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Sample records for active oxygen generation

  1. Microfluidic Platform Generates Oxygen Landscapes for Localized Hypoxic Activation

    PubMed Central

    Rexius, Megan L.; Mauleon, Gerardo; Malik, Asrar B.; Rehman, Jalees; Eddington, David T.

    2014-01-01

    An open-well microfluidic platform generates an oxygen landscape using gas-perfused networks which diffuse across a membrane. The device enables real-time analysis of cellular and tissue responses to oxygen tension to define how cells adapt to heterogeneous oxygen conditions found in the physiological setting. We demonstrate that localized hypoxic activation of cells elicited specific metabolic and gene responses in human microvascular endothelial cells and bone marrow-derived mesenchymal stem cells. A robust demonstration of the compatibility of the device with standard laboratory techniques demonstrates the wide utility of the method. This platform is ideally suited to study real-time cell responses and cell-cell interactions within physiologically relevant oxygen landscapes. PMID:25315003

  2. Bioreductively Activated Reactive Oxygen Species (ROS) Generators as MRSA Inhibitors.

    PubMed

    Khodade, Vinayak S; Sharath Chandra, Mallojjala; Banerjee, Ankita; Lahiri, Surobhi; Pulipeta, Mallikarjuna; Rangarajan, Radha; Chakrapani, Harinath

    2014-07-10

    The number of cases of drug resistant Staphylococcus aureus infections is on the rise globally and new strategies to identify drug candidates with novel mechanisms of action are in urgent need. Here, we report the synthesis and evaluation of a series of benzo[b]phenanthridine-5,7,12(6H)-triones, which were designed based on redox-active natural products. We find that the in vitro inhibitory activity of 6-(prop-2-ynyl)benzo[b]phenanthridine-5,7,12(6H)-trione (1f) against methicillin-resistant Staphylococcus aureus (MRSA), including a panel of patient-derived strains, is comparable or better than vancomycin. We show that the lead compound generates reactive oxygen species (ROS) in the cell, contributing to its antibacterial activity. PMID:25050164

  3. On-Orbit Checkout and Activation of the ISS Oxygen Generation System

    NASA Technical Reports Server (NTRS)

    Bagdigian, Robert M.; Prokhorov, Kimberlee S.

    2007-01-01

    NASA has developed and; deployed an Oxygen Generation System (OGS) into the Destiny Module of the International Space Station (ISS). The major. assembly; included in this system is the Oxygen Generator Assembly. (OGA) which was developed under NASA contract by Hamilton Sundstrand Space Systems International (HSSSI), Inc. This paper summarizes the installation of the system into the Destiny Module, its initial checkout and periodic preventative maintenance activities, and its operational activation. Trade studies and analyses that were conducted with the goal of mitigating on-orbit operational risks are also discussed.

  4. A ligand field chemistry of oxygen generation by the oxygen-evolving complex and synthetic active sites

    PubMed Central

    Betley, Theodore A; Surendranath, Yogesh; Childress, Montana V; Alliger, Glen E; Fu, Ross; Cummins, Christopher C; Nocera, Daniel G

    2007-01-01

    Oxygen–oxygen bond formation and O2 generation occur from the S4 state of the oxygen-evolving complex (OEC). Several mechanistic possibilities have been proposed for water oxidation, depending on the formal oxidation state of the Mn atoms. All fall under two general classifications: the AB mechanism in which nucleophilic oxygen (base, B) attacks electrophilic oxygen (acid, A) of the Mn4Ca cluster or the RC mechanism in which radical-like oxygen species couple within OEC. The critical intermediate in either mechanism involves a metal oxo, though the nature of this oxo for AB and RC mechanisms is disparate. In the case of the AB mechanism, assembly of an even-electron count, high-valent metal-oxo proximate to a hydroxide is needed whereas, in an RC mechanism, two odd-electron count, high-valent metal oxos are required. Thus the two mechanisms give rise to very different design criteria for functional models of the OEC active site. This discussion presents the electron counts and ligand geometries that support metal oxos for AB and RC O–O bond-forming reactions. The construction of architectures that bring two oxygen functionalities together under the purview of the AB and RC scenarios are described. PMID:17971328

  5. Testing and Oxygen Assessment Results for a Next Generation Extravehicular Activity Portable Life Support System Fan

    NASA Technical Reports Server (NTRS)

    Paul, Heather L.; Jennings, Mallory A.; Rivera, Fatonia L.; Martin, Devin

    2011-01-01

    NASA is designing a next generation Extravehicular Activity (EVA) Portable Life Support System (PLSS) for use in future surface exploration endeavors. To meet the new requirements for ventilation flow at nominal and buddy modes, a fan has been developed and tested. This paper summarizes the results of the performance and life cycle testing efforts conducted at the NASA Johnson Space Center. Additionally, oxygen compatibility assessment results from an evaluation conducted at White Sands Test Facility (WSTF) are provided, and lessons learned and future recommendations are outlined.

  6. Investigation of a sterilization system using active oxygen species generated by ultraviolet irradiation.

    PubMed

    Yoshino, Kiyoshi; Matsumoto, Hiroyuki; Iwasaki, Tatsuyuki; Kinoshita, Shinobu; Noda, Kazutoshi; Oya, Kei; Iwamori, Satoru

    2015-01-01

    We have been investigating an advanced sterilization system that employs active oxygen species (AOS). We designed the sterilization equipment, including an evacuation system, which generates AOS from pure oxygen gas using ultraviolet irradiation, in order to study the conditions necessary for sterilization in the system's chamber. Using Geobachillus stearothermophilus spores (10(6) CFU) in a sterile bag as a biological indicator (BI) in the chamber of the AOS sterilization apparatus, we examined the viability of the BI as a function of exposure time, assessing the role of the decompression level in the sterilization performance. We found that the survival curves showed exponential reduction, and that the decompression level did not exert a significant influence on the survival curve. Subsequently, we investigated the sterilization effect as influenced by the spatial and environmental temperature variation throughout the chamber, and found that the sterilization effect varied with position, due to the varying environmental temperature in the respective areas. We confirmed that temperature is one of the most important factors influencing sterilization in the chamber, and estimated the temperature effect on the distribution of atomic oxygen concentration, using the quartz crystal microbalance (QCM) method with fluorocarbon thin film prepared by radio frequency sputtering.

  7. Investigation of a sterilization system using active oxygen species generated by ultraviolet irradiation.

    PubMed

    Yoshino, Kiyoshi; Matsumoto, Hiroyuki; Iwasaki, Tatsuyuki; Kinoshita, Shinobu; Noda, Kazutoshi; Oya, Kei; Iwamori, Satoru

    2015-01-01

    We have been investigating an advanced sterilization system that employs active oxygen species (AOS). We designed the sterilization equipment, including an evacuation system, which generates AOS from pure oxygen gas using ultraviolet irradiation, in order to study the conditions necessary for sterilization in the system's chamber. Using Geobachillus stearothermophilus spores (10(6) CFU) in a sterile bag as a biological indicator (BI) in the chamber of the AOS sterilization apparatus, we examined the viability of the BI as a function of exposure time, assessing the role of the decompression level in the sterilization performance. We found that the survival curves showed exponential reduction, and that the decompression level did not exert a significant influence on the survival curve. Subsequently, we investigated the sterilization effect as influenced by the spatial and environmental temperature variation throughout the chamber, and found that the sterilization effect varied with position, due to the varying environmental temperature in the respective areas. We confirmed that temperature is one of the most important factors influencing sterilization in the chamber, and estimated the temperature effect on the distribution of atomic oxygen concentration, using the quartz crystal microbalance (QCM) method with fluorocarbon thin film prepared by radio frequency sputtering. PMID:25817808

  8. Onboard oxygen generation systems.

    PubMed

    Manatt, S A

    1981-11-01

    During the 1970s, the development of onboard oxygen generation systems (OBOGS) progressed through ground and flight test phases to the point where a second-generation concept is now production qualified and additional alternatives are being evaluated. This paper reviews the development of OBOGS and assesses the current state of the art of these systems. High-purity fluomine systems, developed for flight demonstration and qualified for production application, are discussed. Development of enriched air molecular sieve systems for laboratory and flight applications is described, along with a recent study of a permeable membrane-based aircraft oxygen enrichment concept. Capabilities and characteristics of the various OBOGS concepts are compared, showing the greater compliance of high-purity fluomine systems with the current oxygen military standards while noting the advantages of the reduced interface complexity of enriched air systems. Recommendations for future OBOGS development are presented, emphasizing the need to coordinate the development of specifications and hardware so the optimum compromises between physiological requirements and engineering feasibilities can result in OBOGS that best satisfy the metabolic needs of aircrew members.

  9. Inorganic Polyphosphates Regulate Hexokinase Activity and Reactive Oxygen Species Generation in Mitochondria of Rhipicephalus (Boophilus) microplus Embryo

    PubMed Central

    Fraga, Amanda; Moraes, Jorge; da Silva, José Roberto; Costa, Evenilton P.; Menezes, Jackson; da Silva Vaz Jr, Itabajara; Logullo, Carlos; da Fonseca, Rodrigo Nunes; Campos, Eldo

    2013-01-01

    The physiological roles of polyphosphates (poly P) recently found in arthropod mitochondria remain obscure. Here, the possible involvement of poly P with reactive oxygen species generation in mitochondria of Rhipicephalus microplus embryos was investigated. Mitochondrial hexokinase and scavenger antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione reductase were assayed during embryogenesis of R. microplus. The influence of poly P3 and poly P15 were analyzed during the period of higher enzymatic activity during embryogenesis. Both poly Ps inhibited hexokinase activity by up to 90% and, interestingly, the mitochondrial membrane exopolyphosphatase activity was stimulated by the hexokinase reaction product, glucose-6-phosphate. Poly P increased hydrogen peroxide generation in mitochondria in a situation where mitochondrial hexokinase is also active. The superoxide dismutase, catalase and glutathione reductase activities were higher during embryo cellularization, at the end of embryogenesis and during embryo segmentation, respectively. All of the enzymes were stimulated by poly P3. However, superoxide dismutase was not affected by poly P15, catalase activity was stimulated only at high concentrations and glutathione reductase was the only enzyme that was stimulated in the same way by both poly Ps. Altogether, our results indicate that inorganic polyphosphate and mitochondrial membrane exopolyphosphatase regulation can be correlated with the generation of reactive oxygen species in the mitochondria of R. microplus embryos. PMID:23983617

  10. Elaboration of Copper-Oxygen Mediated C–H Activation Chemistry in Consideration of Future Fuel and Feedstock Generation

    PubMed Central

    Lee, Jung Yoon; Karlin, Kenneth D

    2015-01-01

    To contribute solutions for current energy concerns, improvements in the efficiency of C-H bond cleavage chemistry, e.g., selective oxidation of methane to methanol, could minimize losses in natural gas usage or produce feedstocks for fuels. Oxidative C-H activation is also a component of polysaccharide degradation, affording alternative biofuels from abundant biomass. Thus, an understanding of active-site chemistry in copper monooxygenases, those activating strong C-H bonds is briefly reviewed. Then, recent advances in the synthesis-generation and study of various copper-oxygen intermediates are highlighted. Of special interest are cupric-superoxide, Cu-hydroperoxo and Cu-oxy complexes. Such investigations can contribute to an enhanced future application of C-H oxidation or oxygenation processes using air, as concerning societal energy goals. PMID:25756327

  11. Hyperthermal atomic oxygen generator

    NASA Technical Reports Server (NTRS)

    Khandelwal, Govind S.; Wu, Dongchuan

    1990-01-01

    Characterization of the transport properties of oxygen through silver was continued. Specifically, experiments measuring the transport through Ag(111), Ag(110), Ag(100) single crystals and through Ag0.05 Zr alloy were completed. In addition, experiments using glow discharge excitation of oxygen to assist in the transport were completed. It was found that the permeability through the different orientations of single crystal Ag was the same, but significant differences existed in the diffusivity. The experimental ratio of diffusivities, however, was in reasonable agreement with theoretical estimates. Since the solubilities of orientations must be the same, this suggests some problems with the assumption K = DS. The glow discharge experiments show that there is a substantial increase in transport (factor of six) when the upstream pressure is dissociated to some fraction of atoms (which have a much higher sticking coefficient). These results indicate that there is a significant surface limitation because of dissociative adsorption of the molecules. Experiments with the Ag0.05 Zr alloy and its high-grain boundary and defect density show a permeability of greater than a factor of two over ordinary polycrystalline Ag, but it is unclear as to whether this is because of enhanced transport through these defects or whether the Zr and defects on the surface increased the sticking coefficient and therefore the transport.

  12. Lysophosphatidic acid induces reactive oxygen species generation by activating protein kinase C in PC-3 human prostate cancer cells

    SciTech Connect

    Lin, Chu-Cheng; Lin, Chuan-En; Lin, Yueh-Chien; Ju, Tsai-Kai; Huang, Yuan-Li; Lee, Ming-Shyue; Chen, Jiun-Hong; Lee, Hsinyu

    2013-11-01

    Highlights: •LPA induces ROS generation through LPA{sub 1} and LPA{sub 3}. •LPA induces ROS generation by activating PLC. •PKCζ mediates LPA-induced ROS generation. -- Abstract: Prostate cancer is one of the most frequently diagnosed cancers in males, and PC-3 is a cell model popularly used for investigating the behavior of late stage prostate cancer. Lysophosphatidic acid (LPA) is a lysophospholipid that mediates multiple behaviors in cancer cells, such as proliferation, migration and adhesion. We have previously demonstrated that LPA enhances vascular endothelial growth factor (VEGF)-C expression in PC-3 cells by activating the generation of reactive oxygen species (ROS), which is known to be an important mediator in cancer progression. Using flow cytometry, we showed that LPA triggers ROS generation within 10 min and that the generated ROS can be suppressed by pretreatment with the NADPH oxidase (Nox) inhibitor diphenylene iodonium. In addition, transfection with LPA{sub 1} and LPA{sub 3} siRNA efficiently blocked LPA-induced ROS production, suggesting that both receptors are involved in this pathway. Using specific inhibitors and siRNA, phospholipase C (PLC) and protein kinase C (PKC) were also suggested to participate in LPA-induced ROS generation. Overall, we demonstrated that LPA induces ROS generation in PC-3 prostate cancer cells and this is mediated through the PLC/PKC/Nox pathway.

  13. Project of the borehole neutron generator for the direct determination of oxygen and carbon by activation method

    NASA Astrophysics Data System (ADS)

    Bogdanovich, B. Yu; Vovchenko, E. D.; Iliinskiy, A. V.; Isaev, A. A.; Kozlovskiy, K. I.; Nesterovich, A. V.; Senyukov, V. A.; Shikanov, A. E.

    2016-09-01

    The paper deals with application features of borehole neutron generator (BNG) based on the vacuum accelerating tube (AT) with laser-plasma ion source for determination of oxygen isotope 16O and carbon isotope 12C by direct activation. The project of pulsed BNG for realization of an activation method in the conditions of natural presence of productive hydrocarbons is offered. The diode system with radial acceleration, magnetic electron insulation and laser-plasma source of deuterons at the anode in a sealed-off vacuum accelerating tube is applied. The permanent NdFeB magnet with induction about 0.5 T for produce the insulating magnetic field in the diode gap is proposed. In the experiments on the model of BNG with the accelerating voltage source (≈350 kV), performed by the scheme of Arkadiev-Marx generator, the output of (d, d) neutrons was ∼107 pulse-1.

  14. Effect of the solution temperature in a singlet-oxygen generator on the formation of active medium in an ejector oxygen - iodine laser

    SciTech Connect

    Zagidullin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A; Palina, N Yu

    2002-02-28

    The influence of the solution temperature in a singlet-oxygen generator on the formation of the active medium in the ejector oxygen - iodine laser is investigated. The following parameters of the active medium at the solution temperature -20{sup 0}C are obtained: the gain is 7.2 x 10{sup -3} cm{sup -1}, the Mach number is M=2, the temperature is 205 K, and the static pressure is 9.3 mmHg. As the solution temperature is increased to -4{sup 0}C, the gain decreases to 5 x 10{sup 3} cm{sup -1}, the Mach number decreases to 1.78, while the temperature and the static pressure increase to 241 K and 10.7 mmHg, respectively. As the solution temperature increases from -20 to -4{sup 0}C, the losses in O{sub 2}({sup 1}{Delta}) increase by less than 20%, while the dissociation efficiency of molecular iodine decreases by less than 21%. (lasers, active media)

  15. Copper ions strongly activate the phosphoinositide-3-kinase/Akt pathway independent of the generation of reactive oxygen species.

    PubMed

    Ostrakhovitch, Elena A; Lordnejad, Mohammad Reza; Schliess, Freimut; Sies, Helmut; Klotz, Lars-Oliver

    2002-01-15

    Copper is implicated in metabolic disorders, such as Wilson's disease or Alzheimer's disease. Analysis of signaling pathways regulating cellular survival and function in response to a copper stress is crucial for understanding the pathogenesis of such diseases. Exposure of human skin fibroblasts or HeLa cells to Cu(2+) resulted in a dose- and time-dependent activation of the antiapoptotic kinase Akt/protein kinase B, starting at concentrations as low as 3 microM. Only Cu(II), but not Cu(I), had this effect. Activation of Akt was accompanied by phosphorylation of a downstream target of Akt, glycogen synthase kinase-3. Inhibitors of phosphoinositide-3-kinase (PI3K) completely blocked activation of Akt by Cu(2+), indicating a requirement of PI3K for Cu(2+)-induced activation of Akt. Indeed, cellular PI3K activity was strongly enhanced after exposure to Cu(2+). Copper ions may lead to the formation of reactive oxygen species, such as hydrogen peroxide. Activation of Akt by hydrogen peroxide or growth factors is known to proceed via the activation growth factor receptors. In line with this, pretreatment with inhibitors of growth factor receptor tyrosine kinases blocked activation of Akt by hydrogen peroxide and growth factors, as did a src-family tyrosine kinase inhibitor or the broad-spectrum tyrosine kinase inhibitor genistein. Activation of Akt by Cu(2+), however, remained unimpaired, implying (i) that tyrosine kinase activation is not involved in Cu(2+) activation of Akt and (ii) that activation of the PI3K/Akt pathway by Cu(2+) is initiated independently of that induced by reactive oxygen species. Comparison of the time course of the oxidation of 2',7'-dichlorodihydrofluorescein in copper-treated cells with that of Akt activation led to the conclusion that production of hydroperoxides cannot be an upstream event in copper-induced Akt activation. Rather, both activation of Akt and generation of ROS are proposed to occur in parallel, regulating cell survival after a

  16. Enhanced Intrinsic Catalytic Activity of λ-MnO2 by Electrochemical Tuning and Oxygen Vacancy Generation.

    PubMed

    Lee, Sanghan; Nam, Gyutae; Sun, Jie; Lee, Jang-Soo; Lee, Hyun-Wook; Chen, Wei; Cho, Jaephil; Cui, Yi

    2016-07-18

    Chemically prepared λ-MnO2 has not been intensively studied as a material for metal-air batteries, fuel cells, or supercapacitors because of their relatively poor electrochemical properties compared to α- and δ-MnO2 . Herein, through the electrochemical removal of lithium from LiMn2 O4 , highly crystalline λ-MnO2 was prepared as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The ORR activity of the material was further improved by introducing oxygen vacancies (OVs) that could be achieved by increasing the calcination temperature during LiMn2 O4 synthesis; a concentration of oxygen vacancies in LiMn2 O4 could be characterized by its voltage profile as the cathode in a lithiun-metal half-cell. λ-MnO2-z prepared with the highest OV exhibited the highest diffusion-limited ORR current (5.5 mA cm(-2) ) among a series of λ-MnO2-z electrocatalysts. Furthermore, the number of transferred electrons (n) involved in the ORR was >3.8, indicating a dominant quasi-4-electron pathway. Interestingly, the catalytic performances of the samples were not a function of their surface areas, and instead depended on the concentration of OVs, indicating enhancement in the intrinsic catalytic activity of λ-MnO2 by the generation of OVs. This study demonstrates that differences in the electrochemical behavior of λ-MnO2 depend on the preparation method and provides a mechanism for a unique catalytic behavior of cubic λ-MnO2 . PMID:27254822

  17. In situ generated highly active copper oxide catalysts for the oxygen evolution reaction at low overpotential in alkaline solutions.

    PubMed

    Liu, Xiang; Cui, Shengsheng; Qian, Manman; Sun, Zijun; Du, Pingwu

    2016-04-25

    Developing efficient water oxidation catalysts made up of earth-abundant elements has attracted much attention as a step toward for future clean energy production. Herein we report a simple one-step method to generate a low cost copper oxide catalyst film in situ from a copper(ii) ethylenediamine complex. The resulting catalyst has excellent activity toward the oxygen evolution reaction in alkaline solutions. A catalytic current density of 1.0 mA cm(-2) and 10 mA cm(-2) for the catalyst film requires the overpotentials of only ∼370 mV and ∼475 mV in 1.0 M KOH, respectively. This catalytic performance shows that the new catalyst is one of the best Cu-based heterogeneous OER catalysts to date. PMID:27020763

  18. Promoting Active Species Generation by Plasmon-Induced Hot-Electron Excitation for Efficient Electrocatalytic Oxygen Evolution.

    PubMed

    Liu, Guigao; Li, Peng; Zhao, Guixia; Wang, Xin; Kong, Jintao; Liu, Huimin; Zhang, Huabin; Chang, Kun; Meng, Xianguang; Kako, Tetsuya; Ye, Jinhua

    2016-07-27

    Water splitting represents a promising technology for renewable energy conversion and storage, but it is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). Here, using Au-nanoparticle-decorated Ni(OH)2 nanosheets [Ni(OH)2-Au] as catalysts, we demonstrate that the photon-induced surface plasmon resonance (SPR) excitation on Au nanoparticles could significantly activate the OER catalysis, specifically achieving a more than 4-fold enhanced activity and meanwhile affording a markedly decreased overpotential of 270 mV at the current density of 10 mA cm(-2) and a small Tafel slope of 35 mV dec(-1) (no iR-correction), which is much better than those of the benchmark IrO2 and RuO2, as well as most Ni-based OER catalysts reported to date. The synergy of the enhanced generation of Ni(III/IV) active species and the improved charge transfer, both induced by hot-electron excitation on Au nanoparticles, is proposed to account for such a markedly increased activity. The SPR-enhanced OER catalysis could also be observed over cobalt oxide (CoO)-Au and iron oxy-hydroxide (FeOOH)-Au catalysts, suggesting the generality of this strategy. These findings highlight the possibility of activating OER catalysis by plasmonic excitation and could open new avenues toward the design of more-energy-efficient catalytic water oxidation systems with the assistance of light energy. PMID:27380539

  19. Low level laser therapy activates NF-kB via generation of reactive oxygen species in mouse embryonic fibroblasts

    NASA Astrophysics Data System (ADS)

    Chen, Aaron Chih-Hao; Arany, Praveen R.; Huang, Ying-Ying; Tomkinson, Elizabeth M.; Saleem, Taimur; Yull, Fiona E.; Blackwell, Timothy S.; Hamblin, Michael R.

    2009-02-01

    Despite over forty years of investigation on low-level light therapy (LLLT), the fundamental mechanisms underlying photobiomodulation remain unclear. In this study, we isolated murine embryonic fibroblasts (MEF) from transgenic NF-kB luciferase reporter mice and studied their response to 810-nm laser radiation. Significant activation of NFkB was observed for fluences higher than 0.003 J/cm2. NF-kB activation by laser was detectable at 1-hour time point. Moreover, we demonstrated that laser phosphorylated both IKK α/β and NF-kB 15 minutes after irradiation, which implied that laser activates NF-kB via phosphorylation of IKK α/β. Suspecting mitochondria as the source of NF-kB activation signaling pathway, we demonstrated that laser increased both intracellular reactive oxygen species (ROS) by fluorescence microscopy with dichlorodihydrofluorescein and ATP synthesis by luciferase assay. Mitochondrial inhibitors, such as antimycin A, rotenone and paraquat increased ROS and NF-kB activation but had no effect on ATP. The ROS quenchers N-acetyl-L-cysteine and ascorbic acid abrogated laser-induced NF-kB and ROS but not ATP. These results suggested that ROS might play an important role in the signaling pathway of laser induced NF-kB activation. However, the western blot showed that antimycin A, a mitochondrial inhibitor, did not activate NF-kB via serine phosphorylation of IKK α/β as the laser did. On the other hand, LLLT, unlike mitochondrial inhibitors, induced increased cellular ATP levels, which indicates that light also upregulates mitochondrial respiration. ATP upregulation reached a maximum at 0.3 J/cm2 or higher. We conclude that LLLT not only enhances mitochondrial respiration, but also activates the redox-sensitive transcription factor NF-kB by generating ROS as signaling molecules.

  20. Humic acid effect on catalase activity and the generation of reactive oxygen species in corn (Zea mays).

    PubMed

    Cordeiro, Flávio Couto; Santa-Catarina, Claudete; Silveira, Vanildo; de Souza, Sonia Regina

    2011-01-01

    Humic acids (HAs) have positive effects on plant physiology, but the molecular mechanisms underlying these events are only partially understood. The induction of root growth and emission of lateral roots (LRs) promoted by exogenous auxin is a natural phenomenon. Exogenous auxins are also associated with HA. Gas nitric oxide (NO) is a secondary messenger produced endogenously in plants. It is associated with metabolic events dependent on auxin. With the application of auxin, NO production is significantly increased, resulting in positive effects on plant physiology. Thus it is possible to evaluate the beneficial effects of the application of HA as an effect of auxin. To investigate the effects of HA the parameters of root growth, Zea mays was studied by evaluating the application of 3 mM C L⁻¹ of HA extracted from Oxisol and 100 µM SNP (sodium nitroprusside) and the NO donor, subject to two N-NO₃⁻, high dose (5.0 mM N-NO₃⁻) and low dose (5.0 mM N-NO₃⁻). Treatments with HA and NO were positively increased, regardless of the N-NO₃⁻ taken, as assessed by fresh weight and dry root, issue of LRs. The effects were more pronounced in the treatment with a lower dose of N-NO₃⁻. Detection of reactive oxygen species (ROS) in vivo and catalase activity were evaluated; these tests were associated with root growth. Under application of the bioactive substances tested, detection of ROS and catalase activity increased, especially in treatments with lower doses of N-NO₃⁻. The results of this experiment indicate that the effects of HA are dependent on ROS generation, which act as a messenger that induces root growth and the emission of LRs.

  1. Combustion-derived flame generated ultrafine soot generates reactive oxygen species and activates Nrf2 antioxidants differently in neonatal and adult rat lungs

    PubMed Central

    2013-01-01

    Background Urban particulate matter (PM) has been epidemiologically correlated with multiple cardiopulmonary morbidities and mortalities, in sensitive populations. Children exposed to PM are more likely to develop respiratory infections and asthma. Although PM originates from natural and anthropogenic sources, vehicle exhaust rich in polycyclic aromatic hydrocarbons (PAH) can be a dominant contributor to the PM2.5 and PM0.1 fractions and has been implicated in the generation of reactive oxygen species (ROS). Objectives Current studies of ambient PM are confounded by the variable nature of PM, so we utilized a previously characterized ethylene-combusted premixed flame particles (PFP) with consistent and reproducible physiochemical properties and 1) measured the oxidative potential of PFP compared to ambient PM, 2) determined the ability of PFPs to generate oxidative stress and activate the transcription factor using in vitro and ex vivo models, and 3) we correlated these responses with antioxidant enzyme expression in vivo. Methods We compared oxidative stress response (HMOX1) and antioxidant enzyme (SOD1, SOD2, CAT, and PRDX6) expression in vivo by performing a time-course study in 7-day old neonatal and young adult rats exposed to a single 6-hour exposure to 22.4 μg/m3 PFPs. Results We showed that PFP is a potent ROS generator that induces oxidative stress and activates Nrf2. Induction of the oxidative stress responsive enzyme HMOX1 in vitro was mediated through Nrf2 activation and was variably upregulated in both ages. Furthermore, antioxidant enzyme expression had age and lung compartment variations post exposure. Of particular interest was SOD1, which had mRNA and protein upregulation in adult parenchyma, but lacked a similar response in neonates. Conclusions We conclude that PFPs are effective ROS generators, comparable to urban ambient PM2.5, that induce oxidative stress in neonatal and adult rat lungs. PFPs upregulate a select set of antioxidant enzymes in

  2. Technology advancement of an oxygen generation subsystem

    NASA Technical Reports Server (NTRS)

    Lee, M. K.; Burke, K. A.; Schubert, F. H.; Wynveen, R. A.

    1979-01-01

    An oxygen generation subsystem based on water electrolysis was developed and tested to further advance the concept and technology of the spacecraft air revitalization system. Emphasis was placed on demonstrating the subsystem integration concept and hardware maturity at a subsystem level. The integration concept of the air revitalization system was found to be feasible. Hardware and technology of the oxygen generation subsystem was demonstrated to be close to the preprototype level. Continued development of the oxygen generation technology is recommended to further reduce the total weight penalties of the oxygen generation subsystem through optimization.

  3. [Effects of cadmium stress on active oxygen generation, lipid peroxidation and antioxidant enzyme activities in radish seedlings].

    PubMed

    Tang, Chun-Fang; Liu, Yun-Guo; Zeng, Guang-Ming; Li, Cheng-Feng; Xu, Wei-Hua

    2004-08-01

    When seedlings of radish were treated with Cd2+ from 125 to 500 micromol/L, for a period of 12 to 96 h in hydroponic system, increase in ratio of SOD to CAT and levels of O(-.)(2), H(2)O(2), MDA indicate that Cd2+ induces oxidative stress in radish plants. Antioxidant enzyme activities responded differently to the level and time of Cd2+ treatment. Under 125 micromol/L Cd2+ treatment a gradual increase in SOD activity was observed; at 250, 500 micromol/L Cd2+ treatment SOD activity increased first, then declined considerably to even lower than that of the control during later Cd2+ treatment. A gradual decrease in roots and a marked increase in leaves in CAT activity were detected. GR activity in both leaves and roots were enhanced significantly with the increase in content of Cd2+ and time of treatment. The increase in GR activity suggests that AsA-GsH cycle may be activated to scavenge the AOS or the synthesis of PC may be stimulated to chelate cadmium.

  4. Endothelial cell apoptosis induced by bacteria-activated platelets requires caspase-8 and -9 and generation of reactive oxygen species.

    PubMed

    Kuckleburg, Christopher J; Tiwari, Raksha; Czuprynski, Charles J

    2008-02-01

    A common feature of severe sepsis is vascular inflammation and damage to the endothelium. Because platelets can be directly activated by bacteria and endotoxin, these cells may play an important role in determining the outcome of sepsis. For example, inhibiting platelet interactions with the endothelium has been shown to attenuate endothelial cell damage and improve survival during sepsis. Although not entirely understood, the interactions between bacteria-activated platelets and the endothelium may play a key role in the vascular pathology of bacterial sepsis. Haemophilus somnus is a bacterial pathogen that causes diffuse vascular inflammation and endothelial damage. In some cases H. somnus infection results in an acute and fatal form of vasculitis in the cerebral microvasculature known as thrombotic meningoencephalitis (TME). In this study, we have characterized the mechanisms involved in endothelial cell apoptosis induced by activated platelets. We observed that direct contact between H. somnus-activated platelets and endothelial cells induced significant levels of apoptosis; however, Fas receptor activation on bovine endothelial cells was not able to induce apoptosis unless protein synthesis was disrupted. Endothelial cell apoptosis by H. somnus-activated platelets required activation of both caspase-8 and caspase-9, as inhibitors of either caspase inhibited apoptosis. Furthermore, activated platelets induced endothelial cell production of reactive oxygen species (ROS) and disrupting ROS activity in endothelial cells significantly inhibited apoptosis. These findings suggest that bacterial activation of platelets may contribute to endothelial cell dysfunction observed during sepsis, specifically by inducing endothelial cell apoptosis.

  5. Singlet molecular oxygen generated by biological hydroperoxides.

    PubMed

    Miyamoto, Sayuri; Martinez, Glaucia R; Medeiros, Marisa H G; Di Mascio, Paolo

    2014-10-01

    The chemistry behind the phenomenon of ultra-weak photon emission has been subject of considerable interest for decades. Great progress has been made on the understanding of the chemical generation of electronically excited states that are involved in these processes. Proposed mechanisms implicated the production of excited carbonyl species and singlet molecular oxygen in the mechanism of generation of chemiluminescence in biological system. In particular, attention has been focused on the potential generation of singlet molecular oxygen in the recombination reaction of peroxyl radicals by the Russell mechanism. In the last ten years, our group has demonstrated the generation of singlet molecular oxygen from reactions involving the decomposition of biologically relevant hydroperoxides, especially from lipid hydroperoxides in the presence of metal ions, peroxynitrite, HOCl and cytochrome c. In this review we will discuss details on the chemical aspects related to the mechanism of singlet molecular oxygen generation from different biological hydroperoxides.

  6. Thrombin-induced reactive oxygen species generation in platelets: A novel role for protease-activated receptor 4 and GPIbα

    PubMed Central

    Carrim, Naadiya; Arthur, Jane F.; Hamilton, Justin R.; Gardiner, Elizabeth E.; Andrews, Robert K.; Moran, Niamh; Berndt, Michael C.; Metharom, Pat

    2015-01-01

    Background Platelets are essential for maintaining haemostasis and play a key role in the pathogenesis of cardiovascular disease. Upon ligation of platelet receptors through subendothelial matrix proteins, intracellular reactive oxygen species (ROS) are generated, further amplifying the platelet activation response. Thrombin, a potent platelet activator, can signal through GPIbα and protease-activated receptor (PAR) 1 and PAR4 on human platelets, and recently has been implicated in the generation of ROS. While ROS are known to have key roles in intra-platelet signalling and subsequent platelet activation, the precise receptors and signalling pathways involved in thrombin-induced ROS generation have yet to be fully elucidated. Objective To investigate the relative contribution of platelet GPIbα and PARs to thrombin-induced reactive oxygen species (ROS) generation. Methods and results Highly specific antagonists targeting PAR1 and PAR4, and the GPIbα-cleaving enzyme, Naja kaouthia (Nk) protease, were used in quantitative flow cytometry assays of thrombin-induced ROS production. Antagonists of PAR4 but not PAR1, inhibited thrombin-derived ROS generation. Removal of the GPIbα ligand binding region attenuated PAR4-induced and completely inhibited thrombin-induced ROS formation. Similarly, PAR4 deficiency in mice abolished thrombin-induced ROS generation. Additionally, GPIbα and PAR4-dependent ROS formation were shown to be mediated through focal adhesion kinase (FAK) and NADPH oxidase 1 (NOX1) proteins. Conclusions Both GPIbα and PAR4 are required for thrombin-induced ROS formation, suggesting a novel functional cooperation between GPIbα and PAR4. Our study identifies a novel role for PAR4 in mediating thrombin-induced ROS production that was not shared by PAR1. This suggests an independent signalling pathway in platelet activation that may be targeted therapeutically. PMID:26569550

  7. A dual-plate ITO-ITO generator-collector microtrench sensor: surface activation, spatial separation and suppression of irreversible oxygen and ascorbate interference.

    PubMed

    Hasnat, Mohammad A; Gross, Andrew J; Dale, Sara E C; Barnes, Edward O; Compton, Richard G; Marken, Frank

    2014-02-01

    Generator-collector electrode systems are based on two independent working electrodes with overlapping diffusion fields where chemically reversible redox processes (oxidation and reduction) are coupled to give amplified current signals. A generator-collector trench electrode system prepared from two tin-doped indium oxide (ITO) electrodes placed vis-à-vis with a 22 μm inter-electrode gap is employed here as a sensor in aqueous media. The reversible 2-electron anthraquinone-2-sulfonate redox system is demonstrated to give well-defined collector responses even in the presence of oxygen due to the irreversible nature of the oxygen reduction. For the oxidation of dopamine on ITO, novel "Piranha-activation" effects are observed and chemically reversible generator-collector feedback conditions are achieved at pH 7, by selecting a more negative collector potential, again eliminating possible oxygen interference. Finally, dopamine oxidation in the presence of ascorbate is demonstrated with the irreversible oxidation of ascorbate at the "mouth" of the trench electrode and chemically reversible oxidation of dopamine in the trench "interior". This spatial separation of chemically reversible and irreversible processes within and outside the trench is discussed as a potential in situ microscale sensing and separation tool.

  8. H2S Inhibits Hyperglycemia-Induced Intrarenal Renin-Angiotensin System Activation via Attenuation of Reactive Oxygen Species Generation

    PubMed Central

    Ni, Jun; Li, Chen; Shao, Decui; Liu, Jia; Shen, Yang; Wang, Zhen; Zhou, Li; Zhang, Wei; Huang, Yu; Yu, Chen; Wang, Rui; Lu, Limin

    2013-01-01

    Decrease in endogenous hydrogen sulfide (H2S) was reported to participate in the pathogenesis of diabetic nephropathy (DN). This study is aimed at exploring the relationship between the abnormalities in H2S metabolism, hyperglycemia-induced oxidative stress and the activation of intrarenal renin-angiotensin system (RAS). Cultured renal mesangial cells (MCs) and streptozotocin (STZ) induced diabetic rats were used for the studies. The expressions of angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin II (Ang II) type I receptor (AT1), transforming growth factor-β1 (TGF-β1) and collagen IV were measured by real time PCR and Western blot. Reactive oxygen species (ROS) production was assessed by fluorescent probe assays. Cell proliferation was analyzed by 5'-bromo-2'-deoxyuridine incorporation assay. Ang II concentration was measured by an enzyme immunoassay. AGT, ACE and AT1 receptor mRNA levels and Ang II concentration were increased in high glucose (HG) -treated MCs, the cell proliferation rate and the production of TGF-β1 and of collagen IV productions were also increased. The NADPH oxidase inhibitor diphenylenechloride iodonium (DPI) was able to reverse the HG-induced RAS activation and the changes in cell proliferation and collagen synthesis. Supplementation of H2S attenuated HG-induced elevations in ROS and RAS activation. Blockade on H2S biosynthesis from cystathione-γ-lyase (CSE) by DL-propargylglycine (PPG) resulted in effects similar to that of HG treatment. In STZ-induced diabetic rats, the changes in RAS were also reversed by H2S supplementation without affecting blood glucose concentration. These data suggested that the decrease in H2S under hyperglycemic condition leads to an imbalance between oxidative and reductive species. The increased oxidative species results in intrarenal RAS activation, which, in turn, contributes to the pathogenesis of renal dysfunction. PMID:24058553

  9. Reactive oxygen species generation and signaling in plants

    PubMed Central

    Tripathy, Baishnab Charan; Oelmüller, Ralf

    2012-01-01

    The introduction of molecular oxygen into the atmosphere was accompanied by the generation of reactive oxygen species (ROS) as side products of many biochemical reactions. ROS are permanently generated in plastids, peroxisomes, mitochiondria, the cytosol and the apoplast. Imbalance between ROS generation and safe detoxification generates oxidative stress and the accumulating ROS are harmful for the plants. On the other hand, specific ROS function as signaling molecules and activate signal transduction processes in response to various stresses. Here, we summarize the generation of ROS in the different cellular compartments and the signaling processes which are induced by ROS. PMID:23072988

  10. Evidence for singlet-oxygen generation and biocidal activity in photoresponsive metallic nitride fullerene-polymer adhesive films.

    PubMed

    McCluskey, D Michelle; Smith, Tiffany N; Madasu, Praveen K; Coumbe, Curtis E; Mackey, Mary A; Fulmer, Preston A; Wynne, James H; Stevenson, Steven; Phillips, J Paige

    2009-04-01

    The adhesive properties, as measured by bulk tack analysis, are found to decrease in blends of isomerically pure Sc3N@I(h)-C80 metallic nitride fullerene (MNF) and polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymer pressure-sensitive adhesive under white light irradiation in air. The reduction of tack is attributed to the in situ generation of 1O2 and subsequent photooxidative cross-linking of the adhesive film. Comparisons are drawn to classical fullerenes C60 and C70 for this process. This work represents the first demonstration of 1O2 generating ability in the general class of MNFs (M3N@C80). Additional support is provided for the sensitizing ability of Sc3N@I(h)-C80 through the successful photooxygenation of 2-methyl-2-butene to its allylic hydroperoxides in benzene-d(6) under irradiation at 420 nm, a process that occurs at a rate comparable to that of C(60). Photooxygenation of 2-methyl-2-butene is found to be influenced by the fullerene sensitizer concentration and O2 flow rate. Molar extinction coefficients are reported for Sc3N@I(h)-C80 at 420 and 536 nm. Evaluation of the potential antimicrobial activity of films prepared in this study stemming from the in situ generation of 1O2 led to an observed 1 log kill for select Gram-positive and Gram-negative bacteria.

  11. Evidence for singlet-oxygen generation and biocidal activity in photoresponsive metallic nitride fullerene-polymer adhesive films.

    PubMed

    McCluskey, D Michelle; Smith, Tiffany N; Madasu, Praveen K; Coumbe, Curtis E; Mackey, Mary A; Fulmer, Preston A; Wynne, James H; Stevenson, Steven; Phillips, J Paige

    2009-04-01

    The adhesive properties, as measured by bulk tack analysis, are found to decrease in blends of isomerically pure Sc3N@I(h)-C80 metallic nitride fullerene (MNF) and polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymer pressure-sensitive adhesive under white light irradiation in air. The reduction of tack is attributed to the in situ generation of 1O2 and subsequent photooxidative cross-linking of the adhesive film. Comparisons are drawn to classical fullerenes C60 and C70 for this process. This work represents the first demonstration of 1O2 generating ability in the general class of MNFs (M3N@C80). Additional support is provided for the sensitizing ability of Sc3N@I(h)-C80 through the successful photooxygenation of 2-methyl-2-butene to its allylic hydroperoxides in benzene-d(6) under irradiation at 420 nm, a process that occurs at a rate comparable to that of C(60). Photooxygenation of 2-methyl-2-butene is found to be influenced by the fullerene sensitizer concentration and O2 flow rate. Molar extinction coefficients are reported for Sc3N@I(h)-C80 at 420 and 536 nm. Evaluation of the potential antimicrobial activity of films prepared in this study stemming from the in situ generation of 1O2 led to an observed 1 log kill for select Gram-positive and Gram-negative bacteria. PMID:20161355

  12. Macrophages generate reactive oxygen species in response to minimally oxidized LDL: TLR4- and Syk-dependent activation of Nox2

    PubMed Central

    Bae, Yun Soo; Lee, Jee Hyun; Choi, Soo Ho; Kim, Sunah; Almazan, Felicidad; Witztum, Joseph L.; Miller, Yury I.

    2009-01-01

    Oxidative modification of low-density lipoprotein (LDL) plays a causative role in the development of atherosclerosis. In this study, we demonstrate that minimally oxidized LDL (mmLDL) stimulates intracellular reactive oxygen species (ROS) generation in macrophages through NADPH oxidase 2 (gp91phox/Nox2), which in turn induces production of RANTES and migration of smooth muscle cells. Peritoneal macrophages from gp91phox/Nox2−/− mice or J774 macrophages in which Nox2 was knocked down by siRNA failed to generate ROS in response to mmLDL. Because mmLDL-induced cytoskeletal changes were dependent on TLR4, we analyzed ROS generation in peritoneal macrophages from wild type, TLR4−/−, or MyD88−/− mice and found that mmLDL-mediated ROS was generated in a TLR4-dependent, but MyD88-independent manner. Furthermore, we found that ROS generation required the recruitment and activation of spleen tyrosine kinase (Syk) and that mmLDL also induced PLCγ1 phosphorylation and PKC membrane translocation. Importantly, the PLCγ1 phosphorylation was reduced in J774 cells expressing Syk-specific shRNA. Nox2 modulated mmLDL activation of macrophages by regulating the expression of proinflammatory cytokines IL-1β, IL-6 and RANTES. We showed that purified RANTES was able to stimulate migration of mouse aortic smooth muscle cells (MASMC) and addition of neutralizing antibody against RANTES abolished the migration of MASMC stimulated by mmLDL-stimulated macrophages. These results suggest that mmLDL induces generation of ROS through sequential activation of TLR4, Syk, PLCγ1, PKC, and gp91phox/Nox2 and thereby stimulates expression of proinflammatory cytokines. These data help explain mechanisms by which endogenous ligands, such as mmLDL, can induce TLR4-dependent, proatherogenic activation of macrophages. PMID:19096031

  13. 14 CFR 23.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device which produces oxygen by chemical reaction. (b) Each chemical oxygen... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Chemical oxygen generators. 23.1450...

  14. 14 CFR 23.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device which produces oxygen by chemical reaction. (b) Each chemical oxygen... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Chemical oxygen generators. 23.1450...

  15. 14 CFR 23.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... generator is defined as a device which produces oxygen by chemical reaction. (b) Each chemical oxygen... placarded to show— (1) The rate of oxygen flow, in liters per minute; (2) The duration of oxygen flow,...

  16. 14 CFR 23.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... generator is defined as a device which produces oxygen by chemical reaction. (b) Each chemical oxygen... placarded to show— (1) The rate of oxygen flow, in liters per minute; (2) The duration of oxygen flow,...

  17. 14 CFR 23.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... generator is defined as a device which produces oxygen by chemical reaction. (b) Each chemical oxygen... placarded to show— (1) The rate of oxygen flow, in liters per minute; (2) The duration of oxygen flow,...

  18. Singlet Oxygen Generation by Cyclometalated Complexes and Applications†

    PubMed Central

    Ashen-Garry, David; Selke, Matthias

    2014-01-01

    While cyclometalated complexes have been extensively studied for optoelectronic applications, these compounds also represent a relatively new class of photosensitizers for the production of singlet oxygen. Thus far, singlet oxygen generation from cyclometalated Ir and Pt complexes has been studied in detail. In this review, photophysical data for singlet oxygen generation from these complexes is presented, and the mechanism of 1O2 generation is discussed, including evidence for singlet oxygen generation via an electron transfer mechanism for some of cyclometalated Ir complexes. The period from the first report of singlet oxygen generation by a cyclometalated Ir complex in 2002 through August 2013 is covered in this review. This new class of singlet oxygen photosensitizers may prove to be rather versatile due to the ease of substitution of ancillary ligands without loss of activity. Several cyclometalated complexes have been tethered to zeolites, polystyrene, or quantum dots. Applications for photooxygenation of organic molecules, including “traditional” singlet oxygen reactions (ene reaction, [4+2] and [2+2] cycloadditions) as well as oxidative coupling of amines are presented. Potential biomedical applications are also reviewed. PMID:24344628

  19. Green tea polyphenols precondition against cell death induced by oxygen-glucose deprivation via stimulation of laminin receptor, generation of reactive oxygen species, and activation of protein kinase Cε.

    PubMed

    Gundimeda, Usha; McNeill, Thomas H; Elhiani, Albert A; Schiffman, Jason E; Hinton, David R; Gopalakrishna, Rayudu

    2012-10-01

    As the development of synthetic drugs for the prevention of stroke has proven challenging, utilization of natural products capable of preconditioning neuronal cells against ischemia-induced cell death would be a highly useful complementary approach. In this study using an oxygen-glucose deprivation and reoxygenation (OGD/R) model in PC12 cells, we show that 2-day pretreatment with green tea polyphenols (GTPP) and their active ingredient, epigallocatechin-3-gallate (EGCG), protects cells from subsequent OGD/R-induced cell death. A synergistic interaction was observed between GTPP constituents, with unfractionated GTPP more potently preconditioning cells than EGCG. GTPP-induced preconditioning required the 67-kDa laminin receptor (67LR), to which EGCG binds with high affinity. 67LR also mediated the generation of reactive oxygen species (ROS) via activation of NADPH oxidase. An exogenous ROS-generating system bypassed 67LR to induce preconditioning, suggesting that sublethal levels of ROS are indeed an important mediator in GTPP-induced preconditioning. This role for ROS was further supported by the fact that antioxidants blocked GTPP-induced preconditioning. Additionally, ROS induced an activation and translocation of protein kinase C (PKC), particularly PKCε from the cytosol to the membrane/mitochondria, which was also blocked by antioxidants. The crucial role of PKC in GTPP-induced preconditioning was supported by use of its specific inhibitors. Preconditioning was increased by conditional overexpression of PKCε and decreased by its knock-out with siRNA. Collectively, these results suggest that GTPP stimulates 67LR and thereby induces NADPH oxidase-dependent generation of ROS, which in turn induces activation of PKC, particularly prosurvival isoenzyme PKCε, resulting in preconditioning against cell death induced by OGD/R.

  20. Potentiating effect of an endocrine disruptor, paranonylphenol, on the generation of reactive oxygen species (ROS) in human venous blood -- association with the activation of signal transduction pathway.

    PubMed

    Okai, Yasuji; Sato, Eisuke F; Higashi-Okai, Kiyoka; Inoue, Masayasu

    2007-09-01

    An endocrine disruptor, para-nonylphenol (NP), caused a dose-dependent stimulatory effect on the generation of reactive oxygen species (ROS) in human whole blood from 50 to 1000 microM, which was measured by chemiluminescence generation. ROS-scavenging enzymes such as catalase and superoxide dismutase, and the lipophilic antioxidative agents, alpha-tocopherol and beta-carotene, showed preventive effects on NP-induced ROS generation. To analyze the biochemical mechanism of NP-induced ROS generation in human blood, we investigated the effects of different types of metabolic inhibitors on the activation pathways of ROS generation. An NADPH-dependent oxidase inhibitor, diphenyl iodonium chloride (DPI), and a myeloperoxidase inhibitor, sodium azide (NaN3), showed remarkable inhibitory effects on ROS generation induced by NP, but an inhibitor against mitochondrial respiratory function, potassium cyanide (KCN), did not exhibit a significant effect. Furthermore, a phosphatidylinositol-3 (PI3) kinase inhibitor, wortmannin, and a tyrosine kinase inhibitor, protein phosphorylation inhibitor 1 (PP1), caused a strong suppression of NP-induced ROS generation. Selective protein kinase C inhibitor, Ro-32-0432, p38 MAP kinase inhibitor, SB-203580, and ERK MAP kinase inhibitor, PD 98059, showed significant suppressive effects on NP-induced ROS generation. In addition, when human blood was exposed to lower concentrations (5-50 microM) of NP, they did not cause the significant ROS generation by themselves, but the priming and synergistic effects of NP were detected by the addition of secondary stimulants, opsonized zymosan (OZ) or phorbol myristate acetate (PMA). The analysis of the priming and synergistic effects of NP on OZ- or PMA-dependent ROS generation by antioxidative substances and metabolic inhibitors showed similar results compared with those of human blood treated with NP alone. These results suggest that NP causes an enhancing effect by itself, or priming and synergistic

  1. Induction of Apoptosis by [8]-shogaol via Reactive Oxygen Species Generation, Glutathione Depletion and Caspase Activation in Human Leukemia Cells

    PubMed Central

    Shieh, Po-Chuen; Chen, Yi-Own; Kuo, Daih-Huang; Chen, Fu-An; Tsai, Mei-Ling; Chang, Ing-Shing; Wu, Hou; Sang, Shengmin; Ho, Chi-Tang; Pan, Min-Hsiung

    2010-01-01

    Ginger, the rhizome of Zingiber officinale, is a traditional medicine with carminative effect, anti-nausea, anti-inflammatory, and anti-carcinogenic properties. This study examined the growth inhibitory effects of [8]-shogaol, one of pungent phenolic compounds in ginger, on human leukemia HL-60 cells. It demonstrated that [8]-shogaol was able to induce apoptosis in a time- and concentration-dependent manner. Treatment with [8]-shogaol caused a rapid loss of mitochondrial transmembrane potential, stimulation of reactive oxygen species (ROS) production, release of mitochondrial cytochrome c into cytosol, and subsequent induction of procaspase-9 and procaspase-3 processing. Taken together, these results suggest for the first time that ROS production and depletion of the glutathione that committed to [8]-shogaol-induced apoptosis in HL-60 cells. PMID:20163181

  2. Nicotine- and tar-free cigarette smoke induces cell damage through reactive oxygen species newly generated by PKC-dependent activation of NADPH oxidase.

    PubMed

    Asano, Hiroshi; Horinouchi, Takahiro; Mai, Yosuke; Sawada, Osamu; Fujii, Shunsuke; Nishiya, Tadashi; Minami, Masabumi; Katayama, Takahiro; Iwanaga, Toshihiko; Terada, Koji; Miwa, Soichi

    2012-01-01

    We examined cytotoxic effects of nicotine/tar-free cigarette smoke extract (CSE) on C6 glioma cells. The CSE induced plasma membrane damage (determined by lactate dehydrogenase leakage and propidium iodide uptake) and cell apoptosis {determined by MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] reduction activity and DNA fragmentation}. The cytotoxic activity decayed with a half-life of approximately 2 h at 37°C, and it was abolished by N-acetyl-L-cysteine and reduced glutathione. The membrane damage was prevented by catalase and edaravone (a scavenger of (•)OH) but not by superoxide dismutase, indicating involvement of (•)OH. In contrast, the CSE-induced cell apoptosis was resistant to edaravone and induced by authentic H(2)O(2) or O(2)(-) generated by the xanthine/xanthine oxidase system, indicating involvement of H(2)O(2) or O(2)(-) in cell apoptosis. Diphenyleneiodonium [NADPH oxidase (NOX) inhibitor] and bisindolylmaleimide I [BIS I, protein kinase C (PKC) inhibitor] abolished membrane damage, whereas they partially inhibited apoptosis. These results demonstrate that 1) a stable component(s) in the CSE activates PKC, which stimulates NOX to generate reactive oxygen species (ROS), causing membrane damage and apoptosis; 2) different ROS are responsible for membrane damage and apoptosis; and 3) part of the apoptosis is caused by oxidants independently of PKC and NOX. PMID:22302021

  3. Singlet molecular oxygen generation by light-activated DHN-melanin of the fungal pathogen Mycosphaerella fijiensis in black Sigatoka disease of bananas.

    PubMed

    Beltrán-García, Miguel J; Prado, Fernanda M; Oliveira, Marilene S; Ortiz-Mendoza, David; Scalfo, Alexsandra C; Pessoa, Adalberto; Medeiros, Marisa H G; White, James F; Di Mascio, Paolo

    2014-01-01

    In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis.

  4. Singlet Molecular Oxygen Generation by Light-Activated DHN-Melanin of the Fungal Pathogen Mycosphaerella fijiensis in Black Sigatoka Disease of Bananas

    PubMed Central

    Beltrán-García, Miguel J.; Prado, Fernanda M.; Oliveira, Marilene S.; Ortiz-Mendoza, David; Scalfo, Alexsandra C.; Pessoa, Adalberto; Medeiros, Marisa H. G.; White, James F.; Di Mascio, Paolo

    2014-01-01

    In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis. PMID:24646830

  5. Singlet molecular oxygen generation by light-activated DHN-melanin of the fungal pathogen Mycosphaerella fijiensis in black Sigatoka disease of bananas.

    PubMed

    Beltrán-García, Miguel J; Prado, Fernanda M; Oliveira, Marilene S; Ortiz-Mendoza, David; Scalfo, Alexsandra C; Pessoa, Adalberto; Medeiros, Marisa H G; White, James F; Di Mascio, Paolo

    2014-01-01

    In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis. PMID:24646830

  6. Oxygen generator for medical applications (USIC)

    SciTech Connect

    Staiger, C. L.

    2012-03-01

    The overall Project objective is to develop a portable, non-cryogenic oxygen generator capable of supplying medical grade oxygen at sufficient flow rates to allow the field application of the Topical Hyperbaric Oxygen Therapy (THOT{reg_sign}) developed by Numotech, Inc. This project was sponsored by the U.S. Department of Energy Global Initiatives for Proliferation Prevention (GIPP) and is managed by collaboration between Sandia National Laboratories (SNL), Numotech, Inc, and LLC SPE 'Spektr-Conversion.' The project had two phases, with the objective of Phase I being to develop, build and test a laboratory prototype of the membrane-pressure swing adsorber (PSA) system producing at 15 L/min of oxygen with a minimum of 98% oxygen purity. Phase II objectives were to further refine and identify the pre-requisites needed for a commercial product and to determine the feasibility of producing 15 L/min of oxygen with a minimum oxygen purity of 99%. In Phase I, Spektr built up the necessary infrastructure to perform experimental work and proceeded to build and demonstrate a membrane-PSA laboratory prototype capable of producing 98% purity oxygen at a flow rate of 5 L/min. Spektr offered a plausible path to scale up the process for 15 L/min. Based on the success and experimental results obtained in Phase I, Spektr performed work in three areas for Phase II: construction of a 15 L/min PSA; investigation of compressor requirements for the front end of the membrane/PSA system; and performing modeling and simulation of assess the feasibility of producing oxygen with a purity greater than 99%. Spektr successfully completed all of the tasks under Phase II. A prototype 15 L/min PSA was constructed and operated. Spektr determined that no 'off the shelf' air compressors met all of the specifications required for the membrane-PSA, so a custom compressor will likely need to be built. Modeling and simulation concluded that production of oxygen with purities greater than 99% was possible

  7. 21 CFR 868.5440 - Portable oxygen generator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Portable oxygen generator. 868.5440 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5440 Portable oxygen generator. (a) Identification. A portable oxygen generator is a device that is intended to release oxygen for...

  8. 49 CFR 173.168 - Chemical oxygen generators.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Chemical oxygen generators. 173.168 Section 173... Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8 of this subchapter) may be transported only under the following conditions: (a) Approval. A chemical oxygen...

  9. 49 CFR 173.168 - Chemical oxygen generators.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Chemical oxygen generators. 173.168 Section 173... Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8 of this subchapter) may be transported only under the following conditions: (a) Approval. A chemical oxygen...

  10. 21 CFR 868.5440 - Portable oxygen generator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Portable oxygen generator. 868.5440 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5440 Portable oxygen generator. (a) Identification. A portable oxygen generator is a device that is intended to release oxygen for...

  11. 49 CFR 173.168 - Chemical oxygen generators.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Chemical oxygen generators. 173.168 Section 173... Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8 of this subchapter) may be transported only under the following conditions: (a) Approval. A chemical oxygen...

  12. 21 CFR 868.5440 - Portable oxygen generator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Portable oxygen generator. 868.5440 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5440 Portable oxygen generator. (a) Identification. A portable oxygen generator is a device that is intended to release oxygen for...

  13. 49 CFR 173.168 - Chemical oxygen generators.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Chemical oxygen generators. 173.168 Section 173... Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8 of this subchapter) may be transported only under the following conditions: (a) Approval. A chemical oxygen...

  14. 21 CFR 868.5440 - Portable oxygen generator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Portable oxygen generator. 868.5440 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5440 Portable oxygen generator. (a) Identification. A portable oxygen generator is a device that is intended to release oxygen for...

  15. 49 CFR 173.168 - Chemical oxygen generators.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Chemical oxygen generators. 173.168 Section 173... Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8 of this subchapter) may be transported only under the following conditions: (a) Approval. A chemical oxygen...

  16. 21 CFR 868.5440 - Portable oxygen generator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Portable oxygen generator. 868.5440 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5440 Portable oxygen generator. (a) Identification. A portable oxygen generator is a device that is intended to release oxygen for...

  17. Catalysts for electrochemical generation of oxygen

    NASA Technical Reports Server (NTRS)

    Ogrady, W. E.

    1976-01-01

    An investigation of more effective catalysts for the electrolytic evolution of oxygen was made to understand the mechanism and kinetics for the electrocatalysis in relation to the surface electronic and lattice properties of the catalyst. An understanding was obtained for the structural features of the electrocatalysts. The kinetics and mechanism of anodic generation of O2 under well defined conditions in relation to the properties of electrode surface were evaluated.

  18. Electrode system for electric-discharge generation of atomic iodine in a repetitively pulsed oxygen - iodine laser with a large active volume

    SciTech Connect

    Kazantsev, S Yu; Kononov, I G; Podlesnykh, S V; Firsov, K N

    2010-08-03

    Possibilities for increasing the active medium volume of a chemical oxygen - iodine laser (CCOIL) with a pulsed electric-discharge generation of atomic iodine are studied. The reasons are analysed of the low stability of the transverse self-sustained volume discharge in electrode systems with metal cathodes under the conditions of the electric energy input into gas-discharge plasma that are typical for CCOILs: low pressure of mixtures containing a strongly electronegative component, low voltage of discharge burning, low specific energy depositions, and long duration of the current pulse. An efficient electrode system is elaborated with the cathode based on an anisotropically-resistive material, which resulted in a stable discharge in the mixtures of iodide (CH{sub 3}I, n-C{sub 3}H{sub 7}I, C{sub 2}H{sub 5}I) with oxygen and nitrogen at the specific energy depositions of {approx}5 J L{sup -1}, pressures of 10 - 25 Torr, and mixture volume of 2.5 L. (lasers)

  19. Module for Oxygenating Water without Generating Bubbles

    NASA Technical Reports Server (NTRS)

    Gonzalez-Martin, Anuncia; Sidik, Reyimjan; Kim, Jinseong

    2004-01-01

    A module that dissolves oxygen in water at concentrations approaching saturation, without generating bubbles of oxygen gas, has been developed as a prototype of improved oxygenators for water-disinfection and water-purification systems that utilize photocatalyzed redox reactions. Depending on the specific nature of a water-treatment system, it is desirable to prevent the formation of bubbles for one or more reasons: (1) Bubbles can remove some organic contaminants from the liquid phase to the gas phase, thereby introducing a gas-treatment problem that complicates the overall water-treatment problem; and/or (2) in some systems (e.g., those that must function in microgravity or in any orientation in normal Earth gravity), bubbles can interfere with the flow of the liquid phase. The present oxygenation module (see Figure 1) is a modified version of a commercial module that contains >100 hollow polypropylene fibers with a nominal pore size of 0.05 m and a total surface area of 0.5 m2. The module was originally designed for oxygenation in a bioreactor, with no water flowing around or inside the tubes. The modification, made to enable the use of the module to oxygenate flowing water, consisted mainly in the encapsulation of the fibers in a tube of Tygon polyvinyl chloride (PVC) with an inside diameter of 1 in. (approx.=25 mm). In operation, water is pumped along the insides of the hollow fibers and oxygen gas is supplied to the space outside the hollow tubes inside the PVC tube. In tests, the pressure drops of water and oxygen in the module were found to be close to zero at water-flow rates ranging up to 320 mL/min and oxygen-flow rates up to 27 mL/min. Under all test conditions, no bubbles were observed at the water outlet. In some tests, flow rates were chosen to obtain dissolved-oxygen concentrations between 25 and 31 parts per million (ppm) . approaching the saturation level of approx.=35 ppm at a temperature of 20 C and pressure of 1 atm (approx.=0.1 MPa). As one

  20. Identification of differential anti-neoplastic activity of copper bis(thiosemicarbazones) that is mediated by intracellular reactive oxygen species generation and lysosomal membrane permeabilization.

    PubMed

    Stefani, Christian; Al-Eisawi, Zaynab; Jansson, Patric J; Kalinowski, Danuta S; Richardson, Des R

    2015-11-01

    Bis(thiosemicarbazones) and their copper (Cu) complexes possess unique anti-neoplastic properties. However, their mechanism of action remains unclear. We examined the structure-activity relationships of twelve bis(thiosemicarbazones) to elucidate factors regarding their anti-cancer efficacy. Importantly, the alkyl substitutions at the diimine position of the ligand backbone resulted in two distinct groups, namely, unsubstituted/monosubstituted and disubstituted bis(thiosemicarbazones). This alkyl substitution pattern governed their: (1) Cu(II/I) redox potentials; (2) ability to induce cellular (64)Cu release; (3) lipophilicity; and (4) anti-proliferative activity. The potent anti-cancer Cu complex of the unsubstituted bis(thiosemicarbazone) analog, glyoxal bis(4-methyl-3-thiosemicarbazone) (GTSM), generated intracellular reactive oxygen species (ROS), which was attenuated by Cu sequestration by a non-toxic Cu chelator, tetrathiomolybdate, and the anti-oxidant, N-acetyl-l-cysteine. Fluorescence microscopy suggested that the anti-cancer activity of Cu(GTSM) was due, in part, to lysosomal membrane permeabilization (LMP). For the first time, this investigation highlights the role of ROS and LMP in the anti-cancer activity of bis(thiosemicarbazones).

  1. Bamboo Vinegar Decreases Inflammatory Mediator Expression and NLRP3 Inflammasome Activation by Inhibiting Reactive Oxygen Species Generation and Protein Kinase C-α/δ Activation

    PubMed Central

    Ka, Shuk-Man; Chen, Ann; Tasi, Yu-Ling; Liu, May-Lan; Chiu, Yi-Chich; Hua, Kuo-Feng

    2013-01-01

    Bamboo vinegar (BV), a natural liquid derived from the condensation produced during bamboo charcoal production, has been used in agriculture and as a food additive, but its application to immune modulation has not been reported. Here, we demonstrated that BV has anti-inflammatory activities both in vitro and in vivo. BV reduced inducible nitric oxide synthase expression and nitric oxide levels in, and interleukin-6 secretion by, lipopolysaccharide-activated macrophages without affecting tumor necrosis factor-α secretion and cyclooxygenase-2 expression. The mechanism for the anti-inflammatory effect of BV involved decreased reactive oxygen species production and protein kinase C-α/δ activation. Furthermore, creosol (2-methoxy-4-methylphenol) was indentified as the major anti-inflammatory compound in BV. Impaired cytokine expression and NLR family, pyrin domain-containing 3 (NLRP3) inflammasome activation was seen in mice treated with creosol. These findings provide insights into how BV regulates inflammation and suggest that it may be a new source for the development of anti-inflammatory agents or a healthy supplement for preventing and ameliorating inflammation- and NLRP3 inflammasome-related diseases, including metabolic syndrome. PMID:24124509

  2. SPE (trademark) Oxygen Generator Assembly (OGA). (Refurbishment of the technology demonstrator LFSPE oxygen generation subsystem)

    NASA Technical Reports Server (NTRS)

    Roy, Robert J.

    1995-01-01

    The SPE Oxygen Generator Assembly (OGA) has been modified to correct operational deficiencies present in the original system, and to effect changes to the system hardware and software such that its operating conditions are consistent with the latest configuration requirements for the International Space Station Alpha (ISSA). The effectiveness of these changes has recently been verified through a comprehensive test program which saw the SPE OGA operate for over 740 hours at various test conditions, including over 690 hours, or approximately 460 cycles, simulating the orbit of the space station. This report documents the changes made to the SPE OGA, presents and discusses the test results from the acceptance test program, and provides recommendations for additional development activities pertinent to evolution of the SPE OGA to a flight configuration. Copies of the test data from the acceptance test program are provided with this report on 3.5 inch diskettes in self-extracting archive files.

  3. Electrolysis cell functions as water vapor dehumidifier and oxygen generator

    NASA Technical Reports Server (NTRS)

    Clifford, J. E.

    1971-01-01

    Water vapor is absorbed in hygroscopic electrolyte, and oxygen generated by absorbed water electrolysis at anode is added simultaneously to air stream. Cell applications include on-board aircraft oxygen systems, portable oxygen generators, oxygen concentration requirements, and commercial air conditioning and dehumidifying systems.

  4. Catha edulis Extract Induces H9c2 Cell Apoptosis by Increasing Reactive Oxygen Species Generation and Activation of Mitochondrial Proteins

    PubMed Central

    Mohan, Syam; Abdelwahab, Siddig Ibrahim; Hobani, Yahya Hasan; Syam, Suvitha; Al-Zubairi, Adel S.; Al-Sanousi, Rashad; Oraiby, Magbool Essa

    2016-01-01

    Background: Catha edulis (Khat) is an evergreen shrub or small tree, traditionally used by various peoples of the Arabian Peninsula and Africa as an integral component of the socioeconomic traditions. It is believed that the psychostimulant nature and toxic nature of khat is primarily due to the presence of cathinone and cathine respectively. Studies have shown that khat chewing is closely associated with cardiac complications, especially myocardial infarction. Hence in this study, we exposed cathine-rich khat extract in a cardiomyoblast H9c2 (2-1) cell line to check the cell death mechanism. Materials and Methods: Extraction of Catha edulis leaves was done and the presence of cathine was confirmed with LC-MS-MS. The anti-proliferative activity was assayed using MTT and apoptosis detection by acridine orange/propidium iodide assay. The expression of Bcl-2 and Bax protein and caspase-3/7 expression were analyzed. The level of reactive oxygen species generation was also evaluated. Results: The khat extract showed an IC50 value of 86.5 μg/ml at 48 hours treatment. We have observed significant early apoptosis events by intervened acridine orange within the fragmented DNA with bright green fluorescence upon treatment. The Bcl-2 expression in the treatment with IC50 concentration of khat extract for 24, 48 and 72 hours of incubation significantly decreased with increase in bax level. The increased activation of caspase-3/7 was significantly observed upon treatment together with significant increase of ROS was detected at 24 and 48 hours treatment. Conclusion: Collectively, our results provide insight into the mechanisms by which Catha edulis leaves mediate cell death in cardiomyocytes. SUMMARY Catha edulis (Khat) is an evergreen psychotropic shrub or small treeExtraction of khat leaves was done and the presence of cathine was confirmed with liquid chromatography-mass spectrometry-mass spectrometryThe khat extract showed an IC50 value of 86.5 μg/ml at 48 h treatment in

  5. 14 CFR 25.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... device which produces oxygen by chemical reaction. (b) Each chemical oxygen generator must be designed... sustained operation by successive replacement of a generator element must be placarded to show— (1) The...

  6. 14 CFR 25.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... device which produces oxygen by chemical reaction. (b) Each chemical oxygen generator must be designed... sustained operation by successive replacement of a generator element must be placarded to show— (1) The...

  7. 14 CFR 25.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... device which produces oxygen by chemical reaction. (b) Each chemical oxygen generator must be designed... sustained operation by successive replacement of a generator element must be placarded to show— (1) The...

  8. Angiotensin II induces Fat1 expression/activation and vascular smooth muscle cell migration via Nox1-dependent reactive oxygen species generation

    PubMed Central

    Bruder-Nascimento, T; Chinnasamy, P; Riascos-Bernal, DF; Cau, SB; Callera, GE; Touyz, RM; Tostes, RC; Sibinga, NES

    2013-01-01

    Fat1 is an atypical cadherin that controls vascular smooth muscle cell (VSMC) proliferation and migration. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 1 (Nox1) is an important source of reactive oxygen species (ROS) in VSMCs. Angiotensin II (Ang II) induces the expression and/or activation of both Fat1 and Nox1 proteins. This study tested the hypothesis that Ang II-induced Fat1 activation and VSMC migration are mediated by Nox1-dependent ROS generation and redox signaling. Studies were performed in cultured VSMCs from Sprague-Dawley rats. Cells were treated with Ang II (1 μmol/L) for short (5 to 30 min) or long term stimulations (3 to 12 h) in the absence or presence of the antioxidant apocynin (10 μmol/L), extracellular-signal-regulated kinases 1/2 (Erk1/2) inhibitor PD98059 (1 μmol/L), or Ang II type 1 receptor (AT1R) valsartan (1 μmol/L). siRNA was used to knockdown Nox1 or Fat1. Cell migration was determined by Boyden chamber assay. Ang II increased Fat1 mRNA and protein levels and promoted Fat1 translocation to the cell membrane, responses that were inhibited by AT1R antagonist and antioxidant treatment. Downregulation of Nox1 inhibited the effects of Ang II on Fat1 protein expression. Nox1 protein induction, ROS generation, and p44/p42 MAPK phosphorylation in response to Ang II were prevented by valsartan and apocynin, and Nox1 siRNA inhibited Ang II-induced ROS generation. Knockdown of Fat1 did not affect Ang II-mediated increases in Nox1 expression or ROS. Inhibition of p44/p42 MAPK phosphorylation by PD98059 abrogated the Ang II-induced increase in Fat1 expression and membrane translocation. Knockdown of Fat1 inhibited Ang II-induced VSMC migration, which was also prevented by valsartan, apocynin, PD98059, and Nox1 siRNA. Our findings indicate that Ang II regulates Fat1 expression and activity and induces Fat1-dependent VSMC migration via activation of AT1R, ERK1/2, and Nox1-derived ROS, suggesting a role for Fat1 downstream of Ang II

  9. Non-transferrin bound iron, cytokine activation and intracellular reactive oxygen species generation in hemodialysis patients receiving intravenous iron dextran or iron sucrose.

    PubMed

    Pai, Amy Barton; Conner, Todd; McQuade, Charles R; Olp, Jonathan; Hicks, Paul

    2011-08-01

    Intravenous (IV) iron supplementation is widely used to support erythropoeisis in hemodialysis patients. IV iron products are associated with oxidative stress that has been measured principally by circulating biomarkers such as products of lipid peroxidation. The pro-oxidant effects of IV iron are presumed to be due at least in part, by free or non-transferrin bound iron (NTBI). However, the effects of IV iron on intracellular redox status and downstream effectors is not known. This prospective, crossover study compared cytokine activation, reactive oxygen species generation and oxidative stress after single IV doses of iron sucrose and iron dextran. This was a prospective, open-label, crossover study. Ten patients with end-stage renal disease (ESRD) on hemodialysis and four age and sex-matched healthy were assigned to receive 100 mg of each IV iron product over 5 min in random sequence with a 2 week washout between products. Subjects were fasted and fed a low iron diet in the General Clinical Research Center at the University of New Mexico. Serum and plasma samples for IL-1, IL-6, TNF-α and IL-10 and NTBI were obtained at baseline, 60 and 240 min after iron infusion. Peripheral blood mononuclear cells (PBMC) were isolated at the same time points and stained with fluorescent probes to identify intracellular reactive oxygen species and mitochondrial membrane potential (Δψm) by flow cytometry. Lipid peroxidation was assessed by plasma F(2) isoprostane concentration. Mean ± SEM maximum serum NTBI values were significantly higher among patients receiving IS compared to ID (2.59 ± 0.31 and 1.0 ± 0.36 µM, respectively, P = 0.005 IS vs. ID) Mean ± SEM NTBI area under the serum concentration-time curve (AUC) was 3-fold higher after IS versus ID (202 ± 53 vs. 74 ± 23 µM*min/l, P = 0.04) in ESRD patients, indicating increased exposure to NTBI. IV iron administration was associated with increased pro-inflammatory cytokines. Serum IL-6 concentrations increased most

  10. Water Processor and Oxygen Generation Assembly

    NASA Technical Reports Server (NTRS)

    Bedard, John

    1997-01-01

    This report documents the results of the tasks which initiated efforts on design issues relating to the Water Processor (WP) and the Oxygen Generation Assembly (OGA) Flight Hardware for the International Space Station. This report fulfills the Statement of Work deliverables requirement for contract H-29387D. The following lists the tasks required by contract H-29387D: (1) HSSSI shall coordinate a detailed review of WP/OGA Flight Hardware program requirements with personnel from MSFC to identify requirements that can be eliminated without affecting the technical integrity of the WP/OGA Hardware; (2) HSSSI shall conduct the technical interchanges with personnel from MSFC to resolve design issues related to WP/OGA Flight Hardware; (3) HSSSI will initiate discussions with Zellwegger Analytics, Inc. to address design issues related to WP and PCWQM interfaces.

  11. 14 CFR 25.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... device which produces oxygen by chemical reaction. (b) Each chemical oxygen generator must be designed... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Chemical oxygen generators. 25.1450 Section... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment Miscellaneous Equipment § 25.1450...

  12. 14 CFR 25.1450 - Chemical oxygen generators.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... device which produces oxygen by chemical reaction. (b) Each chemical oxygen generator must be designed... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Chemical oxygen generators. 25.1450 Section... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment Miscellaneous Equipment § 25.1450...

  13. Active oxygen doctors the evidence

    NASA Astrophysics Data System (ADS)

    Castelló, Ana; Francès, Francesc; Corella, Dolores; Verdú, Fernando

    2009-02-01

    Investigation at the scene of a crime begins with the search for clues. In the case of bloodstains, the most frequently used reagents are luminol and reduced phenolphthalein (or phenolphthalin that is also known as the Kastle-Meyer colour test). The limitations of these reagents have been studied and are well known. Household cleaning products have evolved with the times, and new products with active oxygen are currently widely used, as they are considered to be highly efficient at removing all kinds of stains on a wide range of surfaces. In this study, we investigated the possible effects of these new cleaning products on latent bloodstains that may be left at a scene of a crime. To do so, various fabrics were stained with blood and then washed using cleaning agents containing active oxygen. The results of reduced phenolphthalein, luminol and human haemoglobin tests on the washed fabrics were negative. The conclusion is that these new products alter blood to such an extent that it can no longer be detected by currently accepted methods employed in criminal investigations. This inability to locate bloodstains means that highly important evidence (e.g. a DNA profile) may be lost. Consequently, it is important that investigators are aware of this problem so as to compensate for it.

  14. Solar Energy Systems for Lunar Oxygen Generation

    NASA Technical Reports Server (NTRS)

    Colozza, Anthony J.; Heller, Richard S.; Wong, Wayne A.; Hepp, Aloysius F.

    2010-01-01

    An evaluation of several solar concentrator-based systems for producing oxygen from lunar regolith was performed. The systems utilize a solar concentrator mirror to provide thermal energy for the oxygen production process. Thermal energy to power a Stirling heat engine and photovoltaics are compared for the production of electricity. The electricity produced is utilized to operate the equipment needed in the oxygen production process. The initial oxygen production method utilized in the analysis is hydrogen reduction of ilmenite. Utilizing this method of oxygen production a baseline system design was produced. This baseline system had an oxygen production rate of 0.6 kg/hr with a concentrator mirror size of 5 m. Variations were performed on the baseline design to show how changes in the system size and process (rate) affected the oxygen production rate. An evaluation of the power requirements for a carbothermal lunar regolith reduction reactor has also been conducted. The reactor had a total power requirement between 8,320 to 9,961 W when producing 1000 kg/year of oxygen. The solar concentrator used to provide the thermal power (over 82 percent of the total energy requirement) would have a diameter of less than 4 m.

  15. Active Learning Crosses Generations.

    ERIC Educational Resources Information Center

    Woodard, Diane K.

    2002-01-01

    Describes the benefits of intergenerational programs, highlighting a child care program that offers age-appropriate and mutually beneficial activities for children and elders within a nearby retirement community. The program has adopted High/Scope's active learning approach to planning and implementing activities that involve both generations. The…

  16. Catalysts for electrochemical generation of oxygen

    NASA Technical Reports Server (NTRS)

    Ogrady, W. E.; Huang, J.

    1975-01-01

    An effort was made to study the effects of cation and anion additions on oxygen evolution kinetics on platinum and the inhibitive or catalytic nature of the additions. The kinetics and mechanism of oxygen evolution on planitum metal in hydrofluoric and sulfuric acids, including the effects of foreign anions, were examined. The LEED-Auger-thin layer electrochemical system was developed for the examination of electrocatalytic surfaces. Samples for electrocatalytic LEED-Auger studies were prepared and examined.

  17. Oxygen Generation from Carbon Dioxide for Advanced Life Support

    NASA Technical Reports Server (NTRS)

    Bishop, Sean; Duncan, Keith; Hagelin-Weaver, Helena; Neal, Luke; Sanchez, Jose; Paul, Heather L.; Wachsman, Eric

    2007-01-01

    The partial electrochemical reduction of carbon dioxide (CO2) using ceramic oxygen generators (COGs) is well known and widely studied. However, complete reduction of metabolically produced CO2 (into carbon and oxygen) has the potential of reducing oxygen storage weight for life support if the oxygen can be recovered. Recently, the University of Florida devel- oped novel ceramic oxygen generators employing a bilayer elec- trolyte of gadolinia-doped ceria and erbia-stabilized bismuth ox- ide (ESB) for NASA's future exploration of Mars. The results showed that oxygen could be reliably produced from CO2 at temperatures as low as 400 C. The strategy discussed here for advanced life support systems employs a catalytic layer com- bined with a COG cell so that CO2 is reduced all the way to solid carbon and oxygen without carbon buildup on the COG cell and subsequent deactivation.

  18. A spectral study of a radio-frequency plasma-generated flux of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Batten, Carmen E.; Brown, Kenneth G.; Lewis, Beverley W.

    1994-01-01

    The active environment of a radio-frequency (RF) plasma generator, with and without low-pressure oxygen, has been characterized through the identification of emission lines in the spectral region from 250 to 900 nm. The environment is shown to be dependent on the partial pressure of oxygen and the power applied to the RF generator. Atomic oxygen has been found in significant amounts as well as atomic hydrogen and the molecular oxygen species O2((sup 1)Sigma). The only charged species observed was the singly charged molecular ion O2(+). With a polymer specimen in the plasma chamber, carbon monoxide was also observed. The significance of these observations with respect to previous studies using this type of generator to stimulate material degradation in space is discussed. The possibility of using these generators as atomic oxygen sources in the development of oxygen atom fluorescence sensors is explored.

  19. Anti-leukemia activity of PVP-coated silver nanoparticles via generation of reactive oxygen species and release of silver ions.

    PubMed

    Guo, Dawei; Zhu, Lingying; Huang, Zhihai; Zhou, Haixia; Ge, Yue; Ma, Wenjuan; Wu, Jie; Zhang, Xiuyan; Zhou, Xuefeng; Zhang, Yu; Zhao, Yun; Gu, Ning

    2013-10-01

    Silver nanoparticles (AgNPs) have anti-cancer effect. However, whether and how these particles could inhibit the growth of acute myeloid leukemia (AML) cells is unclear. In the present study, we prepared AgNPs with various sizes and investigated their cytotoxic effect on AML cells. We found that AgNPs could inhibit the viability of AML cells including the isolates from AML patients. AgNPs caused the production of reactive oxygen species (ROS), losses of mitochondrial membrane potential (MMP), DNA damage and apoptosis. Both vitamin C (Vit C) and N-acetyl-L-cysteine (NAC) could completely reverse the generation of ROS upon AgNPs, however only NAC but not Vit C could protect the cells from losses of MMP, DNA damage and apoptosis thoroughly. Similar results were obtained when cells were treated with silver ions alone. As NAC was not only an antioxidant to scavenge ROS but also a silver ion chelator, these data supported the model that both generation of ROS and release of silver ions played critical roles in the AgNPs-induced cytotoxic effect against AML cells. Taken together, this work elucidated the cytotoxic effect of AgNPs on AML cells and their underlying mechanism and might have significant impact on AML treatment.

  20. Small UHV compatible hyperthermal oxygen atom generator

    NASA Technical Reports Server (NTRS)

    Outlaw, Ronald A. (Inventor); Davison, Mark R. (Inventor)

    1994-01-01

    A high purity, hyperthermal, continuous beam atomic oxygen source capable of retrofitting to existing UHV systems has been developed. The instrument complements a general system capability, while its small size and simplicity of design permits tailoring the instrument for most experimental geometries. The flux level presently available is near 1 x 10 (exp 14) cm(exp -2)s(exp -1)(3P) but may be extended toward the theoretical limit of 3x10(exp 15 cm(exp -2)s(exp -1). The energy distribution of the emitted neutrals shows that the mean kinetic energy is about the same as observed for the ions or about 4 eV. The energy of the oxygen atoms may be substantially reduced for other applications by collision with a temperature controlled, non-reactive surface (with a concomitant spread in the energy distribution).

  1. Catalysts for electrochemical generation of oxygen

    NASA Technical Reports Server (NTRS)

    Hagans, P.; Yeager, E.

    1978-01-01

    Single crystal surfaces of platinum and gold and transition metal oxides of the spinel type were studied to find more effective catalysts for the electrolytic evolution of oxygen and to understand the mechanism and kinetics for the electrocatalysis in relation to the surface electronic and lattice properties of the catalyst. The single crystal studies involve the use of low energy electron diffraction (LEED) and Auger electron spectroscopy as complementary tools to the electrochemical measurements. Modifications to the transfer system and to the thin-layer electrochemical cell used to facilitate the transfer between the ultrahigh vacuum environment of the electron surface physics equipment and the electrochemical environment with a minimal possibility of changes in the surface structure, are described. The electrosorption underpotential deposition of Pb onto the Au(111), (100) and (110) single crystal surfaces with the thin-layer cell-LEED-Auger system is discussed as well as the synthesis of spinels for oxygen evolution studies.

  2. A 99 percent purity molecular sieve oxygen generator

    NASA Technical Reports Server (NTRS)

    Miller, G. W.

    1991-01-01

    Molecular sieve oxygen generating systems (MSOGS) have become the accepted method for the production of breathable oxygen on military aircraft. These systems separate oxygen for aircraft engine bleed air by application of pressure swing adsorption (PSA) technology. Oxygen is concentrated by preferential adsorption in nitrogen in a zeolite molecular sieve. However, the inability of current zeolite molecular sieves to discriminate between oxygen and argon results in an oxygen purity limitations of 93-95 percent (both oxygen and argon concentrate). The goal was to develop a new PSA process capable of exceeding the present oxygen purity limitations. A novel molecular sieve oxygen concentrator was developed which is capable of generating oxygen concentrations of up to 99.7 percent directly from air. The process is comprised of four absorbent beds, two containing a zeolite molecular sieve and two containing a carbon molecular sieve. This new process may find use in aircraft and medical breathing systems, and industrial air separation systems. The commercial potential of the process is currently being evaluated.

  3. A Method for Generating Oxygen from Consumer Chemicals

    NASA Astrophysics Data System (ADS)

    Wright, Stephen W.

    2003-10-01

    The rapidly accelerated combustion of wood, paper, carbon, a candle, and steel wool in oxygen gas is presented. The oxygen gas is generated as needed in the bottles used for the demonstration using chemicals readily available on the retail market: liquid chlorine bleach and 3% hydrogen peroxide.

  4. Catalysts for electrochemical generation of oxygen

    NASA Technical Reports Server (NTRS)

    Hagans, P.; Yeager, E.

    1979-01-01

    Several aspects of the electrolytic evolution of oxygen for use in life support systems are analyzed including kinetic studies of various metal and nonmetal electrode materials, the formation of underpotential films on electrodes, and electrode surface morphology and the use of single crystal metals. In order to investigate the role of surface morphology to electrochemical reactions, a low energy electron diffraction and an Auger electron spectrometer are combined with an electrochemical thin-layer cell allowing initial characterization of the surface, reaction run, and then a comparative surface analysis.

  5. Oxygen Generation System Laptop Bus Controller Flight Software

    NASA Technical Reports Server (NTRS)

    Rowe, Chad; Panter, Donna

    2009-01-01

    The Oxygen Generation System Laptop Bus Controller Flight Software was developed to allow the International Space Station (ISS) program to activate specific components of the Oxygen Generation System (OGS) to perform a checkout of key hardware operation in a microgravity environment, as well as to perform preventative maintenance operations of system valves during a long period of what would otherwise be hardware dormancy. The software provides direct connectivity to the OGS Firmware Controller with pre-programmed tasks operated by on-orbit astronauts to exercise OGS valves and motors. The software is used to manipulate the pump, separator, and valves to alleviate the concerns of hardware problems due to long-term inactivity and to allow for operational verification of microgravity-sensitive components early enough so that, if problems are found, they can be addressed before the hardware is required for operation on-orbit. The decision was made to use existing on-orbit IBM ThinkPad A31p laptops and MIL-STD-1553B interface cards as the hardware configuration. The software at the time of this reporting was developed and tested for use under the Windows 2000 Professional operating system to ensure compatibility with the existing on-orbit computer systems.

  6. Oxygen rich gas generator design and performance analysis

    NASA Technical Reports Server (NTRS)

    Gloyer, P. W.; Knuth, W. H.; Crawford, R. A.

    1993-01-01

    The present oxygen-rich combustion research investigates oxygen gas generator concepts. The theoretical and modeling aspects of a selected concept are presented, together with a refined concept resulting from the findings of the study. This investigation examined a counter-flow gas generator design for O2/H2 mass ratios of 100-200, featuring a near-stoichiometric combustion zone followed by downstream mixing. The critical technologies required to develop a performance model are analyzed and include the following: (1) oxygen flow boiling; (2) two-phase oxygen flow heat transfer; (3) film-cooling in the combustion zone; (4) oxygen-rich combustion with hydrogen; and (5) mixing and dilution.

  7. Manipulation of environmental oxygen modifies reactive oxygen and nitrogen species generation during myogenesis

    PubMed Central

    McCormick, Rachel; Pearson, Timothy; Vasilaki, Aphrodite

    2016-01-01

    Regulated changes in reactive oxygen and nitrogen species (RONS) activities are important in maintaining the normal sequence and development of myogenesis. Both excessive formation and reduction in RONS have been shown to affect muscle differentiation in a negative way. Cultured cells are typically grown in 20% O2 but this is not an appropriate physiological concentration for a number of cell types, including skeletal muscle. The aim was to examine the generation of RONS in cultured skeletal muscle cells under a physiological oxygen concentration condition (6% O2) and determine the effect on muscle myogenesis. Primary mouse satellite cells were grown in 20% or 6% O2 environments and RONS activity was measured at different stages of myogenesis by real-time fluorescent microscopy using fluorescent probes with different specificities i.e. dihydroethidium (DHE), 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM DA) and 5-(and-6)-chloromethyl-2′,7′ -dichlorodihydrofluorescein diacetate (CM-DCFH-DA). Data demonstrate that satellite cell proliferation increased when cells were grown in 6% O2 compared with 20% O2. Myoblasts grown in 20% O2 showed an increase in DCF fluorescence and DHE oxidation compared with myoblasts grown at 6% O2. Myotubes grown in 20% O2 also showed an increase in DCF and DAF-FM fluorescence and DHE oxidation compared with myotubes grown in 6% O2. The catalase and MnSOD contents were also increased in myoblasts and myotubes that were maintained in 20% O2 compared with myoblasts and myotubes grown in 6% O2. These data indicate that intracellular RONS activities in myoblasts and myotubes at rest are influenced by changes in environmental oxygen concentration and that the increased ROS may influence myogenesis in a negative manner. PMID:26827127

  8. Sodium arsenite induced reactive oxygen species generation, nuclear factor (erythroid-2 related) factor 2 activation, heme oxygenase-1 expression, and glutathione elevation in Chang human hepatocytes.

    PubMed

    Li, Bing; Li, Xin; Zhu, Bo; Zhang, Xinyu; Wang, Yi; Xu, Yuanyuan; Wang, Huihui; Hou, Yongyong; Zheng, Quanmei; Sun, Guifan

    2013-07-01

    Liver is one of the major target organs of arsenic toxicity and carcinogenesis. Nuclear factor (erythroid-2 related) factor 2 (Nrf2) is a redox-sensitive transcription factor, regulating critically cellular defense responses against the toxic metallic arsenic in many cell types and tissues. This study was conducted to evaluate the hepato-cellular Nrf2 and Nrf2-regulated antioxidant reactions of sodium arsenite exposure in Chang human hepatocytes. Nrf2 and heme oxygenase-1 (HO-1) protein levels were detected by Western blot, and Nrf2-regulated HO-1 mRNA expressions were determined using semiquantitative RT-PCR by 0∼50 μmol/L of sodium arsenite exposure for 2, 6, 12, and 24 h. We also observed the changes of intracellular reactive oxygen species (ROS) and total cellular glutathione (GSH) by flow cytometry and spectrophotometry, respectively. Our results showed that intracellular ROS were both dose- and time-dependent induced by inorganic arsenic; Cellular Nrf2 protein levels increased rapidly after 2 h of exposure, elevated significantly at 6 h, and reached the maximum at 12 h. The endogenous Nrf2-regulated downstream HO-1 mRNA and protein were also induced dramatically and lasted for as long as 24 h. In addition, intracellular GSH levels elevated in consistent with Nrf2 activation. Our findings here suggest that inorganic arsenic alters cellular redox balance in hepatocytes to trigger Nrf2-regulated antioxidant responses promptly, which may represent an adaptive cell defense mechanism against inorganic arsenic induced liver injuries and hepatoxicity.

  9. Wave activated generator

    SciTech Connect

    Neuenschwander, V. L.

    1985-09-03

    A wave activated generator utilizes the principle of providing relative movement between a permanent magnet and a coil to induce an electrical current in the coil. The coil is situated in a static tube anchored to the sea bed by means of a ballast tank at the base of the tube and guy wires extending from the tube. A plunger with permanent magnets is mounted in the tube for vertical reciprocation of the plunger, the plunger projecting outwardly from the upper end of the tube and terminating in a hull-shaped float which rides the water surface and provides vertical reciprocation of the plunger responsive to wave motion in order to move the magnets relative to the coil and generate current in the coil.

  10. Cycle time control of an onboard oxygen generation system.

    PubMed

    Beaman, J J; Wang, S Y; Masada, G Y

    1987-12-01

    The outlet oxygen concentration of an onboard oxygen generation system (OBOGS) is controlled in this study by varying the cycle time of a pressure swing adsorption process. The control of the oxygen concentration is highly desirable since both high and low concentrations of oxygen can cause physiological problems. This cycle time control method can be easily implemented using a DC motor and a simple electronic controller. The physiological requirements recommended for high-performance tactical aircraft can be met by this method with either an open-loop or closed-loop configuration. The open-loop configuration requires the measurement of crew breathing flowrate and cabin pressure. The closed-loop configuration requires an additional measurement of oxygen concentration, but it has the advantage of being more adaptive to system variability during setup and operation. The method in either configuration requires very little adjustment and setup time in order to meet the specifications.

  11. Effect of oxygen concentration on microsomal oxidation of ethanol and generation of oxygen radicals.

    PubMed Central

    Puntarulo, S; Cederbaum, A I

    1988-01-01

    The iron-catalysed production of hydroxyl radicals, by rat liver microsomes (microsomal fractions), assessed by the oxidation of substrate scavengers and ethanol, displayed a biphasic response to the concentration of O2 (varied from 3 to 70%), reaching a maximal value with 20% O2. The decreased rates of hydroxyl-radical generation at lower O2 concentrations correlates with lower rates of production of H2O2, the precursor of hydroxyl radical, whereas the decreased rates at elevated O2 concentrations correlate with lower rates (relative to 20% O2) of activity of NADPH-cytochrome P-450 reductase, which reduces iron and is responsible for redox cycling of iron by the microsomes. The oxidation of aniline or aminopyrine and the cytochrome P-450/oxygen-radical-independent oxidation of ethanol also displayed a biphasic response to the concentration of O2, reaching a maximum at 20% O2, which correlates with the dithionite-reducible CO-binding spectra of cytochrome P-450. Microsomal lipid peroxidation increased as the concentration of O2 was raised from 3 to 7 to 20% O2, and then began to level off. This different pattern of malondialdehyde generation compared with hydroxyl-radical production probably reflects the lack of a role for hydroxyl radical in microsomal lipid peroxidation. These results point to the complex role for O2 in microsomal generation of oxygen radicals, which is due in part to the critical necessity for maintaining the redox state of autoxidizable components of the reaction system. PMID:3415646

  12. Differential production of active oxygen species in photo-symbiotic and non-symbiotic bivalves.

    PubMed

    Nakayama, K; Maruyama, T

    1998-01-01

    We investigated the generation of active oxygen species in the bivalves, Crassostrea gigas, Fulvia mutica and Tridacna crocea in order to understand the defensive mechanisms in giant clams that allow a stable association with symbiotic zooxanthellae. C. gigas produced active oxygens, superoxide anion and nitric oxide upon stimulation by phorbol myristate acetate. F. mutica generated a little amount of superoxide anion and nitric oxide, and contained significant phenoloxidase activity which catalyzes formation of quinones. T. crocea did not generate any apparent active oxygen species or quinones. The importance of lacking rapid cytotoxic responses consisting of active oxygen species to foreign organisms in the symbiotic clam is discussed.

  13. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    NASA Astrophysics Data System (ADS)

    Azyazov, V. N.; Torbin, A. P.; Pershin, A. A.; Mikheyev, P. A.; Heaven, M. C.

    2015-12-01

    The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O3(υ) formed in O + O2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O2(a1Δ), oxygen atom removal and ozone formation. It is shown that the process O3(υ ⩾ 2) + O2(a1Δ) → 2O2 + O is the main O2(a1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O2(a1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  14. Molecular basis of the low activity of antitumor anthracenediones, mitoxantrone and ametantrone, in oxygen radical generation catalyzed by NADH dehydrogenase. Enzymatic and molecular modelling studies.

    PubMed

    Tarasiuk, Jolanta; Mazerski, Jan; Tkaczyk-Gobis, Katarzyna; Borowski, Edward

    2005-04-01

    Synthetic antitumor anthracenedione drugs, in contrast to anthracycline antibiotics, are ineffective in free radical formation in NADH dehydrogenase system. Our results have indicated that neither the reduction potential nor the side chain conformation and the energies of border orbitals (HOMO and LUMO) determine the ability of anthracenediones to stimulate reactive oxygen species formation in NADH dehydrogenase system. It was shown that the distribution of the molecular electrostatic potential (MEP), around the quinone system was crucial for this ability. We have found for non-stimulating anthracenediones that the clouds of positive MEP cover the quinone carbon atoms while for agents effective in stimulating reactive oxygen species formation the clouds of negative MEP cover continuously the aromatic core together with the quinone system.

  15. Nanostructured Oxygen Generators for Aerospace Life Supporting System

    NASA Astrophysics Data System (ADS)

    Martirosyan, Karen

    2010-10-01

    The solid fuel oxygen generators (SFOG) used as backup oxygen delivery systems for International Space Station (ISS). Well established SFOG formulations include sodium/lithium chlorite and metal micro-particles. However, common SFOG are accompanied by formation of high temperature spots, which decrease the efficiency and safety performance. In this report we present multicomponent nanostructured oxygen generators (NOGs) based on NaClO3-Sn -Co3O4 system that allow reduction of the overall reaction temperature and elimination of the hot temperature fluctuations. The nano size reactant increases the surface contact area between the solid reagents and homogeneity of mixture as well as improves the uniformity of reaction thermal front. We describe here a novel one-step (metal nitrate--glycine) solution combustion synthesis of nanostructured highly crystalline cobalt oxide nanoparticles. Furthermore, we determined the influence of the nitrate/glycine ratio on the crystallinity and particle grain size of the Co3O4. The factors affecting to ignition and performance characteristics of SFOG have shown that many physical and chemical properties of the individual reactants, as well as preparation methods may significant affect on the overall behavior of the oxygen generation rate. The specific application of SFOG requires that the ignition and performance characteristics be tailored to have precise sensitivities and oxygen outputs.

  16. In-situ generation of oxygen-releasing metal peroxides

    DOEpatents

    Looney, Brian B.; Denham, Miles E.

    2007-01-09

    A method for remediation of contaminants in soil and groundwater is disclosed. The method generates oxygen releasing solids in groundwater or soil by injecting an aqueous energetic oxidant solution containing free radicals, oxidative conditions can be created within or ahead of a contaminant plume. Some contaminants may be remediated directly by reaction with the free radicals. Additionally and more importantly, the free radicals create an oxidative condition whereby native or injected materials, especially metals, are converted to peroxides. These peroxides provide a long-term oxygen reservoir, releasing oxygen relatively slowly over time. The oxygen can enhance microbial metabolism to remediate contaminants, can react with contaminant metals either to form immobile precipitants or to mobilize other metals to permit remediation through leaching techniques. Various injection strategies for injecting the energetic oxidant solution are also disclosed.

  17. Generation of reactive oxygen species by the faecal matrix

    PubMed Central

    Owen, R; Spiegelhalder, B; Bartsch, H

    2000-01-01

    BACKGROUND—Reactive oxygen species are implicated in the aetiology of a range of human diseases and there is increasing interest in their role in the development of cancer.
AIM—To develop a suitable method for the detection of reactive oxygen species produced by the faecal matrix.
METHODS—A refined high performance liquid chromatography system for the detection of reactive oxygen species is described.
RESULTS—The method allows baseline separation of the products of hydroxyl radical attack on salicylic acid in the hypoxanthine/xanthine oxidase system, namely 2,5-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, and catechol. The increased efficiency and precision of the method has allowed a detailed evaluation of the dynamics of reactive oxygen species generation in the faecal matrix. The data show that the faecal matrix is capable of generating reactive oxygen species in abundance. This ability cannot be attributed to the bacteria present, but rather to a soluble component within the matrix. As yet, the nature of this soluble factor is not entirely clear but is likely to be a reducing agent.
CONCLUSIONS—The soluble nature of the promoting factor renders it amenable to absorption, and circumstances may exist in which either it comes into contact with either free or chelated iron in the colonocyte, leading to direct attack on cellular DNA, or else it initiates lipid peroxidation processes whereby membrane polyunsaturated fatty acids are attacked by reactive oxygen species propagating chain reactions leading to the generation of promutagenic lesions such as etheno based DNA adducts.


Keywords: colorectal cancer; faecal matrix; hypoxanthine; phytic acid; reactive oxygen species; xanthine oxidase PMID:10644317

  18. Ultrathin Black Phosphorus Nanosheets for Efficient Singlet Oxygen Generation.

    PubMed

    Wang, Hui; Yang, Xianzhu; Shao, Wei; Chen, Shichuan; Xie, Junfeng; Zhang, Xiaodong; Wang, Jun; Xie, Yi

    2015-09-01

    Benefiting from its strong oxidizing properties, the singlet oxygen has garnered serious attentions in physical, chemical, as well as biological studies. However, the photosensitizers for the generation of singlet oxygen bear in low quantum yields, lack of long wavelength absorption band, poor biocompatibility, undegradable in living tissues, and so on. Here we first demonstrate the exfoliated black phosphorus nanosheets to be effective photosensitizers for the generation of singlet oxygen with a high quantum yield of about 0.91, rendering their attractive applications in catalysis and photodynamic therapy. Through in vitro and in vivo studies, the water dispersible black phosphorus nanosheets show notable cancer therapy ability. In addition, the photodegradable character of black phosphorus from element to biocompatible phosphorus oxides further highlights its therapeutic potential against cancer. This study will not only expand the breadth of study in black phosphorus but also offer an efficient catalyst and photodynamic therapy agent.

  19. Electrochemical investigations on the oxygen activation by cytochrome P-450.

    PubMed

    Scheller, F; Renneberg, R; Schwarze, W; Strnad, G; Pommerening, K; Prümke, H J; Mohr, P

    1979-01-01

    The application of cytochrome P-450 in substrate conversion is complicated both due to the limited stability and the cofactor regeneration problems. To overcome the disadvantages of NADPH consumption the transfer of the reduction equivalents from an electrode into the cytochrome P-450-system was studied: 1. NADPH was cathodically reduced at a mercury pool electrode. By immobilization of NADP on dialdehyde Sephadex the reductive recycling was possible. 2. Different forms of reduced oxygen were produced by the cathode: a) The reaction of O2- with deoxycorticosterone yields a carboxylic acid derivative. In contrast the cytochrome P-450 catalyzed NADPH-dependent reaction with the same substrate gives corticosterone, O2- represents only an intermediate in the activation of oxygen and is not the "activated oxygen" species. b) Molecular oxygen was reduced to HO2- and H2O2, respectively. The interaction of adsorbed cytochrome P-450 on the electrode surface with the reduced oxygen species in the absence of NADPH was studied. The electrochemically generated peroxide seems to be more active than added H2O2. 3. In a model of electro-enzyme-reactor several substrates were hydroxylated by microsomal cytochrome P-450 with cathodically reduced oxygen which substitutes NADPH.

  20. Towards photodynamic therapy with ionizing radiation: nanoparticle-mediated singlet oxygen generation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian; Goldys, Ewa

    2016-03-01

    Photodynamic therapy (PDT) is a clinically approved method for the treatment of cancer by using singlet oxygen, a highly reactive oxygen generated from a photosensitizer drug upon photoactivation. Limited light penetration depth into to the tissue means that PDT is unsuitable for deep tissue cancer treatments. This can be overcome by using X-ray /gamma rays activated nanoparticles able to trigger the photosensitizer drug and generate singlet oxygen. Additionally, inorganic nanoparticles interact more strongly with X and/or gamma rays than the tissue, allowing to concentrate the effects of radiation near nanoparticle surface and they can also be molecularly targeted to cancer cells. In this work we synthesized and characterized CeF3 nanoparticles, a well-known scintillator material. The nanoparticles were conjugated with Verteporfin, a photosensitizer drug by electrostatic interaction. We assessed the performance of CeF3 and the conjugates to generate singlet oxygen exposed to X-ray radiation. The X-ray singlet oxygen quantum yield of the nanoparticle-photosensitizer system was accurately quantified for the first time. This provided realistic estimates of the singlet oxygen dose taking into consideration the dose partition of the radiation between CeF3 and the tissue. Furthermore, we investigated gold nanoparticle-photosensitizer systems. We confirmed that pure gold nanoparticles itself generate singlet oxygen which is attributed to plasmonic effects. We found enhanced singlet oxygen generation from gold-Rose Bengal conjugates and gold nanorod-verteporfin conjugates. These singlet-oxygen-generating nanomaterials add a new dimension to radiation-assisted PDT.

  1. Environmental Control and Life Support System, Oxygen Generation System

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Environmental Control and Life Support System (ECLSS) Group of the Flight Projects Directorate at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, is responsible for designing and building the life support systems that will provide the crew of the International Space Station (ISS) a comfortable environment in which to live and work. This is a close-up view of ECLSS Oxygen Generation System (OGS) rack. The ECLSS Group at the MSFC oversees the development of the OGS, which produces oxygen for breathing air for the crew and laboratory animals, as well as for replacing oxygen lost due to experiment use, airlock depressurization, module leakage, and carbon dioxide venting. The OGS consists primarily of the Oxygen Generator Assembly (OGA), provided by the prime contractor, the Hamilton Sundstrand Space Systems, International (HSSSI) in Windsor Locks, Cornecticut and a Power Supply Module (PSM), supplied by the MSFC. The OGA is comprised of a cell stack that electrolyzes (breaks apart the hydrogen and oxygen molecules) some of the clean water provided by the Water Recovery System and the separators that remove the gases from water after electrolysis. The PSM provides the high power to the OGA needed to electrolyze the water.

  2. Singlet oxygen treatment of tumor cells triggers extracellular singlet oxygen generation, catalase inactivation and reactivation of intercellular apoptosis-inducing signaling.

    PubMed

    Riethmüller, Michaela; Burger, Nils; Bauer, Georg

    2015-12-01

    Intracellular singlet oxygen generation in photofrin-loaded cells caused cell death without discrimination between nonmalignant and malignant cells. In contrast, extracellular singlet oxygen generation caused apoptosis induction selectively in tumor cells through singlet oxygen-mediated inactivation of tumor cell protective catalase and subsequent reactivation of intercellular ROS-mediated apoptosis signaling through the HOCl and the NO/peroxynitrite signaling pathway. Singlet oxygen generation by extracellular photofrin alone was, however, not sufficient for optimal direct inactivation of catalase, but needed to trigger the generation of cell-derived extracellular singlet oxygen through the interaction between H2O2 and peroxynitrite. Thereby, formation of peroxynitrous acid, generation of hydroxyl radicals and formation of perhydroxyl radicals (HO2(.)) through hydroxyl radical/H2O2 interaction seemed to be required as intermediate steps. This amplificatory mechanism led to the formation of singlet oxygen at a sufficiently high concentration for optimal inactivation of membrane-associated catalase. At low initial concentrations of singlet oxygen, an additional amplification step needed to be activated. It depended on singlet oxygen-dependent activation of the FAS receptor and caspase-8, followed by caspase-8-mediated enhancement of NOX activity. The biochemical mechanisms described here might be considered as promising principle for the development of novel approaches in tumor therapy that specifically direct membrane-associated catalase of tumor cells and thus utilize tumor cell-specific apoptosis-inducing ROS signaling.

  3. Singlet oxygen treatment of tumor cells triggers extracellular singlet oxygen generation, catalase inactivation and reactivation of intercellular apoptosis-inducing signaling☆

    PubMed Central

    Riethmüller, Michaela; Burger, Nils; Bauer, Georg

    2015-01-01

    Intracellular singlet oxygen generation in photofrin-loaded cells caused cell death without discrimination between nonmalignant and malignant cells. In contrast, extracellular singlet oxygen generation caused apoptosis induction selectively in tumor cells through singlet oxygen-mediated inactivation of tumor cell protective catalase and subsequent reactivation of intercellular ROS-mediated apoptosis signaling through the HOCl and the NO/peroxynitrite signaling pathway. Singlet oxygen generation by extracellular photofrin alone was, however, not sufficient for optimal direct inactivation of catalase, but needed to trigger the generation of cell-derived extracellular singlet oxygen through the interaction between H2O2 and peroxynitrite. Thereby, formation of peroxynitrous acid, generation of hydroxyl radicals and formation of perhydroxyl radicals (HO2.) through hydroxyl radical/H2O2 interaction seemed to be required as intermediate steps. This amplificatory mechanism led to the formation of singlet oxygen at a sufficiently high concentration for optimal inactivation of membrane-associated catalase. At low initial concentrations of singlet oxygen, an additional amplification step needed to be activated. It depended on singlet oxygen-dependent activation of the FAS receptor and caspase-8, followed by caspase-8-mediated enhancement of NOX activity. The biochemical mechanisms described here might be considered as promising principle for the development of novel approaches in tumor therapy that specifically direct membrane-associated catalase of tumor cells and thus utilize tumor cell-specific apoptosis-inducing ROS signaling. PMID:26225731

  4. Layered double hydroxides as highly efficient photocatalysts for visible light oxygen generation from water.

    PubMed

    Gomes Silva, Cláudia; Bouizi, Younès; Fornés, Vicente; García, Hermenegildo

    2009-09-30

    Oxygen generation through photocatalytic water splitting under visible light irradiation is a challenging process. In this work we have synthesized a series of Zn/Ti, Zn/Ce, and Zn/Cr layered double hydroxides (LDH) at different Zn/metal atomic ratio (from 4:2 to 4:0.25) and tested them for the visible light photocatalytic oxygen generation. The most active material was found to be (Zn/Cr)LDH with an atomic ratio of 4:2 that exhibits two absorption bands in the visible region at lambda(max) of 410 and 570 nm. It was found that the efficiency of these chromium layered double oxides for oxygen generation increases asymptotically with the Cr content. Using iron oxalate as chemical actinometer we have determined that the apparent quantum yields for oxygen generation (Phi apparent = 4 x mol oxygen/mol incident photons) are of 60.9% and 12.2% at 410 and 570 nm, respectively. These quantum yields are among the highest values ever determined with visible light for solid materials in the absence of light harvesting dye. The overall efficiency of (Zn/Cr)LDH for visible light oxygen generation was found to be 1.6 times higher than that of WO(3) under the same conditions.

  5. Evaluation of Oxygen Concentrators and Chemical Oxygen Generators at Altitude and Temperature Extremes.

    PubMed

    Blakeman, Thomas C; Rodriquez, Dario; Britton, Tyler J; Johannigman, Jay A; Petro, Michael C; Branson, Richard D

    2016-05-01

    Oxygen cylinders are heavy and present a number of hazards, and liquid oxygen is too heavy and cumbersome to be used in far forward environments. Portable oxygen concentrators (POCs) and chemical oxygen generators (COGs) have been proposed as a solution. We evaluated 3 commercially available POCs and 3 COGs in a laboratory setting. Altitude testing was done at sea level and 8,000, 16,000, and 22,000 ft. Temperature extreme testing was performed after storing devices at 60°C and -35°C for 24 hours. Mean FIO2 decreased after storage at -35°C with Eclipse and iGo POCs and also at the higher volumes after storage at 60°C with the Eclipse. The iGo ceased to operate at 16,000 ft, but the Eclipse and Saros were unaffected by altitude. Oxygen flow, duration of operation, and total oxygen volume varied between COGs and within the same device type. Output decreased after storage at -35°C, but increased at each altitude as compared to sea level. This study showed significant differences in the performance of POCs and COGs after storage at temperature extremes and with the COGs at altitude. Clinicians must understand the performance characteristics of devices in all potential environments. PMID:27168568

  6. Oxygen Generation from Carbon Dioxide for Advanced Life Support

    NASA Technical Reports Server (NTRS)

    Bishop, s. R.; Duncan, K. L.; Hagelin-Weaver, H. E.; Neal, L.; Paul, H. L.; Wachsman, E. D.

    2007-01-01

    The partial electrochemical reduction of CO2 using ceramic oxygen generators (COGs) is well known and has been studied. Conventional COGs use yttria-stabilized zirconia (YSZ) electrolytes and operate at temperatures greater than 700 C (1, 2). Operating at a lower temperature has the advantage of reducing the mass of the ancillary components such as insulation. Moreover, complete reduction of metabolically produced CO2 (into carbon and oxygen) has the potential of reducing oxygen storage weight if the oxygen can be recovered. Recently, the University of Florida developed ceramic oxygen generators employing a bilayer electrolyte of gadolinia-doped ceria and erbia-stabilized bismuth oxide (ESB) for NASA s future exploration of Mars (3). The results showed that oxygen could be reliably produced from CO2 at temperatures as low as 400 C. These results indicate that this technology could be adapted to CO2 removal from a spacesuit and other applications in which CO2 removal is an issue. This strategy for CO2 removal in advanced life support systems employs a catalytic layer combined with a COG so that the CO2 is reduced completely to solid carbon and oxygen. First, to reduce the COG operating temperature, a thin, bilayer electrolyte was employed. Second, to promote full CO2 reduction while avoiding the problem of carbon deposition on the COG cathode, a catalytic carbon deposition layer was designed and the cathode utilized materials shown to be coke resistant. Third, a composite anode was used consisting of bismuth ruthenate (BRO) and ESB that has been shown to have high performance (4). The inset of figure 1 shows the conceptual design of the tubular COG and the rest of the figure shows schematically the test apparatus. Figure 2 shows the microstructure of a COG tube prior to testing. During testing, current is applied across the cell and initially CuO is reduced to copper metal by electrochemical pumping. Then the oxygen source becomes the CO/CO2. This presentation

  7. Investigation, Analysis, and Testing of Self-contained Oxygen Generators

    NASA Technical Reports Server (NTRS)

    Keddy, Christopher P.; Haas, Jon P.; Starritt, Larry

    2008-01-01

    Self Contained Oxygen Generators (SCOGs) have widespread use in providing emergency breathing oxygen in a variety of environments including mines, submarines, spacecraft, and aircraft. These devices have definite advantages over storing of gaseous or liquid oxygen. The oxygen is not generated until a chemical briquette containing a chlorate or perchlorate oxidizer and a solid metallic fuel such as iron is ignited starting a thermal decomposition process allowing gaseous oxygen to be produced. These devices are typically very safe to store, easy to operate, and have primarily only a thermal hazard to the operator that can be controlled by barriers or furnaces. Tens of thousands of these devices are operated worldwide every year without major incident. This report examines the rare case of a SCOG whose behavior was both abnormal and lethal. This particular type of SCOG reviewed is nearly identical to a flight qualified version of SCOG slated for use on manned space vehicles. This Investigative Report is a compilation of a NASA effort in conjunction with other interested parties including military and aerospace to understand the causes of the particular SCOG accident and what preventative measures can be taken to ensure this incident is not repeated. This report details the incident and examines the root causes of the observed SCOG behavior from forensic evidence. A summary of chemical and numerical analysis is provided as a background to physical testing of identical SCOG devices. The results and findings of both small scale and full scale testing are documented on a test-by-test basis along with observations and summaries. Finally, conclusions are presented on the findings of this investigation, analysis, and testing along with suggestions on preventative measures for any entity interested in the safe use of these devices.

  8. Ajoene, a compound of garlic, induces apoptosis in human promyeloleukemic cells, accompanied by generation of reactive oxygen species and activation of nuclear factor kappaB.

    PubMed

    Dirsch, V M; Gerbes, A L; Vollmar, A M

    1998-03-01

    The pharmacological role of garlic in prevention and treatment of cancer has received increasing attention, but thorough investigations into the molecular mechanisms of action of garlic compounds are rare. The present study demonstrates that ajoene, a major compound of garlic induces apoptosis in human leukemic cells, but not in peripheral mononuclear blood cells of healthy donors. The effect was dose and time dependent. Apoptosis was judged by three criteria, morphology of cells, quantification of subdiploid DNA content by flow cytometry, and detection of DNA fragmentation by gel electrophoresis. Ajoene increased the production of intracellular peroxide in a dose- and time-dependent fashion, which could be partially blocked by preincubation of the human leukemic cells with the antioxidant N-acetylcysteine. Interestingly, N-acetylcysteine-treated cells showed a 50% loss of ajoene-induced apoptosis. Moreover, ajoene was demonstrated to activate nuclear translocation of the transcription factor nuclear factor kappaB, an effect that was abrogated in N-acetylcysteine-loaded cells. These results suggested that ajoene might induce apoptosis in human leukemic cells via stimulation of peroxide production and activation of nuclear factor kappaB. This is a novel aspect in the biological profile of this garlic compound and an important step in elucidating the underlying molecular mechanisms of its antitumor action.

  9. Singlet-Oxygen Generation in Alkaline Periodate Solution.

    PubMed

    Bokare, Alok D; Choi, Wonyong

    2015-12-15

    A nonphotochemical generation of singlet oxygen ((1)O2) using potassium periodate (KIO4) in alkaline condition (pH > 8) was investigated for selective oxidation of aqueous organic pollutants. The generation of (1)O2 was initiated by the spontaneous reaction between IO4(-) and hydroxyl ions, along with a stoichiometric conversion of IO4(-) to iodate (IO3(-)). The reactivity of in-situ-generated (1)O2 was monitored by using furfuryl alcohol (FFA) as a model substrate. The formation of (1)O2 in the KIO4/KOH system was experimentally confirmed using electron spin resonance (ESR) measurements in corroboration with quenching studies using azide as a selective (1)O2 scavenger. The reaction in the KIO4/KOH solution in both oxic and anoxic conditions initiated the generation of superoxide ion as a precursor of the singlet oxygen (confirmed by using superoxide scavengers), and the presence of molecular oxygen was not required as a precursor of (1)O2. Although hydrogen peroxide had no direct influence on the FFA oxidation process, the presence of natural organic matter, such as humic and fulvic acids, enhanced the oxidation efficiency. Using the oxidation of simple organic diols as model compounds, the enhanced (1)O2 formation is attributed to periodate-mediated oxidation of vicinal hydroxyl groups present in humic and fulvic constituent moieties. The efficient and simple generation of (1)O2 using the KIO4/KOH system without any light irradiation can be employed for the selective oxidation of aqueous organic compounds under neutral and near-alkaline conditions.

  10. Oxygen Mass Flow Rate Generated for Monitoring Hydrogen Peroxide Stability

    NASA Technical Reports Server (NTRS)

    Ross, H. Richard

    2002-01-01

    Recent interest in propellants with non-toxic reaction products has led to a resurgence of interest in hydrogen peroxide for various propellant applications. Because peroxide is sensitive to contaminants, material interactions, stability and storage issues, monitoring decomposition rates is important. Stennis Space Center (SSC) uses thermocouples to monitor bulk fluid temperature (heat evolution) to determine reaction rates. Unfortunately, large temperature rises are required to offset the heat lost into the surrounding fluid. Also, tank penetration to accomodate a thermocouple can entail modification of a tank or line and act as a source of contamination. The paper evaluates a method for monitoring oxygen evolution as a means to determine peroxide stability. Oxygen generation is not only directly related to peroxide decomposition, but occurs immediately. Measuring peroxide temperature to monitor peroxide stability has significant limitations. The bulk decomposition of 1% / week in a large volume tank can produce in excess of 30 cc / min. This oxygen flow rate corresponds to an equivalent temperature rise of approximately 14 millidegrees C, which is difficult to measure reliably. Thus, if heat transfer were included, there would be no temperature rise. Temperature changes from the surrounding environment and heat lost to the peroxide will also mask potential problems. The use of oxygen flow measurements provides an ultra sensitive technique for monitoring reaction events and will provide an earlier indication of an abnormal decomposition when compared to measuring temperature rise.

  11. Radiosensitizing Pancreatic Cancer Xenografts by an Implantable Micro-Oxygen Generator.

    PubMed

    Cao, Ning; Song, Seung Hyun; Maleki, Teimour; Shaffer, Michael; Stantz, Keith M; Cao, Minsong; Kao, Chinghai; Mendonca, Marc S; Ziaie, Babak; Ko, Song-Chu

    2016-04-01

    Over the past decades, little progress has been made to improve the extremely low survival rates in pancreatic cancer patients. Extreme hypoxia observed in pancreatic tumors contributes to the aggressive and metastatic characteristics of this tumor and can reduce the effectiveness of conventional radiation therapy and chemotherapy. In an attempt to reduce hypoxia-induced obstacles to effective radiation treatment, we used a novel device, the implantable micro-oxygen generator (IMOG), for in situ tumor oxygenation. After subcutaneous implantation of human pancreatic xenograft tumors in athymic rats, the IMOG was wirelessly powered by ultrasonic waves, producing 30 μA of direct current (at 2.5 V), which was then utilized to electrolyze water and produce oxygen within the tumor. Significant oxygen production by the IMOG was observed and corroborated using the NeoFox oxygen sensor dynamically. To test the radiosensitization effect of the newly generated oxygen, the human pancreatic xenograft tumors were subcutaneously implanted in nude mice with either a functional or inactivated IMOG device. The tumors in the mice were then exposed to ultrasonic power for 10 min, followed by a single fraction of 5 Gy radiation, and tumor growth was monitored thereafter. The 5 Gy irradiated tumors containing the functional IMOG exhibited tumor growth inhibition equivalent to that of 7 Gy irradiated tumors that did not contain an IMOG. Our study confirmed that an activated IMOG is able to produce sufficient oxygen to radiosensitize pancreatic tumors, enhancing response to single-dose radiation therapy. PMID:27002539

  12. Biochar activated by oxygen plasma for supercapacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Rakesh Kumar; Dubey, Mukul; Kharel, Parashu; Gu, Zhengrong; Fan, Qi Hua

    2015-01-01

    Biochar, also known as black carbon, is a byproduct of biomass pyrolysis. As a low-cost, environmental-friendly material, biochar has the potential to replace more expensive synthesized carbon nanomaterials (e.g. carbon nanotubes) for use in future supercapacitors. To achieve high capacitance, biochar requires proper activation. A conventional approach involves mixing biochar with a strong base and baking at a high temperature. However, this process is time consuming and energy inefficient (requiring temperatures >900 °C). This work demonstrates a low-temperature (<150 °C) plasma treatment that efficiently activates a yellow pine biochar. Particularly, the effects of oxygen plasma on the biochar microstructure and supercapacitor characteristics are studied. Significant enhancement of the capacitance is achieved: 171.4 F g-1 for a 5-min oxygen plasma activation, in comparison to 99.5 F g-1 for a conventional chemical activation and 60.4 F g-1 for untreated biochar. This enhancement of the charge storage capacity is attributed to the creation of a broad distribution in pore size and a larger surface area. The plasma activation mechanisms in terms of the evolution of the biochar surface and microstructure are further discussed.

  13. Effects of oxygen cover gas and NaOH dilution on gas generation in tank 241-SY-101 waste

    SciTech Connect

    Person, J.C.

    1996-05-30

    Laboratory studies are reported of gas generation in heated waste from tank 241-SY-101. The rates of gas generation and the compositions of product gas were measured. Three types of tests are compared. The tests use: undiluted waste, waste diluted by a 54% addition of 2.5 M NaOH, and undiluted waste with a reactive cover gas of 30% Oxygen in He. The gas generation rate is reduced by dilution, increased by higher temperatures (which determines activation energies), and increased by reactions of Oxygen (these primarily produce H{sub 2}). Gases are generated as reduction products oxidation of organic carbon species by nitrite and oxygen.

  14. Microfabricated Collector-Generator Electrode Sensor for Measuring Absolute pH and Oxygen Concentrations.

    PubMed

    Dengler, Adam K; Wightman, R Mark; McCarty, Gregory S

    2015-10-20

    Fast-scan cyclic voltammetry (FSCV) has attracted attention for studying in vivo neurotransmission due to its subsecond temporal resolution, selectivity, and sensitivity. Traditional FSCV measurements use background subtraction to isolate changes in the local electrochemical environment, providing detailed information on fluctuations in the concentration of electroactive species. This background subtraction removes information about constant or slowly changing concentrations. However, determination of background concentrations is still important for understanding functioning brain tissue. For example, neural activity is known to consume oxygen and produce carbon dioxide which affects local levels of oxygen and pH. Here, we present a microfabricated microelectrode array which uses FSCV to detect the absolute levels of oxygen and pH in vitro. The sensor is a collector-generator electrode array with carbon microelectrodes spaced 5 μm apart. In this work, a periodic potential step is applied at the generator producing transient local changes in the electrochemical environment. The collector electrode continuously performs FSCV enabling these induced changes in concentration to be recorded with the sensitivity and selectivity of FSCV. A negative potential step applied at the generator produces a transient local pH shift at the collector. The generator-induced pH signal is detected using FSCV at the collector and correlated to absolute solution pH by postcalibration of the anodic peak position. In addition, in oxygenated solutions a negative potential step at the generator produces hydrogen peroxide by reducing oxygen. Hydrogen peroxide is detected with FSCV at the collector electrode, and the magnitude of the oxidative peak is proportional to absolute oxygen concentrations. Oxygen interference on the pH signal is minimal and can be accounted for with a postcalibration.

  15. Photosensitizing Nanoparticles and The Modulation of Reactive Oxygen Species generation

    NASA Astrophysics Data System (ADS)

    Tada, Dayane; Baptista, Mauricio

    2015-05-01

    The association of PhotoSensitizer (PS) molecules with nanoparticles (NPs) forming photosensitizing NPs, has emerged as a therapeutic strategy to improve PS tumor targeting, to protect PS from deactivation reactions and to enhance both PS solubility and circulation time. Since association with NPs usually alters PS photophysical and photochemical properties, photosensitizing NPs are an important tool to modulate reactive oxygen species (ROS) generation. Depending on the design of the photosensitizing NP, i.e., type of PS, the NP material and the method applied for the construction of the photosensitizing NP, the deactivation routes of the excited state can be controlled, allowing the generation of either singlet oxygen or other ROS. Controlling the type of generated ROS is desirable not only in biomedical applications, as in Photodynamic Therapy where the type of ROS affects therapeutic efficiency, but also in other technological relevant fields like energy conversion, where the electron and energy transfer processes are necessary to increase the efficiency of photoconversion cells. The current review highlights some of the recent developments in the design of Photosensitizing NPs aimed at modulating the primary photochemical events after light absorption.

  16. Nature of Activated Manganese Oxide for Oxygen Evolution.

    PubMed

    Huynh, Michael; Shi, Chenyang; Billinge, Simon J L; Nocera, Daniel G

    2015-12-01

    Electrodeposited manganese oxide films (MnOx) are promising stable oxygen evolution catalysts. They are able to catalyze the oxygen evolution reaction in acidic solutions but with only modest activity when prepared by constant anodic potential deposition. We now show that the performance of these catalysts is improved when they are "activated" by potential cycling protocols, as measured by Tafel analysis (where lower slope is better): upon activation the Tafel slope decreases from ∼120 to ∼70 mV/decade in neutral conditions and from ∼650 to ∼90 mV/decade in acidic solutions. Electrochemical, spectroscopic, and structural methods were employed to study the activation process and support a mechanism where the original birnessite-like MnOx (δ-MnO2) undergoes a phase change, induced by comproportionation with cathodically generated Mn(OH)2, to a hausmannite-like intermediate (α-Mn3O4). Subsequent anodic conditioning from voltage cycling or water oxidation produces a disordered birnessite-like phase, which is highly active for oxygen evolution. At pH 2.5, the current density of activated MnOx (at an overpotential of 600 mV) is 2 orders of magnitude higher than that of the original MnOx and begins to approach that of Ru and Ir oxides in acid. PMID:26574923

  17. Approaches to Plant Hydrogen and Oxygen Isoscapes Generation

    SciTech Connect

    West, Jason B.; Kreuzer-Martin, Helen W.; Ehleringer, James

    2009-12-01

    Plant hydrogen and oxygen isoscapes have been utilized to address important and somewhat disparate research goals. The isotopic composition of leaf water affects the isotopic composition of atmospheric CO2 and O2 and is a logical starting point for understanding the isotopic composition of plant organic compounds since photosynthesis occurs in the leaf water environment. Leaf water isoscapes have been produced largely as part of efforts to understand atmospheric gas isotopic composition. The isotopic composition of plant organic matter has also been targeted for its potential to serve as a proxy for past environmental conditions. Spatially distributed sampling and modeling of modern plant H & O isoscapes can improve our understanding of the controls of the isotope ratios of compounds such as cellulose or n-alkanes from plants and therefore their utility for paleoreconstructions. Spatially varying plant hydrogen and oxygen isotopes have promise for yielding geographic origin information for a variety of plant products, including objects of criminal forensic interest or food products. The future has rich opportunities for the continued development of mechanistic models, methodologies for the generation of hydrogen and oxygen isoscapes, and cross-disciplinary interactions as these tools for understanding are developed, shared, and utilized to answer large-scale questions.

  18. Micro-plasmas as efficient generators of singlet delta oxygen

    NASA Astrophysics Data System (ADS)

    Puech, Vincent; Bauville, Gerard; Lacour, Bernard; Santos Sousa, Joao; Pitchford, Leanne C.; Touzeau, Michel

    2008-05-01

    This paper discusses the possibility of producing high concentrations of O2(a1Δg) states at pressures up to atmospheric in rare-gas/oxygen/NO mixtures by using micro-plasmas. Micro-plasmas refer to electric discharges created in very small geometries which have been proven able to operate in DC mode at high pressure and high power loading without undergoing any glow to arc transition. The so-called Micro Cathode Sustained Discharge (MCSD), which is a three-electrode configuration using a Micro Hollow Cathode Discharge (MHCD) as a plasma cathode, can be operated as a non-self-sustained discharge with low values of the reduced electric field and of the gas temperature. As a result, these MCSDs can efficiently generate large amounts of singlet delta oxygen. In Ar/O2/NO mixtures, at an oxygen partial pressure of 10 mbar, high values of O2(a1Δg) number density (1.5 1016 cm-3) and of the production yield (6.7 %) can be simultaneously obtained. For lower O2 partial pressure, yields higher than 10 % have been measured. In He/O2/NO mixtures, O2(a1Δg) number densities around 1016 cm-3 were achieved at atmospheric pressure for flow rates in the range 5-30 ln/mn, which could give rise to new applications.

  19. Generator-specific targets of mitochondrial reactive oxygen species.

    PubMed

    Bleier, Lea; Wittig, Ilka; Heide, Heinrich; Steger, Mirco; Brandt, Ulrich; Dröse, Stefan

    2015-01-01

    To understand the role of reactive oxygen species (ROS) in oxidative stress and redox signaling it is necessary to link their site of generation to the oxidative modification of specific targets. Here we have studied the selective modification of protein thiols by mitochondrial ROS that have been implicated as deleterious agents in a number of degenerative diseases and in the process of biological aging, but also as important players in cellular signal transduction. We hypothesized that this bipartite role might be based on different generator sites for "signaling" and "damaging" ROS and a directed release into different mitochondrial compartments. Because two main mitochondrial ROS generators, complex I (NADH:ubiquinone oxidoreductase) and complex III (ubiquinol:cytochrome c oxidoreductase; cytochrome bc1 complex), are known to predominantly release superoxide and the derived hydrogen peroxide (H2O2) into the mitochondrial matrix and the intermembrane space, respectively, we investigated whether these ROS generators selectively oxidize specific protein thiols. We used redox fluorescence difference gel electrophoresis analysis to identify redox-sensitive targets in the mitochondrial proteome of intact rat heart mitochondria. We observed that the modified target proteins were distinctly different when complex I or complex III was employed as the source of ROS. These proteins are potential targets involved in mitochondrial redox signaling and may serve as biomarkers to study the generator-dependent dual role of mitochondrial ROS in redox signaling and oxidative stress.

  20. Inactivation of viruses by chemically and photochemically generated singlet molecular oxygen.

    PubMed

    Müller-Breitkreutz, K; Mohr, H; Briviba, K; Sies, H

    1995-09-01

    Inactivation of viruses in blood plasma can be achieved by photodynamic procedures using methylene blue (MB) or other photoactive dyes. Singlet molecular oxygen (1O2) probably contributes to the virucidal effects of photosensitization. We report the inactivation of herpes simplex virus type 1 (HSV-1) and suid herpes virus type 1 (SHV-1) by chemically generated singlet oxygen, produced by thermal decomposition of the endoperoxide of 3,3'-(1,4-naphthylidene)dipropionate (NDPO2). We demonstrate that viruses can be inactivated by 1O2 generated by chemiexcitation in a reaction in the dark, even in the presence of human plasma. Virus inactivation in phosphate-buffered saline (PBS) was enhanced when water was replaced by deuterium oxide (D2O) and diminished when human plasma or quenchers (imidazole or histidine) were added. The singlet oxygen quenching activities of plasma, imidazole and histidine correlated with their inhibitory effects on virus inactivation. The production of 1O2 was assessed by an indicator reaction: the bleaching of p-nitrosodimethylaniline (RNO) with imidazole as 1O2 acceptor. Virus inactivation and singlet oxygen generation of NDPO2 were compared with those of MB/light-mediated photosensitization. Based on similar amounts of 1O2 generated by either procedure, virus inactivation by MB/light was more effective. Virus inactivation by MB/light was not affected by type I quenchers (e.g. mannitol), but was inhibited by human plasma or singlet oxygen quenchers. Furthermore, in D2O-based PBS, virus inactivation was more effective than that in H2O. These observations confirm that singlet oxygen is involved in virus inactivation by MB/light. Taken together, the results demonstrate that singlet oxygen produced by either procedure is virucidal. The enhanced effect of the photochemical procedure suggests that, in addition to type II, type I reactions and/or the binding affinity of the dye for the virus contribute to virus killing by MB/light.

  1. High-Pressure Oxygen Generation for Outpost EVA Study

    NASA Technical Reports Server (NTRS)

    Jeng, Frank F.; Conger, Bruce; Ewert, Michael K.; Anderson, Molly S.

    2009-01-01

    The amount of oxygen consumption for crew extravehicular activity (EVA) in future lunar exploration missions will be significant. Eight technologies to provide high pressure EVA O2 were investigated. They are: high pressure O2 storage, liquid oxygen (LOX) storage followed by vaporization, scavenging LOX from Lander followed by vaporization, LOX delivery followed by sorption compression, water electrolysis followed by compression, stand-alone high pressure water electrolyzer, Environmental Control and Life Support System (ECLSS) and Power Elements sharing a high pressure water electrolyzer, and ECLSS and In-Situ Resource Utilization (ISRU) Elements sharing a high pressure electrolyzer. A trade analysis was conducted comparing launch mass and equivalent system mass (ESM) of the eight technologies in open and closed ECLSS architectures. Technologies considered appropriate for the two architectures were selected and suggested for development.

  2. Alkaline static feed electrolyzer based oxygen generation system

    NASA Technical Reports Server (NTRS)

    Noble, L. D.; Kovach, A. J.; Fortunato, F. A.; Schubert, F. H.; Grigger, D. J.

    1988-01-01

    In preparation for the future deployment of the Space Station, an R and D program was established to demonstrate integrated operation of an alkaline Water Electrolysis System and a fuel cell as an energy storage device. The program's scope was revised when the Space Station Control Board changed the energy storage baseline for the Space Station. The new scope was aimed at the development of an alkaline Static Feed Electrolyzer for use in an Environmental Control/Life Support System as an oxygen generation system. As a result, the program was divided into two phases. The phase 1 effort was directed at the development of the Static Feed Electrolyzer for application in a Regenerative Fuel Cell System. During this phase, the program emphasized incorporation of the Regenerative Fuel Cell System design requirements into the Static Feed Electrolyzer electrochemical module design and the mechanical components design. The mechanical components included a Pressure Control Assembly, a Water Supply Assembly and a Thermal Control Assembly. These designs were completed through manufacturing drawing during Phase 1. The Phase 2 effort was directed at advancing the Alkaline Static Feed Electrolyzer database for an oxygen generation system. This development was aimed at extending the Static Feed Electrolyzer database in areas which may be encountered from initial fabrication through transportation, storage, launch and eventual Space Station startup. During this Phase, the Program emphasized three major areas: materials evaluation, electrochemical module scaling and performance repeatability and Static Feed Electrolyzer operational definition and characterization.

  3. Generation of Reactive Oxygen Species from Silicon Nanowires

    PubMed Central

    Leonard, Stephen S; Cohen, Guy M; Kenyon, Allison J; Schwegler-Berry, Diane; Fix, Natalie R; Bangsaruntip, Sarunya; Roberts, Jenny R

    2014-01-01

    Processing and synthesis of purified nanomaterials of diverse composition, size, and properties is an evolving process. Studies have demonstrated that some nanomaterials have potential toxic effects and have led to toxicity research focusing on nanotoxicology. About two million workers will be employed in the field of nanotechnology over the next 10 years. The unknown effects of nanomaterials create a need for research and development of techniques to identify possible toxicity. Through a cooperative effort between National Institute for Occupational Safety and Health and IBM to address possible occupational exposures, silicon-based nanowires (SiNWs) were obtained for our study. These SiNWs are anisotropic filamentary crystals of silicon, synthesized by the vapor–liquid–solid method and used in bio-sensors, gas sensors, and field effect transistors. Reactive oxygen species (ROS) can be generated when organisms are exposed to a material causing cellular responses, such as lipid peroxidation, H2O2 production, and DNA damage. SiNWs were assessed using three different in vitro environments (H2O2, RAW 264.7 cells, and rat alveolar macrophages) for ROS generation and possible toxicity identification. We used electron spin resonance, analysis of lipid peroxidation, measurement of H2O2 production, and the comet assay to assess generation of ROS from SiNW and define possible mechanisms. Our results demonstrate that SiNWs do not appear to be significant generators of free radicals. PMID:25452695

  4. Active droplet generation in microfluidics.

    PubMed

    Chong, Zhuang Zhi; Tan, Say Hwa; Gañán-Calvo, Alfonso M; Tor, Shu Beng; Loh, Ngiap Hiang; Nguyen, Nam-Trung

    2016-01-01

    The reliable generation of micron-sized droplets is an important process for various applications in droplet-based microfluidics. The generated droplets work as a self-contained reaction platform in droplet-based lab-on-a-chip systems. With the maturity of this platform technology, sophisticated and delicate control of the droplet generation process is needed to address increasingly complex applications. This review presents the state of the art of active droplet generation concepts, which are categorized according to the nature of the induced energy. At the liquid/liquid interface, an energy imbalance leads to instability and droplet breakup.

  5. Active droplet generation in microfluidics.

    PubMed

    Chong, Zhuang Zhi; Tan, Say Hwa; Gañán-Calvo, Alfonso M; Tor, Shu Beng; Loh, Ngiap Hiang; Nguyen, Nam-Trung

    2016-01-01

    The reliable generation of micron-sized droplets is an important process for various applications in droplet-based microfluidics. The generated droplets work as a self-contained reaction platform in droplet-based lab-on-a-chip systems. With the maturity of this platform technology, sophisticated and delicate control of the droplet generation process is needed to address increasingly complex applications. This review presents the state of the art of active droplet generation concepts, which are categorized according to the nature of the induced energy. At the liquid/liquid interface, an energy imbalance leads to instability and droplet breakup. PMID:26555381

  6. Humic acid in drinking well water induces inflammation through reactive oxygen species generation and activation of nuclear factor-κB/activator protein-1 signaling pathways: a possible role in atherosclerosis.

    PubMed

    Hseu, You-Cheng; Senthil Kumar, K J; Chen, Chih-Sheng; Cho, Hsin-Ju; Lin, Shu-Wei; Shen, Pei-Chun; Lin, Cheng-Wen; Lu, Fung-Jou; Yang, Hsin-Ling

    2014-01-15

    Humic acid (HA) has been implicated as one of the etiological factors in the peripheral vasculopathy of blackfoot disease (BFD) in Taiwan. However, the underlying pathophysiological mechanisms of BFD are not well defined. In this study, we used an in vitro and in vivo model, in which HA (25-200μg/mL) activated macrophages to produce pro-inflammatory molecules by activating their transcriptional factors. HA exposure induced NO and PGE2 production followed by induction of iNOS and COX-2 through NF-κB/AP-1 transactivation in macrophages. In addition, the production of TNF-α and IL-1β was significantly increased by HA. Moreover, HA-induced iNOS and COX-2 expression were down-regulated by the NF-κB and AP-1 inhibitors pyrrolidine dithiocarbamate (PDTC) and Tanshinone, respectively. Furthermore, generations of ROS and nitrotyrosine, as well as activation of the AKT and MAPKs signaling cascades were observed after HA exposure. Specifically, HA-induced NF-κB activation was mediated by ROS and AKT, and that HA-induced AP-1 activation was mediated by JNK and ERK. Notably, HA-mediated AKT, JNK, and ERK activation was ROS-independent. The inflammatory potential of HA was correlated with increased expression of HO-1 and Nrf2. Furthermore, an in vivo study confirms that mice exposed to HA, the serum levels of TNF-α and IL-1β was significantly increased in a dose-dependent manner. This report marks the first confirmation that environmental exposure of HA induces inflammation in macrophages, which may be one of the main causes of early atherogenesis in blackfoot disease.

  7. Generation of reactive oxygen species by raphidophycean phytoplankton.

    PubMed

    Oda, T; Nakamura, A; Shikayama, M; Kawano, I; Ishimatsu, A; Muramatsu, T

    1997-10-01

    Chattonella marina, a raphidophycean flagellate, is one of the most toxic red tide phytoplankton and causes severe damage to fish farming. Recent studies demonstrated that Chattonella sp. generates superoxide (O2-), hydrogen peroxide (H2O2), and hydroxyl radicals (.OH), which may be responsible for the toxicity of C. marina. In this study, we found the other raphidophycean flagellates such as Heterosigma akashiwo, Olisthodiscus luteus, and Fibrocapsa japonica also produce O2- and H2O2 under normal growth condition. Among the flagellate species tested, Chattonella has the highest rates of production of O2- and H2O2 as compared on the basis of cell number. This seems to be partly due to differences in their cell sizes, since Chattonella is larger than other flagellate species. The generation of O2- by these flagellate species was also confirmed by a chemiluminescence assay by using 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin++ +-3-one (MCLA). All these raphidophycean flagellates inhibited the proliferation of a marine bacterium, Vibrio alginolyticus, in a flagellates/bacteria co-culture system, and their toxic effects were suppressed by the addition of superoxide dismutase (SOD) or catalase. Our results suggest that the generation of reactive oxygen species is a common feature of raphidophycean flagellates.

  8. Quantitative assessment of reactive oxygen sonochemically generated by cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Yasuda, Jun; Miyashita, Takuya; Taguchi, Kei; Yoshizawa, Shin; Umemura, Shin-ichiro

    2015-07-01

    Acoustic cavitation bubbles can induce not only a thermal bioeffect but also a chemical bioeffect. When cavitation bubbles collapse and oscillate violently, they produce reactive oxygen species (ROS) that cause irreversible changes to the tissue. A sonosensitizer can promote such ROS generation. A treatment method using a sonosensitizer is called sonodynamic treatment. Rose bengal (RB) is one of the sonosensitizers whose in vivo and in vitro studies have been reported. In sonodynamic treatment, it is important to produce ROS at a high efficiency. For the efficient generation of ROS, a triggered high-intensity focused ultrasound (HIFU) sequence has been proposed. In this study, cavitation bubbles were generated in a chamber where RB solution was sealed, and a high-speed camera captured the behavior of these cavitation bubbles. The amount of ROS was also quantified by a potassium iodide (KI) method and compared with high-speed camera pictures to investigate the effectiveness of the triggered HIFU sequence. As a result, ROS could be obtained efficiently by this sequence.

  9. Mechanisms of polymer degradation using an oxygen plasma generator

    NASA Technical Reports Server (NTRS)

    Colony, Joe A.; Sanford, Edward L.

    1987-01-01

    An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

  10. Efficient singlet oxygen generation from sugar pendant C60 derivatives for photodynamic therapy.

    PubMed

    Yano, Shigenobu; Naemura, Masami; Toshimitsu, Akio; Akiyama, Motofusa; Ikeda, Atsushi; Kikuchi, Jun-ichi; Shen, Xiande; Duan, Qian; Narumi, Atsushi; Inoue, Masahiro; Ohkubo, Kei; Fukuzumi, Shunichi

    2015-12-01

    The amidation reaction between C60 with an activated ester group (1) and acetylated Glc (AcGlc) with an amino group (2) was performed to yield the target AcGlc-pendant C60 compound (3). The water soluble deacetylated compound, Glc-pendant C60 compound (4), exhibited high photocytotoxicity against HeLa cells due to the more efficient singlet oxygen generation as compared with that of Glc-pendant azafulleroids. PMID:26420023

  11. Humic acid in drinking well water induces inflammation through reactive oxygen species generation and activation of nuclear factor-κB/activator protein-1 signaling pathways: A possible role in atherosclerosis

    SciTech Connect

    Hseu, You-Cheng; Senthil Kumar, K.J.; Chen, Chih-Sheng; Cho, Hsin-Ju; Lin, Shu-Wei; Shen, Pei-Chun; Lin, Cheng-Wen; Lu, Fung-Jou; Yang, Hsin-Ling

    2014-01-15

    Humic acid (HA) has been implicated as one of the etiological factors in the peripheral vasculopathy of blackfoot disease (BFD) in Taiwan. However, the underlying pathophysiological mechanisms of BFD are not well defined. In this study, we used an in vitro and in vivo model, in which HA (25–200 μg/mL) activated macrophages to produce pro-inflammatory molecules by activating their transcriptional factors. HA exposure induced NO and PGE{sub 2} production followed by induction of iNOS and COX-2 through NF-κB/AP-1 transactivation in macrophages. In addition, the production of TNF-α and IL-1β was significantly increased by HA. Moreover, HA-induced iNOS and COX-2 expression were down-regulated by the NF-κB and AP-1 inhibitors pyrrolidine dithiocarbamate (PDTC) and Tanshinone, respectively. Furthermore, generations of ROS and nitrotyrosine, as well as activation of the AKT and MAPKs signaling cascades were observed after HA exposure. Specifically, HA-induced NF-κB activation was mediated by ROS and AKT, and that HA-induced AP-1 activation was mediated by JNK and ERK. Notably, HA-mediated AKT, JNK, and ERK activation was ROS-independent. The inflammatory potential of HA was correlated with increased expression of HO-1 and Nrf2. Furthermore, an in vivo study confirms that mice exposed to HA, the serum levels of TNF-α and IL-1β was significantly increased in a dose-dependent manner. This report marks the first confirmation that environmental exposure of HA induces inflammation in macrophages, which may be one of the main causes of early atherogenesis in blackfoot disease. - Highlights: • Humic acid (HA) induce pro-inflammatory cytokines and mediators in macrophages. • HA-induced inflammation is mediated by ROS and NF-κB/AP-1 signaling pathways. • The inflammatory potential of HA correlated with activation of Nrf2/HO-1 genes. • HA exposure to mice increased pro-inflammatory cytokines production in vivo. • HA may be one of the main causes of early

  12. Increased microsomal interaction with iron and oxygen radical generation after chronic acetone treatment.

    PubMed

    Puntarulo, S; Cederbaum, A I

    1988-01-12

    In vivo administration of acetone influences a variety of reactions catalyzed by rat liver microsomes. The effect of chronic treatment with acetone (1% acetone in the water for 10-12 days) on interaction with iron and subsequent oxygen radical generation by liver microsomes was evaluated. Microsomes from the acetone-treated rats displayed elevated rates of H2O2 generation, an increase in iron-dependent lipid peroxidation, and enhanced chemiluminescence upon the addition of t-butylhydroperoxide. The ferric EDTA-catalyzed production of formaldehyde from DMSO or of ethylene from 2-keto-4-thiomethylbutyrate was increased 2-fold after acetone treatment. This increase in hydroxyl radical generation was accompanied by a corresponding increase in NADPH utilization and was sensitive to inhibition by catalase and a competitive scavenger, ethanol, but not to superoxide dismutase. In vitro addition of acetone to microsomes had no effect on oxygen radical generation. Associated with the chronic acetone treatment was a 2-fold increase in the microsomal content of cytochrome P-450 and in the activity of NADPH-cytochrome-P-450 reductase. It appears that increased oxygen radical generation by microsomes after chronic acetone treatment reflects the increase in the major enzyme components which comprise the mixed-function oxidase system.

  13. BIOLOGICALLY ENHANCED OXYGEN TRANSFER IN THE ACTIVATED SLUDGE PROCESS (JOURNAL)

    EPA Science Inventory

    Biologically enhanced oxgyen transfer has been a hypothesis to explain observed oxygen transfer rates in activated sludge systems that were well above that predicted from aerator clean-water testing. The enhanced oxygen transfer rates were based on tests using BOD bottle oxygen ...

  14. Henry's Law Activity of Oxygen in Molten Iron

    NASA Astrophysics Data System (ADS)

    Matousek, J. W.

    2015-09-01

    A model is proposed for the solubility of oxygen in molten iron in dilute solutions in which the oxygen exists in two states, free and associated. Only the free oxygen has thermodynamic activity in the sense of interaction with an electrochemical cell to produce the voltage described by the Nernst equation.

  15. A new generation of high temperature oxygen sensors

    NASA Astrophysics Data System (ADS)

    Spirig, John V.

    -doped manganate perovskite and stabilized zirconia, served as a model system for joining electron carriers to an electrolyte without the creation of undesirable interlayers. Electron microscopy confirmed that intergranular penetration occurred at the joining plane leading to effective bonding between the two dissimilar ceramics. Raman spectral maps of the joining planes obtained with 2-D Raman microscopy demonstrated the absence of any new phases at the interface. A conducting perovskite with a lower Al:Mn ratio, but compensating A-site deficiency, La0.69Sr0.18Al0.45Mn0.55 O3, was joined to YTZP at 1250°C. X-ray diffraction was used to gain structural information on this A-site deficient perovskite. Room temperature resistivity measurements of the electroceramics were performed on joined and unjoined samples to determine the extent to which joining altered electron conduction within the LSAM. Electron microscopy confirmed that intergranular penetration occurred at the joining plane leading to effective bonding between the two dissimilar ceramics. Raman spectral maps of the joined samples demonstrated that joining temperature determines the extent to which interlayers begin to form in the joining plane. X-ray microdiffraction of the joining planes confirmed a threshold temperature for operation of a device created from these materials at 1350°C. A new material with diminished reactivity and high conductivity is presented to serve as a replacement for metal electrodes. In this manner, the model for a new generation of high-temperature oxygen sensors with internal references and ceramic wires is elucidated.

  16. Singlet molecular oxygen generated in dark biological process.

    PubMed

    Di Mascio, Paolo; Medeiros, Marisa H G

    2014-10-01

    Ultraweak chemiluminescence arising from biomolecules oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [(1)O2] and electronically excited triplet carbonyl products involving dioxetane intermediates. As examples, we will discuss the generation of (1)O2 from lipid hydroperoxides, which involves a cyclic mechanism from a linear tetraoxide intermediate. The generation of (1)O2 in aqueous solution via energy transfer from the excited triplet acetone arising from the thermodecomposition of dioxetane a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source, will also be discussed. The approach used to unequivocally demonstrate the generation of (1)O2 in these reactions is the use of (18)O-labeled hydroperoxide / triplet dioxygen ((18)[(3)O2]), the detection of labeled compounds by HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) and the direct spectroscopic detection and characterization of (1)O2 light emission. Characteristic light emission at 1,270nm, corresponding to the singlet delta state monomolecular decay was observed. Using(18)[(3)O2], we observed the formation of (18)O-labeled (1)O2 ((18)[(1)O2]) by the chemical trapping of (18)[(1)O2]with the anthracene-9,10-diyldiethane-2,1-diyl disulfate disodium salt (EAS) and detected the corresponding (18)O-labeled EAS endoperoxide usingHPLC-MS/MS. The combined use of the thermolysis of a water-soluble naphthalene endoperoxide as a generator of (18)O labeled (1)O2 and the sensitivity of HPLC-MS/MS allowed the study of (1)O2reactivity toward biomolecules. Photoemission properties and chemical trapping clearly demonstrate that the production of hydroperoxide and excited carbonyls generates (18)[(1)O2], and points to the involvement of (1)O2 in physiological and pathophysiological mechanism. Supported by FAPESP (2012/12663-1), CAPES, INCT Redoxoma (FAPESP/CNPq/CAPES; 573530/2008-4), NAP Redoxoma (PRPUSP; 2011.1.9352.1.8), CEPID

  17. Photochromic metal-organic frameworks: reversible control of singlet oxygen generation.

    PubMed

    Park, Jihye; Feng, Dawei; Yuan, Shuai; Zhou, Hong-Cai

    2015-01-01

    The controlled generation of singlet oxygen is of great interest owing to its potential applications including industrial wastewater treatment, photochemistry, and photodynamic therapy. Two photochromic metal-organic frameworks, PC-PCN and SO-PCN, have been developed. A photochromic reaction has been successfully realized in PC-PCN while maintaining its single crystallinity. In particular, as a solid-state material which inherently integrates the photochromic switch and photosensitizer, SO-PCN has demonstrated reversible control of (1)O2 generation. Additionally, SO-PCN shows catalytic activity towards photooxidation of 1,5-dihydroxynaphthalene.

  18. Reactive Oxygen Species (ROS) generation by lunar simulants

    NASA Astrophysics Data System (ADS)

    Kaur, Jasmeet; Rickman, Douglas; Schoonen, Martin A.

    2016-05-01

    The current interest in human exploration of the Moon and past experiences of Apollo astronauts has rekindled interest into the possible harmful effects of lunar dust on human health. In comparison to the Apollo-era explorations, human explorers may be weeks on the Moon, which will raise the risk of inhalation exposure. The mineralogical composition of lunar dust is well documented, but its effects on human health are not fully understood. With the aim of understanding the reactivity of dusts that may be encountered on geologically different lunar terrains, we have studied Reactive Oxygen Species (ROS) generation by a suite of lunar simulants of different mineralogical-chemical composition dispersed in water and Simulated Lung Fluid (SLF). To further explore the reactivity of simulants under lunar environmental conditions, we compared the reactivity of simulants both in air and inert atmosphere. As the impact of micrometeorites with consequent shock-induced stresses is a major environmental factor on the Moon, we also studied the effect of mechanical stress on samples. Mechanical stress was induced by hand crushing the samples both in air and inert atmosphere. The reactivity of samples after crushing was analyzed for a period of up to nine days. Hydrogen peroxide (H2O2) in water and SLF was analyzed by an in situ electrochemical probe and hydroxyl radical (•OH) by Electron Spin Resonance (ESR) spectroscopy and Adenine probe. Out of all simulants, CSM-CL-S was found to be the most reactive simulant followed by OB-1 and then JSC-1A simulant. The overall reactivity of samples in the inert atmosphere was higher than in air. Fresh crushed samples showed a higher level of reactivity than uncrushed samples. Simulant samples treated to create agglutination, including the formation of zero-valent iron, showed less reactivity than untreated simulants. ROS generation in SLF is initially slower than in deionized water (DI), but the ROS formation is sustained for as long as 7

  19. Nontoxic singlet oxygen generator as a therapeutic candidate for treating tauopathies

    PubMed Central

    Sheik Mohideen, Sahabudeen; Yamasaki, Yasutoyo; Omata, Yasuhiro; Tsuda, Leo; Yoshiike, Yuji

    2015-01-01

    Methylene blue (MB) inhibits the aggregation of tau, a main constituent of neurofibrillary tangles. However, MB’s mode of action in vivo is not fully understood. MB treatment reduced the amount of sarkosyl-insoluble tau in Drosophila that express human wild-type tau. MB concurrently ameliorated the climbing deficits of transgenic tau flies to a limited extent and diminished the climbing activity of wild-type flies. MB also decreased the survival rate of wild-type flies. Based on its photosensitive efficacies, we surmised that singlet oxygen generated through MB under light might contribute to both the beneficial and toxic effects of MB in vivo. We identified rose bengal (RB) that suppressed tau accumulation and ameliorated the behavioral deficits to a lesser extent than MB. Unlike MB, RB did not reduce the survival rate of flies. Our findings indicate that singlet oxygen generators with little toxicity may be suitable drug candidates for treating tauopathies. PMID:26027742

  20. 78 FR 1765 - Requirements for Chemical Oxygen Generators Installed on Transport Category Airplanes

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-09

    ... Federal Aviation Administration 14 CFR Part 25 RIN 2120-AK14 Requirements for Chemical Oxygen Generators... requirements for chemical oxygen generators installed on transport category airplanes so the generators are... Statement can be found in the Federal Register published on April 11, 2000 (65 FR 19477-19478), as well...

  1. Plasma-generated reactive oxygen species for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sousa, J. S.; Hammer, M. U.; Winter, J.; Tresp, H.; Duennbier, M.; Iseni, S.; Martin, V.; Puech, V.; Weltmann, K. D.; Reuter, S.

    2012-10-01

    To get a better insight into the effects of reactive oxygen species (ROS) on cellular components, fundamental studies are essential to determine the nature and concentration of plasma-generated ROS, and the chemistry induced in biological liquids by those ROS. In this context, we have measured the absolute density of the main ROS created in three different atmospheric pressure plasma sources: two geometrically distinct RF-driven microplasma jets (μ-APPJ [1] and kinpen [2]), and an array of microcathode sustained discharges [3]. Optical diagnostics of the plasma volumes and effluent regions have been performed: UV absorption for O3 and IR emission for O2(a^1δ) [4]. High concentrations of both ROS have been obtained (10^14--10^17cm-3). The effect of different parameters, such as gas flows and mixtures and power coupled to the plasmas, has been studied. For plasma biomedicine, the determination of the reactive species present in plasma-treated liquids is of great importance. In this work, we focused on the measurement of the concentration of H2O2 and NOX radicals, generated in physiological solutions like NaCl and PBS.[4pt] [1] N. Knake et al., J. Phys. D: App. Phys. 41, 194006 (2008)[0pt] [2] K.D. Weltmann et al., Pure Appl. Chem. 82, 1223 (2010)[0pt] [3] J.S. Sousa et al., Appl. Phys. Lett. 97, 141502 (2010)[0pt] [4] J.S. Sousa et al., Appl. Phys. Lett. 93, 011502 (2008)

  2. Small ultrahigh vacuum compatible hyperthermal oxygen atom generator

    NASA Technical Reports Server (NTRS)

    Outlaw, R. A.; Davidson, Mark R.

    1994-01-01

    The development of a compact, ultrahigh vacuum (UHV) compatible instrument for generating a flux of pure hyperthermal oxygen atoms for NASA applications has been achieved. The instrument combines the mechanisms of O2 dissociation and transport through a hot Ag membrane to provide a continuous source of O atoms to a vacuum interface where they are subsequently emitted into the vacuum space by electron-stimulated desorption (ESD). A flux of neutral O atoms 4.5 X 10(exp 13) cm(exp-2) s(exp-l)(P-3) with a mean ion kinetic energy of approximately 5eV and a full width at half maximum of 4eV was detected at a quadrupole mass spectrometer located 10 cm away. The geometry of the instrument is such that it is mounted on a 7 cm flange and can be tailored in length and orientation to fit most UHV systems. The data presented here are for ESD-controlled conditions where increases in the flux are strictly linear with electron bombardment current. Calculation shows that transport-controlled conditions can be achieved at temperatures as low as 350 C with membrane thicknesses on the order of 10 micron.

  3. Endogenous Generation of Singlet Oxygen and Ozone in Human and Animal Tissues: Mechanisms, Biological Significance, and Influence of Dietary Components

    PubMed Central

    2016-01-01

    Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity. PMID:27042259

  4. Balancing the generation and elimination of reactive oxygen species

    USGS Publications Warehouse

    Rodriguez, Rusty; Redman, Regina

    2005-01-01

    Fossil records suggest that bacteria developed the ability to photosynthesize ≈3,500 million years ago (mya), initiating a very slow accumulation of atmospheric oxygen (1). Recent geochemical models suggest that atmospheric oxygen did not accumulate to levels conducive for aerobic life until 500–1,000 mya (2, 3). The oxygenation of Earth's atmosphere resulted in the emergence of aerobic organisms followed by a great diversification of biological species and the eventual evolution of humans.

  5. Reactive oxygen species-activated nanomaterials as theranostic agents.

    PubMed

    Kim, Kye S; Lee, Dongwon; Song, Chul Gyu; Kang, Peter M

    2015-01-01

    Reactive oxygen species (ROS) are generated from the endogenous oxidative metabolism or from exogenous pro-oxidant exposure. Oxidative stress occurs when there is excessive production of ROS, outweighing the antioxidant defense mechanisms which may lead to disease states. Hydrogen peroxide (H2O2) is one of the most abundant and stable forms of ROS, implicated in inflammation, cellular dysfunction and apoptosis, which ultimately lead to tissue and organ damage. This review is an overview of the role of ROS in different diseases. We will also examine ROS-activated nanomaterials with emphasis on hydrogen peroxide, and their potential medical implications. Further development of the biocompatible, stimuli-activated agent responding to disease causing oxidative stress, may lead to a promising clinical use. PMID:26328770

  6. Reactive oxygen species-activated nanomaterials as theranostic agents

    PubMed Central

    Kim, Kye S; Lee, Dongwon; Song, Chul Gyu; Kang, Peter M

    2015-01-01

    Reactive oxygen species (ROS) are generated from the endogenous oxidative metabolism or from exogenous pro-oxidant exposure. Oxidative stress occurs when there is excessive production of ROS, outweighing the antioxidant defense mechanisms which may lead to disease states. Hydrogen peroxide (H2O2) is one of the most abundant and stable forms of ROS, implicated in inflammation, cellular dysfunction and apoptosis, which ultimately lead to tissue and organ damage. This review is an overview of the role of ROS in different diseases. We will also examine ROS-activated nanomaterials with emphasis on hydrogen peroxide, and their potential medical implications. Further development of the biocompatible, stimuli-activated agent responding to disease causing oxidative stress, may lead to a promising clinical use. PMID:26328770

  7. Sexual Preferences in Nutrient Utilization Regulate Oxygen Consumption and Reactive Oxygen Species Generation in Schistosoma mansoni: Potential Implications for Parasite Redox Biology.

    PubMed

    Oliveira, Matheus P; Correa Soares, Juliana B R; Oliveira, Marcus F

    2016-01-01

    Schistosoma mansoni, one of the causative agents of human schistosomiasis, has a unique antioxidant network that is key to parasite survival and a valuable chemotherapeutic target. The ability to detoxify and tolerate reactive oxygen species increases along S. mansoni development in the vertebrate host, suggesting that adult parasites are more exposed to redox challenges than young stages. Indeed, adult parasites are exposed to multiple redox insults generated from blood digestion, activated immune cells, and, potentially, from their own parasitic aerobic metabolism. However, it remains unknown how reactive oxygen species are produced by S. mansoni metabolism, as well as their biological effects on adult worms. Here, we assessed the contribution of nutrients and parasite gender to oxygen utilization pathways, and reactive oxygen species generation in whole unpaired adult S. mansoni worms. We also determined the susceptibilities of both parasite sexes to a pro-oxidant challenge. We observed that glutamine and serum importantly contribute to both respiratory and non-respiratory oxygen utilization in adult worms, but with different proportions among parasite sexes. Analyses of oxygen utilization pathways revealed that respiratory rates were high in male worms, which contrast with high non-respiratory rates in females, regardless nutritional sources. Interestingly, mitochondrial complex I-III activity was higher than complex IV specifically in females. We also observed sexual preferences in substrate utilization to sustain hydrogen peroxide production towards glucose in females, and glutamine in male worms. Despite strikingly high oxidant levels and hydrogen peroxide production rates, female worms were more resistant to a pro-oxidant challenge than male parasites. The data presented here indicate that sexual preferences in nutrient metabolism in adult S. mansoni worms regulate oxygen utilization and reactive oxygen species production, which may differently contribute

  8. Sexual Preferences in Nutrient Utilization Regulate Oxygen Consumption and Reactive Oxygen Species Generation in Schistosoma mansoni: Potential Implications for Parasite Redox Biology

    PubMed Central

    Oliveira, Matheus P.; Correa Soares, Juliana B. R.; Oliveira, Marcus F.

    2016-01-01

    Schistosoma mansoni, one of the causative agents of human schistosomiasis, has a unique antioxidant network that is key to parasite survival and a valuable chemotherapeutic target. The ability to detoxify and tolerate reactive oxygen species increases along S. mansoni development in the vertebrate host, suggesting that adult parasites are more exposed to redox challenges than young stages. Indeed, adult parasites are exposed to multiple redox insults generated from blood digestion, activated immune cells, and, potentially, from their own parasitic aerobic metabolism. However, it remains unknown how reactive oxygen species are produced by S. mansoni metabolism, as well as their biological effects on adult worms. Here, we assessed the contribution of nutrients and parasite gender to oxygen utilization pathways, and reactive oxygen species generation in whole unpaired adult S. mansoni worms. We also determined the susceptibilities of both parasite sexes to a pro-oxidant challenge. We observed that glutamine and serum importantly contribute to both respiratory and non-respiratory oxygen utilization in adult worms, but with different proportions among parasite sexes. Analyses of oxygen utilization pathways revealed that respiratory rates were high in male worms, which contrast with high non-respiratory rates in females, regardless nutritional sources. Interestingly, mitochondrial complex I-III activity was higher than complex IV specifically in females. We also observed sexual preferences in substrate utilization to sustain hydrogen peroxide production towards glucose in females, and glutamine in male worms. Despite strikingly high oxidant levels and hydrogen peroxide production rates, female worms were more resistant to a pro-oxidant challenge than male parasites. The data presented here indicate that sexual preferences in nutrient metabolism in adult S. mansoni worms regulate oxygen utilization and reactive oxygen species production, which may differently contribute

  9. Method of Separating Oxygen From Spacecraft Cabin Air to Enable Extravehicular Activities

    NASA Technical Reports Server (NTRS)

    Graf, John C.

    2013-01-01

    Extravehicular activities (EVAs) require high-pressure, high-purity oxygen. Shuttle EVAs use oxygen that is stored and transported as a cryogenic fluid. EVAs on the International Space Station (ISS) presently use the Shuttle cryo O2, which is transported to the ISS using a transfer hose. The fluid is compressed to elevated pressures and stored as a high-pressure gas. With the retirement of the shuttle, NASA has been searching for ways to deliver oxygen to fill the highpressure oxygen tanks on the ISS. A method was developed using low-pressure oxygen generated onboard the ISS and released into ISS cabin air, filtering the oxygen from ISS cabin air using a pressure swing absorber to generate a low-pressure (high-purity) oxygen stream, compressing the oxygen with a mechanical compressor, and transferring the high-pressure, high-purity oxygen to ISS storage tanks. The pressure swing absorber (PSA) can be either a two-stage device, or a single-stage device, depending on the type of sorbent used. The key is to produce a stream with oxygen purity greater than 99.5 percent. The separator can be a PSA device, or a VPSA device (that uses both vacuum and pressure for the gas separation). The compressor is a multi-stage mechanical compressor. If the gas flow rates are on the order of 5 to 10 lb (.2.3 to 4.6 kg) per day, the compressor can be relatively small [3 16 16 in. (.8 41 41 cm)]. Any spacecraft system, or other remote location that has a supply of lowpressure oxygen, a method of separating oxygen from cabin air, and a method of compressing the enriched oxygen stream, has the possibility of having a regenerable supply of highpressure, high-purity oxygen that is compact, simple, and safe. If cabin air is modified so there is very little argon, the separator can be smaller, simpler, and use less power.

  10. [Russian oxygen generation system "Elektron-VM": hydrogen content in electrolytically produced oxygen for breathing by International Space Station crews].

    PubMed

    Proshkin, V Yu; Kurmazenko, E A

    2014-01-01

    The article presents the particulars of hydrogen content in electrolysis oxygen produced aboard the ISS Russian segment by oxygen generator "Elektron-VM" (SGK) for crew breathing. Hydrogen content was estimated as in the course of SGK operation in the ISS RS, so during the ground life tests. According to the investigation of hydrogen sources, the primary path of H2 appearance in oxygen is its diffusion through the porous diaphragm separating the electrolytic-cell cathode and anode chambers. Effectiveness of hydrogen oxidation in the SGK reheating unit was evaluated.

  11. [Russian oxygen generation system "Elektron-VM": hydrogen content in electrolytically produced oxygen for breathing by International Space Station crews].

    PubMed

    Proshkin, V Yu; Kurmazenko, E A

    2014-01-01

    The article presents the particulars of hydrogen content in electrolysis oxygen produced aboard the ISS Russian segment by oxygen generator "Elektron-VM" (SGK) for crew breathing. Hydrogen content was estimated as in the course of SGK operation in the ISS RS, so during the ground life tests. According to the investigation of hydrogen sources, the primary path of H2 appearance in oxygen is its diffusion through the porous diaphragm separating the electrolytic-cell cathode and anode chambers. Effectiveness of hydrogen oxidation in the SGK reheating unit was evaluated. PMID:25035898

  12. Oxygen-hydrogen torch is a small-scale steam generator

    NASA Technical Reports Server (NTRS)

    Maskell, C. E.

    1966-01-01

    Standard oxygen-hydrogen torch generates steam for corrosion-rate analysis of various metals. The steam is generated through local combustion inside a test chamber under constant temperature and pressure control.

  13. Singlet Oxygen Generation by Laser Irradiation of Gold Nanoparticles

    PubMed Central

    2016-01-01

    The formation of singlet oxygen by irradiation of gold nanoparticles in their plasmon resonance band with continuous or pulsed laser light has been investigated. Citrate-stabilized nanoparticles were found to facilitate the photogeneration of singlet oxygen, albeit with low quantum yield. The reaction caused by pulsed laser irradiation makes use of the equilibrated hot electrons that can reach temperatures of several thousand degrees during the laser pulse. Although less efficient, continuous irradiation, which acts via the short-lived directly excited primary “hot” electrons only, can produce enough singlet oxygen for photodynamic cancer therapy and has significant advantages for practical applications. However, careful design of the nanoparticles is needed, since even a moderately thick capping layer can completely inhibit singlet oxygen formation. Moreover, the efficiency of the process also depends on the nanoparticle size. PMID:27239247

  14. Active site densities, oxygen activation and adsorbed reactive oxygen in alcohol activation on npAu catalysts.

    PubMed

    Wang, Lu-Cun; Friend, C M; Fushimi, Rebecca; Madix, Robert J

    2016-07-01

    The activation of molecular O2 as well as the reactivity of adsorbed oxygen species is of central importance in aerobic selective oxidation chemistry on Au-based catalysts. Herein, we address the issue of O2 activation on unsupported nanoporous gold (npAu) catalysts by applying a transient pressure technique, a temporal analysis of products (TAP) reactor, to measure the saturation coverage of atomic oxygen, its collisional dissociation probability, the activation barrier for O2 dissociation, and the facility with which adsorbed O species activate methanol, the initial step in the catalytic cycle of esterification. The results from these experiments indicate that molecular O2 dissociation is associated with surface silver, that the density of reactive sites is quite low, that adsorbed oxygen atoms do not spill over from the sites of activation onto the surrounding surface, and that methanol reacts quite facilely with the adsorbed oxygen atoms. In addition, the O species from O2 dissociation exhibits reactivity for the selective oxidation of methanol but not for CO. The TAP experiments also revealed that the surface of the npAu catalyst is saturated with adsorbed O under steady state reaction conditions, at least for the pulse reaction. PMID:27376884

  15. Molecular sieve oxygen generating system: the argon question--a brief review.

    PubMed

    Ikels, K G; Adams, J D

    1979-09-01

    The molecular sieve oxygen generating system (MSOG) is currently being considered as a replacement for liquid and gaseous stores on aircraft for the supply of aviator's breathing oxygen. Incorporation of onboard oxygen generation in aircraft not only increases system safety but also minimizes logistic requirements. However, a unique characteristic of the MSOG is that it concentrates not only oxygen but also argon in the process of removing nitrogen from engine bleed air. Maximum concentrations produced by present systems are in the order of 95% oxygen and 5% argon. These results have precipitated numerous questions relating to the physiological effects of argon in the product breathing gas. This report reviews the current literature concerning argon as a minor constituent (less than 10%) in gas breathing systems and recommends studies prior to human compatibility testing of the molecule sieve oxygen generating systems.

  16. Probing Oxygen Activation Sites in Two Flavoprotein Oxidases Using Chloride as an Oxygen Surrogate

    SciTech Connect

    Kommoju, Phaneeswara-Rao; Chen, Zhi-wei; Bruckner, Robert C.; Mathews, F. Scott; Jorns, Marilyn Schuman

    2011-08-16

    A single basic residue above the si-face of the flavin ring is the site of oxygen activation in glucose oxidase (GOX) (His516) and monomeric sarcosine oxidase (MSOX) (Lys265). Crystal structures of both flavoenzymes exhibit a small pocket at the oxygen activation site that might provide a preorganized binding site for superoxide anion, an obligatory intermediate in the two-electron reduction of oxygen. Chloride binds at these polar oxygen activation sites, as judged by solution and structural studies. First, chloride forms spectrally detectable complexes with GOX and MSOX. The protonated form of His516 is required for tight binding of chloride to oxidized GOX and for rapid reaction of reduced GOX with oxygen. Formation of a binary MSOX-chloride complex requires Lys265 and is not observed with Lys265Met. Binding of chloride to MSOX does not affect the binding of a sarcosine analogue (MTA, methylthioactetate) above the re-face of the flavin ring. Definitive evidence is provided by crystal structures determined for a binary MSOX-chloride complex and a ternary MSOX-chloride-MTA complex. Chloride binds in the small pocket at a position otherwise occupied by a water molecule and forms hydrogen bonds to four ligands that are arranged in approximate tetrahedral geometry: Lys265:NZ, Arg49:NH1, and two water molecules, one of which is hydrogen bonded to FAD:N5. The results show that chloride (i) acts as an oxygen surrogate, (ii) is an effective probe of polar oxygen activation sites, and (iii) provides a valuable complementary tool to the xenon gas method that is used to map nonpolar oxygen-binding cavities.

  17. Enhanced Singlet Oxygen Generation in Oxidized Graphitic Carbon Nitride for Organic Synthesis.

    PubMed

    Wang, Hui; Jiang, Shenlong; Chen, Shichuan; Li, Dandan; Zhang, Xiaodong; Shao, Wei; Sun, Xianshun; Xie, Junfeng; Zhao, Zhi; Zhang, Qun; Tian, Yupeng; Xie, Yi

    2016-08-01

    Experimental data reveal that the incorporation of carbonyl groups into polymer matrix can significantly enhance singlet oxygen ((1) O2 ) generation and suppress production of other reactive oxygen species. Excitonic processes investigated by phosphorescence spectroscopy reveal enhanced triplet-exciton generation in the modified g-C3 N4 , which facilitate (1) O2 generation through an energy transfer process. Benefiting from this, the modified g-C3 N4 shows excellent conversion and selectivity in organic synthesis.

  18. Peroxide-based oxygen generating topical wound dressing for enhancing healing of dermal wounds.

    PubMed

    Chandra, Prafulla K; Ross, Christina L; Smith, Leona C; Jeong, Seon S; Kim, Jaehyun; Yoo, James J; Harrison, Benjamin S

    2015-01-01

    Oxygen generating biomaterials represent a new trend in regenerative medicine that aims to generate and supply oxygen at the site of requirement, to support tissue healing and regeneration. To enhance the healing of dermal wounds, we have developed a highly portable, in situ oxygen generating wound dressings that uses sodium percarbonate (SPO) and calcium peroxide (CPO) as chemical oxygen sources. The dressing continuously generated oxygen for more than 3 days, after which it was replaced. In the in vivo testing on porcine full-thickness porcine wound model, the SPO/CPO dressing showed enhanced wound healing during the 8 week study period. Quantitative measurements of wound healing related parameters, such as wound closure, reepithelialization, epidermal thickness and collagen content of dermis showed that supplying oxygen topically using the SPO/CPO dressing significantly accelerated the wound healing. An increase in neovascularization, as determined using Von Willebrand factor (vWF) and CD31 staining, was also observed in the presence of SPO/CPO dressing. This novel design for a wound dressing that contains oxygen generating biomaterials (SPO/CPO) for supplying topical oxygen, may find utility in treating various types of acute to chronic wounds.

  19. The effect of plutonium dioxide water surface coverage on the generation of hydrogen and oxygen

    SciTech Connect

    Veirs, Douglas K.; Berg, John M.; Crowder, Mark L.

    2012-06-20

    The conditions for the production of oxygen during radiolysis of water adsorbed onto plutonium dioxide powder are discussed. Studies in the literature investigating the radiolysis of water show that both oxygen and hydrogen can be generated from water adsorbed on high-purity plutonium dioxide powder. These studies indicate that there is a threshold in the amount of water below which oxygen is not generated. The threshold is associated with the number of monolayers of adsorbed water and is shown to occur at approximately two monolayers of molecularly adsorbed water. Material in equilibrium with 50% relative humidity (RH) will be at the threshold for oxygen generation. Using two monolayers of molecularly adsorbed water as the threshold for oxygen production, the total pressure under various conditions is calculated assuming stoichiometric production of hydrogen and oxygen. The specific surface area of the oxide has a strong effect on the final partial pressure. The specific surface areas resulting in the highest pressures within a 3013 container are evaluated. The potential for oxygen generation is mitigated by reduced relative humidity, and hence moisture adsorption, at the oxide surface which occurs if the oxide is warmer than the ambient air. The potential for oxygen generation approaches zero as the temperature difference between the ambient air and the material approaches 6 C.

  20. Magnetic field dependence of singlet oxygen generation by nanoporous silicon

    NASA Astrophysics Data System (ADS)

    Amonkosolpan, Jamaree; Aliev, Gazi N.; Wolverson, Daniel; Snow, Paul A.; Davies, James John

    2014-07-01

    Energy transfer from photoexcited excitons localized in silicon nanoparticles to adsorbed oxygen molecules excites them to the reactive singlet spin state. This process has been studied experimentally as a function of nanoparticle size and applied external magnetic field as a test of the accepted understanding of this process in terms of the exchange coupling between the nano-Si exciton and the adsorbed O2 molecules.

  1. Activation energies to characterize ease of removal of various kinds of oxygen from bismuth molybdate

    SciTech Connect

    Dadyburjor, D.B.; Ruckenstein, E.

    1980-06-01

    Calculations by the method of minimum energy paths showed that oxygen(-2) anions are more easily displaced from molybdenum(VI) or from the layer between molybdenum and bismuth than from bismuth(III) of a 2:1 bismuth molybdate (Bi/sub 2/MoO/sub 6/). However, available experimental evidence suggests that the oxygen of the bismuth layer is active in the selective oxidation of hydrocarbons; apparently the presence of the hydrocarbon decreases the energy barrier required for transfer of the oxygen anion, and anion vacancies generated, e.g., in a prereduction of the catalyst, also decrease the energy barrier.

  2. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield.

    PubMed

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C; Goldys, Ewa M

    2016-01-01

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 10(8) and (2.0 ± 0.1) × 10(9) singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 10(7)-2 × 10(9) singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.

  3. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield

    NASA Astrophysics Data System (ADS)

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C.; Goldys, Ewa M.

    2016-01-01

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 108 and (2.0 ± 0.1) × 109 singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 107-2 × 109 singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.

  4. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield

    PubMed Central

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C.; Goldys, Ewa M.

    2016-01-01

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 108 and (2.0 ± 0.1) × 109 singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 107–2 × 109 singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality. PMID:26818819

  5. Space Technology Game Changing Development- Next Generation Life Support: Spacecraft Oxygen Recovery (SCOR)

    NASA Technical Reports Server (NTRS)

    Abney, Morgan; Barta, Daniel

    2015-01-01

    The Next Generation Life Support Spacecraft Oxygen Recovery (SCOR) project element is dedicated to developing technology that enables oxygen recovery from metabolically produced carbon dioxide in space habitats. The state-of-the-art system on the International Space Station uses Sabatier technology to recover (is) approximately 50% oxygen from carbon dioxide. The remaining oxygen required for crew respiration is supplied from Earth. For long duration manned missions beyond low-Earth orbit, resupply of oxygen becomes economically and logistically prohibitive. To mitigate these challenges, the SCOR project element is targeting development of technology to increase the recovery of oxygen to 75% or more, thereby reducing the total oxygen resupply required for future missions.

  6. Lactobacillus rhamnosus blocks inflammatory signaling in vivo via reactive oxygen species generation.

    PubMed

    Lin, Patricia W; Myers, Loren E S; Ray, Laurie; Song, Shuh-Chyung; Nasr, Tala R; Berardinelli, Andrew J; Kundu, Kousik; Murthy, Niren; Hansen, Jason M; Neish, Andrew S

    2009-10-15

    Uncontrolled inflammatory responses in the immature gut may play a role in the pathogenesis of many intestinal inflammatory syndromes that present in newborns or children, such as necrotizing enterocolitis (NEC), idiopathic inflammatory bowel diseases (IBD), or infectious enteritis. Consistent with previous reports that murine intestinal function matures over the first 3 weeks of life, we show that inflammatory signaling in the neonatal mouse gut increases during postnatal maturation, with peak responses occurring at 2-3 weeks. Probiotic bacteria can block inflammatory responses in cultured epithelia by inducing the generation of reactive oxygen species (ROS), which inhibit NF-kappaB activation through oxidative inactivation of the key regulatory enzyme Ubc12. We now report for the first time that the probiotic Lactobacillus rhamnosus GG (LGG) can induce ROS generation in intestinal epithelia in vitro and in vivo. Intestines from immature mice gavage fed LGG exhibited increased GSH oxidation and cullin-1 deneddylation, reflecting local ROS generation and its resultant Ubc12 inactivation, respectively. Furthermore, prefeeding LGG prevented TNF-alpha-induced intestinal NF-kappaB activation. These studies indicate that LGG can reduce inflammatory signaling in immature intestines by inducing local ROS generation and may be a mechanism by which probiotic bacteria can prevent NEC in premature infants or reduce the severity of IBD in children.

  7. Thermochemical generation of hydrogen and oxygen from water

    DOEpatents

    Robinson, Paul R.; Bamberger, Carlos E.

    1981-01-01

    A thermochemical cyclic process for the production of hydrogen exploits the reaction between sodium manganate (NaMnO.sub.2) and titanium dioxide (TiO.sub.2) to form sodium titanate (Na.sub.2 TiO.sub.3), manganese (II) titanate (MnTiO.sub.3) and oxygen. The titanate mixture is treated with sodium hydroxide, in the presence of steam, to form sodium titanate, sodium manganate (III), water and hydrogen. The sodium titanate-manganate (III) mixture is treated with water to form sodium manganate (III), titanium dioxide and sodium hydroxide. Sodium manganate (III) and titanium dioxide are recycled following dissolution of sodium hydroxide in water.

  8. Thermochemical generation of hydrogen and oxygen from water

    DOEpatents

    Robinson, Paul R.; Bamberger, Carlos E.

    1982-01-01

    A thermochemical cyclic process for the production of hydrogen exploits the reaction between sodium manganate (NaMnO.sub.2) and titanium dioxide (TiO.sub.2) to form sodium titanate (Na.sub.2 TiO.sub.3), manganese (II) titanate (MnTiO.sub.3) and oxygen. The titanate mixture is treated with sodium hydroxide, in the presence of steam, to form sodium titanate, sodium manganate (III), water and hydrogen. The sodium titanate-manganate (III) mixture is treated with water to form sodium manganate (III), titanium dioxide and sodium hydroxide. Sodium manganate (III) and titanium dioxide are recycled following dissolution of sodium hydroxide in water.

  9. International Space Station United States Orbital Segment Oxygen Generation System On-Orbit Operational Experience

    NASA Technical Reports Server (NTRS)

    Erickson, Robert J.; Howe, John, Jr.; Kulp, Galen W.; VanKeuren, Steven P.

    2008-01-01

    The International Space Station (ISS) United States Orbital Segment (USOS) Oxygen Generation System (OGS) was originally intended to be installed in ISS Node 3. The OGS rack delivery was accelerated, and it was launched to ISS in July of 2006 and installed in the US Laboratory Module. Various modification kits were installed to provide its interfaces, and the OGS was first activated in July of 2007 for 15 hours, In October of 2007 it was again activated for 76 hours with varied production rates and day/night cycling. Operational time in each instance was limited by the quantity of feedwater in a Payload Water Reservoir (PWR) bag. Feedwater will be provided by PWR bag until the USOS Water Recovery System (WRS) is delivered to SS in fall of 2008. This paper will discuss operating experience and characteristics of the OGS, as well as operational issues and their resolution.

  10. A new approach to oxygen enriched high temperature blast generation

    SciTech Connect

    Queille, P.H.; Macauley, D.

    1996-12-31

    When increasing fuel injection in a blast furnace in order to reduce coke consumption and/or to increase production, the blast furnace operator tries to keep similar raceway conditions, for instance, an equivalent flame temperature. To compensate for the cooling effect due to the higher injection rate, two solutions can be selected or combined: to raise the temperature of the blast and/or to increase the level of oxygen in the blast. Whatever the choice, the Blast Furnace manager will certainly try to reduce the resulting investment and operating costs to a minimum. Air Liquide and Kvaerner Davy are trying to provide a new way to address these needs by offering a new technology for blast heating. A higher blast temperature will not only allow a higher fuel injection at tuyere level, a lower coke consumption, but also a lower oxygen consumption. Air Liquide and Kvaerner Davy are now able to offer a new heat regenerator with major advantages over conventional stoves. This new device can be used as a permanent substitute for a stove, or as a temporary one during repair, or stove improvement. It can also be added to an existing set of stoves to increase the average blast temperature.

  11. A polydimethylsiloxane-polycarbonate hybrid microfluidic device capable of generating perpendicular chemical and oxygen gradients for cell culture studies.

    PubMed

    Chang, Chia-Wen; Cheng, Yung-Ju; Tu, Melissa; Chen, Ying-Hua; Peng, Chien-Chung; Liao, Wei-Hao; Tung, Yi-Chung

    2014-10-01

    This paper reports a polydimethylsiloxane-polycarbonate (PDMS-PC) hybrid microfluidic device capable of performing cell culture under combinations of chemical and oxygen gradients. The microfluidic device is constructed of two PDMS layers with microfluidic channel patterns separated by a thin PDMS membrane. The top layer contains an embedded PC film and a serpentine channel for a spatially confined oxygen scavenging chemical reaction to generate an oxygen gradient in the bottom layer for cell culture. Using the chemical reaction method, the device can be operated with a small amount of chemicals, without bulky gas cylinders and sophisticated flow control schemes. Furthermore, it can be directly used in conventional incubators with syringe pumps to simplify the system setup. The bottom layer contains arrangements of serpentine channels for chemical gradient generation and a cell culture chamber in the downstream. The generated chemical and oxygen gradients are experimentally characterized using a fluorescein solution and an oxygen-sensitive fluorescent dye, respectively. For demonstration, a 48 hour cell-based drug test and a cell migration assay using human lung adenocarcinoma epithelial cells (A549) are conducted under various combinations of the chemical and oxygen gradients in the experiments. The drug testing results show an increase in A549 cell apoptosis due to the hypoxia-activated cytotoxicity of tirapazamine (TPZ) and also suggest great cell compatibility and gradient controllability of the device. In addition, the A549 cell migration assay results demonstrate an aerotactic behavior of the A549 cells and suggest that the oxygen gradient plays an essential role in guiding cell migration. The migration results, under combinations of chemokine and oxygen gradients, cannot be simply superposed with single gradient results. The device is promising to advance the control of in vitro microenvironments, to better study cellular responses under various

  12. A polydimethylsiloxane-polycarbonate hybrid microfluidic device capable of generating perpendicular chemical and oxygen gradients for cell culture studies.

    PubMed

    Chang, Chia-Wen; Cheng, Yung-Ju; Tu, Melissa; Chen, Ying-Hua; Peng, Chien-Chung; Liao, Wei-Hao; Tung, Yi-Chung

    2014-10-01

    This paper reports a polydimethylsiloxane-polycarbonate (PDMS-PC) hybrid microfluidic device capable of performing cell culture under combinations of chemical and oxygen gradients. The microfluidic device is constructed of two PDMS layers with microfluidic channel patterns separated by a thin PDMS membrane. The top layer contains an embedded PC film and a serpentine channel for a spatially confined oxygen scavenging chemical reaction to generate an oxygen gradient in the bottom layer for cell culture. Using the chemical reaction method, the device can be operated with a small amount of chemicals, without bulky gas cylinders and sophisticated flow control schemes. Furthermore, it can be directly used in conventional incubators with syringe pumps to simplify the system setup. The bottom layer contains arrangements of serpentine channels for chemical gradient generation and a cell culture chamber in the downstream. The generated chemical and oxygen gradients are experimentally characterized using a fluorescein solution and an oxygen-sensitive fluorescent dye, respectively. For demonstration, a 48 hour cell-based drug test and a cell migration assay using human lung adenocarcinoma epithelial cells (A549) are conducted under various combinations of the chemical and oxygen gradients in the experiments. The drug testing results show an increase in A549 cell apoptosis due to the hypoxia-activated cytotoxicity of tirapazamine (TPZ) and also suggest great cell compatibility and gradient controllability of the device. In addition, the A549 cell migration assay results demonstrate an aerotactic behavior of the A549 cells and suggest that the oxygen gradient plays an essential role in guiding cell migration. The migration results, under combinations of chemokine and oxygen gradients, cannot be simply superposed with single gradient results. The device is promising to advance the control of in vitro microenvironments, to better study cellular responses under various

  13. Feasibility Analysis of Liquefying Oxygen Generated from Water Electrolysis Units on Lunar Surface

    NASA Technical Reports Server (NTRS)

    Jeng, Frank F.

    2009-01-01

    Concepts for liquefying oxygen (O2) generated from water electrolysis subsystems on the Lunar surface were explored. Concepts for O2 liquefaction units capable of generating 1.38 lb/hr (0.63 kg/hr) liquid oxygen (LOX) were developed. Heat and mass balance calculations for the liquefaction concepts were conducted. Stream properties, duties of radiators, heat exchangers and compressors for the selected concepts were calculated and compared.

  14. Molecular sieve generation of aviator's oxygen: Performance of a prototype system under simulated flight conditions.

    PubMed

    Miller, R L; Ikels, K G; Lamb, M J; Boscola, E J; Ferguson, R H

    1980-07-01

    The molecular sieve method of generating an enriched-oxygen breathing gas is one of several candidate onboard oxygen generation (OBOG) systems under joint Army-Navy-Air Force development for application in tactical aircraft. The performance of a nominal two-man-capacity molecular sieve oxygen generation system was characterized under simulated flight conditions. Data are given on the composition of the molecular sieve-generated breathing gas (oxygen, nitrogen, carbon dioxide, and argon) as a function of inlet air pressure, altitude, breathing gas flow rate, and ambient temperature. The maximum oxygen concentration observed was 95%, with the balance argon. At low demand flow rates and certain conditions of pressure and altitude, the argon enrichment factor exceeded that of oxygen giving a maximum argon concentration of 6.6% with the balance oxygen. The structural integrity of the unit was verified by vibration and centrifuge testing. The performance of the molecular sieve unit is discussed in the context of aircraft operating envelopes using both diluter-demand and 100% delivery subsystems. PMID:6774707

  15. Molecular sieve generation of aviator's oxygen: Performance of a prototype system under simulated flight conditions.

    PubMed

    Miller, R L; Ikels, K G; Lamb, M J; Boscola, E J; Ferguson, R H

    1980-07-01

    The molecular sieve method of generating an enriched-oxygen breathing gas is one of several candidate onboard oxygen generation (OBOG) systems under joint Army-Navy-Air Force development for application in tactical aircraft. The performance of a nominal two-man-capacity molecular sieve oxygen generation system was characterized under simulated flight conditions. Data are given on the composition of the molecular sieve-generated breathing gas (oxygen, nitrogen, carbon dioxide, and argon) as a function of inlet air pressure, altitude, breathing gas flow rate, and ambient temperature. The maximum oxygen concentration observed was 95%, with the balance argon. At low demand flow rates and certain conditions of pressure and altitude, the argon enrichment factor exceeded that of oxygen giving a maximum argon concentration of 6.6% with the balance oxygen. The structural integrity of the unit was verified by vibration and centrifuge testing. The performance of the molecular sieve unit is discussed in the context of aircraft operating envelopes using both diluter-demand and 100% delivery subsystems.

  16. Targeting cancer cells with reactive oxygen and nitrogen species generated by atmospheric-pressure air plasma.

    PubMed

    Ahn, Hak Jun; Kim, Kang Il; Hoan, Nguyen Ngoc; Kim, Churl Ho; Moon, Eunpyo; Choi, Kyeong Sook; Yang, Sang Sik; Lee, Jong-Soo

    2014-01-01

    The plasma jet has been proposed as a novel therapeutic method for cancer. Anticancer activity of plasma has been reported to involve mitochondrial dysfunction. However, what constituents generated by plasma is linked to this anticancer process and its mechanism of action remain unclear. Here, we report that the therapeutic effects of air plasma result from generation of reactive oxygen/nitrogen species (ROS/RNS) including H2O2, Ox, OH-, •O2, NOx, leading to depolarization of mitochondrial membrane potential and mitochondrial ROS accumulation. Simultaneously, ROS/RNS activate c-Jun NH2-terminal kinase (JNK) and p38 kinase. As a consequence, treatment with air plasma jets induces apoptotic death in human cervical cancer HeLa cells. Pretreatment of the cells with antioxidants, JNK and p38 inhibitors, or JNK and p38 siRNA abrogates the depolarization of mitochondrial membrane potential and impairs the air plasma-induced apoptotic cell death, suggesting that the ROS/RNS generated by plasma trigger signaling pathways involving JNK and p38 and promote mitochondrial perturbation, leading to apoptosis. Therefore, administration of air plasma may be a feasible strategy to eliminate cancer cells.

  17. Antioxidative activity and growth regulation of Brassicaceae induced by oxygen radical irradiation

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Ono, Reoto; Shiratani, Masaharu; Yonesu, Akira

    2015-06-01

    The growth regulation characteristics of plants are investigated when plant seeds are irradiated with atmospheric discharge plasma. Enhancement of the germination and lengths of the stem and root of plants are observed after seeding. The total length of the stem and root increases approximately 1.6 times after a cultivation period of 72 h. The growth regulation effect is found to be maintained for 80 h of cultivation after seeding. The growth regulation originates from the change in the antioxidative activity of plant cells induced by active oxygen species generated in the oxygen plasma, which leads to the production of growth factor in plants.

  18. Generation of reactive oxygen species by human mesothelioma cells

    PubMed Central

    Kahlos, K; Pitkänen, S; Hassinen, I; Linnainmaa, K; Kinnula, V L

    1999-01-01

    Malignant mesothelioma cells contain elevated levels of manganese superoxide dismutase (MnSOD) and are highly resistant to oxidants compared to non-malignant mesothelial cells. Since the level of cellular free radicals may be important for cell survival, we hypothesized that the increase of MnSOD in the mitochondria of mesothelioma cells may alter the free radical levels of these organelles. First, MnSOD activity was compared to the activities of two constitutive mitochondrial enzymes; MnSOD activity was 20 times higher in the mesothelioma cells than in the mesothelial cells, whereas the activities of citrate synthase and cytochrome c oxidase did not differ significantly in the two cell lines. This indicates that the activity of MnSOD per mitochondrion was increased in the mesothelioma cells. Superoxide production was assayed in the isolated mitochondria of these cells using lucigenin chemiluminescence. Mitochondrial superoxide levels were significantly lower (72%) in the mesothelioma cells compared to the mesothelial cells. Oxidant production in intact cells, assayed by fluorimetry using 2′,7′-dichlorodihydrofluorescein as a fluorescent probe, did not differ significantly between these cells. We conclude that mitochondrial superoxide levels are lower in mesothelioma cells compared to nonmalignant mesothelial cells, and that this difference may be explained by higher MnSOD activity in the mitochondria of these cells. Oxidant production was not different in these cells, which may be due to the previously observed increase in H2O2-scavenging mechanisms of mesothelioma cells. © 1999 Cancer Research Campaign PMID:10389973

  19. Excited states in the active media of oxygen - iodine lasers

    SciTech Connect

    Azyazov, V N

    2009-11-30

    A review of investigations of kinetic processes in active media oxygen - iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O{sub 2} and I{sub 2} molecules are considered, and dissociation mechanisms of I{sub 2} in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended. (review)

  20. Reactive oxygen species generated from skeletal muscles are required for gecko tail regeneration.

    PubMed

    Zhang, Qing; Wang, Yingjie; Man, Lili; Zhu, Ziwen; Bai, Xue; Wei, Sumei; Liu, Yan; Liu, Mei; Wang, Xiaochuan; Gu, Xiaosong; Wang, Yongjun

    2016-01-01

    Reactive oxygen species (ROS) participate in various physiological and pathological functions following generation from different types of cells. Here we explore ROS functions on spontaneous tail regeneration using gecko model. ROS were mainly produced in the skeletal muscle after tail amputation, showing a temporal increase as the regeneration proceeded. Inhibition of the ROS production influenced the formation of autophagy in the skeletal muscles, and as a consequence, the length of the regenerating tail. Transcriptome analysis has shown that NADPH oxidase (NOX2) and the subunits (p40(phox) and p47(phox)) are involved in the ROS production. ROS promoted the formation of autophagy through regulation of both ULK and MAPK activities. Our results suggest that ROS produced by skeletal muscles are required for the successful gecko tail regeneration. PMID:26853930

  1. Reactive oxygen species generated from skeletal muscles are required for gecko tail regeneration.

    PubMed

    Zhang, Qing; Wang, Yingjie; Man, Lili; Zhu, Ziwen; Bai, Xue; Wei, Sumei; Liu, Yan; Liu, Mei; Wang, Xiaochuan; Gu, Xiaosong; Wang, Yongjun

    2016-02-08

    Reactive oxygen species (ROS) participate in various physiological and pathological functions following generation from different types of cells. Here we explore ROS functions on spontaneous tail regeneration using gecko model. ROS were mainly produced in the skeletal muscle after tail amputation, showing a temporal increase as the regeneration proceeded. Inhibition of the ROS production influenced the formation of autophagy in the skeletal muscles, and as a consequence, the length of the regenerating tail. Transcriptome analysis has shown that NADPH oxidase (NOX2) and the subunits (p40(phox) and p47(phox)) are involved in the ROS production. ROS promoted the formation of autophagy through regulation of both ULK and MAPK activities. Our results suggest that ROS produced by skeletal muscles are required for the successful gecko tail regeneration.

  2. High fluence laser irradiation induces reactive oxygen species generation in human lung adenocarcinoma cells

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Xing, Da; Chen, Tong-Sheng

    2006-09-01

    Low-power laser irradiation (LPLI) has been used for therapies such as curing spinal cord injury, healing wound et al. Yet, the mechanism of LPLI remains unclear. Our previous study showed that low fluences laser irradiation induces human lung adenocarcinoma cells (ASTC-a-1) proliferation, but high fluences induced apoptosis and caspase-3 activation. In order to study the mechanism of apoptosis induced by high fluences LPLI further, we have measured the dynamics of generation of reactive oxygen species (ROS) using H IIDCFDA fluorescence probes during this process. ASTC-a-1 cells apoptosis was induced by He-Ne laser irradiation at high fluence of 120J/cm2. A confocal laser scanning microscope was used to perform fluorescence imaging. The results demonstrated that high fluence LPLI induced the increase of mitochondria ROS. Our studies contribute to clarify the biological mechanism of high fluence LPLI-induced cell apoptosis.

  3. Direct detection of singlet oxygen generated by UVA irradiation in human cells and skin.

    PubMed

    Baier, Jürgen; Maisch, Tim; Maier, Max; Landthaler, Michael; Bäumler, Wolfgang

    2007-06-01

    UVA light produces deleterious biological effects in which singlet oxygen plays a major role. These effects comprise a significant risk of carcinogenesis in the skin and cataract formation of the eye lens. Singlet oxygen is generated by UVA light absorption in endogenous molecules present in the cells. To elucidate the primary processes and sources of singlet oxygen in tissue, it is a major goal to uncover the hidden process of singlet oxygen generation, in particular in living tissue. When exposing keratinocytes or human skin in vivo to UVA laser light (355 nm) at 6 J/cm2, we measured the luminescence of singlet oxygen at 1,270 nm. This is a positive and direct proof of singlet oxygen generation in cells and skin by UVA light. Moreover, a clear signal of singlet oxygen luminescence was detected in phosphatidylcholine suspensions (water or ethanol) irradiated by UVA. Oxidized products of phosphatidylcholine are the likely chromophores because phosphatidylcholine itself does not absorb at 355 nm. The signal intensity was reduced by mannitol or super oxide dismutase. Additionally, the monochromatic UVA irradiation at 355 nm leads to upregulation of the key cytokine IL-12. This affects the balance of UV radiation on the immune system, which is comparable to effects of broadband UVA irradiation. PMID:17363921

  4. Measurements of UV-generated free radicals/reactive oxygen species (ROS) in skin

    NASA Astrophysics Data System (ADS)

    Herrling, Th.; Jung, K.; Fuchs, J.

    2006-03-01

    Free radicals/reactive oxygen species (ROS) generated in skin by UV irradiation were measured by electron spin resonance (ESR). To increase the sensitivity of measurement the short life free radicals/ROS were scavenged and accumulated by using the nitroxyl probe 3-carboxy-2,2,5,5-tetrametylpyrrolidine-1-oxyl (PCA). The spatial distribution of free radicals/ROS measured in pig skin biopsies with ESR imaging after UV irradiation corresponds to the intensity decay of irradiance in the depth of the skin. The main part of free radicals/ROS were generated by UVA (320-400 nm) so that the spatial distribution of free radicals reaches up to the lower side of the dermis. In vivo measurements on human skin were performed with a L-band ESR spectrometer and a surface coil integrating the signal intensities from all skin layers to get a sufficient signal amplitude. Using this experimental arrangement the protection of UVB and UVA/B filter against the generation of free radicals/ROS in skin were measured. The protection against ROS and the repair of damages caused by them can be realized with active antioxidants characterized by a high antioxidative power (AP). The effect of UV filter and antioxidants corresponding to their protection against free radicals/ROS in skin generated by UVAB irradiation can be quantified by the new radical sun protection factor (RSF). The RSF indicates the increase of time for staying in the sun to generate the same number of free radicals/ROS in the skin like for the unprotected skin. Regarding the amount of generated free radicals/ROS in skin as an biophysical endpoint the RSF characterizes both the protection against UVB and UVA radiation.

  5. Water-soluble fullerene materials for bioapplications: photoinduced reactive oxygen species generation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The photoinduced reactive oxygen species (ROS) generation from several water-soluble fullerenes was examined. Macromolecular or small molecular water-soluble fullerene complexes/derivatives were prepared and their 1O2 and O2•- generation abilities were evaluated by EPR spin-trapping methods. As a r...

  6. Performance of a Small Gas Generator Using Liquid Hydrogen and Liquid Oxygen

    NASA Technical Reports Server (NTRS)

    Acker, Loren W.; Fenn, David B.; Dietrich, Marshall W.

    1961-01-01

    The performance and operating problems of a small hot-gas generator burning liquid hydrogen with liquid oxygen are presented. Two methods of ignition are discussed. Injector and combustion chamber design details based on rocket design criteria are also given. A carefully fabricated showerhead injector of simple design provided a gas generator that yielded combustion efficiencies of 93 and 96 percent.

  7. Exposure of vitamins to UVB and UVA radiation generates singlet oxygen.

    PubMed

    Knak, Alena; Regensburger, Johannes; Maisch, Tim; Bäumler, Wolfgang

    2014-05-01

    Deleterious effects of UV radiation in tissue are usually attributed to different mechanisms. Absorption of UVB radiation in cell constituents like DNA causes photochemical reactions. Absorption of UVA radiation in endogenous photosensitizers like vitamins generates singlet oxygen via photosensitized reactions. We investigated two further mechanisms that might be involved in UV mediated cell tissue damage. Firstly, UVB radiation and vitamins also generate singlet oxygen. Secondly, UVB radiation may change the chemical structure of vitamins that may change the role of such endogenous photosensitizers in UVA mediated mechanisms. Vitamins were irradiated in solution using monochromatic UVB (308 nm) or UVA (330, 355, or 370 nm) radiation. Singlet oxygen was directly detected and quantified by its luminescence at 1270 nm. All investigated molecules generated singlet oxygen with a quantum yield ranging from 0.007 (vitamin D3) to 0.64 (nicotinamide) independent of the excitation wavelength. Moreover, pre-irradiation of vitamins with UVB changed their absorption in the UVB and UVA spectral range. Subsequently, molecules such as vitamin E and vitamin K1, which normally exhibit no singlet oxygen generation in the UVA, now produce singlet oxygen when exposed to UVA at 355 nm. This interplay of different UV sources is inevitable when applying serial or parallel irradiation with UVA and UVB in experiments in vitro. These results should be of particular importance for parallel irradiation with UVA and UVB in vivo, e.g. when exposing the skin to solar radiation. PMID:24691875

  8. Exposure of vitamins to UVB and UVA radiation generates singlet oxygen.

    PubMed

    Knak, Alena; Regensburger, Johannes; Maisch, Tim; Bäumler, Wolfgang

    2014-05-01

    Deleterious effects of UV radiation in tissue are usually attributed to different mechanisms. Absorption of UVB radiation in cell constituents like DNA causes photochemical reactions. Absorption of UVA radiation in endogenous photosensitizers like vitamins generates singlet oxygen via photosensitized reactions. We investigated two further mechanisms that might be involved in UV mediated cell tissue damage. Firstly, UVB radiation and vitamins also generate singlet oxygen. Secondly, UVB radiation may change the chemical structure of vitamins that may change the role of such endogenous photosensitizers in UVA mediated mechanisms. Vitamins were irradiated in solution using monochromatic UVB (308 nm) or UVA (330, 355, or 370 nm) radiation. Singlet oxygen was directly detected and quantified by its luminescence at 1270 nm. All investigated molecules generated singlet oxygen with a quantum yield ranging from 0.007 (vitamin D3) to 0.64 (nicotinamide) independent of the excitation wavelength. Moreover, pre-irradiation of vitamins with UVB changed their absorption in the UVB and UVA spectral range. Subsequently, molecules such as vitamin E and vitamin K1, which normally exhibit no singlet oxygen generation in the UVA, now produce singlet oxygen when exposed to UVA at 355 nm. This interplay of different UV sources is inevitable when applying serial or parallel irradiation with UVA and UVB in experiments in vitro. These results should be of particular importance for parallel irradiation with UVA and UVB in vivo, e.g. when exposing the skin to solar radiation.

  9. Higher respiratory activity decreases mitochondrial reactive oxygen release and increases life span in Saccharomyces cerevisiae.

    PubMed

    Barros, Mario H; Bandy, Brian; Tahara, Erich B; Kowaltowski, Alicia J

    2004-11-26

    Increased replicative longevity in Saccharomyces cerevisiae because of calorie restriction has been linked to enhanced mitochondrial respiratory activity. Here we have further investigated how mitochondrial respiration affects yeast life span. We found that calorie restriction by growth in low glucose increased respiration but decreased mitochondrial reactive oxygen species production relative to oxygen consumption. Calorie restriction also enhanced chronological life span. The beneficial effects of calorie restriction on mitochondrial respiration, reactive oxygen species release, and replicative and chronological life span could be mimicked by uncoupling agents such as dinitrophenol. Conversely, chronological life span decreased in cells treated with antimycin (which strongly increases mitochondrial reactive oxygen species generation) or in yeast mutants null for mitochondrial superoxide dismutase (which removes superoxide radicals) and for RTG2 (which participates in retrograde feedback signaling between mitochondria and the nucleus). These results suggest that yeast aging is linked to changes in mitochondrial metabolism and oxidative stress and that mild mitochondrial uncoupling can increase both chronological and replicative life span.

  10. Oxygen saturation during daily activities in chronic obstructive pulmonary disease.

    PubMed

    Soguel Schenkel, N; Burdet, L; de Muralt, B; Fitting, J W

    1996-12-01

    Patients with chronic obstructive pulmonary disease (COPD) frequently develop nocturnal oxygen desturation because of alveolar hypoventilation, worsening of ventilation-perfusion mismatch, and sometimes obstructive sleep apnoeas. In contrast, little is known about their oxygen status during the various activities of daily life. The aim of this study was to compare the oxygen saturation profile during day and night, and to assess the influence of different daily activities in COPD. During a rehabilitation programme, we studied 30 patients with moderate-to-severe COPD (median forced expiratory volume in one second (FEV1) 37% of predicted), without marked hypoxaemia (median arterial oxygen tension (Pa,O2) 9.1 kPa). Arterial oxygen saturation (Sa,O2) was assessed by pulse oximetry during night (8 h) and day (10.5 h). The mean and minimal Sa,O2 were calculated, and desaturations were defined as Sa,O2 falls > 4%.h-1. Daily activities were identified by the patients as resting, eating, washing, nebulization therapy and walking. Mean Sa,O2 was lower during the night (88%) than during the day (89%). In contrast, minimal Sa,O2 was lower during the day (69%) than during the night (72%), and the number of desaturations was higher during the day (8.6 desaturations.h-1) than during the night (6.8 desaturations.h-1). Mean Sa,O2 was 88% during walking, which was lower than during resting (90%), nebulization (90%), and meals (89%). The number of desaturations was higher during walking (13.1 desaturations.h-1), washing (12.6 desaturations.h-1), and eating (9.2 desaturations.h-1) than during resting (5.3 desaturations.h-1). We conclude that daily activities, such as walking, washing and eating, are associated with transient oxygen desaturation in patients with moderate-to-severe chronic obstructive pulmonary disease, even without marked resting hypoxaemia.

  11. Cytotoxicity But No Mutagenicity In Bacteria With Externally Generated Singlet Oxygen

    NASA Astrophysics Data System (ADS)

    Midden, W. Robert; Dahl, Thomas A.; Hartman, Philip E.

    1988-02-01

    Singlet oxygen is believed to be an important intermediate responsible for the cytotoxicity of HpD phototherapy. It has been recognized as a possible intermediate in photosensitization for more than 20 years. However, it has been difficult to obtain conclusive evidence of its biological characteristics in the past because most of the methods available for its generation that are compatible with biological systems also generate other reactive intermediates whose effects are difficult to distinguish from singlet oxygen. We have used a recently devised separated-surface-sensi-tizer (S-S-S) system for singlet oxygen generation' to measure the cytotoxicity and mutagenicity of singlet oxygen in bacteria. The S-S-S system employs rose bengal as a sensitizer immobilized on one surface of a glass plate. The glass plate is placed sensitizer-side down a small distance (< 1.5 mm) above a microscopically flat membrane (MilliporeTM or NucleoporeTM) that carries a monocellular layer of bacteria. The sensi-tizer-coated plate is illuminated from above to generate singlet oxygen at the surface of the sensitizer. The singlet oxygen thus generated can diffuse the short dis-tance to the surface of the membrane to react with the bacteria. Because of the short lifetime of singlet oxygen in air, increasing the distance between the sensitizer and the membrane causes a decline in the amount of singlet oxygen reaching the membrane according to a function derived from the Einstein-Smoluchowski equation for net displacement by diffusion. Plotting the log of the effect measured (e.g., cytotoxicity) vs. the square of the distance gives a straight line. The slope of this line can be used to calculate the gas phase half life of the intermediate responsible for the observed effects. We have found that bacteria are rapidly killed in the illuminated S-S-S system and that the gas phase half life of the agent responsible for cell killing is the same as that of singlet oxygen. This observation and other

  12. Theoretical analysis of ozone generation by pulsed dielectric barrier discharge in oxygen

    NASA Astrophysics Data System (ADS)

    Wei, L. S.; Zhou, J. H.; Wang, Z. H.; Cen, K. F.

    2007-08-01

    The use of very short high-voltage pulses combined with a dielectric layer results in high-energy electrons that dissociate oxygen molecules into atoms, which are a prerequisite for the subsequent production of ozone by collisions with oxygen molecules and third particles. The production of ozone depends on both the electrical and the physical parameters. For ozone generation by pulsed dielectric barrier discharge in oxygen, a mathematical model, which describes the relation between ozone concentration and these parameters that are of importance in its design, is developed according to dimensional analysis theory. A formula considering the ozone destruction factor is derived for predicting the characteristics of the ozone generation, within the range of the corona inception voltage to the gap breakdown voltage. The trend showing the dependence of the concentration of ozone in oxygen on these parameters generally agrees with the experimental results, thus confirming the validity of the mathematical model.

  13. Snapshots of enzymatic Baeyer-Villiger catalysis: oxygen activation and intermediate stabilization.

    PubMed

    Orru, Roberto; Dudek, Hanna M; Martinoli, Christian; Torres Pazmiño, Daniel E; Royant, Antoine; Weik, Martin; Fraaije, Marco W; Mattevi, Andrea

    2011-08-19

    Baeyer-Villiger monooxygenases catalyze the oxidation of carbonylic substrates to ester or lactone products using NADPH as electron donor and molecular oxygen as oxidative reactant. Using protein engineering, kinetics, microspectrophotometry, crystallography, and intermediate analogs, we have captured several snapshots along the catalytic cycle which highlight key features in enzyme catalysis. After acting as electron donor, the enzyme-bound NADP(H) forms an H-bond with the flavin cofactor. This interaction is critical for stabilizing the oxygen-activating flavin-peroxide intermediate that results from the reaction of the reduced cofactor with oxygen. An essential active-site arginine acts as anchoring element for proper binding of the ketone substrate. Its positively charged guanidinium group can enhance the propensity of the substrate to undergo a nucleophilic attack by the flavin-peroxide intermediate. Furthermore, the arginine side chain, together with the NADP(+) ribose group, forms the niche that hosts the negatively charged Criegee intermediate that is generated upon reaction of the substrate with the flavin-peroxide. The fascinating ability of Baeyer-Villiger monooxygenases to catalyze a complex multistep catalytic reaction originates from concerted action of this Arg-NADP(H) pair and the flavin subsequently to promote flavin reduction, oxygen activation, tetrahedral intermediate formation, and product synthesis and release. The emerging picture is that these enzymes are mainly oxygen-activating and "Criegee-stabilizing" catalysts that act on any chemically suitable substrate that can diffuse into the active site, emphasizing their potential value as toolboxes for biocatalytic applications.

  14. Active oxygen and cell death in cereal aleurone cells.

    PubMed

    Fath, Angelika; Bethke, Paul; Beligni, Veronica; Jones, Russell

    2002-05-01

    The cereal aleurone layer is a secretory tissue whose function is regulated by gibberellic acid (GA) and abscisic acid (ABA). Aleurone cells lack functional chloroplasts, thus excluding photosynthesis as a source of active oxygen species (AOS) in cell death. Incubation of barley aleurone layers or protoplasts in GA initiated the cell death programme, but incubation in ABA delays programmed cell death (PCD). Light, especially blue and UV-A light, and H(2)O(2) accelerate PCD of GA-treated aleurone cells, but ABA-treated aleurone cells are refractory to light and H(2)O(2) and are not killed. It was shown that light elevated intracellular H(2)O(2), and that the rise in H(2)O(2) was greater in GA-treated cells compared to cells in ABA. Experiments with antioxidants show that PCD in aleurone is probably regulated by AOS. The sensitivity of GA-treated aleurone to light and H(2)O(2) is a result of lowered amounts of enzymes that metabolize AOS. mRNAs encoding catalase, ascorbate peroxidase and superoxide dismutase are all reduced during 6-18 h of incubation in GA, but these mRNAs were present in higher amounts in cells incubated in ABA. The amounts of protein and enzyme activities encoded by these mRNAs were also dramatically reduced in GA-treated cells. Aleurone cells store and metabolize neutral lipids via the glyoxylate cycle in response to GA, and glyoxysomes are one potential source of AOS in the GA-treated cells. Mitochondria are another potential source of AOS in GA-treated cells. AOS generated by these organelles bring about membrane rupture and cell death.

  15. Curcumin-induced inhibition of cellular reactive oxygen species generation: novel therapeutic implications.

    PubMed

    Balasubramanyam, M; Koteswari, A Adaikala; Kumar, R Sampath; Monickaraj, S Finny; Maheswari, J Uma; Mohan, V

    2003-12-01

    There is evidence for increased levels of circulating reactive oxygen species (ROS) in diabetics, as indirectly inferred by the findings of increased lipid peroxidation and decreased antioxidant status. Direct measurements of intracellular generation of ROS using fluorescent dyes also demonstrate an association of oxidative stress with diabetes. Although phenolic compounds attenuate oxidative stress-related tissue damage, there are concerns over toxicity of synthetic phenolic antioxidants and this has considerably stimulated interest in investigating the role of natural phenolics in medicinal applications. Curcumin (the primary active principle in turmeric, Curcuma longa Linn.) has been claimed to represent a potential antioxidant and antiinflammatory agent with phytonutrient and bioprotective properties. However there are lack of molecular studies to demonstrate its cellular action and potential molecular targets. In this study the antioxidant effect of curcumin as a function of changes in cellular ROS generation was tested. Our results clearly demonstrate that curcumin abolished both phorbol-12 myristate-13 acetate (PMA) and thapsigargin-induced ROS generation in cells from control and diabetic subjects. The pattern of these ROS inhibitory effects as a function of dose-dependency suggests that curcumin mechanistically interferes with protein kinase C (PKC) and calcium regulation. Simultaneous measurements of ROS and Ca2+ influx suggest that a rise in cytosolic Ca2+ may be a trigger for increased ROS generation. We suggest that the antioxidant and antiangeogenic actions of curcumin, as a mechanism of inhibition of Ca2+ entry and PKC activity, should be further exploited to develop suitable and novel drugs for the treatment of diabetic retinopathy and other diabetic complications. PMID:14660871

  16. Photochemical inactivation of viruses by antibody conjugates of compounds generating singlet oxygen

    NASA Astrophysics Data System (ADS)

    Savitsky, Alexander P.; Tourkin, Andrey I.; Tourkina, Elena V.; Cherednikova, Tatyana V.; Ponomarev, Gely V.; Poglazov, Boris F.

    1994-03-01

    For the first time a method is proposed for targeted destruction of viral particles with a photoimmuno-toxin. The photoinununotoxin is a conjugate of antibodies and dimethoxy haematoporphyrin (a potent singlet oxygen generator), binding with the viral particle and upon illumination with visible light inactivating the virus by singlet oxygen. The method can be used to combat viral infection in humans and to prevent lysis of industrial micro-organisms by lysogenic bacteriophage strains.

  17. Generation of singlet oxygen with the use of optically excited fullerenes and fullerene-like nanoparticles

    NASA Astrophysics Data System (ADS)

    Danilov, O. B.; Belousova, I. M.; Mak, A. A.; Belousov, V. P.; Grenishin, A. S.; Kiselev, V. M.; Kris'ko, A. V.; Ponomarev, A. N.; Sosnov, E. N.

    2003-12-01

    Experimental results and a kinetic model of generation of singlet oxygen during the interaction of oxygen molecules with optically pumped (lamp or laser radiation) fullerenes or fullerene-like nanoclusters in solutions, suspensions, and the form of various solid-phase membranes (surfaces) are presented. The experimental data on the photoluminescence of singlet oxygen in solutions of fullerenes are compared with the results of numerical simulation on the basis of the kinetic model with specified constants of photochemical processes. On the basis of the experimental results, it is shown that evaporation of a solution caused by pumping radiation yields long-lived gas-phase singlet oxygen. Release of gas-phase singlet oxygen from solid-phase fullerene-containing membranes (surfaces) is also demonstrated; however, this process is hindered by adsorption of singlet oxygen on the membrane surface. The prospects for creation of a singlet-oxygen generator on the basis of photoexcited fullerene molecules and fullerene-like nanoclusters are discussed.

  18. Reactive oxygen species in signalling the transcriptional activation of WIPK expression in tobacco.

    PubMed

    Xu, Juan; Yang, Kwang-Yeol; Yoo, Seung Jin; Liu, Yidong; Ren, Dongtao; Zhang, Shuqun

    2014-07-01

    Plant mitogen-activated protein kinases represented by tobacco WIPK (wounding-induced protein kinase) and its orthologs in other species are unique in their regulation at transcriptional level in response to stress and pathogen infection. We previously demonstrated that transcriptional activation of WIPK is essential for induced WIPK activity, and activation of salicylic acid-induced protein kinase (SIPK) by the constitutively active NtMEK2(DD) is sufficient to induce WIPK gene expression. Here, we report that the effect of SIPK on WIPK gene expression is mediated by reactive oxygen species (ROS). Using a combination of pharmacological and gain-of-function transgenic approaches, we studied the relationship among SIPK activation, WIPK gene activation in response to fungal cryptogein, light-dependent ROS generation in chloroplasts, and ROS generated via NADPH oxidase. In the conditional gain-of-function GVG-NtMEK2(DD) transgenic tobacco, induction of WIPK expression is dependent on the ROS generation in chloroplasts. Consistently, methyl viologen, an inducer of ROS generation in chloroplasts, highly activated WIPK expression. In addition to chloroplast-originated ROS, H(2)O(2) generated from the cell-surface NADPH oxidase could also activate WIPK gene expression, and inhibition of cryptogein-induced ROS generation also abolished WIPK gene activation. Our data demonstrate that WIPK gene activation is mediated by ROS, which provides a mechanism by which ROS influence cellular signalling processes in plant stress/defence response.

  19. Early oxygen-utilization and brain activity in preterm infants.

    PubMed

    Tataranno, Maria Luisa; Alderliesten, Thomas; de Vries, Linda S; Groenendaal, Floris; Toet, Mona C; Lemmers, Petra M A; Vosse van de, Renè E; van Bel, Frank; Benders, Manon J N L

    2015-01-01

    The combined monitoring of oxygen supply and delivery using Near-InfraRed spectroscopy (NIRS) and cerebral activity using amplitude-integrated EEG (aEEG) could yield new insights into brain metabolism and detect potentially vulnerable conditions soon after birth. The relationship between NIRS and quantitative aEEG/EEG parameters has not yet been investigated. Our aim was to study the association between oxygen utilization during the first 6 h after birth and simultaneously continuously monitored brain activity measured by aEEG/EEG. Forty-four hemodynamically stable babies with a GA < 28 weeks, with good quality NIRS and aEEG/EEG data available and who did not receive morphine were included in the study. aEEG and NIRS monitoring started at NICU admission. The relation between regional cerebral oxygen saturation (rScO2) and cerebral fractional tissue oxygen extraction (cFTOE), and quantitative measurements of brain activity such as number of spontaneous activity transients (SAT) per minute (SAT rate), the interval in seconds (i.e. time) between SATs (ISI) and the minimum amplitude of the EEG in μV (min aEEG) were evaluated. rScO2 was negatively associated with SAT rate (β=-3.45 [CI=-5.76- -1.15], p=0.004) and positively associated with ISI (β=1.45 [CI=0.44-2.45], p=0.006). cFTOE was positively associated with SAT rate (β=0.034 [CI=0.009-0.059], p=0.008) and negatively associated with ISI (β=-0.015 [CI=-0.026- -0.004], p=0.007). Oxygen delivery and utilization, as indicated by rScO2 and cFTOE, are directly related to functional brain activity, expressed by SAT rate and ISI during the first hours after birth, showing an increase in oxygen extraction in preterm infants with increased early electro-cerebral activity. NIRS monitored oxygenation may be a useful biomarker of brain vulnerability in high-risk infants. PMID:25965343

  20. Changes to coral health and metabolic activity under oxygen deprivation.

    PubMed

    Murphy, James W A; Richmond, Robert H

    2016-01-01

    On Hawaiian reefs, the fast-growing, invasive algae Gracilaria salicornia overgrows coral heads, restricting water flow and light, thereby smothering corals. Field data shows hypoxic conditions (dissolved oxygen (DO2) < 2 mg/L) occurring underneath algal mats at night, and concurrent bleaching and partial tissue loss of shaded corals. To analyze the impact of nighttime oxygen-deprivation on coral health, this study evaluated changes in coral metabolism through the exposure of corals to chronic hypoxic conditions and subsequent analyses of lactate, octopine, alanopine, and strombine dehydrogenase activities, critical enzymes employed through anaerobic respiration. Following treatments, lactate and octopine dehydrogenase activities were found to have no significant response in activities with treatment and time. However, corals subjected to chronic nighttime hypoxia were found to exhibit significant increases in alanopine dehydrogenase activity after three days of exposure and strombine dehydrogenase activity starting after one overnight exposure cycle. These findings provide new insights into coral metabolic shifts in extremely low-oxygen environments and point to ADH and SDH assays as tools for quantifying the impact of hypoxia on coral health. PMID:27114888

  1. Changes to coral health and metabolic activity under oxygen deprivation

    PubMed Central

    Richmond, Robert H.

    2016-01-01

    On Hawaiian reefs, the fast-growing, invasive algae Gracilaria salicornia overgrows coral heads, restricting water flow and light, thereby smothering corals. Field data shows hypoxic conditions (dissolved oxygen (DO2) < 2 mg/L) occurring underneath algal mats at night, and concurrent bleaching and partial tissue loss of shaded corals. To analyze the impact of nighttime oxygen-deprivation on coral health, this study evaluated changes in coral metabolism through the exposure of corals to chronic hypoxic conditions and subsequent analyses of lactate, octopine, alanopine, and strombine dehydrogenase activities, critical enzymes employed through anaerobic respiration. Following treatments, lactate and octopine dehydrogenase activities were found to have no significant response in activities with treatment and time. However, corals subjected to chronic nighttime hypoxia were found to exhibit significant increases in alanopine dehydrogenase activity after three days of exposure and strombine dehydrogenase activity starting after one overnight exposure cycle. These findings provide new insights into coral metabolic shifts in extremely low-oxygen environments and point to ADH and SDH assays as tools for quantifying the impact of hypoxia on coral health. PMID:27114888

  2. Changes to coral health and metabolic activity under oxygen deprivation.

    PubMed

    Murphy, James W A; Richmond, Robert H

    2016-01-01

    On Hawaiian reefs, the fast-growing, invasive algae Gracilaria salicornia overgrows coral heads, restricting water flow and light, thereby smothering corals. Field data shows hypoxic conditions (dissolved oxygen (DO2) < 2 mg/L) occurring underneath algal mats at night, and concurrent bleaching and partial tissue loss of shaded corals. To analyze the impact of nighttime oxygen-deprivation on coral health, this study evaluated changes in coral metabolism through the exposure of corals to chronic hypoxic conditions and subsequent analyses of lactate, octopine, alanopine, and strombine dehydrogenase activities, critical enzymes employed through anaerobic respiration. Following treatments, lactate and octopine dehydrogenase activities were found to have no significant response in activities with treatment and time. However, corals subjected to chronic nighttime hypoxia were found to exhibit significant increases in alanopine dehydrogenase activity after three days of exposure and strombine dehydrogenase activity starting after one overnight exposure cycle. These findings provide new insights into coral metabolic shifts in extremely low-oxygen environments and point to ADH and SDH assays as tools for quantifying the impact of hypoxia on coral health.

  3. PKCα promotes generation of reactive oxygen species via DUOX2 in hepatocellular carcinoma

    SciTech Connect

    Wang, Jiajun; Shao, Miaomiao; Liu, Min; Peng, Peike; Li, Lili; Wu, Weicheng; Wang, Lan; Duan, Fangfang; Zhang, Mingming; Song, Shushu; Jia, Dongwei; Ruan, Yuanyuan; Gu, Jianxin

    2015-08-07

    Hepatocellular carcinoma (HCC) remains the second leading cause of cancer-related death worldwide, and elevated rates of reactive oxygen species (ROS) have long been considered as a hallmark of almost all types of cancer including HCC. Protein kinase C alpha (PKCα), a serine/threonine kinase among conventional PKC family, is recognized as a major player in signal transduction and tumor progression. Overexpression of PKCα is commonly observed in human HCC and associated with its poor prognosis. However, how PKCα is involved in hepatocellular carcinogenesis remains not fully understood. In this study, we found that among the members of conventional PKC family, PKCα, but not PKCβI or βII, promoted ROS production in HCC cells. PKCα stimulated generation of ROS by up-regulating DUOX2 at post-transcriptional level. Depletion of DUOX2 abrogated PKCα-induced activation of AKT/MAPK pathways as well as cell proliferation, migration and invasion in HCC cells. Moreover, the expression of DUOX2 and PKCα was well positively correlated in both HCC cell lines and patient samples. Collectively, our findings demonstrate that PKCα plays a critical role in HCC development by inducing DUOX2 expression and ROS generation, and propose a strategy to target PKCα/DUOX2 as a potential adjuvant therapy for HCC treatment. - Highlights: • PKCα promotes the generation of ROS in hepatocellular carcinoma. • PKCα induces ROS production by up-regulating DUOX2 at post-transcriptional level. • DUOX2 is required for PKCα-induced AKT/MAPK activation and tumor progression in HCC. • The expression of PKCα is positively correlated with DUOX2 in HCC.

  4. Development of ITM oxygen technology for integration in IGCC and other advanced power generation

    SciTech Connect

    Armstrong, Phillip A.

    2015-03-31

    Ion Transport Membrane (ITM) technology is based on the oxygen-ion-conducting properties of certain mixed-metal oxide ceramic materials that can separate oxygen from an oxygen-containing gas, such as air, under a suitable driving force. The “ITM Oxygen” air separation system that results from the use of such ceramic membranes produces a hot, pure oxygen stream and a hot, pressurized, oxygen-depleted stream from which significant amounts of energy can be extracted. Accordingly, the technology integrates well with other high-temperature processes, including power generation. Air Products and Chemicals, Inc., the Recipient, in conjunction with a dozen subcontractors, developed ITM Oxygen technology under this five-phase Cooperative Agreement from the laboratory bench scale to implementation in a pilot plant capable of producing power and 100 tons per day (TPD) of purified oxygen. A commercial-scale membrane module manufacturing facility (the “CerFab”), sized to support a conceptual 2000 TPD ITM Oxygen Development Facility (ODF), was also established and operated under this Agreement. In the course of this work, the team developed prototype ceramic production processes and a robust planar ceramic membrane architecture based on a novel ceramic compound capable of high oxygen fluxes. The concept and feasibility of the technology was thoroughly established through laboratory pilot-scale operations testing commercial-scale membrane modules run under industrial operating conditions with compelling lifetime and reliability performance that supported further scale-up. Auxiliary systems, including contaminant mitigation, process controls, heat exchange, turbo-machinery, combustion, and membrane pressure vessels were extensively investigated and developed. The Recipient and subcontractors developed efficient process cycles that co-produce oxygen and power based on compact, low-cost ITMs. Process economics assessments show significant benefits relative to state

  5. Photochemistry of Dissolved Black Carbon Released from Biochar: Reactive Oxygen Species Generation and Phototransformation.

    PubMed

    Fu, Heyun; Liu, Huiting; Mao, Jingdong; Chu, Wenying; Li, Qilin; Alvarez, Pedro J J; Qu, Xiaolei; Zhu, Dongqiang

    2016-02-01

    Dissolved black carbon (BC) released from biochar can be one of the more photoactive components in the dissolved organic matter (DOM) pool. Dissolved BC was mainly composed of aliphatics and aromatics substituted by aromatic C-O and carboxyl/ester/quinone moieties as determined by solid-state nuclear magnetic resonance. It underwent 56% loss of absorbance at 254 nm, almost complete loss of fluorescence, and 30% mineralization during a 169 h simulated sunlight exposure. Photoreactions preferentially targeted aromatic and methyl moieties, generating CH2/CH/C and carboxyl/ester/quinone functional groups. During irradiation, dissolved BC generated reactive oxygen species (ROS) including singlet oxygen and superoxide. The apparent quantum yield of singlet oxygen was 4.07 ± 0.19%, 2-3 fold higher than many well-studied DOM. Carbonyl-containing structures other than aromatic ketones were involved in the singlet oxygen sensitization. The generation of superoxide apparently depended on electron transfer reactions mediated by silica minerals in dissolved BC, in which phenolic structures served as electron donors. Self-generated ROS played an important role in the phototransformation. Photobleaching of dissolved BC decreased its ability to further generate ROS due to lower light absorption. These findings have significant implications on the environmental fate of dissolved BC and that of priority pollutants. PMID:26717492

  6. Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes. The Role of Oxygen

    PubMed Central

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P.; Smirnov, Sergei

    2015-01-01

    Recently it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photo-excitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,5,3′,5′-tetramethyl-benzidine (TMB), as well as, analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes’ activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC towards oxidation of TMB is very high and shows direct two-electrons oxidation when the surface of PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent but only with appropriate drug delivery system. PMID:25886644

  7. Screening of antibacterial activities of twenty-one oxygenated monoterpenes.

    PubMed

    Kotan, Recep; Kordali, Saban; Cakir, Ahmet

    2007-01-01

    Plant essential oils are widely used as fragrances and flavours in the cosmetic, perfume, drug and food industries. Oxygenated monoterpenes are widespread components of the essential oils, usually occurring in high amount. In this paper, the antibacterial activities of twenty-one oxygenated monoterpenes (borneol, borneol acetate, camphor, carvone, 1,8-cineole, citronellal, beta-citronellol, dihydrocarvone, fenchol, fenchone, geraniol acetate, isomenthol, limonene oxide, linalool, linalool acetate, nerol, nerol acetate, terpinen-4-ol, alpha-terpineol, menthol and menthone) and penicillin (standard antibiotic) were determined using a disc diffusion method (in vitro) against 63 bacterial strains, belonging to 37 different genera and 54 species (plant, food and clinic origins). The results showed that the oxygenated monoterpenes exhibited a variable degree of antibacterial activities. These compounds also inhibited the growth of bacterial strains by producing a weak zone of inhibition from 7 to 11 mm in diameter, depending on the susceptibility of the tested bacteria. Among the tested compounds, nerol, linalool alpha-terpineol, fenchol and terpinen-4-ol showed antibacterial activity at a broad spectrum. However, their antibacterial activities were lower than those of penicillin. In contrast to these compounds, camphor and 1,8-cineole exhibited no inhibition effects on the growth of all tested bacteria.

  8. Singlet-Oxygen Generation From Individual Semiconducting and Metallic Nanostructures During Near-Infrared Laser Trapping

    SciTech Connect

    Smith, Bennett E.; Roder, Paden B.; Hanson, Jennifer L.; Manandhar, Sandeep; Devaraj, Arun; Perea, Daniel E.; Kim, Woo-Joong; Kilcoyne, Arthur L.; Pauzauskie, Peter J.

    2015-03-13

    Photodynamic therapy has been used for several decades in the treatment of solid tumors through the generation of reactive singlet-oxygen species (1O2). Recently, nanoscale metallic and semiconducting materials have been reported to act as photosensitizing agents with additional diagnostic and therapeutic functionality. To date there have been no reports of observing the generation of singlet-oxygen at the level of single nanostructures, particularly at near infrared (NIR) wavelengths. Here we demonstrate that NIR laser-tweezers can be used to observe the formation of singlet-oxygen produced from individual silicon and gold nanowires via use of a commercially available reporting dye. The laser trap also induces 2-photon photoexcitation of the dye following a chemical reaction with singlet oxygen. Corresponding 2-photon emission spectra confirms the generation of singlet oxygen from individual silicon nanowires at room temperature (30°C), suggesting a range of applications in understanding the impact of 1O2 on individual cancer cells.

  9. Protoporphyrin IX nanoparticle carrier: preparation, optical properties, and singlet oxygen generation.

    PubMed

    Rossi, Liane M; Silva, Paulo R; Vono, Lucas L R; Fernandes, Adjaci U; Tada, Dayane B; Baptista, Maurício S

    2008-11-01

    The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 micros, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (eta Delta) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization. PMID:18834155

  10. The influence of excitation radiation parameters on photosensitized generation of singlet oxygen in water

    NASA Astrophysics Data System (ADS)

    Il'ina, A. D.; Glazov, A. L.; Semenova, I. V.; Vasyutinskii, O. S.

    2016-06-01

    Photosensitized generation of singlet oxygen with the aid of Radahlorin® photosensitizer has been investigated. The dependences of the intensity of singlet oxygen phosphorescence and photosensitizer fluorescence on the excitation radiation wavelength in the range of 350-440 nm and on the irradiation dose have been obtained. The dependence of the ratio of the sensitizer fluorescence intensity at about 670 nm to the singlet oxygen phosphorescence intensity at a wavelength of 1270 nm on the excitation radiation wavelength is found to be nonmonotonic and have a minimum near the center of the absorption band on its red wing. The results obtained can be used to monitor the singlet oxygen concentration in solutions.

  11. Visualisation of nitric oxide generated by activated murine macrophages.

    PubMed

    Leone, A M; Furst, V W; Foxwell, N A; Cellek, S; Moncada, S

    1996-04-01

    We have visualised the release and approximate diffusion profile of nitric oxide (NO) from activated murine macrophages using a high transmission microscope coupled to a high sensitivity photon counting camera. The images generated by NO were cell-associated and spread over an area of approximately 175 micrometers from the activated macrophage. The signals obtained were dependent on the presence of exogenous L-arginine in the medium and followed a time course similar to that previously described for the generation of NO by the inducible form of NO synthase. The light signal was attenuated by the inhibitor of NO synthase, N omega-nitro-L-arginine methyl ester. Studies using superoxide-deficient macrophages further confirmed that the signals detected were generated by NO rather than reactive oxygen intermediates. PMID:8660339

  12. Removal of Biologically Active Organic Contaminants using Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Banks, Michael A. (Inventor); Banks, Eric B. (Inventor)

    2003-01-01

    Biomedical devices that are to come into contact with living tissue, such as prosthetic and other implants for the human body and the containers used to store and transport them, are together cleaned of non-living, but biologically active organic materials, including endotoxins such as lipopolysaccharides, and assembled into a hermetically sealed package without recontamination. This is achieved by cleaning both the device and package components together in an apparatus, which includes a hermetically sealed chamber, in which they are contacted with atomic oxygen which biocleans them, by oxidizing the biologically active organic materials. The apparatus also includes means for manipulating the device and container and hermetically sealing the cleaned device into the cleaned container to form the package. A calibrated witness coupon visually indicates whether or not the device and container have received enough exposure to the atomic oxygen to have removed the organic materials from their surfaces. Gamma radiation is then used to sterilize the device in the sealed container.

  13. Conversion of Mixed Oxygenates Generated from Synthesis Gas to Fuel Range Hydrocarbon

    SciTech Connect

    Ramasamy, Karthikeyan K.; Gerber, Mark A.; Lilga, Michael A.; Flake, Matthew D.

    2012-08-19

    The growing dependence in the U.S. on foreign crude oil supplies and increased concerns regarding greenhouse gas emission has generated considerable interest in research to develop renewable and environmentally friendly liquid hydrocarbon transportation fuels. One of the strategies for achieving this is to produce intermediate compounds such as alcohols and other simple oxygenates from biomass generated synthesis gas (mixture of carbon monoxide and hydrogen) and further convert them into liquid hydrocarbons. The focus of this research is to investigate the effects of mixed oxygenates intermediate product compositions on the conversion step to produce hydrocarbon liquids. A typical mixed oxygenate stream is expected to contain water (around 50%), alcohols, such as methanol and ethanol (around 35%), and smaller quantities of oxygenates such as acetaldehyde, acetic acid and ethyl acetate. However the ratio and the composition of the mixed oxygenate stream generated from synthesis gas vary significantly depending on the catalyst used and the process conditions. Zeolite catalyzed deoxygenation of methanol accompanied by chain growth is well understood under Methanol-to-Gasoline (MTG) like reaction conditions using an H-ZSM-5 zeolite as the catalyst6-8. Research has also been conducted to a limited extent in the past with higher alcohols, but not with other oxygenates present9-11. Also there has been little experimental investigation into mixtures containing substantial amounts of water. The latter is of particular interest because water separation from the hydrocarbon product would be less energy intensive than first removing it from the oxygenate intermediate stream prior to hydrocarbon synthesis, potentially reducing overall processing costs.

  14. Field test of two high-pressure direct-contact downhole steam generators. Volume II. Oxygen/diesel system

    SciTech Connect

    Moreno, J.B.

    1983-07-01

    A field test of an oxygen/diesel fuel, direct contact steam generator has been completed. The field test, which was a part of Project DEEP STEAM and was sponsored by the US Department of Energy, involved the thermal stimulation of a well pattern in the Tar Zone of the Wilmington Oil Field. The activity was carried out in cooperation with the City of Long Beach and the Long Beach Oil Development Company. The steam generator was operated at ground level, with the steam and combustion products delivered to the reservoir through 2022 feet of calcium-silicate insulated tubing. The objectives of the test included demonstrations of safety, operational ease, reliability and lifetime; investigations of reservoir response, environmental impact, and economics; and comparison of those points with a second generator that used air rather than oxygen. The test was extensively instrumented to provide the required data. Excluding interruptions not attributable to the oxygen/diesel system, steam was injected 78% of the time. System lifetime was limited by the combustor, which required some parts replacement every 2 to 3 weeks. For the conditions of this particular test, the use of trucked-in LOX resulted in liess expense than did the production of the equivalent amount of high pressure air using on site compressors. No statistically significant production change in the eight-acre oxygen system well pattern occurred during the test, nor were any adverse effects on the reservoir character detected. Gas analyses during the field test showed very low levels of SOX (less than or equal to 1 ppM) in the generator gaseous effluent. The SOX and NOX data did not permit any conclusion to be drawn regarding reservoir scrubbing. Appreciable levels of CO (less than or equal to 5%) were measured at the generator, and in this case produced-gas analyses showed evidence of significant gas scrubbing. 64 figures, 10 tables.

  15. Onboard Inert Gas Generation System/Onboard Oxygen Gas Generation System (OBIGGS/OBOGS) Study. Part 1; Aircraft System Requirements

    NASA Technical Reports Server (NTRS)

    Reynolds, Thomas L.; Bailey, Delbert B.; Lewinski, Daniel F.; Roseburg, Conrad M.; Palaszewski, Bryan (Technical Monitor)

    2001-01-01

    The purpose of this technology assessment is to define a multiphase research study program investigating Onboard Inert Gas Generation Systems (OBIGGS) and Onboard Oxygen Generation Systems (OBOGS) that would identify current airplane systems design and certification requirements (Subtask 1); explore state-of-the-art technology (Subtask 2); develop systems specifications (Subtask 3); and develop an initial system design (Subtask 4). If feasible, consideration may be given to the development of a prototype laboratory test system that could potentially be used in commercial transport aircraft (Subtask 5). These systems should be capable of providing inert nitrogen gas for improved fire cargo compartment fire suppression and fuel tank inerting and emergency oxygen for crew and passenger use. Subtask I of this research study, presented herein, defines current production aircraft certification requirements and design objectives necessary to meet mandatory FAA certification requirements and Boeing design and performance specifications. These requirements will be utilized for baseline comparisons for subsequent OBIGGS/OBOGS application evaluations and assessments.

  16. Study of the photochemically generated of oxygen species by fullerene photosensitized CoS{sub 2} nanocompounds

    SciTech Connect

    Meng, Ze-Da; Zhu, Lei; Ullah, Kefayat; Ye, Shu; Sun, Qian; Jang, Won Kweon; Oh, Won-Chun

    2014-01-01

    Graphical abstract: - Highlights: • Reactive oxygen species was detected through oxidation reaction from DPCI to DPCO. • Generated reactive oxygen species and hydroxyl radicals can be analysis by DPCI degradation. • C{sub 60} has good effect during the photo-degradation processes. • Photocatalytic activity attributed to photo-absorption effect by C{sub 60} and cooperative effect of CoS{sub 2}. - Abstract: Reactive oxygen species (ROS) can be produced by interactions between sunlight and light-absorbing substance in natural water environment and can completely destroy various organic pollutants in wastewaters. In this study, CoS{sub 2} and CoS{sub 2}–fullerene were irradiated by visible light respectively. The generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). In comparison with the separate effects of CoS{sub 2} and fullerene nanoparticles, the photochemically effect of the fullerene photosensitized CoS{sub 2} composites is increased significantly due to the synergetic effect between the fullerene and the CoS{sub 2} nanoparticles.

  17. Procyanidins from Nelumbo nucifera Gaertn. Seedpod induce autophagy mediated by reactive oxygen species generation in human hepatoma G2 cells.

    PubMed

    Duan, Yuqing; Xu, Hui; Luo, Xiaoping; Zhang, Haihui; He, Yuanqing; Sun, Guibo; Sun, Xiaobo

    2016-04-01

    In this study, autophagic effect of procyanidins from lotus (Nelumbo nucifera Gaertn.) seedpod (LSPCs) on human hepatoma G2 (HepG2) cells, and the inherent correlation between autophagic levels and reactive oxygen species (ROS) generation were investigated. The results showed that LSPCs increased monodansylcadaverine (MDC) fluorescence intensity and LC3-I/LC3-II conversion in HepG2 cells. In addition, the typically autophagic characteristics (autophagosomes and autolysosomes) were observed in LSPCs-treated cells, but not found in the cells treated with autophagy inhibitor 3-methyladenine (3-MA). Furthermore, the elevated ROS level was in line with the increasing of autophagy activation caused by LSPCs, however, both 3-MA and the ROS scavenger N-acetylcyteine (NAC) inhibitors effectively suppressed the autophagy and ROS generation triggered by LSPCs. As a result, these results indicated that LSPCs induced HepG2 cell autophagy in a time- and dose-dependent manner, and promoted reactive oxygen species (ROS) generation on HepG2 cells. Moreover, we found that LSPCs caused DNA damage, S phase arrest and the decrement of mitochondria membrane potential (MMP) which were associated with ROS generation. In summary, our findings demonstrated that the LSPCs-induced autophagy and autophagic cell death were triggered by the ROS generation in HepG2 cells, which might be associated with ROS generation through the mitochondria-dependent signaling way. PMID:27044822

  18. Singlet Oxygen Generation on Porous Superhydrophobic Surfaces: Effect of Gas Flow and Sensitizer Wetting on Trapping Efficiency

    PubMed Central

    2015-01-01

    We describe physical-organic studies of singlet oxygen generation and transport into an aqueous solution supported on superhydrophobic surfaces on which silicon–phthalocyanine (Pc) particles are immobilized. Singlet oxygen (1O2) was trapped by a water-soluble anthracene compound and monitored in situ using a UV–vis spectrometer. When oxygen flows through the porous superhydrophobic surface, singlet oxygen generated in the plastron (i.e., the gas layer beneath the liquid) is transported into the solution within gas bubbles, thereby increasing the liquid–gas surface area over which singlet oxygen can be trapped. Higher photooxidation rates were achieved in flowing oxygen, as compared to when the gas in the plastron was static. Superhydrophobic surfaces were also synthesized so that the Pc particles were located in contact with, or isolated from, the aqueous solution to evaluate the relative effectiveness of singlet oxygen generated in solution and the gas phase, respectively; singlet oxygen generated on particles wetted by the solution was trapped more efficiently than singlet oxygen generated in the plastron, even in the presence of flowing oxygen gas. A mechanism is proposed that explains how Pc particle wetting, plastron gas composition and flow rate as well as gas saturation of the aqueous solution affect singlet oxygen trapping efficiency. These stable superhydrophobic surfaces, which can physically isolate the photosensitizer particles from the solution may be of practical importance for delivering singlet oxygen for water purification and medical devices. PMID:24885074

  19. Graphene oxide functionalized with methylene blue and its performance in singlet oxygen generation

    SciTech Connect

    Wojtoniszak, M.; Rogińska, D.; Machaliński, B.; Drozdzik, M.; Mijowska, E.

    2013-07-15

    Graphical abstract: - Highlights: • Adsorption of methylene blue (MB) on graphene oxide (GO). • Characterization of graphene oxide–methylene blue nanocomposite (MB–GO). • Examination of MB–GO efficiency in singlet oxygen generation (SOG). • MB–GO performs higher SOG efficiency than pristine MB. - Abstract: Due to unique electronic, mechanical, optical and structural properties, graphene has shown promising applications in many fields, including biomedicine. One of them is noninvasive anticancer therapy – photodynamic therapy (PDT), where singlet oxygen (SO), generated under the irradiation of light with appropriate wavelengths, kills cancer cells. In this study, authors report graphene oxide (GO) noncovalent functionalization with methylene blue (MB). MB molecules underwent adsorption on the surface of GO. Detailed characterization of the obtained material was carried out with UV–vis spectroscopy, Raman spectroscopy, FT-IR spectroscopy, and confocal laser scanning microscopy. Furthermore, its performance in singlet oxygen generation (SOG) under irradiation of laser with excitation wavelengths of 785 nm was investigated. Interestingly, GO functionalized with MB (MB–GO) showed enhanced efficiency in singlet oxygen generation compared to pristine MB. The efficiency in SOG was detected by photobleaching of 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABMDMA). These results indicate the material is promising in PDT anticancer therapy and further in vitro and in vivo studies are required.

  20. ARSENIC SPECIES CAUSE RELEASE OF IRON FROM FERRITIN GENERATING REACTIVIE OXYGEN SPECIES

    EPA Science Inventory

    ARSENIC SPECIES. CAUSE RELEASE OF IRON , FROM FERRITIN GENERATING REACTIVE OXYGEN SPECIES

    Arsenic-associated cancer (lung, bladder, skin, liver, kidney) remains a significant world- wide public health problem (e.g., Taiwan, Chile, Bangladesh, India, China and Thailand). R...

  1. ARSENIC SPECIES CAUSE RELEASE OF IRON FROM FERRITIN GENERATING REACTIVE OXYGEN SPECIES

    EPA Science Inventory

    ARSENIC SPECIES CAUSE RELEASE OF IRON FROM FERRITIN GENERATING REACTIVE OXYGEN SPECIES

    Arsenic-associated cancer (lung, bladder, skin, liver, kidney) remains a significant world- wide public health problem (e.g., Taiwan, Chile, Bangladesh, India, China and Thailand). Rece...

  2. In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity.

    PubMed

    Trześniewski, Bartek J; Diaz-Morales, Oscar; Vermaas, David A; Longo, Alessandro; Bras, Wim; Koper, Marc T M; Smith, Wilson A

    2015-12-01

    Ni-based oxygen evolution catalysts (OECs) are cost-effective and very active materials that can be potentially used for efficient solar-to-fuel conversion process toward sustainable energy generation. We present a systematic spectroelectrochemical characterization of two Fe-containing Ni-based OECs, namely nickel borate (Ni(Fe)-B(i)) and nickel oxyhydroxide (Ni(Fe)OOH). Our Raman and X-ray absorption spectroscopy results show that both OECs are chemically similar, and that the borate anions do not play an apparent role in the catalytic process at pH 13. Furthermore, we show spectroscopic evidence for the generation of negatively charged sites in both OECs (NiOO(-)), which can be described as adsorbed "active oxygen". Our data conclusively links the OER activity of the Ni-based OECs with the generation of those sites on the surface of the OECs. The OER activity of both OECs is strongly pH dependent, which can be attributed to a deprotonation process of the Ni-based OECs, leading to the formation of the negatively charged surface sites that act as OER precursors. This work emphasizes the relevance of the electrolyte effect to obtain catalytically active phases in Ni-based OECs, in addition to the key role of the Fe impurities. This effect should be carefully considered in the development of Ni-based compounds meant to catalyze the OER at moderate pHs. Complementarily, UV-vis spectroscopy measurements show strong darkening of those catalysts in the catalytically active state. This coloration effect is directly related to the oxidation of nickel and can be an important factor limiting the efficiency of solar-driven devices utilizing Ni-based OECs.

  3. Utilization of a BGO detector as an active oxygen target

    NASA Astrophysics Data System (ADS)

    Loveman, R.; Gozani, T.; Bendahan, J.; Krivicich, J.; Elias, E.; Altschuler, E.

    1994-12-01

    The (n, n'γx) cross section for the 6.13 MeV state in oxygen has recently become of general interest because of the possibility of using this process to assay oxygen as a part of non-intrusive inspections. Localized densities of carbon, oxygen, and nitrogen are particularly useful in determining the presence of explosives and/or drugs in containers of all sizes, from suitcases to cargo containers. The presence of oxygen in BGO (Bi 4Ge 3O 12) scintillator makes this detector suitable for use as an active target for the measurement of the energy dependence of the excitation, of the first (6.049 MeV O +) and second (6.130 MeV 3 -) excited states in 16O by fast neutron interactions. An active target functions as both a target and an active device such as a detector. The de-excitations of the 6.049 and 6.130 states take place by nuclear pair production and γ-ray emission respectively. There is a large probability of absorbing all of the de-excitation energy in the scintillator in either of these cases. Since the energies deposited in the scintillator by these transitions are very close, the de-excitations are indistinguishable. However, since the cross section for the excitation of the 6.13 MeV state is believed to be larger than that of the 6.049 MeV, the major measured features of the energy variations are those related to the second state. The validity of the technique was initially tested using (MCNP) calculations. The calculations established that the detected neutron count rate in the crystal was proportional to the cross-sections used as input for the calculations, and that the constant of proportionality did not vary with neutron energy. Subsequently, measurements were made with a BGO detector as an active oxygen target. The results clearly show a strong energy dependence including several resonances.

  4. Estimates of Optimal Operating Conditions for Hydrogen-Oxygen Cesium-Seeded Magnetohydrodynamic Power Generator

    NASA Technical Reports Server (NTRS)

    Smith, J. M.; Nichols, L. D.

    1977-01-01

    The value of percent seed, oxygen to fuel ratio, combustion pressure, Mach number, and magnetic field strength which maximize either the electrical conductivity or power density at the entrance of an MHD power generator was obtained. The working fluid is the combustion product of H2 and O2 seeded with CsOH. The ideal theoretical segmented Faraday generator along with an empirical form found from correlating the data of many experimenters working with generators of different sizes, electrode configurations, and working fluids, are investigated. The conductivity and power densities optimize at a seed fraction of 3.5 mole percent and an oxygen to hydrogen weight ratio of 7.5. The optimum values of combustion pressure and Mach number depend on the operating magnetic field strength.

  5. Development of a novel electrochemical system for oxygen control (ESOC) to examine dissolved oxygen inhibition on algal activity.

    PubMed

    Keymer, Philip C; Pratt, Steven; Lant, Paul A

    2013-09-01

    The development of an Electrochemical System for Oxygen Control (ESOC) for examining algal photosynthetic activity as a function of dissolved oxygen (DO) is outlined. The main innovation of the tool is coulombic titration in order to balance the electrochemical reduction of oxygen with the oxygen input to achieve a steady DO set-point. ESOC allows quantification of algal oxygen production whilst simultaneously maintaining a desired DO concentration. The tool was validated abiotically by comparison with a mass transfer approach for quantifying oxygenation. It was then applied to quantify oxygen inhibition of algal activity. Five experiments, using an enriched culture of Scenedesmus sp. as the inoculum, are presented. For each experiment, ESOC was used to quantify algal activity at a series of DO set-points. In all experiments substantial oxygen inhibition was observed at DO >30 mgO2 L-1. Inhibition was shown to fit a Hill inhibition model, with a common Hill coefficient of 0.22±0.07 L mg-1 and common log10  CI50 of 27.2±0.7 mg L-1. This is the first time that the oxygen inhibition kinetic parameters have been quantified under controlled DO conditions.

  6. Evaluation of UV-radiation induced singlet oxygen generation potential of selected drugs.

    PubMed

    Pandey, R; Mehrotra, S; Ray, R S; Joshi, P C; Hans, R K

    2002-05-01

    Photosensitization reaction of drugs leading to the formation of reactive oxygen species under ultraviolet radiation (UVR) can cause tissue injury, resulting in damage to various cellular macromolecules. The aim of this study was to determine the singlet oxygen generation potential of some commonly used antibiotics so that due precautions can be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce singlet oxygen (1O2) under artificial UVA (320-400 nm). Singlet oxygen generation of various screened antibiotics under UVA is of the following order: Nalidixic acid > Amphotericin-B > Cephradine > Cefazolin > Nafcillin > Cephalothin > Ampicillin > Cephalexin > Puromycin > Kanamycin > Lincomycin > Tetracycline > Nystatin > Gentamicin sulphate. Nalidixic acid, the most potent generator of 1O2 among the screened antibiotics, was selected to carry out further studies. Certain specific quenchers of 1O2 such as beta-carotene, 1,4-diazabicyclo[2.2.2] octane (DABCO), and sodium azide (NaN3) accorded significant inhibition in the production of 1O2. The results suggest that precautions are necessary to avoid ultraviolet radiation after the intake of photoreactive drugs, especially in tropical countries such as India. These findings are significant because UVB radiation is reportedly increasing on earth surface in part due to depletion of stratospheric ozone layer. The selected drugs are commonly used for the treatment of various diseases. Thus, the synergistic action of both can lead to undesirable phototoxic responses.

  7. Student Activities Can Generate Positive PR.

    ERIC Educational Resources Information Center

    Armistead, Lew

    1985-01-01

    To counter negative news about education it is important to make sure that positive school activities receive their fair share of exposure in the news media. Presents tips on how to generate positive public relations. Includes a list of newsworthy activities ideas. (MD)

  8. Cryptococcus neoformans capsule protects cell from oxygen reactive species generated by antimicrobial photodynamic inactivation

    NASA Astrophysics Data System (ADS)

    Prates, Renato Araujo; Hamblin, Michael R.; Kato, Ilka T.; Fuchs, Beth; Mylonakis, Eleytherios; Simões Ribeiro, Martha; Tegos, George

    2011-03-01

    Antimicrobial photodynamic inactivation (APDI) is based on the utilization of substances that can photosensitize biological tissues and are capable of being activated in the presence of light. Cryptococcus neoformans is an yeast surrounded by a capsule composed primarily of glucoronoxylomannan that plays an important role in its virulence. This yeast causes infection on skin, lungs and brain that can be associated with neurological sequelae and neurosurgical interventions, and its conventional treatment requires prolonged antifungal therapy, which presents important adverse effects. The aim of this study was to evaluate the protective effect of Cryptococcus neoformans capsule against reactive oxygen species generated by APDI. Cryptococcus neoformans KN99α, which is a strain able to produce capsule, and CAP59 that does not present capsule production were submitted to APDI using methylene blue (MB), rose bengal (RB), and pL-ce6 as photosensitizers (PS). Then microbial inactivation was evaluated by counting colony form units following APDI and confocal laser scanning microscopy (CLSM) illustrated localization as well as the preferential accumulation of PS into the fungal cells. C. neoformans KN99α was more resistant to APDI than CAP59 for all PSs tested. CLSM showed incorporation of MB and RB into the cytoplasm and a preferential uptake in mitochondria. A nuclear accumulation of MB was also observed. Contrarily, pL-ce6 appears accumulated in cell wall and cell membrane and minimal florescence was observed inside the fungal cells. In conclusion, the ability of C. neoformans to form capsule enhances survival following APDI.

  9. Silver nanoparticle-algae interactions: oxidative dissolution, reactive oxygen species generation and synergistic toxic effects.

    PubMed

    He, Di; Dorantes-Aranda, Juan José; Waite, T David

    2012-08-21

    The short-term toxicity of citrate-stabilized silver nanoparticles (AgNPs) and ionic silver Ag(I) to the ichthyotoxic marine raphidophyte Chattonella marina has been examined using the fluorometric indicator alamarBlue. Aggregation and dissolution of AgNPs occurred after addition to GSe medium while uptake of dissolved Ag(I) occurred in the presence of C. marina. Based on total silver mass, toxicity was much higher for Ag(I) than for AgNPs. Cysteine, a strong Ag(I) ligand, completely removed the inhibitory effects of Ag(I) and AgNPs on the metabolic activity of C. marina, suggesting that the toxicity of AgNPs was due to the release of Ag(I). Synergistic toxic effects of AgNPs/Ag(I) and C. marina to fish gill cells were observed with these effects possibly attributable to enhancement in the generation of reactive oxygen species by C. marina on exposure of the organism to silver.

  10. Design and test status for life support applications of SPE oxygen generation systems. [Solid Polymer Electrolyte

    NASA Technical Reports Server (NTRS)

    Titterington, W. A.; Erickson, A. C.

    1975-01-01

    An advanced six-man rated oxygen generation system has been fabricated and tested as part of a NASA/JSC technology development program for a long lived, manned spacecraft life support system. Details of the design and tests results are presented. The system is based on the Solid Polymer Electrolyte (SPE) water electrolysis technology and its nominal operating conditions are 2760 kN/sq m (400 psia) and 355 K (180 F) with an electrolysis module current density capability up to 350 mA/sq cm (326 ASF). The system is centered on a 13-cell SPE water electrolysis module having a single cell active area of 214 sq cm (33 sq in) and it incorporates instrumentation and controls for single pushbutton automatic startup/shutdown, component fault detection and isolation, and self-contained sensors and controls for automatic safe emergency shutdown. The system has been tested in both the orbital cyclic and continuous mode of operation. Various parametric tests have been completed to define the system capability for potential application in spacecraft environmental systems.

  11. Dynamics of a pulsed laser generated tin plasma expanding in an oxygen atmosphere

    NASA Astrophysics Data System (ADS)

    Barreca, F.; Fazio, E.; Neri, F.; Barletta, E.; Trusso, S.; Fazio, B.

    2005-10-01

    Semiconducting tin oxide can be successfully deposited by means of the laser ablation technique. In particular by ablating metallic tin in a controlled oxygen atmosphere, thin films of SnOx have been deposited. The partial oxygen pressure at which the films are deposited strongly influences both the stoichiometry and the structural properties of the films. In this work, we present a study of the expansion dynamics of the plasma generated by ablating a tin target by means of a pulsed laser using time and space resolved optical emission spectroscopy and fast photography imaging of the expanding plasma. Both Sn I and Sn II optical emission lines have been observed from the time-integrated spectroscopy. Time resolved-measurements revealed the dynamics of the expanding plasma in the ambient oxygen atmosphere. Stoichiometry of the films has been determined by means of X-ray photoelectron spectroscopy and correlated to the expansion dynamics of the plasma.

  12. Oxygen suppresses light-driven anodic current generation by a mixed phototrophic culture.

    PubMed

    Darus, Libertus; Ledezma, Pablo; Keller, Jürg; Freguia, Stefano

    2014-12-01

    This paper describes the detrimental effect of photosynthetically evolved oxygen on anodic current generation in the presence of riboflavin upon illumination of a mixed phototrophic culture enriched from a freshwater pond at +0.6 V vs standard hydrogen electrode. In the presence of riboflavin, the phototrophic biomass in the anodic compartment produced an electrical current in response to light/dark cycles (12 h/12 h) over 12 months of operation, generating a maximum current density of 17.5 mA x m(-2) during the dark phase, whereas a much lower current of approximately 2 mA x m(-2) was generated during illumination. We found that the low current generation under light exposure was caused by high rates of reoxidation of reduced riboflavin by oxygen produced during photosynthesis. Quantification of biomass by fluorescence in situ hybridization images suggested that green algae were predominant in both the anode-based biofilm (55.1%) and the anolyte suspension (87.9%) with the remaining biovolume accounted for by bacteria. Genus-level sequencing analysis revealed that bacteria were dominated by cyanobacterium Leptolyngbia (∼35%), while the prevailing algae were Dictyosphaerium, Coelastrum, and Auxenochlorella. This study offers a key comprehension of mediator sensitivity to reoxidation by dissolved oxygen for improvement of microbial solar cell performance.

  13. Pathophysiological and pharmacological implications of mitochondria-targeted reactive oxygen species generation in astrocytes.

    PubMed

    Jou, Mei-Jie

    2008-01-01

    Astrocytes, in addition to passively supporting neurons, have recently been shown to be actively involved in synaptic transmission and neurovascular coupling in the central nervous system (CNS). This review summarizes briefly our previous observations using fluorescent probes coupled with laser scanning digital imaging microscopy to visualize spatio-temporal alteration of mitochondrial reactive oxygen species (mROS) generation in intact astrocytes. mROS formation is enhanced by exogenous oxidants exposure, Ca2+ stress and endogenous pathological defect of mitochondrial respiratory complexes. In addition, mROS formation can be specifically stimulated by visible light or visible laser irradiation and can be augmented further by photodynamic coupling with photosensitizers, particularly with mitochondria-targeted photosensitizers. "Severe" oxidative insult often results in massive and homogeneous augmentation of mROS formation which causes cessation of mitochondrial movement, pathological fission and irreversible swelling of mitochondria and eventually apoptosis or necrosis of cells. Mitochondria-targeted antioxidants and protectors such as MitoQ, melatonin and nanoparticle C(60) effectively prevent "severe" mROS generation. Intriguingly, "minor" oxidative insults enhance heterogeneity of mROS and mitochondrial dynamics. "Minor" mROS formation-induced fission and fusion of mitochondria relocates mitochondrial network to form a mitochondria free gap, i.e., "firewall", which may play a crucial role in mROS-mediated protective "preconditioning" by preventing propagation of mROS during oxidative insults. These mROS-targeted strategies for either enhancement or prevention of mitochondrial oxidative stress in astrocytes may provide new insights for future development of therapeutic interventions in the treatment of cancer such as astrocytomas and gliomas and astrocyte-associated neurodegeneration, mitochondrial diseases and aging. PMID:18692534

  14. New Active Optical Technique Developed for Measuring Low-Earth-Orbit Atomic Oxygen Erosion of Polymers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Demko, Rikako

    2003-01-01

    uniformly thick sheet of semitransparent polymer such as Kapton H polyimide, then as atomic oxygen erodes the polymer, the short-circuit current from the photodiode will increase in an exponential manner with fluence. This nonlinear response with fluence results in a lack of sensitivity for measuring low atomic oxygen fluences. However, if one uses a variable-thickness polymer or carbon sample, which is configured as shown in the preceding figure, then a linear response can be achieved for opaque materials using a parabolic well for a circular geometry detector or a V-shaped well for a rectangular-geometry detector. Variable-thickness samples can be fabricated using many thin polymer layers. For semitransparent polymers such as Kapton H polyimide, there is an initial short-circuit current that is greater than zero. This current has a slightly nonlinear dependence on atomic oxygen fluence in comparison to opaque materials such as black Kapton as shown in the graph. For this graph figure, the total thickness of Kapton H was assumed to be 0.03 cm. The photodiode short-circuit current shown in the graph was generated on the basis of preliminary measurements-a total reflectance rho of 0.0424 and an optical absorption coefficient a of 146.5 cm(sup -1). In addition to obtaining on-orbit data, the advantage of this active erosion and erosion yield measurement technique is its simplicity and reliance upon well-characterized fluence witness materials as well as a nearly linear photodiode short-circuit current dependence upon atomic oxygen fluence. The optical technique is useful for measuring either atomic oxygen fluence or erosion, depending on the information desired. To measure the atomic oxygen erosion yield of a test material, one would need to have two photodiode sensors, one for the test material and one that uses a known erosion yield material (such as Kapton) to measure the atomic oxygen fluence.

  15. Device for measuring oxygen activity in liquid sodium

    DOEpatents

    Roy, P.; Young, R.S.

    1973-12-01

    A composite ceramic electrolyte in a configuration (such as a closed end tube or a plate) suitable to separate liquid sodium from a reference electrode with a high impedance voltmeter connected to measure EMF between the sodium and the reference electrode as a measure of oxygen activity in the sodium is described. The composite electrolyte consists of zirconiacalcia with a bonded layer of thoria-yttria. The device is used with a gaseous reference electrode on the zirconia-calcia side and liquid sodium on the thoria-yttria side of the electrolyte. (Official Gazette)

  16. Status of the Node 3 Regenerative ECLSS Water Recovery and Oxygen Generation Systems

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Robyn L.; Cloud, Dale; Bedard, Jake

    2004-01-01

    NASA's Marshall Space Flight Center is providing three racks containing regenerative water recovery and oxygen generation systems (WRS and OGS) for flight on the International Space Station's (ISS) Node 3 element. The major assemblies included in these racks are the Water Processor Assembly (WPA), Urine Processor Assembly (UPA), Oxygen Generation Assembly (OGA), and the Power Supply Module (PSM) supporting the OGA. The WPA and OGA are provided by Hamilton Sundstrand Space Systems International (HSSSI), while the UPA and PSM are being designed and manufactured in-house by MSFC. The assemblies are completing the manufacturing phase and are in various stages of ORU and system level testing, to be followed by integration into the flight racks. This paper gives a current status, along with technical challenges encountered and lessons learned.

  17. Status of the International Space Station Regenerative ECLSS Water Recovery and Oxygen Generation Systems

    NASA Technical Reports Server (NTRS)

    Bagdigian, Robert M.; Cloud, Dale

    2005-01-01

    NASA is developing three racks containing regenerative water recovery and oxygen generation systems (WRS and OGS) for deployment on the International Space Station (ISS). The major assemblies included in these racks are the Water Processor Assembly (WPA), Urine Processor Assembly (UPA), Oxygen Generation Assembly (OGA), and the Power Supply Module (PSM) supporting the OGA. The WPA and OGA are provided by Hamilton Sundstrand Space Systems International (HSSSI), Inc., while the UPA and PSM are developed in- house by the Marshall Space Flight Center (MSFC). The assemblies have completed the manufacturing phase and are in various stages of testing and integration into the flight racks. This paper summarizes the status as of April 2005 and describes some of the technical challenges encountered and lessons learned over the past year.

  18. Status of the Node 3 Regenerative Environmental Cpntrol& Life Support System Water Recovery & Oxygen Generation Systems

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Robyn L.

    2003-01-01

    NASA s Marshall Space Flight Center is providing three racks containing regenerative water recovery and oxygen generation systems (WRS and OGS) for flight on the lnternational Space Station s (ISS) Node 3 element. The major assemblies included in these racks are the Water Processor Assembly (WPA), Urine Processor Assembly (UPA), Oxygen Generation Assembly (OGA), and the Power Supply Module (PSM) supporting the OGA. The WPA and OGA are provided by Hamilton Sundstrand Space Systems lnternational (HSSSI), while the UPA and PSM are being designed and manufactured in-house by MSFC. The assemblies are currently in the manufacturing and test phase and are to be completed and integrated into flight racks this year. This paper gives an overview of the technologies and system designs, technical challenges encountered and solved, and the current status.

  19. Hydroquinone-quinone oxidation by molecular oxygen: a simple tool for signal amplification through auto-generation of hydrogen peroxide.

    PubMed

    Sella, Eran; Shabat, Doron

    2013-08-21

    Signal amplification methods are of obvious importance for various diagnostic assays. We have developed a new small-molecule-based probe that, upon activation with sub-stoichiometric amounts of hydrogen peroxide, produces an auto-inductive amplification reaction. The signal is produced through the oxidation reaction of hydroquinone to the corresponding quinone derivative by molecular oxygen. This oxidation is accompanied by the formation of hydrogen peroxide, which can enter the amplification sequence and initiate a new diagnostic cycle. The generated quinone is composed of a donor-acceptor conjugated pair and fluoresces at a distinct wavelength, allowing the formation to be monitored by a convenient fluorescence assay.

  20. Investigation into the High Voltage Shutdown of the Oxygen Generator System in the International Space Station

    NASA Technical Reports Server (NTRS)

    Carpenter, Joyce E.; Gentry, Gregory J.; Diderich, Greg S.; Roy, Robert J.; Golden, John L.; VanKeuren, Steve; Steele, John W.; Rector, Tony J.; Varsik, Jerome D.; Montefusco, Daniel J.; Wilson, Mark E.; Worthy, Erica S.

    2012-01-01

    The Oxygen Generation System (OGS) Hydrogen Dome Assembly Orbital Replacement Unit (ORU) serial number 00001 suffered a cell stack high-voltage shutdown on July 5, 2010. The Hydrogen Dome Assembly ORU was removed and replaced with the on-board spare ORU serial number 00002 to maintain OGS operation. The Hydrogen Dome Assembly ORU was returned from ISS on STS-133/ULF-5 in March 2011 with test, teardown and evaluation (TT&E) and failure analysis to follow.

  1. [Generation of reactive oxygen species in water under exposure of visible or infrared irradiation at absorption band of molecular oxygen].

    PubMed

    Gudkov, S V; Karp, O E; Garmash, S A; Ivanov, V E; Chernikov, A V; Manokhin, A A; Astashev, M E; Iaguzhinskiĭ, L S; Bruskov, V I

    2012-01-01

    It is found that in bidistilled water saturated with oxygen hydrogen peroxide and hydroxyl radicals are formed under the influence of visible and infrared radiation in the absorption bands of molecular oxygen. Formation of reactive oxygen species (ROS) occurs under the influence of both solar and artificial light sourses, including the coherent laser irradiation. The oxygen effect, i.e. the impact of dissolved oxygen concentration on production of hydrogen peroxide induced by light, is detected. It is shown that the visible and infrared radiation in the absorption bands of molecular oxygen leads to the formation of 8-oxoguanine in DNA in vitro. Physicochemical mechanisms of ROS formation in water when exposed to visible and infrared light are studied, and the involvement of singlet oxygen and superoxide anion radicals in this process is shown.

  2. Variation in structure of proteins by adjusting reactive oxygen and nitrogen species generated from dielectric barrier discharge jet

    PubMed Central

    Park, Ji Hoon; Kim, Minsup; Shiratani, Masaharu; Cho, Art. E.; Choi, Eun Ha; Attri, Pankaj

    2016-01-01

    Over the last few years, the variation in liquid chemistry due to the development of radicals generated by cold atmospheric plasma (CAP) has played an important role in plasma medicine. CAP direct treatment or CAP activated media treatment in cancer cells shows promising anticancer activity for both in vivo and in vitro studies. However, the anticancer activity or antimicrobial activity varies between plasma devices due to the different abilities among plasma devices to generate the reactive oxygen and nitrogen species (RONS) at different ratios and in different concentrations. While the generation of RONS depends on many factors, the feeding gas plays the most important role among the factors. Hence, in this study we used different compositions of feeding gas while fixing all other plasma characteristics. We used Ar, Ar-O2 (at different ratios), and Ar-N2 (at different ratios) as the working gases for CAP and investigated the structural changes in proteins (Hemoglobin (Hb) and Myoglobin (Mb)). We then analyzed the influence of RONS generated in liquid on the conformations of proteins. Additionally, to determine the influence of H2O2 on the Hb and Mb structures, we used molecular dynamic simulation. PMID:27779212

  3. Phenomenological model of photoluminescence degradation and photoinduced defect formation in silicon nanocrystal ensembles under singlet oxygen generation

    SciTech Connect

    Gongalsky, Maxim B. Timoshenko, Victor Yu.

    2014-12-28

    We propose a phenomenological model to explain photoluminescence degradation of silicon nanocrystals under singlet oxygen generation in gaseous and liquid systems. The model considers coupled rate equations, which take into account the exciton radiative recombination in silicon nanocrystals, photosensitization of singlet oxygen generation, defect formation on the surface of silicon nanocrystals as well as quenching processes for both excitons and singlet oxygen molecules. The model describes well the experimentally observed power law dependences of the photoluminescence intensity, singlet oxygen concentration, and lifetime versus photoexcitation time. The defect concentration in silicon nanocrystals increases by power law with a fractional exponent, which depends on the singlet oxygen concentration and ambient conditions. The obtained results are discussed in a view of optimization of the photosensitized singlet oxygen generation for biomedical applications.

  4. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-08-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases.

  5. Resveratrol induced inhibition of Escherichia coli proceeds via membrane oxidation and independent of diffusible reactive oxygen species generation.

    PubMed

    Subramanian, Mahesh; Goswami, Manish; Chakraborty, Saikat; Jawali, Narendra

    2014-01-01

    Resveratrol (5-[(E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol), a redox active phytoalexin with a large number of beneficial activities is also known for antibacterial property. However the mechanism of action of resveratrol against bacteria remains unknown. Due to its extensive redox property it was envisaged if reactive oxygen species (ROS) generation by resveratrol could be a reason behind its antibacterial activity. Employing Escherichia coli as a model organism we have evaluated the role of diffusible reactive oxygen species in the events leading to inhibition of this organism by resveratrol. Evidence for the role of ROS in E. coli treated with resveratrol was investigated by direct quantification of ROS by flow cytometry, supplementation with ROS scavengers, depletion of intracellular glutathione, employing mutants devoid of enzymatic antioxidant defences, induction of adaptive response prior to resveratrol challenge and monitoring oxidative stress response elements oxyR, soxS and soxR upon resveratrol treatment. Resveratrol treatment did not result in scavengable ROS generation in E. coli cells. However, evidence towards membrane damage was obtained by potassium leakage (atomic absorption spectrometry) and propidium iodide uptake (flow cytometry and microscopy) as an early event. Based on the comprehensive evidences this study concludes for the first time the antibacterial property of resveratrol against E. coli does not progress via the diffusible ROS but is mediated by site-specific oxidative damage to the cell membrane as the primary event.

  6. Resveratrol induced inhibition of Escherichia coli proceeds via membrane oxidation and independent of diffusible reactive oxygen species generation

    PubMed Central

    Subramanian, Mahesh; Goswami, Manish; Chakraborty, Saikat; Jawali, Narendra

    2014-01-01

    Resveratrol (5-[(E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol), a redox active phytoalexin with a large number of beneficial activities is also known for antibacterial property. However the mechanism of action of resveratrol against bacteria remains unknown. Due to its extensive redox property it was envisaged if reactive oxygen species (ROS) generation by resveratrol could be a reason behind its antibacterial activity. Employing Escherichia coli as a model organism we have evaluated the role of diffusible reactive oxygen species in the events leading to inhibition of this organism by resveratrol. Evidence for the role of ROS in E. coli treated with resveratrol was investigated by direct quantification of ROS by flow cytometry, supplementation with ROS scavengers, depletion of intracellular glutathione, employing mutants devoid of enzymatic antioxidant defences, induction of adaptive response prior to resveratrol challenge and monitoring oxidative stress response elements oxyR, soxS and soxR upon resveratrol treatment. Resveratrol treatment did not result in scavengable ROS generation in E. coli cells. However, evidence towards membrane damage was obtained by potassium leakage (atomic absorption spectrometry) and propidium iodide uptake (flow cytometry and microscopy) as an early event. Based on the comprehensive evidences this study concludes for the first time the antibacterial property of resveratrol against E. coli does not progress via the diffusible ROS but is mediated by site-specific oxidative damage to the cell membrane as the primary event. PMID:25009788

  7. Oxygenation of Organoboronic Acids by a Nonheme Iron(II) Complex: Mimicking Boronic Acid Monooxygenase Activity.

    PubMed

    Chatterjee, Sayanti; Paine, Tapan Kanti

    2015-10-19

    Phenolic compounds are important intermediates in the bacterial biodegradation of aromatic compounds in the soil. An Arthrobacter sp. strain has been shown to exhibit boronic acid monooxygenase activity through the conversion of different substituted phenylboronic acids to the corresponding phenols using dioxygen. While a number of methods have been reported to cleave the C-B bonds of organoboronic acids, there is no report on biomimetic iron complex exhibiting this activity using dioxygen as the oxidant. In that direction, we have investigated the reactivity of a nucleophilic iron-oxygen oxidant, generated upon oxidative decarboxylation of an iron(II)-benzilate complex [(Tp(Ph2))Fe(II)(benzilate)] (Tp(Ph2) = hydrotris(3,5-diphenyl-pyrazol-1-yl)borate), toward organoboronic acids. The oxidant converts different aryl/alkylboronic acids to the corresponding oxygenated products with the incorporation of one oxygen atom from dioxygen. This method represents an efficient protocol for the oxygenation of boronic acids with dioxygen as the terminal oxidant.

  8. Oxygenation of Organoboronic Acids by a Nonheme Iron(II) Complex: Mimicking Boronic Acid Monooxygenase Activity.

    PubMed

    Chatterjee, Sayanti; Paine, Tapan Kanti

    2015-10-19

    Phenolic compounds are important intermediates in the bacterial biodegradation of aromatic compounds in the soil. An Arthrobacter sp. strain has been shown to exhibit boronic acid monooxygenase activity through the conversion of different substituted phenylboronic acids to the corresponding phenols using dioxygen. While a number of methods have been reported to cleave the C-B bonds of organoboronic acids, there is no report on biomimetic iron complex exhibiting this activity using dioxygen as the oxidant. In that direction, we have investigated the reactivity of a nucleophilic iron-oxygen oxidant, generated upon oxidative decarboxylation of an iron(II)-benzilate complex [(Tp(Ph2))Fe(II)(benzilate)] (Tp(Ph2) = hydrotris(3,5-diphenyl-pyrazol-1-yl)borate), toward organoboronic acids. The oxidant converts different aryl/alkylboronic acids to the corresponding oxygenated products with the incorporation of one oxygen atom from dioxygen. This method represents an efficient protocol for the oxygenation of boronic acids with dioxygen as the terminal oxidant. PMID:26430780

  9. Laser controlled singlet oxygen generation in mitochondria to promote mitochondrial DNA replication in vitro.

    PubMed

    Zhou, Xin; Wang, Yupei; Si, Jing; Zhou, Rong; Gan, Lu; Di, Cuixia; Xie, Yi; Zhang, Hong

    2015-11-18

    Reports have shown that a certain level of reactive oxygen species (ROS) can promote mitochondrial DNA (mtDNA) replication. However, it is unclear whether it is the mitochondrial ROS that stimulate mtDNA replication and this requires further investigation. Here we employed a photodynamic system to achieve controlled mitochondrial singlet oxygen ((1)O2) generation. HeLa cells incubated with 5-aminolevulinic acid (ALA) were exposed to laser irradiation to induce (1)O2 generation within mitochondria. Increased mtDNA copy number was detected after low doses of 630 nm laser light in ALA-treated cells. The stimulated mtDNA replication was directly linked to mitochondrial (1)O2 generation, as verified using specific ROS scavengers. The stimulated mtDNA replication was regulated by mitochondrial transcription factor A (TFAM) and mtDNA polymerase γ. MtDNA control region modifications were induced by (1)O2 generation in mitochondria. A marked increase in 8-Oxoguanine (8-oxoG) level was detected in ALA-treated cells after irradiation. HeLa cell growth stimulation and G1-S cell cycle transition were also observed after laser irradiation in ALA-treated cells. These cellular responses could be due to a second wave of ROS generation detected in mitochondria. In summary, we describe a controllable method of inducing mtDNA replication in vitro.

  10. Laser controlled singlet oxygen generation in mitochondria to promote mitochondrial DNA replication in vitro

    PubMed Central

    Zhou, Xin; Wang, Yupei; Si, Jing; Zhou, Rong; Gan, Lu; Di, Cuixia; Xie, Yi; Zhang, Hong

    2015-01-01

    Reports have shown that a certain level of reactive oxygen species (ROS) can promote mitochondrial DNA (mtDNA) replication. However, it is unclear whether it is the mitochondrial ROS that stimulate mtDNA replication and this requires further investigation. Here we employed a photodynamic system to achieve controlled mitochondrial singlet oxygen (1O2) generation. HeLa cells incubated with 5-aminolevulinic acid (ALA) were exposed to laser irradiation to induce 1O2 generation within mitochondria. Increased mtDNA copy number was detected after low doses of 630 nm laser light in ALA-treated cells. The stimulated mtDNA replication was directly linked to mitochondrial 1O2 generation, as verified using specific ROS scavengers. The stimulated mtDNA replication was regulated by mitochondrial transcription factor A (TFAM) and mtDNA polymerase γ. MtDNA control region modifications were induced by 1O2 generation in mitochondria. A marked increase in 8-Oxoguanine (8-oxoG) level was detected in ALA-treated cells after irradiation. HeLa cell growth stimulation and G1-S cell cycle transition were also observed after laser irradiation in ALA-treated cells. These cellular responses could be due to a second wave of ROS generation detected in mitochondria. In summary, we describe a controllable method of inducing mtDNA replication in vitro. PMID:26577055

  11. Developing mononuclear copper-active-oxygen complexes relevant to reactive intermediates of biological oxidation reactions.

    PubMed

    Itoh, Shinobu

    2015-07-21

    Active-oxygen species generated on a copper complex play vital roles in several biological and chemical oxidation reactions. Recent attention has been focused on the reactive intermediates generated at the mononuclear copper active sites of copper monooxygenases such as dopamine β-monooxygenase (DβM), tyramine β-monooxygenase (TβM), peptidylglycine-α-hydroxylating monooxygenase (PHM), and polysaccharide monooxygenases (PMO). In a simple model system, reaction of O2 and a reduced copper(I) complex affords a mononuclear copper(II)-superoxide complex or a copper(III)-peroxide complex, and subsequent H(•) or e(-)/H(+) transfer, which gives a copper(II)-hydroperoxide complex. A more reactive species such as a copper(II)-oxyl radical type species could be generated via O-O bond cleavage of the peroxide complex. However, little had been explored about the chemical properties and reactivity of the mononuclear copper-active-oxygen complexes due to the lack of appropriate model compounds. Thus, a great deal of effort has recently been made to develop efficient ligands that can stabilize such reactive active-oxygen complexes in synthetic modeling studies. In this Account, I describe our recent achievements of the development of a mononuclear copper(II)-(end-on)superoxide complex using a simple tridentate ligand consisting of an eight-membered cyclic diamine with a pyridylethyl donor group. The superoxide complex exhibits a similar structure (four-coordinate tetrahedral geometry) and reactivity (aliphatic hydroxylation) to those of a proposed reactive intermediate of copper monooxygenases. Systematic studies based on the crystal structures of copper(I) and copper(II) complexes of the related tridentate supporting ligands have indicated that the rigid eight-membered cyclic diamine framework is crucial for controlling the geometry and the redox potential, which are prerequisites for the generation of such a unique mononuclear copper(II)-(end-on)superoxide complex

  12. Antioxidative activity of lactobacilli measured by oxygen radical absorbance capacity.

    PubMed

    Saide, J A O; Gilliland, S E

    2005-04-01

    The reducing ability and antioxidative activity of some species of Lactobacillus were compared under in vitro conditions. Cultures of Lactobacillus delbrueckii ssp. lactis, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus, and Lactobacillus casei were grown at 37 degrees C in de Man, Rogosa, Sharpe (MRS) broth supplemented with 0.5% 2,3,5 triphenyl tetrazolium chloride (TTC) to evaluate reducing activity. Reduced TTC was extracted from the cultures with acetone, and the intensity of the red color measured colorimetrically at 485 nm was an indication of reducing activity. The lactobacilli varied significantly in relative ability to reduce TTC when grown in MRS broth for 15 h. The relative amounts of growth as indicated by pH values at 18 h appeared to influence the amount of reduction. Antioxidative activity was evaluated by the ability of the whole cells or the cell-free extracts from cultures to protect a protein from being attacked by free radicals. These analyses were performed using the oxygen radical absorbance capacity method. All cultures tested exhibited some degree of antioxidative activity. Among the treatments, the cell-free extracts from cells grown in MRS broth exhibited significantly higher values than did whole cells. There was no apparent relationship between the reducing and antioxidative activities of the cultures evaluated. The results from this study show that these cultures can provide a source of dietary antioxidants. Furthermore, selection of cultures that produce antioxidants as starters could provide yet another health or nutritional benefit from cultured or culture-containing dairy products.

  13. Activation of Oxygen by Cytochrome P-450 and Other Haemoproteins

    NASA Astrophysics Data System (ADS)

    Metelitsa, D. I.

    1982-11-01

    Data on the activation of molecular oxygen by the full microsomal hydroxylating system containing cytochrome P-450 as the terminal oxygenase are examined. The nature of the hydroxylating agent, which is the oxenoid Fe3+O, is analysed. The autoxidation reactions of cytochrome P-450 from various sources, haemoglobin, myoglobin, and peroxidases are compared and the role of the axial ligands of the haem iron and the structure of the active centres of the haemoproteins in this process is demonstrated. The possible mechanisms of the oxidation of organic compounds by peroxides with participation of cytochrome P-450, cytochrome c, haemoglobin, and catalase are examined critically. Haemoproteins have been divided into three groups in terms of the type of peroxide oxidation reactions. The relative contributions of the radical and two-electron reactions in the oxidation of compounds by peroxides with participation of different haemoproteins are analysed. The bibliography includes 184 references.

  14. Generation of oxygen radicals by minerals and its correlation to cytotoxicity

    SciTech Connect

    Vallyathan, V.

    1994-12-01

    Occupational exposure to mineral dust causes pneumoconiosis and other diseases. A cytotoxicity assay to predict the potential of minerals to cause disease would be of great value as a prevention strategy. This study compares the ability of several minerals to generate the more potent oxidizing agent, hydroxyl radical ({sm_bullet}OH), and their cytotoxicity and lipid peroxidation potentials. Crystalline silica, the most potent cytotoxic and pathogenic mineral studied, showed the least ability to generate {sm_bullet}OH radicals while inducing the maximal lipid peroxidation. Coal mine dust, showing the maximal ability to generate {sm_bullet}OH radicals, was the least cytotoxic in bioassays of toxicity and induction of lipid peroxidation. Based on these results, it would appear that the ability of minerals to induce lipid peroxidation provides a better correlation with known cytotoxicity and pathogenicity of minerals than does their ability to generate oxygen radicals. 21 refs., 8 figs., 1 tab.

  15. Knee extensor muscle oxygen consumption in relation to muscle activation.

    PubMed

    Kooistra, R D; Blaauboer, M E; Born, J R; de Ruiter, C J; de Haan, A

    2006-12-01

    Recently, fatigability and muscle oxygen consumption (mVO(2)) during sustained isometric contractions were found to be less at shorter (30 degrees knee angle; 0 degrees = full extension) compared to longer knee extensor muscle lengths (90 degrees ) and, at low torques, less in the rectus femoris (RF) muscle than in the vastus lateralis and medialis. In the present study we hypothesized that these findings could be accounted for by a knee angle- and a muscle-dependent activation respectively. On two experimental days rectified surface EMG (rsEMG) was obtained as a measure of muscle activation in nine healthy young males. In addition, on day 1 maximal torque capacity (MTC) was carefully determined using superimposed nerve stimulation on brief high intensity contractions (> 70%MVC) at 30, 60 and 90 degrees knee angles. On day 2, subjects performed longer lasting isometric contractions (10-70%MTC) while mVO(2) was measured using near-infrared spectroscopy (NIRS). At 30 degrees , maximal mVO(2) was reached significantly later (11.0 s +/- 6.5 s) and was 57.9 +/- 8.3% less (average +/- SD, across intensities and muscles) than mVO(2) at 60 and 90 degrees (p < 0.05). However, rsEMG was on average only 18.0 +/- 11.8% (p = 0.062) less at the start of the contraction at 30 degrees . At 10%MTC at all knee angles, maximal mVO(2) of the RF occurred significantly later (28.8 +/- 36.0 s) and showed a significantly smaller increase in rsEMG compared to both vasti. In conclusion, it is unlikely that the tendency for less intense muscle activation could fully account for the approximately 60% lower oxygen consumption at 30 degrees , but the later increase in RFmVO(2) seemed to be caused by a less strong activation of the RF.

  16. The interrelationship between muscle oxygenation, muscle activation, and pulmonary oxygen uptake to incremental ramp exercise: influence of aerobic fitness.

    PubMed

    Boone, Jan; Barstow, Thomas J; Celie, Bert; Prieur, Fabrice; Bourgois, Jan

    2016-01-01

    We investigated whether muscle and ventilatory responses to incremental ramp exercise would be influenced by aerobic fitness status by means of a cross-sectional study with a large subject population. Sixty-four male students (age: 21.2 ± 3.2 years) with a heterogeneous peak oxygen uptake (51.9 ± 6.3 mL·min(-1)·kg(-1), range 39.7-66.2 mL·min(-1)·kg(-1)) performed an incremental ramp cycle test (20-35 W·min(-1)) to exhaustion. Breath-by-breath gas exchange was recorded, and muscle activation and oxygenation were measured with surface electromyography and near-infrared spectroscopy, respectively. The integrated electromyography (iEMG), mean power frequency (MPF), deoxygenated [hemoglobin and myoglobin] (deoxy[Hb+Mb]), and total[Hb+Mb] responses were set out as functions of work rate and fitted with a double linear function. The respiratory compensation point (RCP) was compared and correlated with the breakpoints (BPs) (as percentage of peak oxygen uptake) in muscle activation and oxygenation. The BP in total[Hb+Mb] (83.2% ± 3.0% peak oxygen uptake) preceded (P < 0.001) the BP in iEMG (86.7% ± 4.0% peak oxygen uptake) and MPF (86.3% ± 4.1% peak oxygen uptake), which in turn preceded (P < 0.01) the BP in deoxy[Hb+Mb] (88.2% ± 4.5% peak oxygen uptake) and RCP (87.4% ± 4.5% peak oxygen uptake). Furthermore, the peak oxygen uptake was significantly (P < 0.001) positively correlated to the BPs and RCP, indicating that the BPs in total[Hb+Mb] (r = 0.66; P < 0.001), deoxy[Hb+Mb] (r = 0.76; P < 0.001), iEMG (r = 0.61; P < 0.001), MPF (r = 0.63; P < 0.001), and RCP (r = 0.75; P < 0.001) occurred at a higher percentage of peak oxygen uptake in subjects with a higher peak oxygen uptake. In this study a close relationship between muscle oxygenation, activation, and pulmonary oxygen uptake was found, occurring in a cascade of events. In subjects with a higher aerobic fitness level this cascade occurred at a higher relative intensity.

  17. [Several indicators of tissue oxygen during modeling of extravehicular activity of man].

    PubMed

    Lan'shina, O E; Loginov, V A; Akinfiev, A V; Kovalenko, E A

    1995-01-01

    Investigations of tissue oxygen indices during simulation of extravehicular activity (EVA) of cosmonauts demonstrated that breathing pure oxygen at approximately 280 mmHg elevates oxygen tension in capillary blood, and capillary-tissue gradient during physical work. Physical work alone stimulates tissue oxygenation due to, apparently, intensification of the processes of oxidative phosphorylation. The observed shifts in oxygen status reverse significantly within the first 5 min after completion of the experiment.

  18. In vivo modulation of interacting central pattern generators in lobster stomatogastric ganglion: influence of feeding and partial pressure of oxygen.

    PubMed

    Clemens, S; Massabuau, J C; Legeay, A; Meyrand, P; Simmers, J

    1998-04-01

    The stomatogastric ganglion (STG) of the European lobster Homarus gammarus contains two rhythm-generating networks (the gastric and pyloric circuits) that in resting, unfed animals produce two distinct, yet strongly interacting, motor patterns. By using simultaneous EMG recordings from the gastric and pyloric muscles in vivo, we found that after feeding, the gastropyloric interaction disappears as the two networks express accelerated motor rhythms. The return to control levels of network activity occurs progressively over the following 1-2 d and is associated with a gradual reappearance of the gastropyloric interaction. In parallel with this change in network activity is an alteration of oxygen levels in the blood. In resting, unfed animals, arterial partial pressure of oxygen (PO2) is most often between 1 and 2 kPa and then doubles within 1 hr after feeding, before returning to control values some 24 hr later. In vivo, experimental prevention of the arterial PO2 increase after feeding leads to a slowing of pyloric rhythmicity toward control values and a reappearance of the gastropyloric interaction, without apparent effect on gastric network operation. Using in vitro preparations of the stomatogastric nervous system and by changing oxygen levels uniquely at the level of the STG within the range observed in the intact animal, we were able to mimic most of the effects observed in vivo. Our data indicate that the gastropyloric interaction appears only during a "free run" mode of foregut activity and that the coordinated operation of multiple neural networks may be modulated by local changes in oxygenation. PMID:9502835

  19. Metal bacteriochlorins which act as dual singlet oxygen and superoxide generators.

    PubMed

    Fukuzumi, Shunichi; Ohkubo, Kei; Zheng, Xiang; Chen, Yihui; Pandey, Ravindra K; Zhan, Riqiang; Kadish, Karl M

    2008-03-01

    A series of stable free-base, Zn(II) and Pd(II) bacteriochlorins containing a fused six- or five-member diketo- or imide ring have been synthesized as good candidates for photodynamic therapy sensitizers, and their electrochemical, photophysical, and photochemical properties were examined. Photoexcitation of the palladium bacteriochlorin affords the triplet excited state without fluorescence emission, resulting in formation of singlet oxygen with a high quantum yield due to the heavy atom effect of palladium. Electrochemical studies revealed that the zinc bacteriochlorin has the smallest HOMO-LUMO gap of the investigated compounds, and this value is significantly lower than the triplet excited-state energy of the compound in benzonitrile. Such a small HOMO-LUMO gap of the zinc bacteriochlorin enables intermolecular photoinduced electron transfer from the triplet excited state to the ground state to produce both the radical cation and the radical anion. The radical anion thus produced can transfer an electron to molecular oxygen to produce superoxide anion which was detected by electron spin resonance. The same photosensitizer can also act as an efficient singlet oxygen generator. Thus, the same zinc bacteriochlorin can function as a sensitizer with a dual role in that it produces both singlet oxygen and superoxide anion in an aprotic solvent (benzonitrile). PMID:18254618

  20. The interaction of copper (Cu++) with the erythrocyte membrane and 2,3-dimercaptopropanesulphonate in vitro: a source of activated oxygen species.

    PubMed

    Aaseth, J; Ribarov, S; Bochev, P

    1987-10-01

    The therapy of copper poisoning and of Wilson's disease with 2,3-dimercaptopropane-1-sulphonate (DMPS) may increase the copper-induced haemolysis. Some aspects of the mechanism of this effect were investigated. The possible generation of activated oxygen species during the interaction of Cu++ and DMPS was studied using a chemiluminescent method detecting oxygen radicals. It was found that incubation of DMPS with copper ions (free or bond with erythrocyte membranes) is accompanied with generation of oxygen radicals. Activated oxygen species produced via O2- are able to increase the haemolytic effects of cupric salts. Hence DMPS treatment in cases of copper poisonings or Wilson's disease may involve risk of side effects on the basis of activated oxygen species generation.

  1. Immobilised activated sludge based biosensor for biochemical oxygen demand measurement.

    PubMed

    Liu, J; Björnsson, L; Mattiasson, B

    2000-02-01

    A biochemical oxygen demand (BOD) sensor, based on an immobilised mixed culture of microorganisms in combination with a dissolved oxygen electrode, has been developed for the purpose of on-line monitoring of the biological treatment process for waste and wastewater. The sensor was designed for easy replacement of the biomembrane, thereby making it suitable for short-term use. The drawbacks of activated sludge based sensor, such as short sensor lifetime, were thereby circumvented. The sensor BOD measurements were carried out in the kinetic mode using a flow injection system, resulting in 25 s for one measurement followed by 4-8 min recovery time. Based on the results of normalised sensor responses, the OECD synthetic wastewater was considered to be a more suitable calibration solution in comparison with the GGA solution. Good agreement was achieved between the results of the sensor BOD measurement and those obtained from BOD5 analysis of a wastewater sample from a food-processing factory. Reproducibility of responses using one sensor was below +/- 5.6%, standard deviation. Reproducibility of responses using different sensors was within acceptable bias limits, viz. +/- 15% standard deviation.

  2. Light Emitting Diode-Generated Blue Light Modulates Fibrosis Characteristics: Fibroblast Proliferation, Migration Speed, and Reactive Oxygen Species Generation

    PubMed Central

    Mamalis, Andrew; Garcha, Manveer; Jagdeo, Jared

    2016-01-01

    Background and Objective Blue light is part of the visible light spectrum that does not generate harmful DNA adducts associated with skin cancer and photoaging, and may represent a safer therapeutic modality for treatment of keloid scars and other fibrotic skin diseases. Our laboratory previously demonstrated that light-emitting diode (LED) red and infrared light inhibits proliferation of skin fibroblasts. Moreover, different wavelengths of light can produce different biological effects. Furthermore, the effects of LED blue light (LED-BL) on human skin fibroblasts are not well characterized. This study investigated the effects of LED-BL on human skin fibroblast proliferation, viability, migration speed, and reactive oxygen-species (ROS) generation. Methods and Materials Irradiation of adult human skin fibroblasts using commercially-available LED-BL panels was performed in vitro, and modulation of proliferation and viability was quantified using the trypan blue dye exclusion assay, migratory speed was assessed using time-lapse video microscopy, and intracellular ROS generation was measured using the dihydrorhodamine flow cytometry assay. Statistical differences between groups were determined by ANOVA and Student s t-test. Results Human skin fibroblasts treated with LED-BL fluences of 5, 30, 45, and 80 J/cm2 demonstrated statistically significant dose-dependent decreases in relative proliferation of 8.4%, 29.1%, 33.8%, 51.7%, and 55.1%, respectively, compared to temperature and environment matched bench control plates, respectively. LED-BL fluences of 5, 30, 45 and 80 J/cm2 decreased fibroblast migration speed to 95 ± 7.0% (p = 0.64), 81.3 ± 5.5% (p = 0.021), 48.5 ± 2.7% (p < 0.0001), and 32.3 ± 1.9% (p < 0.0001), respectively, relative to matched controls. LED fluences of 5, 10, 30, and 80 J/cm2 resulted in statistically significant increases in reactive oxygen species of 110.4%, 116.6%, 127.5%, and 130%, respectively, relative to bench controls. Conclusion At

  3. Cancer Therapy by Catechins Involves Redox Cycling of Copper Ions and Generation of Reactive Oxygen Species

    PubMed Central

    Farhan, Mohd; Khan, Husain Yar; Oves, Mohammad; Al-Harrasi, Ahmed; Rehmani, Nida; Arif, Hussain; Hadi, Sheikh Mumtaz; Ahmad, Aamir

    2016-01-01

    Catechins, the dietary phytochemicals present in green tea and other beverages, are considered to be potent inducers of apoptosis and cytotoxicity to cancer cells. While it is believed that the antioxidant properties of catechins and related dietary agents may contribute to lowering the risk of cancer induction by impeding oxidative injury to DNA, these properties cannot account for apoptosis induction and chemotherapeutic observations. Catechin (C), epicatechin (EC), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG) are the four major constituents of green tea. In this article, using human peripheral lymphocytes and comet assay, we show that C, EC, EGC and EGCG cause cellular DNA breakage and can alternatively switch to a prooxidant action in the presence of transition metals such as copper. The cellular DNA breakage was found to be significantly enhanced in the presence of copper ions. Catechins were found to be effective in providing protection against oxidative stress induced by tertbutylhydroperoxide, as measured by oxidative DNA breakage in lymphocytes. The prooxidant action of catechins involved production of hydroxyl radicals through redox recycling of copper ions. We also determined that catechins, particularly EGCG, inhibit proliferation of breast cancer cell line MDA-MB-231 leading to a prooxidant cell death. Since it is well established that tissue, cellular and serum copper levels are considerably elevated in various malignancies, cancer cells would be more subject to redox cycling between copper ions and catechins to generate reactive oxygen species (ROS) responsible for DNA breakage. Such a copper dependent prooxidant cytotoxic mechanism better explains the anticancer activity and preferential cytotoxicity of dietary phytochemicals against cancer cells. PMID:26861392

  4. Cancer Therapy by Catechins Involves Redox Cycling of Copper Ions and Generation of Reactive Oxygen species.

    PubMed

    Farhan, Mohd; Khan, Husain Yar; Oves, Mohammad; Al-Harrasi, Ahmed; Rehmani, Nida; Arif, Hussain; Hadi, Sheikh Mumtaz; Ahmad, Aamir

    2016-02-04

    Catechins, the dietary phytochemicals present in green tea and other beverages, are considered to be potent inducers of apoptosis and cytotoxicity to cancer cells. While it is believed that the antioxidant properties of catechins and related dietary agents may contribute to lowering the risk of cancer induction by impeding oxidative injury to DNA, these properties cannot account for apoptosis induction and chemotherapeutic observations. Catechin (C), epicatechin (EC), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG) are the four major constituents of green tea. In this article, using human peripheral lymphocytes and comet assay, we show that C, EC, EGC and EGCG cause cellular DNA breakage and can alternatively switch to a prooxidant action in the presence of transition metals such as copper. The cellular DNA breakage was found to be significantly enhanced in the presence of copper ions. Catechins were found to be effective in providing protection against oxidative stress induced by tertbutylhydroperoxide, as measured by oxidative DNA breakage in lymphocytes. The prooxidant action of catechins involved production of hydroxyl radicals through redox recycling of copper ions. We also determined that catechins, particularly EGCG, inhibit proliferation of breast cancer cell line MDA-MB-231 leading to a prooxidant cell death. Since it is well established that tissue, cellular and serum copper levels are considerably elevated in various malignancies, cancer cells would be more subject to redox cycling between copper ions and catechins to generate reactive oxygen species (ROS) responsible for DNA breakage. Such a copper dependent prooxidant cytotoxic mechanism better explains the anticancer activity and preferential cytotoxicity of dietary phytochemicals against cancer cells.

  5. Time-Resolved Insight into the Photosensitized Generation of Singlet Oxygen in Endoperoxides

    PubMed Central

    2014-01-01

    A synergistic approach combining high-level multiconfigurational static calculations and full-dimensional ab initio surface hopping dynamics has been employed to gain insight into the photochemistry of endoperoxides. Electronic excitation of endoperoxides triggers two competing pathways, cycloreversion and O–O homolysis, that result in the generation of singlet oxygen and oxygen diradical rearrangement products. Our results reveal that cycloreversion or the rupture of the two C–O bonds occurs via an asynchronous mechanism that can lead to the population of a ground-state intermediate showing a single C–O bond. Furthermore, singlet oxygen is directly generated in its most stable excited electronic state 1Δg. The triplet states do not intervene in this mechanism, as opposed to the O–O homolysis where the exchange of population between the singlet and triplet manifolds is remarkable. In line with recent experiments performed on the larger anthracene-9,10-endoperoxide, upon excitation to the spectroscopic ππ* electronic states, the primary photoreactive pathway that governs deactivation of endoperoxides is O–O homolysis with a quantum yield of 65%. PMID:25688180

  6. Health assessment of gasoline and fuel oxygenate vapors: generation and characterization of test materials.

    PubMed

    Henley, Michael; Letinski, Daniel J; Carr, John; Caro, Mario L; Daughtrey, Wayne; White, Russell

    2014-11-01

    In compliance with the Clean Air Act regulations for fuel and fuel additive registration, the petroleum industry, additive manufacturers, and oxygenate manufacturers have conducted comparative toxicology testing on evaporative emissions of gasoline alone and gasoline containing fuel oxygenates. To mimic real world exposures, a generation method was developed that produced test material similar in composition to the re-fueling vapor from an automotive fuel tank at near maximum in-use temperatures. Gasoline vapor was generated by a single-step distillation from a 1000-gallon glass-lined kettle wherein approximately 15-23% of the starting material was slowly vaporized, separated, condensed and recovered as test article. This fraction was termed vapor condensate (VC) and was prepared for each of the seven test materials, namely: baseline gasoline alone (BGVC), or gasoline plus an ether (G/MTBE, G/ETBE, G/TAME, or G/DIPE), or gasoline plus an alcohol (G/EtOH or G/TBA). The VC test articles were used for the inhalation toxicology studies described in the accompanying series of papers in this journal. These studies included evaluations of subchronic toxicity, neurotoxicity, immunotoxicity, genotoxicity, reproductive and developmental toxicity. Results of these studies will be used for comparative risk assessments of gasoline and gasoline/oxygenate blends by the US Environmental Protection Agency. PMID:24852493

  7. Health assessment of gasoline and fuel oxygenate vapors: generation and characterization of test materials.

    PubMed

    Henley, Michael; Letinski, Daniel J; Carr, John; Caro, Mario L; Daughtrey, Wayne; White, Russell

    2014-11-01

    In compliance with the Clean Air Act regulations for fuel and fuel additive registration, the petroleum industry, additive manufacturers, and oxygenate manufacturers have conducted comparative toxicology testing on evaporative emissions of gasoline alone and gasoline containing fuel oxygenates. To mimic real world exposures, a generation method was developed that produced test material similar in composition to the re-fueling vapor from an automotive fuel tank at near maximum in-use temperatures. Gasoline vapor was generated by a single-step distillation from a 1000-gallon glass-lined kettle wherein approximately 15-23% of the starting material was slowly vaporized, separated, condensed and recovered as test article. This fraction was termed vapor condensate (VC) and was prepared for each of the seven test materials, namely: baseline gasoline alone (BGVC), or gasoline plus an ether (G/MTBE, G/ETBE, G/TAME, or G/DIPE), or gasoline plus an alcohol (G/EtOH or G/TBA). The VC test articles were used for the inhalation toxicology studies described in the accompanying series of papers in this journal. These studies included evaluations of subchronic toxicity, neurotoxicity, immunotoxicity, genotoxicity, reproductive and developmental toxicity. Results of these studies will be used for comparative risk assessments of gasoline and gasoline/oxygenate blends by the US Environmental Protection Agency.

  8. RhoA and Rac1 GTPases Differentially Regulate Agonist-Receptor Mediated Reactive Oxygen Species Generation in Platelets

    PubMed Central

    Akbar, Huzoor; Duan, Xin; Saleem, Saima; Davis, Ashley K.; Zheng, Yi

    2016-01-01

    Agonist induced generation of reactive oxygen species (ROS) by NADPH oxidases (NOX) enhances platelet aggregation and hence the risk of thrombosis. RhoA and Rac1 GTPases are involved in ROS generation by NOX in a variety of cells, but their roles in platelet ROS production remain unclear. In this study we used platelets from RhoA and Rac1 conditional knockout mice as well as human platelets treated with Rhosin and NSC23767, rationally designed small molecule inhibitors of RhoA and Rac GTPases, respectively, to better define the contributions of RhoA and Rac1 signaling to ROS generation and platelet activation. Treatment of platelets with Rhosin inhibited: (a) U46619 induced activation of RhoA; (b) phosphorylation of p47phox, a critical component of NOX; (c) U46619 or thrombin induced ROS generation; (d) phosphorylation of myosin light chain (MLC); (e) platelet shape change; (f) platelet spreading on immobilized fibrinogen; and (g) release of P-selectin, secretion of ATP and aggregation. Conditional deletion of RhoA or Rac1 gene inhibited thrombin induced ROS generation in platelets. Addition of Y27632, a RhoA inhibitor, NSC23766 or Phox-I, an inhibitor of Rac1-p67phox interaction, to human platelets blocked thrombin induced ROS generation. These data suggest that: (a) RhoA/ROCK/p47phox signaling axis promotes ROS production that, at least in part, contributes to platelet activation in conjunction with or independent of the RhoA/ROCK mediated phosphorylation of MLC; and (b) RhoA and Rac1 differentially regulate ROS generation by inhibiting phosphorylation of p47phox and Rac1-p67phox interaction, respectively. PMID:27681226

  9. Organic aerosols associated with the generation of reactive oxygen species (ROS) by water-soluble PM2.5.

    PubMed

    Verma, Vishal; Fang, Ting; Xu, Lu; Peltier, Richard E; Russell, Armistead G; Ng, Nga Lee; Weber, Rodney J

    2015-04-01

    We compare the relative toxicity of various organic aerosol (OA) components identified by an aerosol mass spectrometer (AMS) based on their ability to generate reactive oxygen species (ROS). Ambient fine aerosols were collected from urban (three in Atlanta, GA and one in Birmingham, AL) and rural (Yorkville, GA and Centerville, AL) sites in the Southeastern United States. The ROS generating capability of the water-soluble fraction of the particles was measured by the dithiothreitol (DTT) assay. Water-soluble PM extracts were further separated into the hydrophobic and hydrophilic fractions using a C-18 column, and both fractions were analyzed for DTT activity and water-soluble metals. Organic aerosol composition was measured at selected sites using a high-resolution time-of-flight AMS. Positive matrix factorization of the AMS spectra resolved the organic aerosol into isoprene-derived OA (Isop_OA), hydrocarbon-like OA (HOA), less-oxidized oxygenated OA, (LO-OOA), more-oxidized OOA (MO-OOA), cooking OA (COA), and biomass burning OA (BBOA). The association of the DTT activity of water-soluble PM2.5 (WS_DTT) with these factors was investigated by linear regression techniques. BBOA and MO-OOA were most consistently linked with WS_DTT, with intrinsic water-soluble activities of 151 ± 20 and 36 ± 22 pmol/min/μg, respectively. Although less toxic, MO-OOA was most widespread, contributing to WS_DTT activity at all sites and during all seasons. WS_DTT activity was least associated with biogenic secondary organic aerosol. The OA components contributing to WS_DTT were humic-like substances (HULIS), which are abundantly emitted in biomass burning (BBOA) and include highly oxidized OA from multiple sources (MO-OOA). Overall, OA contributed approximately 60% to the WS_DTT activity, with the remaining probably from water-soluble metals, which were mostly associated with the hydrophilic WS_DTT fraction. PMID:25748105

  10. Generativity as a Route to Active Ageing

    PubMed Central

    Kruse, Andreas; Schmitt, Eric

    2012-01-01

    We elucidate the significance of active ageing from an individual as well as from a societal perspective. Taking an individual perspective, maintaining activity in later years is linked to successful ageing because of empirical relationships to positive self-perception, satisfaction with life, and development of competences, whereas from a societal perspective, active ageing implies usage of older people's life competences as a human capital of society—a societal imperative, particularly in times of demographic change but also more basically substantiated in an ethics of responsibility, intergenerational solidarity, and generation equity. We focus on the psychological construct of generativity which is interpreted as an aspect of the philosophical-anthropological category of joint responsibility. Our own research in Mexico and the Baltic States supports the notion that maintaining access to the public sphere and active engagement for others is a more basic individual concern than a life-stages specific developmental task. We report background and results of a Dialogue Forum Project Funding, a research cooperation between our institute and the Foundation Remembrance, Responsibility, and Future aimed to improve generativity in Belarus, Russia, and Ukraine by implementing and supporting local initiatives offering opportunities for intergenerational dialogue. PMID:22919378

  11. Improvement of the efficiency of a space oxygen-hydrogen electrochemical generator

    NASA Astrophysics Data System (ADS)

    Glukhikh, I. N.; Shcherbakov, A. N.; Chelyaev, V. F.

    2014-12-01

    This paper describes the method used for cooling of an on-board oxygen-hydrogen electrochemical generator (ECG). Apart from electric power, such a unit produces water of reaction and heat; the latter is an additional load on the thermal control system of a space vehicle. This load is undesirable in long-duration space flights, when specific energy characteristics of on-board systems are the determining factors. It is suggested to partially compensate the energy consumption by the thermal control system of a space vehicle required for cooling of the electrochemical generator through evaporation of water of reaction from the generator into a vacuum (or through ice sublimation if the pressure in the ambient space is lower than that in the triple point of water.) Such method of cooling of an electrochemical generator improves specific energy parameters of an on-board electric power supply system, and, due to the presence of the negative feedback, it makes the operation of this system more stable. Estimates suggest that it is possible to compensate approximately one half of heat released from the generator through evaporation of its water of reaction at the electrical efficiency of the electrochemical generator equal to 60%. In this case, even minor increase in the efficiency of the generator would result in a considerable increase in the efficiency of the evaporative system intended for its cooling.

  12. Advancements in oxygen generation and humidity control by water vapor electrolysis

    NASA Technical Reports Server (NTRS)

    Heppner, D. B.; Sudar, M.; Lee, M. C.

    1988-01-01

    Regenerative processes for the revitalization of manned spacecraft atmospheres or other manned habitats are essential for realization of long-term space missions. These processes include oxygen generation through water electrolysis. One promising technique of water electrolysis is the direct conversion of the water vapor contained in the cabin air to oxygen. This technique is the subject of the present program on water vapor electrolysis development. The objectives were to incorporate technology improvements developed under other similar electrochemical programs and add new ones; design and fabricate a mutli-cell electrochemical module and a testing facility; and demonstrate through testing the improvements. Each aspect of the water vapor electrolysis cell was reviewed. The materials of construction and sizing of each element were investigated analytically and sometime experimentally. In addition, operational considerations such as temperature control in response to inlet conditions were investigated. Three specific quantitative goals were established.

  13. Influence of Rust on Electrodes of Oxygen-fed Ozonizer to Ozone Generation

    NASA Astrophysics Data System (ADS)

    Tanaka, Masaaki; Ogawa, Shuji; Wada, Noboru; Yoshiyasu, Hajimu; Yagi, Shigenori

    The rust is generated on a metal electrode when the oxygen-fed ozonizer with a short gap is driven in a high discharge density. The ozonizer consists of a metal electrode and glass one, and the rust on a metal electrode disperses to a glass electrode. We found that the ozone yield efficiency improves about 20% in some condition when the rust adheres on the glass electrode. The rust is the oxidized chemical compounds of Fe, Ni, Cr, Mo which are a materials of a metal electrode(SUS304). We examined the characteristics of ozone generation using the glass electrode painting various kinds of the oxidized chemical compounds including above materials. As a result, the same characteristic in case of generation of rust is obtained when CrO3 is painted. We conclude that the change of characteristics is caused by the Cr in the rust.

  14. Elevated Cytoplasmic Free Zinc and Increased Reactive Oxygen Species Generation in the Context of Brain Injury.

    PubMed

    Stork, Christian J; Li, Yang V

    2016-01-01

    Intracellular zinc release and the generation of reactive oxygen species (ROS) have been reported to be common ingredients in numerous toxic signaling mechanisms in neurons. A key source for intracellular zinc release is its liberation from metallothionein-III (MT-III). MT-III binds and regulates intracellular zinc levels under physiological conditions, but the zinc-binding thiols readily react with certain ROS and reactive nitrogen species (RNS) to result in intracellular zinc liberation. Liberated zinc induces ROS and RNS generation by multiple mechanisms, including the induction of mitochondrial ROS production, and also promotes ROS formation outside the mitochondria by interaction with the enzymes NADPH oxidase and 12-lipoxygenase. Of particular relevance to neuronal injury in the context of ischemia and prolonged seizures, the positive feedback cycle between ROS/RNS generation and increasing zinc liberation will be examined.

  15. Oxygen Generator System Mars In-Situ Propellant Production Precursor Flight

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Gottmann, M.; Baird, R. S.

    1999-01-01

    The 2001 Lander to Mars will carry the first ever In situ Resource Utilization (ISRU) payload to Mars. This payload, the Mars In-situ Propellant production Precursor (MIP), will demonstrate a variety of technologies that will be required for future ISRU Mars indigenous material processing plant designs. One of those technologies is that of extracting oxygen from the predominantly carbon dioxide atmosphere of Mars, a prerequisite for future sample return and human missions to Mars. The Oxygen Generator Subsystem (OGS) portion of the MIP will demonstrate this and is the focus of this paper. The primary objective of the OGS is to demonstrate the production of oxygen from Mars atmospheric gases. Secondary objectives are to measure the performance and reliability of oxygen generation hardware in actual mission environments over an extended time. Major constraints on the OGS design came from several sources. The Lander provides power to the system from solar power that is harnessed by photovoltaic arrays. This limited OGS to daytime only operations (six to eight hours) and a maximum power of 15W. The reliance on solar power necessitated thermal cycling of the OGS between Mars ambient and OGS operating temperatures. The Lander also limited the total mass of the MIP payload to 7.5 kg with a correspondingly small volume, and the OGS was one of six experiments in the MIP Mass and volume were to be minimized. Another constraint was cost. Mission funding, as always, was tight. Cost was to be minimized. In short the OGS design had to be low power (<15 Watts), low mass (1 kg), low volume, low cost, and be capable of cyclical operations for an extended stay on Mars. After extensive research, a zirconia based solid oxide electrolyzer design was selected.

  16. Oxygen Generator System Mars In-Situ Propellant Production Precursor Flight

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Gottmann, M.; Baird, R. S.

    1999-01-01

    The 2001 Lander to Mars will carry the first ever ISRU payload to Mars. This payload, the Mars In-situ Propellant production Precursor (MIP), will demonstrate a variety of technologies that will be required for future ISRU Mars indigenous material processing plant designs. One of those technologies is that of extracting oxygen from the predominantly carbon dioxide atmosphere of Mars, a prerequisite for future sample return and human missions to Mars. The Oxygen Generator Subsystem (OGS) portion of the MIP will demonstrate this and is the focus of this paper. The primary objective of the OGS is to demonstrate the production of oxygen from Mars atmospheric gases. Secondary objectives are to measure the performance and reliability of oxygen generation hardware in actual mission environments over an extended time. Major constraints on the OGS design came from several sources. The Lander provides power to the system from solar power that is harnessed by photovoltaic arrays. This limited OGS to daytime only operations (six to eight hours) and a maximum power of 15W. The reliance on solar power necessitated thermal cycling of the OGS between Mars ambient and OGS operating temperatures. The Lander also limited the total mass of the MIP payload to 7.5 kg with a correspondingly small volume, and the OGS was one of six experiments in the MIP. Mass and volume were to be minimized. Another constraint was cost. Mission funding, as always, was tight. Cost was to be minimized. In short the OGS design had to be low power (<15 Watts), low mass (1 kg), low volume, low cost, and be capable of cyclical operations for an extended stay on Mars. After extensive research, a zirconia based solid oxide electrolyzer design was selected.

  17. Reactive Oxygen Species Production by Potato Tuber Mitochondria Is Modulated by Mitochondrially Bound Hexokinase Activity1

    PubMed Central

    Camacho-Pereira, Juliana; Meyer, Laudiene Evangelista; Machado, Lilia Bender; Oliveira, Marcus Fernandes; Galina, Antonio

    2009-01-01

    Potato tuber (Solanum tuberosum) mitochondria (PTM) have a mitochondrially bound hexokinase (HK) activity that exhibits a pronounced sensitivity to ADP inhibition. Here we investigated the role of mitochondrial HK activity in PTM reactive oxygen species generation. Mitochondrial HK has a 10-fold higher affinity for glucose (Glc) than for fructose (KMGlc = 140 μm versus KMFrc = 1,375 μm). Activation of PTM respiration by succinate led to an increase in hydrogen peroxide (H2O2) release that was abrogated by mitochondrial HK activation. Mitochondrial HK activity caused a decrease in the mitochondrial membrane potential and an increase in oxygen consumption by PTM. Inhibition of Glc phosphorylation by mannoheptulose or GlcNAc induced a rapid increase in H2O2 release. The blockage of H2O2 release sustained by Glc was reverted by oligomycin and atractyloside, indicating that ADP recycles through the adenine nucleotide translocator and F0F1ATP synthase is operative during the mitochondrial HK reaction. Inhibition of mitochondrial HK activity by 60% to 70% caused an increase of 50% in the maximal rate of H2O2 release. Inhibition in H2O2 release by mitochondrial HK activity was comparable to, or even more potent, than that observed for StUCP (S. tuberosum uncoupling protein) activity. The inhibition of H2O2 release in PTM was two orders of magnitude more selective for the ADP produced from the mitochondrial HK reaction than for that derived from soluble yeast (Saccharomyces cerevisiae) HK. Modulation of H2O2 release and oxygen consumption by Glc and mitochondrial HK inhibitors in potato tuber slices shows that hexoses and mitochondrial HK may act as a potent preventive antioxidant mechanism in potato tubers. PMID:19109413

  18. Determination of reactive oxygen species from ZnO micro-nano structures with shape-dependent photocatalytic activity

    SciTech Connect

    He, Weiwei; Zhao, Hongxiao; Jia, Huimin; Yin, Jun-Jie; Zheng, Zhi

    2014-05-01

    Graphical abstract: ZnO micro/nano structures with shape dependent photocatalytic activity were prepared by hydrothermal reaction. The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were identified precisely by electron spin resonance spectroscopy. The type of reactive oxygen species was determined by band gap structure of ZnO. - Highlights: • ZnO micro/nano structures with different morphologies were prepared by solvothermal reaction. • Multi-pod like ZnO structures exhibited superior photocatalytic activity. • The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were characterized precisely by electron spin resonance spectroscopy. • The type of reactive oxygen species was determined by band gap structure of ZnO. - Abstract: ZnO micro/nano structures with different morphologies have been prepared by the changing solvents used during their synthesis by solvothermal reaction. Three typical shapes of ZnO structures including hexagonal, bell bottom like and multi-pod formed and were characterized by scanning electron microscopy and X-ray diffraction. Multi pod like ZnO structures exhibited the highest photocatalytic activity toward degradation of methyl orange. Using electron spin resonance spectroscopy coupled with spin trapping techniques, we demonstrate an effective way to identify precisely the generation of hydroxyl radicals, superoxide and singlet oxygen from the irradiated ZnO multi pod structures. The type of reactive oxygen species formed was predictable from the band gap structure of ZnO. These results indicate that the shape of micro-nano structures significantly affects the photocatalytic activity of ZnO, and demonstrate the value of electron spin resonance spectroscopy for characterizing the type of reactive oxygen species formed during photoexcitation of semiconductors.

  19. Correlation between the sorption of dissolved oxygen onto chitosan and its antimicrobial activity against Esherichia coli.

    PubMed

    Gylienė, Ona; Servienė, Elena; Vepštaitė, Iglė; Binkienė, Rima; Baranauskas, Mykolas; Lukša, Juliana

    2015-10-20

    The ability of chitosan to adsorb dissolved oxygen from solution depends on its physical shape and is related to the surface area. Depending on conditions chitosan is capable of adsorbing or releasing oxygen. Chitosan, modificated by the substances possessing antimicrobial activity, such as succinic acid, Pd(II) ions, metallic Pd or Ag, distinctly increases the ability to adsorb the dissolved oxygen. The additional treatment of chitosan with air oxygen or electrochemically produced oxygen also increases the uptake of dissolved oxygen by chitosan. A strong correlation between the amount of oxygen adsorbed onto chitosan and its antimicrobial activity against Esherichia coli has been observed. This finding suggests that one of the sources of antimicrobial activity of chitosan is the ability to sorb dissolved oxygen, along with other well-known factors such as physical state and chemical composition.

  20. Singlet molecular oxygen-quenching activity of carotenoids: relevance to protection of the skin from photoaging

    PubMed Central

    Terao, Junji; Minami, Yuko; Bando, Noriko

    2011-01-01

    Carotenoids are known to be potent quenchers of singlet molecular oxygen [O2 (1Δg)]. Solar light-induced photooxidative stress causes skin photoaging by accelerating the generation of reactive oxygen species via photodynamic actions in which O2 (1Δg) can be generated by energy transfer from excited sensitizers. Thus, dietary carotenoids seem to participate in the prevention of photooxidative stress by accumulating as antioxidants in the skin. An in vivo study using hairless mice clarified that a O2 (1Δg) oxygenation-specific peroxidation product of cholesterol, cholesterol 5α-hydroperoxide, accumulates in skin lipids due to ultraviolet-A exposure. Matrix metalloproteinase-9, a metalloproteinase family enzyme responsible for the formation of wrinkles and sagging, was enhanced in the skin of ultraviolet-A -irradiated hairless mice. The activation of metalloproteinase-9 and the accumulation of 5α-hydroperoxide, as well as formation of wrinkles and sagging, were lowered in mice fed a β-carotene diet. These results strongly suggest that dietary β-carotene prevents the expression of metalloproteinase-9 (at least in part), by inhibiting the photodynamic action involving the formation of 5α-hydroperoxide in the skin. Intake of β-Carotene therefore appears to be helpful in slowing down ultraviolet-A -induced photoaging in human skin by acting as a O2 (1Δg) quencher. PMID:21297913

  1. Singlet oxygen generation in porphyrin-doped polymeric surface coating enables antimicrobial effects on Staphylococcus aureus.

    PubMed

    Felgenträger, Ariane; Maisch, Tim; Späth, Andreas; Schröder, Josef A; Bäumler, Wolfgang

    2014-10-14

    Surfaces can be coated with photosensitizer molecules, which generate singlet oxygen ((1)O2) when the surface is exposed to light. (1)O2 may diffuse from the coating and has the potential to kill microorganisms present on the surface. In the present study a derivative of the meso-tetraphenylporphyrin (TPP) was immobilized onto polyurethane (PU) after being sprayed and polymerized as a thin layer onto poly-methylmethacrylate (PMMA). PU is gas permeable and thus a sufficient amount of oxygen reaches the photosensitizer in this coating. The surface generation of (1)O2 and its diffusion were investigated by detecting its luminescence at 1270 nm and a tri-iodide assay. Antimicrobial photodynamic surface effects were tested on Staphylococcus aureus. The spectrally resolved detection of (1)O2 luminescence yielded a clear peak at 1275 nm. The time-resolved luminescence showed multi-exponential decay, revealing rise and decay times in the range of 5-2 × 10(2)μs. The photodynamic inactivation of S. aureus was monitored at different photosensitizer concentrations and radiant exposures of light. A photodynamic killing of >99.9% (>3log10-steps) was achieved within an irradiation time of 30 min. The photodynamic killing on the bioactive surface confirmed the antimicrobial effect of (1)O2 that was generated in the PU-coating and reached the bacteria by diffusion. PMID:25155698

  2. Electrochemical generation of oxygen. 1: The effects of anions and cations on hydrogen chemisorption and anodic oxide film formation on platinum electrode. 2: The effects of anions and cations on oxygen generation on platinum electrode

    NASA Technical Reports Server (NTRS)

    Huang, C. J.; Yeager, E.; Ogrady, W. E.

    1975-01-01

    The effects were studied of anions and cations on hydrogen chemisorption and anodic oxide film formation on Pt by linear sweep voltammetry, and on oxygen generation on Pt by potentiostatic overpotential measurement. The hydrogen chemisorption and anodic oxide film formation regions are greatly influenced by anion adsorption. In acids, the strongly bound hydrogen occurs at more cathodic potential when chloride and sulfate are present. Sulfate affects the initial phase of oxide film formation by produced fine structure while chloride retards the oxide-film formation. In alkaline solutions, both strongly and weakly bound hydrogen are influenced by iodide, cyanide, and barium and calcium cations. These ions also influence the oxide film formation. Factors considered to explain these effects are discussed. The Tafel slope for oxygen generation was found to be independent on the oxide thickness and the presence of cations or anions. The catalytic activity indicated by the exchange current density was observed decreasing with increasing oxide layer thickness, only a minor dependence on the addition of certain cations and anions was found.

  3. Production and Characterization of Active Transparent PET Films for Oxygen Sensitive Foods Packaging

    NASA Astrophysics Data System (ADS)

    Rosaria Galdi, Maria; Incarnato, Loredana

    2010-06-01

    The aim of this work is to investigate possible solutions to realize active, transparent PET film suitable for packaging oxygen sensitive foods. At this purpose, monolayer active PET films at different oxygen scavenger concentrations and multilayer active ones were produced by cast extrusion laboratory scale equipments. To assess their activity and to verify the efficacy of such solutions, O2 absorption analyses were carried out in continuous by an innovative oxygen meter.

  4. Generation of reactive oxygen species (ROS) is a key factor for stimulation of macrophage proliferation by ceramide 1-phosphate

    SciTech Connect

    Arana, Lide; Gangoiti, Patricia; Ouro, Alberto; Rivera, Io-Guane; Ordonez, Marta; Trueba, Miguel; Lankalapalli, Ravi S.; Bittman, Robert; Gomez-Munoz, Antonio

    2012-02-15

    We previously demonstrated that ceramide 1-phosphate (C1P) is mitogenic for fibroblasts and macrophages. However, the mechanisms involved in this action were only partially described. Here, we demonstrate that C1P stimulates reactive oxygen species (ROS) formation in primary bone marrow-derived macrophages, and that ROS are required for the mitogenic effect of C1P. ROS production was dependent upon prior activation of NADPH oxidase by C1P, which was determined by measuring phosphorylation of the p40phox subunit and translocation of p47phox from the cytosol to the plasma membrane. In addition, C1P activated cytosolic calcium-dependent phospholipase A{sub 2} and protein kinase C-{alpha}, and NADPH oxidase activation was blocked by selective inhibitors of these enzymes. These inhibitors, and inhibitors of ROS production, blocked the mitogenic effect of C1P. By using BHNB-C1P (a photolabile caged-C1P analog), we demonstrate that all of these C1P actions are caused by intracellular C1P. It can be concluded that the enzyme responsible for C1P-stimulated ROS generation in bone marrow-derived macrophages is NADPH oxidase, and that this enzyme is downstream of PKC-{alpha} and cPLA{sub 2}-{alpha} in this pathway. -- Highlights: Black-Right-Pointing-Pointer Ceramide 1-phosphate (C1P) stimulates reactive oxygen species (ROS) formation. Black-Right-Pointing-Pointer The enzyme responsible for ROS generation by C1P in macrophages is NADPH oxidase. Black-Right-Pointing-Pointer NADPH oxidase lies downstream of cPLA{sub 2}-{alpha} and PKC-{alpha} in this pathway. Black-Right-Pointing-Pointer ROS generation is essential for the stimulation of macrophage proliferation by C1P.

  5. Pd-Pt Bimetallic Nanodendrites with High Activity for Oxygen Reduction

    SciTech Connect

    Lim, B.; Tao, J.; Jiang, M.; Camargo, P.H.C.; Cho, E.C.; Lu, X.; Zhu, Y.; Xia, Y.

    2009-06-05

    Controlling the morphology of Pt nanostructures can provide a great opportunity to improve their catalytic properties and increase their activity on a mass basis. We synthesized Pd-Pt bimetallic nanodendrites consisting of a dense array of Pt branches on a Pd core by reducing K{sub 2}PtCl{sub 4} with L-ascorbic acid in the presence of uniform Pd nanocrystal seeds in an aqueous solution. The Pt branches supported on faceted Pd nanocrystals exhibited relatively large surface areas and particularly active facets toward the oxygen reduction reaction (ORR), the rate-determining step in a proton-exchange membrane fuel cell. The Pd-Pt nanodendrites were two and a half times more active on the basis of equivalent Pt mass for the ORR than the state-of-the-art Pt/C catalyst and five times more active than the first-generation supportless Pt-black catalyst.

  6. In situ fluorescence spectroscopy correlates ionomer degradation to reactive oxygen species generation in an operating fuel cell.

    PubMed

    Prabhakaran, Venkateshkumar; Arges, Christopher G; Ramani, Vijay

    2013-11-21

    The rate of generation of reactive oxygen species (ROS) within the polymer electrolyte membrane (PEM) of an operating proton exchange member fuel cell (PEMFC) was monitored using in situ fluorescence spectroscopy. A modified barrier layer was introduced between the PEM and the electrocatalyst layer to eliminate metal-dye interactions and fluorescence resonance energy transfer (FRET) effects during measurements. Standard fuel cell operating parameters (temperature, relative humidity, and electrode potential) were systematically varied to evaluate their influence on the rate of ROS generation during PEMFC operation. Independently, the macroscopic rate of PEM degradation was measured by monitoring the fluoride ion emission rate (FER) in the effluent stream at each operating condition. The ROS generation reaction rate constant (estimated from the in situ fluorescence experiments) correlated perfectly with the measured FER across all conditions, demonstrating unequivocally for the first time that a direct correlation exists between in situ ROS generation and PEM macroscopic degradation. The activation energy for ROS generation within the PEM was estimated to be 12.5 kJ mol(-1).

  7. Apoptosis induction of U937 human leukemia cells by diallyl trisulfide induces through generation of reactive oxygen species

    PubMed Central

    2012-01-01

    Background Diallyl trisulfide (DATS) is one of the major constituents in garlic oil and has demonstrated various pharmacological activities, including antimicrobial, antihyperlipidemic, antithrombotic, and anticancer effects. However, the mechanisms of antiproliferative activity in leukemia cells are not fully understood. In this study, the apoptotic effects of DATS were investigated in human leukemia cells. Results Results of this study indicated that treatment with DATS resulted in significantly inhibited leukemia cell growth in a concentration- and time-dependent manner by induction of apoptosis. In U937 cells, DATS-induced apoptosis was correlated with down-regulation of Bcl-2, XIAP, and cIAP-1 protein levels, cleavage of Bid proteins, activation of caspases, and collapse of mitochondrial membrane potential. The data further demonstrated that DATS increased intracellular reactive oxygen species (ROS) generation, which was attenuated by pretreatment with antioxidant N-acetyl-l-cysteine (NAC), a scavenger of ROS. In addition, administration of NAC resulted in significant inhibition of DATS-induced apoptosis by inhibiting activation of caspases. Conclusions The present study reveals that the cytotoxicity caused by DATS is mediated by generation of ROS and subsequent activation of the ROS-dependent caspase pathway in U937 leukemia cells. PMID:22578287

  8. Microbial activities and phosphorus cycling: An application of oxygen isotope ratios in phosphate

    NASA Astrophysics Data System (ADS)

    Stout, Lisa M.; Joshi, Sunendra R.; Kana, Todd M.; Jaisi, Deb P.

    2014-08-01

    Microorganisms carry out biochemical transformations of nutrients that make up their cells. Therefore, understanding how these nutrients are transformed or cycled in natural environments requires knowledge of microbial activity. Commonly used indicators for microbial activity typically include determining microbial respiration by O2/CO2 measurements, cell counts, and measurement of enzyme activities. However, coupled studies on nutrient cycling and microbial activity are not given enough emphasis. Here we apply phosphate oxygen isotope ratios (δ18OP) as a tool for measurement of microbial activity and compare the rate of isotope exchange with methods of measuring microbial activities that are more commonly applied in environmental studies including respiration, dehydrogenase activity, alkaline phosphatase activity, and cell counts. Our results show that different bacteria may have different strategies for P uptake, storage and release, their respiration and consequently expression of DHA and APase activities, but in general the trend of their enzyme activities are comparable. Phosphate δ18OP values correlated well with these other parameters used to measure microbial activity with the strongest linear relationships between δ18OP and CO2 evolution (r = -0.99). Even though the rate of isotope exchange for each microorganism used in this study is different, the rate per unit CO2 respiration showed one general trend, where δ18OP values move towards equilibrium while CO2 is generated. While this suggests that P cycling among microorganisms used in this study can be generalized, further research is needed to determine whether the microorganism-specific isotope exchange trend may occur in natural environments. In summary, phosphate oxygen isotope measurements may offer an alternative for use as a tracer to measure microbial activity in soils, sediments, and many other natural environments.

  9. Shoulder and forearm oxygenation and myoelectric activity in patients with work-related muscle pain and healthy subjects.

    PubMed

    Elcadi, Guilherme H; Forsman, Mikael; Aasa, Ulrika; Fahlstrom, Martin; Crenshaw, Albert G

    2013-05-01

    We tested hypotheses of (a) reduced oxygen usage, oxygen recovery, blood flow and oxygen consumption; and (b) increased muscle activity for patients diagnosed with work-related muscle pain (WRMP) in comparison to healthy controls. Oxygenation was measured with near infrared spectroscopy (NIRS), and muscle activity with EMG for the extensor carpi radialis (ECR) and trapezius descendens (TD) muscles. Eighteen patients with diffuse neck-shoulder-arm pain and 17 controls (matched in age and sex) were equipped with NIRS and EMG probes. After determining an individual's maximum voluntary contraction (MVC) force, short-term (20 s) isometric contractions for the ECR and TD of 10, 30, 50 and 70 % MVC generated ∆StO₂ and StO₂% recovery (Rslope) from NIRS, and RMS%max from EMG signals. In addition, upper arm venous (VO) and arterial (AO) occlusions generated slopes of total hemoglobin (HbTslope) and deoxyhemoglobin (HHbslope) for the resting ECR as surrogates of blood flow and oxygen consumption, respectively. Mixed model analyses, t tests, and Mann-Whitney test were used to assess differences between groups. There was no significant difference in MVC between groups for either muscle. Also, ∆StO₂%, Rslope for either muscle, and ECR-HbTslope were not different between groups, thus our hypotheses of reduced oxygen use, recovery, and blood flow for patients were not confirmed. However, patients had a significantly lower ECR-HHbslope confirming our hypothesis of reduced consumption. Further, there was no difference in RMS%max during contractions meaning that the hypothesis of increased activity for patients was not confirmed. When taking into account the number of NIRS variables studied, differences we found between our patient group and healthy controls (i.e., in forearm oxygen consumption and shoulder oxygen saturation level) may be considered modest. Overall our findings may have been impacted by the fact that our patients and controls were similar in muscle strength

  10. Chlorite dismutases – a heme enzyme family for use in bioremediation and generation of molecular oxygen

    PubMed Central

    Hofbauer, Stefan; Schaffner, Irene; Furtmüller, Paul G; Obinger, Christian

    2014-01-01

    Chlorite is a serious environmental concern, as rising concentrations of this harmful anthropogenic compound have been detected in groundwater, drinking water, and soil. Chlorite dismutases (Clds) are therefore important molecules in bioremediation as Clds catalyze the degradation of chlorite to chloride and molecular oxygen. Clds are heme b-containing oxidoreductases present in numerous bacterial and archaeal phyla. This review presents the phylogeny of functional Clds and Cld-like proteins, and demonstrates the close relationship of this novel enzyme family to the recently discovered dye-decolorizing peroxidases. The available X-ray structures, biophysical and enzymatic properties, as well as a proposed reaction mechanism, are presented and critically discussed. Open questions about structure-function relationships are addressed, including the nature of the catalytically relevant redox and reaction intermediates and the mechanism of inactivation of Clds during turnover. Based on analysis of currently available data, chlorite dismutase from “Candidatus Nitrospira defluvii” is suggested as a model Cld for future application in biotechnology and bioremediation. Additionally, Clds can be used in various applications as local generators of molecular oxygen, a reactivity already exploited by microbes that must perform aerobic metabolic pathways in the absence of molecular oxygen. For biotechnologists in the field of chemical engineering and bioremediation, this review provides the biochemical and biophysical background of the Cld enzyme family as well as critically assesses Cld's technological potential. PMID:24519858

  11. Flight Hydrogen Sensor for use in the ISS Oxygen Generation Assembly

    NASA Technical Reports Server (NTRS)

    MSadoques, George, Jr.; Makel, Darby B.

    2005-01-01

    This paper provides a description of the hydrogen sensor Orbital Replacement Unit (ORU) used on the Oxygen Generation Assembly (OGA), to be operated on the International Space Station (ISS). The hydrogen sensor ORU is being provided by Makel Engineering, Inc. (MEI) to monitor the oxygen outlet for the presence of hydrogen. The hydrogen sensor ORU is a triple redundant design where each sensor converts raw measurements to actual hydrogen partial pressure that is reported to the OGA system controller. The signal outputs are utilized for system shutdown in the event that the hydrogen concentration in the oxygen outlet line exceeds the specified shutdown limit. Improvements have been made to the Micro-Electro-Mechanical Systems (MEMS) based sensing element, screening, and calibration process to meet OGA operating requirements. Two flight hydrogen sensor ORUs have successfully completed the acceptance test phase. This paper also describes the sensor s performance during acceptance testing, additional tests planned to extend the operational performance calibration cycle, and integration with the OGA system.

  12. Cytotoxicity of InP/ZnS quantum dots related to reactive oxygen species generation.

    SciTech Connect

    Chibli, H.; Carlini, L.; Park, S.; Dimitrijevic, N. M.; Nadeau, J. L.

    2011-01-01

    Indium phosphide (InP) quantum dots (QDs) have emerged as a presumably less hazardous alternative to cadmium-based particles, but their cytotoxicity has not been well examined. Although their constituent elements are of very low toxicity to cells in culture, they nonetheless exhibit phototoxicity related to generation of reactive oxygen species by excited electrons and/or holes interacting with water and molecular oxygen. Using spin-trap electron paramagnetic resonance (EPR) spectroscopy and reporter assays, we find a considerable amount of superoxide and a small amount of hydroxyl radical formed under visible illumination of biocompatible InP QDs with a single ZnS shell, comparable to what is seen with CdTe. A double thickness shell reduces the reactive oxygen species concentration approximately two-fold. Survival assays in five cell lines correspondingly indicate a distinct reduction in toxicity with the double-shell InP QDs. Toxicity varies significantly across cell lines according to the efficiency of uptake, being overall significantly less than what is seen with CdTe or CdSe/ZnS. This indicates that InP QDs are a useful alternative to cadmium-containing QDs, while remaining capable of electron-transfer processes that may be undesirable or which may be exploited for photosensitization applications.

  13. Effect of oxygen on the microbial activities of thermophilic anaerobic biomass.

    PubMed

    Pedizzi, C; Regueiro, L; Rodriguez-Verde, I; Lema, J M; Carballa, M

    2016-07-01

    Low oxygen levels (μgO2L(-1)) in anaerobic reactors are quite common and no relevant consequences are expected. On the contrary, higher concentrations could affect the process. This work aimed to study the influence of oxygen (4.3 and 8.8mgO2L(-1), respectively) on the different microbial activities (hydrolytic, acidogenic and methanogenic) of thermophilic anaerobic biomass and on the methanogenic community structure. Batch tests in presence of oxygen were conducted using specific substrates for each biological activity and a blank (with minimum oxygen) was included. No effect of oxygen was observed on the hydrolytic and acidogenic activities. In contrast, the methane production rate decreased by 40% in all oxygenated batches and the development of active archaeal community was slower in presence of 8.8mgO2L(-1). However, despite this sensitivity of methanogens to oxygen at saturation levels, the inhibition was reversible. PMID:27020398

  14. 2D gasdynamic simulation of the kinetics of an oxygen-iodine laser with electric-discharge generation of singlet oxygen

    SciTech Connect

    Chukalovsky, A. A.; Rakhimova, T. V.; Klopovsky, K. S.; Mankelevich, Yu. A.; Proshina, O. V.

    2011-03-15

    The kinetic processes occurring in an electric-discharge oxygen-iodine laser are analyzed with the help of a 2D (r, z) gasdynamic model taking into account transport of excited oxygen, singlet oxygen, and radicals from the electric discharge and their mixing with the iodine-containing gas. The main processes affecting the dynamics of the gas temperature and gain are revealed. The simulation results obtained using the 2D model agree well with the experimental data on the mixture gain. A subsonic oxygen-iodine laser in which singlet oxygen is generated by a 350 W transverse RF discharge excited in an oxygen flow at a pressure P = 10 Torr and the discharge tube wall is covered with mercury oxide is simulated. The simulated mixing system is optimized in terms of the flow rate and the degree of preliminary dissociation of the iodine flow. The optimal regime of continuous operation of a subsonic electric-discharge oxygen-iodine laser is found.

  15. Oxygen Generating Biomaterials Preserve Skeletal Muscle Homeostasis under Hypoxic and Ischemic Conditions

    PubMed Central

    Ward, Catherine L.; Corona, Benjamin T.; Yoo, James J.; Harrison, Benjamin S.; Christ, George J.

    2013-01-01

    Provision of supplemental oxygen to maintain soft tissue viability acutely following trauma in which vascularization has been compromised would be beneficial for limb and tissue salvage. For this application, an oxygen generating biomaterial that may be injected directly into the soft tissue could provide an unprecedented treatment in the acute trauma setting. The purpose of the current investigation was to determine if sodium percarbonate (SPO), an oxygen generating biomaterial, is capable of maintaining resting skeletal muscle homeostasis under otherwise hypoxic conditions. In the current studies, a biologically and physiologically compatible range of SPO (1–2 mg/mL) was shown to: 1) improve the maintenance of contractility and attenuate the accumulation of HIF1α, depletion of intramuscular glycogen, and oxidative stress (lipid peroxidation) that occurred following ∼30 minutes of hypoxia in primarily resting (duty cycle = 0.2 s train/120 s contraction interval <0.002) rat extensor digitorum longus (EDL) muscles in vitro (95% N2–5% CO2, 37°C); 2) attenuate elevations of rat EDL muscle resting tension that occurred during contractile fatigue testing (3 bouts of 25 100 Hz tetanic contractions; duty cycle = 0.2 s/2 s = 0.1) under oxygenated conditions in vitro (95% O2–5% CO2, 37°C); and 3) improve the maintenance of contractility (in vivo) and prevent glycogen depletion in rat tibialis anterior (TA) muscle in a hindlimb ischemia model (i.e., ligation of the iliac artery). Additionally, injection of a commercially available lipid oxygen-carrying compound or the components (sodium bicarbonate and hydrogen peroxide) of 1 mg/mL SPO did not improve EDL muscle contractility under hypoxic conditions in vitro. Collectively, these findings demonstrate that a biological and physiological concentration of SPO (1–2 mg/mL) injected directly into rat skeletal muscle (EDL or TA muscles) can partially preserve resting skeletal muscle homeostasis under

  16. Radiation therapy generates platelet-activating factor agonists

    PubMed Central

    Sahu, Ravi P.; Harrison, Kathleen A.; Weyerbacher, Jonathan; Murphy, Robert C.; Konger, Raymond L.; Garrett, Joy Elizabeth; Chin-Sinex, Helen Jan; Johnston, Michael Edward; Dynlacht, Joseph R.; Mendonca, Marc; McMullen, Kevin; Li, Gengxin; Spandau, Dan F.; Travers, Jeffrey B.

    2016-01-01

    Pro-oxidative stressors can suppress host immunity due to their ability to generate oxidized lipid agonists of the platelet-activating factor-receptor (PAF-R). As radiation therapy also induces reactive oxygen species, the present studies were designed to define whether ionizing radiation could generate PAF-R agonists and if these lipids could subvert host immunity. We demonstrate that radiation exposure of multiple tumor cell lines in-vitro, tumors in-vivo, and human subjects undergoing radiation therapy for skin tumors all generate PAF-R agonists. Structural characterization of radiation-induced PAF-R agonistic activity revealed PAF and multiple oxidized glycerophosphocholines that are produced non-enzymatically. In a murine melanoma tumor model, irradiation of one tumor augmented the growth of the other (non-treated) tumor in a PAF-R-dependent process blocked by a cyclooxygenase-2 inhibitor. These results indicate a novel pathway by which PAF-R agonists produced as a byproduct of radiation therapy could result in tumor treatment failure, and offer important insights into potential therapeutic strategies that could improve the overall antitumor effectiveness of radiation therapy regimens. PMID:26959112

  17. Radiation therapy generates platelet-activating factor agonists.

    PubMed

    Sahu, Ravi P; Harrison, Kathleen A; Weyerbacher, Jonathan; Murphy, Robert C; Konger, Raymond L; Garrett, Joy Elizabeth; Chin-Sinex, Helen Jan; Johnston, Michael Edward; Dynlacht, Joseph R; Mendonca, Marc; McMullen, Kevin; Li, Gengxin; Spandau, Dan F; Travers, Jeffrey B

    2016-04-12

    Pro-oxidative stressors can suppress host immunity due to their ability to generate oxidized lipid agonists of the platelet-activating factor-receptor (PAF-R). As radiation therapy also induces reactive oxygen species, the present studies were designed to define whether ionizing radiation could generate PAF-R agonists and if these lipids could subvert host immunity. We demonstrate that radiation exposure of multiple tumor cell lines in-vitro, tumors in-vivo, and human subjects undergoing radiation therapy for skin tumors all generate PAF-R agonists. Structural characterization of radiation-induced PAF-R agonistic activity revealed PAF and multiple oxidized glycerophosphocholines that are produced non-enzymatically. In a murine melanoma tumor model, irradiation of one tumor augmented the growth of the other (non-treated) tumor in a PAF-R-dependent process blocked by a cyclooxygenase-2 inhibitor. These results indicate a novel pathway by which PAF-R agonists produced as a byproduct of radiation therapy could result in tumor treatment failure, and offer important insights into potential therapeutic strategies that could improve the overall antitumor effectiveness of radiation therapy regimens. PMID:26959112

  18. Comparison of stainless and mild steel welding fumes in generation of reactive oxygen species

    PubMed Central

    2010-01-01

    Background Welding fumes consist of a wide range of complex metal oxide particles which can be deposited in all regions of the respiratory tract. The welding aerosol is not homogeneous and is generated mostly from the electrode/wire. Over 390,000 welders were reported in the U.S. in 2008 while over 1 million full-time welders were working worldwide. Many health effects are presently under investigation from exposure to welding fumes. Welding fume pulmonary effects have been associated with bronchitis, metal fume fever, cancer and functional changes in the lung. Our investigation focused on the generation of free radicals and reactive oxygen species from stainless and mild steel welding fumes generated by a gas metal arc robotic welder. An inhalation exposure chamber located at NIOSH was used to collect the welding fume particles. Results Our results show that hydroxyl radicals (.OH) were generated from reactions with H2O2 and after exposure to cells. Catalase reduced the generation of .OH from exposed cells indicating the involvement of H2O2. The welding fume suspension also showed the ability to cause lipid peroxidation, effect O2 consumption, induce H2O2 generation in cells, and cause DNA damage. Conclusion Increase in oxidative damage observed in the cellular exposures correlated well with .OH generation in size and type of welding fumes, indicating the influence of metal type and transition state on radical production as well as associated damage. Our results demonstrate that both types of welding fumes are able to generate ROS and ROS-related damage over a range of particle sizes; however, the stainless steel fumes consistently showed a significantly higher reactivity and radical generation capacity. The chemical composition of the steel had a significant impact on the ROS generation capacity with the stainless steel containing Cr and Ni causing more damage than the mild steel. Our results suggest that welding fumes may cause acute lung injury. Since type of

  19. Solid oxide fuel cells developed by the sol-gel process for oxygen generation

    NASA Astrophysics Data System (ADS)

    Finch, Joshua S.

    Electrochemical fuel cells convert chemical energy directly to electrical energy through the reaction of a fuel and an oxidant. Solid oxide fuel cells (SOFC) are solid-state devices that operate at temperatures around 800°C, using a solid oxygen electrolyte. The goal of this thesis is to prepare a defect-free solid oxygen electrolyte by a sol-gel process that is capable of (a) functioning in a fuel cell; and (b) producing measurable oxygen when operated as an oxygen generator. Sol-gel processing was chosen for membrane development because it offers a means of applying high-purity layers with controlled doping and a variety of geometries. In this study, the sol-gel process was used to produce yttria-stabilized zirconia (YSZ) electrolyte membranes as well as the electrodes required for an operational fuel cell. Zirconium oxychloride (ZOC) was used as the precursor material for the electrolyte. The YSZ solution was prepared by mixing yttrium nitrate and ZOC in a 50/50 ETOH and water solvent. The reaction was catalyzed with 1.5M NH4OH. Viscosity and solution application techniques were varied to monitor the effect on membrane development. The YSZ layer was sintered to full density. The sol-gel process was used to synthesize supported lanthanum strontium manganate (LSM) electrodes separated by a YSZ electrolyte. The LSM solution was made by mixing strontium nitrate, lanthanum chloride, and manganese acetate solutions. The LSM layers were sintered but were porous. After the membranes were assembled by successive layering and sintering, the membranes and completed fuel cells were characterized using TGA, XRD, FE-SEM, a gas pressurization technique, and electrochemical testing. The YSZ membrane exhibited a stable tetragonal crystal phase and formed a triple phase boundary (TPB) with the cathode. The three phases are the electrode, the electrolyte, and air. Electrochemical testing showed successful membrane development. Although oxygen production was not measured

  20. Design Insights for Tuning the Electrocatalytic Activity of Perovskite Oxides for the Oxygen Evolution Reaction

    SciTech Connect

    Malkhandi, S; Trinh, P; Manohar, AK; Manivannan, A; Balasubramanian, M; Prakash, GKS; Narayanan, SR

    2015-04-16

    Rechargeable metal-air batteries and water electrolyzers based on aqueous alkaline electrolytes hold the potential to be sustainable solutions to address the challenge of storing large amounts of electrical energy generated from solar and wind resources. For these batteries and electrolyzers to be economically viable, it is essential to have efficient, durable, and inexpensive electrocatalysts for the oxygen evolution reaction. In this article, we describe new insights for predicting and tuning the activity of inexpensive transition metal oxides for designing efficient and inexpensive electrocatalysts. We have focused on understanding the factors determining the electrocatalytic activity for oxygen evolution in a strong alkaline medium. To this end, we have conducted a systematic investigation of nanophase calcium-doped lanthanum cobalt manganese oxide, an example of a mixed metal oxide that can be tuned for its electrocatalytic activity by varying the transition metal composition. Using X-ray absorption spectroscopy (XANES), X-ray photoelectron spectroscopy (XPS), electrochemical polarization experiments, and analysis of mechanisms, we have identified the key determinants of electrocatalytic activity. We have found that the Tafel slopes are determined by the oxidation states and the bond energy of the surface intermediates of Mn-OH and Co-OH bonds while the catalytic activity increased with the average d-electron occupancy of the sigma* orbital of the M-OH bond. We anticipate that such understanding will be very useful in predicting the behavior of other transition metal oxide catalysts.

  1. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    NASA Astrophysics Data System (ADS)

    Yan, Wei; He, Hao; Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-01

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca2+ release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  2. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    SciTech Connect

    Yan, Wei; He, Hao Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-24

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca{sup 2+} release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  3. Swim Pressure: Stress Generation in Active Matter

    NASA Astrophysics Data System (ADS)

    Takatori, S. C.; Yan, W.; Brady, J. F.

    2014-07-01

    We discover a new contribution to the pressure (or stress) exerted by a suspension of self-propelled bodies. Through their self-motion, all active matter systems generate a unique swim pressure that is entirely athermal in origin. The origin of the swim pressure is based upon the notion that an active body would swim away in space unless confined by boundaries—this confinement pressure is precisely the swim pressure. Here we give the micromechanical basis for the swim stress and use this new perspective to study self-assembly and phase separation in active soft matter. The swim pressure gives rise to a nonequilibrium equation of state for active matter with pressure-volume phase diagrams that resemble a van der Waals loop from equilibrium gas-liquid coexistence. Theoretical predictions are corroborated by Brownian dynamics simulations. Our new swim stress perspective can help analyze and exploit a wide class of active soft matter, from swimming bacteria to catalytic nanobots to molecular motors that activate the cellular cytoskeleton.

  4. Swim pressure: stress generation in active matter.

    PubMed

    Takatori, S C; Yan, W; Brady, J F

    2014-07-11

    We discover a new contribution to the pressure (or stress) exerted by a suspension of self-propelled bodies. Through their self-motion, all active matter systems generate a unique swim pressure that is entirely athermal in origin. The origin of the swim pressure is based upon the notion that an active body would swim away in space unless confined by boundaries-this confinement pressure is precisely the swim pressure. Here we give the micromechanical basis for the swim stress and use this new perspective to study self-assembly and phase separation in active soft matter. The swim pressure gives rise to a nonequilibrium equation of state for active matter with pressure-volume phase diagrams that resemble a van der Waals loop from equilibrium gas-liquid coexistence. Theoretical predictions are corroborated by Brownian dynamics simulations. Our new swim stress perspective can help analyze and exploit a wide class of active soft matter, from swimming bacteria to catalytic nanobots to molecular motors that activate the cellular cytoskeleton.

  5. UVB Dependence of Quantum Dot Reactive Oxygen Species Generation in Common Skin Cell Models.

    PubMed

    Mortensen, Luke J; Faulknor, Renea; Ravichandran, Supriya; Zheng, Hong; DeLouise, Lisa A

    2015-09-01

    Studies have shown that UVB can slightly increase the penetration of nanoparticles through skin and significantly alter skin cell biology, thus it is important to understand if and how UVB may impact subsequent nanoparticle skin cell interactions. The research presented herein evaluates the effect of UVB on quantum dot (QD) uptake and reactive oxygen species (ROS) generation in primary keratinocytes, primary melanocytes, and related cell lines. QD exposure induced cell type dependent ROS responses increased by pre-exposing cells to UVB and correlated with the level of QD uptake. Our results suggest that keratinocytes may be at greater risk for QD induced ROS generation than melanocytes, and raise awareness about the differential cellular effects that topically applied nanomaterials may have on UVB exposed skin.

  6. Symbiotic lactobacilli stimulate gut epithelial proliferation via Nox-mediated generation of reactive oxygen species.

    PubMed

    Jones, Rheinallt M; Luo, Liping; Ardita, Courtney S; Richardson, Arena N; Kwon, Young Man; Mercante, Jeffrey W; Alam, Ashfaqul; Gates, Cymone L; Wu, Huixia; Swanson, Phillip A; Lambeth, J David; Denning, Patricia W; Neish, Andrew S

    2013-11-27

    The resident prokaryotic microbiota of the metazoan gut elicits profound effects on the growth and development of the intestine. However, the molecular mechanisms of symbiotic prokaryotic-eukaryotic cross-talk in the gut are largely unknown. It is increasingly recognized that physiologically generated reactive oxygen species (ROS) function as signalling secondary messengers that influence cellular proliferation and differentiation in a variety of biological systems. Here, we report that commensal bacteria, particularly members of the genus Lactobacillus, can stimulate NADPH oxidase 1 (Nox1)-dependent ROS generation and consequent cellular proliferation in intestinal stem cells upon initial ingestion into the murine or Drosophila intestine. Our data identify and highlight a highly conserved mechanism that symbiotic microorganisms utilize in eukaryotic growth and development. Additionally, the work suggests that specific redox-mediated functions may be assigned to specific bacterial taxa and may contribute to the identification of microbes with probiotic potential.

  7. Symbiotic lactobacilli stimulate gut epithelial proliferation via Nox-mediated generation of reactive oxygen species

    PubMed Central

    Jones, Rheinallt M; Luo, Liping; Ardita, Courtney S; Richardson, Arena N; Kwon, Young Man; Mercante, Jeffrey W; Alam, Ashfaqul; Gates, Cymone L; Wu, Huixia; Swanson, Phillip A; Lambeth, J David; Denning, Patricia W; Neish, Andrew S

    2013-01-01

    The resident prokaryotic microbiota of the metazoan gut elicits profound effects on the growth and development of the intestine. However, the molecular mechanisms of symbiotic prokaryotic–eukaryotic cross-talk in the gut are largely unknown. It is increasingly recognized that physiologically generated reactive oxygen species (ROS) function as signalling secondary messengers that influence cellular proliferation and differentiation in a variety of biological systems. Here, we report that commensal bacteria, particularly members of the genus Lactobacillus, can stimulate NADPH oxidase 1 (Nox1)-dependent ROS generation and consequent cellular proliferation in intestinal stem cells upon initial ingestion into the murine or Drosophila intestine. Our data identify and highlight a highly conserved mechanism that symbiotic microorganisms utilize in eukaryotic growth and development. Additionally, the work suggests that specific redox-mediated functions may be assigned to specific bacterial taxa and may contribute to the identification of microbes with probiotic potential. PMID:24141879

  8. Direct imaging of singlet oxygen luminescence generated in blood vessels during photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Lin, Lisheng; Lin, Huiyun; Chen, Defu; Chen, Longchao; Wang, Min; Xie, Shusen; Gu, Ying; Wilson, Brian C.; Li, Buhong

    2014-05-01

    Singlet oxygen (1O2) is commonly recognized to be a major phototoxic component for inducing the biological damage during photodynamic therapy (PDT). In this study, a novel configuration of a thermoelectrically-cooled near-infrared sensitive InGaAs camera was developed for imaging of photodynamically-generated 1O2 luminescence. The validation of 1O2 luminescence images for solution samples was performed with the model photosensitizer Rose Bengal (RB). Images of 1O2 luminescence generated in blood vessels in vivo in a well-controlled dorsal skinfold window chamber model were also recorded during PDT. This study demonstrated the capacity of the newly-developed imaging system for imaging of 1O2 luminescence, and the first reported images of 1O2 luminescence in blood vessels in vivo. This system has potential for elucidating the mechanisms of vascular targeted PDT.

  9. UVB Dependence of Quantum Dot Reactive Oxygen Species Generation in Common Skin Cell Models.

    PubMed

    Mortensen, Luke J; Faulknor, Renea; Ravichandran, Supriya; Zheng, Hong; DeLouise, Lisa A

    2015-09-01

    Studies have shown that UVB can slightly increase the penetration of nanoparticles through skin and significantly alter skin cell biology, thus it is important to understand if and how UVB may impact subsequent nanoparticle skin cell interactions. The research presented herein evaluates the effect of UVB on quantum dot (QD) uptake and reactive oxygen species (ROS) generation in primary keratinocytes, primary melanocytes, and related cell lines. QD exposure induced cell type dependent ROS responses increased by pre-exposing cells to UVB and correlated with the level of QD uptake. Our results suggest that keratinocytes may be at greater risk for QD induced ROS generation than melanocytes, and raise awareness about the differential cellular effects that topically applied nanomaterials may have on UVB exposed skin. PMID:26485933

  10. Solid polymer electrolyte water electrolysis system development. [to generate oxygen for manned space station applications

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Solid polymer electrolyte technology used in a water electrolysis system (WES) to generate oxygen and hydrogen for manned space station applications was investigated. A four-man rated, low pressure breadboard water electrolysis system with the necessary instrumentation and controls was fabricated and tested. A six man rated, high pressure, high temperature, advanced preprototype WES was developed. This configuration included the design and development of an advanced water electrolysis module, capable of operation at 400 psig and 200 F, and a dynamic phase separator/pump in place of a passive phase separator design. Evaluation of this system demonstrated the goal of safe, unattended automated operation at high pressure and high temperature with an accumulated gas generation time of over 1000 hours.

  11. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency.

    PubMed

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-01-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases. PMID:27527403

  12. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency

    PubMed Central

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-01-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases. PMID:27527403

  13. Generating Singlet Oxygen Bubbles: A New Mechanism for Gas-Liquid Oxidations in Water

    PubMed Central

    Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

    2012-01-01

    Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (1Δg)] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiber-optic receptacles loaded with 150-μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O2 gas to the reactor chambers. In the presence of O2, singlet oxygen was generated by illuminating the sensitizer particles with 669-nm light from an optical fiber coupled to the top of the reactor. The generated 1O2 was transported through the membrane by the O2 stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (either 9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, and N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that 1O2 transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow, it arose only from 1O2-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves 1O2 mass transfer and solvation, where smaller bubbles provide better penetration of 1O2 into the flowing stream due to higher surface-to-volume contact between the probe molecules and 1O2. PMID:22260325

  14. The mechanism of cell-damaging reactive oxygen generation by colloidal fullerenes.

    PubMed

    Markovic, Zoran; Todorovic-Markovic, Biljana; Kleut, Duska; Nikolic, Nadezda; Vranjes-Djuric, Sanja; Misirkic, Maja; Vucicevic, Ljubica; Janjetovic, Kristina; Isakovic, Aleksandra; Harhaji, Ljubica; Babic-Stojic, Branka; Dramicanin, Miroslav; Trajkovic, Vladimir

    2007-12-01

    Because of the ability to induce cell death in certain conditions, the fullerenes (C(60)) are potential anticancer and toxic agents. The colloidal suspension of crystalline C(60) (nano-C(60), nC(60)) is extremely toxic, but the mechanisms of its cytotoxicity are not completely understood. By combining experimental analysis and mathematical modelling, we investigate the requirements for the reactive oxygen species (ROS)-mediated cytotoxicity of different nC(60) suspensions, prepared by solvent exchange method in tetrahydrofuran (THF/nC(60)) and ethanol (EtOH/nC(60)), or by extended mixing in water (aqu/nC(60)). With regard to their capacity to generate ROS and cause mitochondrial depolarization followed by necrotic cell death, the nC(60) suspensions are ranked in the following order: THF/nC(60)>EtOH/nC(60)>aqu/nC(60). Mathematical modelling of singlet oxygen ((1)O(2)) generation indicates that the (1)O(2)-quenching power (THF/nC(60)

  15. Berberine-induced apoptosis in human prostate cancer cells is initiated by reactive oxygen species generation

    SciTech Connect

    Meeran, Syed M.; Katiyar, Suchitra; Katiyar, Santosh K.

    2008-05-15

    Phytochemicals show promise as potential chemopreventive or chemotherapeutic agents against various cancers. Here we report the chemotherapeutic effects of berberine, a phytochemical, on human prostate cancer cells. The treatment of human prostate cancer cells (PC-3) with berberine induced dose-dependent apoptosis but this effect of berberine was not seen in non-neoplastic human prostate epithelial cells (PWR-1E). Berberine-induced apoptosis was associated with the disruption of the mitochondrial membrane potential, release of apoptogenic molecules (cytochrome c and Smac/DIABLO) from mitochondria and cleavage of caspase-9,-3 and PARP proteins. This effect of berberine on prostate cancer cells was initiated by the generation of reactive oxygen species (ROS) irrespective of their androgen responsiveness, and the generation of ROS was through the increased induction of xanthine oxidase. Treatment of cells with allopurinol, an inhibitor of xanthine oxidase, inhibited berberine-induced oxidative stress in cancer cells. Berberine-induced apoptosis was blocked in the presence of antioxidant, N-acetylcysteine, through the prevention of disruption of mitochondrial membrane potential and subsequently release of cytochrome c and Smac/DIABLO. In conclusion, the present study reveals that the berberine-mediated cell death of human prostate cancer cells is regulated by reactive oxygen species, and therefore suggests that berberine may be considered for further studies as a promising therapeutic candidate for prostate cancer.

  16. Oxygen dependency of one-electron reactions generating ascorbate radicals and hydrogen peroxide from ascorbic acid.

    PubMed

    Boatright, William L

    2016-04-01

    The effect of oxygen on the two separate one-electron reactions involved in the oxidation of ascorbic acid was investigated. The rate of ascorbate radical (Asc(-)) formation (and stability) was strongly dependent on the presence of oxygen. A product of ascorbic acid oxidation was measurable levels of hydrogen peroxide, as high as 32.5 μM from 100 μM ascorbic acid. Evidence for a feedback mechanism where hydrogen peroxide generated during the oxidation of ascorbic acid accelerates further oxidation of ascorbic acid is also presented. The second one-electron oxidation reaction of ascorbic acid leading to the disappearance of Asc(-) was also strongly inhibited in samples flushed with argon. In the range of 0.05-1.2 mM ascorbic acid, maximum levels of measurable hydrogen peroxide were achieved with an initial concentration of 0.2 mM ascorbic acid. Hydrogen peroxide generation was greatly diminished at ascorbic acid levels of 0.8 mM or above.

  17. Cellular Metabolic Activity and the Oxygen and Hydrogen Stable Isotope Composition of Intracellular Water and Metabolites

    NASA Astrophysics Data System (ADS)

    Kreuzer-Martin, H. W.; Hegg, E. L.

    2008-12-01

    Intracellular water is an important pool of oxygen and hydrogen atoms for biosynthesis. Intracellular water is usually assumed to be isotopically identical to extracellular water, but an unexpected experimental result caused us to question this assumption. Heme O isolated from Escherichia coli cells grown in 95% H218O contained only a fraction of the theoretical value of labeled oxygen at a position where the O atom was known to be derived from water. In fact, fewer than half of the oxygen atoms were labeled. In an effort to explain this surprising result, we developed a method to determine the isotope ratios of intracellular water in cultured cells. The results of our experiments showed that during active growth, up to 70% of the oxygen atoms and 50% of the hydrogen atoms in the intracellular water of E. coli are generated during metabolism and can be isotopically distinct from extracellular water. The fraction of isotopically distinct atoms was substantially less in stationary phase and chilled cells, consistent with our hypothesis that less metabolically-generated water would be present in cells with lower metabolic activity. Our results were consistent with and explained the result of the heme O labeling experiment. Only about 40% of the O atoms on the heme O molecule were labeled because, presumably, only about 40% of the water inside the cells was 18O water that had diffused in from the culture medium. The rest of the intracellular water contained 16O atoms derived from either nutrients or atmospheric oxygen. To test whether we could also detect metabolically-derived hydrogen atoms in cellular constituents, we isolated fatty acids from log-phase and stationary phase E. coli and determined the H isotope ratios of individual fatty acids. The results of these experiments showed that environmental water contributed more H atoms to fatty acids isolated in stationary phase than to the same fatty acids isolated from log-phase cells. Stable isotope analyses of

  18. Active Ageing: Intergenerational Relationships and Social Generativity.

    PubMed

    Rossi, Giovanna; Boccacin, Lucia; Bramanti, Donatella; Meda, Stefania G

    2014-01-01

    This contribution is a reflection on the concept of active ageing from the perspective of relational sociology. At the same time, it offers practical implications and outlines possible future courses of action, in the face of demographic and relational scenarios rapidly changing, and the challenges that each day people of all generations are called to cope with. Active ageing is quite a recent concept and indicates an attitude towards ageing that enhances the quality of life as people become older. The goal of active ageing is to enable people to realise their potential for physical, social and mental well-being and to participate in social life also in the last stage of the life cycle. In this phase, the presence of a network of support, security and care adequate to the possible onset of problems and criticalities is crucial. Relational sociology frames the phenomenon of an ageing population in a dense network of social relations, primarily at the level of family and community. For this reason, as supported by the most recent sociological literature and evidence from studies conducted in Italy and abroad (cf. SHARE), it is extremely important to investigate the link between active ageing, intergenerational orientation (solidarity and exchanges) and practices of prosociality (i.e. engagement in third-sector activities and volunteering in later life).

  19. A mutation in the mitochondrial protein UQCRB promotes angiogenesis through the generation of mitochondrial reactive oxygen species

    SciTech Connect

    Chang, Junghwa; Jung, Hye Jin; Jeong, Seung Hun; Kim, Hyoung Kyu; Han, Jin; Kwon, Ho Jeong

    2014-12-12

    Highlights: • We constructed mitochondrial protein UQCRB mutant stable cell lines on the basis of a human case report. • These mutant cell lines exhibit pro-angiogenic activity with enhanced VEGF expression. • Proliferation of mutant cell lines was regulated by UQCRB inhibitors. • UQCRB may have a functional role in angiogenesis. - Abstract: Ubiquinol-cytochrome c reductase binding protein (UQCRB) is one of the subunits of mitochondrial complex III and is a target protein of the natural anti-angiogenic small molecule terpestacin. Previously, the biological role of UQCRB was thought to be limited to the maintenance of complex III. However, the identification and validation of UQCRB as a target protein of terpestacin enabled the role of UQCRB in oxygen sensing and angiogenesis to be elucidated. To explore the biological role of this protein further, UQCRB mutant stable cell lines were generated on the basis of a human case report. We demonstrated that these cell lines exhibited glycolytic and pro-angiogenic activities via mitochondrial reactive oxygen species (mROS)-mediated HIF1 signal transduction. Furthermore, a morphological abnormality in mitochondria was detected in UQCRB mutant stable cell lines. In addition, the proliferative effect of the UQCRB mutants was significantly regulated by the UQCRB inhibitors terpestacin and A1938. Collectively, these results provide a molecular basis for UQCRB-related biological processes and reveal potential key roles of UQCRB in angiogenesis and mitochondria-mediated metabolic disorders.

  20. Xanthohumol induces generation of reactive oxygen species and triggers apoptosis through inhibition of mitochondrial electron transfer chain complex I.

    PubMed

    Zhang, Bo; Chu, Wei; Wei, Peng; Liu, Ying; Wei, Taotao

    2015-12-01

    Xanthohumol is a prenylflavonoid extracted from hops (Humulus lupulus). It possesses anti-cancer and anti-inflammatory activities in vitro and in vivo, and offers therapeutic benefits for treatment of metabolic syndromes. However, the precise mechanisms underlying its pharmacological effects remain to be elucidated, together with its cellular target. Here, we provide evidence that xanthohumol directly interacts with the mitochondrial electron transfer chain complex I (NADH dehydrogenase), inhibits the oxidative phosphorylation, triggers the production of reactive oxygen species, and induces apoptosis. In addition, we show that as a result of the inhibition of the mitochondrial oxidative phosphorylation, xanthohumol exposure causes a rapid decrease of mitochondrial transmembrane potential. Furthermore, we showed that xanthohumol up-regulates the glycolytic capacity in cells, and thus compensates cellular ATP generation. Dissection of the multiple steps of aerobic respiration by extracellular flux assays revealed that xanthohumol specifically inhibits the activity of mitochondrial complex I, but had little effect on that of complex II, III and IV. Inhibition of complex I by xanthohumol caused the overproduction of reactive oxygen species, which are responsible for the induction of apoptosis in cancer cells. We also found that isoxanthohumol, the structural isomer of xanthohumol, is inactive to cells, suggesting that the reactive 2-hydroxyl group of xanthohumol is crucial for its targeting to the mitochondrial complex I. Together, the remodeling of cell metabolism revealed here has therapeutic potential for the use of xanthohumol.

  1. Mechanisms of Rapid Reactive Oxygen Species Generation in Response to Cytosolic Ca2+ or Zn2+ Loads in Cortical Neurons

    PubMed Central

    Clausen, Aaron; McClanahan, Taylor; Ji, Sung G.; Weiss, John H.

    2013-01-01

    Excessive “excitotoxic” accumulation of Ca2+ and Zn2+ within neurons contributes to neurodegeneration in pathological conditions including ischemia. Putative early targets of these ions, both of which are linked to increased reactive oxygen species (ROS) generation, are mitochondria and the cytosolic enzyme, NADPH oxidase (NOX). The present study uses primary cortical neuronal cultures to examine respective contributions of mitochondria and NOX to ROS generation in response to Ca2+ or Zn2+ loading. Induction of rapid cytosolic accumulation of either Ca2+ (via NMDA exposure) or Zn2+ (via Zn2+/Pyrithione exposure in 0 Ca2+) caused sharp cytosolic rises in these ions, as well as a strong and rapid increase in ROS generation. Inhibition of NOX activation significantly reduced the Ca2+-induced ROS production with little effect on the Zn2+- triggered ROS generation. Conversely, dissipation of the mitochondrial electrochemical gradient increased the cytosolic Ca2+ or Zn2+ rises caused by these exposures, consistent with inhibition of mitochondrial uptake of these ions. However, such disruption of mitochondrial function markedly suppressed the Zn2+-triggered ROS, while partially attenuating the Ca2+-triggered ROS. Furthermore, block of the mitochondrial Ca2+ uniporter (MCU), through which Zn2+ as well as Ca2+ can enter the mitochondrial matrix, substantially diminished Zn2+ triggered ROS production, suggesting that the ROS generation occurs specifically in response to Zn2+ entry into mitochondria. Finally, in the presence of the sulfhydryl-oxidizing agent 2,2'-dithiodipyridine, which impairs Zn2+ binding to cytosolic metalloproteins, far lower Zn2+ exposures were able to induce mitochondrial Zn2+ uptake and consequent ROS generation. Thus, whereas rapid acute accumulation of Zn2+ and Ca2+ each can trigger injurious ROS generation, Zn2+ entry into mitochondria via the MCU may do so with particular potency. This may be of particular relevance to conditions like ischemia

  2. Mechanisms of rapid reactive oxygen species generation in response to cytosolic Ca2+ or Zn2+ loads in cortical neurons.

    PubMed

    Clausen, Aaron; McClanahan, Taylor; Ji, Sung G; Weiss, John H

    2013-01-01

    Excessive "excitotoxic" accumulation of Ca(2+) and Zn(2+) within neurons contributes to neurodegeneration in pathological conditions including ischemia. Putative early targets of these ions, both of which are linked to increased reactive oxygen species (ROS) generation, are mitochondria and the cytosolic enzyme, NADPH oxidase (NOX). The present study uses primary cortical neuronal cultures to examine respective contributions of mitochondria and NOX to ROS generation in response to Ca(2+) or Zn(2+) loading. Induction of rapid cytosolic accumulation of either Ca(2+) (via NMDA exposure) or Zn(2+) (via Zn(2+)/Pyrithione exposure in 0 Ca(2+)) caused sharp cytosolic rises in these ions, as well as a strong and rapid increase in ROS generation. Inhibition of NOX activation significantly reduced the Ca(2+)-induced ROS production with little effect on the Zn(2+)- triggered ROS generation. Conversely, dissipation of the mitochondrial electrochemical gradient increased the cytosolic Ca(2+) or Zn(2+) rises caused by these exposures, consistent with inhibition of mitochondrial uptake of these ions. However, such disruption of mitochondrial function markedly suppressed the Zn(2+)-triggered ROS, while partially attenuating the Ca(2+)-triggered ROS. Furthermore, block of the mitochondrial Ca(2+) uniporter (MCU), through which Zn(2+) as well as Ca(2+) can enter the mitochondrial matrix, substantially diminished Zn(2+) triggered ROS production, suggesting that the ROS generation occurs specifically in response to Zn(2+) entry into mitochondria. Finally, in the presence of the sulfhydryl-oxidizing agent 2,2'-dithiodipyridine, which impairs Zn(2+) binding to cytosolic metalloproteins, far lower Zn(2+) exposures were able to induce mitochondrial Zn(2+) uptake and consequent ROS generation. Thus, whereas rapid acute accumulation of Zn(2+) and Ca(2+) each can trigger injurious ROS generation, Zn(2+) entry into mitochondria via the MCU may do so with particular potency. This may be of

  3. Tuning the surface oxygen concentration of {111} surrounded ceria nanocrystals for enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Younis, Adnan; Chu, Dewei; Kaneti, Yusuf Valentino; Li, Sean

    2015-12-01

    For oxide semiconductors, the morphology, particle size and oxygen vacancies are usually considered as key influential parameters for photocatalytic degradation of organic pollutants/dyes. It is widely accepted that cation doping not only modifies their phase and microstructures but also introduces variations in oxygen vacancy concentration. Herein, we report the fabrication of sub-10 nm sized pure and indium doped CeO2 nanocrystals (NCs) via a facile, green hydrothermal method for the investigation of photocatalytic activities. X-ray diffraction and transmission electron microscopy were employed to examine the crystal phase and morphology of the as-prepared nanocrystals. Raman and X-ray photoelectron spectroscopy techniques were implemented to investigate the presence and variations in oxygen vacancy concentration in un-doped and indium doped CeO2 nanocrystals. The photocatalytic activity results revealed that 10 at% doping is the optimal indium doping level to demonstrate superior dye removal efficiency (~40%) over un-doped and doped CeO2 NCs. Moreover, the 10% In-doped CeO2 nanocrystals expressed excellent cycling stability and superior photocatalytic performance toward other dye pollutants. Finally, on the basis of our findings, a possible photocatalytic mechanism in which indium doping can generate more surface oxygen vacancies in the ceria lattice which delay the electron-hole recombination rates, thus increasing the lifetime of electron-hole separation for enhanced photocatalytic performances was proposed.For oxide semiconductors, the morphology, particle size and oxygen vacancies are usually considered as key influential parameters for photocatalytic degradation of organic pollutants/dyes. It is widely accepted that cation doping not only modifies their phase and microstructures but also introduces variations in oxygen vacancy concentration. Herein, we report the fabrication of sub-10 nm sized pure and indium doped CeO2 nanocrystals (NCs) via a facile

  4. Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution

    PubMed Central

    Bergmann, Arno; Martinez-Moreno, Elias; Teschner, Detre; Chernev, Petko; Gliech, Manuel; de Araújo, Jorge Ferreira; Reier, Tobias; Dau, Holger; Strasser, Peter

    2015-01-01

    Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co3+/4+ ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions. PMID:26456525

  5. Redox cycling and generation of reactive oxygen species in commercial infant formulas.

    PubMed

    Boatright, William L; Crum, Andrea D

    2016-04-01

    Three nationally prominent commercial powdered infant formulas generated hydrogen peroxide, ranging from 10.46 to 11.62 μM, when prepared according to the manufacturer's instructions. Treating infant formulas with the chelating agent diethylene triamine pentaacetic acid (DTPA) significantly reduced H2O2 generation. In contrast, the addition of disodium ethylenediaminetetraacetic acid (EDTA) elevated the level of H2O2 generated in the same infant formulas by approximately 3- to 4-fold above the untreated infant formulas. The infant formulas contained ascorbate radicals ranging from about 138 nM to 40 nM. Treatment with catalase reduced the ascorbate radical contents by as much as 67%. Treatment with DTPA further reduced ascorbate radical signals to below quantifiable levels in most samples, further implicating the involvement of transition metal redox cycling in reactive oxygen species (ROS) formation. Supportive evidence of the generation of ROS is provided using luminol-enhanced luminescence (LEL) in both model mixtures of ascorbic acid and in commercial infant formulas. PMID:26593482

  6. Redox cycling and generation of reactive oxygen species in commercial infant formulas.

    PubMed

    Boatright, William L; Crum, Andrea D

    2016-04-01

    Three nationally prominent commercial powdered infant formulas generated hydrogen peroxide, ranging from 10.46 to 11.62 μM, when prepared according to the manufacturer's instructions. Treating infant formulas with the chelating agent diethylene triamine pentaacetic acid (DTPA) significantly reduced H2O2 generation. In contrast, the addition of disodium ethylenediaminetetraacetic acid (EDTA) elevated the level of H2O2 generated in the same infant formulas by approximately 3- to 4-fold above the untreated infant formulas. The infant formulas contained ascorbate radicals ranging from about 138 nM to 40 nM. Treatment with catalase reduced the ascorbate radical contents by as much as 67%. Treatment with DTPA further reduced ascorbate radical signals to below quantifiable levels in most samples, further implicating the involvement of transition metal redox cycling in reactive oxygen species (ROS) formation. Supportive evidence of the generation of ROS is provided using luminol-enhanced luminescence (LEL) in both model mixtures of ascorbic acid and in commercial infant formulas.

  7. Mesoscale Activity and Nitrogen-loss in the Oxygen Minimum Zone of the Eastern Tropical Pacific During ENSO Conditions

    NASA Astrophysics Data System (ADS)

    Montes, I.; Dewitte, B.; Gutknecht, E.; Paulmier, A.; Dadou, I.; Oschlies, A.; Garçon, V. C.

    2015-12-01

    The Eastern Tropical South Pacific encompasses one of the most extended Oxygen Minimum zones, which is mainly maintained by a combination of sluggish circulation and high biological productivity in the surface layer leading to elevate organic matter decomposition consuming dissolved oxygen. Low-oxygen areas are important not only for macroorganisms that cannot survive in oxygen-poor conditions, but also because of special biogeochemical processes occurring at low oxygen concentrations. In particular, a large fraction of oceanic nitrogen-loss occurs in these areas via anaerobic microbial processes. These include denitrification and axammox that both lead to a net loss of fixed nitrogen once oxygen concentrations have fallen below some threshold of a few umol/l. Recently it has been found that eddies may act as nitrogen-loss hotspots, possibly by shielding enclosed water parcels from lateral mixing with better ventilated oxygen-richer waters outside the eddies. Here we used a regional coupled biogeochemical model to investigate the relationship between eddies and the nitrogen-loss. We also investigate the mechanisms responsible for the generation of eddies and for possible modulations of eddy activity on interannual timescales, in particular during cold and warm phases of the El Nino Southern Oscillation.

  8. Liquid-liquid reaction of hydrogen peroxide and sodium hypochlorite for the production of singlet oxygen in a centrifugal flow singlet oxygen generator

    SciTech Connect

    Cui Rongrong; Deng Liezheng; Shi Wenbo; Yang Heping; Sha Guohe; Zhang Cunhao

    2011-02-28

    An attempt is made to produce gas-phase singlet oxygen O{sub 2}(a{sup 1{Delta}}{sub g}) in a liquid-liquid reaction between acidic hydrogen peroxide (AHP) and sodium hypochlorite (NaOCl). The attempt arises from the fact that basic hydrogen peroxide (BHP) has long been the prime source for producing singlet delta oxygen through its reaction with chlorine. However, BHP suffers from the defect of being unstable during storage. Exploratory experiments were performed in a centrifugal flow singlet oxygen generator (CF-SOG) with two streams of solutions, AHP and NaOCl, mixed in a slit nozzle and then injected into the arc-shaped concavity in the CF-SOG to form a rotating liquid flow with a remarkable centrifugal force. With the help of this centrifugal force, the product of the O{sub 2}({sup 1{Delta}}) reaction was quickly separated from the liquid phase. The gas-phase O{sub 2}({sup 1{Delta}}) was detected via the spectrum of O{sub 2}({sup 1{Delta}}) cooperative dimolecular emission with a CCD spectrograph. Experimental results show that it is feasible to produce gas-phase O{sub 2}({sup 1{Delta}}) from the AHP + NaOCl reaction, and the stronger the acidity, the more efficient the O{sub 2}({sup 1{Delta}}) production. However, since in the AHP + NaOCl reaction, Cl{sub 2} unavoidably appears as a byproduct, its catalytic action on the decomposition of H{sub 2}O{sub 2} into ground-state O{sub 2} remains a major obstacle to utilising the AHP + NaOCl reaction in producing gas-phase O{sub 2}({sup 1{Delta}}). Qualitative interpretation shows that the AHP + NaOCl reaction is virtually the reaction of interaction of molecular H{sub 2}O{sub 2} with molecular HOCl, its mechanism being analogous to that of reaction of BHP with Cl{sub 2}, where HOOCl is the key intermediate. It is difficult to form the intermediate HOOCl via the H{sub 2}O{sub 2} + NaOCl reaction in a basic medium, thus gas-phase O{sub 2}({sup 1{Delta}}) cannot be obtained in appreciable quantities. (active media)

  9. Antimicrobial mechanism based on H2O2 generation at oxygen vacancies in ZnO crystals.

    PubMed

    Xu, Xiaoling; Chen, Dan; Yi, Zhigang; Jiang, Man; Wang, Li; Zhou, Zuowan; Fan, Ximei; Wang, Yong; Hui, David

    2013-05-01

    The production of H2O2 has been taken for a crucial reason for antimicrobial activity of ZnO without light irradiation. However, how the H2O2 generates in ZnO suspension is not clear. In the present work, the comparatively detections on three kinds of ZnO, tetrapod-like ZnO whiskers (t-ZnO), nanosized ZnO particles (n-ZnO), and microsized ZnO particles (m-ZnO), showed that the antimicrobial activity of ZnO was correlated with its production of H2O2. Oxygen vacancy (V(O)) in the surface layer of ZnO crystals determined by XPS indicated that it was quite probably involved in the production of H2O2. To validate the role of V(O), the concentration of VO in t-ZnO was adjusted by heat-treatment under the atmospheres of H2, vacuum, and O2, respectively, and the H2O2 production and antimicrobial effect were detected. Consistently, the t-ZnO treated in H2, which possessed the most V(O) in its crystal, produced the most H2O2 and displayed the best antimicrobial activity. These results provide the basis for developing a more detailed mechanism for H2O2 generation catalyzed by ZnO and for taking greater advantage of this type of antimicrobial agent.

  10. UV-B-Induced PR-1 Accumulation Is Mediated by Active Oxygen Species.

    PubMed

    Green, R.; Fluhr, R.

    1995-02-01

    Depletion of the stratospheric ozone layer may result in an increase in the levels of potentially harmful UV-B radiation reaching the surface of the earth. We have found that UV-B is a potent inducer of the plant pathogenesis-related protein PR-1 in tobacco leaves. UV-B fluences required for PR-1 accumulation are similar to those of other UV-B-induced responses. The UV-B-induced PR-1 accumulation was confined precisely to the irradiated area of the leaf but displayed no leaf tissue specificity. A study of some of the possible components of the signal transduction pathway between UV-B and PR-1 induction showed that photosynthetic processes are not essential, and photoreversible DNA damage is not involved. Antioxidants and cycloheximide were able to block the induction of PR-1 by UV-B, and treatment of leaves with a generator of reactive oxygen resulted in the accumulation of PR-1 protein. These results demonstrate an absolute requirement for active oxygen species and protein synthesis in this UV-B signal transduction pathway. In contrast, we also show that other elicitors, notably salicylic acid, are able to elicit PR-1 via nonreactive oxygen species-requiring pathways.

  11. Mountain cedar pollen induces IgE-independent mast cell degranulation, IL-4 production, and intracellular reactive oxygen species generation

    PubMed Central

    Endo, Shuichiro; Hochman, Daniel J.; Midoro-Horiuti, Terumi; Goldblum, Randall M.; Brooks, Edward G.

    2011-01-01

    Cedar pollens cause severe allergic disease throughout the world. We have previously characterized allergenic pollen glycoproteins from mountain cedar (Juniperus ashei) that bind to allergen-specific immunoglobulin E (IgE). In the present report, we investigated an alternative pathway of mast cell activation by mountain cedar pollen extract through IgE-independent mechanisms. We show that mountain cedar pollen directly induces mast cell serotonin and IL-4 release and enhances release induced by IgE cross-linking. Concomitant with mediator release, high levels of intracellular reactive oxygen species (ROS) were generated, and both ROS and serotonin release were inhibited by anti-oxidants. These findings suggest that alternative mechanisms exist whereby pollen exposure enhances allergic inflammatory mediator release through mechanisms that involve ROS. These mechanisms have the potential for enhancing the allergenic potency of pollens. PMID:21944563

  12. Growth enhancement and gene expression of Arabidopsis thaliana irradiated with active oxygen species

    NASA Astrophysics Data System (ADS)

    Watanabe, Satoshi; Ono, Reoto; Hayashi, Nobuya; Shiratani, Masaharu; Tashiro, Kosuke; Kuhara, Satoru; Inoue, Asami; Yasuda, Kaori; Hagiwara, Hiroko

    2016-07-01

    The characteristics of plant growth enhancement effect and the mechanism of the enhancement induced by plasma irradiation are investigated using various active species in plasma. Active oxygen species in oxygen plasma are effective for growth enhancement of plants. DNA microarray analysis of Arabidopsis thaliana indicates that the genes coding proteins that counter oxidative stresses by eliminating active oxygen species are expressed at significantly high levels. The size of plant cells increases owing to oxygen plasma irradiation. The increases in gene expression levels and cell size suggest that the increase in the expression level of the expansin protein is essential for plant growth enhancement phenomena.

  13. Lysosomal membrane permeabilization: Carbon nanohorn-induced reactive oxygen species generation and toxicity by this neglected mechanism

    SciTech Connect

    Yang, Mei; Zhang, Minfang; Tahara, Yoshio; Chechetka, Svetlana; Miyako, Eijiro; Iijima, Sumio; Yudasaka, Masako

    2014-10-01

    Understanding the molecular mechanisms responsible for the cytotoxic effects of carbon nanomaterials is important for their future biomedical applications. Carbon nanotubular materials induce the generation of reactive oxygen species (ROS), which causes cell death; however, the exact details of this process are still unclear. Here, we identify a mechanism of ROS generation that is involved in the apoptosis of RAW264.7 macrophages caused by excess uptake of carbon nanohorns (CNHs), a typical type of carbon nanotubule. CNH accumulated in the lysosomes, where they induced lysosomal membrane permeabilization (LMP) and the subsequent release of lysosomal proteases, such as cathepsins, which in turn caused mitochondrial dysfunction and triggered the generation of ROS in the mitochondria. The nicotinamide adenine dinucleotide phosphate oxidase was not directly involved in CNH-related ROS production, and the ROS generation cannot be regulated by mitochondrial electron transport chain. ROS fed back to amplify the mitochondrial dysfunction, leading to the subsequent activation of caspases and cell apoptosis. Carbon nanotubules commonly accumulate in the lysosomes after internalization in cells; however, lysosomal dysfunction has not attracted much attention in toxicity studies of these materials. These results suggest that LMP, a neglected mechanism, may be the primary reason for carbon nanotubule toxicity. - Highlights: • We clarify an apoptotic mechanism of RAW264.7 cells caused by carbon nanohorns. • In the meantime, the mechanism of CNH-induced ROS generation is identified. • LMP is the initial factor of CNH-induced ROS generation and cell death. • Cathepsins work as mediators that connect LMP and mitochondrial dysfunction.

  14. Generation of Reactive Oxygen and Anti-Oxidant Species by Hydrodynamically-Stressed Suspensions of Morinda citrofolia

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The generation of reactive oxygen species (ROS) by plant cell suspension cultures, in response to the imposition of both biotic and abiotic stress, is well-documented. This study investigated the generation of hydrogen peroxide by hydrodynamically-stressed cultures of Morinda citrifolia, over a 5-ho...

  15. Singlet oxygen generation from the decomposition of alpha-linolenic acid hydroperoxide by cytochrome c and lactoperoxidase.

    PubMed

    Sun, Shuna; Bao, Zhijuan; Ma, Huimin; Zhang, Deqing; Zheng, Xiaoping

    2007-06-01

    Generation of singlet oxygen is first investigated in the decomposition of polyunsaturated lipid peroxide, alpha-linolenic acid hydroperoxide (LAOOH), by heme-proteins such as cytochrome c and lactoperoxidase. Chemiluminescence and electron spin resonance methods are used to confirm the singlet oxygen generation and quantify its yield. Decomposition products of LAOOH are characterized by HPLC-ESI-MS, which suggests that singlet oxygen is produced via the decomposition of a linear tetraoxide intermediate (Russell's mechanism). Free radicals formed in the decomposition are also identified by the electron spin resonance technique, and the results show that peroxyl, alkyl, and epoxyalkyl radicals are involved. The changes of cytochrome c and lactoperoxidase in the reaction are monitored by UV-visible spectroscopy, revealing the action of a monoelectronic and two-electronic oxidation for cytochrome c and lactoperoxidase, respectively. These results suggest that cytochrome c causes a homolytic reaction of LAOOH, generating alkoxyl radical and then peroxyl radical, which in turn releases singlet oxygen following the Russell mechanism, whereas lactoperoxidase leads to a heterolytic reaction of LAOOH, and the resulting ferryl porphyryl radical of lactoperoxidase abstracts the hydrogen atom from LAOOH to give peroxyl radical and then singlet oxygen. This observation would be important for a better understanding of the damage mechanism of cell membrane or lipoprotein by singlet oxygen and various radicals generated in the peroxidation and decomposition of lipids induced by heme-proteins.

  16. Effect of Structural Transformation of Nanoparticulate Zero-Valent Iron on Generation of Reactive Oxygen Species.

    PubMed

    He, Di; Ma, Jinxing; Collins, Richard N; Waite, T David

    2016-04-01

    While it has been recognized for some time that addition of nanoparticlate zerovalent iron (nZVI) to oxygen-containing water results in both corrosion of Fe(0) and oxidation of contaminants, there is limited understanding of either the relationship between transformation of nZVI and oxidant formation or the factors controlling the lifetime and extent of oxidant production. Using Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, we show that while nZVI particles are transformed to ferrihydrite then lepidocrocite in less than 2 h, oxidant generation continues for up to 10 h. The major products (Fe(II) and H2O2) of the reaction of nZVI with oxygenated water are associated, for the most part, with the surface of particles present with these surface-associated Fenton reagents inducing oxidation of a target compound (in this study, (14)C-labeled formate). Effective oxidation of formate only occurred after formation of iron oxides on the nZVI surface with the initial formation of high surface area ferrihydrite facilitating rapid and extensive adsorption of formate with colocation of this target compound and surface-associated Fe(II) and H2O2 apparently critical to formate oxidation. Ongoing formate oxidation long after nZVI is consumed combined with the relatively slow consumption of Fe(II) and H2O2 suggest that these reactants are regenerated during the nZVI-initiated heterogeneous Fenton process. PMID:26958862

  17. Chemical mechanisms of the toxicological properties of nanomaterials: generation of intracellular reactive oxygen species.

    PubMed

    Yan, Liang; Gu, Zhanjun; Zhao, Yuliang

    2013-10-01

    As more and more nanomaterials with novel physicochemical properties or new functions are created and used in different research fields and industrial sectors, the scientific and public concerns about their toxic effects on human health and the environment are also growing quickly. In the past decade, the study of the toxicological properties of nanomaterials/nanoparticles has formed a new research field: nanotoxicology. However, most of the data published relate to toxicological phenomena and there is less understanding of the underlying mechanism for nanomaterial-induced toxicity. Nanomaterial-induced reactive oxygen species (ROS) play a key role in cellular and tissue toxicity. Herein, we classify the pathways for intracellular ROS production by nanomaterials into 1) the direct generation of ROS through nanomaterial-catalyzed free-radical reactions in cells, and 2) the indirect generation of ROS through disturbing the inherent biochemical equilibria in cells. We also discuss the chemical mechanisms associated with above pathways of intracellular ROS generation, from the viewpoint of the high reactivity of atoms on the nanosurface. We hope to aid in the understanding of the chemical origin of nanotoxicity to provide new insights for chemical and material scientists for the rational design and creation of safer and greener nanomaterials.

  18. Generation of reactive oxygen species in cyanobacteria and green algae induced by allelochemicals of submerged macrophytes.

    PubMed

    Wang, Jing; Zhu, Junying; Liu, Shaoping; Liu, Biyun; Gao, Yunni; Wu, Zhenbin

    2011-10-01

    Inhibition of phytoplankton by allelochemicals released by submerged macrophytes is reported to be one of the mechanisms that maintain a clear-water state in shallow lakes. In order to elucidate this mechanism, the ability of six polyphenols and two long-chain fatty acids to induce the generation of reactive oxygen species (ROS) in phytoplankton was studied using the ROS sensitive probe 2',7'- dichlorodihydrofluorescein diacetate (DCFH-DA). The results showed that only (+)-catechin (CA) and pyrogallic acid (PA) could induce ROS formation in Microcystis aeruginosa and Pseudokirchneriella subcapitata. 25 mg L⁻¹ CA caused 1.2, 1.4 and 1.8 times increase of ROS levels in M. aeruginosa at 1, 2 and 4h exposure, respectively, and, correspondingly in P. subcapitata cells, these values were 3.7, 6.2 and 7.7, respectively. PA also significantly increased the levels of intracellular ROS in P. subcapitata (P < 0.01); however, significant ROS generation in M. aeruginosa was observed at only 4h exposure (P < 0.01). Light enhanced ROS generation in CA treated cells, but not in the cells treated with PA. CA and PA may act as redox cyclers after uptake by test organisms and produce ROS successively. These results suggest that the oxidative stress induced by the redox cycling property of allelochemicals may be one of the important causes for the inhibitory effect of some submerged macrophytes towards undesired phytoplankton in natural aquatic ecosystems. PMID:21757220

  19. Surface functionalization of titanium dioxide nanoparticles: Photo-stability and reactive oxygen species (ROS) generation

    NASA Astrophysics Data System (ADS)

    Louis, Kacie M.

    Metal oxide nanoparticles are becoming increasingly prevalent in society for applications of sunscreens, cosmetics, paints, biomedical imaging, and photovoltaics. Due to the increased surface area to volume ratio of nanoparticles compared to bulk materials, it is important to know the health and safety impacts of these materials. One mechanism of toxicity of nominally "safe" materials such as TiO 2 is through the photocatalytic generation of reactive oxygen species (ROS). ROS production and ligand degradation can affect the bioavailability of these particles in aqueous organisms. We have investigated ROS generation by functionalized TiO2 nanoparticles and its influence on aggregation and bioavailability and toxicity to zebrafish embryos/larvae. For these studies we investigated anatase TiO2 nanoparticles. For application purposes and solution stability, the TiO2 nanoparticles were functionalized with a variety of ligands such as citrate, 3,4-dihydroxybenzaldehyde, and ascorbate. We quantitatively examined the amount of ROS produced in aqueous solution using fluorescent probes and see that more ROS is produced under UV light than in the dark control. Our measurements show that TiO2 toxicity reaches a maximum for nanoparticles with smaller diameters, and is correlated with surface area dependent changes in ROS generation. In an effort to reduce toxicity through control of the surface and surface ligands, we synthesized anatase nanoparticles of different sizes, functionalized them with different ligands, and examined the resulting ROS generation and ligand stability. Using a modular ligand containing a hydrophobic inner region and a hydrophilic outer region, we synthesized water-stable nanoparticles, via two different chemical reactions, having much-reduced ROS generation and thus reduced toxicity. These results suggest new strategies for making safer nanoparticles while still retaining their desired properties. We also examine the degradation of the different ligands

  20. P38 activation is more important than ERK activation in lung injury induced by prolonged hyperbaric oxygen.

    PubMed

    Ma, Jun; Fang, Yi-Qun; Gu, Ai-Mei; Wang, Fang-Fang; Zhang, Shi; Li, Kai-Cheng

    2013-01-01

    Prolonged exposure to hyperbaric oxygen can cause pulmonary and nerve system toxicity. Although hyperbaric oxygen treatment has been used for a broad spectrum of ailments, the mechanisms of prolonged hyperbaric oxygen-induced lung injury are not fully understood. The purpose of the present work was to investigate the roles of ERK, p38, and caspase-3 in rat lung tissue exposed to hyperbaric oxygen at 2.3 atmospheres absolute (atm abs) for two, six and 10 hours. The results showed that the ERK and p38 were phosphorylated at two hours and reached a peak at six hours into exposure to hyperbaric oxygen. While the phosphorylation level of ERK decreased, p38 remained at a high level of activation at 10 hours. The activation of ERK and p38 was down-regulated when rats were exposed to normoxic hyperbaric nitrogen for 10 hours. However, caspase-3 was activated at six hours and 10 hours into exposure to hyperbaric oxygen. These results demonstrated different changes of activation of ERK and p38 during lung injury induced by prolonged exposure to hyperbaric oxygen. The time course changes of activated caspase-3 were similar to the process of p38 activation upon exposure to hyperbaric oxygen. In this way, activation of p38, not ERK, seems to be a mechanism associated with prolonged hyperbaric oxygen-induced lung injury.

  1. Activation of the JAK-STAT pathway by reactive oxygen species.

    PubMed

    Simon, A R; Rai, U; Fanburg, B L; Cochran, B H

    1998-12-01

    Reactive oxygen species (ROS) play an important role in the pathogenesis of many human diseases, including the acute respiratory distress syndrome, Parkinson's disease, pulmonary fibrosis, and Alzheimer's disease. In mammalian cells, several genes known to be induced during the immediate early response to growth factors, including the protooncogenes c-fos and c-myc, have also been shown to be induced by ROS. We show that members of the STAT family of transcription factors, including STAT1 and STAT3, are activated in fibroblasts and A-431 carcinoma cells in response to H2O2. This activation occurs within 5 min, can be inhibited by antioxidants, and does not require protein synthesis. STAT activation in these cell lines is oxidant specific and does not occur in response to superoxide- or nitric oxide-generating stimuli. Buthionine sulfoximine, which depletes intracellular glutathione, also activates the STAT pathway. Moreover, H2O2 stimulates the activity of the known STAT kinases JAK2 and TYK2. Activation of STATs by platelet-derived growth factor (PDGF) is significantly inhibited by N-acetyl-L-cysteine and diphenylene iodonium, indicating that ROS production contributes to STAT activation in response to PDGF. These findings indicate that the JAK-STAT pathway responds to intracellular ROS and that PDGF uses ROS as a second messenger to regulate STAT activation.

  2. Auxin-induced reactive oxygen species production requires the activation of phosphatidylinositol 3-kinase.

    PubMed

    Joo, Jung Hee; Yoo, Ho Jung; Hwang, Inhwan; Lee, June Seung; Nam, Kyoung Hee; Bae, Yun Soo

    2005-02-14

    We recently reported that production of reactive oxygen species (ROS) is essential for auxin-induced gravitropic signaling. Here, we investigated the role of phosphatidylinositol 3-kinase and its product, PtdIns(3)P, in auxin-mediated ROS production and the root gravitropic response. Pretreatment with LY294002, an inhibitor of PtdIns 3-kinase activity, blocked auxin-mediated ROS generation, and reduced the sensitivity of root tissue to gravistimulation. The amount of PtdIns(3)P increased in response to auxin, and this effect was abolished by pretreatment with LY294002. In addition, sequestration of PtdIns(3)P by transient expression of the endosome binding domain in protoplasts abrogated IAA-induced ROS accumulation. These results indicate that activation of PtdIns 3-kinase and its product PtdIns(3)P are required for auxin-induced production of ROS and root gravitropism. PMID:15710420

  3. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation

    PubMed Central

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-01-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility. PMID:25105845

  4. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation.

    PubMed

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-01-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen ((1)O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce (1)O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of (1)O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

  5. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation

    NASA Astrophysics Data System (ADS)

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-08-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

  6. Tks5-dependent, Nox-mediated Generation of Reactive Oxygen Species is Necessary for Invadopodia Formation*

    PubMed Central

    Diaz, Begoña; Shani, Gidon; Pass, Ian; Anderson, Diana; Quintavalle, Manuela; Courtneidge, Sara A.

    2009-01-01

    Invadopodia are actin-rich membrane protrusions of cancer cells which facilitate pericellular proteolysis and invasive behavior. We show here that reactive oxygen species (ROS) generated by the NADPH oxidase (Nox) system are necessary for invadopodia formation and function. The invadopodia protein Tks5 is structurally related to p47phox, a Nox component in phagocytic cells. Knockdown of Tks5 reduces total ROS levels in cancer cells. Furthermore, Tks5 and p22phox can associate with each other, suggesting that Tks5 is part of the Nox complex. Tyrosine phosphorylation of Tks5 and Tks4, but not other Src substrates, is reduced by Nox inhibition. We propose that Tks5 facilitates the production of ROS necessary for invadopodia formation, and that in turn ROS modulates Tks5 tyrosine phosphorylation in a positive feedback loop. PMID:19755709

  7. Au nanorods modulated NIR fluorescence and singlet oxygen generation of water soluble dendritic zinc phthalocyanine.

    PubMed

    Zhou, Xuefei; He, Xiaohong; Wei, Shiliang; Jia, Kun; Liu, Xiaobo

    2016-11-15

    A novel cyano-terminated zinc phthalocyanine (ZnPc-CN) exhibiting visible near infrared (vis-NIR) emitting around 690nm in N,N-dimethylformamide (DMF) solvent has been synthesized. Furthermore, the peripheral cyano groups of newly synthesized zinc phthalocyanine were hydrolyzed in strong basic solution, leading to water soluble carboxylated zinc phthalocyanine (ZnPc-COOH) with completely quenched fluorescence in aqueous solution. Interestingly, we found that the NIR fluorescence of aqueous ZnPc-COOH was dramatically recovered in the presence of gold nanorods (Au NR), which was due to the alternation of ZnPc-COOH molecules self-assembling via electrostatic interaction between cetyltrimethylammonium bromide (CTAB) on the surface of Au NR and peripheral carboxyl of ZnPc-COOH. In addition, ZnPc-COOH/Au NR conjugates demonstrated an improved singlet oxygen generation, which could be served as potential bioimaging probe and photosensitizer for photodynamic therapy. PMID:27505278

  8. Hemoglobin fructation promotes heme degradation through the generation of endogenous reactive oxygen species

    NASA Astrophysics Data System (ADS)

    Goodarzi, M.; Moosavi-Movahedi, A. A.; Habibi-Rezaei, M.; Shourian, M.; Ghourchian, H.; Ahmad, F.; Farhadi, M.; Saboury, A. A.; Sheibani, N.

    2014-09-01

    Protein glycation is a cascade of nonenzymatic reactions between reducing sugars and amino groups of proteins. It is referred to as fructation when the reducing monosaccharide is fructose. Some potential mechanisms have been suggested for the generation of reactive oxygen species (ROS) by protein glycation reactions in the presence of glucose. In this state, glucose autoxidation, ketoamine, and oxidative advance glycation end products (AGEs) formation are considered as major sources of ROS and perhaps heme degradation during hemoglobin glycation. However, whether fructose mediated glycation produces ROS and heme degradation is unknown. Here we report that ROS (H2O2) production occurred during hemoglobin fructation in vitro using chemiluminescence methods. The enhanced heme exposure and degradation were determined using UV-Vis and fluorescence spectrophotometry. Following accumulation of ROS, heme degradation products were accumulated reaching a plateau along with the detected ROS. Thus, fructose may make a significant contribution to the production of ROS, glycation of proteins, and heme degradation during diabetes.

  9. Vessel constriction correlated with local singlet oxygen generation during vascular targeted photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Lin, Lisheng; Li, Yirong; Zhang, Jinde; Tan, Zou; Chen, Defu; Xie, Shusen; Gu, Ying; Li, Buhong

    2014-11-01

    In this study, the vessel constriction was measured as a biological indicator of acute vascular response after vascular targeted photodynamic therapy (V-PDT). During V-PDT treatment, the near-infrared (NIR) singlet oxygen (1O2) luminescence at 1270 nm generated in blood vessels in a dorsal skinfold window chamber model in vivo was directly monitored using a custom built high-sensitive NIR imaging system. In order to compare the acute vascular response, various irradiances with the same light dose were utilized for treatments. The obtained results show that the complete arteriole constriction occurred frequently, while some of the larger veins were constricted partially. For the vessels that have significant constriction after V-PDT, our preliminary data suggest that the vasoconstriction in the selected ROIs are roughly correlated with the local cumulative 1O2 luminescence intensities. This study implies that the 1O2 luminescence dosimetry maybe also effective for evaluating V-PDT efficiency.

  10. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation.

    PubMed

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-01-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen ((1)O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce (1)O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of (1)O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility. PMID:25105845

  11. Colony Rheology: Active Arthropods Generate Flows

    NASA Astrophysics Data System (ADS)

    Daniels, Karen; Mann, Michael; Charbonneau, Patrick

    2015-03-01

    Hydrodynamic-like flows are observed in biological systems as varied as bacteria, insects, birds, fish, and mammals. Both the phenomenology (e.g. front instabilities, milling motions) and the interaction types (hydrodynamic, direct contact, psychological, excluded-volume) strongly vary between systems, but a question common to all of them is to understand the role of particle-scale fluctuations in controlling large-scale rheological behaviors. We will address these questions through experiments on a new system, Tyrolichus casei (cheese mites), which live in dense, self-mixing colonies composed of a mixture of living mites and inert flour/detritus. In experiments performed in a Hele-Shaw geometry, we observe that the rheology of a colony is strongly dependent on the relative concentration of active and inactive particles. In addition to spreading flows, we also observe that the system can generate convective circulation and auto-compaction.

  12. Generating passive NIR images from active LIDAR

    NASA Astrophysics Data System (ADS)

    Hagstrom, Shea; Broadwater, Joshua

    2016-05-01

    Many modern LIDAR platforms contain an integrated RGB camera for capturing contextual imagery. However, these RGB cameras do not collect a near-infrared (NIR) color channel, omitting information useful for many analytical purposes. This raises the question of whether LIDAR data, collected in the NIR, can be used as a substitute for an actual NIR image in this situation. Generating a LIDAR-based NIR image is potentially useful in situations where another source of NIR, such as satellite imagery, is not available. LIDAR is an active sensing system that operates very differently from a passive system, and thus requires additional processing and calibration to approximate the output of a passive instrument. We examine methods of approximating passive NIR images from LIDAR for real-world datasets, and assess differences with true NIR images.

  13. Ascorbic acid enhanced activation of oxygen by ferrous iron: A case of aerobic degradation of rhodamine B.

    PubMed

    Hou, Xiaojing; Shen, Wenjuan; Huang, Xiaopeng; Ai, Zhihui; Zhang, Lizhi

    2016-05-01

    Molecular oxygen activation by ferrous ions (Fe(II)) in aqueous solution could generate reactive oxygen species (ROS) with high oxidation potential via reaction between Fe(II) and oxygen molecules (Fe(II)/air), however, ROS yielded in the Fe(II)/air process is insufficient for removal of organic pollutants due to the irreversible ferric ions (Fe(III)) accumulation. In this study, we demonstrate that ascorbic acid (AA) could enhance ROS generation via oxygen activation by ferrous irons (AA/Fe(II)/air) and thus improve the degradation of rhodamine (RhB) significantly. It was found that the first-order aerobic degradation rate of RhB in the AA/Fe(II)/air process in the presence of ascorbic acid is more than 4 times that of the Fe(II)/Air system without adding ascorbic acid. The presence of ascorbic acid could relieve the accumulation of Fe(III) by reductive accelerating the Fe(III)/Fe(II) cycles, as well as lower the redox potential of Fe(III)/Fe(II) through chelating effect, leading to enhanced ROS generation for promoting RhB degradation. This study not only sheds light on the effect of ascorbic acid on aerobic Fe(II) oxidation, but also provides a green method for effective remediation of organic pollutants.

  14. Generation of Reactive Oxygen Species Contributes to the Development of Carbon Black Cytotoxicity to Vascular Cells

    PubMed Central

    Lee, Jong Gwan; Noh, Won Jun; Kim, Hwa

    2011-01-01

    Carbon black, a particulate form of pure elemental carbon, is an industrial chemical with the high potential of occupational exposure. Although the relationship between exposure to particulate matters (PM) and cardiovascular diseases is well established, the cardiovascular risk of carbon black has not been characterized clearly. In this study, the cytotoxicity of carbon black to vascular smooth muscle and endothelial cells were examined to investigate the potential vascular toxicity of carbon black. Carbon black with distinct particle size, N330 (primary size, 28~36 nm) and N990 (250~350 nm) were treated to A-10, rat aortic smooth muscle cells and human umbilical vein endothelial cell line, ECV304, and cell viability was assessed by lactate dehydrogenase (LDH) leakage assay. Treatment of carbon black N990 resulted in the significant reduction of viability in A-10 cells at 100 μg/ml, the highest concentration tested, while N330 failed to cause cell death. Cytotoxicity to ECV304 cells was induced only by N330 at higher concentration, 200 μg/ml, suggesting that ECV304 cells were relatively resistant to carbon black. Treatment of 100 μg/ml N990 led to the elevation of reactive oxygen species (ROS) detected by dichlorodihydrofluorescein (DCF) in A-10 cells. Pretreatment of antioxidants, N-acetylcysteine (NAC) and sulforaphane restored decreased viability of N990-treated A-10 cells, and N-acetylcysteine, but not sulforaphane, attenuated N990-induced ROS generation in A-10 cells. Taken together, present study shows that carbon black is cytotoxic to vascular cells, and the generation of reactive oxygen contributes to the development of cytotoxicity. ROS scavenging antioxidant could be a potential strategy to attenuate the toxicity induced by carbon black exposure. PMID:24278567

  15. A mutation in the mitochondrial protein UQCRB promotes angiogenesis through the generation of mitochondrial reactive oxygen species.

    PubMed

    Chang, Junghwa; Jung, Hye Jin; Jeong, Seung Hun; Kim, Hyoung Kyu; Han, Jin; Kwon, Ho Jeong

    2014-12-12

    Ubiquinol-cytochrome c reductase binding protein (UQCRB) is one of the subunits of mitochondrial complex III and is a target protein of the natural anti-angiogenic small molecule terpestacin. Previously, the biological role of UQCRB was thought to be limited to the maintenance of complex III. However, the identification and validation of UQCRB as a target protein of terpestacin enabled the role of UQCRB in oxygen sensing and angiogenesis to be elucidated. To explore the biological role of this protein further, UQCRB mutant stable cell lines were generated on the basis of a human case report. We demonstrated that these cell lines exhibited glycolytic and pro-angiogenic activities via mitochondrial reactive oxygen species (mROS)-mediated HIF1 signal transduction. Furthermore, a morphological abnormality in mitochondria was detected in UQCRB mutant stable cell lines. In addition, the proliferative effect of the UQCRB mutants was significantly regulated by the UQCRB inhibitors terpestacin and A1938. Collectively, these results provide a molecular basis for UQCRB-related biological processes and reveal potential key roles of UQCRB in angiogenesis and mitochondria-mediated metabolic disorders.

  16. From Oxygen Generation to Metals Production: In Situ Resource Utilization by Molten Oxide Electrolysis

    NASA Technical Reports Server (NTRS)

    Khetpal, Deepak; Ducret, Andrew C.; Sadoway, Donald R.

    2003-01-01

    For the exploration of other bodies in the solar system, electrochemical processing is arguably the most versatile technology for conversion of local resources into usable commodities: by electrolysis one can, in principle, produce (1) breathable oxygen, (2) silicon for the fabrication of solar cells, (3) various reactive metals for use as electrodes in advanced storage batteries, and (4) structural metals such as steel and aluminum. Even so, to date there has been no sustained effort to develop such processes, in part due to the inadequacy of the database. The objective here is to identify chemistries capable of sustaining molten oxide electrolysis in the cited applications and to examine the behavior of laboratory-scale cells designed to generate oxygen and to produce metal. The basic research includes the study of the underlying high-temperature physical chemistry of oxide melts representative of lunar regolith and of Martian soil. To move beyond empirical approaches to process development, the thermodynamic and transport properties of oxide melts are being studied to help set the limits of composition and temperature for the processing trials conducted in laboratory-scale electrolysis cells. The goal of this investigation is to deliver a working prototype cell that can use lunar regolith and Martian soil to produce breathable oxygen along with metal by-product. Additionally, the process can be generalized to permit adaptation to accommodate different feedstock chemistries, such as those that will be encountered on other bodies in the solar system. The expected results of this research include: (1) the identification of appropriate electrolyte chemistries; (2) the selection of candidate anode and cathode materials compatible with electrolytes named above; and (3) performance data from a laboratory-scale cell producing oxygen and metal. On the strength of these results it should be possible to assess the technical viability of molten oxide electrolysis for in

  17. Newly synthesized bis-benzimidazole compound 8 induces apoptosis, autophagy and reactive oxygen species generation in HeLa cells.

    PubMed

    Chu, Naying; Yao, Guodong; Liu, Yuan; Cheng, Maosheng; Ikejima, Takashi

    2016-09-01

    Compound 8 (C8) is a newly synthesized bis-benzimidazole derivative and exerts significant anti-tumor activity in vitro. Previous studies demonstrated that C8 induced apoptosis and autophagy in human promyelocytic leukemia HL60 cells. However, cytotoxicity study on human peripheral blood mononuclear cells (hPBMC) showed that C8 exhibited less toxicity in normal cells. In this study, the molecular mechanism of C8 on human cervical carcinoma HeLa cells was investigated. The results showed that C8 inhibited the growth of HeLa cells and triggered both apoptotic and autophagic cell death. Subsequent experiment also indicated that reactive oxygen species (ROS) generation was induced in C8-treated HeLa cells. Since ROS scavenger decreased the ratio of apoptotic and autophagic cells, ROS generation contributed to C8-induced apoptosis and autophagy. Furthermore, inhibitors of apoptosis and autophagy also reduced ROS generation, respectively. Autophagy inhibition increased cell growth compared to C8-treated group and attenuated apoptotic cell death, indicating that C8-induced autophagy promoted apoptosis for cell death. However, the percentage of autophagic cells was enhanced when limiting apoptosis process. Taken together, C8 induced ROS-mediated apoptosis and autophagy in HeLa cells, autophagy promoted apoptosis but the former was antagonized by the latter. The data also gave us a new perspective on the anti-tumor effect of C8. PMID:27497983

  18. Effect of triiodothyronine on reactive oxygen species generation by leukocytes, indices of oxidative damage, and antioxidant reserve.

    PubMed

    Magsino, C H; Hamouda, W; Ghanim, H; Browne, R; Aljada, A; Dandona, P

    2000-06-01

    We have examined the effect of short-term triiodothyronine (T3) administration on reactive oxygen species (ROS) generation by leukocytes in 9 euthyroid subjects. At a dose of 60 microg/d orally for 7 days, T3 induced a significant increase in ROS generation by mononuclear cells (MNCs) from 183 +/- 102 mV at baseline to 313 +/- 111 mV on the seventh day (P < .02), and by polymorphonuclear leukocytes (PMNLs) from 195 +/- 94 mV at baseline to 302 +/- 104 mV on the seventh day (P < .02). There was also a significant increase in meta-tyrosine (P < .001) and ortho-tyrosine (P < .001), known indices of oxidative damage to proteins and amino acids. However, there was no increase in plasma thiobarbituric acid-reactive substances (TBARS), an index of oxidative damage to lipids, and in the level of carbonylated proteins, a less sensitive index to assess protein oxidation. There was no decrease in the level of antioxidants such as alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin. The stimulatory effect on ROS generation may reflect a generalized increase in metabolic activity or may be a specific effect on NADPH oxidase in leukocyte membranes. The absence of a significant change in TBARS, carbonylated proteins, alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin may reflect the short duration of the increased ROS load.

  19. Newly synthesized bis-benzimidazole compound 8 induces apoptosis, autophagy and reactive oxygen species generation in HeLa cells.

    PubMed

    Chu, Naying; Yao, Guodong; Liu, Yuan; Cheng, Maosheng; Ikejima, Takashi

    2016-09-01

    Compound 8 (C8) is a newly synthesized bis-benzimidazole derivative and exerts significant anti-tumor activity in vitro. Previous studies demonstrated that C8 induced apoptosis and autophagy in human promyelocytic leukemia HL60 cells. However, cytotoxicity study on human peripheral blood mononuclear cells (hPBMC) showed that C8 exhibited less toxicity in normal cells. In this study, the molecular mechanism of C8 on human cervical carcinoma HeLa cells was investigated. The results showed that C8 inhibited the growth of HeLa cells and triggered both apoptotic and autophagic cell death. Subsequent experiment also indicated that reactive oxygen species (ROS) generation was induced in C8-treated HeLa cells. Since ROS scavenger decreased the ratio of apoptotic and autophagic cells, ROS generation contributed to C8-induced apoptosis and autophagy. Furthermore, inhibitors of apoptosis and autophagy also reduced ROS generation, respectively. Autophagy inhibition increased cell growth compared to C8-treated group and attenuated apoptotic cell death, indicating that C8-induced autophagy promoted apoptosis for cell death. However, the percentage of autophagic cells was enhanced when limiting apoptosis process. Taken together, C8 induced ROS-mediated apoptosis and autophagy in HeLa cells, autophagy promoted apoptosis but the former was antagonized by the latter. The data also gave us a new perspective on the anti-tumor effect of C8.

  20. AMPK is involved in mediation of erythropoietin influence on metabolic activity and reactive oxygen species production in white adipocytes.

    PubMed

    Wang, Li; Di, Lijun; Noguchi, Constance Tom

    2014-09-01

    Erythropoietin, discovered for its indispensable role during erythropoiesis, has been used in therapy for selected red blood cell disorders in erythropoietin-deficient patients. The biological activities of erythropoietin have been found in animal models to extend to non-erythroid tissues due to the expression of erythropoietin receptor. We previously demonstrated that erythropoietin promotes metabolic activity and white adipocytes browning to increase mitochondrial function and energy expenditure via peroxisome proliferator-activated receptor alpha and Sirtuin1. Here we report that AMP-activated protein kinase was activated by erythropoietin possibly via Ca(2+)/calmodulin-dependent protein kinase kinase in adipocytes as well as in white adipose tissue from diet induced obese mice. Erythropoietin increased cellular nicotinamide adenine dinucleotide via increased AMP-activated protein kinase activity, possibly leading to Sirtuin1 activation. AMP-activated protein kinase knock down reduced erythropoietin mediated increase in cellular oxidative function including the increased oxygen consumption rate, fatty acid utilization and induction of key metabolic genes. Under hypoxia, adipocytes were found to generate more reactive oxygen species, and erythropoietin reduced the reactive oxygen species and increased antioxidant gene expression, suggesting that erythropoietin may provide protection from oxidative stress in adipocytes. Erythropoietin also reversed increased nicotinamide adenine dinucleotide by hypoxia via increased AMP-activated protein kinase. Additionally, AMP-activated protein kinase is found to be involved in erythropoietin stimulated increase in oxygen consumption rate, fatty acid oxidation and mitochondrial gene expression. AMP-activated protein kinase knock down impaired erythropoietin stimulated increases in antioxidant gene expression. Collectively, our findings identify the AMP-activated protein kinase involvement in erythropoietin signaling in

  1. Transient Thermoelectric Generator: An Active Load Story

    NASA Astrophysics Data System (ADS)

    Stockholm, J. G.; Goupil, C.; Maussion, P.; Ouerdane, H.

    2015-06-01

    Under stationary conditions, the optimization of maximum power output and efficiency of thermoelectric generators (TEG) is a well-known subject. Use of a finite-time thermodynamics (FTT) approach to the description of TEGs has demonstrated that there exists a closed feedback effect between the output electrical load value and the entering heat current. From the practical point of view, this effect is strongly evidenced by the use of direct current (DC-to-DC) converters as active loads. Both transient conditions and FTT contribute to a complex landscape of the optimization of the power and efficiencies of a TEG. It has been claimed that the use of inductive load may lead to a strong enhancement of the efficiency, and the frequency response of a TEG as a band-pass filter has also been recently reported. We consider these results using a classical linear Onsager approach of a TEG operating under transient conditions. We show that a trans-admittance may be defined as a coupling element between the input and the output, leading to the observed electric-to-thermal feedback. We discuss recent experiments on a TEG connected to an active load, which is reported to boast an efficiency exceeding the usual stationary DC thermoelectric efficiency.

  2. Molecular dioxygen enters the active site of 12/15-lipoxygenase via dynamic oxygen access channels.

    PubMed

    Saam, Jan; Ivanov, Igor; Walther, Matthias; Holzhütter, Hermann-Georg; Kuhn, Hartmut

    2007-08-14

    Cells contain numerous enzymes that use molecular oxygen for their reactions. Often, their active sites are buried deeply inside the protein, which raises the question whether there are specific access channels guiding oxygen to the site of catalysis. Choosing 12/15-lipoxygenase as a typical example for such oxygen-dependent enzymes, we determined the oxygen distribution within the protein and defined potential routes for oxygen access. For this purpose, we have applied an integrated strategy of structural modeling, molecular dynamics simulations, site-directed mutagenesis, and kinetic measurements. First, we computed the 3D free-energy distribution for oxygen, which led to identification of four oxygen channels in the protein. All channels connect the protein surface with a region of high oxygen affinity at the active site. This region is localized opposite to the nonheme iron providing a structural explanation for the reaction specificity of this lipoxygenase isoform. The catalytically most relevant path can be obstructed by L367F exchange, which leads to a strongly increased Michaelis constant for oxygen. The blocking mechanism is explained in detail by reordering the hydrogen-bonding network of water molecules. Our results provide strong evidence that the main route for oxygen access to the active site of the enzyme follows a channel formed by transiently interconnected cavities whereby the opening and closure are governed by side chain dynamics. PMID:17675410

  3. Effects of cocaine and its oxidative metabolites on mitochondrial respiration and generation of reactive oxygen species.

    PubMed

    Boess, F; Ndikum-Moffor, F M; Boelsterli, U A; Roberts, S M

    2000-09-01

    Cocaine is capable of producing severe hepatocellular necrosis in laboratory animals and humans. The mechanism of cocaine hepatotoxicity is not well understood, but appears to result from the actions of one or more N-oxidative metabolites of cocaine. Mitochondria have been proposed as critical cellular targets for cocaine toxicity, and previous studies have found depressed mitochondrial respiration and increased mitochondrial generation of reactive oxygen species (ROS) in animals treated with cocaine. To examine the potential role of cocaine N-oxidative metabolites in these effects, mitochondrial respiration and ROS generation were examined in isolated mouse mitochondria treated with cocaine and its N-oxidative metabolites-norcocaine, N-hydroxynorcocaine, and norcocaine nitroxide. Cocaine, in concentrations of 0.25 or 0.5 mM, had no effect on state 3 respiration, state 4 respiration, respiratory control ratio (RCR), or ADP/O ratio. Norcocaine (0.5 mM) inhibited state 3 respiration, and N-hydroxynorcocaine (0.5 mM) inhibited both state 3 and state 4 respiration. Norcocaine nitroxide had the greatest effect on mitochondrial respiration; the lower concentration (0.25 mM) completely inhibited both state 3 and state 4 respiration. Preincubation of mitochondria with cocaine or metabolites increased the inhibitory effect of norcocaine and N-hydroxynorcocaine, but not cocaine. Cocaine, norcocaine, and N-hydroxynorcocaine (0.1 mM) had no effect on ROS generation during state 3 respiration, and cocaine and norcocaine decreased ROS generation under state 4 conditions. Norcocaine nitroxide interfered with the fluorescence ROS assay and could not be assessed. The results suggest that the effects of cocaine on mitochondrial respiration are due to its N-oxidative metabolites. Inhibition of mitochondrial respiration by the N-oxidative metabolites of cocaine may be the underlying cause for observed ATP depletion and subsequent cell death.

  4. [Influence of salicylic and succinic acids on formation of active oxygen forms in wheat coleoptiles].

    PubMed

    Kolupaiev, Iu Ie; Iastreb, T O; Shvidenko, M V; Karpets', Iu V

    2011-01-01

    The comparative study of influence of exogenous salicylic (SaA) and succinic (SuA) acids on the production of reactive oxygen species by isolated wheat coleoptiles has been provided. Under the action of both acids the increase of generation of superoxide anion-radical (O2(.-)) was observed. This increase was partially suppressed by treatment of coleoptiles with inhibitors of peroxidase (salicylhydroxamic acid) and NADP H-oxidase (imidazole and alpha-naphthol). The increase of hydrogen peroxide content, activity of peroxidase and superoxide dismutase (SOD) was registered under the influence of SaA and SuA; catalase activity did not change essentially. The treatment of coleoptiles with the indicated acids resulted in the increase of their resistance to abiotic stress (damaging heating, 43 +/- 0,1 degrees C, 10 min). The conclusion is made, that the increase of O2(.-) generation in wheat coleoptiles under the action of SaA and SuA is related, probably, to the increase of apoplast peroxidase and NADP.H-oxidase activity, and the rise of H2O2 content is related to the growth of SOD activity. These enzymatic systems are involved in the induction of plant cells protective reactions to the hyperthermia. PMID:22276431

  5. Macrophage function in alloxan diabetic mice: expression of adhesion molecules, generation of monokines and oxygen and NO radicals

    PubMed Central

    Ptak, W; Klimek, M; Bryniarski, K; Ptak, M; Majcher, P

    1998-01-01

    The increased incidence of bacterial and mycotic infections in poorly controlled diabetic patients or animals is frequently attributed to impaired activities of professional phagocytes (granulocytes, macrophages) in hypoinsulinaemic milieu. We measured production of monokines (IL-6 and tumour necrosis factor-alpha (TNF-α)), active NO and reactive oxygen intermediates (ROIs), as well as expression of several cell surface adhesion molecules (Mac-1, -2 and -3, intercellular adhesion molecule-1 (ICAM-1) and FcγRII), by thioglycollate medium-induced peritoneal macrophages of normoglycaemic and alloxan diabetic CBA/J mice (blood glucose level in the range 300 or 500 mg/dl). Macrophages of animals with moderate diabetes (300 mg/dl) produced significantly more IL-6 and TNF-α and ROIs than cells of control mice and showed an increased expression of all cell surface molecules, except Mac-3. NO/NO2 production was not affected. Administration of insulin restored enhanced values to normal levels, except for the production of ROIs which remained unusually high. We conclude that two separate mechanisms influence macrophage physiology in diabetes—lack of saturation of insulin receptors on macrophages and an indirect effect due to formation of advanced glycosylation endproducts (AGE) on their surfaces. The latter is possibly responsible for increased generation of ROIs, since it cannot be down-regulated by prolonged insulin treatment. How the increased activity of macrophages of moderately diabetic mice (enhanced production of proinflammatory monokines and oxygen radicals as well as expression of molecules) is related to their ability to kill bacteria is now under investigation. PMID:9764597

  6. Fast oxygen atom studies related to low Earth orbit activities

    NASA Astrophysics Data System (ADS)

    Caledonia, G. E.; Krech, R. H.; Holtzclaw, K. W.; Sonnenfroh, D.

    1993-06-01

    The technique of laser induced gas breakdown to develop a high flux pulsed source of fast oxygen atoms (v = 5 to 12 km/s) is considered. The technique is also used to produce high velocity beams of N/N2 mixtures and can be extended to produce beams of other species. The fast oxygen atoms are of particular current interest since this is the dominant atmospheric species encountered by spacecraft operating in Low Earth Orbit (LEO). The fast oxygen atom source has proven extremely versatile and is used to study a variety of gas-surface and gas-gas collision phenomena. The fast atom facility has reproducibly provided good comparison with LEO observations. Expanded programs involving material testing and measurement of O atom momentum and energy accommodation coefficients with surfaces are presently underway.

  7. Cytotoxicity and reactive oxygen species generation from aggregated carbon and carbonaceous nanoparticulate materials.

    PubMed

    Garza, Kristine M; Soto, Karla F; Murr, Lawrence E

    2008-01-01

    We have investigated the cytotoxicity and reactive oxygen species (ROS) generation for indoor and outdoor soots: candle, wood, diesel, tire, and natural gas burner soots--along with surrogate black carbon, various multiwall carbon nanotube aggregate materials, TiO2 (anatase) and chrysotile asbestos as reference materials. All soots were observed utilizing TEM and FESEM to be composed of aggregated, primary spherules (20-80 nm diameter) forming complex, branched fractal structures. These spherules were composed of intercalated, turbostratic arrangements of curved graphene fragments with varying concentrations ofpolycyclic aromatic hydrocarbon (PAH) isomers. In vitro cultures with an immortalized human lung epithelial carcinoma cell line (A549) treated with these materials showed decreased cell viability and variations in ROS production, with no correlations to PAH content. The data demonstrate that soots are cytotoxic and that cytotoxicity is not related to PAH content but is related to ROS generation, suggesting that soot induces cellular oxidative stress and that cell viability assays can be indicators of ROS production. PMID:18488419

  8. Generation of Reactive Oxygen Species via NOXa Is Important for Development and Pathogenicity of Mycosphaerella graminicola.

    PubMed

    Choi, Yoon-E; Lee, Changsu; Goodwin, Stephen B

    2016-03-01

    The ascomycete fungus Mycosphaerella graminicola (synonym Zymoseptoria tritici) is an important pathogen of wheat causing economically significant losses. The primary nutritional mode of this fungus is thought to be hemibiotrophic. This pathogenic lifestyle is associated with an early biotrophic stage of nutrient uptake followed by a necrotrophic stage aided possibly by production of a toxin or reactive oxygen species (ROS). In many other fungi, the genes CREA and AREA are important during the biotrophic stage of infection, while the NOXa gene product is important during necrotrophic growth. To test the hypothesis that these genes are important for pathogenicity of M. graminicola, we employed an over-expression strategy for the selected target genes CREA, AREA, and NOXa, which might function as regulators of nutrient acquisition or ROS generation. Increased expressions of CREA, AREA, and NOXa in M. graminicola were confirmed via quantitative real-time PCR and strains were subsequently assayed for pathogenicity. Among them, the NOXa over-expression strain, NO2, resulted in significantly increased virulence. Moreover, instead of the usual filamentous growth, we observed a predominance of yeast-like growth of NO2 which was correlated with ROS production. Our data indicate that ROS generation via NOXa is important to pathogenicity as well as development in M. graminicola. PMID:27103853

  9. Controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells using porphyrin conjugated nanoparticles.

    PubMed

    Lavado, Andrea S; Chauhan, Veeren M; Zen, Amer Alhaj; Giuntini, Francesca; Jones, D Rhodri E; Boyle, Ross W; Beeby, Andrew; Chan, Weng C; Aylott, Jonathan W

    2015-09-14

    Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(II) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(II) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn(II) porphyrin and high numbers of irradiations of excitation light were found to generate greater amounts of ROS. A novel dye, which is transformed into fluorescent 7-hydroxy-4-trifluoromethyl-coumarin in the presence of hydrogen peroxide, provided an indirect indicator for cumulative ROS production. The mitochondrial membrane potential was monitored to investigate the destructive effect of increased intracellular ROS production. Flow cytometric analysis of nanoparticle treated hMSCs suggested irradiation with excitation light signalled controlled apoptotic cell death, rather than uncontrolled necrotic cell death. Increased intracellular ROS production did not induce phenotypic changes in hMSC subcultures.

  10. BODIPY-doped silica nanoparticles with reduced dye leakage and enhanced singlet oxygen generation

    PubMed Central

    Wang, Zhuyuan; Hong, Xuehua; Zong, Shenfei; Tang, Changquan; Cui, Yiping; Zheng, Qingdong

    2015-01-01

    Photodynamic therapy (PDT) is a promising modality for cancer treatment. The essential element in PDT is the photosensitizer, which can be excited by light of a specific wavelength to generate cytotoxic oxygen species (ROS) capable of killing tumor cells. The effectiveness of PDT is limited in part by the low yield of ROS from existing photosensitizers and the unwanted side effects induced by the photosensitizers toward normal cells. Thus the design of nanoplatforms with enhanced PDT is highly desirable but remains challenging. Here, we developed a heavy atom (I) containing dipyrromethene boron difluoride (BODIPY) dye with a silylated functional group, which can be covalently incorporated into a silica matrix to form dye-doped nanoparticles. The incorporated heavy atoms can enhance the generation efficiency of ROS. Meanwhile, the covalently dye-encapsulated nanoparticles can significantly reduce dye leakage and subsequently reduce unwanted side effects. The nanoparticles were successfully taken up by various tumor cells and showed salient phototoxicity against these cells upon light irradiation, demonstrating promising applications in PDT. Moreover, the incorporated iodine atom can be replaced by a radiolabeled iodine atom (e.g., I-124, I-125). The resulting nanoparticles will be good contrast agents for positron emission tomography (PET) imaging with their PDT functionality retained. PMID:26211417

  11. Generation of reactive oxygen species mediates butein-induced apoptosis in neuroblastoma cells.

    PubMed

    Chen, Ya-Hui; Yeh, Chi-Wei; Lo, Hui-Chen; Su, Shih-Li; Hseu, You-Cheng; Hsu, Li-Sung

    2012-04-01

    Flavonoids exhibit chemopreventive and chemotherapeutic effects. Butein, a bioactive flavonoid isolated from numerous native plants, has been shown to induce apoptosis in human cancer cells. In the current study, the molecular mechanisms of butein action on cell proliferation and apoptosis of neuroblastoma cells were evaluated. Treatment with butein decreased the viability of Neuro-2A neuroblastoma cells in a dose- and time-dependent manner. The dose-dependent nature of butein-induced apoptosis was characterized by an increase in the sub-G1 phase population. Treatment with butein significantly increased intracellular reactive oxygen species (ROS)levels and reduced the Bcl-2/Bax ratio, triggering the cleavage of pro-caspase 3 and poly-(ADP-ribose) polymerase (PARP). Pre-treatment with the antioxidant agent, N-acetyl cysteine (NAC), blocks butein-induced ROS generation and cell death. NAC also recovers butein-induced apoptosis-related protein alteration. In conclusion, butein-triggered neuroblastoma cells undergo apoptosis via generation of ROS, alteration of the Bcl‑2/Bax ratio, and cleavage of pro-caspase 3 and PARP. Our results suggest that butein may serve as a potential therapeutic agent for the treatment of neuroblastoma.

  12. Ligation of Glycophorin A Generates Reactive Oxygen Species Leading to Decreased Red Blood Cell Function

    PubMed Central

    Khoory, Joseph; Estanislau, Jessica; Elkhal, Abdallah; Lazaar, Asmae; Melhorn, Mark I.; Brodsky, Abigail; Illigens, Ben; Hamachi, Itaru; Kurishita, Yasutaka; Ivanov, Alexander R.; Shevkoplyas, Sergey; Shapiro, Nathan I.; Ghiran, Ionita C.

    2016-01-01

    Acute, inflammatory conditions associated with dysregulated complement activation are characterized by significant increases in blood concentration of reactive oxygen species (ROS) and ATP. The mechanisms by which these molecules arise are not fully understood. In this study, using luminometric- and fluorescence-based methods, we show that ligation of glycophorin A (GPA) on human red blood cells (RBCs) results in a 2.1-fold, NADPH-oxidase-dependent increase in intracellular ROS that, in turn, trigger multiple downstream cascades leading to caspase-3 activation, ATP release, and increased band 3 phosphorylation. Functionally, using 2D microchannels to assess membrane deformability, GPS-ligated RBCs travel 33% slower than control RBCs, and lipid mobility was hindered by 10% using fluorescence recovery after photobleaching (FRAP). These outcomes were preventable by pretreating RBCs with cell-permeable ROS scavenger glutathione monoethyl ester (GSH-ME). Our results obtained in vitro using anti-GPA antibodies were validated using complement-altered RBCs isolated from control and septic patients. Our results suggest that during inflammatory conditions, circulating RBCs significantly contribute to capillary flow dysfunctions, and constitute an important but overlooked source of intravascular ROS and ATP, both critical mediators responsible for endothelial cell activation, microcirculation impairment, platelet activation, as well as long-term dysregulated adaptive and innate immune responses. PMID:26784696

  13. A New Approach for On-Demand Generation of Various Oxygen Tensions for In Vitro Hypoxia Models

    PubMed Central

    Li, Chunyan; Chaung, Wayne; Mozayan, Cameron; Chabra, Ranjeev; Wang, Ping; Narayan, Raj K.

    2016-01-01

    The development of in vitro disease models closely mimicking the functions of human disease has captured increasing attention in recent years. Oxygen tensions and gradients play essential roles in modulating biological systems in both physiologic and pathologic events. Thus, controlling oxygen tension is critical for mimicking physiologically relevant in vivo environments for cell, tissue and organ research. We present a new approach for on-demand generation of various oxygen tensions for in vitro hypoxia models. Proof-of-concept prototypes have been developed for conventional cell culture microplate by immobilizing a novel oxygen-consuming biomaterial on the 3D-printed insert. For the first time, rapid (~3.8 minutes to reach 0.5% O2 from 20.9% O2) and precisely controlled oxygen tensions/gradients (2.68 mmHg per 50 μm distance) were generated by exposing the biocompatible biomaterial to the different depth of cell culture media. In addition, changing the position of 3D-printed inserts with immobilized biomaterials relative to the cultured cells resulted in controllable and rapid changes in oxygen tensions (<130 seconds). Compared to the current technologies, our approach allows enhanced spatiotemporal resolution and accuracy of the oxygen tensions. Additionally, it does not interfere with the testing environment while maintaining ease of use. The elegance of oxygen tension manipulation introduced by our new approach will drastically improve control and lower the technological barrier of entry for hypoxia studies. Since the biomaterials can be immobilized in any devices, including microfluidic devices and 3D-printed tissues or organs, it will serve as the basis for a new generation of experimental models previously impossible or very difficult to implement. PMID:27219067

  14. Implication of reactive oxygen species in the antibacterial activity against Salmonella typhimurium of hepatocyte cell lines.

    PubMed

    Lajarin, F; Rubio, G; Lorenzo, N; Gámiz, P; Hernandez-Caselles, T; Garcia-Peñarrubia, P

    1999-11-01

    We recently described the antibacterial activity of a murine hepatocyte cell line stimulated with interferon-gamma (IFN-gamma), interleukin-1 (IL-1), and lipopolysaccharide (LPS) against intracellular Salmonella organisms. Here we show for the first time the existence of basal antibacterial activity in cultured hepatocyte cell lines. Thus treatment of resting and stimulated hepatocytes with catalase or superoxide dismutase increased bacterial number recovered per monolayer, which suggests that the mechanism involved with antibacterial activity of hepatocytes is mediated by reactive oxygen species (ROS). Also, the capacity of these cell lines to generate intracellular peroxides under resting and stimulated conditions was investigated. This revealed that IL-1 and LPS did not induce any increase in the amount of intracellular peroxides by themselves, but they primed IFN-gamma for maximal induction of peroxides. The intracellular amount of peroxides was highly increased on stimulation with IFN-gamma, IL-1, and LPS, and it was strongly inhibited by catalase. This explains that the mechanism whereby this enzyme inhibits antibacterial activity takes place by decreasing the intracellular pool of peroxides. In turn, experiments performed in the presence of several inhibitors of metabolic pathways involved in ROS generation suggested that cyclo-oxygenase are a source of these species in hepatocyte cell lines. These results attribute a prominent role to the generation of peroxides as effector molecules of antibacterial activity in hepatocyte cell lines. Thus these cells displayed a moderate basal level, which increased on stimulation with proinflammatory cytokines such as IFN-gamma, IL-1, and bacterial products such as LPS. Finally, it has been also shown for the first time that IFN-gamma stimulation induces production of peroxides in human and murine hepatocyte cell lines.

  15. Direct charge radioisotope activation and power generation

    DOEpatents

    Lal, Amit; Li, Hui; Blanchard, James P.; Henderson, Douglass L.

    2002-01-01

    An activator has a base on which is mounted an elastically deformable micromechanical element that has a section that is free to be displaced toward the base. An absorber of radioactively emitted particles is formed on the base or the displaceable section of the deformable element and a source is formed on the other of the displaceable section or the base facing the absorber across a small gap. The radioactive source emits charged particles such as electrons, resulting in a buildup of charge on the absorber, drawing the absorber and source together and storing mechanical energy as the deformable element is bent. When the force between the absorber and the source is sufficient to bring the absorber into effective electrical contact with the source, discharge of the charge between the source and absorber allows the deformable element to spring back, releasing the mechanical energy stored in the element. An electrical generator such as a piezoelectric transducer may be secured to the deformable element to convert the released mechanical energy to electrical energy that can be used to provide power to electronic circuits.

  16. Gas-solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries.

    PubMed

    Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Hy, Sunny; Chen, Yan; An, Ke; Zhu, Yimei; Liu, Zhaoping; Meng, Ying Shirley

    2016-01-01

    Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas-solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high as 301 mAh g(-1) with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g(-1) still remains without any obvious decay in voltage. This study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries. PMID:27363944

  17. Gas-solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries

    DOE PAGES

    Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Chen, Yan; An, Ke; Zhu, Yimei; et al

    2016-07-01

    Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas–solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high asmore » 301 mAh g–1 with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g–1 still remains without any obvious decay in voltage. Lastly, this study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries.« less

  18. Gas-solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Hy, Sunny; Chen, Yan; An, Ke; Zhu, Yimei; Liu, Zhaoping; Meng, Ying Shirley

    2016-07-01

    Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas-solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high as 301 mAh g-1 with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g-1 still remains without any obvious decay in voltage. This study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries.

  19. Gas-solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries.

    PubMed

    Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Hy, Sunny; Chen, Yan; An, Ke; Zhu, Yimei; Liu, Zhaoping; Meng, Ying Shirley

    2016-01-01

    Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas-solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high as 301 mAh g(-1) with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g(-1) still remains without any obvious decay in voltage. This study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries.

  20. Gas–solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries

    PubMed Central

    Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Hy, Sunny; Chen, Yan; An, Ke; Zhu, Yimei; Liu, Zhaoping; Meng, Ying Shirley

    2016-01-01

    Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas–solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high as 301 mAh g−1 with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g−1 still remains without any obvious decay in voltage. This study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries. PMID:27363944

  1. Synthesis and evaluation of sensitizer drug photorelease chemistry: Micro-optic method applied to singlet oxygen generation and drug delivery

    NASA Astrophysics Data System (ADS)

    Ghosh, Goutam

    This thesis summarizes a new micro-optic method for singlet oxygen generation and sensitizer drug delivery, which include i) synthesis and evaluation of a first generation device for drug delivery from native and fluorinated silica probe tips, ii) synthesis of PEG conjugated sensitizers to study phototoxicity in ovarian cancer cells, and iii) synthesis and evaluation of tris-PEGylated chlorin conjugated fluorinated silica for its future integration into the device to use as a 2nd generation device. A first generation micro-optic device was developed that works by sparging O2 gas and light generating cytotoxic singlet oxygen that cleaves the covalently attached drug (sensitizer) from the probe tip at the distal end of the fiber. The aim is to develop a 1st and 2nd generation device for site specific delivery of photosensitizer and singlet oxygen to overcome the challenges involved in systemic administration of the sensitizer. Synthesis and evaluation of drug (pheophorbide-a) delivery applying micro-optic method from native and fluorinated silica probe tip was achieved. The amount of sensitizer photocleavage depends on the loading level of sensitizer onto the probe tips. We also found that photorelease efficiency depends on the nature of the solvents where sensitizer is photocleaved. For example, no photorelease was observed in an aqueous solvent where sensitizer remained adsorbed to the native silica probe-tip. But, 90% photocleavage was obtained in octanol. A significant amount of photosensitizer (formate ester of pyropheophorbide- a) diffused into the liposome when photocleavage study was carried out in liposome. Substantial increase of photorelease was observed in organic solvent when pyropheophorbide-a (PPa) sensitizer was attached to the partially fluorinated porous Vycor glass. We also explored sensitizer photorelease from the fluorinated silica surface at various temperatures and we found that autocatalytic photorelease happened at room temperature and above

  2. Generation of High Pressure Oxygen via Electrochemical Pumping in a Multi-stage Electrolysis Stack

    NASA Technical Reports Server (NTRS)

    Setlock, John A (Inventor); Green, Robert D (Inventor); Farmer, Serene (Inventor)

    2016-01-01

    An oxygen pump can produce high-purity high-pressure oxygen. Oxygen ions (O.sup.2-) are electrochemically pumped through a multi-stage electrolysis stack of cells. Each cell includes an oxygen-ion conducting solid-state electrolyte between cathode and anode sides. Oxygen dissociates into the ions at the cathode side. The ions migrate across the electrolyte and recombine at the anode side. An insulator is between adjacent cells to electrically isolate each individual cell. Each cell receives a similar volt potential. Recombined oxygen from a previous stage can diffuse through the insulator to reach the cathode side of the next stage. Each successive stage similarly incrementally pressurizes the oxygen to produce a final elevated pressure.

  3. Efficient generation of cavitation bubbles and reactive oxygen species using triggered high-intensity focused ultrasound sequence for sonodynamic treatment

    NASA Astrophysics Data System (ADS)

    Yasuda, Jun; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    Sonodynamic treatment is a method of treating cancer using reactive oxygen species (ROS) generated by cavitation bubbles in collaboration with a sonosensitizer at a target tissue. In this treatment method, both localized ROS generation and ROS generation with high efficiency are important. In this study, a triggered high-intensity focused ultrasound (HIFU) sequence, which consists of a short, extremely high intensity pulse immediately followed by a long, moderate-intensity burst, was employed for the efficient generation of ROS. In experiments, a solution sealed in a chamber was exposed to a triggered HIFU sequence. Then, the distribution of generated ROS was observed by the luminol reaction, and the amount of generated ROS was quantified using KI method. As a result, the localized ROS generation was demonstrated by light emission from the luminol reaction. Moreover, it was demonstrated that the triggered HIFU sequence has higher efficiency of ROS generation by both the KI method and the luminol reaction emission.

  4. The Effect of 30% Oxygen on Visuospatial Performance and Brain Activation: An Fmri Study

    ERIC Educational Resources Information Center

    Chung, S.C.; Tack, G.R.; Lee, B.; Eom, G.M.; Lee, S.Y.; Sohn, J.H.

    2004-01-01

    This study aimed to investigate the hypothesis that administration of the air with 30% oxygen compared with normal air (21% oxygen) enhances cognitive functioning through increased activation in the brain. A visuospatial task was presented while brain images were scanned by a 3 T fMRI system. The results showed that there was an improvement in…

  5. Fiber-optic Singlet Oxygen [1O2 (1Δg)] Generator Device Serving as a Point Selective Sterilizer

    PubMed Central

    Aebisher, David; Zamadar, Matibur; Mahendran, Adaickapillai; Ghosh, Goutam; McEntee, Catherine; Greer, Alexander

    2016-01-01

    Traditionally, Type II heterogeneous photo-oxidations produce singlet oxygen via external irradiation of a sensitizer and external supply of ground-state oxygen. A potential improvement is reported here. A hollow-core fiber-optic device was developed with an “internal” supply of light and flowing oxygen, and a porous photosensitizer-end capped configuration. Singlet oxygen was delivered through the fiber tip. The singlet oxygen steady-state concentration in the immediate vicinity of the probe tip was ca 20 fM by N-benzoyl-DL-methionine trapping. The device is portable and the singlet oxygen-generating tip is maneuverable, which opened the door to simple disinfectant studies. Complete Escherichia coli inactivation was observed in 2 h when the singlet oxygen sensitizing probe tip was immersed in 0.1 mL aqueous samples of 0.1–4.4 × 107 cells. Photobleaching of the probe tip occurred after ca 12 h of use, requiring baking and sensitizer reloading steps for reuse. PMID:20497367

  6. Oxygen dependence of two-photon activation of zinc and copper phthalocyanine tetrasulfonate in Jurkat cells.

    PubMed

    Mir, Youssef; van Lier, Johan E; Paquette, Benoit; Houde, Daniel

    2008-01-01

    Photodynamic therapy (PDT), the use of light-activated drugs, is a promising treatment of cancer as well as several nonmalignant conditions. However, the efficacy of one-photon (1-gamma) PDT is limited by hypoxia, which can prevent the production of the cytotoxic singlet oxygen ((1)O(2)) species, leading to tumor resistance to PDT. To solve this problem, we propose an irradiation protocol based on a simultaneous, two-photon (2-gamma) excitation of the photosensitizer (Ps). Excitation of the Ps triplet state leads to an upper excited triplet state T(n) with distinct photochemical properties, which could inflict biologic damage independent of the presence of molecular oxygen. To determine the potential of a 2-gamma excitation process, Jurkat cells were incubated with zinc or copper phthalocyanine tetrasulfonate (ZnPcS(4) or CuPcS(4)). ZnPcS(4) is a potent (1)O(2) generator in 1-gamma PDT, while CuPcS(4) is inactive under these conditions. Jurkat cells incubated with either ZnPcS(4) or CuPcS(4) were exposed to a 670 nm continuous laser (1-gamma PDT), 532 nm pulsed-laser light (2-gamma PDT), or a combination of 532 and 670 nm (2-gamma PDT). The efficacy of ZnPcS(4) to photoinactivate the Jurkat cells decreased as the concentration of oxygen decreased for both the 1-gamma and 2-gamma protocols. In the case of CuPcS(4), cell phototoxicity was measured only following 2-gamma irradiation, and its efficacy also decreased at a lower oxygen concentration. Our results suggest that for CuPcS(4) the T(n) excited state can be populated after 2-gamma irradiation at 532 nm or the combination of 532 and 670 nm light. Dependency of phototoxicity upon aerobic conditions for both 1-gamma and 2-gamma PDT suggests that reactive oxygen species play an important role in 1-gamma and 2-gamma PDT.

  7. Production of active oxygen species by blood phagocytes of pregnant women and their newborns with intrauterine infection.

    PubMed

    Safronova, V G; Matveeva, N K; Lomova, N A; Belyaeva, A S; Vanko, L V

    2013-09-01

    We studied the relationship between changes in the maternal and newborn granulocyte functions under conditions of infection risk and realization. Women with normal gestation and their healthy newborns, pregnant women with a high risk of infection and their newborns, healthy or with intrauterine infection, were examined. Changes in the active oxygen species-dependent phagocytosis system were found in the blood of risk group patients. An inverse relationship between the parameters venous and umbilical cord blood was detected indicating a relationship between changes in functional activities of maternal and newborn granulocytes. The percentage of CD11b(+)cells in venous and umbilical cord blood strictly correlated with the percent of cells that phagocytosed FITC-labeled E. coli. Deviations in the generation of active oxygen species in phagocytosis seemed to be related to the expression of surface receptors in the risk groups. PMID:24288724

  8. Controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells using porphyrin conjugated nanoparticles

    NASA Astrophysics Data System (ADS)

    Lavado, Andrea S.; Chauhan, Veeren M.; Alhaj Zen, Amer; Giuntini, Francesca; Jones, D. Rhodri E.; Boyle, Ross W.; Beeby, Andrew; Chan, Weng C.; Aylott, Jonathan W.

    2015-08-01

    Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(ii) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(ii) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn(ii) porphyrin and high numbers of irradiations of excitation light were found to generate greater amounts of ROS. A novel dye, which is transformed into fluorescent 7-hydroxy-4-trifluoromethyl-coumarin in the presence of hydrogen peroxide, provided an indirect indicator for cumulative ROS production. The mitochondrial membrane potential was monitored to investigate the destructive effect of increased intracellular ROS production. Flow cytometric analysis of nanoparticle treated hMSCs suggested irradiation with excitation light signalled controlled apoptotic cell death, rather than uncontrolled necrotic cell death. Increased intracellular ROS production did not induce phenotypic changes in hMSC subcultures.Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(ii) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(ii) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn

  9. Design of high pressure oxygen filter for extravehicular activity life support system, volume 1

    NASA Technical Reports Server (NTRS)

    Wilson, B. A.

    1977-01-01

    The experience of the National Aeronautics and Space Administration (NASA) with extravehicular activity life support emergency oxygen supply subsystems has shown a large number of problems associated with particulate contamination. These problems have resulted in failures of high pressure oxygen component sealing surfaces. A high pressure oxygen filter was designed which would (a) control the particulate contamination level in the oxygen system to a five-micron glass bead rating, ten-micron absolute condition (b) withstand the dynamic shock condition resulting from the sudden opening of 8000 psi oxygen system shutoff valve. Results of the following program tasks are reported: (1) contaminant source identification tests, (2) dynamic system tests, (3) high pressure oxygen filter concept evaluation, (4) design, (5) fabrication, (6) test, and (7) application demonstration.

  10. A Porous Tissue Engineering Scaffold Selectively Degraded by Cell-Generated Reactive Oxygen Species

    PubMed Central

    Martin, John R.; Gupta, Mukesh K.; Page, Jonathan M.; Yu, Fang; Davidson, Jeffrey M.; Guelcher, Scott A.

    2014-01-01

    Biodegradable tissue engineering scaffolds are commonly fabricated from poly(lactide-co-glycolide) (PLGA) or similar polyesters that degrade by hydrolysis. PLGA hydrolysis generates acidic breakdown products that trigger an accelerated, autocatalytic degradation mechanism that can create mismatched rates of biomaterial breakdown and tissue formation. Reactive oxygen species (ROS) are key mediators of cell function in both health and disease, especially at sites of inflammation and tissue healing, and induction of inflammation and ROS are natural components of the in vivo response to biomaterial implantation. Thus, polymeric biomaterials that are selectively degraded by cell-generated ROS may have potential for creating tissue engineering scaffolds with better matched rates of tissue in-growth and cell-mediated scaffold biodegradation. To explore this approach, a series of poly(thioketal) (PTK) urethane (PTK-UR) biomaterial scaffolds were synthesized that degrade specifically by an ROS-dependent mechanism. PTK-UR scaffolds had significantly higher compressive moduli than analogous poly(ester urethane) (PEUR) scaffolds formed from hydrolytically-degradable ester-based diols (p < 0.05). Unlike PEUR scaffolds, the PTK-UR scaffolds were stable under aqueous conditions out to 25 weeks but were selectively degraded by ROS, indicating that their biodegradation would be exclusively cell-mediated. The in vitro oxidative degradation rates of the PTK-URs followed first-order degradation kinetics, were significantly dependent on PTK composition (p < 0.05), and correlated to ROS concentration. In subcutaneous rat wounds, PTK-UR scaffolds supported cellular infiltration and granulation tissue formation, followed first-order degradation kinetics over 7 weeks, and produced significantly greater stenting of subcutaneous wounds compared to PEUR scaffolds. These combined results indicate that ROS-degradable PTK-UR tissue engineering scaffolds have significant advantages over analogous

  11. Evidence for the generation of reactive oxygen species from hydroquinone and benzoquinone: Roles in arsenite oxidation.

    PubMed

    Qin, Wenxiu; Wang, Yujun; Fang, Guodong; Wu, Tongliang; Liu, Cun; Zhou, Dongmei

    2016-05-01

    Natural organic matter (NOM) significantly affects the fate, bioavailability, and toxicity of arsenic in the environment. In the present study, we investigated the oxidation of As(III) in the presence of hydroquinone (HQ) and benzoquinone (BQ), which were selected as model quinone moieties for NOM. It was found that As(III) was oxidized to As(V) in the presence of HQ or BQ at neutral conditions, and the oxidation efficiency of As(III) increased from 33% to 92% in HQ solutions and from 0 to 80% in BQ solutions with pH increasing from 6.5 to 8.5. The oxidation mechanism was further explored with electron spin resonance (ESR) technique. The results showed that semiquinone radicals (SQ(-)) were generated from the comproportionation reaction between BQ and HQ, which mediated the formation of superoxide anion (O2(-)), hydrogen peroxide (H2O2) and hydroxyl radical (OH). Both the SQ(-), H2O2 and OH contributed to the oxidation of As(III). The increase of pH favored the formation of SQ(-), and thus promoted the generation of reactive oxygen species (ROS) as well as As(III) oxidation. Increasing concentrations of HQ and BQ from 0.1 to 1.0 mM enhanced As(III) oxidation from 65% to 94% and from 10% to 53%, respectively. The findings of this study facilitate our understanding of the fate and transformation of As(III) in organic-rich aquatic environments and highlight quinone moieties as the potential oxidants for As(III) in the remediation of arsenic contaminated sites.

  12. A porous tissue engineering scaffold selectively degraded by cell-generated reactive oxygen species.

    PubMed

    Martin, John R; Gupta, Mukesh K; Page, Jonathan M; Yu, Fang; Davidson, Jeffrey M; Guelcher, Scott A; Duvall, Craig L

    2014-04-01

    Biodegradable tissue engineering scaffolds are commonly fabricated from poly(lactide-co-glycolide) (PLGA) or similar polyesters that degrade by hydrolysis. PLGA hydrolysis generates acidic breakdown products that trigger an accelerated, autocatalytic degradation mechanism that can create mismatched rates of biomaterial breakdown and tissue formation. Reactive oxygen species (ROS) are key mediators of cell function in both health and disease, especially at sites of inflammation and tissue healing, and induction of inflammation and ROS are natural components of the in vivo response to biomaterial implantation. Thus, polymeric biomaterials that are selectively degraded by cell-generated ROS may have potential for creating tissue engineering scaffolds with better matched rates of tissue in-growth and cell-mediated scaffold biodegradation. To explore this approach, a series of poly(thioketal) (PTK) urethane (PTK-UR) biomaterial scaffolds were synthesized that degrade specifically by an ROS-dependent mechanism. PTK-UR scaffolds had significantly higher compressive moduli than analogous poly(ester urethane) (PEUR) scaffolds formed from hydrolytically-degradable ester-based diols (p < 0.05). Unlike PEUR scaffolds, the PTK-UR scaffolds were stable under aqueous conditions out to 25 weeks but were selectively degraded by ROS, indicating that their biodegradation would be exclusively cell-mediated. The in vitro oxidative degradation rates of the PTK-URs followed first-order degradation kinetics, were significantly dependent on PTK composition (p < 0.05), and correlated to ROS concentration. In subcutaneous rat wounds, PTK-UR scaffolds supported cellular infiltration and granulation tissue formation, followed first-order degradation kinetics over 7 weeks, and produced significantly greater stenting of subcutaneous wounds compared to PEUR scaffolds. These combined results indicate that ROS-degradable PTK-UR tissue engineering scaffolds have significant advantages over

  13. Ozone Generation by a DC Driven Micro-Hollow Cathode Discharge in Nitrogen-Mixed Oxygen Flow

    NASA Astrophysics Data System (ADS)

    Yamatake, Atsushi; Yasuoka, Koichi; Ishii, Shozo

    2004-09-01

    The ozone generation characteristic of a DC driven micro-hollow cathode discharge was studied in nitrogen-mixed oxygen gas flow. An ozone concentration of 13.7 g/Nm3 was obtained at an efficiency of 97 g/kWh in pure oxygen. However, ozone concentrations of 8.2 g/Nm3 and 25 ppm ozone were obtained in gas mixtures of 4% and 80% N2-mixed oxygen gases, respectively. There was a threshold specific energy above which ozone concentration markedly decreased. High-energy electrons dissociate the nitrogen molecules and generate NO and NO2 which accelerate the ozone decomposition in high-power-density plasmas such as a micro-hollow cathode discharge.

  14. Roles of oxygen for methanol adsorption on polycrystalline copper surface revealed by sum frequency generation imaging microscopy

    NASA Astrophysics Data System (ADS)

    Fang, Ming; Santos, Greggy; Chen, Xiaole; Baldelli, Steven

    2016-06-01

    The adsorption of atmospheric pressure methanol on the polycrystalline copper surface has been studied by a combination of sum frequency generation imaging microscopy (SFGIM) and temperature programmed desorption (TPD). Methoxy species can be generated by exposing the polycrystalline copper surface to methanol vapor at room temperature. SFGIM results demonstrate that oxygen promotes the surface adsorption of methanol and the increase in the amount of methoxy produced on copper surface. SFGIM orientation analysis suggests the methoxy monolayer is oriented closer to the surface normal with introduction of oxygen. Employing the image statistical analysis approach, the heterogeneities and conformation distribution of methoxy monolayers on copper surface with and without oxygen adsorption are compared. These results illustrate SFGIM indeed could provide more insight for understanding the heterogeneous metal/metal oxide surface in the molecular level.

  15. Chlorine measurement in the jet singlet oxygen generator considering the effects of the droplets

    NASA Astrophysics Data System (ADS)

    Goodarzi, Mohamad S.; Saghafifar, Hossein

    2016-09-01

    A new method is presented to measure chlorine concentration more accurately than conventional method in exhaust gases of a jet-type singlet oxygen generator. One problem in this measurement is the existence of micrometer-sized droplets. In this article, an empirical method is reported to eliminate the effects of the droplets. Two wavelengths from a fiber coupled LED are adopted and the measurement is made on both selected wavelengths. Chlorine is measured by the two-wavelength more accurately than the one-wavelength method by eliminating the droplet term in the equations. This method is validated without the basic hydrogen peroxide injection in the reactor. In this case, a pressure meter value in the diagnostic cell is compared with the optically calculated pressure, which is obtained by the one-wavelength and the two-wavelength methods. It is found that chlorine measurement by the two-wavelength method and pressure meter is nearly the same, while the one-wavelength method has a significant error due to the droplets.

  16. Reductive detoxification as a mechanism of fungal resistance to singlet oxygen-generating photosensitizers.

    PubMed Central

    Daub, M E; Leisman, G B; Clark, R A; Bowden, E F

    1992-01-01

    Fungi that are resistant or sensitive to the singlet oxygen-generating toxin cercosporin were assayed for their ability to detoxify it by reduction. Cercosporin reduction was assayed microscopically by using bandpass filters to differentiate between fluorescence emission from cercosporin and reduced cercosporin. Hyphae of the resistant Cercospora and Alternaria species emitted a green fluorescence, indicative of reduced cercosporin. Hyphae of nonviable cultures and of cercosporin-sensitive fungi did not reduce cercosporin. Sensitive fungi occasionally reduced cercosporin when incubated with reducing agents that protect against cercosporin toxicity. Cercosporin could not be efficiently photoreduced in the absence of the fungus. Cercospora species were also resistant to eosin Y but were sensitive to rose bengal. Microscopic observation demonstrated that Cercospora species were not capable of reducing rose bengal but were capable of reducing eosin Y. These observations were supported by in vitro electrochemical measurements that revealed the following order with respect to ease of reduction: cercosporin >> eosin Y > rose bengal. The formal redox potential (E 0') of cercosporin at pH 7.5 was found to be -0.14 V vs. the normal hydrogen electrode. We conclude that Cercospora species protect themselves against cercosporin by the reduction and detoxification of the toxin molecule. Images PMID:1409670

  17. Light-induced generation of singlet oxygen by naked gold nanoparticles and its implications to cancer cell phototherapy.

    PubMed

    Pasparakis, George

    2013-12-20

    Generation of singlet oxygen by direct irradiation of naked gold nanoparticles is observed using either continuous wave or pulsed laser sources. The underlying mechanism involves plasmon- and hot-electron-mediated reaction pathways and (1) O2 seems to significantly amplify the overall death rates during photothermal treatment of cancer cell lines in vitro.

  18. Effect of reactive oxygen species (ROS) generating system for control of airborne microorganisms in meat processing environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effectiveness of reactive oxygen species (ROS) generating AirOcare equipment on the reduction of airborne bacteria in a meat processing environment was determined. Serratia marcescens and lactic acid bacteria (Lactococcus lactis subsp. lactis and Lactobacillus plantarum) were used to artificiall...

  19. A nonheme manganese(IV)-oxo species generated in photocatalytic reaction using water as an oxygen source.

    PubMed

    Wu, Xiujuan; Yang, Xiaonan; Lee, Yong-Min; Nam, Wonwoo; Sun, Licheng

    2015-03-01

    A nonheme manganese(IV)-oxo complex, [Mn(IV)(O)(BQCN)](2+), was generated in the photochemical and chemical oxidation of [Mn(II)(BQCN)](2+) with water as an oxygen source, respectively. The photocatalytic oxidation of organic substrates, such as alcohol and sulfide, by [Mn(II)(BQCN)](2+) has been demonstrated in both neutral and acidic media. PMID:25658677

  20. Low oxygen tension enhances the generation of lung progenitor cells from mouse embryonic and induced pluripotent stem cells.

    PubMed

    Garreta, Elena; Melo, Esther; Navajas, Daniel; Farré, Ramon

    2014-07-16

    Whole-organ decellularization technology has emerged as a new alternative for the fabrication of bioartificial lungs. Embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) are potentially useful for recellularization since they can be directed to express phenotypic marker genes of lung epithelial cells. Normal pulmonary development takes place in a low oxygen environment ranging from 1 to 5%. By contrast, in vitro ESC and iPSC differentiation protocols are usually carried out at room-air oxygen tension. Here, we sought to determine the role played by oxygen tension on the derivation of Nkx2.1+ lung/thyroid progenitor cells from mouse ESC and iPSC. A step-wise differentiation protocol was used to generate Nkx2.1+ lung/thyroid progenitors under 20% and 5% oxygen tension. On day 12, gene expression analysis revealed that Nkx2.1 and Foxa2 (endodermal and early lung epithelial cell marker) were significantly upregulated at 5% oxygen tension in ESC and iPSC differentiated cultures compared to 20% oxygen conditions. In addition, quantification of Foxa2+Nkx2.1+Pax8- cells corresponding to the lung field, with exclusion of the potential thyroid fate identified by Pax8 expression, confirmed that the low physiologic oxygen tension exerted a significant positive effect on early pulmonary differentiation of ESC and iPSC. In conclusion, we found that 5% oxygen tension enhanced the derivation of lung progenitors from mouse ESC and iPSC compared to 20% room-air oxygen tension.

  1. Reactive oxygen scavenging activity of matured whiskey and its active polyphenols.

    PubMed

    Koga, K; Taguchi, A; Koshimizu, S; Suwa, Y; Yamada, Y; Shirasaka, N; Yoshizumi, H

    2007-04-01

    The quality of whiskey is known to improve remarkably by its storage over many years. This process is commonly termed "maturing." In this process, polyphenols derived from lignin and tannin of the barrel have an important role in not only forming the matured flavor and taste but also contributing to the advance of clustering ethanol and water in whiskey. It is also likely that polyphenols generally possess reactive oxygen (RO) scavenging activity. The present study evaluated the RO scavenging activity (free-radical scavenging activity, H(2)O(2) reduction activity under peroxidase coculture, and H(2)O(2)scavenging activity) of 24 single malt whiskeys with a maturation age of 10 to 30 y produced in Japanese, Scotch (Islay), or Scotch (Speyside and Highland) regions. Single malt whiskey not only showed RO scavenging activity but there was also a positive correlation between this activity and the maturation age of whiskey exceeding the difference resulting from the manufacturing region. A nonvolatile fraction derived from the barrel was responsible for RO scavenging activity. In particular, the contents of ellagic and gallic acids and lyoniresinol, the main polyphenolic compounds in whiskey, increased with maturation age. For the free-radical scavenging activity per molecule, each compound was 1.68 to 3.14 times that of trolox (a water-soluble vitamin E). The activities of ellagic acid, gallic acid, and lyoniresinol in the whiskey (Yamazaki 18) were equivalent to that of 80.3, 31.2, and 11.1 ppm trolox, respectively. Accordingly, the total activity of these 3 compounds accounted for about 20% of the activity of the whiskey (630.7 ppm trolox).

  2. Reactive oxygen scavenging activity of matured whiskey and its active polyphenols.

    PubMed

    Koga, K; Taguchi, A; Koshimizu, S; Suwa, Y; Yamada, Y; Shirasaka, N; Yoshizumi, H

    2007-04-01

    The quality of whiskey is known to improve remarkably by its storage over many years. This process is commonly termed "maturing." In this process, polyphenols derived from lignin and tannin of the barrel have an important role in not only forming the matured flavor and taste but also contributing to the advance of clustering ethanol and water in whiskey. It is also likely that polyphenols generally possess reactive oxygen (RO) scavenging activity. The present study evaluated the RO scavenging activity (free-radical scavenging activity, H(2)O(2) reduction activity under peroxidase coculture, and H(2)O(2)scavenging activity) of 24 single malt whiskeys with a maturation age of 10 to 30 y produced in Japanese, Scotch (Islay), or Scotch (Speyside and Highland) regions. Single malt whiskey not only showed RO scavenging activity but there was also a positive correlation between this activity and the maturation age of whiskey exceeding the difference resulting from the manufacturing region. A nonvolatile fraction derived from the barrel was responsible for RO scavenging activity. In particular, the contents of ellagic and gallic acids and lyoniresinol, the main polyphenolic compounds in whiskey, increased with maturation age. For the free-radical scavenging activity per molecule, each compound was 1.68 to 3.14 times that of trolox (a water-soluble vitamin E). The activities of ellagic acid, gallic acid, and lyoniresinol in the whiskey (Yamazaki 18) were equivalent to that of 80.3, 31.2, and 11.1 ppm trolox, respectively. Accordingly, the total activity of these 3 compounds accounted for about 20% of the activity of the whiskey (630.7 ppm trolox). PMID:17995817

  3. Testosterone induces apoptosis in vascular smooth muscle cells via extrinsic apoptotic pathway with mitochondria-generated reactive oxygen species involvement.

    PubMed

    Lopes, Rheure Alves Moreira; Neves, Karla Bianca; Pestana, Cezar Rangel; Queiroz, André Lima; Zanotto, Camila Ziliotto; Chignalia, Andréia Z; Valim, Yara Maria; Silveira, Leonardo R; Curti, Carlos; Tostes, Rita C

    2014-06-01

    Testosterone exerts both beneficial and harmful effects on the cardiovascular system. Considering that testosterone induces reactive oxygen species (ROS) generation and ROS activate cell death signaling pathways, we tested the hypothesis that testosterone induces apoptosis in vascular smooth muscle cells (VSMCs) via mitochondria-dependent ROS generation. Potential mechanisms were addressed. Cultured VSMCs were stimulated with testosterone (10(-7) mol/l) or vehicle (2-12 h) in the presence of flutamide (10(-5) mol/l), CCCP (10(-6) mol/l), mimetic manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP; 3 × 10(-5) mol/l), Z-Ile-Glu(O-ME)-Thr-Asp(O-Me) fluoromethyl ketone (Z-IETD-FMK; 10(-5) mol/l), or vehicle. ROS were determined with lucigenin and dichlorodihydrofluorescein; apoptosis, with annexin V and calcein; O2 consumption, with a Clark-type electrode, and procaspases, caspases, cytochrome c, Bax, and Bcl-2 levels by immunoblotting. Testosterone induced ROS generation (relative light units/mg protein, 2 h; 162.6 ± 16 vs. 100) and procaspase-3 activation [arbitrary units, (AU), 6 h; 166.2 ± 19 vs. 100]. CCCP, MnTMPyP, and flutamide abolished these effects. Testosterone increased annexin-V fluorescence (AU, 197.6 ± 21.5 vs. 100) and decreased calcein fluorescence (AU, 34.4 ± 6.4 vs. 100), and O2 consumption (nmol O2/min, 18.6 ± 2.0 vs. 34.4 ± 3.9). Testosterone also reduced Bax-to-Bcl-2 ratio but not cytochrome-c release from mitochondria. Moreover, testosterone (6 h) induced cleavage of procaspase 8 (AU, 161.1 ± 13.5 vs. 100) and increased gene expression of Fas ligand (2(ΔΔCt), 3.6 ± 1.2 vs. 0.7 ± 0.5), and TNF-α (1.7 ± 0.4 vs. 0.3 ± 0.1). CCCP, MnTMPyP, and flutamide abolished these effects. These data indicate that testosterone induces apoptosis in VSMCs via the extrinsic apoptotic pathway with the involvement of androgen receptor activation and mitochondria-generated ROS.

  4. Dependence of Ozone Generation on Gas Temperature Distribution in AC Atmospheric Pressure Dielectric Barrier Discharge in Oxygen

    NASA Astrophysics Data System (ADS)

    Takahashi, Go; Akashi, Haruaki

    AC atmospheric pressure multi-filament dielectric barrier discharge in oxygen has been simulated using two dimensional fluid model. In the discharge, three kinds of streamers have been obtained. They are primary streamers, small scale streamers and secondary streamers. The primary streamers are main streamers in the discharge and the small scale streamers are formed after the ceasing of the primary streamers. And the secondary streamers are formed on the trace of the primary streamers. In these streamers, the primary and the small scale streamers are very effective to generate O(3P) oxygen atoms which are precursor of ozone. And the ozone is generated mainly in the vicinity of the dielectrics. In high gas temperature region, ozone generation decreases in general. However, increase of the O(3P) oxygen atom density in high gas temperature region compensates decrease of ozone generation rate coefficient. As a result, amount of ozone generation has not changed. But if the effect of gas temperature was neglected, amount of ozone generation increases 10%.

  5. Copper compound induces autophagy and apoptosis of glioma cells by reactive oxygen species and jnk activation

    PubMed Central

    2012-01-01

    Background Glioblastoma multiforme (GBM) is the most aggressive of the primary brain tumors, with a grim prognosis despite intensive treatment. In the past decades, progress in research has not significantly increased overall survival rate. Methods The in vitro antineoplastic effect and mechanism of action of Casiopeina III-ia (Cas III-ia), a copper compound, on rat malignant glioma C6 cells was investigated. Results Cas III-ia significantly inhibited cell proliferation, inducing autophagy and apoptosis, which correlated with the formation of autophagic vacuoles, overexpression of LC3, Beclin 1, Atg 7, Bax and Bid proteins. A decrease was detected in the mitochondrial membrane potential and in the activity of caspase 3 and 8, together with the generation of intracellular reactive oxygen species (ROS) and increased activity of c-jun NH2-terminal kinase (JNK). The presence of 3-methyladenine (as selective autophagy inhibitor) increased the antineoplastic effect of Cas III-ia, while Z-VAD-FMK only showed partial protection from the antineoplastic effect induced by Cas III-ia, and ROS antioxidants (N-acetylcysteine) decreased apoptosis, autophagy and JNK activity. Moreover, the JNK –specific inhibitor SP600125 prevented Cas III-ia-induced cell death. Conclusions Our data suggest that Cas III-ia induces cell death by autophagy and apoptosis, in part due to the activation of ROS –dependent JNK signaling. These findings support further studies of Cas III-ia as candidate for treatment of human malignant glioma. PMID:22540380

  6. Iridium Oxide Coatings with Templated Porosity as Highly Active Oxygen Evolution Catalysts: Structure-Activity Relationships.

    PubMed

    Bernicke, Michael; Ortel, Erik; Reier, Tobias; Bergmann, Arno; Ferreira de Araujo, Jorge; Strasser, Peter; Kraehnert, Ralph

    2015-06-01

    Iridium oxide is the catalytic material with the highest stability in the oxygen evolution reaction (OER) performed under acidic conditions. However, its high cost and limited availability demand that IrO2 is utilized as efficiently as possible. We report the synthesis and OER performance of highly active mesoporous IrO2 catalysts with optimized surface area, intrinsic activity, and pore accessibility. Catalytic layers with controlled pore size were obtained by soft-templating with micelles formed from amphiphilic block copolymers poly(ethylene oxide)-b-poly(butadiene)-b-poly(ethylene oxide). A systematic study on the influence of the calcination temperature and film thickness on the morphology, phase composition, accessible surface area, and OER activity reveals that the catalytic performance is controlled by at least two independent factors, that is, accessible surface area and intrinsic activity per accessible site. Catalysts with lower crystallinity show higher intrinsic activity. The catalyst surface area increases linearly with film thickness. As a result of the templated mesopores, the pore surface remains fully active and accessible even for thick IrO2 films. Even the most active multilayer catalyst does not show signs of transport limitations at current densities as high as 75 mA cm(-2) . PMID:25958795

  7. Iridium Oxide Coatings with Templated Porosity as Highly Active Oxygen Evolution Catalysts: Structure-Activity Relationships.

    PubMed

    Bernicke, Michael; Ortel, Erik; Reier, Tobias; Bergmann, Arno; Ferreira de Araujo, Jorge; Strasser, Peter; Kraehnert, Ralph

    2015-06-01

    Iridium oxide is the catalytic material with the highest stability in the oxygen evolution reaction (OER) performed under acidic conditions. However, its high cost and limited availability demand that IrO2 is utilized as efficiently as possible. We report the synthesis and OER performance of highly active mesoporous IrO2 catalysts with optimized surface area, intrinsic activity, and pore accessibility. Catalytic layers with controlled pore size were obtained by soft-templating with micelles formed from amphiphilic block copolymers poly(ethylene oxide)-b-poly(butadiene)-b-poly(ethylene oxide). A systematic study on the influence of the calcination temperature and film thickness on the morphology, phase composition, accessible surface area, and OER activity reveals that the catalytic performance is controlled by at least two independent factors, that is, accessible surface area and intrinsic activity per accessible site. Catalysts with lower crystallinity show higher intrinsic activity. The catalyst surface area increases linearly with film thickness. As a result of the templated mesopores, the pore surface remains fully active and accessible even for thick IrO2 films. Even the most active multilayer catalyst does not show signs of transport limitations at current densities as high as 75 mA cm(-2) .

  8. Effects of carbohydrate on the internal oxygen concentration, oxygen uptake, and nitrogenase activity in detached pea nodules

    SciTech Connect

    Monroe, J.D. ); LaRue, T.A. )

    1989-10-01

    The interaction between carbon substrates and O{sub 2} and their effects on nitrogenase activity (C{sub 2}H{sub 2}) were examined in detached nodules of pea (Pisum sativum L. cv Sparkle). The internal O{sub 2} concentration was estimated from the fractional oxygenation of leghemoglobin measured by reflectance spectroscopy. Lowering the endogenous carbohydrate content of nodules by excising the shoots 16 hours before nodule harvest or by incubating detached nodules at 100 kPa O{sub 2} for 2 hours resulted in a 2- to 10-fold increase in internal O{sub 2}, and a decline in nitrogenase activity. Conversely, when detached nodules were supplied with 100 millimolar succinate, the internal O{sub 2} was lowered. Nitrogenase activity was stimulated by succinate but only at high external O{sub 2}. Oxygen uptake increased linearly with external O{sub 2} but was affected only slightly by the carbon treatments. The apparent diffusion resistance in the nodule cortex was similar in all of the treatments. Carbon substrates can thus affect nitrogenase activity indirectly by affecting the O{sub 2} concentration within detached nodules.

  9. Activated human neutrophil response to perfluorocarbon nanobubbles: oxygen-dependent and -independent cytotoxic responses.

    PubMed

    Hwang, Tsong-Long; Fang, Chia-Lang; Al-Suwayeh, Saleh A; Yang, Li-Jia; Fang, Jia-You

    2011-06-10

    Nanobubbles, a type of nanoparticles with acoustically active properties, are being utilized as diagnostic and therapeutic nanoparticles to better understand, detect, and treat human diseases. The objective of this work was to prepare different nanobubble formulations and investigate their physicochemical characteristics and toxic responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP)-activated human neutrophils. The nanobubbles were prepared using perfluoropentane and coconut oil as the respective core and shell, with soybean phosphatidylcholine (SPC) and/or cationic surfactants as the interfacial layers. The cytotoxic effect of the nanobubbles on neutrophils was determined by extracellular O₂(.)⁻ release, intracellular reactive oxygen species (ROS), lactate dehydrogenase (LDH), and elastase release. Particle sizes of the nanobubbles with different percentages of perfluorocarbon, oil, and surfactants in ranged 186-432 nm. The nanobubbles were demonstrated to inhibit the generation of superoxide and intracellular ROS. The cytotoxicity of nanobubbles may be mainly associated with membrane damage, as indicated by the high LDH leakage. Systems with Forestall (FE), a cationic surfactant, or higher SPC contents exhibited the greatest LDH release by 3-fold compared to the control. The further addition of an oil component reduced the cytotoxicity induced by the nanobubbles. Exposure to most of the nanobubble formulations upregulated elastase release by activated neutrophils. Contrary to this result, stearylamine (SA)-containing systems slightly but significantly suppressed elastase release. FE and SA in a free form caused stronger responses by neutrophils than when they were incorporated into nanobubbles. In summary, exposure to nanobubbles resulted in a formulation-dependent toxicity toward human neutrophils that was associated with both oxygen-dependent and -independent pathways. Clinicians should therefore exercise caution when using nanobubbles in patients

  10. Charge separation promoted activation of molecular oxygen by neutral gold clusters.

    PubMed

    Woodham, Alex P; Meijer, Gerard; Fielicke, André

    2013-02-01

    Gold nanoparticles and sub-nanoparticles famously act as highly efficient and selective low-temperature oxidation catalysts with molecular oxygen, in stark contrast to the nobility of the bulk phase. The origins of this activity and the nature of the active species remain open questions. Gas-phase studies of isolated gold clusters hold promise for disentangling these problems. Here we address the interaction of neutral gold clusters (Au(n); 4 ≤ n ≤ 21) with molecular oxygen by probing the highly characteristic O-O vibrational stretch frequencies. This reveals that for selected cluster sizes the oxygen is highly activated with respect to the free moiety. Complementary quantum chemical calculations provide evidence for substantial electron transfer to the O(2) unit and concomitant rearrangement of the parent gold cluster structure upon binding and activation. This gives evidence for a model of the interaction between neutral gold clusters and molecular oxygen.

  11. Healthy F-16 pilots show no evidence of exposure to tri-ortho-cresyl phosphate through the on-board oxygen generating system.

    PubMed

    Tacal, Ozden; Schopfer, Lawrence M

    2014-05-25

    About 18% of fighter pilots complain of ill symptoms that begin during flight and persist for days. A possible source of toxicity is the air supplied through the on board oxygen generating system. The air passes through the jet engine before it is enriched for oxygen and breathed through an oxygen mask. While in the jet engine, the air can become contaminated with jet engine lubricating oil. A potentially toxic component in jet engine oil is tri-ortho-cresyl phosphate (TOCP), which is metabolically activated to the highly reactive cresyl saligenin phosphate. The cresyl saligenin phosphate reacts with butyrylcholinesterase (BChE) to make a covalent adduct on serine 198. The purpose of this work was to determine whether the blood of healthy, active-duty F-16 pilots has measurable levels of the cresyl phosphate adduct. BChE was immunopurified from 0.5ml plasma by binding to immobilized monoclonal mAb2. BChE protein was released with acetic acid, digested with pepsin and analyzed by LC-MS/MS on the 5600 Triple TOF mass spectrometer. Positive controls for quantifying the limit of detection were plasma samples containing known amounts of cresyl saligenin phosphate treated plasma. The cresyl phosphate adduct eluted at 31.3min with an observed parent ion mass of 966.4m/z and characteristic daughter ions 778.3, 673.3, and 602.3m/z. Control experiments demonstrated that as little as 0.1% of the 1-2μg BChE recovered from 0.5ml plasma could be detected as the cresyl phosphate adduct on peptide FGES198AGAAS. Mass spectrometry analysis of plasma from fifteen healthy F-16 pilots showed that none had evidence of exposure to TOCP. It was concluded that the on-board oxygen generating system, when operating properly, did not deliver tri-ortho-cresyl phosphate in the oxygen supply. PMID:24661946

  12. Investigation on the reaction mechanisms of generation and loss of oxygen-related species in atmospheric-pressure pulsed dielectric barrier discharge in argon/oxygen mixture

    NASA Astrophysics Data System (ADS)

    Pan, Jie; Tan, Zhenyu; Pan, Guangsheng; Shan, Chunhong; Wang, Xiaolong; Liu, Yadi; Jiang, Jixiang

    2016-07-01

    This work presents a numerical investigation, using a 1-D fluid model, on the generation and loss of oxygen-related species and the spatial-temporal evolutions of the species densities in the atmospheric-pressure pulsed dielectric barrier discharge in the argon/oxygen mixture. The reaction pathways as well as their contributions to the generation and loss of oxygen-related species are given. The considered oxygen-related species include O, O(1D), O2(1Δg), O3, O+, O2+, O-, O2-, and O3-. The following significant results are obtained. O, O(1D), O2(1Δg), and O- are produced mainly via the electron impact with O2. Ar+ plays an essential role in the generation of O+ and O2+. Almost all of O3 derives from the reaction O2 + O2 + O → O3 + O2. The O3-related reactions produce an essential proportion of O2- and O3-. The substantial loss of O-, O2-, and O3- is induced by their reactions with O2+. Loss of O+, O, and O(1D) is mainly due to their reactions with O2, loss of O2(1Δg) due to O2(1Δg) impacts with O3 as well as the de-excitation reactions between O2(1Δg) and e, O2, and O, and loss of O3 due to the reactions between O3 and other neutral species. In addition, the densities of O+ and O(1D) present two obvious peaks at the pulse duration, but the densities of O2+, O, O2(1Δg), and O3 are almost unchanged. The densities of negative oxygen ions increase at the pulse duration and then decline. O- density is obviously large nearby the dielectric surfaces and the densities of O2- and O3- present generally uniform distributions.

  13. Study of oxygen scavenging PET-based films activated by water

    NASA Astrophysics Data System (ADS)

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana

    2016-05-01

    In this work an active barrier system consisting of a thin and transparent film based on polyethylene terephthalate (PET) was studied. Dynamic oxygen absorption measurements were performed at different values of relative humidity and temperature, pointing out that humidity is a key factor in activating the oxidation of the polymer sample. Moreover, the thermal and optical properties of the films were investigated and a good correlation was found between the crystallinity increase and the consequent transparency reduction occurring after the oxygen absorption.

  14. Effect of arsenic on the activity of oxygen dissolved in dilute liquid copper solutions

    NASA Astrophysics Data System (ADS)

    Walqui, H.; Seetharaman, S.; Staffansson, L. I.

    1985-06-01

    The influence of arsenic additions on the activity of oxygen in liquid copper was studied by the solid-electrolyte galvanic cell (-) Pt, W/Cu-O-As ∥ ZrO2-CaO ∥ NiO-Ni/Pt (+) in the temperature range 1373 to 1473 K. The activity coefficient of oxygen in liquid copper was found to be unaffected by the addition of arsenic. The interaction parameter values for group V B elements in the periodic table with respect to oxygen are discussed in the light of the solute interactions in copper.

  15. Oxygen requirements for formation and activity of the squalene expoxidase in Saccharomyces cerevisiae

    NASA Technical Reports Server (NTRS)

    Jahnke, L.; Klein, H. P.

    1983-01-01

    The effect of oxygen on squalene epoxidase activity in Saccharomyces cerevisiae was investigated. In cells grown in standing cultures, the epoxidase was localized mainly in the 'mitochondrial' fraction. Upon aeration, enzyme activity increased and the newly formed enzyme was associated with the 'microsomal' fraction. At 0.03 percent (vol/vol) oxygen, epoxidase levels doubled, whereas the ergosterol level was only slightly increased. Cycloheximide inhibited the increase in epoxidase under these conditions. An apparent K sub m for oxygen of 0.38 percent (vol/vol) was determined from a crude particulate preparation for the epoxidase.

  16. Oxidative stress of vanadium-mediated oxygen free radical generation stimulated by aluminium on human erythrocytes.

    PubMed

    Abou-Seif, M A

    1998-03-01

    It has been suggested that aluminium stimulates vanadium-mediated superoxide radical generation. The oxidative stress of generated superoxide radicals on antioxidant enzyme activity, oxidation of NADH and NADPH, membrane lipid peroxidation and osmotic fragility in human red blood cells (RBC) was investigated. RBC were incubated with varying concentrations of vanadium and aluminium ions at 37 degrees C for 2 h. RBC incubated with vanadium ions showed significantly increased superoxide dismutase and catalase activities, and oxidized NADH and NADPH concentrations compared with control RBC preparations. Erythrocyte lipid peroxidation was assessed by measuring thiobarbituric acid reactivity. RBC incubated with elevated levels of vanadium showed significantly increased membrane lipid peroxidation when compared with control RBC; it increased further on addition of aluminium. A significant positive correlation was observed between the extent of vanadium induced membrane lipid peroxidation and the osmotic fragility of treated RBC. In the presence of vanadium, aluminium stimulates superoxide dismutase and catalase activities. NADH and NADPH oxidation and membrane lipid peroxidation, as well as increasing osmotic fragility of human erythrocytes. The stimulatory effect of aluminium was dependent on concentration. These results may have implications for the mechanism of toxicity of aluminium and vanadium in haemodialysis patients. PMID:9547897

  17. The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors.

    PubMed

    Jahandar Lashaki, Masoud; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

    2016-11-01

    The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials. PMID:27295065

  18. Detection of oxygen species generated by WO{sub 3} modification fullerene/TiO{sub 2} in the degradation of 1,5-diphenyl carbazide

    SciTech Connect

    Meng, Ze-Da; Zhu, Lei; Ullah, Kefayat; Ye, Shu; Oh, Won-Chun

    2014-08-15

    Highlights: • Reactive oxygen species were detected through oxidation reaction from DPCI to DPCO. • Generated reactive oxygen species and hydroxyl radicals can be analysed by DPCI degradation. • C{sub 60} have good effect in photo/ultrasonic degradation process. • Enhanced adsorption capacity can increase the degradation effect. • Photocatalytic activity attributed to photo-absorption effect by C{sub 60} and cooperative effect of WO{sub 3} and TiO{sub 2}. - Abstract: In the present work, powders with different relative mole ratios of WO{sub 3}-fullerene/TiO{sub 2} were irradiated by visible light and ultrasonic. The composite obtained was characterized by BET surface area measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and UV–vis analysis. A methylene blue (MB) solution under visible light and ultrasonic irradiation was used to determine the catalytic activity. The generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Finally, we performed experiments to find the optimum relative mole ratio of fullerene for the degradation of MB.

  19. In vitro incubation of human spermatozoa promotes reactive oxygen species generation and DNA fragmentation.

    PubMed

    Cicaré, J; Caille, A; Zumoffen, C; Ghersevich, S; Bahamondes, L; Munuce, M J

    2015-10-01

    The aim of this study was to investigate the oxidative process associated with sperm capacitation and its impact on DNA fragmentation and sperm function. Redox activity and lipid peroxidation were analysed in human spermatozoa after 3, 6 and 22 h of incubation in Ham's F10 medium plus bovine albumin at 37° and 5% CO2 for capacitation. DNA status, tyrosine phosphorylation pattern and induced acrosome reaction were evaluated after capacitating conditions. At 22 h of incubation, there was a significant (P < 0.05) increase in oxygen-free radicals and lipid peroxidation, with no effect on sperm viability. There also was a significant (P < 0.001) increase in fragmented DNA in capacitated spermatozoa compared to semen values with higher rates being found after the occurrence of the induced acrosome reaction. Protein tyrosine phosphorylation pattern confirms that capacitation took place in parallel with the occurrence of DNA fragmentation. These results indicate that when spermatozoa are incubated for several hours (22 h), a common practice in assisted reproductive techniques, an increase in oxidative sperm metabolism and in the proportion of fragmented DNA should be expected. However, there was no effect on any of the other functional parameters associated with sperm fertilising capacity.

  20. Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

    2015-12-01

    The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during substorms. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during substorms. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner magnetosphere. We obtained the following results. (1) Just after the substorm onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.

  1. A statistical review of the oxygen data from the gas generation tests supporting the revision of the 9975 SARP

    SciTech Connect

    Edwards, T.B.

    2000-01-20

    The Chemical and Hydrogen Technology Section (CHT) of the Savannah River Technology Center (SRTC) has conducted a series of gas generation tests in support of the revision of the safety analysis report for packaging (SARP) for the 9975 container, developed at the Savannah River Site (SRS). The Packaging and Transportation Group of SRTC is coordinating the revision to this SARP. A Task Technical and Quality Assurance Plan directing this work was issued by CHT in February 1999. Initially, the primary interest in this testing was hydrogen generation. From these ``gas generation tests can be tracked in real-time by measuring the pressure of a sealed container of the materials being studied. Because multiple gas phase reactions are produced in the radiation field of the sample, material pressure measurements do not necessarily define the quantity of H{sub 2} generated. However, the change in total molecules of gas can be calculated using the ideal gas law from the pressure measurement, known container volume and sample temperature. A measurement of the actual headspace gases must be completed to calculate the H{sub 2} generation rate for a particular sample.'' As the results from these tests were reviewed, however, questions arose regarding the oxygen in the headspace gases. Specifically, do the data from some tests indicate that oxygen was generated for those tests? And do the data for other tests indicate that the oxygen was depleted for them? A statistical analysis of the oxygen data derived from these tests is provided in this report to help answer these questions.

  2. Testosterone improves erectile function through inhibition of reactive oxygen species generation in castrated rats

    PubMed Central

    Li, Rui; Meng, Xianghu; Zhang, Yan; Wang, Tao; Yang, Jun; Niu, Yonghua; Cui, Kai; Wang, Shaogang

    2016-01-01

    Testosterone is overwhelmingly important in regulating erectile physiology. However, the associated molecular mechanisms are poorly understood. The purpose of this study was to explore the effects and mechanisms of testosterone in erectile dysfunction (ED) in castrated rats. Forty male Sprague-Dawley rats were randomized to four groups (control, sham-operated, castration and castration-with-testosterone-replacement). Reactive oxygen species (ROS) production was measured by dihydroethidium (DHE) staining. Erectile function was assessed by the recording of intracavernous pressure (ICP) and mean arterial blood pressure (MAP). Protein expression levels were examined by western blotting. We found that castration reduced erectile function and that testosterone restored it. Nitric oxide synthase (NOS) activity was decrease in the castrated rats, and testosterone administration attenuated this decrease (each p < 0.05). The testosterone, dihydrotestosterone, cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) concentrations were lower in the castrated rats, and testosterone restored these levels (each p < 0.05). Furthermore, the cyclooxygenase-2 (COX-2) and prostacyclin synthase (PTGIS) expression levels and phospho-endothelial nitric oxide synthase (p-eNOS, Ser1177)/endothelial nitric oxide synthase (eNOS) ratio were reduced in the castrated rats compared with the controls (each p < 0.05). In addition, the p40phox and p67phox expression levels were increased in the castrated rats, and testosterone reversed these changes (each p < 0.05). Overall, our results demonstrate that testosterone ameliorates ED after castration by reducing ROS production and increasing the activity of the eNOS/cGMP and COX-2/PTGIS/cAMP signaling pathways. PMID:27168996

  3. Smoke extract impairs adenosine wound healing: implications of smoke-generated reactive oxygen species.

    PubMed

    Allen-Gipson, Diane S; Zimmerman, Matthew C; Zhang, Hui; Castellanos, Glenda; O'Malley, Jennifer K; Alvarez-Ramirez, Horacio; Kharbanda, Kusum; Sisson, Joseph H; Wyatt, Todd A

    2013-05-01

    Adenosine concentrations are elevated in the lungs of patients with asthma and chronic obstructive pulmonary disease, where it balances between tissue repair and excessive airway remodeling. We previously demonstrated that the activation of the adenosine A2A receptor promotes epithelial wound closure. However, the mechanism by which adenosine-mediated wound healing occurs after cigarette smoke exposure has not been investigated. The present study investigates whether cigarette smoke exposure alters adenosine-mediated reparative properties via its ability to induce a shift in the oxidant/antioxidant balance. Using an in vitro wounding model, bronchial epithelial cells were exposed to 5% cigarette smoke extract, were wounded, and were then stimulated with either 10 μM adenosine or the specific A2A receptor agonist, 5'-(N-cyclopropyl)-carboxamido-adenosine (CPCA; 10 μM), and assessed for wound closure. In a subset of experiments, bronchial epithelial cells were infected with adenovirus vectors encoding human superoxide dismutase and/or catalase or control vector. In the presence of 5% smoke extract, significant delay was evident in both adenosine-mediated and CPCA-mediated wound closure. However, cells pretreated with N-acetylcysteine (NAC), a nonspecific antioxidant, reversed smoke extract-mediated inhibition. We found that cells overexpressing mitochondrial catalase repealed the smoke extract inhibition of CPCA-stimulated wound closure, whereas superoxide dismutase overexpression exerted no effect. Kinase experiments revealed that smoke extract significantly reduced the A2A-mediated activation of cyclic adenosine monophosphate-dependent protein kinase. However, pretreatment with NAC reversed this effect. In conclusion, our data suggest that cigarette smoke exposure impairs A2A-stimulated wound repair via a reactive oxygen species-dependent mechanism, thereby providing a better understanding of adenosine signaling that may direct the development of pharmacological

  4. Electrocatalytic Activity of Transition Metal Oxide-Carbon Composites for Oxygen Reduction in Alkaline Batteries and Fuel Cells

    SciTech Connect

    Malkhandi, S; Trinh, P; Manohar, AK; Jayachandrababu, KC; Kindler, A; Prakash, GKS; Narayanan, SR

    2013-06-07

    Conductive transition metal oxides (perovskites, spinels and pyrochlores) are attractive as catalysts for the air electrode in alkaline rechargeable metal-air batteries and fuel cells. We have found that conductive carbon materials when added to transition metal oxides such as calcium-doped lanthanum cobalt oxide, nickel cobalt oxide and calcium-doped lanthanum manganese cobalt oxide increase the electrocatalytic activity of the oxide for oxygen reduction by a factor of five to ten. We have studied rotating ring-disk electrodes coated with (a) various mass ratios of carbon and transition metal oxide, (b) different types of carbon additives and (c) different types of transition metal oxides. Our experiments and analysis establish that in such composite catalysts, carbon is the primary electro- catalyst for the two-electron electro-reduction of oxygen to hydroperoxide while the transition metal oxide decomposes the hydroperoxide to generate additional oxygen that enhances the observed current resulting in an apparent four-electron process. These findings are significant in that they change the way we interpret previous reports in the scientific literature on the electrocatalytic activity of various transition metal oxide- carbon composites for oxygen reduction, especially where carbon is assumed to be an additive that just enhances the electronic conductivity of the oxide catalyst. (C) 2013 The Electrochemical Society. All rights reserved.

  5. Oxygen dependence of metabolic fluxes and energy generation of Saccharomyces cerevisiae CEN.PK113-1A

    PubMed Central

    Jouhten, Paula; Rintala, Eija; Huuskonen, Anne; Tamminen, Anu; Toivari, Mervi; Wiebe, Marilyn; Ruohonen, Laura; Penttilä, Merja; Maaheimo, Hannu

    2008-01-01

    Background The yeast Saccharomyces cerevisiae is able to adjust to external oxygen availability by utilizing both respirative and fermentative metabolic modes. Adjusting the metabolic mode involves alteration of the intracellular metabolic fluxes that are determined by the cell's multilevel regulatory network. Oxygen is a major determinant of the physiology of S. cerevisiae but understanding of the oxygen dependence of intracellular flux distributions is still scarce. Results Metabolic flux distributions of S. cerevisiae CEN.PK113-1A growing in glucose-limited chemostat cultures at a dilution rate of 0.1 h-1 with 20.9%, 2.8%, 1.0%, 0.5% or 0.0% O2 in the inlet gas were quantified by 13C-MFA. Metabolic flux ratios from fractional [U-13C]glucose labelling experiments were used to solve the underdetermined MFA system of central carbon metabolism of S. cerevisiae. While ethanol production was observed already in 2.8% oxygen, only minor differences in the flux distribution were observed, compared to fully aerobic conditions. However, in 1.0% and 0.5% oxygen the respiratory rate was severely restricted, resulting in progressively reduced fluxes through the TCA cycle and the direction of major fluxes to the fermentative pathway. A redistribution of fluxes was observed in all branching points of central carbon metabolism. Yet only when oxygen provision was reduced to 0.5%, was the biomass yield exceeded by the yields of ethanol and CO2. Respirative ATP generation provided 59% of the ATP demand in fully aerobic conditions and still a substantial 25% in 0.5% oxygenation. An extensive redistribution of fluxes was observed in anaerobic conditions compared to all the aerobic conditions. Positive correlation between the transcriptional levels of metabolic enzymes and the corresponding fluxes in the different oxygenation conditions was found only in the respirative pathway. Conclusion 13C-constrained MFA enabled quantitative determination of intracellular fluxes in conditions of

  6. Growth inhibition dependent on reactive oxygen species generated by C9-UK-2A, a derivative of the antifungal antibiotic UK-2A, in Saccharomyces cerevisiae.

    PubMed

    Fujita, Ken-Ichi; Tani, Kazunori; Usuki, Yoshinosuke; Tanaka, Toshio; Taniguchi, Makoto

    2004-08-01

    UK-2A is a potent antifungal antibiotic and its structure is highly similar to that of antimycin A3 (AA). UK-2A and AA inhibit mitochondrial electron transport at complex III. C9-UK-2A, which has been prepared to improve the duration of the antifungal activity of UK-2A, shows durable fungicidal activities against various species of fungi and induces both membrane injury and the generation of cellular reactive oxygen species (ROS) against Rhodotorula mucilaginosa IFO 0001 cells. We found that C9-UK-2A inhibited the vegetative growth of Saccharomyces cerevisiae IFO 0203 cells accompanying cellular ROS generation in Sabouraud dextrose (SD) medium, which contained a fermentable carbon source. The ROS generation was completely restricted by pretreatment with a lipophilic antioxidant alpha-tocopherol. In addition, the pretreatment with the antioxidant protected against the growth inhibition induced by C9-UK-2A. C9-UK-2A also induced ROS generation in isolated mitochondria of the S. cerevisiae cells. The addition of both a complex I inhibitor rotenone and a complex II inhibitor thenoyltrifluoroacetone reduced ROS generation induced by C9-UK-2A in the whole cells and the isolated mitochondria. The addition of the inhibitors of complex III, AA or myxothiazol, or of complex IV, KCN, did not reduce ROS generation. These results suggest that C9-UK-2A induces ROS generation due to the blockade of electron flow at complex III, thereby inhibiting the growth of S. cerevisiae in SD medium. PMID:15515888

  7. Singlet oxygen generation from [bis(trifluoroacetoxy)iodo]benzene and hydrogen peroxide.

    PubMed

    Catir, Mustafa; Kilic, Hamdullah; Nardello-Rataj, Véronique; Aubry, Jean-Marie; Kazaz, Cavit

    2009-06-19

    Decomposition of hydrogen peroxide with a hypervalent iodine compound was examined. The results indicate that treatment of a hypervalent iodine compound with hydrogen peroxide produces singlet molecular oxygen ((1)O(2)). Convergent evidence for the production of singlet molecular oxygen ((1)O(2)) by decomposition of hydrogen peroxide with a hypervalent iodine compound comes from chemical trapping experiments and the specific chemiluminescence detection of (1)O(2) at 1270 nm. Substantial evidence demonstrates that hydroperoxyl radical produced from hydrogen peroxide with hypervalent iodine reacts via a tetraoxidane intermediate, decomposing to give singlet molecular oxygen. PMID:19449850

  8. Salinomycin simultaneously induces apoptosis and autophagy through generation of reactive oxygen species in osteosarcoma U2OS cells.

    PubMed

    Kim, Sang-Hun; Choi, Young-Jun; Kim, Kwang-Youn; Yu, Sun-Nyoung; Seo, Young-Kyo; Chun, Sung-Sik; Noh, Kyung-Tae; Suh, Jeung-Tak; Ahn, Soon-Cheol

    2016-04-29

    Salinomycin, a polyether antibiotic, acts as a highly selective potassium ionophore. It was reported to anticancer activity on various cancer cell lines. In this study, salinomycin was examined on apoptosis and autophagy through generation of reactive oxygen species (ROS) in osteosarcoma U2OS cells. Apoptosis, autophagy, mitochondrial membrane potential (MMP) and ROS were analyzed using flow cytometry. Also, expressions of apoptosis- and autophagy-related proteins were determined by western blotting. As a result, salinomycin triggered apoptosis of U2OS cells, which was accompanied by change of MMP and cleavage of caspases-3 and poly (ADP-ribose) polymerase. And salinomycin increased the expression of autophagy-related protein and accumulation of acidic vesicular organelles (AVO). Salinomycin-induced ROS production promotes both apoptosis and autophagy, as evidenced by the result that treatment of N-acetyl-l-cysteine (NAC), a ROS scavenger, attenuated both apoptosis and autophagy. In addition, inhibition of autophagy by 3-methyladenine (3 MA) enhanced the salinoymcin-induced apoptosis. Taken together, these results suggested that salinomycin-induced autophagy, as a survival mechanism, might be a potential strategy through ROS regulation in cancer therapy. PMID:27033598

  9. Polymeric micelles of zinc protoporphyrin for tumor targeted delivery based on EPR effect and singlet oxygen generation.

    PubMed

    Iyer, Arun K; Greish, Khaled; Seki, Takahiro; Okazaki, Shoko; Fang, Jun; Takeshita, Keizo; Maeda, Hiroshi

    2007-01-01

    Polymeric micelles of zinc protoporphyrin (ZnPP) with water soluble biocompatible and amphiphilic polymer, polyethylene glycol (PEG) demonstrated unique characteristics to target tumor tissues selectively based on the enhanced permeability and retention (EPR) effect. The micellar macromolecular drug of ZnPP (SMA-ZnPP and PEG-ZnPP) previously showed notable anticancer activity as a consequence of selective tumor targeting ability and its potent HO-1 inhibitory potential, resulting in suppressed biliverdin/bilirubin production in tumors thereby leading to oxystress induced tumor cell killing. Furthermore, recent findings also showed that ZnPP efficiently generated reactive singlet oxygen under illumination of visible light, laser, or xenon light source, which could augment its oxystress induced cell killing abilities. In the present paper, we report the synergistic effects of light induced photosensitizing capabilities and HO-1 inhibitory potentials of these unique micelles when tested in vitro and in vivo on tumor models under localized, mild illumination conditions using a tungsten-xenon light source. The results indicate that these water soluble polymeric micelles of ZnPP portend to be promising candidates for targeted chemotherapy as well as photodynamic therapy against superficial tumors as well as solid tumors located at light penetrable depths.

  10. Estimating evaporative vapor generation from automobiles based on parking activities.

    PubMed

    Dong, Xinyi; Tschantz, Michael; Fu, Joshua S

    2015-07-01

    A new approach is proposed to quantify the evaporative vapor generation based on real parking activity data. As compared to the existing methods, two improvements are applied in this new approach to reduce the uncertainties: First, evaporative vapor generation from diurnal parking events is usually calculated based on estimated average parking duration for the whole fleet, while in this study, vapor generation rate is calculated based on parking activities distribution. Second, rather than using the daily temperature gradient, this study uses hourly temperature observations to derive the hourly incremental vapor generation rates. The parking distribution and hourly incremental vapor generation rates are then adopted with Wade-Reddy's equation to estimate the weighted average evaporative generation. We find that hourly incremental rates can better describe the temporal variations of vapor generation, and the weighted vapor generation rate is 5-8% less than calculation without considering parking activity.

  11. Curcumin induces ER stress-mediated apoptosis through selective generation of reactive oxygen species in cervical cancer cells.

    PubMed

    Kim, Boyun; Kim, Hee Seung; Jung, Eun-Ji; Lee, Jung Yun; K Tsang, Benjamin; Lim, Jeong Mook; Song, Yong Sang

    2016-05-01

    Prolonged accumulation of misfolded or unfolded proteins caused by cellular stress, including oxidative stress, induces endoplasmic reticulum stress, which then activates an unfolded protein response (UPR). ER stress is usually maintained at higher levels in cancer cells as compared to normal cells due to altered metabolism in cancer. Here, we investigated whether curcumin is ER stress-mediated apoptosis in cervical cancer cells, and ROS increased by curcumin are involved in the process as an upstream contributor. Curcumin inhibited proliferation of cervical cancer cells (C33A, CaSki, HeLa, and ME180) and induced apoptotic cell death. Curcumin activated ER-resident UPR sensors, such as PERK, IRE-1α, and ATF6, and their downstream-signaling proteins in cervical cancer cells, but not in normal epithelial cells and peripheral blood mononuclear cells (PBMCs). CHOP, a key factor involved in ER stress-mediated apoptosis, was also activated by curcumin. CHOP decreased the ratio of anti-apoptotic protein Bcl-2 to pro-apoptotic protein Bax expression, and subsequently increased the apoptotic population of cervical cancer cells. Furthermore, curcumin elevated levels of intracellular reactive oxygen species (ROS) in cervical cancer cells, but not in normal epithelial cells. Scavenging ROS resulted in inhibition of ER stress and partially restored cell viability in curcumin-treated cancer cells. Collectively, these observations show that curcumin promotes ER stress-mediated apoptosis in cervical cancer cells through increase of cell type-specific ROS generation. Therefore, modulation of these differential responses to curcumin between normal and cervical cancer cells could be an effective therapeutic strategy without adverse effects on normal cells.

  12. Leinamycin E1 acting as an anticancer prodrug activated by reactive oxygen species

    PubMed Central

    Huang, Sheng-Xiong; Yun, Bong-Sik; Ma, Ming; Basu, Hirak S.; Church, Dawn R.; Ingenhorst, Gudrun; Huang, Yong; Yang, Dong; Lohman, Jeremy R.; Tang, Gong-Li; Ju, Jianhua; Liu, Tao; Wilding, George; Shen, Ben

    2015-01-01

    Leinamycin (LNM) is a potent antitumor antibiotic produced by Streptomyces atroolivaceus S-140, featuring an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring. Upon reductive activation in the presence of cellular thiols, LNM exerts its antitumor activity by an episulfonium ion-mediated DNA alkylation. Previously, we have cloned the lnm gene cluster from S. atroolivaceus S-140 and characterized the biosynthetic machinery responsible for the 18-membered lactam backbone and the alkyl branch at C3 of LNM. We now report the isolation and characterization of leinamycin E1 (LNM E1) from S. atroolivacues SB3033, a ΔlnmE mutant strain of S. atroolivaceus S-140. Complementary to the reductive activation of LNM by cellular thiols, LNM E1 can be oxidatively activated by cellular reactive oxygen species (ROS) to generate a similar episulfonium ion intermediate, thereby alkylating DNA and leading to eventual cell death. The feasibility of exploiting LNM E1 as an anticancer prodrug activated by ROS was demonstrated in two prostate cancer cell lines, LNCaP and DU-145. Because many cancer cells are under higher cellular oxidative stress with increased levels of ROS than normal cells, these findings support the idea of exploiting ROS as a means to target cancer cells and highlight LNM E1 as a novel lead for the development of anticancer prodrugs activated by ROS. The structure of LNM E1 also reveals critical new insights into LNM biosynthesis, setting the stage to investigate sulfur incorporation, as well as the tailoring steps that convert the nascent hybrid peptide–polyketide biosynthetic intermediate into LNM. PMID:26056295

  13. The effect of mayfly (Hexagenia spp.) burrowing activity on sediment oxygen demand in western Lake Erie

    USGS Publications Warehouse

    Edwards, William J.; Soster, Frederick M.; Matisoff, Gerald; Schloesser, Donald W.

    2009-01-01

    Previous studies support the hypothesis that large numbers of infaunal burrow-irrigating organisms in the western basin of Lake Erie may increase significantly the sediment oxygen demand, thus enhancing the rate of hypolimnetic oxygen depletion. We conducted laboratory experiments to quantify burrow oxygen dynamics and increased oxygen demand resulting from burrow irrigation using two different year classes of Hexagenia spp. nymphs from western Lake Erie during summer, 2006. Using oxygen microelectrodes and hot film anemometry, we simultaneously determined oxygen concentrations and burrow water flow velocities. Burrow oxygen depletion rates ranged from 21.7 mg/nymph/mo for 15 mm nymphs at 23 °C to 240.7 mg/nymph/mo for 23 mm nymphs at 13 °C. Sealed microcosm experiments demonstrated that mayflies increase the rate of oxygen depletion by 2-5 times that of controls, depending on size of nymph and water temperature, with colder waters having greater impact. At natural population densities, nymph pumping activity increased total sediment oxygen demand 0.3-2.5 times compared to sediments with no mayflies and accounted for 22-71% of the total sediment oxygen demand. Extrapolating laboratory results to the natural system suggest that Hexagenia spp. populations may exert a significant control on oxygen depletion during intermittent stratification. This finding may help explain some of the fluctuations in Hexagenia spp. population densities in western Lake Erie and suggests that mayflies, by causing their own population collapse irrespective of other environmental conditions, may need longer term averages when used as a bio-indicator of the success of pollution-abatement programs in western Lake Erie and possibly throughout the Great Lakes.

  14. Fluidic Active Transducer for Electricity Generation.

    PubMed

    Yang, YoungJun; Park, Junwoo; Kwon, Soon-Hyung; Kim, Youn Sang

    2015-01-01

    Flows in small size channels have been studied for a long time over multidisciplinary field such as chemistry, biology and medical through the various topics. Recently, the attempts of electricity generation from the small flows as a new area for energy harvesting in microfluidics have been reported. Here, we propose for the first time a new fluidic electricity generator (FEG) by modulating the electric double layer (EDL) with two phase flows of water and air without external power sources. We find that an electric current flowed by the forming/deforming of the EDL with a simple separated phase flow of water and air at the surface of the FEG. Electric signals between two electrodes of the FEG are checked from various water/air passing conditions. Moreover, we verify the possibility of a self-powered air slug sensor by applying the FEG in the detection of an air slug.

  15. Fluidic Active Transducer for Electricity Generation

    PubMed Central

    Yang, YoungJun; Park, Junwoo; Kwon, Soon-Hyung; Kim, Youn Sang

    2015-01-01

    Flows in small size channels have been studied for a long time over multidisciplinary field such as chemistry, biology and medical through the various topics. Recently, the attempts of electricity generation from the small flows as a new area for energy harvesting in microfluidics have been reported. Here, we propose for the first time a new fluidic electricity generator (FEG) by modulating the electric double layer (EDL) with two phase flows of water and air without external power sources. We find that an electric current flowed by the forming/deforming of the EDL with a simple separated phase flow of water and air at the surface of the FEG. Electric signals between two electrodes of the FEG are checked from various water/air passing conditions. Moreover, we verify the possibility of a self-powered air slug sensor by applying the FEG in the detection of an air slug. PMID:26511626

  16. Fluidic Active Transducer for Electricity Generation.

    PubMed

    Yang, YoungJun; Park, Junwoo; Kwon, Soon-Hyung; Kim, Youn Sang

    2015-01-01

    Flows in small size channels have been studied for a long time over multidisciplinary field such as chemistry, biology and medical through the various topics. Recently, the attempts of electricity generation from the small flows as a new area for energy harvesting in microfluidics have been reported. Here, we propose for the first time a new fluidic electricity generator (FEG) by modulating the electric double layer (EDL) with two phase flows of water and air without external power sources. We find that an electric current flowed by the forming/deforming of the EDL with a simple separated phase flow of water and air at the surface of the FEG. Electric signals between two electrodes of the FEG are checked from various water/air passing conditions. Moreover, we verify the possibility of a self-powered air slug sensor by applying the FEG in the detection of an air slug. PMID:26511626

  17. Cytotoxic and Antitumor Activity of Sulforaphane: The Role of Reactive Oxygen Species

    PubMed Central

    Sestili, Piero; Fimognari, Carmela

    2015-01-01

    According to recent estimates, cancer continues to remain the second leading cause of death and is becoming the leading one in old age. Failure and high systemic toxicity of conventional cancer therapies have accelerated the identification and development of innovative preventive as well as therapeutic strategies to contrast cancer-associated morbidity and mortality. In recent years, increasing body of in vitro and in vivo studies has underscored the cancer preventive and therapeutic efficacy of the isothiocyanate sulforaphane. In this review article, we highlight that sulforaphane cytotoxicity derives from complex, concurring, and multiple mechanisms, among which the generation of reactive oxygen species has been identified as playing a central role in promoting apoptosis and autophagy of target cells. We also discuss the site and the mechanism of reactive oxygen species' formation by sulforaphane, the toxicological relevance of sulforaphane-formed reactive oxygen species, and the death pathways triggered by sulforaphane-derived reactive oxygen species. PMID:26185755

  18. Induction of Reactive Oxygen Species Generation Inhibits Epithelial-Mesenchymal Transition and Promotes Growth Arrest in Prostate Cancer Cells

    PubMed Central

    Das, Trinath P; Suman, Suman; Damodaran, Chendil

    2013-01-01

    Oxidative stress is one causative factor of the pathogenesis and aggressiveness of most of the cancer types, including prostate cancer (CaP). A moderate increase in reactive oxygen species (ROS) induces cell proliferation whereas excessive amounts of ROS promote apoptosis. In this study, we explored the pro-oxidant property of 3, 9-dihydroxy-2-prenylcoumestan [psoralidin (pso)], a dietary agent, on CaP (PC-3 and C4-2B) cells. Pso greatly induced ROS expression (more than 20-fold) that resulted in the growth inhibition of CaP cells. Overexpression of anti-oxidant enzymes superoxide dismutase 1 (SOD1), SOD2, and catalase, or pretreatment with the pharmacological inhibitor N-acetylcysteine (NAC) significantly attenuated both pso-mediated ROS generation and pso-mediated growth inhibition in CaP cells. Furthermore, pso administration significantly inhibited the migratory and invasive property of CaP cells by decreasing the transcription of β-catenin, snail, and slug, which promote epithelial mesenchymal transition (EMT), and by concurrently inducing E-cadherin expression in CaP cells. Pso-induced ROS generation in CaP cells resulted in loss of mitochondrial membrane potential, cytochrome-c release, and activation of caspase-3 and -9 and poly (ADP-ribose) polymerase (PARP), which led to apoptosis. On the other hand, overexpression of anti-oxidants rescued pso-mediated effects on CaP cells. These findings suggest that increasing the threshold of intracellular ROS could prevent or treat CaP growth and metastasis. PMID:23475579

  19. Singlet oxygen scavenging activity and cytotoxicity of essential oils from rutaceae.

    PubMed

    Ao, Yoko; Satoh, Kazue; Shibano, Katsushige; Kawahito, Yukari; Shioda, Seiji

    2008-07-01

    Since we have been exposed to excessive amounts of stressors, aromatherapy for the relaxation has recently become very popular recently. However, there is a problem which responds to light with the essential oil used by aromatherapy. It is generally believed that singlet oxygen is implicated in the pathogenesis of various diseases such as light-induced skin disorders and inflammatory responses. Here we studied whether essential oils can effectively scavenge singlet oxygen upon irradiation, using the electron spin resonance (ESR) method. Green light was used to irradiate twelve essential oils from rutaceae. Among these twelve essential oils, eight were prepared by the expression (or the compression) method (referred to as E oil), and four samples were prepared by the steam distillation method (referred to as SD oil). Five E oils enhanced singlet oxygen production. As these essential oils may be phototoxic, it should be used for their use whit light. Two E oils and three SD oils showed singlet oxygen scavenging activity. These results may suggest that the antioxidant activity of essential oils are judged from their radical scavenging activity. Essential oils, which enhance the singlet oxygen production and show higher cytotoxicity, may contain much of limonene. These results suggest that limonene is involved not only in the enhancement of singlet oxygen production but also in the expression of cytotoxic activity, and that attention has to be necessary for use of blended essential oils.

  20. Benzene's metabolites alter c-MYB activity via reactive oxygen species in HD3 cells

    SciTech Connect

    Wan, Joanne; Winn, Louise M. . E-mail: winnl@queensu.ca

    2007-07-15

    Benzene is a known leukemogen that is metabolized to form reactive intermediates and reactive oxygen species (ROS). The c-Myb oncoprotein is a transcription factor that has a critical role in hematopoiesis. c-Myb transcript and protein have been overexpressed in a number of leukemias and cancers. Given c-Myb's role in hematopoiesis and leukemias, it is hypothesized that benzene interferes with the c-Myb signaling pathway and that this involves ROS. To investigate our hypothesis, we evaluated whether benzene, 1,4-benzoquinone, hydroquinone, phenol, and catechol generated ROS in chicken erythroblast HD3 cells, as measured by 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (DCFDA) and dihydrorhodamine-123 (DHR-123), and whether the addition of 100 U/ml of the antioxidating enzyme superoxide dismutase (SOD) could prevent ROS generation. Reduced to oxidized glutathione ratios (GSH:GSSG) were also assessed as well as hydroquinone and benzoquinone's effects on c-Myb protein levels and activation of a transiently transfected reporter construct. Finally we attempted to abrogate benzene metabolite mediated increases in c-Myb activity with the use of SOD. We found that benzoquinone, hydroquinone, and catechol increased DCFDA fluorescence, increased DHR-123 fluorescence, decreased GSH:GSSG ratios, and increased reporter construct expression after 24 h of exposure. SOD was able to prevent DCFDA fluorescence and c-Myb activity caused by benzoquinone and hydroquinone only. These results are consistent with other studies, which suggest metabolite differences in benzene-mediated toxicity. More importantly, this study supports the hypothesis that benzene may mediate its toxicity through ROS-mediated alterations in the c-Myb signaling pathway.

  1. Gardenin B-induced cell death in human leukemia cells involves multiple caspases but is independent of the generation of reactive oxygen species.

    PubMed

    Cabrera, Javier; Saavedra, Ester; Del Rosario, Henoc; Perdomo, Juan; Loro, Juan F; Cifuente, Diego A; Tonn, Carlos E; García, Celina; Quintana, José; Estévez, Francisco

    2016-08-25

    Flavonoids have attracted great interest due to their possible anticancer activities. Here we investigated the antiproliferative activity of the flavonoids isolated from Baccharis scandens against human leukemia cell lines and found that the methoxyflavonoid gardenin B was the most cytotoxic compound against HL-60 and U-937 cells, showing IC50 values between 1.6 and 3.0 μM, but had no significant cytotoxic effects against quiescent or proliferating human peripheral blood mononuclear cells. These effects on viability were accompanied by the concentration- and time-dependent appearance of apoptosis as evidenced by DNA fragmentation, formation of apoptotic bodies and a sub-G1 ratio increase. Comparative studies with the best-studied bioflavonoid quercetin indicate that gardenin B is a more cytotoxic and more apoptotic inducer than quercetin. Cell death induced by gardenin B was associated with: (i) a significant induction of caspase-2, -3, -8 and -9 activities; (ii) cleavage of the initiator caspases (caspase-2, -8 and -9), of the executioner caspase-3, and of poly(ADP-ribose) polymerase; and (iii) a concentration-dependent reactive oxygen species generation. In conclusion, apoptosis induced by gardenin B is associated with activation of both the extrinsic and the intrinsic apoptotic pathways of cell death and occurs through a mechanism that is independent of the generation of reactive oxygen species. PMID:27423764

  2. Gardenin B-induced cell death in human leukemia cells involves multiple caspases but is independent of the generation of reactive oxygen species.

    PubMed

    Cabrera, Javier; Saavedra, Ester; Del Rosario, Henoc; Perdomo, Juan; Loro, Juan F; Cifuente, Diego A; Tonn, Carlos E; García, Celina; Quintana, José; Estévez, Francisco

    2016-08-25

    Flavonoids have attracted great interest due to their possible anticancer activities. Here we investigated the antiproliferative activity of the flavonoids isolated from Baccharis scandens against human leukemia cell lines and found that the methoxyflavonoid gardenin B was the most cytotoxic compound against HL-60 and U-937 cells, showing IC50 values between 1.6 and 3.0 μM, but had no significant cytotoxic effects against quiescent or proliferating human peripheral blood mononuclear cells. These effects on viability were accompanied by the concentration- and time-dependent appearance of apoptosis as evidenced by DNA fragmentation, formation of apoptotic bodies and a sub-G1 ratio increase. Comparative studies with the best-studied bioflavonoid quercetin indicate that gardenin B is a more cytotoxic and more apoptotic inducer than quercetin. Cell death induced by gardenin B was associated with: (i) a significant induction of caspase-2, -3, -8 and -9 activities; (ii) cleavage of the initiator caspases (caspase-2, -8 and -9), of the executioner caspase-3, and of poly(ADP-ribose) polymerase; and (iii) a concentration-dependent reactive oxygen species generation. In conclusion, apoptosis induced by gardenin B is associated with activation of both the extrinsic and the intrinsic apoptotic pathways of cell death and occurs through a mechanism that is independent of the generation of reactive oxygen species.

  3. Activity and Stability of Nanoscale Oxygen Reduction Catalysts

    SciTech Connect

    Shao-Horn, Yang

    2015-07-28

    Design of highly active and stable nanoscale catalysts for electro-oxidation of small organic molecules is of great importance to the development of efficient fuel cells. The amount and instability of Pt-based catalysts in the cathode limits the cost, efficiency and lifetime of proton exchange membrane fuel cells. We developed a microscopic understanding of the factors governing activity and stability in Pt and PtM alloys. Experimental efforts were focused on probing the size and shape dependence of ORR activity of Pt-based nanoparticles supported on carbon nanotubes. A microscopic understanding of the activity was achieved by correlating voltammetry and rotating ring disk electrodes to surface atomic and electronic structures, which were elucidated predominantly by high-resolution transmission electron microscopy (HRTEM), Scanning transmission electron microscopy energy dispersive X-ray Spectroscopy (STEM-EDS) and synchrotron X-ray absorption spectroscopy (XAS).

  4. Generation of radical oxygen species by neural crest cells treated in vitro with isotretinoin and 4-oxo-isotretinoin.

    PubMed

    Davis, W L; Crawford, L A; Cooper, O J; Farmer, G R; Thomas, D; Freeman, B L

    1990-01-01

    The effects of isotretinoin (IR) and its primary metabolite (in the human), 4-oxo-isotretinoin (4-OIR or OIR), on isolated chick neural crest cells (NCC's) in culture were studied. NCC's were found to be deficient in both superoxide dismutase (SOD) and catalase, two of the enzymes known to function in the "scavenging" (dismutation) of toxic radical oxygen species (ROS) such as the superoxide anion and hydrogen peroxide. The addition of IR or OIR to the culture medium significantly depressed the viability of the NCC's when compared to untreated cells. OIR was more potent in this regard than IR. In the presence of either IR or OIR, NCC's generated superoxide anions (O2.), hydrogen peroxide (H2O2), and hydroxyl anions (OH.). OIR was again more potent. The cytotoxicity of IR or OIR was demonstrated by the "leakage" of radioactive chromium from prelabeled cells. The latter is suggestive of a primary surface membrane defect, most logically via the induction of lipid peroxides by the retinoids. The latter is accompanied by an increase in membrane permeability and porosity as evidenced by the fact that various fluorescently labeled molecules, including BSA-FITC (MW 69,000), gain entrance into the cytoplasm of the retinoid treated cells. No label was seen in the cytoplasm of similarly treated control cells. When SOD (200 units/ml) or catalase (400 units/ml) was added to the culture media of IR- or OIR-treated NCCs, cell viability was increased and the concentration of the various ROS generated was decreased. Membrane leakiness to chromium and FITC-BSA was also decreased in the presence of these enzymes. Free radicals, when not inactivated (dismutated), are known to be pathobiotic to most cells. Cell membranes are at a particular high risk from ROS which induce structural, physiological, and biochemical alterations in the cell membrane. The latter can have a negative effect on cell permeability, maintenance of normal ionic gradients, membrane enzyme activity, cell

  5. Temperature dependence of oxygen evolution through catalase-like activity of horseradish peroxidase

    NASA Astrophysics Data System (ADS)

    Popović-Bijelić, A.; Bijelić, G.; Kolar-Anić, Lj.; Vukojević, V.

    2007-09-01

    By experimental investigations of the temperature dependence of catalase-like activity of horseradish peroxidase in the temperature range 278 328 K, different kinetic profiles for oxygen evolution were found below and above 298 K. Extension of the model is proposed to account for these observations. By numeric simulations of the reaction kinetics at different temperatures, it was found that enhanced evaporation of molecular oxygen from the reaction solution is the main root through which oxygen is lost at elevated temperatures in laboratory conditions.

  6. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    NASA Astrophysics Data System (ADS)

    Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

    2015-12-01

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  7. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    SciTech Connect

    Jablonowski, H.; Hammer, M. U.; Reuter, S.; Bussiahn, R.; Weltmann, K.-D.; Woedtke, Th. von

    2015-12-15

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH{sub 2}O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H{sub 2}O{sub 2}) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O{sub 2}{sup •−}) and hydroxyl radicals ({sup •}OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  8. Relationship between Active Oxygen Species, Lipid Peroxidation, Necrosis, and Phytoalexin Production Induced by Elicitins in Nicotiana.

    PubMed Central

    Rusterucci, C.; Stallaert, V.; Milat, M. L.; Pugin, A.; Ricci, P.; Blein, J. P.

    1996-01-01

    Excised leaves of Nicotiana tabacum var Xanthi and Nicotiana rustica were treated with cryptogein and capsicein, basic and acidic elicitins, respectively. Both compounds induced leaf necrosis, the intensity of which depended on concentration and duration of treatment. N. tabacum var Xanthi was the most sensitive species and cryptogein was the most active elicitin. Lipid peroxidation in elicitin-treated Nicotiana leaves was closely correlated with the appearance of necrosis. Elicitin treatments induced a rapid and transient burst of active oxygen species (AOS) in cell cultures of both Nicotiana species, with the production by Xanthi cells being 6-fold greater than that by N. rustica. Similar maximum AOS production levels were observed with both elicitins, but capsicein required 10-fold higher concentrations than those of cryptogein. Phytoalexin production was lower in response to both elicitins in N. tabacum var Xanthi cells than in N. rustica cells, and capsicein was the most efficient elicitor of this response. In cryptogein-treated cell suspensions, phytoalexin synthesis was unaffected by diphenyleneiodonium, which inhibited AOS generation, nor was it affected by tiron or catalase, which suppressed AOS accumulation in the extracellular medium. These results suggest that AOS production, lipid peroxidation, and necrosis are directly related, whereas phytoalexin production depends on neither the presence nor the intensity of these responses. PMID:12226334

  9. Loading effects of silver oxides upon generation of reactive oxygen species in semiconductor photocatalysis.

    PubMed

    Kohtani, Shigeru; Yoshida, Kazuhiro; Maekawa, Toshiyasu; Iwase, Akihide; Kudo, Akihiko; Miyabe, Hideto; Nakagaki, Ryoichi

    2008-05-28

    Superoxide anion radical (O(2)(-*)) and OH radical generations in suspensions of Ag metal-, Ag(2)O-, or AgO-loaded TiO(2) and BiVO(4) photocatalysts in alkaline conditions (pH 12.0) were examined by means of a luminol chemiluminescence (CL) technique and a spin-trapping fluorescence one in which terephthalic acid reacts with an OH radical to afford the highly fluorescent 2-hydroxyterephthalic acid (TAOH), respectively. The observed luminol CL intensity was remarkably enhanced by the AgO loading on TiO(2) as well as BiVO(4). This can be explained by enhancement of O(2)(-*) production on the AgO-loaded photocatalysts caused by the synergetic effects on the thermocatalytic activity upon the AgO surface and the efficient electron-hole separation at the photocatalyst/AgO interface. On the other hand, loading effects of AgO on the TAOH formation were not so significant compared to those on the CL observation, though the TAOH formation rates for the TiO(2) samples were much larger than those for the BiVO(4) ones by about three orders of magnitude. The properties of O(2)(-*) and OH radical generations on these photocatalysts are discussed on the basis of the luminol CL kinetics and approximate band edge positions of TiO(2), BiVO(4), and silver oxides.

  10. Oxygen control of breathing by an olfactory receptor activated by lactate

    PubMed Central

    Chang, Andy J.; Ortega, Fabian E.; Riegler, Johannes; Madison, Daniel V.; Krasnow, Mark A.

    2015-01-01

    Summary Animals have evolved homeostatic responses to changes in oxygen availability that act on different time scales. Although the hypoxia-inducible factor (HIF) transcriptional pathway that controls long term responses to low oxygen (hypoxia) has been established1, the pathway that mediates acute responses to hypoxia in mammals is not well understood. Here we show that the olfactory receptor Olfr78 is highly and selectively expressed in oxygen-sensitive glomus cells of the carotid body, a chemosensory organ at the carotid artery bifurcation that monitors blood oxygen and stimulates breathing within seconds when oxygen declines2. Olfr78 mutants fail to increase ventilation in hypoxia but respond normally to hypercapnia. Glomus cells are present in normal numbers and appear structurally intact, but hypoxia-induced carotid body activity is diminished. Lactate, a metabolite that rapidly accumulates in hypoxia and induces hyperventilation3–6, activates Olfr78 in heterologous expression experiments, induces calcium transients in glomus cells, and stimulates carotid sinus nerve activity through Olfr78. We propose that in addition to its role in olfaction, Olfr78 acts as a hypoxia sensor in the breathing circuit by sensing lactate produced when oxygen levels decline. PMID:26560302

  11. Reporter cell activity within hydrogel constructs quantified from oxygen-independent bioluminescence.

    PubMed

    Lambrechts, Dennis; Roeffaers, Maarten; Kerckhofs, Greet; Hofkens, Johan; Van de Putte, Tom; Schrooten, Jan; Van Oosterwyck, Hans

    2014-09-01

    By providing a three-dimensional (3D) support to cells, hydrogels offer a more relevant in vivo tissue-like environment as compared to two-dimensional cell cultures. Hydrogels can be applied as screening platforms to investigate in 3D the role of biochemical and biophysical cues on cell behaviour using bioluminescent reporter cells. Gradients in oxygen concentration that result from the interplay between molecular transport and cell metabolism can however cause substantial variability in the observed bioluminescent reporter cell activity. To assess the influence of these oxygen gradients on the emitted bioluminescence for various hydrogel geometries, a combined experimental and modelling approach was implemented. We show that the applied model is able to predict oxygen gradient independent bioluminescent intensities which correlate better to the experimentally determined viable cell numbers, as compared to the experimentally measured bioluminescent intensities. By analysis of the bioluminescence reaction dynamics we obtained a quantitative description of cellular oxygen metabolism within the hydrogel, which was validated by direct measurements of oxygen concentration within the hydrogel. Bioluminescence peak intensities can therefore be used as a quantitative measurement of reporter cell activity within a hydrogel, but an unambiguous interpretation of these intensities requires a compensation for the influence of cell-induced oxygen gradients on the luciferase activity.

  12. Reporter cell activity within hydrogel constructs quantified from oxygen-independent bioluminescence.

    PubMed

    Lambrechts, Dennis; Roeffaers, Maarten; Kerckhofs, Greet; Hofkens, Johan; Van de Putte, Tom; Schrooten, Jan; Van Oosterwyck, Hans

    2014-09-01

    By providing a three-dimensional (3D) support to cells, hydrogels offer a more relevant in vivo tissue-like environment as compared to two-dimensional cell cultures. Hydrogels can be applied as screening platforms to investigate in 3D the role of biochemical and biophysical cues on cell behaviour using bioluminescent reporter cells. Gradients in oxygen concentration that result from the interplay between molecular transport and cell metabolism can however cause substantial variability in the observed bioluminescent reporter cell activity. To assess the influence of these oxygen gradients on the emitted bioluminescence for various hydrogel geometries, a combined experimental and modelling approach was implemented. We show that the applied model is able to predict oxygen gradient independent bioluminescent intensities which correlate better to the experimentally determined viable cell numbers, as compared to the experimentally measured bioluminescent intensities. By analysis of the bioluminescence reaction dynamics we obtained a quantitative description of cellular oxygen metabolism within the hydrogel, which was validated by direct measurements of oxygen concentration within the hydrogel. Bioluminescence peak intensities can therefore be used as a quantitative measurement of reporter cell activity within a hydrogel, but an unambiguous interpretation of these intensities requires a compensation for the influence of cell-induced oxygen gradients on the luciferase activity. PMID:24957291

  13. Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance, Photosensitizer Uptake and Reactive Oxygen Species Generation.

    PubMed

    Taraszkiewicz, Aleksandra; Szewczyk, Grzegorz; Sarna, Tadeusz; Bielawski, Krzysztof P; Nakonieczna, Joanna

    2015-01-01

    The increasing applicability of antifungal treatments, the limited range of available drug classes and the emergence of drug resistance in Candida spp. suggest the need for new treatment options. To explore the applicability of C. albicans photoinactivation, we examined nine structurally different imidazoacridinone derivatives as photosensitizing agents. The most effective derivatives showed a >10(4)-fold reduction of viable cell numbers. The fungicidal action of the three most active compounds was compared at different radiant powers (3.5 to 63 mW/cm2), and this analysis indicated that 7 mW/cm2 was the most efficient. The intracellular accumulation of these compounds in fungal cells correlated with the fungicidal activity of all 9 derivatives. The lack of effect of verapamil, an inhibitor targeting Candida ABC efflux pumps, suggests that these imidazoacridinones are not substrates for ABC transporters. Thus, unlike azoles, a major class of antifungals used against Candida, ABC transporter-mediated resistance is unlikely. Electron paramagnetic resonance (EPR)-spin trapping data suggested that the fungicidal light-induced action of these derivatives might depend on the production of superoxide anion. The highest generation rate of superoxide anion was observed for 1330H, 1610H, and 1611. Singlet oxygen production was also detected upon the irradiation of imidazoacridinone derivatives with UV laser light, with a low to moderate yield, depending on the type of compound. Thus, imidazoacridinone derivatives examined in the present study might act via mixed type I/type II photodynamic mechanism. The presented data indicate lack of direct correlation between the structures of studied imidazoacridinones, cell killing ability, and ROS production. However, we showed for the first time that for imidazoacridinones not only intracellular accumulation is necessary prerequisite of lethal photosensitization of C. albicans, but also localization within particular cellular

  14. Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance, Photosensitizer Uptake and Reactive Oxygen Species Generation.

    PubMed

    Taraszkiewicz, Aleksandra; Szewczyk, Grzegorz; Sarna, Tadeusz; Bielawski, Krzysztof P; Nakonieczna, Joanna

    2015-01-01

    The increasing applicability of antifungal treatments, the limited range of available drug classes and the emergence of drug resistance in Candida spp. suggest the need for new treatment options. To explore the applicability of C. albicans photoinactivation, we examined nine structurally different imidazoacridinone derivatives as photosensitizing agents. The most effective derivatives showed a >10(4)-fold reduction of viable cell numbers. The fungicidal action of the three most active compounds was compared at different radiant powers (3.5 to 63 mW/cm2), and this analysis indicated that 7 mW/cm2 was the most efficient. The intracellular accumulation of these compounds in fungal cells correlated with the fungicidal activity of all 9 derivatives. The lack of effect of verapamil, an inhibitor targeting Candida ABC efflux pumps, suggests that these imidazoacridinones are not substrates for ABC transporters. Thus, unlike azoles, a major class of antifungals used against Candida, ABC transporter-mediated resistance is unlikely. Electron paramagnetic resonance (EPR)-spin trapping data suggested that the fungicidal light-induced action of these derivatives might depend on the production of superoxide anion. The highest generation rate of superoxide anion was observed for 1330H, 1610H, and 1611. Singlet oxygen production was also detected upon the irradiation of imidazoacridinone derivatives with UV laser light, with a low to moderate yield, depending on the type of compound. Thus, imidazoacridinone derivatives examined in the present study might act via mixed type I/type II photodynamic mechanism. The presented data indicate lack of direct correlation between the structures of studied imidazoacridinones, cell killing ability, and ROS production. However, we showed for the first time that for imidazoacridinones not only intracellular accumulation is necessary prerequisite of lethal photosensitization of C. albicans, but also localization within particular cellular

  15. Reactive oxygen and nitrogen (ROS and RNS) species generation and cell death in tomato suspension cultures--Botrytis cinerea interaction.

    PubMed

    Pietrowska, E; Różalska, S; Kaźmierczak, A; Nawrocka, J; Małolepsza, U

    2015-01-01

    This article reports events connected to cell survival and Botrytis cinerea infection development in cell suspension cultures of two tomato cultivars which show different levels of susceptibility to the pathogen: cv. Corindo (more susceptible) and cv. Perkoz (less susceptible). In parallel changes in reactive oxygen (ROS) and nitrogen (RNS) species generation and in S-nitrosoglutathione reductase (GSNOR) activity were studied. In vivo staining methods with acridine orange (AO) and ethidium bromide (EB) as well as fluorescent microscopy were used to assess tomato and B. cinerea cells death. The biochemical studies of ROS and RNS concentrations in plant cell extract were complemented by in vivo ROS and nitric oxide (NO) imaging using nitro blue tetrazolium (NBT), diaminobenzidine (DAB) and diaminofluorescein diacetate (DAF-DA) staining methods, and confocal microscope technique. B. cinerea infection proceeded slower in Perkoz cell cultures. It was evidenced by measuring the pathogen conidia germination and germination tube development in which nuclei revealing cell death dominated. Two different types of tomato cell death were observed: cells with necrotic nuclei dominated in Corindo whereas in Perkoz cells with characteristic of vacuolar death type prevailed. In Perkoz cells, constitutive levels of NO and S-nitrosothiols (SNO) were significantly higher and hydrogen peroxide (H₂O₂) and superoxide anion (O₂(-)) concentrations were slightly higher as compared with Corindo cells. Moreover, increases in these molecule concentrations as a result of B. cinerea inoculation were observed in both, Perkoz and Corindo cell cultures. The enzymatic GSNOR activity seems to be an important player in controlling the SNO level in tomato cells. Involvements of the studied compounds in molecular mechanisms of tomato resistance to B. cinerea are discussed in the paper. PMID:25064634

  16. Catalytic activity trends of oxygen reduction reaction for nonaqueous Li-air batteries.

    PubMed

    Lu, Yi-Chun; Gasteiger, Hubert A; Shao-Horn, Yang

    2011-11-30

    We report the intrinsic oxygen reduction reaction (ORR) activity of polycrystalline palladium, platinum, ruthenium, gold, and glassy carbon surfaces in 0.1 M LiClO(4) 1,2-dimethoxyethane via rotating disk electrode measurements. The nonaqueous Li(+)-ORR activity of these surfaces primarily correlates to oxygen adsorption energy, forming a "volcano-type" trend. The activity trend found on the polycrystalline surfaces was in good agreement with the trend in the discharge voltage of Li-O(2) cells catalyzed by nanoparticle catalysts. Our findings provide insights into Li(+)-ORR mechanisms in nonaqueous media and design of efficient air electrodes for Li-air battery applications.

  17. Design and Activation of a LOX/GH Chemical Steam Generator

    NASA Technical Reports Server (NTRS)

    Saunders, G. P.; Mulkey, C. A.; Taylor, S. A.

    2009-01-01

    The purpose of this paper is to give a detailed description of the design and activation of the LOX/GH fueled chemical steam generator installed in Cell 2 of the E3 test facility at Stennis Space Center, MS (SSC). The steam generator uses a liquid oxygen oxidizer with gaseous hydrogen fuel. The combustion products are then quenched with water to create steam at pressures from 150 to 450 psig at temperatures from 350 to 750 deg F (from saturation to piping temperature limits).

  18. Photogenerated charge carriers and reactive oxygen species in ZnO/Au hybrid nanostructures with enhanced photocatalytic and antibacterial activity.

    PubMed

    He, Weiwei; Kim, Hyun-Kyung; Wamer, Wayne G; Melka, David; Callahan, John H; Yin, Jun-Jie

    2014-01-15

    Semiconductor nanostructures with photocatalytic activity have the potential for many applications including remediation of environmental pollutants and use in antibacterial products. An effective way for promoting photocatalytic activity is depositing noble metal nanoparticles (NPs) on a semiconductor. In this paper, we demonstrated the successful deposition of Au NPs, having sizes smaller than 3 nm, onto ZnO NPs. ZnO/Au hybrid nanostructures having different molar ratios of Au to ZnO were synthesized. It was found that Au nanocomponents even at a very low Au/ZnO molar ratio of 0.2% can greatly enhance the photocatalytic and antibacterial activity of ZnO. Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au NPs on the generation of reactive oxygen species and photoinduced charge carriers. Deposition of Au NPs onto ZnO resulted in a dramatic increase in light-induced generation of hydroxyl radical, superoxide and singlet oxygen, and production of holes and electrons. The enhancing effect of Au was dependent on the molar ratio of Au present in the ZnO/Au nanostructures. Consistent with these results from ESR measurements, ZnO/Au nanostructures also exhibited enhanced photocatalytic and antibacterial activity. These results unveiled the enhanced mechanism of Au on ZnO and these materials have great potential for use in water purification and antibacterial products.

  19. Aerobic composting of waste activated sludge: Kinetic analysis for microbiological reaction and oxygen consumption

    SciTech Connect

    Yamada, Y.; Kawase, Y. . E-mail: bckawase@mail.eng.toyo.ac.jp

    2006-07-01

    In order to examine the optimal design and operating parameters, kinetics for microbiological reaction and oxygen consumption in composting of waste activated sludge were quantitatively examined. A series of experiments was conducted to discuss the optimal operating parameters for aerobic composting of waste activated sludge obtained from Kawagoe City Wastewater Treatment Plant (Saitama, Japan) using 4 and 20 L laboratory scale bioreactors. Aeration rate, compositions of compost mixture and height of compost pile were investigated as main design and operating parameters. The optimal aerobic composting of waste activated sludge was found at the aeration rate of 2.0 L/min/kg (initial composting mixture dry weight). A compost pile up to 0.5 m could be operated effectively. A simple model for composting of waste activated sludge in a composting reactor was developed by assuming that a solid phase of compost mixture is well mixed and the kinetics for microbiological reaction is represented by a Monod-type equation. The model predictions could fit the experimental data for decomposition of waste activated sludge with an average deviation of 2.14%. Oxygen consumption during composting was also examined using a simplified model in which the oxygen consumption was represented by a Monod-type equation and the axial distribution of oxygen concentration in the composting pile was described by a plug-flow model. The predictions could satisfactorily simulate the experiment results for the average maximum oxygen consumption rate during aerobic composting with an average deviation of 7.4%.

  20. Flow cytometric assessment of reactive oxygen species generations that are directly related to cellular ZnO nanoparticle uptake.

    PubMed

    Yoo, Hyun Ju; Yoon, Tae Hyun

    2014-07-01

    In this study, a simple flow cytometry protocol to evaluate nanoparticle associated biological response was proposed. Particularly, we have evaluated the effect of surface charge on the cellular nanoparticle associations and nanoparticle-induced apoptosis. Significant enhancement in side scattering intensity was observed for the HeLa cells treated with positively charged (PLL)ZnO nanoparticles, suggesting that the (PLL)ZnO nanoparticles may induce cell death via adsorption and endocytosis of the nanoparticles. On the other hand, the negatively charged (PAA)ZnO nanoparticle seems to cause cell death process indirectly via the released Zn ions, with less contribution from cellular association of nanoparticles. Time- and dose-dependent studies on cellular association of ZnO nanoparticles, and ZnO associated reactive oxygen species generation were also performed for the HeLa cells exposed to the (PLL)ZnO nanoparticle. For those cells associated with (PLL)ZnO nanoparticle, a significant enhancement in reactive oxygen species generation was observed even at a lower concentration (10 ppm), which was not observable for the results with the whole cell population. By using this approach, we are able to distinguish biological responses (e.g., reactive oxygen species (ROS) generation) directly related to the cellular associations of NPs from those indirectly related to the cellular associations of NPs, such as the cytotoxicity caused by the NP released metal ions.

  1. Next Generation Active Buffet Suppression System

    NASA Technical Reports Server (NTRS)

    Galea, Stephen C.; Ryall, Thomas G.; Henderson, Douglas A.; Moses, Robert W.; White, Edward V.; Zimcik, David G.

    2003-01-01

    Buffeting is an aeroelastic phenomenon that is common to high performance aircraft, especially those with twin vertical tails like the F/A-18, at high angles of attack. These loads result in significant random stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. This paper describes an international collaborative research activity among Australia, Canada and the United States involving the use of active structural control to alleviate the damaging structural response to these loads. The research program is being co-ordinated by the Air Force Research Laboratory (AFRL) and is being conducted under the auspices of The Technical Cooperative Program (TTCP). This truly unique collaborative program has been developed to enable each participating country to contribute resources toward a program that coalesces a broad range of technical knowledge and expertise into a single investigation. This collaborative program is directed toward a full-scale test of an F/A-18 empennage, which is an extension of an earlier initial test. The current program aims at applying advanced directional piezoactuators, the aircraft rudder, switch mode amplifiers and advanced control strategies on a full-scale structure to demonstrate the enhanced performance and capability of the advanced active BLA control system in preparation for a flight test demonstration.

  2. Effect of venoruton on hypoxic stress-induced neurotoxicity in mice and oxygen free radical generation by human neutrophils.

    PubMed

    Shukla, V K; Sethi, A K; Garg, S K; Ganguly, N K; Kulkarni, S K

    1989-01-01

    Venoruton offers a protection against hypoxic stress-induced neurotoxicity (convulsions and death) in mice. It also inhibits free radical generation, since it produces a concentration-dependent (5-160 micrograms/10(6) cells/ml) decrease of chemiluminescence response from human neutrophils. The maximum inhibition was observed at 140 micrograms/10(6) cells/ml. The in vivo protective effect against hypoxic stress-induced neurotoxicity has been correlated to the inhibitory action of venoruton on oxygen free radical generation.

  3. Oxygen Activation at Mononuclear Nonheme Iron Centers: A Superoxo Perspective

    PubMed Central

    Mukherjee, Anusree; Cranswick, Matthew A.; Chakraborti, Mrinmoy; Paine, Tapan K.; Fujisawa, Kiyoshi; Münck, Eckard; Que, Lawrence

    2010-01-01

    Dioxygen activation by iron enzymes is responsible for many metabolically important transformations in biology. Often a high-valent iron-oxo oxidant is proposed to form upon dioxygen activation at a mononuclear nonheme iron center, presumably via intervening iron-superoxo and iron-peroxo species. While iron(IV)-oxo intermediates have been trapped and characterized in enzymes and models, less is known of the putative iron(III)-superoxo species. Utilizing a synthetic model for the 2-oxoglutarate-dependent monoiron enzymes, [(TpiPr2)FeII(O2CC(O)CH3)], we have obtained indirect evidence for the formation of the putative iron(III)-superoxo species, which can undergo one-electron reduction, hydrogen-atom transfer, or conversion to an iron(IV)-oxo species, depending on the reaction conditions. These results demonstrate the various roles the iron(III)-superoxo species can play in the course of dioxygen activation at a nonheme iron center. PMID:20380464

  4. Acrolein activates matrix metalloproteinases by increasing reactive oxygen species in macrophages

    SciTech Connect

    O'Toole, Timothy E. Zheng Yuting; Hellmann, Jason; Conklin, Daniel J.; Barski, Oleg; Bhatnagar, Aruni

    2009-04-15

    Acrolein is a ubiquitous component of environmental pollutants such as automobile exhaust, cigarette, wood, and coal smoke. It is also a natural constituent of several foods and is generated endogenously during inflammation or oxidation of unsaturated lipids. Because increased inflammation and episodic exposure to acrolein-rich pollutants such as traffic emissions or cigarette smoke have been linked to acute myocardial infarction, we examined the effects of acrolein on matrix metalloproteinases (MMPs), which destabilize atherosclerotic plaques. Our studies show that exposure to acrolein resulted in the secretion of MMP-9 from differentiated THP-1 macrophages. Acrolein-treatment of macrophages also led to an increase in reactive oxygen species (ROS), free intracellular calcium ([Ca{sup 2+}]{sub i}), and xanthine oxidase (XO) activity. ROS production was prevented by allopurinol, but not by rotenone or apocynin and by buffering changes in [Ca{sup 2+}]{sub I} with BAPTA-AM. The increase in MMP production was abolished by pre-treatment with the antioxidants Tiron and N-acetyl cysteine (NAC) or with the xanthine oxidase inhibitors allopurinol or oxypurinol. Finally, MMP activity was significantly stimulated in aortic sections from apoE-null mice containing advanced atherosclerotic lesions after exposure to acrolein ex vivo. These observations suggest that acrolein exposure results in MMP secretion from macrophages via a mechanism that involves an increase in [Ca{sup 2+}]{sub I}, leading to xanthine oxidase activation and an increase in ROS production. ROS-dependent activation of MMPs by acrolein could destabilize atherosclerotic lesions during brief episodes of inflammation or pollutant exposure.

  5. High-pressure gravity-independent singlet oxygen generator, laser nozzle, and iodine injection system for the chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Emanuel, George

    2004-09-01

    A novel approach is outlined for a singlet oxygen generator (SOG), a laser minimum length nozzle (MLN), and an iodine injector system for a chemical oxygen-iodine laser (COIL). A unified approach, referred to as a SOG/MLN/I2 system, is partly based on past experimental work. For instance, the SOG concept stems from sparger technology and a KSY fesibility experiment. A MLN with a curved sonic line is used for the laser nozzle, and slender struts are used for the injection, in the downstream direction, of iodine/helium vapor. The heated struts are located downstream of the nozzle's throat. The engineering logic behind the approach is discussed; it has a diversity of potential system benefits relative to current technology. These include a compact, scalable laser that can operate in space. The SOG operates at a significantly higher pressure with a high O2(1Δ) yield. In addition, basic hydrogen peroxide reconditioning is not required, a water vapor removal system is not required, and diluent may be unnecessary, although useful for pressure recovery. The impact on a COIL system in terms of power, efficiency, and pressure recovery is briefly assessed.

  6. Airborne particulate matter PM2.5 from Mexico City affects the generation of reactive oxygen species by blood neutrophils from asthmatics: an in vitro approach

    PubMed Central

    Sierra-Vargas, Martha Patricia; Guzman-Grenfell, Alberto Martin; Blanco-Jimenez, Salvador; Sepulveda-Sanchez, Jose David; Bernabe-Cabanillas, Rosa Maria; Cardenas-Gonzalez, Beatriz; Ceballos, Guillermo; Hicks, Juan Jose

    2009-01-01

    Background The Mexico City Metropolitan Area is densely populated, and toxic air pollutants are generated and concentrated at a higher rate because of its geographic characteristics. It is well known that exposure to particulate matter, especially to fine and ultra-fine particles, enhances the risk of cardio-respiratory diseases, especially in populations susceptible to oxidative stress. The aim of this study was to evaluate the effect of fine particles on the respiratory burst of circulating neutrophils from asthmatic patients living in Mexico City. Methods In total, 6 subjects diagnosed with mild asthma and 11 healthy volunteers were asked to participate. Neutrophils were isolated from peripheral venous blood and incubated with fine particles, and the generation of reactive oxygen species was recorded by chemiluminescence. We also measured plasma lipoperoxidation susceptibility and plasma myeloperoxidase and paraoxonase activities by spectrophotometry. Results Asthmatic patients showed significantly lower plasma paraoxonase activity, higher susceptibility to plasma lipoperoxidation and an increase in myeloperoxidase activity that differed significantly from the control group. In the presence of fine particles, neutrophils from asthmatic patients showed an increased tendency to generate reactive oxygen species after stimulation with fine particles (PM2.5). Conclusion These findings suggest that asthmatic patients have higher oxidation of plasmatic lipids due to reduced antioxidant defense. Furthermore, fine particles tended to increase the respiratory burst of blood human neutrophils from the asthmatic group. On the whole, increased myeloperoxidase activity and susceptibility to lipoperoxidation with a concomitant decrease in paraoxonase activity in asthmatic patients could favor lung infection and hence disrupt the control of asthmatic crises. PMID:19563660

  7. Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

    NASA Astrophysics Data System (ADS)

    Binninger, Tobias; Mohamed, Rhiyaad; Waltar, Kay; Fabbri, Emiliana; Levecque, Pieter; Kötz, Rüdiger; Schmidt, Thomas J.

    2015-07-01

    In recent years, the oxygen evolution reaction (OER) has attracted increased research interest due to its crucial role in electrochemical energy conversion devices for renewable energy applications. The vast majority of OER catalyst materials investigated are metal oxides of various compositions. The experimental results obtained on such materials strongly suggest the existence of a fundamental and universal correlation between the oxygen evolution activity and the corrosion of metal oxides. This corrosion manifests itself in structural changes and/or dissolution of the material. We prove from basic thermodynamic considerations that any metal oxide must become unstable under oxygen evolution conditions irrespective of the pH value. The reason is the thermodynamic instability of the oxygen anion in the metal oxide lattice. Our findings explain many of the experimentally observed corrosion phenomena on different metal oxide OER catalysts.

  8. Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

    PubMed Central

    Binninger, Tobias; Mohamed, Rhiyaad; Waltar, Kay; Fabbri, Emiliana; Levecque, Pieter; Kötz, Rüdiger; Schmidt, Thomas J.

    2015-01-01

    In recent years, the oxygen evolution reaction (OER) has attracted increased research interest due to its crucial role in electrochemical energy conversion devices for renewable energy applications. The vast majority of OER catalyst materials investigated are metal oxides of various compositions. The experimental results obtained on such materials strongly suggest the existence of a fundamental and universal correlation between the oxygen evolution activity and the corrosion of metal oxides. This corrosion manifests itself in structural changes and/or dissolution of the material. We prove from basic thermodynamic considerations that any metal oxide must become unstable under oxygen evolution conditions irrespective of the pH value. The reason is the thermodynamic instability of the oxygen anion in the metal oxide lattice. Our findings explain many of the experimentally observed corrosion phenomena on different metal oxide OER catalysts. PMID:26178185

  9. Sequential reduction of mitochondrial transmembrane potential and generation of reactive oxygen species in early programmed cell death

    PubMed Central

    1995-01-01

    Programmed cell death (PCD) is a physiological process commonly defined by alterations in nuclear morphology (apoptosis) and/or characteristic stepwise degradation of chromosomal DNA occurring before cytolysis. However, determined characteristics of PCD such as loss in mitochondrial reductase activity or cytolysis can be induced in enucleated cells, indicating cytoplasmic PCD control. Here we report a sequential disregulation of mitochondrial function that precedes cell shrinkage and nuclear fragmentation. A first cyclosporin A-inhibitable step of ongoing PCD is characterized by a reduction of mitochondrial transmembrane potential, as determined by specific fluorochromes (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine++ + iodide; 3,3'dihexyloxacarbocyanine iodide). Cytofluorometrically purified cells with reduced mitochondrial transmembrane potential are initially incapable of oxidizing hydroethidine (HE) into ethidium. Upon short-term in vitro culture, such cells acquire the capacity of HE oxidation, thus revealing a second step of PCD marked by mitochondrial generation of reactive oxygen species (ROS). This step can be selectively inhibited by rotenone and ruthenium red yet is not affected by cyclosporin A. Finally, cells reduce their volume, a step that is delayed by radical scavengers, indicating the implication of ROS in the apoptotic process. This sequence of alterations accompanying early PCD is found in very different models of apoptosis induction: glucocorticoid-induced death of lymphocytes, activation-induced PCD of T cell hybridomas, and tumor necrosis factor-induced death of U937 cells. Transfection with the antiapoptotic protooncogene Bcl-2 simultaneously inhibits mitochondrial alterations and apoptotic cell death triggered by steroids or ceramide. In vivo injection of fluorochromes such as 5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimidazolcarbocyanine iodide; 3,3'dihexyloxacarbocyanine iodide; or HE allows for the detection of

  10. Optical monitoring of singlet oxygen generation during photodynamic treatment of tumors

    SciTech Connect

    Parker, J.G.

    1987-01-01

    Optical detection of singlet oxygen production accompanying continuous-wave (CW) laser irradiation of subcutaneous murine tumors at 630 nm following prior intraperitoneal injection of a Photofrin II sensitizer has been demonstrated. In order to separate the spectrally discrete, time-delayed, singlet oxygen emission from the dominant, spectrally diffuse, coherent background provided by the combination of sensitizer infrared fluorescence and tissue-related autofluorescence, chopping of the incident laser beam was required. Using the infrared fluorescence to provide a reference, the singlet oxygen emission is shown to be given directly by the frequency-dependent quadrature component of the detector output. Maximum detector quadrature output for the in vivo case was obtained for a chopping frequency between 10 and 20 kHz. The spectral variation of the emission from the tumor was obtained and identified as that characteristic of singlet oxygen. This demonstration provides the rationale for the development of a clinically useful electro-optical system to provide a realistic means for monitoring treatment effectiveness during the photodynamic therapy of tumors as well as the establishment of much-needed dosimetry standards. It is expected that, in the future, development of this capbility will provide an analytical, quantitative means to remove some of the mysteries now impeding progress in this important area of medicine.

  11. Human Platelets Utilize Cycloxygenase-1 to Generate Dioxolane A3, a Neutrophil-activating Eicosanoid*

    PubMed Central

    Hinz, Christine; Aldrovandi, Maceler; Uhlson, Charis; Marnett, Lawrence J.; Longhurst, Hilary J.; Warner, Timothy D.; Alam, Saydul; Slatter, David A.; Lauder, Sarah N.; Allen-Redpath, Keith; Collins, Peter W.; Murphy, Robert C.; Thomas, Christopher P.; O'Donnell, Valerie B.

    2016-01-01

    Eicosanoids are important mediators of fever, pain, and inflammation that modulate cell signaling during acute and chronic disease. We show by using lipidomics that thrombin-activated human platelets generate a new type of eicosanoid that both stimulates and primes human neutrophil integrin (Mac-1) expression, in response to formylmethionylleucylphenylalanine. Detailed characterization proposes a dioxolane structure, 8-hydroxy-9,11-dioxolane eicosatetraenoic acid (dioxolane A3, DXA3). The lipid is generated in nanogram amounts by platelets from endogenous arachidonate during physiological activation, with inhibition by aspirin in vitro or in vivo, implicating cyclooxygenase-1 (COX). Pharmacological and genetic studies on human/murine platelets revealed that DXA3 formation requires protease-activated receptors 1 and 4, cytosolic phospholipase A2 (cPLA2), Src tyrosine kinases, p38 MAPK, phospholipase C, and intracellular calcium. From data generated by purified COX isoforms and chemical oxidation, we propose that DXA3 is generated by release of an intermediate from the active site followed by oxygenation at C8. In summary, a new neutrophil-activating platelet-derived lipid generated by COX-1 is presented that can activate or prime human neutrophils, suggesting a role in innate immunity and acute inflammation. PMID:27129261

  12. Characterization and modelling of the boron-oxygen defect activation in compensated n-type silicon

    SciTech Connect

    Schön, J.; Niewelt, T.; Broisch, J.; Warta, W.; Schubert, M. C.

    2015-12-28

    A study of the activation of the light-induced degradation in compensated n-type Czochralski grown silicon is presented. A kinetic model is established that verifies the existence of both the fast and the slow components known from p-type and proves the quadratic dependence of the defect generation rates of both defects on the hole concentration. The model allows for the description of lifetime degradation kinetics in compensated n-type silicon under various intensities and is in accordance with the findings for p-type silicon. We found that the final concentrations of the slow defect component in compensated n-type silicon only depend on the interstitial oxygen concentration and on neither the boron concentration nor the equilibrium electron concentration n{sub 0}. The final concentrations of the fast defect component slightly increase with increasing boron concentration. The results on n-type silicon give new insight to the origin of the BO defect and question the existing models for the defect composition.

  13. Noninvasive bioluminescence imaging of the dynamics of sanguinarine induced apoptosis via activation of reactive oxygen species

    PubMed Central

    Dai, Yunpeng; Shi, Yaru; Zeng, Qi; Wang, Fu

    2016-01-01

    Most chemotherapeutic drugs exert their anti-tumor effects primarily by triggering a final pathway leading to apoptosis. Noninvasive imaging of apoptotic events in preclinical models would greatly facilitate the development of apoptosis-inducing compounds and evaluation of their therapeutic efficacy. Here we employed a cyclic firefly luciferase (cFluc) reporter to screen potential pro-apoptotic compounds from a number of natural agents. We demonstrated that sanguinarine (SANG) could induce apoptosis in a dose- and time-dependent manner in UM-SCC-22B head and neck cancer cells. Moreover, SANG-induced apoptosis was associated with the generation of reactive oxygen species (ROS) and activation of c-Jun-N-terminal kinase (JNK) and nuclear factor-kappaB (NF-κB) signal pathways. After intravenous administration with SANG in 22B-cFluc xenograft models, a dramatic increase of luminescence signal can be detected as early as 48 h post-treatment, as revealed by longitudinal bioluminescence imaging in vivo. Remarkable apoptotic cells reflected from ex vivo TUNEL staining confirmed the imaging results. Importantly, SANG treatment caused distinct tumor growth retardation in mice compared with the vehicle-treated group. Taken together, our results showed that SANG is a candidate anti-tumor drug and noninvasive imaging of apoptosis using cFluc reporter could provide a valuable tool for drug development and therapeutic efficacy evaluation. PMID:26968950

  14. Noninvasive bioluminescence imaging of the dynamics of sanguinarine induced apoptosis via activation of reactive oxygen species.

    PubMed

    Wang, Yan; Zhang, Beilei; Liu, Wei; Dai, Yunpeng; Shi, Yaru; Zeng, Qi; Wang, Fu

    2016-04-19

    Most chemotherapeutic drugs exert their anti-tumor effects primarily by triggering a final pathway leading to apoptosis. Noninvasive imaging of apoptotic events in preclinical models would greatly facilitate the development of apoptosis-inducing compounds and evaluation of their therapeutic efficacy. Here we employed a cyclic firefly luciferase (cFluc) reporter to screen potential pro-apoptotic compounds from a number of natural agents. We demonstrated that sanguinarine (SANG) could induce apoptosis in a dose- and time-dependent manner in UM-SCC-22B head and neck cancer cells. Moreover, SANG-induced apoptosis was associated with the generation of reactive oxygen species (ROS) and activation of c-Jun-N-terminal kinase (JNK) and nuclear factor-kappaB (NF-κB) signal pathways. After intravenous administration with SANG in 22B-cFluc xenograft models, a dramatic increase of luminescence signal can be detected as early as 48 h post-treatment, as revealed by longitudinal bioluminescence imaging in vivo. Remarkable apoptotic cells reflected from ex vivo TUNEL staining confirmed the imaging results. Importantly, SANG treatment caused distinct tumor growth retardation in mice compared with the vehicle-treated group. Taken together, our results showed that SANG is a candidate anti-tumor drug and noninvasive imaging of apoptosis using cFluc reporter could provide a valuable tool for drug development and therapeutic efficacy evaluation. PMID:26968950

  15. Noninvasive bioluminescence imaging of the dynamics of sanguinarine induced apoptosis via activation of reactive oxygen species.

    PubMed

    Wang, Yan; Zhang, Beilei; Liu, Wei; Dai, Yunpeng; Shi, Yaru; Zeng, Qi; Wang, Fu

    2016-04-19

    Most chemotherapeutic drugs exert their anti-tumor effects primarily by triggering a final pathway leading to apoptosis. Noninvasive imaging of apoptotic events in preclinical models would greatly facilitate the development of apoptosis-inducing compounds and evaluation of their therapeutic efficacy. Here we employed a cyclic firefly luciferase (cFluc) reporter to screen potential pro-apoptotic compounds from a number of natural agents. We demonstrated that sanguinarine (SANG) could induce apoptosis in a dose- and time-dependent manner in UM-SCC-22B head and neck cancer cells. Moreover, SANG-induced apoptosis was associated with the generation of reactive oxygen species (ROS) and activation of c-Jun-N-terminal kinase (JNK) and nuclear factor-kappaB (NF-κB) signal pathways. After intravenous administration with SANG in 22B-cFluc xenograft models, a dramatic increase of luminescence signal can be detected as early as 48 h post-treatment, as revealed by longitudinal bioluminescence imaging in vivo. Remarkable apoptotic cells reflected from ex vivo TUNEL staining confirmed the imaging results. Importantly, SANG treatment caused distinct tumor growth retardation in mice compared with the vehicle-treated group. Taken together, our results showed that SANG is a candidate anti-tumor drug and noninvasive imaging of apoptosis using cFluc reporter could provide a valuable tool for drug development and therapeutic efficacy evaluation.

  16. Lewis Acid Pairs for the Activation of Biomass-derived Oxygenates in Aqueous Media

    SciTech Connect

    Roman, Yuriy

    2015-09-14

    The objective of this project is to understand the mechanistic aspects behind the cooperative activation of oxygenates by catalytic pairs in aqueous media. Specifically, we will investigate how the reactivity of a solid Lewis acid can be modulated by pairing the active site with other catalytic sites at the molecular level, with the ultimate goal of enhancing activation of targeted functional groups. Although unusual catalytic properties have been attributed to the cooperative effects promoted by such catalytic pairs, virtually no studies exist detailing the use heterogeneous water-tolerant Lewis pairs. A main goal of this work is to devise rational pathways for the synthesis of porous heterogeneous catalysts featuring isolated Lewis pairs that are active in the transformation of biomass-derived oxygenates in the presence of bulk water. Achieving this technical goal will require closely linking advanced synthesis techniques; detailed kinetic and mechanistic investigations; strict thermodynamic arguments; and comprehensive characterization studies of both materials and reaction intermediates. For the last performance period (2014-2015), two technical aims were pursued: 1) C-C coupling using Lewis acid and base pairs in Lewis acidic zeolites. Tin-, zirconium-, and hafnium containing zeolites (e.g., Sn-, Zr-, and Hf-Beta) are versatile solid Lewis acids that selectively activate carbonyl functional groups. In this aim, we demonstrate that these zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions. 2) One-pot synthesis of MWW zeolite nanosheets for activation of bulky substrates. Through

  17. Generation of reactive oxygen species by a novel berberine–bile acid analog mediates apoptosis in hepatocarcinoma SMMC-7721 cells

    SciTech Connect

    Li, Qingyong; Zhang, Li; Zu, Yuangang; Liu, Tianyu; Zhang, Baoyou; He, Wuna

    2013-04-19

    Graphical abstract: - Highlights: • Anticancer effects of B4, a novel berberine–bile acid analog, were tested. • B4 inhibited cell proliferation in hepatocellular carcinoma cells. • It also stimulated mitochondrial ROS production and membrane depolarization. • Effects of B4 were inhibited by a non-specific ROS scavenger. • Regulation of ROS generation may be a strategy for treating hepatic carcinoma. - Abstract: 2,3-Methenedioxy-9-O-(3′α,7′α-dihydroxy-5′β-cholan-24′-propy-lester) berberine (B4) is a novel berberine–bile acid analog synthesized in our laboratory. Previously, we showed that B4 exerted greater cytotoxicity than berberine in several human cancer cell lines. Therefore, we further evaluated the mechanism governing its anticancer actions in hepatocellular carcinoma SMMC-7721 cells. B4 inhibited the proliferation of SMMC-7721 cells, and stimulated reactive oxygen species (ROS) production and mitochondrial membrane depolarization; anti-oxidant capacity was reduced. B4 also induced the release of cytochrome c from the mitochondria to the cytosol and an increase in poly ADP-ribose polymerase (PARP) cleavage products, reflective of caspase-3 activation. Moreover, B4 induced the nuclear translocation of apoptosis-inducing factor (AIF) and a rise in DNA fragmentation. Pretreatment with the anti-oxidant N-acetylcysteine (NAC) inhibited B4-mediated effects, including cytotoxicity, ROS production, mitochondrial membrane depolarization increase in intracellular Ca{sup 2+}, cytochrome c release, PARP cleavage, and AIF translocation. Our data suggest that B4 induces ROS-triggered caspase-dependent and caspase-independent apoptosis pathways in SMMC-7721 cells and that ROS production may be a specific potential strategy for treating hepatic carcinoma.

  18. The role of water and structure on the generation of reactive oxygen species in peptide/hypericin complexes.

    PubMed

    Souza, Márcia I; Silva, Emerson R; Jaques, Ygor M; Ferreira, Fabio F; Fileti, Eudes E; Alves, Wendel A

    2014-07-01

    Hybrid associates formed between peptide assemblies and fluorophores are attractive mainly because of their unique properties for biomedical applications. Recently, we demonstrated that the production of reactive oxygen species (ROS) by hypericin and their stability in excited states are enhanced upon conjugation with l,l-diphenylalanine microtubes (FF-MNTs). Although the detailed mechanisms responsible for improving the photophysical properties of ROS remain unclear, tentative hypotheses have suggested that the driving force is the growth of overall dipolar moments ascribed either to coupling between aligned H2O dipoles within the ordered structures or to the organization of hypericin molecules on peptide interfaces. To provide new insights on ROS activity in hypericin/FF-MNTs hybrids and further explore the role of water in this respect, we present results obtained from investigations on the behavior of these complexes organized into different crystalline arrangements. Specifically, we monitored and compared the photophysical performance of hypericin bound to FF-MNTs with peptides organized in both hexagonal (water-rich) and orthorhombic (water-free) symmetries. From a theoretical perspective, we present the results of new molecular dynamics simulations that highlight the distinct hypericin/peptide interaction at the interface of FF-MNTs for the different symmetries. As a conclusion, we propose that although water enhances photophysical properties, the organization induced by peptide structures and the availability of a hydrophobic environment surrounding the hypericin/peptide interface are paramount to optimizing ROS generation. The findings presented here provide useful basic research insights for designing peptide/fluorophore complexes with outstanding technological potential.

  19. Role of Reactive Oxygen Species in the Abrogation of Oxaliplatin Activity by Cetuximab in Colorectal Cancer

    PubMed Central

    Santoro, Valeria; Jia, Ruochen; Thompson, Hannah; Nijhuis, Anke; Jeffery, Rosemary; Kiakos, Konstantinos; Silver, Andrew R.; Hartley, John A.

    2016-01-01

    Background: The antibody cetuximab, targeting epidermal growth factor receptor (EGFR), is used to treat metastatic colorectal cancer (mCRC). Clinical trials suggest reduced benefit from the combination of cetuximab with oxaliplatin. The aim of this study was to investigate potential negative interactions between cetuximab and oxaliplatin. Methods: Thiazolyl blue tetrazolium bromide (MTT) assay and Calcusyn software were used to characterize drug interactions. Reactive oxygen species (ROS) were measured by flow cytometry and real-time polymerase chain reaction oxidative stress arrays identified genes regulating ROS production. Chromatin immunoprecipitation (ChIP) measured signal transducer and activator of transcription 1 (STAT-1) binding to dual oxidase 2 (DUOX2) promoter. SW48, DLD-1 KRAS wild-type cell lines and DLD-1 xenograft models exposed to cetuximab, oxaliplatin, or oxaliplatin + cetuximab (control [saline]; n = 3 mice per treatment group) were used. Statistical tests were two-sided. Results: Cetuximab and oxaliplatin exhibited antagonistic effects on cellular proliferation and apoptosis (caspase 3/7 activity reduced by 1.4-fold, 95% confidence interval [CI] = 0.78 to 2.11, P = .003) as opposed to synergistic effects observed with the irinotecan metabolite 7-Ethyl-10-hydroxycamptothecin (SN-38). Although both oxaliplatin and SN-38 produced ROS, only oxaliplatin-mediated apoptosis was ROS dependent. Production of ROS by oxaliplatin was secondary to STAT1-mediated transcriptional upregulation of DUOX2 (3.1-fold, 95% CI = 1.75 to 2.41, P < .001). Inhibition of DUOX2 induction and p38 activation by cetuximab reduced oxaliplatin cytotoxicity. Conclusions: Inhibition of STAT1 and DUOX2-mediated ROS generation by cetuximab impairs p38-dependent apoptosis by oxaliplatin in preclinical models and may contribute to reduced efficacy in clinical settings. Understanding the rationale for unexpected trial results will inform improved rationales for combining EGFR

  20. Oxygenated drinking water enhances immune activity in pigs and increases immune responses of pigs during Salmonella typhimurium infection.

    PubMed

    Jung, Bock-Gie; Lee, Jin-A; Lee, Bong-Joo

    2012-12-01

    It has been considered that drinking oxygenated water improves oxygen availability, which may increase vitality and improve immune functions. The present study evaluated the effects of oxygenated drinking water on immune function in pigs. Continuous drinking of oxygenated water markedly increased peripheral blood mononuclear cell proliferation, interleukin-1β expression level and the CD4(+):CD8(+) cell ratio in pigs. During Salmonella Typhimurium infection, total leukocytes and relative cytokines expression levels were significantly increased in pigs consuming oxygenated water compared with pigs consuming tap water. These findings suggest that oxygenated drinking water enhances immune activity in pigs and increases immune responses of pigs during S. Typhimurium Infection.

  1. Activity cliffs and activity cliff generators based on chemotype-related activity landscapes.

    PubMed

    Pérez-Villanueva, Jaime; Méndez-Lucio, Oscar; Soria-Arteche, Olivia; Medina-Franco, José L

    2015-11-01

    Activity cliffs have large impact in drug discovery; therefore, their detection and quantification are of major importance. This work introduces the metric activity cliff enrichment factor and expands the previously reported activity cliff generator concept by adding chemotype information to representations of the activity landscape. To exemplify these concepts, three molecular databases with multiple biological activities were characterized. Compounds in each database were grouped into chemotype classes. Then, pairwise comparisons of structure similarities and activity differences were calculated for each compound and used to construct chemotype-based structure-activity similarity (SAS) maps. Different landscape distributions among four major regions of the SAS maps were observed for different subsets of molecules grouped in chemotypes. Based on this observation, the activity cliff enrichment factor was calculated to numerically detect chemotypes enriched in activity cliffs. Several chemotype classes were detected having major proportion of activity cliffs than the entire database. In addition, some chemotype classes comprising compounds with smooth structure activity relationships (SAR) were detected. Finally, the activity cliff generator concept was applied to compounds grouped in chemotypes to extract valuable SAR information.

  2. The relationship between brain cortical activity and brain oxygenation in the prefrontal cortex during hypergravity exposure.

    PubMed

    Smith, Craig; Goswami, Nandu; Robinson, Ryan; von der Wiesche, Melanie; Schneider, Stefan

    2013-04-01

    Artificial gravity has been proposed as a method to counteract the physiological deconditioning of long-duration spaceflight; however, the effects of hypergravity on the central nervous system has had little study. The study aims to investigate whether there is a relationship between prefrontal cortex brain activity and prefrontal cortex oxygenation during exposure to hypergravity. Twelve healthy participants were selected to undergo hypergravity exposure aboard a short-arm human centrifuge. Participants were exposed to hypergravity in the +Gz axis, starting from 0.6 +Gz for women, and 0.8 +Gz for men, and gradually increasing by 0.1 +Gz until the participant showed signs of syncope. Brain cortical activity was measured using electroencephalography (EEG) and localized to the prefrontal cortex using standard low-resolution brain electromagnetic tomography (LORETA). Prefrontal cortex oxygenation was measured using near-infrared spectroscopy (NIRS). A significant increase in prefrontal cortex activity (P < 0.05) was observed during hypergravity exposure compared with baseline. Prefrontal cortex oxygenation was significantly decreased during hypergravity exposure, with a decrease in oxyhemoglobin levels (P < 0.05) compared with baseline and an increase in deoxyhemoglobin levels (P < 0.05) with increasing +Gz level. No significant correlation was found between prefrontal cortex activity and oxy-/deoxyhemoglobin. It is concluded that the increase in prefrontal cortex activity observed during hypergravity was most likely not the result of increased +Gz values resulting in a decreased oxygenation produced through hypergravity exposure. No significant relationship between prefrontal cortex activity and oxygenation measured by NIRS concludes that brain activity during exposure to hypergravity may be difficult to measure using NIRS. Instead, the increase in prefrontal cortex activity might be attributable to psychological stress, which could pose a problem for the use of a

  3. Effect of olive mill wastewaters on the oxygen consumption by activated sludge microorganisms: an acute toxicity test method.

    PubMed

    Paixão, S M; Anselmo, A M

    2002-01-01

    The test for inhibition of oxygen consumption by activated sludge (ISO 8192-1986 (E)) was evaluated as a tool for assessing, the acute toxicity of olive mill wastewaters (OMW). According to the ISO test, information generated by this method may be helpful in estimating the effect of a test material on bacterial communities in the aquatic environment, especially in aerobic biological treatment systems. However, the lack of standardized bioassay methodology for effluents imposed that the test conditions were modified and adapted. The experiments were conducted in the presence or absence of an easily biodegradable carbon source (glucose) with different contact times (20 min and 24 h). The results obtained showed a remarkable stimulatory effect of this effluent to the activated sludge microorganisms. In fact, the oxygen uptake rate values increase with increasing effluent concentrations and contact times up to 0.98 microl O(2) h(-1) mg(-1) dry weight for a 100% OMW sample, 24 h contact time, with blanks exhibiting an oxygen uptake rate of ca. 1/10 of this value (0.07-0.10). It seems that the application of the ISO test as an acute toxicity test for effluents should be reconsidered, with convenient adaptation for its utilization as a method of estimating the effect on bacterial communities present in aerobic biological treatment systems. PMID:12015797

  4. Nonstoichiometric perovskite CaMnO(3-δ) for oxygen electrocatalysis with high activity.

    PubMed

    Du, Jing; Zhang, Tianran; Cheng, Fangyi; Chu, Wangsheng; Wu, Ziyu; Chen, Jun

    2014-09-01

    Perovskite oxides offer efficient and cheap electrocatalysts for both oxygen reduction reactions and oxygen evolution reactions (ORR/OER) in diverse oxygen-based electrochemical technologies. In this study, we report a facile strategy to enhance the electrocatalytic activity of CaMnO3 by introducing oxygen defects. The nonstoichiometric CaMnO(3-δ) (0 < δ ≤ 0.5) was prepared through thermal reduction of pristine perovskite microspheres and nanoparticles, which were synthesized from thermal-decomposition of carbonate precursors and the Pechini route, respectively. The as-prepared samples were analyzed by chemical titration, structural refinement, thermogravimetric analysis, and energy spectrometry. In 0.1 M KOH aqueous solution, the nonstoichiometric CaMnO(3-δ) with δ near 0.25 and an average Mn valence close to 3.5 exhibited the highest ORR activity (36.7 A g(-1) at 0.70 V vs RHE, with onset potential of 0.96 V), which is comparable to that of benchmark Pt/C. Density functional theory (DFT) studies and electrical conductivity measurement revealed that the enhanced ORR kinetics is due to facilitated oxygen activation and improved electrical properties. Besides high activity, the nonstoichiometric perovskite oxides showed respectable catalytic stability. Furthermore, the moderate oxygen-defective CaMnO(3-δ) (δ ≈ 0.25) favored the OER because of the improved electrical conductivity. This study makes nonstoichiometric CaMnO(3-δ) a promising active, inexpensive bifunctional catalytic material for reversible ORR and OER.

  5. Deconvoluting Mixtures ofEmissions Sources to Investigate PM2.5's Ability to Generate Reactive Oxygen Species and its Associations with Cardiorespiratory Effects

    NASA Astrophysics Data System (ADS)

    Weber, R. J.; Bates, J.; Abrams, J.; Verma, V.; Fang, T.; Klein, M.; Strickland, M. J.; Sarnat, S. E.; Chang, H. H.; Mulholland, J. A.; Tolbert, P. E.; Russell, A. G.

    2015-12-01

    It is hypothesized that fine particulate matter (PM2.5) inhalation can catalytically generate reactive oxygen species (ROS) in excess of the body's antioxidant capacity, leading to oxidative stress and ultimately adverse health. PM2.5 emissions from different sources vary widely in chemical composition, with varied effects on the body. Here, the ability of mixtures of different sources of PM2.5 to generate ROS and associations of this capability with acute health effects were investigated. A dithiothreitol (DTT) assay that integrates over different sources was used to quantify ROS generation potential of ambient water-soluble PM2.5 in Atlanta from June 2012 - June 2013. PM2.5 source impacts, estimated using the Chemical Mass Balance method with ensemble-averaged source impact profiles, we