Oxygen is a key regulator of both development and homeostasis and a promising candidate to bridge the influence of the environment and the evolution of new traits. To clarify the various ways in which oxygen may modulate embryogenesis, its effects are reviewed at distinct organizational levels. First, the role of pathways that sense dioxygen levels and reactive oxygen species are reviewed. Then, the effects of microenvironmental oxygen on metabolism, stemness, and differentiation throughout embryogenesis are discussed. Last, (...) the interplay between ecology and development are reexamined with a focus on the evolution of tetrapods, including during the emergence of a novel mechanism that shapes amniote limbs—interdigital cell death. Both genetic and environmental components work together during the formation of organisms, highlighting the importance of a multidisciplinary approach for understanding the evolution of new traits. (shrink)

Recent studies challenge the classical view that the origin of animal life was primarily controlled by atmospheric oxygen levels. For example, some modern sponges, representing early‐branching animals, can live under 200 times less oxygen than currently present in the atmosphere – levels commonly thought to have been maintained prior to their origination. Furthermore, it is increasingly argued that the earliest animals, which likely lived in low oxygen environments, played an active role in constructing the well‐oxygenated conditions typical (...) of the modern oceans. Therefore, while oxygen is still relevant to understanding early animal evolution, the relationships between the two might be less straightforward than previously thought. (shrink)

Introduction of O2 to Earth's early biosphere stimulated remarkable evolutionary adaptations, and a wide range of electron acceptors allowed diverse, energy-yielding metabolic pathways. Enzymatic reduction of O2 yielded a several-fold increase in energy production, enabling evolution of multi-cellular animal life. However, utilization of O2 also presented major challenges as O2 and many of its derived reactive oxygen species are highly toxic, possibly impeding multicellular evolution after the Great Oxidation Event. Remarkably, ROS, and especially hydrogen peroxide, seem to play a (...) major part in early diversification and further development of cellular respiration and other oxygenic pathways, thus becoming an intricate part of evolution of complex life. Hence, although harnessing of chemical and thermo-dynamic properties of O2 for aerobic metabolism is generally considered to be an evolutionary milestone, the ability to use ROS for cell signaling and regulation may have been the first true breakthrough in development of complex life. The importance of Earth's oxygen cycle and reactive oxygen species produced on the evolution of complex life. The ability to detoxify oxygen species is not a trait that emerged as a response to increased O2 levels but rather crucial adaptation to the early Earth's weakly oxic microenvironments. (shrink)

Reactive oxygen species (ROS) are known as toxic metabolic products in plants and other aerobic organisms. An elaborate and highly redundant plant ROS network, composed of antioxidant enzymes, antioxidants and ROS-producing enzymes, is responsible for maintaining ROS levels under tight control. This allows ROS to serve as signaling molecules that coordinate an astonishing range of diverse plant processes. The specificity of the biological response to ROS depends on the chemical identity of ROS, intensity of the signal, sites of production, (...) plant developmental stage, previous stresses encountered and interactions with other signaling molecules such as nitric oxide, lipid messengers and plant hormones. Although many components of the ROS signaling network have recently been identified, the challenge remains to understand how ROS-derived signals are integrated to eventually regulate such biological processes as plant growth, development, stress adaptation and programmed cell death. (shrink)

Reactive oxygen species (ROS) are highly reactive molecules produced in cells. So far, they have mostly been connected to diseases and pathological conditions. More recent results revealed a somewhat unexpected role of ROS in control of developmental processes. In this review, we elaborate on ROS in development, focussing on their connection to epithelial tissue morphogenesis. After briefly summarising unique characteristics of epithelial cells, we present some characteristic features of ROS species, their production and targets, with a focus on proteins (...) important for epithelial development and function. Finally, we provide examples of regulation of epithelial morphogenesis by ROS, and also of developmental genes that regulate the overall redox status. We conclude by discussing future avenues of research that will further elucidate ROS regulation in epithelial development. (shrink)

The respiration of oxygen, while essential to aerobic organisms for the generation of energy, leads to the formation of reactive oxygen intermediates (ROIs) as harmful byproducts. ROIs damage nucleic acids, lipids and proteins. Therefore, protective mechanisms against elevated intracellular ROI levels, referred to as oxidative stress, have evolved. These include the activation of transcription factors which elevate the expression of protective enzymes. Eukaryotic cells have also evolved the ability to specifically generate ROIs are used as second messengers to (...) activate gene expression. Here we will discuss both prokaryotic and eukaryotic transcription factors that respond to ROIs. In addition, transcription factors will be described that are activated by either exposure to antioxidants, which reduce the intracellular ROI concentration, or by hypoxia, the absence of oxygen. (shrink)

The influence of sediment oxygen heterogeneity, due to bioturbation, on diffusive oxygen flux was investigated. Laboratory experiments were carried out with 3 macrobenthic species presenting different bioturbation behaviour patterns: the polychaetes Nereis diversicolor and Nereis virens, both constructing ventilated galleries in the sediment column, and the gastropod Cyclope neritea, a burrowing species which does not build any structure. Oxygen two-dimensional distribution in sediments was quantified by means of the optical planar optode technique. Diffusive oxygen fluxes and (...) a variability index were calculated on the captured oxygen images. All species increased sediment oxygen heterogeneity compared to the controls without animals. This was particularly noticeable with the polychaetes because of the construction of more or less complex burrows. Integrated diffusive oxygen flux increased with oxygen heterogeneity due to the production of interface available for solute exchanges between overlying water and sediments. This work shows that sediment heterogeneity is an important feature of the control of oxygen exchanges at the sediment–water interface. (shrink)

Since Deleuze’s suicide on Saturday, 4 November 1995, there have been a number of attempts to reconcile this event with the sense of vitalistic affirmation that pervaded his philosophy. This article questions the tendency to reterritorialise the event of Deleuze death in accordance with a Deleuzian orthodoxy, while taking particular issue with an all too ‘evidential’ account that was recently offered by Beaulieu and Ord. In contrast to this, our design fictional approach rallies images, anecdotes and constructive falsehoods in order (...) to explore the intolerably sadomasochistic coupling of Deleuze to his oxygen machine, his umbilical attachment to Guattari, and his creative misuse of architecture (both philosophical and otherwise), in a bid to foreground the pluralistic, evential nature of Deleuze’s death – positioned, masochistically, as a beckoning for a people to come. (shrink)

Although the generation of reactive oxygen species is an activity normally associated with phagocytic leucocytes, mammalian spermatozoa were, in fact, the first cell type in which this activity was described. In recent years it has become apparent that spermatozoa are not the only nonphagocytic cells to exhibit a capacity for reactive oxygen species production, because this activity has been detected in a wide variety of different cells including fibroblasts, mesangial cells, oocytes, Leyding cells endothelial cells, thryroid cells, adipocytes, (...) tumour cell and platelets. Since the capacity to generate reactive oxygen species is apparently so widespread, the risk‐benefit equation for these potentially pernicious molecules becomes a matter of intese interest. In the case of human spermatozoa, the risk of manufacturing reactive oxygen metabolites is considerable because these cells are particularly vulnerable to lipid peroxidation. Indeed, there is now good evidence to indicate that oxygen radicals are involved in the initiation of peroxidative damage to the sperm plasma membrane, seen in many cases of male infertility. This risk is off‐set by recent data suggesting that superoxide anions and hydrogen peroxide also participate in the induction of key biological events such as hyperactiavated motility and the acrosome reaction. Thus, human spermatozoa appear to use reactive oxygen species for a physiological purpose and have the difficult task of ensuring the balanced generation of these potentially harmful, but biologically important, modulators of cellular function. (shrink)

Extracorporeal membrane oxygenation (ECMO) is a form of life support for cardiac and/or pulmonary failure with unique ethical challenges compared to other forms of life support. Ethical challenges with ECMO exist when conventional standards of care apply, and are exacerbated during periods of absolute ECMO scarcity when “crisis standards of care” are instituted. When conventional standards of care apply, we propose that it is ethically permissible to withhold placing patients on ECMO for reasons of technical futility or when patients have (...) terminal, short-term prognoses that are untreatable by ECMO. Under crisis standards of care, it is ethically permissible to broaden exclusionary criteria to also withhold ECMO from patients who have a low likelihood of recovery, to maximize the overall number of lives saved. Unilateral withdrawal of ECMO against a patient’s preferences is unethical under conventional standards of care, but is ethical under crisis standards of care to increase access to ECMO to others in society. ECMO should only be rationed when true scarcity exists, and allocation protocols should be transparent to the public. When rationing must occur under crisis standards of care, it is imperative that oversight bodies assess for inequities in the allocation of ECMO and make frequent changes to improve any inequities. (shrink)

In two studies, children's concepts of various types of ordinarily unobservable entities were examined. Study 1 confirmed earlier findings in showing that children aged 4–9 years are confident of the existence of scientific entities such as germs as well as religious beings such as God. At the same time, both age groups are skeptical of the existence of various mythical beings such as mermaids. In Study 2, older children aged 10–12 years were probed for their concepts of religious as compared (...) to scientific phenomena. Despite considerable confidence in each type, older children differentiated between them, both with respect to their level of confidence and their pattern of justification. (shrink)

Tissue oxygen saturation quantification was obtained using a frequency-domain multi-source method based on two wavelength light-emitting diodes. Brain saturation was 60·3±1·1%. Brachioradial muscle saturation declined during forearm ischaemia and maximal voluntary contraction from 73·7±1·8 and 74·7±1·8% at rest to 44·2±3·3 and 61·4±2·9%, respectively. © 1995 IFMBE.

Oxygenated derivatives of cholesterol (oxysterols) are widely distributed in nature, being found in the blood and tissues of animals and man as well as in foodstuff. They exhibit many biological activities which are of potential physiological, pathological or pharmacological importance. Many oxysterols have been found to be potent inhibitors of cholesterol biosynthesis and one or more oxysterols may play a role as the physiologic feedback regulator of cholesterol synthesis. Oxysterols also inhibit cell replication and have cytotoxic properties effects which suggest (...) that these sterols may participate in the regulation of cell proliferation and may be potentially useful as therapeutic agents for cancer. Furthermore, there is considerable evidence that oxysterols may be involved in the pathogenesis of atherosclerosis. Although the mechanism of action of oxysterols in all these instances is not well understood, the existence of cytosolic and microsomal proteins which bind oxysterols with high affinity and specificity suggests that this group of compounds may represent a family of intracellular regulatory molecules. (shrink)

In an in vivo situation, the tissue near a blood vessel is rich in oxygen supply compared to the one far from a blood vessel. In this article, our objective is to explore the effect of non-uniform oxygen supply on the development of the necrotic core of a tumor. We adopt a multiphase continuum-based approach to model the growth of a tumor. To simulate the model, a finite-difference-based numerical approach in line with the “Semi-Implicit Method for Pressure-Linked Equations" (...) (SIMPLE) algorithm is adopted. Investigations reveal that the necrotic core develops near the boundary with lower oxygen concentration. The position of the necrotic core strongly depends on the oxygen supply through the tumor boundary. The results predict asymmetrical tumor growth under unequal oxygen supply at tumor boundaries. Also, it is hinted that a tumor with a larger necrotic core grows more slowly than a tumor containing a smaller necrotic core. The present model has the potential to anticipate in vivo and in vitro situations. The findings will be beneficial for clinicians and medical practitioners in predicting the stage of a tumor. (shrink)

Neonatal extracorporeal membrane oxygenation (ECMO), a technology for the treatment of respiratory failure in newborns, is used as a case study to examine statistical and ethical aspects of clinical trials and to illustrate a proposed 'ethics of evidence', an approach to medical uncertainty within the context of contemporary biomedical ethics. Discussion includes the twofold aim of the ethics of evidence: to clarify the role of uncertainty and scientific evidence in medical decision-making, and to call attention to the need to confront (...) the irreducible nature of uncertainty. (shrink)

Inner membranes of mitochondria are extensively folded, forming cristae. The observed overall correlation between efficient eukaryotic ATP generation and the area of internal mitochondrial inner membranes both in unicellular organisms and metazoan tissues seems to explain why they evolved. However, the crucial use of molecular oxygen (O2) as final acceptor of the electron transport chain is still not sufficiently appreciated. O2 was an essential prerequisite for cristae development during early eukaryogenesis and could be the factor allowing cristae retention upon (...) loss of mitochondrial ATP generation. Here I analyze illuminating bacterial and unicellular eukaryotic examples. I also discuss formative influences of intracellular O2 consumption on the evolution of the last eukaryotic common ancestor (LECA). These considerations bring about an explanation for the many genes coming from other organisms than the archaeon and bacterium merging at the start of eukaryogenesis. (shrink)

This paper deals with the computational modelling of the bioluminescence pattern formation in suspensions of luminous Escherichia coli bacteria. The aim of this work is to improve the reaction–diffusion–chemotaxis model by introducing modulation functions applied to the rates of the bacterial growth, the chemoattractant production and the oxygen consumption as well as to investigate the influence of the function form on the spatiotemporal pattern formation in an E. coli colony. The nonlinear two-dimensional-in-space model was used to simulate the pattern (...) formation in aqueous cultures of bacteria along the inner lateral surface and along the three-phase contact line of a cylindrical micro-container. The simulated patterns are analysed in order to determine the form of the modulation functions and values of the model parameters closely matching patterns experimentally observed in a luminous E. coli colony. A linear stability analysis of the corresponding one-dimensional-in-space model is applied to determine values of the parameters triggering the self-organisation of the bacterial colony. The numerical simulation at the transient conditions was carried out using the finite difference technique. (shrink)

The so-called Chemical Revolution in the late 18th century often related chemistry to Lavoisier’s discovery of oxygen. It is argued that modern chemistry, and its rise as a scientific discipline, which began maybe from the 17th century but reached a kind of maturity with Lavoisier, or later, with Dalton, needs a more thorough analysis of its scientific and epistemic networks. Though a lot of detailed work devoted to the discoveries of “oxygen” has done, a more thorough understanding of (...) the Chemical Revolution needs a deeper understanding of the following crucial issues: I) The interrelatedness of seemingly unconnected disciplines such as historiography of chemistry, philosophy of chemistry and sociology of science; II) The merits of different concepts of phlogiston theories as well as the rise of Lavoisier’s chemical theories were transmitted and transformed in scientific networks. Analyses of how the inner circle of Lavoisierians—as a scientific community—exchanged ideas as well as adherents of phlogiston theories, such as Scheele and Priestley, lead us to the conclusion: Rejecting phlogiston theory as a whole is as irrational and fruitless as asserting that Lavoisier’s oxygen theory is—in plain and simple terms—correct. III) We agree that in a very specific notion we are justified to label the changing chemical paradigms from 1770s to 1790s a chemical revolution. We will argue that Lavoisier, as the head of a scientific research group, was part of a chemical revolution for several reasons: a) revolution of vocational training for chemists, b) growing and intensified importance of manifold communication, c) chemical theory with unifying and explanatory power as a “package deal”, and d) a special version of rationalism that was very much influenced by social factors and shaped a style of chemical reasoning. (shrink)

It has been assumed that at the whole organismal level, the mitochondrial reactive oxygen species (ROS) production is proportional to the oxygen consumption. Recently, a number of researchers have challenged this assumption, based on the observation that the ROS production per unit oxygen consumed in the resting state of mitochondrial respiration is much higher than that in the active state. Here, we develop a simple model to investigate the validity of the assumption and the challenge of it. (...) The model highlights the significance of the time budget that mitochondria operate in the different respiration states. The model suggests that under three physiologically possible conditions, the difference in ROS production per unit oxygen consumed between the respiration states does not upset the proportionality between the whole animal ROS production and oxygen consumption. The model also shows that mitochondrial uncoupling generally enhances the proportionality. (shrink)

The paper covers detailed analysis of scientific revolution in chemistry showing the mutual biases between phlogiston and oxygen theory.

SummaryFrom a survey of the literature it appears that many inorganic oxidations yield hydrogen while inorganic reductions may yield oxygen.As many organisms are known to be able to utilize hydrogen as a source of energy in their carbon dioxide assimilation the generation of hydrogen in the inorganic milieu may be the unifying principle in the metabolism of the chemo-autotroph.Such is in keeping with the Unitarian theory of biochemistry proposed by the late Professor A. J.Kluyver in 1925.

Background In Switzerland, right-to-die organisations assist their members with suicide by lethal drugs, usually barbiturates. One organisation, Dignitas, has experimented with oxygen deprivation as an alternative to sodium pentobarbital. Objective To analyse the process of assisted suicide by oxygen deprivation with helium and a common face mask and reservoir bag. Method This study examined four cases of assisted suicide by oxygen deprivation using helium delivered via a face mask. Videos of the deaths were provided by the Zurich (...) police. Dignitas provided protocol and consent information. Results One man and three women were assisted to death by oxygen deprivation. There was wide variation in the time to unconsciousness and the time to death, probably due to the poor mask fit. Swiss law prevented attendants from effectively managing the face mask apparatus. Purposeless movements of the extremities were disconcerting for Dignitas attendants, who are accustomed to assisting suicide with barbiturates. None of the dying individuals attempted self-rescue. Conclusions The dying process of oxygen deprivation with helium is potentially quick and appears painless. It also bypasses the prescribing role of physicians, effectively demedicalising assisted suicide. Oxygen deprivation with a face mask is not acceptable because leaks are difficult to control and it may not eliminate rebreathing. These factors will extend time to unconsciousness and time to death. A hood method could reduce the problem of mask fit. With a hood, a flow rate of helium sufficient to provide continuous washout of expired gases would remedy problems observed with the mask. (shrink)

The mathematical dynamic model of oxidative phosphorylation in muscle mitochondria developed previously was used to calculate the flux control coefficients of particular steps of this process in isolated mitochondria at different amounts of hexokinase and oxygen concentrations. The pattern of control was completely different under different conditions. For normoxic concentration, the main controlling steps in state 4, state 3.5 and state 3 were proton leak, ATP usage (hexokinase) and complex III, respectively. The pattern of control in state 4 was (...) not changed at hypoxic oxygen concentration, while in state 3.5 and state 3 much of the control was shifted from other steps to cytochrome oxidase. The implications of the theoretical results obtained for the regulation of oxidative phosphorylation in intact muscle are discussed. (shrink)

Extra-corporeal membrane oxygenation has been introduced to clinical practice for several decades. It is unclear how internet and newspapers portray the use of extra-corporeal membrane oxygenation. This study were: (1) to quantify the coverage of extra-corporeal membrane oxygenation use in newspapers and on the Internet; (2) to describe the characteristics of extra-corporeal membrane oxygenation users presented in newspaper articles and the Internet web pages in comparison with those shown in extra-corporeal membrane oxygenation studies in Taiwan; and (3) to examine the (...) survival rates of extra-corporeal membrane oxygenation users presented in newspaper articles and the Internet web pages in comparison with those in Taiwan and in the Extracorporeal Life Support Registry Report International Summary for January 2014. (shrink)

Most studies have examined the outcomes of patients supported by extracorporeal membrane oxygenation as a life-sustaining treatment. It is unclear whether significant social events are associated with the use of life-sustaining treatment. This study aimed to compare the trend of extracorporeal membrane oxygenation use in Taiwan with that in the world, and to examine the influence of significant social events on the trend of extracorporeal membrane oxygenation use in Taiwan.

The article proposes a new, interspecies interpretation of Joanna Rajkowska’s Oxygenator. Read as what Anna Tsing calls latent commons and problematized through Chantal Mouffe’s concept of agonistic spaces, the canonical piece of public art is shown to have been an experimental site of more-than-human resurgence.

Background Pediatric critical care physician attitudes about withdrawal of ventricular assist devices (VAD) and extracorporeal membrane oxygenation (ECMO) in cases of medical futility are poorly defined. Our aim was to define current attitudes regarding the withdrawal of these devices. Methods IRB-approved, cross-sectional observational survey conducted among pediatric critical care attending physicians and fellow physicians in the United States between 2016 and 2017. Data was collected anonymously and statistically analyzed. Results A total of 158 physicians responded with 67% being attending physicians. (...) Compared to a VAD, a higher percentage had taken care of a patient on ECMO where the device was turned off because care was believed to be futile (99% vs. 84%), including currently (95% vs. 57%). Nearly all reported that it can be ethically permissible to withdraw support from a patient with a VAD and on ECMO (97% vs. 99%), but varied opinions existed as to who should ultimately make this decision if the patient/their family disagrees. More respondents agreed that a patient/their family should agree to withdrawal of VAD or ECMO support prior to initiation if futility is later determined (60% vs. 58%) and that protocols should be created for VAD and ECMO withdrawal (77% vs. 76%). Conclusion Most pediatric critical care physicians felt that it can be ethically permissible to withdraw VAD and ECMO support. Our study indicates that pediatric VAD and ECMO withdrawal protocols are desired, but further investigation is needed to determine how to best design protocols that would incorporate multiple stakeholders. (shrink)

Luminescence‐based sensing schemes for oxygen have experienced a fast growth and are in the process of replacing the Clark electrode in many fields. Unlike electrodes, sensing is not limited to point measurements via fiber optic microsensors, but includes additional features such as planar sensing, imaging, and intracellular assays using nanosized sensor particles. In this essay, I review and discuss the essentials of (i) common solid‐state sensor approaches based on the use of luminescent indicator dyes and host polymers; (ii) fiber (...) optic and planar sensing schemes; (iii) nanoparticle‐based intracellular sensing; and (iv) common spectroscopies. Optical sensors are also capable of multiple simultaneous sensing (such as O2 and temperature). Sensors for O2 are produced nowadays in large quantities in industry. Fields of application include sensing of O2 in plant and animal physiology, in clinical chemistry, in marine sciences, in the chemical industry and in process biotechnology. (shrink)

Hyperbaric oxygen (HBO) therapy still lacks proper interpretations of its many actions. This hypothesis is based on reports of temporarily elevated peripheral vascular resistance (PVR) during HBO sessions. Besides that, during HBO sessions, hyperoxygenated tissues can reduce their perfusion so much that CO2 can accumulate in them. Tissue perfusion depends on vascular innervation and on the balance between systemic constrictors and local dilators. During an HBO session, increased tissue oxygen levels suppress dilatory mechanisms. Tissue hyperoxygenation increases PVR, suggesting (...) that the HBO action on an edematous tissue may be caused by an oxygen‐induced disbalance among Starling capillary forces. The presented hypothesis is that oxygen‐caused arteriolar constriction reduces the hydrostatic pressure in downstream capillaries. Thus, more tissue fluid is absorbed in vascular capillaries, under the condition that the plasma colloid osmotic pressure remains unaltered during the HBO session. Among several known mechanisms behind the HBO actions, the vasoconstriction has been listed as a therapeutic modality for the reduction of the tissue edema, for a crush injury, for burns (in an acute phase), and for the compartment syndrome. The Bell's palsy is among often listed indications for the HBO treatment, although evidence is poor and reports of randomized trials are scarce. (shrink)

Darwinian evolution can be simply stated: natural selection of inherited variations increasing differential reproduction. However, formulated thus, links with biochemistry, cell biology, ecology, and population dynamics remain unclear. To understand interactive contributions of chance and selection, higher levels of biological organization (e.g., endosymbiosis), complexities of competing selection forces, and emerging biological novelties (such as eukaryotes or meiotic sex), we must analyze actual examples. Focusing on mitochondria, I will illuminate how biology makes sense of life's evolution, and the concepts involved. First, (...) looking at the bacterium – mitochondrion transition: merging with an archaeon, it lost its independence, but played a decisive role in eukaryogenesis, as an extremely efficient aerobic ATP generator and internal ROS source. Second, surveying later mitochondrion adaptations and diversifications illustrates concepts such as constructive neutral evolution, dynamic interactions between endosymbionts and hosts, the contingency of life histories, and metabolic reprogramming. Without oxygen, mitochondria disappear; with (intermittent) oxygen diversification occurs in highly complex ways, especially upon (temporary) phototrophic substrate supply. These expositions show the Darwinian model to be a highly fruitful paradigm. (shrink)