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Sequestration
Kinds of Sequestration Terms modified by Sequestration Selected AbstractsSequestration and turnover of plant- and microbially derived sugars in a temperate grassland soil during 7 years exposed to elevated atmospheric pCO2GLOBAL CHANGE BIOLOGY, Issue 2 2007MICHAEL BOCK Abstract Temperate grasslands contribute about 20% to the global terrestrial carbon (C) budget with sugars contributing 10,50% to this soil C pool. Whether the observed increase of the atmospheric CO2 concentration (pCO2) leads to additional C sequestration into these ecosystems or enhanced mineralization of soil organic matter (SOM) is still unclear. Therefore, the aim of the presented study was to investigate the impact of elevated atmospheric pCO2 on C sequestration and turnover of plant- (arabinose and xylose) and microbially derived (fucose, rhamnose, galactose, mannose) sugars in soil, representing a labile SOM pool. The study was carried out at the Swiss Free Air Carbon Dioxide Enrichment (FACE) experiment near Zurich. For 7 years, Lolium perenne swards were exposed to ambient and elevated pCO2 (36 and 60 Pa, respectively). The additional CO2 in the FACE plots was depleted in 13C compared with ambient plots, so that ,new' (<7 years) C inputs could be determined by means of compound-specific stable isotope analysis (13C : 12C). Samples were fractionated into clay, silt, fine sand and coarse sand, which yielded relatively stable and labile SOM pools with different turnover rates. Total sugar sequestration into bulk soil after 7 years of exposure to elevated pCO2 was about 28% compared with the control plots. In both ambient and elevated plots, total sugar concentrations in particle size fractions increased in the order sand The conversion of the corn/soybean ecosystem to no-till agriculture may result in a carbon sinkGLOBAL CHANGE BIOLOGY, Issue 11 2005Carl J. Bernacchi Abstract Mitigating or slowing an increase in atmospheric carbon dioxide concentration ([CO2]) has been the focus of international efforts, most apparent with the development of the Kyoto Protocol. Sequestration of carbon (C) in agricultural soils is being advocated as a method to assist in meeting the demands of an international C credit system. The conversion of conventionally tilled agricultural lands to no till is widely accepted as having a large-scale sequestration potential. In this study, C flux measurements over a no-till corn/soybean agricultural ecosystem over 6 years were coupled with estimates of C release associated with agricultural practices to assess the net biome productivity (NBP) of this no-till ecosystem. Estimates of NBP were also calculated for the conventionally tilled corn/soybean ecosystem assuming net ecosystem exchange is C neutral. These measurements were scaled to the US as a whole to determine the sequestration potential of corn/soybean ecosystems, under current practices where 10% of agricultural land devoted to this ecosystem is no-tilled and under a hypothetical scenario where 100% of the land is not tilled. The estimates of this analysis show that current corn/soybean agriculture in the US releases ,7.2 Tg C annually, with no-till sequestering ,2.2 Tg and conventional-till releasing ,9.4 Tg. The complete conversion of land area to no till might result in 21.7 Tg C sequestered annually, representing a net C flux difference of ,29 Tg C. These results demonstrate that large-scale conversion to no-till practices, at least for the corn/soybean ecosystem, could potentially offset ca. 2% of annual US carbon emissions. [source] SiO2 Nanoparticle Sequestration via Reactive Functionalization in Holographic Polymer-Dispersed Liquid CrystalsADVANCED MATERIALS, Issue 36 2009John D. Busbee Holographic photopolymerization of reactively functionalized silica nanoparticles in polymer/liquid-crystal systems leads to sequestration of the silica nanoparticles in the polymeric domain of holographic polymer-dispersed liquid-crystals Bragg gratings. Excellent dispersion of the nanoparticles maintains the optical properties of the reflection grating without additional scattering while lowering the voltage necessary to switch the state of the grating. [source] Healing Following Cranial Trauma,JOURNAL OF FORENSIC SCIENCES, Issue 2 2008Lenore T. Barbian Ph.D. Abstract:, This paper reports on the gross appearance of the initial osseous response following cranial gunshot wounds. A total of 127 adult crania and cranial sections were analyzed for four types of bone response: osteoblastic, osteoclastic, line of demarcation, and sequestration. In general, no osteoblastic or osteoclastic response was noted during the first week. This response was followed by an increasing prevalence of expression after this time. By the sixth week postfracture both osteoclastic and osteoblastic activity was scored for 100% of the sample. Further, our observations suggest that the line of demarcation may establish the boundary between the living bone and bone not surviving the fracture. Sequestration appears to be a long-term event and was scored as present well past the eighth week of healing. The osseous expression of infection following fracture was also considered. [source] Carbon Sequestration in Two Alpine Soils on the Tibetan PlateauJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2009Yu-Qiang Tian Abstract Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests (known as bomb- 14C). Soil organic matter was physically separated into light and heavy fractions. The concentration spike of bomb- 14C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil. Based on the depth of the bomb- 14C spike, the carbon sequestration rate was determined to be 38.5 g C/m2 per year for the forest soil and 27.1 g C/m2 per year for the alpine meadow soil. Considering that more than 60% of soil organic carbon (SOC) is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau, these alpine ecosystems might partially contribute to "the missing carbon sink". [source] Occlusion of an Aberrant Artery to a Pulmonary Sequestration Using a Duct OccluderJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 5 2002D.C.H., ELLEN CRUSHELL M.D., M.R.C.P.I. This report describes a female infant with a rare chromosome defect, del. 12 (q22-24.1), who has severe pulmonary valve stenosis, an atrial septal defect, and a small muscular ventricular septal defect. At 4 months of age a balloon pulmonary valvuloplasty was performed in the cardiac catheterization laboratory. During the procedure, a large aberrant artery from the aorta to a sequestration of the right lower lobe of lung was found. The flow-off from the sequestration was into a dilated left atrium. The single artery supplying the sequestration was successfully occluded using an Amplatzer Duct Occluder device. There were no complications and the infant remains well at 1-yearfollow-up. [source] Sequestration of serum response factor in the hippocampus impairs long-term spatial memoryJOURNAL OF NEUROCHEMISTRY, Issue 2 2005Pramod K. Dash Abstract The formation of long-term memory has been shown to require protein kinase-mediated gene expression. One such kinase, mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK), can lead to the phosphorylation of serum response factor (SRF) and Elk-1, enhancing the expression of target genes. However, a direct involvement of these transcription factors in memory storage has not been demonstrated. We have employed an oligonucleotide decoy technique to interrogate SRF and Elk-1. Previously, it has been shown that intra-amygdalal infusion of small double-stranded decoy oligonucleotides for nuclear factor-kappaB (NFkappaB) can impair long-term memory for fear-potentiated startle. Using this approach, we found that intra-hippocampal infusion of NFkappaB decoy oligonucleotides also impairs long-term spatial memory, consistent with a role for this factor in long-term memory storage. Decoy oligonucleotides containing the binding site for SRF, as confirmed by shift-western, did not influence memory acquisition but impaired long-term spatial memory. Analysis of search behavior during the transfer test revealed deficits consistent with a loss of precise platform location information. In contrast, oligonucleotides with a binding site for either Elk-1 or another target of ERK activity, SMAD3/SMAD4, did not interfere with memory formation or storage. These findings suggest that SRF-mediated gene expression is required for long-term spatial memory. [source] Microvessels Promote Motor Nerve Survival and Regeneration Through Local VEGF Release Following Ectopic ReattachmentMICROCIRCULATION, Issue 8 2004SHAWN E. BEARDEN ABSTRACT Objectives: Nerves and blood vessels form a close association during embryogenesis. Growth and guidance factors initially attributed to either nerves or vessels are now known to affect both tissues; prominent among these is vascular endothelial growth factor (VEGF). The authors investigated whether axons would associate with blood vessels in a regenerating system and questioned whether VEGF is integral to neurotization following axotomy. Methods: In hamsters 8,12 weeks of age, the accessory nerve (CN XI) to the retractor muscle of the cheek pouch was cut and the proximal stump was reattached ectopically onto the muscle. Vascular casting and immunolabeling were used to quantify the extent of neurovascular association during regeneration. A role for VEGF was investigated using immunolocalization of VEGF and its receptor (sVEGFR2) as well as local sequestration of VEGF with soluble receptor (sVEGFR1). Results: Regenerating axons aligned with microvessels of the vasa nervorum along a "chaperone" region during outgrowth from the reattachment site and while entering the muscle. In this ,1-mm region, VEGF protein was expressed by growing microvessels despite a ,50% reduction (p < .05) in total muscle VEGF concentration. VEGFR2 was expressed by regenerating axons and growth cones. Sequestration of VEGF by sVEGFR1 impaired neurotization by ,40% (p < .05). The chaperone region ended where regenerating microvessels anastomosed with the native microcirculation and their expression of VEGF protein diminished. Conclusions: Regenerating axons and blood vessels align during outgrowth from ectopic reattachment. This interaction dissipates as vascular anastomoses form with established microvessels and axons target muscle fibers. Local production of VEGF by growing microvessels supports motor nerve survival and regeneration. [source] Ternary complex formation between AmtB, GlnZ and the nitrogenase regulatory enzyme DraG reveals a novel facet of nitrogen regulation in bacteriaMOLECULAR MICROBIOLOGY, Issue 6 2007Luciano F. Huergo Summary Ammonium movement across biological membranes is facilitated by a class of ubiquitous channel proteins from the Amt/Rh family. Amt proteins have also been implicated in cellular responses to ammonium availability in many organisms. Ammonium sensing by Amt in bacteria is mediated by complex formation with cytosolic proteins of the PII family. In this study we have characterized in vitro complex formation between the AmtB and PII proteins (GlnB and GlnZ) from the diazotrophic plant-associative bacterium Azospirillum brasilense. AmtB,PII complex formation only occurred in the presence of adenine nucleotides and was sensitive to 2-oxoglutarate when Mg2+ and ATP were present, but not when ATP was substituted by ADP. We have also shown in vitro complex formation between GlnZ and the nitrogenase regulatory enzyme DraG, which was stimulated by ADP. The stoichiometry of this complex was 1:1 (DraG monomer : GlnZ trimer). We have previously reported that in vivo high levels of extracellular ammonium cause DraG to be sequestered to the cell membrane in an AmtB and GlnZ-dependent manner. We now report the reconstitution of a ternary complex involving AmtB, GlnZ and DraG in vitro. Sequestration of a regulatory protein by the membrane-bound AmtB,PII complex defines a new regulatory role for Amt proteins in Prokaryotes. [source] MicroReview: The role of Plasmodium falciparum var genes in malaria in pregnancyMOLECULAR MICROBIOLOGY, Issue 4 2004J. A. Rowe Summary Sequestration of Plasmodium falciparum -infected erythrocytes in the placenta is responsible for many of the harmful effects of malaria during pregnancy. Sequestration occurs as a result of parasite adhesion molecules expressed on the surface of infected erythrocytes binding to host receptors in the placenta such as chondroitin sulphate A (CSA). Identification of the parasite ligand(s) responsible for placental adhesion could lead to the development of a vaccine to induce antibodies ,to ,prevent ,placental ,sequestration. ,Such a vaccine would reduce the maternal anaemia and infant deaths that are associated with malaria in pregnancy. Current research indicates that the parasite ligands mediating placental adhesion may be members of the P. falciparum variant surface antigen family PfEMP1, encoded by var genes. Two relatively well-conserved subfamilies of var genes have been implicated in placental adhesion, however, their role remains controversial. This review examines the evidence for and against the involvement of var genes in placental adhesion, and considers whether the most appropriate vaccine candidates have yet been identified. [source] Sequestration of soil nitrogen as tannin,protein complexes may improve the competitive ability of sheep laurel (Kalmia angustifolia) relative to black spruce (Picea mariana)NEW PHYTOLOGIST, Issue 1 2009G. D. Joanisse Summary ,,The role of litter tannins in controlling soil nitrogen (N) cycling may explain the competitive ability of Kalmia relative to black spruce (Picea mariana), although this has not been demonstrated experimentally. ,,Here, the protein-precipitation capacities of purified tannins and leaf extracts from Kalmia and black spruce were compared. The resistance to degradation of tannin,protein precipitates from both species were compared by monitoring carbon (C) and N dynamics in humus amended with protein, purified tannins or protein,tannin precipitates. The purity of the precipitates was verified using solid-state 13C nuclear magnetic resonance (NMR) spectra. The ability of mycorrhizal fungi associated with both species to grow on media amended with tannin,protein complexes as the principal N source was also compared. ,,The protein precipitation capacity of Kalmia tannins was superior to those of black spruce. Humus amended with protein increased both mineral and microbial N, whereas humus amended with tannin,protein precipitates increased dissolved organic N. Mycorrhizal fungi associated with Kalmia showed better growth than those associated with black spruce when N was provided as tannin,protein precipitates. ,,These data suggest that Kalmia litter increases the amount of soil N sequestered as tannin,protein complexes, which may improve the competitive ability of Kalmia relative to black spruce by favouring N uptake by mycorrhizas associated with the former. [source] The Economics of an Efficient Reliance on Biomass, Carbon Capture and Carbon Sequestration in a Kyoto-style Emissions Control EnvironmentOPEC ENERGY REVIEW, Issue 3 2001Gary W. Yohe This note employs the economics paradigm to sort through the complications of relying simultaneously on biomass fuels, carbon capture with active sequestration and passive carbon sequestration to meet Kyoto-style carbon emission limits. It does so by exploiting the structure of a tax cum repurchase scheme for carbon. Under such a scheme, the carbon content of fossil fuel should be taxed at the point of purchase at a price that matches the shadow price of the carbon emission limit, but carbon embedded in biomass fuel should go un-taxed. The price of biomass fuel would, though, have to reflect the marginal cost of any externalities it might cause and the opportunity cost of its land-use requirements. Captured carbon could be repurchased at a price equal to the shadow price of carbon, net of the cost of active sequestration, itself the sum of private and social marginal costs. Finally, the price of the passive sequestration of carbon should equal the shadow price of carbon, net of the opportunity cost of setting those resources aside. Since a marketable permit system would support direct estimates of the requisite shadow price of carbon, such a system would also provide direct information about base prices for the tax cum repurchase scheme. To support long-term investment in biomass supply and sequestration, though, changes over time in emission limits must be accomplished in a smooth and predictable manner. [source] Growth and Parasite Defence in Plants; the Balance between Resource Sequestration and Retention: In Lieu of a Guest EditorialPLANT BIOLOGY, Issue 2 2002R. Matyssek Abstract: A hypothesis on regulation of the balance between growth and parasite defence in plants is formulated, namely that plants regulate their resource allocation in a way where stress tolerance and resistance inherently lead to constraints on growth and competitiveness. Seven reviews and the subsequent article in this issue of Plant Biology contributing to this problem are briefly introduced in context. [source] Sequestration of organometallic compounds by natural organic matter. binding of trimethyltin(IV) by fulvic and alginic acidsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 10 2006Alba Giacalone Abstract The binding capacity of fulvic and alginic acids towards trimethyl tin(IV) cation was quantitatively determined in order to evaluate the sequestering ability of toxic organometallic compounds by natural organic matter. Investigations were performed in the pH range of natural waters (5,8.5) where the carboxylate groups, largely present in both sequestering agents, are the main binding sites. A chemical interaction model, according to which both the protonation of polyelectrolyte ligands and the hydrolysis of the organotin cation in NaCl aqueous solution were considered, was used to define the speciation of the systems under investigation. Measurements performed at different ionic strength values (0.1, 0.25, 0.5 and 0.7 mol L,1, NaCl) allowed us to consider the dependence of stability constants on the ionic strength, and to calculate the formation constants at infinite dilution. Results obtained show the formation of the complex species TMT(L), TMT(L)2 and TMT(L)(OH) for L = fulvic acid and TMT(L) for L = alginic acid, respectively. In order to compare the strength of interaction of these natural poly electrolytes with other analogous synthetic polyelectrolytes, measurements were also carried out on the trimethyltin(IV),polyacrylate (5.1 kDa) system, and in this case the formation of TMT(L), TMT(L)2 and TMT(L)(OH) species was found. Results show the following trend of stability for the species TMT(L) in the systems investigated: TMT,fulvate , TMT,polyacrylate > TMT,alginate. On the basis of the stability data obtained, the lowest concentration of fulvic and alginic acids, able to act as sequestering agents towards triorganotin(IV) cation in the conditions of natural waters, was also calculated. Copyright © 2006 John Wiley & Sons, Ltd. [source] Selective Lanthanides Sequestration Based on a Self-Assembled OrganosilicaCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010Eric Besson Dr. Abstract In this paper, we investigate the cation-exchange properties of a self-assembled hybrid material towards trivalent ions, lanthanides (La3+, Eu3+, Gd3+, Yb3+) and Fe3+. The bis-zwitterionic lamellar material was prepared by sol,gel process from only 3-aminopropyltriethoxysilane (APTES), succinic anhydride, and ethylenediamine. In ethanol heated under reflux, the exchange ethylenediammonium versus Ln3+ proved to be complete by complexometry measurements and elemental analyses, one Cl, ion per one LnIII remaining as expected for charge balance. In aqueous solution at 20,°C, the material was found to be selective towards lanthanide in spite of the similarity of their ionic radii. The cation uptake depends on the nature of the salt, the difference between two lanthanides reaching up to 20,% in some cases. Finally, ion-exchange reaction with FeCl3 was chosen as a probe to get more information on the material after incorporation of trivalent ions. Based on Mössbauer spectroscopic investigations on the resulting material in conjunction with the XRD analysis of materials containing trivalent ions, a structural model was proposed to describe the incorporation of trivalent ions by exchange reaction within the original zwitterionic material. [source] Sequestration of Heavy Metals from Water with Layered Metal SulfidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2009Manolis Abstract Extraordinarily effective heavy metal ion scavenger: We show here that the material K2xMnxSn3,xS6 (x=0.5,0.95) (KMS-1) overcomes the limitations of the known heavy metal ion sorbents, showing the capability to rapidly reduce the concentrations of Cd, Hg, and Pb ions well-below the legally acceptable levels for drinking water. KMS-1 is inexpensive, easily prepared in large quantities, and may play a role in addressing the global problem of water contamination with heavy metal ions. The paradigm of heavy metal ion absorption of KMS-1 is the ability to form very strong MS bonds. [source] Why We Need Megareserves in AmazoniaCONSERVATION BIOLOGY, Issue 3 2005CARLOS A. PERES I consider several large-scale issues in biodiversity conservation planning (e.g., resource extraction, large areas needed for top predators, species migration, fire, and carbon sequestration) in light of our severely deficient understanding of basinwide patterns of species distribution and little-known Amazonian biota. The long-term persistence of this biota is best served by strictly protected and sustainable development forest reserves that are both embedded in a benign forest matrix and sufficiently large to support a full complement of species and landscape-scale ecological processes. Given rapidly accelerating trends in agricultural frontier expansion into previously unclaimed public lands, protection and controlled development of forests is urgent. Resumen:,La Amazonía brasileña enfrenta una de las mayores amenazas y oportunidades para la conservación de la biodiversidad tropical de nuestros tiempos. Considero varios aspectos de planificación de conservación de biodiversidad a gran escala (e. g. extracción de recursos, áreas extensas para depredadores mayores, migración de especies, fuego y secuestro de carbono) a la luz de nuestro entendimiento severamente deficiente de patrones de distribución de especies a nivel cuenca y de la poco conocida biota Amazónica. La persistencia a largo plazo de esta biota es favorecida por la protección estricta y por reservas forestales de desarrollo sustentable que estén embebidas en una matriz forestal benigna y que sean suficientemente extensas para sostener a un complemento completo de especies y procesos ecológicos a nivel paisaje. La protección y desarrollo controlado de bosques es urgente debido a la rápida aceleración de las tendencias en la expansión de la frontera agrícola hacia terrenos públicos no reclamados. [source] THE EFFICIENCY OF SEQUESTERING CARBON IN AGRICULTURAL SOILSCONTEMPORARY ECONOMIC POLICY, Issue 2 2001GR Pautsch Agricultural tillage practices are important human-induced activities that can alter carbon emissions from agricultural soils and have the potential to contribute significantly to reductions in greenhouse gas emission (Lal et al., The Potential of U.S. Cropland, 1998). This research investigates the expected costs of sequestering carbon in agricultural soils under different subsidy and market-based policies. Using detailed National Resources Inventory data, we estimate the probability that farmers adopt conservation tillage practices based on a variety of exogenous characteristics and profit from conventional practices. These estimates are used with physical models of carbon sequestration to estimate the subsidy costs of achieving increased carbon sequestration with alternative subsidy schemes. [source] A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emissionECOLOGY LETTERS, Issue 10 2009Lingli Liu Abstract Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO2, CH4 and N2O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO2 exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH4 emission by 97%, reduced CH4 uptake by 38% and increased N2O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO2 reduction could be largely offset (53,76%) by N stimulation of global CH4 and N2O emission from multiple ecosystems. [source] Plant functional traits and soil carbon sequestration in contrasting biomesECOLOGY LETTERS, Issue 5 2008Gerlinde B. De Deyn Abstract Plant functional traits control a variety of terrestrial ecosystem processes, including soil carbon storage which is a key component of the global carbon cycle. Plant traits regulate net soil carbon storage by controlling carbon assimilation, its transfer and storage in belowground biomass, and its release from soil through respiration, fire and leaching. However, our mechanistic understanding of these processes is incomplete. Here, we present a mechanistic framework, based on the plant traits that drive soil carbon inputs and outputs, for understanding how alteration of vegetation composition will affect soil carbon sequestration under global changes. First, we show direct and indirect plant trait effects on soil carbon input and output through autotrophs and heterotrophs, and through modification of abiotic conditions, which need to be considered to determine the local carbon sequestration potential. Second, we explore how the composition of key plant traits and soil biota related to carbon input, release and storage prevail in different biomes across the globe, and address the biome-specific mechanisms by which plant trait composition may impact on soil carbon sequestration. We propose that a trait-based approach will help to develop strategies to preserve and promote carbon sequestration. [source] Cycle analysis of low and high H2 utilization SOFCs/gas turbine combined cycle for CO2 recoveryELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2008Takuya Taniuchi Abstract Global warming is mainly caused by CO2 emission from thermal power plants, which burn fossil fuel with air. One of the countermeasure technologies to prevent global warming is CO2 recovery from combustion flue gas and the sequestration of CO2 underground or in the ocean. SOFC and other fuel cells can produce high-concentration CO2, because the reformed fuel gas reacts with oxygen electrochemically without being mixed with air, or diluted by N2. Thus, we propose to operate the multistage SOFCs under high utilization of reformed fuel for obtaining high-concentration CO2. In this report, we have estimated the multistage SOFCs' performance considering H2 diffusion and the combined cycle efficiency of multistage SOFC/gas turbine/CO2 recovery power plant. The power generation efficiency of our CO2 recovery combined cycle is 68.5% and the efficiency of conventional SOFC/GT cycle is 57.8% including the CO2 recovery amine process. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(10): 38,45, 2008; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecj.10165 [source] Cadmium induced oxidative stress influence on glutathione metabolic genes of Camellia sinensis (L.) O. KuntzeENVIRONMENTAL TOXICOLOGY, Issue 4 2007Prashant Mohanpuria Abstract Glutathione, a tripeptide with sulfhydryl (-SH) group is a very crucial compound primarily involved in redox balance maintenance of the cellular environment. In this study, we monitored the influence of Cd exposure on the transcript levels of glutathione metabolic genes in bud tissues, the youngest leaf, of Camellia sinensis L. In addition, some physiochemical parameters were also studied. Cd exposure decreased chlorophyll and protein contents, while increase was observed in lipid peroxidation upon Cd treatments. These changes were found to be concentration and duration dependent, indicating the occurrence of oxidative stress upon Cd exposure. The transcript levels of glutathione biosynthetic genes viz. ,-glutamylcysteine synthetase (,-ECS) and glutathione synthetase (GSHS) increased upon Cd exposure. Furthermore, transcript levels of glutathione reductase (GR), an enzyme involved in reduction of oxidized glutathione (GSSG) to reduced glutathione (GSH), also showed upregulation on Cd exposure. However, the transcript levels of glutathione-S-transferase (GST), an enzyme involved in forming metal,GSH complex and help in sequestration of high levels of metal ions to vacuole, did not show any change on Cd treatment. This study document that Cd exposure induces oxidative stress in Camellia sinensis and the upregulation in transcript levels of glutathione metabolic genes except GST have suggested the role of these enzymes in the protection of plants from high level Cd exposure. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 368,374, 2007. [source] Acute CO2 tolerance during the early developmental stages of four marine teleostsENVIRONMENTAL TOXICOLOGY, Issue 6 2003T. Kikkawa Abstract Ocean sequestration of CO2 is proposed as a possible measure to mitigate climate changes caused by increasing atmospheric concentrations of the gas, but its impact on the marine ecosystem is unknown. We investigated the acute lethal effect of CO2 during the early developmental stages of four marine teleosts: red sea bream (Pagrus major), Japanese whiting (Sillago japonica), Japanese flounder (Paralichthys olivaceus), and eastern little tuna (Euthynnus affinis). The percentages of larvae that hatched and survived were not affected by exposure to water with a PCO2 of 1.0 kPa (= 7.5 mmHg) within 24 h. Median lethal PCO2 values for a 360-min exposure were 1.4 kPa (cleavage), 5.1 kPa (embryo), 7.3 kPa (preflexion), 4.2 kPa (flexion), 4.6 kPa (postflexion), and 2.5 kPa (juvenile) for red sea bream; 2.4 kPa (cleavage), 4.9 kPa (embryo), 5.9 kPa (preflexion), 6.1 kPa (flexion), 4.1 kPa (postflexion), and 2.7 kPa (juvenile) for Japanese whiting; 2.8 kPa (cleavage) and > 7.0 kPa (young) for Japanese flounder; and 11.8 kPa (cleavage) for eastern little tuna. Red sea bream and Japanese whiting of all ontogenetic stages had similar susceptibilities to CO2: the most susceptible stages were cleavage and juvenile, whereas the most tolerant stages were preflexion and flexion. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 375,382, 2003 [source] Binding of ciprofloxacin by humic substances: A molecular dynamics studyENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2010Ludmilla Aristilde Abstract A comprehensive assessment of the potential impacts of antimicrobials released into the environment requires an understanding of their sequestration by natural particles. Of particular interest are the strong interactions of antimicrobials with natural organic matter (NOM), which are believed to reduce their bioavailability, retard their abiotic and biotic degradation, and facilitate their persistence in soils and aquatic sediments. Molecular dynamics (MD) relaxation studies of a widely used fluoroquinolone antibiotic, ciprofloxacin (Cipro), interacting with a model humic substance (HS) in a hydrated environment, were performed to elucidate the mechanisms of these interactions. Specifically, a zwitterionic Cipro molecule, the predominant species at circumneutral pH, was reacted either with protonated HS or deprotonated HS bearing Ca, Mg, or Fe(II) cations. The HS underwent conformational changes through rearrangements of its hydrophobic and hydrophilic regions and disruption of its intramolecular H-bonds to facilitate favorable intermolecular H-bonding interactions with Cipro. Complexation of the metal cations with HS carboxylates appeared to impede binding of the positively charged amino group of Cipro with these negatively charged HS complexation sites. On the other hand, an outer-sphere complex between Cipro and the HS-bound cation led to ternary Cipro,metal,HS complexes in the case of Mg,HS and Fe(II),HS, but no such bridging interaction occurred with Ca,HS. The results suggested that the ionic potential (valence/ionic radius) of the divalent cation may be a determining factor in the formation of the ternary complex, with high ionic potential favoring the bridging interaction. Environ. Toxicol. Chem. 2010;29:90,98. © 2009 SETAC [source] Development of a simulated earthworm gut for determining bioaccessible arsenic, copper, and zinc from soil,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2009Wai K. Ma Abstract Soil physicochemical characteristics and contamination levels alter the bioavailability of metals to terrestrialinvertebrates. Current laboratory-derived benchmark concentrations used to estimate risk do not take into account site-specific conditions, such as contaminant sequestration, and site-specific risk assessment requires a battery of time-consuming and costly toxicity tests. The development of an in vitro simulator for earthworm bioaccessibility would significantly shorten analytical time and enable site managers to focus on areas of greatest concern. The simulated earthworm gut (SEG) was developed to measure the bioaccessibility of metals in soil to earthworms by mimicking the gastrointestinal fluid composition of earthworms. Three formulations of the SEG (enzymes, microbial culture, enzymes and microbial culture) were developed and used to digest field soils from a former industrial site with varying physicochemical characteristics and contamination levels. Formulations containing enzymes released between two to 10 times more arsenic, copper, and zinc from contaminated soils compared with control and 0.01 M CaCl2 extractions. Metal concentrations in extracts from SEG formulation with microbial culture alone were not different from values for chemical extractions. The mechanism for greater bioaccessible metal concentrations from enzyme-treated soils is uncertain, but it is postulated that enzymatic digestion of soil organic matter might release sequestered metal. The relevance of these SEG results will need validation through further comparison and correlation with bioaccumulation tests, alternative chemical extraction tests, and a battery of chronic toxicity tests with invertebrates and plants. [source] Molecular modeling of metal complexation by a fluoroquinolone antibioticENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2008Ludmilla Aristilde Abstract An understanding of the factors controlling the chemodynamics of fluoroquinolone antibiotics in different environmental matrices is a necessary prerequisite to the assessment of their potential impact on nontarget organisms in soils and receiving waters. Of particular interest are the complexes formed between fluoroquinolones and metal cations, which are believed to be important in the mechanism of sequestration of the antibiotic by minerals and natural organic matter. The structures of these complexes have not been fully resolved by conventional spectroscopy; therefore, molecular simulations may provide useful complementary insights. We present results from apparently the first molecular dynamics simulations of a widely used fluoroquinolone antibiotic, ciprofloxacin (Cipro), in aqueous complexes with five metal cations typically found in soils and surface waters: Ca2+, Mg2+, Fe2+, Na+, and K+. The interatomic potential functions employed in the simulations were validated by comparison with available structural data for solid-phase Cipro-hexahydrate and for the metal cations in aqueous solution. Although no comprehensive structural data on the aqueous complexes appear to be available, properties of the metal complexes predicted by our simulations agree with available data for solid-phase metal,Cipro complexes. Our results indicate that the ionic potential of the metal cation controls the stability of the complex formed and that the hydration number of the metal cation in aqueous solution determines its coordination number with O atoms in the metal,Cipro complex. In respect to environmental chemodynamics, our results imply that Cipro will form two configurations of bidendate chelates with metal centers on exposed surfaces of mineral oxides, water-bridged surface complexes with exchangeable cations in clay mineral interlayers, and cation-bridged complexes with functional groups in natural organic matter. [source] Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in dated sediment coresENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2007Charles S. Wong Abstract ,Enantiomer fractions (EFs) of seven chiral poly chlorinated biphenyls (PCBs) were measured in dated sediment cores of Lake Hartwell (SC, USA) and Lake Ontario (USA) to detect, quantify, and gain insight regarding microbial reductive dechlorination of PCBs in lake sediments with high and low concentrations, respectively. Lake Hartwell sediments had high total PCBs (5,60 ,g/g), with significantly nonracemic EFs that generally were consistent with those from previous laboratory microcosm reductive dechlorination experiments using sediments from these sites. Thus, stereoselective reductive dechlorination had occurred in situ, including at total PCB concentrations of less than the threshold of approximately 30 to 80 ,g/g suggested as being necessary for reductive dechlorination. Enantiomer fractions of PCBs 91, 95, 132, and 136 in Lake Hartwell cores were significantly correlated both with concentrations of those individual congeners and with total PCB concentration for some sites. This result indicates that enantioselective microbial dechlorination activity increases with higher concentrations within sediments for these congeners. Enantiomer composition reversed with depth for PCBs 91, 132, and 176, suggesting that multiple microbial populations may be present within the same core that are enantioselectively dechlorinating PCBs. Such observations indicate that concentration and time are not the only factors affecting biotransformation, complicating prediction of enantioselectivity. Comparison of EFs with dates suggested biotransformation half-lives of approximately 30 years, which is on the same time scale as sequestration by burial. In contrast, Lake Ontario sediments (maximum total PCBs, 400 ng/g) had racemic or near-racemic amounts of most congeners throughout the core profile, which is consistent with achiral indicators suggesting no microbial biotransformation within Lake Ontario sediments. Thresholds for reductive dechlorination may exist, but they would be at concentrations of less than 30 to 80 ,g/g. [source] Congener-specific toxicokinetics of polychlorinated dibenzo- p -dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in black-eared kites (Milvus migrans): Cytochrome P4501A,dependent hepatic sequestrationENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2006Akira Kubota Abstract Concentrations of dioxins and related compounds (DRCs), such as polychlorinated dibenzo- p -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs), were determined in black-eared kites (BEKs; Milvus migrans) collected from the Kanto district in Japan. Total 2,3,7,8-tetra-CDD toxic equivalents (TEQs) were in the range of 99 to 3,800 pg/g lipid weight in the liver and 42 to 760 pg/g lipid weight in the pectoral muscle. Three congeners, including PCB 126, 2,3,4,7,8-penta-CDF, and 1,2,3,7,8-penta-CDD, made a greater contribution to total TEQs in both tissues. Levels of ethoxy-resorufin- O -deethylase activity and a cross-reactive protein with anti-rat cytochrome P4501A (CYP1A) polyclonal antibodies showed no significant correlation with hepatic TEQs. This may be attributed to low sensitivity and insufficient TEQ levels to cause CYP1A induction, high metabolic potential of a series of congeners, and influence of CYP1A inducers other than DRCs. Most of the PCDD/Fs and non- ortho Co-PCBs exhibited a total TEQ- and CYP1A-dependent increase in the liver to muscle concentration ratios, implying their concentration-dependent hepatic sequestration in which CYP1A was involved. Comparison of the toxicokinetics in avian species revealed that BEKs possibly have higher potentials than common cormorants for metabolizing and sequestering certain congeners in the liver in terms of hepatic concentration profiles and liver:muscle concentration ratios, respectively. These results clearly indicate that the toxicokinetics of DRCs is congener-, tissue-, and species-specific as well as concentration-dependent. Therefore, CYP1A expression is one of the critical factors that determine the toxicokinetics in wild avian species. [source] Comparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Randhir S. Makkar Abstract Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost-competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low-cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant-associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant,PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant-enhanced PAH bioavailability and thus better bioremediation design. [source] Standing oral extraction of cheek teeth in 100 horses (1998-2003)EQUINE VETERINARY JOURNAL, Issue 2 2005P. M. DIXON Summary Reasons for performing study: Extraction of cheek teeth (CT) by the conventional repulsion technique requires general anaesthesia and carries a high rate of post operative complications. Consequently, an alternative method of extraction, i.e. orally in standing horses, was evaluated. Hypothesis: The need for and risks of general anaesthesia could be avoided and post extraction sequelae reduced by performing extractions orally in standing horses. Methods: One hundred mainly younger horses (median age 8, range 2-18 years) with firmly attached CT that required extraction because of apical infections, displacements, diastemata, idiopathic fractures and the presence of supernumerary CT had the affected teeth (n = 111) extracted orally under standing sedation. Follow-up information was obtained for all cases, a median of 16 months later. Results: Oral extraction was successful in 89 horses and unsuccessful in 11 due to damage to the CT clinical crown (n = 9) during extraction, for behavioural reasons (n = 1) and because the apex of a partly extracted CT fell back into the alveolus following sectioning (n = 1). Predispositions to extraction-related CT fractures were present in 5 of the 9 cases, i.e. advanced dental caries (n = 2) and pre-existing ,idiopathic' fractures (n = 3). The iatrogenically fractured CT were later repulsed under standing sedation (n = 3) and under general anaesthesia (n = 6). Eighty-one of the remaining 89 horses had successful oral CT extraction with no or minimal intra- or post operative complications occurring. Post operative complications in the other 8 cases included post extraction alveolar sequestration (n = 3), alveolar sequestration and localised osteomyelitis (n = 1), localised osteomyelitis (n = 1), incorporation of alveolar packing material into alveolar granulation tissue (n = 1), and nasal discharge due to continued intranasal presence of purulent food material (n = 1) and to ongoing sinusitis (n = 1). The above sequelae were treated successfully in all cases, with general anaesthesia required in just one case. Following oral extraction, significantly (P<0.001) fewer post operative problems developed in 54 horses with apically infected CT in comparison with 71 previous cases that had repulsion of apically infected CT at our clinic. Conclusions and potential relevance: Oral extraction of cheek teeth is a successful technique in the majority of younger horses with firmly attached CT and greatly reduces the post operative sequelae, compared with CT repulsion. Additionally, the costs and risks of general anaesthesia are avoided. Further experience and refinement in the described protocol could potentially increase the success of this procedure and also reduce the incidence of post operative sequelae. [source]
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