Variable Oxygen Levels Research Articles

Abstract 26 The Role of Oxygen in Cord Blood Hematopoietic Stem and Progenitor Cell Expansion and Engraftment

Abstract Introduction Hematopoietic stem (HSC) and progenitor cells (HPCs) are exposed to differing oxygen tensions ranging from <1% to 21% as they reside in/move through different tissues or are harvested for clinical utility. Functional changes in HSCs/HPCs are induced by acute changes in oxygen tension (e.g., a change in percent of cells in cycle). Objectives We sought to determine if variable oxygen levels affect expansion and/or functional properties of cord blood (CB) HSCs/HPCs ex vivo and in vivo. Methods Human CB CD34+ cells were grown in expansion culture +/-UM171, an agonist of HSC self-renewal that expands transplantable CB HSCs, in five oxygen tensions: 1%O2, 3%O2, 5%O2, 14%O2, and 21%O2. HSCs/HPCs were enumerated by flow cytometry. Functional HPCs were enumerated by plating in semi solid media for colony forming unit assays (CFU). Cell cycle and reactive oxygen species (ROS) were measured by flow cytometry. Ability of expanded cells to engraft was determined by transplantation in non-lethally irradiated NSG mice. Results Immunophenotypic HPCs and functional HPC CFUs expanded significantly more after 7 days of growth in higher oxygen tensions (5%O2-21%O2) compared to lower (1%O2-3%O2), while immunophenotypic HSCs expanded best at 5% O2. HSCs/HPCs grown in low oxygen tensions had significantly lower ROS levels, significantly higher percentage of cells in G0, and were slightly but reproducibly smaller/less granular than those grown in high oxygen levels. HSC/HPC numbers were reduced in high oxygen tensions 1-2 days after plating but were better maintained in low, suggesting cells undergo a culture shock/stress after plating that is mitigated by reduced oxygen. In the presence of UM171, HSCs expanded significantly better at higher oxygen levels, but HPCs are better maintained in 5%O2. Ex vivo CD34+ expansions maintained under physiological O2 levels (1-14%O2) demonstrated significantly better/faster neutrophil recovery following transplantation compared to cells expanded at 21%O2 or input. Discussion HSCs/HPCs proliferate rapidly in high oxygen but have fewer quiescent cells, higher ROS, and are larger and more granular which are all characteristics associated with exhaustion. While high oxygen allows for faster growth, low tensions may mitigate cell stress and allow for prolonged growth (i.e., HSC/HPC expansion) while maintaining functional properties.

PALLAS’ SPADEFOOT, <i>PELOBATES VESPERTINUS</i> (PALLAS 1771) (AMPHIBIA, PELOBATIDAE), THE SECOND AMPHIBIAN SPECIES TO TOLERATE EXTREME HYPOXIA

Pallas’ spadefoot is a Eurasian species of amphibian that winters for about half a year at a depth to 200 cm, always below the level of freezing, since it does not survive negative temperatures. However, significantly digging into the soil can cause oxygen deficiency. The minimum sufficient for a long-term existence of Pelobates vespertinus and the lethal oxygen content in the air were revealed, as well as metabolic pathways were evaluated under the conditions of normoxia and hypoxia in laboratory experiments. Beside this, the seasonal dynamics of temperatures and oxygen concentrations in sandy loam soils at different depths were determined in a typical wintering biotope of the species (the Oka River valley). Animals have been found to be capable of withstanding a tenfold decrease in oxygen content in soils compared to atmospheric oxygen for more than two months, thereby remaining quite active. When the concentration is decrease 20 times (up to 1%), a state of coma occurs, which is reversible if it lasts not more than a day. This shows a high degree of resistance of the species to stress resulting from reoxygenation and staying in an environment with variable oxygen levels. Thus, P. vespertinus is the second amphibian species following the Siberian frog (Rana amurensis), which can tolerate its complete absence for a long time (several months). Compared to body weight, the spadefoot has small storage organs (fat bodies and liver) and a low content of reserve substances (lipids and glycogen) in tissues, which are usually consumed at a low rate in normoxia at 3°C. During hypoxia, lipid utilisation is suspended and glycogen consumption is increased, indicating a shift from aerobic to predominantly anaerobic metabolism. The cumulative effect of reduced metabolism due to low temperature (3°C) and the activation of glycolysis due to the lack of oxygen provides a high level of resistance to hypoxia, distinguishing Pallas’ spadefoot from other swarming amphibian species studied. The oxygen content in the ground air of typical places at wintering depths (in sandy massifs) is shown to coincide with the atmospheric oxygen. The ubiquitous choice by the species of wintering areas with loose soils is assumed to be associated not with their excellent aeration, but rather with the ease of digging. The results obtained seem to be promising for using the study spadefoot (and possibly other species of the spadefoot genus, as well as burrowing toads) as model for exploring the adaptations to air oxygen deficiency.

Physiology in Perspective

EditorialPhysiology in PerspectiveNikki ForresterNikki ForresterAmerican Physiological Society, Rockville, MarylandPublished Online:20 Jan 2023https://doi.org/10.1152/physiol.00002.2023MoreSectionsPDF (79 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat This issue of Physiology features four outstanding review articles that summarize current knowledge and uncover areas for future research across a range of topics in physiology. First, we analyze how developmental hypoxia affects the vertebrate cardiovascular system. Next, we describe the role of coupling delay in synchronized oscillations, with a focus on the segmentation clock. Third, we evaluate mechanistic models for how the insular cortex regulates the physiological needs of organisms and their need-driven behaviors. Finally, we explore how breakthroughs in precision medicine can improve diagnoses and treatments for people with mental illness.The environment during early development can have profound effects on an organism’s morphology, physiology, function, and behavior. Adaptive responses to adverse temperature, oxygen, or pH conditions can persist throughout an organism’s lifetime and even across generations through epigenetic changes. Hypoxia, or an insufficient supply of oxygen, is a particularly common and disruptive environmental stressor. Whereas oxygen levels are tightly regulated in mammalian wombs, embryonic birds and ectothermic vertebrates can experience highly variable oxygen levels during development. Because the vertebrate cardiovascular system is heavily involved in mitigating oxygen deprivation, it is especially sensitive to developmental hypoxia. In this review, Galli et al. (1) conduct a comparative analysis of vertebrate cardiovascular responses to developmental hypoxia to identify common and novel responses as well as potential medical and ecological implications.In segmented animals, cells must be able to communicate with one another to ensure the proper segmentation of somites. Cells achieve this by sending and receiving information via signaling pathways, such as the Notch signaling pathway. The Notch signaling pathway plays a critical role in somitogenesis by coordinating the segmentation clock, which is a molecular oscillator that regulates the periodic formation of somites in embryos. If these oscillations are out of synchrony between cells, then somite segmentation does not occur properly, potentially causing respiratory complications or death. Mathematical models suggest that the time required to transmit signals between cells, or coupling delay, is important for oscillatory dynamics, but the biological implications of coupling delay remain less understood. In this review, Kageyama et al. (2) describe the biological importance of coupling delay in synchronized oscillations of the segmentation clock and reveal areas for future analysis.All cellular organisms must maintain the appropriate intracellular environment. When the necessary conditions for homeostasis are not met by the environment and cannot be regulated internally, organisms must take actions to fulfill their physiological needs. In multicellular animals, this process often involves powerful motivations, such as thirst or hunger, and the concerted action of different tissues and organs. However, the neural basis of the motivations that drive these behaviors is relatively unclear. Animal models suggest that the insular cortex receives internal sensory information and regulates physiological needs and need-driven behavior. In this review, Prilutski and Livneh (3) discuss mechanistic models for how the insular cortex regulates physiological needs, develop a framework for testing these models, and outline implications for various diseases and disorders.Diagnostic errors in mental disorders are common, with low inter-reliability and some studies reporting misdiagnosis rates of up to 66%. Even when patients are correctly diagnosed, the lack of clinical guidelines for drug selection can complicate a psychiatrist’s ability to select accurate treatments. Precision medicine holds the potential to improve care for patients with mental illness, in part through comprehensively exploring the physiological basis of such conditions. In addition, recent advancements in multi-omics technologies and data analytics can pave the way for better diagnostic tests and treatment decisions. In this review, Scala et al. (4) explore how breakthroughs in precision medicine and multi-omic physiological profiling can improve disease classification, psychiatric diagnoses, and treatments.No conflicts of interest, financial or otherwise, are declared by the author.

Oxygen Vacancy‐Mediated Catalysts toward Selective H2O2 Reduction in Cellular Environment

AbstractAbnormal hydrogen peroxide (H2O2) levels in the cellular environment are closely related to cell dysfunction and serious diseases. Thus, selective and sensitive H2O2 detections are urgently needed for clinical diagnosis and therapy. Herein, via surface defect engineering, an oxygen‐tolerant electrocatalyst based on tin oxide for selective H2O2 reduction and detection with exceptional stability and activity is designed and developed. When introduced at an appropriate level (≈5.3%), surface oxygen vacancies help lower the charge transfer resistance for enhancing the H2O2 reduction reaction, while maintain the weak oxygen (O2) adsorption, which enables a constant H2O2 reduction (sensing) response in the electrolyte at variable oxygen levels. Moreover, the tin oxide‐based assay system exhibits outstanding stability over a wide pH range of 4–9, as well as selectivity in the presence of interferent endogenous and exogenous electroactive species, which is suitable for trace H2O2 monitoring secreted from NB4 cells, a model cancer cell. The oxygen vacancy‐mediated tin oxide achieves the highest stability as well as high selectivity compared to reported electrochemical probes for specific H2O2 detection in biological environments, with the potential for biological and biomedical applications.

Live reporting for hypoxia: Hypoxia sensor-modified mesenchymal stem cells as in vitro reporters.

Natural oxygen gradients occur in tissues of biological organisms and also in the context of three-dimensional (3D) in vitro cultivation. Oxygen diffusion limitation and metabolic oxygen consumption by embedded cells produce areas of hypoxia in the tissue/matrix. However, reliable systems to detect oxygen gradients and cellular response to hypoxia in 3D cell culture systems are still missing. In this study, we developed a system for visualization of oxygen gradients in 3D using human adipose tissue-derived mesenchymal stem cells (hAD-MSCs) modified to stably express a fluorescent genetically engineered hypoxia sensor HRE-dUnaG. Modified cells retained their stem cell characteristics in terms of proliferation and differentiation capacity. The hypoxia-reporter cells were evaluated by fluorescence microscopy and flow cytometry under variable oxygen levels (2.5%, 5%, and 7.5% O2 ). We demonstrated that reporter hAD-MSCs output is sensitive to different oxygen levels and displays fast decay kinetics after reoxygenation. Additionally, the reporter cells were encapsulated in bulk hydrogels with a variable cell number, to investigate the sensor response in model 3D cell culture applications. The use of hypoxia-reporting cells based on MSCs represents a valuable tool for approaching the genuine in vivo cellular microenvironment and will allow a better understanding of the regenerative potential of AD-MSCs.

Variability in metagenomic samples from the Puget Sound: Relationship to temporal and anthropogenic impacts.

Whole-metagenome sequencing (WMS) has emerged as a powerful tool to assess potential public health risks in marine environments by measuring changes in microbial community structure and function in uncultured bacteria. In addition to monitoring public health risks such as antibiotic resistance determinants, it is essential to measure predictors of microbial variation in order to identify natural versus anthropogenic factors as well as to evaluate reproducibility of metagenomic measurements.This study expands our previous metagenomic characterization of Puget Sound by sampling new nearshore environments including the Duwamish River, an EPA superfund site, and the Hood Canal, an area characterized by highly variable oxygen levels. We also resampled a wastewater treatment plant, nearshore and open ocean sites introducing a longitudinal component measuring seasonal and locational variations and establishing metagenomics sampling reproducibility. Microbial composition from samples collected in the open sound were highly similar within the same season and location across different years, while nearshore samples revealed multi-fold seasonal variation in microbial composition and diversity. Comparisons with recently sequenced predominant marine bacterial genomes helped provide much greater species level taxonomic detail compared to our previous study. Antibiotic resistance determinants and pollution and detoxification indicators largely grouped by location showing minor seasonal differences. Metal resistance, oxidative stress and detoxification systems showed no increase in samples proximal to an EPA superfund site indicating a lack of ecosystem adaptation to anthropogenic impacts. Taxonomic analysis of common sewage influent families showed a surprising similarity between wastewater treatment plant and open sound samples suggesting a low-level but pervasive sewage influent signature in Puget Sound surface waters. Our study shows reproducibility of metagenomic data sampling in multiple Puget Sound locations while establishing baseline measurements of antibiotic resistance determinants, pollution and detoxification systems. Combining seasonal and longitudinal data across these locations provides a foundation for evaluating variation in future studies.

Late Artinskian–Early Kungurian (Early Permian) warming and maximum marine flooding in the East Gondwana interior rift, Timor and Western Australia, and comparisons across East Gondwana

Substantial new information is presented on upper Artinskian–Kungurian deposits in Timor-Leste and in the Canning, Southern Carnarvon and northern Perth basins of Western Australia. These basins, situated between about 35°S and 55°S palaeolatitude, formed part of the East Gondwana interior rift, a precursor to the rift that 100 my later formed the Indian Ocean in this region. Timor lay near the main axis of the East Gondwana interior rift, whereas the Western Australian basins were marginal splays from the rift axis. The main depocentres developed as a result of faulting that was initiated during the Late Pennsylvanian. Detailed lithostratigraphic and biostratigraphic analyses have been made on the newly recognized Bua-bai limestone and the type Cribas Group in Timor, the Noonkanbah Formation in the Canning Basin, the Byro Group in the Merlinleigh Sub-basin of the Southern Carnarvon Basin, and the Carynginia Formation in the northern Perth Basin. In Timor the succession, which is highly disrupted by faulting, was deposited under open-marine conditions probably in a shelf–basin setting. Restricted, very shallow-water seas flooded the Canning Basin and the Merlinleigh–Byro–Irwin sub-basins of the Southern Carnarvon and northern Perth basins and had highly variable oxygen levels and salinities typical of estuarine environments.A similar pattern of warming and bathymetric change is recognized in all studied basins. During the early part of the late Artinskian cool conditions prevailed, with water temperatures 0–4°C forming sea ice in the Merlinleigh–Byro–Irwin rift. Rapid warming during the latter part of the late Artinskian was accompanied by maximum marine flooding close to the Artinskian–Kungurian boundary. Climatic and bathymetric conditions then allowed carbonate mounds, with larger fusulines and a variety of algae, to develop in the northern part of the rift system, and Tubiphytes, conodonts, and brachiopods with Tethyan affinities to migrate into the marginal-rift basins despite the generally adverse water quality at these depositional sites.Comparison between the stratigraphic record from the East Gondwana interior rift and coeval records from Lhasa and Sibumasu indicate a similar pattern of climate change during the Carboniferous to end Cisuralian. Similar trends probably are present in Eastern Australia although there is confusion over the correlation of some units.

Oxygen and Nitrate Respiration in Streptomyces coelicolor A3(2).

Streptomyces species belong to the phylum Actinobacteria and can only grow with oxygen as a terminal electron acceptor. Like other members of this phylum, such as corynebacteria and mycobacteria, the aerobic respiratory chain lacks a soluble cytochrome c. It is therefore implicit that direct electron transfer between the cytochrome bc1 and the cytochrome aa3 oxidase complexes occurs. The complex developmental cycle of streptomycetes manifests itself in the production of spores, which germinate in the presence of oxygen into a substrate mycelium that greatly facilitates acquisition of nutrients necessary to support their saprophytic lifestyle in soils. Due to the highly variable oxygen levels in soils, streptomycetes have developed means of surviving long periods of hypoxia or even anaerobiosis but they fail to grow under these conditions. Little to nothing is understood about how they maintain viability under conditions of oxygen limitation. It is assumed that they can utilise a number of different electron acceptors to help them maintain a membrane potential, one of which is nitrate. The model streptomycete remains Streptomyces coelicolor A3(2), and it synthesises three nonredundant respiratory nitrate reductases (Nar). These Nar enzymes are synthesised during different phases of the developmental cycle and they are functional only under oxygen-limiting (<5% oxygen in air) conditions. Nevertheless, the regulation of their synthesis does not appear to be responsive to nitrate and in the case of Nar1, it appears to be developmentally regulated. This review highlights some of the novel aspects of our current, but somewhat limited, knowledge of respiration in these fascinating bacteria.

Cultivation of Arabidopsis cell cultures in a stirred bioreactor at variable oxygen levels: Influence on tocopherol production

In plants, an increased production of toxic oxygen species is commonly observed under low oxygen stress, but cellular responses still have to be fully investigated. Plant cell cultures can be a valuable tool to study plant metabolic responses to various environmental stresses including low oxygen condition. Arabidopsis suspension cultures growing in shake flasks were subjected to hypoxia by stopping shaking for different intervals, showing an increase of the antioxidant metabolite α‐tocopherol. In order to obtain a more controlled condition, cultivation of Arabidopsis suspension cultures was established in a 5‐l stirred bioreactor. A constant aeration of 20% dissolved oxygen was found to be the most suitable for cell growth. A 4‐h anoxic shock was induced by suspending the aeration and flushing into the vessel with nitrogen. During the anoxic stress, tocopherol levels resulted increased at the end of the treatment, indicating that the complete oxygen deprivation, indeed, induced a defence response involving antioxidant metabolism. The presence of an oxidative stress as a consequence of anoxic condition was also confirmed by the increased levels of H2O2. Overall, these results indicate that Arabidopsis suspension cultures grown in a stirred bioreactor can be a useful in vitro system for investigating low oxygen stress.

Response of ostracods to abrupt climate changes in the Western Mediterranean (Gulf of Lions) during the last 30kyr

Abstract Global climate changes attract the attention of researchers working with paleoceanographic proxies for reconstructing past ocean circulation changes and the physico-chemical parameters that control environmental conditions. Moreover, recent studies highlight the importance of climate change on deep sea benthic biodiversity. Deep sea benthic fauna are not isolated from atmospheric processes and climate changes controlling surface ocean biota, for benthic assemblages respond to changing climatic conditions as well. Substrate and physico-chemical characteristics of bottom waters have particularly strong influence on ostracod species distribution in all marine settings, making them excellent environmental indicators. This paper focuses on changes in ostracod assemblages at MD99-2348 site, located on the continental slope of the Gulf of Lions to determine the relationship between climatic-driven oceanographic changes and ostracod diversity and abundance. High abundances of Henryhowella asperrima and Echinocythereis echinata during Heinrich events (HE1 and HE2) may result from increased oxygenation of the bottom water and a more pulsed supply of nutrients (organic matter). Formation of surface cold water that increases the oxygen content in deep layers in the water column is linked to the intensification of northerly wind (Tramontane and Mistral) in northwestern Mediterranean during the acme of HEs, when high latitudes bodies of cold air (Mobile Polar Highs) reach the Mediterranean area. Moreover, the concomitant high abundance of Krithe pernoides , which proved to be very sensitive to variable oxygen levels, probably records even shorter (millennial to centennial scale) climate oscillations. Changes in environmental conditions are illustrated by the shift of C . testudo–Loxoconcha spp. vs. Pseudocythere sp.– Macrocypris sp. that indicates detrital input, primary productivity and the possible impact of sea level oscillation on benthic assemblages since the LGM.

Macrobenthic community structure in a high-productivity region: Upper Campanian Mishash Formation (Israel)

A paleoecological study of molluscan fossils from the Upper Campanian Mishash Formation of southern Israel was undertaken to provide new insights into the inference of bottom-oxygen levels, food availability and bottom water energy on high-productivity seafloors. Quantitative data for molluscan analysis were collected from each of the main lithologies that comprises the high-productivity facies-mosaic of the Mishash sea, i.e., organic-rich carbonates, thin-porcelanite and -chert beds, and loosely- to densely-packed shell beds. Diagenesis has obliterated faunal remains in carbonate layers. Pollution studies in modern environments have demonstrated the close connection between stressful conditions – such as organic load, toxicity and water and sediment aeration – and benthic community structure, as expressed through species richness, evenness, taxonomic composition, body sizes, and trace fossil assemblages. These connections and behavior patterns were investigated in the varied benthic fossil assemblages of the Phosphate Member of the Mishash Formation. Bivalves and gastropods dominated the macrofauna in all rock types but in varying abundance and taxonomic compositions, changing from diverse assemblages (15–22 species per sample) to less rich ones (5–7 species) and even barren intervals. This range of abundance neatly describes the lateral mosaic and heterogeneous nature of the upwelling environment of the Upper Campanian and is comparable to the mosaic of sub-facies that characterize modern upwelling facies-belts today (e.g., in the Benguela upwelling system). The variations shown for the macrobenthic assemblages within the Mishash Formation high-productivity regime are associated with proximity to the high-productivity center or to periods of intensified upwelling. The inferred, variable oxygen levels and organic-load changes point up how dynamic these regions really are. This is expressed in community structure and composition, which vary between two extremes: The low-oxygen biofacies 1 is characterized by a smaller range of shell sizes, infaunal deposit feeders and low species richness, while the high-oxygen biofacies 3 is characterized by greater ranges in shell size, infaunal but also epifaunal suspension feeders and higher species richness. The chert and porcelanite beds exhibit a variety of sub-environments and seem to represent an intermediate facies that bridges the two extremes of biofacies 1 and 3. The above ecological criteria may provide evidence of the original carbonate environment for the thin-chert and -porcelanite layers. The chert or porcelanite samples that contain a moderately even and rich assemblage of species intermediate to the values of the two end-member facies are taken to represent a shallow-water carbonate marine environment marginal to the upwelling center, whereas layers of chert and porcelanite containing very low species richness and evenness are taken to characterize primary depositional environments proximal to the paleo-upwelling cells.