviewed. The corrosion mitigation mechanisms, the oxygen control methods, and the oxygen concentration measurements are discussed. The study also analyzes the current technology issues and near future studies needed. For comparisons, the study also reviews other corrosion inhibitors that have also been applied for mitigating corrosion by liquid lead and lead–bismuth.

Development of an air fuel control system for a domestic wood pellet boiler

Wood pellets are a kind of solid biomass energy and a renewable energy source. Made by compressing sawdust, wood pellets have a higher energy density than split firewood and wood chips. In 2007, the new and renewable energy (NRE) portion was 2.4% with respect to total primary energy in Korea. The Korean government wants to increase the new and renewable energy (NRE) portion up to 6.1% by 2020 [1]. To achieve this target, the government has been establishing some policies, such as incentive policy, NRE mandatory use for public building and renewable portfolio standard (RPS) and so on. To supply wood pellets as fuel for the combustion chamber of a wood pellet boiler, most domestic wood pellet boilers put a constant volume by using an auger type fuel feed system. In an auger system as fuel feeding, there is the possibility of changing energy input due to the different density of wood pellets even in a constant volume flow rate of wood pellets. If fuel input rate is changed without any correction of air flow rate for combustion, the condition of combustion in a wood pellet boiler can be deteriorated. We have developed an air-fuel control system for a domestic wood pellet boiler by using flue gas oxygen concentration measurement and a PID controller. To measure O2 concentration of flue gas, a wide band O2 sensor was adopted. We changed fuel input from 100% to 50% by artificial manipulation to confirm the control system. The O2 concentration in flue gas can be controlled to be 8.5% ± 1% without significant change of CO and NOx concentration.

Physiological and behavioral responses of poultry exposed to gas-filled high expansion foam

Disease control measures require poultry to be killed on farms to minimize the risk of disease being transmitted to other poultry and, in some cases, to protect public health. We assessed the welfare implications for poultry of the use of high-expansion gas-filled foam as a potentially humane, emergency killing method. In laboratory trials, broiler chickens, adult laying hens, ducks, and turkeys were exposed to air-, N2-, or CO2-filled high expansion foam (expansion ratio 300:1) under standardized conditions. Birds were equipped with sensors to measure cardiac and brain activity, and measurements of oxygen concentration in the foam were carried out. Initial behavioral responses to foam were not pronounced but included headshakes and brief bouts of wing flapping. Both N2- and CO2-filled foam rapidly induced ataxia/loss of posture and vigorous wing flapping in all species, characteristic of anoxic death. Immersion in air-filled, high expansion foam had little effect on physiology or behavior. Physiological responses to both N2- and CO2-filled foam were characterized by a pronounced bradyarrythymia and a series of consistent changes in the appearance of the electroencephalogram. These were used to determine an unequivocal time to loss of consciousness in relation to submersion. Mean time to loss of consciousness was 30 s in hens and 18 s in broilers exposed to N2-filled foam, and 16 s in broilers, 1 s in ducks, and 15 s in turkeys exposed to CO2-filled foam. Euthanasia achieved with anoxic foam was particularly rapid, which is explained by the very low oxygen concentrations (below 1%) inside the foam. Physiological observations and postmortem examination showed that the mode of action of high expansion, gas-filled foam is anoxia, not occlusion of the airway. These trials provide proof-of-principle that submersion in gas-filled, high expansion foam provides a rapid and highly effective method of euthanasia, which may have potential to provide humane emergency killing or routine depopulation.

WINDII observations and TIME-GCM simulations of O(1S) polar spirals during geomagnetic disturbances

[1] The daytime O(1S) emission at 557.7 nm observed at 250 km with the Wind Imaging Interferometer (WINDII) is dominantly excited by photoelectron impact on atomic oxygen, so the volume emission rate is normally a measure of the atomic oxygen concentration. Daily polar maps of the 250 km volume emission rate during geomagnetic disturbances display polar spirals extending out of the auroral region and down to the equator. Since the local time is fixed for a given latitude for a single day, the spiral maps form a spatio-temporal pattern in which the longitudinal variations cannot be distinguished from those in universal time. Simulations for 2 January 1993 implemented with the National Center for Atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) using the equivalent satellite perspective show a remarkably similar spiral pattern. Hourly universal time simulations reveal a rapid equatorward expansion of the spirals during this modest geomagnetic event of Kp = 4.7, which are mirrored in the meridional and vertical winds. Simulations of the electron density show that the emission within the spirals is caused by the recombination of O2+ ions with electrons, and not the atomic oxygen enhancement itself. All of this strongly suggests that the spirals are in fact large-scale Traveling Ionospheric Disturbances (TIDs), and comparisons of the WINDII data made with TID observations reported in the literature, including those made on the same day, support this conclusion. The TIME-GCM simulations suggest that a component of the spirals originates in the lower atmosphere and appears at thermospheric heights.

An optical sensor for monitoring of dissolved oxygen based on phase detection

Dissolved oxygen (DO) monitoring is of vital importance to water treatment, sewage treatment, aquaculture and biological research. The traditional method for DO detection is an electrochemical method called the Clark electrode. This electrochemical method has been widely used as it is simple and inexpensive; however, the critical drawback for this kind of sensor is that it is easily affected by pH variations, and by the concentration of H2S and SO2. Optical sensing for DO detection is a newly developed technology, which can avoid most of the drawbacks of the electrochemical sensors. A DO sensor using fluorescence detection is described in this paper. The oxygen concentration measurement principle is based on optical phase detection, which is more precise than the traditional intensity detection method. Emission is carried out by a low-cost, specially designed light emitting diode (LED) source. To avoid an unwanted phase shift, a reference LED is used to improve the degree of accuracy. The sensing material for fluorescence is a ruthenium complex. A discrete Fourier transform (DFT) algorithm was used for the phase calculation. The system was designed into a stainless steel probe, and dissolved oxygen concentration measurement results for various applications are presented in this paper.

Dissolved Oxygen Concentration Interlaboratory Comparison: What Can We Learn?

Dissolved oxygen concentration is a key parameter for characterizing natural and wastewaters and for assessing the global state of the environment in general. The decrease of dissolved oxygen levels in the world’s oceans, which is becoming increasingly obvious, is expected to have an impact on the whole ecosystem of the Earth, including the carbon cycle, the climate, etc. Dissolved oxygen measurements by sensors are often deemed easy measurements by routine laboratories. In reality, the physical and chemical processes underlying the measurements are complex and these measurements are not at all as robust as often considered. Recently an international in situ interlaboratory comparison measurement of dissolved oxygen concentration took place at the University of Tartu. The results revealed that the routine laboratories as a rule still do not fully master the art of dissolved oxygen concentration measurement: Out of altogether 63 measurement results obtained by the participants 52% were unacceptable according to the En numbers. Based on the analysis of the results of the intercomparison a set of tools and recommendations are given to the participants of how to improve the quality of their results.

Telemetry‐based oxygen sensor to continuously monitor renal cortical oxygenation in the conscious rat

Multiple forms of acute and chronic kidney disease are associated with renal tissue hypoxia. Yet the precise roles of hypoxia in the initiation and progression of kidney disease remain unresolved. A major technical limitation has been the absence of methods allowing long‐term measurement of kidney tissue oxygen concentration in unrestrained animals. Previously we developed a fully implantable telemetric method for the measurement of tissue oxygen concentration in the renal medulla of freely moving rats, using carbon past electrodes (CPEs). Using this CPE‐telemetry system we continuously recorded tissue oxygen concentration in the renal cortex for 3 weeks in rats. Oxygen values were stable over time and comparable between animals. It also provided reproducible responses to systemic hypoxia and hyperoxia over this time period, and these responses were similar to those previously observed in the renal medulla. There was little evidence of fibrosis or scarring after three weeks of electrode implantation. This new technology provides, for the first time, the opportunity to examine the temporal relationships between tissue hypoxia in different renal compartments and the progression of renal disease. EU, FP7, Marie Curie Actions, International Outgoing Fellowship.

Abstract A10: Stromal CAIX expression in oral squamous cell carcinoma and corresponding lymph node metastases

Abstract Background: Hypoxia is an almost ubiquitous feature of human solid tumours. However, the direct measurement of oxygen concentration in head and neck squamous cell carcinoma (HNSCC) has been conducted almost exclusively in the metastatic lymph nodes, not the primary tumor. Hypoxia is associated with resistance to both radiotherapy (RT) and chemotherapy in squamous cell cancers (SCCs). However, endogenous markers of hypoxia (EMH) have not reproducibly predicted clinical outcome. However, historically, the method used to assign hypoxic status according to directly measured oxygen concentration (polarographic electrode) and EMH (typically immunohistochemistry) have fundamentally differed. Methods: Demographic data and clinical outcomes of 61 patients with oral squamous cell carcinoma (OSCC) treated with primary surgery +/- adjuvant radiation were collected. Tissue microarray's with representative samples of patients' tumors were constructed from paraffin-embedded blocks. Automated quantitative immunohistochemistry (AQUA) was performed to measure expression and distribution of carbonic anhydrase IX (CAIX). Kaplan-Meier survival analysis and the log-rank test was used to assess the impact of vimentin-defined stromal CAIX (in both primary tumor and nodal metastases) on survival. Results: High stromal CAIX expression in the primary tumor was associated with significantly worse 5-year disease-specific survival. There was a statistically significant but relatively weak correlation between stromal CAIX expression in the primary tumor and the corresponding lymph nodes (r2:0.359; p=0.013). Stromal CAIX expression in the lymph node metastases was not significantly associated with 5-year disease-specific survival. Conclusions: Previous literature presenting the prognostic impact of directly measured hypoxia, using a polarographic electrode, was based predominantly on measurements from lymph nodes, not the primary tumor. Furthermore, comparisons with EMH were based solely on percentage of tumor cells that were positively stained, not the intensity of staining. We present the results of a tumor comparment-specific, quantitative fluorescent IHC method and the survival associated with EMH in the tumor microenvironment in the primary tumor and lymph node metastases. Citation Format: Shamir Chandarana, Pinaki Bose, Alexander C. Klimowicz, Stephanie K. Petrillo, Mie Konno, Luke Rudmik, Steven C. Nakoneshny, Wayne T. Matthews, Anthony M. Magliocco, Joseph C. Dort, Nigel T. Brockton. Stromal CAIX expression in oral squamous cell carcinoma and corresponding lymph node metastases. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A10.