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Sample records for high calcium ca

  1. CaRuby-Nano: a novel high affinity calcium probe for dual color imaging.

    Science.gov (United States)

    Collot, Mayeul; Wilms, Christian D; Bentkhayet, Asma; Marcaggi, Païkan; Couchman, Kiri; Charpak, Serge; Dieudonné, Stéphane; Häusser, Michael; Feltz, Anne; Mallet, Jean-Maurice

    2015-03-31

    The great demand for long-wavelength and high signal-to-noise Ca(2+) indicators has led us to develop CaRuby-Nano, a new functionalizable red calcium indicator with nanomolar affinity for use in cell biology and neuroscience research. In addition, we generated CaRuby-Nano dextran conjugates and an AM-ester variant for bulk loading of tissue. We tested the new indicator using in vitro and in vivo experiments demonstrating the high sensitivity of CaRuby-Nano as well as its power in dual color imaging experiments.

  2. High vitamin D and calcium intakes increase bone mineral (Ca and P) content in high-fat diet-induced obese mice.

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    Song, Qingming; Sergeev, Igor N

    2015-02-01

    Vitamin D and calcium are essential for bone formation, mineralization, and remodeling. Recent studies demonstrated that an increased body mass can be detrimental to bone health. However, whether an increase in dietary vitamin D and calcium intakes in obesity is beneficial to bone health has not been established. The aim of this study was to examine the effects of increased vitamin D and calcium intakes, alone or in combination, on bone status in a high-fat diet-induced obesity (DIO) mouse model. We hypothesized that DIO in growing mice affects bone mineral status and that high vitamin D and calcium intakes will promote mineralization of the growing bone in obesity via Ca(2+) regulatory hormones, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and parathyroid hormone (PTH). Male mice were fed high vitamin D3 (10 000 IU/kg), high calcium (1.2%), or high vitamin D3 plus high-calcium diets containing 60% energy as fat for 10 weeks. Bone weight, specific gravity, mineral (Ca and P), and collagen (hydroxyproline) content were measured in the femur and the tibia. Regulators of Ca(2+) metabolism and markers of bone status (PTH, 25-hydroxyvitamin D [25(OH)D], 1,25(OH)2D3, and osteocalcin) were measured in blood plasma. Diet-induced obese mice exhibited lower bone Ca and P content and relative bone weight compared with the normal-fat control mice, whereas collagen (hydroxyproline) content was not different between the two groups. High vitamin D3 and calcium intakes significantly increased bone Ca and P content and relative bone weight in DIO mice, which was accompanied by an increase in 1,25(OH)2D3 and a decrease in PTH and osteocalcin concentrations in blood. The findings obtained indicate that increased vitamin D and calcium intakes are effective in increasing mineral (Ca and P) content in the growing bone of obese mice and that the hormonal mechanism of this effect may involve the vitamin D-PTH axis. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Study on calcium precursors for CaO preparation to capture CO2 at high temperature%CaO高温吸附捕集CO2-制备CaO的钙基前驱体材料筛选

    Institute of Scientific and Technical Information of China (English)

    张明明; 计超; 孙泽; 汪瑾; 李平; 于建国

    2012-01-01

    价格低廉的CaO材料在高温下能高效吸附捕集CO2气体,被认为是碳减排的有效方法之一.然而,CaO长时间循环碳酸化/煅烧解吸后,其CO2的化学吸附容量下降,稳定性较差,限制了该材料的工业应用.本文采用天然钙源(牡蛎壳和方解石等)和化学试剂(醋酸钙)为钙基前驱材料制备CaO.采用扫描电子显微镜(SEM),X射线衍射仪(XRD)和氮气吸附仪等手段对制备的CaO材料进行形貌和物理结构的分析表征;在高温和模拟的烟道气氛条件下(10% CO2和90% N2),采用热重分析仪测量CaO吸附CO2的能力和长时间循环碳酸化/煅烧解吸后的稳定性.我们经过与目前所报道的其他钙基吸附材料进行比较,并结合钙基前驱材料的市场价格,发现CaO(醋酸钙)的CO2吸附能力和稳定性较为理想,醋酸钙在高温烟气捕碳方面具有非常好的应用前景.%As an abundant and cheap material, calcium oxide (CaO) is an efficient sorbent for CO2 capture at high temperature. The carbonation/calcination loop of CaO/CaCO3 is an effective process for CO2 capture and storage (CCS). However, both the gradual decline of the CO2 capture capacity and the poor stability, because of the pore filling and pore closure at the high calcination temperature, limit the industrial application of calcium-based sorbents. In this paper, study on calcium precursors was carried out in order to obtain CaO sorbents to capture CO2 with high efficiency. The candidate materials include seashell materials (oyster shells), natural minerals (calcite) and chemical reagents (calcium acetate hydrate). Oyster shell powder and calcite powder were analyzed by XRD, and CaO sorbents prepared from various precursors were characterized by nitrogen physisorption apparatus. The fresh CaO sorbents and CaO after multiple cycles to capture CO2 were characterized by scanning electron microscopy (SEM). The capture CO2 capability and the stability of CaO sorbents were

  4. Decrease of high voltage Ca(2+) currents in the dentate gyrus granule cells by entorhinal amyloidopathy is reversed by calcium channel blockade.

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    Pourbadie, Hamid Gholami; Naderi, Nima; Delavar, Hadi Mirzapour; Hosseinzadeh, Mahshid; Mehranfard, Nasrin; Khodagholi, Fariba; Janahmadi, Mahyar; Motamedi, Fereshteh

    2017-01-05

    In the Alzheimer's disease (AD), entorhinal-hippocampal circuit is one of the earliest affected networks. There are some evidences indicating abnormal neuronal excitability and impaired synaptic plasticity in the dentate gyrus (DG) of AD animal model. However, the underlying mechanism leading to DG dysfunction particularly in the early phase of AD is not known. Since calcium dyshomeostasis has a critical role in the etiology of AD, it is possible that this phenomenon precedes electrophysiological alteration in the DG. Here, the effect of the amyloid pathogenesis in the entorhinal cortex (EC) on high activated Ca(2+) currents in the DG granule cells was investigated. One week after bilaterally injection of amyloid beta (Aβ) 1-42 into the EC, Ca(2+) currents in the DG granule cells were assessed by whole cell patch clamp. Voltage clamp recording showed the amplitude of high voltage calcium currents in the DG granule cells was decreased following EC amyloidopathy. However, the Ca(2+) current decay was slower than control. Double-pulse recording revealed that Ca(2+)-dependent inactivation of calcium current (CDI) was more pronounced in the EC-Aβ group compared to the control group. However, chronic treatment by calcium channel blocker (CCBs), isradipine or nimodipine, reverse the Ca(2+) currents toward the control level. On the other hand, there was no significant difference in the calbindin level in the DG of different groups. In conclusion, our results suggest that Aβ in the EC independent of calbindin level triggers a decreased Ca(2+) currents along with increased CDI in the DG granule cells which may lead to further electrophysiological alterations in these cells, and treatment by CCBs could preserve normal calcium current and may ultimately normal function against the Aβ toxicity. Copyright © 2016. Published by Elsevier B.V.

  5. Calcium aluminate silicate Ca2Al2SiO7 single crystal applicable to piezoelectric sensors at high temperature

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    Takeda, Hiroaki; Hagiwara, Manabu; Noguchi, Hiroaki; Hoshina, Takuya; Takahashi, Tomoko; Kodama, Nobuhiro; Tsurumi, Takaaki

    2013-06-01

    Ca2Al2SiO7 (CAS) bulk single crystals were grown by the Czochralski method. Material constants of the crystal were determined over the driving temperature range of a typical combustion pressure sensor. The electrical resistivity at 800 °C was found to be of the order of 108 Ωcm. We constructed a measurement system for the direct piezoelectric effect at high temperature, and characterized the crystals in a simulated engine cylinder combustion environment. Output charge signal against applied stress was detected at 700 °C. These observations suggest that CAS crystals are superior candidate materials for high temperature for stress sensing.

  6. A comparative study on Ca content and distribution in two Gesneriaceae species reveals distinctive mechanisms to cope with high rhizospheric soluble calcium.

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    Li, Wenlong; Xu, Falun; Chen, Shixuan; Zhang, Zhennan; Zhao, Yan; Jin, Yukuan; Li, Meijing; Zhu, Yan; Liu, Yongxiu; Yang, Yi; Deng, Xin

    2014-01-01

    Excessive Ca is toxic to plants thus significantly affects plant growth and species distribution in Ca-rich karst areas. To understand how plants survive high Ca soil, laboratory experiments were established to compare the physiological responses and internal Ca distribution in organ, tissue, cell, and intracellular levels under different Ca levels for Lysionotus pauciflorus and Boea hygrometrica, two karst habitant Gesneriaceae species in Southwest China. In the controlled condition, L. pauciflorus could survive as high as 200 mM rhizospheric soluble Ca, attributed to a series of physiological responses and preferential storage that limited Ca accumulation in chloroplasts of palisade cells. In contrast, B. hygrometrica could survive only 20 mM rhizospheric soluble Ca, but accumulated a high level of internal Ca in both palisade and spongy cells without disturbance on photosynthetic activity. By phenotype screening of transgenic plants expressing high Ca-inducible genes from B. hygrometrica, the expression of BhDNAJC2 in A. thaliana was found to enhance plant growth and photosynthesis under high soluble Ca stress. BhDNAJC2 encodes a recently reported heat shock protein (HSP) 40 family DnaJ-domain protein. The Ca-resistant phenotype of BhDNAJC2 highlights the important role of chaperone-mediated protein quality control in Ca tolerance in B. hygrometrica. Taken together, our results revealed that distinctive mechanisms were employed in the two Gesneriaceae karst habitants to cope with a high Ca environment.

  7. A comparative study on Ca content and distribution in two Gesneriaceae species reveals distinctive mechanisms to cope with high rhizospheric soluble calcium

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    Wenlong eLi

    2014-11-01

    Full Text Available Excessive Ca is toxic to plants thus significantly affects plant growth and species distribution in Ca-rich karst areas. To understand how plants survive high Ca soil, laboratory experiments were established to compare the physiological responses and internal Ca distribution in organ, tissue, cell and intracellular levels under different Ca levels for Lysionotus pauciflorus and Boea hygrometrica, two karst habitant Gesneriaceae species in Southwest China. In the controlled condition, L. pauciflorus could survive as high as 200 mM rhizospheric soluble Ca, attributed to a series of physiological responses and preferential storage that limited Ca accumulation in chloroplasts of palisade cells. In contrast, B. hygrometrica could survive only 20 mM rhizospheric soluble Ca, but accumulated a high level of internal Ca in both palisade and spongy cells without disturbance on photosynthetic activity. By phenotype screening of transgenic plants expressing high Ca-inducible genes from B. hygrometrica, the expression of BhDNAJC2 in A. thaliana was found to enhance plant growth and photosynthesis under high soluble Ca stress. BhDNAJC2 encodes a recently reported heat shock protein (HSP 40 family DnaJ-domain protein. The Ca-resistant phenotype of BhDNAJC2 highlights the important role of chaperone-mediated protein quality control in Ca tolerance in B. hygrometrica. Taken together, our results revealed that distinctive mechanisms were employed in the two Gesneriaceae karst habitants to cope with a high Ca environment.

  8. Excessive signal transduction of gain-of-function variants of the calcium-sensing receptor (CaSR are associated with increased ER to cytosol calcium gradient.

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    Marianna Ranieri

    Full Text Available In humans, gain-of-function mutations of the calcium-sensing receptor (CASR gene are the cause of autosomal dominant hypocalcemia or type 5 Bartter syndrome characterized by an abnormality of calcium metabolism with low parathyroid hormone levels and excessive renal calcium excretion. Functional characterization of CaSR activating variants has been so far limited at demonstrating an increased sensitivity to external calcium leading to lower Ca-EC50. Here we combine high resolution fluorescence based techniques and provide evidence that for the efficiency of calcium signaling system, cells expressing gain-of-function variants of CaSR monitor cytosolic and ER calcium levels increasing the expression of the Sarco-Endoplasmic Reticulum Calcium-ATPase (SERCA and reducing expression of Plasma Membrane Calcium-ATPase (PMCA. Wild-type CaSR (hCaSR-wt and its gain-of-function (hCaSR-R990G; hCaSR-N124K variants were transiently transfected in HEK-293 cells. Basal intracellular calcium concentration was significantly lower in cells expressing hCaSR-wt and its gain of function variants compared to mock. In line, FRET studies using the D1ER probe, which detects [Ca2+]ER directly, demonstrated significantly higher calcium accumulation in cells expressing the gain of function CaSR variants compared to hCaSR-wt. Consistently, cells expressing activating CaSR variants showed a significant increase in SERCA activity and expression and a reduced PMCA expression. This combined parallel regulation in protein expression increases the ER to cytosol calcium gradient explaining the higher sensitivity of CaSR gain-of-function variants to external calcium. This control principle provides a general explanation of how cells reliably connect (and exacerbate receptor inputs to cell function.

  9. Excessive signal transduction of gain-of-function variants of the calcium-sensing receptor (CaSR) are associated with increased ER to cytosol calcium gradient.

    Science.gov (United States)

    Ranieri, Marianna; Tamma, Grazia; Di Mise, Annarita; Vezzoli, Giuseppe; Soldati, Laura; Svelto, Maria; Valenti, Giovanna

    2013-01-01

    In humans, gain-of-function mutations of the calcium-sensing receptor (CASR) gene are the cause of autosomal dominant hypocalcemia or type 5 Bartter syndrome characterized by an abnormality of calcium metabolism with low parathyroid hormone levels and excessive renal calcium excretion. Functional characterization of CaSR activating variants has been so far limited at demonstrating an increased sensitivity to external calcium leading to lower Ca-EC50. Here we combine high resolution fluorescence based techniques and provide evidence that for the efficiency of calcium signaling system, cells expressing gain-of-function variants of CaSR monitor cytosolic and ER calcium levels increasing the expression of the Sarco-Endoplasmic Reticulum Calcium-ATPase (SERCA) and reducing expression of Plasma Membrane Calcium-ATPase (PMCA). Wild-type CaSR (hCaSR-wt) and its gain-of-function (hCaSR-R990G; hCaSR-N124K) variants were transiently transfected in HEK-293 cells. Basal intracellular calcium concentration was significantly lower in cells expressing hCaSR-wt and its gain of function variants compared to mock. In line, FRET studies using the D1ER probe, which detects [Ca2+]ER directly, demonstrated significantly higher calcium accumulation in cells expressing the gain of function CaSR variants compared to hCaSR-wt. Consistently, cells expressing activating CaSR variants showed a significant increase in SERCA activity and expression and a reduced PMCA expression. This combined parallel regulation in protein expression increases the ER to cytosol calcium gradient explaining the higher sensitivity of CaSR gain-of-function variants to external calcium. This control principle provides a general explanation of how cells reliably connect (and exacerbate) receptor inputs to cell function.

  10. Highly biocompatible chitosan with super paramagnetic calcium ferrite (CaFe2O4) nanoparticle for the release of ampicillin.

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    Bilas, Ram; Sriram, K; Maheswari, P Uma; Sheriffa Begum, K M Meera

    2017-04-01

    The CaFe2O4 nanoparticles (CFNP) were synthesized using the solution combustion method. The CFNP-chitosan-ampicillin was prepared by the ionic gelation method using tripolyphosphate (TPP). The CFNP, chitosan-CFNP, chitosan-CFNP-ampicillin materials were characterized by XRD, FT-IR and TGA analysis in order to evaluate the particle nature and size, the presence of functional groups and their thermal stability. The FESEM and EDAX analysis were performed to understand the surface morphology of the materials and the presence of CFNP in the material, respectively. The vibrating sample magnetometer (VSM) analysis was performed to analyze the magnetic property of the chitosan-CFNP material. The squareness value of 0.1733 obtained by VSM measurements indicates the super paramagnetic nature of chitosan-CFNP. Taguchi orthogonal array method was applied to identify the significant impacting parameters for maximizing the drug encapsulation of chitosan-CFNP. The drug release studies showed that the drug was released rapidly in acidic medium as compared to the basic or neutral medium. The drug release kinetic data were fitted with different linear kinetic model equations and the best fit was obtained with Korsmeyer-Peppas model. The model drug ampicillin release from chitosan-CFNP was tested against staphylococcus epidermis bacteria through disc diffusion method for checking biocompatibility and antibacterial activity.

  11. Preparation of nano CaCO3 from calcium carbide residue by CO2 precipitation with high Ca2+ concentration%高Ca2+浓度CO2沉淀法由电石渣制备纳米CaCO3

    Institute of Scientific and Technical Information of China (English)

    王百年; 葛礼响; 曹萌; 杨保俊

    2016-01-01

    Nano CaCO3 was prepared from calcium carbide residue using NH4Cl solution as leaching agent,CO2 as carbonation agent,sodium tripolyphosphate(STP) as additive agent. The experimental results show that:When Ca2+ concentration of calcium carbide residue leaching solution is1.0 mol/L and STP dosage is 3.00%,the nano CaCO3 with 30-60 nm of particle size is prepared;STP has good effect on control of particle size and morphology of nano CaCO3;Under the optimum technological conditions,the yield of nano CaCO3 from calcium carbide residue is 80%,and the economic benefits of calcium carbide residue treatment is 2 670 yuan per ton.%以NH4Cl溶液为浸取剂、CO2为碳化剂、多聚磷酸钠(STP)为添加剂,由电石渣制备纳米CaCO3。实验结果表明:电石渣浸取液Ca2+浓度为1.0 mol/L、STP加入量为3.00%时,可制备出粒径为30~60 nm的纳米CaCO3;STP可有效控制纳米CaCO3的粒度和形貌;在最佳工艺条件下,由电石渣制备纳米CaCO3的产率为80%,处理1 t电石渣产生的经济效益约为2670元。

  12. Elevation of extracellular Ca2+ induces store-operated calcium entry via calcium-sensing receptors: a pathway contributes to the proliferation of osteoblasts.

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    Fen Hu

    Full Text Available AIMS: The local concentration of extracellular Ca(2+ ([Ca(2+]o in bone microenvironment is accumulated during bone remodeling. In the present study we investigated whether elevating [Ca(2+]o induced store-operated calcium entry (SOCE in primary rat calvarial osteoblasts and further examined the contribution of elevating [Ca(2+]o to osteoblastic proliferation. METHODS: Cytosolic Ca(2+ concentration ([Ca(2+]c of primary cultured rat osteoblasts was detected by fluorescence imaging using calcium-sensitive probe fura-2/AM. Osteoblastic proliferation was estimated by cell counting, MTS assay and ATP assay. Agonists and antagonists of calcium-sensing receptors (CaSR as well as inhibitors of phospholipase C (PLC, SOCE and voltage-gated calcium (Cav channels were applied to study the mechanism in detail. RESULTS: Our data showed that elevating [Ca(2+]o evoked a sustained increase of [Ca(2+]c in a dose-dependent manner. This [Ca(2+]c increase was blocked by TMB-8 (Ca(2+ release inhibitor, 2-APB and BTP-2 (both SOCE blockers, respectively, whereas not affected by Cav channels blockers nifedipine and verapamil. Furthermore, NPS2143 (a CaSR antagonist or U73122 (a PLC inhibitor strongly reduced the [Ca(2+]o-induced [Ca(2+]c increase. The similar responses were observed when cells were stimulated with CaSR agonist spermine. These data indicated that elevating [Ca(2+]o resulted in SOCE depending on the activation of CaSR and PLC in osteoblasts. In addition, high [Ca(2+]o significantly promoted osteoblastic proliferation, which was notably reversed by BAPTA-AM (an intracellular calcium chelator, 2-APB, BTP-2, TMB-8, NPS2143 and U73122, respectively, but not affected by Cav channels antagonists. CONCLUSIONS: Elevating [Ca(2+]o induced SOCE by triggering the activation of CaSR and PLC. This process was involved in osteoblastic proliferation induced by high level of extracellular Ca(2+ concentration.

  13. Effect of biomolecules from human renal matrix of calcium oxalate monohydrate (CaOx stones on in vitro calcium phosphate crystallization

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    Priyadarshini Pathak

    2010-10-01

    Full Text Available PURPOSE: Investigate the activity of high and low molecular weight biomolecules present in the matrix of human calcium oxalate (CaOx stones not only on the initial mineral phase formation of calcium and phosphate (CaP but also on its growth and demineralization of the preformed mineral phase. MATERIALS AND METHODS: Surgically removed renal stones were analyzed by Fourier Transform Infra Red (FTIR spectroscopy and only CaOx stones were extracted with 0.05M EGTA, 1 mM PMSF and 1% ß-mercaptoethanol. Renal CaOx stone extract was separated into > 10 kDa and 10 kDa and 10 kDa fraction lane. CONCLUSION: Both high and low molecular weight biomolecules extracted from human renal matrix of calcium oxalate (CaOx stones have a significant influence on calcium and phosphate (CaP crystallization.

  14. Behavior of CaO and Calcium in pure Magnesium

    Institute of Scientific and Technical Information of China (English)

    HA Seong-Ho; LEE Jin-Kyu; JO Hyung-Ho; JUNG Seung-Boo; KIM Shae K.

    2006-01-01

    Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength.However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting process due to their high reactivity.The purpose of this study is to investigate effects of Ca and CaO on pure Mg through microstructure observation, ignition test and phase analysis.With increasing Ca and CaO contents, the ignition resistance of Ca or CaO added pure Mg is increased and the grains are refined.As results of XRD and EDS, CaO is reduced to Ca in CaO added pure Mg.Mg2Ca phase is formed even in 0.1 wt.%CaO added pure Mg by reduction mechanism, while Mg2Ca phase is formed over 1.35 wt.% Ca added pure Mg.

  15. Calcium platinum aluminium, CaPtAl

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    Charles Fon Abi

    2011-10-01

    Full Text Available A preliminary X-ray study of CaPtAl has been reported previously by Hulliger [J. Alloys Compd (1993, 196, 225–228] based on X-ray powder diffraction data without structure refinement. With the present single-crystal X-ray study, we confirm the assignment of the TiNiSi type for CaPtAl, in a fully ordered inverse structure. All three atoms of the asymmetric unit have .m. site symmetry. The structure features a ∞3[AlPt] open framework with a fourfold coordination of Pt by Al atoms and vice versa. The Ca atoms are located in the large channels of the structure.

  16. Zebrafish CaV2.1 Calcium Channels Are Tailored for Fast Synchronous Neuromuscular Transmission

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    Naranjo, David; Wen, Hua; Brehm, Paul

    2015-01-01

    The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925

  17. The Plasma Membrane Ca2+ ATPase and the Plasma Membrane Sodium Calcium Exchanger Cooperate in the Regulation of Cell Calcium

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    Brini, Marisa; Carafoli, Ernesto

    2011-01-01

    Calcium is an ambivalent signal: it is essential for the correct functioning of cell life, but may also become dangerous to it. The plasma membrane Ca2+ ATPase (PMCA) and the plasma membrane Na+/Ca2+ exchanger (NCX) are the two mechanisms responsible for Ca2+ extrusion. The NCX has low Ca2+ affinity but high capacity for Ca2+ transport, whereas the PMCA has a high Ca2+ affinity but low transport capacity for it. Thus, traditionally, the PMCA pump has been attributed a housekeeping role in maintaining cytosolic Ca2+, and the NCX the dynamic role of counteracting large cytosolic Ca2+ variations (especially in excitable cells). This view of the roles of the two Ca2+ extrusion systems has been recently revised, as the specific functional properties of the numerous PMCA isoforms and splicing variants suggests that they may have evolved to cover both the basal Ca2+ regulation (in the 100 nM range) and the Ca2+ transients generated by cell stimulation (in the μM range). PMID:21421919

  18. Do Ca2+-adsorbing ceramics reduce the release of calcium ions from gypsum-based biomaterials?

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    Belcarz, Anna; Zalewska, Justyna; Pałka, Krzysztof; Hajnos, Mieczysław; Ginalska, Grazyna

    2015-02-01

    Bone implantable materials based on calcium sulfate dihydrate dissolve quickly in tissue liquids and release calcium ions at very high levels. This phenomenon induces temporary toxicity for osteoblasts, may cause local inflammation and delay the healing process. Reduction in the calcium ion release rate by gypsum could be therefore beneficial for the healing of gypsum-filled bone defects. The aim of this study concerned the potential use of calcium phosphate ceramics of various porosities for the reduction of high Ca(2+) ion release from gypsum-based materials. Highly porous ceramics failed to reduce the level of Ca(2+) ions released to the medium in a continuous flow system. However, it succeeded to shorten the period of high calcium level. It was not the phase composition but the high porosity of ceramics that was found crucial for both the shortening of the Ca(2+) release-related toxicity period and intensification of apatite deposition on the composite. Nonporous ceramics was completely ineffective for this purpose and did not show any ability to absorb calcium ions at a significant level. Moreover, according to our observations, complex studies imitating in vivo systems, rather than standard tests, are essential for the proper evaluation of implantable biomaterials.

  19. Optical Zeeman Spectroscopy of Calcium Fluoride, CaF.

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    Steimle, Timothy; Kokkin, Damian L.; Delvin, Jack; Tarbutt, Michael

    2015-06-01

    Recently laser cooling has been demonstrated for the diatomic radical calcium fluoride, CaF. The mechanism of magneto-optical trapping for diatomic molecules has been elucidated recently by Tarbutt where a rate model was used to model the interaction of molecules with multiple frequencies of laser light. It was shown that the correct choice of laser polarization depends on the sign of the upper state magnetic g-factor. The magnetic tuning of the low rotational levels in the X^2σ^+, A^2Π and B^2σ^+ electronic states of CaF, have been experimentally investigated using high resolution optical Zeeman spectroscopy of a cold molecular beam sample. The observed Zeeman-induced shifts and splittings were successfully modeled using a traditional effective Hamiltonian approach to account for the interaction between the (ν=0) A^2Π and (ν=0) B^2σ^+ states. The determined magnetic g-factors for the X^2σ^+, A^2Π and B^2σ^+ states are compared to those predicted by perturbation theory. V. Zhelyazkova, A. Cournol, T.E. Wall, A. Matsushima, J.J. Hudson, E.A. Hinds, M.R. Tarbutt and B.E. Sauer, Phys. Rev. A 89, 053416 (2014) M. R. Tarbutt, New J. Phys 17, 015007 (2015)

  20. High Blood Calcium (Hypercalcemia)

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    ... as well as kidney function and levels of calcium in your urine. Your provider may do other tests to further assess your condition, such as checking your blood levels of phosphorus (a mineral). Imaging studies also may be helpful, such as bone ...

  1. Functional proteins involved in regulation of intracellular Ca(2+) for drug development: chronic nicotine treatment upregulates L-type high voltage-gated calcium channels.

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    Katsura, Masashi; Ohkuma, Seitaro

    2005-03-01

    Neurochemical mechanisms underlying drug dependence and withdrawal syndrome remain unclear. In this review, we discuss how chronic nicotine exposure to neurons affects expression of diazepam binding inhibitor (DBI), an endogenous anxiogenic neuropeptide supposed to be a common substance participating drug dependence, and function of L-type high voltage-gated Ca(2+) channels (HVCCs). We also discuss the functional interaction between DBI and L-type HVCCs in nicotine dependence. Both DBI levels and [(45)Ca(2+)] influx significantly increased in the brain from mice treated with nicotine for long term, which was further enhanced after abrupt cessation of nicotine and was abolished by nicotinic acetylcholine receptor (nAChR) antagonists. Similar responses of DBI expression and L-type HVCC function were observed in cerebral cortical neurons after sustained exposure to nicotine. In addition, increased DBI expression was inhibited by antagonists of nAChR and L-type HVCCs. Sustained exposure of neurons to nicotine significantly enhanced expression of alpha(1) and alpha(2)/delta(1) subunits for L-type HVCCs and caused an increase in the B(max) value of [(3)H]verapamil binding to the particulate fractions. Therefore, it is concluded that the alterations in DBI expression is mediated via increased influx of Ca(2+) through upregulated L-type HVCCs and these neurochemical changes have a close relationship with development of nicotine dependence and/or its withdrawal syndrome.

  2. Differential modulation of intracellular Ca2+ responses associated with calcium-sensing receptor activation in renal collecting duct cells.

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    Valenti, Giovanna; Mira, Annalisa; Mastrofrancesco, Lisa; Lasorsa, Domenica Rita; Ranieri, Marianna; Svelto, Maria

    2010-01-01

    In this work, we studied G protein-coupled Extracellular Calcium Sensing Receptor (CaR) signaling in mouse cortical collecting duct cells (MCD4) expressing endogenous CaR. Intracellular [Ca(2+)] measurements performed with real time video imaging revealed that CaR stimulation with 5 mM Ca(2+), 300 μM Gd(3+) and with 10 μM of specific allosteric modulator NPS-R 568, all resulted in an increase in [Ca(2+)](i) although displaying different features. Specifically, Ca(2+) as well as stimulation with NPS-R 568 induced a rapid peak of [Ca(2+)](i) while stimulation with Gd(3+) induced transient intracellular Ca(2+) oscillations. PLC inhibition completely abolished any [Ca(2+)](i) increase after stimulation with CaR agonists. Inhibition of Rho or Rho kinase (ROK) abolished [Ca(2+)](i) oscillations induced by Gd(3+), while the peak induced by high Ca(2+) was similar to control. Conversely, emptying the intracellular calcium stores abolished the response to Gd(3+). On the other hand, the inhibition of calcium influx did not alter calcium changes. We conclude that in our cell model, CaR stimulation with distinct agonists activates two distinct transduction pathways, both PLC-dependent. The transient cytosolic Ca(2+) oscillations produced by Gd(3+) are modulated by Rho-Rho kinase signaling, whereas the rapid peak of intracellular Ca(2+) in response to 5 mM [Ca(2+)](o) is mainly due to PLC/IP3 pathway activation. Copyright © 2010 S. Karger AG, Basel.

  3. Differential CaMKII regulation by voltage-gated calcium channels in the striatum.

    Science.gov (United States)

    Pasek, Johanna G; Wang, Xiaohan; Colbran, Roger J

    2015-09-01

    Calcium signaling regulates synaptic plasticity and many other functions in striatal medium spiny neurons to modulate basal ganglia function. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is a major calcium-dependent signaling protein that couples calcium entry to diverse cellular changes. CaMKII activation results in autophosphorylation at Thr286 and sustained calcium-independent CaMKII activity after calcium signals dissipate. However, little is known about the mechanisms regulating striatal CaMKII. To address this, mouse brain slices were treated with pharmacological modulators of calcium channels and punches of dorsal striatum were immunoblotted for CaMKII Thr286 autophosphorylation as an index of CaMKII activation. KCl depolarization increased levels of CaMKII autophosphorylation ~2-fold; this increase was blocked by an LTCC antagonist and was mimicked by treatment with pharmacological LTCC activators. The chelation of extracellular calcium robustly decreased basal CaMKII autophosphorylation within 5min and increased levels of total CaMKII in cytosolic fractions, in addition to decreasing the phosphorylation of CaMKII sites in the GluN2B subunit of NMDA receptors and the GluA1 subunit of AMPA receptors. We also found that the maintenance of basal levels of CaMKII autophosphorylation requires low-voltage gated T-type calcium channels, but not LTCCs or R-type calcium channels. Our findings indicate that CaMKII activity is dynamically regulated by multiple calcium channels in the striatum thus coupling calcium entry to key downstream substrates.

  4. High concentration of calcium ions in Golgi apparatus

    Institute of Scientific and Technical Information of China (English)

    XUESHAOBAI; M.ROBERTNICOUD; 等

    1994-01-01

    The interphase NIH3T3 cells were vitally fluorescentstained with calcium indicator fluo-3 and Glogi probe C6-NBD-ceramide,and then the single cells were examined by laser scanning confocal microscopy(LSCFM) for subcellular distributions of Ca2+ and the location of Golgi apparatus.In these cells,the intracellular Ca2+ were found to be highly concentrated in the Golgi apparatus.The changes of distribution of cytosolic high Ca2+ region and the Golgi apparatus coincided with the cell cycle phase.In calcium free medium,when the plasma membrane of the cells which had been loaded with fluo-3/AM were permeated by digitonin,the fluorescence of the Golgi region decreased far less than that of the cytosol.Our results indicated that the Glogi lumen retained significantly high concentration of free calcium.

  5. Differential NMDA receptor-dependent calcium loading and mitochondrial dysfunction in CA1 vs. CA3 hippocampal neurons.

    Science.gov (United States)

    Stanika, Ruslan I; Winters, Christine A; Pivovarova, Natalia B; Andrews, S Brian

    2010-02-01

    Hippocampal CA1 pyramidal neurons are selectively vulnerable to ischemia, while adjacent CA3 neurons are relatively resistant. Although glutamate receptor-mediated mitochondrial Ca(2+) overload and dysfunction is a major component of ischemia-induced neuronal death, no direct relationship between selective neuronal vulnerability and mitochondrial dysfunction has been demonstrated in intact brain preparations. Here, we show that in organotypic slice cultures NMDA induces much larger Ca(2+) elevations in vulnerable CA1 neurons than in resistant CA3. Consequently, CA1 mitochondria exhibit stronger calcium accumulation, more extensive swelling and damage, stronger depolarization of their membrane potential, and a significant increase in ROS generation. NMDA-induced Ca(2+) and ROS elevations were abolished in Ca(2+)-free medium or by NMDAR antagonists, but not by zinc chelation. We conclude that Ca(2)(+) overload-dependent mitochondrial dysfunction is a determining factor in the selective vulnerability of CA1 neurons.

  6. CaV1.2 calcium channels: just cut out to be regulated?

    Science.gov (United States)

    Groth, Rachel D; Tirko, Natasha N; Tsien, Richard W

    2014-06-04

    Tight regulation of calcium entry through the L-type calcium channel CaV1.2 ensures optimal excitation-response coupling. In this issue of Neuron, Michailidis et al. (2014) demonstrate that CaV1.2 activity triggers negative feedback regulation through proteolytic cleavage of the channel within the core of the pore-forming subunit.

  7. Ca2+ signals induced from calcium stores in pancreatic islet β cells

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In single rat pancreatic β cells,using fura-2 microfluorometry to measure [Ca2+]i response upon different stimuli,the ways of calcium regulation have been studied.When the extracellular calcium concentration was 2.5 mmol/L,either 60 mmol/L KCl,20 mmol/L D-glucose or 0.1 mmol/L tolbutamide induced increase in [Ca2+]i.Such increase in [Ca2+]i was absent when the same stimuli were applied under zero extracellular calcium.These results indicate that the increase of [Ca2+]i is induced by the activation of voltage-dependent calcium channels in β cells.The manifold forms of [Ca2+]i change induced by glucose imply that the effects of glucose are complex.5 mmol/L caffeine or 5 mmol/L MCh increase the [Ca2+]i ,which is independent of the external calcium,suggesting that [Ca2+]i can be regulated by Ca2+ release from not only the IP3-sensitive but also the ryanodine sensitive calcium stores in β cells.The latency of Ca responses for IP3 pathway (5 s) is faster than that for ryanodine pathway (30 s).It is concluded that there are multiple calcium stores in rat pancreatic β cells.

  8. Measurement of intracellular Ca2+ concentration in single cells using ratiometric calcium dyes.

    Science.gov (United States)

    Srikanth, Sonal; Gwack, Yousang

    2013-01-01

    Measurement of intracellular Ca(2+) concentration ([Ca(2+)](i)) is useful to study the upstream and downstream events of Ca(2+) signaling. Ca(2+)-binding proteins including EF-hand-containing proteins are important downstream effector molecules after an increase of [Ca(2+)](i). Conversely, these proteins can also act as key modulators for regulation of [Ca(2+)](i) by sensing the Ca(2+) levels in the intracellular organelles and cytoplasm. Here we describe a single-cell Ca(2+) imaging technique that was used to measure the intracellular Ca(2+) levels to examine the function of Ca(2+)-binding proteins, STIM1 and Calcium release-activated Calcium channel regulator 2A (CRACR2A), using ratiometric Ca(2+) dye Fura-2 in adherent and non-adherent cells.

  9. Presynaptic calcium stores contribute to nicotine-elicited potentiation of evoked synaptic transmission at CA3-CA1 connections in the neonatal rat hippocampus.

    Science.gov (United States)

    Le Magueresse, Corentin; Cherubini, Enrico

    2007-01-01

    Nicotine acetylcholine (ACh) receptors (nAChRs) are ligand-gated ion channels that are widely expressed throughout the central nervous system. It is well established that presynaptic, alpha7-containing nAChRs modulate glutamate release in several brain areas, and that this modulation requires extracellular calcium. However, the intracellular mechanisms consecutive to nAChR opening are unclear. Recent studies have suggested a role for presynaptic calcium stores in the increase of neurotransmitter release following nAChR activation. Using the minimal stimulation protocol at low-probability Schaffer collateral synapses in acute hippocampal slices from neonatal rats, we show that nicotine acting on presynaptic alpha7 nAChRs persistently upregulates glutamate release. We tested the role of calcium stores in this potentiation. First, we examined the relationship between calcium stores and glutamate release. We found that bath application of SERCA pump inhibitors (cyclopiazonic acid and thapsigargin), as well as an agonist of ryanodine receptors (ryanodine 2 microM) increases the probability of glutamate release at CA3-CA1 synapses, decreases the coefficient of variation and the paired-pulse ratio, indicating that presynaptic activation of calcium-induced calcium release can modulate glutamatergic transmission. Next, we investigated whether blocking calcium release from internal stores could alter the effect of nicotine. Preincubation with thapsigargin (10 microM), cyclopiazonic acid (30 microM), or with a high (blocking) concentration of ryanodine (100 microM) for 30 min to 5 h failed to block the effect of nicotine. However, after preincubation in ryanodine, nicotine-elicited potentiation was significantly shortened. These results indicate that at immature Schaffer collateral-CA1 synapses, activation of presynaptic calcium stores is not necessary for but contributes to nicotine-elicited increase of neurotransmitter release.

  10. Synthesis of CaTiO3 from calcium titanyl oxalate hexahydrate (CTO) as precursor employing microwave heating technique

    Indian Academy of Sciences (India)

    B M Patil; R S Srinivasa; S R Dharwadkar

    2007-06-01

    Calcium titanate, CaTiO3, an important microwave dielectric material and one of major phases in synroc (synthetic rock), a titanate ceramic with potential application for fixation of high level nuclear waste was synthesized from calcium titanyl oxalate [CaTiO (C2O4)2.6H2O] (CTO) by employing microwave heating technique. CTO heated in microwave heating system in air at 500°C for 1 h gave a perovskite, CaTiO3. The product obtained by heating of CTO in the same system at 700°C for the same duration was however, much more crystalline. CaTiO3 obtained by the present method was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET surface area measurement.

  11. Calcium carbene complexes with boranophosphorano side-arms: CaC[P(Ph)(2)BH(3)](2).

    Science.gov (United States)

    Orzechowski, Lars; Jansen, Georg; Lutz, Martin; Harder, Sjoerd

    2009-04-28

    The ligand H(2)C(PPh(2)BH(3))(2) (-H(2)) reacted with one or a half equivalent of (para-tBu-C(6)H(4)CH(2))(2)Ca.(THF)(4) to form the calcium complexes Ca[HC(PPh(2)BH(3))(2)](2) (-H)(2)Ca and CaC(PPh(2)BH(3))(2) (-Ca), respectively. The crystal structures of their THF adducts (-H)(2)Ca.THF and [-Ca.(THF)](2) follow the same trends as observed for the corresponding iminophosphorano substituted complexes Ca[HC(PPh(2)NR)(2)](2) and [CaC(PPh(2)NR)(2)](2). The P-C bonds shorten upon gradual deprotonation, whereas the P-B and P-N bonds elongate. The geometries of DFT-optimized model systems and complete molecular structures show similar trends. Also the charge distribution within the boranophosphorano complexes is similar to that in the iminophosphorano complexes. The high positive charges on Ca (1.74-1.75) indicate a predominantly ionic ligand-Ca bonding. High negative charges on the central carbon atom (-1.103 in Ca[HC(PH(2)BH(3))(2)](2) and -1.775 in [CaC(PH(2)BH(3))(2)](2)) compare well to those calculated for analogous iminophosphorano complexes (-1.126 Ca[HC(PH(2)NH)(2)](2) and -1.847 [CaC(PH(2)NH)(2)](2), respectively). Thus, in both types of complexes delocalization of electron density over the boranophosphorano or iminophosphorano substituents does not play a major role. Complex [-Ca.(THF)](2) does not react with adamantyl cyanide. Instead the adduct (-Ca)(2).(THF).(adamantyl-C[triple bond, length as m-dash]N) formed (a crystal structure has been determined).

  12. Some commonly overlooked properties of calcium buffer systems: a simple method for detecting and correcting stoichiometric imbalance in CaEGTA stock solutions.

    Science.gov (United States)

    Klabusay, M; Blinks, J R

    1996-09-01

    When the two-solution approach is used to make CaEGTA buffers, the most critical requirement is that the CaEGTA stock solution contain equimolar quantities of calcium and chelator. The impact on [Ca2+] of errors in the molar ratio is magnified at high buffer ratios, so stoichiometric imbalance is most readily detected there. In this paper we examine some of the properties of calcium buffer systems that illustrate these principles, and describe a simple and sensitive method for detecting and correcting stoichiometric imbalance in the CaEGTA stock solution. The method derives its high sensitivity from the fact that the CaEGTA stock solution itself represents a calcium buffer system with a very high buffer ratio.

  13. Trabecular bone response to injectable calcium phosphate (Ca-P) cement.

    NARCIS (Netherlands)

    Ooms, E.M.; Wolke, J.G.C.; Waerden, J.P.C.M. van der; Jansen, J.A.

    2002-01-01

    The aim of this study was to investigate the physicochemical, biological, and handling properties of a new developed calcium phosphate (Ca-P) cement when implanted in trabecular bone. Ca-P cement consisting of a powder and a liquid phase was implanted as a paste into femoral trabecular bone of goats

  14. Relationship between serum calcium and CA 19-9 levels in colorectal cancer

    Institute of Scientific and Technical Information of China (English)

    Peter Fuszek; Peter Lakatos; Adam Tabak; Janos Papp; Zsolt Nagy; Istvan Takacs; Henrik Csaba Horvath; Peter Laszlo Lakatos; Gabor Speer

    2004-01-01

    AIM: To examine the calcium metabolism of colorectal cancer(CRC) in patients with colorectal cancer and control patients.METHODS: Seventy newly diagnosed CRC patients were included. The healthy control group was age and gender matched (n=32). Particular attention was devoted to the relationship between serum calcium of patients, and levels of AFP, CEA, carbohydrate antigen 19-9 (CA 19-9) (that could be considered as prognostic factors). Furthermore, the Ca-sensing receptor (CaSR) gene A986S polymorphism was investigated in these patients, as well as the relationship between different CaSR genotypes and the data stated above.RESULTS: A lower level of ionized calcium (also corrected for albumin) was found in the serum of CRC patients with normal 25(OH) vitamin D levels. The ionized calcium concentration was inversely correlated with the serum level of CA 19-9. There was no difference in the distribution of CaSR genotypes, between CRC patients and general population. The genotypes did not correlate with other data examined.CONCLUSION: Based on these results, lower levels of serum calcium might be a pathogenic and prognostic factor in colorectal cancer.

  15. Concerted but Noncooperative Activation of Nucleotide and Actuator Domains of the Ca-ATPase Upon Calcium Binding

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Baowei; Mahaney, James E.; Mayer, M. Uljana; Bigelow, Diana J.; Squier, Thomas C.

    2008-11-25

    Calcium-dependent domain movements of the nucleotide (N) and actuator (A) domains of the SERCA2a isoform of the Ca-ATPase were assessed using constructs containing engineered tetracysteine binding motifs, which were expressed in insect High-Five cells and subsequently labeled with the biarsenical fluorophore 4’,5’-bis(1,3,2-dithoarsolan-2-yl)fluorescein (FlAsH-EDT2). Maximum catalytic function is retained in microsomes isolated from High-Five cells and labeled with FlAsH-EDT2. Distance measurements using the nucleotide analog TNP-ATP, which acts as a fluorescence resonance energy transfer (FRET) acceptor from FlAsH, identify a 2.4 Å increase in the spatial separation between the N- and A-domains induced by high-affinity calcium binding; this structural change is comparable to that observed in crystal structures. No significant distance changes occur across the N-domain between FlAsH and TNP-ATP, indicating that calcium activation induces rigid body domain movements rather than intradomain conformational changes. Calcium-dependent decreases in the fluorescence of FlAsH bound respectively to either the N- or A-domains indicate coordinated and noncooperative domain movements, where both N- and A-domains domains display virtually identical calcium dependencies (i.e., Kd = 4.8 ± 0.4 μM). We suggest that occupancy of a single high-affinity calcium binding site induces the rearrangement of the A- and N-domains of the Ca-ATPase to form an intermediate state, which facilitates ATP utilization upon occupancy of the second high-affinity calcium site to enhance transport efficiency.

  16. SO{sub 2} retention on CaO/activated carbon sorbents. Part I: Importance of calcium loading and dispersion

    Energy Technology Data Exchange (ETDEWEB)

    M.C. Macias-Perez; A. Bueno-Lopez; M.A. Lillo-Rodenas; C. Salinas-Martinez de Lecea; A. Linares-Solano [University of Alicante, Alicante (Spain). Department of Inorganic Chemistry

    2007-03-15

    Sorbents for SO{sub 2} retention at low temperature consisting of CaO supported on activated carbons have been prepared by different methods (physical mixing, incipient wetness impregnation, rotary evaporator impregnation, complex formation and ionic exchange). Ca(OH){sub 2}, CaCO{sub 3}, CaO, Ca(CH{sub 3}COO){sub 2} and Ca(C{sub 2}H{sub 5}COO){sub 2} have been used as calcium precursors. The preparation method affects calcium loading as well as calcium dispersion. SO{sub 2} retention depends both on the calcium loading and on the calcium dispersion. The best preparation method, among those tested, was impregnation of the activated carbon with calcium acetate. Similar calcium loading can be obtained by the physical mixing method but the resulting calcium dispersion is low. On the contrary, samples with higher calcium dispersion were obtained by the complex formation method, presenting the disadvantage of the low calcium loading reached. The molar calcium conversion results are much higher than values reported for unsupported calcium compounds. 20 refs., 7 figs., 2 tabs.

  17. Influences of calcium availability and tree species on Ca isotope fractionation in soil and vegetation

    Science.gov (United States)

    Page, B.D.; Bullen, T.D.; Mitchell, M.J.

    2008-01-01

    The calcium (Ca) isotope system is potentially of great use for understanding biogeochemical processes at multiple scales in forest ecosystems, yet remains largely unexplored for this purpose. In order to further our understanding of Ca behavior in forests, we examined two nearly adjacent hardwood-dominated catchments with differing soil Ca concentrations, developed from crystalline bedrock, to determine the variability of 44Ca/ 40Ca ratios (expressed as ??44Ca) within soil and vegetation pools. For both sugar maple and American beech, the Ca isotope compositions of the measured roots and calculated bulk trees were considerably lighter than those of soil pools at these sites, suggesting that the trees were able to preferentially take up light Ca at the root-soil interface. The Ca isotope compositions of three of four root samples were among the lightest values yet reported for terrestrial materials (??44Ca ???-3.95???). Our results further indicate that Ca isotopes were fractionated along the transpiration streams of both tree species with roots having the least ??44Ca values and leaf litter the greatest. An approximately 2??? difference in ??44Ca values between roots and leaf litter of both tree species suggests a persistent fractionation mechanism along the transpiration stream, likely related to Ca binding in wood tissue coupled with internal ion exchange. Finally, our data indicate that differing tree species demand for Ca and soil Ca concentrations together may influence Ca isotope distribution within the trees. Inter-catchment differences in Ca isotope distributions in soils and trees were minor, indicating that the results of our study may have broad transferability to studies of forest ecosystems in catchments developed on crystalline substrates elsewhere. ?? 2008 Springer Science+Business Media B.V.

  18. Suppression of experimental atherosclerosis by the Ca++-antagonist lanthanum. Possible role of calcium in atherogenesis.

    Science.gov (United States)

    Kramsch, D M; Aspen, A J; Apstein, C S

    1980-05-01

    Agents inhibiting calcium deposition into arteries are known to suppress atherosclerosis in animals. However, the precise role of calcium in atherogenesis is unknown. In this study, the specific Ca2+-antagonist lanthanum was used to attempt suppression of experimental atherosclerosis and to gain more insight into the possible effects of calcium on atherogenesis. Rabbits were fed an atherogenic diet with and without increasing doses of LaCl3. All cholesterol-fed rabbits showed marked increases in serum cholesterol and ca2+. Untreated atherogenic animals revealed pronounced gross and microscopic atherosclerosis and striking increases in the aortic content of cholesterol, collagen, "elastin," and calcium as well as of elastin calcium, polar amino acids, and cholesterol. With increasing LaCl3 dosage these abnormalities progressively decreased and were completely abolished at the highest dose. The ingested La3+ was absorbed only in small quantities and had no discernible effect on the calcium and connective tissue content of bone, skin, lung, heart, and skeletal muscle nor on myocardial function (left ventricle pressure and left ventricle dp/dt) or myocardial and muscle content in ATP and creatine phosphate. The data suggest that shifts in arterial Ca2+-distribution may play a decisive part in atherogenesis, and provision of arterial calcium homeostasis by La3+ a pivotal role in its prevention, despite hypercholesteremia. Other inhibitors of calcium deposition into arteries may exert their protective effect by similar mechanisms. However, a direct inhibition of atherogenesis by La3+ cannot entirely be ruled out in this study, although no direct effects of La3+ on tissue metabolism have as yet been reported.

  19. Synthesis and characterization of Ag-containing calcium phosphates with various Ca/P ratios

    Energy Technology Data Exchange (ETDEWEB)

    Gokcekaya, Ozkan, E-mail: gokcekaya@dc.tohoku.ac.jp [Department of Materials Processing, Tohoku University, 6-6-02 Aza Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Ueda, Kyosuke; Narushima, Takayuki [Department of Materials Processing, Tohoku University, 6-6-02 Aza Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Ergun, Celaletdin [Faculty of Mechanical Engineering, Istanbul Technical University, 65 Inonu Street, Gumussuyu, Istanbul 34437 (Turkey)

    2015-08-01

    Ag-containing calcium phosphate (CaP) powders were synthesized by a precipitation method using aqueous solutions of calcium nitrate, silver nitrate, and ammonium phosphate. The powders were sintered at temperatures ranging from 1173 to 1473 K. The charged atomic ratios of (Ca + Ag)/P and Ag/(Ca + Ag) in solution were varied from 1.33 to 1.67 and from 0 to 0.30, respectively. The Ag content in the as-precipitated CaP powders increased with the charged Ag/(Ca + Ag) atomic ratio in solution and was lower than the charged Ag/(Ca + Ag) value. The as-precipitated CaP powders consisted of hydroxyapatite (HA) as the main phase. Ag nanoparticles were observed on the as-precipitated HA particles under all conditions of Ag addition. After the sintering, HA, β-TCP (tricalcium phosphate), α-TCP, and β-CPP (calcium pyrophosphate) were mainly detected as CaPs on the basis of the Ca/P atomic ratio of the as-precipitated powders. The addition of Ag stabilized the β-TCP phase, and the distribution of Ag in β-TCP was homogeneous. A metallic Ag phase coexisted with HA. The solubility of Ag in HA was estimated to be 0.0019–0.0061 (Ag/(Ca + Ag)) atomic ratio, which was lower than that in β-TCP (higher than 0.0536) and higher than that of β-CPP (below the detection limit of analyses). - Highlights: • The HA powders with Ag nanoparticles were synthesized by a precipitation method. • Metallic Ag particles were detected with the HA phase after sintering. • The distribution of Ag in β-TCP was homogeneous after sintering. • The addition of Ag stabilized the β-ΤCP phase. • β-TCP exhibited higher solubility of Ag than HA and β-CPP.

  20. Kinetics of dissolution of calcium phosphate (Ca-P bioceramics

    Directory of Open Access Journals (Sweden)

    Lukas Brazda

    2008-06-01

    Full Text Available Hydroxyapatite (HAp and β-tricalcium phosphate (β-TCP are widely used bioceramics for surgical or dental applications. This paper is dealing with dissolution kinetics of synthetically prepared β-TCP and four types of HAp granules. Two groups of HAp, treated at different temperatures, each of them with two different granule sizes, were tested. Three corrosive solutions with different pH and simulated body fluid (SBF were used for immersing of the samples. Changes in concentrations of calcium and phosphate ions, pH level and weight changes of the samples were observed. It was found that presence of TRIS buffer enhanced dissolution rate of the β-TCP approximately two times. When exposed to SBF solution, calcium phosphate (most probably hydroxyapatite precipitation predominates over β-TCP dissolution. Results from HAp samples dissolution showed some unexpected findings. Neither heat treatment nor HAp particle size made any major differences in dissolution rate of the same mass of each HAp sample.

  1. Integration of calcium and chemical looping combustion using composite CaO/CuO-based materials.

    Science.gov (United States)

    Manovic, Vasilije; Anthony, Edward J

    2011-12-15

    Calcium looping cycles (CaL) and chemical looping combustion (CLC) are two new, developing technologies for reduction of CO(2) emissions from plants using fossil fuels for energy production, which are being intensively examined. Calcium looping is a two-stage process, which includes oxy-fuel combustion for sorbent regeneration, i.e., generation of a concentrated CO(2) stream. This paper discuss the development of composite materials which can use copper(II)-oxide (CuO) as an oxygen carrier to provide oxygen for the sorbent regeneration stage of calcium looping. In other words, the work presented here involves integration of calcium looping and chemical looping into a new class of postcombustion CO(2) capture processes designated as integrated CaL and CLC (CaL-CLC or Ca-Cu looping cycles) using composite pellets containing lime (CaO) and CuO together with the addition of calcium aluminate cement as a binder. Their activity was tested in a thermogravimetric analyzer (TGA) during calcination/reduction/oxidation/carbonation cycles. The calcination/reduction typically was performed in methane (CH(4)), and the oxidation/carbonation stage was carried out using a gas mixture containing both CO(2) and O(2). It was confirmed that the material synthesized is suitable for the proposed cycles; with the very favorable finding that reduction/oxidation of the oxygen carrier is complete. Various schemes for the Ca-Cu looping process have been explored here that would be compatible with these new composite materials, along with some different possibilities for flow directions among carbonator, calciner, and air reactor.

  2. New high-capacity, calcium-based sorbents, calcium silicate sorbents. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kenney, M.E.

    1996-02-28

    A search is being carried out for new calcium-based SO{sub 2} sorbents for induct injection. More specifically, a search is being carried out for induct injection calcium silicate sorbents that are highly cost effective. The current year objectives include the study of sorbents made by hydrating ordinary or Type I portland cement or portland cement clinker (a cement intermediate) under carefully selected conditions. Results of this study show that an excellent portland cement sorbent can be prepared by milling cement at 120{degrees}C at 600 rpm for 15 minutes with MgO-stabilized ZrO{sub 2} beads. They also show that clinker, which is cheaper than cement can be used interchangeably with cement as a starting material. Further, it is clear that while a high surface area may be a desirable property of a good sorbent, it is not a requisite property. Among the hydration reaction variables, milling time is highly important, reaction temperature is important and stirring rate and silicate-to-H{sub 2}O ratio are moderately important. The components of hydrated cement sorbent are various combinations of C-S-H, calcium silicate hydrate:Ca(OH){sub 2};AFm. a phase in hydrated cement.

  3. Aberrant Splicing Promotes Proteasomal Degradation of L-type Ca v 1.2 Calcium Channels by Competitive Binding for CaV β Subunits in Cardiac Hypertrophy

    NARCIS (Netherlands)

    Hu, Zhenyu; Wang, Jiong Wei; Yu, Dejie; Soon, Jia Lin; De Kleijn, Dominique P V; Foo, Roger; Liao, Ping; Colecraft, Henry M.; Soong, Tuck Wah

    2016-01-01

    Decreased expression and activity of Ca V1.2 calcium channels has been reported in pressure overload-induced cardiac hypertrophy and heart failure. However, the underlying mechanisms remain unknown. Here we identified in rodents a splice variant of Ca V1.2 channel, named Ca V1.2 e21+22, that contain

  4. Human calcium metabolism including bone resorption measured with {sup 41}Ca tracer

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, S.P.H.T. [Lawrence Livermore National Lab., CA (United States); King, J.C. [California Univ., Berkeley, CA (United States). Dept. of Nutritional Science; Vieira, N.E. [National Inst. of Child Health and Human Development, Bethesda, MD (United States); Woodhouse, L.R. [California Univ., Berkeley, CA (United States). Dept. of Nutritional Science; Yergey, A.L. [National Inst. of Child Health and Human Development, Bethesda, MD (United States)

    1996-08-01

    Accelerator mass spectrometry is so sensitive to small quantities of {sup 41}Ca that it might be used as a tracer in the study of human calcium kinetics to generate unique kinds of data. In contrast with the use of other Ca isotopic tracers, {sup 41}Ca tracer can be so administered that the tracer movements between the various body pools achieve a quasi steady state. Resorbing bone may thus be directly measured. We have tested such a protocol against a conventional stable isotope experiment with good agreement.

  5. Ca2+ released from calcium alginate gels can promote inflammatory responses in vitro and in vivo

    Science.gov (United States)

    Chan, Gail; Mooney, David J.

    2013-01-01

    In general, alginate hydrogels are considered to be biologically inert and are commonly used for biomedical purposes that require minimum inflammation. However, Ca2+, which is commonly used to crosslink alginate, is a critical second messenger in immune cell signaling, and little has been done to understand its effect on immune cell fate when delivered as a component of alginate gels. We found that dendritic cells (DCs) encapsulated in Ca2+-crosslinked alginate (calcium alginate) secreted at least fivefold more of the inflammatory cytokine IL-1β when compared to DCs encapsulated in agarose and collagen gels, as well as DCs plated on tissue-culture polystyrene (TCPS). Plating cells on TCPS with the alginate polymer could not reproduce these results, whereas culturing DCs on TCPS with increasing concentrations of Ca2+ increased IL-1β, MHC class II and CD86 expression in a dose-dependent manner. In agreement with these findings, calcium alginate gels induced greater maturation of encapsulated DCs compared to barium alginate gels. When injected subcutaneously in mice, calcium alginate gels significantly upregulated IL-1β secretion from surrounding tissue relative to barium alginate gels, and similarly, the inflammatory effects of LPS were enhanced when it was delivered from calcium alginate gels rather than barium alginate gels. These results confirm that the Ca2+ used to crosslink alginate gels can be immunostimulatory and suggest that it is important to take into account Ca2+’s bioactive effects on all exposed cells (both immune and non-immune) when using calcium alginate gels for biomedical purposes. This work may strongly impact the way people use alginate gels in the future as well as provide insights into past work utilizing alginate gels. PMID:23938198

  6. Biodegradable Orthopedic Magnesium-Calcium (MgCa Alloys, Processing, and Corrosion Performance

    Directory of Open Access Journals (Sweden)

    Yuebin Guo

    2012-01-01

    Full Text Available Magnesium-Calcium (Mg-Ca alloy has received considerable attention as an emerging biodegradable implant material in orthopedic fixation applications. The biodegradable Mg-Ca alloys avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. They also provide sufficient mechanical strength in load carrying applications as opposed to biopolymers. However, the key issue facing a biodegradable Mg-Ca implant is the fast corrosion in the human body environment. The ability to adjust degradation rate of Mg-Ca alloys is critical for the successful development of biodegradable orthopedic implants. This paper focuses on the functions and requirements of bone implants and critical issues of current implant biomaterials. Microstructures and mechanical properties of Mg-Ca alloys, and the unique properties of novel magnesium-calcium implant materials have been reviewed. Various manufacturing techniques to process Mg-Ca based alloys have been analyzed regarding their impacts on implant performance. Corrosion performance of Mg-Ca alloys processed by different manufacturing techniques was compared. In addition, the societal and economical impacts of developing biodegradable orthopedic implants have been emphasized.

  7. Preparation and Properties of Nanoparticles of Calcium Phosphates With Various Ca/P Ratios.

    Science.gov (United States)

    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.

  8. Impaired presynaptic cytosolic and mitochondrial calcium dynamics in aged compared to young adult hippocampal CA1 synapses ameliorated by calcium chelation.

    Science.gov (United States)

    Tonkikh, A A; Carlen, P L

    2009-04-10

    Impaired regulation of presynaptic intracellular calcium is thought to adversely affect synaptic plasticity and cognition in the aged brain. We studied presynaptic cytosolic and mitochondrial calcium (Ca) dynamics using axonally loaded Calcium Green-AM and Rhod-2 AM fluorescence respectively in young (2-3 months) and aged (23-26 months) CA3 to CA1 Schaffer collateral excitatory synapses in hippocampal brain slices from Fisher 344 rats. After a tetanus (100 Hz, 200 ms), the presynaptic cytosolic Ca peaked at approximately 10 s in the young and approximately 12 s in the aged synapses. Administration of the membrane permeant Ca chelator, bis (O-aminophenoxy)-ethane-N,N,N,N-tetraacetic acid (BAPTA-AM), significantly attenuated the Ca response in the aged slices, but not in the young slices. The presynaptic mitochondrial Ca signal was much slower, peaking at approximately 90 s in both young and aged synapses, returning to baseline by 300 s. BAPTA-AM significantly attenuated the mitochondrial calcium signal only in the young synapses. Uncoupling mitochondrial respiration by carbonyl cyanide m-chlorophenylhydrazone (CCCP) application evoked a massive intracellular cytosolic Ca increase and a significant drop of mitochondrial Ca, especially in aged slices wherein the cytosolic Ca signal disappeared after approximately 150 s of washout and the mitochondrial Ca signal disappeared after 25 s of washout. These signals were preserved in aged slices by BAPTA-AM. Five minutes of oxygen glucose deprivation (OGD) was associated with a significant increase in cytosolic Ca in both young and aged synapses, which was irreversible in the aged synapses. These responses were significantly attenuated by BAPTA-AM in both the young and aged synapses. These results support the hypothesis that increasing intracellular calcium neuronal buffering in aged rats ameliorates age-related impaired presynaptic Ca regulation.

  9. Calcium Sulfoaluminate Sodalite (Ca 4 Al 6 O 12 SO 4 ) Crystal Structure Evaluation and Bulk Modulus Determination

    KAUST Repository

    Hargis, Craig W.

    2013-12-12

    The predominant phase of calcium sulfoaluminate cement, Ca 4(Al6O12)SO4, was investigated using high-pressure synchrotron X-ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al 6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O 12)SO4. The compressibility of Ca4(Al 6O12)SO4 was studied using cubic, orthorhombic, and tetragonal crystal structures due to the lack of consensus on the actual space group, and all three models provided similar results of 69(6) GPa. With its divalent cage ions, the bulk modulus of Ca4(Al6O 12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H 2O. Likewise, comparing this study to previous ones shows the lattice compressibility of aluminate sodalites decreases with increasing size of the caged ions. Ca4(Al6O12)SO4 is more compressible than other cement clinker phases such as tricalcium aluminate and less compressible than hydrated cement phases such as ettringite and hemicarboaluminate. © 2013 The American Ceramic Society.

  10. Nano-sized calcium phosphate (CaP) carriers for non-viral gene deilvery

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Donghyun, E-mail: dhlee@cau.ac.kr [Department of Biomedical Engineering, Division of Integrative Engineering, Chung-Ang University, 221 Heukseok-Dong, Dongjak-Gu, Seoul 156-756 (Korea, Republic of); Upadhye, Kalpesh [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Kumta, Prashant N., E-mail: pkumta@pitt.edu [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Department of Mechanical Engineering and Materials Sceince, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, Pittsburgh, PA 15261 (United States)

    2012-02-25

    Highlights: Black-Right-Pointing-Pointer Nanostructured calcium phosphates (NanoCaPs): comprehensive review. Black-Right-Pointing-Pointer Non viral gene delivery mechanisms: detailed mechanisms are outlined. Black-Right-Pointing-Pointer Barriers to non-viral gene delivery: detailed barriers are discussed. - Abstract: Gene therapy has garnered much interest due to the potential for curing multiple inherited and/or increases in the acquired diseases. As a result, there has been intense activity from multiple research groups for developing effective delivery methods and carriers, which is a critical step in advancing gene delivery technologies. In order for the carriers to effectively deliver the genetic payloads, multiple extracellular and intracellular barriers need to be overcome. Although overcoming these challenges to improve the effectiveness is critical, the development of safe gene delivery agents is even more vital to assure its use in clinical applications. The development of safe and effective strategies has therefore been a major challenge impeding gene therapy progress. In this regard, calcium phosphate (CaP) based nano-particles has been considered as one of the candidate non-viral gene delivery vehicles, but has been plagued by inconsistent and low transfection efficiencies limiting its progress. There has been major research effort to improve the consistency and effectiveness of CaP based vectors. Currently, it is therefore thought that by controlling the various synthesis factors such as Ca/P ratio, mode of mixing, and type of calcium phosphate phase, such variability and inefficiency could be modulated. This review attempts to provide a comprehensive analysis of the current research activity in the development of CaP based ceramic and polymer-ceramic hybrid systems for non-viral gene delivery. Preliminary transfection results of hydroxyapatite (HA or NanoCaPs), amorphous calcium phosphate (ACP) and brushite phases are also compared to assess the

  11. Fish bones--a highly available calcium source for growing pigs.

    Science.gov (United States)

    Malde, M K; Graff, I E; Siljander-Rasi, H; Venäläinen, E; Julshamn, K; Pedersen, J I; Valaja, J

    2010-10-01

    In general, there is a lack of scientific documentation of nutritional value of marine by-products. The bone fraction from fish has been regarded as waste. Due to the high mineral content of fish bones, this material can be well suitable as a natural calcium source. In the present study, apparent calcium absorption of different fish bone sources was tested using growing pigs. The experimental diets consisted of boiled salmon frames, or salmon, saithe or cod bones treated with enzymes. Calcium carbonate (CaCO(3)) was used as control. The experimental diets were formulated to contain 0.7% total calcium of which the added calcium source to be tested contributed about 71% (study 1) and 86% (study 2). Except for the calcium and phosphorus sources, the animals received similar basal diets. Apparent calcium digestibility coefficient was calculated using yttrium as indicator (both studies) and was based on complete collection of faeces and urine (study 2). The experimental design was parallel and cross-over in study 1 and study 2, respectively. In study 1, piglets getting salmon bone treated with enzymes had significantly higher calcium absorption than piglets getting boiled fish bone or calcium carbonate. Therefore, in the second study only enzymatically treated fish bones were included. The higher calcium absorption from enzymatically treated salmon bone was also found in study 2, but this time not significant. Calcium from boiled salmon bones in study I, and from enzymatically treated saithe and cod bones in study II were absorbed as well as the calcium carbonate control. The results indicate that fish bones may be a useful and well absorbed calcium source. Due to the high mineral content of the bone fraction, salmon bones can be well suitable as a natural calcium and phosphorus source in, for example, food, feed or as supplement.

  12. Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement

    Directory of Open Access Journals (Sweden)

    Tae-Hyun Kim

    2014-12-01

    Full Text Available We have successfully prepared layered double hydroxide (LDH nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH. The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1% of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.

  13. Polymer coated CaAl-layered double hydroxide nanomaterials for potential calcium supplement.

    Science.gov (United States)

    Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

    2014-12-05

    We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.

  14. New high-capacity, calcium-based sorbents, calcium silicate sorbents. Final report, 1993--August 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Kenney, M.C.; Chiang, R.K.; Fillgrove, K.L. [Case Western Reserve Univ., Cleveland, OH (United States)

    1995-02-01

    A search is being carried out for new calcium-based S0{sub 2} sorbents for induct injection. More specifically, a search is being carried out for induct injection calcium silicate sorbents that are highly cost effective. The objectives for the current year include the study of sorbents made from Ca(OH){sub 2}, from mixtures of Ca(OH){sub 2} and SiO{sub 2}, and from portland cement. They also include the study of sorbents made from model compounds. During this year, sorbents prepared from Ca(OH){sub 2} and from mixtures of Ca(OH){sub 2} and fumed SiO{sub 2} were investigated. The results show that very good SiO{sub 2}-modified Ca(OH){sub 2} sorbents in which the Si-to-Ca reactant ratio is low can be prepared from Ca(OH){sub 2} and fumed SiO{sub 2}. Sorbents prepared from Ca(OH){sub 2} and natural SiO{sub 2} or natural SiO{sub 2} sources were also studied. The results obtained show that very good SiO{sub 2}-modified Ca(OH){sub 2} sorbents and calcium silicate hydrate sorbents, C-S-H sorbents, can be prepared from Ca(OH){sub 2} and diatomite, pumice or perlite, minerals that are readily available. In addition. sorbents prepared from Ca{sub 3}SiO{sub 5} and {beta}-Ca{sub 2}SiO{sub 4} and from mixtures of these compounds and SiO{sub 2} were studied. The results secured demonstrate that very good C-S-H rich sorbents can be prepared from these compounds and from mixtures of them with SiO{sub 2}. They also provide information useful for interpreting the cement sorbent results. Sorbents prepared from cement and from mixtures of cement and natural SiO{sub 2} or SiO{sub 2} sources were investigated as well. The results secured show that cement and mixtures of it with diatomite, pumice or perlite rapidly yield excellent sorbents with the proper reaction conditions.

  15. Effects of low calcium plus high aluminum diet on magnesium and calcium contents in spinal cord and trabecular bone of rats

    Energy Technology Data Exchange (ETDEWEB)

    Yasui, Masayuki; Ota, Kiichiro [Wakayama Medical Coll. (Japan); Sasajima, Kazuhisa

    1998-01-01

    Current epidemiological surveys in the Western Pacific area and Kii Peninsula have suggested that low calcium (Ca), magnesium (Mg), and high aluminum (Al) and manganese (Mn) in river, soil and drinking water may be implicated in the pathogenetic process of amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD). The condition of unbalanced minerals was experimentally duplicated in this study using rats. Male Wistar rats, weighing 200 g, were maintained for 60 days on the following diets: (A) standard diet, (B) low Ca diet, (C) low Ca diet with high Al. Magnesium concentration was determined in spinal cord and trabecular bone using inductively coupled plasma emission spectrometry (ICP) and the calcium concentration was determined using neutron activation method. In the group maintained on low Ca high Al diet, magnesium content of the spinal cord was lower than the group fed standard diet. Also, magnesium content of lumbar bone showed lower values in the unbalanced diet group fed low Ca high Al diet than those in the standard diet and low Ca diet groups. Calcium content of spinal cord was highest in rats maintained on low Ca high Al diet. Calcium content in lumbar bone of rats significantly decreased in rats maintained on the low Ca diet (group B and C) compared to rats given a standard diet (group A). Our data indicate that low Ca and high Al dietary intake influence Mg concentration in bone and central nervous system (CNS) tissues and that low Ca and high Al diet diminish Mg in bone and CNS tissues, thereby inducing loss of calcification in bone and degeneration of CNS tissues due to disturbance of the normal biological effects of Mg. (author)

  16. Effect of calcium content on the microstructure, hardness and in-vitro corrosion behavior of biodegradable Mg-Ca binary alloy

    Directory of Open Access Journals (Sweden)

    Shervin Eslami Harandi

    2013-02-01

    Full Text Available Effect of calcium addition on microstructure, hardness value and corrosion behavior of five different Mg-xCa binary alloys (x = 0.7, 1, 2, 3, 4 wt. (% was investigated. Notable refinement in microstructure of the alloy occurred with increasing calcium content. In addition, more uniform distribution of Mg2Ca phase was observed in a-Mg matrix resulted in an increase in hardness value. The in-vitro corrosion examination using Kokubo simulated body fluid showed that the addition of calcium shifted the fluid pH value to a higher level similar to those found in pure commercial Mg. The high pH value amplified the formation and growth of bone-like apatite. Higher percentage of Ca resulted in needle-shaped growth of the apatite. Electrochemical measurements in the same solution revealed that increasing Ca content led to higher corrosion rates due to the formation of more cathodic Mg2Ca precipitate in the microstructure. The results therefore suggested that Mg-0.7Ca with the minimum amount of Mg2Ca is a good candidate for bio-implant applications.

  17. Effect of calcium content on the microstructure, hardness and in-vitro corrosion behavior of biodegradable Mg-Ca binary alloy

    Directory of Open Access Journals (Sweden)

    Shervin Eslami Harandi

    2012-01-01

    Full Text Available Effect of calcium addition on microstructure, hardness value and corrosion behavior of five different Mg-xCa binary alloys (x = 0.7, 1, 2, 3, 4 wt. (% was investigated. Notable refinement in microstructure of the alloy occurred with increasing calcium content. In addition, more uniform distribution of Mg2Ca phase was observed in a-Mg matrix resulted in an increase in hardness value. The in-vitro corrosion examination using Kokubo simulated body fluid showed that the addition of calcium shifted the fluid pH value to a higher level similar to those found in pure commercial Mg. The high pH value amplified the formation and growth of bone-like apatite. Higher percentage of Ca resulted in needle-shaped growth of the apatite. Electrochemical measurements in the same solution revealed that increasing Ca content led to higher corrosion rates due to the formation of more cathodic Mg2Ca precipitate in the microstructure. The results therefore suggested that Mg-0.7Ca with the minimum amount of Mg2Ca is a good candidate for bio-implant applications.

  18. Modulation of intracellular calcium waves and triggered activities by mitochondrial ca flux in mouse cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Zhenghang Zhao

    Full Text Available Recent studies have suggested that mitochondria may play important roles in the Ca(2+ homeostasis of cardiac myocytes. However, it is still unclear if mitochondrial Ca(2+ flux can regulate the generation of Ca(2+ waves (CaWs and triggered activities in cardiac myocytes. In the present study, intracellular/cytosolic Ca(2+ (Cai (2+ was imaged in Fluo-4-AM loaded mouse ventricular myocytes. Spontaneous sarcoplasmic reticulum (SR Ca(2+ release and CaWs were induced in the presence of high (4 mM external Ca(2+ (Cao (2+. The protonophore carbonyl cyanide p-(trifluoromethoxyphenylhydrazone (FCCP reversibly raised basal Cai (2+ levels even after depletion of SR Ca(2+ in the absence of Cao (2+ , suggesting Ca(2+ release from mitochondria. FCCP at 0.01 - 0.1 µM partially depolarized the mitochondrial membrane potential (Δψ m and increased the frequency and amplitude of CaWs in a dose-dependent manner. Simultaneous recording of cell membrane potentials showed the augmentation of delayed afterdepolarization amplitudes and frequencies, and induction of triggered action potentials. The effect of FCCP on CaWs was mimicked by antimycin A (an electron transport chain inhibitor disrupting Δψ m or Ru360 (a mitochondrial Ca(2+ uniporter inhibitor, but not by oligomycin (an ATP synthase inhibitor or iodoacetic acid (a glycolytic inhibitor, excluding the contribution of intracellular ATP levels. The effects of FCCP on CaWs were counteracted by the mitochondrial permeability transition pore blocker cyclosporine A, or the mitochondrial Ca(2+ uniporter activator kaempferol. Our results suggest that mitochondrial Ca(2+ release and uptake exquisitely control the local Ca(2+ level in the micro-domain near SR ryanodine receptors and play an important role in regulation of intracellular CaWs and arrhythmogenesis.

  19. Calcium isolation from large-volume human urine samples for 41Ca analysis by accelerator mass spectrometry.

    Science.gov (United States)

    Miller, James J; Hui, Susanta K; Jackson, George S; Clark, Sara P; Einstein, Jane; Weaver, Connie M; Bhattacharyya, Maryka H

    2013-08-01

    Calcium oxalate precipitation is the first step in preparation of biological samples for (41)Ca analysis by accelerator mass spectrometry. A simplified protocol for large-volume human urine samples was characterized, with statistically significant increases in ion current and decreases in interference. This large-volume assay minimizes cost and effort and maximizes time after (41)Ca administration during which human samples, collected over a lifetime, provide (41)Ca:Ca ratios that are significantly above background.

  20. Calcium Isolation from Large-Volume Human Urine Samples for 41Ca Analysis by Accelerator Mass Spectrometry

    Science.gov (United States)

    Miller, James J; Hui, Susanta K; Jackson, George S; Clark, Sara P; Einstein, Jane; Weaver, Connie M; Bhattacharyya, Maryka H

    2013-01-01

    Calcium oxalate precipitation is the first step in preparation of biological samples for 41Ca analysis by accelerator mass spectrometry. A simplified protocol for large-volume human urine samples was characterized, with statistically significant increases in ion current and decreases in interference. This large-volume assay minimizes cost and effort and maximizes time after 41Ca administration during which human samples, collected over a lifetime, provide 41Ca:Ca ratios that are significantly above background. PMID:23672965

  1. Thermoluminescence characteristics of copper activated calcium borate nanocrystals (CaB{sub 4}O{sub 7}:Cu)

    Energy Technology Data Exchange (ETDEWEB)

    Erfani Haghiri, Maryam, E-mail: maryam.erfani59@gmail.com [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Saion, Elias; Soltani, Nayereh [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Wan Abdullah, Wan Saffiey [Radiation Protection and Health Division, Malaysian Nuclear Agency (Nuclear Malaysia), Bangi, 43000 Kajang (Malaysia); Navasery, Manizheh; Hashim, Mansor [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2013-09-15

    The copper activated calcium tetraborate (CaB{sub 4}O{sub 7}:Cu) nanophosphor was synthesized by a combination of facile co-precipitation and thermal treatment methods for the first time. Thermoluminescence and dosimetric characteristics of the gamma irradiated CaB{sub 4}O{sub 7}:Cu nanophosphor was reported. The glow curves shows two well resolved TL peaks centered at about 120 °C and 260 °C. The copper concentration was varied from 1 to 3 mol% and it was found that the nanocrystalline CaB{sub 4}O{sub 7}:Cu with a dopant concentration of 2 mol% has the highest sensitivity among the other dopant concentrations. The results demonstrated that copper can enhance TL efficiency to 2.26 times more than that of un-doped nanocrystalline samples. Moreover, the dose response of the dosimetric peak at 260 °C follows a good linearity up to 3 kGy whereas the linearity of lower temperature peak at 120 °C extended up to 30 Gy. The linearity characteristic of the present nanophosphor suggests it as a candidate towards dosimetric applications. -- Highlights: • The TL characterization of calcium tetraborate nanoparticles was reported for the first time. • The addition of copper to host lattice can enhance the TL efficiency well. • The interesting feature of this study is a linearity of nanophosphor for wide range of doses. • The nanophosphor showed simple glow curve, good reproducibility and high sensitivity.

  2. Short communication: Urinary oxalate and calcium excretion by dogs and cats diagnosed with calcium oxalate urolithiasis

    NARCIS (Netherlands)

    Dijcker, J.C.; Kummeling, A.; Hagen-Plantinga, E.A.; Hendriks, W.H.

    2012-01-01

    Introduction Urine concentrations of oxalate and calcium play an important role in calcium oxalate (CaOx) urolith formation in dogs and cats, with high excretions of both substances increasing the chance of CaOx urolithiasis. In 17 CaOx-forming dogs, urine calcium:creatinine ratio (Ca:Cr) was found

  3. The calcium-dust relationship in high-resolution data from Dome C, Antarctica

    Directory of Open Access Journals (Sweden)

    F. Lambert

    2011-04-01

    Full Text Available Ice core data from Antarctica provide detailed insights into the characteristics of past climate, atmospheric circulation, as well as changes in the aerosol load of the atmosphere. We present high-resolution records of soluble calcium (Ca2+, non-sea-salt soluble calcium (nssCa2+, and insoluble mineral aerosol dust from the East Antarctic Plateau at a depth resolution of 1 cm, spanning the past 800 000 yr. The comparison shows that the ratio of ionic proxies such as CaCa2+ (or nssCa2+ to particulate dust aerosol is variable in time. Accordingly, the insoluble dust record is representative of large and small atmospheric particulate dust load changes and better suited to quantify the aerosol effect on the radiation balance in the past. In contrast soluble dust proxies such as Ca2+ and nssCa2+ will underestimate this effect but may be better suited to quantify the deposition of chemically active Ca2+ or other soluble dust derived nutrients into the Southern Ocean. The correlation between nssCa2+ and particulate dust is time dependent with high correlations during glacial and low correlation during interglacial times. The low correlation during warm times may be partly caused by changes in the soluble calcium content of dust particles, possibly due to a more acidic atmosphere during interglacials. The ratio of nssCa2+ to dust is dependent on the dust concentration itself. A simple mixing of two dust end members for glacial and interglacial conditions with nssCa2+ to dust ratios of 0.045 and approximately 0.3, respectively, can explain the overall temporal change in the nssCa2+ to dust ratio over time.

  4. High-normal calcium (1.35 mmol/l) dialysate in patients on CAPD

    DEFF Research Database (Denmark)

    Bro, S; Brandi, L; Olgaard, K

    1996-01-01

    AIM: The aim of the present study was to examine the long-term efficacy and safety of treatment with a high-normal calcium dialysate with a calcium concentration of 1.35 mmol/l in patients on CAPD. This dialysate calcium concentration is close to the high-normal plasma ionized calcium level aimed......-containing phosphate binders, and (5) bone mineral density (BMD). RESULTS: Thirty-seven non-selected patients on CAPD treatment were followed for an average of 10 months after switching from a dialysate Ca of 1.75 to 1.35 mmol/l. After 1 week, a significant decrease of mean iCa from 1.26 +/- 0.01 to 1.23 +/- 0.01 mmol...... from a dialysate Ca of 1.75 to 1.35 mmol/l, the doses of calcium carbonate and alfacalcidol could be significantly increased. Furthermore, using the dialysate Ca of 1.35 mmol/l made it possible to induce a controlled increase of PTH levels to 80-100 pg/ml by a temporarily discontinuation...

  5. The Properties of Sintered Calcium Phosphate with [Ca]/[P] = 1.50

    Directory of Open Access Journals (Sweden)

    Moo-Chin Wang

    2012-10-01

    Full Text Available In order to obtain the properties of the sintered as-dried calcium phosphate with [Ca]/[P] = 1.50, the characteristics of sintered pellets have been investigated using X-ray diffraction (XRD, inductively coupled plasma-mass spectrometry (ICP-MS, Fourier-transform infrared (FT-IR spectra, Vickers hardness indentation and scanning electron microscopy (SEM. When the pellet samples were sintered between 700 °C and 1200 °C for 4 h, the hydroxyapatite (Ca10(PO46(OH2, HA still maintained the major phase, accompanied with the rhenanite (NaCaPO4 as the secondary phase and β-tricalcium phosphate (β-Ca3(PO42, β-TCP as the minor phases. In addition, the HA partially transformed to α-tricalcium phosphate (α-Ca3(PO42, α-TCP and tetracalcium phosphate (Ca4(PO42O, TTCP, when the pellet samples were sintered at 1300 °C and 1400 °C, respectively, for 4 h. The maximum density and Vickers Hardness (HV of sintered pellet samples were 2.85 g/cm3 (90.18% theoretical density (T.D. and 407, which appeared at 1200 °C and 900 °C, respectively.

  6. High Performance Calcium Titanate Nanoparticle ER Fluids

    Science.gov (United States)

    Wang, Xuezhao; Shen, Rong; Wen, Weijia; Lu, Kunquan

    A type of calcium titanate (CTO) nanoparticles was synthesized by means of wet chemical method [1] without coating on the particles. The CTO/silicone oil ER fluid exhibits excellent electrorheological properties: high shear stress (~50-100 kPa) under dc electric field, a low current density (less than 2μA/cm2 at 5kV/mm), and long term stability against sedimentation. Although there are not special additives in the ER fluids, it is found from the chemical analysis that a trace of alkyl group, hydroxyl group, carbonyl group and some ions is remained in the particles which may dominate the ER response.

  7. The influence of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation

    Science.gov (United States)

    Putro, Triswantoro; Endarko

    2016-04-01

    The influences of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation in water have been successfully investigated. The study used three pairs of magnetic field 0.1 T whilst the electron discharge was generated from television flyback transformer type BW00607 and stainless steel SUS 304 as an electrode. The water sample with an initial condition of 230 mg/L placed in the reactor with flow rate 375 mL/minutes, result showed that the electron discharge can be reduced contain of calcium carbonate the water sample around 17.39% within 2 hours. Meanwhile for the same long period of treatment and flow rate, around 56.69% from initial condition of 520 mg/L of calcium carbonate in the water sample can be achieved by three pairs of magnetic field 0.1 T. When the combination of three pairs of magnetic field 0.1 T and the electron discharge used for treatment, the result showed that the combination of electron discharge and magnetic field methods can be used to precipitate calcium carbonate in the water sample 300 mg/L around 76.66% for 2 hours of treatment. The study then investigated the influence of the polar position of the magnetic field on calcium carbonate precipitation. Two positions of magnetic field were tested namely the system with alternated polar magnetics and the system without inversion of the polar magnetics. The influence of the polar position showed that the percentage reduction in levels of calcium carbonate in the water sample (360 mg/L) is significant different. Result showed that the system without inversion of the polar magnetics is generally lower than the system with alternated polar magnetics, with reduction level at 30.55 and 57.69%, respectively.

  8. Calcium rubies: a family of red-emitting functionalizable indicators suitable for two-photon Ca2+ imaging.

    Science.gov (United States)

    Collot, Mayeul; Loukou, Christina; Yakovlev, Aleksey V; Wilms, Christian D; Li, Dongdong; Evrard, Alexis; Zamaleeva, Alsu; Bourdieu, Laurent; Léger, Jean-François; Ropert, Nicole; Eilers, Jens; Oheim, Martin; Feltz, Anne; Mallet, Jean-Maurice

    2012-09-12

    We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca(2+)) indicators as new tools for biological Ca(2+) imaging. The specificity of this Ca(2+)-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca(2+)-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca(2+) uncaging or optogenetic stimulation with Ca(2+) imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca(2+) transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca(2+)-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca(2+) chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca(2+)-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca(2+) concentrations are feasible.

  9. The pmr gene, encoding a Ca2+-ATPase, is required for calcium and manganese homeostasis and normal development of hyphae and conidia in Neurospora crassa.

    Science.gov (United States)

    Bowman, Barry J; Abreu, Stephen; Johl, Jessica K; Bowman, Emma Jean

    2012-11-01

    The pmr gene is predicted to encode a Ca(2+)-ATPase in the secretory pathway. We examined two strains of Neurospora crassa that lacked PMR: the Δpmr strain, in which pmr was completely deleted, and pmr(RIP), in which the gene was extensively mutated. Both strains had identical, complex phenotypes. Compared to the wild type, these strains required high concentrations of calcium or manganese for optimal growth and had highly branched, slow-growing hyphae. They conidiated poorly, and the shape and size of the conidia were abnormal. Calcium accumulated in the Δpmr strains to only 20% of the wild-type level. High concentrations of MnCl(2) (1 to 5 mM) in growth medium partially suppressed the morphological defects but did not alter the defect in calcium accumulation. The Δpmr Δnca-2 double mutant (nca-2 encodes a Ca(2+)-ATPase in the plasma membrane) accumulated 8-fold more calcium than the wild type, and the morphology of the hyphae was more similar to that of wild-type hyphae. Previous experiments failed to show a function for nca-1, which encodes a SERCA-type Ca(2+)-ATPase in the endoplasmic reticulum (B. J. Bowman, S. Abreu, E. Margolles-Clark, M. Draskovic, and E. J. Bowman, Eukaryot. Cell 10:654-661, 2011). The pmr(RIP) Δnca-1 double mutant accumulated small amounts of calcium, like the Δpmr strain, but exhibited even more extreme morphological defects. Thus, PMR can apparently replace NCA-1 in the endoplasmic reticulum, but NCA-1 cannot replace PMR. The morphological defects in the Δpmr strain are likely caused, in part, by insufficient concentrations of calcium and manganese in the Golgi compartment; however, PMR is also needed to accumulate normal levels of calcium in the whole cell.

  10. Effect of High-Calcium Diet on Coronary Artery Disease in Ossabaw Miniature Swine With Metabolic Syndrome.

    Science.gov (United States)

    Phillips-Eakley, Alyssa K; McKenney-Drake, Mikaela L; Bahls, Martin; Newcomer, Sean C; Radcliffe, John S; Wastney, Meryl E; Van Alstine, William G; Jackson, George; Alloosh, Mouhamad; Martin, Berdine R; Sturek, Michael; Weaver, Connie M

    2015-08-13

    Calcium is a shortfall essential nutrient that has been a mainstay of osteoporosis management. Recent and limited findings have prompted concern about the contribution of calcium supplementation to cardiovascular risk. A proposed mechanism is through the acceleration of coronary artery calcification. Determining causality between calcium intake and coronary artery calcification has been hindered by a lack of sensitive methodology to monitor early vascular calcium accumulation. The primary study aim was to assess the impact of high calcium intake on coronary artery calcification using innovative calcium tracer kinetic modeling in Ossabaw swine with diet-induced metabolic syndrome. Secondary end points (in vitro wire myography, histopathology, intravascular ultrasound) assessed coronary disease. Pigs (n=24; aged ≈15 months) were fed an atherogenic diet with adequate calcium (0.33% by weight) or high calcium (1.90% from calcium carbonate or dairy) for 6 months. Following 5 months of feeding, all pigs were dosed intravenously with (41)Ca, a rare isotope that can be measured in serum and tissues at a sensitivity of 10(-18) mol/L by accelerator mass spectrometry. Kinetic modeling evaluated early coronary artery calcification using (41)Ca values measured in serial blood samples (collected over 27 days) and coronary artery samples obtained at sacrifice. Serum disappearance of (41)Ca and total coronary artery (41)Ca accumulation did not differ among groups. Secondary end points demonstrated no treatment differences in coronary artery disease or function. There was no detectable effect of high calcium diets (from dairy or calcium carbonate) on coronary artery calcium deposition in metabolic syndrome swine. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  11. High-resolution /sup 27/Al NMR study of calcium aluminate catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Yakerson, V.I.; Nissenbaum, V.D.; Golosman, E.Z.; Mastikhin, V.M.

    1987-06-01

    The high-resolution /sup 27/Al NMR spectra of calcium aluminates, calcium hydroaluminates, and calcium alumina supports and catalysts have been studied. The structures of the anhydrous calcium aluminates (CaAl/sub 2/O/sub 3/, CaAl/sub 4/O/sub 7/, 3CaO x Al/sub 2/O/sub 3/, 12CaO x 7Al/sub 2/O/sub 3/, talyum) consist of aluminum-oxygen tetrahedra and contain various types of aluminum atoms, the nonequivalence of which increases in going from strongly basic to weakly basic aluminates. In the NMR spectrum the signal of octahedrally coordinated aluminum is due to disordered aluminum-oxygen structures. During the forming of the calcium-alumina catalysts and supports the process (AlO/sub 4/) ..-->.. (AlO/sub 6/) takes place during hydration, and (AlO/sub 6/) ..-->.. (AlO/sub 4/) during thermolysis; the nonequivalence of the tetrahedrally coordinated aluminum atoms decreases, while the (AlO/sub 4/):(AlO/sub 6/) ratio decreases as the degree of hydration increases.

  12. Effect of Calcium Oxide Additive on the Performance of Iron Oxide Sorbent for High-Temperature Coal Gas Desulfurization

    Institute of Scientific and Technical Information of China (English)

    Huiling Fan; Kechang Xie; Ju Shangguan; Fang Shen; Chunhu Li

    2007-01-01

    The effect of calcium oxide additive in iron oxide sorbent for hot gas desulfurization was investigated by XRD and TPR techniques. XRD characterization showed that CaO was highly dispersed after the calcination of sorbents. Calcium sulfate formed in the desulfurization was decomposed and regenerated to CaO by reacting with CO before the next sulfidation process. Calcium participated in every sulfidation/regeneration cycle and contributed to the enhancement of sulfur capacity. The TPR results showed that the reduction temperature of the sorbent increased with the increase of the content of calcium. Calcium played a role of retarding reduction. Therefore, the addition of calcium oxide additive will benefit the utilization of iron oxide sorbent in strongly reducing atmospheres.

  13. Recovery of iron and calcium aluminate slag from high-ferrous bauxite by high-temperature reduction and smelting process

    Institute of Scientific and Technical Information of China (English)

    Ying-yi Zhang; Wei L; Yuan-hong Qi; Zong-shu Zou

    2016-01-01

    A high-temperature reduction and smelting process was used to recover iron and calcium aluminate slag from high-ferrous bauxite. The effects of w(CaO)/w(SiO2) ratio, anthracite ratio, and reduction temperature and time on the recovery and size of iron nuggets and on the Al2O3 grade of the calcium aluminate slag were investigated through thermodynamic calculations and experiments. The optimized process conditions were the bauxite/anthracite/slaked lime weight ratio of 100:16.17:59.37, reduction temperature of 1450°C and reduction time of 20 min. Under these conditions, high-quality iron nuggets and calcium aluminate slag were obtained. The largest size and the highest recov-ery rate of iron nuggets were 11.42 mm and 92.79wt%, respectively. The calcium aluminate slag mainly comprised Ca2SiO4 and Ca12Al14O33, with small amounts of FeAl2O4, CaAl2O4, and Ca2Al2SiO7.

  14. Polyamines mediate abnormal Ca/sup 2 +/ transport and Ca/sup 2 +/-induced cardiac cell injury in the calcium paradox

    Energy Technology Data Exchange (ETDEWEB)

    Trout, J.J.; Koenig, H.; Goldstone, A.D.; Lu, C.Y.; Fan, C.C.

    1986-03-05

    Ca/sup 2 +/-free perfusion renders heart cells Ca/sup 2 +/-sensitive so that readmission of Ca/sup 2 +/ causes a sudden massive cellular injury attributed to abnormal entry of Ca/sup 2 +/ into cells (Ca paradox). Hormonal stimulation of Ca/sup 2 +/ fluxes was earlier shown to be mediated by polyamines (PA). 5 min perfusion of rat heart with Ca/sup 2 +/-free medium induce a prompt 40-50% decline in levels of the PA putrescine (PUT), spermidine and spermine and their rate-regulatory synthetic enzyme ornithine decarboxylase (ODC), and readmission of Ca/sup 2 +/-containing medium abruptly (< 30-60 sec) increased the levels of ODC and PA. The ODC inhibitor ..cap alpha..-difluoromethylornithine (DFMO, 5mM) blocked Ca/sup 2 +/ reperfusion-induced increases in ODC and PA and also prevented increased /sup 45/Ca/sup 2 +/ uptake and heart injury, manifested by loss of contractility, release of enzymes (CPK, LDH), myoglobin and protein, and E.M. lesions (contracture bands, mitochondrial changes). 1 mM PUT negated DFMO inhibition, repleted heart PA and restored Ca/sup 2 +/ reperfusion-induced /sup 45/Ca/sup 2 +/ influx and cell injury. These data indicate that the Ca/sup 2 +/-directed depletion-repletion cycle of ODC and PA triggers excessive transsarcolemmal Ca/sup 2 +/ transport leading to the calcium paradox.

  15. Brief RU 38486 Treatment Normalizes the Effects of Chronic Stress on Calcium Currents in Rat Hippocampal CA1 Neurons.

    NARCIS (Netherlands)

    Karst, H.; Joëls, M.

    2007-01-01

    Chronic stress alters many properties in rat brain, like serotonin responsiveness and dendritic morphology. In the present study, we examined (i) whether unpredictable stress during 21 days affects calcium (Ca) currents of CA1 pyramidal neurons recorded on day 22; and (ii) if so, whether this change

  16. Effect of Chemistry and Particle Size on the Performance of Calcium Disilicide Primers. Part 1 - Synthesis of Calcium Silicide (CaSi2) by Rotary Atomization

    Science.gov (United States)

    2010-02-01

    refs. 8 and 9); electrolysis (refs. 10 and 11); calcium hydride (CaH2) and Si (ref. 12); SiC and CaO (ref. 13); and combustion synthesis (ref. 14...obtained using a goiniometer (Phillips Model PW 3040, Phillips, Eindhoven, the Netherlands) using copper (Cu) K„ radiation (X - 1.54183 A) with a graphite...34 Electrolysis of Molten Alkali and Alkaline Earth Silicates." Bull. Soc. Chim., 6,206, 1939. 12. Louis, V. and Franck, H. H., "Silicide of Calcium," Z. Anorq

  17. Biological influence of Ca/P ratio on calcium phosphate coatings by sol-gel processing

    Energy Technology Data Exchange (ETDEWEB)

    Catauro, M., E-mail: michelina.catauro@unina2.it [Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29 (Italy); Papale, F. [Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29 (Italy); Sapio, L.; Naviglio, S. [Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Via L. De Crecchio 7, 80138 Naples (Italy)

    2016-08-01

    The objective of this work has been to develop low temperature sol-gel glass coatings to modify the substrate surface and to evaluate their bioactivity and biocompatibility. Glasses, based on SiO{sub 2}·CaO·P{sub 2}O{sub 5}, were synthesized by the sol-gel technique using tetraethyl orthosilicate, calcium nitrate tetrahydrate and triethyl phosphate as precursors of SiO{sub 2}, CaO and P{sub 2}O{sub 5}, respectively. Those materials, still in the sol phase, have been used to coat substrates by means of the dip-coating technique. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) has been used for characterize coatings and a microstructural analysis has been obtained using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated substrate was immersed in simulated body fluid (SBF) for 21 days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. In order to study the cell behavior and response to our silica based materials, prepared via the sol-gel method, with various Ca/P ratio and coating substrate, we have used the human osteoblast-like U2OS cell line. - Highlights: • Coatings consisting of SiO{sub 2}·CaO·P{sub 2}O{sub 5} glasses were prepared via sol-gel dip coating. • Ca/P molar ratio affects the film morphology and biocompatibility. • Higher cell proliferation was found in response to higher Ca/P ratios coatings. • A growth cell proliferation inhibition was observed in response to lower Ca/P ratio.

  18. Effects of a high intake of unsaturated and saturated oils on intestinal transference of calcium and calcium mobilization from bone in an ovariectomized rat model of osteoporosis.

    Science.gov (United States)

    Chanda, S; Islam, N; Ghosh, T K; Mitra, C

    1999-06-01

    Intestinal transference of calcium and rate of bone turnover were evaluated in ovariectomized rats fed for 15 days with a high amount (30%) of lipid enriched with monounsaturated (groundnut oil), polyunsaturated (sunflower oil) and saturated (coconut oil) fatty acids. The results were compared with those for sham-operated control and ovariectomized groups fed a normal diet (7% groundnut oil). Irrespective of the saturation and unsaturation characteristics, all lipids (edible oils) used in our study considerably decreased the rate of in situ intestinal transference of calcium. Likewise, the activities of intestinal mucosal enzymes, alkaline phosphatase (AP) and calcium ATPase (Ca2+-ATPase) were decreased significantly in all the segments of the small intestine in a descending gradient. Significant changes in bone turnover and bone calcium (Ca) mobilization were confirmed in these animals by marked alterations in plasma AP activity, urinary calcium and phosphate excretion and calcium to creatinine (Ca:creatinine) ratio. Lipid supplementation (30%) in such ovariectomized rats using groundnut oil (monounsaturated), sunflower oil (polyunsaturated) or coconut oil (saturated) for 15 days further enhanced all of the above observed parameters. These results suggest that the intake of high amounts of lipids with different unsaturation and saturation characteristics may be an important factor in determining bone loss in ovariectomized rats.

  19. Interplay of Ca(2+) and Mg (2+) in sodium-calcium exchanger and in other Ca(2+)-binding proteins: magnesium, watchdog that blocks each turn if able.

    Science.gov (United States)

    Levitsky, Dmitri O; Takahashi, Masayuki

    2013-01-01

    Sodium-calcium exchange across plasma membrane is regulated by intracellular calcium ions. The sodium-calcium exchanger (NCX1) is activated by successive saturation of numerous Ca(2+)-binding sites located in the intracellular loop of the protein. The progressive saturation of the binding domain CBD12 by Ca(2+) results in a series of conformational changes of CBD12 as well as of entire NCX1 molecule. Like other soluble and membrane Ca(2+)-binding proteins, NCX1 can also be regulated by Mg(2+) that antagonises Ca(2+) at the level of divalent cation-binding sites. This chapter summarises data on Mg(2+) impacts in the cells. Regulatory action of Mg(2+) on intracellular Ca(2+)-dependent processes can be achieved due to changes of its cytoplasmic level, which take place in the range of [Mg(2+)](i) from 0.5 to 3 mM. Under normal conditions, these changes are ensured by activation of plasmalemmal Mg(2+) transport systems and by variations in ATP level in cytoplasm. In heart and in brain, some pathological conditions, such as hypoxia, ischemia and ischemia followed by reperfusion, are associated with an important increase in intracellular Ca(2+). The tissue damage due to Ca(2+) overload may be prevented by Mg(2+). The protective actions of Mg(2+) can be achieved due to its ability to compete with Ca(2+) for the binding sites in a number of proteins responsible for the rise in intracellular free Ca(2+), including NCX1, in case when the reverse mode of Na(+)/Ca(2+) exchange becomes predominant. Saturation of CBD12 by Mg(2+) results in important changes of NCX1 conformation. Modulating actions of Mg(2+) on the conformation of NCX1 were detected at a narrow range of Mg(2+) concentration, from 0.5 to 1 mM. These data support an idea that variations of intracellular Mg(2+) could modify transmembrane Ca(2+) movements ensured by NCX1.

  20. Direct transformation of calcium sulfite to {alpha}-calcium sulfate hemihydrate in a concentrated Ca-Mg-Mn chloride solution under atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Baohong Guan; Hailu Fu; Jie Yu; Guangming Jiang; Bao Kong; Zhongbiao Wu [Zhejiang University, Hangzhou (China). Department of Environmental Engineering

    2011-01-15

    Massive quantities of sulfite-rich flue gas desulfurization (FGD) scrubber sludge have been generated by coal burning power plants. Utilization of the sulfite-rich sludge for preparing {alpha}-calcium sulfate hemihydrate ({alpha}-HH), an important kind of cementitious material, is of particular interest to electric utilities and environmental preservation. In the experiment, calcium sulfite hemihydrate was directly transformed to {alpha}-HH without the occurrence of calcium sulfate dihydrate (DH). The transformation was performed in a concentrated CaCl{sub 2} solution containing Mg{sup 2+} and Mn{sup 2+} at 95{sup o}C, atmospheric pressure and low pH. The oxidation of calcium sulfite and the subsequent crystallization of {alpha}-HH constitute the whole conversion, during which the oxidation turns out to be the rate controlling step. Solid solution comprised of calcium sulfite hemihydrate and calcium sulfate was found to coexist with {alpha}-HH in the suspension. Calcium sulfate increases and calcium sulfite decreases spontaneously until the solid solution disappears. Thus, it is a potential alternative to utilize sulfite-rich FGD scrubber sludge for the direct preparation of {alpha}-HH. 36 refs., 10 figs., 1 tab.

  1. BARP suppresses voltage-gated calcium channel activity and Ca2+-evoked exocytosis.

    Science.gov (United States)

    Béguin, Pascal; Nagashima, Kazuaki; Mahalakshmi, Ramasubbu N; Vigot, Réjan; Matsunaga, Atsuko; Miki, Takafumi; Ng, Mei Yong; Ng, Yu Jin Alvin; Lim, Chiaw Hwee; Tay, Hock Soon; Hwang, Le-Ann; Firsov, Dmitri; Tang, Bor Luen; Inagaki, Nobuya; Mori, Yasuo; Seino, Susumu; Launey, Thomas; Hunziker, Walter

    2014-04-28

    Voltage-gated calcium channels (VGCCs) are key regulators of cell signaling and Ca(2+)-dependent release of neurotransmitters and hormones. Understanding the mechanisms that inactivate VGCCs to prevent intracellular Ca(2+) overload and govern their specific subcellular localization is of critical importance. We report the identification and functional characterization of VGCC β-anchoring and -regulatory protein (BARP), a previously uncharacterized integral membrane glycoprotein expressed in neuroendocrine cells and neurons. BARP interacts via two cytosolic domains (I and II) with all Cavβ subunit isoforms, affecting their subcellular localization and suppressing VGCC activity. Domain I interacts at the α1 interaction domain-binding pocket in Cavβ and interferes with the association between Cavβ and Cavα1. In the absence of domain I binding, BARP can form a ternary complex with Cavα1 and Cavβ via domain II. BARP does not affect cell surface expression of Cavα1 but inhibits Ca(2+) channel activity at the plasma membrane, resulting in the inhibition of Ca(2+)-evoked exocytosis. Thus, BARP can modulate the localization of Cavβ and its association with the Cavα1 subunit to negatively regulate VGCC activity.

  2. Heterologous expression and biochemical characterization of two calcium-dependent protein kinase isoforms CaCPK1 and CaCPK2 from chickpea.

    Science.gov (United States)

    Syam Prakash, S R; Jayabaskaran, Chelliah

    2006-11-01

    In plants, calcium-dependent protein kinases (CPKs) constitute a unique family of enzymes consisting of a protein kinase catalytic domain fused to carboxy-terminal autoregulatory and calmodulin-like domains. We isolated two cDNAs encoding calcium-dependent protein kinase isoforms (CaCPK1 and CaCPK2) from chickpea. Both isoforms were expressed as fusion proteins in Escherichia coli. Biochemical analyses have identified CaCPK1 and CaCPK2 as Ca(2+)-dependent protein kinases since both enzymes phosphorylated themselves and histone III-S as substrate only in the presence of Ca(2+). The kinase activity of the recombinant enzymes was calmodulin independent and sensitive to CaM antagonists W7 [N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide] and calmidazoilum. Phosphoamino acid analysis revealed that the isoforms transferred the gamma-phosphate of ATP only to serine residues of histone III-S and their autophosphorylation occurred on serine and threonine residues. These two isoforms showed considerable variations with respect to their biochemical and kinetic properties including Ca(2+) sensitivities. The recombinant CaCPK1 has a pH and temperature optimum of pH 6.8-8.6 and 35-42 degrees C, respectively, whereas CaCPK2 has a pH and temperature optimum of pH 7.2-9 and 35-42 degrees C, respectively. Taken together, our results suggest that CaCPK1 and CaCPK2 are functional serine/threonine kinases and may play different roles in Ca(2+)-mediated signaling in chickpea plants.

  3. Calcium receptor expression and function in oligodendrocyte commitment and lineage progression: potential impact on reduced myelin basic protein in CaR-null mice.

    Science.gov (United States)

    Chattopadhyay, Naibedya; Espinosa-Jeffrey, Araceli; Tfelt-Hansen, Jacob; Yano, Shozo; Bandyopadhyay, Sanghamitra; Brown, Edward M; de Vellis, Jean

    2008-08-01

    Oligodendrocytes develop from oligodendrocyte progenitor cells (OPCs), which in turn arise from a subset of neuroepithelial precursor cells during midneurogenesis. Development of the oligodendrocyte lineage involves a plethora of cell-intrinsic and -extrinsic signals. A cell surface calcium-sensing receptor (CaR) has been shown to be functionally expressed in immature oligodendrocytes. Here, we investigated the expression and function of the CaR during oligodendrocyte development. We show that the order of CaR mRNA expression as assessed by quantitative polymerase chain reaction is mature oligodendrocyte > neuron > astrocyte. We next determined the rank order of CaR expression on inducing specification of neural stem cells to the neuronal, oligodendroglial, or astrocytic lineages and found that the relative levels of CaR mRNA expression are OPC > neuron > astrocytes. CaR mRNA expression in cells at various stages of development along the oligodendrocyte lineage revealed that its expression is robustly up-regulated during the OPC stage and remains high until the premyelinating stage, decreasing thereafter by severalfold in the mature oligodendrocyte. In OPCs, high Ca(2+) acting via the CaR promotes cellular proliferation. We further observed that high Ca(2+) stimulates the mRNA levels of myelin basic protein in preoligodendrocytes, which is also CaR mediated. Finally, myelin basic protein levels were significantly reduced in the cerebellum of CaR-null mice during development. Our results show that CaR expression is up-regulated when neural stem cells are specified to the oligodendrocyte lineage and that activation of the receptor results in OPC expansion and differentiation. We conclude that the CaR may be a novel regulator of oligodendroglial development and function.

  4. External bioenergy-induced increases in intracellular free calcium concentrations are mediated by Na+/Ca2+ exchanger and L-type calcium channel.

    Science.gov (United States)

    Kiang, Juliann G; Ives, John A; Jonas, Wayne B

    2005-03-01

    External bioenergy (EBE, energy emitted from a human body) has been shown to increase intracellular calcium concentration ([Ca2+]i, an important factor in signal transduction) and regulate the cellular response to heat stress in cultured human lymphoid Jurkat T cells. In this study, we wanted to elucidate the underlying mechanisms. A bioenergy specialist emitted bioenergy sequentially toward tubes of cultured Jurkat T cells for one 15-minute period in buffers containing different ion compositions or different concentrations of inhibitors. [Ca2+], was measured spectrofluorometrically using the fluorescent probe fura-2. The resting [Ca2+]i in Jurkat T cells was 70 +/- 3 nM (n = 130) in the normal buffer. Removal of external calcium decreased the resting [Ca2+]i to 52 +/- 2 nM (n = 23), indicating that Ca2+ entry from the external source is important for maintaining the basal level of [Ca2+]i. Treatment of Jurkat T cells with EBE for 15 min increased [Ca2+]i by 30 +/- 5% (P EBE did not attenuate [Ca2+]i responsiveness to EBE. Removal of external Ca2+ or Na+, but not Mg2+, inhibited the EBE-induced increase in [Ca2+]i. Dichlorobenzamil, an inhibitor of Na+/Ca2+ exchangers, also inhibited the EBE-induced increase in [Ca2+]i in a concentration-dependent manner with an IC50 of 0.11 +/- 0.02 nM. When external [K+] was increased from 4.5 mM to 25 mM, EBE decreased [Ca2+]i. The EBE-induced increase was also blocked by verapamil, an L-type voltage-gated Ca2+ channel blocker. These results suggest that the EBE-induced [Ca2+]i increase may serve as an objective means for assessing and validating bioenergy effects and those specialists claiming bioenergy capability. The increase in [Ca2+]i is mediated by activation of Na+/Ca2+ exchangers and opening of L-type voltage-gated Ca2+ channels.

  5. The contribution of the sodium-calcium exchanger (NCX) and plasma membrane Ca(2+) ATPase (PMCA) to cerebellar synapse function.

    Science.gov (United States)

    Roome, Chris J; Empson, Ruth M

    2013-01-01

    The cerebellum, a part of the brain critically involved in motor learning and sensory adaptation, expresses high levels of the sodium-calcium exchanger (NCX) and the plasma membrane calcium ATPase (PMCA). Both these transporters control calcium dynamics at a variety of synapses, and here, we draw upon the available literature to discuss how NCX and PMCA work together to shape pre-synaptic calcium dynamics at cerebellar synapses.

  6. High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats.

    Science.gov (United States)

    Charoenphandhu, Narattaphol; Tudpor, Kukiat; Thongchote, Kanogwun; Saengamnart, Wasana; Puntheeranurak, Supaporn; Krishnamra, Nateetip

    2007-02-01

    High physiological prolactin induced positive calcium balance by stimulating intestinal calcium absorption, reducing renal calcium excretion, and increasing bone calcium deposition in female rats. Although prolactin-induced increase in trabecular bone calcium deposition was absent after ovariectomy, its effects on cortical bones were still controversial. The present investigation, therefore, aimed to study the effect of in vivo long-term high physiological prolactin induced by either anterior pituitary (AP) transplantation or 2.5 mg/kg prolactin injection on cortical bones in ovariectomized rats. Since the presence of prolactin receptors (PRLR) in different bones of normal adult rats has not been reported, we first determined mRNA expression of both short- and long-form PRLRs at the cortical sites (tibia and femur) and trabecular sites (calvaria and vertebrae) by using the RT-PCR. Our results showed the mRNA expression of both PRLR isoforms with predominant long form at all sites. However, high prolactin levels induced by AP transplantation in normal rats did not have any effect on the femoral bone mineral density or bone mineral content. By using (45)Ca kinetic study, 2.5 mg/kg prolactin did not alter bone formation, bone resorption, calcium deposition, and total calcium content in tibia and femur of adult ovariectomized rats. AP transplantation also had no effect on the cortical total calcium content in adult ovariectomized rats. Because previous work showed that the effects of prolactin were age dependent and could be modulated by high-calcium diet, interactions between prolactin and these two parameters were investigated. The results demonstrated that 2.0% wt/wt high-calcium diet significantly increased the tibial total calcium content in 9-wk-old young AP-grafted ovariectomized rats but decreased the tibial total calcium content in 22-wk-old adult rats. As for the vertebrae, the total calcium contents in both young and adult rats were not changed by high-calcium

  7. Rare-Earth Calcium Oxyborate Piezoelectric Crystals ReCa4O(BO33: Growth and Piezoelectric Characterizations

    Directory of Open Access Journals (Sweden)

    Fapeng Yu

    2014-07-01

    Full Text Available Rare-earth calcium oxyborate crystals, ReCa4O(BO33 (ReCOB, Re = Er, Y, Gd, Sm, Nd, Pr, and La , are potential piezoelectric materials for ultrahigh temperature sensor applications, due to their high electrical resistivity at elevated temperature, high piezoelectric sensitivity and temperature stability. In this paper, different techniques for ReCOB single-crystal growth are introduced, including the Bridgman and Czochralski pulling methods. Crystal orientations and the relationships between the crystallographic and physical axes of the monoclinic ReCOB crystals are discussed. The procedures for dielectric, elastic, electromechanical and piezoelectric property characterization, taking advantage of the impedance method, are presented. In addition, the maximum piezoelectric coefficients for different piezoelectric vibration modes are explored, and the optimized crystal cuts free of piezoelectric cross-talk are obtained by rotation calculations.

  8. High-Frequency Stimulation-Induced Synaptic Potentiation in Dorsal and Ventral CA1 Hippocampal Synapses: The Involvement of NMDA Receptors, mGluR5, and (L-Type) Voltage-Gated Calcium Channels

    Science.gov (United States)

    Papatheodoropoulos, Costas; Kouvaros, Stylianos

    2016-01-01

    The ability of the ventral hippocampus (VH) for long-lasting long-term potentiation (LTP) and the mechanisms underlying its lower ability for shortlasting LTP compared with the dorsal hippocampus (DH) are unknown. Using recordings of field excitatory postsynaptic potentials (EPSPs) from the CA1 field of adult rat hippocampal slices, we found that…

  9. Calcium-sensing receptors regulate cardiomyocyte Ca2+ signaling via the sarcoplasmic reticulum-mitochondrion interface during hypoxia/reoxygenation

    Directory of Open Access Journals (Sweden)

    Lu Fang-hao

    2010-06-01

    Full Text Available Abstract Communication between the SR (sarcoplasmic reticulum, SR and mitochondria is important for cell survival and apoptosis. The SR supplies Ca2+ directly to mitochondria via inositol 1,4,5-trisphosphate receptors (IP3Rs at close contacts between the two organelles referred to as mitochondrion-associated ER membrane (MAM. Although it has been demonstrated that CaR (calcium sensing receptor activation is involved in intracellular calcium overload during hypoxia/reoxygenation (H/Re, the role of CaR activation in the cardiomyocyte apoptotic pathway remains unclear. We postulated that CaR activation plays a role in the regulation of SR-mitochondrial inter-organelle Ca2+ signaling, causing apoptosis during H/Re. To investigate the above hypothesis, cultured cardiomyocytes were subjected to H/Re. We examined the distribution of IP3Rs in cardiomyocytes via immunofluorescence and Western blotting and found that type 3 IP3Rs were located in the SR. [Ca2+]i, [Ca2+]m and [Ca2+]SR were determined using Fluo-4, x-rhod-1 and Fluo 5N, respectively, and the mitochondrial membrane potential was detected with JC-1 during reoxygenation using laser confocal microscopy. We found that activation of CaR reduced [Ca2+]SR, increased [Ca2+]i and [Ca2+]m and decreased the mitochondrial membrane potential during reoxygenation. We found that the activation of CaR caused the cleavage of BAP31, thus generating the pro-apoptotic p20 fragment, which induced the release of cytochrome c from mitochondria and the translocation of bak/bax to mitochondria. Taken together, these results reveal that CaR activation causes Ca2+ release from the SR into the mitochondria through IP3Rs and induces cardiomyocyte apoptosis during hypoxia/reoxygenation.

  10. Calcium-sensing receptors regulate cardiomyocyte Ca2+ signaling via the sarcoplasmic reticulum-mitochondrion interface during hypoxia/reoxygenation.

    Science.gov (United States)

    Lu, Fang-hao; Tian, Zhiliang; Zhang, Wei-hua; Zhao, Ya-jun; Li, Hu-lun; Ren, Huan; Zheng, Hui-shuang; Liu, Chong; Hu, Guang-xia; Tian, Ye; Yang, Bao-feng; Wang, Rui; Xu, Chang-qing

    2010-06-17

    Communication between the SR (sarcoplasmic reticulum, SR) and mitochondria is important for cell survival and apoptosis. The SR supplies Ca2+ directly to mitochondria via inositol 1,4,5-trisphosphate receptors (IP3Rs) at close contacts between the two organelles referred to as mitochondrion-associated ER membrane (MAM). Although it has been demonstrated that CaR (calcium sensing receptor) activation is involved in intracellular calcium overload during hypoxia/reoxygenation (H/Re), the role of CaR activation in the cardiomyocyte apoptotic pathway remains unclear. We postulated that CaR activation plays a role in the regulation of SR-mitochondrial inter-organelle Ca2+ signaling, causing apoptosis during H/Re. To investigate the above hypothesis, cultured cardiomyocytes were subjected to H/Re. We examined the distribution of IP3Rs in cardiomyocytes via immunofluorescence and Western blotting and found that type 3 IP3Rs were located in the SR. [Ca2+]i, [Ca2+]m and [Ca2+]SR were determined using Fluo-4, x-rhod-1 and Fluo 5N, respectively, and the mitochondrial membrane potential was detected with JC-1 during reoxygenation using laser confocal microscopy. We found that activation of CaR reduced [Ca2+]SR, increased [Ca2+]i and [Ca2+]m and decreased the mitochondrial membrane potential during reoxygenation. We found that the activation of CaR caused the cleavage of BAP31, thus generating the pro-apoptotic p20 fragment, which induced the release of cytochrome c from mitochondria and the translocation of bak/bax to mitochondria. Taken together, these results reveal that CaR activation causes Ca2+ release from the SR into the mitochondria through IP3Rs and induces cardiomyocyte apoptosis during hypoxia/reoxygenation.

  11. Characterization of EhCaBP, a calcium-binding protein of Entamoeba histolytica and its binding proteins.

    Science.gov (United States)

    Yadava, N; Chandok, M R; Prasad, J; Bhattacharya, S; Sopory, S K; Bhattacharya, A

    1997-01-01

    A novel calcium-binding protein (EhCaBP) has been recently identified and characterized from the protozoan parasite Entamoeba histolytica. In order to decipher the function of this protein, a few basic properties were investigated and compared with the ubiquitous Ca(2+)-signal transducing protein calmodulin (CaM). Indirect immunofluorescence and immunoprecipitation analyses using specific antibodies against EhCaBP suggest that it is a soluble cytoplasmic protein with no major post-translational modification. EhCaBP did not stimulate cAMP-phosphodiesterase activity, differentiating it from all known CaMs. Affinity chromatography of [35S]methionine-labelled proteins of E. histolytica trophozoites using EhCaBP-sepharose column showed Ca(2+)-dependent binding of a group of proteins. Radiolabelled proteins from the same extract also bound to CaM-sepharose. However, the proteins bound to the two columns were different as revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. At least one of the EhCaBP-binding proteins became phosphorylated as revealed by in vivo phosphorylation analysis. The binding-proteins could not be detected in E. invadens (a species that is pathogenic in reptiles) and E. moshkovskii (which is found in the human gut but is not pathogenic), two species in which EhCaBP-like protein has not been found. Two distinct Ca(2+)-dependent protein kinases, which get activated by EhCaBP and CaM respectively, were detected in E. histolytica. These kinases require different levels of Ca2+ for their maximal activities. Affinity chromatography also showed the binding of protein kinase(s) to EhCaBP in a Ca(2+)-dependent manner. Our data suggest that there may be novel Ca(2+)-signal transduction pathway in E. histolytica mediated by EhCaBP.

  12. Biological influence of Ca/P ratio on calcium phosphate coatings by sol-gel processing.

    Science.gov (United States)

    Catauro, M; Papale, F; Sapio, L; Naviglio, S

    2016-08-01

    The objective of this work has been to develop low temperature sol-gel glass coatings to modify the substrate surface and to evaluate their bioactivity and biocompatibility. Glasses, based on SiO2·CaO·P2O5, were synthesized by the sol-gel technique using tetraethyl orthosilicate, calcium nitrate tetrahydrate and triethyl phosphate as precursors of SiO2, CaO and P2O5, respectively. Those materials, still in the sol phase, have been used to coat substrates by means of the dip-coating technique. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) has been used for characterize coatings and a microstructural analysis has been obtained using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated substrate was immersed in simulated body fluid (SBF) for 21days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. In order to study the cell behavior and response to our silica based materials, prepared via the sol-gel method, with various Ca/P ratio and coating substrate, we have used the human osteoblast-like U2OS cell line.

  13. CaO insulator coatings on a vanadium-base alloy in liquid 2 at.% calcium-lithium

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.H.; Kassner, T.F. [Argonne National Laboratory, IL (United States)

    1996-10-01

    The electrical resistance of CaO coatings produced on V-4%Cr-4%Ti and V-15%Cr-5%Ti by exposure of the alloy (round bottom samples 6-in. long by 0.25-in. dia.) to liquid lithium that contained 2 at.% dissolved calcium was measured as a function of time at temperatures between 300-464{degrees}C. The solute element, calcium in liquid lithium, reacted with the alloy substrate at these temperatures for 17 h to produce a calcium coating {approx}7-8 {mu}m thick. The calcium-coated vanadium alloy was oxidized to form a CaO coating. Resistance of the coating layer on V-15Cr-5Ti, measured in-situ in liquid lithium that contained 2 at.% calcium, was 1.0 x 10{sup 10} {Omega}-cm{sup 2} at 300{degrees}C and 400 h, and 0.9 x 10{sup 10} {Omega}-cm{sup 2} at 464{degrees}C and 300 h. Thermal cycling between 300 and 464{degrees}C changed the resistance of the coating layer, which followed insulator behavior. Examination of the specimen after cooling to room temperature revealed no cracks in the CaO coating. The coatings were evaluated by optical microscopy, scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), and X-ray analysis. Adhesion between CaO and vanadium alloys was enhanced as exposure time increased.

  14. A highly calcium-selective cation current activated by intracellular calcium release in MDCK cells.

    Science.gov (United States)

    Delles, C; Haller, T; Dietl, P

    1995-08-01

    methods, stimulates La(3+)-inhibitable Ca2+ entry in MDCK cells. Ca2+ entry is at least, in part, mediated by a cation current, which is highly, but not exclusively, selective for Ca2+ over Na+ and insensitive to SK&F 96365.

  15. Calcium chloride doped zinc-cobalt metal-cyanide complex: Unexpected highly activity towards ring-opening polymerization of propylene oxide

    Institute of Scientific and Technical Information of China (English)

    Yi Jun Huang; Xing Hong Zhang; Zheng Jiang Hua; Guo Rong Qi

    2010-01-01

    Highly active calcium chloride (CaCl2) doped Zn-CoⅢ double metal-cyanide (Ca-DMC) catalysts were firstly reported. Ca-DMCs presented a very higher polymer yield (54 kg polymer/g catalyst) at relative low temperature (80-115 ℃) toward ring-opening polymerization (ROP) of propylene oxide (PO) than did DMC catalysts without modification.

  16. A Putative Chloroplast-Localized Ca(2+)/H(+) Antiporter CCHA1 Is Involved in Calcium and pH Homeostasis and Required for PSII Function in Arabidopsis.

    Science.gov (United States)

    Wang, Chao; Xu, Weitao; Jin, Honglei; Zhang, Taijie; Lai, Jianbin; Zhou, Xuan; Zhang, Shengchun; Liu, Shengjie; Duan, Xuewu; Wang, Hongbin; Peng, Changlian; Yang, Chengwei

    2016-08-01

    Calcium is important for chloroplast, not only in its photosynthetic but also nonphotosynthetic functions. Multiple Ca(2+)/H(+) transporters and channels have been described and studied in the plasma membrane and organelle membranes of plant cells; however, the molecular identity and physiological roles of chloroplast Ca(2+)/H(+) antiporters have remained unknown. Here we report the identification and characterization of a member of the UPF0016 family, CCHA1 (a chloroplast-localized potential Ca(2+)/H(+) antiporter), in Arabidopsis thaliana. We observed that the ccha1 mutant plants developed pale green leaves and showed severely stunted growth along with impaired photosystem II (PSII) function. CCHA1 localizes to the chloroplasts, and the levels of the PSII core subunits and the oxygen-evolving complex were significantly decreased in the ccha1 mutants compared with the wild type. In high Ca(2+) concentrations, Arabidopsis CCHA1 partially rescued the growth defect of yeast gdt1Δ null mutant, which is defective in a Ca(2+)/H(+) antiporter. The ccha1 mutant plants also showed significant sensitivity to high concentrations of CaCl2 and MnCl2, as well as variation in pH. Taken these results together, we propose that CCHA1 might encode a putative chloroplast-localized Ca(2+)/H(+) antiporter with critical functions in the regulation of PSII and in chloroplast Ca(2+) and pH homeostasis in Arabidopsis.

  17. All three Ca[superscript 2+]-binding loops of photoproteins bind calcium ions: The crystal structures of calcium-loaded apo-aequorin and apo-obelin

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Lu; Vysotski, Eugene S.; Markova, Svetlana V.; Liu, Zhi-Jie; Lee, John; Rose, John; Wang, Bi-Cheng (Georgia)

    2010-07-13

    The crystal structures of calcium-loaded apoaequorin and apo-obelin have been determined at resolutions 1.7 {angstrom} and 2.2 {angstrom}, respectively. A calcium ion is observed in each of the three EF-hand loops that have the canonical calcium-binding sequence, and each is coordinated in the characteristic pentagonal bipyramidal configuration. The calcium-loaded apo-proteins retain the same compact scaffold and overall fold as the unreacted photoproteins containing the bound substrate, 2-hydroperoxycoelenterazine, and also the same as the Ca{sup 2+}-discharged obelin bound with the product, coelenteramide. Nevertheless, there are easily discerned shifts in both helix and loop regions, and the shifts are not the same between the two proteins. It is suggested that these subtle shifts are the basis of the ability of these photoproteins to sense Ca{sup 2+} concentration transients and to produce their bioluminescence response on the millisecond timescale. A mechanism of intrastructural transmission of the calcium signal is proposed.

  18. Imaging intracellular Ca²⁺ signals in striatal astrocytes from adult mice using genetically-encoded calcium indicators.

    Science.gov (United States)

    Jiang, Ruotian; Haustein, Martin D; Sofroniew, Michael V; Khakh, Baljit S

    2014-11-19

    Astrocytes display spontaneous intracellular Ca(2+) concentration fluctuations ([Ca(2+)]i) and in several settings respond to neuronal excitation with enhanced [Ca(2+)]i signals. It has been proposed that astrocytes in turn regulate neurons and blood vessels through calcium-dependent mechanisms, such as the release of signaling molecules. However, [Ca(2+)]i imaging in entire astrocytes has only recently become feasible with genetically encoded calcium indicators (GECIs) such as the GCaMP series. The use of GECIs in astrocytes now provides opportunities to study astrocyte [Ca(2+)]i signals in detail within model microcircuits such as the striatum, which is the largest nucleus of the basal ganglia. In the present report, detailed surgical methods to express GECIs in astrocytes in vivo, and confocal imaging approaches to record [Ca(2+)]i signals in striatal astrocytes in situ, are described. We highlight precautions, necessary controls and tests to determine if GECI expression is selective for astrocytes and to evaluate signs of overt astrocyte reactivity. We also describe brain slice and imaging conditions in detail that permit reliable [Ca(2+)]i imaging in striatal astrocytes in situ. The use of these approaches revealed the entire territories of single striatal astrocytes and spontaneous [Ca(2+)]i signals within their somata, branches and branchlets. The further use and expansion of these approaches in the striatum will allow for the detailed study of astrocyte [Ca(2+)]i signals in the striatal microcircuitry.

  19. Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca(2+) release during the quasi-steady level of release in twitch fibers from frog skeletal muscle.

    Science.gov (United States)

    Fénelon, Karine; Lamboley, Cédric R H; Carrier, Nicole; Pape, Paul C

    2012-10-01

    Experiments were performed to characterize the properties of the intrinsic Ca(2+) buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([Ca(T)](SR) and [Ca(2+)](SR)) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca(2+) indicator). Results indicate SR Ca(2+) buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca(2+). Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca(2+)](SR) and [Ca(T)](SR) are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca(2+) permeability of the SR, namely d[Ca(T)](SR)/dt ÷ [Ca(2+)](SR) (denoted release permeability), in experiments in which only [Ca(T)](SR) or [Ca(2+)](SR) is measured. In response to a voltage-clamp step to -20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ~50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca(2+) release of 2.3 SR Ca(2+) release channels neighboring each channel activated by its associated voltage sensor. Release permeability at -60 mV increases as [Ca(T)](SR) decreases from its resting physiological level to ~0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca(2+)](SR) inhibits

  20. Effect of calcium-deficiency upon physical properties of La0.6Ca0.4MnO3

    Science.gov (United States)

    Walha, I.; Cheikh-Rouhou, A.; Ehrenberg, H.; Fuess, H.

    2006-09-01

    Structural and magnetic properties of the calcium-defect La0.6Ca0.4-xxMnO3 (0 x 0.2) perovskite manganites have been investigated. Our powder samples have been prepared by the conventional solid state reaction technique at high temperature. Rietveld analysis show that all our synthesized samples crystallize in the orthorhombic perovskite structure with Pnma space group. The Mn atom is coordinated by six oxygen atoms forming an irregular octahedron. With decreasing Ca content the unit cell volume increases. Magnetic measurements as a function of temperature show that all our samples exhibit a paramagnetic-ferromagnetic transition with decreasing temperature.

  1. When is high-Ca+ microdomain required for mitochondrial Ca+ uptake?

    Science.gov (United States)

    Spät, A; Fülöp, L; Koncz, P; Szanda, G

    2009-01-01

    Ca(2+) release from IP(3)-sensitive stores in the endoplasmic reticulum (ER) induced by Ca(2+)-mobilizing agonists generates high-Ca(2+) microdomains between ER vesicles and neighbouring mitochondria. Here we present a model that describes when such microdomains are required and when submicromolar [Ca(2+)] is sufficient for mitochondrial Ca(2+) uptake. Mitochondrial Ca(2+) uptake rate in angiotensin II-stimulated H295R adrenocortical cells correlates with the proximity between ER vesicles and the mitochondrion, reflecting the uptake promoting effect of high-Ca(2+) peri-mitochondrial microdomains. Silencing or inhibition of p38 mitogen-activated protein kinase (MAPK) or inhibition of the novel isoforms of protein kinase C enhances mitochondrial Ca(2+) uptake and abolishes the positive correlation between Ca(2+) uptake and ER-mitochondrion proximity. Inhibition of protein phosphatases attenuates mitochondrial Ca(2+) uptake and also abolishes its positive correlation with ER-mitochondrion proximity. We postulate that during IP(3)-induced Ca(2+) release, Ca(2+) uptake is confined to ER-close mitochondria, because of the simultaneous activation of the protein kinases. Attenuation of Ca(2+) uptake prevents Ca(2+) overload of mitochondria and thus protects the cell against apoptosis. On the other hand, all the mitochondria accumulate Ca(2+) at a non-inhibited rate during physiological Ca(2+) influx through the plasma membrane. Membrane potential is higher in ER-distant mitochondria, providing a bigger driving force for Ca(2+) uptake. Our model explains why comparable mitochondrial Ca(2+) signals are formed in response to K(+) and angiotensin II (equipotent in respect to global cytosolic Ca(2+) signals), although only the latter generates high-Ca(2+) microdomains.

  2. Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete

    Directory of Open Access Journals (Sweden)

    Wei-Jie Fan

    2015-09-01

    Full Text Available High-calcium fly ash (FH is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found.

  3. Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete.

    Science.gov (United States)

    Fan, Wei-Jie; Wang, Xiao-Yong; Park, Ki-Bong

    2015-09-07

    High-calcium fly ash (FH) is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found.

  4. Evaluation of calcium (Ca2+) and hydroxide (OH-) ion diffusion rates of indirect pulp capping materials.

    Science.gov (United States)

    Kurun Aksoy, Merve; Tulga Oz, Firdevs; Orhan, Kaan

    2017-07-08

    The aim of this study was to evaluate and compare the calcium (Ca2+) and hydroxide (OH-) ion release of 4 artificially produced pulp capping materials (MTA, Biodentin, TheraCal LC, Calsimol) used for indirect pulp capping treatment. In total, 70 freshly extracted human third molar teeth were used for the study. Cavities of extracted teeth were prepared by round burs. The remaining dentin thickness (1 ± 0.3 mm) tissue was measured by a micrometer and cone beam computerized tomography. Indirect pulp capping was performed in the cavities using Calcimol, MTA, TheraCal LC and Biodentin. The leached Ca2+ were measured using optical emission spectrometry and the release of OH- ions using a pH meter. The measurements were performed after 24 hours, 7 days and 28 days in saline solution. Statistical analysis was performed using 1-way and 2-way analysis of variance (ANOVA) tests (pmaterials. All the measurements of Biodentin and Theracal LC levels for Ca2+ ions were higher than those of the other materials (pmaterials, Ca2+-ion release increased during the first 7 days followed by a linear decrease during the subsequent study periods. The Biodentine group showed the highest OH- ion rates compared to the other materials in the 24-hour examination period, while the scores gradually decreased during the subsequent measurement periods (pmaterials such as Biodentine and TheraCal LC used in this study may be preferable for indirect pulp capping because of their stimulation of hard tissue formation and ion-releasing ability.

  5. Dry reforming reaction over nickel catalysts supported on nanocrystalline calcium aluminates with different CaO/Al2O3 ratios

    Institute of Scientific and Technical Information of China (English)

    Atiyeh Ranjbar; Mehran Rezaei

    2012-01-01

    Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG,MW:5800) as a surfactant.They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide.The prepared samples were characterized by X-ray diffraction (XRD),N2 adsorption (BET),temperature-programmed reduction and oxidation (TPR-TPO),and scanning electron microscopy (SEM) techniques.Catalysts showed a relatively high catalytic activity and stability.TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced.TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C 12A7 catalysts with higher CaO amount were effective against coke deposition.

  6. Properties of Calcium Acetate Manufactured with Etching Waste Solution and Limestone Sludge as a Cementitious High-Early-Strength Admixture

    Directory of Open Access Journals (Sweden)

    Deuck-Mo Kim

    2016-01-01

    Full Text Available Concrete is one of the most widely used construction materials. There are several methods available to improve its performance, with one of them being the use of high-early-strength admixtures (HESAs. Typical HESAs include calcium nitrate, calcium chloride, and calcium formate (CF. Industrial by-products, such as acetic acid and lime stone sludge (LSS, can be used together to produce calcium acetate (CA, which can subsequently be used as a cementitious HESA. In this study, calcium carbonate and LSS were mixed with cement in weight ratios of 1 : 1, 1 : 1.5, and 1 : 2, and the properties of the as-produced CA were evaluated. CA and CF were mixed with cement in different weight ratios (0, 1, 2, and 3 wt% to obtain CA- and CF-mortars, respectively. The flow behavior, setting time, pH, and compressive strength of these mortars were evaluated, and their X-ray diffraction patterns were also analyzed. It was found that as the CF content in the CF-mortar increased, the initial strength of the mortar also increased. However, it impaired its long-term strength. On the other hand, when 1% CA was mixed with cement, satisfactory early and long-term strengths were achieved. Thus, CA, which is obtained from industrial by-products, can be an effective HESA.

  7. Determination of the Ca/P ratio in calcium phosphates during the precipitation of hydroxyapatite using X-ray diffractometry

    Directory of Open Access Journals (Sweden)

    Zoltan Z. Zyman

    2013-06-01

    Full Text Available The applicability of the X-ray powder diffraction method to the determination of phase composition and Ca/P ratio in precipitates during the nitrous wet synthesis of hydroxyapatite (HA has been shown. The plotted dependences of the phase composition and the Ca/P ratio on the synthesis time can be used as initial data for the development of new and simple processing routes of calcium phosphate ceramics based on HA of any desired composition.

  8. Dynamics and energetics: a consensus analysis of the impact of calcium on EF-CaM protein complex.

    Science.gov (United States)

    Laine, Elodie; Blondel, Arnaud; Malliavin, Thérèse E

    2009-02-18

    We have studied the relationship between dynamical correlations and energetic contributions in an attempt to model the transmission of information inside protein-protein complexes. The complex formed between the edema factor (EF) of Bacillus anthracis and calmodulin (CaM) was taken as an example, as the formation and stability of the complex depend on the calcium complexation level. The effect of calcium through EF-CaM residue network has been investigated with various approaches: 1), the elastic network model; 2), the local feature analysis; 3), the generalized correlations; and 4), the energetic dependency maps (EDMs), on 15-ns molecular dynamics simulations of the complex loaded with 0, 2, or 4 Ca2+ ions. The elastic network model correctly describes the basic architecture of the complex but is poorly sensitive to the level of calcium compared to the other methods. The local feature analysis allows us to characterize the local dynamics of the complex and the propagation of the calcium signal through CaM. The analyses of global dynamics and energetics--through generalized correlations and EDMs--provide a comprehensive picture of EF-CaM architecture and can be unified by using the concept of residue network connectedness. A medium connectedness, defined as the ability of each residue to communicate with all remaining parts of the complex, is observed for the 2Ca2+ level, which was experimentally identified as the most stable form of EF-CaM. The hierarchy of relative stabilities given by the EDMs sheds a new light on the EF-CaM interaction mechanism described experimentally and supports an organization of the complex architecture centered around nucleation points.

  9. Domain III regulates N-type (CaV2.2) calcium channel closing kinetics

    Science.gov (United States)

    Yarotskyy, Viktor; Gao, Guofeng; Peterson, Blaise Z.

    2012-01-01

    CaV2.2 (N-type) and CaV1.2 (L-type) calcium channels gate differently in response to membrane depolarization, which is critical to the unique physiological functions mediated by these channels. We wondered if the source for these differences could be identified. As a first step, we examined the effect of domain exchange between N-type and L-type channels on activation-deactivation kinetics, which were significantly different between these channels. Kinetic analysis of chimeric channels revealed N-channel-like deactivation for all chimeric channels containing N-channel domain III, while activation appeared to be a more distributed function across domains. This led us to hypothesize that domain III was an important regulator of N-channel closing. This idea was further examined with R-roscovitine, which is a trisubstituted purine that slows N-channel deactivation by exclusively binding to activated N-channels. L-channels lack this response to roscovitine, which allowed us to use N-L chimeras to test the role of domain III in roscovitine modulation of N-channel deactivation. In support of our hypothesis, all chimeric channels containing the N-channel domain III responded to roscovitine with slowed deactivation, while those chimeric channels with L-channel domain III did not. Thus a combination of kinetic and pharmacological evidence supports the hypothesis that domain III is an important regulator of N-channel closing. Our results support specialization of gating functions among calcium channel domains. PMID:22205645

  10. Splice variants of the CaV1.3 L-type calcium channel regulate dendritic spine morphology

    Science.gov (United States)

    Stanika, Ruslan; Campiglio, Marta; Pinggera, Alexandra; Lee, Amy; Striessnig, Jörg; Flucher, Bernhard E.; Obermair, Gerald J.

    2016-01-01

    Dendritic spines are the postsynaptic compartments of glutamatergic synapses in the brain. Their number and shape are subject to change in synaptic plasticity and neurological disorders including autism spectrum disorders and Parkinson’s disease. The L-type calcium channel CaV1.3 constitutes an important calcium entry pathway implicated in the regulation of spine morphology. Here we investigated the importance of full-length CaV1.3L and two C-terminally truncated splice variants (CaV1.342A and CaV1.343S) and their modulation by densin-180 and shank1b for the morphology of dendritic spines of cultured hippocampal neurons. Live-cell immunofluorescence and super-resolution microscopy of epitope-tagged CaV1.3L revealed its localization at the base-, neck-, and head-region of dendritic spines. Expression of the short splice variants or deletion of the C-terminal PDZ-binding motif in CaV1.3L induced aberrant dendritic spine elongation. Similar morphological alterations were induced by co-expression of densin-180 or shank1b with CaV1.3L and correlated with increased CaV1.3 currents and dendritic calcium signals in transfected neurons. Together, our findings suggest a key role of CaV1.3 in regulating dendritic spine structure. Under physiological conditions it may contribute to the structural plasticity of glutamatergic synapses. Conversely, altered regulation of CaV1.3 channels may provide an important mechanism in the development of postsynaptic aberrations associated with neurodegenerative disorders. PMID:27708393

  11. Calcium-ammonium exchange experiments on clay minerals using a (45)Ca tracer technique in marine pore water.

    Science.gov (United States)

    Ockert, Charlotte; Wehrmann, Laura M; Kaufhold, Stephan; Ferdelman, Tim G; Teichert, Barbara M A; Gussone, Nikolaus

    2014-01-01

    Understanding cation exchange processes is important for evaluating early diagenetic and synsedimentary processes taking place in marine sediments. To quantify calcium (Ca) exchange and Ca-ammonium exchange in a seawater environment, we performed experiments with a radioactive (45)Ca tracer on clay mineral standards (Fithian illite, montmorillonite and kaolinite) and marine sediments from the North Atlantic Integrated Ocean Drilling Program Site U1306A in artificial seawater (ASW). The results show that equilibrium during the initial attachment of Ca as well as the exchange of Ca by [Formula: see text] is attained in less than 2 min. On average 8-20% of the exchangeable sites of the clay minerals were occupied by Ca in a seawater medium. The conditional selectivity coefficient, describing the [Formula: see text] exchange in ASW is mineral specific and it was determined to be 0.07 for montmorillonite, 0.05 for a natural marine sediment and 0.013 for Fithian illite.

  12. Calcium sensing receptor suppresses human pancreatic tumorigenesis through a novel NCX1/Ca(2+)/β-catenin signaling pathway.

    Science.gov (United States)

    Tang, Bo; Chow, Jimmy Y C; Dong, Tobias Xiao; Yang, Shi-Ming; Lu, De-Sheng; Carethers, John M; Dong, Hui

    2016-07-10

    The calcium sensing receptor (CaSR) is functionally expressed in normal human pancreases, but its pathological role in pancreatic tumorigenesis is currently unknown. We sought to investigate the role of CaSR in pancreatic cancer (PC) and the underlying molecular mechanisms. We revealed that the expression of CaSR was consistently downregulated in the primary cancer tissues from PC patients, which was correlated with tumor size, differentiation and poor survival of the patients. CaSR activation markedly suppressed pancreatic tumorigenesis in vitro and in vivo likely through the Ca(2+) entry mode of Na(+)/Ca(2+) exchanger 1 (NCX1) to induce Ca(2+) entry into PC cells. Moreover, NCX1-mediated Ca(2+) entry resulted in Ca(2+)-dependent inhibition of β-catenin signaling in PC cells, eventually leading to the inhibition of pancreatic tumorigenesis. Collectively, we demonstrate for the first time that CaSR exerts a suppressive function in pancreatic tumorigenesis through a novel NCX1/Ca(2+)/β-catenin signaling pathway. Targeting this specific signaling pathway could be a potential therapeutic strategy for PC.

  13. Automated analysis of calcium spiking profiles with CaSA software: two case studies from root-microbe symbioses.

    Science.gov (United States)

    Russo, Giulia; Spinella, Salvatore; Sciacca, Eva; Bonfante, Paola; Genre, Andrea

    2013-12-26

    Repeated oscillations in intracellular calcium (Ca2+) concentration, known as Ca2+ spiking signals, have been described in plants for a limited number of cellular responses to biotic or abiotic stimuli and most notably the common symbiotic signaling pathway (CSSP) which mediates the recognition by their plant hosts of two endosymbiotic microbes, arbuscular mycorrhizal (AM) fungi and nitrogen fixing rhizobia. The detailed analysis of the complexity and variability of the Ca2+ spiking patterns which have been revealed in recent studies requires both extensive datasets and sophisticated statistical tools. As a contribution, we have developed automated Ca2+ spiking analysis (CaSA) software that performs i) automated peak detection, ii) statistical analyses based on the detected peaks, iii) autocorrelation analysis of peak-to-peak intervals to highlight major traits in the spiking pattern.We have evaluated CaSA in two experimental studies. In the first, CaSA highlighted unpredicted differences in the spiking patterns induced in Medicago truncatula root epidermal cells by exudates of the AM fungus Gigaspora margarita as a function of the phosphate concentration in the growth medium of both host and fungus. In the second study we compared the spiking patterns triggered by either AM fungal or rhizobial symbiotic signals. CaSA revealed the existence of different patterns in signal periodicity, which are thought to contribute to the so-called Ca2+ signature. We therefore propose CaSA as a useful tool for characterizing oscillatory biological phenomena such as Ca2+ spiking.

  14. {sup 41}Ca as a tracer for calcium uptake and deposition in heart tissue during ischemia and reperfusion

    Energy Technology Data Exchange (ETDEWEB)

    Southon, J.R. [Lawrence Livermore National Lab., CA (United States); Bishop, M.S.; Kost, G.J. [California Univ., Davis, CA (United States). Dept. of Medical Pathology and Biomedical Engineering

    1993-09-17

    We have developed techniques and are commencing experiments using enriched {sup 41}Ca as a tracer in isolated rabbit heart preparations. The aims of the study are to measure calcium uptake and deposition in response to cardiac ischemia and reperfusion, and to investigate events and mechanism leading to irreversible myocyte injury.

  15. Penta-substituted benzimidazoles as potent antagonists of the calcium-sensing receptor (CaSR-antagonists).

    Science.gov (United States)

    Gerspacher, Marc; Altmann, Eva; Beerli, René; Buhl, Thomas; Endres, Ralf; Gamse, Rainer; Kameni-Tcheudji, Jacques; Kneissel, Michaela; Krawinkler, Karl Heinz; Missbach, Martin; Schmidt, Alfred; Seuwen, Klaus; Weiler, Sven; Widler, Leo

    2010-09-01

    A series of novel benzimidazole derivatives has been designed via a scaffold morphing approach based on known calcilytics chemotypes. Subsequent lead optimisation led to the discovery of penta-substituted benzimidazoles that exhibit attractive in vitro and in vivo calcium-sensing receptor (CaSR) inhibitory profiles. In addition, synthesis and structure-activity relationship data are provided.

  16. Calcium-activated K+ Channels of Mouse β-cells are Controlled by Both Store and Cytoplasmic Ca2+

    OpenAIRE

    Goforth, P. B.; Bertram, R.; Khan, F. A.; Zhang, M.; Sherman, A.; Satin, L. S.

    2002-01-01

    A novel calcium-dependent potassium current (Kslow) that slowly activates in response to a simulated islet burst was identified recently in mouse pancreatic β-cells (Göpel, S.O., T. Kanno, S. Barg, L. Eliasson, J. Galvanovskis, E. Renström, and P. Rorsman. 1999. J. Gen. Physiol. 114:759–769). Kslow activation may help terminate the cyclic bursts of Ca2+-dependent action potentials that drive Ca2+ influx and insulin secretion in β-cells. Here, we report that when [Ca2+]i handling was disrupted...

  17. Synthesis and characterization of tungsten or calcium doped PZT ceramics; Sintese e caracterizacao do PZT dopado com W ou Ca

    Energy Technology Data Exchange (ETDEWEB)

    Santos, D.M.; Caracas, L.B.; Noronha, R.G.; Santos, M.M.T. dos [Universidade Federal do Maranhao (UFMA), Sao Luis, MA (Brazil). Dept. de Desenho e Tecnologia. Curso de Desenho Industrial; Paiva-Santos, C.O., E-mail: denilson@ufma.b [Universidade Estadual Paulista (IQ/UNESP), Araraquara, SP (Brazil). Inst. de Quimica

    2009-07-01

    Pure and doped (tungsten or calcium) PZT ceramics were prepared by association of the polymeric precursor and partial oxalate method. The phase formation was investigated by thermal analysis (TG/DSC) and X-ray diffraction (XRD). The affect of W or Ca doping PZT and their electrical properties was evaluated. Substitution of W by Ti and Ca by Pb leads to an increase of Curie temperature and broadening of dielectric constant. A typical hysteresis loop was observed at room temperature and the remnant polarization was increased with the content of W and Ca. (author)

  18. Calcium

    Science.gov (United States)

    ... in luck if you like sardines and canned salmon with bones. Almond milk. previous continue Working Calcium ... drinks, and cereals. Other Considerations for Building Bones Vitamin D is essential for calcium absorption, so it's ...

  19. CaV3.2 T-type Ca2+ channels mediate the augmented calcium influx in carotid body glomus cells by chronic intermittent hypoxia.

    Science.gov (United States)

    Makarenko, Vladislav V; Ahmmed, Gias U; Peng, Ying-Jie; Khan, Shakil A; Nanduri, Jayasri; Kumar, Ganesh K; Fox, Aaron P; Prabhakar, Nanduri R

    2016-01-01

    Chronic intermittent hypoxia (CIH) is a hallmark manifestation of sleep apnea. A heightened carotid body activity and the resulting chemosensory reflex mediate increased sympathetic nerve activity by CIH. However, the mechanisms underlying heightened carotid body activity by CIH are not known. An elevation of intracellular calcium ion concentration ([Ca(2+)]i) in glomus cells, the primary oxygen-sensing cells, is an essential step for carotid body activation by hypoxia. In the present study, we examined the effects of CIH on the glomus cell [Ca(2+)]i response to hypoxia and assessed the underlying mechanisms. Glomus cells were harvested from adult rats or wild-type mice treated with 10 days of either room air (control) or CIH (alternating cycles of 15 s of hypoxia and 5 min of room air; 9 episodes/h; 8 h/day). CIH-treated glomus cells exhibited an enhanced [Ca(2+)]i response to hypoxia, and this effect was absent in the presence of 2-(4-cyclopropylphenyl)-N-((1R)-1-[5-[(2,2,2-trifluoroethyl)oxo]-pyridin-2-yl]ethyl)acetamide (TTA-A2), a specific inhibitor of T-type Ca(2+) channels, and in voltage-gated calcium channel, type 3.2 (CaV3.2), null glomus cells. CaV3.2 knockout mice exhibited an absence of CIH-induced hypersensitivity of the carotid body. CIH increased reactive oxygen species (ROS) levels in glomus cells. A ROS scavenger prevented the exaggerated TTA-A2-sensitive [Ca(2+)]i response to hypoxia. CIH had no effect on CaV3.2 mRNA levels. CIH augmented Ca(2+) currents and increased CaV3.2 protein in plasma membrane fractions of human embryonic kidney-293 cells stably expressing CaV3.2, and either a ROS scavenger or brefeldin-A, an inhibitor of protein trafficking, prevented these effects. These findings suggest that CIH leads to an augmented Ca(2+) influx via ROS-dependent facilitation of CaV3.2 protein trafficking to the plasma membrane.

  20. Calcium antagonistic effects of Bambusa Rigida investigated by 45Ca and its protection on myocardial ischemia of rats

    Institute of Scientific and Technical Information of China (English)

    LIN Rushan; YE Ling; YANG Yuanyou; LIAO Jiali; MO Shangwu; LIU Ning

    2008-01-01

    An investigation was conducted using 45Ca as a radioactive tracer to evaluate calcium antagonistic effects of several extracts from Bambusa Rigida in living rats. The relationship between the flavonoid and saccharide contents of Bambusa Rigida and calcium antagonistic effects were also analyzed. The protective effects of the alkali extracts ofBambusa Rigida on myocardial ischemia were investigated in living rats. The results indicated that the alkali extracts of Bambusa Rigida had a prominent influence on Ca2+ influx and efflux in the isolated rat aorta and heart, as they could obviously block 45Ca entering into cells and stimulate efflux of intracellular Ca2+. Moreover, the alkali extracts of Bambusa Rigida had favorable protective effects on myocardial ischemia induced either by isoproterenol injection (ISO) or by the ligation of coronary artery. These results implied that the Bambusa Rigida had attractive potential for the treatment of heart, cerebrovascular and other diseases. However, the conclusion that whether the flavonoid or saccharide in Bambusa Rigida affected the calcium antagonistic effects and Ca2+ channels or not was hard to make within the results of the investigation.

  1. An in vitro evaluation of the Ca/P ratio for the cytocompatibility of nano-to-micron particulate calcium phosphates for bone regeneration.

    Science.gov (United States)

    Liu, Huinan; Yazici, Hilal; Ergun, Celaletdin; Webster, Thomas J; Bermek, Hakan

    2008-09-01

    Calcium phosphate based bioceramics have been widely used for orthopedic applications due to their chemical similarity to natural bone. The Ca/P stoichiometry of calcium phosphates strongly influences their performance under biological conditions, which have not yet been fully elucidated to date. For this reason, the objective of this in vitro study was to understand the relationship between the Ca/P ratio of nano-to-micron particulate calcium phosphate substrates and their biological properties, such as osteoblast (bone-forming cell) viability, collagen production, alkaline phosphatase activity and nitric oxide (NO) production. A group of calcium phosphates with Ca/P ratios between 0.5 and 2.5 were obtained by intentionally adjusting the Ca/P stoichiometry of the initial reactants necessary for calcium phosphate precipitation. For samples with 0.5 and 0.75 Ca/P ratios, tricalcium phosphate (TCP) and Ca(2)P(2)O(7) phases were observed. In contrast, for samples with 1.0 and 1.33 Ca/P ratios, the only stable phase was TCP. For samples with a 1.5 Ca/P ratio, the TCP phase was dominant; however, small amounts of the hydroxyapatite (HA) phase started to appear. For samples with a 1.6 Ca/P ratio, the HA phase was dominant. Lastly, for samples with 2.0 and 2.5 Ca/P ratios, the CaO phase started to appear in the HA phase which was the dominant phase. Moreover, the average grain size and the average pore size decreased from micron-scale (e.g. 1370nm for a 0.5 Ca/P ratio) to nano-scale (e.g. 262nm for a 2.5 Ca/P ratio) with increasing Ca/P ratios. The porosity (%) of calcium phosphate substrates also decreased with increasing Ca/P ratios. Previous in vitro results demonstrated increased osteoblast adhesion on calcium phosphates with higher Ca/P ratios (up to 2.5). The present study showed that the collagen production by osteoblasts was similar between all the calcium phosphates but slightly lower with a 1.6 Ca/P ratio. Greater alkaline phosphatase activity by osteoblasts was

  2. Calcium in pollen-pistil interaction in `Petunia hybrida Hat`. Pt. 3. Localization of Ca{sup 2+} ions and Ca{sup 2+}-ATPase in pollinated pistil

    Energy Technology Data Exchange (ETDEWEB)

    Bednarska, E.; Butowt, R. [Uniwersytet Mikolaja Kopernika, Torun (Poland)

    1995-12-31

    Studies were carried out of Ca{sup 2+} and Ca{sup 2+}-ATPase localization in pollinated (6 and 48 h after pollination) pistils of `Petunia hybrida`. The results were confronted with Ca{sup 2+} localization in mature pollen grain and in unpollinated pistil. It has been found that after pollination the number of Ca{sup 2+} sequestered in the stigmal exudate and in the sporoderm of the pollen grain gets lower. That phenomenon was associated with the appearance of a large number of Sb/Ca precipitates in the submembrane cytoplasm of the germinating pollen. In the vacuolized pollen grain, i.e. grown into a pollen tube, there were only a few precipitates. In the pollen tube, Ca{sup 2+} were found in the organelles of the tip cytoplasm and in the external pectin cell wall. Studies with the use of {sup 45}Ca{sup 2+} have revealed that the source of calcium ions incorporated into the pollen tube tip and its pectin wall is the transmitting tract of the style. In the transmitting tract overgrown with pollen tubes, Ca{sup 2+} were localized in the intercellular matrix and in the transmitting cell. Sb/Ca precipitates occurred in the nuclei, around the secretary vesicles and on the plasmalemma in the transverse walls region. Elevated Ca{sup 2+} level was found in degenerating cells (inhibited pollen tubes, transmitting cells, nucellar cells). The progressing degeneration process of the cells of the transmitting tract of the pollinated pistil was associated with a decrease in the activity of plasmalemma Ca{sup 2+}-ATPase. (author). 30 refs, 19 figs.

  3. Blood compatibility of zinc-calcium phosphate conversion coating on Mg-1.33Li-0.6Ca alloy

    Science.gov (United States)

    Zou, Yu-Hong; Zeng, Rong-Chang; Wang, Qing-Zhao; Liu, Li-Jun; Xu, Qian-Qian; Wang, Chuang; Liu, Zhi-Wei

    2016-09-01

    Magnesium alloys as a new class of biomaterials possess biodegradability and biocompatibility in comparison with currently used metal implants. However, their rapid corrosion rates are necessary to be manipulated by appropriate coatings. In this paper, a new attempt was used to develop a zinc-calcium phosphate (Zn-Ca-P) conversion coating on Mg-1.33Li-0.6Ca alloys to increase the biocompatibility and improve the corrosion resistance. In vitro blood biocompatibility of the alloy with and without the Zn-Ca-P coating was investigated to determine its suitability as a degradable medical biomaterial. Blood biocompatibility was assessed from the hemolysis test, the dynamic cruor time test, blood cell count and SEM observation of the platelet adhesion to membrane surface. The results showed that the Zn-Ca-P coating on Mg-1.33Li-0.6Ca alloys had good blood compatibility, which is in accordance with the requirements for medical biomaterials.

  4. The crystal growth kinetics of alpha calcium sulfate hemihydrate in concentrated CaCl2-HCl solutions

    Science.gov (United States)

    Feldmann, Thomas; Demopoulos, George P.

    2012-07-01

    The crystal growth kinetics of calcium sulfate α-hemihydrate (α-HH) in nearly constant supersaturated HCl-CaCl2 solutions were investigated. Two types of solutions were used, the first had a low HCl (1.4 mol/L) and high CaCl2 (2.8 mol/L) concentration and the second had a high HCl (5.6 mol/L) and low CaCl2 (0.7 mol/L) concentration. These conditions were chosen to represent the first and last stage of a newly developed stage-wise HCl regeneration process. The seeded growth experiments were carried out in a stirred, temperature controlled semi-batch reactor in which supersaturation was kept constant by simultaneous addition of CaCl2 and Na2SO4 solutions. The influence of the following parameters on α-HH crystal growth was studied: temperature (70-95 °C), specific power input of stirring (0.02-1.29 W/kg) and equimolar inflow rate of CaCl2 and Na2SO4 (0-0.6 mol/h). The crystal growth rate was derived from particle size distribution measurements made with the laser light diffraction technique. It was found that the surface area normalized crystal growth rate increased linearly with the molar inflow rate up to 0.3 mol/h, at higher inflow rates no further increase of the growth rate was observed. Temperature and specific power input, within the investigated ranges, did not show a marked effect on the growth rate, attributable to a diffusion/adsorption controlled growth process. An interesting finding of the present research is the establishment of a positive relationship between the narrowing of the width of the particle size distribution with increasing crystal growth rate. The results show that the resulting particle size distribution is positively related to the reagent inflow rate, a finding that can be applied to the industrial design and scale-up of the α-HH crystallization/HCl regeneration process.

  5. Thermoelectric properties of high pressure synthesized lithium and calcium double-filled CoSb3

    Directory of Open Access Journals (Sweden)

    Xiaohui Li

    2017-01-01

    Full Text Available Lithium and calcium are inefficient filling elements of CoSb3 at ambient pressure, but show nice filling behavior under high pressure. In this work, we synthesized Li/Ca double-filled CoSb3 with high pressure synthesis method. The products show the skutterudite structure of Im3¯ symmetry. Thermoelectric properties were effectively enhanced through Li and Ca co-filling. For the optimal Li0.08Ca0.18Co4Sb12 sample, the power factor maintains a relatively high value over the whole measurement temperature range and peaks at 4700μWm−1K−2, meanwhile the lattice thermal conductivity is greatly suppressed, leading to a maximal ZT of 1.18 at 700 K. Current work demonstrates high pressure synthesis as an effective method to produce multiple elemental filled CoSb3 skutterudites.

  6. Effect of the calcium halides, CaCl{sub 2} and CaBr{sub 2}, on hydrogen desorption in the Li–Mg–N–H system

    Energy Technology Data Exchange (ETDEWEB)

    Bill, Rachel F. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Reed, Daniel; Book, David [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Anderson, Paul A., E-mail: p.a.anderson@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2015-10-05

    Highlights: • H{sub 2} desorption from 2LiNH{sub 2}–MgH{sub 2}–xCaX{sub 2} (x = 0, 0.1, 0.15; X = Cl, Br) samples studied. • Addition of calcium halides reduced the desorption temperature in all samples. • Peak H{sub 2} release was around 150 °C lower in ball-milled than in hand-ground samples. • The 2LiNH{sub 2}–MgH{sub 2}–0.15CaBr{sub 2} sample showed the lowest peak desorption temperature. • CaBr{sub 2} reduced the activation energy to 78.8 kJ mol{sup −1}, 24% less than the undoped sample. - Abstract: Calcium-halide-doped lithium amide–magnesium hydride samples were prepared both by hand-grinding and ball-milling 2LiNH{sub 2}–MgH{sub 2}–xCaX{sub 2} (x = 0, 0.1, and 0.15; X = Cl or Br). The addition of calcium halides reduced the hydrogen desorption temperature in all samples. The ball-milled undoped sample (2LiNH{sub 2}–MgH{sub 2}) began to desorb hydrogen at around 125 °C and peaked at 170 °C. Hydrogen desorption from the 0.15 mol CaCl{sub 2}-containing sample began ca 30 °C lower than that of the undoped sample and peaked at 150 °C. Both the onset and peak temperatures of the CaBr{sub 2} sample (x = 0.15) were reduced by 15 °C compared to the chloride. Kissinger’s method was used to calculate the effective activation energy (E{sub a}) for the systems: E{sub a} for the 0.15 mol CaCl{sub 2}-containing sample was found to be 91.8 kJ mol{sup −1} and the value for the 0.15 mol CaBr{sub 2}-containing sample was 78.8 kJ mol{sup −1}.

  7. The Reliability of Highly Elevated CA 19-9 Levels

    Directory of Open Access Journals (Sweden)

    B. R. Osswald

    1993-01-01

    Full Text Available CA 19-9 is used as a tumour marker of the upper gastrointestinal tract. However, extremely elevated CA 19-9 levels are found also in patients with benign diseases. Cholestasis was present in 97.1 % of patients with high elevated CA 19-9, independent of their primary disease. 50% of patients with non-malignant diseases and increased CA 19-9 levels showed liver cirrhosis, cholecystitis, pancreatitis and/or hepatitis. In 8.8% no explanation was found for the extremely high CA 19-9 level. The results provide evidence of different factors influencing the CA 19-9 level.

  8. Effects of calcium phosphate nanoparticles on Ca-PO4 composite.

    Science.gov (United States)

    Xu, H H K; Weir, M D; Sun, L; Takagi, S; Chow, L C

    2007-04-01

    Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO(4) release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0-75%. The flexural strengths in MPa (mean +/- SD; n = 6) of DCPA-whisker composites ranged from (106 +/- 39) at 0% fillers to (114 +/- 23) at 75% fillers, similar to (112 +/- 22) of a non-releasing composite (TPH) (p > 0.1). The composite with 75% fillers in a NaCl solution (133 mmol/L, pH = 7.4, 37 degrees C) yielded a Ca concentration of (0.65 +/- 0.02) mmol/L and PO(4) of (2.29 +/- 0.07) mmol/L. Relationships were established between ion-release and DCPA volume fraction V(DCPA): Ca = 4.46 V(DCPA)(1.6,) and = 66.9 V(DCPA)(2.6). Nano-DCPA-whisker PO(4) composites had high strength and released high levels of Ca-PO(4) requisite for remineralization. These new nano-composites could provide the needed combination of stress-bearing and caries-inhibiting capabilities.

  9. High Glucose Enhances Isoflurane-Induced Neurotoxicity by Regulating TRPC-Dependent Calcium Influx.

    Science.gov (United States)

    Liu, ZhongJie; Ma, ChangQing; Zhao, Wei; Zhang, QingGuo; Xu, Rui; Zhang, HongFei; Lei, HongYi; Xu, ShiYuan

    2017-01-06

    Isoflurane is a commonly used inhalational anesthetic that can induce neurotoxicity via elevating cytosolic calcium (Ca(2+)). High glucose regulates the expression of a family of non-selective cation channels termed transient receptor potential canonical (TRPC) channels that may contribute to Ca(2+) influx. In the present study, we investigated whether high glucose enhances isoflurane-induced neurotoxicity by regulating TRPC-dependent Ca(2+) influx. First, we evaluated toxic damage in mice primary cultured hippocampal neurons and human neuroblastoma cells (SH-SY5Y cells) after hyperglycemia and isoflurane exposure. Next, we investigated cytosolic Ca(2+) concentrations, TRPC mRNA expression levels and tested the effect of the TRPC channel blocker SKF96365 on cytosolic Ca(2+) levels in cells treated with high glucose or/and isoflurane. Finally, we employed knocked down TRPC6 to demonstrate the role of TRPC in high glucose-mediated enhancement of isoflurane-induced neurotoxicity. The results showed that high glucose could enhance isoflurane-induecd toxic damage in primary hippocampal neurons and SH-SY5Y cells. High glucose enhanced the isoflurane-induced increase of cytosolic Ca(2+) in SH-SY5Y cells. High glucose elevated TRPC mRNA expression, especially that of TRPC6. SKF96365 and knock down of TRPC6 were able to inhibit the high glucose-induced increase of cytosolic Ca(2+) and decrease isoflurane-induced neurotoxicity in SH-SY5Y cells cultured with high glucose. Our findings indicate that high glucose could elevate TRPC expression, thus increasing Ca(2+) influx and enhancing isoflurane-induced neurotoxicity.

  10. Treatment of Ruptured Ovarian Endometrioma with Extremely High CA 125, Moderately High CA 19-9 and CA 15-3 Level

    Directory of Open Access Journals (Sweden)

    Muzeyyen Duran

    2013-06-01

    Full Text Available In this case report, a ruptured ovarian endometrioma with a very high CA-125 level, moderately elevated CA 19-9, and CA 15-3 levels is presented. A 20 years old patient, complaining from pelvic pain, 5 cm adnexial mass was detected on left side. Biochemical examination was revealed very high CA-125 value (2556IU/ml, moderately elevated CA 19-9 (134IU/ml, and CA 15-3 (65IU/ml values. Laparoscopy was done and a ruptured ovarian endometrioma of 5 cm was seen during operation. After the total excision of the cyst, tumor markers fell rapidly. Very high CA-125 value, moderately elevated CA19-9, and CA 15-3 values can be seen in cases with ruptured endometrioma. In young patients, endometrioma must be considered firstly and laparoscopy should be applied instead of more invasive methods unless there was any finding or strong suspicion about malignancy.

  11. Mitochondrial calcium uniporter MCU supports cytoplasmic Ca2+ oscillations, store-operated Ca2+ entry and Ca2+-dependent gene expression in response to receptor stimulation.

    Directory of Open Access Journals (Sweden)

    Krishna Samanta

    Full Text Available Ca2+ flux into mitochondria is an important regulator of cytoplasmic Ca2+ signals, energy production and cell death pathways. Ca2+ uptake can occur through the recently discovered mitochondrial uniporter channel (MCU but whether the MCU is involved in shaping Ca2+ signals and downstream responses to physiological levels of receptor stimulation is unknown. Here, we show that modest stimulation of leukotriene receptors with the pro-inflammatory signal LTC4 evokes a series of cytoplasmic Ca2+ oscillations that are rapidly and faithfully propagated into mitochondrial matrix. Knockdown of MCU or mitochondrial depolarisation, to reduce the driving force for Ca2+ entry into the matrix, prevents the mitochondrial Ca2+ rise and accelerates run down of the oscillations. The loss of cytoplasmic Ca2+ oscillations appeared to be a consequence of enhanced Ca2+-dependent inactivation of InsP3 receptors, which arose from the loss of mitochondrial Ca2+ buffering. Ca2+ dependent gene expression in response to leukotriene receptor activation was suppressed following knockdown of the MCU. In addition to buffering Ca2+ release, mitochondria also sequestrated Ca2+ entry through store-operated Ca2+ channels and this too was prevented following loss of MCU. MCU is therefore an important regulator of physiological pulses of cytoplasmic Ca2+.

  12. Mitochondrial calcium uniporter MCU supports cytoplasmic Ca2+ oscillations, store-operated Ca2+ entry and Ca2+-dependent gene expression in response to receptor stimulation.

    Science.gov (United States)

    Samanta, Krishna; Douglas, Sophie; Parekh, Anant B

    2014-01-01

    Ca2+ flux into mitochondria is an important regulator of cytoplasmic Ca2+ signals, energy production and cell death pathways. Ca2+ uptake can occur through the recently discovered mitochondrial uniporter channel (MCU) but whether the MCU is involved in shaping Ca2+ signals and downstream responses to physiological levels of receptor stimulation is unknown. Here, we show that modest stimulation of leukotriene receptors with the pro-inflammatory signal LTC4 evokes a series of cytoplasmic Ca2+ oscillations that are rapidly and faithfully propagated into mitochondrial matrix. Knockdown of MCU or mitochondrial depolarisation, to reduce the driving force for Ca2+ entry into the matrix, prevents the mitochondrial Ca2+ rise and accelerates run down of the oscillations. The loss of cytoplasmic Ca2+ oscillations appeared to be a consequence of enhanced Ca2+-dependent inactivation of InsP3 receptors, which arose from the loss of mitochondrial Ca2+ buffering. Ca2+ dependent gene expression in response to leukotriene receptor activation was suppressed following knockdown of the MCU. In addition to buffering Ca2+ release, mitochondria also sequestrated Ca2+ entry through store-operated Ca2+ channels and this too was prevented following loss of MCU. MCU is therefore an important regulator of physiological pulses of cytoplasmic Ca2+.

  13. Slowed N-Type Calcium Channel (CaV2.2) Deactivation by the Cyclin-Dependent Kinase Inhibitor Roscovitine

    OpenAIRE

    Buraei, Zafir; Anghelescu, Mircea; Elmslie, Keith S.

    2005-01-01

    The lack of a calcium channel agonist (e.g., BayK8644) for CaV2 channels has impeded their investigation. Roscovitine, a potent inhibitor of cyclin-dependent kinases 1, 2, and 5, has recently been reported to slow the deactivation of P/Q-type calcium channels (CaV2.1). We show that roscovitine also slows deactivation (EC50 ∼53 μM) of N-type calcium channels (CaV2.2) and investigate gating alterations induced by roscovitine. The onset of slowed deactivation was rapid (∼2 s), which contrasts wi...

  14. Expression of the calcium receptor CaR in the parathyroid of secondary hyperparathyroidism patients

    Institute of Scientific and Technical Information of China (English)

    王宁宁; 王笑云; 彭韬; 吴宏飞; 胡建明; 赵卫红; 俞香宝

    2004-01-01

    @@ The effects of calcium on parathyroid hormone (PTH) has further discovered in recent years. It has been known that calcium ion concentration in the extracellular fluid is a major determinant of PTH secretion. The relationship between serum intact PTH (iPTH) and calcium ion levels is described by a sigmoidal curve. The calcium concentration that produces half-maximal change in PTH release (the midpoint between maximal and minimal change in PTH release) represents the sensitivity of parathyroid cells to serum calcium. In secondary hyperparathyroidism (SHPT) patients, higher calcium concentrations are needed to suppress PTH secretion, as demonstrated by the PTH-calcium sigmoidal curve. The loss of physiological control over the secretory function and growth of parathyroid tissue in hyperparathyroid disease is still incompletely understood.

  15. Reusability and Stability Tests of Calcium Oxide Based Catalyst (K2O/CaO-ZnO for Transesterification of Soybean Oil to Biodiesel

    Directory of Open Access Journals (Sweden)

    Istadi Istadi

    2016-03-01

    Full Text Available This paper was purposed for testing reusability and stability of calcium oxide-based catalyst (K2O/CaO-ZnO over transesterification reaction of soybean oil with methanol to produce biodiesel. The K2O/CaO-ZnO catalyst was synthesized by co-precipitation method of calcium and zinc nitrates followed by impregnation of potassium nitrate. The fresh and used catalysts were tested after regeneration. The catalysts were characterized by Scanning Electron Microscopy (SEM, X-ray Diffraction (XRD, and BET Surface Area in order to compare the catalyst structure between the fresh and used catalysts. The catalyst testing in transesterification proses was carried out at following operating conditions, i.e. catalyst weight of 6 wt.%, oil to methanol mole ratio of 1:15, and temperature of 60 oC. In addition, metal oxide leaching of K2O/CaO-ZnO catalyst during reaction was also tested. From the results, the catalysts exhibited high catalytic activity (80% fatty acid methyl ester (FAME yield after three-cycles of usage and acceptable reusability after regeneration. The catalyst also showed acceptable stability of catalytic activity, even after three-cycles of usage. Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th November 2015; Revised: 16th January 2016; Accepted: 16th January 2016 How to Cite: Istadi, I., Mabruro, U., Kalimantini, B.A.,  Buchori, L., Anggoro, D.D. (2016. Reusability and Stability Tests of Calcium Oxide Based Catalyst (K2O/CaO-ZnO for Transesterification of Soybean Oil to Biodiesel. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 34-39. (doi:10.9767/bcrec.11.1.413.34-39 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.413.34-39

  16. Structure and magnetic properties of lanthanum and calcium-deficient La{sub 0.5}Ca{sub 0.5}MnO{sub 3} manganites

    Energy Technology Data Exchange (ETDEWEB)

    Walha, I. [Institute for Materials Science, University of Technology, D64287-Darmstadt (Germany); Laboratoire de Physique des Materiaux, Faculte des Sciences de Sfax, BP 802, 3018 Sfax (Tunisia); Ehrenberg, H. [Institute for Materials Science, University of Technology, D64287-Darmstadt (Germany); Fuess, H. [Institute for Materials Science, University of Technology, D64287-Darmstadt (Germany); Cheikhrouhou, A. [Laboratoire de Physique des Materiaux, Faculte des Sciences de Sfax, BP 802, 3018 Sfax (Tunisia)]. E-mail: Abdel.Cheikhrouhou@fss.rnu.tn

    2007-05-16

    The effects of small amounts (5%) of calcium and lanthanum-deficiency on the structure and magnetic properties of polycrystalline La{sub 0.5}Ca{sub 0.5}MnO{sub 3} manganite have been investigated. Our samples have been synthesized using the conventional solid-state reaction technique at high temperatures. Rietveld analysis confirms the orthorhombic perovskite structure with Pnma space group. The calcium-deficiency leads to an increase of the unit cell volume while the lanthanum-deficient material exhibits a decrease in the unit cell volume compared to the parent compound. At high temperature, La{sub 0.5}Ca{sub 0.5}MnO{sub 3} is a paramagnetic insulator and upon cooling it exhibits a paramagnetic-ferromagnetic transition at T {sub C} {approx} 230 K followed by a ferromagnetic-antiferromagnetic one at T {sub N} {approx} 150 K. Five percent of Ca-deficient destroys the ferromagnetic-antiferromagnetic transition observed at low temperature in the parent compound while the sample with 5% of La-deficient behaves as antiferromagnet below 100 K.

  17. Early infantile epileptic encephalopathy associated with a high voltage gated calcium channelopathy.

    Science.gov (United States)

    Edvardson, Simon; Oz, Shimrit; Abulhijaa, Fida Aziz; Taher, Flora Barghouthi; Shaag, Avraham; Zenvirt, Shamir; Dascal, Nathan; Elpeleg, Orly

    2013-02-01

    Early infantile epileptic encephalopathies usually manifest as severely impaired cognitive and motor development and often result in a devastating permanent global developmental delay and intellectual disability. A large set of genes has been implicated in the aetiology of this heterogeneous group of disorders. Among these, the ion channelopathies play a prominent role. In this study, we investigated the genetic cause of infantile epilepsy in three affected siblings. Homozygosity mapping in DNA samples followed by exome analysis in one of the patients resulted in the identification of a homozygous mutation, p.L1040P, in the CACNA2D2 gene. This gene encodes the auxiliary α(2)δ2 subunit of high voltage gated calcium channels. The expression of the α(2)δ2-L1040P mutant instead of α(2)δ2 wild-type (WT) in Xenopus laevis oocytes was associated with a notable reduction of current density of both N (Ca(V)2.2) and L (Ca(V)1.2) type calcium channels. Western blot and confocal imaging analyses showed that the α(2)δ2-L1040P mutant was synthesised normally in oocyte but only the α(2)δ2-WT, and not the α(2)δ2-L1040P mutant, increased the expression of α(1B), the pore forming subunit of Ca(V)2.2, at the plasma membrane. The expression of α(2)δ2-WT with Ca(V)2.2 increased the surface expression of α(1B) 2.5-3 fold and accelerated current inactivation, whereas α(2)δ2-L1040P did not produce any of these effects. L1040P mutation in the CACNA2D2 gene is associated with dysfunction of α(2)δ2, resulting in reduced current density and slow inactivation in neuronal calcium channels. The prolonged calcium entry during depolarisation and changes in surface density of calcium channels caused by deficient α(2)δ2 could underlie the epileptic phenotype. This is the first report of an encephalopathy caused by mutation in the auxiliary α(2)δ subunit of high voltage gated calcium channels in humans, illustrating the importance of this subunit in normal physiology of the

  18. Calcium modulates promoter occupancy by the Entamoeba histolytica Ca2+-binding transcription factor URE3-BP.

    Science.gov (United States)

    Gilchrist, Carol A; Leo, Megan; Line, C Genghis; Mann, Barbara J; Petri, William A

    2003-02-14

    The Entamoeba histolytica upstream regulatory element 3-binding protein (URE3-BP) binds to the URE3 sequence of the Gal/GalNAc-inhibitable lectin hgl5 and ferredoxin 1 (fdx) gene promoters. This binding can be inhibited in vitro by addition of calcium. Two EF-hand motifs, which are associated with the ability to bind calcium, are present in the amino acid sequence of URE3-BP. Mutation of the second EF-hand motif in URE3-BP resulted in the loss of calcium inhibition of DNA binding as monitored by electrophoretic mobility shift assay. Chromatin immunoprecipitation assays revealed that URE3-BP was physically bound to the hgl5 and fdx promoters in vivo. Parasite intracellular calcium concentrations were altered by changes in extracellular calcium. Promoter occupancy was lost when intracellular calcium levels were increased by coordinate increases in extracellular calcium. Increased intracellular calcium also resulted in decreased levels of URE3-BP mRNA. Together these results demonstrate that changes in extracellular calcium result in changes in URE3-BP mRNA and in the ability of URE3-BP to bind to URE3-containing promoters. Modulation of URE3-BP by calcium may represent an important mechanism of control of gene expression in E. histolytica.

  19. Enhanced structural and optical properties of the polyaniline-calcium tungstate (PANI-CaWO4 nanocomposite for electronics applications

    Science.gov (United States)

    Sabu, N. Aloysius; Francis, Xavier; Anjaly, Jose; Sankararaman, S.; Varghese, Thomas

    2017-06-01

    In this article, we report the synthesis and characterization of polyaniline-calcium tungstate nanocomposite, a novel material for potential applications. The PANI-CaWO4 nanocomposite was prepared by in situ oxidative polymerization of aniline in the presence of CaWO4 nanoparticles dispersed in ethanol. Investigations using X-ray diffraction, Fourier-transformed infrared spectroscopy, UV-visible, photoluminescence and Raman spectroscopy confirmed the formation of the nanocomposite of PANI with CaWO4 nanoparticles. Scanning electron microscopy revealed almost uniform distribution of CaWO4 nanoparticles in the polyaniline matrix. These studies also confirmed electronic structure modification as a result of incorporating CaWO4 nanoparticles in PANI. Composite formation resulted in large decrease in the optical band gap and enhanced photoluminescence. The augmented structural, optical and photoluminescence properties of the PANI-CaWO4 nanocomposite can be used to explore potential applications in micro- and optoelectronics. This is the first report presenting synthesis and characterization of the PANI-CaWO4 nanocomposite.

  20. Microdomain Ca2+ Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca2+ Influx

    Science.gov (United States)

    Erxleben, Christian; Klauke, Norbert; Flötenmeyer, Matthias; Blanchard, Marie-Pierre; Braun, Claudia; Plattner, Helmut

    1997-01-01

    In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca2+-activated currents across the cell membrane (Erxleben, C., and H. Plattner. 1994. J. Cell Biol. 127:935– 945). We now show by voltage clamp and extracellular recordings that the product of current × time (As) closely parallels the number of exocytotic events. We suggest that Ca2+ mobilization from subplasmalemmal storage compartments, covering almost the entire cell surface, is a key event. In fact, after local stimulation, Ca2+ imaging with high time resolution reveals rapid, transient, local signals even when extracellular Ca2+ is quenched to or below resting intracellular Ca2+ concentration ([Ca2+]e ⩽ [Ca2+]i). Under these conditions, quenched-flow/freeze-fracture analysis shows that membrane fusion is only partially inhibited. Increasing [Ca2+]e alone, i.e., without secretagogue, causes rapid, strong cortical increase of [Ca2+]i but no exocytosis. In various cells, the ratio of maximal vs. minimal currents registered during maximal stimulation or single exocytotic events, respectively, correlate nicely with the number of Ca stores available. Since no quantal current steps could be observed, this is again compatible with the combined occurrence of Ca2+ mobilization from stores (providing close to threshold Ca2+ levels) and Ca2+ influx from the medium (which per se does not cause exocytosis). This implies that only the combination of Ca2+ flushes, primarily from internal and secondarily from external sources, can produce a signal triggering rapid, local exocytotic responses, as requested for Paramecium defense. PMID:9024690

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

    Science.gov (United States)

    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.

  2. Measuring mitochondrial and cytoplasmic Ca2+ in EGFP expressing cells with a low-affinity calcium Ruby and its dextran conjugate.

    Science.gov (United States)

    Luccardini, Camilla; Yakovlev, Aleksey V; Pasche, Mathias; Gaillard, Stéphane; Li, Dongdong; Rousseau, France; Ly, Romain; Becherer, Ute; Mallet, Jean-Maurice; Feltz, Anne; Oheim, Martin

    2009-03-01

    The limited choice and poor performance of red-emitting calcium (Ca(2+)) indicators have hampered microfluorometric measurements of the intracellular free Ca(2+) concentration in cells expressing yellow- or green-fluorescent protein constructs. A long-wavelength Ca(2+) indicator would also permit a better discrimination against cellular autofluorescence than the commonly used fluorescein-based probes. Here, we report an improved synthesis and characterization of Calcium Ruby, a red-emitting probe consisting of an extended rhodamine chromophore (578/602 nm peak excitation/emission) conjugated to BAPTA and having an additional NH(2) linker arm. The low-affinity variant (K(D,Ca) approximately 30 microM) with a chloride in meta position that was specifically designed for the detection of large and rapid Ca(2+) transients. While Calcium Ruby is a mitochondrial Ca(2+)probe, its conjugation, via the NH(2) tail, to a 10,000 MW dextran abolishes the sub-cellular compartmentalization and generates a cytosolic Ca(2+) probe with an affinity matched to microdomain Ca(2+) signals. As an example, we show depolarization-evoked Ca(2+) signals triggering the exocytosis of individual chromaffin granules. Calcium Ruby should be of use in a wide range of applications involving dual- or triple labeling schemes or targeted sub-cellular Ca(2+) measurements.

  3. Influence of precipitated calcium carbonate (CaCO3) on shiitake (Lentinula edodes) yield and mushroom size.

    Science.gov (United States)

    Royse, Daniel J; Sanchez-Vazquez, Jose E

    2003-11-01

    Synthetic substrate consisting of oak sawdust (50%), white millet (28%), winter rye (11%) and soft red wheat bran (11%) was non-supplemented or supplemented with 0.2%, 0.4% or 0.6% (dry weight basis) precipitated calcium carbonate (CaCO(3)). Shiitake (Lentinula edodes) was grown in two crops to determine the effect of three CaCO(3) levels on mushroom yield and size. Yields and biological efficiencies (averages for two crops) from substrates non-supplemented with CaCO(3) were lower by 14.1%, 18.4% and 24.9% compared to treatments supplemented with 0.2%, 0.4% and 0.6% CaCO(3), respectively. Mushroom size (weight) was larger with non-supplemented substrate (16.8 g) compared to substrate supplemented with 0.6% CaCO(3) (15.1 g). However, mushroom production was more consistent from crop to crop when 0.6% CaCO(3) was added to substrate.

  4. Salicylic Acid and Calcium Treatments Improves Wheat Vigor, Lipids and Phenolics Under High Salinity.

    Science.gov (United States)

    Yücel Candan, Nilgün; Heybet Elif, Haklı

    2016-12-01

    Seed vigor is a complex physiological trait required to ensure the rapid and uniform emergence of plants in the field under different environmental conditions. Therefore, salicylic acid (SA, 0.5 mM) and calcium (Ca2+, 50 mM) priming were used as exogenous growth enhancers to stimulate wheat (Triticum durum Desf. cv. Yelken) seed vigor under high salinity. The main aim was to address whether priming of wheat with SA, Ca2+ and SA+Ca (SA, 0.5 mM + Ca2+, 50 mM; their combination) could bring about supplementary agronomic benefits particularly under stressful environments such as salinity. Exogenous application of SA or Ca2+ alone improved plant behavior in the presence of salinity stress. Nevertheless, the best results in terms of growth, seed vigor and total phenolic - flavonoids, chlorophyll - carotenoids contents and phenylalanine ammonia-lyase (PAL), ascorbic acide oxidase (AAO) activities and lipid peroxidation levels (LPO) were obtained in response to the combined SA+Ca treatment.

  5. Genetic interactions between the Golgi Ca2+/H+ exchanger Gdt1 and the plasma membrane calcium channel Cch1/Mid1 in the regulation of calcium homeostasis, stress response and virulence in Candida albicans.

    Science.gov (United States)

    Wang, Yanan; Wang, Junjun; Cheng, Jianqing; Xu, Dayong; Jiang, Linghuo

    2015-11-01

    The Golgi-localized Saccharomyces cerevisiae ScGdt1 is a member of the cation/Ca(2+) exchanger superfamily. We show here that Candida albicans CaGdt1 is the functional homolog of ScGdt1 in calcium sensitivity, and shows genetic interactions with CaCch1 or CaMid1 in response to ER stresses. In addition, similar to ScCCH1 and ScMID1, deletion of either CaCCH1 or CaMID1 leads to a growth sensitivity of cells to cold stress, which can be suppressed by deletion of CaGDT1. Furthermore, deletion of CaCCH1 leads to a severe delay in filamentation of C. albicans cells, and this defect is abolished by deletion of CaGDT1. In contrast, CaGDT1 does not show genetic interaction with CaMID1 in filamentation. Interestingly, C. albicans cells lacking both CaMID1 and CaGDT1 exhibit an intermediate virulence between C. albicans cells lacking CaCCH1 (non-virulent) and C. albicans cells lacking CaGDT1 (partially virulent), while C. albicans cells lacking both CaCCH1 and CaGDT1 are not virulent in a mouse model of systemic candidiasis. Therefore, CaGdt1 genetically interacts with the plasma membrane calcium channel, CaCch1/CaMid1, in the response of C. albicans cells to cold and ER stresses and antifungal drug challenge as well as in filamentation and virulence.

  6. Extracellular Ca2+ is a danger signal activating the NLRP3 inflammasome through G protein-coupled calcium sensing receptors

    DEFF Research Database (Denmark)

    Rossol, Manuela; Pierer, Matthias; Raulien, Nora;

    2012-01-01

    Activation of the NLRP3 inflammasome enables monocytes and macrophages to release high levels of interleukin-1ß during inflammatory responses. Concentrations of extracellular calcium can increase at sites of infection, inflammation or cell activation. Here we show that increased extracellular cal......, and this effect was inhibited in GPRC6A(-/-) mice. Our results demonstrate that G-protein-coupled receptors can activate the inflammasome, and indicate that increased extracellular calcium has a role as a danger signal and amplifier of inflammation....

  7. Cloning and characterization of a novel calcium channel toxin-like gene BmCa1 from Chinese scorpion Mesobuthus martensii Karsch.

    Science.gov (United States)

    Zhijian, Cao; Yun, Xie; Chao, Dai; Shunyi, Zhu; Shijin, Yin; Yingliang, Wu; Wenxin, Li

    2006-06-01

    Many studies have been carried on peptides and genes encoding scorpion toxins from the venom of Mesobuthus martensii Karsch (synonym: Buthus martensii Karsch, BmK), such as Na+, K+ and Cl- channel modulators. In this study, a novel calcium channel toxin-like gene BmCa1 was isolated and characterized from the venom of Mesobuthus martensii Karsch. First, a partial cDNA sequence of the Ca2+ channel toxin-like gene was identified by random sequencing method from a venomous gland cDNA library of Mesobuthus martensii Karsch. The full-length sequence of BmCa1 was then obtained by 5'RACE technique. The peptide deduced from BmCa1 precursor nucleotide sequence contains a 27-residue signal peptide and a 37-residue mature peptide. Although BmCa1 and other scorpion toxins are different at the gene and protein primary structure levels, BmCa1 has the same precursor nucleotide organization and cysteine arrangement as that of the first subfamily members of calcium channel scorpion toxins. Genomic DNA sequence of BmCa1 was also cloned by PCR. Sequence analysis showed that BmCa1 gene consists of three exons separated by two introns of 72 bp and 1076 bp in length, respectively. BmCa1 is the first calcium channel toxin-like gene cloned from the venom of Mesobuthus martensii Karsch and potentially represents a novel class of calcium channel toxins in scorpion venoms.

  8. Effect of calcium-deficiency upon physical properties of La{sub 0.6}Ca{sub 0.4}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Walha, I. [Laboratoire de Physique des Materiaux, Faculte des Sciences de Sfax, B.P. 802, 3018 Sfax (Tunisia); Institute for Materials Science, University of Technology, 64287 Darmstadt (Germany); Cheikh-Rouhou, A. [Laboratoire de Physique des Materiaux, Faculte des Sciences de Sfax, B.P. 802, 3018 Sfax (Tunisia); Ehrenberg, H.; Fuess, H. [Institute for Materials Science, University of Technology, 64287 Darmstadt (Germany)

    2006-09-15

    Structural and magnetic properties of the calcium-defect La{sub 0.6}Ca{sub 0.4-x}{open_square}{sub x}MnO{sub 3} (0{<=}x{<=}0.2) perovskite manganites have been investigated. Our powder samples have been prepared by the conventional solid state reaction technique at high temperature. Rietveld analysis show that all our synthesized samples crystallize in the orthorhombic perovskite structure with Pnma space group. The Mn atom is coordinated by six oxygen atoms forming an irregular octahedron. With decreasing Ca content the unit cell volume increases. Magnetic measurements as a function of temperature show that all our samples exhibit a paramagnetic-ferromagnetic transition with decreasing temperature. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Osmotic induction of calcium accumulation in human embryonic kidney cells detected with a high sensitivity FRET calcium sensor.

    Science.gov (United States)

    Hou, Bi-Huei; Takanaga, Hitomi; Griesbeck, Oliver; Frommer, Wolf B

    2009-08-01

    Calcium serves as a second messenger in glucose-triggered insulin secretion of pancreatic cells. Less is known about sugar signaling in non-excitable cells. Here, the high sensitivity FRET calcium sensor TN-XXL was used to characterize glucose-induced calcium responses in non-excitable human embryonic kidney HEK293T cells. HEK293T cells responded to perfusion with glucose with a sustained and concentration-dependent increase in cytosolic calcium levels. Sucrose and mannitol triggered comparable calcium responses, suggesting that the increase of the calcium concentration was caused by osmotic effects. HEK293T cells are characterized by low endogenous glucose uptake capacity as shown with a high sensitivity glucose sensor. Consistently, when glucose influx was artificially increased by co-expression of GLUT glucose transporters, the glucose-induced calcium increase was significantly reduced. Neither calcium depletion, nor gadolinium or thapsigargin were able to inhibit the calcium accumulation. Taken together, membrane impermeable osmolytes such as sucrose and mannitol lead to an increase in calcium levels, while the effect of glucose depends on the cell's glucose uptake capacity and will thus vary between cell types in the body that differ in their glucose uptake capacity.

  10. Auranofin, an Anti-Rheumatic Gold Compound, Modulates Apoptosis by Elevating the Intracellular Calcium Concentration ([Ca2+]i in MCF-7 Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Elizabeth Varghese

    2014-11-01

    Full Text Available Auranofin, a transition metal complex is used for the treatment of rheumatoid arthritis but is also an effective anti-cancer drug. We investigate the effects of Auranofin in inducing cell death by apoptosis and whether these changes are correlated to changes of intracellular calcium concentration ([Ca2+]i in breast cancer cells (MCF-7. Cytotoxicity of Auranofin was evaluated using MTS assay and the Trypan blue dye exclusion method. With fluorescent dyes SR-FLICA and 7-AAD apoptotic death and necrotic death were differentiated by Flow cytometry. A concentration dependent decrease in the viability occurred and cells were shifted to the apoptotic phase. Intracellular calcium ([Ca2+]i was recorded using florescence microscopy and a calcium sensitive dye (Fluo-4 AM with a strong negative correlation (r = −0.713 to viability. Pharmacological modulators 2-APB (50 μM, Nimodipine (10 μM, Caffeine (10 mM, SKF 96365(20 μM were used to modify calcium entry and release. Auranofin induced a sustained increase of [Ca2+]i in a concentration and time dependent manner. The use of different blockers of calcium channels did not reveal the source for the rise of [Ca2+]i. Overall, elevation of [Ca2+]i by Auranofin might be crucial for triggering Ca2+-dependent apoptotic pathways. Therefore, in anti-cancer therapy, modulating [Ca2+]i should be considered as a crucial factor for the induction of cell death in cancer cells.

  11. Crystal structure of dimeric cardiac L-type calcium channel regulatory domains bridged by Ca[superscript 2+]·calmodulins

    Energy Technology Data Exchange (ETDEWEB)

    Fallon, Jennifer L.; Baker, Mariah R.; Xiong, Liangwen; Loy, Ryan E.; Yang, Guojun; Dirksen, Robert T.; Hamilton, Susan L.; Quiocho, Florante A.; (Baylor); (Rochester-Med)

    2009-11-10

    Voltage-dependent calcium channels (Ca(V)) open in response to changes in membrane potential, but their activity is modulated by Ca(2+) binding to calmodulin (CaM). Structural studies of this family of channels have focused on CaM bound to the IQ motif; however, the minimal differences between structures cannot adequately describe CaM's role in the regulation of these channels. We report a unique crystal structure of a 77-residue fragment of the Ca(V)1.2 alpha(1) subunit carboxyl terminus, which includes a tandem of the pre-IQ and IQ domains, in complex with Ca(2+).CaM in 2 distinct binding modes. The structure of the Ca(V)1.2 fragment is an unusual dimer of 2 coiled-coiled pre-IQ regions bridged by 2 Ca(2+).CaMs interacting with the pre-IQ regions and a canonical Ca(V)1-IQ-Ca(2+).CaM complex. Native Ca(V)1.2 channels are shown to be a mixture of monomers/dimers and a point mutation in the pre-IQ region predicted to abolish the coiled-coil structure significantly reduces Ca(2+)-dependent inactivation of heterologously expressed Ca(V)1.2 channels.

  12. Effect of the calcium antagonists bepridil (CERM-1978) and verapamil on Ca++-dependent slow action potentials in frog skeletal muscle.

    Science.gov (United States)

    Kerr, L M; Sperelakis, N

    1982-07-01

    The calcium slow channels found in cardiac and smooth muscle are blocked by calcium-antagonistic agents. In the present study, the effects of the Ca++-antagonistic drugs bepridil and verapamil on the slow action potentials (APs) found in the frog skeletal muscle were examined. Slow APs were induced in Cl-- free (acetate substituted), Na+-free (sucrose substituted), high K+ (25 mM)media. A conventional two-microelectrode recording technique was used. Amplitude of the slow APs increases linearly with log [Ca]o with a slope of 28.2 mV/decade, suggesting that Ca++ is the major inward current carrier because this value approaches the theoretical slope of 29 mV/decade (at 21 degrees C) predicted by the Nernst equation for a divalent cation. Duration also increases with increases in [Ca]o. The slow APs were abolished by glycerol shock treatment, which disconnects the T-tubules from the surface membrane, suggesting that the slow APs originate in the T-tubules. Verapamil and bepridil depress the amplitude of the slow APs in a use-dependent manner at concentrations of 5 X 10-9 to 1 X 10-6 M and abolish the slow APs at 5 X 10-6 M. These drugs also decrease the rates of rise of the slow APs. Bepridil decreases the duration of the slow APs, whereas verapamil has little effect, suggesting that bepridil, in addition to blocking the slow channels, might also increase gk. Thus, the slow channels found in the T-tubular system of frog skeletal muscle have some of the same properties of slow channels in vascular smooth muscle and cardiac muscle.

  13. The initial phases of calcium and magnesium phosphates precipitated from solutions of high to medium concentrations

    Science.gov (United States)

    Abbona, F.; Madsen, H. E. Lundager; Boistelle, R.

    1986-04-01

    The precipitation of calcium and magnesium phosphates is performed at 25°C by mixing solutions of ammonium phosphate and solutions of calcium and magnesium chlorides under the condition [ P] = [ Ca] + [ Mg] in large pH intervals. Before any nucleation the phosphate concentration ranges from 0.50M to 0.01M. The phases first precipitated are CaHPO 4·2H 2O (brushite), CaHPO 4 (monetite), Ca 3(PO 4) 2· xH 2O (amorphous calcium phosphate), MgNH 4PO 4·6H 2O (struvite), and MgHPO 4·3H 2O (newberyite). The precipitation fields of each phase are determined and discussed as a function of pH, composition and supersaturation. The solutions are even supersaturated with respect to several other calcium phosphates but they never occur first even if their supersaturation is the highest.

  14. Caveats and limitations of plate reader-based high-throughput kinetic measurements of intracellular calcium levels.

    Science.gov (United States)

    Heusinkveld, Harm J; Westerink, Remco H S

    2011-08-15

    Calcium plays a crucial role in virtually all cellular processes, including neurotransmission. The intracellular Ca(2+) concentration ([Ca(2+)](i)) is therefore an important readout in neurotoxicological and neuropharmacological studies. Consequently, there is an increasing demand for high-throughput measurements of [Ca(2+)](i), e.g. using multi-well microplate readers, in hazard characterization, human risk assessment and drug development. However, changes in [Ca(2+)](i) are highly dynamic, thereby creating challenges for high-throughput measurements. Nonetheless, several protocols are now available for real-time kinetic measurement of [Ca(2+)](i) in plate reader systems, though the results of such plate reader-based measurements have been questioned. In view of the increasing use of plate reader systems for measurements of [Ca(2+)](i) a careful evaluation of current technologies is warranted. We therefore performed an extensive set of experiments, using two cell lines (PC12 and B35) and two fluorescent calcium-sensitive dyes (Fluo-4 and Fura-2), for comparison of a linear plate reader system with single cell fluorescence microscopy. Our data demonstrate that the use of plate reader systems for high-throughput real-time kinetic measurements of [Ca(2+)](i) is associated with many pitfalls and limitations, including erroneous sustained increases in fluorescence, limited sensitivity and lack of single cell resolution. Additionally, our data demonstrate that probenecid, which is often used to prevent dye leakage, effectively inhibits the depolarization-evoked increase in [Ca(2+)](i). Overall, the data indicate that the use of current plate reader-based strategies for high-throughput real-time kinetic measurements of [Ca(2+)](i) is associated with caveats and limitations that require further investigation. Copyright © 2011 Elsevier Inc. All rights reserved.

  15. In vivo imaging of human breast cancer mouse model with high level expression of calcium sensing receptor at 3T.

    Science.gov (United States)

    Baio, Gabriella; Fabbi, Marina; Emionite, Laura; Cilli, Michele; Salvi, Sandra; Ghedin, Piero; Prato, Sabina; Carbotti, Grazia; Tagliafico, Alberto; Truini, Mauro; Neumaier, Carlo Emanuele

    2012-03-01

    To demonstrate that manganese can visualise calcium sensing receptor (CaSR)-expressing cells in a human breast cancer murine model, as assessed by clinical 3T magnetic resonance (MR). Human MDA-MB-231-Luc or MCF7-Luc breast cancer cells were orthotopically grown in NOD/SCID mice to a minimum mass of 5 mm. Mice were evaluated on T1-weighted sequences before and after intravenous injection of MnCl(2). To block the CaSR-activated Ca(2+) channels, verapamil was injected at the tumour site 5 min before Mn(2+) administration. CaSR expression in vivo was studied by immunohistochemistry. Contrast enhancement was observed at the tumour periphery 10 min after Mn(2+) administration, and further increased up to 40 min. In verapamil-treated mice, no contrast enhancement was observed. CaSR was strongly expressed at the tumour periphery. Manganese enhanced magnetic resonance imaging can visualise CaSR-expressing breast cancer cells in vivo, opening up possibilities for a new MR contrast agent. • Manganese contrast agents helped demonstrate breast cancer cells in an animal model. • Enhancement was most marked in cells with high calcium sensing receptor expression. • Manganese uptake was related to the distribution of CaSR within the tumour. • Manganese MRI may become useful to investigate human breast cancer.

  16. Behavior in Wet Atmosphere of an Amorphous Calcium Phosphate with an Atomic Ca/P Ratio of 1.33

    Science.gov (United States)

    Rodrigues, A.; Lebugle, A.

    1999-12-01

    This study deals with the behavior, in a wet atmosphere at 40, 60, and 80°C, of an amorphous calcium phosphate with an atomic Ca/P ratio of 1.33. The wet atmosphere treatment leads to the formation of a thin film of water on the sample surface, allowing its maturation. At 40 and 60°C, the upper surface, rich in adsorbed water, crystallizes into triclinic OCP, a compound with structural water. The other deeper part leads to apatitic OCP. Whatever the temperature, both types of crystal decompose with time, in various stages, to finally lead to a mixture of hydroxyapatite and monetite.

  17. Formation of calcium phosphates by vapour diffusion in highly concentrated ionic micro-droplets

    Energy Technology Data Exchange (ETDEWEB)

    Iafisco, M. [Alma Mater Studiorum Universita di Bologna, Dipartimento di Chimica ' ' G. Ciamician' ' , Via Selmi 2, 40126 Bologna (Italy); Universita del Piemonte Orientale, Dipartimento di Scienze Mediche, Via Solaroli 4, 28100 Novara (Italy); Delgado-Lopez, J.M.; Gomez-Morales, J.; Hernandez-Hernandez, M.A.; Rodriguez-Ruiz, I. [Laboratorio de Estudios Cristalograficos, IACT CSIC-UGR, Edificio Lopez Neyra, Avenida del Conocimiento, s/n 18100 Armilla (Spain); Roveri, N. [Alma Mater Studiorum Universita di Bologna, Dipartimento di Chimica ' ' G. Ciamician' ' , Via Selmi 2, 40126 Bologna (Italy)

    2011-08-15

    In this work we have used the sitting drop vapour diffusion technique, employing the ''crystallization mushroom '' to analyze the evolution of calcium phosphate crystallization in micro-droplets containing high initial concentrations of Ca{sup 2+} and HPO{sub 4}{sup 2-}. The decomposition of NH{sub 4}HCO{sub 3} solution produces vapours of NH{sub 3} and CO{sub 2} which diffuse through the droplets containing an aqueous solution of Ca(CH{sub 3}COO){sub 2} and (NH{sub 4}){sub 2}HPO{sub 4}. The result is the increase of pH by means of the diffusion of NH{sub 3} gas and the doping of the calcium phosphate with CO{sub 3}{sup 2-} ions by means of the diffusion of CO{sub 2} gas. The pH of the crystallization process is monitored and the precipitates at different times are characterized by XRD, FTIR, TGA, SEM and TEM techniques. The slow increase of pH and the high concentration of Ca{sup 2+} and HPO{sub 4}{sup 2-} in the droplets induce the crystallization of three calcium phosphate phases: dicalcium phosphate dihydrate (DCPD, brushite), octacalcium phosphate (OCP) and carbonate-hydroxyapatite (HA). The amount of HA nanocrystals with needle-like morphology and dimensions of about 100 nm, closely resembling the inorganic phase of bones, gradually increases, with the precipitation time up to 7 days, whereas the amount of DCPD, growing along the b axis, increases up to 3 days. Then, DCDP crystals start to hydrolyze yielding OCP nanoribbons and HA nanocrystals. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Utilization of Snail (Achatina fulica Shell Waste for Synthesis of Calcium Tartrate Tetrahydrate (CaC4H4O6.4H2O Single Crystals in Silica Gel

    Directory of Open Access Journals (Sweden)

    Imam Sakdi

    2012-01-01

    Full Text Available Snail (Achatina fulica shell waste is massively produced by many home industries in Indonesia, especially in East Java. The snail shell is known for high calcium; therefore it is potential to be used as calcium source of supernatant in the synthesis of piezoeletric material, such as single crystal of calcium tartrate tetrahydrate (CaTT. The aim of this research is to study the synthesis and characterization of CaTT or CaC4H4O6.4H2O from snail shell waste in silica gel. Supernatant solution of CaCl2 was prepared from CaO, which previously made by calcinating the shell at 1000°C, and then reacted with HCl 1,5M. Synthesis of CaTT was conducted in a single-tube reaction at room temperature in which silica gel was used as growth medium with gelling time of 10 days and growth time of 2 weeks. The pH of gel and CaCl2 concentration were varied, 3.00; 3.50; 4.00; 4.50; 5.00; and 0.27; 0.36; 0.45; 0.54 M respectively, in order to obtain optimum condition of the synthesis, which is indicated from crystal yields. The synthesized crystals were characterized by atomic adsorption spectrophotometry (AAS, infrared spectroscopy (IR and powder X-ray diffraction (XRD. Experimental data shows that optimum condition was obtained at pH of 3.50 and [CaCl2] of 0.45M with yield of 69.37%. The obtained single crystal has clear color and octahedral-like shape with size ranged between 4 – 9 mm. Analysis data by FTIR and powder XRD confirmed that the obtained crystal was CaTT single crystals with crystal system of orthorhombic.

  19. Numerical Modeling Calcium and CaMKII Effects in the SA Node.

    Science.gov (United States)

    Yaniv, Yael; Maltsev, Victor A

    2014-01-01

    Sinoatrial node (SAN) is the primary heart pacemaker which initiates each heartbeat under normal conditions. Numerous experimental data have demonstrated that Ca(2+-) and CaMKII-dependent processes are crucially important for regulation of SAN cells. However, specific mechanisms of this regulation and their relative contribution to pacemaker function remain mainly unknown. Our review summarizes available data and existing numerical modeling approaches to understand Ca(2+) and CaMKII effects on the SAN. Data interpretation and future directions to address the problem are given within the coupled-clock theory, i.e., a modern view on the cardiac pacemaker cell function generated by a system of sarcolemmal and intracellular proteins.

  20. A diet high in meat protein and potential renal acid load increases fractional Ca absorption and urinary Ca excretion, without affecting markers of bone resorption or formation in postmenopausal women

    Science.gov (United States)

    Objective: The objective was to determine the effects of high dietary protein (mostly meat) and high potential renal acid load (PRAL) on calcium (Ca) balance and markers of bone metabolism. Methods: In a randomized crossover design, sixteen healthy postmenopausal women consumed two diets: one with l...

  1. Concentration changeability of phosphorus, calcium and magnesium in selected partial drainage basins of the River Drwęca

    Directory of Open Access Journals (Sweden)

    Pius Bożena

    2015-12-01

    Full Text Available The paper presents the results of the research conducted between November 2008 and October 2009. The research included seasonal dynamics of the flow and runoff of phosphorus compounds (TP and P-PO43-, as well as Ca2+ and Mg2+ from 13 partial drainage basins of the River Drwęca. Water levels were registered automatically every day by recorders, and measurements of the flow were conducted once a month. Major differences were found in the water abundance as indicated by specific discharges in individual, partial drainage basins: from 1.87 dm3 s-1 km-2 (Lubianka - a lower part of the River Drwęca drainage basin to 8.22 dm3 s-1 km-2 (Gizela - an upper part of the River Drwęca drainage basin. The studied rivers were characterised by very diverse average content of total phosphorus compounds: from 0.047 mg dm-3 (Iłga to 0.816 mg dm-3 (Sandela; calcium: from 47.18 mg dm-3 (Iłga to 131.65 mg dm-3 (Trynka; and magnesium: from 9.71 mg dm-3 (Wel to 36.76 mg dm-3 (Struga Rychnowska. Analysis of variance carried out on hydrochemical properties of the studied rivers divides the rivers into two separate groups: rivers with much higher content of phosphorus, calcium and magnesium compounds (Struga Rychnowska, Trynka, Ruziec, Lubianka, Kujawka, Sandela and Gizela, and a group of rivers with low content of these compounds (Brynica, Brodniczanka, Skarlanka, Wel, Iłga.

  2. A High-Throughput Automated Microfluidic Platform for Calcium Imaging of Taste Sensing

    Directory of Open Access Journals (Sweden)

    Yi-Hsing Hsiao

    2016-07-01

    Full Text Available The human enteroendocrine L cell line NCI-H716, expressing taste receptors and taste signaling elements, constitutes a unique model for the studies of cellular responses to glucose, appetite regulation, gastrointestinal motility, and insulin secretion. Targeting these gut taste receptors may provide novel treatments for diabetes and obesity. However, NCI-H716 cells are cultured in suspension and tend to form multicellular aggregates, preventing high-throughput calcium imaging due to interferences caused by laborious immobilization and stimulus delivery procedures. Here, we have developed an automated microfluidic platform that is capable of trapping more than 500 single cells into microwells with a loading efficiency of 77% within two minutes, delivering multiple chemical stimuli and performing calcium imaging with enhanced spatial and temporal resolutions when compared to bath perfusion systems. Results revealed the presence of heterogeneity in cellular responses to the type, concentration, and order of applied sweet and bitter stimuli. Sucralose and denatonium benzoate elicited robust increases in the intracellular Ca2+ concentration. However, glucose evoked a rapid elevation of intracellular Ca2+ followed by reduced responses to subsequent glucose stimulation. Using Gymnema sylvestre as a blocking agent for the sweet taste receptor confirmed that different taste receptors were utilized for sweet and bitter tastes. This automated microfluidic platform is cost-effective, easy to fabricate and operate, and may be generally applicable for high-throughput and high-content single-cell analysis and drug screening.

  3. Ecto-nucleoside triphosphate diphosphohydrolase 2 modulates local ATP-induced calcium signaling in human HaCaT keratinocytes.

    Directory of Open Access Journals (Sweden)

    Chia-Lin Ho

    Full Text Available Keratinocytes are the major building blocks of the human epidermis. In many physiological and pathophysiological conditions, keratinocytes release adenosine triphosphate (ATP as an autocrine/paracrine mediator that regulates cell proliferation, differentiation, and migration. ATP receptors have been identified in various epidermal cell types; therefore, extracellular ATP homeostasis likely determines its long-term, trophic effects on skin health. We investigated the possibility that human keratinocytes express surface-located enzymes that modulate ATP concentration, as well as the corresponding receptor activation, in the pericellular microenvironment. We observed that the human keratinocyte cell line HaCaT released ATP and hydrolyzed extracellular ATP. Interestingly, ATP hydrolysis resulted in adenosine diphosphate (ADP accumulation in the extracellular space. Pharmacological inhibition by ARL 67156 or gene silencing of the endogenous ecto-nucleoside triphosphate diphosphohydrolase (NTPDase isoform 2 resulted in a 25% reduction in both ATP hydrolysis and ADP formation. Using intracellular calcium as a reporter, we found that although NTPDase2 hydrolyzed ATP and generated sustainable ADP levels, only ATP contributed to increased intracellular calcium via P2Y2 receptor activation. Furthermore, knocking down NTPDase2 potentiated the nanomolar ATP-induced intracellular calcium increase, suggesting that NTPDase2 globally attenuates nucleotide concentration in the pericellular microenvironment as well as locally shields receptors in the vicinity from being activated by extracellular ATP. Our findings reveal an important role of human keratinocyte NTPDase2 in modulating nucleotide signaling in the extracellular milieu of human epidermis.

  4. Dispersed-Fluorescence Spectroscopy of Jet-Cooled Calcium Ethoxide Radical (CaOC_2H_5)

    Science.gov (United States)

    Paul, Anam C.; Reza, Md Asmaul; Liu, Jinjun

    2016-06-01

    Metal-containing free radicals are important intermediates in metal-surface reactions and in the interaction between metals and organic molecules. In the present work, dispersed fluorescence (DF) spectra of the calcium ethoxide radical (CaOC_2H_5) have been obtained by pumping the {tilde A^2}{A}' ← {tilde X^2}{A}' and the {tilde B^2}{A}'' ← {tilde X^2}{A}' origin bands in its laser-induced fluorescence (LIF) spectrum. CaOC_2H_5 radicals were produced by 1064 nm laser ablation of calcium grains in the presence of ethanol under jet-cooled conditions. Dominant transitions in the vibrationally resolved DF spectra are well reproduced using Franck-Condon factors predicted by complete active space self-consistent (CASSCF) calculations. Differences in transition intensities between the {tilde A^2}{A}' → {tilde X^2}{A}' and the {tilde B^2}{A}'' → {tilde X^2}{A}' DF spectra are attributed to the pseudo-Jahn-Teller interaction between the tilde A ^2 A' and the tilde B ^2 A'' states. Collision-induced population transfer between these two excited electronic states results in additional peaks in the DF spectra.

  5. Incorporating magnesium and calcium cations in porous organic frameworks for high-capacity hydrogen storage.

    Science.gov (United States)

    Wang, Lin; Sun, Yingxin; Sun, Huai

    2011-01-01

    We propose incorporating a bi-functional group consisting of magnesium or calcium cations and a 1,2,4,5-benzenetetroxide anion (C6H2O4(4-)) in porous materials to enhance the hydrogen storage capacity. The C6H2O4M2 bifunctional group is highly stable and polarized, and each group provides 18 (M = Mg) or 22 (M = Ca) binding sites for hydrogen molecules with an average binding energy of ca. 10 kJ mol(-1) per hydrogen molecule based on RIMP2/ TZVPP calculations. Two porous materials (PAF-Mg or PAF-Ca) constructed with the bi-functional groups show remarkable improvement in hydrogen uptakes at normal ambient conditions. At 233 K and 10 MPa, the predicted gravimetric uptakes are 6.8 and 6.4 wt% for PAF-Mg and PAF-Ca respectively. This work reveals that fabricating materials with large numbers of binding sites and relatively low binding energies is a promising approach to achieve high capacity for on-board storage of hydrogen.

  6. Calcium signaling in physiology and pathophysiology

    Institute of Scientific and Technical Information of China (English)

    He-ping CHENG; Sheng WEI; Li-ping WEI; Alexei VERKHRATSKY

    2006-01-01

    Calcium ions are the most ubiquitous and pluripotent cellular signaling molecules that control a wide variety of cellular processes.The calcium signaling system is represented by a relatively limited number of highly conserved transporters and channels,which execute Ca2+ movements across biological membranes and by many thousands of Ca2+-sensitive effectors.Molecular cascades,responsible for the generation of calcium signals,are tightly controlled by Ca2+ ions themselves and by genetic factors,which tune the expression of different Ca2+-handling molecules according to adaptational requirements.Ca2+ ions determine normal physiological reactions and the development of many pathological processes.

  7. Calcium carbonate as a possible dosimeter for high irradiation doses

    Energy Technology Data Exchange (ETDEWEB)

    Negron M, A.; Ramos B, S.; Camargo R, C. [UNAM, Instituto de Ciencias Nucleares, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Uribe, R. M. [Kent State University, College of Technology, Kent OH (United States); Gomez V, V. [UNAM, Instituto de Quimica, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Kobayashi, K., E-mail: negron@nucleares.unam.mx [Yokohama National University (Japan)

    2014-08-15

    The aim of this work is to analyze the interactions of 5 MeV electron beam radiation and a 290 MeV/u Carbon beam with calcium carbonate (powder) at 298 K and at different irradiation doses, for the potential use of calcium carbonate as a high-dose dosimeter. The irradiation doses with the electron beam were from 0.015 to 9 MGy, and with Carbon beam from 1.5 kGy to 8 kGy. High-energy radiation induces the formation of free radicals in solid calcium carbonate that can be detected and measured by electron paramagnetic resonance (EPR). An increase of the EPR response for some of the free radicals produced in the sample was observed as a function of the irradiation dose. The response of one of the radicals decreased with the dose. These measurements are reproducible; the preparation of the sample is simple and inexpensive; and the signal is stable for several months. The response curves show that the dosimeter tends to saturate at 10 MGy. Based on these properties, we propose this chemical compound as a high-dose dosimeter, mainly for electron irradiation. (author)

  8. Effects of extracellular iron concentration on calcium absorption and relationship between Ca2+ and cell apoptosis in Caco-2 cells

    Institute of Scientific and Technical Information of China (English)

    Li Wang; Qing Li; Xiang-Lin Duan; Yan-Zhong Chang

    2005-01-01

    AIM: To determine the method of growing small intestinal epithelial cells in short-term primary culture and to investigate the effect of extracellular iron concentration ([Fe3+]) on calcium absorption and the relationship between the rising intracellular calcium concentration ([Ca2+]i) and cell apoptosis in human intestinal epithelial Caco-2 cells. METHODS: Primary culture was used for growing small intestinal epithelial cells. [Ca2+]i was detected by a confocal laser scanning microscope. The changes in [Ca2+]i were represented by fluorescence intensity (FI). The apoptosis was evaluated by flow cytometry.RESULTS: Isolation of epithelial cells and preservation of its three-dimensional integrity were achieved using the digestion technique of a mixture of collagenase Ⅺ and dispase Ⅰ. Purification of the epithelial cells was facilitated by using a simple differential sedimentation method. The results showed that proliferation of normal gut epithelium in vitro was initially dependent upon the maintenance of structural integrity of the tissue. If 0.25% trypsin was used for digestion, the cells were severely damaged and very difficult to stick to the Petri dish for growing. The Fe3+ chelating agent desferrioxamine (100, 200 and 300 μmol/L) increased the FI of Caco-2 cells from 27.50±13.18 (control,n = 150) to 35.71±13.99 (n = 150, P<0.01), 72.19±35.40 (n = 150, P<0.01) and 211.34±29.03 (n = 150, P<0.01) in a concentration-dependent manner. There was a significant decrease in the FI of Caco-2 cells treated by ferric ammonium citrate (FAC, a Fe3+ donor; 10, 50 and 100 μmol/L). The FIvalue of Caco-2 cells treated by FAC was 185.85±33.77 (n = 150, P<0.01), 122.73±58.47 (n = 150, P<0.01), and 53.29±19.82 (n = 150, P<0.01), respectively, suggesting that calcium absorption was influenced by [Fe3+]. Calcium ionophore A23187 (0.1, 1.0 and 10 μmol/L) increased the FI of Caco-2 cells from 40.45±13.95 (control, n = 150) to 45.19±21.95 (n = 150, P<0

  9. Superconductive "sodalite"-like clathrate calcium hydride at high pressures

    CERN Document Server

    Wang, Hui; Tanaka, Kaori; Iitaka, Toshiaki; Ma, Yanming

    2012-01-01

    Hydrogen-rich compounds hold promise as high-temperature superconductors under high pressures. Recent theoretical hydride structures on achieving high-pressure superconductivity are composed mainly of H2 fragments. Through a systematic investigation of Ca hydrides with different hydrogen contents using particle-swam optimization structural search, we show that in the stoichiometry CaH6 a body-centred cubic structure with hydrogen that forms unusual "sodalite" cages containing enclathrated Ca stabilizes above pressure 150 GPa. The stability of this structure is derived from the acceptance by two H2 of electrons donated by Ca forming a "H4" unit as the building block in the construction of the 3-dimensional sodalite cage. This unique structure has a partial occupation of the degenerated orbitals at the zone centre. The resultant dynamic Jahn-Teller effect helps to enhance electron-phonon coupling and leads to superconductivity of CaH6. A superconducting critical temperature (Tc) of 220-235 K at 150 GPa obtained...

  10. Numerical Modeling Calcium and CaMKII Effects in the SA Node

    Directory of Open Access Journals (Sweden)

    Yael eYaniv

    2014-04-01

    Full Text Available Sinoatrial node (SAN is the primary heart pacemaker which initiates each heartbeat under normal conditions. Numerous experimental data have demonstrated that Ca2+- and CaMKII-dependent processes are crucially important for regulation of SAN cells. However specific mechanisms of this regulation and their relative contribution to pacemaker function remain mainly unknown. Our review summarizes available data and existing numerical modeling approaches to understand Ca2+ and CaMKII effects on the SAN. Data interpretation and future directions to address the problem are given within the coupled-clock theory, i.e. a modern view on the cardiac pacemaker cell function generated by a system of sarcolemmal and intracellular proteins.

  11. 利用 AMS 测量方法研究大鼠的钙吸收率%Study on Calcium Absorptivity of Rats by 41 Ca-AMS Measurement

    Institute of Scientific and Technical Information of China (English)

    窦亮; 何明; 董克君; 武绍勇; 庞芳芳; 王小明; 杨旭冉; 赵庆章; 姜山

    2016-01-01

    Calcium is one of the essential elements that form human bone (the main form of calcium is Ca1 0 (PO4 )6 (OH)2 )),and it participates and regulates many life processes. Osteoporosis is the most common disease of calcium deficiency,while recent research shows that organisms(especially osteoporosis organisms)take in too much calcium,pos-sibly causing some other diseases.Thus,the accuracy of calcium absorption rate meas-urement is very meaningful for reasonable calcium supplement and prevention diseases of calcium metabolism.Based on the high sensitivity of 41 Ca measurement with accelerator mass spectrometry and the innovative methods of 41 Ca labeling endogenous calcium,the calcium absorption rate of rats was studied.The results show that rats intake 28 mg calcium carbonate,28 mg calcium citrate and 10 mg calcium citrate per 100 g body weight each day,the apparent absorption rates are (67.57±2.79)%,(65.21±2.96)%and (87.50±1.10)%,the static absorption rates are (73.19±3.60)%,(71.47±4.01)%and (92.74 ± 1.81 )%,respectively.This method can obtain the true absorption of calcium without extrinsic labeling,and it is not affected by the chemical structure and sorts of calcium supplements.%钙是人体所必需的元素之一,参与众多的生命生理调控,准确测量生物体的钙吸收率,对于合理补钙和预防钙代谢疾病具有重要意义。本研究采用41 Ca 标记 SD 大鼠体内钙库,利用加速器质谱(AMS)法测量长寿命放射性核素41 Ca 灵敏度高的特点,开展对大鼠钙吸收率的准确测定。结果表明:大鼠每100 g 体重每天摄入28 mg 碳酸钙、28 mg 柠檬酸钙、10 mg 碳酸钙的表观吸收率分别为(67.57±2.79)%、(65.21±2.96)%、(87.50±1.10)%,净吸收率分别为(73.19±3.60)%、(71.47±4.01)%、(92.74±1.81)%。该方法可以得出钙的真实吸收率,且不受所评价的钙剂中钙的化学形式和种类的影响,进一步拓展了同位素评价钙吸收率的应用领域,

  12. High-performance calcium-doped zinc oxide thin-film transistors fabricated on glass at low temperature

    Science.gov (United States)

    Yu, Wen; Han, Dedong; Cui, Guodong; Cong, Yingying; Dong, Junchen; Zhang, Xiaomi; Zhang, Xing; Wang, Yi; Zhang, Shengdong

    2016-04-01

    High-performance calcium-doped zinc oxide thin-film transistors (Ca-ZnO TFTs) have been successfully fabricated on transparent glass at low temperature by RF magnetron sputtering. To study the effects of calcium doping on zinc oxide thin-film transistors, the characteristics of Ca-ZnO TFTs and ZnO TFTs are compared and analyzed in detail from different perspectives, including electrical performance, surface morphology, and crystal structure of the material. The results suggest that the incorporation of calcium element can decrease the root-mean-square roughness of the material, suppress growth of a columnar structure, and improve device performance. The TFTs with Ca-ZnO active layer exhibit excellent electrical properties with the saturation mobility (μsat) of 147.1 cm2 V-1 s-1, threshold voltage (V t) of 2.91 V, subthreshold slope (SS) of 0.271 V/dec, and I on/I off ratio of 2.34 × 108. In addition, we also study the uniformity of the devices. The experimental results show that the Ca-ZnO TFTs possess good uniformity, which is important for large-area application.

  13. Calcium oxalate contribution to calcium cycling in forests of contrasting nutrient status

    Science.gov (United States)

    Dauer, Jenny M.; Perakis, Steven S.

    2014-01-01

    Calcium oxalate (Ca oxalate) is an insoluble biomineral that forms in plants and fungi, and occurs in soils across many types of ecosystems. Assessing how Ca oxalate may shape ecosystem Ca cycling requires information on the distribution of Ca oxalate among plant biomass, detritus, and mineral soil, and how it varies with ecosystem Ca status. We compared two Douglas-fir forests of contrasting ecosystem Ca availability, and found that Ca oxalate was partitioned similarly among plant biomass, detritus and mineral soil major ecosystem compartments at both sites, and total pools of Ca oxalate were greater in the high-Ca forest. However, the proportional importance of Ca oxalate was greater in the low-Ca than high-Ca forest (18% versus 4% of actively cycling ecosystem Ca, respectively). And calcium oxalate in mineral soil, which is of particular interest as a potential long-term Ca reservoir, was a larger portion of total available Ca (exchangeable Ca plus Ca oxalate Ca) in the low-Ca site than the high-Ca site (9% versus 1% of available soil Ca, respectively). Calcium oxalate was the dominant form of Ca returned from plants to soil as leaf litterfall at the high-Ca site, yet calcium oxalate disappeared rapidly from decomposing litter (0.28 yr−1 or faster) at both sites. We conclude that accumulation of Ca oxalate in forest ecosystems appears most closely related to overall Ca supply for live biomass pools, and that the accumulation of Ca oxalate in forest floor and mineral soil is limited by rapid microbial degradation of putatively unavailable Ca oxalate.

  14. Risk of High Dietary Calcium for Arterial Calcification in Older Adults

    Directory of Open Access Journals (Sweden)

    Philip J. Klemmer

    2013-09-01

    Full Text Available Concern has recently arisen about the potential adverse effects of excessive calcium intakes, i.e., calcium loading from supplements, on arterial calcification and risks of cardiovascular diseases (CVD in older adults. Published reports that high calcium intakes in free-living adults have relatively little or no beneficial impact on bone mineral density (BMD and fracture rates suggest that current recommendations of calcium for adults may be set too high. Because even healthy kidneys have limited capability of eliminating excessive calcium in the diet, the likelihood of soft-tissue calcification may increase in older adults who take calcium supplements, particularly in those with age or disease-related reduction in renal function. The maintenance of BMD and bone health continues to be an important goal of adequate dietary calcium consumption, but eliminating potential risks of CVDs from excessive calcium intakes needs to be factored into policy recommendations for calcium by adults.

  15. The Ca(2+)/Calmodulin/CaMKK2 Axis: Nature's Metabolic CaMshaft.

    Science.gov (United States)

    Marcelo, Kathrina L; Means, Anthony R; York, Brian

    2016-10-01

    Calcium (Ca(2+)) is an essential ligand that binds its primary intracellular receptor calmodulin (CaM) to trigger a variety of downstream processes and pathways. Central to the actions of Ca(2+)/CaM is the activation of a highly conserved Ca(2+)/CaM kinase (CaMK) cascade that amplifies Ca(2+) signals through a series of subsequent phosphorylation events. Proper regulation of Ca(2+) flux is necessary for whole-body metabolism and disruption of Ca(2+) homeostasis has been linked to various metabolic diseases. Here we provide a synthesis of recent advances that highlight the roles of the Ca(2+)/CaMK axis in key metabolic tissues. An appreciation of this information is critical to understanding the mechanisms by which Ca(2+)/CaM-dependent signaling contributes to metabolic homeostasis and disease.

  16. Structural studies of calcium phosphate doped with titanium and zirconium obtained by high-energy mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Silva, C C; Sombra, A S B [Telecommunications and Materials Science and Engineering Laboratory (LOCEM), Physics Department, Federal University of Ceara, Campus do Pii, Postal Code 6030, 60455-760, Fortaleza-Ceara (Brazil)], E-mail: sombra@fisica.ufc.br

    2009-12-15

    In this paper, we present a new variation of the solid-state procedure on the synthesis of bioceramics with titanium (CapTi) and zirconium (CapZr), considering that zirconium (ZrO{sub 2}) and titanium oxide (TiO{sub 2}) are strengthening agents, due to their superb force and fracture toughness. The high efficiency of the calcination process opens a new way of producing commercial amounts of nanocrystalline bioceramics. In this work, a new variation of the solid-state procedure method was used to produce nanocrystalline powders of titanium and zirconium, using two different experimental chemical routes: CapTi: Ca(H{sub 2}PO{sub 4}){sub 2}+TiO{sub 2} and CapZr: Ca(H{sub 2}PO{sub 4}){sub 2}+ZrO{sub 2}. The powders were submitted to calcination processes (CapTic and CapZrc) at 800, 900 and 1000 deg. C. The calcium titanium phosphate phase, CaTi{sub 4}P{sub 6}O{sub 24}, was obtained in the CapTic reaction and the calcium zirconium phosphate, CaZr{sub 4}P{sub 6}O{sub 24}, was obtained in the CapZrc reaction. The obtained ceramics were characterized by x-ray powder diffraction (XRD), infrared (IR) spectroscopy, Raman scattering spectroscopy (RSS) and scanning electron microscopy (SEM) analysis. This method was compared with the milling process (CapTim and CapZrm), where in the last process the melting is not necessary and the powder obtained is nanocrystalline. The calcium titanium phosphate phase, CaTi{sub 4}P{sub 6}O{sub 24}, was obtained in the reaction CapTim, but in CapZrm the formation of any calcium phosphate phase even after 15 h of dry mechanical alloying was not observed.

  17. Structural studies of calcium phosphate doped with titanium and zirconium obtained by high-energy mechanical alloying

    Science.gov (United States)

    Silva, C. C.; Sombra, A. S. B.

    2009-12-01

    In this paper, we present a new variation of the solid-state procedure on the synthesis of bioceramics with titanium (CapTi) and zirconium (CapZr), considering that zirconium (ZrO2) and titanium oxide (TiO2) are strengthening agents, due to their superb force and fracture toughness. The high efficiency of the calcination process opens a new way of producing commercial amounts of nanocrystalline bioceramics. In this work, a new variation of the solid-state procedure method was used to produce nanocrystalline powders of titanium and zirconium, using two different experimental chemical routes: CapTi: Ca(H2PO4)2+TiO2 and CapZr: Ca(H2PO4)2+ZrO2. The powders were submitted to calcination processes (CapTic and CapZrc) at 800, 900 and 1000 °C. The calcium titanium phosphate phase, CaTi4P6O24, was obtained in the CapTic reaction and the calcium zirconium phosphate, CaZr4P6O24, was obtained in the CapZrc reaction. The obtained ceramics were characterized by x-ray powder diffraction (XRD), infrared (IR) spectroscopy, Raman scattering spectroscopy (RSS) and scanning electron microscopy (SEM) analysis. This method was compared with the milling process (CapTim and CapZrm), where in the last process the melting is not necessary and the powder obtained is nanocrystalline. The calcium titanium phosphate phase, CaTi4P6O24, was obtained in the reaction CapTim, but in CapZrm the formation of any calcium phosphate phase even after 15 h of dry mechanical alloying was not observed.

  18. Preparation of α-calcium sulfate hemihydrate from phosphogypsum in Ca-Na-Cl solutions under atmospheric pressure%常压水热Ca-Na-Cl溶液中用磷石膏制备α-半水石膏

    Institute of Scientific and Technical Information of China (English)

    马保国; 茹晓红; 邹开波; 卢斯文; 付浩兵

    2013-01-01

    Preparation of a-calcium sulfate hemihydrate from phosphogypsum in hydrothermal electrolyte solutions under atmospheric pressure has been a promising way of effective utilization of phosphogypsum.In this paper preparation of α-calcium sulfate hemihydrate from phosphogypsum in Ca-Na-Cl solutions at 95℃was studied.Reaction time and solid products identification in 18.8% NaCl solution,24% CaCl2 and CaCl2 +NaCl solutions were investigated through morphologic observation,water of crystalization determination and phase analysis methods.The results showed that NaCl solution was not favorable as the dehydration reaction medium of phosphogypsum though reaction time was only 20 min,because the dehydration product was α-calcium sulfate hemihydrate containing omangwaite (Na2Ca5 (SO4)6 · 3H2O) which had no hydration property of gypsum.In 24% CaCl2 solution α-calcium sulfate hemihydrate phase could be obtained at reaction time of 240 min,reaction time was reduced obviously with increasing NaCl content in Ca-Na-Cl solution,but it was accompanied by increase of Na2O content and irregular uncompleted crystal shapes in the reaction product.Therefore,Ca-Na-Cl solution could be a suitable medium for dehydration reaction of phosphogypsum to form α-calcium sulfate hemihydrate in hydrothermal electrolyte solution under atmospheric pressure.Meanwhile NaCl content should be limited to 2%.

  19. Auranofin, an Anti-Rheumatic Gold Compound, Modulates Apoptosis by Elevating the Intracellular Calcium Concentration ([Ca{sup 2+}]{sub i}) in MCF-7 Breast Cancer Cells

    Energy Technology Data Exchange (ETDEWEB)

    Varghese, Elizabeth; Büsselberg, Dietrich, E-mail: dib2015@qatar-med.cornell.edu [Weil Cornell Medical College in Qatar, Qatar Foundation-Education City, P.O. Box 24144 Doha (Qatar)

    2014-11-06

    Auranofin, a transition metal complex is used for the treatment of rheumatoid arthritis but is also an effective anti-cancer drug. We investigate the effects of Auranofin in inducing cell death by apoptosis and whether these changes are correlated to changes of intracellular calcium concentration ([Ca{sup 2+}]{sub i}) in breast cancer cells (MCF-7). Cytotoxicity of Auranofin was evaluated using MTS assay and the Trypan blue dye exclusion method. With fluorescent dyes SR-FLICA and 7-AAD apoptotic death and necrotic death were differentiated by Flow cytometry. A concentration dependent decrease in the viability occurred and cells were shifted to the apoptotic phase. Intracellular calcium ([Ca{sup 2+}]{sub i}) was recorded using florescence microscopy and a calcium sensitive dye (Fluo-4 AM) with a strong negative correlation (r = −0.713) to viability. Pharmacological modulators 2-APB (50 μM), Nimodipine (10 μM), Caffeine (10 mM), SKF 96365(20 μM) were used to modify calcium entry and release. Auranofin induced a sustained increase of [Ca{sup 2+}]{sub i} in a concentration and time dependent manner. The use of different blockers of calcium channels did not reveal the source for the rise of [Ca{sup 2+}]{sub i}. Overall, elevation of [Ca{sup 2+}]{sub i} by Auranofin might be crucial for triggering Ca{sup 2+}-dependent apoptotic pathways. Therefore, in anti-cancer therapy, modulating [Ca{sup 2+}]{sub i} should be considered as a crucial factor for the induction of cell death in cancer cells.

  20. Chemical and physical controls on the transformation of amorphous calcium carbonate into crystalline CaCO3 polymorphs

    Science.gov (United States)

    Blue, C. R.; Giuffre, A.; Mergelsberg, S.; Han, N.; De Yoreo, J. J.; Dove, P. M.

    2017-01-01

    Calcite and other crystalline polymorphs of CaCO3 can form by pathways involving amorphous calcium carbonate (ACC). Apparent inconsistencies in the literature indicate the relationships between ACC composition, local conditions, and the subsequent crystalline polymorphs are not yet established. This experimental study quantifies the control of solution composition on the transformation of ACC into crystalline polymorphs in the presence of magnesium. Using a mixed flow reactor to control solution chemistry, ACC was synthesized with variable Mg contents by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within the output suspension under stirred or quiescent conditions while characterizing the evolving solutions and solids. As the ACC transforms into a crystalline phase, the solutions record a polymorph-specific evolution of pH and Mg/Ca. The data provide a quantitative framework for predicting the initial polymorph that forms from ACC based upon the solution aMg2+/aCa2+ and aCO32-/aCa2+ and stirring versus quiescent conditions. This model reconciles discrepancies among previous studies that report on the nature of the polymorphs produced from ACC and supports the previous claim that monohydrocalcite may be an important, but overlooked, transient phase on the way to forming some aragonite and calcite deposits. By this construct, organic additives and extreme pH are not required to tune the composition and nature of the polymorph that forms. Our measurements show that the Mg content of ACC is recorded in the resulting calcite with a ≈1:1 dependence. By correlating composition of these calcite products with the Mgtot/Catot of the initial solutions, we find a ≈3:1 dependence that is approximately linear and general to whether calcite is formed via an ACC pathway or by the classical step-propagation process. Comparisons to calcite grown in synthetic seawater show a ≈1:1 dependence. The relationships suggest that the

  1. High-pressure studies on the calcium-ion-sensitive fluorophore Fluo-4

    Science.gov (United States)

    Frey, Eric W.; Urayama, Paul

    2007-10-01

    Fluorescence-based methods for intracellular calcium ion sensing are well established at ambient pressure. Because calcium ions play a ubiquitous role in cellular signaling, extending techniques of intracellular calcium-sensing to high pressures would play an important role in understanding the large variety of piezophysiologic effects. Here, we characterize the intracellular calcium-ion-sensitive fluorophore Fluo-4 under hydrostatic pressures up to 500 atm (50 MPa). Using an EGTA/MOPS solution as a calcium-buffer reference, we investigate the pressure dependence of the reaction pK and determine the thermodynamic volume change associated with the Fluo-4 calcium-binding reaction.

  2. In situ synthesis of calcium phosphate-polycaprolactone nanocomposites with high ceramic volume fractions.

    Science.gov (United States)

    Makarov, C; Gotman, I; Jiang, X; Fuchs, S; Kirkpatrick, C J; Gutmanas, E Y

    2010-06-01

    Biodegradable calcium phosphate-PCL nanocomposite powders with unusually high ceramic volume fractions (80-95%) and uniform PCL distribution were synthesized by a non-aqueous chemical reaction in the presence of the dissolved polymer. No visible polymer separation occurred during processing. Depending on the reagents combination, either dicalcium phosphate (DCP) or Ca-deficient HA (CDHA) was obtained. CDHA-PCL composite powders were high pressure consolidated at room temperature yielding dense materials with high compressive strengths. Such densification route provides the possibility of incorporating drug and proteins without damaging their biological activity. The CDHA-PCL composites were tested in osteoblastic and endothelial cell line cultures and were found to support the attachment and proliferation of both cell types.

  3. Calcium carbide (CaC2): Effect on fruit set and yield of mango ...

    African Journals Online (AJOL)

    Reviewer

    ethylene. The effects of different application rates of slow release of CaC2 on the growth and ... NP and K fertilizers) was the most effective treatment with respect to yield ..... nitrification inhibitors on methane and nitrous oxide fluxes in irrigated.

  4. Dispersed-fluorescence spectroscopy of jet-cooled calcium ethoxide radical (CaOC2H5)

    Science.gov (United States)

    Paul, Anam C.; Reza, Md. Asmaul; Liu, Jinjun

    2016-12-01

    Dispersed fluorescence (DF) spectra of the calcium ethoxide radical (CaOC2H5) have been obtained by pumping the A˜12 A‧ ←X˜2A‧ and the A˜22 A‧‧ ←X˜2A‧ origin bands in its laser-induced fluorescence spectrum. Dominant transitions in the vibrationally resolved DF spectra are well reproduced using Franck-Condon factors predicted by complete active space self-consistent field (CASSCF) calculations. Collision-induced population transfer between the A˜12 A‧ and the A22 A‧‧ states results in additional peaks in the experimental DF spectra. Differences between the intensities of vibronic bands in the A˜12 A‧ →X˜2A‧ and the A˜22 A‧‧ →X˜2A‧ DF spectra are attributed to different symmetries of the two excited electronic states.

  5. Calcium-activated K+ channels of mouse beta-cells are controlled by both store and cytoplasmic Ca2+: experimental and theoretical studies.

    Science.gov (United States)

    Goforth, P B; Bertram, R; Khan, F A; Zhang, M; Sherman, A; Satin, L S

    2002-09-01

    A novel calcium-dependent potassium current (K(slow)) that slowly activates in response to a simulated islet burst was identified recently in mouse pancreatic beta-cells (Göpel, S.O., T. Kanno, S. Barg, L. Eliasson, J. Galvanovskis, E. Renström, and P. Rorsman. 1999. J. Gen. Physiol. 114:759-769). K(slow) activation may help terminate the cyclic bursts of Ca(2+)-dependent action potentials that drive Ca(2+) influx and insulin secretion in beta-cells. Here, we report that when [Ca(2+)](i) handling was disrupted by blocking Ca(2+) uptake into the ER with two separate agents reported to block the sarco/endoplasmic calcium ATPase (SERCA), thapsigargin (1-5 microM) or insulin (200 nM), K(slow) was transiently potentiated and then inhibited. K(slow) amplitude could also be inhibited by increasing extracellular glucose concentration from 5 to 10 mM. The biphasic modulation of K(slow) by SERCA blockers could not be explained by a minimal mathematical model in which [Ca(2+)](i) is divided between two compartments, the cytosol and the ER, and K(slow) activation mirrors changes in cytosolic calcium induced by the burst protocol. However, the experimental findings were reproduced by a model in which K(slow) activation is mediated by a localized pool of [Ca(2+)] in a subspace located between the ER and the plasma membrane. In this model, the subspace [Ca(2+)] follows changes in cytosolic [Ca(2+)] but with a gradient that reflects Ca(2+) efflux from the ER. Slow modulation of this gradient as the ER empties and fills may enhance the role of K(slow) and [Ca(2+)] handling in influencing beta-cell electrical activity and insulin secretion.

  6. Study on Different Forms of Calcium Metabolic Behavior in Normal and Osteoporosis Rats by ~(41)Ca Tracing

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Because of calcium deficiency,there were about 90 million Chinese people suffering from osteoporosis which caused a great calcium supplement boom in 2009. However, recent studies have shown that excess calcium supplement may cause some other diseases

  7. Roscovitine, a cyclin-dependent kinase inhibitor, affects several gating mechanisms to inhibit cardiac L-type (Ca(V)1.2) calcium channels.

    Science.gov (United States)

    Yarotskyy, V; Elmslie, K S

    2007-10-01

    L-type calcium channels (Ca((V))1.2) play an important role in cardiac contraction. Roscovitine, a cyclin-dependent kinase inhibitor and promising anticancer drug, has been shown to affect Ca((V))1.2 by inhibiting current amplitude and slowing activation. This research investigates the mechanism by which roscovitine inhibits Ca((V))1.2 channels. Ca((V))1.2 channels were transfected into HEK 293 cells, using the calcium phosphate precipitation method, and currents were measured using the whole-cell patch clamp technique. Roscovitine slows activation at all voltages, which precludes one previously proposed mechanism. In addition, roscovitine enhances voltage-dependent, but not calcium-dependent inactivation. This enhancement resulted from both an acceleration of inactivation and a slowing of the recovery from inactivation. Internally applied roscovitine failed to affect Ca((V))1.2 currents, which supports a kinase-independent mechanism and extracellular binding site. Unlike the dihydropyridines, closed state inactivation was not affected by roscovitine. Inactivation was enhanced in a dose-dependent manner with an IC(50)=29.5+/-12 microM, which is close to that for slow activation and inhibition. We conclude that roscovitine binds to an extracellular site on Ca((V))1.2 channels to inhibit current by both slowing activation and enhancing inactivation. Purine-based drugs could become a new option for treatment of diseases that benefit from L-channel inhibition such as cardiac arrhythmias and hypertension.

  8. The Effect of a Novel Highly Selective Inhibitor of the Sodium/Calcium Exchanger (NCX) on Cardiac Arrhythmias in In Vitro and In Vivo Experiments

    OpenAIRE

    Kohajda, Zsófia; Farkas-Morvay, Nikolett; Jost, Norbert; Nagy, Norbert; Geramipour, Amir; Horváth, András; Varga, Richárd S.; Hornyik, Tibor; Corici, Claudia; Acsai, Károly; Horváth, Balázs; Prorok, János; Ördög, Balázs; Déri, Szilvia; Tóth, Dániel

    2016-01-01

    Background In this study the effects of a new, highly selective sodium-calcium exchanger (NCX) inhibitor, ORM-10962 were investigated on cardiac NCX current, Ca2+ transients, cell shortening and in experimental arrhythmias. The level of selectivity of the novel inhibitor on several major transmembrane ion currents (L-type Ca2+ current, major repolarizing K+ currents, late Na+ current, Na+/K+ pump current) was also determined. Methods Ion currents in single dog ventricular cells (cardiac myocy...

  9. Effect of calcium fluoride on sintering behaviour of SiO2-CaO-Na2O-MgO glass-ceramic system

    Directory of Open Access Journals (Sweden)

    Bahman Mirhadi

    2012-09-01

    Full Text Available The crystallization characteristics of glasses based on the SiO2-CaO-Na2O-MgO (SCNM system containing calcium fluoride (CaF2 have been investigated by differential thermal analysis (DTA, X-ray diffraction (XRD and scanning electron microscopy (SEM. The partial replacement of CaO by CaF2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including wollastonite and diopside using various heat-treatment processes. With the increase of CaF2 content, the crystallization temperature of the glass and the strength of the crystallization peak temperature decreases. Addition of CaF2 up to 6.0 mol%, as expected, improved the sinterability. This sample reached to maximum density by sintering at 950 °C.

  10. Calcium receptor expression and function in oligodendrocyte commitment and lineage progression: potential impact on reduced myelin basic protein in CaR-null mice

    DEFF Research Database (Denmark)

    Chattopadhyay, N.; Espinosa-Jeffrey, A.; Yano, S.

    2008-01-01

    Oligodendrocytes develop from oligodendrocyte progenitor cells (OPCs), which in turn arise from a subset of neuroepithelial precursor cells during midneurogenesis. Development of the oligodendrocyte lineage involves a plethora of cell-intrinsic and -extrinsic signals. A cell surface calcium......-sensing receptor (CaR) has been shown to be functionally expressed in immature oligodendrocytes. Here, we investigated the expression and function of the CaR during oligodendrocyte development. We show that the order of CaR mRNA expression as assessed by quantitative polymerase chain reaction is mature...... oligodendrocyte > neuron > astrocyte. We next determined the rank order of CaR expression on inducing specification of neural stem cells to the neuronal, oligodendroglial, or astrocytic lineages and found that the relative levels of CaR mRNA expression are OPC > neuron > astrocytes. CaR mRNA expression in cells...

  11. Biomimetic mineralization of CaCO3 on a phospholipid monolayer: from an amorphous calcium carbonate precursor to calcite via vaterite.

    Science.gov (United States)

    Xiao, Junwu; Wang, Zhining; Tang, Yecang; Yang, Shihe

    2010-04-06

    A phospholipid monolayer, approximately half the bilayer structure of a biological membrane, can be regarded as an ideal model for investigating biomineralization on biological membranes. In this work on the biomimetic mineralization of CaCO(3) under a phospholipid monolayer, we show the initial heterogeneous nucleation of amorphous calcium carbonate precursor (ACC) nanoparticles at the air-water interface, their subsequent transformation into the metastable vaterite phase instead of the most thermodynamically stable calcite phase, and the ultimate phase transformation to calcite. Furthermore, the spontaneity of the transformation from vaterite to calcite was found to be closely related to the surface tension; high surface pressure could inhibit the process, highlighting the determinant of surface energy. To understand better the mechanisms for ACC formation and the transformation from ACC to vaterite and to calcite, in situ Brewster angle microscopy (BAM), ex situ scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction analysis were employed. This work has clarified the crystallization process of calcium carbonate under phospholipid monolayers and therefore may further our understanding of the biomineralization processes induced by cellular membranes.

  12. Thermoluminescent dosimetry properties of double doped calcium tetraborate (CaB{sub 4}O{sub 7}:Cu–Mn) nanophosphor exposed to gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Erfani Haghiri, Maryam, E-mail: maryam.erfani59@gmail.com [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Saion, Elias; Soltani, Nayereh [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Wan Saffiey wan Abdullah [Radiation Protection and Health Division, Malaysian Nuclear Agency (Nuclear Malaysia), Bangi, 43000 Kajang (Malaysia); Navasery, Manizheh [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Rezaee Ebrahim Saraee, Khadijeh [Department of Nuclear Engineering, Faculty of Advance Sciences and Technologies, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Deyhimi, Najmeh [Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2014-01-05

    Highlights: • TL properties of CaBT:Cu–Mn nanoparticles was reported for the first time. • The combined impurities of Cu and Mn ions could enhance the TL efficiency well. • Striking feature of this study is linearity dose response for a long span of exposures. • This nanophosphor showed simple glow curves, good re-usability and high sensitivity. -- Abstract: This study reports the dosimeteric properties of double Cu–Mn doped calcium tetraborate nanophosphor prepared by co-precipitation technique. The structure and the morphology of the synthesized nanocrystals were characterized by X-ray diffraction and transmission electron microscope. The presented XRD patterns showed the monoclinic structure and transmission electron microscopy revealed the formation of spherical shape nanoparticles with an average particle size of 8 nm. The results demonstrated that the synthesized calcium borate nanophosphor has the highest dosimetric sensitivity at combined concentration of 2% and 1%, copper and manganese molar ratio, respectively. TL glow curve of this material showed two well resolved peaks located at around 124 and 256 °C. The most striking dosimeteric feature of this nanomaterial is the linearity response, which has a long range of 0.05–3000 Gy for both temperature peaks.

  13. Characterization and Utilization of Calcium Oxide (CaO Thermally Decomposed from Fish Bones as a Catalyst in the Production of Biodiesel from Waste Cooking Oil

    Directory of Open Access Journals (Sweden)

    Aldes Lesbani

    2016-12-01

    Full Text Available Thermal decomposition of fish bones to obtain calcium oxide (CaO was conducted at various temperatures of 400, 500, 800, 900, 1000, and 1100 °C. The calcium oxide was then characterized using X-ray diffractometer, FTIR spectrophotometer, and SEM analysis. The calcium oxide obtained from the decomposition at 1000 °C was then used as a catalyst in the production of biodiesel from waste cooking oil. Diffraction pattern of the calcium oxide produced from decomposition at 1000 °C showed a pattern similar to that of the calcium oxide produced by the Joint Committee on Powder Diffraction Standard (JCDPS. The diffractions of 2θvalues at 1000 °C were 32.2, 37.3, 53.8, 64.1, and67.3 deg. The FTIR spectrum of calcium oxide decomposed at 1000 °C has a specific vibration at wave-length 362 cm-1, which is similar to the specific vibration of Ca-O. SEM analysis of the calcium oxide indicated that the calcium oxide’s morphology shows a smaller size and a more homogeneous structure, compared to those of fish bones. Theuse of calcium oxide as a catalyst in the production of biodiesel from waste cooking oil resulted in iod number of 15.23 g/100 g KOH, density of 0.88 g/cm3, viscosity of 6.00 cSt, and fatty acid value of 0.56 mg/KOH. These characteristic values meet the National Standard of Indonesia (SNI for biodiesel.

  14. A confocal study of mechanism of 5-hydroxytryptaminoinduced intracellular calcium dynamics in cultured ratstomach fundus smooth muscle cells with a new Ca2+indicator STDIn-AM

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xiaoling; (张小玲); YAN; Hongtao; (阎宏涛)

    2002-01-01

    A new fluorescent Ca2+ indicator STDIn-AM for detecting i transients in cultured smooth muscle cells is presented. By making a comparison, the difference between STDIn and fluo-3 is discussed in detail. Using the new Ca2+ indicator, the mechanism of 5-hydroxytryptamino (5-HT) induced intracellular calcium dynamics in stomach fundus smooth muscle cells (SFSMC) of rats is investigated. It is shown that in contrast with fluo-3, STDIn is uniformly distributed in the cytosolic compartment but excluded from the nucleus, when it is transfected into cells. This feature makes it a real cytosol Ca2+ indicator and can reflect changes of cytosol more accurately than that of fluo-3. In addition, STDIn responds to the i transients more sensitive and faster than fluo-3. The results also show that, the L-type Ca2+ channel inhibitor Mn9202 and the PLC inhibitor Compound 48/80 can significantly inhibit the i elevation induced by 5-HT, while the PKC inhibitor D-Sphingosine can enhance the effect of 5-HT. The results suggest that 5-HT acts by the way of 5-HT2 receptors on SFSMC, then through 5-HT2 receptors coupled IP3/Ca2+ and GC/PKC double signal transduction pathways to make Ca2+ release from intracellular Ca2+ stores and Ca2+ influx possibly through L-type calcium channels.

  15. Magnesium and Calcium Aluminate Liquids: In Situ High-Temperature 27Al NMR Spectroscopy.

    Science.gov (United States)

    Poe, B T; McMillan, P F; Coté, B; Massiot, D; Coutures, J P

    1993-02-05

    The use of high-temperature nuclear magnetic resonance (NMR) spectroscopy provides a means of investigating the structure of refractory aluminate liquids at temperatures up to 2500 K. Time-averaged structural information indicates that the average aluminum coordination for magnesium aluminate (MgAl(2)O(4)) liquid is slightly greater than for calcium aluminate (CaAl(2)O(4)) liquid and that in both liquids it is close to four. Ion dynamics simulations for these liquids suggest the presence of four-, five-, and six-coordinated aluminate species, in agreement with NMR experiments on fast-quenched glasses. These species undergo rapid chemical exchange in the high-temperature liquids, which is evidenced by a single Lorentzian NMR line.

  16. Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

    Science.gov (United States)

    Zhong, Lihua; He, Xiaoman; Qu, Jun; Li, Xuewei; Lei, Zhiwu; Zhang, Qiwu; Liu, Xinzhong

    2017-01-01

    Al(OH)3 and Ca(OH)2 powders are co-ground to prepare a precursor which hydrates into a layered double hydroxide (LDH) phase by agitation in aqueous solution with target hexavalent chromium (Cr(VI)) at room temperature, to achieve an obvious improvement in removal efficiency of Cr(VI) through an easy incorporation into the structure. Although the prepared precursor transforms into LDH phases also when agitated in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. The adsorption isotherm and kinetic studies show that the phenomena occurring on the Al-Ca precursor fit a pseudo-second-order kinetics with a Langmuir adsorption capacity of 59.45 mg/g. Besides, characterizations of the prepared precursor and the samples after adsorption are also performed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscope (TEM) to understand the reason of the preferential incorporation of Cr(VI) to the coexisting chloride salts during the LDH phase formation.

  17. COOH-terminal association of human smooth muscle calcium channel Ca(v)1.2b with Src kinase protein binding domains: effect of nitrotyrosylation.

    Science.gov (United States)

    Kang, Minho; Ross, Gracious R; Akbarali, Hamid I

    2007-12-01

    The carboxyl terminus of the calcium channel plays an important role in the regulation of calcium entry, signal transduction, and gene expression. Potential protein-protein interaction sites within the COOH terminus of the L-type calcium channel include those for the SH3 and SH2 binding domains of c-Src kinase that regulates calcium currents in smooth muscle. In this study, we examined the binding sites involved in Src kinase-mediated phosphorylation of the human voltage-gated calcium channel (Ca(v)) 1.2b (hCav1.2b) and the effect of nitrotyrosylation. Cotransfection of human embryonic kidney (HEK)-293 cells with hCa(v)1.2b and c-Src resulted in tyrosine phosphorylation of the calcium channel, which was prevented by nitration of tyrosine residues by peroxynitrite. Whole cell calcium currents were reduced by 58 + 5% by the Src kinase inhibitor PP2 and 64 + 6% by peroxynitrite. Nitrotyrosylation prevented Src-mediated regulation of the currents. Glutathione S-transferase fusion protein of the distal COOH terminus of hCa(v)1.2b (1809-2138) bound to SH2 domain of Src following tyrosine phosphorylation, while binding to SH3 required the presence of the proline-rich motif. Site-directed mutation of Y(2134) prevented SH2 binding and resulted in reduced phosphorylation of hCa(v)1.2b. Within the distal COOH terminus, single, double, or triple mutations of Y(1837), Y(1861), and Y(2134) were constructed and expressed in HEK-293 cells. The inhibitory effects of PP2 and peroxynitrite on calcium currents were significantly reduced in the double mutant Y(1837-2134F). These data demonstrate that the COOH terminus of hCa(v)1.2b contains sites for the SH2 and SH3 binding of Src kinase. Nitrotyrosylation of these sites prevents Src kinase regulation and may be importantly involved in calcium influx regulation during inflammation.

  18. COOH-terminal association of human smooth muscle calcium channel Ca^sub v^1.2b with Src kinase protein binding domains: effect of nitrotyrosylation

    National Research Council Canada - National Science Library

    Minho Kang; Gracious R Ross; Hamid I Akbarali

    2007-01-01

    ...) and the effect of nitrotyrosylation. Cotransfection of human embryonic kidney (HEK)-293 cells with hCa...1.2b and c-Src resulted in tyrosine phosphorylation of the calcium channel, which was prevented by nitration of tyrosine residues by peroxynitrite...

  19. COOH-terminal association of human smooth muscle calcium channel Ca(v)1.2b with Src kinase protein binding domains: effect of nitrotyrosylation

    National Research Council Canada - National Science Library

    Kang, Minho; Ross, Gracious R; Akbarali, Hamid I

    2007-01-01

    ...) and the effect of nitrotyrosylation. Cotransfection of human embryonic kidney (HEK)-293 cells with hCa(v)1.2b and c-Src resulted in tyrosine phosphorylation of the calcium channel, which was prevented by nitration of tyrosine residues by peroxynitrite...

  20. In vivo resorption behavior of a high strength injectable calcium-phosphate cement

    Energy Technology Data Exchange (ETDEWEB)

    Wolke, J.G.C.; Ooms, E.M.; Jansen, J.A. [Univ. Medical Center, Nijmegen (Netherlands). Dept. Biomaterials

    2001-07-01

    A high strength calcium-phosphate-cement powder was prepared from a composition comprising of {alpha}-TCP, CaHPO{sub 4} (monetite), CaCO{sub 3} and some seeds of precipitated apatite. An aqueous solution of 4% Na{sub 2}HPO{sub 4} was used as liquid to start the setting reaction. The powder was mixed with cement liquid in three different liquid/powder ratios respectively 0.3, 0.35 and 0.4. Observation of the setting reaction versus time revealed that the maximum of compressive strength was achieved after 3 days reaching the value of 81 MPa. The X-ray diffraction pattern of the Ca-P cement measured 3 days after mixing and storage in Ringer's solution at 37 C showed that the {alpha}-TCP was transformed to hydroxylapatite with superposition of the peaks for monetite. XRD showed that after eight weeks of implantation the monetite peaks had disappeared. Further, the clinical handling properties of all three types of Ca-P cement appeared to be excellent. No problems in setting time or cavity filling were met during the application. The histological evaluation after two weeks of implantation showed abundant bone apposition on the cement surface without inflammatory reaction. At later time points the Ca-P cements were totally covered by a thin layer of bone and osteoclast-like cells in remodeling lacunae at the interface were resorbing the cement. At all implantation periods the PMMA controls showed the presence of a thin fibrous membrane. (orig.)

  1. Calcilytic Ameliorates Abnormalities of Mutant Calcium-Sensing Receptor (CaSR) Knock-In Mice Mimicking Autosomal Dominant Hypocalcemia (ADH).

    Science.gov (United States)

    Dong, Bingzi; Endo, Itsuro; Ohnishi, Yukiyo; Kondo, Takeshi; Hasegawa, Tomoka; Amizuka, Norio; Kiyonari, Hiroshi; Shioi, Go; Abe, Masahiro; Fukumoto, Seiji; Matsumoto, Toshio

    2015-11-01

    Activating mutations of calcium-sensing receptor (CaSR) cause autosomal dominant hypocalcemia (ADH). ADH patients develop hypocalcemia, hyperphosphatemia, and hypercalciuria, similar to the clinical features of hypoparathyroidism. The current treatment of ADH is similar to the other forms of hypoparathyroidism, using active vitamin D3 or parathyroid hormone (PTH). However, these treatments aggravate hypercalciuria and renal calcification. Thus, new therapeutic strategies for ADH are needed. Calcilytics are allosteric antagonists of CaSR, and may be effective for the treatment of ADH caused by activating mutations of CaSR. In order to examine the effect of calcilytic JTT-305/MK-5442 on CaSR harboring activating mutations in the extracellular and transmembrane domains in vitro, we first transfected a mutated CaSR gene into HEK cells. JTT-305/MK-5442 suppressed the hypersensitivity to extracellular Ca(2+) of HEK cells transfected with the CaSR gene with activating mutations in the extracellular and transmembrane domains. We then selected two activating mutations locating in the extracellular (C129S) and transmembrane (A843E) domains, and generated two strains of CaSR knock-in mice to build an ADH mouse model. Both mutant mice mimicked almost all the clinical features of human ADH. JTT-305/MK-5442 treatment in vivo increased urinary cAMP excretion, improved serum and urinary calcium and phosphate levels by stimulating endogenous PTH secretion, and prevented renal calcification. In contrast, PTH(1-34) treatment normalized serum calcium and phosphate but could not reduce hypercalciuria or renal calcification. CaSR knock-in mice exhibited low bone turnover due to the deficiency of PTH, and JTT-305/MK-5442 as well as PTH(1-34) increased bone turnover and bone mineral density (BMD) in these mice. These results demonstrate that calcilytics can reverse almost all the phenotypes of ADH including hypercalciuria and renal calcification, and suggest that calcilytics can become a

  2. Hybrid functional study rationalizes the simple cubic phase of calcium at high pressures.

    Science.gov (United States)

    Liu, Hanyu; Cui, Wenwen; Ma, Yanming

    2012-11-14

    Simple cubic (SC) phase has been long experimentally determined as the high-pressure phase III of elemental calcium (Ca) since 1984. However, recent density functional calculations within semi-local approximation showed that this SC phase is structurally unstable by exhibiting severely imaginary phonons, and is energetically unstable with respect to a theoretical body-centered tetragonal I4(1)/amd structure over the pressure range of phase III. These calculations generated extensive debates on the validity of SC phase. Here we have re-examined the SC structure by performing more precise density functional calculations within hybrid functionals of Heyd-Scuseria-Erhzerhof and PBE0. Our calculations were able to rationalize fundamentally the phase stability of SC structure over all other known phases by evidence of its actual energetic stability above 33 GPa and its intrinsically dynamical stability without showing any imaginary phonons in the entire pressure range studied. We further established that the long-thought theoretical I4(1)/amd structure remains stable in a narrow pressure range before entering SC phase and is actually the structure of experimental Ca-III(') synthesized recently at low temperature 14 K as supported by the excellent agreement between our simulated x-ray diffraction patterns and the experimental data. Our results shed strong light on the crucial role played by the precise electron exchange energy in a proper description of the potential energy of Ca.

  3. High quality fuel gas from biomass pyrolysis with calcium oxide.

    Science.gov (United States)

    Zhao, Baofeng; Zhang, Xiaodong; Chen, Lei; Sun, Laizhi; Si, Hongyu; Chen, Guanyi

    2014-03-01

    The removal of CO2 and tar in fuel gas produced by biomass thermal conversion has aroused more attention due to their adverse effects on the subsequent fuel gas application. High quality fuel gas production from sawdust pyrolysis with CaO was studied in this paper. The results of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments indicate that the mass ratio of CaO to sawdust (Ca/S) remarkably affects the behavior of sawdust pyrolysis. On the basis of Py-GC/MS results, one system of a moving bed pyrolyzer coupled with a fluid bed combustor has been developed to produce high quality fuel gas. The lower heating value (LHV) of the fuel gas was above 16MJ/Nm(3) and the content of tar was under 50mg/Nm(3), which is suitable for gas turbine application to generate electricity and heat. Therefore, this technology may be a promising route to achieve high quality fuel gas for biomass utilization.

  4. Effects of Calcium Phosphate Nanoparticles on Ca-PO4 Composite

    OpenAIRE

    Xu, H.H.K.; Weir, M.D.; Sun, L.; Takagi, S.; Chow, L. C.

    2007-01-01

    Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO4 release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0–75%. The flexural strengths in MPa (mean ± SD; n = 6) of DCPA-whisker composites ranged from (106 ± 39) at 0% fillers to (11...

  5. Induced Bone by Calcium Ohosphate(Ca-P) Ceramics after 2-years Implantation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhiyong; KURITA Hiroshi; KOBAYASHI Hiroichi; KURASHINA Kenji

    2009-01-01

    The changes of induced bone with four kinds of Ca-P ceramics after 2 years im-plantation in the dorsal muscles of rabbits were investigated.After 2 years implantation,mature bone (with a lamellar structure after the remodeling process)with bone marrow was observed in HA1100 (HA,micro+macro porous),HA900(HA,micro+macro porous)and BCP(HA/TCP=7:3,mi-cro+macro porous),and no bone formation was observed in HA1200(HA,macro porous)ceramics. The induced bone neither disappeared nor grew uncontrollably,and was seen inside the pores of the implants or on the outer surface under the fibrous layer after 2 years.No bone formation was ob-served in the soft tissues distant from the implants.These results indicate that heterotopic bone for-mation induced by Ca-P materials did not give rise to uncontrolled growth over time,and the induced bone is limited to the inside or around the implants.Moreover,ectopic bone formation on the outer surface of the implants was detected in rabbits after 2 years.

  6. FhCaBP2: a Fasciola hepatica calcium-binding protein with EF-hand and dynein light chain domains.

    Science.gov (United States)

    Thomas, Charlotte M; Timson, David J

    2015-09-01

    FhCaBP2 is a Fasciola hepatica protein which belongs to a family of helminth calcium-binding proteins which combine an N-terminal domain containing two EF-hand motifs and a C-terminal dynein light chain-like (DLC-like) domain. Its predicted structure showed two globular domains joined by a flexible linker. Recombinant FhCaBP2 interacted reversibly with calcium and manganese ions, but not with magnesium, barium, strontium, copper (II), colbalt (II), iron (II), nickel, lead or potassium ions. Cadmium (II) ions appeared to bind non-site-specifically and destabilize the protein. Interaction with either calcium or magnesium ions results in a conformational change in which the protein's surface becomes more hydrophobic. The EF-hand domain alone was able to interact with calcium and manganese ions; the DLC-like domain was not. Alteration of a residue (Asp-58 to Ala) in the second EF-hand motif in this domain abolished ion-binding activity. This suggests that the second EF-hand is the one responsible for ion-binding. FhCaBP2 homodimerizes and the extent of dimerization was not affected by calcium ions or by the aspartate to alanine substitution in the second EF-hand. The isolated EF-hand and DLC-like domains are both capable of homodimerization. FhCaBP2 interacted with the calmodulin antagonists trifluoperazine, chlorpromazine, thiamylal and W7. Interestingly, while chlorpromazine and thiamylal interacted with the EF-hand domain (as expected), trifluoperazine and W7 bound to the DLC-like domain. Overall, FhCaBP2 has distinct biochemical properties compared with other members of this protein family from Fasciola hepatica, a fact which supports the hypothesis that these proteins have different physiological roles.

  7. The Kinetics of Calcination of High Calcium Limestone

    Directory of Open Access Journals (Sweden)

    P. C. Okonkwo

    2012-02-01

    Full Text Available The kinetics of calcination of a high calcium type of limestone was studied. Ukpilla limestone found in the central region of Nigeria was studied. The limestone composition shows that the limestone has 51.29% calcium oxide and 41.53% loss on ignition and magnesium oxide content of 2.23%. The following parameters were determined; diffusion coefficient of lime layer, and mass transfer coefficient, conductivity of lime layer and beat transfer coefficient, convective parameter and diffusive parameter for temperatures 9000C, 10000C, 10600C and 10800C. The reaction was found to be limited by mass and heat transfers across the tune layer of the calcining article, theoptimal temperature of calcination was found to be 10600C. Diffusivity and mass transfer coefficient decreases with increase in calcination temperature. The thermal conductivity increases with increase in temperature. The diffusive and convective parameter decreases with increase in temperature. The reactivity of lime calcined at different temperatures were determined. The reactivity of the lime increases with decrease in calcination temperature.

  8. Isolation and characterization of calcium sensing receptor null cells: a highly malignant and drug resistant phenotype of colon cancer.

    Science.gov (United States)

    Singh, Navneet; Liu, Guangming; Chakrabarty, Subhas

    2013-05-01

    The expression of calcium sensing receptor (CaSR) in the human colonic crypt epithelium is linked to cellular differentiation while its lack of expression is associated with undifferentiated and invasive colon carcinoma. Human colon carcinoma cell lines contain small subpopulations (10-20%) that do not express CaSR (termed CaSR null cells). Here, we report on the isolation, propagation, maintenance and characterization of CaSR null cells from the CBS and HCT116 human colon carcinoma cell lines. CaSR null cells grew as three-dimensional non-adherent spherical clusters with increased propensity for anchorage independent growth, cellular proliferation and invasion of matrigels. CaSR null cells were highly resistant to fluorouracil and expressed abundant amount of thymidylate synthase and survivin. Molecular profiling by real time reverse transcription-polymerase chain reaction (RT-PCR) and Western blots showed a high level of expression of the previously reported cancer stem cell markers CD133, CD44 and Nanog in CaSR null cells. A significant increase in the expression of epithelial-mesenchymal transitional molecules and transcription factors was also observed. These include N-cadherin, β-catenin, vimentin, fibronectin, Snail1, Snail2, Twist and FOXC2. The expression of the tumor suppressive E-cadherin and miR145, on the other hand, was greatly reduced while expression of the oncogenic microRNAs: miR21, miR135a and miR135b was significantly up-regulated. CaSR null cells possess a myriad of cellular and molecular features that drive and sustain the malignant phenotype. We conclude that CaSR null constitutes a highly malignant and drug resistant phenotype of colon cancer.

  9. Effects of high concentrations of calcium salts in the substrate and its pH on the growth of selected rhododendron cultivars

    Directory of Open Access Journals (Sweden)

    Piotr Giel

    2011-07-01

    Full Text Available For proper growth and development, rhododendrons need acidic soils, whereas calcium carbonate (CaCO3 in the substrate markedly limits their growth. In this study, we analysed the reactions of rhododendrons to high concentrations of calcium salts and pH in the substrate. We used 4-month-old seedlings of Rhododendron 'Cunningham's White' and 1.5-year-old seedlings and rooted cuttings of R. 'Cunningham's White' and R. 'Catawbiense Grandiflorum'. Their reactions depended mostly on calcium salt type added to the substrate (sulphate or carbonate. An increase in concentrations of phenolic compounds was detected mostly in roots of the plants grown in a substrate with a high calcium carbonate content. Addition of calcium salts to the substrate caused a significant rise in total nonstructural carbohydrates in leaves and roots of the studied plants. As compared to the control, an increase in substrate pH in the variant with calcium carbonate limited the activity of acid phosphatase, while lowering of substrate pH in the variant with calcium sulphate, significantly increased its activity. Along with the rise in substrate pH, a remarkable increase was observed in the activity of nonspecific dehydrogenase (DHA in the substrate with CaCO3, as compared to the control. Unfavourable soil conditions (high calcium content and alkaline pH caused a decrease in assimilation of minerals by the studied plants (mostly phosphorus and manganese. Our results show that the major factor limiting rhododendron growth is an increase in substrate pH, rather than an increase in the concentration of calcium ions.

  10. Expression of mRNA Encoding Mcu and Other Mitochondrial Calcium Regulatory Genes Depends on Cell Type, Neuronal Subtype, and Ca2+ Signaling.

    Science.gov (United States)

    Márkus, Nóra M; Hasel, Philip; Qiu, Jing; Bell, Karen F S; Heron, Samuel; Kind, Peter C; Dando, Owen; Simpson, T Ian; Hardingham, Giles E

    2016-01-01

    Uptake of Ca2+ into the mitochondrial matrix controls cellular metabolism and survival-death pathways. Several genes are implicated in controlling mitochondrial Ca2+ uptake (mitochondrial calcium regulatory genes, MCRGs), however, less is known about the factors which influence their expression level. Here we have compared MCRG mRNA expression, in neural cells of differing type (cortical neurons vs. astrocytes), differing neuronal subtype (CA3 vs. CA1 hippocampus) and in response to Ca2+ influx, using a combination of qPCR and RNA-seq analysis. Of note, we find that the Mcu-regulating Micu gene family profile differs substantially between neurons and astrocytes, while expression of Mcu itself is markedly different between CA3 and CA1 regions in the adult hippocampus. Moreover, dynamic control of MCRG mRNA expression in response to membrane depolarization-induced Ca2+ influx is also apparent, resulting in repression of Letm1, as well as Mcu. Thus, the mRNA expression profile of MCRGs is not fixed, which may cause differences in the coupling between cytoplasmic and mitochondrial Ca2+, as well as diversity of mitochondrial Ca2+ uptake mechanisms.

  11. Expression of mRNA Encoding Mcu and Other Mitochondrial Calcium Regulatory Genes Depends on Cell Type, Neuronal Subtype, and Ca2+ Signaling.

    Directory of Open Access Journals (Sweden)

    Nóra M Márkus

    Full Text Available Uptake of Ca2+ into the mitochondrial matrix controls cellular metabolism and survival-death pathways. Several genes are implicated in controlling mitochondrial Ca2+ uptake (mitochondrial calcium regulatory genes, MCRGs, however, less is known about the factors which influence their expression level. Here we have compared MCRG mRNA expression, in neural cells of differing type (cortical neurons vs. astrocytes, differing neuronal subtype (CA3 vs. CA1 hippocampus and in response to Ca2+ influx, using a combination of qPCR and RNA-seq analysis. Of note, we find that the Mcu-regulating Micu gene family profile differs substantially between neurons and astrocytes, while expression of Mcu itself is markedly different between CA3 and CA1 regions in the adult hippocampus. Moreover, dynamic control of MCRG mRNA expression in response to membrane depolarization-induced Ca2+ influx is also apparent, resulting in repression of Letm1, as well as Mcu. Thus, the mRNA expression profile of MCRGs is not fixed, which may cause differences in the coupling between cytoplasmic and mitochondrial Ca2+, as well as diversity of mitochondrial Ca2+ uptake mechanisms.

  12. Presynaptic CaV2.1 calcium channels carrying familial hemiplegic migraine mutation R192Q allow faster recovery from synaptic depression in mouse calyx of Held.

    Science.gov (United States)

    Inchauspe, Carlota González; Urbano, Francisco J; Di Guilmi, Mariano N; Ferrari, Michel D; van den Maagdenberg, Arn M J M; Forsythe, Ian D; Uchitel, Osvaldo D

    2012-12-01

    Ca(V)2.1 Ca(2+) channels have a dominant and specific role in initiating fast synaptic transmission at central excitatory synapses, through a close association between release sites and calcium sensors. Familial hemiplegic migraine type 1 (FHM-1) is an autosomal-dominant subtype of migraine with aura, caused by missense mutations in the CACNA1A gene that encodes the α(1A) pore-forming subunit of Ca(V)2.1 channel. We used knock-in (KI) transgenic mice harboring the FHM-1 mutation R192Q to study the consequences of this mutation in neurotransmission at the giant synapse of the auditory system formed by the presynaptic calyx of Held terminal and the postsynaptic neurons of the medial nucleus of the trapezoid body (MNTB). Although synaptic transmission seems unaffected by low-frequency stimulation in physiological Ca(2+) concentration, we observed that with low Ca(2+) concentrations (<1 mM) excitatory postsynaptic currents (EPSCs) showed increased amplitudes in R192Q KI mice compared with wild type (WT), meaning significant differences in the nonlinear calcium dependence of nerve-evoked transmitter release. In addition, when EPSCs were evoked by broadened presynaptic action potentials (achieved by inhibition of K(+) channels) via Ca(v)2.1-triggered exocytosis, R192Q KI mice exhibited further enhancement of EPSC amplitude and charge compared with WT mice. Repetitive stimulation of afferent axons to the MNTB at different frequencies caused short-term depression of EPSCs that recovered significantly faster in R192Q KI mice than in WT mice. Faster recovery in R192Q KI mice was prevented by the calcium chelator EGTA-AM, pointing to enlarged residual calcium as a key factor in accelerating the replenishment of synaptic vesicles.

  13. Orange-red light emitting europium-doped calcium molybdate phosphor prepared by high-energy ball milling

    Science.gov (United States)

    Hong, Woo Tae; Lee, Joo Hyun; Park, Jin Young; Yang, Hyun Kyoung; Jeong, Jung Hyun; Moon, Byung Kee

    2016-09-01

    Europium-doped calcium molybdates (CaMoO4:Eu3+) were successfully synthesized by a high-energy ball milling method. The x-ray diffraction patterns confirmed their powellite structure, and the field emission scanning electron microscope image exhibited the spherical particles with submicron size. The photoluminescence (PL) properties of Eu3+ in these phosphors were also studied by analyzing the excitation and emission spectra for the effect of europium concentration. The CaMoO4:Eu3+ PL excitation and PL spectra show charge transfer band and several transition peaks correlated with host lattice band gap and f-f transitions of Eu3+, respectively. By sintering Ca0.95MoO4:0.05Eu3+ phosphor at 1200°C, PL intensity has a maximum value at 618 nm with Commision Internationale de I'Eclairage 1931 (CIE 1931) chromaticity coordinates (0.609, 0.343).

  14. Determination of the forms of calcium present in coal chars by Ca K-edge XANES with Synchrotron Radiation

    CERN Document Server

    Liu, Lijuan; Cui, Mingqi; Hu, Yongfeng; Zheng, Lei; Zhao, Yidong; Ma, Chenyan; Xi, Shibo; Yang, Dongliang; Guo, Zhiying; Wang, Jie

    2012-01-01

    This work is concerned with the Ca transformations during the pyrolysis of Ca(OH)2 or CaCO3-added coals. Ca K-edge X-ray absorption near edge structure (XANES) spectroscopy was applied to determine the forms of Ca in chars prepared from the pyrolysis of Ca-added coal. Results showed that Ca(OH)2 and CaSO4 existed in both the Ca(OH)2-added chars and the CaCO3-added chars, while CaS and CaO only existed in the chars prepared from the Ca(OH)2-added coal. Moreover, it was found that carboxyl Ca was formed during pyrolysis for either the Ca(OH)2-added coal or the CaCO3-added coals.

  15. Calcium Green FlAsH as a genetically targeted small-molecule calcium indicator.

    Science.gov (United States)

    Tour, Oded; Adams, Stephen R; Kerr, Rex A; Meijer, Rene M; Sejnowski, Terrence J; Tsien, Richard W; Tsien, Roger Y

    2007-07-01

    Intracellular Ca(2+) regulates numerous proteins and cellular functions and can vary substantially over submicron and submillisecond scales, so precisely localized fast detection is desirable. We have created a approximately 1-kDa biarsenical Ca(2+) indicator, called Calcium Green FlAsH (CaGF, 1), to probe [Ca(2+)] surrounding genetically targeted proteins. CaGF attached to a tetracysteine motif becomes ten-fold more fluorescent upon binding Ca(2+), with a K(d) of approximately 100 microM, <1-ms kinetics and good Mg(2+) rejection. In HeLa cells expressing tetracysteine-tagged connexin 43, CaGF labels gap junctions and reports Ca(2+) waves after injury. Total internal reflection microscopy of tetracysteine-tagged, CaGF-labeled alpha(1C) L-type calcium channels shows fast-rising depolarization-evoked Ca(2+) transients, whose lateral nonuniformity suggests that the probability of channel opening varies greatly over micron dimensions. With moderate Ca(2+) buffering, these transients decay surprisingly slowly, probably because most of the CaGF signal comes from closed channels feeling Ca(2+) from a tiny minority of clustered open channels. With high Ca(2+) buffering, CaGF signals decay as rapidly as the calcium currents, as expected for submicron Ca(2+) domains immediately surrounding active channels. Thus CaGF can report highly localized, rapid [Ca(2+)] dynamics.

  16. Inhibition of tumor invasion and metastasis by calcium spirulan (Ca-SP), a novel sulfated polysaccharide derived from a blue-green alga, Spirulina platensis.

    Science.gov (United States)

    Mishima, T; Murata, J; Toyoshima, M; Fujii, H; Nakajima, M; Hayashi, T; Kato, T; Saiki, I

    1998-08-01

    We have investigated the effect of calcium spirulan (Ca-SP) isolated from a blue-green alga, Spirulina platensis, which is a sulfated polysaccharide chelating calcium and mainly composed of rhamnose, on invasion of B16-BL6 melanoma, Colon 26 M3.1 carcinoma and HT-1080 fibrosarcoma cells through reconstituted basement membrane (Matrigel). Ca-SP significantly inhibited the invasion of these tumor cells through Matrigel/fibronectin-coated filters. Ca-SP also inhibited the haptotactic migration of tumor cells to laminin, but it had no effect on that to fibronectin. Ca-SP prevented the adhesion of B16-BL6 cells to Matrigel and laminin substrates but did not affect the adhesion to fibronectin. The pretreatment of tumor cells with Ca-SP inhibited the adhesion to laminin, while the pretreatment of laminin substrates did not. Ca-SP had no effect on the production and activation of type IV collagenase in gelatin zymography. In contrast, Ca-SP significantly inhibited degradation of heparan sulfate by purified heparanase. The experimental lung metastasis was significantly reduced by co-injection of B16-BL6 cells with Ca-SP. Seven intermittent i.v. injections of 100 microg of Ca-SP caused a marked decrease of lung tumor colonization of B16-BL6 cells in a spontaneous lung metastasis model. These results suggest that Ca-SP, a novel sulfated polysaccharide, could reduce the lung metastasis of B16-BL6 melanoma cells, by inhibiting the tumor invasion of basement membrane probably through the prevention of the adhesion and migration of tumor cells to laminin substrate and of the heparanase activity.

  17. Selection of common bean lines with high grain yield and high grain calcium and iron concentrations

    Directory of Open Access Journals (Sweden)

    Nerinéia Dalfollo Ribeiro

    2014-02-01

    Full Text Available Genetic improvement of common bean nutritional quality has advantages in marketing and can contribute to society as a food source. The objective of this study was to evaluate the genetic variability for grain yield, calcium and iron concentrations in grains of inbred common bean lines obtained by different breeding methods. For this, 136 F7 inbred lines were obtained using the Pedigree method and 136 F7 inbred lines were obtained using the Single-Seed Descent (SSD method. The lines showed genetic variability for grain yield, and concentrations of calcium and iron independently of the method of advancing segregating populations. The Pedigree method allows obtaining a greater number of lines with high grain yield. Selection using the SSD method allows the identification of a larger number of lines with high concentrations of calcium and iron in grains. Weak negative correlations were found between grain yield and calcium concentration (r = -0.0994 and grain yield and iron concentration (r = -0.3926. Several lines show genetic superiority for grain yield and concentrations of calcium and iron in grains and their selection can result in new common bean cultivars with high nutritional quality.

  18. Hallmarks of the channelopathies associated with L-type calcium channels: a focus on the Timothy mutations in Ca(v)1.2 channels.

    Science.gov (United States)

    Bidaud, Isabelle; Lory, Philippe

    2011-12-01

    Within the voltage-gated calcium channels (Cav channels) family, there are four genes coding for the L-type Cav channels (Cav1). The Cav1 channels underly many important physiological functions like excitation-contraction coupling, hormone secretion, neuronal excitability and gene transcription. Mutations found in the genes encoding the Cav channels define a wide variety of diseases called calcium channelopathies and all four genes coding the Cav1 channels are carrying such mutations. L-type calcium channelopathies include muscular, neurological, cardiac and vision syndromes. Among them, the Timothy syndrome (TS) is linked to missense mutations in CACNA1C, the gene that encodes the Ca(v)1.2 subunit. Here we review the important features of the Cav1 channelopathies. We also report on the specific properties of TS-Ca(v)1.2 channels, which display non-inactivating calcium current as well as higher plasma membrane expression. Overall, we conclude that both electrophysiological and surface expression properties must be investigated to better account for the functional consequences of mutations linked to calcium channelopathies. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  19. Ab initio structure dertermination and property characterization of high-pressure Ca-O compounds and Li2(OH)Br crystals

    Science.gov (United States)

    Higgins, Christopher A.

    Theoretical modeling and computational simulations play an important role in materials research. In this thesis, we report on the study of two material systems using various computational methods. The first material system studied here are Cax-Oy compounds under high pressure. Calcium and oxygen are amongst the most abundant elements on Earth, and they form the compound calcium oxide (CaO) that is widely used and very stable at ambient pressures. Although the crystal structure and chemical composition of CaO seems to be simple and well understood, metastable or stable Ca-O compounds with unconventional stoichiometry may exist at high pressures. In this work, first-principles density functional theory calculations and ab initio evolutionary simulations have been used to predict high pressure Ca-O structures. We show that under increasing pressure, the stability of the Ca-O system changes and new materials emerge with different stable or metastable structures. In addition to CaO, we systematically examined structures for Ca, Ca2O, Ca2O3, Ca3O, Ca 3O2, Ca7O, CaO2, CaO3, CaO 7, and O at high pressures. The high-pressure phase diagram for these compounds is determined along with the electronic density of states and stoichiometry plots. Our energetic analysis identified three new stable Ca-O compounds, namely Ca2O3 and CaO2 that are thermodynamically stable above 40 GPa, and CaO3 becomes thermodynamically stable at 150 GPa. The second material system studied in this work is the compound Li 2(OH)Br. This compound has been shown by experiment to be a promising solid electrolyte for advanced solid state ionic battery applications. However, the crystal structure of this compound is highly complex and has not been determined accurately. This has impeded its further investigation and potential applications. We modeled the structure effectively using the density functional theory via VASP software. Having successfully determined the correct structure within our model and

  20. Effect of CaF2 on the Performance of Alite-strontium Calcium Sulfoaluminate Cement%CaF2对阿利特-硫铝酸锶钙水泥性能的影响

    Institute of Scientific and Technical Information of China (English)

    李秋英; 芦令超; 王守德

    2011-01-01

    Alite-strontium calcium sulphoaluminate cement, a new type of cementitious material is synthesized by combining strontium calcium sulphoaluminate with minerals of Portland cement. The influence of CaF2 on the synthesis and performance of the cement is studied by XRD, SEM-EDS, and lithofacies. The results show that suitable amount of CaF2 can benefit f-CaO combination and promote the formation of alite and strontium calcium sulphoaluminate at low temperature. The optimal mass fraction of CaF2 is 0. 6%. The compressive strength of the cement prepared under these conditions reaches to 32.8 MPa, 67.7 MPa and 120.4 MPa at 1 d,3 d and 28 d.%将硫铝酸锶钙矿物引入到硅酸盐熟料矿物体系中,合成阿利特-硫铝酸锶钙水泥.利用XRD,SEM-EDS和岩相等测试手段研究了CaF2对阿利特-硫铝酸锶钙水泥熟料矿物组成和水泥性能的影响.结果表明,CaF2能够促进固相反应使得阿利特在较低温度下形成,有利于阿利特和硫铝酸锶钙矿物的共存.当CaF2在熟料中的掺入量为0.6%时,阿利特-硫铝酸锶钙水泥的1 d、3 d和28 d抗压强度分别达到32.8 MPa、67.7 MPa和120.4 MPa,表现出良好的力学性能.

  1. The final phases of calcium and magnesium phosphates precipitated from solutions of high to medium concentration

    Science.gov (United States)

    Abbona, Francesco; Lundager Madsen, Hans Erik; Boistelle, Roland

    1988-07-01

    The phases of calcium and magnesium phosphates, which are obtained by evolution at 25°C of the first precipitates in their mother solutions, are described in terms of pH and composition of solutions. The initial conditions were: 0.050M ≤ [P] ≤ 0.500M; [P] = [Ca] + [Mg]; 0 ≤ [Mg]/[Ca] ≤ 1. The most abundant final phases are brushite, CaHPO 4·2H 2O; monetite, CaHPO 4; newberyite, MgHPO 4·3H 2O and struvite, MgNH 4PO 4·6H 2O. At low concentration whitlockite, Ca 9MgH(PO 4) 7, occurs with the amorphous phase previously precipitated, Ca 3(PO 4) 2·nH 2O. The conditions for stability are discussed and the changes observed are interpreted.

  2. Synthesis, crystal structure refinement, and nonlinear-optical properties of CaB{sub 3}O{sub 5}(OH): Comparative crystal chemistry of calcium triborates

    Energy Technology Data Exchange (ETDEWEB)

    Yamnova, N. A., E-mail: aks.crys@gmail.com; Aksenov, S. M. [Moscow State University, Faculty of Geology (Russian Federation); Stefanovich, S. Yu. [Moscow State University, Faculty of Chemistry (Russian Federation); Volkov, A. S.; Dimitrova, O. V. [Moscow State University, Faculty of Geology (Russian Federation)

    2015-09-15

    Calcium triborate CaB{sub 3}O5(OH) obtained by hydrothermal synthesis in the Ca(OH){sub 2}–H{sub 3}BO{sub 3}–Na{sub 2}CO{sub 3}–KCl system is studied by single-crystal X-ray diffraction. The parameters of the orthorhombic unit cell are as follows: a = 13.490(1), b = 6.9576(3), and c = 4.3930(2) Å; V = 412.32(3) Å{sup 3} and space group Pna2{sub 1}. The structure is refined in the anisotropic approximation of the atomic displacement parameters to R = 4.28% using 972 vertical bar F vertical bar > 4σ(F). It is confirmed that the crystal structure of Ca triborate CaB{sub 3}O{sub 5}(OH) is identical to that described earlier. The hydrogen atom is localized. An SHG signal stronger than that of the quartz standard is registered. The phase transition of calcium triborate into calciborite is found on heating. The comparative crystal-chemical analysis of a series of borates with the general chemical formula 2CaO · 3B{sub 2}O{sub 3} · nH{sub 2}O (n = 0–13) with the constant CaO: B{sub 2}O{sub 3}= 2: 3 ratio and variable content of water is performed.

  3. Highly-efficient multi-watt Yb:CaLnAlO4 microchip lasers

    Science.gov (United States)

    Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Yumashev, Konstantin; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

    2017-02-01

    Tetragonal rare-earth calcium aluminates, CaLnAlO4 where Ln = Gd or Y (CALGO and CALYO, respectively), are attractive laser crystal hosts due to their locally disordered structure and high thermal conductivity. In the present work, we report on highly-efficient power-scalable microchip lasers based on 8 at.% Yb:CALGO and 3 at.% Yb:CALYO crystals grown by the Czochralski method. Pumped by an InGaAs laser diode at 978 nm, the 6 mm-long Yb:CALGO microchip laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η = 84% (with respect to the absorbed pump power) and an optical-to-optical efficiency of ηopt = 49%. The 3 mm-long Yb:CALYO microchip laser generated 5.06 W at 1048-1056 nm corresponding to η = 91% and ηopt = 32%. Both lasers produced linearly polarized output (σ- polarization) with an almost circular beam profile and beam quality factors M2 x,y <1.1. The output performance of the developed lasers was modeled yielding a loss coefficient as low as 0.004-0.007 cm-1. The results indicate that the Yb3+- doped calcium aluminates are very promising candidates for high-peak-power passively Q-switched microchip lasers.

  4. Some aspects of the aqueous solution chemistry of the Na+/Ca2+/OH-/Cit3- system: The structure of a new calcium citrate complex forming under hyperalkaline conditions

    Science.gov (United States)

    Gácsi, Attila; Kutus, Bence; Buckó, Ákos; Csendes, Zita; Peintler, Gábor; Pálinkó, István; Sipos, Pál

    2016-08-01

    In the present study, we show that in hyperalkaline (pH > 13) aqueous solutions, Ca2+ forms a new, so far unknown complex species with the citrate ion, the structure of which is different from the well-known CaCit-(aq) species present in solutions of close to neutral pH. The solubility of Ca3Cit2(s) was found to increase significantly under hyperalkaline conditions. The decrease in the electric conductivity and the variations observed in the freezing point depression of such solutions also indicate complexation. From 1H NMR measurements, in this complex, the citrate ion is suggested to be in quadruply deprotonated form. From the variation of the 2JHH geminal proton coupling constant, two neighboring carboxylate groups are coordinated to the calcium ion in a monodentate mode (besides the alcoholate). The optimal structure of the complex with the composition of CaCitH-12-(aq) has also been calculated using DFT calculations, applying the Polarizable Continuum Model. Sodium ion-pairing was found to compete efficiently with this calcium complexation process, and in solutions with high Na-ion content, the equilibria are shifted towards the formation of NaCit2-(aq) and Na2Cit-(aq) ion pairs.

  5. Calcium contributes to photoprotection and repair of photosystem II in peanut leaves during heat and high irradiance

    Institute of Scientific and Technical Information of China (English)

    Sha Yang; Fang Wang; Feng Guo; Jing-Jing Meng; Xin-Guo Li; Shu-Bo Wan

    2015-01-01

    In this study, we investigated the effects of exogenous calcium nitrate on photoinhibition and thylakoid protein level in peanut plants under heat (40 °C) and high irradiance (HI) (1,200 mmol/m2 per s) stress. Compared with control seedlings (cultivated in 0 mmol/L Ca(NO3)2 medium), the maximal photochemical efficiency of photosystem II (PSII) in Ca2þ‐treated plants showed a slight decrease after 5 h stress, accompanied by lower degree of PSII closure (1‐qP), higher non‐photochemical quenching, and lower level of membrane damage. Ca2þ inhibitors were used to analyze the varieties of antioxidant enzymes activity and PSII proteins. These results indicated that Ca2þ could protect the subunits of PSII reaction centers from photoinhibition by reducing the generation of reactive oxygen species. In the presence of both ethyleneglycol‐bis(2‐aminoethylether)‐tetraacetic acid and ascorbic acid (AsA), the net degradation of the damaged D1 protein was faster than that only treated with AsA. Our previous study showed that either the transcriptional or the translational level of calmodulin was obviously higher in Ca2þ‐treated plants. These results suggested that, under heat and HI stress, the Ca2þ signal transduction pathway can al eviate the photoinhibition through regulating the protein repair process besides an enhanced capacity for scavenging reactive oxygen species.

  6. Thermoelectric properties of layered calcium cobaltite Ca3Co4O9 from hybrid functional first-principles calculations

    Science.gov (United States)

    Lemal, Sébastien; Varignon, Julien; Bilc, Daniel I.; Ghosez, Philippe

    2017-02-01

    Using a combination of first-principles calculations based on density functional theory and Boltzmann semiclassical transport theory, we compute and study the properties of pristine layered calcium cobaltite Ca3Co4O9 . We model the system with the B1WC hybrid functional. Two supercells of increasing size which approximate the incommensurate crystallographic structure of the compound are studied and we determine their structural, magnetic, and electronic properties. It is found that the B1WC hybrid functional is appropriate to reproduce the structural, electronic, and magnetic properties, which are then extensively discussed. From the electronic band structure, the Seebeck (S ) and electrical resistivity (ρ ) tensors are computed using Boltzmann transport theory within the constant relaxation-time approximation. The differences between the diagonal components are detailed and reveal a strong in-plane anisotropy of the properties. The qualitative behavior of the averaged in-plane properties, S// and ρ//, is consistent with the measurements reported in the literature. Our calculation clarifies and provides a broad picture of the evolution of the thermoelectric properties with both carrier density and temperature, and suggests that the change in S// and ρ// around 100 K is not necessarily related to the magnetic transitions occurring around 100 K.

  7. Study on Treatment of acidic and highly concentrated fluoride waste water using calcium oxide-calcium chloride

    Science.gov (United States)

    Ren, T.; Gao, X. R.; Zheng, T.; Wang, P.

    2016-08-01

    There are problems with treating acidic waste water containing high concentration fluorine by chemical precipitation, including the low sludge setting velocity and the high difficulty of reaching the criterion. In Heilongjiang province, a graphite factory producing high-purity graphite generates acidic waste water with a high concentration of fluorine. In this paper, the effect of removals on the concentration of fluoride with the combined treatment of calcium oxide and calcium chloride were discussed with regard to acid waste water. The study improved the sludge characteristics by using polyacrylamide (PAM) and polymeric aluminum chloride (PAC). The effect of different coagulants on sludge was evaluated by the sludge settlement ratio (SV), sludge volume index (SVI) and sludge moisture content. The results showed that the optimal combination for 100 ml waste water was calcium oxide addition amount of 14 g, a calcium chloride addition amount of 2.5 g, a PAM addition amount of 350 mg/L, and the effluent fluoride concentration was below 6 mg/L. PAM significantly improved the sludge settling velocity. The sludge settlement ratio reduced from 87.6% to 60%. The process for wastewater treatment was easily operated and involved low expenditure.

  8. Synthesis of highly phase pure (Bi, Pb)-Sr-Ca-Cu-O superconductor

    Science.gov (United States)

    Dorris, Stephen E.; Poeppel, Roger B.; Prorok, Barton C.; Lanagan, Michael T.; Maroni, Victor A.

    1994-01-01

    An article and method of manufacture of (Bi,Pb)-Sr-Ca-Cu-O superconductor. The superconductor is manufactured by preparing a first powdered mixture of bismuth oxide, lead oxide, strontium carbonate, calcium carbonate and copper oxide. A second powdered mixture is then prepared of strontium carbonate, calcium carbonate and copper oxide. The mixtures are calcined separately with the two mixtures then combined. The resulting combined mixture is then subjected to a powder in tube deformation and thermal processing to produce a substantially phase pure (Bi,Pb)-Sr-Ca-Cu-O superconductor.

  9. The Role of CaMKII in Calcium-Activated Death Pathways in Bone Marrow B Cells

    OpenAIRE

    2010-01-01

    Calcium is an essential signaling molecule in developing B cells, thus altering calcium dynamics represents a potential target for toxicant effects. GW7845, a tyrosine analog and potent peroxisome proliferator-activated receptor γ agonist, induces rapid mitogen-activated protein kinase (MAPK)–dependent apoptosis in bone marrow B cells. Changes in calcium dynamics are capable of mediating rapid initiation of cell death; therefore, we investigated the contribution of calcium to GW7845-induced a...

  10. Carbon Dioxide Captured from Flue Gas by Modified Ca-based Sorbents in Fixed-bed Reactor at High Temperature

    Institute of Scientific and Technical Information of China (English)

    YANG Lei; YU Hongbing; WANG Shengqiang; WANG Haowen; ZHOU Qibin

    2013-01-01

    Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors: calcium hydroxide,calcium carbonate,calcium acetate monohydrate and calcium oxide.The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350 650 ℃.It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃.The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg·g-1.The morphology of those sorbents was examined by scanning electron microscope(SEM),and the changes of composition before and after carbonation were also determined by X-ray diffraction(XRD).Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca(OH)2],and CaCO3 is the main component after carbonation reaction.The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction,and became much denser than before.The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area,larger pore volume and appropriate pore size distribution than that of CaO-CaO and Ca(OH)2-CaO.

  11. High calcium and dobutamine positive inotropy in the perfused mouse heart: myofilament calcium responsiveness, energetic economy, and effects of protein kinase C inhibition

    Directory of Open Access Journals (Sweden)

    Du Congwu

    2001-08-01

    Full Text Available Abstract Background In perfused hearts, high calcium-induced inotropy results in less developed pressure relative to myocardial oxygen consumption compared to the β-adrenergic agonist dobutamine. Calcium handling is an important determinant of myocardial oxygen consumption. Therefore, we hypothesized that this phenomenon was due to reduced myofilament responsiveness to calcium, related to protein kinase C activation. Results Developed pressure was significantly higher with dobutamine compared to high perfusate calcium of 3.5 mM (73 ± 10 vs 63 ± 10 mmHg, p Conclusions By measuring intracellular calcium, developed pressures and myocardial oxygen consumption in perfused mouse hearts, these results demonstrate that high perfusate calcium positive inotropy compared to dobutamine results in reduced myofilament responsiveness to intracellular calcium, which is associated with energetic inefficiency and evidence of protein kinase C activation.

  12. Structural behavior of the acetylide carbides Li2C2 and CaC2 at high pressure

    Science.gov (United States)

    Nylén, Johanna; Konar, Sumit; Lazor, Peter; Benson, Daryn; Häussermann, Ulrich

    2012-12-01

    The effects of high pressure (up to 30 GPa) on the structural properties of lithium and calcium carbide, Li2C2 and CaC2, were studied at room temperature by Raman spectroscopy in a diamond anvil cell. Both carbides consist of C2 dumbbells which are coordinated by metal atoms. At standard pressure and temperature two forms of CaC2 co-exist. Monoclinic CaC2-II is not stable at pressures above 2 GPa and tetragonal CaC2-I possibly undergoes a minor structural change between 10 and 12 GPa. Orthorhombic Li2C2 transforms to a new structure type at around 15 GPa. At pressures above 18 GPa (CaC2) and 25 GPa (Li2C2) Raman spectra become featureless, and remain featureless upon decompression which suggests an irreversible amorphization of the acetylide carbides. First principles calculations were used to analyze the pressure dependence of Raman mode frequencies and structural stability of Li2C2 and CaC2. A structure model for the high pressure phase of Li2C2 was searched by applying an evolutionary algorithm.

  13. Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Eun-Hee [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 151-744 (Korea, Republic of); Yoo, Jun-Sang [Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Seoul 110-749 (Korea, Republic of); Kim, Bo-Hye; Choi, Sung-Woo [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 151-744 (Korea, Republic of); Hong, Seong-Hyeon, E-mail: shhong@snu.ac.kr [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2014-02-15

    Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.

  14. Crystallization of calcium carbonate (CaCO3) in a flowing system: Influence of Cu2+ additives on induction time and crystalline phase transformation

    Science.gov (United States)

    Usmany, Y.; Putranto, W. A.; Bayuseno, A. P.; Muryanto, S.

    2016-04-01

    Scaling of calcium carbonate (CaCO3) is commonly found in piping systems in oil, gas, desalination and other chemical processes. The scale may create technical problems, leading to the reduction of heat transfer, increase of energy consumption and unscheduled equipment shutdown. This paper presents crystallization scaling experiments and evaluation of the effect of Cu2+ additives on the induction time and calcium carbonate transformation. The crystals precursors were prepared using equimolar of CaCl2 and Na2CO3 resulted in concentrations of 3000 ppm Ca2+ in the solution. The Cu2+ in amounts of 0, 1 and 10 ppm was separately added in the solution. The flow rates (20, 35, and 60 mL/min) and elevated temperatures (27, 35 and 45°C) were selected in the study. The induction time for crystallization of CaCO3 was observed by measuring the solution conductivity over time, while the phase transformation of calcium carbonate was examined by XRD method and SEM/EDX. It was found that the conductivity remained steady for a certain period reflecting to the induction time of crystal formation, and then decreased sharply afterwards,. The induction time was increased from 34 and 48 minutes in the presence of Cu additives (1 and 10 ppm), depending on the flow rates and temperature observed. In all the experiments, the Cu2+ addition leads to the reduction of mass of crystals. Apparently, the presence of Cu2+ could inhibit the CaCO3 crystallization. In the absence of Cu2+ and at elevated temperature, the crystals obtained were a mixture of vaterite and calcite. In the presence of Cu2+ and at elevated temperature, the crystals formed were aragonite and calcite. Here, the presence of Cu2+ additives might have controlled the crystal transformation of CaCO3.

  15. Calcium in plant cells

    Directory of Open Access Journals (Sweden)

    V. V. Schwartau

    2014-04-01

    Full Text Available The paper gives the review on the role of calcium in many physiological processes of plant organisms, including growth and development, protection from pathogenic influences, response to changing environmental factors, and many other aspects of plant physiology. Initial intake of calcium ions is carried out by Ca2+-channels of plasma membrane and they are further transported by the xylem owing to auxins’ attractive ability. The level of intake and selectivity of calcium transport to ove-ground parts of the plant is controlled by a symplast. Ca2+enters to the cytoplasm of endoderm cells through calcium channels on the cortical side of Kaspary bands, and is redistributed inside the stele by the symplast, with the use of Ca2+-АТPases and Ca2+/Н+-antiports. Owing to regulated expression and activity of these calcium transporters, calclum can be selectively delivered to the xylem. Important role in supporting calcium homeostasis is given to the vacuole which is the largest depo of calcium. Regulated quantity of calcium movement through the tonoplast is provided by a number of potential-, ligand-gated active transporters and channels, like Ca2+-ATPase and Ca2+/H+ exchanger. They are actively involved in the inactivation of the calcium signal by pumping Ca2+ to the depo of cells. Calcium ATPases are high affinity pumps that efficiently transfer calcium ions against the concentration gradient in their presence in the solution in nanomolar concentrations. Calcium exchangers are low affinity, high capacity Ca2+ transporters that are effectively transporting calcium after raising its concentration in the cell cytosol through the use of protons gradients. Maintaining constant concentration and participation in the response to stimuli of different types also involves EPR, plastids, mitochondria, and cell wall. Calcium binding proteins contain several conserved sequences that provide sensitivity to changes in the concentration of Ca2+ and when you

  16. Calcium isotopic composition of high-latitude proxy carrier Neogloboquadrina pachyderma (sin.

    Directory of Open Access Journals (Sweden)

    A. Eisenhauer

    2009-01-01

    Full Text Available The accurate reconstruction of sea surface temperature (SST history in climate-sensitive regions (e.g. tropical and polar oceans became a challenging task in palaeoceanographic research. Biogenic shell carbonate SST proxies successfully developed for tropical regions often fail in cool water environments. Their major regional shortcomings and the cryptic diversity now found within the major high latitude proxy carrier Neogloboquadrina pachyderma (sin. highlight an urgent need to explore complementary SST proxies for these cool-water regions. Here we incorporate the genetic component into a calibration study of a new SST proxy for the high latitudes. We found that the calcium isotopic composition (δ44/40Ca of calcite from genotyped net catches and core-top samples of the planktonic foraminifera Neogloboquadrina pachyderma (sin. is related to temperature and unaffected by genetic variations. The temperature sensitivity has been found to be 0.17 (±0.02‰ per 1°C, highlighting its potential for downcore applications in open marine cool-water environments. Our results further indicate that in extreme polar environments, below a critical threshold temperature of 2.0 (±0.5°C associated with salinities below 33.0 (±0.5‰, a prominent shift in biomineralization affects the δ44/40Ca of genotyped and core-top N. pachyderma (sin., becoming insensitive to temperature. These findings highlight the need of more systematic calibration studies on single planktonic foraminiferal species in order to unravel species-specific factors influencing the temperature sensitivity of Ca isotope fractionation and to validate the proxies' applicability.

  17. Reduced Expression of the Extracellular Calcium-Sensing Receptor (CaSR Is Associated with Activation of the Renin-Angiotensin System (RAS to Promote Vascular Remodeling in the Pathogenesis of Essential Hypertension.

    Directory of Open Access Journals (Sweden)

    Yuan-Yuan Qu

    Full Text Available The proliferation of vascular smooth muscle cells (VSMCs, remodeling of the vasculature, and the renin-angiotensin system (RAS play important roles in the development of essential hypertension (EH, which is defined as high blood pressure (BP in which secondary causes, such as renovascular disease, are absent. The calcium-sensing receptor (CaSR is involved in the regulation of BP. However, the underlying mechanisms by which the CaSR regulates BP are poorly understood. In the present study, the role of the CaSR in EH was investigated using male spontaneously hypertensive rats (SHRs and rat and human plasma samples. The percentages of medial wall thickness to external diameter (WT%, total vessel wall cross-sectional area to the total area (WA% of thoracic arteries, as well as the percentage of wall area occupied by collagen to total vessel wall area (CA% were determined. Tissue protein expression and plasma concentrations of the CaSR, cyclic adenosine monophosphate (cAMP, renin, and angiotensin II (Ang II were additionally assessed. WT%, WA%, and CA% were found to increase with increasing BP, whereas the plasma concentration of CaSR was found to decrease. With increasing BP, the levels of smooth muscle actin and calponin decreased, whereas those of osteopontin and proliferating cell nuclear antigen increased. The CaSR level negatively correlated with the levels of cAMP and Ang II, but positively correlated with those of renin. Our data suggest that reduced expression of the CaSR is correlated with activation of the RAS, which induces increased vascular remodeling and VSMC proliferation, and thereby associated with EH in the SHR model and in the Han Chinese population. Our findings provide new insights into the pathogenesis of EH.

  18. Age-dependent impact of CaV3.2 T-type calcium channel deletion on myogenic tone and flow-mediated vasodilatation in small arteries

    DEFF Research Database (Denmark)

    Mikkelsen, Miriam F.; Björling, Karl; Jensen, Lars Jørn

    2016-01-01

    .2-dependent and -independent effects. No changes in mRNA expression of several important K(+) and Ca(2+) channel genes were induced by CaV3.2 knock-out. However, the expression of the other T-type channel isoform (CaV3.1) was reduced at the mRNA and protein level in mature adult compared to young WT arteries......The myogenic response and flow-mediated vasodilatation are important regulators of local blood perfusion and total peripheral resistance, and are known to entail a calcium influx into vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), respectively. CaV3.2 T-type calcium channels...... are expressed in both VSMCs and ECs of small arteries. The T-type channels are important drug targets but due to the lack of specific antagonists our understanding of the role of CaV3.2 channels in vasomotor tone at various ages is scarce. We evaluated the myogenic response, flow-mediated vasodilatation...

  19. Calcium in pollen-pistil interaction in `Petunia hybrida Hor`. Pt. 1. Localization of Ca{sup 2+} ions in mature pollen grain using pyroantimonate and autoradiographic methods

    Energy Technology Data Exchange (ETDEWEB)

    Bednarska, E.; Butowt, R. [Uniwersytet Mikolaja Kopernika, Torun (Poland)

    1994-12-31

    The localization of Ca{sup 2+} in the mature pollen grain and the flow of these ions the somatic tissues of the anther to the pollen grains has been studied using pyroantimonate and autoradiographic methods. In the pollen grain, Ca{sup 2+} ions have been localized in the sporoderm in the cytoplasmic vesicles of probably dictyosomal origin. Calcium ions were transported into the sporoderm together with the compounds of degenerating tapetum. The material of degenerating tapetum forms pollen coat surrounding the mature pollen grains. (author). 18 refs, 9 figs.

  20. Nitric oxide-dependent activation of CaMKII increases diastolic sarcoplasmic reticulum calcium release in cardiac myocytes in response to adrenergic stimulation.

    Directory of Open Access Journals (Sweden)

    Jerry Curran

    Full Text Available Spontaneous calcium waves in cardiac myocytes are caused by diastolic sarcoplasmic reticulum release (SR Ca(2+ leak through ryanodine receptors. Beta-adrenergic (β-AR tone is known to increase this leak through the activation of Ca-calmodulin-dependent protein kinase (CaMKII and the subsequent phosphorylation of the ryanodine receptor. When β-AR drive is chronic, as observed in heart failure, this CaMKII-dependent effect is exaggerated and becomes potentially arrhythmogenic. Recent evidence has indicated that CaMKII activation can be regulated by cellular oxidizing agents, such as reactive oxygen species. Here, we investigate how the cellular second messenger, nitric oxide, mediates CaMKII activity downstream of the adrenergic signaling cascade and promotes the generation of arrhythmogenic spontaneous Ca(2+ waves in intact cardiomyocytes. Both SCaWs and SR Ca(2+ leak were measured in intact rabbit and mouse ventricular myocytes loaded with the Ca-dependent fluorescent dye, fluo-4. CaMKII activity in vitro and immunoblotting for phosphorylated residues on CaMKII, nitric oxide synthase, and Akt were measured to confirm activity of these enzymes as part of the adrenergic cascade. We demonstrate that stimulation of the β-AR pathway by isoproterenol increased the CaMKII-dependent SR Ca(2+ leak. This increased leak was prevented by inhibition of nitric oxide synthase 1 but not nitric oxide synthase 3. In ventricular myocytes isolated from wild-type mice, isoproterenol stimulation also increased the CaMKII-dependent leak. Critically, in myocytes isolated from nitric oxide synthase 1 knock-out mice this effect is ablated. We show that isoproterenol stimulation leads to an increase in nitric oxide production, and nitric oxide alone is sufficient to activate CaMKII and increase SR Ca(2+ leak. Mechanistically, our data links Akt to nitric oxide synthase 1 activation downstream of β-AR stimulation. Collectively, this evidence supports the hypothesis

  1. Formation of ettringite, Ca 6Al 2(SO 4) 3(OH) 12·26H 2O, AFt, and monosulfate, Ca 4Al 2O 6(SO 4)·14H 2O, AFm-14, in hydrothermal hydration of Portland cement and of calcium aluminum oxide—calcium sulfate dihydrate mixtures studied by in situ synchrotron X-ray powder diffraction

    Science.gov (United States)

    Christensen, Axel Nørlund; Jensen, Torben R.; Hanson, Jonathan C.

    2004-06-01

    In the hydration of calcium aluminum oxide-gypsum mixtures, i.e., Ca 3Al 2O 6, Ca 12Al 14O 33 and CaSO 4·2H 2O, the reaction products can be ettringite, Ca 6Al 2(SO 4) 3(OH) 12·26H 2O, monosulfate, Ca 4Al 2O 6(SO 4)·14H 2O, or the calcium aluminum oxide hydrate, Ca 4Al 2O 7·19H 2O. Ettringite is formed if sufficient CaSO 4·2H 2O is present in the mixture. Ettringite is converted to monosulfate when all CaSO 4·2H 2O is consumed in the synthesis of ettringite. The reactions were investigated in the temperature range 25-170°C using in situ synchrotron X-ray powder diffraction. This technique allows the study of very fast chemical reactions that are observed here under hydrothermal conditions. A new experimental approach was developed to perform in situ mixing of the reactants during X-ray data collection.

  2. Sodium-calcium exchanger and R-type Ca(2+) channels mediate spontaneous [Ca(2+)]i oscillations in magnocellular neurones of the rat supraoptic nucleus.

    Science.gov (United States)

    Kortus, Stepan; Srinivasan, Chinnapaiyan; Forostyak, Oksana; Zapotocky, Martin; Ueta, Yoichi; Sykova, Eva; Chvatal, Alexandr; Verkhratsky, Alexei; Dayanithi, Govindan

    2016-06-01

    Isolated supraoptic neurones generate spontaneous [Ca(2+)]i oscillations in isolated conditions. Here we report in depth analysis of the contribution of plasmalemmal ion channels (Ca(2+), Na(+)), Na(+)/Ca(2+) exchanger (NCX), intracellular Ca(2+) release channels (InsP3Rs and RyRs), Ca(2+) storage organelles, plasma membrane Ca(2+) pump and intracellular signal transduction cascades into spontaneous Ca(2+) activity. While removal of extracellular Ca(2+) or incubation with non-specific voltage-gated Ca(2+) channel (VGCC) blocker Cd(2+) suppressed the oscillations, neither Ni(2+) nor TTA-P2, the T-type VGCC blockers, had an effect. Inhibitors of VGCC nicardipine, ω-conotoxin GVIA, ω-conotoxin MVIIC, ω-agatoxin IVA (for L-, N-, P and P/Q-type channels, respectively) did not affect [Ca(2+)]i oscillations. In contrast, a specific R-type VGCC blocker SNX-482 attenuated [Ca(2+)]i oscillations. Incubation with TTX had no effect, whereas removal of the extracellular Na(+) or application of an inhibitor of the reverse operation mode of Na(+)/Ca(2+) exchanger KB-R7943 blocked the oscillations. The mitochondrial uncoupler CCCP irreversibly blocked spontaneous [Ca(2+)]i activity. Exposure of neurones to Ca(2+) mobilisers (thapsigargin, cyclopiazonic acid, caffeine and ryanodine); 4-aminopyridine (A-type K(+) current blocker); phospholipase C and adenylyl cyclase pathways blockers U-73122, Rp-cAMP, SQ-22536 and H-89 had no effect. Oscillations were blocked by GABA, but not by glutamate, apamin or dynorphin. In conclusion, spontaneous oscillations in magnocellular neurones are mediated by a concerted action of R-type Ca(2+) channels and the NCX fluctuating between forward and reverse modes.

  3. Effects of fructose-1,6-diphosphate on concentration of calcium and activities of sarcoplosnic Ca2+-ATPase in cardiomyocytes of Adriamycin-treated rats

    Institute of Scientific and Technical Information of China (English)

    CAI Wei; CHEN Jun-zhu; RUAN Li-ming; WANG Yi-na

    2005-01-01

    Objective: To observe the effects of fructose-1,6-diphosphate (FDP) on serum levels of cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB), as well as the concentration of calcium in cardiomyocytes (Myo[Ca2+]) and activity of sarcoplosnic Ca2+-ATPase (SRCa2+-ATPase) in Adriamycin (ADR)-treated rats. Methods: Rats were intraperitoneally injected with ADR (2.5mg/kg every other day for 6 times) and then with different dosages of FDP (every other day for twenty-one times). Bi-antibodies sandwich Enzyme linked immune absorption assay (ELISA) was performed to detect serum level of cTnI. CK-MB was detected by monoclonal antibody, Myo[Ca2+] was detected by fluorescent spectrophotometry and the activity of SRCa2+-ATPase was detected by inorganic phosphate method. Results: FDP (300, 600, 1200 mg/kg) significantly reduced the serum levels of cTnI and CK-MB, while at the same time decreased calcium concentration and increased SRCa2+-ATPase activity in cardiomyocytes of ADR-treated rats (P<0.01). Conclusions: FDP might alleviate the cardiotoxic effects induced by ADR through decreasing calcium level as well as increasing SRCa2+-ATPase activity in cardiomyocytes.

  4. Durability Study on High Calcium Fly Ash Based Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Ganesan Lavanya

    2015-01-01

    Full Text Available This study presents an investigation into the durability of geopolymer concrete prepared using high calcium fly ash along with alkaline activators when exposed to 2% solution of sulfuric acid and 5% magnesium sulphate for up to 45 days. The durability was also assessed by measuring water absorption and sorptivity. Ordinary Portland cement concrete was also prepared as control concrete. The grades chosen for the investigation were M20, M40, and M60. The alkaline solution used for present study is the combination of sodium silicate and sodium hydroxide solution with the ratio of 2.50. The molarity of sodium hydroxide was fixed as 12. The test specimens were 150×150×150 mm cubes, 100×200 mm cylinders, and 100×50 mm discs cured at ambient temperature. Surface deterioration, density, and strength over a period of 14, 28, and 45 days were observed. The results of geopolymer and ordinary Portland cement concrete were compared and discussed. After 45 days of exposure to the magnesium sulfate solution, the reduction in strength was up to 12% for geopolymer concrete and up to 25% for ordinary Portland cement concrete. After the same period of exposure to the sulphuric acid solution, the compressive strength decrease was up to 20% for geopolymer concrete and up to 28% for ordinary Portland cement concrete.

  5. High energy electron beams characterization using CaSO{sub 4}:Dy+PTFE Phosphors for clinical therapy applications

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, T., E-mail: trivera@ipn.mx [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, Col. Irrigacion. 11500 Mexico DF (Mexico); Espinoza, A.; Von, S.M. [Centro Estatal de Cancerologia de los Servicios de Salud de Nayarit, Enfermeria S/n, Fracc, Fray Junipero Serra, 63169 Tepic Nay (Mexico); Alvarez, R.; Jimenez, Y. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, Col. Irrigacion. 11500 Mexico DF (Mexico)

    2012-07-15

    In the present work high energy electron beam dosimetry from linear accelerator (LINACs) for clinical applications using dysprosium doped calcium sulfate embedded in polytetrafluorethylene (CaSO{sub 4}:Dy+PTFE) was studied. The irradiations were carried out using high electron beams (6 to 18 MeV) from a linear accelerator (LINAC) Varian, CLINAC 2300C/D, for clinical practice purpose. The electron irradiations were obtained using the water solid in order to guarantee electronic equilibrium conditions (EEC). Field shaping for electron beams was obtained with electron cones. Glow curve and other thermoluminescent characteristics of CaSO{sub 4}:Dy+PTFE were conducted under high electrons beams irradiations. The TL response of the pellets showed an intensity peak centered at around 215 Degree-Sign C. TL response of CaSO{sub 4}:Dy+PTFE as a function of high electron absorbed dose showed a linearity in a wide range. To obtain reproducibility characteristic, a set of pellets were exposed repeatedly for the same electron absorbed dose. The results obtained in this study can suggest the applicability of CaSO{sub 4}:Dy+PTFE pellets for high electron beam dosimetry, provided fading is correctly accounted for. - Highlights: Black-Right-Pointing-Pointer Developing of CaSO{sub 4}:Dy to electron beams dosimetry. Black-Right-Pointing-Pointer Characterization of caSO{sub 4}:Dy to radiation safety in LINACs. Black-Right-Pointing-Pointer TL characteristics of CaSO{sub 4}:Dy for electron beams quality control.

  6. Active Calcium/Calmodulin-Dependent Protein Kinase II (CaMKII Regulates NMDA Receptor Mediated Postischemic Long-Term Potentiation (i-LTP by Promoting the Interaction between CaMKII and NMDA Receptors in Ischemia

    Directory of Open Access Journals (Sweden)

    Ning Wang

    2014-01-01

    Full Text Available Active calcium/calmodulin-dependent protein kinase II (CaMKII has been reported to take a critical role in the induction of long-term potentiation (LTP. Changes in CaMKII activity were detected in various ischemia models. It is tempting to know whether and how CaMKII takes a role in NMDA receptor (NMDAR-mediated postischemic long-term potentiation (NMDA i-LTP. Here, we monitored changes in NMDAR-mediated field excitatory postsynaptic potentials (NMDA fEPSPs at different time points following ischemia onset in vitro oxygen and glucose deprivation (OGD ischemia model. We found that 10 min OGD treatment induced significant i-LTP in NMDA fEPSPs, whereas shorter (3 min or longer (25 min OGD treatment failed to induce prominent NMDA i-LTP. CaMKII activity or CaMKII autophosphorylation displays a similar bifurcated trend at different time points following onset of ischemia both in vitro OGD or in vivo photothrombotic lesion (PT models, suggesting a correlation of increased CaMKII activity or CaMKII autophosphorylation with NMDA i-LTP. Disturbing the association between CaMKII and GluN2B subunit of NMDARs with short cell-permeable peptides Tat-GluN2B reversed NMDA i-LTP induced by OGD treatment. The results provide support to a notion that increased interaction between NMDAR and CaMKII following ischemia-induced increased CaMKII activity and autophosphorylation is essential for induction of NMDA i-LTP.

  7. Anti-epileptic effect of Ganoderma lucidum polysaccharides by inhibition of intracellular calcium accumulation and stimulation of expression of CaMKII α in epileptic hippocampal neurons.

    Directory of Open Access Journals (Sweden)

    Shu-Qiu Wang

    Full Text Available To investigate the mechanism of the anti-epileptic effect of Ganoderma lucidum polysaccharides (GLP, the changes of intracellular calcium and CaMK II α expression in a model of epileptic neurons were investigated.Primary hippocampal neurons were divided into: 1 Control group, neurons were cultured with Neurobasal medium, for 3 hours; 2 Model group I: neurons were incubated with Mg(2+ free medium for 3 hours; 3 Model group II: neurons were incubated with Mg(2+ free medium for 3 hours then cultured with the normal medium for a further 3 hours; 4 GLP group I: neurons were incubated with Mg(2+ free medium containing GLP (0.375 mg/ml for 3 hours; 5 GLP group II: neurons were incubated with Mg(2+ free medium for 3 hours then cultured with a normal culture medium containing GLP for a further 3 hours. The CaMK II α protein expression was assessed by Western-blot. Ca(2+ turnover in neurons was assessed using Fluo-3/AM which was added into the replacement medium and Ca(2+ turnover was observed under a laser scanning confocal microscope.The CaMK II α expression in the model groups was less than in the control groups, however, in the GLP groups, it was higher than that observed in the model group. Ca(2+ fluorescence intensity in GLP group I was significantly lower than that in model group I after 30 seconds, while in GLP group II, it was reduced significantly compared to model group II after 5 minutes.GLP may inhibit calcium overload and promote CaMK II α expression to protect epileptic neurons.

  8. Gentamicin Blocks the ACh-Induced BK Current in Guinea Pig Type II Vestibular Hair Cells by Competing with Ca2+ at the l-Type Calcium Channel

    Directory of Open Access Journals (Sweden)

    Hong Yu

    2014-04-01

    Full Text Available Type II vestibular hair cells (VHCs II contain big-conductance Ca2+-dependent K+ channels (BK and L-type calcium channels. Our previous studies in guinea pig VHCs II indicated that acetylcholine (ACh evoked the BK current by triggering the influx of Ca2+ ions through l-type Ca2+ channels, which was mediated by M2 muscarinic ACh receptor (mAChRs. Aminoglycoside antibiotics, such as gentamicin (GM, are known to have vestibulotoxicity, including damaging effects on the efferent nerve endings on VHCs II. This study used the whole-cell patch clamp technique to determine whether GM affects the vestibular efferent system at postsynaptic M2-mAChRs or the membrane ion channels. We found that GM could block the ACh-induced BK current and that inhibition was reversible, voltage-independent, and dose-dependent with an IC50 value of 36.3 ± 7.8 µM. Increasing the ACh concentration had little influence on GM blocking effect, but increasing the extracellular Ca2+ concentration ([Ca2+]o could antagonize it. Moreover, 50 µM GM potently blocked Ca2+ currents activated by (--Bay-K8644, but did not block BK currents induced by NS1619. These observations indicate that GM most likely blocks the M2 mAChR-mediated response by competing with Ca2+ at the l-type calcium channel. These results provide insights into the vestibulotoxicity of aminoglycoside antibiotics on mammalian VHCs II.

  9. Scheelite CaWO{sub 4} at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Grzechnik, Andrzej [Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth (Germany); Crichton, Wilson A [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble cedex (France); Hanfland, Michael [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble cedex (France); Smaalen, Sander van [Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth (Germany)

    2003-11-05

    The high-pressure room-temperature behaviour of scheelite CaWO{sub 4} (I4{sub 1}/a,Z = 4) is studied using high-resolution synchrotron angle-dispersive x-ray powder diffraction in diamond anvil cells loaded with helium or a mixture of methanol and ethanol as the pressure-transmitting media. At about 10 GPa, there occurs a phase transition to the fergusonite type (I 2/a,Z = 4) without any discontinuity in the pressure dependence of the unit cell volumes. These observations are discussed in relation to the high-pressure-high-temperature systematics of the AMX{sub 4} and AX{sub 2} type compounds.

  10. Surface properties, crystallinity and optical properties of anodised titanium in mixture of β-glycerophosphate (β-GP) and calcium acetate (CA)

    Energy Technology Data Exchange (ETDEWEB)

    Chuan, Lee Te, E-mail: gd130079@siswa.uthm.edu.my; Abdullah, Hasan Zuhudi, E-mail: hasan@uthm.edu.my; Idris, Maizlinda Izwana, E-mail: izwana@uthm.edu.my [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor (Malaysia)

    2015-07-22

    Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It had been widely used to deposit the ceramic coatings on the metals surface. This method has been widely used in surface modification of biomaterials especially for dental implants. In this study, the surface morphology, crystallinity and optical properties of titanium foil was modified by anodising in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA). The experiments were carried out at high voltage (350 V), different anodising time (5 and 10 minutes) and current density (10-70 mA.cm{sup −2}) at room temperature. Anodised titanium was characterised by using field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), and UV-Vis spectrometry. The result of the experiment showed that surface morphology, crystallinity and optical properties depended strongly on the current density and anodising time. More porous surface and large amount of anatase and rutile was produced at higher current density and longer anodising time. Apart from that, it is also revealed that the energy band gap of anodised titanium increases as the increase in current density due to the presence of anatase and rutile TiO{sub 2}.

  11. Surface properties, crystallinity and optical properties of anodised titanium in mixture of β-glycerophosphate (β-GP) and calcium acetate (CA)

    Science.gov (United States)

    Chuan, Lee Te; Abdullah, Hasan Zuhudi; Idris, Maizlinda Izwana

    2015-07-01

    Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It had been widely used to deposit the ceramic coatings on the metals surface. This method has been widely used in surface modification of biomaterials especially for dental implants. In this study, the surface morphology, crystallinity and optical properties of titanium foil was modified by anodising in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA). The experiments were carried out at high voltage (350 V), different anodising time (5 and 10 minutes) and current density (10-70 mA.cm-2) at room temperature. Anodised titanium was characterised by using field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), and UV-Vis spectrometry. The result of the experiment showed that surface morphology, crystallinity and optical properties depended strongly on the current density and anodising time. More porous surface and large amount of anatase and rutile was produced at higher current density and longer anodising time. Apart from that, it is also revealed that the energy band gap of anodised titanium increases as the increase in current density due to the presence of anatase and rutile TiO2.

  12. The crystal structure and luminescent properties of nitrogen-rich Ca-α-sialon:Eu with saturated calcium solubility fabricated by the alloy-nitridation method

    Institute of Scientific and Technical Information of China (English)

    Yang Jian-Jun; Chen Guo-Dong; Du Fei-Fei; Liu Quan-Lin

    2012-01-01

    Nitrogen-rich Ca-α-sialon:Eu2+ phosphors with saturated calcium solubility are synthesized through a solidstate reaction (SSR) at 2173 K with stable alloy and nitride as the starting materials.The Ca1.83-1.5xSi8.34 A13.66OxN16-x:xEu phosphors have intensive orange emissions,whose peaks are located at approximately 585-600 nm,and the emission wavelengths tend to shift toward the red region when the Eu concentrations increase from 0.5% to 18% (mole percentage).When the Eu concentration is equal to 9%,the phosphors suffer from concentration quenching.The low-temperature photoluminescence properties indicate that Ca1.83-1.5xSi8.34Al3.66OxN16-x:xEu phosphors show excellent thermal quenching.The crystal structures of Ca1.83-1.5xSis.34Al3.66OxN16-x:xEu are also investigated,and are found to have nitrogen-rich compositions with saturated calcium cations at the interstitial sites of the α-sialons.In addition,the influencing factors of α-sialons with different compositions on the crystal lattice are discussed in detail.

  13. Bioinformatic analysis of CaBP/calneuron proteins reveals a family of highly conserved vertebrate Ca2+-binding proteins

    Directory of Open Access Journals (Sweden)

    Burgoyne Robert D

    2010-04-01

    Full Text Available Abstract Background Ca2+-binding proteins are important for the transduction of Ca2+ signals into physiological outcomes. As in calmodulin many of the Ca2+-binding proteins bind Ca2+ through EF-hand motifs. Amongst the large number of EF-hand containing Ca2+-binding proteins are a subfamily expressed in neurons and retinal photoreceptors known as the CaBPs and the related calneuron proteins. These were suggested to be vertebrate specific but exactly which family members are expressed outside of mammalian species had not been examined. Findings We have carried out a bioinformatic analysis to determine when members of this family arose and the conserved aspects of the protein family. Sequences of human members of the family obtained from GenBank were used in Blast searches to identify corresponding proteins encoded in other species using searches of non-redundant proteins, genome sequences and mRNA sequences. Sequences were aligned and compared using ClustalW. Some families of Ca2+-binding proteins are known to show a progressive expansion in gene number as organisms increase in complexity. In contrast, the results for CaBPs and calneurons showed that a full complement of CaBPs and calneurons are present in the teleost fish Danio rerio and possibly in cartilaginous fish. These findings suggest that the entire family of genes may have arisen at the same time during vertebrate evolution. Certain members of the family (for example the short form of CaBP1 and calneuron 1 are highly conserved suggesting essential functional roles. Conclusions The findings support the designation of the calneurons as a distinct sub-family. While the gene number for CaBPs/calneurons does not increase, a distinctive evolutionary change in these proteins in vertebrates has been an increase in the number of splice variants present in mammals.

  14. Synthesis and luminescent properties of low oxygen contained Eu2+-doped Ca-α-SiAlON phosphor from calcium cyanamide reduction

    Institute of Scientific and Technical Information of China (English)

    PIAO Xianqing; Ken-ichi Machida; Takashi Horikawa; Hiromasa Hanzawa

    2008-01-01

    A new convenient calcium cyanamide (CaCN2) reduction route was developed to synthesize the Eu2+ activated Ca-α-SiAlON phosphors containing low oxygen content. The luminescence properties of the obtained products were investigated for white LEDs application. The critical Eu2+ concentration in various hosts and its effect on the photoluminescence properties were studied. The optimized sample (10at.% Eu2+ vs. Ca2+) could be efficiently excited by the current GaN/InGaN blue LED chips and provided emission intensity competitive with that of YAG:Ce3+ (P46-Y3) standard, revealing that this phosphor was a potential candidate for phosphor-converted white LEDs.

  15. Structural and electrochemical characterization of calcium cobaltites (Ca{sub 3}Co{sub 4}O{sub 9}) obtained by the modified Pechini Method; Caracterizacao estrutural e eletroquimica de cobaltita de calcio (Ca{sub 3}Co{sub 4}O{sub 9}) obtida pelo Metodo Pechini modificado

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.M.; Aquino, F. de M.; Macedo, D. A. de, E-mail: rinaldo_mendesa@hotmail.com [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil)

    2016-07-01

    This work deals with the synthesis and characterization of calcium cobaltite (Ca{sub 3}Co{sub 4}O{sub 9}, C349), a p-type semiconductor with high Seebeck coefficient (S), high electrical conductivity and low thermal conductivity that has emerged as thermoelectric material. The synthesis method used to obtain the compound C349 uses commercial gelatin as complexing and polymerizing agent. The obtained material was characterized by X-ray diffraction with Rietveld refinement of the diffraction data. The results indicated that the modified Pechini method using gelatin allows to obtain powders of calcium cobaltite (with monoclinic structure) associated with a small content (2% by volume) of Co{sub 3}O{sub 4} with cubic structure. Impedance spectroscopy measurements in air indicated that the composite C349/Co{sub 3}O{sub 4} is a promising material for use as solid oxide fuel cell cathode.(author)

  16. 48Ca Production in Matter Expanding from High Temperature and Density

    Science.gov (United States)

    Meyer, Bradley S.; Krishnan, Tracy D.; Clayton, Donald D.

    1996-05-01

    We calculate with a large nuclear reaction network the nuclear dynamics associated with the expansions and cooling of initially hot and dense matter. We study matter with neutron excess near that of 48Ca, because one objective is to clarify the nucleosynthesis of that abundant neutron-rich nucleus, whose origin has been enigmatic. Expecting that supernovae provide the site of its origin, we take initial temperatures near T9 = 10 but survey a wide range of initial densities, corresponding to a wide range in initial entropies. The highest entropies are probably associated with winds from newborn neutron stars in Type II collapse events, whereas the smallest entropies are probably associated with very high density Type Ia cores. Our survey objective is the analysis of the dynamics of the nuclear assembly as it cools, and how the correct description of it depends on the specific entropy. We show that resultant abundances of neutron-rich nuclei are very poorly represented by nuclear statistical equilibrium (NSE). The deviations from NSE are governed by the number of heavy nuclei assembled during the expansion, which differs significantly from the number demanded by NSE at both high and low entropy. High-entropy expansions are shown to contain too few nuclei, with the result that 48Ca cannot survive the expansion even though it would be expected to be abundant using NSE guidelines. Low-entropy expansions contain too many nuclei with respect to that guideline, with the result that 48Ca is more abundant than expected. In this case it is especially significant that the ratio of 48Ca to other major neutron-rich nuclei (e.g., 66Zn, 82Se) is substantially greater than NSE guidelines, which ameliorates overproduction limits from the latter. We show, furthermore, that the 48Ca nucleus itself plays a key role in the nuclear dynamics. In the low-entropy expansion, which is the one to which we must look for 48Ca origin, abundant 48Ca is a refractory post, a local abundance maximum

  17. "Slow" Voltage-Dependent Inactivation of CaV2.2 Calcium Channels Is Modulated by the PKC Activator Phorbol 12-Myristate 13-Acetate (PMA.

    Directory of Open Access Journals (Sweden)

    Lei Zhu

    Full Text Available CaV2.2 (N-type voltage-gated calcium channels (Ca2+ channels play key roles in neurons and neuroendocrine cells including the control of cellular excitability, neurotransmitter / hormone secretion, and gene expression. Calcium entry is precisely controlled by channel gating properties including multiple forms of inactivation. "Fast" voltage-dependent inactivation is relatively well-characterized and occurs over the tens-to- hundreds of milliseconds timeframe. Superimposed on this is the molecularly distinct, but poorly understood process of "slow" voltage-dependent inactivation, which develops / recovers over seconds-to-minutes. Protein kinases can modulate "slow" inactivation of sodium channels, but little is known about if/how second messengers control "slow" inactivation of Ca2+ channels. We investigated this using recombinant CaV2.2 channels expressed in HEK293 cells and native CaV2 channels endogenously expressed in adrenal chromaffin cells. The PKC activator phorbol 12-myristate 13-acetate (PMA dramatically prolonged recovery from "slow" inactivation, but an inactive control (4α-PMA had no effect. This effect of PMA was prevented by calphostin C, which targets the C1-domain on PKC, but only partially reduced by inhibitors that target the catalytic domain of PKC. The subtype of the channel β-subunit altered the kinetics of inactivation but not the magnitude of slowing produced by PMA. Intracellular GDP-β-S reduced the effect of PMA suggesting a role for G proteins in modulating "slow" inactivation. We postulate that the kinetics of recovery from "slow" inactivation could provide a molecular memory of recent cellular activity and help control CaV2 channel availability, electrical excitability, and neurotransmission in the seconds-to-minutes timeframe.

  18. Calcium isotope constraints on the marine carbon cycle and CaCO3 deposition during the late Silurian (Ludfordian) positive δ13C excursion

    Science.gov (United States)

    Farkaš, Juraj; Frýda, Jiří; Holmden, Chris

    2016-10-01

    This study investigates calcium isotope variations (δ 44 / 40 Ca) in late Silurian marine carbonates deposited in the Prague Basin (Czech Republic), which records one of the largest positive carbon isotope excursion (CIE) of the entire Phanerozoic, the mid-Ludfordian CIE, which is associated with major climatic changes (abrupt cooling) and global sea-level fluctuations. Our results show that during the onset of the CIE, when δ13 C increases rapidly from ∼0‰ to ∼8.5‰, δ 44 / 40Ca remains constant at about 0.3 ± 0.1 ‰ (relative to NIST 915a), while 87Sr/86Sr in well-preserved carbonates are consistent with a typical Ludfordian seawater composition (ranging from ∼0.70865 to ∼0.70875). Such decoupling between δ13 C and δ 44 / 40Ca trends during the onset of the CIE is consistent with the expected order-of-magnitude difference in the residence times of Ca (∼106yr) and C (∼105yr) in the open ocean, suggesting that the mid-Ludfordian CIE was caused by processes where the biogeochemical pathways of C and Ca in seawater were mechanistically decoupled. These processes may include: (i) near shore methanogenesis and photosynthesis, (ii) changes in oceanic circulation and stratification, and/or (iii) increased production and burial of organic C in the global ocean. The latter, however, is unlikely due to the lack of geological evidence for enhanced organic C burial, and also because of unrealistic parameterization of the ocean C cycle needed to generate the observed CIE over the relatively short time interval. In contrast, higher up in the section where δ13 C shifts back to pre-excursion baseline values, there is a correlated shift to higher δ 44 / 40Ca values. Such coupling of the records of Ca and C isotope changes in this part of the study section is inconsistent with the abovementioned differences in oceanic Ca and C residence times, indicating that the record of δ 44 / 40Ca changes does not faithfully reflect the evolution of the oceanic Ca

  19. Calcium biogeochemical cycle at the beech tree-soil solution interface from the Strengbach CZO (NE France): insights from stable Ca and radiogenic Sr isotopes

    Science.gov (United States)

    Schmitt, Anne-Désirée; Gangloff, Sophie; Labolle, François; Chabaux, François; Stille, Peter

    2017-09-01

    Calcium (Ca) is the fourth most abundant element in mineral nutrition and plays key physiological and structural roles in plant metabolism. At the soil-water-plant scale, stable Ca isotopes are a powerful tool for the identification of plant-mineral interactions and recycling via vegetation. Radiogenic Sr isotopes are often used as tracers of Ca sources and mixtures of different reservoirs. In this study, stable Ca and radiogenic Sr are combined and analysed in several organs from two beech trees that were collected in June and September in the Strengbach critical zone observatory (CZO) (NE France) and in corresponding soil solutions. At the beech-tree scale, this study confirms the field Ca adsorption (i.e., physico-chemical mechanism and not vital effects) on carboxyl acid groups of pectin in the apoplasm of small roots. The analysis of the xylem sap and corresponding organs shows that although the Strengbach CZO is nutrient-poor, Ca seems to be non-limiting for tree-growth. Different viscosities of xylem sap between the stemwood and branches or leaves can explain δ44/40Ca values in different tree-organs. The bark and phloem 40Ca-enrichments could be due to Ca-oxalate precipitation in the bark tissues and in the phloem. The results from this study regarding the combination of these two isotopic systems show that the isotopic signatures of the roots are dominated by Ca fractionation mechanisms and Sr, and thus Ca, source variations. In contrast, translocation mechanisms are only governed by Ca fractionation processes. This study showed that at the root-soil solution interface, litter degradation was not the main source of Ca and Sr and that the soil solutions are not the complement of uptake by roots for samples from the 2011/2013 period. The opposite is observed for older samples. These observations indicate the decreasing contribution of low radiogenic Sr fluxes, such as recycling, alimenting the soil solutions. Such reduced importance of nutrient uptake and

  20. Protein Kinase Cα and P-Type Ca2+ Channel CaV2.1 in Red Blood Cell Calcium Signalling

    Directory of Open Access Journals (Sweden)

    Lisa Wagner-Britz

    2013-06-01

    Full Text Available Background/Aims: Protein kinase Cα (PKCα is activated by an increase in cytosolic Ca2+ in red blood cells (RBCs. Previous work has suggested that PKCα directly stimulates the CaV2.1 channel, whereas other studies revealed that CaV2.1 is insensitive to activation by PKC. The aim of this study was to resolve this discrepancy. Methods: We performed experiments based on a single cell read-out of the intracellular Ca2+ concentration in terms of Fluo-4 fluorescence intensity and phosphatidylserine exposure to the external membrane leaflet. Measurement modalities included flow cytometry and live cell imaging. Results: Treatment of RBCs with phorbol 12-myristate 13-acetate (PMA led to two distinct populations of cells with an increase in intracellular Ca2+: a weak-responding and a strong-responding population. The EC50 of PMA for the number of cells with Ca2+ elevation was 2.7±1.2 µM; for phosphatidylserine exposure to the external membrane surface, it was 2.8±0.5 µM; and for RBC haemolysis, it was 2.9±0.5 µM. Using pharmacological manipulation with the CaV2.1 inhibitor ω-agatoxin TK and the broad protein kinase C inhibitor Gö6983, we are able to show that there are two independent PMA-activated Ca2+ entry processes: the first is independent of CaV2.1 and directly PKCα-activated, while the second is associated with a likely indirect activation of CaV2.1. Further studies using lysophosphatidic acid (LPA as a stimulation agent have provided additional evidence that PKCα and CaV2.1 are not directly interconnected in a signalling chain. Conclusion: Although we provide evidence for a lack of interaction between PKCα and CaV2.1 in RBCs, further studies are required to decipher the signalling relationship between LPA, PKCα and CaV2.1.

  1. Calcium-Sensing Receptor Regulates Cytosolic [Ca2+] and Plays a Major Role in the Development of Pulmonary Hypertension

    Directory of Open Access Journals (Sweden)

    Kimberly A. Smith

    2016-11-01

    Full Text Available AbstractPulmonary arterial hypertension (PAH is a progressive disease characterized by elevated pulmonary vascular resistance (PVR leading to right heart failure and premature death. The increased PVR results in part from pulmonary vascular remodeling and sustained pulmonary vasoconstriction. Excessive pulmonary vascular remodeling stems from increased pulmonary arterial smooth muscle cell (PASMC proliferation and decreased PASMC apoptosis. A rise in cytosolic free Ca2+ concentration ([Ca2+]cyt in PASMC is a major trigger for pulmonary vasoconstriction and a key stimulus for PASMC proliferation and migration, both contributing to the development of pulmonary vascular remodeling. PASMC from patients with idiopathic PAH (IPAH have increased resting [Ca2+]cyt and enhanced Ca2+ influx. Enhanced Ca2+ entry into PASMC due to upregulation of membrane receptors and/or Ca2+ channels may contribute to PASMC contraction and proliferation and to pulmonary vasoconstriction and pulmonary vascular remodeling. We have shown that the extracellular Ca2+-sensing receptor (CaSR, which is a member of G protein-coupled receptor (GPCR subfamily C, is upregulated and the extracellular Ca2+-induced increase in [Ca2+]cyt is enhanced in PASMC from patients with IPAH in comparison to PASMC from normal subjects. Pharmacologically blockade of CaSR significantly attenuate the development and progression of experimental pulmonary hypertension in animals. Additionally, we have demonstrated that dihydropyridine Ca2+ channel blockers (e.g., nifedipine, which are used to treat PAH patients but are only effective in 15-20% of patients, activate CaSR resulting in an increase in [Ca2+]cyt in IPAH-PASMC, but not normal PASMC. Our data indicate that CaSR functionally couples with transient receptor potential canonical (TRPC channels to mediate extracellular Ca2+-induced Ca2+ influx and increase in [Ca2+]cyt in IPAH-PASMC. Upregulated CaSR is necessary for the enhanced extracellular Ca2

  2. Calcium aluminate cement hydration in a high alkalinity environment

    Directory of Open Access Journals (Sweden)

    Palomo, Á.

    2009-03-01

    Full Text Available The present paper forms part of a broader research project that aims primarily to devise new cementitious products via the alkali activation of silico-aluminous materials. This work addresses the possibility of using small percentages of calcium aluminate cement (CAC as a source of reactive aluminium. For this reason, a preliminary review was needed of the behaviour of CACs in highly alkaline media (2, 8 and 12M NaOH solutions. Two, 28- and 180-day mechanical strength was determined and the reaction products were characterized with XRD and FTIR. The water-hydrated CAC was used as the control.The results obtained showed that CAC hardening took place much more slowly in highly alkaline media than in water. Nonetheless, the 28-day compressive strength obtained, ≥80MPa. As main reaction products, to ambient temperature and from the two days of cured, cubic aluminate C3AH6, and AH3 polymorphs are formed, instead of the usual hexagonal aluminatos (CAH10 and C2AH8 that are formed in the normal hydrate with water.El presente trabajo forma parte de una amplia investigación cuyo objetivo principal es el de elaborar nuevos materiales con propiedades cementantes mediante la activación alcalina de materiales de naturaleza silito-aluminosa. En estos estudios se contempla la posibilidad de utilizar pequeños porcentajes de cemento de aluminato de calcio (CAC como fuente de aluminio reactivo. Por ello inicialmente se ha estudiado el comportamiento de los CAC en medios fuertemente alcalinos (disoluciones de NaOH 2M, 8M y 12M. Se determinaron las resistencias mecánicas a 2, 28 y 180 días y se realizó una caracterización de los productos de reacción formados por DRX, FTIR. Como sistema de referencia se consideró la hidratación del CAC con agua.Los resultados obtenidos muestran que en medios fuertemente alcalinos se retrasan los procesos de rápido endurecimiento de CAC con agua. No obstante a 28 días se obtienen valores de resistencia a compresión

  3. Evolution of precipitation during non-isothermal ageing of an Mg-Ca-Zn alloy with high Ca content

    Energy Technology Data Exchange (ETDEWEB)

    Langelier, Brian, E-mail: blangeli@engmail.uwaterloo.ca [University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Wang, Xiang [McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8 (Canada); Esmaeili, Shahrzad [University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Precipitation hardening characterized for an Mg-Ca-Zn alloy with high Ca content. Black-Right-Pointing-Pointer Evolution of precipitation during non-isothermal ageing identified by TEM and DSC. Black-Right-Pointing-Pointer DSC data de-convoluted using heat treatments developed from thermodynamic analysis. Black-Right-Pointing-Pointer De-convoluted DSC provides further insight into the complex precipitation behaviour. - Abstract: In this work, the precipitation behaviour of an Mg-Ca-Zn alloy with high content of Ca relative to Zn was studied. Differential scanning calorimetry (DSC) was combined with transmission electron microscopy (TEM) and hardness measurement to examine the precipitate evolution in this alloy. A non-isothermal age-hardening heat treatment was performed to allow for a direct comparison to DSC results. Thermodynamic analysis aided in identifying ageing heat treatments to further de-convolute the overlapping DSC data. Results suggested the precipitation events followed sequential evolution towards the formation of two types of equilibrium phases (i.e. Mg{sub 2}Ca and Mg{sub 6}Ca{sub 2}Zn{sub 3}). Early stage decomposition of the solid solution had no observable effect on hardness, but was followed by the formation of hardening GP zones. Fine basal plates, as well as large coarse basal plates of Mg{sub 2}Ca-type formed on further ageing. Contrast due to fine unidentified nanoscale precipitates was also observed in the over-aged state. These precipitates tended to disappear, while blocky Mg{sub 2}Ca equilibrium phase precipitates formed as the heat treatment progressed to the highest temperature studied (i.e. 300 Degree-Sign C). However, the equilibrium Mg{sub 6}Ca{sub 2}Zn{sub 3}phase was not observed when this final test temperature was achieved at the end of the non-isothermal heat treatment process.

  4. Modeling calcium dissolution from oil shale ash: Part 1. Ca dissolution during ash washing in a batch reactor

    Energy Technology Data Exchange (ETDEWEB)

    Velts, O.; Kallas, J. [Tallinn University of Technology, Laboratory of Inorganic Materials, 5 Ehitajate Str., Tallinn 19086 (Estonia); Lappeenranta University of Technology, Laboratory of Separation Technology, Skinnarilankatu 34, Lappeenranta 53851 (Finland); Hautaniemi, M. [Lappeenranta University of Technology, Laboratory of Separation Technology, Skinnarilankatu 34, Lappeenranta 53851 (Finland); Kuusik, R. [Tallinn University of Technology, Laboratory of Inorganic Materials, 5 Ehitajate Str., Tallinn 19086 (Estonia)

    2010-05-15

    Batch dissolution experiments were carried out to investigate Ca leachability from oil shale ashes formed in boilers operating with different combustion technologies. The main characteristics of Ca dissolution equilibrium and dynamics, including Ca internal mass transfer through effective diffusion coefficients inside the ash particle were evaluated. Based on the collected data, models allowing simulation of the Ca dissolution process from oil shale ashes during ash washing in a batch reactor were developed. The models are a set of differential equations that describe the changes in Ca content in the solid and liquid phase of the ash-water suspension. (author)

  5. Advances in lithium and calcium high-rate oxyhalide batteries

    Science.gov (United States)

    Hagan, W. P.; Green, S.; Sargeant, D. G.; Packer, R. K.

    The characteristics of lithium and calcium oxyhalide battery systems are considered, with special attention given to those of lithium-thionyl chloride and lithium-sulfuryl chloride cells. It is shown that, for a capability of above 50 mA/sq cm, lithium-sulfuryl chloride is the preferred cell chemistry, although calcium-thionyl chloride (which is acceptable up to 50 mA/sq cm) may be preferrable if thermal management is a problem. Lithium-sulfuryl chloride cells were found to exhibit a form of concentration polarization which is strongly dependent on interelectrode separation. In such cells, interelectrode separations have to be minimized if premature failure is to be avoided.

  6. Ca(2+)-free, high-Ca2+ coronary perfusion suppresses contractility and excitation-contraction coupling energy.

    Science.gov (United States)

    Araki, J; Takaki, M; Namba, T; Mori, M; Suga, H

    1995-03-01

    We studied the mechanoenergetic effects of a short-term Ca(2+)-free, high-Ca2+ Tyrode solution coronary perfusion in eight excised, cross-circulated canine hearts. The perfusion protocol consisted of coronary perfusion with Ca(2+)-free Tyrode solution for 10 min followed by high-Ca2+ (16 mM) Tyrode solution for 5 min. This new protocol successfully induced acute contractile failure in seven hearts, without myocardial ultrastructural changes. We studied the end-systolic pressure-volume relation (slope = Emax, a contractility index) and the relation between oxygen consumption per beat (VO2) and systolic pressure-volume area (PVA) in these failing hearts. These hearts had no increase in end-diastolic pressure at a given volume, a 40% decrease in Emax and a proportional decrease in the PVA-independent VO2 for 1-4 h, but no decrease in the oxygen cost of PVA, defined as the slope of the VO2-PVA relation. The oxygen cost of Emax for Ca2+ handling, defined as the slope of the relation between PVA-independent VO2 and Emax, was unchanged in the failing hearts. We conclude that the present protocol induced left ventricular contractile failure, primarily involving the suppression of Ca2+ handling energy for excitation-contraction coupling.

  7. Phase relation of CaSO4 at high pressure and temperature up to 90 GPa and 2300 K

    Science.gov (United States)

    Fujii, Taku; Ohfuji, Hiroaki; Inoue, Toru

    2016-05-01

    Calcium sulfate (CaSO4), one of the major sulfate minerals in the Earth's crust, is expected to play a major role in sulfur recycling into the deep mantle. Here, we investigated the crystal structure and phase relation of CaSO4 up to ~90 GPa and 2300 K through a series of high-pressure experiments combined with in situ X-ray diffraction. CaSO4 forms three thermodynamically stable polymorphs: anhydrite (stable below 3 GPa), monazite-type phase (stable between 3 and ~13 GPa) and barite-type phase (stable up to at least 93 GPa). Anhydrite to monazite-type phase transition is induced by pressure even at room temperature, while monazite- to barite-type transition requires heating at least to 1500 K at ~20 GPa. The barite-type phase cannot always be quenched from high temperature and is distorted to metastable AgMnO4-type structure or another modified barite structure depending on pressure. We obtained the pressure-volume data and density of anhydrite, monazite- and barite-type phases and found that their densities are lower than those calculated from the PREM model in the studied P-T conditions. This suggests that CaSO4 is gravitationally unstable in the mantle and fluid/melt phase into which sulfur dissolves and/or sulfate-sulfide speciation may play a major role in the sulfur recycling into the deep Earth.

  8. Anion-sensitive regions of L-type CaV1.2 calcium channels expressed in HEK293 cells.

    Directory of Open Access Journals (Sweden)

    Norbert Babai

    Full Text Available L-type calcium currents (I(Ca are influenced by changes in extracellular chloride, but sites of anion effects have not been identified. Our experiments showed that CaV1.2 currents expressed in HEK293 cells are strongly inhibited by replacing extracellular chloride with gluconate or perchlorate. Variance-mean analysis of I(Ca and cell-attached patch single channel recordings indicate that gluconate-induced inhibition is due to intracellular anion effects on Ca(2+ channel open probability, not conductance. Inhibition of CaV1.2 currents produced by replacing chloride with gluconate was reduced from approximately 75%-80% to approximately 50% by omitting beta subunits but unaffected by omitting alpha(2delta subunits. Similarly, gluconate inhibition was reduced to approximately 50% by deleting an alpha1 subunit N-terminal region of 15 residues critical for beta subunit interactions regulating open probability. Omitting beta subunits with this mutant alpha1 subunit did not further diminish inhibition. Gluconate inhibition was unchanged with expression of different beta subunits. Truncating the C terminus at AA1665 reduced gluconate inhibition from approximately 75%-80% to approximately 50% whereas truncating it at AA1700 had no effect. Neutralizing arginines at AA1696 and 1697 by replacement with glutamines reduced gluconate inhibition to approximately 60% indicating these residues are particularly important for anion effects. Expressing CaV1.2 channels that lacked both N and C termini reduced gluconate inhibition to approximately 25% consistent with additive interactions between the two tail regions. Our results suggest that modest changes in intracellular anion concentration can produce significant effects on CaV1.2 currents mediated by changes in channel open probability involving beta subunit interactions with the N terminus and a short C terminal region.

  9. Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of Photosystem II

    Energy Technology Data Exchange (ETDEWEB)

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

    2002-08-02

    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 angstroms, 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 {approx}; 3.5 angstroms 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.

  10. Strong bioresorbable Ca phosphate-PLA nanocomposites with uniform phase distribution by attrition milling and high pressure consolidation.

    Science.gov (United States)

    Rakovsky, Artoum; Gotman, Irena; Rabkin, Eugen; Gutmanas, Elazar Y

    2013-02-01

    Highly dense bioresorbable Ca-deficient HA-PLA (CDHA-PLA) and β-TCP-PLA nanocomposite materials with high (up to 80 vol%) contents of the calcium phosphate (CaP) phase and homogeneous phase distribution were prepared via attrition milling followed by high pressure consolidation at ambient temperature. The microstructure and mechanical properties of the materials obtained were studied as a function of milling time and PLA amount. Attrition milling resulted in disintegration of β-TCP powder agglomerates down to 50-150 nm, disintegration of CDHA agglomerates and refinement of 15 × 150 nm(2) CDHA nanoparticles to a size of 8 × 20 nm(2), and in a uniform distribution of the polymer component. Very high compressive strengths up to 400 MPa and high bending strengths up to 70 MPa were obtained. For both β-TCP and CDHA-based nanocomposites, the strength characteristics increased with milling time and decreased with increasing PLA content. For CDHA-based nanocomposites, attrition milling resulted in decrease of ductility while for β-TCP-40 vol% PLA the ductility increased. The observed behavior may be a result of formation of homogeneous, relatively thick (tens of nanometers), ductile PLA layers in β-TCP-PLA nanocomposites, but very thin (several nanometers) PLA layers in attrition milled CDHA-PLA nanocomposites. Degradation of compressive and bending strength in aqueous solutions was observed for all the studied CaP-PLA nanocomposites.

  11. Cell surface topology creates high Ca2+ signalling microdomains

    DEFF Research Database (Denmark)

    Brasen, Jens Christian; Olsen, Lars Folke; Hallett, Maurice B

    2010-01-01

    It has long been speculated that cellular microdomains are important for many cellular processes, especially those involving Ca2+ signalling. Measurements of cytosolic Ca2+ report maximum concentrations of less than few micromolar, yet several cytosolic enzymes require concentrations of more than...

  12. Effect of hydroxyapatite, octacalcium phosphate and calcium phosphate on the auto-flocculation of the microalgae in a high-rate algal pond.

    Science.gov (United States)

    Baya, D T; Effebi, K R; Tangou, T T; Keffala, C; Vasel, J L

    2013-01-01

    Recovering microalgae is one of the main technological and economic concerns in a high-rate algal pond (HRAP) because of their small size and their low density. This paper emphasizes the characterization (identification and assessment of potential flocculation) of chemical compounds involved in microalgae auto-flocculation in a HRAP. First, thermodynamic simulations were performed, using two models (i.e. Visual Minteq and a simplified thermodynamic model) in order to determine the chemical compounds of interest. Experimental tests were then carried out with these compounds for assessing their flocculation ability. Both models revealed that precipitates of calcium phosphates and their substituted forms were the compounds involved in the auto-flocculation. Moreover, experimental tests showed that the stoichiometric neutralization of algal charges by calcium phosphates (i.e. hydroxyapatite (Ca5(PO4)3OH), octacalcium phosphate (Ca4H(PO4)3) and amorphous calcium phosphate (Ca3(PO4)2)), at a pH within the range 7-10 yields 70-82% recovered algal biomass. The optimum ratio required for algae auto-flocculation was 0.33 Ca5(PO4)3OH/g DM(algae) at pH 10, 0.11 Ca4H(PO4)3/g DM(algae) at pH 7 and 0.23 g Ca3(PO4)2/g DM(algae) at pH 9. Auto-flocculation appears as a simple, sustainable and promising method for efficient harvesting of microalgae in a HRAP.

  13. Two distinct voltage-sensing domains control voltage sensitivity and kinetics of current activation in CaV1.1 calcium channels.

    Science.gov (United States)

    Tuluc, Petronel; Benedetti, Bruno; Coste de Bagneaux, Pierre; Grabner, Manfred; Flucher, Bernhard E

    2016-06-01

    Alternative splicing of the skeletal muscle CaV1.1 voltage-gated calcium channel gives rise to two channel variants with very different gating properties. The currents of both channels activate slowly; however, insertion of exon 29 in the adult splice variant CaV1.1a causes an ∼30-mV right shift in the voltage dependence of activation. Existing evidence suggests that the S3-S4 linker in repeat IV (containing exon 29) regulates voltage sensitivity in this voltage-sensing domain (VSD) by modulating interactions between the adjacent transmembrane segments IVS3 and IVS4. However, activation kinetics are thought to be determined by corresponding structures in repeat I. Here, we use patch-clamp analysis of dysgenic (CaV1.1 null) myotubes reconstituted with CaV1.1 mutants and chimeras to identify the specific roles of these regions in regulating channel gating properties. Using site-directed mutagenesis, we demonstrate that the structure and/or hydrophobicity of the IVS3-S4 linker is critical for regulating voltage sensitivity in the IV VSD, but by itself cannot modulate voltage sensitivity in the I VSD. Swapping sequence domains between the I and the IV VSDs reveals that IVS4 plus the IVS3-S4 linker is sufficient to confer CaV1.1a-like voltage dependence to the I VSD and that the IS3-S4 linker plus IS4 is sufficient to transfer CaV1.1e-like voltage dependence to the IV VSD. Any mismatch of transmembrane helices S3 and S4 from the I and IV VSDs causes a right shift of voltage sensitivity, indicating that regulation of voltage sensitivity by the IVS3-S4 linker requires specific interaction of IVS4 with its corresponding IVS3 segment. In contrast, slow current kinetics are perturbed by any heterologous sequences inserted into the I VSD and cannot be transferred by moving VSD I sequences to VSD IV. Thus, CaV1.1 calcium channels are organized in a modular manner, and control of voltage sensitivity and activation kinetics is accomplished by specific molecular mechanisms

  14. Growth kinetics of calcium fluoride at high supersaturation in a fluidized bed reactor.

    Science.gov (United States)

    Jiang, K; Zhou, K G; Yang, Y C; Du, H

    2014-01-01

    Crystallization process in a fluidized bed reactor (FBR) has been regarded as an environmentally friendly technology for the removal and recovery of fluoride from industrial wastewater. The growth kinetics of calcium fluoride at high supersaturation was studied for design, control, and operation of an FBR. The main variables, including supersaturation, superficial velocity, pH value, and particle size of seed that influenced the crystal growth were investigated. Then, a growth model was used to predict the linear growth rate of calcium fluoride at a high influent concentration of fluoride. The pressure difference in the FBR was used as a feature to characterize the growth rate of calcium fluoride. The aggregation and adsorption between seeds and fine particles were proven to be a possible mechanism for growth of calcium fluoride.

  15. Inclusion variations and calcium treatment optimization in pipeline steel production

    Science.gov (United States)

    Liu, Jian-Hua; Wu, Hua-Jie; Bao, Yan-Ping; Wang, Min

    2011-10-01

    SiCa line and SiCaBaFe alloy were injected into liquid pipeline steel at the end of LF refining as calcium treatment, and samples were taken from the ladles, mould, and slabs. Analysis of Ca content and inclusions shows that Ca content in steel decreases obviously in the following process after calcium treatment; the compositions, morphology, and sizes of inclusions also vary much in the production; primary inclusions in the ladles prior to calcium treatment are mainly Al2O3 inclusions, but they turn to fine irregular CaS-CaO-Al2O3 compound inclusions after the treatment, then become fine globular CaO-Al2O3 inclusions in the mould, and finally change to a few larger irregular CaS-CaO-Al2O3 complex inclusions in the slabs. Thermodynamic study reveals that inclusion variations are related with the preferential reactions among Ca, Al2O3, and S and the precipitation of S in CaO-Al2O3 inclusions with high sulfur capacity. New evaluation standards for calcium treatment in high-grade pipeline steel were put forward according to the inclusion variations and requirements of pipeline steel on inclusion controlling, and the calcium process was studied and optimized.

  16. Troponin T3 regulates nuclear localization of the calcium channel Ca{sub v}β{sub 1a} subunit in skeletal muscle

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tan; Taylor, Jackson; Jiang, Yang [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Pereyra, Andrea S. [Department of Histology, National University of La Plata, 1900 La Plata (Argentina); Messi, Maria Laura; Wang, Zhong-Min [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Hereñú, Claudia [Department of Histology, National University of La Plata, 1900 La Plata (Argentina); Delbono, Osvaldo, E-mail: odelbono@wakehealth.edu [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States)

    2015-08-15

    The voltage-gated calcium channel (Ca{sub v}) β{sub 1a} subunit (Ca{sub v}β{sub 1a}) plays an important role in excitation–contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Ca{sub v}β{sub 1a} subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160–244 aa) and Ca{sub v}β{sub 1a} NH{sub 2}-terminus (1–99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Ca{sub v}β{sub 1a}/YFP shows that TnT3 facilitates Ca{sub v}β{sub 1a} nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation. - Highlights: • Previously, we demonstrated that Ca{sub v}β{sub 1a} is a gene transcription regulator. • Here, we show that TnT3 interacts with Ca{sub v}β{sub 1a}. • We mapped TnT3 and Ca{sub v}β{sub 1a} interaction domain. • TnT3 facilitates Ca{sub v}β{sub 1a} nuclear enrichment. • The two proteins play a heretofore unknown role during early muscle differentiation.

  17. Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes

    Directory of Open Access Journals (Sweden)

    Dmitry eSamigullin

    2015-01-01

    Full Text Available At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers—which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal—has hitherto been technically impossible. With the aim of quantifying both Ca2+ currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 рА and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 µM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

  18. Combined system for high-time-resolution dual-excitation fluorescence photometry and fluorescence imaging of calcium transients in single normal and diseased skeletal muscle fibers

    Science.gov (United States)

    Uttenweiler, Dietmar; Wojciechowski, Reinhold; Makabe, Makoto; Veigel, Claudia; Fink, Rainer H.

    1994-12-01

    Fast photometric measurements and video-imaging of fluorescent indicators both are powerful tools in measuring the intracellular free calcium concentration of muscle and many other cells. as photometric systems yield a high temporal resolution, calcium imaging systems have high spatial but significantly reduced temporal resolution. Therefore we have developed an integrated system combining both methods and based mostly on standard components. As a common, sensitive Ca2+- indicator we used the fluorescent probe Fura-2, which is alternatingly excited for ratio measurements at 340/380 nm. We used a commercially available dual excitation photometric system (OSP-3; Olympus) for attaching a CCD-camera and a frame grabber board. To achieve the synchronization we had to design circuitries for external triggering, synchronization and accurate control of the filter changer, which we added to the system. Additionally, the software for a triggered image acquisition was developed. With this integrated setup one can easily switch between the fast photometric mode (ratio frequency 100 Hz) and the imaging mode (ratio frequency 4.17 Hz). The calcium images are correlated with the 25 times faster spot measurements and are analyzed by means of image processing. With this combined system we study release and uptake of calcium ions of normal and diseased skeletal muscle from mdx mice. Such a system will also be important for other cellular studies in which fluorescence indicators are used to monitor similar time dependent alterations as well as changes in cellular distributions of calcium.

  19. Determination of Iron (Fe and Calcium (Ca in NIST SRM 1566b (Oyster tissue using Flame Atomic Absorption Spectrometry (F-AAS by Standard Addition Method

    Directory of Open Access Journals (Sweden)

    Fitri Dara

    2017-03-01

    Full Text Available NIST Standard Reference Material (SRM 1566b was employed for the determination of Iron (Fe andCalcium (Ca as nutrients in food matrix using Flame Atomic Absorption Spectrometry (F-AAS. Thecertified value of SRM 1566b for Fe and Ca are 205.8 ± 6.8 mg/kg and 0.0838 ± 0.0020 (% or 838 ±20 mg/kg, respectively. This certified values are based on results obtained by single primary method(Isotope Dilution Inductively Couple Plasma Mass Spectrometry at NIST with confirmation by othermethods at National Metrology Institute of P.R. China. This paper proposed a method fordetermination of Fe and Ca in food matrix as recommended by AOAC official with a littlemodification. The method was commenced from the destruction of all organic matter by dry oxidationbefore analysis by standard addition. Under optimum condition, the results of the determination of Feand Ca in SRM 1566b were agreed well with the certificate value. This method would be useful forroutine analysis in food testing laboratories.

  20. Intracellular calcium elevation during plateau potentials mediated by extrasynaptic NMDA receptor activation in rat hippocampal CA1 pyramidal neurons is primarily due to calcium entry through voltage-gated calcium channels.

    Science.gov (United States)

    Oda, Yoshiaki; Kodama, Satoshi; Tsuchiya, Sadahiro; Inoue, Masashi; Miyakawa, Hiroyoshi

    2014-05-01

    We reported previously that plateau potentials mediated by extrasynaptic N-methyl-d-aspartate receptors (NMDARs) can be induced either by synaptic stimulation in the presence of glutamate transporter antagonist or by iontophoresis of NMDA in rat hippocampal CA1 pyramidal neurons. To examine whether the plateau potentials are accompanied by an elevation of intracellular Ca2+ and to determine the source of Ca2+ elevation, we performed Ca2+ imaging during the plateau potential. Neurons were loaded with Ca2+ indicator fluo-4, and the plateau potentials were generated either synaptically in the presence of glutamate transporter antagonist or by iontophoretically applying NMDA. We have found that a transient elevation in intracellular Ca2+ accompanies the plateau potential. The synaptically induced plateau potential and the Ca2+ elevation were blocked by 5,7-dichlorokynurenic acid (5,7-dCK), an antagonist for the glycine-binding sites of NMDAR. A mixture of Cd2+ and tetrodotoxin did not block NMDA-induced plateau potentials, but completely abolished the accompanying Ca2+ elevation in both the presence and absence of Mg2+ ions in the bathing solution. The NMDA-induced plateau potential was blocked by further adding 5,7-dCK. Our results show that the NMDAR-mediated plateau potential is accompanied by elevation of intracellular Ca2+ that is primarily caused by the influx of Ca2+ through voltage-gated Ca2+ channels. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  1. Modification of calcium carbonate by polyether coupling and the properties of CaCO3/PP material%聚醚偶联剂改性碳酸钙及CaCO3/PP复合材料的性能

    Institute of Scientific and Technical Information of China (English)

    曲燕; 杨大伟; 李乾斌; 程如清; 魏鑫

    2013-01-01

    自制了偶联剂四氢呋喃均聚醚(PTHF),并用其对轻质碳酸钙表面进行处理,将处理后的碳酸钙填充到聚丙烯塑料中,探讨了新型改性剂对复合材料力学性能的影响.结果表明,四氢呋喃均聚醚能够使碳酸钙的吸油值降低到22%,接触角降低到68.6°.改性后的碳酸钙填充进聚丙烯,能在一定程度上缓解拉伸强度的下降趋势,使复合材料的断裂伸长率达到28.47%、冲击强度达到6.7 kJ/m2.SEM观察四氢呋喃均聚醚添加前后复合材料的断面形态,表明碳酸钙在聚丙烯中分散良好.%Homemade agent-tetrahydrofuran polyether (PTHF) was used to treat the surface of the precipitated calcium carbonate.The impacts of surface modified CaCO3 with coupling agent of PTHF on CaCO3/PP mechanical properties of composite material were studied.The result showed that tetrahydrofuran polyether was able to make the oil absorption of calcium carbonate reduced to 22% and the contact angle decreased to 68.6°.CaCO3 with PTHF filling in the polypropylene can also alleviate the downward trend of the tensile strength to a certain extent,making the elongation at break of composites reached 28.47% and the impact strength of the composites reached 6.7 kJ/m2.Calcium carbonate with PTHF dispersed better in polypropylene than calcium carbonate by scanning electron microscopy (SEM).

  2. A molecular dynamics study of densification mechanisms in calcium silicate glasses CaSi2O5 and CaSiO3 at pressures of 5 and 10 GPa.

    Science.gov (United States)

    Mead, R N; Mountjoy, G

    2006-10-21

    Molecular dynamics is used to obtain models of (CaO)(x)(SiO(2))(1-x) glasses, with compositions CaSi(2)O(5) (x=0.33) and CaSiO(3) (x=0.50), at pressures of 5 and 10 GPa. At 5 GPa there are increases in Ca and Si coordinations for x=0.33, whereas for x=0.50 there is distortion of CaO(N) polyhedra but no substantial change in coordination. At 10 GPa the Ca coordination increases by approximately 20% for x=0.33 and by approximately 10% for x=0.50. This increase is due to increased Ca bonds to bridging oxygens (O(b)), since nonbridging oxygens (O(nb)) are already highly bonded to Ca, and the proportion of O(nb) is decreasing due to changes in the silica network. At 10 GPa there are approximately 20% of fivefold and a few percent of sixfold coordinated Si. Since the new Si-O bonds involve the conversion of O(nb) to O(b), there is a corresponding increase in the network connectivity. The x=0.50 glass is more resistant to deformation because there is less possibility to convert O(nb) to O(b) due to lower Si content. The changes in Ca-O, Si-Ca, and Ca-Ca correlations are predicted to produce changes in the x-ray diffraction structure factor S(Q), including a shift of the first sharp diffraction peak to higher Q values.

  3. Calcium-sensing receptor (CaSR)-mediated anti-inflammatory effects of L-amino acids in intestinal epithelial cells.

    Science.gov (United States)

    Mine, Yoshinori; Zhang, Hua

    2015-11-18

    Calcium-sensing receptor (CaSR) plays an essential role in sensing nutrients and monitoring ion balance in the human gut. However, no discovery of CaSR-mediated anti-inflammatory effect of l-amino acids (l-AAs) on the gut system has been reported. The aim of this study is to screen and identify the anti-inflammatory activity of various l-AAs in intestinal epithelial cells (IECs) and stepwise illustrate a possible molecular mechanism for anti-inflammation. We used Caco-2 and HT-29 cell lines to evaluate the anti-inflammatory activity of l-AAs and revealed that l-tryptophan (l-Trp) and l-valine (l-Val) have strong anti-inflammatory activity consistent in both cell lines. l-Trp treatment (5 mM) reduced TNF-α-induced IL-8 secretion from HT-29 or Caco-2 cells to about 50 or 40%, respectively. l-Trp also significantly inhibited the expression of phosphorylation of JNK or IκBα to around 50% in HT-29 cells. However, the above inhibitory effects of l-Trp on inflammatory responses in TNF-α-induced HT-29 cells were abrogated by NPS-2143. The result of CaSR antagonist NPS-2143 pretreatment study suggests l-Trp exerts anti-inflammatory effects on IECs through CaSR activation. The involvement of β-arrestin2 was then found to block tumor necrosis factor (TNF)-α-induced signaling pathways after CaSR activated by l-Trp. These results validate a novel mechanism underlying CaSR agonistic l-AAs exerting anti-inflammatory effects on human intestinal epithelia.

  4. Effects of octreotide on expression of L-type voltage-operated calcium channels and on intracellular Ca2+ in activated hepatic stellate cells

    Institute of Scientific and Technical Information of China (English)

    丁惠国; 王宝恩; 贾继东; 夏华向; 王振宇; 赵春惠; 徐燕琳

    2004-01-01

    Background The contractility of hepatic stellate cells (HSCs) may play an important role in the pathogenesis of cirrhosis with portal hypertension. The aim of this study was to research the effects of octreotide, an analogue of somatostatin, on intracellular Ca2+ and on the expression of L-type voltage-operated calcium channels (L-VOCCs) in activated HSCs, and to try to survey the use of octreotide in treatment and prevention of cirrhosis with portal hypertension complications. Methods HSC-T6, an activated HSCs line, was plated on small glass coverslips in 35-mm culture dishes at a density of 1×105/ml, and incubated in DMEM media for 24 hours. After the cells were loaded with Fluo-3/AM, intracellular Ca2+ was measured by Laser Scanning Confocal Microscopy (LSCM). The dynamic changes in activated HSCs of intracellular Ca2+, stimulated by octreotide, endothelin-1, and KCl, respectively, were also determined by LSCM. Each experiment was repeated six times. L-VOCC expression in HSCs was estimated by immunocytochemistry. Results After octreotide stimulation, a signifcant decrease in the intracellular Ca2+ of activated HSCs was observed. However, octreotide did not inhibit the increases in intracellular Ca2+ after stimulation by KCl and endothelin-1. Moreover, octreotide did not significantly affect L-VOCC expression. These results suggest that neither L-VOCC nor endothelin-1 receptors in activated HSCs are inhibited by octreotide. Conclusions Octreotide may decrease portal hypertension and intrahepatic vascular tension by inhibiting activated HSCs contractility through decreases in intracellular Ca2+. The somatostatin receptors in activated HSCs may be inhibited by octreotide.

  5. Follicle-stimulating hormone receptor-mediated uptake of sup 45 Ca sup 2+ by proteoliposomes and cultured rat sertoli cells: Evidence for involvement of voltage-activated and voltage-independent calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Grasso, P.; Reichert, L.E. Jr. (Albany Medical College, NY (USA))

    1989-12-01

    We have previously reported incorporation into liposomes of Triton X-100-solubilized FSH receptor-G-protein complexes derived from purified bovine calf testis membranes. In the present study we have used this model system to show that FSH induces flux of 45Ca2+ into such proteoliposomes in a hormone-specific concentration-dependent manner. FSH, inactivated by boiling, had no stimulatory effect on 45Ca2+ flux, nor did isolated alpha- or beta-subunits of FSH. Addition of GTP (or its analogs 5'-guanylylimidodiphosphate and guanosine-5'-O-(3-thiotriphosphate)) or sodium fluoride (in the presence or absence of GTP or its analogs) failed to induce 45Ca2+ flux into proteoliposomes, suggesting that the uptake of 45Ca2+ was receptor, and not G-protein, related. Voltage-independent (ruthenium red and gadolinium chloride) and voltage-activated (methyoxyverapamil and nifedipine) calcium channel-blocking agents reduced FSH-stimulated 45Ca2+ flux into proteoliposomes to control levels. FSH also induced uptake of 45Ca2+ by cultured rat Sertoli cells. Ruthenium red and gadolinium chloride had no effect on basal levels of 45Ca2+ uptake or estradiol secretion by cultured rat Sertoli cells, nor did methoxyverapamil or nifedipine. All four calcium channel blockers, however, were able to reduce FSH-induced 45Ca2+ uptake to basal levels and FSH-stimulated conversion of androstenedione to estradiol by up to 50%, indicating an involvement of Ca2+ in FSH-stimulated steroidogenesis. Our results suggest that the well documented changes in intracellular calcium levels consequent to FSH binding may be due, at least in part, to an influx of calcium through FSH receptor-regulated calcium channels.

  6. Process Optimization for Ethyl Ester Production in Fixed Bed Reactor Using Calcium Oxide Impregnated Palm Shell Activated Carbon (CaO/PSAC

    Directory of Open Access Journals (Sweden)

    A Buasri

    2012-11-01

    Full Text Available : The continuous production of ethyl ester was studied by using a steady-state fixed bed reactor (FBR. Transesterification of palm stearin (PS and waste cooking palm oil (WCPO with ethanol in the presence of calcium oxide impregnated palm shell activated carbon (CaO/PSAC solid catalyst was investigated. This work was determined the optimum conditions for the production of ethyl ester from PS and WCPO in order to obtain fatty acid ethyl ester (FAEE with the highest yield. The effects of reaction variables such as residence time, ethanol/oil molar ratio, reaction temperature, catalyst bed height and reusability of catalyst in a reactor system on the yield of biodiesel were considered. The optimum conditions were the residence time 2-3 h, ethanol/oil molar ratio 16-20, reaction temperature at 800C, and catalyst bed height 300 mm which yielded 89.46% and 83.32% of the PS and WCPO conversion, respectively. CaO/PSAC could be used repeatedly for 4 times without any activation treatment and no obvious activity loss was observed. It has potential for industrial application in the transesterification of triglyceride (TG. The fuel properties of biodiesel were determined. Keywords: biodiesel, calcium oxide, ethyl ester, fixed bed reactor, palm shell activated carbon

  7. Enhancement of yield point at high pressure high temperature wells by using polymer nanocomposites based on ZnO & CaCO3 nanoparticles

    Directory of Open Access Journals (Sweden)

    A.Z. Noah

    2017-03-01

    Full Text Available Zinc oxide nanoparticles (ZnO-NPs and modified calcium carbonate (nano-CaCO3 nanoparticles were successfully prepared and added to polystyrene-butadiene rubber copolymer (PSBR matrix to prepare PSBR nanocomposites. The prepared nanomaterials (ZnO-NPs & nano-CaCO3 were characterized using scanning electron microscope (SEM, transmission electron microscope (TEM and X-ray diffraction (XRD. Furthermore, the prepared polymer nanocomposites and oil base mud were used for drilling in high pressure high temperature (HPHT wells. The consequence of using polymer nanocomposites based on different loading of ZnO-NPs and nano-CaCO3 on the rheological properties of oil base mud was evaluated and enhanced the yield point at high pressure high temperature wells (HPHT. The using of the polymer with different percentage from (0.5 in all percent the obtained results is very promising; this means that the increase of polymer is reasonable for the increase of apparent viscosity, plastic viscosity and yield point at high temperature. Correspondingly, polymer nanocomposites displayed rise of apparent viscosity, plastic viscosity, and yield point, decreased in fluid loss and increased in electrical stability at high pressure high temperature wells.

  8. Structures of apicomplexan calcium-dependent protein kinases reveal mechanism of activation by calcium

    Energy Technology Data Exchange (ETDEWEB)

    Wernimont, Amy K; Artz, Jennifer D.; Jr, Patrick Finerty; Lin, Yu-Hui; Amani, Mehrnaz; Allali-Hassani, Abdellah; Senisterra, Guillermo; Vedadi, Masoud; Tempel, Wolfram; Mackenzie, Farrell; Chau, Irene; Lourido, Sebastian; Sibley, L. David; Hui, Raymond (Toronto); (WU-MED)

    2010-09-21

    Calcium-dependent protein kinases (CDPKs) have pivotal roles in the calcium-signaling pathway in plants, ciliates and apicomplexan parasites and comprise a calmodulin-dependent kinase (CaMK)-like kinase domain regulated by a calcium-binding domain in the C terminus. To understand this intramolecular mechanism of activation, we solved the structures of the autoinhibited (apo) and activated (calcium-bound) conformations of CDPKs from the apicomplexan parasites Toxoplasma gondii and Cryptosporidium parvum. In the apo form, the C-terminal CDPK activation domain (CAD) resembles a calmodulin protein with an unexpected long helix in the N terminus that inhibits the kinase domain in the same manner as CaMKII. Calcium binding triggers the reorganization of the CAD into a highly intricate fold, leading to its relocation around the base of the kinase domain to a site remote from the substrate binding site. This large conformational change constitutes a distinct mechanism in calcium signal-transduction pathways.

  9. A strategy of precipitated calcium carbonate (CaCO{sub 3}) fillers for enhancing the mechanical properties of polypropylene polymers

    Energy Technology Data Exchange (ETDEWEB)

    Thenepalli, Thriveni; Ahn, Ji Whan [Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon (Korea, Republic of); Ahn, Young Jun; Han, Choon [Kwangwoon University, Seoul (Korea, Republic of); Ramakrishna, Chilakala [Hanil Cement, Danyang (Korea, Republic of)

    2015-06-15

    A wide variety of fillers are currently used in more than twenty types of polymer resins, although four of them alone (polypropylene, polyamides, thermoplastic polyesters, and polyvinyl chloride) account for 90% of the market of mineral fillers in plastics. Polypropylene (PP) and PVC dominate the market for calcium carbonate. PP is a versatile reinforcement material that can meet engineering and structural specifications and is widely used for automotive components, home appliances, and industrial applications. Talc, mica, clay, kaolin, wollastonite, calcium carbonates, feldspar, aluminum hydroxide, glass fibers, and natural fibers are commonly used in fillers. Among these, calcium carbonate (both natural and synthetic) is the mos abundant and affords the possibility of improved surface finishing, control over the manufacture of products, and increased electric resistance and impact resistance. Meeting the global challenge to reduce the weight of vehicles by using plastics is a significant issue. The current the global plastic and automobile industry cannot survive without fillers, additives, and reinforcements. Polypropylene is a major component of the modern plastic industry, and currently is used in dashboards, wheel covers, and some engine parts in automobiles. This article reports that the use of calcium carbonate fillers with polypropylene is the best choice to enhance the mechanical properties of plastic parts used in automobiles.

  10. Ca analysis: an Excel based program for the analysis of intracellular calcium transients including multiple, simultaneous regression analysis.

    Science.gov (United States)

    Greensmith, David J

    2014-01-01

    Here I present an Excel based program for the analysis of intracellular Ca transients recorded using fluorescent indicators. The program can perform all the necessary steps which convert recorded raw voltage changes into meaningful physiological information. The program performs two fundamental processes. (1) It can prepare the raw signal by several methods. (2) It can then be used to analyze the prepared data to provide information such as absolute intracellular Ca levels. Also, the rates of change of Ca can be measured using multiple, simultaneous regression analysis. I demonstrate that this program performs equally well as commercially available software, but has numerous advantages, namely creating a simplified, self-contained analysis workflow.

  11. Raman spectroscopy of CaSnO{sub 3} at high temperature: a highly quasi-harmonic perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Redfern, S A T; Salje, E K H [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Chen, C-J; Kung, J [Department of Earth Sciences, National Chen Kung University, 1 University Road, 701-Tainan, Taiwan (China); Chaix-Pluchery, O; Kreisel, J, E-mail: satr@cam.ac.uk [Laboratoire des Materiaux et du Genie Physique, Grenoble INP, CNRS, Minatec, 3 Parvis Louis Neel, F-38016 Grenoble (France)

    2011-10-26

    Calcium stannate perovskite (CaSnO{sub 3}) has been studied by Raman spectroscopy at two excitation wavelengths (514.5 and 632.8 nm). No phase transition was observed. Rather, the thermal evolution of the Raman lines showed a high degree of harmonicity with small Grueneisen parameters and thermal line broadening following {Gamma} = Acoth{theta}/T, where the quantum temperature {theta} is determined by the phonon branch without further coupling with other degrees of freedom. The geometrical nature of phonon lines has been identified. High-temperature powder x-ray diffraction measurements provide thermal expansion coefficients of {alpha}{sub x} = 13.9 x 10{sup -6} K{sup -1}, {alpha}{sub y} = 2.7 x 10{sup -6} K{sup -1}, {alpha}{sub z} = 14.3 x 10{sup -6} K{sup -1}. The strongly quasi-harmonic behaviour observed and the lack of any indication of instability with respect to the post-perovskite structure points to the strongly first-order character of the reported perovskite to post-perovskite phase transition in this material, which appears to behave as a very good analogue to MgSiO{sub 3} in the Earth's interior. (paper)

  12. Microdomain texture and oxygen excess in the calcium-lanthanum ferrite: Ca 2LaFe 3O 8

    Science.gov (United States)

    Alario-Franco, Miguel A.; Henche, María Jesús R.; Vallet, María; Calbet, JoséM. G.; Grenier, Jean-Claude; Wattiaux, Alain; Hagenmuller, Paul

    1983-01-01

    The analysis by TEM and electron diffraction of the anion-deficient perovskite Ca 2LaFe 3O 8 confirms the model previously proposed by J. C. Grenier et al. ( Mater. Res. Bull.11, 1219 (1976) ) with a structure intermediate between perovskite and brownmillerite. The unit cell parameters are ˜√2 ac, 3 ac, √2 ac (where ac is the cubic perovskite unit cell parameter). However, the unit cell is sometimes doubled along the b axis. When the sample is treated in air at temperatures around 1400°C, an oxidation process is observed and the unit cell becomes cubic ( ac = 3.848(3) Å). Nevertheless, electron diffraction investigations suggest the existence of a much more complex situation in which three-dimensional microdomains intergrow within one crystal. Each of these microdomains appears to have a structure clearly related to the low-temperature sample, but the superstructure is randomly found along each of the three cubic subcell directions (i.e., the unit cell √2 ac, √2 ac, 3 ac alternates randomly with 3 ac, √2 ac, √2 a, and with √2 ac, 3 ac, √2 ac). High-resolution electron microscopy allows one to ascertain this microdomain texture of the real crystal.

  13. Chelating properties of beer: Implications on calcium homeostasis in PE/CA-PJ15 cells

    Directory of Open Access Journals (Sweden)

    Letizia Granieri

    2017-03-01

    These results support the notion that beer may be considered a natural source of chemical entities that, based on their binding activity to Ca2+ and, possibly, other metal ions, might be considered as nutritional supplements, detoxification agents, or antibiotics.

  14. Topological organization of CA3-to-CA1 excitation.

    Science.gov (United States)

    Hongo, Yoshie; Ogawa, Koichi; Takahara, Yuji; Takasu, Keiko; Royer, Sebastien; Hasegawa, Minoru; Sakaguchi, Gaku; Ikegaya, Yuji

    2015-09-01

    The CA1-projecting axons of CA3 pyramidal cells, called Schaffer collaterals, constitute one of the major information flow routes in the hippocampal formation. Recent anatomical studies have revealed the non-random structural connectivity between CA3 and CA1, but little is known regarding the functional connectivity (i.e. how CA3 network activity is functionally transmitted downstream to the CA1 network). Using functional multi-neuron calcium imaging of rat hippocampal slices, we monitored the spatiotemporal patterns of spontaneous CA3 and CA1 burst activity under pharmacological GABAergic blockade. We found that spatially clustered CA3 activity patterns were transformed into layered CA1 activity sequences. Specifically, synchronized bursts initiated from multiple hot spots in CA3 ensembles, and CA1 neurons located deeper in the pyramidal cell layer were recruited during earlier phases of the burst events. The order of these sequential activations was maintained across the bursts, but the sequence velocity varied depending on the inter-burst intervals. Thus, CA3 axons innervate CA1 neurons in a highly topographical fashion.

  15. The cardiac L-type calcium channel distal carboxy terminus autoinhibition is regulated by calcium.

    Science.gov (United States)

    Crump, Shawn M; Andres, Douglas A; Sievert, Gail; Satin, Jonathan

    2013-02-01

    The L-type calcium channel (LTCC) provides trigger Ca(2+) for sarcoplasmic reticulum Ca-release, and LTCC function is influenced by interacting proteins including the LTCC distal COOH terminus (DCT) and calmodulin. DCT is proteolytically cleaved and reassociates with the LTCC complex to regulate calcium channel function. DCT reduces LTCC barium current (I(Ba,L)) in reconstituted channel complexes, yet the contribution of DCT to LTCC Ca(2+) current (I(Ca,L)) in cardiomyocyte systems is unexplored. This study tests the hypothesis that DCT attenuates cardiomyocyte I(Ca,L). We measured LTCC current and Ca(2+) transients with DCT coexpressed in murine cardiomyocytes. We also heterologously coexpressed DCT and Ca(V)1.2 constructs with truncations corresponding to the predicted proteolytic cleavage site, Ca(V)1.2Δ1801, and a shorter deletion corresponding to well-studied construct, Ca(V)1.2Δ1733. DCT inhibited I(Ba,L) in cardiomyocytes, and in human embryonic kidney (HEK) 293 cells expressing Ca(V)1.2Δ1801 and Ca(V)1.2Δ1733. Ca(2+)-CaM relieved DCT block in cardiomyocytes and HEK cells. The selective block of I(Ba,L) combined with Ca(2+)-CaM effects suggested that DCT-mediated blockade may be relieved under conditions of elevated Ca(2+). We therefore tested the hypothesis that DCT block is dynamic, increasing under relatively low Ca(2+), and show that DCT reduced diastolic Ca(2+) at low stimulation frequencies but spared high frequency Ca(2+) entry. DCT reduction of diastolic Ca(2+) and relief of block at high pacing frequencies and under conditions of supraphysiological bath Ca(2+) suggests that a physiological function of DCT is to increase the dynamic range of Ca(2+) transients in response to elevated pacing frequencies. Our data motivate the new hypothesis that DCT is a native reverse use-dependent inhibitor of LTCC current.

  16. A highly sensitive CaF{sub 2}:Dy nanophosphor as an efficient low energy ion dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Bhadane, Mahesh S.; Hareesh, K.; Dahiwale, S.S.; Sature, K.R. [Microtron Accelerator Laboratory, Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Patil, B.J. [Department of Physics, Abasaheb Garware College, Pune 411004 (India); Asokan, K.; Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Bhoraskar, V.N. [Microtron Accelerator Laboratory, Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Dhole, S.D., E-mail: sanjay@physics.unipune.ac.in [Microtron Accelerator Laboratory, Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

    2016-11-01

    Highlights: • CaF{sub 2}:Dy nanophosphor synthesized by chemical co-precipitation route. • Phosphors are irradiated by H, Ar and N low energy ions at different fluences. • LEBI irradiated phosphors are characterized by XRD, TEM, FTIR and PL spectroscopy. • First time report to LEIB irradiated for thermoluminescence dosimetric applications. - Abstract: Dysprosium doped calcium fluoride (CaF{sub 2}:Dy) powers synthesized by co-precipitation method were irradiated with low energy ion beams (LEIB) viz. 100 keV H, 200 keV Ar and 350 keV N beams at different fluences and demonstrated for low energy ion dosimetric application. X-ray Diffraction and Transmission electron microscopy revealed the formation of highly crystalline cubic structured particles with size ∼45–50 nm. FTIR spectra of the CaF{sub 2}:Dy samples show changes of some bonds such as N–O asymmetric, C–F bonding and C–H aromatic contain stretching mode after LEIB irradiation. The thermoluminescence (TL) glow curve peaks were observed at 207 °C for Ar ion, at 203 °C for H ion and at 216 °C and 270 °C for N ion. It has been found that CaF{sub 2}:Dy nanophosphor shows a linear response with minimum fading for all the ion species. Computerized Glow Curve Deconvolution was performed for TL curve of high fluence ion irradiated nanophosphor to estimate the trapping parameters and the respective figure of merit (FOM) found to be very appropriate for all the nanophosphor. These results indicated that the CaF{sub 2}:Dy can be used as a low energy ion detector or dose.

  17. Ca stabilized zirconia based composites by wet consolidation of zirconia and high alumina cement mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Bruni, Y.L.; Garrido, L.B.; Aglietti, E.F., E-mail: lgarrido@cetmic.unlp.edu.ar [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC/CIC-CONICET La Plata), Buenos Aires (Argentina)

    2012-07-01

    Composites of the CaO-Al{sub 2}O{sub 3}-ZrO{sub 2} system are widely used in many industrial applications. In this study, porous Ca stabilized ZrO{sub 2} composites were developed from a starting mixture of m-ZrO{sub 2} and calcium aluminate cement. Ceramics were produced by wet consolidation of aqueous suspensions with and without corn starch as pore former agent and sintering at 1000-1500 °C. The influence of processing parameters on crystalline phases, sintering behavior and textural characteristics was examined. Stabilized c-ZrO{sub 2} formed with the composition of Ca{sub 0.15}Zr{sub 0.85}O{sub 1.85}. The sintering of the mixtures lead to porous composites materials. Textural properties were analyzed considering the initial composition and the present crystalline phases. (author)

  18. Aberrant calcium/calmodulin-dependent protein kinase II (CaMKII) activity is associated with abnormal dendritic spine morphology in the ATRX mutant mouse brain.

    Science.gov (United States)

    Shioda, Norifumi; Beppu, Hideyuki; Fukuda, Takaichi; Li, En; Kitajima, Isao; Fukunaga, Kohji

    2011-01-05

    In humans, mutations in the gene encoding ATRX, a chromatin remodeling protein of the sucrose-nonfermenting 2 family, cause several mental retardation disorders, including α-thalassemia X-linked mental retardation syndrome. We generated ATRX mutant mice lacking exon 2 (ATRX(ΔE2) mice), a mutation that mimics exon 2 mutations seen in human patients and associated with milder forms of retardation. ATRX(ΔE2) mice exhibited abnormal dendritic spine formation in the medial prefrontal cortex (mPFC). Consistent with other mouse models of mental retardation, ATRX(ΔE2) mice exhibited longer and thinner dendritic spines compared with wild-type mice without changes in spine number. Interestingly, aberrant increased calcium/calmodulin-dependent protein kinase II (CaMKII) activity was observed in the mPFC of ATRX(ΔE2) mice. Increased CaMKII autophosphorylation and activity were associated with increased phosphorylation of the Rac1-guanine nucleotide exchange factors (GEFs) T-cell lymphoma invasion and metastasis 1 (Tiam1) and kalirin-7, known substrates of CaMKII. We confirmed increased phosphorylation of p21-activated kinases (PAKs) in mPFC extracts. Furthermore, reduced protein expression and activity of protein phosphatase 1 (PP1) was evident in the mPFC of ATRX(ΔE2) mice. In cultured cortical neurons, PP1 inhibition by okadaic acid increased CaMKII-dependent Tiam1 and kalirin-7 phosphorylation. Together, our data strongly suggest that aberrant CaMKII activation likely mediates abnormal spine formation in the mPFC. Such morphological changes plus elevated Rac1-GEF/PAK signaling seen in ATRX(ΔE2) mice may contribute to mental retardation syndromes seen in human patients.

  19. Elucidation of real-time hardening mechanisms of two novel high-strength calcium phosphate bone cements.

    Science.gov (United States)

    Smirnov, Valery V; Rau, Julietta V; Generosi, Amanda; Albertini, Valerio Rossi; Ferro, Daniela; Barinov, Sergey M

    2010-04-01

    Despite the numerous literature data available in the field of calcium phosphate bone cements, the mechanism and kinetics of their hardening, both of which are of great importance for cements application, in most cases, is unknown. In this work, the mechanism and kinetics of hardening of two novel high-strength calcium phosphate bone cements were studied using the energy dispersive X-ray diffraction technique, which allows rapid collection of the patterns. The phase transformations occurring on the setting and hardening processes were monitored in situ. Containing minimal quantity of components, whose mixing leads to the formation of cements with pH close to neutral, the cements under study are simple in handling. The main component of both formulations is tetracalcium phosphate. In both cements, the effect of the addition of high- and low-molecular weight chitosan on phase development and kinetics was investigated in detail. One of the cements has the compressive strength of about 70 MPa, whereas the strength of the other, containing Ca(3)Al(2)O(6), is much higher, about 100 MPa. This latter cement could be regarded as an alternative to the common low-strength bioresorbable brushite cements.

  20. Thermoluminescent characteristics of CaSO{sub 4}:Dy+PTFE irradiated with high energy electron beams; Caracteristicas termoluminiscentes del CaSO{sub 4}:Dy+PTFE irradiado con haces de electrones de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, R.; Rivera, T.; Calderon, J. A.; Jimenez, Y. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Rodriguez, J. [Hospital General de Mexico, Dr. Balmis 148, Col. Doctores, 06726 Mexico D. F. (Mexico); Oviedo, O. [Centro Medico ABC, Sur 136 No. 116, Col. Las Americas, 01120 Mexico D. F. (Mexico); Azorin, J., E-mail: chagua@hotmail.com [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, 09340 Mexico D. F. (Mexico)

    2011-10-15

    In the present work thermoluminescent response of dysprosium doped calcium sulfate embedded in polytetrafluorethylene (CaSO{sub 4}:Dy+PTFE) under high electron beam irradiations from linear accelerator for clinical applications was investigated. The irradiations were carried out using high electron beams (6 to 18 MeV) from a linear accelerator Varian, C linac 2300C/D, for clinical practice purpose. The electron irradiations were obtained by using the water solid in order to guarantee electronic equilibrium conditions. Field shaping for electron beams was obtained with electron cones. Glow curve and other thermoluminescent characteristics of CaSO{sub 4}:Dy+PTFE were conducted under high electron beams irradiations. The thermoluminescent response of the pellets showed and intensity peak centered at around 235 C. Thermoluminescent response of CaSO{sub 4}:Dy+PTFE as a function of high electron absorbed dose showed a linearity in a wide range. To obtain reproducibility characteristic, a set of pellets were exposed repeatedly for the same electron absorbed dose. The results obtained in this study can suggest the applicability of CaSO{sub 4}:Dy+PTFE pellets for high electron beam dosimetry, provided fading is correctly accounted for. (Author)

  1. Thermodynamics and Kinetics of Boron Removal from Metallurgical Grade Silicon by Addition of High Basic Potassium Carbonate to Calcium Silicate Slag

    Science.gov (United States)

    Wu, Jijun; Wang, Fanmao; Ma, Wenhui; Lei, Yun; Yang, Bin

    2016-06-01

    In this study, we investigated the thermodynamics and kinetics of boron removal from metallurgical grade silicon (MG-Si) using a calcium silicate slag containing a high basic potassium carbonate. The distribution of boron between slag and silicon was theoretically derived and the distribution coefficients ( L B) of boron with different compositions of CaO, SiO2, and K2CO3 in slag reagents were determined. The maximal value of L B reached 2.08 with a high basicity slag of 40 pctCaO-40 pctSiO2-20 pctK2CO3 (Λ = 0.73). The boron removal rates from MG-Si using CaO-SiO2 and CaO-SiO2-K2CO3 slags at 1823 K (1550 °C) were investigated in an electromagnetic induction furnace. The results showed that the boron concentration in MG-Si can be reduced from 22 to 1.8 ppmw at 1823 K (1550 °C) with 20 pct K2CO3 addition to calcium silicate slag, where the removal efficiency of boron reached 91.8 pct. The mass transfer coefficient ( β S) of boron in binary 50 pctCaO-50 pctSiO2 slag was 3.16 × 10-6 m s-1 at 1823 K (1550 °C) and was 2.43 × 10-5 m s-1 in ternary 40 pctCaO-40 pctSiO2-20 pctK2CO3 slag.

  2. Stability of calcium silicate in basic solution

    Institute of Scientific and Technical Information of China (English)

    刘桂华; 李小斌; 彭志宏; 周秋生

    2003-01-01

    Mixture of CaO and SiO2 was sintered at 1 200 or 1 400 ℃ according to the mole ratio of CaO/SiO2 of 1 or 2, and then calcium silicate was leached in pure caustic or soda solution. The results indicated that calcium silicate exists much more stably in caustic solution than that in soda solution, and CaO*SiO2 is more stable than β-2CaO*SiO2 whether in caustic solution or in soda solution. The increase of sintering temperature favored the stability of calcium silicate in the leaching process. When β-2CaO*SiO2 was leached in soda solution, the increase of leaching temperature and time resulted in decomposing of more calcium silicate. And when β-2CaO*SiO2 was leached in caustic solution at high temperature, much 2CaO*SiO2*H2O but little CaO*SiO2*H2O appeared in slag.

  3. Petrogenesis of High-CaO Lavas Recovered from Hawaii Scientific Drilling Project

    Science.gov (United States)

    Huang, S.

    2015-12-01

    Mauna Kea tholeiitic lavas recovered from Hawaii Scientific Drilling Project (HSDP) can be divided into three groups based on their major element compositions: High-SiO2, Low-SiO2, and High-CaO groups. Detailed geochemical and isotopic studies have been focused on the High- and Low-SiO2 group lavas, and High-CaO lavas were not well studied because they were not included in the original reference suite samples. Here we report trace element compositions determined on a suite of High-CaO glasses, and use these data to constrain the petrogenesis of High-CaO lavas. When normalized to Low-SiO2 lavas, High-CaO lavas form a U-shaped trace element pattern. That is, High-CaO lavas are enriched in both the most (Nb, Th) and the least (Sc, V) incompatible elements. This trace element difference is best explained if High-CaO parental magma represents a mixture of low degree partial melt of the Low-SiO2 mantle source and a mafic cumulate component. This mafic cumulate must be clinopyroxene-rich, and it could be delaminated mafic cumulate formed under arcs during continent formation, lower continental crust, or lower oceanic crust.Mauna Kea tholeiitic lavas recovered from Hawaii Scientific Drilling Project (HSDP) can be divided into three groups based on their major element compositions: High-SiO2, Low-SiO2, and High-CaO groups. Detailed geochemical and isotopic studies have been focused on the High- and Low-SiO2 group lavas, and High-CaO lavas were not well studied because they were not included in the original reference suite samples. Here we report trace element compositions determined on a suite of High-CaO glasses, and use these data to constrain the petrogenesis of High-CaO lavas. When normalized to Low-SiO2 lavas, High-CaO lavas form a U-shaped trace element pattern. That is, High-CaO lavas are enriched in both the most (Nb, Th) and the least (Sc, V) incompatible elements. This trace element difference is best explained if High-CaO parental magma represents a mixture of

  4. Precipitation and Solubility of Calcium Hydrogenurate Hexahydrate.

    Science.gov (United States)

    Babić-Ivančić, V; Füredi-Milhofer, H; Brničević, N; Marković, M

    1992-01-01

    Solid phases formed in the quaternary system: uric acid-calcium hydroxide -hydrochloric acid-water aged for 2 months at 310 K were studied to determine conditions for calcium hydrogenurate hexahydrate, Ca(C5H3N4O)2 · 6H2O precipitation. The precipitates were identified by chemical and thermogravimetric analyses, x-ray powder diffraction, infrared spectroscopy, light microscopy, and scanning electron microscopy. In the precipitation diagram the concentration region in which calcium hydrogenurate hexahydrate precipitated as a single solid phase was established. The solubility of calcium hydrogenurate hexahydrate was investigated in the pH range from 6.2 to 10.1 at different temperatures. The total soluble and ionic concentration of calcium (atomic absorption spectroscopy and Ca-selective electrode), total urate concentration (spectrophotometry), and pH were determined in equilibrated solutions. The data are presented in the form of tables and chemical potential diagrams. By using these data the thermodynamic solubility products of calcium hydrogenurate hexahydrate, Ks = a(Ca(2+)) · a(2)(C5H3N4O3(-)), were determined: [Formula: see text]The formation of calcium hydrogenurate hexahydrate crystals in urinary tract of patients with pathologically high concentrations of calcium and urates (hypercalciuria and hyperuricosiuria) is possible.

  5. NiF2/NaF:CaF2/Ca Solid-State High-Temperature Battery Cells

    Science.gov (United States)

    West, William; Whitacre, Jay; DelCastillo, Linda

    2009-01-01

    Experiments and theoretical study have demonstrated the promise of all-solid-state, high-temperature electrochemical battery cells based on NiF2 as the active cathode material, CaF2 doped with NaF as the electrolyte material, and Ca as the active anode material. These and other all-solid-state cells have been investigated in a continuing effort to develop batteries for instruments that must operate in environments much hotter than can be withstood by ordinary commercially available batteries. Batteries of this type are needed for exploration of Venus (where the mean surface temperature is about 450 C), and could be used on Earth for such applications as measuring physical and chemical conditions in geothermal wells and oil wells. All-solid-state high-temperature power cells are sought as alternatives to other high-temperature power cells based, variously, on molten anodes and cathodes or molten eutectic salt electrolytes. Among the all-solid-state predecessors of the present NiF2/NaF:CaF2/Ca cells are those described in "Solid-State High-Temperature Power Cells" (NPO-44396), NASA Tech Briefs, Vol. 32, No. 5 (May 2008), page 40. In those cells, the active cathode material is FeS2, the electrolyte material is a crystalline solid solution of equimolar amounts of Li3PO4 and LiSiO4, and the active anode material is Li contained within an alloy that remains solid in the intended high operational temperature range.

  6. Tropical Cyclones Cause CaCO3 Undersaturation of Coral Reef Seawater in a High-CO2 World

    Science.gov (United States)

    Manzello, D.; Enochs, I.; Carlton, R.; Musielewicz, S.; Gledhill, D. K.

    2013-12-01

    Ocean acidification is the global decline in seawater pH and calcium carbonate (CaCO3) saturation state (Ω) due to the uptake of anthropogenic CO2 by the world's oceans. Acidification impairs CaCO3 shell and skeleton construction by marine organisms. Coral reefs are particularly vulnerable, as they are constructed by the CaCO3 skeletons of corals and other calcifiers. We understand relatively little about how coral reefs will respond to ocean acidification in combination with other disturbances, such as tropical cyclones. Seawater carbonate chemistry data collected from two reefs in the Florida Keys before, during, and after Tropical Storm Isaac provide the most thorough data to-date on how tropical cyclones affect the seawater CO2-system of coral reefs. Tropical Storm Isaac caused both an immediate and prolonged decline in seawater pH. Aragonite saturation state was depressed by 1.0 for a full week after the storm impact. Based on current 'business-as-usual' CO2 emissions scenarios, we show that tropical cyclones with high rainfall and runoff can cause periods of undersaturation (Ω strength, frequency, and rainfall of the most severe tropical cyclones with climate change in combination with ocean acidification will negatively impact the structural persistence of coral reefs over this century.

  7. A Low Resistance Calcium/Reduced Titania Passivated Contact for High Efficiency Crystalline Silicon Solar Cells

    KAUST Repository

    Allen, Thomas G.

    2017-02-04

    Recent advances in the efficiency of crystalline silicon (c-Si) solar cells have come through the implementation of passivated contacts that simultaneously reduce recombination and resistive losses within the contact structure. In this contribution, low resistivity passivated contacts are demonstrated based on reduced titania (TiOx) contacted with the low work function metal, calcium (Ca). By using Ca as the overlying metal in the contact structure we are able to achieve a reduction in the contact resistivity of TiOx passivated contacts of up to two orders of magnitude compared to previously reported data on Al/TiOx contacts, allowing for the application of the Ca/TiOx contact to n-type c-Si solar cells with partial rear contacts. Implementing this contact structure on the cell level results in a power conversion efficiency of 21.8% where the Ca/TiOx contact comprises only ≈6% of the rear surface of the solar cell, an increase of 1.5% absolute compared to a similar device fabricated without the TiOx interlayer.

  8. The system CaHPO 4·2H 2O-CaSO 4·2H 2O: crystallizations from calcium phosphate solutions in the presence of SO 2-4

    Science.gov (United States)

    Rinaudo, C.; Lanfranco, A. M.; Franchini-Angela, M.

    1994-09-01

    The crystallization from solutions of 36 × 10 -3M in [Ca] 2- = [HPO 4] 2-, with ratios [SO 4] 2-/[HPO 4] 2- ranging from 0.11 to 1, was studied at 25°C. When [SO 4] 2- was present in the starting solutions in small amounts (ratios 0.11-0.43), only brushite, twinned following the [010] direction, crystallized. The morphology and habit of the crystals were strongly dependent on the supersaturation of the solution. Higher concentrations in [SO 4] 2- (ratios 0.66-1) allowed the crystallization, on the brushite first precipitated, of a phase showing, by EDS and X-ray analyses, a calcium sulphate phosphate hydrate composition.

  9. The Combined Effect of High Hydrostatic Pressure and Calcium Salts on the Stability, Solubility and Gel Formation of β-Lactoglobulin.

    Science.gov (United States)

    Saalfeld, Daniel; Riegel, Ina; Kulozik, Ulrich; Gebhardt, Ronald

    2015-06-08

    Stability, aggregation and gelation of β-Lactoglobulin are affected by high pressure and salts of the Hofmeister series. Little is known about their combined effects on structure formation processes of β-Lactoglobulin, mainly because many salts of the series are not suitable for use in food. Here, we investigate the effect of calcium salts on the strength of pressure-induced gels, inspired by the fact that high pressure and salts change the water structure in a similar way. We find that the larger the applied pressures, the higher the strength of the gels. In addition to pressure, there is a significant influence by the type of anions and the amount of added calcium salts. Gel strength increases in the order CaCl₂ formation by taking reaction rates for unfolding and aggregation, as well as specific/non-specific salts effect into consideration.

  10. CaV2.1 voltage activated calcium channels and synaptic transmission in familial hemiplegic migraine pathogenesis.

    Science.gov (United States)

    Uchitel, Osvaldo D; Inchauspe, Carlota González; Urbano, Francisco J; Di Guilmi, Mariano N

    2012-01-01

    Studies on the genetic forms of epilepsy, chronic pain, and migraine caused by mutations in ion channels have given crucial insights into the molecular mechanisms, pathogenesis, and therapeutic approaches to complex neurological disorders. In this review we focus on the role of mutated CaV2.1 (i.e., P/Q-type) voltage-activated Ca2+ channels, and on the ultimate consequences that mutations causing familial hemiplegic migraine type-1 (FHM1) have in neurotransmitter release. Transgenic mice harboring the human pathogenic FHM1 mutation R192Q or S218L (KI) have been used as models to study neurotransmission at several central and peripheral synapses. FHM1 KI mice are a powerful tool to explore presynaptic regulation associated with expression of CaV2.1 channels. Mutated CaV2.1 channels activate at more hyperpolarizing potentials and lead to a gain-of-function in synaptic transmission. This gain-of-function might underlie alterations in the excitatory/ inhibitory balance of synaptic transmission, favoring a persistent state of hyperexcitability in cortical neurons that would increase the susceptibility for cortical spreading depression (CSD), a mechanism believed to initiate the attacks of migraine with aura. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Potential roles for calcium-sensing receptor (CaSR) and transient receptor potential ankyrin-1 (TRPA1) in murine anorectic response to deoxynivalenol (vomitoxin).

    Science.gov (United States)

    Wu, Wenda; Zhou, Hui-Ren; Pestka, James J

    2017-01-01

    Food contamination by the trichothecene mycotoxin deoxynivalenol (DON, vomitoxin) has the potential to adversely affect animal and human health by suppressing food intake and impairing growth. In mice, the DON-induced anorectic response results from aberrant satiety hormone secretion by enteroendocrine cells (EECs) of the gastrointestinal tract. Recent in vitro studies in the murine STC-1 EEC model have linked DON-induced satiety hormone secretion to activation of calcium-sensing receptor (CaSR), a G-coupled protein receptor, and transient receptor potential ankyrin-1 (TRPA1), a TRP channel. However, it is unknown whether similar mechanisms mediate DON's anorectic effects in vivo. Here, we tested the hypothesis that DON-induced food refusal and satiety hormone release in the mouse are linked to activation of CaSR and TRPA1. Oral treatment with selective agonists for CaSR (R-568) or TRPA1 (allyl isothiocyanate (AITC)) suppressed food intake in mice, and the agonist's effects were suppressed by pretreatment with corresponding antagonists NPS-2143 or ruthenium red (RR), respectively. Importantly, NPS-2143 or RR inhibited both DON-induced food refusal and plasma elevations of the satiety hormones cholecystokinin (CCK) and peptide YY3-36 (PYY3-36); cotreatment with both antagonists additively suppressed both anorectic and hormone responses to DON. Taken together, these in vivo data along with prior in vitro findings support the contention that activation of CaSR and TRPA1 contributes to DON-induced food refusal by mediating satiety hormone exocytosis from EEC.

  12. Lack of excitatory amino acid-induced effects on calcium fluxes measured with sup 45 Ca sup 2+ in rat cerebral cortex synaptosomes

    Energy Technology Data Exchange (ETDEWEB)

    Simonato, M.; Jope, R.S.; Bianchi, C.; Beani, L. (Univ. of Ferrara (Italy))

    1989-07-01

    Ca{sup 2+} uptake was measured in purified rat cerebral cortex synaptosomes (P3 pellets) using {sup 45}Ca{sup 2+} as a tracer. Ca{sup 2+} influx increased in time, and with an increase in external K+ concentration and temperature. The net (external K+-induced, depolarization-dependent) uptake follows a two-component course. The exponential term, due to the opening of voltage-operated calcium channels (VOC), has a rate constant which increases with an increase in the depolarization level (1.04 versus 0.54 nmol/s/mg protein for 50 mM - versus 15 mM (K+)-dependent net influx). The linear term, due to the Na{sup +}/Ca{sup 2+} exchange system, has a similar rate constant at all depolarization levels (0.16 +/- 0.05 and 0.11 +/- 0.02 nmol/s/mg protein). Excitatory amino acids (glutamate, kainate and n-methyl-d-aspartate-NMDA-) were tested on this preparation at doses ranging between 5 x 10(-5) M and 5 x 10(-3) M and at multiple incubation times, under resting conditions and under two depolarizing conditions (partial depolarization: 15 mM external K{sup +} and maximal depolarization: 50 mM external K+). NMDA was also tested in the absence of Mg{sup 2+}. No effect was detectable under any of these experimental conditions. Hypotheses to interpret these data are discussed. Further studies on other preparations are needed in order to directly investigate the presynaptic effects of excitatory amino acids.

  13. Stimulation of AIDS lymphocytes with calcium ionophore (A23187) and phorbol ester (PMA): studies of cytoplasmic free Ca, IL-2 receptor expression, IL-2 production, and proliferation

    DEFF Research Database (Denmark)

    Hofmann, B; Moller, J; Langhoff, E

    1989-01-01

    nine patients with AIDS with the response of lymphocytes from nine control subjects showed that the response of AIDS lymphocytes was severely decreased when stimulated with PHA and no further response could be achieved by stimulation with A23187/PMA. On the other hand, no significant difference between...... the PHA-induced rise of cytoplasmic free calcium concentration ([Ca2+]1) in normal and AIDS lymphocytes was observed. The percentage of cells expressing IL-2 receptors (CD25) was also normal both after addition of PHA and after addition of A23187/PMA and the expression was normal on both CD4 and CD8 cells....... The production of IL-2 in normal lymphocytes stimulated with A23187/PMA was 33 times higher than that after stimulation with PHA. In AIDS lymphocytes the production of IL-2 induced by all activators was severely decreased compared to control subjects, although the production of IL-2 after stimulation with A23187...

  14. Calcium electrotransfer for termination of transgene expression in muscle

    DEFF Research Database (Denmark)

    Hojman, Pernille; Spanggaard, Iben; Olsen, Caroline Holkman;

    2011-01-01

    in vivo imaging of infrared fluorescent "Katushka" and erythropoietin evaluated by ELISA and hemoglobin. Histology was performed. Electrotransfer of Katushka and erythropoietin yielded significant expression. Maximal calcium uptake occurred after injection of Ca(2+) before electropulsing using eight high......Gene electrotransfer is expanding in clinical use, thus we have searched for an emergency procedure to stop transgene expression in case of serious adverse events. Calcium is cytotoxic at high intracellular levels, so we tested effects of calcium electrotransfer on transgene expression in muscle....... A clinical grade calcium solution (20 µl, 168 mM) was injected into transfected mouse or rat tibialis cranialis muscle. Ca(2+) uptake was quantified using calcium 45 ((45)Ca), and voltage and time between injection and pulsation were varied. Extinction of transgene expression was investigated by using both...

  15. 铝酸钙系冶金熔剂和CaF2对镁碳砖的侵蚀比较%Corrosion comparison of calcium aluminate system metallurgy flux and CaF2 to magnesia carbon brick

    Institute of Scientific and Technical Information of China (English)

    李文平; 李士明; 陈俊红; 孙加林; 吴克芳; Christoph Wohrmeyer

    2013-01-01

    为了降低精炼渣对钢包渣线镁碳砖的侵蚀,分别以20%(w)的冶金熔剂铝酸钙、铝镁酸钙和CaF2与80%(w)的初始钢渣配制成三种精炼渣,以镁碳砖为感应炉的坩埚,在坩埚内放入钢样,待钢样熔化并升温到1 600℃时,加精炼渣持续冶炼5h(期间共更换渣8次),冷却后测镁碳砖渣线部位的侵蚀(渗透)深度并进行SEM分析.结果表明:以铝酸钙和铝镁酸钙为熔剂的精炼渣都比以CaF2为熔剂的精炼渣对镁碳砖的渗透浅、侵蚀小,而以铝镁酸钙冶金熔剂为精炼渣比以铝酸钙冶金熔剂为精炼渣对镁碳砖的渗透和侵蚀性都大大降低.这是由于铝镁酸钙中含有饱和的MgO,减缓了镁碳砖中MgO向CMA渣中的溶解,从而降低了渣对镁碳砖的侵蚀.%In order to reduce the corrosion of refining slag to ladle slag line MgO-C brick,three kinds of refining slags were prepared with 20 mass% metallurgy fluxes of calcium aluminate (CA) and calcium magnesia aluminate (CMA) and CaF2 and 80 mass% original steel slag,and MgO-C bricks were made into crucibles of electric induction furnace. Add steel sample into the crucible,heat up to 1 600 ℃after the steel sample melts,then add refining slag,and hold for 5 h. In the meantime,the refining slags were replaced for 8 times. The corrosion (penetration) depth of the MgO-C brick in slag line was determined and the corroded brick was observed by SEM. The research shows that the MgO-C brick can better resist the penetration and corrosion of refining slags containing CA flux and CMA flux than those of refining slag containing CaF2; refining slag containing CMA flux penetrates and corrodes MgO-C brick obviously slightly than refining slag containing CA flux. CMA flux contains the saturated MgO which reduces the dissolving speed of MgO from MgO-C brick to refining slag containing CMA flux,corresponding decreases the corrosion of the slag.

  16. MINERALIZATION STUDY OF RENAL RATS FOLLOWING OVARYOHYSTERECTOMY AND ADMINISTRATION HIGH DOSE CALCIUM CARBONATE

    Directory of Open Access Journals (Sweden)

    Wiwik Misaco Yuniarti

    2008-06-01

    Full Text Available The aim of this study was to determine the effect of high dose calcium carbonate in rat (Rattus norvegicus following ovaryohysterectomy. A total of twenty female rats at 13 week-old were used in this study. Following ovaryohitectomy, the animals were randomized in four treatment groups. Group P0 were :fed with standard food only P1, P2 and P2 groups treated with standard food but supplemented calcium carbonate respectively at the dose of 75 mg per animal per day, 225 mg per animal per day , and 450 mg per animal per day. The calcium carbonate supplement were given daily in the morning for 42 days. The experimental animals were sacrificed at 21 week-old. Calcium and phosphor level in sinister kidneys were determined by spectrofotometric method. The data obtained from this study were analysed using one way analysis of variance. No significant difference was observed in calcium level among four treatment groups, with the lowest level were found in P3 group. However, the phosphor level of P1 was significantly lower than those of P2 and P3 groups. The highest phosphor level was observed in P3 group, indicating a phosphorous retension and the signs of renal failure.

  17. MINERALIZATION STUDY OF RENAL RATS FOLLOWING OVARYOHYSTERECTOMY AND ADMINISTRATION HIGH DOSE CALCIUM CARBONATE

    OpenAIRE

    Wiwik Misaco Yuniarti; Ira Sari Yudaniayanti; Nusdianto Triakoso

    2008-01-01

    The aim of this study was to determine the effect of high dose calcium carbonate in rat (Rattus norvegicus) following ovaryohysterectomy. A total of twenty female rats at 13 week-old were used in this study. Following ovaryohitectomy, the animals were randomized in four treatment groups. Group P0 were :fed with standard food only P1, P2 and P2 groups treated with standard food but supplemented calcium carbonate respectively at the dose of 75 mg per animal per day, 225 mg per animal per day , ...

  18. Regulation of voltage-gated calcium channels by proteolysis%蛋白质水解对电压门控Ca2+通道的调节

    Institute of Scientific and Technical Information of China (English)

    ABELE Kathryn; 杨建

    2012-01-01

    电压门控Ca2+通道是由多个亚基组成的膜蛋白,其分布广泛,生理功能极为重要,可被众多蛋白和信号传导通路调节.本综述重点介绍蛋白质水解对电压门控Ca2+通道的调节作用及其生理功能.Ca2+通道的主亚基Cavα1可被蛋白质水解,从而调控Ca2+通道的功能和降解,影响基因表达和细胞兴奋性.根据其组织分布,L类Ca2+通道有两种水解模式:在心脏和骨骼肌,Cavα1的羧基末端被水解后与剩余的羧基端结合,抑制Ca2+通道电流.这种自身抑制可被体内分泌的肾上腺素解除,引发心肌和骨骼肌Ca2+电流大量增加,在“打或逃”之类的应激反应中起重要作用,Cavα1羧基末端水解在大脑也存在,并可能是由calpain蛋白质水解酶催化;在某些大脑区域,Cavα1的整个羧基端可被水解并迁移至细胞核,起到转录因子的作用.P/Q类Ca2+通道Cavα1的羧基末端也可被水解,并迁移到细胞核.许多基因突变产生截断型P/Q Cavα1,而这些截断型Cavα1可严重影响正常Ca2+通道的功能,导致人类的疾病.截断型N类Ca2+通道Cavα1可通过诱变产生,影响正常通道的表达.新型Ca2+通道水解新模式可能是未来Ca2+通道研究中一个重要的探索方向.%Voltage gated calcium channels (VGCCs) are multi-subunit membrane proteins present in a variety of tissues and control many essential physiological processes.Due to their vital importance,VGCCs are regulated by a myriad of proteins and signaling pathways.Here we review the literature on the regulation of VGCCs by proteolysis of the pore-forming α1 subunit,Cavα1.This form of regulation modulates channel function and degradation and affects cellular gene expression and excitability.L-type Ca2+ channels are proteolyzed in two ways,depending on tissue localization.In the heart and skeletal muscle,the distal C-terminus of Cavα1 is cleaved and acts as an autoinhibitor when it reassociates with the proximal C

  19. The Combined Effect of High Hydrostatic Pressure and Calcium Salts on the Stability, Solubility and Gel Formation of β-Lactoglobulin

    Directory of Open Access Journals (Sweden)

    Daniel Saalfeld

    2015-06-01

    Full Text Available Stability, aggregation and gelation of β-Lactoglobulin are affected by high pressure and salts of the Hofmeister series. Little is known about their combined effects on structure formation processes of β-Lactoglobulin, mainly because many salts of the series are not suitable for use in food. Here, we investigate the effect of calcium salts on the strength of pressure-induced gels, inspired by the fact that high pressure and salts change the water structure in a similar way. We find that the larger the applied pressures, the higher the strength of the gels. In addition to pressure, there is a significant influence by the type of anions and the amount of added calcium salts. Gel strength increases in the order CaCl2 < Ca (NO32 < CaI2. This trend correlates with the position of the salts in the Hofmeister series. The results are explained by analogy with the thermal aggregate formation by taking reaction rates for unfolding and aggregation, as well as specific/non-specific salts effect into consideration.

  20. The Combined Effect of High Hydrostatic Pressure and Calcium Salts on the Stability, Solubility and Gel Formation of β-Lactoglobulin

    Science.gov (United States)

    Saalfeld, Daniel; Riegel, Ina; Kulozik, Ulrich; Gebhardt, Ronald

    2015-01-01

    Stability, aggregation and gelation of β-Lactoglobulin are affected by high pressure and salts of the Hofmeister series. Little is known about their combined effects on structure formation processes of β-Lactoglobulin, mainly because many salts of the series are not suitable for use in food. Here, we investigate the effect of calcium salts on the strength of pressure-induced gels, inspired by the fact that high pressure and salts change the water structure in a similar way. We find that the larger the applied pressures, the higher the strength of the gels. In addition to pressure, there is a significant influence by the type of anions and the amount of added calcium salts. Gel strength increases in the order CaCl2 < Ca (NO3)2 < CaI2. This trend correlates with the position of the salts in the Hofmeister series. The results are explained by analogy with the thermal aggregate formation by taking reaction rates for unfolding and aggregation, as well as specific/non-specific salts effect into consideration. PMID:28231200

  1. Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

    NARCIS (Netherlands)

    Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

  2. A new crystallization process in polypropylene highly filled with calcium carbonate

    NARCIS (Netherlands)

    Schawe, Jurgen E.K.; Vermeulen, Paul A.; van Drongelen, Martin

    2015-01-01

    The influence of high amounts of calcium carbonate filler on the crystallization behavior of polypropylene (PP) is investigated by differential scanning calorimetry (DSC) and fast scanning DSC measurements. The non-isothermal crystallization process at industrially relevant cooling rates of about

  3. Inhibition effects of high calcium concentration on anaerobic biological treatment of MSW leachate.

    Science.gov (United States)

    Xia, Yi; He, Pin-Jing; Pu, Hong-Xia; Lü, Fan; Shao, Li-Ming; Zhang, Hua

    2016-04-01

    With the increasing use of municipal solid waste incineration (MSWI) and more stringent limits on landfilling of organic waste, more MSWI bottom ash is being landfilled, and the proportion of inorganic wastes in landfills is increasing, causing the increased Ca concentrations in landfill leachate. In this research, the inhibition effect of Ca concentration on the anaerobic treatment of landfill leachate was studied using a biochemical methane potential experiment. Slight inhibition of methane production occurred when the addition of Ca concentration was less than 2000 mg/L. When the addition of Ca concentration was between 6000 and 8000 mg/L, methane production was significantly reduced (to 29.4-34.8 % of that produced by the BLK reactor), and the lag phase was increased from 8.55 to 16.32 d. Moreover, when the dosage of Ca concentration increased from zero to 8000 mg/L, reductions in solution Ca concentration increased from 929 to 2611 mg/L, and the proportion of Ca in the residual sludge increased from 22.58 to 46.87 %. Based on the results, when the dosage of Ca concentration was less than 4000 mg/L, the formation of Ca precipitates on the surface of sludge appeared to prevent mass transfer and was the dominant reason for the reduction in methane production and sludge biomass. At higher Ca concentrations (6000-8000 mg/L), the severe inhibition of methane production appeared to be caused by the toxic effect of highly concentrated Ca on sludge as well as mass transfer blockage.

  4. Ca-rich Ca-Al-oxide, high-temperature-stable sorbents prepared from hydrotalcite precursors: synthesis, characterization, and CO2 capture capacity.

    Science.gov (United States)

    Chang, Po-Hsueh; Chang, Yen-Po; Chen, San-Yuan; Yu, Ching-Tsung; Chyou, Yau-Pin

    2011-12-16

    We present the design and synthesis of Ca-rich Ca-Al-O oxides, with Ca(2+)/Al(3+) ratios of 1:1, 3:1, 5:1, and 7:1, which were prepared by hydrothermal decomposition of coprecipitated hydrotalcite-like Ca-Al-CO(3) precursors, for high-temperature CO(2) adsorption at 500-700 °C. In situ X-ray diffraction measurements indicate that the coprecipitated, Ca-rich, hydrotalcite-like powders with Ca(2+)/Al(3+) ratios of 5:1 and 7:1 contained Ca(OH)(2) and layered double hydroxide (LDH) phases. Upon annealing, LDH was first destroyed at approximately 200 °C to form an amorphous matrix, and then at 450-550 °C, the Ca(OH)(2) phase was converted into a CaO matrix with incorporated Al(3+) to form a homogeneous solid solution without a disrupted lattice structure. CaO nanocrystals were grown by thermal treatment of the weakly crystalline Ca-Al-O oxide matrix. Thermogravimetric analysis indicates that a CO(2) adsorption capacity of approximately 51 wt. % can be obtained from Ca-rich Ca-Al-O oxides prepared by calcination of 7:1 Ca-Al-CO(3) LDH phases at 600-700 °C. Furthermore, a relatively high CO(2) capture capability can be achieved, even with gas flows containing very low CO(2) concentrations (CO(2)/N(2) = 10 %). Approximately 95.6 % of the initial CO(2) adsorption capacity of the adsorbent is retained after 30 cycles of carbonation-calcination. TEM analysis indicates that carbonation-promoted CaCO(3) formation in the Ca-Al-O oxide matrix at 600 °C, but a subsequent desorption in N(2) at 700 °C, caused the formation CaO nanocrystals of approximately 10 nm. The CaO nanocrystals are widely distributed in the weakly crystalline Ca-Al-O oxide matrix and are present during the carbonation-calcination cycles. This demonstrates that Ca-Al-O sorbents that developed through the synthesis and calcination of Ca-rich Ca-Al LDH phases are suitable for long-term cyclic operation in severe temperature environments.

  5. Calmodulin activation by calcium transients in the postsynaptic density of dendritic spines.

    Directory of Open Access Journals (Sweden)

    Daniel X Keller

    Full Text Available The entry of calcium into dendritic spines can trigger a sequence of biochemical reactions that begins with the activation of calmodulin (CaM and ends with long-term changes to synaptic strengths. The degree of activation of CaM can depend on highly local elevations in the concentration of calcium and the duration of transient increases in calcium concentration. Accurate measurement of these local changes in calcium is difficult because the spaces are so small and the numbers of molecules are so low. We have therefore developed a Monte Carlo model of intracellular calcium dynamics within the spine that included calcium binding proteins, calcium transporters and ion channels activated by voltage and glutamate binding. The model reproduced optical recordings using calcium indicator dyes and showed that without the dye the free intracellular calcium concentration transient was much higher than predicted from the fluorescent signal. Excitatory postsynaptic potentials induced large, long-lasting calcium gradients across the postsynaptic density, which activated CaM. When glutamate was released at the synapse 10 ms before an action potential occurred, simulating activity patterns that strengthen hippocampal synapses, the calcium gradient and activation of CaM in the postsynaptic density were much greater than when the order was reversed, a condition that decreases synaptic strengths, suggesting a possible mechanism underlying the induction of long-term changes in synaptic strength. The spatial and temporal mechanisms for selectivity in CaM activation demonstrated here could be used in other signaling pathways.

  6. Effect of applied voltage on surface properties of anodised titanium in mixture of β-glycerophosphate (β-GP) and calcium acetate (CA)

    Energy Technology Data Exchange (ETDEWEB)

    Chuan, Lee Te, E-mail: gd130079@siswa.uthm.edu.my; Rathi, Muhammad Fareez Mohamad, E-mail: cd110238@siswa.uthm.edu.my; Abidin, Muhamad Yusuf Zainal, E-mail: cd110221@siswa.uthm.edu.my; Abdullah, Hasan Zuhudi, E-mail: hasan@uthm.edu.my; Idris, Maizlinda Izwana, E-mail: izwana@uthm.edu.my [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor (Malaysia)

    2015-07-22

    Anodic oxidation is a surface modification method which combines electric field driven metal and oxygen ion diffusion for formation of oxide layer on the anode surface. This method has been widely used to modify the surface morphology of biomaterial especially titanium. This study aimed to investigate the effect of applied voltage on titanium. Specifically, the titanium foil was anodised in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA) with different applied voltage (50-350 V), electrolyte concentration (0.04 M β-GP + 0.4 M CA), anodising time (10minutes) and current density (50 and 70 mA.cm{sup −2}) at room temperature. Surface oxide properties of anodised titanium were characterised by digital single-lens reflex camera (DSLR camera), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM). At lower applied voltage (≤150 V), surface of titanium foils were relatively smooth. With increasing applied voltage (≥250 V), the oxide layer became more porous and donut-shaped pores were formed on the surface of titanium foils. The AFM results indicated that the surface roughness of anodised titanium increases with increasing of applied voltage. The porous and rough surface is able to promote the osseointegration and reduce the suffering time of patient.

  7. Dispersion of linear and nonlinear optical susceptibilities in calcium neodymium oxyborate Ca4NdO(BO3)3-LDA versus GGA.

    Science.gov (United States)

    Reshak, Ali H; Auluck, S; Kityk, I V

    2009-02-26

    We have performed ab inito theoretical calculations of the electronic structure and the linear and nonlinear optical susceptibilities for calcium neodymium oxyborate Ca4NdO(BO3)3 using two approximations for the exchange correlation (XC) potentials, the local density approximation (LDA) and the generalized gradient approximation (GGA). Our calculations show that this compound is metallic-like, with density of states at the Fermi energy E(F), N(E(F)), of 5.95 and 10.33 states/Ry-cell or bare electronic specific heat coefficients of 1.03 and 1.79 mJ/mol-K2 for LDA and GGA, respectively. The overlap between the valence and conduction bands is strong, resulting in metallic behavior. We found that Nd-s/p/d, Ca-s/p, B-p, and O-s/p states controlled the overlapping around E(F). The effect of LDA and GGA on the band structure, density of states, and linear optical properties is very small, while for the nonlinear optical properties, it is very pronounced. Our calculations show that χ(111)(2)(ω) is the dominant component for both LDA and GGA. We find opposite signs of the contributions of the 2ω and 1ω inter/intraband to the real and imaginary parts for the dominant component throughout the wide optical frequency range.

  8. Extracellular calcium sensing receptor in human pancreatic cells

    Science.gov (United States)

    Rácz, G Z; Kittel, Á; Riccardi, D; Case, R M; Elliott, A C; Varga, G

    2002-01-01

    Background and aims: The extracellular calcium sensing receptor (CaR) plays a key role in the calcium homeostatic system and is therefore widely expressed in tissues involved in calcium metabolism. However, the CaR has also been identified in other tissues where its role is less clear. We have investigated the presence of the CaR in the human pancreas. Methods: Messenger RNA for the CaR was detected by reverse transcription-polymerase chain reaction and the protein was localised by immunostaining. CaR function was assayed in Capan-1 cells by measuring intracellular calcium and [3H] thymidine incorporation. Results: The receptor was highly expressed in human pancreatic ducts. It was also expressed in exocrine acinar cells, in islets of Langerhans, and in intrapancreatic nerves and blood vessels. The CaR was expressed in both normal and neoplastic human tissue samples but was detected in only one of five ductal adenocarcinoma cells lines examined. Experiments on the CaR expressing adenocarcinoma cell line Capan-1 showed that the CaR was functional and was linked to mobilisation of intracellular calcium. Stimulation of the CaR reduced Capan-1 cell proliferation. Conclusions: We propose that the CaR may play multiple functional roles in the human pancreas. In particular, the CaR on the duct luminal membrane may monitor and regulate the Ca2+ concentration in pancreatic juice by triggering ductal electrolyte and fluid secretion. This could help to prevent precipitation of calcium salts in the duct lumen. The CaR may also help to regulate the proliferation of pancreatic ductal cells. PMID:12377811

  9. Test and evaluation of different ifllers and calcium carbonate in paper-process reconstituted tobacco%造纸法烟草薄片中不同填料CaCO3的测试及评价

    Institute of Scientific and Technical Information of China (English)

    刘旭强; 李军; 王亚明; 刘维娟; 冯文超; 冀雅文; 朱红琴

    2014-01-01

    Through experiment, the influence of different fillers and additives on retention of paper-process reconstituted tobacco was analyzed. The results show that different fillers and additives on the retention are obviously different, the sedimentation volume of Rui bosi’s calcium carbonate is between precipitated calcium carbonate and ground calcium carbonate; the changing trend in basis weight of reconstituted tobacco made with different additives is different;ash content of different reconstituted tobacco leaves with different calcium carbonate ifller is also different.%分析研究了不同填料、不同助剂对造纸法再造烟叶薄片留着率的影响。结果表明:不同的填料和助剂制成的薄片的留着率存在明显差异;#4CaCO3沉降体积要介于轻质CaCO3和重质CaCO3的沉降体积之间;不同助剂的再造烟叶定量变化趋势有所不同;不同类型CaCO3填料的再造烟叶灰分不同。

  10. Efficacité du traitement par calcimimétiques dans l'hyperparathyroïdie néonatale sévère, associée à des mutations du calcium sensing receptor (CaSR)

    OpenAIRE

    Wilhelm-Bals, Alexandra Marina

    2013-01-01

    L'Hyperparathyroïdie néonatale sévère (NPHT) est associée à des mutations homozygotes inactivatrices du récepteur du calcium (CaSR). Le CaSR est exprimé majoritairement dans les glandes parathyroïdes et les reins où il régule l'homéostasie du calcium en modulant la sécrétion de PTH et la réabsorption rénale du calcium. L'NPHT se présente avec une hypercalcémie sévère mettant en jeu le pronostic vital. La chirurgie est le traitement de choix. Les bisphosphonates offrent une bonne alternative d...

  11. Mitochondrial calcium uptake capacity modulates neocortical excitability.

    Science.gov (United States)

    Sanganahalli, Basavaraju G; Herman, Peter; Hyder, Fahmeed; Kannurpatti, Sridhar S

    2013-07-01

    Local calcium (Ca(2+)) changes regulate central nervous system metabolism and communication integrated by subcellular processes including mitochondrial Ca(2+) uptake. Mitochondria take up Ca(2+) through the calcium uniporter (mCU) aided by cytoplasmic microdomains of high Ca(2+). Known only in vitro, the in vivo impact of mCU activity may reveal Ca(2+)-mediated roles of mitochondria in brain signaling and metabolism. From in vitro studies of mitochondrial Ca(2+) sequestration and cycling in various cell types of the central nervous system, we evaluated ranges of spontaneous and activity-induced Ca(2+) distributions in multiple subcellular compartments in vivo. We hypothesized that inhibiting (or enhancing) mCU activity would attenuate (or augment) cortical neuronal activity as well as activity-induced hemodynamic responses in an overall cytoplasmic and mitochondrial Ca(2+)-dependent manner. Spontaneous and sensory-evoked cortical activities were measured by extracellular electrophysiology complemented with dynamic mapping of blood oxygen level dependence and cerebral blood flow. Calcium uniporter activity was inhibited and enhanced pharmacologically, and its impact on the multimodal measures were analyzed in an integrated manner. Ru360, an mCU inhibitor, reduced all stimulus-evoked responses, whereas Kaempferol, an mCU enhancer, augmented all evoked responses. Collectively, the results confirm aforementioned hypotheses and support the Ca(2+) uptake-mediated integrative role of in vivo mitochondria on neocortical activity.

  12. High affinity group III mGluRs regulate mossy fiber input to CA3 interneurons.

    Science.gov (United States)

    Cosgrove, Kathleen E; Meriney, Stephen D; Barrionuevo, Germán

    2011-12-01

    Stratum lacunosum-moleculare interneurons (L-Mi) in hippocampal area CA3 target the apical dendrite of pyramidal cells providing feedforward inhibition. Here we report that selective activation of group III metabotropic glutamate receptors (mGluRs) 4/8 with L(+)-2-amino-4-phosphnobytyric acid (L-AP4; 10 μM) decreased the probability of glutamate release from the mossy fiber (MF) terminals synapsing onto L-Mi. Consistent with this interpretation, application of L-AP4 in the presence of 3 mM strontium decreased the frequency of asynchronous MF EPSCs in L-Mi. Furthermore, the dose response curve showed that L-AP4 at 400 μM produced no further decrease in MF EPSC amplitude compared with 20 μM L-AP4, indicating the lack of mGluRs 7 at these MF terminals. We also found that one mechanism of mGluRs 4/8-mediated inhibition of release is linked to N-type voltage gated calcium channels at MF terminals. Application of the group III mGluR antagonist MSOP (100 μM) demonstrated that mGluRs 4/8 are neither tonically active nor activated by low and moderate frequencies of activity. However, trains of stimuli to the MF at 20 and 40 Hz delivered during the application of MSOP revealed a relief of inhibition of transmitter release and an increase in the overall probability of action potential firing in the postsynaptic L-Mi. Interestingly, the time to first action potential was significantly shorter in the presence of MSOP, indicating that mGluR 4/8 activation delays L-Mi firing in response to MF activity. Taken together, our data demonstrate that the timing and probability of action potentials in L-Mi evoked by MF synaptic input is regulated by the activation of presynaptic high affinity group III mGluRs.

  13. Highly cooperative feedback control of retinal rod guanylate cyclase by calcium ions.

    Science.gov (United States)

    Koch, K W; Stryer, L

    1988-07-07

    Visual excitation in retinal rod cells is mediated by a cascade that leads to the amplified hydrolysis of cyclic GMP (cGMP) and the consequent closure of cGMP-activated cation-specific channels in the plasma membrane. Recovery of the dark state requires the resynthesis of cGMP, which is catalysed by guanylate cyclase, an axoneme-associated enzyme. The lowering of the cytosolic calcium concentration (Cai) following illumination is thought to be important in stimulating cyclase activity. This hypothesis is supported by the finding that the cGMP content of rod outer segments increases several-fold when Cai is lowered to less than 10 nM. It is evident that cGMP and Cai levels are reciprocally controlled by negative feedback. Guanylate cyclase from toad ROS is strongly stimulated when the calcium level is lowered from 10 microM to 10 nM, but only if they are excited by light. We show here that the guanylate cyclase activity of unilluminated bovine rod outer segments increases markedly (5 to 20-fold) when the calcium level is lowered from 200 nM to 50 nM. This steep dependence of guanylate cyclase activity on the calcium level in the physiological range has a Hill coefficient of 3.9. Stimulation at low calcium levels is mediated by a protein that can be released from the outer segment membranes by washing with a low salt buffer. Calcium sensitivity is partially restored by adding the soluble extract back to the washed membranes. The highly cooperative activation of guanylate cyclase by the light-induced lowering of Cai is likely to be a key event in restoring the dark current after excitation.

  14. Expression of calcium channel CaV1.3 in cat spinal cord: light and electron microscopic immunohistochemical study

    DEFF Research Database (Denmark)

    Zhang, Mengliang; Møller, Morten; Broman, Jonas;

    2008-01-01

    in the cat spinal cord by light and electron microscopic immunohistochemistry. The results show that Ca(V)1.3-like immunoreactivity is widely distributed in all segments of the spinal cord but that the distribution in the different laminae of the spinal gray matter varies, with the highest density of labeled...... associated with the rough endoplasmic reticulum but some also with the plasma membrane. In dendrites, they were associated with both intracellular organelles, including microtubules and microchondria, and the plasma membrane. These results indicate that significant proportions of the neurons in cat spinal...

  15. The changes of CaSR activity on the formation of calcium oxalate stones%钙敏感受体活性改变对大鼠泌尿系草酸钙结石形成的影响

    Institute of Scientific and Technical Information of China (English)

    李笑然; 岳中瑾; 马俊海; 裴薇; 辛文虎; 明星; 杨雄

    2013-01-01

    Objective To study the changes of CaSR activity on the formation of calcium oxalate stones. Methods A-dult male Sprague Dawley rats were given ethylene glycol and ammonium chloride to induce urolithiasis. Meanwhile, different doses of CaSR inhibitors (NPS-2390) were administered. The values of serum urea, creatinine,P,Ca2+ and Mg2+ ,PTH,24 h urine volume,urine pH,Ca2+ , Mg2+and oxalate were evaluated at the end of the experiment. Kidney sections were examined under a light microscope to study the calcium oxalate crystal deposition, pathological changes and the expression of CaSR. Results The urolithiasis induced by ethylene glycol and ammonium chloride caused not only significant increase of serum ure-a,creatinine, urine oxalate and Ca2+ ,but also great amount of calcium oxalate crystal deposition in kidney. PTH secretion of CaSR inhibitor group increased and blood Ca2+ urine Ca2+ raised. Renal histopathologic examination showed significant increase of calcium oxalate crystals in the kidney tissue of the CaSR inhibitor group,and kidney tissue damage was obvious.Conclusions In the kidney and parathyroid gland the low expression of CaSR can increase the formation of calcium oxalate crystal.%目的 探讨钙敏感受体(CaSR)活性改变对草酸钙结石形成的影响.方法 在实验期间给予乙二醇和氯化铵诱导雄性SD大鼠产生泌尿系草酸钙结石.在造模期间给予不同剂量的CaSR抑制剂(NPS-2390).实验结束时检测各组大鼠血尿素氮(BUN)、肌酐(Cr)、血磷、血钙、血镁、PTH的含量、24 h尿量、尿pH值、尿钙、镁、尿草酸的分泌量,显微镜下观察肾组织切片中草酸钙结晶沉积及病理变化情况及肾脏中CaSR表达情况.从而评价CaSR活性的改变对泌尿系结石形成的影响.结果 成石对照组大鼠血BUN、Cr、尿草酸、尿钙较空白组明显升高并且有大量结晶形成,表明建模成功.CaSR抑制剂组较成石对照组甲状旁腺激素(PTH)的分泌增加并且血Ca

  16. Differential mitochondrial calcium responses in different cell types detected with a mitochondrial calcium fluorescent indicator, mito-GCaMP2

    Institute of Scientific and Technical Information of China (English)

    Min Chen; Yanru Wang; Tingting Hou; Huiliang Zhang; Aijuan Qu; Xianhua Wang

    2011-01-01

    Mitochondrial calcium plays a crucial role in mitochondriai metabolism,cell calcium handling,and cell death.However,some mechanisms concerning mitochondrial calcium regulation are still unknown,especially how mitochondrial calcium couples with cytosolic calcium.In this work,we constructed a novel mitochondrial calcium fluorescent indicator (mito-GCaMP2) by genetic manipulation.Mito-GCaMP2 was imported into mitochondria with high efficiency and the fluorescent signals co-localized with that of tetramethyl rhodamine methyl ester,a mitochondrial membrane potential indicator.The mitochondrial inhibitors specifically decreased the signals of mito-GCaMP2.The apparent Kd of mito-GCaMP2 was 195.0 nmol/L at pH 8.0 in adult rat cardiomyocytes.Furthermore,we observed that mito-GCaMP2 preferred the alkaline pH surrounding of mitochondria.In HeLa cells,we found that mitochondrial calcium ([Ca2+]mito)responded to the changes of cytosolic calcium ([Ca2+]cyto)induced by histamine or thapasigargin.Moreover,external Ca2+ (100 μmol/L) directly induced an increase of [Ca2+]mito in permeabilized HeLa cells.However,in rat cardiomyocytes [Ca2+]mito did not respond to cytosolic calcium transients stimulated by electric pacing or caffeine.In permeabilized cardiomyocytes,600 nmol/L free Ca2+ repeatedly increased the fluorescent signals of mito-GCaMP2,which excluded the possibility that mito-GCaMP2 lost its function in cardiomyocytes mitochondria.These results showed that the response of mitochondrial calcium is diverse in different cell lineages and suggested that mitochondria in cardiomyocytes may have a special defense mechanism to control calcium flux.

  17. Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction.

    Science.gov (United States)

    Combes, C; Bareille, R; Rey, C

    2006-11-01

    The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.

  18. Calcium decorated and doped phosphorene for gas adsorption

    Science.gov (United States)

    Lalitha, Murugan; Nataraj, Yuvarani; Lakshmipathi, Senthilkumar

    2016-07-01

    In this paper, we present the results from first-principles study based on the electronic structure and adsorption characteristics of CH4, CO2, H2 and NH3 adsorbed on Ca decorated/doped phosphorene. Our study finds that phosphorene exhibits n-type behaviour on decorating calcium, and p-type on doping calcium. Gas molecules are physisorbed on both pristine and calcium-mediated phosphorene, visible through their lower binding energy and charge transfer values. Ca decorated phosphorene is suitable for hydrogen storage due to its higher binding energy for H2. Ca doped structures shows increased binding affinity towards CH4 and NH3 in zigzag1 direction and armchair directions respectively. The extracts of our study implies that Ca doped phosphorene possess increased binding affinity towards gas molecules, and the results are highly helpful for gas adsorption and to design gas sensors based on calcium doped or decorated phosphorene.

  19. Effects of Astragalus membranaceus with supplemental calcium on bone mineral density and bone metabolism in calcium-deficient ovariectomized rats.

    Science.gov (United States)

    Kang, Se-Chan; Kim, Hee Jung; Kim, Mi-Hyun

    2013-01-01

    It has been reported that Astragalus membranaceus, an Asian traditional herb, has an estrogenic effect in vitro. To examine the possible role of A. membranaceus extract with supplemental calcium (Ca) on bone status in calcium-deficient (LCa) ovariectomized (OVX) rats, a total of 48 female rats were divided into six groups: (1) normal control, (2) sham operation with LCa (sham-LCa), (3) OVX with LCa (OVX-LCa), (4) A. membranaceus supplementation with OVX-LCa (OVX-MLCa), (5) Ca supplementation with OVX (OVX-Ca), and (6) A. membranaceus and Ca supplementation with OVX (OVX-MCa). A. membranaceus ethanol extract (500 mg/kg BW) and/or Ca (800 mg/kg BW) were administered orally for 8 weeks along with a Ca-deficient diet. Results revealed that Ca supplementation with or without A. membranaceus extract significantly improved bone mineral density, biomechanical strength, and ash weight of the femur and tibia in OVX rats. High Ca with A. membranaceus combination supplementation significantly increased the ash weight of the femur and tibia and decreased urinary Ca excretion compared with supplementation of Ca alone. Uterine weight was not changed by A. membranaceus administration in OVX rats. These results suggest that A. membranaceus extract combined with supplemental Ca may be more protective against the Ca loss of bone than A. membranaceus or supplementation of Ca alone in calcium-insufficient postmenopausal women.

  20. Sarcoplasmic Reticulum Ca2+ Cycling Protein Phosphorylation in a Physiologic Ca2+ Milieu Unleashes a High-Power, Rhythmic Ca2+ Clock in Ventricular Myocytes: Relevance to Arrhythmias and Bio-Pacemaker Design

    Science.gov (United States)

    Sirenko, Syevda; Maltsev, Victor A; Maltseva, Larissa A; Yang, Dongmei; Lukyanenko, Yevgeniya; Vinogradova, Tatiana; Jones, Larry; Lakatta, Edward G.

    2014-01-01

    Basal phosphorylation of sarcoplasmic reticulum (SR) Ca2+ proteins is high in sinoatrial nodal cells (SANC), which generate partially synchronized, spontaneous, rhythmic, diastolic local Ca2+ releases (LCRs), but low in ventricular myocytes (VM), which exhibit rare diastolic, stochastic SR-generated Ca2+ sparks. We tested the hypothesis that in a physiologic Ca2+ milieu, and independent of increased Ca2+ influx, an increase in basal phosphorylation of SR Ca2+ cycling proteins will convert stochastic Ca2+ sparks into periodic, high-power Ca2+ signals of the type that drives SANC normal automaticity. We measured phosphorylation of SR-associated proteins, phospholamban (PLB) and ryanodine receptors (RyR), and spontaneous local Ca2+ release characteristics (LCR) in permeabilized single, rabbit VM in physiologic [Ca2+], prior to and during inhibition of protein phosphatase (PP) and phosphodiesterase (PDE), or addition of exogenous cAMP, or in the presence of an antibody (2D12), that specifically inhibits binding of the PLB to SERCA-2. In the absence of the aforementioned perturbations, VM could only generate stochastic local Ca2+ releases of low power and low amplitude, as assessed by confocal Ca2+ imaging and spectral analysis. When the kinetics of Ca2+ pumping into the SR were increased by an increase in PLB phosphorylation (via PDE and PP inhibition or addition of cAMP) or by 2D12, self-organized, “clock-like” local Ca2+ releases, partially synchronized in space and time (Ca2+ wavelets), emerged, and the ensemble of these rhythmic local Ca2+ wavelets generated a periodic high-amplitude Ca2+ signal. Thus, a Ca2+ clock is not specific to pacemaker cells, but can also be unleashed in VM when SR Ca2+ cycling increases and spontaneous local Ca2+ release becomes partially synchronized. This unleashed Ca2+ clock that emerges in a physiological Ca2+ milieu in VM has two faces, however: it can provoke ventricular arrhythmias; or if harnessed, can be an important feature

  1. Highly basic CaO nanoparticles in mesoporous carbon materials and their excellent catalytic activity.

    Science.gov (United States)

    Raja, Pradeep Kumar; Chokkalingam, Anand; Priya, Subramaniam V; Balasubramanian, Veerappan V; Benziger, Mercy R; Aldeyab, Salem S; Jayavell, Ramasamy; Ariga, Katsukiho; Vinu, Ajayan

    2012-06-01

    Highly basic CaO nanoparticles immobilized mesoporous carbon materials (CaO-CMK-3) with different pore diameters have been successfully prepared by using wet-impregnation method. The prepared materials were subjected to extensive characterization studies using sophisticated techniques such as XRD, nitrogen adsorption, HRSEM-EDX, HRTEM and temperature programmed desorption of CO2 (TPD of CO2). The physico-chemical characterization results revealed that these materials possess highly dispersed CaO nanoparticles, excellent nanopores with well-ordered structure, high specific surface area, large specific pore volume, pore diameter and very high basicity. We have also demonstrated that the basicity of the CaO-CMK-3 samples can be controlled by simply varying the amount of CaO loading and pore diameter of the carbon support. The basic catalytic performance of the samples was investigated in the base-catalyzed transesterification of ethylacetoacetate by aryl, aliphatic and cyclic primary alcohols. CMK-3 catalyst with higher CaO loading and larger pore diameter was found to be highly active with higher conversion within a very short reaction time. The activity of 30% CaO-CMK3-150 catalyst for transesterification of ethylacetoacetate using different alcohols increases in the following order: octanol > butanol > cyclohexanol > benzyl alcohol > furfuryl alcohol.

  2. Hypermethylation of the CaSR and VDR genes in the parathyroid glands in chronic kidney disease rats with high-phosphate diet.

    Science.gov (United States)

    Uchiyama, Taketo; Tatsumi, Norifumi; Kamejima, Sahoko; Waku, Tsuyoshi; Ohkido, Ichiro; Yokoyama, Keitaro; Yokoo, Takashi; Okabe, Masataka

    2016-10-01

    Chronic kidney disease (CKD) disrupts mineral homeostasis and its representative pathosis is defined as secondary hyperparathyroidism (SHPT). SHPT occurs during the early course of progressive renal insufficiency, and is associated with mortality and cardiovascular events. SHPT results in reduction of calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) in the parathyroid glands during CKD. However, the precise mechanism of CaSR and VDR reduction is largely unknown. CKD was induced through two-step 5/6 nephrectomy, and then CKD rats and sham-operated rats were maintained for 8 weeks on diets containing 0.7 % phosphorus (normal phosphate) or 1.2 % phosphorus (high phosphate). In gene expression analysis, TaqMan probes were used for quantitative real-time polymerase chain reaction. Finally, CaSR and VDR protein expressions were analyzed using immunohistochemistry. DNA methylation analysis was performed using a restriction digestion and quantitative PCR. CaSR and VDR mRNA were reduced only in CKD rats fed the high-phosphorus diets (CKD HP), then CaSR and VDR immunohistochemical expressions were compatible with gene expression assay. SHPT was then confirmed only in CKD HP rats. Furthermore, sole CKD HP rats showed the hypermethylation in CaSR and VDR genes; however, the percentage methylation of both genes was low. Although CaSR and VDR hypermethylation was demonstrated in PTGs of CKD HP rats, the extent of hypermethylation was insufficient to support the relevance between hypermethylation and down-regulation of gene expression because of the low percentage of methylation. Consequently, our data suggest that mechanisms, other than DNA hypermethylation, were responsible for the reduction in mRNA and protein levels of CaSR and VDR in PTGs of CKD HP rats.

  3. Stability and breakdown of Ca{sup 13}CO{sub 3} melt associated with formation of {sup 13}C-diamond in static high pressure experiments up to 43 GPa and 3900 K

    Energy Technology Data Exchange (ETDEWEB)

    Spivak, A.V., E-mail: spivak@iem.ac.ru [Institute of Experimental Mineralogy of the Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation); Litvin, Yu.A. [Institute of Experimental Mineralogy of the Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation); Ovsyannikov, S.V. [Bayerishes Geoinstitut, University of Bayreuth, Bayreuth (Germany); Dubrovinskaia, N.A. [Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, Bayreuth (Germany); Dubrovinsky, L.S. [Bayerishes Geoinstitut, University of Bayreuth, Bayreuth (Germany)

    2012-07-15

    Melting of calcium carbonate Ca{sup 13}CO{sub 3}, stability of the melt and its decomposition were studied in static high pressure experiments at pressures of 11-43 GPa and temperatures of 1600-3900 K using diamond anvil cell technique with laser heating. We observed formation of {sup 13}C-graphite (below 16 GPa) and {sup 13}C-diamond (between 16 and 43 GPa) on decomposition of the Ca{sup 13}CO{sub 3} melt at temperatures above 3400 K. At temperatures below 3400 K congruent melting of calcium carbonate was confirmed. The experimental results were applied to construction of the phase diagram of CaCO{sub 3} up to 43 GPa and 3900 K focusing at the melting curve of calcium carbonate and the decomposition phase boundary of CaCO{sub 3} melt. - Graphical abstract: Highlights: Black-Right-Pointing-Pointer Phase states of CaCO{sub 3} were studied at P=11-43 GPa and T=1600-3900 K. Black-Right-Pointing-Pointer {sup 13}C-diamond easily crystallizes in carbonate-carbon (Ca{sup 13}CO{sub 3-}{sup 13}C-graphite) melt-solutions. Black-Right-Pointing-Pointer Ca-carbonate melts congruently that was observed in experiments in DAC with laser heating. Black-Right-Pointing-Pointer Decomposition of CaCO{sub 3} melt, indicated by formation of graphite and/or diamond. Black-Right-Pointing-Pointer Decomposition of CaCO{sub 3} was observed at temperatures above 3400 K in the pressure interval studied.

  4. The sarcoplasmic calcium pump - a most efficient ion translocating system.

    Science.gov (United States)

    Hasselbach, W

    1977-04-21

    In contrast to the sodium-potassium transporting plasma membranes, the sarcoplasmic membranes (SR) are highly specialized structures into which only two major intrinsic proteins, a calcium transporting protein and a calcium binding protein are embedded. The calcium transporting protein is a highly asymmetric molecule. It binds two calcium ions with a very high affinity at its external, and two calcium ions with low affinity at the internal section of the molecule. ATP is bound with high afffinity to an external binding site, inducing a conformational change. When the vesicular membranes are exposed to solutions containing Ca++, Mg++ and ATP, ATP is hydrolyzed and simultaneously calcium ions are translocated from the external medium into the vesicular space. When calcium ions are translocated in the opposite direction, ATP is synthesized. The calcium-ATP ratio for ATP cleavage as well as for ATP synthesis is 2. Thus, the SR membranes can transform reversibly chemical into osmotical energy. Inward and outward movements of calcium ions are relatively slow processes connected with the appearance and disappearance of different phosphorylated intermediates. One phosphorylated intermediate is formed by phosphoryltransfer from ATP when calcium ions are present in the medium. In contrast, when calcium ions are absent from the external medium, two different intermediates can be formed by the incorporation of inorganic phosphate. Only when calcium ions present in the internal space of the vesicles are released, the incorporation of inorganic phosphate gives rise to an intermediate who phosphoryl group can be transferred to ADP.

  5. Effect of Calcium Oxide on the Crushing Strength, Reduction, and Smelting Performance of High-Chromium Vanadium–Titanium Magnetite Pellets

    Directory of Open Access Journals (Sweden)

    Gongjin Cheng

    2017-05-01

    Full Text Available The effect of calcium oxide on the crushing strength, reduction, and smelting performance of high-chromium vanadium–titanium magnetite pellets (HCVTMP was studied in this work. The main characterization methods of an electronic universal testing machine (EUTM, X-ray fluorescent (XRF, inductively-coupled plasma-atomic emission spectroscopy (ICP-AES, X-ray diffraction (XRD, and scanning electron microscope-energy disperse spectroscopy (SEM-EDS were employed. The crushing strength was affected by the mineral phases generated during oxidative baking and the subsequently-formed pellet microstructures owing to CaO addition. The reduction and smelting properties of HCVTMP with different CaO additives were measured and characterized with different softening-melting-dripping indices. Although HCVTMP showed the highest crushing strength with CaO addition of ca. 2 wt %, more CaO addition may be needed to achieve high permeability of the furnace burdens and a good separation condition of the slag and melted iron. In the formation process of the slag and melted iron, it can be determined that CaO could have a relationship with the transformation behavior of Cr, V, and Ti to some extent, with respect to the predominant chemical composition analysis of ICP-AES and XRF. With the microscopic examination, the restraining formation of Ti(C,N and the promoting formation of CaTiO3 are in accordance with the improved melting-dripping indices, including the decrease of the maximum external static load and gas permeability, and the increase of the melting-dripping zone and dripping difficulty.

  6. Long-term effects of intravenous 1 alpha (OH)D3 combined with CaCO3 and low-calcium dialysis on secondary hyperparathyroidism and biochemical bone markers in patients on chronic hemodialysis

    DEFF Research Database (Denmark)

    Brandi, L; Daugaard, H; Nielsen, P K

    1996-01-01

    doses of CaCO3 and to reduce the doses of an aluminium-containing oral phosphate binder. A decrease in p-Ca2+ during dialysis was induced, and special care had to focus on the compliance to CaCO3, in order not to aggravate the secondary hyperparathyroidism. (2) The combination of 'low......The effects of intravenous administration of 1 alpha-hydroxycholecalciferol [1 alpha (OH)D3] in combination with CaCO3 and 'low-calcium dialysis' (1.25 mmol/l) on plasma (p) parathyroid hormone (PTH) and biochemical bone markers (osteocalcin, alkaline phosphatase, procollagen type 1 c......-terminal extension peptide) were examined in 54 patients on chronic hemodialysis with either normal or elevated PTH. Increasing doses of 1 alpha (OH)D3 were administered intravenously under careful control of p-Ca2+ and inorganic phosphate. Blood samples were obtained 1 week before the start of treatment...

  7. Long-term effects of intravenous 1 alpha (OH)D3 combined with CaCO3 and low-calcium dialysis on secondary hyperparathyroidism and biochemical bone markers in patients on chronic hemodialysis

    DEFF Research Database (Denmark)

    Brandi, L; Daugaard, H; Nielsen, P K

    1996-01-01

    The effects of intravenous administration of 1 alpha-hydroxycholecalciferol [1 alpha (OH)D3] in combination with CaCO3 and 'low-calcium dialysis' (1.25 mmol/l) on plasma (p) parathyroid hormone (PTH) and biochemical bone markers (osteocalcin, alkaline phosphatase, procollagen type 1 c...... doses of CaCO3 and to reduce the doses of an aluminium-containing oral phosphate binder. A decrease in p-Ca2+ during dialysis was induced, and special care had to focus on the compliance to CaCO3, in order not to aggravate the secondary hyperparathyroidism. (2) The combination of 'low......-terminal extension peptide) were examined in 54 patients on chronic hemodialysis with either normal or elevated PTH. Increasing doses of 1 alpha (OH)D3 were administered intravenously under careful control of p-Ca2+ and inorganic phosphate. Blood samples were obtained 1 week before the start of treatment...

  8. Susceptibility to calcium dysregulation during brain aging

    Directory of Open Access Journals (Sweden)

    Ashok Kumar

    2009-11-01

    Full Text Available Calcium (Ca2+ is a highly versatile intracellular signaling molecule that is essential for regulating a variety of cellular and physiological processes ranging from fertilization to programmed cell death. Research has provided ample evidence that brain aging is associated with altered Ca2+ homeostasis. Much of the work has focused on the hippocampus, a brain region critically involved in learning and memory, which is particularly susceptible to dysfunction during senescence. The current review takes a broader perspective, assessing age-related changes in Ca2+ sources, Ca2+ sequestration, and Ca2+ binding proteins throughout the nervous system. The nature of altered Ca2+ homeostasis is cell specific and may represent a deficit or a compensatory mechanism, producing complex patterns of impaired cellular function. Incorporating the knowledge of the complexity of age-related alterations in Ca2+ homeostasis will positively shape the development of highly effective therapeutics to treat brain disorders.

  9. Ca2+对植物——微生物互作反应的调控%The Advancement of Research on Calcium Signal in the Interaction of Plant and Microbe

    Institute of Scientific and Technical Information of China (English)

    杨民和; 王国红

    2001-01-01

    Mounting evidences show that calcium is important in regulation of the interaction of plant and microbe. In this article, a review is presented to the latest advancement in effects of calcium on the interaction of plant-microbe in following aspects: (1) the research methods of calcium signal; (2) the effects of calcium on inducing plant resistance responses; (3) the significance of calcium in the interaction of plant and Rhizobium sp.; (4) the problems and future prospects of research on calcium signal in plant and microbe interaction.%植物对微生物信号接收、传递及应答的研究是当前植物——微生物互作的分子生物学领域中最具吸引力的课题之一,Ca2+是迄今为止唯一被证实的植物细胞内信号。大量研究表明,Ca2+也参与了植物——微生物互作的信号传递。近15年来,随着细胞生物学、生物化学、分子生物学研究技术的飞速发展,人们对Ca2+在植物——微生物互作中生理意义的认识大为加深。从Ca2+信号的研究方法、Ca2+在植物抗病防卫反应中的作用、Ca2+在植物——微生物共生关系中的作用及Ca2+信号研究中存在的问题及展望等几方面综述了近年来相关研究的进展。

  10. The calcium and vitamin D controversy

    DEFF Research Database (Denmark)

    Abrahamsen, Bo

    2017-01-01

    Areas of the world where vitamin D levels are low for months of the year and intakes of calcium are high have a high prevalence of osteoporosis and cardiovascular disease. This suggests a public health message of avoiding calcium supplements and increasing vitamin D intake. No message could be more...... welcome as vitamin D can be given as a bolus while calcium must be taken daily and may be poorly tolerated. This approach is based on no evidence from intervention studies. Randomized controlled trials (RCTs) suggest that vitamin D given with calcium elicits a small reduction in fracture risk and deaths....... This has not been demonstrated for D given alone. The cardiovascular safety of calcium and vitamin D (CaD) supplements is difficult to ascertain due to weaknesses in RCT designs and adjudication that cannot be remedied by subanalysis. Moreover, no major new RCTs are in process to provide better evidence...

  11. High-pressure synthesis and superconductivity of the Laves phase compound Ca(Al,Si)2 composed of truncated tetrahedral cages Ca@(Al,Si))12.

    Science.gov (United States)

    Tanaka, Masashi; Zhang, Shuai; Inumaru, Kei; Yamanaka, Shoji

    2013-05-20

    The Zintl compound CaAl2Si2 peritectically decomposes to a new ternary cubic Laves phase Ca(Al,Si)2 and an Al-Si eutectic at temperatures above 750 °C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca(Al(1-x)Si(x))2 (0.35 ≤ x ≤ 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)12. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements.

  12. High dietary calcium intake does not counteract disuse-induced bone loss

    Science.gov (United States)

    Baecker, N.; Boese, A.; Smith, S. M.; Heer, M.

    Reduction of mechanical stress on bone inhibits osteoblast-mediated bone formation, increases osteoclast-mediated bone resorption, and leads to what has been called disuse osteoporosis. Prolonged therapeutic bed rest, immobilization and space flight are common causes of disuse osteoporosis. There are sufficient data supporting the use of calcium in combination with vitamin D in the prevention and treatment of postmenopausal osteoporosis. In our study we examined the potential of high dietary calcium intake as a nutrition therapy for disuse-induced bone loss during head-down bed rest in healthy young men. In 2 identical metabolic ward, head-down bed rest (HDBR) experiments (crossover design), we studied the effect of high dietary calcium intake (2000 mg/d) in comparison to the recommended calcium intake of 1000 mg/d on markers of bone turnover. Experiment A (EA) was a 6-day randomized, controlled HDBR study. Experiment B (EB) was a 14-day randomized, controlled HDBR study. In both experiments, the test subjects stayed under well-controlled environmental conditions in our metabolic ward. Subjects' diets in the relevant study phases (HDBR versus Ambulatory Control) of EA and EB were identical except for the calcium intake. The subjects obtained 2000 mg/d Calcium in EA and 2000 mg/d in EB. Blood was drawn at baseline, before entering the relevant intervention period, on day 5 in study EA, and on days 6, 11 and 14 in study EB. Serum calcium, bone formation markers - Procollagen-I-C-Propeptide (PICP) and bone alkaline phosphatase (bAP) were analyzed in serum. 24h-urine was collected throughout the studies for determination of the excretion of calcium (UCaV) and a bone resorption marker, C-terminal telopeptide of collagen type I (UCTX). In both studies, serum calcium levels were unchanged. PICP tended to decrease in EA (p=0.08). In EB PICP decreased significantly over time (p=0.003) in both the control and HDBR periods, and tended to further decrease in the HDBR period (p

  13. High-pressure compressibility and vibrational properties of (Ca,Mn)CO 3

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jin; Caracas, Razvan; Fan, Dawei; Bobocioiu, Ema; Zhang, Dongzhou; Mao, Wendy L.

    2016-12-01

    Knowledge of potential carbon carriers such as carbonates is critical for our understanding of the deep-carbon cycle and related geological processes within the planet. Here we investigated the high-pressure behavior of (Ca,Mn)CO3 up to 75 GPa by synchrotron single-crystal X-ray diffraction, laser Raman spectroscopy, and theoretical calculations. MnCO3-rich carbonate underwent a structural phase transition from the CaCO3-I structure into the CaCO3-VI structure at 45–48 GPa, while CaCO3-rich carbonate transformed into CaCO3-III and CaCO3-VI at approximately 2 and 15 GPa, respectively. The equation of state and vibrational properties of MnCO3-rich and CaCO3-rich carbonates changed dramatically across the phase transition. The CaCO3-VI-structured CaCO3-rich and MnCO3-rich carbonates were stable at room temperature up to at least 53 and 75 GPa, respectively. The addition of smaller cations (e.g., Mn2+, Mg2+, and Fe2+) can enlarge the stability field of the CaCO3-I phase as well as increase the pressure of the structural transition into the CaCO3-VI phase.

  14. Calcium phosphate polymer hybrid materials

    OpenAIRE

    2011-01-01

    Calcium phosphate (CaP) is of strong interest to the medical field because of its potential for bone repair, gene transfection, etc.1-3 Nowadays, the majority of the commercially available materials are fabricated via “classical” materials science approaches, i.e. via high temperature or high pressure approaches, from rather poorly defined slurries, or from organic solvents.3,4 Precipitation of inorganics with (polymeric) additives from aqueous solution on the other hand enables the synthesis...

  15. REMOVAL OF H2S AND SO2 BY CaCO3-BASED SORBENTS AT HIGH PRESSURES

    Energy Technology Data Exchange (ETDEWEB)

    Prof. Stratis V. Sotirchos

    2000-09-01

    The mechanism of the removal of SO{sub 2} and H{sub 2}S by CaCO{sub 3}-based sorbents in pressurized fluidized-bed coal combustors (PFBC) and high pressure gasifiers was investigated in this project. Reactivity evolution experiments were carried out in thermogravimetric apparatuses both under simulated high pressure conditions and at high pressures. Experiments at high pressure were conducted in a high pressure thermogravimetric arrangement that was set up and developed under this project. Two calcitic solids of high calcium carbonate content (over 97%) were employed in the experiments: a fine-grained distributed by Greer Limestone Co. (Greer Limestone) and a solid supplied in the form of large calcitic crystals (Iceland Spar). The decision to work with these solids was mainly based on the fact that they have been employed in several past studies of sulfation, sulfidation, and calcination in our laboratory, and therefore, a large volume of data on their performance under different conditions was available for comparison purposes. In addition to the experimental studies, work was also done on the development of rigorous mathematical models for the description of the occurrence of simultaneous processes (e.g., calcination and sulfation and carbonation and sulfation) in the interior of porous solids and for the simulation of the evolution of the pore structure of porous solids that undergo chemical transformation in their interior.

  16. Crystal Structures and Mechanical Properties of Ca2C at High Pressure

    Directory of Open Access Journals (Sweden)

    Qun Wei

    2016-07-01

    Full Text Available Recently, a new high-pressure semiconductor phase of Ca2C (space group Pnma was successfully synthesized, it has a low-pressure metallic phase (space group C2/m. In this paper, a systematic investigation of the pressure-induced phase transition of Ca2C is studied on the basis of first-principles calculations. The calculated enthalpy reveals that the phase transition which transforms from C2/m-Ca2C to Pnma-Ca2C occurs at 7.8 GPa, and it is a first-order phase transition with a volume drop of 26.7%. The calculated elastic constants show that C2/m-Ca2C is mechanically unstable above 6.4 GPa, indicating that the structural phase transition is due to mechanical instability. Both of the two phases exhibit the elastic anisotropy. The semiconductivity of Pnma-Ca2C and the metallicity of C2/m-Ca2C have been demonstrated by the electronic band structure calculations. The quasi-direct band gap of Pnma-Ca2C at 0 GPa is 0.86 eV. Furthermore, the detailed analysis of the total and partial density of states is performed to show the specific contribution to the Fermi level.

  17. Repeated high-intensity exercise modulates Ca(2+) sensitivity of human skeletal muscle fibers

    DEFF Research Database (Denmark)

    Gejl, K D; Hvid, L G; Willis, S J;

    2016-01-01

    The effects of short-term high-intensity exercise on single fiber contractile function in humans are unknown. Therefore, the purposes of this study were: (a) to access the acute effects of repeated high-intensity exercise on human single muscle fiber contractile function; and (b) to examine whether...... the fourth sprint with respect to Ca(2+) sensitivity and maximal Ca(2+) -activated force. To investigate the oxidative effects of exercise on single fiber contractile function, a subset of fibers was incubated with dithiothreitol (DTT) before analysis. Ca(2+) sensitivity was enhanced by exercise in both MHC...... I (17%, P exercise. In conclusion, repeated high-intensity exercise increased Ca(2+) sensitivity in both MHC I and MHC II...

  18. Regulation of neuronal high-voltage activated Ca(V)2 Ca(2+) channels by the small GTPase RhoA.

    Science.gov (United States)

    Rousset, Matthieu; Cens, Thierry; Menard, Claudine; Bowerman, Melissa; Bellis, Michel; Brusés, Juan; Raoul, Cedric; Scamps, Frédérique; Charnet, Pierre

    2015-10-01

    High-Voltage-Activated (HVA) Ca(2+) channels are known regulators of synapse formation and transmission and play fundamental roles in neuronal pathophysiology. Small GTPases of Rho and RGK families, via their action on both cytoskeleton and Ca(2+) channels are key molecules for these processes. While the effects of RGK GTPases on neuronal HVA Ca(2+) channels have been widely studied, the effects of RhoA on the HVA channels remains however elusive. Using heterologous expression in Xenopus laevis oocytes, we show that RhoA activity reduces Ba(2+) currents through CaV2.1, CaV2.2 and CaV2.3 Ca(2+) channels independently of CaVβ subunit. This inhibition occurs independently of RGKs activity and without modification of biophysical properties and global level of expression of the channel subunit. Instead, we observed a marked decrease in the number of active channels at the plasma membrane. Pharmacological and expression studies suggest that channel expression at the plasma membrane is impaired via a ROCK-sensitive pathway. Expression of constitutively active RhoA in primary culture of spinal motoneurons also drastically reduced HVA Ca(2+) current amplitude. Altogether our data revealed that HVA Ca(2+) channels regulation by RhoA might govern synaptic transmission during development and potentially contribute to pathophysiological processes when axon regeneration and growth cone kinetics are impaired.

  19. A novel monoclinic phase of impurity-doped CaGa2S4 as a phosphor with high emission intensity

    Directory of Open Access Journals (Sweden)

    Akihiro Suzuki

    2012-06-01

    Full Text Available In the solid-state synthesis of impurity-doped CaGa2S4, calcium tetrathiodigallate(III, a novel phosphor material (denominated as the X-phase, with monoclinic symmetry in the space group P21/a, has been discovered. Its emission intensity is higher than that of the known orthorhombic polymorph of CaGa2S4 crystallizing in the space group Fddd. The asymmetric unit of the monoclinic phase consists of two Ca, four Ga and eight S sites. Each of the Ca and Ga atoms is surrounded by seven and four sulfide ions, respectively, thereby sharing each of the sulfur sites with the nearest neighbours. In contrast, the corresponding sites in the orthorhombic phase are surrounded by eight and four S atoms, respectively. The photoluminescence peaks from Mn2+ and Ce3+ in the doped X-phase, both of which are supposed to replace Ca2+ ions, have been observed to shift towards the high energy side in comparison with those in the orthorhombic phase. This suggests that the crystal field around the Mn2+ and Ce3+ ions in the X-phase is weaker than that in the orthorhombic phase.

  20. Ultracytochemical Localization and Effects of Calcium on Isoenzyme in the Leaves of Cucumis melo L.Under the Stress of Powdery Mildew%白粉病菌胁迫下甜瓜叶片中Ca2+的细胞化学定位及外源Ca2+对POD、CAT和SOD同功酶的影响

    Institute of Scientific and Technical Information of China (English)

    钟俐; 李冠

    2012-01-01

    [Objective] The aim of this experiment is to study the uhracytochemical localization of calcium in mesophyll cells of Cucumis melo L. before and after inoculating Podosphaera xanthii and the effects of exogenous calcium on three isoenzymes of defense enzymes which will be useful for further elucidating the process of calcium signal transduction and resistance mechanism to powdery mildew of melon. [Method] With the method of electron microscope and cytochemistry technology, a hydroponic experiment was carried out to explore the effects of different calcium treatments on isoenzymes of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) in leaves of the melon seedlings under powdery mildew stress. [Result] The calcium in mesophyll cells of resistant variety 'MR-1' and in susceptible variety 'JS' gathered in cytoplasm and there were a remarkable increase of calcium level in cytoplasm and reduced greatly in vacuolate and intercellular space when inoculating P. xanthii for 2 d. The calcium localization in leaf cells of 'MR-1' trended to the status as before inoculating when the seedlings were treated for 6 d. However, larger calcium deposited and localized together in the cytoplasm of 'JS' and the structure of mesophyll cells were destroyed until to death and there were no recover of calcium from cytoplasm into vacuolate and intercellular space. Compared with the control, the application 6 mmol-L-1 CaCl2 in nutrient solution significantly alleviated the stress on the melon leaves system that the activities of SOD, POD and CAT isoenzymes were significantly improved, while application of 75 mmol-L-1 LaCl3 in nutrient solution significantly inhibited the three isoenzymes activities. [Conclusion] Calcium ditribution in leaf cells of C. melo L. changed greatly due to its resistance ability at the stress of powdery mildew. A lot of Ca2+was released from Ca2+pool (vacuoles) into cytoplasm, then was pumped return vacuoles in mesophyll cells of resistance variety 'MR

  1. Structural basis for the high Ca2+ affinity of the ubiquitous SERCA2b Ca2+ pump.

    Science.gov (United States)

    Vandecaetsbeek, Ilse; Trekels, Mieke; De Maeyer, Marc; Ceulemans, Hugo; Lescrinier, Eveline; Raeymaekers, Luc; Wuytack, Frank; Vangheluwe, Peter

    2009-11-03

    Sarco(endo)plasmic reticulum Ca(2+) ATPase (SERCA) Ca(2+) transporters pump cytosolic Ca(2+) into the endoplasmic reticulum, maintaining a Ca(2+) gradient that controls vital cell functions ranging from proliferation to death. To meet the physiological demand of the cell, SERCA activity is regulated by adjusting the affinity for Ca(2+) ions. Of all SERCA isoforms, the housekeeping SERCA2b isoform displays the highest Ca(2+) affinity because of a unique C-terminal extension (2b-tail). Here, an extensive structure-function analysis of SERCA2b mutants and SERCA1a2b chimera revealed how the 2b-tail controls Ca(2+) affinity. Its transmembrane (TM) segment (TM11) and luminal extension functionally cooperate and interact with TM7/TM10 and luminal loops of SERCA2b, respectively. This stabilizes the Ca(2+)-bound E1 conformation and alters Ca(2+)-transport kinetics, which provides the rationale for the higher apparent Ca(2+) affinity. Based on our NMR structure of TM11 and guided by mutagenesis results, a structural model was developed for SERCA2b that supports the proposed 2b-tail mechanism and is reminiscent of the interaction between the alpha- and beta-subunits of Na(+),K(+)-ATPase. The 2b-tail interaction site may represent a novel target to increase the Ca(2+) affinity of malfunctioning SERCA2a in the failing heart to improve contractility.

  2. Endothelin-1 induces intracellular [Ca2+] increase via Ca2+ influx through the L-type Ca2+ channel, Ca2+-induced Ca2+ release and a pathway involving ETA receptors, PKC, PKA and AT1 receptors in cardiomyocytes

    Institute of Scientific and Technical Information of China (English)

    ZENG QingHua; LI XingTing; ZHONG GuoGan; ZHANG WenJie; SUN ChengWen

    2009-01-01

    Using fura-2-acetoxymethyl eater (AM) fluorescence imaging and patch clamp techniques, we found that endothelin-1 (ET-1) significantly elevated the intracellular calcium level ([Ca2+]1) in a dose-dependent manner and activated the L-type Ca2+ channel in cardiomyocytes isolated from rats.The effect of ET-1 on [Ca2+]1 elevation was abolished in the presence of the ETA receptor blocker BQ123,but was not affected by the ETa receptor blocker BQ788. ET-1-induced an increase in [Ca2+]1, which was inhibited 46.7% by pretreatment with a high concentration of ryanodine (10 μmol/L), a blocker of the ryanodine receptor. The ET-1-induced [Ca2+]i increase was also inhibited by the inhibltors of protein kinase A (PKA), protein kinase C (PKC) and angiotensin type 1 receptor (AT1 receptor). We found that ET-1 induced an enhancement of the amplitude of the whole cell L-type Ca2+ channel current and an Increase of open-state probability (NPo) of an L-type single Ca2+ channel. BQ123 completely blocked the ET-1-induced increase in calcium channel open-state probability. In this study we demonstrated that ET-1 regulates calcium overload through a series of mechanisms that include L-type Ca2+ channel activation and Ca2+-induced Ca2+ release (CICR). ETa receptors, PKC, PKA and AT1 receptors may also contribute to this pathway.

  3. Endothelin-1 induces intracellular [Ca2+] increase via Ca2+ influx through the L-type Ca2+ channel, Ca2+-induced Ca2+ release and a pathway involving ETA receptors, PKC, PKA and AT1 receptors in cardiomyocytes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Using fura-2-acetoxymethyl ester (AM) fluorescence imaging and patch clamp techniques, we found that endothelin-1 (ET-1) significantly elevated the intracellular calcium level ([Ca2+]i) in a dose-dependent manner and activated the L-type Ca2+ channel in cardiomyocytes isolated from rats. The effect of ET-1 on [Ca2+]i elevation was abolished in the presence of the ETA receptor blocker BQ123, but was not affected by the ETB receptor blocker BQ788. ET-1-induced an increase in [Ca2+]i, which was inhibited 46.7% by pretreatment with a high concentration of ryanodine (10 μmol/L), a blocker of the ryanodine receptor. The ET-1-induced [Ca2+]i increase was also inhibited by the inhibitors of protein kinase A (PKA), protein kinase C (PKC) and angiotensin type 1 receptor (AT1 receptor). We found that ET-1 induced an enhancement of the amplitude of the whole cell L-type Ca2+ channel current and an increase of open-state probability (NPo) of an L-type single Ca2+ channel. BQ123 completely blocked the ET-1-induced increase in calcium channel open-state probability. In this study we demonstrated that ET-1 regulates calcium overload through a series of mechanisms that include L-type Ca2+ channel activation and Ca2+-induced Ca2+ release (CICR). ETA receptors, PKC, PKA and AT1 receptors may also contribute to this pathway.

  4. Fabrication and materials properties of high-density polyethylene (HDPE)/biphasic calcium phosphate (BCP) hybrid bone plates

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Sun Young; Youn, Min Ho; Lim, Youn Mook; Gwon, Hui Jeong; Park, Jong Seok; Nho, Young Chang [Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of)

    2010-06-15

    Biphasic calcium phosphate-reinforced high-density polyethylene (BCP/HDPE) hybrid composite is a new orthopedic biomaterial, which was made to simulate a natural bone composition. Calcium phosphate systems and HDPE hybrid composites have been used in biomedical applications without any inflammatory response. Differences in natural bone of both materials have motivated the use of coupling agents to improve their interfacial interfacial interactions. The composites were prepared using medical grade BCP powder and granular polyethylene. This material was produced by replacing the mineral component and collagen soft tissue of the bone with BCP and HDPE, respectively. As expected, increased volume fraction of either reinforcement type over 0 {approx} 50 vol.% resulted in a increased Vickers hardness and Young's modulus. Thus, BCP particle-reinforced HDPE composites possessed improved material and mechanical properties. BCP particles-reinforced composites were anisotropic due to an alignment of the particles in the matrix during a processing. On the other hand, bending and tensile strength was dramatically changed in the matrix. To change the material and mechanical properties of HDPE/BCP composites, the process of a blending was used, and its effect on the microstructure and mechanical proprieties of HDPE/BCP composites were investigated by means of FT-IR/ATR spectroscopy, XRD, FE-SEM, Vickers Hardness Testing Machine, Universal Testing Machine, Mercury Porosimeter and Ultrasonic Flaw Detector at room temperature. For the evaluation of the cell viability and proliferation onto the external surface of HDPE/BCP hybrid plates with a HaCaT cell line, which is a multipotent cell line able to differentiate towards different phenotypes under the action of biological factors, has been evaluated with in vitro studies and quantified by colormetric assays. These findings indicate that the HDPE/BCP hybrid plates are biocompatible and non-toxic.

  5. Highly efficient CO2 sorbents: development of synthetic, calcium-rich dolomites.

    Science.gov (United States)

    Filitz, Rainer; Kierzkowska, Agnieszka M; Broda, Marcin; Müller, Christoph R

    2012-01-03

    The reaction of CaO with CO(2) is a promising approach for separating CO(2) from hot flue gases. The main issue associated with the use of naturally occurring CaCO(3), that is, limestone, is the rapid decay of its CO(2) capture capacity over repeated cycles of carbonation and calcination. Interestingly, dolomite, a naturally occurring equimolar mixture of CaCO(3) and MgCO(3), possesses a CO(2) uptake that remains almost constant with cycle number. However, owing to the large quantity of MgCO(3) in dolomite, the total CO(2) uptake is comparatively small. Here, we report the development of a synthetic Ca-rich dolomite using a coprecipitation technique, which shows both a very high and a stable CO(2) uptake over repeated cycles of calcination and carbonation. To obtain such an excellent CO(2) uptake characteristic it was found to be crucial to mix the Ca(2+) and Mg(2+) on a molecular level, that is, within the crystalline lattice. For sorbents which were composed of mixtures of microscopic crystals of CaCO(3) and MgCO(3), a decay behavior similar to natural limestone was observed. After 15 cycles, the CO(2) uptake of the best sorbent was 0.51 g CO(2)/g sorbent exceeding the CO(2) uptake of limestone by almost 100%.

  6. Methods of use of calcium hexa aluminate refractory linings and/or chemical barriers in high alkali or alkaline environments

    Science.gov (United States)

    McGowan, Kenneth A; Cullen, Robert M; Keiser, James R; Hemrick, James G; Meisner, Roberta A

    2013-10-22

    A method for improving the insulating character/and or penetration resistance of a liner in contact with at least one of an alkali and/or alkaline environments is provided. The method comprises lining a surface that is subject to wear by an alkali environment and/or an alkaline environment with a refractory composition comprising a refractory aggregate consisting essentially of a calcium hexa aluminate clinker having the formula CA.sub.6, wherein C is equal to calcium oxide, wherein A is equal to aluminum oxide, and wherein the hexa aluminate clinker has from zero to less than about fifty weight percent C.sub.12A.sub.7, and wherein greater than 98 weight percent of the calcium hexa aluminate clinker having a particle size ranging from -20 microns to +3 millimeters, for forming a liner of the surface. This method improves the insulating character/and or penetration resistance of the liner.

  7. High-throughput screen detects calcium signaling dysfunction in typical sporadic autism spectrum disorder

    Science.gov (United States)

    Schmunk, Galina; Nguyen, Rachel L.; Ferguson, David L.; Kumar, Kenny; Parker, Ian; Gargus, J. Jay

    2017-01-01

    Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders without any defined uniting pathophysiology. Ca2+ signaling is emerging as a potential node in the genetic architecture of the disorder. We previously reported decreased inositol trisphosphate (IP3)-mediated Ca2+ release from the endoplasmic reticulum in several rare monogenic syndromes highly comorbid with autism – fragile X and tuberous sclerosis types 1 and 2 syndromes. We now extend those findings to a cohort of subjects with sporadic ASD without any known mutations. We developed and applied a high throughput Fluorometric Imaging Plate Reader (FLIPR) assay to monitor agonist-evoked Ca2+ signals in human primary skin fibroblasts. Our results indicate that IP3 -mediated Ca2+ release from the endoplasmic reticulum in response to activation of purinergic receptors is significantly depressed in subjects with sporadic as well as rare syndromic forms of ASD. We propose that deficits in IP3-mediated Ca2+ signaling represent a convergent hub function shared across the spectrum of autistic disorders – whether caused by rare highly penetrant mutations or sporadic forms – and holds promise as a biomarker for diagnosis and novel drug discovery. PMID:28145469

  8. Structural stability of infinite- layer CaCuO2 under high pressure

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In situ high-pressure energy dispersive X-ray diffraction measurements on polycrystalline powder CaCuO2 with an infinite layer structure (IL CaCuO2) have been performed by using diamond anvil cell (DAC) instrument with synchrotron radiation. The results suggest that the crystal structure of IL CaCuO2 is stable under pressure up to 30 GPa at room temperature. According to Birch-Murn- aghan equation of state, assuming pressure derivative the bulk modulus B0=181 ± 9 GPa is obtained.

  9. High-Strength Low-Alloy (HSLA) Mg-Zn-Ca Alloys with Excellent Biodegradation Performance

    Science.gov (United States)

    Hofstetter, J.; Becker, M.; Martinelli, E.; Weinberg, A. M.; Mingler, B.; Kilian, H.; Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

    2014-04-01

    This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg6Zn3Ca2. A reduction of the Zn content results in (Mg,Zn)2Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg6Zn3Ca2, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)2Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material's strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R p = 240 MPa, ultimate tensile strength R m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)2Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.

  10. Causative and preventive action of calcium in cataractogenesis

    Institute of Scientific and Technical Information of China (English)

    Purshottam Das GUPTA; Kaid JOHAR; Abhay VASAVADA

    2004-01-01

    Calcium and Ca-dependent enzymes play specific role in the development of human cataracts. Entry of Ca2+ into the lens epithelial cells (LEC) is highly regulated by quantum of receptors. The Ca2+ level controls homeostasis and growth of entire lens. Intracellular overload of Ca2+ in the LEC trigger a series of events such as activation of Ca-dependent enzymes, irreversible breakdown of important structural proteins and cell death. Proper maintenance of Ca2+ levels by regulating activity of Ca-pumps and Ca-channels and inhibition of Ca-dependent enzymes can help in prevention of cataract. Induction of cell death in the LEC by increase in the intracellular Ca2+ may be utilized for the prevention of posterior capsular opacification.

  11. Nonisothermal Thermogravimetric Analysis of Thai Lignite with High CaO Content

    Directory of Open Access Journals (Sweden)

    Pakamon Pintana

    2013-01-01

    Full Text Available Thermal behaviors and combustion kinetics of Thai lignite with different SO3-free CaO contents were investigated. Nonisothermal thermogravimetric method was carried out under oxygen environment at heating rates of 10, 30, and 50°C min−1 from ambient up to 1300°C. Flynn-Wall-Ozawa (FWO and Kissinger-Akahira-Sunose (KAS methods were adopted to estimate the apparent activation energy (E for the thermal decomposition of these coals. Different thermal degradation behaviors were observed in lignites with low (14% and high (42% CaO content. Activation energy of the lignite combustion was found to vary with the conversion fraction. In comparison with the KAS method, higher E values were obtained by the FWO method for all conversions considered. High CaO lignite was observed to have higher activation energy than the low CaO coal.

  12. High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning.

    Science.gov (United States)

    Engebretsen, Kristin M; Kaczmarek, Kathleen M; Morgan, Jenifer; Holger, Joel S

    2011-04-01

    INTRODUCTION. High-dose insulin therapy, along with glucose supplementation, has emerged as an effective treatment for severe beta-blocker and calcium channel-blocker poisoning. We review the experimental data and clinical experience that suggests high-dose insulin is superior to conventional therapies for these poisonings. PRESENTATION AND GENERAL MANAGEMENT. Hypotension, bradycardia, decreased systemic vascular resistance (SVR), and cardiogenic shock are characteristic features of beta-blocker and calcium-channel blocker poisoning. Initial treatment is primarily supportive and includes saline fluid resuscitation which is essential to correct vasodilation and low cardiac filling pressures. Conventional therapies such as atropine, glucagon and calcium often fail to improve hemodynamic status in severely poisoned patients. Catecholamines can increase blood pressure and heart rate, but they also increase SVR which may result in decreases in cardiac output and perfusion of vascular beds. The increased myocardial oxygen demand that results from catecholamines and vasopressors may be deleterious in the setting of hypotension and decreased coronary perfusion. METHODS. The Medline, Embase, Toxnet, and Google Scholar databases were searched for the years 1975-2010 using the terms: high-dose insulin, hyperinsulinemia-euglycemia, beta-blocker, calcium-channel blocker, toxicology, poisoning, antidote, toxin-induced cardiovascular shock, and overdose. In addition, a manual search of the Abstracts of the North American Congress of Clinical Toxicology and the Congress of the European Association of Poisons Centres and Clinical Toxicologists published in Clinical Toxicology for the years 1996-2010 was undertaken. These searches identified 485 articles of which 72 were considered relevant. MECHANISMS OF HIGH-DOSE INSULIN BENEFIT. There are three main mechanisms of benefit: increased inotropy, increased intracellular glucose transport, and vascular dilatation. EFFICACY OF HIGH

  13. High-throughput measurement of the Ca2+-dependent ATPase activity in COS microsomes.

    Science.gov (United States)

    Vandecaetsbeek, Ilse; Holemans, Tine; Wuytack, Frank; Vangheluwe, Peter

    2014-08-01

    We provide a detailed procedure to determine the Ca(2+)-dependent ATPase activity in COS or HEK293 cells overexpressing a Ca(2+) pump. The ATPase activity is determined by the Baginsky method, which allows measurement of the steady-state production of inorganic phosphate (Pi). We have adapted this widely applied method into a sensitive, fast, and semi-high-throughput protocol suitable for use in a 96-well plate format.

  14. 次乌头碱对心肌细胞Ca2+调控蛋白mRNA表达的影响%Effects of hypaconitine on expression of mRNA of calcium regulated proteins in myocardial cells

    Institute of Scientific and Technical Information of China (English)

    李志勇; 谭鹏; 赵晖; 李飞; 孙建宁

    2011-01-01

    Objective To observe the effects of Hypaconitine( HA)on mRNA expression of calcium regulated proteins such as L-type calcium channel α1C, calmodulin(CaM) and RyR2 in myocardial cells.Methods Primary neonatal rat myocardial cells were generated and cultured.L-type calcium channel α1C,CaM and RyR2 mRNA were measured by transcription-polymerase chain reaction(RT-PCR) respectively.Results After coincubating with HA for 15 min,60,120 μM/L HA can improve the expression of Ltype calcium channel α1C mRNA in myocardial cells (P<0.05) , 30 , 60 , 120 μM/L HA also can increase CaM mRNA in myocardial cells(P<0.01) ,60, 120 μM/L HA increased the expression of RyR2 mRNA in myocardial cells(P <0.05).After coincubation with HA for 5,15,60 min, 60 μM/L HA increased the expression of L-type calcium channel α1C mRNA of myocardial cells in 5min(P<0.05).The expression of CaM mRNA of myocardial cells were increased after coincubating with 30 , 60 μM/L HA for 15 ,60 min(P<0.01).Conclusion HA(>60 μM/L)can induce the calcium overload in myocardial cells, which will result in arrhythmia.This action maybe relates to the increasing expression of L-type calcium channel α1C,CaM and RyR2 mRNA of myocardial cells caused by HA.The clinical toxic arrhythmias can be relieved through tnterfering these target genes when toxic reaction happens.%目的 考察次乌头碱(HA)对原代培养乳大鼠心肌细胞L-钙通道、钙调蛋白(CaM)、肌质网雷诺定受体(RyR2)mRNA表达的影响.方法 体外培养乳大鼠心肌细胞,采用RT-PCR法测定L-钙通道α1C亚基、CaM及RyR2 mRNA的表达.结果 HA作用15 min时,60、120 μΜ/L能提高心肌细胞膜L-钙α1C mRNA的表达(P<0.05);30、60、120 μΜ/L能使CaMmRNA的表达增高(P<0.01);60、120 μΜ/L能提高RyR2 mRNA表达(P<0.05); 60 μM/L作用心肌细胞5 min时引发L-钙通道α1C mRNA表达增多(P<0.05);30、60 μM/L作用15、60 min时可引起CaM mRNA表达增多(P<0.01).结论 HA(≥60 μΜ/L

  15. Synthesis of Calcium Silicate (Casio3) Using Calcium Fluoride, Quartz and Microbes

    National Research Council Canada - National Science Library

    B. Gopal Krishna; M. Jagannadha Rao

    2015-01-01

    .... In this paper, synthesis of calcium silicate (CaSiO3) using calcium fluoride (CaF2) and quartz (SiO2) under microbial environment in a laboratory is being adopted to produce the required material...

  16. Petrogenesis of high-CaO lavas from Mauna Kea, Hawaii: Constraints from trace element abundances

    Science.gov (United States)

    Huang, Shichun; Humayun, Munir

    2016-07-01

    The role of a mafic component in the petrogenesis of Oceanic Island Basalts (OIBs) is highly debated. As the best studied OIB, Hawaiian lavas provide critical insights into OIB genesis. At a given MgO content, the CaO content in the melt has been used to distinguish between partial melts of peridotite and garnet pyroxenite/eclogite. However, calculations using the BATCH program show that CaO contents in volatile-free melts saturated with all four phases, garnet, clinopyroxene, orthopyroxene and olivine, are controlled by both degrees of partial melting and source compositions, and low melt CaO content is not diagnostic of partial melts from garnet pyroxenite/eclogite. This is an important consideration in understanding the origin of high-CaO lavas recovered from the Hawaii Scientific Drilling Project (HSDP). Detailed geochemical and isotopic studies have been focused on the HSDP high- and low-SiO2 group lavas, and high-CaO lavas were not well studied because they were not included in the original reference suite samples. Here, we report trace element abundances obtained on a suite of high-CaO glasses and compared the trace element abundances of high-CaO lavas to those in high- and low-SiO2 lavas. When normalized to the average composition of low-SiO2 lavas, high-CaO lavas form a U-shaped trace element pattern, enriched in both the most incompatible (Nb, Th) and the least incompatible (Sc, V) elements. This compositional distinction is best explained if high-CaO parental magma represents a mixture of a low degree partial melt of the low-SiO2 mantle source with a high degree (>80%) partial melt derived from a mafic cumulate component. This mafic cumulate must be clinopyroxene-rich, and it could be delaminated mafic cumulate formed under arcs during continent formation, lower continental crust, recycled lower oceanic crust, or high pressure cumulates from a magma chamber.

  17. Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

    Science.gov (United States)

    Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

    2012-12-18

    The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.

  18. High performance metal/air fuel cells. Part 1. General review. [Li, Al, Ca, Cd, Mg

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, J. F.

    1977-08-15

    Metal/air fuel cells are reviewed in terms of their potential application in electric vehicles. Attention is focused on those metals (light alkali and alkaline earth metals, and aluminum) which, in combination with oxygen, have theoretical energy densities (2--13 kWh/kg-metal) exceeding that of gasoline (utilized in automobiles at 2--3 kWh/kg). Lithium and aluminum have yielded 8- and 4 kWh/kg, respectively, in laboratory experimental cells. The slurry Zn/air system achieves 0.85 kWh/kg-Zn in prototype vehicle cells and is reviewed for comparison. Calcium can probably yield 1.8 kWh/kg-Ca, but its potential as a fuel has not yet been fully explored. The remaining metals appear to be unsuitable for use in aqueous electrolyte fuel cells. The discharge characteristics of lithium, aluminum, and (possibly) calcium/air cells indicate the potential for electric vehicles of the highway performance and minimum range (300 miles) of subcompact automobiles, rapid refueling for unlimited range extension, and the storage in the fuel cell of sufficient metal for ranges in excess of 1000 miles. Barriers to the concept are the economic necessity of recycling cell reaction products (except in the case of calcium), the expansion or creation of vast metal production industries, and the change-over of existing service station infrastructures to allow electric vehicle servicing. The energy efficiency of a transportation system using aluminum was estimated using data on the current aluminum production industry. The total estimated cost of ownership and operation of an aluminum/air cell was 3.0--3.6 cents/km. The relative rarity of lithium would complicate its use. 6 tables.

  19. Development and implementation of a high-throughput compound screening assay for targeting disrupted ER calcium homeostasis in Alzheimer's disease.

    Directory of Open Access Journals (Sweden)

    Kamran Honarnejad

    Full Text Available Disrupted intracellular calcium homeostasis is believed to occur early in the cascade of events leading to Alzheimer's disease (AD pathology. Particularly familial AD mutations linked to Presenilins result in exaggerated agonist-evoked calcium release from endoplasmic reticulum (ER. Here we report the development of a fully automated high-throughput calcium imaging assay utilizing a genetically-encoded FRET-based calcium indicator at single cell resolution for compound screening. The established high-throughput screening assay offers several advantages over conventional high-throughput calcium imaging technologies. We employed this assay for drug discovery in AD by screening compound libraries consisting of over 20,000 small molecules followed by structure-activity-relationship analysis. This led to the identification of Bepridil, a calcium channel antagonist drug in addition to four further lead structures capable of normalizing the potentiated FAD-PS1-induced calcium release from ER. Interestingly, it has recently been reported that Bepridil can reduce Aβ production by lowering BACE1 activity. Indeed, we also detected lowered Aβ, increased sAPPα and decreased sAPPβ fragment levels upon Bepridil treatment. The latter findings suggest that Bepridil may provide a multifactorial therapeutic modality for AD by simultaneously addressing multiple aspects of the disease.

  20. Ryanodine receptor gating controls generation of diastolic calcium waves in cardiac myocytes

    Science.gov (United States)

    Petrovič, Pavol; Valent, Ivan; Cocherová, Elena; Pavelková, Jana

    2015-01-01

    The role of cardiac ryanodine receptor (RyR) gating in the initiation and propagation of calcium waves was investigated using a mathematical model comprising a stochastic description of RyR gating and a deterministic description of calcium diffusion and sequestration. We used a one-dimensional array of equidistantly spaced RyR clusters, representing the confocal scanning line, to simulate the formation of calcium sparks. Our model provided an excellent description of the calcium dependence of the frequency of diastolic calcium sparks and of the increased tendency for the production of calcium waves after a decrease in cytosolic calcium buffering. We developed a hypothesis relating changes in the propensity to form calcium waves to changes of RyR gating and tested it by simulation. With a realistic RyR gating model, increased ability of RyR to be activated by Ca2+ strongly increased the propensity for generation of calcium waves at low (0.05–0.1-µM) calcium concentrations but only slightly at high (0.2–0.4-µM) calcium concentrations. Changes in RyR gating altered calcium wave formation by changing the calcium sensitivity of spontaneous calcium spark activation and/or the average number of open RyRs in spontaneous calcium sparks. Gating changes that did not affect RyR activation by Ca2+ had only a weak effect on the propensity to form calcium waves, even if they strongly increased calcium spark frequency. Calcium waves induced by modulating the properties of the RyR activation site could be suppressed by inhibiting the spontaneous opening of the RyR. These data can explain the increased tendency for production of calcium waves under conditions when RyR gating is altered in cardiac diseases. PMID:26009544

  1. Interactions between calcium and phosphorus in the regulation of the production of fibroblast growth factor 23 in vivo

    DEFF Research Database (Denmark)

    Quinn, S.J.; Thomsen, A.R.B.; Pang, J.L.

    2013-01-01

    Calcium and phosphorus homeostasis are highly interrelated and share common regulatory hormones, including FGF23. However, little is known about calcium's role in the regulation of FGF23. We sought to investigate the regulatory roles of calcium and phosphorus in FGF23 production using genetic mouse...... models with targeted inactivation of PTH (PTH KO) or both PTH and the calcium-sensing receptor (CaSR; PTH-CaSR DKO). In wild-type, PTH KO, and PTH-CaSR DKO mice, elevation of either serum calcium or phosphorus by intraperitoneal injection increased serum FGF23 levels. In PTH KO and PTH-CaSR DKO mice......, however, increases in serum phosphorus by dietary manipulation were accompanied by severe hypocalcemia, which appeared to blunt stimulation of FGF23 release. Increases in dietary phosphorus in PTH-CaSR DKO mice markedly decreased serum 1,25-dihydroxyvitamin D [1,25(OH)D] despite no change in FGF23...

  2. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

    Science.gov (United States)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

    2016-04-01

    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  3. Ca2+ dynamics in zebrafish morphogenesis

    Directory of Open Access Journals (Sweden)

    Yusuke Tsuruwaka

    2017-01-01

    Full Text Available Intracellular calcium ion (Ca2+ signaling is heavily involved in development, as illustrated by the use of a number of Ca2+ indicators. However, continuous Ca2+ patterns during morphogenesis have not yet been studied using fluorescence resonance energy transfer to track the Ca2+ sensor. In the present study, we monitored Ca2+ levels during zebrafish morphogenesis and differentiation with yellow cameleon, YC2.12. Our results show not only clear changes in Ca2+ levels but also continuous Ca2+ patterns at 24 hpf and later periods for the first time. Serial Ca2+dynamics during early pharyngula period (Prim-5-20; 24–33 hpf was successfully observed with cameleon, which have not reported anywhere yet. In fact, high Ca2+ level occurred concurrently with hindbrain development in segmentation and pharyngula periods. Ca2+ patterns in the late gastrula through segmentation periods which were obtained with cameleon, were similar to those obtained previously with other Ca2+sensor. Our results suggested that the use of various Ca2+ sensors may lead to novel findings in studies of Ca2+ dynamics. We hope that these results will prove valuable for further research in Ca2+ signaling.

  4. Intracellular calcium modulates basolateral K(+)-permeability in frog skin epithelium

    DEFF Research Database (Denmark)

    Brodin, Birger; Rytved, K A; Nielsen, R

    1994-01-01

    Cytosolic calcium ([Ca2+]i) has been suggested as a key modulator in the regulation of active sodium transport across electrically "tight" (high resistance) epithelia. In this study we investigated the effects of calcium on cellular electrophysiological parameters in a classical model tissue......, the frog skin. [Ca2+]i was measured with fura-2 in an epifluorescence microscope setup. An inhibition of basolateral potassium permeability was observed when cytosolic calcium was increased. This inhibition was reversible upon removal of calcium from the serosal solution....

  5. 钾通道阻断剂4-氨基吡啶诱导海马CA1锥体神经元钙瞬变%Calcium transient of CA1 pyramidal neurons induced by potassium blocker 4-aminopyridine in acute hippocampal slices

    Institute of Scientific and Technical Information of China (English)

    苏涛; 丛文东; 廖卫平

    2011-01-01

    Objective To investigate the calcium transient of CA1 pyramidal neurons induced by potassium blocker 4-aminopyridine (4-AP) in acute hippocampal slices to explore the relation between potassium channel function and calcium transient, and their mechanism. Methods Fluorescent probe was employed to mark the hippocampai neurons in acute brain slices of rats; confocal microscopy was used to perform calcium imaging to observe the influences of different concentrations of 4-AP and perfusate with/without calcium on calcium transient of CA1 pyramidal neurons. Results The response of [Ca2+]I to lower concentration of 4-AP (<15 mmol/L) was in a dose-dependent manner (r2=0.910, P=0.000); the higher the concentration of 4-AP (20-80 mmol/L), the lower the peak level of calcium transient. The latency and amplitude of calcium transient induced by 4-AP were obviously reduced when the extracellular condition was switched to an absence of calcium, which was significantly different as compared with that with calcium (P<0.05). Conclusion Blockade of potassium channels with 4-AP can increase [Ca2+]I in the hippocampal pyramidal neurons of acute slices. The increase of [Ca2+]1 to 4-AP could be ascribe to calcium release from intracellular stores and calcium influx from extracellular matrix.%目的 研究4-氨基吡啶(4-AP)诱导的急性脑片海马CA1锥体神经元钙瞬变现象,探讨钾通道功能与钙瞬变的关系及可能机制.方法 荧光探针标记正常大鼠急性脑片海马神经元.共聚焦显微镜技术进行钙成像,观察不同浓度4-AP及细胞灌流液条件对神经元钙瞬变的影响.结果 低浓度(<15 mmol/L)4-AP诱导的钙瞬变峰值与剂量呈线性相关(r2=0.910,P=0.000),高浓度(20~80 mmol/L)4-AP诱导的钙瞬变峰值随浓度增高而下降.在无钙灌流液条件下,4-AP诱导的钙瞬变峰值水平下降,达峰时间延长,与含钙灌流液比较差异有统计学意义(P<0.05).结论 4-AP可诱导急性脑片海马CA1锥体神经

  6. Reconnaissance investigation of high-calcium marble in the Beaver Creek area, St. Lawrence County, New York

    Science.gov (United States)

    Brown, C. Ervin

    1978-01-01

    Three belts of marble of the Grenville Series were mapped in the Beaver Creek drainage basin, St. Lawrence County, N.Y. One of these, on the west side of Beaver Creek, consists of coarsely crystalline pure calcitic marble that occurs in a zone at least 10 by 0.8 km in extent. Samples of marble show CaCO3 content to be greater than 93 percent, and some samples contain greater than 96 percent, and only small amounts of MgO and Fe203 are present. Marble in two other belts to the east of Beaver Creek are variable in composition, but locally have high content of calcium carbonate material. The marble deposit west of Beaver Creek has a chemical composition favorable for specialized chemical, industrial, and metallurgical uses. Another favorable aspect of the deposit is its proximity to inexpensive water transportation on the St. Lawrence Seaway only 27.5 km away by road, at Ogdensburg, N.Y.

  7. Seeded Growth Route to Noble Calcium Carbonate Nanocrystal.

    Directory of Open Access Journals (Sweden)

    Aminul Islam

    Full Text Available A solution-phase route has been considered as the most promising route to synthesize noble nanostructures. A majority of their synthesis approaches of calcium carbonate (CaCO3 are based on either using fungi or the CO2 bubbling methods. Here, we approached the preparation of nano-precipitated calcium carbonate single crystal from salmacis sphaeroides in the presence of zwitterionic or cationic biosurfactants without external source of CO2. The calcium carbonate crystals were rhombohedron structure and regularly shaped with side dimension ranging from 33-41 nm. The high degree of morphological control of CaCO3 nanocrystals suggested that surfactants are capable of strongly interacting with the CaCO3 surface and control the nucleation and growth direction of calcium carbonate nanocrystals. Finally, the mechanism of formation of nanocrystals in light of proposed routes was also discussed.

  8. Effect of CaF2 on Process of Mineral Formation and Hydration of Calcium Strontium Sulphoaluminate Cement%CaF2对硫铝酸锶钙水泥矿物形成及水化过程的影响

    Institute of Scientific and Technical Information of China (English)

    谭文杰; 艾红梅; 常钧; 鲁统卫; 王勇威

    2012-01-01

    The compressive strength of calcium strontium sulphoaluminate cement with CaF2 added was tested. The influence of CaF2 on process of mineral formation and hydration of calcium strontium sulphoaluminate cement were studied by thermal analysis(DTA-TG), X-ray diffractionCXRD) and scanning electron microscopy(SEM). The results show that compressive strength of calcium strontium sulphoaluminate cement with 0. 2% ( by mass) of CaF2 added is optimal, the compressive strength for 3.28 d is 65. 0, 86.2 MPa respectively, CaF2 accelerates decomposition of CaCO3 and formation of C1.50 Sr2.50 A3S during sintering of clinker. Due to CaF2 , hydration rate of cement is speeded up and CAH10 changes to C3 AH6.%测试了掺CaF2硫铝酸锶钙水泥的抗压强度.通过热分析、X射线衍射分析和扫描电子显微镜观察,研究了CaF2对硫铝酸锶钙水泥熟料矿物形成和水化过程的影响.结果表明,当CaF2掺量为0.2%(质量分数)时,硫铝酸锶钙水泥抗压强度最高,3,28 d抗压强度分别达到65.0,86.2 MPa.在水泥煅烧过程中,CaF2能加速CaCO3的分解及C1.50Sr2.50A3S矿物的形成.此外,CaF2可以加快硫铝酸锶钙水泥的水化速率并促使水化产物CAH10转化为C3 AH6.

  9. Role of magnesium on the biomimetic deposition of calcium phosphate

    Science.gov (United States)

    Sarma, Bimal K.; Sarma, Bikash

    2016-10-01

    Biomimetic depositions of calcium phosphate (CaP) are carried out using simulated body fluid (SBF), calcifying solution and newly developed magnesium containing calcifying solution. Calcium phosphate has a rich phase diagram and is well known for its excellent biocompatibility and bioactivity. The most common phase is hydroxyapatite (HAp), an integral component of human bone and tooth, widely used in orthopedic and dental applications. In addition, calcium phosphate nanoparticles show promise for the targeted drug delivery. The doping of calcium phosphate by magnesium, zinc, strontium etc. can change the protein uptake by CaP nanocrystals. This work describes the role of magnesium on the nucleation and growth of CaP on Ti and its oxide substrates. X-ray diffraction studies confirm formation of HAp nanocrystals which closely resemble the structure of bone apatite when grown using SBF and calcifying solution. It has been observed that magnesium plays crucial role in the nucleation and growth of calcium phosphate. A low magnesium level enhances the crystallinity of HAp while higher magnesium content leads to the formation of amorphous calcium phosphate (ACP) phase. Interestingly, the deposition of ACP phase is rapid when magnesium ion concentration in the solution is 40% of calcium plus magnesium ions concentration. Moreover, high magnesium content alters the morphology of CaP films.

  10. Cokrigagem na estimativa dos teores de Ca e Mg em um Latossolo Vermelho distroférrico Cokriging to estimate levels of calcium and magnesium in a Rhodic Hapludox

    Directory of Open Access Journals (Sweden)

    Eduardo Leonel Bottega

    2011-12-01

    Full Text Available Buscou-se, com este estudo, estimar, através do uso da cokrigagem, valores de cálcio e magnésio, utilizando como co-variável valores de pH. Em um Latossolo Vermelho Distroférrico, amostrou-se a camada de 0-0,2 m, utilizando grade de 25 x 25 m, totalizando 60 pontos em 5,02 ha. Realizou-se, inicialmente, análise descritiva e de correlação e, posteriormente, análise geoestatística, para identificar a dependência espacial das variáveis estudadas. Utilizando a técnica da cokrigagem, os valores de pH mostraram-se eficientes na estimativa de teores de Ca e Mg, devido a elevada correlação entre esta co-variável e as variáveis a serem estimadas.Sought, with this study, estimating, through the use of cokriging, values of calcium and magnesium, using as covariate pH. In a Rhodic Hapludox, sampled the layer of 0-0.2 m, using the grid of 25 x 25 m, totaling 60 points from 5.02 ha. Was held, initially, descriptive analysis and correlation, and subsequently, geostatistical analysis to identify the spatial dependence of variables. Using the technique of cokriging pH values were efficient in the estimation of Ca and Mg, due to the high correlation between this covariate and the variables to be estimated.

  11. Research into crystallization metastable zone property of calcium sulfate in K-Ca-Mg-Cl-H2O system%K-Ca-Mg-Cl-H2O体系中硫酸钙结晶介稳区的研究

    Institute of Scientific and Technical Information of China (English)

    吴晓琴; 孔艳萍

    2011-01-01

    The crystallization metastable zone of calcium sulfate in the system of K-Ca-Mg-Cl-H2O was investigated. The supersaturated solution of calcium sulfate was formed by reaction of calcium chloride solution and magnesium sulfate solution with certain concentrations, and the relationship between the supersaturation of calcium sulfate and its crystallization was studied in mixed salt solutions at different salt concentrations and different temperatures by the laser light scattering method. The corresponding solubilities of calcium sulfate were also determined in this system. Accordingly, the width of metastable zone of calcium sulfate crystallization was then determined. Further, the paper investigated the factors influencing the metastable zone, and also the inner connection among calcium sulfate crystallization and its phases with the factors of mixed salt solutions concentration,temperature and the crystallization metastable zone.%对K-Ca-Mg-Cl-H2O体系中硫酸钙结晶介稳区进行了研究.以一定浓度氯化钙溶液与硫酸镁溶液反应结晶的方式,采用激光散射法测定了不同浓度复合盐溶液和温度下硫酸钙过饱和度与结晶之间的关系,并测定了与之平衡的溶解度,从而确定该体系中硫酸钙结晶介稳区宽度,探讨了影响结晶介稳区的因素,以及硫酸钙结晶和结晶相与复合盐溶液浓度、温度、结晶介稳区之间的关系.

  12. Diagnostic value of thrombocytosis and high CA 125 level in women with adnexal masses.

    Science.gov (United States)

    Atacag, T

    2012-01-01

    The aim of this study was to determine the diagnostic value of thrombocytosis and high CA 125 levels in women with benign and malign adnexal masses. Thrombocytosis (platelet counts > 400 x 10(9)/l) has been identified as a poor prognostic factor in many cancers including certain gynecologic malignant tumors such as endometrial, cervical, and ovarian cancers. Medical charts of 180 patients with adnexal masses were retrospectively reviewed and analyzed for the association of preoperative thrombocytosis and high CA 125 level with other clinical prognostic factors. Of the 180 participants, 68 (68% of malignant adnexal masses) had thrombocytosis and 74 patients (74% of malignant adnexal masses) had elevated CA 125 levels. The patients with preoperative thrombocytosis were found to have greater elevations of CA 125 levels, more advanced stage disease, and higher grade tumors. Presence of thrombocytosis and high CA 125 alone and in combination may be used as a prognostic factor in the management of women with adnexal masses since they are already used as clinical tests for several purposes.

  13. Preparation of DNA/Gold Nanoparticle Encapsulated in Calcium Phosphate

    Directory of Open Access Journals (Sweden)

    Tomoko Ito

    2011-01-01

    Full Text Available Biocompatible DNA/gold nanoparticle complex with a protective calcium phosphate (CaP coating was prepared by incubating DNA/gold nanoparticle complex coated by hyaluronic acid in SBF (simulated body fluid with a Ca concentration above 2 mM. The CaP-coated DNA complex was revealed to have high compatibility with cells and resistance against enzymatic degradation. By immersion in acetate buffer (pH 4.5, the CaP capsule released the contained DNA complex. This CaP capsule including a DNA complex is promising as a sustained-release system of DNA complexes for gene therapy.

  14. Calcium oxide based catalysts for ethanolysis of soybean oil

    Directory of Open Access Journals (Sweden)

    Kornkanok Watcharathamrongkul

    2010-12-01

    Full Text Available Transesterification of soybean oil and ethanol catalyzed by calcium oxides prepared from the calcinations of CaO,Ca(OH2, limestone, and Ca(OH2/CaO as solid base catalysts was investigated. It was found that the catalytic activitiessignificantly depended upon their base site strengths and their structures. Increases in catalytic performance of CaO could beachieved by loading Ca(OH2 on CaO and calcinations at a high temperature. The catalytic reaction using a 9:1 molar ratio ofethanol to oil at 70 °C, using CaO loaded with 3.7 wt% Ca(OH2 exhibited the optimal results, where the conversion of soybeanoil reached 96.3% after 10 hrs of the reaction.

  15. Multiple Modes of Calcium-Induced Calcium Release in Sympathetic Neurons II

    Science.gov (United States)

    Hongpaisan, Jarin; Pivovarova, Natalia B.; Colegrove, Stephen L.; Leapman, Richard D.; Friel, David D.; Andrews, S. Brian

    2001-01-01

    CICR from an intracellular store, here directly characterized as the ER, usually refers to net Ca2+ release that amplifies evoked elevations in cytosolic free calcium ([Ca2+]i). However, the companion paper (Albrecht, M.A., S.L. Colegrove, J. Hongpaisan, N.B. Pivovarova, S.B. Andrews, and D.D. Friel. 2001. J. Gen. Physiol. 118:83–100) shows that in sympathetic neurons, small [Ca2+]i elevations evoked by weak depolarization stimulate ER Ca accumulation, but at a rate attenuated by activation of a ryanodine-sensitive CICR pathway. Here, we have measured depolarization-evoked changes in total ER Ca concentration ([Ca]ER) as a function of [Ca2+]i, and found that progressively larger [Ca2+]i elevations cause a graded transition from ER Ca accumulation to net release, consistent with the expression of multiple modes of CICR. [Ca]ER is relatively high at rest (12.8 ± 0.9 mmol/kg dry weight, mean ± SEM) and is reduced by thapsigargin or ryanodine (5.5 ± 0.7 and 4.7 ± 1.1 mmol/kg, respectively). [Ca]ER rises during weak depolarization (to 17.0 ± 1.6 mmol/kg over 120s, [Ca2+]i less than ∼350 nM), changes little in response to stronger depolarization (12.1 ± 1.1 mmol/kg, [Ca2+]i ∼700 nM), and declines (to 6.5 ± 1.0 mmol/kg) with larger [Ca2+]i elevations (>1 μM) evoked by the same depolarization when mitochondrial Ca2+ uptake is inhibited (FCCP). Thus, net ER Ca2+ transport exhibits a biphasic dependence on [Ca2+]i. With mitochondrial Ca2+ uptake enabled, [Ca]ER rises after repolarization (to 16.6 ± 1.8 mmol/kg at 15 min) as [Ca2+]i falls within the permissive range for ER Ca accumulation over a period lengthened by mitochondrial Ca2+ release. Finally, although spatially averaged [Ca]ER is unchanged during strong depolarization, net ER Ca2+ release still occurs, but only in the outermost ∼5-μm cytoplasmic shell where [Ca2+]i should reach its highest levels. Since mitochondrial Ca accumulation occurs preferentially in peripheral cytoplasm, as demonstrated

  16. Fabrication of highly porous keratin sponges by freeze-drying in the presence of calcium alginate beads

    Energy Technology Data Exchange (ETDEWEB)

    Hamasaki, Shinichi; Tachibana, Akira; Tada, Daisuke; Yamauchi, Kiyoshi [Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Tanabe, Toshizumi [Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan)], E-mail: tanabe@bioa.eng.osaka-cu.ac.jp

    2008-12-01

    Novel fabrication method of highly porous and flexible keratin sponges was developed by combining a particulate-leaching method and a freeze-drying method. Reduced keratin aqueous solution was mixed with dried calcium alginate beads and was lyophilized to give keratin/calcium alginate complex, which was subsequently treated with EDTA solution to leach out calcium alginate beads. The resultant keratin sponge was flexible enough to handle even in dried state because of its quite high porosity (98.9 {+-} 0.1%), which was brought about by the large and small pores formed by the elimination of calcium alginate beads and water. The sponge supported the attachment and the proliferation of mouse fibroblast cells. Thus, the keratin sponge given by the present fabrication method afforded one alternative as a cell scaffold for tissue engineering.

  17. Red blood cells of sickle cell disease patients exhibit abnormally high abundance of N-methyl D-aspartate receptors mediating excessive calcium uptake.

    Science.gov (United States)

    Hänggi, Pascal; Makhro, Asya; Gassmann, Max; Schmugge, Markus; Goede, Jeroen S; Speer, Oliver; Bogdanova, Anna

    2014-10-01

    Recently we showed that N-methyl D-aspartate receptors (NMDARs) are expressed in erythroid precursors (EPCs) and present in the circulating red blood cells (RBCs) of healthy humans, regulating intracellular Ca(2+) in these cells. This study focuses on investigating the possible role of NMDARs in abnormally high Ca(2+) permeability in the RBCs of patients with sickle cell disease (SCD). Protein levels of the NMDAR subunits in the EPCs of SCD patients did not differ from those in EPCs of healthy humans. However, the number and activity of the NMDARs in circulating SCD-RBCs was substantially up-regulated, being particularly high during haemolytic crises. The number of active NMDARs correlated negatively with haematocrit and haemoglobin levels in the blood of SCD patients. Calcium uptake via these non-selective cation channels was induced by RBC treatment with glycine, glutamate and homocysteine and was facilitated by de-oxygenation of SCD-RBCs. Oxidative stress and RBC dehydration followed receptor stimulation and Ca(2+) uptake. Inhibition of the NMDARs with an antagonist memantine caused re-hydration and largely prevented hypoxia-induced sickling. The EPCs of SCD patients showed higher tolerance to memantine than those of healthy subjects. Consequently, NMDARs in the RBCs of SCD patients appear to be an attractive target for pharmacological intervention.

  18. A highly sensitive fluorescent indicator dye for calcium imaging of neural activity in vitro and in vivo.

    Science.gov (United States)

    Tada, Mayumi; Takeuchi, Atsuya; Hashizume, Miki; Kitamura, Kazuo; Kano, Masanobu

    2014-06-01

    Calcium imaging of individual neurons is widely used for monitoring their activity in vitro and in vivo. Synthetic fluorescent calcium indicator dyes are commonly used, but the resulting calcium signals sometimes suffer from a low signal-to-noise ratio (SNR). Therefore, it is difficult to detect signals caused by single action potentials (APs) particularly from neurons in vivo. Here we showed that a recently developed calcium indicator dye, Cal-520, is sufficiently sensitive to reliably detect single APs both in vitro and in vivo. In neocortical neurons, calcium signals were linearly correlated with the number of APs, and the SNR was > 6 for in vitro slice preparations and > 1.6 for in vivo anesthetised mice. In cerebellar Purkinje cells, dendritic calcium transients evoked by climbing fiber inputs were clearly observed in anesthetised mice with a high SNR and fast decay time. These characteristics of Cal-520 are a great advantage over those of Oregon Green BAPTA-1, the most commonly used calcium indicator dye, for monitoring the activity of individual neurons both in vitro and in vivo.

  19. High performance Prussian Blue cathode for nonaqueous Ca-ion intercalation battery

    Science.gov (United States)

    Kuperman, Neal; Padigi, Prasanna; Goncher, Gary; Evans, David; Thiebes, Joseph; Solanki, Raj

    2017-02-01

    Potassium iron hexacyanoferrate, or Prussian blue (PB), is investigated as a cathode material for nonaqueous divalent calcium ion batteries. PB is an attractive prospect due to its high specific capacity, nontoxicity, low cost, and simple synthesis. Charge/discharge performances are examined at current densities of 23 mAg-1, 45 mAg-1, 90 mAg-1, and 125 mAg-1 that produced reversible specific capacities ranging from 150 mAhg-1 (at 23 mAg-1 current density) to over 120 mAhg-1 (at 125 mAg-1 current density). These are the highest storage capacities to date for a divalent calcium ion cathode over extended period of charge/discharge cycling and are comparable in performance to monovalent intercalating ions.

  20. 掺高 fCaO物料的水泥抗硫酸盐性的初步研究%Preliminary study on the property of sulfate resistance of cement with the addition of high f- CaO materials

    Institute of Scientific and Technical Information of China (English)

    范付忠; 冯涛; 施惠生; 赖振宇

    2001-01-01

    测试了掺入不同量的高钙粉煤灰、高 fCaO熟料、钢渣及石膏的试样抗蚀系数、质量增量和强度,结果表明,掺高 fCaO物料的水泥抗硫酸盐性与引入的 fCaO量、浸渍的硫酸盐种类和浓度有关,掺高 fCaO熟料和钢渣的水泥抗硫酸盐性优于掺高钙粉煤灰的水泥,适量石膏的掺入可改善试样的抗硫酸盐性,在实际应用中可通过控制引入的 fCaO量和掺入适量石膏来提高掺高 fCaO物料的水泥抗硫酸盐性。%Parameters as corrosion resistance ratio, the increment in quantity and strength of cement with different addition of high calcium pfa, high fCaO clinker, steel slag and gypsum were tested. The results indicate that the property of sulfate resistance of cement is associated with the amount of fCaO and the type and concentration of sulfate in the corrosive agent. The addition of high fCaO clinker and steel slag in cement possesses higher performance in the sulfate resistance compared with the addition of pfa. The introduction of proper quantity of gypsum can improve the sulfate resistance property. This property can be improved in practice through the proper introduction of fCaO and gypsum.

  1. Segment-specific Ca(2+) transport by isolated Malpighian tubules of Drosophila melanogaster: A comparison of larval and adult stages.

    Science.gov (United States)

    Browne, Austin; O'Donnell, Michael J

    2016-04-01

    Haemolymph calcium homeostasis in insects is achieved through the regulation of calcium excretion by Malpighian tubules in two ways: (1) sequestration of calcium within biomineralized granules and (2) secretion of calcium in soluble form within the primary urine. Using the scanning ion-selective electrode technique (SIET), basolateral Ca(2+) transport was measured at the distal, transitional, main and proximal tubular segments of anterior tubules isolated from both 3rd instar larvae and adults of the fruit fly Drosophila melanogaster. Basolateral Ca(2+) transport exceeded transepithelial secretion by 800-fold and 11-fold in anterior tubules of larvae and adults, respectively. The magnitude of Ca(2+) fluxes across the distal tubule of larvae and adults were larger than fluxes across the downstream segments by 10 and 40 times, respectively, indicating a dominant role for the distal segment in whole animal Ca(2+) regulation. Basolateral Ca(2+) transport across distal tubules of Drosophila varied throughout the life cycle; Ca(2+) was released by distal tubules of larvae, taken up by distal tubules of young adults and was released once again by tubules of adults ⩾ 168 h post-eclosion. In adults and larvae, SIET measurements revealed sites of both Ca(2+) uptake and Ca(2+) release across the basolateral surface of the distal segment of the same tubule, indicating that Ca(2+) transport is bidirectional. Ca(2+) uptake across the distal segment of tubules of young adults and Ca(2+) release across the distal segment of tubules of older adults was also suggestive of reversible Ca(2+) storage. Our results suggest that the distal tubules of D. melanogaster are dynamic calcium stores which allow efficient haemolymph calcium regulation through active Ca(2+) sequestration during periods of high dietary calcium intake and passive Ca(2+) release during periods of calcium deficiency.

  2. The effects of thermal stimuli on intracellular calcium change and histamine releases in rat basophilic leukemia mast cells

    Science.gov (United States)

    Wu, Zu-Hui; Zhu, Dan; Chen, Ji-Yao; Zhou, Lu-Wei

    2012-05-01

    The effects of thermal stimuli on rat basophilic leukemia mast cells were studied. The cells in calcium-contained or calcium-free buffers were thermally stimulated in the temperature range of 25-60 °C. The corresponding calcium ion concentration in cells [Ca2+]i as well as the released histamine from cells was measured with fluorescence staining methods. The ruthenium red (RR), a block of membrane calcium channels (transient receptor potential family V (TRPV)), was used in experiments. Under the stimulus of 25-50 °C, no significant difference on [Ca2+]i was found between these three groups of the cells in calcium-contained buffer without or with RR and cells in calcium-free saline, indicating that the increased calcium in cytosol did not result from the extracellular buffer but came from the intracellular calcium stores. The [Ca2+]i continuously increased under the temperature of 50-60 °C, but the RR and calcium-free saline can obviously diminish the [Ca2+]i increase at these high temperatures, reflecting that the opening of the TRPV2 channels leads to a calcium influx resulting in the [Ca2+]i increment. The histamine release also became significant in these cases. Since the released histamine is a well-known mediator for the microcirculation promotion, the histamine release from mast cells could be one of the mechanisms of thermal therapy.

  3. Calcium, essential for health

    Science.gov (United States)

    Martínez de Victoria, Emilio

    2016-07-12

    Calcium (Ca) is the most abundant mineral element in our body. It accounts for about 2% of body weight. The functions of calcium are: a) functions skeletal and b) regulatory functions. Bone consists of a protein matrix that mineralizes mainly with calcium (the most abundant), phosphate and magnesium, for it is essential an adequate dietary intake of Ca, phosphorus and vitamin D. The ionic Ca (Ca2+) is essential to maintain and / or perform different specialized functions of, virtually, all body cells cellular. Because of its important functions Ca2+ must be closely regulated, keeping plasma concentrations within narrow ranges. For this reason there is an accurate response against hypocalcemia or hypercalcemia in which the parathormone, calcitriol, calcitonin and vitamin K are involved. Ca intakes in the Spanish population are low in a significant percentage of the older adult’s population, especially in women. The main source of Ca in the diet is milk and milk derivatives. Green leafy vegetables, fruits and legumes can be important sources of Ca in a Mediterranean dietary pattern. The bioavailability of dietary Ca depends on physiological and dietary factors. Physiological include age, physiological status (gestation and lactation) Ca and vitamin D status and disease. Several studies relate Ca intake in the diet and various diseases, such as osteoporosis, cancer, cardiovascular disease and obesity.

  4. Precision isotope shift measurements in Ca$^+$ using highly sensitive detection schemes

    CERN Document Server

    Gebert, Florian; Wolf, Fabian; Angstmann, Christopher N; Berengut, Julian C; Schmidt, Piet O

    2015-01-01

    We demonstrate an efficient high-precision optical spectroscopy technique for single trapped ions with non-closed transitions. In a double-shelving technique, the absorption of a single photon is first amplified to several phonons of a normal motional mode shared with a co-trapped cooling ion of a different species, before being further amplified to thousands of fluorescence photons emitted by the cooling ion using the standard electron shelving technique. We employ this extension of the photon recoil spectroscopy technique to perform the first high precision absolute frequency measurement of the $^{2}$D$_{3/2}$ $\\rightarrow$ $^{2}$P$_{1/2}$ transition in $^{40}$Ca$^{+}$, resulting in a transition frequency of $f=346\\, 000\\, 234\\, 867(96)$ kHz. Furthermore, we determine the isotope shift of this transition and the $^{2}$S$_{1/2}$ $\\rightarrow$ $^{2}$P$_{1/2}$ transition for $^{42}$Ca$^{+}$, $^{44}$Ca$^{+}$ and $^{48}$Ca$^{+}$ ions relative to $^{40}$Ca$^{+}$ with an accuracy below 100 kHz. Improved field and ...

  5. High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst from X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yachandra, Vittal; Yano, Junko; Kern, Jan; Pushkar, Yulia; Sauer, Kenneth; Glatzel, Pieter; Bergmann, Uwe; Messinger, Johannes; Zouni, Athina; Yachandra, Vittal K.

    2007-08-01

    The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, are described. Issues of X-ray damage especially at the metal sites in the Mn4Ca cluster are discussed. The structure of the Mn4Ca catalyst at high-resolution which has so far eluded attempts of determination by X-ray diffraction, EXAFS and other spectroscopic techniques has been addressed using polarized EXAFS techniques applied to oriented PS II membrane preparations and PS II single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K? emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.

  6. Improved four-color flow cytometry method using fluo-3 and triple immunofluorescence for analysis of intracellular calcium ion ([Ca2+]i) fluxes among mouse lymph node B- and T-lymphocyte subsets.

    Science.gov (United States)

    Greimers, R; Trebak, M; Moutschen, M; Jacobs, N; Boniver, J

    1996-03-01

    A visible-light, dual-laser, flow cytometric method was developed for the simultaneous analysis of intracellular ionized calcium concentration ([Ca2+]i) and three cell-surface markers (CD4, CD8, and Thy-1.2 antigens) by using the calcium probe fluo-3 and using R-phycoerythrin (PE), peridinin chlorophyll-alpha protein (PerCP), and allophycocyanin (APC) conjugated monoclonal antibodies (MoAbs). This improved method was used in the analysis of [Ca2+]i mobilization upon in vitro stimulation with mitogenic lectins [phytohaemagglutinin (PHA) or concanavalin A (ConA)], anti-CD3 MoAbs, or A23187 calcium ionophore in the heterogeneous lymph node cell populations from healthy C57BL/Ka mice. The present results show that the calcium responses were heterogeneous and dependent on the cellular immunophenotype, not only on lectins or anti-CD3 MoAbs stimulation, but also on the receptor-independent A23187 ionophore stimulation. An in situ fluo-3 calibration method (using A23187 and metabolic poisons in Ca2+ /EGTA buffers with known free calcium concentrations) indicated a resting [Ca2+]i in lymphocytes of 103 +/- 23 nM (mean +/- S.D.) but with significant differences between the [Ca2+]i in B cells and in all of the T-cell subsets (CD4+Thy-1+, CD4+Thy-1-, and CD8+T cells). Both the B cells and the T-cell subsets showed an increase of fluo-3 fluorescence upon in vitro stimulation with ConA or PHA, but the calcium mobilization following lectin stimulation was time delayed in all T-cell subsets. Only the T cells, including the CD4+Thy-1- subset, responded to anti-CD3 MoAbs. The percentage of responding cells upon stimulation with ConA was higher in T cells than in B cells. By contrast, PHA gave a higher response in B cells. After stimulation with different mitogens, [Ca2+]i increased in both CD4+ and CD8+ T-cell subsets. However, the percentage of responding cells was far higher in the CD4+Thy-1+ subset than in the CD4+Thy-1- or the CD8+T-cell subsets. The stimulation with A23187

  7. Calcium Electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha;

    2015-01-01

    BACKGROUND: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill...... efficacy-and normal cell sensitivity. METHODS: Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780......), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). RESULTS: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p

  8. Calcium Phosphate Biomaterials: An Update

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Current calcium phosphate (CaP) biomaterials for bone repair, substitution, augmentation and regeneration include hydroxyapatite ( HA ) from synthetic or biologic origin, beta-tricalcium phosphate ( β-TCP ) , biphasic calcium phosphate (BCP), and are available as granules, porous blocks, components of composites (CaP/polymer) cements, and as coatings on orthopedic and dental implants. Experimental calcium phosphate biomaterials include CO3- and F-substituted apatites, Mg-and Zn-substituted β-TCP, calcium phosphate glasses. This paper is a brief review of the different types of CaP biomaterials and their properties such as bioactivity, osteoconductivity, osteoinductivity.

  9. Normal mode coordinates of high T c superconductors TlCaBa 2Cu 2O 7 and Tl 2CaBa 2Cu 2O 8

    Science.gov (United States)

    Mori, T.; Nakaoka, K.; Onari, S.; Arai, T.

    1989-10-01

    Normal mode coordinates of high Tc superconductors TlCaBa 2Cu 2O 7- (Tl-1122) and Tl 2CaBa 2Cu 2O 8(Tl-2122) are analyzed by the shell model calculations. The model calculations have reproduced very well the observed Raman frequencies. The vibrational frequencies of the oxygens on the CuO 2 layers are found to depend on the ionic charges of the oxygens on the CuO 2 layers.

  10. The catalytic dehydrochlorination of pentachloroethane with activated carbon supported calcium chloride%活性炭负载CaCl2催化五氯乙烷脱HCl的研究

    Institute of Scientific and Technical Information of China (English)

    王智春; 陈胜洲; 陈汉伦; 谢文健

    2012-01-01

    Supported catalyst calcium chloride/activated carbon(CaCl2/AC) was prepared and used in dehydrochlorination of pentachloroethane to produce perchloroethylene.Influences of reaction temperature,space velocity and CaCl2 loading amount on catalytic activity of CaCl2/AC were investigated.Stability of catalytic activity of catalyst was also studied.Results of the experiment showed that the optimal conditions were reaction temperature 240℃,space velocity 3.4h-1,CaCl2 loading amount 0.3mmol/g.Under the optimal conditions,the conversion of pentachloroethane and the yield of perchloroethylene can reach more than 99% and 95%,respectively.And the repeatability of catalytic activity of catalyst was fine.The catalysts were characterized by X-ray diffraction(XRD) and nitrogen adsorption-desorption method.The results showed that the dispersion of CaCl2 on activated carbon surface was good.The BET surface area and pore volume of CaCl2/AC catalyst gradually decreased with the CaCl2 loading amount increased.%筛选出了催化性能较好的活性炭负载氯化钙(CaCl2/AC)催化剂用于五氯乙烷脱HCl制备四氯乙烯。考察了反应温度、空速、CaCl2负载量对CaCl2/AC催化剂催化性能的影响及催化剂的稳定性。实验结果表明最佳反应条件:反应温度为240℃,空速为3.4h-1,CaCl2负载量为0.3mmol/g,在此反应条件下五氯乙烷的转化率可达99%以上,四氯乙烯的收率达95%以上,催化剂催化性能重现性良好。采用X射线衍射(XRD)、氮气吸附-脱附对催化剂进行了表征。结果表明CaCl2在活性炭表面分散良好;随着CaCl2负载量的增加,CaCl2/AC催化剂的BET比表面及孔容逐渐减小。

  11. [Salidroside attenuates high glucose-induced apoptosis in human umbilical vein endothelial cells via activating the Ca(2)+/CaM/CAMKIIδ/eNOS pathway].

    Science.gov (United States)

    Chen, Ziwei; Wu, Xiang

    2014-04-01

    Endothelial oxidative stress plays an important role in the pathogenesis of cardiovascular disease. Salidroside, a phenylpropanoid glycoside isolated from Rhodiola rosea L, could exert potent antioxidant properties. In this study, we investigated the protective effects, and related mechanism of salidroside against high glucose (33 mmol/L)-induced cell damage in human umbilical vein endothelial cells (HUVECs). HUVECs were cultured in normal glucose (5.5 mmol/L), high glucose (33 mmol/L), high salidroside (10 µg/ml+33 mmol/L glucose), moderate salidroside (4 µg/ml+33 mmol/L glucose), low salidroside (1 µg/ml+33 mmol/L glucose) and very low salidroside (0.1 µg/ml+33 mmol/L glucose) for 48 h. Cell viability, the level of malondialdehyde (MDA) , reactive oxygen species (ROS) , nitric oxide (NO) , [Ca(2)+]i, calmodulin (CaM) , calmodulin-dependent kinase (CaMK) IIδ, endothelial nitric oxide synthase (eNOS) , active caspase-3 protein expression and eNOS ser 1177 phosphorylation of HUVECs post various treatments were measured. The cell viability was assessed with MTT assay, and the level of ROS, and [Ca(2)+]i was analyzed using flow cytometry. Nitric oxide and MDA was detected by Nitric Oxide Assay Kit and MDA Assay Kit. Western blot was performed to detect the protein expressions of eNOS, active caspase-3 and eNOS ser 1177 phosphorylation. Comparing to the normal glucose group, high glucose treatment increased the cell damage, the level of NO and [Ca(2)+]i (P Salidroside treatment significantly attenuated high glucose-induce cell damage on cultured HUVECs in a dose-dependent manner. Comparing to the high glucose group, 10 µg/ml Salidroside significantly increased cell viability (P salidroside could attenuate high glucose induced apoptosis in HUVEC, partly through activating the Ca(2)+/CaM/CAMKIIδ/eNOS pathway.

  12. Imaging calcium in neurons.

    Science.gov (United States)

    Grienberger, Christine; Konnerth, Arthur

    2012-03-08

    Calcium ions generate versatile intracellular signals that control key functions in all types of neurons. Imaging calcium in neurons is particularly important because calcium signals exert their highly specific functions in well-defined cellular subcompartments. In this Primer, we briefly review the general mechanisms of neuronal calcium signaling. We then introduce the calcium imaging devices, including confocal and two-photon microscopy as well as miniaturized devices that are used in freely moving animals. We provide an overview of the classical chemical fluorescent calcium indicators and of the protein-based genetically encoded calcium indicators. Using application examples, we introduce new developments in the field, such as calcium imaging in awake, behaving animals and the use of calcium imaging for mapping single spine sensory inputs in cortical neurons in vivo. We conclude by providing an outlook on the prospects of calcium imaging for the analysis of neuronal signaling and plasticity in various animal models.

  13. Microdomain Ca{sup 2+} dynamics in mammalian muscle following prolonged high pressure treatments

    Energy Technology Data Exchange (ETDEWEB)

    Schnee, S; Schuermann, S; Fink, R [Medical Biophysics, Institute of Physiology and Pathophysiology, University of Heidelberg, INF326, 69120 Heidelberg (Germany); Ludwig, H [Physical Chemistry, Institute of Molecular Biotechnology and Biopharmacy, University of Heidelberg, INF 366 (Germany); Wegner, F von; Friedrich, O, E-mail: oliver.friedrich@physiologie.uni-heidelberg.de

    2008-07-15

    High pressure (HP) applications are an important thermodynamic tool to influence cellular processes. Especially processes that undergo large volume changes, e.g. opening or closing of ion channels, are in particular susceptible to HP treatments. Such volume changes are extremely difficult to assess for intracellular ion channels, like ryanodine receptors (RyR) residing in the membrane of organelles. In skeletal muscle, RyR act as Ca{sup 2+} release channels. We previously showed that plasmalemmal Na{sup +} and Ca{sup 2+} ion channels were irreversibly altered after prolonged 20 MPa treatments. Here, changes in microdomain Ca{sup 2+} levels due to elementary Ca{sup 2+} release events (ECRE) were monitored using confocal fluorescence microscopy. We studied ECRE in mammalian skeletal muscle following 3 h HP treatments up to 30 MPa to clarify whether RyR induced intracellular microdomain Ca{sup 2+} dynamics was more susceptible to HP treatment compared to surface membrane ion currents. ECRE frequencies exponentially declined with pressure. ECRE amplitudes and rise times (RT) were quite robust towards HP treatments. In contrast, spatial and temporal ECRE extension showed a tendency towards larger values up to 20 MPa but declined for higher pressures. Activation volumes for pressure-induced persistent ECRE alterations were zero for RT but showed a bimodal behavior for event duration. It seems that although ECRE frequencies are markedly reduced, ECRE morphology is less affected by HP. In particular, RyR opening time is practically unaltered and the observed morphological ECRE changes might reflect alterations in local Ca{sup 2+} buffers and Ca{sup 2+} concentration profiles rather than involvement of RyR in mammalian skeletal muscle.

  14. First-principles study of the thermodynamical, structural, transport properties of liquid CaO and CaSiO3 at high pressure

    Science.gov (United States)

    Bajgain, S. K.; Karki, B. B.; Ghosh, D. B.

    2014-12-01

    We have performed first principles molecular dynamics simulations of CaO and CaSiO3 liquids overbroad ranges of pressure (0 to 150 GPa) and temperature (2500 to 8000 K) within density functionaltheory. They show that both liquids are much more compressible than their solid counterpartsimplying possible liquid-solid density crossover. The liquid Grüneisen parameter increases onpressure, which is opposite of crystalline phases. Our analysis shows that the liquid structurechanges considerably on compression, with the mean cation-anion coordination numbers increasingnearly linearly with volume. The Ca-O coordination number increases from 7 (5) near the ambientpressure to 9 (7) at high pressure for CaSiO3 (CaO) liquid. The Si-O coordination number increasesfrom 4 to 6 over the same pressure regime. The calculated self-diffusion coefficients are stronglydependent on temperature and pressure and require non-Arrhenian representation with variableactivation volume. The diffusivity differences between the two liquids are considerable in low-temperature and low-pressure regime. Also, comparisons with MgSiO3 liquid suggest that networkmodifier cations Ca and Mg behave similarly though Ca is more coordinated and more mobile ascompared with Mg.

  15. Thermal treatment and utilization of Al-rich waste in high calcium fly ash geopolymeric materials

    Science.gov (United States)

    Chindaprasirt, Prinya; Rattanasak, Ubolluk; Vongvoradit, Pimdao; Jenjirapanya, Supichart

    2012-09-01

    The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its use to adjust the silica/alumina ratio of the high calcium fly ash geopolymer were studied. To recycle the raw Al-rich waste, the waste was dried at 110°C and calcined at 400 to 1000°C. Mineralogical analyses were conducted using X-ray diffraction (XRD) to study the phase change. The increase in calcination temperature to 600, 800, and 1000°C resulted in the phase transformation. The more active alumina phase of active γ-Al2O3 was obtained with the increase in calcination temperature. The calcined Al-rich waste was then used as an additive to the fly ash geopolymer by mixing with high calcium fly ash, water glass, 10 M sodium hydroxide (NaOH), and sand. Test results indicated that the calcined Al-rich waste could be used as an aluminium source to adjust the silica/alumina ratio and the strength of geopolymeric materials. The fly ash geopolymer mortar with 2.5wt% of the Al-rich waste calcined at 1000°C possessed the 7-d compressive strength of 34.2 MPa.

  16. Apical entry channels in calcium-transporting epithelia.

    Science.gov (United States)

    Peng, Ji-Bin; Brown, Edward M; Hediger, Matthias A

    2003-08-01

    The identification of the apical calcium channels CaT1 and ECaC revealed the key molecular mechanisms underlying apical calcium entry in calcium-transporting epithelia. These channels are regulated directly or indirectly by vitamin D and dietary calcium and undergo feedback control by intracellular calcium, suggesting their rate-limiting roles in transcellular calcium transport.

  17. Stratification of the Bi-Sr-Ca-Cu-O system melted under high gravity conditions

    Science.gov (United States)

    Volkov, M. P.; Melekh, B. T.; Parfen'ev, R. V.; Kartenko, N. F.; Turchaninov, A. M.; Regel, L. L.

    1992-08-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed.

  18. Cosmic ray source abundance of calcium

    CERN Document Server

    Perron, C

    1978-01-01

    Re-examines the results of experiments in which ultra-high purity iron targets were irradiated by protons from the two CERN accelerators (600 MeV and 21 GeV); the spallation products were then chemically separated, and their isotopic composition determined by mass spectrometry. Ratios of cross-sections for calcium production by spallation of iron show that /sup 42/Ca, /sup 43/Ca and /sup 44/Ca have about the same abundance, about 10-15% that of iron, confirming earlier studies. (11 refs).

  19. Impact of High Calcium Intake from Calcium Carbonate or Dairy on Cardiovascular Function, Coronary Artery Calcification and Coronary Artery Disease Burden in Ossabaw Miniature Swine

    OpenAIRE

    Phillips, Alyssa K.

    2013-01-01

    Recent secondary analyses have associated supplemental calcium use with increased risk for myocardial infarction and cardiovascular-related death in healthy, older adults. Subsequent concern over the safety of calcium supplements has spurred a calcium controversy, because calcium is a shortfall essential nutrient that is critical for bone health and a mainstay of osteoporosis prevention and treatment. The proposed mechanism by which calcium intake may detriment cardiovascular health is throug...

  20. Superconductivity in the high-Tc Bi-Ca-Sr-Cu-O system - Phase identification

    Science.gov (United States)

    Hazen, R. M.; Prewitt, C. T.; Angel, R. J.; Ross, N. L.; Finger, L. W.

    1988-01-01

    Four phases are observed in superconducting Bi-Ca-Sr-Cu-O samples. The superconducting phase, with onset temperature near 120 K, is a 15.4-A-layered compound with composition near Bi2Ca1Sr2Cu2O9 and an A-centered orthorhombic unit subcell 5.41 x 5.44 x 30.78 A. X-ray diffraction and electron microscopy data are consistent with a structure of alternating perovskite and Bi2O2 layers. High-resolution transmission electron microscopy images reveal a b-axis superstructure of 27.2 A, numerous (001) stacking faults, and other defects.

  1. Local chemical composition of HgBaCaCuO high-temperature superconductors

    Science.gov (United States)

    Alméras, P.; Dell'Orto, T.; Coluzza, C.; Almeida, J.; Margaritondo, G.; Xue, Y. Y.; Meng, R. L.; Chu, C. W.

    1994-07-01

    The microchemical composition and the electronic structure of the two superconductors HgBa2Ca2Cu3O8+δ (Hg-1223) and HgBa2Ca1Cu2O6+δ (Hg-1212) were analyzed with the technique of photoemission with high spatial resolution. This enabled primary spectral peaks to be separated from their satellites due to local charging induced by the primary photon beam. Each sample contains superconducting and impurity phases with inhomogeneous spatial distributions. The oxygenation-induced increase in the critical temperature is related to a increase in the Cu-O plane carrier concentration.

  2. CNTF inhibits high voltage activated Ca2+ currents in fetal mouse cortical neurones

    DEFF Research Database (Denmark)

    Holm, Ninna R; Christophersen, Palle; Hounsgaard, Jørn;

    2002-01-01

    Neurotrophic factors yield neuroprotection by mechanisms that may be related to their effects as inhibitors of apoptosis as well as their effects on ion channels. The effect of ciliary neurotrophic factor (CNTF) on high-threshold voltage-activated Ca channels in cultured fetal mouse brain cortical...... neurones was investigated. Addition of CNTF into serum-free growth medium resulted in delayed reduction of the Ca2+ currents. The currents decreased to 50% after 4 h and stabilized at this level during incubation with CNTF for 48 h. Following removal of CNTF the inhibition was completely reversed after 18...

  3. Calcium fertilization increases the concentration of calcium in sapwood and calcium oxalate in foliage of red spruce

    Science.gov (United States)

    Kevin T. Smith; Walter C. Shortle; Jon H. Connolly; Rakesh Minocha; Jody Jellison

    2009-01-01

    Calcium cycling plays a key role in the health and productivity of red spruce forests in the northeastern US. A portion of the flowpath of calcium within forests includes translocation as Ca2+ in sapwood and accumulation as crystals of calcium oxalate in foliage. Concentrations of Ca in these tree tissues have been used as markers of...

  4. PHASE TRANSITION IN LAYERED PEROVSKITE LIKE MANGANATE Ca3Mn2O7 UNDER HIGH PRESSURE

    Institute of Scientific and Technical Information of China (English)

    J.L.ZHU; L.C.CHEN; R.C.YU; F.Y.LI; J.LIU; C.Q.JIN

    2001-01-01

    In situ high pressure energy dispersive X-ray diffraction measurements on layered perovskite-like manganate Ca3Mn2O7 under pressures up to 35 GPa have been Performed by using diamond anvil cell with synchrotron radiation.The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks.The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35GPa.One was at about 1.3GPa with the crystal structure changing from tetragonalt go orthorhombic.The other was at about 9.5GPa with the crystal structure changing form orthorhombic back to another tetragonal.

  5. Role of claudins in renal calcium handling

    Directory of Open Access Journals (Sweden)

    Armando Luis Negri

    2015-07-01

    Full Text Available Paracellular channels occurring in tight junctions play a major role in transepithelial ionic flows. This pathway includes a high number of proteins, such as claudins. Within renal epithelium, claudins result in an ionic selectivity in tight junctions. Ascending thick limb of loop of Henle (ATLH is the most important segment for calcium reabsorption in renal tubules. Its cells create a water-proof barrier, actively transport sodium and chlorine through a transcellular pathway, and provide a paracellular pathway for selective calcium reabsorption. Several studies have led to a model of paracellular channel consisting of various claudins, particularly claudin-16 and 19. Claudin-16 mediates cationic paracellular permeability in ATLH, whereas claudin-19 increases cationic selectivity of claudin-16 by blocking anionic permeability. Recent studies have shown that claudin-14 promoting activity is only located in ATLH. When co-expressed with claudin-16, claudin-14 inhibits the permeability of claudin-16 and reduces paracellular permeability to calcium. Calcium reabsorption process in ATLH is closely regulated by calcium sensor receptor (CaSR, which monitors circulating Ca levels and adjusts renal excretion rate accordingly. Two microRNA, miR-9 and miR-374, are directly regulated by CaSR. Thus, miR-9 and miR-374 suppress mRNA translation for claudin-14 and induce claudin-14 decline.

  6. Roscovitine increases intracellular calcium release and capacitative calcium entry in PC12 cells.

    Science.gov (United States)

    Choi, Ho Sook; Chung, Sul-Hee

    2010-01-18

    Cyclin-dependent kinase 5 (Cdk5), which is activated by the non-cyclin regulator p35 or p39, is a proline-directed serine/threonine kinase that is implicated in many physiological and pathological processes. Here, we studied calcium signaling using the fluorescent cytosolic calcium indicator, Fura-4, in NGF-differentiated PC12 cells treated with roscovitine, a Cdk5 inhibitor. As compared to the control cells, the roscovitine-treated cells significantly potentiated intracellular calcium release by membrane depolarization (high K(+)) or through thapsigargin. In addition, roscovitine increased the magnitude of capacitative calcium entry (CCE), i.e., a calcium influx mechanism triggered by the depletion of intracellular calcium stores. Notably, roscovitine markedly slowed the rate of Ca(2+) removal from the plasma membrane. These results suggest that Cdk5 regulates intracellular calcium homeostasis and that the dysregulation of Cdk5 may contribute to disease pathogenesis by perturbing cellular Ca(2+) signaling. (c) 2009 Elsevier Ireland Ltd. All rights reserved.

  7. Calcium-dependent calcium decay explains STDP in a dynamic model of hippocampal synapses.

    Directory of Open Access Journals (Sweden)

    Dominic Standage

    Full Text Available It is widely accepted that the direction and magnitude of synaptic plasticity depends on post-synaptic calcium flux, where high levels of calcium lead to long-term potentiation and moderate levels lead to long-term depression. At synapses onto neurons in region CA1 of the hippocampus (and many other synapses, NMDA receptors provide the relevant source of calcium. In this regard, post-synaptic calcium captures the coincidence of pre- and post-synaptic activity, due to the blockage of these receptors at low voltage. Previous studies show that under spike timing dependent plasticity (STDP protocols, potentiation at CA1 synapses requires post-synaptic bursting and an inter-pairing frequency in the range of the hippocampal theta rhythm. We hypothesize that these requirements reflect the saturation of the mechanisms of calcium extrusion from the post-synaptic spine. We test this hypothesis with a minimal model of NMDA receptor-dependent plasticity, simulating slow extrusion with a calcium-dependent calcium time constant. In simulations of STDP experiments, the model accounts for latency-dependent depression with either post-synaptic bursting or theta-frequency pairing (or neither and accounts for latency-dependent potentiation when both of these requirements are met. The model makes testable predictions for STDP experiments and our simple implementation is tractable at the network level, demonstrating associative learning in a biophysical network model with realistic synaptic dynamics.

  8. Calcium spikes and calcium plateaux evoked by differential polarization in dendrites of turtle motoneurones in vitro

    DEFF Research Database (Denmark)

    Hounsgaard, J; Kiehn, O

    1993-01-01

    -evoked regenerative responses was relatively insensitive to somatic bias current. 6. TTX-resistant Ca(2+)-mediated plateau potentials promoted by apamin were evoked by differential polarization in both the soma-depolarizing and soma-hyperpolarizing direction. 7. It is concluded that Ca2+ channels responsible for Ca2......The ability of dendrites in turtle motoneurones to support calcium spikes and calcium plateaux was investigated using differential polarization by applied electric fields. 2. Electric fields were generated by passing current through transverse slices of the turtle spinal cord between two plate......-hyperpolarizing and soma-depolarizing direction of the field. The different components of Ca2+ spikes were discrete and additive. High amplitude components had higher threshold and faster time course and were followed by larger after-hyperpolarizations, than low amplitude components. The frequency of field...

  9. Solar Imagery - Chromosphere - Calcium

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset consists of full-disk images of the sun in Calcium (Ca) II K wavelength (393.4 nm). Ca II K imagery reveal magnetic structures of the sun from about 500...

  10. Preparation and Powdering Mechanism of Nano Calcium Carbonate Filled Powdered Rubber Composite Particle%纳米CaCO3填充型粉末橡胶复合粒子的制备及成粉机理

    Institute of Scientific and Technical Information of China (English)

    张周达; 陈雪梅; 马新胜

    2012-01-01

    以纳米CaCO3浆料和丁苯胶乳(SBR)为原料,将两者直接混合制得了纳米CaCO3填充型粉末橡胶复合粒子。研究表明,当粉末化体系中纳米CaCO3和SBR的重量比≥1时,纳米CaCO3兼具隔离剂和凝聚剂的作用。复合粒子的粒径随着纳米CaCO3填充量的增加而减小,所制得的复合粒子的颗粒尺寸均小于200tLm,纳米CaCO3以50nm原始粒径均匀分散在复合粒子中;其成粉机理为纳米CaCO3表面的钙离子和胶乳粒子表面的负离子发生键合作用,破乳而形成粉末橡胶复合粒子。%Powdered rubber composite particle with nano-calcium carbonate filled was prpeared by simply blending nano-CaCOa slurry and styrene-butadiene latex. It was demonstrated that nano-CaCO3 could served as both separant and coagulant in the powdering system when the weight ratio of nano-CaCO3 to SBR was greater than 1. The size of the composite particle decreased with increasing nano-CaCOa loading and was always smaller than 200htm, the nano-CaCO3 dispersed uniformly with the original size of 50nm in the composite particle matrix. The powdering mechanism could be described as the demulsification due to the attractive interaction of dissolved positive ion and the anion originating from the surface of CaCOa and latex respectively.

  11. Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

    OpenAIRE

    Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward; Wysolmerski, John

    2013-01-01

    To meet the demands for milk calcium, the lactating mother adjusts systemic calcium and bone metabolism by increasing dietary calcium intake, increasing bone resorption, and reducing renal calcium excretion. As part of this adaptation, the lactating mammary gland secretes PTHrP into the maternal circulation to increase bone turnover and mobilize skeletal calcium stores. Previous data have suggested that, during lactation, the breast relies on the calcium-sensing receptor (CaSR) to coordinate ...

  12. 舒张性心力衰竭患者Ca2+调控蛋白 基因转录和蛋白质表达的研究%Molecular mechanisms underlying calcium handling in diastolic heart failure

    Institute of Scientific and Technical Information of China (English)

    钟明; 张运; 张薇; 赵静; 卞继峰; 耿昭

    2001-01-01

    目的探讨心肌细胞内Ca2+超负荷及Ca2+调控蛋白在舒张性心力衰竭(DHF)患者发生中的作用。方法采用RT-PCR和Western blot技术测定DHF患者和正常对照组Ca2+调控蛋白mRNA转录和蛋白质表达的变化。结果与正常组相比,DHF患者心肌细胞内Ca2+含量提高3倍以上(1 163.88±568.67 vs 247.75±146.86,P<0.01);肌浆网(SR) Ca2+-ATPase mRNA水平减低33.64%(0.71±0.19 vs 1.07±0.11,P<0.05),细胞膜L型Ca2+通道mRNA水平减低30.19%(0.74±0.20 vs 1.06±0.13,P<0.05),SR磷酸受纳蛋白和兰尼碱受体、肌集钙蛋白的mRNA转录无显著性差异(P>0.05);Ca2+-ATPase蛋白的相对含量明显低于对照组(0.76±0.11 vs 1.01±0.03, P<0.05);磷酸受纳蛋白的相对含量无显著性差异(0.98±0.04 vs 1.00±0.02,P>0.05)。结论 SR Ca2+-ATPase基因转录和蛋白质表达减低以及细胞膜L型Ca2+通道基因转录减低是导致心肌细胞内Ca2+超负荷和DHF发生的主要分子机制之一。%Department of Senior Health Care, the Affiliated Hospital of Shandong Medical University, Jinan 250012, China   【Abstract】 Objective To elucidate molecular mechanisms underlying calcium handling in patients with diastolic heart failure (DHF) from mRNA level and protein expression. Methods 6 patients with DHF and 6 control subjects were included. The content of calcium was assayed by spectrocomparator. The mRNA amounts of these calcium handling genes including L-type calcium channel, sarcoplasmic reticular (SR) Ca2+-ATPase, ryanodine receptor, calsequestrin and phospholamban were measured by reverse transcription-polymerase chain reaction (RT-PCR) and normalized to the mRNA levels of actin. The protein levels of SR Ca2+-ATPase and phospholamban were analyzed by Western blot analysis. Results The content of calcium was significantly increased by 369.78% in patients with DHF. RT-PCR analyses showed that the steady-state level of m

  13. STIM1/Orai1-mediated store-operated Ca2+ entry: the tip of the iceberg

    Directory of Open Access Journals (Sweden)

    F.R. Giachini

    2011-11-01

    Full Text Available Highly efficient mechanisms regulate intracellular calcium (Ca2+ levels. The recent discovery of new components linking intracellular Ca2+ stores to plasma membrane Ca2+ entry channels has brought new insight into the understanding of Ca2+ homeostasis. Stromal interaction molecule 1 (STIM1 was identified as a Ca2+ sensor essential for Ca2+ store depletion-triggered Ca2+ influx. Orai1 was recognized as being an essential component for the Ca2+ release-activated Ca2+ (CRAC channel. Together, these proteins participate in store-operated Ca2+ channel function. Defective regulation of intracellular Ca2+ is a hallmark of several diseases. In this review, we focus on Ca2+ regulation by the STIM1/Orai1 pathway and review evidence that implicates STIM1/Orai1 in several pathological conditions including cardiovascular and pulmonary diseases, among others.

  14. Calcium Biofortification: Three Pronged Molecular Approaches for Dissecting Complex Trait of Calcium Nutrition in Finger Millet (Eleusine coracana) for Devising Strategies of Enrichment of Food Crops

    Science.gov (United States)

    Sharma, Divya; Jamra, Gautam; Singh, Uma M.; Sood, Salej; Kumar, Anil

    2017-01-01

    Calcium is an essential macronutrient for plants and animals and plays an indispensable role in structure and signaling. Low dietary intake of calcium in humans has been epidemiologically linked to various diseases which can have serious health consequences over time. Major staple food-grains are poor source of calcium, however, finger millet [Eleusine coracana (L.) Gaertn.], an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Understanding the existing genetic variation as well as molecular mechanisms underlying the uptake, transport, accumulation of calcium ions (Ca2+) in grains is of utmost importance for development of calcium bio-fortified crops. In this review, we have discussed molecular mechanisms involved in calcium accumulation and transport thoroughly, emphasized the role of molecular breeding, functional genomics and transgenic approaches to understand the intricate mechanism of calcium nutrition in finger millet. The objective is to provide a comprehensive up to date account of molecular mechanisms regulating calcium nutrition and highlight the significance of bio-fortification through identification of potential candidate genes and regulatory elements from finger millet to alleviate calcium malnutrition. Hence, finger millet could be used as a model system for explaining the mechanism of elevated calcium (Ca2+) accumulation in its grains and could pave way for development of nutraceuticals or designer crops. PMID:28144246

  15. Calcium Biofortification: Three Pronged Molecular Approaches for Dissecting Complex Trait of Calcium Nutrition in Finger Millet (Eleusine coracana) for Devising Strategies of Enrichment of Food Crops.

    Science.gov (United States)

    Sharma, Divya; Jamra, Gautam; Singh, Uma M; Sood, Salej; Kumar, Anil

    2016-01-01

    Calcium is an essential macronutrient for plants and animals and plays an indispensable role in structure and signaling. Low dietary intake of calcium in humans has been epidemiologically linked to various diseases which can have serious health consequences over time. Major staple food-grains are poor source of calcium, however, finger millet [Eleusine coracana (L.) Gaertn.], an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Understanding the existing genetic variation as well as molecular mechanisms underlying the uptake, transport, accumulation of calcium ions (Ca(2+)) in grains is of utmost importance for development of calcium bio-fortified crops. In this review, we have discussed molecular mechanisms involved in calcium accumulation and transport thoroughly, emphasized the role of molecular breeding, functional genomics and transgenic approaches to understand the intricate mechanism of calcium nutrition in finger millet. The objective is to provide a comprehensive up to date account of molecular mechanisms regulating calcium nutrition and highlight the significance of bio-fortification through identification of potential candidate genes and regulatory elements from finger millet to alleviate calcium malnutrition. Hence, finger millet could be used as a model system for explaining the mechanism of elevated calcium (Ca(2+)) accumulation in its grains and could pave way for development of nutraceuticals or designer crops.

  16. Effect of Hypoxia on the Calcium and Magnesium Content, Lipid Peroxidation Level, and Ca2+-ATPase Activity of Syncytiotrophoblast Plasma Membranes from Placental Explants

    Directory of Open Access Journals (Sweden)

    Delia I. Chiarello

    2014-01-01

    Full Text Available In the current study the possible relationship between the Ca2+/Mg2+ ratio of human syncytiotrophoblast plasma membranes and their lipid peroxidation and Ca2+-ATPase activity was determined. Syncytiotrophoblast plasma membranes of placental explants cultured under hypoxia increased their lipid peroxidation and Ca2+ content, diminished their Ca2+-ATPase activity, and kept their Mg2+ content unchanged. Membranes preincubated with different concentrations of Ca2+ increased their Ca2+ content without changes in their Mg2+ content. There is a direct relationship between Ca2+ content and lipid peroxidation of the membranes, as well as an inverse relationship between their Ca2+ content and Ca2+-ATPase activity. On the contrary, preincubation of membranes with different concentrations of Mg2+ showed a higher Mg2+ content without changing their lipid peroxidation and Ca2+-ATPase activity. Explants cultured under hypoxia in the presence of 4 mM MgSO4 showed similar values of lipid peroxidation and Ca2+-ATPase activity of their membranes compared to those of explants cultured under normoxia. Increased Ca2+ content of the membranes by interacting with negatively charged phospholipids could result in destabilizing effects of the membrane structure, exposing hydrocarbon chains of fatty acids to the action of free radicals. Mg2+ might exert a stabilizing effect of the membranes, avoiding their exposure to free radicals.

  17. A novel calcium sensor stimulating inositol phosphate formation and [Ca2+](i) signaling expressed by GCT23 osteoclast-like cells

    NARCIS (Netherlands)

    Seuwen, K; Boddeke, HGWM; Migliaccio, S; Perez, M; Taranta, A; Teti, A

    1999-01-01

    Osteoclast activity is inhibited by elevated [Ca2+](o); however. the: underlying molecular mechanism is unknown. We used the human osteoclast-like cells GCT23 to elucidate their cation-sensing properties. Cells responded to elevated [Ca2+](o) with rapid concentration-dependent [Ca2+](i) transients

  18. A novel calcium sensor stimulating inositol phosphate formation and [Ca(2+)](i) signaling expressed by GCT23 osteoclast-like cells

    NARCIS (Netherlands)

    Seuwen, K.; Boddeke, H.G.W.M.; Migliaccio, S.; Perez, M.; Taranta, A.; Teti, A.

    1999-01-01

    Osteoclast activity is inhibited by elevated [Ca2+](o); however, the underlying molecular mechanism is unknown. We used the human osteoclast-like cells GCT23 to elucidate their cation-sensing properties. Cells responded to elevated [Ca2+](o) with rapid concentration-dependent [Ca2+](i) transients

  19. Role of calcium in the constriction of isolated cerebral arteries

    Energy Technology Data Exchange (ETDEWEB)

    Wendling, W.W.

    1987-01-01

    Calcium entry blockers (CEB) have been used in the experimental treatment or prevention of many cerebrovascular disorders including stroke, post-ischemic hypoperfusion after cardiac arrest, cerebral vasospasm after subarachnoid hemorrhage, and migraine headache. However, the mechanism of action of these drugs on the cerebral circulation is poorly understood. This study examined the effects of calcium antagonists, Ca/sup 2 +/-deficient solutions, and vasocostrictors on cerebrovascular tone and /sup 45/Ca fluxes, to determine the role of calcium in cerebral arterial constriction. A Scatchard plot of /sup 45/Ca binding to BMCA showed that Ca/sup 2 +/ was bound at either low or high affinity binding sties. The four vasoconstrictors (potassium, serotonin, PGF/sub 2 ..cap alpha../, or SQ-26,655) each increased low affinity /sup 45/Ca uptake into BMCA. The results demonstrate that: (1) Potassium and serotonin constrict BMCA mainly by promoting Ca/sup 2 +/ influx through CEB-sensitive channels; (2) PGF/sub 2 ..cap alpha../ and SQ-26,655 constrict BMCA in part by promoting Ca/sup 2 +/ influx through CEB-sensitive channels, and in part by releasing Ca/sup 2 +/ from depletable internal stores; (3) The major action of CEB on BMCA is to block vasoconstrictor-induced Ca/sup 2 +/ uptake through both potential-operated (K/sup +/-stimulated) and receptor-operated channels.

  20. Immunological evaluation of a DNA cocktail vaccine with co-delivery of calcium phosphate nanoparticles (CaPNs) against the Toxoplasma gondii RH strain in BALB/c mice.

    Science.gov (United States)

    Rahimi, Mohammad Taghi; Sarvi, Shahabeddin; Sharif, Mahdi; Abediankenari, Saeid; Ahmadpour, Ehsan; Valadan, Reza; Ramandie, Mahdi Fasihi-; Hosseini, Seyed-Abdollah; Daryani, Ahmad

    2017-02-01

    Many recent studies have been conducted to evaluate protective immunity mediated by DNA vaccines against toxoplasmosis. Cocktail DNA vaccines showed better immune responses compared to single vaccines. The objective of the current study was to evaluate the protective efficacy of rhomboid 4 (ROM4) and cocktail DNA vaccines (ROM4 + GRA14) of the Toxoplasma gondii RH strain with or without coated calcium phosphate nanoparticles (CaPNs) as the adjuvant to improve the immunogenicity against the T. gondii RH strain in BALB/c mice. Cocktail DNA vaccines of pcROM4 + pcGRA14 of the T. gondii RH strain were constructed. CaPNs were synthesized and the cocktail DNA vaccine was coated with the adjuvant of CaPNs. Immunogenicity and the protective effects of cocktail DNA vaccines with or without CaPNs against lethal challenge were evaluated in BALB/c mice. pcROM4 and cocktail DNA vaccine coated with CaPNs significantly enhanced cellular and humoral immune responses against Toxoplasma compared to pcROM4 and cocktail DNA vaccine without CaPNs (p < 0.05). These findings indicate that the survival time of immunized mice after challenge with the RH strain of T. gondii was increased compared to that of controls and the DNA vaccine provided significant protection in mice (p < 0.05). The CaPN-based cocktail DNA vaccine of pcROM4 + pcGRA14 showed the longest survival time compared to the other groups. Co-immunization with CaPN-based cocktail DNA vaccine (pcROM4 + pcGRA14) boosted immune responses and increased the protective efficacy against acute toxoplasmosis in BALB/c mice compared to both single gene and bivalent DNA vaccine without nano-adjuvants.

  1. 热化学法制备CaTiO3涂层及涂层的生物相容性%Biocompatibility of calcium-titanate coating prepared by thermochemical treatment

    Institute of Scientific and Technical Information of China (English)

    黄晶; 蓝琳; 肖东琴; 罗会涛; 智伟; 段可; 翁杰; 张聪

    2011-01-01

    背景:钛酸钙(CaTiO3)作为一种有前途的涂层,应用于钛基医用植入体表面.目的:通过一种简单的热化学处理技术,Ti6Al4V基体上制备均匀的CaTiO3涂层,时通过培养成骨细胞观察涂层生物相容性.方法:通过将Ti6Al4V基体埋于无水硝酸钙(Ca(NO3)2)粉末中,且升高温度;当温度处在Ca(NO3)2熔点以上时,Ti6Al4V基体上能够生成一层均匀的CaTiO3层.同时在热化学处理温度为570 ℃的Ti6Al4V基体材料上进行成骨细胞培养,察所制备涂层的生物相容性.结果与结论:该涂层转化只有在Ca(NO3)2熔点(561 ℃)以上时才会发生,时随着处理温度的升高,aTiO3晶体尺寸随之增大;经过热化学处理后的样品具有良好的生物相容性,成骨细胞黏附、增殖具有更好的促进作用.该方法简单、有效,制备的涂层具有良好的生物相容性,望在钛植入体表面处理中获得应用,提高金属表面与细胞、组织的相容性.%BACKGROUND:Calcium-titanate (CaTiO3) is a promising coating candidate on titanium biomedical implants.OBJECRIVE:To prepare uniform CaTiO3 coatings on Ti6Al4V substrates by a simple thermochemical surface transformation technique and to evaluate its biocompatibility by in vitro culture of rat osteoblasts.METHODS:Ti6Al4V substrates were embedded in anhydrous calcium nitrate powders and the temperature was increased;reaction between the molten nitrate and Ti6Al4V formed a uniform layer of calcium nitrate. The biocompatibility of Ti6Al4V thermochemically treated at 570 ℃ was evaluted by in vitro culture of SD rat osteoblasts.RESULTS AND CONCLUSION:The transformation occurred only above the melting point of anhydrous calcium nitrate (561 ℃),and that the size of the calcium titanate crystals increased with the treatment temperature. Proliferation and adhesion of osteoblasts was promoted on the thermochemically treated substrates. This technique is simple and efficient, and may find applications in the

  2. Effect of CaF2 on Interfacial Phenomena of High Alumina Refractories with Al Alloy

    Science.gov (United States)

    Koshy, Pramod; Gupta, Sushil; Sahajwalla, Veena; Edwards, Phil

    2008-08-01

    An experimental study was conducted to investigate the interfacial phenomena between Al-alloy and industrial grade high alumina refractories containing varying contents of CaF2 at 1250 °C. Interfacial reaction products and phases formed in the heat-treated refractory samples were characterized using electron probe microanalysis (EPMA) and X-ray diffraction (XRD), respectively, while interfacial phenomena including dynamic wetting behavior were analyzed using the sessile drop technique. Refractories containing less than 5 wt pct CaF2 showed good resistance to reactions with the molten alloy, due to the dominance of corundum, and the presence of anorthite at the interface. However, with a further increase in the additive content, a glassy matrix of anorthite with CaF2 was formed. Formation of this phase significantly increased the intensity of reactions resulting in the buildup of an interfacial layer. The study thus revealed the strong catalytic effect of CaF2 on reactions of high alumina refractories with Al-alloy.

  3. Backbone and side-chain resonance assignments of (Ca(2+))4-calmodulin bound to beta calcineurin A CaMBD peptide.

    Science.gov (United States)

    Fowler, C Andrew; Núñez Hernandez, Maria F; O'Donnell, Susan E; Yu, Liping; Shea, Madeline A

    2017-08-16

    Calcineurin (CaN) is a heterodimeric and highly conserved serine/threonine phosphatase (PP2B) that plays a critical role in coupling calcium signals to physiological processes including embryonic cardiac development, NF-AT-regulated gene expression in immune responses, and apoptosis. The catalytic subunit (CaNA) has three isoforms (α, β, and γ,) in humans and seven isoforms in Paramecium. In all eukaryotes, the EF-hand protein calmodulin (CaM) regulates CaN activity in a calcium-dependent manner. The N- and C-domains of CaM (CaMN and CaMC) recognize a CaM-binding domain (CaMBD) within an intrinsically disordered region of CaNA that precedes the auto-inhibitory domain (AID) of CaNA. Here we present nearly complete (1)H, (13)C, and (15)N resonance assignments of (Ca(2+))4-CaM bound to a peptide containing the CaMBD sequence in the beta isoform of CaNA (βCaNA-CaMBDp). Its secondary structure elements predicted from the assigned chemical shifts were in good agreement with those observed in the high-resolution structures of (Ca(2+))4-CaM bound to CaMBDs of multiple enzymes. Based on the reported literature, the CaMBD of the α isoform of CaNA can bind to CaM in two opposing orientations which may influence the regulatory function of CaM. Because a high resolution structure of (Ca(2+))4-CaM bound to βCaNA-CaMBDp has not been reported, our studies serve as a starting point for determining the solution structure of this complex. This will demonstrate the preferred orientation of (Ca(2+))4-CaM on the CaMBD as well as the orientations of CaMN and CaMC relative to each other and to the AID of βCaNA.

  4. Effect of NH4-N/P and Ca/P molar ratios on the reactive crystallization of calcium phosphates for phosphorus recovery from wastewater

    Science.gov (United States)

    Vasenko, Liubov; Qu, Haiyan

    2017-02-01

    In this work, the effects of operational parameters, initial phosphorus concentration and molar ratios of Ca/P and NH4-N/P (further in the text N/P), on the nature and purity of precipitated phosphorus products have been investigated in an artificial system that mimics the supernatant in wastewater treatment plants. Metastable zone width was determined for two target phosphorus products: DCPD (dicalcium phosphate dihydrate) and HAp (hydroxyapatite) in the range of pH 4.5 - 7. HAp crystallizes at final pH higher than 6.3 while DCPD crystallizes at the final pH in between 4.7 and 5.7. At the final pH 5.7 - 6.3 and at pH lower than 4.7 the mixtures of DCPD and HAp were obtained. It was observed that N/P ratio affects not only the metastable zone width but also the kinetics of crystal growth for both DCPD and HAp: the higher the N/P ratio, the lower is the growth rate for both P-products. Investigation of the effect of Ca/P and N/P ratios on the nucleation and crystal growth of DCPD in batch crystallization experiment was performed. It showed that at high supersaturation level, crystals with larger median size can be obtained at higher N/P ratio despite the negative effects of N/P ratio on the growth rate of the crystals.

  5. 固体碱CaO催化橡胶籽油制备生物柴油的研究%Preparation of biodiesel from rubber seed oil catalyzed by solid base of calcium oxide

    Institute of Scientific and Technical Information of China (English)

    刘守庆; 李雪梅; 赵雷修; 郑志锋; 刘祥义

    2012-01-01

    研究了固体碱CaO催化橡胶籽油与甲醇进行酯交换反应制备生物柴油的工艺条件.结果表明,焙烧温度为800℃,焙烧时间为2h时,由CaCO3分解制得的CaO具有最高的反应活性.以此CaO为催化剂制备橡胶籽油生物柴油的最佳工艺条件为:催化剂CaO用量为油质量的1.5%,反应温度65℃,醇油摩尔比为15∶1,反应时间6h.在此反应条件下,橡胶籽油生物柴油转化率为90.70%.%The preparation technique of biodiesel from rubber seed oil catalyzed by solid base of calcium oxide was studied. The result indicated that the optimal conditions for catalyst preparation of calcium oxide and transesterfication of rubber seed oil were as follows: calcination temperature 800 ℃,calcination time 2 h,catalyst dosage 1.5% (based on the mass of oil) ,the molar rate of methanol to oil 15:1 ,reaction temperature 65℃ , reaction time 6 h. Under the optimal conditions, the transesterification rate of biodiesel from rubber seed oil was 90.70%.

  6. Development of microscopic systems for high-speed dual-excitation ratiometric Ca2+ imaging.

    Science.gov (United States)

    Fukano, Takashi; Shimozono, Satoshi; Miyawaki, Atsushi

    2008-08-01

    For quantitative measurements of Ca(2+) concentration ([Ca(2+)]), ratiometric dyes are preferable, because the use of such dyes allows for correction of uneven loading or partitioning of dye within the cell as well as variations in cell thickness. Although dual-excitation ratiometric dyes for measuring [Ca(2+)], such as Fura-2, Fura-Red, and ratiometric-pericam, are widely used for a variety of applications, it has been difficult to use them for monitoring very fast Ca(2+) dynamics or