High Oxygen Concentrations Research Articles

Aerated drip irrigation improves water and nitrogen uptake efficiencies of tomato roots with associated changes in the antioxidant system

• After aerated drip irrigation, soil oxygen content significantly increased. • The duration and sequence of aeration changed the root antioxidant system. • The root antioxidant system correlated root morphology of tomato. • Root antioxidant systems and growth affect water and nitrogen uptake efficiency of tomato. China has the largest area of vegetable cultivation in greenhouse vegetable system in the world. However, the excessive application of irrigation and fertilizers has caused soil degradation and hardening, even leading to injury and yield loss in vegetable. Increasing soil aeration oxygen can improve crop water and nutrient uptake efficiencies. However, its effects on crop antioxidant systems are less known. Due to the sensitivity of the antioxidant system to changes in soil oxygen content, it is expected that aerated drip irrigation (ADI) delivering microbubble water to the crop rhizosphere will alter root antioxidant enzyme activities, malondialdehyde (MDA) content, and osmotic regulators in tomato plants. We conducted pot experiments under eight irrigation regimes: five aerated durations (0%, 25%, 50%, 75%, and 100%) of the subsurface drip irrigation period aerated (CK, A 25% , A 50% , A 75% , and A), with two aerated sequences (L: subsurface drip irrigation follow by aerated drip irrigation, F: aerated drip irrigation follow by subsurface drip irrigation) for the A 25% , A 50% and A 75% treatments. All treatments with ADI had an average of 7.63% higher oxygen concentration (OC) than the CK treatment at 74 d after transplanting. The principal component analysis revealed that MDA of all treatments had the greatest effect on the antioxidant system, while aerated drip irrigation reduced MDA content. Increasing aeration duration from A 25% to A 75% significantly affected antioxidant enzyme activities and root growth parameters, and the L treatment had higher values than the F treatment. The L -A 75% treatment had the highest water use efficiency, nitrogen uptake efficiency, and yield. The structural equation model demonstrated that ADI indirectly promotes tomato water and nitrogen uptake efficiencies by affecting the antioxidant system and root growth.

Perfluorodecalin-based oxygenated emulsion as a topical treatment for chemical burn to the eye

Chemical injuries to the eye are emergencies with limited acute treatment options other than prompt irrigation and can cause permanent vision loss. We developed a perfluorodecalin-based supersaturated oxygen emulsion (SSOE) to topically deliver high concentration of oxygen to the eye. SSOE is manufactured in hyperbaric conditions and stored in a ready-to-use canister. Upon dispensation, SSOE rapidly raises partial oxygen pressure 3 times over atmospheric level. SSOE is biocompatible with human corneal cells and safe on mouse eyes in vivo. A single topical application of SSOE to the eye after alkali injury significantly promotes corneal epithelial wound healing, decreases anterior chamber exudation, and reduces optical opacity and cataract formation in mice. SSOE treatment reduces intraocular hypoxia, cell death, leukocyte infiltration, production of inflammatory mediators, and hypoxia-inducible factor 1-alpha signaling, thus hastening recovery of normal tissue integrity during the wound healing process. Here, we show that SSOE is an effective topical therapeutic in the acute treatment of ocular chemical injuries.

Increased fire activity under high atmospheric oxygen concentrations is compatible with the presence of forests

Throughout Earth’s history, the abundance of oxygen in our atmosphere has varied, but by how much remains debated. Previously, an upper limit for atmospheric oxygen has been bounded by assumptions made regarding the fire window: atmospheric oxygen concentrations higher than 30–40% would threaten the regeneration of forests in the present world. Here we have tested these assumptions by adapting a Dynamic Global Vegetation Model to run over high atmospheric oxygen concentrations. Our results show that whilst global tree cover is significantly reduced under high O2 concentrations, forests persist in the wettest parts of the low and high latitudes and fire is more dependent on fuel moisture than O2 levels. This implies that the effect of fire on suppressing global vegetation under high O2 may be lower than previously assumed and questions our understanding of the mechanisms involved in regulating the abundance of oxygen in our atmosphere, with moisture as a potentially important factor.

Discrimination of phosgene from cyanogen chloride in recovered chemical munitions using tagged neutron interrogation with high-resolution gamma-ray spectroscopy

The associated particle (AP) technique has recently been used with a high-purity germanium γ-ray spectrometer to assess its capability to improve field identification of recovered chemical warfare (CW) materiel through prompt gamma-ray neutron activation analysis (PGNAA) measurements. A particularly challenging pair of CW agents commonly found in recovered munitions are phosgene (CG) and cyanogen chloride (CK), which have two of three elements in common, i.e. chlorine and carbon, but differ in the third being either oxygen or nitrogen. The detection of both latter elements is complicated by high oxygen concentration in the field environment which interferes with the small signal produced from the chemical agents. The matter is further complicated by the precautionary field practice of overpacking recovered munitions with vermiculite in larger steel multiple round containers (MRCs), which places additional oxygen-rich material in contact with the munition while further attenuating an already weak signal emitted from the munition center. This work reports quantitative results from realistic field measurements of CG and CK simulants in mock 4.2-inch (11 cm) mortar rounds overpacked with vermiculite in a large MRC. Results obtained with the AP technique are compared to those obtained with the traditional PGNAA approach for both overpacked- and bare-munition measurements. The AP technique is shown to provide a much more confident discrimination between the two chemicals, particularly for the more challenging field-relevant overpacked measurements, where a significant gain in sensitivity to all the key elements (chlorine, carbon, nitrogen and oxygen) is achieved.

Modeling and simulation study of simultaneous nitrification–denitrification in membrane aerated bioreactor

This study introduces a two-dimensional multi-species biofilm model to investigate the mechanisms of simultaneous nitrification–denitrification (SND) in membrane aerated bioreactors. We focus here on the effect of bulk concentration of oxygen, ammonium, and acetate on the SND performance, biofilm composition, and SND mechanism. The simulation results revealed that the oxygen distribution within the biofilm plays a determining role in achieving simultaneous nitrification and denitrification in MABR. The distribution of the autotrophs and heterotrophs within the biofilm is not clearly stratified due to the combined impact of cell diffusion and cross-diffusion of different species. The nitrification rate increases with the increase in bulk ammonium and oxygen concentrations while remaining relatively steady when the biofilm thickness increases. Biofilm thickness and acetate concentration have been substantiated as two regulating factors affecting the denitrification of MABR biofilm. High bulk oxygen and ammonium concentrations can significantly delay the establishment of the denitrification capacity of the biofilm but their impact on the denitrification rate drastically diminishes after the biofilm grows to a certain thickness. According to the modeling results, to achieve a quick establishment of denitrification capacity of the MABR biofilm, the bulk ammonia nitrogen and acetate concentrations should be in a range greater than 25 and 12 [gm−3], respectively, while the oxygen partial pressure on the gas side should be less than 0.342 bar. Thus, this study provides extensive insight into the impact of the bulk oxygen, ammonium, and acetate on the SND performance and biofilm composition and structure of MABR.

Preterm rabbit-derived Precision Cut Lung Slices as alternative model of bronchopulmonary dysplasia in preclinical study: a morphological fine-tuning approach

Bronchopulmonary dysplasia (BPD) is the most common complication of preterm delivery, with significant morbidity and mortality in a neonatal intensive care setting. Research in this field aims to identify the mechanisms of late lung development with possible therapeutic targets and the improvement of medical management. Rabbits represent a suitable lab preclinical tool for mimicking the clinical BPD phenotype. Rabbits are born at term in the alveolar phase as occurs in large animals and humans and in addition, they can be delivered prematurely in contrast to mice and rats. Continuous exposure to high oxygen concentration (95% O2) for 7 days induces functional and morphological lung changes in preterm rabbits that resemble those observed in BPD-affected babies. The preclinical research pays great attention to optimize the experimental procedures, reduce the number of animals used in experiments and, where possible, replace animal models with alternative assays, following the principle of the 3 Rs (Replace, Reduce and Refine). The use of in vitro assays based on the ex vivo culture of Precision Cut Lung Slices (PCLS) goes in this direction, representing a good compromise between controlled and flexible in vitro models and the more physiologically relevant in vivo ones. This work aims to set up morphological analyses to be applied in preclinical tests using preterm rabbits derived PCLS, cultured up to 7 days in different oxygen conditions, as a model. After a preliminary optimization of both lung preparation and histological processing methods of the lung slices of 300 µm, the morphological analysis was conducted evaluating a series of histomorphometric parameters derived from those widely used to follow the phases of lung development and its alterations in vivo. Our histomorphometric results demonstrated that the greatest differences from pseudo-normoxia and hyperoxia exposed samples at day 0, used as starting points to compare changes due to treatments and time, are detectable after 4 days of in vitro culture, representing the most suitable time point for analysis in preclinical screening. The combination of parameters suitable for evaluating PCLS morphology in vitro resulted to be Tissue Density and Septal Thickness. Shape Factor and Roughness, evaluated to highlight the increasing complexity of the airspaces, due to the formation of septal crests, gave useful information, however, without significant differences up to day 4. Other parameters like Mean Linear Intercept and Septal Density did not allow to highlight significant differences between different oxygen conditions and time points. Instead, Radial Alveolar Count, could not be applied to PCLS, due to the tissue changes following agar infusion and culture conditions.

Device modeling of two-steps oxygen anneal-based submicron InGaZnO back-end-of-line field-effect transistor enabling short-channel effects suppression

Amorphous oxide semiconductor (AOS) field-effect transistors (FETs) have been integrated with complementary metal-oxide-semiconductor (CMOS) circuitry in the back end of line (BEOL) CMOS process; they are promising devices creating new and various functionalities. Therefore, it is urgent to understand the physics determining their scalability and establish a physics-based model for a robust device design of AOS BEOL FETs. However, the advantage emphasized to date has been mainly an ultralow leakage current of these devices. A device modeling that comprehensively optimizes the threshold voltage (VT), the short-channel effect (SCE), the subthreshold swing (SS), and the field-effect mobility (µFE) of short-channel AOS FETs has been rarely reported. In this study, the device modeling of two-steps oxygen anneal-based submicron indium-gallium-zinc-oxide (IGZO) BEOL FET enabling short-channel effects suppression is proposed and experimentally demonstrated. Both the process parameters determining the SCE and the device physics related to the SCE are elucidated through our modeling and a technology computer-aided design (TCAD) simulation. In addition, the procedure of extracting the model parameters is concretely supplied. Noticeably, the proposed device model and simulation framework reproduce all of the measured current–voltage (I–V), VT roll-off, and drain-induced barrier lowering (DIBL) characteristics according to the changes in the oxygen (O) partial pressure during the deposition of IGZO film, device structure, and channel length. Moreover, the results of an analysis based on the proposed model and the extracted parameters indicate that the SCE of submicron AOS FETs is effectively suppressed when the locally high oxygen-concentration region is used. Applying the two-step oxygen annealing to the double-gate (DG) FET can form this region, the beneficial effect of which is also proven through experimental results; the immunity to SCE is improved as the O-content controlled according to the partial O pressure during oxygen annealing increases. Furthermore, it is found that the essential factors in the device optimization are the subgap density of states (DOS), the oxygen content-dependent diffusion length of either the oxygen vacancy (VO) or O, and the separation between the top-gate edge and the source-drain contact hole. Our modeling and simulation results make it feasible to comprehensively optimize the device characteristic parameters, such as VT, SCE, SS, and µFE, of the submicron AOS BEOL FETs by independently controlling the lateral profile of the concentrations of VO and O in two-step oxygen anneal process.

Microstructure evolution and mechanical property of powder metallurgy Ti6Al4V alloy with high oxygen concentrations

ABSTRACT High oxygen Ti6Al4V alloys are fabricated by vacuum sintering and hot rolling using hydrogenation-dehydrogenation Ti6Al4V powder and ZrO2 powder as raw materials. The complete dissolution of oxygen and zirconium atoms results in an increase in lattice constant and strength. As-rolled Ti64-ZrO2 sample exhibits a bimodal structure with a fine acicular α phase of around 1 μm. Ti64-0.75 ZrO2 alloy with equivalent oxygen content close to 0.6 wt.-% presents a good combination of the high tensile strength (1180.2 MPa) and sufficient elongation (7.3%). Therefore, the critical oxygen content for the ductile-to-brittle transition of powder metallurgy Ti6Al4V alloy can be improved by suitable preparation methods. The formation of a fine β transformation structure may be one of the reasons for maintaining sufficient ductility.

Preoxygenation with a 50% Concentration of Oxygen for 15 Minutes might Safely and Feasibly Prolong the Breath-Hold Duration during Radiotherapy: A Pilot Study

<h3>Purpose/Objective(s)</h3> Voluntary deep inspiration breath-hold (DIBH) has been wildly used during radiation for thoracic and abdominal tumors. While the main disadvantage of voluntary DIBH is its short duration per single breath-hold. Preoxygenation with a high concentration of oxygen (more than 50%) combined with mechanical hyperventilation induced hypocapnia has been used for prolonging the single breath-hold duration, however, its safety is still a concern. In this study, we aimed to investigate whether simple preoxygenation with a relatively safe oxygen concentration of 50% can feasibly prolong the single breath-hold duration. <h3>Materials/Methods</h3> 12 healthy volunteers aged 21-48 years (6 males and 6 females) without previous cardiovascular diseases were included. The single DIBH duration of room air in resting-state, the single DIBH duration of room air after 5 min, 15 min, and 30 min preoxygenation with 50% concentration of oxygen, respectively, were evaluated and compared using paired t-test. <h3>Results</h3> The mean DIBH duration in room air in resting-state was 51.5 ± 12.97 seconds. Compared with DIBH in room air, after 5, 15, and 30 minutes preoxygenation with 50% concentration of oxygen, the DIBH duration in room air was significantly increased up to 91.9 ± 28.3 (p<0.0001), 115.5 ±25.5 (p<0.0001), and 122.1 ±28.4 seconds (p<0.0001), respectively. Furthermore, compared with 5 minutes of preoxygenation, the DIBH duration after 15 and 30 minutes of preoxygenation was significantly increased with 23.5 ± 9.7 (p<0.0001) and 30.2 ± 13.7 seconds (p<0.0001). Compared with 15 minutes of preoxygenation, the DIBH duration after 30 minutes of preoxygenation was only increased with 6.7 ± 5.4 seconds (p=0.0013). <h3>Conclusion</h3> This pilot study demonstrated that simple preoxygenation with a 50% concentration of oxygen for 15 minutes might safely and feasibly prolong the DIBH duration during radiotherapy. Further studies are warranted to confirm these results and to identify how many cycles of a single breath-hold can be prolonged. This study has been supported by the National Nature Science Foundation of China (82171890 & 81701683), Key Research and Development Projects of Zhejiang Provincial Science and Technology Department (2021C03122), Health Commission of Zhejiang Province (2020KY131), and Zhejiang Provincial Key Discipline of Traditional Chinese Medicine (2017-XK-A32).

Dissolved and particulate iron redox speciation during the LOHAFEX fertilization experiment.

The redox speciation of iron was determined during the iron fertilization LOHAFEX and for the first time, the chemiluminescence assay of filtered and unfiltered samples was systematically compared. We hypothesize that higher chemiluminescence in unfiltered samples was caused by Fe(II) adsorbed onto biological particles. Dissolved and particulate Fe(II) increased in the mixed layer steadily 6-fold during the first two weeks and decreased back to initial levels by the end of LOHAFEX. Both Fe(II) forms did not show diel cycles downplaying the role of photoreduction. The chemiluminescence of unfiltered samples across the patch boundaries showed strong gradients, correlated significantly to biomass and the photosynthetic efficiency and were higher at night, indicative of a biological control. At 150m deep, a secondary maximum of dissolved Fe(II) was associated with maxima of nitrite and ammonium despite high oxygen concentrations. We hypothesize that during LOHAFEX, iron redox speciation was mostly regulated by trophic interactions.

Optical study of oxygen enrichment on methane combustion characteristics under high compression-ratio conditions

Natural gas is a promising fuel for IC engines with low carbon emissions, whereas its poor lean combustion performance at low load and low engine power output at high load remain a challenge for automobile manufacturers. Oxygen-enriched combustion can provide more opportunities for collisions between fuel and oxygen molecules; thus, methane combustion performance can be improved. In this work, using a high-compression-ratio optical engine, the effects of oxygen enrichment on methane combustion were comprehensively investigated, addressing the similarities and differences between high load and low load conditions. High-speed direct photography and simultaneous pressure were performed to capture detailed combustion evolutions. The results show that high oxygen concentration can greatly increase methane flame propagation speed under high energy density condition (high load). As a result, advanced combustion phase and high peak pressure are obtained by more concentrated heat release, which in turn are indicators for improvised thermal efficiencies. Under low energy density condition (low load), oxygen enrichment mainly acts as a promoter of the initial flame formation, which in turn are indicators for improvised combustion stability. A detailed comparison of flame characteristics confirms the different effects of oxygen enrichment on methane combustion under different energy density conditions. Besides, oxygen enrichment can significantly promote initial flame formation with a higher rate and lower cyclic variation, and a low degree of oxygen enrichment can also have a great effect. The current study shall give insights into the strategies for oxygen enrichment on methane engines’ performance at different loads.

A One-Dimensional Model of a PEM Fuel Cell with the Cathode Catalyst Layer Hydrophobically Treated for Water Management

A PEM fuel cell with a hydrophobically treated cathode catalyst layer (CL) demonstrates ∼220% peak power increase with humidified air at 70 °C. To understand the reasons of the increase, a mathematical model was developed focusing on the oxygen-water two-phase transport phenomena in the CL. It suggests the treatment affects the CL in two ways. First, the interface of the ionomer layer exposed to the gas pores becomes more hydrophobic, facilitating less liquid water coverage and faster water drainage from the CL and resulting in better performance at high current densities. Second, it also affects the hydration level in the ionomer phase resulting in higher oxygen concentration in the ionomer phase on and in the catalyst agglomerates, leading to higher performance over the whole polarization curve. The properties having significant influence on the model fitting the experimental data are the capillary pressure property of the CL, the hydrophobic ionomer ratio in the catalyst agglomerate, and the oxygen solubility/diffusivity in the Nafion® phases. With this experimentally verified model, additional case studies combining the hydrophobic gas diffusion material with the hydrophobic CL demonstrate that the membrane’s self-humidification (zero-net-water flux) and peak power enhancement (∼15%) can be reached simultaneously, providing direction for the future materials development.

GSOR22 Presentation Time: 12:15 PM: A Novel Radiosensitizer Kortuc Enhanced Brachytherapy for Unresectable Recurrent Uterine Cervical Cancer

<h3>Purpose</h3> To evaluate the tolerability, safety and efficacy of KORTUC Intratumoral injection with brachytherapy in unresectable recurrent cervical cancer. <h3>Materials and Methods</h3> A novel radiosensitizer KORTUC (Kochi Oxydol Radiation Therapy for Unresectable Carcinoma) was invested by Dr. Yasuhiro Ogawa at Kochi University (Japan) in 2006 and was developed for the treatment of malignant solid tumours that contain numerous hypoxic cancer cells and/or large quantities of antioxidative enzymes. Hydrogen peroxide is the only agent known to be capable of inactivating antioxidative enzymes and producing oxygen simultaneously when applied to tumour tissues. KORTUC is a solution that contains 3% hydrogen peroxide with 1% sodium hyaluronate. Hydrogen peroxide is the active ingredient for this radiosensitizer. Sodium hyaluronate viscosity sustains the hydrogen peroxide in the tumour as well as delays decomposition of hydrogen peroxide and maintains a high concentration of oxygen in the tumour. Injecting the two components together at a particular ratio is the key feature of this product. Currently Phase 2 clinical trial for locally advanced and recurrent breast cancer has been conducted in the United Kingdom and India. Our institution, (Osaka Medical and Pharmaceutical University, Japan) has conducted single-arm clinical research of KORTUC since May 2010, we dosed KORTUC more than 250 patients of various solid cancers including more than 40 patients of the gynecological tumors treated with brachytherapy as of today. In this study we report our experiences of KORTUC with brachytherapy in recurrent local advanced cervical cancer patients who are likely the high risk of poor prognosis.From April 2012 to January 2020, 15 female patients with recurrent cervical cancer received KORTUC with brachytherapy. Previous treatments of 15 recurrent patients were surgery (n=4), radiation therapy (n=8), surgery + radiation therapy (n=3). The primary lesion of these 15 patients were vaginal stump (n=5), pelvic wall (n=3), cervix (n=3), vaginal wall (n=2), and lymph node (n=2). KORTUC was injected intratumorally under direct vision of colposcopy prior to radiation therapy. The dose of KORTUC ranged from 4 to 12 mL adjusted by tumor size. For patients who had the Interstitial brachytherapy, KORTUC was administered before and after the applicator insertion prior to irradiation. <h3>Results</h3> Intratumoral injection of KORTUC was completed without any technical and safety issues in all 15 patients. KORTUC was well tolerated and no adverse events judged to be related to KORTUC injection were observed, except the transient local pain at the injection site in some patients. KORTUC also showed efficacy in local control in recurrent patients. <h3>Conclusion</h3> Based on this result, we would like to confirm in a future study, KORTUC's efficacy with external irradiation as well as brachytherapy for the newly diagnosed unresectable locally advanced cervical cancer with high risk factors of poor prognosis. KORTUC may have potential as an effective radiation response enhancer in multiple cancer types in which locoregional control after RT alone remains poor.

Analyte Enrichment via Ion Concentration Polarization with Hydrogel Plugs Polymerized in PDMS Microchannels by a Facile and Comprehensive Method for Improved Polymerization.

Hydrogels are incorporated into microfluidic devices to provide enhanced functionality by enabling processes such as enzyme immobilization, sample enrichment, and ionic current rectification. However, in the microfluidic devices with the commonly used material poly(dimethylsiloxane) (PDMS), hydrogels are very difficult to polymerize in situ in an ambient atmosphere because of the high oxygen concentration in PDMS. Even with very high (1.8%) photoinitiator concentrations, the polymerized hydrogel does not completely fill the microchannel. Here, we report a facile and broadly applicable protocol that utilizes microchannel pretreatment with 20% benzophenone in acetone to provide a hydrogel plug that completely fills the microchannel cross section by consuming the oxygen in the PDMS substrate near the microchannel wall. Both negatively charged and neutral hydrogels are polymerized from monomer solutions that utilize the photoinitiator/solvent combinations of VA-086 in water and benzophenone or IRG in DMSO. The photoinitiators were tested at different concentrations and in devices with different levels of oxidation. The hydrogel morphology is characterized using phase contrast microscopy and is related to the hydrogel's performance for concentration enrichment and ionic current rectification. A novel method is employed to confine the precursor solution in desired locations so that a photomask is not required for the spatial control of the plug location. Among six hydrogel formulations, at 100 V, the best current rectification factor obtained is ∼600 and the best analyte enrichment achieved is ∼120-fold in 5 min. This method provides a rapid and simple approach to increase the capabilities of PDMS microfluidic devices through improved polymerization of nanoporous hydrogels.

Exploration of oxygen-mediated disinfection of medical devices reveals a high sensitivity of Pseudomonas aeruginosa to elevated oxygen levels

The microbiological safety of medical devices is of paramount importance for patients and manufacturers alike. However, during usage medical devices will inevitably become contaminated with microorganisms, including opportunistic pathogens. This is a particular problem if these devices come in contact with body sites that carry high bacterial loads, such as the oral cavity. In the present study, we investigated whether high oxygen concentrations can be applied to disinfect surfaces contaminated with different Gram-positive and Gram-negative bacteria. We show that some opportunistic pathogens, exemplified by Pseudomonas aeruginosa, are particularly sensitive to oxygen concentrations above the atmospheric oxygen concentration of 21%. Our observations also show that high oxygen concentrations can be applied to reduce the load of P. aeruginosa on nebulizers that are used by cystic fibrosis patients, who are particularly susceptible to colonization and infection by this bacterium. We conclude that the efficacy of oxygen-mediated disinfection depends on the bacterial species, duration of oxygen exposure and the oxygen concentration. We consider these observations relevant, because gas mixtures with high oxygen content can be readily applied for microbial decontamination. However, the main challenge for oxygen-based disinfection approaches resides in a potentially incomplete elimination of microbial contaminants, which makes combined usage with other disinfectants like ethanol or hydrogen peroxide recommendable.

Association between timing of intubation and mortality in patients with idiopathic pulmonary fibrosis.

Delayed intubation is associated with poor prognosis in patients with respiratory failure. However, the effect of delayed intubation in patients with idiopathic pulmonary fibrosis (IPF) remains unknown. This study aimed to analyze whether timing of intubation after high-concentration oxygen therapy was associated with worse clinical outcomes in IPF patients. This retrospective propensity score-matched study enrolled adult patients with IPF who underwent mechanical ventilation between January 2011 and July 2021. Patients were divided into early and delayed intubation groups. Delayed intubation was defined as use of high-concentration oxygen therapy for at least 48 hours before tracheal intubation. The primary outcome was intensive care unit (ICU) mortality, and a conditional logistic regression model was used to evaluate the association between timing of intubation and clinical outcomes. The median duration of high-concentration oxygen therapy before intubation was 0.5 days in the early intubation group (n=60) and 5.1 days in the delayed intubation group (n=36). The ICU mortality rate was 56.7% and 75% in the early and delayed intubation groups, respectively, before propensity matching (P=0.075). After matching for demographic and clinical covariates, 33 matched pairs were selected. In the propensity-matched cohort, delayed intubation significantly increased the risk of ICU mortality (adjusted odds ratio, 3.99; 95% confidence interval, 1.02-15.63; P=0.046). However, in-hospital mortality did not differ significantly between the groups. In patients with IPF, delayed intubation after initiation of high-concentration oxygen therapy was significantly associated with increased risk of ICU mortality compared to early intubation.

Hypoxia promotes osteogenesis by facilitating acetyl-CoA-mediated mitochondrial-nuclear communication.

Bone-derived mesenchymal stem cells (MSCs) reside in a hypoxic niche that maintains their differentiation potential. While hypoxia (low oxygen concentration) was reported to critically support stem cell function and osteogenesis, the molecular events triggering changes in stem cell fate decisions in response to normoxia (high oxygen concentration) remain elusive. Here, we study the impact of normoxia on mitochondrial-nuclear communication during stem cell differentiation. We show that normoxia-cultured murine MSCs undergo profound transcriptional alterations which cause irreversible osteogenesis defects. Mechanistically, high oxygen promotes chromatin compaction and histone hypo-acetylation, particularly on promoters and enhancers of osteogenic genes. Although normoxia induces metabolic rewiring resulting in elevated acetyl-CoA levels, histone hypo-acetylation occurs due to the trapping of acetyl-CoA inside mitochondria owing to decreased citrate carrier (CiC) activity. Restoring the cytosolic acetyl-CoA pool remodels the chromatin landscape and rescues the osteogenic defects. Collectively, our results demonstrate that the metabolism-chromatin-osteogenesis axis is perturbed upon exposure to high oxygen levels and identifies CiC as a novel, oxygen-sensitive regulator of the MSC function.

Pocket reduction with High Concentrated oxygen oral gel: A Preliminary Case Report

Introduction: Oxygen is a prerequisite for successful wound healing due to the increased demand for reparative processes such as cell proliferation, bacterial defense, angiogenesis and collagen synthesis. Even though the role of oxygen in wound healing is not fully ascertained many experimental investigations and clinical observations have shown wound healing to be impaired under hypoxia. Since the periodontal pocket harbours anaerobic microorganisms a high concentrated oxygen formulation could prove to be a lethal elimination tool. Objective: The main objective of this study was to evaluate efficacy of high concentrated oxygen oral gel on the reduction of periodontal pocket. Materials and methods: A female patient of age 28 years without any systemic complication or allergic reaction reporting to Outpatient department of Krishnadevaraya College of Dental Sciences was examined. After ascertaining the presence of periodontal pocket (≥ 5mm) without infrabony defects, she was enlisted for the study. Following scaling and root planing and oral hygiene reinforcement, daily application of (Blue®M) TM oral gel for 7 days into the pocket was carried out, re-evaluation of the pocket depth was done after 30 days. Conclusion: High concentrated oxygen (Blue®M)TM oral gel could be locally delivering drug in reduction of periodontal pocket.

Hypoxia activates the unfolded protein response signaling network: An adaptive mechanism for endometriosis.

Endometriosis (EMS) is a chronic gynecological disease that affects women of childbearing age. However, the exact cause remains unclear. The uterus is a highly vascularized organ that continuously exposes endometrial cells to high oxygen concentrations. According to the "planting theory" of EMS pathogenesis, when endometrial cells fall from the uterine cavity and retrograde to the peritoneal cavity, they will face severe hypoxic stress. Hypoxic stress remains a key issue even if successfully implanted into the ovaries or peritoneum. In recent years, increasing evidence has confirmed that hypoxia is closely related to the occurrence and development of EMS. Hypoxia-inducible factor-1α (HIF-1α) can play an essential role in the pathological process of EMS by regulating carbohydrate metabolism, angiogenesis, and energy conversion of ectopic endometrial cells. However, HIF-1α alone is insufficient to achieve the complete program of adaptive changes required for cell survival under hypoxic stress, while the unfolded protein response (UPR) responding to endoplasmic reticulum stress plays an essential supplementary role in promoting cell survival. The formation of a complex signal regulation network by hypoxia-driven UPR may be the cytoprotective adaptation mechanism of ectopic endometrial cells in unfavorable microenvironments.

The Effects of Hypoxia on Threshold Food Concentrations in Different Daphnia Species

Numerous studies have revealed a negative correlation between the body size and temperature among a variety of aquatic ectotherms. Many studies at individual and population levels indicated that this mechanism may be explained by the decrease of competitive abilities of larger- over smaller-bodied individuals, as the production of larger-bodied individuals is more limited due to greater susceptibility to decreased oxygen concentrations (i.e., environmental hypoxia) at elevated temperatures. However, this hypothesis is still not tested at the community level. To test this, we performed several experiments on the food thresholds (which is a proxy for competitive ability) of 6 zooplankton (Daphnia) species varying in body size, at high or low oxygen concentrations. Contrary to the hypothesis tested, hypoxia increased threshold food concentrations to a relatively greater extent in smaller species than in larger ones. This may be attributed to the better evolutionary adaptations of larger-bodied daphnids to oxygen-poor environments manifested in higher production of haemoglobin. The results obtained in this study cannot exclude the possibility that environmental hypoxia is responsible for the temperature-size pattern in aquatic ectotherms, as our experiments did not take into account the long-term energetic costs of expedited haemoglobin synthesis, which could shift size-dependent competitive power.