Monitoring Of Oxygen Levels Research Articles

Mesocosm Studies on the Effect of Propanil on the Water Quality and Plankton Communities of Four Aquaculture Pond Systems

A study was conducted to evaluate propanil effects on water quality and plankton of four different aquaculture systems: penaeid shrimp, goldfish, hybrid striped bass, and channel catfish. Propanil or Stam is a common rice herbicide, which has impacted adjacent channel catfish ponds by reducing phytoplankton. The experimental design utilized 500-L outdoor mesocosms filled in triplicate with water from the four systems in four trials. After filling from nearby pond systems, propanil was added at 0.2 times the full rice field application rate, which was judged to be a potential drift or runoff level. This was equivalent to 0.1 mg/L. Beginning 24 h after application, morning water column samples were taken daily until the treatments returned to normal as indicated by no differences from the controls. Ten parameters were measured. Although results indicated short-term impacts, dissolved oxygen and zooplankton levels (for fry ponds) were reduced to potentially harmful levels. In addition, impacts depended on the phytoplankton levels, as indicated by chlorophyll a. Low levels (shrimp ponds), and high levels (goldfish ponds) were least affected. Greatest impacts were in the mid-range of approximately 200 ug/L (channel catfish). Farmers should monitor oxygen levels and zooplankton in fry ponds if propanil contamination is suspected.

Lifetime-resolved Photoacoustic (LPA) Spectroscopy for monitoring Oxygen change and Photodynamic Therapy (PDT).

The Methylene Blue loaded Polyacrylamide Nanoparticles (MB-PAA NPs) are used for oxygen sensing and Photodynamic therapy (PDT), a promising therapeutic modality employed for various tumors, with distinct advantages of delivery of biomedical agents and protection from other bio-molecules overcoming inherent limitations of molecular dyes. Lifetime-resolved photoacoustic spectroscopy using quenched-phosphorescence method is applied with MB-PAA NPs so as to sense oxygen, while the same light source is used for PDT. The dye is excited by absorbing 650 nm wavelength light from a pump laser to reach triplet state. The probe laser at 810 nm wavelength is used to excite the first triplet state at certain delayed time to measure the dye lifetime which indicates oxygen concentration. The 9L cells (106 cells/ml) incubated with MB-PAA NP solution are used for monitoring oxygen level change during PDT in situ test. The oxygen level and PDT efficacy are confirmed with a commercial oximeter, and fluorescence microscope imaging and flow cytometry results. This technique with the MB-PAA NPs allowed us to demonstrate a potential non-invasive theragnostic operation, by monitoring oxygen depletion during PDT in situ, without the addition of secondary probes. Here, we demonstrate this theragnostic operation, in vitro, performing PDT while monitoring oxygen depletion. We also show the correlation between O2 depletion and cell death.

Pulse oximeters to self monitor oxygen saturation levels as part of a personalised asthma action plan for people with asthma.

We became aware through talking with people with asthma that some are using pulse oximeters to monitor their own blood oxygen levels during an asthma attack. Pulse oximeters are marketed by some suppliers as essential equipment for the home medicine cabinet. We wanted to find out if reliable evidence is available on use of pulse oximeters to self monitor asthma exacerbations at home. We decided to include only trials that used pulse oximeters as part of a personalised asthma action plan because it is important that decisions are made on the basis of symptoms as well as oxygen saturation, and that patients have a clear protocol to follow when their asthma worsens. To determine whether pulse oximeters used as part of a personalised asthma action plan for people with asthma are safer and more effective than a personalised asthma action plan alone. We searched the Cochrane Airways Group Specialised Register (CAGR), which includes reports identified through systematic searches of bibliographic databases including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Allied and Complementary Medicine Database (AMED) and PsycINFO, and by handsearching. We also searched ClinicalTrials.gov and the World Health Organization (WHO) trials portal. We planned to include randomised controlled trials (RCTs). Participants would have included adults, children or both with a diagnosis of asthma. We planned to include trials in which investigators compared participants who used pulse oximeters to monitor oxygen levels at home during an asthma exacerbation as part of a personalised asthma action plan (PAAP) versus those who used a PAAP without a pulse oximeter. We planned to include studies involving people receiving any treatment regimen provided that no medicine was included as part of the randomisation schedule. We planned to use standard methods as recommended by The Cochrane Collaboration. We found no studies and no evidence to support or refute the use of home pulse oximetry in self management of asthma; therefore, we can make no recommendations about use of a pulse oximeter as part of a PAAP. We found no reliable data to support or refute patient use of pulse oximeters to monitor oxygen saturation levels when experiencing an asthma attack. People should not use a pulse oximeter without seeking advice from a qualified healthcare professional.We identified no compelling rationale for home monitoring of oxygen levels in isolation for most people with asthma. Some people have a reduced perception of the severity of their own breathlessness when exposed to hypoxia. If trials on self monitoring of oxygen levels in the blood by pulse oximeter at home by people with asthma are conducted, the pulse oximeter must be given as part of a personalised asthma action plan.

Monitoring oxygen levels in orthotopic human glioma xenograft following carbogen inhalation and chemotherapy by implantable resonator-based oximetry.

Hypoxia is a critical hallmark of glioma, and significantly compromises treatment efficacy. Unfortunately, techniques for monitoring glioma pO2 to facilitate translational research are lacking. Furthermore, poor prognosis of patients with malignant glioma, in particular glioblastoma multiforme, warrant effective strategies that can inhibit hypoxia and improve treatment outcome. EPR oximetry using implantable resonators was implemented for monitoring pO2 in normal cerebral tissue and U251 glioma in mice. Breathing carbogen (95% O2 + 5% CO2 ) was tested for hyperoxia in the normal brain and glioma xenografts. A new strategy to inhibit glioma growth by rationally combining gemcitabine and MK-8776, a cell cycle checkpoint inhibitor, was also investigated. The mean pO2 of left and right hemisphere were ∼56-69 mmHg in the normal cerebral tissue of mice. The mean baseline pO2 of U251 glioma on the first and fifth day of measurement was 21.9 ± 3.7 and 14.1 ± 2.4 mmHg, respectively. The mean brain pO2 including glioma increased by at least 100% on carbogen inhalation, although the response varied between the animals over days. Treatment with gemcitabine + MK-8776 significantly increased pO2 and inhibited glioma growth assessed by MRI. In conclusion, EPR oximetry with implantable resonators can be used to monitor the efficacy of carbogen inhalation and chemotherapy on orthotopic glioma in mice. The increase in glioma pO2 of mice breathing carbogen can be used to improve treatment outcome. The treatment with gemcitabine + MK-8776 is a promising strategy that warrants further investigation.

Monitoring oxygen levels in hypoxic tissues with a solid MRI contrast agent

Monitoring oxygen levels in hypoxic tissues with a solid MRI contrast agent

Nondestructive and Continuous Monitoring of Oxygen Levels in Modified Atmosphere Packaged Ready‐to‐Eat Mixed Salad Products Using Optical Oxygen Sensors, and Its Effects on Sensory and Microbiological Counts during Storage

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready-to-eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O2 , 5% CO2 , 90% N2 (MAPC-commercial control), 21% O2 , 5% CO2 , 74% N2 (MAP 1), 45% O2 , 5% CO2 , 50% N2 (MAP 2), and 60% O2 , 5% CO2 , 35% N2 (MAP 3)) and 4 °C for up to 10 d. The quality and shelf-life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf-life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf-life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products.

Spatially monitoring oxygen level in 3D microfabricated cell culture systems using optical oxygen sensing beads

Capability of measuring and monitoring local oxygen concentration at the single cell level (tens of microns scale) is often desirable but difficult to achieve in cell culture. In this study, biocompatible oxygen sensing beads were prepared and tested for their potential for real-time monitoring and mapping of local oxygen concentration in 3D micro-patterned cell culture systems. Each oxygen sensing bead is composed of a silica core loaded with both an oxygen sensitive Ru(Ph2phen3)Cl2 dye and oxygen insensitive Nile blue reference dye, and a poly-dimethylsiloxane (PDMS) shell rendering biocompatibility. Human intestinal epithelial Caco-2 cells were cultivated on a series of PDMS and type I collagen based substrates patterned with micro-well arrays for 3 or 7 days, and then brought into contact with oxygen sensing beads. Using an image analysis algorithm to convert florescence intensity of beads to partial oxygen pressure in the culture system, tens of microns-size oxygen sensing beads enabled the spatial measurement of local oxygen concentration in the microfabricated system. Results generally indicated lower oxygen level inside wells than on top of wells, and local oxygen level dependence on structural features of cell culture surfaces. Interestingly, chemical composition of cell culture substrates also appeared to affect oxygen level, with type-I collagen based cell culture systems having lower oxygen concentration compared to PDMS based cell culture systems. In general, results suggest that oxygen sensing beads can be utilized to achieve real-time and local monitoring of micro-environment oxygen level in 3D microfabricated cell culture systems.

A novel minimally invasive method for monitoring oxygen in microbial fuel cells

Oxygen availability is a potential rate-limiting step in the bioelectrochemical process catalyzed by microbes in microbial fuel cells (MFC). Determination of oxygen availability using a minimally invasive oxygen sensor is advantageous in terms of ease of usage, maintenance and cost-effectiveness as compared to using conventional probe-type oxygen sensors. The utility of this method is substantiated by using this sensor to demonstrate the relationship between oxygen availability and current density. 10 % drop in oxygen concentration resulted in a concomitant drop in current density by about 36 %, further establishing the criticality of monitoring oxygen levels in the MFC. The detachable sensor membrane of the minimally invasive sensor confers multiple advantages. The novel method would enable real-time monitoring of oxygen in MFCs, simplify process optimization and validation and more importantly, provide an impetus for development of more efficient MFC designs.

Fluorescent silica particles for monitoring oxygen levels in three‐dimensional heterogeneous cellular structures

Bacterial biofilms are a major obstacle challenging the development of more effective therapies to treat implant infections. Oxygen availability to bacterial cells has been implicated in biofilm formation and planktonic cell detachment; however, there are insufficient tools available to measure oxygen concentrations within complex three-dimensional structures with ∼ 1 µm resolution. Such measurements may complement measures of biofilm structure and cell activity to provide a more comprehensive understanding of biofilm biology. Thus, we developed oxygen-sensing microparticles specifically designed to characterize oxygen transport through the volume of bacterial biofilms. The Stöber method was used to synthesize monodisperse silica microparticles of approximately the same size as a bacterium (∼ 1 µm). Two fluorophores, oxygen-sensitive Ru(Ph(2) phen(3))Cl(2), and the reference fluorophore Nile blue chloride were immobilized on the surface of the particles. We demonstrate application of the microparticles toward measuring the oxygen concentration profiles within a live Staphylococcus aureus biofilm.

A TR(i)P in the air

Monitoring oxygen (O2) levels is essential to optimizing aerobic metabolism and ensuring proper biological processes in most eukaryotes. The spice chemosensor TRPA1 is a previously unidentified O2 sensor in the mammalian sensory nervous system that warns against hyperoxia and hypoxia.

HIF-1α mRNA levels in Eurasian perch (Perca fluviatilis) exposed to acute and chronic hypoxia

The big advantage of using molecular biomarkers to monitor oxygen levels in aquatic systems is that responses at the molecular level tend to be more sensitive, and usually occur earlier than those at higher levels of biological organization Aquatic hypoxia is a frequent event, which can occur naturally in a variety of marine, estuarine and freshwater habitats. More often, however, hypoxia arises as a result of euthrophication of aquatic ecosystem and can lead to changes in community structure by eliminating hypoxia-sensitive species. Consequently fish have develop various physiological and biochemical mechanisms to cope with this environmental stress. Many of these adjustments depend to changes in expression of a wide range of genes. The transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor-1 (HIF-1), a heterodimer composed of an α and β subunit. This study investigated if HIF-1α mRNA levels were regulated by hypoxia in Eurasian perch (Perca fluviatilis), a hypoxia-sensitive fresh water species. The real-time PCR was utilized to monitor dynamic changes in levels of HIF-1α mRNA in response to acute (DO 0.4±0.1mg/l for 1h) and chronic (DO 2.8±0.3mg/l for 15days) hypoxia. Our results indicated an up-regulation of HIF-1α in brain and liver, but not in muscle tissue after acute hypoxic treatment, whereas significant changes of HIF-1α mRNA levels were detected in muscle, but not in brain and liver after chronic hypoxia exposure. This study suggests that HIF-1α mRNA level in selected perch tissues could be an useful indicator of acute exposure to hypoxia.

Identification of robust hypoxia biomarker candidates from fin of medaka ( Oryzias latipes)

Aquatic hypoxia caused by organic pollution and eutrophication is a pressing worldwide water pollution problem. Better methods for monitoring oxygen levels are needed to assist efforts to maintain and protect the health of natural aquatic environments. In this project, we used a Japanese ricefish (medaka, Oryzias latipes) 8K oligonucleotide array as a platform to identify potential hypoxic biomarkers in different organs (fin, gill, liver and brain) upon exposure to hypoxia. The microarray results were validated by qRT-PCR employing a subset of candidate biomarkers. Interestingly, the largest number and most significant of hypoxia responding array features were detected in hypoxia exposed fin tissues. We identified 173 array features that exhibited a significant response (over 2 fold change in expression) upon exposure to hypoxic conditions and validated a subset of these by quantitative RT-PCR. These gene targets were subjected to annotation and gene ontology mining. Positively identifiable gene targets that may be useful for development of a rapid and accurate biomarker test using fin clips are discussed in relation to previous reports on hypoxia responsive genes.

Do monoamine-synthesizing cells constitute a complex network of oxygen sensors?

Oxygen represents an essential molecule for organisms. Because of this, sophisticated systems of sensors have evolved to monitor oxygenation of tissues. We propose that monoamine-synthesizing cells represent an important part of this system. It is well known that the carotid body, which contains chromaffin cells, serves as a chemical sensor of blood oxygenation. Similarly, the activity of adrenal medullary chromaffin cells is increased during hypoxia. Moreover, neurons located in the central nervous system containing catecholamines, serotonin, and histamine are also sensitive to hypoxia. On the basis of this common sensitivity of monoamine-synthesizing cells to changes in oxygenation we propose the hypothesis that these cells constitute a widely distributed network of sensors that monitor oxygen levels. The role of monoamine-synthesizing cells in monitoring tissue oxygen supply during both physiological and pathological conditions is also discussed.

Retrievable micro-inserts containing oxygen sensors for monitoring tissue oxygenation using EPR oximetry

Tissue oxygenation is a crucial parameter in various physiopathological situations and can influence the therapeutic response of tumours. EPR oximetry is a reliable method for assessing and monitoring oxygen levels in vivo over long periods of time. Among the different paramagnetic oxygen sensors available for EPR oximetry, lithium phthalocyanine (LiPc) is a serious candidate for in vivo applications because of its narrow linewidth and its high signal-to-noise ratio. To enhance the biocompatibility of the sensors, fluoropolymer Teflon AF2400 was used to make cylindrical micro-inserts containing LiPc crystals. This new micro-pellet design has several advantages for in vivo studies, including the possibility of being able to choose the implant size, a high sensor content, the facility of in vivo insertion and complete protection with preservation of the oxygen sensor's characteristics. The response to oxygen and the kinetics of this response were tested using in vivo EPR: no differences were observed between micro-inserts and uncoated LiPc crystals. Pellets implanted in vivo in muscles conserved their responsiveness over a long period of time (∼two months), which is much longer than the few days of stability observed using LiPc crystals without protection by the implant. Finally, evaluation of the biocompatibility of the implants revealed no inflammatory reaction around the implantation area.

Evaluation of oxygen content in commercial modified atmosphere packs (MAP) of processed cooked meats

Twenty-five packs of each of 13 processed cooked meats products, produced by three manufacturers, were analysed. Analysis was performed 1, 7, 14 and 21 days after obtaining samples at the point of manufacture. Although all products were packaged in modified atmospheres of 70% N 2 and 30% CO 2, oxygen was present in 88% of packs 24 h after packaging. Overall percentages of packs containing 0.0, 0.01–0.5, 0.51–1.2 and >1.2% oxygen were 11.7, 38.4, 29.4 and 20.4%, respectively on day 1 and 0.0, 15.5, 5.3 and 79.3%, respectively, on day 21. Three comparable pork products produced by three different manufacturers contained different levels of oxygen on day 1. The high proportion of packages containing rejectably high levels of oxygen may pose a potential risk of product quality deterioration and reduced shelf-life of muscle-based foods. Results emphasize the necessity to monitor oxygen levels within packs of oxygen-sensitive foods, including processed, cooked muscle foods.

An Intermediate-Scale Lysimeter Facility for Subsurface Bioremediation Research

A lysimeter facility at Oak Ridge National Laboratory, originally constructed to investigate leaching from low-level radioactive waste, was converted for use as an intermediate-scale facility for subsurface bioremediation research. The six experimental lysimeters are 2.5 m diameter by 4 m deep. The number and size of the lysimeters allow for replicate experiments and extensive sampling of the soil under controlled conditions. The facility provided containment of the contaminated soil, leachate, and microorganisms; positive control of the water table within the lysimeter; the ability to aerate the subsurface; multiple means of adding nutrients, electron acceptors, and electron donors to the subsurface; instrumentation for monitoring oxygen level, temperature, and moisture level; and means for obtaining samples of groundwater, soil, and liquid and gas samples from the soil pores. The flexibility of the facility allows for simulation of a wide range of subsurface bioremediation technologies. Startup and operational procedures and the advantages and disadvantages of the lysimeter facility are discussed. The facility is currently available to the bioremediation research community.

Oxygen microsensor and its application to single cells and mouse pancreatic islets.

An oxygen microsensor with a < 3-micron tip diameter was developed for monitoring oxygen levels at single cells and mouse pancreatic islets. The sensor was fabricated by electrochemically recessing an etched Pt wire inside a pulled glass micropipet and then coating with cellulose acetate. This fabrication process was found to be simpler than previous oxygen electrode designs of comparable size. The microsensors had a average sensitivity of 0.59 +/- 0.29 pA/mmHg (mean +/- SD, n = 42), signals that were minimally perturbed by convection, and response times of < 1 s. The electrode was used to measure the oxygen gradient around and inside single mouse islets. The measurements demonstrate that oxygen levels within even the largest islets at maximal glucose stimulation are 67 +/- 1.6 mmHg (mean +/- SD, n = 5), indicating that islets have adequate oxygen supplies by diffusion under tissue culture conditions to support insulin secretion. The electrode was also used to record the dynamics of oxygen level at single islets as a function of glucose concentration. As glucose level was changed from 3 to 10 mM, oxygen level decreased by 15.8 +/- 2.3 mmHg (mean +/- SEM, n = 6) and oscillations with a period of 3.3 +/- 0.6 min (mean +/- SEM, n = 6) appeared in the oxygen level. In islets bathed in quiescent solutions containing 10 mM glucose, similar oscillations could be observed. In addition, in the quiet solutions it was possible to detect faster oscillations with a period of 12.1 +/- 1.7 s (mean +/- SEM, n = 6) superimposed on the slower oscillations. Oxygen consumption could also be observed at single insulinoma cells using the electrode. Individual cells also showed oscillations in oxygen consumption with a period of a few seconds. The results demonstrate that the electrode can be used for dynamic oxygen level recordings in biological microenvironments.