Rapid Oxygen Uptake Research Articles

Capsules from synthetic diblock-peptides as potential artificial oxygen carriers

The design of an encapsulation system consisting of a synthetic peptide which is fully biodegradable into non-toxic constituents. This system should be capable of encapsulating perfluorinated hydrocarbons and should be a promising basis for oxygen carriers to be used as artificial blood replacement. A diblock-peptide is synthesised following a phosgene-free method and characterised by 1H-NMR. Subsequently, this diblock-peptide is self-assembled with perfluorodecalin (PFD) to form PFD-filled capsules as potential artificial oxygen carriers allowing for rapid oxygen uptake and release. The diblock-peptide Bu-PAsp10-PPhe10 is successfully synthesised and used to encapsulate PFD. The capsules have a spherical shape with an average diameter of 360 nm in stable aqueous dispersion. NMR measurements prove their physical capability for reversible uptake and release of oxygen. The resulting capsules are expected to be fully biodegradable and possibly could act as oxygen carriers for artificial blood replacement.

Redox Dynamics of Pd Supported on CeO2–ZrO2 during Oxygen Storage/Release Cycles Analyzed by Time-Resolved in Situ Reflectance Spectroscopy

In situ time-resolved diffuse reflectance spectroscopy provided the redox dynamics of Pd nanoparticles supported on an oxygen storage material CeO2–ZrO2 (CZ) under lean/rich perturbation conditions. Because the reflectance at 450 nm is sensitive to the Pd oxidation state but is not affected by the redox of Ce3+/Ce4+ species of CZ, the real-time Pd redox can be monitored every second during oxygen storage/release in simulated engine combustion exhaust gas (CO–C3H6–NO–O2) corresponding to gasoline air-to-fuel ratios of 14.1 (rich) and 15.0 (lean). Although a large amount of O2 was stored by CZ upon the rich-to-lean switch, the rate of Pd oxidation during this event was found to be much more moderate compared to that with a reference catalyst, Pd/Al2O3. Because rapid oxygen uptake by CZ reduces the local O2 partial pressure near the surface, the oxidation of Pd should be retarded. This can preserve active metallic Pd and thus contribute to longer retention of high NO reduction efficiency even under the lean ...

The effect of priming exercise on O2 uptake kinetics, muscle O2 delivery and utilization, muscle activity, and exercise tolerance in boys

This study used priming exercise in young boys to investigate (i) how muscle oxygen delivery and oxygen utilization, and muscle activity modulate oxygen uptake kinetics during exercise; and (ii) whether the accelerated oxygen uptake kinetics following priming exercise can improve exercise tolerance. Seven boys that were aged 11.3 ± 1.6 years completed either a single bout (bout 1) or repeated bouts with 6 min of recovery (bout 2) of very heavy-intensity cycling exercise. During the tests oxygen uptake, muscle oxygenation, muscle electrical activity and exercise tolerance were measured. Priming exercise most likely shortened the oxygen uptake mean response time (change, ±90% confidence limits; -8.0 s, ±3.0), possibly increased the phase II oxygen uptake amplitude (0.11 L·min(-1), ±0.09) and very likely reduced the oxygen uptake slow component amplitude (-0.08 L·min(-1), ±0.07). Priming resulted in a likely reduction in integrated electromyography (-24% baseline, ±21% and -25% baseline, ±19) and a very likely reduction in Δ deoxyhaemoglobin/Δoxygen uptake (-0.16, ±0.11 and -0.09, ±0.05) over the phase II and slow component portions of the oxygen uptake response, respectively. A correlation was present between the change in tissue oxygenation index during bout 2 and the change in the phase II (r = -0.72, likely negative) and slow component (r = 0.72, likely positive) oxygen uptake amplitudes following priming exercise, but not for muscle activity. Exercise tolerance was likely reduced (change -177 s, ±180) following priming exercise. The altered phase II and slow component oxygen uptake amplitudes in boys following priming exercise are linked to an improved localised matching of muscle oxygen delivery to oxygen uptake and not muscle electrical activity. Despite more rapid oxygen uptake kinetics following priming exercise, exercise tolerance was not enhanced.

Pyridinones Are Not Antioxidants As Shown by Kinetics of Free Radical Autoxidation, but They Prevent Radical Oxidations Catalyzed by Toxic Heavy Metals

Three 2-methyl-3-hydroxypyridinones, 1-methyl-, 1; 1-(4-methoxy)phenyl-, 2; and 1-(4-dimethylamino)phenyl-, 3, were discovered not to possess strong antioxidant properties contrary to literature reports. These pyridinones were not active chain-breaking antioxidants toward peroxyl radicals generated from styrene or methyl oleate initiated by azobis-2-methylpropylnitrile (AIBN) in solution compared to known phenolic antioxidants, 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC) or 2,6-di-tert-butyl-4-methoxyphenyl (DBHA). Pyridinone 2 exhibited weak antioxidant activity in cumene, kinh = 1.3 × 10(3) M(-1) s(-1), compared to 2,6-di-tert-butyl-4-methylphenol (BHT), kinh = 4.3 × 10(3) M(-1) s(-1). The pyridinones were not active antioxidants during lipid peroxidation initiated by azobis-2-amidinopropane·2HCl (ABAP) in aqueous-lipid dispersions of 0.50 M sodium dodecyl sulfate (SDS) micelles where 2 did not inhibit peroxidation of methyl oleate at pH 7.0 or 4.0, while BHT exhibited effective suppression of oxygen uptake. In addition, 2 did not exhibit any cooperative antioxidant effect in combination with Trolox during inhibited peroxidation of linoleic acid in micelles. Pyridinones were effective preventative antioxidants in aqueous-lipid dispersions against reactions initiated by heavy metal ions, notably copper; for example, 2 blocked peroxidation of linoleic acid initiated by Cu ions in SDS micelles. In particular, both 2 and 3 were active in preventing the rapid pro-oxidation effects, "spikes", of very rapid oxygen uptake when phenolic antioxidants PMHC or Trolox were added to peroxidations initiated by Cu(2+). A proposal is given to account for such pro-oxidant effects.

Effect of oxygen uptake and aromatization on the skin–core morphology during the oxidative stabilization of polyacrylonitrile fibers

AbstractThe isothermal oxidative stabilization of polyacrylonitrile fibers has been carried out at 210, 230, and 250°C. The stabilized fibers, treated for different times, have been characterized with elemental analysis, wide‐angle X‐ray diffraction, optical microscopy, and field emission scanning electron microscopy. A parabola relationship has been established between the oxygen uptake and stabilization time, whereas the aromatization index shows a trend of moderate ascension, retention, and acceleration. With increasing temperature and time, the skin–core morphology of the stabilized fibers becomes more and more distinct, but the skin thickness is almost unchanged for 60 and 120 min at 250°C. The fracture mechanism is ductile fracture in the core but is brittle fracture in the skin. The results indicate that the initial rapid oxygen uptake at a high temperature and the subsequent intense aromatization are responsible for the formation of the skin–core morphology. On the basis of the isothermal stabilization, an onion‐like model is proposed for the structure of stabilized fibers that are treated by stepwise increasing temperatures in industrial production. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Herbicidal indolizine‐5,8‐diones: photosystem I redox mediators

6,7-Disubstituted indolizine-5,8-diones showed activity as herbicides, giving rapid desiccation symptomology in whole-plant tests and bleaching in leaf-disc assays. In isolated chloroplasts, such compounds initiated rapid uptake of oxygen in Photosystem I. A redox mediator mode of action was further supported by electrochemical studies. Several compounds described had low photostability, high volatility, hydrolytic instability or reactivity with glutathione. The detrimental effects that these factors may have had on expression of herbicidal activity are discussed.

Oxygen uptake during the mixing of saliva with ascorbic acid under acidic conditions: possibility of its occurrence in the stomach

Human saliva, which contains nitrite, is normally mixed with gastric juice, which contains ascorbic acid (AA). When saliva was mixed with an acidic buffer in the presence of 0.1 mM AA, rapid nitric oxide formation and oxygen uptake were observed. The oxygen uptake was due to the oxidation of nitric oxide, which was formed by AA-dependent reduction of nitrite under acidic conditions, by molecular oxygen. A salivary component SCN − enhanced the nitric oxide formation and oxygen uptake by the AA/nitrite system. The oxygen uptake by the AA/nitrite/SCN − system was also observed in an acidic buffer solution. These results suggest that oxygen is normally taken up in the stomach when saliva and gastric juice are mixed.

Photoemission study of oxygen adsorption on Rb 6C 60 film surface

X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) have been used to investigate oxygen adsorption on the surface of Rb 6C 60 film at room temperature. The results show that the Rb 6C 60 surface is sensitive to oxygen adsorption. The absorbed oxygen changes the crystal structure of the film by pulling intercalated Rb atoms to the surface, forming Rb oxides. An initial rapid oxygen uptake is mainly related to the formation of rubidium peroxide (Rb 2O 2). There exists a strong reaction between C 60 and Rb 2O 2, leading to the formation of rubidium carbonate (Rb 2CO 3). At high oxygen exposures, a slow further adsorption of oxygen is associated with the intensity increases of both Rb 2CO 3 and rubidium superoxide (RbO 2) species.

Storage parameters affecting red blood cell survival and function after transfusion

A LTHOUGH OUR understanding of the various parameters influencing the collection, separation, and storage of blood cells has progressively improved during past decades, with the exception of apheresis technologies, there have been surprisingly few advances in the practice of routine blood collection and component separation. This review attempts to summarize recent developments and to suggest steps that might be taken to improve the quality of stored red blood cells (RBCs) to maximize their safety and their benefits for the transfused recipient. The RBC is a highly specialized cell .without a nucleus and devoid of protein synthesis. This means that it has to rely on its original contents of enzymes and other proteins for the whole of its limited lifetime. In addition, because it lacks mitochondria, it cannot use oxidative phosphorylation for adenosine triphosphate (ATP) regeneration but has to rely on metabolizing glucose to lactate. This results in a net gain of 2 moles of ATP, 2 H +, and 2 moles of lactate per 1 mole of glucose metabol ized--an ineffective mechanism for energy supply compared with mitochondrial oxidation via the citric acid cycle. Approximately 10% of the metabolic flux passes by way of the pentose phosphate pathway in which oxygen is consumed and carbon dioxide formed. A simplified metabolic outline is presented in Figure 1, which also illustrates some substances that can be used to influence the metabolism under in vitro storage conditions. The most important function of RBCs, oxygen transport, exposes the cell to toxic oxygen species, free oxygen radicals such as O 2 and OH', and to hydrogen peroxide. For protection against denaturation by peroxidation of the lipids in the membrane bilayer, its proteins and enzymes, a number of antioxidants such as vitamin E are available in both the liquid and cellular components of the blood, and redox machinery is provided within the red cell. A highly flexible membrane is essential for rapid uptake and release of oxygen and carbon dioxide. In this way, the RBC will have a great contact surface area between its own membrane and that of the capillaries as it rolls through these vessels like a small wheel with a big flat tire. This rolling also helps mix the viscous intracellular content. The degree of saturation of the RBC hemoglobin (Hb) and its dependence on the surrounding partial pressure of oxygen (pO2), can be graphically represented by a sigmoidal curve, the oxygen dissociation curve (ODC). The inflection point of this curve is at 50% Hb saturation. This point, the p50, normally has a value of approximately 3.6 kPa (27 mm Hg). The factors that most potently influence p50 are pH (H + and CO2) and 2,3-diphosphoglycerate (2,3-DPG). As pH is lowered, the ODC is shifted to the right, which means that the affinity of Hb for oxygen is reduced, oxygen is less readily bound and more readily released. In the normally functioning lung, pO2,is sufficiently high to result in nearly complete saturation, at both normal and moderately rightshifted ODC. In the peripheral circulation, the pH is lower than in the lungs, which promotes oxygen release. If the ODC is left-shifted, less oxygen will be delivered at a certain pO2. Because of competition between 2,3-DPG and oxygen at the same site on the Hb molecule, an increased concentration of 2,3-DPG will cause reduced oxygen affinity and a right shift of the ODC. Patients with chronic anemia usually have an increased erythrocyte 2,3-DPG concentration and a right-shifted ODC, which seems to give some compensation for the lower concentration of circulating cellular Hb. All currently used methods for the liquid storage of RBCs result in depletion of 2,3-DPG, generally after I to 2 weeks of storage. These RBCs will have a left-shifted ODC, greater oxygen affinity, and may supply less oxygen to the tissues. Cells with depleted 2,3-DPG will normalize within 48 to 72 hours after transfusion. 1-3

Greater erythrocyte deformability in world-class endurance athletes.

Because athletes during endurance events require rapid uptake of oxygen, the ability of red blood cells (RBC) to move through capillaries may limit performance. Using ektacytometry, we determined whether RBC deformability (RCD) differed between elite road cyclists (n = 9) and sedentary controls (n = 5). Density profiles and standard hematological measurements were also performed. The deformability index (DI) was higher in the cyclists (0.723 +/- 0.027) compared with that in controls (0.619 +/- 0.040, P < 0.001). Cyclists also had a larger percentage of low-density RBCs (P < 0. 001), and mean cell volume (MCV) was also higher (P = 0.013). These findings are indicative of a larger proportion of "young" RBCs in the blood of elite cyclists and provide further evidence that the turnover of RBCs in endurance athletes is higher than in the general population. With a younger more deformable RBC population and providing the destruction does not exceed replacement, performance potential should be enhanced. Furthermore, examination of factors that contribute to increased RBC turnover in athletes may help us understand the mechanisms that cause RBC aging.

Compositional changes in plasma-deposited fluorocarbon films during ageing

Plasma polymer coatings were deposited from perfluoro-1,3-dimethylcyclohexane (PFDMCH) and their composition and surface properties studied by XPS, grazing-angle Fourier transform infrared spectroscopy and contact angle measurements as a function of time after fabrication as they were stored under ambient conditions for more than 2 years. The spontaneous ambient oxidation of PFDMCH plasma polymers was found to be multi-step process. The rapid initial oxygen uptake, assigned to reaction between carbon-centred radicals incorporated into the coating during deposition and in-diffusing atmospheric O 2 , was similar to that of plasma polymers deposited from hydrocarbon-based monomers (alkanes, alkylamines, alcohols), suggesting that the density of radicals incorporated during deposition was similar. Subsequently, however, the extent of oxidation was much lower for PFDMCH coatings. This can be attributed to the lack of availability of hydrogen abstraction reactions, which are important for radical propagation in hydrocarbon-based plasma polymers. While XPS recorded a continuous incorporation of oxygen for more than 2 years, the air/water contact angles decreased only during the first 2 months and on further storage remained stable. There appeared to be only a small extent of surface restructuring as assessed from the small depth variations of compositions. The surface was enriched in CF 3 groups at all times.

GREATER ERYTHROCYTE DEFORMABILITY IN ELITE ENDURANCE ATHLETES

1901 Because rapid delivery and uptake of oxygen are required by athletes during intense exercise, the ability of red blood cells (RBC) to move through the microcirculation may be a limiting factor in endurance sports. We addressed this issue by using ektacytometry to measure RBC deformability in venous samples (taken at rest) from 9 elite road cyclists and 5 sedentary controls. As an indicator of RBC age, a separate sample of cells were separated on Stractan II density gradients. Standard hematological variables were also measured. The RBC deformability index (DI) was higher in the cyclists (0.72± 0.03) compared to controls (0.62 ± 0.04; P < 0.001). Cyclists also contained a larger percentage (70%) of low-density RBCs (P < 0.001) compared to controls (53%); the correlation between DI and low density was r = 0.81. These findings are indicative of a larger proportion of“young” RBCs in the blood of elite cyclists and provide further evidence that the turnover of RBCs in endurance athletes is higher than in the general population. Providing the rate of destruction does not exceed that of replacement - with a younger more deformable RBC population - endurance performance potential should be greater. Furthermore, examination of factors that contribute to increased RBC turnover in athletes may help unravel the mechanisms that limit the life span of RBCs to around 120 days in normal human subjects.

The effect of Rb coverage on the oxidation of [formula omitted] interfaces

Core-level and valence-band photoemission and work-function measurements have been used to investigate the effect of Rb coverage on the oxidation of Rb InSb (111) interfaces as a function of oxygen exposure at room temperature. The results show that a rapid oxygen uptake at low oxygen exposures is basically independent of the Rb coverage. For low Rb coverages, the oxygen adsorption is mainly related to the chemisorbed atomic oxygen and/or the oxidation of Sb on the surface, which is associated with an increase in the work function. In the case of high Rb coverages, the oxidation of the Sb atoms takes place at the interface between the peroxide (Rb 2O 2) and the substrate at low oxygen exposures, causing an initial decrease in the work function. The O 2− 2 ion appears to have four features in the valence band. The O − 2 species of the superoxide (RbO 2) located in the topmost layer is stabilized only after a certain amount of O 2 has been dosed to the surface. At high oxygen exposure the intensity ratio of O − 2 to O 2− 2 increases with Rb coverage.

Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia.

Toxic aromatic pollutants, concentrated in industrial wastes and contaminated sites, can potentially be eliminated by low cost bioremediation systems. Most commonly, the goal of these treatment systems is directed at providing optimum environmental conditions for the mineralization of the pollutants by naturally occurring microflora. Electrophilic aromatic pollutants with multiple chloro, nitro and azo groups have proven to be persistent to biodegradation by aerobic bacteria. These compounds are readily reduced by anaerobic consortia to lower chlorinated aromatics or aromatic amines but are not mineralized further. The reduction increases the susceptibility of the aromatic molecule for oxygenolytic attack. Sequencing anaerobic and and aerobic biotreatment steps provide enhanced mineralization of many electrophilic aromatic pollutants. The combined activity of anaerobic and aerobic bacteria can also be obtained in a single treatment step if the bacteria are immobilized in particulate matrices (e.g. biofilm, soil aggregate, etc.). Due to the rapid uptake of oxygen by aerobes and facultative bacteria compared to the slow diffusion of oxygen, oxygen penetration into active biofilms seldom exceeds several hundred micrometers. The anaerobic microniches established inside the biofilms can be applied to the reduction of electron withdrawing functional groups in order to prepare recalcitrant aromatic compounds for further mineralization in the aerobic outer layer of the biofilm. Aside from mineralization, polyhydroxylated and chlorinated phenols as well as nitroaromatics and aromatic amines are susceptible to polymerization in aerobic environments. Consequently an alternative approach for bioremediation systems can be directed towards incorporating these aromatic pollutants into detoxified humic-like substances. The activation of aromatic pollutants for polymerization can potentially be encouraged by an anaerobic pretreatment step prior to oxidation. Anaerobic bacteria can modify aromatic pollutants by demethylating methoxy groups and reducing nitro groups. The resulting phenols and aromatic amines are readily polymerized in a subsequent aerobic step.

Oxidation kinetics of cast TiAl 3

The isothermal oxidation kinetics of the TiAl3 compound over a wide temperature range is documented, and these rates are related to exclusive alpha-Al2O3 scale growth. The specific weight change vs time curves are shown. Two abnormalities are immediately apparent. One is that a rapid initial uptake of oxygen occurs at times less than 5 h, followed by a lower oxidation rate at longer times, for tests at 900 C and below. The other is that the final weight changes for the 700, 800, and 900 C tests are not in the sequence expected with respect to temperature. Isothermal oxidation of drop cast TiAl above 1000 C was found to exhibit parabolic oxidation controlled by protective alpha-Al2O3 scale formation. TiAl is the only phase in the binary Ti-Al system that forms exclusive scales of alpha-Al2O3 in isothermal oxidation. High anomalous rates at short times and at temperatures below 1000 C resulted from the internal oxidation of a second phase of aluminum.

Susceptibility of Neonatal Lipoproteins to Oxidative Stress

We compared peroxidizability of neonatal and adult lipoproteins exposed to oxidative stress initiated by an azo-compound. Oxygen uptake showed a two-phase pattern, with slow oxygen uptake in the first phase and faster uptake in the second phase. During the first phase, tocopherol was consumed progressively, inhibiting lipid peroxidation by scavenging peroxy radicals. After the tocopherol concentration fell below a critical level, extensive propagation of chain oxidative reactions produced the rapid oxygen uptake in the second phase. In the first phase of neonatal lipoprotein oxidation, a faster oxygen uptake was observed and the length of this phase was shorter than in adults. The oxygen uptake rate in the second phase was smaller in the neonatal lipoproteins. In other words, neonatal lipoproteins were more susceptible to oxidative stress than were adult ones when tocopherol remained in lipoproteins, but after tocopherol depletion the reverse was true. These results were consistent with the finding that in neonatal lipoproteins the tocopherol/lipid ratio was significantly lower (length of the inhibitory phase was closely correlated to the lipoprotein tocopherol content). In addition, the average number of active bisallylic hydrogen atoms, which are considered to determine the relative susceptibility of polyunsaturated fatty acids to oxidation, was significantly smaller (oxygen uptake rate in the second phase was closely correlated to the active bisallylic hydrogen number) in neonatal lipoproteins, and the ratio of active bisallylic hydrogen to tocopherol content (which closely correlated to oxygen uptake rate in the first phase) was also significantly lower compared with the adult ratio. Under physiologic conditions, an intensive oxidation of lipoproteins sufficient to cause lipoprotein tocopherol to fall below critical levels is unlikely to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct and respiratory chain-mediated redox cycling of adrenochrome

Adrenochrome is reduced by ascorbate in a reaction accompanied by a large and rapid oxygen uptake. The rates of adrenochrome reduction and the concomitant oxygen uptake are decreased in the presence of superoxide dismutase or catalase. The species formed on the one-electron reduction of adrenochrome (i.e., the semiquinone) was shown by pulse radiolysis to rapidly react with oxygen (9 · 10 8 M −1 · s −1), indicating the occurrence of a redox cycling in a system formed by adrenochrome, a reducing agent, and oxygen. Adrenochrome is also reduced to the corresponding semiquinone by complex I of beef heart submitochondrial particles supplemented with NADH, while succinate is unable to support this reduction. The o-semiquinone is the intermediate species in the superoxide-generating cycle resulting from both non-enzymatic and enzymatic reduction. The toxic effects of adrenochrome and its pathophysiological role can be explained, at least in part, on the basis of the demonstrated cycle.

Oxidation of Fe-24%Cr-11%Mo at room temperature and low Oxygen pressure

Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and angle resolved X-ray photoelectron spectroscopy (ARXPS) have been used to characterize the initial stages of the interaction of oxygen with a clean Fe-24%Cr-11%Mo alloy in an oxygen atmosphere (10 −8 − 10 −6 Torr) at room temperature. The interaction of oxygen with the alloy proceeds in several stages. Rapid oxygen uptake taking place up to ∼ 1 L exposures is followed by the formation in several stages of oxides of chromium, molybdenum and iron. At 10−10 4 L exposures the growth of the oxide film follows a logarithmic law. Angle resolved XPS data can be interpreted by a model which considers three layers with an outer iron oxide film growing on chromium and molybdenum oxides.

Aspects of the surface photo-oxidation of poly 2-(2-hydroxy-3-vinyl-5-methylphenyl)-benzotriazole

ESCA has been used to monitor the changes in the surface chemistry of Poly 2-(2-hydroxy-3-vinyl-5-methylphenyl)-benzotriazole during exposure to UV light in air. Rapid oxygen uptake was observed. The data are discussed with respect to the inability of the functional moiety in the polymer to retard surface photo-oxidation.

Oxidation Kinetics of Silicon Surfaces: Reactive Sticking Coefficient, Apparent Saturation Coverage and Effect of Surface Hydrogen

ABSTRACTThe kinetics of the initial oxidation of silicon surfaces by O2 were studied using laser-induced thermal desorption (LITD), temperature programmed desorption (TPD) and Fourier Transform Infrared (FTIR) spectroscopy. The LITD results showed that the oxidation of Si(111)7×7 by O2 was characterized by two kinetic processes: an initial rapid oxygen uptake followed by a slower growth that asymptotically approached an apparent saturation oxygen coverage. The initial reactive sticking coefficient of O2 on Si(111)7×7 decreased with surface temperature. In contrast, TPD experiments on Si(111)7×7 and FTIR studies on porous silicon demonstrated that the apparent saturation oxygen coverage increased as a function of surface temperature. Experiments with preadsorbed hydrogen also revealed that silicon oxidation was inhibited as a function of increasing hydrogen coverage on the Si(111)7×7 surface.