Changes In Oxygen Concentration Research Articles

Phosphorescent O2-Probes Based on Ir(III) Complexes for Bioimaging Applications

The design, synthesis, and investigation of new molecular oxygen probes for bioimaging, based on phosphorescent transition metal complexes are among the topical problems of modern chemistry and advanced bioimaging. Three new iridium [Ir(N^C)2(N^N)]+ complexes with cyclometallating 4-(pyridin-2-yl)-benzoic acid derivatives and different di-imine chelate ligands have been synthesized and characterized by mass spectrometry and NMR spectroscopy. The periphery of these complexes is decorated with three relatively small “double-tail” oligo(ethylene glycol) fragments. All these complexes exhibit phosphorescence; their photophysical properties have been thoroughly studied, and quantum chemical calculations of their photophysical properties were also performed. It turned out that the changes in the nature of the di-imine ligand greatly affected the character of the electronic transitions responsible for their emission. Two complexes in this series show the desired photophysical characteristics; they demonstrate appreciable quantum yield (14–15% in degassed aqueous solutions) and a strong response to the changes in oxygen concentration, ca. three-fold increase in emission intensity, and an excited state lifetime upon deaeration of the aqueous solution. The study of their photophysical properties in model biological systems (buffer solutions containing fetal bovine serum—FBS) and cytotoxicity assays (MTT) showed that these complexes satisfy the requirements for application in bioimaging experiments. It was found that these molecular probes are internalized into cultured cancer cells and localized mainly in mitochondria and lysosomes. Phosphorescent lifetime imaging (PLIM) experiments showed that under hypoxic conditions in cells, a 1.5-fold increase in the excitation state lifetime was observed compared to aerated cells, suggesting the applicability of these complexes for the analysis of hypoxia in biological objects.

Investigating the hemodynamics of Berlin Heart EXCOR support in Norwood patients across diverse clinical scenarios with computational modeling.

Infants with single-ventricle (SV) physiology undergo the 3-stage Fontan surgery. Norwood patients, who have completed the first stage, face the highest interstage mortality. The Berlin Heart EXCOR (BH), a pediatric pulsatile ventricular assist device, has shown promise in supporting these patients. However, clinical questions regarding device configurations prevent optimal support. We developed a combined idealized mechanics-lumped parameter model of a Norwood patient and simulated two additional patient-specific cases: pulmonary hypertension (PH) and post-operative treatment with milrinone. We quantified the effects of BH support across different device volumes, rates, and inflow connections on patient hemodynamics and BH performance. Increasing device volume and rate increased cardiac output, but with unsubstantial changes in specific arterial oxygen content. We identified distinct SV-BH interactions that may impact patient myocardial health and contribute to poor clinical outcomes. Our results suggested BH settings for patients with PH and for patients treated post-operatively with milrinone. We present a computational model to characterize and quantify patient hemodynamics and BH support for infants with Norwood physiology. Our results emphasized that oxygen delivery does not increase with BH rate or volume, which may not meet patient needs and contribute to suboptimal clinical outcomes. Our findings demonstrated that an atrial BH may provide optimal cardiac loading for patients with diastolic dysfunction. Meanwhile, a ventricular BH decreased active stress in the myocardium and countered the effects of milrinone. Patients with PH showed greater sensitivity to device volume. In this work, we demonstrate the adaptability of our model to analyze BH support across varied clinical situations.

Future climate-induced changes in mixing and deep oxygen content of a caldera lake with hydrothermal heat and salt inputs

Vertical profiles of temperature, salinity and dissolved oxygen in Crater Lake, a caldera lake in the Oregon Cascade Range that receives hydrothermal inputs of heat and salt, were simulated with a 1-dimensional model. Twelve Global Circulation Models and two Representative Concentration Pathways (RCPs) were used to develop boundary conditions from 1950 to 2099. The model simulated the ventilation of deep water initiated by reverse stratification and subsequent thermobaric instability. All models predicted a reduction in the frequency of deep ventilation events, from an ensemble median frequency of 5.4 winters decade−1 during 1950–2005 to 4.3 (RCP4.5) or 2.5 (RCP8.5) winters decade−1 during 2045–2099. Favorable conditions for thermobaric instability-induced mixing currently occur infrequently and will become rare in the future. The salinity gradient resulting from hydrothermal inputs presents an additional barrier to thermobaric instability that will continue through 2099. A redistribution of salt to the deep lake may prevent ventilation all the way to the bottom in the future. Hypolimnetic dissolved oxygen percent saturation remained above 75% within the 21st century, consistent with oligotrophy and very small oxygen demands. The rate of change in all variables accelerated approaching 2099, coincident with elimination of winter reverse stratification. Historically, about half of the hydrothermal heat added to Crater Lake has been vented to the atmosphere. In the RCP8.5 scenario, the hydrothermal heat will cease to be vented to the atmosphere by the end of the 21st century, and then the temperature of the deep waters will increase rapidly.

Modulating influence of wistar rats’ oxygen status on behavioural manifestations of nitrogen narcosis: experimental study

OBJECTIVE of the study is to determine the influence of changing oxygen status in the animal’s body on nitrogen toxic effect under pressure. MATERIALS AND METHODS: A hyperbaric chamber was used to create normothermic effect of hyperbaric nitrogen up to 4,1 MPa amid changing oxygen concentration from 0,03 to 0,004 MPa, recording rats’ motor activity and posture reflexes. RESULTS: Oxygen decrease in the respiratory gas medium from 0,021 to 0,004 MPa due to nitrogen compression raised biphasic sensitivity of Wistar rates to nitrogen toxic effect. Yet in the sites of non-compensable hypoxia sensitivity to hyperbaric nitrogen effect increased 4,5 times. Preliminary exposure of pregnant rats in hypoxia led to decrease in the offspring’s sensitivity to toxic effect of hyperbaric nitrogen by 35% on average after reaching puberty. DISCUSSION: The obtained data allows to regard toxic effect of hyperbaric nitrogen as oxygen-dependent process. While hypoxia along with hyperbaric nitrogen effect enhances nitrogen narcosis, hypoxia, prior to nitrogen compression, reduces intoxication of this gas.

Spontaneous combustion of coal in regenerated roof and its prevention technology

The dangerous zone of spontaneous combustion of coal in regenerated roof cannot be directly identified and the air leakage law is not clear, which makes it difficult to take effective control measures. Aiming at these problems, taking the 5304 working face of Zhoujing coal mine as the research object, the law of air leakage and the law of oxygen concentration change were studied and the dangerous zone of coal spontaneous combustion in the regenerated roof was delineated through experimental test and numerical simulation. The law of temperature rose in the dangerous zone was further analyzed. The hidden danger of spontaneous combustion was eliminated by using composite spraying materials and water injection. The results showed that when the temperature rose to 80℃, the coal sample of 5304 working face started to oxidize rapidly. The air leakage velocity and oxygen concentration of were directly affected by the ventilation rate in the regenerated roof. By superimposing the oxidation zone of air leakage velocity and the oxidation zone of oxygen concentration, the dangerous zone of coal spontaneous combustion was delineated and it was known that reducing air leakage can effectively eliminate the dangerous zone of coal spontaneous combustion. Composite spraying materials were used for the wall of the return airway and water was injected into the dangerous zone of coal spontaneous combustion, the roadway surface temperature and backwater temperature were reduced to 28.5℃ and 30.3℃ respectively. The oxygen concentration was reduced to 3.8–6.2%.

Abstract 4844: Development of an oxygen consumption rate assay for a standard plate reader

Abstract Cells generate ATP by two metabolic pathways, oxidative phosphorylation (OXPHOS) and glycolysis. Together, the amount of ATP generated by both OXPHOS and glycolysis define a cell’s metabolic phenotype and fitness. Researchers are interested in methods to characterize cellular metabolic fitness, which can be a powerful a selection criterion for cell-based therapies such as CAR-T cell therapy. Researchers are also interested in measuring the effects of drug treatment on metabolic fitness, to identify metabolic targets for cancer therapeutics and to determine mitochondrial toxicity of novel therapeutics. Here, we have developed a low-cost strategy for a standard plate reader to monitor the rate change of oxygen concentration, or the oxygen consumption rate (OCR), which is a measure of OXPHOS activity. In our assay, oxygen quenches a phosphorescent porphyrin dye in a concentration dependent manner, allowing one to calculate the oxygen concentration of the culture system with the Stern-Volmer relationship. The porphyrin dye is embedded within nanobeads that are suspended above the cell monolayer and the phosphorescence of the beads is measured from the bottom of the well with a standard plate reader. We found that the OCR increased with cell seeding density in three separate cell lines: HEP-G2, HCT-116, and K-562 suspension cells. We showed that inhibitors of the electron transport chain (ETC) decreased OCR, whereas an uncoupler of the electron transport chain, FCCP, increased OCR in a dose dependent manner. Lastly, mitochondrial fitness (e.g., spare respiratory capacity) was determined by sequentially dosing the mitochondria with poisons specific to the different ETC complexes. Citation Format: Ian Marozas, Zhiyang Zeng, Mike Valley, Jolanta Vidugiriene, James Cali, Wenhui Zhou. Development of an oxygen consumption rate assay for a standard plate reader. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4844.

The Late Miocene‐Early Pliocene Biogenic Bloom: An Integrated Study in the Tasman Sea

AbstractThe Late Miocene‐Early Pliocene Biogenic Bloom (∼9–3.5 Ma) was a paleoceanographic phenomenon defined by anomalously high accumulations of biological components at multiple open ocean sites, especially in certain regions of the Indian, and Pacific oceans. Its temporal and spatial extent with available information leaves fundamental questions about driving forces and responses unanswered. In this work, we focus on the middle part of the Biogenic Bloom (7.4–4.5 Ma) at International Ocean Discovery Program Site U1506 in the Tasman Sea, where we provide an integrated age model based on orbital tuning of the Natural Gamma Radiation, benthic foraminiferal oxygen isotopes, and calcareous nannofossil biostratigraphy. Benthic foraminiferal assemblages suggest changes in deep water oxygen concentration and seafloor nutrient supply during generally high export productivity conditions. From 7.4 to 6.7 Ma, seafloor conditions were characterized by episodic nutrient supply, perhaps related to seasonal phytoplankton blooms. From 6.7 to 4.5 Ma, the regime shifted to a more stable interval characterized by eutrophic and dysoxic conditions. Combined with seismic data, a regional change in paleoceanography is inferred at around 6.7 Ma, from stronger and well‐oxygenated bottom currents to weaker, oxygen‐depleted bottom currents. Our results support the hypothesis that the Biogenic Bloom was a complex, multiphase phenomenon driven by changes in ocean currents, rather than a single uniform period of sustained sea surface water productivity. Highly resolved studies are thus fundamental to its understanding and the disentanglement of local, regional, and global imprints.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ УСЛОВИЙ ИЗГОТОВЛЕНИЯ НА ФОТОПРОВОДИМОСТЬ ГРАНИЦЫ РАЗДЕЛА ДВУХ ПОЛИМЕРНЫХ ПЛЕНОК

The study of optical properties in organic materials requires taking into account a wide range of features of these materials in connection with their sensitivity to external influences and aggressive environment. In this work, we studied the features of the photoconductivity of the interface between two dielectrics (polydiphenylene phthalide (PDP)) manufactured under different conditions. Drying was carried out in air and in vacuum. This study is necessary to determine the features of the manufacturing process and its effect on the photoconductive properties of the interface. Currently, the structure of the polymer / polymer interface has been fairly well studied by various methods, in particular, atomic force microscopy. However, there is a certain difficulty in obtaining repeatable results due to the presence of dilution of the lower PDP film when the upper polymer layer is applied. In this work, the photoconductive properties were studied on the basis of the measurements of the current-voltage characteristics (CVC) and the curves of the growth and relaxation of the photocurrent. Based on the results obtained within the framework of this work, it is possible to draw conclusions about the contribution of the drying method of experimental structures to the photoconductivity of the interface. It is known that oxygen makes a significant contribution to the electrical conductivity of thin PDP films. Earlier, it was shown on this polymer material that the presence of oxygen leads to a decrease in the conductivity of PDP films due to the formation of charge carrier traps. Moreover, when oxygen interacts with fragments of a polymer molecule, a chemical bond does not arise, which leads to a reversible change in electrical conductivity with a change in oxygen concentration. Due to this, the PDP films demonstrate a high stability of the electrophysical characteristics for several years when repeated measurements are carried out in an open atmosphere and at room temperature. It can be argued that the effect on the response of photoconductivity in organic materials, as well as on the relaxation time, can be associated with the presence of oxygen traps in the PDP films, increasing the relaxation time. This result is extremely important from the point of view of the practical application of these structures.

Fixing skeletal muscle PO2 eliminates hyperinsulinemic microvascular blood flow response.

To determine if insulin-mediated hyperemia is partially dependent on local muscle oxygen concentration. Sprague-Dawley rats were anesthetized, and the extensor digitorum longus (EDL) was reflected onto an inverted microscope. Intravital video microscopy sequences were recorded during baseline and hyperinsulinemic euglycemia. The muscle was reflected over a glass stage insert (Experiment 1a and 1b), or over a gas exchange chamber (Experiment 2), and microvascular capillary blood flow was recorded during sequential changes (7%-12%-2%-7%) of oxygen (O2 ) concentration. Blood flow was measured by the red blood cell supply rate (SR) in number of cells per second. All animal protocols were approved by Memorial University's Institutional Animal Care Committee. In Experiment 1a, SR increased from 8.0 to 14.0 cells/s at baseline to euglycemia (p=.01), while no significant SR variation was detected after performing a sham hyperinsulinemic euglycemic clamp (Experiment 1b). In Experiment 2, SR decreased at 12% O2 and increased at 2% O2 , compared to 7% O2 , under both experimental conditions. Magnitude of SR responses to oxygen oscillations during euglycemia were not different to those at baseline at each O2 concentration (p > .9). Our results suggest that increased blood flow observed in response to insulin is eliminated if tissue oxygen microenvironment is fixed at a given oxygen concentration.

Optimization of Parylene C and Parylene N thin films for use in cellular co-culture and tissue barrier models

Parylene has been used widely used as a coating on medical devices. It has also been used to fabricate thin films and porous membranes upon which to grow cells. Porous membranes are integral components of in vitro tissue barrier and co-culture models, and their interaction with cells and tissues affects the performance and physiological relevance of these model systems. Parylene C and Parylene N are two biocompatible Parylene variants with potential for use in these models, but their effect on cellular behavior is not as well understood as more commonly used cell culture substrates, such as tissue culture treated polystyrene and glass. Here, we use a simple approach for benchtop oxygen plasma treatment and investigate the changes in cell spreading and extracellular matrix deposition as well as the physical and chemical changes in material surface properties. Our results support and build on previous findings of positive effects of plasma treatment on Parylene biocompatibility while showing a more pronounced improvement for Parylene C compared to Parylene N. We measured relatively minor changes in surface roughness following plasma treatments, but significant changes in oxygen concentration at the surface persisted for 7 days and was likely the dominant factor in improving cellular behavior. Overall, this study offers facile and relatively low-cost plasma treatment protocols that provide persistent improvements in cell-substrate interactions on Parylene that match and exceed tissue culture polystyrene.

Ethanol fermentation- and ethylene physiology-related gene expression profiles in Red Delicious apples stored under variable hypoxic conditions and protocols

Dynamic Controlled Atmosphere (DCA) is beneficial in maintaining specific quality parameters but, due to the extreme oxygen levels applied, can cause adverse effects on the fruit by inducing excessive anaerobic metabolism and the production of off-flavors. The metabolic adaptation and responses of apples (Malus domestica Borkh.) cv. Red Delicious to static or dynamic oxygen concentrations (0.3 and 0.8%, with sequential shifts) during cold storage for 7 months were studied by monitoring quality parameters and the expression of genes involved in sugar, fermentative metabolism, and ethylene physiology. Ethanol content reached the highest levels (around 400 mg/kg FW) under 0.3% oxygen concentration and fruit firmness appeared to be reduced in samples accumulating the highest levels of ethanol. Oxygen switch was effective in reducing the ethanol concentrations with timing-dependent variable effects. The expression of fermentative (alcohol dehydrogenase, lactate dehydrogenase, pyruvate decarboxylase) and sugar metabolism (β-amylase; phosphofructokinase; sucrose synthase) genes resulted to be differently affected by the hypoxic conditions imposed, in particular during the early stages of storage. Sucrose synthase expression appeared to be highly sensitive to changes in low oxygen concentration. Ethylene biosynthesis (ACC synthase and oxidase) genes showed marked differences in their expression in relation to the static and dynamic protocols and the hypoxic conditions, as well as six Ethylene Responsive Factors (ERF) genes, some of them possibly involved in the oxygen sensing mechanism operating in fruit tissues.

Comparison of Oropharyngeal Oxygen Pooling and Suctioning During Intubated and Nonintubated Dental Office-Based Anesthesia.

The risk of a spontaneous surgical fire increases as oxygen concentrations surrounding the surgical site rise above the normal atmospheric level of 21%. Previously published in vitro findings imply this phenomenon (termed oxygen pooling) occurs during dental procedures under sedation and general anesthesia; however, it has not been clinically documented. Thirty-one children classified as American Society of Anesthesiologists I and II between 2 and 6 years of age undergoing office-based general anesthesia for complete dental rehabilitation were monitored for intraoral ambient oxygen concentration, end-tidal CO2, and respiratory rate changes immediately following nasotracheal intubation or insertion of nasopharyngeal airways, followed by high-speed suctioning of the oral cavity during simulated dental treatment. Mean ambient intraoral oxygen concentrations ranging from 46.9% to 72.1%, levels consistent with oxygen pooling, occurred in the nasopharyngeal airway group prior to the introduction of high-speed oral suctioning. However, 1 minute of suctioning reversed the oxygen pooling to 31.2%. Oropharyngeal ambient oxygen concentrations in patients with uncuffed endotracheal tubes ranged from 24.1% to 26.6% prior to high-speed suctioning, which reversed the pooling to 21.1% after 1 minute. This study demonstrated significant oxygen pooling with nasopharyngeal airway use before and after high-speed suctioning. Uncuffed endotracheal intubation showed minimal pooling, which was reversed to room air ambient oxygen concentrations after 1 minute of suctioning.

Water Formation Kinetics on Co(0001) at Low and Near-Ambient Hydrogen Pressures in the Context of Fischer–Tropsch Synthesis

Understanding the kinetics of oxygen removal from catalytically active metal surfaces by hydrogen is important for several catalytic reactions such as Fischer–Tropsch synthesis, methanation of CO or CO2, and the reverse-water–gas-shift reaction. Motivated by FTS, a Co(0001) single crystal model catalyst was used to study the kinetics of oxygen removal through reaction with hydrogen. Kinetic studies in the 10–7–10–4 mbar H2 pressure regime show that water formation is first order in the surface hydrogen concentration while the order in oxygen concentration changes from one at low oxygen coverage to zero at high oxygen coverage. In situ XPS shows that the hydrogen surface concentration saturates around 10–1 mbar and on this basis the typical temperature of 450 K needed for water formation in this pressure regime can be considered as typical for high pressures as well. The absence of OH buildup during the reaction points to O + H as the rate-limiting step, with a barrier of ∼120 kJ mol–1. Such a high barrier shows that slow removal of adsorbed oxygen from the surface of reactive metal catalysts such as cobalt may be rate-limiting for the overall reaction.

Investigation of VxOy thin films using Raman Spectroscopy: Role of oxygen vacancies and structural phase transformation on thermochromic properties

Vanadium Oxide is a well-known transition metal oxide showing metal–insulator transition and is important for thermochromic and smart window applications. We have grown amorphous vanadium oxide thin films on barium borosilicate 7059 glass using cathodic arc- deposition methods. Especially, here we present a detailed investigation of these films using Raman spectroscopy performed at different temperatures and laser powers and correlate these results with XRD measurements. We demonstrate the static and dynamic structural phase transformations induced by laser and explain these results due to oxygen content changes.

Numerical investigations to identify environmental factors for field-scale reactive transport of pathogens at riverbank filtration sites

While induced bank filtration is a proven method for facilitating sustainable drinking water production, it is at risk from surface water contaminations (e.g., pathogens). Induced bank filtration and pathogen transport in groundwater have been studied extensively. However, long-term studies that consider real-world conditions are missing. These conditions include seasonal changes to environmental conditions and waterworks operations. Therefore, to analyze the effect of seasonal changes on the transport of human pathogenic viruses and their indicators in induced bank filtration, concentrations of adenoviruses and pathogen indicators were monitored over 16 months at an active bank filtration plant at the Rhine River, in Düsseldorf (Germany). Based on this data, a 2D groundwater model was created in PFLOTRAN that simulated flow, heat transport, conservative transport of chloride and the resulting electrical conductivity, reactive transport of oxygen and nitrate, and colloid-based transport of coliforms, somatic coliphages, and adenoviruses. The results show that reduced travel time was the key factor determining periods with a low removal of coliforms and somatic coliphages in the aquifer. Travel time was controlled by river level variations during rainy seasons, and the waterworks extraction rates during dry seasons. For adenovirus transport, travel distance in the subsurface appeared to be the key factor, while travel time had no significant impact. Coliform removal increased when the colmation layer permeability decreased, while coliphage and adenovirus removal was unaffected by the colmation layer permeability. Seasonal changes in temperature and oxygen content did not significantly impact the removal of coliphages and adenoviruses in groundwater. Denitrifying conditions correlated with a lowered coliform removal, but the modelling could not establish a connection between denitrifying conditions and coliform removal. Our study showed that removal of pathogens and pathogen indicators at induced bank filtration plants varies greatly in time and space (e.g., for coliforms from 1 to 4 log-levels at 20 m travel distance), and that adenovirus transport differs considerably from transport of coliforms and somatic coliphages

Accelerated methane emission from permafrost regions since the 20th century

Carbon dioxide has been increasing in the atmosphere since the industrialization, resulting in global warming, which in turn enhanced methane emissions from permafrost regions. However, methane emitted into the atmosphere is quickly oxidized, such that the intensity and threat of methane emission in the past are severely underestimated. Here we show that the ratio between annual changes in atmospheric oxygen and carbon dioxide concentrations (ΔO2/ΔCO2 index) dropped dramatically between 1945 and 1958. There are no such abrupt changes in the fossil fuel combustion curve. Considering that atmospheric methane has the residence time less than ∼9 years through biological and chemical processes, this crisis is attributed to the World War II, which had disturbed gas hydrates underneath ocean floors and permafrost regions. Consistently, the land-ocean temperature index fluctuated more severely in permafrost regions than the global average during the WWII, indicating stronger greenhouse effects induced by methane emission. This is supported by the changes in the ΔO2/ΔCO2 index, coupled with higher atmospheric methane concentrations and lower δ13CO2 in permafrost regions in the last three decades, suggesting accelerated methane emission. The anthropogenic carbon dioxide emission has been pushing the accelerated thawing of permafrost, which promotes methane emission that further intensifies permafrost thawing and global warming. Such a positive feedback at an inflection point of Earth climate may break the glacial-interglacial cycle and initiate a long-lasting greenhouse period.

Study on the Relationship between Indoor Vertical Greening and Oxygen Content in High-Rise Buildings

This article clarifies the quantitative relationship between vertical greening, indoor ventilation, and the oxygen content in high-rise buildings, with the aim of determining values for a high-oxygen-content threshold to assess the ventilation and greening of high-rise buildings. The quantitative index could be provided to architects to assist in the sustainable design of vertical greening in high-rise buildings. The quantitative index offers an effective, convenient, and environmentally friendly oxygen-content-testing method for interior spaces, while avoiding the air pollution caused by the current red phosphorus combustion method. Firstly, a floor of a high-rise building in Harbin was selected for on-site and fixed-point experiments. Secondly, through the design of a candle-burning experiment in a gas bottle, we measured the change in candle-burning time before and after installing vertical greening, as well as under different ventilation states. Finally, the changes in relative oxygen content in each functional space before and after vertical greening and under different ventilation states were statistically analyzed. The results showed that there was a potential correlation between indoor oxygen content and vertical greening placement in high-rise buildings; this correlation was found to be directly related to room orientation, the degree of the plants’ photosynthesis, and indoor airflow. In general, vertical greening should be placed in south-facing rooms. For daily ventilation, two or more windows should be opened to ensure convection in rooms, which can increase their oxygen content.

Do Ultrafine Bubbles Work as Oxygen Carriers?

Fine bubbles (FBs) are bubbles with sizes less than 100 μm and are divided into ultrafine bubbles (UFBs, < 1 μm) and microbubbles (MBs, 1-100 μm) depending on their size. Although FB aeration is known as a more efficient way than macrobubble aeration to increase the oxygen level in unoxygenated water, few reports have demonstrated whether dispersed UFBs work as oxygen carriers or not. Furthermore, oxygen supersaturation is one of the attractive characteristics of FB dispersion, but the reason is yet to be revealed. In this study, we evaluated the relationship between the FBs, especially UFB concentration, and oxygen content in several situations to reveal the two questions. The FB concentration and oxygen content were examined using particle analyzers and our developed oxygen measurement method, which can measure the oxygen content in FB dispersion, respectively. First, in the evaluations of the oxygen dispersion from UFBs with respect to the surrounding oxygen level, UFBs did become neither small nor diminish even in degassed water. Second, the changes in UFBs and oxygen content upon storage temperature and the existence of a lid during storage were evaluated, and there was no correlation between them. It means UFBs contribute little to the oxygen content in UFB dispersion. Furthermore, the oxygen content in the UFB dispersion decreased over time identically as that of the oxygen-supersaturated water with little UFBs. Third, we evaluated the relationship between FB concentration and oxygen content during FB generation by measuring them simultaneously. The results showed that dispersed MB and UFB concentrations did not account for the supersaturation of the FB dispersion. From the result, it was revealed that 100-200 nm of UFBs themselves did not work as oxygen carriers, and the oxygen supersaturation in FB dispersions was due to the supersaturated state of dissolved oxygen that was prepared during the FB generation process.

Assessment of Bioenergetics in BAT Mitochondria.

High-resolution respirometry is commonly used to quantify mitochondrial respiratory rates. In the respirometry chamber, a change in oxygen concentration is measured by a polarographic electrode to derive the rate of oxygen consumption (JO2). Here, we describe our adapted protocol to bioenergetically phenotype mitochondria from mouse brown adipose tissue (BAT). Given the presence of uncoupling protein 1 (UCP1), mitochondria from BAT provide unique challenges and opportunities in applying high-resolution respirometry to understand energy transduction through oxidative phosphorylation (OXPHOS).

Effect of Antioxidant on Sperm Freezing

A major cause of male infertility, which includes 50 causes of infertility, is oxidative stress. Aerobic respiration in the sperm cell is associated with the production of reactive oxygen species (ROS). Some reactions, such as sperm capacitation and acrosome reactions require moderate levels of ROS. However, when the amount of ROS production surpasses the natural antioxidant defense of the cell, it causes a harmful effect called oxidative stress. This results in the oxidation of lipids, proteins, carbohydrates, and nucleotides. The production of ROS is increased by various factors, including the presence of leukocytes, sperms with abnormal and immature morphology, centrifugation of samples, and changes in oxygen concentration, pH, and temperature. Sperm freezing is a method widely used in assisted reproductive technology (ART) as well as infertility treatment. The process of freezing also contributes to increased oxidative stress because it alters the fluidity of the mitochondrial membrane, leading to increased production and release of ROS. Sperm have defense mechanisms against oxidative stress caused by increased ROS production, which includes the presence of enzymatic and non-enzymatic antioxidants in semen. The utilization of supplementary antioxidants in the freezing environment is a strategy to combat oxidative stress. This review aims to summarize the current evidence on the effect of antioxidants on sperm freezing.