Comparative NEXAFS study of the selected icefish hard tissues and hydroxyapatite

NASA Astrophysics Data System (ADS)

Petrova, O. V.; Nekipelov, S. V.; Sivkov, D. V.; Mingaleva, A. E.; Nikolaev, A.; Frank-Kamenetskaya, O. V.; Bazhenov, V. V.; Vyalikh, D. V.; Molodtsov, S. L.; Sivkov, V. N.; Ehrlich, H.

2017-11-01

The structure of native Champsocephalus gunnari icefish otoliths, scales, teeth, bones and pristine hydroxyapatite (HA) were examined using Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. NEXAFS Cls-absorption spectra of the selected icefish hard tissues indicate that otoliths contain anion [CO3]2-. NEXAFS P2p-spectra clearly indicate the absence of phosphorus atoms only within otoliths and scales samples. However, the icefish teeth and bones P2p-spectra demonstrate identical spectral feature typical for the HA. NEXAFS Ca2p-spectra of the icefish hard tissues studied also shows features, which are in good correspondence with HA spectra. Interestingly, there is a red shift ≈ 0.1 eV of the 2p1/2,3/2 → 3d transition energies in NEXAFS Ca2p-spectra of teethes and bones of the C. gunnari in comparison to HA.

Symmetry of the oxygen hole states in Bi 2Sr 2CaCu 2O 8 investigated by XAS

NASA Astrophysics Data System (ADS)

Kuiper, P.; Grioni, M.; Sawatzky, G. A.; Mitzi, D. B.; Kapitulnik, A.; Santaniello, A.; de Padova, P.; Thiry, P.

1989-02-01

We have observed strong polarization dependence in the X-ray absorption near the oxygen K edge in a single crystal of Bi 2Sr 2CaCu 2O 8 ( Tc=85 K). The results show that O-derived holes near the Fermi-level have p x, y (perpendicular to the c-axis) symmetry. Some consequences for models of superconductivity are discussed. The concentration of holes is estimated to be about equal to that in YBa 2Cu 3O 7.

Structures of the carbohydrate recognition domain of Ca2+-independent cargo receptors Emp46p and Emp47p.

PubMed

Satoh, Tadashi; Sato, Ken; Kanoh, Akira; Yamashita, Katsuko; Yamada, Yusuke; Igarashi, Noriyuki; Kato, Ryuichi; Nakano, Akihiko; Wakatsuki, Soichi

2006-04-14

Emp46p and Emp47p are type I membrane proteins, which cycle between the endoplasmic reticulum (ER) and the Golgi apparatus by vesicles coated with coat protein complexes I and II (COPI and COPII). They are considered to function as cargo receptors for exporting N-linked glycoproteins from the ER. We have determined crystal structures of the carbohydrate recognition domains (CRDs) of Emp46p and Emp47p of Saccharomyces cerevisiae, in the absence and presence of metal ions. Both proteins fold as a beta-sandwich, and resemble that of the mammalian ortholog, p58/ERGIC-53. However, the nature of metal binding is distinct from that of Ca(2+)-dependent p58/ERGIC-53. Interestingly, the CRD of Emp46p does not bind Ca(2+) ion but instead binds K(+) ion at the edge of a concave beta-sheet whose position is distinct from the corresponding site of the Ca(2+) ion in p58/ERGIC-53. Binding of K(+) ion to Emp46p appears essential for transport of a subset of glycoproteins because the Y131F mutant of Emp46p, which cannot bind K(+) ion fails to rescue the transport in disruptants of EMP46 and EMP47 genes. In contrast the CRD of Emp47p binds no metal ions at all. Furthermore, the CRD of Emp46p binds to glycoproteins carrying high mannosetype glycans and the is promoted by binding not the addition of Ca(2+) or K(+) ion in These results suggest that Emp46p can be regarded as a Ca(2+)-independent intracellular lectin at the ER exit sites.

Characterization of fossil remains using XRF, XPS and XAFS spectroscopies

NASA Astrophysics Data System (ADS)

Zougrou, I. M.; Katsikini, M.; Pinakidou, F.; Brzhezinskaya, M.; Papadopoulou, L.; Vlachos, E.; Tsoukala, E.; Paloura, E. C.

2016-05-01

Synchrotron radiation micro-X-Ray Fluorescence (μ-XRF), X-ray photoelectron (XPS) and X-ray Absorption Fine Structure (XAFS) spectroscopies are applied for the study of paleontological findings. More specifically the costal plate of a gigantic terrestrial turtle Titanochelon bacharidisi and a fossilized coprolite of the cave spotted hyena Crocuta crocuta spelaea are studied. Ca L 2,3-edge NEXAFS and Ca 2p XPS are applied for the identification and quantification of apatite and Ca containing minerals. XRF mapping and XAFS are employed for the study of the spatial distribution and speciation of the minerals related to the deposition environment.

Relationships between water and paddlefish Polyodon spathula dentary elemental and stable-isotopic signatures: potential application for reconstructing environmental history

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

Bock, Lindsey R.; Whitledge, Gregory W.; Pracheil, Brenda M.

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ 18O and stable hydrogen isotope ratio (δD) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δD and δ 18O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δD and δ 18O were observed, although the relationship between water and dentary δ 18O wasmore » weaker than those for Sr:Ca and δD. Classification success for individual fish to collection locations that differed in water Sr:Ca, δD and δ 18O ranged from 86 to 100% based on dentary-edge Sr:Ca, δD and δ18O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur.« less

Relationships between water and paddlefish Polyodon spathula dentary elemental and stable-isotopic signatures: potential application for reconstructing environmental history

DOE PAGES

Bock, Lindsey R.; Whitledge, Gregory W.; Pracheil, Brenda M.; ...

2016-07-26

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ 18O and stable hydrogen isotope ratio (δD) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δD and δ 18O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δD and δ 18O were observed, although the relationship between water and dentary δ 18O wasmore » weaker than those for Sr:Ca and δD. Classification success for individual fish to collection locations that differed in water Sr:Ca, δD and δ 18O ranged from 86 to 100% based on dentary-edge Sr:Ca, δD and δ18O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur.« less

Bone char effects on soil: sequential fractionations and XANES spectroscopy

NASA Astrophysics Data System (ADS)

Morshedizad, Mohsen; Panten, Kerstin; Klysubun, Wantana; Leinweber, Peter

2018-01-01

The acceptability of novel bone char fertilizers depends on their P release, but reactions at bone char surfaces and impacts on soil P speciation are insufficiently known. By using sequential fractionation and synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy we investigated whether and how the chemical composition of bone char particles has been altered in soil and has consequently affected the P speciation of amended soils. Therefore, two different kinds of bone char particles (BC produced by the pyrolysis of degreased animal bone chips at 800 °C and BCplus, a BC enriched with reduced sulfur compounds) were manually separated from the soil at the end of two different experiments: incubation leaching and ryegrass cultivation. Sequential P fractionation of amended soils showed P enrichment in all fractions compared to the control. The most P increase between all treatments significantly occurred in the NaOH-P and resin-P fractions in response to BCplus application in both incubation-leaching and ryegrass cultivation experiments. This increase in the readily available P fraction in BCplus-treated soils was confirmed by linear combination fitting (LCF) analysis on P K-edge XANES spectra of BC particles and amended soils. The proportion of Ca hydroxyapatite decreased, whereas the proportion of CaHPO4 increased in BCplus particles after amended soils had been incubated and leached and cropped by ryegrass. Based on P XANES speciation as determined by LCF analysis, the proportion of inorganic Ca(H2PO4)2 increased in amended soils after BCplus application. These results indicate that soil amendment with BCplus particles leads to elevated P concentration and maintains more soluble P species than BC particles even after 230 days of ryegrass cultivation.

The central role of the Hikurangi Plateau in the Cenozoic tectonics of New Zealand and the Southwest Pacific

NASA Astrophysics Data System (ADS)

Reyners, Martin

2013-01-01

Recent work involving relocation of New Zealand seismicity using a nationwide 3-D seismic velocity model has located the subducted western edge of the Hikurangi Plateau. Both the thickness (ca. 35 km) and the area of the plateau subducted in the Cenozoic (ca. 287,000 km2) are much larger than previously supposed. From ca. 45 Ma, the westernmost tip of the plateau controlled the transition at the Pacific/Australia plate boundary from subduction to the north to Emerald Basin opening to the south. At ca. 23 Ma, curvature of the subduction zone against the western flank of the buoyant plateau became extreme, and a Subduction-Transform Edge Propagator (STEP fault) developed along the western edge of the plateau. This STEP fault corresponds to the Alpine Fault, and the resulting Pacific slab edge is currently defined by intermediate-depth seismicity under the northernmost South Island. Alpine STEP fault propagation was terminated at ca. 15 Ma, when the western edge of the plateau became parallel to the trench, and thus STEP fault formation was no longer favoured. Wholesale subduction of the plateau at the Hikurangi subduction zone began at ca. 10 Ma. The development of a subduction décollement above the plateau mechanically favoured deformation within the overlying Australian plate continental crust. This led to inception of the Marlborough fault system at ca. 7 Ma, and the North Island fault system at 1-2 Ma. At ca. 7 Ma, the western edge of the converging plateau again became more normal to the trench, and there is evidence supporting the development of a second STEP fault beneath the Taupo Volcanic Zone until ca. 3 Ma. Both episodes of STEP fault development at the plateau edge led to rapid slab rollback, and correspond closely with episodes of backarc basin opening to the north in the wider Southwest Pacific. The Cenozoic tectonics of New Zealand and the Southwest Pacific has been strongly influenced not only by the resistance to subduction of the buoyant Hikurangi Plateau, but also by the shape of its western edge and changing angle of attack of this edge at the plate boundary.

Otolith edge fingerprints as approach for stock identification of Genidens barbus

NASA Astrophysics Data System (ADS)

Avigliano, Esteban; Maichak de Carvalho, Barbara; Leisen, Mathieu; Romero, Rurik; Velasco, Gonzalo; Vianna, Marcelo; Barra, Fernando; Volpedo, Alejandra Vanina

2017-07-01

The purpose of this paper is to assess the use of multi-elemental otolith fingerprints as a tool to delimit catfish Genidens barbus fish stocks in four estuaries from the southwestern Atlantic Ocean. Barium:Calcium (Ca), Magnesium:Ca, Manganese:Ca, Sodium:Ca and Strontium:Ca ratios in the otolith edge were determined by LA-ICPMS. PERMANOVA analysis reveal significant differences in the multi-element signatures among estuaries (p = 0.0001-0.002). Reclassification rates of quadratic discriminant analysis are high, averaging 89.9% (78-100%). The new data presented here show that the otolith chemistry is a potential tool for stock identification, and indicates the presence of at least four stocks which should probably be handled independently.

Aqueous solubility diagrams for cementitious waste stabilization systems. 3. Mechanism of zinc immobilizaton by calcium silicate hydrate.

PubMed

Tommaseo, C E; Kersten, M

2002-07-01

Zinc oxide was added during hydration of alite (C3S) as an analogue for solidification/stabilization by cement of metal-bearing hazardous waste. Curing of samples was stopped at various intervals between 8 h and 100 d, and the reaction products were analyzed by both X-ray diffraction (XRD) and X-ray absorption spectroscopy (EXAFS at Zn, Ca, and Si K-edges). Calcium zincate hydrate (CaZn2(OH)6 x 2H2O) initially formed together with calcium silicate hydrate (CSH) vanishes from X-ray diffractograms after 14 d, and no other crystalline Zn-bearing phase could be detected thereafter. EXAFS Zn K-edge data analysis reveals that Zn(O,OH)4 tetrahedra continue to determine the first shell coordination. However, a new Zn-Si bond appears in the second coordination shell as indicated by both Zn K-edge and Si K-edge EXAFS. Together with the Ca-Zn and Ca-Ca shells derived from the Ca K-edge EXAFS spectra, a structural model for the site occupation of Zn in CSH is proposed, whereby the Zn(O,OH)4 tetrahedra are bound in layer rather than interlayer positions substituting for the silicate bridging tetrahedra and/or at terminal silicate chain sites. This structural model enables ultimately the formulation of a thermodyamic Lippmann model to predict the aqueous solubility of Zn in solid solution with a CSH phase of a Ca/Si ratio fixed to unity.

Liming Poultry Manures to Kill Pathogens and Decrease Soluble Phosphorus

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

Maguire,R.; Hesterberg, D.; Gernat, A.

2006-01-01

Received for publication September 9, 2005. Stabilizing phosphorus (P) in poultry waste to reduce P losses from manured soils is important to protect surface waters, while pathogens in manures are an emerging issue. This study was conducted to evaluate CaO and Ca(OH){sub 2} for killing manure bacterial populations (pathogens) and stabilizing P in poultry wastes and to investigate the influence on soils following amendment with the treated wastes. Layer manure and broiler litter varying in moisture content were treated with CaO and Ca(OH){sub 2} at rates of 2.5, 5, 10, and 15% by weight. All treated wastes were analyzed formore » microbial plate counts, pH, and water-soluble phosphorus (WSP), while a few selected layer manures were analyzed by phosphorus X-ray absorption near edge structure (XANES). A loamy sand and a silt loam were amended with broiler litter and layer manure treated with CaO at rates of 0, 2.5, 5, 10, and 15% and soil WSP and pH were measured at times 1, 8, and 29 d. Liming reduced bacterial populations, with greater rates of lime leading to greater reductions; for example 10% CaO applied to 20% solids broiler litter reduced the plate counts from 793 000 to 6500 mL{sup -1}. Liming also reduced the WSP in the manures by over 90% in all cases where at least 10% CaO was added. Liming the manures also reduced WSP in soils immediately following application and raised soil pH. The liming process used successfully reduced plate counts and concerns about P losses in runoff following land application of these limed products due to decreased WSP.« less

Liming poultry manures to decrease soluble phosphorus and suppress the bacteria population.

PubMed

Maguire, R O; Hesterberg, D; Gernat, A; Anderson, K; Wineland, M; Grimes, J

2006-01-01

Stabilizing phosphorus (P) in poultry waste to reduce P losses from manured soils is important to protect surface waters, while pathogens in manures are an emerging issue. This study was conducted to evaluate CaO and Ca(OH)2 for killing manure bacterial populations (pathogens) and stabilizing P in poultry wastes and to investigate the influence on soils following amendment with the treated wastes. Layer manure and broiler litter varying in moisture content were treated with CaO and Ca(OH)2 at rates of 2.5, 5, 10, and 15% by weight. All treated wastes were analyzed for microbial plate counts, pH, and water-soluble phosphorus (WSP), while a few selected layer manures were analyzed by phosphorus X-ray absorption near edge structure (XANES). A loamy sand and a silt loam were amended with broiler litter and layer manure treated with CaO at rates of 0, 2.5, 5, 10, and 15% and soil WSP and pH were measured at times 1, 8, and 29 d. Liming reduced bacterial populations, with greater rates of lime leading to greater reductions; for example 10% CaO applied to 20% solids broiler litter reduced the plate counts from 793,000 to 6500 mL-1. Liming also reduced the WSP in the manures by over 90% in all cases where at least 10% CaO was added. Liming the manures also reduced WSP in soils immediately following application and raised soil pH. The liming process used successfully reduced plate counts and concerns about P losses in runoff following land application of these limed products due to decreased WSP.

West wing, west elevation, seen entirety from the pasture at ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

West wing, west elevation, seen entirety from the pasture at the west edge of state park property. (recreation of HABS No. CA-38-P152-1). - Vallejo Adobe, Adobe Road at Casa Grande, Petaluma, Sonoma County, CA

[A novel tissue-engineered bone constructed by using human adipose-derived stem cells and biomimetic calcium phosphate scaffold coprecipitated with bone morphogenetic protein-2].

PubMed

Jiang, W R; Zhang, X; Liu, Y S; Wu, G; Ge, Y J; Zhou, Y S

2017-02-18

To construct a novel biomimetic calcium phosphate (BioCaP) scaffold loaded with bone morphogenetic protein-2 (BMP-2), and to investigate its role in the osteogenesis of human adipose-derived stem cells (hASCs) in vitro and in vivo. The BioCaP scaffold coprecipitated with BMP-2 (BMP-2-BioCaP) was constructed in this study. Field emission scanning electron microscopy (SEM) was used to analyze the morphology of the surfaces. The release kinetics was measured to evaluate the slow-release characteristics in vitro. BMP-2-BioCaP was immersed in proliferation medium (PM) or osteogenic medium (OM), respectively. The supernatants were collected and used to culture hASCs in vitro. Cell numbers were determined using the cell-counting kit-8 (CCK-8) to assess the cell proliferation. After 7 and 14 days, alkaline phosphatase (ALP) staining and quantification were performed to test the activity of ALP. After 14 and 21 days, the calcification deposition was determined by alizarin red S (ARS) staining and quantification. The expressions of the osteoblast-related genes were tested on day 4 and day 14. In the in vivo study, 6 nude mice were used and implanted subcutaneously into the back of the nude mice for 4 groups: (1) BioCaP scaffold only, (2) BioCaP scaffold+hASCs, (3) BMP-2-BioCaP scaffold, (4) BMP-2-BioCaP scaffold+hASCs (test group). After 4 weeks of implantation, hematoxylin-eosin (HE) staining was performed to evaluate the in vivo osteogenesis of hASCs. SEM observations showed that BioCaP and BMP-2-BioCaP scaffold were entirely composed of straight, plate-like and sharp-edged crystal units, and the length of the crystal units varied between 5 and 10 μm. Release kinetics analysis demonstrated that BMP-2 incorporated with BioCaP could be released at certain concentration and last for more than 21 days, and the accumulative protein release could reach 20%. CCK-8 assays showed that cell proliferation was not significantly affected by BMP-2-BioCaP. ALP activity was higher by the induction of OM+BMP-2-BioCaP than of the other groups (P<0.01). More mineralization deposition and more expressions of osteoblast-related genes such as Runt-related transcription factor 2 (RUNX2), ALP, osteopontin (OPN) and osteocalcin (OC) were determined in the OM+BMP-2-BioCaP group at different time points (P<0.01). HE staining showed that, in the test group and BMP-2-BioCaP scaffold group, the extracellular matrix (ECM) with eosinophilic staining were observed around hASCs, and newly-formed bone-like tissues could be found in ECM around the scaffold materials. Moreover, compared with the BMP-2-BioCaP scaffold group, more bone-like tissues could be observed in ECM with typical structure of bone tissue in the test groups. No obvious positive results were found in the other groups. BMP-2-BioCaP scaffold could achieve slow-release of BMP-2 and promote the osteogenic differentiation of hASCs in vitro and in vivo. The novel tissue-engineered bone composed of hASCs and BMP-2-BioCaPis promising for the repair of bone defect.

Electrochemical lithium intercalation into Bi2Sr2CaCu2O8+δ

NASA Astrophysics Data System (ADS)

Shimono, Takahiro; Kobayashi, Wataru; Nitani, Hiroaki; Kumai, Reiji; Moritomo, Yutaka

2013-04-01

We have prepared Li-intercalated LixBi2Sr2CaCu2O8+δ (x =0-2.0) samples by using electrochemical method, and performed synchrotron x-ray diffraction, Cu K-edge x-ray absorption fine structure (XAFS), and magnetic susceptibility measurements. With increasing x, a- and c-lattice parameters monotonically increase, which shows lithium intercalation into Bi2Sr2CaCu2O8+δ. Accompanied by the lithium insertion, the valence of Cu ion changes from Cu2+/Cu3+ to Cu1+/Cu2+ to realize charge neutrality. This change of the valence was detected by Cu K-edge XAFS measurement. A clear increase of spectral weight that corresponds to 1s→ 4pπ(3d10L) was observed at around 8982 eV with x. The superconducting (SC) transition temperature TC significantly changes from 74 K for x = 0 to 90 K for x = 0.8, which is attributed to modified density of states by the decrease of hole concentration. A volume fraction of the superconducting phase was 1-2 % for x >= 0.6 implying phase separation where Li-rich non SC phase and Li-poor SC phase coexist. Such a phase separation is universally seen in electrode active materials.

Silversides (Odontesthes bonariensis) reside within freshwater and estuarine habitats, not marine environments

NASA Astrophysics Data System (ADS)

Avigliano, Esteban; Miller, Nathan; Volpedo, Alejandra Vanina

2018-05-01

Otolith core-to-edge Sr:Ca ratio was determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze the salinity-habitat migration history of the silverside, Odontesthes bonariensis, within the Uruguay River (freshwater) and Río de la Plata Estuary (estuarine water) (Plata Basin, South America). Regular core-to-edge oscillations in Sr:Ca suggest that the silverside makes annual migrations between freshwater (<1 PSU) and brackish (>1 PSU) habitats, with no evidence of marine incursion or non-migratory individuals. Empirical equations that represent the relationship between conductivity/salinity and otolith Sr:Ca ratio were used to identify where in an otolith an individual transitioned between freshwater and brackish habitats. In most specimens, the first migration between habitats likely occurred within the first year of life. Average numbers of changes between stable Sr:Ca signatures (sites with different salinities) determined by Change-Point analysis were similar from Uruguay River (8.9 ± 3.7) and Río de la Plata Estuary (7.5 ± 2.5) for comparable age fish (p < 0.05), suggesting that habitat use is similar in both collection sites.

Temperature dependence of pre-edge features in Ti K-edge XANES spectra for ATiO₃ (A = Ca and Sr), A₂TiO₄ (A = Mg and Fe), TiO₂ rutile and TiO₂ anatase.

PubMed

Hiratoko, Tatsuya; Yoshiasa, Akira; Nakatani, Tomotaka; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

2013-07-01

XANES (X-ray absorption near-edge structure) spectra of the Ti K-edges of ATiO3 (A = Ca and Sr), A2TiO4 (A = Mg and Fe), TiO2 rutile and TiO2 anatase were measured in the temperature range 20-900 K. Ti atoms for all samples were located in TiO6 octahedral sites. The absorption intensity invariant point (AIIP) was found to be between the pre-edge and post-edge. After the AIIP, amplitudes damped due to Debye-Waller factor effects with temperature. Amplitudes in the pre-edge region increased with temperature normally by thermal vibration. Use of the AIIP peak intensity as a standard point enables a quantitative comparison of the intensity of the pre-edge peaks in various titanium compounds over a wide temperature range.

REE Incorporation into Calcite Individual Crystals as One Time Spike Addition

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

Gabitov, Rinat; Sadekov, Aleksey; Migdisov, Artas

Experiments on the incorporation of trace elements into calcite were performed, and rare earth elements (REE) were used to mark the growth zones of individual crystals. Experiments were conducted at different pH (7.7 to 8.8) and temperatures (2 °C to 24.6 °C) in NH 4Cl + CaCl 2 solutions, where REE were rapidly consumed by growing calcite. LA-ICP-MS line-scans yielded the distribution of (REE/Ca) calcite within individual crystals in a manner consistent with the addition of REE into fluid. A sharp decrease of (REE/Ca) calcite toward the crystal edge suggests the fast depletion of (REE/Ca) fluid due to strong REEmore » consumption by growing calcite. An attempt was made to estimate the lower limit of the partition coefficients between calcite and fluid using selected REE/Ca data within individual calcite crystals and the amount of REE added into fluid.« less

REE Incorporation into Calcite Individual Crystals as One Time Spike Addition

DOE PAGES

Gabitov, Rinat; Sadekov, Aleksey; Migdisov, Artas

2017-10-26

Experiments on the incorporation of trace elements into calcite were performed, and rare earth elements (REE) were used to mark the growth zones of individual crystals. Experiments were conducted at different pH (7.7 to 8.8) and temperatures (2 °C to 24.6 °C) in NH 4Cl + CaCl 2 solutions, where REE were rapidly consumed by growing calcite. LA-ICP-MS line-scans yielded the distribution of (REE/Ca) calcite within individual crystals in a manner consistent with the addition of REE into fluid. A sharp decrease of (REE/Ca) calcite toward the crystal edge suggests the fast depletion of (REE/Ca) fluid due to strong REEmore » consumption by growing calcite. An attempt was made to estimate the lower limit of the partition coefficients between calcite and fluid using selected REE/Ca data within individual calcite crystals and the amount of REE added into fluid.« less

Table of periodic properties of fullerenes based on structural parameters.

PubMed

Torrens, Francisco

2004-01-01

The periodic table (PT) of the elements suggests that hydrogen could be the origin of everything else. The construction principle is an evolutionary process that is formally similar to those of Darwin and Oparin. The Kekulé structure count and permanence of the adjacency matrix of fullerenes are related to structural parameters involving the presence of contiguous pentagons p, q and r. Let p be the number of edges common to two pentagons, q the number of vertices common to three pentagons, and r the number of pairs of nonadjacent pentagon edges shared between two other pentagons. Principal component analysis (PCA) of the structural parameters and cluster analysis (CA) of the fullerenes permit classifying them and agree. A PT of the fullerenes is built based on the structural parameters, PCA and CA. The periodic law does not have the rank of the laws of physics. (1) The properties of the fullerenes are not repeated; only, and perhaps, their chemical character. (2) The order relationships are repeated, although with exceptions. The proposed statement is the following: The relationships that any fullerene p has with its neighbor p + 1 are approximately repeated for each period.

A Lifting Surface Theory for Wings Experiencing Leading-Edge Separation

DTIC Science & Technology

1977-06-30

CSR -CHCRÜ TO SPAN RATIO N-l N’SECIION NO. INDICAIOR FORM SCALES TO KURHALUt E0U»T|CNS Fl • 2.» ALEA /IP|»P| I fi ■ AIFA...Documentation Center Cameron Station, Bldg. 5 Alexandria, VA 22314 12 Nielsen Engineering & Research, Inc. 510 Clyde Avenue Mountain View, CA 94043 1 RASA

Local electronic structure and nanolevel hierarchical organization of bone tissue: theory and NEXAFS study

NASA Astrophysics Data System (ADS)

Pavlychev, A. A.; Avrunin, A. S.; Vinogradov, A. S.; Filatova, E. O.; Doctorov, A. A.; Krivosenko, Yu S.; Samoilenko, D. O.; Svirskiy, G. I.; Konashuk, A. S.; Rostov, D. A.

2016-12-01

Theoretical and experimental investigations of native bone are carried out to understand relationships between its hierarchical organization and local electronic and atomic structure of the mineralized phase. The 3D superlattice model of a coplanar assembly of the hydroxyapatite (HAP) nanocrystallites separated by the hydrated nanolayers is introduced to account the interplay of short-, long- and super-range order parameters in bone tissue. The model is applied to (i) predict and rationalize the HAP-to-bone spectral changes in the electronic structure and (ii) describe the mechanisms ensuring the link of the hierarchical organization with the electronic structure of the mineralized phase in bone. To check the predictions the near-edge x-ray absorption fine structure (NEXAFS) at the Ca 2p, P 2p and O 1s thresholds is measured for native bone and compared with NEXAFS for reference compounds. The NEXAFS analysis has demonstrated the essential hierarchy induced HAP-to-bone red shifts of the Ca and P 2p-to-valence transitions. The lowest O 1s excitation line at 532.2 eV in bone is assigned with superposition of core transitions in the hydroxide OH-(H2O) m anions, Ca2+(H2O) n cations, the carboxyl groups inside the collagen and [PO4]2- and [PO4]- anions with unsaturated P-O bonds.

EELS characterisation of bulk CaCu3Ti4O12 ceramics.

PubMed

Calvert, Clair C; Rainforth, W Mark; Sinclair, Derek C; West, Anthony R

2006-01-01

CaCu3Ti4O12 (CCTO) is a cubic perovskite phase and sintered ceramics exhibit high permittivity at room temperature. Electron energy-loss spectroscopy (EELS) and energy dispersive X-ray spectrometry (EDS) data have been collected from samples of CCTO to relate the observed electrical properties to the microstructure and chemistry on the nanoscale. CCTO ceramics were sintered for 24h at 1115 degrees C in air, giving a grain size of 50-300 microm. Ti L(2,3)-, Cu L(2,3)- and O K-edge EEL data were collected for bulk CCTO (within grain) and compared with well characterised Ti-oxides, CaTiO3 and BaTiO3 perovskites. The bulk metal L(2,3)-edge data for CCTO suggest that Cu is divalent and Ti is present as Ti4+. The O K-edge of CCTO shows increased near-edge structure (NES) compared to those of the simple perovskites.

Carbonic Anhydrase IX Interacts with Bicarbonate Transporters in Lamellipodia and Increases Cell Migration via Its Catalytic Domain*

PubMed Central

Svastova, Eliska; Witarski, Wojciech; Csaderova, Lucia; Kosik, Ivan; Skvarkova, Lucia; Hulikova, Alzbeta; Zatovicova, Miriam; Barathova, Monika; Kopacek, Juraj; Pastorek, Jaromir; Pastorekova, Silvia

2012-01-01

Carbonic anhydrase IX (CA IX) is a hypoxia-induced cell surface enzyme expressed in solid tumors, and functionally involved in acidification of extracellular pH and destabilization of intercellular contacts. Since both extracellular acidosis and reduced cell adhesion facilitate invasion and metastasis, we investigated the role of CA IX in cell migration, which promotes the metastatic cascade. As demonstrated here, ectopically expressed CA IX increases scattering, wound healing and transwell migration of MDCK cells, while an inactive CA IX variant lacking the catalytic domain (ΔCA) fails to do so. Correspondingly, hypoxic HeLa cells exhibit diminished migration upon inactivation of the endogenous CA IX either by forced expression of the dominant-negative ΔCA variant or by treatment with CA inhibitor, implying that the catalytic activity is indispensable for the CA IX function. Interestingly, CA IX improves cell migration both in the absence and presence of hepatocyte growth factor (HGF), an established inducer of epithelial-mesenchymal transition. On the other hand, HGF up-regulates CA IX transcription and triggers CA IX protein accumulation at the leading edge of lamellipodia. In these membrane regions CA IX co-localizes with sodium bicarbonate co-transporter (NBCe1) and anion exchanger 2 (AE2) that are both components of the migration apparatus and form bicarbonate transport metabolon with CA IX. Moreover, CA IX physically interacts with AE2 and NBCe1 in situ, as shown here for the first time. Thus, our findings suggest that CA IX actively contributes to cell migration via its ability to facilitate ion transport and pH control at protruding fronts of moving cells. PMID:22170054

Substantial Cd-Cd Bonding in Ca6PtCd11: A Condensed Intermetallic Phase Built of Pentagonal Cd7 and Rectangular Cd4/2Pt Pyramids

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

Gulo, Fakhili; Samal, Saroj L.; Corbett, John D.

The new trail-breaking compound Ca6PtCd11 has been synthesized and its structural and bonding properties investigated. This unusual phase features an unprecedented degree of cadmium aggregation, including linear chains, novel Cd7 PBP aggregates, and edge-shared chains of PtCd4/2 square pyramids. Manifestations of this chemistry elsewhere has evidently been precluded in earlier work by the inclusion of larger amounts of the strong d-metal bonding Au or Pt. Under the right conditions Cd seems quite effective as an open s,p-band metal.

Strontium hydroxyapatite and strontium carbonate as templates for the precipitation of calcium-phosphates in the absence and presence of fluoride

NASA Astrophysics Data System (ADS)

Sternitzke, Vanessa; Janousch, Markus; Heeb, Michèle B.; Hering, Janet G.; Johnson, C. Annette

2014-06-01

The heterogeneous precipitation of calcium-phosphates on calcium hydroxyapatite (Ca10(PO4)6(OH)2 or HAP) in the presence and absence of fluoride is important in the formation of bone and teeth, protection against tooth decay, dental and skeletal fluorosis and defluoridation of drinking water. Strontium hydroxyapatite (Sr10(PO4)6(OH)2 or SrHAP) and strontium carbonate (SrCO3) were used as calcium-free seed templates in precipitation experiments conducted with varying initial calcium-to-phosphate (Ca/P) or calcium-to-phosphate-to-fluoride (Ca/P/F) ratios. Suspensions of SrHAP or SrCO3 seed templates (which were calcium-limited for both templates and phosphate-limited in the case of SrCO3) were reacted at pH 7.3 (25 °C) over 3 days. The resulting solids were examined with Scanning Transmission Electron Microscopy (STEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Near Edge Structure (XANES), and Extended X-ray Absorption Fine Structure spectroscopy (EXAFS). Calcium apatite was the predominant phase identified by all techniques independent of the added Ca/P ratios and of the presence of fluoride. It was not possible to make an unambiguous distinction between HAP and fluorapatite (Ca10(PO4)6F2, FAP). The apatite was calcium-deficient and probably contained some strontium.

Sorption selectivity of birnessite particle edges: a d-PDF analysis of Cd(ii) and Pb(ii) sorption by δ-MnO2 and ferrihydrite.

PubMed

van Genuchten, Case M; Peña, Jasquelin

2016-08-10

Birnessite minerals (layer-type MnO2), which bear both internal (cation vacancies) and external (particle edges) metal sorption sites, are important sinks of contaminants in soils and sediments. Although the particle edges of birnessite minerals often dominate the total reactive surface area, especially in the case of nanoscale crystallites, the metal sorption reactivity of birnessite particle edges remains elusive. In this study, we investigated the sorption selectivity of birnessite particle edges by combining Cd(ii) and Pb(ii) adsorption isotherms at pH 5.5 with surface structural characterization by differential pair distribution function (d-PDF) analysis. We compared the sorption reactivity of δ-MnO2 to that of the nanomineral, 2-line ferrihydrite, which exhibits only external surface sites. Our results show that, whereas Cd(ii) and Pb(ii) both bind to birnessite layer vacancies, only Pb(ii) binds extensively to birnessite particle edges. For ferrihydrite, significant Pb(ii) adsorption to external sites was observed (roughly 20 mol%), whereas Cd(ii) sorption was negligible. These results are supported by bond valence calculations that show comparable degrees of saturation of oxygen atoms on birnessite and ferrihydrite particle edges. Therefore, we propose that the sorption selectivity of birnessite edges follows the same order of that reported previously for ferrihydrite: Ca(ii) < Cd(ii) < Ni(ii) < Zn(ii) < Cu(ii) < Pb(ii).

Inhibition of phosphorus sorption on calcite by dairy manure-sourced DOC.

PubMed

Weyers, Eva; Strawn, Daniel G; Peak, Derek; Baker, Leslie L

2017-10-01

In confined animal feeding operations, such as dairies, manure is amended to soils at high rates leading to increases in P and organic matter in the soils. Phosphorus reacts with soil-Ca to form Ca-P minerals, which controls P availability for leaching and transport through the watershed. In this research, the effects of manure sourced dissolved organic matter (DOM) on P sorption on calcite were measured at different reaction times and concentrations. Reactions were monitored in 1% and 10% manure-to-water extract solutions spiked with P. When manure-DOM was present, a significant reduction in P sorption occurred (2-90% absolute decrease) compared to samples without manure-DOM. The greatest decrease occurred in the samples reacted in the 10% manure solution. XANES spectroscopic analysis showed that at 1% manure solution, a Ca-P phase similar to hydroxyapatite formed. In the calcite samples reacted in the 10% manure solution, K-edge XANES spectroscopy revealed that P occurred as a Ca-Mg-P phase instead of the less soluble hydroxyapatite-like phase. Results from this study suggest that in manure-amended calcareous soils, increased DOM from manure will decrease P sorption capacity and increase the overall P concentration in solution, which will increase the mobility of P and subsequently pose greater risks for impairment of surface water quality. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ca 3d unoccupied states in Bi2Sr2CaCu2O8 investigated by Ca L2,3 x-ray-absorption near-edge structure

NASA Astrophysics Data System (ADS)

Borg, A.; King, P. L.; Pianetta, P.; Lindau, I.; Mitzi, D. B.; Kapitulnik, A.; Soldatov, A. V.; della Longa, S.; Bianconi, A.

1992-10-01

The high-resolution Ca L2,3 x-ray-absorption near-edge-structure (XANES) spectrum of a Bi2Sr2CaCu2O8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200×200 μm2. The Ca L2,3 XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF2. Good agreement between the calculated and experimental crystal-field splitting Δf of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O(in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, we have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO2 planes separated by the Ca ions.

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

Altay, A.; Carter, C.B., E-mail: cbcarter@engr.uconn.ed; Rulis, P.

Calcium aluminates, compounds in the CaO-Al{sub 2}O{sub 3} phase system, are used in high-temperature cements and refractory oxides and have wide range of potential technological applications due to their interesting optical, electrical, thermal, and mechanical properties. They are used in both crystalline and glassy form; the glass is an isotropic material while the crystalline materials may be highly anisotropic. This paper will consider two particular crystalline materials, CA{sub 2} and CA{sub 6}, but the results should be applicable to all calcium aluminates. Although CA{sub 2} and CA{sub 6} crystals contain the same chemical species, Ca, Al, and O, the coordinationmore » and local environments of these species are different in the two structures and hence they show very different energy-loss near-edge structures (ELNES) when examined by electron energy-loss spectroscopy (EELS) in the TEM. The data obtained using ELNES can effectively provide a fingerprint for each compound and a map for their electronic structure. Once such fingerprints are obtained, they can be used to identify nano-sized particles/grains or material at interfaces and grain boundaries. In the present study, the local symmetry fingerprints for CA{sub 2} and CA{sub 6} structures are reported combining experimental spectra with electronic-structure calculations that allow the different features in the spectra to be interpreted. Al-L{sub 2,3} and O-K edge core-loss spectra from CA{sub 2} and CA{sub 6} were measured experimentally using electron energy-loss spectroscopy in a monochromated scanning transmission electron microscope. The near-edge structures were calculated for the different phases using the orthogonalized linear combination of atomic-orbitals method, and took account of core-hole interactions. It is shown that CA{sub 2} and CA{sub 6} structures exhibit distinctive experimental ELNES fingerprints so that these two phases can be separately identified even when present in small volumes. - Graphical abstract: Projection of the CA{sub 2} structure viewed in the [010] direction. Green atoms represent the Ca{sup 2+} ions and blue atoms represent the Al{sup 3+} ions. Two unit cells are outlined..« less

Soft X-ray spectromicroscopy study of mineral-organic matter associations in pasture soil clay fractions.

PubMed

Chen, Chunmei; Dynes, James J; Wang, Jian; Karunakaran, Chithra; Sparks, Donald L

2014-06-17

There is a growing acceptance that associations with soil minerals may be the most important overarching stabilization mechanism for soil organic matter. However, direct investigation of organo-mineral associations has been hampered by a lack of methods that can simultaneously characterize organic matter (OM) and soil minerals. In this study, STXM-NEXAFS spectroscopy at the C 1s, Ca 2p, Fe 2p, Al 1s, and Si 1s edges was used to investigate C associations with Ca, Fe, Al, and Si species in soil clay fractions from an upland pasture hillslope. Bulk techniques including C and N NEXAFS, Fe K-edge EXAFS spectroscopy, and XRD were applied to provide additional information. Results demonstrated that C was associated with Ca, Fe, Al, and Si with no separate phase in soil clay particles. In soil clay particles, the pervasive C forms were aromatic C, carboxyl C, and polysaccharides with the relative abundance of carboxyl C and polysaccharides varying spatially at the submicrometer scale. Only limited regions in the soil clay particles had aliphatic C. Good C-Ca spatial correlations were found for soil clay particles with no CaCO3, suggesting a strong role of Ca in organo-mineral assemblage formation. Fe EXAFS showed that about 50% of the total Fe in soils was contained in Fe oxides, whereas Fe-bearing aluminosilicates (vermiculite and Illite) accounted for another 50%. Fe oxides in the soil were mainly crystalline goethite and hematite, with lesser amounts of poorly crystalline ferrihydrite. XRD revealed that soil clay aluminosilicates were hydroxy-interlayered vermiculite, Illite, and kaolinite. C showed similar correlation with Fe to Al and Si, implying a similar association of Fe oxides and aluminosilicates with organic matter in organo-mineral associations. These direct microscopic determinations can help improve understanding of organo-mineral interactions in soils.

Reproducing ten years of road ageing--accelerated carbonation and leaching of EAF steel slag.

PubMed

Suer, Pascal; Lindqvist, Jan-Erik; Arm, Maria; Frogner-Kockum, Paul

2009-09-01

Reuse of industrial aggregates is still hindered by concern for their long-term properties. This paper proposes a laboratory method for accelerated ageing of steel slag, to predict environmental and technical properties, starting from fresh slag. Ageing processes in a 10-year old asphalt road with steel slag of electric arc furnace (EAF) type in the subbase were identified by scanning electron microscopy (SEM) and leaching tests. Samples from the road centre and the pavement edge were compared with each other and with samples of fresh slag. It was found that slag from the pavement edge showed traces of carbonation and leaching processes, whereas the road centre material was nearly identical to fresh slag, in spite of an accessible particle structure. Batches of moisturized road centre material exposed to oxygen, nitrogen or carbon dioxide (CO2) were used for accelerated ageing. Time (7-14 days), temperature (20-40 degrees C) and initial slag moisture content (8-20%) were varied to achieve the carbonation (decrease in pH) and leaching that was observed in the pavement edge material. After ageing, water was added to assess leaching of metals and macroelements. 12% moisture, CO2 and seven days at 40 degrees C gave the lowest pH value. This also reproduced the observed ageing effect for Ca, Cu, Ba, Fe, Mn, Pb, Ca (decreased leaching) and for V, Si, and Al (increased leaching). However, ageing effects on SO4, DOC and Cr were not reproduced.

Variation in throughfall deposition across a deciduous beech (Fagus sylvatica L.) forest edge in Flanders.

PubMed

Devlaeminck, Rebecca; De Schrijver, An; Hermy, Martin

2005-01-20

Throughfall deposition and canopy exchange of acidifying and eutrophying compounds and major base cations were studied by means of throughfall analysis in a deciduous beech (Fagus sylvatica L.) forest edge in Belgium over a period of 1 year. Throughfall fluxes of Cl(-), NH(4)(+) and Na(+) were significantly elevated at the forest edge compared to the forest interior. As no edge effect on throughfall water volume could be detected, the observed edge enhancement effects were mainly due to dry deposition and canopy exchange patterns. Indeed, there was an elevated dry deposition of Cl(-), Na(+), K(+), Ca(2+) and Mg(2+) up to 50 m from the field/forest border. Within the forest, throughfall and dry deposition of SO(4)(2-) were highly variable and no significant differences were observed between the forest edge and the forest interior. Leaching of K(+) and Ca(2+) was reduced in the forest edge up to a distance of 30 m from the border. The measured nitrogen and acidic depositions far exceeded the current Flemish critical loads with respect to the protection of biodiversity in forests, especially at the forest edge. This points to an urgent need for controlling emissions as well as the need to consider the elevated deposition load in forest edges when calculating the critical loads in forests.

Essential role for calcium waves in migration of human vascular smooth muscle cells.

PubMed

Espinosa-Tanguma, Ricardo; O'Neil, Caroline; Chrones, Tom; Pickering, J Geoffrey; Sims, Stephen M

2011-08-01

Vascular smooth muscle cell (SMC) migration is characterized by extension of the lamellipodia at the leading edge, lamellipodial attachment to substrate, and release of the rear (uropod) of the cell, all of which enable forward movement. However, little is known regarding the role of intracellular cytosolic Ca(2+) concentration ([Ca(2+)](i)) in coordinating these distinct activities of migrating SMCs. The objective of our study was to determine whether regional changes of Ca(2+) orchestrate the migratory cycle in human vascular SMCs. We carried out Ca(2+) imaging using digital fluorescence microscopy of fura-2 loaded human smooth muscle cells. We found that motile SMCs exhibited Ca(2+) waves that characteristically swept from the rear of polarized cells toward the leading edge. Ca(2+) waves were less evident in nonpolarized, stationary cells, although acute stimulation of these SMCs with the agonists platelet-derived growth factor-BB or histamine could elicit transient rise of [Ca(2+)](i). To investigate a role for Ca(2+) waves in the migratory cycle, we loaded cells with the Ca(2+) chelator BAPTA, which abolished Ca(2+) waves and significantly reduced retraction, supporting a causal role for Ca(2+) in initiation of retraction. However, lamellipod motility was still evident in BAPTA-loaded cells. The incidence of Ca(2+) oscillations was reduced when Ca(2+) release from intracellular stores was disrupted with the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin or by treatment with the inositol 1,4,5-trisphosphate receptor blocker 2-aminoethoxy-diphenyl borate or xestospongin C, implicating Ca(2+) stores in generation of waves. We conclude that Ca(2+) waves are essential for migration of human vascular SMCs and can encode cell polarity.

Molecular Dynamics Simulation of Resin Adsorption at Kaolinite Edge Sites: Effect of Surface Deprotonation on Interfacial Structure

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

Zeitler, T. R.; Greathouse, J. A.; Cygan, R. T.

Low-salinity water flooding, a method of enhanced oil recovery, consists of injecting low ionic strength fluids into an oil reservoir in order to detach oil from mineral surfaces in the underlying formation. Although highly successful in practice, the approach is not completely understood at the molecular scale. Molecular dynamics simulations have been used to investigate the effect of surface protonation on the adsorption of an anionic crude oil component on clay mineral edge surfaces. A set of interatomic potentials appropriate for edge simulations has been applied to the kaolinite (010) surface in contact with an aqueous nanopore. Decahydro-2-napthoic acid inmore » its deprotonated form (DHNA –) was used as a representative resin component of crude oil, with monovalent and divalent counterions, to test the observed trends in low-salinity water flooding experiments. Surface models include fully protonated (neutral) and deprotonated (negative) edge sites, which require implementation of a new deprotonation scheme. The surface adsorptive properties of the kaolinite edge under neutral and deprotonated conditions have been investigated for low and high DHNA – concentrations with Na + and Ca 2+ as counterions. The tendency of DHNA – ions to coordinate with divalent (Ca 2+) rather than monovalent (Na +) ions greatly influences adsorption tendencies of the anion. Additionally, the formation of net positively charged surface sites due to Ca 2+ at deprotonated sites results in increased DHNA – adsorption. Divalent cations such as Ca 2+ are able to efficiently bridge surface sites and organic anions. Replacing those cations with monovalent cations such as Na + diminishes the bridging mechanism, resulting in reduced adsorption of the organic species. As a result, a clear trend of decreased DHNA – adsorption is observed in the simulations as Ca 2+ is replaced by Na + for deprotonated surfaces, as would be expected for oil detachment from reservoir formations following a low-salinity flooding event.« less

Molecular Dynamics Simulation of Resin Adsorption at Kaolinite Edge Sites: Effect of Surface Deprotonation on Interfacial Structure

DOE PAGES

Zeitler, T. R.; Greathouse, J. A.; Cygan, R. T.; ...

2017-10-05

Low-salinity water flooding, a method of enhanced oil recovery, consists of injecting low ionic strength fluids into an oil reservoir in order to detach oil from mineral surfaces in the underlying formation. Although highly successful in practice, the approach is not completely understood at the molecular scale. Molecular dynamics simulations have been used to investigate the effect of surface protonation on the adsorption of an anionic crude oil component on clay mineral edge surfaces. A set of interatomic potentials appropriate for edge simulations has been applied to the kaolinite (010) surface in contact with an aqueous nanopore. Decahydro-2-napthoic acid inmore » its deprotonated form (DHNA –) was used as a representative resin component of crude oil, with monovalent and divalent counterions, to test the observed trends in low-salinity water flooding experiments. Surface models include fully protonated (neutral) and deprotonated (negative) edge sites, which require implementation of a new deprotonation scheme. The surface adsorptive properties of the kaolinite edge under neutral and deprotonated conditions have been investigated for low and high DHNA – concentrations with Na + and Ca 2+ as counterions. The tendency of DHNA – ions to coordinate with divalent (Ca 2+) rather than monovalent (Na +) ions greatly influences adsorption tendencies of the anion. Additionally, the formation of net positively charged surface sites due to Ca 2+ at deprotonated sites results in increased DHNA – adsorption. Divalent cations such as Ca 2+ are able to efficiently bridge surface sites and organic anions. Replacing those cations with monovalent cations such as Na + diminishes the bridging mechanism, resulting in reduced adsorption of the organic species. As a result, a clear trend of decreased DHNA – adsorption is observed in the simulations as Ca 2+ is replaced by Na + for deprotonated surfaces, as would be expected for oil detachment from reservoir formations following a low-salinity flooding event.« less

X-ray spectroscopy for chemistry in the 2-4 keV energy regime at the XMaS beamline: ionic liquids, Rh and Pd catalysts in gas and liquid environments, and Cl contamination in γ-Al2O3.

PubMed

Thompson, Paul B J; Nguyen, Bao N; Nicholls, Rachel; Bourne, Richard A; Brazier, John B; Lovelock, Kevin R J; Brown, Simon D; Wermeille, Didier; Bikondoa, Oier; Lucas, Christopher A; Hase, Thomas P A; Newton, Mark A

2015-11-01

The 2-4 keV energy range provides a rich window into many facets of materials science and chemistry. Within this window, P, S, Cl, K and Ca K-edges may be found along with the L-edges of industrially important elements from Y through to Sn. Yet, compared with those that cater for energies above ca. 4-5 keV, there are relatively few resources available for X-ray spectroscopy below these energies. In addition, in situ or operando studies become to varying degrees more challenging than at higher X-ray energies due to restrictions imposed by the lower energies of the X-rays upon the design and construction of appropriate sample environments. The XMaS beamline at the ESRF has recently made efforts to extend its operational energy range to include this softer end of the X-ray spectrum. In this report the resulting performance of this resource for X-ray spectroscopy is detailed with specific attention drawn to: understanding electrostatic and charge transfer effects at the S K-edge in ionic liquids; quantification of dilution limits at the Cl K- and Rh L3-edges and structural equilibria in solution; in vacuum deposition and reduction of [Rh(I)(CO)2Cl]2 to γ-Al2O3; contamination of γ-Al2O3 by Cl and its potential role in determining the chemical character of supported Rh catalysts; and the development of chlorinated Pd catalysts in `green' solvent systems. Sample environments thus far developed are also presented, characterized and their overall performance evaluated.

Adsorption of Lysine on Na-Montmorillonite and Competition with Ca(2+): A Combined XRD and ATR-FTIR Study.

PubMed

Yang, Yanli; Wang, Shengrui; Liu, Jingyang; Xu, Yisheng; Zhou, Xiaoyun

2016-05-17

Lysine adsorption at clay/aqueous interfaces plays an important role in the mobility, bioavailability, and degradation of amino acids in the environment. Knowledge of these interfacial interactions facilitates our full understanding of the fate and transport of amino acids. Here, X-ray diffraction (XRD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) measurements were used to explore the dynamic process of lysine adsorption on montmorillonite and the competition with Ca(2+) at the molecular level. Density functional theory (DFT) calculations were employed to determine the peak assignments of dissolved lysine in the solution phase. Three surface complexes, including dicationic, cationic, and zwitterionic structures, were observed to attach to the clay edge sites and penetrate the interlayer space. The increased surface coverage and Ca(2+) competition did not affect the interfacial lysine structures at a certain pH, whereas an elevated lysine concentration contributed to zwitterionic-type coordination at pH 10. Moreover, clay dissolution at pH 4 could be inhibited at a higher surface coverage with 5 and 10 mM lysine, whereas the inhibition effect was inconspicuous or undetected at pH 7 and 10. The presence of Ca(2+) not only could remove a part of the adsorbed lysine but also could facilitate the readsorption of dissolved Si(4+) and Al(3+) and surface protonation. Our results provide new insights into the process of lysine adsorption and its effects on montmorillonite surface sites.

Removal of Ca 2+ from the Oxygen-Evolving Complex in Photosystem II Has Minimal Effect on the Mn 4O 5 Core Structure: A Polarized Mn X-ray Absorption Spectroscopy Study

DOE PAGES

Lohmiller, Thomas; Shelby, Megan L.; Long, Xi; ...

2015-05-19

We studied Ca 2+ -depleted and Ca 2+ -reconstituted spinach photosystem II using polarized X-ray absorption spectroscopy of oriented PS II preparations to investigate the structural and functional role of the Ca 2+ ion in the Mn 4O 5Ca cluster of the oxygen-evolving complex (OEC). Samples were prepared by low pH/citrate treatment as one-dimensionally ordered membrane layers and poised in the Ca 2+ -depleted S 1 (S 1') and S 2 (S 2') states, the S 2'Y Z• state, at which point the catalytic cycle of water oxidation is inhibited, and the Ca 2+ -reconstituted S 1 state. Polarized Mnmore » K-edge XANES and EXAFS spectra exhibit pronounced dichroism. Polarized EXAFS data of all states of Ca 2+ -depleted PS II investigated show only minor changes in distances and orientations of the Mn-Mn vectors compared to the Ca 2+ -containing OEC, which may be attributed to some loss of rigidity of the core structure. Thus, removal of the Ca 2+ ion does not lead to fundamental distortion or rearrangement of the tetranuclear Mn cluster, which indicates that the Ca 2+ ion in the OEC is not critical for structural maintenance of the cluster, at least in the S 1 and S 2 states, but fulfills a crucial catalytic function in the mechanism of the water oxidation reaction. On the basis of this structural information, reasons for the inhibitory effect of Ca 2+ removal are discussed, attributing to the Ca 2+ ion a fundamental role in organizing the surrounding (substrate) water framework and in proton-coupled electron transfer to Y Z• (D1-Tyr161).« less

Removal of Ca(2+) from the Oxygen-Evolving Complex in Photosystem II Has Minimal Effect on the Mn4O5 Core Structure: A Polarized Mn X-ray Absorption Spectroscopy Study.

PubMed

Lohmiller, Thomas; Shelby, Megan L; Long, Xi; Yachandra, Vittal K; Yano, Junko

2015-10-29

Ca(2+)-depleted and Ca(2+)-reconstituted spinach photosystem II was studied using polarized X-ray absorption spectroscopy of oriented PS II preparations to investigate the structural and functional role of the Ca(2+) ion in the Mn4O5Ca cluster of the oxygen-evolving complex (OEC). Samples were prepared by low pH/citrate treatment as one-dimensionally ordered membrane layers and poised in the Ca(2+)-depleted S1 (S1') and S2 (S2') states, the S2'YZ(•) state, at which point the catalytic cycle of water oxidation is inhibited, and the Ca(2+)-reconstituted S1 state. Polarized Mn K-edge XANES and EXAFS spectra exhibit pronounced dichroism. Polarized EXAFS data of all states of Ca(2+)-depleted PS II investigated show only minor changes in distances and orientations of the Mn-Mn vectors compared to the Ca(2+)-containing OEC, which may be attributed to some loss of rigidity of the core structure. Thus, removal of the Ca(2+) ion does not lead to fundamental distortion or rearrangement of the tetranuclear Mn cluster, which indicates that the Ca(2+) ion in the OEC is not critical for structural maintenance of the cluster, at least in the S1 and S2 states, but fulfills a crucial catalytic function in the mechanism of the water oxidation reaction. On the basis of this structural information, reasons for the inhibitory effect of Ca(2+) removal are discussed, attributing to the Ca(2+) ion a fundamental role in organizing the surrounding (substrate) water framework and in proton-coupled electron transfer to YZ(•) (D1-Tyr161).

Strong excitonic interactions in the oxygen K-edge of perovskite oxides.

PubMed

Tomita, Kota; Miyata, Tomohiro; Olovsson, Weine; Mizoguchi, Teruyasu

2017-07-01

Excitonic interactions of the oxygen K-edge electron energy-loss near-edge structure (ELNES) of perovskite oxides, CaTiO 3 , SrTiO 3 , and BaTiO 3 , together with reference oxides, MgO, CaO, SrO, BaO, and TiO 2 , were investigated using a first-principles Bethe-Salpeter equation calculation. Although the transition energy of oxygen K-edge is high, strong excitonic interactions were present in the oxygen K-edge ELNES of the perovskite oxides, whereas the excitonic interactions were negligible in the oxygen K-edge ELNES of the reference compounds. Detailed investigation of the electronic structure suggests that the strong excitonic interaction in the oxygen K-edge ELNES of the perovskite oxides is caused by the directionally confined, low-dimensional electronic structure at the Ti-O-Ti bonds. Copyright © 2016 Elsevier B.V. All rights reserved.

In situ observation of electron beam-induced phase transformation of CaCO3 to CaO via ELNES at low electron beam energies.

PubMed

Golla-Schindler, Ute; Benner, Gerd; Orchowski, Alexander; Kaiser, Ute

2014-06-01

It is demonstrated that energy-filtered transmission electron microscope enables following of in situ changes of the Ca-L2,3 edge which can originate from variations in both local symmetry and bond lengths. Low accelerating voltages of 20 and 40 kV slow down radiation damage effects and enable study of the start and finish of phase transformations. We observed electron beam-induced phase transformation of single crystalline calcite (CaCO3) to polycrystalline calcium oxide (CaO) which occurs in different stages. The coordination of Ca in calcite is close to an octahedral one streched along the <111> direction. Changes during phase transformation to an octahedral coordination of Ca in CaO go along with a bond length increase by 5 pm, where oxygen is preserved as a binding partner. Electron loss near-edge structure of the Ca-L2,3 edge show four separated peaks, which all shift toward lower energies during phase transformation at the same time the energy level splitting increases. We suggest that these changes can be mainly addressed to the change of the bond length on the order of picometers. An important pre-condition for such studies is stability of the energy drift in the range of meV over at least 1 h, which is achieved with the sub-Ångström low-voltage transmission electron microscope I prototype microscope.

The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

NASA Astrophysics Data System (ADS)

Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

2004-05-01

X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2Ge 0.8Cr 0.2O 4, Ba 2Ge 0.1Cr 0.9O 4, Sr 2CrO 4, Ca 2(PO 4) x(CrO 4) 1- xCl ( x=0.25,0.5), Ca 5(CrO 4) 3Cl, CrO 3, the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3, CrF 3, Cr 2O 3, KCr(SO 4) 2 · 12H 2O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

Sorption selectivity of birnessite particle edges: a d-PDF analysis of Cd( ii ) and Pb( ii ) sorption by δ-MnO 2 and ferrihydrite

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

van Genuchten, Case M.; Peña, Jasquelin

2016-01-01

Birnessite minerals (layer-type MnO2), which bear both internal (cation vacancies) and external (particle edges) metal sorption sites, are important sinks of contaminants in soils and sediments. Although the particle edges of birnessite minerals often dominate the total reactive surface area, especially in the case of nanoscale crystallites, the metal sorption reactivity of birnessite particle edges remains elusive. In this study, we investigated the sorption selectivity of birnessite particle edges by combining Cd(II) and Pb(II) adsorption isotherms at pH 5.5 with surface structural characterization by differential pair distribution function (d-PDF) analysis. We compared the sorption reactivity of δ-MnO2 to that ofmore » the nanomineral, 2-line ferrihydrite, which exhibits only external surface sites. Our results show that, whereas Cd(II) and Pb(II) both bind to birnessite layer vacancies, only Pb(II) binds extensively to birnessite particle edges. For ferrihydrite, significant Pb(II) adsorption to external sites was observed (roughly 20 mol%), whereas Cd(II) sorption was negligible. These results are supported by bond valence calculations that show comparable degrees of saturation of oxygen atoms on birnessite and ferrihydrite particle edges. Therefore, we propose that the sorption selectivity of birnessite edges follows the same order of that reported previously for ferrihydrite: Ca(II) < Cd(II) < Ni(II) < Zn(II) < Cu(II) < Pb(II).« less

How Shigella Utilizes Ca(2+) Jagged Edge Signals during Invasion of Epithelial Cells.

PubMed

Bonnet, Mariette; Tran Van Nhieu, Guy

2016-01-01

Shigella, the causative agent of bacillary dysentery invades intestinal epithelial cells using a type III secretion system (T3SS). Through the injection of type III effectors, Shigella manipulates the actin cytoskeleton to induce its internalization in epithelial cells. At early invasion stages, Shigella induces atypical Ca(2+) responses confined at entry sites allowing local cytoskeletal remodeling for bacteria engulfment. Global Ca(2+) increase in the cell triggers the opening of connexin hemichannels at the plasma membrane that releases ATP in the extracellular milieu, favoring Shigella invasion and spreading through purinergic receptor signaling. During intracellular replication, Shigella regulates inflammatory and death pathways to disseminate within the epithelium. At later stages of infection, Shigella downregulates hemichannel opening and the release of extracellular ATP to dampen inflammatory signals. To avoid premature cell death, Shigella activates cell survival by upregulating the PI3K/Akt pathway and downregulating the levels of p53. Furthermore, Shigella interferes with pro-apoptotic caspases, and orients infected cells toward a slow necrotic cell death linked to mitochondrial Ca(2+) overload. In this review, we will focus on the role of Ca(2+) responses and their regulation by Shigella during the different stages of bacterial infection.

How Shigella Utilizes Ca2+ Jagged Edge Signals during Invasion of Epithelial Cells

PubMed Central

Bonnet, Mariette; Tran Van Nhieu, Guy

2016-01-01

Shigella, the causative agent of bacillary dysentery invades intestinal epithelial cells using a type III secretion system (T3SS). Through the injection of type III effectors, Shigella manipulates the actin cytoskeleton to induce its internalization in epithelial cells. At early invasion stages, Shigella induces atypical Ca2+ responses confined at entry sites allowing local cytoskeletal remodeling for bacteria engulfment. Global Ca2+ increase in the cell triggers the opening of connexin hemichannels at the plasma membrane that releases ATP in the extracellular milieu, favoring Shigella invasion and spreading through purinergic receptor signaling. During intracellular replication, Shigella regulates inflammatory and death pathways to disseminate within the epithelium. At later stages of infection, Shigella downregulates hemichannel opening and the release of extracellular ATP to dampen inflammatory signals. To avoid premature cell death, Shigella activates cell survival by upregulating the PI3K/Akt pathway and downregulating the levels of p53. Furthermore, Shigella interferes with pro-apoptotic caspases, and orients infected cells toward a slow necrotic cell death linked to mitochondrial Ca2+ overload. In this review, we will focus on the role of Ca2+ responses and their regulation by Shigella during the different stages of bacterial infection. PMID:26904514

Effects of calcium and phosphate on uranium(IV) oxidation: Comparison between nanoparticulate uraninite and amorphous UIV-phosphate

NASA Astrophysics Data System (ADS)

Latta, Drew E.; Kemner, Kenneth M.; Mishra, Bhoopesh; Boyanov, Maxim I.

2016-02-01

The mobility of uranium in subsurface environments depends strongly on its redox state, with UIV phases being significantly less soluble than UVI minerals. This study compares the oxidation kinetics and mechanisms of two potential products of UVI reduction in natural systems, a nanoparticulate UO2 phase and an amorphous UIV-Ca-PO4 analog to ningyoite (CaUIV(PO4)2·1-2H2O). The valence of U was tracked by X-ray absorption near-edge spectroscopy (XANES), showing similar oxidation rate constants for UIVO2 and UIV-phosphate in solutions equilibrated with atmospheric O2 and CO2 at pH 7.0 (kobs,UO2 = 0.17 ± 0.075 h-1 vs. kobs,UIVPO4 = 0.30 ± 0.25 h-1). Addition of up to 400 μM Ca and PO4 decreased the oxidation rate constant by an order of magnitude for both UO2 and UIV-phosphate. The intermediates and products of oxidation were tracked by electron microscopy, powder X-ray diffraction (pXRD), and extended X-ray absorption fine-structure spectroscopy (EXAFS). In the absence of Ca or PO4, the product of UO2 oxidation is Na-uranyl oxyhydroxide (under environmentally relevant concentrations of sodium, 15 mM NaClO4 and low carbonate concentration), resulting in low concentrations of dissolved UVI (<2.5 × 10-7 M). Oxidation of UIV-phosphate produced a Na-autunite phase (Na2(UO2)PO4·xH2O), resulting in similarly low dissolved U concentrations (<7.3 × 10-8 M). When Ca and PO4 are present in the solution, the EXAFS data and the solubility of the UVI phase resulting from oxidation of UO2 and UIV-phosphate are consistent with the precipitation of Na-autunite. Bicarbonate extractions and Ca K-edge X-ray absorption spectroscopy of oxidized solids indicate the formation of a Ca-UVI-PO4 layer on the UO2 surface and suggest a passivation layer mechanism for the decreased rate of UO2 oxidation in the presence of Ca and PO4. Interestingly, the extractions were unable to remove all of the oxidized U from partially oxidized UO2 solids, suggesting that oxidized U is distributed between the interior of the UO2 nanoparticles and the labile surface layer. Accounting for the entire pool of oxidized U by XANES is the likely reason for the higher UO2 oxidation rate constants determined here relative to prior studies. Our results suggest that the natural presence or addition of Ca and PO4 in groundwater could slow the rates of UIV oxidation, but that the rates are still fast enough to cause complete oxidation of UIV within days under fully oxygenated conditions.

Complexation of carboxylate on smectite surfaces.

PubMed

Liu, Xiandong; Lu, Xiancai; Zhang, Yingchun; Zhang, Chi; Wang, Rucheng

2017-07-19

We report a first principles molecular dynamics (FPMD) study of carboxylate complexation on clay surfaces. By taking acetate as a model carboxylate, we investigate its inner-sphere complexes adsorbed on clay edges (including (010) and (110) surfaces) and in interlayer space. Simulations show that acetate forms stable monodentate complexes on edge surfaces and a bidentate complex with Ca 2+ in the interlayer region. The free energy calculations indicate that the complexation on edge surfaces is slightly more stable than in interlayer space. By integrating pK a s and desorption free energies of Al coordinated water calculated previously (X. Liu, X. Lu, E. J. Meijer, R. Wang and H. Zhou, Geochim. Cosmochim. Acta, 2012, 81, 56-68; X. Liu, J. Cheng, M. Sprik, X. Lu and R. Wang, Geochim. Cosmochim. Acta, 2014, 140, 410-417), the pH dependence of acetate complexation has been revealed. It shows that acetate forms inner-sphere complexes on (110) in a very limited mildly acidic pH range while it can complex on (010) in the whole common pH range. The results presented in this study form a physical basis for understanding the geochemical processes involving clay-organics interactions.

Edge-shape barrier irreversibility and decomposition of vortices in Bi 2Sr 2CaCu 2O 8

NASA Astrophysics Data System (ADS)

Indenbom, M. V.; D'Anna, G.; André, M.-O.; Kabanov, V. V.; Benoit, W.

1994-12-01

Magnetic flux dynamics is studied in Bi 2Sr 2CaCu 2O 8 single crystals by means of magneto-optical technique. It is clearly demonstrated that the magnetic irreversibility of these crystals in a magnetic field perpendicular to the basal plane at temperatures higher than approximately 35 K is governed by an edge-shape barrier and its disappearance determines the high temperature part of the magnetic irreversibility line which is commonly associated in the literature with vortex lattice melting. We argue that this barrier exists because of the non ellipsoidal shape of the samples and can disappear only when the flux lines lose their rigidity decomposing into pancakes, which is the only true magnetic phase transition on the B-T diagram for Bi 2Sr 2CaCu 2O 8.

Structural motifs of pre-nucleation clusters.

PubMed

Zhang, Y; Türkmen, I R; Wassermann, B; Erko, A; Rühl, E

2013-10-07

Structural motifs of pre-nucleation clusters prepared in single, optically levitated supersaturated aqueous aerosol microparticles containing CaBr2 as a model system are reported. Cluster formation is identified by means of X-ray absorption in the Br K-edge regime. The salt concentration beyond the saturation point is varied by controlling the humidity in the ambient atmosphere surrounding the 15-30 μm microdroplets. This leads to the formation of metastable supersaturated liquid particles. Distinct spectral shifts in near-edge spectra as a function of salt concentration are observed, in which the energy position of the Br K-edge is red-shifted by up to 7.1 ± 0.4 eV if the dilute solution is compared to the solid. The K-edge positions of supersaturated solutions are found between these limits. The changes in electronic structure are rationalized in terms of the formation of pre-nucleation clusters. This assumption is verified by spectral simulations using first-principle density functional theory and molecular dynamics calculations, in which structural motifs are considered, explaining the experimental results. These consist of solvated CaBr2 moieties, rather than building blocks forming calcium bromide hexahydrates, the crystal system that is formed by drying aqueous CaBr2 solutions.

Influence of depositional environment in fossil teeth: a micro-XRF and XAFS study

NASA Astrophysics Data System (ADS)

Zougrou, I. M.; Katsikini, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

2014-04-01

The formation of metal-rich phases during the fossilization of vertebrate fossil teeth, recovered from various deposition environments in northern Greece, is studied by means of synchrotron radiation X-ray fluorescence (SR-XRF) as well as Fe and Mn K edge X-ray absorption fine structure (XAFS) spectroscopy. XRF line-scans from the samples' cross-sections revealed different contamination paths for Mn and Fe. The two-dimensional XRF maps illustrate the spatial distribution of P, Ca, Mn and Fe as well as the precipitation of Fe-rich phases in cementum, dentin and dentinal tubules. Goethite, lepidocrocite and ferrihydrite were detected in the samples' cross-section by means of Fe K edge EXAFS spectroscopy. Moreover the Fe and Mn K edge EXAFS revealed the presence of vivianite and birnessite (MnO2) on the external surface of two samples.

Effect of humic acid on nickel(II) sorption to Ca-montmorillonite by batch and EXAFS techniques study.

PubMed

Hu, Jun; Tan, Xiaoli; Ren, Xuemei; Wang, Xiangke

2012-09-21

The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA-montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni-HA-montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of ∼6 O atoms at the interatomic distances of ∼2.04 Å in an octahedral structure. At high pH, binary Ni-montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni-Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA-Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni-Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni-Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.

Long-term field-scale experiment on using lime filters in an agricultural catchment.

PubMed

Kirkkala, Teija; Ventelä, Anne-Mari; Tarvainen, Marjo

2012-01-01

The River Yläneenjoki catchment in southwest Finland is an area with a high agricultural nutrient load. We report here on the nutrient removal performance of three on-site lime-sand filters (F1, F2, and F3), established within or on the edge of the buffer zones. The filters contain burnt lime (CaO) or spent lime [CaO, Ca(OH), and CaCO]. Easily soluble lime results in a high pH level (>11) and leads to an efficient precipitation of soluble phosphorus (P) from the runoff. Water samples were taken from the inflow and outflow of each site in different hydrological situations. The length of the monitoring period was 4 yr for F1, 6 yr for F2, and 1.5 yr for F3. F1 and F2 significantly reduced the suspended solids (SS), total P (PTOT), and dissolved reactive P (DRP) in the treated water. The proportional reduction (%) varied but was usually clearly positive. Filter F3 was divided into two equal parts, one containing burnt lime and the other spent lime. Both filter parts removed PTOT and SS efficiently from the water; the burnt-lime part also removed DRP. The mixed-lime part removed DRP for a year, but then the efficiency decreased. The effect of filters on nitrogen compounds varied. We conclude that sand filters incorporating lime can be used together with buffer zones to reduce both P and SS load to watercourses. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Calcium EXAFS Establishes the Mn-Ca Cluster in the Oxygen-Evolving Complex of Photosystem II†

PubMed Central

Cinco, Roehl M.; Holman, Karen L. McFarlane; Robblee, John H.; Yano, Junko; Pizarro, Shelly A.; Bellacchio, Emanuele; Sauer, Kenneth; Yachandra, Vittal K.

2014-01-01

The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared subsequent to Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 Å, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is ~ 3.5 Å distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster. PMID:12390018

Effects of X-ray irradiation on the Eu3+ → Eu2+ conversion in CaAl2O4 phosphors

NASA Astrophysics Data System (ADS)

Gomes, Manassés A.; Carvalho, Jéssica C.; Andrade, Adriano B.; Rezende, Marcos V.; Macedo, Zélia S.; Valerio, Mário E. G.

2018-01-01

This paper reports structural and luminescence properties of Eu-doped CaAl2O4 produced by an alternative sol-gel method using coconut water. Results of differential thermal analysis (DTA), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) allowed us to identify the best synthesis conditions for sample preparation. Simultaneous measurements of X-ray absorption spectroscopy (XAS) and X-ray excited optical luminescence (XEOL) were also performed in the X-ray energy range of the Eu LIII edge. Results from photoluminescence (PL) showed only the characteristic Eu3+ emission. However, radioluminescence emission spectra from Eu-doped CaAl2O4 shows a process of conversion of Eu3+ to Eu2+, which is induced by X-ray irradiation and is dependent on the radiation dose energy. X-ray absorption near edge structure (XANES) measurements corroborate Eu reduction due to irradiation, showing that only the Eu3+ ion is present in stable form in the CaAl2O4.

Computational study of electronic, optical and thermoelectric properties of X3PbO (X = Ca, Sr, Ba) anti-perovskites

NASA Astrophysics Data System (ADS)

Hassan, M.; Arshad, I.; Mahmood, Q.

2017-11-01

We report the structural, electronic, optical and thermoelectric (TE) properties of X3PbO (X = Ca, Sr, Ba) anti-perovskites as a function of X cations belonging to the group IIA. The computations are done by using the most recently introduced modified Becke-Johnson potential. It has been observed that the cubic lattice constant increases as the cations change from Ca to Ba, consequently, the bulk modulus reduces. The bottom of conduction band shows strong hybridization between Pb-6p, O-2p and X-s states, in contrast, valence band maxima are mainly manufactured by Pb-6p states. The anti-perovskites exhibit narrow direct band gap that show an inverse relation to the static real dielectric constants that verifies Penn’s model. In addition, the X cations induced tuning of the absorption edge in the visible and the ultraviolet energy suggest optical device applications. The computed TE parameters have been found sensitive to the X cations and have been demonstrated to be best suited for the TE devices operating at high temperatures.

Iodate in calcite and vaterite: Insights from synchrotron X-ray absorption spectroscopy and first-principles calculations

NASA Astrophysics Data System (ADS)

Podder, J.; Lin, J.; Sun, W.; Botis, S. M.; Tse, J.; Chen, N.; Hu, Y.; Li, D.; Seaman, J.; Pan, Y.

2017-02-01

Calcium carbonates such as calcite are the dominant hosts of inorganic iodine in nature and are potentially important for the retention and removal of radioactive iodine isotopes (129I and 131I) in contaminated water. However, little is known about the structural environment of iodine in carbonates. In this study, iodate (IO3-) doped calcite and vaterite have been synthesized using the gel-diffusion method at three NaIO3 concentrations (0.002; 0.004; 0.008 M) and a pH value of 9.0, under ambient temperature and pressure. Inductively coupled plasma mass spectrometry (ICP-MS) analyses show that iodine is preferentially incorporated into calcite over vaterite. Synchrotron iodine K-edge X-ray absorption near-edge structure (XANES) spectra confirm that IO3- is the dominant iodine species in synthetic calcite and vaterite. Analyses of iodine K-edge extended X-ray absorption fine structure (EXAFS) data, complemented by periodic first-principles calculations at the density functional theory (DFT) levels, demonstrate that the I5+ ion of the IO3- group in calcite and vaterite is bonded by three and two additional O atoms (i.e., coordination numbers = 6 and 5), respectively, and is incorporated via the charged coupled substitution I5+ + Na+ ↔ C4+ + Ca2+, with the Na+ cation at a nearest Ca2+ site being the most energetically favorable configuration.

Tracing the pathway of compositional changes in bone mineral with age: Preliminary study of bioapatite aging in hypermineralized dolphin’s bulla

PubMed Central

Li, Zhen; Pasteris, Jill D.

2014-01-01

Background Studies of mineral compositional effects during bone aging are complicated by the presence of collagen. Methods Hypermineralized bullae of Atlantic bottlenose dolphins of < 3 months, 2.5 years, and 20 years underwent micrometer-scale point analysis by Raman spectroscopy and electron microprobe in addition to bulk analysis for carbon. Results Bulla central areas have a mineral content of ~96 wt.% and 9–10 wt.% carbonate in their bioapatite, which is ~2 wt.% more than edge areas. Ca/P atomic ratios (~1.8) and concentrations of Mg, S, and other minor/trace elements are almost constant in central areas over time. Maturity brings greater over-all homogeneity in mineral content, stoichiometry, and morphology throughout central and edge areas of the bullae. During aging, edge areas become less porous, whereas the concentration of organics in the edge is reduced. Enhancement of coupled substitutions of CO32− for PO43− and Na for Ca during aging increases carbonate content up to ~10 wt.% in the adult bulla. Conclusions 1) Changes in physical properties during aging did not occur simultaneously with changes in chemical properties of the bone mineral. 2) Compositional changes in bone mineral were minor during the neonatal to sub-adult stage, but significant during later maturity. 3) Na and CO3 concentrations covary in a 1:1 molar proportion during aging. 4) The mineral’s crystallinity did not decrease as CO3 concentration increased during aging. General Significance Hypermineralized dolphin’s bulla, due to extreme depletion in collagen, is an ideal material for investigating mineralogical changes in bioapatite during bone aging. PMID:24650888

Evaluation of potential substrates for restenosis and thrombosis in overlapped versus edge-to-edge juxtaposed bioabsorbable scaffolds: Insights from a computed fluid dynamic study.

PubMed

Rigatelli, Gianluca; Zuin, Marco; Dell'Avvocata, Fabio; Cardaioli, Paolo; Vassiliev, Dobrin; Ferenc, Miroslaw; Nghia, Nguyen Tuan; Nguyen, Thach; Foin, Nicholas

2018-04-01

Multiple BRSs and specifically the Absorb scaffold (BVS) (Abbott Vascular, Santa Clara, CA USA) have been often used to treat long diffuse coronary artery lesions. We evaluate by a computational fluid dynamic(CFD) study the impact on the intravascular fluid rheology on multiple bioabsorbable scaffolds (BRS) by standard overlapping versus edge-to-edge technique. We simulated the treatment of a real long significant coronary lesion (>70% luminal narrowing) involving the left anterior descending artery (LAD) treated with a standard or edge-to-edge technique, respectively. Simulations were performed after BVS implantations in two different conditions: 1) Edge-to-edge technique, where the scaffolds are kissed but not overlapped resulting in a luminal encroachment of 0.015cm (150μm); 2) Standard overlapping, where the scaffolds are overlapped resulting in a luminal encroachment of 0.030cm (300μm). After positioning the BVS across the long lesion, the implantation procedure was performed in-silico following all the usual procedural steps. Analysis of the wall shear stress (WSS) suggested that at the vessel wall level the WSS were lower in the overlapping zones overlapping compared to the edge-to-edge zone (∆=0.061Pa, p=0.01). At the struts level the difference between the two WSS was more striking (∆=1.065e-004 p=0.01) favouring the edge-to-edge zone. Our study suggested that at both vessel wall and scaffold struts levels, there was lowering WSS when multiple BVS were implanted with the standard overlapping technique compared to the "edge-to-edge" technique. This lower WSS might represent a substrate for restenosis, early and late BVS thrombosis, potentially explaining at least in part the recent evidences of devices poor performance. Copyright © 2017 Elsevier Inc. All rights reserved.

XANES evidence for sulphur speciation in Mn-, Ni- and W-bearing silicate melts

NASA Astrophysics Data System (ADS)

Evans, K. A.; O'Neill, H. St. C.; Mavrogenes, J. A.; Keller, N. S.; Jang, L.-Y.; Lee, J.-F.

2009-11-01

S K-edge XANES and Mn-, W- and Ni-XANES and EXAFS spectra of silicate glasses synthesised at 1400 °C and 1 bar with compositions in the CaO-MgO-Al 2O 3-SiO 2-S plus MnO, NiO, or WO 3 systems were used to investigate sulphur speciation in silicate glasses. S K-edge spectra comprised a composite peak with an edge between 2470 and 2471.4 eV, which was attributed to S 2-, and a peak of variable height with an edge at 2480.2-2480.8 eV, which is consistent with the presence of S 6+. The latter peak was attributed to sample oxidation during sample storage. W-rich samples produced an additional lower energy peak at 2469.8 eV that is tentatively attributed to the existence of S 3p orbitals hybridised with the W 5d states. Deconvolution of the composite peak reveals that the composite peak for Mn-bearing samples fits well to a model that combines three Lorentzians at 2473.1, 2474.9 and 2476.2 eV with an arctan edge step. The composite peak for W-bearing samples fits well to the same combination plus an additional Lorentzian at 2469.8 eV. The ratio of the proportions of the signal accounted for by peaks at 2473.1 and 2476.2 eV correlates with Mn:Ca molar ratios, but not with W:Ca ratios. Spectra from Ni-bearing samples were qualitatively similar but S levels were too low to allow robust quantification of peak components. Some part of the signal accounted for by the 2473.1 eV peak was therefore taken to record the formation of Mn-S melt species, while the 2469.8 peak is interpreted to record the formation of W-S melt species. The 2474.9 and 2476.2 eV peaks were taken to be dominated by Ca-S and Mg-S interactions. However, a 1:1 relationship between peak components and specific energy transitions is not proposed. This interpretation is consistent with known features of the lower parts of the conduction band in monosulphide minerals and indicates a similarity between sulphur species in the melts and the monosulphides. S-XANES spectra cannot be reproduced by a combination of the spectra of the component element monosulphides. Mn-, W- and Ni-XANES and EXAFS for synthetic glasses without sulphide exsolution did not show any sensitivity to the presence of sulphur, which is unsurprising as S:O ratios were sufficiently low that metals would be mostly co-ordinated by O. Mn EXAFS spectra were consistent with divalent Mn in 5 co-ordinated Mn-O melt species. W spectra were consistent with tetrahedrally co-ordinated hexavalent W, most likely in scheelite-like melt species, and Ni spectra were consistent with [4] co-ordinated divalent Ni. These results indicate lower co-ordinations for both W and Ni than those inferred by some previous workers. Cation co-ordination may reflect the proportion of non-bridging oxygens, which is lower in the Ca-rich and Al-poor samples investigated here than for previous studies.

Natural fertility and heavy metals in the soil in border areas of Atlantic Forest located in an urban area

NASA Astrophysics Data System (ADS)

Longo, R. M.; Ribeiro, A. I.

2017-12-01

Regina Márcia Longo2, Deborah Regina Mendes2, Admilson Irio Ribeiro31 Part of the project funded by the Foundation of the State of São Paulo Research - Brazil (FAPESP - process 2012 / 14423-8)2 Pontifícal Catholic University of Campinas - Brazil; email: regina.longo@puc-campinas.edu.br 3 Paulista State University (UNESP-Sorocaba - Brazil)Due to the disorderly growth of cities, especially in tropical areas, it is observed that the destruction or fragmentation of natural ecosystems has presented itself as one of the great problems of the present time. The forest fragments, although important for the maintenance of microclimate, genetic variety and species diversity, are increasingly impacted due to the activities that are developed in their environment. The present work had as main objective to quantify the level of natural fertility and the presence of heavy metals in the soil in border areas of a forest remnant located in an urban area in the city of Campinas / SP - Brazil in order to verify possible interferences of the anthropic actions carried out in adjacent areas. Soil composite samples were collected at 40 points equidistant at 200 m along the edge. In the samples were determined the contents of: pH (CaCl2); organic matter (OM); phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg), Cation Exchange Capacity (CEC), base sum (SB) and percentage saturation of bases in addition to heavy metals lead (Pb), chromium (Cr) and nickel (Ni). The results indicated that the nutritional quality of the soil was adequate for the tropical regions. In relation to micronutrients, high levels of copper, zinc and manganese were observed. Regarding the metals, it was observed that iron was the one that accused the most irregularities along the edge, while the lead had higher indices for all the edges evaluated. In general, the presented results indicated that the forest remnant presents its border areas under external pressures, presenting several factors of degradation as real estate occupation, presence of access roads and traffic of vehicles and people, of the production of sugar cane, fire and deposition of solid waste, or other degradation factor that directly interfere in the areas of the edges of this important remnant of Atlantic Forest. Key words: forest remnants, tropical soils, edge effect

X-ray absorption studies of chlorine valence and local environments in borosilicate waste glasses

NASA Astrophysics Data System (ADS)

McKeown, David A.; Gan, Hao; Pegg, Ian L.; Stolte, W. C.; Demchenko, I. N.

2011-01-01

Chlorine (Cl) is a constituent of certain types of nuclear wastes and its presence can affect the physical and chemical properties of silicate melts and glasses developed for the immobilization of such wastes. Cl K-edge X-ray absorption spectra (XAS) were collected and analyzed to characterize the unknown Cl environments in borosilicate waste glass formulations, ranging in Cl-content from 0.23 to 0.94 wt.%. Both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data for the glasses show trends dependent on calcium (Ca) content. Near-edge data for the Ca-rich glasses are most similar to the Cl XANES of CaCl 2, where Cl - is coordinated to three Ca atoms, while the XANES for the Ca-poor glasses are more similar to the mineral davyne, where Cl is most commonly coordinated to two Ca in one site, as well as Cl and oxygen nearest-neighbors in other sites. With increasing Ca content in the glass, Cl XANES for the glasses approach that for CaCl 2, indicating more Ca nearest-neighbors around Cl. Reliable structural information obtained from the EXAFS data for the glasses is limited, however, to Cl sbnd Cl, Cl sbnd O, and Cl sbnd Na distances; Cl sbnd Ca contributions could not be fit to the glass data, due to the narrow k-space range available for analysis. Structural models that best fit the glass EXAFS data include Cl sbnd Cl, Cl sbnd O, and Cl sbnd Na correlations, where Cl sbnd O and Cl sbnd Na distances decrease by approximately 0.16 Å as glass Ca content increases. XAS for the glasses indicates Cl - is found in multiple sites where most Cl-sites have Ca neighbors, with oxygen, and possibly, Na second-nearest neighbors. EXAFS analyses suggest that Cl sbnd Cl environments may also exist in the glasses in minor amounts. These results are generally consistent with earlier findings for silicate glasses, where Cl - was associated with Ca 2+ and Na + in network modifier sites.

Effects of calcium and phosphate on uranium(IV) oxidation: Comparison between nanoparticulate uraninite and amorphous U IV–phosphate

DOE PAGES

Latta, Drew E.; Kemner, Kenneth M.; Mishra, Bhoopesh; ...

2015-11-17

The mobility of uranium in subsurface environments depends strongly on its redox state, with U IV phases being significantly less soluble than U VI minerals. This study compares the oxidation kinetics and mechanisms of two potential products of U VI reduction in natural systems, a nanoparticulate UO 2 phase and an amorphous U IV–Ca–PO 4 analog to ningyoite (CaU IV(PO 4) 2·1–2H 2O). The valence of U was tracked by X-ray absorption near-edge spectroscopy (XANES), showing similar oxidation rate constants for U IVO 2 and U IV–phosphate in solutions equilibrated with atmospheric O 2 and CO 2 at pH 7.0more » (k obs,UO2 = 0.17 ± 0.075 h -1 vs. k obs,U IV PO4 = 0.30 ± 0.25 h -1). Addition of up to 400 μM Ca and PO 4 decreased the oxidation rate constant by an order of magnitude for both UO 2 and U IV–phosphate. The intermediates and products of oxidation were tracked by electron microscopy, powder X-ray diffraction (pXRD), and extended X-ray absorption fine-structure spectroscopy (EXAFS). In the absence of Ca or PO 4, the product of UO 2 oxidation is Na–uranyl oxyhydroxide (under environmentally relevant concentrations of sodium, 15 mM NaClO 4 and low carbonate concentration), resulting in low concentrations of dissolved U VI (<2.5 × 10 -7 M). Oxidation of U IV–phosphate produced a Na-autunite phase (Na 2(UO 2)PO 4·xH 2O), resulting in similarly low dissolved U concentrations (<7.3 × 10 -8 M). When Ca and PO 4 are present in the solution, the EXAFS data and the solubility of the UVI phase resulting from oxidation of UO 2 and UIV–phosphate are consistent with the precipitation of Na-autunite. Bicarbonate extractions and Ca K-edge X-ray absorption spectroscopy of oxidized solids indicate the formation of a Ca–UVI–PO 4 layer on the UO 2 surface and suggest a passivation layer mechanism for the decreased rate of UO 2 oxidation in the presence of Ca and PO 4. Interestingly, the extractions were unable to remove all of the oxidized U from partially oxidized UO 2 solids, suggesting that oxidized U is distributed between the interior of the UO 2 nanoparticles and the labile surface layer. Accounting for the entire pool of oxidized U by XANES is the likely reason for the higher UO 2 oxidation rate constants determined here relative to prior studies. In conclusion, our results suggest that the natural presence or addition of Ca and PO 4 in groundwater could slow the rates of U IV oxidation, but that the rates are still fast enough to cause complete oxidation of U IV within days under fully oxygenated conditions.« less

Investigations on the crystal-structure and non-ambient behaviour of K2Ca2Si8O19 - a new potassium calcium silicate

NASA Astrophysics Data System (ADS)

Schmidmair, Daniela; Kahlenberg, Volker; Praxmarer, Alessandra; Perfler, Lukas; Mair, Philipp

2017-09-01

Within the context of a systematic re-investigation of phase relationships between compounds of the ternary system K2O-CaO-SiO2 a new potassium calcium silicate with the chemical formula K2Ca2Si8O19 was synthesized via solid state reactions as well as the flux method using KCl as a solvent. Its crystal structure was determined from single-crystal X-ray diffraction data by applying direct methods. The new compound crystallizes in the triclinic space group P 1 bar . Unit cell dimensions are a = 7.4231(7) Å, b = 10.7649(10) Å, c = 12.1252(10) Å, α = 70.193(8)°, β = 83.914(7)° and γ = 88.683(7)°. K2Ca2Si8O19 is built up of corner-connected, slightly distorted [SiO4]-tetrahedra forming double-sheets, which are linked by double-chains of edge-sharing [CaO6]-octahedra. Electroneutrality of the material is provided by additional potassium atoms that are located within the voids of the silicate layers and between adjacent [Ca2O6]-double-chains. Further characterization of the compound was performed by Raman spectroscopy and differential thermal analysis. The behaviour of K2Ca2Si8O19 under high-temperature and high-pressure was investigated by in-situ high-temperature powder X-ray diffraction up to a maximum temperature of 1125 °C and a piston cylinder experiment at 1.5 GPa and 1100 °C. Additionally an overview of known double-layer silicates is given as well as a comparison of K2Ca2Si8O19 to closely related structures.

X-ray dual energy spectral parameter optimization for bone Calcium/Phosphorus mass ratio estimation

NASA Astrophysics Data System (ADS)

Sotiropoulou, P. I.; Fountos, G. P.; Martini, N. D.; Koukou, V. N.; Michail, C. M.; Valais, I. G.; Kandarakis, I. S.; Nikiforidis, G. C.

2015-09-01

Calcium (Ca) and Phosphorus (P) bone mass ratio has been identified as an important, yet underutilized, risk factor in osteoporosis diagnosis. The purpose of this simulation study is to investigate the use of effective or mean mass attenuation coefficient in Ca/P mass ratio estimation with the use of a dual-energy method. The investigation was based on the minimization of the accuracy of Ca/P ratio, with respect to the Coefficient of Variation of the ratio. Different set-ups were examined, based on the K-edge filtering technique and single X-ray exposure. The modified X-ray output was attenuated by various Ca/P mass ratios resulting in nine calibration points, while keeping constant the total bone thickness. The simulated data were obtained considering a photon counting energy discriminating detector. The standard deviation of the residuals was used to compare and evaluate the accuracy between the different dual energy set-ups. The optimum mass attenuation coefficient for the Ca/P mass ratio estimation was the effective coefficient in all the examined set-ups. The variation of the residuals between the different set-ups was not significant.

Phosphovanadylite: a new vanadium phosphate mineral with a zeolite-type structure

USGS Publications Warehouse

Medrano, M.D.; Evans, H.T.; Wenk, H.-R.; Piper, D.Z.

1998-01-01

Phosphovanadylite, whose simplified formula is (Ba,Ca,K,Na)x([(Va,Al)4P2(P,OH)16].12H2), is a new vanadium phosphate zeolite mineral found in the Phosphoria Formation at Monsanto's Enoch Valley Mine, Soda Springs, Idaho. Its formula in more detail is (Ba0.38Ca0.20K0.006Na0.02)??0.66 [P2(V3.44Al0.046)??3.90O10.34(OH)5.66] .12H2O. The drusy mineral occurs as pale greenish-blue euhedral cubes (20-50 ??m edge) coating phosphatic, organic-rich mudstone. The chemical composition determined by electron microprobe is (in weight percent) V-28.02, P-9.91, Al-1.97, Ca-1.31, Ba-8.28, Cd-0.09, Zn-0.34, Na-0.15, K-0.73, O-46.57, and F-0.03. The index of refraction is nD = 1.566 (4) and specific gravity is 2.16 (3). The X-ray powder pattern shows strong reflections at 3.16 A (422), 2.58 (600), 2.44 (620), and 7.73 (200), which are indexed on the basis of a cubic body-centered unit cell with a = 15.470 (4) A. From the single-crystal structure analysis, its space group was determined to be I43m, Z = 6, and its structure consists of V4O18 16 octahedral clusters linked to each other by P atoms to form a cubic lattice, creating cavities 7.0 and 5.5 A in diameter where mainly H2O resides. Final residual indexes are R = 0.066, Rw = 0.061, goodness-of-fit = 0.75, and 93 observations and 24 parameters.

Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi 2O 7)

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

Clark, Braeden M.; Sundaram, S. K.; Misture, Scott T.

Compounds with the formulae CaZr 1–xCe xTi 2O 7 with x = 0.1–0.5 were synthesized by solid state reaction. Cerium was used as a surrogate for actinide elements. A transition from the 2M polymorph to the 4M polymorph (expanded unit cell due to cation ordering) in zirconolite was observed with increasing cerium content. The presence of both tri- and tetravalent Ce, contrary to formulation, was confirmed using X-ray absorption near edge spectroscopy, suggesting substitution on both Ca and Zr sites. Sintering was carried out via spark plasma sintering, during which the perovskite phase (Ca 0.4Ce 0.4TiO 3) was stabilized duemore » to the reducing conditions of this technique. Scanning electron microscopy and energy dispersive spectrometry revealed that the 2M polymorph was dilute in Ce content in comparison to the 4M-zirconolite. High temperature X-ray diffraction was used to detail the kinetics of perovskite to zirconolite transition. It was found that CaCeTi 2O 7 (cubic pyrochlore) formed as an intermediate phase during the transition. Lastly, our results show that a transition from 2M- to 4M-zirconolite occurs with increasing Ce content and can be controlled by adjusting the P O2 and the heat treatment temperature.« less

Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi 2O 7)

DOE PAGES

Clark, Braeden M.; Sundaram, S. K.; Misture, Scott T.

2017-07-19

Compounds with the formulae CaZr 1–xCe xTi 2O 7 with x = 0.1–0.5 were synthesized by solid state reaction. Cerium was used as a surrogate for actinide elements. A transition from the 2M polymorph to the 4M polymorph (expanded unit cell due to cation ordering) in zirconolite was observed with increasing cerium content. The presence of both tri- and tetravalent Ce, contrary to formulation, was confirmed using X-ray absorption near edge spectroscopy, suggesting substitution on both Ca and Zr sites. Sintering was carried out via spark plasma sintering, during which the perovskite phase (Ca 0.4Ce 0.4TiO 3) was stabilized duemore » to the reducing conditions of this technique. Scanning electron microscopy and energy dispersive spectrometry revealed that the 2M polymorph was dilute in Ce content in comparison to the 4M-zirconolite. High temperature X-ray diffraction was used to detail the kinetics of perovskite to zirconolite transition. It was found that CaCeTi 2O 7 (cubic pyrochlore) formed as an intermediate phase during the transition. Lastly, our results show that a transition from 2M- to 4M-zirconolite occurs with increasing Ce content and can be controlled by adjusting the P O2 and the heat treatment temperature.« less

Polarization Dependent X-ray Absorption Spectroscopy of the TiO2 Polymorphs Anatase (001) and Rutile (001)

NASA Astrophysics Data System (ADS)

Ederer, D. L.; Ruzycki, N.; Schuler, T.; Zhang, G. P.; Callcott, T. A.; Nachimuthu, P.; Perera, R. C. C.

2002-03-01

Polarization Dependent X-ray Absorption Spectroscopy of the TiO2 Polymorphs Anatase (001) and Rutile (001) N. Ruzycki^a, T. Schuler^a, D.L. Ederer^a, T. A. Callcott^, G. P. Zhang^b, P. Nachimuthu^c,d, and R.C.C. Perera^c a-Tulane University, Department of Physics, New Orleans, LA, 70118 b- Univesity of Tennessee, Department of Physics and Astronomy, Knoxville, TN, 37996 c- Center for X-ray Optics, Lawrence Berkeley Laboratory, Berkeley, CA, d- Department of Chemistry, University of Nevada Las Vegas, Las Vegas NV, 89154 TiO2 is a useful industrial catalyst and has applications in gas sensing and photoelectric devices. All structures consist of octrahedrally-coordinated Ti atoms and three-fold coordinated O atoms. Anatase and rutile differ mainly in the amount of distortion in the octahedra. Because Soft X-ray Absorption Spectroscoy (SXAS) is sensitive to the ligand field, these small differences are reflected the spectra. In the experiment the electronic polarization vector was varied angulary along the equatorial and the longitudnal axes of the sixfold coordinated titanium atoms. This study showed a strong polarization dependence at the oxygen K-edge for rutile (001) and the anatase (001) in the t_2g and eg region for the equatorial bonds. The Titanium L-edge showed a smaller polarization dependence. There was no polarization dependence in the longitudinal direction for anatase (001) or rutile (001) in either the oxygen K-edge or the Ti-L edge. These data are compared with calculations of polarization-dependent matrix elements of the transitions.

Significance of out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu2p edge

NASA Astrophysics Data System (ADS)

Janowitz, Christoph; Schmeißer, Dieter

2018-04-01

In high-temperature superconductors with a layered crystal structure, the copper-oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. As a consequence, out-of-plane contributions are often neglected in the description of these materials. Here we report on a resonant photoemission study of Pb0,4Bi1,6Sr2,0CaCu2O8 ((Pb, Bi)-2212) and Pb0,6Bi1,4Sr1.5La0.5CuO6 ((Pb, Bi)-2201)) single crystals to unravel the resonant decay mechanisms at the Cu2p absorption edge. We find evidence for a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state—which is involved in the two Auger processes—consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and O2p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu-O plane, and spills out perpendicular to it. This suggests that out-of-plane electronic degrees of freedom should be included in future consistent theoretical models of these materials.

Ca2+-dependent nitric oxide release in the injured endothelium of excised rat aorta: a promising mechanism applying in vascular prosthetic devices in aging patients

PubMed Central

2013-01-01

Background Nitric oxide is key to endothelial regeneration, but it is still unknown whether endothelial cell (EC) loss results in an increase in NO levels at the wound edge. We have already shown that endothelial damage induces a long-lasting Ca2+ entry into surviving cells though connexin hemichannels (CxHcs) uncoupled from their counterparts on ruptured cells. The physiological outcome of injury-induced Ca2+ inflow is, however, unknown. Methods In this study, we sought to determine whether and how endothelial scraping induces NO production (NOP) in the endothelium of excised rat aorta by exploiting the NO-sensitive fluorochrome, DAF-FM diacetate and the Ca2+-sensitive fluorescent dye, Fura-2/AM. Results We demonstrated that injury-induced NOP at the lesion site is prevented in presence of the endothelial NO synthase inhibitor, L-NAME, and in absence of extracellular Ca2+. Unlike ATP-dependent NO liberation, the NO response to injury is insensitive to BTP-2, which selectively blocks store-operated Ca2+ inflow. However, injury-induced NOP is significantly reduced by classic gap junction blockers, and by connexin mimetic peptides specifically targeting Cx37Hcs, Cx40HCs, and Cx43Hcs. Moreover, disruption of caveolar integrity prevents injury-elicited NO signaling, but not the accompanying Ca2+ response. Conclusions The data presented provide the first evidence that endothelial scraping stimulates NO synthesis at the wound edge, which might both exert an immediate anti-thrombotic and anti-inflammatory action and promote the subsequent re-endothelialization. PMID:24266895

Formation of CaB6 in the thermal decomposition of the hydrogen storage material Ca(BH4)2.

PubMed

Sahle, Christoph J; Sternemann, Christian; Giacobbe, Carlotta; Yan, Yigang; Weis, Christopher; Harder, Manuel; Forov, Yury; Spiekermann, Georg; Tolan, Metin; Krisch, Michael; Remhof, Arndt

2016-07-20

Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopy at the B K- and Ca L2,3-edges, we analyzed the reaction products of Ca(BH4)2 after annealing at 350 °C and 400 °C under vacuum conditions. We observed the formation of nanocrystalline/amorphous CaB6 mainly and found only small contributions from amorphous B for annealing times larger than 2 h. For short annealing times of 0.5 h at 400 °C we observed neither CaB12H12 nor CaB6. The results indicate a reaction pathway in which Ca(BH4)2 decomposes to B and CaH2 and finally reacts to form CaB6. These findings confirm the potential of using Ca(BH4)2 as a hydrogen storage medium and imply the desired cycling capabilities for achieving high-density hydrogen storage materials.

Probing the calcium and sodium local environment in bones and teeth using multinuclear solid state NMR and X-ray absorption spectroscopy.

PubMed

Laurencin, Danielle; Wong, Alan; Chrzanowski, Wojciech; Knowles, Jonathan C; Qiu, Dong; Pickup, David M; Newport, Robert J; Gan, Zhehong; Duer, Melinda J; Smith, Mark E

2010-02-07

Despite the numerous studies of bone mineral, there are still many questions regarding the exact structure and composition of the mineral phase, and how the mineral crystals become organised with respect to each other and the collagen matrix. Bone mineral is commonly formulated as hydroxyapatite, albeit with numerous substitutions, and has previously been studied by (31)P and (1)H NMR, which has given considerable insight into the complexity of the mineral structure. However, to date, there has been no report of an NMR investigation of the other major component of bone mineral, calcium, nor of common minority cations like sodium. Here, direct analysis of the local environment of calcium in two biological apatites, equine bone (HB) and bovine tooth (CT), was carried out using both (43)Ca solid state NMR and Ca K-edge X-ray absorption spectroscopy, revealing important structural information about the calcium coordination shell. The (43)Ca delta(iso) in HB and CT is found to correlate with the average Ca-O bond distance measured by Ca K-edge EXAFS, and the (43)Ca NMR linewidths show that there is a greater distribution in chemical bonding around calcium in HB and CT, compared to synthetic apatites. In the case of sodium, (23)Na MAS NMR, high resolution 3Q-MAS NMR, as well as (23)Na{(31)P} REDOR and (1)H{(23)Na} R(3)-HMQC correlation experiments give the first direct evidence that some sodium is located inside the apatite phase in HB and CT, but with a greater distribution of environments compared to a synthetic sodium substituted apatite (Na-HA).

Electronic Structure of HgBa2CaCu2O(6+delta) Epitaxial films measured by x-ray Photoemission

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Rupp, M.; Gupta, A.; Tsuei, C. C.

1995-01-01

The electronic structure and chemical states of HgBa2CaCu20(sub 6 + delta), epitaxial films have been studied with x-ray photelectron spectroscopy. Signals from the superconducting phase dominate all the core-level spectra, and a clear Fermi edge is observed in the valence-band region. The Ba, Ca, Cu, and O core levels are similar to those of Tl2Ba2CaCu208(+)O(sub 6 + delta), but distinct differences are observed in the valence bands which are consistent with differences in the calculated densities of states.

Resolution Properties of a Calcium Tungstate (CaWO4) Screen Coupled to a CMOS Imaging Detector

NASA Astrophysics Data System (ADS)

Koukou, Vaia; Martini, Niki; Valais, Ioannis; Bakas, Athanasios; Kalyvas, Nektarios; Lavdas, Eleftherios; Fountos, George; Kandarakis, Ioannis; Michail, Christos

2017-11-01

The aim of the current work was to assess the resolution properties of a calcium tungstate (CaWO4) screen (screen coating thickness: 50.09 mg/cm2, actual thickness: 167.2 μm) coupled to a high resolution complementary metal oxide semiconductor (CMOS) digital imaging sensor. A 2.7x3.6 cm2 CaWO4 sample was extracted from an Agfa Curix universal screen and was coupled directly with the active area of the active pixel sensor (APS) CMOS sensor. Experiments were performed following the new IEC 62220-1-1:2015 International Standard, using an RQA-5 beam quality. Resolution was assessed in terms of the Modulation Transfer Function (MTF), using the slanted-edge method. The CaWO4/CMOS detector configuration was found with linear response, in the exposure range under investigation. The final MTF was obtained through averaging the oversampled edge spread function (ESF), using a custom-made software developed by our team, according to the IEC 62220-1-1:2015. Considering the renewed interest in calcium tungstate for various applications, along with the resolution results of this work, CaWO4 could be also considered for use in X-ray imaging devices such as charged-coupled devices (CCD) and CMOS.

Elucidation of reaction mechanisms of Ni2SnP in Li-ion and Na-ion systems

NASA Astrophysics Data System (ADS)

Marino, C.; Dupré, N.; Villevieille, C.

2017-10-01

Electrochemical performance of Ni2SnP was assessed in Li-ion and Na-ion battery systems. When cycled versus Li, Ni2SnP exhibited a reversible specific charge of 700 mAh.g-1 (theoretical specific charge: 742 mAh.g-1). In the Na system, the specific observed charge was ca. 200 mAh.g-1 (theoretical specific charge: 676 mAh.g-1). X-ray diffraction, Ni K-edge X-ray absorption spectroscopy, and 31P and 7Li/23Na nuclear magnetic resonance spectroscopy were used to elucidate the electrochemical mechanisms in both systems. Versus Li, Ni2SnP undergoes a conversion reaction resulting in the extrusion of Ni and the alloying of Li-Sn and Li-P. On delithiation, the material partially recombines into a Sn- and Ni-deficient form. In the Na system, Ni2SnP reacts through the conversion of P into Na3P. These results indicate that the recombination of the pristine material (even partially) increases cycling stability.

Bismuth zinc vanadate, BiZn{sub 2}VO{sub 6}: New crystal structure type and electronic structure

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

Eliziario Nunes, Sayonara; Department of Materials Engineering, Federal University of São Carlos, 13565-905 São Carlos, SP; Wang, Chun-Hai

2015-02-15

We report a combined experimental and computational study of the crystal structure and electronic properties of bismuth zinc vanadate, BiZn{sub 2}VO{sub 6}, known for its visible light photocatalytic activity. The crystal structure has been solved from laboratory powder X-ray diffraction data using the repeated minimisations from random starting values method. BiZn{sub 2}VO{sub 6} adopts a new structure type, based on the following building blocks: corner- and edge-sharing ZnO{sub 4} tetrahedra, ZnO{sub 6} octahedra and VO{sub 4} tetrahedra, and Bi{sub 2}O{sub 12} dimers. It is the only known member of the BiM{sub 2}AO{sub 6} (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu;more » A=V, P, As) family which does not appear to be structurally closely related to others. The electronic structure of BiZn{sub 2}VO{sub 6}, calculated by DFT methods, shows that it is an indirect gap semiconductor with a calculated band gap of 1.6 eV, which compares favourably to the experimentally measured value of 2.4 eV. - Graphical abstract: The crystal structure of BiZn{sub 2}VO{sub 6}, a new structure type in the BiM{sub 2}AO{sub 6} (M=Mg, Ca, Cd, Cu, Pb, Mn, Zn; A=V, P, As) family. - Highlights: • Structure solution from PXRD data by repeated minimisations from random starting values. • New structure type in the BiM{sub 2}AO{sub 6} (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu; A=V, P, As) family. • Electronic structure calculation.« less

Tetracycline adsorption on kaolinite: pH, metal cations and humic acid effects.

PubMed

Zhao, Yanping; Geng, Jinju; Wang, Xiaorong; Gu, Xueyuan; Gao, Shixiang

2011-07-01

Contamination of environmental matrixes by human and animal wastes containing antibiotics is a growing health concern. Because tetracycline is one of the most widely-used antibiotics in the world, it is important to understand the factors that influence its mobility in soils. This study investigated the effects of pH, background electrolyte cations (Li(+), Na(+), K(+), Ca(2+) and Mg(2+)), heavy metal Cu(2+) and humic acid (HA) on tetracycline adsorption onto kaolinite. Results showed that tetracycline was greatly adsorbed by kaolinite over pH 3-6, then decreased with the increase of pH, indicating that tetracycline adsorption mainly through ion exchange of cations species and complexation of zwitterions species. In the presence of five types of cations (Li(+), Na(+), K(+), Ca(2+) and Mg(2+)), tetracycline adsorption decreased in accordance with the increasing of atomic radius and valence of metal cations, which suggested that outer-sphere complexes formed between tetracycline and kaolinite, and the existence of competitor ions lead to the decreasing adsorption. The presence of Cu(2+) greatly enhanced the adsorption probably by acting as a bridge ion between tetracycline species and the edge sites of kaolinite. HA also showed a major effect on the adsorption: at pH < 6, the presence of HA increased the adsorption, while the addition of HA showed little effect on tetracycline adsorption at higher pH. The soil environmental conditions, like pH, metal cations and soil organic matter, strongly influence the adsorption behavior of tetracycline onto kaolinite and need to be considered when assessing the environmental toxicity of tetracycline.

Cation-induced folding of alginate-bearing bilayer gels: an unusual example of spontaneous folding along the long axis.

PubMed

Athas, Jasmin C; Nguyen, Catherine P; Kummar, Shailaa; Raghavan, Srinivasa R

2018-04-04

The spontaneous folding of flat gel films into tubes is an interesting example of self-assembly. Typically, a rectangular film folds along its short axis when forming a tube; folding along the long axis has been seen only in rare instances when the film is constrained. Here, we report a case where the same free-swelling gel film folds along either its long or short axis depending on the concentration of a solute. Our gels are sandwiches (bilayers) of two layers: a passive layer of cross-linked N,N'-dimethylyacrylamide (DMAA) and an active layer of cross-linked DMAA that also contains chains of the biopolymer alginate. Multivalent cations like Ca2+ and Cu2+ induce these bilayer gels to fold into tubes. The folding occurs instantly when a flat film of the gel is introduced into a solution of these cations. The likely cause for folding is that the active layer stiffens and shrinks (because the alginate chains in it get cross-linked by the cations) whereas the passive layer is unaffected. The resulting mismatch in swelling degree between the two layers creates internal stresses that drive folding. Cations that are incapable of cross-linking alginate, such as Na+ and Mg2+, do not induce gel folding. Moreover, the striking aspect is the direction of folding. When the Ca2+ concentration is high (100 mM or higher), the gels fold along their long axis, whereas when the Ca2+ concentration is low (40 to 80 mM), the gels fold along their short axis. We hypothesize that the folding axis is dictated by the inhomogeneous nature of alginate-cation cross-linking, i.e., that the edges get cross-linked before the faces of the gel. At high Ca2+ concentration, the stiffer edges constrain the folding; in turn, the gel folds such that the longer edges are deformed less, which explains the folding along the long axis. At low Ca2+ concentration, the edges and the faces of the gel are more similar in their degree of cross-linking; therefore, the gel folds along its short axis. An analogy can be made to natural structures (such as leaves and seed pods) where stiff elements provide the directionality for folding.

Sequestration of Sr(II) By Calcium Oxalate - a Batch Uptake Study And EXAFS Analysis of Model Compounds And Reaction Products

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

Singer, D.M.; Johnson, S.B.; Catalano, J.G.

Calcium oxalate monohydrate (CaC{sub 2}O{sub 4}{center_dot}H{sub 2}O -- abbreviated as CaOx) is produced by two-thirds of all plant families, comprising up to 80 wt.% of the plant tissue and found in many surface environments. It is unclear, however, how CaOx in plants and soils interacts with metal ions and possibly sequesters them. This study examines the speciation of Sr(II){sub aq} following its reaction with CaOx. Batch uptake experiments were conducted over the pH range 4--10, with initial Sr solution concentrations, [Sr]{sub aq}, ranging from 1 x 10{sup -4} to 1 x 10{sup -3} M and ionic strengths ranging of 0.001--0.1more » M, using NaCl as the background electrolyte. Experimental results indicate that Sr uptake is independent of pH and ionic strength over these ranges. After exposure of CaOx to Sr{sub aq} for two days, the solution Ca concentration, [Ca]{sup aq}, increased for all samples relative to the control CaOx suspension (with no Sr added). The amount of Sr{sub aq} removed from solution was nearly equal to the total [Ca]{sup aq} after exposure of CaOx to Sr. These results suggest that nearly 90% of the Sr is removed from solution to a solid phase as Ca is released into solution. We suggest that the other 10% is sequestered through surface adsorption on a solid phase, although we have no direct evidence for this. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the molecular-level speciation of Sr in the reaction products. Deconvolutions of the Sr K-edge EXAFS spectra were performed to identify multi-electron excitation (MEE) features. MEE effects were found to give rise to low-frequency peaks in the Fourier transform before the first shell of oxygen atoms and do not affect EXAFS fitting results. Because of potential problems caused by asymmetric distributions of Sr-O distances when fitting Sr K-edge EXAFS data using the standard harmonic model, we also employed a cumulant expansion model and an asymmetric analytical model to account for anharmonic effects in the EXAFS data. For Sr-bearing phases with low to moderate first-shell (Sr-O pair correlation) anharmonicity, the cumulant expansion model is sufficient for EXAFS fitting; however, for higher degrees of anharmonicity, an analytical model is required. Based on batch uptake results and EXAFS analyses of reaction products, we conclude that Sr is dominantly sequestered by a solid phase at the CaOx surface, likely the result of a dissolution-reprecipitation mechanism, to form SrC{sub 2}O{sub 4} of mixed hydration state (i.e. SrO{sub x}{center_dot}nH{sub 2}O, where n = 0, 1, or 2). Surprisingly, no spectroscopic or XRD evidence was found for a (Sr,Ca)Ox solid solution or for a separate SrCO3 phase. In addition, we found no evidence for Sr(II) inner-sphere sorption complexes on CaOx surfaces based on lack of Sr-Ca second-neighbor pair correlations in the EXAFS spectra, although some type of Sr(II) surface complex (perhaps a type B Sr-oxalate ternary complex or an outer-sphere Sr(II) complex) or some as yet undetected Sr-bearing solid phases are needed to account for approximately 10% of Sr uptake by CaOx. The formation of a hydrated SrOx phase in environments under conditions similar to those of our experiments should retard Sr mobility and could be a significant factor in the biogeochemical cycling of Sr in soils and sediments or in plants and plant litter where CaOx is present.« less

Hierarchy effect on electronic structure and core-to-valence transitions in bone tissue: perspectives in medical nanodiagnostics of mineralized bone

NASA Astrophysics Data System (ADS)

Samoilenko, Dmitrii O.; Avrunin, Alexander S.; Pavlychev, Andrey A.

2017-06-01

Electronic structure and core-to-valence transitions in bone tissue are examined in the framework of the morphological 3DSL model that takes into account (i) structural and functional organization of the skeleton in the normal and pathological conditions and (ii) peculiarities of electron wave propagation in a three-dimensional superlattice of "black-nanocrystallites-in-muddy-waters". Our focus is on the HAP-to-bone red shifts of core-to-valence transitions near Ca and P 2p and O 1s edges in single-crystal hydroxyapatite (HAP) Ca10(PO4)6(OH)2. The origin of the HAP-to-bone shift is discussed and the extended comparative analysis of the experimental data is performed. The detected spectral shift is assigned with the effect of hierarchical organization of bone tissue. This hierarchy effect on the core-to-valence transition energies is regarded as a promising tool for medical imaging and perspective pathway for nanodiagnostics of mineralized bone. Contribution to the Topical Issue "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

Gallium(III) adsorption on carbonates and oxides: X-ray absorption fine structure spectroscopy study and surface complexation modeling.

PubMed

Pokrovsky, O S; Pokrovski, G S; Schott, J

2004-11-15

Adsorption of Ga on calcite, magnesite, amorphous silica, and manganese oxide as a function of pH and gallium concentration in solution was studied using a batch adsorption technique. Adsorbed complexes of Ga on calcite, magnesite, and delta-MnO2 were further characterized using XAFS spectroscopy. At high surface loadings from supersaturated solutions, Ga is likely to form a polymeric network at the surface (edge- and corner-sharing octahedra). At low surface loadings, Ga presents as isolated octahedra, probably attached to the Me-O sites on the surface, and coordinated by water molecules and hydroxide groups at 1.90-1.94 A. At pH>6, Ga therefore changes its coordination from 4 to 6 when adsorbing from solution (Ga(OH)(-)4(aq)) onto metal surface sites (MeOGa(OH)n(H2O)2-n(5-n), Me = Ca, Mg, or Mn, and n=1 and 2 for carbonate minerals and MnO2, respectively). Because the EXAFS is not capable of seeing hydrogen atoms, the protonation of surface complexes was determined by fitting the experimental pH-dependent Ga adsorption edge. A surface complexation model which assumes the constant capacitance of the electric double layer (CCM) and postulates the formation of positively charged, neutral and negatively charged surface complexes for carbonates, manganese oxide and silica, respectively, was used to describe the dependence of adsorption equilibria on aqueous solution composition in a wide range of pH and Ga concentration.

Zinc speciation in mining and smelter contaminated overbank sediments by EXAFS spectroscopy

NASA Astrophysics Data System (ADS)

Van Damme, An; Degryse, Fien; Smolders, Erik; Sarret, Géraldine; Dewit, Julie; Swennen, Rudy; Manceau, Alain

2010-07-01

Overbank sediments contaminated with metalliferous minerals are a source of toxic metals that pose risks to living organisms. The overbank sediments from the Geul river in Belgium contain 4000-69,000 mg/kg Zn as a result of mining and smelting activities, principally during the 19th century. Three main Zn species were identified by powder Zn K-edge EXAFS spectroscopy: smithsonite (ZnCO 3), tetrahedrally coordinated sorbed Zn (sorbed IVZn) and Zn-containing trioctahedral phyllosilicate. Smithsonite is a primary mineral, which accounts for approximately 20-60% of the Zn in sediments affected by mining and smelting of oxidized Zn ores (mostly carbonates and silicates). This species is almost absent in sediments affected by mining and smelting of both sulphidic (ZnS, PbS) and oxidized ores, presumably because of acidic dissolution associated with the oxidation of sulphides, as suggested by the lower pH of this second type of sediment (pH(CaCl 2) <7.0 vs. pH(CaCl 2) >7.0 for the first type). Thus, sulphide minerals in sediment deposits can act as a secondary source of dissolved metals by a chemical process analogous to acid mine drainage. The sorbed IVZn component ranges up to approximately 30%, with the highest proportion occurring at pH(CaCl 2) <7.0 as a result of the readsorption of dissolved Zn 2+ on sediments constituents. Kerolite-like Zn-rich phyllosilicate is the major secondary species in all samples, and in some the only detected species, thus providing the first evidence for pervasive sequestration of Zn into this newly formed precipitate at the field scale.

High-level ab initio calculations for the four low-lying families of minima of (H2O)(20): 1. Estimates of MP2/CBS binding energies and comparison with empirical potentials

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

Fanourgakis, Georgios S.; Apra, Edoardo; Xantheas, Sotiris S.

2004-08-08

We report estimates of complete basis set (CBS) limits at the second-order Møller-Plesset perturbation level of theory (MP2) for the binding energies of the lowest lying isomers within each of the four major families of minima of (H2O)20. These were obtained by performing MP2 calculations with the family of correlation-consistent basis sets up to quadruple zeta quality, augmented with additional diffuse functions (aug-cc-pVnZ, n=D, T, Q). The MP2/CBS estimates are: -200.1 kcal/mol (dodecahedron, 30 hydrogen bonds), -212.6 kcal/mol (fused cubes, 36 hydrogen bonds), -215.0 (face-sharing pentagonal prisms, 35 hydrogen bonds) and –217.9 kcal/mol (edge-sharing pentagonal prisms, 34 hydrogen bonds). Themore » energetic ordering of the various (H2O)20 isomers does not follow monotonically the number of hydrogen bonds as in the case of smaller clusters such as the different isomers of the water hexamer. The dodecahedron lies ca. 18 kcal/mol higher in energy than the most stable edge-sharing pentagonal prism isomer. The TIP4P, ASP-W4, TTM2-R, AMOEBA and TTM2-F empirical potentials also predict the energetic stabilization of the edge-sharing pentagonal prisms with respect to the dodecahedron, albeit they universally underestimate the cluster binding energies with respect to the MP2/CBS result. Among them, the TTM2-F potential was found to predict the absolute cluster binding energies to within < 1% from the corresponding MP2/CBS values, whereas the error for the rest of the potentials considered in this study ranges from 3-5%.« less

Use of X-ray absorption near edge structure (XANES) to identify physisorption and chemisorption of phosphate onto ferrihydrite-modified diatomite.

PubMed

Xiong, Wenhui; Peng, Jian; Hu, Yongfeng

2012-02-15

This paper presents a novel technique integrating bulk-sensitive and surface-sensitive XANES methods to distinguish between physisorption and chemisorption for phosphate adsorption onto ferrihydrite-modified diatomite (FHMD). XANES P K-edge, L-edge, and Fe M-edge spectra were obtained for reference samples (K(2)HPO(4) and FePO(4)·2H(2)O) and test samples (phosphate adsorbed onto FHMD (FHMD-Ps) and Si-containing ferrihydrite (FHYD-Ps)). A resolvable pre-edge peak in the P K-edge spectra of FHMD-Ps and FHYD-Ps provided direct evidence for the formation of P-O-Fe(III) coordination and the occurrence of chemisorption. The resemblance between the P L-edge spectra of K(2)HPO(4) and FHMD-Ps and the marked difference between the spectra of FHMD-Ps and FePO(4)·2H(2)O indicated the intact existence of the adsorbate and the adsorbent. The similarity between Fe M-edge spectra of FHMD and FHMD-Ps and the difference between the spectra of FHMD-Ps and FePO(4)·2H(2)O confirmed the findings from P L-edge analyses. Therefore, chemisorption and physisorption coexisted during phosphate adsorption onto FHMD. Phosphate chemisorption occurred in the deeper zone of FHMD (from 50 nm to 5 μm); whereas physisorption occurred in the zone of FHMD shallower than 50 nm since the probing depth of XANES P K-edge method is 5 μm and that of P L-edge and Fe M-edge methods is 50 nm. Copyright © 2011 Elsevier Inc. All rights reserved.

Effect of experimental variables onto Co(2+) and Sr(2+) sorption behavior in red mud-water suspensions.

PubMed

Milenković, Aleksandra S; Smičiklas, Ivana D; Šljivić-Ivanović, Marija Z; Živković, Ljiljana S; Vukelić, Nikola S

2016-07-02

The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.

Amorphous manganese-calcium oxides as a possible evolutionary origin for the CaMn₄ cluster in photosystem II.

PubMed

Najafpour, Mohammad Mahdi

2011-06-01

In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn(3+) in a distorted octahedral environment and eight-coordinate Ca(2+) centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn₂O₄), pyrolusite (MnO₂) and compared with hollandite (Ba(0.2)Ca(0.15)K(0.3)Mn(6.9)Al(0.2)Si(0.3)O(16)), hausmannite (Mn₃O₄), Mn₂O₃.H₂O, Ca Mn₃O₆.H₂O, CaMn₄O₈.H₂O, CaMn₂O₄.H₂O and synthetic marokite (CaMn₂O₄). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II.

Contribution of elevated intracellular calcium to pulmonary arterial myocyte alkalinization during chronic hypoxia

PubMed Central

Luke, Trevor; Shimoda, Larissa A.

2016-01-01

Abstract In the lung, exposure to chronic hypoxia (CH) causes pulmonary hypertension, a debilitating disease. Development of this condition arises from increased muscularity and contraction of pulmonary vessels, associated with increases in pulmonary arterial smooth muscle cell (PASMC) intracellular pH (pHi) and Ca2+ concentration ([Ca2+]i). In this study, we explored the interaction between pHi and [Ca2+]i in PASMCs from rats exposed to normoxia or CH (3 weeks, 10% O2). PASMC pHi and [Ca2+]i were measured with fluorescent microscopy and the dyes BCECF and Fura-2. Both pHi and [Ca2+]i levels were elevated in PASMCs from hypoxic rats. Exposure to KCl increased [Ca2+]i and pHi to a similar extent in normoxic and hypoxic PASMCs. Conversely, removal of extracellular Ca2+ or blockade of Ca2+ entry with NiCl2 or SKF 96365 decreased [Ca2+]i and pHi only in hypoxic cells. Neither increasing pHi with NH4Cl nor decreasing pHi by removal of bicarbonate impacted PASMC [Ca2+]i. We also examined the roles of Na+/Ca2+ exchange (NCX) and Na+/H+ exchange (NHE) in mediating the elevated basal [Ca2+]i and Ca2+-dependent changes in PASMC pHi. Bepridil, dichlorobenzamil, and KB-R7943, which are NCX inhibitors, decreased resting [Ca2+]i and pHi only in hypoxic PASMCs and blocked the changes in pHi induced by altering [Ca2+]i. Exposure to ethyl isopropyl amiloride, an NHE inhibitor, decreased resting pHi and prevented changes in pHi due to changing [Ca2+]i. Our findings indicate that, during CH, the elevation in basal [Ca2+]i may contribute to the alkaline shift in pHi in PASMCs, likely via mechanisms involving reverse-mode NCX and NHE. PMID:27076907

Defect-induced wetting on BaF 2(111) and CaF 2(111) at ambient conditions

NASA Astrophysics Data System (ADS)

Cardellach, M.; Verdaguer, A.; Fraxedas, J.

2011-12-01

The interaction of water with freshly cleaved (111) surfaces of isostructural BaF2 and CaF2 single crystals at ambient conditions (room temperature and under controlled humidity) has been studied using scanning force microscopy in different operation modes and optical microscopy. Such surfaces exhibit contrasting behaviors for both materials: while on BaF2(111) two-dimensional water layers are formed after accumulation at step edges, CaF2(111) does not promote the formation of such layers. We attribute such opposed behavior to lattice match (mismatch) between hexagonal water ice and the hexagonal (111) surfaces of BaF2(CaF2). Optical microscope images reveal that this behavior also determines the way the surfaces become wetted at a macroscopic level.

Epidermal keratinocyte polarity and motility require Ca2+ influx through TRPV1

PubMed Central

Graham, David M.; Huang, Ling; Robinson, Kenneth R.; Messerli, Mark A.

2013-01-01

Summary Ca2+ has long been known to play an important role in cellular polarity and guidance. We studied the role of Ca2+ signaling during random and directed cell migration to better understand whether Ca2+ directs cell motility from the leading edge and which ion channels are involved in this function by using primary zebrafish keratinocytes. Rapid line-scan and time-lapse imaging of intracellular Ca2+ (Ca2+i) during migration and automated image alignment enabled us to characterize and map the spatiotemporal changes in Ca2+i. We show that asymmetric distributions of lamellipodial Ca2+ sparks are encoded in frequency, not amplitude, and that they correlate with cellular rotation during migration. Directed migration during galvanotaxis increases the frequency of Ca2+ sparks over the entire lamellipod; however, these events do not give rise to asymmetric Ca2+i signals that correlate with turning. We demonstrate that Ca2+-permeable channels within these cells are mechanically activated and include several transient receptor potential family members, including TRPV1. Last, we demonstrate that cell motility and Ca2+i activity are affected by pharmacological agents that target TRPV1, indicating a novel role for this channel during cell migration. PMID:23943873

Ca K-Edge XAS as a Probe of Calcium Centers in Complex Systems

DOE PAGES

Martin-Diaconescu, Vlad; Gennari, Marcello; Gerey, Bertrand; ...

2014-12-10

Calcium K-edge pre-edges coupled with TD-DFT theoretical calculation of spectra provide a powerful approach for the characterization of complex calcium centers in inorganic and bioinorganic chemistry. Herein, Ca K-edge X-ray absorption spectroscopy (XAS) is developed as a means to characterize the local environment of calcium centers. The spectra for six, seven, and eight coordinate inorganic and molecular calcium complexes were analyzed and determined to be primarily influenced by the coordination environment and site symmetry at the calcium center. The experimental results are closely correlated to time-dependent density functional theory (TD-DFT) calculations of the XAS spectra. The applicability of this methodologymore » to complex systems was investigated using structural mimics of the oxygen-evolving complex (OEC) of PSII. It was found that Ca K-edge XAS is a sensitive probe for structural changes occurring in the cubane heterometallic cluster due to Mn oxidation. Future applications to the OEC are discussed.« less

Functional characterization of P2Y1 versus P2X receptors in RBA-2 astrocytes: elucidate the roles of ATP release and protein kinase C.

PubMed

Weng, Ju-Yun; Hsu, Tsan-Ting; Sun, Synthia H

2008-05-15

A physiological concentration of extracellular ATP stimulated biphasic Ca(2+) signal, and the Ca(2+) transient was decreased and the Ca(2+) sustain was eliminated immediately after removal of ATP and Ca(2+) in RBA-2 astrocytes. Reintroduction of Ca(2+) induced Ca(2+) sustain. Stimulation of P2Y(1) receptors with 2-methylthioadenosine 5'-diphosphate (2MeSADP) also induced a biphasic Ca(2+) signaling and the Ca(2+) sustains were eliminated using Ca(2+)-free buffer. The 2MeSADP-mediated biphasic Ca(2+) signals were inhibited by phospholipase C (PLC) inhibitor U73122, and completely blocked by P2Y(1) selective antagonist MRS2179 and protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) whereas enhanced by PKC inhibitors GF109203X and Go6979. Inhibition of capacitative Ca(2+) entry (CCE) decreased the Ca(2+)-induced Ca(2+) entry; nevertheless, ATP further enhanced the Ca(2+)-induced Ca(2+) entry in the intracellular Ca(2+) store-emptied and CCE-inhibited cells indicating that ATP stimulated Ca(2+) entry via CCE and ionotropic P2X receptors. Furthermore, the 2MeSADP-induced Ca(2+) sustain was eliminated by apyrase but potentiated by P2X(4) allosteric effector ivermectin (IVM). The agonist ADPbetaS stimulated a lesser P2Y(1)-mediated Ca(2+) signal and caused a two-fold increase in ATP release but that were not affected by IVM whereas inhibited by PMA, PLC inhibitor ET-18-OCH(3) and phospholipase D (PLD) inhibitor D609, and enhanced by removal of intra- or extracellular Ca(2+). Taken together, the P2Y(1)-mediated Ca(2+) sustain was at least in part via P2X receptors activated by the P2Y(1)-induced ATP release, and PKC played a pivotal role in desensitization of P2Y(1) receptors in RBA-2 astrocytes. Copyright 2007 Wiley-Liss, Inc.

Stimulatory effect of calcium on metabolism and its sensitivity to pH in kidney mitochondria.

PubMed

Drewnowska, K; Schoolwerth, A C

1994-07-01

The relationship between mitochondrial matrix free Ca2+ concentration ([Ca2+]m) and pH was evaluated by incubating isolated rat kidney mitochondria with different extramitochondrial Ca2+ concentrations ([Ca2+]e) at medium pH (pHe) 7.0 and 7.4. [Ca2+]m was monitored using the fluorescent signal from mitochondria loaded with the Ca2+ indicator fura 2. The changes in [Ca2+]m were compared with alpha-ketoglutarate dehydrogenase (alpha-KGDH) flux, measured as O2 consumption (nmol.min-1.mg protein-1) from 185 microM alpha-ketoglutarate (alpha-KG). The apparent dissociation constant of the matrix fluorescent probe for Ca2+ was determined in each experiment and was 323 +/- 45 nM (n = 14). When mitochondria were exposed to [Ca2+]e below 160 nM, [Ca2+]m was greater at pHe 7.0 than at pHe 7.4. However, above 160 nM [Ca2+]e, [Ca2+]m plateaued at pHe 7.0 but rose progressively at pHe 7.4. Increasing [Ca2+]m by consecutive additions of Ca2+ to the medium had a significantly more pronounced acceleratory effect on alpha-KG oxidation at pHe 7.0 than at pHe 7.4. Kinetic analysis of alpha-KGDH revealed a 45% decrease in the Michaelis constant (Km) for alpha-KG at pHe 7.0, but the Km was unchanged at pHe 7.4 with elevation of [Ca2+]m from 32 to 751 nM. Maximal velocity (Vmax) increased significantly at both pHe values. Half-maximal alpha-KG oxidation occurred at [Ca2+]m of 76 +/- 11 nM and 105 +/- 31 nM at pHe 7.0 and 7.4, respectively. These studies demonstrate a direct, pH-sensitive correlation between [Ca2+]e and [Ca2+]m; [Ca2+]m changed over a range that may regulate alpha-KGDH flux in intact kidney mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)

Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers

PubMed Central

Kubin, Markus; Kern, Jan; Gul, Sheraz; Kroll, Thomas; Chatterjee, Ruchira; Löchel, Heike; Fuller, Franklin D.; Sierra, Raymond G.; Quevedo, Wilson; Weniger, Christian; Rehanek, Jens; Firsov, Anatoly; Laksmono, Hartawan; Weninger, Clemens; Alonso-Mori, Roberto; Nordlund, Dennis L.; Lassalle-Kaiser, Benedikt; Glownia, James M.; Krzywinski, Jacek; Moeller, Stefan; Turner, Joshua J.; Minitti, Michael P.; Dakovski, Georgi L.; Koroidov, Sergey; Kawde, Anurag; Kanady, Jacob S.; Tsui, Emily Y.; Suseno, Sandy; Han, Zhiji; Hill, Ethan; Taguchi, Taketo; Borovik, Andrew S.; Agapie, Theodor; Messinger, Johannes; Erko, Alexei; Föhlisch, Alexander; Bergmann, Uwe; Mitzner, Rolf; Yachandra, Vittal K.; Yano, Junko; Wernet, Philippe

2017-01-01

X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexes (Mn ∼ 6–15 mmol/l) with no visible effects of radiation damage. We also present the first L-edge absorption spectra of the oxygen evolving complex (Mn4CaO5) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions. PMID:28944255

Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers

DOE PAGES

Kubin, Markus; Kern, Jan; Gul, Sheraz; ...

2017-09-01

X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. But, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexesmore » (Mn ~ 6-15 mmol/l) with no visible effects of radiation damage. We then present the first L-edge absorption spectra of the oxygen evolving complex (Mn 4 CaO 5 ) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions.« less

Concave Urinary Crystallines: Direct Evidence of Calcium Oxalate Crystals Dissolution by Citrate In Vivo

PubMed Central

Shang, Yun-Feng; Xu, Meng; Zhang, Guang-Na; Ouyang, Jian-Ming

2013-01-01

The changes in urinary crystal properties in patients with calcium oxalate (CaOx) calculi after oral administration of potassium citrate (K3cit) were investigated via atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and zeta potential analyzer. The AFM and SEM results showed that the surface of urinary crystals became concave, the edges and corners of crystals became blunt, the average size of urinary crystallines decreased significantly, and aggregation of urinary crystals was reduced. These changes were attributed to the significant increase in concentration of excreted citrate to 492 ± 118 mg/L after K3cit intake from 289 ± 83 mg/L before K3cit intake. After the amount of urinary citrate was increased, it complexed with Ca2+ ions on urinary crystals, which dissolved these crystals. Thus, the appearance of concave urinary crystals was a direct evidence of CaOx dissolution by citrate in vivo. The XRD results showed that the quantities and species of urinary crystals decreased after K3cit intake. The mechanism of inhibition of formation of CaOx stones by K3cit was possibly due to the complexation of Ca2+ with citrate, increase in urine pH, concentration of urinary inhibitor glycosaminoglycans (GAGs), and the absolute value of zeta potential after K3cit intake. PMID:24363634

Montreal Cognitive Assessment (MoCA) screening mild cognitive impairment in patients with chronic kidney disease (CKD) pre-dialysis.

PubMed

Paraizo, Marilise de Andrade; Almeida, Ana Laura Maciel; Pires, Leopoldo Antônio; Abrita, Renata Silva Almeida; Crivellari, Mary Hellen Teixeira; Pereira, Beatriz Dos Santos; Fernandes, Natália Maria da Silva; Bastos, Marcus Gomes

2016-03-01

Individuals with chronic kidney disease (CKD) are at higher risk of developing cognitive impairment (CI), initially mild (MCI), potentially identifiable, but still poorly diagnosed and treated. The Montreal Cognitive Assessment (MoCA) has been indicated for MCI screening in CKD. To assess MCI in patients with CKD not yet on dialysis. Study conducted in 72 non-elderly subjects with pre-dialysis CKD. The neuropsychological assessment included: The global cognitive assessment test MoCA; the clock drawing (CD); the digit span forward (DSF) and reverse (DSR); phonemic verbal (VF) fluency (FAS) and semantics (animals); the fist-edge-palm (FEP); and the memory 10 pictures. The average age of the participants was 56.74 ± 7.63 years, with predominance of male sex (55.6%), mainly with ≥ 4 years of education (84.3%), with CKD cathegories 1, 2 and 3a and 3b (67.6%), hypertension (93.1%) and diabetes mellitus (52.1%). MCI (MoCA ≤ 24) was observed in 73.6% of the patients. We did not find association among MCI with demographic and clinical variables, but a tendency to association with age (p = 0.07), educational level (p= 0.06) and diabetes (0.06). The executive function tests CD, DS-reverse and FEP, individually were able to identify CI with good sensibility and negative predictive value compared to MoCA and together, showed the same capability to identify MCI when compared to MoCA. The MCI is common in non-elderly patients with CKD not yet on dialysis. Together, the CD, DSR and FEP showed similar performance in identify MCI in this population when compared to MoCA, suggesting impairment of executive functions.

Potentiation of inositol trisphosphate-induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

PubMed Central

Yao, Y; Parker, I

1992-01-01

1. The ability of cytosolic Ca2+ ions to modulate inositol 1,4,5-trisphosphate (Insp3)-induced Ca2+ liberation from intracellular stores was studied in Xenopus oocytes using light flash photolysis of caged InsP3. Changes in cytosolic free Ca2+ level were effected by inducing Ca2+ entry through ionophore and voltage-gated plasma membrane channels and by injection of Ca2+ through a micropipette. Their effects on Ca2+ liberation were monitored by video imaging of Fluo-3 fluorescence and by voltage clamp recording of Ca(2+)-activated membrane Cl- currents. 2. Treatment of oocytes with the Ca2+ ionophores A23187 and ionomycin caused a transient elevation of cytosolic Ca2+ level when cells were bathed in Ca(2+)-free solution, which probably arose because of release of Ca2+ from intracellular stores. 3. Membrane current and Fluo-3 Ca2+ signals evoked by photoreleased InsP3 in ionophore-treated oocytes were potentiated when the intracellular Ca2+ level was elevated by raising the Ca2+ level in the bathing solution. 4. Responses to photoreleased InsP3 were similarly potentiated following activation of Ca2+ entry through voltage-gated Ca2+ channels expressed in the plasma membrane. 5. Ca(2+)-activated membrane currents evoked by depolarization developed a delayed 'hump' component during sustained photorelease of InsP3, probably because Ca2+ ions entering through the membrane channels triggered liberation of Ca2+ from intracellular stores. 6. Ba2+ and Sr2+ ions were able to substitute for Ca2+ in potentiating InsP3-mediated Ca2+ liberation. 7. Gradual photorelease of InsP3 by weak photolysis light evoked Ca2+ liberation that began at particular foci and then propagated throughout, but not beyond that area of the oocyte exposed to the light. Local elevations of intracellular Ca2+ produced by microinjection of Ca2+ acted as new foci for the initiation of Ca2+ liberation by InsP3. 8. In resting oocytes, intracellular injections of Ca2+ resulted only in localized elevation of intracellular Ca2+, and did not evoke propagating waves. 9. The results show that cytosolic Ca2+ ions potentiate the ability of InsP3 to liberate Ca2+ from intracellular stores. This process may be important for the positive feedback mechanism underlying the generation of Ca2+ spikes and waves, and for interactions between the InsP3 pathway and Ca2+ ions entering cells through voltage- and ligand-gated channels. Images Fig. 5 PMID:1284567

From Quasicrystals to Crystals with Interpenetrating Icosahedra in Ca–Au–Al: In Situ Variable-Temperature Transformation

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

Pham, Joyce; Meng, Fanqiang; Lynn, Matthew J.

The irreversible transformation from an icosahedral quasicrystal (i-QC) CaAu 4.39Al 1.61 to its cubic 2/1 crystalline approximant (CA) Ca 13Au 56.31(3)Al 21.69 (CaAu 4.33(1)Al1.67, Pamore » $$\\bar{3}$$ (No. 205); Pearson symbol: cP728; a = 23.8934(4)), starting at ~570 °C and complete by ~650 °C, is discovered from in situ, high-energy, variable-temperature powder X-ray diffraction (PXRD), thereby providing direct experimental evidence for the relationship between QCs and their associated CAs. The new cubic phase crystallizes in a Tsai-type approximant structure under the broader classification of polar intermetallic compounds, in which atoms of different electronegativities, viz., electronegative Au + Al vs electropositive Ca, are arranged in concentric shells. From a structural chemical perspective, the outermost shell of this cubic approximant may be described as interpenetrating and edge-sharing icosahedra, a perspective that is obtained by splitting the traditional structural description of this shell as a 92-atom rhombic triacontahedron into an 80-vertex cage of primarily Au [Au 59.86(2)Al 17.14⟂ 3.00] and an icosahedral shell of only Al [Al 10.5⟂ 1.5]. Following the proposal that the cubic 2/1 CA approximates the structure of the i-QC and on the basis of the observed transformation, an atomic site analysis of the 2/1 CA, which shows a preference to maximize the number of heteroatomic Au–Al nearest neighbor contacts over homoatomic Al–Al contacts, implies a similar outcome for the i-QC structure. Analysis of the most intense reflections in the diffraction pattern of the cubic 2/1 CA that changed during the phase transformation shows correlations with icosahedral symmetry, and the stability of this cubic phase is assessed using valence electron counts. Finally, according to electronic structure calculations, a cubic 1/1 CA, “Ca 24Au 88Al 64” (CaAu 3.67Al 2.67) is proposed.« less

From Quasicrystals to Crystals with Interpenetrating Icosahedra in Ca–Au–Al: In Situ Variable-Temperature Transformation

DOE PAGES

Pham, Joyce; Meng, Fanqiang; Lynn, Matthew J.; ...

2017-12-29

The irreversible transformation from an icosahedral quasicrystal (i-QC) CaAu 4.39Al 1.61 to its cubic 2/1 crystalline approximant (CA) Ca 13Au 56.31(3)Al 21.69 (CaAu 4.33(1)Al1.67, Pamore » $$\\bar{3}$$ (No. 205); Pearson symbol: cP728; a = 23.8934(4)), starting at ~570 °C and complete by ~650 °C, is discovered from in situ, high-energy, variable-temperature powder X-ray diffraction (PXRD), thereby providing direct experimental evidence for the relationship between QCs and their associated CAs. The new cubic phase crystallizes in a Tsai-type approximant structure under the broader classification of polar intermetallic compounds, in which atoms of different electronegativities, viz., electronegative Au + Al vs electropositive Ca, are arranged in concentric shells. From a structural chemical perspective, the outermost shell of this cubic approximant may be described as interpenetrating and edge-sharing icosahedra, a perspective that is obtained by splitting the traditional structural description of this shell as a 92-atom rhombic triacontahedron into an 80-vertex cage of primarily Au [Au 59.86(2)Al 17.14⟂ 3.00] and an icosahedral shell of only Al [Al 10.5⟂ 1.5]. Following the proposal that the cubic 2/1 CA approximates the structure of the i-QC and on the basis of the observed transformation, an atomic site analysis of the 2/1 CA, which shows a preference to maximize the number of heteroatomic Au–Al nearest neighbor contacts over homoatomic Al–Al contacts, implies a similar outcome for the i-QC structure. Analysis of the most intense reflections in the diffraction pattern of the cubic 2/1 CA that changed during the phase transformation shows correlations with icosahedral symmetry, and the stability of this cubic phase is assessed using valence electron counts. Finally, according to electronic structure calculations, a cubic 1/1 CA, “Ca 24Au 88Al 64” (CaAu 3.67Al 2.67) is proposed.« less

Diadophis Puntatus Puntatus (Southern Ring-neck Snake) Predation

USGS Publications Warehouse

Gotte, Steve W.

2016-01-01

DIADOPHIS PUNCTATUS PUNCTATUS (Southern Ring-necked Snake). PREDATION. Here I present the first record of Buteo lineatus (Red-shouldered Hawk) predator on a Diadophis p. punctatus. At ca. 1100h on l2 February2 013,I observed a B. lineatus eating a katydid in Corkscrew Swamp Sanctuary (26.2730'N, 81.6079"W;WGS 84), Collier Co., Florida, USA. The hawk was in a Pond Cypress tree on the edge of a small prairie bordered on one side by a cypress swamp and by pine woodland on the other. Immediately upon consuming the katydid, the hawk flew to the ground ca. 1.5 m from an elevated boardwalk to grab an adult D. punctatus. It then flew with the snake in its talons to a branch 3 m high ca. l0 m from the boardwalk. The hawk stretched and otherwise manipulated the struggling snake (Fig.1) before consuming the still moving snake. Although snakes are a well-known component of B. lineatus diet (Clark1 987A. Field Guide to the Hawks of North America. Houghton Mifflin Co. Boston, Massachusetts 198 pp.), I found only one literature reference to Red-shouldered Hawks eating Ring-neck Snakes (Fisher 1893.Hawks and Owls of the United States in their Relation to Agriculture. U.S. Dept. Agric., Div Ornith. Mamm. Bull. 3). That specimen was from Canton, New York (taken 26 Oct IBBB) and would be a D. p. edwardisii (Northern Ring-necked Snake), while the snake reported on here is a Diadophis p. punctatus (USNM Herp Image 2847a -c). Based on evidence presented by Fontanella et al. (2008. Mol. Phylogenet Evol.46:1049-1070), D. p. edwardisii and D. p. punctatus are likely different species.

PLCζ Induced Ca2+ Oscillations in Mouse Eggs Involve a Positive Feedback Cycle of Ca2+ Induced InsP3 Formation From Cytoplasmic PIP2

PubMed Central

Sanders, Jessica R.; Ashley, Bethany; Moon, Anna; Woolley, Thomas E.; Swann, Karl

2018-01-01

Egg activation at fertilization in mammalian eggs is caused by a series of transient increases in the cytosolic free Ca2+ concentration, referred to as Ca2+ oscillations. It is widely accepted that these Ca2+ oscillations are initiated by a sperm derived phospholipase C isoform, PLCζ that hydrolyses its substrate PIP2 to produce the Ca2+ releasing messenger InsP3. However, it is not clear whether PLCζ induced InsP3 formation is periodic or monotonic, and whether the PIP2 source for generating InsP3 from PLCζ is in the plasma membrane or the cytoplasm. In this study we have uncaged InsP3 at different points of the Ca2+ oscillation cycle to show that PLCζ causes Ca2+ oscillations by a mechanism which requires Ca2+ induced InsP3 formation. In contrast, incubation in Sr2+ media, which also induces Ca2+ oscillations in mouse eggs, sensitizes InsP3-induced Ca2+ release. We also show that the cytosolic level Ca2+ is a key factor in setting the frequency of Ca2+ oscillations since low concentrations of the Ca2+ pump inhibitor, thapsigargin, accelerates the frequency of PLCζ induced Ca2+ oscillations in eggs, even in Ca2+ free media. Given that Ca2+ induced InsP3 formation causes a rapid wave during each Ca2+ rise, we use a mathematical model to show that InsP3 generation, and hence PLCζ's substate PIP2, has to be finely distributed throughout the egg cytoplasm. Evidence for PIP2 distribution in vesicles throughout the egg cytoplasm is provided with a rhodamine-peptide probe, PBP10. The apparent level of PIP2 in such vesicles could be reduced by incubating eggs in the drug propranolol which also reversibly inhibited PLCζ induced, but not Sr2+ induced, Ca2+ oscillations. These data suggest that the cytosolic Ca2+ level, rather than Ca2+ store content, is a key variable in setting the pace of PLCζ induced Ca2+ oscillations in eggs, and they imply that InsP3 oscillates in synchrony with Ca2+ oscillations. Furthermore, they support the hypothesis that PLCζ and sperm induced Ca2+ oscillations in eggs requires the hydrolysis of PIP2 from finely spaced cytoplasmic vesicles. PMID:29666796

Credit PSR. View looking north northeast (12°) across surface remains ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Credit PSR. View looking north northeast (12°) across surface remains of North Base swimming pool. The southeast edge of the pool appearing in the foreground may seem to be a sidewalk to the casual observer; the wavy inside edge of this walk matches the pool side visible in historic construction photos (See HAER photo CA-170-Q-2). The telephone pole in the midground of the view is inside the pool proper. Building 4312 (Liquid Oxygen Repair Facility) appears in left background, Building 4456 (Fire House No. 4) in middle background, and Building 4444 (Communications Building) in right background - Edwards Air Force Base, North Base, Swimming Pool, Second Street, Boron, Kern County, CA

Evidence of Multiple Sorption Modes in Layered Double Hydroxides Using Mo As Structural Probe.

PubMed

Ma, Bin; Fernandez-Martinez, Alejandro; Grangeon, Sylvain; Tournassat, Christophe; Findling, Nathaniel; Claret, Francis; Koishi, Ayumi; Marty, Nicolas C M; Tisserand, Delphine; Bureau, Sarah; Salas-Colera, Eduardo; Elkaïm, Erik; Marini, Carlo; Charlet, Laurent

2017-05-16

Layered double hydroxides (LDHs) have been considered as effective phases for the remediation of aquatic environments, to remove anionic contaminants mainly through anion exchange mechanisms. Here, a combination of batch isotherm experiments and X-ray techniques was used to examine molybdate (MoO 4 2- ) sorption mechanisms on CaAl LDHs with increasing loadings of molybdate. Advanced modeling of aqueous data shows that the sorption isotherm can be interpreted by three retention mechanisms, including two types of edge sites complexes, interlayer anion exchange, and CaMoO 4 precipitation. Meanwhile, Mo geometry evolves from tetrahedral to octahedral on the edge, and back to tetrahedral coordination at higher Mo loadings, indicated by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based X-ray diffraction, remarkably agreeing with the sorption isotherm. This detailed molecular view shows that different uptake mechanisms-edge sorption, interfacial dissolution-reprecipitation-are at play and control anion uptake under environmentally relevant conditions, which is contrast to the classical view of anion exchange as the primary retention mechanism. This work puts all these mechanisms in perspective, offering a new insight into the complex interplay of anion uptake mechanisms by LDH phases, by using changes in Mo geometry as powerful molecular-scale probe.

Bandgap behavior and singularity of the domain-induced light scattering through the pressure-induced ferroelectric transition in relaxor ferroelectric AxBa1-xNb2O6 (A: Sr,Ca)

NASA Astrophysics Data System (ADS)

Ruiz-Fuertes, J.; Gomis, O.; Segura, A.; Bettinelli, M.; Burianek, M.; Mühlberg, M.

2018-01-01

In this letter, we have investigated the electronic structure of AxBa1-xNb2O6 relaxor ferroelectrics on the basis of optical absorption spectroscopy in unpoled single crystals with A = Sr and Ca under high pressure. The direct character of the fundamental transition could be established by fitting Urbach's rule to the photon energy dependence of the absorption edge yielding bandgaps of 3.44(1) eV and 3.57(1) eV for A = Sr and Ca, respectively. The light scattering by ferroelectric domains in the pre-edge spectral range has been studied as a function of composition and pressure. After confirming with x-ray diffraction the occurrence of the previously observed ferroelectric to paraelelectric phase transition at 4 GPa, the light scattering produced by micro- and nano-ferroelectric domains at 3.3 eV in Ca0.28Ba0.72Nb2O6 has been probed. The direct bandgap remains virtually constant under compression with a drop of only 0.01 eV around the phase transition. Interestingly, we have also found that light scattering by the polar nanoregions in the paraelectric phase is comparable to the dispersion due to ferroelectric microdomains in the ferroelectric state. Finally, we have obtained that the bulk modulus of the ferroelectric phase of Ca0.28Ba0.72Nb2O6 is B0 = 222(9) GPa.

Monitoring of peri-distal gastrectomy carbohydrate antigen 19-9 level in gastric juice and its significance

PubMed Central

Xu, A-Man; Huang, Lei; Han, Wen-Xiu; Wei, Zhi-Jian

2014-01-01

Gastric carcinoma is one of the most common and deadly malignancies nowadays, and carbohydrate antigen 19-9 (CA 19-9) in gastric juice has been rarely studied. To compare peri-distal gastrectomy (DG) gastric juice and serum CA 19-9 and reveal its significance, we selected 67 patients diagnosed with gastric carcinoma who underwent DG, and collected their perioperative gastric juice whose CA 19-9 was detected, with serum CA 19-9 monitored as a comparison. We found that: gastric juice CA 19-9 pre-gastrectomy was significantly correlated with tumor TNM classification, regarding tumor size, level of gastric wall invaded, differentiated grade and number of metastatic lymph nodes as influencing factors, while serum CA 19-9 revealed little information; gastric juice CA 19-9 was significantly correlated with radical degree, and regarded number of resected lymph nodes and classification of cutting edge as impact factors; thirteen patients whose gastric juice CA 19-9 rose post-DG showed features indicating poor prognosis; the difference of gastric juice CA 19-9 between pre- and post-gastrectomy was correlated with tumor TNM classification and radical degree, and regarded tumor size, number of resected metastatic and normal lymph nodes, sum of distances from tumor to cutting edges and classification of cutting edge as influential factors. We conclude that peri-DG gastric juice CA 19-9 reveals much information about tumor and radical gastrectomy, and may indicate prognosis; while serum CA 19-9 has limited significance. PMID:24482710

ScMO(BO3) (M = Ca and Cd): new Sc-based oxyborates featuring interesting edge-sharing sandwich-like chains and UV cut-off edges.

PubMed

Ma, Ruru; Xu, Dongdong; Yang, Yun; Su, Xin; Lei, Binghua; Yang, Zhihua; Pan, Shilie

2017-11-07

Two new isostructural rare-earth oxyborates ScMO(BO 3 ) (M = Ca and Cd) with a three-dimensional (3D) cationic framework and parallel arranged [BO 3 ] triangles have been synthesized by the flux method. In the 3D cationic framework, an interesting sandwich-like basic building unit (BBU) is constructed by two [Ca(1)O 4 ] 6- chains and two [Sc(1)O 4 ] 5- chains. ScMO(BO 3 ) melt incongruently, which shows that title compounds can be grown by the flux method. The UV cut-off edges for ScCaO(BO 3 ) and ScCdO(BO 3 ) are 230 and 249 nm, respectively. In addition, the first-principles calculations are performed to gain further insights into the relationship between the microscopic electronic structures and associated optical properties.

Spin and orbital states in single-layered La2-xCaxCoO4 studied by doping- and temperature-dependent near-edge x-ray absorption fine structure

NASA Astrophysics Data System (ADS)

Merz, M.; Fuchs, D.; Assmann, A.; Uebe, S.; v. Löhneysen, H.; Nagel, P.; Schuppler, S.

2011-07-01

The doping-dependent valence, orbital, and spin-state configurations of single-layered La2-xCaxCoO4 (x=0, 0.5, 1, and 1.5) were investigated with temperature-dependent near-edge x-ray absorption fine structure at the Co L2,3 and O K edges. The spectra show that in La2CoO4, the superexchange between neighboring Co2+ HS states is responsible for the strong antiferromagnetism. With increasing hole doping, the superexchange interactions between Co2+ HS ions are rapidly reduced by interlaced nonmagnetic Co3+ LS. For La1.5Ca0.5CoO4, the low Néel temperature of the samples together with the 50% Co2+ HS and 50% Co3+ LS configuration suggests a checkerboard arrangement of these ions. The spin blockade resulting from this arrangement naturally explains the high resistivity of La1.5Ca0.5CoO4. Upon further doping, Co2+ HS ions are replaced by Co3+ HS, and for LaCaCoO4 a mixture of Co3+ LS and Co3+ HS occurs. Superexchange via configuration fluctuation processes between these two species seems to induce long-range ferromagnetism, while the superexchange between adjacent Co3+ HS neighbors may lead to a competing antiferromagnetic exchange. For a doping content beyond x=1, Co4+ HS is introduced to the system at the expense of Co3+ LS, and a t2g double exchange between Co3+ HS and Co4+ HS is established, which further enhances ferromagnetic interactions and reduces resistivity. No indications for a Co3+ IS state are found throughout the La2-xCaxCoO4 doping series.

Io's Sodium Cloud (Green-yellow Filter)

NASA Technical Reports Server (NTRS)

1997-01-01

This image of Jupiter's moon Io and its surrounding sky is shown in false color. North is at the top, and east is to the right. Most of Io's visible surface is in shadow, though one can see part of a white crescent on its western side. This crescent is being illuminated mostly by 'Jupitershine' (i.e. sunlight reflected off Jupiter).

The striking burst of white light near Io's eastern equatorial edge is sunlight being scattered by the plume of the volcano Prometheus. Prometheus lies just beyond the visible edge of the moon on Io's far side. Its plume extends about 100 kilometers above the surface, and is being hit by sunlight just a little east of Io's eastern edge.

Scattered light from Prometheus' plume and Io's lit crescent also contribute to the diffuse yellowish emission which appears throughout much of the sky. However, much of this emission comes from Io's Sodium Cloud: sodium atoms within Io's extensive material halo are scattering sunlight at the yellow wavelength of about 589 nanometers.

This image was taken at 5 hours 30 minutes Universal Time on Nov. 9, 1996 through the green-yellow filter of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft. Galileo was then in Jupiter's shadow, and located about 2.3 million kilometers (about 32 Jovian radii) from both Jupiter and Io.

The Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA's Office of Space Science, Washington D.C. This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at: http://galileo.jpl.nasa.gov.

Model System Study of Environmentally Persistent Free Radicals Formation in a Semiconducting Polymer Modified Copper Clay System at Ambient Temperature

PubMed Central

Nwosu, Ugwumsinachi G.; Khachatryan, Lavrent; Youm, Sang Gil; Roy, Amitava; dela Cruz, Albert Leo N.; Nesterov, Evgueni E.; Dellinger, Barry; Cook, Robert L.

2016-01-01

This paper systematically investigates how environmentally persistent free radicals (EPFRs) are formed in a phenol contaminated model soil. Poly-p-phenylene (PPP) modified and copper-loaded montmorillonite (MMT) clays were developed and used as models of soil organic matter and the clay mineral component, respectively, with phenol being employed as a precursor pollutant. The polymer modification of the clays was carried out via surface-confined Kumada catalyst-transfer chain-growth polymerization. The presence and location of the polymer were confirmed by a combination of thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction data. EPFRs were formed by the Cu(II)-clay (Cu(II)CaMMT) and poly-p-phenylene-Cu(II)clay (PPP-Cu(II)CaMMT) composite systems under environmentally relevant conditions. The g-factor and concentration of EPFRs formed by the Cu(II)CaMMT and PPP-Cu(II)CaMMT systems were found to be 2.0034 and 1.22 × 1017 spins/g and 2.0033 and 1.58 × 1017spins/g, respectively. These g-factors are consistent with the formation of phenoxyl radicals. Extended X-Ray absorption fine structure (EXAFS) analysis shows that there are distinct differences in the local stuctures of the phenoxyl radicals associated with only the Cu(II) redox centers and those formed in the presences of the PPP polymer. X-ray absorption near edge spectroscopy (XANES) results provided evidence for the reduction of Cu(II) to Cu(I) in the EPFR forming process. The 1/e lifetimes of the formed EPFRs revealed a decay time of ~20 h for the Cu(II)CaMMT system and a two-step decay pattern for the PPP-Cu(II)CaMMT system with decay times of ~13.5 h and ~55.6 h. Finally, the generation of reactive oxygen species (hydroxyl radical; •OH) by these clay systems was also investigated, with higher concentrations of •OH detected for the phenol-dosed Cu(II)CaMMT and PPP-Cu(II)CaMMT systems, compared to the non-EPFR containing undosed PPP-Cu(II)CaMMT system. PMID:28670444

Kinetic Studies of Calcium-Induced Calcium Release in Cardiac Sarcoplasmic Reticulum Vesicles

PubMed Central

Sánchez, Gina; Hidalgo, Cecilia; Donoso, Paulina

2003-01-01

Fast Ca2+ release kinetics were measured in cardiac sarcoplasmic reticulum vesicles actively loaded with Ca2+. Release was induced in solutions containing 1.2 mM free ATP and variable free [Ca2+] and [Mg2+]. Release rate constants (k) were 10-fold higher at pCa 6 than at pCa 5 whereas Ryanodine binding was highest at pCa ≤5. These results suggest that channels respond differently when exposed to sudden [Ca2+] changes than when exposed to Ca2+ for longer periods. Vesicles with severalfold different luminal calcium contents exhibited double exponential release kinetics at pCa 6, suggesting that channels undergo time-dependent activity changes. Addition of Mg2+ produced a marked inhibition of release kinetics at pCa 6 (K0.5 = 63 μM) but not at pCa 5. Coexistence of calcium activation and inhibition sites with equally fast binding kinetics is proposed to explain this behavior. Thimerosal activated release kinetics at pCa 5 at all [Mg2+] tested and increased at pCa 6 the K0.5 for Mg2+ inhibition, from 63 μM to 136 μM. We discuss the possible relevance of these results, which suggest release through RyR2 channels is subject to fast regulation by Ca2+ and Mg2+ followed by time-dependent regulation, to the physiological mechanisms of cardiac channel opening and closing. PMID:12668440

Plasma-Filled Rod-Pinch Diode Research on Gamble II

DTIC Science & Technology

2007-06-01

by the dashed red line in Fig. 3. CaF2 thermoluminescent dosimeters ( TLDs ) located on the front surface of the rolled edge measure the dose. The...half-maximum line-spread function] and high dose [23 rad(CaF2) at 1 m] with 1-2 MeV electron energies are unique capabilities that the PFRP offers...for radiographic imaging in this electron -energy range. The source distribution has a narrow central peak that can enhance the spatial resolution

Solid energy calibration standards for P K-edge XANES: electronic structure analysis of PPh4Br.

PubMed

Blake, Anastasia V; Wei, Haochuan; Donahue, Courtney M; Lee, Kyounghoon; Keith, Jason M; Daly, Scott R

2018-03-01

P K-edge X-ray absorption near-edge structure (XANES) spectroscopy is a powerful method for analyzing the electronic structure of organic and inorganic phosphorus compounds. Like all XANES experiments, P K-edge XANES requires well defined and readily accessible calibration standards for energy referencing so that spectra collected at different beamlines or under different conditions can be compared. This is especially true for ligand K-edge X-ray absorption spectroscopy, which has well established energy calibration standards for Cl (Cs 2 CuCl 4 ) and S (Na 2 S 2 O 3 ·5H 2 O), but not neighboring P. This paper presents a review of common P K-edge XANES energy calibration standards and analysis of PPh 4 Br as a potential alternative. The P K-edge XANES region of commercially available PPh 4 Br revealed a single, highly resolved pre-edge feature with a maximum at 2146.96 eV. PPh 4 Br also showed no evidence of photodecomposition when repeatedly scanned over the course of several days. In contrast, we found that PPh 3 rapidly decomposes under identical conditions. Density functional theory calculations performed on PPh 3 and PPh 4 + revealed large differences in the molecular orbital energies that were ascribed to differences in the phosphorus oxidation state (III versus V) and molecular charge (neutral versus +1). Time-dependent density functional theory calculations corroborated the experimental data and allowed the spectral features to be assigned. The first pre-edge feature in the P K-edge XANES spectrum of PPh 4 Br was assigned to P 1s → P-C π* transitions, whereas those at higher energy were P 1s → P-C σ*. Overall, the analysis suggests that PPh 4 Br is an excellent alternative to other solid energy calibration standards commonly used in P K-edge XANES experiments.

Functional distribution of Ca2+-coupled P2 purinergic receptors among adrenergic and noradrenergic bovine adrenal chromaffin cells.

PubMed

Tomé, Angelo R; Castro, Enrique; Santos, Rosa M; Rosário, Luís M

2007-06-14

Adrenal chromaffin cells mediate acute responses to stress through the release of epinephrine. Chromaffin cell function is regulated by several receptors, present both in adrenergic (AD) and noradrenergic (NA) cells. Extracellular ATP exerts excitatory and inhibitory actions on chromaffin cells via ionotropic (P2X) and metabotropic (P2Y) receptors. We have taken advantage of the actions of the purinergic agonists ATP and UTP on cytosolic free Ca2+ concentration ([Ca2+]i) to determine whether P2X and P2Y receptors might be asymmetrically distributed among AD and NA chromaffin cells. The [Ca2+]i and the [Na+]i were recorded from immunolabeled bovine chromaffin cells by single-cell fluorescence imaging. Among the ATP-sensitive cells ~40% did not yield [Ca2+]i responses to ATP in the absence of extracellular Ca2+ (Ca2+o), indicating that they expressed P2X receptors and did not express Ca2+- mobilizing P2Y receptors; the remainder expressed Ca2+-mobilizing P2Y receptors. Relative to AD-cells approximately twice as many NA-cells expressed P2X receptors while not expressing Ca2+- mobilizing P2Y receptors, as indicated by the proportion of cells lacking [Ca2+]i responses and exhibiting [Na+]i responses to ATP in the absence and presence of Ca2+o, respectively. The density of P2X receptors in NA-cells appeared to be 30-50% larger, as suggested by comparing the average size of the [Na+]i and [Ca2+]i responses to ATP. Conversely, approximately twice as many AD-cells expressed Ca2+-mobilizing P2Y receptors, and they appeared to exhibit a higher (~20%) receptor density. UTP raised the [Ca2+]i in a fraction of the cells and did not raise the [Na+]i in any of the cells tested, confirming its specificity as a P2Y agonist. The cell density of UTP-sensitive P2Y receptors did not appear to vary among AD- and NA-cells. Although neither of the major purinoceptor types can be ascribed to a particular cell phenotype, P2X and Ca2+-mobilizing P2Y receptors are preferentially located to noradrenergic and adrenergic chromaffin cells, respectively. ATP might, in addition to an UTP-sensitive P2Y receptor, activate an UTP-insensitive P2Y receptor subtype. A model for a short-loop feedback interaction is presented whereby locally released ATP acts upon P2Y receptors in adrenergic cells, inhibiting Ca2+ influx and contributing to terminate evoked epinephrine secretion.

Computer Programs for Calculating Partially Cavitating Blunt Trailing Edged Cascade Flows in Nonlinear Theory.

DTIC Science & Technology

1980-01-01

I may $Vs ssauS@.. UNCLASSIFIED ’-X SINPIT CL6*41P-41 Iam Op THIS IAGr (Whom DAmOKo" UNCLASSIFIED -. j=U C%.A * CATO OIP I Thsa ,aOCett Di e Eee , 20...necessary only 6E13.6 if IFLAG = 1; SXSI(I), I =-1,6 correspond to b, c, f, A, a2 , and E . Values for SXSI(I) must be arbitrarily assumed and tried to...length ( = zc in Figure 1). 28 SXSI(I),I= 1,7 This card is necessary only 7F10.7 if IFLAG = 1; SXSI(I), I = 1, 7 correspond to b, c, f, A, o2’ a, and E . 0

Optical spectroscopy and band gap analysis of hybrid improper ferroelectric Ca3Ti2O7

NASA Astrophysics Data System (ADS)

Musfeldt, Janice; Cherian, Judy; Birol, Turan; Harms, Nathan; Gao, Bin; Cheong, Sang; Vanderbilt, David

We bring together optical absorption spectroscopy, photoconductivity, and first principles calculations to reveal the electronic structure of the room temperature ferroelectric Ca3Ti2O7. The 3.94 eV direct gap in Ca3Ti2O7 is charge transfer in nature and noticeably higher than that in CaTiO3 (3.4 eV), a finding that we attribute to dimensional confinement in the n = 2 member of the Ruddlesden-Popper series. While Sr substitution introduces disorder and broadens the gap edge slightly, oxygen deficiency reduces the gap to 3.7 eV and gives rise to a broad tail that persists to much lower energies. MSD, BES, U. S. DoE and DMREF, NSF.

Optical spectroscopy and band gap analysis of hybrid improper ferroelectric Ca{sub 3}Ti{sub 2}O{sub 7}

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

Cherian, Judy G.; Harms, Nathan C.; Birol, Turan

2016-06-27

We bring together optical absorption spectroscopy, photoconductivity, and first principles calculations to reveal the electronic structure of the room temperature ferroelectric Ca{sub 3}Ti{sub 2}O{sub 7}. The 3.94 eV direct gap in Ca{sub 3}Ti{sub 2}O{sub 7} is charge transfer in nature and noticeably higher than that in CaTiO{sub 3} (3.4 eV), a finding that we attribute to dimensional confinement in the n = 2 member of the Ruddlesden-Popper series. While Sr substitution introduces disorder and broadens the gap edge slightly, oxygen deficiency reduces the gap to 3.7 eV and gives rise to a broad tail that persists to much lower energies.

Sorption of Sr, Co and Zn on illite: Batch experiments and modelling including Co in-diffusion measurements on compacted samples

NASA Astrophysics Data System (ADS)

Montoya, V.; Baeyens, B.; Glaus, M. A.; Kupcik, T.; Marques Fernandes, M.; Van Laer, L.; Bruggeman, C.; Maes, N.; Schäfer, T.

2018-02-01

Experimental investigations on the uptake of divalent cations (Sr, Co and Zn) onto illite (Illite du Puy, Le-Puy-en-Velay, France) were carried out by three different international research groups (Institute for Nuclear Waste Disposal, KIT (Germany), Group Waste & Disposal, SCK-CEN, (Belgium) and Laboratory for Waste Management, PSI (Switzerland)) in the framework of the European FP7 CatClay project. The dependence of solid-liquid distribution ratios (Rd values) on pH at trace metal conditions (sorption edges) and on the metal ion concentration (sorption isotherms) was determined in dilute suspensions of homo-ionic Na-illite (Na-IdP) under controlled N2 atmosphere. The experimental results were modelled using the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) sorption model. The sorption of Sr depends strongly on ionic strength, while a rather weak pH dependence is observed in a pH range between 3 and 11. The data were modelled with cation exchange reactions, taking into account competition with H, K, Ca, Mg and Al, and surface complexation on weak amphotheric edge sites at higher pH values. The sorption of Co on Na-IdP, however, is strongly pH dependent. Cation exchange on the planar sites and surface complexation on strong and weak amphoteric edge sites were used to describe the Co sorption data. Rd values for Co derived from in-diffusion measurements on compacted Na-IdP samples (bulk-dry density of 1700 kg m-3) between pH 5.0 and 9.0 are in good agreement with the batch sorption data. The equivalence of both approaches to measure sorption was thus confirmed for the present test system. In addition, the results highlight the importance of both major and minor surface species for the diffusive transport behaviour of strongly sorbing metal cations. While surface complexes at the edge sites determine largely the Rd value, the diffusive flux may be governed by those species bound to the planar sites, even at low fractional occupancies. The pH dependent sorption determined for trace Zn concentrations showed large Rd values across the entire pH range with almost no dependence on the background electrolyte concentration. Additional sorption experiments carried out at substantial fractional Zn loadings demonstrated that the selectivity for the exchange of Na+ for Zn2+ at the planar sites could not explain the large Rd values measured at low pH and trace Zn concentrations. This suggests that another mechanism is ruling Zn uptake under these conditions.

Low pH overrides the need of calcium ions for the shape-function relationship of calmodulin: resolving prevailing debates.

PubMed

Pandey, Kalpana; Dhoke, Reema R; Rathore, Yogendra Singh; Nath, Samir K; Verma, Neha; Bawa, Simranjot; Ashish

2014-05-15

Calmodulin (CaM) regulates numerous cellular functions by sensing Ca(2+) levels inside cells. Although its structure as a function of the Ca(2+)-bound state remains hotly debated, no report is available on how pH independently or in interaction with Ca(2+) ions regulates shape and function of CaM. From SAXS data analysis of CaM at different levels of Ca(2+)-ion concentration and buffer pH, we found that (1) CaM molecules possess a Gaussian-chain-like shape in solution even in the presence of Ca(2+) ion or at low pH, (2) the global shape of apo CaM is very similar to its NMR structure rather than the crystal structures, (3) about 16 Ca(2+) ions or more are required per CaM molecule in solution to achieve the four-Ca(2+)-bound crystal structure, (4) low pH alone can impart shape changes in CaM similar to Ca(2+) ions, and (5) at different [Ca(2+)]/[CaM] ratio or pH values, the predominant shape of CaM is essentially a weighted average of its apo and fully activated shape. Results were further substantiated by analysis of sedimentation coefficient values from analytical ultracentrifugation and peptide binding assays using two peptides, each known to preferentially bind the apo or the Ca(2+)-activated state.

Light Control and Image Transmission Through Photonic Lattices with Engineered Coupling

DTIC Science & Technology

2015-05-05

HOLLOWAY AVE BUILDING NAD ROOM 358C SAN FRANCISCO, CA 941321722 US 8.  PERFORMING ORGANIZATION      REPORT NUMBER 9.  SPONSORING/MONITORING AGENCY NAME(S...include mainly beam control in engineered photonic lattices, Tamm and Shockley-like edge states and topological surface states in 2D honey- comb lattices...like edge states and topological surface states in 2D honey- comb lattices (“photonic graphene”), and light localization and transport in disordered

Calcium release through P2X4 activates calmodulin to promote endolysosomal membrane fusion.

PubMed

Cao, Qi; Zhong, Xi Zoë; Zou, Yuanjie; Murrell-Lagnado, Ruth; Zhu, Michael X; Dong, Xian-Ping

2015-06-22

Intra-endolysosomal Ca(2+) release is required for endolysosomal membrane fusion with intracellular organelles. However, the molecular mechanisms for intra-endolysosomal Ca(2+) release and the downstream Ca(2+) targets involved in the fusion remain elusive. Previously, we demonstrated that endolysosomal P2X4 forms channels activated by luminal adenosine triphosphate in a pH-dependent manner. In this paper, we show that overexpression of P2X4, as well as increasing endolysosomal P2X4 activity by alkalinization of endolysosome lumen, promoted vacuole enlargement in cells and endolysosome fusion in a cell-free assay. These effects were prevented by inhibiting P2X4, expressing a dominant-negative P2X4 mutant, and disrupting the P2X4 gene. We further show that P2X4 and calmodulin (CaM) form a complex at endolysosomal membrane where P2X4 activation recruits CaM to promote fusion and vacuolation in a Ca(2+)-dependent fashion. Moreover, P2X4 activation-triggered fusion and vacuolation were suppressed by inhibiting CaM. Our data thus suggest a new molecular mechanism for endolysosomal membrane fusion involving P2X4-mediated endolysosomal Ca(2+) release and subsequent CaM activation. © 2015 Cao et al.

Calcium release through P2X4 activates calmodulin to promote endolysosomal membrane fusion

PubMed Central

Cao, Qi; Zhong, Xi Zoë; Zou, Yuanjie; Murrell-Lagnado, Ruth; Zhu, Michael X.

2015-01-01

Intra-endolysosomal Ca2+ release is required for endolysosomal membrane fusion with intracellular organelles. However, the molecular mechanisms for intra-endolysosomal Ca2+ release and the downstream Ca2+ targets involved in the fusion remain elusive. Previously, we demonstrated that endolysosomal P2X4 forms channels activated by luminal adenosine triphosphate in a pH-dependent manner. In this paper, we show that overexpression of P2X4, as well as increasing endolysosomal P2X4 activity by alkalinization of endolysosome lumen, promoted vacuole enlargement in cells and endolysosome fusion in a cell-free assay. These effects were prevented by inhibiting P2X4, expressing a dominant-negative P2X4 mutant, and disrupting the P2X4 gene. We further show that P2X4 and calmodulin (CaM) form a complex at endolysosomal membrane where P2X4 activation recruits CaM to promote fusion and vacuolation in a Ca2+-dependent fashion. Moreover, P2X4 activation-triggered fusion and vacuolation were suppressed by inhibiting CaM. Our data thus suggest a new molecular mechanism for endolysosomal membrane fusion involving P2X4-mediated endolysosomal Ca2+ release and subsequent CaM activation. PMID:26101220

Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae=Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8

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

Samal, Saroj L.; Gulo, Fakhili; Corbett, John D.

Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae–Pt–Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse ofmore » the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ≈ 8.30 Å, c ≈ 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt–Cd and Pd–Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca–Cd versus Er–Pd.« less

Effects of luminal flow and nucleotides on [Ca(2+)](i) in rabbit cortical collecting duct.

PubMed

Woda, Craig B; Leite, Maurilo; Rohatgi, Rajeev; Satlin, Lisa M

2002-09-01

Nucleotide binding to purinergic P2 receptors contributes to the regulation of a variety of physiological functions in renal epithelial cells. Whereas P2 receptors have been functionally identified at the basolateral membrane of the cortical collecting duct (CCD), a final regulatory site of urinary Na(+), K(+), and acid-base excretion, controversy exists as to whether apical purinoceptors exist in this segment. Nor has the distribution of receptor subtypes present on the unique cell populations that constitute Ca(2+) the CCD been established. To examine this, we measured nucleotide-induced changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) in fura 2-loaded rabbit CCDs microperfused in vitro. Resting [Ca(2+)](i) did not differ between principal and intercalated cells, averaging approximately 120 nM. An acute increase in tubular fluid flow rate, associated with a 20% increase in tubular diameter, led to increases in [Ca(2+)](i) in both cell types. Luminal perfusion of 100 microM UTP or ATP-gamma-S, in the absence of change in flow rate, caused a rapid and transient approximately fourfold increase in [Ca(2+)](i) in both cell types (P < 0.05). Luminal suramin, a nonspecific P2 receptor antagonist, blocked the nucleotide- but not flow-induced [Ca(2+)](i) transients. Luminal perfusion with a P2X (alpha,beta-methylene-ATP), P2X(7) (benzoyl-benzoyl-ATP), P2Y(1) (2-methylthio-ATP), or P2Y(4)/P2Y(6) (UDP) receptor agonist had no effect on [Ca(2+)](i). The nucleotide-induced [Ca(2+)](i) transients were inhibited by the inositol-1,4,5-triphosphate receptor blocker 2-aminoethoxydiphenyl borate, thapsigargin, which depletes internal Ca(2+) stores, luminal perfusion with a Ca(2+)-free perfusate, or the L-type Ca(2+) channel blocker nifedipine. These results suggest that luminal nucleotides activate apical P2Y(2) receptors in the CCD via pathways that require both internal Ca(2+) mobilization and extracellular Ca(2+) entry. The flow-induced rise in [Ca(2+)](i) is apparently not mediated by apical P2 purinergic receptor signaling.

North Base hangars as seen from the edge of Rogers ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

North Base hangars as seen from the edge of Rogers Dry Lake, looking north northwest (338°). The security fence surrounding the hangars and aircraft apron appears in the foreground. From left to right appear Building 4305 (Unicon Portable Hangar), Building 4401 (Hangar No. 1), Building 4400 (warehouse), Building 4402 (Hangar No. 2) and Building 4505. - Edwards Air Force Base, North Base, North Base Road, Boron, Kern County, CA

Synthesis, crystal structure, and magnetism of A 2Co 12As 7 (A=Ca, Y, Ce–Yb)

DOE PAGES

Tan, Xiaoyan; Ovidiu Garlea, V.; Chai, Ping; ...

2015-08-28

In this study, ternary intermetallics, A 2Co 12As 7 (A=Ca, Y, Ce–Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P6 3/m variant of the Zr 2Fe 12P 7 structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1),more » respectively, at room temperature. Magnetic behavior of A 2Co 12As 7 is generally characterized by ferromagnetic ordering of Co 3d moments at 100–140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr–Sm to ferromagnetic for A=Ce and Eu–Yb. Finally, polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce 2Co 12As 7 and Nd 2Co 12As 7, respectively.« less

XANES analysis of dried and calcined bones.

PubMed

Rajendran, Jayapradhi; Gialanella, Stefano; Aswath, Pranesh B

2013-10-01

The structure of dried and calcined bones from chicken, bovine, deer, pig, sheep and chamois was examined using X-ray Absorption Near Edge Structure (XANES) spectroscopy. The oxygen K-edge absorption edge indicates that the surface of dried bone has a larger proportion of carbonate than the interior that is made up of phosphates. The phosphorus L and K edge clearly indicate that pyrophosphates, α-tricalcium phosphate (α-TCP) and hydrogen phosphates of Ca do not exist in either the dried bone or calcined bone and phosphorus exists as either β-tricalcium phosphate (β-TCP) or hydroxyapatite, both in the dried and calcined conditions. The Ca K-edge analysis indicates that β-TCP is the likely form of phosphate in both the dried and calcined conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

High pH-Sensitive TRPA1 Activation in Odontoblasts Regulates Mineralization.

PubMed

Kimura, M; Sase, T; Higashikawa, A; Sato, M; Sato, T; Tazaki, M; Shibukawa, Y

2016-08-01

Calcium hydroxide and mineral trioxide aggregate are widely used for indirect and direct pulp capping and root canal filling. Their dissociation into Ca(2+) and OH(-) in dental pulp creates an alkaline environment, which activates reparative/reactionary dentinogenesis. However, the mechanisms by which odontoblasts detect the pH of the extracellular environment remain unclear. We examined the alkali-sensitive intracellular Ca(2+) signaling pathway in rat odontoblasts. In the presence or absence of extracellular Ca(2+), application of alkaline solution increased intracellular Ca(2+) concentration, or [Ca(2+)]i Alkaline solution-induced [Ca(2+)]i increases depended on extracellular pH (8.5 to 10.5) in both the absence and the presence of extracellular Ca(2+) The amplitude was smaller in the absence than in the presence of extracellular Ca(2+) Each increase in [Ca(2+)]i, activated by pH 7.5, 8.5, or 9.5, depended on extracellular Ca(2+) concentration; the equilibrium binding constant for extracellular Ca(2+) concentration decreased as extracellular pH increased (1.04 mM at pH 7.5 to 0.11 mM at pH 9.5). Repeated applications of alkaline solution did not have a desensitizing effect on alkali-induced [Ca(2+)]i increases and inward currents. In the presence of extracellular Ca(2+), alkaline solution-induced [Ca(2+)]i increases were suppressed by application of an antagonist of transient receptor potential ankyrin subfamily member 1 (TRPA1) channels. Ca(2+) exclusion efficiency during alkaline solution-induced [Ca(2+)]i increases was reduced by a Na(+)-Ca(2+) exchanger antagonist. Alizarin red and von Kossa staining revealed increased mineralization levels under repeated high pH stimulation, whereas the TRPA1 antagonist strongly reduced this effect. These findings indicate that alkaline stimuli-such as the alkaline environment inside dental pulp treated with calcium hydroxide or mineral trioxide aggregate-activate Ca(2+) mobilization via Ca(2+) influx mediated by TRPA1 channels and intracellular Ca(2+) release in odontoblasts. High pH-sensing mechanisms in odontoblasts are important for activating dentinogenesis induced by an alkaline environment. © International & American Associations for Dental Research 2016.

Rice-like hollow nano-CaCO3 synthesis

NASA Astrophysics Data System (ADS)

Ulkeryildiz, Eda; Kilic, Sevgi; Ozdemir, Ekrem

2016-09-01

We have shown that Ca(OH)2 solution is a natural stabilizer for CaCO3 particles. We designed a CO2 bubbling crystallization reactor to produce nano-CaCO3 particles in homogenous size distribution without aggregation. In the experimental set-up, the crystallization region was separated from the stabilization region. The produced nanoparticles were removed from the crystallization region into the stabilization region before aggregation or crystal growth. It was shown that rice-like hollow nano-CaCO3 particles in about 250 nm in size were produced with almost monodispersed size distribution. The particles started to dissolve through their edges as CO2 bubbles were injected, which opened-up the pores inside the particles. At the late stages of crystallization, the open pores were closed as a result of dissolution-recrystallization of the newly synthesized CaCO3 particles. These particles were stable in Ca(OH)2 solution and no aggregation was detected. The present methodology can be used in drug encapsulation into inorganic CaCO3 particles for cancer treatment with some modifications.

Study on the Anti-Poison Performance of Al-Y-P Master Alloy for Impurity Ca in Aluminum Alloys.

PubMed

Zuo, Min; Dong, Yu; Zhao, Degang; Wang, Yan; Teng, Xinying

2017-11-26

In this article, the anti-poison performance of novel Al-6Y-2P master alloy for impurity Ca in hypereutectic Al-Si alloys was investigated in detail. According to the microstructural analysis, it can be found that the primary Si and eutectic Si particles could be relatively modified and refined. In order to investigate the influence mechanism of Ca on the limited refinement performance of Al-6Y-2P master alloy, types of Al-xSi-2Ca-3Y-1P (x = 0, 6, 12, 18, and 30) alloys were prepared. It is observed that Ca takes the form of more stable Ca3P2 compounds by reacting with YP, and the surface of Ca3P2 particles are unsmooth, and even some have wrinkles in Al Al-2Ca-3Y-1P alloy. With the increase of Si content in Al-xSi-2Ca-3Y-1P (x = 6, 12, 18 and 30) systems, the multi-encapsulation structures, i.e., the phosphide (AlP and YP), hexagonal Al2Si2Ca, the Al3Si2Y2 or primary Si from inside to outside in order were examined.The excapsulation of YP and AlP caused by Al2Si2Ca might be the reason for the limited refinement effect of Al-6Y-2P master alloy for hypereutectic Al-18Si alloys.

DA-6034-induced mucin secretion via Ca2+-dependent pathways through P2Y receptor stimulation.

PubMed

Lee, Hun; Kim, Eung Kweon; Kim, Ji Yeon; Yang, Yu-Mi; Shin, Dong Min; Kang, Kyung Koo; Kim, Tae-im

2014-09-11

We evaluated whether DA-6034 is involved in mucin secretion via P2Y receptor activation and/or intracellular Ca2+ concentration ([Ca2+]i) change. Also, we investigated the effect of P2Y receptor inhibitors or Ca2+ chelators on the DA-6034-induced mucin secretion and [Ca2+]i increases. Effects of DA-6034 on mucin expression in primary, cultured, conjunctival epithelial cells was studied using RT-PCR, Western blot analysis, and periodic acid-schiff (PAS) staining. To evaluate thin film layer thickness generated by mucin and fluid secretion, cells were incubated in DA-6034 with/without P2Y antagonists or extracellular/intracellular Ca2+ chelators, and were imaged with confocal microscope using Texas Red-dextran dye. In addition, DA-6034-induced Ca2+-dependent Cl- channels opening was evaluated using perforated patch clamp. Fluo-4/AM was used to measure changes in [Ca2+]i induced by DA-6034 in Ca2+-free or Ca2+-containing buffered condition, as well as P2Y antagonists. DA-6034 induced the expression of mucin genes, production of mucin protein, and increase of number of mucin-secreting cells. P2Y antagonists inhibited DA-6034-induced mucin and fluid secretion, which was also affected by extracellular/intracellular Ca2+ chelators. DA-6034 stimulated Cl- channel opening and [Ca2+]i elevation. Further, [Ca2+]i increases induced by DA-6034 were lacking in either P2Y antagonists or Ca2+-free buffered condition, and diminished when endoplasmic reticulum Ca2+ was depleted by cyclopiazonic acid in Ca2+-free buffered condition. This study demonstrated that DA-6034 has a potential to induce mucin secretion via Ca2+-dependent pathways through P2Y receptors in multilayer, cultured, human conjunctival epithelial cells. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Uranium Reduction by Fe(II) in the Presence of Montmorillonite and Nontronite.

PubMed

Tsarev, Sergey; Waite, T David; Collins, Richard N

2016-08-02

Uranium(VI) interactions with three smectites (one montmorillonite and two nontronites - NAu1 and NAu2) were examined with 0, 1, and 2 mM aqueous concentrations of Fe(II) over the pH range of 3-9.5 in a background electrolyte of 100 mM NaCl and 1 mM CaCl2 in equilibration with 400 ppmv CO2(g) ([U(VI)] = 4 μM and 0.5 g smectite/L). In the absence of Fe(II), no differences were observed in the U(VI) sorption curves for the three clay minerals. In the presence of 1 or 2 mM Fe(II), under anoxic conditions, U(VI) uptake by the smectites changed slightly between ∼pH 3 and 6; however, uranium uptake increased significantly above ∼pH 6 and was proportional to the concentration of Fe(II) added to the system, particularly at pH values >8. The uptake of Fe(II) showed a sharp edge starting from ∼pH 6.5 with 95%-100% uptake occurring at pH values >7.5, with no difference observed between the iron-rich nontronites and montmorillonite. After 3 days of reaction at pH 7.6 (i.e., above the Fe(II) "sorption" edge), U(VI) was transformed to a mixture of U(IV) and U(VI) sorption complexes, and after 14 days of reaction, 100% of the U was found to be reduced to U(IV) in the form of nanocrystalline uraninite. In contrast, U remained as sorbed species until 14 days of reaction at pH 6.5. Ferrihydrite (NAu1), lepidocrocite, and magnetite (NAu2) were detected as secondary mineralization products upon reaction of the nontronites with Fe(II) but appeared to have no effect on the partitioning or speciation of uranium.

Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes

PubMed Central

Occhipinti, Rossana; Boron, Walter F.

2014-01-01

Human carbonic anhydrase IV (CA IV) is GPI-anchored to the outer membrane surface, catalyzing CO2/HCO3− hydration-dehydration. We examined effects of heterologously expressed CA IV on intracellular-pH (pHi) and surface-pH (pHS) transients caused by exposing oocytes to CO2/HCO3−/pH 7.50. CO2 influx causes a sustained pHi fall and a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA IV increases magnitudes of maximal rate of pHi change (dpHi/dt)max, and maximal pHS change (ΔpHS) and decreases time constants for pHi changes (τpHi) and pHS relaxations (τpHS). Decreases in time constants indicate that CA IV enhances CO2 fluxes. Extracellular acetazolamide blocks all CA IV effects, but not those of injected CA II. Injected acetazolamide partially reduces CA IV effects. Thus, extracellular CA is required for, and the equivalent of cytosol-accessible CA augments, the effects of CA IV. Increasing the concentration of the extracellular non-CO2/HCO3− buffer (i.e., HEPES), in the presence of extracellular CA or at high [CO2], accelerates CO2 influx. Simultaneous measurements with two pHS electrodes, one on the oocyte meridian perpendicular to the axis of flow and one downstream from the direction of extracellular-solution flow, reveal that the downstream electrode has a larger (i.e., slower) τpHS, indicating [CO2] asymmetry over the oocyte surface. A reaction-diffusion mathematical model (third paper in series) accounts for the above general features, and supports the conclusion that extracellular CA, which replenishes entering CO2 or consumes exiting CO2 at the extracellular surface, enhances the gradient driving CO2 influx across the cell membrane. PMID:24965590

Roles of Ras Homolog A in Invasive Ductal Breast Carcinoma

PubMed Central

Murakami, Eriko; Nakanishi, Yoko; Hirotani, Yukari; Ohni, Sumie; Tang, Xiaoyan; Masuda, Shinobu; Enomoto, Katsuhisa; Sakurai, Kenichi; Amano, Sadao; Yamada, Tsutomu; Nemoto, Norimichi

2016-01-01

Breast cancer has a poor prognosis owing to tumor cell invasion and metastasis. Although Ras homolog (Rho) A is involved in tumor cell invasion, its role in breast carcinoma is unclear. Here, RhoA expression was examined in invasive ductal carcinoma (IDC), with a focus on its relationships with epidermal-mesenchymal transition (EMT) and collective cell invasion. Forty-four surgical IDC tissue samples and two normal breast tissue samples were obtained. RhoA, E-cadherin, vimentin, and F-actin protein expression were analyzed by immunohistochemistry. RhoA, ROCK, mTOR, AKT1, and PIK3CA mRNA expression were conducted using laser microdissection and semi-nested quantitative reverse transcription-polymerase chain reaction. RhoA expression was stronger on the tumor interface of IDCs than the tumor center (P<0.001). RhoA expression was correlated with ROCK expression only in HER2-subtype IDC (P<0.05). In IDCs co-expressing RhoA and ROCK, F-actin expression was stronger on the tumor interface, particularly at the edges of tumor cells, than it was in ROCK-negative IDCs (P<0.0001). In conclusion, RhoA expression was not correlated with EMT in IDC, but enhanced F-actin expression was localized on the edge of tumor cells that co-expressed ROCK. RhoA/ROCK signaling may be associated with collective cell invasion, particularly in HER2-subtype IDC. PMID:27917007

Roles of Ras Homolog A in Invasive Ductal Breast Carcinoma.

PubMed

Murakami, Eriko; Nakanishi, Yoko; Hirotani, Yukari; Ohni, Sumie; Tang, Xiaoyan; Masuda, Shinobu; Enomoto, Katsuhisa; Sakurai, Kenichi; Amano, Sadao; Yamada, Tsutomu; Nemoto, Norimichi

2016-11-01

Breast cancer has a poor prognosis owing to tumor cell invasion and metastasis. Although Ras homolog (Rho) A is involved in tumor cell invasion, its role in breast carcinoma is unclear. Here, RhoA expression was examined in invasive ductal carcinoma (IDC), with a focus on its relationships with epidermal-mesenchymal transition (EMT) and collective cell invasion. Forty-four surgical IDC tissue samples and two normal breast tissue samples were obtained. RhoA, E-cadherin, vimentin, and F-actin protein expression were analyzed by immunohistochemistry. RhoA , ROCK , mTOR , AKT1 , and PIK3CA mRNA expression were conducted using laser microdissection and semi-nested quantitative reverse transcription-polymerase chain reaction. RhoA expression was stronger on the tumor interface of IDCs than the tumor center ( P <0.001). RhoA expression was correlated with ROCK expression only in HER2-subtype IDC ( P <0.05). In IDCs co-expressing RhoA and ROCK , F-actin expression was stronger on the tumor interface, particularly at the edges of tumor cells, than it was in ROCK -negative IDCs ( P <0.0001). In conclusion, RhoA expression was not correlated with EMT in IDC, but enhanced F-actin expression was localized on the edge of tumor cells that co-expressed ROCK. RhoA/ROCK signaling may be associated with collective cell invasion, particularly in HER2-subtype IDC.

Credit USAF, ca. 1943. Original housed in the Muroc Flight ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Credit USAF, ca. 1943. Original housed in the Muroc Flight Test Base, Unit History, 1 September 1942 - 30 June 1945. Alfred F. Simpson Historical Research Agency. United States Air Force. Maxwell AFB, Alabama. Historic view looking northeast along southeast edge of swimming pool during construction. The wavy edge of the pool visible here remains as a ground surface feature in 1995. Building in the background is the second Bachelor Officers' Quarters (T-15) built in 1943 - Edwards Air Force Base, North Base, Swimming Pool, Second Street, Boron, Kern County, CA

Dietary calcium attenuates platelet aggregation and intracellular Ca2+ mobilization in spontaneously hypertensive rats

NASA Technical Reports Server (NTRS)

Otsuka, K.; Watanabe, M.; Yue, Q.; McCarron, D. A.; Hatton, D.

1997-01-01

Spontaneously hypertensive rats (SHR) are known to be blood pressure sensitive to dietary calcium. The effects of dietary calcium on platelet aggregation and intracellular Ca2+ mobilization were assessed by turbidimetric methods and fura-2 methods, respectively, in washed platelets of SHR. Ca2+ ATPase activity was examined in aortic membrane fractions. Six weeks of dietary calcium supplementation attenuated the increase of systolic blood pressure (SBP 199 +/- 16 v 170 +/- 9 mm Hg, P < .001) and thrombin-induced platelet aggregation (84.5 +/- 3.7 v 73.7 +/- 7.4%, P < .004) at 9 weeks of age. The ionomycin-induced intracellular calcium ([Ca2+]i) peak in the absence of external Ca2+, which reflects [Ca2+]i storage size, and thrombin-evoked [Ca2+]i release from [Ca2+]i storage were decreased by 2.0% Ca diet (472 +/- 55 v 370 +/- 23 nmol/L, P < .001, 339 +/- 29 v 278 +/- 33 nmol/L, P < .002). In addition, SBP was positively correlated with platelet aggregation (r = 0.703, P = .0088), thrombin-evoked [Ca2+]i (r = 0.739, P = .0044), and ionomycin-induced [Ca2+]i (r = 0.591, P = .0415), respectively. However, there was no significant effect of dietary calcium on Ca2+-ATPase activity in aortic membranes. These results suggest that dietary calcium supplementation had a beneficial effect on platelets of SHR by attenuating [Ca2+]i mobilization from [Ca2+]i storage. The hypotensive effect of dietary calcium might be associated with attenuated [Ca2+]i mobilization in SHR.

Ca2+-exchange in layered zirconium orthophosphate, α-ZrP: Chemical study and potential application for zinc corrosion inhibition

NASA Astrophysics Data System (ADS)

Bouali, Imane; Rocca, Emmanuel; Veys-Renaux, Delphine; Rhouta, Benaissa; Khalil, Aziza; Aït Aghzzaf, Ahmed

2017-11-01

The control of the corrosion phenomenon occurring at the metal interface requires the development of new non-toxic anticorrosion additives. For this purpose, zirconium orthophosphate compounds (Zr(HPO4)2,H2O noted α-ZrP) were synthesized by both hydrothermal and refluxing methods The Ca2+-cationic exchange in the layered structure is kinetically favoured by low crystallinity of α-ZrP synthesized by refluxing process, and leads to the formation of CaZr(PO4)2,4H2O, noted Ca2+-ZrP. The H+/Ca2+ exchange mechanism is mainly triggered by acid-base considerations, and especially the pKa of α-ZrP/Ca2+-ZrP acid-base couple (evaluated to 2.5). Both compounds are acidic compounds by internal exchangeable H+ for α-ZrP and surface protons for Ca2+-ZrP, and can be used as potential inhibitors of zinc corrosion. Electrochemical measurements show that Ca2+-ZrP compounds dispersed in the NaCl electrolyte buffer the pH value over a long time and therefore allow controlling the corrosion rate of zinc.

Effects of deoxygenation on active and passive Ca2+ transport and cytoplasmic Ca2+ buffering in normal human red cells.

PubMed Central

Tiffert, T; Etzion, Z; Bookchin, R M; Lew, V L

1993-01-01

1. The effects of deoxygenation on cytoplasmic Ca2+ buffering, saturated Ca2+ extrusion rate through the Ca2+ pump (Vmax), passive Ca2+ influx and physiological [Ca2+]i level were investigated in human red cells to assess whether or not their Ca2+ metabolism might be altered by deoxygenation in capillaries and venous circulation. 2. The study was performed in fresh human red cells maintained in a tonometer either fully oxygenated or deoxygenated. Cytoplasmic Ca2+ buffering was estimated from the equilibrium distribution of 45Ca2+ induced by the divalent cation ionophore A23187 and the Vmax of the Ca2+ pump was measured either by the Co(2+)-exposure method or following ionophore wash-out. The passive Ca2+ influx and physiological [Ca2+]i were determined in cells preloaded with the Ca2+ chelator benz-2 and resuspended in autologous plasma. 3. Deoxygenation increased the fraction of ionized Ca2+ in cell water by 34-74% and reduced the Vmax of the Ca2+ pump by 18-32%. 4. To elucidate whether or not these effects were secondary to deoxygenation-induced pH shifts, the effects of deoxygenation on cell and medium pH, and of pH on cytoplasmic Ca2+ binding and Ca2+ pump Vmax in oxygenated cells were examined in detail. 5. Deoxygenation generated large alkaline pH shifts that could be explained if the apparent isoelectric point (pI) of haemoglobin increased by 0.2-0.4 pH units in intact cells, consistently higher than the value of 0.15 reported for pure haemoglobin solutions. 6. In oxygenated cells, the fraction of ionized cell calcium, alpha, was little affected by pH within the 7.0-7.7 range. Ca2+ pump Vmax was maximal at a medium pH of about 7.55. Comparison between pH effects elicited by HCl-NaOH additions and by replacing Cl- with gluconate suggested that Vmax was inhibited by both internal acidification and external alkalinization. Since deoxygenation alkalinized cells and medium within a range stimulatory for Vmax, the inhibition observed was not due to pH. 7. There was no significant effect of deoxygenation on passive Ca2+ uptake, or steady-state physiological [Ca2+]i level. 8. The deoxygenation-induced reduction in Ca2+ binding capacity may result from the increased protonation of haemoglobin on deoxygenation and from binding of 2,3-diphosphoglyceric acid (2,3-DPG) and ATP to deoxyhaemoglobin; inhibition of the Ca2+ pump may result from shifts in the [Mg2+]i/[ATP]i ratio away from a near optimal stimulatory value in the oxygenated state. PMID:8229816

Identification of P2X3 and P2X7 Purinergic Receptors Activated by ATP in Rat Lacrimal Gland

PubMed Central

Vrouvlianis, Joanna; Scott, Rachel; Dartt, Darlene A.

2011-01-01

Purpose. To identify the type of purinergic receptors activated by adenosine triphosphate (ATP) in rat lacrimal gland and to determine their role in protein secretion. Methods. Purinergic receptors were identified by RT-PCR, Western blot analysis, and immunofluorescence techniques. Acini from rat lacrimal gland were isolated by collagenase digestion. Acini were incubated with the fluorescence indicator fura-2 tetra-acetoxylmethyl ester, and intracellular [Ca2+] ([Ca2+]i) was determined. Protein secretion was measured by fluorescence assay. Results. The authors previously showed that P2X7 receptors were functional in the lacrimal gland. In this study, they show that P2X1–4, and P2X6receptors were identified in the lacrimal gland by RT-PCR, Western blot, and immunofluorescence analyses. P2X5 receptors were not detected. ATP increased [Ca2+]i and protein secretion in a concentration-dependent manner. Removal of extracellular Ca2+ significantly reduced the ATP-stimulated increase in [Ca2+]i. Repeated applications of ATP caused desensitization of the [Ca2+]i response. Incubation with the P2X1 receptor inhibitor NF023 did not alter ATP-stimulated [Ca2+]i. Incubation with zinc, which potentiates P2X2 and P2X4 receptor responses, or lowering the pH to 6.8, which potentiates P2X2 receptor responses, did not alter the ATP-stimulated [Ca2+]i. P2X3 receptor inhibitors A-317491 and TNP-ATP significantly decreased ATP-stimulated [Ca2+]i and protein secretion, whereas the P2X3 receptor agonist α,β methylene ATP significantly increased them. The P2X7 receptor inhibitor A438079 had no effect on ATP-stimulated [Ca2+]i at 10−6 M but did have an effect at 10−4 M. Conclusions. Purinergic receptors P2X1–4 and P2X6 are present in the lacrimal gland. ATP uses P2X3 and P2X7 receptors to stimulate an increase in [Ca2+]i and protein secretion. PMID:21421865

Direct observation of trapped charges under field-plate in p-GaN gate AlGaN/GaN high electron mobility transistors by electric field-induced optical second-harmonic generation

NASA Astrophysics Data System (ADS)

Katsuno, Takashi; Manaka, Takaaki; Soejima, Narumasa; Iwamoto, Mitsumasa

2017-02-01

Trapped charges underneath the field-plate (FP) in a p-gallium nitride (GaN) gate AlGaN/ GaN high electron mobility transistor device were visualized by using electric field-induced optical second-harmonic generation imaging. Second-harmonic (SH) signals in the off-state of the device with FP indicated that the electric field decreased at the p-GaN gate edge and concentrated at the FP edge. Nevertheless, SH signals originating from trapped charges were slightly observed at the p-GaN gate edge and were not observed at the FP edge in the on-state. Compared with the device without FP, reduction of trapped charges at the p-GaN gate edge of the device with FP is attributed to attenuation of the electric field with the aid of the FP. Negligible trapped charges at the FP edge is owing to lower trap density of the SiO2/AlGaN interface at the FP edge compared with that of the SiO2/p-GaN sidewall interface at the p-GaN gate edge and attenuated electric field by the thickness of the SiO2 passivation layer on the AlGaN surface.

Homeostatic Regulation of the PI(4,5)P2-Ca2+ Signaling System at ER-PM Junctions

PubMed Central

Chang, Chi-Lun; Liou, Jen

2016-01-01

The phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2)-Ca2+ signaling system is important for cell activation in response to various extracellular stimuli. This signaling system is initiated by receptor-induced hydrolysis of PI(4,5)P2 in the plasma membrane (PM) to generate the soluble second messenger inositol 1,4,5-trisphosphate (IP3). IP3 subsequently triggers the release of Ca2+ from the endoplasmic reticulum (ER) store to the cytosol to activate Ca2+-mediated responses, such as secretion and proliferation. The consumed PM PI(4,5)P2 and ER Ca2+ must be quickly restored to sustain signaling responses, and to maintain the homeostasis of PI(4,5)P2 and Ca2+. Since phosphatidylinositol (PI), the precursor lipid for PM PI(4,5)P2, is synthesized in the ER membrane, and a Ca2+ influx across the PM is required to refill the ER Ca2+ store, efficient communications between the ER and the PM are critical for the homeostatic regulation of the PI(4,5)P2-Ca2+ signaling system. This review describes the major findings that established the framework of the PI(4,5)P2-Ca2+ signaling system, and recent discoveries on feedback control mechanisms at ER-PM junctions that sustain the PI(4,5)P2-Ca2+ signaling system. Particular emphasis is placed on the characterization of ER-PM junctions where efficient communications between the ER and the PM occurs, and the activation mechanisms of proteins that dynamically localize to ER-PM junctions to provide the feedback control during PI(4,5)P2-Ca2+ signaling, including the ER Ca2+ sensor STIM1, the extended synaptotagmin E-Syt1, and the PI transfer protein Nir2. This review is part of a Special Issue entitled The Cellular Lipid Landscape. PMID:26924250

Selective stimulation of catecholamine release from bovine adrenal chromaffin cells by an ionotropic purinergic receptor sensitive to 2-methylthio ATP.

PubMed

Tomé, Angelo R; Castro, Enrique; Santos, Rosa M; Rosário, Luís M

2007-06-20

2-Methylthioadenosine 5'-triphosphate (2-MeSATP), formerly regarded as a specific P2Y (metabotropic) purinergic receptor agonist, stimulates Ca2+ influx and evokes catecholamine release from adrenal chromaffin cells. These cells express P2Y and P2X (ionotropic) purinoceptors, with the latter providing an important Ca2+ influx pathway. Using single cell calcium imaging techniques, we have determined whether 2-MeSATP might be a specific P2X receptor agonist in bovine chromaffin cells and assessed the relative role of P2X and P2Y receptors on catecholamine secretion from these cells. ATP raised the [Ca2+]i in ~50% of the cells. Removing extracellular Ca2+ suppressed the [Ca2+]i-raising ability of 2-MeSATP, observed in ~40% of the ATP-sensitive cells. This indicates that 2-MeSATP behaves as a specific ionotropic purinoceptor agonist in bovine chromaffin cells. The 2-MeSATP-induced [Ca2+]i-rises were suppressed by PPADS. UTP raised the [Ca2+]i in ~40% of the ATP-sensitive cells, indicating that these expressed Ca2+-mobilizing P2Y receptors. UTP-sensitive receptors may not be the only P2Y receptors present, as suggested by the observation that ~20% of the ATP-sensitive pool did not respond to either 2-MeSATP or UTP. The average sizes of the ATP- and 2-MeSATP-evoked [Ca2+]i responses were identical in UTP-insensitive cells. 2-MeSATP stimulated Ca2+ influx and evoked catecholamine release, whereas UTP elicited Ca2+ release from intracellular stores but did not evoke secretion. 2-MeSATP-induced secretion was strongly inhibited by Cd2+ and suppressed by extracellular Ca2+ or Na+ removal. TTX inhibited 2-MeSATP-evoked secretion by ~20%. 2-MeSATP is a specific P2X purinoceptor agonist and a potent secretagogue in bovine chromaffin cells. Activation of 2-MeSATP-sensitive receptors stimulates Ca2+ influx mainly via voltage-sensitive Ca2+ channels. For the most part, these are activated by the depolarization brought about by Na+ influx across P2X receptor pores.

YCrWO 6 : Polar and Magnetic Oxide with CaTa 2O 6 -Related Structure

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

Kim, Sun Woo; Emge, Thomas J.; Deng, Zheng

Here, a new polar and magnetic oxide, YCrWO 6, was successfully synthesized and characterized. YCrWO 6 crystallizes in polar orthorhombic space group Pna21 (no. 33) of edge-sharing dimers of CrO 6 and WO 6 octahedra, which are connected by corner-sharing to form a three-dimensional framework structure with Y 3+ cations located in the channels. The structure of YCrWO 6 is related to that of CaTa2O 6; however, the ordering of Cr 3+ and W 6+ in the octahedral sites breaks the inversion symmetry of the parent CaTa 2O 6 structure. X-ray absorption near edge spectroscopy of YCrWO 6 confirmed themore » oxidation state of Cr 3+ and W 6+. Temperature-dependent optical second harmonic generation measurements on YCrWO 6 confirmed the noncentrosymmetric character and evidenced a noncentrosymmetric-to-centrosymmetric phase transition above 800 °C. Piezoresponse force microscopy measurements on YCrWO 6 at room temperature show strong piezoelectric domains. Magnetic measurements of YCrWO 6 indicate antiferromagnetic order at T N of ~22 K with Weiss temperature of -34.66 K.« less

YCrWO 6 : Polar and Magnetic Oxide with CaTa 2O 6 -Related Structure

DOE PAGES

Kim, Sun Woo; Emge, Thomas J.; Deng, Zheng; ...

2018-01-05

Here, a new polar and magnetic oxide, YCrWO 6, was successfully synthesized and characterized. YCrWO 6 crystallizes in polar orthorhombic space group Pna21 (no. 33) of edge-sharing dimers of CrO 6 and WO 6 octahedra, which are connected by corner-sharing to form a three-dimensional framework structure with Y 3+ cations located in the channels. The structure of YCrWO 6 is related to that of CaTa2O 6; however, the ordering of Cr 3+ and W 6+ in the octahedral sites breaks the inversion symmetry of the parent CaTa 2O 6 structure. X-ray absorption near edge spectroscopy of YCrWO 6 confirmed themore » oxidation state of Cr 3+ and W 6+. Temperature-dependent optical second harmonic generation measurements on YCrWO 6 confirmed the noncentrosymmetric character and evidenced a noncentrosymmetric-to-centrosymmetric phase transition above 800 °C. Piezoresponse force microscopy measurements on YCrWO 6 at room temperature show strong piezoelectric domains. Magnetic measurements of YCrWO 6 indicate antiferromagnetic order at T N of ~22 K with Weiss temperature of -34.66 K.« less

[Matrix metalloproteinases and their inhibitors in lung cancer with malignant pleural effusion].

PubMed

Moche, M; Hui, D S C; Huse, K; Chan, K S; Choy, D K L; Scholz, G H; Gosse, H; Winkler, J; Schauer, J; Sack, U; Hoheisel, G

2005-08-01

Matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) play a crucial role in physiological and pathological matrix turnover. This study aimed to determine the occurrence of MMP and TIMP in lung cancer patients with malignant pleural effusions (CA). MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, TIMP-1, and IMP-2 oncentrations were determined by ELISA and zymography in pleural effusions and plasma of 31 CA and 14 congestive heart failure (CHF) patients and in plasma of 18 healthy controls (CON). MMP-2, TIMP-1, and TIMP-2 ELISA-concentrations were increased in CA pleural fluid vs. CA plasma (p < 0.005, p < 0.005, p < 0.05), in contrast to MMP-9 being higher in plasma (p < 0.005). Pleural fluid MMP-1 and MMP-8 were increased in CA vs. CHF (p < 0.05, p < 0.005). MMP and TIMP plasma concentrations were not different in CA vs. CHF, but MMP-9, TIMP-1, and TIMP-2 were increased vs. CON (p < 0.005, each). Gelatine zymography MMP-9/MMP-2 ratios were increased in CA plasma vs. effusion fluid (p < 0.005), in CA vs. CHF plasma, CA vs. CHF effusions (p < 0.005 each), and in CA vs. CON plasma (p < 0.05). MMP-2, TIMP-1, and TIMP-2 accumulate in the pleural compartment in CA and CHF, probably reflecting an unspecific pleural reaction. MMP-1 and MMP-8 are increased in cellular rich CA pleural effusions only. The determination of MMP-9/MMP-2 ratios in pleural fluid may contribute to differentiate CHF from CA effusions.

Computer simulation of CaSiO3 glass under compression: correlation between Si-Si pair radial distribution function and intermediate range order structure

NASA Astrophysics Data System (ADS)

Lan, Mai Thi; Thuy Duong, Tran; Iitaka, Toshiaki; Van Hong, Nguyen

2017-06-01

The structural organization of CaSiO3 glass at 600 K and under pressure of 0-100 GPa is investigated by molecular dynamics simulation (MDS). Results show that the atomic structure of CaSiO3 comprises SiO n and CaO m units considered as basic structural polyhedra. At low pressure, most of the basic structural polyhedra are SiO4, CaO5, CaO6 and CaO7. At high pressure most of the basic structural polyhedra are SiO5, SiO6 and CaO9, CaO10 and CaO11. The distribution of basic structural polyhedra is not uniform resulting in formation of Ca-rich and Si-rich regions. The distribution of SiO4, SiO5 and SiO6 polyhedra is also not uniform, but it tends to form SiO4-, SiO5-, and SiO6-clusters. For the Si-O network, under compression there is a gradual transition from the tetrahedral network (SiO4) to the octahedral network (SiO6) via SiO5 polyhedra. The SiO5-clusters are the same as immediate-phase in the transformation process. The size and shape of SiO4 tetrahedra change strongly under compression. While the size of SiO5 and SiO6 has also changed significantly, but the shape is almost unchanged under compression. The SiO n polyhedra can connect to each other via one common oxygen ion (corner-sharing bond), two common oxygen ions (edge-sharing bond) or three common oxygen ions (face-sharing bond). The Si-Si bond length in corner-sharing bonds is much longer than the ones in edge-sharing and face-sharing bonds. The change of intermediate range order (IRO) structure under compression relating to edge- and face-sharing bonds amongst SiO n at high pressure is the origin of the first peak splitting of the radial distribution functions of Si-Si pair. Under compression, the number of non-bridging oxygen (NBO) decreases. This makes the Si-O network more polymerized. At low pressure, most of the Ca2+ ions incorporate into the Si-O network via NBOs. At high pressure, the amount of NBO decreases, Ca2+ ions mainly incorporate into the Si-O network via bridging oxygen (BO) that belongs to SiO5 and SiO6 with a negative charge. And this is the principle for immobilization of heavy metal as well as fissile materials in hazardous waste (nuclear waste).

Uptake and speciation of uranium in synthetic gypsum (CaSO4•2H2O): Applications to radioactive mine tailings.

PubMed

Lin, Jinru; Sun, Wei; Desmarais, Jacques; Chen, Ning; Feng, Renfei; Zhang, Patrick; Li, Dien; Lieu, Arthur; Tse, John S; Pan, Yuanming

2018-01-01

Phosphogypsum formed from the production of phosphoric acid represents by far the biggest accumulation of gypsum-rich wastes in the world and commonly contains elevated radionuclides, including uranium, as well as other heavy metals and metalloids. Therefore, billions-of-tons of phosphogypsum stockpiled worldwide not only possess serious environmental problems but also represent a potential uranium resource. Gypsum is also a major solid constituent in many other types of radioactive mine tailings, which stems from the common usage of sulfuric acid in extraction processes. Therefore, management and remediation of radioactive mine tailings as well as future beneficiation of uranium from phosphogysum all require detailed knowledge about the nature and behavior of uranium in gypsum. However, little is known about the uptake mechanism or speciation of uranium in gypsum. In this study, synthesis experiments suggest an apparent pH control on the uptake of uranium in gypsum at ambient conditions: increase in U from 16 μg/g at pH = 6.5 to 339 μg/g at pH = 9.5. Uranium L 3 -edge synchrotron X-ray absorption spectroscopic analyses of synthetic gypsum show that uranyl (UO 2 ) 2+ at the Ca site is the dominant species. The EXAFS fitting results also indicate that uranyl in synthetic gypsum occurs most likely as carbonate complexes and yields an average U-O distance ∼0.25 Å shorter than the average Ca-O distance, signifying a marked local structural distortion. Applications to phosphogypsum from the New Wales phosphoric acid plant (Florida, USA) and uranium mine tailings from the Key Lake mill (Saskatchewan, Canada) show that gypsum is an important carrier of uranium over a wide range of pH and controls the fate of this radionuclide in mine tailings. Also, development of new technologies for recovering U from phosphogypsum in the future must consider lattice-bound uranyl in gypsum. Copyright © 2017 Elsevier Ltd. All rights reserved.

Energy and Resource Saving of Steelmaking Process: Utilization of Innovative Multi-phase Flux During Dephosphorization Process

NASA Astrophysics Data System (ADS)

Matsuura, Hiroyuki; Hamano, Tasuku; Zhong, Ming; Gao, Xu; Yang, Xiao; Tsukihashi, Fumitaka

2014-09-01

An increase in the utilization efficiency of CaO, one of the major fluxing agents used in various steelmaking processes, is required to reduce the amount of discharged slag and energy consumption of the process. The authors have intensively focused on the development of innovative dephosphorization process by using so called "multi-phase flux" composed of solid and liquid phases. This article summarizes the research on the above topic done by the authors, in which the formation mechanisms of P2O5-containing phase during CaO or 2CaO·SiO2 dissolution into molten slag, the phase relationship between solid and liquid phases at equilibrium, and thermodynamic properties of P2O5-containing phase have been clarified. The reactions between solid CaO or 2CaO·SiO2 and molten CaO-FeO x -SiO2-P2O5 slag were observed by dipping solid specimen in the synthesized slag at 1573 K or 1673 K. The formation of the CaO-FeO layer and dual-phase layer of solid 2CaO·SiO2 and FeO x -rich liquid phase was observed around the interface from the solid CaO side toward the bulk slag phase side. Condensation of P2O5 into 2CaO·SiO2 phase as 2CaO·SiO2-3CaO·P2O5 solid solution was observed in both cases of CaO and 2CaO·SiO2 as solid specimens. Measurement of the phase relationship for the CaO-FeO x -SiO2-P2O5 system confirmed the condensation of P2O5 in solid phase at low oxygen partial pressure. The thermodynamics of 2CaO·SiO2-3CaO·P2O5 solid solution are to be clarified to quantitatively simulate the dephosphorization process, and the current results are also introduced. Based on the above results, the reduction of CaO consumption, the discharged slag curtailment, and energy-saving effects have been discussed.

3. EASTERN EDGE OF POST ENGINEER'S SHOPS AND YARD, LOOKING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. EASTERN EDGE OF POST ENGINEER'S SHOPS AND YARD, LOOKING 312 DEGREES NORTH WEST, EUCALYPTUS TREES DENOTE EDGE OF PRESIDIO. - Presidio of San Francisco, Post Engineer's Headquarters Office, Crissy Field North cantonment, San Francisco, San Francisco County, CA

Induction of intracellular Ca2+ and pH changes in Sf9 insect cells by rhodojaponin-III, a natural botanic insecticide isolated from Rhododendron molle.

PubMed

Cheng, Xing-An; Xie, Jian-Jun; Hu, Mei-Ying; Zhang, Yan-Bo; Huang, Jing-Fei

2011-04-15

Many studies on intracellular calcium ([Ca2+](i)) and intracellular pH (pH(i)) have been carried out due to their importance in regulation of different cellular functions. However, most of the previous studies are focused on human or mammalian cells. The purpose of the present study was to characterize the effect of Rhodojaponin-III (R-III) on [Ca2+](i) and pH(i) and the proliferation of Sf9 cells. R-III strongly inhibited Sf9 cells proliferation with a time- and dose-dependent manner. Flow cytometry established that R-III interfered with Sf9 cells division and arrested them in G2/M. By using confocal scanning technique, effects of R-III on intracellular free calcium ([Ca2+](i)) and intracellular pH (pH(i)) in Sf9 cells were determined. R-III induced a significant dose-dependent (1, 10, 100, 200 μg/mL) increase in [Ca2+](i) and pH(i) of Sf9 cells in presence of Ca2+-containing solution (Hanks) and an irreversible decrease in the absence of extra cellular Ca2+. We also found that both extra cellular Ca2+ and intracellular Ca2+ stores contributed to the increase of [Ca2+](i), because completely treating Sf9 cells with CdCl(2) (5 mM), a Ca2+ channels blocker, R-III (100 μg/mL) induced a transient elevation of [Ca2+](i) in case of cells either in presence of Ca2+ containing or Ca2+ free solution. In these conditions, pH(i) showed similar changes with that of [Ca2+](i) on the whole. Accordingly, we supposed that there was a certain linkage for change of [Ca2+](i), cell cycle arrest, proliferation inhibition in Sf9 cells induced by R-III.

On the duration and intensity of cumulative advantage competitions

NASA Astrophysics Data System (ADS)

Jiang, Bo; Sun, Liyuan; Figueiredo, Daniel R.; Ribeiro, Bruno; Towsley, Don

2015-11-01

Network growth can be framed as a competition for edges among nodes in the network. As with various other social and physical systems, skill (fitness) and luck (random chance) act as fundamental forces driving competition dynamics. In the context of networks, cumulative advantage (CA)—the rich-get-richer effect—is seen as a driving principle governing the edge accumulation process. However, competitions coupled with CA exhibit non-trivial behavior and little is formally known about duration and intensity of CA competitions. By isolating two nodes in an ideal CA competition, we provide a mathematical understanding of how CA exacerbates the role of luck in detriment of skill. We show, for instance, that when nodes start with few edges, an early stroke of luck can place the less skilled in the lead for an extremely long period of time, a phenomenon we call ‘struggle of the fittest’. We prove that duration of a simple skill and luck competition model exhibit power-law tails when CA is present, regardless of skill difference, which is in sharp contrast to the exponential tails when fitness is distinct but CA is absent. We also prove that competition intensity is always upper bounded by an exponential tail, irrespective of CA and skills. Thus, CA competitions can be extremely long (infinite mean, depending on fitness ratio) but almost never very intense. The theoretical results are corroborated by extensive numerical simulations. Our findings have important implications to competitions not only among nodes in networks but also in contexts that leverage socio-physical models embodying CA competitions.

Recycling slaughterhouse waste into fertilizer: how do pyrolysis temperature and biomass additions affect phosphorus availability and chemistry?

PubMed

Zwetsloot, Marie J; Lehmann, Johannes; Solomon, Dawit

2015-01-01

Pyrolysis of slaughterhouse waste could promote more sustainable phosphorus (P) usage through the development of alternative P fertilizers. This study investigated how pyrolysis temperature (220, 350, 550 and 750 °C), rendering before pyrolysis, and wood or corn biomass additions affect P chemistry in bone char, plant availability, and its potential as P fertilizer. Linear combination fitting of synchrotron-based X-ray absorption near edge structure spectra demonstrated that higher pyrolysis temperatures decreased the fit with organic P references, but increased the fit with a hydroxyapatite (HA) reference, used as an indicator of high calcium phosphate (CaP) crystallinity. The fit to the HA reference increased from 0% to 69% in bone with meat residue and from 20% to 95% in rendered bone. Biomass additions to the bone with meat residue reduced the fit to the HA reference by 83% for wood and 95% for corn, and additions to rendered bone by 37% for wood. No detectable aromatic P forms were generated by pyrolysis. High CaP crystallinity was correlated with low water-extractable P, but high formic acid-extractable P indicative of high plant availability. Bone char supplied available P which was only 24% lower than Triple Superphosphate fertilizer and two- to five-fold higher than rock phosphate. Pyrolysis temperature and biomass additions can be used to design P fertilizer characteristics of bone char through changing CaP crystallinity that optimize P availability to plants. © 2014 Society of Chemical Industry.

A steady-state mechanism can account for the properties of inositol 2,4,5-trisphosphate-stimulated Ca2+ release from permeabilized L1210 cells.

PubMed Central

Loomis-Husselbee, J W; Dawson, A P

1993-01-01

We have investigated the effects of sub-maximal Ins(2,4,5)P3 concentrations on the Ca2+ permeability of the residual undischarged Ca2+ stores in electroporated or digitonin-permeabilized L1210 cells by measuring Ca(2+)-efflux rate after addition of the ATPase inhibitor thapsigargin. Low concentrations of Ins(2,4,5)P3, causing rapid discharge of a small proportion of the releasable Ca2+, result in a substantial stimulation of Ca2+ efflux after thapsigargin addition. This indicates firstly that in the absence of thapsigargin there must have been a substantial, counterbalancing, increase in rate of Ca2+ pumping, and secondly that the increased Ca2+ permeability is more consistent with a steady state than with a quantal model of Ca2+ release. Similar increases in passive Ca2+ permeability are produced by addition of concentrations of ionomycin which produce equivalent changes in Ca2+ loading to those produced by Ins(2,4,5)P3, although the time course and initial rate of Ca2+ release are very much slower. In the presence of a Ca(2+)-buffering system, the time course of Ca2+ release by Ins(2,4,5)P3 becomes superimposable on that of ionomycin, indicating that the initial rapid phase of Ins(2,4,5)P3-stimulated Ca2+ is at least partially due to positive feedback from extravesicular Ca2+. PMID:8382056

Electronic Structure of Ytterbium-Doped Strontium Fluoroapatite: Photoemission and Photoabsorption Investigation

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

Nelson, Art J.; Van Buuren, Tony W.; Bostedt, C

X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium-doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure and Sr 3d, P 2p and 2s, Yb 4d and 4p, F 1s and O 1s core lines were used to evaluate the surface and near surface chemistry of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N4,5-edge), Sr 3d (M4,5-edge), P 2p (L2,3-edge), F 1s and O 1s (K-edges) absorption edges. These results provide themore » first measurements of the electronic structure and surface chemistry of this material.« less

Periodontal regeneration using an injectable bone cement combined with BMP-2 or FGF-2.

PubMed

Oortgiesen, Daniël A W; Walboomers, X Frank; Bronckers, Antonius L J J; Meijer, Gert J; Jansen, John A

2014-03-01

Periodontitis is a frequently diagnosed oral disease characterized by bone resorption and soft tissue loss around teeth. Unfortunately, currently available therapies only slow or arrest progress of the disease. Ideally, treatment of periodontal defects should be focused on complete regeneration of the lost tissues [(bone and periodontal ligament (PDL)]. As a result, this study used intrabony defects to evaluate the regenerative potential of an injectable macroporous calcium phosphate cement (CaP) in combination with bone morphogenetic protein-2 (BMP-2) or fibroblast growth factor-2 (FGF-2). After creating 30 periodontal defects in 15 Wistar rats, three treatment strategies were conducted: application of CaP only, CaP + BMP-2 and CaP + FGF-2. Animals were euthanized after 12 weeks and processed for histology and histomorphometry. Using CaP alone resulted in limited effects on PDL and bone healing. CaP + BMP-2 showed a good response for bone healing; a significant 2.4 fold increase in bone healing score was observed compared to CaP. However, for PDL healing, CaP + BMP-2 treatment showed no difference compared to the CaP group. The best results were observed with the combined treatment of CaP + FGF-2, which showed a significant 3.3 fold increase in PDL healing score compared to CaP + BMP-2 and a significant 2.6 fold increase compared to CaP. For bone healing, CaP +  FGF-2 showed a significant 1.9 fold increase compared to CaP but no significant difference was noted compared to the CaP + BMP-2 group. The combination of a topical application of FGF-2 and an injectable CaP seems to be a promising treatment modality for periodontal regeneration. Copyright © 2012 John Wiley & Sons, Ltd.

Uncovering the Atomistic Mechanism for Calcite Step Growth

DOE PAGES

De La Pierre, Marco; Raiteri, Paolo; Stack, Andrew G.; ...

2017-04-13

Determining a complete atomic-level picture of how minerals grow from aqueous solution remains a challenge as macroscopic rates can be a convolution of many reactions. For the case of calcite (CaCO 3) in water, computer simulations have been used in this paper to map the complex thermodynamic landscape leading to growth of the two distinct steps, acute and obtuse, on the basal surface. The carbonate ion is found to preferentially adsorb at the upper edge of acute steps while Ca 2+ only adsorbs after CO 3 2-. In contrast to the conventional picture, ion pairs prefer to bind at themore » upper edge of the step with only one ion, at most, coordinated to the step and lower terrace. Finally, migration of the first carbonate ion to a growth site is found to be rate-limiting for kink nucleation, with this process having a lower activation energy on the obtuse step.« less

Photocatalytic activity of silicon-based nanoflakes for the decomposition of nitrogen monoxide.

PubMed

Itahara, Hiroshi; Wu, Xiaoyong; Imagawa, Haruo; Yin, Shu; Kojima, Kazunobu; Chichibu, Shigefusa F; Sato, Tsugio

2017-07-04

The photocatalytic decomposition of nitrogen monoxide (NO) was achieved for the first time using Si-based nanomaterials. Nanocomposite powders composed of Si nanoflakes and metallic particles (Ni and Ni 3 Si) were synthesized using a simple one-pot reaction of layered CaSi 2 and NiCl 2 . The synthesized nanocomposites have a wide optical absorption band from the visible to the ultraviolet. Under the assumption of a direct transition, the photoabsorption behavior is well described and an absorption edge of ca. 1.8 eV is indicated. Conventional Si and SiO powders with indirect absorption edges of 1.1 and 1.4 eV, respectively, exhibit considerably low photocatalytic activities for NO decomposition. In contrast, the synthesized nanocomposites exhibited photocatalytic activities under irradiation with light at wavelengths >290 nm (<4.28 eV). The photocatalytic activities of the nanocomposites were confirmed to be constant and did not degrade with the light irradiation time.

Prevalence, Features, and Prognostic Importance of Edge Dissection After Drug-Eluting Stent Implantation: An ADAPT-DES Intravascular Ultrasound Substudy.

PubMed

Kobayashi, Nobuaki; Mintz, Gary S; Witzenbichler, Bernhard; Metzger, D Christopher; Rinaldi, Michael J; Duffy, Peter L; Weisz, Giora; Stuckey, Thomas D; Brodie, Bruce R; Parvataneni, Rupa; Kirtane, Ajay J; Stone, Gregg W; Maehara, Akiko

2016-07-01

Intravascular ultrasound detects stent edge dissections after percutaneous coronary intervention that are not seen angiographically. This study investigated the association between stent edge dissections and clinical outcomes. ADAPT-DES (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents) was a large-scale, prospective, multicenter study of patients undergoing drug-eluting stent implantation. In this prospective substudy, 2062 patients (2433 lesions) were evaluated with intravascular ultrasound to characterize the morphological features and clinical outcomes of stent edge dissection after percutaneous coronary intervention. The prevalence of post-percutaneous coronary intervention stent edge dissection was 6.6% per lesion (161 of 2433). Calcified plaque at the proximal stent edge (relative risk [RR]=1.72; P=0.04) and proximal stent edge expansion (RR=1.18; P=0.004) were predictors for proximal dissection; attenuated plaque at the distal stent edge (RR=3.52; P=0.004), distal reference plaque burden (RR=1.56; P<0.0001), and distal edge stent expansion (RR=1.11; P=0.02) were predictors for distal dissection. At 1-year follow-up, target lesion revascularization was more common in lesions with versus without dissection (5.2% versus 2.7%; P=0.04). Multivariable analysis indicated that residual dissection was associated with target lesion revascularization at 1-year follow-up (RR=2.67; P=0.02). Among lesions with dissection, smaller effective lumen area increased the risk of target lesion revascularization at 1-year follow-up (cutoff value of 5.1 mm(2); P=0.05). Greater stent expansion and the presence of large, calcified, and/or attenuated plaques were independent predictors of stent edge dissection. Residual stent edge dissection, especially with a smaller effective lumen area, was associated with target lesion revascularization during 1-year follow-up after drug-eluting stent implantation. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00638794. © 2016 American Heart Association, Inc.

ATP promotes cell survival via regulation of cytosolic [Ca2+] and Bcl-2/Bax ratio in lung cancer cells

PubMed Central

Song, Shanshan; Jacobson, Krista N.; McDermott, Kimberly M.; Reddy, Sekhar P.; Cress, Anne E.; Tang, Haiyang; Dudek, Steven M.; Black, Stephen M.; Garcia, Joe G. N.; Makino, Ayako

2015-01-01

Adenosine triphosphate (ATP) is a ubiquitous extracellular messenger elevated in the tumor microenvironment. ATP regulates cell functions by acting on purinergic receptors (P2X and P2Y) and activating a series of intracellular signaling pathways. We examined ATP-induced Ca2+ signaling and its effects on antiapoptotic (Bcl-2) and proapoptotic (Bax) proteins in normal human airway epithelial cells and lung cancer cells. Lung cancer cells exhibited two phases (transient and plateau phases) of increase in cytosolic [Ca2+] ([Ca2+]cyt) caused by ATP, while only the transient phase was observed in normal cells. Removal of extracellular Ca2+ eliminated the plateau phase increase of [Ca2+]cyt in lung cancer cells, indicating that the plateau phase of [Ca2+]cyt increase is due to Ca2+ influx. The distribution of P2X (P2X1-7) and P2Y (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11) receptors was different between lung cancer cells and normal cells. Proapoptotic P2X7 was nearly undetectable in lung cancer cells, which may explain why lung cancer cells showed decreased cytotoxicity when treated with high concentration of ATP. The Bcl-2/Bax ratio was increased in lung cancer cells following treatment with ATP; however, the antiapoptotic protein Bcl-2 demonstrated more sensitivity to ATP than proapoptotic protein Bax. Decreasing extracellular Ca2+ or chelating intracellular Ca2+ with BAPTA-AM significantly inhibited ATP-induced increase in Bcl-2/Bax ratio, indicating that a rise in [Ca2+]cyt through Ca2+ influx is the critical mediator for ATP-mediated increase in Bcl-2/Bax ratio. Therefore, despite high ATP levels in the tumor microenvironment, which would induce cell apoptosis in normal cells, the decreased P2X7 and elevated Bcl-2/Bax ratio in lung cancer cells may enable tumor cells to survive. Increasing the Bcl-2/Bax ratio by exposure to high extracellular ATP may, therefore, be an important selective pressure promoting transformation and cancer progression. PMID:26491047

Calcium aluminate in alumina

NASA Astrophysics Data System (ADS)

Altay, Arzu

The properties of ceramic materials are determined not only by the composition and structure of the phases present, but also by the distribution of impurities, intergranular films and second phases. The phase distribution and microstructure both depend on the fabrication techniques, the raw materials used, the phase-equilibrium relations, grain growth and sintering processes. In this dissertation research, various approaches have been employed to understand fundamental phenomena such as grain growth, impurity segregation, second-phase formation and crystallization. The materials system chosen was alumina intentionally doped with calcium. Atomic-scale structural analyses of grain boundaries in alumina were carried on the processed samples. It was found that above certain calcium concentrations, CA6 precipitated as a second phase at all sintering temperatures. The results also showed that abnormal grain growth can occur after precipitation and it is not only related to the calcium level, but it is also temperature dependent. In order to understand the formation mechanism of CA6 precipitates in calcium doped alumina samples, several studies have been carried out using either bulk materials or thin films The crystallization of CA2 and CA6 powders has been studied. Chemical processing techniques were used to synthesize the powders. It was observed that CA2 powders crystallized directly, however CA6 powders crystallized through gamma-Al 2O3 solid solution. The results of energy-loss near-edge spectrometry confirmed that gamma-Al2O3 can dissolve calcium. Calcium aluminate/alumina reaction couples have also been investigated. All reaction couples were heat treated following deposition. It was found that gamma-Al2O3 was formed at the interface as a result of the interfacial reaction between the film and the substrate. gamma-Al 2O3 at the interface was stable at much higher temperatures compared to the bulk gamma-Al2O3 formed prior to the CA6 crystallization. In order to complement the studies carried out on the calcium aluminate phases, energy-loss near-edge structure (ELNES) fingerprints of CA2 and CA6 were obtained. It was shown that it is possible to distinguish these phases from each other by comparing the ELNES fingerprints. Theoretical calculations of ELNES were used to assign spectral features to certain symmetry environments that can later be used to understand the structures of unknown materials.

Cytosolic acidification and intracellular zinc release in hippocampal neurons

PubMed Central

Kiedrowski, Lech

2012-01-01

In neurons exposed to glutamate, Ca2+ influx triggers intracellular Zn2+ release via an as yet unclear mechanism. Since glutamate induces a Ca2+-dependent cytosolic acidification, the present work tested the relationships among intracellular Ca2+ concentration ([Ca2+]i), intracellular pH (pHi), and [Zn2+]i. Cultured hippocampal neurons were exposed to glutamate and glycine (Glu/Gly), while [Zn2+]i, [Ca2+]i and pHi were monitored using FluoZin-3, Fura2-FF, and 2′,7′-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein, respectively. Glu/Gly applications decreased pHi to 6.1 and induced intracellular Zn2+ release in a Ca2+-dependent manner, as expected. The pHi drop reduced the affinity of FluoZin-3 and Fura-2-FF for Zn2+. The rate of Glu/Gly-induced [Zn2+]i increase was not correlated with the rate of [Ca2+]i increase. Instead, the extent of [Zn2+]i elevations corresponded well to the rate of pHi drop. Namely, [Zn2+]i increased more in more highly acidified neurons. Inhibiting the mechanisms responsible for the Ca2+-dependent pHi drop (plasmalemmal Ca2+ pump and mitochondria) counteracted the Glu/Gly-induced intracellular Zn2+ release. Alkaline pH (8.5) suppressed Glu/Gly-induced intracellular Zn2+ release whereas acidic pH (6.0) enhanced it. A pHi drop to 6.0 (without any Ca2+ influx or glutamate receptor activation) led to intracellular Zn2+ release; the released Zn2+ (free Zn2+ plus Zn2+ bound to Fura-2FF and FluoZin-3) reached 1 μM. PMID:22339672

Local and systemic effects of leg cycling training on arterial wall thickness in healthy humans.

PubMed

Thijssen, Dick H J; Dawson, Ellen A; van den Munckhof, Inge C L; Birk, Gurpreet K; Timothy Cable, N; Green, Daniel J

2013-08-01

Exercise training is associated with direct effects on conduit artery function and structure. Cross-sectional studies suggest the presence of systemic changes in wall thickness as a result of exercise in healthy subjects, but no previous study has examined this question in humans undertaking exercise training. To examine the change in superficial femoral (SFA, i.e. local effect) and carotid (CA, i.e. systemic effect) artery wall thickness across 8 weeks of lower limb cycle training in healthy young men. Fourteen healthy young male subjects were assigned to an 8-week training study of cycling exercise (n = 9) or a control period (n = 5). Before, during (2, 4 and 6 weeks) and after training, SFA and CA wall thickness was examined using automated edge-detection of high resolution ultrasound images. We also measured resting diameter and calculated the wall:lumen(W:L)-ratio. Exercise training did not alter CA or SFA baseline diameter (P = 0.14), but was associated with gradual, consistent and significant decreases in wall thickness and W:L-ratio in both the CA and SFA (P < 0.001 and 0.002, respectively). Two-way ANOVA revealed a comparable magnitude of decrease in wall thickness and W:L-ratio in both arteries across the 8-week period (interaction-effect; P = 0.29 and 0.12, respectively). No changes in artery diameter, wall thickness or W:L-ratio were apparent in controls (0.82, 0.38 and 0.52, respectively). We found that cycle exercise training in healthy young individuals is associated with modest, but significant, decreases in wall thickness in the superficial femoral and carotid arteries. These findings suggest that exercise training causes systemic adaptation of the arterial wall in healthy young subjects. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

The interplay of dietary nutrient level and varying calcium to phosphorus ratios on efficacy of a bacterial phytase: 2. Ileal and total tract nutrient utilization.

PubMed

Olukosi, O A; Fru-Nji, F

2014-12-01

A 14-d broiler experiment was conducted to assess the effects of 2 dietary variables on efficacy of a bacterial 6-phytase from Citobacter braakii on nutrient and phytate P (PP) utilization. Diets were formulated with or without nutrient matrix values (matrix) for phytase as negative control (NC) or positive control (PC), respectively, and with 2 Ca:total P (tP) levels (2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg of diet, thus producing a 2 × 2 × 3 factorial arrangement. Excreta were collected on d 19 to 21 and ileal digesta on d 21. There was no 3-way interaction on digestibility of any nutrient. There was matrix × phytase (P < 0.01) interaction for Ca and DM digestibility and Ca:tP × phytase interaction (P < 0.05) for acid hydrolyzed fat and Ca and P digestibility. Prececal flow of Mn, Zn, and Na was greater (P < 0.05) in NC diets, whereas phytase increased (P < 0.05) prececal flow of Mg, Fe, Mn, and Zn but decreased (P < 0.05) prececal Na flow. Total tract PP disappearance and total tract Ca retention increased (P < 0.05) with phytase supplementation in diets with 2:1 Ca:tP, whereas there was no effect of phytase supplementation on PP disappearance or Ca retention in diets with 2.5:1 Ca:tP. Total P and Ca retention were reduced (P < 0.05) in PC and NC diets when Ca:tP increased to 2.5:1, but the depression was more pronounced in the NC diet. In addition, PP disappearance decreased (P < 0.05) with increasing Ca:tP in the PC diets, but there was no effect of widening Ca:tP on PP disappearance in NC diets. It was concluded from the current study that the effect of phytase supplementation on P utilization is reduced when diets contain adequate P as exemplified in the PC diets and that the negative impact of wide Ca:tP is more pronounced in diets with phytase matrix allowance as exemplified in the NC diets. ©2014 Poultry Science Association Inc.

Basic Studies of Distributed Discharge Limiters

DTIC Science & Technology

2014-02-10

Sputtered Lanthanum Hexaboride Film Thickness on Field Emission from Metallic Knife Edge Cathodes,” M.P. Kirley, B. Novakovic , N. Sule, M. J. Weber, I...IEEE ICOPS, San Diego, CA (2009). 99. Nishant Sule, Matt Kirley, Bozidar Novakovic , John Scharer, Irena Knezevic and John H. Booske...M. Kirley, B. Novakovic , J. Scharer, I. Knezevic, and J.H. Booske, “Field emission from low work function cathode coatings,”, Intl. Conf. Plasma

Ca²⁺-dependent nitric oxide release in the injured endothelium of excised rat aorta: a promising mechanism applying in vascular prosthetic devices in aging patients.

PubMed

Berra-Romani, Roberto; Avelino-Cruz, José Everardo; Raqeeb, Abdul; Della Corte, Alessandro; Cinelli, Mariapia; Montagnani, Stefania; Guerra, Germano; Moccia, Francesco; Tanzi, Franco

2013-01-01

Nitric oxide is key to endothelial regeneration, but it is still unknown whether endothelial cell (EC) loss results in an increase in NO levels at the wound edge. We have already shown that endothelial damage induces a long-lasting Ca²⁺ entry into surviving cells though connexin hemichannels (CxHcs) uncoupled from their counterparts on ruptured cells. The physiological outcome of injury-induced Ca²⁺ inflow is, however, unknown. In this study, we sought to determine whether and how endothelial scraping induces NO production (NOP) in the endothelium of excised rat aorta by exploiting the NO-sensitive fluorochrome, DAF-FM diacetate and the Ca²⁺-sensitive fluorescent dye, Fura-2/AM. We demonstrated that injury-induced NOP at the lesion site is prevented in presence of the endothelial NO synthase inhibitor, L-NAME, and in absence of extracellular Ca²⁺. Unlike ATP-dependent NO liberation, the NO response to injury is insensitive to BTP-2, which selectively blocks store-operated Ca²⁺ inflow. However, injury-induced NOP is significantly reduced by classic gap junction blockers, and by connexin mimetic peptides specifically targeting Cx37Hcs, Cx40HCs, and Cx43Hcs. Moreover, disruption of caveolar integrity prevents injury-elicited NO signaling, but not the accompanying Ca²⁺ response. The data presented provide the first evidence that endothelial scraping stimulates NO synthesis at the wound edge, which might both exert an immediate anti-thrombotic and anti-inflammatory action and promote the subsequent re-endothelialization.

Interband interference effects at the edge of a multiband chiral p -wave superconductor

NASA Astrophysics Data System (ADS)

Zhang, Jia-Long; Huang, Wen; Sigrist, Manfred; Yao, Dao-Xin

2017-12-01

Chiral superconductors support chiral edge modes and potentially spontaneous edge currents at their boundaries. Motivated by the putative multiband chiral p -wave superconductor Sr2RuO4 , we study the influence of the interference between different bands at the edges, which may appear in the presence of moderate edge disorder or in edge tunneling measurements. We show that interband interference can strongly modify the measurable quantities at the edges when the order parameter exhibits phase difference between the bands. This is illustrated by investigating the edge dispersion and the edge current distribution in the presence of interband mixing, as well as the conductance at a tunneling junction. The results are discussed in connection with the putative chiral p -wave superconductor Sr2RuO4 . In passing, we also discuss similar interference effects in multiband models with other pairing symmetries.

Mechanism of Ca2+-influx and Ca2+/calmodulin-dependent protein kinase IV activity during in utero hypoxia in cerebral cortical neuronal nuclei of the guinea pig fetus at term.

PubMed

Vibert, Yanick M; Ashraf, Qazi M; Mishra, Om P; Delivoria-Papadopoulos, Maria

2008-08-08

Previously we showed that following hypoxia there is an increase in nuclear Ca(2+)-influx and Ca(2+)/calmodulin-dependent protein kinase IV activity (CaMK IV) in the cerebral cortex of term guinea pig fetus. The present study tests the hypothesis that clonidine administration will prevent hypoxia-induced increased neuronal nuclear Ca(2+)-influx and increased CaMK IV activity, by blocking high-affinity Ca(2+)-ATPase. Studies were conducted in 18 pregnant guinea pigs at term, normoxia (Nx, n=6), hypoxia (Hx, n=6) and clonidine with Hx (Hx+Clo, n=6). The pregnant guinea pig was exposed to a decreased FiO(2) of 0.07 for 60 min. Clonidine, an imidazoline inhibitor of high-affinity Ca(2+)-ATPase, was administered 12.5 microg/kg IP 30 min prior to hypoxia. Hypoxia was determined biochemically by ATP and phosphocreatine (PCr) levels. Nuclei were isolated and ATP-dependent (45)Ca(2+)-influx was determined. CaMK IV activity was determined by (33)P-incorporation into syntide 2 for 2 min at 37 degrees C in a medium containing 50mM HEPES (pH 7.5), 2mM DTT, 40muM syntide 2, 0.2mM (33)P-ATP, 10mM magnesium acetate, 5 microM PKI 5-24, 2 microM PKC 19-36 inhibitor peptides, 1 microM microcystine LR, 200 microM sodium orthovanadate and either 1mM EGTA (for CaMK IV-independent activity) or 0.8mM CaCl(2) and 1mM calmodulin (for total activity). ATP (mumoles/gbrain) values were significantly different in the Nx (4.62+/-0.2), Hx (1.65+/-0.2, p<0.05 vs. Nx), and Hx+Clo (1.92+/-0.6, p<0.05 vs. Nx). PCr (mumoles/g brain) values in the Nx (3.9+/-0.1), Hx (1.10+/-0.3, p<0.05 vs. Nx), and Hx+Clo (1.14+/-0.3, p<0.05 vs. Nx). There was a significant difference between nuclear Ca(2+)-influx (pmoles/mg protein/min) in Nx (3.98+/-0.4), Hx (10.38+/-0.7, p<0.05 vs. Nx), and Hx+Clo (7.35+/-0.9, p<0.05 vs. Nx, p<0.05 vs. Hx), and CaM KIV (pmoles/mg protein/min) in Nx (1314.00+/-195.4), Hx (2315.14+/-148.5, p<0.05 vs. Nx), and Hx+Clo (1686.75+/-154.3, p<0.05 vs. Nx, p<0.05 vs. Hx). We conclude that the mechanism of hypoxia-induced increased nuclear Ca(2+)-influx is mediated by high-affinity Ca(2+)-ATPase and that CaMK IV activity is nuclear Ca(2+)-influx-dependent. We speculate that hypoxia-induced alteration of high-affinity Ca(2+)-ATPase is a key step that triggers nuclear Ca(2+)-influx, leading to CREB protein-mediated increased expression of apoptotic proteins and hypoxic neuronal death.

Nutritional status of the cauliflower cultivar 'verona' grown with omission of out added macronutrients.

PubMed

Bianco, Matheus Saraiva; Cecílio Filho, Arthur Bernardes; de Carvalho, Leonardo Bianco

2015-01-01

Knowledge of plant nutritional status allows an understanding of the physiological responses of plants to crop fertilization. A hydroponic experiment evaluated the symptoms of macronutrient deficiency in cauliflower 'Verona' and determined: a) the macronutrient contents of foliar tissues when visual symptoms were observed, b) macronutrients content of foliar and inflorescence tissues at harvest. The effect of nutrient deficiency on inflorescence mass was also evaluated. Nitrogen deficiency caused chlorosis followed by purple color in the old leaves, while P deficiency caused only chlorosis in old leaves. Chlorosis at the edge of old leaves progressing to the center of the leaves was observed with the omission of K, and after was observed necrosis in the chlorotic areas. Ca deficiency caused tip burn in new leaves, while Mg deficiency caused internerval chlorosis in old leaves. The omission of each macronutrient reduced inflorescence dry matter. This deleterious effect was larger for N, P, and K deficiencies, reducing inflorescence dry matter by 87, 49, and 42%, respectively. When the nutrient solutions without N, P, K, Ca, or Mg were supplied to cauliflower plants, the macronutrient contents at harvest were 8.8, 0.6, 3.5, 13.0, and 0.8 g kg-1 in the foliar tissues and 27.3, 2.2, 21.6, 1.1, and 0.7 g kg-1 in the inflorescence tissues, respectively.

Nutritional Status of the Cauliflower Cultivar ‘Verona’ Grown with Omission of out Added Macronutrients

PubMed Central

Bianco, Matheus Saraiva; Cecílio Filho, Arthur Bernardes; de Carvalho, Leonardo Bianco

2015-01-01

Knowledge of plant nutritional status allows an understanding of the physiological responses of plants to crop fertilization. A hydroponic experiment evaluated the symptoms of macronutrient deficiency in cauliflower ‘Verona’ and determined: a) the macronutrient contents of foliar tissues when visual symptoms were observed, b) macronutrients content of foliar and inflorescence tissues at harvest. The effect of nutrient deficiency on inflorescence mass was also evaluated. Nitrogen deficiency caused chlorosis followed by purple color in the old leaves, while P deficiency caused only chlorosis in old leaves. Chlorosis at the edge of old leaves progressing to the center of the leaves was observed with the omission of K, and after was observed necrosis in the chlorotic areas. Ca deficiency caused tip burn in new leaves, while Mg deficiency caused internerval chlorosis in old leaves. The omission of each macronutrient reduced inflorescence dry matter. This deleterious effect was larger for N, P, and K deficiencies, reducing inflorescence dry matter by 87, 49, and 42%, respectively. When the nutrient solutions without N, P, K, Ca, or Mg were supplied to cauliflower plants, the macronutrient contents at harvest were 8.8, 0.6, 3.5, 13.0, and 0.8 g kg-1 in the foliar tissues and 27.3, 2.2, 21.6, 1.1, and 0.7 g kg-1 in the inflorescence tissues, respectively. PMID:25856380

Properties of a Novel pH-dependent Ca2+ Permeation Pathway Present in Male Germ Cells with Possible Roles in Spermatogenesis and Mature Sperm Function

PubMed Central

Santi, Celia M.; Santos, Teresa; Hernández-Cruz, Arturo; Darszon, Alberto

1998-01-01

Rises of intracellular Ca2+ ([Ca2+]i) are key signals for cell division, differentiation, and maturation. Similarly, they are likely to be important for the unique processes of meiosis and spermatogenesis, carried out exclusively by male germ cells. In addition, elevations of [Ca2+]i and intracellular pH (pHi) in mature sperm trigger at least two events obligatory for fertilization: capacitation and acrosome reaction. Evidence implicates the activity of Ca2+ channels modulated by pHi in the origin of these Ca2+ elevations, but their nature remains unexplored, in part because work in individual spermatozoa are hampered by formidable experimental difficulties. Recently, late spermatogenic cells have emerged as a model system for studying aspects relevant for sperm physiology, such as plasmalemmal ion fluxes. Here we describe the first study on the influence of controlled intracellular alkalinization on [Ca2+]i on identified spermatogenic cells from mouse adult testes. In BCECF [(2′,7′)-bis(carboxymethyl)- (5,6)-carboxyfluorescein]-AM-loaded spermatogenic cells, a brief (30–60 s) application of 25 mM NH4Cl increased pHi by ∼1.3 U from a resting pHi ∼6.65. A steady pHi plateau was maintained during NH4Cl application, with little or no rebound acidification. In fura-2-AM-loaded cells, alkalinization induced a biphasic response composed of an initial [Ca2+]i drop followed by a two- to threefold rise. Maneuvers that inhibit either Ca2+ influx or intracellular Ca2+ release demonstrated that the majority of the Ca2+ rise results from plasma membrane Ca2+ influx, although a small component likely to result from intracellular Ca2+ release was occasionally observed. Ca2+ transients potentiated with repeated NH4Cl applications, gradually obliterating the initial [Ca2+]i drop. The pH-sensitive Ca2+ permeation pathway allows the passage of other divalents (Sr2+, Ba2+, and Mn2+) and is blocked by inorganic Ca2+ channel blockers (Ni2+ and Cd2+), but not by the organic blocker nifedipine. The magnitude of these Ca2+ transients increased as maturation advanced, with the largest responses being recorded in testicular sperm. By extrapolation, these findings suggest that the pH-dependent Ca2+ influx pathway could play significant roles in mature sperm physiology. Its pharmacology and ion selectivity suggests that it corresponds to an ion channel different from the voltage-gated T-type Ca2+ channel also present in spermatogenic cells. We postulate that the Ca2+ permeation pathway regulated by pHi, if present in mature sperm, may be responsible for the dihydropyridine-insensitive Ca2+ influx required for initiating the acrosome reaction and perhaps other important sperm functions. PMID:9649582

Heterologous desensitization of both phosphoinositide and Ca2+ signaling in SH-SY5Y neuroblastoma cells: a role for intracellular Ca2+ store depletion?

PubMed

Willars, G B; Nahorski, S R

1995-03-01

Measurement of the intracellular Ca2+ concentration ([Ca2+]i) in fura-2-loaded single cells of the human neuroblastoma line SH-SY5Y indicated coexpression of muscarinic and bradykinin receptors linked to activation of phosphoinositidase C (PIC). Both agonists elevated [Ca2+]i and inositol-1,4,5-trisphosphate [Ins(1,4,5)P3] levels in populations of adherent cells, although in cells used directly upon attainment of confluence the responses to carbachol were greater than those to bradykinin and displayed additional sustained components. This model system was used to examine heterologous interactions when a second PIC-linked agonist was added 100-300 sec after but in the continued presence of the first. Maximal (1 mM) carbachol concentrations abolished the elevation of [Ca2+]i produced by bradykinin but the muscarinic antagonist atropine (10 microM) restored the response, provided that extracellular Ca2+ was present throughout the experiment or was added before bradykinin. Carbachol also abolished bradykinin-mediated Ins(1,4,5)P3 elevation. In contrast, bradykinin did not influence [Ca2+]i or Ins(1,4,5)P3 responses to carbachol in the presence of extracellular Ca2+. In cells maintained at confluence for 2 weeks, the rapid peak elevations of [Ca2+]i and Ins(1,4,5)P3 levels induced by carbachol and bradykinin were approximately equivalent in magnitude. In these cells carbachol again abolished bradykinin-mediated elevation of [Ca2+]i but only attenuated, rather than abolished, the elevation of Ins(1,4,5)P3 levels. The [Ca2+]i and Ins(1,4,5)P3 responses to bradykinin were fully restored 100 sec after atropine only in the presence of extracellular Ca2+. Thus, depletion of an intracellular Ins(1,4,5)P3-sensitive Ca2+ store may underlie the ability of carbachol to produce not only heterologous desensitization of the [Ca2+]i elevation induced by bradykinin but also that of the Ins(1,4,5)P3 response. This suggests a feed-forward activation of PIC by Ca2+ released from Ins(1,4,5)P3-sensitive stores. Furthermore, studies in which Ins(1,4,5)P3-sensitive stores were depleted with thapsigargin and cells were challenged in the presence or absence of extracellular Ca2+ indicated that Ca2+, irrespective of its origin (intra- or extracellular), potentiated the Ins(1,4,5)P3 response to bradykinin alone. In cells maintained at confluence for 2 weeks, bradykinin was again unable to influence either [Ca2+]i or Ins(1,4,5)P3 responses to carbachol in the presence of Ca2+. This lack of heterologous desensitization may be due to the rapid, full, homologous desensitization of bradykinin receptors, compared with an incomplete homologous desensitization of muscarinic receptors.

Glutamate 90 at the Luminal Ion Gate of Sarcoplasmic Reticulum Ca2+-ATPase Is Critical for Ca2+ Binding on Both Sides of the Membrane*

PubMed Central

Clausen, Johannes D.; Andersen, Jens Peter

2010-01-01

The roles of Ser72, Glu90, and Lys297 at the luminal ends of transmembrane helices M1, M2, and M4 of sarcoplasmic reticulum Ca2+-ATPase were examined by transient and steady-state kinetic analysis of mutants. The dependence on the luminal Ca2+ concentration of phosphorylation by Pi (“Ca2+ gradient-dependent E2P formation”) showed a reduction of the apparent affinity for luminal Ca2+ in mutants with alanine or leucine replacement of Glu90, whereas arginine replacement of Glu90 or Ser72 allowed E2P formation from Pi even at luminal Ca2+ concentrations much too small to support phosphorylation in wild type. The latter mutants further displayed a blocked dephosphorylation of E2P and an increased rate of conversion of the ADP-sensitive E1P phosphoenzyme intermediate to ADP-insensitive E2P as well as insensitivity of the E2·BeF3− complex to luminal Ca2+. Altogether, these findings, supported by structural modeling, indicate that the E2P intermediate is stabilized in the mutants with arginine replacement of Glu90 or Ser72, because the positive charge of the arginine side chain mimics Ca2+ occupying a luminally exposed low affinity Ca2+ site of E2P, thus identifying an essential locus (a “leaving site”) on the luminal Ca2+ exit pathway. Mutants with alanine or leucine replacement of Glu90 further displayed a marked slowing of the Ca2+ binding transition as well as slowing of the dissociation of Ca2+ from Ca2E1 back toward the cytoplasm, thus demonstrating that Glu90 is also critical for the function of the cytoplasmically exposed Ca2+ sites on the opposite side of the membrane relative to where Glu90 is located. PMID:20421308

Capstone Report on the Application, Monitoring, and Performance of Permeable Reactive Barriers for Ground-Water Remediation: Volume 1: Performance Evaluations at Two Sites

DTIC Science & Technology

2003-08-01

sepiolite , Mg 4 (OH) 2 Si 6 O 15 ·H 2 O...EC050801-3-5 EC050801-3-3 EC050801-3-2 EC050801-3-1 In te n si ty degrees 2-theta In te n si ty In te n si ty downgradient edge upgradient edge In te n...400 b ic a rb o n a te , m g /L 0 2 4 6 8 10 12 14 16 si lic a , m g /L Figure 4.12 Average (± 1 s.d.) concentrations of Na, K , Ca,

Microdomains of muscarinic acetylcholine and Ins(1,4,5)P3 receptors create ‘Ins(1,4,5)P3 junctions’ and sites of Ca2+ wave initiation in smooth muscle

PubMed Central

Olson, Marnie L.; Sandison, Mairi E.; Chalmers, Susan; McCarron, John G.

2012-01-01

Summary Increases in cytosolic Ca2+ concentration ([Ca2+]c) mediated by inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3, hereafter InsP3] regulate activities that include division, contraction and cell death. InsP3-evoked Ca2+ release often begins at a single site, then regeneratively propagates through the cell as a Ca2+ wave. The Ca2+ wave consistently begins at the same site on successive activations. Here, we address the mechanisms that determine the Ca2+ wave initiation site in intestinal smooth muscle cells. Neither an increased sensitivity of InsP3 receptors (InsP3R) to InsP3 nor regional clustering of muscarinic receptors (mAChR3) or InsP3R1 explained the selection of an initiation site. However, examination of the overlap of mAChR3 and InsP3R1 localisation, by centre of mass analysis, revealed that there was a small percentage (∼10%) of sites that showed colocalisation. Indeed, the extent of colocalisation was greatest at the Ca2+ wave initiation site. The initiation site might arise from a selective delivery of InsP3 from mAChR3 activity to particular InsP3Rs to generate faster local [Ca2+]c increases at sites of colocalisation. In support of this hypothesis, a localised subthreshold ‘priming’ InsP3 concentration applied rapidly, but at regions distant from the initiation site, shifted the wave to the site of the priming. Conversely, when the Ca2+ rise at the initiation site was rapidly and selectively attenuated, the Ca2+ wave again shifted and initiated at a new site. These results indicate that Ca2+ waves initiate where there is a structural and functional coupling of mAChR3 and InsP3R1, which generates junctions in which InsP3 acts as a highly localised signal by being rapidly and selectively delivered to InsP3R1. PMID:22946060

Investigation of the stability of glass-ceramic composites containing CeTi 2 O 6 and CaZrTi 2 O 7 after ion implantation

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

Paknahad, Elham; Grosvenor, Andrew P.

Glass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements. A key property that needs to be understood when developing nuclear waste sequestration materials is how the structure of the material responds to radioactive decay of nuclear waste elements, which can be simulated by high energy ion implantation. Borosilicate glass-ceramic composites containing brannerite-type (CeTi2O6) or zirconolite-type (CaZrTi2O7) oxides were synthesized at different annealing temperatures and investigated after being implanted with high-energy Au ions to mimic radiation induced structural damage. Backscattered electron (BSE) images were collected to investigatemore » the interaction of the brannerite crystallites with the glass matrix before and after implantation and showed that the morphology of the crystallites in the composite materials were not affected by radiation damage. Surface sensitive Ti K-edge glancing angle XANES spectra collected from the implanted composite materials showed that the structures of the CeTi2O6 and CaZrTi2O7 ceramics were damaged as a result of implantation; however, analysis of Si L2,3-edge XANES spectra indicated that the glass matrix was not affected by ion implantation.« less

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

NASA Astrophysics Data System (ADS)

Paknahad, Elham; Grosvenor, Andrew P.

2017-12-01

Glass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements. A key property that needs to be understood when developing nuclear waste sequestration materials is how the structure of the material responds to radioactive decay of nuclear waste elements, which can be simulated by high energy ion implantation. Borosilicate glass-ceramic composites containing brannerite-type (CeTi2O6) or zirconolite-type (CaZrTi2O7) oxides were synthesized at different annealing temperatures and investigated after being implanted with high-energy Au ions to mimic radiation induced structural damage. Backscattered electron (BSE) images were collected to investigate the interaction of the brannerite crystallites with the glass matrix before and after implantation and showed that the morphology of the crystallites in the composite materials were not affected by radiation damage. Surface sensitive Ti K-edge glancing angle XANES spectra collected from the implanted composite materials showed that the structures of the CeTi2O6 and CaZrTi2O7 ceramics were damaged as a result of implantation; however, analysis of Si L2,3-edge XANES spectra indicated that the glass matrix was not affected by ion implantation.

Role of Ce 4 + in the scintillation mechanism of codoped Gd 3 Ga 3 Al 2 O 12 : Ce

DOE PAGES

Wu, Yuntao; Meng, Fang; Li, Qi; ...

2014-10-17

To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce 4+, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce 4+ is still lacking. The aim of this work is to clarify the role of Ce 4+ in scintillators by studying Ca 2+ codoped Gd 3Ga 3Al 2O1 2∶Ce (GGAG∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca 2+codopingmore » content and the Ce 4+ fraction is seen. The energy-level diagrams of Ce 3+ and Ce 4+ in the Gd 3Ga 3Al 2O 12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d 1 state of Ce 4+ in the forbidden gap in comparison to that of Ce 3+. Underlying reasons for the decay-time acceleration resulting from Ca 2+ codoping are revealed, and the physical processes of the Ce 4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.« less

Lysosomes shape Ins(1,4,5)P3-evoked Ca2+ signals by selectively sequestering Ca2+ released from the endoplasmic reticulum

PubMed Central

López-Sanjurjo, Cristina I.; Tovey, Stephen C.; Prole, David L.; Taylor, Colin W.

2013-01-01

Summary Most intracellular Ca2+ signals result from opening of Ca2+ channels in the plasma membrane or endoplasmic reticulum (ER), and they are reversed by active transport across these membranes or by shuttling Ca2+ into mitochondria. Ca2+ channels in lysosomes contribute to endo-lysosomal trafficking and Ca2+ signalling, but the role of lysosomal Ca2+ uptake in Ca2+ signalling is unexplored. Inhibition of lysosomal Ca2+ uptake by dissipating the H+ gradient (using bafilomycin A1), perforating lysosomal membranes (using glycyl-L-phenylalanine 2-naphthylamide) or lysosome fusion (using vacuolin) increased the Ca2+ signals evoked by receptors that stimulate inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] formation. Bafilomycin A1 amplified the Ca2+ signals evoked by photolysis of caged Ins(1,4,5)P3 or by inhibition of ER Ca2+ pumps, and it slowed recovery from them. Ca2+ signals evoked by store-operated Ca2+ entry were unaffected by bafilomycin A1. Video-imaging with total internal reflection fluorescence microscopy revealed that lysosomes were motile and remained intimately associated with the ER. Close association of lysosomes with the ER allows them selectively to accumulate Ca2+ released by Ins(1,4,5)P3 receptors. PMID:23097044

Evolution of Tethyan phosphogenesis along the northern edges of the Arabian--African shield during the Cretaceous--Eocene as deduced from temporal variations of Ca and Nd isotopes and rates of P accumulation

NASA Astrophysics Data System (ADS)

Soudry, D.; Glenn, C. R.; Nathan, Y.; Segal, I.; VonderHaar, D.

2006-09-01

The evolution of Tethyan phosphogenesis during the Cretaceous-Eocene is examined to try to explain fluctuations of phosphogenesis through time, and whether or not they reflect long-term changes in ocean circulation or in continental weathering. Twenty-seven time-stratigraphic phosphate levels in various Tethyan sites, covering a time span of about 90 Myr from the Hauterivian to the Eocene, were analyzed for 44Ca/ 42Ca and 143Nd/ 144Nd in their carbonate fluorapatite (CFA) fraction. P and Ca accumulation rates and bulk sedimentation rates were quantified throughout the Cretaceous-Eocene Negev sequence to examine how changes in 44Ca/ 42Ca and 143Nd/ 144Nd are reflected in the intensity of phosphogenesis. A clear-cut change occurs in ɛNd( T) and δ44Ca and in the rates of P and Ca accumulation and bulk sedimentation through the time analyzed. ɛNd( T) is much lower in the Hauterivian-Lower Cenomanian (- 12.8 to - 10.9) than in the Upper Cenomanian-Eocene (- 7.8 to - 5.9). Much lower δ44Ca values occur in the Hauterivian-Turonian (- 0.22 to + 0.02) than in the Coniacian-Eocene (+ 0.23 to + 0.40). P accumulation rates in the Negev steeply increase from < 200 μmol cm - 2 k yr - 1 in the Albian-Coniacian to ˜ 1500 μmol cm - 2 k yr - 1 in the Campanian, whereas a strong decrease is concomitantly recorded in the rates of Ca accumulation and bulk sedimentation. In addition, distinct ɛNd( T) values are shown by the phosphorites of the Negev (- 6.7 to - 6.4) and Egypt (- 9.1 to - 7.6) during the Campanian, and by those of the Negev (- 7.8 to - 6.3) and North Africa (- 10.1 to - 8.9) during the Maastrichtian-Eocene. The culmination of P accumulation rates in the Negev during the Campanian, occurring with a high in ɛNd( T) and δ44Ca and a low in sedimentation rates, indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area. The abrupt ɛNd( T) rise after the Cenomanian is attributed to increased incursion of Pacific (radiogenic) water masses into the Tethys, driven by the Late Cretaceous global sea-level rise, the connection between North and South Atlantic, the global post-Santonian cooling, and the progressive widening of the Caribbean threshold, all acting in combination to significantly intensify the Tethyan circumglobal current (TCC). It also reflects a weakening of the continental Nd signal due to a reduction of exposed landmasses caused by increased flooding of continental shelves. High δ44Ca values at those times also point to a decrease in weathering Ca +2 fluxes and expansion of carbonate sedimentation in shelves, both enriching seawater with isotopically heavy Ca +2. Deep ocean circulation intensified by the post-Santonian cooling of high latitudes increased P inventory in the Tethys basin, whereas the strengthened TCC and the folded shelf likely resulted in coastal and topographically-induced upwelling, supplying P-rich intermediate waters to southeastern Tethys shelves. Only in the Paleocene-Eocene, following major changes in global circulation produced by narrowing of Tethys and widening of the Atlantic, did phosphogenesis shifts its locus of high intensity to the western (Atlantic) Tethys and West African Atlantic coasts. This change in paleocirculation is expressed by distinctly differing ɛNd( T) in the Middle East and the North and West African phosphorites, suggesting different oceanic P sources and current systems for these two major groups of phosphorites. Our Nd isotope results further suggest a weaker TCC during the Mid-Cretaceous, becoming more intense in Late Cretaceous times. They also point to the North Pacific Ocean as major source of deep water formation for the intermediate-deep waters in the Tethys Basin during the Late Cretaceous.

Femtosecond time-resolved X-ray absorption spectroscopy of anatase TiO2 nanoparticles using XFEL

PubMed Central

Obara, Yuki; Ito, Hironori; Ito, Terumasa; Kurahashi, Naoya; Thürmer, Stephan; Tanaka, Hiroki; Katayama, Tetsuo; Togashi, Tadashi; Owada, Shigeki; Yamamoto, Yo-ichi; Karashima, Shutaro; Nishitani, Junichi; Yabashi, Makina; Suzuki, Toshinori; Misawa, Kazuhiko

2017-01-01

The charge-carrier dynamics of anatase TiO2 nanoparticles in an aqueous solution were studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser in combination with a synchronized ultraviolet femtosecond laser (268 nm). Using an arrival time monitor for the X-ray pulses, we obtained a temporal resolution of 170 fs. The transient X-ray absorption spectra revealed an ultrafast Ti K-edge shift and a subsequent growth of a pre-edge structure. The edge shift occurred in ca. 100 fs and is ascribed to reduction of Ti by localization of generated conduction band electrons into shallow traps of self-trapped polarons or deep traps at penta-coordinate Ti sites. Growth of the pre-edge feature and reduction of the above-edge peak intensity occur with similar time constants of 300–400 fs, which we assign to the structural distortion dynamics near the surface. PMID:28713842

2. VIEW OF LOWER MILL FLOOR FOUNDATION, SHOWING, LEFT TO ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. VIEW OF LOWER MILL FLOOR FOUNDATION, SHOWING, LEFT TO RIGHT, EDGE OF MILLING FLOOR, TABLE FLOOR, VANNING FLOOR, LOADING LEVEL, TAILINGS POND IN RIGHT BACKGROUND. VIEW IS LOOKING FROM THE NORTHWEST - Mountain King Gold Mine & Mill, 4.3 Air miles Northwest of Copperopolis, Copperopolis, Calaveras County, CA

2. VIEW, LOOKING FROM THE NORTHEAST. THESE THREE CONCRETE MORTAR ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. VIEW, LOOKING FROM THE NORTHEAST. THESE THREE CONCRETE MORTAR BLOCKS WERE FOR THE MILL'S 3-STAMP BATTERIES ERECTED IN 1903, NORTH OF THE TWO 1901 BATTERIES WHICH WERE MOUNTED ON WOODEN TIMBERS - Wilbur-Womble Mill, Southern Edge Of Salt Spring Valley, Copperopolis, Calaveras County, CA

Voltage-dependent inward currents in smooth muscle cells of skeletal muscle arterioles

PubMed Central

Shirokov, Roman E.

2018-01-01

Voltage-dependent inward currents responsible for the depolarizing phase of action potentials were characterized in smooth muscle cells of 4th order arterioles in mouse skeletal muscle. Currents through L-type Ca2+ channels were expected to be dominant; however, action potentials were not eliminated in nominally Ca2+-free bathing solution or by addition of L-type Ca2+ channel blocker nifedipine (10 μM). Instead, Na+ channel blocker tetrodotoxin (TTX, 1 μM) reduced the maximal velocity of the upstroke at low, but not at normal (2 mM), Ca2+ in the bath. The magnitude of TTX-sensitive currents recorded with 140 mM Na+ was about 20 pA/pF. TTX-sensitive currents decreased five-fold when Ca2+ increased from 2 to 10 mM. The currents reduced three-fold in the presence of 10 mM caffeine, but remained unaltered by 1 mM of isobutylmethylxanthine (IBMX). In addition to L-type Ca2+ currents (15 pA/pF in 20 mM Ca2+), we also found Ca2+ currents that are resistant to 10 μM nifedipine (5 pA/pF in 20 mM Ca2+). Based on their biophysical properties, these Ca2+ currents are likely to be through voltage-gated T-type Ca2+ channels. Our results suggest that Na+ and at least two types (T- and L-) of Ca2+ voltage-gated channels contribute to depolarization of smooth muscle cells in skeletal muscle arterioles. Voltage-gated Na+ channels appear to be under a tight control by Ca2+ signaling. PMID:29694371

Role of Ce4+ in the Scintillation Mechanism of Codoped Gd3Ga3Al2O12∶Ce

NASA Astrophysics Data System (ADS)

Wu, Yuntao; Meng, Fang; Li, Qi; Koschan, Merry; Melcher, Charles L.

2014-10-01

To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce44, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce4+ is still lacking. The aim of this work is to clarify the role of Ce4+ in scintillators by studying Ca2+ codoped Gd3Ga3Al2O12∶Ce (GGAG ∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca2+ codoping content and the Ce4+ fraction is seen. The energy-level diagrams of Ce3+ and Ce4+ in the Gd3Ga3Al2O12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d1 state of Ce4+ in the forbidden gap in comparison to that of Ce3+. Underlying reasons for the decay-time acceleration resulting from Ca2+ codoping are revealed, and the physical processes of the Ce4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.

Effects of calcium magnesium carbonate and roughage level on feedlot performance, ruminal metabolism, and site and extent of digestion in steers fed high-grain diets.

PubMed

Crawford, G I; Keeler, C D; Wagner, J J; Krehbiel, C R; Erickson, G E; Crombie, M B; Nunnery, G A

2008-11-01

A feedlot growth performance experiment and 2 metabolism experiments were conducted to evaluate dietary roughage concentration and calcium magnesium carbonate in steers fed a high-grain diet. In Exp. 1, one hundred ninety-two crossbred yearling steers (320 +/- 10 kg of initial BW) were fed diets based on steam-flaked corn with 0, 0.75, or 1.5% CaMg(CO(3))(2). There were no effects (P > or = 0.13) on ADG, DMI, G:F, or total water intake due to CaMg(CO(3))(2). In Exp. 2, five ruminally and duodenally fistulated steers (263 +/- 9 kg of initial BW) were used in a 5 x 5 Latin square design, with 5 dietary treatments arranged in a 2 x 2 + 1 factorial: 1) 3.8% dietary roughage and no CaMg(CO(3))(2); 2) 7.6% dietary roughage and no CaMg(CO(3))(2); 3) 11.4% dietary roughage and no CaMg(CO(3))(2); 4) 3.8% dietary roughage and 1.5% CaMg(CO(3))(2); and 5) 7.6% dietary roughage and 1.5% CaMg(CO(3))(2). Water consumption was less (quadratic, P = 0.003) when 7.6% dietary roughage was fed compared with 3.8 or 11.4% dietary roughage. Intake of DM was not affected (P > or = 0.16) by dietary roughage or by CaMg(CO(3))(2). Poststomach and total tract starch digestion decreased (linear, P < 0.01) as dietary roughage increased. Ruminal pH tended (P = 0.08) to increase as dietary roughage increased but was not affected (P = 0.60) by CaMg(CO(3))(2). In Exp. 3, DMI and ruminal pH were continuously monitored in a 6 x 6 Latin square design using 6 ruminally and duodenally fistulated Holstein steers (229 +/- 10 kg of initial BW). A 3 x 2 factorial treatment structure was utilized, with factors consisting of dietary roughage concentration (4.5, 9.0, or 13.5%) and CaMg(CO(3))(2) inclusion (0 or 1.0%) to replace MgO and partially replace lime-stone. A dietary roughage x CaMg(CO(3))(2) interaction (P = 0.01) occurred as steers consuming 13.5% roughage, 1.0% CaMg(CO(3))(2) had greater DMI per meal than those consuming 4.5% dietary roughage, no CaMg(CO(3))(2) and 9.0% dietary roughage, 1.0% CaMg(CO(3))(2). Steers consuming 13.5% dietary roughage, 1.0% CaMg(CO(3))(2) and 9.0% dietary roughage, no CaMg(CO(3))(2) had greater meal length (min/meal; P = 0.01) than steers consuming 4.5% dietary roughage, no CaMg(CO(3))(2). Total tract OM digestibility decreased linearly (P = 0.01), and ruminal pH increased linearly (P = 0.01) with increasing dietary roughage concentration. Inclusion of CaMg(CO(3))(2) can replace limestone and MgO but did not produce ruminal pH responses similar to those observed by increasing dietary roughage in high-concentrate diets.

Role of Ca2+-independent phospholipase A2 and cytochrome P-450 in store-operated calcium entry in 3T6 fibroblasts.

PubMed

Martínez, Javier; Moreno, Juan J

2005-09-01

Store-operated calcium (SOC) channels and capacitative Ca2+ entry play a key role in cellular functions, but their mechanism of activation remains unclear. Here, we show that thapsigargin induces [3H] arachidonic acid (AA) release, 45Ca2+ influx and a subsequent enhancement of intracellular calcium concentration ([Ca2+]i. Thapsigargin-induced elevation of [Ca2+]i was inhibited by cytochrome P-450 inhibitors and by cytochrome P-450 epoxygenase inhibitor and was reverted by 11,12 EET addition. However, cyclooxygenase and lipoxygenase inhibitors have no effect. Moreover, we observed that four EETs were able to induce 45Ca2+ influx. Finally, we reported that the effect of 11,12 EET on 45Ca2+ influx was sensible to receptor-operated Ca2+ channel blockers (NiCl2, LaCl3) but not to voltage-dependent Ca2+ channel blocker as verapamil. Thus, AA released by Ca2+-independent phospholipase A2 and AA metabolism through cytochrome P-450 pathway may be crucial molecular determinant in thapsigargin activation of SOC channels and store-operated Ca2+ entry pathway in 3T6 fibroblasts. Moreover, EETs, the main cytochrome P-450 epoxygenase metabolites of AA, are involved in thapsigargin-stimulated Ca2+ influx. In summary, our results suggest that EETs are components of calcium influx factor(s).

[Genetic, epidemiologic and clinical study of familial prostate cancer].

PubMed

Valéri, Antoine

2002-01-01

Prostate cancer (CaP) is the most frequent cancer among men over 50 and its frequency increases with age. It has become a significant public health problem due to the ageing population. Epidemiologists report familial aggregation in 15 to 25% of cases and inherited susceptibility with autosomal dominant or X-linked model in 5 to 10% of cases. Clinical and biological features of familial CaP remain controversial. To perform: (1) Genetic study of familial Cap (mapping of susceptibility genes), (2) epidemiologic study (prevalence, associated cancers in the genealogy, model of transmission), and clinical study of familial CaP. (I) conducting a nationwide family collection (ProGène study) with 2+ CaP we have performed a genomewide linkage analysis and identified a predisposing locus on 1q42.2-43 named PCaP (Predisposing to Cancer of the Prostate); (II) conducting a systematic genealogic analysis of 691 CaP followed up in 3 University departments of urology (Hospitals of Brest, Paris St Louis and Nancy) we have observed: (1) 14.2% of familial and 3.6% of hereditary CaP, (2) a higher risk of breast cancer in first degree relatives of probands (CaP+) in familial CaP than in sporadic CaP and in early onset CaP (< 55 years) when compared with late onset CaP ([dG]75 years), (3) an autosomal dominant model with brother-brother dependance), (4) the lack of specific clinical or biological feature (except for early onset) in hereditary CaP when compared with sporadic CaP. (1) The mapping of a susceptibility locus will permit the cloning of a predisposing gene on 1q42.2-43, offer the possibility of genetic screening in families at risk and permit genotype/phenotype correlation studies; (2) the transmission model will improve parameteric linkage studies; (3) the lack of distinct specific clinical patterns suggest diagnostic and follow up modalities for familial and hereditary CaP similar to sporadic cancer while encouraging early screening of families at risk, given the earlier onset (5 to 10 years earlier) observed.

Study on the Anti-Poison Performance of Al–Y–P Master Alloy for Impurity Ca in Aluminum Alloys

PubMed Central

Zuo, Min; Dong, Yu; Zhao, Degang; Wang, Yan; Teng, Xinying

2017-01-01

In this article, the anti-poison performance of novel Al–6Y–2P master alloy for impurity Ca in hypereutectic Al–Si alloys was investigated in detail. According to the microstructural analysis, it can be found that the primary Si and eutectic Si particles could be relatively modified and refined. In order to investigate the influence mechanism of Ca on the limited refinement performance of Al–6Y–2P master alloy, types of Al–xSi–2Ca–3Y–1P (x = 0, 6, 12, 18, and 30) alloys were prepared. It is observed that Ca takes the form of more stable Ca3P2 compounds by reacting with YP, and the surface of Ca3P2 particles are unsmooth, and even some have wrinkles in Al Al–2Ca–3Y–1P alloy. With the increase of Si content in Al–xSi–2Ca–3Y–1P (x = 6, 12, 18 and 30) systems, the multi-encapsulation structures, i.e., the phosphide (AlP and YP), hexagonal Al2Si2Ca, the Al3Si2Y2 or primary Si from inside to outside in order were examined.The excapsulation of YP and AlP caused by Al2Si2Ca might be the reason for the limited refinement effect of Al–6Y–2P master alloy for hypereutectic Al–18Si alloys. PMID:29186862

Investigation on the interfacial chemical state and band alignment for the sputtering-deposited CaF2/p-GaN heterojunction by angle-resolved X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Kexiong; Liao, Meiyong; Sumiya, Masatomo; Koide, Yasuo; Sang, Liwen

2016-11-01

The interfacial chemical state and the band alignment of the sputtering-deposited CaF2/p-GaN hetero-structure were investigated by angle-resolved X-ray photoelectron spectroscopy. The dependence of Ga 3p core-level positions on the collection angles proves that the downward band bending of p-GaN is reduced from 1.51 to 0.85 eV after the deposition of CaF2, which may be due to the reduction of Mg-Ga-O-related interface states by the oxygen-free deposition of CaF2. The band gap of sputtering-deposited CaF2 is estimated to be about 7.97 eV with a potential gradient of 0.48 eV obtained by the variation of the Ca 2p3/2 position on different collection angles. By taking into account the p-GaN surface band bending and potential gradient in the CaF2 layer, large valence and conduction band offsets of 2.66 ± 0.20 and 1.92 ± 0.20 eV between CaF2 and p-GaN are obtained. These results indicate that CaF2 is a promising gate dielectric layer on the p-GaN for the application of metal-insulator-semiconductor devices.

The MAP kinase-activated protein kinase Rck2p regulates cellular responses to cell wall stresses, filamentation and virulence in the human fungal pathogen Candida albicans.

PubMed

Li, Xichuan; Du, Wei; Zhao, Jingwen; Zhang, Lilin; Zhu, Zhiyan; Jiang, Linghuo

2010-06-01

Rck2p is the Hog1p-MAP kinase-activated protein kinase required for the attenuation of protein synthesis in response to an osmotic challenge in Saccharomyces cerevisiae. Rck2p also regulates rapamycin sensitivity in both S. cerevisiae and Candida albicans. In this study, we demonstrate that the deletion of CaRCK2 renders C. albicans cells sensitive to, and CaRck2p translocates from the cytosol to the nucleus in response to, cell wall stresses caused by Congo red, Calcoflor White, elevated heat and zymolyase. However, the kinase activity of CaRck2p is not required for the cellular response to these cell wall stresses. Furthermore, transcripts of cell wall protein-encoding genes CaBGL2, CaHWP1 and CaXOG1 are reduced in C. albicans cells lacking CaRCK2. The deletion of CaRCK2 also reduces the in vitro filamentation of C. albicans and its virulence in a mouse model of systemic candidasis. The kinase activity of CaRck2p is required for the virulence, but not for the in vitro filamentation, in C. albicans. Therefore, Rck2p regulates cellular responses to cell wall stresses, filamentation and virulence in the human fungal pathogen C. albicans.

Akt activation by Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) in ovarian cancer cells.

PubMed

Gocher, Angela M; Azabdaftari, Gissou; Euscher, Lindsey M; Dai, Shuhang; Karacosta, Loukia G; Franke, Thomas F; Edelman, Arthur M

2017-08-25

Hyperactivation of Akt is associated with oncogenic changes in the growth, survival, and chemoresistance of cancer cells. The PI3K/phosphoinositide-dependent kinase (PDK) 1 pathway represents the canonical mechanism for phosphorylation of Akt at its primary activation site, Thr-308. We observed that Ca 2+ /calmodulin (CaM)-dependent protein kinase kinase 2 (β) (CaMKK2) is highly expressed in high-grade serous ovarian cancer, and we investigated its role in Akt activation in ovarian cancer (OVCa) cell lines (OVCAR-3, SKOV-3, and Caov-3). Knockdown or pharmacological inhibition of CaMKK2 produced phenotypes expected of Akt inhibition, including reductions in cell growth and cell viability and in the regulation of Akt downstream targets involved in G 1 /S transition and apoptosis. CaMKK2 knockdown or inhibition decreased Akt phosphorylation at Thr-308 and Ser-473 to extents similar to those of PDK1 knockdown or PI3K inhibition. Combined CaMKK2 and PDK1 knockdown or CaMKK and PI3K inhibition, respectively, produced additive effects on p-Akt and cell growth, consistent with direct Akt phosphorylation by CaMKK2. This conclusion was supported by the absence of effects of CaMKK2 knockdown/inhibition on alternative means of activating Akt via p-Akt Thr-450, p-PDK1 Ser-241, or p-IRS1 Ser-636/639. Recombinant CaMKK2 directly activated recombinant Akt by phosphorylation at Thr-308 in a Ca 2+ /CaM-dependent manner. In OVCa cells, p-Akt Thr-308 was significantly inhibited by intracellular Ca 2+ i chelation or CaM inhibition. Ionomycin-induced Ca 2+ influx promoted p-Akt, an effect blocked by PDK1, and/or CaMKK2, siRNAs, and by PI3K and/or CaMKK inhibitors. CaMKK2 knockdown potentiated the effects of the chemotherapeutic drugs carboplatin and PX-866 to reduce proliferation and survival of OVCa cells. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

p53 and Ca(2+) signaling from the endoplasmic reticulum: partners in anti-cancer therapies.

PubMed

Bittremieux, Mart; Bultynck, Geert

2015-01-01

Ca(2+) transfer from the endoplasmic reticulum (ER) to the mitochondria critically controls cell survival and cell death decisions. Different oncogenes and deregulation of tumor suppressors exploit this mechanism to favor the survival of altered, malignant cells. Two recent studies of the Pinton team revealed a novel, non-transcriptional function of cytosolic p53 in cell death. During cell stress, p53 is recruited to the ER and the ER-mitochondrial contact sites. This results in augmented ER Ca(2+) levels by enhancing sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) activity, ultimately promoting mitochondrial Ca(2+) overload. The boosting of "toxic" Ca(2+) signaling by p53 appears to be a critical component of the cell death-inducing properties of chemotherapeutic agents and anti-cancer treatments, like photodynamic stress. Strikingly, the resistance of p53-deficient cancer cells to these treatments could be overcome by facilitating Ca(2+) transfer between the ER and the mitochondria via overexpression of SERCA or of the mitochondrial Ca(2+) uniporter (MCU). Importantly, these concepts have also been supported by in vivo Ca(2+) measurements in tumor masses in mice. Collectively, these studies link for the first time the major tumor suppressor, p53, to Ca(2+) signaling in dictating cell-death outcomes and by the success of anti-cancer treatments.

Pathophysiologic Changes in Extracellular pH Modulate Parathyroid Calcium-Sensing Receptor Activity and Secretion via a Histidine-Independent Mechanism.

PubMed

Campion, Katherine L; McCormick, Wanda D; Warwicker, Jim; Khayat, Mohd Ezuan Bin; Atkinson-Dell, Rebecca; Steward, Martin C; Delbridge, Leigh W; Mun, Hee-Chang; Conigrave, Arthur D; Ward, Donald T

2015-09-01

The calcium-sensing receptor (CaR) modulates renal calcium reabsorption and parathyroid hormone (PTH) secretion and is involved in the etiology of secondary hyperparathyroidism in CKD. Supraphysiologic changes in extracellular pH (pHo) modulate CaR responsiveness in HEK-293 (CaR-HEK) cells. Therefore, because acidosis and alkalosis are associated with altered PTH secretion in vivo, we examined whether pathophysiologic changes in pHo can significantly alter CaR responsiveness in both heterologous and endogenous expression systems and whether this affects PTH secretion. In both CaR-HEK and isolated bovine parathyroid cells, decreasing pHo from 7.4 to 7.2 rapidly inhibited CaR-induced intracellular calcium (Ca(2+)i) mobilization, whereas raising pHo to 7.6 potentiated responsiveness to extracellular calcium (Ca(2+)o). Similar pHo effects were observed for Ca(2+)o-induced extracellular signal-regulated kinase phosphorylation and actin polymerization and for L-Phe-induced Ca(2+)i mobilization. Intracellular pH was unaffected by acute 0.4-unit pHo changes, and the presence of physiologic albumin concentrations failed to attenuate the pHo-mediated effects. None of the individual point mutations created at histidine or cysteine residues in the extracellular domain of CaR attenuated pHo sensitivity. Finally, pathophysiologic pHo elevation reversibly suppressed PTH secretion from perifused human parathyroid cells, and acidosis transiently increased PTH secretion. Therefore, pathophysiologic pHo changes can modulate CaR responsiveness in HEK-293 and parathyroid cells independently of extracellular histidine residues. Specifically, pathophysiologic acidification inhibits CaR activity, thus permitting PTH secretion, whereas alkalinization potentiates CaR activity to suppress PTH secretion. These findings suggest that acid-base disturbances may affect the CaR-mediated control of parathyroid function and calcium metabolism in vivo. Copyright © 2015 by the American Society of Nephrology.

Magic Clusters of MoS2 by Edge S2 Interdimer Spacing Modulation.

PubMed

Ryou, Junga; Kim, Yong-Sung

2018-05-17

Edge atomic and electronic structures of S-saturated Mo-edge triangular MoS 2 nanoclusters are investigated using density functional theory calculations. The edge electrons described by the S 2 -p x p x π* (S 2 -Π x ) and Mo-d xy orbitals are found to interplay to pin the S 2 -Π x Fermi wavenumber at k F = 2/5 as the nanocluster size increases, and correspondingly, the ×5 Peierls edge S 2 interdimer spacing modulation is induced. For the particular sizes of N = 5 n - 2 and 5 n, where N is the number of Mo atoms at one edge representing the nanocluster size and n is a positive integer, the effective ×5 interdimer spacing modulation stabilizes the nanoclusters, which are identified here to be the magic S-saturated Mo-edge triangular MoS 2 nanoclusters. With the S 2 -Π x Peierls gap, the MoS 2 nanoclusters become far-edge S 2 -Π x semiconducting and subedge Mo-d xy metallic as N → ∞.

Modulation of sarcoplasmic reticulum Ca(2+)-release channels by caffeine, Ca2+, and Mg2+ in skinned myocardial fibers of fetal and adult rats.

PubMed

Su, J Y; Chang, Y I

1993-05-01

Ryanodine causes depression of the caffeine-induced tension transient (ryanodine depression) in skinned muscle fibers, because it blocks the sarcoplasmic reticulum (SR) Ca(2+)-release channels [Su, J. Y. (1988) Pflügers Arch 411:132-136, 371-377; (1992) Pflügers Arch 421:1-6]. This study was performed to examine the sensitivity of SR Ca(2+)-release channels to ryanodine in fetal compared to adult myocardium and to investigate the influence of Ca2+, caffeine, and Mg2+ on ryanodine depression in skinned fibers. Ryanodine (0.3 nM-1 microM) caused a dose-dependent depression in skinned myocardial fibers of the rat, and the fetal fibers (IC50 approximately 74 nM) were 26-fold less sensitive than those of the adult (IC50 approximately 2.9 nM). The depression induced by 0.1 microM or 1 microM ryanodine was a function of [caffeine], or [Ca2+] (pCa < 6.0), which was potentiated by caffeine, and an inverse function of [Mg2+]. At pCa > 8.0 plus 25 mM caffeine, a 20% ryanodine depression was observed in both the fetal and adult fibers, indicating independence from Ca2+. Ryanodine depression in skinned fibers of the fetus was less affected than that seen in the adult by pCai, [caffeine]i, or 25 mM caffeine plus pCai or plus pMgi (IC50 approximately pCa 4.5 versus 5.1; caffeine 12.7 mM versus 2 mM; pCa 6.7 versus 7.3; and pMg 3.9 versus 3.3 respectively). The results show that the SR Ca(2+)-release channel in both fetal and adult myocardium is modulated by Ca2+, caffeine, and Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term treatment with calcium-alpha-ketoglutarate corrects secondary hyperparathyroidism.

PubMed

Zimmermann, E; Wassmer, S; Steudle, V

1996-01-01

Calcium-alpha-ketoglutarate (Ca-ket) is known as a highly effective phosphate (P) binder in hemodialysis (HD) patients. In addition, alpha-ketoglutarate has been shown to improve metabolic alterations. We investigated the effect of long-term P-binding therapy with Ca-ket to determine whether P accumulation is the main reason of secondary hyperparathyroidism (HPT) in HD patients or not. Ca-ket was prescribed to 14 HD patients as a soluble preparation in a mean dosage of 4.5 g/day (0.975 g elemental Ca) for a period of 36 months. Serum P continuously dropped from prestudy 2.6 +/- 0.1 (mean +/- SEM) to 1.9 +/- 0.07 mmol/l (p < 0.001), whereas serum Ca increased from 2.2 +/- 0.1 to 2.47 +/- 0.08 mmol/l (p < 0.05). Thus, Ca/P ratio in serum converted significantly from 0.91 +/- 0.02 (prestudy) to 1.28 +/- 0.01 (p < 0.001). Intact parathyroid hormone (iPTH) continuously normalized in all patients from 29 +/- 5 to 8 +/- 2 pmol/l (p < 0.001). The present data show that long-term treatment with Ca-ket normalizes secondary HPT by simultaneously P binding and correcting Ca/P ratio in serum without vitamin D treatment.

Correlation between pH dependence of O2 evolution and sensitivity of Mn cations in the oxygen-evolving complex to exogenous reductants.

PubMed

Semin, Boris K; Davletshina, Lira N; Rubin, Andrei B

2015-08-01

Effects of pH, Ca(2+), and Cl(-) ions on the extraction of Mn cations from oxygen-evolving complex (OEC) in Ca-depleted photosystem II (PSII(-Ca)) by exogenous reductants hydroquinone (H2Q) and H2O2 were studied. Two of 4 Mn cations are released by H2Q and H2O2 at pHs 5.7, 6.5, and 7.5, and their extraction does not depend on the presence of Ca(2+) and Cl(-) ions. One of Mn cations ("resistant" Mn cation) cannot be extracted by H2Q and H2O2 at any pH. Extraction of 4th Mn ion ("flexible" Mn cation) is sensitive to pH, Ca(2+), and Cl(-). This Mn cation is released by reductants at pH 6.5 but not at pHs 5.7 and 7.5. A pH dependence curve of the oxygen-evolving activity in PSII(-Ca) membranes (in the presence of exogenous Ca(2+)) has a bell-shaped form with the maximum at pH 6.5. Thus, the increase in the resistance of flexible Mn cation in OEC to the action of reductants at acidic and alkaline pHs coincides with the decrease in oxygen evolution activity at these pHs. Exogenous Ca(2+) protects the extraction of flexible Mn cation at pH 6.5. High concentration of Cl(-) anions (100 mM) shifts the pH optimum of oxygen evolution to alkaline region (around pH 7.5), while the pH of flexible Mn extraction is also shifted to alkaline pH. This result suggests that flexible Mn cation plays a key role in the water-splitting reaction. The obtained results also demonstrate that only one Mn cation in Mn4 cluster is under strong control of calcium. The change in the flexible Mn cation resistance to exogenous reductants in the presence of Ca(2+) suggests that Ca(2+) can control the redox potential of this cation.

A Pseudomonas aeruginosa EF-Hand Protein, EfhP (PA4107), Modulates Stress Responses and Virulence at High Calcium Concentration

PubMed Central

Sarkisova, Svetlana A.; Lotlikar, Shalaka R.; Guragain, Manita; Kubat, Ryan; Cloud, John

2014-01-01

Pseudomonas aeruginosa is a facultative human pathogen, and a major cause of nosocomial infections and severe chronic infections in endocarditis and in cystic fibrosis (CF) patients. Calcium (Ca2+) accumulates in pulmonary fluids of CF patients, and plays a role in the hyperinflamatory response to bacterial infection. Earlier we showed that P. aeruginosa responds to increased Ca2+ levels, primarily through the increased production of secreted virulence factors. Here we describe the role of putative Ca2+-binding protein, with an EF-hand domain, PA4107 (EfhP), in this response. Deletion mutations of efhP were generated in P. aeruginosa strain PAO1 and CF pulmonary isolate, strain FRD1. The lack of EfhP abolished the ability of P. aeruginosa PAO1 to maintain intracellular Ca2+ homeostasis. Quantitative high-resolution 2D-PAGE showed that the efhP deletion also affected the proteomes of both strains during growth with added Ca2+. The greatest proteome effects occurred when the pulmonary isolate was cultured in biofilms. Among the proteins that were significantly less abundant or absent in the mutant strains were proteins involved in iron acquisition, biosynthesis of pyocyanin, proteases, and stress response proteins. In support, the phenotypic responses of FRD1 ΔefhP showed that the mutant strain lost its ability to produce pyocyanin, developed less biofilm, and had decreased resistance to oxidative stress (H2O2) when cultured at high [Ca2+]. Furthermore, the mutant strain was unable to produce alginate when grown at high [Ca2+] and no iron. The effect of the ΔefhP mutations on virulence was determined in a lettuce model of infection. Growth of wild-type P. aeruginosa strains at high [Ca2+] causes an increased area of disease. In contrast, the lack of efhP prevented this Ca2+-induced increase in the diseased zone. The results indicate that EfhP is important for Ca2+ homeostasis and virulence of P. aeruginosa when it encounters host environments with high [Ca2+]. PMID:24918783

ACTIVATION OF EXTRACELLULAR-SIGNAL REGULATED KINASE (ERK1/2) BY FLUID SHEAR IS CA2+- AND ATP-DEPENDENT IN MC3T3-E1 OSTEOBLASTS

PubMed Central

Liu, Dawei; Genetos, Damian C.; Shao, Ying; Geist, Derik J.; Li, Jiliang; Ke, Hua Zhu; Turner, Charles H.; Duncan, Randall L.

2010-01-01

To determine the role of Ca2+ signaling in activation of the Mitogen-Activated Protein Kinase (MAPK) pathway, we subjected MC3T3-E1 pre-osteoblastic cells to inhibitors of Ca2+ signaling during application of fluid shear stress (FSS). FSS only activated ERK1/2, rapidly inducing phosphorylation within 5 minutes of the onset of shear. Phosphorylation of ERK1/2 (pERK1/2) was significantly reduced when Ca2+i was chelated with BAPTA or when Ca2+ was removed from the flow media. Inhibition of both the L-type voltage-sensitive Ca2+ channel and the mechanosensitive cation-selective channel blocked FSS-induced pERK1/2. Inhibition of phospholipase C with U73122 significantly reduced pERK1/2. This inhibition did not result from block of intracellular Ca2+ release, but a loss of PKC activation. Recent data suggests a role of ATP release and purinergic receptor activation in mechanotransduction. Apyrase-mediated hydrolysis of extracellular ATP completely blocked FSS-induced phosphorylation of ERK1/2, while addition of exogenous ATP to static cells mimicked the effects of FSS on pERK1/2. Two P2 receptors, P2Y2 and P2X7, have been associated with the anabolic responses of bone to mechanical loading. Using both iRNA techniques and primary osteoblasts isolated from P2X7 knockout mice, we found that the P2X7, but not the P2Y2, purinergic receptor was involved in ERK1/2 activation under FSS. These data suggest that FSS-induced ERK1/2 phosphorylation requires Ca2+-dependent ATP release, however both increased Ca2+i and PKC activation are needed for complete activation. Further, this ATP-dependent ERK1/2 phosphorylation is mediated through P2X7, but not P2Y2, purinergic receptors. PMID:18291742

Properties of Ca2+ release induced by clofibric acid from the sarcoplasmic reticulum of mouse skeletal muscle fibres

PubMed Central

Ikemoto, Takaaki; Endo, Makoto

2001-01-01

To characterize the effect of clofibric acid (Clof) on the Ca2+ release mechanism in the sarcoplasmic reticulum (SR) of skeletal muscle, we analysed the properties of Clof-induced Ca2+ release under various conditions using chemically skinned skeletal muscle fibres of the mouse.Clof (>0.5 mM) released Ca2+ from the SR under Ca2+-free conditions buffered with 10 mM EGTA (pCa >8).Co-application of ryanodine and Clof at pCa >8 but not ryanodine alone reduced the Ca2+ uptake capacity of the SR. Thus, Ca2+ release induced by Clof at pCa >8 must be a result of the activation of the ryanodine receptor (RyR).At pCa >8, (i) Clof-induced Ca2+ release was inhibited by adenosine monophosphate (AMP), (ii) the inhibitory effect of Mg2+ on the Clof-induced Ca2+ release was saturated at about 1 mM, and (iii) Clof-induced Ca2+ release was not inhibited by procaine (10 mM). These results indicate that Clof may activate the RyR-Ca2+ release channels in a manner different from Ca2+-induced Ca2+ release (CICR).In addition to this unique mode of opening, Clof also enhanced the CICR mode of opening of RyR-Ca2+ release channels.Apart from CICR, a high concentration of Ca2+ might also enhance the unique mode of opening by Clof.These results suggest that some features of Ca2+ release activated by Clof are similar to those of physiological Ca2+ release (PCR) in living muscle cells and raise the possibility that Clof may be useful in elucidating the mechanism of PCR in skeletal muscle. PMID:11606311

[Effect of Ca(OH)2 on the cytotoxicity of lipopolysaccharide extracted from Porphyromonas endodontalis in vitro].

PubMed

Guo, Jia-jie; Qiu, Li-hong; Yu, Ya-qiong; Xu, Li-ya; Fan, Yun-qian; Zhong, Ming

2014-02-01

To detect the degradation of Ca(OH)2 on lipopolysaccharide (LPS) extracted from Porphyromonas endodontalis (P.e) in vitro and estimate the influence of P.e LPS pretreated with Ca(OH)2 on the proliferation of MC3T3-E1 cells. The effect of Ca(OH)2 on MC3T3-E1 cell proliferation was detected by methyl thiazolyl tetrazolium (MTT) assay. Then P.e LPS was treated with Ca(OH)2 for 30 mins or 60 mins at 37 degrees centigrade in vitro and the activity of P.e LPS was evaluated by Chromogenic End-point Tachypleus Amebocyte Lysate (CE TAL) test. Finally, MC3T3-E1 cells were exposed to P.e LPS pretreated with 15% Ca(OH)2 for 1, 3 and 5 d, and the cell proliferation was measured using the MTT assay comparing with the P.e LPS control group. SPSS 13.0 software package was used for statistical analysis. Compared with the negative control, exposing cells to 5%, 10% and 15% Ca(OH)2 had greatly promoted MC3T3-E1 cell proliferation. P.e LPS treated with 10% and 15% Ca(OH)2 both presented the best results by CE TAL and significant difference compared with P.e LPS control group. When 10 μg/mL P.e LPS was pretreated with 15% Ca(OH)2, no inhibition of MC3T3-E1 cell proliferation was noted. Ca(OH)2 detoxifies P.e LPS in vitro, mitigates the impact of P.e LPS on MC3T3-E1 cell proliferation. Supported by Science and Technology Projects of Liaoning Province (2011225020).

Differential effects of arginine, glutamate and phosphoarginine on Ca(2+)-activation properties of muscle fibres from crayfish and rat.

PubMed

Jame, David W; West, Jan M; Dooley, Philip C; Stephenson, D George

2004-01-01

The effects of two amino acids, arginine which has a positively charged side-chain and glutamate which has a negatively charged side-chain on the Ca2+-activation properties of the contractile apparatus were examined in four structurally and functionally different types of skeletal muscle; long- and short-sarcomere fibres from the claw muscle of the yabby (a freshwater decapod crustacean), and fast- and slow-twitch fibres from limb muscles of the rat. Single skinned fibres were activated in carefully balanced solutions of different pCa (-log10[Ca2+]) that either contained the test solute ("test") or not ("control"). The effect of phosphoarginine, a phosphagen that bears a nett negative charge, was also compared to the effects of arginine. Results show that (i) arginine (33-36 mmol l(-1)) significantly shifted the force-pCa curve by 0.08-0.13 pCa units in the direction of increased sensitivity to Ca2+-activated contraction in all fibre types; (ii) phosphoarginine (9-10 mmol l(-1)) induced a significant shift of the force-pCa curve by 0.18-0.24 pCa units in the direction of increased sensitivity to Ca2+ in mammalian fast- and slow-twitch fibres, but had no significant effects on the force-pCa relation in either long- or short-sarcomere crustacean fibres; (iii) glutamate (36-40 mmol l(-1)), like arginine affected the force-pCa relation of all fibre types investigated, but in the opposite direction, causing a significant decrease in the sensitivity to Ca2+-activated contraction by 0.08-0.19 pCa units; (iv) arginine, phosphoarginine and glutamate had little or no effect on the maximum Ca2+-activated force of crustacean and mammalian fibres. The results suggest that the opposing effects of glutamate and arginine are not related to simply their charge structure, but must involve complex interactions between these molecules, Ca2+ and the regulatory and other myofibrillar proteins.

NCI-H295R, a human adrenal cortex-derived cell line, expresses purinergic receptors linked to Ca²⁺-mobilization/influx and cortisol secretion.

PubMed

Nishi, Haruhisa; Arai, Hirokazu; Momiyama, Toshihiko

2013-01-01

Purinergic receptor expression and involvement in steroidogenesis were examined in NCI-H295R (H295R), a human adrenal cortex cell line which expresses all the key enzymes necessary for steroidogenesis. mRNA/protein for multiple P1 (A(2A) and A(2B)), P2X (P2X₅ and P2X₇), and P2Y (P2Y₁, P2Y₂, P2Y₆, P2Y₁₂, P2Y₁₃, and P2Y₁₄) purinergic receptors were detected in H295R. 2MeS-ATP (10-1000 µM), a P2Y₁ agonist, induced glucocorticoid (GC) secretion in a dose-dependent manner, while other extracellular purine/pyrimidine agonists (1-1000 µM) had no distinct effect on GC secretion. Extracellular purines, even non-steroidogenic ones, induced Ca²⁺-mobilization in the cells, independently of the extracellular Ca²⁺ concentration. Increases in intracellular Ca²⁺ concentration induced by extracellular purine agonists were transient, except when induced by ATP or 2MeS-ATP. Angiotensin II (AngII: 100 nM) and dibutyryl-cyclic AMP (db-cAMP: 500 µM) induced both GC secretion and Ca²⁺-mobilization in the presence of extracellular Ca²⁺ (1.2 mM). GC secretion by AngII was reduced by nifedipine (10-100 µM); whereas the Ca²⁺ channel blocker did not inhibit GC secretion by 2MeS-ATP. Thapsigargin followed by extracellular Ca²⁺ exposure induced Ca²⁺-influx in H295R, and the cells expressed mRNA/protein of the component molecules for store-operated calcium entry (SOCE): transient receptor C (TRPC) channels, calcium release-activated calcium channel protein 1 (Orai-1), and the stromal interaction molecule 1 (STIM1). In P2Y₁-knockdown, 2MeS-ATP-induced GC secretion was significantly inhibited. These results suggest that H295R expresses a functional P2Y₁ purinergic receptor for intracellular Ca²⁺-mobilization, and that P2Y₁ is linked to SOCE-activation, leading to Ca²⁺-influx which might be necessary for glucocorticoid secretion.

Effects of cannabidiol on contractions and calcium signaling in rat ventricular myocytes.

PubMed

Ali, Ramez M; Al Kury, Lina T; Yang, Keun-Hang Susan; Qureshi, Anwar; Rajesh, Mohanraj; Galadari, Sehamuddin; Shuba, Yaroslav M; Howarth, Frank Christopher; Oz, Murat

2015-04-01

Cannabidiol (CBD), a major nonpsychotropic cannabinoid found in Cannabis plant, has been shown to influence cardiovascular functions under various physiological and pathological conditions. In the present study, the effects of CBD on contractility and electrophysiological properties of rat ventricular myocytes were investigated. Video edge detection was used to measure myocyte shortening. Intracellular Ca(2+) was measured in cells loaded with the Ca(2+) sensitive fluorescent indicator fura-2 AM. Whole-cell patch clamp was used to measure action potential and Ca(2+) currents. Radioligand binding was employed to study pharmacological characteristics of CBD binding. CBD (1μM) caused a significant decrease in the amplitudes of electrically evoked myocyte shortening and Ca(2+) transients. However, the amplitudes of caffeine-evoked Ca(2+) transients and the rate of recovery of electrically evoked Ca(2+) transients following caffeine application were not altered. CBD (1μM) significantly decreased the duration of APs. Further studies on L-type Ca(2+) channels indicated that CBD inhibits these channels with IC50 of 0.1μM in a voltage-independent manner. Radioligand studies indicated that the specific binding of [(3)H]Isradipine, was not altered significantly by CBD. The results suggest that CBD depresses myocyte contractility by suppressing L-type Ca(2+) channels at a site different than dihydropyridine binding site and inhibits excitation-contraction coupling in cardiomyocytes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of calcium oxide inclusion in beef feedlot diets containing 60% dried distillers grains with solubles on ruminal fermentation, diet digestibility, performance, and carcass characteristics.

PubMed

Nuñez, A J C; Felix, T L; Lemenager, R P; Schoonmaker, J P

2014-09-01

Two experiments were conducted to determine the effect of increasing dietary CaO on ruminal fermentation, diet digestibility, performance, and carcass characteristics of feedlot steers fed 60% dried distillers grains with solubles ( DDGS: ). In Exp. 1, 120 steers were allotted by weight (355 ± 7.9 kg) to 1 of 4 treatments containing 60% DDGS, 20% corn silage, 13.5 to 14.4% ground corn, 4% supplement, and 0 to 2.5% limestone on DM basis to determine the effects of CaO on performance and carcass characteristics. Treatments consisted of 0, 0.8, 1.6, or 2.4% CaO inclusion in the diet (DM basis), with CaO replacing limestone. Steers were slaughtered at a target BW of approximately 641 kg. In Exp. 2, 4 steers (initial BW = 288 ± 3 kg) were randomly allotted to the same diets in a 4 × 4 Latin square design (14-d periods) to determine the effects of CaO on ruminal pH, VFA, and nutrient digestibility. Statistical analyses were conducted using the MIXED procedure of SAS. Inclusion of CaO at 0.8, 1.6, and 2.4% increased ADG by 5.0, 3.9, and 0%, respectively, compared to 0% CaO (quadratic; P = 0.03). Intake was linearly decreased (P = 0.04) and G:F was linearly increased (P = 0.02) by CaO inclusion. Dressing percentage increased as CaO increased from 0 to 1.6% and then decreased for 2.4% CaO (quadratic; P < 0.01). In Exp. 2, steers fed 0% CaO had the greatest prefeeding ruminal pH, steers fed 0 and 0.8% CaO exhibited the most rapid postfeeding decline in ruminal pH, and steers fed 2.4% CaO exhibited a relatively stable ruminal pH throughout the 24-h period (treatment × time; P ≤ 0.01). Acetate, butyrate, and total VFA concentrations increased linearly (P ≤ 0.05) at 0, 3, 6, and 12 h postfeeding with increasing CaO. Propionate at 3 h postfeeding increased from 0 to 1.6% CaO and decreased from 1.6 to 2.4% CaO (quadratic; P = 0.10). Urine pH increased linearly (P ≤ 0.01) while urine output and urine ammonia decreased linearly (P ≤ 0.05) as CaO inclusion increased. Apparent NDF digestibility tended to increase (P = 0.07) and ADF digestibility did (P = 0.01) increase linearly with increasing concentrations of CaO. In conclusion, CaO improved ruminal pH variation, increased fiber digestibility, and decreased metabolic acid load in cattle fed 60% DDGS-based diets. Inclusion of CaO up to 1.6% was effective in improving performance of feedlot cattle.

Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner.

PubMed

Yokota, Etsuo; Tominaga, Motoki; Mabuchi, Issei; Tsuji, Yasunori; Staiger, Christopher J; Oiwa, Kazuhiro; Shimmen, Teruo

2005-10-01

From germinating pollen of lily, two types of villins, P-115-ABP and P-135-ABP, have been identified biochemically. Ca(2+)-CaM-dependent actin-filament binding and bundling activities have been demonstrated for both villins previously. Here, we examined the effects of lily villins on the polymerization and depolymerization of actin. P-115-ABP and P-135-ABP present in a crude protein extract prepared from germinating pollen bound to a DNase I affinity column in a Ca(2+)-dependent manner. Purified P-135-ABP reduced the lag period that precedes actin filament polymerization from monomers in the presence of either Ca(2+) or Ca(2+)-CaM. These results indicated that P-135-ABP can form a complex with G-actin in the presence of Ca(2+) and this complex acts as a nucleus for polymerization of actin filaments. However, the nucleation activity of P-135-ABP is probably not relevant in vivo because the assembly of G-actin saturated with profilin, a situation that mimics conditions found in pollen, was not accelerated in the presence of P-135-ABP. P-135-ABP also enhanced the depolymerization of actin filaments during dilution-mediated disassembly. Growth from filament barbed ends in the presence of Ca(2+)-CaM was also prevented, consistent with filament capping activity. These results suggested that lily villin is involved not only in the arrangement of actin filaments into bundles in the basal and shank region of the pollen tube, but also in regulating and modulating actin dynamics through its capping and depolymerization (or fragmentation) activities in the apical region of the pollen tube, where there is a relatively high concentration of Ca(2+).

Can Polyphosphate Biochemistry Affect Biological Apatite Saturation?

NASA Astrophysics Data System (ADS)

Omelon, S. J.; Matsuura, N.; Gorelikov, I.; Wynnyckyj, C.; Grynpas, M. D.

2010-12-01

Phosphorus (P) is an important and limiting element for life. One strategy for storing ortho phosphates (Pi) is polymerization. Polymerized Pi's (polyphosphates: (PO3-)n: polyPs) serve as a Pi bank, as well as a catiion chelator, energy source, & regulator of responses to stresses in the stationary phase of culture growth and development1. PolyP biochemistry has been investigated in yeasts, bacteria & plants2. Bigeochemical cycling of P includes the condensation of Pi into pyro (P2O7-4), & polyPs, & the release of Pi from these compounds by the hydrolytic degradation of Pi from phosphomonoester bonds. Alkaline phosphatase (ALP) is one of the predominate enzymes for regenerating Pi in aquatic systems3, & it cleaves Pi from polyPs. ALP is also the enzyme associated with apatite biomineralization in vertebrates4. PolyP was proposed to be the ALP substrate in bone mineralization5. Where calcium ions are plentiful in many aquatic environments, there is no requirement for aquatic life to generate Ca-stores. However, terrestrial vertebrates benefit from a bioavailable Ca-store such as apatite. The Pi storage strategy of polymerizing PO4-3 into polyPs dovetails well with Ca-banking, as polyPs sequester Ca, forming a neutral calcium polyphosphate (Ca-polyP: (Ca(PO3)2)n) complex. This neutral complex represents a high total [Ca+2] & [PO4-3], without the threat of inadvertent apatite precipitation, as the free [Ca+2] & [PO4-3], and therefore apatite saturation, are zero. Recent identification of polyP in regions of bone resorption & calcifying cartilage5 suggests that vertebrates may use polyP chemistry to bank Ca+2 and PO4-3. In vitro experiments with nanoparticulate Ca-polyP & ALP were undertaken to determine if carbonated apatite could precipitate from 1M Ca-polyP in Pi-free “physiological fluid” (0.1 M NaCl, 2 mM Ca+2, 0.8 mM Mg+2, pH ~8.0 ±0.5, 37 °C), as this is estimated to generate the [Ca+2] & [PO4-3] required to form the apatite content of bone tissue (estimated to be 1 g apatite/mL). Carbonates (as NaHCO3 or CaCO3) were used to buffer the protons produced upon polyP hydrolytic degradation to Pi, releasing Ca+2, increasing apatite saturation for precipitation. Initial Ca:P ratios (by EDS) was <1, indicative of Ca-polyP. After incubation, Ca:P ratios were >1, suggesting the formation of Ca-PO4 minerals. XRD results identified Na-Ca- carbonate phases, & hydroxyapatite & carbonated apatite, & residual carbonate reagent. Further optimization of this biological apatite precipitation system will be presented. 1 Kornberg, A., Ann Rev Biochem 1999 (68) 89 2 Kulaev IS, Vagabov VM, Kulakovskaya TV (2004) The Biochemistry of Inorganic Polyphosphates. Chichester, England, John Wiley & Sons, Ltd. 3 Blake, R. E., O’Neil, J.R., and Surov, A. Am J Sci 2005 (305) 596 4 Heersche, J. N. M. et al. (1990) Bone Regulatory Factors; Plenum Press: New York 5 Omelon et al., PLoS ONE 2009 4(5), e5634

Modification of nanostructured calcium carbonate for efficient gene delivery.

PubMed

Zhao, Dong; Wang, Chao-Qun; Zhuo, Ren-Xi; Cheng, Si-Xue

2014-06-01

In this study, a facile method to modify nanostructured calcium carbonate (CaCO3) gene delivery systems by adding calcium phosphate (CaP) component was developed. CaCO3/CaP/DNA nanoparticles were prepared by the co-precipitation of Ca(2+) ions with plasmid DNA in the presence of carbonate and phosphate ions. For comparison, CaCO3/DNA nanoparticles and CaP/DNA co-precipitates were also prepared. The effects of carbonate ion/phosphate ion (CO3(2-)/PO4(3-)) ratio on the particle size and gene delivery efficiency were investigated. With an appropriate CO3(2-)/PO4(3-) ratio, the co-existence of carbonate and phosphate ions could control the size of co-precipitates effectively, and CaCO3/CaP/DNA nanoparticles with a decreased size and improved stability could be obtained. The in vitro gene transfections mediated by different nanoparticles in 293T cells and HeLa cells were carried out, using pGL3-Luc as a reporter plasmid. The gene transfection efficiency of CaCO3/CaP/DNA nanoparticles could be significantly improved as compared with CaCO3/DNA nanoparticles and CaP/DNA co-precipitates. The confocal microscopy study indicated that the cellular uptake and nuclear localization of CaCO3/CaP/DNA nanoparticles were significantly enhanced as compared with unmodified CaCO3/DNA nanoparticles. Copyright © 2014 Elsevier B.V. All rights reserved.

Conversion of D-hamamelose into 2-carboxy-D-arabinitol and 2-carboxy-D-arabinitol 1-phosphate in leaves of Phaseolus vulgaris L.

PubMed

Andralojc, P J; Keys, A J; Martindale, W; Dawson, G W; Parry, M A

1996-10-25

[1-14C]Hamamelose (2-hydroxymethyl-D-ribose) was synthesized by reaction of ribulose 5-phosphate with potassium [14C]cyanide, catalytic hydrogenation of the resulting cyanohydrin, and dephosphorylation of the product. Its identity was established by a chromatographic comparison with hamamelose isolated from the bark of witch hazel (Hamamelis virginiana L.). Following vacuum infiltration of the [1-14C]hamamelose into leaf discs from Phaseolus vulgaris L., 14C-labeled 2carboxy-D-arabinitol (CA) and 2-carboxy-D-arabinitol 1-phosphate (CA1P) were formed, in the dark. Conversion of hamamelose to both CA and CA1P in the leaf discs was inhibited by dithiothreitol and sodium fluoride, although at high concentrations of these inhibitors conversion into CA was still evident when conversion into CA1P was totally inhibited. Wheat (Triticum aestivum L.) leaves converted hamamelose into CA without formation of CA1P. Leaves from P. vulgaris contained 68 nmol.g-1 fresh weight of hamamelose in the light and 35 nmol.g-1 fresh weight in the dark. A pathway for the biosynthesis of CA1P from Calvin cycle intermediates is proposed which includes the sequence: hamamelose --> CA --> CA1P.

Edge profiles in K shell photoabsorption spectra of gaseous hydrides of 3p elements and homologues

NASA Astrophysics Data System (ADS)

Hauko, R.; Gomilšek, J. Padežnik; Kodre, A.; Arčon, I.; Aquilanti, G.

2017-10-01

Photoabsorption spectra of gaseous hydrides of 3p elements (PH3, H2S, HCl) are measured in the energy region of photoexcitations pertaining to K edge. The analysis of the edge profile is extended to hydrides of 4p series (GeH4, AsH3, H2Se, HBr) from an earlier experiment, and to published spectra of 2p hydrides (CH4, NH3, H2O, HF) and noble gases Ar, Kr and Ne and SiH4. The edge profiles are modelled with a linear combination of lorentzian components, describing excitations to individual bound states and to continuum. Transition energies and probabilities are also calculated in the non-relativistic molecular model of the ORCA code, in good agreement with the experiment. Edge profiles in the heavier homologues are closely similar, the symmetry of the molecule governs the transitions to the lowest unoccupied orbitals. In 2p series the effect of the strong nuclear potential prevails. Transitions to higher, atomic-like levels remain very much the same as in free atoms.

Comparative study of perovskite-type scintillator materials CsCaI3 and KCaI3 via first-principles calculations

NASA Astrophysics Data System (ADS)

Kang, Byungkyun; Feng, Qingguo; Biswas, Koushik

2018-02-01

Several members of a large family of perovskite-like halides with a common chemical formula, ABX3 (A  =  monovalent, B  =  divalent, and X  =  halogen ion), are being investigated for their interesting properties and potential technological applications. CsCaI3 and KCaI3 are two such ionic compounds who are of interest in the quest for superior and cost-effective alternatives to NaI or CsI based scintillators. They are the subject of this first-principles based computational study. Both are wide-gap materials having primarily I 5p and Ca 3d characters near the valence and conduction band edges, respectively. Although built from [CaI6] octahedral motifs, structural differences between the two compounds is reflected in anisotropic electron effective mass and distinctive formation and migration of self-trapped holes. We discuss these properties as they relate to scintillation decay and proportional light yield.

Dynamic Inositol Trisphosphate-mediated Calcium Signals within Astrocytic Endfeet Underlie Vasodilation of Cerebral Arterioles

PubMed Central

Straub, Stephen V.; Bonev, Adrian D.; Wilkerson, M. Keith; Nelson, Mark T.

2006-01-01

Active neurons communicate to intracerebral arterioles in part through an elevation of cytosolic Ca2+ concentration ([Ca2+]i) in astrocytes, leading to the generation of vasoactive signals involved in neurovascular coupling. In particular, [Ca2+]i increases in astrocytic processes (“endfeet”), which encase cerebral arterioles, have been shown to result in vasodilation of arterioles in vivo. However, the spatial and temporal properties of endfoot [Ca2+]i signals have not been characterized, and information regarding the mechanism by which these signals arise is lacking. [Ca2+]i signaling in astrocytic endfeet was measured with high spatiotemporal resolution in cortical brain slices, using a fluorescent Ca2+ indicator and confocal microscopy. Increases in endfoot [Ca2+]i preceded vasodilation of arterioles within cortical slices, as detected by simultaneous measurement of endfoot [Ca2+]i and vascular diameter. Neuronal activity–evoked elevation of endfoot [Ca2+]i was reduced by inhibition of inositol 1,4,5-trisphosphate (InsP3) receptor Ca2+ release channels and almost completely abolished by inhibition of endoplasmic reticulum Ca2+ uptake. To probe the Ca2+ release mechanisms present within endfeet, spatially restricted flash photolysis of caged InsP3 was utilized to liberate InsP3 directly within endfeet. This maneuver generated large amplitude [Ca2+]i increases within endfeet that were spatially restricted to this region of the astrocyte. These InsP3-induced [Ca2+]i increases were sensitive to depletion of the intracellular Ca2+ store, but not to ryanodine, suggesting that Ca2+-induced Ca2+ release from ryanodine receptors does not contribute to the generation of endfoot [Ca2+]i signals. Neuronally evoked increases in astrocytic [Ca2+]i propagated through perivascular astrocytic processes and endfeet as multiple, distinct [Ca2+]i waves and exhibited a high degree of spatial heterogeneity. Regenerative Ca2+ release processes within the endfeet were evident, as were localized regions of Ca2+ release, and treatment of slices with the vasoactive neuropeptides somatostatin and vasoactive intestinal peptide was capable of inducing endfoot [Ca2+]i increases, suggesting the potential for signaling between local interneurons and astrocytic endfeet in the cortex. Furthermore, photorelease of InsP3 within individual endfeet resulted in a local vasodilation of adjacent arterioles, supporting the concept that astrocytic endfeet function as local “vasoregulatory units” by translating information from active neurons into complex InsP3-mediated Ca2+ release signals that modulate arteriolar diameter. PMID:17130519

On P2 ⋄ Pn -supermagic labeling of edge corona product of cycle and path graph

NASA Astrophysics Data System (ADS)

Yulianto, R.; Martini, Titin S.

2018-04-01

A simple graph G = (V, E) admits a H-covering, where H is subgraph of G, if every edge in E belongs to a subgraph of G isomorphic to H. Graph G is H-magic if there is a total labeling f:V(G)\\cup E(G)\\to 1,2,\\ldots,|V(G)|+|E(G)|, such that each subgraph {H}{\\prime }=({V}{\\prime },{E}{\\prime }) of G isomorphic to H and satisfying f{({H}{\\prime })}=def{\\sum }\\upsilon \\in {V{\\prime }}f(\\upsilon )+{\\sum }e\\in {E{\\prime }}f(e)=m(f) where m(f) is a constant magic sum. Additionaly, G admits H-supermagic if f(V)=1,2,\\ldots,|V|. The edge corona {C}n \\diamond {P}n of Cn and Pn is defined as the graph obtained by taking one copy of Cn and n copies of Pn , and then joining two end-vertices of the i-th edge of Cn to every vertex in the i-th copy of Pn . This research aim is to find H-supermagic covering on an edge corona product of cycle and path graph {C}n \\diamond {P}n where H is {P}2 \\diamond {P}n. We use k-balanced multiset to solve our reserarch. Here, we find that an edge corona product of cycle and path graph {C}n \\diamond {P}n is {P}2 \\diamond {P}n supermagic for n > 3.

Ca2+ spike initiation from sensitized inositol 1,4,5-trisphosphate-sensitive Ca2+ stores in megakaryocytes.

PubMed

Ikeda, M; Kurokawa, K; Maruyama, Y

1994-06-01

Ca(2+)-mediated Ca2+ spikes were analysed in fura-2-loaded megakaryocytes. Direct Ca2+ loading using whole-cell dialysis induced an all-or-none Ca2+ spike on top of a tonic increase in cellular Ca2+ concentration ([Ca2+]i) with a latency of 3-7 s. The latency decreased with increasingly higher concentrations of Ca2+ in the dialysing solution. Spike size and its initiation did not correlate with the tonic level of [Ca2+]i. Thapsigargin completely abolished the Ca(2+)-induced spike initiation, suggesting that Ca2+ spikes originate from thapsigargin-sensitive Ca2+ pools. An inhibitor of phosphatidylinositide-specific phospholipase C (PLC), 2-nitro-4-carboxyphenyl-N,N-diphenyl-carbamate prolonged the latency without changes of spike size in most cases (6/9 cells), but abolished the spike initiation in the other cells (3/9). The results suggest that an increase in [Ca2+]i charges up the inositol-1,4,5-trisphosphate-(InsP3)- and thapsigargin-sensitive Ca2+ pools which progressively sensitize to low or slightly elevated levels of InsP3 by the action of Ca(2+)-dependent PLC until a critical Ca2+ content is reached, and then the Ca2+ spike is triggered. Thus, the limiting step of Ca2+ spike triggering is the initial filling process and the level of InsP3 in megakaryocytes.

Edge Antimagic Total Labeling on Two Copies of Path

NASA Astrophysics Data System (ADS)

Nurdin; Abrar, A. M.; Bhayangkara, A. R. M.; Muliani; Samsir, A. U.; Nahdi, M. R. An

2018-03-01

A graph G = (V(G), E(G)) denotes the vertex set and the edge set, respectively. A (p,q)-graph G is a graph such that |V(G) | = p and |E(G) | = q. Graph of order p and size q is called (a,d)-edge-anti magic total if there exists a bijection f : V(G) U E(G)→ {1,2,..., p + q} such that the edge weights w(u,v) = f(u) + f(uv) + f(v) form an arithmetic sequence {a, a + d, a + 2d,...,a + (q - 1)d} with the first term a and common difference d. Two copies of path is disjoint union of two path graph with same order (Pn ∪Pn ) denoted by 2Pn . In this paper we construct the (a,d)-edge-anti magic total labeling in two copies of path for some differences d.

P2X7 receptor-mediated calcium dynamics in HEK293 cells: experimental characterization and modelling approach

NASA Astrophysics Data System (ADS)

Di Garbo, A.; Alloisio, S.; Nobile, M.

2012-04-01

The P2X7 receptor (P2X7R) induces ionotropic Ca2 + signalling in different cell types. It plays an important role in the immune response and in the nervous system. Here, the mechanisms underlying intracellular Ca2 + variations evoked by 3‧-O-(4-benzoyl)benzoyl-ATP (BzATP), a potent agonist of the P2X7R, in transfected HEK293 cells, are investigated both experimentally and theoretically. We propose a minimal model of P2X7R that is capable of reproducing, qualitatively and quantitatively, the experimental data. This approach was also adopted for the P2X7R variant, which lacks the entire C-terminus tail (trP2X7R). Then we introduce a biophysical model describing the Ca2 + dynamics in HEK293. Our model gives an account of the ionotropic Ca2 + influx evoked by BzATP on the basis of the kinetics model of P2X7R. To explain the complex Ca2 + responses evoked by BzATP, the model predicted that an impairment in Ca2 + extrusion flux through the plasma membrane is a key factor for Ca2 + homeostasis in HEK293 cells.

Activity of calcium activated protease in skeletal muscles and its changes in atrophy and stretch

NASA Technical Reports Server (NTRS)

Ellis, S.; Nagainis, P. A.

1984-01-01

The reduction of protein content in skeletal muscle undergoing disuse-induced atrophy is correlated with accelerated rates of protein degradation and reduced rates of protein synthesis (Goldspink, 1977). It is not known in what manner myofibers are partially disassembled during disuse atrophy to fibers of smaller diameter; nor is it known which proteases are responsible for this morphological change in contractile protein mass. Dayton and colleagues (1975) have suggested that the Ca(2+)-activated protease (CaP) may initiate myofibril degradation. The discovery of a form of CaP that is activatable by nano-molar concentrations of Ca(2+) indicates that CaP activity may be regulated by physiological concentrations of Ca(2+) (Mellgren, 1980). The enhancement of proteolysis by the Ca(2+) ionophore A23187, reported by Etlinger (1979), is consistent with a significant role for CaP in protein degradation. It was of interest, therefore, to measure the levels of CaP activity and the CaP inhibitor in extracts obtained from skeletal muscles of rat and chicken limbs undergoing disuse atrophy or stretch hypertrophy, respectively.

Effects of feeding dry or modified wet distillers grains with solubles with or without supplemental calcium oxide on ruminal metabolism and microbial enzymatic activity of beef cattle.

PubMed

Schroeder, A R; Iakiviak, M; Felix, T L

2014-09-01

The objectives of this study were to determine the interaction of feeding dry (DDGS) or modified wet (MDGS) distillers grains with solubles (DGS) with or without supplemental CaO on in situ DM and NDF disappearance; ruminal pH, VFA, and methane concentration; and cellulase and xylanase activity. Fistulated steers (n = 8; average initial BW = 540 ± 250 kg) were used in a replicated 4 × 4 Latin square design. Treatments were arranged in a 2 × 2 factorial, and steers were randomly allotted to 1 of 4 dietary treatments: 1) 50% DDGS with 0% CaO, 2) 48.8% DDGS supplemented with 1.2% CaO, 3) 50% MDGS with 0% CaO, or 4) 48.8% MDGS supplemented with 1.2% CaO (DM basis). The remainder of the diet was husklage, dry-rolled corn, and vitamin and mineral supplement. There were no interactions (P ≥ 0.12) of DGS type and CaO addition on any parameters measured. Steers fed DDGS had a 17% increase (P < 0.01) in DMI compared to steers fed MDGS; however, CaO supplementation reduced (P = 0.03) DMI by 12%, regardless of DGS type. As expected, addition of CaO increased the pH of the diet by 1.82 pH units. This caused a time by CaO interaction (P = 0.05) for ruminal pH. Regardless of DGS type, steers supplemented with CaO tended to have increased (P = 0.09) ruminal pH at 1.5 h and had increased (P = 0.03) ruminal pH at 3 h postfeeding; however, ruminal pH did not differ (P ≥ 0.24) for the remainder of the day. There was no difference (P = 0.46) in ruminal cellulase activity when comparing type of DGS fed. However, there was a time by CaO interaction (P < 0.01); cattle fed 1.2% CaO diets had 28% greater ruminal cellulase activity only at 0 h postfeeding when compared to cattle fed 0% CaO. Furthermore, feeding supplemental CaO increased (P = 0.04) acetate to propionate ratio (A:P) regardless of type of DGS fed. Increased initial ruminal pH and cellulase activity from supplemental CaO did not increase (P = 0.48) in situ NDF disappearance. No differences (P ≥ 0.48) in ruminal methane concentration were found when comparing DGS type or supplemental CaO. In conclusion, the type of DGS fed had little effect on ruminal metabolism. Even though CaO increased ruminal pH and cellulase activity at some times postfeeding, it was not enough to affect in situ fiber disappearance.

Early Effects of Combretastatin A4 Phosphate Assessed by Anatomic and Carbogen-Based Functional Magnetic Resonance Imaging on Rat Bladder Tumors Implanted in Nude Mice1

PubMed Central

Thomas, Carole D.; Walczak, Christine; Kaffy, Julia; Pontikis, Renée; Jouanneau, Jacqueline; Volk, Andreas

2006-01-01

Abstract Combretastatin A4 phosphate (CA4P) causes rapid disruption of the tumor vasculature and is currently being evaluated for antivascular therapy. We describe the initial results obtained with a noninvasive multi-parametric magnetic resonance imaging (MRI) approach to assess the early effects of CA4P on rat bladder tumors implanted on nude mice. MRI (4.7 T) comprised a fast spin-echo sequence for growth curve assessment; a multislice multiecho sequence for T2 measurement before, 15 minutes after, and 24 hours after CA4P (100 mg/kg); and a fast T2w* gradient-echo sequence to assess MR signal modification under carbogen breathing before, 35 minutes after, and 24 hours after CA4P. The tumor fraction with increased T2w* signal intensity under carbogen (T+) was used to quantify CA4P effect on functional vasculature. CA4P slowed tumor growth over 24 hours and accelerated necrosis development. T+ decrease was observed already at 35 minutes post-CA4P. Early T2 increase was observed in regions becoming necrotic at 24 hours post-CA4P, as confirmed by high T2 and histology. These regions exhibited, under carbogen, a switch from T2w* signal increase before CA4P to a decrease post-CA4P. The combination of carbogen-based functional MRI and T2 measurement may be useful for the early follow-up of antivascular therapy without the administration of contrast agents. PMID:16867221

Early effects of combretastatin A4 phosphate assessed by anatomic and carbogen-based functional magnetic resonance imaging on rat bladder tumors implanted in nude mice.

PubMed

Thomas, Carole D; Walczak, Christine; Kaffy, Julia; Pontikis, Renée; Jouanneau, Jacqueline; Volk, Andreas

2006-07-01

Combretastatin A4 phosphate (CA4P) causes rapid disruption of the tumor vasculature and is currently being evaluated for antivascular therapy. We describe the initial results obtained with a noninvasive multiparametric magnetic resonance imaging (MRI) approach to assess the early effects of CA4P on rat bladder tumors implanted on nude mice. MRI (4.7 T) comprised a fast spin-echo sequence for growth curve assessment; a multislice multiecho sequence for T2 measurement before, 15 minutes after, and 24 hours after CA4P (100 mg/kg); and a fast T2w* gradient-echo sequence to assess MR signal modification under carbogen breathing before, 35 minutes after, and 24 hours after CA4P. The tumor fraction with increased T2w* signal intensity under carbogen (T+) was used to quantify CA4P effect on functional vasculature. CA4P slowed tumor growth over 24 hours and accelerated necrosis development. T+ decrease was observed already at 35 minutes post-CA4P. Early T2 increase was observed in regions becoming necrotic at 24 hours post-CA4P, as confirmed by high T2 and histology. These regions exhibited, under carbogen, a switch from T2w* signal increase before CA4P to a decrease postCA4P. The combination of carbogen-based functional MRI and T2 measurement may be useful for the early follow-up of antivascular therapy without the administration of contrast agents.

Increase in cytosolic Ca2+ produced by hypoxia and other depolarizing stimuli activates a non-selective cation channel in chemoreceptor cells of rat carotid body

PubMed Central

Kang, Dawon; Wang, Jiaju; Hogan, James O; Vennekens, Rudi; Freichel, Marc; White, Carl; Kim, Donghee

2014-01-01

The current model of O2 sensing by carotid body chemoreceptor (glomus) cells is that hypoxia inhibits the outward K+ current and causes cell depolarization, Ca2+ influx via voltage-dependent Ca2+ channels and a rise in intracellular [Ca2+] ([Ca2+]i). Here we show that hypoxia (<5% O2), in addition to inhibiting the two-pore domain K+ channels TASK-1/3 (TASK), indirectly activates an ∼20 pS channel in isolated glomus cells. The 20 pS channel was permeable to K+, Na+ and Cs+ but not to Cl− or Ca2+. The 20 pS channel was not sensitive to voltage. Inhibition of TASK by external acid, depolarization of glomus cells with high external KCl (20 mm) or opening of the Ca2+ channel with FPL64176 activated the 20 pS channel when 1 mm Ca2+ was present in the external solution. Ca2+ (10 μm) applied to the cytosolic side of inside-out patches activated the 20 pS channel. The threshold [Ca2+]i for activation of the 20 pS channel in cell-attached patches was ∼200 nm. The reversal potential of the 20 pS channel was estimated to be −28 mV. Our results reveal a sequential mechanism in which hypoxia (<5% O2) first inhibits the K+ conductance and then activates a Na+-permeable, non-selective cation channel via depolarization-induced rise in [Ca2+]i. Our results suggest that inhibition of K+ efflux and stimulation of Na+ influx both contribute to the depolarization of glomus cells during moderate to severe hypoxia. PMID:24591572

P/Q-type calcium channels activate neighboring calcium-dependent potassium channels in mouse motor nerve terminals.

PubMed

Protti, D A; Uchitel, O D

1997-08-01

The identity of the voltage-dependent calcium channels (VDCC), which trigger the Ca2+-gated K+ currents (IK(Ca)) in mammalian motor nerve terminals, was investigated by means of perineurial recordings. The effects of Ca2+ chelators with different binding kinetics on the activation of IK(Ca) were also examined. The calcium channel blockers of the P/Q family, omega-agatoxin IVA (omega-Aga-IVA) and funnel-web spider toxin (FTX), have been shown to exert a strong blocking effect on IK(Ca). In contrast, nitrendipine and omega-conotoxin GVIA (omega-CgTx) did not affect the Ca2+-activated K+ currents. The intracellular action of the fast Ca2+ buffers BAPTA and DM-BAPTA prevented the activation of the IK(Ca), while the slow Ca2+ buffer EGTA was ineffective at blocking it. These data indicate that P/Q-type VDCC mediate the Ca2+ influx which activates IK(Ca). The spatial association between Ca2+ and Ca2+-gated K+ channels is discussed, on the basis of the differential effects of the fast and slow Ca2+ chelators.

Local order structure and surface acidity properties of a Nb 2O 5/SiO 2 mixed oxide prepared by the sol-gel processing method

NASA Astrophysics Data System (ADS)

Francisco, Maria Suzana P.; Landers, Richard; Gushikem, Yoshitaka

2004-07-01

The sol-gel processing method was used as an alternative route to obtain Nb 2O 5 phase homogenously dispersed in the SiO 2 matrix, improving the thermal stability of the Brønsted acid sites, Nb-OH and Nb-OH-Si groups. The local niobium structure and the influence of the amount of niobia on the surface of the Nb 2O 5/SiO 2 system were studied by XAS and XPS, respectively. For the samples calcined at 423 and 873 K, the 3 d5/2 BE values are at ca. 208.2 eV, indicating an ionic character for Nb(V) species in the SiO 2 matrix, probably associated to Si-O-Nb linkages. The features of Nb K-edge XANES spectra of samples show the absence of NbO species. The Nb K-edge EXAFS oscillations exhibit a shoulder at ca. 5.6 Å -1, which probably arises from Nb-O-Si. This fact corroborates the EXAFS simulation data of the second coordination shell, whose best fitting is achieved with three distances, two Nb-Nb lengths and one Nb-Si.

The dynamics of plasma membrane PtdIns(4,5)P(2) at fertilization of mouse eggs.

PubMed

Halet, Guillaume; Tunwell, Richard; Balla, Tamas; Swann, Karl; Carroll, John

2002-05-15

A series of intracellular Ca2+ oscillations are responsible for triggering egg activation and cortical granule exocytosis at fertilization in mammals. These Ca2+ oscillations are generated by an increase in inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)], which results from the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)]. Using confocal imaging to simultaneously monitor Ca2+ and plasma membrane PtdIns(4,5)P(2) in single living mouse eggs we have sought to establish the relationship between the kinetics of PtdIns(4,5)P(2) metabolism and the Ca2+ oscillations at fertilization. We report that there is no detectable net loss of plasma membrane PtdIns(4,5)P(2) either during the latent period or during the subsequent Ca2+ oscillations. When phosphatidylinositol 4-kinase is inhibited with micromolar wortmannin a limited decrease in plasma membrane PtdIns(4,5)P(2) is detected in half the eggs studied. Although we were unable to detect a widespread loss of PtdIns(4,5)P(2), we found that fertilization triggers a net increase in plasma membrane PtdIns(4,5)P(2) that is localized to the vegetal cortex. The fertilization-induced increase in PtdIns(4,5)P(2) follows the increase in Ca2+, is blocked by Ca2+ buffers and can be mimicked, albeit with slower kinetics, by photoreleasing Ins(1,4,5)P(3). Inhibition of Ca2+-dependent exocytosis of cortical granules, without interfering with Ca2+ transients, inhibits the PtdIns(4,5)P(2) increase. The increase appears to be due to de novo synthesis since it is inhibited by micromolar wortmannin. Finally, there is no increase in PtdIns(4,5)P(2) in immature oocytes that are not competent to extrude cortical granules. These studies suggest that fertilization does not deplete plasma membrane PtdIns(4,5)P(2) and that one of the pathways for increasing PtdIns(4,5)P(2) at fertilization is invoked by exocytosis of cortical granules.

Hippocampal sclerosis: volumetric evaluation of the substructures of the hippocampus by magnetic resonance imaging.

PubMed

Granados Sánchez, A M; Orejuela Zapata, J F

2018-05-25

The pathological classification of hippocampal sclerosis is based on the loss of neurons in the substructures of the hippocampus. This study aimed to evaluate these substructures in patients with hippocampal sclerosis by magnetic resonance imaging and to compare the usefulness of this morphological analysis compared to that of volumetric analysis of the entire hippocampus. We included 25 controls and 25 patients with hippocampal sclerosis whose diagnosis was extracted from the institutional epilepsy board. We used FreeSurfer to process the studies and obtain the volumetric data. We evaluated overall volume and volume by substructure: fimbria, subiculum, presubiculum, hippocampal sulcus, CA1, CA2-CA3, CA4, and dentate gyrus (DG). We considered p < 0.05 statistically significant. We observed statistically significant decreases in the volume of the hippocampus ipsilateral to the epileptogenic focus in 19 (76.0%) of the 25 cases. With the exception of the hippocampal sulcus, we observed a decrease in all ipsilateral hippocampal substructures in patients with right hippocampal sclerosis (CA1, p=0.0223; CA2-CA3, p=0.0066; CA4-GD, p=0.0066; fimbria, p=0.0046; presubiculum, p=0.0087; subiculum, p=0.0017) and in those with left hippocampal sclerosis (CA1, p<0.0001; CA2-CA3, p<0. 0001; CA4-GD, p<0. 0001; fimbria, p=0.0183; presubiculum, p<0. 0001; subiculum, p<0. 0001). In four patients with left hippocampal sclerosis, none of the substructures had statistically significant alterations, although a trend toward atrophy was observed, mainly in CA2-CA3 and CA4-GD. The findings suggest that it can be useful to assess the substructures of the hippocampus to improve the performance of diagnostic imaging in patients with hippocampal sclerosis. Copyright © 2018 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

Dissolution of uranophane: An AFM, XPS, SEM and ICP study

NASA Astrophysics Data System (ADS)

Schindler, Michael; Freund, Michael; Hawthorne, Frank C.; Burns, Peter C.; Maurice, Patricia A.

2009-05-01

Dissolution experiments on single crystals of uranophane and uranophane-β, Ca(H 2O) 5[(UO 2)(SiO 3(OH)] 2, from the Shinkolobwe mine of the Democratic Republic of Congo, were done in an aqueous HCl solution of pH 3.5 for 3 h, in HCl solutions of pH 2 for 5, 10 and 30 min, and in Pb 2+-, Ba-, Sr-, Ca- and Mg-HCl solutions of pH 2 for 30 min. The basal surfaces of the treated uranophane crystals were examined using atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Solutions after dissolution experiments on single crystals and synthetic powders were analysed with inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectroscopy (ICP-MS). The morphology of the observed etch pits (measured by AFM) were compared to the morphology, predicted on the basis of the bond-valence deficiency of polyhedron chains along the edges of the basal surface. Etch pits form in HCl solutions of pH 2. Their decrease in depth with the duration of the dissolution experiment is explained with the stepwave dissolution model, which describes the lowering of the surrounding area of an etch pit with continuous waves of steps emanated from the etch pit into the rest of the crystal surface. Hillocks form in an HCl solution of pH 3.5, and the chemical composition of the surface (as indicated by XPS) shows that these hillocks are the result of the precipitation of a uranyl-hydroxy-hydrate phase. Well-orientated hillocks form on the surface of uranophane in a SrCl 2-HCl solution of pH 2. They are part of an aged silica coating of composition Si 2O 2(OH) 4(H 2O) n. An amorphous layer forms on the surface of uranophane in a MgCl 2-HCl solution of pH 2, which has a composition and structure similar to silicic acid. Small crystallites of uranyl-hydroxy-hydrate phases form on the surface of uranophane after treatment in Pb(NO 3) 2-HCl and BaCl 2-HCl solutions of pH 2. Dissolution experiments on synthetic uranophane powders show that in the early stage of the experiments, the dissolution rate of uranophane increase in the sequence Pb(NO 3) 2-HCl < BaCl 2-HCl < CaCl 2-HCl < HCl < SrCl 2-HCl < MgCl 2-HCl, indicating that the dissolution of uranophane is more enhanced in solutions containing divalent cations of small ionic radii and high Lewis acidity (Mg, MgCl +).

Intestinal absorption of calcium from calcium ascorbate in rats.

PubMed

Tsugawa, N; Yamabe, T; Takeuchi, A; Kamao, M; Nakagawa, K; Nishijima, K; Okano, T

1999-01-01

The intestinal absorption of calcium (Ca) from Ca ascorbate (Ca-AsA) was investigated in normal rats. Each animal was perorally administered either 5mg (low dose) or 10mg (high dose) of Ca in 1ml of distilled water as Ca-AsA, Ca carbonate (CaCO3), or Ca chloride (CaCl2), which were intrinsically labeled with 45Ca using 45CaCl2. The amount of radioactivity in plasma was measured periodically up to 34h after dosing, and pharmacokinetic parameters were calculated from the radioactivity in plasma. The time taken to reach the maximum 45Ca level (Tmax) did not differ among the three groups. The area under the plasma 45Ca level/time curve (AUCinfinity) value for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups. The radioactivity at Tmax (Cmax) for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups for the low dose, and comparable with or significantly higher than those for the CaCl2 and CaCO3 groups for the high dose. Similar results were observed for whole-body 45Ca retention. Radioactivity in the femur 34h after dosing was the highest in the Ca-AsA group and the lowest in the CaCO3 group. The rank order of solubility in water, the first fluid (pH 1.2, JP-1) of JPXIII disintegration medium, acetate buffer solution (pH 4.0), triethanolamine-malate buffer solution (pH 7.0) and ammonium chloride buffer solution (pH 10.0) at 37 degrees C was CaCl2 > Ca-AsA > CaCO3. In contrast, the rank order of the solubility in the second fluid (pH 6.8, JP-2) of JPXIII disintegration medium at 37 degrees C was Ca-AsA > CaCl2 > CaCO3. These results indicate that the absorbability of Ca from Ca-AsA is almost comparable with, or higher than, that from CaCl2 and significantly higher than that from CaCO3 because of its high degree of solubility in the intestine. Therefore, Ca-AsA would be useful as a Ca supplement with relatively high absorption from intestine.

Growth of Pollen Tubes of Papaver rhoeas Is Regulated by a Slow-Moving Calcium Wave Propagated by Inositol 1,4,5-Trisphosphate.

PubMed Central

Franklin-Tong, V. E.; Drobak, B. K.; Allan, A. C.; Watkins, PAC.; Trewavas, A. J.

1996-01-01

A signaling role for cytosolic free Ca2+ ([Ca2+]i) in regulating Papaver rhoeas pollen tube growth during the self-incompatibility response has been demonstrated previously. In this article, we investigate the involvement of the phosphoinositide signal transduction pathway in Ca2+-mediated pollen tube inhibition. We demonstrate that P. rhoeas pollen tubes have a Ca2+-dependent polyphosphoinositide-specific phospholipase C activity that is inhibited by neomycin. [Ca2+]i imaging after photolysis of caged inositol (1,4,5)-trisphosphate (Ins[1,4,5]P3) in pollen tubes demonstrated that Ins(1,4,5)P3 could induce Ca2+ release, which was inhibited by heparin and neomycin. Mastoparan, which stimulated Ins(1,4,5)P3 production, also induced a rapid increase in Ca2+, which was inhibited by neomycin. These data provide direct evidence for the involvement of a functional phosphoinositide signal-transducing system in the regulation of pollen tube growth. We suggest that the observed Ca2+ increases are mediated, at least in part, by Ins(1,4,5)P3-induced Ca2+ release. Furthermore, we provide data suggesting that Ca2+ waves, which have not previously been reported in plant cells, can be induced in pollen tubes. PMID:12239415

Cytosolic Calcium Coordinates Mitochondrial Energy Metabolism with Presynaptic Activity

PubMed Central

Chouhan, Amit K.; Ivannikov, Maxim V.; Lu, Zhongmin; Sugimori, Mutsuyuki; Llinas, Rodolfo R.; Macleod, Gregory T.

2012-01-01

Most neurons fire in bursts, imposing episodic energy demands, but how these demands are coordinated with oxidative phosphorylation is still unknown. Here, using fluorescence imaging techniques on presynaptic termini of Drosophila motor neurons (MNs), we show that mitochondrial matrix pH (pHm), inner membrane potential (Δψm), and NAD(P)H levels ([NAD(P)H]m) increase within seconds of nerve stimulation. The elevations of pHm, Δψm, and [NAD(P)H]m indicate an increased capacity for ATP production. Elevations in pHm were blocked by manipulations which blocked mitochondrial Ca2+ uptake, including replacement of extracellular Ca2+ with Sr2+, and application of either tetraphenylphosphonium chloride or KB-R7943, indicating that it is Ca2+ that stimulates presynaptic mitochondrial energy metabolism. To place this phenomenon within the context of endogenous neuronal activity, the firing rates of a number of individually identified MNs were determined during fictive locomotion. Surprisingly, although endogenous firing rates are significantly different, there was little difference in presynaptic cytosolic Ca2+ levels ([Ca2+]c) between MNs when each fires at its endogenous rate. The average [Ca2+]c level (329±11nM) was slightly above the average Ca2+ affinity of the mitochondria (281±13nM). In summary, we show that when MNs fire at endogenous rates [Ca2+]c is driven into a range where mitochondria rapidly acquire Ca2+. As we also show that Ca2+ stimulates presynaptic mitochondrial energy metabolism, we conclude that [Ca2+]c levels play an integral role in coordinating mitochondrial energy metabolism with presynaptic activity in Drosophila MNs. PMID:22279208

Apical P2XR contribute to [Ca2+]i signaling and Isc in mouse renal MCD.

PubMed

Li, Liuzhe; Lynch, I Jeanette; Zheng, Wencui; Cash, Melanie N; Teng, Xueling; Wingo, Charles S; Verlander, Jill W; Xia, Shen-Ling

2007-08-03

We examined P2X receptor expression and distribution in the mouse collecting duct (CD) and their functional role in Ca(2+) signaling. Both P2X(1) and P2X(4) were detected by RT-PCR and Western blot. Immunohistochemistry demonstrated apical P2X(1) and P2X(4) immunoreactivity in principal cells in the outer medullary CD (OMCD) and inner medullary CD (IMCD). Luminal ATP induced an increase in Ca(2+) signaling in native medullary CD (MCD) as measured by fluorescence imaging. ATP also induced an increase in Ca(2+) signaling in MCD cells grown in primary culture but not in the presence of P2XR antagonist PPNDS. Short circuit current (I(sc)) measurement with mouse IMCD cells showed that P2XR agonist BzATP induced a larger I(sc) than did P2YR agonist UTP in the apical membrane. Our data reveal for the first time that P2X(1) and P2X(4) are cell-specific with prominent immunoreactivity in the apical area of MCD cells. The finding that P2XR blockade inhibits ATP-induced Ca(2+) signaling suggests that activation of P2XR is a key step in Ca(2+)-dependent purinergic signaling. The result that activation of P2XR produces large I(sc) indicates the necessity of P2XR in renal CD ion transport.

Dietary calcium, phosphorus, and phytase effects on bird performance, intestinal morphology, mineral digestibility, and bone ash during a natural necrotic enteritis episode.

PubMed

Paiva, Diego; Walk, Carrie; McElroy, Audrey

2014-11-01

The objective of this study was to evaluate the effects of dietary Ca, P, and phytase on performance, intestinal morphology, bone ash, and Ca and P digestibility during a necrotic enteritis (NE) outbreak. The 35-d trial was designed as a 2 × 2 × 2 factorial, which included 2 Ca levels (0.6 and 0.9%), 2 P levels (0.3 and 0.45%), and 2 levels of phytase [0 and 1,000 phytase units (FTU)/kg]. Birds were placed on litter from a previous flock that exhibited clinical signs of NE. Birds and feed were weighed on d 12, 19, and 35, and BW gain, feed intake, and feed conversion were calculated. Mortality was recorded daily, and gastrointestinal pH was measured. Tibias and ileal digesta were also collected. Birds began exhibiting clinical signs of NE on d 9, and NE-associated mortality persisted until d 26. Dietary Ca supplemented at 0.9% or inclusion of 1,000 FTU/kg of phytase significantly increased mortality compared with 0.6% Ca or 0 FTU/kg of phytase, respectively. From d 0 to 12, birds fed 0.9% Ca and 0.45% available P with phytase had greater BW gain compared with birds fed 0.6% Ca, 0.45% available P, and phytase. From d 0 to 19, birds fed diets with 0.9% Ca and 0.3% available P had decreased feed intake and improved feed conversion compared with birds fed 0.9% Ca and 0.45% available P. Calcium at 0.9% increased gizzard (d 19) and jejunum (d 12) pH. Phytase supplementation significantly increased Ca digestibility regardless of Ca and P levels of the diets. In addition, diets containing 0.6% Ca and 1,000 FTU/kg of phytase resulted in a significant increase in P digestibility. The results suggest that dietary Ca level may influence NE-associated mortality. In addition, bird performance was affected by interactions of Ca, P, and phytase during the exposure to Clostridium perfringens and the subsequent NE outbreak. Results showed improvements in bird performance when birds were fed 0.6% Ca and 0.3% P in diets supplemented with phytase, which was likely consequent to the influence of Ca in NE pathogenesis. ©2014 Poultry Science Association Inc.

Sarcoplasmic reticulum Ca2+ uptake and leak properties, and SERCA isoform expression, in type I and type II fibres of human skeletal muscle.

PubMed

Lamboley, C R; Murphy, R M; McKenna, M J; Lamb, G D

2014-03-15

The Ca(2+) uptake properties of the sarcoplasmic reticulum (SR) were compared between type I and type II fibres of vastus lateralis muscle of young healthy adults. Individual mechanically skinned muscle fibres were exposed to solutions with the free [Ca(2+)] heavily buffered in the pCa range (-log10[Ca(2+)]) 7.3-6.0 for set times and the amount of net SR Ca(2+) accumulation determined from the force response elicited upon emptying the SR of all Ca(2+). Western blotting was used to determine fibre type and the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) isoform present in every fibre examined. Type I fibres contained only SERCA2 and displayed half-maximal Ca(2+) uptake rate at ∼pCa 6.8, whereas type II fibres contained only SERCA1 and displayed half-maximal Ca(2+) uptake rate at ∼pCa 6.6. Maximal Ca(2+) uptake rate was ∼0.18 and ∼0.21 mmol Ca(2+) (l fibre)(-1) s(-1) in type I and type II fibres, respectively, in good accord with previously measured SR ATPase activity. Increasing free [Mg(2+)] from 1 to 3 mM had no significant effect on the net Ca(2+) uptake rate at pCa 6.0, indicating that there was little or no calcium-induced calcium release occurring through the Ca(2+) release channels during uptake in either fibre type. Ca(2+) leakage from the SR at pCa 8.5, which is thought to occur at least in part through the SERCA, was ∼2-fold lower in type II fibres than in type I fibres, and was little affected by the presence of ADP, in marked contrast to the larger SR Ca(2+) leak observed in rat muscle fibres under the same conditions. The higher affinity of Ca(2+) uptake in the type I human fibres can account for the higher relative level of SR Ca(2+) loading observed in type I compared to type II fibres, and the SR Ca(2+) leakage characteristics of the human fibres suggest that the SERCAs are regulated differently from those in rat and contribute comparatively less to resting metabolic rate.

Effect of dietary calcium level and source on mineral utilisation by piglets fed diets containing exogenous phytase.

PubMed

Schlegel, P; Gutzwiller, A

2017-10-01

Calcium and phosphorus are essential minerals, closely linked in digestive processes and metabolism. With widespread use of low P diets containing exogenous phytase, the optimal dietary Ca level was verified. The 40-day study evaluated the effects of Ca level (4, 7 and 10 g/kg diet) and Ca source (Ca from CaCO 3 and from Lithothamnium calcareum) on mineral utilisation in 72 piglets (7.9 ± 1.0 kg BW) fed an exogenous phytase containing diet with 2.9 g digestible P/kg. Measured parameters were growth performance, stomach mineral solubility, bone breaking strength and urinary, serum and bone mineral concentration. The apparent total tract digestibility of minerals was also assessed in the two diets with 7 g Ca/kg, using 12 additional pigs. Regardless of Ca source, increasing dietary Ca impaired feed conversion ratio, increased urinary pH, increased serum and urinary Ca, decreased serum and urinary P, decreased serum Mg and increased urinary Mg, increased serum AP activity, decreased bone Mg increased bone Zn. Bone breaking strength was improved with 7 compared to 4 g Ca/kg. Compared to CaCO 3 , Ca from Lithothamnium calcareum increased serum Mg and with, 10 g Ca/kg, it limited body weight gain. The dose response of Ca in a diet with 2.9 g digestible P/kg and including exogenous phytase indicated that: (i) a low dietary Ca was beneficial for piglet growth, but was limiting the metabolic use of P; (ii) a high dietary Ca level impaired P utilisation; (iii) the optimal P utilisation and bone breaking strength was obtained with a dietary Ca-to-digestible P ratio of 2.1 to 2.4:1; (iv). Increasing dietary Ca reduced Mg utilisation, but not Zn status, when fed at adequate level. Finally, Ca from Lithothamnium calcareum had similar effects on Ca and P metabolism as CaCO 3 , but impaired growth when fed at the highest inclusion level. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.

Ascorbyl coumarates as multifunctional cosmeceutical agents that inhibit melanogenesis and enhance collagen synthesis.

PubMed

Kwak, Jun Yup; Park, Soojin; Seok, Jin Kyung; Liu, Kwang-Hyeon; Boo, Yong Chool

2015-09-01

L-Ascorbic acid (AA) and p-coumaric acid (p-CA) are naturally occurring antioxidants that are known to enhance collagen synthesis and inhibit melanin synthesis, respectively. The purpose of this study was to examine hybrid compounds between AA and p-CA as multifunctional cosmeceutical agents. Ascorbyl 3-p-coumarate (A-3-p-C), ascorbyl 2-p-coumarate (A-2-p-C), and their parent compounds were tested for their effects on cellular melanin synthesis and collagen synthesis. At 100 μM, A-3-p-C and A-2-p-C decreased melanin content of human dermal melanocytes stimulated by L-tyrosine, by 65 and 59%, respectively, compared to 11% inhibition of AA and 70% inhibition of p-CA. A-3-p-C and A-2-p-C were less effective than p-CA but more effective than AA at inhibiting tyrosinase activity. A-3-p-C and A-2-p-C were more effective than p-CA at inhibiting the autoxidation of L-3,4-dihydroxyphenylalanine. At 100-300 μM, A-3-p-C and A-2-p-C augmented collagen release from human dermal fibroblasts by 120-144% and 125-191%, respectively, compared to 126-133% increase of AA and 120-146% increase of p-CA. They increased procollagen type I C-peptide release (A-3-p-C, and A-2-p-C) like AA, and decreased matrix metalloproteinase 1 level (A-2-p-C) like p-CA, implicating that they might regulate collagen metabolism by multiple mechanisms. This study suggests that A-3-p-C and A-2-p-C could be used as multifunctional cosmeceutical agents for the attenuation of certain aspects of skin aging.

Dramatic effects of external alkalinity on neuronal calcium recovery following a short-duration glutamate challenge: the role of the plasma membrane Ca2+/H+ pump.

PubMed

Khodorov, B; Pinelis, V; Vergun, O; Storozhevykh, T; Fajuk, D; Vinskaya, N; Arsenjeva, E; Khaspekov, L; Lyzin, A; Isaev, N

1995-09-11

Alkalinization of the external medium has been shown to suppress Ca2+ extrusion from neurons due to inhibition of the plasmalemmal Ca2+/H+ pump. In our experiments on fura-2-loaded rat cerebellar granule cells and mouse hippocampal neurons, an increase in pHo from 7.4 to 8.5 following a 1-min glutamate or NMDA challenge caused a dramatic delay in [Ca2+]i recovery which in some cases was accompanied by an additional increase in [Ca2+]i. Normalization of pHo, or removal of Ca2+ from the alkaline solution allowed [Ca2+]i to decrease rapidly again. External alkalinity did not affect the initial rapid decline in [Ca2+]i following a 25 mMK+ pulse. In cerebellar granule cells, the alkaline pHo considerably increased the 45Ca2+ uptake both at rest and following a 2-min GLU pulse. A comparison of these effects of alkaline pHo with those produced by removal of the external Na+ led us to conclude that the Ca2+/H+ pump plays a dominant role in the mechanism of the fast Ca2+ extrusion from glutamate- or NMDA-treated neurons.

[Effects of nitric oxide on peritoneal lymphatic stomata and lymph drainage via NO-cGMP-Ca2+ pathway].

PubMed

Li, Yan-Yuan; Li, Ji-Cheng

2005-02-25

To study the cell signal transduction mechanism of nitric oxide (NO) on the peritoneal lymphatic stomata and lymph drainage in the rat, cGMP content were measured by a commercially available radioimmunoassay kit, and the [Ca(2+)](i) were observed by a confocal laser scanning microscope in the cultured peritoneal mesothelial cell. Animal experiment was practiced to study the effect of NO-cGMP-Ca(2+) pathway on the lymphatic stomata and lymph absorption. The results showed that: (1) Sper/NO increased cGMP of the rat peritoneal mesothelial cell (RPMC) in a dose-dependent manner (P<0.01) compared to the control group. This effect was blocked by 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) (P<0.05), a specific inhibitor of soluble guanylyl cyclase (sGC). The level of [Ca(2+)](i) in single RPMC decreased by adding Sper/NO (P<0.05). Pretreatment with ODQ for 10 min blocked the Sper/NO-induced decrease in [Ca(2+)](i). L-typed calcium channel blocker nifedipine induced an immediate and marked decrease in [Ca(2+)](i) (P<0.05).. After [Ca(2+)](i) reached a balance again, adding Sper/NO could not change [Ca(2+)](i) (P>0.05). (2) Sper/NO increased the area of the stomata (P<0.01) and the quantity of the tracer in a dose-dependent manner (P<0.05) compared to the control group. Pretreatment with ODQ significantly inhibited Sper/NO-induced change of lymphatic stomata and lymph drainage (P<0.01). Nifedipine increased the opening area of the lymphatic stomata (P< 0.01) and the concentration of absorbed trypan blue of the diaphragm (P<0.05). Sper/NO could not make a further change in the samples pretreated by nifedipine (P> 0.05). The results indicate that NO can decrease [Ca(2+)](i) in the RPMC through the NO-cGMP pathway. This procession is related with the L- type voltage-gated Ca(2+) channel. NO enlarges the opening area of the lymphatic stomata and enhances the lymph drainage of tracer by NO-cGMP-[Ca(2+)](i) pathway.

Geochemical survey of the Lusk Creek Roadless Area, Pope County, Illinois

USGS Publications Warehouse

Klasner, John S.; Day, Gordon W.

1984-01-01

The Lusk Creek Roadless Area (Index map) lies along the western edge of the Illinois-Kentucky fluorspar district in which flourite deposits occur as lenticular-type veins emplaced along fult zones or as tratiform-shaped bedding-replacement deposits that occur along fault zones (Grogan and Bradbury, 1967; Trace, 1974). Although mineralogy varies between deposits, Trace (1974) points out that the principal minerals are fluorite (CaF) and calcite (CaCO3), and associated with these minerals are lesser amounts of sphalerite (ZnS), galena (PbS), and barite (BaSO4). Minor quantites of iron-rich dolomite (CaMg(CO3)2), pyrite (FeS2),  and alteration products of zinc, lead, and copper minerals also are found. 

First-principles calculations for XAS of infinite-layer iron oxides

NASA Astrophysics Data System (ADS)

Kodera, Mitsuru; Shishidou, Tatsuya; Oguchi, Tamio

2011-03-01

The oxygen defect perovskite SrFe O3 - x shows various properties such as the giant magnetoresistance effect and the thermoelectric effect. It had been believed that the oxygen content in SrFe O3 - x changes up to x = 0.5 . Recently, Tsujimoto et al . have succeeded in synthesizing the infinite-layer iron oxide SrFe O2 . SrFe O2 has a square-planar oxygen coordination, while the iron oxides usually have the tetrahedral and octahedral coordination. CaFe O2 has also infinite layer structure and the same magnetic ordering as SrFe O2 . However, it is suggested that the oxygen coordination of CaFe O2 is different from that of SrFe O2 . In order to investigate the electronic structure of iron in (Ca, Sr) Fe O2 , the x-ray absorption spectroscopy (XAS) spectrum has been measured. In this work, we perform the calculation for XAS spectrum near the Fe-K edge of (Ca, Sr) Fe O2 using the first-principles calculations. We compare the results with the experiment and discuss the electronic structure of iron in (Ca, Sr) Fe O2 .

Role of different types of Ca2+ channels and a reticulum-like Ca2+ pump in neurotransmitter release.

PubMed

Fossier, P; Baux, G; Tauc, L

1993-01-01

The factors controlling the Ca2+ concentration directly responsible for triggering acetylcholine (ACh) release were investigated at an identified neuro-neuronal synapse of the Aplysia buccal ganglion. The types of presynaptic voltage-gated Ca2+ channels associated with transmitter release were determined by using selective blockers such as nifedipine, omega-conotoxin and a partially purified extract from the venom of a funnel web spider (FTx). L-type, N-type and P-type Ca2+ channels are present in the presynaptic neuron. The influx of Ca2+ through both N- and P-types induces the release of ACh whereas Ca2+ flowing through L-type channels modulates the duration of the presynaptic action potential by controlling the Ca(2+)-dependent K+ current. tBuBHQ, a blocker of the reticulum Ca2+ pump, induces a potentiation of evoked release without modifying the presynaptic Ca2+ influx. This seems to indicate that a part of the Ca2+ entering the presynaptic terminal through N- and P-type Ca2+ channels is sequestered in a presynaptic reticulum-like Ca2+ buffer preventing these ions from contributing to ACh release. To exert its control, this Ca2+ buffer must be located close to both the presynaptic Ca2+ channels and the transmitter release mechanism.

Effect of calcium level and phytase addition on ileal phytate degradation and amino acid digestibility of broilers fed corn-based diets.

PubMed

Amerah, A M; Plumstead, P W; Barnard, L P; Kumar, A

2014-04-01

This study investigated the effect of dietary Ca to available P (AvP) ratio and phytase supplementation on bone ash, ileal phytate degradation, and nutrient digestibility in broilers fed corn-based diets. The experimental design was a 4 × 2 factorial arrangement of treatments evaluating 4 Ca:AvP ratios (1.43, 2.14, 2.86, and 3.57) and 2 levels of phytase (0 and 1,000 phytase units/kg of feed). The 4 Ca:AvP ratios were achieved by formulating all diets to a constant AvP level of 0.28% and varying Ca levels (0.4, 0.6, 0.8, and 1.0%). Each treatment was fed to 6 cages of 8 male Ross 308 broilers from 5 to 21 d. At 21 d, digesta from the terminal ileum was collected and analyzed for energy, phytate, P, Ca, and amino acids (AA) to determine digestibility. Digesta pH was measured in each segment (crop, gizzard, duodenum, and ileum) of the digestive tract. Data were analyzed by 2-way analysis of covariance. There was a significant interaction between dietary Ca:AvP ratio and phytase supplementation for weight gain (WG), feed intake (FI), and feed conversion ratio (FCR). In diets with no phytase, Ca:AvP ratio had a greater effect on WG, FI, and FCR compared with those fed diets without phytase. The orthogonal polynomial contrasts showed that the increase in dietary Ca:AvP ratio significantly decreased WG and FI in a quadratic manner, whereas FCR increased (P < 0.05) linearly with higher dietary Ca:AvP ratio. Increasing dietary Ca:AvP ratio led to a significant quadratic decrease in phytate degradation and significant linear decreases in P digestibility and bone ash. Phytase addition increased (P < 0.05) phytate degradation and improved (P < 0.05) energy, AA, and P digestibility at all levels of Ca:AvP with no interaction (P > 0.05) between the main factors. Digestibility of AA was positively correlated (P < 0.05) with the degree of phytate degradation. Increasing dietary Ca:AvP ratio significantly increased gizzard pH in a linear manner. In conclusion, phytase (1,000 phytase units/kg of feed) improved phytate, and P and AA digestibility at all Ca:AvP ratios evaluated in this study.

Cadmium is acutely toxic for murine hepatocytes: effects on intracellular free Ca(2+) homeostasis.

PubMed

Wang, S S; Chen, L; Xia, S K

2007-01-01

We studied cadmium toxicity in murine hepatocytes in vitro. Cadmium effects on intracellular free Ca(2+) concentration ([Ca(2+)](i)) were assayed, using a laser scanning confocal microscope with a fluorescent probe, Fluo-3/AM. The results showed that administration of cadmium chloride (CdCl(2), 5, 10, 25 microM) resulted in a dose-dependent decrease of hepatocyte viability and an elevated aspartate aminotransferase (AST) activity in the culture medium (p<0.05 for 25 microM CdCl(2) vs. control). Significant increases of lactate dehydrogenase (LDH) activities in 10 and 25 microM CdC1(2)-exposed groups were observed (p<0.05 and p<0.01, respectively). A greatly decreased albumin content and a more malondialdehyde (MDA) formation also occurred after CdC1(2) treatment. The Ca(2+) concentrations in the culture medium of CdCl(2)-exposed hepatocytes were significantly decreased, while [Ca(2+)](i) appeared to be significantly elevated (p<0.05 or p<0.01 vs. control). We found that in Ca(2+)-containing hydroxyethyl piperazine ethanesulfonic acid-buffered salt solution (HBSS) only, CdCl(2) elicited [Ca(2+)](i) increases, which comprised an initially slow ascent and a strong elevated phase. However, in Ca(2+)-containing HBSS with addition of 2-aminoethoxydiphenyl borane (2-APB), CdCl(2) caused a mild [Ca(2+)](i) elevation in the absence of an initial rise phase. Removal of extracellular Ca(2+) showed that CdCl(2) induced an initially slow [Ca(2+)](i) rise alone without being followed by a markedly elevated phase, but in a Ca(2+)-free HBSS with addition of 2-APB, CdCl(2) failed to elicit the [Ca(2+)](i) elevation. These results suggest that abnormal Ca(2+) homeostasis due to cadmium may be an important mechanism of the development of the toxic effect in murine hepatocytes. [Ca(2+)](i) elevation in acutely cadmium-exposed hepatocytes is closely related to the extracellular Ca(2+) entry and an excessive release of Ca(2+) from intracellular stores.

Ca2+ Induces Spontaneous Dephosphorylation of a Novel P5A-type ATPase

PubMed Central

Sørensen, Danny Mollerup; Møller, Annette B.; Jakobsen, Mia K.; Jensen, Michael K.; Vangheluwe, Peter; Buch-Pedersen, Morten J.; Palmgren, Michael G.

2012-01-01

P5 ATPases constitute the least studied group of P-type ATPases, an essential family of ion pumps in all kingdoms of life. Although P5 ATPases are present in every eukaryotic genome analyzed so far, they have remained orphan pumps, and their biochemical function is obscure. We show that a P5A ATPase from barley, HvP5A1, locates to the endoplasmic reticulum and is able to rescue knock-out mutants of P5A genes in both Arabidopsis thaliana and Saccharomyces cerevisiae. HvP5A1 spontaneously forms a phosphorylated reaction cycle intermediate at the catalytic residue Asp-488, whereas, among all plant nutrients tested, only Ca2+ triggers dephosphorylation. Remarkably, Ca2+-induced dephosphorylation occurs at high apparent [Ca2+] (Ki = 0.25 mm) and is independent of the phosphatase motif of the pump and the putative binding site for transported ligands located in M4. Taken together, our results rule out that Ca2+ is a transported substrate but indicate the presence of a cytosolic low affinity Ca2+-binding site, which is conserved among P-type pumps and could be involved in pump regulation. Our work constitutes the first characterization of a P5 ATPase phosphoenzyme and points to Ca2+ as a modifier of its function. PMID:22730321

Role of Cyclin E as an Early Event in Ovarian Carcinogenesis

DTIC Science & Technology

2012-04-01

degradation . P27 is a powerful negative regulator of the cell cycle, preventing activation of cyclin E- cdk2 or cyclin D-cdk4 complexes and cell cycle...Ahmed M, Bavi P, et al. Bortezomib (Velcade) induces p27Kip1 expression through S-phase kinase protein 2 degradation in colorectal cancer. Cancer Res...CA1251CA72·4 CA 125 CA72-4 M-CSF CA 125/CA 72-4/M-CSFICA 15-3 CA125 CA 125/mesothelin CA 125/IL·6JIL·8NEGF;EGF CA 125/IL-6,G-CSFNEGF/EGF Leptin

The influence of calcium and pH on growth in primary roots of Zea mays

NASA Technical Reports Server (NTRS)

Hasenstein, K. H.; Evans, M. L.

1988-01-01

We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 x Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 mM CaCl2) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 mM MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45Ca2+. Release of 45Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots.

Synchronization of calcium waves by mitochondrial substrates in Xenopus laevis oocytes

NASA Astrophysics Data System (ADS)

Jouaville, Laurence S.; Ichas, François; Holmuhamedov, Ekhson L.; Camacho, Patricia; Lechleiter, James D.

1995-10-01

INXenopus oocytes, as well as other cells, inositol-l,4,5-tris-phosphate (Ins(l,4,5)P3)-induced Ca2+ release1-4 is an excitable process that generates propagating Ca2+ waves5-7 that annihilate upon collision8-12. The fundamental property responsible for excitability13 appears to be the Ca2+ dependency of the Ins(l,4,5)P3 receptor9. Here we report that Ins(l,4,5)P3-induced Ca2+ wave activity is strengthened by oxidizable substrates that energize mitochondria, increasing Ca2+ wave amplitude, velocity and interwave period. The effects of pyruvate/malate are blocked by ruthenium red at the Ca2+ uniporter, by rotenone at complex I, and by antimycin A at complex III, and are subsequently rescued at complex IV by ascorbate tetramethylphenylenediamine (TMPD)14. Our data reveal that potential-driven mitochondrial Ca2+ uptake is a major factor in the regulation of Ins(l,4,5)P3-induced Ca2+ release and clearly demonstrate a physiological role of mitochondria in intracellular Ca2+ signalling.

Effect of dietary calcium and phosphorus levels on the total tract digestibility of innate and supplemental organic and inorganic microminerals in a corn-soybean meal based diet of grower pigs.

PubMed

Jolliff, J S; Mahan, D C

2013-06-01

The effects of Ca and P (CaP) levels and micromineral sources on mineral digestibility were evaluated in growing pigs. Treatments consisted of 2 levels of CaP and 3 trace mineral (TM) treatments arranged as a 2 × 3 factorial in a randomized complete block design with 8 replicates. The CaP levels evaluated were: 1) 0.65% Ca and 0.55% P [standard CaP (Std CaP)], and 2) 1.00% Ca and 0.85% P (High CaP). The TM treatments were: 1) Basal, without supplemental TM, 2) Basal supplemented with organic TM, and 3) Basal supplemented with inorganic TM. Both organic and inorganic TM premixes added 15 mg Cu, 150 mg Fe, 10 mg Mn, 0.3 mg Se, and 140 mg Zn/kg diet. Diets were formulated using corn soybean meal with a Ca to P ratio of 1.18 in both CaP treatments. Barrows with an initial BW of 45 kg were acclimated to stainless steel metabolism crates where diets were fed for 14 d before a 10-d collection period. Pigs within replicates were fed equivalent amounts of feed at 0800 and 1600 h each day with water provided free choice. Total feces, urine, and feed orts were collected daily. Essential macro- and microminerals were analyzed by inductively coupled plasma analysis. Increasing dietary CaP decreased the digestibility of Ca and Zn. Phosphorus digestibility did not change when the P inclusion level increased from 0.55 to 0.85% Ptotal. The High CaP level resulted in a lower urinary excretion of most minerals, particularly Cu (P < 0.05) and Mn (P < 0.05), as dietary CaP level increased but the others were not statistically significant. A summary of the ATTD for each of the experimental variables was statistically analyzed and averaged for the experiment. Although there were few statistical differences with individual minerals, they generally demonstrated a decline in digestibility when the High CaP was fed, averaging a 3% lower digestibility consistently than when the Std CaP level was fed. Organic TM averaged an approximately 5% greater digestibility than the average inorganic microminerals with the difference between minerals within each source relatively consistent. These results indicate that CaP level had the greatest effect on mineral digestibility, organic microminerals had a greater digestibility than inorganic minerals, and the innate microminerals had an average apparent digestibility of 45%.

Soft X-ray scanning transmission X-ray microscopy (STXM) of actinide particles.

PubMed

Nilsson, Hans J; Tyliszczak, Tolek; Wilson, Richard E; Werme, Lars; Shuh, David K

2005-09-01

A descriptive account is given of our most recent research on the actinide dioxides with the Advanced Light Source Molecular Environmental Science (ALS-MES) Beamline 11.0.2 soft X-ray scanning transmission X-ray microscope (STXM) at the Lawrence Berkeley National Laboratory (LBNL). The ALS-MES STXM permits near-edge X-ray absorption fine structure (NEXAFS) and imaging with 30-nm spatial resolution. The first STXM spectromicroscopy NEXAFS spectra at the actinide 4d5/2 edges of the imaged transuranic particles, NpO2 and PuO2, have been obtained. Radiation damage induced by the STXM was observed in the investigation of a mixed oxidation state particle (Np(V,VI)) and was minimized during collection of the actual spectra at the 4d5/2 edge of the Np(V,VI) solid. A plutonium elemental map was obtained from an irregular PuO2 particle with the dimensions of 650 x 650 nm. The Pu 4d5/2 NEXAFS spectra were collected at several different locations from the PuO2 particle and were identical. A representative oxygen K-edge spectrum from UO2 was collected and resembles the oxygen K-edge from the bulk material. The unique and current performance of the ALS-MES STXM at extremely low energies (ca. 100 eV) that may permit the successful measurement of the actinide 5d edge is documented. Finally, the potential of STXM as a tool for actinide investigations is briefly discussed.

High- T c superconductivity at the interface between the CaCuO 2 and SrTiO 3 insulating oxides

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

Di Castro, D.; Cantoni, C.; Ridolfi, F.

2015-09-28

At interfaces between complex oxides it is possible to generate electronic systems with unusual electronic properties, which are not present in the isolated oxides. One important example is the appearance of superconductivity at the interface between insulating oxides, although, until now, with very low T c. We report the occurrence of high T c superconductivity in the bilayer CaCuO 2/SrTiO 3, where both the constituent oxides are insulating. In order to obtain a superconducting state, the CaCuO 2/SrTiO 3 interface must be realized between the Ca plane of CaCuO 2 and the TiO 2 plane of SrTiO 3. Only inmore » this case can oxygen ions be incorporated in the interface Ca plane, acting as apical oxygen for Cu and providing holes to the CuO 2 planes. In addition, a detailed hole doping spatial profile can be obtained by scanning transmission electron microscopy and electron-energy-loss spectroscopy at the O K edge, clearly showing that the (super)conductivity is confined to about 1–2 CaCuO 2 unit cells close to the interface with SrTiO 3. The results obtained for the CaCuO 2/SrTiO 3 interface can be extended to multilayered high T c cuprates, contributing to explaining the dependence of T c on the number of CuO 2 planes in these systems.« less

Incorporation of Mg, Sr, Ba, U, and B in High-Mg Calcite Benthic Foraminifers Cultured Under Controlled pCO2

NASA Astrophysics Data System (ADS)

Not, C.; Thibodeau, B.; Yokoyama, Y.

2018-01-01

Measurement of elemental ratios (E/Ca) has been performed in two symbiont-bearing species of high-Mg calcite benthic foraminifers (hyaline, Baculogypsina sphaerulata and porcelaneous, Amphisorus hemprichii), cultured under five pCO2 levels, representing preindustrial, modern, and three predicted future values. E/Ca ratios were analyzed by Laser Ablation coupled with Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). We measured several E/Ca, such as Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca simultaneously. We observed that high-Mg calcite benthic foraminifers possess higher E/Ca than low-Mg calcite foraminifers, irrespective of their calcification mode (hyaline or porcelaneous). In both modes of calcification, Mg, Sr, Ba, U, and B incorporation could be controlled by Rayleigh fractionation. However, more data are needed to validate and quantify the relative importance of this process and closely investigate the presence/absence of other mechanism. Therefore, it highlights the need for a multielemental approach when looking at trace element incorporation. Finally, no significant relationship was observed between the different ratios and the pCO2 of the water, suggesting that none of the Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca is sensitive to bottom water pCO2 or pH for these species.

Laser photolysis of caged calcium: rates of calcium release by nitrophenyl-EGTA and DM-nitrophen.

PubMed Central

Ellis-Davies, G C; Kaplan, J H; Barsotti, R J

1996-01-01

Nitrophenyl-EGTA and DM-nitrophen are Ca2+ cages that release Ca2+ when cleaved upon illumination with near-ultraviolet light. Laser photolysis of nitrophenyl-EGTA produced transient intermediates that decayed biexponentially with rates of 500,000 s-1 and 100,000 s-1 in the presence of saturating Ca2+ and 290,000 s-1 and 68,000 s-1 in the absence of Ca2+ at pH 7.2 and 25 degrees C. Laser photolysis of nitrophenyl-EGTA in the presence of Ca2+ and the Ca2+ indicator Ca-orange-5N produced a monotonic increase in the indicator fluorescence, which had a rate of 68,000 s-1 at pH 7.2 and 25 degrees C. Irradiation of DM-nitrophen produced similar results with somewhat slower kinetics. The transient intermediates decayed with rates of 80,000 s-1 and 11,000 s-1 in the presence of Ca2+ and 59,000 s-1 and 3,600 s-1 in the absence of Ca2+ at pH 7.2 and 25 degrees C. The rate of increase in Ca(2+)-indicator fluorescence produced upon photolysis of the DM-nitrophen: Ca2+ complex was 38,000 s-1 at pH 7.2 and 25 degrees C. In contrast, pulses in Ca2+ concentration were generated when the chelator concentrations were more than the total Ca2+ concentration. Photoreleased Ca2+ concentration stabilized under these circumstances to a steady state within 1-2 ms. PMID:8789118

Phosphorus digestibility response of broiler chickens to dietary calcium-to-phosphorus ratios.

PubMed

Liu, J B; Chen, D W; Adeola, O

2013-06-01

This study was conducted to evaluate the true digestibility of P in soybean meal (SBM) for broiler chickens fed diets with different dietary calcium-to-phosphorus ratios (Ca:P) using the regression method. The experiment used a 4 × 3 factorial arrangement with 12 diets formulated to contain combinations of 4 levels of dietary Ca:P: 0.8, 1.2, 1.6, or 2.0 and 3 levels of SBM: 31.0, 44.0, or 57.0%. A total of 576 male Ross 708 broilers were allocated to 12 dietary treatments with 8 cages (6 birds per cage) per treatment from d 15 to 22 posthatching, and the BW between groups were similar. Chromic dioxide was used as an indigestible marker to calculate P digestibility and retention. The results showed that BW gain and feed efficiency were increased (linear, P < 0.01), and prececal DM digestibility and DM retention were decreased (linear, P < 0.01) with graded SBM in diets for each Ca:P. Decreasing linear (P < 0.01) relationships were observed for apparent prececal P digestibility and total tract P retention with increased dietary SBM levels. The prececal and excreta P output increased (linear, P < 0.01; quadratic, P < 0.05) as increasing levels of SBM were added to the experimental diets. True prececal P digestibility in SBM was greater (P < 0.05) for birds fed a diet with Ca:P of 0.8 compared with those fed higher Ca:P, but there was no difference among the Ca:P ratios between 1.2 and 2.0. However, the total tract retention of P from SBM was not affected by Ca:P between 0.8 and 2.0. In conclusion, results of the present experiment demonstrated that prececal digestibility of P in SBM was not affected by Ca:P ratio between 1.2 and 2.0; and there was no difference in total tract retention of P from SBM among the Ca:P ratios between 0.8 and 2.0 in broiler chickens.

Cellular characteristics of primary and immortal canine embryonic fibroblast cells.

PubMed

You, Seungkwon; Moon, Jai-Hee; Kim, Tae-Kyung; Kim, Sung-Chan; Kim, Jai-Woo; Yoon, Du-Hak; Kwak, Sungwook; Hong, Ki-Chang; Choi, Yun-Jaie; Kim, Hyunggee

2004-08-31

Using normal canine embryonic fibroblasts (CaEF) that were shown to be senescent at passages 7th-9th, we established two spontaneously immortalized CaEF cell lines (designated CGFR-Ca-1 and -2) from normal senescent CaEF cells, and an immortal CaEF cell line by exogenous introduction of a catalytic telomerase subunit (designated CGFR-Ca-3). Immortal CGFR- Ca-1, -2 and -3 cell lines grew faster than primary CaEF counterpart in the presence of either 0.1% or 10% FBS. Cell cycle analysis demonstrated that all three immortal CaEF cell lines contained a significantly high proportion of S-phase cells compared to primary CaEF cells. CGFR-Ca-1 and -3 cell lines showed a loss of p53 mRNA and protein expression leading to inactivation of p53 regulatory function, while the CGFR-Ca-2 cell line was found to have the inactive mutant p53. Unlike the CGFR-Ca-3 cell line that down-regulated p16INK4a mRNA due to its promoter methylation but had an intact p16INK4a regulatory function, CGFR-Ca-1 and -2 cell lines expressed p16INK4a mRNA but had a functionally inactive p16INK4a regulatory pathway as judged by the lack of obvious differences in cell growth and phenotype when reconstituted with wild-type p16INK4a. All CGFR-Ca-1, -2 and -3 cell lines were shown to be untransformed but immortal as determined by anchorage-dependent assay, while these cell lines were fully transformed when overexpressed oncogenic H-rasG12V. Taken together, similar to the nature of murine embryo fibroblasts, the present study suggests that normal primary CaEF cells have relatively short in vitro lifespans and should be spontaneously immortalized at high frequency.

Removal of Ca2+ and Zn2+ from aqueous solutions by zeolites NaP and KP.

PubMed

Yusof, Alias Mohd; Malek, Nik Ahmad Nizam Nik; Kamaruzaman, Nurul Asyikin; Adil, Muhammad

2010-01-01

Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca2+) and zinc (Zn2+) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K+ with Na+ which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K+ on zeolite NaP was determined through the Freundlich isotherm equilibrium study. Characterization of zeolite KP was determined using infrared spectroscopy and X-ray diffraction (XRD) techniques. From the characterization, the structure of zeolite KP was found to remain stable after the ion exchange process. Zeolites KP and NaP were used for the removal of Ca and Zn from solution. The amount of Ca2+ and Zn2+ in aqueous solution before and after the adsorption by zeolites was analysed using the flame atomic absorption spectroscopy method. The removal of Ca2+ and Zn2+ followed the Freundlich isotherm rather than the Langmuir isotherm model. This result also revealed that zeolite KP adsorbs Ca2+ and Zn2+ more than zeolite NaP and proved that modification of zeolite NaP with potassium leads to an increase in the adsorption efficiency of the zeolite. Therefore, the zeolites NaP and KP can be used for water softening (Ca removal) and reducing water pollution/toxicity (Zn removal).

Precipitation of CaCO3 due to the Uptake of CO2 in Aqueous Solutions - Mechanisms and Rates

NASA Astrophysics Data System (ADS)

Dietzel, M.; Purgstaller, B.; Rinder, T.; Niedermayr, A.

2012-12-01

In natural and man-made environments the exchange of CO2 between aqueous solutions and the atmosphere frequently induces precipitation of CaCO3 polymorphs. Liberation of gaseous CO2 is well known to induce carbonate formation and extensively studied. In contrast significant gaps of knowledge exist with respect to the combined CO2 uptake and CaCO3 formation, although it is known to be highly valid for many natural and man-made surroundings causing e.g. travertine and scaling in analogy to CO2 liberation. Recently CO2 uptake is also discussed for biomineralization issues and debated for CO2 sequestration by using alkaline residue materials. In the present study CO2 uptake and CaCO3 precipitation mechanisms and rates were experimentally studied by diffusion of CO2 through a polyethylene membrane from an inner to an outer solution containing carbonic acid and CaCl2 (10 mM), respectively. The pH of the outer solution was kept constant between 8.3 and 11.5 by pH stat. technique (25°C). At a critical Ion Activity Product (IAP) CaCO3 is formed in the outer solution. The NaOH titration curve and Ca2+ concentrations reflect CO2 uptake and CaCO3 precipitation rates. To discover the impact of a drift in pH due to CO2 uptake on CaCO3 precipitation hydrogeochemical modeling was applied. XRD, (micro)Raman pattern and SEM imaging reveal the formation of calcite and vaterite at pH 8.3 and 9, whereas at pH > 10 vaterite is additionally formed. However at a given pH the formation of individual CaCO3 polymorphs strongly depends on the CO2 uptake rate (adjusted by membrane thickness), which controls carbonate accumulation in the solution. At elevated pH of the outer solution the uptake rate of CO2 is significantly higher and less time for nucleation of CaCO3 is required compared to lower pH. Surprisingly at the total experimental time of ≈ 20 h the amount of precipitated CaCO3 is similar for all experiments. This can be explained by significant higher CaCO3 precipitation rates at low versus high pH if once a critical IAP is reached. If a drift in pH is permitted the internal Pco2 value can be used as a reliable proxy to evaluate whether uptake of CO2 results in an increase or decrease of IAP with a threshold value of 10-6.15 atm at 25°C (pH ≈ 11). The obtained relationships for CaCO3 formation through CO2 uptake are discussed for selected alkaline environments.

Ca2+ and Mn2+ Influx Through Receptor-Mediated Activation of Nonspecific Cation Channels in Mast Cells

NASA Astrophysics Data System (ADS)

Fasolato, Cristina; Hoth, Markus; Matthews, Gary; Penner, Reinhold

1993-04-01

Whole-cell patch-clamp recordings of membrane currents and Fura-2 measurements of free intracellular calcium concentration ([Ca2+]_i) were used to study calcium influx through receptor-activated cation channels in rat peritoneal mast cells. Cation channels were activated by the secretagogue compound 48/80, whereas a possible concomitant Ca2+ entry through pathways activated by depletion of calcium stores was blocked by dialyzing cells with heparin. Heparin effectively suppressed the transient Ca2+ release induced by 48/80 and abrogated inositol 1,4,5-trisphosphate-induced calcium influx without affecting activation of 50-pS cation channels. There was a clear correlation between changes in [Ca2+]_i and the activity of 50-pS channels. The changes in [Ca2+]_i increased with elevation of extracellular Ca2+. At the same time, inward currents through 50-pS channels were diminished as more Ca2+ permeated. This effect was due to a decrease in slope conductance and a reduction in the open probability of the cation channels. In physiological solutions, 3.6% of the total current was carried by Ca2+. The cation channels were not only permeable to Ca2+ but also to Mn2+, as evidenced by the quench of Fura-2 fluorescence. Mn2+ current through 50-pS channels could not be resolved at the single-channel level. Our results suggest that 50-pS cation channels partially contribute to sustained increases of [Ca2+]_i in mast cells following receptor activation.

PIK3CA oncogenic mutations represent a major mechanism of resistance to trastuzumab in HER2/neu overexpressing uterine serous carcinomas

PubMed Central

Black, Jonathan D; Lopez, Salvatore; Cocco, Emiliano; Bellone, Stefania; Altwerger, Gary; Schwab, Carlton L; English, Diana P; Bonazzoli, Elena; Predolini, Federica; Ferrari, Francesca; Ratner, Elena; Silasi, Dan-Arin; Azodi, Masoud; Schwartz, Peter E; Santin, Alessandro D

2015-01-01

Objectives: We evaluated the role of PIK3CA-mutations as mechanism of resistance to trastuzumab in primary HER2/neu-amplified uterine-serous-carcinoma (USC) cell lines. Methods: Fifteen whole-exome-sequenced USC cell lines were tested for HER2/neu-amplification and PIK3CA-mutations. Four HER2/neu-amplified USC (2-harbouring wild-type-PIK3CA-genes and 2-harbouring oncogenic-PIK3CA-mutations) were evaluated in in vitro dose-titration-proliferation-assays, cell-viability and HER2 and S6-protein-phosphorylation after exposure to trastuzumab. USC harbouring wild-type-PIK3CA were transfected with plasmids encoding oncogenic PIK3CA-mutations (i.e., H1047R/R93Q) and exposed to trastuzumab. Finally, trastuzumab efficacy was tested by using two USC xenograft mouse models. Results: Seven out of fifteen (46%) of the USC cell lines were HER2/neu-amplified by fluorescence in situ hybridisation. Within these tumours four out of seven (57%) were found to harbour oncogenic PIK3CA-mutations vs two out of eight (25%) of the HER2/neu not amplified cell lines (P=0.01). HER2/neu-amplified/PIK3CA-mutated USC were highly resistant to trastuzumab when compared with HER2/neu-amplified/wild-type-PIK3CA cell lines (P=0.02). HER2/neu-amplified/PIK3CA wild-type cell lines transfected with oncogenic PIK3CA-mutations increased their resistance to trastuzumab (P<0.0001). Trastuzumab was effective in reducing tumour growth (P=0.001) and improved survival (P=0.0001) in mouse xenografts harbouring HER2-amplified/PIK3CA wild-type USC but not in HER2-amplified/PIK3CA-mutated tumours. Conclusions: Oncogenic PIK3CA mutations are common in HER2/neu-amplified USC and may constitute a major mechanism of resistance to trastuzumab treatment. PMID:26325104

PIK3CA oncogenic mutations represent a major mechanism of resistance to trastuzumab in HER2/neu overexpressing uterine serous carcinomas.

PubMed

Black, Jonathan D; Lopez, Salvatore; Cocco, Emiliano; Bellone, Stefania; Altwerger, Gary; Schwab, Carlton L; English, Diana P; Bonazzoli, Elena; Predolini, Federica; Ferrari, Francesca; Ratner, Elena; Silasi, Dan-Arin; Azodi, Masoud; Schwartz, Peter E; Santin, Alessandro D

2015-09-29

We evaluated the role of PIK3CA-mutations as mechanism of resistance to trastuzumab in primary HER2/neu-amplified uterine-serous-carcinoma (USC) cell lines. Fifteen whole-exome-sequenced USC cell lines were tested for HER2/neu-amplification and PIK3CA-mutations. Four HER2/neu-amplified USC (2-harbouring wild-type-PIK3CA-genes and 2-harbouring oncogenic-PIK3CA-mutations) were evaluated in in vitro dose-titration-proliferation-assays, cell-viability and HER2 and S6-protein-phosphorylation after exposure to trastuzumab. USC harbouring wild-type-PIK3CA were transfected with plasmids encoding oncogenic PIK3CA-mutations (i.e., H1047R/R93Q) and exposed to trastuzumab. Finally, trastuzumab efficacy was tested by using two USC xenograft mouse models. Seven out of fifteen (46%) of the USC cell lines were HER2/neu-amplified by fluorescence in situ hybridisation. Within these tumours four out of seven (57%) were found to harbour oncogenic PIK3CA-mutations vs two out of eight (25%) of the HER2/neu not amplified cell lines (P=0.01). HER2/neu-amplified/PIK3CA-mutated USC were highly resistant to trastuzumab when compared with HER2/neu-amplified/wild-type-PIK3CA cell lines (P=0.02). HER2/neu-amplified/PIK3CA wild-type cell lines transfected with oncogenic PIK3CA-mutations increased their resistance to trastuzumab (P<0.0001). Trastuzumab was effective in reducing tumour growth (P=0.001) and improved survival (P=0.0001) in mouse xenografts harbouring HER2-amplified/PIK3CA wild-type USC but not in HER2-amplified/PIK3CA-mutated tumours. Oncogenic PIK3CA mutations are common in HER2/neu-amplified USC and may constitute a major mechanism of resistance to trastuzumab treatment.

NCLX protein, but not LETM1, mediates mitochondrial Ca2+ extrusion, thereby limiting Ca2+-induced NAD(P)H production and modulating matrix redox state.

PubMed

De Marchi, Umberto; Santo-Domingo, Jaime; Castelbou, Cyril; Sekler, Israel; Wiederkehr, Andreas; Demaurex, Nicolas

2014-07-18

Mitochondria capture and subsequently release Ca(2+) ions, thereby sensing and shaping cellular Ca(2+) signals. The Ca(2+) uniporter MCU mediates Ca(2+) uptake, whereas NCLX (mitochondrial Na/Ca exchanger) and LETM1 (leucine zipper-EF-hand-containing transmembrane protein 1) were proposed to exchange Ca(2+) against Na(+) or H(+), respectively. Here we study the role of these ion exchangers in mitochondrial Ca(2+) extrusion and in Ca(2+)-metabolic coupling. Both NCLX and LETM1 proteins were expressed in HeLa cells mitochondria. The rate of mitochondrial Ca(2+) efflux, measured with a genetically encoded indicator during agonist stimulations, increased with the amplitude of mitochondrial Ca(2+) ([Ca(2+)]mt) elevations. NCLX overexpression enhanced the rates of Ca(2+) efflux, whereas increasing LETM1 levels had no impact on Ca(2+) extrusion. The fluorescence of the redox-sensitive probe roGFP increased during [Ca(2+)]mt elevations, indicating a net reduction of the matrix. This redox response was abolished by NCLX overexpression and restored by the Na(+)/Ca(2+) exchanger inhibitor CGP37157. The [Ca(2+)]mt elevations were associated with increases in the autofluorescence of NAD(P)H, whose amplitude was strongly reduced by NCLX overexpression, an effect reverted by Na(+)/Ca(2+) exchange inhibition. We conclude that NCLX, but not LETM1, mediates Ca(2+) extrusion from mitochondria. By controlling the duration of matrix Ca(2+) elevations, NCLX contributes to the regulation of NAD(P)H production and to the conversion of Ca(2+) signals into redox changes. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

NCLX Protein, but Not LETM1, Mediates Mitochondrial Ca2+ Extrusion, Thereby Limiting Ca2+-induced NAD(P)H Production and Modulating Matrix Redox State*

PubMed Central

De Marchi, Umberto; Santo-Domingo, Jaime; Castelbou, Cyril; Sekler, Israel; Wiederkehr, Andreas; Demaurex, Nicolas

2014-01-01

Mitochondria capture and subsequently release Ca2+ ions, thereby sensing and shaping cellular Ca2+ signals. The Ca2+ uniporter MCU mediates Ca2+ uptake, whereas NCLX (mitochondrial Na/Ca exchanger) and LETM1 (leucine zipper-EF-hand-containing transmembrane protein 1) were proposed to exchange Ca2+ against Na+ or H+, respectively. Here we study the role of these ion exchangers in mitochondrial Ca2+ extrusion and in Ca2+-metabolic coupling. Both NCLX and LETM1 proteins were expressed in HeLa cells mitochondria. The rate of mitochondrial Ca2+ efflux, measured with a genetically encoded indicator during agonist stimulations, increased with the amplitude of mitochondrial Ca2+ ([Ca2+]mt) elevations. NCLX overexpression enhanced the rates of Ca2+ efflux, whereas increasing LETM1 levels had no impact on Ca2+ extrusion. The fluorescence of the redox-sensitive probe roGFP increased during [Ca2+]mt elevations, indicating a net reduction of the matrix. This redox response was abolished by NCLX overexpression and restored by the Na+/Ca2+ exchanger inhibitor CGP37157. The [Ca2+]mt elevations were associated with increases in the autofluorescence of NAD(P)H, whose amplitude was strongly reduced by NCLX overexpression, an effect reverted by Na+/Ca2+ exchange inhibition. We conclude that NCLX, but not LETM1, mediates Ca2+ extrusion from mitochondria. By controlling the duration of matrix Ca2+ elevations, NCLX contributes to the regulation of NAD(P)H production and to the conversion of Ca2+ signals into redox changes. PMID:24898248

Jagged-1 Signaling Pathway in Prostate Cancer Cell Growth and Angiogenesis

DTIC Science & Technology

2010-04-01

18 . NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON a. REPORT b. ABSTRACT c. THIS PAGE 80 19b. TELEPHONE... LN Ca P C4 -2 B M DA P Ca 2B Notch-2 Notch-1 Notch-4 Notch-3 β-actin Jagged-1 PC -3 DU 14 5 LN Ca P C4 -2 B M DA P Ca 2B β-actin Jagged-2 DLL-4 DLL-1...frequently up-regulated in most human malignancies including lung cancer, glioblastomas , PCa, basal cell carcinomas, hepatocellular carcinoma,

The interplay of dietary nutrient specification and varying calcium to total phosphorus ratio on efficacy of a bacterial phytase: 1. Growth performance and tibia mineralization.

PubMed

Olukosi, O A; Fru-Nji, F

2014-12-01

A 14-d experiment was conducted to study the effects of 2 dietary variables on efficacy of a 6-phytase from Citrobacter braakii on broiler growth performance and tibia mineralization. Diets were formulated with or without nutrient matrix values for phytase as negative or positive control (NC or PC, respectively) and with 2 Ca:total P (tP; 2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg, thus producing a 2 × 2 × 3 factorial arrangement. Birds and feed were weighed on d 7 and 21, and tibia bones were collected from all the birds on d 21. The main effects of nutrient matrix, Ca:tP, and phytase supplementation were significant (P < 0.05) for all the growth performance responses (except for G:F for which there was no effect of matrix). The Ca:tP × phytase and matrix × phytase interactions were significant (P < 0.05) for weight gain. In the PC diets, phytase increased weight gain (P < 0.05) relative to the control only in diets with 2,000 FYT/kg, whereas in NC diets weight gain increased (P < 0.01) only from 0 to 1,000 FYT/kg levels. Broilers consuming diets with 2.5:1 Ca:tP had lower (P < 0.05) tibia ash, whereas phytase increased (P < 0.01) tibia ash, Ca, P, and Zn but decreased (P < 0.01) tibia K. Phytase supplementation of diets with 2:1 Ca:tP increased (P < 0.05) tibia P in birds receiving 1,000 FYT/kg relative to the control with no further increase at 2,000 FYT/kg, whereas each level of phytase supplementation increased (P < 0.05) tibia P in the diets with 2.5:1 Ca:tP. It was concluded that the best response to lower phytase supplementation (1,000 FYT/kg) was in NC diets with narrow Ca:tP, whereas the best response to higher level of phytase supplementation (2,000 FYT/kg) was achieved in diets in PC diets with wide Ca:tP. ©2014 Poultry Science Association Inc.

Regulation of intracellular free calcium concentration during heterocyst differentiation by HetR and NtcA in Anabaena sp. PCC 7120.

PubMed

Shi, Yunming; Zhao, Weixing; Zhang, Wei; Ye, Zi; Zhao, Jindong

2006-07-25

Calcium ions are important to some prokaryotic cellular processes, such as heterocyst differentiation of cyanobacteria. Intracellular free Ca(2+)concentration, [Ca(2+)](i), increases several fold in heterocysts and is regulated by CcbP, a Ca(2+)-binding protein found in heterocyst-forming cyanobacteria. We demonstrate here that CcbP is degraded by HetR, a serine-type protease that controls heterocyst differentiation. The degradation depends on Ca(2+) and appears to be specific because HetR did not digest other tested proteins. CcbP was found to bind two Ca(2+) per molecule with K(D) values of 200 nM and 12.8 microM. Degradation of CcbP releases bound Ca(2+) that contributes significantly to the increase of [Ca(2+)](i) during the process of heterocyst differentiation in Anabaena sp. strain PCC 7120. We suggest that degradation of CcbP is a mechanism of positive autoregulation of HetR. The down-regulation of ccbP in differentiating cells and mature heterocysts, which also is critical to the regulation of [Ca(2+)](i), depends on NtcA. Coexpression of ntcA and a ccbP promoter-controlled gfp in Escherichia coli diminished production of GFP, and the decrease is enhanced by alpha-ketoglutarate. It was also found that NtcA could bind a fragment of the ccbP promoter containing an NtcA-binding sequence in a alpha-ketoglutarate-dependent fashion. Therefore, [Ca(2+)](i) is regulated by a collaboration of HetR and NtcA in heterocyst differentiation in Anabaena sp. strain PCC 7120.

Regulation of intracellular free calcium concentration during heterocyst differentiation by HetR and NtcA in Anabaena sp. PCC 7120

PubMed Central

Shi, Yunming; Zhao, Weixing; Zhang, Wei; Ye, Zi; Zhao, Jindong

2006-01-01

Calcium ions are important to some prokaryotic cellular processes, such as heterocyst differentiation of cyanobacteria. Intracellular free Ca2+concentration, [Ca2+]i, increases several fold in heterocysts and is regulated by CcbP, a Ca2+-binding protein found in heterocyst-forming cyanobacteria. We demonstrate here that CcbP is degraded by HetR, a serine-type protease that controls heterocyst differentiation. The degradation depends on Ca2+ and appears to be specific because HetR did not digest other tested proteins. CcbP was found to bind two Ca2+ per molecule with KD values of 200 nM and 12.8 μM. Degradation of CcbP releases bound Ca2+ that contributes significantly to the increase of [Ca2+]i during the process of heterocyst differentiation in Anabaena sp. strain PCC 7120. We suggest that degradation of CcbP is a mechanism of positive autoregulation of HetR. The down-regulation of ccbP in differentiating cells and mature heterocysts, which also is critical to the regulation of [Ca2+]i, depends on NtcA. Coexpression of ntcA and a ccbP promoter-controlled gfp in Escherichia coli diminished production of GFP, and the decrease is enhanced by α-ketoglutarate. It was also found that NtcA could bind a fragment of the ccbP promoter containing an NtcA-binding sequence in a α-ketoglutarate-dependent fashion. Therefore, [Ca2+]i is regulated by a collaboration of HetR and NtcA in heterocyst differentiation in Anabaena sp. strain PCC 7120. PMID:16849429

Controlled delivery of antimicrobial gallium ions from phosphate-based glasses.

PubMed

Valappil, S P; Ready, D; Abou Neel, E A; Pickup, D M; O'Dell, L A; Chrzanowski, W; Pratten, J; Newport, R J; Smith, M E; Wilson, M; Knowles, J C

2009-05-01

Gallium-doped phosphate-based glasses (PBGs) have been recently shown to have antibacterial activity. However, the delivery of gallium ions from these glasses can be improved by altering the calcium ion concentration to control the degradation rate of the glasses. In the present study, the effect of increasing calcium content in novel gallium (Ga2O3)-doped PBGs on the susceptibility of Pseudomonas aeruginosa is examined. The lack of new antibiotics in development makes gallium-doped PBG potentially a highly promising new therapeutic agent. The results show that an increase in calcium content (14, 15 and 16 mol.% CaO) cause a decrease in degradation rate (17.6, 13.5 and 7.3 microg mm(-2) h(-1)), gallium ion release and antimicrobial activity against planktonic P. aeruginosa. The most potent glass composition (containing 14 mol.% CaO) was then evaluated for its ability to prevent the growth of biofilms of P. aeruginosa. Gallium release was found to reduce biofilm growth of P. aeruginosa with a maximum effect (0.86 log(10) CFU reduction compared to Ga2O3-free glasses) after 48 h. Analysis of the biofilms by confocal microscopy confirmed the anti-biofilm effect of these glasses as it showed both viable and non-viable bacteria on the glass surface. Results of the solubility and ion release studies show that this glass system is suitable for controlled delivery of Ga3+. 71Ga NMR and Ga K-edge XANES measurements indicate that the gallium is octahedrally coordinated by oxygen atoms in all samples. The results presented here suggest that PBGs may be useful in controlled drug delivery applications, to deliver gallium ions in order to prevent infections due to P. aeruginosa biofilms.

Kinetic properties of the sodium-calcium exchanger in rat brain synaptosomes.

PubMed Central

Fontana, G; Rogowski, R S; Blaustein, M P

1995-01-01

1. The kinetic properties of the internal Na+ (Na+i)- dependent 45Ca2+ influx and external Na+ (Na+o)-dependent 45Ca2+ efflux were determined in isolated rat brain nerve terminals (synaptosomes) under conditions which the concentrations of internal Na+ ([Na+]i), external Na+ ([Na+]o), external Ca2+ (Ca2+]o), and external K+ ([K+]o) were varied. Both fluxes are manifestations of Na(+)-Ca2+ exchange. 2. Ca2+ uptake was augmented by raising [Na+]i and / or lowering [Na+]o. The increase in Ca2+ uptake induced by removing external Na+ was, in most instances, quantitatively equal to the Na+i-dependent Ca2+ uptake. 3. The Na+i-dependent Ca2+ uptake (measured at 1 s) was activated with an apparent half-maximal [Ca2+]o (KCa(o)) of about 0.23 mM. External Na+ inhibited the uptake in a non- competitive manner: increasing [Na+]o from 4.7 to 96 mM reduced the maximal Na+(i)-dependent Ca2+ uptake but did not affect KCa(o). 4. The inhibition of Ca2+ uptake by Na+o was proportional to ([Na+]o)2, and had a Hill coefficient (nH) of approximately 2.0. The mean apparent half-maximal [Na+]o for inhibition (KI(Na)) was about 60mM, and was independent of [Ca2+]o between 0.1 and 1.2mM; this, too, is indicative of non-competitive inhibition. 5. Low concentrations of alkali metal ions (M+) in the medium, including Na+, stimulated the Na+i-dependent uptake. The external Na+ and K+ concentrations required for apparent half-maximal activation (KM(Na) and KM(K), respectively) were 0.12 and 0.10mM. Thus, the relationship between Ca2+ uptake and [Na+]o was biphasic: uptake was stimulated by [Na+]o < or = 10 mM, and inhibited by higher [Na+]o. 6. The calculated maximal Na+i-dependent Ca2+ uptake (Jmax) was about 1530 pmol (mg protein) -1s-1 at 30 degrees C saturating [Ca2+]o and external M+ concentration ([M+]o), and with negligible inhibition by external Na+. 7. Internal Na+ activated the Ca2+ uptake with an apparent half-maximal concentration (KNa(i)) of about 20 mM and a Hill coefficient, nH, of approximately 3.0. 8. The Jmax for the Na+o-dependent efflux of Ca2+ from 45Ca(2+)-loaded synaptosomes treated with carbonyl cyanide p-trifluormethoxy-phenylhydrazone (FCCP) and caffeine (to release stored Ca2+ and raise the internal Ca2+ concentration ([Ca2+]i) was about 1800-2000 pmol (mg protein -1s-1 at 37 degrees C. 9. When the membrane potential (Vm) was reduced (depolarized) by increasing [K+]o, the Na+i-dependent Ca2+ influx increased, and the Na+o-dependent Ca2+ efflux declined. Both fluxes changed about 2-fold per 60 mV change in Vm. This voltage sensitivity corresponds to the movement of one elementary charge through about 60% of the membrane electric field. The symmetry suggests that the voltage-sensitive step is reversible. 10. The Jmax values for both Ca2P influx and efflux correspond to a Na+-Ca2+ exchange-mediated flux of about 425-575 jumol Ca2P (1 cell water)-' s-' or a turnover of about one quarter of the total synaptosome Ca2P in 1 s. We conclude that the Na+-Ca2P exchanger may contribute to Ca2P entry during nerve terminal depolarization; it is likely to be a major mechanism mediating Ca2P extrusion during subsequent repolarization and recovery. PMID:7666363

Inositol 1,4,5-trisphosphate-induced calcium release in the organelle layers of the stratified, intact egg of Xenopus laevis

PubMed Central

1990-01-01

Using double-barreled, Ca2(+)-sensitive microelectrodes, we have examined the characteristics of the Ca2+ release by inositol 1,4,5- trisphosphate (Ins(1,4,5)P3) in the various layers of Xenopus laevis eggs in which the organelles had been stratified by centrifugation. Centrifugation of living eggs stratifies the organelles yet retains them in the normal cytoplasmic milieu. The local increase in intracellular free Ca2+ in each layer was directly measured under physiological conditions using theta-tubing, double-barreled, Ca2(+)- sensitive microelectrodes in which one barrel was filled with the Ca2+ sensor and the other was filled with Ins(1,4,5)P3 for microinjection. The two tips of these electrodes were very close to each other (3 microns apart) enabling us to measure the kinetics of both the highly localized intracellular Ca2+ release and its subsequent removal in response to Ins(1,4,5)P3 injection. Upon Ins(1,4,5)P3 injection, the ER- enriched layer exhibited the largest release of Ca2+ in a dosage- dependent manner, whereas the other layers, mitochondria, lipid, and yolk, released 10-fold less Ca2+ in a dosage-independent manner. The removal of released Ca2+ took place within approximately 1 min. The sensitivity to Ins(1,4,5)P3 and the time course of intracellular Ca2+ release in the unstratified (unactivated) egg is nearly identical to that observed in the ER layer of the stratified egg. Our data suggest that the ER is the major organelle of the Ins(1,4,5)P3-sensitive Ca2+ store in the egg of Xenopus laevis. PMID:2324195

E-1020, a water soluble imidazopyridine, has direct effects on Ca(2+)-dependent force and ATP hydrolysis of canine and bovine cardiac myofilaments.

PubMed

Powers, F M; Palmiter, K A; Solaro, R J

1996-01-01

E-1020 is a cardiotonic agent that acts as a cyclic-AMP phosphodiesterase inhibitor but also may have actions which alter myofilament response to Ca2+. To identify direct actions of E-1020 on cardiac contractile proteins, effects of E-1020 on myofibrillar Ca2+ dependent MgATPase and force generation in chemically skinned fiber bundles were measured. In bovine cardiac myofibrils, E-1020 (100 microM) significantly increased myofilament Ca2+ sensitivity and Ca(2+)-dependent ATPase activity at submaximal pCa values. At pCa 6.75, E-1020 significantly increased ATPase activity in bovine (10-100 microM) and canine (1-100 microM) cardiac myofibrils but had no effect on rat cardiac myofibrils. Moreover, in one population of canine ventricular fiber bundles, E-1020 (0.01-10 microM) significantly increased isometric tension at pCa 6.5 and 6.0, whereas in another population of bundles E-1020 had no effect on tension. In no case was resting (pCa 8.0) or maximal tension (pCa 4.5) increased by E-1020. Measurements of Ca2+ binding to canine ventricular skinned fiber preparations demonstrated that E-1020 does not alter the affinity of myofilament troponin C for Ca2+. We conclude that part of the mechanism by which E-1020 acts as an inotropic agent may involve alterations in the responsiveness of contractile proteins to Ca2+. The lack of effect of E-1020 on some preparations may be dependent on isoform populations of myofilament proteins.

Near-edge x-ray absorption fine structure spectroscopy at atmospheric pressure with a table-top laser-induced soft x-ray source

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

Kühl, Frank-Christian, E-mail: Frank-christian.kuehl@mail.de; Müller, Matthias, E-mail: matthias.mueller@llg-ev.de; Schellhorn, Meike

2016-07-15

The authors present a table-top soft x-ray absorption spectrometer, accomplishing investigations of the near-edge x-ray absorption fine structure (NEXAFS) in a laboratory environment. The system is based on a low debris plasma ignited by a picosecond laser in a pulsed krypton gas jet, emitting soft x-ray radiation in the range from 1 to 5 nm. For absorption spectroscopy in and around the “water window” (2.3–4.4 nm), a compact helium purged sample compartment for experiments at atmospheric pressure has been constructed and tested. NEXAFS measurements on CaCl{sub 2} and KMnO{sub 4} samples were conducted at the calcium and manganese L-edges, as well asmore » at the oxygen K-edge in air, atmospheric helium, and under vacuum, respectively. The results indicate the importance of atmospheric conditions for an investigation of sample hydration processes.« less

11. EASTERN EDGE OF POST ENGINEER'S SHOPS AND YARD BUILDINGS, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

11. EASTERN EDGE OF POST ENGINEER'S SHOPS AND YARD BUILDINGS, WITH BUILDING 283 ON RIGHT, LOOKING 186 DEGREES SOUTH. - Presidio of San Francisco, Warehouse & Auto Shop, Crissy Field North cantonment, San Francisco, San Francisco County, CA

Diadenosine polyphosphates induce intracellular Ca2+ mobilization in human neutrophils via a pertussis toxin sensitive G-protein.

PubMed Central

Gasmi, L; McLennan, A G; Edwards, S W

1997-01-01

The diadenosine polyphosphates diadenosine 5',5"'-P1,P3-triphosphate (Ap3A), diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A), diadenosine 5',5"'-P1,P5-pentaphosphate (Ap5A) and diadenosine 5',5"'-P1,P6-hexaphosphate (Ap6A) all stimulated increases in intracellular Ca2+ in human neutrophils. Maximal increases in intracellular Ca2+ of 650 nM were obtained at dinucleotide concentrations of 500-700 microM. These increases in intracellular, Ca2+ were completely abolished by pre-treatment of the neutrophils with pertussis toxin and were hardly affected when the extracellular buffer was devoid of Ca2+. On the other hand, adenosine triphosphate (ATP) could stimulate much greater increases in intracellular Ca2+ (up to 1.1 microM) at much lower concentrations (half maximal responses obtained at around 5 microM ATP). Receptor de-sensitization experiments indicate that human neutrophils may possess two types of P2-purinoceptors. The first of these may bind ATP (but not the dinucleotides) with high affinity whilst the second may bind the dinucleotides with lower affinity and also bind ATP. PMID:9038726

Free calcium ions in neurones of Helix aspersa measured with ion-selective micro-electrodes.

PubMed Central

Alvarez-Leefmans, F J; Rink, T J; Tsien, R Y

1981-01-01

1. Intracellular free calcium concentration, [Ca2+]i, was measured in giant neurones of the sub-oesophageal ganglia of Helix aspersa, using Ca-selective micro-electrodes containing a PVC-gelled, neutral-ligand sensor. 2. In calibration solutions the electrodes had a virtually ideal, Nernstian, response down to 1 microM-Ca2+ in the presence of 0.125 M-K+, 18-24 mV from 1 to 0.1 microM-Ca2+ and 8-14 mV from 0.1 to 0.01 microM-Ca2+. Interference from H+ and Mg2+ was negligible. The small response to Na+ at sub-micromolar Ca2+ was taken into account, when necessary, in measurement of [Ca2+]i. 3. Measurements of basal [Ca2+]i were made in ganglia from animals kept only a few weeks in captivity, in a bathing solution equilibrated with air and containing 2 mM-Ca2+. In thirteen measurements from impalements which met stringent criteria for electrode performance and cell viability, the mean basal pCa (--log10[Ca2+]) was 6.77 +/- 0.07 (S.E.), corresponding to a mean free Ca2+ concentration of 0.17 microM. 4. The basal [Ca2+]i in neurones from a group of snails kept hibernating for several months was higher, mean pCa 6.15, for ganglia handled in 2 mM-Ca2+ solution. 5. Intracellular injections of Ca2+ or EGTA raised and lowered, respectively, the indicated basal [Ca2+]i, showing that the electrodes responded appropriately inside the cells and that unknown or untested components of cytoplasm were not significantly interfering with the Ca-sensor. 6. Altering the external Ca2+ concentration between 0.1 and 10 mM usually produced only small, +/- 0.1 pCa units, changes in basal [Ca2+]i of satisfactorily impaled, quiescent cells. 7. In cell 1F, which has repetitive spikes with a substantial Ca current, changes in Ca gradient or blockade of voltage-dependent Ca channels sometimes markedly altered [Ca2+]i, showing that Ca entry with the spikes was elevating [Ca2+]i. 8. Replacing external Na+ with Li+ or bis(2-hydroxyethyl)dimethylammonium had little effect on [Ca2+]i. 9. Elevating CO2 to 5% or 79% lowered [Ca2+]i by an average of 0.16 and 0.26 pCa units respectively. PMID:6273543

WE-DE-207B-08: Towards Standardization of X-Ray Filters in Digital Mammography-Enabled Breast Tomosynthesis Systems

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

Shrestha, S; Vedantham, S; Karellas, A

Purpose: In digital breast tomosynthesis (DBT) systems capable of digital mammography (DM), Al filters are used during DBT and K-edge filters during DM. The potential for standardizing the x-ray filters with Al, instead of K-edge filters, was investigated with intent to reduce exposure duration and to promote a simpler system design. Methods: Analytical computations of the half-value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for K-edge filters (50µm Rh; 50µm Ag) were compared with Al filters of varying thickness. Two strategies for matching the HVT from K-edge and Al filtered spectra were investigated: varying the kVp for fixedmore » Al thickness, or varying the Al thickness at matched kVp. For both strategies, Al filters were an order of magnitude thicker than K-edge filters. Hence, Monte Carlo simulations were conducted with the GEANT4 toolkit to determine if the scatter-to-primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Al and K-edge filters. Results: Results show the potential for replacing currently used Kedge filters with Al. For fixed Al thickness (700µm), ±1 kVp and +(1–3) kVp change, matched HVT of Rh and Ag filtered spectra. At matched kVp, Al thickness range (650,750)µm and (750,860)µm matched the HVT from Rh and Ag filtered spectra. Photon fluence/mAs with Al filters were 1.5–2.5 times higher, depending on kVp and Al thickness, compared to K-edge filters. Although Al thickness was an order higher than K-edge filters, neither the SPR nor the scatter PSF differed from K-edge filters. Conclusion: The use of Al filters for digital mammography is potentially feasible. The increased fluence/mAs with Al could decrease exposure duration for the combined DBT+DM exam and simplify system design. Effect of x-ray spectrum change due to Al filtration on radiation dose, signal, noise, contrast and related metrics are being investigated. Funding support: Supported in part by NIH R21CA176470 and R01CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.« less

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

Blanpied, G.D.

Trees of seedling apple (Malus domesticas borkh.) received 2.5 cm of artificial rain at pH 3.3 or 4.2, each with 0.4 or 1.4 mg Ca/liter of rain water during 7-hour periods. In the early summer period (June 19-July 10) artificial rain reduced Ca in apple leaves, but there were no significant differences due to pH or Ca concentration in the rain. Ca losses during rain treatment appeared to be recovered during 1 week holding periods after treatment. In the autumn period (September 25-October 16) the reduction in leaf Ca was greatest wih low pH, low Ca rain and least withmore » high pH, high Ca rain, which increased Ca in the leaves. K in the leaves was reduced more than Ca, but was not affected by pH or Ca in the rain during either period of observation.« less

Monitoring of urinary calcium and phosphorus excretion in preterm infants: comparison of 2 methods.

PubMed

Staub, Eveline; Wiedmer, Nicolas; Staub, Lukas P; Nelle, Mathias; von Vigier, Rodo O

2014-04-01

Premature babies require supplementation with calcium (Ca) and phosphorus (P) to prevent metabolic bone disease of prematurity. To guide mineral supplementation, 2 methods of monitoring urinary excretion of Ca and P are used: urinary Ca or P concentration and Ca/creatinine (Crea) or P/Crea ratios. We compare these 2 methods in regards to their agreement on the need for mineral supplementation. Retrospective chart review of 230 premature babies with birth weight <1500 g, undergoing screening of urinary spot samples from day 21 of life and fortnightly thereafter. Hypothetical cutoff values for urine Ca or P concentration (1 mmol/L) and urine Ca/Crea ratio (0.5 mol/mol) or P/Crea ratio (4 mol/mol) were applied to the sample results. The agreement on whether to supplement the respective minerals based on the results with the 2 methods was compared. Multivariate general linear models sought to identify patient characteristics to predict discordant results. A total of 24.8% of cases did not agree on the indication for Ca supplementation, and 8.8% for P. Total daily Ca intake was the only patient characteristic associated with discordant results. With the intention to supplement the respective mineral, comparison of urinary mineral concentration with mineral/Crea ratio is moderate for Ca and good for P. The results do not allow identifying superiority of either method on the decision as to which babies require Ca and/or P supplements.

Malfunction Investigation of the XM935 Point Detonating Fuze

DTIC Science & Technology

1977-04-01

1 PSK* UNCHANGED FUMLY AR! 2 PSM UNCHANGED FULLY ARMED 3 OK PS4 UNCHANGD 4 CK P24 UNC DNGED 5 PSK (more than S.Q. Det Edge Visible FuLLY AP1M other...Continued) F= NO. DRC NO. 1 2 3 4 5 6 7 8 9 10 3 PSK UNCH UNCH UNCE SEE SQ UNCH UNCH UNCH UNCH UN1H 4 PS4 UNCH SKH E SQ UNCH tNCH UNCH UNCH U2 L!CH...EDGE 5 PS UNCH tCH SE SQ UNCH MMH UNCH UNCH UWCH WECH 6 P4M UNCH UNCH Q SEE SQ EDGE 7 PSK UNCH UNCH SEE SO WXC EDGE a P UNCP L4 UNCH SC E SQ 9 PS4 UNCX

Measurement of the mass attenuation coefficients and electron densities for BiPbSrCaCuO superconductor at different energies

NASA Astrophysics Data System (ADS)

Çevik, U.; Baltaş, H.

2007-03-01

The mass attenuation coefficients for Bi, Pb, Sr, Ca, Cu metals, Bi2O3, PbO, SrCO3, CaO, CuO compounds and solid-state forms of Bi1.7Pb0.3Sr2Ca2Cu3O10 superconductor were determined at 57.5, 65.2, 77.1, 87.3, 94.6, 122 and 136 keV energies. The samples were irradiated using a 57Co point source emitted 122 and 136 keV γ-ray energies. The X-ray energies were obtained using secondary targets such as Ta, Bi2O3 and (CH3COO)2UO22H2O. The γ- and X-rays were counted by a Si(Li) detector with a resolution of 0.16 keV at 5.9 keV. The effect of absorption edges on electron density, effective atomic numbers and their variation with photon energy in composite superconductor samples was discussed. Obtained values were compared with theoretical values.

Sulfate but not thiosulfate reduces calculated and measured urinary ionized calcium and supersaturation: implications for the treatment of calcium renal stones.

PubMed

Rodgers, Allen; Gauvin, Daniel; Edeh, Samuel; Allie-Hamdulay, Shameez; Jackson, Graham; Lieske, John C

2014-01-01

Urinary sulfate (SO4(2-)) and thiosulfate (S2O3(2-)) can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa) and on supersaturation (SS) of calcium oxalate (CaOx) and calcium phosphate (CaP), and measured their in vitro effects on iCa and the upper limit of stability (ULM) of these salts. Urine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1). A second data set was obtained from healthy controls and hypercalciuric stone formers in the literature who had been treated with sodium thiosulfate (STS) (Model 2). The Joint Expert Speciation System (JESS) was used to calculate iCa and SS. In Model 1, these parameters were calculated as a function of sulfate and thiosulfate concentrations. In Model 2, data from pre- and post STS urines were analyzed. ULM and iCa were determined in human urine as a function of sulfate and thiosulfate concentrations. Calculated iCa and SS values for all calcium salts decreased with increasing sulfate concentration. Thiosulfate had no effect on these parameters. In Model 2, calculated iCa and CaOx SS increased after STS treatment, but CaP SS decreased, perhaps due to a decrease in pH after STS treatment. In confirmatory in vitro experiments supplemental sulfate, but not thiosulfate, significantly increased the calcium needed to achieve the ULM of CaP and tended to increase the oxalate needed to reach the ULM of CaOx. Sulfate also significantly decreased iCa in human urine, while thiosulfate had no effect. Increasing urinary sulfate could theoretically reduce CaOx and CaP stone risk. Although STS may reduce CaP stone risk by decreasing urinary pH, it might also paradoxically increase iCa and CaOx SS. As such, STS may not be a viable treatment option for stone disease.

Phosphorus retention mechanisms of a water treatment residual.

PubMed

Ippolito, J A; Barbarick, K A; Heil, D M; Chandler, J P; Redente, E F

2003-01-01

Water treatment residuals (WTRs) are a by-product of municipal drinking water treatment plants and can have the capacity to adsorb tremendous amounts of P. Understanding the WTR phosphorus adsorption process is important for discerning the mechanism and tenacity of P retention. We studied P adsorbing mechanism(s) of an aluminum-based [Al2(SO4)3 x 14H2O] WTR from Englewood, CO. In a laboratory study, we shook mixtures of P-loaded WTR for 1 to 211 d followed by solution pH analysis, and solution Ca, Al, and P analysis via inductively coupled plasma atomic emission spectroscopy. After shaking periods, we also examined the solids fraction by X-ray diffraction (XRD) and electron microprobe analysis using wavelength dispersive spectroscopy (EMPA-WDS). The shaking results indicated an increase in pH from 7.2 to 8.2, an increase in desorbed Ca and Al concentrations, and a decrease in desorbed P concentration. The pH and desorbed Ca concentration increases suggested that CaCO3 controlled Ca solubility. Increased desorbed Al concentration may have been due to Al(OH)4 formation. Decreased P content, in conjunction with the pH increase, was consistent with calcium phosphate formation or precipitation. The system appeared to be undersaturated with respect to dicalcium phosphate (DCP; CaHPO4) and supersaturated with respect to octacalcium phosphate [OCP; Ca4H(PO4)3 x 2.5H2O]. The Ca and Al increases, as well as OCP formation, were supported by MINTEQA2 modeling. The XRD and EMPA-WDS results for all shaking times, however, suggested surface P chemisorption as an amorphous Al-P mineral phase.

Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris

PubMed Central

Brinza, Loredana; Schofield, Paul F.; Hodson, Mark E.; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D.; Mosselmans, J. Frederick W.

2014-01-01

The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced. PMID:24365942

Intracellular pH (pHin) and cytosolic calcium ([Ca2+]cyt) regulation via ATPases: studies in cell populations, single cells, and subcellular compartments

NASA Astrophysics Data System (ADS)

Rojas, Jose D.; Sanka, Shankar C.; Gyorke, Sandor; Wesson, Donald E.; Minta, Akwasi; Martinez-Zaguilan, Raul

1999-07-01

Changes in pHin and (Ca2+)cyt are important in the signal transduction mechanisms leading to many physiological responses including cell growth, motility, secretion/exocytosis, etc. The concentrations of these ions are regulated via primary and secondary ion transporting mechanisms. In diabetes, specific pH and Ca2+ regulatory mechanism might be altered. To study these ions, we employ fluorescence spectroscopy, and cell imagin spectroscopy/confocal microscopy. pH and Ca2+ indicators are loaded in the cytosol with acetoxymethyl ester forms of dyes, and in endosomal/lysosomal (E/L) compartments by overnight incubation of cells with dextran- conjugated ion fluorescent probes. We focus on specific pH and Ca2+ regulatory systems: plasmalemmal vacuolar- type H+-ATPases (pm V-ATPases) and sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCA). As experimental models, we employ vascular smooth muscle (VSM) and microvascular endothelial cells. We have chosen these cells because they are important in blood flow regulation and in angiogenesis. These processes are altered in diabetes. In many cell types, ion transport processes are dependent on metabolism of glucose for maximal activity. Our main findings are: (a) glycolysis coupling the activity of SERCA is required for cytosolic Ca2+ homeostasis in both VSM and microvascular endothelial cells; (b) E/L compartments are important for pH and Ca2+ regulation via H+-ATPases and SERCA, respectively; and (c) pm-V- ATPases are important for pHin regulation in microvascular endothelial cells.

The distribution of calcium in toad cardiac pacemaker cells during spontaneous firing.

PubMed

Ju, Y K; Allen, D G

2000-12-01

Isolated, spontaneously active pacemaker cells from the sinus venosus region of the toad heart were loaded with the calcium indicator fluo-3. The cells were examined with a confocal microscope to investigate the distribution of calcium during spontaneous activity. Three classes of calcium-related signals were present. First, intense, localised, time-invariant signals were detected from structures distributed across the cell interior. Based on the insensitivity to saponin and the distribution in the cell, these signals appear to arise from fluo-3 located in the sarcoplasmic reticulum and the nuclear envelope. Second, spatially uniform signals from the cytoplasm were present at rest and showed spontaneous increases in [Ca2+]i which propagated along the cell. These Ca2+ transients were uniform in intensity across the diameter of the cell and we could detect no significant delay in the middle of the cell compared to the edges. However, within the nucleus the Ca2+ transient showed a clear delay compared to the cytoplasm. Third, localised, transient increases in [Ca2+]i (Ca2+ sparks) which did not propagate were also detectable. These could be detected both near the surface membrane and in the interior of the cell and reduced in magnitude and increased in duration in the presence of ryanodine. The frequency of firing of Ca2+ sparks significantly increased in the 200-ms period preceding a spontaneous Ca2+ transient. These results suggest that pacemaker cells contain sarcoplasmic reticulum which is distributed across the cell. The Ca2+ transient is uniform across the cell indicating that near-synchronous release of Ca2+ from the sarcoplasmic reticulum is achieved. Ca2+ sparks occur in pacemaker cells though their role in pacemaker function remains to be elucidated.

44Ca doped remineralization study on dentin by isotope microscopy.

PubMed

Hiraishi, N; Kobayashi, S; Yurimoto, H; Tagami, J

2018-04-01

The dental caries is developed as a result of an alternative course of mineral gain and loss. In order to distinguish between intrinsic Ca (tooth-derived mineral) and extrinsic Ca (solution-derived mineral) uptakes, a 44 Ca doped pH-cycling was performed using 44 Ca (a stable calcium isotope) remineralization solution. The natural abundance of 40 Ca and 44 Ca is 96.9% and 2.1%, respectively. The remineralization solution was prepared using 44 Ca to contain 1.5mmol/L CaCl 2 ( 44 Ca), 0.9mmol/L KH 2 PO 4, 130mmol/L KCl, 20mmol/L HEPES at pH 7.0. The pH-cycling was conducted on bovine root dentin daily by demineralization (pH 5.0) for 2h, incubation in 0% (control) and 0.2% NaF (900ppm fluoride) for 2h and 44 Ca doped remineralization for 20h. After 14days pH-cycling, the specimens were sectioned longitudinally. On the sectioned surface, isotope imaging of 40 Ca and 44 Ca labeled mineral distribution was observed by a high mass-resolution stigmatic secondary ion 77 (Camera IMS 1270, Gennevilliers Cedex, France). Uptake of 44 Ca was greater in intensity for the 0.2% fluoride group than the control, especially in the superficial lesions. The control group showed 40 Ca (intrinsic) distribution in the subsurface lesions and in the superficial lesions, meanwhile the fluoride group showed 40 Ca distribution limited in subsurface lesions. The total Ca ( 44 Ca+ 40 Ca) image revealed more homogeneously for the control than the fluoride group. Since the fluoride-treated surface is more acid-resistant than intrinsic dentin, alternative minerals were dissolved from the intact intrinsic lesion in the demineralization cycle. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Ca2+-pumping impairment during repetitive fatiguing contractions in single myofibers: role of cross-bridge cycling

PubMed Central

Shiah, Amy A.; Gandra, Paulo G.; Hogan, Michael C.

2013-01-01

The energy cost of contractions in skeletal muscle involves activation of both actomyosin and sarcoplasmic reticulum (SR) Ca2+-pump (SERCA) ATPases, which together determine the overall ATP demand. During repetitive contractions leading to fatigue, the relaxation rate and Ca2+ pumping become slowed, possibly because of intracellular metabolite accumulation. The role of the energy cost of cross-bridge cycling during contractile activity on Ca2+-pumping properties has not been investigated. Therefore, we inhibited cross-bridge cycling by incubating isolated Xenopus single fibers with N-benzyl-p-toluene sulfonamide (BTS) to study the mechanisms by which SR Ca2+ pumping is impaired during fatiguing contractions. Fibers were stimulated in the absence (control) and presence of BTS and cytosolic calcium ([Ca2+]c) transients or intracellular pH (pHi) changes were measured. BTS treatment allowed normal [Ca2+]c transients during stimulation without cross-bridge activation. At the time point that tension was reduced to 50% in the control condition, the fall in the peak [Ca2+]c and the increase in basal [Ca2+]c did not occur with BTS incubation. The progressively slower Ca2+ pumping rate and the fall in pHi during repetitive contractions were reduced during BTS conditions. However, when mitochondrial ATP supply was blocked during contractions with BTS present (BTS + cyanide), there was no further slowing in SR Ca2+ pumping during contractions compared with the BTS-alone condition. Furthermore, the fall in pHi was significantly less during the BTS + cyanide condition than in the control conditions. These results demonstrate that factors related to the energetic cost of cross-bridge cycling, possibly the accumulation of metabolites, inhibit the Ca2+ pumping rate during fatiguing contractions. PMID:23678027

Growth of p-type hematite by atomic layer deposition and its utilization for improved solar water splitting.

PubMed

Lin, Yongjing; Xu, Yang; Mayer, Matthew T; Simpson, Zachary I; McMahon, Gregory; Zhou, Sa; Wang, Dunwei

2012-03-28

Mg-doped hematite (α-Fe(2)O(3)) was synthesized by atomic layer deposition (ALD). The resulting material was identified as p-type with a hole concentration of ca. 1.7 × 10(15) cm(-3). When grown on n-type hematite, the p-type layer was found to create a built-in field that could be used to assist photoelectrochemical water splitting reactions. A nominal 200 mV turn-on voltage shift toward the cathodic direction was measured, which is comparable to what has been measured using water oxidation catalysts. This result suggests that it is possible to achieve desired energetics for solar water splitting directly on metal oxides through advanced material preparations. Similar approaches may be used to mitigate problems caused by energy mismatch between water redox potentials and the band edges of hematite and many other low-cost metal oxides, enabling practical solar water splitting as a means for solar energy storage.

Kinetics and mechanism of natural fluorapatite dissolution at 25 °C and pH from 3 to 12

NASA Astrophysics Data System (ADS)

Chaïrat, Claire; Schott, Jacques; Oelkers, Eric H.; Lartigue, Jean-Eric; Harouiya, Najatte

2007-12-01

The dissolution rates of natural fluorapatite (FAP), Ca 10(PO 4) 6F 2, were measured at 25 °C in mixed-flow reactors as a function of pH from 3.0 to 11.7, and aqueous calcium, phosphorus, and fluoride concentration. After an initial preferential Ca and/or F release, stoichiometric Ca, P, and F release was observed. Measured FAP dissolution rates decrease with increasing pH at 3 ⩽ pH ⩽ 7, FAP dissolution rates are pH independent at 7 ⩽ pH ⩽ 10, and FAP dissolution rates again decrease with increasing pH at pH ⩾ 10. Measured FAP dissolution rates are independent of aqueous Ca, P, and F concentration at pH ≈ 3 and pH ≈ 10. Apatite dissolution appears to be initiated by the relatively rapid removal from the near surface of F and the Ca located in the M1 sites, via proton for Ca exchange reactions. Dissolution rates are controlled by the destruction of this F and Ca depleted surface layer. The destruction of this layer is facilitated by the adsorption/penetration of protons into the surface at acidic conditions, and by surface hydration at neutral and basic conditions. Taking into account these two parallel mechanisms, measured fluorapatite forward dissolution rates can be accurately described using r+(molms)=6.61×10-6{aK}/{1+aK+aCa4aF1.4aOH0.6aH6K}+3.69×10-8[tbnd CaOH2+] where ai refers to the activity of the ith aqueous species, [tbnd CaOH2+] denotes the concentration of hydrated calcium sites at the surface of the leached layer (mol m -2), and Kex and Kads stand for the apparent stability constants of the Ca 2+/H + exchange and adsorption/penetration reactions, respectively.

Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings

NASA Technical Reports Server (NTRS)

Bright, Michelle M.; Korntheuer, Andrea; Komadina, Steve; Lin, John C.

2013-01-01

This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar flow wings. Based on a known laminar cruise airfoil that incorporated an NGAS-developed integrated slot design, this effort involved using Computational Fluid Dynamics (CFD) analysis and quality function deployment (QFD) analysis on several leading edge concepts, and subsequently down-selected to two blown leading-edge concepts for testing. A 7-foot-span AHLLE airfoil model was designed and fabricated at NGAS and then tested at the NGAS 7 x 10 Low Speed Wind Tunnel in Hawthorne, CA. The model configurations tested included: baseline, deflected trailing edge, blown deflected trailing edge, blown leading edge, morphed leading edge, and blown/morphed leading edge. A successful demonstration of high lift leading edge technology was achieved, and the target goals for improved lift were exceeded by 30% with a maximum section lift coefficient (Cl) of 5.2. Maximum incremental section lift coefficients ( Cl) of 3.5 and 3.1 were achieved for a blown drooped (morphed) leading edge concept and a non-drooped leading edge blowing concept, respectively. The most effective AHLLE design yielded an estimated 94% lift improvement over the conventional high lift Krueger flap configurations while providing laminar flow capability on the cruise configuration.

Graphene oxide papers modified by divalent ions-enhancing mechanical properties via chemical cross-linking.

PubMed

Park, Sungjin; Lee, Kyoung-Seok; Bozoklu, Gulay; Cai, Weiwei; Nguyen, Sonbinh T; Ruoff, Rodney S

2008-03-01

Significant enhancement in mechanical stiffness (10-200%) and fracture strength (approximately 50%) of graphene oxide paper, a novel paperlike material made from individual graphene oxide sheets, can be achieved upon modification with a small amount (less than 1 wt %) of Mg(2+) and Ca(2+). These results can be readily rationalized in terms of the chemical interactions between the functional groups of the graphene oxide sheets and the divalent metals ions. While oxygen functional groups on the basal planes of the sheets and the carboxylate groups on the edges can both bond to Mg(2+) and Ca(2+), the main contribution to mechanical enhancement of the paper comes from the latter.

Discrete influx events refill depleted Ca2+ stores in a chick retinal neuron

PubMed Central

Borges, Salvador; Lindstrom, Sarah; Walters, Cameron; Warrier, Ajithkumar; Wilson, Martin

2008-01-01

The depletion of ER Ca2+ stores, following the release of Ca2+ during intracellular signalling, triggers the Ca2+ entry across the plasma membrane known as store-operated calcium entry (SOCE). We show here that brief, local [Ca2+]i increases (motes) in the thin dendrites of cultured retinal amacrine cells derived from chick embryos represent the Ca2+ entry events of SOCE and are initiated by sphingosine-1-phosphate (S1P), a sphingolipid with multiple cellular signalling roles. Externally applied S1P elicits motes but not through a G protein-coupled membrane receptor. The endogenous precursor to S1P, sphingosine, also elicits motes but its action is suppressed by dimethylsphingosine (DMS), an inhibitor of sphingosine phosphorylation. DMS also suppresses motes induced by store depletion and retards the refilling of depleted stores. These effects are reversed by exogenously applied S1P. In these neurons formation of S1P is a step in the SOCE pathway that promotes Ca2+ entry in the form of motes. PMID:18033816

Discrete influx events refill depleted Ca2+ stores in a chick retinal neuron.

PubMed

Borges, Salvador; Lindstrom, Sarah; Walters, Cameron; Warrier, Ajithkumar; Wilson, Martin

2008-01-15

The depletion of ER Ca2+ stores, following the release of Ca2+ during intracellular signalling, triggers the Ca2+ entry across the plasma membrane known as store-operated calcium entry (SOCE). We show here that brief, local [Ca2+]i increases (motes) in the thin dendrites of cultured retinal amacrine cells derived from chick embryos represent the Ca2+ entry events of SOCE and are initiated by sphingosine-1-phosphate (S1P), a sphingolipid with multiple cellular signalling roles. Externally applied S1P elicits motes but not through a G protein-coupled membrane receptor. The endogenous precursor to S1P, sphingosine, also elicits motes but its action is suppressed by dimethylsphingosine (DMS), an inhibitor of sphingosine phosphorylation. DMS also suppresses motes induced by store depletion and retards the refilling of depleted stores. These effects are reversed by exogenously applied S1P. In these neurons formation of S1P is a step in the SOCE pathway that promotes Ca2+ entry in the form of motes.

Synthesis and effect of Ce and Mn co-doping on photoluminescence characteristics of Ca6AlP5O20:Eu novel phosphors.

PubMed

Shinde, K N; Dhoble, S J

2013-01-01

A series of Ca6AlP5O20 doped with rare earths (Eu and Ce) and co-doped (Eu, Ce and Eu,Mn) were prepared by combustion synthesis. Under Hg-free excitation, Ca6AlP5O20:Eu exhibited Eu(2+) (486 nm) emission in the blue region of the spectrum and under near Hg excitation (245 nm), Ca6AlP5O20:Ce phosphor exhibited Ce(3+) emission (357 nm) in the UV range. Photoluminescence (PL) peak intensity increased in Ca6AlP5O20:Eu,Ce and Ca6AlP5O20:Eu, Mn phosphors due to co-activators of Ce(3+) and Mn(2+) ions. As a result, these ions played an important role in PL emission in the present matrix. Ca6AlP5O20:Eu, Ce and Ca6AlP5O20:Eu, Mn phosphors provided energy transfer mechanisms via Ce(3+) → Eu(2+) and Eu(2+) → Mn(2+), respectively. Eu ions acted as activators and Ce ions acted as sensitizers. Ce emission energy was well matched with Eu excitation energy in the case of Ca6AlP5O20:Eu, Ce and Eu ions acted as activators and Mn ions acted as sensitizers in Ca6AlP5O20:Eu, Mn. This study included synthesis of new and efficient phosphate phosphors. The impact of doping and co-doping on photoluminescence properties and energy transfer mechanisms were investigated and we propose a feasible interpretation. Copyright © 2012 John Wiley & Sons, Ltd.

EPS composition and calcification potential of tufa-dominating cyanobacteria investigated by Scanning Transmission X-ray Microscopy (STXM) and Laser Scanning Microscopy (LSM)

NASA Astrophysics Data System (ADS)

Zippel, Barbara; Dynes, James J.; Obst, Martin; Lawrence, John R.; Neu, Thomas R.

2010-05-01

Tufa deposits in freshwater habitats are the result of calcium carbonate precipitation within interfacial microbial ecosystems. Calcite precipitation is influenced by the saturation index and the occurrence of extracellular polymeric substances (EPS) which are produced by a variety of microorganisms. In theory, the first important step of biologically induced calcification processes is the adsorption of calcium ions by extracellular polymeric substances (EPS) produced by cyanobacteria. In the present study we take advantage of Laser Scanning Microscopy (LSM) and combine it with Synchrotron imaging using Scanning Transmission X-ray Microscopy (STXM). STXM represents a technique that allows simultaneous analysis of inorganic and organic constituents as a scale of 50 nm. By means of STXM it is possible to differentiate between calcium carbonate phases at the Ca L-edge. Furthermore, STXM has also been used at the C K-edge to map the major biomolecules (proteins, lipids, and polysaccharides). The purpose of this study is to find out if there are differences in calcium adsorption depending on specific composition of the EPS produced by filamentous cyanobacteria isolated from a German hard water creek (Westerhöfer Bach, Harz Mountains). The goal was to elucidate the potential of biofilms constituents, including microbial cell surfaces as well as extracellular polymeric substances, in triggering the formation of calcium carbonate in tufa systems. For this purpose three filamentous cyanobacteria (Pseudanabaena sp., Leptolyngbya sp. and Nostoc sp.) were cultivated in creek-adapted as well as standard media (BG11) on polycarbonate slides. In situ EPS composition was detected by means of fluorescence lectin-binding approach (FLBA) using 23 commercially available lectins with different specificities for mono- and disaccharides and amino sugars. For CaCO3 nucleation experiments cyanobacterial biofilms grown on polycarbonate slides were deposited in NaHCO3/CaCl2 solutions supersaturated 10 times with respect to calcite for 48, 72 and 144 hours. For the STXM experiment on beamline 10-ID1 at the Canadian Light Source (CLS), the biofilm samples were scrapped off, suspended in a slurry and deposited carefully on a Si3N4 window. In order to obtain quantitative speciation maps of cyanobacterial sheath EPS, image sequences (stacks) were recorded at the C-1s (280-320 eV) and Ca-2p (340-360 eV) edges. Data analysis was done by using the software aXis2000, and energy spectra were fitted with available reference spectra. Nearly the same lectins specific for fucose, mannose, N-acetylgalactosamine and N-acetylglucosamine, as well as sialic acid bound preferentially to the EPS of cyanobacterial sheaths of Pseudanabaena sp. and Leptolyngbya sp. Surprisingly, in case of Nostoc sp. only two lectins specific for fucose, and N-acetylgalactosamine showed a clear binding to the EPS of sheaths. Qualitative, lectin-specific EPS composition was not influenced by nutrient concentrations within the medium during cultivation. In order to biochemically characterize the CaCO3 nucleation sites within the sheaths of the cyanobacteria investigated, carbon maps of the most abundant organic components were derived from C-1s image sequences. The sheaths of the cyanobacteria contained mainly polysaccharides followed by proteins, and a small amount of lipids. The highest amount of polysaccharides was detected in EPS produced by Pseudanabaena sp., whereas in Nostoc sp. only one-fifth was found. All samples investigated contained spectral signatures of Ca2+ adsorbed to EPS. Aragonite-like CaCO3 was detected in close association with the cell surface of Leptolyngbya sp. only. Highest amount of adsorbed Ca to EPS was found in Pseudanabaena sp., whereas only one-third was detected within the EPS of sheaths in Leptolyngbya sp. and Nostoc sp. Results of this combined approach show that the cyanobacteria investigated are may be involved in calcification processes to different degrees.

Induction of the pi class of glutathione S-transferase by carnosic acid in rat Clone 9 cells via the p38/Nrf2 pathway.

PubMed

Lin, Chia-Yuan; Wu, Chi-Rei; Chang, Shu-Wei; Wang, Yu-Jung; Wu, Jia-Jiuan; Tsai, Chia-Wen

2015-06-01

Induction of phase II enzymes is important in cancer chemoprevention. We compared the effect of rosemary diterpenes on the expression of the pi class of glutathione S-transferase (GSTP) in rat liver Clone 9 cells and the signaling pathways involved. Culturing cells with 1, 5, 10, or 20 μM carnosic acid (CA) or carnosol (CS) for 24 h in a dose-dependent manner increased the GSTP expression. CA was more potent than CS. The RNA level and the enzyme activity of GSTP were also enhanced by CA treatment. Treatment with 10 μM CA highly induced the reporter activity of the enhancer element GPEI. Furthermore, CA markedly increased the translocation of nuclear factor erythroid-2 related factor 2 (Nrf2) from the cytosol to the nucleus after 30 to 60 min. CA the stimulated the protein induction of p38, nuclear Nrf2, and GSTP was diminished in the presence of SB203580 (a p38 inhibitor). In addition, SB203580 pretreatment or silencing of Nrf2 by siRNA suppressed the CA-induced GPEI-DNA binding activity and GSTP protein expression. Knockdown of p38 or Nrf2 by siRNA abolished the activation of p38 and Nrf2 as well as the protein induction and enzyme activity of GSTP by CA. These results suggest that CA up-regulates the expression and enzyme activity of GSTP via the p38/Nrf2/GPEI pathway.

Extracellular nucleotides act through P2U purinoceptors to elevate [Ca2+]i and enhance basic fibroblast growth factor-induced proliferation in sheep chondrocytes.

PubMed

Kaplan, A D; Kilkenny, D M; Hill, D J; Dixon, S J

1996-11-01

Extracellular nucleotides interact with specific cell surface receptors to mediate a variety of biological responses, including elevation of the cytosolic free Ca2+ concentration ([Ca2+]i) in a number of cell types. Although extracellular ATP has been shown to affect chondrocyte function, the underlying mechanisms are poorly understood. In the present study, we investigated whether Ca2+-mobilizing purinoceptors are present on sheep chondrocytes. Chondrocytes were isolated from the proximal tibial growth plate of day 120-130 sheep fetuses. Early passage cells were loaded with indo-1 or fluo-3, and [Ca2+]i was monitored by fluorescence spectrophotometry. ATP (0.3-100 microM) induced transient elevation of [Ca2+]i, lasting approximately 1 min. Half-maximal elevation of [Ca2+]i was observed at an ATP concentration of 5.0 +/- 0.2 microM. Responses were still observed in the absence of extracellular Ca2+, and were abolished by pretreatment with thapsigargin, consistent with the release of Ca2+ from intracellular stores. Several nucleotides were tested for their ability to elevate [Ca2+]i. In order of potency, these were UTP approximately ATP > ADP approximately 2-methylthio-ATP. No responses were elicited by benzoylbenzoic-ATP, a P2Z-selective agonist; alpha,beta-methylene-ATP, an agonist selective for certain P2X purinoceptors; AMP; adenosine; or pyrophosphate (all at 100 microM), demonstrating specificity. Taken together, these data indicate that nucleotides elevate [Ca2+]i in chondrocytes through interaction with the P2U purinoceptor subtype. Although pretreatment with pertussis toxin virtually abolished the Ca2+ response to lysophosphatidic acid, the response to UTP was relatively insensitive, suggesting that P2U purinoceptors are not linked to a pertussis toxin-sensitive G protein in chondrocytes. In contrast, the Ca2+ response to UTP was markedly inhibited by the biologically active phorbol ester 12-O-tetradecanoyl-beta-phorbol 13-acetate, but not by the inactive control compound 4 alpha-phorbol 12,13-didecanoate, suggesting that a 12-O-tetradecanoyl-beta-phorbol 13-acetate-sensitive isoform of protein kinase C regulates P2U purinoceptor signaling in these cells. UTP (10 microM) enhanced the proliferative response to basic fibroblast growth factor. The response to basic fibroblast growth factor was also enhanced by ATP, but not by 2-methylthio-ATP, consistent with involvement of P2U purinoceptors. Nucleotides released during trauma, inflammation, or cell death may act through P2U purinoceptors to regulate chondrocyte function in an autocrine or paracrine manner.

Calcium/calmodulin‐dependent kinase 2 mediates Epac‐induced spontaneous transient outward currents in rat vascular smooth muscle

PubMed Central

Humphries, Edward S. A.; Kamishima, Tomoko; Quayle, John M.

2017-01-01

Key points The Ca2+ and redox‐sensing enzyme Ca2+/calmodulin‐dependent kinase 2 (CaMKII) is a crucial and well‐established signalling molecule in the heart and brain.In vascular smooth muscle, which controls blood flow by contracting and relaxing in response to complex Ca2+ signals and oxidative stress, surprisingly little is known about the role of CaMKII.The vasodilator‐induced second messenger cAMP can relax vascular smooth muscle via its effector, exchange protein directly activated by cAMP (Epac), by activating spontaneous transient outward currents (STOCs) that hyperpolarize the cell membrane and reduce voltage‐dependent Ca2+ influx. How Epac activates STOCs is unknown.In the present study, we map the pathway by which Epac increases STOC activity in contractile vascular smooth muscle and show that a critical step is the activation of CaMKII.To our knowledge, this is the first report of CaMKII activation triggering cellular activity known to induce vasorelaxation. Abstract Activation of the major cAMP effector, exchange protein directly activated by cAMP (Epac), induces vascular smooth muscle relaxation by increasing the activity of ryanodine (RyR)‐sensitive release channels on the peripheral sarcoplasmic reticulum. Resultant Ca2+ sparks activate plasma membrane Ca2+‐activated K+ (BKCa) channels, evoking spontaneous transient outward currents (STOCs) that hyperpolarize the cell and reduce voltage‐dependent Ca2+ entry. In the present study, we investigate the mechanism by which Epac increases STOC activity. We show that the selective Epac activator 8‐(4‐chloro‐phenylthio)‐2′‐O‐methyladenosine‐3′, 5‐cyclic monophosphate‐AM (8‐pCPT‐AM) induces autophosphorylation (activation) of calcium/calmodulin‐dependent kinase 2 (CaMKII) and also that inhibition of CaMKII abolishes 8‐pCPT‐AM‐induced increases in STOC activity. Epac‐induced CaMKII activation is probably initiated by inositol 1,4,5‐trisphosphate (IP3)‐mobilized Ca2+: 8‐pCPT‐AM fails to induce CaMKII activation following intracellular Ca2+ store depletion and inhibition of IP3 receptors blocks both 8‐pCPT‐AM‐mediated CaMKII phosphorylation and STOC activity. 8‐pCPT‐AM does not directly activate BKCa channels, but STOCs cannot be generated by 8‐pCPT‐AM in the presence of ryanodine. Furthermore, exposure to 8‐pCPT‐AM significantly slows the initial rate of [Ca2+]i rise induced by the RyR activator caffeine without significantly affecting the caffeine‐induced Ca2+ transient amplitude, a measure of Ca2+ store content. We conclude that Epac‐mediated STOC activity (i) occurs via activation of CaMKII and (ii) is driven by changes in the underlying behaviour of RyR channels. To our knowledge, this is the first report of CaMKII initiating cellular activity linked to vasorelaxation and suggests novel roles for this Ca2+ and redox‐sensing enzyme in the regulation of vascular tone and blood flow. PMID:28731505

Tuning the competition between ferromagnetism and antiferromagnetism in a half-doped manganite through magnetoelectric coupling.

PubMed

Yi, Di; Liu, Jian; Okamoto, Satoshi; Jagannatha, Suresha; Chen, Yi-Chun; Yu, Pu; Chu, Ying-Hao; Arenholz, Elke; Ramesh, R

2013-09-20

We investigate the possibility of controlling the magnetic phase transition of the heterointerface between a half-doped manganite La(0.5)Ca(0.5)MnO(3) and a multiferroic BiFeO(3) (BFO) through magnetoelectric coupling. Using macroscopic magnetometry and element-selective x-ray magnetic circular dichroism at the Mn and Fe L edges, we discover that the ferroelectric polarization of BFO controls simultaneously the magnetization of BFO and La(0.5)Ca(0.5)MnO(3) (LCMO). X-ray absorption spectra at the oxygen K edge and linear dichroism at the Mn L edge suggest that the interfacial coupling is mainly derived from the superexchange between Mn and Fe t(2g) spins. The combination of x-ray absorption spectroscopy and mean-field theory calculations reveals that the d-electron modulation of Mn cations changes the magnetic coupling in LCMO, which controls the enhanced canted moments of interfacial BFO via the interfacial coupling. Our results demonstrate that the competition between ferromagnetic and antiferromagnetic instability can be modulated by an electric field at the heterointerface, providing another pathway for the electrical field control of magnetism.

Microbial, Physical and Chemical Drivers of COS and 18O-CO2 Exchange in Soils

NASA Astrophysics Data System (ADS)

Meredith, L. K.; Boye, K.; Whelan, M.; Pang, E.; von Sperber, C.; Brueggemann, N.; Berry, J. A.; Welander, P. V.

2015-12-01

Carbonyl sulfide (COS) and the oxygen isotope composition (δ18O) of CO2 are potential tools for differentiating the contributions of photosynthesis and respiration to the balance of global carbon cycling. These processes are coupled at the leaf level via the enzyme carbonic anhydrase (CA), which hydrolyzes CO2 in the first biochemical step of the photosynthetic pathway (CO2 + H2O ⇌ HCO3- + H+) and correspondingly structural analogue COS (COS + H2O → CO2 + H2S). CA also accelerates the exchange of oxygen isotopes between CO2 and H2O leading to a distinct isotopic imprint [1]. The biogeochemical cycles of these tracers include significant, yet poorly characterized soil processes that challenge their utility for probing the carbon cycle. In soils, microbial CA also hydrolyze COS and accelerate O isotope exchange between CO2 and soil water. Soils have been observed to emit COS by undetermined processes. To account for these soil processes, measurements are needed to identify the key microbial, chemical, and physical factors. In this study, we survey COS and δ18O exchange in twenty different soils spanning a variety of biomes and soil properties. By comparing COS fluxes and δ18O-CO2 values emitted from moist soils we investigate whether the same types of CA catalyze these two processes. Additionally, we seek to identify the potential chemical drivers of COS emissions by measuring COS fluxes in dry soils. These data are compared with soil physical (bulk density, volumetric water content, texture), chemical (pH, elemental analysis, sulfate, sulfur K-edge XANES), and microbial measurements (biomass and phylogeny). Furthermore, we determine the abundance and diversity of CA-encoding genes to directly link CA with measured soil function. This work will define the best predictors for COS fluxes and δ18O-CO2 values from our suite of biogeochemical measurements. The suitability of identified predictor variables can be tested in follow-up studies and applied for modeling purposes. References: [1] Von Sperber, C., Weiler, M. and Brüggemann, N.: The effect of soil moisture, soil particle size, litter layer and carbonic anhydrase on the oxygen isotopic composition of soil-released CO2, Eur. J. Soil Sci., 66(3), doi:10.1111/ejss.12241, 2015.

Antidiabetic and antihyperlipidemic activity of p-coumaric acid in diabetic rats, role of pancreatic GLUT 2: In vivo approach.

PubMed

Amalan, Venkatesan; Vijayakumar, Natesan; Indumathi, Dhananjayan; Ramakrishnan, Arumugam

2016-12-01

P-coumaric acid (p-CA, 3-[4-hydroxyphenyl]-2-propenoic acid), the major component widely found in nutritious plant foods, has various antioxidant, antiinflammatory and anticancer property. To evaluate the antidiabetic and antihyperlipidemic mechanisms, via the effects on carbohydrate, lipids and lipoproteins responses in adult male albino Wistar rats were examined by treated with p-CA. Rats were injected with streptozotocin (STZ, 40mg/kg b.w.) by intraperitonially (i.p.) 30days for the induction of experimental diabetes mellitus. Diabetic rats were treated with p-CA orally at a dose of 100mg/kg b.w. The potential defending character of p-CA against diabetic rats was evaluated by performing the various biochemical parameters and glucose transporter such as GLUT2 mRNA expression of pancreas. Administration of p-CA significantly lowers the blood glucose level, gluconeogenic enzymes such as glucose-6-phosphatase and fructose-1,6-bisphosphatase whereas increases the activities of hexokinase, glucose-6 phosphatase dehydrogenase and GSH via by increasing level of insulin. p-CA reduces the total cholesterol and triglycerides in both plasma and tissues i.e. liver and kidney. p-CA also decreases the LDL-C, VLDL-C and it considerably increase the level of HDL-C. A significant decreased expression of GLUT 2 mRNA in the pancreas was recorded in the supplementation of p-CA treated groups. Taken together, these results suggest that p-CA modulates glucose and lipid metabolism via GLUT 2 activation in the pancreatic and has potentially beneficial effects in improving or treating metabolic disorders. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

AB Initi Molecular Dynamics Simulation of the Amorphous Structure of Ca-Mg-Cu and Ca-Mg-Zn Alloys (Postprint)

DTIC Science & Technology

2012-09-26

characteristic coordination poly- hedra present in an amorphous structure.[23,42] A coor- dination polyhedron is defined as an i-centered cluster with...vertices at the first-shell atom positions and edges coinciding with the interatomic bonds in the first shell.[45] Each coordination polyhedron can be...assigned a Voronoi signature (n3, n4, n5, n6), where nm is the number of vertices common to m polyhedron faces (or edges).[46] m is also called the

Enhanced pyruvate dehydrogenase activity improves cardiac outcomes in a murine model of cardiac arrest.

PubMed

Piao, Lin; Fang, Yong-Hu; Kubler, Manfred M; Donnino, Michael W; Sharp, Willard W

2017-01-01

Post-ischemic changes in cellular metabolism alter myocardial and neurological function. Pyruvate dehydrogenase (PDH), the limiting step in mitochondrial glucose oxidation, is inhibited by increased expression of PDH kinase (PDK) during ischemia/reperfusion injury. This results in decreased utilization of glucose to generate cellular ATP. Post-cardiac arrest (CA) hypothermia improves outcomes and alters metabolism, but its influence on PDH and PDK activity following CA are unknown. We hypothesized that therapeutic hypothermia (TH) following CA is associated with the inhibition of PDK activity and increased PDH activity. We further hypothesized that an inhibitor of PDK activity, dichloroacetate (DCA), would improve PDH activity and post-CA outcomes. Anesthetized and ventilated adult female C57BL/6 wild-type mice underwent a 12-minute KCl-induced CA followed by cardiopulmonary resuscitation. Compared to normothermic (37°C) CA controls, administering TH (30°C) improved overall survival (72-hour survival rate: 62.5% vs. 28.6%, P<0.001), post-resuscitation myocardial function (ejection fraction: 50.9±3.1% vs. 27.2±2.0%, P<0.001; aorta systolic pressure: 132.7±7.3 vs. 72.3±3.0 mmHg, P<0.001), and neurological scores at 72-hour post CA (9.5±1.3 vs. 5.4±1.3, P<0.05). In both heart and brain, CA increased lactate concentrations (1.9-fold and 3.1-fold increase, respectively, P<0.01), decreased PDH enzyme activity (24% and 50% reduction, respectively, P<0.01), and increased PDK protein expressions (1.2-fold and 1.9-fold, respectively, P<0.01). In contrast, post-CA treatment with TH normalized lactate concentrations (P<0.01 and P<0.05) and PDK expressions (P<0.001 and P<0.05), while increasing PDH activity (P<0.01 and P<0.01) in both the heart and brain. Additionally, treatment with DCA (0.2 mg/g body weight) 30 min prior to CA improved both myocardial hemodynamics 2 hours post-CA (aortic systolic pressure: 123±3 vs. 96±4 mmHg, P<0.001) and 72-hour survival rates (50% vs. 19%, P<0.05) in normothermic animals. Enhanced PDH activity in the setting of TH or DCA administration is associated with improved post-CA resuscitation outcomes. PDH is a promising therapeutic target for improving post-CA outcomes.

Impaired Compensation for Salt-Induced Urinary Calcium Loss in a Space Flight Model

NASA Technical Reports Server (NTRS)

Navidi, Meena; Harper, J. S.; Evans, J.; Fung, P.; Wolinsky, I.; Arnaud, S. B.; Wade, Charles E. (Technical Monitor)

1994-01-01

The loss of urinary calcium (UCa) induced by high sodium (HiNa) diets is compensated for by an increase in net intestinal Ca absorption (abs.). To determine the capacity of the intestine to absorb Ca in a space flight model in which the formation of 1,25-dihydroxyvitamin D (1,25-D) is suppressed, we induced Ca loss with HiNa diets (8%) and restricted dietary Ca (0.2%). In 200 g rats with hind limbs unloaded by tail suspension (S), we examined intestinal Ca abs. by direct measurement in the duodenum (everted gut sac or S/M), vitamin D receptors (VDR) and Ca balance. We also measured serum ionized calcium (ICa), pH, parathyroid hormone (PTH) and 1,25D. PTH was related to ICa (r = -0.44, p is less than 0.02), pH (r = -0.47, p is less than 0.02) and %Ca abs. (r = -0.40, p is less than 0.05). 1,25-D was related to %Ca abs. (r = 0.60, p is less than 0.001) but not VDR or S/M. Effects of the model were lower serum 1,25-D (110 +/- 59 vs. 199 +/- 80 pg/ml, p is less than 0.005), %Ca abs. (83 +/- 6.9 vs. 93 +/- 3.2, p is less than 0.03) and Ca balance (27 +/- 0.2 vs. 30 +/- 0.3 mg/d, p is less than 0.001) in S than controls (C). The HiNa diet increased UCa excretion from 2 to 13% of dietary Ca. Responses to HiNa diets, compared to normal Na, revealed no differences in 1,25-D, Ca abs. or VDR. Ca balances were lower in HiNa (27 +/- 0.3 vs. 30 +/- 0.4 mg/d, p is less than 0.001) in spite of higher Ca intakes. The failure of S rats fed HiNa diets to increase Ca abs. in response to Na-induced Ca loss appears to be related to suppressed 1,25-D in the space flight model, the cause of which remains obscure.

Effects of calcium feeding strategy on true ileal phosphorus digestibility and true phosphorus retention determined with growing broilers.

PubMed

Perryman, K R; Masey O'Neill, H V; Bedford, M R; Dozier, W A

2016-05-01

An experiment utilizing 960 Ross × Ross 708 male broilers was conducted to determine the effects of Ca feeding strategy on true ileal (prececal) P digestibility (TIPD) and true P retention (TPR) of corn. Experimental diets were formulated with 1 of 3 dietary Ca feeding strategies (0.95%, 0.13%, or variable Ca concentrations to maintain a 2.1:1 Ca:P ratio) and contain 0, 25, 50, or 75% corn. A practical corn-soybean meal diet (1.4:1 Ca:P ratio) was fed as a control. After receiving a common starter diet, experimental diets were fed from 19 to 26 d of age. After a 48-h dietary adaptation period, a 48-h retention assay was conducted. At 25 and 26 d of age, ileal digesta were collected from 8 birds per cage. Broilers consuming the control diet had higher (P<0.001) BW gain, feed intake, digesta P, and excreta P than broilers consuming the corn titration diets. Digesta and excreta P increased (linear, P<0.05) with graded increases of corn. True ileal P digestibility and TPR were highest (P<0.05) for diets with 0.13% Ca (57.3 and 69.5%, respectively) compared with diets formulated with a 2.1:1 Ca:P ratio (41.2 and 37.8%, respectively) or 0.95% Ca (25.4 and 39.0%, respectively). Values for TPR were higher (P<0.05) than those for TIPD except when the dietary Ca:P ratio was fixed. Additionally, negative endogenous P losses were predicted by regression equations when TPR was estimated for birds fed titration diets with the fixed Ca:P ratio. Changing the Ca concentration of the diets to maintain a fixed Ca:P ratio influenced (P<0.001) apparent P retention, which affected the estimate for TPR due to the prediction of negative endogenous P losses. These data demonstrated that regression analysis may have limitations when estimating the TIPD or TPR of corn when formulating diets with different Ca feeding strategies. More research is necessary to elucidate the factors that contributed to regression equations predicting negative endogenous P losses. © 2016 Poultry Science Association Inc.

Syntheses of near-net-shaped monolithic hydroxyapatite and hydroxyapatite-ASTM F75 composites by the oxidation of solid metal-bearing precursors

NASA Astrophysics Data System (ADS)

Saw, Eaden

A novel powder-metallurgical route was used to fabricate near net-shaped hydroxyapatite, Ca10(PO4)6(OH)2 (HA) and HA+Co-C-Mo composite bodies. Ca and beta-Ca2P 2O7 with Ca/P ˜ 1.67 was intimately mixed by high-energy mechanical alloying, formed into desired shapes by pressing and machining, and then converted into HA with a series of heat treatments: a 600°C annealing in dry O2 completely oxidized calcium within 3 h, and a subsequent annealing at ≤1150°C in moist O2 yielded phase-pure HA. The reduction in solid volume associated with the oxidation of calcium (Vm[CaO] < Vm[Ca]) was offset by the increase in solid volume associated with the conversion of CaO and Ca2P2O7 into HA. Thus, the overall dimensional changes upon transformation of Ca+beta-Ca2P 2O7 precursors into HA can be relatively small. A mixture of Co-Cr-Mo powder with the precursor prepared from Ca and beta-Ca 2P2O7, targeted to yield a 75 to 25 volume ratio of Co-Cr-Mo to stoichiometric HA were prepared with the same method but different annealing cycles: annealing at 1150°C in de-oxygenized, flowing Ar resulted in partial densification of the composite bodies, and subsequent annealing at 850°C in a moist O2 atmosphere yielded a composite of Co-Cr-Mo alloy with phase-pure HA. The overall dimensional changes upon transformation of Ca+beta-Ca2P2O7+CO-Cr-Mo precursors into HA/Co-Cr-Mo composite were relatively small. In this thesis, the phase and microstructural evolution at various stages of transformation to monolithic HA and to HA/Co-Cr-Mo alloy composites are discussed. Planar reaction couples and powder compacts of CaO-TCP were prepared to study the kinetics for HA formation from CaO+TCP. Pt strips were used in the planar reaction couples as inert markers. These reaction couples were heated at 1150°C for various times in moist O2. The results of powder compact analyses fits Carter's model, which indicated that the rate of HA conversion from CaO and TCP is limited by solid state diffusion of Ca 2+ and/or OH- through the HA layer.

In vivo Ca2+ buffering capacity and microvascular oxygen pressures following muscle contractions in diabetic rat skeletal muscles: fiber-type specific effects.

PubMed

Eshima, Hiroaki; Poole, David C; Kano, Yutaka

2015-07-15

In Type 1 diabetes, skeletal muscle resting intracellular Ca(2+) concentration ([Ca(2+)]i) homeostasis is impaired following muscle contractions. It is unclear to what degree this behavior is contingent upon fiber type and muscle oxygenation conditions. We tested the hypotheses that: 1) the rise in resting [Ca(2+)]i evident in diabetic rat slow-twitch (type I) muscle would be exacerbated in fast-twitch (type II) muscle following contraction; and 2) these elevated [Ca(2+)]i levels would relate to derangement of microvascular partial pressure of oxygen (PmvO2 ) rather than sarcoplasmic reticulum dysfunction per se. Adult male Wistar rats were divided randomly into diabetic (DIA: streptozotocin ip) and healthy (CONT) groups. Four weeks later extensor digitorum longus (EDL, predominately type II fibers) and soleus (SOL, predominately type I fibers) muscle contractions were elicited by continuous electrical stimulation (120 s, 100 Hz). Ca(2+) imaging was achieved using fura 2-AM in vivo (i.e., circulation intact). DIA increased fatigability in EDL (P < 0.05) but not SOL. In recovery, SOL [Ca(2+)]i either returned to its resting baseline within 150 s (CONT 1.00 ± 0.02 at 600 s) or was not elevated in recovery at all (DIA 1.03 ± 0.02 at 600 s, P > 0.05). In recovery, EDL CONT [Ca(2+)]i also decreased to values not different from baseline (1.06 ± 0.01, P > 0.05) at 600 s. In marked contrast, EDL DIA [Ca(2+)]i remained elevated for the entire recovery period (i.e., 1.23 ± 0.03 at 600 s, P < 0.05). The inability of [Ca(2+)]i to return to baseline in EDL DIA was not associated with any reduction of SR Ca(2+)-ATPase (SERCA) 1 or SERCA2 protein levels (both increased 30-40%, P < 0.05). However, Pmv(O2) recovery kinetics were markedly slowed in EDL such that mean Pmv(O2) was substantially depressed (CONT 27.9 ± 2.0 vs. DIA 18.4 ± 2.0 Torr, P < 0.05), and this behavior was associated with the elevated [Ca(2+)]i. In contrast, this was not the case for SOL (P > 0.05) in that neither [Ca(2+)]i nor Pmv(O2) were deranged in recovery with DIA. In conclusion, recovery of [Ca(2+)]i homeostasis is impaired in diabetic rat fast-twitch but not slow-twitch muscle in concert with reduced Pmv(O2) pressures. Copyright © 2015 the American Physiological Society.

Phosphate and Calcium Control in Short Frequent Hemodialysis with the NxStage System One Cycler: Mass Balance Studies and Comparison with Standard Thrice-Weekly Bicarbonate Dialysis.

PubMed

Brunati, Chiara Carla Maria; Gervasi, Francesca; Casati, Costanza; Querques, Maria Luisa; Montoli, Alberto; Colussi, Giacomo

2018-01-01

Short frequent dialysis with NxStage System One cycler (NSO) has become increasingly popular as home hemodialysis prescription. Short dialysis sessions with NSO might not allow adequate phosphate (P) removal. Single-session and weekly balances of P and calcium (Ca) were compared in 14 patients treated with NSO (6 sessions/week) and in 14 patients on standard bicarbonate dialysis (BHD). NSO and BHD showed similar plasma P fall, with end-dialysis plasma P slightly lower in BHD (2.2 ± 0.5 vs. 2.7 ± 0.8 mg/dL, p < 0.02). Single-session P removal was lower in NSO, but weekly removal was higher (3,488 ± 1,181 mg vs. 2,634 ± 878, p < 0.003). Plasma Ca increase was lower in NSO, with similar PTH fall. Ca balance varied according to start plasma Ca, dialysate to blood Ca gradient and net ultrafiltration. short, frequent home hemodialysis with NSO, on a 6/week-based prescription, allows higher weekly P removal than BHD. With the dialysate Ca concentration in use (6 mg/dL), total plasma Ca and iCa concentration increase is lower in NSO. © 2018 S. Karger AG, Basel.

Expression and subcellular localization of the ryanodine receptor in rat pancreatic acinar cells.

PubMed Central

Leite, M F; Dranoff, J A; Gao, L; Nathanson, M H

1999-01-01

The ryanodine receptor (RyR) is the principal Ca2+-release channel in excitable cells, whereas the inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) is primarily responsible for Ca2+ release in non-excitable cells, including epithelia. RyR also is expressed in a number of non-excitable cell types, but is thought to serve as an auxiliary or alternative Ca2+-release pathway in those cells. Here we use reverse transcription PCR to show that a polarized epithelium, the pancreatic acinar cell, expresses the type 2, but not the type 1 or 3, isoform of RyR. We furthermore use immunochemistry to demonstrate that the type 2 RyR is distributed throughout the basolateral and, to a lesser extent, the apical region of the acinar cell, but is excluded from the trigger zone, where cytosolic Ca2+ signals originate in this cell type. Since propagation of Ca2+ waves in acinar cells is sensitive to ryanodine, caffeine and Ca2+, these findings suggest that Ca2+ waves in this cell type result from the co-ordinated release of Ca2+, first from InsP3Rs in the trigger zone, then from RyRs elsewhere in the cell. RyR may play a fundamental role in Ca2+ signalling in polarized epithelia, including for Ca2+ signals initiated by InsP3. PMID:9882629

Chelating effect of citric acid is negligible for development of enamel erosions.

PubMed

Azadi-Schossig, Parastu; Becker, Klaus; Attin, Thomas

2016-09-01

Citric acid (CA) is a component in beverages responsible for dental erosion. The aim of this study was to examine the influence of CA with different pH, titratable acid and buffer capacity (ß), and the impact of the chelating effect of CA on development of enamel erosions. In a superfusion model, hydroxy apatite (HAp) dissolution of bovine enamel was measured in four experiments (EXP 1-4) with 27 experimental groups (n = 8 per group). The samples were superfused with different CA variations and respective controls. EXP-1: Dilution series of HCl (pH 2.15-3.02). EXP-2: Dilution series of natural CA (56-1.75 mmol l(-1); pH 2.15-3.02). EXP-3: CA solutions (56 and 14 mmol l(-1), ß: 39.7 and 10.2 mmol l(-1) pH(-1), respectively) with different titratable acidity at equal pH values. EXP-4: CA concentrations (56-1.75 mmol l(-1)) neutralized to pH 7. CA led to higher HAp-dissolution than HCl. With higher pH, the difference in HAp-dissolution rate between the two acids became increasingly smaller. At equal pH, HAp-dissolution was higher for the CA with the higher amount of titratable acid. However, no clear correlation between erosion and titratable acid or ß could be found. Only minimal amounts of HAp were dissolved by neutralized CA compared to CA with natural pH. Under the chosen conditions chelating effects of CA do not have a relevant influence of HAp-dissolution of enamel. Moreover, amount of HAp-dissolution by CA is not attributed to a single factor alone. The interplay between the different parameters of CA seems to be responsible for its erosive potential. The erosive potential of solutions containing citric acid with unknown concentrations could not be predicted using a single parameter alone, and should at best determined in experimental set-ups.

Microprocessor Realization of a Linear Predictive Vocoder. Appendix C. LPCM Detail Drawings and Layouts

DTIC Science & Technology

1977-02-07

CHG12 1 Dr.%VC 8 DB ILA8 DC1II 29 FTLE: FDS TAPIRWLST Al 1/19/77 16:1~2 H.I.T. LINCOLN LAB3ORATORY 1 DB116 DB16 D11G12 1 DI)V8 DD V,"R DWl 1 DBV16 DBV...5 CD27 CA27 CDC.6 CAC6 "F23 CD25 CA25 CD%.4 CAt4 IN ,7 F2’ C!ൠ CA24 CDV3 CA.^ ELI 11 CI)22 CA23 CP,2 CA,2 1D1.. CA22 CDI CA. 1 "FH𔃼 CD39 CA38 CD17...FC17 FE22 ,26 FC19 UE24 1 ’P27 FC19 F21 1 IP 29 FA V7 EF21 1 !p33* FA10 FF12" I %P32 FG𔄀 EE1 1 IP3 FG ’i^7 EF15 1 ’P 34 FGF12 Ffl2 1 1115FG ’ 1 F12

Deficiency of MIP phosphatase induces a muscle disorder by disrupting Ca2+ homeostasis

PubMed Central

Shen, Jinhua; Yu, Wen-Mei; Brotto, Marco; Scherman, Joseph A.; Guo, Caiying; Stoddard, Christopher; Nosek, Thomas M.; Valdivia, Héctor H.; Qu, Cheng-Kui

2009-01-01

The intracellular Ca2+ ([Ca2+]i) level of skeletal muscles must be rapidly regulated during the excitation-contraction-relaxation process 1. However, the signaling components involved in such rapid Ca2+ movement are not fully understood. Here, we report that mice deficient in the novel phosphatidylinositol phosphate (PIP) phosphatase MIP displayed muscle weakness and fatigue. Muscles isolated from MIP−/− mice produced less contractile force, markedly prolonged relaxation, and exhibited exacerbated fatigue. Further analyses revealed that MIP deficiency resulted in spontaneous Ca2+ leak from the internal store — the sarcoplasmic reticulum (SR). This was attributed to the decreased metabolism/dephosphorylation and the subsequent accumulation of MIP substrates, especially PI(3,5)P2 and PI(3,4)P2. Furthermore, we found that PI(3,5)P2 and PI(3,4)P2 bound to and directly activated the Ca2+ release channel/ryanodine receptor (RyR1) of the SR. These studies provide the first evidence that finely controlled PIP levels in muscle cells are essential for maintaining Ca2+ homeostasis and muscle performance. PMID:19465920

Electronic structure study of wide band gap magnetic semiconductor (La0.6Pr0.4)0.65Ca0.35MnO3 nanocrystals in paramagnetic and ferromagnetic phases

NASA Astrophysics Data System (ADS)

Dwivedi, G. D.; Joshi, Amish G.; Kumar, Shiv; Chou, H.; Yang, K. S.; Jhong, D. J.; Chan, W. L.; Ghosh, A. K.; Chatterjee, Sandip

2016-04-01

X-ray circular magnetic dichroism (XMCD), X-ray photoemission spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS) techniques were used to study the electronic structure of nanocrystalline (La0.6Pr0.4)0.65Ca0.35MnO3 near Fermi-level. XMCD results indicate that Mn3+ and Mn4+ spins are aligned parallel to each other at 20 K. The low M-H hysteresis curve measured at 5 K confirms ferromagnetic ordering in the (La0.6Pr0.4)0.65Ca0.35MnO3 system. The low temperature valence band XPS indicates that coupling between Mn3d and O2p is enhanced and the electronic states near Fermi-level have been suppressed below TC. The valence band UPS also confirms the suppression of electronic states near Fermi-level below Curie temperature. UPS near Fermi-edge shows that the electronic states are almost absent below 0.5 eV (at 300 K) and 1 eV (at 115 K). This absence clearly demonstrates the existence of a wide band-gap in the system since, for hole-doped semiconductors, the Fermi-level resides just above the valence band maximum.

A novel calmodulin-regulated Ca2+-ATPase (ACA2) from Arabidopsis with an N-terminal autoinhibitory domain

NASA Technical Reports Server (NTRS)

Harper, J. F.; Hong, B.; Hwang, I.; Guo, H. Q.; Stoddard, R.; Huang, J. F.; Palmgren, M. G.; Sze, H.; Evans, M. L. (Principal Investigator)

1998-01-01

To study transporters involved in regulating intracellular Ca2+, we isolated a full-length cDNA encoding a Ca2+-ATPase from a model plant, Arabidopsis, and named it ACA2 (Arabidopsis Ca2+-ATPase, isoform 2). ACA2p is most similar to a "plasma membrane-type" Ca2+-ATPase, but is smaller (110 kDa), contains a unique N-terminal domain, and is missing a long C-terminal calmodulin-binding regulatory domain. In addition, ACA2p is localized to an endomembrane system and not the plasma membrane, as shown by aqueous-two phase fractionation of microsomal membranes. ACA2p was expressed in yeast as both a full-length protein (ACA2-1p) and an N-terminal truncation mutant (ACA2-2p; Delta residues 2-80). Only the truncation mutant restored the growth on Ca2+-depleted medium of a yeast mutant defective in both endogenous Ca2+ pumps, PMR1 and PMC1. Although basal Ca2+-ATPase activity of the full-length protein was low, it was stimulated 5-fold by calmodulin (50% activation around 30 nM). In contrast, the truncated pump was fully active and insensitive to calmodulin. A calmodulin-binding sequence was identified within the first 36 residues of the N-terminal domain, as shown by calmodulin gel overlays on fusion proteins. Thus, ACA2 encodes a novel calmodulin-regulated Ca2+-ATPase distinguished by a unique N-terminal regulatory domain and a non-plasma membrane localization.

Platelet aggregation caused by a partially purified jellyfish toxin from Carybdea rastonii.

PubMed

Azuma, H; Sekizaki, S; Satoh, A; Nakajima, T; Ishikawa, M

1986-01-01

A partially purified toxin (pCrTX) was obtained from the tentacles of the jellyfish, Carybdea rastonii. When pCrTX (3 X 10(-8) - 3 X 10(-7) g/ml) was added to citrated platelet-rich plasma, aggregation was produced in a concentration-dependent manner. Scanning electron microscopic examination revealed that both pCrTX and collagen produced aggregates of platelets possessing many pseudopods. The concentration which produced 50% aggregation for pCrTX was 1.8 X 10(-7) g/ml, as compared to 2.3 X 10(-6) g/ml for collagen. The pCrTX-induced aggregation was only slightly inhibited by indomethacin and quinacrine in concentrations sufficient to inhibit arachidonic acid- and collagen-induced aggregation. pCrTX was less active in washed platelets suspended in Ca2+ free medium, whereas the pCrTX-induced aggregation was significantly augmented in the presence of Ca2+. The augmentation of aggregation by Ca2+ was only slightly attenuated by pretreatment with 100 microM verapamil. pCrTX significantly increased the concentration of cytoplasmic free Ca2+ ([Ca2+]i) and depolarized the platelet membrane in concentrations that produced aggregation. The increase in [Ca2+]i caused by pCrTX was little affected by verapamil. The depolarization by pCrTX was unchanged in the presence or absence of Ca2+, or by sodium or potassium transport inhibitors. The movement of 22Na+ into platelets was significantly increased by pCrTX. This increase in the movement of 22N+ into platelets was unaffected by tetrodotoxin. On the other hand, pCrTX-induced aggregation, depolarization and the increase in [Ca2+]i were all significantly attenuated in low Na+ medium. These results suggest that pCrTX causes a massive depolarization by increasing cation permeability indiscriminately and this generalized depolarization permits an inward movement of calcium down an electrochemical gradient which, in turn triggers platelet aggregation.

Large magnetoresistance in antiferromagnetic CaMnO3-δ

NASA Astrophysics Data System (ADS)

Zeng, Z.; Greenblatt, M.; Croft, M.

1999-04-01

CaMnO3-δ with δ=0, 0.06, and 0.11 was prepared by the Pechini citrate gel process at 1100 °C. Oxygen defects were created by quenching the sample from high temperature. Chemical analysis and x-ray absorption show that the formal valence of Mn in CaMnO3 is close to 4+, and that Mn(III) is created in the quenched samples. Moreover the x-ray absorption near-edge spectra results support the creation of two Mn(III) five coordinate sites for each O vacancy. CaMnO3-δ (δ=0-0.11) are n-type semiconductors and order antiferromagnatically with Néel temperatures close to 125 K. The activation energy decreases with increasing δ. A relatively large (~40%) negative magnetoresistance (MR) is observed for CaMnO2.89. This result shows that a substantial MR can occur in these G-type antiferromagnetic materials.

Differential roles of PKC isoforms (PKCs) and Ca2+ in GnRH and phorbol 12-myristate 13-acetate (PMA) stimulation of p38MAPK phosphorylation in immortalized gonadotrope cells.

PubMed

Mugami, Shany; Kravchook, Shani; Rahamim-Ben Navi, Liat; Seger, Rony; Naor, Zvi

2017-01-05

We examined the role of PKCs and Ca 2+ in GnRH-stimulated p38MAPK phosphorylation in the gonadotrope derived αT3-1 and LβT2 cell lines. GnRH induced a slow and rapid increase in p38MAPK phosphorylation in αT3-1 and LβT2 cells respectively, while PMA gave a slow response. The use of dominant negatives for PKCs and peptide inhibitors for the receptors for activated C kinase (RACKs), has revealed differential role for PKCα, PKCβII, PKCδ and PKCε in p38MAPK phosphorylation in a ligand-and cell context-dependent manner. The paradoxical findings that PKCs activated by GnRH and PMA play a differential role in p38MAPK phosphorylation may be explained by differential localization of the PKCs. Basal, GnRH- and PMA- stimulation of p38MAPK phosphorylation in αT3-1 cells is mediated by Ca 2+ influx via voltage-gated Ca 2+ channels and Ca 2+ mobilization, while in the differentiated LβT2 gonadotrope cells it is mediated only by Ca 2+ mobilization. p38MAPK resides in the cell membrane and is relocated to the nucleus by GnRH (∼5 min). Thus, we have identified the PKCs and the Ca 2+ pools involved in GnRH stimulated p38MAPK phosphorylation. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Structural Investigation of Phosphorus in CaO-SiO2-P2O5 Ternary Glass

NASA Astrophysics Data System (ADS)

Wang, Zhanjun; Cai, Shengjia; Zhang, Mei; Guo, Min; Zhang, Zuotai

2017-04-01

The system of CaO-SiO2-P2O5 ternary glass is not only among the major constituents of steelmaking slags in iron and steel industry, but also play a significant role in other industrial process, such as chemical engineering and glass industry. In the present study, the structure of CaO-SiO2-P2O5 ternary glass with varying P2O5 content from 0 to 15 wt pct at a fixed CaO/SiO2 = 1.4 was investigated using molecular dynamics (MD) simulation combined with X-ray photoelectron spectroscopy and Raman spectra techniques. The results indicated that P5+ ions have a higher affinity to Ca2+ ions which are then stripped away from the silicate network with the addition of P2O5, resulting in the formation of Ca-O-P and Si-O-Si linkages. In addition, almost all P5+ ions displayed as {{Q}}_{{P}}0 ( {{Q}}_{{P}}n , n is the number of bridging oxygen in one [PO4]-tetrahedra units) and a small fraction of P5+ ions behave as {{Q}}_{{P}}1 (P-O-P) and P-O-Si. The enhanced degree of polymerization can be detected from the increase of {{X}}_{{Si}}3 and X_{{P}}1 /X_{{P}}0 (mole fraction of {{Q}}_{{Si}}i or {{Q}}_{{P}}i ). Furthermore, the ratio of Raman scattering coefficients for Q_{{Si}}i /Q_{{Si}}1 and Q_{{P}}i /Q_{{P}}1 were determined by combining MD simulated result with Raman spectra, which were considered to be suitable to the present study.

Role of guanine nucleotide-binding proteins--ras-family or trimeric proteins or both--in Ca2+ sensitization of smooth muscle.

PubMed Central

Gong, M C; Iizuka, K; Nixon, G; Browne, J P; Hall, A; Eccleston, J F; Sugai, M; Kobayashi, S; Somlyo, A V; Somlyo, A P

1996-01-01

The purpose of this study was to identify guanine nucleotide-binding proteins (G proteins) involved in the agonist- and guanosine 5'-[gamma-thio]triphosphate (GTP[gamma-S])-induced increase in the Ca2+ sensitivity of 20-kDa myosin light chain (MLC20) phosphorylation and contraction in smooth muscle. A constitutively active, recombinant val14p21rhoA.GTP expressed in the baculovirus/Sf9 system, but not the protein expressed without posttranslational modification in Escherichia coli, induced at constant Ca2+ (pCa 6.4) a slow contraction associated with increased MLC20 phosphorylation from 19.8% to 29.5% (P < 0.05) in smooth muscle permeabilized with beta-esein. The effect of val14p21rhoA.GTP was inhibited by ADP-ribosylation of the protein and was absent in smooth muscle extensively permeabilized with Triton X-100. ADP-ribosylation of endogenous p21rho with epidermal cell differentiation inhibitor (EDIN) inhibited Ca2+ sensitization induced by GTP [in rabbit mesenteric artery (RMA) and rabbit ileum smooth muscles], by carbachol (in rabbit ileum), and by endothelin (in RMA), but not by phenylephrine (in RMA), and only slowed the rate without reducing the amplitude of contractions induced in RMA by 1 microM GTP[gamma-S] at constant Ca2+ concentrations. AlF(4-)-induced Ca2+ sensitization was inhibited by both guanosine 5'-[beta-thio]diphosphate (GDP[beta-S]) and by EDIN. EDIN also inhibited, to a lesser extent, contractions induced by Ca2+ alone (pCa 6.4) in both RMA and rabbit ileum. ADP-ribosylation of trimeric G proteins with pertussis toxin did not inhibit Ca2+ sensitization. We conclude that p21rho may play a role in physiological Ca2+ sensitization as a cofactor with other messengers, rather than as a sole direct inhibitor of smooth muscle MLC20 phosphatase. Images Fig. 3 Fig. 4 PMID:8577766

Calculated and measured [Ca(2+)] in buffers used to calibrate Ca(2+) macroelectrodes.

PubMed

McGuigan, John A S; Stumpff, Friederike

2013-05-01

The ionized concentration of calcium in physiological buffers ([Ca(2+)]) is normally calculated using either tabulated constants or software programs. To investigate the accuracy of such calculations, the [Ca(2+)] in EGTA [ethylene glycol-bis(β-aminoethylether)-N,N,N|,N|-tetraacetic acid], BAPTA [1,2-bis(o-aminophenoxy) ethane-N,N,N|,N|-tetraacetic acid], HEDTA [N-(2-hydroxyethyl)-ethylenediamine-N,N|,N|-triacetic acid], and NTA [N,N-bis(carboxymethyl)glycine] buffers was estimated using the ligand optimization method, and these measured values were compared with calculated values. All measurements overlapped in the pCa range of 3.51 (NTA) to 8.12 (EGTA). In all four buffer solutions, there was no correlation between measured and calculated values; the calculated values differed among themselves by factors varying from 1.3 (NTA) to 6.9 (EGTA). Independent measurements of EGTA purity and the apparent dissociation constants for HEDTA and NTA were not significantly different from the values estimated by the ligand optimization method, further substantiating the method. Using two calibration solutions of pCa 2.0 and 3.01 and seven buffers in the pCa range of 4.0-7.5, calibration of a Ca(2+) electrode over the pCa range of 2.0-7.5 became a routine procedure. It is proposed that such Ca(2+) calibration/buffer solutions be internationally defined and made commercially available to allow the precise measurement of [Ca(2+)] in biology. Copyright © 2013 Elsevier Inc. All rights reserved.

pH modulation of currents that contribute to the medium and slow afterhyperpolarizations in rat CA1 pyramidal neurones

PubMed Central

Kelly, Tony; Church, John

2004-01-01

We examined the effects of changes in pHo and pHi on currents contributing to the medium and slow afterhyperpolarizations (mIAHP and sIAHP, respectively) in rat CA1 neurones. Reducing pHo from 7.4 to 6.7 inhibited mIAHP and sIAHP whereas increasing pHo to 7.7 augmented mIAHP and, to a greater extent, sIAHP. The ability of changes in pHo to modulate mIAHP reflected changes in the Ca2+-activated K+ current, IAHP, and a Co2+- and XE991-resistant component of mIAHP, but not the muscarine-sensitive current, IM. In the presence of 1 μm TTX and 5 mm TEA, low pHo-evoked reductions in sIAHP were associated with reductions in Ca2+-dependent depolarizing potentials; because neither effect was attenuated when internal H+ buffering power was raised by including 100 mm tricine in the patch pipette, the actions of reductions in pHo to inhibit sIAHP and, possibly, IAHP in large part appear to reflect a low pHo-dependent decrease in Ca2+ influx. In contrast, the effects of high pHo to augment mIAHP and sIAHP were associated with relatively small increases in Ca2+ potentials but were significantly attenuated by 100 mm internal tricine, indicating that a rise in pHi consequent upon the rise in pHo was largely responsible. The possibility that changes in pHi could act to modulate mIAHP and sIAHP, independently of changes in Ca2+ influx, was also suggested by experiments in which pHi was lowered at a constant pHo by the external application of propionate or by the withdrawal of HCO3− from the perfusing medium. Lowering pHi at a constant pHo had little effect on Ca2+ potentials but inhibited mIAHP and, to a greater extent, sIAHP, effects that were attenuated by 100 mm internal tricine. Together, the results indicate that changes in pHo and pHi modulate mIAHP and sIAHP in rat CA1 neurones and suggest that, depending on the direction of the pHo change, the sensitivities of the underlying currents to changes in Ca2+ influx and/or pHi may contribute to the effects of changes in pHo to modulate mIAHP and sIAHP. PMID:14608014

Manganese-dependent carboanhydrase activity of photosystem II proteins.

PubMed

Shitov, A V; Pobeguts, O V; Smolova, T N; Allakhverdiev, S I; Klimov, V V

2009-05-01

Four sources of carbonic anhydrase (CA) activity in submembrane preparations of photosystem II (PS II) isolated from pea leaves were examined. Three of them belong to the hydrophilic proteins of the oxygen-evolving complex of PS II with molecular mass 33 kDa (protein PsbO), 24 kDa (protein PsbP), and 18 kDa (protein PsbQ). The fourth source of CA activity is associated with a pigment-protein complex of PS II after removing three hydrophilic proteins by salt treatment. Except for protein PsbQ, the CA activity of all these proteins depends on the presence of Mn2+: the purified protein PsbO did not show CA activity before adding Mn2+ into the medium (concentration of Mn2+ required for 50% effect, EC(50), was 670 microM); CA activity of protein mixture composed of PsbP and PsbQ increased more than 5-fold upon adding Mn2+ (EC(50) was 45 microM). CA activity of purified protein PsbP increased 2-fold in the presence of 200 microM Mn2+. As indicated for the mixture of two proteins (PsbP and PsbQ), Mg2+, Ca2+, and Zn2+, in contrast to Mn2+, suppressed CA activity (both initial and Mn2+-induced activity). Since the found sources of CA activity demonstrated properties different from ones of typical CA (need for Mn2+, insensitivity or low sensitivity to acetazolamide or ethoxyzolamide) and such CA activity was found only among PS II proteins, we cannot exclude that they belong to the type of Mn-dependent CA associated with PS II.

Silicene-terminated surface of calcium and strontium disilicides: properties and comparison with bulk structures by computational methods

NASA Astrophysics Data System (ADS)

Brázda, Petr; Mutombo, Pingo; Ondráček, Martin; Corrêa, Cinthia Antunes; Kopeček, Jaromír; Palatinus, Lukáš

2018-05-01

The bulk and surface structures of calcium and strontium disilicides are investigated by computational methods using density functional theory. The investigated structures are R6, R3 and P1-CaSi2 and P1-SrSi2. The investigated properties are the cleavage energy at the silicene sheet, buckling of the bulk and surface silicene layers, charge transfer from calcium to silicon, band structure of bulk and surface-terminated structures and adsorption energies on H atoms and H2 molecules on the silicene-terminated surface of the R3 phase. The cleavage energy at the silicene surface is low in all cases. Structures P1-CaSi2 and R3-CaSi2 contain silicene sheets with different coordination to Ca, while R6-CaSi2 contains both types of the sheets. It is shown that the properties of the two types of silicene-like sheets in R6-CaSi2 are similar to those of the corresponding sheets in P1-CaSi2 and R3-CaSi2, and the thermodynamically stable R6 phase is a good candidate for experimental investigation of silicene-terminated surface in calcium disilicide.

UTP - Gated Signaling Pathways of 5-HT Release from BON Cells as a Model of Human Enterochromaffin Cells.

PubMed

Liñán-Rico, Andromeda; Ochoa-Cortes, Fernando; Zuleta-Alarcon, Alix; Alhaj, Mazin; Tili, Esmerina; Enneking, Josh; Harzman, Alan; Grants, Iveta; Bergese, Sergio; Christofi, Fievos L

2017-01-01

Background: Enterochromaffin cells (EC) synthesize and release 5-HT and ATP to trigger or modulate gut neural reflexes and transmit information about visceral/pain sensation. Alterations in 5-HT signaling mechanisms may contribute to the pathogenesis of IBD or IBS, but the pharmacologic or molecular mechanisms modulating Ca 2+ -dependent 5-HT release are not understood. Previous studies indicated that purinergic signaling via ATP and ADP is an important mechanism in modulation of 5-HT release. However, EC cells also respond to UTP and UDP suggesting uridine triphosphate receptor and signaling pathways are involved as well. We tested the hypothesis that UTP is a regulator of 5-HT release in human EC cells. Methods: UTP signaling mechanisms were studied in BON cells, a human EC model, using Fluo-4/Ca 2+ imaging, patch-clamp, pharmacological analysis, immunohistochemistry, western blots and qPCR. 5-HT release was monitored in BON or EC isolated from human gut surgical specimens (hEC). Results: UTP, UTPγS, UDP or ATP induced Ca 2+ oscillations in BON. UTP evoked a biphasic concentration-dependent Ca 2+ response. Cells responded in the order of UTP, ATP > UTPγS > UDP > MRS2768, BzATP, α,β-MeATP > MRS2365, MRS2690, and NF546. Different proportions of cells activated by UTP and ATP also responded to UTPγS (P2Y 4 , 50% cells), UDP (P2Y 6 , 30%), UTPγS and UDP (14%) or MRS2768 (<3%). UTP Ca 2+ responses were blocked with inhibitors of PLC, IP3R, SERCA Ca 2+ pump, La 3+ sensitive Ca 2+ channels or chelation of intracellular free Ca 2+ by BAPTA/AM. Inhibitors of L-type, TRPC, ryanodine-Ca 2+ pools, PI3-Kinase, PKC or SRC-Kinase had no effect. UTP stimulated voltage-sensitive Ca 2+ currents (I Ca ), V m -depolarization and inhibited I K (not I A ) currents. An I Kv 7.2/7.3 K + channel blocker XE-991 mimicked UTP-induced V m -depolarization and blocked UTP-responses. XE-991 blocked I K and UTP caused further reduction. La 3+ or PLC inhibitors blocked UTP depolarization; PKC inhibitors, thapsigargin or zero Ca 2+ buffer did not. UTP stimulated 5-HT release in hEC expressing TPH1, 5-HT, P2Y 4 /P2Y 6 R. Zero-Ca 2+ buffer augmented Ca 2+ responses and 5-HT release. Conclusion: UTP activates a predominant P2Y 4 R pathway to trigger Ca 2+ oscillations via internal Ca 2+ mobilization through a PLC/IP 3 /IP3R/SERCA Ca 2+ signaling pathway to stimulate 5-HT release; Ca 2+ influx is inhibitory. UTP-induced V m -depolarization depends on PLC signaling and an unidentified K channel (which appears independent of Ca 2+ oscillations or I ca /VOCC). UTP-gated signaling pathways triggered by activation of P2Y 4 R stimulate 5-HT release.

p-Type CuRhO 2 as a Self-Healing Photoelectrode for Water Reduction under Visible Light

DOE PAGES

Gu, Jing; Krizan, Jason W.; Gibson, Quinn D.; ...

2013-12-30

Polycrystalline CuRhO 2 is investigated as a photocathode for the splitting of water under visible irradiation. The band edge positions of this material straddle the water oxidation and reduction redox potentials. Thus, photogenerated conduction band electrons are sufficiently energetic to reduce water, while the associated valence band holes are energetically able to oxidize water to O 2. Under visible illumination, H 2 production is observed with ~0.2 V underpotential in an air-saturated solution. In contrast, H 2 production in an Ar-saturated solution was found to be unstable. This instability is associated with the reduction of the semiconductor forming Cu(s). However,more » in the presence of air or O 2, bulk Cu(s) was not detected, implying that CuRhO 2 is self-healing when air is present. Here, this property allows for the stable formation of H 2 with ca. 80% Faradaic efficiency.« less

p-Type CuRhO 2 as a Self-Healing Photoelectrode for Water Reduction under Visible Light

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

Gu, Jing; Krizan, Jason W.; Gibson, Quinn D.

Polycrystalline CuRhO 2 is investigated as a photocathode for the splitting of water under visible irradiation. The band edge positions of this material straddle the water oxidation and reduction redox potentials. Thus, photogenerated conduction band electrons are sufficiently energetic to reduce water, while the associated valence band holes are energetically able to oxidize water to O 2. Under visible illumination, H 2 production is observed with ~0.2 V underpotential in an air-saturated solution. In contrast, H 2 production in an Ar-saturated solution was found to be unstable. This instability is associated with the reduction of the semiconductor forming Cu(s). However,more » in the presence of air or O 2, bulk Cu(s) was not detected, implying that CuRhO 2 is self-healing when air is present. Here, this property allows for the stable formation of H 2 with ca. 80% Faradaic efficiency.« less

Suppression in the electrical hysteresis by using CaF2 dielectric layer for p-GaN MIS capacitors

NASA Astrophysics Data System (ADS)

Sang, Liwen; Ren, Bing; Liao, Meiyong; Koide, Yasuo; Sumiya, Masatomo

2018-04-01

The capacitance-voltage (C-V) hysteresis in the bidirectional measurements of the p-GaN metal-insulator-semiconductor (MIS) capacitor is suppressed by using a CaF2 dielectric layer and a post annealing treatment. The density of trapped charge states at the CaF2/p-GaN interface is dramatically reduced from 1.3 × 1013 cm2 to 1.1 × 1011/cm2 compared to that of the Al2O3/p-GaN interface with a large C-V hysteresis. It is observed that the disordered oxidized interfacial layer can be avoided by using the CaF2 dielectric. The downward band bending of p-GaN is decreased from 1.51 to 0.85 eV as a result of the low-density oxides-related trap states. Our work indicates that the CaF2 can be used as a promising dielectric layer for the p-GaN MIS structures.

Evidence from mathematical modeling that carbonic anhydrase II and IV enhance CO2 fluxes across Xenopus oocyte plasma membranes

PubMed Central

Musa-Aziz, Raif; Boron, Walter F.

2014-01-01

Exposing an oocyte to CO2/HCO3− causes intracellular pH (pHi) to decline and extracellular-surface pH (pHS) to rise to a peak and decay. The two companion papers showed that oocytes injected with cytosolic carbonic anhydrase II (CA II) or expressing surface CA IV exhibit increased maximal rate of pHi change (dpHi/dt)max, increased maximal pHS changes (ΔpHS), and decreased time constants for pHi decline and pHS decay. Here we investigate these results using refinements of an earlier mathematical model of CO2 influx into a spherical cell. Refinements include 1) reduced cytosolic water content, 2) reduced cytosolic diffusion constants, 3) refined CA II activity, 4) layer of intracellular vesicles, 5) reduced membrane CO2 permeability, 6) microvilli, 7) refined CA IV activity, 8) a vitelline membrane, and 9) a new simulation protocol for delivering and removing the bulk extracellular CO2/HCO3− solution. We show how these features affect the simulated pHi and pHS transients and use the refined model with the experimental data for 1.5% CO2/10 mM HCO3− (pHo = 7.5) to find parameter values that approximate ΔpHS, the time to peak pHS, the time delay to the start of the pHi change, (dpHi/dt)max, and the change in steady-state pHi. We validate the revised model against data collected as we vary levels of CO2/HCO3− or of extracellular HEPES buffer. The model confirms the hypothesis that CA II and CA IV enhance transmembrane CO2 fluxes by maximizing CO2 gradients across the plasma membrane, and it predicts that the pH effects of simultaneously implementing intracellular and extracellular-surface CA are supra-additive. PMID:24965589

A model of cardiac ryanodine receptor gating predicts experimental Ca2+-dynamics and Ca2+-triggered arrhythmia in the long QT syndrome

NASA Astrophysics Data System (ADS)

Wilson, Dan; Ermentrout, Bard; Němec, Jan; Salama, Guy

2017-09-01

Abnormal Ca2+ handling is well-established as the trigger of cardiac arrhythmia in catecholaminergic polymorphic ventricular tachycardia and digoxin toxicity, but its role remains controversial in Torsade de Pointes (TdP), the arrhythmia associated with the long QT syndrome (LQTS). Recent experimental results show that early afterdepolarizations (EADs) that initiate TdP are caused by spontaneous (non-voltage-triggered) Ca2+ release from Ca2+-overloaded sarcoplasmic reticulum (SR) rather than the activation of the L-type Ca2+-channel window current. In bradycardia and long QT type 2 (LQT2), a second, non-voltage triggered cytosolic Ca2+ elevation increases gradually in amplitude, occurs before overt voltage instability, and then precedes the rise of EADs. Here, we used a modified Shannon-Puglisi-Bers model of rabbit ventricular myocytes to reproduce experimental Ca2+ dynamics in bradycardia and LQT2. Abnormal systolic Ca2+-oscillations and EADs caused by SR Ca2+-release are reproduced in a modified 0-dimensional model, where 3 gates in series control the ryanodine receptor (RyR2) conductance. Two gates control RyR2 activation and inactivation and sense cytosolic Ca2+ while a third gate senses luminal junctional SR Ca2+. The model predicts EADs in bradycardia and low extracellular [K+] and cessation of SR Ca2+-release terminate salvos of EADs. Ca2+-waves, systolic cell-synchronous Ca2+-release, and multifocal diastolic Ca2+ release seen in subcellular Ca2+-mapping experiments are observed in the 2-dimensional version of the model. These results support the role of SR Ca2+-overload, abnormal SR Ca2+-release, and the subsequent activation of the electrogenic Na+/Ca2+-exchanger as the mechanism of TdP. The model offers new insights into the genesis of cardiac arrhythmia and new therapeutic strategies.

Hypertrophic cardiomyopathy mutation in cardiac troponin T (R95H) attenuates length-dependent activation in guinea pig cardiac muscle fibers.

PubMed

Mickelson, Alexis V; Chandra, Murali

2017-12-01

The central region of cardiac troponin T (TnT) is important for modulating the dynamics of muscle length-mediated cross-bridge recruitment. Therefore, hypertrophic cardiomyopathy mutations in the central region may affect cross-bridge recruitment dynamics to alter myofilament Ca 2+ sensitivity and length-dependent activation of cardiac myofilaments. Given the importance of the central region of TnT for cardiac contractile dynamics, we studied if hypertrophic cardiomyopathy-linked mutation (TnT R94H )-induced effects on contractile function would be differently modulated by sarcomere length (SL). Recombinant wild-type TnT (TnT WT ) and the guinea pig analog of the human R94H mutation (TnT R95H ) were reconstituted into detergent-skinned cardiac muscle fibers from guinea pigs. Steady-state and dynamic contractile measurements were made at short and long SLs (1.9 and 2.3 µm, respectively). Our results demonstrated that TnT R95H increased pCa 50 (-log of free Ca 2+ concentration) to a greater extent at short SL; TnT R95H increased pCa 50 by 0.11 pCa units at short SL and 0.07 pCa units at long SL. The increase in pCa 50 associated with an increase in SL from 1.9 to 2.3 µm (ΔpCa 50 ) was attenuated nearly twofold in TnT R95H fibers; ΔpCa 50 was 0.09 pCa units for TnT WT fibers but only 0.05 pCa units for TnT R95H fibers. The SL dependency of rate constants of cross-bridge distortion dynamics and tension redevelopment was also blunted by TnT R95H Collectively, our observations on the SL dependency of pCa 50 and rate constants of cross-bridge distortion dynamics and tension redevelopment suggest that mechanisms underlying the length-dependent activation cardiac myofilaments are attenuated by TnT R95H NEW & NOTEWORTHY Mutant cardiac troponin T (TnT R95H ) differently affects myofilament Ca 2+ sensitivity at short and long sarcomere length, indicating that mechanisms underlying length-dependent activation are altered by TnT R95H TnT R95H enhances myofilament Ca 2+ sensitivity to a greater extent at short sarcomere length, thus attenuating the length-dependent increase in myofilament Ca 2+ sensitivity. Copyright © 2017 the American Physiological Society.

Conditions of Mytilus edulis extracellular body fluids and shell composition in a pH-treatment experiment: Acid-base status, trace elements and δ11B

NASA Astrophysics Data System (ADS)

Heinemann, Agnes; Fietzke, Jan; Melzner, Frank; BöHm, Florian; Thomsen, JöRn; Garbe-SchöNberg, Dieter; Eisenhauer, Anton

2012-01-01

Mytilus edulis were cultured for 3 months under six different seawater pCO2 levels ranging from 380 to 4000 μatm. Specimen were taken from Kiel Fjord (Western Baltic Sea, Germany) which is a habitat with high and variable seawater pCO2 and related shifts in carbonate system speciation (e.g., low pH and low CaCO3 saturation state). Hemolymph (HL) and extrapallial fluid (EPF) samples were analyzed for pH and total dissolved inorganic carbon (CT) to calculate pCO2 and [HCO3-]. A second experiment was conducted for 2 months with three different pCO2 levels (380, 1400 and 4000 μatm). Boron isotopes (δ11B) were investigated by LA-MC-ICP-MS (Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry) in shell portions precipitated during experimental treatment time. Additionally, elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF of specimen from the second experiment were measured via ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry). Extracellular pH was not significantly different in HL and EPF but systematically lower than ambient water pH. This is due to high extracellular pCO2 values, a prerequisite for metabolic CO2 excretion. No accumulation of extracellular [HCO3-] was measured. Elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF increased slightly with pH which is in accordance with increasing growth and calcification rates at higher seawater pH values. Boron isotope ratios were highly variable between different individuals but also within single shells. This corresponds to a high individual variability in fluid B/Ca ratios and may be due to high boron concentrations in the organic parts of the shell. The mean δ11B value shows no trend with pH but appears to represent internal pH (EPF) rather than ambient water pH.

Calcium signaling in liver.

PubMed

Gaspers, Lawrence D; Thomas, Andrew P

2005-01-01

In hepatocytes, hormones linked to the formation of the second messenger inositol 1,4,5-trisphosphate (InsP3) evoke transient increases or spikes in cytosolic free calcium ([Ca2+]i), that increase in frequency with the agonist concentration. These oscillatory Ca2+ signals are thought to transmit the information encoded in the extracellular stimulus to down-stream Ca2+-sensitive metabolic processes. We have utilized both confocal and wide field fluorescence microscopy techniques to study the InsP3-dependent signaling pathway at the cellular and subcellular levels in the intact perfused liver. Typically InsP3-dependent [Ca2+]i spikes manifest as Ca2+ waves that propagate throughout the entire cytoplasm and nucleus, and in the intact liver these [Ca2+]i increases are conveyed through gap junctions to encompass entire lobular units. The translobular movement of Ca2+ provides a means to coordinate the function of metabolic zones of the lobule and thus, liver function. In this article, we describe the characteristics of agonist-evoked [Ca2+]i signals in the liver and discuss possible mechanisms to explain the propagation of intercellular Ca2+ waves in the intact organ.

Local structure in LaMnO3 and CaMnO3 perovskites: A quantitative structural refinement of Mn K -edge XANES data

NASA Astrophysics Data System (ADS)

Monesi, C.; Meneghini, C.; Bardelli, F.; Benfatto, M.; Mobilio, S.; Manju, U.; Sarma, D. D.

2005-11-01

Hole-doped perovskites such as La1-xCaxMnO3 present special magnetic and magnetotransport properties, and it is commonly accepted that the local atomic structure around Mn ions plays a crucial role in determining these peculiar features. Therefore experimental techniques directly probing the local atomic structure, like x-ray absorption spectroscopy (XAS), have been widely exploited to deeply understand the physics of these compounds. Quantitative XAS analysis usually concerns the extended region [extended x-ray absorption fine structure (EXAFS)] of the absorption spectra. The near-edge region [x-ray absorption near-edge spectroscopy (XANES)] of XAS spectra can provide detailed complementary information on the electronic structure and local atomic topology around the absorber. However, the complexity of the XANES analysis usually prevents a quantitative understanding of the data. This work exploits the recently developed MXAN code to achieve a quantitative structural refinement of the Mn K -edge XANES of LaMnO3 and CaMnO3 compounds; they are the end compounds of the doped manganite series LaxCa1-xMnO3 . The results derived from the EXAFS and XANES analyses are in good agreement, demonstrating that a quantitative picture of the local structure can be obtained from XANES in these crystalline compounds. Moreover, the quantitative XANES analysis provides topological information not directly achievable from EXAFS data analysis. This work demonstrates that combining the analysis of extended and near-edge regions of Mn K -edge XAS spectra could provide a complete and accurate description of Mn local atomic environment in these compounds.

Formation of the Shelf-edge Cretaceous-Tertiary contact off the southeastern U.S. Coast

USGS Publications Warehouse

Poppe, L.J.; Hathaway, J.C.; Hall, R.E.; Commeau, R.F.

1986-01-01

Submarine erosion, associated with changes in position of the proto-Gulf Stream, was the dominant mechanism controlling the formation of the Cretaceous-Tertiary unconformity in AMCOR borehole 6004. Paleontologic evidence indicates that this unconformity, which is marked by a gravelly-sand enriched in glauconitic and phosphoritic concretions, represents a hiatus of about 7 m.y. Both Cretaceous and Paleocene sediments contain middle-outer neritic foraminiferal assemblages that become more diverse with distance from the contact. Of the elemental abundances measured, Al, Ba, Co, Fe, Ga, K, Mg/Ca, Mo, Ni, P, Sr/Ca, V, Y, and Zn show a strong positive correlation with proximity to the contact, probably as a result of the concentration of authigenic and heavy minerals present as lag sediments on the erosion surface. ?? 1986.

HER2 over-expressing high grade endometrial cancer expresses high levels of p95HER2 variant.

PubMed

Growdon, Whitfield B; Groeneweg, Jolijn; Byron, Virginia; DiGloria, Celeste; Borger, Darrell R; Tambouret, Rosemary; Foster, Rosemary; Chenna, Ahmed; Sperinde, Jeff; Winslow, John; Rueda, Bo R

2015-04-01

Subsets of high grade endometrial cancer (EnCa) over-express HER2 (ERBB2), yet clinical trials have failed to demonstrate any anti-tumor activity utilizing trastuzumab, an approved platform for HER2 positive breast cancer (BrCa). A truncated p95HER2 variant lacking the trastuzumab binding site may confer resistance. The objective of this investigation was to characterize the expression of the p95HER2 truncated variant in EnCa. With institutional approval, 86 high grade EnCa tumors were identified with tumor specimens from surgeries performed between 2000 and 2011. Clinical data were collected and all specimens underwent tumor genotyping, HER2 immunohistochemistry (IHC, HercepTest®), HER2 fluorescent in situ hybridization (FISH), along with total HER2 (H2T) and p95HER2 assessment with VeraTag® testing. Regression models were used to compare a cohort of 86 breast tumors selected for equivalent HER2 protein expression. We identified 44 high grade endometrioid and 42 uterine serous carcinomas (USC). IHC identified high HER2 expression (2+ or 3+) in 59% of the tumors. HER2 gene amplification was observed in 16 tumors (12 USC, 4 endometrioid). Both HER2 gene amplification and protein expression correlated with H2T values. High p95HER2 expression above 2.8RF/mm2 was observed in 53% (n=54) with significant correlation with H2T levels. When matched to a cohort of 107 breast tumors based on HercepTest HER2 expression, high grade EnCa presented with higher p95 levels (p<0.001). These data demonstrate that compared to BrCa, high grade EnCa expresses higher levels of p95HER2 possibly providing rationale for the trastuzumab resistance observed in EnCa. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Effects of substance P on spontaneous contraction in the flexure region of the guinea pig colon.

PubMed

Chowdhury, J U; Nahar, N S

2007-01-01

Effects of Substance P on spontaneous contractions of the circular muscle of the flexure region of guinea pig colon were studied by mechanical tension recording. Substance P (3 nM-10 nM) produced tonic contraction associated with phasic activities but the contraction was found stronger at higher concentration. Verapamil (3 microM), a voltage dependent L-type Ca(2+) channel blocker completely blocked the spontaneous activities and also Substance P induced contraction. These results suggest that Substance P produce contraction by Ca(2+) influx and the Ca(2+) influx occurs by activating verapamil sensitive Ca(2+) channel.

Temperature-dependence of L-type Ca(2+) current in ventricular cardiomyocytes of the Alaska blackfish (Dallia pectoralis).

PubMed

Kubly, Kerry L; Stecyk, Jonathan A W

2015-12-01

To lend insight into the overwintering strategy of the Alaska blackfish (Dallia pectoralis), we acclimated fish to 15 or 5 °C and then utilized whole-cell patch clamp to characterize the effects of thermal acclimation and acute temperature change on the density and kinetics of ventricular L-type Ca(2+) current (I Ca). Peak I Ca density at 5 °C (-1.1 ± 0.1 pA pF(-1)) was 1/8th that at 15 °C (-8.8 ± 0.6 pA pF(-1)). However, alterations of the Ca(2+)- and voltage-dependent inactivation properties of L-type Ca(2+) channels partially compensated against the decrease. The time constant tau (τ) for the kinetics of inactivation of I Ca was ~4.5 times greater at 5 °C than at 15 °C, and the voltage for half-maximal inactivation was shifted from -23.3 ± 1.0 mV at 15 °C to -19.8 ± 1.2 mV at 5 °C. These modifications increase the open probability of the channel and culminate in an approximate doubling of the L-type Ca(2+) window current, which contributes to approximately 15% of the maximal Ca(2+) conductance at 5 °C. Consequently, the charge density of I Ca (Q Ca) and the total Ca(2+) transferred through the L-type Ca(2+) channels (Δ[Ca(2+)]) were not as severely reduced at 5 °C as compared to peak I Ca density. In combination, the results suggest that while the Alaska blackfish substantially down-regulates I Ca with acclimation to low temperature, there is sufficient compensation in the kinetics of the L-type Ca(2+) channel to support the level of cardiac performance required for the fish to remain active throughout the winter.

A pK change of acidic residues contributes to cation countertransport in the Ca-ATPase of sarcoplasmic reticulum. Role of H+ in Ca(2+)-ATPase countertransport.

PubMed

Yu, X; Hao, L; Inesi, G

1994-06-17

Proteoliposomal vesicles reconstituted with sarcoplasmic reticulum ATPase and exogenous lipids sustain ATP-dependent Ca2+ uptake and H+ ejection, as well as net charge displacement by Ca2+. We have studied the effect of lumenal (inner) and medium (extravesicular) pH variations on the countertransport ratios of H+ and Ca2+. We find that the Ca2+/H+ molar ratio is approximately 1 when the lumenal and medium pH is near neutrality, but changes with a specific pattern when the medium pH is varied in the presence of a constant lumenal pH and when the lumenal pH is varied in the presence of a constant medium pH. Empirical analysis of the experimental data shows that the apparent pK of the residue(s) releasing H+ into the medium is approximately 6.1, whereas the apparent pK of the residue(s) binding lumenal H+ is approximately 7.7. Assuming that the same acidic residues are involved in H+ and Ca2+ countertransport, our findings suggest a lower affinity for H+ in their outward orientation (prevalent in the ground state of the enzyme) and a higher affinity for H+ in lumenal orientation (prevalent in the phosphorylated state of the enzyme). Cyclic pK changes, coupled to ATP utilization, promote cation exchange, Ca2+ uptake, and H+ ejection by the vesicles. The stoichiometry of countertransport and net charge displacement is matched by a corresponding electrogenic behavior. A calculation of voltage development related to initial rates of charge transfer (dV/dt = (dQ/dt)/Cm) is given as a corrective replacement of a previous steady state calculation.

High calcium to phosphorus ratio impairs growth and bone mineralization in Pekin ducklings.

PubMed

Zhu, Y W; Wen, J; Jiang, X X; Wang, W C; Yang, L

2018-04-01

Two experiments were conducted to investigate the effect of high dietary calcium (Ca) level on growth performance, Ca and phosphorus (P) metabolism, and nutrient utilization in ducklings subjected to normal and low P levels in diets. A completely randomized design was used with a factorial arrangement of 2 total dietary P levels [normal-P (0.60%) and low-P (0.45%) groups] × 4 dietary Ca levels [low-Ca (0.55%), normal-Ca (0.75%), medium-Ca (0.95%) and high-Ca (1.15%) groups)]. Compared to normal-P group, low-P group had lower (P < 0.05) final body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI) and reduced (P < 0.05) serum Ca and P levels, bone Ca, P, and ash content, and bone mineral density in ducklings during the starter period. Under the low-P group, birds from high-Ca group had lower (P < 0.05) final BW, ADG, ADFI, bone ash content, bone mineral density, and the utilization of energy, Ca, and P than those from low-Ca, normal-Ca, and medium-Ca groups. Our results indicate that high-Ca diet induced greater growth suppression and bone mineralization loss in ducklings fed a low-P diet. The aggravated negative effect of high dietary Ca level with a low P level might be related to the elevated serum alkaline phosphatase activity and the reduced utilization of energy, Ca, and P.

Immunolocalization of NR1, NR2A, and PSD-95 in rat hippocampal subregions during postnatal development.

PubMed

Ling, Wei; Chang, Lirong; Song, Yizhi; Lu, Tao; Jiang, Yuhua; Li, Youxiang; Wu, Yan

2012-05-01

Although the expression of NMDARs and synaptic-associated proteins has been widely studied, the temporospatial distribution of NMDAR subunits and synaptic proteins in different hippocampal subregions during postnatal development still lacks detailed information, and the relationship between NR1 or NR2 subunits and PSD-95 family proteins is controversial. In this study, we used immunofluorescent staining to assess NR1 or NR2A and PSD-95 expressions and the relationship between them in CA1, CA3, and DG of rat hippocampus on postnatal (P) days: P0, P4, P7, P10, P14, P21, P28, P56. The results showed that from P0 to P56, NR1, NR2A, and PSD-95 expressions increased gradually, and the time points of their expression peak differed in CA1, CA3, and DG during postnatal development. Interestingly, although the expression of PSD-95 was positively correlated to both NR1 and NR2A, the NR1 and PSD-95 coexpressed puncta were greatest in CA3, while NR2A and PSD-95 coexpressed puncta were greatest in CA1, compared to other subregions. Surprisingly, at P21, among different strata of CA1, the area of highest expression of NR2A was dramatically changed from stratum pyramidale to stratum polymorphum and stratum moleculare, and returned to stratum pyramidale gradually on the later observed days again, indicating that P21 may be one critical timepoint during postnatal development in CA1. The specific temporospatial distribution pattern of NR1, NR2A, and PSD-95 might be related to the different physiological functions during postnatal development. Discovering the alteration of the relationship between PSD-95 and NMDAR subunits expression may be helpful for understanding mechanisms and therapy of neurodegenerative diseases. Copyright © 2011 Elsevier GmbH. All rights reserved.

MUC1, MUC2, MUC4, MUC5AC and MUC6 expression in the progression of prostate cancer.

PubMed

Cozzi, Paul J; Wang, Jian; Delprado, Warick; Perkins, Alan C; Allen, Barry J; Russell, Pamela J; Li, Yong

2005-01-01

Molecular changes are vital for the development of prognostic markers and therapeutic modalities of prostate cancer (CaP). There is growing interest in mucins as treatment targets in human malignancies, including CaP. The role of their expression in the progression of CaP is however unclear. We examined the expressions MUC1, MUC2, MUC4, MUC5AC and MUC6 in CaP tissues using tissue microarrays (TMAs) to look for tumor-associated antigens (TAAs) for targeted therapy. In this study, 120 paraffin-embedded specimens were selected from patients who underwent radical retro-pubic prostatectomy (RRP) or trans-urethral-resection of the prostate (TURP) for primary, untreated CaP and 10 matched lymph node metastases. A series of MUC monoclonal antibodies (mAbs) was used on TMAs by standard immunohistochemistry. Our results indicate that the over-expression of MUC1 was detected in 58% of primary CaP tissues and 90% of lymph node metastases but not in normal prostate or benign tissues, while the expression of MUC2, MUC4, MUC5AC and MUC6 was found to be negative in both normal and cancer tissues. Of the MUC1 positive tumors 86% were Gleason grade 7 or higher. Over-expression of MUC1 was found in late stage CaP while MUC2, 4, 5AC and 6 were negative in CaP. MUC1 is a TAA that is highly related to tumor progression in CaP patients. This antigen is ideal for targeted therapy to control micrometastases and hormone refractory disease but additional studies are necessary to assess its usefulness in patient biopsies and CaP bone metastases before clinical trial.

A Putative Mechanism of Age-Related Synaptic Dysfunction Based on the Impact of IGF-1 Receptor Signaling on Synaptic CaMKIIα Phosphorylation.

PubMed

Ogundele, Olalekan M; Pardo, Joaquin; Francis, Joseph; Goya, Rodolfo G; Lee, Charles C

2018-01-01

Insulin-like growth factor 1 receptor (IGF-1R) signaling regulates the activity and phosphorylation of downstream kinases linked to inflammation, neurodevelopment, aging and synaptic function. In addition to the control of Ca 2+ currents, IGF-1R signaling modulates the activity of calcium-calmodulin-dependent kinase 2 alpha (CaMKIIα) and mitogen activated protein kinase (MAPK/ErK) through multiple signaling pathways. These proteins (CaMKIIα and MAPK) regulate Ca 2+ movement and long-term potentiation (LTP). Since IGF-1R controls the synaptic activity of Ca 2+ , CaMKIIα and MAPK signaling, the possible mechanism through which an age-dependent change in IGF-1R can alter the synaptic expression and phosphorylation of these proteins in aging needs to be investigated. In this study, we evaluated the relationship between an age-dependent change in brain IGF-1R and phosphorylation of CaMKIIα/MAPK. Furthermore, we elucidated possible mechanisms through which dysregulated CaMKIIα/MAPK interaction may be linked to a change in neurotransmitter processing and synaptic function. Male C57BL/6 VGAT-Venus mice at postnatal days 80 (P80), 365 and 730 were used to study age-related neural changes in two brain regions associated with cognitive function: hippocampus and prefrontal cortex (PFC). By means of high throughput confocal imaging and quantitative immunoblotting, we evaluated the distribution and expression of IGF-1, IGF-1R, CaMKIIα, p-CaMKIIα, MAPK and p-MAPK in whole brain lysate, hippocampus and cortex. Furthermore, we compared protein expression patterns and regional changes at P80, P365 and P730. Ultimately, we determined the relative phosphorylation pattern of CaMKIIα and MAPK through quantification of neural p-CaMKIIα and p-MAPK/ErK, and IGF-1R expression for P80, P365 and P730 brain samples. In addition to a change in synaptic function, our results show a decrease in neural IGF-1/IGF-1R expression in whole brain, hippocampus and cortex of aged mice. This was associated with a significant upregulation of phosphorylated neural MAPK (p-MAPK) and decrease in total brain CaMKIIα (i.e., CaMKIIα and p-CaMKIIα) in the aged brain. Taken together, we showed that brain aging is associated with a change in neural IGF-1/IGF-1R expression and may be linked to a change in phosphorylation of synaptic kinases (CaMKIIα and MAPK) that are involved in the modulation of LTP.

Digestive utilization of phosphorus from plant-based diets in the Cassie line of transgenic Yorkshire pigs that secrete phytase in the saliva.

PubMed

Meidinger, R G; Ajakaiye, A; Fan, M Z; Zhang, J; Phillips, J P; Forsberg, C W

2013-03-01

A line of transgenic Yorkshire pigs referred to as the Cassie (CA) line was generated, which possessed a stable, low copy number phytase transgene insertion that enabled phytase secretion in the saliva. This study was conducted to assess growth and efficacy for improving P, Ca, and other macromineral utilization in the CA pigs receiving diets typical of those used for commercial swine production. In Exp. 1, 12 CA boars and 12 CA gilts fed diets without supplemental P gained weight and exhibited feed efficiency similar to conventional age-matched 12 Yorkshire boars and 12 Yorkshire gilts raised on similar diets with supplemental P. Serum concentrations of P and Ca were similar for CA and Yorkshire pigs during the growing and finishing phases, indicating that the CA pigs were not P limited. In Exp. 2, 6 CA (13.1 kg BW) and 6 Yorkshire barrows (8.8 kg BW) were fed 3 diets (control; low in Ca and P; and low in Ca, P, and CP) over 3 phases. The CA barrows fed the diet without supplemental P retained 25 to 40% (P < 0.001), 77 to 91% (P < 0.001), and 27 to 56% (P < 0.001) more P during the weaning, growing, and finishing phases, respectively, than conventional Yorkshire barrows fed similar diets without supplemental P. In Exp. 3, CA and Yorkshire barrows of similar ages weighing 66.2 ± 1.7 kg (n = 10) and 50.0 ± 1.0 kg (n = 10), respectively, were used. The P retention of CA finisher barrows fed a diet without supplemental P was 34% greater (P < 0.001) than conventional Yorkshire barrows fed the same diet with 750 units of exogenous phytase/kg diet. Urinary Ca to P ratio in the CA pigs was 0.27, whereas that for the Yorkshire barrows was 30, thereby, indicating that the Yorkshire barrows suffered a P deficiency. Furthermore, digestive utilization of major electrolyte macrominerals, K and Na, was improved (P < 0.05) by 18 and 16%, respectively, in the CA finisher pigs compared with the conventional Yorkshire finisher pigs fed phytase; however, only K exhibited enhanced retention. In conclusion, the CA line pigs secrete sufficient phytase from the salivary glands to enable efficient digestion of plant P, Ca, and major electrolyte macrominerals.

Characteristics of inositol trisphosphate-mediated Ca/sup 2 +/ release from permeabilized hepatocytes

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

Joseph, S.K.; Williamson, J.R.

1986-11-05

Ca/sup 2 +/ release triggered by inositol trisphosphate (Ins(1,4,5)P/sub 3/) has been measured in saponin-permeabilized hepatocytes with /sup 45/Ca/sup 2 +/ or Quin 2. The initial rate of Ca/sup 2 +/ release was not greatly affected by the incubation temperature. The amount of Ca/sup 2 +/ released by Ins(1,4,5)P/sub 3/ was not affected by pH (6.5-8.0). La/sup 3 +/ (100 ..mu..M) markedly inhibited the effect of 1 ..mu..M Ins(1,4,5)P/sub 3/. The possibility that La/sup 3 +/ chelates Ins(1,4,5)P/sub 3/ cannot be excluded since the effect of La/sup 3 +/ could be overcome by increasing the Ins(1,4,5)P/sub 3/ concentration. Ins(1,4,5)P/sub 3/-mediatedmore » Ca/sup 2 +/ release showed a requirement for permeant cations in the incubation medium. Optimal release was observed with potassium gluconate. Other monovalent cations, with the exception of Li/sup +/, can substitute for K/sup +/. Permeant anions, at concentrations above 40 mM, inhibited Ca/sup 2 +/ release produced by Ins(1,4,5)P/sub 3/. Cl/sup -/, Br/sup -/, I/sup -/, and SO/sup 2 -//sub 4/ were equally effective as inhibitors. Ins(1,4,5)P/sub 3/ also caused the release of /sup 54/Mn/sup 2 +/ and /sup 85/Sr/sup 2 +/ accumulated by the permeabilized hepatocytes. The results are consistent with Ins(1,4,5)P/sub 3/ promoting the membrane translocation of divalent cations through an ion channel rather than an ion carrier. The translocation of positive charge through this channel is balanced by ancillary movements of monovalent cations and anions across the reticular membranes. The transport systems responsible for these compensatory ion movements may represent a potential site for the regulation of the hormone-mediated Ca/sup 2 +/ signal.« less

Calcium Hypochlorite Solutions: Evaluation of Surface Tension and Effect of Different Storage Conditions and Time Periods over pH and Available Chlorine Content.

PubMed

Leonardo, Natália Gomes e Silva; Carlotto, Israel Bangel; Luisi, Simone Bonato; Kopper, Patrícia Maria Poli; Grecca, Fabiana Soares; Montagner, Francisco

2016-04-01

The aim of this study was to evaluate the pH and the available chlorine content from sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca[OCl]2) solutions stored in different conditions and time periods and the surface tension of Ca(OCl)2 solutions in comparison with NaOCl. Solutions at 0.5%, 1%, 2.5%, and 5.25% concentrations were prepared. The pH level and the available chlorine content of freshly prepared solutions and solutions stored for 30, 60, and 90 days at 25°C, 4°C, or 37°C were evaluated in a digital pH meter and by titration, respectively. Surface tension was tested using a Du Nouy tensiometer (Sigma 702, Force Tensiometer; Attension, Espoo, Finland). Descriptive and inferential statistical analyses were performed. A precipitate formed by 2.5% and 5.25% Ca(OCl)2 solutions was observed. Ca(OCl)2 showed a higher concentration of available chlorine than NaOCl. Both 2.5% and 5.25% NaOCl and Ca(OCl)2 had a decrease in the available chlorine content when compared with freshly prepared solutions; 0.5% and 1% NaOCl tend to have a lower pH compared with 0.5% and 1% Ca(OCl)2. NaOCl, 5.25%, showed higher pH compared with 5.25% Ca(OCl)2. NaOCl and Ca(OCl)2 in 0.5% and 1% concentrations tend to show a reduced pH level, whereas 2.5% and 5.25% solutions showed an increase in pH. The heat contributed to the instability of the solutions. NaOCl showed lower surface tension values than Ca(OCl)2. Ca(OCl)2 solutions are extremely alkaline and tend to have more available chlorine content than NaOCl but have a higher surface tension than NaOCl. Regarding the available chlorine content, these solutions tend to be stable to 30 days of storage when kept at 4°C or at 25°C. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effect of Ca sup 2+ on Cl sup minus transport in thin ascending limb of Henle's loop

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

Kondo, Yoshiaki; Yoshitomi, Koji; Imai, Masashi

1988-02-01

Effects of ambient Ca{sup 2+} concentration on Cl{sup {minus}} transport across the thin ascending limb of Henle's loop (TAL) were examined by the in vitro microperfusion technique. When Ca{sup 2+} concentration in the bathing fluid was decreased from 1.5 mM to nominally 0 mM at 37{degree}C, the relative permeability of Cl{sup {minus}} to Na{sup +} (P{sub Cl}/P{sub Na}) estimated from the NaCl diffusion voltage changed from 2.44 to 1.27. When Ca{sup 2+} concentration of the luminal fluid was reduced, P{sub Cl}/P{sub Na} was unchanged. When Ca{sup 2+} concentration in the bathing fluid was change from 4.5 to nominally 0 mM,more » the lumen-to-bath flux coefficient for {sup 36}Cl (K{sub 1{yields}b}{sup 36Cl}) was decreased, whereas the value of {sup 22}Na was unchanged, indicating that the reduction of Ca{sup 2+} concentration in the bathing fluid selectively inhibits Cl{sup {minus}} transport without affecting Na{sup +} transport. The pH titration curves of relative Cl{sup {minus}} permeability examined at three different Ca{sup 2+} concentrations at 37{degree}C revealed that the interaction between proton and Ca{sup +} was noncompetitive. Addition of quin 2-AM, which reduced intracellular Ca{sup 2+} concentration, to the bath caused an irreversible suppression of Cl{sup {minus}} permeability, suggesting that the decrease in intracellular Ca{sup 2+} concentration also inhibits the Cl{sup {minus}} transport across the TAL. From these observations the authors suggest: (1) Cl{sup {minus}} transport across the TAL is regulated by Ca{sup 2+} preferentially on the basolateral membrane; (2) this regulation depends on temperature; and (3) there is a noncompetitive interaction between Ca{sup 2+} and proton in the regulation of the conductive Cl{sup {minus}} pathway.« less

Ca(2+)-stores mobilization by diadenosine tetraphosphate, Ap4A, through a putative P2Y purinoceptor in adrenal chromaffin cells.

PubMed Central

Castro, E.; Pintor, J.; Miras-Portugal, M. T.

1992-01-01

1. Diadenosine tetraphosphate (Ap4A) evoked a concentration-dependent increase in cytosolic [Ca2+] in resting chromaffin cells. The EC50 value for this action was 28.2 +/- 6.6 microM. This effect was also produced by diadenosine pentaphosphate (Ap5A) with an EC50 of 50 +/- 7 microM. 2. In contrast with this effect, pretreatment with Ap4A or Ap5A induced a 30% reduction in Ca2+ entry following 10 microM dimethylphenylpiperazinium. 3. The elevation in cytosolic [Ca2+] induced by Ap4A was persistent in approximately 100 nM external [Ca2+] and was sensitive to depletion of internal Ca2+ stores by a bradykinin prepulse or whole cell depletion in Ca2+. 4. The effect of Ap4A was mimicked and desensitized by the agonist adenosine 5'-O-(2-thiodiphosphate), and blocked by the P2Y-receptor antagonist, cibachrome blue. The P2X-receptor agonist alpha,beta-methylene adenosine 5'-triphosphate was inactive both by itself or in combination with Ap4A. This is compatible with a P2Y-purinoceptor-mediated action. PMID:1393282

Ca(2+)-stores mobilization by diadenosine tetraphosphate, Ap4A, through a putative P2Y purinoceptor in adrenal chromaffin cells.

PubMed

Castro, E; Pintor, J; Miras-Portugal, M T

1992-08-01

1. Diadenosine tetraphosphate (Ap4A) evoked a concentration-dependent increase in cytosolic [Ca2+] in resting chromaffin cells. The EC50 value for this action was 28.2 +/- 6.6 microM. This effect was also produced by diadenosine pentaphosphate (Ap5A) with an EC50 of 50 +/- 7 microM. 2. In contrast with this effect, pretreatment with Ap4A or Ap5A induced a 30% reduction in Ca2+ entry following 10 microM dimethylphenylpiperazinium. 3. The elevation in cytosolic [Ca2+] induced by Ap4A was persistent in approximately 100 nM external [Ca2+] and was sensitive to depletion of internal Ca2+ stores by a bradykinin prepulse or whole cell depletion in Ca2+. 4. The effect of Ap4A was mimicked and desensitized by the agonist adenosine 5'-O-(2-thiodiphosphate), and blocked by the P2Y-receptor antagonist, cibachrome blue. The P2X-receptor agonist alpha,beta-methylene adenosine 5'-triphosphate was inactive both by itself or in combination with Ap4A. This is compatible with a P2Y-purinoceptor-mediated action.

Preparation and characterizations of bioglass ceramic cement/Ca-P coating on pure magnesium for biomedical applications.

PubMed

Zhang, Xue; Li, Xiao-Wu; Li, Ji-Guang; Sun, Xu-Dong

2014-01-08

Magnesium has been recently recognized as a biodegradable metal for bone substitute applications. In order to improve the biocompatibility and osteointegration of pure Mg, two kinds of coatings, i.e., the Ca-P coating and bioglass ceramic cement (BGCC)/Ca-P coating, were prepared on the pure Mg ribbons in the present work. The Ca-P coating was obtained by aqueous solution method. Subsequently, Ca-P coated Mg was immersed into the BGCC slurry, which was prepared by the mix of SiO2-CaO-P2O5 bioglass ceramic (BGC) powders and phosphate liquid with a liquid-to-solid ratio (L/S) of 1.6, to obtain BGCC/Ca-P coating by a dipping-pulling method. The microstructures, morphologies, and compositions of these coatings have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The effect of these coatings on the mineralization activity of pure Mg has been investigated. The results indicated that both the Ca-P coating and BGCC/Ca-P coating could promote the nucleation of osteoconductive minerals, i.e., bone-like apatite, and the hydroxyapatite (HA) layer formed on the surface of the BGCC/Ca-P coating is obviously more dense, thick, and stable than that formed on the Ca-P coating after immersion in SBF solution for 15 days. The potentiodynamic polarization test indicated that the corrosion current density of the BGCC/Ca-P coated Mg is obviously lower than that of the Ca-P coating and 10 times lower than that of uncoated Mg. These results demonstrated that the BGCC/Ca-P coating can increase significantly the corrosion resistance of Mg and introduce a high biocompatibility of the bone-Mg substrate interface. In summary, the newly developed BGCC/Ca-P coated Mg has a good potential for biomedical applications.

Excitation-contraction coupling in zebrafish ventricular myocardium is regulated by trans-sarcolemmal Ca2+ influx and sarcoplasmic reticulum Ca2+ release.

PubMed

Haustein, Moritz; Hannes, Tobias; Trieschmann, Jan; Verhaegh, Rabea; Köster, Annette; Hescheler, Jürgen; Brockmeier, Konrad; Adelmann, Roland; Khalil, Markus

2015-01-01

Zebrafish (Danio rerio) have become a popular model in cardiovascular research mainly due to identification of a large number of mutants with structural defects. In recent years, cardiomyopathies and other diseases influencing contractility of the heart have been studied in zebrafish mutants. However, little is known about the regulation of contractility of the zebrafish heart on a tissue level. The aim of the present study was to elucidate the role of trans-sarcolemmal Ca(2+)-flux and sarcoplasmic reticulum Ca(2+)-release in zebrafish myocardium. Using isometric force measurements of fresh heart slices, we characterised the effects of changes of the extracellular Ca(2+)-concentration, trans-sarcolemmal Ca(2+)-flux via L-type Ca(2+)-channels and Na(+)-Ca(2+)-exchanger, and Ca(2+)-release from the sarcoplasmic reticulum as well as beating frequency and β-adrenergic stimulation on contractility of adult zebrafish myocardium. We found an overall negative force-frequency relationship (FFR). Inhibition of L-type Ca(2+)-channels by verapamil (1 μM) decreased force of contraction to 22 ± 7% compared to baseline (n=4, p<0.05). Ni(2+) was the only substance to prolong relaxation (5 mM, time after peak to 50% relaxation: 73 ± 3 ms vs. 101 ± 8 ms, n=5, p<0.05). Surprisingly though, inhibition of the sarcoplasmic Ca(2+)-release decreased force development to 54 ± 3% in ventricular (n=13, p<0.05) and to 52 ± 8% in atrial myocardium (n=5, p<0.05) suggesting a substantial role of SR Ca(2+)-release in force generation. In line with this finding, we observed significant post pause potentiation after pauses of 5 s (169 ± 7% force compared to baseline, n=8, p<0.05) and 10 s (198 ± 9% force compared to baseline, n=5, p<0.05) and mildly positive lusitropy after β-adrenergic stimulation. In conclusion, force development in adult zebrafish ventricular myocardium requires not only trans-sarcolemmal Ca2+-flux, but also intact sarcoplasmic reticulum Ca(2+)-cycling. In contrast to mammals, FFR is strongly negative in the zebrafish heart. These aspects need to be considered when using zebrafish to model human diseases of myocardial contractility.

Excitation-Contraction Coupling in Zebrafish Ventricular Myocardium Is Regulated by Trans-Sarcolemmal Ca2+ Influx and Sarcoplasmic Reticulum Ca2+ Release

PubMed Central

Trieschmann, Jan; Verhaegh, Rabea; Köster, Annette; Hescheler, Jürgen; Brockmeier, Konrad; Adelmann, Roland; Khalil, Markus

2015-01-01

Zebrafish (Danio rerio) have become a popular model in cardiovascular research mainly due to identification of a large number of mutants with structural defects. In recent years, cardiomyopathies and other diseases influencing contractility of the heart have been studied in zebrafish mutants. However, little is known about the regulation of contractility of the zebrafish heart on a tissue level. The aim of the present study was to elucidate the role of trans-sarcolemmal Ca2+-flux and sarcoplasmic reticulum Ca2+-release in zebrafish myocardium. Using isometric force measurements of fresh heart slices, we characterised the effects of changes of the extracellular Ca2+-concentration, trans-sarcolemmal Ca2+-flux via L-type Ca2+-channels and Na+-Ca2+-exchanger, and Ca2+-release from the sarcoplasmic reticulum as well as beating frequency and β-adrenergic stimulation on contractility of adult zebrafish myocardium. We found an overall negative force-frequency relationship (FFR). Inhibition of L-type Ca2+-channels by verapamil (1 μM) decreased force of contraction to 22±7% compared to baseline (n=4, p<0.05). Ni2+ was the only substance to prolong relaxation (5 mM, time after peak to 50% relaxation: 73±3 ms vs. 101±8 ms, n=5, p<0.05). Surprisingly though, inhibition of the sarcoplasmic Ca2+-release decreased force development to 54±3% in ventricular (n=13, p<0.05) and to 52±8% in atrial myocardium (n=5, p<0.05) suggesting a substantial role of SR Ca2+-release in force generation. In line with this finding, we observed significant post pause potentiation after pauses of 5 s (169±7% force compared to baseline, n=8, p<0.05) and 10 s (198±9% force compared to baseline, n=5, p<0.05) and mildly positive lusitropy after β-adrenergic stimulation. In conclusion, force development in adult zebrafish ventricular myocardium requires not only trans-sarcolemmal Ca2+-flux, but also intact sarcoplasmic reticulum Ca2+-cycling. In contrast to mammals, FFR is strongly negative in the zebrafish heart. These aspects need to be considered when using zebrafish to model human diseases of myocardial contractility. PMID:25938412

Multi-technology Investigation of the Atomic Structure of Calcium Silicate Hydrates

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

Geng, Guoqing; Kilcoyne, David A.; Benmore, Chris J.

2015-01-01

In this study, synthetic C-S-H samples were investigated to reveal the feature at atomic scale. Rietveld refinement was applied to high resolution X-ray scattering data, yielding the lattice constants of the pseudocrystal structure, as well as the crystallinity along three axes. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra was collected at calcium L3,2-edge. Evolution of calcium coordination symmetry were studied by investigating spectra characteristics. Pair Distribution Function (PDF) study yields the statistics of atom pair distribution. Coordination number of Ca and Si were obtained by integrating Radial distribution function. Atomic model based on dimeric structure were discussed and comparedmore » with experimental data. Synthetic C-S-H samples with increasing Ca/Si ratio exhibit pseudo-crystal structure, resembling Dreierketten configuration similar to natural tobermorite structure. Along c-axis, the repeated structure could not survives two layers in case of low Ca/Si ratio (0.70, 1.05). But in high Ca/Si ratio (1.42) case, the crystallinity along c-axis is much bigger. The coordination number of Ca decreases with increasing Ca/Si ratio. Octahedrally coordinated Ca are observed in sample with Ca/Si ratio of 1.42. Various dimeric models are compared with experimental data. In case of Ca/Si ratio of 1.42, SiO4 tetrahedron chain needs to be shortened in linkage, most probably by substituting bridging SiO4 tetrahedron with CaO6 octahedron. These octahedrons in interlayer space act like pins to join two adjacent layer structures together. The crystallinity is thus increased along c-axis, and average coordination number is therefore reduced. In case of Ca/Si 1.05, crystallinity is low along c-axis since, indicating that not too many Ca ions exist in interlayer space to hold two layers together. Instead, negative charge of end oxygen could be balanced by proton. Ca/Si 0.70 has long tetrahedron chain linkage within layer while the linkage between adjacent layers are not strong, resulting in low crystallinity along c-axis. Neither Ca/Si ratio 0.70 nor 1.42 sample contains any Ca in octahedral symmetry, as indicated by the weak crystal field splitting of NEXAFS spectra.« less

Effects of Ca2+ on oxidative phosphorylation in mitochondria from the thermogenic organ of marlin.

PubMed

O'Brien, J; Block, B A

1996-12-01

Mitochondria from the muscle-derived thermogenic (heater) organ and oxidative red muscle of the blue marlin (Makaira nigricans) were studied in order to evaluate aspects of the mechanism of thermogenesis in heater tissue. We investigated whether short-term Ca(2+)-induced uncoupling of mitochondria contributes to the thermogenic cycle of the heater organ by enhancing the respiration rate. Specific electrodes were used to obtain simultaneous measurements of oxygen consumption and Ca2+ fluxes on isolated mitochondria, and the effects of various concentrations of Ca2+ on respiration rates and the ADP phosphorylated/atomic oxygen consumed (P/O) ratio were examined. Addition of Ca2+ in excess of 10 mumol l-1 to respiring heater organ or red muscle mitochondria partially inhibited state 3 respiration and reduced the P/O ratio, indicating that the mitochondria were partially uncoupled. These effects were blocked by 2 mumol l-1 Ruthenium Red. In heater organ mitochondria, state 3 respiration rate and the P/O ratio were not significantly reduced by 1 mumol l-1 free Ca2+, a concentration likely to be near the maximum achieved in a stimulated cell. This indicates that transient increases in cytosolic Ca2+ concentration may not significantly reduce the P/O ratio of heater organ mitochondria. The activity of 2-oxoglutarate dehydrogenase in heater organ mitochondria was stimulated by approximately 15% by Ca2+ concentrations between 0.2 and 1 mumol l-1. These results suggest that heater organ mitochondria are able to maintain a normal P/O ratio and should maintain ATP output during transient increases in Ca2+ concentration, supporting a model in which an ATP-consuming process drives thermogenesis. Activation of mitochondrial dehydrogenases by low levels of Ca2+ may also enhance respiration and contribute to thermogenesis.

Insight into the optoelectronic and thermoelectric properties of Ca-based Zintl phase CaCd2X2 (X = P, As) from first principles calculation

NASA Astrophysics Data System (ADS)

Belfarh, T.; Batouche, M.; Seddik, T.; Uğur, G.; Omran, S. Bin; Bouhemadou, A.; Sandeep; Wang, Xiaotian; Sun, Xiao-Wei; Khenata, R.

2018-06-01

We have studied the structural, optical, electronic and thermoelectric properties of the CaCd2X2 (X = P, As) compounds by using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). The exchange-correlation potential was treated using both the gradient generalized approximation (WC-GGA) and local density approximation (LDA). The estimated structural parameters, including the lattice parameters and internal coordinates agree well with the available experimental data. Our computed band structure shows that both studied compounds are semiconductors, with direct band gaps (Γ-Γ) of approximately 1.78 eV and 1.2 eV for CaCd2P2 and CaCd2As2, respectively, using GGA-TB-mBJ approach. The calculated optical spectra reveal a strong response of these materials in the energy range between the visible light and extreme UV regions, making them a good candidate for optoelectronic devices. Thermoelectric parameters, such as thermal conductivity, electrical conductivity, Seebeck coefficient, power factor and figure of merit were calculated. We note that both the CaCd2P2 and CaCd2As2 compounds show promising thermoelectric properties.

Crystalline and Electronic Structures and Magnetic and Electrical Properties of La-Doped Ca2Fe2O5 Compounds

NASA Astrophysics Data System (ADS)

Phan, T. L.; Tho, P. T.; Tran, N.; Kim, D. H.; Lee, B. W.; Yang, D. S.; Thiet, D. V.; Cho, S. L.

2018-01-01

Brownmillerite Ca2Fe2O5 has been observed to exhibit many outstanding properties that are applicable to ecotechnology. However, very little work on doped Ca2Fe2O5 compounds has been carried out to widen their application scope. We present herein a detailed study of the crystalline/geometric and electronic structures and magnetic and electrical properties of Ca2- x La x Fe2O5 ( x = 0 to 1) prepared by conventional solid-state reaction. X-ray diffraction patterns indicated that the compounds with x = 0 to 0.05 exhibited brownmillerite-type single phase. La doping with higher content ( x ≥ 0.1) stimulated additive formation of Grenier- (LaCa2Fe3O8) and perovskite-type (LaFeO3) phases. Extended x-ray absorption fine structure spectroscopy at the Fe K-edge and electron spin resonance spectroscopy revealed presence of Fe3+ in the parent Ca2Fe2O5 ( x = 0) and both Fe3+ and Fe4+ in the doped compounds ( x ≥ 0.05). The Fe4+ content tended to increase with increasing x. This stimulates ferromagnetic exchange interactions between Fe3+ and Fe4+ ions and directly influences the magnetic properties of Ca2- x La x Fe2O5. Electrical resistivity ( ρ) measurements in the temperature range of T = 20 K to 400 K revealed that all the compounds exhibit insulator behavior; the ρ( T) data for x ≥ 0.1 could be described based on the adiabatic small polaron hopping model.

Consumer Acceptability of Cucumber Pickles Produced by Fermentation in Calcium Chloride Brine for Reduced Environmental Impact.

PubMed

Wilson, Emily M; Johanningsmeier, Suzanne D; Osborne, Jason A

2015-06-01

Fermentation of cucumbers in calcium chloride (CaCl2 ) brine has been proposed as an alternative process to reduce the environmental impact of traditional, high salt fermentations. The objective of this research was to determine whether consumer acceptability of pickle products would be impacted by fermentation and storage of cucumbers in CaCl2 brine. Cucumbers were fermented and stored with 0.1M CaCl2 or 1M sodium chloride (NaCl) in open-air, 3000 gal tanks at a commercial facility and processed into hamburger dill chips containing 0.38M NaCl. Cucumbers fermented in CaCl2 required additional desalting to reduce CaCl2 concentrations to that of current products. Consumers (n = 101) showed no significant preference for pickles from different fermentation treatments, whether stored for 2 mo (P = 0.75) or 8 mo (P = 0.68) prior to processing. In contrast, NaCl fermented pickles were preferred over CaCl2 fermented pickles stored for 10 mo and desalted only once (P < 0.01). A series of preference tests indicated that the taste of CaCl2 was not the factor affecting consumer preference, and the 50% detection threshold of CaCl2 in dill pickle chips was found to be 61.8 ± 7.6 mM, indicating that processors could potentially use CaCl2 fermentations with a single desalting step. Consumer liking of flavor (n = 73) was not influenced by fermentation in CaCl2 or by 23 or 35 mM CaCl2 in finished products (P > 0.05), but variability in texture decreased consumer liking (P < 0.05). Although promising, individual fermentation variability and texture quality of CaCl2 fermented products should be further evaluated prior to broad implementation of this process. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

PubMed

Osborn, Hannah L; Alonso-Cantabrana, Hugo; Sharwood, Robert E; Covshoff, Sarah; Evans, John R; Furbank, Robert T; von Caemmerer, Susanne

2017-01-01

In C 4 species, the major β-carbonic anhydrase (β-CA) localized in the mesophyll cytosol catalyses the hydration of CO 2 to HCO 3 - , which phosphoenolpyruvate carboxylase uses in the first step of C 4 photosynthesis. To address the role of CA in C 4 photosynthesis, we generated transgenic Setaria viridis depleted in β-CA. Independent lines were identified with as little as 13% of wild-type CA. No photosynthetic defect was observed in the transformed lines at ambient CO 2 partial pressure (pCO 2 ). At low pCO 2 , a strong correlation between CO 2 assimilation rates and CA hydration rates was observed. C 18 O 16 O isotope discrimination was used to estimate the mesophyll conductance to CO 2 diffusion from the intercellular air space to the mesophyll cytosol (g m ) in control plants, which allowed us to calculate CA activities in the mesophyll cytosol (C m ). This revealed a strong relationship between the initial slope of the response of the CO 2 assimilation rate to cytosolic pCO 2 (AC m ) and cytosolic CA activity. However, the relationship between the initial slope of the response of CO 2 assimilation to intercellular pCO 2 (AC i ) and cytosolic CA activity was curvilinear. This indicated that in S. viridis, mesophyll conductance may be a contributing limiting factor alongside CA activity to CO 2 assimilation rates at low pCO 2 . © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Creation of a 3Mn/1Fe cluster in the oxygen-evolving complex of photosystem II and investigation of its functional activity.

PubMed

Semin, B К; Davletshina, L N; Seibert, M; Rubin, A B

2018-01-01

Extraction of Mn cations from the oxygen-evolving complex (OEC) of Ca-depleted PSII membranes (PSII[-Ca,4Mn]) by reductants like hydroquinone (H 2 Q) occurs with lower efficiency at acidic pH (2Mn/reaction center [RC] are extracted at pH5.7) than at neutral pH (3Mn/RC are extracted at pH6.5) [Semin et al. Photosynth. Res. 125 (2015) 95]. Fe(II) also extracts Mn cations from PSII(-Ca,4Mn), but only 2Mn/RC at pH6.5, forming a heteronuclear 2Mn/2Fe cluster [Semin and Seibert, J. Bioenerg. Biomembr. 48 (2016) 227]. Here we investigated the efficiency of Mn extraction by Fe(II) at acidic pH and found that Fe(II) cations can extract only 1Mn/RC from PSII(-Ca,4Mn) membranes at pH 5.7, forming a 3Mn/1Fe cluster. Also we found that the presence of Fe cations in a heteronuclear cluster (2Mn/2Fe) increases the resistance of the remaining Mn cations to H 2 Q action, since H 2 Q can extract Mn cations from homonuclear Mn clusters of PSII(-Ca,4Mn) and PSII(-Ca,2Mn) membranes but not from the heteronuclear cluster in PSII(-Ca,2Mn,2Fe) membranes. H 2 Q also cannot extract Mn from PSII membranes obtained by incubation of PSII(-Ca,4Mn) membranes with Fe(II) cations at pH5.7, which suggests the formation of a heteronuclear 3Mn/1Fe cluster in the OEC. Functional activity of PSII with a 3Mn/1Fe cluster was investigated. PSII preparations with a 3Mn/1Fe cluster in the OEC are able to photoreduce the exogenous electron acceptor 2,6-dichlorophenolindophenol, possibly due to incomplete oxidation of water molecules as is the case with PSII(-Ca,2Mn,2Fe) samples. However, in the contrast to PSII(-Ca,2Mn,2Fe) samples PSII(-Ca,3Mn,1Fe) membranes can evolve O 2 at a low rate in the presence of exogenous Ca 2+ (at about 27% of the rate of O 2 evolution in native PSII membranes). The explanation for this phenomenon (either water splitting and production of molecular O 2 by the 3Mn/1Fe cluster or apparent O 2 evolution due to minor contamination of PSII(3Mn,1Fe) samples with PSII(-Ca,4Mn) membranes) is discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Ca2+ release triggered by nicotinate adenine dinucleotide phosphate in intact sea urchin eggs.

PubMed Central

Perez-Terzic, C M; Chini, E N; Shen, S S; Dousa, T P; Clapham, D E

1995-01-01

Nicotinate adenine dinucleotide phosphate (NAADP) was recently identified [Lee and Aarhus (1995) J. Biol. Chem. 270, 2152-2157; Chini, Beers and Dousa (1995) J. Biol. Chem. 270, 3116-3223] as a potent Ca(2+)-releasing agent in sea urchin egg homogenates. NAADP triggered Ca2+ release by a mechanism that was distinct from inositol 1,4,5-trisphosphate (InsP3)- and cyclic ADP-ribose (cADPR)-induced Ca2+ release. When NAADP was microinjected into intact sea urchin eggs it induced a dose-dependent increase in cytoplasmic free Ca2+ which was independent of the extracellular [Ca2+]. The Ca2+ waves elicited by microinjections of NAADP originated at the site of injection and swept across the cytosol. As previously found in sea urchin egg homogenates, NAADP-induced Ca2+ release in intact eggs was not blocked by heparin or by prior desensitization to InsP3 or cADPR. Thio-NADP, a specific inhibitor of the NAADP-induced Ca2+ release in sea urchin homogenates [Chini, Beers and Dousa (1995) J. Biol. Chem. 270, 3116-3223] blocked NAADP (but not InsP3 or cADPR) injection-induced Ca2+ release in intact sea urchin eggs. Finally, fertilization of sea urchin eggs abrogated subsequent NAADP-induced Ca2+ release, suggesting that the NAADP-sensitive Ca2+ pool may participate in the fertilization response. This study demonstrates that NAADP acts as a selective Ca(2+)-releasing agonist in intact cells. Images Figure 2 PMID:8554544

Aconitine-induced Ca{sup 2+} overload causes arrhythmia and triggers apoptosis through p38 MAPK signaling pathway in rats

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

Sun, Gui-bo; Sun, Hong; Meng, Xiang-bao

Aconitine is a major bioactive diterpenoid alkaloid with high content derived from herbal aconitum plants. Emerging evidence indicates that voltage-dependent Na{sup +} channels have pivotal roles in the cardiotoxicity of aconitine. However, no reports are available on the role of Ca{sup 2+} in aconitine poisoning. In this study, we explored the importance of pathological Ca{sup 2+} signaling in aconitine poisoning in vitro and in vivo. We found that Ca{sup 2+} overload lead to accelerated beating rhythm in adult rat ventricular myocytes and caused arrhythmia in conscious freely moving rats. To investigate effects of aconitine on myocardial injury, we performed cytotoxicitymore » assay in neonatal rat ventricular myocytes (NRVMs), as well as measured lactate dehydrogenase level in the culture medium of NRVMs and activities of serum cardiac enzymes in rats. The results showed that aconitine resulted in myocardial injury and reduced NRVMs viability dose-dependently. To confirm the pro-apoptotic effects, we performed flow cytometric detection, cardiac histology, transmission electron microscopy and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay. The results showed that aconitine stimulated apoptosis time-dependently. The expression analysis of Ca{sup 2+} handling proteins demonstrated that aconitine promoted Ca{sup 2+} overload through the expression regulation of Ca{sup 2+} handling proteins. The expression analysis of apoptosis-related proteins revealed that pro-apoptotic protein expression was upregulated, and anti-apoptotic protein BCL-2 expression was downregulated. Furthermore, increased phosphorylation of MAPK family members, especially the P-P38/P38 ratio was found in cardiac tissues. Hence, our results suggest that aconitine significantly aggravates Ca{sup 2+} overload and causes arrhythmia and finally promotes apoptotic development via phosphorylation of P38 mitogen-activated protein kinase. - Highlights: • Aconitine-induced Ca{sup 2+} overload causes arrhythmia in rats. • Aconitine induces Ca{sup 2+} overload through the activation of L-type Ca{sup 2+} channels. • Aconitine-induced Ca{sup 2+} overload triggers apoptotic responses in vitro and in vivo. • Aconitine promotes apoptotic development via activation of P38 MAPK.« less

Calcium and stretch activation modulate power generation in Drosophila flight muscle.

PubMed

Wang, Qian; Zhao, Cuiping; Swank, Douglas M

2011-11-02

Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca(2+)]). In vivo myoplasmic calcium levels in Drosophila flight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca(2+)] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinned Drosophila asynchronous flight muscle fibers increased with increasing [Ca(2+)]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca(2+)] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca(2+)]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca(2+)]. However, calcium tension saturated at slightly lower [Ca(2+)] than stretch-activated tension, such that as [Ca(2+)] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca(2+)] is the main mechanism by which power is varied during flight. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Extracellular nucleotides potentiate the cytosolic Ca2+, but not cyclic adenosine 3', 5'-monophosphate response to parathyroid hormone in rat osteoblastic cells.

PubMed

Kaplan, A D; Reimer, W J; Feldman, R D; Dixon, S J

1995-04-01

Binding to PTH to its cell surface receptor activates both adenylyl cyclase and phospholipase-C, leading to elevation of cytosolic cAMP and free Ca2+. We have shown previously that extracellular nucleotides interact with P2U and P2Y subtypes of purinoceptor on osteoblastic cells, both linked to Ca2+ mobilization. In the present study, we investigated possible interactions between nucleotide and PTH signaling pathways in osteoblastic cells. The cytosolic free Ca2+ concentration ([Ca2+]i) of UMR-106 osteoblastic cells was monitored by fluorescence spectrophotometry. PTH (0.01-1 microM; bovine 1-84 or human 1-34) induced a small transient elevation of [Ca2+]i, lasting less than 1 min. A number of nucleotides, including ATP, UTP, and UDP, induced transient elevation of [Ca2+]i and potentiated the subsequent Ca2+ response to PTH. Of the nucleotides tested, UDP was the most effective at potentiating the PTH-induced Ca2+ transient. Treatment of cells with UDP (100 microM for 2.5 min), but not inorganic phosphate or uridine, reversibly potentiated the Ca2+ response to PTH (0.1 microM) by 11 +/- 2-fold (mean +/- SEM; n = 39). In contrast, UDP did not affect the cAMP response to PTH, indicating a selective action on Ca2+ signaling. Potentiation of the Ca2+ signal was still observed in the absence of extracellular Ca2+, establishing that nucleotides enhance PTH-induced release of Ca2+ from intracellular stores. Studies using selective purinoceptor agonists suggest that potentiation of PTH signaling is mediated by the P2U receptor subtype. In vivo, nucleotides released during trauma or inflammation may modulate PTH-induced Ca2+ signaling in osteoblasts.

Unoccupied states in Cu and Zn octaethyl-porphyrin and phthalocyanine.

PubMed

Cook, Peter L; Yang, Wanli; Liu, Xiaosong; García-Lastra, Juan María; Rubio, Angel; Himpsel, F J

2011-05-28

Copper and zinc phthalocyanines and porphyrins are used in organic light emitting diodes and dye-sensitized solar cells. Using near edge x-ray absorption fine structure (NEXAFS) spectroscopy at the Cu 2p and Zn 2p edges, the unoccupied valence states at the Cu and Zn atoms are probed and decomposed into 3d and 4s contributions with the help of density functional calculations. A comparison with the N 1s edge provides the 2p states of the N atoms surrounding the metal, and a comparison with inverse photoemission provides a combined density of states. © 2011 American Institute of Physics

Arsenate uptake and arsenite simultaneous sorption and oxidation by Fe-Mn binary oxides: influence of Mn/Fe ratio, pH, Ca2+, and humic acid.

PubMed

Zhang, Gaosheng; Liu, Huijuan; Qu, Jiuhui; Jefferson, William

2012-01-15

Arsenate retention, arsenite sorption and oxidation on the surfaces of Fe-Mn binary oxides may play an important role in the mobilization and transformation of arsenic, due to the common occurrence of these oxides in the environment. However, no sufficient information on the sorption behaviors of arsenic on Fe-Mn binary oxides is available. This study investigated the influences of Mn/Fe molar ratio, solution pH, coexisting calcium ions, and humic acids have on arsenic sorption by Fe-Mn binary oxides. To create Fe-Mn binary oxides, simultaneous oxidation and co-precipitation methods were employed. The Fe-Mn binary oxides exhibited a porous crystalline structure similar to 2-line ferrihydrite at Mn/Fe ratios 1:3 and below, whereas exhibited similar structures to δ-MnO(2) at higher ratios. The As(V) sorption maximum was observed at a Mn/Fe ratio of 1:6, but As(III) uptake maximum was at Mn/Fe ratio 1:3. However, As(III) adsorption capacity was much higher than that of As(V) at each Mn/Fe ratio. As(V) sorption was found to decrease with increasing pH, while As(III) sorption edge was different, depending on the content of MnO(2) in the binary oxides. The presence of Ca(2+) enhanced the As(V) uptake under alkaline pH, but did not significantly influence the As(III) sorption by 1:9 Fe-Mn binary oxide; whereas the presence of humic acid slightly reduced both As(V) and As(III) uptake. These results indicate that As(III) is more easily immobilized than As(V) in the environment, where Fe-Mn binary oxides are available as sorbents and they represent attractive adsorbents for both As(V) and As(III) removal from water and groundwater. Copyright © 2011 Elsevier Inc. All rights reserved.

[Epidemiology of familial prostatic cancer: 4-year assessment of French studies].

PubMed

Valeri, A; Drelon, E; Azzouzi, R; Delannoy, A; Teillac, P; Fournier, G; Mangin, P; Berthon, P; Cussenot, O

1999-09-01

(1) To determine the frequency of familial (at least 2 cases) and hereditary forms of prostate cancer (CaP), (2) to define the results according to the patient's age at diagnosis, as various epidemiological studies have demonstrated a possible familial aggregation of CaP in about 15 to 25% of cases. Carter's familial segregation study (P.N.A.S. 1992, 89, 3367-71) showed that a genetic predisposition, with autosomal dominant transmission, could be responsible for 9% of all cases of prostate cancer. We conducted a systematic genealogy study of patients suffering from newly diagnosed CaP or followed for known CaP in 3 French urological centres, by means of questionnaires completed by the patients. Subsequently, a national collection of families with at least 2 cases of CaP identified families with hereditary forms of CaP. Hereditary cases were considered to be those presenting at least: one CaP in three 1st degree relatives, or 3 cases over 3 generations in the same branch of the family (paternal or maternal), or finally 2 early cases before the age of 55 years. Statistical analysis used the univariate logistic regression test between family status and the medical centre or the patient's age at diagnosis. From July 1994 onwards, we included 801 patients (all stages combined) in the systematic study and 110 patients (13.7%) were excluded (refusal to participate, advanced age). For 691 of the families studied (Brest: 225, Nancy: 249, Paris St Louis: 217), we observed 32 (14.2%), 29 (11.6%), 37 (17.1%) of familial forms (mean: 14.2%) and 11 (4.9%), 6 (2.4%), 8 (3.7%) of hereditary forms (mean: 3.6%), respectively (no significant differences between centres). Analysis of the results according to age at diagnosis of CaP also showed a higher incidence of familial (significant difference) and hereditary forms (limit of significance) for CaP occurring at a younger age (before 65 years). The national collection collected a total of 624 familial forms of CaP, including 236 (37.8%) cases of hereditary forms; 115 families were informative for the genetic linkage study. These results confirm the data of earlier studies, revealing about 15 to 25% of familial forms of CaP and 5 to 10% of hereditary forms. Similarly, the systematic study confirmed the earlier onset of CaP in patients with a genetic predisposition. These data therefore encourage systematic questioning of patients for a family history of CaP in order to propose targeted screening of high-risk subjects in the families concerned and to intensify identification of hereditary forms in order to investigate the genes involved.

Carbon-Based Solid-State Calcium Ion-Selective Microelectrode and Scanning Electrochemical Microscopy: A Quantitative Study of pH-Dependent Release of Calcium Ions from Bioactive Glass.

PubMed

Ummadi, Jyothir Ganesh; Downs, Corey J; Joshi, Vrushali S; Ferracane, Jack L; Koley, Dipankar

2016-03-15

Solid-state ion-selective electrodes are used as scanning electrochemical microscope (SECM) probes because of their inherent fast response time and ease of miniaturization. In this study, we report the development of a solid-state, low-poly(vinyl chloride), carbon-based calcium ion-selective microelectrode (Ca(2+)-ISME), 25 μm in diameter, capable of performing an amperometric approach curve and serving as a potentiometric sensor. The Ca(2+)-ISME has a broad linear response range of 5 μM to 200 mM with a near Nernstian slope of 28 mV/log[a(Ca(2+))]. The calculated detection limit for Ca(2+)-ISME is 1 μM. The selectivity coefficients of this Ca(2+)-ISME are log K(Ca(2+),A) = -5.88, -5.54, and -6.31 for Mg(2+), Na(+), and K(+), respectively. We used this new type of Ca(2+)-ISME as an SECM probe to quantitatively map the chemical microenvironment produced by a model substrate, bioactive glass (BAG). In acidic conditions (pH 4.5), BAG was found to increase the calcium ion concentration from 0.7 mM ([Ca(2+)] in artificial saliva) to 1.4 mM at 20 μm above the surface. In addition, a solid-state dual SECM pH probe was used to correlate the release of calcium ions with the change in local pH. Three-dimensional pH and calcium ion distribution mapping were also obtained by using these solid-state probes. The quantitative mapping of pH and Ca(2+) above the BAG elucidates the effectiveness of BAG in neutralizing and releasing calcium ions in acidic conditions.

Spatial Associations and Chemical Composition of Organic Carbon Sequestered in Fe, Ca, and Organic Carbon Ternary Systems.

PubMed

Sowers, Tyler D; Adhikari, Dinesh; Wang, Jian; Yang, Yu; Sparks, Donald L

2018-05-25

Organo-mineral associations of organic carbon (OC) with iron (Fe) oxides play a major role in environmental OC sequestration, a process crucial to mitigating climate change. Calcium has been found to have high coassociation with OC in soils containing high Fe content, increase OC sorption extent to poorly crystalline Fe oxides, and has long been suspected to form bridging complexes with Fe and OC. Due to the growing realization that Ca may be an important component of C cycling, we launched a scanning transmission X-ray microscopy (STXM) investigation, paired with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, in order to spatially resolve Fe, Ca, and OC relationships and probe the effect of Ca on sorbed OC speciation. We performed STXM-NEXAFS analysis on 2-line ferrihydrite reacted with leaf litter-extractable dissolved OC and citric acid in the absence and presence of Ca. Organic carbon was found to highly associate with Ca ( R 2 = 0.91). Carboxylic acid moieties were dominantly sequestered; however, Ca facilitated the additional sequestration of aromatic and phenolic moieties. Also, C NEXAFS revealed polyvalent metal ion complexation. Our results provide evidence for the presence of Fe-Ca-OC ternary complexation, which has the potential to significantly impact how organo-mineral associations are modeled.

Developmental changes in Ca2+ channel subtypes regulating endocytosis at the calyx of Held

PubMed Central

Midorikawa, Mitsuharu; Okamoto, Yuji; Sakaba, Takeshi

2014-01-01

At the mammalian central synapse, Ca2+ influx through Ca2+ channels triggers neurotransmitter release by exocytosis of synaptic vesicles, which fuse with the presynaptic membrane and are subsequently retrieved by endocytosis. At the calyx of Held terminal, P/Q-type Ca2+ channels mainly mediate exocytosis, while N- and R-type channels have a minor role in young terminals (postnatal days 8–11). The role of each Ca2+ channel subtype in endocytosis remains to be elucidated; therefore, we examined the role of each type of Ca2+ channel in endocytosis, by using whole-cell patch-clamp recordings in conjunction with capacitance measurement techniques. We found that at the young calyx terminal, when R-type Ca2+ channels were blocked, the slow mode of endocytosis was further slowed, while blocking of either P/Q- or N-type Ca2+ channels had no major effect. In more mature terminals (postnatal days 14–17), the slow mode of endocytosis was mainly triggered by P/Q-type Ca2+ channels, suggesting developmental changes in the regulation of the slow mode of endocytosis by different Ca2+ channel subtypes. In contrast, a fast mode of endocytosis was observed after strong stimulation in young terminals that was mediated mainly by P/Q-type, but not R- or N-type Ca2+ channels. These results suggest that different types of Ca2+ channels regulate the two different modes of endocytosis. The results may also suggest that exo- and endocytosis are regulated independently at different sites in young animals but are more tightly coupled in older animals, allowing more efficient synaptic vesicle cycling adapted for fast signalling. PMID:24907302

UTP – Gated Signaling Pathways of 5-HT Release from BON Cells as a Model of Human Enterochromaffin Cells

PubMed Central

Liñán-Rico, Andromeda; Ochoa-Cortes, Fernando; Zuleta-Alarcon, Alix; Alhaj, Mazin; Tili, Esmerina; Enneking, Josh; Harzman, Alan; Grants, Iveta; Bergese, Sergio; Christofi, Fievos L.

2017-01-01

Background: Enterochromaffin cells (EC) synthesize and release 5-HT and ATP to trigger or modulate gut neural reflexes and transmit information about visceral/pain sensation. Alterations in 5-HT signaling mechanisms may contribute to the pathogenesis of IBD or IBS, but the pharmacologic or molecular mechanisms modulating Ca2+-dependent 5-HT release are not understood. Previous studies indicated that purinergic signaling via ATP and ADP is an important mechanism in modulation of 5-HT release. However, EC cells also respond to UTP and UDP suggesting uridine triphosphate receptor and signaling pathways are involved as well. We tested the hypothesis that UTP is a regulator of 5-HT release in human EC cells. Methods: UTP signaling mechanisms were studied in BON cells, a human EC model, using Fluo-4/Ca2+imaging, patch-clamp, pharmacological analysis, immunohistochemistry, western blots and qPCR. 5-HT release was monitored in BON or EC isolated from human gut surgical specimens (hEC). Results: UTP, UTPγS, UDP or ATP induced Ca2+oscillations in BON. UTP evoked a biphasic concentration-dependent Ca2+response. Cells responded in the order of UTP, ATP > UTPγS > UDP >> MRS2768, BzATP, α,β-MeATP > MRS2365, MRS2690, and NF546. Different proportions of cells activated by UTP and ATP also responded to UTPγS (P2Y4, 50% cells), UDP (P2Y6, 30%), UTPγS and UDP (14%) or MRS2768 (<3%). UTP Ca2+responses were blocked with inhibitors of PLC, IP3R, SERCA Ca2+pump, La3+sensitive Ca2+channels or chelation of intracellular free Ca2+ by BAPTA/AM. Inhibitors of L-type, TRPC, ryanodine-Ca2+pools, PI3-Kinase, PKC or SRC-Kinase had no effect. UTP stimulated voltage-sensitive Ca2+currents (ICa), Vm-depolarization and inhibited IK (not IA) currents. An IKv7.2/7.3 K+ channel blocker XE-991 mimicked UTP-induced Vm-depolarization and blocked UTP-responses. XE-991 blocked IK and UTP caused further reduction. La3+ or PLC inhibitors blocked UTP depolarization; PKC inhibitors, thapsigargin or zero Ca2+buffer did not. UTP stimulated 5-HT release in hEC expressing TPH1, 5-HT, P2Y4/P2Y6R. Zero-Ca2+buffer augmented Ca2+responses and 5-HT release. Conclusion: UTP activates a predominant P2Y4R pathway to trigger Ca2+oscillations via internal Ca2+mobilization through a PLC/IP3/IP3R/SERCA Ca2+signaling pathway to stimulate 5-HT release; Ca2+influx is inhibitory. UTP-induced Vm-depolarization depends on PLC signaling and an unidentified K channel (which appears independent of Ca2+oscillations or Ica/VOCC). UTP-gated signaling pathways triggered by activation of P2Y4R stimulate 5-HT release. PMID:28751862

Different rate-limiting activities of intracellular pH regulators for HCO3- secretion stimulated by forskolin and carbachol in rat parotid intralobular ducts.

PubMed

Ueno, Kaori; Hirono, Chikara; Kitagawa, Michinori; Shiba, Yoshiki; Sugita, Makoto

2016-11-01

Intracellular pH (pH i ) regulation fundamentally participates in maintaining HCO 3 - release from HCO 3 - -secreting epithelia. We used parotid intralobular ducts loaded with BCECF to investigate the contributions of a carbonic anhydrase (CA), anion channels and a Na + -H + exchanger (NHE) to pH i regulation for HCO 3 - secretion by cAMP and Ca 2+ signals. Resting pH i was dispersed between 7.4 and 7.9. Forskolin consistently decreased pH i showing the dominance of pH i -lowering activities, but carbachol gathered pH i around 7.6. CA inhibition suppressed the forskolin-induced decrease in pH i , while it allowed carbachol to consistently increase pH i by revealing that carbachol prominently activated NHE via Ca 2+ -calmodulin. Under NHE inhibition, forskolin and carbachol induced the remarkable decreases in pH i , which were slowed predominantly by CA inhibition and by CA or anion channel inhibition, respectively. Our results suggest that forskolin and carbachol primarily activate the pH i -lowering CA and pH i -raising NHE, respectively, to regulate pH i for HCO 3 - secretion.

Intracellular Ca2+ and antioxidant values induced positive effect on fertilisation ratio and oocyte quality of granulosa cells in patients undergoing in vitro fertilisation.

PubMed

Tola, Esra Nur; Mungan, Muhittin Tamer; Uğuz, Abdülhadi Cihangir; Naziroğlu, Mustafa

2013-01-01

Oxidative stress is important for promoting oocyte maturation and ovulation within the follicle through calcium ion (Ca(2+)) influx. The relationship between antioxidant and cytosolic Ca(2+) levels and oocyte quality and fertilisation rate in the granulosa cells of patients undergoing in vitro fertilisation was investigated. Granulosa cells were collected from 33 patients. Cytosolic free Ca(2+) ([Ca(2+)]i) concentration, lipid peroxidation, reduced glutathione, glutathione peroxidase and oocyte quality were measured in the granulosa cells. The relationship between two drug protocols was also examined (gonadotrophin-releasing hormone antagonist and agonist protocols) and the same parameters investigated. The [Ca(2+)]i concentration (P<0.001), glutathione (P<0.05) and oocyte quality (P<0.001) values were significantly higher in the fertilised group than in the non-fertilised group, although glutathione peroxidase activity was significantly (P<0.05) higher in the non-fertilised group than in the fertilised group. The [Ca(2+)]i concentrations were also higher (P<0.001) in the good-quality oocyte groups than in the poor-quality oocyte group. There was no correlation between the two drug protocols and investigated parameters. In conclusion, it was observed that high glutathione and cytosolic Ca(2+) concentrations in granulosa cells of patients undergoing in vitro fertilisation tended to increase the fertilisation potential of oocytes.

Carbon K-edge spectra of carbonate minerals.

PubMed

Brandes, Jay A; Wirick, Sue; Jacobsen, Chris

2010-09-01

Carbon K-edge X-ray spectroscopy has been applied to the study of a wide range of organic samples, from polymers and coals to interstellar dust particles. Identification of carbonaceous materials within these samples is accomplished by the pattern of resonances in the 280-320 eV energy region. Carbonate minerals are often encountered in the study of natural samples, and have been identified by a distinctive resonance at 290.3 eV. Here C K-edge and Ca L-edge spectra from a range of carbonate minerals are presented. Although all carbonates exhibit a sharp 290 eV resonance, both the precise position of this resonance and the positions of other resonances vary among minerals. The relative strengths of the different carbonate resonances also vary with crystal orientation to the linearly polarized X-ray beam. Intriguingly, several carbonate minerals also exhibit a strong 288.6 eV resonance, consistent with the position of a carbonyl resonance rather than carbonate. Calcite and aragonite, although indistinguishable spectrally at the C K-edge, exhibited significantly different spectra at the Ca L-edge. The distinctive spectral fingerprints of carbonates provide an identification tool, allowing for the examination of such processes as carbon sequestration in minerals, Mn substitution in marine calcium carbonates (dolomitization) and serpentinization of basalts.

A helix-breaking mutation in the epithelial Ca2+ channel TRPV5 leads to reduced Ca2+-dependent inactivation

PubMed Central

Lee, Kyu Pil; Nair, Anil V.; Grimm, Christian; van Zeeland, Femke; Heller, Stefan; Bindels, René J.M.; Hoenderop, Joost G.J.

2013-01-01

TRPV5, a member of transient receptor potential (TRP) superfamily of ion channels, plays a crucial role in epithelial calcium transport in the kidney. This channel has a high selectivity for Ca2+ and is tightly regulated by intracellular Ca2+ concentrations. Recently it was shown that the molecular basis of deafness in varitint-waddler mouse is the result of hair cell death caused by the constitutive activity of transient receptor potential mucolipin 3 (TRPML3) channel carrying a helix breaking mutation, A419P, at the intracellular proximity of the fifth transmembrane domain (TM5). This mutation significantly elevates intracellular Ca2+ concentration and causes rapid cell death. Here we show that substituting the equivalent location in TRPV5, the M490, to proline significantly modulates Ca2+-dependent inactivation of TRPV5. The single channel conductance, time constant of inactivation (τ) and half maximal inhibition constant (IC50) of TRPV5(M490P) were increased compared to TRPV5(WT). Moreover TRPV5(M490P) showed lower Ca2+ permeability. Out of different point mutations created to characterize the importance of M490 in Ca2+-dependent inactivation, only TRPV5(M490P)-expressing cells showed apoptosis and extremely altered Ca2+-dependent inactivation. In conclusion, the TRPV5 channel is susceptible for helix breaking mutations and the proximal intracellular region of TM5 of this channel plays an important role in Ca2+-dependent inactivation. PMID:21035851

Acidity of edge surface sites of montmorillonite and kaolinite

NASA Astrophysics Data System (ADS)

Liu, Xiandong; Lu, Xiancai; Sprik, Michiel; Cheng, Jun; Meijer, Evert Jan; Wang, Rucheng

2013-09-01

Acid-base chemistry of clay minerals is central to their interfacial properties, but up to now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of surface groups on (0 1 0)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 and 1:1-type clay minerals, respectively. It shows that tbnd Si-OH and tbnd Al-OH2OH groups of kaolinite have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of titration curves, indicating that tbnd Si-OH and tbnd Al-OH2OH groups are the major acidic sites responsible to pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is investigated and it is found that Mg substitution increases the pKas of the neighboring tbnd Si-OH and tbnd Si-OH2 groups by 2-3 pKa units. Furthermore, our calculation shows that the pKa of edge tbnd Mg-(OH2)2 is as high as 13.2, indicating the protonated state dominates under common pH. Together with previous adsorption experiments, our derived acidity constants suggest that tbnd Si-O- and tbnd Al-(OH)2 groups are the most probable edge sites for complexing heavy metal cations.

The evaluation of the statistical monomineral thermobarometric methods for the reconstruction of the lithospheric mantle structure

NASA Astrophysics Data System (ADS)

Ashchepkov, I.; Vishnyakova, E.

2009-04-01

The modified versions of the thermobarometers for the mantle assemblages were revised sing statistical calibrations on the results of Opx thermobarometry. The modifications suggest the calculation of the Fe# of coexisting olivine Fe#Ol according to the statistical approximations by the regressions obtained from the xenoliths from kimberlite data base including >700 associations. They allow reproduces the Opx based TP estimates and to receive the complete set of the TP values for mantle xenoliths and xenocrysts. For GARNET Three variants of barometer give similar results. The first is published (Ashchepkov, 2006). The second is calculating the Al2O3 from Garnet for Orthopyroxene according to procedure: xCrOpx=Cr2O3/CaO)/FeO/MgO/500 xAlOpx=1/(3875*(exp(Cr2O3^0.2/CaO)-0.3)*CaO/989+16)-XcrOpx Al2O3=xAlOp*24.64/Cr2O3^0.2*CaO/2.+FeO*(ToK-501)/1002 And then it suppose using of the Al2O3 in Opx barometer (McGregor, 1974). The third variant is transformation of the G. Grutter (2006) method by introducing of the influence of temperature. P=40+(Cr2O3)-4.5)*10/3-20/7*CaO+(ToC)*0.0000751*MgO)*CaO+2.45*Cr2O3*(7-xv(5,8)) -Fe*0.5 with the correction for P>55: P=55+(P-55)*55/(1+0.9*P) Average from this three methods give appropriate values comparable with determined with (McGregor,1974) barometer. Temperature are estimating according to transformed Krogh thermometer Fe#Ol_Gar=Fe#Gar/2+(T(K)-1420)*0.000112+0.01 For the deep seated associations P>55 kbar T=T-(0.25/(0.4-0.004*(20-P))-0.38/Ca)*275+51*Ca*Cr2-378*CaO-0.51)-Cr/Ca2*5+Mg/(Fe+0.0001)*17.4 ILMENITE P= ((TiO2-23.)*2.15-(T0-973)/20*MgO*Cr2O3 and next P=(60-P)/6.1+P ToK is determined according to (Taylor et al , 1998) Fe#Ol_Chr =(Fe/(Fe+Mg)ilm -0.35)/2.252-0.0000351*(T(K)-973) CHROMITE The equations for PT estimates with chromite compositions P=Cr/(Cr+Al)*T(K)/14.+Ti*0.10 with the next iteration P=-0.0053*P^2+1.1292*P+5.8059 +0.00135*T(K)*Ti*410-8.2 For P> 57 P=P+(P-57)*2.75 Temperature estimates are according to the O'Neill- Wall, 1987 The Fe#Ol values are estimated according to three iterations Fe#Ol_Chr=(Fe/Fe+Mg)/4.5-(P-32)*0.00115-0.03 Fe#Ol_Chr =( Fe#Ol -0.074)*0.45+0.086 Fe#Ol _Chr= Fe#Ol -( Fe#Ol -0.06)*(T(K)-1300)*0.000115+0.01 CLINOPYROXENE (Ash2009)=0.32 (1-0.2*Na/Al+0.012*Fe/Na)*Kd ^(3/4)*ToK/(1+Fe)-35*ln(1273/ToK)*(Al+Ti+2.5Na+1.5Fe3+)+(0.9-CaO)*10+Na20/Al2O3* ToK /200 with the second iteration P=(0.0000002* P4 +0.000002+P^3-0.0027*P^2+1.2241*P) The TP estimates were statistically tested wit the available experimental results in peridotite (315 runs) and eclogite (302 runs) system and show good agreement with the TP conditions of runs. The methods are joined together with the other 40 thermometers and 30 barometers for mantle associations in the FORTRAN program allowing simultaneous calculations of 10 pairs of T and P and write the matrix of calculated TPFO2 values together with the compositions of minerals or their formula coefficients. Grant RBRF 05-05-64718.

Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

PubMed

Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

2015-04-30

We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees well with the MD-generated counterparts. Our results on the Na/Ca intermixing in soda-lime-silicate glasses are discussed in relation to previous reports, highlighting the dependence of the conclusion on the approach to data evaluation.

Effects of dietary calcium on atherosclerosis, aortic calcification, and icterus in rabbits fed a supplemental cholesterol diet.

PubMed

Hsu, Howard H T; Culley, Nathan C

2006-06-23

Vascular calcification is implicated in myocardial infarction, instability and rigidity of the aortic wall, and bioprosthetic failures. Although an increase in the calcium (Ca) content in atherogenic diets has been shown to decrease atherosclerosis in rabbits, whether Ca supplementation and deficiency can affect atherosclerosis-related aortic calcification remains unknown. New Zealand White male rabbit littermates were fed an atherogenic diet containing 0.5% cholesterol and 2% peanut oil. The Ca content of the diet, which normally contains 1%, was adjusted to 0.5 or 3%. Segments of thoracic aortas were dissected from rabbits for histological evaluations and Ca and Pi determinations. Rabbits with calcium supplementation were maintained for 4 months, whereas those with calcium deficiency were maintained for 2 1/2 months due to severe icterus beyond this stage. The ratios of intimal to medial areas and calcified to intimal areas were used to semi-quantify lesion accumulation and calcification, respectively. Icterus was estimated from the extent of yellowing of the skin, sclera, and mucous membranes along with gross evidence of hepatic lipidosis and/or biliary obstructions. Statistical analysis of 16 matched littermates shows that Ca supplementation significantly decreased the lesions by 41% (p < 0.05) and markedly inhibited calcification by 62% (p < 0.05). Statistical analysis of 11 matched littermates shows that Ca deficiency significantly increased the lesions by 2.7-fold (p < 0.05) and that the diet caused a small but significant calcification not seen in the sibling groups with normal dietary Ca. Ca supplementation caused a significant 30% decrease in serum cholesterol (p < 0.05). Calcium deficiency increased serum cholesterol by 57% (p < 0.001). Serum cholesterol and LDL-cholesterol levels in Ca deficient rabbits were 2-fold higher than those with high Ca diets. Ca supplementation decreased soluble Ca and Pi content in aortas, suggesting that this effect may underlie the effects of Ca supplementation on calcification. Calcium deficiency increased icterus by 33% (p < 0.05), which may affect hepatic clearance of cholesterol, while calcium supplementation decreased it by 43% (p < 0.001). Ca supplementation to an atherogenic diet inhibits atherosclerosis, aortic calcification, and icterus, whereas a Ca deficient-diet promotes them.

Altered myocardial force generation in end-stage human heart failure.

PubMed

Papp, Zoltán; van der Velden, Jolanda; Borbély, Attila; Édes, István; Stienen, Ger J M

2014-12-01

This study aimed to elucidate the molecular background of increased Ca 2+ sensitivity of force production in cardiomyocytes of end-stage human heart failure. Ca 2+ -activated isometric force and the cross-bridge specific rate of force redevelopment (k tr ) were determined in Triton-skinned myocytes from end-stage failing and non-failing donor hearts. Measurements (control: pH 7.2, 0 mM inorganic phosphate (P i )) were performed under test conditions that probed either the Ca 2+ -regulatory function of the thin filaments (pH 6.5), the kinetics of the actin-myosin cross-bridge cycle (10 mM P i ), or both (pH 6.5, 10 mM P i ). The control maximal Ca 2+ -activated force (F o ) and k trmax did not differ between failing and non-failing myocytes. At submaximal [Ca 2+ ], however, both force and k tr were higher in failing than in donor myocytes. The difference in the Ca 2+ sensitivities of force production was preserved when the thin filament regulatory function was perturbed by acidosis (pH 6.5) but was abolished by cross-bridge modulation (i.e. by P i ) both at pH 7.2 and at pH 6.5. P i induced a larger reduction in force but a smaller increase in k tr in the failing myocytes than in the non-failing myocytes at submaximal [Ca 2+ ]. The enhanced P i sensitivity of the actin-myosin interaction suggests that the P i release step of the actin-myosin cross-bridge cycle is modified during end-stage human heart failure. This might be of functional importance when P i accumulates (e.g. during cardiac ischaemia). Moreover, this alteration can influence cardiac energetics and the clinical efficacy of sarcomere targeted agents in human heart failure. © 2015 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.

Myofibril ATPase activity of cardiac and skeletal muscle of exhaustively exercised rats.

PubMed

Belcastro, A N; Turcotte, R; Rossiter, M; Secord, D; Maybank, P E

1984-01-01

The activation characteristics of Mg-ATP and Ca2+ on cardiac and skeletal muscle myofibril ATPase activity were studied in rats following a run to exhaustion. In addition, the effect of varying ionic strength was determined on skeletal muscle from exhausted animals. The exhausted group (E) ran at a speed of 25 m min-1 with an 8% incline. Myofibril ATPase activities for control (C) and E were determined with 1, 3 and 5 mM Mg-ATP and 1 and 10 microM Ca2+ at pH 7.0 and 30 degrees C. For control skeletal muscle, at 1 and 10 microM Ca2+, there was an increase in ATPase activity from 1 to 5 mM Mg-ATP (P less than 0.05). For E animals the myofibril ATPase activities at 10 microM Ca2+ and all Mg-ATP concentrations were similar to C (P greater than 0.05). At 1.0 microM Ca2+ and all Mg-ATP concentrations were similar to C (P greater than 0.05). At 1.0 microM Ca2+ the activities at 3 and 5 mM Mg-ATP were greater for the E animals (P less than 0.05). Increasing KCl concentrations resulted in greater inhibition for E animals. With cardiac muscle, the myofibril ATPase activities at 1.0 microM free Ca2+ were lower for E at all Mg-ATP levels (P less than 0.05). In contrast, at 10 microM Ca2+, the E group exhibited an elevated myofibril ATPase activity. The results indicate that Mg-ATP and Ca2+ activation of cardiac and skeletal muscle myofibril ATPase is altered with exhaustive exercise.

Influence of oxygen vacancy on the electronic structure of CaCu3Ti4O12 and its deep-level vacancy trap states by first-principle calculation

NASA Astrophysics Data System (ADS)

Xiao, H. B.; Yang, C. P.; Huang, C.; Xu, L. F.; Shi, D. W.; Marchenkov, V. V.; Medvedeva, I. V.; Bärner, K.

2012-03-01

The electronic structure, formation energy, and transition energy levels of intrinsic defects have been studied using the density-functional method within the generalized gradient approximation for neutral and charged oxygen vacancy in CaCu3Ti4O12 (CCTO). It is found that oxygen vacancies with different charge states can be formed in CCTO under both oxygen-rich and poor conditions for nonequilibrium and higher-energy sintering processes; especially, a lower formation energy is obtained for poor oxygen environment. The charge transition level (0/1+) of the oxygen vacancy in CCTO is located at 0.53 eV below the conduction-band edge. The (1+/2+) transition occurs at 1.06 eV below the conduction-band edge. Oxygen vacancies of Vo1+ and Vo2+ are positive stable charge states in most gap regions and can act as a moderately deep donor for Vo1+ and a borderline deep for Vo2+, respectively. The polarization and dielectric constant are considerably enhanced by oxygen vacancy dipoles, due to the off-center Ti and Cu ions in CCTO.

Interactive effects of phosphorus, calcium, and phytase supplements on products of phytate degradation in the digestive tract of broiler chickens

PubMed Central

Sommerfeld, V; Schollenberger, M; Kühn, I

2018-01-01

Abstract This study aimed to distinguish between the single and interactive effects of phosphorus (P), calcium (Ca), and phytase on products of phytate degradation, including the disappearance of myo-inositol (MI), P, Ca, and amino acids (AA) in different segments of the digestive tract in broiler chickens. Additionally, all dephosphorylation steps from myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) to MI were investigated in the digesta of the terminal ileum. Unsexed Ross 308 broiler chickens were allocated to 56 pens with 19 birds per pen, and assigned to one of 8 dietary treatments. The dietary treatments included diets without (P−, 4.1 g/kg DM) or with (P+, 6.9 g/kg DM) monosodium phosphate supplementation, without (Ca−, 6.2 g/kg DM) or with (Ca+, 10.3 g/kg DM) additional fine limestone supplementation, and without or with 1,500 FTU phytase/kg feed in a factorial design. Adding Ca or P had no effect on InsP6 disappearance in the crop when phytase was added. InsP6 disappearance up to the terminal ileum (P−Ca− 56%) was decreased in P+Ca− (40%), and even more so in P+Ca+ (21%), when no phytase was added. Adding phytase removed all effects of P and Ca (77 to 87%); however, P+Ca+ increased the concentrations of lower InsP esters and reduced free MI in the ileum, even in the presence of phytase. These results indicate that mineral supplements, especially P and Ca combined, reduce the efficacy of endogenous microbial or epithelial phosphatases. Supplementation with phytase increased, while supplementation with Ca decreased the concentration of MI in all segments of the digestive tract and in blood plasma, demonstrating the ability of broilers to fully degrade phytate and absorb released MI. While AA disappearance was not affected by P or Ca, or an interaction among P, Ca, and phytase, it increased with the addition of phytase by 2 to 6%. This demonstrates the potential of the phytase used to increase AA digestibility, likely independent of P and Ca supply. PMID:29325118

Edge detection and mathematic fitting for corneal surface with Matlab software.

PubMed

Di, Yue; Li, Mei-Yan; Qiao, Tong; Lu, Na

2017-01-01

To select the optimal edge detection methods to identify the corneal surface, and compare three fitting curve equations with Matlab software. Fifteen subjects were recruited. The corneal images from optical coherence tomography (OCT) were imported into Matlab software. Five edge detection methods (Canny, Log, Prewitt, Roberts, Sobel) were used to identify the corneal surface. Then two manual identifying methods (ginput and getpts) were applied to identify the edge coordinates respectively. The differences among these methods were compared. Binomial curve (y=Ax 2 +Bx+C), Polynomial curve [p(x)=p1x n +p2x n-1 +....+pnx+pn+1] and Conic section (Ax 2 +Bxy+Cy 2 +Dx+Ey+F=0) were used for curve fitting the corneal surface respectively. The relative merits among three fitting curves were analyzed. Finally, the eccentricity (e) obtained by corneal topography and conic section were compared with paired t -test. Five edge detection algorithms all had continuous coordinates which indicated the edge of the corneal surface. The ordinates of manual identifying were close to the inside of the actual edges. Binomial curve was greatly affected by tilt angle. Polynomial curve was lack of geometrical properties and unstable. Conic section could calculate the tilted symmetry axis, eccentricity, circle center, etc . There were no significant differences between 'e' values by corneal topography and conic section ( t =0.9143, P =0.3760 >0.05). It is feasible to simulate the corneal surface with mathematical curve with Matlab software. Edge detection has better repeatability and higher efficiency. The manual identifying approach is an indispensable complement for detection. Polynomial and conic section are both the alternative methods for corneal curve fitting. Conic curve was the optimal choice based on the specific geometrical properties.

Optimization of calcium concentration of saliva with phosphoryl oligosaccharides of calcium (POs-Ca) for enamel remineralization in vitro.

PubMed

Tanaka, Tomoko; Kobayashi, Takatsugu; Takii, Hiroshi; Kamasaka, Hiroshi; Ohta, Noboru; Matsuo, Tatsuhito; Yagi, Naoto; Kuriki, Takashi

2013-02-01

Phosphoryl oligosaccharides of calcium (POs-Ca) are highly soluble calcium source made from potato starch. The aim of this study was to investigate the optimal concentrations of POs-Ca for the remineralization of subsurface enamel lesions in vitro. Demineralized bovine enamel slabs (n=5) were remineralized in vitro for 24h at 37°C with artificial saliva (AS) containing 0-0.74% POs-Ca to adjust the Ca/P ratio to 0.4-3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n=11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl2-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann-Whitney U-test. The highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2±7.4%) was significantly higher than that for AS containing CaCl2 (12.5±11.3%) (mean±SD, p<0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7±10.9%) was also significantly higher than that for AS containing CaCl2 (23.1±13.5%) (p<0.05). The restored crystallites were oriented in the same directions as in sound enamel. POs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67. Copyright © 2012 Elsevier Ltd. All rights reserved.

Preparation and Properties of Nanoparticles of Calcium Phosphates With Various Ca/P Ratios.

PubMed

Sun, Limin; Chow, Laurence C; Frukhtbeyn, Stanislav A; Bonevich, John E

2010-01-01

This study aimed at preparing and studying the properties of nanoparticles of calcium phosphate (nCaP) with Ca/P ratios ranging from 1.0 to 1.67 using a spray-drying technique. Micro-structural analyses suggested that the nCaPs with Ca/P ratios of 1.67 to 1.33 were nano-sized amorphous calcium phosphate (ACP) containing varying amounts of acid phosphate and carbonate. The nCaP with Ca/P ratio of 1 contained only nano-sized low crystalline dicalcium phosphate (DCP). BET measurements of the nCaPs showed specific surface areas of (12 ± 2 to 50 ± 1) m(2)/g, corresponding to estimated equivalent spherical diameters of (38 to 172) nm. However, dynamic light scattering measurements revealed much larger particles of (380 ± 49 to 768 ± 111) nm, owing to agglomeration of the smaller primary nano particles as revealed by Scanning Electron Microscopy (SEM). Thermodynamic solubility measurements showed that the nCaPs with Ca/P ratio of 1.33 - 1.67 all have similar solubility behavior. The materials were more soluble than the crystalline hydroxyapatite (HA) at pH greater than about 4.7, and more soluble than β-tricalcium phosphate (β-TCP), octacalcium phosphate (OCP) and DCP at pH above 5.5. Their solubility approached that of α-tricalcium phosphate (α-TCP) at about pH 7. These nCaPs, which cannot be readily prepared by other currently available methods for nanoparticle preparation, have potential biomedical applications.

Small Ca2+ releases enable hour-long high-frequency contractions in midshipman swimbladder muscle.

PubMed

Nelson, Frank E; Hollingworth, Stephen; Marx, James O; Baylor, Stephen M; Rome, Lawrence C

2018-01-02

Type I males of the Pacific midshipman fish ( Porichthys notatus ) vibrate their swimbladder to generate mating calls, or "hums," that attract females to their nests. In contrast to the intermittent calls produced by male Atlantic toadfish ( Opsanus tau ), which occur with a duty cycle (calling time divided by total time) of only 3-8%, midshipman can call continuously for up to an hour. With 100% duty cycles and frequencies of 50-100 Hz (15°C), the superfast muscle fibers that surround the midshipman swimbladder may contract and relax as many as 360,000 times in 1 h. The energy for this activity is supported by a large volume of densely packed mitochondria that are found in the peripheral and central regions of the fiber. The remaining fiber cross section contains contractile filaments and a well-developed network of sarcoplasmic reticulum (SR) and triadic junctions. Here, to understand quantitatively how Ca 2+ is managed by midshipman fibers during calling, we measure (a) the Ca 2+ pumping-versus-pCa and force-versus-pCa relations in skinned fiber bundles and (b) changes in myoplasmic free [Ca 2+ ] (Δ[Ca 2+ ]) during stimulated activity of individual fibers microinjected with the Ca 2+ indicators Mag-fluo-4 and Fluo-4. As in toadfish, the force-pCa relation in midshipman is strongly right-shifted relative to the Ca 2+ pumping-pCa relation, and contractile activity is controlled in a synchronous, not asynchronous, fashion during electrical stimulation. SR Ca 2+ release per action potential is, however, approximately eightfold smaller in midshipman than in toadfish. Midshipman fibers have a larger time-averaged free [Ca 2+ ] during activity than toadfish fibers, which permits faster Ca 2+ pumping because the Ca 2+ pumps work closer to their maximum rate. Even with midshipman's sustained release and pumping of Ca 2+ , however, the Ca 2+ energy cost of calling (per kilogram wet weight) is less than twofold more in midshipman than in toadfish. © 2018 Nelson et al.

An oxidized metabolite of linoleic acid increases intracellular calcium in rat adrenal glomerulosa cells.

PubMed

Payet, Marcel D; Goodfriend, Theodore L; Bilodeau, Lyne; Mackendale, Cherilu; Chouinard, Lucie; Gallo-Payet, Nicole

2006-12-01

EKODE, an epoxy-keto derivative of linoleic acid, was previously shown to stimulate aldosterone secretion in rat adrenal glomerulosa cells. In the present study, we investigated the effect of exogenous EKODE on cytosolic [Ca(2+)] increase and aimed to elucidate the mechanism involved in this process. Through the use of the fluorescent Ca(2+)-sensitive dye Fluo-4, EKODE was shown to rapidly increase intracellular [Ca(2+)] ([Ca(2+)](i)) along a bell-shaped dose-response relationship with a maximum peak at 5 microM. Experiments performed in the presence or absence of Ca(2+) revealed that this increase in [Ca(2+)](i) originated exclusively from intracellular pools. EKODE-induced [Ca(2+)](i) increase was blunted by prior application of angiotensin II, Xestospongin C, and cyclopiazonic acid, indicating that inositol trisphosphate (InsP(3))-sensitive Ca(2+) stores can be mobilized by EKODE despite the absence of InsP(3) production. Accordingly, EKODE response was not sensitive to the phospholipase C inhibitor U-73122. EKODE mobilized a Ca(2+) store included in the thapsigargin (TG)-sensitive stores, although the interaction between EKODE and TG appears complex, since EKODE added at the plateau response of TG induced a rapid drop in [Ca(2+)](i). 9-oxo-octadecadienoic acid, another oxidized derivative of linoleic acid, also increases [Ca(2+)](i), with a dose-response curve similar to EKODE. However, arachidonic and linoleic acids at 10 microM failed to increase [Ca(2+)](i) but did reduce the amplitude of the response to EKODE. It is concluded that EKODE mobilizes Ca(2+) from an InsP(3)-sensitive store and that this [Ca(2+)](i) increase is responsible for aldosterone secretion by glomerulosa cells. Similar bell-shaped dose-response curves for aldosterone and [Ca(2+)](i) increases reinforce this hypothesis.

Cry8Ca2-containing layer-by-layer microcapsules for the pH-controlled release of crystal protein.

PubMed

Li, Feng; Yan, Yue; Wang, Dandan; Zhang, Jie; Guo, Shuyuan

2014-01-01

To extend the activity of crystal proteins by protection from environmental stress, we developed a new type of microcapsule containing Cry8Ca2 protoxins. Layer-by-layer (LbL) microcapsules containing Cry8Ca2 were successfully prepared for the first time by the alternate deposition of poly(acrylic acid) (PAH) and Cry8Ca2 at pH 6 on the surface of poly(styrene sulphonate) (PSS)-doped CaCO3 microbeads. Scanning electron microscopy (SEM) photos showed that microparticles were spherical in shape, approximately 2 μm in diameter. After removing the templates, the loading results were observed with a confocal laser scattering microscope (CLSM) by using fluorescein-labelled Cry8Ca2. The Cry8Ca2 protoxins were released from the microcapsules when they were exposed to a pH higher than 6 due to the loss of the electrostatic attraction. The microcapsules displayed resistance to proteinase K. Bioassay result demonstrated that the microcapsules with Cry8Ca2 displayed approximately equivalent insecticidal activity to the larvae of Anomala corpulenta compared to the free Cry8Ca2.

Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition

NASA Astrophysics Data System (ADS)

Posavec, Lidija; Knijnenburg, Jesper T. N.; Hilty, Florentine M.; Krumeich, Frank; Pratsinis, Sotiris E.; Zimmermann, Michael B.

2016-10-01

Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO3) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO3 made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO3 and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO3, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca2P2O7 with increasing hydroxyapatite content at higher Ca:P. Aging of powders with Ca:P = 1.0 and 1.5 for over 500 days gradually increased particle size (but less than for CaCO3) without a change in phase composition or crystallinity. In 0.01 M H3PO4 calcium phosphate nanopowders dissolved ≈4 times more Ca than micronsized compounds and about twice more Ca than CaCO3 nanopowders, confirming that nanosizing and/or amorphous structuring sharply increases Ca powder dissolution. Because higher Ca solubility in vitro generally leads to greater absorption in vivo, these novel FASP-made Ca nanostructured compounds may prove useful for nutrition applications, including supplementation and/or food fortification.

Photoemission and Photoabsorption Investigation of the Electronic Structure of Ytterbium Doped Strontium Fluoroapatite

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

Nelson, A J; van Buuren, T; Bostedt, C

X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure was used to evaluate the density of occupied states of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N{sub 4,5}-edge), Sr 3d (M{sub 4,5}-edge), P 2p (L{sub 2,3}-edge), F 1s and O 1s (K-edges) absorption edges. These results provide the first measurements of the electronic structure and surface chemistry of this material.

Impact of interventional edge-to-edge repair on mitral valve geometry.

PubMed

Schueler, Robert; Kaplan, Sarah; Melzer, Charlotte; Öztürk, Can; Weber, Marcel; Sinning, Jan-Malte; Welz, Armin; Werner, Nikos; Nickenig, Georg; Hammerstingl, Christoph

2017-03-01

The acute and long-term effects of interventional edge-to-edge repair on the mitral valve (MV) geometry are unclear. We sought to assess MV-annular geometry and the association of changes in MV-diameters with functional response one year after MitraClip implantation. Consecutive patients (n=84; age 81.2±8.3years, logistic EuroSCORE 21.7±17.9%) with symptomatic moderate-to-severe mitral regurgitation (MR) underwent MitraClip-procedure. MV-annular geometry was assessed with 3D TOE before, immediately and one year after clip implantation. 96.7% of secondary mitral regurgitation (SMR) patients presented with moderate-to-severe MR, 3.3% with severe SMR, respectively. 66.7% of primary MR (PMR) patients had moderate-to-severe MR, and 33.3% severe PMR respectively. When analyzing immediate effects of MitraClipC on mitral geometry, only patients with SMR (n=60, 71.4%) experienced significant reductions of the diastolic MV anterior-posterior diameters (AP: 3.9±0.5cm, 3.5±0.7cm; p<0.001), and annulus-areas (2D: 12.9±3.8cm2, 12.6±3.7cm2; p<0.001; 3D: 13.4±3.8, 13.1±3.2cm2; p<0.001). All measures on MV annular geometry were not significantly altered in patients with PMR (p>0.05). After one year of follow-up, MV annular parameters remained significantly reduced in SMR patients (p<0.05) and remained unchanged in subjects with PMR (p>0.05). Only SMR patients experienced significant increase in 6min walking distances (p=0.004), decrease in pulmonary pressures (p=0.007) and functional NYHA-class (p<0.001); in patients with PMR only NYHA class improved after one year (p<0.001). Edge-to-edge repair with the MitraClip-system impacts on MV-geometry in patients with SMR with stable results after 12months. Reduction of MV-annular dimensions was associated with higher rates of persisting MR reduction and better functional status in patients with SMR. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Iron K-edge X-ray absorption near-edge structure spectroscopy of aerodynamically levitated silicate melts and glasses

DOE PAGES

Alderman, O. L. G.; Wilding, M. C.; Tamalonis, A.; ...

2017-01-26

Here, the local structure about Fe(II) and Fe(III) in silicate melts was investigated in-situ using iron K-edge X-ray absorption near-edge structure (XANES) spectroscopy. An aerodynamic levitation and laser heating system was used to allow access to high temperatures without contamination, and was combined with a chamber and gas mixing system to allow the iron oxidation state, Fe 3+/ΣFe, to be varied by systematic control of the atmospheric oxygen fugacity. Eleven alkali-free, mostly iron-rich and depolymerized base compositions were chosen for the experiments, including pure oxide FeO, olivines (Fe,Mg) 2SiO 4, pyroxenes (Fe,Mg)SiO 3, calcic FeO-CaSiO 3, and a calcium aluminosilicatemore » composition, where total iron content is denoted by FeO for convenience. Melt temperatures varied between 1410 and 2160 K and oxygen fugacities between FMQ – 2.3(3) to FMQ + 9.1(3) log units (uncertainties in parentheses) relative to the fayalite-magnetite-β-quartz (FMQ) buffer.« less

Convergent regulation of the lysosomal two-pore channel-2 by Mg2+, NAADP, PI(3,5)P2 and multiple protein kinases

PubMed Central

Jha, Archana; Ahuja, Malini; Patel, Sandip; Brailoiu, Eugen; Muallem, Shmuel

2014-01-01

Lysosomal Ca2+ homeostasis is implicated in disease and controls many lysosomal functions. A key in understanding lysosomal Ca2+ signaling was the discovery of the two-pore channels (TPCs) and their potential activation by NAADP. Recent work concluded that the TPCs function as a PI(3,5)P2 activated channels regulated by mTORC1, but not by NAADP. Here, we identified Mg2+ and the MAPKs, JNK and P38 as novel regulators of TPC2. Cytoplasmic Mg2+ specifically inhibited TPC2 outward current, whereas lysosomal Mg2+ partially inhibited both outward and inward currents in a lysosomal lumen pH-dependent manner. Under controlled Mg2+, TPC2 is readily activated by NAADP with channel properties identical to those in response to PI(3,5)P2. Moreover, TPC2 is robustly regulated by P38 and JNK. Notably, NAADP-mediated Ca2+ release in intact cells is regulated by Mg2+, PI(3,5)P2, and P38/JNK kinases, thus paralleling regulation of TPC2 currents. Our data affirm a key role for TPC2 in NAADP-mediated Ca2+ signaling and link this pathway to Mg2+ homeostasis and MAP kinases, pointing to roles for lysosomal Ca2+ in cell growth, inflammation and cancer. PMID:24502975

Thrombin-induced activation of RhoA in platelet shape change.

PubMed

Bodie, S L; Ford, I; Greaves, M; Nixon, G F

2001-09-14

Thrombin-induced activation of RhoA and its involvement in the regulation of myosin II light chain(20) phosphorylation (MLC-P) in alpha-toxin permeabilized platelets was investigated. Permeabilized platelets, expressing normal levels of P-selectin, displayed a Ca(2+)-dependent increase in shape change and MLC-P. Thrombin activated RhoA as measured by a rhotekin-binding assay within 30 s of stimulation under conditions of constant [Ca(2+)](i). Under the same conditions and timecourse, thrombin or GTPgammaS induced an increase in MLC-P and platelet shape change which was not dependent on an increase in [Ca(2+)](i). The thrombin- and GTPgammaS-induced MLC-P in constant [Ca(2+)](i) was inhibited by the addition of Y27632, a Rho-kinase inhibitor. This study directly demonstrates that thrombin can activate RhoA in platelets in a timecourse compatible with a role in increasing MLC-P and shape change (not involving an increase in [Ca(2+)](i)). This is also Rho-kinase-dependent. Copyright 2001 Academic Press.

Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes

PubMed Central

Occhipinti, Rossana; Boron, Walter F.

2014-01-01

The α-carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the interconversion of CO2 and HCO3−. Here, we focus on human CA II (CA II), a ubiquitous cytoplasmic enzyme. In the second paper in this series, we examine CA IV at the extracellular surface. After microinjecting recombinant CA II in a Tris solution (or just Tris) into oocytes, we expose oocytes to 1.5% CO2/10 mM HCO3−/pH 7.50 while using microelectrodes to monitor intracellular pH (pHi) and surface pH (pHS). CO2 influx causes the familiar sustained pHi fall as well as a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA II increases the magnitudes of the maximal rate of pHi change, (dpHi/dt)max, and the maximal change in pHS, ΔpHS. Preincubating oocytes with the inhibitor ethoxzolamide eliminates the effects of CA II. Compared with pHS, pHi begins to change only after a delay of ∼9 s and its relaxation has a larger (i.e., slower) time constant (τpHi > τpHS). Simultaneous measurements with two pHi electrodes, one superficial and one deep, suggest that impalement depth contributes to pHi delay and higher τpHi. Using higher CO2/HCO3− levels, i.e., 5%/33 mM HCO3− or 10%/66 mM HCO3−, increases (dpHi/dt)max and ΔpHS, though not in proportion to the increase in [CO2]. A reaction-diffusion mathematical model (described in the third paper in this series) accounts for the above general features and supports the conclusion that cytosolic CA—consuming entering CO2 or replenishing exiting CO2—increases CO2 fluxes across the cell membrane. PMID:24965587

Prognostic value of preoperative serum CA 242 in Esophageal squamous cell carcinoma cases.

PubMed

Feng, Ji-Feng; Huang, Ying; Chen, Qi-Xun

2013-01-01

Carbohydrate antigen (CA) 242 is inversely related to prognosis in many cancers. However, few data regarding CA 242 in esophageal cancer (EC) are available. The aim of this study was to determine the prognostic value of CA 242 and propose an optimum cut-off point in predicting survival difference in patients with esophageal squamous cell carcinoma (ESCC). A retrospective analysis was conducted of 192 cases. A receiver operating characteristic (ROC) curve for survival prediction was plotted to verify the optimum cuf- off point. Univariate and multivariate analyses were performed to evaluate prognostic parameters for survival. The positive rate for CA 242 was 7.3% (14/192). The ROC curve for survival prediction gave an optimum cut-off of 2.15 (U/ml). Patients with CA 242 ≤ 2.15 U/ml had significantly better 5-year survival than patients with CA 242 >2.15 U/ml (45.4% versus 22.6%; P=0.003). Multivariate analysis showed that differentiation (P=0.033), CA 242 (P=0.017), T grade (P=0.004) and N staging (P<0.001) were independent prognostic factors. Preoperative CA 242 is a predictive factor for long-term survival in ESCC, especially in nodal-negative patients. We conclude that 2.15 U/ml may be the optimum cuf-off point for CA 242 in predicting survival in ESCC.

Spermatozoa in the sperm-peak-fraction of the boar ejaculate show a lower flow of Ca(2+) under capacitation conditions post-thaw which might account for their higher membrane stability after cryopreservation.

PubMed

Hossain, Md Sharoare; Johannisson, Anders; Siqueira, Amanda Pimenta; Wallgren, Margareta; Rodriguez-Martinez, Heriberto

2011-10-01

Boar spermatozoa collected in the ejaculate sperm peak-portion (P1, first 10 mL of the sperm-rich fraction, SRF), had shown a higher resilience to freezing and thawing compared to spermatozoa from the rest of the ejaculate (2nd portion of the SRF plus the post-sperm-rich fraction, PSRF), even when using a simplified freezing technique, as long as spermatozoa were incubated in their own seminal plasma (SP). This experiment studied the stability of P1- and SRF-P1 boar spermatozoa frozen in MiniFlatPacks (MFP), post-thaw, using flow cytometry. Since spermatozoa from either portion showed similar cryosurvival and low proportions of unstable membranes (<3%, annexin-V/propidium iodide staining), and only a tendency for SRF-P1 live spermatozoa to depict acrosome exocytosis (FITC-PNA/PI/H33342); they were explored for Ca(2+) contents using a Fluo-4 probe under in vitro capacitating conditions (mBO+ medium), as well they were tested for their ability to sustain a short Ca(2+)-ionophore (A23187) in vitro challenge. The proportions of live spermatozoa depicting high Ca(2+)-levels were initially <2% but increased over incubation time, particularly in SRF-P1(P<0.05), while proportions of live spermatozoa with low Ca(2+)-levels were basically constant over incubation time (~11-14%), for either portion. Incubation in capacitation medium did not modify the proportions of low-Ca(2+) but dramatically increased the proportions of high-Ca(2+) spermatozoa (P<0.001) already after 15 min exposure, highest for SRF-P1 spermatozoa. While the proportion of live spermatozoa with intact acrosome was significantly decreased among SRF-P1 (P<0.001), that of P1-spermatozoa remained unchanged, probably owing to the lowest relative content of cytosolic Ca(2+). The results suggest that spermatozoa in the P1-portion are more resilient to express acrosome exocytosis post-thaw compared to those bathing in the rest of the SRF-fraction when cryopreserved using a simplified technique, in MFPs. Copyright © 2011 Elsevier B.V. All rights reserved.

Study of SiRNA-loaded PS-mPEG/CaP nanospheres on lung cancer

NASA Astrophysics Data System (ADS)

Wang, Qi; Qin, Liubin; Sun, Ying; Shen, Ming; Duan, Yourong

2014-05-01

An ultrasound-adsorption method was used to prepare Bcl-2-SiRNA-loaded PS-mPEG/CaP nanospheres. The size and zeta potential were 18.41 ± 4.31 nm ( n = 5) and -23.5 ± 0.6 mV, respectively. The entrapment efficiency of SiRNA was 92.86 %. MTT assay results confirmed that the blank nanospheres demonstrated a negligible cytotoxicity response in H1299 cells. Flow cytometer analysis results demonstrated that PS-mPEG/CaP NSs could carry SiRNA into the cells effectively. RT-PCR experiments and apoptosis assay results approved that, compared with free SiRNA, SiRNA-loaded PS-mPEG/CaP NSs could silence Bcl-2 gene and induce cell apoptosis effectively. In vivo distribution results confirmed PS-mPEG/CaP NSs could carry SiRNA enter the tumor tissue effectively. Taken together, these results suggest that the Bcl-2-SiRNA-loaded PS-mPEG/CaP nanospheres have great potential to be used to cure lung cancer.

A limited role for carbonic anhydrase in C 4 photosynthesis as revealed by a ca1ca2 double mutant in maize.

DOE PAGES

Studer, Anthony J.; Gandin, Anthony; Kolbe, Allison R.; ...

2014-04-04

Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon concentrating mechanism of C 4 plants, and in C 4 monocots, it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon induced mutant alleles of Ca1 and Ca2 in Zea mays. In addition, these two isoforms account for more than 85% of the CA transcript pool. A significant change in isotopic discrimination is observed in mutant plants, which have as little as 3% of wild-type CA activity, but surprisingly, photosynthesis is not reduced under current or elevatedmore » pCO 2. However, growth and rates of photosynthesis under sub-ambient pCO 2 are significantly impaired in the mutants. These findings suggest, that while CA is not limiting for C 4 photosynthesis in Z. mays at current pCO 2, it likely maintains high rates of photosynthesis when CO 2 availability is reduced. Current atmospheric CO 2 levels now exceed 400 ppm (~40.53 Pa) and contrast the low CO 2 partial pressure (pCO 2) conditions under which C 4 plants expanded their range ~10 million years ago when the global atmospheric CO 2 was below 300 ppm (~30.40 Pa). Thus, as CO 2 levels continue to rise, selective pressures for high levels of CA may be limited to arid climates where stomatal closure reduces CO 2 availability to the leaf.« less

The type III inositol 1,4,5-trisphosphate receptor preferentially transmits apoptotic Ca2+ signals into mitochondria.

PubMed

Mendes, Carolina C P; Gomes, Dawidson A; Thompson, Mayerson; Souto, Natalia C; Goes, Tercio S; Goes, Alfredo M; Rodrigues, Michele A; Gomez, Marcus V; Nathanson, Michael H; Leite, M Fatima

2005-12-09

There are three isoforms of the inositol 1,4,5- trisphosphate receptor (InsP(3)R), each of which has a distinct effect on Ca(2+) signaling. However, it is not known whether each isoform similarly plays a distinct role in the activation of Ca(2+)-mediated events. To investigate this question, we examined the effects of each InsP(3)R isoform on transmission of Ca(2+) signals to mitochondria and induction of apoptosis. Each isoform was selectively silenced using isoform-specific small interfering RNA in Chinese hamster ovary cells, which express all three InsP(3)R isoforms. ATP-induced cytosolic Ca(2+) signaling patterns were altered, regardless of which isoform was silenced, but in a different fashion depending on the isoform. ATP also induced Ca(2+) signals in mitochondria, which were inhibited more effectively by silencing the type III InsP(3)R than by silencing either the type I or type II isoform. The type III isoform also co-localized most strongly with mitochondria. When apoptosis was induced by activation of either the extrinsic or intrinsic apoptotic pathway, induction was reduced most effectively by silencing the type III InsP(3)R. These findings provide evidence that the type III isoform of the InsP(3)R plays a special role in induction of apoptosis by preferentially transmitting Ca(2+) signals into mitochondria.

Reverse Micelle Mediated synthesis of Calcium Phosphate Nanocarriers for Controlled Release of Bovine Serum Albumin (BSA)

PubMed Central

Dasgupta, Sudip; Bandyopadhyay, Amit; Bose, Susmita

2010-01-01

Calcium phosphate (CaP) nanoparticle with calcium to phosphorus (Ca:P) molar ratio of 1.5:1 were synthesized using reverse micro emulsion. Ca(NO3)2.4H2O and H3PO4 were used as aqueous phase, cyclohexane as organic phase, and poly(oxyethylene)12 nonylphenol ether (NP-12) as surfactant. Depending on calcination temperature between 600 and 800 °C, CaP nanoparticle showed different phases calcium deficient hydroxyapatite (CDHA) and β-tricalcium phosphate (β-TCP), particle size between 48 and 69 nm, the BET specific average surface area between 73 m2/g and 57 m2/g. Bovine serum albumin (BSA) was used as a model protein to study loading and release behavior. Adsorptive property of BSA was investigated with the change in BET surface area of these nanoparticle and the pH of the suspension. At pH 7.5, maximum amount of BSA was adsorbed onto CaP nanoparticle. The release kinetics of BSA showed a gradual time dependent increase at pH 4.0 and 6.0 buffer solutions. However, the amount of released protein was significantly smaller at pH 7.2. BSA release rate also varied depending on the presence of different phases of CaPs in the system, β-TCP or CDHA. These results suggest that BSA protein release rate can be controlled by changing particle size, surface area and phase composition of CaP nanocarriers. PMID:19435617

Calcium hydroxide as a processing base in alkali-aided pH-shift protein recovery process.

PubMed

Paker, Ilgin; Jaczynski, Jacek; Matak, Kristen E

2017-02-01

Protein may be recovered by using pH shifts to solubilize and precipitate protein. Typically, sodium hydroxide is used as the processing base; however, this has been shown to significantly increase sodium in the final recovered protein. Protein was extracted from black bullhead catfish (Ameiurus melas) using a pH-shift method. Protein was solubilized using either sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH) 2 ) and precipitated at pH 5.5 using hydrochloric acid (HCl). Protein solubility was greater when Ca(OH) 2 was used compared to NaOH during this process. Using Ca(OH) 2 as the processing base yielded the greatest lipid recovery (P < 0.05) at 77 g 100 g -1 , whereas the greatest (P < 0.05) protein recovery yield was recorded as 53 g 100 g -1 protein using NaOH. Protein solubilized with Ca(OH) 2 had more (P < 0.05) calcium in the protein fraction, whereas using NaOH increased (P < 0.05) sodium content. Results of our study showed that protein solubility was increased and the recovered protein had significantly more calcium when Ca(OH) 2 was used as the processing base. Results showed both NaOH and Ca(OH) 2 to be an effective processing base for pH-shift protein recovery processes. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Intracellular Ca2+ transients in mouse soleus muscle after hindlimb unloading and reloading

NASA Technical Reports Server (NTRS)

Ingalls, C. P.; Warren, G. L.; Armstrong, R. B.; Hamilton, S. L. (Principal Investigator)

1999-01-01

The objective of this study was to determine whether altered intracellular Ca(2+) handling contributes to the specific force loss in the soleus muscle after unloading and/or subsequent reloading of mouse hindlimbs. Three groups of female ICR mice were studied: 1) unloaded mice (n = 11) that were hindlimb suspended for 14 days, 2) reloaded mice (n = 10) that were returned to their cages for 1 day after 14 days of hindlimb suspension, and 3) control mice (n = 10) that had normal cage activity. Maximum isometric tetanic force (P(o)) was determined in the soleus muscle from the left hindlimb, and resting free cytosolic Ca(2+) concentration ([Ca(2+)](i)), tetanic [Ca(2+)](i), and 4-chloro-m-cresol-induced [Ca(2+)](i) were measured in the contralateral soleus muscle by confocal laser scanning microscopy. Unloading and reloading increased resting [Ca(2+)](i) above control by 36% and 24%, respectively. Although unloading reduced P(o) and specific force by 58% and 24%, respectively, compared with control mice, there was no difference in tetanic [Ca(2+)](i). P(o), specific force, and tetanic [Ca(2+)](i) were reduced by 58%, 23%, and 23%, respectively, in the reloaded animals compared with control mice; however, tetanic [Ca(2+)](i) was not different between unloaded and reloaded mice. These data indicate that although hindlimb suspension results in disturbed intracellular Ca(2+) homeostasis, changes in tetanic [Ca(2+)](i) do not contribute to force deficits. Compared with unloading, 24 h of physiological reloading in the mouse do not result in further changes in maximal strength or tetanic [Ca(2+)](i).

Ca2+ release by inositol-trisphosphorothioate in isolated triads of rabbit skeletal muscle.

PubMed Central

Valdivia, C; Valdivia, H H; Potter, B V; Coronado, R

1990-01-01

The effectiveness of the nonmetabolizable second messenger analogue DL-myo-inositol 1,4,5-trisphosphorothioate (IPS3) described by Cooke, A. M., R. Gigg, and B. V. L. Potter, (1987b. Jour. Chem. Soc. Chem. Commun. 1525-1526.) was examined in triads purified from rabbit skeletal muscle. A Ca2+ electrode uptake-release assay was used to determine the size and sensitivity of the IPS3-releasable pool of Ca2+ in isolated triads. Uptake was initiated by 1 mM MgATP, pCa 5.8, pH 7.5 Release was initiated when the free Ca2+ had lowered to pCa approximately 7. We found that 5-25 microM myo-inositol 1,4,5-trisphosphate (IP3), and separately IPS3, consistently released 5-20% of the Ca2+ pool actively loaded into triads. Single channel recording was used to determine if ryanodine receptor Ca2+ release channels were affected by IPS3 at the same myoplasmic Ca2+ and IPS3 concentrations. Open probability of ryanodine receptor Ca2+ release channels was monitored in triads fused to bilayers over long periods (200 s) in the absence and following addition of 30 microM IPS3 to the same channel. At myoplasmic pCa approximately 7, IPS3 had no effect in the absence of MgATP (Po = 0.0094 +/- 0.001 in control and Po = 0.01 +/- 0.006 after IPS3) and slightly increased activity in the presence of 1 mM MgATP (Po = 0.024 +/- 0.03 in control and Po = 0.05 +/- 0.03 after IPS3). Equally small effects were observed at higher myoplasmic Ca2+. The onset of channel activation by IPS3 or IP3 was slow, on the time scale 20-60 s. We suggest that in isolated triads of rabbit skeletal muscle, IP3-induced release of stored Ca2+ is probably not mediated by the opening of Ca2+ release channels. PMID:2168221

Dietary maifanite supplementation did not affect the apparent total tract digestibility of calcium and phosphorus in growing pigs

PubMed Central

Bai, Li Li; Ming, Dong Xu; Dong, Shu Ren; Yang, Zhong Yue; Wang, Wen Hui; Zhang, Shuai; Piao, Xiang Shu

2018-01-01

Objective This study was conducted to determine the effects of dietary maifanite supplementation and fecal collection method on the apparent total tract digestibility (ATTD) of calcium (Ca) and phosphorus (P) and blood parameters in growing pigs. Methods Thirty-six growing barrows (Duroc×Landrace×Yorkshire; 27.0±2.6 kg) were allotted to six dietary treatments with 6 pigs per treatment according to body weight in a completely randomized design. The experimental treatments were: i) Low Ca+cornstarch (2.25%), ii) Low Ca+maifanite (2.25%), iii) Medium Ca+cornstarch (1.42%), iv) Medium Ca+maifanite (1.42%), v) High Ca+cornstarch (0.64%), and vi) High Ca+maifanite (0.64%). Feces were collected by the total collection (TC) and indicator method (IM). At the beginning and the end of the experiment, blood samples were collected from each pig. Results For the TC method, there were no difference in Ca intake, fecal Ca output, Ca retention and the ATTD of Ca between cornstarch and maifanite diets at the same dietary Ca level. However, urinary Ca excretion was lower (p = 0.01) in pigs fed low Ca diets without maifanite supplementation compared with other dietary treatments. Dietary maifanite supplementation had no effect on the P metabolism in growing pigs. For the IM method, there was no difference in Ca digestibility between cornstarch and maifanite diets at the same dietary Ca level. The ATTD of P was greater (p<0.01) in pigs fed the high Ca diet with maifanite supplementation compared with the high Ca diet with cornstarch treatment. Dietary inclusion of maifanite had no effect on blood parameters in growing pigs. Conclusion Dietary maifanite supplementation had no effect on the ATTD of Ca and P and serum parameters in growing pigs. The IM resulted in lower digestibility values than the TC method. PMID:28728391

Cardiac microvascular endothelial cells express a functional Ca+ -sensing receptor.

PubMed

Berra Romani, Roberto; Raqeeb, Abdul; Laforenza, Umberto; Scaffino, Manuela Federica; Moccia, Francesco; Avelino-Cruz, Josè Everardo; Oldani, Amanda; Coltrini, Daniela; Milesi, Veronica; Taglietti, Vanni; Tanzi, Franco

2009-01-01

The mechanism whereby extracellular Ca(2+) exerts the endothelium-dependent control of vascular tone is still unclear. In this study, we assessed whether cardiac microvascular endothelial cells (CMEC) express a functional extracellular Ca(2+)-sensing receptor (CaSR) using a variety of techniques. CaSR mRNA was detected using RT-PCR, and CaSR protein was identified by immunocytochemical analysis. In order to assess the functionality of the receptor, CMEC were loaded with the Ca(2+)-sensitive fluorochrome, Fura-2/AM. A number of CaSR agonists, such as spermine, Gd(3+), La(3+) and neomycin, elicited a heterogeneous intracellular Ca(2+) signal, which was abolished by disruption of inositol 1,4,5-trisphosphate (InsP(3)) signaling and by depletion of intracellular stores with cyclopiazonic acid. The inhibition of the Na(+)/Ca(2+) exchanger upon substitution of extracellular Na(+) unmasked the Ca(2+) signal triggered by an increase in extracellular Ca(2+) levels. Finally, aromatic amino acids, which function as allosteric activators of CaSR, potentiated the Ca(2+) response to the CaSR agonist La(3+). These data provide evidence that CMEC express CaSR, which is able to respond to physiological agonists by mobilizing Ca(2+) from intracellular InsP(3)-sensitive stores. Copyright 2008 S. Karger AG, Basel.

Cocaine- and amphetamine-regulated transcript peptide in the nucleus accumbens shell inhibits cocaine-induced locomotor sensitization to transient over-expression of α-Ca2+ /calmodulin-dependent protein kinase II.

PubMed

Xiong, Lixia; Meng, Qing; Sun, Xi; Lu, Xiangtong; Fu, Qiang; Peng, Qinghua; Yang, Jianhua; Oh, Ki-Wan; Hu, Zhenzhen

2018-01-04

Cocaine- and amphetamine-regulated transcript (CART) peptide is a widely distributed neurotransmitter that attenuates cocaine-induced locomotor activity when injected into the nucleus accumbens (NAc). Our previous work first confirmed that the inhibitory mechanism of the CART peptide on cocaine-induced locomotor activity is related to a reduction in cocaine-enhanced phosphorylated Ca 2+ /calmodulin-dependent protein kinaseIIα (pCaMKIIα) and the enhancement of cocaine-induced D3R function. This study investigated whether CART peptide inhibited cocaine-induced locomotor activity via inhibition of interactions between pCaMKIIα and the D3 dopamine receptor (D3R). We demonstrated that lentivirus-mediated gene transfer transiently increased pCaMKIIα expression, which peaked at 10 days after microinjection into the rat NAc shell, and induced a significant increase in Ca 2+ influx along with greater behavioral sensitivity in the open field test after intraperitoneal injections of cocaine (15 mg/kg). However, western blot analysis and coimmunoprecipitation demonstrated that CART peptide treatment in lentivirus-transfected CaMKIIα-over-expressing NAc rat tissues or cells prior to cocaine administration inhibited the cocaine-induced Ca 2+ influx and attenuated the cocaine-increased pCaMKIIα expression in lentivirus-transfected CaMKIIα-over-expressing cells. CART peptide decreased the cocaine-enhanced phosphorylated cAMP response element binding protein (pCREB) expression via inhibition of the pCaMKIIα-D3R interaction, which may account for the prolonged locomotor sensitization induced by repeated cocaine treatment in lentivirus-transfected CaMKIIα-over-expressing cells. These results provide strong evidence for the inhibitory modulation of CART peptide in cocaine-induced locomotor sensitization. © 2018 International Society for Neurochemistry.

Measuring the isoelectric point of the edges of clay mineral particles: the case of montmorillonite.

PubMed

Pecini, Eliana M; Avena, Marcelo J

2013-12-03

The isoelectric point (IEP) of the edge surface of a montmorillonite sample was determined by using electrophoretic mobility measurements. This parameter, which is fundamental for the understanding of the charging behavior of clay mineral surfaces, was never measured so far because of the presence of permanent negative charges within the montmorillonite structure, charges that mask the electrokinetic behavior of the edges. The strategy was to block or neutralize the structural charges with two different cations, methylene blue (MB(+)) and tetraethylenepentaminecopper(II) ([Cu(tetren)](2+)), so that the charging behavior of the particles becomes that of the edge surfaces. Adsorption isotherms of MB(+) and [Cu(tetren)](2+) at different ionic strengths (NaCl) were performed to establish the uptakes that neutralize the cation exchange capacity (CEC, 0.96 meq g(-1)) of the sample. At high adsorptive concentrations, there was a superequivalent adsorption of MB(+) (adsorption exceeding the CEC) and an equivalent adsorption of [Cu(tetren)](2+) (adsorption reaching the CEC). In both cases, structural charges were neutralized at uptakes very close to the CEC. Zeta potential (ζ) vs pH data at different ionic strengths of montmorillonite with adsorbed MB(+) allowed to estimate an upper limit of the edge's IEP, 5.3 ± 0.2. The same kind of data obtained with adsorbed [Cu(tetren)](2+) provided a lower limit of the IEP, 4.0 ± 0.2. These values are in agreement with previously informed IEP and point of zero charge of pyrophyllite, which is structurally analogous to montmorillonite but carries no permanent charges. The importance of knowing the IEP of the edge surface of clay minerals is discussed. This value characterizes the intrinsic reactivity of edges, that is, the protonating capacity of edge groups in absence of any electric field generated by structural charges. It also allows us to correct relative edge charge vs pH curves obtained by potentiometric titrations and to obtain the true edge charge vs pH curves at different electrolyte concentrations.

How Source Content Determines Intracellular Ca2+ Release Kinetics. Simultaneous Measurement of [Ca2+] Transients and [H+] Displacement in Skeletal Muscle

PubMed Central

Pizarro, Gonzalo; Ríos, Eduardo

2004-01-01

In skeletal muscle, the waveform of Ca2+ release under clamp depolarization exhibits an early peak. Its decay reflects an inactivation, which locally corresponds to the termination of Ca2+ sparks, and is crucial for rapid control. In cardiac muscle, both the frequency of spontaneous sparks (i.e., their activation) and their termination appear to be strongly dependent on the Ca2+ content in the sarcoplasmic reticulum (SR). In skeletal muscle, no such role is established. Seeking a robust measurement of Ca2+ release and a way to reliably modify the SR content, we combined in the same cells the “EGTA/phenol red” method (Pape et al., 1995) to evaluate Ca2+ release, with the “removal” method (Melzer et al., 1987) to evaluate release flux. The cytosol of voltage-clamped frog fibers was equilibrated with EGTA (36 mM), antipyrylazo III, and phenol red, and absorbance changes were monitored simultaneously at three wavelengths, affording largely independent evaluations of Δ[H+] and Δ[Ca2+] from which the amount of released Ca2+ and the release flux were independently derived. Both methods yielded mutually consistent evaluations of flux. While the removal method gave a better kinetic picture of the release waveform, EGTA/phenol red provided continuous reproducible measures of calcium in the SR (CaSR). Steady release permeability (P), reached at the end of a 120-ms pulse, increased as CaSR was progressively reduced by a prior conditioning pulse, reaching 2.34-fold at 25% of resting CaSR (four cells). Peak P, reached early during a pulse, increased proportionally much less with SR depletion, decreasing at very low CaSR. The increase in steady P upon depletion was associated with a slowing of the rate of decay of P after the peak (i.e., a slower inactivation of Ca2+ release). These results are consistent with a major inhibitory effect of cytosolic (rather than intra-SR) Ca2+ on the activity of Ca2+ release channels. PMID:15337820

Laser induced fluorescence spectroscopy of the Ca dimer deposited on helium and mixed helium/xenon clusters

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

Gaveau, Marc-André; Pothier, Christophe; Briant, Marc

2014-12-09

We study how the laser induced fluorescence spectroscopy of the calcium dimer deposited on pure helium clusters is modified by the addition of xenon atoms. In the wavelength range between 365 and 385 nm, the Ca dimer is excited from its ground state up to two excited electronic states leading to its photodissociation in Ca({sup 1}P)+Ca({sup 1}S): this process is monitored by recording the Ca({sup 1}P) fluorescence at 422.7nm. One of these electronic states of Ca{sub 2} is a diexcited one correlating to the Ca(4s4p{sup 3}P(+Ca(4s3d{sup 3}D), the other one is a repulsive state correlating to the Ca(4s4p1P)+Ca(4s21S) asymptote, accountingmore » for the dissociation of Ca{sub 2} and the observation of the subsequent Ca({sup 1}P) emission. On pure helium clusters, the fluorescence exhibits the calcium atomic resonance line Ca({sup 1}S←{sup 1}P) at 422.7 nm (23652 cm{sup −1}) assigned to ejected calcium, and a narrow red sided band corresponding to calcium that remains solvated on the helium cluster. When adding xenon atoms to the helium clusters, the intensity of these two features decreases and a new spectral band appears on the red side of calcium resonance line; the intensity and the red shift of this component increase along with the xenon quantity deposited on the helium cluster: it is assigned to the emission of Ca({sup 1}P) associated with the small xenon aggregate embedded inside the helium cluster.« less

Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system

NASA Astrophysics Data System (ADS)

Li, Xudong; Cai, Shu; Zhang, Wenjuang; Xu, Guohua; Zhou, Wei

2009-08-01

The bioactive glass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system were synthesized by the sol-gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca 2P 2O 7 and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP 2O 6 was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca 4P 6O 19 was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.

S-Glutathionylation of troponin I (fast) increases contractile apparatus Ca2+ sensitivity in fast-twitch muscle fibres of rats and humans

PubMed Central

Mollica, J P; Dutka, T L; Merry, T L; Lamboley, C R; McConell, G K; McKenna, M J; Murphy, R M; Lamb, G D

2012-01-01

Oxidation can decrease or increase the Ca2+ sensitivity of the contractile apparatus in rodent fast-twitch (type II) skeletal muscle fibres, but the reactions and molecular targets involved are unknown. This study examined whether increased Ca2+ sensitivity is due to S-glutathionylation of particular cysteine residues. Skinned muscle fibres were directly activated in heavily buffered Ca2+ solutions to assess contractile apparatus Ca2+ sensitivity. Rat type II fibres were subjected to S-glutathionylation by successive treatments with 2,2′-dithiodipyridine (DTDP) and glutathione (GSH), and displayed a maximal increase in pCa50 (−log10µCa2+½ at half-maximal force) of ∼0.24 pCa units, with little or no effect on maximum force or Hill coefficient. Partial similar effect was produced by exposure to oxidized gluthathione (GSSG, 10 mm) for 10 min at pH 7.1, and near-maximal effect by GSSG treatment at pH 8.5. None of these treatments significantly altered Ca2+ sensitivity in rat type I fibres. Western blotting showed that both the DTDP–GSH and GSSG–pH 8.5 treatments caused marked S-glutathionylation of the fast troponin I isoform (TnIf) present in type II fibres, but not of troponin C (TnC) or myosin light chain 2. Both the increased Ca2+ sensitivity and glutathionylation of TnIf were blocked by N-ethylmaleimide (NEM). S-Nitrosoglutathione (GSNO) also increased Ca2+ sensitivity, but only in conditions where it caused S-glutathionylation of TnIf. In human type II fibres from vastus lateralis muscle, DTDP–GSH treatment also caused similar increased Ca2+ sensitivity and S-glutathionylation of TnIf. When the slow isoform of TnI in type I fibres of rat was partially substituted (∼30%) with TnIf, DTDP–GSH treatment caused a significant increase in Ca2+ sensitivity (∼0.08 pCa units). TnIf in type II fibres from toad and chicken muscle lack Cys133 present in mammalian TnIf, and such fibres showed no change in Ca2+ sensitivity with DTDP–GSH nor any S-glutathionylation of TnIf (latter examined only in toad). Following 40 min of cycling exercise in human subjects (at ∼60% peak oxygen consumption), TnIf in vastus lateralis muscle displayed a marked increase in S-glutathionylation (∼4-fold). These findings show that S-glutathionylation of TnIf, most probably at Cys133, increases the Ca2+ sensitivity of the contractile apparatus, and that this occurs in exercising humans, with likely beneficial effects on performance. PMID:22250211

S-glutathionylation of troponin I (fast) increases contractile apparatus Ca2+ sensitivity in fast-twitch muscle fibres of rats and humans.

PubMed

Mollica, J P; Dutka, T L; Merry, T L; Lamboley, C R; McConell, G K; McKenna, M J; Murphy, R M; Lamb, G D

2012-03-15

Oxidation can decrease or increase the Ca2+ sensitivity of the contractile apparatus in rodent fast-twitch (type II) skeletal muscle fibres, but the reactions and molecular targets involved are unknown. This study examined whether increased Ca2+ sensitivity is due to S-glutathionylation of particular cysteine residues. Skinned muscle fibres were directly activated in heavily buffered Ca2+ solutions to assess contractile apparatus Ca2+ sensitivity. Rat type II fibres were subjected to S-glutathionylation by successive treatments with 2,2′-dithiodipyridine (DTDP) and glutathione (GSH), and displayed a maximal increase in pCa50 (−log10 [Ca2+] at half-maximal force) of ∼0.24 pCa units, with little or no effect on maximum force or Hill coefficient. Partial similar effect was produced by exposure to oxidized gluthathione (GSSG, 10 mM) for 10 min at pH 7.1, and near-maximal effect by GSSG treatment at pH 8.5. None of these treatments significantly altered Ca2+ sensitivity in rat type I fibres. Western blotting showed that both the DTDP–GSH and GSSG–pH 8.5 treatments caused marked S-glutathionylation of the fast troponin I isoform (TnI(f)) present in type II fibres, but not of troponin C (TnC) or myosin light chain 2. Both the increased Ca2+ sensitivity and glutathionylation of TnI(f) were blocked by N-ethylmaleimide (NEM). S-nitrosoglutathione (GSNO) also increased Ca2+ sensitivity, but only in conditions where it caused S-glutathionylation of TnI(f). In human type II fibres from vastus lateralis muscle, DTDP–GSH treatment also caused similar increased Ca2+ sensitivity and S-glutathionylation of TnI(f). When the slow isoform of TnI in type I fibres of rat was partially substituted (∼30%) with TnI(f), DTDP–GSH treatment caused a significant increase in Ca2+ sensitivity (∼0.08 pCa units). TnIf in type II fibres from toad and chicken muscle lack Cys133 present in mammalian TnIf, and such fibres showed no change in Ca2+ sensitivity with DTDP–GSH nor any S-glutathionylation of TnI(f) (latter examined only in toad). Following 40 min of cycling exercise in human subjects (at ∼60% peak oxygen consumption), TnI(f) in vastus lateralis muscle displayed a marked increase in S-glutathionylation (∼4-fold). These findings show that S-glutathionylation of TnI(f), most probably at Cys133, increases the Ca2+ sensitivity of the contractile apparatus, and that this occurs in exercising humans, with likely beneficial effects on performance.

Super local edge antimagic total coloring of {P}_{n}\\vartriangleright H

NASA Astrophysics Data System (ADS)

Yuli Kurniawati, Elsa; Hesti Agustin, Ika; Dafik; Alfarisi, Ridho

2018-04-01

In this paper, we consider that all graphs are finite, simple and connected. Let G(V, E) be a graph of vertex set V and edge set E. A bijection f:V(G)\\to \\{1,2,3,\\ldots,|V(G)|\\} is called a local edge antimagic labeling if for any two adjacent edges e 1 and e 2, w({e}1)\

A shell-formation related carbonic anhydrase in Crassostrea gigas modulates intracellular calcium against CO2 exposure: Implication for impacts of ocean acidification on mollusk calcification.

PubMed

Wang, Xiudan; Wang, Mengqiang; Jia, Zhihao; Song, Xiaorui; Wang, Lingling; Song, Linsheng

2017-08-01

Ocean acidification (OA) could decrease the shells and skeletons formation of mollusk by reducing the availability of carbonate ions at calcification sites. Carbonic anhydrases (CAs) convert CO 2 to HCO 3 - and play important roles in biomineralization process from invertebrate to vertebrate. In the present study, a CA (designated as CgCA) was identified and characterized in Pacific oyster C. gigas. The cDNA of CgCA was of 927bp encoding a predicted polypeptide of 308 amino acids with a signal peptide and a CA catalytic function domain. The mRNA transcripts of CgCA were constitutively expressed in all tested tissues with the highest levels in mantle and hemocytes. During the early development period, the mRNA transcripts of CgCA could be detected in all the stages with the highest level in D-veliger larvae. Elevated CO 2 increased the mRNA transcripts of CgCA in muscle, mantle, hepatopancreas, gill and hemocytes significantly (p<0.05) and induced the translocation of CgCA in hemocytes and mantle. Moreover, elevated CO 2 also caused the decrease of intracellular Ca 2+ in hemocytes (p<0.05). The inhibition of CA by acetazolamide and suppression of CgCA gene via RNA interference could increase the intracellular Ca 2+ in hemocytes (p<0.05). Besides, the decrease of intracellular Ca 2+ content caused by Ca 2+ reagent ionomycin could affect localization of CgCA in mantle tissue. The results indicated CgCA played essential roles in calcification and elevated CO 2 accelerated the mutual modulation between calcium and CgCA, implying reduced calcification rate and dissolved shells under OA. Copyright © 2017 Elsevier B.V. All rights reserved.

TPC2 is a novel NAADP-sensitive Ca2+ release channel, operating as a dual sensor of luminal pH and Ca2+.

PubMed

Pitt, Samantha J; Funnell, Tim M; Sitsapesan, Mano; Venturi, Elisa; Rietdorf, Katja; Ruas, Margarida; Ganesan, A; Gosain, Rajendra; Churchill, Grant C; Zhu, Michael X; Parrington, John; Galione, Antony; Sitsapesan, Rebecca

2010-11-05

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a molecule capable of initiating the release of intracellular Ca(2+) required for many essential cellular processes. Recent evidence links two-pore channels (TPCs) with NAADP-induced release of Ca(2+) from lysosome-like acidic organelles; however, there has been no direct demonstration that TPCs can act as NAADP-sensitive Ca(2+) release channels. Controversial evidence also proposes ryanodine receptors as the primary target of NAADP. We show that TPC2, the major lysosomal targeted isoform, is a cation channel with selectivity for Ca(2+) that will enable it to act as a Ca(2+) release channel in the cellular environment. NAADP opens TPC2 channels in a concentration-dependent manner, binding to high affinity activation and low affinity inhibition sites. At the core of this process is the luminal environment of the channel. The sensitivity of TPC2 to NAADP is steeply dependent on the luminal [Ca(2+)] allowing extremely low levels of NAADP to open the channel. In parallel, luminal pH controls NAADP affinity for TPC2 by switching from reversible activation of TPC2 at low pH to irreversible activation at neutral pH. Further evidence earmarking TPCs as the likely pathway for NAADP-induced intracellular Ca(2+) release is obtained from the use of Ned-19, the selective blocker of cellular NAADP-induced Ca(2+) release. Ned-19 antagonizes NAADP-activation of TPC2 in a non-competitive manner at 1 μM but potentiates NAADP activation at nanomolar concentrations. This single-channel study provides a long awaited molecular basis for the peculiar mechanistic features of NAADP signaling and a framework for understanding how NAADP can mediate key physiological events.

Blocking IP3 signal transduction pathways inhibits melatonin-induced Ca2+ signals and impairs P. falciparum development and proliferation in erythrocytes.

PubMed

Pecenin, Mateus Fila; Borges-Pereira, Lucas; Levano-Garcia, Julio; Budu, Alexandre; Alves, Eduardo; Mikoshiba, Katsuhiko; Thomas, Andrew; Garcia, Celia R S

2018-03-14

Inositol 1,4,5 trisphosphate (IP 3 ) signaling plays a crucial role in a wide range of eukaryotic processes. In Plasmodium falciparum, IP 3 elicits Ca 2+ release from intracellular Ca 2+ stores, even though no IP 3 receptor homolog has been identified to date. The human host hormone melatonin plays a key role in entraining the P. falciparum life cycle in the intraerythrocytic stages, apparently through an IP 3 -dependent Ca 2+ signal. The melatonin-induced cytosolic Ca 2+ ([Ca 2+ ] cyt ) increase and malaria cell cycle can be blocked by the IP 3 receptor blocker 2-aminoethyl diphenylborinate (2-APB). However, 2-APB also inhibits store-operated Ca 2+ entry (SOCE). Therefore, we have used two novel 2-APB derivatives, DPB162-AE and DPB163-AE, which are 100-fold more potent than 2-APB in blocking SOCE in mammalian cells, and appear to act by interfering with clustering of STIM proteins. In the present work we report that DPB162-AE and DPB163-AE block the [Ca 2+ ] cyt rise in response to melatonin in P. falciparum, but only at high concentrations. These compounds also block SOCE in the parasite at similarly high concentrations suggesting that P. falciparum SOCE is not activated in the same way as in mammalian cells. We further find that DPB162-AE and DPB163-AE affect the development of the intraerythrocytic parasites and invasion of new red blood cells. Our efforts to episomally express proteins that compete with native IP 3 receptor like IP 3 -sponge and an IP 3 sensor such as IRIS proved to be lethal to P. falciparum during intraerythrocytic cycle. The present findings point to an important role of IP 3 -induced Ca 2+ release in intraerythrocytic stage of P. falciparum. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

In vitro/vivo drug release and anti-diabetic cardiomyopathy properties of curcumin/PBLG-PEG-PBLG nanoparticles.

PubMed

Tong, Fei; Chai, Rongkui; Jiang, Haiying; Dong, Bo

2018-01-01

The objective of this study was to survey the therapeutic function of curcumin-encapsulated poly(gamma-benzyl l-glutamate)-poly(ethylene glycol)-poly(gammabenzyl l-glutamate) (PBLG-PEG-PBLG) (P) on diabetic cardiomyopathy (DCM) via cross regulation effect of calcium-sensing receptor (CaSR) and endogenous cystathionine-γ-lyase (CSE)/hydrogen sulfide (H 2 S). Diabetic rats were preconditioned with 20 mg/kg curcumin or curcumin/P complex continuously for 8 weeks. The blood and myocardiums were collected, the level of serum H 2 S was observed, and the [Ca 2+ ] i content was measured in myocardial cells, and hematoxylin-eosin, CaSR, CSE, and calmodulin (CaM) expression were detected. Both curcumin and curcumin/P pretreatment alleviated pathological morphological damage of myocardium, increased H 2 S and [Ca 2+ ] i levels, and upregulated the expression of CaSR, CSE, and CaM as compared to DCM group, while curcumin/P remarkably augmented this effect. PBLG-PEG-PBLG could improve water-solubility and bioactivity of curcumin and curcumin/PBLG-PEG-PBLG significantly alleviated diabetic cardiomyopathy.

Spin-Orbital Excitations in Ca2 RuO4 Revealed by Resonant Inelastic X-Ray Scattering

NASA Astrophysics Data System (ADS)

Das, L.; Forte, F.; Fittipaldi, R.; Fatuzzo, C. G.; Granata, V.; Ivashko, O.; Horio, M.; Schindler, F.; Dantz, M.; Tseng, Yi; McNally, D. E.; Rønnow, H. M.; Wan, W.; Christensen, N. B.; Pelliciari, J.; Olalde-Velasco, P.; Kikugawa, N.; Neupert, T.; Vecchione, A.; Schmitt, T.; Cuoco, M.; Chang, J.

2018-01-01

The strongly correlated insulator Ca2 RuO4 is considered as a paradigmatic realization of both spin-orbital physics and a band-Mott insulating phase, characterized by orbitally selective coexistence of a band and a Mott gap. We present a high resolution oxygen K -edge resonant inelastic x-ray scattering study of the antiferromagnetic Mott insulating state of Ca2 RuO4 . A set of low-energy (about 80 and 400 meV) and high-energy (about 1.3 and 2.2 eV) excitations are reported, which show strong incident light polarization dependence. Our results strongly support a spin-orbit coupled band-Mott scenario and explore in detail the nature of its exotic excitations. Guided by theoretical modeling, we interpret the low-energy excitations as a result of composite spin-orbital excitations. Their nature unveils the intricate interplay of crystal-field splitting and spin-orbit coupling in the band-Mott scenario. The high-energy excitations correspond to intra-atomic singlet-triplet transitions at an energy scale set by Hund's coupling. Our findings give a unifying picture of the spin and orbital excitations in the band-Mott insulator Ca2 RuO4 .

Effects of 1,25-dihydroxyvitamin D3 on calcium and phosphorus homeostasis in sheep fed diets either adequate or restricted in calcium content.

PubMed

Wilkens, M R; Mrochen, N; Breves, G; Schröder, B

2010-04-01

It was the aim of the present study to collect basic data on calcium (Ca) and phosphorus (P) homoeostasis in sheep. Two series of experiments were carried out to investigate the effects of 1,25-dihydroxyvitammin D(3) (calcitriol) in supraphysiological dosage in combination with varying alimentary Ca supply. In the first series, blood samples were collected over 72 h to determine the concentrations of total Ca (Ca), ionized Ca (Ca(2+)), inorganic phosphate (P(i)), and the bone resorption marker CrossLaps (CL). In the second series, measurements were carried out over 12h. In addition, urine samples were collected to calculate the fractional excretions (FE) of Ca and P(i). Changes in plasma macromineral concentrations (P<0.01) as well as in CL (P<0.001) and endogenous calcitriol (P<0.05) were observed in the alimentary Ca-restricted animals, indicating that the reduction of daily Ca intake challenged the animals' macromineral homeostatic mechanisms. However, the Ca-restricted diet had an effect on neither FE of Ca nor on FE of P(i). The treatment resulted in peak serum calcitriol concentrations between 1,900 and 2,500 pg/mL, and supraphysiological concentrations were maintained for the next 48 h. Irrespective of dietary Ca, calcitriol had hypercalcemic and hyperphosphatemic effects. An increase in CL was revealed only in the Ca-restricted, calcitriol-treated sheep (P<0.01), reflecting a remarkable enhancement of Ca mobilization from the bone by calcitriol exclusively in this group. From these data, it can be concluded that the sheep can be a suitable animal model for studying catabolic effects of Ca deficiency and calcitriol on bone metabolism. Copyright 2009 Elsevier Inc. All rights reserved.

Icebergs Adrift in the Amundsen Sea

NASA Technical Reports Server (NTRS)

2002-01-01

The Thwaites Ice Tongue is a large sheet of glacial ice extending from the West Antarctic mainland into the southern Amundsen Sea. A large crack in the Thwaites Tongue was discovered in imagery from Terra's Moderate Resolution Imaging SpectroRadiometer (MODIS). Subsequent widening of the crack led to the calving of a large iceberg. The development of this berg, designated B-22 by the National Ice Center, can be observed in these images from the Multi-angle Imaging SpectroRadiometer, also aboard Terra. The two views were acquired by MISR's nadir (vertical-viewing)camera on March 10 and 24, 2002.

The B-22 iceberg, located below and to the left of image center, measures approximately 82 kilometers long x 62 kilometers wide. Comparison of the two images shows the berg to have drifted away from the ice shelf edge. The breakup of ice near the shelf edge, in the area surrounding B-22, is also visible in the later image.

These natural-color images were acquired during Terra orbits 11843 and 12047, respectively. At the right-hand edge is Pine Island Bay, where the calving of another large iceberg (B-21) occurred in November 2001. B-21 subsequently split into two smaller bergs, both of which are visible to the right of B-22.

Antarctic researchers have reported an increase in the frequency of iceberg calvings in recent years. Whether this is the result of a regional climate variation, or connected to the global warming trend, has not yet been established.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Biotic Control of Surface pH and Evidence of Light-Induced H+ Pumping and Ca2+-H+ Exchange in a Tropical Crustose Coralline Alga.

PubMed

Hofmann, Laurie C; Koch, Marguerite; de Beer, Dirk

2016-01-01

Presently, an incomplete mechanistic understanding of tropical reef macroalgae photosynthesis and calcification restricts predictions of how these important autotrophs will respond to global change. Therefore, we investigated the mechanistic link between inorganic carbon uptake pathways, photosynthesis and calcification in a tropical crustose coralline alga (CCA) using microsensors. We measured pH, oxygen (O2), and calcium (Ca2+) dynamics and fluxes at the thallus surface under ambient (8.1) and low (7.8) seawater pH (pHSW) and across a range of irradiances. Acetazolamide (AZ) was used to inhibit extracellular carbonic anhydrase (CAext), which mediates hydrolysis of HCO3-, and 4,4' diisothiocyanatostilbene-2,2'-disulphonate (DIDS) that blocks direct HCO3- uptake by anion exchange transport. Both inhibited photosynthesis, suggesting both diffusive uptake of CO2 via HCO3- hydrolysis to CO2 and direct HCO3- ion transport are important in this CCA. Surface pH was raised approximately 0.3 units at saturating irradiance, but less when CAext was inhibited. Surface pH was lower at pHSW 7.8 than pHSW 8.1 in the dark, but not in the light. The Ca2+ fluxes were large, complex and temporally variable, but revealed net Ca2+ uptake under all conditions. The temporal variability in Ca2+ dynamics was potentially related to localized dissolution during epithallial cell sloughing, a strategy of CCA to remove epiphytes. Simultaneous Ca2+ and pH dynamics suggest the presence of Ca2+/H+ exchange. Rapid light-induced H+ surface dynamics that continued after inhibition of photosynthesis revealed the presence of a light-mediated, but photosynthesis-independent, proton pump. Thus, the study indicates metabolic control of surface pH can occur in CCA through photosynthesis and light-inducible H+ pumps. Our results suggest that complex light-induced ion pumps play an important role in biological processes related to inorganic carbon uptake and calcification in CCA.

Biotic Control of Surface pH and Evidence of Light-Induced H+ Pumping and Ca2+-H+ Exchange in a Tropical Crustose Coralline Alga

PubMed Central

Hofmann, Laurie C.; Koch, Marguerite; de Beer, Dirk

2016-01-01

Presently, an incomplete mechanistic understanding of tropical reef macroalgae photosynthesis and calcification restricts predictions of how these important autotrophs will respond to global change. Therefore, we investigated the mechanistic link between inorganic carbon uptake pathways, photosynthesis and calcification in a tropical crustose coralline alga (CCA) using microsensors. We measured pH, oxygen (O2), and calcium (Ca2+) dynamics and fluxes at the thallus surface under ambient (8.1) and low (7.8) seawater pH (pHSW) and across a range of irradiances. Acetazolamide (AZ) was used to inhibit extracellular carbonic anhydrase (CAext), which mediates hydrolysis of HCO3-, and 4,4′ diisothiocyanatostilbene-2,2′-disulphonate (DIDS) that blocks direct HCO3- uptake by anion exchange transport. Both inhibited photosynthesis, suggesting both diffusive uptake of CO2 via HCO3- hydrolysis to CO2 and direct HCO3- ion transport are important in this CCA. Surface pH was raised approximately 0.3 units at saturating irradiance, but less when CAext was inhibited. Surface pH was lower at pHSW 7.8 than pHSW 8.1 in the dark, but not in the light. The Ca2+ fluxes were large, complex and temporally variable, but revealed net Ca2+ uptake under all conditions. The temporal variability in Ca2+ dynamics was potentially related to localized dissolution during epithallial cell sloughing, a strategy of CCA to remove epiphytes. Simultaneous Ca2+ and pH dynamics suggest the presence of Ca2+/H+ exchange. Rapid light-induced H+ surface dynamics that continued after inhibition of photosynthesis revealed the presence of a light-mediated, but photosynthesis-independent, proton pump. Thus, the study indicates metabolic control of surface pH can occur in CCA through photosynthesis and light-inducible H+ pumps. Our results suggest that complex light-induced ion pumps play an important role in biological processes related to inorganic carbon uptake and calcification in CCA. PMID:27459463

MO-FG-CAMPUS-IeP1-01: Alternative K-Edge Filters for Low-Energy Image Acquisition in Contrast Enhanced Spectral Mammography

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

Shrestha, S; Vedantham, S; Karellas, A

Purpose: In Contrast Enhanced Spectral Mammography (CESM), Rh filter is often used during low-energy image acquisition. The potential for using Ag, In and Sn filters, which exhibit K-edge closer to, and just below that of Iodine, instead of the Rh filter, was investigated for the low-energy image acquisition. Methods: Analytical computations of the half-value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for 50µm Rh were compared with other potential K-edge filters (Ag, In and Sn), all with K-absorption edge below that of Iodine. Two strategies were investigated: fixed kVp and filter thickness (50µm for all filters) resulting inmore » HVT variation, and fixed kVp and HVT resulting in variation in Ag, In and Sn thickness. Monte Carlo simulations (GEANT4) were conducted to determine if the scatter-to-primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Rh and other K-edge filters. Results: Ag, In and Sn filters (50µm thick) increased photon fluence/mAs by 1.3–1.4, 1.8–2, and 1.7–2 at 28-32 kVp compared to 50µm Rh, which could decrease exposure time. Additionally, the fraction of spectra closer to and just below Iodine’s K-edge increased with these filters, which could improve post-subtraction image contrast. For HVT matched to 50µm Rh filtered spectra, the thickness range for Ag, In, and Sn were (41,44)µm, (49,55)µm and (45,53)µm, and increased photon fluence/mAs by 1.5–1.7, 1.6–2, and 1.6–2.2, respectively. Monte Carlo simulations showed that neither the SPR nor the scatter PSF of Ag, In and Sn differed from Rh, indicating no additional detriment due to x-ray scatter. Conclusion: The use of Ag, In and Sn filters for low-energy image acquisition in CESM is potentially feasible and could decrease exposure time and may improve post-subtraction image contrast. Effect of these filters on radiation dose, contrast, noise and associated metrics are being investigated. Funding Support: Supported in part by NIH R01CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.« less

Identification and Levels of 2′-Carboxyarabinitol in Leaves 1

PubMed Central

Moore, Brandon d.; Sharkey, Thomas D.; Kobza, John; Seemann, Jeffrey R.

1992-01-01

2′-Carboxyarabinitol 1-phosphate (CA1P) is a naturally occurring inhibitor of ribulose-1,5 bisphosphate carboxylase/oxygenase activity. A chloroplast phosphatase has previously been identified that degrades CA1P in vitro to carboxyarabinitol (CA) plus phosphate, but CA has not yet been detected in plants. Here, we detail procedures to isolate and assay CA from leaves and utilize mass spectrometry to demonstrate for the first time that CA is present in plants. CA was present in leaves of all 13 species examined, including those of C3, C4, and Crassulacean acid metabolism photosynthetic subgroups. CA was present both in species with high levels of CA1P (e.g. Phaseolus vulgaris, Lycopersicon esculentum, Beta vulgaris) as well as in species with low levels of CA1P (e.g. Spinacea oleracea, Triticum aestivum). CA levels in the light were sometimes greater than those in the dark. Bean leaves had the most CA of any species tested, with levels in the light approaching 1 micromole per milligram of chlorophyll. In illuminated bean leaves, about 63% of the CA is located outside the chloroplast. CA is one of only a few branched chain sugar acids to be identified from plants. PMID:16669072

Photon counting x-ray imaging with K-edge filtered x-rays: A simulation study.

PubMed

Atak, Haluk; Shikhaliev, Polad M

2016-03-01

In photon counting (PC) x-ray imaging and computed tomography (CT), the broad x-ray spectrum can be split into two parts using an x-ray filter with appropriate K-edge energy, which can improve material decomposition. Recent experimental study has demonstrated substantial improvement in material decomposition with PC CT when K-edge filtered x-rays were used. The purpose of the current work was to conduct further investigations of the K-edge filtration method using comprehensive simulation studies. The study was performed in the following aspects: (1) optimization of the K-edge filter for a particular imaging configuration, (2) effects of the K-edge filter parameters on material decomposition, (3) trade-off between the energy bin separation, tube load, and beam quality with K-edge filter, (4) image quality of general (unsubtracted) images when a K-edge filter is used to improve dual energy (DE) subtracted images, and (5) improvements with K-edge filtered x-rays when PC detector has limited energy resolution. The PC x-ray images of soft tissue phantoms with 15 and 30 cm thicknesses including iodine, CaCO3, and soft tissue contrast materials, were simulated. The signal to noise ratio (SNR) of the contrast elements was determined in general and material-decomposed images using K-edge filters with different atomic numbers and thicknesses. The effect of the filter atomic number and filter thickness on energy separation factor and SNR was determined. The boundary conditions for the tube load and halfvalue layer were determined when the K-edge filters are used. The material-decomposed images were also simulated using PC detector with limited energy resolution, and improvements with K-edge filtered x-rays were quantified. The K-edge filters with atomic numbers from 56 to 71 and K-edge energies 37.4-63.4 keV, respectively, can be used for tube voltages from 60 to 150 kVp, respectively. For a particular tube voltage of 120 kVp, the Gd and Ho were the optimal filter materials to achieve highest SNR. For a particular K-edge filter of Gd and tube voltage of 120 kVp, the filter thickness 0.6 mm provided maximum SNR for considered imaging applications. While K-edge filtration improved SNR of CaCO3 and iodine by 41% and 36%, respectively, in DE subtracted images, it did not deteriorate SNR in general images. For x-ray imaging with nonideal PC detector, the positive effect of the K-edge filter was increased when FWHM energy resolution was degraded, and maximum improvement was at 60% FWHM. This study has shown that K-edge filtered x-rays can provide substantial improvements of material selective PC x-ray and CT imaging for nearly all imaging applications using 60-150 kVp tube voltages. Potential limitations such as tube load, beam hardening, and availability of filter material were shown to not be critical.

Diadenosine Homodinucleotide Products of ADP-ribosyl Cyclases Behave as Modulators of the Purinergic Receptor P2X7*

PubMed Central

Bruzzone, Santina; Basile, Giovanna; Chothi, Madhu Parakkottil; Nobbio, Lucilla; Usai, Cesare; Jacchetti, Emanuela; Schenone, Angelo; Guse, Andreas H.; Di Virgilio, Francesco; De Flora, Antonio; Zocchi, Elena

2010-01-01

ADP-ribosyl cyclases from both vertebrates and invertebrates were previously shown to produce two isomers of P1,P2 diadenosine 5′,5′"-P1, P2-diphosphate, P18 and P24, from cyclic ADP-ribose (cADPR) and adenine. P18 and P24 are characterized by an unusual N-glycosidic linkage in one of the adenylic mononucleotides (Basile, G., Taglialatela-Scafati, O., Damonte, G., Armirotti, A., Bruzzone, S., Guida, L., Franco, L., Usai, C., Fattorusso, E., De Flora, A., and Zocchi, E. (2005) Proc. Natl. Acad. Sci. U.S.A. 102, 14509–14514). P24, but not P18, proved to increase the intracellular Ca2+ concentration ([Ca2+]i) in HeLa cells and to negatively affect mitochondrial function. Here we show that micromolar P24, but not P18, triggers a slow and sustained influx of extracellular Ca2+ through the opening of the purinergic receptor/channel P2X7. On the other hand, P18 inhibits the Ca2+ influx induced by 0.6 mm ATP in HEK293 cells stably transfected with P2X7, with an IC50 of ∼1 μm. Thus, P18 is devoid of intrinsic P2X7 stimulatory activity and behaves as an ATP antagonist. A P2X7-mediated increase of the basal [Ca2+]i has been demonstrated to negatively affect Schwann cell (SC) function in rats with the inherited, peripheral neuropathy Charcot-Marie-Tooth 1A (CMT1A) (Nobbio, L., Sturla, L., Fiorese, F., Usai, C., Basile, G., Moreschi, I., Benvenuto, F., Zocchi, E., De Flora, A., Schenone, A., and Bruzzone S. (2009) J. Biol. Chem. 284, 23146–23158). Preincubation of CMT1A SC with 200 nm P18 restored the basal [Ca2+]i to values similar to those recorded in wild-type SC. These results identify P18 as a new P2X7 antagonist, potentially useful in the treatment of CMT1A. PMID:20439466

Insight into the impact of two structural calcium ions on the properties of Pleurotus eryngii versatile ligninolytic peroxidase.

PubMed

Gao, Yu; Zheng, Lanyan; Li, Jian-Jun; Du, Yuguang

2016-12-15

Two structural Ca 2+ (proximal and distal) is known to be important for ligninolytic peroxidases. However, few studies toward impact of residues involved in two Ca 2+ on properties of ligninolytic peroxidases have been done, especially the proximal one. In this study, mutants of nine residues involved in liganding two Ca 2+ of Pleurotus eryngii versatile peroxidase (VP) were investigated. Most mutants almost completely lost activities, except the mutants of proximal Ca 2+ - S170A and V192T. In comparison with WT (wild type), optimal pH values of S170A, S170D, and V192T shifted from pH 3.0 to pH 3.5. The order of thermal and pH stabilities of WT, V192T, S170A, and S170D is similar to that of their specific activities: WT > V192T > S170A > S170D. The CD (circular dichroism) results of WT and several mutants indicated that mutations had some effects on secondary structures. For the first time, it was observed that the thermostability of ligninolytic peroxidases is related with proximal Ca 2+ too, and the mutant containing distal Ca 2+ only was obtained. Our results clearly demonstrated that enzymatic activities, pH and thermal stabilities, Ca 2+ content, and secondary structures of VP have close relationship with the residues involved in two structural Ca 2+ . Copyright © 2016 Elsevier Inc. All rights reserved.

Developing a Highly Active Blood Anticoagulant—a Heparin Complex with Glutamic Acid—by Simulating Chemical Equilibria Based on pH-Metric Data

NASA Astrophysics Data System (ADS)

Nikolaeva, L. S.; Semenov, A. N.

2018-02-01

The anticoagulant activity of high-molecular-weight heparin is increased by developing a new highly active heparin complex with glutamate using the thermodynamic model of chemical equilibria based on pH-metric data. The anticoagulant activity of the developed complexes is estimated in the pH range of blood plasma according to the drop in the calculated equilibrium Ca2+ concentration associated with the formation of mixed ligand complexes of Ca2+ ions, heparin (Na4hep), and glutamate (H2Glu). A thermodynamic model is calculated by mathematically modelling chemical equilibria in the CaCl2-Na4hep-H2Glu-H2O-NaCl system in the pH range of 2.30 ≤ pH ≤ 10.50 in diluted saline that acts as a background electrolyte (0.154 M NaCl) at 37°C and initial concentrations of the main components of ν × 10-3 M, where n ≤ 4. The thermodynamic model is used to determine the main complex of the monomeric unit of heparin with glutamate (HhepGlu5-) and the most stable mixed ligand complex of Ca2+ with heparin and glutamate (Ca2hepGlu2-) in the pH range of blood plasma (6.80 ≤ pH ≤ 7.40). It is concluded that the Ca2hepGlu2- complex reduces the Ca2+ concentration 107 times more than the Ca2+ complex with pure heparin. The anticoagulant effect of the developed HhepGlu5- complex is confirmed in vitro and in vivo via coagulation tests on the blood plasma of laboratory rats. Additional antithrombotic properties of the developed complex are identified. The new highly active anticoagulant, HhepGlu5- complex with additional antithrombotic properties, is patented.

SIMS chemical analysis of extended impacts on the leading and trailing edges of LDEF experiment AO187-2

NASA Technical Reports Server (NTRS)

Amari, S.; Foote, J.; Simon, Charles G.; Swan, P.; Walker, R. M.; Zinner, E.; Jessberger, E. K.; Lange, G.; Stadermann, F.

1992-01-01

The Long Duration Exposure Facility (LDEF) Experiment AO187-2 consisted of 237 capture cells, 120 on the leading edge and 117 on the trailing edge. Each cell was made of polished Ge plates covered with 2.5 micron thick mylar foil at 200 microns from the Ge. Although all leading edge cells and 105 trailing edge cells had lost their plastic covers during flight, optical and electron microscope examination revealed extended impacts in bare cells from either edge that apparently were produced by high velocity projectiles while the plastic foils were still in place. Detailed optical scanning yielded 53 extended impacts on 100 bare cells from the trailing edge that were selected for SIMS chemical analysis. Lateral multi-element ion probe profiles were obtained on 40 of these impacts. Material that can be attributed to the incoming projectiles was found in all analyzed extended compact features and most seem to be associated with cosmic dust particles. However, LDEF deposits are systematically enriched in the refractory elements Al, Ca, and Ti relative to Mg and Fe when compared to IDP's collected in the stratosphere and to chondritic compositions. These differences are most likely due to elemental fractionation effects during the high velocity impact but real differences between interplanetary particles captured on LDEF and stratospheric IDP's cannot be excluded. Recently we extended our studies to cells from the leading edge and the covered cells from the trailing edge. The 12 covered cells contain 20 extended impact candidates. Ion probe analysis of 3 yielded results similar to those obtained for impacts on the bare cells from the trailing edge. Optical scanning of the bare leading edge cell also reveals many extended impacts (42 on 22 cells scanned to date), demonstrating that the cover foils remained intact at least for some time. However, SIMS analysis showed elements that can reasonably be attributed to micrometeoroids in only 2 out of 11 impacts. Eight impacts have residues dominated by Al and one dominated by Ti, indicating a preponderance of orbital debris in leading edge impacts.

Function of a STIM1 Homologue in C. elegans: Evidence that Store-operated Ca2+ Entry Is Not Essential for Oscillatory Ca2+ Signaling and ER Ca2+ Homeostasis

PubMed Central

Yan, Xiaohui; Xing, Juan; Lorin-Nebel, Catherine; Estevez, Ana Y.; Nehrke, Keith; Lamitina, Todd; Strange, Kevin

2006-01-01

1,4,5-trisphosphate (IP3)-dependent Ca2+ signaling regulates gonad function, fertility, and rhythmic posterior body wall muscle contraction (pBoc) required for defecation in Caenorhabditis elegans. Store-operated Ca2+ entry (SOCE) is activated during endoplasmic reticulum (ER) Ca2+ store depletion and is believed to be an essential and ubiquitous component of Ca2+ signaling pathways. SOCE is thought to function to refill Ca2+ stores and modulate Ca2+ signals. Recently, stromal interaction molecule 1 (STIM1) was identified as a putative ER Ca2+ sensor that regulates SOCE. We cloned a full-length C. elegans stim-1 cDNA that encodes a 530–amino acid protein with ∼21% sequence identity to human STIM1. Green fluorescent protein (GFP)–tagged STIM-1 is expressed in the intestine, gonad sheath cells, and spermatheca. Knockdown of stim-1 expression by RNA interference (RNAi) causes sterility due to loss of sheath cell and spermatheca contractile activity required for ovulation. Transgenic worms expressing a STIM-1 EF-hand mutant that constitutively activates SOCE in Drosophila and mammalian cells are sterile and exhibit severe pBoc arrhythmia. stim-1 RNAi dramatically reduces STIM-1∷GFP expression, suppresses the EF-hand mutation–induced pBoc arrhythmia, and inhibits intestinal store-operated Ca2+ (SOC) channels. However, stim-1 RNAi surprisingly has no effect on pBoc rhythm, which is controlled by intestinal oscillatory Ca2+ signaling, in wild type and IP3 signaling mutant worms, and has no effect on intestinal Ca2+ oscillations and waves. Depletion of intestinal Ca2+ stores by RNAi knockdown of the ER Ca2+ pump triggers the ER unfolded protein response (UPR). In contrast, stim-1 RNAi fails to induce the UPR. Our studies provide the first detailed characterization of STIM-1 function in an intact animal and suggest that SOCE is not essential for certain oscillatory Ca2+ signaling processes and for maintenance of store Ca2+ levels in C. elegans. These findings raise interesting and important questions regarding the function of SOCE and SOC channels under normal and pathophysiological conditions. PMID:16966474

Function of a STIM1 homologue in C. elegans: evidence that store-operated Ca2+ entry is not essential for oscillatory Ca2+ signaling and ER Ca2+ homeostasis.

PubMed

Yan, Xiaohui; Xing, Juan; Lorin-Nebel, Catherine; Estevez, Ana Y; Nehrke, Keith; Lamitina, Todd; Strange, Kevin

2006-10-01

1,4,5-trisphosphate (IP(3))-dependent Ca(2+) signaling regulates gonad function, fertility, and rhythmic posterior body wall muscle contraction (pBoc) required for defecation in Caenorhabditis elegans. Store-operated Ca(2+) entry (SOCE) is activated during endoplasmic reticulum (ER) Ca(2+) store depletion and is believed to be an essential and ubiquitous component of Ca(2+) signaling pathways. SOCE is thought to function to refill Ca(2+) stores and modulate Ca(2+) signals. Recently, stromal interaction molecule 1 (STIM1) was identified as a putative ER Ca(2+) sensor that regulates SOCE. We cloned a full-length C. elegans stim-1 cDNA that encodes a 530-amino acid protein with approximately 21% sequence identity to human STIM1. Green fluorescent protein (GFP)-tagged STIM-1 is expressed in the intestine, gonad sheath cells, and spermatheca. Knockdown of stim-1 expression by RNA interference (RNAi) causes sterility due to loss of sheath cell and spermatheca contractile activity required for ovulation. Transgenic worms expressing a STIM-1 EF-hand mutant that constitutively activates SOCE in Drosophila and mammalian cells are sterile and exhibit severe pBoc arrhythmia. stim-1 RNAi dramatically reduces STIM-1GFP expression, suppresses the EF-hand mutation-induced pBoc arrhythmia, and inhibits intestinal store-operated Ca(2+) (SOC) channels. However, stim-1 RNAi surprisingly has no effect on pBoc rhythm, which is controlled by intestinal oscillatory Ca(2+) signaling, in wild type and IP(3) signaling mutant worms, and has no effect on intestinal Ca(2+) oscillations and waves. Depletion of intestinal Ca(2+) stores by RNAi knockdown of the ER Ca(2+) pump triggers the ER unfolded protein response (UPR). In contrast, stim-1 RNAi fails to induce the UPR. Our studies provide the first detailed characterization of STIM-1 function in an intact animal and suggest that SOCE is not essential for certain oscillatory Ca(2+) signaling processes and for maintenance of store Ca(2+) levels in C. elegans. These findings raise interesting and important questions regarding the function of SOCE and SOC channels under normal and pathophysiological conditions.

Water-Soluble Combretastatin A4 Phosphate Orally Delivered via Composite Nanoparticles With Improved Inhibition Effect Toward S180 Tumors.

PubMed

Shen, Yurun; Wu, Liping; Qiu, Liyan

2017-10-01

Combretastatin A4 phosphate (CA4P) is a novel vascular disrupting agent for cancer therapy. However, frequent dosing and negative patient compliance have been encountered over CA4P by injection administration due to its quite short-term action and acute side effects. Therefore, it is significant to develop an oral formulation of CA4P. We established a novel method to prepare CA4P-loaded nanoparticles (CA4P-NPs) for oral administration by combining methoxy poly(ethylene glycol)-b-polylactide (PELA) and poly(d,l-lactic-co-glycolic acid) (PLGA) polymers. Transport study in vitro was evaluated on Madin-Darby canine kidney cell models, and antitumor effect evaluation in vivo was performed on S180 subcutaneous xenotransplanted tumor models in mice. The highest entrapment efficiency of CA4P-NPs was achieved when the weight ratio of PELA to PLGA was optimized to 1:1. The apparent permeability coefficient of CA4P-NPs was found to be 2.08-fold higher than that of free CA4P in transport study. CA4P-NPs reached an absolute bioavailability of 77.6% with the tumor inhibition ratio of 41.2% that was significantly superior to free CA4P. These results suggest a promising application of this composite nanoparticle for the oral delivery of water-soluble drugs. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Ca-P spots modified zirconia by liquid precursor infiltration and the effect on osteoblast-like cell responses.

PubMed

Li, Yongmei; Liu, Yan; Zhang, Zutai; Zhuge, Ruishen; Ding, Ning; Tian, Yueming

2018-01-26

Ca-P spots modified zirconia by liquid precursor infiltration and the cell responses were investigated. Pre-sintered zirconia specimens were immersed in Ca-P precursor solution. After dense sintering, scanning electron microscopy showed Ca-P spots were formed on the zirconia and anchored with zirconia substrates. The distribution density was increased with the extension of immersion time. Energy dispersive spectrometer confirmed the stoichiometric Ca/P ratio was about 1.67. After hydrothermal treatment, Ca-P spots turned into rod crystals where diffraction peaks of tricalcium phosphate and hydroxyapatite were detected by X-ray diffraction, and Ca 2+ and PO 4 3- release decreased slightly (p>0.05). There was no significant decrease on three-point bending strength (p>0.05). Osteoblast-like MC3T3-E1 cells attached and spread well and showed higher proliferation on Ca-P spots modified zirconia (p<0.05), though its initial alkaline phosphatase activity was not significant high (p>0.05). In conclusion, Ca-P liquid precursor infiltration is a potential method to modify the zirconia ceramics for improving bioactivity.

Understanding cold bias: Variable response of skeletal Sr/Ca to seawater pCO2 in acclimated massive Porites corals

PubMed Central

Cole, Catherine; Finch, Adrian; Hintz, Christopher; Hintz, Kenneth; Allison, Nicola

2016-01-01

Coral skeletal Sr/Ca is a palaeothermometer commonly used to produce high resolution seasonal sea surface temperature (SST) records and to investigate the amplitude and frequency of ENSO and interdecadal climate events. The proxy relationship is typically calibrated by matching seasonal SST and skeletal Sr/Ca maxima and minima in modern corals. Applying these calibrations to fossil corals assumes that the temperature sensitivity of skeletal Sr/Ca is conserved, despite substantial changes in seawater carbonate chemistry between the modern and glacial ocean. We present Sr/Ca analyses of 3 genotypes of massive Porites spp. corals (the genus most commonly used for palaeoclimate reconstruction), cultured under seawater pCO2 reflecting modern, future (year 2100) and last glacial maximum (LGM) conditions. Skeletal Sr/Ca is indistinguishable between duplicate colonies of the same genotype cultured under the same conditions, but varies significantly in response to seawater pCO2 in two genotypes of Porites lutea, whilst Porites murrayensis is unaffected. Within P. lutea, the response is not systematic: skeletal Sr/Ca increases significantly (by 2–4%) at high seawater pCO2 relative to modern in both genotypes, and also increases significantly (by 4%) at low seawater pCO2 in one genotype. This magnitude of variation equates to errors in reconstructed SST of up to −5 °C. PMID:27241795

Understanding cold bias: Variable response of skeletal Sr/Ca to seawater pCO2 in acclimated massive Porites corals.

PubMed

Cole, Catherine; Finch, Adrian; Hintz, Christopher; Hintz, Kenneth; Allison, Nicola

2016-05-31

Coral skeletal Sr/Ca is a palaeothermometer commonly used to produce high resolution seasonal sea surface temperature (SST) records and to investigate the amplitude and frequency of ENSO and interdecadal climate events. The proxy relationship is typically calibrated by matching seasonal SST and skeletal Sr/Ca maxima and minima in modern corals. Applying these calibrations to fossil corals assumes that the temperature sensitivity of skeletal Sr/Ca is conserved, despite substantial changes in seawater carbonate chemistry between the modern and glacial ocean. We present Sr/Ca analyses of 3 genotypes of massive Porites spp. corals (the genus most commonly used for palaeoclimate reconstruction), cultured under seawater pCO2 reflecting modern, future (year 2100) and last glacial maximum (LGM) conditions. Skeletal Sr/Ca is indistinguishable between duplicate colonies of the same genotype cultured under the same conditions, but varies significantly in response to seawater pCO2 in two genotypes of Porites lutea, whilst Porites murrayensis is unaffected. Within P. lutea, the response is not systematic: skeletal Sr/Ca increases significantly (by 2-4%) at high seawater pCO2 relative to modern in both genotypes, and also increases significantly (by 4%) at low seawater pCO2 in one genotype. This magnitude of variation equates to errors in reconstructed SST of up to -5 °C.

Radical Beam Gettering Epitaxy of Zno and Gan

NASA Astrophysics Data System (ADS)

Georgobiani, A. N.; Demin, V. I.; Vorobiev, M. O.; Gruzintsev, A. N.; Hodos, I. I.; Kotljarevsky, M. B.; Kidalov, V. V.; Rogozin, I. V.

2002-11-01

P-type ZnO layers with a hole mobility about 23 cm2/(V s), and a hole concentration about 1015 cm-3 were grown by means of radical-beam gettering epitaxy (the annealing of n-ZnO single crystals in atomic oxygen flux). The effect of native defects on the photoluminescence spectra of the layers was studied. The dominant bands in the spectra peaked at 370.2 and 400 nm. These bands were attributed to the annihilation of exciton localised on neutral Vzn and to electron transitions from the conduction band to singly positively charged Vzn correspondingly. The effect of annealing in atomic nitrogen flux of p-CaN:Mg films on their photoluminescence spectra and on the value of their conductivity were studied. Such annealing leads to appearance of a number of emission bands that peaked at 404.9, 390.8 and 378.9 nm and increases hole concentration from 5 × 1015 to 5 × 1016 cm-3, and the hole mobility from 120 to 150 cm2/(V s). The n-ZnO - p-GaN:Mg electroluminescence heterostructures were obtained. Their spectrum contains bands in the excitonic region of GaN at the wavelength 360.2 nm and in the edge region at wavelengths 378.9 and 390.8 nm.

Synthesization and characterization of poly(lactic-co-glycolic acid) / calcium phosphate bone cement from crab shells

NASA Astrophysics Data System (ADS)

Hanan, M. R. Abdul; Daud, N. M.; Ismail, L. H.; Saidin, S.

2017-05-01

An injectable calcium phosphate (CaP) bone cement has been widely used for musculoskeletal and bone disorder due to its biocompatible and osteoconductive properties. In this study, CaP was successfully synthesized from crab shells by a wet chemical route. Poly(lactic-co-glycolic acid) (PLGA) microspheres which have been produced through a double emulsion technique were incorporated into the CaP mixture for the purpose of bone cement solidification. The ratio of both compounds, CaP and PLGA, were set at 8:2. The CaP and PLGA/CaP bone cement were analyzed by ATR-FTIR, FESEM-EDX and contact angle analyses. The bone cement was composed of CaP and PLGA where the micro-powders of CaP were agglomerated on the PLGA microspheres. Addition of the PLGA has increased the hydrophilicity of the bone cement which will be beneficial for materials degradation and bone integration.

Optimization of pH, temperature and CaCl2 concentrations for Ricotta cheese production from Buffalo cheese whey using Response Surface Methodology.

PubMed

Rashid, Abdul Ahid; Huma, Nuzhat; Zahoor, Tahir; Asgher, Muhammad

2017-02-01

The recovery of milk constituents from cheese whey is affected by various processing conditions followed during production of Ricotta cheese. The objective of the present investigation was to optimize the temperature (60-90 °C), pH (3-7) and CaCl2 concentration (2·0-6·0 mm) for maximum yield/recovery of milk constituents. The research work was carried out in two phases. In 1st phase, the influence of these processing conditions was evaluated through 20 experiments formulated by central composite design (CCD) keeping the yield as response factor. The results obtained from these experiments were used to optimize processing conditions for maximum yield using response surface methodology (RSM). The three best combinations of processing conditions (90 °C, pH 7, CaCl2 6 mm), (100 °C, pH 5, CaCl2 4 mm) and (75 °C, pH 8·4, CaCl2 4 mm) were exploited in the next phase for Ricotta cheese production from a mixture of Buffalo cheese whey and skim milk (9 : 1) to determine the influence of optimized conditions on the cheese composition. Ricotta cheeses were analyzed for various physicochemical (moisture, fat, protein, lactose, total solids, pH and acidity indicated) parameters during storage of 60 d at 4 ± 2 °C after every 15 d interval. Ricotta cheese prepared at 90 °C, pH 7 and CaCl2 6 mm exhibited the highest cheese yield, proteins and total solids, while high fat content was recorded for cheese processed at 100 °C, pH 5 and 4 mm CaCl2 concentration. A significant storage-related increase in acidity and NPN was recorded for all cheese samples.

Effect of limestone particle size and calcium to non-phytate phosphorus ratio on true ileal calcium digestibility of limestone for broiler chickens.

PubMed

Anwar, M N; Ravindran, V; Morel, P C H; Ravindran, G; Cowieson, A J

2016-10-01

The purpose of this study was to determine the effect of limestone particle size and calcium (Ca) to non-phytate phosphorus (P) ratio on the true ileal Ca digestibility of limestone for broiler chickens. A limestone sample was passed through a set of sieves and separated into fine (<0.5 mm) and coarse (1-2 mm) particles. The analysed Ca concentration of both particle sizes was similar (420 g/kg). Six experimental diets were developed using each particle size with Ca:non-phytate P ratios of 1.5:1, 2.0:1 and 2.5:1, with ratios being adjusted by manipulating the dietary Ca concentrations. A Ca-free diet was also developed to determine the basal ileal endogenous Ca losses. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to 6 replicate cages (8 birds per cage) and fed from d 21 to 24 post hatch. Apparent ileal digestibility of Ca was calculated using the indicator method and corrected for basal endogenous losses to determine the true Ca digestibility. The basal ileal endogenous Ca losses were determined to be 127 mg/kg of dry matter intake. Increasing Ca:non-phytate P ratios reduced the true Ca digestibility of limestone. The true Ca digestibility coefficients of limestone with Ca:non-phytate P ratios of 1.5, 2.0 and 2.5 were 0.65, 0.57 and 0.49, respectively. Particle size of limestone had a marked effect on the Ca digestibility, with the digestibility being higher in coarse particles (0.71 vs. 0.43).

A Fifty-Year Coral Sr/Ca Time Series from Guam, Mariana Islands: In situ Monitoring and Comparison to Observed Pacific Climate

NASA Astrophysics Data System (ADS)

Lander, M.

2016-12-01

Located on the northern edge of the West Pacific Warm Pool, Guam is positioned to obtain uniquely valuable natural records of west Pacific maritime paleoclimate. This study is the first to evaluate the application of the coral Sr/Ca sea surface temperature (SST) proxy to the reconstruction of Guam's climate history. To help test the fidelity of the coral Sr/Ca proxy to actual climate, and how it might be affected by environmental variables—on Guam or elsewhere—the study documented monthly seawater oxygen isotope ratios (δ18O), pH, cation, and nitrate concentrations from September 2009 to December 2010 at a Porites lutea colony in Guam's Apra Harbor. The study site was chosen for its accessibility, so that environmental conditions could be readily monitored. A 50-year Sr/Ca record was carefully compared to instrumental records, the quality and reliability of which were also closely examined. Time series of seawater δ18O, pH, and cation concentrations show some evidence of freshwater input from direct rainfall or stream discharge into the harbor. The Sr/Ca proxy SST results, however, are robust, and do not appear to have been significantly affected. The Sr/Ca proxy reproduces the long-term warming trend observed in the historical records of regional SST and local air temperature. Moreover, it shows remarkable fidelity to regional ocean-atmosphere variations as represented by the indices of the El Niño/Southern Oscillation and the Pacific Decadal Oscillation. The consistency of the results with Guam's historical instrumental records, with previous δ18O results from Guam, and with previous Sr/Ca proxy results in similar environments elsewhere, demonstrate the efficacy of accessible near-shore sites for obtaining reliable Sr/Ca climate proxies, and the utility of Guam as a source for accurate coral records of western Pacific Ocean regional climate.

Effect of high-dose phytase and citric acid, alone or in combination, on growth performance of broilers given diets severely limited in available phosphorus.

PubMed

Taheri, H R; Jabbari, Z; Adibnia, S; Shahir, M H; Hosseini, S A

2015-01-01

1. Two trials were conducted to evaluate the effect of high-dose phytase alone or in combination with citric acid (CA) in the diet severely limited in available phosphorus (P) on performance, plasma P and plasma Ca of broilers from 22 to 42 d of age. 2. In Trial 1, 297 21-d-old female chicks were placed into 27 pens and allocated to 9 maize-soybean meal-based dietary treatments, which were a positive control [PC, 4.23 g/kg non-phytate P (NPP)] and 8 negative control (NC, 1.35 g/kg NPP) groups consisting of two concentrations of CA (0 and 20 g/kg) and 4 concentrations of phytase (0, 1000, 2000 and 4000 U/kg) in a 2 × 4 factorial arrangement. In Trial 2, 192 21-d-old male chicks were placed into 24 pens and allocated to 6 wheat-canola meal-based dietary treatments, which were a PC (4.2 g/kg NPP), a NC (1.68 g/kg NPP) and 4 NC groups consisting of two concentrations of CA (0 and 20 g/kg) and two concentrations of phytase (2000 and 4000 U/kg) in a 2 × 2 factorial arrangement. 3. In both trials, birds fed on the PC had significantly higher average daily gain (ADG), average daily feed intake (ADFI), plasma P and lower feed conversion ratio (FCR) and plasma Ca than those of birds fed on the NC. CA supplementation significantly increased ADG and ADFI. There was a significant interaction between CA and phytase on plasma P where CA improved the effect of phytase on plasma P. In Trial 1, phytase addition improved ADG, ADFI, FCR and plasma Ca linearly. 4. Briefly, this research showed the interaction effect between CA and phytase on plasma P when broilers were fed on diets based on maize-soybean meal or wheat-canola meal. The results showed that CA supplementation lowered the concentration of phytase that is needed in low NPP diets to increase plasma P.

Preparation and Properties of Nanoparticles of Calcium Phosphates With Various Ca/P Ratios

PubMed Central

Sun, Limin; Chow, Laurence C.; Frukhtbeyn, Stanislav A.; Bonevich, John E.

2010-01-01

This study aimed at preparing and studying the properties of nanoparticles of calcium phosphate (nCaP) with Ca/P ratios ranging from 1.0 to 1.67 using a spray-drying technique. Micro-structural analyses suggested that the nCaPs with Ca/P ratios of 1.67 to 1.33 were nano-sized amorphous calcium phosphate (ACP) containing varying amounts of acid phosphate and carbonate. The nCaP with Ca/P ratio of 1 contained only nano-sized low crystalline dicalcium phosphate (DCP). BET measurements of the nCaPs showed specific surface areas of (12 ± 2 to 50 ± 1) m2/g, corresponding to estimated equivalent spherical diameters of (38 to 172) nm. However, dynamic light scattering measurements revealed much larger particles of (380 ± 49 to 768 ± 111) nm, owing to agglomeration of the smaller primary nano particles as revealed by Scanning Electron Microscopy (SEM). Thermodynamic solubility measurements showed that the nCaPs with Ca/P ratio of 1.33 – 1.67 all have similar solubility behavior. The materials were more soluble than the crystalline hydroxyapatite (HA) at pH greater than about 4.7, and more soluble than β-tricalcium phosphate (β-TCP), octacalcium phosphate (OCP) and DCP at pH above 5.5. Their solubility approached that of α-tricalcium phosphate (α-TCP) at about pH 7. These nCaPs, which cannot be readily prepared by other currently available methods for nanoparticle preparation, have potential biomedical applications. PMID:21037948

Fabrication of Double Layered Hybrid Solar Cells Consisting of Low-Temperature Anatase Titanium Oxide and Conducting Polymer

NASA Astrophysics Data System (ADS)

Itoh, Eiji; Takamizawa, Yuta; Miyairi, Keiichi

2008-01-01

We have prepared a photovoltaic device consisting of poly[2-methoxy,5-(2'-ethyl-hexyloxy)-p-phenylenevinylene] (MEHPPV) and an n-type crystalline TiO2 (anatase) thin film by high-temperature process and low-temperature process at a temperature lower than 150 °C by sol-gel techniques. The refluxed sol of titanium-tetraisopropoxide (TTI) with water and nitric acid formed anatase phase TiO2 without requiring the high-temperature process, and the wettability of sol is successfully improved by diluting sol with ethanol. The short circuit current JSC, fill factor, and the power conversion efficiency increase with the heat-treatment temperature of TiO2, which is attributed to the improvement of series resistance of the TiO2 film. On the other hand, the open circuit voltage remains almost constant (ca. 1.0 V) with the change in heat-treatment temperature between 60 and 120 °C, whereas it decreases to 0.76 V in the device prepared on the TiO2 film sintered at 500 °C, probably owing to the change in crystallinity. The origin of open circuit voltage in indium tin oxide (ITO)/TiO2/MEHPPV/Au is also discussed. The open circuit voltage corresponds well to the energy difference of the conduction band edge of TiO2 and the highest occupied molecular orbital (HOMO) of MEHPPV (ca. 1 eV) in the device consisting of the ITO/low-temperature TiO2/MEHPPV/Au system.

Spontaneous Ca(2+) transients in interstitial cells of Cajal located within the deep muscular plexus of the murine small intestine.

PubMed

Baker, Salah A; Drumm, Bernard T; Saur, Dieter; Hennig, Grant W; Ward, Sean M; Sanders, Kenton M

2016-06-15

Interstitial cells of Cajal at the level of the deep muscular plexus (ICC-DMP) in the small intestine generate spontaneous Ca(2+) transients that consist of localized Ca(2+) events and limited propagating Ca(2+) waves. Ca(2+) transients in ICC-DMP display variable characteristics: from discrete, highly localized Ca(2+) transients to regionalized Ca(2+) waves with variable rates of occurrence, amplitude, duration and spatial spread. Ca(2+) transients fired stochastically, with no cellular or multicellular rhythmic activity being observed. No correlation was found between the firing sites in adjacent cells. Ca(2+) transients in ICC-DMP are suppressed by the ongoing release of inhibitory neurotransmitter(s). Functional intracellular Ca(2+) stores are essential for spontaneous Ca(2+) transients, and the sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) pump is necessary for maintenance of spontaneity. Ca(2+) release mechanisms involve both ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP3 Rs). Release from these channels is interdependent. ICC express transcripts of multiple RyRs and InsP3 Rs, with Itpr1 and Ryr2 subtypes displaying the highest expression. Interstitial cells of Cajal in the deep muscular plexus of the small intestine (ICC-DMP) are closely associated with varicosities of enteric motor neurons and generate responses contributing to neural regulation of intestinal motility. Responses of ICC-DMP are mediated by activation of Ca(2+) -activated Cl(-) channels; thus, Ca(2+) signalling is central to the behaviours of these cells. Confocal imaging was used to characterize the nature and mechanisms of Ca(2+) transients in ICC-DMP within intact jejunal muscles expressing a genetically encoded Ca(2+) indicator (GCaMP3) selectively in ICC. ICC-DMP displayed spontaneous Ca(2+) transients that ranged from discrete, localized events to waves that propagated over variable distances. The occurrence of Ca(2+) transients was highly variable, and it was determined that firing was stochastic in nature. Ca(2+) transients were tabulated in multiple cells within fields of view, and no correlation was found between the events in adjacent cells. TTX (1 μm) significantly increased the occurrence of Ca(2+) transients, suggesting that ICC-DMP contributes to the tonic inhibition conveyed by ongoing activity of inhibitory motor neurons. Ca(2+) transients were minimally affected after 12 min in Ca(2+) free solution, indicating these events do not depend immediately upon Ca(2+) influx. However, inhibitors of sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) pump and blockers of inositol triphosphate receptor (InsP3 R) and ryanodine receptor (RyR) channels blocked ICC Ca(2+) transients. These data suggest an interdependence between RyR and InsP3 R in the generation of Ca(2+) transients. Itpr1 and Ryr2 were the dominant transcripts expressed by ICC. These findings provide the first high-resolution recording of the subcellular Ca(2+) dynamics that control the behaviour of ICC-DMP in situ. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Spontaneous Ca2+ transients in interstitial cells of Cajal located within the deep muscular plexus of the murine small intestine

PubMed Central

Baker, Salah A.; Drumm, Bernard T.; Saur, Dieter; Hennig, Grant W.; Ward, Sean M.

2016-01-01

Key points Interstitial cells of Cajal at the level of the deep muscular plexus (ICC‐DMP) in the small intestine generate spontaneous Ca2+ transients that consist of localized Ca2+ events and limited propagating Ca2+ waves.Ca2+ transients in ICC‐DMP display variable characteristics: from discrete, highly localized Ca2+ transients to regionalized Ca2+ waves with variable rates of occurrence, amplitude, duration and spatial spread.Ca2+ transients fired stochastically, with no cellular or multicellular rhythmic activity being observed. No correlation was found between the firing sites in adjacent cells.Ca2+ transients in ICC‐DMP are suppressed by the ongoing release of inhibitory neurotransmitter(s).Functional intracellular Ca2+ stores are essential for spontaneous Ca2+ transients, and the sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) pump is necessary for maintenance of spontaneity.Ca2+ release mechanisms involve both ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP3Rs). Release from these channels is interdependent.ICC express transcripts of multiple RyRs and InsP3Rs, with Itpr1 and Ryr2 subtypes displaying the highest expression. Abstract Interstitial cells of Cajal in the deep muscular plexus of the small intestine (ICC‐DMP) are closely associated with varicosities of enteric motor neurons and generate responses contributing to neural regulation of intestinal motility. Responses of ICC‐DMP are mediated by activation of Ca2+‐activated Cl− channels; thus, Ca2+ signalling is central to the behaviours of these cells. Confocal imaging was used to characterize the nature and mechanisms of Ca2+ transients in ICC‐DMP within intact jejunal muscles expressing a genetically encoded Ca2+ indicator (GCaMP3) selectively in ICC. ICC‐DMP displayed spontaneous Ca2+ transients that ranged from discrete, localized events to waves that propagated over variable distances. The occurrence of Ca2+ transients was highly variable, and it was determined that firing was stochastic in nature. Ca2+ transients were tabulated in multiple cells within fields of view, and no correlation was found between the events in adjacent cells. TTX (1 μm) significantly increased the occurrence of Ca2+ transients, suggesting that ICC‐DMP contributes to the tonic inhibition conveyed by ongoing activity of inhibitory motor neurons. Ca2+ transients were minimally affected after 12 min in Ca2+ free solution, indicating these events do not depend immediately upon Ca2+ influx. However, inhibitors of sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) pump and blockers of inositol triphosphate receptor (InsP3R) and ryanodine receptor (RyR) channels blocked ICC Ca2+ transients. These data suggest an interdependence between RyR and InsP3R in the generation of Ca2+ transients. Itpr1 and Ryr2 were the dominant transcripts expressed by ICC. These findings provide the first high‐resolution recording of the subcellular Ca2+ dynamics that control the behaviour of ICC‐DMP in situ. PMID:26824875

Lowering glucose level elevates [Ca2+]i in hypothalamic arcuate nucleus NPY neurons through P/Q-type Ca2+ channel activation and GSK3β inhibition

PubMed Central

Chen, Yu; Zhou, Jun; Xie, Na; Huang, Chao; Zhang, Jun-qi; Hu, Zhuang-li; Ni, Lan; Jin, You; Wang, Fang; Chen, Jian-guo; Long, Li-hong

2012-01-01

Aim: To identify the mechanisms underlying the elevation of intracellular Ca2+ level ([Ca2+]i) induced by lowering extracellular glucose in rat hypothalamic arcuate nucleus NPY neurons. Methods: Primary cultures of hypothalamic arcuate nucleus (ARC) neurons were prepared from Sprague-Dawley rats. NPY neurons were identified with immunocytochemical method. [Ca2+]i was measured using fura-2 AM. Ca2+ current was recorded using whole-cell patch clamp recording. AMPK and GSK3β levels were measured using Western blot assay. Results: Lowering glucose level in the medium (from 10 to 1 mmol/L) induced a transient elevation of [Ca2+]i in ARC neurons, but not in hippocampal and cortical neurons. The low-glucose induced elevation of [Ca2+]i in ARC neurons depended on extracellular Ca2+, and was blocked by P/Q-type Ca2+channel blocker ω-agatoxin TK (100 nmol/L), but not by L-type Ca2+ channel blocker nifedipine (10 μmol/L) or N-type Ca2+channel blocker ω-conotoxin GVIA (300 nmol/L). Lowering glucose level increased the peak amplitude of high voltage-activated Ca2+ current in ARC neurons. The low-glucose induced elevation of [Ca2+]i in ARC neurons was blocked by the AMPK inhibitor compound C (20 μmol/L), and enhanced by the GSK3β inhibitor LiCl (10 mmol/L). Moreover, lowering glucose level induced the phosphorylation of AMPK and GSK3β, which was inhibited by compound C (20 μmol/L). Conclusion: Lowering glucose level enhances the activity of P/Q type Ca2+channels and elevates [Ca2+]i level in hypothalamic arcuate nucleus neurons via inhibition of GSK3β. PMID:22504905

Leaching characteristics of calcium-based compounds in MSWI Residues: From the viewpoint of clogging risk

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

Xia, Yi; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092; Zhang, Hua, E-mail: zhanghua_tj@tongji.edu.cn

Highlights: • The leaching behavior of Ca-based compounds commonly in MSWI residues was studied. • pH is the crucial factor for calcium leaching process. • CaCO{sub 3} was the most sensitive to leaching temperature and Ca{sub 3}(PO{sub 4}){sub 2} was the least. • Ca leaching of MSWIBA and SAPCR attributed to CaCO{sub 3} and Ca{sub 3}(PO{sub 4}){sub 2} respectively. • Potential clogging ability of MSWI residues leachate in open air was calculated. - Abstract: Leachate collection system (LCS) clogging caused by calcium precipitation would be disadvantageous to landfill stability and operation. Meanwhile, calcium-based compounds are the main constituents in bothmore » municipal solid waste incineration bottom ash (MSWIBA) and stabilized air pollution control residues (SAPCR), which would increase the risk of LCS clogging once these calcium-rich residues were disposed in landfills. The leaching behaviors of calcium from the four compounds and municipal solid waste incineration (MSWI) residues were studied, and the influencing factors on leaching were discussed. The results showed that pH was the crucial factor in the calcium leaching process. CaCO{sub 3} and CaSiO{sub 3} began leaching when the leachate pH decreased to less than 7 and 10, respectively, while Ca{sub 3}(PO{sub 4}){sub 2} leached at pH < 12. CaSO{sub 4} could hardly dissolve in the experimental conditions. Moreover, the sequence of the leaching rate for the different calcium-based compounds is as follows: CaSiO{sub 3} > Ca{sub 3}(PO{sub 4}){sub 2} > CaCO{sub 3}. The calcium leaching from the MSWIBA and SAPCR separately started from pH < 7 and pH < 12, resulting from CaCO{sub 3} and Ca{sub 3}(PO{sub 4}){sub 2} leaching respectively, which was proven by the X-ray diffraction results. Based on the leaching characteristics of the different calcium compounds and the mineral phase of calcium in the incineration residues, simulated computation of their clogging potential was conducted, providing the theoretical basis for the risk assessment pertaining to LCS clogging in landfills.« less

Normocalcemia without hyperparathyroidism in vitamin D-deficient rats.

PubMed

Kollenkirchen, U; Fox, J; Walters, M R

1991-03-01

Despite numerous attempts, no reliable dietary regimen exists to achieve vitamin D deficiency (-D) in rats without attendant changes in plasma parathyroid hormone (PTH), Ca, or phosphate. This represents an important obstacle to proper investigations of the physiologic role(s) of vitamin D metabolites in the function of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] target tissues. This paper describes the successful development of such a diet, which uses a combination of high Ca content, properly controlled Ca/P ratio, and lactose. Normal weanling rats were fed diets containing A, 0.8% Ca, 0.5% P, +D3, or -D diets containing B, 0.8% Ca and 0.5% P; C, 2.0% Ca and 1.25% P; or D, 2.0% Ca, 1.25% P, and 20% lactose. After 6 diet weeks group D rats remained normocalcemic and normophosphatemic, but diet groups B and C became hypocalcemic (6.9 +/- 0.8 and 7.2 +/- 0.4 mg/dl, respectively). Thus high dietary Ca and P was incapable of maintaining normal plasma Ca levels in the absence of dietary lactose. The normocalcemia in group D was not maintained by elevated PTH secretion because N-terminal PTH levels were also normal (14 +/- 3 versus 20 +/- 5 pg/ml). In contrast, PTH levels were markedly elevated in hypocalcemic groups B and C (47 +/- 7 and 48 +/- 10 pg/ml, respectively). Plasma 25-OHD3 and 1,25-(OH)2D3 levels were reduced to less than 120 and less than 12 pg/ml, respectively, in all -D groups. Thus the high-Ca diet and the use of normal weanlings did not impede the development of vitamin D deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Convergent regulation of the lysosomal two-pore channel-2 by Mg²⁺, NAADP, PI(3,5)P₂ and multiple protein kinases.

PubMed

Jha, Archana; Ahuja, Malini; Patel, Sandip; Brailoiu, Eugen; Muallem, Shmuel

2014-03-03

Lysosomal Ca(2+) homeostasis is implicated in disease and controls many lysosomal functions. A key in understanding lysosomal Ca(2+) signaling was the discovery of the two-pore channels (TPCs) and their potential activation by NAADP. Recent work concluded that the TPCs function as a PI(3,5)P2 activated channels regulated by mTORC1, but not by NAADP. Here, we identified Mg(2+) and the MAPKs, JNK and P38 as novel regulators of TPC2. Cytoplasmic Mg(2+) specifically inhibited TPC2 outward current, whereas lysosomal Mg(2+) partially inhibited both outward and inward currents in a lysosomal lumen pH-dependent manner. Under controlled Mg(2+), TPC2 is readily activated by NAADP with channel properties identical to those in response to PI(3,5)P2. Moreover, TPC2 is robustly regulated by P38 and JNK. Notably, NAADP-mediated Ca(2+) release in intact cells is regulated by Mg(2+), PI(3,5)P2, and P38/JNK kinases, thus paralleling regulation of TPC2 currents. Our data affirm a key role for TPC2 in NAADP-mediated Ca(2+) signaling and link this pathway to Mg(2+) homeostasis and MAP kinases, pointing to roles for lysosomal Ca(2+) in cell growth, inflammation and cancer.

Control of glutamate release by calcium channels and κ-opioid receptors in rodent and primate striatum

PubMed Central

Hill, M P; Brotchie, J M

1999-01-01

The modulation of depolarization (4-aminopyridine, 2 mM)-evoked endogenous glutamate release by κ-opioid receptor activation and blockade of voltage-dependent Ca2+-channels has been investigated in synaptosomes prepared from rat and marmoset striatum.4-Aminopyridine (4-AP)-stimulated, Ca2+-dependent glutamate release was inhibited by enadoline, a selective κ-opioid receptor agonist, in a concentration-dependent and nor-binaltorphimine (nor-BNI, selective κ-opioid receptor antagonist)-sensitive manner in rat (IC50=4.4±0.4 μM) and marmoset (IC50=2.9±0.7 μM) striatal synaptosomes. However, in the marmoset, there was a significant (≈23%) nor-BNI-insensitive component.In rat striatal synaptosomes, the Ca2+-channel antagonists ω-agatoxin-IVA (P/Q-type blocker), ω-conotoxin-MVIIC (N/P/Q-type blocker) and ω-conotoxin-GVIA (N-type blocker) reduced 4-AP-stimulated, Ca2+-dependent glutamate release in a concentration-dependent manner with IC50 values of 6.5±0.9 nM, 75.5±5.9 nM and 106.5±8.7 nM, respectively. In marmoset striatal synaptosomes, 4-AP-stimulated, Ca2+-dependent glutamate release was significantly inhibited by ω-agatoxin-IVA (30 nM, 57.6±2.3%, inhibition), ω-conotoxin-MVIIC (300 nM, 57.8±3.1%) and ω-conotoxin-GVIA (1 μM, 56.7±2%).Studies utilizing combinations of Ca2+-channel antagonists suggests that in the rat striatum, two relatively distinct pools of glutamate, released by activation of either P or Q-type Ca2+-channels, exist. In contrast, in the primate there is much overlap between the glutamate released by P and Q-type Ca2+-channel activation.Studies using combinations of enadoline and the Ca2+-channel antagonists suggest that enadoline-induced inhibition of glutamate release occurs primarily via reduction of Ca2+-influx through P-type Ca2+-channels in the rat but via N-type Ca2+-channels in the marmoset.In conclusion, the results presented suggest that there are species differences in the control of glutamate release by κ-opioid receptors and Ca2+-channels. PMID:10369483

Atrial SERCA2a Overexpression Has No Affect on Cardiac Alternans but Promotes Arrhythmogenic SR Ca2+ Triggers

PubMed Central

Nassal, Michelle M. J.; Wan, Xiaoping; Laurita, Kenneth R.; Cutler, Michael J.

2015-01-01

Background Atrial fibrillation (AF) is the most common arrhythmia in humans, yet; treatment has remained sub-optimal due to poor understanding of the underlying mechanisms. Cardiac alternans precede AF episodes, suggesting an important arrhythmia substrate. Recently, we demonstrated ventricular SERCA2a overexpression suppresses cardiac alternans and arrhythmias. Therefore, we hypothesized that atrial SERCA2a overexpression will decrease cardiac alternans and arrhythmias. Methods Adult rat isolated atrial myocytes where divided into three treatment groups 1) Control, 2) SERCA2a overexpression (Ad.SERCA2a) and 3) SERCA2a inhibition (Thapsigargin, 1μm). Intracellular Ca2+ was measured using Indo-1AM and Ca2+ alternans (Ca-ALT) was induced with a standard ramp pacing protocol. Results As predicted, SR Ca2+ reuptake was enhanced with SERCA2a overexpression (p< 0.05) and reduced with SERCA2a inhibition (p<0.05). Surprisingly, there was no difference in susceptibility to Ca-ALT with either SERCA2a overexpression or inhibition when compared to controls (p = 0.73). In contrast, SERCA2a overexpression resulted in increased premature SR Ca2+ (SCR) release compared to control myocytes (28% and 0%, p < 0.05) and concomitant increase in SR Ca2+ load (p<0.05). Based on these observations we tested in-vivo atrial arrhythmia inducibility in control and Ad.SERCA2a animals using an esophageal atrial burst pacing protocol. There were no inducible atrial arrhythmias in Ad.GFP (n = 4) animals though 20% of Ad.SERCA2a (n = 5) animals had inducible atrial arrhythmias (p = 0.20). Conclusions Our findings suggest that unlike the ventricle, SERCA2a is not a key regulator of cardiac alternans in the atrium. Importantly, SERCA2a overexpression in atrial myocytes can increase SCR, which may be arrhythmogenic. PMID:26352986

Additive effect of calcium depletion and low resource quality on Gammarus fossarum (Crustacea, Amphipoda) life history traits.

PubMed

Rollin, Marc; Coulaud, Romain; Danger, Michael; Sohm, Bénédicte; Flayac, Justine; Bec, Alexandre; Chaumot, Arnaud; Geffard, Olivier; Felten, Vincent

2018-04-01

Gammarus fossarum is an often-abundant crustacean detritivore that contributes importantly to leaf litter breakdown in oligotrophic, mainly heterotrophic, headwater streams. This species requires large amounts of Ca to moult, thus allowing growth and reproduction. Because resource quality is tightly coupled to the organism's growth and physiological status, we hypothesised that low Ca concentration [Ca] and low food resource quality (low phosphorus [P] and/or reduced highly unsaturated fatty acid [HUFA] contents) would interactively impair molecular responses (gene expression) and reproduction of G. fossarum. To investigate the effects of food resources quality, we experimentally manipulated the P content of sycamore leaves and also used diatoms because they contain high amounts of HUFAs. Three resource quality treatments were tested: low quality (LQ, unmanipulated leaves: low P content), high quality 1 (HQ1; P-manipulated leaves: high P content), and high quality 2 (unmanipulated leaves supplemented with a pellet containing diatoms: high P and HUFA content). Naturally, demineralised stream water was supplemented with CaSO 4 to obtain three Ca concentrations (2, 3.5, and 10.5 mg Ca L -1 ). For 21 days, pairs of G. fossarum were individually exposed to one of the nine treatments (3 [Ca] × 3 resource qualities). At the individual level, strong and significant delays in moult stage were observed in gammarids exposed to lower [Ca] and to lower resource quality, with additive effects lengthening the duration of the reproductive cycle. Effects at the molecular level were investigated by measuring expression of 12 genes involved in energy production, translation, or Ca or P homeostasis. Expression of ATP synthase beta (higher in HQ2), calcified cuticle protein (higher in HQ1 and HQ2), and tropomyosin (higher in HQ2 compared to HQ1) was significantly affected by resource quality, and significant additive effects on Ca transporting ATPase expression were induced by [Ca] and resource quality (higher for low [Ca] and higher resource quality). These results highlight the potential drastic deleterious effects of water [Ca] depletion on G. fossarum physiology, populations, and ecosystem functioning, especially in oligotrophic environments.

β-Cell Ca(2+) dynamics and function are compromised in aging.

PubMed

Barker, Christopher J; Li, Luosheng; Köhler, Martin; Berggren, Per-Olof

2015-01-01

Defects in pancreatic β-cell function and survival are key components in type 2 diabetes (T2D). An age-dependent deterioration in β-cell function has also been observed, but little is known about the molecular mechanisms behind this phenomenon. Our previous studies indicate that the regulation of cytoplasmic free Ca(2+) concentration ([Ca(2+)]i) may be critical and that this is dependent on the proper function of the mitochondria. The [Ca(2+)]i dynamics of the pancreatic β-cell are driven by an interplay between glucose-induced influx of extracellular Ca(2+) via voltage-dependent Ca(2+) channels and the inositol 1,4,5-trisphosphate (Ins(1,4,5)P3)-mediated liberation of Ca(2+) from intracellular stores. Our previous work has indicated a direct relationship between disruption of Ins(1,4,5)P3-mediated Ca(2+) regulation and loss of β-cell function, including disturbed [Ca(2+)]i dynamics and compromised insulin secretion. To investigate these processes in aging we used three mouse models, a premature aging mitochondrial mutator mouse, a mature aging phenotype (C57BL/6) and an aging-resistant phenotype (129). Our data suggest that age-dependent impairment in mitochondrial function leads to modest changes in [Ca(2+)]i dynamics in mouse β-cells, particularly in the pattern of [Ca(2+)]i oscillations. These changes are driven by modifications in both PLC/Ins(1,4,5)P3-mediated Ca(2+) mobilization from intracellular stores and decreased β-cell Ca(2+) influx over the plasma membrane. Our findings underscore an important concept, namely that even relatively small, time-dependent changes in β-cell signal-transduction result in compromised insulin release and in a diabetic phenotype. Copyright © 2014 Elsevier Ltd. All rights reserved.

Paroxetine-induced apoptosis in human osteosarcoma cells: Activation of p38 MAP kinase and caspase-3 pathways without involvement of [Ca{sup 2+}]{sub i} elevation

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

Chou, C.-T.; Department of Biological Sciences, National Sun Yat-sen University, 804, Taiwan; He Shiping

2007-02-01

Selective serotonin reuptake inhibitors (SSRIs), a group of antidepressants, are generally used for treatment of various mood and anxiety disorders. There has been much research showing the anti-tumor and cytotoxic activities of some antidepressants; but the detailed mechanisms were unclear. In cultured human osteosarcoma cells (MG63), paroxetine reduced cell viability in a concentration- and time-dependent manner. Paroxetine caused apoptosis as assessed by propidium iodide-stained cells and increased caspase-3 activation. Although immunoblotting data revealed that paroxetine could activate the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun NH{sub 2}-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), only SB203580 (a p38more » MAPK inhibitor) partially prevented cells from apoptosis. Paroxetine also induced [Ca{sup 2+}]{sub i} increases which involved the mobilization of intracellular Ca{sup 2+} stored in the endoplasmic reticulum and Ca{sup 2+} influx from extracellular medium. However, pretreatment with BAPTA/AM, a Ca{sup 2+} chelator, to prevent paroxetine-induced [Ca{sup 2+}]{sub i} increases did not protect cells from death. The results suggest that in MG63 cells, paroxetine caused Ca{sup 2+}-independent apoptosis via inducing p38 MAPK-associated caspase-3 activation.« less

Disappearance of superconductivity in the solid solution between (Ca4Al2O6)(Fe2As2) and (Ca4Al2O6)(Fe2P2) superconductors.

PubMed

Shirage, Parasharam M; Kihou, Kunihiro; Lee, Chul-Ho; Takeshita, Nao; Eisaki, Hiroshi; Iyo, Akira

2012-09-19

The effect of alloying the two perovskite-type iron-based superconductors (Ca(4)Al(2)O(6))(Fe(2)As(2)) and (Ca(4)Al(2)O(6))(Fe(2)P(2)) was examined. While the two stoichiometric compounds possess relatively high T(c)'s of 28 and 17 K, respectively, their solid solutions of the form (Ca(4)Al(2)O(6))(Fe(2)(As(1-x)P(x))(2)) do not show superconductivity over a wide range from x = 0.50 to 0.95. The resultant phase diagram is thus completely different from those of other typical iron-based superconductors such as BaFe(2)(As,P)(2) and LaFe(As,P)O, in which superconductivity shows up when P is substituted for As in the non-superconducting "parent" compounds. Notably, the solid solutions in the non-superconducting range exhibit resistivity anomalies at temperatures of 50-100 K. The behavior is reminiscent of the resistivity kink commonly observed in various non-superconducting parent compounds that signals the onset of antiferromagnetic/orthorhombic long-range order. The similarity suggests that the suppression of the superconductivity in the present case also has a magnetic and/or structural origin.

Adaptive response of broilers to dietary phosphorus and calcium restrictions.

PubMed

Rousseau, Xavière; Valable, Anne-Sophie; Létourneau-Montminy, Marie-Pierre; Même, Nathalie; Godet, Estelle; Magnin, Michel; Nys, Yves; Duclos, Michel J; Narcy, Agnès

2016-12-01

The aim of this study was to evaluate the capacity of chickens to adapt to and compensate for early dietary restriction of non-phytate P ( NPP: ) and/or Ca (10 to 21 d) in a later phase (22 to 35 d), and to determine whether compensatory processes depend on the P and Ca concentrations in the finisher diet. Four diets were formulated and fed to broilers from 10 to 21 d in order to generate birds with different mineral status: L 1 (0.6% Ca, 0.30% NPP), L 2 (0.6% Ca, 0.45% NPP), H 1 (1.0% Ca, 0.30% NPP), and H 2 (1.0% Ca, 0.45% NPP). On d 22, each group was divided into three groups which received a low (L, 0.48% Ca, 0.24% NPP), moderate (M, 0.70% Ca, 0.35% NPP), or high (H, 0.90% Ca, 0.35% NPP) finisher diet until 35 d, resulting in a total of 12 treatments. Lowering the Ca level enhanced apparent ileal digestibility of P (P AID) at 21 d especially with the high NPP level (Ca × NPP, P < 0.01). The lower bone mineralization observed at 21 d in broilers fed the L 1 diet compared to those fed the H 2 diet had disappeared by 35 d with long-term stimulation of the P AID with the low NPP level (P < 0.001). Although P AID and growth performance were improved in birds fed the L 1 L compared to the L 1 H and H 2 H treatments, tibia characteristics tended to be lower in birds fed the L 1 L compared to those fed the L 1 H treatment. Birds fed the H 1 M treatment had higher P AID, growth performance and tibia ash content than those fed the H 1 H treatment. A significant increase in the mRNA levels of several genes encoding Ca and P transporters was observed at 35 d in birds fed the L 1 followed by the L diet compared to birds fed the L 1 followed by the M diet. In conclusion, chickens are able to adapt to early dietary changes in P and Ca through improvement of digestive efficiency in a later phase, and the extent of the compensation in terms of growth performance and bone mineralization depends on the P and Ca levels in the subsequent diet. © 2016 Poultry Science Association Inc.

Coupling between phosphate and calcium homeostasis: a mathematical model.

PubMed

Granjon, David; Bonny, Olivier; Edwards, Aurélie

2017-12-01

We developed a mathematical model of calcium (Ca) and phosphate (PO 4 ) homeostasis in the rat to elucidate the hormonal mechanisms that underlie the regulation of Ca and PO 4 balance. The model represents the exchanges of Ca and PO 4 between the intestine, plasma, kidneys, bone, and the intracellular compartment, and the formation of Ca-PO 4 -fetuin-A complexes. It accounts for the regulation of these fluxes by parathyroid hormone (PTH), vitamin D 3 , fibroblast growth factor 23, and Ca 2+ -sensing receptors. Our results suggest that the Ca and PO 4 homeostatic systems are robust enough to handle small perturbations in the production rate of either PTH or vitamin D 3 The model predicts that large perturbations in PTH or vitamin D 3 synthesis have a greater impact on the plasma concentration of Ca 2+ ([Ca 2+ ] p ) than on that of PO 4 ([PO 4 ] p ); due to negative feedback loops, [PO 4 ] p does not consistently increase when the production rate of PTH or vitamin D 3 is decreased. Our results also suggest that, following a large PO 4 infusion, the rapidly exchangeable pool in bone acts as a fast, transient storage PO 4 compartment (on the order of minutes), whereas the intracellular pool is able to store greater amounts of PO 4 over several hours. Moreover, a large PO 4 infusion rapidly lowers [Ca 2+ ] p owing to the formation of CaPO 4 complexes. A large Ca infusion, however, has a small impact on [PO 4 ] p , since a significant fraction of Ca binds to albumin. This mathematical model is the first to include all major regulatory factors of Ca and PO 4 homeostasis. Copyright © 2017 the American Physiological Society.

Electronic structure, bonding, charge distribution, and x-ray absorption spectra of the (001) surfaces of fluorapatite and hydroxyapatite from first principles

NASA Astrophysics Data System (ADS)

Rulis, Paul; Yao, Hongzhi; Ouyang, Lizhi; Ching, W. Y.

2007-12-01

Fluorapatite (FAP) and hydroxyapatite (HAP) are two very important bioceramic crystals. The (001) surfaces of FAP and HAP crystals are studied by ab initio density functional calculations using a supercell slab geometry. It is shown that in both crystals, the O-terminated (001) surface is more stable with calculated surface energies of 0.865 and 0.871J/m2 for FAP and HAP, respectively. In FAP, the two surfaces are symmetric. In HAP, the orientation of the OH group along the c axis reduces the symmetry such that the top and bottom surfaces are no longer symmetric. It is revealed that the atoms near the surface and subsurface are significantly relaxed especially in the case of HAP. The largest relaxations occurred via the lateral movements of the O ions at the subsurface level. The electronic structures of the surface models in the form of layer-by-layer resolved partial density of states for all the atoms show systematic variation from the surface region toward the bulk region. The calculated Mulliken effective charge on each type of atom and the bond order values between cations (Ca, P) and anions (O, F) show different charge transfers and bond strength variations from the bulk crystal values. Electron charge density calculations show that the surfaces of both FAP and HAP crystals are mostly positively charged due to the presence of Ca ions at the surface. The positively charged surfaces have implications for the absorption on apatite surfaces of water and other organic molecules in an aqueous environment which are an important part of its bioactivity. The x-ray absorption near-edge structure (XANES) spectra ( Ca-K , O-K , F-K , P-K , and P-L3 edges) of both the surface models and the bulk crystals are calculated and compared. The calculations use a supercell approach which takes into account the electron-core-hole interaction. It is shown that the site-specific XANES spectra show significant differences between atoms near the surface and in the bulk and are very sensitive to the local atomic environment of each atom. This information will be very valuable for characterizing the apatite materials and in the interpretation of experimental data. Comparisons of several sets of experimental data with the weighted sums of the calculated spectra at different sites for the same element show very good agreement.

Effect of Mg2+ on the control of Ca2+ release in skeletal muscle fibres of the toad.

PubMed Central

Lamb, G D; Stephenson, D G

1991-01-01

1. The effect of myoplasmic Mg2+ on Ca2+ release was examined in mechanically skinned skeletal muscle fibres, in which the normal voltage-sensor control of Ca2+ release is preserved. The voltage sensors could be activated by depolarizing the transverse tubular (T-) system by lowering the [K+] in the bathing solution. 2. Fibres spontaneously contracted when the free [Mg2+] was decreased from 1 to 0.05 mM, with no depolarization or change of total ATP, [Ca2+] or pH (pCa 6.7, 50 microM-EGTA). After such a 'low-Mg2+ response' the sarcoplasmic reticulum (SR) was depleted of Ca2+ and neither depolarization nor caffeine (2 mM) could induce a response, unless the [Mg2+] was raised and the SR reloaded with Ca2+. Exposure to 0.05 mM-Mg2+ at low [Ca2+] (2 mM-free EGTA, pCa greater than 8.7) also induced Ca2+ release and depleted the SR. 3. The response to low [Mg2+] was unaffected by inactivation of the voltage sensors, but was completely blocked by 2 microM-Ruthenium Red indicating that it involved Ca2+ efflux through the normal Ca2+ release channels. 4. In the absence of ATP (and creatine phosphate), complete removal of Mg2+ (i.e. no added Mg2+ with 1 mM-EDTA) did not induce Ca2+ release. Depolarization in the absence of Mg2+ and ATP also did not induce Ca2+ release. 5. Depolarization in 10 mM-Mg2+ (pCa 6.7, 50 microM-EGTA, 8 mM-total ATP) did not produce any response. In the presence of 1 mM-EGTA to chelate most of the released Ca2+, depolarizations in 10 mM-Mg2+ did not noticeably deplete the SR of Ca2+, whereas a single depolarization in 1 mM-Mg2+ (and 1 mM-EGTA) resulted in marked depletion. Depolarization in the presence of D600 and 10 mM-Mg2+ produced use-dependent 'paralysis', indicating that depolarization in 10 mM-Mg2+ did indeed activate the voltage sensors. 6. Depolarization in the presence of 10 mM-Mg2+ and 25 microM-ryanodine neither interfered with the normal voltage control of Ca2+ release nor caused depletion of the Ca2+ in the SR even after returning to 1 mM-Mg2+ for 1 min, indicating that few if any of the release channels had been opened by the depolarization.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1708823

Calmodulin kinase II and protein kinase C mediate the effect of increased intracellular calcium to augment late sodium current in rabbit ventricular myocytes.

PubMed

Ma, Jihua; Luo, Antao; Wu, Lin; Wan, Wei; Zhang, Peihua; Ren, Zhiqiang; Zhang, Shuo; Qian, Chunping; Shryock, John C; Belardinelli, Luiz

2012-04-15

An increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) augments late sodium current (I(Na.L)) in cardiomyocytes. This study tests the hypothesis that both Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) and protein kinase C (PKC) mediate the effect of increased [Ca(2+)](i) to increase I(Na.L). Whole cell and open cell-attached patch clamp techniques were used to record I(Na.L) in rabbit ventricular myocytes dialyzed with solutions containing various concentrations of [Ca(2+)](i). Dialysis of cells with [Ca(2+)](i) from 0.1 to 0.3, 0.6, and 1.0 μM increased I(Na.L) in a concentration-dependent manner from 0.221 ± 0.038 to 0.554 ± 0.045 pA/pF (n = 10, P < 0.01) and was associated with an increase in mean Na(+) channel open probability and prolongation of channel mean open-time (n = 7, P < 0.01). In the presence of 0.6 μM [Ca(2+)](i), KN-93 (10 μM) and bisindolylmaleimide (BIM, 2 μM) decreased I(Na.L) by 45.2 and 54.8%, respectively. The effects of KN-93 and autocamtide-2-related inhibitory peptide II (2 μM) were not different. A combination of KN-93 and BIM completely reversed the increase in I(Na.L) as well as the Ca(2+)-induced changes in Na(+) channel mean open probability and mean open-time induced by 0.6 μM [Ca(2+)](i). Phorbol myristoyl acetate increased I(Na.L) in myocytes dialyzed with 0.1 μM [Ca(2+)](i); the effect was abolished by Gö-6976. In summary, both CaMKII and PKC are involved in [Ca(2+)](i)-mediated augmentation of I(Na.L) in ventricular myocytes. Inhibition of CaMKII and/or PKC pathways may be a therapeutic target to reduce myocardial dysfunction and cardiac arrhythmias caused by calcium overload.

P-type proton ATPases are involved in intracellular calcium and proton uptake in the plant parasite Phytomonas francai.

PubMed

Miranda, Kildare; Vercesi, Anibal E; Catisti, Rosana; De Souza, Wanderley; Rodrigues, Claudia O; Docampo, Roberto

2005-01-01

The use of digitonin to permeabilize the plasma membrane of promastigotes of Phytomonas francai allowed the identification of two non-mitochondrial Ca(2+) compartments; one sensitive to ionomycin and vanadate (neutral or alkaline), possibly the endoplasmic reticulum, and another sensitive to the combination of nigericin plus ionomycin (acidic), possibly the acidocalcisomes. A P-type (phospho-intermediate form) Ca(2+)-ATPase activity was found to be responsible for intracellular Ca(2+) transport in these cells, with no evidence of a mitochondrial Ca(2+) transport activity. ATP-driven acidification of internal compartments in cell lysates and cells mechanically permeabilized was assayed spectrophotometrically with acridine orange. This activity was inhibited by low concentrations of vanadate and digitonin, was insensitive to bafilomycin A(1), and stimulated by Na(+) ions. Taken together, our results indicate that P-type ATPases are involved in intracellular Ca(2+) and H(+) transport in promastigotes of P. francai.

Measurement of four tumor marker antigens in the sera of pregnant women.

PubMed

Cheli, C D; Morris, D L; Neaman, I E; Dai, J; Allard, W J; Yeung, K K

1999-01-01

We sought to determine the maternal serum levels of four tumor-associated antigens during the three trimesters of pregnancy in healthy women. CEA, CA 228, CA 15-3, and Her2/neu oncogene product p105 assay values were determined for 90 healthy pregnant women during the three trimesters of pregnancy at five participating evaluation sites. Results were compared to means and cut-off values determined for healthy nonpregnant women. Differences in assay values in the 1st and 3rd trimester were analyzed for statistical significance (Student's t-test). CEA, CA 228 and CA 15-3 assay values in general were found to be within the normal range. CA 15-3 and Her2/neu p105 serum assay values were above the cut-off (3.3% and 8.2%, respectively) and were significantly elevated in the 3rd trimester as compared to the 1st trimester of pregnancy (P < 0.05 and P < 0.001, respectively). CEA and CA 228 may be of potential value in monitoring pregnant women with malignant disease. Normal elevations in 3rd trimester serum Her2/neu p105 and CA 15-3 assay values should be considered when monitoring a pregnant patient with malignant disease.

Estimation of gastric pH in cynomolgus monkeys, rats, and dogs using [(13)C]-calcium carbonate breath test.

PubMed

Tobita, Kazuki; Inada, Makoto; Sato, Asuka; Sudoh, Kimiyoshi; Sato, Hitoshi

2016-09-01

The determination of gastric pH is important for the confirmation of efficacy of anti-secretory drugs. However, current methods for measurement of gastric pH provide significant stress to animals and humans. The objective of this study is to establish an easy and reliable gastric pH measurement method by determining (13)CO2 concentration in expired air of monkeys, dogs, and rats after oral administration of Ca(13)CO3. A correlation of (13)CO2 concentration determined by a Ca(13)CO3 breath test with gastric pH just before Ca(13)CO3 administration was analyzed in the 3 animal species. The equations and contribution ratios of regression line were calculated from logarithmic (13)CO2 concentrations at 15min after administration of Ca(13)CO3 using the linear regression analysis. The (13)CO2 concentration in the Ca(13)CO3 breath test was well correlated with the gastric pH just before Ca(13)CO3 administration in the 3 animal species (r=-0.977 to -0.952). The equations of regression line between the (13)CO2 concentration and the gastric pH in each animal species showed good contribution ratios (R(2)≥0.89). The Ca(13)CO3 breath test is an informative tool to estimate gastric pH in animals and will be applicable as a new noninvasive tool for patients with GERD/PPI-resistant symptoms. Copyright © 2016 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Differential effects of buffer pH on Ca2+-induced ROS emission with inhibited mitochondrial complexes I and III

PubMed Central

Lindsay, Daniel P.; Camara, Amadou K. S.; Stowe, David F.; Lubbe, Ryan; Aldakkak, Mohammed

2015-01-01

Excessive mitochondrial reactive oxygen species (ROS) emission is a critical component in the etiology of ischemic injury. Complex I and complex III of the electron transport chain are considered the primary sources of ROS emission during cardiac ischemia and reperfusion (IR) injury. Several factors modulate ischemic ROS emission, such as an increase in extra-matrix Ca2+, a decrease in extra-matrix pH, and a change in substrate utilization. Here we examined the combined effects of these factors on ROS emission from respiratory complexes I and III under conditions of simulated IR injury. Guinea pig heart mitochondria were suspended in experimental buffer at a given pH and incubated with or without CaCl2. Mitochondria were then treated with either pyruvate, a complex I substrate, followed by rotenone, a complex I inhibitor, or succinate, a complex II substrate, followed by antimycin A, a complex III inhibitor. H2O2 release rate and matrix volume were compared with and without adding CaCl2 and at pH 7.15, 6.9, or 6.5 with pyruvate + rotenone or succinate + antimycin A to simulate conditions that may occur during in vivo cardiac IR injury. We found a large increase in H2O2 release with high [CaCl2] and pyruvate + rotenone at pH 6.9, but not at pHs 7.15 or 6.5. Large increases in H2O2 release rate also occurred at each pH with high [CaCl2] and succinate + antimycin A, with the highest levels observed at pH 7.15. The increases in H2O2 release were associated with significant mitochondrial swelling, and both H2O2 release and swelling were abolished by cyclosporine A, a desensitizer of the mitochondrial permeability transition pore (mPTP). These results indicate that ROS production by complex I and by complex III is differently affected by buffer pH and Ca2+ loading with mPTP opening. The study suggests that changes in the levels of cytosolic Ca2+ and pH during IR alter the relative amounts of ROS produced at mitochondrial respiratory complex I and complex III. PMID:25805998

Effect of hyper- and hypocapnia on cerebral arterial compliance in normal subjects.

PubMed

Carrera, Emmanuel; Kim, Dong-Joo; Castellani, Gianluca; Zweifel, Christian; Smielewski, Peter; Pickard, John D; Czosnyka, Marek

2011-04-01

Changes in partial pressure of carbon dioxide (PaCO2) are associated with a decrease in cerebral blood flow (CBF) during hypocapnia and an increase in CBF during hypercapnia. However, the effects of changes in PaCO2 on cerebral arterial compliance (Ca) are unknown. We assessed the changes in Ca in 20 normal subjects using monitoring of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). Cerebral arterial blood volume (CaBV) was extracted from CBFV. Ca was defined as the ratio between the pulse amplitudes of CaBV (AMPCaBV ) and ABP (AMPABP). All parameters were recorded during normo-, hyper-, and hypocapnia. During hypocapnia, Ca was significantly lower than during normocapnia (.10±.04 vs. .17±.06; P<.001) secondary to a decrease in AMPCaBV (1.3±.4 vs. 1.9±.5; P<.001) and a concomitant increase in AMPABP (13.8±3.4 vs. 11.6±1.7 mmHg; P<.001). During hypercapnia, there was no change in Ca compared with normocapnia. Ca was inversely correlated with the cerebrovascular resistance during hypo- (R2=0.86; P<.001), and hypercapnia (R2=0.61; P<.001). Using a new mathematical model, we have described a reduction of Ca during hypocapnia. Further studies are needed to determine whether Ca may be an independent predictor of outcome in pathological conditions. Copyright © 2009 by the American Society of Neuroimaging.

BG60S dissolution interferes with osteoblast calcium signals.

PubMed

Valério, P; Pereira, M M; Goes, A M; Leite, M F

2007-02-01

We investigated the influence of extracellular calcium concentration, caused by the dissolution of a bioactive glass with 60% of silicon (BG60S), on intracellular calcium (Ca(i) (2 +)) signals and expression of inositol 1, 4, 5-triphosphate receptors (InsP(3)R) in primary culture of osteoblasts. We found that BG60S caused an increase in Ca(i) (2 +) signals in this cell type. Additionally, osteoblasts pre-incubated in the presence of BG60S showed an increase in Ca(i) (2 +) when cells were stimulated with vasopressin. On the other hand, a decrease in Ca(i) (2 +) signals were observed in osteoblasts pre-treated with BG60S and stimulated with KCl. We furher found that in osteoblasts, the type I InsP(3)R is preferentially distributed in the nucleus while the type II InsP(3)R in the cytoplasm. Preincubation of osteoblasts with BG60S altered the receptor expression level, increasing the type I InsP(3)R in the nucleus and decreasing type II InsP(3)R in the cytosol. Together, our results showed that in osteoblasts, BG60S increased Ca(i) (2 +)signals and altered Ca(i) (2 +) machinery.

P2Y2 receptor activation inhibits the expression of the sodium-chloride cotransporter NCC in distal convoluted tubule cells.

PubMed

Gailly, P; Szutkowska, M; Olinger, E; Debaix, H; Seghers, F; Janas, S; Vallon, V; Devuyst, O

2014-11-01

Luminal nucleotide stimulation is known to reduce Na(+) transport in the distal nephron. Previous studies suggest that this mechanism may involve the thiazide-sensitive Na(+)-Cl(-) cotransporter (NCC), which plays an essential role in NaCl reabsorption in the cells lining the distal convoluted tubule (DCT). Here we show that stimulation of mouse DCT (mDCT) cells with ATP or UTP promoted Ca(2+) transients and decreased the expression of NCC at both mRNA and protein levels. Specific siRNA-mediated silencing of P2Y2 receptors almost completely abolished ATP/UTP-induced Ca(2+) transients and significantly reduced ATP/UTP-induced decrease of NCC expression. To test whether local variations in the intracellular Ca(2+) concentration ([Ca(2+)]i) may control NCC transcription, we overexpressed the Ca(2+)-binding protein parvalbumin selectively in the cytosol or in the nucleus of mDCT cells. The decrease in NCC mRNA upon nucleotide stimulation was abolished in cells overexpressing cytosolic PV but not in cells overexpressing either a nuclear-targeted PV or a mutated PV unable to bind Ca(2+). Using a firefly luciferase reporter gene strategy, we observed that the activity of NCC promoter region from -1 to -2,200 bp was not regulated by changes in [Ca(2+)]i. In contrast, high cytosolic calcium level induced instability of NCC mRNA. We conclude that in mDCT cells: (1) P2Y2 receptor is essential for the intracellular Ca(2+) signaling induced by ATP/UTP stimulation; (2) P2Y2-mediated increase of cytoplasmic Ca(2+) concentration down-regulates the expression of NCC; (3) the decrease of NCC expression occurs, at least in part, via destabilization of its mRNA.

Histochemical changes of occlusal surface enamel of permanent teeth, where dental caries is questionable vs sound enamel surfaces.

PubMed

Michalaki, M; Oulis, C J; Pandis, N; Eliades, G

2016-12-01

This in vitro study was to classify questionable for caries occlusal surfaces (QCOS) of permanent teeth according to ICDAS codes 1, 2, and 3 and to compare them in terms of enamel mineral composition with the areas of sound tissue of the same tooth. Partially impacted human molars (60) extracted for therapeutic reasons with QCOS were used in the study, photographed via a polarised light microscope and classified according to the ICDAS II (into codes 1, 2, or 3). The crowns were embedded in clear self-cured acrylic resin and longitudinally sectioned at the levels of the characterised lesions and studied by SEM/EDX, to assess enamel mineral composition of the QCOS. Univariate and multivariate random effect regressions were used for Ca (wt%), P (wt%), and Ca/P (wt%). The EDX analysis indicated changes in the Ca and P contents that were more prominent in ICDAS-II code 3 lesions compared to codes 1 and 2 lesions. In these lesions, Ca (wt%) and P (wt%) concentrations were significantly decreased (p = 0.01) in comparison with sound areas. Ca and P (wt%) contents were significantly lower (p = 0.02 and p = 0.01 respectively) for code 3 areas in comparison with codes 1 and 2 areas. Significantly higher (p = 0.01) Ca (wt%) and P (wt%) contents were found on sound areas compared to the lesion areas. The enamel of occlusal surfaces of permanent teeth with ICDAS 1, 2, and 3 lesions was found to have different Ca/P compositions, necessitating further investigation on whether these altered surfaces might behave differently on etching preparation before fissure sealant placement, compared to sound surfaces.

Departure gate of acidic Ca2+ confirmed

PubMed Central

Jentsch, Thomas J; Hoegg-Beiler, Maja B; Vogt, Janis

2015-01-01

More potent, but less known than IP3 that liberates Ca2+ from the ER, NAADP releases Ca2+ from acidic stores. The notion that TPC channels mediate this Ca2+ release was questioned recently by studies suggesting that TPCs are rather PI(3,5)P2-activated Na+ channels. Ruas et al (2015) now partially reconcile these views by showing that TPCs significantly conduct both cations and confirm their activation by both NAADP and PI(3,5)P2. They attribute the failure of others to observe TPC-dependent NAADP-induced Ca2+ release in vivo to inadequate mouse models that retain partial TPC function. PMID:26022292

The diagnostic value of serum tumor markers CEA, CA19-9, CA125, CA15-3, and TPS in metastatic breast cancer.

PubMed

Wang, Weigang; Xu, Xiaoqin; Tian, Baoguo; Wang, Yan; Du, Lili; Sun, Ting; Shi, Yanchun; Zhao, Xianwen; Jing, Jiexian

2017-07-01

This study aims to understand the diagnostic value of serum tumor markers carcinoembryonic antigen (CEA), cancer antigen 19-9 (CA19-9), cancer antigen 125 (CA125), cancer antigen 15-3 (CA15-3), and tissue polypeptide-specific antigen (TPS) in metastatic breast cancer (MBC). A total of 164 metastatic breast cancer patients in Shanxi Cancer Hospital were recruited between February 2016 and July 2016. 200 breast cancer patients without metastasis in the same period were randomly selected as the control group. The general characteristics, immunohistochemical, and pathological results were investigated between the two groups, and tumor markers were determined. There were statistical differences in the concentration and the positive rates of CEA, CA19-9, CA125, CA15-3, and TPS between the MBC and control group (P<0.05). The highest sensitivity was in CEA and the highest specificity was in CA125 for the diagnosis of MBC when using a single tumor marker at 56.7% and 97.0%, respectively. In addition, two tumor markers were used for the diagnosis of MBC and the CEA and TPS combination had the highest diagnostic sensitivity with 78.7%, while the CA15-3 and CA125 combination had the highest specificity of 91.5%. Analysis of tumor markers of 164 MBC found that there were statistical differences in the positive rates of CEA and CA15-3 between bone metastases and other metastases (χ 2 =6.00, P=0.014; χ 2 =7.32, P=0.007, respectively). The sensitivity and specificity values of the CEA and CA15-3 combination in the diagnosis of bone metastases were 77.1% and 45.8%, respectively. The positive rate of TPS in the lung metastases group was lower than in other metastases (χ 2 =8.06, P=0.005).There were significant differences in the positive rates of CA15-3 and TPS between liver metastases and other metastases (χ 2 =15.42, P<0.001; χ 2 =9.72, P=0.002, respectively). The sensitivity and specificity of the CA15-3 and TPS combination in the diagnosis of liver metastases were 92.3% and 45.6%, respectively, and the positive rate of CEA in triple-negative metastatic breast cancer is lower than in other subtypes (χ 2 =4.80, P=0.028). Therefore, serum CEA, CA19-9, CA125, CA15-3, and TPS can be used in the diagnosis of MBC, and different combinations of tumor markers have varying diagnostic value. Copyright © 2017 Elsevier B.V. All rights reserved.

Calcium signalling from the type I inositol 1,4,5-trisphosphate receptor is required at early phase of liver regeneration.

PubMed

Oliveira, André G; Andrade, Viviane A; Guimarães, Erika S; Florentino, Rodrigo M; Sousa, Pedro A; Marques, Pedro E; Melo, Flávia M; Ortega, Miguel J; Menezes, Gustavo B; Leite, M Fatima

2015-04-01

Liver regeneration is a multistage process that unfolds gradually, with different mediators acting at different stages of regeneration. Calcium (Ca(2+) ) signalling is essential for liver regeneration. In hepatocytes, Ca(2+) signalling results from the activation of inositol 1,4,5-trisphosphate receptors (InsP3 R) of which two of the three known isoforms are expressed (InsP3 R-I and InsP3 R-II). Here, we investigated the role of the InsP3 R-I-dependent Ca(2+) signals in hepatic proliferation during liver regeneration. Partial hepatectomy (HX) in combination with knockdown of InsP3 R-I (AdsiRNA-I) was used to evaluate the role of InsP3 R-I on liver regeneration and hepatocyte proliferation, as assessed by liver to body mass ratio, PCNA expression, immunoblots and measurements of intracellular Ca(2+) signalling. AdsiRNA-I efficiently infected the liver as demonstrated by the expression of β-galactosidase throughout the liver lobules. Moreover, this construct selectively and efficiently reduced the expression of InsP3 R-I, as evaluated by immunoblots. Expression of AdsiRNA-I in liver decreased peak Ca(2+) amplitude induced by vasopressin in isolated hepatocytes 2 days after HX. Reduced InsP3 R-I expression prior to HX also delayed liver regeneration, as measured by liver to body weight ratio, and reduced hepatocyte proliferation, as evaluated by PCNA staining, at the same time point. At later stages of regeneration, control hepatocytes showed a decreased expression of InsP3 R, as well as reduced InsP3 R-mediated Ca(2+) signalling, events that did not affect liver growth. Together, these results show that InsP3 R-I-dependent Ca(2+) signalling is an early triggering pathway required for liver regeneration. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system.

PubMed

Dias, A G; Gibson, I R; Santos, J D; Lopes, M A

2007-03-01

The aim of this work was to evaluate the in vitro degradation behaviour of a 45CaO-37P(2)O(5)-5MgO-13TiO(2) (mol.%) glass ceramic, under two different simulated physiological conditions: normal physiological pH 7.4, and pH 3.0, which was designed to simulate the acidic conditions produced by osteoclast cells. The in vitro testing was carried out at 37 degrees C for up to 42 days for the pH 7.4 solution and for up to 1 day for the pH 3.0 solution. The incorporation of TiO(2) into the glass structure leads to the precipitation of specific crystalline phases in the glass matrix, namely alpha- and beta-Ca(2)P(2)O(7), TiP(2)O(7) and CaTi(4)(PO(4))(6). The degradation testing at pH 3.0 showed a higher weight loss compared with degradation testing at pH 7.4; the weight loss under the acidic condition after 1 day (24 h) was about 10 times higher than the weight loss after 42 days of immersion at pH 7.4. The ionic release profile of Ca(2+), PO(4)(3-), Mg(2+) and Ti(4+) showed a continuous increase in concentration over all immersion times for both testing solutions. After 1 day of immersion at pH 3.0, the concentration levels of Mg(2+), Ca(2+), PO(4)(3-) were about six times higher than the levels achieved after 42 days of immersion at pH 7.4. The glass ceramic showed similar degradation to hydroxyapatite, and therefore has potential to be used in certain clinical applications where relatively slow resorption of the implant and replacement by bone is required, e.g. cranioplasty.

Exogenous feeding of immediate precursors reveals synergistic effect on picroside-I biosynthesis in shoot cultures of Picrorhiza kurroa Royle ex Benth

NASA Astrophysics Data System (ADS)

Kumar, Varun; Sharma, Neha; Sood, Hemant; Chauhan, Rajinder Singh

2016-07-01

In the current study, we asked how the supply of immediate biosynthetic precursors i.e. cinnamic acid (CA) and catalpol (CAT) influences the synthesis of picroside-I (P-I) in shoot cultures of P. kurroa. Our results revealed that only CA and CA+CAT stimulated P-I production with 1.6-fold and 4.2-fold, respectively at 2.5 mg/100 mL concentration treatment. Interestingly, feeding CA+CAT not only directed flux towards p-Coumaric acid (p-CA) production but also appeared to trigger the metabolic flux through both shikimate/phenylpropanoid and iridoid pathways by utilizing more of CA and CAT for P-I biosynthesis. However, a deficiency in the supply of either the iridoid or the phenylpropanoid precursor limits flux through the respective pathways as reflected by feedback inhibition effect on PAL and decreased transcripts expressions of rate limiting enzymes (DAHPS, CM, PAL, GS and G10H). It also appears that addition of CA alone directed flux towards both p-CA and P-I production. Based on precursor feeding and metabolic fluxes, a current hypothesis is that precursors from both the iridoid and shikimate/phenylpropanoid pathways are a flux limitation for P-I production in shoot cultures of P. kurroa plants. This work thus sets a stage for future endeavour to elevate production of P-I in cultured plant cells.

Polyaspartic Acid Concentration Controls the Rate of Calcium Phosphate Nanorod Formation in High Concentration Systems

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

Krogstad, Daniel V.; Wang, Dongbo; Lin-Gibson, Sheng

Polyelectrolytes are known to greatly affect calcium phosphate (CaP) mineralization. The reaction kinetics as well as the CaP phase, morphology and aggregation state depend on the relative concentrations of the polyelectrolyte and the inorganic ions in a complex, nonlinear manner. This study examines the structural evolution and kinetics of polyaspartic acid (pAsp) directed CaP mineralization at high concentrations of polyelectrolytes, calcium, and total phosphate (19–30 mg/mL pAsp, 50–100 mM Ca2+, Ca/P = 2). Using a novel combination of characterization techniques including cryogenic transmission electron microscopy (cryo-TEM), spectrophotometry, X-ray total scattering pair distribution function analysis, and attenuated total reflectance Fourier transformmore » infrared spectroscopy (ATR-FTIR), it was determined that the CaP mineralization occurred over four transition steps. The steps include the formation of aggregates of pAsp stabilized CaP spherical nanoparticles (sNP), crystallization of sNP, oriented attachment of the sNP into nanorods, and further crystallization of the nanorods. The intermediate aggregate sizes and the reaction kinetics were found to be highly polymer concentration dependent while the sizes of the particles were not concentration dependent. This study demonstrates the complex role of pAsp in controlling the mechanism as well as the kinetics of CaP mineralization.« less

View of structures at rear of parcel with 12' scale ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of structures at rear of parcel with 12' scale (in tenths). From right: edge of Round House, Pencil house, Shell House, edge of School House. Heart Shrine made from mortared car headlights at frame left. Camera facing east. - Grandma Prisbrey's Bottle Village, 4595 Cochran Street, Simi Valley, Ventura County, CA

Effects of zearalenone on calcium homeostasis of splenic lymphocytes of chickens in vitro.

PubMed

Wang, Y C; Deng, J L; Xu, S W; Peng, X; Zuo, Z C; Cui, H M; Wang, Y; Ren, Z H

2012-08-01

Zearalenone (ZEA) is an estrogenic mycotoxin. It is produced by several Fusarium species and can contaminate food and feed. To investigate the role of calcium homeostasis in ZEA-induced toxicity of poultry and elucidate its cytotoxic mechanism, splenic lymphocytes isolated from chickens were exposed to ZEA (0-25 μg/mL) for 48 h. The intracellular calcium concentration ([Ca2+]i), pH, calmodulin (CaM) mRNA levels, and Na+/K+-ATPase activities and Ca2+-ATPase activities were detected by the fluorescent dyes Fluo-3/AM and BCECF/AM, quantitative real-time PCR, and chromatometry. Supernatant CaM concentrations were simultaneously detected by ELISA. As the ZEA exposure concentration increased, the [Ca2+]i and CaM mRNA levels gradually increased, while intracellular pH, CaM concentrations of supernatants, and intracellular Na+,K+-ATPase and Ca2+-ATPase activities gradually decreased in a dose-dependent manner. There were significant differences (P<0.05 or P<0.01) between the treatment groups and the control group. These results indicate that ZEA cytotoxicity arises by causing an imbalance in calcium homeostasis and intracellular acidification in lymphocytes.

Dendritic Zinc Growth in Acid Electrolyte: Effect of the pH

NASA Astrophysics Data System (ADS)

Bengoa, Leandro N.; Pary, Paola; Seré, Pablo R.; Conconi, M. Susana; Egli, Walter A.

2018-03-01

In this paper, dendritic growth at the edges of electrogalvanized steel strip has been studied using a specially designed rotating washer electrode which simulates the fluid dynamic conditions and the current density distribution at the steel strip edge found in a production line. The effect of electrolyte pH and current density on dendritic growth in an acidic zinc plating bath (ZnSO4 and H2SO4) was addressed. The temperature was kept constant at 60 °C. Solution pH was adjusted to 1, 2 or 3 using different amounts of H2SO4. In addition, the influence of temperature on the pH of the solution was determined. The current density was set at 40 or 60 A/dm2, similar to that used in the industry. Deposits were characterized using SEM and XRD. The results showed that pH strongly affects dendrites shape, length and texture. Furthermore, the morphology of dendrites at the washer edge and of deposits on the flat portion of the washer changed considerably as solution pH was increased from 1 to 3. It was found that the morphology of dendrites at the washer edge stems from the morphology of the deposit on its flat portion, which in turn determines their shape.

[Soy isoflavones with supplemental calcium provide protection against the loss of bone mass and influence insulin-like growth factor (IGF)-I after ovariectomy in rat].

PubMed

Cheng, Mao-wei; Liu, Jia-fa; Yi, Guo-qin; Zhang, Xi-ping; Zhu, Qing-hua; Liu, Lie-gang

2006-09-01

To compare the effects of soy isoflavone with supplemental calcium to soy isoflavone or Ca alone on preservation of bone mineral density (BMD) and the expression of insulin-like growth factor (IGF)-I. Sprague-Dawley (SD) female Rats, 6 months old, were ovariectomized and randomized into five groups: sham-operated group (n = 10) or ovx (n = 40) group. Shams were fed a 3.272 g/kg Ca diet. Ovx rats were randomized to a 3.272 g/kg Ca diet alone (OVX) or with soy isoflavone (SI) extract (37.95 mg/kg.bw) or to a supplemental Ca diet (Ca, 4.676 g/kg) alone or a supplemental Ca diet with the isoflavone extract (SI + Ca) for 12 weeks. BMD of femur was measured by scanner of bone mineral density. The level of IGF-1 mRNA expression was measured by reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. There was no significant difference between group Sham (0.267 +/- 0.008) and group SI + Ca (0.263 +/- 0.007) g/cm(2) (P > 0.05) on femur BMD of distal end. Femur BMD of distal end in group Sham and group SI + Ca was greater (P < 0.05) as compared to group OVX (0.245 +/- 0.005) g/cm(2), SI (0.258 +/- 0.011) g/cm(2) or Ca (0.255 +/- 0.004) g/cm(2), P < 0.05. The liver tissue IGF-1 mRNA contents (IGF-1 cDNA/B-actin cDNA) were significantly decreased in group Sham (0.200 +/- 0.023) g/cm(2), SI (0.278 +/- 0.019) g/cm(2), Ca (0.302 +/- 0.026) g/cm(2) or SI + Ca (0.231 +/- 0.025) g/cm(2) as compared to group OVX (0.362 +/- 0.031) g/cm(2), P < 0.05; The liver tissue IGF-1 mRNA contents (IGF-1 cDNA/B-actin cDNA) were significantly decreased in group SI + Ca (0.231 +/- 0.025) g/cm(2) compared to group SI (0.278 +/- 0.019) g/cm(2) and Ca (0.302 +/- 0.026) g/cm(2), P < 0.05. Soy isoflavones combined with supplemental Ca are more protective against the loss of femur BMD than soy isoflavones or supplemental Ca diet alone. The dose of SI (37.95 mg/kg.bw) might significantly restrain the rising of the liver tissue IGF-1 mRNA contents caused by ovariectomy.

Modulation of CaV2.1 channels by neuronal calcium sensor-1 induces short-term synaptic facilitation.

PubMed

Yan, Jin; Leal, Karina; Magupalli, Venkat G; Nanou, Evanthia; Martinez, Gilbert Q; Scheuer, Todd; Catterall, William A

2014-11-01

Facilitation and inactivation of P/Q-type Ca2+ currents mediated by Ca2+/calmodulin binding to Ca(V)2.1 channels contribute to facilitation and rapid depression of synaptic transmission, respectively. Other calcium sensor proteins displace calmodulin from its binding site and differentially modulate P/Q-type Ca2 + currents, resulting in diverse patterns of short-term synaptic plasticity. Neuronal calcium sensor-1 (NCS-1, frequenin) has been shown to enhance synaptic facilitation, but the underlying mechanism is unclear. We report here that NCS-1 directly interacts with IQ-like motif and calmodulin-binding domain in the C-terminal domain of Ca(V)2.1 channel. NCS-1 reduces Ca2 +-dependent inactivation of P/Q-type Ca2+ current through interaction with the IQ-like motif and calmodulin-binding domain without affecting peak current or activation kinetics. Expression of NCS-1 in presynaptic superior cervical ganglion neurons has no effect on synaptic transmission, eliminating effects of this calcium sensor protein on endogenous N-type Ca2+ currents and the endogenous neurotransmitter release machinery. However, in superior cervical ganglion neurons expressing wild-type Ca(V)2.1 channels, co-expression of NCS-1 induces facilitation of synaptic transmission in response to paired pulses and trains of depolarizing stimuli, and this effect is lost in Ca(V)2.1 channels with mutations in the IQ-like motif and calmodulin-binding domain. These results reveal that NCS-1 directly modulates Ca(V)2.1 channels to induce short-term synaptic facilitation and further demonstrate that CaS proteins are crucial in fine-tuning short-term synaptic plasticity.

Effects of Feeding Spodoptera littoralis on Lima Bean Leaves. I. Membrane Potentials, Intracellular Calcium Variations, Oral Secretions, and Regurgitate Components1

PubMed Central

Maffei, Massimo; Bossi, Simone; Spiteller, Dieter; Mithöfer, Axel; Boland, Wilhelm

2004-01-01

Membrane potentials (Vm) and intracellular calcium variations were studied in Lima bean (Phaseolus lunatus) leaves when the Mediterranean climbing cutworm (Spodoptera littoralis) was attacking the plants. In addition to the effect of the feeding insect the impact of several N-acyl Glns (volicitin, N-palmitoyl-Gln, N-linolenoyl-Gln) from the larval oral secretion was studied. The results showed that the early events upon herbivore attack were: a) a strong Vm depolarization at the bite zone and an isotropic wave of Vm depolarization spreading throughout the entire attacked leaf; b) a Vm depolarization observed for the regurgitant but not with volicitin {N-(17-hydroxy-linolenoyl)-Gln} alone; c) an enhanced influx of Ca2+ at the very edge of the bite, which is halved, if the Ca2+ channel blocker Verapamil is used. Furthermore, the dose-dependence effects of N-acyl Gln conjugates-triggered influx of Ca2+ studied in transgenic aequorin-expressing soybean (Glycine max) cells, showed: a) a concentration-dependent influx of Ca2+; b) a configuration-independent effect concerning the stereochemistry of the amino acid moiety; c) a slightly reduced influx of Ca2+ after modification of the fatty acid backbone by functionalization with oxygen and; d) a comparable effect with the detergent SDS. Finally, the herbivore wounding causes a response in the plant cells that cannot be mimicked by mechanical wounding. The involvement of Ca2+ in signaling after herbivore wounding is discussed. PMID:15051862

[Endoplasmic-mitochondrial Ca(2+)-functional unit: dependence of respiration of secretory cells on activity of ryanodine- and IP3 - sensitive Ca(2+)-channels].

PubMed

Velykopols'ka, O Iu; Man'ko, B O; Man'ko, V V

2012-01-01

Using Clark oxygen electrode, dependence of mitochondrial functions on Ca(2+)-release channels activity of Chironomus plumosus L. larvae salivary glands suspension was investigated. Cells were ATP-permeabilized in order to enable penetration of exogenous oxidative substrates. Activation of plasmalemmal P2X-receptors (as well as P2Y-receptors) per se does not modify the endogenous respiration of salivary gland suspension. That is, Ca(2+)-influx from extracellular medium does not influence functional activity of mitochondria, although they are located along the basal part of the plasma membrane. Activation of RyRs intensifies endogenous respiration and pyruvate-malate-stimulated respiration, but not succinate-stimulated respiration. Neither activation of IP3Rs (via P2Y-receptors activation), nor their inhibition alters endogenous respiration. Nevertheless, IP3Rs inhibition by 2-APB intensifies succinate-stimulated respiration. All abovementioned facts testify that Ca2+, released from stores via channels, alters functional activity of mitochondria, and undoubtedly confirm the existence of endoplasmic-mitochondrial Ca(2+)-functional unit in Ch. plumosus larvae salivary glands secretory cells. In steady state of endoplasmic-mitochondrial Ca(2+)-functional unit the spontaneous activity of IP3Rs is observed; released through IP3Rs, Ca2+ is accumulated in mitochondria via uniporter and modulates oxidative processes. Activation of RyRs induces the transition of endoplasmic-mitochondrial Ca(2+)-functional unit to the active state, which is required to intensify cell respiration and oxidative phosphorylation. As expected, the transition of endoplasmic-mitochondrial Ca(2+)-functional unit to inactivated state (i. e. inhibition of Ca(2+)-release channels at excessive [Ca2+]i) limits the duration of signal transduction, has protective nature and prevents apoptosis.

TNFα enhances force generation in airway smooth muscle

PubMed Central

Han, Young-Soo; Delmotte, Philippe

2017-01-01

Airway inflammation is a hallmark of asthma, triggering airway smooth muscle (ASM) hyperreactivity and airway remodeling. TNFα increases both agonist-induced cytosolic Ca2+ concentration ([Ca2+]cyt) and force in ASM. The effects of TNFα on ASM force may also be due to an increase in Ca2+ sensitivity, cytoskeletal remodeling, and/or changes in contractile protein content. We hypothesized that 24 h of exposure to TNFα increases ASM force by changing actin and myosin heavy chain (MyHC) content and/or polymerization. Porcine ASM strips were permeabilized with 10% Triton X-100, and force was measured in response to increasing concentrations of Ca2+ (pCa 9.0 to 4.0) in control and TNFα-treated groups. Relative phosphorylation of the regulatory myosin light chain (p-MLC) and total actin, MLC, and MyHC concentrations were quantified at pCa 9.0, 6.1, and 4.0. Actin polymerization was quantified by the ratio of filamentous to globular actin at pCa 9.0 and 4.0. For determination of total cross-bridge formation, isometric ATP hydrolysis rate at pCa 4.0 was measured using an enzyme-coupled NADH-linked fluorometric technique. Exposure to TNFα significantly increased force across the range of Ca2+ activation but did not affect the intrinsic Ca2+ sensitivity of force generation. The TNFα-induced increase in ASM force was associated with an increase in total actin, MLC, and MyHC content, as well as an increase in actin polymerization and an increase in maximum isometric ATP hydrolysis rate. The results of this study support our hypothesis that TNFα increases force generation in ASM by increasing the number of contractile units (actin-myosin content) contributing to force generation. PMID:28385814

Activation of p42/p44 mitogen-activated protein kinase and contraction by prostaglandin F2alpha, ionomycin, and thapsigargin in cat iris sphincter smooth muscle: inhibition by PD98059, KN-93, and isoproterenol.

PubMed

Ansari, H R; Husain, S; Abdel-Latif, A A

2001-10-01

In the present study we investigated the cross talk between the Ca2+ mobilization pathway and the mitogen-activated protein (MAP) kinase pathway and contraction in the cat iris sphincter smooth muscle. Three Ca2+-mobilizing agonists, namely, prostaglandin F2alpha (PGF2alpha), ionomycin, and thapsigargin, and three specific inhibitors, PD98059, a p42/p44 MAP kinase inhibitor; KN-93, a Ca2+-calmodulin-dependent protein kinase II (CaMKII) blocker; and isoproterenol, a cAMP-elevating agent, were used. Changes in tension in response to the agonists were recorded isometrically and MAP kinase phosphorylation and activation were monitored by Western blotting and by in situ myelin basic protein phosphorylation, respectively. We found that 1) stimulation of the sphincter muscle with PGF2alpha, ionomycin, or thapsigargin resulted in rapid phosphorylation and activation of p42/p44 MAP kinase and contraction; and 2) treatment of the muscles with PD98059, KN-93, or isoproterenol resulted in inhibition of the Ca2+-mobilizing agonist-induced responses. The contractile responses induced by PGF2alpha, ionomycin, and thapsigargin were (mg of tension/mg of wet weight tissue) 15.2, 15.4, and 16.2, respectively; the increases in MAP kinase phosphorylation by these agonists were 228, 203, and 190%, respectively; and the increases in MAP kinase activation by the agonists were 212, 191, and 162%, respectively. The stimulatory effects of the agonists on contraction and on MAP kinase phosphorylation and activation were blocked by preincubation of the muscle with PD98059, KN-93, or isoproterenol. These data demonstrate that in the iris sphincter phosphorylation and activation of p42/p44 MAP kinases by PGF2alpha, ionomycin, or thapsigargin require intracellular Ca2+ either from extracellular sources or from internal stores, that CaMKII plays an important role in the regulation of contraction, that CaMKII acts upstream of MAP kinase to control its activation, and that the MAP kinase signaling pathway can play a significant role in mediating the cellular effects of these Ca2+-mobilizing agonists.