Chemically and geographically distinct solid-phase iron pools in the Southern Ocean.

PubMed

von der Heyden, B P; Roychoudhury, A N; Mtshali, T N; Tyliszczak, T; Myneni, S C B

2012-11-30

Iron is a limiting nutrient in many parts of the oceans, including the unproductive regions of the Southern Ocean. Although the dominant fraction of the marine iron pool occurs in the form of solid-phase particles, its chemical speciation and mineralogy are challenging to characterize on a regional scale. We describe a diverse array of iron particles, ranging from 20 to 700 nanometers in diameter, in the waters of the Southern Ocean euphotic zone. Distinct variations in the oxidation state and composition of these iron particles exist between the coasts of South Africa and Antarctica, with different iron pools occurring in different frontal zones. These speciation variations can result in solubility differences that may affect the production of bioavailable dissolved iron.

Labile Low-Molecular-Mass Metal Complexes in Mitochondria: Trials and Tribulations of a Burgeoning Field.

PubMed

Lindahl, Paul A; Moore, Michael J

2016-08-02

Iron, copper, zinc, manganese, cobalt, and molybdenum play important roles in mitochondrial biochemistry, serving to help catalyze reactions in numerous metalloenzymes. These metals are also found in labile "pools" within mitochondria. Although the composition and cellular function of these pools are largely unknown, they are thought to be comprised of nonproteinaceous low-molecular-mass (LMM) metal complexes. Many problems must be solved before these pools can be fully defined, especially problems stemming from the lability of such complexes. This lability arises from inherently weak coordinate bonds between ligands and metals. This is an advantage for catalysis and trafficking, but it makes characterization difficult. The most popular strategy for investigating such pools is to detect them using chelator probes with fluorescent properties that change upon metal coordination. Characterization is limited because of the inevitable destruction of the complexes during their detection. Moreover, probes likely react with more than one type of metal complex, confusing analyses. An alternative approach is to use liquid chromatography (LC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). With help from a previous lab member, the authors recently developed an LC-ICP-MS approach to analyze LMM extracts from yeast and mammalian mitochondria. They detected several metal complexes, including Fe580, Fe1100, Fe1500, Cu5000, Zn1200, Zn1500, Mn1100, Mn2000, Co1200, Co1500, and Mo780 (numbers refer to approximate masses in daltons). Many of these may be used to metalate apo-metalloproteins as they fold inside the organelle. The LC-based approach also has challenges, e.g., in distinguishing artifactual metal complexes from endogenous ones, due to the fact that cells must be disrupted to form extracts before they are passed through chromatography columns prior to analysis. Ultimately, both approaches will be needed to characterize these intriguing complexes and to

Non-labile Soil 15Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests.Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Concepts and goals in the management of transfusional iron overload.

PubMed

Porter, John B

2007-12-01

In this review, current concepts and goals of iron chelation therapy for thalassemias, sickle cell disease, and myelodysplastic syndromes are discussed. The primary goal of iron chelation therapy is to prevent the accumulation of iron reaching harmful levels by matching iron intake from blood transfusion, with iron excreted by iron chelation. Over 30 years of experience with deferoxamine has shown iron chelation to be an effective therapeutic modality. However, chelation efficiency is limited because most of the body's iron stores are not directly chelatable, and only a small fraction of body iron is chelatable at any moment. Once iron has been deposited in organs other than the liver, for example the heart, removal by chelation is slow and inefficient. Chelation efficiency can be improved by designing regimes where chelators are available 24 hr a day to bind labile iron pools in cells and plasma. Deferoxamine has a short plasma half-life and the parenteral infusions required to achieve steady plasma levels are demanding, with consequent variable adherence to therapy. Once-daily oral administration of deferasirox achieves continuous chelation with trough concentrations sufficient to decrease plasma labile iron species progressively, and achieves an efficiency of chelation not obtainable with deferiprone or deferoxamine monotherapy. 2007 Wiley-Liss, Inc

Detection of a variable intracellular acid-labile carbon pool in Thalassiosira weissflogii (Heterokontophyta) and Emiliania huxleyi (Haptophyta) in response to changes in the seawater carbon system.

PubMed

Isensee, Kirsten; Erez, Jonathan; Stoll, Heather M

2014-02-01

Accumulation of an intracellular pool of carbon (C(i) pool) is one strategy by which marine algae overcome the low abundance of dissolved CO2 (CO2 (aq) ) in modern seawater. To identify the environmental conditions under which algae accumulate an acid-labile C(i) pool, we applied a (14) C pulse-chase method, used originally in dinoflagellates, to two new classes of algae, coccolithophorids and diatoms. This method measures the carbon accumulation inside the cells without altering the medium carbon chemistry or culture cell density. We found that the diatom Thalassiosira weissflogii [(Grunow) G. Fryxell & Hasle] and a calcifying strain of the coccolithophorid Emiliania huxleyi [(Lohmann) W. W. Hay & H. P. Mohler] develop significant acid-labile C(i) pools. C(i) pools are measureable in cells cultured in media with 2-30 µmol l(-1) CO2 (aq), corresponding to a medium pH of 8.6-7.9. The absolute C(i) pool was greater for the larger celled diatoms. For both algal classes, the C(i) pool became a negligible contributor to photosynthesis once CO2 (aq) exceeded 30 µmol l(-1) . Combining the (14) C pulse-chase method and (14) C disequilibrium method enabled us to assess whether E. huxleyi and T. weissflogii exhibited thresholds for foregoing accumulation of DIC or reduced the reliance on bicarbonate uptake with increasing CO2 (aq) . We showed that the C(i) pool decreases with higher CO2 :HCO3 (-) uptake rates. © 2013 Scandinavian Plant Physiology Society.

A new class of high-contrast Fe(II) selective fluorescent probes based on spirocyclized scaffolds for visualization of intracellular labile iron delivered by transferrin.

PubMed

Niwa, Masato; Hirayama, Tasuku; Okuda, Kensuke; Nagasawa, Hideko

2014-09-14

Iron is an essential metal nutrient that plays physiologically and pathologically important roles in biological systems. However, studies on the trafficking, storage, and functions of iron itself in living samples have remained challenging due to the lack of efficient methods for monitoring labile intracellular iron. Herein, we report a new class of Fe(2+)-selective fluorescent probes based on the spirocyclization of hydroxymethylrhodamine and hydroxymethylrhodol scaffolds controlled by using our recently established N-oxide chemistry as a Fe(2+)-selective switch of fluorescence response. By suppressing the background signal, the spirocyclization strategy improved the turn-on rate dramatically, and reducing the size of the substituents of the N-oxide group enhanced the reaction rate against Fe(2+), compared with the first generation N-oxide based Fe(2+) probe, RhoNox-1. These new probes showed significant enhancements in the fluorescence signal against not only the exogenously loaded Fe(2+) but also the endogenous Fe(2+) levels. Furthermore, we succeeded in monitoring the accumulation of labile iron in the lysosome induced by transferrin-mediated endocytosis with a turn-on fluorescence response.

Modeling Effects of Lability on Microbial Uptake of DOM in River Reaches

NASA Astrophysics Data System (ADS)

Li, A.; Drummond, J. D.; Bowen, J. C.; Cory, R. M.; Kaplan, L.; Packman, A. I.

2017-12-01

Rivers are hotspots for biological degradation of dissolved organic matter (DOM), contributing to 1.8 petagrams of carbon emissions per year. DOM represents approximately 60% of the total mass of organic carbon transported within river networks, fueling stream ecosystem metabolism. Not all DOM is biodegradable, biodegradation rates vary based on lability, and lability decreases with reaction time. Fluorescent fractions of DOM (FDOM) are often used as proxies of DOM lability. Humic-like FDOM, previously considered recalcitrant and thought to contribute minimally to the biodegradable DOM pools, has recently been shown to contribute more than 50% to DOM uptake in bioreactor columns colonized by bacteria in stream water. Protein-like FDOM, a proxy for the biodegradable DOM pool, also contributes to the recalcitrant DOM pool in bioreactors. However, the contribution of different lability pools to DOM uptake at the reach scale remains elusive. Here we combine local-scale results from a bioreactor study and measures of stream geomorphology parameters to model reach-scale DOM uptake in White Clay Creek, a Pennsylvania piedmont stream with an intact, forested riparian zone and inputs from upland agriculture. Steady state modeling of a point-source, continuous injection of FDOM shows that humic-like FDOM contributes up to 80% of the total removal of FDOM at the reach scale, suggesting its importance to in-stream DOM uptake. Tryptophan-like FDOM, a protein-like FDOM, contributes to 80% of the remaining fraction of FDOM at the reach scale that incorporates longer timescales of transport and retention. This is consistent with recent local-scale findings that the lability of tryptophan-like FDOM decreases substantially with reaction time in bioreactors, such that it becomes much more recalcitrant as it travels downstream. Steady state modeling of a distributed source, continuous injection of FDOM shows that contributing sources distribute differently along the river reach for

Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms

NASA Astrophysics Data System (ADS)

McQuaid, Jeffrey B.; Kustka, Adam B.; Oborník, Miroslav; Horák, Aleš; McCrow, John P.; Karas, Bogumil J.; Zheng, Hong; Kindeberg, Theodor; Andersson, Andreas J.; Barbeau, Katherine A.; Allen, Andrew E.

2018-03-01

In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbonate ions. In P. tricornutum, the synergistic interaction of labile iron and carbonate ions occurs at environmentally relevant concentrations, revealing that carbonate availability co-limits iron uptake. Phytotransferrin sequences have a broad taxonomic distribution and are abundant in marine environmental genomic datasets, suggesting that acidification-driven declines in the concentration of seawater carbonate ions will have a negative effect on this globally important eukaryotic iron acquisition mechanism.

Iron regulatory proteins and their role in controlling iron metabolism.

PubMed

Kühn, Lukas C

2015-02-01

Cellular iron homeostasis is regulated by post-transcriptional feedback mechanisms, which control the expression of proteins involved in iron uptake, release and storage. Two cytoplasmic proteins with mRNA-binding properties, iron regulatory proteins 1 and 2 (IRP1 and IRP2) play a central role in this regulation. Foremost, IRPs regulate ferritin H and ferritin L translation and thus iron storage, as well as transferrin receptor 1 (TfR1) mRNA stability, thereby adjusting receptor expression and iron uptake via receptor-mediated endocytosis of iron-loaded transferrin. In addition splice variants of iron transporters for import and export at the plasma-membrane, divalent metal transporter 1 (DMT1) and ferroportin are regulated by IRPs. These mechanisms have probably evolved to maintain the cytoplasmic labile iron pool (LIP) at an appropriate level. In certain tissues, the regulation exerted by IRPs influences iron homeostasis and utilization of the entire organism. In intestine, the control of ferritin expression limits intestinal iron absorption and, thus, whole body iron levels. In bone marrow, erythroid heme biosynthesis is coordinated with iron availability through IRP-mediated translational control of erythroid 5-aminolevulinate synthase mRNA. Moreover, the translational control of HIF2α mRNA in kidney by IRP1 coordinates erythropoietin synthesis with iron and oxygen supply. Besides IRPs, body iron absorption is negatively regulated by hepcidin. This peptide hormone, synthesized and secreted by the liver in response to high serum iron, downregulates ferroportin at the protein level and thereby limits iron absorption from the diet. Hepcidin will not be discussed in further detail here.

Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

NASA Astrophysics Data System (ADS)

Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

2016-04-01

Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg-1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike -Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L-1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not yet

Total and labile metals in surface sediments of the tropical river-estuary system of Marabasco (Pacific coast of Mexico): Influence of an iron mine.

PubMed

Marmolejo-Rodríguez, Ana Judith; Prego, Ricardo; Meyer-Willerer, Alejandro; Shumilin, Evgueni; Cobelo-García, Antonio

2007-01-01

Marabasco is a tropical river-estuary system comprising the Marabasco river and the Barra de Navidad Lagoon. The river is impacted by the Peña Colorada iron mine, which produces 3.5 million tons of pellets per year. Thirteen surface sediment samples were collected in May 2005 (dry season) in order to establish background levels of Al, Cd, Co, Cu, Fe, Ni, Pb, and Zn in the system and to ascertain the potential mobility of metals in the sediments. Analyses were carried out in the fraction finer than 63 microm, and labile metals extracted according the BCR procedure. Certified reference materials were used for validation of methods. Total concentrations of Cd, Co, Cu, Ni, Pb, and Zn were in the range of 0.05-0.34, 6-95, 0.7-31, 9-26, 2-18, and 53-179 mgkg(-1), respectively; Al and Fe ranges of 24-127, and 26-69 mgg(-1) correspondingly. Cadmium was found to be significantly labile in the sediments (20-100%), followed by Co (0-35%), Ni (3-16%) and Zn (0-25%), whereas the labile fraction for Cu, Fe and Pb was almost negligible (<4%). According with the total metal concentrations, background levels and normalised enrichment factors (NEF) of the metals studied, the impact of the Peña Colorada iron mine on the Marabasco system is lower than expected when compared with other similar World systems influenced by mining activities.

Mathematical modeling of the dynamic storage of iron in ferritin

PubMed Central

2010-01-01

Background Iron is essential for the maintenance of basic cellular processes. In the regulation of its cellular levels, ferritin acts as the main intracellular iron storage protein. In this work we present a mathematical model for the dynamics of iron storage in ferritin during the process of intestinal iron absorption. A set of differential equations were established considering kinetic expressions for the main reactions and mass balances for ferritin, iron and a discrete population of ferritin species defined by their respective iron content. Results Simulation results showing the evolution of ferritin iron content following a pulse of iron were compared with experimental data for ferritin iron distribution obtained with purified ferritin incubated in vitro with different iron levels. Distinctive features observed experimentally were successfully captured by the model, namely the distribution pattern of iron into ferritin protein nanocages with different iron content and the role of ferritin as a controller of the cytosolic labile iron pool (cLIP). Ferritin stabilizes the cLIP for a wide range of total intracellular iron concentrations, but the model predicts an exponential increment of the cLIP at an iron content > 2,500 Fe/ferritin protein cage, when the storage capacity of ferritin is exceeded. Conclusions The results presented support the role of ferritin as an iron buffer in a cellular system. Moreover, the model predicts desirable characteristics for a buffer protein such as effective removal of excess iron, which keeps intracellular cLIP levels approximately constant even when large perturbations are introduced, and a freely available source of iron under iron starvation. In addition, the simulated dynamics of the iron removal process are extremely fast, with ferritin acting as a first defense against dangerous iron fluctuations and providing the time required by the cell to activate slower transcriptional regulation mechanisms and adapt to iron stress

Mathematical modeling of the dynamic storage of iron in ferritin.

PubMed

Salgado, J Cristian; Olivera-Nappa, Alvaro; Gerdtzen, Ziomara P; Tapia, Victoria; Theil, Elizabeth C; Conca, Carlos; Nuñez, Marco T

2010-11-03

Iron is essential for the maintenance of basic cellular processes. In the regulation of its cellular levels, ferritin acts as the main intracellular iron storage protein. In this work we present a mathematical model for the dynamics of iron storage in ferritin during the process of intestinal iron absorption. A set of differential equations were established considering kinetic expressions for the main reactions and mass balances for ferritin, iron and a discrete population of ferritin species defined by their respective iron content. Simulation results showing the evolution of ferritin iron content following a pulse of iron were compared with experimental data for ferritin iron distribution obtained with purified ferritin incubated in vitro with different iron levels. Distinctive features observed experimentally were successfully captured by the model, namely the distribution pattern of iron into ferritin protein nanocages with different iron content and the role of ferritin as a controller of the cytosolic labile iron pool (cLIP). Ferritin stabilizes the cLIP for a wide range of total intracellular iron concentrations, but the model predicts an exponential increment of the cLIP at an iron content > 2,500 Fe/ferritin protein cage, when the storage capacity of ferritin is exceeded. The results presented support the role of ferritin as an iron buffer in a cellular system. Moreover, the model predicts desirable characteristics for a buffer protein such as effective removal of excess iron, which keeps intracellular cLIP levels approximately constant even when large perturbations are introduced, and a freely available source of iron under iron starvation. In addition, the simulated dynamics of the iron removal process are extremely fast, with ferritin acting as a first defense against dangerous iron fluctuations and providing the time required by the cell to activate slower transcriptional regulation mechanisms and adapt to iron stress conditions. In summary, the model

Iron content of soils as a precipitation proxy

NASA Astrophysics Data System (ADS)

Dzombak, R.; Sheldon, N. D.

2016-12-01

Given that different iron phases form under different precipitation and drainage regimes, soil iron content could be used as a proxy for both volume and seasonality of precipitation. Constraining these factors is important for predicting future precipitation trends, especially for a warmer climate that will likely see more frequent extreme weather events. Specifically, using paleoprecipitation data from periods of higher temperatures and atmospheric CO2 concentrations helps inform models of future `greenhouse' climate. Forty-five modern samples from across the continental United States were analyzed, with MAP ranging from 200 to 1200 mm yr-1 and MAT ranging from 5 to 22°C. Soil types included Alfisols (N=15), Inceptisols (N=8), Mollisols (N=15), and Aridisols (N=7), and ranged from seasonally wet to well-drained. Analytical techniques included combustion-elemental analysis and organic carbon isotope analysis, a sequential iron extraction modified with a sodium hypochlorite step for the extraction of organic matter-bound iron, and the extraction of iron sulfides. The sequential extractions yield five different `pools' of iron found in sediment: crystalline iron oxides (e.g., goethite, hematite), magnetite, carbonate-bound, organic matter-bound, and labile/easily reducible iron minerals (e.g., ferrihydrite). Analysis by ICP-OES yielded a strong relationship between magnetite-bound iron and MAP, and fair relationships between the other iron pools and MAP. Individual soil orders tended to show stronger relationships to the iron pools than all soils analyzed together, potentially indicating the need for separate proxy relationships for each soil order. Pyrite concentrations were well below 1% by weight for these soils, suggesting that none of these soils has a long enough wet season to encourage its formation and that the presence vs. absence of pyrite in paleosols may be a useful proxy for soil moisture state. In contrast to some earlier work, no significant

Estuarine removal of glacial iron and implications for iron fluxes to the ocean

USGS Publications Warehouse

Schroth, Andrew W.; Crusius, John; Hoyer, Ian; Campbell, Robert

2014-01-01

While recent work demonstrates that glacial meltwater provides a substantial and relatively labile flux of the micronutrient iron to oceans, the role of high-latitude estuary environments as a potential sink of glacial iron is unknown. Here we present the first quantitative description of iron removal in a meltwater-dominated estuary. We find that 85% of “dissolved” Fe is removed in the low-salinity region of the estuary along with 41% of “total dissolvable” iron associated with glacial flour. We couple these findings with hydrologic and geochemical data from Gulf of Alaska (GoA) glacierized catchments to calculate meltwater-derived fluxes of size and species partitioned Fe to the GoA. Iron flux data indicate that labile iron in the glacial flour and associated Fe minerals dominate the meltwater contribution to the Fe budget of the GoA. As such, GoA nutrient cycles and related ecosystems could be strongly influenced by continued ice loss in its watershed.

Response of iron overload to deferasirox in rare transfusion-dependent anaemias: equivalent effects on serum ferritin and labile plasma iron for haemolytic or production anaemias

PubMed Central

Porter, John B; Lin, Kai-Hsin; Beris, Photis; Forni, Gian Luca; Taher, Ali; Habr, Dany; Domokos, Gabor; Roubert, Bernard; Thein, Swee Lay

2011-01-01

Objectives It is widely assumed that, at matched transfusional iron-loading rates, responses to chelation therapy are similar, irrespective of the underlying condition. However, data are limited for rare transfusion-dependent anaemias, and it remains to be elucidated if response differs, depending on whether the anaemia has a primary haemolytic or production mechanism. Methods The efficacy and safety of deferasirox (Exjade®) in rare transfusion-dependent anaemias were evaluated over 1 yr, with change in serum ferritin as the primary efficacy endpoint. Initial deferasirox doses were 10–30 mg/kg/d, depending on transfusion requirements; 34 patients had production anaemias, and 23 had haemolytic anaemias. Results Patients with production anaemias or haemolytic anaemias had comparable transfusional iron-loading rates (0.31 vs. 0.30 mL red blood cells/kg/d), mean deferasirox dosing (19.3 vs. 19.0 mg/kg/d) and baseline median serum ferritin (2926 vs. 2682 ng/mL). Baseline labile plasma iron (LPI) levels correlated significantly with the transfusional iron-loading rates and with serum ferritin levels in both cohorts. Reductions in median serum ferritin levels were initially faster in the production than the haemolytic anaemias, but at 1 yr, similar significant reductions of 940 and 617 ng/mL were attained, respectively (−26.0% overall). Mean LPI decreased significantly in patients with production (P < 0.0001) and haemolytic (P = 0.037) anaemias after the first dose and was maintained at normal mean levels (<0.4 μm) subsequently. The most common drug-related, investigator-assessed adverse events were diarrhoea (n = 16) and nausea (n = 12). Conclusions At matched transfusional iron-loading rates, the responses of rare transfusion-dependent anaemias to deferasirox are similar at 1 yr, irrespective of the underlying pathogenic mechanism. PMID:21649735

Response of iron overload to deferasirox in rare transfusion-dependent anaemias: equivalent effects on serum ferritin and labile plasma iron for haemolytic or production anaemias.

PubMed

Porter, John B; Lin, Kai-Hsin; Beris, Photis; Forni, Gian Luca; Taher, Ali; Habr, Dany; Domokos, Gabor; Roubert, Bernard; Thein, Swee Lay

2011-10-01

It is widely assumed that, at matched transfusional iron-loading rates, responses to chelation therapy are similar, irrespective of the underlying condition. However, data are limited for rare transfusion-dependent anaemias, and it remains to be elucidated if response differs, depending on whether the anaemia has a primary haemolytic or production mechanism. The efficacy and safety of deferasirox (Exjade®) in rare transfusion-dependent anaemias were evaluated over 1 yr, with change in serum ferritin as the primary efficacy endpoint. Initial deferasirox doses were 10-30 mg/kg/d, depending on transfusion requirements; 34 patients had production anaemias, and 23 had haemolytic anaemias. Patients with production anaemias or haemolytic anaemias had comparable transfusional iron-loading rates (0.31 vs. 0.30 mL red blood cells/kg/d), mean deferasirox dosing (19.3 vs. 19.0 mg/kg/d) and baseline median serum ferritin (2926 vs. 2682 ng/mL). Baseline labile plasma iron (LPI) levels correlated significantly with the transfusional iron-loading rates and with serum ferritin levels in both cohorts. Reductions in median serum ferritin levels were initially faster in the production than the haemolytic anaemias, but at 1 yr, similar significant reductions of 940 and 617 ng/mL were attained, respectively (-26.0% overall). Mean LPI decreased significantly in patients with production (P < 0.0001) and haemolytic (P = 0.037) anaemias after the first dose and was maintained at normal mean levels (< 0.4 μm) subsequently. The most common drug-related, investigator-assessed adverse events were diarrhoea (n = 16) and nausea (n = 12). At matched transfusional iron-loading rates, the responses of rare transfusion-dependent anaemias to deferasirox are similar at 1 yr, irrespective of the underlying pathogenic mechanism. © 2011 John Wiley & Sons A/S.

Hemorrhagic Shock and Surgical Stress Alter Distribution of Labile Zinc within High and Low Molecular Weight Plasma Fractions

PubMed Central

Kelly, Edward; Mathew, Jeff; Kohler, Jonathan E.; Blass, Amy L.; Soybel, David I.

2012-01-01

Zinc ions (Zn2+) are essential for tissue repair following injury or stress. We hypothesize that during such stresses Zn2+ is redistributed to labile pools in plasma components. Here we tested this hypothesis utilizing a novel assay to monitor labile Zn2+ in plasma in hemorrhagic shock. Adult rats in the Shock (S) group underwent hemorrhage and resuscitation. Blood samples were drawn at baseline, 1 hr, 4 hrs and 24 hrs. The Surgical Control (SC) group was anesthetized and instrumented, but not bled. Albumin, total Zn2+, and labile Zn2+ levels were assayed in plasma. Binding capacity for Zn2+ was assessed in high (HMW) and low (LMW) molecular weight pools. Significant decreases in total Zn2+ were observed by 24 hrs, in both S and SC groups. Albumin levels were significantly reduced in the S group at 1 hr and 4 hr but restored at 24 hrs; significant changes were not observed in other groups. In whole plasma, labile Zn2+ levels were stable initially in the S and SC groups, but declined at 24 hrs. In the HMW pool, marked and significant impairment of binding was noted throughout all time periods following the shock period in the S group. Such changes were observed in the SC group of less intensity and duration. These experiments suggest that Shock alters affinity of plasma proteins for Zn2+, promoting delivery to peripheral tissues during periods of increased Zn2+ utilization. PMID:22744307

Hemorrhagic shock and surgical stress alter distribution of labile zinc within high- and low-molecular-weight plasma fractions.

PubMed

Kelly, Edward; Mathew, Jeff; Kohler, Jonathan E; Blass, Amy L; Soybel, And David I

2012-08-01

Zinc ions (Zn) are essential for tissue repair following injury or stress. We hypothesize that during such stresses Zn is redistributed to labile pools in plasma components. Here we tested this hypothesis using a novel assay to monitor labile Zn in plasma in hemorrhagic shock. Adult rats in the shock group (S group) underwent hemorrhage and resuscitation. Blood samples were drawn at baseline and at 1, 4, and 24 h. The surgical control group (SC group) was anesthetized and instrumented, but not bled. Albumin, total Zn, and labile Zn levels were assayed in plasma. Binding capacity for Zn was assessed in high- and low-molecular-weight pools. Significant decreases in total Zn were observed by 24 h, in both S and SC groups. Albumin levels were significantly reduced in the S group at 1 and 4 h but restored at 24 h; significant changes were not observed in other groups. In whole plasma, labile Zn levels were stable initially in the S and SC groups, but declined at 24 h. In the high-molecular-weight pool, marked and significant impairment of binding was noted throughout all time periods following the shock period in the S group. Such changes were observed in the SC group of less intensity and duration. These experiments suggest that shock alters affinity of plasma proteins for Zn, promoting delivery to peripheral tissues during periods of increased Zn utilization.

Influence of an iron-rich amendment on chemical lability and plant (Raphanus sativus L.) availability of two metallic elements (As and Pb) on mine-impacted agricultural soils.

PubMed

Kim, Juhee; Kim, Yong-Seong; Hyun, Seunghun; Moon, Deok Hyun; Chang, Jun Young

2016-10-01

Variation of the chemical extractability and phytoavailability of two metallic elements (e.g., As and Pb) on amendment-treated soils was investigated. Four mine-impacted agricultural soils contaminated with both As (174-491 mg kg -1 ) and Pb (116-357 mg kg -1 ) were amended with an iron-rich sludge at the rate of 5 % (w/w). After a 4-, 8-, and 16-week incubation, the extractability of metallic elements was assessed by sequential extraction procedure (SEP; F1-F5). The control without amendment was also run. In amended soils, the labile element mass (i.e., F1 + F2) promptly decreased (15-48 % of As and 5-10 % of Pb) in 4 weeks, but the decrement was continued over 16 weeks up to 70 and 28 % for As and Pb, respectively. The labile mass decrement was quantitatively corresponded with the increment of F3 (bound to amorphous metal oxides). In plant test assessed by radish (Raphanus sativus) grown on the 16-week soils, up to 57 % of As and 28 % of Pb accumulation was suppressed and 10-43 % of growth (i.e., shoot/root elongation and fresh weight) was improved. For both the control and amended soils, element uptake by plant was well correlated with their labile soil concentrations (r 2  = 0.799 and 0.499 for As and Pb, respectively). The results confirmed that the iron-rich material can effectively suppress element uptake during R. sativus seedling growth, most likely due to the chemical stabilization of metallic elements in growth medium.

Utility of labile plasma iron and transferrin saturation in addition to serum ferritin as iron overload markers in different underlying anemias before and after deferasirox treatment.

PubMed

Porter, John B; El-Alfy, Mohsen; Viprakasit, Vip; Giraudier, Stephane; Chan, Lee Lee; Lai, Yongrong; El-Ali, Ali; Han, Jackie; Cappellini, Maria D

2016-01-01

Plasma markers in addition to serum ferritin (SF) may be useful for the assessment of iron overload; however, predictive utility may differ depending on underlying, transfusion-dependent, anemias. Data were collected before and after 1 year of deferasirox treatment (end of study; EOS) from the large, 1-year EPIC (Evaluation of Patients' Iron Chelation with Exjade(®) ) study. Trends were evaluated between liver iron concentration (LIC), transferrin saturation (TfSat), predose labile plasma iron (LPI) and their relationship to SF categories in 1530 patients: thalassemia major (TM; n = 1114), myelodysplastic syndromes (MDS, n = 336), and sickle-cell disease (SCD, n = 80). Baseline and EOS SF values showed a clear and similar relationship to LIC for all disease groups. TfSat also showed a relationship to SF, most clearly in patients with SCD, where TfSat was lowest in the lowest relative SF category. Unlike SF or LIC, TfSat did not decrease at EOS in any disease group. Baseline LPI was raised in TM and MDS, but not in patients with SCD, decreasing at EOS in both patient groups. After 1 year of chelation therapy, there was a significant trend for greater LPI reduction in patients with TM achieving LIC <7 mg Fe/g dw (P = 0.0137). Despite limitations, SF showed the clearest relationship, of the plasma markers evaluated, to LIC before and after 1 year of deferasirox in patients with TM, MDS, and SCD. In patients with TM, changes in LPI with chelation show a significant relationship to EOS LIC and may provide an additional indicator of chelation response (clinicaltrials.gov identifier: NCT00171821). © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Evaluating Multiple Drivers of Soil Organic Matter Lability and Structure in a Sub-Alpine Forest Ecosystem

NASA Astrophysics Data System (ADS)

Hall, E.; Fegel, T. S., II; Boot, C. M.

2014-12-01

Aeolian deposition of reactive nitrogen (N) is reaching even the most remote ecosystems. There has been an abundance of research investigating how these subsidies of reactive N may alter fundamental ecosystem characteristics such as soil organic matter (SOM) pool size. Previous studies have reported that additions of reactive N have the potential to both increase and decrease SOM content. While there are a series of different variables that may affect the size of the SOM pool it has been suggested that the lability or recalcitrance of the SOM may be related to its chemical composition (kind and relative abundance of constituent molecules). To address this we sampled 6 experimental plots in a sub-alpine forest in Rocky Mountain National Park (3 control and 3 treated with reactive N for 18 years) during two months in the summers of 2011 and 2012. We found the SOM content of the control plots was greater than that of the experimental plots. To assess lability of each SOM sample we extracted the SOM from each plot with water and incubated the dissolved organic carbon with a common aquatic microbial community from a lake within the watershed. To assess structure of the SOM pool we used ultra performance liquid chromatography (UPLC) coupled with MS of each extract before incubation with the bacterial community. The dissolved component of the SOM showed clear differences in lability both in total quantity and rate of decomposition during incubation with aquatic microorganisms. Principle components analysis indicated season was a stronger driver of DOM composition than fertilization, describing the majority of the variability between July and September 2012. When samples were considered within a season and year there were additional differences in both lability and composition of DOM. Here we evaluate the relative influence of inter- and intra-annual variability and reactive N on both the characteristics and composition of SOM. By linking UPLC-MS with a functional assay of

Stand-scale correspondence in empirical and simulated labile carbohydrates in loblolly pine

Treesearch

David A. Sampson; Kurt H. Johnsen; Kim H. Ludovici; Timothy J. Albaugh; Chris A. Maier

2001-01-01

As investment into intensive forestry increases, the potential trade-offs between productivity and sustainability should be scrutinized. Because of their important role in internal carbon (C) budgets, labile C pools may provide a measure of the potential ability of trees and stands to respond to stress. We modified the process model BIOMASS to...

The novel compound PBT434 prevents iron mediated neurodegeneration and alpha-synuclein toxicity in multiple models of Parkinson's disease.

PubMed

Finkelstein, David I; Billings, Jessica L; Adlard, Paul A; Ayton, Scott; Sedjahtera, Amelia; Masters, Colin L; Wilkins, Simon; Shackleford, David M; Charman, Susan A; Bal, Wojciech; Zawisza, Izabela A; Kurowska, Ewa; Gundlach, Andrew L; Ma, Sheri; Bush, Ashley I; Hare, Dominic J; Doble, Philip A; Crawford, Simon; Gautier, Elisabeth Cl; Parsons, Jack; Huggins, Penny; Barnham, Kevin J; Cherny, Robert A

2017-06-28

Elevated iron in the SNpc may play a key role in Parkinson's disease (PD) neurodegeneration since drug candidates with high iron affinity rescue PD animal models, and one candidate, deferirpone, has shown efficacy recently in a phase two clinical trial. However, strong iron chelators may perturb essential iron metabolism, and it is not yet known whether the damage associated with iron is mediated by a tightly bound (eg ferritin) or lower-affinity, labile, iron pool. Here we report the preclinical characterization of PBT434, a novel quinazolinone compound bearing a moderate affinity metal-binding motif, which is in development for Parkinsonian conditions. In vitro, PBT434 was far less potent than deferiprone or deferoxamine at lowering cellular iron levels, yet was found to inhibit iron-mediated redox activity and iron-mediated aggregation of α-synuclein, a protein that aggregates in the neuropathology. In vivo, PBT434 did not deplete tissue iron stores in normal rodents, yet prevented loss of substantia nigra pars compacta neurons (SNpc), lowered nigral α-synuclein accumulation, and rescued motor performance in mice exposed to the Parkinsonian toxins 6-OHDA and MPTP, and in a transgenic animal model (hA53T α-synuclein) of PD. These improvements were associated with reduced markers of oxidative damage, and increased levels of ferroportin (an iron exporter) and DJ-1. We conclude that compounds designed to target a pool of pathological iron that is not held in high-affinity complexes in the tissue can maintain the survival of SNpc neurons and could be disease-modifying in PD.

Iron deposits in the chronically inflamed central nervous system and contributes to neurodegeneration.

PubMed

Andersen, Hjalte Holm; Johnsen, Kasper Bendix; Moos, Torben

2014-05-01

Neurodegenerative disorders are characterized by the presence of inflammation in areas with neuronal cell death and a regional increase in iron that exceeds what occurs during normal aging. The inflammatory process accompanying the neuronal degeneration involves glial cells of the central nervous system (CNS) and monocytes of the circulation that migrate into the CNS while transforming into phagocytic macrophages. This review outlines the possible mechanisms responsible for deposition of iron in neurodegenerative disorders with a main emphasis on how iron-containing monocytes may migrate into the CNS, transform into macrophages, and die out subsequently to their phagocytosis of damaged and dying neuronal cells. The dying macrophages may in turn release their iron, which enters the pool of labile iron to catalytically promote formation of free-radical-mediated stress and oxidative damage to adjacent cells, including neurons. Healthy neurons may also chronically acquire iron from the extracellular space as another principle mechanism for oxidative stress-mediated damage. Pharmacological handling of monocyte migration into the CNS combined with chelators that neutralize the effects of extracellular iron occurring due to the release from dying macrophages as well as intraneuronal chelation may denote good possibilities for reducing the deleterious consequences of iron deposition in the CNS.

METABOLIC CAPACITY REGULATES IRON HOMEOSTATIS IN ENDOTHELIAL CELLS

EPA Science Inventory

The sensitivity of endothelial cells to oxidative stress and the high concentrations of iron in mitochondria led us to test the hypotheses that (1) changes in respiratory capacity alter iron homeostasis, and (2) lack of aerobic metabolism decreases labile iron stores and attenuat...

Iron Accumulates in Huntington’s Disease Neurons: Protection by Deferoxamine

PubMed Central

Chen, Jianfang; Lai, Barry; Zhang, Zhaojie; Duce, James A.; Lam, Linh Q.; Volitakis, Irene; Bush, Ashley I.; Hersch, Steven

2013-01-01

Huntington’s disease (HD) is a progressive neurodegenerative disorder caused by a polyglutamine-encoding CAG expansion in the huntingtin gene. Iron accumulates in the brains of HD patients and mouse disease models. However, the cellular and subcellular sites of iron accumulation, as well as significance to disease progression are not well understood. We used independent approaches to investigate the location of brain iron accumulation. In R6/2 HD mouse brain, synchotron x-ray fluorescence analysis revealed iron accumulation as discrete puncta in the perinuclear cytoplasm of striatal neurons. Further, perfusion Turnbull’s staining for ferrous iron (II) combined with transmission electron microscope ultra-structural analysis revealed increased staining in membrane bound peri-nuclear vesicles in R6/2 HD striatal neurons. Analysis of iron homeostatic proteins in R6/2 HD mice revealed decreased levels of the iron response proteins (IRPs 1 and 2) and accordingly decreased expression of iron uptake transferrin receptor (TfR) and increased levels of neuronal iron export protein ferroportin (FPN). Finally, we show that intra-ventricular delivery of the iron chelator deferoxamine results in an improvement of the motor phenotype in R6/2 HD mice. Our data supports accumulation of redox-active ferrous iron in the endocytic / lysosomal compartment in mouse HD neurons. Expression changes of IRPs, TfR and FPN are consistent with a compensatory response to an increased intra-neuronal labile iron pool leading to increased susceptibility to iron-associated oxidative stress. These findings, together with protection by deferoxamine, support a potentiating role of neuronal iron accumulation in HD. PMID:24146952

Analytical Measurement of Discrete Hydrogen Sulfide Pools in Biological Specimens

PubMed Central

Shen, Xinggui; Peter, Elvis A.; Bir, Shyamal; Wang, Rui; Kevil, Christopher G.

2015-01-01

Hydrogen sulfide (H2S) is a ubiquitous gaseous signaling molecule that plays a vital role in numerous cellular functions and has become the focus of many research endeavors including pharmaco-therapeutic manipulation. Amongst the challenges facing the field is the accurate measurement of biologically active H2S. We have recently reported that the typically used methylene blue method and its associated results are invalid and do not measure bonafide H2S. The complexity of analytical H2S measurement reflects the fact that hydrogen sulfide is a volatile gas and exists in the body in different forms, including a free form, an acid labile pool and as bound sulfane sulfur. Here we describe a new protocol to discretely measure specific H2S pools using the monobromobimane method coupled with RP-HPLC. This new protocol involves selective liberation, trapping and derivatization of H2S. Acid-labile H2S is released by incubating the sample in an acidic solution (pH 2.6) of 100 mM phosphate buffer with 0.1 mM DTPA, in an enclosed system to contain volatilized H2S. Volatilized H2S is then trapped in 100 mM Tris-HCl (pH 9.5, 0.1 mM DTPA) and then reacted with excess monobromobimane. In a separate aliquot, the contribution of bound sulfane sulfur pool was measured by incubating the sample with 1 mM TCEP (Tris(2-carboxyethyl)phosphine hydrochloride), a reducing agent to reduce disulfide bonds, in 100 mM phosphate buffer (pH 2.6, 0.1 mM DTPA), and H2S measurement performed in an analogous manner to the one described above. The acid labile pool was determined by subtracting the free hydrogen sulfide value from the value obtained by the acid liberation protocol. The bound sulfane sulfur pool was determined by subtracting the H2S measurement from the acid liberation protocol alone compared to that of TCEP plus acidic conditions. In summary, our new method protocol allows very sensitive and accurate measurement of the three primary biological pools of H2S including free, acid labile

Feasibility of labile Zn phytoextraction using enhanced tobacco and sunflower: results of five- and one-year field-scale experiments in Switzerland.

PubMed

Herzig, Rolf; Nehnevajova, Erika; Pfistner, Charlotte; Schwitzguebel, Jean-Paul; Ricci, Arturo; Keller, Charles

2014-01-01

Phytoextraction with somaclonal variants of tobacco and sunflower mutant lines (non-GMs) with enhanced metal uptake and tolerance can be a sustainable alternative to conventional destructive decontamination methods, especially for stripping bioavailable zinc excess in topsoil. The overall results of a 5-year time series experiment at field scale in north-eastern Switzerland confirm that the labile Zn pool in soil can be lowered by 45-70%, whereas subplots without phytoextraction treatment maintained labile Zn concentrations. In 2011, the phytoextraction experiment site was enlarged by a factor of 3, and the labile 0.1 M NaNO3 extractable Zn concentration in the soil was reduced up to 58% one period after harvest. A Mass Balance Analysis confirmed soil Zn decontamination in line with plant Zn uptake. The plants partially take Zn from the non-labile pool of the totaL The sustainability of Zn phytoextraction in subplots that no longer exceed the Swiss trigger value is now assessed over time. In contrary to the phytoextraction of total soil Zn which needs a long cleaning up time, the bioavailable Zn stripping is feasible within a few years period.

Rescuing iron-overloaded macrophages by conservative relocation of the accumulated metal

PubMed Central

Sohn, Yang-Sung; Mitterstiller, Anna-Maria; Breuer, William; Weiss, Guenter; Cabantchik, Z Ioav

2011-01-01

BACKGROUND AND PURPOSE Systemic iron deficiency concomitant with macrophage iron retention is characteristic of iron-refractory anaemias associated with chronic disease. The systemic misdistribution of iron, which is further exacerbated by parenteral iron supplementation, is mainly attributable to iron retention exerted on resident macrophages by hepcidin-mediated down-regulation of the iron exporter ferroportin. We aimed at developing an experimental macrophage-based cell model that recapitulates pathophysiological features of iron misdistribution found in chronic disorders and use it as a screening platform for identifying agents with the potential for relocating the accumulated metal and restoring affected functions. EXPERIMENTAL APPROACH A RAW macrophage subline was selected as cell model of iron retention based on their capacity to take up polymeric iron or aged erythrocytes excessively, resulting in a demonstrable increase of cell labile iron pools and oxidative damage that are aggravated by hepcidin. KEY RESULTS This model provided a three-stage high throughput screening platform for identifying agents with the combined ability to: (i) scavenge cell iron and thereby rescue macrophage cells damaged by iron-overload; (ii) bypass the ferroportin blockade by conveying the scavenged iron to other iron-starved cells in co-culture via transferrin but (iii) without promoting utilization of the scavenged iron by intracellular pathogens. As test agents we used chelators in clinical practice and found the oral chelator deferiprone fulfilled essentially all of the three criteria. CONCLUSIONS AND IMPLICATIONS We provide a proof of principle for conservative iron relocation as complementary therapeutic approach for correcting the misdistribution of iron associated with chronic disease and exacerbated by parenteral iron supplementation. PMID:21091647

Studies of the reactivity of the ferrihydrite surface by iron isotopic exchange and Mossbauer spectroscopy

USGS Publications Warehouse

Rea, Brigid A.; Davis, James A.; Waychunas , Glenn A.

1994-01-01

Two-line ferrihydrite is an important adsorbent of many toxics in natural and anthropogenic systems; however, the specific structural sites responsible for the high adsorption capacity are not well understood. A combination of chemical and spectroscopic techniques have been employed in this study to gain further insight into the structural nature of sites at the ferrihydrite surface. The kinetics of iron isotopic exchange demonstrated that there are at least two types of iron sites in ferrihydrite. One population of sites, referred to as labile sites, approached iron isotopic equilibrium within 24 hr in 59Fe-NTA solutions, while the second population of sites, referred to as non-labile, exhibited a much slower rate of isotopic exchange. Adsorbed arsenate reduced the degree of exchange by labile sites, indicating that the anion blocked or greatly inhibited the rate of exchange of these sites. Mössbauer spectra were collected from a variety of samples including 56Fe-ferrihydrite samples with 57Fe in labile sites, samples containing 57Fe throughout the structure, and samples with 57Fe in non-labile sites. The spectra showed characteristic broad doublets signifying poor structural order. Refined fits of the spectra indicated that labile sites have larger quadrupole splitting, hence more local distortion, than non-labile sites. In all cases, the spectra demonstrated some degree of asymmetry, indicating a distribution of Fe environments in ferrihydrite. Overall spectral findings, combined with recent EXAFS results (Waychunas et al., 1993), indicate that labile sites likely are more reactive (with respect to iron isotopic exchange) because they have fewer neighboring Fe octahedra and are therefore bound less strongly to the ferrihydrite structure. The labile population of sites probably is composed of end sites of the dioctahedral chain structure of 2-line ferrihydrite, which is a subset of the entire population of surface sites. Mössbauer spectra of samples containing

Acetylcholinesterase-independent protective effects of huperzine A against iron overload-induced oxidative damage and aberrant iron metabolism signaling in rat cortical neurons.

PubMed

Tao, Ling-Xue; Huang, Xiao-Tian; Chen, Yu-Ting; Tang, Xi-Can; Zhang, Hai-Yan

2016-11-01

Iron dyshomeostasis is one of the primary causes of neuronal death in Alzheimer's disease (AD). Huperzine A (HupA), a natural inhibitor of acetylcholinesterase (AChE), is a licensed anti-AD drug in China and a nutraceutical in the United Sates. Here, we investigated the protective effects of HupA against iron overload-induced injury in neurons. Rat cortical neurons were treated with ferric ammonium citrate (FAC), and cell viability was assessed with MTT assays. Reactive oxygen species (ROS) assays and adenosine triphosphate (ATP) assays were performed to assess mitochondrial function. The labile iron pool (LIP) level, cytosolic-aconitase (c-aconitase) activity and iron uptake protein expression were measured to determine iron metabolism changes. The modified Ellman's method was used to evaluate AChE activity. HupA significantly attenuated the iron overload-induced decrease in neuronal cell viability. This neuroprotective effect of HupA occurred concurrently with a decrease in ROS and an increase in ATP. Moreover, HupA treatment significantly blocked the upregulation of the LIP level and other aberrant iron metabolism changes induced by iron overload. Additionally, another specific AChE inhibitor, donepezil (Don), at a concentration that caused AChE inhibition equivalent to that of HupA negatively, influenced the aberrant changes in ROS, ATP or LIP that were induced by excessive iron. We provide the first demonstration of the protective effects of HupA against iron overload-induced neuronal damage. This beneficial role of HupA may be attributed to its attenuation of oxidative stress and mitochondrial dysfunction and elevation of LIP, and these effects are not associated with its AChE-inhibiting effect.

Acetylcholinesterase-independent protective effects of huperzine A against iron overload-induced oxidative damage and aberrant iron metabolism signaling in rat cortical neurons

PubMed Central

Tao, Ling-xue; Huang, Xiao-tian; Chen, Yu-ting; Tang, Xi-can; Zhang, Hai-yan

2016-01-01

Aim: Iron dyshomeostasis is one of the primary causes of neuronal death in Alzheimer's disease (AD). Huperzine A (HupA), a natural inhibitor of acetylcholinesterase (AChE), is a licensed anti-AD drug in China and a nutraceutical in the United Sates. Here, we investigated the protective effects of HupA against iron overload-induced injury in neurons. Methods: Rat cortical neurons were treated with ferric ammonium citrate (FAC), and cell viability was assessed with MTT assays. Reactive oxygen species (ROS) assays and adenosine triphosphate (ATP) assays were performed to assess mitochondrial function. The labile iron pool (LIP) level, cytosolic-aconitase (c-aconitase) activity and iron uptake protein expression were measured to determine iron metabolism changes. The modified Ellman's method was used to evaluate AChE activity. Results: HupA significantly attenuated the iron overload-induced decrease in neuronal cell viability. This neuroprotective effect of HupA occurred concurrently with a decrease in ROS and an increase in ATP. Moreover, HupA treatment significantly blocked the upregulation of the LIP level and other aberrant iron metabolism changes induced by iron overload. Additionally, another specific AChE inhibitor, donepezil (Don), at a concentration that caused AChE inhibition equivalent to that of HupA negatively, influenced the aberrant changes in ROS, ATP or LIP that were induced by excessive iron. Conclusion: We provide the first demonstration of the protective effects of HupA against iron overload-induced neuronal damage. This beneficial role of HupA may be attributed to its attenuation of oxidative stress and mitochondrial dysfunction and elevation of LIP, and these effects are not associated with its AChE-inhibiting effect. PMID:27498774

Monitoring changes in soil organic carbon pools, nitrogen, phosphorus, and sulfur under different agricultural management practices in the tropics.

PubMed

Verma, Bibhash C; Datta, Siba Prasad; Rattan, Raj K; Singh, Anil K

2010-12-01

Soil organic matter not only affects sustainability of agricultural ecosystems, but also extremely important in maintaining overall quality of environment as soil contains a significant part of global carbon stock. Hence, we attempted to assess the influence of different tillage and nutrient management practices on various stabilized and active soil organic carbon pools, and their contribution to the extractable nitrogen phosphorus and sulfur. Our study confined to the assessment of impact of agricultural management practices on the soil organic carbon pools and extractable nutrients under three important cropping systems, viz. soybean-wheat, maize-wheat, and rice-wheat. Results indicated that there was marginal improvement in Walkley and Black content in soil under integrated and organic nutrient management treatments in soybean-wheat, maize-wheat, and rice-wheat after completion of four cropping cycles. Improvement in stabilized pools of soil organic carbon (SOC) was not proportional to the applied amount of organic manures. While, labile pools of SOC were increased with the increase in amount of added manures. Apparently, green manure (Sesbania) was more effective in enhancing the lability of SOC as compared to farmyard manure and crop residues. The KMnO(4)-oxidizable SOC proved to be more sensitive and consistent as an index of labile pool of SOC compared to microbial biomass carbon. Under different cropping sequences, labile fractions of soil organic carbon exerted consistent positive effect on the extractable nitrogen, phosphorus, and sulfur in soil.

Carbon pools in an arid shrubland in Chile under natural and afforested conditions

USDA-ARS?s Scientific Manuscript database

Arid and semiarid regions comprise 41% of the continental area of Chile, but no estimates of carbon (C) pools have been reported for these areas. This study quantified the C pools of biomass, litter, and soil for natural compared to afforested (two-year-old Acacia saligna (Labill.) H.L. Wendl.) sit...

Soil respiration, labile carbon pools, and enzyme activities as affected by tillage practices in a tropical rice-maize-cowpea cropping system.

PubMed

Neogi, S; Bhattacharyya, P; Roy, K S; Panda, B B; Nayak, A K; Rao, K S; Manna, M C

2014-07-01

In order to identify the viable option of tillage practices in rice-maize-cowpea cropping system that could cut down soil carbon dioxide (CO2) emission, sustain grain yield, and maintain better soil quality in tropical low land rice ecology soil respiration in terms of CO2 emission, labile carbon (C) pools, water-stable aggregate C fractions, and enzymatic activities were investigated in a sandy clay loam soil. Soil respiration is the major pathway of gaseous C efflux from terrestrial systems and acts as an important index of ecosystem functioning. The CO2-C emissions were quantified in between plants and rows throughout the year in rice-maize-cowpea cropping sequence both under conventional tillage (CT) and minimum tillage (MT) practices along with soil moisture and temperature. The CO2-C emissions, as a whole, were 24 % higher in between plants than in rows, and were in the range of 23.4-78.1, 37.1-128.1, and 28.6-101.2 mg m(-2) h(-1) under CT and 10.7-60.3, 17.3-99.1, and 17.2-79.1 mg m(-2) h(-1) under MT in rice, maize, and cowpea, respectively. The CO2-C emission was found highest under maize (44 %) followed by rice (33 %) and cowpea (23 %) irrespective of CT and MT practices. In CT system, the CO2-C emission increased significantly by 37.1 % with respect to MT on cumulative annual basis including fallow. The CO2-C emission per unit yield was at par in rice and cowpea signifying the beneficial effect of MT in maintaining soil quality and reduction of CO2 emission. The microbial biomass C (MBC), readily mineralizable C (RMC), water-soluble C (WSC), and permanganate-oxidizable C (PMOC) were 19.4, 20.4, 39.5, and 15.1 % higher under MT than CT. The C contents in soil aggregate fraction were significantly higher in MT than CT. Soil enzymatic activities like, dehydrogenase, fluorescein diacetate, and β-glucosidase were significantly higher by 13.8, 15.4, and 27.4 % under MT compared to CT. The soil labile C pools, enzymatic activities, and

The DIRT on Q10: In situ depletion of labile-inputs does not increase temperature sensitivity in a laboratory incubation (Invited)

NASA Astrophysics Data System (ADS)

Reynolds, L. L.; Lajtha, K.; Bowden, R.; Johnson, B. R.; Bridgham, S. D.

2013-12-01

The decomposition of soil organic matter is expected to increase with global warming and has been commonly described by kinetic models with at least two pools with differing turnover times. Pools characterized by rapid turnover are thought to consist of labile substrates. Meanwhile, slower turnover is attributed, in part, to greater chemical complexity and a necessarily higher activation energy which should in turn lead to a higher sensitivity (Q10) to temperature and a proportionally larger response to warming. Experimental tests of the relative Q10 of these pools have been inconclusive and contradictory in part due the fact that all pools are decomposing simultaneously and soils kept under differing conditions over long periods of time diverge in more than the Q10 response making them less comparable over time. We present here a test of the temperature response on soils from a 20 yr litter manipulation experiment incubated under an experimental regime that minimizes divergence among the soils. We hypothesize that 1) if exclusion of inputs has depleted labile substrates and 2) the remaining carbon is more chemically complex, then the input exclusion treatments should show a higher Q10 compared to the ambient or increased input treatments. The soils are taken from the Detritus Input and Removal Treatment (DIRT) plots in the Bousson Forest, Pennsylvania, US. The DIRT treatments consist of litter and root exclusion (no inputs = NI), no roots (NR), no litter (NL), double litter (DL), and ambient conditions (C). Soils were incubated at 25oC for 525 days. Periodically, replicate sets were rotated into 15oC, 35oC or remained at 25oC for 24 hr. The headspace CO2 concentration was measured before and after the 24 hr temperature treatments, and then all replicate sets were returned to 25oC. Twenty years of input exclusion decreased respiration rate, with NI < NR = NL < C = DL, and total carbon content, and thus, we conclude, labile substrates. The respiration rate at 25o

Mood lability and psychopathology in youth.

PubMed

Stringaris, A; Goodman, R

2009-08-01

Mood lability is a concept widely used. However, data on its prevalence and morbid associations are scarce. We sought to establish the occurrence and importance of mood lability in a large community sample of children and adolescents by testing a priori hypotheses. Cross-sectional data were taken from a national mental health survey including 5326 subjects aged 8-19 years in the UK. The outcomes were prevalence and characteristics of mood lability and its associations with psychopathology and overall impairment. Mood lability occurred in more than 5% of the population of children and adolescents, both by parent and self-report. Mood lability was strongly associated with a wide range of psychopathology and was linked to significant impairment even in the absence of psychiatric disorders. Mood lability was particularly strongly associated with co-morbidity between internalizing and externalizing disorders, even when adjusting for the association with individual disorders. The pattern of results did not change after excluding youth with bipolar disorder or with episodes of elated mood. Clinically significant mood lability is relatively common in the community. Our findings indicate that mood lability is not a mere consequence of other psychopathology in that it is associated with significant impairment even in the absence of psychiatric diagnoses. Moreover, the pattern of association of mood lability with co-morbidity suggests that it could be a risk factor shared by both internalizing and externalizing disorders. Our data point to the need for greater awareness of mood lability and its implications for treatment.

Labile and Non-labile Soil Carbon Fractions Equally Contributed to Carbon Changes under Long-term Fertilization

NASA Astrophysics Data System (ADS)

Liang, F.; Li, J.; Xu, M.; Huang, S.

2017-12-01

Soil organic carbon (SOC) storages are altered under long-term fertilization in croplands, it however remains unclear how fast- to slow-cycling SOC fractions each respond to fertilization practices. Based on five two-decade Chinese long-term fertilization experiments (GZL: Gongzhuling; ZZ: Zhengzhou; CQ: Chongqing; JX: Jinxian; QY: Qiyang) under three fertilization treatments (CK: cropping with no fertilizer input; NPK: chemical nitrogen, phosphorus and potassium fertilizers; and NPKM: NPK with manure input), we quantified very labile, labile, non-labile and total SOC stocks at 0-20cm soil depth. Results showed that SOC stocks varied among sites (GZL, JX, CQ > ZZ, QY) and generally increased with fertilizations (CK-1 at ZZ, GZL, QY, CQ and JX, respectively. The corresponding changes of the sum of very labile and labile SOC fractions were 2.6, 2.0, 1.8, 0.8 and -0.5 Mg ha-1 at ZZ, QY, GZL, CQ and JX, respectively. Also, NPKM increased total SOC stock by 18.3, 16.2, 14.4, 10.5, and 6.5 Mg ha-1 at QY, GZL, ZZ, CQ and JX, respectively. The corresponding changes of the sum of very labile and labile SOC fractions were 8.6, 6.8, 6.6, 3.2 and -1.6 Mg ha-1 at QY, GZL, ZZ, CQ and JX, respectively. These results suggested that about half or more than half SOC stock accretions under fertilization were induced by increase in non-labile SOC fractions. It thus informs the importance of non-labile SOC fractions in contributing to soil C sequestration under long-term fertilizations in Chinese croplands. Future research should improve our mechanistic understanding of biogeochemical transformation of non-labile organic C in soils.

The pathophysiology of transfusional iron overload.

PubMed

Porter, John B; Garbowski, Maciej

2014-08-01

The pathophysiologic consequences of transfusional iron overload (TIO) as well as the benefits of iron chelation therapy are best described in thalassemia major, although TIO is increasingly seen in other clinical settings. These consequences broadly reflect the levels and distribution of excess storage iron in the heart, endocrine tissues, and liver. TIO also increases the risk of infection, due to increased availability of labile iron to microorganisms. The authors suggest that extrahepatic iron distribution, and hence toxicity, is influenced by balance between generation of nontransferrin-bound iron from red cell catabolism and the utilization of transferrin iron by the erythron. Copyright © 2014 Elsevier Inc. All rights reserved.

Sensitivity-enhanced detection of non-labile proton and carbon NMR spectra on water resonances.

PubMed

Novakovic, Mihajlo; Martinho, Ricardo P; Olsen, Gregory L; Lustig, Michael S; Frydman, Lucio

2017-12-20

Chemical exchange saturation transfer (CEST) experiments enhance the NMR signals of labile protons by continuously transferring these protons' saturation to an abundant solvent pool like water. The present study expands these principles by fusing into these experiments homonuclear isotropic mixing sequences, enabling the water-enhanced detection of non-exchangeable species. Further opportunities are opened by the addition of coupling-mediated heteronuclear polarization transfers, which then impose on the water resonance a saturation stemming from non-labile heteronuclear species like 13 C. To multiplex the ensuing experiments, these relayed approaches are combined with time-domain schemes involving multiple Ramsey-labeling experiments imparting the frequencies of the non-labile sites on the water resonance, via chemical exchange. 13 C and 1 H NMR spectra were detected in this fashion with about two-fold SNR amplification vis-à-vis conventionally detected spectroscopies. When combined with non-uniform sampling principles, this methodology thus becomes a sensitive alternative to detect non-exchangeable species in biomolecules. Still, multiple parameters including the scalar couplings and solvent exchange rates, will affect the efficiency and consequently the practicality of the overall experiment.

Lability of Cd, Cu, and Zn in polluted soils treated with lime, beringite, and red mud and identification of a non-labile colloidal fraction of metals using istopic techniques.

PubMed

Lombi, Enzo; Hamon, Rebecca E; McGrath, Steve P; McLaughlin, Mike J

2003-03-01

The use of soil amendments has been proposed as a low input alternative for the remediation of metal polluted soils. However, little information is available concerning the stability, and therefore the longevity, of the remediation treatments when important soil parameters change. In this paper we investigate the effect of pH changes on the lability of heavy metals in soils treated with lime, beringite, and red mud using a modified isotopic dilution technique in combination with a stepwise acidification procedure. Significant amounts of nonlabile (fixed) Cu and Zn were found to be associated with colloids <0.2 microm in the solution phase. The results obtained indicated that the mobility of fixed colloidal metals is significant and increases with soil pH. This must be considered because most of the soil amendments are alkaline and increase soil pH. All the soil amendments significantly decreased the lability of Cd, Zn, and Cu in the soils as a whole. However, when the soils were re-acidified, the labile pool of metals increased sharply and in the case of lime and beringite, the lability of the metals was similar, at equal pH, to the untreated soil. In contrast the lability of metals in the red mud treated soils was always smaller than that in the untreated soils across the range of pH values tested. These results suggest that the mechanism of action of lime and beringite is similar and probably related to increased metal adsorption and precipitation of metal hydroxides and carbonates at high pH. In the case of red mud, a combination of pH dependent and independent mechanisms (possibly solid-phase diffusion or migration into micropores) may be responsible for the metal fixation observed.

Non-transferrin bound iron: a key role in iron overload and iron toxicity.

PubMed

Brissot, Pierre; Ropert, Martine; Le Lan, Caroline; Loréal, Olivier

2012-03-01

Besides transferrin iron, which represents the normal form of circulating iron, non-transferrin bound iron (NTBI) has been identified in the plasma of patients with various pathological conditions in which transferrin saturation is significantly elevated. To show that: i) NTBI is present not only during chronic iron overload disorders (hemochromatosis, transfusional iron overload) but also in miscellaneous diseases which are not primarily iron overloaded conditions; ii) this iron species represents a potentially toxic iron form due to its high propensity to induce reactive oxygen species and is responsible for cellular damage not only at the plasma membrane level but also towards different intracellular organelles; iii) the NTBI concept may be expanded to include intracytosolic iron forms which are not linked to ferritin, the major storage protein which exerts, at the cellular level, the same type of protective effect towards the intracellular environment as transferrin in the plasma. Plasma NTBI and especially labile plasma iron determinations represent a new important biological tool since elimination of this toxic iron species is a major therapeutic goal. The NTBI approach represents an important mechanistic concept for explaining cellular iron excess and toxicity and provides new important biochemical diagnostic tools. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders. Copyright © 2011 Elsevier B.V. All rights reserved.

Rhizosphere Environment and Labile Phosphorus Release from Organic Waste-Amended Soils.

NASA Astrophysics Data System (ADS)

Dao, Thanh H.

2015-04-01

Crop residues and biofertilizers are primary sources of nutrients for organic crop production. However, soils treated with large amounts of nutrient-enriched manure have elevated phosphorus (P) levels in regions of intensive animal agriculture. Surpluses occurred in these amended soils, resulting in large pools of exchangeable inorganic P (Pi) and enzyme-labile organic P (Po) that averaging 30.9 and 68.2 mg kg-1, respectively. Organic acids produced during crop residue decomposition can promote the complexation of counter-ions and decouple and release unbound Pi from metal and alkali metal phosphates. Animal manure and cover crop residues also contain large amounts of soluble organic matter, and likely generate similar ligands. However, a high degree of heterogeneity in P spatial distribution in such amended fields, arising from variances in substrate physical forms ranging from slurries to dried solids, composition, and diverse application methods and equipment. Distinct clusters of Pi and Po were observed, where accumulation of the latter forms was associated with high soil microbial biomass C and reduced phosphomonoesterases' activity. Accurate estimates of plant requirements and lability of soil P pools, and real-time plant and soil P sensing systems are critical considerations to optimally manage manure-derived nutrients in crop production systems. An in situ X-ray fluorescence-based approach to sensing canopy and soil XRFS-P was developed to improve the yield-soil P relationship for optimal nutrient recommendations in addition to allowing in-the-field verification of foliar P status.

Using Perls Staining to Trace the Iron Uptake Pathway in Leaves of a Prunus Rootstock Treated with Iron Foliar Fertilizers

PubMed Central

Rios, Juan J.; Carrasco-Gil, Sandra; Abadía, Anunciación; Abadía, Javier

2016-01-01

The aim of this study was to trace the Fe uptake pathway in leaves of Prunus rootstock (GF 677; Prunus dulcis × Prunus persica) plants treated with foliar Fe compounds using the Perls blue method, which detects labile Fe pools. Young expanded leaves of Fe-deficient plants grown in nutrient solution were treated with Fe-compounds using a brush. Iron compounds used were the ferrous salt FeSO4, the ferric salts Fe2(SO4)3 and FeCl3, and the chelate Fe(III)-EDTA, all of them at concentrations of 9 mM Fe. Leaf Fe concentration increases were measured at 30, 60, 90 min, and 24 h, and 70 μm-thick leaf transversal sections were obtained with a vibrating microtome and stained with Perls blue. In vitro results show that the Perls blue method is a good tool to trace the Fe uptake pathway in leaves when using Fe salts, but is not sensitive enough when using synthetic Fe(III)-chelates such as Fe(III)-EDTA and Fe(III)-IDHA. Foliar Fe fertilization increased leaf Fe concentrations with all Fe compounds used, with inorganic Fe salts causing larger leaf Fe concentration increases than Fe(III)-EDTA. Results show that Perls blue stain appeared within 30 min in the stomatal areas, indicating that Fe applied as inorganic salts was taken up rapidly via stomata. In the case of using FeSO4 a progression of the stain was seen with time toward vascular areas in the leaf blade and the central vein, whereas in the case of Fe(III) salts the stain mainly remained in the stomatal areas. Perls stain was never observed in the mesophyll areas, possibly due to the low concentration of labile Fe pools. PMID:27446123

O2 availability impacts iron homeostasis in Escherichia coli.

PubMed

Beauchene, Nicole A; Mettert, Erin L; Moore, Laura J; Keleş, Sündüz; Willey, Emily R; Kiley, Patricia J

2017-11-14

The ferric-uptake regulator (Fur) is an Fe 2+ -responsive transcription factor that coordinates iron homeostasis in many bacteria. Recently, we reported that expression of the Escherichia coli Fur regulon is also impacted by O 2 tension. Here, we show that for most of the Fur regulon, Fur binding and transcriptional repression increase under anaerobic conditions, suggesting that Fur is controlled by O 2 availability. We found that the intracellular, labile Fe 2+ pool was higher under anaerobic conditions compared with aerobic conditions, suggesting that higher Fe 2+ availability drove the formation of more Fe 2+ -Fur and, accordingly, more DNA binding. O 2 regulation of Fur activity required the anaerobically induced FeoABC Fe 2+ uptake system, linking increased Fur activity to ferrous import under iron-sufficient conditions. The increased activity of Fur under anaerobic conditions led to a decrease in expression of ferric import systems. However, the combined positive regulation of the feoABC operon by ArcA and FNR partially antagonized Fur-mediated repression of feoABC under anaerobic conditions, allowing ferrous transport to increase even though Fur is more active. This design feature promotes a switch from ferric import to the more physiological relevant ferrous iron under anaerobic conditions. Taken together, we propose that the influence of O 2 availability on the levels of active Fur adds a previously undescribed layer of regulation in maintaining cellular iron homeostasis.

O2 availability impacts iron homeostasis in Escherichia coli

PubMed Central

Beauchene, Nicole A.; Mettert, Erin L.; Moore, Laura J.; Keleş, Sündüz; Willey, Emily R.; Kiley, Patricia J.

2017-01-01

The ferric-uptake regulator (Fur) is an Fe2+-responsive transcription factor that coordinates iron homeostasis in many bacteria. Recently, we reported that expression of the Escherichia coli Fur regulon is also impacted by O2 tension. Here, we show that for most of the Fur regulon, Fur binding and transcriptional repression increase under anaerobic conditions, suggesting that Fur is controlled by O2 availability. We found that the intracellular, labile Fe2+ pool was higher under anaerobic conditions compared with aerobic conditions, suggesting that higher Fe2+ availability drove the formation of more Fe2+-Fur and, accordingly, more DNA binding. O2 regulation of Fur activity required the anaerobically induced FeoABC Fe2+ uptake system, linking increased Fur activity to ferrous import under iron-sufficient conditions. The increased activity of Fur under anaerobic conditions led to a decrease in expression of ferric import systems. However, the combined positive regulation of the feoABC operon by ArcA and FNR partially antagonized Fur-mediated repression of feoABC under anaerobic conditions, allowing ferrous transport to increase even though Fur is more active. This design feature promotes a switch from ferric import to the more physiological relevant ferrous iron under anaerobic conditions. Taken together, we propose that the influence of O2 availability on the levels of active Fur adds a previously undescribed layer of regulation in maintaining cellular iron homeostasis. PMID:29087312

Efficacy and safety of deferasirox estimated by serum ferritin and labile plasma iron levels in patients with aplastic anemia, myelodysplastic syndrome, or acute myeloid leukemia with transfusional iron overload.

PubMed

Kim, Il-Hwan; Moon, Joon-Ho; Lim, Sung-Nam; Sohn, Sang-Kyun; Kim, Hoon-Gu; Lee, Gyeong-Won; Kim, Yang-Soo; Lee, Ho-Sup; Kwon, Ki-Young; Kim, Sung-Hyun; Park, Kyung-Tae; Chung, Joo-Seop; Lee, Won-Sik; Lee, Sang-Min; Hyun, Myung-Soo; Kim, Hawk; Ryoo, Hun-Mo; Bae, Sung-Hwa; Joo, Young-Don

2015-07-01

Patients receiving red blood cell (RBC) transfusions are at risk of iron overload, which can cause significant organ damage and is an important cause of morbidity and mortality. This study was an open-label, single-arm, prospective clinical study to evaluate the efficacy and safety of deferasirox (DFX) in patients with aplastic anemia (AA), myelodysplastic syndrome (MDS), or acute myeloid leukemia (AML). Patients with serum ferritin levels of at least 1000 ng/mL and ongoing transfusion requirements were enrolled. DFX was administered for up to 1 year. A total of 100 patients were enrolled. Serum ferritin levels decreased significantly following treatment (from 2000 to 1650 ng/mL, p = 0.004). The median absolute reduction in serum ferritin levels was -65 ng/mL in AA (p = 0.037), -647 ng/mL in lower-risk MDS (MDS-LR; p = 0.007), and -552 ng/mL in higher-risk MDS (MDS-HR)/AML (p = 0.482). Mean labile plasma iron (LPI) levels decreased from 0.24 μmol/L at baseline to 0.03 μmol/L at 1 year in all patients (p = 0.036). The mean LPI reduction in each group was -0.17 μmol/L in AA, -0.21 μmol/L in MDS-LR, and -0.30 μmol/L in MDS-HR/AML. Gastrointestinal disorders were commonly observed among groups (16.0%). DFX was temporarily skipped for adverse events in seven patients (7.0%) and was permanently discontinued in 11 patients (11.0%). DFX reduced serum ferritin and LPI levels in patients with transfusional iron overload. Despite the relatively high percentage of gastrointestinal side effects, DFX was tolerable in all subgroups. © 2015 AABB.

Ice sheets as a significant source of highly reactive nanoparticulate iron to the oceans.

PubMed

Hawkings, Jon R; Wadham, Jemma L; Tranter, Martyn; Raiswell, Rob; Benning, Liane G; Statham, Peter J; Tedstone, Andrew; Nienow, Peter; Lee, Katherine; Telling, Jon

2014-05-21

The Greenland and Antarctic Ice Sheets cover ~ 10% of global land surface, but are rarely considered as active components of the global iron cycle. The ocean waters around both ice sheets harbour highly productive coastal ecosystems, many of which are iron limited. Measurements of iron concentrations in subglacial runoff from a large Greenland Ice Sheet catchment reveal the potential for globally significant export of labile iron fractions to the near-coastal euphotic zone. We estimate that the flux of bioavailable iron associated with glacial runoff is 0.40-2.54 Tg per year in Greenland and 0.06-0.17 Tg per year in Antarctica. Iron fluxes are dominated by a highly reactive and potentially bioavailable nanoparticulate suspended sediment fraction, similar to that identified in Antarctic icebergs. Estimates of labile iron fluxes in meltwater are comparable with aeolian dust fluxes to the oceans surrounding Greenland and Antarctica, and are similarly expected to increase in a warming climate with enhanced melting.

Characterisation of the Permafrost Carbon Pool

USGS Publications Warehouse

Kuhry, P.; Grosse, G.; Harden, J.W.; Hugelius, G.; Koven, C.D.; Ping, C.-L.; Schirrmeister, L.; Tarnocai, C.

2013-01-01

The current estimate of the soil organic carbon (SOC) pool in the northern permafrost region of 1672 Petagrams (Pg) C is much larger than previously reported and needs to be incorporated in global soil carbon (C) inventories. The Northern Circumpolar Soil Carbon Database (NCSCD), extended to include the range 0–300 cm, is now available online for wider use by the scientific community. An important future aim is to provide quantitative uncertainty ranges for C pool estimates. Recent studies have greatly improved understanding of the regional patterns, landscape distribution and vertical (soil horizon) partitioning of the permafrost C pool in the upper 3 m of soils. However, the deeper C pools in unconsolidated Quaternary deposits need to be better constrained. A general lability classification of the permafrost C pool should be developed to address potential C release upon thaw. The permafrost C pool and its dynamics are beginning to be incorporated into Earth System models, although key periglacial processes such as thermokarst still need to be properly represented to obtain a better quantification of the full permafrost C feedback on global climate change.

Role of iron in the pathogenesis of cysteamine-induced duodenal ulceration in rats

PubMed Central

Khomenko, Tetyana; Szabo, Sandor; Deng, Xiaoming; Ishikawa, Hideki; Anderson, Gregory J.; McLaren, Gordon D.

2009-01-01

Cysteamine induces perforating duodenal ulcers in rats within 24–48 h. This reducing aminothiol generates hydrogen peroxide in the presence of transition metals (e.g., ferric iron), producing oxidative stress, which may contribute to organ-specific tissue damage. Since most intestinal iron absorption takes place in the proximal duodenum, we hypothesized that cysteamine may disrupt regulation of mucosal iron transport, and iron may facilitate cysteamine-induced duodenal ulceration. We show here that cysteamine-induced ulceration was aggravated by pretreatment of rats with Fe3+ or Fe2+ compounds, which elevated iron concentration in the duodenal mucosa. In contrast, feeding rats an iron-deficient diet was associated with a 4.6-fold decrease in ulcer formation, accompanied by a 34% decrease (P < 0.05) in the duodenal mucosal iron concentration. Administration of deferoxamine inhibited ulceration by 65%. We also observed that the antiulcer effect of H2 receptor antagonist cimetidine included a 35% decrease in iron concentration in the duodenal mucosa. Cysteamine-induced duodenal ulcers were also decreased in iron-deficient Belgrade rats (P < 0.05). In normal rats, cysteamine administration increased the iron concentration in the proximal duodenal mucosa by 33% in the preulcerogenic stage but at the same time decreased serum iron (P < 0.05). Cysteamine also enhanced activation of mucosal iron regulatory protein 1 and increased the expression of divalent metal transporter 1 mRNA and protein. Transferrin receptor 1 protein expression was also increased, although mucosal ferroportin and ferritin remained almost unchanged. These results indicate an expansion of the intracellular labile iron pool in the duodenal mucosa, increasing its susceptibility to oxidative stress, and suggest a role for iron in the pathogenesis of organ-specific tissue injury such as duodenal ulcers. PMID:19342511

Enhanced labile plasma iron and outcome in acute myeloid leukaemia and myelodysplastic syndrome after allogeneic haemopoietic cell transplantation (ALLIVE): a prospective, multicentre, observational trial.

PubMed

Wermke, Martin; Eckoldt, Julia; Götze, Katharina S; Klein, Stefan A; Bug, Gesine; de Wreede, Liesbeth C; Kramer, Michael; Stölzel, Friedrich; von Bonin, Malte; Schetelig, Johannes; Laniado, Michael; Plodeck, Verena; Hofmann, Wolf-Karsten; Ehninger, Gerhard; Bornhäuser, Martin; Wolf, Dominik; Theurl, Igor; Platzbecker, Uwe

2018-05-01

The effect of systemic iron overload on outcomes after allogeneic haemopoietic cell transplantation (HCT) has been a matter of substantial debate. We aimed to investigate the predictive value of both stored (MRI-derived liver iron content) and biologically active iron (enhanced labile plasma iron; eLPI) on post-transplantation outcomes in patients with acute myeloid leukaemia or myelodysplastic syndrome undergoing allogenic HCT. The prospective, multicentre, observational, ALLogeneic Iron inVEstigators (ALLIVE) trial recruited patients at five centres in Germany. We enrolled patients with acute myeloid leukaemia or myelodysplastic syndrome undergoing allogeneic HCT. Patients underwent cytotoxic conditioning for a median of 6 days (IQR 6-7) before undergoing allogeneic HCT and were followed up for up to 1 year (±3 months) post-transplantation. eLPI was measured in serum samples with the FeROS eLPI kit (Aferrix, Tel-Aviv, Israel) and values greater than 0·4 μmol/L were considered to represent raised eLPI. Liver iron content was measured by MRI. The primary endpoints were the quantitative delineation of eLPI dynamics during allogeneic HCT and the correlation coefficient between liver iron content before HCT and dynamic eLPI (eLPI dyn ; maximum eLPI minus baseline eLPI). All patients with available data were included in all analyses. This is the final analysis of this completed trial, which is registered with ClinicalTrials.gov, number NCT01746147. Between Dec 13, 2012, and Dec 23, 2014, 112 patients underwent allogeneic HCT. Liver iron content before allogeneic HCT was not significantly correlated with eLPI dyn (ρ=0·116, p=0·22). Serum eLPI concentrations rapidly increased during conditioning, and most (79 [73%] of 108) patients had raised eLPI by the day of transplantation. Patients with a pretransplant liver iron content greater than or equal to 125 μmol/g had an increased incidence of non-relapse mortality (20%, 95% CI 14-26) compared with those with lower

Biologically labile photoproducts from riverine non-labile dissolved organic carbon in the coastal waters

NASA Astrophysics Data System (ADS)

Kasurinen, V.; Aarnos, H.; Vähätalo, A.

2015-06-01

In order to assess the production of biologically labile photoproducts (BLPs) from non-labile riverine dissolved organic carbon (DOC), we collected water samples from ten major rivers, removed labile DOC and mixed the residual non-labile DOC with artificial seawater for microbial and photochemical experiments. Bacteria grew on non-labile DOC with a growth efficiency of 11.5% (mean; range from 3.6 to 15.3%). Simulated solar radiation transformed a part of non-labile DOC into BLPs, which stimulated bacterial respiration and production, but did not change bacterial growth efficiency (BGE) compared to the non-irradiated dark controls. In the irradiated water samples, the amount of BLPs stimulating bacterial production depended on the photochemical bleaching of chromophoric dissolved organic matter (CDOM). The apparent quantum yields for BLPs supporting bacterial production ranged from 9.5 to 76 (mean 39) (μmol C mol photons-1) at 330 nm. The corresponding values for BLPs supporting bacterial respiration ranged from 57 to 1204 (mean 320) (μmol C mol photons-1). According to the calculations based on spectral apparent quantum yields and local solar radiation, the annual production of BLPs ranged from 21 (St. Lawrence) to 584 (Yangtze) mmol C m-2 yr-1 in the plumes of the examined rivers. Complete photobleaching of riverine CDOM in the coastal ocean was estimated to produce 10.7 Mt C BLPs yr-1 from the rivers examined in this study and globally 38 Mt yr-1 (15% of riverine DOC flux from all rivers), which support 4.1 Mt yr-1 of bacterial production and 33.9 Mt yr-1 bacterial respiration.

Iron Overload and Apoptosis of HL-1 Cardiomyocytes: Effects of Calcium Channel Blockade

PubMed Central

Chen, Mei-pian; Cabantchik, Z. Ioav; Chan, Shing; Chan, Godfrey Chi-fung; Cheung, Yiu-fai

2014-01-01

Background Iron overload cardiomyopathy that prevails in some forms of hemosiderosis is caused by excessive deposition of iron into the heart tissue and ensuing damage caused by a raise in labile cell iron. The underlying mechanisms of iron uptake into cardiomyocytes in iron overload condition are still under investigation. Both L-type calcium channels (LTCC) and T-type calcium channels (TTCC) have been proposed to be the main portals of non-transferrinic iron into heart cells, but controversies remain. Here, we investigated the roles of LTCC and TTCC as mediators of cardiac iron overload and cellular damage by using specific Calcium channel blockers as potential suppressors of labile Fe(II) and Fe(III) ingress in cultured cardiomyocytes and ensuing apoptosis. Methods Fe(II) and Fe(III) uptake was assessed by exposing HL-1 cardiomyocytes to iron sources and quantitative real-time fluorescence imaging of cytosolic labile iron with the fluorescent iron sensor calcein while iron-induced apoptosis was quantitatively measured by flow cytometry analysis with Annexin V. The role of calcium channels as routes of iron uptake was assessed by cell pretreatment with specific blockers of LTCC and TTCC. Results Iron entered HL-1 cardiomyocytes in a time- and dose-dependent manner and induced cardiac apoptosis via mitochondria-mediated caspase-3 dependent pathways. Blockade of LTCC but not of TTCC demonstrably inhibited the uptake of ferric but not of ferrous iron. However, neither channel blocker conferred cardiomyocytes with protection from iron-induced apoptosis. Conclusion Our study implicates LTCC as major mediators of Fe(III) uptake into cardiomyocytes exposed to ferric salts but not necessarily as contributors to ensuing apoptosis. Thus, to the extent that apoptosis can be considered a biological indicator of damage, the etiopathology of cardiosiderotic damage that accompanies some forms of hemosiderosis would seem to be unrelated to LTCC or TTCC, but rather to other

Optimizing therapy for iron overload in the myelodysplastic syndromes: recent developments.

PubMed

Leitch, Heather A

2011-01-22

The myelodysplastic syndromes (MDS) are characterized by cytopenias and risk of progression to acute myeloid leukaemia (AML). Most MDS patients eventually require transfusion of red blood cells for anaemia, placing them at risk of transfusional iron overload. In β-thalassaemia major, transfusional iron overload leads to organ dysfunction and death; however, with iron chelation therapy, organ function is improved, and survival improved to near normal and correlated with the degree of compliance with chelation. In lower-risk MDS, several nonrandomized studies suggest an adverse effect of iron overload on survival and that lowering iron with chelation may minimize this impact. Emerging data indicate that chelation may improve organ function, particularly hepatic function, and a minority of patients may have improvement in cell counts and decreased transfusion requirements. While guidelines for MDS generally recommend chelation in selected lower-risk patients, data from nonrandomized trials suggest iron overload may impact adversely on the outcome of higher-risk MDS and stem cell transplantation (SCT). This effect may be due to increased transplant-related mortality, infection and AML progression, and preliminary data suggest that lowering iron may be beneficial in this patient group. Other areas of active and future investigation include optimizing the monitoring of iron overload using imaging such as T2* MRI and measures of labile iron and oxidative stress; correlating new methods of measuring iron to clinical outcomes; clarifying the contribution of different cellular and extracellular iron pools to iron toxicity; optimizing chelation by using agents that access the appropriate iron pools to minimize the relevant clinical consequences in individual patients; and incorporating measures of quality of life and co-morbidities into clinical trials of chelation in MDS. It should be noted that chelation is costly and potentially toxic, and in MDS should be initiated after

Temporal Changes in Photochemically Labile DOM and Implications for Carbon Budgets in Peatland Aquatic Systems

NASA Astrophysics Data System (ADS)

Pickard, A.

2015-12-01

Aquatic systems in peatland catchments are subject to high loading of dissolved organic matter (DOM) from surrounding terrestrial environments. However the significance of photochemical transformation of DOM in peatland carbon budgets remains poorly constrained. In this study UV irradiation experiments were conducted on water samples collected over one year from two contrasting systems in Scotland: a stream draining a peatland with high levels of DOM and a reservoir draining a peat catchment with low levels of DOM. Further samples were collected from the high DOM system during two storm events. After experimental exposure, optical and chemical analyses were employed to determine photochemical lability of the DOM pool. At both sites irradiation-induced decreases in dissolved organic carbon (DOC) as a percentage of the total carbon pool were greatest in winter, suggesting that DOM was depleted in photo-reactive molecules in summer. Seasonal variability in DOC was high at the stream site and was positively correlated with CO₂ and CO photoproduction (r2 = 0.81 and 0.83, respectively; p<0.05). Lignin phenol analyses indicate considerable contribution of peat to the DOM pool at the stream site, particularly during summer. Whilst DOC concentrations did not vary greatly during storm events, UV-Vis absorbance indicators did, signifying changing DOM source material from activation of different hydrological pathways. The most photo-reactive DOM occurred 5-10 hours after peak discharge, suggesting that storms replenish photochemically labile DOM in headwater streams. Conservative estimates using data from this study suggest that up to 7% of the DOM pool of peatland streams can be lost (primarily as CO₂ and CO) upon exposure to 8 hours of environmentally representative UV irradiation. Further investigation in field campaigns under natural UV exposure are underway to assess the importance of photodegradation of DOM as a loss pathway of carbon based gases from aquatic systems.

Ironing iron out in Parkinson's disease and other neurodegenerative diseases with iron chelators: a lesson from 6-hydroxydopamine and iron chelators, desferal and VK-28.

PubMed

Youdim, Moussa B H; Stephenson, Galia; Ben Shachar, Dorit

2004-03-01

In Parkinson's disease (PD) and its neurotoxin-induced models, 6-hydroxydopamine (6-OHDA) and N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), significant accumulation of iron occurs in the substantia nigra pars compacta. The iron is thought to be in a labile pool, unbound to ferritin, and is thought to have a pivotal role to induce oxidative stress-dependent neurodegeneration of dopamine neurons via Fenton chemistry. The consequence of this is its interaction with H(2)O(2) to generate the most reactive radical oxygen species, the hydroxyl radical. This scenario is supported by studies in both human and neurotoxin-induced parkinsonism showing that disposition of H(2)O(2) is compromised via depletion of glutathione (GSH), the rate-limiting cofactor of glutathione peroxide, the major enzyme source to dispose H(2)O(2) as water in the brain. Further, radical scavengers have been shown to prevent the neurotoxic action of the above neurotoxins and depletion of GSH. However, our group was the first to demonstrate that the prototype iron chelator, desferal, is a potent neuroprotective agent in the 6-OHDA model. We have extended these studies and examined the neuroprotective effect of intracerebraventricular (ICV) pretreatment with the prototype iron chelator, desferal (1.3, 13, 134 mg), on ICV induced 6-OHDA (250 micro g) lesion of striatal dopamine neurons. Desferal alone at the doses studied did not affect striatal tyrosine hydroxylase (TH) activity or dopamine (DA) metabolism. All three pretreatment (30 min) doses of desferal prevented the fall in striatal and frontal cortex DA, dihydroxyphenylacetic acid, and homovalinic acid, as well as the left and right striatum TH activity and DA turnover resulting from 6-OHDA lesion of dopaminergic neurons. A concentration bell-shaped neuroprotective effect of desferal was observed in the striatum, with 13 micro g being the most effective. Neither desferal nor 6-OHDA affected striatal serotonin, 5-hydroxyindole acetic acid, or

The Preparation of an Ultrastable Mesoporous Cr(III)-MOF via Reductive Labilization

DTIC Science & Technology

2015-09-02

of metal clusters from a template MOF with a known structure. Fe(III)-MOFs can serve as practical structural templates because iron resembles chromium ...clusters in PCN-333 are able to accommodate both di- and trivalent metal ions by varying the charges of the terminal ligands, the bridging oxygen atoms, and...molecules in trivalent aqua complexes27 Inert complexes Labile complexes M(OH2) Cr(OH2)6 3+ Ir(OH2)6 3+ V(OH2)6 3+ Fe(OH2)6 3+ Ti(OH2)6 3+ k (s1) 2.4 10

Contrasting Sensitivities of Escherichia coli Aconitases A and B to Oxidation and Iron Depletion

PubMed Central

Varghese, Shery; Tang, Yue; Imlay, James A.

2003-01-01

Superoxide damages dehydratases that contain catalytic [4Fe-4S]2+ clusters. Aconitases are members of that enzyme family, and previous work showed that most aconitase activity is lost when Escherichia coli is exposed to superoxide stress. More recently it was determined that E. coli synthesizes at least two isozymes of aconitase, AcnA and AcnB. Synthesis of AcnA, the less-abundant enzyme, is positively controlled by SoxS, a protein that is activated in the presence of superoxide-generating chemicals. We have determined that this arrangement exists because AcnA is resistant to superoxide in vivo. Surprisingly, purified AcnA is extremely sensitive to superoxide and other chemical oxidants unless it is combined with an uncharacterized factor that is present in cell extracts. In contrast, AcnB is highly sensitive to a variety of chemical oxidants in vivo, in extracts, and in its purified form. Thus, the induction of AcnA during oxidative stress provides a mechanism to circumvent a block in the tricarboxylic acid cycle. AcnA appears to be as catalytically competent as AcnB, so the retention of the latter as the primary housekeeping enzyme must provide some other advantage. We observed that the [4Fe-4S] cluster of AcnB is in dynamic equilibrium with the surrounding iron pool, so that AcnB is rapidly demetallated when intracellular iron pools drop. AcnA and other dehydratases do not show this trait. Demetallated AcnB is known to bind its cognate mRNA. The absence of AcnB activity also causes the accumulation and excretion of citrate, an iron chelator for which E. coli synthesizes a transport system. Thus, AcnB may be retained as the primary aconitase because the lability of its exposed cluster allows E. coli to sense and respond to iron depletion. PMID:12486059

Very-short-term perioperative intravenous iron administration and postoperative outcome in major orthopedic surgery: a pooled analysis of observational data from 2547 patients.

PubMed

Muñoz, Manuel; Gómez-Ramírez, Susana; Cuenca, Jorge; García-Erce, José Antonio; Iglesias-Aparicio, Daniel; Haman-Alcober, Sami; Ariza, Daniel; Naveira, Enrique

2014-02-01

Postoperative nosocomial infection (PNI) is a severe complication in surgical patients. Known risk factors of PNI such as allogeneic blood transfusions (ABTs), anemia, and iron deficiency are manageable with perioperative intravenous (IV) iron therapy. To address potential concerns about IV iron and the risk of PNI, we studied a large series of orthopedic surgical patients for possible relations between IV iron, ABT, and PNI. Pooled data on ABT, PNI, 30-day mortality, and length of hospital stay (LHS) from 2547 patients undergoing elective lower-limb arthroplasty (n = 1186) or hip fracture repair (n = 1361) were compared between patients who received either very-short-term perioperative IV iron (200-600 mg; n = 1538), with or without recombinant human erythropoietin (rHuEPO; 40,000 IU), or standard treatment (n = 1009). Compared to standard therapy, perioperative IV iron reduced rates of ABT (32.4% vs. 48.8%; p = 0.001), PNI (10.7% vs. 26.9%; p = 0.001), and 30-day mortality (4.8% vs. 9.4%; p = 0.003) and the LHS (11.9 days vs. 13.4 days; p = 0.001) in hip fracture patients. These benefits were observed in both transfused and nontransfused patients. Also in elective arthroplasty, IV iron reduced ABT rates (8.9% vs. 30.1%; p = 0.001) and LHS (8.4 days vs.10.7 days; p = 0.001), without differences in PNI rates (2.8% vs. 3.7%; p = 0.417), and there was no 30-day mortality. Despite known limitations of pooled observational analyses, these results suggest that very-short-term perioperative administration of IV iron, with or without rHuEPO, in major lower limb orthopedic procedures is associated with reduced ABT rates and LHS, without increasing postoperative morbidity or mortality. © 2013 American Association of Blood Banks.

Tumor-initiating cells of breast and prostate origin show alterations in the expression of genes related to iron metabolism

PubMed Central

Tomkova, Veronika; Korenkova, Vlasta; Langerova, Lucie; Simonova, Ekaterina; Zjablovskaja, Polina; Alberich-Jorda, Meritxell; Neuzil, Jiri; Truksa, Jaroslav

2017-01-01

The importance of iron in the growth and progression of tumors has been widely documented. In this report, we show that tumor-initiating cells (TICs), represented by spheres derived from the MCF7 cell line, exhibit higher intracellular labile iron pool, mitochondrial iron accumulation and are more susceptible to iron chelation. TICs also show activation of the IRP/IRE system, leading to higher iron uptake and decrease in iron storage, suggesting that level of properly assembled cytosolic iron-sulfur clusters (FeS) is reduced. This finding is confirmed by lower enzymatic activity of aconitase and FeS cluster biogenesis enzymes, as well as lower levels of reduced glutathione, implying reduced FeS clusters synthesis/utilization in TICs. Importantly, we have identified specific gene signature related to iron metabolism consisting of genes regulating iron uptake, mitochondrial FeS cluster biogenesis and hypoxic response (ABCB10, ACO1, CYBRD1, EPAS1, GLRX5, HEPH, HFE, IREB2, QSOX1 and TFRC). Principal component analysis based on this signature is able to distinguish TICs from cancer cells in vitro and also Leukemia-initiating cells (LICs) from non-LICs in the mouse model of acute promyelocytic leukemia (APL). Majority of the described changes were also recapitulated in an alternative model represented by MCF7 cells resistant to tamoxifen (TAMR) that exhibit features of TICs. Our findings point to the critical importance of redox balance and iron metabolism-related genes and proteins in the context of cancer and TICs that could be potentially used for cancer diagnostics or therapy. PMID:28031527

Novel diffusive gradients in thin films technique to assess labile sulfate in soil.

PubMed

Hanousek, Ondrej; Mason, Sean; Santner, Jakob; Chowdhury, Md Mobaroqul Ahsan; Berger, Torsten W; Prohaska, Thomas

2016-09-01

A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10(-6) ± 0.35 × 10(-6) cm(2) s(-1) at 25 °C. The accumulated sulfate was eluted in 1 mol L(-1) HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate.

Effect of warming on the degradation and production of low-molecular-weight labile organic carbon in an Arctic tundra soil

DOE PAGES

Yang, Ziming; Wullschleger, Stan D.; Liang, Liyuan; ...

2016-01-16

The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, andmore » low-molecular-weight (LMW) organic acids were analyzed during incubation at either –2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO 2 and CH 4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO 2 and CH 4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO 2 and CH 4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.« less

The nitroxide Tempo inhibits hydroxyl radical production from the Fenton-like reaction of iron(II)-citrate with hydrogen peroxide.

PubMed

Shi, Fengqiang; Zhang, Peifeng; Mao, Yujia; Wang, Can; Zheng, Meiqing; Zhao, Zhongwei

2017-01-29

In vivo physiological ligand citrate can bind iron(II) ions to form the iron(II)-citrate complex. Inhibition of hydroxyl radical (OH) production from the Fenton-like reaction of iron(II)-citrate with H 2 O 2 is biologically important, as this reaction may account for one of the mechanisms of the labile iron pool in vivo to induce oxidative stress and pathological conditions. Nitroxides have promising potentials as therapeutic antioxidants. However, there are controversial findings indicating that they not only act as antioxidants but also as pro-oxidants when engaged in Fenton reactions. Although the underlying mechanisms are proposed to be the inhibition or enhancement of the OH production by nitroxides, the proposed elucidations are only based on assessing biological damages and not demonstrated directly by measuring the OH production in the presence of nitroxides. In this study, therefore, we employed EPR and fluorescence spectroscopies to show direct evidence that nitroxide 2,2,6,6-tetramethyl-piperidine-1-oxyl (Tempo) inhibited OH production from the Fenton-like reaction of iron(II)-citrate with H 2 O 2 by up to 90%. We also demonstrated spectrophotometrically, for the first time, that this inhibition was due to oxidation of the iron(II)-citrate by Tempo with a stoichiometry of Tempo:Iron(III)-citrate = 1.1:1.0. A scheme was proposed to illustrate the roles of nitroxides engaged in Fenton/Fenton-like reactions. Copyright © 2016 Elsevier Inc. All rights reserved.

[Current understanding of iron overload hazard in patients with myelodysplastic syndrome].

PubMed

Song, Lu-Xi; Su, Ji-Ying; Zhang, Zhen; Chang, Chun-Kang

2013-04-01

Patients with myelodysplastic syndromes (MDS) become dependent on blood transfusions and develop into transfusional iron overload, which is exacerbated by increased absorption of dietary iron in response to ineffective erythropoiesis. However, it is uncertain whether there is an association among iron accumulation, clinical complications, and decreased likelihood of survival in MDS patients. Thereby our current understanding of the effects of transfusion dependency and iron overload in MDS are discussed. Particular emphasis should be placed on further characterizing the role of redox-active forms of labile iron and oxidative stress in iron overload, decreased life expectancy and increased risk of leukemic transformation in MDS patients with iron overload.

Long-term affects of a single P fertilization on Hedley P pools in a South Carolina loblolly pine plantation

Treesearch

Bradley W. Miller; Thomas R. Fox

2010-01-01

While phosphorus (P) fertilization increases plant available or “labile” P immediately after fertilization, it is uncertain how it influences P pools over the long term in forest soils. Phosphorus pools from a 22-year-old loblolly pine (Pinus taeda L.) fertilization study were quantified using the Hedley sequential fractionation procedure, Mehlich-1...

METABOLISM OF IRON STORES

PubMed Central

SAITO, HIROSHI

2014-01-01

ABSTRACT Remarkable progress was recently achieved in the studies on molecular regulators of iron metabolism. Among the main regulators, storage iron, iron absorption, erythropoiesis and hepcidin interact in keeping iron homeostasis. Diseases with gene-mutations resulting in iron overload, iron deficiency, and local iron deposition have been introduced in relation to the regulators of storage iron metabolism. On the other hand, the research on storage iron metabolism has not advanced since the pioneering research by Shoden in 1953. However, we recently developed a new method for determining ferritin iron and hemosiderin iron by computer-assisted serum ferritin kinetics. Serum ferritin increase or decrease curves were measured in patients with normal storage iron levels (chronic hepatitis C and iron deficiency anemia treated by intravenous iron injection), and iron overload (hereditary hemochromatosis and transfusion dependent anemia). We thereby confirmed the existence of two iron pathways where iron flows followed the numbered order (1) labile iron, (2) ferritin and (3) hemosiderin in iron deposition and mobilization among many previously proposed but mostly unproven routes. We also demonstrated the increasing and decreasing phases of ferritin iron and hemosiderin iron in iron deposition and mobilization. The author first demonstrated here the change in proportion between pre-existing ferritin iron and new ferritin iron synthesized by removing iron from hemosiderin in the course of iron removal. In addition, the author disclosed the cause of underestimation of storage iron turnover rate which had been reported by previous investigators in estimating storage iron turnover rate of normal subjects. PMID:25741033

Light availability affects sex lability in a gynodioecious plant.

PubMed

Varga, Sandra; Kytöviita, Minna-Maarit

2016-11-01

Sex lability (i.e., gender diphasy) in plants is classically linked to the larger resource needs associated with the female sexual function (i.e., seed production) compared to the male function (i.e., pollen production). Sex lability in response to the environment is extensively documented in dioecious species, but has been largely overlooked in gynodioecious plants. Here, we tested whether environmental conditions induce sex lability in the gynodioecious Geranium sylvaticum. We conducted a transplantation experiment in the field where plants with different sex expression were reciprocally transplanted between high light and low light habitats. We measured plants' reproductive output and sex expression over four years. Our results show that sex expression was labile over the study period. The light level at the destination habitat had a significant effect on sexual expression and reproductive output, because plants decreased their reproductive output when transplanted to the low light habitat. Transplantation origin did not affect any parameter measured. This study shows that sex expression in Geranium sylvaticum is labile and related to light availability. Sexually labile plants did not produce more seeds or pollen, and thus, there was no apparent fitness gain in sexually labile individuals. Sex lability in gynodioecious plants may be more common than previously believed because detection of sex lability necessitates data on the same individuals over time, which is rare in sexually dimorphic herbaceous plants. © 2016 Botanical Society of America.

Iron Mediates N-Methyl-d-aspartate Receptor-dependent Stimulation of Calcium-induced Pathways and Hippocampal Synaptic Plasticity*

PubMed Central

Muñoz, Pablo; Humeres, Alexis; Elgueta, Claudio; Kirkwood, Alfredo; Hidalgo, Cecilia; Núñez, Marco T.

2011-01-01

Iron deficiency hinders hippocampus-dependent learning processes and impairs cognitive performance, but current knowledge on the molecular mechanisms underlying the unique role of iron in neuronal function is sparse. Here, we investigated the participation of iron on calcium signal generation and ERK1/2 stimulation induced by the glutamate agonist N-methyl-d-aspartate (NMDA), and the effects of iron addition/chelation on hippocampal basal synaptic transmission and long-term potentiation (LTP). Addition of NMDA to primary hippocampal cultures elicited persistent calcium signals that required functional NMDA receptors and were independent of calcium influx through L-type calcium channels or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors; NMDA also promoted ERK1/2 phosphorylation and nuclear translocation. Iron chelation with desferrioxamine or inhibition of ryanodine receptor (RyR)-mediated calcium release with ryanodine-reduced calcium signal duration and prevented NMDA-induced ERK1/2 activation. Iron addition to hippocampal neurons readily increased the intracellular labile iron pool and stimulated reactive oxygen species production; the antioxidant N-acetylcysteine or the hydroxyl radical trapper MCI-186 prevented these responses. Iron addition to primary hippocampal cultures kept in calcium-free medium elicited calcium signals and stimulated ERK1/2 phosphorylation; RyR inhibition abolished these effects. Iron chelation decreased basal synaptic transmission in hippocampal slices, inhibited iron-induced synaptic stimulation, and impaired sustained LTP in hippocampal CA1 neurons induced by strong stimulation. In contrast, iron addition facilitated sustained LTP induction after suboptimal tetanic stimulation. Together, these results suggest that hippocampal neurons require iron to generate RyR-mediated calcium signals after NMDA receptor stimulation, which in turn promotes ERK1/2 activation, an essential step of sustained LTP. PMID:21296883

Re-defining and quantifying inorganic phosphate pools in the Soil and Water Assessment Tool

USDA-ARS?s Scientific Manuscript database

Abstract The Soil and Water Assessment Tool (SWAT), a large-scale hydrologic model, can be used to estimate the impact of land management practices on phosphate (P) loading in streams and water bodies. Three inorganic soil P pools (labile, active, and stable P) are currently defined in the SWAT mo...

Exposure to nitric oxide protects against oxidative damage but increases the labile iron pool in sorghum embryonic axes

PubMed Central

Jasid, Sebastián; Simontacchi, Marcela; Puntarulo, Susana

2008-01-01

Sodium nitroprusside (SNP) and diethylenetriamine NONOate (DETA NONOate), were used as the source of exogenous NO to study the effect of NO upon germination of sorghum (Sorghum bicolor (L.) Moench) seeds through its possible interaction with iron. Modulation of cellular Fe status could be an important factor for the establishment of oxidative stress and the regulation of plant physiology. Fresh and dry weights of the embryonic axes were significantly increased in the presence of 0.1 mM SNP, as compared to control. Spin trapping EPR was used to assess the NO content in axes from control seeds after 24 h of imbibition (2.4±0.2 nmol NO g−1 FW) and seeds exposed to 0.01, 0.1, and 1 mM SNP (3.1±0.3, 4.6±0.2, and 6.0±0.9 nmol NO g−1 FW, respectively) and 1 mM DETA NONOate (6.2±0.6 nmol NO g−1 FW). Incubation of seeds with 1 mM SNP protected against oxidative damage to lipids and maintained membrane integrity. The content of the deferoxamine–Fe (III) complex significantly increased in homogenates of axes excised from seeds incubated in the presence of 1 mM SNP or 1 mM DETA NONOate as compared to the control (19±2 nmol Fe g−1 FW, 15.2±0.5 nmol Fe g−1 FW, and 8±1 nmol Fe g−1 FW, respectively), whereas total Fe content in the axes was not affected by the NO donor exposure. Data presented here provide experimental evidence to support the hypothesis that increased availability of NO drives not only protective effects to biomacromolecules, but to increasing the Fe availability for promoting cellular development as well. PMID:18832188

Skin protection against UVA-induced iron damage by multiantioxidants and iron chelating drugs/prodrugs.

PubMed

Reelfs, Olivier; Eggleston, Ian M; Pourzand, Charareh

2010-03-01

In humans, prolonged sunlight exposure is associated with various pathological states. The continuing drive to develop improved skin protection involves not only approaches to reduce DNA damage by solar ultraviolet B (UVB) but also the development of methodologies to provide protection against ultraviolet A (UVA), the oxidising component of sunlight. Furthermore identification of specific cellular events following ultraviolet (UV) irradiation is likely to provide clues as to the mechanism of the development of resulting pathologies and therefore strategies for protection. Our discovery that UVA radiation, leads to an immediate measurable increase in 'labile' iron in human skin fibroblasts and keratinocytes provides a new insight into UVA-induced skin damage, since iron is a catalyst of biological oxidations. The main purpose of this overview is to bring together some of the new findings related to mechanisms underlying UVA-induced iron release and to discuss novel approaches based on the use of multiantioxidants and light-activated caged-iron chelators for efficient protection of skin cells against UVA-induced iron damage.

Assessing the Selectivity of Extractant Solutions for Recovering Labile Arsenic Associated with Iron (Hydr)oxides and Sulfides in Sediments

EPA Science Inventory

Sequential extractions can provide analytical constraints on the identification of mineral phases that control arsenic speciation in sediments. Model solids were used in this study to evaluate different solutions designed to extract arsenic from relatively labile solid phases. ...

The role of endocytic pathways in cellular uptake of plasma non-transferrin iron

PubMed Central

Sohn, Yang-Sung; Ghoti, Hussam; Breuer, William; Rachmilewitz, Eliezer; Attar, Samah; Weiss, Guenter; Cabantchik, Z. Ioav

2012-01-01

Background In transfusional siderosis, the iron binding capacity of plasma transferrin is often surpassed, with concomitant generation of non-transferrin-bound iron. Although implicated in tissue siderosis, non-transferrin-bound iron modes of cell ingress remain undefined, largely because of its variable composition and association with macromolecules. Using fluorescent tracing of labile iron in endosomal vesicles and cytosol, we examined the hypothesis that non-transferrin-bound iron fractions detected in iron overloaded patients enter cells via bulk endocytosis. Design and Methods Fluorescence microscopy and flow cytometry served as analytical tools for tracing non-transferrin-bound iron entry into endosomes with the redox-reactive macromolecular probe Oxyburst-Green and into the cytosol with cell-laden calcein green and calcein blue. Non-transferrin-bound iron-containing media were from sera of polytransfused thalassemia major patients and model iron substances detected in thalassemia major sera; cell models were cultured macrophages, and cardiac myoblasts and myocytes. Results Exposure of cells to ferric citrate together with albumin, or to non-transferrin-bound iron-containing sera from thalassemia major patients caused an increase in labile iron content of endosomes and cytosol in macrophages and cardiac cells. This increase was more striking in macrophages, but in both cell types was largely reduced by co-exposure to non-transferrin-bound iron-containing media with non-penetrating iron chelators or apo-transferrin, or by treatment with inhibitors of endocytosis. Endosomal iron accumulation traced with calcein-green was proportional to input non-transferrin-bound iron levels (r2=0.61) and also preventable by pre-chelation. Conclusions Our studies indicate that macromolecule-associated non-transferrin-bound iron can initially gain access into various cells via endocytic pathways, followed by iron translocation to the cytosol. Endocytic uptake of plasma non

Comparison of twice-daily vs once-daily deferasirox dosing in a gerbil model of iron cardiomyopathy

PubMed Central

Otto-Duessel, Maya; Aguilar, Michelle; Nick, Hanspeter; Moats, Rex; Wood, John C.

2010-01-01

Objective Despite the availability of deferoxamine chelation therapy for more than 20 years, iron cardiomyopathy remains the leading cause of death in thalassemia major patients. Effective chelation of cardiac iron is difficult; cardiac iron stores respond more slowly to chelation therapy and require a constant gradient of labile iron species between serum and myocytes. We have previously demonstrated the efficacy of once-daily deferasirox in removing previously stored cardiac iron in the gerbil, but changes in cardiac iron were relatively modest compared with hepatic iron. We postulated that daily divided dosing, by sustaining a longer labile iron gradient from myocytes to serum, would produce better cardiac iron chelation than a comparable daily dose. Methods Twenty-four 8- to 10-week-old female gerbils underwent iron dextran—loading for 10 weeks, followed by a 1-week iron equilibration period. Animals were divided into three treatment groups of eight animals each and were treated with deferasirox 100 mg/kg/day as a single dose, deferasirox 100 mg/kg/day daily divided dose, or sham chelation for a total of 12 weeks. Following euthanasia, organs were harvested for quantitative iron and tissue histology. Results Hepatic and cardiac iron contents were not statistically different between the daily single-dose and daily divided-dose groups. However, the ratio of cardiac to hepatic iron content was lower in the divided-dose group (0.78% vs 1.11%, p = 0.0007). Conclusion Daily divided dosing of deferasirox changes the relative cardiac and liver iron chelation profile compared with daily single dosing, trading improvements in cardiac iron elimination for less-effective hepatic chelation. PMID:17588475

Emotional Lability and Affective Synchrony in Borderline Personality Disorder

PubMed Central

Schoenleber, Michelle; Berghoff, Christopher R.; Tull, Matthew T.; DiLillo, David; Messman-Moore, Terri; Gratz, Kim L.

2015-01-01

Extant research on emotional lability in borderline personality disorder (BPD) has focused almost exclusively on lability of individual emotions or emotion types, with limited research considering how different types of emotions shift together over time. Thus, this study examined the temporal dynamics of emotion in BPD at the level of both individual emotions (i.e., self-conscious emotions [SCE], anger, and anxiety) and mixed emotions (i.e., synchrony between emotions). One hundred forty-four women from the community completed a diagnostic interview and laboratory study involving five emotion induction tasks (each of which was preceded and followed by a 5-min resting period or neutral task). State ratings of SCE, anger, and anxiety were provided at 14 time points (before and after each laboratory task and resting period). Hierarchical linear modeling results indicate that women with BPD reported greater mean levels of SCE and Anxiety (but not Anger), and greater lability of Anxiety. Women with BPD also exhibited greater variability in lability of all three emotions (suggestive of within-group differences in the relevance of lability to BPD). Results also revealed synchrony (i.e., positive relations) between each possible pair of emotions, regardless of BPD status. Follow-up regression analyses suggest the importance of accounting for lability when examining the role of synchrony in BPD, as the relation of SCE-Anger synchrony to BPD symptom severity was moderated by Anger and SCE lability. Specifically, synchronous changes in SCE and Anger were associated with greater BPD symptom severity when large shifts in SCE were paired with minor shifts in Anger. PMID:27362623

Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses.

PubMed

Hayes, Sarah M; White, Scott A; Thompson, Thomas L; Maier, Raina M; Chorover, Jon

2009-12-01

Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5 to 8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and "bioavailable" metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 - 13 g kg(-1)) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4 - 6 g kg(-1)) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools.

Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses

PubMed Central

Hayes, Sarah M.; White, Scott A.; Thompson, Thomas L.; Maier, Raina M.; Chorover, Jon

2009-01-01

Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5 to 8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and “bioavailable” metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 – 13 g kg−1) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4 – 6 g kg−1) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools. PMID:20161492

Characterization of plasma labile heme in hemolytic conditions

PubMed Central

Gouveia, Zélia; Carlos, Ana R.; Yuan, Xiaojing; Aires-da-Silva, Frederico; Stocker, Roland; Maghzal, Ghassan J.; Leal, Sónia S.; Gomes, Cláudio M.; Todorovic, Smilja; Iranzo, Olga; Ramos, Susana; Santos, Ana C.; Hamza, Iqbal; Gonçalves, João; Soares, Miguel P.

2018-01-01

Extracellular hemoglobin, a byproduct of hemolysis, can release its prosthetic heme groups upon oxidation. This produces metabolically active heme that is exchangeable between acceptor proteins, macromolecules and low molecular weight ligands, termed here labile heme. As it accumulates in plasma labile heme acts in a pro-oxidant manner and regulates cellular metabolism while exerting pro-inflammatory and cytotoxic effects that foster the pathogenesis of hemolytic diseases. Here, we developed and characterized a panel of heme-specific single domain antibodies (sdAbs) that together with a cellular-based heme reporter assay, allow for quantification and characterization of labile heme in plasma during hemolytic conditions. Using these approaches, we demonstrate that when generated during hemolytic conditions labile heme is bound to plasma molecules with an affinity higher than 10−7 m and that 2–8% (∼ 2–5 μm) of the total amount of heme detected in plasma can be internalized by bystander cells, termed here bioavailable heme. Acute, but not chronic, hemolysis is associated with transient reduction of plasma heme-binding capacity, that is, the ability of plasma molecules to bind labile heme with an affinity higher than 10−7 m. The heme-specific sdAbs neutralize the pro-oxidant activity of soluble heme in vitro, suggesting that these maybe used to counter the pathologic effects of labile heme during hemolytic conditions. Finally, we show that heme-specific sdAbs can be used to visualize cellular heme. In conclusion, we describe a panel of heme-specific sdAbs that when used with other approaches provide novel insights to the pathophysiology of heme. PMID:28783254

Impacts of flocculation on the distribution and diagenesis of iron in boreal estuarine sediments

NASA Astrophysics Data System (ADS)

Jilbert, Tom; Asmala, Eero; Schröder, Christian; Tiihonen, Rosa; Myllykangas, Jukka-Pekka; Virtasalo, Joonas J.; Kotilainen, Aarno; Peltola, Pasi; Ekholm, Päivi; Hietanen, Susanna

2018-03-01

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM) and as colloidal Fe oxyhydroxides, principally ferrihydrite. However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation processes along a salinity gradient in an estuary of the northern Baltic Sea efficiently transfer Fe and OM from the dissolved phase into particulate material that accumulates in the sediments. Flocculation of Fe and OM is partially decoupled. This is likely due to the presence of discrete colloidal ferrihydrite in the freshwater Fe pool, which responds differently from DOM to estuarine mixing. Further decoupling of Fe from OM occurs during sedimentation. While we observe a clear decline with distance offshore in the proportion of terrestrial material in the sedimentary particulate organic matter (POM) pool, the distribution of flocculated Fe in sediments is modulated by focusing effects. Labile Fe phases are most abundant at a deep site in the inner basin of the estuary, consistent with input from flocculation and subsequent focusing. The majority of the labile Fe pool is present as Fe (II), including both acid-volatile sulfur (AVS)-bound Fe and unsulfidized phases. The ubiquitous presence of unsulfidized Fe (II) throughout the sediment column suggests Fe (II)-OM complexes derived from reduction of flocculated Fe (III)-OM, while other Fe (II) phases are likely derived from the reduction of flocculated ferrihydrite. Depth-integrated rates of Fe (II) accumulation (AVS-Fe + unsulfidized Fe (II) + pyrite) for the period 1970-2015 are greater in the inner basin of the estuary with respect to a site further offshore, confirming higher rates of Fe reduction in near-shore areas. Mössbauer 57Fe

Chemical characterization of ambient aerosol collected during the southwest monsoon and intermonsoon seasons over the Arabian Sea: Labile-Fe(II) and other trace metals

NASA Astrophysics Data System (ADS)

Siefert, Ronald L.; Johansen, Anne M.; Hoffmann, Michael R.

1999-02-01

Atmospheric deposition of iron (Fe) to certain regions of the oceans is an important nutrient source of Fe to the biota, and the ability of the biota to uptake Fe is dependent on the speciation of the Fe. Therefore understanding the speciation of Fe in the atmosphere is critical to understanding the role of Fe as a nutrient source in surface ocean waters. Labile ferrous iron (Fe(II)) concentrations as well as total concentrations for Fe and other important trace metals, cations, and anions were determined over the Arabian Sea for two nonconsecutive months during 1995. Ambient aerosol samples were collected during the Indian Ocean intermonsoon and southwest monsoon seasons over the Arabian Sea. Sampling took place aboard the German research vessel Meteor in the months of May (leg M32/3; intermonsoon) and July/August (leg M32/5; southwest monsoon). Both cruise tracks followed the 65th east meridian, traveling for 30 days each (from north to south during leg M32/3 and from south to north during leg M32/5). A high-volume dichotomous virtual impactor with an aerodynamic cutoff size of 3 μm was used to collect the fine and coarse aerosol fractions for metal analysis. A low volume collector was used to collect aerosol samples for anion and cation analysis. The analysis for labile-Fe(II) was done immediately after sample collection to minimize any possible Fe redox reactions which might occur during sample storage. The analytical procedure involved filter extraction in a formate/formic acid buffered solution at pH 4.2 followed by colorimetric quantification of soluble Fe(II). Metals, anions, and cations were analyzed after the cruise. Total atmospheric aqueous-labile-Fe(II) concentrations during the intermonsoon were between 4.75 and <0.4 ng m-3, of which most (>80%) was present in the fine fraction (<3.0 μm). During the southwest monsoon, atmospheric aqueous-labile-Fe(II) concentrations were consistently below the detection limit (<0.34 to <0.089 ng m-3, depending on

A comparison of iron extraction methods for the determination of degree of pyritisation and the recognition of iron-limited pyrite formation

NASA Technical Reports Server (NTRS)

Raiswell, R.; Canfield, D. E.; Berner, R. A.

1994-01-01

Measurements of degree of pyritisation require an estimate of sediment iron which is capable of reaction with dissolved sulphide to form pyrite, either directly or indirectly via iron monosulphide precursors. Three dissolution techniques (buffered dithionite, cold 1 M HCl, boiling 12 M HCl) were examined for their capacity to extract iron from a variety of iron minerals, and iron-bearing sediments, as a function of different extraction times and different grain sizes. All the iron oxides studied are quantitatively extracted by dithionite and boiling HCl (but not by cold HCl). Both HCl techniques extract more iron from silicates than does dithionite but probably about the same amounts as are potentially capable of sulphidation. Modern sediment studies indicate that most sedimentary pyrite is formed rapidly from iron oxides, with smaller amounts formed more slowly from iron silicates (if sufficient geologic time is available). It is therefore recommended that the degree of pyritisation be defined with respect to the dithionite-extractable (mainly iron oxide) pool and/or the boiling HCl-extractable pool (which includes some silicate iron) for the recognition of iron-limited pyritisation.

Distribution of dissolved labile and particulate iron and copper in Terra Nova Bay polynya (Ross Sea, Antarctica) surface waters in relation to nutrients and phytoplankton growth

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Ianni, Carmela; Massolo, Serena; Abelmoschi, M. Luisa; De Vittor, Cinzia; Frache, Roberto

2011-05-01

The distribution of the dissolved labile and of the particulate Fe and Cu together with dissolved oxygen, nutrients, chlorophyll a and total particulate matter was investigated in the surface waters of Terra Nova Bay polynya in mid-January 2003. The measurements were conducted within the framework of the Italian Climatic Long-term Interactions of the Mass balance in Antarctica (CLIMA) Project activities. The labile dissolved fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The dissolved labile Fe ranges from below the detection limit (0.15 nM) to 3.71 nM, while the dissolved labile Cu from below the detection limit (0.10 nM) to 0.90 nM. The lowest concentrations for both metals were observed at 20 m depth (the shallowest depth for which metals were measured). The concentration of the particulate Fe was about 5 times higher than the dissolved Fe concentration, ranging from 0.56 to 24.83 nM with an average of 6.45 nM. The concentration of the particulate Cu ranged from 0.01 to 0.71 nM with an average of 0.17 nM. The values are in agreement with the previous data collected in the same area. We evaluated the role of the Fe and Cu as biolimiting metals. The N:dissolved labile Fe ratios (18,900-130,666) would or would not allow a complete nitrate removal, on the basis of the N:Fe requirement ratios that we calculated considering the N:P and the C:P ratios estimated for diatoms. This finding partially agrees with the Si:N ratio that we found (2.29). Moreover we considered a possible influence of the dissolved labile Cu on the Fe uptake process.

An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability

PubMed Central

D'Andrilli, Juliana; Cooper, William T; Foreman, Christine M; Marshall, Alan G

2015-01-01

Rationale Determining the chemical constituents of natural organic matter (NOM) by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICRMS) remains the ultimate measure for probing its source material, evolution, and transport; however, lability and the fate of organic matter (OM) in the environment remain controversial. FTICRMS-derived elemental compositions are presented in this study to validate a new interpretative method to determine the extent of NOM lability from various environments. Methods FTICRMS data collected over the last decade from the same 9.4 tesla instrument using negative electrospray ionization at the National High Magnetic Field Laboratory in Tallahassee, Florida, was used to validate the application of a NOM lability index. Solid-phase extraction cartridges were used to isolate the NOM prior to FTICRMS; mass spectral peaks were calibrated internally by commonly identified NOM homologous series, and molecular formulae were determined for NOM composition and lability analysis. Results A molecular lability boundary (MLB) was developed from the FTICRMS molecular data, visualized from van Krevelen diagrams, dividing the data into more and less labile constituents. NOM constituents above the MLB at H/C ≥1.5 correspond to more labile material, whereas NOM constituents below the MLB, H/C <1.5, exhibit less labile, more recalcitrant character. Of all marine, freshwater, and glacial environments considered for this study, glacial ecosystems were calculated to contain the most labile OM. Conclusions The MLB extends our interpretation of FTICRMS NOM molecular data to include a metric of lability, and generally ranked the OM environments from most to least labile as glacial > marine > freshwater. Applying the MLB is useful not only for individual NOM FTICRMS studies, but also provides a lability threshold to compare and contrast molecular data with other FTICRMS instruments that survey NOM from around the world. Copyright © 2015

Transient acidosis while retrieving a fear-related memory enhances its lability

PubMed Central

Du, Jianyang; Price, Margaret P; Taugher, Rebecca J; Grigsby, Daniel; Ash, Jamison J; Stark, Austin C; Hossain Saad, Md Zubayer; Singh, Kritika; Mandal, Juthika; Wemmie, John A; Welsh, Michael J

2017-01-01

Attenuating the strength of fearful memories could benefit people disabled by memories of past trauma. Pavlovian conditioning experiments indicate that a retrieval cue can return a conditioned aversive memory to a labile state. However, means to enhance retrieval and render a memory more labile are unknown. We hypothesized that augmenting synaptic signaling during retrieval would increase memory lability. To enhance synaptic transmission, mice inhaled CO2 to induce an acidosis and activate acid sensing ion channels. Transient acidification increased the retrieval-induced lability of an aversive memory. The labile memory could then be weakened by an extinction protocol or strengthened by reconditioning. Coupling CO2 inhalation to retrieval increased activation of amygdala neurons bearing the memory trace and increased the synaptic exchange from Ca2+-impermeable to Ca2+-permeable AMPA receptors. The results suggest that transient acidosis during retrieval renders the memory of an aversive event more labile and suggest a strategy to modify debilitating memories. DOI: http://dx.doi.org/10.7554/eLife.22564.001 PMID:28650315

Complexity of intravenous iron nanoparticle formulations: implications for bioequivalence evaluation.

PubMed

Pai, Amy Barton

2017-11-01

Intravenous iron formulations are a class of complex drugs that are commonly used to treat a wide variety of disease states associated with iron deficiency and anemia. Venofer® (iron-sucrose) is one of the most frequently used formulations, with more than 90% of dialysis patients in the United States receiving this formulation. Emerging data from global markets outside the United States, where many iron-sucrose similars or copies are available, have shown that these formulations may have safety and efficacy profiles that differ from the reference listed drug. This may be attributable to uncharacterized differences in physicochemical characteristics and/or differences in labile iron release. As bioequivalence evaluation guidance evolves, clinicians should be educated on these potential clinical issues before a switch to the generic formulation is made in the clinical setting. © 2017 New York Academy of Sciences.

Toxicity of iron overload and iron overload reduction in the setting of hematopoietic stem cell transplantation for hematologic malignancies.

PubMed

Leitch, Heather A; Fibach, Eitan; Rachmilewitz, Eliezer

2017-05-01

Iron is an essential element for key cellular metabolic processes. However, transfusional iron overload (IOL) may result in significant cellular toxicity. IOL occurs in transfusion dependent hematologic malignancies (HM), may lead to pathological clinical outcomes, and IOL reduction may improve outcomes. In hematopoietic stem cell transplantation (SCT) for HM, IOL may have clinical importance; endpoints examined regarding an impact of IOL and IOL reduction include transplant-related mortality, organ function, infection, relapse risk, and survival. Here we review the clinical consequences of IOL and effects of IOL reduction before, during and following SCT for HM. IOL pathophysiology is discussed as well as available tests for IOL quantification including transfusion history, serum ferritin level, transferrin saturation, hepcidin, labile plasma iron and other parameters of iron-catalyzed oxygen free radicals, and organ IOL by imaging. Data-based recommendations for IOL measurement, monitoring and reduction before, during and following SCT for HM are made. Copyright © 2017 Elsevier B.V. All rights reserved.

A vacuolar iron-transporter homologue acts as a detoxifier in Plasmodium

PubMed Central

Slavic, Ksenija; Krishna, Sanjeev; Lahree, Aparajita; Bouyer, Guillaume; Hanson, Kirsten K.; Vera, Iset; Pittman, Jon K.; Staines, Henry M.; Mota, Maria M.

2016-01-01

Iron is an essential micronutrient but is also highly toxic. In yeast and plant cells, a key detoxifying mechanism involves iron sequestration into intracellular storage compartments, mediated by members of the vacuolar iron-transporter (VIT) family of proteins. Here we study the VIT homologue from the malaria parasites Plasmodium falciparum (PfVIT) and Plasmodium berghei (PbVIT). PfVIT-mediated iron transport in a yeast heterologous expression system is saturable (Km∼14.7 μM), and selective for Fe2+ over other divalent cations. PbVIT-deficient P. berghei lines (Pbvit−) show a reduction in parasite load in both liver and blood stages of infection in mice. Moreover, Pbvit− parasites have higher levels of labile iron in blood stages and are more sensitive to increased iron levels in liver stages, when compared with wild-type parasites. Our data are consistent with Plasmodium VITs playing a major role in iron detoxification and, thus, normal development of malaria parasites in their mammalian host. PMID:26786069

A vacuolar iron-transporter homologue acts as a detoxifier in Plasmodium.

PubMed

Slavic, Ksenija; Krishna, Sanjeev; Lahree, Aparajita; Bouyer, Guillaume; Hanson, Kirsten K; Vera, Iset; Pittman, Jon K; Staines, Henry M; Mota, Maria M

2016-01-20

Iron is an essential micronutrient but is also highly toxic. In yeast and plant cells, a key detoxifying mechanism involves iron sequestration into intracellular storage compartments, mediated by members of the vacuolar iron-transporter (VIT) family of proteins. Here we study the VIT homologue from the malaria parasites Plasmodium falciparum (PfVIT) and Plasmodium berghei (PbVIT). PfVIT-mediated iron transport in a yeast heterologous expression system is saturable (Km ∼ 14.7 μM), and selective for Fe(2+) over other divalent cations. PbVIT-deficient P. berghei lines (Pbvit(-)) show a reduction in parasite load in both liver and blood stages of infection in mice. Moreover, Pbvit(-) parasites have higher levels of labile iron in blood stages and are more sensitive to increased iron levels in liver stages, when compared with wild-type parasites. Our data are consistent with Plasmodium VITs playing a major role in iron detoxification and, thus, normal development of malaria parasites in their mammalian host.

Timed non-transferrin bound iron determinations probe the origin of chelatable iron pools during deferiprone regimens and predict chelation response

PubMed Central

Aydinok, Yesim; Evans, Patricia; Manz, Chantal Y.; Porter, John B.

2012-01-01

Background Plasma non-transferrin bound iron refers to heterogeneous plasma iron species, not bound to transferrin, which appear in conditions of iron overload and ineffective erythropoiesis. The clinical utility of non-transferrin bound iron in predicting complications from iron overload, or response to chelation therapy remains unproven. We undertook carefully timed measurements of non-transferrin bound iron to explore the origin of chelatable iron and to predict clinical response to deferiprone. Design and Methods Non-transferrin bound iron levels were determined at baseline and after 1 week of chelation in 32 patients with thalassemia major receiving deferiprone alone, desferrioxamine alone, or a combination of the two chelators. Samples were taken at baseline, following a 2-week washout without chelation, and after 1 week of chelation, this last sample being taken 10 hours after the previous evening dose of deferiprone and, in those receiving desferrioxamine, 24 hours after cessation of the overnight subcutaneous infusion. Absolute or relative non-transferrin bound iron levels were related to transfusional iron loading rates, liver iron concentration, 24-hour urine iron and response to chelation therapy over the subsequent year. Results Changes in non-transferrin bound iron at week 1 were correlated positively with baseline liver iron, and inversely with transfusional iron loading rates, with deferiprone-containing regimens but not with desferrioxamine monotherapy. Changes in week 1 non-transferrin bound iron were also directly proportional to the plasma concentration of deferiprone-iron complexes and correlated significantly with urine iron excretion and with changes in liver iron concentration over the next 12 months. Conclusions The widely used assay chosen for this study detects both endogenous non-transferrin bound iron and the iron complexes of deferiprone. The week 1 increments reflect chelatable iron derived both from liver stores and from red cell

Repeated Labilization-Reconsolidation Processes Strengthen Declarative Memory in Humans

PubMed Central

Forcato, Cecilia; Rodríguez, María L. C.; Pedreira, María E.

2011-01-01

The idea that memories are immutable after consolidation has been challenged. Several reports have shown that after the presentation of a specific reminder, reactivated old memories become labile and again susceptible to amnesic agents. Such vulnerability diminishes with the progress of time and implies a re-stabilization phase, usually referred to as reconsolidation. To date, the main findings describe the mechanisms associated with the labilization-reconsolidation process, but little is known about its functionality from a biological standpoint. Indeed, two functions have been proposed. One suggests that destabilization of the original memory after the reminder allows the integration of new information into the background of the original memory (memory updating), and the other suggests that the labilization-reconsolidation process strengthens the original memory (memory strengthening). We have previously reported the reconsolidation of human declarative memories, demonstrating memory updating in the framework of reconsolidation. Here we deal with the strengthening function attributed to the reconsolidation process. We triggered labilization-reconsolidation processes successively by repeated presentations of the proper reminder. Participants learned an association between five cue-syllables and their respective response-syllables. Twenty-four hours later, the paired-associate verbal memory was labilized by exposing the subjects to one, two or four reminders. The List-memory was evaluated on Day 3 showing that the memory was improved when at least a second reminder was presented in the time window of the first labilization-reconsolidation process prompted by the earlier reminder. However, the improvement effect was revealed on Day 3, only when at least two reminders were presented on Day2 and not as a consequence of only retrieval. Therefore, we propose central concepts for the reconsolidation process, emphasizing its biological role and the parametrical constrains

The effects of metamorphism on iron mineralogy and the iron speciation redox proxy

NASA Astrophysics Data System (ADS)

Slotznick, Sarah P.; Eiler, John M.; Fischer, Woodward W.

2018-03-01

As the most abundant transition metal in the Earth's crust, iron is a key player in the planetary redox budget. Observations of iron minerals in the sedimentary record have been used to describe atmospheric and aqueous redox environments over the evolution of our planet; the most common method applied is iron speciation, a geochemical sequential extraction method in which proportions of different iron minerals are compared to calibrations from modern sediments to determine water-column redox state. Less is known about how this proxy records information through post-depositional processes, including diagenesis and metamorphism. To get insight into this, we examined how the iron mineral groups/pools (silicates, oxides, sulfides, etc.) and paleoredox proxy interpretations can be affected by known metamorphic processes. Well-known metamorphic reactions occurring in sub-chlorite to kyanite rocks are able to move iron between different iron pools along a range of proxy vectors, potentially affecting paleoredox results. To quantify the effect strength of these reactions, we examined mineralogical and geochemical data from two classic localities where Silurian-Devonian shales, sandstones, and carbonates deposited in a marine sedimentary basin with oxygenated seawater (based on global and local biological constraints) have been regionally metamorphosed from lower-greenschist facies to granulite facies: Waits River and Gile Mountain Formations, Vermont, USA and the Waterville and Sangerville-Vassalboro Formations, Maine, USA. Plotting iron speciation ratios determined for samples from these localities revealed apparent paleoredox conditions of the depositional water column spanning the entire range from oxic to ferruginous (anoxic) to euxinic (anoxic and sulfidic). Pyrrhotite formation in samples highlighted problems within the proxy as iron pool assignment required assumptions about metamorphic reactions and pyrrhotite's identification depended on the extraction techniques

Construction of hierarchically porous metal–organic frameworks through linker labilization

DOE PAGES

Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; ...

2017-05-25

One major goal of metal–organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. W present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragmentsmore » by acid treatment. We also demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.« less

Construction of hierarchically porous metal-organic frameworks through linker labilization

NASA Astrophysics Data System (ADS)

Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; Li, Jialuo; Huang, Lan; Feng, Liang; Wang, Xuan; Bosch, Mathieu; Alsalme, Ali; Cagin, Tahir; Zhou, Hong-Cai

2017-05-01

A major goal of metal-organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.

Construction of hierarchically porous metal–organic frameworks through linker labilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng

One major goal of metal–organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. W present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragmentsmore » by acid treatment. We also demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.« less

Non-labile silver species in biosolids remain stable throughout ...

EPA Pesticide Factsheets

Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110mAg showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO3 extractable Ag from 1.2 to 609 µg/kg (0.002 - 3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability. This paper presents an overview of biosolids Ag chemistry in historic and contemporary biosolids sourced from the UK, USA and Australia from the 1950s until today by drawing on a unique collection of archived, stockpiled and contemporary biosolids samples. Characteristics of biosolids Ag chemistry determined in this study included total Ag measurement by neutron activation analysis (NAA); the assessment of Ag lability by 110mAg isotopic dilution (E-values); and Ag speciation by X-ray Absorp

Freshwater processing of terrestrial dissolved organic matter: What governs lability?

NASA Astrophysics Data System (ADS)

D'Andrilli, J.; Smith, H. J.; Junker, J. R.; Scholl, E. A.; Foreman, C. M.

2016-12-01

Aquatic and terrestrial ecosystems are linked through the transfer of energy and materials. Allochthonous organic matter (OM) is central to freshwater ecosystem function, influencing local food webs, trophic state, and nutrient availability. In order to understand the nature and fate of OM from inland headwaters to the open ocean, it is imperative to understand the links between OM lability and ecosystem function. Thus, biological, chemical, and physical factors need to be evaluated together to inform our understanding of environmental lability. We performed a laboratory processing experiment on naturally occurring OM leachates from riparian leaves, grasses, and pine needles. Measures of water chemistry, OM optical and molecular characterization, bacterial abundances, microbial assemblage composition, respiration, and C:N:P were integrated to discern the nature and fate of labile and recalcitrant OM in a freshwater stream. Peak processing of all OM sources in the stream water occurred after two days, with spikes in bacterial cell abundances, respiration rates, microbial assemblage shifts, and maximum C utilization. Respiration rates and microbial assemblages were dependent on the degree of lability of the OM molecular composition. Within the first few days, no differences in respiration rates were observed between leachate sources, however, beyond day five, the rates diverged with C processing efficiency correlated with OM lability. Originally comprised of amino acid-like, labile fluorescent species, the inoculated stream water OM became more recalcitrant after 16 days, indicating humification processing over time. Our study highlights the importance of interdisciplinary approaches for understanding the processing and fate of OM in aquatic ecosystems.

Solubility of iron from combustion source particles in acidic media linked to iron speciation.

PubMed

Fu, Hongbo; Lin, Jun; Shang, Guangfeng; Dong, Wenbo; Grassian, Vichi H; Carmichael, Gregory R; Li, Yan; Chen, Jianmin

2012-10-16

In this study, iron solubility from six combustion source particles was investigated in acidic media. For comparison, a Chinese loess (CL) dust was also included. The solubility experiments confirmed that iron solubility was highly variable and dependent on particle sources. Under dark and light conditions, the combustion source particles dissolved faster and to a greater extent relative to CL. Oil fly ash (FA) yielded the highest soluble iron as compared to the other samples. Total iron solubility fractions measured in the dark after 12 h ranged between 2.9 and 74.1% of the initial iron content for the combustion-derived particles (Oil FA > biomass burning particles (BP) > coal FA). Ferrous iron represented the dominant soluble form of Fe in the suspensions of straw BP and corn BP, while total dissolved Fe presented mainly as ferric iron in the cases of oil FA, coal FA, and CL. Mössbauer measurements and TEM analysis revealed that Fe in oil FA was commonly presented as nanosized Fe(3)O(4) aggregates and Fe/S-rich particles. Highly labile source of Fe in corn BP could be originated from amorphous Fe form mixed internally with K-rich particles. However, Fe in coal FA was dominated by the more insoluble forms of both Fe-bearing aluminosilicate glass and Fe oxides. The data presented herein showed that iron speciation varies by source and is an important factor controlling iron solubility from these anthropogenic emissions in acidic solutions, suggesting that the variability of iron solubility from combustion-derived particles is related to the inherent character and origin of the aerosols themselves. Such information can be useful in improving our understanding on iron solubility from combustion aerosols when they undergo acidic processing during atmospheric transport.

Pooling Cervical Swabs and Testing by Ligase Chain Reaction Are Accurate and Cost-Saving Strategies for Diagnosis of Chlamydia trachomatis

PubMed Central

Kapala, J.; Copes, D.; Sproston, A.; Patel, J.; Jang, D.; Petrich, A.; Mahony, J.; Biers, K.; Chernesky, M.

2000-01-01

Specimen pooling to achieve efficiency when testing urine specimens for Chlamydia trachomatis nucleic acids has been suggested. We pooled endocervical swabs from 1,288 women and also tested individual swabs by ligase chain reaction (LCR). Out of 53 positive specimens, pools of 4 or 8 specimens missed two positives, providing 96.2% accuracy compared to individual test results. Dilution and positive-control spiking experiments showed that negative specimens with inhibitors of LCR in the pool reduced the signal. Conversely, two extra positives, detected only through pooling, were negative by individual testing but became positive after storage, suggesting that fresh positive specimens with labile inhibitors may be positive in a pool because of dilution of inhibitors. For this population of women with a 4% prevalence of C. trachomatis infection, substantial savings in cost of reagents (55 to 63%) and technologist time (50 to 63%) made pooling strategies a desirable alternative to individual testing. PMID:10878029

Hot regions of labile and stable soil organic carbon in Germany - Spatial variability and driving factors

NASA Astrophysics Data System (ADS)

Vos, Cora; Jaconi, Angélica; Jacobs, Anna; Don, Axel

2018-06-01

Atmospheric carbon dioxide levels can be mitigated by sequestering carbon in the soil. Sequestration can be facilitated by agricultural management, but its influence is not the same on all soil carbon pools, as labile pools with a high turnover may be accumulated much faster but are also more vulnerable to losses. The aims of this study were to (1) assess how soil organic carbon (SOC) is distributed among SOC fractions on a national scale in Germany, (2) identify factors influencing this distribution and (3) identify regions with high vulnerability to SOC losses. The SOC content and proportion of two different SOC fractions were estimated for more than 2500 mineral topsoils (< 87 g kg-1 SOC) covering Germany, using near-infrared reflectance spectroscopy. Drivers of the spatial variability in SOC fractions were determined using the machine learning algorithm cforest. The SOC content and proportions of fractions were predicted with good accuracy (SOC content: R2 = 0.87-0.90; SOC proportions: R2 = 0.83; ratio of performance to deviation (RPD): 2.4-3.2). The main explanatory variables for the distribution of SOC among the fractions were soil texture, bulk soil C / N ratio, total SOC content and pH. For some regions, the drivers were linked to the land-use history of the sites. Arable topsoils in central and southern Germany were found to contain the highest proportions and contents of stable SOC fractions, and therefore have the lowest vulnerability to SOC losses. North-western Germany contains an area of sandy soils with unusually high SOC contents and high proportions of light SOC fractions, which are commonly regarded as representing a labile carbon pool. This is true for the former peat soils in this area, which have already lost and are at high risk of losing high proportions of their SOC stocks. Those black sands can, however, also contain high amounts of stable SOC due to former heathland vegetation and need to be treated and discussed separately from non

Agricultural management and labile carbon additions affect soil microbial community structure and interact with carbon and nitrogen cycling.

PubMed

Berthrong, Sean T; Buckley, Daniel H; Drinkwater, Laurie E

2013-07-01

We investigated how conversion from conventional agriculture to organic management affected the structure and biogeochemical function of soil microbial communities. We hypothesized the following. (1) Changing agricultural management practices will alter soil microbial community structure driven by increasing microbial diversity in organic management. (2) Organically managed soil microbial communities will mineralize more N and will also mineralize more N in response to substrate addition than conventionally managed soil communities. (3) Microbial communities under organic management will be more efficient and respire less added C. Soils from organically and conventionally managed agroecosystems were incubated with and without glucose ((13)C) additions at constant soil moisture. We extracted soil genomic DNA before and after incubation for TRFLP community fingerprinting of soil bacteria and fungi. We measured soil C and N pools before and after incubation, and we tracked total C respired and N mineralized at several points during the incubation. Twenty years of organic management altered soil bacterial and fungal community structure compared to continuous conventional management with the bacterial differences caused primarily by a large increase in diversity. Organically managed soils mineralized twice as much NO3 (-) as conventionally managed ones (44 vs. 23 μg N/g soil, respectively) and increased mineralization when labile C was added. There was no difference in respiration, but organically managed soils had larger pools of C suggesting greater efficiency in terms of respiration per unit soil C. These results indicate that the organic management induced a change in community composition resulting in a more diverse community with enhanced activity towards labile substrates and greater capacity to mineralize N.

Fate and lability of silver in soils: Effect of ageing

EPA Science Inventory

The fate and lability of added soluble Ag in soils over time was examined by measurement of labile metal (E-value) by isotopic dilution using the ^110mAg radioactive isotope and the solid-phase speciation of Ag by X-ray absorption near edge structure (XANES) spectrosco...

High-dose intravenously administered iron versus orally administered iron in blood donors with iron deficiency: study protocol for a randomised, controlled trial.

PubMed

Macher, Susanne; Drexler, Camilla; Lindenau, Ines; Sareban, Nazanin; Schlenke, Peter; Amrein, Karin

2016-10-28

About 2-3 % of the population participates in blood donation programmes. Each whole blood donation or ten apheresis donations cause a loss of 200-250 mg of iron. As a result, one of the most common risks of regular blood donors is iron deficiency. Although this has been known for decades, in most countries, iron status is currently not assessed or treated in this population. Premenopausal women are particularly affected, as they have lower iron reserves and higher daily requirements. Besides anaemia, iron deficiency may lead to fatigue and impaired cognitive and physical performance. Current iron preparations for intravenous administration are well tolerated and allow for application of large doses up to 1 g in one visit. Our hypothesis is that in blood donors with iron deficiency, intravenously administered iron is more efficient and as safe as oral iron supplementation. Since anaemia is one of the most frequent reasons for permanent or intermittent donor deferral, maintaining an iron-replete donor pool may help to prevent shortages in blood supply and to avoid iron deficiency-related comorbidities. In this randomised clinical trial we include male and female blood donors aged ≥18 and ≤65 years with a ferritin value of ≤30 ng/ml. Stratified by gender, participants are randomized with a web-based randomisation tool in a 1:1 ratio to either 1 g of intravenously administered ferric carboxymaltose or 10 g of iron fumarate supplements at one to two daily doses of 100 mg each. Eight to 12 weeks after the first visit, iron status, blood count and symptoms are assessed in both groups. The primary endpoint is the difference in transferrin saturation (%) following the intervention between both groups. Secondary endpoints include other parameters of iron metabolism and red blood cell count, the number of patients with drug-related adverse events, and subjective symptoms including those of the restless legs syndrome, quality of life, and fatigue. Iron

Differences in dissolved organic matter lability between alpine glaciers and alpine rock glaciers of the American West

NASA Astrophysics Data System (ADS)

Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.

2015-12-01

While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

Memory expression is independent of memory labilization/reconsolidation.

PubMed

Barreiro, Karina A; Suárez, Luis D; Lynch, Victoria M; Molina, Víctor A; Delorenzi, Alejandro

2013-11-01

There is growing evidence that certain reactivation conditions restrict the onset of both the destabilization phase and the restabilization process or reconsolidation. However, it is not yet clear how changes in memory expression during the retrieval experience can influence the emergence of the labilization/reconsolidation process. To address this issue, we used the context-signal memory model of Chasmagnathus. In this paradigm a short reminder that does not include reinforcement allows us to evaluate memory labilization and reconsolidation, whereas a short but reinforced reminder restricts the onset of such a process. The current study investigated the effects of the glutamate antagonists, APV (0.6 or 1.5 μg/g) and CNQX (1 μg/g), prior to the reminder session on both behavioral expression and the reconsolidation process. Under conditions where the reminder does not initiate the labilization/reconsolidation process, APV prevented memory expression without affecting long-term memory retention. In contrast, APV induced amnesic effects in the long-term when administered before a reminder session that triggers reconsolidation. Under the present parametric conditions, the administration of CNQX prior to the reminder that allows memory to enter reconsolidation impairs this process without disrupting memory expression. Overall, the present findings suggest that memory reactivation--but not memory expression--is necessary for labilization and reconsolidation. Retrieval and memory expression therefore appear not to be interchangeable concepts. Copyright © 2013 Elsevier Inc. All rights reserved.

Tropical forest soil microbial communities couple iron and carbon biogeochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubinsky, E.A.; Silver, W.L.; Firestone, M.K.

2009-10-15

We report that iron-reducing bacteria are primary mediators of anaerobic carbon oxidation in upland tropical soils spanning a rainfall gradient (3500 - 5000 mm yr-1) in northeast Puerto Rico. The abundant rainfall and high net primary productivity of these tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria. Spatially and temporally dynamic redox conditions make iron-transforming microbial communities central to the belowground carbon cycle in these wet tropical forests. The exceedingly high abundance of iron-reducing bacteria (up to 1.2 x 10{sup 9} cells per gram soil) indicated that they possess extensive metabolic capacity to catalyze the reduction ofmore » iron minerals. In soils from the higher rainfall sites, measured rates of ferric iron reduction could account for up to 44 % of organic carbon oxidation. Iron reducers appeared to compete with methanogens when labile carbon availability was limited. We found large numbers of bacteria that oxidize reduced iron at sites with high rates of iron reduction and large numbers of iron-reducers. the coexistence of large populations of ironreducing and iron-oxidizing bacteria is evidence for rapid iron cycling between its reduced and oxidized states, and suggests that mutualistic interactions among these bacteria ultimately fuel organic carbon oxidation and inhibit CH4 production in these upland tropical forests.« less

Nanoscale and Microscale Iron Emulsions for Treating DNAPL

NASA Technical Reports Server (NTRS)

Geiger, Cherie L.

2002-01-01

This study demonstrated the feasibility of using emulsified nanoscale and microscale iron particles to enhance dehalogenation of (Dense Non-Aqueous Phase Liquid) DNAPL free-phase. The emulsified system consisted of a surfactant-stabilized, biodegradable oil-in-water emulsion with nanoscale or microscale iron particles contained within the emulsion droplets. It was demonstrated that DNAPLs, such as trichloroethene (TCE), diffuse through the oil membrane of the emulsion particle whereupon they reach an aqueous interior and the surface of an iron particle where dehalogenation takes place. The hydrocarbon reaction by-products of the dehalogenation reaction, primarily ethene (no chlorinated products detected), diffuse out of the emulsion droplet. This study also demonstrated that an iron-emulsion system could be delivered in-situ to the DNAPL pool in a soil matrix by using a simulated push well technique. Iron emulsions degraded pure TCE at a rate comparable to the degradation of dissolved phase TCE by iron particles, while pure iron had a very low degradation rate for free-phase TCE. The iron-emulsion systems can be injected into a sand matrix where they become immobilized and are not moved by flowing water. It has been documented that surfactant micelles possess the ability to pull pooled TCE into emulsion droplets where degradation of TCE takes place.

Long-term fertilization alters chemically-separated soil organic carbon pools: Based on stable C isotope analyses

NASA Astrophysics Data System (ADS)

Dou, Xiaolin; He, Ping; Cheng, Xiaoli; Zhou, Wei

2016-01-01

Quantification of dynamics of soil organic carbon (SOC) pools under the influence of long-term fertilization is essential for predicting carbon (C) sequestration. We combined soil chemical fractionation with stable C isotope analyses to investigate the C dynamics of the various SOC pools after 25 years of fertilization. Five types of soil samples (0-20, 20-40 cm) including the initial level (CK) and four fertilization treatments (inorganic nitrogen fertilizer, IN; balanced inorganic fertilizer, NPK; inorganic fertilizer plus farmyard manure, MNPK; inorganic fertilizer plus corn straw residue, SNPK) were separated into recalcitrant and labile fractions, and the fractions were analysed for C content, C:N ratios, δ13C values, soil C and N recalcitrance indexes (RIC and RIN). Chemical fractionation showed long-term MNPK fertilization strongly increased the SOC storage in both soil layers (0-20 cm = 1492.4 gC m2 and 20-40 cm = 1770.6 gC m2) because of enhanced recalcitrant C (RC) and labile C (LC). The 25 years of inorganic fertilizer treatment did not increase the SOC storage mainly because of the offsetting effects of enhanced RC and decreased LC, whereas no clear SOC increases under the SNPK fertilization resulted from the fast decay rates of soil C.

Long-term fertilization alters chemically-separated soil organic carbon pools: Based on stable C isotope analyses.

PubMed

Dou, Xiaolin; He, Ping; Cheng, Xiaoli; Zhou, Wei

2016-01-11

Quantification of dynamics of soil organic carbon (SOC) pools under the influence of long-term fertilization is essential for predicting carbon (C) sequestration. We combined soil chemical fractionation with stable C isotope analyses to investigate the C dynamics of the various SOC pools after 25 years of fertilization. Five types of soil samples (0-20, 20-40 cm) including the initial level (CK) and four fertilization treatments (inorganic nitrogen fertilizer, IN; balanced inorganic fertilizer, NPK; inorganic fertilizer plus farmyard manure, MNPK; inorganic fertilizer plus corn straw residue, SNPK) were separated into recalcitrant and labile fractions, and the fractions were analysed for C content, C:N ratios, δ(13)C values, soil C and N recalcitrance indexes (RIC and RIN). Chemical fractionation showed long-term MNPK fertilization strongly increased the SOC storage in both soil layers (0-20 cm = 1492.4 gC m(2) and 20-40 cm = 1770.6 gC m(2)) because of enhanced recalcitrant C (RC) and labile C (LC). The 25 years of inorganic fertilizer treatment did not increase the SOC storage mainly because of the offsetting effects of enhanced RC and decreased LC, whereas no clear SOC increases under the SNPK fertilization resulted from the fast decay rates of soil C.

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology

PubMed Central

Turan, Belma; Tuncay, Erkan

2017-01-01

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn2+. Although Zn2+ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn2+ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn2+ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn2+-diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn2+ in parallel to the discovery of subcellular localization of Zn2+-transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn2+ in excitation-contraction coupling in cardiomyocytes by shaping Ca2+ dynamics. Cellular labile Zn2+ is tightly regulated against its adverse effects through either Zn2+-transporters, Zn2+-binding molecules or Zn2+-sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn2+ distribution in cardiomyocytes and how a remodeling of cellular Zn2+-homeostasis can be important in proper cell function with Zn2+-transporters under hyperglycemia. We also emphasize the recent investigations on Zn2+-transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes. PMID:29137144

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology.

PubMed

Turan, Belma; Tuncay, Erkan

2017-11-12

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn 2+ . Although Zn 2+ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn 2+ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn 2+ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn 2+ -diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn 2+ in parallel to the discovery of subcellular localization of Zn 2+ -transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn 2+ in excitation-contraction coupling in cardiomyocytes by shaping Ca 2+ dynamics. Cellular labile Zn 2+ is tightly regulated against its adverse effects through either Zn 2+ -transporters, Zn 2+ -binding molecules or Zn 2+ -sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn 2+ distribution in cardiomyocytes and how a remodeling of cellular Zn 2+ -homeostasis can be important in proper cell function with Zn 2+ -transporters under hyperglycemia. We also emphasize the recent investigations on Zn 2+ -transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes.

DNA lability induced by nimustine and ramustine in rat glioma cells.

PubMed Central

Mineura, K; Fushimi, S; Itoh, Y; Kowada, M

1988-01-01

The DNA labile sites induced by two nitrosoureas, nimustine (ACNU) and ramustine (MCNU) synthesised in Japan, have been examined in highly reiterated DNA sequences of rat glioma cells. Reiterated fragments of 167 and 203 base pairs (bp), obtained after Hind III and Hae III restriction endonuclease digestion of rat glioma cells DNA, were used as target DNA sequences to determine the labile sites. In vitro reaction with ACNU and MCNU resulted in scission products corresponding to the locations of guanine. Subsequent piperidine hydrolysis produced more frequent breaks of the phosphodiester bonds at guanine positions, thus forming alkali-labile sites. Images PMID:3236017

Active carbon-pools in rhizosphere of wheat (Triticum aestivum L.) grown under elevated atmospheric carbon dioxide concentration in a Typic Haplustept in sub-tropical India.

PubMed

Kant, Pratap C B; Bhadraray, Subhendu; Purakayastha, T J; Jain, Vanita; Pal, Madan; Datta, S C

2007-05-01

Study on active and labile carbon-pools can serve as a clue for soil organic carbon dynamics on exposure to elevated level of CO2. Therefore, an experimental study was conducted in a Typic Haplustept in sub-tropical semi-arid India with wheat grown in open top chambers at ambient (370 micromol mol-1) and elevated (600 micromol mol-1) concentrations of atmospheric CO2. Elevated atmospheric CO2 caused increase in yield and carbon uptake by all plant parts, and their preferential partitioning to root. Increases in fresh root weight, volume and length have also been observed. Relative contribution of medium-sized root to total root length increased at the expense of very fine roots at elevated CO2 level. All active carbon-fractions gained due to elevated atmospheric CO2 concentration, and the order followed their relative labilities. All the C-pools have recorded a significant increase over initial status, and are expected to impart short-to-medium-term effect on soil carbon sequestration.

Elemental composition and functional groups in soil labile organic matter fractions

USDA-ARS?s Scientific Manuscript database

Labile organic matter fractions are major components involved in nutrient cycle in soil. In this chapter, we examine three labile organic matter fraction: light fraction (LF), humic acid (HA) and fulvic acid (HA) in Alabama cotton soils (ultisol) amended with chemical fertilizer (NH4NO3) and poult...

Maternal emotion socialization differentially predicts third-grade children's emotion regulation and lability.

PubMed

Rogers, Megan L; Halberstadt, Amy G; Castro, Vanessa L; MacCormack, Jennifer K; Garrett-Peters, Patricia

2016-03-01

Numerous parental emotion socialization factors have been implicated as direct and indirect contributors to the development of children's emotional competence. To date, however, no study has combined parents' emotion-related beliefs, behaviors, and regulation strategies in one model to assess their cumulative-as well as unique-contributions to children's emotion regulation. We considered the 2 components that have recently been distinguished: emotion regulation and emotional lability. We predicted that mothers' beliefs about the value of and contempt for children's emotions, mothers' supportive and nonsupportive reactions to their children's emotions, as well as mothers' use of cognitive reappraisal and suppression of their own emotions would each contribute unique variance to their children's emotion regulation and lability, as assessed by children's teachers. The study sample consisted of an ethnically and socioeconomically diverse group of 165 mothers and their third-grade children. Different patterns emerged for regulation and lability: Controlling for family income, child gender, and ethnicity, only mothers' lack of suppression as a regulatory strategy predicted greater emotion regulation in children, whereas mothers' valuing of children's emotions, mothers' lack of contempt for children's emotions, mothers' use of cognitive reappraisal to reinterpret events, and mothers' lack of emotional suppression predicted less lability in children. These findings support the divergence of emotion regulation and lability as constructs and indicate that, during middle childhood, children's lability may be substantially and uniquely affected by multiple forms of parental socialization. (c) 2016 APA, all rights reserved).

Proteomic analysis of human bladder epithelial cells by 2D blue native SDS-PAGE reveals TCDD-induced alterations of calcium and iron homeostasis possibly mediated by nitric oxide.

PubMed

Verma, Nisha; Pink, Mario; Petrat, Frank; Rettenmeier, Albert W; Schmitz-Spanke, Simone

2015-01-02

A proteomic analysis of the interaction among multiprotein complexes involved in 2,3,7,8-dibenzo-p-dioxin (TCDD)-mediated toxicity in urinary bladder epithelial RT4 cells was performed using two-dimensional blue native SDS-PAGE (2D BN/SDS-PAGE). To enrich the protein complexes, unexposed and TCDD-exposed cells were fractionated. BN/SDS-PAGE of the resulting fractions led to an effective separation of proteins and protein complexes of various origins, including cell membrane, mitochondria, and other intracellular compartments. Major differences between the proteome of control and exposed cells involved the alteration of many calcium-regulated proteins (calmodulin, protein S100-A2, annexin A5, annexin A10, gelsolin isoform b) and iron-regulated proteins (ferritin, heme-binding protein 2, transferrin). On the basis of these findings, the intracellular calcium concentration was determined, revealing a significant increase after 24 h of exposure to TCDD. Moreover, the concentration of the labile iron pool (LIP) was also significantly elevated in TCDD-exposed cells. This increase was strongly inhibited by the calmodulin (CaM) antagonist W-7, which pointed toward a possible interaction between iron and calcium signaling. Because nitric oxide (NO) production was significantly enhanced in TCDD-exposed cells and was also inhibited by W-7, we hypothesize that alterations in calcium and iron homeostasis upon exposure to TCDD may be linked through NO generated by CaM-activated nitric oxide synthase. In our model, we propose that NO produced upon TCDD exposure interacts with the iron centers of iron-regulatory proteins (IRPs) that modulate the alteration of ferritin and transferrin, resulting in an augmented cellular LIP and, hence, increased toxicity.

Effects of labile carbon addition on a headwater stream food web

Treesearch

Heidi S. Wilcox; J. Bruce Wallace; Judy L. Meyer; Jonathan P. Benstead

2005-01-01

We added dextrose for two 8-week periods (summer and autumn) to a highly heterotrophic headwater stream in North Carolina, U.S.A., to examine the responses of its benthic food web to increased labile carbon. We hypothesized that addition of labile carbon would elevate microbial abundance and activity, resulting in greater resource availability and higher...

Oxygen consumption and labile dissolved organic carbon uptake by benthic biofilms

NASA Astrophysics Data System (ADS)

de Falco, Natalie; Boano, Fulvio; Arnon, Shai

2015-04-01

Biogeochemical activity in streams is often magnified at interfaces, such as in the case of biofilm growth near the surface of the stream sediments. The objective of this study was to evaluate the relative importance of surficial biofilms versus the biofilm in the hyporheic zone to the processes of biodegradation of a labile dissolved organic carbon (DOC) and to oxygen consumption. Experiments were conducted in a recirculating flume, equipped with a drainage system that enables the control on losing and gaining fluxes. A surficial biofilm was developed over a sandy streambed with dune-shaped bed forms, by providing labile DOC (sodium benzoate) and nitrate. Homogeneously distributed biofilm was obtained by the same feeding strategy but with mixing the sediments manually on a daily basis. After the biofilm growth period, transformation of the labile DOC under different overlying velocities and losing or gaining fluxes was studied after spiking with sodium benzoate and by monitoring the decrease in DOC concentration in the bulk water over time using an online UV/Vis spectrophotometer. In addition, oxygen profiles across the water-streambed interface were measured at different locations along the bed form using oxygen microelectrodes. Preliminary results showed that the rate of labile DOC degradation increased exponentially with increasing overlying water velocity, regardless of the type of biofilm. Gaining and losing conditions did not play a critical role in the DOC degradation regardless of the type of biofilm, because the labile DOC was quickly utilized close to the surface. Under losing conditions, complete depletion of oxygen was observed within the top 5 millimeters, regardless of the biofilm type. In contrast, oxygen profiles under gaining condition showed an incomplete consumption of oxygen followed by an increase in the concentration of oxygen deeper in the sediments due to the upward flow of oxygenated groundwater. The results suggest that the transformation

Mobilization of Iron by Plant-Borne Coumarins.

PubMed

Tsai, Huei Hsuan; Schmidt, Wolfgang

2017-06-01

Iron is one of the most abundant elements in soils, but its low phytoavailability at high pH restricts plant communities on alkaline soils to taxa that have evolved efficient strategies to increase iron solubility. Recent evidence provides support for a previously underestimated role of root-secreted coumarins in mobilizing iron through reduction and chelation as part of an orchestrated strategy evolved to improve the acquisition of iron from recalcitrant pools. Understanding the mechanisms that tune the production of iron-mobilizing coumarins and their intricate interplay with other biosynthesis pathways could yield clues for deciphering the molecular basis of 'iron efficiency' - the ability of plants to thrive on soils with limited iron availability - and may open avenues for generating iron-fortified crops. Copyright © 2017 Elsevier Ltd. All rights reserved.

The five-factor model of impulsivity-like traits and emotional lability in aggressive behavior.

PubMed

Dvorak, Robert D; Pearson, Matthew R; Kuvaas, Nicholas J

2013-01-01

Factors that increase automatic psychological processes may result in impulsive action and, consequently, aggressive behavior. The current cross-sectional study examined the association between the five-factor model of impulsivity-like traits (negative urgency, positive urgency, premeditation, perseverance, and sensation seeking), emotional lability, and physically aggressive behaviors among college students (n = 481) in a negative binomial hurdle model. In the logistic portion of the model, emotional lability was related to a higher likelihood of engaging in aggressive acts in the past 6 months. The association between emotional lability and the likelihood of aggressive behavior was moderated by two impulsivity-like traits: negative urgency and positive urgency. Specifically, emotional lability was related to engaging in aggressive acts among those with high negative urgency, and among those with low positive urgency. In the count portion of the model, emotional lability was uniquely related to the number of aggressive acts in the past 6 months. Our results indicate that emotional lability and facets of impulsivity interactively relate to engagement in aggressive behavior, suggesting that these variables be integrated into models of aggression. © 2013 Wiley Periodicals, Inc.

Long-term fertilization alters chemically-separated soil organic carbon pools: Based on stable C isotope analyses

PubMed Central

Dou, Xiaolin; He, Ping; Cheng, Xiaoli; Zhou, Wei

2016-01-01

Quantification of dynamics of soil organic carbon (SOC) pools under the influence of long-term fertilization is essential for predicting carbon (C) sequestration. We combined soil chemical fractionation with stable C isotope analyses to investigate the C dynamics of the various SOC pools after 25 years of fertilization. Five types of soil samples (0–20, 20–40 cm) including the initial level (CK) and four fertilization treatments (inorganic nitrogen fertilizer, IN; balanced inorganic fertilizer, NPK; inorganic fertilizer plus farmyard manure, MNPK; inorganic fertilizer plus corn straw residue, SNPK) were separated into recalcitrant and labile fractions, and the fractions were analysed for C content, C:N ratios, δ13C values, soil C and N recalcitrance indexes (RIC and RIN). Chemical fractionation showed long-term MNPK fertilization strongly increased the SOC storage in both soil layers (0–20 cm = 1492.4 gC m2 and 20–40 cm = 1770.6 gC m2) because of enhanced recalcitrant C (RC) and labile C (LC). The 25 years of inorganic fertilizer treatment did not increase the SOC storage mainly because of the offsetting effects of enhanced RC and decreased LC, whereas no clear SOC increases under the SNPK fertilization resulted from the fast decay rates of soil C. PMID:26750143

Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mena, Natalia P.; Millennium Institute of Cell Dynamics and Biotechnology, Santiago; Bulteau, Anne Laure

2011-06-03

Highlights: {yields} Mitochondrial complex I inhibition resulted in decreased activity of Fe-S containing enzymes mitochondrial aconitase and cytoplasmic aconitase and xanthine oxidase. {yields} Complex I inhibition resulted in the loss of Fe-S clusters in cytoplasmic aconitase and of glutamine phosphoribosyl pyrophosphate amidotransferase. {yields} Consistent with loss of cytoplasmic aconitase activity, an increase in iron regulatory protein 1 activity was found. {yields} Complex I inhibition resulted in an increase in the labile cytoplasmic iron pool. -- Abstract: Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters aremore » involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given

Affect lability predicts occurrence of suicidal ideation in bipolar patients: a two-year prospective study.

PubMed

Ducasse, D; Jaussent, I; Guillaume, S; Azorin, J M; Bellivier, F; Belzeaux, R; Bougerol, T; Etain, B; Gard, S; Henry, C; Kahn, J P; Leboyer, M; Loftus, J; Passerieux, C; Olié, E; Courtet, P

2017-05-01

The aim of our study was to investigate, in bipolar patients, whether affect lability was associated with suicidal ideation incidence during 2-year follow-up, and which subtype of affect lability was associated with suicidal ideation. A total of 319 euthymic or mildly depressed bipolar outpatients recruited in the French FondaMental Advanced Centres of Expertise for Bipolar Disorder were divided into two subgroups according to the occurrence of suicidal ideation during a 2-year follow-up. Affect lability was assessed by the French version of the Affect Lability Scale. Bipolar patients with high affect lability were more likely to report suicidal ideation during follow-up, even after adjustment for age, study level, rapid cycling, current depression level, anxiety disorder, and lifetime history SA (OR = 2.47; 95% CI [1.15-5.30], P = 0.01). The risk of suicidal ideation increased with the level of affect lability. More specifically, the propensity to switch from neutral to elation affect, from anxious to depressive affect (or inversely), and from neutral to anger affect predicted suicidal ideation. Reducing affective lability could become a new therapeutic target of suicidal prevention in bipolar disorder. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Radiation-induced heat-labile sites that convert into DNA double-strand breaks

NASA Technical Reports Server (NTRS)

Rydberg, B.; Chatterjee, A. (Principal Investigator)

2000-01-01

The yield of DNA double-strand breaks (DSBs) in SV40 DNA irradiated in aqueous solution was found to increase by more than a factor of two as a result of postirradiation incubation of the DNA at 50 degrees C and pH 8.0 for 24 h. This is in agreement with data from studies performed at 37 degrees C that were published previously. Importantly, similar results were also obtained from irradiation of mammalian DNA in agarose plugs. These results suggest that heat-labile sites within locally multiply damaged sites are produced by radiation and are subsequently transformed into DSBs. Since incubation at 50 degrees C is typically employed for lysis of cells in commonly used pulsed-field gel assays for detection of DSBs in mammalian cells, the possibility that heat-labile sites are present in irradiated cells was also studied. An increase in the apparent number of DSBs as a function of lysis time at 50 degrees C was found with kinetics that was similar to that for irradiated DNA, although the magnitude of the increase was smaller. This suggests that heat-labile sites are also formed in the cell. If this is the case, a proportion of DSBs measured by the pulsed-field gel assays may occur during the lysis step and may not be present in the cell as breaks but as heat-labile sites. It is suggested that such sites consist mainly of heat-labile sugar lesions within locally multiply damaged sites. Comparing rejoining of DSBs measured with short and long lysis procedure indicates that the heat-labile sites are repaired with fast kinetics in comparison with repair of the bulk of DSBs.

Intravenous iron treatments for iron deficiency anemia in inflammatory bowel disease: a budget impact analysis of iron isomaltoside 1000 (Monofer) in the UK.

PubMed

Pollock, R F; Muduma, G

2017-12-01

Iron deficiency is the leading cause of anemia in patients with inflammatory bowel disease (IBD). Intravenous iron is the first-line treatment for clinically active IBD or previous oral iron intolerance. The aim of the present study was to develop a comparative model of iron deficiency and delivery for iron isomaltoside (IIM), ferric carboxymaltose (FCM), low molecular weight iron dextran (LMWID), and iron sucrose (IS) in the treatment of iron deficiency anemia associated with IBD. Areas covered: A model was developed to evaluate iron delivery characteristics, resource use and costs associated with IIM, FCM, LMWID and IS. Iron deficiency was modeled using dosing tables and retreatments were modeled based on a pooled retrospective analysis. The analyses were conducted over 5 years in patients with IBD with mean bodyweight of 75.4 kg and hemoglobin levels of 10.77 g/dL based on observational data. Expert opinion: The modeling analysis showed that using IIM required 1.2 infusions (per treatment) to correct the mean iron deficit, compared with 1.6, 1.2, and 7.1 with FCM, LMWID and IS, respectively. Costs were estimated to be 2,518 pounds sterling (GBP) per patient with IIM or LMWID, relative to GBP 3,309 with FCM or GBP 14,382 with IS.

In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu

PubMed Central

Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

2016-01-01

Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

Plant cell nucleolus as a hot spot for iron.

PubMed

Roschzttardtz, Hannetz; Grillet, Louis; Isaure, Marie-Pierre; Conéjéro, Geneviève; Ortega, Richard; Curie, Catherine; Mari, Stéphane

2011-08-12

Many central metabolic processes require iron as a cofactor and take place in specific subcellular compartments such as the mitochondrion or the chloroplast. Proper iron allocation in the different organelles is thus critical to maintain cell function and integrity. To study the dynamics of iron distribution in plant cells, we have sought to identify the different intracellular iron pools by combining three complementary imaging approaches, histochemistry, micro particle-induced x-ray emission, and synchrotron radiation micro X-ray fluorescence. Pea (Pisum sativum) embryo was used as a model in this study because of its large cell size and high iron content. Histochemical staining with ferrocyanide and diaminobenzidine (Perls/diaminobenzidine) strongly labeled a unique structure in each cell, which co-labeled with the DNA fluorescent stain DAPI, thus corresponding to the nucleus. The unexpected presence of iron in the nucleus was confirmed by elemental imaging using micro particle-induced x-ray emission. X-ray fluorescence on cryo-sectioned embryos further established that, quantitatively, the iron concentration found in the nucleus was higher than in the expected iron-rich organelles such as plastids or vacuoles. Moreover, within the nucleus, iron was particularly accumulated in a subcompartment that was identified as the nucleolus as it was shown to transiently disassemble during cell division. Taken together, our data uncover an as yet unidentified although abundant iron pool in the cell, which is located in the nuclei of healthy, actively dividing plant tissues. This result paves the way for the discovery of a novel cellular function for iron related to nucleus/nucleolus-associated processes.

[Effects of understory removal on soil labile organic carbon pool in a Cinnamomum camphora plantation].

PubMed

Wu, Ya-Cong; Li, Zheng-Cai; Cheng, Cai-Fang; Liu, Rong-Jie; Wang, Bin; Geri, Le-Tu

2013-12-01

Taking a 48-year-old Cinnamomum camphora plantation in the eastern area of our subtropics as test object, this paper studied the labile organic carbon contents and their ratios to the total organic carbon (TOC) in 0-60 cm soil layer under effects of understory removal (UR). As compared with no understory removal (CK), the soil TOC and easily-oxidized carbon (EOC) contents under UR decreased, with a decrement of 4.8% - 34.1% and 27.1% - 36.2%, respectively, and the TOC and EOC contents had a significant difference in 0-10 cm and 0-20 cm layers, respectively. The water-soluble organic carbon (WSOC) (except in 0-10 cm and 10-20 cm layers) and light fraction organic matter (LFOM) under UR increaesd, but the difference was not significant. The ratio of soil WSOC to soil TOC in UR stand was higher than that in CK stand, while the ratio of soil EOC to soil TOC showed an opposite trend. In the two stands, soil WSOC, EOC, and LFOM had significant or extremely significant correlations with soil TOC, and the correlation coefficients of soil EOC and LFOM with soil TOC were higher in UR stand than in CK, but the correlation coefficient between soil WSOC and TOC was in opposite. The soil EOC, LFOM, and TOC in the two stands were significantly or extremely significantly correlated with soil nutrients, but the soil WSOC in UR stand had no significant correlations with soil hydrolyzable N, available P, exchangeable Ca, and exchangeable Mg.

Phaeochromocytoma presenting with labile blood pressures following coronary artery bypass grafting.

PubMed

Roy, James; Akhunji, Zakir; Kushwaha, Virag; Mackie, James; Jepson, Nigel

2016-12-01

Pheochromocytomas have been reported prior to and during coronary artery bypass surgery. We present a patient with an undiagnosed pheochromocytoma who presented with labile hypertension following coronary artery bypass surgery. This case calls attention to the inclusion of an undiagnosed pheochromocytoma in the differential diagnosis for all patients who develop labile hypertension in the postoperative period following cardiac surgery. © 2016 Wiley Periodicals, Inc.

Effects of composition of labile organic matter on biogenic production of methane in the coastal sediments of the Arabian Sea.

PubMed

Gonsalves, Maria-Judith; Fernandes, Christabelle E G; Fernandes, Sheryl Oliveira; Kirchman, David L; Bharathi, P A Loka

2011-11-01

Coastal regions are potential zones for production of methane which could be governed by ecological/environmental differences or even sediment properties of a niche. In order to test the hypothesis that methanogenesis in most marine sediments could be driven more by proteins than by carbohydrates and lipid content of labile organic matter (LOM), incubation experiments were carried out with sediments from different environmental niches to measure methane production. The methane production rates were examined in relationship to the sediment biochemistry, i.e., carbohydrates, proteins, and lipids. The gas production measured by head space method ranged from 216 ng g( -1) day( -1) in the mangrove sediments to 3.1 μg g( -1) day( -1) in the shallow Arabian Sea. LOM ranged from 1.56 to 2.85 mg g( -1) in the shallow Arabian Sea, from 3.35 to 5.43 mg g( -1) in the mangrove estuary, and from 0.66 to 0.70 mg g( -1) in the sandy sediments with proteins contributing maximum to the LOM pool. Proteins influenced methane production in the clayey sediments of shallow depths of the Arabian Sea (r = 0.933, p < 0.001) and mangrove estuary (r = 0.981, p < 0.001) but in the sandy beach sediments, carbohydrates (r = 0.924, p < 0.001) governed the net methane production. The gas production was more pronounced in shallow and surface sediments and it decreased with depth apparently governed by the decrease in lability index. Thus, the lability index and protein content are important factors that determine methane production rates in these coastal ecosystems.

Mechanism of Stabilization of Labile Compounds by Silk Fibroin Proteins

DTIC Science & Technology

2017-04-05

AFRL-AFOSR-VA-TR-2017-0076 Mechanism of Stabilization of Labile Compounds by Silk Fibroin Proteins David Kaplan TRUSTEES OF TUFTS COLEGE INC 169... Proteins 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0015 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) David Kaplan 5d.  PROJECT NUMBER 5e...objective of this research was to elucidate the fundamental mechanisms by which labile compounds are entrapped and stabilized by silk fibroin protein . The

Soil organic carbon stabilization by iron in permafrost regions of the Qinghai-Tibet Plateau

NASA Astrophysics Data System (ADS)

Mu, C. C.; Zhang, T. J.; Zhao, Q.; Guo, H.; Zhong, W.; Su, H.; Wu, Q. B.

2016-10-01

A close relationship exists between soil organic carbon (SOC) and reactive iron; however, little is known about the role of iron in SOC preservation in permafrost regions. We determined the amount of SOC associated with reactive iron phases (OC-Fe) in the permafrost regions of the Qinghai-Tibetan Plateau (QTP). The results showed that the percentage of OC-Fe ranged between 0.9% and 59.5% in the upper 30 cm of soil and that the OC-Fe represented 19.5 ± 12.3% of the total SOC pool. No clear vertical distribution pattern in OC-Fe was present in the upper 1 m of soil. Throughout the year, the OC-Fe accounted for relatively stable proportions of the total SOC pool. This study suggests that approximately 20% of SOC is a potential rusty OC pool in the permafrost regions of the QTP. Biogeochemical processes related to the reaction of iron may play important roles in soil carbon cycles in permafrost regions.

How to Compute Labile Metal-Ligand Equilibria

ERIC Educational Resources Information Center

de Levie, Robert

2007-01-01

The different methods used for computing labile metal-ligand complexes, which are suitable for an iterative computer solution, are illustrated. The ligand function has allowed students to relegate otherwise tedious iterations to a computer, while retaining complete control over what is calculated.

Labile rhizosphere soil solution fraction for prediction of bioavailability of heavy metals and rare earth elements to plants.

PubMed

Shan, Xiao-Quan; Wang, Zhongwen; Wang, Weisheng; Zhang, Shuzhen; Wen, Bei

2003-02-01

A labile rhizosphere soil solution fraction has been recommended to predict the bioavailability of heavy metals and rare earth elements to plants. This method used moist rhizosphere soil in combination with a mixture of 0.01 mol L(-1) of low-molecular-weight organic acids (LMWOAs) as extractant. The extracted soil solutions were fractionated into two colloidal fractions of <0.45 microm (F(3)) and <0.2 microm (F(2)), and one truly dissolved fraction including free metal ions and inorganic and organic complexes (fractionlabile rhizosphere soil solution fraction, F(lrss). For the soil solutions extracted with a mixture of LMWOAs the concentrations of heavy metals and rare earth elements in F(2) and F(3) were quite similar. However, the mean concentrations of Cr, Ni, Zn, Cu, Pb, Cd, La, Ce, Pr, and Nd in F(lrss) accounted for 79.9%, 91.3%, 90.8%, 60.1%, 77.5%, 75.3%, 81.2%, 77.2%, 80.3%, and 79.5%, respectively, of their concentrations in F(2). In contrast, there were no differences in the extractable metal concentrations between the three fractions while the first step of the method recommended by the European Community of Reference (BCR), where 0.1 mol L(-1) acetic acid was used as an extractant. The single correlation analysis was made between metal concentrations in the different fractions of soil solutions and their concentrations in wheat. If the first step of BCR method was used there was no good correlation between heavy metals in soil pools and that in wheat shoots and roots. When LMWAOs were used a good correlation was obtained between the concentrations of heavy metals in soil pools and that in wheat roots, which followed a general order of r(1 kD, LMWOAs) >r(0.2 microm, LMWOAs) approximately r(0.45 microm, LMWOAs). In the case of rare earth elements the good correlation was obtained for both the wheat roots and shoots. Generally, the correlation coefficients

Bmp6 Regulates Retinal Iron Homeostasis and Has Altered Expression in Age-Related Macular Degeneration

PubMed Central

Hadziahmetovic, Majda; Song, Ying; Wolkow, Natalie; Iacovelli, Jared; Kautz, Leon; Roth, Marie-Paule; Dunaief, Joshua L.

2011-01-01

Iron-induced oxidative stress causes hereditary macular degeneration in patients with aceruloplasminemia. Similarly, retinal iron accumulation in age-related macular degeneration (AMD) may exacerbate the disease. The cause of retinal iron accumulation in AMD is poorly understood. Given that bone morphogenetic protein 6 (Bmp6) is a major regulator of systemic iron, we examined the role of Bmp6 in retinal iron regulation and in AMD pathogenesis. Bmp6 was detected in the retinal pigment epithelium (RPE), a major site of pathology in AMD. In cultured RPE cells, Bmp6 was down-regulated by oxidative stress and up-regulated by iron. Intraocular Bmp6 protein injection in mice up-regulated retinal hepcidin, an iron regulatory hormone, and altered retinal labile iron levels. Bmp6−/− mice had age-dependent retinal iron accumulation and degeneration. Postmortem RPE from patients with early AMD exhibited decreased Bmp6 levels. Because oxidative stress is associated with AMD pathogenesis and down-regulates Bmp6 in cultured RPE cells, the diminished Bmp6 levels observed in RPE cells in early AMD may contribute to iron build-up in AMD. This may in turn propagate a vicious cycle of oxidative stress and iron accumulation, exacerbating AMD and other diseases with hereditary or acquired iron excess. PMID:21703414

Microbial formation of labile organic carbon in Antarctic glacial environments

USGS Publications Warehouse

Smith, H.J.; Foster, R.; McKnight, D.M.; Lisle, John T.; Littmann, S.; Kuypers, M.M.M.; Foreman, C.M.

2017-01-01

Roughly six petagrams of organic carbon are stored within ice worldwide. This organic carbon is thought to be of old age and highly bioavailable. Along with storage of ancient and new atmospherically deposited organic carbon, microorganisms may contribute substantially to the glacial organic carbon pool. Models of glacial microbial carbon cycling vary from net respiration to net carbon fixation. Supraglacial streams have not been considered in models although they are amongst the largest ecosystems on most glaciers and are inhabited by diverse microbial communities. Here we investigate the biogeochemical sequence of organic carbon production and uptake in an Antarctic supraglacial stream in the McMurdo Dry Valleys using nanometre-scale secondary ion mass spectrometry, fluorescence spectroscopy, stable isotope analysis and incubation experiments. We find that heterotrophic production relies on highly labile organic carbon freshly derived from photosynthetic bacteria rather than legacy organic carbon. Exudates from primary production were utilized by heterotrophs within 24 h, and supported bacterial growth demands. The tight coupling of microbially released organic carbon and rapid uptake by heterotrophs suggests a dynamic local carbon cycle. Moreover, as temperatures increase there is the potential for positive feedback between glacial melt and microbial transformations of organic carbon.

Effect of exogenous phosphate on the lability and phytoavailability of arsenic in soils.

PubMed

Wang, Jinjin; Zeng, Xibai; Zhang, Hao; Li, Yongtao; Zhao, Shizhen; Su, Shiming; Bai, Lingyu; Wang, Yanan; Zhang, Tuo

2018-04-01

The effect of exogenous phosphate (P, 200 mg⋅kg -1 soil) on the lability and phytoavailability of arsenic (As) was studied using the diffusive gradients in thin films (DGT) technique. Lettuce were grown on the As-amended soils following the stabilization of soil labile As after 90 days incubation. Phosphate (P) application generally facilitated plant growth except one grown on P-sufficient soil. Soil labile As concentration increased in all the soils after P application due to a competition effect. Plant As concentration increased in red soils collected from Hunan Province, while decreases were observed in the other soils. Even though, an overall trend of decrease was obtained in As phytoavailability along with the increase of DGT-measured soil labile P/As molar ratio. The functional equation between P/As and As phytoavailability provided a critical value of 1.7, which could be used as a guidance for rational P fertilization, thus avoiding overfertilization. Copyright © 2018 Elsevier Ltd. All rights reserved.

Using isotopic dilution to assess chemical extraction of labile Ni, Cu, Zn, Cd and Pb in soils.

PubMed

Garforth, J M; Bailey, E H; Tye, A M; Young, S D; Lofts, S

2016-07-01

Chemical extractants used to measure labile soil metal must ideally select for and solubilise the labile fraction, with minimal solubilisation of non-labile metal. We assessed four extractants (0.43 M HNO3, 0.43 M CH3COOH, 0.05 M Na2H2EDTA and 1 M CaCl2) against these requirements. For soils contaminated by contrasting sources, we compared isotopically exchangeable Ni, Cu, Zn, Cd and Pb (EValue, mg kg(-1)), with the concentrations of metal solubilised by the chemical extractants (MExt, mg kg(-1)). Crucially, we also determined isotopically exchangeable metal in the soil-extractant systems (EExt, mg kg(-1)). Thus 'EExt - EValue' quantifies the concentration of mobilised non-labile metal, while 'EExt - MExt' represents adsorbed labile metal in the presence of the extractant. Extraction with CaCl2 consistently underestimated EValue for Ni, Cu, Zn and Pb, while providing a reasonable estimate of EValue for Cd. In contrast, extraction with HNO3 both consistently mobilised non-labile metal and overestimated the EValue. Extraction with CH3COOH appeared to provide a good estimate of EValue for Cd; however, this was the net outcome of incomplete solubilisation of labile metal, and concurrent mobilisation of non-labile metal by the extractant (MExtEValue). The Na2H2EDTA extractant mobilised some non-labile metal in three of the four soils, but consistently solubilised the entire labile fraction for all soil-metal combinations (MExt ≈ EExt). Comparison of EValue, MExt and EExt provides a rigorous means of assessing the underlying action of soil chemical extraction methods and could be used to refine long-standing soil extraction methodologies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preservation of labile organic matter in soils of drained thaw lakes in Northern Alaska

NASA Astrophysics Data System (ADS)

Mueller, Carsten W.; Rethemeyer, Janet; Kao-Kniffin, Jenny; Löppmann, Sebastian; Hinkel, Kenneth; Bockheim, James

2014-05-01

A large number of studies predict changing organic matter (OM) dynamics in arctic soils due to global warming. In contrast to rather slowly altering bulk soil properties, single soil organic matter (SOM) fractions can provide a more detailed picture of the dynamics of differently preserved SOM pools in climate sensitive arctic regions. By the study of the chemical composition of such distinctive SOM fractions using nuclear magnetic resonance spectroscopy (NMR) together with radiocarbon analyses it is possible to evaluate the stability of the major OM pools. Approximately 50-75% of Alaska's Arctic Coastal Plain is covered with thaw lakes and drained thaw lakes that follow a 5,000 yr cycle of development (between creation and final drainage), thus forming a natural soil chronosequence. The drained thaw lakes offer the possibility to study SOM dynamics affected by permafrost processes over millennial timescales. In April 2010 we sampled 16 soil cores (including the active and permanent layer) reaching from young drained lakes (0-50 years since drainage) to ancient drained lakes (3000-5500 years since drainage). Air dried soil samples from soil horizons of the active and permanent layer were subjected to density fractionation in order to differentiate particulate OM and mineral associated OM. The chemical composition of the SOM fractions was analyzed by 13C CPMAS NMR spectroscopy. For a soil core of a young and an ancient drained thaw lake basin we also analyzed the 14C content. For the studied soils we can show that up to over 25 kg OC per square meter are stored mostly as labile, easily degradable organic matter rich in carbohydrates. In contrast only 10 kg OC per square meter were sequestered as presumably more stable mineral associated OC dominated by aliphatic compounds. Comparable to soils of temperate regions, we found small POM (< 20 µm) occluded in aggregated soil structures which differed in the chemical composition from larger organic particles. This was

Zooplankton Gut Passage Mobilizes Lithogenic Iron for Ocean Productivity.

PubMed

Schmidt, Katrin; Schlosser, Christian; Atkinson, Angus; Fielding, Sophie; Venables, Hugh J; Waluda, Claire M; Achterberg, Eric P

2016-10-10

Iron is an essential nutrient for phytoplankton, but low concentrations limit primary production and associated atmospheric carbon drawdown in large parts of the world's oceans [1, 2]. Lithogenic particles deriving from aeolian dust deposition, glacial runoff, or river discharges can form an important source if the attached iron becomes dissolved and therefore bioavailable [3-5]. Acidic digestion by zooplankton is a potential mechanism for iron mobilization [6], but evidence is lacking. Here we show that Antarctic krill sampled near glacial outlets at the island of South Georgia (Southern Ocean) ingest large amounts of lithogenic particles and contain 3-fold higher iron concentrations in their muscle than specimens from offshore, which confirms mineral dissolution in their guts. About 90% of the lithogenic and biogenic iron ingested by krill is passed into their fecal pellets, which contain ∼5-fold higher proportions of labile (reactive) iron than intact diatoms. The mobilized iron can be released in dissolved form directly from krill or via multiple pathways involving microbes, other zooplankton, and krill predators. This can deliver substantial amounts of bioavailable iron and contribute to the fertilization of coastal waters and the ocean beyond. In line with our findings, phytoplankton blooms downstream of South Georgia are more intensive and longer lasting during years with high krill abundance on-shelf. Thus, krill crop phytoplankton but boost new production via their nutrient supply. Understanding and quantifying iron mobilization by zooplankton is essential to predict ocean productivity in a warming climate where lithogenic iron inputs from deserts, glaciers, and rivers are increasing [7-10]. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quantification and characterization of chemically-and thermally-labile and recalcitrant biochar fractions.

PubMed

Bakshi, Santanu; Banik, Chumki; Laird, David A

2018-03-01

The C:N ratios of biochar labile fractions is important for assessing biochar stability and N cycling in soil. Here we compare chemically and thermally labile fractions for nine biochars produced from five biomass feedstocks using four production techniques. Biochar fractionation methods included proximate analysis, hot water extraction, acid and base extractions (0.05 M, 0.5 M, 1 M, 2 M, 3 M, and 6 M of either H 2 SO 4 or NaOH), and oxidation with 15% H 2 O 2 and 0.33 M KMnO 4 (pH 7.2). Results show chemical addition reactions cause underestimation of mass of the labile fraction for chemical extraction and oxidation procedures but not the thermal procedure. Estimates of C and N in labile and recalcitrant fractions were not adversely affected by addition reactions, because solvents were independent of C or N. Results indicate that herbaceous biochars may be a source of N fertility while hardwood biochars may immobilize N during the first few years after biochar application to soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Freezing-Enhanced Dissolution of Iron Oxides: Effects of Inorganic Acid Anions.

PubMed

Jeong, Daun; Kim, Kitae; Min, Dae Wi; Choi, Wonyong

2015-11-03

Dissolution of iron from mineral dust particles greatly depends upon the type and amount of copresent inorganic anions. In this study, we investigated the roles of sulfate, chloride, nitrate, and perchlorate on the dissolution of maghemite and lepidocrocite in ice under both dark and UV irradiation and compared the results with those of their aqueous counterparts. After 96 h of reaction, the total dissolved iron in ice (pH 3 before freezing) was higher than that in the aqueous phase (pH 3) by 6-28 times and 10-20 times under dark and UV irradiation, respectively. Sulfuric acid was the most efficient in producing labile iron under dark condition, whereas hydrochloric acid induced the most dissolution of the total and ferrous iron in the presence of light. This ice-induced dissolution result was also confirmed with Arizona Test Dust (AZTD). In the freeze-thaw cycling test, the iron oxide samples containing chloride, nitrate, or perchlorate showed a similar extent of total dissolved iron after each cycling while the sulfate-containing sample rapidly lost its dissolution activity with repeating the cycle. This unique phenomenon observed in ice might be related to the freeze concentration of protons, iron oxides, and inorganic anions in the liquid-like ice grain boundary region. These results suggest that the ice-enhanced dissolution of iron oxides can be a potential source of bioavailable iron, and the acid anions critically influence this process.

Childhood Maltreatment, Emotional Lability, and Alcohol Problems in Young Adults At-Risk for ADHD: Testing Moderation and Moderated Moderation.

PubMed

Bunford, Nóra; Wymbs, Brian T; Dawson, Anne E; Shorey, Ryan C

2017-01-01

Childhood maltreatment and alcohol problems are common among young adults with attention-deficit hyperactivity disorder (ADHD). However, little is known about the degree to which maltreatment and alcohol problems are associated; potential pertinent mediating or moderating mechanisms, such as emotional lability; and whether this association varies by sex. We examined, in a sample of adults at risk for ADHD (N = 122, 37% male), the association between childhood maltreatment and alcohol problems, whether emotional lability mediated or moderated this association, and whether either role of emotional lability differed between men and women. Emotional lability moderated the association between emotional neglect and alcohol problems; maltreatment increased risk for alcohol problems for those scoring high tovery high on emotional lability, but not for those with very low-moderate levels. The association between emotional abuse and alcohol problems depended both on emotional lability and sex; emotional abuse decreased the risk for alcohol problems among men very low/low on emotional lability, but not for men who were moderate to very high on emotional lability, or for women. These findings have implications for the way in which targeting maltreatment and emotional lability may be incorporated into prevention and intervention programs to prevent alcohol problems among men and women at risk for ADHD.

Transcriptome response of high- and low-light-adapted Prochlorococcus strains to changing iron availability

PubMed Central

Thompson, Anne W; Huang, Katherine; Saito, Mak A; Chisholm, Sallie W

2011-01-01

Prochlorococcus contributes significantly to ocean primary productivity. The link between primary productivity and iron in specific ocean regions is well established and iron limitation of Prochlorococcus cell division rates in these regions has been shown. However, the extent of ecotypic variation in iron metabolism among Prochlorococcus and the molecular basis for differences is not understood. Here, we examine the growth and transcriptional response of Prochlorococcus strains, MED4 and MIT9313, to changing iron concentrations. During steady state, MIT9313 sustains growth at an order-of-magnitude lower iron concentration than MED4. To explore this difference, we measured the whole-genome transcriptional response of each strain to abrupt iron starvation and rescue. Only four of the 1159 orthologs of MED4 and MIT9313 were differentially expressed in response to iron in both strains. However, in each strain, the expression of over a hundred additional genes changed, many of which are in labile genomic regions, suggesting a role for lateral gene transfer in establishing diversity of iron metabolism among Prochlorococcus. Furthermore, we found that MED4 lacks three genes near the iron-deficiency-induced gene (idiA) that are present and induced by iron stress in MIT9313. These genes are interesting targets for studying the adaptation of natural Prochlorococcus assemblages to local iron conditions as they show more diversity than other genomic regions in environmental metagenomic databases. PMID:21562599

A Longitudinal Study of Emotion Regulation, Emotion Lability/Negativity, and Internalizing Symptomatology in Maltreated and Nonmaltreated Children

PubMed Central

Kim-Spoon, Jungmeen; Cicchetti, Dante; Rogosch, Fred A.

2013-01-01

The longitudinal contributions of emotion regulation and emotion lability/negativity to internalizing symptomatology were examined in a low-income sample (171 maltreated and 151 nonmaltreated children, from age 7 to 10 years). Latent difference score models indicated that, for both maltreated and nonmaltreated children, emotion regulation was a mediator between emotion lability/negativity and internalizing symptomatology, whereas emotion lability/negativity was not a mediator between emotion regulation and internalizing symptomatology. Early maltreatment was associated with high emotion lability/negativity (age 7) that contributed to poor emotion regulation (age 8), which in turn was predictive of increases in internalizing symptomatology (from age 8 to 9). The results imply important roles of emotion regulation in the development of internalizing symptomatology, especially for children with high emotion lability/negativity. PMID:23034132

'Inconstant males' and the maintenance of labile sex expression in subdioecious plants.

PubMed

Ehlers, Bodil K; Bataillon, Thomas

2007-01-01

* Here, we evaluate the role of pollen limitation and selfing in the maintenance of labile sex expression in subdioecious plant species. * We used a literature survey to explore which factors correlated with a significant occurrence of hermaphrodites in dioecious species. We developed models to explore the selective maintenance of labile sex expression. The models had similar ecological assumptions but differed in the genetic basis of sex lability. * We found that a significant frequency of hermaphrodites was associated with animal pollination, and that hermaphrodites were 'inconstant' males with perfect flowers, suggesting evolution through the gynodioecious pathway. Models showed that a modifier converting pure males into inconstant males could be maintained under a wide range of reduction in both male and female fitness. Pollen limitation and self-fertilization facilitated invasion of the modifier. Depending on the genetics of sex determination, we found pure dioecy, stable subdioecy (trioecy), and situations where inconstant males coexisted with either pure females or pure males. Under selfing and pollen limitation, certain conditions selected for inconstant males which will drive populations to extinction. * We discuss our results in relation to the evolution towards, and the breakdown of, dioecy, and the ecological and evolutionary implications of labile sex expression.

Submillimeter-scale heterogeneity of labile phosphorus in sediments characterized by diffusive gradients in thin films and spatial analysis.

PubMed

Meng, Yuting; Ding, Shiming; Gong, Mengdan; Chen, Musong; Wang, Yan; Fan, Xianfang; Shi, Lei; Zhang, Chaosheng

2018-03-01

Sediments have a heterogeneous distribution of labile redox-sensitive elements due to a drastic downward transition from oxic to anoxic condition as a result of organic matter degradation. Characterization of the heterogeneous nature of sediments is vital for understanding of small-scale biogeochemical processes. However, there are limited reports on the related specialized methodology. In this study, the monthly distributions of labile phosphorus (P), a redox-sensitive limiting nutrient, were measured in the eutrophic Lake Taihu by Zr-oxide diffusive gradients in thin films (Zr-oxide DGT) on a two-dimensional (2D) submillimeter level. Geographical information system (GIS) techniques were used to visualize the labile P distribution at such a micro-scale, showing that the DGT-labile P was low in winter and high in summer. Spatial analysis methods, including semivariogram and Moran's I, were used to quantify the spatial variation of DGT-labile P. The distribution of DGT-labile P had clear submillimeter-scale spatial patterns with significant spatial autocorrelation during the whole year and displayed seasonal changes. High values of labile P with strong spatial variation were observed in summer, while low values of labile P with relatively uniform spatial patterns were detected in winter, demonstrating the strong influences of temperature on the mobility and spatial distribution of P in sediment profiles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dietary zinc and iron intake and risk of depression: A meta-analysis.

PubMed

Li, Zongyao; Li, Bingrong; Song, Xingxing; Zhang, Dongfeng

2017-05-01

The associations between dietary zinc and iron intake and risk of depression remain controversial. Thus, we carried out a meta-analysis to evaluate these associations. A systematic search was performed in PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI) and Wanfang databases for relevant studies up to January 2017. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random effects model. A total of 9 studies for dietary zinc intake and 3 studies for dietary iron intake were finally included in present meta-analysis. The pooled RRs with 95% CIs of depression for the highest versus lowest dietary zinc and iron intake were 0.67 (95% CI: 0.58-0.76) and 0.57 (95% CI: 0.34-0.95), respectively. In subgroup analysis by study design, the inverse association between dietary zinc intake and risk of depression remained significant in the cohort studies and cross-sectional studies. The pooled RRs (95% CIs) for depression did not substantially change in the influence analysis and subgroup analysis by adjustment for body mass index (BMI). The present meta-analysis indicates inverse associations between dietary zinc and iron intake and risk of depression. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Partial coupling and differential regulation of biologically and photo-chemically labile dissolved organic carbon across boreal aquatic networks

NASA Astrophysics Data System (ADS)

Lapierre, J.-F.; del Giorgio, P. A.

2014-05-01

Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC in aquatic environments, little is known on the large-scale patterns in biologically and photo-chemically degradable DOC (Bd-DOC and Pd-DOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explore the patterns of Bd- and Pd-DOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophy and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of Bd- and Pd-DOC co-varied across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM, identified by fluorescence analyses) in ambient waters. A combination of nutrients and protein-like DOM explained nearly half of the variation in Bd-DOC, whereas Pd-DOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific fluorescent DOM (FDOM) pools that we experimentally determined. The concentrations of colored DOM (CDOM), a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both Bd- and Pd-DOC. The concentrations of CDOM and of the putative bio-labile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in browner streams and wetlands. This suggests a baseline autochthonous Bd-DOC pool fuelled by internal production that is gradually overwhelmed by land-derived Bd-DOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photo-chemically degradable DOC for continental watersheds resulted in a partial coupling of those carbon pools in

Labile dissolved organic carbon supply limits hyporheic denitrification

Treesearch

Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

2012-01-01

We used an in situ steady state 15N-labeled nitrate and acetate well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon as acetate influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream.

Low C/N ratio raw textile wastewater reduced labile C and enhanced organic-inorganic N and enzymatic activities in a semiarid alkaline soil.

PubMed

Roohi, Mahnaz; Riaz, Muhammad; Arif, Muhammad Saleem; Shahzad, Sher Muhammad; Yasmeen, Tahira; Ashraf, Muhammad Arslan; Riaz, Muhammad Atif; Mian, Ishaq A

2017-02-01

Application of raw and treated wastewater for irrigation is an extensive practice for agricultural production in arid and semiarid regions. Raw textile wastewater has been used for cultivation in urban and peri-urban areas in Pakistan without any systematic consideration to soil quality. We conducted a laboratory incubation study to investigate the effects of low C/N ratio raw textile wastewater on soil nitrogen (N) contents, labile carbon (C) as water-soluble C (WSC) contents, and activities of urease and dehydrogenase enzymes. The 60-day incubation study used an alkaline clay loam aridisol that received 0 (distilled water), 25, 50, and 100% wastewater concentrations, and microcosms were incubated aerobically under room temperature at 70% water holding capacity. Results revealed that raw wastewater significantly (p < 0.05) changed soil N pools and processes, WSC contents, and enzymatic activities. The organic and inorganic N species increased with increasing wastewater concentrations, whereas WSC contents followed an opposite trend. The highest NH 4 + -N and NO 3 - -N contents were observed in soil treated with 100% wastewater. The extractable organic N (EON) contents always represented >50% of the soil total Kjeldahl N (TKN) contents and served as the major N pool. However, nitrification index (NO 3 - -N/NH 4 + -N ratio) decreased at high wastewater concentrations. A significant negative correlation was observed between EON and WSC (p < 0.05) and between net nitrification and WSC/EON ratio (p < 0.01). In contrast, nitrification index and WSC contents were correlated, positively suggesting WSC potentially controlling N turnover in nutrient-poor aridisol. We found significant (p < 0.0001) positive correlations of soil urease and dehydrogenase enzymatic activities with soil-extractable mineral N contents indicating coupled N cycling and soil biological activity. Higher production and accumulation of soil NO 3 - -N and EON contents in concentrated wastewater

PTSD, alcohol dependence, and conduct problems: Distinct pathways via lability and disinhibition.

PubMed

Simons, Jeffrey S; Simons, Raluca M; O'Brien, Carol; Stoltenberg, Scott F; Keith, Jessica A; Hudson, Jaime A

2017-01-01

This study tested the role of affect lability and disinhibition in mediating associations between PTSD symptoms and two forms of alcohol-related problems, dependence syndrome symptoms (e.g., impaired control over consumption) and conduct problems (e.g., assault, risk behaviors). Genotype at the serotonin transporter linked polymorphic region (5-HTTLPR) was hypothesized to moderate associations between traumatic stress and PTSD symptoms. In addition, the study tested whether childhood traumatic stress moderated associations between combat trauma and PTSD symptoms. Participants were 270 OIF/OEF/OND veterans. The hypothesized model was largely supported. Participants with the low expression alleles of 5-HTTLPR (S or L G ) exhibited stronger associations between childhood (but not combat) traumatic stress and PTSD symptoms. Affect lability mediated the associations between PTSD symptoms and alcohol dependence symptoms. Behavioral disinhibition mediated associations between PTSD symptoms and conduct related problems. Conditional indirect effects indicated stronger associations between childhood traumatic stress and lability, behavioral disinhibition, alcohol consumption, AUD symptoms, and associated conduct problems via PTSD symptoms among those with the low expression 5-HTTLPR alleles. However, interactions between combat trauma and either childhood trauma or genotype were not significant. The results support the hypothesis that affect lability and behavioral disinhibition are potential intermediate traits with distinct associations with AUD and associated externalizing problems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modelling Systemic Iron Regulation during Dietary Iron Overload and Acute Inflammation: Role of Hepcidin-Independent Mechanisms.

PubMed

Enculescu, Mihaela; Metzendorf, Christoph; Sparla, Richard; Hahnel, Maximilian; Bode, Johannes; Muckenthaler, Martina U; Legewie, Stefan

2017-01-01

Systemic iron levels must be maintained in physiological concentrations to prevent diseases associated with iron deficiency or iron overload. A key role in this process plays ferroportin, the only known mammalian transmembrane iron exporter, which releases iron from duodenal enterocytes, hepatocytes, or iron-recycling macrophages into the blood stream. Ferroportin expression is tightly controlled by transcriptional and post-transcriptional mechanisms in response to hypoxia, iron deficiency, heme iron and inflammatory cues by cell-autonomous and systemic mechanisms. At the systemic level, the iron-regulatory hormone hepcidin is released from the liver in response to these cues, binds to ferroportin and triggers its degradation. The relative importance of individual ferroportin control mechanisms and their interplay at the systemic level is incompletely understood. Here, we built a mathematical model of systemic iron regulation. It incorporates the dynamics of organ iron pools as well as regulation by the hepcidin/ferroportin system. We calibrated and validated the model with time-resolved measurements of iron responses in mice challenged with dietary iron overload and/or inflammation. The model demonstrates that inflammation mainly reduces the amount of iron in the blood stream by reducing intracellular ferroportin transcription, and not by hepcidin-dependent ferroportin protein destabilization. In contrast, ferroportin regulation by hepcidin is the predominant mechanism of iron homeostasis in response to changing iron diets for a big range of dietary iron contents. The model further reveals that additional homeostasis mechanisms must be taken into account at very high dietary iron levels, including the saturation of intestinal uptake of nutritional iron and the uptake of circulating, non-transferrin-bound iron, into liver. Taken together, our model quantitatively describes systemic iron metabolism and generated experimentally testable predictions for additional

Modelling Systemic Iron Regulation during Dietary Iron Overload and Acute Inflammation: Role of Hepcidin-Independent Mechanisms

PubMed Central

Sparla, Richard; Hahnel, Maximilian; Bode, Johannes; Muckenthaler, Martina U.; Legewie, Stefan

2017-01-01

Systemic iron levels must be maintained in physiological concentrations to prevent diseases associated with iron deficiency or iron overload. A key role in this process plays ferroportin, the only known mammalian transmembrane iron exporter, which releases iron from duodenal enterocytes, hepatocytes, or iron-recycling macrophages into the blood stream. Ferroportin expression is tightly controlled by transcriptional and post-transcriptional mechanisms in response to hypoxia, iron deficiency, heme iron and inflammatory cues by cell-autonomous and systemic mechanisms. At the systemic level, the iron-regulatory hormone hepcidin is released from the liver in response to these cues, binds to ferroportin and triggers its degradation. The relative importance of individual ferroportin control mechanisms and their interplay at the systemic level is incompletely understood. Here, we built a mathematical model of systemic iron regulation. It incorporates the dynamics of organ iron pools as well as regulation by the hepcidin/ferroportin system. We calibrated and validated the model with time-resolved measurements of iron responses in mice challenged with dietary iron overload and/or inflammation. The model demonstrates that inflammation mainly reduces the amount of iron in the blood stream by reducing intracellular ferroportin transcription, and not by hepcidin-dependent ferroportin protein destabilization. In contrast, ferroportin regulation by hepcidin is the predominant mechanism of iron homeostasis in response to changing iron diets for a big range of dietary iron contents. The model further reveals that additional homeostasis mechanisms must be taken into account at very high dietary iron levels, including the saturation of intestinal uptake of nutritional iron and the uptake of circulating, non-transferrin-bound iron, into liver. Taken together, our model quantitatively describes systemic iron metabolism and generated experimentally testable predictions for additional

Time-dependent calculations of molten pool formation and thermal plasma with metal vapour in gas tungsten arc welding

NASA Astrophysics Data System (ADS)

Tanaka, M.; Yamamoto, K.; Tashiro, S.; Nakata, K.; Yamamoto, E.; Yamazaki, K.; Suzuki, K.; Murphy, A. B.; Lowke, J. J.

2010-11-01

A gas tungsten arc (GTA) was modelled taking into account the contamination of the plasma by metal vapour from the molten anode. The whole region of GTA atmosphere including the tungsten cathode, the arc plasma and the anode was treated using a unified numerical model. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of the shielding gas and metal vapour. The transient two-dimensional distributions of temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the molten pool as a function of time for a 150 A arc current at atmospheric pressure, both for helium and argon gases. It was shown that the thermal plasma in the GTA was influenced by iron vapour from the molten pool surface and that the concentration of iron vapour in the plasma was dependent on the temperature of the molten pool. GTA on high sulfur stainless steel was calculated to discuss the differences between a low sulfur and a high sulfur stainless steel anode. Helium was selected as the shielding gas because a helium GTA produces more metal vapour than an argon GTA. In the GTA on a high sulfur stainless steel anode, iron vapour and current path were constricted. Radiative emission density in the GTA on high sulfur stainless steel was also concentrated in the centre area of the arc plasma together with the iron vapour although the temperature distributions were almost the same as that in the case of a low sulfur stainless steel anode.

The deep permafrost carbon pool of the Yedoma region in Siberia and Alaska

PubMed Central

Strauss, Jens; Schirrmeister, Lutz; Grosse, Guido; Wetterich, Sebastian; Ulrich, Mathias; Herzschuh, Ulrike; Hubberten, Hans-Wolfgang

2013-01-01

[1] Estimates for circumpolar permafrost organic carbon (OC) storage suggest that this pool contains twice the amount of current atmospheric carbon. The Yedoma region sequestered substantial quantities of OC and is unique because its deep OC, which was incorporated into permafrost during ice age conditions. Rapid inclusion of labile organic matter into permafrost halted decomposition and resulted in a deep long-term sink. We show that the deep frozen OC in the Yedoma region consists of two distinct major subreservoirs: Yedoma deposits (late Pleistocene ice- and organic-rich silty sediments) and deposits formed in thaw-lake basins (generalized as thermokarst deposits). We quantified the OC pool based on field data and extrapolation using geospatial data sets to 83 + 61/−57 Gt for Yedoma deposits and to 128 + 99/−96 Gt for thermokarst deposits. The total Yedoma region 211 + 160/−153 Gt is a substantial amount of thaw-vulnerable OC that must be accounted for in global models. PMID:26074633

Assessment of Affect Lability: Psychometric Properties of the ALS-18.

PubMed

Contardi, Anna; Imperatori, Claudio; Amati, Italia; Balsamo, Michela; Innamorati, Marco

2018-01-01

Affect lability, an important aspect of emotion dysregulation, characterizes several psychiatric conditions. The short Affective Lability Scales (ALS-18) measures three aspects of changeability between euthymia and affect states (Anxiety/Depression, AD; Depression/Elation, DE; and Anger, Ang). The aim of our study was to investigate the psychometric characteristics of an Italian version of the ALS-18 in a sample of adults recruited from the general population. The sample was composed of 494 adults (343 women and 151 men) aged 18 and higher (mean age = 31.73 years, SD = 12.6). All participants were administered a checklist assessing socio-demographic variables, the ALS-18 and measures of depression and difficulties in emotion regulation. Confirmatory factor analyses indicated adequate fit of the three-factor model (RMSEA = 0.061, 95% CI = 0.054/0.069; CFI = 0.99; SRMR = 0.055), and the presence of a higher-order general factor. Internal consistency was satisfactory for all the lower-order dimensions and the general factor (ordinal α > 0.70). The ALS-18 was significantly associated with concurrent measures of depression and difficulties in emotion regulation. These findings indicate that the ALS-18 is a valid and reliable instrument for measuring affect lability, although discriminant validity of subdimensions scores could be problematic.

Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina1[W][OA

PubMed Central

Paz, Yakov; Shimoni, Eyal; Weiss, Meira; Pick, Uri

2007-01-01

Uptake of iron in the halotolerant alga Dunaliella salina is mediated by a transferrin-like protein (TTf), which binds and internalizes Fe3+ ions. Recently, we found that iron deficiency induces a large enhancement of iron binding, which is associated with accumulation of three other plasma membrane proteins that associate with TTf. In this study, we characterized the kinetic properties of iron binding and internalization and identified the site of iron internalization. Iron deficiency induces a 4-fold increase in Fe binding, but only 50% enhancement in the rate of iron uptake and also increases the affinity for iron and bicarbonate, a coligand for iron binding. These results indicate that iron deprivation leads to accumulation and modification of iron-binding sites. Iron uptake in iron-sufficient cells is preceded by an apparent time lag, resulting from prebound iron, which can be eliminated by unloading iron-binding sites. Iron is tightly bound to surface-exposed sites and hardly exchanges with medium iron. All bound iron is subsequently internalized. Accumulation of iron inhibits further iron binding and internalization. The vacuolar inhibitor bafilomycin inhibits iron uptake and internalization. Internalized iron was localized by electron microscopy within vacuolar structures that were identified as acidic vacuoles. Iron internalization is accompanied by endocytosis of surface proteins into these acidic vacuoles. A novel kinetic mechanism for iron uptake is proposed, which includes two pools of bound/compartmentalized iron separated by a rate-limiting internalization stage. The major parameter that is modulated by iron deficiency is the iron-binding capacity. We propose that excessive iron binding in iron-deficient cells serves as a temporary reservoir for iron that is subsequently internalized. This mechanism is particularly suitable for organisms that are exposed to large fluctuations in iron availability. PMID:17513481

Ligand lability and chirality inversion in yb heterobimetallic catalysts.

PubMed

Di Bari, Lorenzo; Lelli, Moreno; Salvadori, Piero

2004-09-20

We have investigated the exchange dynamics between the free and bound ligand in K3[Yb[(R)-binol]3], the most active heterobimetallic lanthanoid catalyst for cyclic imine hydrophosphonylation; we found that the Yb-binol bond is labile. The rate constant for this exchange was determined through NMR saturation transfer experiments. Upon addition of (S)-binaphthol, ligand exchange leads to the formation of a small quantity of heterochiral complexes and, in the presence of a molar excess of (S)-binaphthol, to chirality inversion of the whole complex. This demonstrates that, in contrast to other analogous systems, K3[Yb(binol)3] displays a strong chiral discrimination, with the overwhelming preference for ligands of the same configuration. The lability of Yb-binol bond in THF may suggest a ligand-to-substrate exchange as a key step in the catalytic process.

The evolution of labile traits in sex- and age-structured populations.

PubMed

Childs, Dylan Z; Sheldon, Ben C; Rees, Mark

2016-03-01

Many quantitative traits are labile (e.g. somatic growth rate, reproductive timing and investment), varying over the life cycle as a result of behavioural adaptation, developmental processes and plastic responses to the environment. At the population level, selection can alter the distribution of such traits across age classes and among generations. Despite a growing body of theoretical research exploring the evolutionary dynamics of labile traits, a data-driven framework for incorporating such traits into demographic models has not yet been developed. Integral projection models (IPMs) are increasingly being used to understand the interplay between changes in labile characters, life histories and population dynamics. One limitation of the IPM approach is that it relies on phenotypic associations between parents and offspring traits to capture inheritance. However, it is well-established that many different processes may drive these associations, and currently, no clear consensus has emerged on how to model micro-evolutionary dynamics in an IPM framework. We show how to embed quantitative genetic models of inheritance of labile traits into age-structured, two-sex models that resemble standard IPMs. Commonly used statistical tools such as GLMs and their mixed model counterparts can then be used for model parameterization. We illustrate the methodology through development of a simple model of egg-laying date evolution, parameterized using data from a population of Great tits (Parus major). We demonstrate how our framework can be used to project the joint dynamics of species' traits and population density. We then develop a simple extension of the age-structured Price equation (ASPE) for two-sex populations, and apply this to examine the age-specific contributions of different processes to change in the mean phenotype and breeding value. The data-driven framework we outline here has the potential to facilitate greater insight into the nature of selection and its

Accumulation of Apoplastic Iron in Plant Roots 1

PubMed Central

Longnecker, Nancy; Welch, Ross M.

1990-01-01

We hypothesized that the resistance of Hawkeye (HA) soybean (Glycine max L.) to iron-deficiency induced chlorosis (IDC) is correlated to an ability to accumulate a large pool of extracellular-root iron which can be mobilized to shoots as the plants become iron deficient. Iron in the root apoplast was assayed after efflux from the roots of intact plants in nutrient solution treated with sodium dithionite added under anaerobic conditions. Young seedlings of HA soybean accumulated a significantly larger amount of extracellular iron in their roots than did either IDC-susceptible PI-54619 (PI) soybean or IDC-resistant IS-8001 (IS) sunflower (Helianthus annus L.). Concurrently, HA soybean had much higher concentrations of iron in their shoots than either PI soybean or IS sunflower. The concentration of iron in the root apoplast and in shoots of HA soybean decreased sharply within days after the first measurements of extracellular root iron were made, in both +Fe and −Fe treatments. The accumulation of short-term iron reserves in the root apoplast and translocation of iron in large quantities to the shoot may be important characteristics of IDC resistance in soybeans. PMID:16667242

Peroral Immunization of Rats with Escherichia coli Heat-Labile Enterotoxin Delivered by Microspheres

PubMed Central

Klipstein, Frederick A.; Engert, Richard F.; Sherman, William T.

1983-01-01

The antigenicity of the Escherichia coli heat-labile enterotoxin was not protected against the adverse effect of gastric acidity when the toxin was given together with bicarbonate for peroral immunization to rats, but immunization with the heat-labile enterotoxin encapsulated in pH-dependent microspheres aroused the same strong degree of serum and mucosal antitoxin responses and of protection against challenge as was achieved by peroral immunization after ablation of gastric secretions by pretreatment with cimetidine. PMID:6339378

Effect of Reduced Flux Iron Ore Pellets on Removal of Impurities from Pig Iron During Induction Melting: A New Phenomenon

NASA Astrophysics Data System (ADS)

Dishwar, Raj Kumar; Agrawal, Shavi; Mandal, A. K.; Mahobia, G. S.; Sinha, O. P.

2018-06-01

The present work represents a comparative study of impurity removal (sulfur, phosphorus, and carbon) from pig iron melt by the addition of lime powder and reduced fluxed iron ore pellets separately in a 5-kg-capacity induction melting furnace. Two types of reduced flux pellets (80% and 50%) of similar basicity ( 3.06) were charged separately into the pool to obtain the different oxidizing atmospheres of the bath. Results showed that the rate of impurity removal increases up to 6 min of exposure time and decreases afterward. Only lime powder charging, sulfur ( 77%), and a small fraction of carbon were removed from pig iron. Phosphorous ( 41%), sulfur ( 53%), and carbon ( 96%) were removed simultaneously when 80% reduced fluxed pellets were used. The present study indicates that the optimum removal of impurities is possible by charging 80% reduced flux iron ore pellets from the pig iron melt.

Electrodermal lability as an indicator for subjective sleepiness during total sleep deprivation.

PubMed

Michael, Lars; Passmann, Sven; Becker, Ruth

2012-08-01

The present study addresses the suitability of electrodermal lability as an indicator of individual vulnerability to the effects of total sleep deprivation. During two complete circadian cycles, the effects of 48h of total sleep deprivation on physiological measures (electrodermal activity and body temperature), subjective sleepiness (measured by visual analogue scale and tiredness symptom scale) and task performance (reaction time and errors in a go/no go task) were investigated. Analyses of variance with repeated measures revealed substantial decreases of the number of skin conductance responses, body temperature, and increases for subjective sleepiness, reaction time and error rates. For all changes, strong circadian oscillations could be observed as well. The electrodermal more labile subgroup reported higher subjective sleepiness compared with electrodermal more stable participants, but showed no differences in the time courses of body temperature and task performance. Therefore, electrodermal lability seems to be a specific indicator for the changes in subjective sleepiness due to total sleep deprivation and circadian oscillations, but not a suitable indicator for vulnerability to the effects of sleep deprivation per se. © 2011 European Sleep Research Society.

Iatrogenic Iron Overload in Dialysis Patients at the Beginning of the 21st Century.

PubMed

Rostoker, Guy; Vaziri, Nosratola D; Fishbane, Steven

2016-05-01

Iron overload used to be considered rare in hemodialysis patients but its clinical frequency is now increasingly realized. The liver is the main site of iron storage and the liver iron concentration (LIC) is closely correlated with total iron stores in patients with secondary hemosideroses and genetic hemochromatosis. Magnetic resonance imaging is now the gold standard method for LIC estimation and monitoring in non-renal patients. Studies of LIC in hemodialysis patients by quantitative magnetic resonance imaging and magnetic susceptometry have demonstrated a strong relation between the risk of iron overload and the use of intravenous (IV) iron products prescribed at doses determined by the iron biomarker cutoffs contained in current anemia management guidelines. These findings have challenged the validity of both iron biomarker cutoffs and current clinical guidelines, especially with respect to recommended IV iron doses. Three long-term observational studies have recently suggested that excessive IV iron doses may be associated with an increased risk of cardiovascular events and death in hemodialysis patients. We postulate that iatrogenic iron overload in the era of erythropoiesis-stimulating agents may silently increase complications in dialysis patients without creating frank clinical signs and symptoms. High hepcidin-25 levels were recently linked to fatal and nonfatal cardiovascular events in dialysis patients. It is therefore tempting to postulate that the main pathophysiological pathway leading to these events may involve the pleiotropic master hormone hepcidin (synergized by fibroblast growth factor 23), which regulates iron metabolism. Oxidative stress as a result of IV iron infusions and iron overload, by releasing labile non-transferrin-bound iron, might represent a 'second hit' on the vascular bed. Finally, iron deposition in the myocardium of patients with severe iron overload might also play a role in the pathogenesis of sudden death in some patients.

Post-transfusional iron overload in the haemoglobinopathies.

PubMed

Thuret, Isabelle

2013-03-01

In this report, we review the recent advances in evaluation and treatment of transfusional iron overload (IO). Results of the French thalassaemia registry are described. According to the disease, thalassaemia major or sickle cell anaemia, mechanisms and toxicity of iron overload, knowledge about IO long-term outcome and chelation treatment results, respective value of IO markers, differ. The recent tools evaluating organ specific IO and the diversification of iron chelator agents make possible to individualize chelation therapy in clinical practice. The severity of IO and the level of transfusional iron intake, the preferential localization of IO (heart/liver) as well as the tolerance and adherence profiles of the patient can now be taken into account. Introduction of cardiac magnetic resonance imaging for the quantification of myocardial iron and use of oral chelators have already been reported as decreasing the cardiac mortality rate related to IO in thalassaemia major patients. Long-term observation of patients under oral chelators will show if morbidity is also improving via a more continuous control of toxic iron and/or a better accessibility to cellular iron pools. Copyright © 2012 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Transformation kinetics of corn and clover residues in mineral substrates of different composition

NASA Astrophysics Data System (ADS)

Pinskii, D. L.; Maltseva, A. N.; Zolotareva, B. N.; Dmitrieva, E. D.

2017-06-01

Mineralization kinetics of corn and clover residues in quartz sand, loam, sand + 15% bentonite, and sand + 30% kaolinite have been studied. A scheme has been proposed for the transformation of plant residues in mineral substrates. Kinetic parameters of mineralization have been calculated with the use of a first-order two-term exponential polynomial. It has been shown that the share of labile organic carbon pool in the clover biomass is higher (57-63%) than in the corn biomass (47-49%), which is related to the biochemical composition of plant residues. The mineralization constants of clover residues generally significantly exceed those of corn because of the stronger stabilization of the decomposition products of corn residues. The turnover time of the labile clover pool (4-9 days) in all substrates and that of the labile corn pool (8-10 days) in sands and substrates containing kaolinites and bentonite are typical for organic acids, amino acids, and simple sugars. In the loamy substrate, the turnover time of labile corn pool is about 46 days due to the stronger stabilization of components of the labile pool containing large amounts of organic acids. The turnover time of the stable clover pool (0.95 years) is significantly lower than that of the stable corn pool (1.60 years) and largely corresponds to the turnover time of plant biomass.

Ovarian endometriosis-associated stromal cells reveal persistently high affinity for iron.

PubMed

Mori, Masahiko; Ito, Fumiya; Shi, Lei; Wang, Yue; Ishida, Chiharu; Hattori, Yuka; Niwa, Masato; Hirayama, Tasuku; Nagasawa, Hideko; Iwase, Akira; Kikkawa, Fumitaka; Toyokuni, Shinya

2015-12-01

Ovarian endometriosis is a recognized risk for infertility and epithelial ovarian cancer, presumably due to iron overload resulting from repeated hemorrhage. To find a clue for early detection and prevention of ovarian endometriosis-associated cancer, it is mandatory to evaluate catalytic (labile) ferrous iron (catalytic Fe(II)) and to study iron manipulation in ovarian endometriotic lesions. By the use of tissues from women of ovarian endometriosis as well as endometrial tissue from women with and without endometriosis, we for the first time performed histological analysis and cellular detection of catalytic Fe(II) with a specific fluorescent probe (HMRhoNox-M), and further evaluated iron transport proteins in the human specimens and in co-culture experiments using immortalized human eutopic/ectopic endometrial stromal cells (ESCs) in the presence or absence of epithelial cells (EpCs). The amounts of catalytic Fe(II) were higher in ectopic endometrial stromal cells (ecESCs) than in normal eutopic endometrial stromal cells (n-euESCs) both in the tissues and in the corresponding immortalized ESCs. ecESCs exhibited higher transferrin receptor 1 expression both in vivo and in vitro and lower ferroportin expression in vivo than n-euESCs, leading to sustained iron uptake. In co-culture experiments of ESCs with iron-loaded EpCs, ecESCs received catalytic ferrous iron from EpCs, but n-euESCs did not. These data suggest that ecESC play a protective role for cancer-target epithelial cells by collecting excess iron, and that these characteristics are retained in the immortalized ecESCs. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Estimating soil labile organic carbon and potential turnover rates using a sequential fumigation–incubation procedure.

Treesearch

X.M. Zoua; H.H. Ruanc; Y. Fua; X.D. Yanga; L.Q. Sha

2005-01-01

Labile carbon is the fraction of soil organic carbon with most rapid turnover times and its oxidation drives the flux of CO2 between soils and atmosphere. Available chemical and physical fractionation methods for estimating soil labile organic carbon are indirect and lack a clear biological definition. We have modified the well-established Jenkinson and Powlson’s...

Iron status of military personnel deployed to Afghanistan.

PubMed

Wilson, Candy; McClung, James P; Karl, J Philip; Brothers, Michael D

2011-12-01

Iron is a micronutrient necessary for energy metabolism and for oxygen transport and delivery. Depletion of iron stores (iron deficiency [ID]) may lead to iron deficiency anemia (IDA), which affects mood, cognitive function, and physical performance. Previous studies indicated that iron status may decline during military training. This study assessed the iron status and prevalence of ID and IDA in military personnel deployed to Bagram Air Base, Afghanistan (1492 m). Within the pool of 294 participants (149 male and 145 female), 2 males (1%) and 8 females (6%) presented with ID. Although IDA was not observed in males, 3 females (2%) met the criteria for IDA. Female sex (p = 0.05) and self-reported history of anemia (p < 0.05) were associated with diminished iron status. Amenorrhea was associated with higher ferritin (p < 0.05) and hemoglobin (p < 0.05) levels. Although ID and IDA did not affect a large portion of the deployed population assessed in this study, findings suggest that risk factors including female sex, history of anemia, and regular menstruation should be considered in the assessment of iron status in military personnel.

Iron overload across the spectrum of non-transfusion-dependent thalassaemias: role of erythropoiesis, splenectomy and transfusions.

PubMed

Porter, John B; Cappellini, Maria Domenica; Kattamis, Antonis; Viprakasit, Vip; Musallam, Khaled M; Zhu, Zewen; Taher, Ali T

2017-01-01

Non-transfusion-dependent thalassaemias (NTDT) encompass a spectrum of anaemias rarely requiring blood transfusions. Increased iron absorption, driven by hepcidin suppression secondary to erythron expansion, initially causes intrahepatic iron overload. We examined iron metabolism biomarkers in 166 NTDT patients with β thalassaemia intermedia (n = 95), haemoglobin (Hb) E/β thalassaemia (n = 49) and Hb H syndromes (n = 22). Liver iron concentration (LIC), serum ferritin (SF), transferrin saturation (TfSat) and non-transferrin-bound iron (NTBI) were elevated and correlated across diagnostic subgroups. NTBI correlated with soluble transferrin receptor (sTfR), labile plasma iron (LPI) and nucleated red blood cells (NRBCs), with elevations generally confined to previously transfused patients. Splenectomised patients had higher NTBI, TfSat, NRBCs and SF relative to LIC, than non-splenectomised patients. LPI elevations were confined to patients with saturated transferrin. Erythron expansion biomarkers (sTfR, growth differentiation factor-15, NRBCs) correlated with each other and with iron overload biomarkers, particularly in Hb H patients. Plasma hepcidin was similar across subgroups, increased with >20 prior transfusions, and correlated inversely with TfSat, NTBI, LPI and NRBCs. Hepcidin/SF ratios were low, consistent with hepcidin suppression relative to iron overload. Increased NTBI and, by implication, risk of extra-hepatic iron distribution are more likely in previously transfused, splenectomised and iron-overloaded NTDT patients with TfSat >70%. © 2016 The Authors. British Journal of Haematology published by John Wiley & Sons Ltd.

Ineffective Erythropoiesis: Anemia and Iron Overload.

PubMed

Gupta, Ritama; Musallam, Khaled M; Taher, Ali T; Rivella, Stefano

2018-04-01

Stress erythropoiesis (SE) is characterized by an imbalance in erythroid proliferation and differentiation under increased demands of erythrocyte generation and tissue oxygenation. β-thalassemia represents a chronic state of SE, called ineffective erythropoiesis (IE), exhibiting an expansion of erythroid-progenitor pool and deposition of alpha chains on erythrocyte membranes, causing cell death and anemia. Concurrently, there is a decrease in hepcidin expression and a subsequent state of iron overload. There are substantial investigative efforts to target increased iron absorption under IE. There are also avenues for targeting cell contact and signaling within erythroblastic islands under SE, for therapeutic benefits. Copyright © 2017 Elsevier Inc. All rights reserved.

Biotic and abiotic controls on diurnal fluctuations in labile soil phosphorus of a wet tropical forest.

PubMed

Vandecar, Karen L; Lawrence, Deborah; Wood, Tana; Oberbauer, Steven F; Das, Rishiraj; Tully, Katherine; Schwendenmann, Luitgard

2009-09-01

The productivity of many tropical wet forests is generally limited by bioavailable phosphorus (P). Microbial activity is a key regulator of P availability in that it determines both the supply of P through organic matter decomposition and the depletion of bioavailable P through microbial uptake. Both microbial uptake and mineralization occur rapidly, and their net effect on P availability varies with soil moisture, temperature, and soil organic matter quantity and quality. Exploring the mechanisms driving P availability at fine temporal scales can provide insight into the coupling of carbon, water, and nutrient cycles, and ultimately, the response of tropical forests to climate change. Despite the recognized importance of P cycling to the dynamics of wet tropical forests and their potential sensitivity to short-term fluctuations in bioavailable P, the diurnal pattern of P remains poorly understood. This study quantifies diurnal fluctuations in labile soil P and evaluates the importance of biotic and abiotic factors in driving these patterns. To this end, measurements of labile P were made every other hour in a Costa Rican wet tropical forest oxisol. Spatial and temporal variation in Bray-extractable P were investigated in relation to ecosystem carbon flux, soil CO2 efflux, soil moisture, soil temperature, solar radiation, and sap-flow velocity. Spatially averaged bi-hourly (every two hours) labile P ranged from 0.88 to 2.48 microg/g across days. The amplitude in labile P throughout the day was 0.61-0.82 microg/g (41-54% of mean P concentrations) and was characterized by a bimodal pattern with a decrease at midday. Labile P increased with soil CO2 efflux and soil temperature and declined with increasing sap flow and solar radiation. Together, soil CO2 efflux, soil temperature, and sap flow explained 86% of variation in labile P.

A structural equation model analysis of phosphorus transformations in global unfertilized and uncultivated soils

NASA Astrophysics Data System (ADS)

Hou, Enqing; Chen, Chengrong; Kuang, Yuanwen; Zhang, Yuguang; Heenan, Marijke; Wen, Dazhi

2016-09-01

Understanding the soil phosphorus (P) cycle is a prerequisite for predicting how environmental changes may influence the dynamics and availability of P in soil. We compiled a database of P fractions sequentially extracted by the Hedley procedure and its modification in 626 unfertilized and uncultivated soils worldwide. With this database, we applied structural equation modeling to test hypothetical soil P transformation models and to quantify the importance of different soil P pools and P transformation pathways in shaping soil P availability at a global scale. Our models revealed that soluble inorganic P (Pi, a readily available P pool) was positively and directly influenced by labile Pi, labile organic P (Po), and primary mineral P and negatively and directly influenced by secondary mineral P; soluble Pi was not directly influenced by moderately labile Po or occluded P. The overall effect on soluble Pi was greatest for labile Pi followed by the organic P pools, occluded P, and then primary mineral P; the overall influence from secondary mineral P was small. Labile Pi was directly linked to all other soil P pools and was more strongly linked than soluble Pi to labile Po and primary mineral P. Our study highlights the important roles of labile Pi in mediating P transformations and in determining overall P availability in soils throughout the world.

Protective Effect of Active Immunization with Purified Escherichia coli Heat-Labile Enterotoxin in Rats

PubMed Central

Klipstein, Frederick A.; Engert, Richard F.

1979-01-01

The protective effect of active immunization by different routes with a purified preparation of the polymyxin-release form of Escherichia coli heat-labile toxin was evaluated in rats. Immunized animals were challenged by placing toxin into ligated ileal loops at dosages which produced either 50% or the maximum secretory response in unimmunized rats. Immunization exclusively by the parenteral route yielded significant protection. Rats were also protected when parenteral priming was followed by boosting given either directly into the duodenum or perorally 2 h after intragastric cimetidine, but not when the peroral boosts were given with bicarbonate. Immunization administered entirely by the peroral route with cimetidine yielded protection but only when the immunizing dosage was fivefold greater than that found effective in the parenteral-peroral approach. Rats immunized exclusively by the parenteral route and those boosted perorally with cimetidine were also tested, and found to be protected, against challenge with viable organisms of strains that produce either heat-labile toxin alone or both heat-labile and heat-stable toxin, but they were not protected against a strain which produces just heat-stable toxin. Geometric mean serum antibody titers were increased by 16-fold or more over control values in those groups of rats in which protection was achieved, with the exception of those immunized exclusively by the peroral route. These observations demonstrate that (i) active immunization with purified E. coli heat-labile toxin results in significant protection against both this toxin as well as viable organisms which produce it, but not against viable strains which produce heat-stable toxin only, and (ii) concomitant ablation of gastric secretion by the use of cimetidine renders the peroral route of immunization effective. They suggest that prophylactic immunization against diarrheal disease caused by heat-labile toxin-producing strains of E. coli may be feasible in

Soil Iron Content as a Predictor of Carbon and Nutrient Mobilization in Rewetted Fens

PubMed Central

Emsens, Willem-Jan; Aggenbach, Camiel J. S.; Schoutens, Ken; Smolders, Alfons J. P.; Zak, Dominik; van Diggelen, Rudy

2016-01-01

Rewetted, previously drained fens often remain sources rather than sinks for carbon and nutrients. To date, it is poorly understood which soil characteristics stimulate carbon and nutrient mobilization upon rewetting. Here, we assess the hypothesis that a large pool of iron in the soil negatively affects fen restoration success, as flooding-induced iron reduction (Fe3+ to Fe2+) causes a disproportionate breakdown of organic matter that is coupled with a release of inorganic compounds. We collected intact soil cores in two iron-poor and two iron-rich drained fens, half of which were subjected to a rewetting treatment while the other half was kept drained. Prolonged drainage led to the mobilization of nitrate (NO3-, > 1 mmol L-1) in all cores, regardless of soil iron content. In the rewetted iron-rich cores, a sharp increase in pore water iron (Fe) concentrations correlated with concentrations of inorganic carbon (TIC, > 13 mmol L-1) and dissolved organic carbon (DOC, > 16 mmol L-1). Additionally, ammonium (NH4+) accumulated up to phytotoxic concentrations of 1 mmol L-1 in the pore water of the rewetted iron-rich cores. Disproportionate mobilization of Fe, TIC, DOC and NH4+ was absent in the rewetted iron-poor cores, indicating a strong interaction between waterlogging and iron-mediated breakdown of organic matter. Concentrations of dissolved phosphorus (P) rose slightly in all cores upon rewetting, but remained low throughout the experiment. Our results suggest that large pools of iron in the top soil of drained fens can hamper the restoration of the fen’s sink-service for ammonium and carbon upon rewetting. We argue that negative effects of iron should be most apparent in fens with fluctuating water levels, as temporary oxygenation allows frequent regeneration of Fe3+. We conclude that rewetting of iron-poor fens may be more feasible for restoration. PMID:27050837

Characterizing convective cold pools: Characterizing Convective Cold Pools

DOE PAGES

Drager, Aryeh J.; van den Heever, Susan C.

2017-05-09

Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the densitymore » potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.« less

Characterizing convective cold pools: Characterizing Convective Cold Pools

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drager, Aryeh J.; van den Heever, Susan C.

Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the densitymore » potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.« less

Assessment of the labile fractions of copper and zinc in marinas and port areas in Southern Brazil.

PubMed

Costa, Luiza Dy Fonseca; Wallner-Kersanach, Mônica

2013-08-01

The dissolved labile and labile particulate fractions (LPF) of Cu and Zn were analyzed during different seasons and salinity conditions in estuarine waters of marina, port, and shipyard areas in the southern region of the Patos Lagoon (RS, Brazil). The dissolved labile concentration was determined using the diffusive gradients in thin films technique (DGT). DGT devices were deployed in seven locations of the estuary for 72 h and the physicochemical parameters were also measured. The LPF of Cu and Zn was determined by daily filtering of water samples. Seasonal variation of DGT-Cu concentrations was only significant (p < 0.05) at one shipyard area, while DGT-Zn was significant (p < 0.05) in every locations. The LPF of Cu and Zn concentrations demonstrated seasonal and spatial variability in all locations, mainly at shipyard areas during high salinity conditions. In general, except the control location, the sampling locations showed mean variations of 0.11-0.45 μg L(-1) for DGT-Cu, 0.89-9.96 μg L(-1) for DGT-Zn, 0.65-3.69 μg g(-1) for LPF-Cu, and 1.35-10.87 μg g(-1) for LPF-Zn. Shipyard areas demonstrated the most expressive values of labile Cu and Zn in both fractions. Strong relationship between DGT-Zn and LPF-Zn was found suggesting that the DGT-Zn fraction originates from the suspended particulate matter. Water salinity and suspended particulate matter content indicated their importance for the control of the labile concentrations of Cu and Zn in the water column. These parameters must be taken into consideration for comparison among labile metals in estuaries.

Comparison of metal lability in air-dried and fresh dewatered drinking water treatment residuals.

PubMed

Wang, Changhui; Pei, Yuansheng; Zhao, Yaqian

2015-01-01

In this work, the labilities of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in air-dried (for 60 days) and fresh dewatered WTRs were compared using the Toxicity Characteristic Leaching Procedure (TCLP), fractionation, in vitro digestion and a plant enrichment test. The results showed that the air-dried and fresh dewatered WTRs had different properties, e.g., organic matter composition and available nutrients. The air-dried and fresh dewatered WTRs were non-haf zardous according to the TCLP assessment method used in the United States; however, the metals in the two types of WTRs had different lability. Compared with the metals in the fresh dewatered WTRs, those in the air-dried WTRs tended to be in more stable fractions and also exhibited lower bioaccessibility and bioavailability. Therefore, air-drying can decrease the metal lability and thereby reduce the potential metal pollution risk of WTRs.

Impact of temperamental mood lability on depressive mixed state.

PubMed

Benazzi, Franco

2006-01-01

Cyclothymic temperament (which includes mood lability) is common in bipolar II disorder (BP-II). Depressive mixed state (DMX), a major depressive episode (MDE) mixed with intra-episode hypomanic symptoms (3 or more, according to a recently validated definition), was found to be common in BP-II and not uncommon in major depressive disorder (MDD). The study aim was to find the impact of temperamental mood lability (TML) on DMX. Consecutive 148 BP-II and 117 MDD outpatients presenting for MDE treatment were interviewed by the Structured Clinical Interview for DSM-IV as modified by Benazzi and Akiskal to reduce the false negative BP-II. Intra-MDE hypomanic symptoms were systematically assessed. Kraepelin, Angst, and Akiskal's definitions of temperamental mood lability (i.e., frequent up and down fluctuations of mood between major mood episodes since young age) were followed. DMX was present in 61.5%, TML in 52.8%. In the DMX sample, TML was present in 57.6%, and in the non-DMX sample TML was present in 45.0% (OR = 1.6, 95% CI = 1.0-2.7). In the DMX sample, independent predictors of DMX with TML were BP-II and young age at onset. Intra-MDE hypomanic symptoms, and MDE, melancholic and atypical symptoms were not significantly different between DMX patients with TML and DMX patients without TML, apart from more temperamental interpersonal sensitivity in DMX patients with TML (OR = 2.0, 95% CI = 1.0-3.8). DMX patients with TML had a younger onset age, suggesting that TML may facilitate the onset of DMX or that it may be a precursor of DMX. The association of BP-II with DMX, TML, and interpersonal sensitivity can make the course of BP-II more unstable and its treatment more complex.

Size, speciation and lability of NOM-metal complexes in hyperalkaline cave dripwater

NASA Astrophysics Data System (ADS)

Hartland, Adam; Fairchild, Ian J.; Lead, Jamie R.; Zhang, Hao; Baalousha, Mohammed

2011-12-01

Transport of trace metals by natural organic matter (NOM) is potentially an important vector for trace metal incorporation in secondary cave precipitates [speleothems], yet little is known about the size distribution, speciation and metal binding properties of NOM in cave dripwaters. A hyperalkaline cave environment (ca. pH 11) was selected to provide information on colloid-metal interactions in cave waters, and to address the lack of high-pH data in natural systems in general. Colloidal (1 nm-1 μm) NOM in hyperalkaline cave dripwater from Poole's Cavern, UK, was characterised by flow field-flow fractionation (FlFFF) coupled to UV and fluorescence detectors and transmission electron microscopy (TEM) coupled to X-ray energy-dispersive spectroscopy (X-EDS); trace-metal lability was examined by diffusive gradients in thin films (DGT). Colloidal aggregates and small particulates (>1 μm) imaged by TEM were morphologically heterogeneous with qualitative elemental compositions (X-EDS spectra; n = 41) consistent with NOM aggregates containing aluminosilicates, and iron and titanium oxides. Globular organic colloids, with diameters between ca. 1 and 10 nm were the most numerous colloidal class and exhibited high UV-absorbance (254 nm) and fluorescence intensity (320:400 nm excitation: emission) in optical regions characteristic of humic-like compounds. Metal binding with humic substances was modelled using the WHAM 6.1 (model VI) and visual MINTEQ 3.0 (NICA-Donnan) speciation codes. At pH 11, both models predicted dominant humic binding of Cu (ca. 100%) and minimal binding of Ni and Co (ca. <1-7%). A DGT depletion experiment (7 days duration) with the hyperalkaline dripwater showed that the available proportion of each metal was much lower than its total concentration. Metal availability for DGT in the initial stages (24 h) was consistent with weaker binding of alkaline earth metals by humic substances (Ba > Sr > V > Cu > Ni > Co), compared to the transition metals

Iron acquisition in the cystic fibrosis lung and potential for novel therapeutic strategies

PubMed Central

Tyrrell, Jean

2016-01-01

Iron acquisition is vital to microbial survival and is implicated in the virulence of many of the pathogens that reside in the cystic fibrosis (CF) lung. The multifaceted nature of iron acquisition by both bacterial and fungal pathogens encompasses a range of conserved and species-specific mechanisms, including secretion of iron-binding siderophores, utilization of siderophores from other species, release of iron from host iron-binding proteins and haemoproteins, and ferrous iron uptake. Pathogens adapt and deploy specific systems depending on iron availability, bioavailability of the iron pool, stage of infection and presence of competing pathogens. Understanding the dynamics of pathogen iron acquisition has the potential to unveil new avenues for therapeutic intervention to treat both acute and chronic CF infections. Here, we examine the range of strategies utilized by the primary CF pathogens to acquire iron and discuss the different approaches to targeting iron acquisition systems as an antimicrobial strategy. PMID:26643057

13 CFR 120.611 - Pools backing Pool Certificates.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Pools backing Pool Certificates. 120.611 Section 120.611 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION BUSINESS LOANS Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set...

13 CFR 120.611 - Pools backing Pool Certificates.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Pools backing Pool Certificates. 120.611 Section 120.611 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION BUSINESS LOANS Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set...

Measurement of labile copper in wine by medium exchange stripping potentiometry utilising screen printed carbon electrodes.

PubMed

Clark, Andrew C; Kontoudakis, Nikolaos; Barril, Celia; Schmidtke, Leigh M; Scollary, Geoffrey R

2016-07-01

The presence of copper in wine is known to impact the reductive, oxidative and colloidal stability of wine, and techniques enabling measurement of different forms of copper in wine are of particular interest in understanding these spoilage processes. Electrochemical stripping techniques developed to date require significant pretreatment of wine, potentially disturbing the copper binding equilibria. A thin mercury film on a screen printed carbon electrode was utilised in a flow system for the direct analysis of labile copper in red and white wine by constant current stripping potentiometry with medium exchange. Under the optimised conditions, including an enrichment time of 500s and constant current of 1.0μA, the response range was linear from 0.015 to 0.200mg/L. The analysis of 52 red and white wines showed that this technique generally provided lower labile copper concentrations than reported for batch measurement by related techniques. Studies in a model system and in finished wines showed that the copper sulfide was not measured as labile copper, and that loss of hydrogen sulfide via volatilisation induced an increase in labile copper within the model wine system. Copyright © 2016 Elsevier B.V. All rights reserved.

Development and Lability in the Parent-Child Relationship During Adolescence: Associations With Pubertal Timing and Tempo

PubMed Central

Marceau, Kristine; Ram, Nilam; Susman, Elizabeth

2014-01-01

Adolescents' and parents' reactions to pubertal development are hypothesized to contribute to changes in family dynamics. Using 7-year longitudinal data from the NICHD-SECCYD (488 boys, 475 girls) we examined relations between pubertal development (timing, tempo) and trajectories (developmental change and year-to-year lability) of parent-child conflict and closeness from age 8.5 to 15.5 years. Changes were mostly characterized by year-to-year fluctuations – lability. Parent-child conflict increased and closeness decreased some with age. Pubertal timing and tempo were more consistently associated with lability in parent-child relationships than with long-term trends, although faster tempo was associated with steeper decreases in parent-child closeness. Findings provide a platform for examining how puberty contributes to both long-term and transient changes in adolescents' relationships and adjustment. PMID:26321856

Washing older blood units before transfusion reduces plasma iron and improves outcomes in experimental canine pneumonia.

PubMed

Cortés-Puch, Irene; Wang, Dong; Sun, Junfeng; Solomon, Steven B; Remy, Kenneth E; Fernandez, Melinda; Feng, Jing; Kanias, Tamir; Bellavia, Landon; Sinchar, Derek; Perlegas, Andreas; Solomon, Michael A; Kelley, Walter E; Popovsky, Mark A; Gladwin, Mark T; Kim-Shapiro, Daniel B; Klein, Harvey G; Natanson, Charles

2014-02-27

In a randomized controlled blinded trial, 2-year-old purpose-bred beagles (n = 24), with Staphylococcus aureus pneumonia, were exchanged-transfused with either 7- or 42-day-old washed or unwashed canine universal donor blood (80 mL/kg in 4 divided doses). Washing red cells (RBC) before transfusion had a significantly different effect on canine survival, multiple organ injury, plasma iron, and cell-free hemoglobin (CFH) levels depending on the age of stored blood (all, P < .05 for interactions). Washing older units of blood improved survival rates, shock score, lung injury, cardiac performance and liver function, and reduced levels of non-transferrin bound iron and plasma labile iron. In contrast, washing fresh blood worsened all these same clinical parameters and increased CFH levels. Our data indicate that transfusion of fresh blood, which results in less hemolysis, CFH, and iron release, is less toxic than transfusion of older blood in critically ill infected subjects. However, washing older blood prevented elevations in plasma circulating iron and improved survival and multiple organ injury in animals with an established pulmonary infection. Our data suggest that fresh blood should not be washed routinely because, in a setting of established infection, washed RBC are prone to release CFH and result in worsened clinical outcomes.

Washing older blood units before transfusion reduces plasma iron and improves outcomes in experimental canine pneumonia

PubMed Central

Wang, Dong; Sun, Junfeng; Solomon, Steven B.; Remy, Kenneth E.; Fernandez, Melinda; Feng, Jing; Kanias, Tamir; Bellavia, Landon; Sinchar, Derek; Perlegas, Andreas; Solomon, Michael A.; Kelley, Walter E.; Popovsky, Mark A.; Gladwin, Mark T.; Kim-Shapiro, Daniel B.; Klein, Harvey G.; Natanson, Charles

2014-01-01

In a randomized controlled blinded trial, 2-year-old purpose-bred beagles (n = 24), with Staphylococcus aureus pneumonia, were exchanged-transfused with either 7- or 42-day-old washed or unwashed canine universal donor blood (80 mL/kg in 4 divided doses). Washing red cells (RBC) before transfusion had a significantly different effect on canine survival, multiple organ injury, plasma iron, and cell-free hemoglobin (CFH) levels depending on the age of stored blood (all, P < .05 for interactions). Washing older units of blood improved survival rates, shock score, lung injury, cardiac performance and liver function, and reduced levels of non-transferrin bound iron and plasma labile iron. In contrast, washing fresh blood worsened all these same clinical parameters and increased CFH levels. Our data indicate that transfusion of fresh blood, which results in less hemolysis, CFH, and iron release, is less toxic than transfusion of older blood in critically ill infected subjects. However, washing older blood prevented elevations in plasma circulating iron and improved survival and multiple organ injury in animals with an established pulmonary infection. Our data suggest that fresh blood should not be washed routinely because, in a setting of established infection, washed RBC are prone to release CFH and result in worsened clinical outcomes. PMID:24366359

The influence of labile dietary methyl donors on the arginine requirement of young broiler chicks.

PubMed

Chamruspollert, M; Pesti, G M; Bakalli, R I

2002-08-01

Two experiments were conducted with Ross x Ross boiler chicks in battery brooders from 1 to 14 d of age to determine the influence of dietary methyl donors on the Arg requirement of young broiler chicks. Experiment 1 had a 6 x 2 factorial design, with six levels of Arg supplementation (0, 0.1, 0.2, 0.3, 0.4, and 0.5%) and two levels of DL-Met supplementation (0 and 0.2% of the diet). The design of Experiment 2 was identical to Experiment 1, except that a second source of labile methyl groups was added, 0.2% betaine (6 x 3 factorial arrangement). Both experiments had four replicate pens of 10 chicks each per treatment. The basal diet was based on corn (34.52%), whey (26.96%), corn gluten meal (16.53%), soybean meal (11.74%), and poultry fat (23% CP and 3.20 kcal/g of ME). At 14 d, three chicks per replicate were randomly killed, and breast muscle was collected and pooled for creatine analysis. The broken-line linear model was used to estimate the Arg requirements of the chicks. There were no differences in Arg requirements due to methyl source so the data were pooled. In Experiment 1, the Arg requirements were 1.17 +/- 0.04% for gain, 1.23 +/- 0.03% for feed conversion ratio (FCR), and 1.18 +/- 0.03% for muscle creatine, when the diet contained 0.45 or 0.65% Met. In Experiment 2, the Arg requirements were 1.20 +/- 0.05% for gain, 1.23 +/- 0.03% for FCR, and 1.26 +/- 0.02% for muscle creatine. There was no apparent difference in the Arg requirement of young broilers due to methyl donor supplementation.

Substrate lability and plant activity controls greenhouse gas release from Neotropical peatland

NASA Astrophysics Data System (ADS)

Sjogersten, Sofie; Hoyos, Jorge; Lomax, Barry; Turner, Ben; Wright, Emma

2014-05-01

Almost one third of global CO2 emissions resulting from land use change and substantial CH4 emissions originate from tropical peatlands. However, our understanding of the controls of CO2 and CH4 release from tropical peatlands are limited. The aim of this study was to investigate the role of peat lability and the activity of the vegetation on gas release using a combination of field and laboratory experiments. We demonstrated that peat lability constrained CH4 production to the surface peat under anaerobic conditions. The presence of plants shifted the C balance from a C source to a C sink with respect to CO2 while the activity of the root system strongly influenced CH4 emissions through its impact on soil O2 inputs. Both field and laboratory data suggest a coupling between the photosynthetic activity of the vegetation and the release of both CO2 and CH4 following the circadian rhythm of the dominant plant functional types. Forest clearance for agriculture resulted in elevated CH4 release, which we attribute in part to the cessation of root O2 inputs to the peat. We conclude that high emissions of CO2 and CH4 from forested tropical peatlands are likely driven by labile C inputs from the vegetation but that root O2 release may limit CH4 emissions.

Swimming Pools.

ERIC Educational Resources Information Center

Ministry of Housing and Local Government, London (England).

Technical and engineering data are set forth on the design and construction of swimming pools. Consideration is given to site selection, pool construction, the comparative merits of combining open air and enclosed pools, and alternative uses of the pool. Guidelines are presented regarding--(1) pool size and use, (2) locker and changing rooms, (3)…

Photoreduction of Terrigenous Fe-Humic Substances Leads to Bioavailable Iron in Oceans.

PubMed

Blazevic, Amir; Orlowska, Ewelina; Kandioller, Wolfgang; Jirsa, Franz; Keppler, Bernhard K; Tafili-Kryeziu, Myrvete; Linert, Wolfgang; Krachler, Rudolf F; Krachler, Regina; Rompel, Annette

2016-05-23

Humic substances (HS) are important iron chelators responsible for the transport of iron from freshwater systems to the open sea, where iron is essential for marine organisms. Evidence suggests that iron complexed to HS comprises the bulk of the iron ligand pool in near-coastal waters and shelf seas. River-derived HS have been investigated to study their transport to, and dwell in oceanic waters. A library of iron model compounds and river-derived Fe-HS samples were probed in a combined X-ray absorption spectroscopy (XAS) and valence-to-core X-ray emission spectroscopy (VtC-XES) study at the Fe K-edge. The analyses performed revealed that iron complexation in HS samples is only dependent on oxygen-containing HS functional groups, such as carboxyl and phenol. The photoreduction mechanism of Fe III -HS in oceanic conditions into bioavailable aquatic Fe II forms, highlights the importance of river-derived HS as an iron source for marine organisms. Consequently, such mechanisms are a vital component of the upper-ocean iron biogeochemistry cycle.

Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic

PubMed Central

Browning, T. J.; Achterberg, E. P.; Yong, J. C.; Rapp, I.; Utermann, C.; Engel, A.; Moore, C. M.

2017-01-01

In certain regions of the predominantly nitrogen limited ocean, microbes can become co-limited by phosphorus. Within such regions, a proportion of the dissolved organic phosphorus pool can be accessed by microbes employing a variety of alkaline phosphatase (APase) enzymes. In contrast to the PhoA family of APases that utilize zinc as a cofactor, the recent discovery of iron as a cofactor in the more widespread PhoX and PhoD implies the potential for a biochemically dependant interplay between oceanic zinc, iron and phosphorus cycles. Here we demonstrate enhanced natural community APase activity following iron amendment within the low zinc and moderately low iron Western North Atlantic. In contrast we find no evidence for trace metal limitation of APase activity beneath the Saharan dust plume in the Eastern Atlantic. Such intermittent iron limitation of microbial phosphorus acquisition provides an additional facet in the argument for iron controlling the coupling between oceanic nitrogen and phosphorus cycles. PMID:28524880

In situ Identification of Labile Precursor Compounds and their Short-lived Intermediates in Plants using in vivo Nanospray High-resolution Mass Spectrometry.

PubMed

Chang, Qing; Peng, Yue'e; Shi, Bin; Dan, Conghui; Yang, Yijun; Shuai, Qin

2016-05-01

Many secondary metabolites in plants are labile compounds which under environmental stress, are difficult to detect and track due to the lack of rapid in situ identification techniques, making plant metabolomics research difficult. Therefore, developing a reliable analytical method for rapid in situ identification of labile compounds and their short-lived intermediates in plants is of great importance. To develop under atmospheric pressure, a rapid in situ method for effective identification of labile compounds and their short-lived intermediates in fresh plants. An in vivo nanospray high-resolution mass spectrometry (HR-MS) method was used for rapid capture of labile compounds and their short-lived intermediates in plants. A quartz capillary was partially inserted into fresh plant tissues, and the liquid flowed out through the capillary tube owing to the capillary effect. A high direct current (d.c.) voltage was applied to the plant to generate a spray of charged droplets from the tip of the capillary carrying bioactive molecules toward the inlet of mass spectrometer for full-scan and MS/MS analysis. Many labile compounds and short-lived intermediates were identified via this method: including glucosinolates and their short-lived intermediates (existing for only 10 s) in Raphanus sativus roots, alliin and its conversion intermediate (existing for 20 s) in Allium sativum and labile precursor compound chlorogenic acid in Malus pumila Mill. The method is an effective approach for in situ identification of internal labile compounds and their short-lived intermediates in fresh plants and it can be used as an auxiliary tool to explore the degradation mechanisms of new labile plant compounds. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

[Character of brain interhemispheric relation in children at forming labile arterial hypertension].

PubMed

Koroleva, N V; Kolesnikov, S I; Bugun, O V; Dolgikh, V V

2010-01-01

Electroencephalography investigations were carried out twice in 26 schoolchildren in the age of 7-8 years and in the age of 9-10 years. The control group included healthy children: the research group included children in whom in the age of 7-8 years the normal level of arterial pressure was registered, and in whom in the age of 9-10 years labile arterial hypertension was revealed. It is revealed, that in children of younger school age forming of the labile form of arterial hypertension is connected whit infringement of processes of age changes of intercortical and cortical-subcortical interrelations and forming of rigidly integrated system of interhemispheric relations. Its mechanism of realization is carried out due to hyperactivation of the right hemisphere and it is incorporated on preclinical stage.

Improving Phosphorus Availability in an Acid Soil Using Organic Amendments Produced from Agroindustrial Wastes

PubMed Central

Ch'ng, Huck Ywih; Ahmed, Osumanu Haruna; Majid, Nik Muhamad Ab.

2014-01-01

In acid soils, soluble inorganic phosphorus is fixed by aluminium and iron. To overcome this problem, acid soils are limed to fix aluminium and iron but this practice is not economical. The practice is also not environmentally friendly. This study was conducted to improve phosphorus availability using organic amendments (biochar and compost produced from chicken litter and pineapple leaves, resp.) to fix aluminium and iron instead of phosphorus. Amending soil with biochar or compost or a mixture of biochar and compost increased total phosphorus, available phosphorus, inorganic phosphorus fractions (soluble inorganic phosphorus, aluminium bound inorganic phosphorus, iron bound inorganic phosphorus, redundant soluble inorganic phosphorus, and calcium bound phosphorus), and organic phosphorus. This was possible because the organic amendments increased soil pH and reduced exchangeable acidity, exchangeable aluminium, and exchangeable iron. The findings suggest that the organic amendments altered soil chemical properties in a way that enhanced the availability of phosphorus in this study. The amendments effectively fixed aluminium and iron instead of phosphorus, thus rendering phosphorus available by keeping the inorganic phosphorus in a bioavailable labile phosphorus pool for a longer period compared with application of Triple Superphosphate without organic amendments. PMID:25032229

Brain transcriptome perturbations in the Hfe(-/-) mouse model of genetic iron loading.

PubMed

Johnstone, Daniel; Graham, Ross M; Trinder, Debbie; Delima, Roheeth D; Riveros, Carlos; Olynyk, John K; Scott, Rodney J; Moscato, Pablo; Milward, Elizabeth A

2012-04-11

Severe disruption of brain iron homeostasis can cause fatal neurodegenerative disease, however debate surrounds the neurologic effects of milder, more common iron loading disorders such as hereditary hemochromatosis, which is usually caused by loss-of-function polymorphisms in the HFE gene. There is evidence from both human and animal studies that HFE gene variants may affect brain function and modify risks of brain disease. To investigate how disruption of HFE influences brain transcript levels, we used microarray and real-time reverse transcription polymerase chain reaction to assess the brain transcriptome in Hfe(-/-) mice relative to wildtype AKR controls (age 10 weeks, n≥4/group). The Hfe(-/-) mouse brain showed numerous significant changes in transcript levels (p<0.05) although few of these related to proteins directly involved in iron homeostasis. There were robust changes of at least 2-fold in levels of transcripts for prominent genes relating to transcriptional regulation (FBJ osteosarcoma oncogene Fos, early growth response genes), neurotransmission (glutamate NMDA receptor Grin1, GABA receptor Gabbr1) and synaptic plasticity and memory (calcium/calmodulin-dependent protein kinase IIα Camk2a). As previously reported for dietary iron-supplemented mice, there were altered levels of transcripts for genes linked to neuronal ceroid lipofuscinosis, a disease characterized by excessive lipofuscin deposition. Labile iron is known to enhance lipofuscin generation which may accelerate brain aging. The findings provide evidence that iron loading disorders can considerably perturb levels of transcripts for genes essential for normal brain function and may help explain some of the neurologic signs and symptoms reported in hemochromatosis patients. Copyright © 2012 Elsevier B.V. All rights reserved.

Protein degradation by ubiquitin–proteasome system in formation and labilization of contextual conditioning memory

PubMed Central

Sol Fustiñana, María; de la Fuente, Verónica; Federman, Noel; Freudenthal, Ramiro

2014-01-01

The ubiquitin–proteasome system (UPS) of protein degradation has been evaluated in different forms of neural plasticity and memory. The role of UPS in such processes is controversial. Several results support the idea that the activation of this system in memory consolidation is necessary to overcome negative constrains for plasticity. In this case, the inhibition of the UPS during consolidation impairs memory. Similar results were reported for memory reconsolidation. However, in other cases, the inhibition of UPS had no effect on memory consolidation and reconsolidation but impedes the amnesic action of protein synthesis inhibition after retrieval. The last finding suggests a specific action of the UPS inhibitor on memory labilization. However, another interpretation is possible in terms of the synthesis/degradation balance of positive and negative elements in neural plasticity, as was found in the case of long-term potentiation. To evaluate these alternative interpretations, other reconsolidation-interfering drugs than translation inhibitors should be tested. Here we analyzed initially the UPS inhibitor effect in contextual conditioning in crabs. We found that UPS inhibition during consolidation impaired long-term memory. In contrast, UPS inhibition did not affect memory reconsolidation after contextual retrieval but, in fact, impeded memory labilization, blocking the action of drugs that does not affect directly the protein synthesis. To extend these finding to vertebrates, we performed similar experiments in contextual fear memory in mice. We found that the UPS inhibitor in hippocampus affected memory consolidation and blocked memory labilization after retrieval. These findings exclude alternative interpretations to the requirement of UPS in memory labilization and give evidence of this mechanism in both vertebrates and invertebrates. PMID:25135196

Influence of carotene-rich vegetable meals on the prevalence of anaemia and iron deficiency in Filipino schoolchildren.

PubMed

Maramag, C C; Ribaya-Mercado, J D; Rayco-Solon, P; Solon, J A A; Tengco, L W; Blumberg, J B; Solon, F S

2010-05-01

To determine the effects of eating carotene-rich green and yellow vegetables on the prevalence of anaemia, iron deficiency and iron-deficiency anaemia in schoolchildren. Schoolchildren (n=104), aged 9-12 years, received standardized meals containing 4.2 mg of provitamin A carotenoids/day (mainly beta-carotene) from yellow and green leafy vegetables and at least 7 g dietary fat/day. The meals were provided three times/day, 5 days/week, for 9 weeks at school. Before and after the dietary intervention, total-body vitamin A pool size was assessed by using the deuterated-retinol-dilution method; serum retinol and beta-carotene concentrations were measured by high-performance liquid chromatography; and whole blood haemoglobin (Hb) and zinc protoporphyrin (ZnPP) concentrations were measured by using a photometer and a hematofluorometer, respectively. After 9 weeks, the mean total-body vitamin A pool size increased twofold (95% confidence interval (CI): -0.11, -0.07 micromol retinol; P<0.001), and serum beta-carotene concentration increased fivefold (95% CI: -0.97, -0.79 micromol/l; P<0.001). Blood Hb (95% CI: -1.02, -0.52 g per 100 ml; P<0.001) and ZnPP increased (95% CI: -11.82, -4.57 microol/mol haem; P<0.001). The prevalence of anaemia (Hb<11.5 g per 100 ml) decreased from 12.5 to 1.9% (P<0.001). There were no significant changes in the prevalence of iron deficiency or iron-deficiency anaemia. Ingestion of carotene-rich yellow and green leafy vegetables improves the total-body vitamin A pool size and Hb concentration, and decreases anaemia rates in Filipino schoolchildren, with no effect on iron deficiency or iron-deficiency anaemia rates.

Central role for ferritin in the day/night regulation of iron homeostasis in marine phytoplankton

PubMed Central

Botebol, Hugo; Lesuisse, Emmanuel; Šuták, Robert; Six, Christophe; Lozano, Jean-Claude; Schatt, Philippe; Vergé, Valérie; Kirilovsky, Amos; Morrissey, Joe; Léger, Thibaut; Camadro, Jean-Michel; Gueneugues, Audrey; Bowler, Chris; Blain, Stéphane; Bouget, François-Yves

2015-01-01

In large regions of the open ocean, iron is a limiting resource for phytoplankton. The reduction of iron quota and the recycling of internal iron pools are among the diverse strategies that phytoplankton have evolved to allow them to grow under chronically low ambient iron levels. Phytoplankton species also have evolved strategies to cope with sporadic iron supply such as long-term storage of iron in ferritin. In the picophytoplanktonic species Ostreococcus we report evidence from observations both in the field and in laboratory cultures that ferritin and the main iron-binding proteins involved in photosynthesis and nitrate assimilation pathways show opposite diurnal expression patterns, with ferritin being maximally expressed during the night. Biochemical and physiological experiments using a ferritin knock-out line subsequently revealed that this protein plays a central role in the diel regulation of iron uptake and recycling and that this regulation of iron homeostasis is essential for cell survival under iron limitation. PMID:26553998

Central role for ferritin in the day/night regulation of iron homeostasis in marine phytoplankton.

PubMed

Botebol, Hugo; Lesuisse, Emmanuel; Šuták, Robert; Six, Christophe; Lozano, Jean-Claude; Schatt, Philippe; Vergé, Valérie; Kirilovsky, Amos; Morrissey, Joe; Léger, Thibaut; Camadro, Jean-Michel; Gueneugues, Audrey; Bowler, Chris; Blain, Stéphane; Bouget, François-Yves

2015-11-24

In large regions of the open ocean, iron is a limiting resource for phytoplankton. The reduction of iron quota and the recycling of internal iron pools are among the diverse strategies that phytoplankton have evolved to allow them to grow under chronically low ambient iron levels. Phytoplankton species also have evolved strategies to cope with sporadic iron supply such as long-term storage of iron in ferritin. In the picophytoplanktonic species Ostreococcus we report evidence from observations both in the field and in laboratory cultures that ferritin and the main iron-binding proteins involved in photosynthesis and nitrate assimilation pathways show opposite diurnal expression patterns, with ferritin being maximally expressed during the night. Biochemical and physiological experiments using a ferritin knock-out line subsequently revealed that this protein plays a central role in the diel regulation of iron uptake and recycling and that this regulation of iron homeostasis is essential for cell survival under iron limitation.

A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury

DTIC Science & Technology

2010-10-01

comparable to lithium in treating acutely manic bipolar patients, and the FDA approved it in 1995 for this indication. Also, it is used in conjunction with...A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury PRINCIPAL INVESTIGATOR...Lability and Alcohol Use Following Traumatic Brain Injury 5b. GRANT NUMBER W81XWH-08-2-0652 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

Interspecific variations in mangrove leaf litter decomposition are related to labile nitrogenous compounds

NASA Astrophysics Data System (ADS)

Nordhaus, Inga; Salewski, Tabea; Jennerjahn, Tim C.

2017-06-01

Mangrove leaves form a large pool of carbon, nitrogen and energy that is a major driver of element cycles and detrital food webs inside mangrove forests as well as in adjacent coastal waters. However, there are large gaps in knowledge on the transformation pathways and ultimate fate of leaf nitrogen. Therefore, the main objective of this study was to determine the amount and composition of nitrogenous organic matter and possible species-specific differences during the decomposition of mangrove leaf litter. For that purpose a three month decomposition experiment with litterbags was conducted using leaves of Aegiceras corniculatum, Avicennia alba, Ceriops decandra, Rhizophora apiculata, and Sonneratia caseolaris in the mangrove forest of the Segara Anakan Lagoon, Java, Indonesia. Detrital leaves were analyzed for bulk carbon and total nitrogen (N), stable carbon and nitrogen isotope composition (δ13C, δ15N), total hydrolyzable amino acids (THAA) and total hydrolyzable hexosamines (THHA). Decomposition rates (k d-1) were highest and tM50 values (when 50% of the original mass had been degraded) lowest in S. caseolaris (k = 0.0382 d-1; tM50 = 18 days), followed by A. alba, C. decandra, A. corniculatum, and R. apiculata (k = 0.0098 d-1; tM50 = 71 days). The biochemical composition of detrital leaves differed significantly among species and over time. S. caseolaris and A. alba had higher concentrations of N, THAA and THHA and a lower C/N ratio than the other three species. For most of the species concentrations of N, THAA and THHA increased during decomposition. The hexosamine galactosamine, indicative of bacterial cell walls, was first found in leaves after 5-7 days of decomposition and increased afterwards. Our findings suggest an increasing, but species-specific varying, portion of labile nitrogenous OM and total N in decomposing leaves over time that is partly related to the activity of leaf-colonizing bacteria. Despite a higher relative nitrogen content in the

Food Iron Absorption Measured by an Extrinsic Tag

PubMed Central

Cook, J. D.; Layrisse, M.; Martinez-Torres, C.; Walker, R.; Monsen, E.; Finch, C. A.

1972-01-01

The paper describes the use of an extrinsic tag of inorganic radioiron to determine the total absorption of nonheme iron from a complete meal. The method was developed by measuring the iron absorbed from vegetable foods containing biosynthetically incorporated 55Fe (intrinsic tag) and from 59Fe added as a small dose of inorganic iron to the same meal (extrinsic tag). In studies with maize, black bean, and wheat, a consistent extrinsic: intrinsic radioiron absorption ratio averaging 1.10 was observed. Similar results were obtained with either ferrous or ferric iron as the extrinsic tag, and with doses of the latter ranging from 0.001 to 0.5 mg iron added to a test meal containing 2-4 mg of food iron. Adding the radioiron at different stages in preparation of the test meal also had little effect. Separate administration of the extrinsic tag was less satisfactory when small portions of a single food were employed, but with a complete meal, the separate dose was preferable. The extrinsic tag provided a valid measure of absorption despite marked differences in the iron status of the subject, and with wide changes in absorption imposed by adding desferrioxamine or ascorbic acid to the test meal. These findings indicate that there is a common pool of nonheme iron, the absorption of which is influenced by various blocking or enhancing substances present in the meal. PMID:5062612

Iron overload induced death of osteoblasts in vitro: involvement of the mitochondrial apoptotic pathway

PubMed Central

Dai, Zhipeng; Yang, Jingjing; Zheng, Jin

2016-01-01

Background Iron overload is recognized as a new pathogenfor osteoporosis. Various studies demonstrated that iron overload could induce apoptosis in osteoblasts and osteoporosis in vivo. However, the exact molecular mechanisms involved in the iron overload-mediated induction of apoptosis in osteoblasts has not been explored. Purpose In this study, we attempted to determine whether the mitochondrial apoptotic pathway is involved in iron-induced osteoblastic cell death and to investigate the beneficial effect of N-acetyl-cysteine (NAC) in iron-induced cytotoxicity. Methods The MC3T3-E1 osteoblastic cell line was treated with various concentrations of ferric ion in the absence or presence of NAC, and intracellular iron, cell viability, reactive oxygen species, functionand morphology changes of mitochondria and mitochondrial apoptosis related key indicators were detected by commercial kits. In addition, to further explain potential mechanisms underlying iron overload-related osteoporosis, we also assessed cell viability, apoptosis, and osteogenic differentiation potential in bone marrow-derived mesenchymal stemcells(MSCs) by commercial kits. Results Ferric ion demonstrated concentration-dependent cytotoxic effects on osteoblasts. After incubation with iron, an elevation of intracelluar labile iron levels and a concomitant over-generation of reactive oxygen species (ROS) were detected by flow cytometry in osteoblasts. Nox4 (NADPH oxidase 4), an important ROS producer, was also evaluated by western blot. Apoptosis, which was evaluated by Annexin V/propidium iodide staining, Hoechst 33258 staining, and the activation of caspase-3, was detected after exposure to iron. Iron contributed to the permeabilizatio of mitochondria, leading to the release of cytochrome C (cyto C), which, in turn, induced mitochondrial apoptosis in osteoblasts via activation of Caspase-3, up-regulation of Bax, and down-regulation of Bcl-2. NAC could reverse iron-mediated mitochondrial dysfunction and

An anaerobic incubation study of metal lability in drinking water treatment residue with implications for practical reuse.

PubMed

Wang, Changhui; Yuan, Nannan; Pei, Yuansheng

2014-06-15

Drinking water treatment residue (WTR) is an inevitable by-product generated during the treatment of drinking water with coagulating agents. The beneficial reuse of WTR as an amendment for environmental remediation has attracted growing interest. In this work, we investigated the lability of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in Fe/Al hydroxide-comprised WTR based on a 180-day anaerobic incubation test using fractionation, in vitro digestion and a toxicity characteristic leaching procedure. The results indicated that most metals in the WTR were stable during anaerobic incubation and that the WTR before and after incubation could be considered non-hazardous in terms of leachable metal contents according to US EPA Method 1311. However, the lability of certain metals in the WTR after incubation increased substantially, especially Mn, which may be due to the reduction effect. Therefore, although there is no evidence presented to restrict the use of WTR in the field, the lability of metals (especially Mn) in WTR requires further assessment prior to field application. In addition, fractionation (e.g., BCR) is recommended for use to determine the potential lability of metals under various conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

The interactive effects of affect lability, negative urgency, and sensation seeking on young adult problematic drinking.

PubMed

Karyadi, Kenny; Coskunpinar, Ayca; Dir, Allyson L; Cyders, Melissa A

2013-01-01

Prior studies have suggested that affect lability might reduce the risk for problematic drinking among sensation seekers by compensating for their deficiencies in emotional reactivity and among individuals high on negative urgency by disrupting stable negative emotions. Due to the high prevalence of college drinking, this study examined whether affect lability interacted with sensation seeking and negative urgency to influence college student problematic drinking. 414 college drinkers (mean age: 20, 77% female, and 74% Caucasian) from a US Midwestern University completed self-administered questionnaires online. Consistent with our hypotheses, our results indicated that the effects of sensation seeking and negative urgency on problematic drinking weakened at higher levels of affect lability. These findings emphasize the importance of considering specific emotional contexts in understanding how negative urgency and sensation seeking create risk for problematic drinking among college students. These findings might also help us better understand how to reduce problematic drinking among sensation seekers and individuals high on negative urgency.

The Interactive Effects of Affect Lability, Negative Urgency, and Sensation Seeking on Young Adult Problematic Drinking

PubMed Central

Karyadi, Kenny; Coskunpinar, Ayca; Dir, Allyson L.; Cyders, Melissa A.

2013-01-01

Prior studies have suggested that affect lability might reduce the risk for problematic drinking among sensation seekers by compensating for their deficiencies in emotional reactivity and among individuals high on negative urgency by disrupting stable negative emotions. Due to the high prevalence of college drinking, this study examined whether affect lability interacted with sensation seeking and negative urgency to influence college student problematic drinking. 414 college drinkers (mean age: 20, 77% female, and 74% Caucasian) from a US Midwestern University completed self-administered questionnaires online. Consistent with our hypotheses, our results indicated that the effects of sensation seeking and negative urgency on problematic drinking weakened at higher levels of affect lability. These findings emphasize the importance of considering specific emotional contexts in understanding how negative urgency and sensation seeking create risk for problematic drinking among college students. These findings might also help us better understand how to reduce problematic drinking among sensation seekers and individuals high on negative urgency. PMID:24826366

MFehi adipose tissue macrophages compensate for tissue iron pertubations in mice.

PubMed

Hubler, Merla J; Erikson, Keith M; Kennedy, Arion J; Hasty, Alyssa H

2018-05-16

Resident adipose tissue macrophages (ATMs) play multiple roles to maintain tissue homeostasis, such as removing excess FFAs and regulation of extracellular matrix. The phagocytic nature and oxidative resiliency of macrophages not only allows them to function as innate immune cells but also to respond to specific tissue needs, such as iron homeostasis. MFe hi ATMs are a subtype of resident ATMs that we recently identified to have twice the intracellular iron content as other ATMs and elevated expression of iron handling genes. While studies have demonstrated iron homeostasis is important for adipocyte health, little is known about how MFe hi ATMs may respond to and influence AT iron availability. Two methodologies were used to address this question - dietary iron supplementation and intraperitoneal iron injection. Upon exposure to high dietary iron, MFe hi ATMs accumulated excess iron, while the iron content of MFe lo ATMs and adipocytes remained unchanged. In this model of chronic iron excess, MFe hi ATMs exhibited increased expression of genes involved in iron storage. In the injection model, MFe hi ATMs incorporated high levels of iron and adipocytes were spared iron overload. This acute model of iron overload was associated with increased numbers of MFe hi ATMs; 17% could be attributed to monocyte recruitment and 83% to MFe lo ATM incorporation into the MFe hi pool. The MFe hi ATM population maintained its low inflammatory profile and iron cycling expression profile. These studies expand the field's understanding of ATMs and confirm that they can respond as a tissue iron sink in models of iron overload.

Exposure to nitric oxide increases the nitrosyl-iron complexes content in sorghum embryonic axes.

PubMed

Simontacchi, Marcela; Buet, Agustina; Lamattina, Lorenzo; Puntarulo, Susana

2012-02-01

This work was aimed to investigate nitrosyl-Fe complexes formation by reaction of endogenous ligands and Fe, in sorghum embryonic axes exposed to NO-donors. Electron paramagnetic resonance (EPR) was employed to detect the presence of nitrosyl-Fe complexes in plant embryos, as well as changes in labile iron pool (LIP). Nitrosyl-Fe complexes formation was detected in sorghum embryonic axes homogenates incubated in vitro in the presence of 1 mM of NO donors: diethylenetriamine NONOate (DETA NONOate), S-nitrosoglutathione (GSNO) and sodium nitroprusside (SNP). In axes isolated from seeds incubated in vivo in the presence of 1 mM SNP for 24 h, the content of NO was increased by 2-fold, and the EPR spectrum from mononitrosyl-Fe complexes (MNIC) was observed with a concomitant increase in the fresh weight of sorghum axes. The simultaneous exposure to deferoxamine and the NO donor precluded the increase in fresh weight observed in the presence of excess NO. While total Fe content in the axes isolated from seeds exposed to 1mM SNP was not significantly affected as compared to control axes, the LIP was increased by over 2-fold.The data reported suggest a critical role for the generation of complexes between Fe and NO when cells faced a situation leading to a significant increase in NO content. Moreover, demonstrate the presence of MNICs as one of the important components of the LIP, which could actively participate in Fe cellular mobilization. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Analysis and modeling of heat-labile enterotoxins of Escherichia coli suggests a novel space with insights into receptor preference.

PubMed

Krishna Raja, M; Ghosh, Asit Ranjan; Vino, S; Sajitha Lulu, S

2015-01-01

Features of heat-labile enterotoxins of Escherichia coli which make them fit to use as novel receptors for antidiarrheals are not completely explored. Data-set of 14 different serovars of enterotoxigenic Escherichia coli producing heat-labile toxins were taken from NCBI Genbank database and used in the study. Sequence analysis showed mutations in different subunits and also at their interface residues. As these toxins lack crystallography structures, homology modeling using Modeller 9.11 led to the structural approximation for the E. coli producing heat-labile toxins. Interaction of modeled toxin subunits with proanthocyanidin, an antidiarrheal showed several strong hydrogen bonding interactions at the cost of minimized energy. The hits were subsequently characterized by molecular dynamics simulation studies to monitor their binding stabilities. This study looks into novel space where the ligand can choose the receptor preference not as a whole but as an individual subunit. Mutation at interface residues and interaction among subunits along with the binding of ligand to individual subunits would help to design a non-toxic labile toxin and also to improve the therapeutics.

Protection of Pyruvate,Pi Dikinase from Maize against Cold Lability by Compatible Solutes 1

PubMed Central

Krall, John P.; Edwards, Gerald E.; Andreo, Carlos S.

1989-01-01

Most C4 species are chilling sensitive and certain enzymes like pyruvate,Pi dikinase of the C4 pathway are also cold labile. The ability of cations and compatible solutes to protect maize (Zea mays) dikinase against cold lability was examined. The enzyme in desalted extracts at pH 8 from preilluminated leaves could be protected against cold lability (at 0°C) by the divalent cations Mn2+, Mg2+, and Ca2+. There was substantial protection by sulfate based salts but little protection by chloride based salts of potassium or ammonium (concentration 250 millimolar). The degree of protection against cold lability under limiting MgCl2 (5 millimolar) was pH sensitive (maximum protection at pH 8), but independent of ionic strength (up to 250 millimolar by addition of KCl). In catalysis Mg2+ is required and Mn2+ could not substitute as a cofactor. Several compatible solutes reduced or prevented the cold inactivation of dikinase (in desalted extracts and the partially purified enzyme), including glycerol, proline, glycinebetaine and trimethylamine-N-oxide (TMAO). TMAO and Mg2+ had an additive effect in protecting dikinase against cold inactivation. TMAO could largely substitute for the divalent cation and addition of TMAO during cold treatment prevented further inactivation. Cold inactivation was partially reversed by incubation at room temperature; with addition of TMAO reversal was complete. The temperature dependence of inactivation at pH 8 and 3 millimolar MgCl2 was evaluated by incubation at 2 to 17°C for 45 minutes, followed by assay at room temperature. At preincubation temperatures below 11°C there was a progressive inactivation which could be prevented by TMAO (450 millimolar). The results are discussed relative to possible effects of the solutes on the quaternary structure of this enzyme, which is known to dissociate at low temperatures. PMID:16666527

Biolabile ferrous iron bearing nanoparticles in glacial sediments

NASA Astrophysics Data System (ADS)

Hawkings, Jon R.; Benning, Liane G.; Raiswell, Rob; Kaulich, Burkhard; Araki, Tohru; Abyaneh, Majid; Stockdale, Anthony; Koch-Müller, Monika; Wadham, Jemma L.; Tranter, Martyn

2018-07-01

Glaciers and ice sheets are a significant source of nanoparticulate Fe, which is potentially important in sustaining the high productivity observed in the near-coastal regions proximal to terrestrial ice cover. However, the bioavailability of particulate iron is poorly understood, despite its importance in the ocean Fe inventory. We combined high-resolution imaging and spectroscopy to investigate the abundance, morphology and valence state of particulate iron in glacial sediments. Our results document the widespread occurrence of amorphous and Fe(II)-rich and Fe(II)-bearing nanoparticles in Arctic glacial meltwaters and iceberg debris, compared to Fe(III)-rich dominated particulates in an aeolian dust sample. Fe(II) is thought to be highly biolabile in marine environments. Our work shows that glacially derived Fe is more labile than previously assumed, and consequently that glaciers and ice sheets are therefore able to export potentially bioavailable Fe(II)-containing nanoparticulate material to downstream ecosystems, including those in a marine setting. Our findings provide further evidence that Greenland Ice Sheet meltwaters may provide biolabile particulate Fe that may fuel the large summer phytoplankton bloom in the Labrador Sea, and that Fe(II)-rich particulates from a region of very high productivity downstream of a polar ice sheet may be glacial in origin.

Characteristics of labile organic carbon fractions in reclaimed mine soils: Evidence from three reclaimed forests in the Pingshuo opencast coal mine, China.

PubMed

Yuan, Ye; Zhao, Zhongqiu; Li, Xuezhen; Wang, Yangyang; Bai, Zhongke

2018-02-01

The reclamation of discarded spoils has the potential to stimulate carbon (C) sequestration in reclaimed mine soils (RMSs). Nevertheless, to date the temporal dynamics of labile organic C fractions have not been sufficiently elucidated in RMSs. In this study, soil organic carbon (SOC) and labile organic C fractions, including microbial biomass organic C (MBC), easily oxidizable organic C (EOC) and dissolved organic C (DOC), were determined in Robinia pseudoacacia monoculture forests (reclamation periods of 0, 8, 10, 13, 15, 18 and 30years), Pinus tabuliformis forests (reclamation periods of 0, 10, 19, 23 and 25years) and Ulmus pumila forests (reclamation periods of 0, 18, 20 and 22years) situated on RMSs in the Pingshuo opencast coal mine, China. Changes in labile organic C fractions within the soil profiles (0-100cm) were also identified at the 18- or 19-year plots under the three monoculture forests. Our results showed that, SOC and labile organic C fractions, together with soil microbial quotient (SMQ) and C management index (CMI), increased with time since reclamation, indicating that the quality of RMSs improved over time after initial reclamation under the three forest types. R. pseudoacacia significantly increased the accretion of SOC and EOC in the early stage of reclamation while P. tabuliformis accelerated the accumulation of the MBC fraction. Results for U. pumila indicated that this species had a better ability to store C in RMSs 10years or more after reclamation. SOC and labile organic C fractions both had S-shaped distributions within the soil profiles (0-100cm), with the 0-20cm layer recording the highest values (P<0.05). Labile organic C fractions were closely associated and correlated with soil physicochemical properties; our results also showed that nitrogen played an important role in the development of labile organic C fractions. Overall, reclamation accelerated the accretion of both SOC and labile organic C fractions, results of which varied

The Relationship between Environmental Dioxygen and Iron-Sulfur Proteins Explored at the Genome Level

PubMed Central

Andreini, Claudia; Rosato, Antonio; Banci, Lucia

2017-01-01

About 2 billion years ago, the atmosphere of the Earth experienced a great change due to the buildup of dioxygen produced by photosynthetic organisms. This transition caused a reduction of iron bioavailability and at the same time exposed living organisms to the threat of oxidative stress. Iron-sulfur (Fe-S) clusters require iron ions for their biosynthesis and are labile if exposed to reactive oxygen species. To assess how the above transition influenced the usage of Fe-S clusters by organisms, we compared the distribution of the Fe-S proteins encoded by the genomes of more than 400 prokaryotic organisms as a function of their dioxygen requirements. Aerobic organisms use less Fe-S proteins than the majority of anaerobic organisms with a similar genome size. Furthermore, aerobes have evolved specific Fe-S proteins that bind the less iron-demanding and more chemically stable Fe2S2 clusters while reducing the number of Fe4S4-binding proteins in their genomes. However, there is a shared core of Fe-S protein families composed mainly by Fe4S4-binding proteins. Members of these families are present also in humans. The distribution of human Fe-S proteins within cell compartments shows that mitochondrial proteins are inherited from prokaryotic proteins of aerobes, whereas nuclear and cytoplasmic Fe-S proteins are inherited from anaerobic organisms. PMID:28135316

Precipitation overrides warming in mediating soil nitrogen pools in an alpine grassland ecosystem on the Tibetan Plateau.

PubMed

Lin, Li; Zhu, Biao; Chen, Chengrong; Zhang, Zhenhua; Wang, Qi-Bing; He, Jin-Sheng

2016-08-16

Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock. Increased precipitation reduced nitrate N, dissolved organic N and amino acid N stocks, but increased MBN stock in the topsoil. No change in soil total N was detected under warming and altered precipitation regimes. Redundancy analysis further revealed that soil moisture (26.3%) overrode soil temperature (10.4%) in explaining the variations of soil N stocks across the treatments. Our results suggest that precipitation exerted stronger influence than warming on soil N pools in this mesic and high-elevation grassland ecosystem. This indicates that the projected rise in future precipitation may lead to a significant loss of dissolved soil N pools by stimulating the biogeochemical processes in this alpine grassland.

Factors influencing As(V) stabilization in the mine soils amended with iron-rich materials.

PubMed

Kim, Mijin; Kim, Juhee; Kim, Minhee; Kim, Yong-Seong; Nam, Seung Mo; Moon, Deok Hyun; Hyun, Seunghun

2017-09-04

Chemical stability of As(V) in amended mine-impacted soils was assessed according to functions of incubation period (0, 1, 2, 4, and 6 months), amendment dose (2.5 and 5%), and application timing (0 and 3rd month). Six soils contaminated with 26-209 mg kg -1 of As(V) were collected from two abandoned mine sites and were treated with two alkaline iron-rich materials (mine discharge sludge (MS) and steel-making slag (SS)). Seventeen to 23% of As(V) in soils was labile. After each designated time, As(V) stability was assessed by the labile fractions determined with sequential extraction procedures (F1-F5). Over 6 months, a reduction (26.9-70.4%) of the two labile fractions (F1 and F2) and a quantitative increase (7.4-29.9%) of As(V) in F3 were observed (r 2  = 0.956). Two recalcitrant fractions (F4 and F5) remained unchanged. Temporal change of As(V) stability in a sample was well described by the two-domain model (k fast , k slow , and F fast ). The stabilization (%) correlated well with the fast-stabilizing domain (F fast ), clay content (%), and Fe oxide content (mg kg -1 ), but correlated poorly with kinetic rate constants (k fast and k slow ). Until the 3rd month, the 2.5%-MS amended sample resulted in lower As(V) stabilization (25-40%) compared to the 5% sample (50-60%). However, the second 2.5% MS addition on the 2.5% sample upon the lapse of the 3rd month led to a substantial reduction (up to 38%) of labile As(V) fraction in the following 4th and 6th months. As a result, an additional 15-25% of As(V) stability was obtained when splitting the amendment dose into 3-month intervals. In conclusion, the As(V) stabilization by Fe-rich amendment is time-dependent and its efficacy can be improved by optimizing the amendment dose and its timing.

Contribution of anthropogenic phosphorus to agricultural soil fertility and food production

NASA Astrophysics Data System (ADS)

Ringeval, B.; Nowak, B.; Nesme, T.; Delmas, M.; Pellerin, S.

2014-07-01

Agricultural intensification over the last few decades has been accompanied by the extensive use of anthropogenic phosphorus (P) derived from mined phosphate rock. Given the increasing scarcity of P resources, accurate estimates of the reliance of agriculture on anthropogenic P are required. Here we propose a modeling approach for assessing the contribution of anthropogenic P to agricultural soil fertility and food production. We performed computations at country level, and France was chosen as a typical western European country with intensive agriculture. Four soil P pools were identified based on their bioavailability (labile versus stable) and origin (anthropogenic versus natural). Pool evolution between 1948 and 2009 was estimated by combining international databases and a simple biogeochemical model. An optimization procedure demonstrated the necessity of representing a stable P pool capable of replenishing the labile pool within 14 to 33 years in order to match country-scale observations. Mean simulated P pool sizes for 2009 (0-35 cm soil horizon) were 146, 616, 31, and 156 kgP/ha for natural stable, anthropogenic stable, natural labile, and anthropogenic labile pools, respectively. We found that, on average, 82% (min-max: 68-91%) of soil P (sum of labile and above defined stable) in that year was anthropogenic. The temporal evolution of this contribution is directly related to the integral of chemical fertilizer use over time, starting from 1948. The contribution of anthropogenic P to food production was similar at 84% (min-max: 72-91%), which is greater than budget-based estimates ( 50-60%) commonly reported in the literature. By focusing on soil fertility and food production, this study provides a quantitative estimation of human perturbations of the P cycle in agroecosystems.

Mechanism-based design of labile precursors for chromium(I) chemistry

DOE PAGES

Akturk, Eser S.; Yap, Glenn P. A.; Theopold, Klaus H.

2015-08-27

Here, we report that dinitrogen complexes of the type Tp R,RCr–N 2–CrTp R,R are not the most labile precursors for Cr(I) chemistry, as they are sterically protected from obligatory associative ligand substitution. A mononuclear alkyne complex – Tp tBu,MeCr(η 2-C 2(SiMe 3) 2) – proved to be much more reactive.

Immunologic Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins

DTIC Science & Technology

1980-01-15

PUBLICATIONS Supported by Contract No. DAMD 17-77-C-7032 1. Klipstein FA, Engert RF: Immunological interrelationships between cholera toxin and the...heat-labile and heat-stable enterotoxins of coliform bacteria. Infec Immun 18:110, 1977 2. Klipstein FA, Engert RF: Immunological relationship of...different preparations of coliform enterotoxins. Infec Immun 21:771, 1978 3. Klipstein FA, Engert RF: Reversal of jejunal water secretion by glucose in

Immunological Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins

DTIC Science & Technology

1981-01-01

FA, Engert RF: Immunological interrelationships between cholera toxin and the heat-labile and heat-stable enterotoxins of coliforn, bacteria. Infec...Irnmun 18:110, 1977 2. Klipstein FA, Engert RF: Immunological relaticnsh~p of different preparations of coliform enterotoxins. Infec Immun 21:771, 1918...3 Klipstein FA, Engert RF: Reversal of jejunal water secretion by glucose in rats exposed to coliform enterotoxcins. Gastroenterology 75:255, 1978 4

Immunological Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins

DTIC Science & Technology

1981-09-01

FA, Engert RF: Immunological interrelationships between cholera toxin and the heat -labile and hoat-stable enterotoxins of coliform bacteria. Infec...Immun 18:110, 1977 2. Klipstein FA, Engert RF: Immunological relationship of different preparations of coliform enterotoxins. Infec Immun 21:771, 1978...3. Klipstein FA, Engert RF: Reversal of jejunal water secretion by glucose in rats exposed to coliform enterotoxins. Gastroenteroloj y 75:255, 1978 4

Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

NASA Astrophysics Data System (ADS)

Koch, B. P.; Kattner, G.; Witt, M.; Passow, U.

2014-08-01

The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle. For our understanding of the kinetics of organic matter cycling in the ocean, it is crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids and transparent exopolymer particles (TEP) for 2 years. The molecular characterization of extracted DOM was performed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after 70 days and after ∼2 years of incubation. Although glucose quickly degraded, a non-labile DOC background (5-9% of the initial DOC) was generated in the glucose incubations. Only 20% of the organic carbon from the algal exudate degraded within the 2 years of incubation. The degradation rates for the non-labile DOC background in the different treatments varied between 1 and 11 μmol DOC L-1 year-1. Transparent exopolymer particles, which are released by microorganisms, were produced during glucose degradation but decreased back to half of the maximum concentration within less than 3 weeks (degradation rate: 25 μg xanthan gum equivalents L-1 d-1) and were below detection in all treatments after 2 years. Additional glucose was added after 2 years to test whether labile substrate can promote the degradation of background DOC (co-metabolism; priming effect). A priming effect was not observed but the glucose addition led to a slight increase of background DOC. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM transformed during the degradation of the algal exudates. Our

Microbial control of soil organic matter mineralization responses to labile carbon in subarctic climate change treatments.

PubMed

Rousk, Kathrin; Michelsen, Anders; Rousk, Johannes

2016-12-01

Half the global soil carbon (C) is held in high-latitude systems. Climate change will expose these to warming and a shift towards plant communities with more labile C input. Labile C can also increase the rate of loss of native soil organic matter (SOM); a phenomenon termed 'priming'. We investigated how warming (+1.1 °C over ambient using open top chambers) and litter addition (90 g m -2  yr -1 ) treatments in the subarctic influenced the susceptibility of SOM mineralization to priming, and its microbial underpinnings. Labile C appeared to inhibit the mineralization of C from SOM by up to 60% within hours. In contrast, the mineralization of N from SOM was stimulated by up to 300%. These responses occurred rapidly and were unrelated to microbial successional dynamics, suggesting catabolic responses. Considered separately, the labile C inhibited C mineralization is compatible with previously reported findings termed 'preferential substrate utilization' or 'negative apparent priming', while the stimulated N mineralization responses echo recent reports of 'real priming' of SOM mineralization. However, C and N mineralization responses derived from the same SOM source must be interpreted together: This suggested that the microbial SOM-use decreased in magnitude and shifted to components richer in N. This finding highlights that only considering SOM in terms of C may be simplistic, and will not capture all changes in SOM decomposition. The selective mining for N increased in climate change treatments with higher fungal dominance. In conclusion, labile C appeared to trigger catabolic responses of the resident microbial community that shifted the SOM mining to N-rich components; an effect that increased with higher fungal dominance. Extrapolating from these findings, the predicted shrub expansion in the subarctic could result in an altered microbial use of SOM, selectively mining it for N-rich components, and leading to a reduced total SOM-use. © 2016 John Wiley

Trauma exposure and heavy drinking and drug use among college students: Identifying the roles of negative and positive affect lability in a daily diary study.

PubMed

Weiss, Nicole H; Bold, Krysten W; Contractor, Ateka A; Sullivan, Tami P; Armeli, Stephen; Tennen, Howard

2018-04-01

Trauma exposure is linked to heavy drinking and drug use among college students. Extant research reveals positive associations between negative affect lability and both trauma exposure and alcohol use. This study aimed to extend past research by using daily diary methods to test whether (a) individuals with (versus without) trauma exposure experience greater negative and positive affect lability, (b) negative and positive affect lability are associated with heavy drinking and drug use, and (c) negative and positive affect lability mediate the relations between trauma exposure and heavy drinking and drug use. Participants were 1640 college students (M age=19.2, 54% female, 80% European American) who provided daily diary data for 30days via online surveys. Daily diaries assessed negative and positive affect and substance use (i.e., percent days of heavy drinking, percent days of drug use, total number of drugs used). Individuals with (versus without) a history of trauma exposure demonstrated higher levels of negative and positive affect lability. Negative, but not positive, affect lability was associated with percent days of heavy drinking, percent days of drug use, and total number of drugs used, and mediated the associations between trauma exposure and heavy drinking and drug use outcomes. Findings provide support for the underlying role of negative affect lability in the relations between trauma exposure and heavy drinking and drug use among college students, suggesting that treatments targeting negative affect lability may potentially serve to reduce heavy drinking and drug use among trauma-exposed college students. Copyright © 2017 Elsevier Ltd. All rights reserved.

DETERMINATION OF APPARENT QUANTUM YIELD SPECTRA FOR THE FORMATION OF BIOLOGICALLY LABILE PHOTOPRODUCTS

EPA Science Inventory

Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, a...

Conquering the Dark Side: Colloidal Iron Oxide Nanoparticles

PubMed Central

Senpan, Angana; Caruthers, Shelton D.; Rhee, Ilsu; Mauro, Nicholas A.; Pan, Dipanjan; Hu, Grace; Scott, Michael J.; Fuhrhop, Ralph W.; Gaffney, Patrick J.; Wickline, Samuel A.; Lanza, Gregory M.

2009-01-01

Nanomedicine approaches to atherosclerotic disease will have significant impact on the practice and outcomes of cardiovascular medicine. Iron oxide nanoparticles have been extensively used for nontargeted and targeted imaging applications based upon highly sensitive T2* imaging properties, which typically result in negative contrast effects that can only be imaged 24 or more hours after systemic administration due to persistent blood pool interference. Although recent advances involving MR pulse sequences have converted these dark contrast voxels into bright ones, the marked delays in imaging from persistent magnetic background interference and prominent dipole blooming effects of the magnetic susceptibility remain barriers to overcome. We report a T1-weighted (T1w) theranostic colloidal iron oxide nanoparticle platform, CION, which is achieved by entrapping oleate-coated magnetite particles within a cross-linked phospholipid nanoemulsion. Contrary to expectations, this formulation decreased T2 effects thus allowing positive T1w contrast detection down to low nanomolar concentrations. CION, a vascular constrained nanoplatform administered in vivo permitted T1w molecular imaging 1 hour after treatment without blood pool interference, although some T2 shortening effects on blood, induced by the superparamagnetic particles persisted. Moreover, CION was shown to encapsulate antiangiogenic drugs, like fumagillin, and retained them under prolonged dissolution, suggesting significant theranostic functionality. Overall, CION is a platform technology, developed with generally recognized as safe components, that overcomes the temporal and spatial imaging challenges associated with current iron oxide nanoparticle T2 imaging agents, and which has theranostic potential in vascular diseases for detecting unstable ruptured plaque or treating atherosclerotic angiogenesis. PMID:19908850

Siderophores as iron storage compounds in the yeasts Rhodotorula minuta and Ustilago sphaerogena detected by in vivo Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Matzanke, B. F.; Bill, E.; Trautwein, A. X.; Winkelmann, G.

1990-07-01

In the yeasts Rhodotorula minuta and Ustilago sphaerogena siderophores represent the main intracellular iron pool. We suggest a ferritin substituting function of these siderophores in addition to their role as iron transport agents. In Rhodotorula transport and storage siderophore is the same compound whereas in Ustilago the iron-storage siderophore is ferrichrome. Besides siderophores, merely two iron metabolites can be observed. Other iron-requiring compounds are at least one order of magnitude less abundant in these yeasts. The ferrous metabolite has been detected in many other microbial systems and seems to be of general occurence and importance.

13 CFR 120.1704 - Pool Loans eligible for Pooling.

Code of Federal Regulations, 2010 CFR

2010-01-01

..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation. SBA...

13 CFR 120.1704 - Pool Loans eligible for Pooling.

Code of Federal Regulations, 2013 CFR

2013-01-01

..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation. SBA...

13 CFR 120.1704 - Pool Loans eligible for Pooling.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation. SBA...

13 CFR 120.1704 - Pool Loans eligible for Pooling.

Code of Federal Regulations, 2014 CFR

2014-01-01

..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation. SBA...

13 CFR 120.1704 - Pool Loans eligible for Pooling.

Code of Federal Regulations, 2012 CFR

2012-01-01

..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation. SBA...

Microbially driven export of labile organic carbon from the Greenland ice sheet

NASA Astrophysics Data System (ADS)

Musilova, Michaela; Tranter, Martyn; Wadham, Jemma; Telling, Jon; Tedstone, Andrew; Anesio, Alexandre M.

2017-04-01

Glaciers and ice sheets are significant sources of dissolved organic carbon and nutrients to downstream subglacial and marine ecosystems. Climatically driven increases in glacial runoff are expected to intensify the impact of exported nutrients on local and regional downstream environments. However, the origin and bioreactivity of dissolved organic carbon from glacier surfaces are not fully understood. Here, we present simultaneous measurements of gross primary production, community respiration, dissolved organic carbon composition and export from different surface habitats of the Greenland ice sheet, throughout the ablation season. We found that microbial production was significantly correlated with the concentration of labile dissolved organic species in glacier surface meltwater. Further, we determined that freely available organic compounds made up 62% of the dissolved organic carbon exported from the glacier surface through streams. We therefore conclude that microbial communities are the primary driver for labile dissolved organic carbon production and recycling on glacier surfaces, and that glacier dissolved organic carbon export is dependent on active microbial processes during the melt season.

Labile dissolved organic carbon supply limits hyporheic denitrification

NASA Astrophysics Data System (ADS)

Zarnetske, Jay P.; Haggerty, Roy; Wondzell, Steven M.; Baker, Michelle A.

2011-12-01

We used an in situ steady state 15N-labeled nitrate (15NO3-) and acetate (AcO-) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO-influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl- and Br) and reactive (15NO3-) solute tracers had hyporheic median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (<1.5 mg O2 L-1). All receiving wells demonstrated 15N2 production during ambient conditions, indicating that the hyporheic zone was an environment with active denitrification. The subsequent addition of AcO- stimulated more denitrification as evidenced by significant δ15N2 increases by factors of 2.7 to 26.1 in receiving wells and significant decreases of NO3- and DO in the two wells most hydrologically connected to the injection. The rate of nitrate removal in the hyporheic zone increased from 218 kg ha-1 yr-1 to 521 kg ha-1 yr-1 under elevated AcO- conditions. In all receiving wells, increases of bromide and 15N2 occurred without concurrent increases in AcO-, indicating that 100% of AcO- was retained or lost in the hyporheic zone. These results support the hypothesis that denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.

Relationships between soil organic matter pools and nitrous oxide emissions of agroecosystems in the Brazilian Cerrado.

PubMed

de Figueiredo, Cícero Célio; de Oliveira, Alexsandra Duarte; Dos Santos, Isis Lima; Ferreira, Eloisa Aparecida Belleza; Malaquias, Juaci Vitoria; de Sá, Marcos Aurélio Carolino; de Carvalho, Arminda Moreira; Dos Santos, João de Deus Gomes

2018-03-15

In the Brazilian Cerrado, despite the increasing adoption of no-till systems, there are still extended areas under conventional soil management systems that reduce soil carbon (C) and nitrogen (N) stocks and increase the emissions of greenhouse gases, such as nitrous oxide (N 2 O). Conservation agroecosystems, such as no-till, have been proposed as a strategy to mitigate agriculture-induced climatic changes through reductions in N 2 O emissions. However, the relationship between organic matter and N 2 O emissions from soils under different agroecosystems is not yet clear. This study hypothesized that agroecosystems under no-till promote an accumulation of labile and stable SOM fractions along with a reduction of N 2 O emissions. This study evaluated the effects of crop-rotation agroecosystems: i) on C and N pools and labile and stable SOM fractions; ii) on cumulative N 2 O emissions; and iii) on the relationships between SOM fractions and N 2 O emissions. The agricultural systems consisted of: (I) soybean followed by sorghum under no-tillage (NT1); (II) maize followed by pigeon pea under no-tillage (NT2); (III) soybean under conventional tillage followed by fallow soil (CT); (IV) and native Cerrado (CER). After CT for 18years, following the replacement of CER, the soil C stock in the 0-20cm layer was reduced by 0.64tha -1 year -1 . The no-till systems were more efficient in accumulating labile and stable C fractions with values close to those observed under CER, and were directly related to lower soil N 2 O emissions. The cumulative pattern of N 2 O emissions was inverse to that of the following SOM fractions: microbial biomass carbon, permanganate-oxidizable carbon, particulate organic carbon, inert carbon, and humic substances. Based on principal component analysis, the CT was generally separated from the other land use systems. This separation was strongly influenced by the low C contents in the different SOM fractions and higher N 2 O emissions promoted by the

[Impact of Land Utilization Pattern on Distributing Characters of Labile Organic Carbon in Soil Aggregates in Jinyun Mountain].

PubMed

Li, Rui; Jiang, Chang-sheng; Hao, Qing-ju

2015-09-01

Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (<0. 053 mm) were obtained by wet sieving method to measure the content of organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the

Oxidation in the nucleotide pool, the DNA damage response and cellular senescence: Defective bricks build a defective house.

PubMed

Rai, Priyamvada

2010-11-28

Activation of persistent DNA damage response (DDR) signaling is associated with the induction of a permanent proliferative arrest known as cellular senescence, a phenomenon intrinsically linked to both tissue aging as well as tumor suppression. The DNA damage observed in senescent cells has been attributed to elevated levels of reactive oxygen species (ROS), failing DNA damage repair processes, and/or oncogenic activation. It is not clear how labile molecules such as ROS are able to damage chromatin-bound DNA to a sufficient extent to invoke persistent DNA damage and DDR signaling. Recent evidence suggests that the nucleotide pool is a significant target for oxidants and that oxidized nucleotides, once incorporated into genomic DNA, can lead to the induction of a DNA strand break-associated DDR that triggers senescence in normal cells and in cells sustaining oncogene activation. Evasion of this DDR and resulting senescence is a key step in tumor progression. This review will explore the role of oxidation in the nucleotide pool as a major effector of oxidative stress-induced genotoxic damage and DDR in the context of cellular senescence and tumorigenic transformation. 2010 Elsevier B.V. All rights reserved.

Measuring “Free” Iron Levels in Caenorhabditis Elegans Using Low-Temperature Fe(III) Electron Paramagnetic Resonance Spectroscopy

PubMed Central

Pate, Kira T.; Rangel, Natalie A.; Fraser, Brian; Clement, Matthew H. S.; Srinivasan, Chandra

2007-01-01

Oxidative stress, caused by free radicals within the body, has been associated with the process of aging and many human diseases. As free radicals, in particular superoxide, are difficult to measure, an alternative indirect method for measuring oxidative stress levels has been successfully used in E. coli and yeast. This method is based on a proposed connection between elevated superoxide levels and release of iron from solvent exposed [4Fe-4S] enzyme clusters, which eventually leads to an increase in hydroxyl radical production. In past studies using bacteria and yeast, a positive correlation was found between superoxide production or oxidative stress due to superoxide within the organism and EPR (electron paramagnetic resonance) detectable “free” iron levels. In the present study, we have developed a reliable and an efficient method for measuring “free” iron levels in C. elegans using low temperature Fe(III) EPR at g = 4.3. This method utilizes synchronized worm cultures grown on plates, which are homogenized and treated with desferrioxamine, an Fe(III) chelator, prior to packing the EPR tube. Homogenization was found not to alter “free” iron levels, while desferrioxamine treatment significantly raised these levels, indicating presence of both Fe(II) and Fe(III) in the “free” iron pool. The correlation between free radical levels and the observed “free” iron levels was examined by using heat stress and paraquat treatment. The intensity of the Fe(III) EPR signal and thus, the concentration of the “free” iron pool, varied with the treatments that altered radical levels without changing the total iron levels. This study provides the groundwork needed to uncover the correlation between oxidative stress, “free” iron levels, and longevity in C. elegans. PMID:17010298

Can hydroxyurea serve as a free radical scavenger and reduce iron overload in β-thalassemia patients?

PubMed

Italia, Khushnooma; Chandrakala, S; Ghosh, Kanjaksha; Colah, Roshan

2016-09-01

In this study, we hypothesize that hydroxyurea could provide an additional benefit as a free radical scavenger and/or iron chelator in β-thalassemia patients with iron overload. Twenty-one β-thalassemia intermedia patients who presented between 3 and 17 years but later required regular blood transfusions were enrolled for hydroxyurea therapy for a year. Fourteen patients responded to the therapy with hemoglobin levels maintained above 7.5 g/dl without transfusions. Hydroxyurea was discontinued after 6 months in seven patients who did not respond to the therapy and had to be continued on regular blood transfusions. We observed a statistically significant decrease in serum ferritin levels from 4194 ± 4850 ng/ml to 2129 ± 2380 ng/ml among the responders and from 2955 ± 2909 ng/ml to 2040 ± 2432 ng/ml among the non-responders and statistically significant decrease in labile iron pool from 18678.7 ± 10067.4 mean fluorescence intensity (MFI) to 14888.5 ± 5284.0 MFI among responders and from 17986.3 ± 9079.8 MFI to 15634.8 ± 8976.9 MFI among the non-responders after therapy. Phosphatidylserine externalization also showed a statistically significant decrease from 44.2 ± 22.2 MFI to 16.6 ± 6.7 MFI among the responders and from 46.9 ± 33.1 MFI to 39.8 ± 7.4 MFI among the non-responders along with a statistically significant decrease in the levels of reactive oxygen species from 72.8 ± 35.5 MFI to 29.0 ± 8.3 MFI among the responders and from 80.9 ± 41.4 MFI to 40.5 ± 15.8 MFI among the non-responders after therapy. A statistically significant increase in reduced glutathione levels was also observed from 430.8 ± 201.1 MFI to 715.5 ± 292.4 MFI among the responders and from 359.6 ± 165.6 MFI to 450.3 ± 279.5 MFI among the non-responders after therapy. This suggests the possible additional role of hydroxyurea as a free radical scavenger and

The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater

PubMed Central

Kim, Ja-Myung; Baars, Oliver

2016-01-01

A poorly studied but potentially important consequence of the CO2-induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis, demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035261

The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater.

PubMed

Kim, Ja-Myung; Baars, Oliver; Morel, François M M

2016-11-28

A poorly studied but potentially important consequence of the CO 2 -induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis , demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Affective lability mediates the association between childhood trauma and suicide attempts, mixed episodes and co-morbid anxiety disorders in bipolar disorders.

PubMed

Aas, M; Henry, C; Bellivier, F; Lajnef, M; Gard, S; Kahn, J-P; Lagerberg, T V; Aminoff, S R; Bjella, T; Leboyer, M; Andreassen, O A; Melle, I; Etain, B

2017-04-01

Many studies have shown associations between a history of childhood trauma and more severe or complex clinical features of bipolar disorders (BD), including suicide attempts and earlier illness onset. However, the psychopathological mechanisms underlying these associations are still unknown. Here, we investigated whether affective lability mediates the relationship between childhood trauma and the severe clinical features of BD. A total of 342 participants with BD were recruited from France and Norway. Diagnosis and clinical characteristics were assessed using the Diagnostic Interview for Genetic Studies (DIGS) or the Structured Clinical Interview for DSM-IV Axis I disorders (SCID-I). Affective lability was measured using the short form of the Affective Lability Scale (ALS-SF). A history of childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Mediation analyses were performed using the SPSS process macro. Using the mediation model and covariation for the lifetime number of major mood episodes, affective lability was found to statistically mediate the relationship between childhood trauma experiences and several clinical variables, including suicide attempts, mixed episodes and anxiety disorders. No significant mediation effects were found for rapid cycling or age at onset. Our data suggest that affective lability may represent a psychological dimension that mediates the association between childhood traumatic experiences and the risk of a more severe or complex clinical expression of BD.

Liver receptor homolog-1 is a critical determinant of methyl-pool metabolism

USDA-ARS?s Scientific Manuscript database

Balance of labile methyl groups (choline, methionine, betaine, and folate) is important for normal liver function. Quantitatively, a significant use of labile methyl groups is in the production of phosphatidylcholines (PCs), which are ligands for the nuclear liver receptor homolog-1 (LRH-1). We stud...

The unique fold and lability of the [2Fe-2S] clusters of NEET proteins mediate their key functions in health and disease.

PubMed

Karmi, Ola; Marjault, Henri-Baptiste; Pesce, Luca; Carloni, Paolo; Onuchic, Jose' N; Jennings, Patricia A; Mittler, Ron; Nechushtai, Rachel

2018-02-12

NEET proteins comprise a new class of [2Fe-2S] cluster proteins. In human, three genes encode for NEET proteins: cisd1 encodes mitoNEET (mNT), cisd2 encodes the Nutrient-deprivation autophagy factor-1 (NAF-1) and cisd3 encodes MiNT (Miner2). These recently discovered proteins play key roles in many processes related to normal metabolism and disease. Indeed, NEET proteins are involved in iron, Fe-S, and reactive oxygen homeostasis in cells and play an important role in regulating apoptosis and autophagy. mNT and NAF-1 are homodimeric and reside on the outer mitochondrial membrane. NAF-1 also resides in the membranes of the ER associated mitochondrial membranes (MAM) and the ER. MiNT is a monomer with distinct asymmetry in the molecular surfaces surrounding the clusters. Unlike its paralogs mNT and NAF-1, it resides within the mitochondria. NAF-1 and mNT share similar backbone folds to the plant homodimeric NEET protein (At-NEET), while MiNT's backbone fold resembles a bacterial MiNT protein. Despite the variation of amino acid composition among these proteins, all NEET proteins retained their unique CDGSH domain harboring their unique 3Cys:1His [2Fe-2S] cluster coordination through evolution. The coordinating exposed His was shown to convey the lability to the NEET proteins' [2Fe-2S] clusters. In this minireview, we discuss the NEET fold and its structural elements. Special attention is given to the unique lability of the NEETs' [2Fe-2S] cluster and the implication of the latter to the NEET proteins' cellular and systemic function in health and disease.

Siderophore-based microbial adaptations to iron scarcity across the eastern Pacific Ocean.

PubMed

Boiteau, Rene M; Mende, Daniel R; Hawco, Nicholas J; McIlvin, Matthew R; Fitzsimmons, Jessica N; Saito, Mak A; Sedwick, Peter N; DeLong, Edward F; Repeta, Daniel J

2016-12-13

Nearly all iron dissolved in the ocean is complexed by strong organic ligands of unknown composition. The effect of ligand composition on microbial iron acquisition is poorly understood, but amendment experiments using model ligands show they can facilitate or impede iron uptake depending on their identity. Here we show that siderophores, organic compounds synthesized by microbes to facilitate iron uptake, are a dynamic component of the marine ligand pool in the eastern tropical Pacific Ocean. Siderophore concentrations in iron-deficient waters averaged 9 pM, up to fivefold higher than in iron-rich coastal and nutrient-depleted oligotrophic waters, and were dominated by amphibactins, amphiphilic siderophores with cell membrane affinity. Phylogenetic analysis of amphibactin biosynthetic genes suggests that the ability to produce amphibactins has transferred horizontally across multiple Gammaproteobacteria, potentially driven by pressures to compete for iron. In coastal and oligotrophic regions of the eastern Pacific Ocean, amphibactins were replaced with lower concentrations (1-2 pM) of hydrophilic ferrioxamine siderophores. Our results suggest that organic ligand composition changes across the surface ocean in response to environmental pressures. Hydrophilic siderophores are predominantly found across regions of the ocean where iron is not expected to be the limiting nutrient for the microbial community at large. However, in regions with intense competition for iron, some microbes optimize iron acquisition by producing siderophores that minimize diffusive losses to the environment. These siderophores affect iron bioavailability and thus may be an important component of the marine iron cycle.

Siderophore-based microbial adaptations to iron scarcity across the eastern Pacific Ocean

PubMed Central

Mende, Daniel R.; Hawco, Nicholas J.; McIlvin, Matthew R.; Fitzsimmons, Jessica N.; Saito, Mak A.; Sedwick, Peter N.; DeLong, Edward F.; Repeta, Daniel J.

2016-01-01

Nearly all iron dissolved in the ocean is complexed by strong organic ligands of unknown composition. The effect of ligand composition on microbial iron acquisition is poorly understood, but amendment experiments using model ligands show they can facilitate or impede iron uptake depending on their identity. Here we show that siderophores, organic compounds synthesized by microbes to facilitate iron uptake, are a dynamic component of the marine ligand pool in the eastern tropical Pacific Ocean. Siderophore concentrations in iron-deficient waters averaged 9 pM, up to fivefold higher than in iron-rich coastal and nutrient-depleted oligotrophic waters, and were dominated by amphibactins, amphiphilic siderophores with cell membrane affinity. Phylogenetic analysis of amphibactin biosynthetic genes suggests that the ability to produce amphibactins has transferred horizontally across multiple Gammaproteobacteria, potentially driven by pressures to compete for iron. In coastal and oligotrophic regions of the eastern Pacific Ocean, amphibactins were replaced with lower concentrations (1–2 pM) of hydrophilic ferrioxamine siderophores. Our results suggest that organic ligand composition changes across the surface ocean in response to environmental pressures. Hydrophilic siderophores are predominantly found across regions of the ocean where iron is not expected to be the limiting nutrient for the microbial community at large. However, in regions with intense competition for iron, some microbes optimize iron acquisition by producing siderophores that minimize diffusive losses to the environment. These siderophores affect iron bioavailability and thus may be an important component of the marine iron cycle. PMID:27911777

Long-term frequent prescribed fire decreases surface soil carbon and nitrogen pools in a wet sclerophyll forest of Southeast Queensland, Australia.

PubMed

Muqaddas, Bushra; Zhou, Xiaoqi; Lewis, Tom; Wild, Clyde; Chen, Chengrong

2015-12-01

Prescribed fire is one of the most widely-used management tools for reducing fuel loads in managed forests. However the long-term effects of repeated prescribed fires on soil carbon (C) and nitrogen (N) pools are poorly understood. This study aimed to investigate how different fire frequency regimes influence C and N pools in the surface soils (0-10 cm). A prescribed fire field experiment in a wet sclerophyll forest established in 1972 in southeast Queensland was used in this study. The fire frequency regimes included long unburnt (NB), burnt every 2 years (2yrB) and burnt every 4 years (4yrB), with four replications. Compared with the NB treatment, the 2yrB treatment lowered soil total C by 44%, total N by 54%, HCl hydrolysable C and N by 48% and 59%, KMnO4 oxidizable C by 81%, microbial biomass C and N by 42% and 33%, cumulative CO2-C by 28%, NaOCl-non-oxidizable C and N by 41% and 51%, and charcoal-C by 17%, respectively. The 4yrB and NB treatments showed no significant differences for these soil C and N pools. All soil labile, biologically active and recalcitrant and total C and N pools were correlated positively with each other and with soil moisture content, but negatively correlated with soil pH. The C:N ratios of different C and N pools were greater in the burned treatments than in the NB treatments. This study has highlighted that the prescribed burning at four year interval is a more sustainable management practice for this subtropical forest ecosystem. Copyright © 2015 Elsevier B.V. All rights reserved.

Post-test examination of a pool boiler receiver

NASA Technical Reports Server (NTRS)

Dreshfield, Robert L.; Moore, Thomas J.; Bartolotta, Paul A.

1992-01-01

A subscale pool boiler test apparatus to evaluate boiling stability developed a leak after being operated with boiling NaK for 791.4 hr at temperatures from 700 to 750 C. The boiler was constructed using Inconel 625 with a type 304L stainless steel wick for the boiler and type 316 stainless steel for the condenser. The boiler assembly was metallurgically evaluated to determine the cause of the leak and to assess the effects of the NaK on the materials. It was found that the leak was caused by insufficient (about 30 pct.) joint penetration in a butt joint. There was no general corrosion of the construction materials, but the room temperature ductility of the Inconel 625 was only about 6.5 pct. A crack in the heat affected zone of the Inconel 625 near the Inconel 625 to type 316 stainless steel butt joint was probably caused by excessive heat input. The crack was observed to have a zone depleted of iron at the crack surface and porosity below that zone. The mechanism of the iron depletion was not conclusively determined.

Relationship between the lability of sediment-bound Cd and its bioaccumulation in edible oyster.

PubMed

Chakraborty, Parthasarathi; Ramteke, Darwin; Chakraborty, Sucharita; Chennuri, Kartheek; Bardhan, Pratirupa

2015-11-15

A linkage between Cd speciation in sediments and its bioaccumulation in edible oyster (Crassostrea sp.) from a tropical estuarine system was established. Bioaccumulation of Cd in edible oyster increased with the increasing lability and dissociation rate constants of Cd-sediment complexes in the bottom sediments. Total Cd concentration in sediment was not a good indicator of Cd-bioavailability. Increasing trace metal competition in sediments increased lability and bioavailability of Cd in the tropical estuarine sediment. Low thermodynamic stability and high bioavailability of Cd in the estuarine sediment were responsible for high bioaccumulation of Cd in edible oysters (3.2-12.2mgkg(-1)) even though the total concentration of Cd in the bottom sediment was low (0.17-0.49mgkg(-1)). Copyright © 2015 Elsevier Ltd. All rights reserved.

Cell Motility by Labile Association of Molecules

PubMed Central

Inoué, Shinya; Sato, Hidemi

1967-01-01

This article summarizes our current views on the dynamic structure of the mitotic spindle and its relation to mitotic chromosome movements. The following statements are based on measurements of birefringence of spindle fibers in living cells, normally developing or experimentally modified by various physical and chemical agents, including high and low temperatures, antimitotic drugs, heavy water, and ultraviolet microbeam irradiation. Data were also obtained concomitantly with electron microscopy employing a new fixative and through measurements of isolated spindle protein. Spindle fibers in living cells are labile dynamic structures whose constituent filaments (microtubules) undergo cyclic breakdown and reformation. The dynamic state is maintained by an equilibrium between a pool of protein molecules and their linearly aggregated polymers, which constitute the microtubules or filaments. In living cells under physiological conditions, the association of the molecules into polymers is very weak (absolute value of ΔF 25°C < 1 kcal), and the equilibrium is readily shifted to dissociation by low temperature or by high hydrostatic pressure. The equilibrium is shifted toward formation of polymer by increase in temperature (with a large increase in entropy: ΔS 25°C ≃ 100 eu) or by the addition of heavy water. The spindle proteins tend to polymerize with orienting centers as their geometrical foci. The centrioles, kinetochores, and cell plate act as orienting centers successively during mitosis. Filaments are more concentrated adjacent to an orienting center and yield higher birefringence. Astral rays, continuous fibers, chromosomal fibers, and phragmoplast fibers are thus formed by successive reorganization of the same protein molecules. During late prophase and metaphase, polymerization takes place predominantly at the kinetochores; in metaphase and anaphase, depolymerization is prevalent near the spindle poles. When the concentration of spindle protein is high

Increased iron export by ferroportin induces restriction of HIV-1 infection in sickle cell disease.

PubMed

Kumari, Namita; Ammosova, Tatiana; Diaz, Sharmin; Lin, Xionghao; Niu, Xiaomei; Ivanov, Andrey; Jerebtsova, Marina; Dhawan, Subhash; Oneal, Patricia; Nekhai, Sergei

2016-12-27

The low incidence of HIV-1 infection in patients with sickle cell disease (SCD) and inhibition of HIV-1 replication in vitro under the conditions of low intracellular iron or heme treatment suggests a potential restriction of HIV-1 infection in SCD. We investigated HIV-1 ex vivo infection of SCD peripheral blood mononuclear cells (PBMCs) and found that HIV-1 replication was inhibited at the level of reverse transcription (RT) and transcription. We observed increased expression of heme and iron-regulated genes, previously shown to inhibit HIV-1, including ferroportin, IKBα, HO-1, p21, and SAM domain and HD domain-containing protein 1 (SAMHD1). HIV-1 inhibition was less pronounced in hepcidin-treated SCD PBMCs and more pronounced in the iron or iron chelators treated, suggesting a key role of iron metabolism. In SCD PBMCs, labile iron levels were reduced and protein levels of ferroportin, HIF-1α, IKBα, and HO-1 were increased. Hemin treatment induced ferroportin expression and inhibited HIV-1 in THP-1 cells, mimicking the HIV-1 inhibition in SCD PBMCs, especially as hepcidin similarly prevented HIV-1 inhibition. In THP-1 cells with knocked down ferroportin, IKBα, or HO-1 genes but not HIF-1α or p21, HIV-1 was not inhibited by hemin. Activity of SAMHD1-regulatory CDK2 was decreased, and SAMHD1 phosphorylation was reduced in SCD PBMCs and hemin-treated THP-1 cells, suggesting SAMHD1-mediated HIV-1 restriction in SCD. Our findings point to ferroportin as a trigger of HIV-1 restriction in SCD settings, linking reduced intracellular iron levels to the inhibition of CDK2 activity, reduction of SAMHD1 phosphorylation, increased IKBα expression, and inhibition of HIV-1 RT and transcription.

Increased iron export by ferroportin induces restriction of HIV-1 infection in sickle cell disease

PubMed Central

Kumari, Namita; Ammosova, Tatiana; Diaz, Sharmin; Lin, Xionghao; Niu, Xiaomei; Ivanov, Andrey; Jerebtsova, Marina; Dhawan, Subhash; Oneal, Patricia

2016-01-01

The low incidence of HIV-1 infection in patients with sickle cell disease (SCD) and inhibition of HIV-1 replication in vitro under the conditions of low intracellular iron or heme treatment suggests a potential restriction of HIV-1 infection in SCD. We investigated HIV-1 ex vivo infection of SCD peripheral blood mononuclear cells (PBMCs) and found that HIV-1 replication was inhibited at the level of reverse transcription (RT) and transcription. We observed increased expression of heme and iron-regulated genes, previously shown to inhibit HIV-1, including ferroportin, IKBα, HO-1, p21, and SAM domain and HD domain-containing protein 1 (SAMHD1). HIV-1 inhibition was less pronounced in hepcidin-treated SCD PBMCs and more pronounced in the iron or iron chelators treated, suggesting a key role of iron metabolism. In SCD PBMCs, labile iron levels were reduced and protein levels of ferroportin, HIF-1α, IKBα, and HO-1 were increased. Hemin treatment induced ferroportin expression and inhibited HIV-1 in THP-1 cells, mimicking the HIV-1 inhibition in SCD PBMCs, especially as hepcidin similarly prevented HIV-1 inhibition. In THP-1 cells with knocked down ferroportin, IKBα, or HO-1 genes but not HIF-1α or p21, HIV-1 was not inhibited by hemin. Activity of SAMHD1-regulatory CDK2 was decreased, and SAMHD1 phosphorylation was reduced in SCD PBMCs and hemin-treated THP-1 cells, suggesting SAMHD1-mediated HIV-1 restriction in SCD. Our findings point to ferroportin as a trigger of HIV-1 restriction in SCD settings, linking reduced intracellular iron levels to the inhibition of CDK2 activity, reduction of SAMHD1 phosphorylation, increased IKBα expression, and inhibition of HIV-1 RT and transcription. PMID:28203649

Affective lability and difficulties with regulation are differentially associated with amygdala and prefrontal response in women with Borderline Personality Disorder

PubMed Central

Silvers, Jennifer A.; Hubbard, Alexa D.; Biggs, Emily; Shu, Jocelyn; Fertuck, Eric; Chaudhury, Sadia; Grunebaum, Michael F.; Weber, Jochen; Kober, Hedy; Chesin, Megan; Brodsky, Beth S.; Koenigsberg, Harold; Ochsner, Kevin N.; Stanley, Barbara

2016-01-01

The present neuroimaging study investigated two aspects of difficulties with emotion associated with Borderline Personality Disorder (BPD1): affective lability and difficulty regulating emotion. While these two characteristics have been previously linked to BPD symptomology, it remains unknown whether individual differences in affective lability and emotion regulation difficulties are subserved by distinct neural substrates within a BPD sample. To address this issue, sixty women diagnosed with BPD were scanned while completing a task that assessed baseline emotional reactivity as well as top-down emotion regulation. More affective instability, as measured by the Affective Lability Scale (ALS2), positively correlated with greater amygdala responses on trials assessing emotional reactivity. Greater difficulties with regulating emotion, as measured by the Difficulties with Emotion Regulation Scale (DERS3), was negatively correlated with left inferior frontal gyrus (IFG4) recruitment on trials assessing regulatory ability. These findings suggest that, within a sample of individuals with BPD, greater bottom-up amygdala activity is associated with heightened affective lability. By contrast, difficulties with emotion regulation are related to reduced IFG recruitment during emotion regulation. These results point to distinct neural mechanisms for different aspects of BPD symptomology. PMID:27379614

The Basic Leucine Zipper Stress Response Regulator Yap5 Senses High-Iron Conditions by Coordination of [2Fe-2S] Clusters

PubMed Central

Rietzschel, Nicole; Pierik, Antonio J.; Bill, Eckhard; Mühlenhoff, Ulrich

2014-01-01

Iron is an essential, yet at elevated concentrations toxic trace element. To date, the mechanisms of iron sensing by eukaryotic iron-responsive transcription factors are poorly understood. The Saccharomyces cerevisiae transcription factor Yap5, a member of the Yap family of bZIP stress response regulators, administrates the adaptive response to high-iron conditions. Despite the central role of the iron-sensing process for cell viability, the molecule perceived by Yap5 and the underlying regulatory mechanisms are unknown. Here, we show that Yap5 senses high-iron conditions by two Fe/S clusters bound to its activator domain (Yap5-AD). The more stable iron-regulatory Fe/S cluster at the N-terminal cysteine-rich domain (n-CRD) of Yap5 is detected in vivo and in vitro. The second cluster coordinated by the C-terminal CRD can only be shown after chemical reconstitution, since it is bound in a labile fashion. Both clusters are of the [2Fe-2S] type as characterized by UV/visible (UV/Vis), circular dichroism, electron paramagnetic resonance (EPR), and Mössbauer spectroscopy. Fe/S cluster binding to Yap5-AD induces a conformational change that may activate transcription. The cluster-binding motif of the n-CRD domain is highly conserved in HapX-like transcription factors of pathogenic fungi and thus may represent a general sensor module common to many eukaryotic stress response regulators. PMID:25368382

A novel blood-pooling MR contrast agent: Carboxymethyl-diethylaminoethyl dextran magnetite.

PubMed

Sonoda, Akinaga; Nitta, Norihisa; Tsuchiya, Keiko; Nitta-Seko, Ayumi; Ohta, Shinichi; Otani, Hideji; Murata, Kiyoshi

2016-12-01

Gadofosveset trisodium is available as a prolonged pooling vascular contrast agent for magnetic resonance imaging. As gadolinium (Gd)-based agents may increase the risk for nephrogenic systemic fibrosis in patients with severe renal insufficiency, the present study synthesized carboxymethyl-diethylaminoethyl dextran magnetite (CMEADM) particles as a blood-pooling, non-Gd‑based contrast agent. CMEADM particles carry a negative or positive charge due to the binding of amino and carboxyl groups to the hydroxyl group of dextran. The present study evaluated whether the degree of charge alters the blood‑pooling time. The evaluation was performed by injecting four groups of three Japanese white rabbits each with CMEADM‑, CMEADM2‑, CMEADM+ (surface charges: ‑10.4, ‑41.0 and +9.6 mV, respectively) or with ultrasmall superparamagnetic iron oxide (USPIO; ‑11.5 mV). The relative signal intensity (SIrel) of each was calculated using the following formula: SIrel = (SI post‑contrast ‑ SI pre‑contrast / SI pre‑contrast) x 100. Following injection with the CMEADMs, but not with USPIO, the in vivo pooling time was prolonged to >300 min. No significant differences were attributable to the electric charge among the CMEADM‑, CMEADM2‑ or and CMEADM+ particles when analyzed with analysis of variance and Tukey's HSD test. Taken together, all three differently‑charged CMEADM2 particles exhibited prolonged vascular enhancing effects, compared with the USPIO. The degree of charge of the contrast agents used in the present study did not result in alteration of the prolonged blood pooling time.

Sequential induction of Fur-regulated genes in response to iron limitation in Bacillus subtilis.

PubMed

Pi, Hualiang; Helmann, John D

2017-11-28

Bacterial cells modulate transcription in response to changes in iron availability. The ferric uptake regulator (Fur) senses intracellular iron availability and plays a central role in maintaining iron homeostasis in Bacillus subtilis Here we utilized FrvA, a high-affinity Fe 2+ efflux transporter from Listeria monocytogenes , as an inducible genetic tool to deplete intracellular iron. We then characterized the responses of the Fur, FsrA, and PerR regulons as cells transition from iron sufficiency to deficiency. Our results indicate that the Fur regulon is derepressed in three distinct waves. First, uptake systems for elemental iron ( efeUOB ), ferric citrate ( fecCDEF ), and petrobactin ( fpbNOPQ ) are induced to prevent iron deficiency. Second, B. subtilis synthesizes its own siderophore bacillibactin ( dhbACEBF ) and turns on bacillibactin ( feuABC ) and hydroxamate siderophore ( fhuBCGD ) uptake systems to scavenge iron from the environment and flavodoxins ( ykuNOP ) to replace ferredoxins. Third, as iron levels decline further, an "iron-sparing" response ( fsrA , fbpAB , and fbpC ) is induced to block the translation of abundant iron-utilizing proteins and thereby permit the most essential iron-dependent enzymes access to the limited iron pools. ChIP experiments demonstrate that in vivo occupancy of Fur correlates with derepression of each operon, and the graded response observed here results, at least in part, from higher-affinity binding of Fur to the "late"-induced genes.

The Deep Permafrost Carbon Pool of Siberia and Alaska (Invited)

NASA Astrophysics Data System (ADS)

Strauss, J.; Schirrmeister, L.; Grosse, G.; Ulrich, M.; Wetterich, S.; Herzschuh, U.; Hubberten, H. W.

2013-12-01

Estimating the amount of organic carbon stored in Arctic permafrost and its biogeochemical characteristics are important topics in today's permafrost research. While the uppermost cryosoil horizons are reasonably studied and recorded in the Northern Circumpolar Soil Carbon Database (NCSCD), there are large uncertainties concerning the quantity and distribution of permafrost deep organic carbon. We studied the organic carbon content of the Yedoma region of unglaciated Siberia and Alaska. This region is unique because of its long-term accumulation of organic carbon, which was deeply incorporated into permafrost during the late Quaternary. Inclusion of labile organic matter into permafrost halted decomposition and resulted in a deep long-term carbon sink. Organic carbon in the Yedoma region occurs mainly as peat inclusions, twigs and root fragments, other solid and fine detrital plant remains, fossil remains of mammals, insects, aquatic plankton and soil microorganisms, and finally their decompositional and metabolic products in terms of particulate and dissolved organic matter. With our study we show that two major sub-reservoirs compose the Yedoma region deep frozen organic carbon; Yedoma deposits (late Pleistocene ice- and organic-rich silty sediments) and deposits formed in thaw-lake basins (generalised as thermokarst deposits). Thaw-lake basins result when lake formation degrades Yedoma deposits, then the lakes drain and deposits refreeze. Therefore, the deep Yedoma region organic carbon pool is far from homogeneous and strongly linked to depositional and permafrost dynamics as well as the ecological and climatic history. Using of approximately 1000 frozen samples from 23 Siberian and Alaskan study sites and a new approach for upscaling, we find significant differences to former estimates of the Yedoma coverage area, thickness of the relevant frozen deposits, ground ice content and finally in organic carbon content that lead to a reassessment of the deep

Systematic review with network meta-analysis: comparative efficacy and tolerability of different intravenous iron formulations for the treatment of iron deficiency anaemia in patients with inflammatory bowel disease.

PubMed

Aksan, A; Işık, H; Radeke, H H; Dignass, A; Stein, J

2017-05-01

Iron deficiency anaemia (IDA) is a common complication of inflammatory bowel disease (IBD) associated with reduced quality of life and increased hospitalisation rates. While the best way of treating IDA in IBD patients is not clearly established, current European guidelines recommend intravenous iron therapy in IBD patients with severe anaemia or intolerance to oral iron compounds. To compare the efficacy and tolerability of different intravenous iron formulations used to treat IDA in IBD patients in a systematic review and Bayesian network meta-analysis (NMA), PROSPERO registration number: 42016046565. In June 2016, we systematically searched for studies analysing efficacy and safety of intravenous iron for IDA therapy in IBD. Primary outcome was therapy response, defined as Hb normalisation or increase ≥2 g/dL. Five randomised, controlled trials (n = 1143 patients) were included in a network meta-analysis. Only ferric carboxymaltose was significantly more effective than oral iron [OR=1.9, 95% CrI: (1.1;3.2)]. Rank probabilities showed ferric carboxymaltose to be most effective, followed by iron sucrose, iron isomaltose and oral iron. Pooled data from the systematic review (n = 1746 patients) revealed adverse event rates of 12.0%, 15.3%, 12.0%, 17.0% for ferric carboxymaltose, iron sucrose, iron dextran and iron isomaltose respectively. One drug-related serious adverse event (SAE) each was reported for ferric carboxymaltose and iron isomaltoside, and one possibly drug-related SAE for iron sucrose. Ferric carboxymaltose was the most effective intravenous iron formulation, followed by iron sucrose. In addition, ferric carboxymaltose tended to be better tolerated. Thus, nanocolloidal IV iron products exhibit differing therapeutic and safety characteristics and are not interchangeable. © 2017 John Wiley & Sons Ltd.

Precipitation overrides warming in mediating soil nitrogen pools in an alpine grassland ecosystem on the Tibetan Plateau

PubMed Central

Lin, Li; Zhu, Biao; Chen, Chengrong; Zhang, Zhenhua; Wang, Qi-Bing; He, Jin-Sheng

2016-01-01

Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock. Increased precipitation reduced nitrate N, dissolved organic N and amino acid N stocks, but increased MBN stock in the topsoil. No change in soil total N was detected under warming and altered precipitation regimes. Redundancy analysis further revealed that soil moisture (26.3%) overrode soil temperature (10.4%) in explaining the variations of soil N stocks across the treatments. Our results suggest that precipitation exerted stronger influence than warming on soil N pools in this mesic and high-elevation grassland ecosystem. This indicates that the projected rise in future precipitation may lead to a significant loss of dissolved soil N pools by stimulating the biogeochemical processes in this alpine grassland. PMID:27527683

Chronic Iron Limitation Confers Transient Resistance to Oxidative Stress in Marine Diatoms.

PubMed

Graff van Creveld, Shiri; Rosenwasser, Shilo; Levin, Yishai; Vardi, Assaf

2016-10-01

Diatoms are single-celled, photosynthetic, bloom-forming algae that are responsible for at least 20% of global primary production. Nevertheless, more than 30% of the oceans are considered "ocean deserts" due to iron limitation. We used the diatom Phaeodactylum tricornutum as a model system to explore diatom's response to iron limitation and its interplay with susceptibility to oxidative stress. By analyzing physiological parameters and proteome profiling, we defined two distinct phases: short-term (<3 d, phase I) and chronic (>5 d, phase II) iron limitation. While at phase I no significant changes in physiological parameters were observed, molecular markers for iron starvation, such as Iron Starvation Induced Protein and flavodoxin, were highly up-regulated. At phase II, down-regulation of numerous iron-containing proteins was detected in parallel to reduction in growth rate, chlorophyll content, photosynthetic activity, respiration rate, and antioxidant capacity. Intriguingly, while application of oxidative stress to phase I and II iron-limited cells similarly oxidized the reduced glutathione (GSH) pool, phase II iron limitation exhibited transient resistance to oxidative stress, despite the down regulation of many antioxidant proteins. By comparing proteomic profiles of P. tricornutum under iron limitation and metatranscriptomic data of an iron enrichment experiment conducted in the Pacific Ocean, we propose that iron-limited cells in the natural environment resemble the phase II metabolic state. These results provide insights into the trade-off between optimal growth rate and susceptibility to oxidative stress in the response of diatoms to iron quota in the marine environment. © 2016 American Society of Plant Biologists. All Rights Reserved.

Pool Purification

NASA Technical Reports Server (NTRS)

1988-01-01

Caribbean Clear, Inc. used NASA's silver ion technology as a basis for its automatic pool purifier. System offers alternative approach to conventional purification chemicals. Caribbean Clear's principal markets are swimming pool owners who want to eliminate chlorine and bromine. Purifiers in Caribbean Clear System are same silver ions used in Apollo System to kill bacteria, plus copper ions to kill algae. They produce spa or pool water that exceeds EPA Standards for drinking water.

Genetic Linkage of Soil Carbon Pools and Microbial Functions in Subtropical Freshwater Wetlands in Response to Experimental Warming

PubMed Central

Wang, Hang; He, Zhili; Lu, Zhenmei; Zhou, Jizhong; Van Nostrand, Joy D.; Xu, Xinhua

2012-01-01

Rising climate temperatures in the future are predicted to accelerate the microbial decomposition of soil organic matter. A field microcosm experiment was carried out to examine the impact of soil warming in freshwater wetlands on different organic carbon (C) pools and associated microbial functional responses. GeoChip 4.0, a functional gene microarray, was used to determine microbial gene diversity and functional potential for C degradation. Experimental warming significantly increased soil pore water dissolved organic C and phosphorus (P) concentrations, leading to a higher potential for C emission and P export. Such losses of total organic C stored in soil could be traced back to the decomposition of recalcitrant organic C. Warming preferentially stimulated genes for degrading recalcitrant C over labile C. This was especially true for genes encoding cellobiase and mnp for cellulose and lignin degradation, respectively. We confirmed this with warming-enhanced polyphenol oxidase and peroxidase activities for recalcitrant C acquisition and greater increases in recalcitrant C use efficiency than in labile C use efficiency (average percentage increases of 48% versus 28%, respectively). The relative abundance of lignin-degrading genes increased by 15% under warming; meanwhile, soil fungi, as the primary decomposers of lignin, were greater in abundance by 27%. This work suggests that future warming may enhance the potential for accelerated fungal decomposition of lignin-like compounds, leading to greater microbially mediated C losses than previously estimated in freshwater wetlands. PMID:22923398

Iron status of one-year-olds and association with breast milk, cow's milk or formula in late infancy.

PubMed

Thorisdottir, Asa V; Ramel, Alfons; Palsson, Gestur I; Tomassson, Helgi; Thorsdottir, Inga

2013-09-01

Studies on iron status in infancy and early childhood have shown contradicting results concerning prolonged breast-feeding and cow's milk intake. The aim of the present study was to investigate associations between iron status among one-year-olds and feeding, with focus on the type of milk. Randomly selected healthy infants were prospectively investigated until 1 year of age in two cohorts born 1995-1996 (n = 114) and 2005 (n = 140). Information on birth data, feeding and growth until 12 months and iron status at 12 months was collected. Data from the two cohorts were pooled and the infants categorized into three groups according to their predominant milk consumption at 9 months of age, that is, breast milk, cow's milk or follow-on formula. The prevalence of iron deficiency was highest in the cow's milk group and lowest in the follow-on formula group. According to a linear model, adjusted for gender, birth weight and exclusive breast-feeding duration, cow's milk consumption was negatively associated with serum ferritin (SF) and formula positively, but breast milk not. Predicted SF (μg/l) = 11.652(intercept) - 5.362(boy) + 0.005 × birth weight (g) + 2.826(exclusively breastfed ≥ 4 months) + 0.027 × formula (ml) - 0.022 × cow's milk (ml) + 0.005 × breast milk (ml). Correction for other dietary factors did not change these results. In this pooled analysis, cow's milk intake in late infancy associated negatively, and follow-on formula positively, with iron status. Prolonged partial breast-feeding does not seem to be of importance for iron status. Fortified food seems to improve iron status in late infancy.

Lability of Secondary Organic Particulate Matter

DOE PAGES

Liu, Pengfei; Li, Yong Jie; Wang, Yan; ...

2016-10-24

Accurate simulations of the consenctrations of atmospheric organic particulate matter (PM) are needed for predicting energy flow in the Earth’s climate system. In the past, simulations of organic PM widely assume equilibrium partitioning of semivolatile organic compounds (SVOCs) between the PM and surrounding vapor. Herein, we test this assumption by measuring evaporation rates and associated vapor mass concentration of organic films representative of atmospheric PM. For films representing anthropogenic PM, evaporation rates and vapor mass concentrations increased above a threshold relative humidity (RH), indicating equilibrium partitioning above a transition RH but not below. In contrast for films representing biogenic PM,more » no threshold was observed, indicating equilibrium partitioning at all RHs. The results suggest that the mass lability of atmospheric organic PM can differ in consequential ways among Earth’s natural biomes, polluted regions, and regions of land-use change, and these differences need to be considered when simulating atmospheric organic PM.« less

Assessing SOC labile fractions through respiration test, density-size fractionation and thermal analysis - A comparison of methods

NASA Astrophysics Data System (ADS)

Soucemarianadin, Laure; Cécillon, Lauric; Chenu, Claire; Baudin, François; Nicolas, Manuel; Savignac, Florence; Barré, Pierre

2017-04-01

Soil organic matter (SOM) is the biggest terrestrial carbon reservoir, storing 3 to 4 times more carbon than the atmosphere. However, despite its major importance for climate regulation SOM dynamics remains insufficiently understood. For instance, there is still no widely accepted method to assess SOM lability. Soil respiration tests and particulate organic matter (POM) obtained by different fractionation schemes have been used for decades and are now considered as classical estimates of very labile and labile soil organic carbon (SOC), respectively. But the pertinence of these methods to characterize SOM turnover can be questioned. Moreover, they are very time-consuming and their reproducibility might be an issue. Alternate ways of determining the labile SOC component are thus well-needed. Thermal analyses have been used to characterize SOM among which Rock-Eval 6 (RE6) analysis of soil has shown promising results in the determination of SOM biogeochemical stability (Gregorich et al., 2015; Barré et al., 2016). Using a large set of samples of French forest soils representing contrasted pedoclimatic conditions, including deep samples (up to 1 m depth), we compared different techniques used for SOM lability assessment. We explored whether results from soil respiration test (10-week laboratory incubations), SOM size-density fractionation and RE6 thermal analysis were comparable and how they were correlated. A set of 222 (respiration test and RE6), 103 (SOM fractionation and RE6) and 93 (respiration test, SOM fractionation and RE6) forest soils samples were respectively analyzed and compared. The comparison of the three methods (n = 93) using a principal component analysis separated samples from the surface (0-10 cm) and deep (40-80 cm) layers, highlighting a clear effect of depth on the short-term persistence of SOC. A correlation analysis demonstrated that, for these samples, the two classical methods of labile SOC determination (respiration and SOM fractionation

The role of labile sulfur compounds in thermochemical sulfate reduction

USGS Publications Warehouse

Amrani, A.; Zhang, T.; Ma, Q.; Ellis, G.S.; Tang, Y.

2008-01-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S??, organic S) at temperatures of 330 and 356 ??C under a constant confining pressure. The in-situ pH was buffered to 3.5 (???6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (???0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

The role of labile sulfur compounds in thermochemical sulfate reduction

NASA Astrophysics Data System (ADS)

Amrani, Alon; Zhang, Tongwei; Ma, Qisheng; Ellis, Geoffrey S.; Tang, Yongchun

2008-06-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S°, organic S) at temperatures of 330 and 356 °C under a constant confining pressure. The in-situ pH was buffered to 3.5 (∼6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (∼0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

Suppression of inflammation in a mouse model of rheumatoid arthritis using targeted lipase-labile fumagillin prodrug nanoparticles.

PubMed

Zhou, Hui-Fang; Yan, Huimin; Senpan, Angana; Wickline, Samuel A; Pan, Dipanjan; Lanza, Gregory M; Pham, Christine T N

2012-11-01

Nanoparticle-based therapeutics are emerging technologies that have the potential to greatly impact the treatment of many human diseases. However, drug instability and premature release from the nanoparticles during circulation currently preclude clinical translation. Herein, we use a lipase-labile (Sn 2) fumagillin prodrug platform coupled with a unique lipid surface-to-surface targeted delivery mechanism, termed contact-facilitated drug delivery, to counter the premature drug release and overcome the inherent photo-instability of fumagillin, an established anti-angiogenic agent. We show that α(v)β(3)-integrin targeted fumagillin prodrug nanoparticles, administered at 0.3 mg of fumagillin prodrug/kg of body weight suppress the clinical disease indices of KRN serum-mediated arthritis in a dose-dependent manner when compared to treatment with the control nanoparticles with no drug. This study demonstrates the effectiveness of this lipase-labile prodrug nanocarrier in a relevant preclinical model that approximates human rheumatoid arthritis. The lipase-labile prodrug paradigm offers a translatable approach that is broadly applicable to many targeted nanosystems and increases the translational potential of this platform for many diseases. Copyright © 2012 Elsevier Ltd. All rights reserved.

Apoprotein isolation and activation, and vibrational structure of the Helicobacter mustelae iron urease

PubMed Central

Carter, Eric L.; Proshlyakov, Denis A.; Hausinger, Robert P.

2011-01-01

The micro-aerophilic pathogen Helicobacter mustelae synthesizes an oxygen-labile, iron-containing urease (UreA2B2) in addition to its standard nickel-containing enzyme (UreAB). An apoprotein form of the iron urease was prepared from ureA2B2-expressing recombinant Escherichia coli cells that were grown in minimal medium. Temperature-dependent circular dichroism measurements of holoprotein and apoprotein demonstrate an enhancement of thermal stability associated with the UreA2B2 metallocenter. In parallel to the situation reported for nickel activation of the standard urease apoprotein, incubation of UreA2B2 apoprotein with ferrous ions and bicarbonate generated urease activity in a portion of the nascent active sites. In addition, ferrous ions were shown to be capable of reductively activating the oxidized metallocenter. Resonance Raman spectra of the inactive, aerobically-purified UreA2B2 holoprotein exhibit vibrations at 495 cm−1 and 784 cm−1, consistent with νs and νas modes of an Fe(III)-O-Fe(III) center; these modes undergo downshifts upon binding of urea and were unaffected by changes in pH. The low-frequency mode also exhibits an isotopic shift from 497 to 476 cm−1 upon 16O/18O bulk water isotope substitution. Expression of subunits of the conventional nickel-containing Klebsiella aerogenes urease in cells grown in rich medium without nickel resulted in iron incorporation into a portion of the protein. The inactive iron-loaded species exhibited a UV-visible spectrum similar to oxidized UreA2B2 and was capable of being reductively activated under anoxic conditions. Results from these studies more clearly define the formation and unique properties of the iron urease metallocenter. PMID:22196017

Identification of the iron-sulfur center of spinach ferredoxin-nitrite reductase as a tetranuclear center, and preliminary EPR studies of mechanism.

PubMed

Lancaster, J R; Vega, J M; Kamin, H; Orme-Johnson, N R; Orme-Johnson, W H; Krueger, R J; Siegel, L M

1979-02-25

EPR spectroscopic and chemical analyses of spinach nitrite reductase show that the enzyme contains one reducible iron-sulfur center, and one site for binding either cyanide or nitrite, per siroheme. The heme is nearly all in the high spin ferric state in the enzyme as isolated. The extinction coefficient of the enzyme has been revised to E386 = 7.6 X 10(4) cm-1 (M heme)-1. The iron-sulfur center is reduced with difficulty by agents such as reduced methyl viologen (equilibrated with 1 atm of H2 at pH 7.7 in the presence of hydrogenase) or dithionite. Complexation of the enzyme with CO (a known ligand for nitrite reductase heme) markedly increases the reducibility of the iron-sulfur center. New chemical analyses and reinterpretation of previous data show that the enzyme contains 6 mol of iron and 4 mol of acid-labile S2-/mol of siroheme. The EPR spectrum of reduced nitrite reductase in 80% dimethyl sulfoxide establishes clearly that the enzyme contains a tetranuclear iron-sulfur (Fe4S4) center. The ferriheme and Fe4S4 centers are reduced at similar rates (k = 3 to 4 s-1) by dithionite. The dithionite-reduced Fe4S4 center is rapidly (k = 100 s-1) reoxidized by nitrite. These results indicate a role for the Fe4S4 center in catalysis.

Iron isotope biogeochemistry of Neoproterozoic marine shales

NASA Astrophysics Data System (ADS)

Kunzmann, Marcus; Gibson, Timothy M.; Halverson, Galen P.; Hodgskiss, Malcolm S. W.; Bui, Thi Hao; Carozza, David A.; Sperling, Erik A.; Poirier, André; Cox, Grant M.; Wing, Boswell A.

2017-07-01

decreasing supply of Fe(II) to the ferrous seawater iron reservoir could have caused the reservoir to decrease in size, allowing a higher degree of partial oxidation, irrespective of increasing environmental oxygen levels. Alternatively, increasing oxygen levels would have led to a higher proportion of Fe(II) being oxidized, without decreasing the initial size of the ferrous seawater iron pool. We consider the latter explanation as the most likely. According to this hypothesis, the δ 56Fe record reflects the redox evolution of Earth's surface environments. δ 56Fe values in pre-Sturtian samples significantly heavier than bulk crust and hydrothermal iron imply partial oxidation of a ferrous seawater iron reservoir. In contrast, mean δ 56Fe values closer to that of hydrothermal iron in post-Sturtian shales reflects oxidation of a larger proportion of the ferrous seawater iron reservoir, and by inference, higher environmental oxygen levels. Nevertheless, significant iron isotopic variation in post-Sturtian shales suggest redox heterogeneity and possibly a dominantly anoxic deep ocean, consistent with results from recent studies using iron speciation and redox sensitive trace metals. However, the interpretation of generally increasing environmental oxygen levels after the Sturtian glaciation highlights the need to better understand the sensitivity of different redox proxies to incremental changes in oxygen levels to enable us to reconcile results from different paleoredox proxies.

Combined effects of hydrographic structure and iron and copper availability on the phytoplankton growth in Terra Nova Bay Polynya (Ross Sea, Antarctica)

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Luisa Abelmoschi, Maria; Grotti, Marco; Ianni, Carmela; Magi, Emanuele; Margiotta, Francesca; Massolo, Serena; Saggiomo, Vincenzo

2012-04-01

Surface water (<100 m) samples were collected from the Terra Nova Bay polynya region of the Ross Sea (Antarctica) in January 2006, with the aim of evaluating the individual and combined effects of hydrographic structure, iron and copper concentration and availability on the phytoplankton growth. The measurements were conducted within the framework of the Climatic Long Term Interaction for the Mass-balance in Antarctica (CLIMA) Project of the Programma Nazionale di Ricerca in Antartide activities. Dissolved oxygen, nutrients, phytoplankton pigments and concentration and complexation of dissolved trace metals were determined. Experimental data were elaborated by Principal Component Analysis (PCA). As a result of solar heating and freshwater inputs from melting sea-ice, the water column was strongly stratified with an Upper Mixed Layer 4-16 m deep. The integrated Chl a in the layer 0-100 m ranged from 60 mg m-2 to 235 mg m-2, with a mean value of 138 mg m-2. The pigment analysis showed that diatoms dominated the phytoplankton assemblage. Major nutrients were generally high, with the lowest concentration at the surface and they were never fully depleted. The Si:N drawdown ratio was close to the expected value of 1 for Fe-replete diatoms. We evaluated both the total and the labile dissolved fraction of Fe and Cu. The labile fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The total dissolved Fe ranged from 0.48 to 3.02 nM, while the total dissolved Cu from 3.68 to 6.84 nM. The dissolved labile Fe ranged from below the detection limit (0.15 nM) to 1.22 nM, and the dissolved labile Cu from 0.31 to 1.59 nM, respectively. The labile fractions measured at 20 m were significantly lower than values in 40-100 m samples. As two stations were re-sampled 5 days later, we evaluated the short-term variability of the physical and biogeochemical properties. In particular, in a re-sampled station

Exciting Pools

ERIC Educational Resources Information Center

Wright, Bradford L.

1975-01-01

Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

The Origin of Life in a Terrestrial Hydrothermal Pool? The Importance of a Catalytic Surface

NASA Astrophysics Data System (ADS)

Sydow, L. A.; Bennett, P.

2013-12-01

A premise of one chemoautotrophic theory for the origin of life is that a recurring reaction catalyzed on the charged surfaces of pyrite served as the first metabolism and was later enveloped by a primitive cellular membrane. This proposed 'surface metabolism' is analogous to the reductive acetyl-CoA pathway (Wächtershäuser 1988) and requires the abiotic formation of methanethiol (CH3SH), the simplest of the alkyl thiols, which would serve the role of coenzyme-A in the surface metabolism. Abiogenic CH3SH has not previously been identified in terrestrial hot springs, but it has been produced in the laboratory under hydrothermal conditions in the presence of a catalyst, usually FeS. Its formation would occur via the following reactions, with reaction 2 requiring catalysis: CO2 + 2H2S --> CS2 + 2H2O (1) CS2 + 3H2 --> CH3SH + H2S (2) We have identified CH3SH in Cinder Pool, an acid-sulfate-chloride hot spring in Yellowstone National Park. This spring is unusual in that it contains a subaqueous molten sulfur layer (~18 m depth) and thousands of iron-sulfur-spherules floating on the surface, which are created by gas bubbling through the molten floor of the spring. Analysis with EDS has shown that cinder material, largely composed of elemental sulfur, also contains trace iron sulfide minerals, meaning it could serve as a reactive and catalytic surface for abiogenic CH3SH formation in Cinder Pool. Furthermore, the cinders themselves are highly porous, and these void spaces could trap necessary reactants near the catalytic surface. Gas samples were collected from Cinder pool in fall of 2011 using the bubble strip method. One sample contained measurable quantities of CH3SH, and all samples contained related reactant sulfur gases such as large amounts of H2S, and smaller amounts of CS2 and dimethyl disulfide. Laboratory microcosm experiments were conducted to replicate these findings in a sterile environment to ensure CH3SH generation was abiotic. Analog Cinder Pool water

Chronic Iron Limitation Confers Transient Resistance to Oxidative Stress in Marine Diatoms1

PubMed Central

Graff van Creveld, Shiri; Rosenwasser, Shilo; Vardi, Assaf

2016-01-01

Diatoms are single-celled, photosynthetic, bloom-forming algae that are responsible for at least 20% of global primary production. Nevertheless, more than 30% of the oceans are considered “ocean deserts” due to iron limitation. We used the diatom Phaeodactylum tricornutum as a model system to explore diatom’s response to iron limitation and its interplay with susceptibility to oxidative stress. By analyzing physiological parameters and proteome profiling, we defined two distinct phases: short-term (<3 d, phase I) and chronic (>5 d, phase II) iron limitation. While at phase I no significant changes in physiological parameters were observed, molecular markers for iron starvation, such as Iron Starvation Induced Protein and flavodoxin, were highly up-regulated. At phase II, down-regulation of numerous iron-containing proteins was detected in parallel to reduction in growth rate, chlorophyll content, photosynthetic activity, respiration rate, and antioxidant capacity. Intriguingly, while application of oxidative stress to phase I and II iron-limited cells similarly oxidized the reduced glutathione (GSH) pool, phase II iron limitation exhibited transient resistance to oxidative stress, despite the down regulation of many antioxidant proteins. By comparing proteomic profiles of P. tricornutum under iron limitation and metatranscriptomic data of an iron enrichment experiment conducted in the Pacific Ocean, we propose that iron-limited cells in the natural environment resemble the phase II metabolic state. These results provide insights into the trade-off between optimal growth rate and susceptibility to oxidative stress in the response of diatoms to iron quota in the marine environment. PMID:27503604

Erythrocyte haemolysate interacts with ATP-Fe to form a complex containing iron, ATP and 13 800 MW polypeptide.

PubMed

Weaver, J; Zhan, H; Pollack, S

1993-01-01

Iron first entering the reticulocyte is bound to ATP in the low MW cytosolic pool; some is also 'loosely bound' to haemoglobin, coeluting with haemoglobin from a molecular sieve column though not incorporated into haem. When haemolysate is mixed with ATP-Fe in vitro a similar high MW iron-containing complex is formed: the ATP-Fe interacts with a non-haemoglobin constituent of the haemolysate to form a high MW ATP-Fe complex in which the ratio of ATP:Fe (originally 6:1) is reversed, so that the complex contains more iron than ATP. The high MW ATP-Fe complex is formed even when ATP is in 150-fold molar excess and is formed without detectable hydrolysis of the ATP. The activity of haemolysate in forming the high MW ATP-Fe complex is not diminished by dialysis; all of the activity is recovered in the haemoglobin-containing fraction obtained from an Ultrogel AcA 44 column. The activity does not derive from haemoglobin since 85% of the activity is removed when haemoglobin is purified from haemolysate with DEAE-Sephadex. The chelatable iron pool of the cell probably includes both the high MW ATP-Fe complex and low MW ATP-Fe. Shunting of ATP-Fe to a high MW aggregate reduces the amount of iron present in the highly reactive low MW form and thus probably serves to limit the formation of cell damaging radicals.

Temperature sensitivity (Q10), and dynamics of soil organic matter (SOM) decomposition in permafrost soils with different carbon quality and under experimental warming. R. Bracho1, E.A.G Schuur1, E. Pegoraro1, K.G. Crummer1, S. Natali2, J. Zhou, Y Luo3, J. L. Wu3, M. Tiedje4, K. Konstantinidis5 1Department of Biology, University of Florida, Gainesville, FL. 2Woods Hole Research Center, Falmouth, MA. 3Institute for Environmental Genomics and Department of Botany and Microbiology, University of Oklahoma, Norman, OK, 4Center for Microbial Ecology, Michigan State University, East Lansing, MI; 5Center for Bioinformatics and Computational Genomics and School of Biology, Georgia Institute of Technology, Atlanta, GA

NASA Astrophysics Data System (ADS)

Bracho, R. G.; Schuur, E. A.; Pegoraro, E.; Crummer, K. G.; Natali, S.; Zhou, J.; Wu, L.; Luo, Y.; Tiedje, J. M.; Konstantinidis, K.

2013-12-01

Permafrost soils contain approximately1700 Pg of carbon (C), twice the amount of C in the atmosphere. Temperatures in higher latitudes are increasing, inducing permafrost thaw and subsequent microbial decomposition of previously frozen C. This process is one of the most likely positive feedbacks to climate change. Understanding the temperature sensitivity (Q10) and dynamics of SOM decomposition under warming is essential to predict the future state of the earth - climate system. Alaskan tundra soils were exposed to two winter warming (WW) seasons in the field, which warmed the soils by 4°C to 40 cm depth. Soils were obtained from three depths (0 - 15, 15 - 25 and 45 - 55 cm) and differed in initial amounts of labile and recalcitrant C. Soils were incubated in the lab under aerobic conditions, at 15 and 25°C over 365 days. Q10 was estimated at 14, 100 & 280 days of incubation (DOI); C fluxes were measured periodically and dynamics of SOM decomposition (C pool sizes and decay rates) were estimated by fitting a two pool C model to cumulative respired C (Ccum, mgC/ginitialC). After two WW seasons, initial C content tended to decrease through the soil profile and C:N ratio was significantly decreased in the top 15 cm. After one year of incubation, Ccum was twice as high at 25°C as at 15°C and significantly decreased with depth. No significant WW field treatment was detected, although Ccum tended to be lower in warmed soils. Labile C accounted for up to 5% of initial soil C content in the top 15 cm and decreased with depth. Soils exposed to WW had smaller labile C pools, and higher labile C decay rates in the top 25 cm. Q10 significantly decreased with time and depth as labile pool decreased, especially for WW. This decrease with time indicates a lower temperature sensitivity of the most recalcitrant C pool. The deepest WW soil layer, where warming was more pronounced, had significantly lower Q10 compared to control soils at the same depth. After two seasons, the

Labile Dissolved Organic Carbon Availability Controls Hyporheic Denitrification: a 15N Tracer Study

NASA Astrophysics Data System (ADS)

Zarnetske, J. P.; Haggerty, R.; Wondzell, S. M.; Baker, M. A.

2009-12-01

We used an in situ 15N-labeled nitrate (15NO3-) and acetate injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as acetate influences microbial denitrification in the hyporheic zone (HZ) of an upland (3rd-order) agricultural stream. A 48 h steady-state injection of a conservative tracer, chloride, and 15NO3- was used to quantify ambient HZ denitrification via 15N2 production. Following ambient plateau measurements of denitrification during the first 24 h, a second conservative tracer, bromide, and labile DOC source, acetate, were co-injected for an additional 24 h to measure HZ denitrification under increased DOC supply. Conservative tracers were observed at 4 of the 6 down gradient wells. Receiving wells represented HZ median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (7.5 to 9.3 mg-O2 L-1 deficit). All 4 receiving wells demonstrated 15N2 production during ambient conditions indicating that the HZ was an active denitrification environment. Acetate addition stimulated significant increases in 15N2 production by factors of 2.7 to 26.1 in all receiving wells, and significant decreases of NO3- and DOC aromaticity (via SUVA254) in the two wells most hydrologically connected to the injection. In all receiving wells, increases of bromide and 15N2 production occurred without concurrent increases in acetate indicating that 100% of acetate was retained in the HZ, a portion of which is due to biological consumption. These results support our hypothesis that microbial denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.

[Effects of residue management and fertilizer application mode on soil organic carbon pools in an oasis cotton region.

PubMed

Zhang, Peng Peng; Liu, Yan Jie; Pu, Xiao Zhen; Zhang, Guo Juan; Wang, Jin; Zhang, Wang Feng

2016-11-18

To reveal the regulation mechanisms of agricultural management practices on soil organic carbon (SOC) pools and provide scientific basis for improving soil productivity and formulating agricultural fixed carbon and reducing discharge measures, we monitored the changes of SOC pools and organic carbon fractions in an oasis cotton field under different residue management and fertilizer application modes. A split-plot experimental design was used with differing residue management including residue incorporation (S) and residue removing (NS) in the main plots and differing fertilizer application modes including no fertilizer (CK), NPK fertilizer (NPK), organic manure (OM) and NPK fertilizer plus organic manure (NPK+OM) in the subplot. The results showed that fertilization and residue incorporation significantly increased SOC pool, soil organic carbon (C T ), labile carbon (C L ), microbial biomass carbon (C MB ), water-soluble organic carbon (C WS ), hot-water-soluble organic carbon (C HWS ), accumulative amount of soil organic carbon mineralization (C TM ) and carbon management index (CMI). The SOC pool was increased by 20.6% by residue incorporation compared to residue removing. SOC pools were increased by 7.8%, 29.5% and 37.7% in NPK, OM and NPK+OM treatments compared to CK, respectively. The contents of C T , C L , C MB , C WS and C HWS under different fertilization treatments were shown as NPK+OM>OM>NPK>CK. C TM was increased by 5.9% by residue incorporation compared to residue removing and C TM was increased by 32.7%, 59.5% and 97.3% in NPK, OM and NPK+OM treatments compared to CK, respectively. There was a significant correlation between CMI and C T , C MB , C L , C WS , C HWS , C TM , C pool and C sequestration. Therefore, we concluded that CMI is an important index for evaluating the effect of agricultural management practices on soil quality. In order to construct high-standard oasis farmland in arid region and develop cotton production, we should consider

Apparatus for draining lower drywell pool water into suppresion pool in boiling water reactor

DOEpatents

Gluntz, Douglas M.

1996-01-01

An apparatus which mitigates temperature stratification in the suppression pool water caused by hot water drained into the suppression pool from the lower drywell pool. The outlet of a spillover hole formed in the inner bounding wall of the suppression pool is connected to and in flow communication with one end of piping. The inlet end of the piping is above the water level in the suppression pool. The piping is routed down the vertical downcomer duct and through a hole formed in the thin wall separating the downcomer duct from the suppression pool water. The piping discharge end preferably has an elevation at or near the bottom of the suppression pool and has a location in the horizontal plane which is removed from the point where the piping first emerges on the suppression pool side of the inner bounding wall of the suppression pool. This enables water at the surface of the lower drywell pool to flow into and be discharged at the bottom of the suppression pool.

Evolutionary lability of a complex life cycle in the aphid genus Brachycaudus.

PubMed

Emmanuelle, Jousselin; Gwenaelle, Genson; Armelle, Coeur d'acier

2010-09-28

Most aphid species complete their life cycle on the same set of host-plant species, but some (heteroecious species) alternate between different hosts, migrating from primary (woody) to secondary (herbaceous) host plants. The evolutionary processes behind the evolution of this complex life cycle have often been debated. One widely accepted scenario is that heteroecy evolved from monoecy on woody host plants. Several shifts towards monoecy on herbaceous plants have subsequently occurred and resulted in the radiation of aphids. Host alternation would have persisted in some cases due to developmental constraints preventing aphids from shifting their entire life cycle to herbaceous hosts (which are thought to be more favourable). According to this scenario, if aphids lose their primary host during evolution they should not regain it. The genus Brachycaudus includes species with all the types of life cycle (monoecy on woody plants, heteroecy, monoecy on herbs). We used this genus to test hypotheses concerning the evolution of life cycles in aphids. Phylogenetic investigation and character reconstruction suggest that life cycle is evolutionary labile in the genus. Though ancestral character states can be ambiguous depending on optimization methods, all analyses suggest that transitions from monoecy on herbs towards heteroecy have occurred several times. Transitions from heteroecy towards monoecy, are also likely. There have been many shifts in feeding behaviour but we found no significant correlation between life cycle changes and changes in diet. The transitions from monoecy on herbs towards heteroecy observed in this study go against a widely accepted evolutionary scenario: aphids in the genus Brachycaudus seem to be able to recapture their supposedly ancestral woody host. This suggests that the determinants of host alternation are probably not as complicated as previously thought. Definitive proofs of the lability of life cycle in Brachycaudus will necessitate

Fraction of organic carbon predicts labile desorption rates of chlorinated organic pollutants in laboratory-spiked geosorbents.

PubMed

Ginsbach, Jake W; Killops, Kato L; Olsen, Robert M; Peterson, Brittney; Dunnivant, Frank M

2010-05-01

The resuspension of large volumes of sediments that are contaminated with chlorinated pollutants continues to threaten environmental quality and human health. Whereas kinetic models are more accurate for estimating the environmental impact of these events, their widespread use is substantially hampered by the need for costly, time-consuming, site-specific kinetics experiments. The present study investigated the development of a predictive model for desorption rates from easily measurable sorbent and pollutant properties by examining the relationship between the fraction of organic carbon (fOC) and labile release rates. Duplicate desorption measurements were performed on 46 unique combinations of pollutants and sorbents with fOC values ranging from 0.001 to 0.150. Labile desorption rate constants indicate that release rates predominantly depend upon the fOC in the geosorbent. Previous theoretical models, such as the macro-mesopore and organic matter (MOM) diffusion model, have predicted such a relationship but could not accurately predict the experimental rate constants collected in the present study. An empirical model was successfully developed to correlate the labile desorption rate constant (krap) to the fraction of organic material where log(krap)=0.291-0.785 . log(fOC). These results provide the first experimental evidence that kinetic pollution releases during resuspension events are governed by the fOC content in natural geosorbents. Copyright (c) 2010 SETAC.

Fractional solubility of aerosol iron: Synthesis of a global-scale data set

NASA Astrophysics Data System (ADS)

Sholkovitz, Edward R.; Sedwick, Peter N.; Church, Thomas M.; Baker, Alexander R.; Powell, Claire F.

2012-07-01

Aerosol deposition provides a major input of the essential micronutrient iron to the open ocean. A critical parameter with respect to biological availability is the proportion of aerosol iron that enters the oceanic dissolved iron pool - the so-called fractional solubility of aerosol iron (%FeS). Here we present a global-scale compilation of total aerosol iron loading (FeT) and estimated %FeS values for ∼1100 samples collected over the open ocean, the coastal ocean, and some continental sites, including a new data set from the Atlantic Ocean. Despite the wide variety of methods that have been used to define 'soluble' aerosol iron, our global-scale compilation reveals a remarkably consistent trend in the fractional solubility of aerosol iron as a function of total aerosol iron loading, with the great bulk of the data defining an hyperbolic trend. The hyperbolic trends that we observe for both global- and regional-scale data are adequately described by a simple two-component mixing model, whereby the fractional solubility of iron in the bulk aerosol reflects the conservative mixing of 'lithogenic' mineral dust (high FeT and low %FeS) and non-lithogenic 'combustion' aerosols (low FeT and high %FeS). An increasing body of empirical and model-based evidence points to anthropogenic fuel combustion as the major source of these non-lithogenic 'combustion' aerosols, implying that human emissions are a major determinant of the fractional solubility of iron in marine aerosols. The robust global-scale relationship between %FeS and FeT provides a simple heuristic method for estimating aerosol iron solubility at the regional to global scale.

Orbitrap-MS and FT-ICR-MS of Free and Labile Organic Matter from Carbonaceous Chondrites

NASA Astrophysics Data System (ADS)

Orthous-Daunay, F.-R.; Thissen, R.; Vuitton, V.; Somogyi, A.; Mespoulede, M.; Beck, P.; Bonnet, J.-Y.; Dutuit, O.; Schmitt, B.; Quirico, E.

2011-03-01

We used two types of high-resolution FT-MS to analyze the free and labile organic matter in carbonaceous chondrites of type 1 and 2. The methanol extraction and laser desorption gave access to highly and poorly functionalized molecules respectively.

Metallographic Cooling Rates of IAB Iron Meteorites

NASA Astrophysics Data System (ADS)

Meibom, A.; Haack, H.; Jensen, S. K.; Ulff-Moller, F.; Rasmussen, K. L.

1995-09-01

Non-metals can play an important role for the diffusion-controlled growth of the Widmanstatten structure in iron meteorites. The presence of P significantly changes the diffusivity and equilibrium concentration of Ni in kamacite and taenite [1,2], and the effects of P have therefore been included in metallographic cooling rate calculations for many years. The presence of C probably increases the diffusivity of Ni in taenite up to a factor of two, which is considerably smaller than the effect of P that increases the Ni diffusivity by up to a factor of 10 [3,1]. On the other hand, C partitions strongly into taenite leaving kamacite essentially C-free (<10 micrograms/g [4]) and significantly reduces the equilibrium Ni-concentration in taenite [5]. Therefore, the effect of C should be included in metallographic cooling rate calculations of C-rich iron meteorites [6]. IAB iron meteorites have much higher bulk C-concentrations than most other iron meteorites and the metallic phases of the IAB irons were probably saturated with C soon after kamacite nucleation commenced. Since C is expected to decrease the solubility of P in taenite [7] we have based our cooling rate estimate of Toluca (IAB) on the Fe-Ni-C system rather than the Fe-Ni-P system. Previous metallographic cooling rates determined for IAB irons, including the effect of P, are low (1-10 degrees C/My [8] and 30-70 degrees C/My [9]). Fractional crystallization of S-rich cores [10, 11] and impact generated melt pools [12] have been proposed as origins of the IAB iron meteorites. Since we expect melt pools near the surface to have cooled significantly faster than the core of a differentiated parent body, the metallographic cooling rates may be used to discriminate between the two models. We have performed thermodynamic calculations on the C-saturated Fe-Ni-C-system at temperatures above 400 degrees C [13]. The results agree with earlier experimental work [5] and indicate that C, to the same degree as P, reduces the

The actin-binding protein profilin 2 is a novel regulator of iron homeostasis.

PubMed

Luscieti, Sara; Galy, Bruno; Gutierrez, Lucia; Reinke, Michael; Couso, Jorge; Shvartsman, Maya; Di Pascale, Antonio; Witke, Walter; Hentze, Matthias W; Pilo Boyl, Pietro; Sanchez, Mayka

2017-10-26

Cellular iron homeostasis is controlled by the iron regulatory proteins (IRPs) 1 and 2 that bind cis -regulatory iron-responsive elements (IRE) on target messenger RNAs (mRNA). We identified profilin 2 ( Pfn2 ) mRNA, which encodes an actin-binding protein involved in endocytosis and neurotransmitter release, as a novel IRP-interacting transcript, and studied its role in iron metabolism. A combination of electrophoretic mobility shift assay experiments and bioinformatic analyses led to the identification of an atypical and conserved IRE in the 3' untranslated region of Pfn2 mRNA. Pfn2 mRNA levels were significantly reduced in duodenal samples from mice with intestinal IRP ablation, suggesting that IRPs exert a positive effect on Pfn2 mRNA expression in vivo. Overexpression of Pfn2 in HeLa and Hepa1-6 cells reduced their metabolically active iron pool. Importantly, Pfn2-deficient mice showed iron accumulation in discrete areas of the brain (olfactory bulb, hippocampus, and midbrain) and reduction of the hepatic iron store without anemia. Despite low liver iron levels, hepatic hepcidin expression remained high, likely because of compensatory activation of hepcidin by mild inflammation. Splenic ferroportin was increased probably to sustain hematopoiesis. Overall, our results indicate that Pfn2 expression is controlled by the IRPs in vivo and that Pfn2 contributes to maintaining iron homeostasis in cell lines and mice. © 2017 by The American Society of Hematology.

Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic

NASA Astrophysics Data System (ADS)

Browning, Thomas; Achterberg, Eric; Yong, Jaw Chuen; Rapp, Insa; Utermann, Caroline; Engel, Anja; Moore, Mark

2017-04-01

Growth-limitation of marine phytoplankton by fixed nitrogen (N) has been demonstrated for most of the low-latitude oceans; however, in the (sub)tropical North Atlantic enhanced N2 fixation leads to secondary/(co-)limitation by phosphorus (P). The dissolved organic P pool is rarely fully depleted in the modern ocean and potentially represents a substantial additional P source. Microbes can use a variety of alkaline phosphatase enzymes to access P from a major fraction of this pool. In contrast to the relatively well studied PhoA family of alkaline phosphatases that utilize zinc (Zn) as a cofactor, the recent discovery of iron (Fe) as a cofactor in the more widespread PhoX[1] and PhoD[2] enzymes imply potential for a complex, biochemically-dependant interplay between oceanic Zn, Fe and P cycles. Here we demonstrate enhanced natural community alkaline phosphatase activity (APA) following Fe amendment within the low Zn and moderately low Fe western tropical North Atlantic. In contrast, beneath the Saharan dust plume in the Eastern Atlantic no APA response to trace metal addition was observed. This is the first demonstration of intermittent Fe limitation of microbial P acquisition, providing an additional facet in the argument for Fe control of the coupling between oceanic N and P cycles. 1. Yong, S. C. et al. A complex iron-calcium cofactor catalyzing phosphotransfer chemistry. Science 345, 1170-3 (2014). 2. Rodriguez, F. et al. Crystal structure of the Bacillus subtilis phosphodiesterase PhoD reveals an iron and calcium-containing active site. J. Biol. Chem. 289, 30889-30899 (2014).

Soil organic matter composition affected by potato cropping managements

USDA-ARS?s Scientific Manuscript database

Organic matter is a small but important soil component. As a heterogeneous mixture of geomolecules and biomolecules, soil organic matter (SOM) can be fractionated into distinct pools with different solubility and lability. Water extractable organic matter (WEOM) fraction is the most labile and mobil...

Characterization of labile organic carbon in coastal wetland soils of the Mississippi River deltaic plain: relationships to carbon functionalities.

PubMed

Dodla, Syam K; Wang, Jim J; Delaune, Ronald D

2012-10-01

Adequate characterization of labile organic carbon (LOC) is essential to the understanding of C cycling in soil. There has been very little evaluation about the nature of LOC characterizations in coastal wetlands, where soils are constantly influenced by different redox fluctuations and salt water intrusions. In this study, we characterized and compared LOC fractions in coastal wetland soils of the Mississippi River deltaic plain using four different methods including 1) aerobically mineralizable C (AMC), 2) cold water extractable C (CWEC), 3) hot water extractable C (HWEC), and 4) salt extractable C (SEC), as well as acid hydrolysable C (AHC) which includes both labile and slowly degradable organic C. Molecular organic C functional groups of these wetland soils were characterized by (13)C solid-state nuclear magnetic resonance (NMR). The LOC and AHC increased with soil organic C (SOC) regardless of wetland soil type. The LOC estimates by four different methods were positively and significantly linearly related to each other (R(2)=0.62-0.84) and with AHC (R(2)=0.47-0.71). The various LOC fractions accounted for ≤4.3% of SOC whereas AHC fraction represented 16-49% of SOC. AMC was influenced positively by O/N-alkyl and carboxyl C but negatively by alkyl C, whereas CWEC and SEC fractions were influenced only positively by carboxyl C but negatively by alkyl C in SOC. On the other hand, HWEC fraction was found to be only influenced positively by carbonyl C, and AHC positively by O/N-alkyl and alkyl C but negatively by aromatic C groups in SOC. Overall these relations suggested different contributions of various molecular organic C moieties to LOC in these wetlands from those often found for upland soils. The presence of more than 50% non-acid hydrolysable C suggested the dominance of relatively stable SOC pool that would be sequestered in these Mississippi River deltaic plain coastal wetland soils. The results have important implications to the understanding of the

Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing.

EPA Science Inventory

Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that...

Forms and Lability of Phosphorus in Humic Acid Fractions of Hord Silt Loam Soil

USDA-ARS?s Scientific Manuscript database

Phosphorus (P) has long been known to be present in soil humic fractions, but little is known about specific P forms in humic fractions, or their lability. We extracted the mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fractions from a Nebraska Hord silt loam soil under continuous c...

IscR Regulates Synthesis of Colonization Factor Antigen I Fimbriae in Response to Iron Starvation in Enterotoxigenic Escherichia coli

PubMed Central

Arnaud-Barbe, Nadège; Poncet, David; Reverchon, Sylvie; Wawrzyniak, Julien; Nasser, William

2015-01-01

ABSTRACT Iron availability functions as an environmental cue for enteropathogenic bacteria, signaling arrival within the human host. As enterotoxigenic Escherichia coli (ETEC) is a major cause of human diarrhea, the effect of iron on ETEC virulence factors was evaluated here. ETEC pathogenicity is directly linked to production of fimbrial colonization factors and secretion of heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST). Efficient colonization of the small intestine further requires at least the flagellin binding adhesin EtpA. Under iron starvation, production of the CFA/I fimbriae was increased in the ETEC H10407 prototype strain. In contrast, LT secretion was inhibited. Furthermore, under iron starvation, gene expression of the cfa (CFA/I) and etp (EtpBAC) operons was induced, whereas transcription of toxin genes was either unchanged or repressed. Transcriptional reporter fusion experiments focusing on the cfa operon further showed that iron starvation stimulated cfaA promoter activity in ETEC, indicating that the impact of iron on CFA/I production was mediated by transcriptional regulation. Evaluation of cfaA promoter activity in heterologous E. coli single mutant knockout strains identified IscR as the regulator responsible for inducing cfa fimbrial gene expression in response to iron starvation, and this was confirmed in an ETEC ΔiscR strain. The global iron response regulator, Fur, was not implicated. IscR binding sites were identified in silico within the cfaA promoter and fixation confirmed by DNase I footprinting, indicating that IscR directly binds the promoter region to induce CFA/I. IMPORTANCE Pathogenic enterobacteria modulate expression of virulence genes in response to iron availability. Although the Fur transcription factor represents the global regulator of iron homeostasis in Escherichia coli, we show that several ETEC virulence factors are modulated by iron, with expression of the major fimbriae under the control of the iron

Diving into Cold Pools

NASA Astrophysics Data System (ADS)

van den Heever, S. C.; Grant, L. D.; Drager, A. J.

2017-12-01

Cold pools play a significant role in convective storm initiation, organization and longevity. Given their role in convective life cycles, recent efforts have been focused on improving the representation of cold pool processes within weather forecast models, as well as on developing cold pool parameterizations in order to better represent their impacts within global climate models. Understanding the physical processes governing cold pool formation, intensity and dissipation is therefore critical to these efforts. Cold pool characteristics are influenced by numerous factors, including those associated with precipitation formation and evaporation, variations in the environmental moisture and shear, and land surface interactions. The focus of this talk will be on the manner in which the surface characteristics and associated processes impact cold pool genesis and dissipation. In particular, the results from high-resolution modeling studies focusing on the role of sensible and latent heat fluxes, soil moisture and SST will be presented. The results from a recent field campaign examining cold pools over northern Colorado will also be discussed.

Impact of labile metal nanoparticles on cellular homeostasis. Current developments in imaging, synthesis and applications.

PubMed

Chevallet, Mireille; Veronesi, Giulia; Fuchs, Alexandra; Mintz, Elisabeth; Michaud-Soret, Isabelle; Deniaud, Aurélien

2017-06-01

The use of nanomaterials is constantly increasing in electronics, cosmetics, food additives, and is emerging in advanced biomedical applications such as theranostics, bio-imaging and therapeutics. However their safety raises concerns and requires appropriate methods to analyze their fate in vivo. In this review, we describe the current knowledge about the toxicity of labile metal (ZnO, CuO and Ag) nanoparticles (NPs) both at the organism and cellular levels, and describe the pathways that are triggered to maintain cellular homeostasis. We also describe advanced elemental imaging approaches to analyze intracellular NP fate. Finally, we open the discussion by presenting recent developments in terms of synthesis and applications of Ag and CuO NPs. Labile metal nanoparticles (MeNPs) release metal ions that trigger a cellular response involving biomolecules binding to the ions followed by regulation of the redox balance. In addition, specific mechanisms are set up by the cell in response to physiological ions such as Cu(I) and Zn(II). Among all types of NPs, labile MeNPs induce the strongest inflammatory responses which are most probably due to the combined effects of the NPs and of its released ions. Interestingly, recent developments in imaging technologies enable the intracellular visualization of both the NPs and their ions and promise new insights into nanoparticle fate and toxicity. The exponential use of nanotechnologies associated with the difficulties of assessing their impact on health and the environment has prompted scientists to develop novel methodologies to characterize these nanoobjects in a biological context. Copyright © 2016 Elsevier B.V. All rights reserved.

Acid-Labile Amphiphilic PEO-b-PPO-b-PEO Copolymers: Degradable Poloxamer Analogs.

PubMed

Worm, Matthias; Kang, Biao; Dingels, Carsten; Wurm, Frederik R; Frey, Holger

2016-05-01

Poly ((ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)) triblock copolymers commonly known as poloxamers or Pluronics constitute an important class of nonionic, biocompatible surfactants. Here, a method is reported to incorporate two acid-labile acetal moieties in the backbone of poloxamers to generate acid-cleavable nonionic surfactants. Poly(propylene oxide) is functionalized by means of an acetate-protected vinyl ether to introduce acetal units. Three cleavable PEO-PPO-PEO triblock copolymers (Mn,total = 6600, 8000, 9150 g·mol(-1) ; Mn,PEO = 2200, 3600, 4750 g·mol(-1) ) have been synthesized using anionic ring-opening polymerization. The amphiphilic copolymers exhibit narrow molecular weight distributions (Ð = 1.06-1.08). Surface tension measurements reveal surface-active behavior in aqueous solution comparable to established noncleavable poloxamers. Complete hydrolysis of the labile junctions after acidic treatment is verified by size exclusion chromatography. The block copolymers have been employed as surfactants in a miniemulsion polymerization to generate polystyrene (PS) nanoparticles with mean diameters of ≈200 nm and narrow size distribution, as determined by dynamic light scattering and scanning electron microscopy. Acid-triggered precipitation facilitates removal of surfactant fragments from the nanoparticles, which simplifies purification and enables nanoparticle precipitation "on demand." © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of lability of metal complex on free ion measurement using DMT.

PubMed

Weng, Liping; Van Riemsdijk, Willem H; Temminghoff, Erwin J M

2010-04-01

Very low concentrations of free metal ion in natural samples can be measured using the Donnan membrane technique (DMT) based on ion transport kinetics. In this paper, the possible effects of slow dissociation of metal complexes on the interpretation of kinetic DMT are investigated both theoretically and experimentally. The expressions of the lability parameter, Lgrangian , were derived for DMT. Analysis of new experimental studies using synthetic solution containing NTA as the ligand and Cu(2+) ions shows that when the ionic strength is low (labile species measured using other dynamic sensors (DGT, GIME) in several freshwaters, it is concluded that in most waters ion transport in DMT is controlled by diffusion in the membrane. Only in very soft waters (<0.7 mM Ca+Mg), the dissociation rate of natural metal complex may influence ion transport in DMT. In this case, neglecting this effect may lead to an underestimation of the free metal ion concentration measured.

Cinder Pool's Sulfur Chemistry: Implications for the Origin of Life in Hydrothermal Environments

NASA Astrophysics Data System (ADS)

Sydow, L.; Bennett, P.; Nordstrom, D.

2012-12-01

One theory of the origin of life posits the abiotic formation of alkyl thiols as an initial step to forming biomolecules and eventually a simple chemoautotrophic cell. The premise of this theory is that a recurring reaction on the charged surfaces of pyrite served as a primordial metabolism analogous to the Acetyl-CoA pathway (Wächtershäuser 1988) and was later enveloped by a primitive cellular membrane. However, alkyl thiols have not previously been identified in terrestrial hot springs as unequivocally abiogenic. We have identified methanethiol (CH3SH), the simplest of the alkyl thiols, as well as dimethyl sulfide and dimethyldisulfide, in Cinder Pool, an acid-sulfate-chloride hot spring in the One Hundred Spring Plain of Norris Geyser Basin, Yellowstone National Park. It is unusual in that it contains a molten sulfur layer on the bottom (~20 m depth) and thousands of iron-sulfur-spherules floating on the surface (the iconic "cinders" the pool is named for), created by gas bubbling through the molten basement of the spring. These unique features make it a good candidate for abiotically generated CH3SH. Gas samples were collected from Cinder pool as well as an adjacent hydrothermal feature in the autumn of 2011 using the bubble strip method modified for use with hydrothermal waters. Several samples contained measurable quantities of methanethiol and other organic sulfur gases, with concentrations increasing with depth in the pool. Laboratory microcosm experiments were conducted to investigate the geochemical conditions required to abiotically form CH3SH. Sterile, artificial Cinder Pool water was injected into sterilized 60 mL serum bottles containing different iron-sulfur compounds, including cinders collected from the pool itself, as catalytic surfaces for the methanethiol-generating reaction. The bottles were then charged with hydrogen and carbon dioxide as reaction gases and incubated for a week at temperatures between 60 and 120oC. Bottles using FeS as a

Dual, differential isotope labeling shows the preferential movement of labile plant constituents into mineral-bonded soil organic matter.

PubMed

Haddix, Michelle L; Paul, Eldor A; Cotrufo, M Francesca

2016-06-01

The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral-bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual (13) C and (15) N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched (13) C and (15) N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance (13) C-CO2 and (15) N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in (13) C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral-associated organic matter. © 2016 John Wiley & Sons Ltd.

Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity.

PubMed

Mena, Natalia P; Bulteau, Anne Laure; Salazar, Julio; Hirsch, Etienne C; Núñez, Marco T

2011-06-03

Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters are involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given that inhibition of complex I and iron accumulation are hallmarks of idiopathic Parkinson's disease, the findings reported here may have relevance for understanding the pathophysiology of this disease. Copyright © 2011 Elsevier Inc. All rights reserved.

Constraints on Transport and Emplacement Mechanisms of Labile Fractions in Lunar Cold Traps

NASA Technical Reports Server (NTRS)

Rickman, D.; Gertsch, L.

2014-01-01

Sustaining the scientific exploration of the Solar System will require a significant proportion of the necessary fuels and propellants, as well as other bulk commodities, to be produced from local raw materials [1]. The viability of mineral production depends on the ability to locate and characterize mineable deposits of the necessary feedstocks. This requires, among other things, a workable understanding of the mechanisms by which such deposits form, which is the subject of Economic Geology. Multiple deposition scenarios are possible for labile materials on the Moon. This paper suggests labile fractions moved diffusely through space; deposits may grow richer with depth until low porosity rock; lateral transport is likely to have occurred with the regolith, at least for short distances; crystalline ice may not exist; the constituent phases could be extremely complex. At present we can constrain the sources only mildly; once on the Moon, the transport mechanisms inherently mix and therefore obscure the origins. However, the importance of expanding our understanding of ore-forming processes on the Moon behooves us to make the attempt. Thus begins a time of new inquiry for Economic Geology.

Pool spacing in forest channels

Treesearch

David R. Montgomery; John M. Buffington; Richard D. Smith; Kevin M. Schmidt; George Pess

1995-01-01

Field surveys of stream channels in forested mountain drainage basins in southeast Alaska and Washington reveal that pool spacing depends on large woody debris (LWD) loading and channel type, slope, and width. Mean pool spacing in pool-riffle, plane-bed, and forced pool-riffle channels systematically decreases from greater than 13 channel widths per pool to less than 1...

Iron Homeostasis and Nutritional Iron Deficiency123

PubMed Central

Theil, Elizabeth C.

2011-01-01

Nonheme food ferritin (FTN) iron minerals, nonheme iron complexes, and heme iron contribute to the balance between food iron absorption and body iron homeostasis. Iron absorption depends on membrane transporter proteins DMT1, PCP/HCP1, ferroportin (FPN), TRF2, and matriptase 2. Mutations in DMT1 and matriptase-2 cause iron deficiency; mutations in FPN, HFE, and TRF2 cause iron excess. Intracellular iron homeostasis depends on coordinated regulation of iron trafficking and storage proteins encoded in iron responsive element (IRE)-mRNA. The noncoding IRE-mRNA structures bind protein repressors, IRP1 or 2, during iron deficiency. Integration of the IRE-RNA in translation regulators (near the cap) or turnover elements (after the coding region) increases iron uptake (DMT1/TRF1) or decreases iron storage/efflux (FTN/FPN) when IRP binds. An antioxidant response element in FTN DNA binds Bach1, a heme-sensitive transcription factor that coordinates expression among antioxidant response proteins like FTN, thioredoxin reductase, and quinone reductase. FTN, an antioxidant because Fe2+ and O2 (reactive oxygen species generators) are consumed to make iron mineral, is also a nutritional iron concentrate that is an efficiently absorbed, nonheme source of iron from whole legumes. FTN protein cages contain thousands of mineralized iron atoms and enter cells by receptor-mediated endocytosis, an absorption mechanism distinct from transport of nonheme iron salts (ferrous sulfate), iron chelators (ferric-EDTA), or heme. Recognition of 2 nutritional nonheme iron sources, small and large (FTN), will aid the solution of iron deficiency, a major public health problem, and the development of new policies on iron nutrition. PMID:21346101

Dynamics of particulate and dissolved organic and inorganic phosphorus during the peak and declining phase of an iron-induced phytoplankton bloom in the eastern subarctic Pacific

NASA Astrophysics Data System (ADS)

Yoshimura, Takeshi; Nishioka, Jun; Ogawa, Hiroshi; Tsuda, Atsushi

2018-01-01

Phosphorus (P) is an essential element for all organisms and thus the P cycle plays a key role in determining the dynamics of lower trophic levels in marine ecosystems. P in seawater occurs conceptually in particulate and dissolved organic and inorganic (POP, PIP, DOP, and DIP, respectively) pools and clarification of the dynamics in these P pools is the basis to assess the biogeochemical cycle of P. Despite its importance, behaviors of each P pool with phytoplankton dynamics have not been fully examined. We measured the four operationally defined P pools (POPop, PIPop, DOPop, and SRP) during an iron-induced phytoplankton bloom (as part of the subarctic ecosystem response to iron enrichment study (SERIES)) in the eastern subarctic Pacific in summer 2002. During our observations of the iron-enriched patch from day 15 to day 26 after the iron infusion, chlorophyll-a concentration in the surface layer decreased from 6.3 to 1.2 μg L- 1, indicating the peak through decline phase of the phytoplankton bloom. At the bloom peak, P was partitioned into POPop, PIPop, and DOPop in proportions of 60, 27, and 13%, respectively. While chlorophyll-a and POPop showed similar temporal variations during the declining phase, PIPop showed a different peak timing with a 2 day delay compared to POPop, resulting in a rapid change in the relative proportion of PIPop to total particulate P (TPP = POPop + PIPop) at the peak (25%) and during the declining phase of the bloom (50%). A part of POPop was replaced by PIPop just after slowing down of phytoplankton growth. This process may have a significant role in the subsequent regeneration of P. We conclude that measurement of TPP alone is insufficient to show the interaction between P and phytoplankton dynamics and fractionation of TPP into POPop and PIPop provides useful insights to clarify the biogeochemical cycle of P.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lam, P.J.; Bishop, J.K.B

Here we show that labile particulate iron and manganese concentrations in the upper 500m of the Western Subarctic Pacific, an iron-limited High Nutrient Low Chlorophyll (HNLC) region, have prominent subsurface maxima between 100-200 m, reaching 3 nM and 600 pM, respectively. The subsurface concentration maxima in particulate Fe are characterized by a more reduced oxidation state, suggesting a source from primary volcagenic minerals such as from the Kuril/Kamchatka margin. The systematics of these profiles suggest a consistently strong lateral advection of labile Mn and Fe from redox-mobilized labile sources at the continental shelf supplemented by a more variable source ofmore » Fe from the upper continental slope. This subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing, and is likely a key source of bioavailable Fe to the HNLC North Pacific.« less

Glaciers as a source of ancient and labile organic matter to the marine environment.

Treesearch

Eran Hood; Jason Fellman; Robert G.M. Spencer; Peter J. Hernes; Rick Edwards; David D' Amore; Durelle Scott

2009-01-01

Riverine organic matter supports of the order of one-fifth of estuarine metabolism. Coastal ecosystems are therefore sensitive to alteration of both the quantity and lability of terrigenous dissolved organic matter (DOM) delivered by rivers. Here we characterize streamwater DOM from 11 coastal watersheds on the Gulf of Alaska that vary widely in glacier coverage. In...

Swimming pool granuloma

MedlinePlus

... this page: //medlineplus.gov/ency/article/001357.htm Swimming pool granuloma To use the sharing features on this page, please enable JavaScript. A swimming pool granuloma is a long-term (chronic) skin ...

From antidunes to step-pools

NASA Astrophysics Data System (ADS)

Recking, Alain; Leduc, Pauline

2014-05-01

Step-pools are bed morphologies that are typical in high-gradient streams , recognizable by a staircase-like longitudinal profile resulting from accumulation of cobbles and boulders that are transverse to the channel and alternating with pools containing finer sediments. Within the last two decades step-pools have been the subject of increased efforts to characterize their nature; however their origin is still in debate. Researchers have very soon suspected step-pools to be the residual form of antidunes produced during flooding, but this hypothesis was continuously contested. Other theories has been proposed, considering, that step-pool profile develops a maximum flow resistance, or that pools geometry is controlled by the energy of a falling jet, or that steps form by boulders accumulation in a channel-spanning manner. All these theories gave very satisfying results when compared with experimental data, but does it mean that the antidune theory should we abandoned? We performed new flume experiments on steep slopes to investigate the antidune origin for step-pools. Our experiments showed that step-pools can have several origins, depending on the flow conditions and sediment mixture used. In some circumstances antidunes were well observed but did not produce stable step-pools morphology. In many occasions, step-pools obtained in the flume were isolated step-pools, with no real apparent periodicity. Only a few flow and sediment conditions allowed us to reproduce trains of antidunes which stabilized at the flow recession to produce stable periodical step-pools. These conditions are presented and discussed.

Interactions between pool geometry and hydraulics

USGS Publications Warehouse

Thompson, Douglas M.; Nelson, Jonathan M.; Wohl, Ellen E.

1998-01-01

An experimental and computational research approach was used to determine interactions between pool geometry and hydraulics. A 20-m-long, 1.8-m-wide flume was used to investigate the effect of four different geometric aspects of pool shape on flow velocity. Plywood sections were used to systematically alter constriction width, pool depth, pool length, and pool exit-slope gradient, each at two separate levels. Using the resulting 16 unique geometries with measured pool velocities in four-way factorial analyses produced an empirical assessment of the role of the four geometric aspects on the pool flow patterns and hence the stability of the pool. To complement the conclusions of these analyses, a two-dimensional computational flow model was used to investigate the relationships between pool geometry and flow patterns over a wider range of conditions. Both experimental and computational results show that constriction and depth effects dominate in the jet section of the pool and that pool length exhibits an increasing effect within the recirculating-eddy system. The pool exit slope appears to force flow reattachment. Pool length controls recirculating-eddy length and vena contracta strength. In turn, the vena contracta and recirculating eddy control velocities throughout the pool.

Recognition- and reactivity-based fluorescent probes for studying transition metal signaling in living systems.

PubMed

Aron, Allegra T; Ramos-Torres, Karla M; Cotruvo, Joseph A; Chang, Christopher J

2015-08-18

Metals are essential for life, playing critical roles in all aspects of the central dogma of biology (e.g., the transcription and translation of nucleic acids and synthesis of proteins). Redox-inactive alkali, alkaline earth, and transition metals such as sodium, potassium, calcium, and zinc are widely recognized as dynamic signals, whereas redox-active transition metals such as copper and iron are traditionally thought of as sequestered by protein ligands, including as static enzyme cofactors, in part because of their potential to trigger oxidative stress and damage via Fenton chemistry. Metals in biology can be broadly categorized into two pools: static and labile. In the former, proteins and other macromolecules tightly bind metals; in the latter, metals are bound relatively weakly to cellular ligands, including proteins and low molecular weight ligands. Fluorescent probes can be useful tools for studying the roles of transition metals in their labile forms. Probes for imaging transition metal dynamics in living systems must meet several stringent criteria. In addition to exhibiting desirable photophysical properties and biocompatibility, they must be selective and show a fluorescence turn-on response to the metal of interest. To meet this challenge, we have pursued two general strategies for metal detection, termed "recognition" and "reactivity". Our design of transition metal probes makes use of a recognition-based approach for copper and nickel and a reactivity-based approach for cobalt and iron. This Account summarizes progress in our laboratory on both the development and application of fluorescent probes to identify and study the signaling roles of transition metals in biology. In conjunction with complementary methods for direct metal detection and genetic and/or pharmacological manipulations, fluorescent probes for transition metals have helped reveal a number of principles underlying transition metal dynamics. In this Account, we give three recent

Experimental evidence for an effect of early-diagenetic interaction between labile and refractory marine sedimentary organic matter on nitrogen dynamics

NASA Astrophysics Data System (ADS)

Turnewitsch, Robert; Domeyer, Bettina; Graf, Gerhard

2007-05-01

In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here 'DIN' is the sum of ammonium, nitrite and nitrate.) After ˜ 30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher

Changes in labile soil organic matter fractions following land use change from monocropping to poplar-based agroforestry systems in a semiarid region of Northeast China.

PubMed

Mao, Rong; Zeng, De-Hui; Li, Lu-Jun; Hu, Ya-Lin

2012-11-01

Labile fractions of soil organic matter (SOM) respond rapidly to land management practices and can be used as a sensitive indicator of changes in SOM. However, there is little information about the effect of agroforestry practices on labile SOM fractions in semiarid regions of China. In order to test the effects of land use change from monocropping to agroforestry systems on labile SOM fractions, we investigated soil microbial biomass C (MBC) and N, particulate organic matter C (POMC) and N (POMN), as well as total organic C (TOC) and total N (TN) in the 0- to 15-cm and the 15- to 30-cm layers in 4-year-old poplar-based agroforestry systems and adjoining monocropping systems with two different soil textures (sandy loam and sandy clay loam) in a semiarid region of Northeast China. Our results showed that poplar-based agroforestry practices affected soil MBC, POMC, and POMN, albeit there was no significant difference in TOC and TN. Agroforestry practices increased MBC, POMC, and POMN in sandy clay loam soils. However, in sandy loam soils, agroforestry practices only increased MBC and even decreased POMC and POMN at the 0- to 15-cm layer. Our results suggest that labile SOM fractions respond sensitively to poplar-based agroforestry practices and can provide early information about the changes in SOM in semiarid regions of Northeast China and highlight that the effects of agroforestry practices on labile SOM fractions vary with soil texture.

Initial cloning and sequencing of hydHG, an operon homologous to ntrBC and regulating the labile hydrogenase activity in Escherichia coli K-12.

PubMed Central

Stoker, K; Reijnders, W N; Oltmann, L F; Stouthamer, A H

1989-01-01

To isolate genes from Escherichia coli which regulate the labile hydrogenase activity, a plasmid library was used to transform hydL mutants lacking the labile hydrogenase. A single type of gene, designated hydG, was isolated. This gene also partially restored the hydrogenase activity in hydF mutants (which are defective in all hydrogenase isoenzymes), although the low hydrogenase 1 and 2 levels were not induced. Therefore, hydG apparently regulates, specifically, the labile hydrogenase activity. Restoration of this latter activity in hydF mutants was accompanied by a proportional increase of the H2 uptake activity, suggesting a functional relationship. H2:fumarate oxidoreductase activity was not restored in complemented hydL mutants. These latter strains may therefore lack, in addition to the labile hydrogenase, a second component (provisionally designated component R), possibly an electron carrier coupling H2 oxidation to the anerobic respiratory chain. Sequence analysis showed an open reading frame of 1,314 base pairs for hydG. It was preceded by a ribosome-binding site but apparently lacked a promoter. Minicell experiments revealed a single polypeptide of approximately 50 kilodaltons. Comparison of the predicted amino acid sequence with a protein sequence data base revealed strong homology to NtrC from Klebsiella pneumoniae, a DNA-binding transcriptional activator. The 411 base pairs upstream from pHG40 contained a second open reading frame overlapping hydG by four bases. The deduced amino acid sequence showed considerable homology with the C-terminal part of NtrB. This sequence was therefore assumed to be part of a second gene, encoding the NtrB-like component, and was designated hydH. The labile hydrogenase activity in E. coli is apparently regulated by a multicomponent system analogous to the NtrB-NtrC system. This conclusion is in agreement with the results of Birkmann et al. (A. Birkmann, R. G. Sawers, and A. Böck, Mol. Gen. Genet. 210:535-542, 1987), who

13 CFR 120.1706 - Pool Originator's retained interest in Pool.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Pool Originator's retained interest in Pool. 120.1706 Section 120.1706 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION BUSINESS LOANS Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan...

Type II Heat-labile Enterotoxins: Structure, Function, and Immunomofdulatory Properties

PubMed Central

Hajishengallis, George; Connell, Terry D.

2012-01-01

The heat-labile enterotoxins (HLTs) of Escherichia coli and Vibrio cholerae are classified into two major types on the basis of genetic, biochemical, and immunological properties. Type I and Type II HLT have been intensively studied for their exceptionally strong adjuvant activities. Despite general structural similarities, these molecules, in intact or derivative (non-toxic) forms, display notable differences in their mode of immunomodulatory action. The molecular basis of these differences has remained largely uncharacterized until recently. This review focuses on the Type II HLTs and their immunomodulatory properties which depend largely on interactions with unique gangliosides and Toll-like receptors that are not utilized by the Type I HLTs. PMID:23137790

Evolution of phenotypic plasticity and environmental tolerance of a labile quantitative character in a fluctuating environment.

PubMed

Lande, R

2014-05-01

Quantitative genetic models of evolution of phenotypic plasticity are used to derive environmental tolerance curves for a population in a changing environment, providing a theoretical foundation for integrating physiological and community ecology with evolutionary genetics of plasticity and norms of reaction. Plasticity is modelled for a labile quantitative character undergoing continuous reversible development and selection in a fluctuating environment. If there is no cost of plasticity, a labile character evolves expected plasticity equalling the slope of the optimal phenotype as a function of the environment. This contrasts with previous theory for plasticity influenced by the environment at a critical stage of early development determining a constant adult phenotype on which selection acts, for which the expected plasticity is reduced by the environmental predictability over the discrete time lag between development and selection. With a cost of plasticity in a labile character, the expected plasticity depends on the cost and on the environmental variance and predictability averaged over the continuous developmental time lag. Environmental tolerance curves derived from this model confirm traditional assumptions in physiological ecology and provide new insights. Tolerance curve width increases with larger environmental variance, but can only evolve within a limited range. The strength of the trade-off between tolerance curve height and width depends on the cost of plasticity. Asymmetric tolerance curves caused by male sterility at high temperature are illustrated. A simple condition is given for a large transient increase in plasticity and tolerance curve width following a sudden change in average environment. © 2014 The Author. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Impact of Restoration of Soil in a Humid Tropical Region on Storage of Organic Carbon in a Recalcitrant Pool

NASA Astrophysics Data System (ADS)

Jyoti Nath, Arun; Brahma, Biplab; Lal, Rattan; Das, Ashesh Kumar

2017-04-01

Quantifying soil organic carbon (SOC) changes through restoration of degraded lands is important to assessing the changes in soil properties. However, SOC measures all C fractions and its assessment is not adequate to distinguish between the more dynamic or active C (AC) fractions and the recalcitrant or passive C (PC) form. SOC fractions comprising of the recalcitrant pools have been suggested as a driver for long term soil C sink management. Therefore, the present study was undertaken at a site within the North Eastern India (NEI) region with an objective to explore whether or not SOC fractions change with restoration of degraded lands under humid tropical climate. An age-chronosequence study was established comprising of four different aged rubber plantations (6, 15, 27 and 34 yr. old) planted on Imperata grasslands. The site was selected to study changes in the different fractions of SOC and total SOC stock, and the data were compared with that of a native forest. The data indicated that the SOC stock increased from 106 Mg ha-1 under 6 yr. to 130 Mg ha-1 under 34 yr. old plantations. The SOC stock after 34 yr. of plantation was 20% higher than that under Imperata grassland, but was 34% lower than that under the native forest soil. With respect to lability of C fractions, proportion of AC pool decreased linearly with increase in plantation age from 59 % under 6 yr to 33 % under 34 yr. old plantations. In contrast, proportion of PC pool increased from 41 % of SOC stock under 6 yr. to 67 % of SOC under 34 yr. old plantations, suggesting the significant role of old aged plantation in C sink management.

In situ application of a cellulose bag and an ion exchanger for differentiation of labile and inert metal species in aquatic systems.

PubMed

Goveia, Danielle; Rosa, André Henrique; Bellin, Iramaia Corrêa; Lobo, Fabiana Aparecida; Fraceto, Leonardo Fernandes; Roveda, José Arnaldo Frutuoso; Romão, Luciane Pimenta Cruz; Dias Filho, Newton Luiz

2008-02-01

This work involved the development and application of a new analytical procedure for in-situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory. The in-situ application involved immersing the DM-Cell-PAB system in two different rivers, enabling us to study the relative lability of metal species (Cu, Cd, Fe, Mn, and Ni) as a function of time and quantity of exchanger. The procedure is simple and opens up a new perspective for understanding environmental phenomena relating to the complexation, transport, stability, and lability of metal species in aquatic systems rich in organic matter.

Carbon Mineralization and Nitrogen Transformation During a Long Term Permafrost Incubation

NASA Astrophysics Data System (ADS)

Salmon, V. G.; Mack, M. C.; Schuur, E. A. G.

2014-12-01

As the limiting nutrient in warming high latitude ecosystems, nitrogen (N) is expected to play a key role in determining the future balance between permafrost carbon (C) losses and increased C sequestration by plants. During decomposition, nitrogen previously locked in soil organic matter is released into the soil solution in the form of dissolved organic molecules following depolymerization by extracellular enzymes. These dissolved organic forms of N can be consumed by the soil microbial community and incorporated in their biomass or mineralized if they are in excess of microbial demand. Once mineralized and released into the soil solutions, N can be lost from the soil system via denitrification. In well drained, low N tussock tundra, however, this pathway is unlikely. Dissolved inorganic N (DIN) and dissolved organic N (DON) are both biologically available to arctic plants. Understanding how the size of these pools changes with depth and continuing decomposition is therefore crucial to projecting the C balance of high latitude systems in a warmer future. N transformations associated with decomposition may differ greatly in surface soils, where a large labile C pool is present and soil has a high C:N ratio, versus deep soils that have a relatively small labile C pool and a lower C:N ratio. In this experiment, the relationship between N availability and C release from permafrost soils was addressed with a 225 day soil incubation performed at 15°C. Seven soil cores were collected from undisturbed, well drained tussock tundra and were partitioned into ten centimeter depth intervals to a depth of 80 cm. Carbon dioxide (CO2) fluxes were measured throughout the incubation period and were used to assess cumulative carbon losses and determine the size of the labile C pool. Destructive harvests at days 16,34,55,83, 143 and 225 were performed and pools of plant available DON and DIN were measured using 2M KCl extractions. At day 225 the microbial biomass N pool was also

Convenient yet not a convenience sample: Jury pools as experimental subject pools.

PubMed

Murray, Gregg R; Rugeley, Cynthia R; Mitchell, Dona-Gene; Mondak, Jeffery J

2013-01-01

Scholars greatly benefit from access to convenient, inexpensive data sources. Many researchers rely on student subject pools, a practice that raises concern about the "college sophomore problem," or the possibility that findings from student subjects do not generalize beyond the campus. As an accessible, low cost, and heterogeneous data source, some researchers have used subjects recruited from jury pools, which are drawn from randomly-selected citizens required by law to appear for jury duty. In this paper, we discuss the strengths and weaknesses of this approach. First, we review pragmatic considerations involving access to jury pools, substantive content, the administration of survey-experiments, and the financial costs and benefits of this approach. Next, we present evidence regarding the quality of jury pool samples in terms of response rates, diversity, and representativeness. We conclude that jury pools, given proper attention to their limitations, offer an attractive addition to the viable sources of experimental data. Copyright © 2012 Elsevier Inc. All rights reserved.

Fusion of Escherichia coli heat-stable enterotoxin and heat-labile enterotoxin B subunit.

PubMed

Guzman-Verduzco, L M; Kupersztoch, Y M

1987-11-01

The 3' terminus of the DNA coding for the extracellular Escherichia coli heat-stable enterotoxin (ST) devoid of transcription and translation stop signals was fused to the 5' terminus of the DNA coding for the periplasmic B subunit of the heat-labile enterotoxin (LTB) deleted of ribosomal binding sites and leader peptide. By RNA-DNA hybridization analysis, it was shown that the fused DNA was transcribed in vivo into an RNA species in close agreement with the expected molecular weight inferred from the nucleotide sequence. The translation products of the fused DNA resulted in a hybrid molecule recognized in Western blots (immunoblots) with antibodies directed against the heat-labile moiety. Anti-LTB antibodies coupled to a solid support bound ST and LTB simultaneously when incubated with ST-LTB cellular extracts. By [35S]cysteine pulse-chase experiments, it was shown that the fused ST-LTB polypeptide was converted from a precursor with an equivalent electrophoretic mobility of 20,800 daltons to an approximately 18,500-dalton species, which accumulated within the cell. The data suggest that wild-type ST undergoes at least two processing steps during its export to the culture supernatant. Blocking the natural carboxy terminus of ST inhibited the second proteolytic step and extracellular delivery of the hybrid molecule.

Vernal Pool Lessons and Activities.

ERIC Educational Resources Information Center

Childs, Nancy; Colburn, Betsy

This curriculum guide accompanies Certified: A Citizen's Step-by-Step Guide to Protecting Vernal Pools which is designed to train volunteers in the process of identifying vernal pool habitat so that as many of these pools as possible can be certified by the Massachusetts Natural Heritage and Endangered Species Program. Vernal pools are a kind of…

Morphology of drying blood pools

NASA Astrophysics Data System (ADS)

Laan, Nick; Smith, Fiona; Nicloux, Celine; Brutin, David; D-Blood project Collaboration

2016-11-01

Often blood pools are found on crime scenes providing information concerning the events and sequence of events that took place on the scene. However, there is a lack of knowledge concerning the drying dynamics of blood pools. This study focuses on the drying process of blood pools to determine what relevant information can be obtained for the forensic application. We recorded the drying process of blood pools with a camera and measured the weight. We found that the drying process can be separated into five different: coagulation, gelation, rim desiccation, centre desiccation, and final desiccation. Moreover, we found that the weight of the blood pool diminishes similarly and in a reproducible way for blood pools created in various conditions. In addition, we verify that the size of the blood pools is directly related to its volume and the wettability of the surface. Our study clearly shows that blood pools dry in a reproducible fashion. This preliminary work highlights the difficult task that represents blood pool analysis in forensic investigations, and how internal and external parameters influence its dynamics. We conclude that understanding the drying process dynamics would be advancement in timeline reconstitution of events. ANR funded project: D-Blood Project.

Outcome of impact disruption of iron meteorites at room temperature

NASA Astrophysics Data System (ADS)

Katsura, T.; Nakamura, A.; Takabe, A.; Okamoto, T.; Sangen, K.; Hasegawa, S.; Liu, X.; Mashimo, T.

2014-07-01

The iron meteorites and some M-class asteroids are generally understood to originate in the cores of differentiated planetesimals or in the local melt pools of primitive bodies. On these primitive bodies and planetesimals, a wide range of collisional events at different mass scales, temperatures, and impact velocities would have occurred. Iron materials have a brittle-ductile transition at a certain temperature, which depends on metallurgical factors such as grain size and purity, and on conditions such as strain-rate and confining pressure [1]. An evolutional scenario of iron meteorite parent bodies was proposed in which they formed in the terrestrial planet region, after which they were scattered into the main belt by collisions, Yarkovsky thermal forces, and resonances [2]. In this case, they may have experienced collisional evolution in the vicinity of the Earth before they were scattered into the main belt. The size distribution of iron bodies in the main belt may therefore have depended on the disruption threshold of iron bodies at temperature above the brittle-ductile transition. This paper presents the results of impact-disruption experiments of iron meteorite and steel specimens mm-cm in size as projectiles or targets conducted at room temperature using three light-gas guns and one powder gun. Our iron specimens were almost all smaller in size than their counterparts (as targets or projectiles, respectively). The fragment size distribution of iron material was different from that of rocks. In iron fragmentation, a higher percentage of the mass is concentrated in larger fragments, i.e., the mass fraction of fine fragments is much less than that of rocks shown in the Figure (left). This is probably due to the ductile nature of the iron materials at room temperature. Furthermore, the Figure (right) shows that the largest fragment mass fraction f is dependent not only on the energy density but also on the size of the specimens. In order to obtain a generalized

Magnetic Particle / Magnetic Resonance Imaging: In-Vitro MPI-Guided Real Time Catheter Tracking and 4D Angioplasty Using a Road Map and Blood Pool Tracer Approach.

PubMed

Salamon, Johannes; Hofmann, Martin; Jung, Caroline; Kaul, Michael Gerhard; Werner, Franziska; Them, Kolja; Reimer, Rudolph; Nielsen, Peter; Vom Scheidt, Annika; Adam, Gerhard; Knopp, Tobias; Ittrich, Harald

2016-01-01

In-vitro evaluation of the feasibility of 4D real time tracking of endovascular devices and stenosis treatment with a magnetic particle imaging (MPI) / magnetic resonance imaging (MRI) road map approach and an MPI-guided approach using a blood pool tracer. A guide wire and angioplasty-catheter were labeled with a thin layer of magnetic lacquer. For real time MPI a custom made software framework was developed. A stenotic vessel phantom filled with saline or superparamagnetic iron oxide nanoparticles (MM4) was equipped with bimodal fiducial markers for co-registration in preclinical 7T MRI and MPI. In-vitro angioplasty was performed inflating the balloon with saline or MM4. MPI data were acquired using a field of view of 37.3×37.3×18.6 mm3 and a frame rate of 46 volumes/sec. Analysis of the magnetic lacquer-marks on the devices were performed with electron microscopy, atomic absorption spectrometry and micro-computed tomography. Magnetic marks allowed for MPI/MRI guidance of interventional devices. Bimodal fiducial markers enable MPI/MRI image fusion for MRI based roadmapping. MRI roadmapping and the blood pool tracer approach facilitate MPI real time monitoring of in-vitro angioplasty. Successful angioplasty was verified with MPI and MRI. Magnetic marks consist of micrometer sized ferromagnetic plates mainly composed of iron and iron oxide. 4D real time MP imaging, tracking and guiding of endovascular instruments and in-vitro angioplasty is feasible. In addition to an approach that requires a blood pool tracer, MRI based roadmapping might emerge as a promising tool for radiation free 4D MPI-guided interventions.

Collagenase-labile polyurethane urea synthesis and processing into hollow fiber membranes.

PubMed

Fu, Hui-Li; Hong, Yi; Little, Steven R; Wagner, William R

2014-08-11

As a means to stimulate wound healing, a hollow fiber membrane system might be placed within a wound bed to provide local and externally regulated controlled delivery of regenerative factors. After sufficient healing, it would be desirable to triggerably degrade these fibers as opposed to pulling them out. Accordingly, a series of enzymatically degradable thermoplastic elastomers was developed as potential hollow fiber base material. Polyurethane ureas (PUUs) were synthesized based on 1, 4-diisocyanatobutane, polycaprolactone (PCL) diol and polyethylene glycol (PEG) at different molar fractions as soft segments, and collagenase-sensitive peptide GGGLGPAGGK-NH2 as a chain extender (defined as PUU-CLxEGy-peptide, where x and y are the respective molar percents). In these polymers, PEG in the polymer backbone decreased tensile strengths and initial moduli of solvent-cast films in the wet state, while increasing water absorption. Collagenase degradation was observed at 75% relative PEG content in the soft segment. Control PUUs with putrescine or nonsense peptide chain extenders did not degrade acutely in collagenase. Conduits electrospun from PUU-CL25EG75-peptide and PUU-CL50EG50-peptide exhibited appropriate mechanical strength and sustained release of a model protein from the tube lumen for 7 days. Collapse of PUU-CL25EG75-peptide tubes occurred after collagenase degradation for 3 days. In conclusion, through molecular design, synthesis and characterization, a collagenase-labile PUU-CL25EG75-peptide polymer was identified that exhibited the desired traits of triggerable lability, processability, and the capacity to act as a membrane to facilitate controlled protein release.

Simultaneous experimental determination of labile proton fraction ratio and exchange rate with irradiation radio frequency power-dependent quantitative CEST MRI analysis.

PubMed

Sun, Phillip Zhe; Wang, Yu; Xiao, Gang; Wu, Renhua

2013-01-01

Chemical exchange saturation transfer (CEST) imaging is sensitive to dilute proteins/peptides and microenvironmental properties, and has been increasingly evaluated for molecular imaging and in vivo applications. However, the experimentally measured CEST effect depends on the CEST agent concentration, exchange rate and relaxation time. In addition, there may be non-negligible direct radio-frequency (RF) saturation effects, particularly severe for diamagnetic CEST (DIACEST) agents owing to their relatively small chemical shift difference from that of the bulk water resonance. As such, the commonly used asymmetry analysis only provides CEST-weighted information. Recently, it has been shown with numerical simulation that both labile proton concentration and exchange rate can be determined by evaluating the RF power dependence of DIACEST effect. To validate the simulation results, we prepared and imaged two CEST phantoms: a pH phantom of serially titrated pH at a fixed creatine concentration and a concentration phantom of serially varied creatine concentration titrated to the same pH, and solved the labile proton fraction ratio and exchange rate per-pixel. For the concentration phantom, we showed that the labile proton fraction ratio is proportional to the CEST agent concentration with negligible change in the exchange rate. Additionally, we found the exchange rate of the pH phantom is dominantly base-catalyzed with little difference in the labile proton fraction ratio. In summary, our study demonstrated quantitative DIACEST MRI, which remains promising to augment the conventional CEST-weighted MRI analysis. Copyright © 2013 John Wiley & Sons, Ltd.

Mayolenes: Labile defensive lipids from the glandular hairs of a caterpillar (Pieris rapae)

PubMed Central

Smedley, Scott R.; Schroeder, Frank C.; Weibel, Douglas B.; Meinwald, Jerrold; Lafleur, Katie A.; Renwick, J. Alan; Rutowski, Ronald; Eisner, Thomas

2002-01-01

Larvae of the European cabbage butterfly, Pieris rapae (Pieridae), are beset with glandular hairs, bearing droplets of a clear oily secretion at their tip. The fluid consists primarily of a series of chemically labile, unsaturated lipids, the mayolenes, which are derived from 11-hydroxylinolenic acid. In bioassays with the ant Crematogaster lineolata, the secretion was shown to be potently deterrent, indicating that the fluid plays a defensive role in nature. PMID:11997469

Iron

MedlinePlus

... too little iron, you may develop iron deficiency anemia. Causes of low iron levels include blood loss, poor diet, or an inability to absorb enough iron from foods. People at higher risk of having too little iron are young children and women who are pregnant or have periods. ...

The Rusty Sink: Iron Promotes the Preservation of Organic Matter in Sediments

NASA Astrophysics Data System (ADS)

Lalonde, K. M.; Mucci, A.; Moritz, A.; Ouellet, A.; Gelinas, Y.

2011-12-01

The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved Fe [1], whereas in soils, solid Fe phases provide a sheltering and preservative effect for organic matter [2]. Until now however, the role of iron in the preservation of OC in sediments has not been clearly established. Here we show that 21.5 ± 8.6% of the OC in sediments is directly bound to reactive iron phases, which promote the preservation of OC in sediments. Iron-bound OC represents a global mass of 19 to 45 × 10^15 g of OC in surface marine sediments. This pool of OC is different from the rest of sedimentary OC, with 13C and nitrogen-enriched organic matter preferentially bound to Fe which suggests that biochemical fractionation occurs with OC-Fe binding. Preferential binding also affects the recovery of high molecular weight lipid biomarkers and acidic lignin oxidation products, changing the environmental message of proxies derived from these biomarkers. [1] Johnson, K. S., Gordon, R. M. & Coale, K. H. What controls dissolved iron in the world ocean? Marine Chemistry 57, 137-161 (1997). [2] Kaiser, K. & Guggenberger, G. The role of DOM sorption to mineral surfaces in the preservation of organic matter in soils. Organic Geochemistry 31, 711-725 (2000).

Iron and alloys of iron. [lunar resources

NASA Technical Reports Server (NTRS)

Sastri, Sankar

1992-01-01

All lunar soil contains iron in the metallic form, mostly as an iron-nickel alloy in concentrations of a few tenths of 1 percent. Some of this free iron can be easily separated by magnetic means. It is estimated that the magnetic separation of 100,000 tons of lunar soil would yield 150-200 tons of iron. Agglutinates contain metallic iron which could be extracted by melting and made into powder metallurgy products. The characteristics and potential uses of the pure-iron and iron-alloy lunar products are discussed. Processes for working iron that might be used in a nonterrestrial facility are also addressed.

Data Pool Description

Atmospheric Science Data Center

2016-04-29

ASDC Data Pool   Notices   • DataPool will transition from ...  • Use IE7 for FTP sessions: a) Select "View", "Open FTP site in Windows Explorer" or b) Open Windows Explorer and enter the URL for the FTP site in the address bar ...

Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions.

USDA-ARS?s Scientific Manuscript database

This study aimed to investigate the content of carbohydrates and amino compounds in three labile fraction of soil organic matter (SOM). Soil samples were collected from two agricultural fields in southern Italy and the light fraction (LF), the 500–53-µm particulate organic matter (POM) and the mobil...

Efficacy and safety of IV ferumoxytol for iron deficiency anemia in patients with cancer.

PubMed

Vadhan-Raj, Saroj; Dahl, Naomi V; Bernard, Kristine; Li, Zhu; Strauss, William E

2017-01-01

Iron deficiency anemia (IDA) is common in cancer patients due to blood loss and inflammation. Many do not tolerate oral iron or adequately respond. Intravenous (IV) iron is commonly used as an adjunct to erythropoiesis-stimulating agents; data on the use of IV iron monotherapy in these patients are limited. This study aimed to evaluate IV ferumoxytol for the treatment of cancer patients with IDA with a history of unsatisfactory oral iron therapy or in whom oral iron could not be used. This post hoc analysis of pooled data from two multicenter, randomized, controlled, Phase III trials evaluating IV ferumoxytol (510 mg ×2) vs placebo or iron sucrose (200 mg ×5) included a subgroup of 98 patients with cancer that the investigator identified as the primary cause of their IDA, or with cancer whose IDA was attributed to another comorbid condition (ferumoxytol, n=75; iron sucrose, n=13; placebo, n=10). Gastrointestinal cancers were most common (42), followed by breast (14), cervix (ten), and lung (nine). The primary endpoint was the mean change in hemoglobin (Hgb) from baseline to week 5. At week 5, both ferumoxytol and iron sucrose produced significant increases in Hgb from baseline (1.8 g/dL [ P <0.0001] and 1.9 g/dL [ P =0.002], respectively). During the studies, 45 patients received chemotherapy, 19 with platinum-based regimens. Erythropoiesis-stimulating agent doses were neither increased >20% nor initiated in any treatment group. Overall rates of adverse events and serious adverse events in the cancer subgroup mirrored those in the overall study population. Monotherapy with IV iron appears to be an effective option for cancer patients with IDA who do not respond to or cannot tolerate oral iron therapy.

Lability of High Molecular Weight Dissolved Organic Matter Polysaccharides Increases with Mild Acid or Base Treatment.

NASA Astrophysics Data System (ADS)

Pedler Sherwood, B.; Sosa, O.; Nelson, C. E.; Repeta, D.; DeLong, E.

2016-02-01

Approximately 662 Pg of dissolved organic carbon (DOC) has accumulated in the global ocean, yet the biological and chemical constraints on DOC turnover remain poorly understood. High molecular weight dissolved organic matter (HMWDOM) is largely comprised of semi-labile polysaccharides. These polysaccharides resist degradation even in the presence of nutrient amendments, suggesting unknown factors of polysaccharide composition affect microbial degradation. In a series of microcosm incubations conducted at station ALOHA in the North Pacific Subtropical Gyre, we tested the affect of mild base (KOH-DOM) and acid (HCl-DOM) treatments on polysaccharide lability. KOH-DOM, HCl-DOM, and untreated HMWDOM was added to seawater from the deep chlorophyll maximum and 200m. Microcosms amended with KOH-DOM and HCl-DOM yielded higher bacterial abundance and greater carbon drawdown relative to untreated HMWDOM and unamended controls. Microcosms amended with KOH-DOM and HCl-DOM also showed significant production of fluorescent DOM (fDOM), whereas untreated HMWDOM and unamended controls showed a net decrease in fDOM as measured by parallel factor analysis of DOM excitation-emission spectra. Metagenomic analyses revealed that microcosms amended with untreated HMWDOM and controls became dominated by Alteromonas genera ( 60% total sequence reads). In contrast, KOH-DOM and HCl-DOM amended microcosms yielded greater bacterial diversity; Alteromonas genera comprised 25% of sequence reads, with differences primarily accounted for by proportional increases in vibrio, roseobacter, rugeria and marinomonas clades. Transcriptomic analyses identified differential gene expression during growth on each DOM fraction. This study provides new insight into specific chemical moieties that may limit the bacterial degradation rate of semi-labile HMWDOM in the ocean.

Treatments for iron-deficiency anaemia in pregnancy.

PubMed

Reveiz, Ludovic; Gyte, Gillian Ml; Cuervo, Luis Gabriel; Casasbuenas, Alexandra

2011-10-05

Iron deficiency, the most common cause of anaemia in pregnancy worldwide, can be mild, moderate or severe. Severe anaemia can have very serious consequences for mothers and babies, but there is controversy about whether treating mild or moderate anaemia provides more benefit than harm. To assess the effects of different treatments for anaemia in pregnancy attributed to iron deficiency (defined as haemoglobin less than 11 g/dL or other equivalent parameters) on maternal and neonatal morbidity and mortality. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (7 June 2011), CENTRAL (2011, Issue 5), PubMed (1966 to June 2011), the International Clinical Trials Registry Platform (ICTRP) (2 May 2011), Health Technology Assessment Program (HTA) (2 May 2011) and LATINREC (Colombia) (2 May 2011). Randomised controlled trials comparing treatments for anaemia in pregnancy attributed to iron deficiency. We identified 23 trials, involving 3.198 women. We assessed their risk of bias. Three further studies identified are awaiting classification. Many of the trials were from low-income countries; they were generally small and frequently methodologically poor. They covered a very wide range of differing drugs, doses and routes of administration, making it difficult to pool data. Oral iron in pregnancy showed a reduction in the incidence of anaemia (risk ratio 0.38, 95% confidence interval 0.26 to 0.55, one trial, 125 women) and better haematological indices than placebo (two trials). It was not possible to assess the effects of treatment by severity of anaemia. A trend was found between dose and reported adverse effects. Most trials reported no clinically relevant outcomes nor adverse effects. Although the intramuscular and intravenous routes produced better haematological indices in women than the oral route, no clinical outcomes were assessed and there were insufficient data on adverse effects, for example, on venous thrombosis and severe allergic reactions

Preservation of organic matter in marine sediments by inner-sphere interactions with reactive iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barber, Andrew; Brandes, Jay; Leri, Alessandra

Interactions between organic matter and mineral matrices are critical to the preservation of soil and sediment organic matter. In addition to clay minerals, Fe(III) oxides particles have recently been shown to be responsible for the protection and burial of a large fraction of sedimentary organic carbon (OC). Through a combination of synchrotron X-ray techniques and high-resolution images of intact sediment particles, we assessed the mechanism of interaction between OC and iron, as well as the composition of organic matter co-localized with ferric iron. We present scanning transmission x-ray microscopy images at the Fe L 3 and C K1 edges showingmore » that the organic matter co-localized with Fe(III) consists primarily of C=C, C=O and C-OH functional groups. Coupling the co-localization results to iron K-edge X-ray absorption spectroscopy fitting results allowed to quantify the relative contribution of OC-complexed Fe to the total sediment iron and reactive iron pools, showing that 25–62% of total reactive iron is directly associated to OC through inner-sphere complexation in coastal sediments, as much as four times more than in low OC deep sea sediments. Direct inner-sphere complexation between OC and iron oxides (Fe-O-C) is responsible for transferring a large quantity of reduced OC to the sedimentary sink, which could otherwise be oxidized back to CO 2.« less

Iron excretion in iron dextran-overloaded mice

PubMed Central

Musumeci, Marco; Maccari, Sonia; Massimi, Alessia; Stati, Tonino; Sestili, Paola; Corritore, Elisa; Pastorelli, Augusto; Stacchini, Paolo; Marano, Giuseppe; Catalano, Liviana

2014-01-01

Background Iron homeostasis in humans is tightly regulated by mechanisms aimed to conserve iron for reutilisation, with a negligible role played by excretory mechanisms. In a previous study we found that mice have an astonishing ability to tolerate very high doses of parenterally administered iron dextran. Whether this ability is linked to the existence of an excretory pathway remains to be ascertained. Materials and methods Iron overload was generated by intraperitoneal injections of iron dextran (1 g/kg) administered once a week for 8 weeks in two different mouse strains (C57bl/6 and B6D2F1). Urinary and faecal iron excretion was assessed by inductively coupling plasma-mass spectrometry, whereas cardiac and liver architecture was evaluated by echocardiography and histological methods. For both strains, 24-hour faeces and urine samples were collected and iron concentration was determined on days 0, 1 and 2 after iron administration. Results In iron-overloaded C57bl/6 mice, the faecal iron concentration increased by 218% and 157% on days 1 and 2, respectively (p<0.01). The iron excreted represented a loss of 14% of total iron administered. Similar but smaller changes was also found in B6D2F1 mice. Conversely, we found no significant changes in the concentration of iron in the urine in either of the strains of mice. In both strains, histological examination showed accumulation of iron in the liver and heart which tended to decrease over time. Conclusions This study indicates that mice have a mechanism for removal of excess body iron and provides insights into the possible mechanisms of excretion. PMID:24960657

Serum Iron Levels and the Risk of Parkinson Disease: A Mendelian Randomization Study

PubMed Central

Gögele, Martin; Lill, Christina M.; Bertram, Lars; Do, Chuong B.; Eriksson, Nicholas; Foroud, Tatiana; Myers, Richard H.; Nalls, Michael; Keller, Margaux F.; Benyamin, Beben; Whitfield, John B.; Pramstaller, Peter P.; Hicks, Andrew A.; Thompson, John R.; Minelli, Cosetta

2013-01-01

Background Although levels of iron are known to be increased in the brains of patients with Parkinson disease (PD), epidemiological evidence on a possible effect of iron blood levels on PD risk is inconclusive, with effects reported in opposite directions. Epidemiological studies suffer from problems of confounding and reverse causation, and mendelian randomization (MR) represents an alternative approach to provide unconfounded estimates of the effects of biomarkers on disease. We performed a MR study where genes known to modify iron levels were used as instruments to estimate the effect of iron on PD risk, based on estimates of the genetic effects on both iron and PD obtained from the largest sample meta-analyzed to date. Methods and Findings We used as instrumental variables three genetic variants influencing iron levels, HFE rs1800562, HFE rs1799945, and TMPRSS6 rs855791. Estimates of their effect on serum iron were based on a recent genome-wide meta-analysis of 21,567 individuals, while estimates of their effect on PD risk were obtained through meta-analysis of genome-wide and candidate gene studies with 20,809 PD cases and 88,892 controls. Separate MR estimates of the effect of iron on PD were obtained for each variant and pooled by meta-analysis. We investigated heterogeneity across the three estimates as an indication of possible pleiotropy and found no evidence of it. The combined MR estimate showed a statistically significant protective effect of iron, with a relative risk reduction for PD of 3% (95% CI 1%–6%; p = 0.001) per 10 µg/dl increase in serum iron. Conclusions Our study suggests that increased iron levels are causally associated with a decreased risk of developing PD. Further studies are needed to understand the pathophysiological mechanism of action of serum iron on PD risk before recommendations can be made. Please see later in the article for the Editors' Summary PMID:23750121

Sedimentary and tectonic history of the Holowilena Ironstone, a Neoproterozoic iron formation in South Australia

NASA Astrophysics Data System (ADS)

Lechte, Maxwell Alexander; Wallace, Malcolm William

2015-11-01

The Holowilena Ironstone is a Neoproterozoic iron formation in South Australia associated with glacial deposits of the Sturtian glaciation. Through a comprehensive field study coupled with optical and scanning electron microscopy, X-ray fluorescence, and X-ray diffraction, a detailed description of the stratigraphy, sedimentology, mineralogy, and structure of the Holowilena Ironstone was obtained. The Holowilena Ironstone comprises ferruginous shales, siltstones, diamictites, and is largely made up of hematite and jasper, early diagenetic replacement minerals of precursor iron oxyhydroxides, and silica. These chemical precipitates are variably influenced by turbidites and debris flows contributing clastic detritus to the depositional system. Structural and stratigraphic evidence suggests deposition within a synsedimentary half-graben. A model for the Holowilena Ironstone is proposed, in which dense oxic fluids expelled during sea ice formation in the Cryogenian pool in the depression of the half-graben, allowing for long-lived mixing with the ferruginous seawater and the deposition of iron oxides. This combination of glacial dynamics, tectonism, and ocean chemistry may explain the return of iron formations in the Neoproterozoic.

Factors influencing the dissolved iron input by river water to the open ocean

NASA Astrophysics Data System (ADS)

Krachler, R.; Jirsa, F.; Ayromlou, S.

The influence of natural metal chelators on the bio-available iron input to the ocean by river water was studied. Ferrous and ferric ions present as suspended colloidal particles maintaining the semblance of a dissolved load are coagulated and settled as their freshwater carrier is mixed with seawater at the continental boundary. However, we might argue that different iron-binding colloids become sequentially destabilized in meeting progressively increasing salinities. By use of a 59Fe tracer method, the partitioning of the iron load from the suspended and dissolved mobile fraction to storage in the sediments was measured with high accuracy in mixtures of natural river water with artificial sea water. The results show a characteristic sequence of sedimentation. Various colloids of different stability are removed from a water of increasing salinity, such as it is the case in the transition from a river water to the open sea. However, the iron transport capacities of the investigated river waters differed greatly. A mountainous river in the Austrian Alps would add only about 5% of its dissolved Fe load, that is about 2.0 µg L-1 Fe, to coastal waters. A small tributary draining a sphagnum peat-bog, which acts as a source of refractory low-molecular-weight fulvic acids to the river water, would add approximately 20% of its original Fe load, that is up to 480 µg L-1 Fe to the ocean's bio-available iron pool. This points to a natural mechanism of ocean iron fertilization by terrigenous fulvic-iron complexes originating from weathering processes occurring in the soils upstream.

Factors influencing the dissolved iron input by river water to the open ocean

NASA Astrophysics Data System (ADS)

Krachler, R.; Jirsa, F.; Ayromlou, S.

2005-05-01

The influence of natural metal chelators on the bio-available iron input to the ocean by river water was studied. Ferrous and ferric ions present as suspended colloidal particles maintaining the semblance of a dissolved load are coagulated and settled as their freshwater carrier is mixed with seawater at the continental boundary. However, we might argue that different iron-binding colloids become sequentially destabilized in meeting progressively increasing salinities. By use of a 59Fe tracer method, the partitioning of the iron load from the suspended and dissolved mobile fraction to storage in the sediments was measured with high accuracy in mixtures of natural river water with artificial sea water. The results show a characteristic sequence of sedimentation. Various colloids of different stability are removed from a water of increasing salinity, such as it is the case in the transition from a river water to the open sea. However, the iron transport capacities of the investigated river waters differed greatly. A mountainous river in the Austrian Alps would add only about 5% of its dissolved Fe load, that is about 2.0 µg L-1 Fe, to coastal waters. A small tributary draining a sphagnum peat-bog, which acts as a source of refractory low-molecular-weight fulvic acids to the river water, would add approximately 20% of its original Fe load, that is up to 480 µg L-1 Fe to the ocean's bio-available iron pool. This points to a natural mechanism of ocean iron fertilization by terrigenous fulvic-iron complexes originating from weathering processes occurring in the soils upstream.

Purification and characterization of an oxygen-labile, NAD-dependent alcohol dehydrogenase from Desulfovibrio gigas.

PubMed Central

Hensgens, C M; Vonck, J; Van Beeumen, J; van Bruggen, E F; Hansen, T A

1993-01-01

A NAD-dependent, oxygen-labile alcohol dehydrogenase was purified from Desulfovibrio gigas. It was decameric, with subunits of M(r) 43,000. The best substrates were ethanol (Km, 0.15 mM) and 1-propanol (Km, 0.28 mM). N-terminal amino acid sequence analysis showed that the enzyme belongs to the same family of alcohol dehydrogenases as Zymomonas mobilis ADH2 and Bacillus methanolicus MDH. Images PMID:8491707

Microwave-assisted extraction performed in low temperature and in vacuo for the extraction of labile compounds in food samples.

PubMed

Xiao, Xiaohua; Song, Wei; Wang, Jiayue; Li, Gongke

2012-01-27

In this study, low temperature vacuum microwave-assisted extraction, which simultaneous performed microwave-assisted extraction (MAE) in low temperature and in vacuo environment, was proposed. The influencing parameters including solid/liquid ratio, extraction temperature, extraction time, degree of vacuum and microwave power were discussed. The predominance of low temperature vacuum microwave-assisted extraction was investigated by comparing the extraction yields of vitamin C, β-carotene, aloin A and astaxanthin in different foods with that in MAE and solvent extraction, and 5.2-243% increments were obtained. On the other hand, the chemical kinetics of vitamin C and aloin A, which composed two different steps including the extraction step of analyte transferred from matrix into solvent and the decomposition step of analyte degraded in the extraction solvent, were proposed. All of the decomposition rates (K(2)) for the selected analyte in low temperature, in vacuo and in nitrogen atmosphere decreased significantly comparing with that in conventional MAE, which are in agreement with that obtained from experiments. Consequently, the present method was successfully applied to extract labile compound from different food samples. These results showed that low temperature and/or in vacuo environment in microwave-assisted extraction system was especially important to prevent the degradation of labile components and have good potential on the extraction of labile compound in foods, pharmaceutical and natural products. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect of dietary intervention treatment on children with iron deficiency anemia in China: a meta-analysis.

PubMed

Sun, Jian; Zhang, Lei; Cui, Jing; Li, Shanshan; Lu, Hongting; Zhang, Yong; Li, Haiming; Sun, Jianping; Baloch, Zulqarnain

2018-05-10

Previous studies have shown beneficial effects of dietary approaches for iron deficiency anemia (IDA) control. This study was design to investigate the effect of dietary intervention treatment on children with iron deficiency anemia. We performed a systematic review of published dietary interventions effect on IDA treatment through meta-analysis. CBM, CNKI, Wanfang database, EMBASE, VIP, PubMed and Web of science database were searched to identify studies published between January, 1980 and December, 2016. Statistical analysis was performed by Revmen5.2 software. Initially we retrieved for 373 studies, and then 6 studies with a total of 676 individuals were included in the analysis according to the inclusion and exclusion criteria for meta-analysis. The overall pooled estimate of odds ratio [(OR), 95% confidence intervals (95% CI)] in the dietary intervention on children with iron deficiency anemia was 6.54 (95% CI: 3.48-12.31, Z = 5.82, p<0.001) and funnel plot is symmetric. Our meta-analysis suggested that dietary interventions are effective in improving the iron deficiency in children with iron deficiency anemia (IDA) and should be considered in the overall strategy of IDA management.

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems

NASA Astrophysics Data System (ADS)

Maldonado, Maria T.; Surma, Szymon; Pakhomov, Evgeny A.

2016-11-01

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km-2) were converted to biogenic Fe pools (kg Fe km-2) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems.

PubMed

Maldonado, Maria T; Surma, Szymon; Pakhomov, Evgeny A

2016-11-28

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km -2 ) were converted to biogenic Fe pools (kg Fe km -2 ) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Design of association studies with pooled or un-pooled next-generation sequencing data.

PubMed

Kim, Su Yeon; Li, Yingrui; Guo, Yiran; Li, Ruiqiang; Holmkvist, Johan; Hansen, Torben; Pedersen, Oluf; Wang, Jun; Nielsen, Rasmus

2010-07-01

Most common hereditary diseases in humans are complex and multifactorial. Large-scale genome-wide association studies based on SNP genotyping have only identified a small fraction of the heritable variation of these diseases. One explanation may be that many rare variants (a minor allele frequency, MAF <5%), which are not included in the common genotyping platforms, may contribute substantially to the genetic variation of these diseases. Next-generation sequencing, which would allow the analysis of rare variants, is now becoming so cheap that it provides a viable alternative to SNP genotyping. In this paper, we present cost-effective protocols for using next-generation sequencing in association mapping studies based on pooled and un-pooled samples, and identify optimal designs with respect to total number of individuals, number of individuals per pool, and the sequencing coverage. We perform a small empirical study to evaluate the pooling variance in a realistic setting where pooling is combined with exon-capturing. To test for associations, we develop a likelihood ratio statistic that accounts for the high error rate of next-generation sequencing data. We also perform extensive simulations to determine the power and accuracy of this method. Overall, our findings suggest that with a fixed cost, sequencing many individuals at a more shallow depth with larger pool size achieves higher power than sequencing a small number of individuals in higher depth with smaller pool size, even in the presence of high error rates. Our results provide guidelines for researchers who are developing association mapping studies based on next-generation sequencing. (c) 2010 Wiley-Liss, Inc.

Acid-Labile Acyclic Cucurbit[n]uril Molecular Containers for Controlled Release.

PubMed

Mao, Dake; Liang, Yajun; Liu, Yamin; Zhou, Xianhao; Ma, Jiaqi; Jiang, Biao; Liu, Jia; Ma, Da

2017-10-02

Stimuli-responsive molecular containers are of great importance for controlled drug delivery and other biomedical applications. A new type of acid labile acyclic cucurbit[n]uril (CB[n]) molecular containers is presented that can degrade and release the encapsulated cargo at accelerated rates under mildly acidic conditions (pH 5.5-6.5). These containers retain the excellent recognition properties of CB[n]-type hosts. A cell culture study demonstrated that the cellular uptake of cargos could be fine-tuned by complexation with different containers. The release and cell uptake of cargo dye was promoted by acidic pH. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Localization of alkali-labile sites in donkey (Equus asinus) and stallion (Equus caballus) spermatozoa.

PubMed

Cortés-Gutiérrez, Elva I; Dávila-Rodríguez, Martha I; López-Fernández, Carmen; Fernández, José Luis; Crespo, Francisco; Gosálvez, Jaime

2014-01-15

The presence of constitutive alkali-labile sites (ALS) has been investigated using a protocol of DNA breakage detection-fluorescence in situ hybridization and comet assay in spermatozoa of donkey (Equus asinus) and stallion (Equus caballus). These results were compared with those obtained using a similar experimental approach using somatic cells. The relative abundance of ALS was of the order of four times more in spermatozoa than in somatic cells. Alkali-labile sites showed a tendency to cluster localized at the equatorial-distal regions of the sperm. The amount of hybridized signal in the ALS in the sperm of donkey (Equus asinus) was 1.3 times greater than in stallion (Equus caballus), and the length of the comet tail obtained in donkey sperm was 1.6 times longer than that observed in stallion (P < 0.05); however, these differences were not appreciated in somatic cells. In conclusion, ALS localization in sperm is not a randomized event and a different pattern of ALS distribution occurs for each species. These results suggest that ALS represents a species-specific issue related to chromatin organization in sperm and somatic cells in mammalian species, and they might diverge even with very short phylogenetic distances. Copyright © 2014 Elsevier Inc. All rights reserved.

A relay network of extracellular heme-binding proteins drives C. albicans iron acquisition from hemoglobin.

PubMed

Kuznets, Galit; Vigonsky, Elena; Weissman, Ziva; Lalli, Daniela; Gildor, Tsvia; Kauffman, Sarah J; Turano, Paola; Becker, Jeffrey; Lewinson, Oded; Kornitzer, Daniel

2014-10-01

Iron scavenging constitutes a crucial challenge for survival of pathogenic microorganisms in the iron-poor host environment. Candida albicans, like many microbial pathogens, is able to utilize iron from hemoglobin, the largest iron pool in the host's body. Rbt5 is an extracellular glycosylphosphatidylinositol (GPI)-anchored heme-binding protein of the CFEM family that facilitates heme-iron uptake by an unknown mechanism. Here, we characterize an additional C. albicans CFEM protein gene, PGA7, deletion of which elicits a more severe heme-iron utilization phenotype than deletion of RBT5. The virulence of the pga7-/- mutant is reduced in a mouse model of systemic infection, consistent with a requirement for heme-iron utilization for C. albicans pathogenicity. The Pga7 and Rbt5 proteins exhibit distinct cell wall attachment, and discrete localization within the cell envelope, with Rbt5 being more exposed than Pga7. Both proteins are shown here to efficiently extract heme from hemoglobin. Surprisingly, while Pga7 has a higher affinity for heme in vitro, we find that heme transfer can occur bi-directionally between Pga7 and Rbt5, supporting a model in which they cooperate in a heme-acquisition relay. Together, our data delineate the roles of Pga7 and Rbt5 in a cell surface protein network that transfers heme from extracellular hemoglobin to the endocytic pathway, and provide a paradigm for how receptors embedded in the cell wall matrix can mediate nutrient uptake across the fungal cell envelope.

A novel approach to quantify different iron forms in ex-vivo human brain tissue

NASA Astrophysics Data System (ADS)

Kumar, Pravin; Bulk, Marjolein; Webb, Andrew; van der Weerd, Louise; Oosterkamp, Tjerk H.; Huber, Martina; Bossoni, Lucia

2016-12-01

We propose a novel combination of methods to study the physical properties of ferric ions and iron-oxide nanoparticles in post-mortem human brain, based on the combination of Electron Paramagnetic Resonance (EPR) and SQUID magnetometry. By means of EPR, we derive the concentration of the low molecular weight iron pool, as well as the product of its electron spin relaxation times. Additionally, by SQUID magnetometry we identify iron mineralization products ascribable to a magnetite/maghemite phase and a ferrihydrite (ferritin) phase. We further derive the concentration of magnetite/maghemite and of ferritin nanoparticles. To test out the new combined methodology, we studied brain tissue of an Alzheimer’s patient and a healthy control. Finally, we estimate that the size of the magnetite/maghemite nanoparticles, whose magnetic moments are blocked at room temperature, exceeds 40-50 nm, which is not compatible with the ferritin protein, the core of which is typically 6-8 nm. We believe that this methodology could be beneficial in the study of neurodegenerative diseases such as Alzheimer’s Disease which are characterized by abnormal iron accumulation in the brain.

A novel approach to quantify different iron forms in ex-vivo human brain tissue

PubMed Central

Kumar, Pravin; Bulk, Marjolein; Webb, Andrew; van der Weerd, Louise; Oosterkamp, Tjerk H.; Huber, Martina; Bossoni, Lucia

2016-01-01

We propose a novel combination of methods to study the physical properties of ferric ions and iron-oxide nanoparticles in post-mortem human brain, based on the combination of Electron Paramagnetic Resonance (EPR) and SQUID magnetometry. By means of EPR, we derive the concentration of the low molecular weight iron pool, as well as the product of its electron spin relaxation times. Additionally, by SQUID magnetometry we identify iron mineralization products ascribable to a magnetite/maghemite phase and a ferrihydrite (ferritin) phase. We further derive the concentration of magnetite/maghemite and of ferritin nanoparticles. To test out the new combined methodology, we studied brain tissue of an Alzheimer’s patient and a healthy control. Finally, we estimate that the size of the magnetite/maghemite nanoparticles, whose magnetic moments are blocked at room temperature, exceeds 40–50 nm, which is not compatible with the ferritin protein, the core of which is typically 6–8 nm. We believe that this methodology could be beneficial in the study of neurodegenerative diseases such as Alzheimer’s Disease which are characterized by abnormal iron accumulation in the brain. PMID:27941952

Design of hydrotherapy exercise pools.

PubMed

Edlich, R F; Abidin, M R; Becker, D G; Pavlovich, L J; Dang, M T

1988-01-01

Several hydrotherapy pools have been designed specifically for a variety of aquatic exercise. Aqua-Ark positions the exerciser in the center of the pool for deep-water exercise. Aqua-Trex is a shallow underwater treadmill system for water walking or jogging. Swim-Ex generates an adjustable laminar flow that permits swimming without turning. Musculoskeletal conditioning can be accomplished in the above-ground Arjo shallow-water exercise pool. A hydrotherapy pool also can be custom designed for musculoskeletal conditioning in its shallow part and cardiovascular conditioning in a deeper portion of the pool. Regardless of the type of exercise, there is general agreement that the specific exercise conducted in water requires significantly more energy expenditure than when the same exercise is performed on land.

Magnitude and Mechanism of Siderophore-Mediated Competition at Low Iron Solubility in the Pseudomonas aeruginosa Pyochelin System.

PubMed

Schiessl, Konstanze T; Janssen, Elisabeth M-L; Kraemer, Stephan M; McNeill, Kristopher; Ackermann, Martin

2017-01-01

A central question in microbial ecology is whether microbial interactions are predominantly cooperative or competitive. The secretion of siderophores, microbial iron chelators, is a model system for cooperative interactions. However, siderophores have also been shown to mediate competition by sequestering available iron and making it unavailable to competitors. The details of how siderophores mediate competition are not well understood, especially considering the complex distribution of iron phases in the environment. One pertinent question is whether sequestering iron through siderophores can indeed be effective in natural conditions; many natural environments are characterized by large pools of precipitated iron, and it is conceivable that any soluble iron that is sequestered by siderophores is replenished by the dissolution of these precipitated iron sources. Our goal here was to address this issue, and investigate the magnitude and mechanism of siderophore-mediated competition in the presence of precipitated iron. We combined experimental work with thermodynamic modeling, using Pseudomonas aeruginosa as a model system and ferrihydrite precipitates as the iron source with low solubility. Our experiments show that competitive growth inhibition by the siderophore pyochelin is indeed efficient, and that inhibition of a competitor can even have a stronger growth-promoting effect than solubilization of precipitated iron. Based on the results of our thermodynamic models we conclude that the observed inhibition of a competitor is effective because sequestered iron is only very slowly replenished by the dissolution of precipitated iron. Our research highlights the importance of competitive benefits mediated by siderophores, and underlines that the dynamics of siderophore production and uptake in environmental communities could be a signature of competitive, not just cooperative, dynamics.

Nanophase iron phosphate, iron arsenate, iron vanadate, and iron molybdate minerals synthesized within the protein cage of ferritin.

PubMed

Polanams, Jup; Ray, Alisha D; Watt, Richard K

2005-05-02

Nanoparticles of iron phosphate, iron arsenate, iron molybdate, and iron vanadate were synthesized within the 8 nm interior of ferritin. The synthesis involved reacting Fe(II) with ferritin in a buffered solution at pH 7.4 in the presence of phosphate, arsenate, vanadate, or molybdate. O2 was used as the oxidant to deposit the Fe(III) mineral inside ferritin. The rate of iron incorporation into ferritin was stimulated when oxo-anions were present. The simultaneous deposition of both iron and the oxo-anion was confirmed by elemental analysis and energy-dispersive X-ray analysis. The ferritin samples containing iron and one of the oxo-anions possessed different UV/vis spectra depending on the anion used during mineral formation. TEM analysis showed mineral cores with approximately 8 nm mineral particles consistent with the formation of mineral phases inside ferritin.

Intravenous iron-dextran: studies on unsaturated iron-binding capacity

PubMed Central

Cox, J. S. G.; Moss, G. F.; Bremner, I.; Reason, Janet

1968-01-01

A method is described for measuring the plasma unsaturated iron-binding capacity in the presence of very high concentrations of iron as iron-dextran. The procedure utilizes 59Fe to label the apotransferrin with subsequent separation of ionic iron from transferrin-bound iron on an ion exchange or Sephadex G.25 column. The unsaturated iron-binding capacity has been measured in rabbits and dogs after intravenous injection of iron-dextran and in human subjects after total dose infusion of iron-dextran. No evidence of saturation of the unsaturated iron-binding capacity was found even when the plasma iron values were greater than 40,000 μg Fe/100 ml. PMID:5697365

Swimming pool cleaner poisoning

MedlinePlus

Swimming pool cleaner poisoning occurs when someone swallows this type of cleaner, touches it, or breathes in ... The harmful substances in swimming pool cleaner are: Bromine ... copper Chlorine Soda ash Sodium bicarbonate Various mild acids

A Longitudinal Study of Emotion Regulation, Emotion Lability-Negativity, and Internalizing Symptomatology in Maltreated and Nonmaltreated Children

ERIC Educational Resources Information Center

Kim-Spoon, Jungmeen; Cicchetti, Dante; Rogosch, Fred A.

2013-01-01

The longitudinal contributions of emotion regulation and emotion lability-negativity to internalizing symptomatology were examined in a low-income sample (171 maltreated and 151 nonmaltreated children, from age 7 to 10 years). Latent difference score models indicated that for both maltreated and nonmaltreated children, emotion regulation was a…

Estimating rates and patterns of morphological evolution from phylogenies: lessons in limb lability from Australian Lerista lizards

PubMed Central

Wiens, John J

2009-01-01

Squamates (lizards and snakes) offer an exciting model system for research on the evolution of body form. A new phylogenetic study in BMC Evolutionary Biology of Australian lizards shows remarkable evolutionary lability in digit numbers among closely related species, but also highlights important challenges in this area. PMID:19291259

Metal speciation and potential bioavailability changes during discharge and neutralisation of acidic drainage water.

PubMed

Simpson, Stuart L; Vardanega, Christopher R; Jarolimek, Chad; Jolley, Dianne F; Angel, Brad M; Mosley, Luke M

2014-05-01

The discharge of acid drainage from the farm irrigation areas to the Murray River in South Australia represents a potential risk to water quality. The drainage waters have low pH (2.9-5.7), high acidity (up to 1190 mg L(-1) CaCO3), high dissolved organic carbon (10-40 mg L(-1)), and high dissolved Al, Co, Ni and Zn (up to 55, 1.25, 1.30 and 1.10 mg L(-1), respectively) that represent the greatest concern relative to water quality guidelines (WQGs). To provide information on bioavailability, changes in metal speciation were assessed during mixing experiments using filtration (colloidal metals) and Chelex-lability (free metal ions and weak inorganic metal complexes) methods. Following mixing of drainage and river water, much of the dissolved aluminium and iron precipitated. The concentrations of other metals generally decreased conservatively in proportion to the dilution initially, but longer mixing periods caused increased precipitation or adsorption to particulate phases. Dissolved Co, Mn and Zn were typically 95-100% present in Chelex-labile forms, whereas 40-70% of the dissolved nickel was Chelex-labile and the remaining non-labile fraction of dissolved nickel was associated with fine colloids or complexed by organic ligands that increased with time. Despite the different kinetics of precipitation, adsorption and complexation reactions, the dissolved metal concentrations were generally highly correlated for the pooled data sets, indicating that the major factors controlling the concentrations were similar for each metal (pH, dilution, and time following mixing). For dilutions of the drainage waters of less than 1% with Murray River water, none of the metals should exceed the WQGs. However, the high concentrations of metals associated with fine precipitates within the receiving waters may represent a risk to some aquatic organisms. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

SEQUENTIAL EXTRACTIONS FOR PARTITIONING OF ARSENIC ON HYDROUS IRON OXIDES AND IRON SULFIDES

EPA Science Inventory

The objective of this study was to use model solids to test solutions designed to extract arsenic from relatively labile solid phase fractions. The use of sequential extractions provides analytical constraints on the identification of mineral phases that control arsenic mobility...

Efficient catalysis of Nazarov cyclization using a cationic iridium complex possessing adjacent labile coordination sites.

PubMed

Janka, Mesfin; He, Wei; Frontier, Alison J; Eisenberg, Richard

2004-06-09

The dicationic Ir(III) complex [IrMe(CO)(dppe)(DIB)](BARF)2 having adjacent labile sites has been found to be a very effective catalyst for promoting the Nazarov cyclization of aryl vinyl and divinyl ketones. Spectroscopic evidence for a substate-catalyst complex before cyclization is presented. The efficiency of the cyclization is attributed to the electrophilicity of the Ir(III) complex and substrate activation via chelation.

Ferritin accumulation under iron scarcity in Drosophila iron cells.

PubMed

Mehta, A; Deshpande, A; Bettedi, L; Missirlis, F

2009-10-01

Ferritins are highly stable, multi-subunit protein complexes with iron-binding capacities that reach 4500 iron atoms per ferritin molecule. The strict dependence of cellular physiology on an adequate supply of iron cofactors has likely been a key driving force in the evolution of ferritins as iron storage molecules. The insect intestine has long been known to contain cells that are responsive to dietary iron levels and a specialized group of "iron cells" that always accumulate iron-loaded ferritin, even when no supplementary iron is added to the diet. Here, we further characterize ferritin localization in Drosophila melanogaster larvae raised under iron-enriched and iron-depleted conditions. High dietary iron intake results in ferritin accumulation in the anterior midgut, but also in garland (wreath) cells and in pericardial cells, which together filter the circulating hemolymph. Ferritin is also abundant in the brain, where levels remain unaltered following dietary iron chelation, a treatment that depletes ferritin from the aforementioned tissues. We attribute the stability of ferritin levels in the brain to the function of the blood-brain barrier that may shield this organ from systemic iron fluctuations. Most intriguingly, our dietary manipulations demonstrably iron-depleted the iron cells without a concomitant reduction in their production of ferritin. Therefore, insect iron cells may constitute an exception from the evolutionary norm with respect to iron-dependent ferritin regulation. It will be of interest to decipher both the physiological purpose served and the mechanism employed to untie ferritin regulation from cellular iron levels in this cell type.

Evaluation of the use of pooled serum, pooled muscle tissue fluid (meat juice) and pooled faeces for monitoring pig herds for Salmonella.

PubMed

Davies, R H; Heath, P J; Coxon, S M; Sayers, A R

2003-01-01

Monitoring for Salmonella in slaughter pigs is important to enable targeted control measures to be applied on problem farms and at the abattoir. The aim of this study was to determine whether pooled serum and meat juice could be used to identify finishing pig herds with a high prevalence of infection. Samples of meat juice, serum, caecal contents, carcase swabs and pooled faeces from pig pens were taken from 20 commercial pig finishing farms and comparisons were made between the results of Salmonella culture, individual ELISA tests on serum and meat juice and pooled samples of serum and meat juice. Salmonella was isolated from samples from 19 of 20 farms. None of the ELISA tests showed a statistically significant correlation with caecal carriage of Salmonella or contamination of carcases. Serum mean optical density (O.D.) from pools of five, 10 or 20 sera showed a significant correlation with the Salmonella status of farm pen faeces. All pooled serum O.D. and sample/positive control ratio results correlated significantly with the results of the conventional individual sample ELISA. There was a statistically significant correlation between the incidence of Salmonella in farm pen pooled faeces and the prevalence of Salmonella in caeca of slaughter pigs. The results show a generally poor correlation between serological and bacteriological results but pooled serum or meat juice samples could be used as a cheaper substitute for serological screening of farms for Salmonella than individual samples. The availability of a cheaper test should allow the costs of Salmonella monitoring of pig farms to be reduced or allow more regular testing to enhance the designation of farm Salmonella risk status.

Revisiting the iron pools in cucumber roots: identification and localization.

PubMed

Kovács, Krisztina; Pechoušek, Jiří; Machala, Libor; Zbořil, Radek; Klencsár, Zoltán; Solti, Ádám; Tóth, Brigitta; Müller, Brigitta; Pham, Hong Diep; Kristóf, Zoltán; Fodor, Ferenc

2016-07-01

Fe deficiency responses in Strategy I causes a shift from the formation of partially removable hydrous ferric oxide on the root surface to the accumulation of Fe-citrate in the xylem. Iron may accumulate in various chemical forms during its uptake and assimilation in roots. The permanent and transient Fe microenvironments formed during these processes in cucumber which takes up Fe in a reduction based process (Strategy I) have been investigated. The identification of Fe microenvironments was carried out with (57)Fe Mössbauer spectroscopy and immunoblotting, whereas reductive washing and high-resolution microscopy was applied for the localization. In plants supplied with (57)Fe(III)-citrate, a transient presence of Fe-carboxylates in removable forms and the accumulation of partly removable, amorphous hydrous ferric oxide/hydroxyde have been identified in the apoplast and on the root surface, respectively. The latter may at least partly be the consequence of bacterial activity at the root surface. Ferritin accumulation did not occur at optimal Fe supply. Under Fe deficiency, highly soluble ferrous hexaaqua complex is transiently formed along with the accumulation of Fe-carboxylates, likely Fe-citrate. As (57)Fe-citrate is non-removable from the root samples of Fe deficient plants, the major site of accumulation is suggested to be the root xylem. Reductive washing results in another ferrous microenvironment remaining in the root apoplast, the Fe(II)-bipyridyl complex, which accounts for ~30 % of the total Fe content of the root samples treated for 10 min and rinsed with CaSO4 solution. When (57)Fe(III)-EDTA or (57)Fe(III)-EDDHA was applied as Fe-source higher soluble ferrous Fe accumulation was accompanied by a lower total Fe content, confirming that chelates are more efficient in maintaining soluble Fe in the medium while less stable natural complexes as Fe-citrate may perform better in Fe accumulation.

Prevalence of Celiac Disease in Patients with Iron Deficiency Anemia - a Systematic Review with Meta-analysis.

PubMed

Mahadev, Srihari; Laszkowska, Monika; Sundström, Johan; Björkholm, Magnus; Lebwohl, Benjamin; Green, Peter Hr; Ludvigsson, Jonas F

2018-04-21

Anemia is common in patients with celiac disease and a frequent presentation. Guidelines recommend screening iron-deficient patients with anemia for celiac disease. However, the reported prevalence of celiac disease among patients with iron-deficiency anemia (IDA) varies. We performed a systematic review to determine the prevalence of biopsy-verified celiac disease in patients with IDA. We performed a systematic review of manuscripts published in PubMed Medline or EMBASE through July 2017 for the term celiac disease combined with anemia or iron-deficiency. We used fixed-effects inverse variance-weighted models to measure the pooled prevalence of celiac disease. Meta-regression was used to assess subgroup heterogeneity. We identified 18 studies comprising 2998 patients with IDA for inclusion in our analysis. Studies originated from the United Kingdom, United States, Italy, Turkey, Iran, and Israel. The crude unweighted prevalence of celiac disease was 4.8% (n=143). Using a weighted pooled analysis, we demonstrated a prevalence of biopsy-confirmed celiac disease 3.2% (95% CI, 2.6%-3.9%) in patients with IDA. However, heterogeneity was high (I 2 = 67.7%). The prevalence of celiac disease was not significantly higher in studies with a mean participant age older or younger than years, nor in studies with a mixed-sex vs female-predominant (≥60%) population. On meta-regression, year of publication, the proportion of females, age at celiac disease testing, and the prevalence of in the general population were not associated with the prevalence of celiac disease in patients with IDA. In the 8 studies fulfilling all our quality criteria, the pooled prevalence of celiac disease was 5.5% (95% CI, 4.1%-6.9%). In a systematic review and meta-analysis, we found that approximately 1 in 31 patients with IDA have histologic evidence of celiac disease. This prevalence value justifies the practice of testing patients with IDA for celiac disease. Copyright © 2018 AGA Institute

An introduction to mid-Atlantic seasonal pools

USGS Publications Warehouse

Brown, L.J.; Jung, R.E.

2005-01-01

Seasonal pools, also known as vernal ponds, provide important ecological services to the mid-Atlantic region. This publication serves as an introduction to seasonal pool ecology and management; it also provides tools for exploring seasonal pools, including a full-color field guide to wildlife. Seasonal pools are defined as having four distinctive features: surface water isolation, periodic drying, small size and shallow depth, and support of a characteristic biological community. Seasonal pools experience regular drying that excludes populations of predatory fish. Thus, pools in the mid-Atlantic region provide critical breeding habitat for amphibian and invertebrate species (e.g., spotted salamander (Ambystoma maculatum), wood frog (Rana sylvatica), and fairy shrimp (Order Anostraca)) that would be at increased risk of predation in more permanent waters. The distinctive features of seasonal pools also make them vulnerable to human disturbance. In the mid-Atlantic region, land-use changes pose the greatest challenges to seasonal pool conservation. Seasonal pools are threatened by direct loss (e.g., filling or draining of the pool) as well as by destruction and fragmentation of adjoining terrestrial habitat. Many of the species that depend on seasonal pools for breeding spend the majority of their lives in the surrounding lands that extend a radius of 1000 feet or more from the pools; these vital habitats are being transected by roads and converted to other land uses. Other threats to seasonal pools include biological introductions and removals, mosquito control practices, amphibian diseases, atmospheric deposition, and climate change. The authors recommend a three-pronged strategy for seasonal pool conservation and management in the mid-Atlantic region: education and research, inventory and monitoring of seasonal pools, and landscape-level planning and management.

Iron deficiency and iron deficiency anaemia in women.

PubMed

Percy, Laura; Mansour, Diana; Fraser, Ian

2017-04-01

Iron deficiency (ID) is the most common micronutrient deficiency worldwide with >20% of women experiencing it during their reproductive lives. Hepcidin, a peptide hormone mostly produced by the liver, controls the absorption and regulation of iron. Understanding iron metabolism is pivotal in the successful management of ID and iron deficiency anaemia (IDA) using oral preparations, parenteral iron or blood transfusion. Oral preparations vary in their iron content and can result in gastrointestinal side effects. Parenteral iron is indicated when there are compliance/tolerance issues with oral iron, comorbidities which may affect absorption or ongoing iron losses that exceed absorptive capacity. It may also be the preferred option when rapid iron repletion is required to prevent physiological decompensation or given preoperatively for non-deferrable surgery. As gynaecologists, we focus on managing women's heavy menstrual bleeding (HMB) and assume that primary care clinicians are treating the associated ID/IDA. We now need to take the lead in diagnosing, managing and initiating treatment for ID/IDA and treating HMB simultaneously. This dual management will significantly improve their quality of life. In this chapter we will summarise the importance of iron in cellular functioning, describe how to diagnose ID/IDA and help clinicians choose between the available treatment options. Copyright © 2016. Published by Elsevier Ltd.

Tidal Pools--Miniature Oceans

ERIC Educational Resources Information Center

Plake, Linda Perry

1977-01-01

A comprehensive discussion of the biological activity in tidal pools is provided. The importance of environmental factors such as oxygen supply, temperature, salinity, and light is detailed. Plants and animals that might be found in a tidal pool are identified and described. (BT)

Development of the laboratory prototype "CavyPool" for assessing treatments and materials for swimming pools.

PubMed

Valeriani, F; Gianfranceschi, G; Vitali, M; Protano, C; Romano Spica, V

2017-01-01

Hygiene and surveillance in swimming pools are established by WHO Guidelines and national laws. Progress in water management and pool construction is revolutionizing the field, introducing new materials, systems, disinfection procedures or monitoring markers. Innovation advances challenge the upgrading of safety and quality in pools and the appropriate implementation of guidelines. In order to provide a device for laboratory test, a prototype was realized and applied to study and compare swimming pool materials and treatments. A pool scale-model was engineered and evaluated by computational fluid dynamics algorithms. An automated real time monitoring assured steady state. Critical control points along the water circuit were made accessible to allow the placing of different biocides or water sampling. Simulations were safely performed in a standard hood. Materials for pool surfaces and pipelines were evaluated for biofilm formation under different disinfection conditions. Adherent microorganisms were assayed by mfDNA analysis using real time PCR. The prototype reached the steady state within 5-25 hours under different conditions, showing chemical, physical and fluid-dynamic stability. A method was optimized for testing materials showing their different response to biofilm induction. Several innovative PVC samples displayed highest resistance to bacterial adhesion. A device and method was developed for testing swimming pool hygienic parameters in laboratory. It allowed to test materials for pools hygiene and maintenance, including biofilm formation. It can be applied to simulate contaminations under different water treatments or disinfection strategies. It may support technical decisions and help policymakers in acquiring evidences for comparing or validating innovative solutions.

46 CFR 56.60-10 - Cast iron and malleable iron.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Cast iron and malleable iron. 56.60-10 Section 56.60-10... APPURTENANCES Materials § 56.60-10 Cast iron and malleable iron. (a) The low ductility of cast iron and... avoided. Cast iron and malleable iron components shall not be used at temperatures above 450 °F. Cast iron...

10 CFR 36.63 - Pool water purity.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 1 2010-01-01 2010-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool water...

10 CFR 36.63 - Pool water purity.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 1 2011-01-01 2011-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool water...

10 CFR 36.63 - Pool water purity.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 1 2012-01-01 2012-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool water...

10 CFR 36.63 - Pool water purity.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 1 2013-01-01 2013-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool water...

10 CFR 36.63 - Pool water purity.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 1 2014-01-01 2014-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool water...

Emotional Lability in Children and Adolescents with Attention Deficit/Hyperactivity Disorder (ADHD): Clinical Correlates and Familial Prevalence

ERIC Educational Resources Information Center

Sobanski, Esther; Banaschewski, Tobias; Asherson, Philip; Buitelaar, Jan; Chen, Wai; Franke, Barbara; Holtmann, Martin; Krumm, Bertram; Sergeant, Joseph; Sonuga-Barke, Edmund; Stringaris, Argyris; Taylor, Eric; Anney, Richard; Ebstein, Richard P.; Gill, Michael; Miranda, Ana; Mulas, Fernando; Oades, Robert D.; Roeyers, Herbert; Rothenberger, Aribert; Steinhausen, Hans-Christoph; Faraone, Stephen V.

2010-01-01

Background: The goal of this study was to investigate the occurrence, severity and clinical correlates of emotional lability (EL) in children with attention deficit/hyperactivity disorder (ADHD), and to examine factors contributing to EL and familiality of EL in youth with ADHD. Methods: One thousand, one hundred and eighty-six children with ADHD…

Higher iron bioavailability of a human-like collagen iron complex.

PubMed

Zhu, Chenhui; Yang, Fan; Fan, Daidi; Wang, Ya; Yu, Yuanyuan

2017-07-01

Iron deficiency remains a public health problem around the world due to low iron intake and/or bioavailability. FeSO 4 , ferrous succinate, and ferrous glycinate chelate are rich in iron but have poor bioavailability. To solve the problem of iron deficiency, following previous research studies, a thiolated human-like collagen-ironcomplex supplement with a high iron content was prepared in an anaerobic workstation. In addition, cell viability tests were evaluated after conducting an MTT assay, and a quantitative analysis of the thiolated human-like collagen-iron digesta samples was performed using the SDS-PAGE method coupled with gel filtration chromatography. The iron bioavailability was assessed using Caco-2 cell monolayers and iron-deficiency anemia mice models. The results showed that (1) one mole of thiolated human-like collagen-iron possessed approximately 35.34 moles of iron; (2) thiolated human-like collagen-iron did not exhibit cytotoxity and (3) thiolated human-like collagen- iron digesta samples had higher bioavailability than other iron supplements, including FeSO 4 , ferrous succinate, ferrous glycine chelate and thiolated human-like collagen-Fe iron. Finally, the iron bioavailability was significantly enhanced by vitamin C. These results indicated that thiolated human-like collagen-iron is a promising iron supplement for use in the future.

Recognition- and Reactivity-Based Fluorescent Probes for Studying Transition Metal Signaling in Living Systems

PubMed Central

2015-01-01

Conspectus Metals are essential for life, playing critical roles in all aspects of the central dogma of biology (e.g., the transcription and translation of nucleic acids and synthesis of proteins). Redox-inactive alkali, alkaline earth, and transition metals such as sodium, potassium, calcium, and zinc are widely recognized as dynamic signals, whereas redox-active transition metals such as copper and iron are traditionally thought of as sequestered by protein ligands, including as static enzyme cofactors, in part because of their potential to trigger oxidative stress and damage via Fenton chemistry. Metals in biology can be broadly categorized into two pools: static and labile. In the former, proteins and other macromolecules tightly bind metals; in the latter, metals are bound relatively weakly to cellular ligands, including proteins and low molecular weight ligands. Fluorescent probes can be useful tools for studying the roles of transition metals in their labile forms. Probes for imaging transition metal dynamics in living systems must meet several stringent criteria. In addition to exhibiting desirable photophysical properties and biocompatibility, they must be selective and show a fluorescence turn-on response to the metal of interest. To meet this challenge, we have pursued two general strategies for metal detection, termed “recognition” and “reactivity”. Our design of transition metal probes makes use of a recognition-based approach for copper and nickel and a reactivity-based approach for cobalt and iron. This Account summarizes progress in our laboratory on both the development and application of fluorescent probes to identify and study the signaling roles of transition metals in biology. In conjunction with complementary methods for direct metal detection and genetic and/or pharmacological manipulations, fluorescent probes for transition metals have helped reveal a number of principles underlying transition metal dynamics. In this Account, we give

Model of large pool fires.

PubMed

Fay, J A

2006-08-21

A two zone entrainment model of pool fires is proposed to depict the fluid flow and flame properties of the fire. Consisting of combustion and plume zones, it provides a consistent scheme for developing non-dimensional scaling parameters for correlating and extrapolating pool fire visible flame length, flame tilt, surface emissive power, and fuel evaporation rate. The model is extended to include grey gas thermal radiation from soot particles in the flame zone, accounting for emission and absorption in both optically thin and thick regions. A model of convective heat transfer from the combustion zone to the liquid fuel pool, and from a water substrate to cryogenic fuel pools spreading on water, provides evaporation rates for both adiabatic and non-adiabatic fires. The model is tested against field measurements of large scale pool fires, principally of LNG, and is generally in agreement with experimental values of all variables.

Laboratory experiments on the impact disruption of iron meteorites at temperature of near-Earth space

NASA Astrophysics Data System (ADS)

Katsura, Takekuni; Nakamura, Akiko M.; Takabe, Ayana; Okamoto, Takaya; Sangen, Kazuyoshi; Hasegawa, Sunao; Liu, Xun; Mashimo, Tsutomu

2014-10-01

Iron meteorites and some M-class asteroids are generally understood to be fragments that were originally part of cores of differentiated planetesimals or part of local melt pools on primitive bodies. The parent bodies of iron meteorites may have formed in the terrestrial planet region, from which they were then scattered into the main belt (Bottke, W.F., Nesvorný, D., Grimm, R.E., Morbidelli, A., O'Brien, D.P. [2006]. Nature 439, 821-824). Therefore, a wide range of collisional events at different mass scales, temperatures, and impact velocities would have occurred between the time when the iron was segregated and the impact that eventually exposed the iron meteorites to interplanetary space. In this study, we performed impact disruption experiments of iron meteorite specimens as projectiles or targets at room temperature to increase understanding of the disruption process of iron bodies in near-Earth space. Our iron specimens (as projectiles or targets) were almost all smaller in size than their counterparts (as targets or projectiles, respectively). Experiments of impacts of steel specimens were also conducted for comparison. The fragment mass distribution of the iron material was different from that of rocks. In the iron fragmentation, a higher percentage of the mass was concentrated in larger fragments, probably due to the ductile nature of the material at room temperature. The largest fragment mass fraction f was dependent not only on the energy density but also on the size d of the specimen. We assumed a power-law dependence of the largest fragment mass fraction to initial peak pressure P0 normalized by a dynamic strength, Y, which was defined to be dependent on the size of the iron material. A least squares fit to the data of iron meteorite specimens resulted in the following relationship: f∝∝d, indicating a large size dependence of f. Additionally, the deformation of the iron materials in high-velocity shots was found to be most significant when the

Contribution of macrophages in the contrast loss in iron oxide-based MRI cancer cell tracking studies

PubMed Central

Danhier, Pierre; Deumer, Gladys; Joudiou, Nicolas; Bouzin, Caroline; Levêque, Philippe; Haufroid, Vincent; Jordan, Bénédicte F.; Feron, Olivier; Sonveaux, Pierre; Gallez, Bernard

2017-01-01

Magnetic resonance imaging (MRI) cell tracking of cancer cells labeled with superparamagnetic iron oxides (SPIO) allows visualizing metastatic cells in preclinical models. However, previous works showed that the signal void induced by SPIO on T2(*)-weighted images decreased over time. Here, we aim at characterizing the fate of iron oxide nanoparticles used in cell tracking studies and the role of macrophages in SPIO metabolism. In vivo MRI cell tracking of SPIO positive 4T1 breast cancer cells revealed a quick loss of T2* contrast after injection. We next took advantage of electron paramagnetic resonance (EPR) spectroscopy and inductively coupled plasma mass spectroscopy (ICP-MS) for characterizing the evolution of superparamagnetic and non-superparamagnetic iron pools in 4T1 breast cancer cells and J774 macrophages after SPIO labeling. These in vitro experiments and histology studies performed on 4T1 tumors highlighted the quick degradation of iron oxides by macrophages in SPIO-based cell tracking experiments. In conclusion, the release of SPIO by dying cancer cells and the subsequent uptake of iron oxides by tumor macrophages are limiting factors in MRI cell tracking experiments that plead for the use of (MR) reporter-gene based imaging methods for the long-term tracking of metastatic cells. PMID:28467814

Evidence that stainable bone marrow iron following parenteral iron therapy does not correlate with serum iron studies and may not represent readily available storage iron.

PubMed

Thomason, Ronald W; Almiski, Muhamad S

2009-04-01

We recently reported that parenteral iron therapy is associated with a characteristic pattern of iron staining on bone marrow aspirate smears. We now present clinical information from 6 patients who received parenteral iron and, at one or more points in follow-up, were found to have low or borderline low serum ferritin levels and/or serum iron levels, even though marrow aspirate smears revealed abundant stainable iron in the pattern characteristic of prior parenteral iron therapy. We conclude that stainable iron seen in this pattern does not correlate with serum iron studies and may not represent functionally available storage iron. This pattern of iron staining should not be used as evidence to withhold further iron therapy in patients who otherwise continue to have features of iron deficiency anemia.

A Relay Network of Extracellular Heme-Binding Proteins Drives C. albicans Iron Acquisition from Hemoglobin

PubMed Central

Kuznets, Galit; Vigonsky, Elena; Weissman, Ziva; Lalli, Daniela; Gildor, Tsvia; Kauffman, Sarah J.; Turano, Paola; Becker, Jeffrey; Lewinson, Oded; Kornitzer, Daniel

2014-01-01

Iron scavenging constitutes a crucial challenge for survival of pathogenic microorganisms in the iron-poor host environment. Candida albicans, like many microbial pathogens, is able to utilize iron from hemoglobin, the largest iron pool in the host's body. Rbt5 is an extracellular glycosylphosphatidylinositol (GPI)-anchored heme-binding protein of the CFEM family that facilitates heme-iron uptake by an unknown mechanism. Here, we characterize an additional C. albicans CFEM protein gene, PGA7, deletion of which elicits a more severe heme-iron utilization phenotype than deletion of RBT5. The virulence of the pga7−/− mutant is reduced in a mouse model of systemic infection, consistent with a requirement for heme-iron utilization for C. albicans pathogenicity. The Pga7 and Rbt5 proteins exhibit distinct cell wall attachment, and discrete localization within the cell envelope, with Rbt5 being more exposed than Pga7. Both proteins are shown here to efficiently extract heme from hemoglobin. Surprisingly, while Pga7 has a higher affinity for heme in vitro, we find that heme transfer can occur bi-directionally between Pga7 and Rbt5, supporting a model in which they cooperate in a heme-acquisition relay. Together, our data delineate the roles of Pga7 and Rbt5 in a cell surface protein network that transfers heme from extracellular hemoglobin to the endocytic pathway, and provide a paradigm for how receptors embedded in the cell wall matrix can mediate nutrient uptake across the fungal cell envelope. PMID:25275454

Rank-based pooling for deep convolutional neural networks.

PubMed

Shi, Zenglin; Ye, Yangdong; Wu, Yunpeng

2016-11-01

Pooling is a key mechanism in deep convolutional neural networks (CNNs) which helps to achieve translation invariance. Numerous studies, both empirically and theoretically, show that pooling consistently boosts the performance of the CNNs. The conventional pooling methods are operated on activation values. In this work, we alternatively propose rank-based pooling. It is derived from the observations that ranking list is invariant under changes of activation values in a pooling region, and thus rank-based pooling operation may achieve more robust performance. In addition, the reasonable usage of rank can avoid the scale problems encountered by value-based methods. The novel pooling mechanism can be regarded as an instance of weighted pooling where a weighted sum of activations is used to generate the pooling output. This pooling mechanism can also be realized as rank-based average pooling (RAP), rank-based weighted pooling (RWP) and rank-based stochastic pooling (RSP) according to different weighting strategies. As another major contribution, we present a novel criterion to analyze the discriminant ability of various pooling methods, which is heavily under-researched in machine learning and computer vision community. Experimental results on several image benchmarks show that rank-based pooling outperforms the existing pooling methods in classification performance. We further demonstrate better performance on CIFAR datasets by integrating RSP into Network-in-Network. Copyright © 2016 Elsevier Ltd. All rights reserved.

Transient Response of Arc Temperature and Iron Vapor Concentration Affected by Current Frequency with Iron Vapor in Pulsed Arc

NASA Astrophysics Data System (ADS)

Tanaka, Tatsuro; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

2016-10-01

TIG arc welding is chemically a joining technology with melting the metallic material and it can be high quality. However, this welding should not be used in high current to prevent cathode melting. Thus, the heat transfer is poor. Therefore, the deep penetration cannot be obtained and the weld defect sometimes occurs. The pulsed arc welding has been used for the improvement of this defect. The pulsed arc welding can control the heat flux to anode. The convention and driving force in the weld pool are caused by the arc. Therefore, it is important to grasp the distribution of arc temperature. The metal vapor generate from the anode in welding. In addition, the pulsed current increased or decreased periodically. Therefore, the arc is affected by such as a current value and current frequency, the current rate of increment and the metal vapor. In this paper, the transient response of arc temperature and the iron vapor concentration affected by the current frequency with iron vapor in pulsed arc was elucidated by the EMTF (ElectroMagnetic Thermal Fluid) simulation. As a result, the arc temperature and the iron vapor were transient response as the current frequency increase. Thus, the temperature and the electrical conductivity decreased. Therefore, the electrical field increased in order to maintain the current continuity. The current density and electromagnetic force increased at the axial center. In addition, the electronic flow component of the heat flux increased at the axial center because the current density increased. However, the heat conduction component of the heat flux decreased.

Processing thermally labile drugs by hot-melt extrusion: The lesson with gliclazide.

PubMed

Huang, Siyuan; O'Donnell, Kevin P; Delpon de Vaux, Sophie M; O'Brien, John; Stutzman, John; Williams, Robert O

2017-10-01

The formation of molecularly dispersed amorphous solid dispersions by the hot-melt extrusion technique relies on the thermal and mechanical energy inputs, which can cause chemical degradation of drugs and polymeric carriers. Additionally, drug degradation may be exacerbated as drugs convert from a more stable crystalline form to a higher energy amorphous form. Therefore, it is imperative to study how drug degrades and evaluate methods to minimize drug degradation during the extrusion process. In this work, gliclazide was used as a model thermally labile drug for the degradation kinetics and process optimization studies. Preformulation studies were conducted using thermal analyses, and liquid chromatography-mass spectroscopy to identify drug degradation pathways and to determine initial extrusion conditions. Formulations containing 10% drug and 90% AFFINISOL™ HPMC HME 100LV were then extruded using a twin screw extruder, and the extrudates were characterized using X-ray powder diffraction, modulated dynamic scanning calorimetry, and potency testing to evaluate physicochemical properties. The energies of activation for both amorphous gliclazide, crystalline gliclazide, and gliclazide solution were calculated using the Arrhenius equation to further guide the extrusion optimization process. Preformulation studies identify two hydrolysis degradation pathways of gliclazide at elevated temperatures. The activation energy study indicates a significantly higher degradation rate for the amorphous gliclazide compared to the crystalline form. After optimization of the hot-melt extrusion process, including improved screw designs, machine setup, and processing conditions, gliclazide amorphous solid dispersion with ∼95% drug recovery was achieved. The ability to process thermally labile drugs and polymers using hot-melt extrusion will significantly expand the possible applications of this manufacturing process. Copyright © 2017 Elsevier B.V. All rights reserved.

POOL WATER TREATMENT AND COOLING SYSTEM DESCRIPTION DOCUMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

V. King

2000-06-19

The Pool Water Treatment and Cooling System is located in the Waste Handling Building (WHB), and is comprised of various process subsystems designed to support waste handling operations. This system maintains the pool water temperature within an acceptable range, maintains water quality standards that support remote underwater operations and prevent corrosion, detects leakage from the pool liner, provides the capability to remove debris from the pool, controls the pool water level, and helps limit radiological exposure to personnel. The pool structure and liner, pool lighting, and the fuel staging racks in the pool are not within the scope of themore » Pool Water Treatment and Cooling System. Pool water temperature control is accomplished by circulating the pool water through heat exchangers. Adequate circulation and mixing of the pool water is provided to prevent localized thermal hotspots in the pool. Treatment of the pool water is accomplished by a water treatment system that circulates the pool water through filters, and ion exchange units. These water treatment units remove radioactive and non-radioactive particulate and dissolved solids from the water, thereby providing the water clarity needed to conduct waste handling operations. The system also controls pool water chemistry to prevent advanced corrosion of the pool liner, pool components, and fuel assemblies. Removal of radioactivity from the pool water contributes to the project ALARA (as low as is reasonably achievable) goals. A leak detection system is provided to detect and alarm leaks through the pool liner. The pool level control system monitors the water level to ensure that the minimum water level required for adequate radiological shielding is maintained. Through interface with a demineralized water system, adequate makeup is provided to compensate for loss of water inventory through evaporation and waste handling operations. Interface with the Site Radiological Monitoring System provides

Quantitative chemical exchange saturation transfer (qCEST) MRI--RF spillover effect-corrected omega plot for simultaneous determination of labile proton fraction ratio and exchange rate.

PubMed

Sun, Phillip Zhe; Wang, Yu; Dai, ZhuoZhi; Xiao, Gang; Wu, Renhua

2014-01-01

Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute proteins and peptides as well as microenvironmental properties. However, the complexity of the CEST MRI effect, which varies with the labile proton content, exchange rate and experimental conditions, underscores the need for developing quantitative CEST (qCEST) analysis. Towards this goal, it has been shown that omega plot is capable of quantifying paramagnetic CEST MRI. However, the use of the omega plot is somewhat limited for diamagnetic CEST (DIACEST) MRI because it is more susceptible to direct radio frequency (RF) saturation (spillover) owing to the relatively small chemical shift. Recently, it has been found that, for dilute DIACEST agents that undergo slow to intermediate chemical exchange, the spillover effect varies little with the labile proton ratio and exchange rate. Therefore, we postulated that the omega plot analysis can be improved if RF spillover effect could be estimated and taken into account. Specifically, simulation showed that both labile proton ratio and exchange rate derived using the spillover effect-corrected omega plot were in good agreement with simulated values. In addition, the modified omega plot was confirmed experimentally, and we showed that the derived labile proton ratio increased linearly with creatine concentration (p < 0.01), with little difference in their exchange rate (p = 0.32). In summary, our study extends the conventional omega plot for quantitative analysis of DIACEST MRI. Copyright © 2014 John Wiley & Sons, Ltd.

Dietary iron intake, iron status, and gestational diabetes.

PubMed

Zhang, Cuilin; Rawal, Shristi

2017-12-01

Pregnant women are particularly vulnerable to iron deficiency and related adverse pregnancy outcomes and, as such, are routinely recommended for iron supplementation. Emerging evidence from both animal and population-based studies, however, has raised potential concerns because significant associations have been observed between greater iron stores and disturbances in glucose metabolism, including increased risk of type 2 diabetes among nonpregnant individuals. Yet, the evidence is uncertain regarding the role of iron in the development of gestational diabetes mellitus (GDM), a common pregnancy complication which has short-term and long-term adverse health ramifications for both women and their children. In this review, we critically and systematically evaluate available data examining the risk of GDM associated with dietary iron, iron supplementation, and iron status as measured by blood concentrations of several indicators. We also discuss major methodologic concerns regarding the available epidemiologic studies on iron and GDM. © 2017 American Society for Nutrition.

The Irony of Iron – Biogenic Iron Oxides as an Iron Source to the Ocean

PubMed Central

Emerson, David

2016-01-01

Primary productivity in at least a third of the sunlit open ocean is thought to be iron-limited. Primary sources of dissolved iron (dFe) to the ocean are hydrothermal venting, flux from the sediments along continental margins, and airborne dust. This article provides a general review of sources of hydrothermal and sedimentary iron to the ocean, and speculates upon the role that iron-cycling microbes play in controlling iron dynamics from these sources. Special attention is paid to iron-oxidizing bacteria (FeOB) that live by oxidizing iron and producing biogenic iron oxides as waste products. The presence and ubiquity of FeOB both at hydrothermal systems and in sediments is only beginning to be appreciated. The biogenic oxides they produce have unique properties that could contribute significantly to the dynamics of dFe in the ocean. Changes in the physical and chemical characteristics of the ocean due to climate change and ocean acidification will undoubtedly impact the microbial iron cycle. A better understanding of the contemporary role of microbes in the iron cycle will help in predicting how these changes could ultimately influence marine primary productivity. PMID:26779157

Effect of iron on accumulation of exotoxin A-specific mRNA in Pseudomonas aeruginosa.

PubMed Central

Lory, S

1986-01-01

A DNA probe from an internal fragment of the exotoxin A structural gene was used to study the effects of selected culture conditions on steady-state levels of exotoxin-specific mRNA in Pseudomonas aeruginosa. Cells grown under conditions of iron deprivation began to synthesize and excrete the exotoxin A polypeptide during the late exponential phase of growth and throughout the stationary phase of growth, concomitant with a sharp increase in exotoxin A mRNA pools in P. aeruginosa cells. The addition of iron to the medium resulted in the failure of these cells to synthesize exotoxin A mRNA, despite significantly enhanced growth. The inhibition of the production of exotoxin A and the accumulation of its mRNA by iron was dose dependent, with a half-maximal inhibitory concentration of FeSO4 of 5 to 10 microM. A blockade of the initiation of transcription by rifampin resulted in the decay of exotoxin A mRNA, with a half-life of approximately 8 to 10 min, depending on the media used for growth. The addition of iron to cells actively engaged in exotoxin A synthesis also resulted in a gradual decrease in the amount of this mRNA in bacteria. However, the rate of decline of mRNA induced by iron was relatively slow (half-life, 90 min), with a considerable lag time between the iron addition and the first detectable effect on mRNA. While iron clearly appears to influence the production of exotoxin A at the transcriptional level, the molecular basis of this effect may involve several interacting factors affecting the initiation of transcription and perhaps mRNA turnover. Images PMID:2430950

Interactions between iron and organic matter may influence the fate of permafrost carbon in the Arctic

NASA Astrophysics Data System (ADS)

Cory, R. M.; Trusiak, A.; Ward, C.; Kling, G. W.; Tfaily, M.; Paša-Tolić, L.; Noel, V.; Bargar, J.

2017-12-01

The ongoing thawing of permafrost soils is the only environmental change that allows tremendous stores of organic carbon (C) to be converted into carbon dioxide (CO2) on decadal time scales, thus providing a positive and accelerating feedback to global warming. Evidence suggests that iron enhances abiotic reactions that convert dissolved organic matter (DOM) to CO2 in dark soils and in sunlit surface waters depending on its redox state and association with DOM (i.e., iron-DOM complexation). However, the complexation of iron in surface waters and soils remains too poorly understood to predict how iron influences the rates of oxidation of DOM to CO2. To address this knowledge gap, we characterized iron-DOM complexation in iron-rich soil and surface waters of the Arctic, in combination with measurements of DOM oxidation to CO2. These waters contain high concentrations of dissolved iron and DOM (up to 1 and 2 mM, respectively), and low concentrations of other potential ligands for iron such as sulfide, carbonate, chloride, or bromide. Ultra-high resolution mass spectrometry (FT-ICR MS) was used to identify ligands for iron within the DOM pool, and synchrotron based X-ray analysis (XAS and EXAFS) was used to assess iron's oxidation state, to detect iron complexation, and to constrain the chemical composition of the complexes. Across a natural gradient of dissolved iron and DOM concentrations, many potential ligands were identified within DOM that are expected to complex with iron (e.g., aromatic acids). EXAFS showed substantial complexation of reduced ferrous iron (Fe(II)) to DOM in arctic soil waters, on the basis of comparison to Fe(II)-DOM reference spectra. Identification of iron complexed to DOM in soil waters is consistent with strongly co-varying iron and DOM concentrations in arctic soil and surface waters, and supports our hypothesis that complexation of iron by DOM influences dark and light redox reactions that oxidize DOM to CO2. Understanding the molecular