Activation by O2 of AgxPd1-x Alloy Catalysts for Ethylene Hydrogenation

A composition spread alloy film (CSAF) spanning all of AgxPd1-x composition space, xPd = 0 → 1, was used to study catalytic ethylene hydrogenation with and without the presence of O2 in the feed gas. High-throughput measurements of the ethylene hydrogenation activity of AgxPd1-x alloys were performed at 100 Pd compositions spanning xPd = 0 → 1. The extent of ethylene hydrogenation was measured versus xPd at reaction temperatures spanning T = 300 → 405 K and inlet hydrogen partial pressures spanning PH2in = 70 → 690 Torr. The inlet ethylene partial pressure was constant at PC2H4in = 25 Torr, and the O2 inlet partial pressure was either PO2in = 0 or 15 Torr. When PO2in = 0 Torr, only those alloys with xPd ≥ 0.90 displayed observable ethylene hydrogenation activity. As expected, the most active catalyst was pure Pd, which yielded a maximum conversion of ∼0.4 at T = 405 K and PH2in = 690 Torr. Adding a constant O2 partial pressure of PO2in = 15 Torr to the feed stream dramatically increased the catalytic activity across the CSAF at all experimental conditions and catalyst compositions without inducing catalytic ethylene combustion and without measurable O2 consumption. The presence of PO2in = 15 Torr more than doubled the maximum achievable conversion on Pd to ∼0.9 and activated alloys with as little as xPd = 0.6 for ethylene hydrogenation. Measurement of the reaction order with respect to hydrogen, nH2, showed that nH2 ≈ 0 when PO2in = 15 Torr on high xPd alloys but that nH2 increases to values between 0.5 and 1 as xPd decreases or when PO2in = 0 Torr. We attribute this PO2in-induced change in nH2 to a change in the reaction mechanism resulting from different functional catalyst surfaces: one that is O2-activated and Pd-rich and one that is Ag-capped with low activity. Both are extremely sensitive to the bulk alloy composition, xPd, and the reaction temperature, T. These results show that the activity of AgPd catalysts for ethylene hydrogenation depends strongly on the operational conditions. Furthermore, we demonstrate that the exposure of AgPd catalysts to 15 Torr of O2 at moderate temperatures leads to enhanced catalyst performance, presumably by stimulating both Pd segregation to the topmost surface and Pd activation for ethylene hydrogenation.

Nanomedicine Strategies in Conquering and Utilizing the Cancer Hypoxia Environment

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

The Task Matters: A Comprehensive Review and Proposed Literature Score of the Effects of Chemical and Physical Parameters on Embryo Developmental Competence

To explore the effects of chemical and physical parameters on embryo developmental competence, we conducted a systematic search on PubMed for peer-reviewed original papers using specific keywords and medical subject heading terms. Studies of interest were selected from an initial cohort of 4141 potentially relevant records retrieved. The most relevant publications were critically evaluated to identify the effect of these parameters on embryo development. Moreover, we generated a literature score (LS) using the following procedure: (i) the number of studies favoring a reference group was expressed as a fraction of all analyzed papers; (ii) the obtained fraction was multiplied by 10 and converted into a decimal number. We identified and discussed six parameters (oxygen, temperature, humidity, oil overlay, light, pH). Moreover, we generated a LS according to five different comparisons (37 °C vs. <37 °C; 5% vs. 20% oxygen; 5-2% vs. 5% oxygen; humidity conditions vs. dry conditions; light exposure vs. reduced/protected light exposure). Only two comparisons (37 °C vs. <37 °C and 5% vs. 20% oxygen) yielded a medium-high LS (8.3 and 7, respectively), suggesting a prevalence of studies in favor of the reference group (37 °C and 5% oxygen). In summary, this review and LS methodology offer semi-quantitative information on studies investigating the effects of chemical and physical parameters on embryo developmental competence.

An oxygen-releasing agent promotes healing of skin wounds in rats

OBJECTIVE

To evaluate the local effect of a slow oxygen-release gel on the healing of standardised skin wounds caused in rats.

METHOD

Skin wounds were created on the backs of male rats (Rattus norvegicus, Wistar) that were randomly allocated into two groups. In the treated (T) and control (C) groups, oxygen gel and distilled water, respectively, were applied to the wounds on alternate days for 28 days. Postoperatively, euthanasia was performed at 5, 10, 14, 21 and 28 days, followed by clinical, histological (Masson's trichrome) and immunohistochemical analysis. Data were subjected to analysis of variance (ANOVA) and Bonferroni's test.

RESULTS

The cohort comprised 50 rats. On clinical and histological analysis, groups C and T showed similar characteristics 5 days post-operation. Subsequently, group T showed better healing at 14, 21 and 28 days and presented more intense inflammatory infiltrate up to 10 days. At days 14, 21 and 28, group T exhibited a reduction in oedema and increased angiogenesis, granulation tissue formation, and deposition of collagen fibres than group C. Immunohistochemical analysis showed the presence of tumour necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF) in both the groups, but the levels were significantly higher in group T (p<0.05).

CONCLUSION

The local application of slow oxygen-release gel accelerated the healing of standardised skin wounds created surgically in rats, with increased angiogenesis and better collagen fibre formation.

Accuracy of Pulse Oximetry for Long-Term Oxygen Therapy Assessment in Chronic Obstructive Pulmonary Disease

Rationale: Landmark studies of long-term oxygen therapy (LTOT) in patients with chronic obstructive pulmonary disease (COPD) used arterial oxygen pressure (PaO2) to define severe hypoxemia; however, oxygen saturation as measured by pulse oximetry (SpO2) is commonly used instead. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines recommend evaluation with arterial blood gas (ABG) analysis if SpO2 is ⩽92%. This recommendation has not been evaluated in stable outpatients with COPD undergoing testing for LTOT. Objectives: To evaluate the performance of SpO2 compared with ABG analysis of PaO2 and arterial oxygen saturation (SaO2) to detect severe resting hypoxemia in patients with COPD. Methods: Retrospective analysis of paired SpO2 and ABG values from stable outpatients with COPD who underwent LTOT assessment in a single center. We calculated false negatives (FNs) as an SpO2 >88% or >89% in the presence of pulmonary hypertension with a PaO2 ⩽55 mm Hg or ⩽59 mm Hg in the presence of pulmonary hypertension. Test performance was assessed using receiver operating characteristic (ROC) analysis, intraclass correlation coefficient (ICC), test bias, precision, and accuracy root-mean-square (Arms). An adjusted multivariate analysis was used to evaluate factors affecting SpO2 bias. Results: Of 518 patients, the prevalence of severe resting hypoxemia was 74 (14.3%), with 52 missed by SpO2 (FN, 10%), including 13 (2.5%) with an SpO2 > 92% (occult hypoxemia). FNs and occult hypoxemia in Black patients were 9% and 1.5%, respectively, and were 13% and 5%, respectively, among active smokers. The correlation between SpO2 and SaO2 was acceptable (ICC = 0.78; 95% confidence interval, 0.74-0.81); and the bias of SpO2 was 0.45%, with a precision of 2.6 (-4.65 to +5.55%) and Arms of 2.59. These measurements were similar in Black patients, but in active smokers, correlation was lower and bias showed greater overestimation of SpO2. ROC analysis suggests that the optimal SpO2 cutoff to warrant LTOT evaluation by ABG analysis is ⩽94%. Conclusions: SpO2 as the only measure of oxygenation carries a high FN rate in detecting severe resting hypoxemia in patients with COPD undergoing evaluation for LTOT. Reflex measurement of PaO2 by ABG analysis should be used as recommended by GOLD, ideally at a cutoff higher than an SpO2 ⩽92%, especially in active smokers.

Medium Depth Influences O2 Availability and Metabolism in Human RPE Cultures

Purpose

Retinal pigment epithelium (RPE) oxidative metabolism is critical for normal retinal function and is often studied in cell culture systems. Here, we show that conventional culture media volumes dramatically impact O2 availability, limiting oxidative metabolism. We suggest optimal conditions to ensure cultured RPE is in a normoxic environment permissive to oxidative metabolism.

Methods

We altered the availability of O2 to human primary and induced pluripotent stem cell-derived RPE cultures directly via a hypoxia chamber or indirectly via the amount of medium over cells. We measured oxygen consumption rates (OCRs), glucose consumption, lactate production, 13C6-glucose and 13C5-glutamine flux, hypoxia inducible factor 1α (HIF-1α) stability, intracellular lipid droplets after a lipid challenge, transepithelial electrical resistance, cell morphology, and pigmentation.

Results

Medium volumes commonly employed during RPE culture limit diffusion of O2 to cells, triggering hypoxia, activating HIF-1α, limiting OCR, and dramatically altering cell metabolism, with only minor effects on typical markers of RPE health. Media volume effects on O2 availability decrease acetyl-CoA utilization, increase glycolysis and reductive carboxylation, and alter the size and number of intracellular lipid droplets under lipid-rich conditions.

Conclusions

Despite having little impact on visible and typical markers of RPE culture health, media volume dramatically affects RPE physiology "under the hood." As RPE-centric diseases like age-related macular degeneration involve oxidative metabolism, RPE cultures need to be optimized to study such diseases. We provide guidelines for optimal RPE culture volumes that balance ample nutrient availability from larger media volumes with adequate O2 availability seen with smaller media volumes.

Chalcogen bonds formed by protein sulfur atoms in proteins. A survey of high-resolution structures deposited in the protein data bank

The presence of chalcogen bonds in native proteins was investigated on a non-redundant and high-resolution (≤ 1 Angstrom) set of protein crystal structures deposited in the Protein Data Bank. It was observed that about one half of the sulfur atoms of methionines and disulfide bridges from chalcogen bonds with nucleophiles (oxygen and sulfur atoms, and aromatic rings). This suggests that chalcogen bonds are a non-bonding interaction important for protein stability. Quite numerous chalcogen bonds involve water molecules. Interestingly, in the case of disulfide bridges, chalcogen bonds have a marked tendency to occur along the S-S bond extension rather than along the C-S bond extension. Additionally, it has been observed that closer residues have a higher probability of being connected by a chalcogen bonds, while the secondary structure of the two residues connected by a chalcogen bond do not correlate with its formation.Communicated by Ramaswamy H. Sarma.

Calcium-Dependent Interaction of Nitric Oxide Synthase with Cytochrome c Oxidase: Implications for Brain Bioenergetics

Targeted nitric oxide production is relevant for maintaining cellular energy production, protecting against oxidative stress, regulating cell death, and promoting neuroprotection. This study aimed to characterize the putative interaction of nitric-oxide synthase with mitochondrial proteins. The primary finding of this study is that cytochrome c oxidase (CCO) subunit IV (CCOIV) is associated directly with NOS in brain mitochondria when calcium ions are present. The matrix side of CCOIV binds to the N-terminus of NOS, supported by the abrogation of the binding by antibodies towards the N-terminus of NOS. Evidence supporting the interaction between CCOIV and NOS was provided by the coimmunoprecipitation of NOS from detergent-solubilized whole rat brain mitochondria with antibodies to CCOIV and the coimmunoprecipitation of CCOIV from crude brain NOS preparations using antibodies to NOS. The CCOIV domain that interacts with NOS was identified using a series of overlapping peptides derived from the primary sequence of CCOIV. As calcium ions not only activate NOS, but also facilitate the docking of NOS to CCOIV, this study points to a dynamic mechanism of controlling the bioenergetics by calcium changes, thereby adapting bioenergetics to cellular demands.

Encapsulation in Oxygen-Loaded Nanobubbles Enhances the Antimicrobial Effectiveness of Photoactivated Curcumin

In both healthcare and agriculture, antibiotic resistance is an alarming issue. Biocompatible and biodegradable ingredients (e.g., curcumin) are given priority in "green" criteria supported by the Next Generation EU platform. The solubility and stability of curcumin would be significantly improved if it were enclosed in nanobubbles (NB), and photoactivation with the correct wavelength of light can increase its antibacterial efficacy. A continuous release of curcumin over a prolonged period was provided by using innovative chitosan-shelled carriers, i.e., curcumin-containing nanobubbles (Curc-CS-NBs) and oxygen-loaded curcumin-containing nanobubbles (Curc-Oxy-CS-NBs). The results demonstrated that after photoactivation, both types of NBs exhibited increased effectiveness. For Staphylococcus aureus, the minimum inhibitory concentration (MIC) for Curc-CS-NBs remained at 46 µg/mL following photodynamic activation, whereas it drastically dropped to 12 µg/mL for Curc-Oxy-CS-NBs. Enterococcus faecalis shows a decreased MIC for Curc-CS-NB and Curc-Oxy-CS-NB (23 and 46 µg/mL, respectively). All bacterial strains were more effectively killed by NBs that had both oxygen and LED irradiation. A combination of Curc-Oxy-CS-NB and photodynamic stimulation led to a killing of microorganisms due to ROS-induced bacterial membrane leakage. This approach was particularly effective against Escherichia coli. In conclusion, this work shows that Curc-CS-NBs and Curc-Oxy-CS-exhibit extremely powerful antibacterial properties and represent a potential strategy to prevent antibiotic resistance and encourage the use of eco-friendly substitutes in agriculture and healthcare.

Fabricated Gamma-Alumina-Supported Zinc Ferrite Catalyst for Solvent-Free Aerobic Oxidation of Cyclic Ethers to Lactones

The aim of this work was to fabricate a new heterogeneous catalyst as zinc ferrite (ZF) supported on gamma-alumina (γ-Al2O3) for the conversion of cyclic ethers to the corresponding, more valuable lactones, using a solvent-free method and O2 as an oxidant. Hence, the ZF@γ-Al2O3 catalyst was prepared using a deposition-coprecipitation method, then characterized using TEM, SEM, EDS, TGA, FTIR, XRD, ICP, XPS, and BET surface area, and further applied for aerobic oxidation of cyclic ethers. The structural analysis indicated spherical, uniform ZF particles of 24 nm dispersed on the alumina support. Importantly, the incorporation of ZF into the support influenced its texture, i.e., the surface area and pore size were reduced while the pore diameter was increased. The product identification indicated lactone compound as the major product for saturated cyclic ether oxidation. For THF as a model reaction, it was found that the supported catalyst was 3.2 times more potent towards the oxidation of cyclic ethers than the unsupported one. Furthermore, the low reactivity of the six-membered ethers can be tackled by optimizing the oxidant pressure and the reaction time. In the case of unsaturated ethers, deep oxidation and polymerization reactions were competitive oxidations. Furthermore, it was found that the supported catalyst maintained good stability and catalytic activity, even after four cycles.

D-dimer trends predict COVID-19 patient's prognosis: A retrospective chart review study

This is a retrospective study of patients admitted to Jackson Hospital, Montgomery, Alabama, with a diagnosis of COVID-19 from January 1, 2021, to February 15, 2022. The independent variables used in the models were patient sex, age, race, BMI category, daily D-dimer categories, categories of anticoagulation doses, bleeding episodes, and vaccination status. The three different categories of anticoagulation doses were considered for the purpose of the study which were Enoxaparin 40 mg daily vs Enoxaparin 80 mg daily vs Enoxaparin 1 mg/kg or equivalent daily. The study reviewed a total of 100 hospitalized patients. Intermediate-dose anticoagulation was found to be the optimal dose as only 14% patients died compared to a 36 and 50% death rate among those treated with low-dose and high-dose anticoagulation, respectively. The multivariate linear regression model predicting patient oxygen requirements revealed D-dimer and bleeding status to be statistically significant predictors with a p value of <0.01. For the patients who had a D-dimer value ≥2 µg/mL, the oxygenation requirement was predicted to be 31 L higher than those with a D-dimer <2 µg/mL (99% CI; p < 0.01). When mean D-dimer and corresponding oxygen requirements were calculated per hospitalization days category, the D-dimer levels and oxygen requirements were noted to follow the same trends indicating that both values tended to increase and decrease simultaneously. The study concludes daily D-dimer trends can predict COVID-19 patient survival or daily oxygen requirements indicating that D-dimer can be the miracle molecule for COVID-19 prognosis.

Absolute oxygen-guided radiation therapy improves tumor control in three preclinical tumor models

Background

Clinical attempts to find benefit from specifically targeting and boosting resistant hypoxic tumor subvolumes have been promising but inconclusive. While a first preclinical murine tumor type showed significant improved control with hypoxic tumor boosts, a more thorough investigation of efficacy from boosting hypoxic subvolumes defined by electron paramagnetic resonance oxygen imaging (EPROI) is necessary. The present study confirms improved hypoxic tumor control results in three different tumor types using a clonogenic assay and explores potential confounding experimental conditions.

Materials and methods

Three murine tumor models were used for multi-modal imaging and radiotherapy: MCa-4 mammary adenocarcinomas, SCC7 squamous cell carcinomas, and FSa fibrosarcomas. Registered T2-weighted MRI tumor boundaries, hypoxia defined by EPROI as pO2 ≤ 10 mmHg, and X-RAD 225Cx CT boost boundaries were obtained for all animals. 13 Gy boosts were directed to hypoxic or equal-integral-volume oxygenated tumor regions and monitored for regrowth. Kaplan-Meier survival analysis was used to assess local tumor control probability (LTCP). The Cox proportional hazards model was used to assess the hazard ratio of tumor progression of Hypoxic Boost vs. Oxygenated Boost for each tumor type controlling for experimental confounding variables such as EPROI radiofrequency, tumor volume, hypoxic fraction, and delay between imaging and radiation treatment.

Results

An overall significant increase in LTCP from Hypoxia Boost vs. Oxygenated Boost treatments was observed in the full group of three tumor types (p < 0.0001). The effects of tumor volume and hypoxic fraction on LTCP were dependent on tumor type. The delay between imaging and boost treatments did not have a significant effect on LTCP for all tumor types.

Conclusion

This study confirms that EPROI locates resistant tumor hypoxic regions for radiation boost, increasing clonogenic LTCP, with potential enhanced therapeutic index in three tumor types. Preclinical absolute EPROI may provide correction for clinical hypoxia images using additional clinical physiologic MRI.

Superoxide dismutase for bronchopulmonary dysplasia in preterm infants

BACKGROUND

Free oxygen radicals have been implicated in the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm infants. Superoxide dismutase (SOD) is a naturally occurring enzyme which provides a defense against such oxidant injury. Providing supplementary SOD has been tested in clinical trials to prevent BPD in preterm infants.

OBJECTIVES

To determine the efficacy and safety of SOD in the prevention and treatment of BPD on mortality and other complications of prematurity in infants at risk for, or having BPD.

SEARCH METHODS

We searched CENTRAL, PubMed, Embase, and three trials registers on 22 September 2022 together with reference checking, citation searching and contact with study authors to identify additional studies.

SELECTION CRITERIA

Randomized, quasi-randomized and cluster-randomized controlled trials (RCTs) where the participants were preterm infants who had developed, or were at risk of developing BPD, and who were randomly allocated to receive either SOD (in any form, by any route, any dose, anytime) or placebo, or no treatment.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were BPD defined as an oxygen requirement at 28 days, BPD defined as oxygen at 36 weeks' postmenstrual age, neonatal mortality, mortality prior to discharge, and BPD or death at 36 weeks' postmenstrual age. We reported risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CIs) for the dichotomous outcomes. We used GRADE to assess certainty of evidence for each outcome.

MAIN RESULTS

We included three RCTs (380 infants) on SOD administration in preterm infants at risk for BPD, and no studies in preterm infants with evolving BPD / early respiratory insufficiency. The evidence is very uncertain about the effect of SOD on BPD defined as an oxygen requirement at 28 days (RR 1.09, 95% CI 0.94 to 1.26; RD 0.06, 95% CI -0.05 to 0.16, 1 study, 302 infants; I2 for RR and RD not applicable), BPD defined as oxygen at 36 weeks' postmenstrual age (RR 0.96, 95% CI 0.72 to 1.29; RD -0.01, 95% CI -0.11 to 0.09, 2 studies, 335 infants; I2 for RR and RD = 0%), neonatal mortality (RR 0.98, 95% CI 0.57 to 1.68; RD -0.00, 95% CI -0.08 to 0.07, 2 studies, 335 infants; I2 for RR and RD = 0%), and mortality prior to discharge (RR 1.20, 95% CI 0.53 to 2.71; RD 0.04, 95% CI -0.14 to 0.23, 2 studies, 78 infants; I2 for RR and RD = 0%). No studies reported BPD or death at 36 weeks' postmenstrual age. The evidence is very uncertain about the effect of SOD on retinopathy of prematurity any stage (RR 0.95, 95% CI 0.78 to 1.15; RD -0.03, 95% CI -0.15 to 0.08, 2 studies, 335 infants; I2for RR = 0%, I2 for RD = 8%), and severe retinopathy of prematurity (ROP) (RR 0.97, 95% CI 0.57 to 1.65; RD -0.01, 95% CI -0.10 to 0.09, 1 study, 244 infants; I2 for RR and RD not applicable). No studies reported moderate to severe neurodevelopmental outcome at 18 to 24 months. Certainty of evidence was very low for all outcomes. We identified no ongoing trials.

AUTHORS' CONCLUSIONS

The evidence is very uncertain about the effect of SOD on BPD defined as an oxygen requirement at 28 days, BPD defined as oxygen at 36 weeks' postmenstrual age, neonatal mortality and mortality prior to discharge compared to placebo. No studies reported BPD or death at 36 weeks' postmenstrual age and need for supplemental oxygen. The evidence is very uncertain about the effect of SOD on retinopathy of prematurity any stage and severe retinopathy of prematurity. No studies reported moderate to severe neurodevelopmental outcome at 18 to 24 months. The effects of SOD in preterm infants has not been reported in any trial in the last few decades, considering that the most recent trial on SOD in preterm infants was conducted in 1997/1998, and no new studies are ongoing. In the light of the limited available evidence, new data from preclinical and observational studies are needed to justify the conduction of new RCTs. Observational studies might report how SOD is administered, including indication, dose and association with relevant outcomes such as mortality, BPD and long-term neurodevelopment.

Can guidelines rein in oxygen use? A retrospective cross-sectional study using routinely collected data

Oxygen is one of the most commonly used emergency therapies. Like other therapies, oxygen can cause harm if used inappropriately. During the COVID-19 pandemic, guidelines were released to optimize oxygen and medication use. In the current study, we examine whether oxygen and medication use during the first wave of the COVID-19 pandemic was in concordance with new guidelines. A retrospective cross-sectional study was conducted using routinely collected data from University of Birmingham NHS Foundation Trust in England. Patients were admitted between April 2020 and September 2020, were over the age of 18 years, and had a confirmed diagnosis of COVID-19. To assess adherence to the oxygen guidelines (i.e. SpO2 adherence), the percentage of times oxygen therapy was administered within, over, and under guideline specifications were calculated for patients overall, and then for patients with and without chronic obstructive pulmonary disease (COPD)/pulmonary disease separately. Next, two multinomial regression analyses were conducted to assess whether clinical processes, pre-admission diagnoses, and other demographic factors were related to oxygen use. Analysis 1 included patients not diagnosed with COPD/pulmonary disease. Analysis 2 included patients diagnosed with COPD/pulmonary disease. Results are reported as tallies, percentages, and odds ratios with 95% confidence intervals. To assess adherence to a new medication guideline, the percentage of patients administered oxygen and dexamethasone was calculated for those admitted after 25 June 2020. The overall number of patients included in our SpO2 adherence analyses was 8751 (female = 4168). Oxygen was used within guideline specifications less than half the time, i.e. 41.6% (n = 3638/8751); non-adherence involving under-administering (3.5%, n = 304/8751) was markedly lower than over-administering (55.0%, n = 4809/8751). Adherence was higher for patients without COPD (43.7%, n = 3383/7741) than with COPD (25.2%, n = 255/1010). Under-administering was low across groups (non-COPD 3.5%, n = 274/7741 and COPD 2.9%, n = 30/1010). Over-administering was markedly lower for non-COPD (52.3%, n = 4084/7741) than COPD (71.8%, n = 725/1010) patients. Diagnoses associated with over-administering varied across the groups. Regarding the dexamethasone guidelines, of the 6397 patients admitted after the 24th of June, only 12.6% (n = 805) received dexamethasone. Suboptimal use of oxygen and medication were common during the first wave of the COVID-19 pandemic. As found in previous studies, over-administering was more common than under-administering. The new guidelines issued during the COVID-19 pandemic were not by themselves sufficient to optimize oxygen use. Behavioural strategies are explored which may help policymakers optimize oxygen use.

Controlling pericellular oxygen tension in cell culture reveals distinct breast cancer responses to low oxygen tensions

Oxygen (O2) tension plays a key role in tissue function and pathophysiology. O2-controlled cell culture, in which the O2 concentration in an incubator's gas phase is controlled, is an indispensable tool to study the role of O2 in vivo. For this technique, it is presumed that the incubator setpoint is equal to the O2 tension that cells experience (i.e., pericellular O2). We discovered that physioxic (5% O2) and hypoxic (1% O2) setpoints regularly induce anoxic (0.0% O2) pericellular tensions in both adherent and suspension cell cultures. Electron transport chain inhibition ablates this effect, indicating that cellular O2 consumption is the driving factor. RNA-seq revealed that primary human hepatocytes cultured in physioxia experience ischemia-reperfusion injury due to anoxic exposure followed by rapid reoxygenation. To better understand the relationship between incubator gas phase and pericellular O2 tensions, we developed a reaction-diffusion model that predicts pericellular O2 tension a priori. This model revealed that the effect of cellular O2 consumption is greatest in smaller volume culture vessels (e.g., 96-well plate). By controlling pericellular O2 tension in cell culture, we discovered that MCF7 cells have stronger glycolytic and glutamine metabolism responses in anoxia vs. hypoxia. MCF7 also expressed higher levels of HIF2A, CD73, NDUFA4L2, etc. and lower levels of HIF1A, CA9, VEGFA, etc. in response to hypoxia vs. anoxia. Proteomics revealed that 4T1 cells had an upregulated epithelial-to-mesenchymal transition (EMT) response and downregulated reactive oxygen species (ROS) management, glycolysis, and fatty acid metabolism pathways in hypoxia vs. anoxia. Collectively, these results reveal that breast cancer cells respond non-monotonically to low O2, suggesting that anoxic cell culture is not suitable to model hypoxia. We demonstrate that controlling atmospheric O2 tension in cell culture incubators is insufficient to control O2 in cell culture and introduce the concept of pericellular O2-controlled cell culture.

An overview of oxygen transport in plants: diffusion and convection

The movement of gases within plants is crucial for species that live in flood-prone areas with limited soil oxygen. These plants adapt to hypoxia/anoxia not by using oxygen more efficiently, but by ensuring a steady oxygen supply to their cells. Wetland plants typically form gas-filled spaces (aerenchyma) in their tissues, providing a low-resistance pathway for gas movement between shoots and roots, especially when the shoots are above water, and the roots are submerged. Oxygen movement in plant roots is mainly through diffusion. However, in certain species, such as emergent and floating-leaved plants, pressurized flows can also facilitate the movement of gases within their stems and rhizomes. Three types of pressurized (convective) flows have been identified: humidity-induced pressurization (positive pressure), thermal osmosis (positive pressure with air flow against the heat gradient), and venturi-induced suction (negative pressure) caused by wind passing over broken culms. A clear diel variation in pressurized flows exists, with higher pressures and flows during the day and negligible pressures and flows during the night. This article discusses some key aspects of these mechanisms for oxygen movement.

Methemoglobinemia: A Case Report

Methemoglobinemia is a potentially life-threatening condition in which there is diminution of the oxygen-carrying capacity of circulating hemoglobin. It can result from either congenital or acquired processes. Methemoglobin forms when hemoglobin is oxidized to contain iron in the ferric (Fe3+) rather than the normal ferrous (Fe2+) state. Methemoglobinemia is a clinical diagnosis and is suspected in the presence of hypoxemia refractory to supplemental oxygen and the presence of chocolate-colored blood. Symptoms are usually dependent on methemoglobin levels; at levels higher than 35%, systemic symptoms from tissue hypoxia may be fatal. A high index of suspicion is required in patients with refractory hypoxia or cyanosis when treated with oxygen. Treatment options involve the removal of the inciting agent and treatment with the antidote methylene blue. Here we present a case of methemoglobinemia in a young patient who attended a college rave party.

Use of Palliative Oxygen in Cancer Patients

Background: Despite the lack of evidence to support the use of palliative oxygen to relieve dyspnea at the end of life, its prescription is widespread and often supported by local and national practice guidelines. Objectives: The objectives of this study were (1) to determine to what extent oxygen prescriptions meet the proposed prescription criteria in our institution, (2) to examine the indication of individual prescriptions in relation to the severity of dyspnea and (3) to review the utilization of opioids in patients receiving palliative oxygen. Methods: Retrospective chart review of cancer patients who were prescribed palliative oxygen between April 2015 and January 2020 through a respiratory home care program in Quebec City, Canada. According to provincial prescription guidelines, palliative oxygen was provided and reimbursed in case of severe hypoxemia (pulse oximetry saturation at rest < 88%) in cancer patients with an estimated prognosis of less than 3 months. Results: 134 patients receiving palliative oxygen were included; 25 (19%) did not fulfill reimbursement criteria. Median survival was 44 days. At initiation of palliative oxygen, 48 patients (36%) had only mild or moderate dyspnea (Medical Research Council dyspnea score 1-3), 26 (19%) did not receive opioids, and 9 (7%) were prescribed palliative oxygen without being dyspneic or receiving opioids. Conclusion: Most prescriptions of palliative oxygen met the proposed prescription criteria in our institution. Half of those who received palliative oxygen were only mildly dyspneic and/or were not receiving opioids at the time of the prescription.

Conservative versus Liberal Oxygenation Targets in Intensive Care Unit Patients (ICONIC): A Randomized Clinical Trial

Rationale: Supplemental oxygen is widely administered to ICU patients, but appropriate oxygenation targets remain unclear. Objectives: This study aimed to determine whether a low-oxygenation strategy would lower 28-day mortality compared with a high-oxygenation strategy. Methods: This randomized multicenter trial included mechanically ventilated ICU patients with an expected ventilation duration of at least 24 hours. Patients were randomized 1:1 to a low-oxygenation (PaO2, 55-80 mm Hg; or oxygen saturation as measured by pulse oximetry, 91-94%) or high-oxygenation (PaO2, 110-150 mm Hg; or oxygen saturation as measured by pulse oximetry, 96-100%) target until ICU discharge or 28 days after randomization, whichever came first. The primary outcome was 28-day mortality. The study was stopped prematurely because of the COVID-19 pandemic when 664 of the planned 1,512 patients were included. Measurements and Main Results: Between November 2018 and November 2021, a total of 664 patients were included in the trial: 335 in the low-oxygenation group and 329 in the high-oxygenation group. The median achieved PaO2 was 75 mm Hg (interquartile range, 70-84) and 115 mm Hg (interquartile range, 100-129) in the low- and high-oxygenation groups, respectively. At Day 28, 129 (38.5%) and 114 (34.7%) patients had died in the low- and high-oxygenation groups, respectively (risk ratio, 1.11; 95% confidence interval, 0.9-1.4; P = 0.30). At least one serious adverse event was reported in 12 (3.6%) and 17 (5.2%) patients in the low- and high-oxygenation groups, respectively. Conclusions: Among mechanically ventilated ICU patients with an expected mechanical ventilation duration of at least 24 hours, using a low-oxygenation strategy did not result in a reduction of 28-day mortality compared with a high-oxygenation strategy. Clinical trial registered with the National Trial Register and the International Clinical Trials Registry Platform (NTR7376).

Reproducible Preparation of Primary Rat Hepatocyte Sheets Using a Thermoresponsive Culture Dish

Hepatocyte transplantation has been utilized as a therapy for congenital metabolic liver diseases such as hemophilia and for liver function support in acute liver failure. Hepatocyte sheet technology using a thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-grafted dish is expected to provide an efficient cell transplantation method because the resulting hepatocyte sheet possesses extracellular matrix (ECM) on the basal surface, which enhances attachment to the target sites. However, the cultured hepatocytes consume large amounts of oxygen, leading to the loss of a few hepatocytes within the confluent culture sheet owing to a lack of oxygen. To circumvent this problem, this work demonstrates the shortening of diffusion distance, that is, the medium depth, to accelerate oxygen supply from the gas phase/medium interface to the cultured hepatocytes, allowing them to form a monolayer hepatocyte sheet. Incubation of hepatocytes with medium at a depth of 1.3 mm facilitates confluent culture of hepatocytes for 72 h, whereas viable hepatocytes decreased at 2.6 mm depth. Hepatocyte sheets are formed on a 0.5 μg/cm2 fibronectin-physisorbed PIPAAm-grafted dish during 72 h incubation at 37°C. Detachment of the cultured hepatocyte sheet from the PIPAAm-grafted dish where the surface becomes hydrophilic at 20°C is accomplished by scraping the periphery of the sheet using a cell scraper. Furthermore, the apical side of the hepatocyte sheet can be physically grabbed using a gelatin-coated membrane, and the sheet with ECM on the basal surface can be readily transferred to the target site after melting the coated gelatin at 37°C. Both methods are beneficial for creating tissue models by layering with another type of cell sheets, and for quick transplantation, such as into the subcutaneous space and orthotopic transplantation on the surface of the liver.

Limited Effects of Ultra-low Oxygen Concentration during Extended Embryo Culture on In vitro Fertilisation Outcomes in Indian Women: A Retrospective Cross-sectional Study

Background

Amongst various other factors, oxygen (O2) concentration in embryo culture plays an important role in determining pregnancy outcomes in women undergoing in vitro fertilisation. Some studies have reported that lowering O2 levels in embryo culture provides better results.

Aims

To explore the effects of low- and ultra-low- O2 concentrations (5% and 2%, respectively) in extended embryo culture on various outcome parameters of pregnancy.

Settings and Design

This was a retrospective cross-sectional study.

Materials and Methods

In this study 382 participants had their embryos cultured in varying O2 concentrations (5% or 2%), followed by either a fresh embryo transfer (ET) or frozen embryo transfer (FET). Outcomes such as pregnancy rate, implantation rate, abortion rate, twinning rate, and live birth rate were compared between the groups.

Statistical Analysis Used

Chi square test was applied to compare the primary and secondary outcomes between different groups.

Results

No significant differences were observed in pregnancy rate and implantation rate between 5% and 2% O2 groups, irrespective of their mode of ET. The abortion rate was significantly higher in 5% O2 group than in 2% group during FET (24.71% vs. 11.49%, P = 0.02). While the proportion of good-quality embryos was higher in 5% O2 group, these did not translate to better pregnancy outcomes. Additionally, embryos cultured in 2% O2 concentration had a significantly better implantation rate when they were transferred fresh rather than frozen (71.34% vs. 61.46%, P = 0.04). There were no other differences observed.

Conclusion

Only marginal benefits were observed in switching human embryos to ultra-low O2 concentration after the initial days of culture.

Relative hypoxemia at depth during breath-hold diving investigated through arterial blood gas analysis and lung ultrasound

Pulmonary gas exchange in breath-hold diving (BHD) consists of a progressive increase in arterial partial pressures of oxygen ([Formula: see text]) and carbon dioxide ([Formula: see text]) during descent. However, recent findings have demonstrated that [Formula: see text] does not consistently rise in all subjects. This study aimed at verifying and explaining [Formula: see text] derangements during BHD analyzing arterial blood gases and searching for pulmonary alterations with lung ultrasound. After ethical approval, 14 fit breath-hold divers were included. Experiments were performed in warm water (temperature: 31°C). We analyzed arterial blood gases immediately before, at depth, and immediately after a breath-hold dive to -15 m of fresh water (mfw) and -42 mfw. Signs of lung interstitial edema and atelectasis were searched simultaneously with a marinized lung ultrasound. In five subjects (-15 mfw) and four subjects (-42 mfw), the [Formula: see text] at depth seems to decrease instead of increasing. [Formula: see text] and lactate showed slight variations. At depth, no lung ultrasound alterations were seen except in one subject (hypoxemia and B-lines at -15 mfw; B-lines at the surface). Lung interstitial edema was detected in 3 and 12 subjects after resurfacing from -15 to -42 mfw, respectively. Two subjects developed hypoxemia at depth and a small lung atelectasis (a focal pleural irregularity of triangular shape, surrounded by thickened B-lines) after resurfacing from -42 mfw. Current experiments confirmed that some BH divers can experience hypoxemia at depth. The hypothesized explanation for such a discrepancy is lung atelectasis, which could not be detected in all subjects probably due to limited time available at depth.NEW & NOTEWORTHY During breath-hold diving, arterial partial pressure of oxygen ([Formula: see text]) and arterial partial pressure of carbon dioxide ([Formula: see text]) are believed to increase progressively during descent, as explained by theory, previous end-tidal alveolar gas measurements, and arterial blood gas analysis in hyperbaric chambers. Recent experiments in real underwater environment found a paradoxical [Formula: see text] drop at depth in some divers. This work confirms that some breath-hold divers can experience hypoxemia at depth. The hypothesized explanation for such a discrepancy is lung atelectasis, as suggested by lung ultrasound findings.

Reducing inappropriate oxygen use in hospitalized medicine patients

INTRODUCTION

Evidence suggests inappropriate oxygenation may be harmful to patients. To improve oxygen use in our hospital, we initiated a quality improvement project with a goal to reduce the percentage of inappropriate utilization of oxygen by 50% within a year.

METHODS

Nasal cannula (NC) oxygen use data for medicine inpatients was abstracted weekly for chart review. A multidisciplinary team developed a guideline for use. Initiation of NC O2 with a baseline SPO2 > 92% was deemed inappropriate and 3+ consecutive SPO2 > 96% was defined as over-supplementation. Formal interventions included an oxygen use guideline, updated EMR order, unit-specific feedback, and magnetic placards. Progress was tracked by control charts.

RESULTS

Baseline data revealed 40% of patients were inappropriately placed on oxygen and 55% of patients had one instance of excessive supplementation. Only half of all improper uses of oxygen had charted medical reasoning, and 30% had a corresponding order. Instances of proper oxygen use had orders 48% of the time. Run charts revealed inappropriate initiation was significantly reduced to 27.1% (p < 0.0001) and excessive oxygenation decreased significantly to 34.4% (p < 0.0001) following interventions with no effect on other variables.

CONCLUSIONS

Our interventions significantly decreased improper oxygen initiation and excessive supplementation.

A vanguard randomised feasibility trial comparing three regimens of peri-operative oxygen therapy on recovery after major surgery

International recommendations encourage liberal administration of oxygen to patients having surgery under general anaesthesia, ostensibly to reduce surgical site infection. However, the optimal oxygen regimen to minimise postoperative complications and enhance recovery from surgery remains uncertain. The hospital operating theatre randomised oxygen (HOT-ROX) trial is a multicentre, patient- and assessor-blinded, parallel-group, randomised clinical trial designed to assess the effect of a restricted, standard care, or liberal peri-operative oxygen therapy regimen on days alive and at home after surgery in adults undergoing prolonged non-cardiac surgery under general anaesthesia. Here, we report the findings of the internal vanguard feasibility phase of the trial undertaken in four large metropolitan hospitals in Australia and New Zealand that included the first 210 patients of a planned overall 2640 trial sample, with eight pre-specified endpoints evaluating protocol implementation and safety. We screened a total of 956 participants between 1 September 2019 and 26 January 2021, with data from 210 participants included in the analysis. Median (IQR [range]) time-weighted average intra-operative Fi O2 was 0.30 (0.26-0.35 [0.20-0.59]) and 0.47 (0.44-0.51 [0.37-0.68]) for restricted and standard care, respectively (mean difference (95%CI) 0.17 (0.14-0.20), p < 0.001). Median time-weighted average intra-operative Fi O2 was 0.83 (0.80-0.85 [0.70-0.91]) for liberal oxygen therapy (mean difference (95%CI) compared with standard care 0.36 (0.33-0.39), p < 0.001). All feasibility endpoints were met. There were no significant patient adverse events. These data support the feasibility of proceeding with the HOT-ROX trial without major protocol modifications.

Three-Dimensional Regulation of Ferroptosis at the Intersection of Iron, Sulfur, and Oxygen Executing Scrap and Build Toward Evolution

Significance: Iron is an essential element for every life on earth as a primary media for electron flow. Sulfur compounds as sulfhydryls counteract catalytic activity of iron whereas sulfur overdose is also toxic. In aerobic organisms, oxygen is the major media for electron transfer with higher intracellular mobility, which cooperates with the iron system. Based on the importance of iron, there is no active pathway to excrete iron outside the body in higher species. Whereas bacterial infection causes a scramble for iron in situ, cancer can be the outcome of the side effects of long use of iron and oxygen. Recent Advances: Ferroptosis is a recently coined cell death, defined as catalytic Fe(II)-dependent regulated necrosis accompanied by lipid peroxidation. Researchers recently recognized that ferroptosis is involved in a variety of physiological and pathological contexts, including embryonic erythropoiesis, aging, neurodegeneration and cancer cell death. Alternatively, carcinogenesis is a process to obtain iron addiction with ferroptosis-resistance, based on rodent animal studies. Critical Issues: Here we propose that ferroptosis is three-dimensionally regulated by iron, sulfur and oxygen, which correspond to oxidants, antioxidants and membrane fluidity with susceptibility to lipid peroxidation, respectively. Future Directions: Whereas life attempts to prevent ferroptosis, ferroptotic cells eventually emit iron-loaded ferritin as extracellular vesicles to maintain monopoly of iron. Antioxid. Redox Signal. 39, 807-815.