Increased Oxygen Availability Research Articles

High‐Pressure Reactor Technology for Aerated Biotransformations

AbstractUtilizing pressure as a process parameter can make biotechnological processes more efficient and attractive compared to established ones. This paper presents a high‐pressure reactor setup for enzymatically catalyzed gas–liquid reactions, which can be operated up to 15.0 MPa. The reactor is equipped with optical measurement technology for inline and in situ monitoring of the oxygen concentration under high‐pressure conditions. The setup is characterized by assessing the influence of the process parameter pressure on the conversion of the glucose oxidation to d‐glucono‐δ‐lactone by immobilized glucose oxidase. The study demonstrates that the increased oxygen availability due to higher solubility reduces the reaction time in a batch reactor from 270 to 90 min.

Hyperbaric Oxygen Therapy (HBOT) in Moderate Traumatic Brain Injury (TBI): A Randomized Controlled Trial

Abstract Introduction Hyperbaric oxygen therapy (HBOT) is a novel technique recently under investigation with intention to improve outcomes in traumatic brain injury (TBI). It increases the partial pressure of oxygen in the blood and tissues by inhaling pure oxygen in an environment pressurized to at least 1.4 times normal atmospheric pressure (ATM) at sea level. The rationale behind the use of HBOT in TBI is its potential to mitigate the secondary brain injury cascade initiated by the primary mechanical trauma. Tissue damage and neuroinflammation secondary to intricate and complex cellular biochemical processes are expected to be counteracted by increased oxygen availability during HBOT, which reduces oxidative stress and improves neuroplasticity. Materials and Methods All patients, except whose legal guardians denied informed consent, with moderate TBI presenting to the neurotrauma center, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India, were included within the study period of June 2022 to July 2023. Patient allocation was randomized into two arms: namely, treatment and control arm. Simple randomization was done using randomization mobile app, RRApp. Each patient received standard of care per the Brain Trauma Foundation guidelines. Patients randomized under the treatment arm additionally received adjuvant HBOT sessions. One session daily for 10 consecutive days. Session duration was for 60 minutes each at 1.4 ATM. The primary objective of the study was to compare the Glasgow Coma Score (GCS) at discharge and 3-month post-TBI Glasgow Outcome Scale-Extended (GOS-E) among patients in the treatment arm (those who received adjuvant HBOT) with those in the control arm (those who received only standard of care). Results The mean GCS (±standard deviation [SD]) at discharge in the treatment arm was 14.37 (±00.51) with a median of 14 and a range of 14 to 15. Comparatively, the mean GCS (±SD) at discharge in the control arm was 13.40 (±00.84) with a median of 13 and a range of 12 to 15. The difference between the two arms was statistically significant (p < 0.001). GOS-E at 3 months postinjury for the treatment arm was 7.62 ± 00.51 (mean ± SD) with a median of 8 (range: 7–8). For the control arm, GOS-E at 3 months postinjury was 6.40 ± 1.50 (mean ± SD) with a median of 7 (range: 4–8). The difference between the two arms was statistically significant (p < 0.001). Conclusion The current study concludes that early adjuvant HBOT using 1.4 ATM with one session of one-hour daily for 10 days among adults sustaining moderate TBI significantly improves GCS at 10 days. Early adjuvant HBOT is also associated with significantly improved GOS-E at 3 months postinjury compared to standard of care alone.

Hyperbaric oxygen treatment reveals spatiotemporal OXPHOS plasticity in the porcine heart.

Cardiomyocytes meet their high ATP demand almost exclusively by oxidative phosphorylation (OXPHOS). Adequate oxygen supply is an essential prerequisite to keep OXPHOS operational. At least two spatially distinct mitochondrial subpopulations facilitate OXPHOS in cardiomyocytes, i.e. subsarcolemmal (SSM) and interfibrillar mitochondria (IFM). Their intracellular localization below the sarcolemma or buried deep between the sarcomeres suggests different oxygen availability. Here, we studied SSM and IFM isolated from piglet hearts and found significantly lower activities of electron transport chain enzymes and F1FO-ATP synthase in IFM, indicative for compromised energy metabolism. To test the contribution of oxygen availability to this outcome, we ventilated piglets under hyperbaric hyperoxic (HBO) conditions for 240 min. HBO treatment raised OXPHOS enzyme activities in IFM to the level of SSM. Complexome profiling analysis revealed that a high proportion of the F1FO-ATP synthase in the IFM was in a disassembled state prior to the HBO treatment. Upon increased oxygen availability, the enzyme was found to be largely assembled, which may account for the observed increase in OXPHOS complex activities. Although HBO also induced transcription of genes involved in mitochondrial biogenesis, a full proteome analysis revealed only minimal alterations, meaning that HBO-mediated tissue remodeling is an unlikely cause for the observed differences in OXPHOS. We conclude that a previously unrecognized oxygen-regulated mechanism endows cardiac OXPHOS with spatiotemporal plasticity that may underlie the enormous metabolic and contractile adaptability of the heart.

Decreased microbial phylogenetic diversity and community stability due to less bioavailable carbon and greater oxygen supply in Mollisols along a cultivation chronosequence

Soil microorganisms support multiple agroecosystem functions, but responses of the microbiome to prolonged agricultural land-use and underlying mechanisms remain poorly understood. In this study, upland soils in the Mollisol region of Northeast China were selected along a 100-year cultivation chronosequence to examine the effects of intensive agriculture on the diversity, composition and co-occurrence network of bacterial and fungal communities. To elucidate the determinants driving the dynamics and interactions of microbial communities, the researchers quantified the functional groups and bioavailable fractions of soil organic carbon, and estimated the microenvironments including soil texture and oxygen availability. Our findings revealed that fungal diversity and community stability decreased over cultivation time, while that of bacteria showed a less significant decline. The increased oxygen availability and decreased soil carbon supply, particularly polyphenols, jointly drove the dynamics in the composition and stability of the microbial communities. Crucially, these microbial responses were significantly regulated by interspecific associations. Phylotypes showing stronger responses to changes in oxygen availability and carbon supply demonstrated a higher level of connectivity within co-occurrence networks, signifying their potential role as pivotal “hubs” in transmitting the environmental influences across the entire community via interspecific associations. Moreover, the decline in fungal diversity over longer cultivation periods could liberate more survival niches for bacterial species through fungi-bacteria associations, thereby bolstering the stability of the bacterial community. Overall, this study accentuates the pivotal role of trophic associations in facilitating the oxygen and carbon-induced succession of belowground microbiota in long-term cultivated Mollisols. In view of the agricultural intensification propelled by the increasing demand for crop production, these findings suggest strategies integrating improvements in soil structure and carbon with microbial processes to ensure the sustainability of agroecosystem functions.

Antitumour effect of the mitochondrial complex III inhibitor Atovaquone in combination with anti-PD-L1 therapy in mouse cancer models

Immune checkpoint blockade (ICB) provides effective and durable responses for several tumour types by unleashing an immune response directed against cancer cells. However, a substantial number of patients treated with ICB develop relapse or do not respond, which has been partly attributed to the immune-suppressive effect of tumour hypoxia. We have previously demonstrated that the mitochondrial complex III inhibitor atovaquone alleviates tumour hypoxia both in human xenografts and in cancer patients by decreasing oxygen consumption and consequently increasing oxygen availability in the tumour. Here, we show that atovaquone alleviates hypoxia and synergises with the ICB antibody anti-PD-L1, significantly improving the rates of tumour eradication in the syngeneic CT26 model of colorectal cancer. The synergistic effect between atovaquone and anti-PD-L1 relied on CD8+ T cells, resulted in the establishment of a tumour-specific memory immune response, and was not associated with any toxicity. We also tested atovaquone in combination with anti-PD-L1 in the LLC (lung) and MC38 (colorectal) cancer syngeneic models but, despite causing a considerable reduction in tumour hypoxia, atovaquone did not add any therapeutic benefit to ICB in these models. These results suggest that atovaquone has the potential to improve the outcomes of patients treated with ICB, but predictive biomarkers are required to identify individuals likely to benefit from this intervention.

Study on the Effect of High-Concentration Oxygen Enrichment on Engine Performance and Exhaust Emissions Using Diesel Fuel and Palm Biodiesel Substitute Fuel

Air pollution remains a big issue in many countries. One form of air pollution comes from the use of fossil fuels as the primary fuel in the power generating and transportation sectors. Diesel engines are employed in a variety of industries due to their dependability, durability, and efficiency. Enhancing the availability of oxygen within the combustion chamber is one technique for reducing exhaust gas emissions and optimizing diesel engine combustion. The aim of this study is to investigate how oxygen enrichment in diesel engines with diesel fuel and biodiesel affects their performance and emissions. The modeling in this research was carried out using AVL BOOST version 2011 software based on experimental results of the YANMAR TF 155 R-DI diesel engine at 1200 rpm with and without oxygen enrichment. Modeling was performed based on the baseline parameter of a diesel engine with gradual loads at 50%, 75%, and 100%. The oxygen concentration was increased to 30.6%, 37.8%, 45%, and 54% by mass. The results show an increase in the maximum heat release rate (HRR) and the mass fraction burned (MFB) up to 90% for both fuels. The peak heat release rate of biodiesel shifts around 6 J/degree and the brake-specific fuel consumption (BSFC) is up to 0.0035 kg/kWh higher than that of diesel fuel. When compared to diesel fuel, the thermal efficiency and BSFC of biodiesel usage are around 0.3% and 0.028 kg/kWh, respectively. NOx emissions increase due to higher combustion temperatures and more oxygen availability. Biodiesel emits 50% less NOx than diesel fuel, presumably due to a lower combustion temperature. As a result, while high-concentration oxygen enrichment improves combustion and lowers soot emissions, it raises NOx emissions. Soot emissions were reduced as a result of the enhanced combustion process, while NOx emissions rose due to higher combustion temperatures and increased oxygen availability.

Human impact leads to unexpected oligotrophication and deepwater oxygen increase in a Swiss mountain lake

Human impacts on lakes can lead to nutrient release, increased algal productivity and consequently low oxygen concentrations in deepwater environments. Here we report the unexpected and contrasting finding of a pronounced shift to chironomid and invertebrate assemblages suggesting oligotrophication and oxygen increase in Lac de Champex, a Swiss mountain lake, due to human activities during the Mediaeval period. Chironomid assemblages in the lower part of the lake sediment record show changes that agree with known climatic shifts during the Lateglacial period and early Holocene and a progressively stronger influence of peat development, and possibly humic conditions, from ca. 8500 calibrated 14C years BP (cal. BP) onwards. This resulted in low chironomid influx and assemblages with high abundances of Procladius and Chaoborus ca. 2000–3000 cal. BP. These assemblages resemble those found in relatively nutrient-rich, oxygen-poor lakes and may have developed due to natural, long-term development to more nutrient-rich and possibly humic conditions, and from the Bronze Age (ca. 4000 cal. BP) onwards, due to human activities such as pasturing. Ca. 1000 cal. BP, an abrupt increase in sediment accumulation, chironomid influx and distinct changes in the chironomid assemblage composition were observed, coinciding with evidence for local human activities from pollen data. A major transition in chironomid and invertebrate assemblages followed ca. 500 cal. BP with the disappearance of Chaoborus, a decrease in Procladius, and the increase or appearance of several chironomid taxa, including several rheophilous groups. We conclude that Late-Holocene human impact led to re-oligotrophication and increased oxygen availability for invertebrates in the lake. This reversal of the long-term Holocene trend was possibly promoted by increased erosion from the Mediaeval period onwards and from ca. 500 cal. BP likely by the construction of an irrigation canal (bisse), leading to inflow of clear, cool water which changed the lake’s hydrological characteristics.

Oceanic Redox State During the Early Cambrian: Insights From Mo‐S Isotopes and Geochemistry of Himalayan Shales

AbstractThe Precambrian‐Cambrian (Pc‐C) boundary marks significant biological, atmospheric, and oceanic changes. These changes include extinction of the Ediacaran fauna, initiation of complex lifeforms, and oxygenation of the atmosphere and oceans. In this contribution, elemental and Mo‐S isotopic compositions of organic‐rich shales overlying the Pc‐C boundary from the Tal Formation, Lesser Himalaya, have been investigated. These datasets are used to reconstruct past oceanic redox state and sulfate concentrations. The principal component analysis of the elemental dataset identifies six major factors, with factors associated with organic matter and sulfide phases accounting for about half of the total variance. Iron speciation and Mo/U data suggest that the shales were deposited in anoxic and ferruginous deep water conditions. The δ98Mo data (1.5 ± 0.2‰) and their mass balance calculations indicate that the areal extent of sulfidic waters and pyrite burial rates were about 2–4 times higher during the Pc‐C transition than in the modern ocean. The pyrite‐δ34S values (3.6–8.3‰) for the Tal shales are isotopically heavier compared to modern‐day sedimentary pyrites (∼−21‰). Calculations involving earlier‐reported δ34S values for early Cambrian seawater and our measured pyrite‐δ34S data estimate the seawater sulfate concentration (8 ± 3 mM) during their deposition. This sulfate value for the Tal basin is higher than that reported for the late Neoproterozoic ocean (<5 mM), attributable to increasing oxygen availability and continental supply during this time. The observed basinal conditions and high terrestrial input may have influenced metazoan diversification.

Experimental investigation of emission parameters of diesel engine fueled with various plastic pyrolysis oils

Plastic has various advantages and is becoming more ubiquitous by the year, yet recycling and disposal remain challenges for the world. We conduct tests in this study to evaluate the appropriateness of various Plastic Pyrolysis Oils (PPOs) made from Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), and Polypropylene (PP) for diesel engine fuel. Determine which type of plastic pyrolysis oil would function best as an alternative fuel in an experimental investigation. The elemental composition of pyrolysis oil generated from LDPE, HDPE, and PP to diesel was assessed, tabulated, and compared in this study. This study examines emission characteristics (Nitrogen Oxide (NOX), Hydro Carbon (HC), and Carbon Monoxide (CO)) for Diesel, LDPE, HDPE and PP in CI engines using different injection pressure, compression ratio, and load in a specific configuration. In the result of experimental work the CO emission range for diesel and LDPE is exceeded only during overload situations or when the engine load is 100%. The average NOX emission is lowest when PP is used in comparison to other fuels, and the highest NOX emission occurs when LDPE is utilised as a fuel. Increased fumigation rates may be to blame for the rising hydrocarbon content of plastic oil. Unburned hydrocarbon levels are lower at lighter loads due to increased oxygen availability. The use of this whole pyrolysis oil results in a significant decrease in Nitrogen Oxide (NOX), Hydro Carbon (HC), and Carbon Monoxide (CO) exhaust emissions. With the help of this current study. one can solve plastic waste disposal problem and also find any unknown fuel (PPOs) that can be used as an alternative fuel for CI engine or not.

Kinetics of oxygen consumption, a key factor in the changes of young wines composition

The oxygen that a wine receives during the winemaking process defines its properties. The aim of this work was to evaluate the oxygen consumption capacity of wines and its influence on the modification of their composition. This preliminary work evaluated the changes after 3 months in the chemical composition of twenty-seven Spanish commercial red, white and rosé wines after their air saturation and oxidation process at 35 °C for 7 days. All the wines studied were high oxygen consumers, while the white and rosé wines showed greater variability according to their chemical composition. Wines that consumed a lot of oxygen did so quickly or slowly, while wines that consumed little oxygen did so slowly. All the wines showed a significant decrease in ethyl esters of straight-chain fatty acids (50–58%), ethyl esters of branched-chain fatty acids (48–56%) and alcohol acetates (34–65%) content, and a significant increase in Strecker aldehydes (24%) because of oxygen consumption. This paper presents a preliminary approach to determine the oxidation tendency of different wines showing the importance of controlling the winemaking processes that can increase oxygen availability and of establishing the minimum appropriate level of free sulfur dioxide.

Fetal oxygenation in the last weeks of pregnancy evaluated through the umbilical cord blood gas analysis.

Embryo and fetus grow and mature over the first trimester of pregnancy in a dynamic hypoxic environment, where placenta development assures an increased oxygen availability. However, it is unclear whether and how oxygenation changes in the later trimesters and, more specifically, in the last weeks of pregnancy. Observational study that evaluated the gas analysis of the umbilical cord blood collected from a cohort of healthy newborns with gestational age ≥37 weeks. Umbilical venous and arterial oxygen levels as well as fetal oxygen extraction were calculated to establish whether oxygenation level changes over the last weeks of pregnancy. In addition, fetal lactate, and carbon dioxide production were analyzed to establish whether oxygen oscillations may induce metabolic effects in utero. This study demonstrates a progressive increase in fetal oxygenation levels from the 37th to the 41st weeks of gestation (mean venous PaO2 approximately from 20 to 25 mmHg; p < 0.001). This increase is largely attributable to growing umbilical venous PaO2, regardless of delivery modalities. In neonates born by vaginal delivery, the increased oxygen availability is associated with a modest increase in oxygen extraction, while in neonates born by cesarean section, it is associated with reduced lactate production. Independently from the type of delivery, carbon dioxide production moderately increased. These findings suggest a progressive shift from a prevalent anaerobic metabolism (Warburg effect) towards a growing aerobic metabolism. This study confirms that fetuses grow in a hypoxic environment that becomes progressively less hypoxic in the last weeks of gestation. The increased oxygen availability seems to favor aerobic metabolic shift during the last weeks of intrauterine life; we hypothesize that this environmental change may have implications for fetal maturation during intrauterine life.

Contribution of a groundwater-influenced hinterland drainage system to the restoration of salmonid spawning grounds at the upper river Danube

Groundwater-influenced ditches, so called hinterland drainage systems (HDS), accompany many heavily modified water bodies (HMWBs). Herein, we evaluate the usefulness of including HDS as functional habitats in river restoration approaches by assessing their role as salmonid recruitment areas in HMWBs. We tested the functionality of spawning grounds in a groundwater-influenced HDS compared to the quality of those not influenced by groundwater (OHB 1 and OHB 2), based on bioindication using brown trout eggs. Eggs were placed in each compartment of a two-layered container of 20 cm diameter and 30 cm total depth (known as the HydroEcoSedimentary Tool or HEST) pre-filled with sediment, mimicking hyporheic conditions. A total of 81 HESTs were evenly distributed across the three sites to assess egg and larvae mortality whilst exposed at two substrate depths (5–10 cm and 17–22 cm). In addition, key physico-chemical variables such as dissolved oxygen, temperature, pH, turbidity, electric conductance and substratum composition were analyzed. Mean egg mortality in the HDS was 33% lower than in both non-groundwater-influenced spawning grounds, whereas mean larval mortality was highest in the HDS (95%) compared to 74% at OHB 1 and 66% at OHB 2. The exposure depth of eggs had a significant influence on mortality, with more dead eggs and larvae in the deeper substrate layers, most likely attributed to an increase of fine sediment and a decrease of oxygen availability over time. Particularly the HDS revealed high mortality rates of larvae since it had a 17% lower mean oxygen level compared to the other spawning grounds. These findings suggest that if additional measures such as substratum restoration were undertaken to increase oxygen availability within HDS, these groundwater-dominated ditches could be incorporated as part of an efficient river restoration strategy.

Going with the flow - how a stream insect, Pteronarcys californica, exploits local flows to increase oxygen availability.

For insects, life in water is challenging because oxygen supply is typically low compared with in air. Oxygen limitation may occur when oxygen levels or water flows are low or when warm temperatures stimulate metabolic demand for oxygen. A potential mechanism for mitigating oxygen shortages is behavior - moving to cooler, more oxygenated or faster flowing microhabitats. Whether stream insects can make meaningful choices, however, depends on: (i) how temperature, oxygen and flow vary at microspatial scales and (ii) the ability of insects to sense and exploit that variation. To assess the extent of microspatial variation in conditions, we measured temperature, oxygen saturation and flow velocity within riffles of two streams in Montana, USA. In the lab, we then examined preferences of nymphs of the stonefly Pteronarcys californica to experimental gradients based on field-measured values. Temperature and oxygen level varied only slightly within stream riffles. By contrast, flow velocity was highly heterogeneous, often varying by more than 125 cm s-1 within riffles and 44 cm s-1 around individual cobbles. Exploiting micro-variation in flow may thus be the most reliable option for altering rates of oxygen transport. In support of this prediction, P. californica showed little ability to exploit gradients in temperature and oxygen but readily exploited micro-variation in flow - consistently choosing higher flows when conditions were warm or hypoxic. These behaviors may help stream insects mitigate low-oxygen stress from climate change and other anthropogenic disturbances.

Oxygen availability regulates the quality of soil dissolved organic matter by mediating microbial metabolism and iron oxidation

Dissolved organic matter (DOM) plays a vital role in biogeochemical processes and in determining the responses of soil organic matter (SOM) to global change. Although the quantity of soil DOM has been inventoried across diverse spatio-temporal scales, the underlying mechanisms accounting for variability in DOM dynamics remain unclear especially in upland ecosystems. Here, a gradient of SOM storage across 12 croplands in northeast China was used to understand links between DOM dynamics, microbial metabolism, and abiotic conditions. We assessed the composition, biodegradability, and key biodegradable components of DOM. In addition, SOM and mineral-associated organic matter (MAOM) composition, soil enzyme activities, oxygen availability, soil texture, and iron (Fe), Fe-bound organic matter, and nutrient concentrations were quantified to clarify the drivers of DOM quality (composition and biodegradability). The proportion of biodegradable DOM increased exponentially with decreasing initial DOM concentration due to larger fractions of depolymerized DOM that was rich in small-molecular phenols and proteinaceous components. Unexpectedly, the composition of DOM was decoupled from that of SOM or MAOM, but significantly related to enzymatic properties. These results indicate that microbial metabolism exhibited a dominant role in DOM generation. As DOM concentration declined, increased soil oxygen availability regulated DOM composition and enhanced its biodegradability mainly through mediating microbial metabolism and Fe oxidation. The oxygen-induced oxidation of Fe(II) to Fe(III) removed complex DOM compounds with large molecular weight. Moreover, increased oxygen availability stimulated oxidase-catalyzed depolymerization of aromatic substances, and promoted production of protein-like DOM components due to lower enzymatic C/N acquisition ratio. As global changes in temperature and moisture will have large impacts on soil oxygen availability, the role of oxygen in regulating DOM dynamics highlights the importance of integrating soil oxygen supply with microbial metabolism and Fe redox status to improve model predictions of soil carbon under climate change.

Oxygen in Corneal Collagen Crosslinking to Treat Keratoconus: A Systematic Review and Meta-Analysis.

Keratoconus is a disorder that results in visual loss from increased corneal high-order aberrations and irregular astigmatism and reduces quality of life. The primary treatment for progressive keratoconus is crosslinking (CXL). Recently, it has been suggested that oxygen enhances the type II photodynamic reaction of CXL that is oxygen dependent. Our study investigated the effect of increased oxygen availability in epithelium-on CXL on visual acuity and corneal curvature. We searched PubMed, EMBASE, Medline, Web of Science, and Scopus databases on November 3, 2021. We included studies that reported increased oxygen availability during CXL in patients with keratoconus published within the last 10 years. A meta-analysis on the primary outcomes, maximum keratometry, and corrected distance visual acuity, was conducted. The search yielded 108 publications which were screened and assessed for eligibility. Six studies were included in the systematic review and 5 studies were included in our meta-analysis of the outcomes of increased oxygen availability in accelerated CXL. The meta-analysis on data after 6 months of follow-up found a significant decrease in mean maximum keratometry of 1.2 diopter (95% confidence interval: 0.2-2.3; P =0.02) and an improvement in mean corrected distance visual acuity by 0.08 logMAR (95% confidence interval, 0.02-0.13; P =0.01). There were no serious adverse events reported. Increasing oxygen during epithelium-on CXL improved visual acuity and produced corneal flattening without any serious adverse events in patients with keratoconus. The demarcation line depth was significantly higher with oxygen compared to the control group. Further data are required with a control group and long-term follow-up across a range of CXL protocols for implementation into standard clinical practice.

Why and How is Burrow Ventilation Initiated? A Case Study of Polychaete Behavior in the Burrow at Different Temperatures

Bioirrigation is a process corresponding to animal-induced transport of porewater solute or exchange between interstitial and overlying waters. How and why the burrowing macrobenthos complete this process remain unclear. Here, we used two infaunal-behavior observation devices to investigate the ventilation behaviors of the benthic polychaete Perinereis aibuhitensis Grube, a species that is widespread along the Asian coast with a wide temperature range, at various temperatures (5°C, 10°C, 15°C, 20°C, and 25°C). The two typical movement behaviors of P. aibuhitensis, axial crawling and radial undulation, as well as associated parameters, were delimited and quantified. We found that the radial undulation frequency of P. aibuhitensis and the associated pumping rate (PR) increased significantly with temperature (T, 5-25°C); this relationship can be described by the regression equation PR = −0.0067T2 + 0.29T - 0.52 (R2 = 0.749, P &amp;lt; 0.05; n = 15). The relationship between axial crawling velocity (ACV) and temperature (T, 5-25°C) can be expressed by the regression equation ACV = -0.0001T3 + 0.0059T2 - 0.063T + 0.28 (R2 = 0.997, P&amp;lt;0.05; n = 15). In general, pumping efficiency increased as temperature decreased, implying that the polychaete increasingly conserved energy at lower temperatures. Peak pumping volume (4.36 L d-1) was observed at 25°C, as a result of radial undulations. Thus, we concluded that radial undulation was the primary movement that led to bioirrigation. The dissolved oxygen demand was the key factor driving the initiation of radial undulation, and the specific aim of radial undulation was to increase oxygen availability by pumping new seawater into the burrow. Thus, radial undulation is critical for polychaete survival. The dissolved oxygen threshold level at which pumping was initiated increased with temperature, suggesting more energy conserved at lower temperatures. This pumping strategy of P. aibuhitensis is consistent with optimality theory, and is here designated the “optimal dissolved oxygen obtainment strategy”.

SRI LANKA OXYGEN READINESS AND STRATEGIES ADAPTED FOR COVID-19 PATIENTS’ MANAGEMENT

Background: Shortly after the Covid-19 oxygen crisis in India, the Sri Lanka Ministry of Health started investigating and analyzing gaps in oxygen production, supplies and demands. Aims: This study aimed to evaluate the preparedness in Covid-19 cases management and recommend strategies to prevent oxygen crisis in healthcare facilities. Methods: This study used information on oxygen source redundancy and delivery methods to assess whether a healthcare facility is prepared to provide the necessary oxygen demand for patients in need and to estimate the number of patients that can be treated with the currently available oxygen supplies. The predicted oxygen supplies and demands were assessed with a panel of experts using qualitative and quantitative methods. Data were collected using the Health Information Update System. Results: Sri Lanka had 39,529 designated hospital beds including Intensive Care Unit and High Dependency Unit beds for Covid-19 patients. Even though an average number of patients were reaching 30,000, the actual oxygen demands were around 1,200 which were easily manageable with the current capacity of 80 tons per day. Conclusions: Sri Lanka has made progress to increase access to oxygen by using novel methods to procure and increase oxygen availability, storing, and carrying capacity.

Air-loaded Gas Vesicle Nanoparticles Promote Cell Growth in Three-dimensional Bioprinted Tissue Constructs.

Three-dimensional (3D) bioprinting has emerged as a promising method for the engineering of tissues and organs. Still, it faces challenges in its widespread use due to issues with the development of bioink materials and the nutrient diffusion barrier inherent to these scaffold materials. Herein, we introduce a method to promote oxygen diffusion throughout the printed constructs using genetically encoded gas vesicles derived from haloarchaea. These hollow nanostructures are composed of a protein shell that allows gases to permeate freely while excluding the water flow. After printing cells with gas vesicles of various concentrations, the cells were observed to have increased activity and proliferation. These results suggest that air-filled gas vesicles can help overcome the diffusion barrier throughout the 3D bioprinted constructs by increasing oxygen availability to cells within the center of the construct. The biodegradable nature of the gas vesicle proteins combined with our promising results encourage their potential use as oxygen-promoting materials in biological samples.

Hypoxia Stress Induces Tissue Damage, Immune Defense, and Oxygen Transport Change in Gill of Silver Carp (Hypophthalmichthys molitrix): Evaluation on Hypoxia by Using Transcriptomics

The silver carp (Hypophthalmichthys molitrix) is an economically, as well as environmentally, important fish that harbors low environmental hypoxia tolerance and frequently contributes to a loss of aquaculture productivity. The gill is the first tissue attacked by hypoxia; however, the response of the gills of H. molitrix to hypoxia stress at the tissue, cellular, and molecular levels has not been clearly established. The influence of hypoxia on histological features along with gene expression in silver carp gills were explored in this research. The hematoxylin and eosin-stained sections and electron microscopy examinations of gills indicated that the gill lamellae were seriously twisted, gill filaments were dehisced, and the swelling and shedding of epithelial cell layer in the gill tissue were intensified along with the degree of hypoxia. In the hypoxia, semi-asphyxia, and asphyxia groups, the gill transcriptomic assessment of shifts in key genes, as well as modulatory networks in response to hypoxic conditions revealed 587, 725, and 748 differentially expressed genes, respectively. These genes are abundant in immune response signaling cascades (e.g., complement and coagulation cascades, Nucleotide-binding and oligomerization domain (NOD)-like receptor signaling cascade, and differentiation of Th1 along with Th2 cells) and oxygen transport [e.g., MAPK, PI3K-Akt, and hypoxia-inducible factor 1 (HIF-1) signaling cascades]. Genes linked to immune response (e.g., c2, c3, c6, klf4, cxcr4, cd45, and cd40) and oxygen transport (e.g., egln1, egln3, epo, ldh, and vegfa) were additionally identified. According to our findings, the silver carp may be using “HIF-1” to obtain additional oxygen during hypoxia. These findings illustrate that hypoxia stress might damage gill tissue, trigger an immunological response, and activate HIF-1 signaling to increase oxygen availability under hypoxic situations. The findings of this work will help scientists better understand the molecular mechanisms driving hypoxia responses in hypoxia-sensitive fish and speed up the development of hypoxia-resistant varieties.

Repeated Exposure to Mild Intermittent Hypoxia Mitigates the Severity of OSA, Reduces Blood Pressure and Improves Microvascular Function and Walking Endurance in Adults with OSA for 4 ‐ 8 Weeks Post Therapy

ObjectiveWe previously reported that repeated exposure to mild intermittent hypoxia (MIH) improves autonomic function and lowers blood pressure (BP) in adults with hypertension and obstructive sleep apnea (OSA). We also showed that the reduction in BP was concurrent with an improvement in upper airway (UA) collapsibility that might lead to a reduction in the severity of OSA. However, whether mitigation of OSA severity occurs and whether decreases in BP and UA collapsibility are sustained for long periods of time is unknown. Moreover, whether improved microvascular (MV) function is coupled to reductions in BP following MIH is unknown in OSA. Improved MV function could lead to increased oxygen availability to skeletal muscles and improved exercise endurance. Thus, we investigated if MIH promotes long‐term positive effects on UA collapsibility, BP, MV function and walking endurance in adults with hypertension and OSA.MethodsTwo males (age: 46 ± 7 yrs; BMI: 32.5 ± 2.3 kg/m2; systolic BP: 158 ± 6 mmHg) with OSA [apnea hypopnea index (AHI): 55.7 ± 2.8 events/hr] were exposed to twelve 2‐min hypoxic episodes (PETO2 ≍ 50 mmHg) separated by 2‐min normoxic intervals with sustained PETCO2 maintained 2 mmHg above baseline for 15 days and were treated with in‐home continuous positive airway pressure on nightly basis throughout the study. The active critical closing pressure (Acrit), AHI, 24‐hr BP, BP variability, post‐occlusion reactive hyperemia (PORH), and fatigability (i.e. 10‐min walk test) were measured before and 1 day, 4 weeks and 8 weeks after exposure to MIH. Based on the small sample size, Cohen’s D effect sizes are reported. Data are expressed as Δ from baseline ± SE.ResultsSystolic BP was reduced 1 day after (17.2 ± 2.1 mmHg, d = 2.4), and 4 (12.8 ± 1.2 mmHg, d = 1.7) and 8 wks. (4.1 ± 0.7 mmHg, d = 0.5) after MIH. Likewise, improvements in autonomic function were evident at the three time points after MIH (HF norm: 23 ± 19, 8 ± 7 and 11 ± 5 n.u. LF norm: ‐26 ± 14, ‐10 ± 3 and ‐13 ± 3 n.u., d &gt; 0.8 for all measures). Acrit decreased (‐2 ± 0 cmH2O) following MIH and the magnitude of this response was sustained for 4 and 8 wks. after MIH (d = 0.7 for all measures). Similarly, the AHI decreased at the three time points (‐10 ± 1.5 events/hr, d = 3.1, ‐20 ± 3 events/hr, d = 7.2, ‐24 ± 0.9 events/hr, d = 5.2) after MIH. In addition, the PORH response increased immediately after the MIH protocol (12.6 ± 2.2%, d = 5.9) and remained elevated at 4 wks. post MIH (3 ± 0.7%, d = 3.6) before returning to baseline values 8 wks. after MIH. The 10‐min walking distance increased (217 ± 48 m, d = 3.9) and fatigability reduced (‐17 ± 3.4% reduction in d = 4.9) 1 day following the MIH protocol. These modifications were sustained for 4 wks. (+151 ± 9 m, ‐11 ± 0.3% respectively, both d &gt; 0.8) and 8 wks. (+86 ± 38 m, ‐6 ± 2% respectively, both d &gt; 0.8) after MIH.ConclusionOur preliminary results suggest that exposure to MIH improves UA collapsibility and reduces the severity of OSA. Likewise, BP is reduced, and MV function is improved leading to increased walking endurance in adults with OSA. These modifications may be sustained for up to 8 weeks.