Research

12 pages, 2266 KiB

Open AccessArticle

Fitting Parameters of a Modified Hill’s Equation and Their Influence on the Shape of the Model Hemoglobin Oxygenation Curve

by Igor A. Lavrinenko, Gennady A. Vashanov, José L. Hernández Cáceres and Yury D. Nechipurenko

Oxygen 2023, 3(1), 90-101; https://doi.org/10.3390/oxygen3010007 - 28 Feb 2023

Cited by 3 | Viewed by 3622

Abstract

Oxygen binds to hemoglobin cooperatively, and a correct description of this binding is relevant not only for understanding the mechanisms of involved molecular processes but also for clinical purposes. Hill’s equation, derived over a hundred years ago, is still the simplest and most [...] Read more.

Oxygen binds to hemoglobin cooperatively, and a correct description of this binding is relevant not only for understanding the mechanisms of involved molecular processes but also for clinical purposes. Hill’s equation, derived over a hundred years ago, is still the simplest and most efficient way to perform this description. However, in terms of accuracy, it is inferior to Adair´s equation, which contains more parameters. We proposed to use a modified Hill equation and showed that it allows a more accurate description of the binding of oxygen to hemoglobin than Adair’s equation. At the same time, unlike Adair’s equation, our model retains the physical meaning given to the original Hill equation. We considered and analyzed the influence of the equation parameters on the course of the oxygenation curve and presented the relationship between the fitting parameters and other parameters derived from them in the form of a diagram-graph, which, in our opinion, simplifies the perception of these estimates and can be useful in solving a number of problems for which the traditional way of analyzing the degree of cooperative interaction was via the Hill equation. We suggest that the newly proposed parameter h_max introduced in our model should be regarded as crucial for a better description of the oxygenation curve. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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19 pages, 3139 KiB

Open AccessArticle

Effect of Water-Soluble Chlorine-Containing Buckminsterfullerene Derivative on the Metabolism of Reactive Oxygen Species in Human Embryonic Lung Fibroblasts

by Ekaterina A. Savinova, Tatiana A. Salimova, Elena V. Proskurnina, Ivan V. Rodionov, Olga A. Kraevaya, Pavel A. Troshin, Larisa V. Kameneva, Elena M. Malinovskaya, Olga A. Dolgikh, Natalia N. Veiko and Svetlana V. Kostyuk

Oxygen 2023, 3(1), 1-19; https://doi.org/10.3390/oxygen3010001 - 27 Dec 2022

Viewed by 1639

Abstract

The development of novel biologically active nanopharmaceuticals is a topical problem of medicine. Water-soluble fullerene derivatives are of particular interest due to their ability to regulate intracellular metabolism of reactive oxygen species (ROS) by direct oxidation or effects on oxidative and signaling enzymes. [...] Read more.

The development of novel biologically active nanopharmaceuticals is a topical problem of medicine. Water-soluble fullerene derivatives are of particular interest due to their ability to regulate intracellular metabolism of reactive oxygen species (ROS) by direct oxidation or effects on oxidative and signaling enzymes. Here, we studied the effect of a water-soluble chlorine-containing derivative of C₆₀ fullerene on human embryonic lung fibroblasts. MTT tests, intracellular ROS visualization, detection of the ROS-associated gene and protein expression, repair, cell proliferation and cell cycle regulation, and quantitation of oxidative DNA damage were used. Within the first three hours after exposure, antioxidant effects were revealed. Later, oxidative damage appeared. Thus, the studied compound had an ambiguous effect on ROS metabolism associated with a switch in the regulatory effect, which must be taken into account when assessing its biological activity and toxicity. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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11 pages, 2133 KiB

Open AccessArticle

Lag Time Determinations in Beer Samples. Influence of Alcohol and PBN Concentration in EPR Spin Trapping Experiments

by Maria Cristina Porcu, Angela Fadda and Daniele Sanna

Oxygen 2022, 2(4), 605-615; https://doi.org/10.3390/oxygen2040040 - 18 Nov 2022

Viewed by 1515

Abstract

The beers’ lag time measured with the PBN (N-t-Butyl-α-phenylnitrone) spin trapping experiments coupled with EPR spectroscopy is related to their antioxidant capacity and shelf life. The effect on the lag time of the alcohol content of the beer (starting values, 9 [...] Read more.

The beers’ lag time measured with the PBN (N-t-Butyl-α-phenylnitrone) spin trapping experiments coupled with EPR spectroscopy is related to their antioxidant capacity and shelf life. The effect on the lag time of the alcohol content of the beer (starting values, 9 and 13%) and PBN concentration (50 or 200 mM) was analyzed on three samples, a pilsner, a strong lager, and a blonde Ale heated at 60 °C to trigger the production of the 1-hydroxyethyl radical. The lag time was determined only for the strong lager beer, with the values depending on the experimental conditions, being higher when PBN had a lower concentration. The antioxidant activity of the three beers gave the following values: 0.9089 mL pilsner beer/mg DPPH, 0.8510 mL strong lager beer/mg DPPH, and 0.7184 mL blonde Ale beer/mg DPPH, indicating that the unsuccessful determination of the lag time was not due to stale beers. The EPR intensity of the PBN adduct after 150 min (I₁₅₀) and the area under the curve (AUC) were also measured and related to the oxidative stability of beers. Further studies are needed to verify the influence of the heating temperature in samples that do not show a lag time at 60 °C. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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10 pages, 285 KiB

Open AccessArticle

Optimization of Pulsed Electric-Field-Based Total Polyphenols’ Extraction from Elaeagnus pungens ‘Limelight’ Leaves Using Hydroethanolic Mixtures

by Vasileios M. Pappas, Dimitrios Palaiogiannis, Vassilis Athanasiadis, Theodoros Chatzimitakos, Eleni Bozinou, Dimitris P. Makris and Stavros I. Lalas

Oxygen 2022, 2(4), 537-546; https://doi.org/10.3390/oxygen2040035 - 31 Oct 2022

Cited by 3 | Viewed by 1245

Abstract

In this study, the use of pulsed electric field (PEF) for the extraction of polyphenols from mature Elaeagnus pungens ‘Limelight’ leaves is discussed. Optimization of the main parameters that affect the extraction process was carried out. More specifically, the composition of the solvent [...] Read more.

In this study, the use of pulsed electric field (PEF) for the extraction of polyphenols from mature Elaeagnus pungens ‘Limelight’ leaves is discussed. Optimization of the main parameters that affect the extraction process was carried out. More specifically, the composition of the solvent (ethanol, water, and mixtures of the two at a 25% v/v step gradient) and the main PEF-related parameters (i.e., pulse duration, pulse period, and electric field intensity) was optimized. The obtained extracts were examined for their polyphenol content with the Folin–Ciocalteu assay and individual polyphenols were also assessed with high-performance liquid chromatography. The extracts obtained with PEF were compared to the extract compared without PEF, in terms of total polyphenols. According to the results, the optimum extraction parameters were found to be a pulse duration of 10 μs, a pulse period of 1000 μs, and an electric field intensity of 0.85 kV cm⁻¹ after 20 min of extraction. The optimum solvent was found to be the 50% (v/v) ethanol/water mixture. The extract prepared under the optimum conditions was found to contain 58% more polyphenols compared with the extract prepared without PEF. Moreover, an increase of up to 92% was recorded for specific polyphenols. Based on the above, it was evidenced that the examined parameters influenced the recovery of polyphenols, suggesting that such parameters should be also examined in similar studies, in order to maximize the extraction yield of polyphenols. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

19 pages, 2247 KiB

Open AccessArticle

Analyzing the Effects of Multi-Layered Porous Intraluminal Thrombus on Oxygen Flow in Abdominal Aortic Aneurysms

by Alexis Throop, Durwash Badr, Michael Durka, Martina Bukač and Rana Zakerzadeh

Oxygen 2022, 2(4), 518-536; https://doi.org/10.3390/oxygen2040034 - 24 Oct 2022

Cited by 3 | Viewed by 2553

Abstract

Determination of abdominal aortic aneurysm (AAA) rupture risk involves the accurate prediction of mechanical stresses acting on the arterial tissue, as well as the wall strength which has a correlation with oxygen supply within the aneurysmal wall. Our laboratory has previously reported the [...] Read more.

Determination of abdominal aortic aneurysm (AAA) rupture risk involves the accurate prediction of mechanical stresses acting on the arterial tissue, as well as the wall strength which has a correlation with oxygen supply within the aneurysmal wall. Our laboratory has previously reported the significance of an intraluminal thrombus (ILT) presence and morphology on localized oxygen deprivation by assuming a uniform consistency of ILT. The aim of this work is to investigate the effects of ILT structural composition on oxygen flow by adopting a multilayered porous framework and comparing a two-layer ILT model with one-layer models. Three-dimensional idealized and patient-specific AAA geometries are generated. Numerical simulations of coupled fluid flow and oxygen transport between blood, arterial wall, and ILT are performed, and spatial variations of oxygen concentrations within the AAA are obtained. A parametric study is conducted, and ILT permeability and oxygen diffusivity parameters are individually varied within a physiological range. A gradient of permeability is also defined to represent the heterogenous structure of ILT. Results for oxygen measures as well as filtration velocities are obtained, and it is found that the presence of any ILT reduces and redistributes the concentrations in the aortic wall markedly. Moreover, it is found that the integration of a porous ILT significantly affects the oxygen transport in AAA and the concentrations are linked to ILT’s permeability values. Regardless of the ILT stratification, maximum variation in wall oxygen concentrations is higher in models with lower permeability, while the concentrations are not sensitive to the value of the diffusion coefficient. Based on the observations, we infer that average one-layer parameters for ILT material characteristics can be used to reasonably estimate the wall oxygen concentrations in aneurysm models. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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14 pages, 3250 KiB

Open AccessArticle

Bifunctional Catalytic Activity of γ-NiOOH toward Oxygen Reduction and Oxygen Evolution Reactions in Alkaline Solutions

by Ridwan P. Putra, Ihsan Budi Rachman, Hideyuki Horino and Izabela I. Rzeznicka

Oxygen 2022, 2(4), 479-492; https://doi.org/10.3390/oxygen2040031 - 13 Oct 2022

Cited by 4 | Viewed by 3261

Abstract

Nickel oxyhydroxides (NiOOHs) are well-known for their superior activity toward oxygen evolution reaction (OER) in alkaline solutions. However, their activity toward oxygen reduction reaction (ORR) has been largely unexplored. There exist three NiOOH polymorphs: α-, β-, and γ-NiOOH, characterized by [...] Read more.

Nickel oxyhydroxides (NiOOHs) are well-known for their superior activity toward oxygen evolution reaction (OER) in alkaline solutions. However, their activity toward oxygen reduction reaction (ORR) has been largely unexplored. There exist three NiOOH polymorphs: α-, β-, and γ-NiOOH, characterized by different interlayer spacing. Although still debated, γ-NiOOH with a large layer spacing has been indicated as the active phase for OER. Here, a highly crystalline γ-NiOOH was prepared in a carbon matrix by the in situ electrochemical transformation of nickel dithiooxamide Ni(dto) in 1 M KOH solution. The catalyst prepared in this way showed low overpotential not only for OER, but also for ORR in alkaline solutions. The onset potential for ORR is ~0.81 V vs. RHE, and the reaction proceeds via the 2e⁻ transfer pathway. The high OER catalytic activity and relatively low ORR overpotential make this nanocomposite catalyst a good candidate for bifunctional OER/ORR catalyst, stable in alkaline solutions. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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13 pages, 2277 KiB

Open AccessArticle

β-Cyclodextrin-Aided Aqueous Extraction of Antioxidant Polyphenols from Peppermint (Mentha × piperita L.)

by Vassilis Athanasiadis, Dimitrios Palaiogiannis, Eleni Bozinou, Stavros I. Lalas and Dimitris P. Makris

Oxygen 2022, 2(4), 424-436; https://doi.org/10.3390/oxygen2040029 - 29 Sep 2022

Cited by 9 | Viewed by 1601

Abstract

This study explored the use of β-cyclodextrin (β-CD) as an additive to improve the aqueous extraction of antioxidant polyphenols from peppermint (Mentha × piperita). For this purpose, an initial single-factor screening was performed to test the effect of β-CD concentration on [...] Read more.

This study explored the use of β-cyclodextrin (β-CD) as an additive to improve the aqueous extraction of antioxidant polyphenols from peppermint (Mentha × piperita). For this purpose, an initial single-factor screening was performed to test the effect of β-CD concentration on the yield of polyphenol extraction. In the following step, the extraction process was optimized through response surface methodology, considering β-CD and temperature as the process variables. The experimental design included the yield in total polyphenols and total flavonoids, the ferric-reducing power and the antiradical activity as the responses. The optimization showed that each response was maximized at different levels of β-CD concentration, but in all cases, 80 °C was the optimum extraction temperature. The composition of the extracts produced was profiled by high-performance liquid chromatography (HPLC). A comparison of the β-CD extract with the aqueous and hydroethanolic extracts revealed that the addition of β-CD at a specified concentration might boost aqueous polyphenol extraction. On the other hand, the hydroethanolic extract exhibited the richest polyphenolic profile. It was also shown that the β-CD extracts might possess improved antiradical activity. It was concluded that β-CD-aided polyphenol extraction from M. piperita may provide extracts with enriched polyphenolic composition and improved antioxidant characteristics, and this technique may be considered an alternative to solvent extraction. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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14 pages, 1660 KiB

Open AccessArticle

The Effect of Additives on the Hydrothermal Synthesis and Thermochromic Performance of Monoclinic Vanadium Dioxide Powder

by Leila Zouridi, Emmanouil Gagaoudakis, Eleni Mantsiou, Theodora Dragani, Xristina Maragaki, Elias Aperathitis, George Kiriakidis and Vassilios Binas

Oxygen 2022, 2(4), 410-423; https://doi.org/10.3390/oxygen2040028 - 28 Sep 2022

Cited by 1 | Viewed by 1496

Abstract

Monoclinic vanadium dioxide VO₂(M) is a well-known thermochromic material, with its critical transition temperature (68 °C) being the closest to room temperature (RT). Among the variety of grown methods, hydrothermal synthesis is a simple and cost-effective technique to grow thermochromic VO [...] Read more.

Monoclinic vanadium dioxide VO₂(M) is a well-known thermochromic material, with its critical transition temperature (68 °C) being the closest to room temperature (RT). Among the variety of grown methods, hydrothermal synthesis is a simple and cost-effective technique to grow thermochromic VO₂ in the form of powder. In the present work, VO₂ nanoparticles were prepared by hydrothermal synthesis in mild conditions, followed by a thermal annealing process at 700 °C under nitrogen flow for two hours. Vanadium pentoxide (V₂O₅) was used as the vanadium precursor, while two different reducing agents, namely oxalic and succinic acid, were employed for the reduction of V₂O₅ to VO₂. Additionally, urea as well as thiourea were used as additives, in order to investigate their effects on the thermochromic performance of VO₂. As a result, the VO₂ (M) phase was obtained after annealing the crystalline powder, grown hydrothermally using oxalic acid and thiourea as a reducing agent and additive, respectively. This synthesis had a high yield of 90%, and led to a VO₂(M) powder of high purity and crystallinity. In particular, the VO2 (M) nanoparticles had an average crystallite size of approximately 45 nm, a critical transition temperature of approximately 68 °C and a hysteresis width of 11 °C. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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10 pages, 379 KiB

Open AccessArticle

Correlation of the Isotropic NMR Chemical Shift with Oxygen Coordination Distances in Periodic Solids

by Jennifer Steinadler, Otto E. O. Zeman and Thomas Bräuniger

Oxygen 2022, 2(3), 327-336; https://doi.org/10.3390/oxygen2030023 - 05 Aug 2022

Cited by 1 | Viewed by 1691

Abstract

In Nuclear Magnetic Resonance (NMR) spectroscopy, the isotropic chemical shift

δ_{i s o}

is a measure of the electron density around the observed nuclide. For characterization of solid materials and compounds, it is desirable to find correlations between

δ_{i s o}

[...] Read more.

In Nuclear Magnetic Resonance (NMR) spectroscopy, the isotropic chemical shift

δ_{i s o}

is a measure of the electron density around the observed nuclide. For characterization of solid materials and compounds, it is desirable to find correlations between

δ_{i s o}

and structural parameters such as coordination numbers and distances to neighboring atoms. Correlations of good quality are easier to find when the coordination sphere is formed by only one element, as the electron density is obviously strongly dependent on the atomic number. The current study is therefore restricted to nuclides in pure oxygen coordination. It is shown that the isotropic shift

δ_{i s o}

correlates well with the average oxygen distances (as defined by the coordination sphere) for the nuclides

^{23}

Na (with spin

I = 3 / 2

),

^{27}

Al (

I = 5 / 2

), and

^{43}

Ca (

I = 7 / 2

), using literature data for a range of periodic solids. It has been previously suggested for

^{207}

Pb (

I = 1 / 2

) that

δ_{i s o}

may alternatively be related to the shortest oxygen distance in the structure, and our study corroborates this also for the nuclides considered here. While the correlation with the minimal distance is not always better, it has the advantage of being uniquely defined. In contrast, the average distance is strongly dependent on the designation of the oxygen coordination sphere, which may be contentious in some crystal structures. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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19 pages, 2106 KiB

Open AccessFeature PaperArticle

Lost in Translation: Exploring microRNA Biogenesis and Messenger RNA Fate in Anoxia-Tolerant Turtles

by Sarah A. Breedon and Kenneth B. Storey

Oxygen 2022, 2(2), 227-245; https://doi.org/10.3390/oxygen2020017 - 17 Jun 2022

Cited by 3 | Viewed by 2582

Abstract

Red-eared slider turtles face natural changes in oxygen availability throughout the year. This includes long-term anoxic brumation where they reduce their metabolic rate by ~90% for months at a time, which they survive without apparent tissue damage. This metabolic rate depression (MRD) is [...] Read more.

Red-eared slider turtles face natural changes in oxygen availability throughout the year. This includes long-term anoxic brumation where they reduce their metabolic rate by ~90% for months at a time, which they survive without apparent tissue damage. This metabolic rate depression (MRD) is underlaid by various regulatory mechanisms, including messenger RNA (mRNA) silencing via microRNA (miRNA), leading to mRNA decay or translational inhibition in processing bodies (P-bodies) and stress granules. Regulation of miRNA biogenesis was assessed in red-eared slider turtle liver and skeletal muscle via immunoblotting. Hepatic miRNA biogenesis was downregulated in early processing steps, while later steps were upregulated. These contradictory findings indicate either overall decreased miRNA biogenesis, or increased biogenesis if sufficient pre-miRNA stores were produced in early anoxia. Conversely, muscle showed clear upregulation of multiple biogenesis steps indicating increased miRNA production. Additionally, immunoblotting indicated that P-bodies may be favoured by the liver for mRNA storage/decay during reoxygenation with a strong suppression of stress granule proteins in anoxia and reoxygenation. Muscle however showed downregulation of P-bodies during anoxia and reoxygenation, and upregulation of stress granules for mRNA storage during reoxygenation. This study advances our understanding of how these champion anaerobes regulate miRNA biogenesis to alter miRNA expression and mRNA fate during prolonged anoxia. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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12 pages, 3542 KiB

Open AccessArticle

Cell Localization of DPI-Dependent Production of Superoxide in Reproductive Tissues of the Olive Tree (Olea europaea L.)

by María José Jiménez-Quesada, Antonio Jesús Castro, Elena Lima-Cabello and Juan de Dios Alché

Oxygen 2022, 2(2), 79-90; https://doi.org/10.3390/oxygen2020007 - 19 Apr 2022

Cited by 1 | Viewed by 1906

Abstract

Reactive Oxygen Species (ROS) are compounds derived from oxygen with important implications in biological processes in plants, some of them related to reproduction. Among ROS, superoxide is the primary oxidant, since an array of other ROS are eventually derived from this anion. Therefore, [...] Read more.

Reactive Oxygen Species (ROS) are compounds derived from oxygen with important implications in biological processes in plants, some of them related to reproduction. Among ROS, superoxide is the primary oxidant, since an array of other ROS are eventually derived from this anion. Therefore, analysis of the molecular systems able to generate this molecule and the cellular compartmentalization of these events is of paramount importance. We have used the fluorochrome DCFH₂-DA and the chromogenic substrate NBT in association with DPI (a specific inhibitor of Rboh enzymes generating superoxide in plants) in combination with confocal microscopy and stereomicroscopy, respectively to identify cell localization of ROS in general, and superoxide accumulation in olive reproductive tissues. A significant production of both ROS and superoxide has been described, showing a fairly precise spatial and temporal location throughout olive flower development. The reduction of the NBT signal after the addition of DPI suggests that the generation of superoxide is largely due to Rboh or other flavin oxidase activity. At the subcellular level, accumulation of O₂^●− has been located in the plasma membrane of mature pollen and germinated pollen, as well as in the rough endoplasmic reticulum and in mitochondria. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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8 pages, 1432 KiB

Open AccessArticle

Lung Diffusing Capacity in Dutch Special Operations Forces Divers Exposed to Oxygen Rebreathers over 18 Years

by Tom H.B. den Ouden, Thijs T. Wingelaar, Edwin L. Endert and Pieter-Jan A.M. van Ooij

Oxygen 2022, 2(2), 40-47; https://doi.org/10.3390/oxygen2020005 - 31 Mar 2022

Cited by 2 | Viewed by 1790

Abstract

Exposure to hyperoxic conditions can induce pulmonary oxygen toxicity (POT). Divers of the Special Operations Forces (SOF) use oxygen rebreather systems during dives, and therefore are frequently exposed to hyperoxic conditions. Few studies have reported on POT in this population. This study reports [...] Read more.

Exposure to hyperoxic conditions can induce pulmonary oxygen toxicity (POT). Divers of the Special Operations Forces (SOF) use oxygen rebreather systems during dives, and therefore are frequently exposed to hyperoxic conditions. Few studies have reported on POT in this population. This study reports on long-term pulmonary function tests (PFTs) and diffusing capacity in SOF divers to test the hypothesis that these measures of pulmonary function do not change clinically significantly during their career. The Royal Netherlands Navy performs yearly medical assessments of its military divers. All PFT and diffusing capacity data of SOF divers between the years 2000 and 2020 were analyzed using generalized estimating equations. The study included 257 SOF divers (median age, 27; interquartile range, 24–32), with 1612 dive medical assessments and a maximum follow-up time of 18.8 years. Alveolar volume (V_A) and the diffusing capacity of carbon monoxide (TL_CO) were significantly lower at baseline in smokers. Although these parameters were within the normal range, they declined over time and were significantly associated with age and years of diving. Smoking additionally affected TL_CO and the transfer coefficient for carbon monoxide (K_CO). TL_CO and K_CO were reduced by years of diving with oxygen rebreathers, albeit over clinically insignificant ranges, but smoking increased these changes by factors of 10 and 15, respectively. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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9 pages, 2029 KiB

Open AccessArticle

An Inexpensive Incubator for Mammalian Cell Culture Capable of Regulating O₂, CO₂, and Temperature

by Philip Samokhin, Georgina L. Gardner, Chris Moffatt and Jeffrey A. Stuart

Oxygen 2022, 2(1), 22-30; https://doi.org/10.3390/oxygen2010003 - 14 Mar 2022

Cited by 4 | Viewed by 5169

Abstract

Mammalian cell culture is widely used for discovery and development. Recently, increasing attention has been paid to the importance of maintaining physiologically-relevant conditions in cell culture. Although oxygen level is a particularly important consideration, it is rarely regulated by experimentalists. The atmospheric O [...] Read more.

Mammalian cell culture is widely used for discovery and development. Recently, increasing attention has been paid to the importance of maintaining physiologically-relevant conditions in cell culture. Although oxygen level is a particularly important consideration, it is rarely regulated by experimentalists. The atmospheric O₂ levels commonly used in cell culture are significantly higher than those experienced by most mammalian cells in vivo, leaving cells susceptible to oxidative damage, senescence, transformation, and otherwise aberrant physiology. A barrier to incorporating O₂ regulation into most cell culture workflows has been the expense of investing in new equipment, as the vast majority of laboratory CO₂ incubators do not regulate O₂. Here, we describe an inexpensive (<CAD 1000), portable and user-friendly O₂/CO₂ incubator that can establish and maintain physiological O₂, CO₂, and temperature values within their physiological ranges. We used an Arduino-based approach to add O₂ and CO₂ control to a temperature-regulating egg incubator. Our incubator was tested against a commercial laboratory O₂/CO₂ incubator. Using Presens OxoDish technology, we demonstrate that at a setpoint value of 5% gas-phase incubator O₂, media O₂ averaged 5.03 (SD = 0.03) with a range of 4.98–5.09%. MCF7, LNCaP and C2C12 cell lines cultured in the incubator displayed normal morphology, proliferation, and viability. Culture for up to one week produced no contamination. Thus, our incubator provides an inexpensive means of maintaining physioxia in routine mammalian cell culture. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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Review

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13 pages, 322 KiB

Open AccessReview

Understanding Hydrogen: Lessons to Be Learned from Physical Interactions between the Inert Gases and the Globin Superfamily

by John T. Hancock, Grace Russell, Tim J. Craig, Jennifer May, H. Ruth Morse and Jonathan S. Stamler

Oxygen 2022, 2(4), 578-590; https://doi.org/10.3390/oxygen2040038 - 08 Nov 2022

Cited by 6 | Viewed by 2542

Abstract

Hydrogen gas (molecular hydrogen, H₂) has significant effects in a range of organisms, from plants to humans. Many inert gases have been reported to have similar effects, and such responses may be most pronounced when cells are stressed. Xenon (Xe), for [...] Read more.

Hydrogen gas (molecular hydrogen, H₂) has significant effects in a range of organisms, from plants to humans. Many inert gases have been reported to have similar effects, and such responses may be most pronounced when cells are stressed. Xenon (Xe), for example, is a well-known anesthetic. The direct targets of these gases, in most cases, remain elusive. Myoglobin and hemoglobin are known for their roles in the transport of gases through coordinate interactions with metals (O₂, NO, CO) and covalent modifications of thiols (NO, H₂S) and amines (CO₂). These are well exemplified in biotrophic reactions of NO with heme iron (to form iron nitrosyl heme) and cysteine (to form bioactive S-nitrosothiols) essential for tissue oxygenation. Here, we consider an alternative “third mode” of gas transport in what have been dubbed “Xenon pockets”, whereby inert gases may have functional effects. Many proteins have similar cavities, and possible effects include alterations in allosteric properties of proteins (potentially altering protein hydration). Here, it is suggested that similar to other inert gases, H₂ also has biological effects by utilizing these protein structures. This ought to be investigated further, in a range of species, to determine if this is the mode of action of H₂. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

23 pages, 918 KiB

Open AccessReview

Plant Antioxidants Affect Human and Gut Health, and Their Biosynthesis Is Influenced by Environment and Reactive Oxygen Species

by Duroy A. Navarre, Meijun Zhu and Hanjo Hellmann

Oxygen 2022, 2(3), 348-370; https://doi.org/10.3390/oxygen2030025 - 01 Sep 2022

Viewed by 2140

Abstract

Many environmental stresses cause an increase in reactive oxygen species in plants and alter their nutritional value. Plants respond to many stresses by producing increased amounts of compounds with antioxidant properties including vitamins, phenylpropanoids and carotenoids. Such compounds have wide-ranging health-promoting effects in [...] Read more.

Many environmental stresses cause an increase in reactive oxygen species in plants and alter their nutritional value. Plants respond to many stresses by producing increased amounts of compounds with antioxidant properties including vitamins, phenylpropanoids and carotenoids. Such compounds have wide-ranging health-promoting effects in humans that are partly due to their antioxidant function because oxidative stress underlies many human diseases. Some of these compounds have complex interactions with the gut, promoting gut health and changing the gut microbiome, whereas the gut influences the bioavailability of the ingested compounds and may metabolize them into products with different effects on health than the original compound. Substantial efforts have been made to increase the nutritional value of crops through breeding or transgenic approaches, but comparatively little effort has been directed towards increasing nutritional value through crop management and environment, which may present another approach to enhance the nutritional quality. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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22 pages, 2519 KiB

Open AccessReview

Molecular Oxygen as a Probe Molecule in EPR Spin Labeling Studies of Membrane Structure and Dynamics

by Witold K. Subczynski, Justyna Widomska, Marija Raguz and Marta Pasenkiewicz-Gierula

Oxygen 2022, 2(3), 295-316; https://doi.org/10.3390/oxygen2030021 - 04 Aug 2022

Cited by 3 | Viewed by 2062

Abstract

Molecular oxygen (O₂) is the perfect probe molecule for membrane studies carried out using the saturation recovery EPR technique. O₂ is a small, paramagnetic, hydrophobic enough molecule that easily partitions into a membrane’s different phases and domains. In membrane studies, [...] Read more.

Molecular oxygen (O₂) is the perfect probe molecule for membrane studies carried out using the saturation recovery EPR technique. O₂ is a small, paramagnetic, hydrophobic enough molecule that easily partitions into a membrane’s different phases and domains. In membrane studies, the saturation recovery EPR method requires two paramagnetic probes: a lipid-analog nitroxide spin label and an oxygen molecule. The experimentally derived parameters of this method are the spin–lattice relaxation times (T₁s) of spin labels and rates of bimolecular collisions between O₂ and the nitroxide fragment. Thanks to the long T₁ of lipid spin labels (from 1 to 10 µs), the approach is very sensitive to changes of the local (around the nitroxide fragment) O₂ diffusion-concentration product. Small variations in the lipid packing affect O₂ solubility and O₂ diffusion, which can be detected by the shortening of T₁ of spin labels. Using O₂ as a probe molecule and a different lipid spin label inserted into specific phases of the membrane and membrane domains allows data about the lateral arrangement of lipid membranes to be obtained. Moreover, using a lipid spin label with the nitroxide fragment attached to its head group or a hydrocarbon chain at different positions also enables data about molecular dynamics and structure at different membrane depths to be obtained. Thus, the method can be used to investigate not only the lateral organization of the membrane (i.e., the presence of membrane domains and phases), but also the depth-dependent membrane structure and dynamics and, hence, the membrane properties in three dimensions. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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16 pages, 2143 KiB

Open AccessFeature PaperReview

Conquering Space with Crops That Produce Ample Oxygen and Antioxidants

by Stephanie K. Polutchko, William W. Adams III, Christine M. Escobar and Barbara Demmig-Adams

Oxygen 2022, 2(2), 211-226; https://doi.org/10.3390/oxygen2020016 - 06 Jun 2022

Cited by 8 | Viewed by 2761

Abstract

Sustainable long-term space missions require regenerative life support from plants. Traditional crop plants lack some features desirable for use in space environments. The aquatic plant family Lemnaceae (duckweeds) has enormous potential as a space crop, featuring (i) fast growth, with very high rates [...] Read more.

Sustainable long-term space missions require regenerative life support from plants. Traditional crop plants lack some features desirable for use in space environments. The aquatic plant family Lemnaceae (duckweeds) has enormous potential as a space crop, featuring (i) fast growth, with very high rates of O₂ production and CO₂ sequestration, (ii) an exceptional nutritional quality (with respect to radiation-fighting antioxidants and high-quality protein), (iii) easy propagation and high productivity in small spaces, and (iv) resilience to the stresses (radiation, microgravity, and elevated CO₂) of the human-inhabited space environment. These traits of Lemnaceae are placed into the context of their unique adaptations to the aquatic environment. Furthermore, an overview is provided of the challenges of galactic cosmic radiation to plant and human physiology and the mechanisms involved in oxidative injury and the prevention/mitigation of such effects by antioxidant micronutrients. A focus is placed on the carotenoid zeaxanthin accumulated by Lemnaceae in unusually high amounts and its role in counteracting system-wide inflammation, cognitive dysfunction, and other oxidative injuries in humans. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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34 pages, 6517 KiB

Open AccessReview

Oxidative Stress and Its Role in Cd-Induced Epigenetic Modifications: Use of Antioxidants as a Possible Preventive Strategy

by Estefani Yaquelin Hernández-Cruz, Yalith Lyzet Arancibia-Hernández, Deyanira Yael Loyola-Mondragón and José Pedraza-Chaverri

Oxygen 2022, 2(2), 177-210; https://doi.org/10.3390/oxygen2020015 - 29 May 2022

Cited by 6 | Viewed by 2946

Abstract

Oxidative stress (OS) represents one of the main mechanisms of toxicity induced by environmental pollutants such as cadmium (Cd). OS is a natural physiological process where the presence of oxidants, such as reactive oxygen-derived species (ROS), outweighs the strategy of antioxidant defenses, culminating [...] Read more.

Oxidative stress (OS) represents one of the main mechanisms of toxicity induced by environmental pollutants such as cadmium (Cd). OS is a natural physiological process where the presence of oxidants, such as reactive oxygen-derived species (ROS), outweighs the strategy of antioxidant defenses, culminating in the interruption of signaling and redox control. It has been suggested that Cd increases ROS mainly by inducing damage to the electron transport chain and by increasing the activity of nicotinamide adenine dinucleotide hydrogen phosphate (NADPH) oxidase (NOX) and the concentration of free iron (Fe), as well as causing a decrease in antioxidant defense. On the other hand, OS has been related to changes in the biology of the epigenome, causing adverse health effects. Recent studies show that Cd generates alterations in deoxyribonucleic acid (DNA) methylation, histone modifications, and noncoding RNA (ncRNA) expression. However, the role of OS in Cd-induced epigenetic modifications is still poorly explored. Therefore, this review provides an update on the basic concepts of OS and its relationship with Cd-induced epigenetic changes. Furthermore, the use of antioxidant compounds is proposed to mitigate Cd-induced epigenetic alterations. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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12 pages, 2073 KiB

Open AccessFeature PaperReview

Solid and Liquid Oxygen under Ultrahigh Magnetic Fields

by Toshihiro Nomura, Yasuhiro H. Matsuda and Tatsuo C. Kobayashi

Oxygen 2022, 2(2), 152-163; https://doi.org/10.3390/oxygen2020013 - 25 May 2022

Cited by 1 | Viewed by 3962

Abstract

Oxygen is a unique molecule that possesses a spin quantum number

S = 1

. In the condensed phases of oxygen, the delicate balance between the antiferromagnetic interaction and van der Waals force results in the various phases with different crystal structures. By [...] Read more.

Oxygen is a unique molecule that possesses a spin quantum number

S = 1

. In the condensed phases of oxygen, the delicate balance between the antiferromagnetic interaction and van der Waals force results in the various phases with different crystal structures. By applying ultrahigh magnetic fields, the antiferromagnetic coupling between O

_{2}

molecules breaks, and novel high-field phases can appear. We have investigated the physical properties of condensed oxygen under ultrahigh magnetic fields and have found that the stable crystal structure of solid oxygen changes around 100 T. Even in liquid oxygen, we observed a strong acoustic attenuation, which indicates the fluctuation of local molecular arrangements. These results demonstrate that magnetic fields can modulate the packing structure of oxygen through spin-lattice coupling. Our study implies the possibility of controlling oxygen-related (bio-)chemical processes by using an external magnetic field. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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31 pages, 1144 KiB

Open AccessFeature PaperReview

Free Radical Properties, Source and Targets, Antioxidant Consumption and Health

by Giovanni Martemucci, Ciro Costagliola, Michele Mariano, Luca D’andrea, Pasquale Napolitano and Angela Gabriella D’Alessandro

Oxygen 2022, 2(2), 48-78; https://doi.org/10.3390/oxygen2020006 - 12 Apr 2022

Cited by 152 | Viewed by 25102

Abstract

Free radicals have acquired growing importance in the fields of biology and medicine. They are produced during many different endogenous and exogenous processes. Mitochondria are the main source of endogenous reactive oxygen species (ROS) produced at cell level. The overproduction of free radicals [...] Read more.

Free radicals have acquired growing importance in the fields of biology and medicine. They are produced during many different endogenous and exogenous processes. Mitochondria are the main source of endogenous reactive oxygen species (ROS) produced at cell level. The overproduction of free radicals can damage macromolecules such as nucleic acids, proteins and lipids. This leads to tissue damage in various chronic and degenerative diseases. Antioxidants play a crucial role in the body’s defense against free radicals. This review concerns the main properties of free radicals, their sources and deleterious effects. It highlights the potential role of the dietary supplementation of antioxidants and discusses unsolved problems regarding antioxidant supplements in the prevention and therapy of diseases. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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9 pages, 256 KiB

Open AccessFeature PaperReview

A Brief History of Oxygen: 250 Years on

by John T. Hancock

Oxygen 2022, 2(1), 31-39; https://doi.org/10.3390/oxygen2010004 - 15 Mar 2022

Cited by 3 | Viewed by 11533

Abstract

Although there has been some controversy surrounding exactly when oxygen was first discovered, it is likely that that accolade should go to Carl Wilhelm Scheele, who isolated oxygen in 1772, or even a year earlier. Others since then have been given the credit [...] Read more.

Although there has been some controversy surrounding exactly when oxygen was first discovered, it is likely that that accolade should go to Carl Wilhelm Scheele, who isolated oxygen in 1772, or even a year earlier. Others since then have been given the credit for the instrumental work leading to the discovery including Joseph Priestley in 1774 and Antoine-Laurent Lavoisier. Oxygen, a paramagnetic, diradical gaseous (at room temperature) molecule, is instrumental to life as we know it. It is also crucial to some medical therapies, used in multiple industries and has even been found on other planets. The importance of oxygen cannot be overplayed. Now, 250 years since oxygen was discovered, it is timely to revisit some of the history, the controversies and look at how oxygen has evolved during that time. Here, a few of the highlights in oxygen research are discussed. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

11 pages, 286 KiB

Open AccessFeature PaperReview

Beneficial Effects of Antioxidants in Male Infertility Management: A Narrative Review

by Simone Cilio, Monica Rienzo, Gianluca Villano, Benito Fabio Mirto, Gaetano Giampaglia, Federico Capone, Gianpiero Ferretti, Erika Di Zazzo and Felice Crocetto

Oxygen 2022, 2(1), 1-11; https://doi.org/10.3390/oxygen2010001 - 28 Jan 2022

Cited by 11 | Viewed by 7174

Abstract

Background: Infertility, defined as the failure to conceive after one year of regular, unprotected intercourse, affects 50–80 million people worldwide. A male factor is involved in approximately 20–30% of cases. In the etiology of male infertility, the association between poor semen quality and [...] Read more.

Background: Infertility, defined as the failure to conceive after one year of regular, unprotected intercourse, affects 50–80 million people worldwide. A male factor is involved in approximately 20–30% of cases. In the etiology of male infertility, the association between poor semen quality and oxidative stress (OS) is well known. High levels of reactive oxygen species (ROS) allow the oxidation of DNA, proteins, and lipids of sperm cells, modifying their vitality, motility, and morphology. Methods: To evaluate the effects of antioxidants on sperm in infertile men, we queried the MEDLINE database (via the PubMed interface) for published studies in the last 10 years (2011–2021). The following keywords were used: “infertility” and -“inositol”, -“alpha-lipoic acid”, -“zinc”, -“folate”, -“coenzyme Q10”, -“selenium”, and -“vitamin”. Results: Inositol regulates OS levels in sperm cells thanks to its role in mitochondrial reactions and is involved in several processes favoring sperm–oocyte interactions. Alpha-lipoic acid (ALA) reduces ROS damage and improves semen parameters in terms of spermatozoa’s motility, morphology, and count. Poor zinc nutrition may be related to low quality of sperm. Supplementation of folate plus zinc has a positive effect on the sperm concentration and morphology. Supplementation with CoQ10 increases sperm concentration, total and progressive motility. Selenium (Se) supplementation improves the overall semen quality and is related to a higher ejaculated volume. Among vitamins, only vitamin B12 shows a positive effect on semen quality; it increases sperm count and motility and reduces sperm DNA damage. Conclusions: In men showing low-quality semen, diet supplementation with antioxidants may improve the sperm quality by alleviating OS-induced sperm damage and enhancing hormone synthesis and spermatozoa concentration, motility, and morphology. Future clinical trials should be focused on the possible association of several antioxidants to take advantage of combined mechanisms of action. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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25 pages, 1856 KiB

Open AccessReview

Role of Oxygen Radicals in Alzheimer’s Disease: Focus on Tau Protein

by Anna Atlante, Daniela Valenti, Valentina Latina and Giuseppina Amadoro

Oxygen 2021, 1(2), 96-120; https://doi.org/10.3390/oxygen1020010 - 27 Nov 2021

Cited by 5 | Viewed by 3067

Abstract

Oxygen free radical burst is a prominent early event in the pathogenesis of Alzheimer’s disease (AD). Posttranslational modifications of Tau protein, primarily hyper-phosphorylation and truncation, are indicated as critical mediators of AD pathology. This finding is confirmed by the high levels of oxidative [...] Read more.

Oxygen free radical burst is a prominent early event in the pathogenesis of Alzheimer’s disease (AD). Posttranslational modifications of Tau protein, primarily hyper-phosphorylation and truncation, are indicated as critical mediators of AD pathology. This finding is confirmed by the high levels of oxidative stress markers and by the increased susceptibility to oxygen radicals found in cultured neurons and in brains from transgenic animal models expressing toxic Tau forms, in concomitance with a dramatic reduction in their viability/survival. Here, we collect the latest progress in research focused on the reciprocal and dynamic interplay between oxygen radicals and pathological Tau, discussing how these harmful species cooperate and/or synergize in the progression of AD. In this context, a better understanding of the role of oxidative stress in determining Tau pathology, and vice versa, primarily could be able to define novel biomarkers of early stages of human tauopathies, including AD, and then to develop therapeutic strategies aimed at attenuating, halting, or reversing disease progression. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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8 pages, 1190 KiB

Open AccessBrief Report

Effects of Acute Beetroot Juice Ingestion on Reactive Agility Performance

by Rebecca R. Rogers, Ashleigh M. Davis, Ashley E. Rice and Christopher G. Ballmann

Oxygen 2022, 2(4), 570-577; https://doi.org/10.3390/oxygen2040037 - 07 Nov 2022

Cited by 1 | Viewed by 1733

Abstract

Beetroot juice (BRJ) is high in inorganic nitrate (NO₃) which has been shown to enhance vascular function, cognition, and physical performance. Acute BRJ supplementation has been reported to enhance explosive resistance exercise performance and simple reaction time in diseased populations. However, [...] Read more.

Beetroot juice (BRJ) is high in inorganic nitrate (NO₃) which has been shown to enhance vascular function, cognition, and physical performance. Acute BRJ supplementation has been reported to enhance explosive resistance exercise performance and simple reaction time in diseased populations. However, it remains unknown if acute BRJ supplementation can enhance agility and reactive drills in healthy individuals, which are relevant to many sports. The purpose of this study was to investigate the effects of acute BRJ supplementation on simple reaction time and reactive agility performance. In a counterbalanced double-blinded manner, physically active males completed two trials each with a differing single-dose treatment: (1) Placebo (PL), (2) BRJ. Each treatment was consumed 2-hrs before experimental testing. Plasma Nitrate (NO₃) and Nitrite (NO₂) were measured via capillary blood sampling and colorimetric assay. Reaction time was assessed using a simple reaction time light test. Reactive agility was measured via a semi-circle drill and a get-up-and-go drill. All tests used FITLIGHT LED sensors to record response time. Each visit was separated by a 72-h washout period. Acute BRJ ingestion resulted in significantly greater plasma NO₃ (p < 0.001) and NO₂ (p = 0.008) compared to PL. BRJ significantly improved response time during the semi-circle drill (p = 0.011) and get-up and go drill (p = 0.027) compared to PL. No differences between treatments were observed for simple reaction time (p = 0.279). Collectively, these findings suggest that acute BRJ ingestion may improve reactive agility performance likely mediated by systemic increases in NO₃/NO₂. Future research is needed to investigate how these findings translate to game-play and sports competition. Full article

(This article belongs to the Special Issue Feature Papers in Oxygen)

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