Physiological development of the embryonic and larval crayfish heart

The cardiovascular system is the first system to become functional in a developing animal and must perform key physiological functions even as it develops and grows. The ontogeny of cardiac physiology was studied throughout embryonic and larval developmental stages in the red swamp crayfish Procambarus clarkii using videomicroscopic dimensional analysis. The heart begins to contract by day 13 of development (at 25 degrees C, 20 kPa O(2)). Cardiac output is primarily regulated by changes in heart rate because stroke volume remains relatively constant throughout embryogenesis. Prior to eclosion, heart rate and cardiac output decreased significantly. Previous data suggest that the decrease in cardiac parameters prior to hatching may be due to an oxygen limitation to the embryo. Throughout development, metabolizing mass and embryonic oxygen consumption increased, while egg surface area remained constant. The surface area of the egg membrane is a constraint on gas exchange; this limitation, in combination with the increasing oxygen demand of the embryo, results in an inadequate diffusive supply of oxygen to developing tissues. To determine if the decrease in cardiac function was the result of an internal hypoxia experienced during late embryonic development, early and late-stage embryos were exposed to hyperoxic water (PO(2) = 40 kPa O(2)). Heart rate in late-stage embryos exposed to hyperoxic water increased significantly over control values, which suggests that the suppression in cardiac function observed in late-stage embryos is due to a limited oxygen supply.     

The tracheal supply and muscle metabolism during muscle growth in the puparium of Calliphora vomitoria

Thirty hours after puparium formation in Calliphora, the larval tracheal system is replaced by an air-filled pupal system. This is characterized initially by many tufts of tracheae and coiled tracheoles lying in the blood. Between the third and fourth day, the sixth dorsal longitudinal flight muscles are practically without attached tracheae and their longitudinal growth can partially occur when oxygen uptake is inhibited with potassium cyanide. Sodium iodoacetate prevents muscle growth. After the fifth day of development the pupal tracheoles spread out over the surface of the developing adult muscles. Between the seventh and ninth day, longitudinal growth and increases in the diameter of the myofibrils are halted by cyanide and iodoacetate. Some longitudinal growth and an increase in the total protein content of the muscles can occur in 1% oxygen. Air filling of the adult tracheae takes place 2–3 hr before the emergence of the adult and is accompanied by an increase in oxygen consumption of the thorax. The metabolism and growth of the muscles is discussed with respect to their changing oxygen supply.     

The scaling of diving time budgets: insights from an optimality approach

Simple scaling arguments suggest that, among air-breathing divers, dive duration should scale approximately with mass to the one-third power. Recent phylogenetic analyses appear to confirm this. The same analyses showed that duration of time spent at the surface between dives has scaling very similar to that of dive duration, with the result that the ratio of dive duration to surface pause duration is approximately mass invariant. This finding runs counter to other arguments found in the diving literature that suggest that surface pause duration should scale more positively with mass, leading to a negative scaling of the dive-pause ratio. We use a published model of optimal time allocation in the dive cycle to show that optimal decisions can predict approximate mass invariance in the dive-pause ratio, especially if metabolism scales approximately with mass to the two-thirds power (as indicated by some recent analyses) and oxygen uptake is assumed to have evolved to supply the body tissues at the required rate. However, emergent scaling rules are sensitive to input parameters, especially to the relationship between the scaling of metabolism and oxygen uptake rate at the surface. Our results illustrate the utility of an optimality approach for developing predictions and identifying key areas for empirical research on the allometry of diving behavior.     

Influence of repeated exposure to rapidly developing hypoxaemia on the arousal and cardiopulmonary response to rapidly developing hypoxaemia in lambs

Experiments were done on four lambs to determine if repeated exposure to rapidly developing hypoxaemia influences the cardiopulmonary and arousal response from sleep. Each lamb was anaesthetized and instrumented for sleep staging and measurements of arterial haemoglobin oxygen saturation. No sooner than three days after surgery, measurements were made in quiet sleep and active sleep during control periods when the animal was breathing 21% oxygen and during experimental periods of rapidly developing hypoxaemia when the animal was breathing 5% oxygen for approximately 100 epochs of sleep. Arousal occurred from both sleep states during rapidly developing hypoxaemia but was delayed in active sleep compared to quiet sleep. The time to arousal and the decrease in arterial haemoglobin oxygen saturation were significantly increased with repeated exposure to rapidly developing hypoxaemia during both quiet sleep and active sleep. Thus, our data provide evidence that repeated exposure to rapidly developing hypoxaemia produces an arousal response decrement in lambs. Since it is possible that alterations in the arousal response to respiratory stimuli play a role in sudden infant death, studies to investigate the mechanism of the arousal response decrement following repeated exposure to rapidly developing hypoxaemia are warranted.     

Hypoxia in childhood pneumonia: better detection and more oxygen needed in developing countries.

Even though hypoxia is a major risk factor for death in children with acute respiratory infection in developing countries, oxygen is not part of first line treatment. Because oxygen is not readily available in developing countries it tends to be given to the most seriously ill children, whose outcome is poor. Oxygen might be useful if given earlier in the course of the disease. Clinical signs are not clear cut, however, though the presence of cyanosis and grunting together with a raised respiratory rate can significantly increase the detection of hypoxaemia. A simple oximeter would make detection easier, and oxygen concentrators are more cost effective than bottled oxygen. Ideally oxygen should be given to children in the early stages of clinical pneumonia to prevent deterioration.     

System for measuring oxygen consumption rates of mammalian cells in static culture under hypoxic conditions

Estimating the oxygen consumption rates (OCRs) of mammalian cells in hypoxic environments is essential for designing and developing a three‐dimensional (3‐D) cell culture system. However, OCR measurements under hypoxic conditions are infrequently reported in the literature. Here, we developed a system for measuring OCRs at low oxygen levels. The system injects nitrogen gas into the environment and measures the oxygen concentration by an optical oxygen microsensor that consumes no oxygen. The developed system was applied to HepG2 cells in static culture. Specifically, we measured the spatial profiles of the local dissolved oxygen concentration in the medium, then estimated the OCRs of the cells. The OCRs, and also the pericellular oxygen concentrations, decreased nonlinearly as the oxygen partial pressure in the environment decreased from 19% to 1%. The OCRs also depended on the culture period and the matrix used for coating the dish surface. Using this system, we can precisely estimate the OCRs of various cell types under environments that mimic 3‐D culture conditions, contributing crucial data for an efficient 3‐D culture system design. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:189–197, 2016     

Nitrogen cycling in coastal marine ecosystems

It is generally considered that nitrogen availability is one of the major factors regulating primary production in temperate coastal marine environments. Coastal regions often receive large anthropogenic inputs of nitrogen that cause eutrophication. The impact of these nitrogen additions has a profound effect in estuaries and coastal lagoons where water exchange is limited. Such increased nutrient loading promotes the growth of phytoplankton and fast growing pelagic macroalgae while rooted plants (sea-grasses) and benthic are suppressed due to reduced light availability. This shift from benthic to pelagic primary production introduces large diurnal variations in oxygen concentrations in the water column. In addition oxygen consumption in the surface sediments increases due to the deposition of readily degradable biomass. In this review the physico-chemical and biological factors regulating nitrogen cycling in coastal marine ecosystems are considered in relation to developing effective management programmes to rehabilitate seagrass communities in lagoons currently dominated by pelagic macroalgae and/or cyanobacteria.     

Capsule walls as barriers to oxygen availability: Implications for the development of brooded embryos by the estuarine gastropod Crepipatella dilatata (Calyptraeidae)

Encapsulation of developing embryos imposes potential restrictions, because the capsule wall must allow for adequate inward diffusion of oxygen and for increased diffusion of oxygen as metabolic demand increases with continued development. Samples of egg capsules from the gastropod Crepipatella dilatata were used to document surface characteristics, composition of the different capsule wall layers, and alterations in wall thickness during development. The diffusion coefficient and capsule wall permeability were determined experimentally for capsules containing embryos at different developmental stages. We also determined oxygen consumption rates for various embryonic stages and for nurse eggs, which provide food for embryos during development. The capsule wall of C. dilatata possesses 2 differentiated layers: the external capsular wall (ECW) and the internal capsular wall (ICW). The ECW is compact and fibrous, features that remain invariable during development, and lacks surface features that might make some portions of the capsule wall more permeable to oxygen than others. On the other hand, the ICW is initially spongy and thick, but significantly decreases in thickness over time, particularly before the embryos begin feeding on nurse eggs. Although the capsule wall is a serious barrier to diffusion, permeability to oxygen increases over time by 112% due to the dramatic thinning of the inner capsule wall layer. Nurse eggs consume oxygen but at very low rates, supporting the idea that they correspond to living embryonic cells that have stopped their development. Respiration measurements indicated that embryos are initially supplied with enough oxygen within the egg capsules to carry out the activities characteristic of embryogenesis, even though the capsular walls show their maximum thickness and lowest permeability at this time. However, as the embryo develops its velum and becomes more active, capsule wall thickness decreases and capsule permeability to oxygen increases. Correspondingly, the oxygen demands of metamorphosed but still encapsulated specimens are approximately 135% higher than those of pre-metamorphosed sibling embryos.     

An inhibitory effect of excess moisture on the early development of Sinapis alba L. seedlings

Abstract. Mustard seedlings in the early stages of growth are sensitive to the presence of excess moisture, growth of the radicle and anthocyanin synthesis being retarded by water at a suction of less than 3 cm water for seedlings growing on a plane surface. This inhibitory effect commences at about 12-15 h from wetting of the seed. It can be counteracted by increasing the partial pressure of oxygen in the atmosphere or by de-coating the seed, suggesting that the inhibition is caused by a restricted flow of oxygen through the mucilaginous seed coat. The positive effect of gravity on anthocyanin synthesis in the developing seedling can be wholly accounted for in terms of the removal of excess moisture. This explanation largely accounts for the improved growth of the root, but a tonic effect of gravity on root growth can also be discerned.     

Cell surface oxygen consumption: a major contributor to cellular oxygen consumption in glycolytic cancer cell lines

Oxygen consumption for bioenergetic purposes has long been thought to be the prerogative of mitochondria. Nevertheless, mitochondrial gene knockout (rho(0)) cells that are defective in mitochondrial respiration require oxygen for growth and consume oxygen at the cell surface via trans-plasma membrane electron transport (tPMET). This raises the possibility that cell surface oxygen consumption may support glycolytic energy metabolism by reoxidising cytosolic NADH to facilitate continued glycolysis. In this paper we determined the extent of cell surface oxygen consumption in a panel of 19 cancer cell lines. Non-mitochondrial (myxothiazol-resistant) oxygen consumption was demonstrated to consist of at least two components, cell surface oxygen consumption (inhibited by extracellular NADH) and basal oxygen consumption (insensitive to both myxothiazol and NADH). The extent of cell surface oxygen consumption varied considerably between parental cell lines from 1% to 80% of total oxygen consumption rates. In addition, cell surface oxygen consumption was found to be associated with low levels of superoxide production and to contribute significantly (up to 25%) to extracellular acidification in HL60rho(0) cells. In summary, cell surface oxygen consumption contributes significantly to total cellular oxygen consumption, not only in rho(0) cells but also in mitochondrially competent tumour cell lines with glycolytic metabolism.     

Cell surface oxygen consumption: A major contributor to cellular oxygen consumption in glycolytic cancer cell lines

Oxygen consumption for bioenergetic purposes has long been thought to be the prerogative of mitochondria. Nevertheless, mitochondrial gene knockout (ρ⁰) cells that are defective in mitochondrial respiration require oxygen for growth and consume oxygen at the cell surface via trans-plasma membrane electron transport (tPMET). This raises the possibility that cell surface oxygen consumption may support glycolytic energy metabolism by reoxidising cytosolic NADH to facilitate continued glycolysis. In this paper we determined the extent of cell surface oxygen consumption in a panel of 19 cancer cell lines. Non-mitochondrial (myxothiazol-resistant) oxygen consumption was demonstrated to consist of at least two components, cell surface oxygen consumption (inhibited by extracellular NADH) and basal oxygen consumption (insensitive to both myxothiazol and NADH). The extent of cell surface oxygen consumption varied considerably between parental cell lines from 1% to 80% of total oxygen consumption rates. In addition, cell surface oxygen consumption was found to be associated with low levels of superoxide production and to contribute significantly (up to 25%) to extracellular acidification in HL60ρ⁰ cells. In summary, cell surface oxygen consumption contributes significantly to total cellular oxygen consumption, not only in ρ⁰ cells but also in mitochondrially competent tumour cell lines with glycolytic metabolism.     

A multiparallel bioreactor for the cultivation of mammalian cells in a 3D‐ceramic matrix

For adherently growing cells, cultivation is limited by the provided growth surface. Excellent surface‐to‐volume ratios are found in highly porous matrices, which have to face the challenge of nutrient supply inside the matrices' caverns. Therefore, perfusion strategies are recommended which often have to deal with the need of developing an encompassing bioreactor periphery. We present a modular bioreactor system based on a porous ceramic matrix that enables the supply of cells with oxygen and nutrients by perfusion. The present version of the reactor system focuses on simple testing of various inoculation and operation modes. Moreover, it can be used to efficiently test different foam structures. Protocols are given to set‐up the system together with handling procedures for long‐time cultivation of a CHO cell line. Experimental results confirm vital growth of cells inside the matrices' caverns. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Haemoglobin-oxygen affinity in developing embryonic erythroid cells of the mouse

Summary Haemoglobin-oxygen equilibrium curves have been measured in developing embryonic mouse erythroid cells. At 11.5 days gestation, shortly after blood islands from the yolk sac have formed but before the placenta is complete, erythrocytes have a high affinity for oxygen and a reverse Bohr effect below pH 7.0 (Figs. 1, 2, 3). By 13.5 days both the Bohr shift and the shape of the equilibrium curves are similar to those obtained from adult mice. From 13.5 days onwards, 2,3-diphosphoglycerate plays an important role in regulating oxygen affinity (Figs. 2, 4). It is suggested that the oxygen equilibrium properties of embryonic erythrocytes are adapted to service the developing embryo with oxygen under hypoxic and hypercapnic conditions in the intra-uterine environment up until the time when the embryonic circulation makes contact with the placenta.     

Oxygen consumption by developing and diapausing eggs of Eupholidoptera smyrnensis (Orthoptera: Tettigoniidae)

Oxygen consumption by eggs of the Mediterranean bush-cricket Eupholidoptera smyrnesis was manometrically measured at 18, 24, 30 and 33°C. The aim was to study changes in oxygen consumption during embryonic development, and to compare a facultative initial and a facultative penultimate diapause with subitaneous developing eggs and an obligatory final diapause. In developing eggs, oxygen consumption increased as the embryo grew, but remained constant during katatrepsis. A comparison of the different diapauses revealed that in the initial diapause, oxygen consumption was lower than that of the corresponding embryonic stage in subitaneous eggs; the temperature dependence of oxygen consumption was also low. In contrast, in penultimate and in final diapause, oxygen consumption remained at the same high level as in developing embryos of the same size, and the temperature dependence of oxygen consumption was high. The results suggest that it is energetically profitable to the embryo to spend the hot season in a facultative initial and/or penultimate diapause.     

Antiproliferative Potential of Olneya tesota PF2 Lectin in Human Acute Monocytic Leukemia Cells

Acute monocytic leukemia is a type of myeloid leukemia that develops in monocytes. The current clinical therapies for leukemia are unsatisfactory due to their side effects and nonspecificity toward target cells. Some lectins display antitumor activity and may specifically recognize cancer cells by binding to carbohydrate structures on their surface. Therefore, this study evaluated the response of the human monocytic leukemia cell lines THP-1 to the Olneya tesota PF2 lectin. The induction of apoptosis and reactive oxygen species production in PF2-treated cells was evaluated by flow cytometry, and the lectin-THP-1 cell interaction and mitochondrial membrane potential were evaluated by confocal fluorescence microscopy. PF2 genotoxicity was evaluated by DNA fragmentation analysis via gel electrophoresis. The results showed that PF2 binds to THP-1 cells, triggers apoptosis and DNA degradation, changes the mitochondrial membrane potential, and increases reactive oxygen species levels in PF2-treated THP-1 cells. These results suggest the potential use of PF2 for developing alternative anticancer treatments with enhanced specificity.     

Engineering Catalytic Active Sites on Cobalt Oxide Surface for Enhanced Oxygen Electrocatalysis

Tuning the catalytic active sites plays a crucial role in developing low cost and highly durable oxygen electrode catalysts with precious metal‐competitive activity. In an attempt to engineer the active sites in Co₃O₄ spinel for oxygen electrocatalysis in alkaline electrolyte, herein, controllable synthesis of surface‐tailored Co₃O₄ nanocrystals including nanocube (NC), nanotruncated octahedron (NTO), and nanopolyhedron (NP) anchored on nitrogen‐doped reduced graphene oxide (N‐rGO), through a facile and template‐free hydrothermal strategy, is provided. The as‐synthesized Co₃O₄ NC, NTO, and NP nanostructures are predominantly enclosed by {001}, {001} + {111}, and {112} crystal planes, which expose different surface atomic configurations of Co²⁺ and Co³⁺ active sites. Electrochemical results indicate that the unusual {112} plane enclosed Co₃O₄ NP on rGO with abundant Co³⁺ sites exhibit superior bifunctional activity for oxygen reduction and evolution reactions, as well as enhanced metal–air battery performance in comparison with other counterparts. Experimental and theoretical simulation studies demonstrate that the surface atomic arrangement of Co²⁺/Co³⁺ active sites, especially the existence of octahedrally coordinated Co³⁺ sites, optimizes the adsorption, activation, and desorption features of oxygen species. This work paves the way to obtain highly active, durable, and cost‐effective electrocatalysts for practical clean energy devices through regulating the surface atomic configuration and catalytic active sites.     

Mapping oxygen accessibility to ribonuclease a using high-resolution NMR relaxation spectroscopy

Paramagnetic contributions to nuclear magnetic spin-lattice relaxation rate constant induced by freely diffusing molecular oxygen measured at hundreds of different protein proton sites provide a direct means for characterizing the exploration of the protein by oxygen. This report focuses on regions of ribonuclease A where the rate constant enhancements are either quite large or quite small. We find that there are several regions of enhanced oxygen affinity for the protein both on the surface and in interior pockets where sufficient free volume permits. Oxygen has weak associative interactions with a number of surface crevices that are generally between secondary structural elements of the protein fold. Several regions near the surface have higher than expected accessibility to oxygen indicating that structural fluctuations in the protein provide intermolecular access. Oxygen penetrates part of the hydrophobic interior, but affinity does not correlate simply with hydrophobicity indices. Oxygen is excluded from regions of high interior packing density and a few surface sites where x-ray diffraction data have indicated the presence of specific hydration with high occupancy.     

A paleosol record of the evolution of Cr redox cycling and evidence for an increase in atmospheric oxygen during the Neoproterozoic

Atmospheric oxygen levels control the oxidative side of key biogeochemical cycles and place limits on the development of high‐energy metabolisms. Understanding Earth's oxygenation is thus critical to developing a clearer picture of Earth's long‐term evolution. However, there is currently vigorous debate about even basic aspects of the timing and pattern of the rise of oxygen. Chemical weathering in the terrestrial environment occurs in contact with the atmosphere, making paleosols potentially ideal archives to track the history of atmospheric O₂ levels. Here we present stable chromium isotope data from multiple paleosols that offer snapshots of Earth surface conditions over the last three billion years. The results indicate a secular shift in the oxidative capacity of Earth's surface in the Neoproterozoic and suggest low atmospheric oxygen levels (<1% PAL pO₂) through the majority of Earth's history. The paleosol record also shows that localized Cr oxidation may have begun as early as the Archean, but efficient, modern‐like transport of hexavalent Cr under an O₂‐rich atmosphere did not become common until the Neoproterozoic.     

Temporal and vertical distribution of ciliophoran communities in the benthos of a small eutrophic loch with particular reference to the redox profile

SUMMARY. The ciliate communities occurring at three benthic sites in a small eutrophic loch have heen investigated over a 2-year period. Two characteristics of the community were studied in detail, the pattern of vertical distribution within the sediment and the temporal distribution of ciliates occurring in the surface sediment. The relationships between ciliate distributions and the environmental factors recorded were analysed by multiple regression. Significant relationships were revealed between vertical distribution of ciliates and the sediment redox (Eh) profile, the larger ciliate communities being associated with regions of higher potential. Other factors such as sediment density, organic matter, temperature and daylength, combined with other indicators of benthic metabolism (sulphide ion activity (Es^2?), pH, oxygen flux) were selected in the regression analysis as accounting for much of the variation in the depth distribution of ciliates. In analysing the temporal distribution of ciliates in the surface sediment, numbers were inversely related to Eh, Es^2? and oxygen flux, a result of the upwards migration of reducing conditions and greater microbial activity in the sediment surface during the summer. Daylength, temperature, organic carbon and benthic chlorophyll-a were also selected as accounting for much of the variation in ciliate number. It is proposed that the large increases in number and biomass of surface-sediment cilates in the summer months resulted from an intolerance of reducing conditions developing immediately beneath the surface and the increased productivity of the benthos as a whole during this period. Methods are also described for the construction, calibration and operation of electrodes used in measuring Eh, Es^2? and oxygen flux in the freshwater benthos. Data recorded for these three variables revealed similar seasonal patterns at each site in each of two consecutive years.