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Sample records for calcium ca2o-sensing receptor

  1. Calcium-sensing receptor (CaSR): pharmacological properties and signaling pathways.

    Science.gov (United States)

    Conigrave, Arthur D; Ward, Donald T

    2013-06-01

    In this article we consider the mechanisms by which the calcium-sensing receptor (CaSR) induces its cellular responses via the control (activation or inhibition) of signaling pathways. We consider key features of CaSR-mediated signaling including its control of the heterotrimeric G-proteins Gq/11, Gi/o and G12/13 and the downstream consequences recognizing that very few CaSR-mediated cell phenomena have been fully described. We also consider the manner in which the CaSR contributes to the formation of specific signaling scaffolds via peptide recognition sequences in its intracellular C-terminal along with the origins of its high level of cooperativity, particularly for Ca(2+)o, and its remarkable resistance to desensitization. We also consider the nature of the mechanisms by which the CaSR controls oscillatory and sustained Ca(2+)i mobilizing responses and inhibits or elevates cyclic adenosine monophosphate (cAMP) levels dependent on the cellular and signaling context. Finally, we consider the diversity of the receptor's ligands, ligand binding sites and broader compartment-dependent physiological roles leading to the identification of pronounced ligand-biased signaling for agonists including Sr(2+) and modulators including l-amino acids and the clinically effective calcimimetic cinacalcet. We note the implications of these findings for the development of new designer drugs that might target the CaSR in pathophysiological contexts beyond those established for the treatment of disorders of calcium metabolism. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. 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

    calcium activates the NLRP3 inflammasome via stimulation of G protein-coupled calcium sensing receptors. Activation is mediated by signalling through the calcium-sensing receptor and GPRC6A via the phosphatidyl inositol/Ca(2+) pathway. The resulting increase in the intracellular calcium concentration......, 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....

  3. Solubility of calcium in CaO-CaCl2

    International Nuclear Information System (INIS)

    Perry, G.S.; Shaw, S.J.

    1991-06-01

    The Direct Oxide Reduction (DOR) process is well established as a process to produce plutonium metal from plutonium dioxide by reaction with calcium. Calcium chloride is added to dissolve the calcium oxide produced, allowing the metal to coalesce into a button. Since calcium metal melts at 840 0 C and DOR can take place successfully below this temperature, it is likely calcium dissolved in calcium chloride reacts with the plutonium dioxide. The solubility of calcium in calcium chloride is reasonably well established but the effect of the CaO formed during the DOR process on the solubility of calcium has not been previously determined. For this reason the solubility of calcium in CaCl 2 -CaO melts at 800 o C has been studied. The solubility decreases from 2.7 mol % in CaCl 2 to 0.4 mol % in 9 mol % CaO-CaCl 2 . (author)

  4. Activation of calcium-sensing receptor increases TRPC3 expression in rat cardiomyocytes

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    Feng, Shan-Li [Department of Clinical Laboratory, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086 (China); Sun, Ming-Rui [Department of Pharmacology, Qiqihaer Medical College, Qiqihaer 160001 (China); Li, Ting-Ting; Yin, Xin [Department of Clinical Laboratory, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086 (China); Xu, Chang-Qing [Department of Pathophysiology, Harbin Medical University, Harbin 150086 (China); Sun, Yi-Hua, E-mail: syh200415@126.com [Department of Clinical Laboratory, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086 (China)

    2011-03-11

    Research highlights: {yields} Calcium-sensing receptor (CaR) activation stimulates TRP channels. {yields} CaR promoted transient receptor potential C3 (TRPC3) expression. {yields} Adult rat ventricular myocytes display capacitative calcium entry (CCE), which was operated by TRPCs. {yields} TRPC channels activation induced by CaR activator sustained the increased [Ca{sup 2+}]{sub i} to evoke cardiomyocytes apoptosis. -- Abstract: Transient receptor potential (TRP) channels are expressed in cardiomyocytes, which gate a type of influx of extracellular calcium, the capacitative calcium entry. TRP channels play a role in mediating Ca{sup 2+} overload in the heart. Calcium-sensing receptors (CaR) are also expressed in rat cardiac tissue and promote the apoptosis of cardiomyocytes by Ca{sup 2+} overload. However, data about the link between CaR and TRP channels in rat heart are few. In this study, reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting were used to examine the expression of the TRP canonical proteins TRPC1 and TRPC3 in adult and neonatal rat cardiomyocytes. Laser scan confocal microscopy was used to detect intracellular [Ca{sup 2+}]{sub i} levels in isolated adult rat ventricular myocytes. The results showed that, in adult rat cardiomyocytes, the depletion of Ca{sup 2+} stores in the endoplasmic/sarcoplasmic reticulum (ER/SR) by thapsigargin induced a transient increase in [Ca{sup 2+}]{sub i} in the absence of [Ca{sup 2+}]{sub o} and the subsequent restoration of [Ca{sup 2+}]{sub o} sustained the increased [Ca{sup 2+}]{sub i} for a few minutes, whereas, the persisting elevation of [Ca{sup 2+}]{sub i} was reduced in the presence of the TRPC inhibitor SKF96365. The stimulation of CaR by its activator gadolinium chloride (GdCl{sub 3}) or spermine also resulted in the same effect and the duration of [Ca{sup 2+}]{sub i} increase was also shortened in the absence of [Ca{sup 2+}]{sub o}. In adult and neonatal rat cardiomyocytes, GdCl{sub 3

  5. Molecular Basis of the Extracellular Ligands Mediated Signaling by the Calcium Sensing Receptor

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    Chen Zhang

    2016-09-01

    Full Text Available Ca2+-sensing receptors (CaSRs play a central role in regulating extracellular calcium concentration ([Ca2+]o homeostasis and many (pathophysiological processes in multiple organs. This regulation is orchestrated by a cooperative response to extracellular stimuli such as small changes in Ca2+, Mg2+, amino acids and other ligands. In addition, CaSR is a pleiotropic receptor regulating several intracellular signaling pathways, including calcium mobilization and intracellular calcium oscillation. Nearly 200 mutations and polymorphisms have been found in CaSR in relation to a variety of human disorders associated with abnormal Ca2+ homeostasis. In this review, we summarize efforts directed at identifying binding sites for calcium and amino acids. Both homotropic cooperativity among multiple calcium binding sites and heterotropic cooperativity between calcium and amino acid were revealed using computational modeling, predictions, and site-directed mutagenesis coupled with functional assays. The hinge region of the bilobed Venus flytrap (VFT domain of CaSR plays a pivotal role in coordinating multiple extracellular stimuli, leading to cooperative responses from the receptor. We further highlight the extensive number of disease-associated mutations that have also been shown to affect CaSR’s cooperative action via several types of mechanisms. These results provide insights into the molecular bases of the structure and functional cooperativity of this receptor and other members of family C of the G protein-coupled receptors (cGPCRs in health and disease states, and may assist in the prospective development of novel receptor-based therapeutics.

  6. ZnO:Ca nanopowders with enhanced CO2 sensing properties

    International Nuclear Information System (INIS)

    Dhahri, R; Hjiri, M; El Mir, L; Fazio, E; Neri, F; Barreca, F; Donato, N; Bonavita, A; Leonardi, S G; Neri, G

    2015-01-01

    Calcium doped ZnO (CZO) nanopowders with [Ca]/[Zn] atomic ratios of 0, 0.01, 0.03 and 0.05 were prepared via a sol-gel route and characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy (FT-IR). Characterization data showed that undoped and Ca-doped ZnO samples have a hexagonal wurtzite structure with a slight distortion of the ZnO lattice and no extra secondary phases, suggesting the substitution of Ca ions in the ZnO structure.Chemo-resistive devices based on a thick layer of the synthesized CZO nanoparticles were fabricated and their electrical and sensing properties towards CO 2 were investigated. Sensing tests have demonstrated that Ca loading is the key factor in modulating the electrical properties and strongly improving the response of ZnO matrix towards CO 2 . An increased CO 2 adsorption with Ca loading has been also evidenced by FT-IR, providing the basis for the formulation of a plausible mechanism for CO 2 sensing operating on these sensors. (paper)

  7. 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.

  8. Calcium-sensing receptor: Role in health and disease

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    R V Thakker

    2012-01-01

    Full Text Available The calcium-sensing receptor (CaSR is a 1,078 amino acid G protein-coupled receptor (GPCR, which is predominantly expressed in the parathyroids and kidney. The CaSR allows regulation of parathyroid hormone (PTH secretion and renal tubular calcium re-absorption in response to alterations in extracellular calcium concentrations. Loss-of-function CaSR mutations have been reported in the hypercalcemic disorders of familial benign (hypocalciuric hypercalcemia (FBH or FHH, neonatal severe primary hyperparathyroidism (NSHPT, and adult primary hyperparathyroidism. However, some individuals with loss-of-function CaSR mutations remain normocalcemic. Gain-of-function CaSR mutations have been shown to result in autosomal-dominant hypocalcemia with hypercalciuria (ADHH and Bartter′s syndrome type V. CaSR auto-antibodies have been found in FHH patients who did not have loss-of-function CaSR mutations and in patients with an acquired form (i.e. autoimmune of hypoparathyroidism. Thus, abnormalities of the CaSR are associated with 4 hypercalcemic and 3 hypocalcemic disorders.

  9. Diverse roles of extracellular calcium-sensing receptor in the central nervous system

    DEFF Research Database (Denmark)

    Bandyopadhyay, Sanghamitra; Tfelt-Hansen, Jacob; Chattopadhyay, Naibedya

    2010-01-01

    The G-protein-coupled calcium-sensing receptor (CaSR), upon activation by Ca(2+) or other physiologically relevant polycationic molecules, performs diverse functions in the brain. The CaSR is widely expressed in the central nervous system (CNS) and is characterized by a robust increase in its...... to astrocytic or neuronal lineages. In adult CNS, CaSR has broad relevance in maintaining local ionic homeostasis. CaSR shares an evolutionary relationship with the metabotropic glutamate receptor and forms heteromeric complexes with the type B-aminobutyric acid receptor subunits that affects its cell surface...

  10. Ordering of calcium and vacancies in calcium catapleiite CaZr[Si3O9] • 2H2O

    International Nuclear Information System (INIS)

    Aksenov, S. M.; Portnov, A. M.; Chukanov, N. V.; Rastsvetaeva, R. K.; Nelyubina, Yu. V.; Kononkova, N. N.; Akimenko, M. I.

    2016-01-01

    A sample of holotypic calcium catapleiite from the Burpala alkaline massif (Northern Baikal, Russia) is studied by single crystal X-ray analysis at 120 K and IR spectroscopy. The empirical formula of calcium catapleiite is Ca 0.97 Na 0.02 Zr 1.01 Si 3 O 9 • 2H 2 O (Z = 4). The X-ray diffraction study confirms the orthorhombic unit cell with the following parameters: a = 7.406(1), b = 12.687(1), and c = 10.112(1) Å; V = 950.1(2) Å 3 ; space group Pbnn. The crystal structure is refined in the anisotropic approximation of atomic displacement parameters using 1177 reflections with I > 2σ(I) to the final R = 2.91%. The structure of calcium catapleiite under study is based on the microporous heteropolyhedral framework formed by ZrO 6 octahedra and threemembered silicon–oxygen rings [Si 3 O 9 ]. It is on the whole analogous to the structures of the samples studied earlier, but differs from them by a high degree of ordering of calcium and vacancies at extraframework positions. The distribution of calcium over Ca1 and Ca2 positions in the calcium catapleiite structure leads to the formation of zigzag chains of the …Ca1–Zr–Ca1–Zr… and …Ca2–h–Ca2–□… types. Low occupancy of the Ca2 position and its alternation with the vacancy are prerequisites for potential Ca 2+ cationic conduction.

  11. The Calcium-Sensing Receptor in Health and Disease.

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    Díaz-Soto, G; Rocher, A; García-Rodríguez, C; Núñez, L; Villalobos, C

    2016-01-01

    The extracellular calcium-sensing receptor (CaSR) is a unique G protein-coupled receptor (GPCR) activated by extracellular Ca 2+ and by other physiological cations including Mg 2+ , amino acids, and polyamines. CaSR is the most important master controller of the extracellular Ca 2+ homeostatic system being expressed at high levels in the parathyroid gland, kidney, gut and bone, where it regulates parathyroid hormone (PTH) secretion, vitamin D synthesis, and Ca 2+ absorption and resorption, respectively. Gain and loss of function mutations in the CaSR are responsible for severe disturbances in extracellular Ca 2+ metabolism. CaSR agonists (calcimimetics) and antagonists (calcilytics) are in use or under intense research for treatment of hyperparathyroidism secondary to kidney failure and hypocalcemia with hypercalciuria, respectively. Expression of the CaSR extends to other tissues and systems beyond the extracellular Ca 2+ homeostatic system including the cardiovascular system, the airways, and the nervous system where it may play physiological functions yet to be fully understood. As a consequence, CaSR has been recently involved in different pathologies including uncontrolled blood pressure, vascular calcification, asthma, and Alzheimer's disease. Finally, the CaSR has been shown to play a critical role in cancer either contributing to bone metastasis and/or acting as a tumor suppressor in some forms of cancer (parathyroid cancer, colon cancer, and neuroblastoma) and as oncogene in others (breast and prostate cancers). Here we review the role of CaSR in health and disease in calciotropic tissues and others beyond the extracellular calcium homeostatic system. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Physiological studies in heterozygous calcium sensing receptor (CaSR gene-ablated mice confirm that the CaSR regulates calcitonin release in vivo

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    Kovacs Christopher S

    2004-04-01

    Full Text Available Abstract Background The calcium sensing receptor (CaSR regulates serum calcium by suppressing secretion of parathyroid hormone; it also regulates renal tubular calcium excretion. Inactivating mutations of CaSR raise serum calcium and reduce urine calcium excretion. Thyroid C-cells (which make calcitonin express CaSR and may, therefore, be regulated by it. Since calcium stimulates release of calcitonin, the higher blood calcium caused by inactivation of CaSR should increase serum calcitonin, unless CaSR mutations alter the responsiveness of calcitonin to calcium. To demonstrate regulatory effects of CaSR on calcitonin release, we studied calcitonin responsiveness to calcium in normal and CaSR heterozygous-ablated (Casr+/- mice. Casr+/- mice have hypercalcemia and hypocalciuria, and live normal life spans. Each mouse received either 500 μl of normal saline or one of two doses of elemental calcium (500 μmol/kg or 5 mmol/kg by intraperitoneal injection. Ionized calcium was measured at baseline and 10 minutes, and serum calcitonin was measured on the 10 minute sample. Results At baseline, Casr+/- mice had a higher blood calcium, and in response to the two doses of elemental calcium, had greater increments and peak levels of ionized calcium than their wild type littermates. Despite significantly higher ionized calcium levels, the calcitonin levels of Casr+/- mice were consistently lower than wild type at any ionized calcium level, indicating that the dose-response curve of calcitonin to increases in ionized calcium had been significantly blunted or shifted to the right in Casr+/- mice. Conclusions These results confirm that the CaSR is a physiological regulator of calcitonin; therefore, in response to increases in ionized calcium, the CaSR inhibits parathyroid hormone secretion and stimulates calcitonin secretion.

  13. 40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Calcium hydroxide oxide silicate (Ca6... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate (Ca6(OH)2O2... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...

  14. Structural mechanism of ligand activation in human calcium-sensing receptor

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    Geng, Yong; Mosyak, Lidia; Kurinov, Igor; Zuo, Hao; Sturchler, Emmanuel; Cheng, Tat Cheung; Subramanyam, Prakash; Brown, Alice P.; Brennan, Sarah C.; Mun, Hee-chang; Bush, Martin; Chen, Yan; Nguyen, Trang X.; Cao, Baohua; Chang, Donald D.; Quick, Matthias; Conigrave, Arthur D.; Colecraft, Henry M.; McDonald, Patricia; Fan, Qing R.

    2016-07-19

    Human calcium-sensing receptor (CaSR) is a G-protein-coupled receptor (GPCR) that maintains extracellular Ca2+homeostasis through the regulation of parathyroid hormone secretion. It functions as a disulfide-tethered homodimer composed of three main domains, the Venus Flytrap module, cysteine-rich domain, and seven-helix transmembrane region. Here, we present the crystal structures of the entire extracellular domain of CaSR in the resting and active conformations. We provide direct evidence that L-amino acids are agonists of the receptor. In the active structure, L-Trp occupies the orthosteric agonist-binding site at the interdomain cleft and is primarily responsible for inducing extracellular domain closure to initiate receptor activation. Our structures reveal multiple binding sites for Ca2+and PO43-ions. Both ions are crucial for structural integrity of the receptor. While Ca2+ions stabilize the active state, PO43-ions reinforce the inactive conformation. The activation mechanism of CaSR involves the formation of a novel dimer interface between subunits.

  15. Testin, a novel binding partner of the calcium-sensing receptor, enhances receptor-mediated Rho-kinase signalling

    International Nuclear Information System (INIS)

    Magno, Aaron L.; Ingley, Evan; Brown, Suzanne J.; Conigrave, Arthur D.; Ratajczak, Thomas; Ward, Bryan K.

    2011-01-01

    Highlights: → A yeast two-hybrid screen revealed testin bound to the calcium-sensing receptor. → The second zinc finger of LIM domain 1 of testin is critical for interaction. → Testin bound to a region of the receptor tail important for cell signalling. → Testin and receptor interaction was confirmed in mammalian (HEK293) cells. → Overexpression of testin enhanced receptor-mediated Rho signalling in HEK293 cells. -- Abstract: The calcium-sensing receptor (CaR) plays an integral role in calcium homeostasis and the regulation of other cellular functions including cell proliferation and cytoskeletal organisation. The multifunctional nature of the CaR is manifested through ligand-dependent stimulation of different signalling pathways that are also regulated by partner binding proteins. Following a yeast two-hybrid library screen using the intracellular tail of the CaR as bait, we identified several novel binding partners including the focal adhesion protein, testin. Testin has not previously been shown to interact with cell surface receptors. The sites of interaction between the CaR and testin were mapped to the membrane proximal region of the receptor tail and the second zinc-finger of LIM domain 1 of testin, the integrity of which was found to be critical for the CaR-testin interaction. The CaR-testin association was confirmed in HEK293 cells by coimmunoprecipitation and confocal microscopy studies. Ectopic expression of testin in HEK293 cells stably expressing the CaR enhanced CaR-stimulated Rho activity but had no effect on CaR-stimulated ERK signalling. These results suggest an interplay between the CaR and testin in the regulation of CaR-mediated Rho signalling with possible effects on the cytoskeleton.

  16. Calcium Overload Accelerates Phosphate-Induced Vascular Calcification Via Pit-1, but not the Calcium-Sensing Receptor.

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    Masumoto, Asuka; Sonou, Tomohiro; Ohya, Masaki; Yashiro, Mitsuru; Nakashima, Yuri; Okuda, Kouji; Iwashita, Yuko; Mima, Toru; Negi, Shigeo; Shigematsu, Takashi

    2017-07-01

    Vascular calcification (VC) is a risk factor of cardiovascular and all-cause mortality in patients with chronic kidney disease (CKD). CKD-mineral and bone metabolism disorder is an important problem in patients with renal failure. Abnormal levels of serum phosphate and calcium affect CKD-mineral and bone metabolism disorder and contribute to bone disease, VC, and cardiovascular disease. Hypercalcemia is a contributing factor in progression of VC in patients with CKD. However, the mechanisms of how calcium promotes intracellular calcification are still unclear. This study aimed to examine the mechanisms underlying calcium-induced calcification in a rat aortic tissue culture model. Aortic segments from 7-week-old male Sprague-Dawley rats were cultured in serum-supplemented medium for 10 days. We added high calcium (HiCa; calcium 3.0 mM) to high phosphate (HPi; phosphate 3.8 mM) medium to accelerate phosphate and calcium-induced VC. We used phosphonoformic acid and the calcimimetic R-568 to determine whether the mechanism of calcification involves Pit-1 or the calcium-sensing receptor. Medial VC was significantly augmented by HPi+HiCa medium compared with HPi alone (300%, p<0.05), and was associated with upregulation of Pit-1 protein. Pit-1 protein concentrations in HPi+HiCa medium were greater than those in HPi medium. Phosphonoformic acid completely negated the augmentation of medial VC induced by HPi+HiCa. R-568 had no additive direct effect on medial VC. These results indicated that exposure to HPi+HiCa accelerates medial VC, and this is mediated through Pit-1, not the calcium-sensing receptor.

  17. The calcium-sensing receptor and the reproductive system

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    Isabella Ellinger

    2016-08-01

    Full Text Available Active placental transport of maternal serum calcium (Ca2+ to the offspring is pivotal for proper development of the fetal skeleton as well as various organ systems. Moreover, extracellular Ca2+ levels impact on distinct processes in mammalian reproduction. The calcium-sensing receptor (CaSR translates changes in extracellular Ca2+-concentrations into cellular reactions. This review summarizes current knowledge on the expression of CaSR and its putative functions in reproductive organs. CaSR was detected in placental cells mediating materno-fetal Ca2+-transport such as the the murine intraplacental yolk sac and the human syncytiotrophoblast. As shown in casr knock-out mice, ablation of CaSR downregulates transplacental Ca2+-transport. Receptor expression was reported in human and rat ovarian surface epithelial cells, where CaSR activation stimulates cell proliferation. In follicles of various species a role of CaSR activation in oocyte maturation was suggested. Based on studies in avian follicles, the activation of CaSR expressed in granulosa cells may support the survival of follicles after their selection. CaSR in rat and equine sperms was functionally linked to sperm motility and sperm capacitation. Implantation involves complex interactions between the blastocyst and the uterine epithelium. During early pregnancy, CaSR expression at the implantation site as well as in decidual cells indicates that CaSR is important for blastocyst implantation and decidualization in the rat uterus. Localization of CaSR in human extravillous cytotrophoblasts suggests a role of CaSR in placentation. Overall, evidence for functional involvement of CaSR in physiologic mammalian reproductive processes exists. Moreover, several studies reported altered expression of CaSR in cells of reproductive tissues under pathologic conditions. However, in many tissues we still lack knowledge on physiological ligands activating CaSR, CaSR-linked G-proteins, activated

  18. Functional characterization of calcium sensing receptor polymorphisms and absence of association with indices of calcium homeostasis and bone mineral density.

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    Harding, Brian; Curley, Alan J; Hannan, Fadil M; Christie, Paul T; Bowl, Michael R; Turner, Jeremy J O; Barber, Mathew; Gillham-Nasenya, Irina; Hampson, Geeta; Spector, Tim D; Thakker, Rajesh V

    2006-11-01

    Associations between calcium-sensing receptor (CaSR) polymorphisms and serum calcium, PTH and bone mineral density (BMD) have been reported by six studies. However, three other studies have failed to detect such associations. We therefore further investigated three CaSR coding region polymorphisms (Ala986Ser, Arg990Gly and Gln1011Glu) for associations with indices of calcium homeostasis and BMD and for alterations in receptor function. One hundred and ten adult, Caucasian, female, dizygotic twin pairs were investigated for associations between the three CaSR polymorphisms and serum calcium, albumin, PTH, 25-hydroxyvitamin D(3) (25OHD(3)), 1,25-dihydroxyvitamin D(3)[1,25(OH)(2)D(3)], urinary calcium excretion and BMD. Each polymorphic CaSR was also transfected into HEK293 cells and functionally evaluated. There was a lack of association between each of these three CaSR polymorphisms and serum calcium corrected for albumin, PTH, 25OHD(3), 1,25(OH)(2)D(3), urinary calcium excretion or BMD at the hip, forearm and lumbar spine. These findings were supported by a lack of functional differences in the dose-response curves of the CaSR variants, with the EC(50) values (mean +/- SEM) of the wild-type (Ala986/Arg990/Gln1011), Ser986, Gly990 and Glu1011 CaSR variants being 2.74 +/- 0.29 mm, 3.09 +/- 0.34 mm (P > 0.4), 2.99 +/- 0.23 mm (P > 0.4) and 2.96 +/- 0.30 mm (P > 0.5), respectively. Our study, which was sufficiently powered to detect effects that would explain up to 5%, but not less than 1%, of the variance has revealed that the three CaSR polymorphisms of the coding region have no major influence on indices of calcium homeostasis in this female population, and that they do not alter receptor function.

  19. Kokumi Substances, Enhancers of Basic Tastes, Induce Responses in Calcium-Sensing Receptor Expressing Taste Cells

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    Maruyama, Yutaka; Yasuda, Reiko; Kuroda, Motonaka; Eto, Yuzuru

    2012-01-01

    Recently, we reported that calcium-sensing receptor (CaSR) is a receptor for kokumi substances, which enhance the intensities of salty, sweet and umami tastes. Furthermore, we found that several γ-glutamyl peptides, which are CaSR agonists, are kokumi substances. In this study, we elucidated the receptor cells for kokumi substances, and their physiological properties. For this purpose, we used Calcium Green-1 loaded mouse taste cells in lingual tissue slices and confocal microscopy. Kokumi substances, applied focally around taste pores, induced an increase in the intracellular Ca2+ concentration ([Ca2+]i) in a subset of taste cells. These responses were inhibited by pretreatment with the CaSR inhibitor, NPS2143. However, the kokumi substance-induced responses did not require extracellular Ca2+. CaSR-expressing taste cells are a different subset of cells from the T1R3-expressing umami or sweet taste receptor cells. These observations indicate that CaSR-expressing taste cells are the primary detectors of kokumi substances, and that they are an independent population from the influenced basic taste receptor cells, at least in the case of sweet and umami. PMID:22511946

  20. Moessbauer characterization of calcium-ferrite oxides prepared by calcining Fe2O3 and CaO

    International Nuclear Information System (INIS)

    Hirabayashi, Daisuke; Sakai, Yoichi; Yoshikawa, Takeshi; Mochizuki, Kazuhiro; Kojima, Yoshihiro; Suzuki, Kenzi; Ohshita, Kazumasa; Watanabe, Yasuo

    2006-01-01

    Calcium ferrite oxides were prepared by calcining a mixture powder of iron- and calcium oxide. The 57 Fe-Moessbauer spectra of the calcium ferrites oxides were measured, revealing that the products should be Ca 2 Fe 2 O 5 and CaFe 2 O 4 , the ratio of which was dependent of the Fe/Ca atomic ratio of the mixture powder.

  1. Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

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    Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward

    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 PTHrP secretion and milk calcium transport with calcium availability. To test this idea genetically, we bred BLG-Cre mice with CaSR-floxed mice to ablate the CaSR specifically from mammary epithelial cells only at the onset of lactation (CaSR-cKO mice). Loss of the CaSR in the lactating mammary gland did not disrupt alveolar differentiation or milk production. However, it did increase the secretion of PTHrP into milk and decreased the transport of calcium from the circulation into milk. CaSR-cKO mice did not show accelerated bone resorption, but they did have a decrease in bone formation. Loss of the mammary gland CaSR resulted in hypercalcemia, decreased PTH secretion, and increased renal calcium excretion in lactating mothers. Finally, loss of the mammary gland CaSR resulted in decreased calcium accrual by suckling neonates, likely due to the combination of increased milk PTHrP and decreased milk calcium. These results demonstrate that the mammary gland CaSR coordinates maternal bone and calcium metabolism, calcium transport into milk, and neonatal calcium accrual during lactation. PMID:23782944

  2. Association of Calcium-Sensing Receptor (CASR rs 1801725 with Colorectal Cancer

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    Fateme Rostami

    2012-07-01

    Full Text Available Background: Calcium induces apoptosis in intestinal epithelial cells and subsequently prevents colorectal cancer through ion calcium receptor. Calcium-sensing receptor mutation reduces the expression of this receptor, and subsequently in reduces calcium transportation. Many studies have shown that Calcium-sensing receptor gene polymorphism may increase the risk of colorectal cancer. The purpose of this study is to assess the prevalence of calcium-sensing receptor polymorphisms (rs 1801725 in Iran society and to examine the role of this polymorphism in the increased risk of colorectal cancer (CRC.Materials and Methods: The research was a case-control study. 105 patients with colorectal cancer and 105 controls were randomly studied using polymerase chain reaction and restriction fragment length polymorphism. χ2 test and software 16- SPSS were used for statistical analysis.Results: In patient samples, the frequency of the genotypes TT, GT, GG in gene CASR rs 1801725 was respectively 64.8, 32.4, and 2.9 and the frequency of this polymorphism in control samples was respectively 51.2, 45.7, and 2.9. Frequency of allele G in patient samples was 0/48 and frequency of allele T was 0.25. In addition, Frequency of allele G in control samples was 0.74 and Frequency of allele T was calculated 0.19.Conclusion: The results show that calcium-sensing receptor variant (1801725 rs is not associated with increased risk of colorectal cancer.

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

    Science.gov (United States)

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

    2015-09-01

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

  4. Electrolytic recovery of calcium from molten CaO-CaCl2 salt-mix

    International Nuclear Information System (INIS)

    Mishra, B.; Olson, D.L.

    1993-01-01

    Calciothermic reduction of plutonium oxide is an industrial process for producing plutonium metal. The process is carried out in a molten calcium chloride medium which has a significantly high solubility for calcium oxide. However, the CaO-CaCl 2 salt-mix is radioactively contaminated and can not be discarded as such. Fused salt electrolysis of a simulated mix has been carried out using graphite anode and steel cathode to produce calcium. The dissolved calcium in CaCl 2 salt can be used insitu to reduce plutonium oxide. The primary difficulty in obtaining a cathodic calcium deposit was the use of graphite anose which indirectly controls all the back-reactions in the cell through which the deposited calcium is lost. A porous ceramic sheath has been used to essentially keep the anodic and cathodic products separate. The porosity of the sheath has been optimized by measuring its diffusion coefficient as a function of temperature. The influence of a porous sheath on the cell potential has been also analyzed

  5. High calcium concentration in bones promotes bone metastasis in renal cell carcinomas expressing calcium-sensing receptor.

    Science.gov (United States)

    Joeckel, Elke; Haber, Tobias; Prawitt, Dirk; Junker, Kerstin; Hampel, Christian; Thüroff, Joachim W; Roos, Frederik C; Brenner, Walburgis

    2014-02-28

    The prognosis for renal cell carcinoma (RCC) is related to a high rate of metastasis, including 30% of bone metastasis. Characteristic for bone tissue is a high concentration of calcium ions. In this study, we show a promoting effect of an enhanced extracellular calcium concentration on mechanisms of bone metastasis via the calcium-sensing receptor (CaSR) and its downstream signaling molecules. Our analyses were performed using 33 (11/category) matched specimens of normal and tumor tissue and 9 (3/category) primary cells derived from RCC patients of the 3 categories: non-metastasized, metastasized into the lung and metastasized into bones during a five-year period after nephrectomy. Expression of CaSR was determined by RT-PCR, Western blot analyses and flow cytometry, respectively. Cells were treated by calcium and the CaSR inhibitor NPS 2143. Cell migration was measured in a Boyden chamber with calcium (10 μM) as chemotaxin and proliferation by BrdU incorporation. The activity of intracellular signaling mediators was quantified by a phospho-kinase array and Western blot. The expression of CaSR was highest in specimens and cells of patients with bone metastases. Calcium treatment induced an increased migration (19-fold) and proliferation (2.3-fold) exclusively in RCC cells from patients with bone metastases. The CaSR inhibitor NPS 2143 elucidated the role of CaSR on the calcium-dependent effects. After treatment with calcium, the activity of AKT, PLCγ-1, p38α and JNK was clearly enhanced and PTEN expression was almost completely abolished in bone metastasizing RCC cells. Our results indicate a promoting effect of extracellular calcium on cell migration and proliferation of bone metastasizing RCC cells via highly expressed CaSR and its downstream signaling pathways. Consequently, CaSR may be regarded as a new prognostic marker predicting RCC bone metastasis.

  6. Cross talk between the calcium-sensing receptor and the vitamin D system in prevention of cancer

    Directory of Open Access Journals (Sweden)

    Enikö Kallay

    2016-10-01

    Full Text Available There is epidemiological evidence for the cancer preventive effect of dietary calcium (Ca2+ and vitamin D. This effect is strongest in colorectal cancer (CRC. The active vitamin D metabolite, 1,25-dihydroxyvitamin D3 (1,25D3, bound to its receptor, the vitamin D receptor (VDR regulates the expression of hundreds of different genes in a cell- and tissue-specific manner. While Ca2+ acts through multiple mechanisms and pathways, some of its effects are mediated by the calcium-sensing receptor (CaSR. The joint action of Ca2+ and 1,25D3 is due to the fact that both regulate some of the main processes involved in the development of various cancers, such as proliferation, differentiation, apoptosis, migration, and inflammation. Moreover, 1,25D3, bound to VDR can induce translation of the CaSR, while the amount and activity of the CaSR affects 1,25D3 signalling. However, the complexity of the cross-talk between the CaSR and the vitamin D system goes beyond regulating similar pathways and affecting each other’s expression. Our aim was to review some of the mechanisms that drive the cross-talk between the vitamin D system and the CaSR with a special focus on the interaction in colorectal cancer cells. We evaluated the molecular evidence that supports the epidemiological observation that both vitamin D and calcium are needed for protection against malignant transformation of the colon and that their effect is modulated by the presence of a functional CaSR.

  7. 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

  8. Behind the curtain: cellular mechanisms for allosteric modulation of calcium-sensing receptors

    Science.gov (United States)

    Cavanaugh, Alice; Huang, Ying; Breitwieser, Gerda E

    2012-01-01

    Calcium-sensing receptors (CaSR) are integral to regulation of systemic Ca2+ homeostasis. Altered expression levels or mutations in CaSR cause Ca2+ handling diseases. CaSR is regulated by both endogenous allosteric modulators and allosteric drugs, including the first Food and Drug Administration-approved allosteric agonist, Cinacalcet HCl (Sensipar®). Recent studies suggest that allosteric modulators not only alter function of plasma membrane-localized CaSR, but regulate CaSR stability at the endoplasmic reticulum. This brief review summarizes our current understanding of the role of membrane-permeant allosteric agonists in cotranslational stabilization of CaSR, and highlights additional, indirect, signalling-dependent role(s) for membrane-impermeant allosteric drugs. Overall, these studies suggest that allosteric drugs act at multiple cellular organelles to control receptor abundance and hence function, and that drug hydrophobicity can bias the relative contributions of plasma membrane and intracellular organelles to CaSR abundance and signalling. LINKED ARTICLES This article is part of a themed section on the Molecular Pharmacology of G Protein-Coupled Receptors (GPCRs). To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-6. To view the 2010 themed section on the same topic visit http://onlinelibrary.wiley.com/doi/10.1111/bph.2010.159.issue-5/issuetoc PMID:21470201

  9. Amino alcohol- (NPS-2143 and quinazolinone-derived calcilytics (ATF936 and AXT914 differentially mitigate excessive signalling of calcium-sensing receptor mutants causing Bartter syndrome Type 5 and autosomal dominant hypocalcemia.

    Directory of Open Access Journals (Sweden)

    Saskia Letz

    Full Text Available Activating calcium sensing receptor (CaSR mutations cause autosomal dominant hypocalcemia (ADH characterized by low serum calcium, inappropriately low PTH and relative hypercalciuria. Four activating CaSR mutations cause additional renal wasting of sodium, chloride and other salts, a condition called Bartter syndrome (BS type 5. Until today there is no specific medical treatment for BS type 5 and ADH. We investigated the effects of different allosteric CaSR antagonists (calcilytics on activating CaSR mutants.All 4 known mutations causing BS type 5 and five ADH mutations were expressed in HEK 293T cells and receptor signalling was studied by measurement of intracellular free calcium in response to extracellular calcium ([Ca2+]o. To investigate the effect of calcilytics, cells were stimulated with 3 mM [Ca2+]o in the presence or absence of NPS-2143, ATF936 or AXT914.All BS type 5 and ADH mutants showed enhanced signalling activity to [Ca2+]o with left shifted dose response curves. In contrast to the amino alcohol NPS-2143, which was only partially effective, the quinazolinone calcilytics ATF936 and AXT914 significantly mitigated excessive cytosolic calcium signalling of all BS type 5 and ADH mutants studied. When these mutants were co-expressed with wild-type CaSR to approximate heterozygosity in patients, ATF936 and AXT914 were also effective on all mutants.The calcilytics ATF936 and AXT914 are capable of attenuating enhanced cytosolic calcium signalling activity of CaSR mutations causing BS type 5 and ADH. Quinazolinone calcilytics might therefore offer a novel treatment option for patients with activating CaSR mutations.

  10. Calcium Nutrition and Extracellular Calcium Sensing: Relevance for the Pathogenesis of Osteoporosis, Cancer and Cardiovascular Diseases

    Science.gov (United States)

    Peterlik, Meinrad; Kállay, Enikoe; Cross, Heide S.

    2013-01-01

    Through a systematic search in Pubmed for literature, on links between calcium malnutrition and risk of chronic diseases, we found the highest degree of evidence for osteoporosis, colorectal and breast cancer, as well as for hypertension, as the only major cardiovascular risk factor. Low calcium intake apparently has some impact also on cardiovascular events and disease outcome. Calcium malnutrition can causally be related to low activity of the extracellular calcium-sensing receptor (CaSR). This member of the family of 7-TM G-protein coupled receptors allows extracellular Ca2+ to function as a “first messenger” for various intracellular signaling cascades. Evidence demonstrates that Ca2+/CaSR signaling in functional linkage with vitamin D receptor (VDR)-activated pathways (i) promotes osteoblast differentiation and formation of mineralized bone; (ii) targets downstream effectors of the canonical and non-canonical Wnt pathway to inhibit proliferation and induce differentiation of colorectal cancer cells; (iii) evokes Ca2+ influx into breast cancer cells, thereby activating pro-apoptotic intracellular signaling. Furthermore, Ca2+/CaSR signaling opens Ca2+-sensitive K+ conductance channels in vascular endothelial cells, and also participates in IP3-dependent regulation of cytoplasmic Ca2+, the key intermediate of cardiomyocyte functions. Consequently, impairment of Ca2+/CaSR signaling may contribute to inadequate bone formation, tumor progression, hypertension, vascular calcification and, probably, cardiovascular disease. PMID:23340319

  11. Calcium-sensing receptor gene polymorphism (rs7652589) is associated with calcium nephrolithiasis in the population of Yi nationality in Southwestern China.

    Science.gov (United States)

    Li, Hao; Zhang, Jianhua; Long, Jiang; Shi, Jiarun; Luo, Yuhui

    2018-04-16

    The calcium-sensing receptor (CaSR) gene plays an important role in regulating the Ca 2+ balance and reducing the risk for calcium stones. In this study, we evaluated the association of CaSR polymorphisms with calcium nephrolithiasis in the population of Yi nationality in Southwestern China. Biochemical variables were evaluated in 624 calcium nephrolithiasis patients and 470 age-matched healthy controls without a history of nephrolithiasis. CaSR polymorphisms rs7652589, rs1501899, rs1801725 (Ala986Ser), rs1042636 (Arg990Gly) and rs1801726 (Gln1011Glu) were investigated between the calcium nephrolithiasis patients and healthy controls, using direct sequencing. Compared with the healthy controls, serum creatinine and 24-hour urine calcium levels were significantly higher in calcium nephrolithiasis patients. Among these five polymorphisms, the genotypic and allelic frequency distributions of rs7652589 SNP was significantly associated with the risk of calcium nephrolithiasis. However, there were no genotypic or allelic distribution differences for rs1501899, rs1801725, rs1042636, and rs1801726 polymorphisms between calcium nephrolithiasis patients and healthy controls. Moreover, the association between rs7652589 SNP genotypes and the biochemical variables was not found. Our study showed that CaSR rs7652589 polymorphism had a significant effect on the risk of developing calcium nephrolithiasis in the population of Yi nationality in Southwestern China. © 2018 John Wiley & Sons Ltd/University College London.

  12. 14-3-3 Proteins Buffer Intracellular Calcium Sensing Receptors to Constrain Signaling.

    Directory of Open Access Journals (Sweden)

    Michael P Grant

    Full Text Available Calcium sensing receptors (CaSR interact with 14-3-3 binding proteins at a carboxyl terminal arginine-rich motif. Mutations identified in patients with familial hypocalciuric hypercalcemia, autosomal dominant hypocalcemia, pancreatitis or idiopathic epilepsy support the functional importance of this motif. We combined total internal reflection fluorescence microscopy and biochemical approaches to determine the mechanism of 14-3-3 protein regulation of CaSR signaling. Loss of 14-3-3 binding caused increased basal CaSR signaling and plasma membrane levels, and a significantly larger signaling-evoked increase in plasma membrane receptors. Block of core glycosylation with tunicamycin demonstrated that changes in plasma membrane CaSR levels were due to differences in exocytic rate. Western blotting to quantify time-dependent changes in maturation of expressed wt CaSR and a 14-3-3 protein binding-defective mutant demonstrated that signaling increases synthesis to maintain constant levels of the immaturely and maturely glycosylated forms. CaSR thus operates by a feed-forward mechanism, whereby signaling not only induces anterograde trafficking of nascent receptors but also increases biosynthesis to maintain steady state levels of net cellular CaSR. Overall, these studies suggest that 14-3-3 binding at the carboxyl terminus provides an important buffering mechanism to increase the intracellular pool of CaSR available for signaling-evoked trafficking, but attenuates trafficking to control the dynamic range of responses to extracellular calcium.

  13. Functional importance of the Ala(116)-Pro(136) region in the calcium-sensing receptor. Constitutive activity and inverse agonism in a family C G-protein-coupled receptor

    DEFF Research Database (Denmark)

    Jensen, Anders A.; Spalding, T A; Burstein, E S

    2000-01-01

    The calcium-sensing receptor (CaR) belongs to family C of the G-protein-coupled receptor superfamily. To date 14 activating mutations in CaR showing increased sensitivity to Ca(2+) have been identified in humans with autosomal dominant hypocalcemia. Four of these activating mutations are found......, suppressed the elevated basal response of the constitutively activated Ca/1a mutants demonstrating inverse agonist activity of CPCCOEt. Taken together, our results demonstrate that the Ala(116)-Pro(136) region is of key importance for the maintenance of the inactive conformation of CaR....

  14. 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.

  15. Calcium sensing receptor expression in ovine amniotic fluid mesenchymal stem cells and the potential role of R-568 during osteogenic differentiation.

    Directory of Open Access Journals (Sweden)

    Pamela Di Tomo

    Full Text Available Amniotic fluid-derived stem (AFS cells have been identified as a promising source for cell therapy applications in bone traumatic and degenerative damage. Calcium Sensing Receptor (CaSR, a G protein-coupled receptor able to bind calcium ions, plays a physiological role in regulating bone metabolism. It is expressed in different kinds of cells, as well as in some stem cells. The bone CaSR could potentially be targeted by allosteric modulators, in particular by agonists such as calcimimetic R-568, which may potentially be helpful for the treatment of bone disease. The aim of our study was first to investigate the presence of CaSR in ovine Amniotic Fluid Mesenchymal Stem Cells (oAFMSCs and then the potential role of calcimimetics in in vitro osteogenesis. oAFMSCs were isolated, characterized and analyzed to examine the possible presence of CaSR by western blotting and flow cytometry analysis. Once we had demonstrated CaSR expression, we worked out that 1 µM R-568 was the optimal and effective concentration by cell viability test (MTT, cell number, Alkaline Phosphatase (ALP and Alizarin Red S (ARS assays. Interestingly, we observed that basal diffuse CaSR expression in oAFMSCs increased at the membrane when cells were treated with R-568 (1 µM, potentially resulting in activation of the receptor. This was associated with significantly increased cell mineralization (ALP and ARS staining and augmented intracellular calcium and Inositol trisphosphate (IP3 levels, thus demonstrating a potential role for calcimimetics during osteogenic differentiation. Calhex-231, a CaSR allosteric inhibitor, totally reversed R-568 induced mineralization. Taken together, our results demonstrate for the first time that CaSR is expressed in oAFMSCs and that calcimimetic R-568, possibly through CaSR activation, can significantly improve the osteogenic process. Hence, our study may provide useful information on the mechanisms regulating osteogenesis in oAFMSCs, perhaps

  16. Human cartilaginous endplate degeneration is induced by calcium and the extracellular calcium-sensing receptor in the intervertebral disc

    Directory of Open Access Journals (Sweden)

    MP Grant

    2016-07-01

    Full Text Available The cartilaginous endplates (CEPs are thin layers of hyaline cartilage found adjacent to intervertebral discs (IVDs. In addition to providing structural support, CEPs regulate nutrient and metabolic exchange in the disc. In IVD pathogenesis, CEP undergoes degeneration and calcification, compromising nutrient availability and disc cell metabolism. The mechanism(s underlying the biochemical changes of CEP in disc degeneration are currently unknown. Since calcification is often observed in later stages of IVD degeneration, we hypothesised that elevations in free calcium (Ca2+ impair CEP homeostasis. Indeed, our results demonstrated that the Ca2+ content was consistently higher in human CEP tissue with grade of disc degeneration. Increasing the levels of Ca2+ resulted in decreases in the secretion and accumulation of collagens type I, II and proteoglycan in cultured human CEP cells. Ca2+ exerted its effects on CEP matrix protein synthesis through activation of the extracellular calcium-sensing receptor (CaSR; however, aggrecan content was also affected independent of CaSR activation as increases in Ca2+ directly enhanced the activity of aggrecanases. Finally, supplementing Ca2+ in our IVD organ cultures was sufficient to induce degeneration and increase the mineralisation of CEP, and decrease the diffusion of glucose into the disc. Thus, any attempt to induce anabolic repair of the disc without addressing Ca2+ may be impaired, as the increased metabolic demand of IVD cells would be compromised by decreases in the permeability of the CEP.

  17. Calcium-Sensing Receptor Tumor Expression and Lethal Prostate Cancer Progression.

    Science.gov (United States)

    Ahearn, Thomas U; Tchrakian, Nairi; Wilson, Kathryn M; Lis, Rosina; Nuttall, Elizabeth; Sesso, Howard D; Loda, Massimo; Giovannucci, Edward; Mucci, Lorelei A; Finn, Stephen; Shui, Irene M

    2016-06-01

    Prostate cancer metastases preferentially target bone, and the calcium-sensing receptor (CaSR) may play a role in promoting this metastatic progression. We evaluated the association of prostate tumor CaSR expression with lethal prostate cancer. A validated CaSR immunohistochemistry assay was performed on tumor tissue microarrays. Vitamin D receptor (VDR) expression and phosphatase and tensin homolog tumor status were previously assessed in a subset of cases by immunohistochemistry. Cox proportional hazards models adjusting for age and body mass index at diagnosis, Gleason grade, and pathological tumor node metastasis stage were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association of CaSR expression with lethal prostate cancer. The investigation was conducted in the Health Professionals Follow-up Study and Physicians' Health Study. We studied 1241 incident prostate cancer cases diagnosed between 1983 and 2009. Participants were followed up or cancer-specific mortality or development of metastatic disease. On average, men were followed up 13.6 years, during which there were 83 lethal events. High CaSR expression was associated with lethal prostate cancer independent of clinical and pathological variables (HR 2.0; 95% CI 1.2-3.3). Additionally, there was evidence of effect modification by VDR expression; CaSR was associated with lethal progression among men with low tumor VDR expression (HR 3.2; 95% CI 1.4-7.3) but not in cases with high tumor VDR expression (HR 0.8; 95% CI 0.2-3.0). Tumor CaSR expression is associated with an increased risk of lethal prostate cancer, particularly in tumors with low VDR expression. These results support further investigating the mechanism linking CaSR with metastases.

  18. Follicle-stimulating hormone receptor-mediated uptake of 45Ca2+ by proteoliposomes and cultured rat sertoli cells: Evidence for involvement of voltage-activated and voltage-independent calcium channels

    International Nuclear Information System (INIS)

    Grasso, P.; Reichert, L.E. Jr.

    1989-01-01

    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

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

    International Nuclear Information System (INIS)

    Park, J.H.; Kassner, T.F.

    1996-01-01

    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 ∼7-8 μm 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 10 Ω-cm 2 at 300 degrees C and 400 h, and 0.9 x 10 10 Ω-cm 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

  20. Regulation of Bicarbonate Secretion in Marine Fish Intestine by the Calcium-Sensing Receptor

    Directory of Open Access Journals (Sweden)

    Sílvia F. Gregório

    2018-04-01

    Full Text Available In marine fish, high epithelial intestinal HCO3− secretion generates luminal carbonate precipitates of divalent cations that play a key role in water and ion homeostasis. The present study was designed to expose the putative role for calcium and the calcium-sensing receptor (CaSR in the regulation of HCO3− secretion in the intestine of the sea bream (Sparus aurata L.. Effects on the expression of the CaSR in the intestine were evaluated by qPCR and an increase was observed in the anterior intestine in fed fish compared with unfed fish and with different regions of intestine. CaSR expression reflected intestinal fluid calcium concentration. In addition, anterior intestine tissue was mounted in Ussing chambers to test the putative regulation of HCO3− secretion in vitro using the anterior intestine. HCO3− secretion was sensitive to varying calcium levels in luminal saline and to calcimimetic compounds known to activate/block the CaSR i.e., R 568 and NPS-2143. Subsequent experiments were performed in intestinal sacs to measure water absorption and the sensitivity of water absorption to varying luminal levels of calcium and calcimimetics were exposed as well. It appears, that CaSR mediates HCO3− secretion and water absorption in marine fish as shown by responsiveness to calcium levels and calcimimetic compounds.

  1. An i.r. investigation on some calcium aluminate hydrates, Ca2Al(OH)6+X-.yH2O (= 3CaO.Al2O3.CaX2.nH2O, X- = univalent anion)

    NARCIS (Netherlands)

    Houtepen, C.J.M.; Stein, H.N.

    1976-01-01

    The i.r. spectra of some hydrated and dehydrated calcium aluminate hydrates of the type Ca2Al(OH)6+X-·yH2O with X- = Cl-, Br-, J-, ClO3-, NO3-, ClO4- (y = 2) and X- = BrO3-, JO3- (2

  2. Protein-induced satiation and the calcium-sensing receptor

    Directory of Open Access Journals (Sweden)

    Ojha U

    2018-03-01

    Full Text Available Utkarsh Ojha Faculty of Medicine, Imperial College School of Medicine, Imperial College London, London, UK Abstract: Obesity is a major global health issue. High-protein diets have been shown to be associated with weight loss and satiety. The precise mechanism by which protein-rich diets promote weight loss remains unclear. Evidence suggests amino acids, formed as a consequence of protein digestion, are sensed by specific receptors on L-cells in the gastrointestinal (GI tract. These L-cells respond by secreting gut hormones that subsequently induce satiety. In recent years, the calcium-sensing receptor has been identified in several cells of the GI tract, including L-cells, and suggested to sense specific amino acids. This review evaluates the evidence for protein-rich diets in inducing weight loss and how the calcium-sensing receptor may be implicated in this phenomenon. Commandeering the mechanisms by which elements of a protein-rich diet suppress appetite may provide another successful avenue for developing anti-obesity drugs. Keywords: amino acids, energy regulation, obesity therapy, glucagon-like-peptide-1, peptide YY

  3. Synthetic water soluble di-/tritopic molecular receptors exhibiting Ca2+/Mg2+ exchange.

    Science.gov (United States)

    Lavie-Cambot, Aurélie; Tron, Arnaud; Ducrot, Aurélien; Castet, Frédéric; Kauffmann, Brice; Beauté, Louis; Allouchi, Hassan; Pozzo, Jean-Luc; Bonnet, Célia S; McClenaghan, Nathan D

    2017-05-23

    Structural integration of two synthetic water soluble receptors for Ca 2+ and Mg 2+ , namely 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and o-aminophenol-N,N,O-triacetic acid (APTRA), respectively, gave novel di- and tritopic ionophores (1 and 2). As Mg 2+ and Ca 2+ cannot be simultaneously complexed by the receptors, allosteric control of complexation results. Potentiometric measurements established stepwise protonation constants and showed high affinity for Ca 2+ (log K = 6.08 and 8.70 for 1 and 2, respectively) and an excellent selectivity over Mg 2+ (log K = 3.70 and 5.60 for 1 and 2, respectively), which is compatible with magnesium-calcium ion exchange. While ion-exchange of a single Mg 2+ for a single Ca 2+ is possible in both 1 and 2, the simultaneous binding of two Mg 2+ by 2 appears prohibitive for replacement of these two ions by a single Ca 2+ . Ion-binding and exchange was further rationalized by DFT calculations.

  4. Synthesis of CaTiO 3 from calcium titanyl oxalate hexahydrate (CTO)

    Indian Academy of Sciences (India)

    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.

  5. Familial hypocalciuric hypercalcemia and calcium sensing receptor

    DEFF Research Database (Denmark)

    Mrgan, Monija; Nielsen, Sanne; Brixen, Kim

    2014-01-01

    Familial hypocalciuric hypercalcemia (FHH) is a lifelong, benign autosomal dominant disease characterized by hypercalcemia, normal to increased parathyroid hormone level, and a relatively low renal calcium excretion. Inactivation of the calcium-sensing receptor in heterozygous patients results...... in FHH, while in homozygous patients as well as in compound heterozygous or dominant negative heterozygous patients, it may result in neonatal severe hyperparathyroidism (NSHPT). Parathyroid surgery is not indicated in FHH and does not lower plasma calcium unless total parathyroidectomy is performed...

  6. Role of Calcium Sensing Receptor in Streptozotocin-Induced Diabetic Rats Exposed to Renal Ischemia Reperfusion Injury

    Directory of Open Access Journals (Sweden)

    Bo Hu

    2018-02-01

    Full Text Available Background/Aims: Renal ischemia/reperfusion (I/R injury (RI/RI is a common complication of diabetes, and it may be involved in altering intracellular calcium concentrations at its onset, which can result in inflammation, abnormal lipid metabolism, the production of reactive oxygen species (ROS, and nitroso-redox imbalance. The calcium-sensing receptor (CaSR is a G-protein coupled receptor, however, the functional involvement of CaSR in diabetic RI/ RI remains unclear. The present study was intended to investigate the role of CaSR on RI/RI in diabetes mellitus (DM. Methods: The bilateral renal arteries and veins of streptozotocin (STZ-induced diabetic rats were subjected to 45-min ischemia followed by 2-h reperfusion with or without R-568 (agonist of CaSR and NPS-2143 (antagonist of CaSR at the beginning of I/R procedure. DM without renal I/R rats served as control group. The expressions of CaSR, calmodulin (CaM, and p47phox in the renal tissue were analyzed by qRT-PCR and Western blot. The renal pathomorphology, renal function, oxidative stress, inflammatory response, and calcium disorder were evaluated by detection of a series of indices by hematoxylin-eosin (HE staining, transmission electron microscope (TEM, commercial kits, enzyme-linked immunosorbent assay (ELISA, and spectrophotofluorometry, respectively. Results: Results showed that the expressions of CaSR, CaM, and p47phox in I/R group were significantly up-regulated as compared with those in DM group, which were accompanied by renal tissue injury, increased calcium, oxidative stress, inflammation, and nitroso-redox imbalance. Conclusion: These results suggest that activation of CaSR is involved in the induction of damage of renal tubular epithelial cell during diabetic RI/RI, resulting in lipid peroxidation, inflammatory response, nitroso-redox imbalance, and apoptosis.

  7. [Pharmacological characteristics of drugs targeted on calcium-sensing receptor.-properties of cinacalcet hydrochloride as allosteric modulator].

    Science.gov (United States)

    Nagano, Nobuo; Tsutsui, Takaaki

    2016-06-01

    Calcimimetics act as positive allosteric modulators of the calcium-sensing receptor (CaSR), thereby decreasing parathyroid hormone (PTH) secretion from the parathyroid glands. On the other hand, negative allosteric modulators of the CaSR with stimulatory effect on PTH secretion are termed calcilytics. The calcimimetic cinacalcet hydrochloride (cinacalcet) is the world's first allosteric modulator of G protein-coupled receptor to enter the clinical market. Cinacalcet just tunes the physiological effects of Ca(2+), an endogenous ligand, therefore, shows high selectivity and low side effects. Calcimimetics also increase cell surface CaSR expression by acting as pharmacological chaperones (pharmacoperones). It is considered that the cinacalcet-induced upper gastrointestinal problems are resulted from enhanced physiological responses to Ca(2+) and amino acids via increased sensitivity of digestive tract CaSR by cinacalcet. While clinical developments of calcilytics for osteoporosis were unfortunately halted or terminated due to paucity of efficacy, it is expected that calcilytics may be useful for the treatment of patients with activating CaSR mutations, asthma, and idiopathic pulmonary artery hypertension.

  8. Electrospun Gelatin/β-TCP Composite Nanofibers Enhance Osteogenic Differentiation of BMSCs and In Vivo Bone Formation by Activating Ca2+-Sensing Receptor Signaling

    Directory of Open Access Journals (Sweden)

    Xuehui Zhang

    2015-01-01

    Full Text Available Calcium phosphate- (CaP- based composite scaffolds have been used extensively for the bone regeneration in bone tissue engineering. Previously, we developed a biomimetic composite nanofibrous membrane of gelatin/β-tricalcium phosphate (TCP and confirmed their biological activity in vitro and bone regeneration in vivo. However, how these composite nanofibers promote the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs is unknown. Here, gelatin/β-TCP composite nanofibers were fabricated by incorporating 20 wt% β-TCP nanoparticles into electrospun gelatin nanofibers. Electron microscopy showed that the composite β-TCP nanofibers had a nonwoven structure with a porous network and a rough surface. Spectral analyses confirmed the presence and chemical stability of the β-TCP and gelatin components. Compared with pure gelatin nanofibers, gelatin/β-TCP composite nanofibers caused increased cell attachment, proliferation, alkaline phosphatase activity, and osteogenic gene expression in rat BMSCs. Interestingly, the expression level of the calcium-sensing receptor (CaSR was significantly higher on the composite nanofibrous scaffolds than on pure gelatin. For rat calvarial critical sized defects, more extensive osteogenesis and neovascularization occurred in the composite scaffolds group compared with the gelatin group. Thus, gelatin/β-TCP composite scaffolds promote osteogenic differentiation of BMSCs in vitro and bone regeneration in vivo by activating Ca2+-sensing receptor signaling.

  9. Identification and Functional Characterization of a Novel Mutation in the Human Calcium-Sensing Receptor That Co-Segregates With Autosomal-Dominant Hypocalcemia

    Directory of Open Access Journals (Sweden)

    Anne Qvist Rasmussen

    2018-04-01

    Full Text Available The human calcium-sensing receptor (CASR is the key controller of extracellular Cao2+ homeostasis, and different mutations in the CASR gene have been linked to different calcium diseases, such as familial hypocalciuric hypercalcemia, severe hyperparathyroidism, autosomal-dominant hypocalcemia (ADH, and Bartter’s syndrome type V. In this study, two generations of a family with biochemically and clinically confirmed ADH who suffered severe muscle pain, arthralgia, tetany, abdominal pain, and fatigue were evaluated for mutations in the CASR gene. The study comprises genotyping of all family members, functional characterization of a potential mutant receptor by in vitro analysis related to the wild-type receptor to reveal an association between the genotype and phenotype in the affected family members. The in vitro analysis of functional characteristics includes measurements of inositol trisphosphate accumulation, Ca2+ mobilization in response to [Ca2+]o-stimulation and receptor expression. The results reveal a significant leftward shift of inositol trisphosphate accumulation as a result of the “gain-of-function” mutant receptor and surprisingly a normalization of the response in (Ca2+i release in the downstream pathway and additionally the maximal response of (Ca2+i release was significantly decreased compared to the wild type. However, no gross differences were seen in D126V and the D126V/WT CASR dimeric >250 kDa band expression compared to the WT receptor, however, the D126V and D126V/WT CASR immature ~140 kDa species appear to have reduced expression compared to the WT receptor. In conclusion, in this study, a family with a clinical diagnosis of ADH in two generations was evaluated to identify a mutation in the CASR gene and reveal an association between genotype and phenotype in the affected family members. The clinical condition was caused by a novel, activating, missense mutation (D126V in the CASR gene and the in vitro functional

  10. Thermodynamic investigation of the CaO-Al2O3-CaCO3-H2O closed system at 25 C and the influence of Na2O

    International Nuclear Information System (INIS)

    Damidot, D.; Stronach, S.; Kindness, A.; Atkins, M.; Glasser, F.P.

    1994-01-01

    The solubilities of calcium hemicarboaluminate, calcium monocarboaluminate and calcium tricarboaluminate have been determined and the equilibrium phase diagram for the CaO-Al 2 O 3 -CaCO 3 -H 2 O closed system at 25 C has been calculated. Six isothermally invariant points have been located involving six stable hydrates: CH, C 3 AH 6 , AH 3 , calcium hemicarboaluminate, calcium monocarboaluminate and calcite. Calcium tricarboaluminate, the carbonate analogue of ettringite, does not appear to be stable at 25 C. This study was part of a larger study on radioactive waste solidification

  11. Identification of potent, nonabsorbable agonists of the calcium-sensing receptor for GI-specific administration.

    Science.gov (United States)

    Sparks, Steven M; Spearing, Paul K; Diaz, Caroline J; Cowan, David J; Jayawickreme, Channa; Chen, Grace; Rimele, Thomas J; Generaux, Claudia; Harston, Lindsey T; Roller, Shane G

    2017-10-15

    Modulation of gastrointestinal nutrient sensing pathways provides a promising a new approach for the treatment of metabolic diseases including diabetes and obesity. The calcium-sensing receptor has been identified as a key receptor involved in mineral and amino acid nutrient sensing and thus is an attractive target for modulation in the intestine. Herein we describe the optimization of gastrointestinally restricted calcium-sensing receptor agonists starting from a 3-aminopyrrolidine-containing template leading to the identification of GI-restricted agonist 19 (GSK3004774). Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. (Solid + liquid) phase equilibria of (Ca(H2PO2)2 + CaCl2 + H2O) and (Ca(H2PO2)2 + NaH2PO2 + H2O) ternary systems at T = 323.15 K

    International Nuclear Information System (INIS)

    Cao, Hong-yu; Zhou, Huan; Bai, Xiao-qin; Ma, Ruo-xin; Tan, Li-na; Wang, Jun-min

    2016-01-01

    Graphical abstract: Solubility diagram of the (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) system at T = (323.15 and 298.15) K. - Highlights: • Phase diagrams of Ca 2+ -H 2 PO 2 − -Cl − -H 2 O, Ca 2+ -Na + -H 2 PO 2 − -H 2 O at 323.15 K were obtained. • Incompatible double salt of NaCa(H 2 PO 2 ) 3 in Ca 2+ -Na + -H 2 PO 2 − -H 2 O system was determined. • Density diagram of the corresponding liquid were simultaneously measured. - Abstract: Calcium hypophosphite has been widely used as an anti-corrosive agent, flame retardant, fertilizer, assistant for Ni electroless plating, and animal nutritional supplement. High purity calcium hypophosphite can be synthesized via the replacement reaction of sodium hypophosphite and calcium chloride. In this work, the (solid + liquid) phase equilibria of (Ca(H 2 PO 2 ) 2 + CaCl 2 + H 2 O) and (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) ternary systems at T = 323.15 K were studied experimentally via the classical isothermal solubility equilibrium method, and the phase diagrams for these two systems were obtained. It was found that two solid salts of CaCl 2 ·2H 2 O and Ca(H 2 PO 2 ) 2 exist in the (Ca(H 2 PO 2 ) 2 + CaCl 2 + H 2 O) system, and three salts of Ca(H 2 PO 2 ) 2 , NaH 2 PO 2 ·H 2 O and one incompatible double salt, NaCa(H 2 PO 2 ) 3 occur in the (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) system.

  13. First investigations on the quaternary system Na2O-K2O-CaO-SiO2: synthesis and crystal structure of the mixed alkali calcium silicate K1.08Na0.92Ca6Si4O15

    Science.gov (United States)

    Kahlenberg, Volker; Mayerl, Michael Jean-Philippe; Schmidmair, Daniela; Krüger, Hannes; Tribus, Martina

    2018-04-01

    In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been obtained from slow cooling of a melt in the range between 1250 and 1050 °C. Electron probe micro analysis suggested the following idealized molar ratios of the oxides for the novel compound: K2O:Na2O:CaO:SiO2 = 1:1:12:8 (or KNaCa6Si4O15). Single-crystal diffraction measurements on a crystal with chemical composition K1.08Na0.92Ca6Si4O15 resulted in the following basic crystallographic data: monoclinic symmetry, space group P 21/ c, a = 8.9618(9) Å, b = 7.3594(6) Å, c = 11.2453(11) Å, β= 107.54(1)°, V = 707.2(1) Å3, Z = 2. Structure solution was performed using direct methods. The final least-squares refinement converged at a residual of R(|F|) = 0.0346 for 1288 independent reflections and 125 parameters. From a structural point of view, K1.08Na0.92Ca6Si4O15 belongs to the group of mixed-anion silicates containing [Si2O7]- and [SiO4]-units in the ratio 1:2. The mono- and divalent cations occupy a total of four crystallographically independent positions located in voids between the tetrahedra. Three of these sites are exclusively occupied by calcium. The fourth site is occupied by 54(1)% K and 46%(1) Na, respectively. Alternatively, the structure can be described as a heteropolyhedral framework based on corner-sharing silicate tetrahedra and [CaO6]-octahedra. The network can build up from kröhnkite-like [Ca(SiO4)2O2]-chains running along [001]. A detailed comparison with other A2B6Si4O15-compounds including topological and group-theoretical aspects is presented.

  14. Clinical characterization of a novel calcium sensing receptor genetic alteration in a Greek patient with autosomal dominant hypocalcemia type 1.

    Science.gov (United States)

    Papadopoulou, Anna; Gole, Evangelia; Melachroinou, Katerina; Trangas, Theoni; Bountouvi, Evaggelia; Papadimitriou, Anastasios

    2017-04-01

    Autosomal dominant hypocalcemia (ADH) is a rare familial or sporadic syndrome associated with activating mutations in the calcium sensing receptor (CaSR) gene. The aim of this study was to assess the functional significance of a novel CaSR mutation and, moreover, to present the clinical characteristics and the bone mineral density (BMD) progression from early childhood to late puberty in a patient with ADH. Genetic analysis of the CaSR gene was performed in a patient who presented in the neonatal period with hypocalcemic seizures and biochemical features of ADH. The functional impact of the novel mutation identified was assessed in cultured HEK 293T cells, transfected with either the wild type (WT) or mutant CaSR, by evaluating intracellular calcium ([Ca2+]i) influx after stimulation with extracellular calcium (Ca2+). Several BMD measurements were performed during the patient's follow-up until late puberty. A novel CaSR mutation (p.L123S) was identified, which, as demonstrated by functional analysis, renders CaSR more sensitive to extracellular changes of Ca2+ compared with the WT, although the difference is not statistically significant. BMD measurements, from early childhood to late puberty, revealed high normal to elevated BMD. We present the first Greek patient, to our knowledge, with sporadic ADH due to a novel gain-of-function mutation of the CaSR gene.

  15. Cardiac microvascular endothelial cells express a functional Ca+ -sensing receptor.

    Science.gov (United States)

    Berra Romani, Roberto; Raqeeb, Abdul; Laforenza, Umberto; Scaffino, Manuela Federica; Moccia, Francesco; Avelino-Cruz, Josè Everardo; Oldani, Amanda; Coltrini, Daniela; Milesi, Veronica; Taglietti, Vanni; Tanzi, Franco

    2009-01-01

    The mechanism whereby extracellular Ca(2+) exerts the endothelium-dependent control of vascular tone is still unclear. In this study, we assessed whether cardiac microvascular endothelial cells (CMEC) express a functional extracellular Ca(2+)-sensing receptor (CaSR) using a variety of techniques. CaSR mRNA was detected using RT-PCR, and CaSR protein was identified by immunocytochemical analysis. In order to assess the functionality of the receptor, CMEC were loaded with the Ca(2+)-sensitive fluorochrome, Fura-2/AM. A number of CaSR agonists, such as spermine, Gd(3+), La(3+) and neomycin, elicited a heterogeneous intracellular Ca(2+) signal, which was abolished by disruption of inositol 1,4,5-trisphosphate (InsP(3)) signaling and by depletion of intracellular stores with cyclopiazonic acid. The inhibition of the Na(+)/Ca(2+) exchanger upon substitution of extracellular Na(+) unmasked the Ca(2+) signal triggered by an increase in extracellular Ca(2+) levels. Finally, aromatic amino acids, which function as allosteric activators of CaSR, potentiated the Ca(2+) response to the CaSR agonist La(3+). These data provide evidence that CMEC express CaSR, which is able to respond to physiological agonists by mobilizing Ca(2+) from intracellular InsP(3)-sensitive stores. Copyright 2008 S. Karger AG, Basel.

  16. Association of calcium sensing receptor polymorphisms at rs1801725 with circulating calcium in breast cancer patients.

    Science.gov (United States)

    Wang, Li; Widatalla, Sarrah E; Whalen, Diva S; Ochieng, Josiah; Sakwe, Amos M

    2017-08-02

    Breast cancer (BC) patients with late-stage and/or rapidly growing tumors are prone to develop high serum calcium levels which have been shown to be associated with larger and aggressive breast tumors in post and premenopausal women respectively. Given the pivotal role of the calcium sensing receptor (CaSR) in calcium homeostasis, we evaluated whether polymorphisms of the CASR gene at rs1801725 and rs1801726 SNPs in exon 7, are associated with circulating calcium levels in African American and Caucasian control subjects and BC cases. In this retrospective case-control study, we assessed the mean circulating calcium levels, the distribution of two inactivating CaSR SNPs at rs1801725 and rs1801726 in 199 cases and 384 age-matched controls, and used multivariable regression analysis to determine whether these SNPs are associated with circulating calcium in control subjects and BC cases. We found that the mean circulating calcium levels in African American subjects were higher than those in Caucasian subjects (p calcium levels were higher in BC cases compared to control subjects (p calcium levels in BC patients were independent of race. We also show that in BC cases and control subjects, the major alleles at rs1801725 (G/T, A986S) and at rs1801726 (C/G, Q1011E) were common among Caucasians and African Americans respectively. Compared to the wild type alleles, polymorphisms at the rs1801725 SNP were associated with higher calcium levels (p = 0.006) while those at rs1801726 were not. Using multivariable linear mixed-effects models and adjusting for age and race, we show that circulating calcium levels in BC cases were associated with tumor grade (p = 0.009), clinical stage (p = 0.003) and more importantly, with inactivating mutations of the CASR at the rs1801725 SNP (p = 0.038). These data suggest that decreased sensitivity of the CaSR to calcium due to inactivating polymorphisms at rs1801725, may predispose up to 20% of BC cases to high circulating calcium

  17. Strontium is a biased agonist of the calcium-sensing receptor in rat medullary thyroid carcinoma 6-23 cells

    DEFF Research Database (Denmark)

    Thomsen, Alex Rojas Bie; Worm, Jesper; Jacobsen, Stine Engesgaard

    2012-01-01

    The calcium-sensing receptor (CaSR)-specific allosteric modulator cinacalcet has revolutionized the treatment of secondary hyperparathyroidism in patients with chronic kidney disease. However, its application is limited to patients with end-stage renal disease because of hypocalcemic side effects......SR-stimulated signaling bias, which may be used to develop novel drugs for the treatment of secondary hyperparathyroidism....

  18. Promiscuous Seven Transmembrane Receptors Sensing L-α-amino Acids

    DEFF Research Database (Denmark)

    Smajilovic, Sanela; Wellendorph, Petrine; Bräuner-Osborne, Hans

    2014-01-01

    A number of nutrient sensing seven trans-membrane (7TM) receptors have been identified and characterized over the past few years. While the sensing mechanisms to carbohydrates and free fatty acids are well understood, the molecular basis of amino acid sensing has recently come to the limelight....... The present review describes the current status of promiscuous L-α-amino acid sensors, the calcium sensing receptor (CaSR), the GPRC6A receptor, the T1R1/T1R3 receptor and also their molecular pharmacology, expression pattern and physiological significance....

  19. The cargo receptor p24A facilitates calcium sensing receptor maturation and stabilization in the early secretory pathway

    Science.gov (United States)

    Stepanchick, Ann; Breitwieser, Gerda E.

    2010-01-01

    The calcium sensing receptor (CaSR) is a Family 3/C G protein-coupled receptor with slow and partial targeting to the plasma membrane in both native and heterologous cells. We identified cargo receptor family member p24A in yeast two-hybrid screens with the CaSR carboxyl terminus. Interactions were confirmed by immunoprecipitation of either p24A or CaSR in transiently transfected HEK293 cells. Only the immaturely glycosylated form of CaSR interacts with p24A. Dissociation likely occurs in the endoplasmic reticulum Golgi intermediate compartment (ERGIC) or cis-Golgi, since only the uncleaved form of a CaSR mutant sensitive to the trans-Golgi enzyme furin was coimmunoprecipitated with p24A. p24A and p24A(ΔGOLD) significantly increased total and plasma membrane CaSR protein but p24A(FF/AA) did not. The CaSR carboxyl terminus distal to T868 is required for differential sensitivity to p24A and its mutants. Interaction with p24A therefore increases CaSR stability in the ER and enhances plasma membrane targeting. Neither wt Sar1p or the T39N mutant increased CaSR maturation or abundance while the H79G mutant increased abundance but prevented maturation of CaSR. These results suggest that p24A is the limiting factor in CaSR trafficking in the early secretory pathway, and that cycling between the ER and ERGIC protects CaSR from degradation. PMID:20361938

  20. Autosomal dominant hypocalcemia with Bartter syndrome due to a novel activating mutation of calcium sensing receptor, Y829C.

    Science.gov (United States)

    Choi, Keun Hee; Shin, Choong Ho; Yang, Sei Won; Cheong, Hae Il

    2015-04-01

    The calcium sensing receptor (CaSR) plays an important role in calcium homeostasis. Activating mutations of CaSR cause autosomal dominant hypocalcemia by affecting parathyroid hormone secretion in parathyroid gland and calcium resorption in kidney. They can also cause a type 5 Bartter syndrome by inhibiting the apical potassium channel in the thick ascending limb of the loop of Henle in the kidney. This study presents a patient who had autosomal dominant hypocalcemia with Bartter syndrome due to an activating mutation Y829C in the transmembrane domain of the CaSR. Symptoms of hypocalcemia occurred 12 days after birth and medication was started immediately. Medullary nephrocalcinosis and basal ganglia calcification were found at 7 years old and at 17 years old. Three hypercalcemic episodes occurred, one at 14 years old and two at 17 years old. The Bartter syndrome was not severe while the serum calcium concentration was controlled, but during hypercalcemic periods, the symptoms of Bartter syndrome were aggravated.

  1. Activation of the Ca2+-sensing receptors increases currents through inward rectifier K+ channels via activation of phosphatidylinositol 4-kinase

    OpenAIRE

    Liu, Chung-Hung; Chang, Hsueh-Kai; Lee, Sue-Ping; Shieh, Ru-Chi

    2016-01-01

    Inward rectifier K+ channels are important for maintaining normal electrical function in many cell types. The proper function of these channels requires the presence of membrane phosphoinositide 4,5-bisphosphate (PIP2). Stimulation of the Ca2+-sensing receptor CaR, a pleiotropic G protein-coupled receptor, activates both Gq/11, which decreases PIP2, and phosphatidylinositol 4-kinase (PI-4-K), which, conversely, increases PIP2. How membrane PIP2 levels are regulated by CaR activation and wheth...

  2. Expression profiling of colorectal cancer cells reveals inhibition of DNA replication licensing by extracellular calcium.

    Science.gov (United States)

    Aggarwal, Abhishek; Schulz, Herbert; Manhardt, Teresa; Bilban, Martin; Thakker, Rajesh V; Kallay, Enikö

    2017-06-01

    Colorectal cancer is one of the most common cancers in industrialised societies. Epidemiological studies, animal experiments, and randomized clinical trials have shown that dietary factors can influence all stages of colorectal carcinogenesis, from initiation through promotion to progression. Calcium is one of the factors with a chemoprophylactic effect in colorectal cancer. The aim of this study was to understand the molecular mechanisms of the anti-tumorigenic effects of extracellular calcium ([Ca 2+ ] o ) in colon cancer cells. Gene expression microarray analysis of colon cancer cells treated for 1, 4, and 24h with 2mM [Ca 2+ ] o identified significant changes in expression of 1571 probe sets (ANOVA, pcalcium-sensing receptor (CaSR), a G protein-coupled receptor is a mediator involved in this process. To test whether these results were physiologically relevant, we fed mice with a standard diet containing low (0.04%), intermediate (0.1%), or high (0.9%) levels of dietary calcium. The main molecules regulating replication licensing were inhibited also in vivo, in the colon of mice fed high calcium diet. We show that among the mechanisms behind the chemopreventive effect of [Ca 2+ ] o is inhibition of replication licensing, a process often deregulated in neoplastic transformation. Our data suggest that dietary calcium is effective in preventing replicative stress, one of the main drivers of cancer and this process is mediated by the calcium-sensing receptor. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  3. The Calcium-Sensing Receptor Gene Polymorphism rs1801725 and Calcium-Related Phenotypes in Hemodialysis Patients

    Directory of Open Access Journals (Sweden)

    Alicja E. Grzegorzewska

    2018-05-01

    Full Text Available Background/Aims: The calcium-sensing receptor gene (CASR rs1801725 variant is responsible for a non-conservative amino-acid change (A986S in the calcium-sensing receptor cytoplasmic tail. We hypothesized that rs1801725 polymorphism might be helpful in understanding Ca-related abnormalities in HD patients. Methods: In 1215 subjects (245 on cinacalcet, we determined the associations of rs1801725 with secondary hyperparathyroidism (sHPT-related laboratory parameters, PTH-decreasing effect of cinacalcet hydrochloride, coronary artery disease (CAD, myocardial infarction (MI, nephrolithiasis-related ESRD, and mortality. CASR rs7652589(AT haplotypes and rs1801725 epistatic interactions with vitamin D signaling pathway genes were examined for associations with selected phenotypes. Results: The rs1801725 variant allele showed an increasing independent effect on plasma PTH (Pcorrected = 0.009. CASR rs7652589_rs1801725 AT haplotype was associated with 1.7-fold higher frequency of PTH levels over 437 pg/mL than the reference haplotype GG (P = 0.001. CASR rs7652589_rs1801725 AG haplotype was 1.5-fold more frequent in nephrolithiasis-related ESRD than the GG haplotype (P = 0.004. There were no significant associations between rs1801725, CAD, MI, and response to cinacalcet. Variant homozygosity of rs1801725 correlated independently with higher infection-related mortality compared with heterozygosity (HR 7.95, 95%CI 2.15 – 29.37, P = 0.003 and major homozygosity (HR 5.89, 95%CI 1.69 – 20.55, P = 0.040. CASR rs1801725 did not show epistatic interactions with vitamin D signaling pathway genes concerning tested associations. Conclusion: The variant allele of CASR rs1801725 solely and together with the variant allele of rs7652589 increases risk of more advanced sHPT. Homozygosity of the rs1801725 variant allele contributes to infection-related mortality in HD patients.

  4. 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

  5. Active vitamin D potentiates the anti-neoplastic effects of calcium in the colon: A cross talk through the calcium-sensing receptor.

    Science.gov (United States)

    Aggarwal, Abhishek; Höbaus, Julia; Tennakoon, Samawansha; Prinz-Wohlgenannt, Maximilian; Graça, João; Price, Sally A; Heffeter, Petra; Berger, Walter; Baumgartner-Parzer, Sabina; Kállay, Enikö

    2016-01-01

    Epidemiological studies suggest an inverse correlation between dietary calcium (Ca(2+)) and vitamin D intake and the risk of colorectal cancer (CRC). It has been shown in vitro that the active vitamin D metabolite, 1,25-dihydroxyvitamin D3 (1,25-D3) can upregulate expression of the calcium-sensing receptor (CaSR). In the colon, CaSR has been suggested to regulate proliferation of colonocytes. However, during tumorigenesis colonic CaSR expression is downregulated and we hypothesized that the loss of CaSR could influence the anti-tumorigenic effects of Ca(2+) and vitamin D. Our aim was to assess the impact of CaSR expression and function on the anti-neoplastic effects of 1,25-D3 in colon cancer cell lines. We demonstrated that in the healthy colon of mice, high vitamin D diet (2500 IU/kg diet) increased expression of differentiation and apoptosis markers, decreased expression of proliferation markers and significantly upregulated CaSR mRNA expression, compared with low vitamin D diet (100 IU/kg diet). To determine the role of CaSR in this process, we transfected Caco2-15 and HT29 CRC cells with wild type CaSR (CaSR-WT) or a dominant negative CaSR mutant (CaSR-DN) and treated them with 1,25-D3 alone, or in combination with CaSR activators (Ca(2+) and NPS R-568). 1,25-D3 enhanced the anti-proliferative effects of Ca(2+) and induced differentiation and apoptosis only in cells with a functional CaSR, which were further enhanced in the presence of NPS R-568, a positive allosteric modulator of CaSR. The mutant CaSR inhibited the anti-tumorigenic effects of 1,25-D3 suggesting that the anti-neoplastic effects of 1,25-D3 are, at least in part, mediated by the CaSR. Taken together, our data provides molecular evidence to support the epidemiological observation that both, vitamin D and calcium are needed for protection against malignant transformation of the colon and that their effect is modulated by the presence of a functional CaSR. This article is part of a Special Issue

  6. Nanosilica supported CaO: A regenerable and mechanically hard CO2 sorbent at Ca-looping conditions

    International Nuclear Information System (INIS)

    Sanchez-Jimenez, P.E.; Perez-Maqueda, L.A.; Valverde, J.M.

    2014-01-01

    Highlights: • A synthetic CO 2 sorbent is prepared by impregnation of calcium nitrate on a nanosilica matrix. • Sintering of the nascent CaO in the calcination stage of carbonation/calcination cycles is hindered. • CaO conversion reaches a stable value well above the residual conversion of natural limestone. • Particle fragmentation as caused by ultrasonic irradiation in a liquid dispersion is hindered. - Abstract: This work presents a CO 2 sorbent that may be synthesized from low-cost and widely available materials following a simple method basically consisting of impregnation of a nanostructured silica support with a saturated solution of calcium nitrate. In a first impregnation stage, the use of a stoichiometric CaO/SiO 2 ratio serves to produce a calcium silicate matrix after calcination. This calcium silicate matrix acts as a thermally stable and mechanically hard support for CaO deposited on it by further impregnation. The CaO-impregnated sorbent exhibits a stable CaO conversion at Ca-looping conditions whose value depends on the CaO wt% deposited on the calcium silicate matrix, which can be increased by successive reimpregnations. A 10 wt% CaO impregnated sorbent reaches a stable conversion above 0.6 whereas the stable conversion of a 30 wt% CaO impregnated sorbent is around 0.3, which is much larger than the residual conversion of CaO derived from natural limestone (between 0.07 and 0.08). Moreover, particle size distribution measurements of samples predispersed in a liquid and subjected to high energy ultrasonic waves indicate that the CaO-impregnated sorbent has a relatively high mechanical strength as compared to limestone derived CaO

  7. The calcium-sensing receptor changes cell shape via a beta-arrestin-1 ARNO ARF6 ELMO protein network.

    Science.gov (United States)

    Bouschet, Tristan; Martin, Stéphane; Kanamarlapudi, Venkateswarlu; Mundell, Stuart; Henley, Jeremy M

    2007-08-01

    G-protein-coupled receptors (GPCRs) transduce the binding of extracellular stimuli into intracellular signalling cascades that can lead to morphological changes. Here, we demonstrate that stimulation of the calcium-sensing receptor (CaSR), a GPCR that promotes chemotaxis by detecting increases in extracellular calcium, triggers plasma membrane (PM) ruffling via a pathway that involves beta-arrestin 1, Arf nucleotide binding site opener (ARNO), ADP-ribosylating factor 6 (ARF6) and engulfment and cell motility protein (ELMO). Expression of dominant negative beta-arrestin 1 or its knockdown with siRNA impaired the CaSR-induced PM ruffling response. Expression of a catalytically inactive ARNO also reduced CaSR-induced PM ruffling. Furthermore, beta-arrestin 1 co-immunoprecipitated with the CaSR and ARNO under resting conditions. Agonist treatment did not markedly alter beta-arrestin 1 binding to the CaSR or to ARNO but it did elicit the translocation and colocalisation of the CaSR, beta-arrestin 1 and ARNO to membrane protrusions. Furthermore, ARF6 and ELMO, two proteins known to couple ARNO to the cytoskeleton, were required for CaSR-dependent morphological changes and translocated to the PM ruffles. These data suggest that cells ruffle upon CaSR stimulation via a mechanism that involves translocation of beta-arrestin 1 pre-assembled with the CaSR or ARNO, and that ELMO plays an essential role in this CaSR-signalling-induced cytoskeletal reorganisation.

  8. Ozone (O{sub 3}) elicits neurotoxicity in spinal cord neurons (SCNs) by inducing ER Ca{sup 2+} release and activating the CaMKII/MAPK signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yun; Lin, Xiaowen; Zhao, XueJun; Xie, Juntian; JunNan, Wang; Sun, Tao; Fu, Zhijian, E-mail: zhijian_fu@163.com

    2014-11-01

    Ozone (O{sub 3}) is widely used in the treatment of spinal cord related diseases. Excess or accumulation of this photochemical air can however be neurotoxic. In this study, in vitro cultured Wister rat spinal cord neurons (SCNs) were used to investigate the detrimental effects and underlying mechanisms of O{sub 3}. Ozone in a dose-dependent manner inhibited cell viability at a range of 20 to 500 μg/ml, with the dose at 40 μg/ml resulting in a decrease of cell viability to 75%. The cell death after O{sub 3} exposure was related to endoplasmic reticulum (ER) calcium (Ca{sup 2+}) release. Intracellular Ca{sup 2+} chelator, ER stabilizer (inositol 1,4,5-trisphosphate receptor (IP3R) antagonist and ryanodine receptor (RyR) antagonist) and calcium/calmodulin-dependent protein kinase II (CaMKII) antagonist could effectively block Ca{sup 2+} mobilization and inhibit cell death following 40 μg/ml O{sub 3} exposure. In addition, ER Ca{sup 2+} release due to O{sub 3} exposure enhanced phospho-p38 and phospho-JNK levels and apoptosis of SCNs through activating CaMKII. Based on these results, we confirm that ozone elicits neurotoxicity in SCNs via inducing ER Ca{sup 2+} release and activating CaMKII/MAPK signaling pathway. Therefore, physicians should get attention to the selection of treatment concentrations of oxygen/ozone. And, approaches, such as chelating intracellular Ca{sup 2+} and stabilizing neuronal Ca{sup 2+} homeostasis could effectively ameliorate the neurotoxicity of O{sub 3}. - Highlights: • Exposure to O{sub 3} can reduce the viability of SCNs and cause the cell death. • Exposure to O{sub 3} can trigger RyR and IP3R dependent intracellular Ca{sup 2+} release. • Exposure to O{sub 3} can enhance the phospho-CaMKII, phospho-JNK and phospho-p38 levels.

  9. Calcium sensing receptor as a novel mediator of adipose tissue dysfunction: mechanisms and potential clinical implications

    Directory of Open Access Journals (Sweden)

    Roberto Bravo

    2016-09-01

    Full Text Available Obesity is currently a serious worldwide public health problem, reaching pandemic levels. For decades, dietary and behavioral approaches have failed to prevent this disease from expanding, and health authorities are challenged by the elevated prevalence of co-morbid conditions. Understanding how obesity-associated diseases develop from a basic science approach is recognized as an urgent task to face this growing problem. White adipose tissue is an active endocrine organ, with a crucial influence on whole-body homeostasis. White adipose tissue dysfunction plays a key role linking obesity with its associated diseases such as type 2 diabetes mellitus, cardiovascular disease and some cancers. Among the regulators of white adipose tissue physiology, the calcium-sensing receptor has arisen as a potential mediator of white adipose tissue dysfunction. Expression of the receptor has been described in human preadipocytes, adipocytes, and the human adipose cell lines LS14 and SW872. The evidence suggests that calcium-sensing receptor activation in the visceral (i.e. unhealthy white adipose tissue is associated with an increased proliferation of adipose progenitor cells and elevated adipocyte differentiation. In addition, exposure of adipose cells to calcium-sensing receptor activators in vitro elevates proinflammatory cytokine expression and secretion. An increased proinflammatory environment in white adipose tissue plays a key role in the development of white adipose tissue dysfunction that leads to peripheral organ fat deposition and insulin resistance, among other consequences. We propose that calcium-sensing receptor may be one relevant therapeutic target in the struggle to confront the health consequences of the current worldwide obesity pandemic.

  10. Hydrolysis of molten CaCl2-CaF2 with additions of CaO

    Directory of Open Access Journals (Sweden)

    Espen Olsen

    2017-10-01

    Full Text Available Calcium halide based molten salts have recently attracted interest for a number of applications such as direct reduction of oxides for metal production and as liquefying agent in cyclic sorption processes for CO2 by CaO from dilute flue gases (Ca-looping. A fundamental aspect of these melts is the possible hydrolysis reaction upon exposure to gaseous H2O forming corrosive and poisonous hydrogen halides. In this work experiments have been performed investigating the formation of HCl and HF from a molten salt consisting of a 13.8 wt% CaF2 in CaCl2 eutectic exposed to a flowing gas consisting of 10 vol% H2O in N2. Hydrolysis has been investigated as function of content of CaO and temperature. HCl and HF are shown to be formed at elevated temperatures; HCl forms to a substantially larger extent than HF. Addition of CaO has a marked, limiting effect on the hydrolysis. Thermodynamic modeling of the reaction indicates activity coefficients for CaO above unity in the system. For cyclic CO2-capture based on thermal swing, it is advisable to keep the temperature in the carbonation (absorption reactor well below 850 ℃ while maintaining a high CaO content if molten CaCl2 is employed. Similar conclusions can be drawn with regards to CaF2.

  11. Review article: loss of the calcium-sensing receptor in colonic epithelium is a key event in the pathogenesis of colon cancer.

    LENUS (Irish Health Repository)

    Rogers, Ailín C

    2012-03-01

    The calcium-sensing receptor (CaSR) is expressed abundantly in normal colonic epithelium and lost in colon cancer, but its exact role on a molecular level and within the carcinogenesis pathway is yet to be described. Epidemiologic studies show that inadequate dietary calcium predisposes to colon cancer; this may be due to the ability of calcium to bind and upregulate the CaSR. Loss of CaSR expression does not seem to be an early event in carcinogenesis; indeed it is associated with late stage, poorly differentiated, chemo-resistant tumors. Induction of CaSR expression in neoplastic colonocytes arrests tumor progression and deems tumors more sensitive to chemotherapy; hence CaSR may be an important target in colon cancer treatment. The CaSR has a complex role in colon cancer; however, more investigation is required on a molecular level to clarify its exact function in carcinogenesis. This review describes the mechanisms by which the CaSR is currently implicated in colon cancer and identifies areas where further study is needed.

  12. Inhibition of hydrogen sulfide on the proliferation of vascular smooth muscle cells involved in the modulation of calcium sensing receptor in high homocysteine

    International Nuclear Information System (INIS)

    Wang, Yuwen; Wang, Xiyao; Liang, Xiaohui; Wu, Jichao; Dong, Shiyun; Li, Hongzhu; Jin, Meili; Sun, Dianjun; Zhang, Weihua; Zhong, Xin

    2016-01-01

    Hyperhomocysteinemia induces the proliferation of vascular smooth muscle cells (VSMCs). Hydrogen sulfide (H 2 S) inhibits the phenotype switch of VSMCs and calcium-sensing receptor (CaSR) regulated the production of endogenous H 2 S. However, whether CaSR inhibits the proliferation of VSMCs by regulating the endogenous cystathionine-gamma-lyase (CSE, a major enzyme that produces H 2 S) pathway in high homocysteine (HHcy) has not been previously investigated. The intracellular calcium concentration, the concentration of H 2 S, the cell viability, the proliferation and the expression of proteins of cultured VSMCs from rat thoracic aortas were measured, respectively. The results showed that the [Ca 2+ ] i and the expression of p-CaMK and CSE increased upon treatment with CaSR agonist. In HHcy, the H 2 S concentration decrease, the proliferation and migration rate increased, the expression of Cyclin D1, PCNA, Osteopontin and p-Erk1/2 increased while the α-SM actin, P21 Cip/WAK−1 and Calponin decreased. The CaSR agonist or exogenous H 2 S significantly reversed the changes of VSMCs caused by HHcy. In conclusion, our results demonstrated that CaSR regulate the endogenous CSE/H 2 S is related to the PLC-IP 3 receptor and CaM signal pathways which inhibit the proliferation of VSMCs, and the latter is involved in the Erk1/2 dependent signal pathway in high homocysteine. - Highlights: • CaSR activation increased the production of endogenous H 2 S in high homocysteine VSMCs. • CaSR modulated the CSE/H 2 S are related to the PLC-IP 3 R and Ca 2+ -CaM signal pathways. • Inhibition of H 2 S on the proliferation of VSMCs is involved in the Erk1/2 pathway. • Explore the potential roles of CaSR in regulating VSMCs proliferation in high homocysteine.

  13. Ca doping of TSMTG-YBa2Cu3O7-δ/Y2BaCuO5 composites

    International Nuclear Information System (INIS)

    Delorme, F.; Harnois, C.; Monot-Laffez, I.; Marinel, S.

    2002-01-01

    Calcium doped YBa 2 Cu 3 O 7-δ /Y 2 BaCuO 5 bulk samples have been synthesised by the top-seeding-melt-texture growth (TSMTG) process up to 1 wt.% of CaCO 3 . Calcium additions up to 0.25 wt.% of CaCO 3 do not change the decomposition temperature whereas additions of 1 wt.% of CaCO 3 lead to an increase of the decomposition temperature of about 10 deg. C. This difference is not important enough to change the thermal cycle used to process YBa 2 Cu 3 O 7-δ undoped bulk samples. Microstructure studies show that no precursor or secondary phases containing calcium are present in the samples. Energy dispersive spectroscopy analyses have shown that Ca is present both in the YBa 2 Cu 3 O 7-δ matrix and the Y 2 BaCuO 5 particles. The position of the calcium atoms in the superconducting matrix is discussed. The calcium doped samples present slightly depressed critical temperatures but drastically depressed critical current densities

  14. Cr6+-containing phases in the system CaO-Al2O3-CrO42--H2O at 23 °C

    Science.gov (United States)

    Pöllmann, Herbert; Auer, Stephan

    2012-01-01

    Synthesis and investigation of lamellar calcium aluminium hydroxy salts was performed to study the incorporation of chromate ions in the interlayer of lamellar calcium aluminium hydroxy salts. Different AFm-phases (calcium aluminate hydrate with alumina, ferric oxide, mono-anion phase) containing chromate were synthesized. These AFm-phases belong to the group of layered double hydroxides (LDHs). 3CaO·Al2OCaCrO4·nH2O and C3A·1/2Ca(OH)2·1/2CaCrO4·12H2O were obtained as pure phases and their different distinct interlayer water contents and properties determined. Solid solution of chromate-containing phases and tetracalcium-aluminate-hydrate (TCAH) were studied. The uptake of chromate into TCAH from solutions was proven. Chromate contents in solution decrease to <0.2 mg/l.

  15. Effective role of CaO/P2O5 ratio on SiO2-CaO-P2O5 glass system

    Directory of Open Access Journals (Sweden)

    P. Kiran

    2017-05-01

    Full Text Available In the present work, the effect of the CaO/P2O5 ratio on the composition of sol-gel synthesized 58SiO2-(19 − xP2O5–(23 + xCaO (x = 0, 5, 10 and 15 mol% glass samples was studied. Further, the effect of NBO/BO ratio on hydroxy carbonated apatite layer (HCA forming ability based on dissolution behavior in simulated body fluid (SBF solution was also investigated. CaO/P2O5 ratios of synthesized glass samples were 1.2, 2, 3.6, and 9.5, respectively. NBO/BO ratios were obtained using Raman spectroscopic analysis as 0.58, 1.20, 1.46, and 1.78, respectively. All samples were soaked in the SBF solution for 7 days. The calculated weight losses of these samples were 58%, 64%, 83%, and 89% for corresponding NBO/BO ratios. The increase in CaO/P2O5 ratio increases the NBO/BO ratios. However, the increase in NBO/BO ratio increases HCA forming ability of SBF treated samples. The HCA crystalline layer formation was confirmed through X-ray Diffraction (XRD, Transmission Electron Microscopy (TEM, Scanning Electron Microscopy (SEM, Raman and Infrared spectroscopic analysis. Higher CaO/P2O5 ratio favors the increase in HCA formation for SBF treated calcium phospho silicate glasses.

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

    Science.gov (United States)

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

    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. PMID:15222030

  17. Vanadium oxide V2O5 reaction with calcium metavanadate

    International Nuclear Information System (INIS)

    Krasnenko, T.I.; Slobodin, B.V.; Zhilyaev, V.A.

    1983-01-01

    Complex physicochemical studies on the V 2 O 5 Ca(VO 3 ) 2 mixtures, annealed under different conditions, were conducted. It was established that the V 2 O 5 -Ca(VO 3 ) 2 system is characterized by the following features: defective structure of initial components, which are in equilibrium state; irreversible structural transformation without changes in the macrosymmetry (530 deg C) of calcium metavanadate, deficient in calcium and oxygen; melting of eutectic mixture of components which are in equilibrium at 616+-3 deg C; Ca(VO 3 ) 2 melting with decomposition at 775+-3 deg C. Besides this, the formation of oxide vanadium bronze of β-type calcium is possible under some conditions (narrow temperature range, certain partial oxygen pressure, etc)

  18. Inhibition of hydrogen sulfide on the proliferation of vascular smooth muscle cells involved in the modulation of calcium sensing receptor in high homocysteine

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuwen; Wang, Xiyao [Department of Clinical Laboratory, The second Affiliated Hospital of Harbin Medical University, Harbin 150081 (China); Liang, Xiaohui [Department of Radiology, Central Hospital of the Red Cross, Harbin 150080 (China); Wu, Jichao; Dong, Shiyun; Li, Hongzhu [Department of Pathophysiology, Harbin Medical University, Harbin 150081 (China); Jin, Meili [Department of Clinical Laboratory, The second Affiliated Hospital of Harbin Medical University, Harbin 150081 (China); Sun, Dianjun [Center for Endemic Disease Control, Chinese Center for Disease Control and Prevention, Harbin Medical University, Harbin 150086 (China); Zhang, Weihua [Department of Pathophysiology, Harbin Medical University, Harbin 150081 (China); Zhong, Xin, E-mail: xzhong1111@163.com [Department of Pathophysiology, Harbin Medical University, Harbin 150081 (China)

    2016-09-10

    Hyperhomocysteinemia induces the proliferation of vascular smooth muscle cells (VSMCs). Hydrogen sulfide (H{sub 2}S) inhibits the phenotype switch of VSMCs and calcium-sensing receptor (CaSR) regulated the production of endogenous H{sub 2}S. However, whether CaSR inhibits the proliferation of VSMCs by regulating the endogenous cystathionine-gamma-lyase (CSE, a major enzyme that produces H{sub 2}S) pathway in high homocysteine (HHcy) has not been previously investigated. The intracellular calcium concentration, the concentration of H{sub 2}S, the cell viability, the proliferation and the expression of proteins of cultured VSMCs from rat thoracic aortas were measured, respectively. The results showed that the [Ca{sup 2+}]{sub i} and the expression of p-CaMK and CSE increased upon treatment with CaSR agonist. In HHcy, the H{sub 2}S concentration decrease, the proliferation and migration rate increased, the expression of Cyclin D1, PCNA, Osteopontin and p-Erk1/2 increased while the α-SM actin, P21{sup Cip/WAK−1} and Calponin decreased. The CaSR agonist or exogenous H{sub 2}S significantly reversed the changes of VSMCs caused by HHcy. In conclusion, our results demonstrated that CaSR regulate the endogenous CSE/H{sub 2}S is related to the PLC-IP{sub 3} receptor and CaM signal pathways which inhibit the proliferation of VSMCs, and the latter is involved in the Erk1/2 dependent signal pathway in high homocysteine. - Highlights: • CaSR activation increased the production of endogenous H{sub 2}S in high homocysteine VSMCs. • CaSR modulated the CSE/H{sub 2}S are related to the PLC-IP{sub 3}R and Ca{sup 2+}-CaM signal pathways. • Inhibition of H{sub 2}S on the proliferation of VSMCs is involved in the Erk1/2 pathway. • Explore the potential roles of CaSR in regulating VSMCs proliferation in high homocysteine.

  19. Calcium-Induced Activation of a Mutant G-Protein-Coupled Receptor Causes In Vitro Transformation of NIH/3T3 Cells

    Directory of Open Access Journals (Sweden)

    Ana O. Hoff

    1999-12-01

    Full Text Available The calcium-sensing receptor (CaR is a G-proteincoupled receptor that is widely expressed, has tissuespecific functions, regulates cell growth. Activating mutations of this receptor cause autosomal dominant hypocalcemia, a syndrome characterized by hypocalcemia and hypercalciuria. The identification of a family with an activating mutation of the CaR (Thr151 Met in which hypocalcemia cosegregates with several unusual neoplasms led us to examine the transforming effects of this mutant receptor. Transfection of NIH/3T3 cells with the mutant but not the normal receptor supported colony formation in soft agar at subphysiologic calcium concentrations. The mutant CaR causes a calcium-dependent activation of the extracellular signal-regulated protein kinase (ERK 1/2 and Jun-N-terminal kinase/stress-activated (JNK/ SAPK pathways, but not P38 MAP kinase. These findings contribute to a growing body of information suggesting that this receptor plays a role in the regulation of cellular proliferation, that aberrant activation of the mutant receptor in this family may play a role in the unusual neoplastic manifestations.

  20. Crystallization and sintering characteristics of CaO-Al2O3-SiO2 glasses in the presence of TiO2, CaF2 and ZrO2

    International Nuclear Information System (INIS)

    Banijamali, S.; Eftekhari Yekta, B.; Rezaie, H.R.; Marghussian, V.K.

    2009-01-01

    In this study, the effects of different amounts of TiO 2 , ZrO 2 and CaF 2 nucleating agents on sinterability, crystallization, mechanical properties and chemical resistance of glass-ceramics belonging to the CaO-Al 2 O 3 -SiO 2 system were investigated, using differential thermal analysis (DTA), X-ray diffractometry (XRD), scanning electron microscopy (SEM), mechanical and chemical resistance measurements. It was found that in CaF 2 containing samples, the sinterability, crystallization and mechanical properties were improved by increasing of CaF 2 amount. However, addition of ZrO 2 and TiO 2 increases the firing temperature required for complete densification of specimens. Our experiments showed that fluctuations of chemical composition of the residual glass phases during sintering were responsible for these dissimilar trends and greatly influenced mechanical and chemical properties. According to the obtained results, appropriate sinterability, acceptable mechanical and chemical properties, as well as desirable whiteness of the most promising specimens make them suitable choices for floor tile applications. The main crystallization phases in all fully sintered glass-ceramics were wollastonite, anorthite and calcium aluminum silicate.

  1. Calcium signaling through CaMKII regulates hepatic glucose production in fasting and obesity.

    Science.gov (United States)

    Ozcan, Lale; Wong, Catherine C L; Li, Gang; Xu, Tao; Pajvani, Utpal; Park, Sung Kyu Robin; Wronska, Anetta; Chen, Bi-Xing; Marks, Andrew R; Fukamizu, Akiyoshi; Backs, Johannes; Singer, Harold A; Yates, John R; Accili, Domenico; Tabas, Ira

    2012-05-02

    Hepatic glucose production (HGP) is crucial for glucose homeostasis, but the underlying mechanisms have not been fully elucidated. Here, we show that a calcium-sensing enzyme, CaMKII, is activated in a calcium- and IP3R-dependent manner by cAMP and glucagon in primary hepatocytes and by glucagon and fasting in vivo. Genetic deficiency or inhibition of CaMKII blocks nuclear translocation of FoxO1 by affecting its phosphorylation, impairs fasting- and glucagon/cAMP-induced glycogenolysis and gluconeogenesis, and lowers blood glucose levels, while constitutively active CaMKII has the opposite effects. Importantly, the suppressive effect of CaMKII deficiency on glucose metabolism is abrogated by transduction with constitutively nuclear FoxO1, indicating that the effect of CaMKII deficiency requires nuclear exclusion of FoxO1. This same pathway is also involved in excessive HGP in the setting of obesity. These results reveal a calcium-mediated signaling pathway involved in FoxO1 nuclear localization and hepatic glucose homeostasis. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. H2O2 augments cytosolic calcium in nucleus tractus solitarii neurons via multiple voltage-gated calcium channels.

    Science.gov (United States)

    Ostrowski, Tim D; Dantzler, Heather A; Polo-Parada, Luis; Kline, David D

    2017-05-01

    Reactive oxygen species (ROS) play a profound role in cardiorespiratory function under normal physiological conditions and disease states. ROS can influence neuronal activity by altering various ion channels and transporters. Within the nucleus tractus solitarii (nTS), a vital brainstem area for cardiorespiratory control, hydrogen peroxide (H 2 O 2 ) induces sustained hyperexcitability following an initial depression of neuronal activity. The mechanism(s) associated with the delayed hyperexcitability are unknown. Here we evaluate the effect(s) of H 2 O 2 on cytosolic Ca 2+ (via fura-2 imaging) and voltage-dependent calcium currents in dissociated rat nTS neurons. H 2 O 2 perfusion (200 µM; 1 min) induced a delayed, slow, and moderate increase (~27%) in intracellular Ca 2+ concentration ([Ca 2+ ] i ). The H 2 O 2 -mediated increase in [Ca 2+ ] i prevailed during thapsigargin, excluding the endoplasmic reticulum as a Ca 2+ source. The effect, however, was abolished by removal of extracellular Ca 2+ or the addition of cadmium to the bath solution, suggesting voltage-gated Ca 2+ channels (VGCCs) as targets for H 2 O 2 modulation. Recording of the total voltage-dependent Ca 2+ current confirmed H 2 O 2 enhanced Ca 2+ entry. Blocking VGCC L, N, and P/Q subtypes decreased the number of cells and their calcium currents that respond to H 2 O 2 The number of responder cells to H 2 O 2 also decreased in the presence of dithiothreitol, suggesting the actions of H 2 O 2 were dependent on sulfhydryl oxidation. In summary, here, we have shown that H 2 O 2 increases [Ca 2+ ] i and its Ca 2+ currents, which is dependent on multiple VGCCs likely by oxidation of sulfhydryl groups. These processes presumably contribute to the previously observed delayed hyperexcitability of nTS neurons in in vitro brainstem slices. Copyright © 2017 the American Physiological Society.

  3. Calcium Occupancy of N-terminal Sites within Calmodulin Induces Inhibition of the Ryanodine Receptor Calcium Release Channel

    Energy Technology Data Exchange (ETDEWEB)

    Boschek, Curt B; Jones, Terry E; Squier, Thomas C; Bigelow, Diana J

    2007-08-01

    Calmodulin (CaM) regulates calcium release from intracellular stores in skeletal muscle through its association with the ryanodine receptor (RyR1) calcium release channel, where CaM association enhances channel opening at resting calcium levels and its closing at micromolar calcium levels associated with muscle contraction. A high-affinity CaM-binding sequence (RyRp) has been identified in RyR1, which corresponds to a 30-residue sequence (i.e., K3614 – N3643) located within the central portion of the primary sequence. However, it is currently unclear whether the identified CaM-binding sequence a) senses calcium over the physiological range of calcium-concentrations associated with RyR1 regulation or b) plays a structural role unrelated to the calcium-dependent modulation of RyR1 function. Therefore, we have measured the calcium-dependent activation of the individual domains of CaM in association with RyRp and their relationship to the CaM-dependent regulation of RyR1. These measurements utilize an engineered CaM, permitting the site-specific incorporation of N-(1-pyrene) maleimide at either T34C (PyN-CaM) or T110C (PyC-CaM) in the N- and C-domains, respectively. Consistent with prior measurements, we observe a high-affinity association between both apo- and calcium-activated CaM and RyRp. Upon association with RyRp, fluorescence changes in PyN-CaM or PyC-CaM permit the measurement of the calcium-activation of these individual domains. Fluorescence changes upon calcium-activation of PyC-CaM in association with RyRp are indicative of high-affinity calcium-dependent activation of the C-terminal domain of CaM bound to RyRp at resting calcium levels and the activation of the N-terminal domain at levels of calcium associated cellular activation. In comparison, occupancy of calcium-binding sites in the N-domain of CaM mirrors the calcium-dependence of RyR1 inhibition observed at activating calcium levels, where [Ca]1/2 = 4.3 0.4 μM, suggesting a direct regulation of Ry

  4. Nucleotide transmitters ATP and ADP mediate intercellular calcium wave communication via P2Y12/13 receptors among BV-2 microglia.

    Directory of Open Access Journals (Sweden)

    Pengchong Jiang

    Full Text Available Nerve injury is accompanied by a liberation of diverse nucleotides, some of which act as 'find/eat-me' signals in mediating neuron-glial interplay. Intercellular Ca2+ wave (ICW communication is the main approach by which glial cells interact and coordinate with each other to execute immune defense. However, the detailed mechanisms on how these nucleotides participate in ICW communication remain largely unclear. In the present work, we employed a mechanical stimulus to an individual BV-2 microglia to simulate localized injury. Remarkable ICW propagation was observed no matter whether calcium was in the environment or not. Apyrase (ATP/ADP-hydrolyzing enzyme, suramin (broad-spectrum P2 receptor antagonist, 2-APB (IP3 receptor blocker and thapsigargin (endoplasmic reticulum calcium pump inhibitor potently inhibited these ICWs, respectively, indicating the dependence of nucleotide signals and P2Y receptors. Then, we detected the involvement of five naturally occurring nucleotides (ATP, ADP, UTP, UDP and UDP-glucose by desensitizing receptors. Results showed that desensitization with ATP and ADP could block ICW propagation in a dose-dependent manner, whereas other nucleotides had little effect. Meanwhile, the expression of P2Y receptors in BV-2 microglia was identified and their contributions were analyzed, from which we suggested P2Y12/13 receptors activation mostly contributed to ICWs. Besides, we estimated that extracellular ATP and ADP concentration sensed by BV-2 microglia was about 0.3 μM during ICWs by analyzing calcium dynamic characteristics. Taken together, these results demonstrated that the nucleotides ATP and ADP were predominant signal transmitters in mechanical stimulation-induced ICW communication through acting on P2Y12/13 receptors in BV-2 microglia.

  5. Modulation of CaV1.2 calcium channel by neuropeptide W regulates vascular myogenic tone via G protein-coupled receptor 7.

    Science.gov (United States)

    Ji, Li; Zhu, Huayuan; Chen, Hong; Fan, Wenyong; Chen, Junjie; Chen, Jing; Zhu, Guoqing; Wang, Juejin

    2015-12-01

    Neuropeptide W (NPW), an endogenous ligand for the G protein-coupled receptor 7 (GPR7), was first found to make important roles in central nerve system. In periphery, NPW was also present and regulated intracellular calcium homeostasis by L-type calcium channels. This study was designed to discover the effects of NPW-GPR7 on the function of CaV1.2 calcium channels in the vascular smooth muscle cells (VSMCs) and vasotone of arterial vessels. By whole-cell patch clamp, we studied the effects of NPW-23, the active form of NPW, on the CaV1.2 channels in the heterologously transfected human embryonic kidney 293 cells and VSMCs isolated from rat. Living system was used to explore the physiological function of NPW-23 in arterial myogenic tone. To investigate the pathological relevance, NPW mRNA level of mesenteric arteries was measured in the hypertensive and normotensive rats. NPW's receptor GPR7 was coexpressed with CaV1.2 channels in arterial smooth muscle. NPW-23 increased the ICa,L in transfected human embryonic kidney 293 cells and VSMCs via GPR7, which could be abrogated by phospholipase C (PLC)/protein kinase C (PKC) inhibitors, not protein kinase A or protein kinase G inhibitor. After NPW-23 application, the expression of pan phospho-PKC was increased; moreover, intracellular diacylglycerol level, the second messenger catalyzed by PLC, was increased 1.5-2-fold. Application with NPW-23 increased pressure-induced vasotone of the rat mesenteric arteries. Importantly, the expression of NPW was decreased in the hypertensive rats. NPW-23 regulates ICa,L via GPR7, which is mediated by PLC/PKC signaling, and such a mechanism plays a role in modulating vascular myogenic tone, which may involve in the development of vascular hypertension.

  6. Interaction of CPCCOEt with a chimeric mGlu1b and calcium sensing receptor

    DEFF Research Database (Denmark)

    Bräuner-Osborne, H; Jensen, Anders A.; Krogsgaard-Larsen, P

    1999-01-01

    7-Hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt) has previously been shown to be a selective non-competitive antagonist at the metabotropic glutamate (mGlu) receptor subtype 1. In this study we have tested the effect of CPCCOEt on mGlu1b, the calcium sensing receptor (...

  7. Modeling the Onset of Phase Separation in CaO-SiO2-CaCl2 Chlorine-Containing Silicate Glasses.

    Science.gov (United States)

    Swansbury, Laura A; Mountjoy, Gavin; Chen, Xiaojing; Karpukhina, Natalia; Hill, Robert

    2017-06-08

    The addition of chlorine into a bioactive glass composition is expected to reduce its abrasiveness and increase its bioactivity, which is important for dental applications such as toothpastes. There is a lack of information and understanding regarding the structural role of chlorine in chlorine-containing bioactive silicate glasses. This has prompted classical core-shell model molecular dynamics simulations of (50 - x/2)CaO-(50 - x/2)SiO 2 -xCaCl 2 glasses to be performed, where x ranges from x = 0.0 to 43.1 mol % CaCl 2 . These ternary glasses are advantageous for a fundamental study because they do not have additional network formers (e.g., phosphorus pentoxide) or modifiers (e.g., sodium) typically found in bioactive glass compositions. The (50 - x/2)CaO-(50 - x/2)SiO 2 -xCaCl 2 glasses were seen to become phase-separated around the x = 16.1 mol % CaCl 2 composition, and chlorine predominantly coordinated with calcium. These findings provide a solid foundation for further computational modeling work on more complex chlorine-containing bioactive glass compositions.

  8. Calcium flouride (CaF2) from oyster shell as a raw material for thermoluminescence dosimeter

    International Nuclear Information System (INIS)

    Coloma, Lyra C.; Fanuga, Lyn N.; Ocreto, Cherries Ann; Rodriguez, Richita

    2006-03-01

    This study aims to develop a thermoluminescence dosimeter raw material made of calcium fluoride from locally available seashells that is suitable for personal radiation monitoring. Oyster shells were collected and grounded as powder samples and analyzed for calcium fluoride (CaF 2 ) content using XRF and XRD testing. Samples include pure CaF 2 , pure oyster shell, and oyster shells treated with acid. Based from the XRF results, natural oyster shell (w/ and w/o HNO 3 ) had high percentage of calcium about 49.64% and 47.45%, next to the pure calcium fluoride of 51.08%. X-ray diffractrogram shows that oyster sample had the nearest desired structure of CaF 2 compared with two seashells relative to the pure CaF 2 as standard materials. Results show that all of the natural oyster samples displayed TL emission glow curves at the temperature range 200-300 o C. It was also found that pure oyster sample has better TL response as compared to the treated ones. The researchers concluded that the calcium fluoride from oyster shells (without acid and heated) is a potentially good low-cost TLD raw material and may be used as an alternative for the much more expensive LiF dosimeters. (Authors)

  9. Synthesis and hydration behavior of calcium zirconium aluminate (Ca7ZrAl6O18) cement

    International Nuclear Information System (INIS)

    Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

    2014-01-01

    Calcium zirconium aluminate (Ca 7 ZrAl 6 O 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 7 ZrAl 6 O 18 was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO 3 coexisted with Ca 7 ZrAl 6 O 18 even at higher temperature (1400 °C). Unexpectedly, Ca 7 ZrAl 6 O 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 7 ZrAl 6 O 18 was similar to that of Ca 3 Al 2 O 6 (C3A), but the hydration products were Ca 3 Al 2 O 6 ·6H 2 O (C3AH6) and several intermediate products. Thus, Zr (or ZrO 2 ) stabilized the intermediate hydration products of C3A

  10. Polyvalent cation receptor proteins (CaRs) are salinity sensors in fish.

    Science.gov (United States)

    Nearing, J; Betka, M; Quinn, S; Hentschel, H; Elger, M; Baum, M; Bai, M; Chattopadyhay, N; Brown, E M; Hebert, S C; Harris, H W

    2002-07-09

    To determine whether calcium polyvalent cation-sensing receptors (CaRs) are salinity sensors in fish, we used a homology-based cloning strategy to isolate a 4.1-kb cDNA encoding a 1,027-aa dogfish shark (Squalus acanthias) kidney CaR. Expression studies in human embryonic kidney cells reveal that shark kidney senses combinations of Ca(2+), Mg(2+), and Na(+) ions at concentrations present in seawater and kidney tubules. Shark kidney is expressed in multiple shark osmoregulatory organs, including specific tubules of the kidney, rectal gland, stomach, intestine, olfactory lamellae, gill, and brain. Reverse transcriptase-PCR amplification using specific primers in two teleost fish, winter flounder (Pleuronectes americanus) and Atlantic salmon (Salmo salar), reveals a similar pattern of CaR tissue expression. Exposure of the lumen of winter flounder urinary bladder to the CaR agonists, Gd(3+) and neomycin, reversibly inhibit volume transport, which is important for euryhaline teleost survival in seawater. Within 24-72 hr after transfer of freshwater-adapted Atlantic salmon to seawater, there are increases in their plasma Ca(2+), Mg(2+), and Na(+) that likely serve as a signal for internal CaRs, i.e., brain, to sense alterations in salinity in the surrounding water. We conclude that CaRs act as salinity sensors in both teleost and elasmobranch fish. Their tissue expression patterns in fish provide insights into CaR functions in terrestrial animals including humans.

  11. Structure of Na2O·MO·SiO2·CaF2 (M=Mg, Ca) oxyfluoride glasses

    International Nuclear Information System (INIS)

    Cheng Jinshu; Deng Wei; Wang Mitang

    2012-01-01

    (9-x)CaO·xMgO·15Na 2 O·60SiO 2 ·16CaF 2 (x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with 29 Si and 19 F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q 3 →Q 4 +Q 2 (Q n is a SiO 4 tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO 4 , and removed other modifying ions for charge compensation. This reaction was confirmed by 29 Si MAS NMR. 19 F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si-F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF + species. Meanwhile, some part of Na + ions complex F - in the form of F-Na(6).

  12. Comparison of phosgene, chlorine, and hydrogen chloride as reagents for converting molten CaO.CaCl2 to CaCl2

    International Nuclear Information System (INIS)

    Fife, K.W.

    1985-01-01

    One method at Los Alamos for preparing impure plutonium metal from the impure oxide is by batch reduction with calcium metal at 850 0 C in a CaCl 2 solvent. The solvent salt from this reduction is currently discarded as low-level radioactivity waste only because it is saturated with the CaO byproduct. We have demonstrated a pyrochemical technique for converting the CaO to CaCl 2 thereby incorporating solvent recycling into the batch reduction process. We will discuss the effectiveness of HCl, Cl 2 , and COCl 2 as chlorinating agents and recycling actual spent process solvent salts. 6 refs., 8 figs

  13. 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.

  14. Crystal structure and spectroscopic behavior of synthetic novgorodovaite Ca2(C2O4)Cl2·2H2O and its twinned triclinic heptahydrate analog

    Science.gov (United States)

    Piro, Oscar E.; Echeverría, Gustavo A.; González-Baró, Ana C.; Baran, Enrique J.

    2018-02-01

    Synthetic novgorodovaite analog Ca2(C2O4)Cl2·2H2O is identical to its natural counterpart. It crystallizes in the monoclinic I2/ m space group with a = 6.9352(3), b = 7.3800(4), c = 7.4426(3) Å, β = 94.303(4)°, V = 379.85(3) Å3 and Z = 2. The heptahydrate analog, Ca2(C2O4)Cl2·7H2O, crystallizes as triclinic twins in the P \\overline{1} space group with a = 7.3928(8), b = 8.9925(4), c = 10.484(2) Å, α = 84.070(7), β = 70.95(1), γ = 88.545(7)°, V = 655.3(1) Å3 and Z = 2. The crystal packing of both calcium oxalate-chloride double salts favors the directional bonding of oxalate, C2O4 2-, ligands to calcium ions as do other related calcium oxalate minerals. The π-bonding between C and O atoms of the C2O4 2- oxalate group leaves sp 2-hydridised orbitals of the oxygen atoms available for bonding to Ca. Thus, the Ca-O bonds in both calcium oxalate-chloride double salts are directed so as to lie in the plane of the oxalate group. This behavior is reinforced by the short O···O distances between the oxygens attached to a given carbon atom, which favors them bonding to a shared Ca atom in bidentate fashion. Strong bonding in the plane of the oxalate anion and wide spacing perpendicular to that plane due to repulsion between oxalate π-electron clouds gives rise to a polymerized structural units which are common to both hydrates, explaining the nearly equal cell constants 7.4 Å which are defined by the periodicity of Ca-oxalate chains in the framework (monoclinic b ≈ triclinic a). When compared with novgorodovaite, the higher water content of Ca2(C2O4)Cl2·7H2O leads to some major differences in their structures and ensuing physical properties. While novgorodovaite has a three-dimensional framework structure, in the higher hydrate, the highly polar water molecules displace chloride ions from the calcium coordination sphere and surround them through OwH···Cl hydrogen bonds. As a result, polymerization in Ca2(C2O4)Cl2·7H2O solid is limited to the formation

  15. The role of calcium-sensing receptor and signalling pathways in the pathophysiology in two in vitro models of malignant hypercalcemia: the rat rice H-500 Leydig testis cancer and prostate cancer (PC-3) cells. Expression and regulation of pituitary tumor transforming gene in Leydig testis cancer

    DEFF Research Database (Denmark)

    Tfelt-Hansen, J.

    2008-01-01

    The calcium-sensing receptor (CaR) is a seven transmembrane receptor incorporated into the cell membrane that is sensitive to extracellular calcium and other cations. The finding that the CaR is expressed on cancer cells has opened the door to a new understanding of the role of extracellular...... too many adverse effects on calcium homeostasis. In conclusion, the CaR plays diverse roles in cancer-acting as an inhibitor of cell proliferation in the colon crypt cells giving rise to colon cancer but as a promalignant receptor in most other cancer types, including Leydig cell cancers...... calcium as a promalignant stimulus through the CaR and its signaling apparatus as demonstrated in this thesis. I found, in a model of humoral hypercalcemia of malignancy (HHM), that stimulation of the CaR worsens the promalignant features of the testicular H-500 Leydig cancer cells that were used in my...

  16. Interaction between Ca++-channel antagonists and α2-adrenergic receptors in rabbit ileal cell membrane

    International Nuclear Information System (INIS)

    Homeidan, F.R.; Wicks, J.; Cusolito, S.; El-Sabban, M.E.; Sharp, G.W.G.; Donowitz, M.

    1986-01-01

    An interaction between Ca ++ -channel antagonists and the α 2 -adrenergic receptor on active electrolyte transport was demonstrated in rabbit ileum. Clonidine, an α 2 -agonist, stimulated NaCl absorption apparently by Ca ++ -channel antagonism since it inhibited 45 Ca ++ uptake across the basolateral membrane and decreased total ileal calcium content. This stimulation was inhibited by the Ca ++ -channel antagonists dl- and l-verapamil and cadmium but not by nifedipine. The binding of 3 H-yohimbine, a specific α 2 -adrenergic antagonist, was studied on purified ileal cell membranes using a rapid filtration technique. dl-Verapamil and Cd ++ inhibited the specific binding of 3 H-yohimbine over the same concentration range in which they affected transport. In contrast, nifedipine had no effect on binding, just as it had no effect on clonidine-stimulated NaCl absorption. These data demonstrate that there is an interaction between Ca ++ -channels and α 2 -adrenergic receptors in ileal basolateral membranes. Some Ca ++ -channel antagonists alter α 2 -adrenergic binding to the receptor and α 2 -agonist binding leads to changes in Ca ++ entry. A close spatial relationship between the Ca ++ -channel and the α 2 -receptor could explain the data

  17. Mitigation of nitrous oxide (N2O) emissions from denitrifying fluidized bed bioreactors (DFBBRs) using calcium.

    Science.gov (United States)

    Eldyasti, Ahmed; Nakhla, George; Zhu, Jesse

    2014-12-01

    Nitrous oxide (N2O) is a significant anthropogenic greenhouse gases (AnGHGs) emitted from biological nutrient removal (BNR) processes. In this study, N2O production from denitrifying fluidized bed bioreactors (DFBBR) was reduced using calcium (Ca2+) dosage. The DFBBRs were operated on a synthetic municipal wastewater at four different calcium concentrations ranging from the typical municipal wastewater Ca2+ concentration (60 mg Ca2+/L) to 240 mg Ca2+/L at two different COD/N ratios. N2O emission rates, extracellular polymeric substances (EPS), water quality parameters, and microscopic images were monitored regularly in both phases. Calcium concentrations played a significant role in biofilm morphology with the detachment rates for R120Ca, R180Ca, and R240Ca 75% lower than for R60Ca, respectively. The N2O conversion rate at the typical municipal wastewater Ca2+ concentration (R60Ca) was about 0.53% of the influent nitrogen loading as compared with 0.34%, 0.42%, and 0.41% for R120Ca, R180Ca, and R240Ca, respectively corresponding to 21-36% reduction. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Analysis of α-Klotho, Fibroblast Growth Factor-, Vitamin-D and Calcium-Sensing Receptor in 70 Patients with Secondary Hyperparathyroidism

    Directory of Open Access Journals (Sweden)

    Joerg Latus

    2013-03-01

    Full Text Available Background/Aims: Secondary hyperparathyroidism (sHPT is known as a very common complication in patients with chronic kidney disease, and G-protein-coupled calcium-sensing receptor (CaSR, Vitamin D receptor (VDR and Fibroblast growth factor receptor (FGFR/Klotho complexes seem to be involved in its development. Methods: Hyperplastic parathyroid glands from 70 sHPT patients and normal parathyroid tissue from 7 patients were obtained during parathyroidectomy. Conventional morphological and immunohistochemical analysis of parathyroid glands was performed after dividing each slide in a 3x3 array. Results: The presence of lipocytes in the normal parathyroid gland and tissue architecture (nodal in patients with sHPT allows for discrimination between normal parathyroid glands and parathyroid glands of patients with sHPT. Protein expression of Klotho, FGFR, CaSR and VDR was higher in the normal parathyroid glands compared to the sHPT group (p0.05. Conclusions: CaSR, VDR and an impaired Klotho-FGFR-axis seem to be the major players in the development of sHPT. Whether the detected correlation between FGFR and VDR and the shift to a more mixed nuclear/cytoplasmic staining of VDR will yield new insights into the pathogenesis of the disease has to be evaluated in further studies.

  19. Calcium Sensing Receptor Mutations Implicated in Pancreatitis and Idiopathic Epilepsy Syndrome Disrupt an Arginine-rich Retention Motif

    Science.gov (United States)

    Stepanchick, Ann; McKenna, Jennifer; McGovern, Olivia; Huang, Ying; Breitwieser, Gerda E.

    2010-01-01

    Calcium sensing receptor (CaSR) mutations implicated in familial hypocalciuric hypercalcemia, pancreatitis and idiopathic epilepsy syndrome map to an extended arginine-rich region in the proximal carboxyl terminus. Arginine-rich motifs mediate endoplasmic reticulum retention and/or retrieval of multisubunit proteins so we asked whether these mutations, R886P, R896H or R898Q, altered CaSR targeting to the plasma membrane. Targeting was enhanced by all three mutations, and Ca2+-stimulated ERK1/2 phosphorylation was increased for R896H and R898Q. To define the role of the extended arginine-rich region in CaSR trafficking, we independently determined the contributions of R890/R891 and/or R896/K897/R898 motifs by mutation to alanine. Disruption of the motif(s) significantly increased surface expression and function relative to wt CaSR. The arginine-rich region is flanked by phosphorylation sites at S892 (protein kinase C) and S899 (protein kinase A). The phosphorylation state of S899 regulated recognition of the arginine-rich region; S899D showed increased surface localization. CaSR assembles in the endoplasmic reticulum as a covalent disulfide-linked dimer and we determined whether retention requires the presence of arginine-rich regions in both subunits. A single arginine-rich region within the dimer was sufficient to confer intracellular retention comparable to wt CaSR. We have identified an extended arginine-rich region in the proximal carboxyl terminus of CaSR (residues R890 - R898) which fosters intracellular retention of CaSR and is regulated by phosphorylation. Mutation(s) identified in chronic pancreatitis and idiopathic epilepsy syndrome therefore increase plasma membrane targeting of CaSR, likely contributing to the altered Ca2+ signaling characteristic of these diseases. PMID:20798521

  20. Sigma-1 Receptor Plays a Negative Modulation on N-type Calcium Channel

    Directory of Open Access Journals (Sweden)

    Kang Zhang

    2017-05-01

    Full Text Available The sigma-1 receptor is a 223 amino acids molecular chaperone with a single transmembrane domain. It is resident to eukaryotic mitochondrial-associated endoplasmic reticulum and plasma membranes. By chaperone-mediated interactions with ion channels, G-protein coupled receptors and cell-signaling molecules, the sigma-1 receptor performs broad physiological and pharmacological functions. Despite sigma-1 receptors have been confirmed to regulate various types of ion channels, the relationship between the sigma-1 receptor and N-type Ca2+ channel is still unclear. Considering both sigma-1 receptors and N-type Ca2+ channels are involved in intracellular calcium homeostasis and neurotransmission, we undertake studies to explore the possible interaction between these two proteins. In the experiment, we confirmed the expression of the sigma-1 receptors and the N-type calcium channels in the cholinergic interneurons (ChIs in rat striatum by using single-cell reverse transcription-polymerase chain reaction (scRT-PCR and immunofluorescence staining. N-type Ca2+ currents recorded from ChIs in the brain slice of rat striatum was depressed when sigma-1 receptor agonists (SKF-10047 and Pre-084 were administrated. The inhibition was completely abolished by sigma-1 receptor antagonist (BD-1063. Co-expression of the sigma-1 receptors and the N-type calcium channels in Xenopus oocytes presented a decrease of N-type Ca2+ current amplitude with an increase of sigma-1 receptor expression. SKF-10047 could further depress N-type Ca2+ currents recorded from oocytes. The fluorescence resonance energy transfer (FRET assays and co-immunoprecipitation (Co-IP demonstrated that sigma-1 receptors and N-type Ca2+ channels formed a protein complex when they were co-expressed in HEK-293T (Human Embryonic Kidney -293T cells. Our results revealed that the sigma-1 receptors played a negative modulation on N-type Ca2+ channels. The mechanism for the inhibition of sigma-1 receptors on

  1. Solid solubility of MgO in the calcium silicates of portland clinker. The effect of CaF2

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    1992-03-01

    Full Text Available The solid solubility of MgO in the calcium silicates of portland clinker has been determined by XRD and XDS. The influence that the presence of CaF2 has on said solubility has also been verified. The solid solution limit of MgO in C3S at 1275 ºC lies at about 1.0% wt, where the triclinic form II stabilizes. The presence of CaF2 does not alter the maximum value of the MgO solubilized in that silicate, although there does take place the stabilization of the triclinic polymorph II at lower MgO contents (between 0.3 - 0.6% wt. The maximum amount of solubilized MgO in βC2 at 1.050 ºC lies around 0.5% wt. This value does not change by the presence of CaF2.Se ha determinado por DRX y EDX la solubilidad sólida del MgO en los silicatos cálcicos del clínker portland. Se ha comprobado, así mismo la influencia que sobre dicha solubilidad tiene la presencia de CaF2. El límite de disolución sólida del MgO en el C3S a 1.275º C se sitúa alrededor del 1,0% en peso, estabilizándose la forma triclínica II. La presencia de CaF2 no altera el valor máximo de MgO solubilizado en este silicato, aunque si se produce la estabilización del polimorfo triclínico II a contenidos menores de MgO (entre 0,3 – 0,6% en peso. La cantidad máxima de MgO solubilizado en e/ βC2S a 1.050 ºC se sitúa en torno al 0,5% en peso. Este valor no se ve modificado por la presencia de CaF2.

  2. 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.

  3. Preparation and characterization of coating sodium trisilicate (Na2O.nSiO2) at calcium carbonate (CaCO3) for blowing agent in Mg alloy foam

    Science.gov (United States)

    Erryani, Aprilia; Lestari, Franciska Pramuji; Annur, Dhyah; Kartika, Ika

    2018-05-01

    The role of blowing agent in the manufacture of porous metal alloys is very important to produce the desired pore. The thermal stability and speed of foam formation have an effect on the resulting pore structure. In porous metal alloys, uniformity of size and pore deployment are the main determinants of the resulting alloys. The coating process of calcium carbonate (CaCO3) has been done using Sodium trisilicate solution by sol-gel method. Foaming agent was pretreated by coating SiO2 passive layer on the surface of CaCO3. This coating aims to produce a more stable blowing agent so that the foaming process can produce a more uniform pore size. The microstructure of the SiO2 passive was observed using Scanning Electron Microscope (SEM) equipped by Energy Dispersive X-Ray Spectrometer (EDS) mapping. The results showed coating CaCO3 using sodium trisilicate was successfully done creating a passive layer of SiO2 on the surface of CaCO3. By the coating process, the thermal stability of coated CaCO3 increased compared to uncoated CaCO3.

  4. The effect of CaO/SiO2 molar ratio of CaO-Al2O3-SiO2 glasses on their structure and reactivity in alkali activated system.

    Science.gov (United States)

    Kucharczyk, Sylwia; Sitarz, Maciej; Zajac, Maciej; Deja, Jan

    2018-04-05

    The influence of CaO/SiO 2 molar ratio of calcium aluminosilicate glasses on resulting structure and reactivity was investigated. Chemical compositions of glasses were chosen to mimic the composition of the fly ash and slag amorphous phase. Understanding the reactivity of these materials is of high importance allowing further development of the composite cements to limit the environmental footprint of cement industry. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were employed to examine the structure of glasses. Reactivity of the glasses was analyzed on paste samples after 1, 2, 7, 28 and 90days of curing by means of thermogravimetry (TGA), X-ray diffraction (XRD) and FTIR. Spectroscopic results emphasize dependence of the structure on the chemical composition of the glasses. The higher CaO/SiO 2 the more depolymerized the glass network is, though there is no direct correlation with the reactivity. Significant differences in reactivity is observed primarily between the glasses of peraluminous (CaO/Al 2 O 3 1). Amongst the pastes made of glasses of percalcic region a higher degree of reaction at later ages is observed for the paste containing glass of lower CaO/SiO 2 molar ratio. This is due to both degree of depolimerization and the nature of these glasses (pozzolanic and hydraulic materials). No difference of degree of reaction has been observed within the glasses of CaO/SiO 2 lower than 1. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. The effect of CaO/SiO2 molar ratio of CaO-Al2O3-SiO2 glasses on their structure and reactivity in alkali activated system

    Science.gov (United States)

    Kucharczyk, Sylwia; Sitarz, Maciej; Zajac, Maciej; Deja, Jan

    2018-04-01

    The influence of CaO/SiO2 molar ratio of calcium aluminosilicate glasses on resulting structure and reactivity was investigated. Chemical compositions of glasses were chosen to mimic the composition of the fly ash and slag amorphous phase. Understanding the reactivity of these materials is of high importance allowing further development of the composite cements to limit the environmental footprint of cement industry. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were employed to examine the structure of glasses. Reactivity of the glasses was analyzed on paste samples after 1, 2, 7, 28 and 90 days of curing by means of thermogravimetry (TGA), X-ray diffraction (XRD) and FTIR. Spectroscopic results emphasize dependence of the structure on the chemical composition of the glasses. The higher CaO/SiO2 the more depolymerized the glass network is, though there is no direct correlation with the reactivity. Significant differences in reactivity is observed primarily between the glasses of peraluminous (CaO/Al2O3 1). Amongst the pastes made of glasses of percalcic region a higher degree of reaction at later ages is observed for the paste containing glass of lower CaO/SiO2 molar ratio. This is due to both degree of depolimerization and the nature of these glasses (pozzolanic and hydraulic materials). No difference of degree of reaction has been observed within the glasses of CaO/SiO2 lower than 1.

  6. Investigating the solubility and cytocompatibility of CaO-Na2 O-SiO2 /TiO2 bioactive glasses.

    Science.gov (United States)

    Wren, Anthony W; Coughlan, Aisling; Smith, Courtney M; Hudson, Sarah P; Laffir, Fathima R; Towler, Mark R

    2015-02-01

    This study aims to investigate the solubility of a series of titanium (TiO2 )-containing bioactive glasses and their subsequent effect on cell viability. Five glasses were synthesized in the composition range SiO2 -Na2 O-CaO with 5 mol % of increments TiO2 substituted for SiO2 . Glass solubility was investigated with respect to (1) exposed surface area, (2) particle size, (3) incubation time, and (4) compositional effects. Ion release profiles showed that sodium (Na(+) ) presented high release rates after 1 day and were unchanged between 7 and 14 days. Calcium (Ca(2+) ) release presented a significant change at each time period and was also composition dependent, where a reduction in Ca(2+) release is observed with an increase in TiO2 concentration. Silica (Si(4+) ) release did not present any clear trends while no titanium (Ti(4+) ) was released. Cell numbers were found to increase up to 44%, compared to the growing control population, with a reduction in particle size and with the inclusion of TiO2 in the glass composition. © 2014 Wiley Periodicals, Inc.

  7. Arsenic trioxide (As2O3) induced calcium signals and cytotoxicity in two human cell lines: SY-5Y neuroblastoma and 293 embryonic kidney (HEK)

    International Nuclear Information System (INIS)

    Florea, Ana-Maria; Splettstoesser, Frank; Buesselberg, Dietrich

    2007-01-01

    Arsenic trioxide (As 2 O 3 ) has anticancer properties; however, its use also leads to neuro-, hepato- or nephro-toxicity, and therefore, it is important to understand the mechanism of As 2 O 3 toxicity. We studied As 2 O 3 influence on intracellular calcium ([Ca 2+ ] i ) homeostasis of human neuroblastoma SY-5Y and embryonic kidney cells (HEK 293).We also relate the As 2 O 3 induced [Ca 2+ ] i modifications with cytotoxicity. We used Ca 2+ sensitive dyes (fluo-4 and rhod-2) combined with laser scanning microscopy or fluorescence activated cell sorting to measure Ca 2+ changes during the application of As 2 O 3 and we approach evaluation of cytotoxicity. As 2 O 3 (1 μM) increased [Ca 2+ ] i in SY-5Y and HEK 293 cells. Three forms of [Ca 2+ ] i -elevations were found: (1) steady-state increases (2) transient [Ca 2+ ] i -elevations and (3) Ca 2+ -spikes. [Ca 2+ ] i modifications were independent from extracellular Ca 2+ but dependent on internal calcium stores. The effect was not reversible. Inositol triphosphate (IP 3 ) and ryanodine (Ry) receptors are involved in regulation of signals induced by As 2 O 3 . 2-APB and dantrolene significantly reduced the [Ca 2+ ] i -rise (p 2+ ] i -elevation or spiking. This indicates that other Ca 2+ regulating mechanisms are involved. In cytotoxicity tests As 2 O 3 significantly reduced cell viability in both cell types. Staining with Hoechst 33342 showed occurrence of apoptosis and DNA damage. Our data suggest that [Ca 2+ ] i is an important messenger in As 2 O 3 induced cell death

  8. The Intron 4 Polymorphism in the Calcium-Sensing Receptor Gene in Diabetes Mellitus and its Chronic Complications, Diabetic Nephropathy and Non-Diabetic Renal Disease

    Directory of Open Access Journals (Sweden)

    Viera Železníková

    2014-10-01

    Full Text Available Background/Aims: Calcium-Sensing Receptor (CaSR significantly affects calcium-phosphate metabolism in kidneys, and it is implicated in the pathogenesis of diabetes mellitus (DM due to its expression in pancreatic F-cells. The role of CaSR as one of the players in pathogenesis of chronic kidney disease (CKD has been speculated. Methods: 158 Type 2 diabetic patients divided into three groups according to occurrence and type of kidney complications, 66 nondiabetic patients CKD, and 93 healthy subjects were enrolled into the study to analyze the role of two CaSR polymorphisms (in the codon 990 and in the intron 4 in ethiopathogenesis of DM and CKD. The Type 2 diabetic groups consisted of 48 patients without any kidney abnormalities, 58 patients with diabetic nephropathy (DN, and 52 patients with nondiabetic renal disease (NDRD. The distribution of genotype and allele frequencies was studied using PCR with the TaqMan Discrimination Assay or followed by the Restriction Fragment Length Polymorphism method, respectively. Results: We have found that the intron 4 polymorphism is a risk factor for the development of DM and CKD, except DN, while the codon 990 does not show any disease association. Conclusion: We conclude that CaSR is a general factor in pancreas and kidney pathologies. i 2014 S. Karger AG, Basel

  9. Activation of the Ca2+-sensing receptors increases currents through inward rectifier K+ channels via activation of phosphatidylinositol 4-kinase.

    Science.gov (United States)

    Liu, Chung-Hung; Chang, Hsueh-Kai; Lee, Sue-Ping; Shieh, Ru-Chi

    2016-11-01

    Inward rectifier K + channels are important for maintaining normal electrical function in many cell types. The proper function of these channels requires the presence of membrane phosphoinositide 4,5-bisphosphate (PIP 2 ). Stimulation of the Ca 2+ -sensing receptor CaR, a pleiotropic G protein-coupled receptor, activates both G q/11 , which decreases PIP 2 , and phosphatidylinositol 4-kinase (PI-4-K), which, conversely, increases PIP 2 . How membrane PIP 2 levels are regulated by CaR activation and whether these changes modulate inward rectifier K + are unknown. In this study, we found that activation of CaR by the allosteric agonist, NPSR568, increased inward rectifier K + current (I K1 ) in guinea pig ventricular myocytes and currents mediated by Kir2.1 channels exogenously expressed in HEK293T cells with a similar sensitivity. Moreover, using the fluorescent PIP 2 reporter tubby-R332H-cYFP to monitor PIP 2 levels, we found that CaR activation in HEK293T cells increased membrane PIP 2 concentrations. Pharmacological studies showed that both phospholipase C (PLC) and PI-4-K are activated by CaR stimulation with the latter played a dominant role in regulating membrane PIP 2 and, thus, Kir currents. These results provide the first direct evidence that CaR activation upregulates currents through inward rectifier K + channels by accelerating PIP 2 synthesis. The regulation of I K1 plays a critical role in the stability of the electrical properties of many excitable cells, including cardiac myocytes and neurons. Further, synthetic allosteric modulators that increase CaR activity have been used to treat hyperparathyroidism, and negative CaR modulators are of potential importance in the treatment of osteoporosis. Thus, our results provide further insight into the roles played by CaR in the cardiovascular system and are potentially valuable for heart disease treatment and drug safety.

  10. The enthalpies of interactions of Ca2+(aq) and C2O{4/2-} (aq) ions in complexon solutions: Competition between complexation and precipitation

    Science.gov (United States)

    Kustov, A. V.; Smirnova, N. L.; Berezin, B. D.; Trostin, V. N.

    2010-04-01

    The thermal effects of mixing of aqueous calcium chloride with sodium citrate and ethylenedi-aminetetraacetate in the absence and presence of sodium oxalate have been measured at 25°C. The thermal effects of dilution of aqueous calcium chloride solutions were determined. The thermal effects of calcium oxalate precipitation and formation of calcium complexes with citrate and ethylenediaminetetraacetate ions were calculated. The 1% solution of sodium citrate inhibited the formation of CaC2O4 (s); in a 1% solution of sodium ethylenediaminetetraacetate with [Ca2+][C2O{4/2-}] > 10-5, the endothermal formation of the [CaEdta]2- complex quickly changed to exothermal precipitation. The 3 and 5% solutions of complexons showed a pronounced inhibiting effect on the formation of urinary stones even when the concentration of calcium and oxalate ions in solution exceeded the product of solubility of CaC2O4 by four and more orders of magnitude.

  11. Synthesis, crystal structure refinement, and nonlinear-optical properties of CaB3O5(OH): Comparative crystal chemistry of calcium triborates

    International Nuclear Information System (INIS)

    Yamnova, N. A.; Aksenov, S. M.; Stefanovich, S. Yu.; Volkov, A. S.; Dimitrova, O. V.

    2015-01-01

    Calcium triborate CaB 3 O5(OH) obtained by hydrothermal synthesis in the Ca(OH) 2 –H 3 BO 3 –Na 2 CO 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 3 and space group Pna2 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 3 O 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 2 O 3 · nH 2 O (n = 0–13) with the constant CaO: B 2 O 3 = 2: 3 ratio and variable content of water is performed

  12. Micelle-Assisted Synthesis of Al2OCaO Nanocatalyst: Optical Properties and Their Applications in Photodegradation of 2,4,6-Trinitrophenol

    Directory of Open Access Journals (Sweden)

    Ayesha Imtiaz

    2013-01-01

    Full Text Available Calcium oxide (CaO nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS, as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2OCaO nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2OCaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP, which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2OCaO nanocatalyst was found as 3.3 eV.

  13. Membrane Estrogen Receptor-α Interacts with Metabotropic Glutamate Receptor Type 1a to Mobilize Intracellular Calcium in Hypothalamic Astrocytes

    Science.gov (United States)

    Kuo, John; Hariri, Omid R.; Bondar, Galyna; Ogi, Julie; Micevych, Paul

    2009-01-01

    Estradiol, acting on a membrane-associated estrogen receptor-α (mERα), induces an increase in free cytoplasmic calcium concentration ([Ca2+]i) needed for progesterone synthesis in hypothalamic astrocytes. To determine whether rapid estradiol signaling involves an interaction of mERα with metabotropic glutamate receptor type 1a (mGluR1a), changes in [Ca2+]i were monitored with the calcium indicator, Fluo-4 AM, in primary cultures of female postpubertal hypothalamic astrocytes. 17β-Estradiol over a range of 1 nm to 100 nm induced a maximal increase in [Ca2+]i flux measured as a change in relative fluorescence [ΔF Ca2+ = 615 ± 36 to 641 ± 47 relative fluorescent units (RFU)], whereas 0.1 nm of estradiol stimulated a moderate [Ca2+]i increase (275 ± 16 RFU). The rapid estradiol-induced [Ca2+]i flux was blocked with 1 μm of the estrogen receptor antagonist ICI 182,780 (635 ± 24 vs. 102 ± 11 RFU, P estradiol-induced membrane signaling in astrocytes. PMID:18948402

  14. Radioisotope 45Ca labeling four calcium chemical compounds and tracing calcium bioavailability

    International Nuclear Information System (INIS)

    Zheng Hui; Zhen Rong; Niu Huisheng; Li Huaifen

    2004-01-01

    Objective: To build up a new method of the radioisotope 45 Ca labeling four calcium chemical compounds, observe and tracing bioavailability change of calcium labeled with radioisotope 45 Ca. Methods: The calcium gluconate (Ca-Glu), calcium citrate (Ca-Cit), calcium carbonate (Ca-Car) and calcium L-threonate (Ca-Thr)were labeled by radioisotope 45 Ca. Four calcium chemical compounds of 45 Ca labeling were used of calcium content 200 mg/kg in the rats and measure the absorption content and bioavailability of calcium in tissue of heart, lever spleen, stomach, kidney, brain, intestine, whole blood, urine, faeces. Results: 1) Radioisotope 45 Ca labeling calcium chemical compound has high radio intensity, more steady standard curve and recover rate. 2) The absorption of organic calcium chemical compounds is higher than the inorganic calcium chemical compound in the study of calcium bioavailability. Conclusion: The method of tracing with radioisotope 45 Ca labeling calcium chemical compounds has the characteristic of the sensitive, objective, accurate and steady in the study of calcium bioavailability

  15. Calcium aluminates hydration in presence of amorphous SiO2 at temperatures below 90 deg. C

    International Nuclear Information System (INIS)

    Rivas Mercury, J.M.; Turrillas, X.; Aza, A.H. de; Pena, P.

    2006-01-01

    The hydration behaviour of Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 with added amorphous silica at 40, 65 and 90 deg. C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x ) and gibbsite, Al(OH) 3 , were identified, likewise amorphous phases like Al(OH) x , calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), which was the main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy. - Graphical abstract: Katoite, Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), was identified besides gibbsite, Al(OH) 3 , as a crystalline stable hydration products in Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 hydrated with added amorphous silica between 40 and 90 deg. C

  16. Calcium and strontium salts of (glycinato-κ(2)N,O)oxidobis(peroxido-κ(2)O,O')vanadate(V) tetrahydrate.

    Science.gov (United States)

    Higuchi, Takeshi; Uchida, Ayana; Hashimoto, Masato

    2013-12-15

    The title salts calcium (glycinato-κ(2)N,O)oxidobis(peroxido-κ(2)O,O')vanadate(V) tetrahydrate, Ca[VO(O2)2(NH2CH2COO)]·4H2O, and strontium (glycinato-κ(2)N,O)oxidobis(peroxido-κ(2)O,O')vanadate(V) tetrahydrate, Sr[VO(O2)2(NH2CH2COO)]·4H2O, crystallized at pH ca 7.4 with similar lattice parameters. The glycinate anion acts as a bidentate N,O-chelating ligand, and the V atom has a pentagonal bipyramidal geometry, with two η(2)-peroxo groups and the glycinate N atom in the equatorial plane, and one terminal oxo and a glycinate O atom at the axial positions. The H atoms of three of the four water molecules in the strontium salt exhibited disorder over three positions for each molecule.

  17. Preparation and Supercooling Modification of Salt Hydrate Phase Change Materials Based on CaCl₂·2H₂O/CaCl₂.

    Science.gov (United States)

    Xu, Xiaoxiao; Dong, Zhijun; Memon, Shazim Ali; Bao, Xiaohua; Cui, Hongzhi

    2017-06-23

    Salt hydrates have issues of supercooling when they are utilized as phase change materials (PCMs). In this research, a new method was adopted to prepare a salt hydrate PCM (based on a mixture of calcium chloride dihydrate and calcium chloride anhydrous) as a novel PCM system to reduce the supercooling phenomenon existing in CaCl₂·6H₂O. Six samples with different compositions of CaCl₂ were prepared. The relationship between the performance and the proportion of calcium chloride dihydrate (CaCl₂·2H₂O) and calcium chloride anhydrous (CaCl₂) was also investigated. The supercooling degree of the final PCM reduced with the increase in volume of CaCl₂·2H₂O during its preparation. The PCM obtained with 66.21 wt % CaCl₂·2H₂O reduced the supercooling degree by about 96.8%. All six samples, whose ratio of CaCl₂·2H₂O to (CaCl₂ plus CaCl₂·2H₂O) was 0%, 34.03%, 53.82%, 76.56%, 90.74%, and 100% respectively, showed relatively higher enthalpy (greater than 155.29 J/g), and have the possibility to be applied in buildings for thermal energy storage purposes. Hence, CaCl₂·2H₂O plays an important role in reducing supercooling and it can be helpful in adjusting the solidification enthalpy. Thereafter, the influence of adding different percentages of Nano-SiO₂ (0.1 wt %, 0.3 wt %, 0.5 wt %) in reducing the supercooling degree of some PCM samples was investigated. The test results showed that the supercooling of the salt hydrate PCM in Samples 6 and 5 reduced to 0.2 °C and 0.4 °C respectively. Finally, the effect of the different cooling conditions, including frozen storage (-20 °C) and cold storage (5 °C), that were used to prepare the salt hydrate PCM was considered. It was found that both cooling conditions are effective in reducing the supercooling degree of the salt hydrate PCM. With the synergistic action of the two materials, the performance and properties of the newly developed PCM systems were better especially in terms of reducing

  18. An inhibitory effect of extracellular Ca2+ on Ca2+-dependent exocytosis.

    Directory of Open Access Journals (Sweden)

    Wei Xiong

    Full Text Available AIM: Neurotransmitter release is elicited by an elevation of intracellular Ca(2+ concentration ([Ca(2+](i. The action potential triggers Ca(2+ influx through Ca(2+ channels which causes local changes of [Ca(2+](i for vesicle release. However, any direct role of extracellular Ca(2+ (besides Ca(2+ influx on Ca(2+-dependent exocytosis remains elusive. Here we set out to investigate this possibility on rat dorsal root ganglion (DRG neurons and chromaffin cells, widely used models for studying vesicle exocytosis. RESULTS: Using photolysis of caged Ca(2+ and caffeine-induced release of stored Ca(2+, we found that extracellular Ca(2+ inhibited exocytosis following moderate [Ca(2+](i rises (2-3 µM. The IC(50 for extracellular Ca(2+ inhibition of exocytosis (ECIE was 1.38 mM and a physiological reduction (∼30% of extracellular Ca(2+ concentration ([Ca(2+](o significantly increased the evoked exocytosis. At the single vesicle level, quantal size and release frequency were also altered by physiological [Ca(2+](o. The calcimimetics Mg(2+, Cd(2+, G418, and neomycin all inhibited exocytosis. The extracellular Ca(2+-sensing receptor (CaSR was not involved because specific drugs and knockdown of CaSR in DRG neurons did not affect ECIE. CONCLUSION/SIGNIFICANCE: As an extension of the classic Ca(2+ hypothesis of synaptic release, physiological levels of extracellular Ca(2+ play dual roles in evoked exocytosis by providing a source of Ca(2+ influx, and by directly regulating quantal size and release probability in neuronal cells.

  19. [Effects of desulfurization waste on calcium distribution, Ca(2+)-ATPase activity, and antioxidant characteristics of rice leaf under alkali stress].

    Science.gov (United States)

    Mao, Gui-Lian; Xu, Xing; Zeng, Jin; Yue, Zi-Hui; Yang, Shu-Juan

    2012-02-01

    To approach the action mechanisms of desulfurization waste on alleviating alkali stress-induced injury of rice, a pot experiment was conducted to study the variations of leaf total calcium content, calcium distribution, plasma membrane Ca(2+)-ATPase activity, and reactive oxygen content of rice seedlings under alkali stress after the application of desulfurization waste. In the control, a few calcium particulates scattered in the cell wall and chloroplasts, while applying desulfurization waste or CaSO4 increased the calcium particulates in the plasma membrane, intercellular space, cell wall, and vacuole significantly. With the increasing application rate of desulfurization waste or CaSO4, the leaf total calcium content increased, Ca(2+)-ATPase activity in plasma membrane and tonoplast presented an increasing trend, plasma membrane relative permeability, MDA content, and O2 production rate decreased, and SOD and POD activities increased. The desulfurization waste could relieve the alkali stress to rice in some extent, and the main reactive compound in the waste could be CaSO4.

  20. Clinical Expression of Calcium Sensing Receptor Polymorphism (A986S) in Normocalcemic and Asymptomatic Hyperparathyroidism.

    Science.gov (United States)

    Díaz-Soto, G; Romero, E; Castrillón, J L P; Jauregui, O I; de Luis Román, D

    2016-03-01

    Normocalcemic and asymptomatic hyperparathyroidism diagnosis are becoming more common. However, their pathophysiology is incompletely known. The aim of the present study was to evaluate the clinical effect of calcium-sensing receptor polymorphism (A986S) in normocalcemic and asymtomatic HPT. Prospective study conducted with 61 consecutive normocalcemic and asymptomatic HPT patients was followed up during a minimum period of 1 year. Secondary causes of hyperparathyroidism were ruled out. Calcium and phosphorus metabolism parameters were evaluated in at least 2 determinations during follow-up to classify as normocalcemic or asymptomatic hyperparathyroidism. Bone mineral density and A986S polymorphism genotype were also analyzed. Thiry-eight patients (62.3%) had the genotype A986A, and 23 (36.7%) patients had A986S (20 patients, 32.8%) or S986S (3 patients, 4.9%). Age, sex, and genotype distributions were comparable in both normocalcemic and asymptomatic hyperparathyroidism. In normocalcemic patients, S allele genotype was associated to statistically significant higher level of intact PTH: 92.0 (SD 18.5) vs. 110.6 (SD 24.4) pg/ml, phyperparathyroidism, A986A genotype resulted in a statistically significant higher level of intact PTH, alkaline phosphatase and procollagen amino-terminal propeptide; but only serum calcium remained as an independent predictor of serum intact PTH levels after a multiple linear regression. Bone mineral densitometry between genotypes did not show statistically significant differences. A986S polymorphism of CaSR is an independent predictor of PTH level in normocalcemic hyperparathyroidism patients, but not in asymptomatic hyperparathyroidism. More studies are needed to evaluate the effect of other polymorphisms in normocalcemic and asymptomatic hyperparathyroidism. © Georg Thieme Verlag KG Stuttgart · New York.

  1. The role of Sr2+ on the structure and reactivity of SrO-CaO-ZnO-SiO2 ionomer glasses.

    Science.gov (United States)

    Boyd, Daniel; Towler, Mark R; Watts, Sally; Hill, Robert G; Wren, Anthony W; Clarkin, Owen M

    2008-02-01

    The suitability of Glass Polyalkenoate Cements (GPCs) for use in orthopaedics is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium free GPCs may be formulated based on calcium zinc silicate glasses and these novel materials exhibit significant potential as hard tissue biomaterials. To further improve their potential, and given that Strontium (Sr) based drugs have had success in the treatment of osteoporosis, the authors have substituted Calcium (Ca) with Sr in the glass phase of a series of aluminium free GPCs. However to date little data exists on the effect SrO has on the structure and reactivity of SrO-CaO-ZnO-SiO(2) glasses. The objective of this work was to characterise the effect of the Ca/Sr substitution on the structure of such glasses, and evaluate the subsequent reactivity of these glasses with an aqueous solution of Polyacrylic acid (PAA). To this end (29)Si MAS-NMR, differential scanning calorimetry (DSC), X-ray diffraction, and network connectivity calculations, were used to characterize the structure of four strontium calcium zinc silicate glasses. Following glass characterization, GPCs were produced from each glass using a 40 wt% solution of PAA (powder:liquid = 2:1.5). The working times and setting times of the GPCs were recorded as per International standard ISO9917. The results acquired as part of this research indicate that the substitution of Ca for Sr in the glasses examined did not appear to significantly affect the structure of the glasses investigated. However it was noted that increasing the amount of Ca substituted for Sr did result in a concomitant increase in setting times, a feature that may be attributable to the higher basicity of SrO over CaO.

  2. Influence of ER leak on resting cytoplasmic Ca2+ and receptor-mediated Ca2+ signalling in human macrophage.

    Science.gov (United States)

    Layhadi, Janice A; Fountain, Samuel J

    2017-06-03

    Mechanisms controlling endoplasmic reticulum (ER) Ca 2+ homeostasis are important regulators of resting cytoplasmic Ca 2+ concentration ([Ca 2+ ] cyto ) and receptor-mediated Ca 2+ signalling. Here we investigate channels responsible for ER Ca 2+ leak in THP-1 macrophage and human primary macrophage. In the absence of extracellular Ca 2+ we employ ionomycin action at the plasma membrane to stimulate ER Ca 2+ leak. Under these conditions ionomycin elevates [Ca 2+ ] cyto revealing a Ca 2+ leak response which is abolished by thapsigargin. IP 3 receptors (Xestospongin C, 2-APB), ryanodine receptors (dantrolene), and translocon (anisomycin) inhibition facilitated ER Ca 2+ leak in model macrophage, with translocon inhibition also reducing resting [Ca 2+ ] cyto . In primary macrophage, translocon inhibition blocks Ca 2+ leak but does not influence resting [Ca 2+ ] cyto . We identify a role for translocon-mediated ER Ca 2+ leak in receptor-mediated Ca 2+ signalling in both model and primary human macrophage, whereby the Ca 2+ response to ADP (P2Y receptor agonist) is augmented following anisomycin treatment. In conclusion, we demonstrate a role of ER Ca 2+ leak via the translocon in controlling resting cytoplasmic Ca 2+ in model macrophage and receptor-mediated Ca 2+ signalling in model macrophage and primary macrophage. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Comparative Study of the Corrosion Resistance of Air-Plasma-Sprayed Ca2SiO4 and Al2O3 Coatings in Salt Water

    Directory of Open Access Journals (Sweden)

    Yuan Xiao

    2018-03-01

    Full Text Available In this study, Ca2SiO4 coating was sprayed on stainless steel substrate and the corrosion resistance of the as-sprayed coating was studied in salt water. At the same time, Al2O3 coatings were produced by air-plasma-sprayed technology as comparison. Immersion test was carried out to evaluate the protection performance of coatings. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS plots were also analyzed. The results indicated that Ca2SiO4 coatings showed a better protection performance than Al2O3 coatings. During the immersion, various calcium carbonate crystals appeared on the surface of Ca2SiO4 coatings. Ca(OH2 was released from Ca2SiO4 coatings into NaCl aqueous solution, increasing the alkalinity, which is in favor of the formation of passivation film, and thus improves the corrosion resistance. Ca2SiO4 coatings became denser after immersion due to the fact that the pores and micro cracks were filled with hydration products i.e., hydrated calcium silicate (C–S–H gel. On the contrary, the microstructure of Al2O3 coatings became loose and obvious rusty spots were observed on the surface after the immersion test.

  4. Electronic structure of lanthanum calcium oxoborate LaCa4O(BO3)3

    International Nuclear Information System (INIS)

    Nelson, A.J.; Buuren, T. van; Willey, Trevor M.; Bostedt, C.; Adams, J.J.; Schaffers, K.I.; Terminello, Lou; Callcott, T.A.

    2004-01-01

    Lanthanum calcium oxoborate (LaCOB) is a nonlinear optical (NLO) material that belongs to the calcium-rare-earth (R) oxoborate family, with general composition Ca 4 RO(BO 3 ) 3 (R 3+ =La, Sm, Gd, Lu, Y). X-ray photoemission, photoabsorption, and resonant fluorescence were applied to study the electronic structure of this material. High resolution photoemission measurements on the valence band (VB) electronic structure and La 3d and 4d, Ca 2p, B 1s, and O 1s core lines were used to evaluate the surface and near surface chemistry. Element specific density of unoccupied electronic states in LaCOB were probed by X-ray absorption spectroscopy (XAS) at the La 3d (M 4,5 -edge), B 1s, and O 1s (K-edges) absorption edges. Soft X-ray fluorescence was used to further examine valence band states associated with spectral differences noted in the absorption measurements. These results provide the first measurements of the electronic structure and surface chemistry of this rare-earth oxoborate

  5. Calcium is the switch in the moonlighting dual function of the ligand-activated receptor kinase phytosulfokine receptor 1

    KAUST Repository

    Muleya, Victor

    2014-09-23

    Background: A number of receptor kinases contain guanylate cyclase (GC) catalytic centres encapsulated in the cytosolic kinase domain. A prototypical example is the phytosulfokine receptor 1 (PSKR1) that is involved in regulating growth responses in plants. PSKR1 contains both kinase and GC activities however the underlying mechanisms regulating the dual functions have remained elusive. Findings: Here, we confirm the dual activity of the cytoplasmic domain of the PSKR1 receptor. We show that mutations within the guanylate cyclase centre modulate the GC activity while not affecting the kinase catalytic activity. Using physiologically relevant Ca2+ levels, we demonstrate that its GC activity is enhanced over two-fold by Ca2+ in a concentration-dependent manner. Conversely, increasing Ca2+ levels inhibits kinase activity up to 500-fold at 100 nM Ca2+. Conclusions: Changes in calcium at physiological levels can regulate the kinase and GC activities of PSKR1. We therefore propose a functional model of how calcium acts as a bimodal switch between kinase and GC activity in PSKR1 that could be relevant to other members of this novel class of ligand-activated receptor kinases.

  6. Ammonia sensing properties of V-doped ZnO:Ca nanopowders prepared by sol–gel synthesis

    International Nuclear Information System (INIS)

    Fazio, E.; Hjiri, M.; Dhahri, R.; El Mir, L.; Sabatino, G.; Barreca, F.; Neri, F.; Leonardi, S.G.; Pistone, A.; Neri, G.

    2015-01-01

    V-doped ZnO:Ca nanopowders with different V loading were prepared by sol–gel synthesis and successive drying in ethanol under supercritical conditions. Characterization data of nanopowders annealed at 700 °C in air, revealed that they have the wurtzite structure. Raman features of V-doped ZnO:Ca samples were found to be substantially modified with respect to pure ZnO or binary ZnO:Ca samples, which indicate the substitution of vanadium ions in the ZnO lattice. The ammonia sensing properties of V-doped ZnO:Ca thick films were also investigated. The results obtained demonstrate the possibility of a fine tuning of the sensing characteristics of ZnO-based sensors by Ca and V doping. In particular, their combined effect has brought to an enhanced response towards NH 3 compared to bare ZnO and binary V-ZnO and Ca-ZnO samples. Raman investigation suggested that the presence of Ca play a key role in enhancing the sensor response in these ternary composite nanomaterials. - Graphical abstract: V-doped ZnO:Ca nanopowders prepared by sol–gel synthesis possess enhanced sensing characteristics towards NH 3 compared to bare ZnO. - Highlights: • V-doped ZnO:Ca nanopowders with different V loading were prepared by sol–gel synthesis. • Raman features of V-doped ZnO:Ca samples indicate the substitution of V ions in the ZnO lattice. • Combined effects of dopants have brought to an enhanced response to NH 3 compared to ZnO. • Ca play a key role in enhancing the sensor response of ternary V-doped ZnO:Ca composites

  7. A novel mutation in the calcium-sensing receptor gene in an Irish pedigree showing familial hypocalciuric hypercalcemia: a case report.

    LENUS (Irish Health Repository)

    Elamin, Wael F

    2010-01-01

    Familial hypocalciuric hypercalcemia is a rare autosomal dominant disorder characterized by asymptomatic and non-progressive hypercalcemia due to mutations of the calcium-sensing receptor gene. Disorders of calcium metabolism are very common in the elderly, and they can coexist with familial hypocalciuric hypercalcemia in affected families.

  8. Calcium antagonistic effects of Chinese crude drugs: Preliminary investigation and evaluation by 45Ca

    International Nuclear Information System (INIS)

    Liu Ning; Yang Yuanyou; Mo Shangwu; Liao Jiali; Jin Jiannan

    2005-01-01

    Coronary and other diseases in cardiac or brain blood vessels are considered to be due to the excessive influx of Ca 2+ into cytoplasm. If Ca 2+ channels in cell membrane are blocked by medicines or other substances with considerable calcium antagonistic effects, these diseases might be cured or controlled. The influence of some Chinese crude drugs, including Crocus sativus, Carthamus tinctorius, Ginkgo biloba and Bulbus allii macrostemi on Ca 2+ influx in isolated rat aortas was investigated by using 45 Ca as a radioactive tracer, and their calcium antagonistic effects were evaluated. It can be noted that Ca 2+ uptake in isolated rat aorta rings in normal physiological status was not markedly altered by these drugs, whereas the Ca 2+ influxes induced by norepinephrine of 1.2 μmol/L and KCl of 100 mmol/L were significantly inhibited by Crocus, Carthamus and Bulbus in a concentration-dependent manner, but not by Ginkgo. The results show that extracellular Ca 2+ influx through receptor-operated Ca 2+ channels and potential-dependent Ca 2+ channels can be blocked by Crocus, Carthamus and Bulbus. This implies that these Chinese crude drugs have obvious calcium antagonistic effects

  9. Structural basis for the differential effects of CaBP1 and calmodulin on CaV1.2 calcium-dependent inactivation

    Science.gov (United States)

    Findeisen, Felix; Minor, Daniel L.

    2010-01-01

    Calcium-binding protein 1 (CaBP1), a calmodulin (CaM) homolog, endows certain voltage-gated calcium channels (CaVs) with unusual properties. CaBP1 inhibits CaV1.2 calcium-dependent inactivation (CDI) and introduces calcium-dependent facilitation (CDF). Here, we show that the ability of CaBP1 to inhibit CaV1.2 CDI and induce CDF arises from interaction between the CaBP1 N-lobe and interlobe linker residue Glu94. Unlike CaM, where functional EF hands are essential for channel modulation, CDI inhibition does not require functional CaBP1 EF-hands. Furthermore, CaBP1-mediated CDF has different molecular requirements than CaM-mediated CDF. Overall, the data show that CaBP1 comprises two structural modules having separate functions: similar to CaM, the CaBP1 C-lobe serves as a high-affinity anchor that binds the CaV1.2 IQ domain at a site that overlaps with the Ca2+/CaM C-lobe site, whereas the N-lobe/linker module houses the elements required for channel modulation. Discovery of this division provides the framework for understanding how CaBP1 regulates CaVs. PMID:21134641

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

    Science.gov (United States)

    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

  11. IP3 Receptor-Dependent Cytoplasmic Ca2+ Signals Are Tightly Controlled by Cavβ3

    Directory of Open Access Journals (Sweden)

    Anouar Belkacemi

    2018-01-01

    Full Text Available Voltage-gated calcium channels (Cavs are major Ca2+ entry pathways in excitable cells. Their β subunits facilitate membrane trafficking of the channel’s ion-conducting α1 pore and modulate its gating properties. We report that one β subunit, β3, reduces Ca2+ release following stimulation of phospholipase C-coupled receptors and inositol 1,4,5-trisphosphate (IP3 formation. This effect requires the SH3-HOOK domain of Cavβ3, includes physical β3/IP3 receptor interaction, and prevails when agonist-induced IP3 formation is bypassed by photolysis of caged IP3. In agreement with β3 acting as a brake on Ca2+ release, fibroblast migration is enhanced in vitro, and in vivo, closure of skin wounds is accelerated in the absence of β3. To mediate specific physiological responses and to prevent Ca2+ toxicity, cytoplasmic Ca2+ signals must be tightly controlled. The described function of β3, unrelated to its function as a Cav subunit, adds to this tight control.

  12. Localization of Mg2+-sensing shark kidney calcium receptor SKCaR in kidney of spiny dogfish, Squalus acanthias.

    Science.gov (United States)

    Hentschel, Hartmut; Nearing, Jacqueline; Harris, H William; Betka, Marlies; Baum, Michelle; Hebert, Steven C; Elger, Marlies

    2003-09-01

    We recently cloned a homologue of the bovine parathyroid calcium receptor from the kidney of a spiny dogfish (Squalus acanthias) and termed this new protein SKCaR. SKCaR senses alterations in extracellular Mg2+ after its expression in human embryonic kidney cells (Nearing J, Betka M, Quinn S, Hentschel H, Elger M, Baum M, Bai M, Chattopadyhay N, Brown E, Hebert S, and Harris HW. Proc Natl Acad. Sci USA 99: 9231-9236, 2002). In this report, we used light and electron microscopic immunocytochemical techniques to study the distribution of SKCaR in dogfish kidney. SKCaR antiserum bound to the apical membranes of shark kidney epithelial cells in the following tubular segments: proximal tubules (PIa and PIIb), late distal tubule, and collecting tubule/collecting duct as well as diffusely labeled cells of early distal tubule. The highly specific distribution of SKCaR in mesial tissue as well as lateral countercurrent bundles of dogfish kidney is compatible with a role for SKCaR to sense local tubular Mg2+ concentrations. This highly specific distribution of SKCaR protein in dogfish kidney could possibly work in concert with the powerful Mg2+ secretory system present in the PIIa segment of elasmobranch fish kidney to affect recycling of Mg2+ from putative Mg2+-sensing/Mg2+-reabsorbing segments. These data provide support for the possible existence of Mg2+ cycling in elasmobranch kidney in a manner analogous to that described for mammals.

  13. 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.

  14. Structural basis for the differential effects of CaBP1 and calmodulin on Ca(V)1.2 calcium-dependent inactivation.

    Science.gov (United States)

    Findeisen, Felix; Minor, Daniel L

    2010-12-08

    Calcium-binding protein 1 (CaBP1), a calmodulin (CaM) homolog, endows certain voltage-gated calcium channels (Ca(V)s) with unusual properties. CaBP1 inhibits Ca(V)1.2 calcium-dependent inactivation (CDI) and introduces calcium-dependent facilitation (CDF). Here, we show that the ability of CaBP1 to inhibit Ca(V)1.2 CDI and induce CDF arises from interaction between the CaBP1 N-lobe and interlobe linker residue Glu94. Unlike CaM, where functional EF hands are essential for channel modulation, CDI inhibition does not require functional CaBP1 EF hands. Furthermore, CaBP1-mediated CDF has different molecular requirements than CaM-mediated CDF. Overall, the data show that CaBP1 comprises two structural modules having separate functions: similar to CaM, the CaBP1 C-lobe serves as a high-affinity anchor that binds the Ca(V)1.2 IQ domain at a site that overlaps with the Ca²+/CaM C-lobe site, whereas the N-lobe/linker module houses the elements required for channel modulation. Discovery of this division provides the framework for understanding how CaBP1 regulates Ca(V)s. Copyright © 2010 Elsevier Ltd. All rights reserved.

  15. Improved CO_2 adsorption capacity and cyclic stability of CaO sorbents incorporated with MgO

    International Nuclear Information System (INIS)

    Farah Diana Mohd Daud; Kumaravel Vignesh; Srimala Sreekantan; Abdul Rahman Mohamed

    2016-01-01

    Calcium oxide (CaO) sorbents incorporated with magnesium oxide (MgO) were synthesized using a co-precipitation route. The sorbents were prepared with different MgO concentrations (from 5 wt% to 30 wt%). The as-prepared sorbents were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and BET surface area analysis techniques. The sintering effect of CaO sorbents was decreased after the incorporation of MgO. The sorbents with 5 wt% and 10 wt% of MgO retained their CO_2 adsorption capacity over multiple cycles. Most importantly, CaO with 10 wt% MgO showed constant CO_2 adsorption capacity over 30 carbonation cycles. The results revealed that CaO with 10 wt% MgO is sufficient to produce sorbents with high surface area, good structural stability and enhanced CO_2 adsorption capacity. (authors)

  16. Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

    Science.gov (United States)

    Li, H C; Wang, D G; Chen, C Z; Weng, F

    2015-03-01

    To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    Najafpour, Mohammad Mahdi

    2011-06-01

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

  18. Novel calcium-sensing receptor cytoplasmic tail deletion mutation causing autosomal dominant hypocalcemia: molecular and clinical study.

    Science.gov (United States)

    Obermannova, Barbora; Sumnik, Zdenek; Dusatkova, Petra; Cinek, Ondrej; Grant, Michael; Lebl, Jan; Hendy, Geoffrey N

    2016-04-01

    Autosomal dominant hypocalcemia (ADH) is a rare disorder caused by activating mutations of the calcium-sensing receptor (CASR). The treatment of ADH patients with 1α-hydroxylated vitamin D derivatives can cause hypercalciuria leading to nephrocalcinosis. We studied a girl who presented with hypoparathyroidism and asymptomatic hypocalcemia at age 2.5 years. Mutations of CASR were investigated by DNA sequencing. Functional analyses of mutant and WT CASRs were done in transiently transfected human embryonic kidney (HEK293) cells. The proband and her father are heterozygous for an eight-nucleotide deletion c.2703_2710delCCTTGGAG in the CASR encoding the intracellular domain of the protein. Transient expression of CASR constructs in kidney cells in vitro suggested greater cell surface expression of the mutant receptor with a left-shifted extracellular calcium dose-response curve relative to that of the WT receptor consistent with gain of function. Initial treatment of the patient with calcitriol led to increased urinary calcium excretion. Evaluation for mosaicism in the paternal grandparents of the proband was negative. We describe a novel naturally occurring deletion mutation within the CASR that apparently arose de novo in the father of the ADH proband. Functional analysis suggests that the cytoplasmic tail of the CASR contains determinants that regulate the attenuation of signal transduction. Early molecular analysis of the CASR gene in patients with isolated idiopathic hypoparathyroidism is recommended because of its relevance to clinical outcome and treatment choice. In ADH patients, calcium supplementation and low-dose cholecalciferol avoids hypocalcemic symptoms without compromising renal function. © 2016 European Society of Endocrinology.

  19. Atomic layer deposition of calcium oxide and calcium hafnium oxide films using calcium cyclopentadienyl precursor

    International Nuclear Information System (INIS)

    Kukli, Kaupo; Ritala, Mikko; Sajavaara, Timo; Haenninen, Timo; Leskelae, Markku

    2006-01-01

    Calcium oxide and calcium hafnium oxide thin films were grown by atomic layer deposition on borosilicate glass and silicon substrates in the temperature range of 205-300 o C. The calcium oxide films were grown from novel calcium cyclopentadienyl precursor and water. Calcium oxide films possessed refractive index 1.75-1.80. Calcium oxide films grown without Al 2 O 3 capping layer occurred hygroscopic and converted to Ca(OH) 2 after exposure to air. As-deposited CaO films were (200)-oriented. CaO covered with Al 2 O 3 capping layers contained relatively low amounts of hydrogen and re-oriented into (111) direction upon annealing at 900 o C. In order to examine the application of CaO in high-permittivity dielectric layers, mixtures of Ca and Hf oxides were grown by alternate CaO and HfO 2 growth cycles at 230 and 300 o C. HfCl 4 was used as a hafnium precursor. When grown at 230 o C, the films were amorphous with equal amounts of Ca and Hf constituents (15 at.%). These films crystallized upon annealing at 750 o C, showing X-ray diffraction peaks characteristic of hafnium-rich phases such as Ca 2 Hf 7 O 16 or Ca 6 Hf 19 O 44 . At 300 o C, the relative Ca content remained below 8 at.%. The crystallized phase well matched with rhombohedral Ca 2 Hf 7 O 16 . The dielectric films grown on Si(100) substrates possessed effective permittivity values in the range of 12.8-14.2

  20. A model of cardiac ryanodine receptor gating predicts experimental Ca2+-dynamics and Ca2+-triggered arrhythmia in the long QT syndrome

    Science.gov (United States)

    Wilson, Dan; Ermentrout, Bard; Němec, Jan; Salama, Guy

    2017-09-01

    Abnormal Ca2+ handling is well-established as the trigger of cardiac arrhythmia in catecholaminergic polymorphic ventricular tachycardia and digoxin toxicity, but its role remains controversial in Torsade de Pointes (TdP), the arrhythmia associated with the long QT syndrome (LQTS). Recent experimental results show that early afterdepolarizations (EADs) that initiate TdP are caused by spontaneous (non-voltage-triggered) Ca2+ release from Ca2+-overloaded sarcoplasmic reticulum (SR) rather than the activation of the L-type Ca2+-channel window current. In bradycardia and long QT type 2 (LQT2), a second, non-voltage triggered cytosolic Ca2+ elevation increases gradually in amplitude, occurs before overt voltage instability, and then precedes the rise of EADs. Here, we used a modified Shannon-Puglisi-Bers model of rabbit ventricular myocytes to reproduce experimental Ca2+ dynamics in bradycardia and LQT2. Abnormal systolic Ca2+-oscillations and EADs caused by SR Ca2+-release are reproduced in a modified 0-dimensional model, where 3 gates in series control the ryanodine receptor (RyR2) conductance. Two gates control RyR2 activation and inactivation and sense cytosolic Ca2+ while a third gate senses luminal junctional SR Ca2+. The model predicts EADs in bradycardia and low extracellular [K+] and cessation of SR Ca2+-release terminate salvos of EADs. Ca2+-waves, systolic cell-synchronous Ca2+-release, and multifocal diastolic Ca2+ release seen in subcellular Ca2+-mapping experiments are observed in the 2-dimensional version of the model. These results support the role of SR Ca2+-overload, abnormal SR Ca2+-release, and the subsequent activation of the electrogenic Na+/Ca2+-exchanger as the mechanism of TdP. The model offers new insights into the genesis of cardiac arrhythmia and new therapeutic strategies.

  1. Formulation of calcium dialuminate (Ca2Al2O3 refractory cement from local bauxite

    Directory of Open Access Journals (Sweden)

    A.B. Tchamba

    2015-06-01

    Full Text Available Three types of bauxites containing aluminum hydroxide of 58.1% gibbsite and 19.3% boehmite for BX3, 95.5% of gibbsite for BX55 and 84.5% of gibbsite for BX8 were used with lime at 95% of CaO through solid state sintering in one stage to prepare a refractory clinker at 1550 °C. The powder obtained after grinding the clinker showed in the XRD curves the presence of Ca2Al2O3 and CaO·TiO2 phases in the cement samples. The density of cement powder varied between 2.95 and 3.17 g/cm3 and the specific area of powder obtained after grinding was between 0.72 and 0.85 m2/g. The properties of hydrated cement, W/C = 0.33, after stabilization of cement components for 48 h at 105 °C were showed by XRD, DTA, DTG and SEM (C3AH6, AH3, CA2 and CaO·TiO2. The Young's modulus of the cement made varied between 35.5 and 39.4 GPa, and these Young's moduli were compared to conventional CA14M cement.

  2. Sigma-1 receptor chaperones at the ER-mitochondrion interface regulate Ca(2+) signaling and cell survival.

    Science.gov (United States)

    Hayashi, Teruo; Su, Tsung-Ping

    2007-11-02

    Communication between the endoplasmic reticulum (ER) and mitochondrion is important for bioenergetics and cellular survival. The ER supplies Ca(2+) 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). We found here that the ER protein sigma-1 receptor (Sig-1R), which is implicated in neuroprotection, carcinogenesis, and neuroplasticity, is a Ca(2+)-sensitive and ligand-operated receptor chaperone at MAM. Normally, Sig-1Rs form a complex at MAM with another chaperone, BiP. Upon ER Ca(2+) depletion or via ligand stimulation, Sig-1Rs dissociate from BiP, leading to a prolonged Ca(2+) signaling into mitochondria via IP3Rs. Sig-1Rs can translocate under chronic ER stress. Increasing Sig-1Rs in cells counteracts ER stress response, whereas decreasing them enhances apoptosis. These results reveal that the orchestrated ER chaperone machinery at MAM, by sensing ER Ca(2+) concentrations, regulates ER-mitochondrial interorganellar Ca(2+) signaling and cell survival.

  3. CaSeO4-0.625H2O - Water Channel Occupation in a bassanite Related Structure

    Energy Technology Data Exchange (ETDEWEB)

    S Fritz; H Schmidt; I Paschke; O Magdysyuk; R Dinnebier; D Freyer; W Voigt

    2011-12-31

    Calcium selenate subhydrate, CaSeO{sub 4} {center_dot} 0.625H{sub 2}O, was prepared by hydrothermal conversion of CaSeO{sub 4} {center_dot} 2H{sub 2}O at 463 K. From the single crystals obtained in the shape of hexagonal needles, 50-300 {micro}m in length, the crystal structure could be solved in a trigonal unit cell with space group P3{sub 2}21. The cell was confirmed and refined by high-resolution synchrotron powder diffraction. The subhydrate was characterized by thermal analysis and Raman spectroscopy.

  4. Thermoluminescence properties of CaO powder obtained from chicken eggshells

    International Nuclear Information System (INIS)

    Nagabhushana, K.R.; Lokesha, H.S.; Satyanarayana Reddy, S.; Prakash, D.; Veerabhadraswamy, M.; Bhagyalakshmi, H.; Jayaramaiah, J.R.

    2017-01-01

    Eggshell wastage has created serious problem in disposal of the food processing industry which has been triggered the thoughts of researchers to use wasted eggshells as good source of calcium. In the present work, calcium oxide (CaO) has been synthesized by combustion process in furnace (F–CaO) and microwave oven (M–CaO) using the source of chicken eggshells. The obtained F–CaO and M–CaO are characterized by XRD, SEM with EDX and thermoluminescence (TL) technique. XRD pattern of both the samples show cubic phase with crystallite size 45–52 nm. TL glow curves are recorded for various gamma radiation dose (300–4000 Gy). Two TL glows, a small peak at 424 K and stronger peak at 597 K are observed. TL response of M–CaO is 2.67 times higher than F–CaO sample. TL kinetic parameters are calculated by computerized curve deconvolution analysis (CCDA) and discussed. - Highlights: • Calcium oxide powders have been synthesized using chicken egg shells as raw material. • Crystallite size was found to be 45–52 nm. • CaO derived from eggshells shows good thermoluminescence TL response. • TL response of the M–CaO is 2.67 times higher than the F–CaO sample.

  5. Preparation of orthophosphate glasses in the MgO-CaO-SiO2-Nb2O5-P2O5 system.

    Science.gov (United States)

    Lee, Sungho; Ueda, Kyosuke; Narushima, Takayuki; Nakano, Takayoshi; Kasuga, Toshihiro

    2017-01-01

    Niobia/magnesia-containing orthophosphate invert glasses were successfully prepared in our earlier work. Orthophosphate groups in the glasses were cross-linked by tetrahedral niobia (NbO4) and magnesia. The aim of this work is to prepare calcium orthophosphate invert glasses containing magnesia and niobia, incorporating silica, and to evaluate their structures and releasing behaviors. The glasses were prepared by melt-quenching, and their structures and ion-releasing behaviors were evaluated. 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies showed the glasses consist of orthophosphate (PO4), orthosilicate (SiO4), and NbO4 tetrahedra. NbO4 and MgO in the glasses act as network formers. By incorporating SiO2 into the glasses, the chemical durability of the glasses was slightly improved. The glasses reheated at 800°C formed the orthophosphate crystalline phases, such as β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4 in the glasses. The chemical durability of the crystallized glasses was slightly improved. Orthosilicate groups and NbO4 in the glasses coordinated with each other to form Si-O-Nb bonds. The chemical durability of the glasses was slightly improved by addition of SiO2, since the field strength of Si is larger than that of Ca or Mg.

  6. In situ scanning tunneling microscopy study of Ca-modified rutile TiO2(110 in bulk water

    Directory of Open Access Journals (Sweden)

    Giulia Serrano

    2015-02-01

    Full Text Available Despite the rising technological interest in the use of calcium-modified TiO2 surfaces in biomedical implants, the Ca/TiO2 interface has not been studied in an aqueous environment. This investigation is the first report on the use of in situ scanning tunneling microscopy (STM to study calcium-modified rutile TiO2(110 surfaces immersed in high purity water. The TiO2 surface was prepared under ultrahigh vacuum (UHV with repeated sputtering/annealing cycles. Low energy electron diffraction (LEED analysis shows a pattern typical for the surface segregation of calcium, which is present as an impurity on the TiO2 bulk. In situ STM images of the surface in bulk water exhibit one-dimensional rows of segregated calcium regularly aligned with the [001] crystal direction. The in situ-characterized morphology and structure of this Ca-modified TiO2 surface are discussed and compared with UHV-STM results from the literature. Prolonged immersion (two days in the liquid leads to degradation of the overlayer, resulting in a disordered surface. X-ray photoelectron spectroscopy, performed after immersion in water, confirms the presence of calcium.

  7. Production of 34S-labeled gypsum (Ca34SO4.2H2O Produção de gesso (Ca34SO4.2H2O, marcado com 34S

    Directory of Open Access Journals (Sweden)

    Alexssandra Luiza Rodrigues Molina Rossete

    2006-08-01

    Full Text Available Agricultural gypsum (CaSO4.2H2O stands out as an effective source of calcium and sulfur, and to control aluminum saturation in the soil. Labeled as 34S it can elucidate important aspects of the sulfur cycle. Ca34SO4.2H2O was obtained by chemical reaction between Ca(OH2 and H2(34SO4, performed under slow agitation. The acid was produced by ion exchange chromatography using the Dowex 50WX8 cation exchange resin and a Na2(34SO4 eluting solution. After precipitation, the precipitate was separated and dried in a ventilated oven at 60ºC. From 2.2 L H2SO4 0.2 mol L-1 and 33.6 g Ca(OH2, 73.7 ± 0.6 g Ca34SO4.2H2O were produced on average in the tests, representing a mean yield of 94.6 ± 0.8%, with 98% purity. The 34SO2 gas was obtained from Ca34SO4.2H2O in the presence of NaPO3 in a high vacuum line and was used for the isotopic determination of S in an ATLAS-MAT model CH-4 mass spectrometer.O gesso agrícola (CaSO4.2H2O destaca-se como fonte eficiente de cálcio e enxofre e na redução da saturação de alumínio no solo. O 34S como traçador isotópico pode elucidar aspectos importantes no ciclo do enxofre. Para tanto o Ca34SO4.2H2O foi obtido por reação química entre o Ca(OH2 e solução de H2(34SO4, realizada sob agitação lenta. O ácido foi produzido por cromatografia de troca iônica, utilizando resina catiônica Dowex 50WX8 e solução eluente de Na2(34SO4. Após a precipitação foi separado o precipitado e realizada a secagem em estufa ventilada à temperatura de 60ºC. Nos testes, a partir de 2,2 L de H2SO4 0,2 mol L-1 e 33,6 g de Ca(OH2, foram produzidos em média 73,7 ± 0,6 g de Ca34SO4.2H2O representando um rendimento médio de 94,6 ± 0,8%, com pureza de 98%. A partir do Ca34SO4.2H2O na presença de NaPO3, em linha de alto vácuo, obteve-se o gás 34SO2 utilizado para a determinação isotópica do S no espectrômetro de massas ATLAS-MAT modelo CH-4.

  8. Dopamine receptors on adrenal chromaffin cells modulate calcium uptake and catecholamine release

    Energy Technology Data Exchange (ETDEWEB)

    Bigornia, L; Suozzo, M; Ryan, K A; Napp, D; Schneider, A S

    1988-10-01

    The presence of dopamine-containing cells in sympathetic ganglia, i.e., small, intensely fluorescent cells, has been known for some time. However, the role of dopamine as a peripheral neurotransmitter and its mechanism of action are not well understood. Previous studies have demonstrated the presence of D2 dopamine receptors on the surface of bovine adrenal chromaffin cells using radioligand binding methods and dopamine receptor inhibition of catecholamine release from perfused adrenal glands. In the present study, we provide evidence confirming a role of dopamine receptors as inhibitory modulators of adrenal catecholamine release from bovine chromaffin cell cultures and further show that the mechanism of modulation involves inhibition of stimulated calcium uptake. Apomorphine gave a dose-dependent inhibition (IC50 = 1 microM) of 45Ca2+ uptake stimulated by either nicotine (10 microM) or membrane depolarization with an elevated K+ level (60 mM). This inhibition was reversed by a series of specific (including stereospecific) dopamine receptor antagonists: haloperidol, spiperone, sulpiride, and (+)-butaclamol, but not (-)-butaclamol. In addition, the calcium channel agonist Bay K 8644 was used to stimulate uptake of 45Ca2+ into chromaffin cells, and this uptake was also inhibited by the dopamine receptor agonist apomorphine. The combined results suggest that dopamine receptors on adrenal chromaffin cells alter Ca2+ channel conductance, which, in turn, modulates catecholamine release.

  9. Polyamines mediate abnormal Ca2+ transport and Ca2+-induced cardiac cell injury in the calcium paradox

    International Nuclear Information System (INIS)

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

    1986-01-01

    Ca 2+ -free perfusion renders heart cells Ca 2+ -sensitive so that readmission of Ca 2+ causes a sudden massive cellular injury attributed to abnormal entry of Ca 2+ into cells (Ca paradox). Hormonal stimulation of Ca 2+ fluxes was earlier shown to be mediated by polyamines (PA). 5 min perfusion of rat heart with Ca 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 2+ -containing medium abruptly ( 2+ reperfusion-induced increases in ODC and PA and also prevented increased 45 Ca 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 2+ reperfusion-induced 45 Ca 2+ influx and cell injury. These data indicate that the Ca 2+ -directed depletion-repletion cycle of ODC and PA triggers excessive transsarcolemmal Ca 2+ transport leading to the calcium paradox

  10. Calcium Input Frequency, Duration and Amplitude Differentially Modulate the Relative Activation of Calcineurin and CaMKII

    Science.gov (United States)

    Li, Lu; Stefan, Melanie I.; Le Novère, Nicolas

    2012-01-01

    NMDA receptor dependent long-term potentiation (LTP) and long-term depression (LTD) are two prominent forms of synaptic plasticity, both of which are triggered by post-synaptic calcium elevation. To understand how calcium selectively stimulates two opposing processes, we developed a detailed computational model and performed simulations with different calcium input frequencies, amplitudes, and durations. We show that with a total amount of calcium ions kept constant, high frequencies of calcium pulses stimulate calmodulin more efficiently. Calcium input activates both calcineurin and Ca2+/calmodulin-dependent protein kinase II (CaMKII) at all frequencies, but increased frequencies shift the relative activation from calcineurin to CaMKII. Irrespective of amplitude and duration of the inputs, the total amount of calcium ions injected adjusts the sensitivity of the system to calcium input frequencies. At a given frequency, the quantity of CaMKII activated is proportional to the total amount of calcium. Thus, an input of a small amount of calcium at high frequencies can induce the same activation of CaMKII as a larger amount, at lower frequencies. Finally, the extent of activation of CaMKII signals with high calcium frequency is further controlled by other factors, including the availability of calmodulin, and by the potency of phosphatase inhibitors. PMID:22962589

  11. 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.

  12. The in vivo anti-fibrotic function of calcium sensitive receptor (CaSR) modulating poly(p-dioxanone-co-l-phenylalanine) prodrug.

    Science.gov (United States)

    Wang, Bing; Wen, Aiping; Feng, Chengmin; Niu, Lijing; Xiao, Xin; Luo, Le; Shen, Chengyi; Zhu, Jiang; Lei, Jun; Zhang, Xiaoming

    2018-04-13

    In present study, the apoptosis induction and proliferation suppression effects of l-phenylalanine (l-Phe) on fibroblasts were confirmed. The action sites of l-Phe on fibroblasts suppression were deduced to be calcium sensitive receptor (CaSR) which could cause the release of endoplasmic reticulum (ER) Ca 2+ stores; disruption of intracellular Ca 2+ homeostasis triggers cell apoptosis via the ER or mitochondrial pathways. The down-regulation of CaSR were observed after the application of l-Phe, and the results those l-Phe triggered the increasing of intracellular Ca 2+ concentration and calcineurin expression, and then the apoptosis and increasing G1 fraction of fibroblasts have verified our deduction. Hence, l-Phe could be seen as a kind of anti-fibrotic drugs for the crucial participation of fibroblast in the occurrence of fibrosis. And then, poly(p-dioxanone-co-l-phenylalanine) (PDPA) which could prolong the in-vivo anti-fibrotic effect of l-Phe for the sustained release of l-Phe during its degradation could be treated as anti-fibrotic polymer prodrugs. Based on the above, the in vivo anti-fibrotic function of PDPA was evaluated in rabbit ear scarring, rat peritoneum lipopolysaccharide, and rat sidewall defect/cecum abrasion models. PDPA reduced skin scarring and suppressed peritoneal fibrosis and post operation adhesion as well as secretion of transforming growth factor-β1 in injured tissue. These results indicate that PDPA is an effective agent for preventing fibrosis following tissue injury. We have previously demonstrated that poly(p-dioxanone-co-l-phenylalanine) (PDPA) could induce apoptosis to fibroblast and deduced that the inhibitory effect comes from l-phenylalanine. In present study, the inhibition mechanism of l-phenylalanine on fibroblast proliferation was demonstrated. The calcium sensitive receptor (CaSR) was found to be the action site. The CaSR was downregulated after the application of l-phenylalanine, and then the ER Ca 2+ stores were released

  13. CaO-Based CO2 Sorbents Effectively Stabilized by Metal Oxides.

    Science.gov (United States)

    Naeem, Muhammad Awais; Armutlulu, Andac; Imtiaz, Qasim; Müller, Christoph R

    2017-11-17

    Calcium looping (i.e., CO 2 capture by CaO) is a promising second-generation CO 2 capture technology. CaO, derived from naturally occurring limestone, offers an inexpensive solution, but due to the harsh operating conditions of the process, limestone-derived sorbents undergo a rapid capacity decay induced by the sintering of CaCO 3 . Here, we report a Pechini method to synthesize cyclically stable, CaO-based CO 2 sorbents with a high CO 2 uptake capacity. The sorbents synthesized feature compositional homogeneity in combination with a nanostructured and highly porous morphology. The presence of a single (Al 2 O 3 or Y 2 O 3 ) or bimetal oxide (Al 2 O 3 -Y 2 O 3 ) provides cyclic stability, except for MgO which undergoes a significant increase in its particle size with the cycle number. We also demonstrate a direct relationship between the CO 2 uptake and the morphology of the synthesized sorbents. After 30 cycles of calcination and carbonation, the best performing sorbent, containing an equimolar mixture of Al 2 O 3 and Y 2 O 3 , exhibits a CO 2 uptake capacity of 8.7 mmol CO 2  g -1 sorbent, which is approximately 360 % higher than that of the reference limestone. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

    International Nuclear Information System (INIS)

    Li, Xuerun; Zhang, Yu; Shen, Xiaodong; Wang, Qianqian; Pan, Zhigang

    2014-01-01

    The formation kinetics of tricalcium aluminate (C 3 A) and calcium sulfate yielding calcium sulfoaluminate (C 4 A 3 $) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C 3 A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca 3 Al 2 O 6 + CaSO 4 → Ca 4 Al 6 O 12 (SO 4 ) + 6CaO was the primary reaction 4 Al 6 O 12 (SO 4 ) + 10CaO → 6Ca 3 Al 2 O 6 + 2SO 2 ↑ + O 2 ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C 4 A 3 $ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C 4 A 3 $ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca 2+ and SO 4 2− were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C 3 A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion

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

    KAUST Repository

    Hargis, Craig W.; Moon, Juhyuk; Lothenbach, Barbara; Winnefeld, Frank; Wenk, Hans-Rudolf; Monteiro, Paulo J. M.

    2013-01-01

    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

  16. PDMS-SiO{sub 2}-TiO{sub 2}-CaO hybrid materials – Cytocompatibility and nanoscale surface features

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, J. Carlos [CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Wacha, András [Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok körútja 2, Budapest 1117 (Hungary); Gomes, Pedro S.; Fernandes, M. Helena R. [Laboratory for Bone Metabolism and Regeneration, Faculdade de Medicina Dentária, Universidade do Porto (Portugal); Fernandes, M. Helena Vaz [CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Salvado, Isabel M. Miranda, E-mail: isabelmsalvado@ua.pt [CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal)

    2016-07-01

    Two PDMS-SiO{sub 2}-TiO{sub 2}-CaO porous hybrid materials were prepared using the same base composition, precursors, and solvents, but following two different sol-gel procedures, based on the authors' previous works where for the first time, in this hybrid system, calcium acetate was used as calcium source. The two different procedures resulted in monolithic materials with different structures, microstructures, and surface wettability. Even though both are highly hydrophobic (contact angles of 127.2° and 150.6°), and present different filling regimes due to different surface topographies, they have demonstrated to be cytocompatible when tested with human osteoblastic cells, against the accepted idea that high-hydrophobic surfaces are not suitable to cell adhesion and proliferation. At the nanoscale, the existence of hydrophilic silica domains containing calcium, where water molecules are physisorbed, is assumed to support this capability, as discussed. - Highlights: • Two hybrid materials were prepared following two different sol-gel procedures. • Both are highly hydrophobic but demonstrated to be cytocompatible. • Different filling regimes were observed.

  17. Modulation of intracellular Ca2+ via L-type calcium channels in heart cells by the autoantibody directed against the second extracellular loop of the alpha1-adrenoceptors.

    Science.gov (United States)

    Bkaily, Ghassan; El-Bizri, Nesrine; Bui, Michel; Sukarieh, Rami; Jacques, Danielle; Fu, Michael L X

    2003-03-01

    The effects of methoxamine, a selective alpha1-adrenergic receptor agonist, and the autoantibody directed against the second extracellular loop of alpha1-adrenoceptors were studied on intracellular free Ca2+ levels using confocal microscopy and ionic currents using the whole-cell patch clamp technique in single cells of 10-day-old embryonic chick and 20-week-old fetal human hearts. We observed that like methoxamine, the autoantibody directed against the second extracellular loop of alpha1-adrenoreceptors significantly increased the L-type calcium current (I(Ca(L))) but had no effect on the T-type calcium current (I(Ca(T))), the delayed outward potassium current, or the fast sodium current. This effect of the autoantibody was prevented by a prestimulation of the receptors with methoxamine and vice versa. Moreover, treating the cells with prazosin, a selective alpha1-adrenergic receptor antagonist blocked the methoxamine and the autoantibody-induced increase in I(Ca(L)), respectively. In absence of prazosin, both methoxamine and the autoantibody showed a substantial enhancement in the frequency of cell contraction and that of the concomitant cytosolic and nuclear free Ca2+ variations. The subsequent addition of nifedipine, a specific L-type Ca2+ channel blocker, reversed not only the methoxamine or the autoantibody-induced effect but also completely abolished cell contraction. These results demonstrated that functional alpha1-adrenoceptors exist in both 10-day-old embryonic chick and 20-week-old human fetal hearts and that the autoantibody directed against the second extracellular loop of this type of receptors plays an important role in stimulating their activity via activation of L-type calcium channels. This loop seems to have a functional significance by being the target of alpha1-receptor agonists like methoxamine.

  18. 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.

  19. Phytic acid derived bioactive CaO-P2O5-SiO2 gel-glasses.

    Science.gov (United States)

    Li, Ailing; Qiu, Dong

    2011-12-01

    The possibility of using phytic acid as a precursor to synthesize CaO-P(2)O(5)-SiO(2) glasses by sol-gel method has been explored and the pseudo ternary phase diagram has been established. It was shown that gel-glasses over a broader range of compositions could be prepared compared to other phosphorus precursors or melt-quenching method. Furthermore, phytic acid was found to assist calcium being incorporated into glass networks. In vitro tests in simulated body fluid (SBF) were performed on the above gel-glasses and it was found that they were bioactive over a much broader compositional range especially at high phosphate content, thus enabling one to design bioactive materials with various degradation rates by adjusting the phosphate content.

  20. High-temperature crystal chemistry of layered calcium borosilicates: CaBSiO4(OH) (datolite), Ca4B5Si3O15(OH)5 (`bakerite') and Ca2B2SiO7 (synthetic analogue of okayamalite)

    Science.gov (United States)

    Krzhizhanovskaya, Maria G.; Gorelova, L. A.; Bubnova, R. S.; Pekov, I. V.; Krivovichev, S. V.

    2018-05-01

    The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30-900 °C for natural samples of datolite, CaBSiO4(OH), and `bakerite', Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °C. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30-500 °C, datolite and `bakerite' demonstrate very similar and relatively low volumetric thermal expansion: α v = 29 and 27 × 10-6 °C-1, respectively. A high thermal expansion anisotropy ( α max/ α min 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the ( a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) Å, V = 256.76(3) Å3, R wp = 6.61, R Bragg = 2.68%].

  1. Novel mechanism for the modification of Al2O3-based inclusions in ultra-low carbon Al-killed steel considering the effects of magnesium and calcium

    Science.gov (United States)

    Guo, Jing; Cheng, Shu-sen; Guo, Han-jie; Mei, Ya-guang

    2018-03-01

    Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al2O3-based inclusions during secondary refining. The results showed that Al2O3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO-MgO-Al2O3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3wt% and the temperature is higher than 1843 K.

  2. A molecular dynamics study of the atomic structure of (CaO)x(SiO2)1-x glasses.

    Science.gov (United States)

    Mead, Robert N; Mountjoy, Gavin

    2006-07-27

    The local atomic environment of Ca in (CaO)x(SiO2)1-x glasses is of interest because of the role of Ca in soda-lime glass, the application of calcium silicate glasses as biomaterials, and the previous experimental measurement of the Ca-Ca correlation in CaSiO(3) glass. Molecular dynamics has been used to obtain models of (CaO)x(SiO2)1-x glasses with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5, and with approximately 1000 atoms and size approximately 25 A. As expected, the models contain a tetrahedral silica network, the connectivity of which decreases as x increases. In the glass-forming region, i.e., x = 0.4 and 0.5, Ca has a mixture of 6- and 7-fold coordination. Bridging oxygen makes an important contribution to the coordination of Ca, with most bridging oxygens coordinated to 2 Si plus 1 Ca. The x = 0.5 model is in reasonable agreement with previous experimental studies, and does not substantiate the previous theory of cation ordering, which predicted Ca arranged in sheets. In the phase-separated region, i.e., x = 0.1 and 0.2, there is marked clustering of Ca.

  3. Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

    Directory of Open Access Journals (Sweden)

    Jingbin Yang

    2017-06-01

    Full Text Available C-A-S-H (CaO-Al2O3-SiO2-H2O and N-A-S-H (Na2O-Al2O3-SiO2-H2O have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali

  4. [Cognitive Function and Calcium. Structures and functions of Ca2+-permeable channels].

    Science.gov (United States)

    Kaneko, Shuji

    2015-02-01

    Calcium is essential for living organisms where the increase in intracellular Ca2+ concentration functions as a second messenger for many cellular processes including synaptic transmission and neural plasticity. The cytosolic concentration of Ca2+ is finely controlled by many Ca2+-permeable ion channels and transporters. The comprehensive view of their expression, function, and regulation will advance our understanding of neural and cognitive functions of Ca2+, which leads to the future drug discovery.

  5. Kinetics of dissolution of sapphire in melts in the CaO-Al2O3-SiO2 system

    Science.gov (United States)

    Shaw, Cliff S. J.; Klausen, Kim B.; Mao, Huahai

    2018-05-01

    The dissolution rate of sapphire in melts in the CAS system of varying silica activity, viscosity and degree of alumina saturation has been determined at 1600 °C and 1.5 GPa. After an initiation period of up to 1800 s, dissolution is controlled by diffusion of cations through the boundary layer adjacent to the dissolving sapphire. The dissolution rate decreases with increasing silica activity, viscosity and molar Al2O3/CaO. The calculated diffusion matrix for each solvent melt shows that CAS 1 and 9 which have molar Al2O3/CaO of 0.33 and 0.6 and dissolution rate constants of 0.65 × 10-6 and 0.59 × 10-6 m/s0.5 have similar directions and magnitudes of diffusive coupling: DCaO-Al2O3 and DAl2O3-CaO are both negative are approximately equal. The solvent with the fastest dissolution rate: CAS 4, which has a rate constant of 1.5 × 10-6 m/s0.5 and Al2O3/CaO of 0.31 has positive DCaO-Al2O3 and negative DAl2O3-CaO and the absolute values vary by a factor of 4. Although many studies show that aluminium is added to the melts via the reaction: Si4+ =Al3+ + 0.5Ca2+ the compositional profiles show that this reaction is not the only one involved in accommodating the aluminium added during sapphire dissolution. Rather, aluminium is incorporated as both tetrahedrally coordinated Al charge balanced by Ca and as aluminium not charge balanced by Ca (termed Alxs). This reaction: AlIV -Ca =Alxs +CaNBO where CaNBO is a non-bridging oxygen associated with calcium, may involve the formation of aluminium triclusters. The shape of the compositional profiles and oxide-oxide composition paths is controlled by the aluminium addition reaction. When Alxs exceeds 2%, CaO diffusion becomes increasingly anomalous and since the bond strength of Alxs correlates with CaO/CaO + Al2O3, the presence of more than 2% Alxs leads to significantly slower dissolution than when Alxs is absent or at low concentration. Thus, dissolution is controlled by diffusion of cations through the boundary layer, but this

  6. NCS-1 associates with adenosine A2A receptors and modulates receptor function

    Directory of Open Access Journals (Sweden)

    Gemma eNavarro

    2012-04-01

    Full Text Available Modulation of G protein-coupled receptor (GPCR signalling by local changes in intracellular calcium concentration is an established function of Calmodulin which is known to interact with many GPCRs. Less is known about the functional role of the closely related neuronal EF-hand Ca2+-sensor proteins that frequently associate with calmodulin targets with different functional outcome. In the present study we aimed to investigate if a target of calmodulin – the A2A adenosine receptor, is able to associate with two other neuronal calcium binding proteins, namely NCS-1 and caldendrin. Using bioluminescence resonance energy transfer and co-immunoprecipitation experiments we show the existence of A2A - NCS-1 complexes in living cells whereas caldendrin did not associate with A2A receptors under the conditions tested. Interestingly, NCS-1 binding modulated downstream A2A receptor intracellular signalling in a Ca2+-dependent manner. Taken together this study provides further evidence that neuronal Ca2+-sensor proteins play an important role in modulation of GPCR signalling.

  7. Molecular and functional profiling of histamine receptor-mediated calcium ion signals in different cell lines.

    Science.gov (United States)

    Meisenberg, Annika; Kaschuba, Dagmar; Balfanz, Sabine; Jordan, Nadine; Baumann, Arnd

    2015-10-01

    Calcium ions (Ca(2+)) play a pivotal role in cellular physiology. Often Ca(2+)-dependent processes are studied in commonly available cell lines. To induce Ca(2+) signals on demand, cells may need to be equipped with additional proteins. A prominent group of membrane proteins evoking Ca(2+) signals are G-protein coupled receptors (GPCRs). These proteins register external signals such as photons, odorants, and neurotransmitters and convey ligand recognition into cellular responses, one of which is Ca(2+) signaling. To avoid receptor cross-talk or cross-activation with introduced proteins, the repertoire of cell-endogenous receptors must be known. Here we examined the presence of histamine receptors in six cell lines frequently used as hosts to study cellular signaling processes. In a concentration-dependent manner, histamine caused a rise in intracellular Ca(2+) in HeLa, HEK 293, and COS-1 cells. The concentration for half-maximal activation (EC50) was in the low micromolar range. In individual cells, transient Ca(2+) signals and Ca(2+) oscillations were uncovered. The results show that (i) HeLa, HEK 293, and COS-1 cells express sufficient amounts of endogenous receptors to study cellular Ca(2+) signaling processes directly and (ii) these cell lines are suitable for calibrating Ca(2+) biosensors in situ based on histamine receptor evoked responses. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. The utilization of hydroxyapatite-supported CaO-CeO_2 catalyst for biodiesel production

    International Nuclear Information System (INIS)

    Yan, Beibei; Zhang, Ying; Chen, Guanyi; Shan, Rui; Ma, Wenchao; Liu, Changye

    2016-01-01

    Highlights: • Hydroxyapatite derived from waste animal bones was served as the support for bimetallic CaO-CeO_2 catalyst. • The 30%CaO-CeO_2/HAP-650 catalyst exhibited excellent performance on biodiesel production. • The yield of FAME was 84.4 % after eight cycles. • Minor leaching concentrations of cerium and calcium species were detected in the product. - Abstract: The study investigated the effect of a bimetallic supported catalyst in biodiesel production. Calcined waste bone derived hydroxyapatite (HAP), a solid waste from animal, was served as the support for CaO-CeO_2 catalyst. Various characterization techniques such as FT-IR, BET, SEM-EDS, CO_2-TPD and XRD analysis were used to analyse the activity of this heterogeneous catalyst. The effect of main parameters in preparation process such as calcination temperature and active component loading on catalyst performance were discussed to obtain the optimal preparation conditions. Under the optimal reaction conditions (11 wt.% dosage of 30%CaO-CeO_2/HAP-650 catalyst and 9:1 methanol to oil molar ratio at 65 °C for 3 h) the highest biodiesel yield of 91.84% was obtained. Stability test indicated that the yield (84.4%) of fatty acid methyl ester was produced after 8 re-used cycles due to the low leaching of catalyst components. The experimental results showed that biodiesel production cost might be lowered while producing relatively high yield at the present of long life-span catalyst.

  9. Structural, dynamical & electronic properties of CaCuO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, B.K.; Agrawal, S. [Allahabad Univ. (India)

    1994-12-31

    The scalar relativistic version of an accurate first principles full potential self- consistent linearized muffin tin orbital (LMTO) method has been employed for describing the physical properties of the parent system of the high-Tc oxide superconductors, i.e., CaCuO2. The presently employed modified version of the LMTO method is quite fast and goes beyond the usual LMTO-ASA method in the sense that it permits a completely general shape of the potential and the charge density. Also, in contrast to LMTO-ASA, the present method is also capable of treating distorted lattice structures accurately. The calculated values of the lattice parameters of pure CaCuO2 lie within 3% of the experimentally measured values for the Sr-doped system Ca(.86)Sr(.14)CuO(2). The computed electronic structures and the density of states is quite similar to those of the other oxide superconductors, except of their three- dimensional character because of the presence of strong coupling between the closely spaced CuO2 layers. The van Hove singularity peak appears slightly below the Fermi level and a small concentration of oxygenation /or/ substitutional doping may pin it as the Fermi level. The calculated frequencies for some symmetric frozen phonons for undoped CaCuO2 are quite near to the measured data for the Sr-doped CaCuO2.

  10. Sol-Gel SiO2-CaO-P2O5 biofilm with surface engineered for medical application

    Directory of Open Access Journals (Sweden)

    Sonia Regina Federman

    2007-06-01

    Full Text Available Sol-gel film in the SiO2-CaO-P2O5 system was prepared from TEOS, TEP, alcohol and hydrated calcium nitrate in an acidic medium. The coatings were deposited on stainless steel using the dip-coating technique. After deposition, the composite was submitted to heat treatment, at different temperatures and exposure times to investigate the influence of such parameters on the surface morphology of the composite. The coated surfaces were characterized by AFM, SEM and FTIR. The present study showed that the formation of different textures (an important parameter in implant fixation could be controlled by temperature and time of heat treatment.

  11. Calcium sensing in exocytosis

    DEFF Research Database (Denmark)

    Gustavsson, Natalia; Wu, Bingbing; Han, Weiping

    2012-01-01

    an increase in intracellular calcium levels. Besides the triggering role, calcium signaling modulates the precise amount and kinetics of vesicle release. Thus, it is a central question to understand the molecular machineries responsible for calcium sensing in exocytosis. Here we provide an overview of our...... current understanding of calcium sensing in neurotransmitter release and hormone secretion....

  12. Characterizing ligand-gated ion channel receptors with genetically encoded Ca2++ sensors.

    Directory of Open Access Journals (Sweden)

    John G Yamauchi

    2011-01-01

    Full Text Available We present a cell based system and experimental approach to characterize agonist and antagonist selectivity for ligand-gated ion channels (LGIC by developing sensor cells stably expressing a Ca(2+ permeable LGIC and a genetically encoded Förster (or fluorescence resonance energy transfer (FRET-based calcium sensor. In particular, we describe separate lines with human α7 and human α4β2 nicotinic acetylcholine receptors, mouse 5-HT(3A serotonin receptors and a chimera of human α7/mouse 5-HT(3A receptors. Complete concentration-response curves for agonists and Schild plots of antagonists were generated from these sensors and the results validate known pharmacology of the receptors tested. Concentration-response relations can be generated from either the initial rate or maximal amplitudes of FRET-signal. Although assaying at a medium throughput level, this pharmacological fluorescence detection technique employs a clonal line for stability and has versatility for screening laboratory generated congeners as agonists or antagonists on multiple subtypes of ligand-gated ion channels. The clonal sensor lines are also compatible with in vivo usage to measure indirectly receptor activation by endogenous neurotransmitters.

  13. PEG/CaFe2O4 nanocomposite: Structural, morphological, magnetic and thermal analyses

    International Nuclear Information System (INIS)

    Khanna, Lavanya; Verma, Narendra K.

    2013-01-01

    The coating of Polyethylene Glycol (PEG) on calcium ferrite (CaFe 2 O 4 ) nanoparticles has been reported in the present study. The X-ray diffraction pattern revealed the formation of orthorhombic structure of bare CaFe 2 O 4 nanoparticles, which was also retained after the PEG coating, along with additional characteristic peaks of PEG at 19° and 23°. The rings of CaFe 2 O 4 nanoparticles were identified by the selected area electron diffraction pattern. The characteristic bands of PEG as observed in its Fourier transform infrared spectrum were also present in PEG coated CaFe 2 O 4 nanoparticles, hence confirming its presence. In the thermal gravimetric studies, the complete thermal decomposition of PEG occurred in a one step process, but in case of PEG coated CaFe 2 O 4 nanoparticles, the decomposition took place at a higher temperature owing to the formation of covalent bonds of PEG with CaFe 2 O 4 nanoparticles. The presence of PEG on CaFe 2 O 4 nanoparticles, spherical formation of PEG coated CaFe 2 O 4 nanoparticles and reduced agglomeration in the CaFe 2 O 4 nanoparticles were revealed by high resolution transmission electron microscope, transmission electron microscope and scanning electron microscope studies, respectively. In vibrating sample magnetometer analysis, both bare as well as coated CaFe 2 O 4 nanoparticles exhibited superparamagnetic behavior. However, a drop in the magnetic saturation value was observed from 36.76 emu/g for CaFe 2 O 4 nanoparticles to 6.74 emu/g for PEG coated CaFe 2 O 4 nanoparticles, due to the formation of magnetically dead layer of PEG. In ZFC and FC analyses, superparamagnetic behavior with blocking temperature for bare and coated nanoparticles has been observed at ∼40 K and ∼60 K, respectively. The increase in the blocking temperature is attributed to the increase in the particle size after PEG coating

  14. Obtention of agricultural gypsum traced on 34 S (Ca34 SO4.2H2O), by chemical reaction between H234 SO4 and Ca(OH)2

    International Nuclear Information System (INIS)

    Rossete, Alessandra L.R.M.; Bendassolli, Jose A.; Ignoto, Raquel de Fatima; Batagello, Hugo Henrique

    2002-01-01

    The gypsum (CaSO 4 .2H 2 O) has double function in the soil: as source of calcium and sulfur and reducing agent of aluminum saturation. The sulfur for the plants has acting in the vital functions and it is proven fact increase of the S deficiency in Brazilian soils. The isotope tracer 34 S can elucidate important aspects in the sulfur cycle. The Ca 34 SO 4 .2H 2 O was obtained by chemical reaction between Ca(OH) 2 and H 2 34 SO 4 solution. The acid was obtained by chromatography ionic change, using cationic resin Dowex 50WX8 and Na 2 34 SO 4 solution. The reaction was realized under slow agitation. After the reaction, the precipitate was separated and dried in ventilated stove at 60 deg C temperature. The Mass of the Ca 34 SO 4 .2H 2 O produced was determined by method gravimetric. This way, a system contends resin 426 cm 3 , considering volume of 2.2 liters can be obtained a solution contends 44.2 g of H 2 34 SO 4 , theoretically could be produced 78.0 g of Ca 34 SO 4 .2H 2 O approximately. With results of the tests were verified that there was not total precipitation of the Ca 34 SO 4 .2H 2 O. Were produced 73.7± 0.6 g of Ca 34 SO 4 .2H 2 O representing average income 94.6±0.8 %. The purity of the produced CaSO 4 .2H 2 O was 98%. (author)

  15. Kinetic and equilibrium properties of regulatory Ca(2+)-binding domains in sodium-calcium exchangers 2 and 3.

    Science.gov (United States)

    Tal, Inbal; Kozlovsky, Tom; Brisker, Dafna; Giladi, Moshe; Khananshvili, Daniel

    2016-04-01

    In mammals, three sodium-calcium exchanger (NCX) protein isoforms (NCX1, NCX2, and NCX3) mediate Ca(2+) fluxes across the membrane to maintain cellular Ca(2+) homeostasis. NCX isoforms and their splice variants are expressed in a tissue-specific manner to meet physiological demands. NCX1 is ubiquitously expressed, NCX2 is expressed in the brain and spinal cord, and NCX3 is expressed in the brain and skeletal muscle. Eukaryotic NCXs contain two cytosolic regulatory Ca(2+)-binding domains, CBD1 and CBD2, which form a two-domain tandem (CBD12) through a short linker. Ca(2+) binding to the CBDs underlies allosteric regulation of NCX. Previous structural and functional studies in NCX1 have shown that the CBDs synergistically interact, where their interactions are modulated in a splice variant-specific manner by splicing segment at CBD2. Here, we analyze the equilibrium and kinetic properties of Ca(2+) binding to purified preparations of CBD1, CBD2, and CBD12 from NCX2 and from NCX3 splice variants. We show that CBD1 interacts with CBD2 in the context of the CBD12 tandem in all NCX isoforms, where these interactions specifically modulate Ca(2+) sensing at the primary sensor of CBD1 to meet the physiological requirements. For example, the rate-limiting slow dissociation of "occluded" Ca(2+) from the primary allosteric sensor of variants expressed in skeletal muscle is ∼10-fold slower than that of variants expressed in the brain. Notably, these kinetic differences between NCX variants occur while maintaining a similar Ca(2+) affinity of the primary sensor, since the resting [Ca(2+)]i levels are similar among different cell types. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Thermoluminescence properties of CaO powder obtained from chicken eggshells

    Science.gov (United States)

    Nagabhushana, K. R.; Lokesha, H. S.; Satyanarayana Reddy, S.; Prakash, D.; Veerabhadraswamy, M.; Bhagyalakshmi, H.; Jayaramaiah, J. R.

    2017-09-01

    Eggshell wastage has created serious problem in disposal of the food processing industry which has been triggered the thoughts of researchers to use wasted eggshells as good source of calcium. In the present work, calcium oxide (CaO) has been synthesized by combustion process in furnace (F-CaO) and microwave oven (M-CaO) using the source of chicken eggshells. The obtained F-CaO and M-CaO are characterized by XRD, SEM with EDX and thermoluminescence (TL) technique. XRD pattern of both the samples show cubic phase with crystallite size 45-52 nm. TL glow curves are recorded for various gamma radiation dose (300-4000 Gy). Two TL glows, a small peak at 424 K and stronger peak at 597 K are observed. TL response of M-CaO is 2.67 times higher than F-CaO sample. TL kinetic parameters are calculated by computerized curve deconvolution analysis (CCDA) and discussed.

  17. Intracellular Ca2+ Regulation in Calcium Sensitive Phenotype of Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    HERMANSYAH

    2010-03-01

    Full Text Available Intracellular cytosolic Ca2+ concentration accumulation plays an essential information in Saccharomyces cerevisiae i.e. to explain cellular mechanism of Ca2+ sensitive phenotype. Disruption both S. cerevisiae PPase PTP2 and MSG5 genes showed an inhibited growth in the presence of Ca2+. On the other hand, by using Luminocounter with apoaequorin system, a method based upon luminescent photoprotein aequorin, intracellular Ca2+ concentration was accumulated as a consequence of calcium sensitive phenotype of S. cerevisiae. This fact indicated that PPase ptp2Δ and msg5Δ were involved in intracellular Ca2+ transport in addition their already known pathways i.e Mitogen Activated Protein Kinase cell wall integrity pathway, high osmolarity glycerol (HOG pathway, and pheromone response FUS3 pathway.

  18. Calcium binding properties of calcium dependent protein kinase 1 (CaCDPK1) from Cicer arietinum.

    Science.gov (United States)

    Dixit, Ajay Kumar; Jayabaskaran, Chelliah

    2015-05-01

    Calcium plays a crucial role as a secondary messenger in all aspects of plant growth, development and survival. Calcium dependent protein kinases (CDPKs) are the major calcium decoders, which couple the changes in calcium level to an appropriate physiological response. The mechanism by which calcium regulates CDPK protein is not well understood. In this study, we investigated the interactions of Ca(2+) ions with the CDPK1 isoform of Cicer arietinum (CaCDPK1) using a combination of biophysical tools. CaCDPK1 has four different EF hands as predicted by protein sequence analysis. The fluorescence emission spectrum of CaCDPK1 showed quenching with a 5 nm red shift upon addition of calcium, indicating conformational changes in the tertiary structure. The plot of changes in intensity against calcium concentrations showed a biphasic curve with binding constants of 1.29 μM and 120 μM indicating two kinds of binding sites. Isothermal calorimetric (ITC) titration with CaCl2 also showed a biphasic curve with two binding constants of 0.027 μM and 1.7 μM. Circular dichroism (CD) spectra showed two prominent peaks at 208 and 222 nm indicating that CaCDPK1 is a α-helical rich protein. Calcium binding further increased the α-helical content of CaCDPK1 from 75 to 81%. Addition of calcium to CaCDPK1 also increased fluorescence of 8-anilinonaphthalene-1-sulfonic acid (ANS) indicating exposure of hydrophobic surfaces. Thus, on the whole this study provides evidence for calcium induced conformational changes, exposure of hydrophobic surfaces and heterogeneity of EF hands in CaCDPK1. Copyright © 2015 Elsevier GmbH. All rights reserved.

  19. Piezoelectrically-induced stress-luminescence phenomenon in CaAl2O4:Eu2+

    International Nuclear Information System (INIS)

    Wei, Yongbin; Wu, Zheng; Jia, Yanmin; Liu, Yongsheng

    2015-01-01

    Piezoelectrically-induced stress-luminescence in the CaAl 2 O 4 :Eu 2+ was investigated. Blue light that was visible to the naked eye could be observed in the dark when a pulse force of ∼7.7 kN was applied to the sample. The intensity of the stress-luminescence strongly depended on the magnitude of the applied force during a pulse cycle. The intensity decreased with repetitive application of pulse stress and was completely recovered after irradiation with ultraviolet light. It is suggested that the stress-luminescence effect in CaAl 2 O 4 :Eu 2+ arises from the piezoelectrically-induced de-trapping of the charge carriers. A CaAl 2 O 4 :Eu 2+ ceramic that exhibits a stress-luminescence effect has potential applications in smart stress optically-sensing devices. - Highlights: • The strong induced stress-luminescence in CaAl 2 O 4 :Eu 2+ was observed. • The stress-luminescent intensity strongly depends on the magnitude of force. • The stress-luminescence could be completely recovered after the UV irradiation. • The strong stress-luminescent effect is potential in stress-light sensors

  20. The putative imidazoline receptor agonist, harmane, promotes intracellular calcium mobilisation in pancreatic beta-cells.

    Science.gov (United States)

    Squires, Paul E; Hills, Claire E; Rogers, Gareth J; Garland, Patrick; Farley, Sophia R; Morgan, Noel G

    2004-10-06

    beta-Carbolines (including harmane and pinoline) stimulate insulin secretion by a mechanism that may involve interaction with imidazoline I(3)-receptors but which also appears to be mediated by actions that are additional to imidazoline receptor agonism. Using the MIN6 beta-cell line, we now show that both the imidazoline I(3)-receptor agonist, efaroxan, and the beta-carboline, harmane, directly elevate cytosolic Ca(2+) and increase insulin secretion but that these responses display different characteristics. In the case of efaroxan, the increase in cytosolic Ca(2+) was readily reversible, whereas, with harmane, the effect persisted beyond removal of the agonist and resulted in the development of a repetitive train of Ca(2+)-oscillations whose frequency, but not amplitude, was concentration-dependent. Initiation of the Ca(2+)-oscillations by harmane was independent of extracellular calcium but was sensitive to both dantrolene and high levels (20 mM) of caffeine, suggesting the involvement of ryanodine receptor-gated Ca(2+)-release. The expression of ryanodine receptor-1 and ryanodine receptor-2 mRNA in MIN6 cells was confirmed using reverse transcription-polymerase chain reaction (RT-PCR) and, since low concentrations of caffeine (1 mM) or thimerosal (10 microM) stimulated increases in [Ca(2+)](i), we conclude that ryanodine receptors are functional in these cells. Furthermore, the increase in insulin secretion induced by harmane was attenuated by dantrolene, consistent with the involvement of ryanodine receptors in mediating this response. By contrast, the smaller insulin secretory response to efaroxan was unaffected by dantrolene. Harmane-evoked changes in cytosolic Ca(2+) were maintained by nifedipine-sensitive Ca(2+)-influx, suggesting the involvement of L-type voltage-gated Ca(2+)-channels. Taken together, these data imply that harmane may interact with ryanodine receptors to generate sustained Ca(2+)-oscillations in pancreatic beta-cells and that this effect

  1. Characterization of Calcium Compounds in Opuntia ficus indica as a Source of Calcium for Human Diet

    Directory of Open Access Journals (Sweden)

    Isela Rojas-Molina

    2015-01-01

    Full Text Available Analyses of calcium compounds in cladodes, soluble dietary fiber (SDF, and insoluble dietary fiber (IDF of Opuntia ficus indica are reported. The characterization of calcium compounds was performed by using Scanning Electron Microscopy, Energy Dispersive Spectrometry, X-ray diffraction, and infrared spectroscopy. Atomic Absorption Spectroscopy and titrimetric methods were used for quantification of total calcium and calcium compounds. Whewellite (CaC2O4·H2O, weddellite (CaC2O4·(H2O2.375, and calcite (CaCO3 were identified in all samples. Significant differences (P≤0.05 in the total calcium contents were detected between samples. CaC2O4·H2O content in cladodes and IDF was significantly higher (P≤0.05 in comparison to that observed in SDF, whereas minimum concentration of CaCO3 was detected in IDF with regard to CaCO3 contents observed in cladodes and SDF. Additionally, molar ratio oxalate : Ca2+ in all samples changed in a range from 0.03 to 0.23. These results support that calcium bioavailability in O. ficus indica modifies according to calcium compounds distribution.

  2. Investigations on FCAM-III (Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36): A new homologue of the aenigmatite structure-type in the system CaO-MgO-Fe2O3-Al2O3

    Science.gov (United States)

    Zöll, Klaus; Kahlenberg, Volker; Krüger, Hannes; Tropper, Peter

    2018-02-01

    In the course of a systematic study of a part of the quaternary system Fe2O3-CaO-Al2O3-MgO (FCAM) the previously unknown compound Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36 (FCAM-III) has been synthesized. By analogy with the so-called SFCA series [1-5], our investigation in the system of FCAM shows the existence of a stoichiometric homologous series M14+6nO20+8n, where M = Fe, Ca, Al, Mg and n = 1 or 2. In air, we can prove the formation of coexisting FCAM-III and FCAM-I solid solutions at 1400 °C. By increasing the temperature up to 1425 °C FCAM-I disappears completely and FCAM-III co-exists with magnesiumferrite and a variety of calcium iron oxides. At 1450 °C FCAM-III breaks down to a mixture of FCAM-I again as well as magnesioferrite and melt. Small single-crystals of FCAM-III up to 35 μm in size could be retrieved from the 1425 °C experiment and were subsequently characterized using electron microprobe analysis and synchroton X-ray single-crystal diffraction. Finally the Fe2+/Fetot ratio was calculated from the total iron content based on the crystal-chemical formula obtained from EMPA measurements and charge balance considerations. FCAM-III or Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36 has a triclinic crystal structure (space group P 1 ̅). The basic crystallographic data are: a = 10.223(22) Å, b = 10.316(21) Å, c = 14.203(15) Å, α = 93.473(50)°, β = 107.418(67)°, γ = 109.646(60)°, V = 1323.85(2) ų, Z = 1. Using Schreinemaker's technique to analyze the phase relations in the system Fe2O3-CaO-Al2O3-MgO it was possible to obtain the semi-quantitative stability relations between the participating phases and construct a topologically correct phase sequence as a function of T and fO2. The analysis shows that Ca2Al0.5Fe1.5O5 (C2A0.25F0.75) and CaAl1.5Fe2.5O7 (CA0.75F1.25) with higher calculated Fe2+ contents are preferably formed at lower oxygen fugacity and react to CaAl0.5Fe1.5O4 (CA0.25F0.75) by increasing fO2. Spinel-type magnesium

  3. Investigation of structural and optical properties of CaTiO3 powders doped with Mg2+ and Eu3+ ions

    International Nuclear Information System (INIS)

    Oliveira, Larissa H.; Savioli, Julia; Moura, Ana P. de; Nogueira, Içamira C.; Li, Maximo S.; Longo, Elson; Varela, José A.; Rosa, Ieda L.V.

    2015-01-01

    In this work, CaTiO 3 powders doped with Mg 2+ ions and CaTiO 3 powders co-doped with Mg 2+ and Eu 3+ ions were prepared by the polymeric precursor method (PPM). These powders were characterized by different characterization techniques to study the influence of Mg 2+ doping as well as Mg 2+ and Eu 3+ co-doping in structural and optical properties of CaTiO 3 perovskite-type structure. The Rietveld refinement and Micro-Raman analyses suggested the substitution Mg 2+ and Eu 3+ ions in the A-site of CaTiO 3 perovskite. The influence of Mg 2+ doping can be detected by the displacement of calcium and oxygen atomic positions when compared to the non-doped CaTiO 3 powder. When Eu 3+ ions are added to the A-site of this perovskite the excess of positive charge can be compensated by the formation of calcium vacancies. Luminescence data showed that Ca 1-x Mg x TiO 3 and Ca 1x Mg x/2 Eu 2y/3 TiO 3 powders are potential materials for fabrication of lighting devices based on near-UV and blue LED using an excitation wavelength of 397 and/or 450 nm. - Highlights: • CaTiO 3 co-doped with Mg 2+ and Eu 3+ were obtained by the Polymeric Precursor Method. • Incorporation of Mg 2+ and Eu 3+ ions in the CaTiO 3 lattice. • Enhancement of the Eu 3+ photoluminescence

  4. THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgOCaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2CaF2

    Directory of Open Access Journals (Sweden)

    В. Судавцова

    2012-04-01

    Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgOCaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

  5. Application of nanostructured Ca doped CeO2 for ultraviolet filtration

    International Nuclear Information System (INIS)

    Truffault, Laurianne; Ta, Minh-Tri; Devers, Thierry; Konstantinov, Konstantin; Harel, Valerie; Simmonard, Cyriaque; Andreazza, Caroline; Nevirkovets, Ivan P.; Pineau, Alain; Veron, Olivier; Blondeau, Jean-Philippe

    2010-01-01

    Calcium doped CeO 2 nanoparticles with doping concentrations between 0 and 50 mol% were synthesized by a co-precipitation method for ultraviolet filtration application. Below 20 mol% doping concentration, the samples were single-phase. From 30 mol%, CaCO 3 appears as a secondary phase. The calculated CeO 2 mean crystallite size was 9.3 nm for the pure and 5.7 nm for the 50 mol% Ca-doped sample. Between 250 and 330 nm, the absorbance increased for the 10, 30, and 40 mol% Ca-doped samples compared to the pure one. The band-gap was found to be 3.20 eV for the undoped, and between 3.36 and 3.51 eV for the doped samples. The blue shifts are attributed to the quantum confinement effect. X-ray photoelectron spectroscopy showed that the Ce 3+ atomic concentration in the pure sample was higher than that of the 20 mol% Ca-doped sample.

  6. Crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses; Li2O-SiO2, Na2O-SiO2, Na2O-CaO-SiO2 kei glass no kessho sekishutsu kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, K.; Otake, J.; Nagasaka, T.; Hino, M. [Tohoku University, Sendai (Japan)

    1998-06-01

    It has been known that crystallization of mold powder is effective on the disturbance of heat transfer between mold and solidified shell in production of middle carbon steel slabs in continuous casting process. But it has not yet been made clear which composition of mold powder is the most suitable for crystallization. The crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses was observed by differential thermal analysis (DTA) and hot-thermocouple methods with DTA in the present work. As a result, addition of alkaline metal and alkaline earth metal oxides to SiO2 increased the critical cooling rate for glass formation in binary system of Li2O-SiO2 and Na2O-SiO2 and Li2O-SiO2 system crystallized easier than Na2O-SiO2 system. In ternary system of Na2O-CaO-SiO2, addition of Na2O hurried the critical cooling rate at CaO/SiO2=0.93 mass ratio, but the rate was almost constant in the composition range of more than 15 mass% Na2O. The slag of CaO/SiO2=0.93 made the rate faster than the slag of CaO/SiO2=0.47 at constant content of 10mass% Na2O. 17 refs., 10 figs., 3 tabs.

  7. Calcium modulates calmodulin/α-actinin 1 interaction with and agonist-dependent internalization of the adenosine A2A receptor.

    Science.gov (United States)

    Piirainen, Henni; Taura, Jaume; Kursula, Petri; Ciruela, Francisco; Jaakola, Veli-Pekka

    2017-04-01

    Adenosine receptors are G protein-coupled receptors that sense extracellular adenosine to transmit intracellular signals. One of the four adenosine receptor subtypes, the adenosine A 2A receptor (A 2A R), has an exceptionally long intracellular C terminus (A 2A R-ct) that mediates interactions with a large array of proteins, including calmodulin and α-actinin. Here, we aimed to ascertain the α-actinin 1/calmodulin interplay whilst binding to A 2A R and the role of Ca 2+ in this process. First, we studied the A 2A R-α-actinin 1 interaction by means of native polyacrylamide gel electrophoresis, isothermal titration calorimetry, and surface plasmon resonance, using purified recombinant proteins. α-Actinin 1 binds the A 2A R-ct through its distal calmodulin-like domain in a Ca 2+ -independent manner with a dissociation constant of 5-12μM, thus showing an ~100 times lower affinity compared to the A 2A R-calmodulin/Ca 2+ complex. Importantly, calmodulin displaced α-actinin 1 from the A 2A R-ct in a Ca 2+ -dependent fashion, disrupting the A 2A R-α-actinin 1 complex. Finally, we assessed the impact of Ca 2+ on A 2A R internalization in living cells, a function operated by the A 2A R-α-actinin 1 complex. Interestingly, while Ca 2+ influx did not affect constitutive A 2A R endocytosis, it abolished agonist-dependent internalization. In addition, we demonstrated that the A 2A R/α-actinin interaction plays a pivotal role in receptor internalization and function. Overall, our results suggest that the interplay of A 2A R with calmodulin and α-actinin 1 is fine-tuned by Ca 2+ , a fact that might power agonist-mediated receptor internalization and function. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Dynamics of receptor-operated Ca2+ Currents Through TRPC Channels Controlled via the PI(4,5P2-PLC Signaling Pathway

    Directory of Open Access Journals (Sweden)

    Masayuki X Mori

    2015-02-01

    Full Text Available Transient receptor potential canonical (TRPC channels are Ca2+-permeable, nonselective cation channels that carry receptor-operated Ca2+ currents (ROCs triggered by receptor-induced, phospholipase C (PLC-catalyzed hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5P2. Within the vasculature, TRPC channel ROCs contribute to smooth muscle cell depolarization, vasoconstriction and vascular remodeling. However, TRPC channel ROCs exhibit a variable response to receptor-stimulation, and the regulatory mechanisms governing TRPC channel activity remain obscure. The variability of ROCs may be explained by their complex regulation by PI(4,5P2 and its metabolites, which differentially affect TRPC channel activity. To resolve the complex regulation of ROCs, the use of voltage-sensing phosphoinositide phosphatases and model simulation have helped to reveal the time-dependent contribution of PI(4,5P2 and the possible role of PI(4,5P2 in the regulation of ROCs. These approaches may provide unprecedented insight into the dynamics of PI(4,5P2 regulation of TRPC channels and the fundamental mechanisms underlying transmembrane ion flow. Within that context, we summarize the regulation of TRPC channels and their coupling to receptor-mediated signaling, as well as the application of voltage-sensing phosphoinositide phosphatases to this research. We also discuss the controversial bidirectional effects of PI(4,5P2 using a model simulation that could explain the complicated effects of PI(4,5P2 on different ROCs.

  9. Dynamics of receptor-operated Ca(2+) currents through TRPC channels controlled via the PI(4,5)P2-PLC signaling pathway.

    Science.gov (United States)

    Mori, Masayuki X; Itsuki, Kyohei; Hase, Hideharu; Sawamura, Seishiro; Kurokawa, Tatsuki; Mori, Yasuo; Inoue, Ryuji

    2015-01-01

    Transient receptor potential canonical (TRPC) channels are Ca(2+)-permeable, nonselective cation channels that carry receptor-operated Ca(2+) currents (ROCs) triggered by receptor-induced, phospholipase C (PLC)-catalyzed hydrolysis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Within the vasculature, TRPC channel ROCs contribute to smooth muscle cell depolarization, vasoconstriction, and vascular remodeling. However, TRPC channel ROCs exhibit a variable response to receptor-stimulation, and the regulatory mechanisms governing TRPC channel activity remain obscure. The variability of ROCs may be explained by their complex regulation by PI(4,5)P2 and its metabolites, which differentially affect TRPC channel activity. To resolve the complex regulation of ROCs, the use of voltage-sensing phosphoinositide phosphatases and model simulation have helped to reveal the time-dependent contribution of PI(4,5)P2 and the possible role of PI(4,5)P2 in the regulation of ROCs. These approaches may provide unprecedented insight into the dynamics of PI(4,5)P2 regulation of TRPC channels and the fundamental mechanisms underlying transmembrane ion flow. Within that context, we summarize the regulation of TRPC channels and their coupling to receptor-mediated signaling, as well as the application of voltage-sensing phosphoinositide phosphatases to this research. We also discuss the controversial bidirectional effects of PI(4,5)P2 using a model simulation that could explain the complicated effects of PI(4,5)P2 on different ROCs.

  10. Obtention of agricultural gypsum traced on {sup 34} S (Ca{sup 34} SO{sub 4}.2H{sub 2}O), by chemical reaction between H{sub 2}{sup 34} SO{sub 4} and Ca(OH){sub 2}; Obtencao do gesso agricola marcado no {sup 34} S (Ca{sup 34} SO{sub 4}.2H{sub 2}O), por reacao quimica entre o H{sub 2}{sup 34} SO{sub 4} e Ca(OH){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Rossete, Alessandra L.R.M.; Bendassolli, Jose A.; Ignoto, Raquel de Fatima; Batagello, Hugo Henrique [Centro de Energia Nuclear na Agricultura (CENA), Piracicaba, SP (Brazil). Lab. de Isotopos Estaveis

    2002-07-01

    The gypsum (CaSO{sub 4}.2H{sub 2}O) has double function in the soil: as source of calcium and sulfur and reducing agent of aluminum saturation. The sulfur for the plants has acting in the vital functions and it is proven fact increase of the S deficiency in Brazilian soils. The isotope tracer {sup 34} S can elucidate important aspects in the sulfur cycle. The Ca{sup 34} SO{sub 4}.2H{sub 2}O was obtained by chemical reaction between Ca(OH){sub 2} and H{sub 2}{sup 34} SO{sub 4} solution. The acid was obtained by chromatography ionic change, using cationic resin Dowex 50WX8 and Na{sub 2}{sup 34} SO{sub 4} solution. The reaction was realized under slow agitation. After the reaction, the precipitate was separated and dried in ventilated stove at 60 deg C temperature. The Mass of the Ca{sup 34} SO{sub 4}.2H{sub 2}O produced was determined by method gravimetric. This way, a system contends resin 426 cm{sup 3}, considering volume of 2.2 liters can be obtained a solution contends 44.2 g of H{sub 2}{sup 34} SO{sub 4}, theoretically could be produced 78.0 g of Ca{sup 34} SO{sub 4}.2H{sub 2}O approximately. With results of the tests were verified that there was not total precipitation of the Ca{sup 34}SO{sub 4}.2H{sub 2}O. Were produced 73.7{+-} 0.6 g of Ca{sup 34} SO{sub 4}.2H{sub 2}O representing average income 94.6{+-}0.8 %. The purity of the produced CaSO{sub 4}.2H{sub 2}O was 98%. (author)

  11. Calcium Domains around Single and Clustered IP3 Receptors and Their Modulation by Buffers

    Science.gov (United States)

    Rüdiger, S.; Nagaiah, Ch.; Warnecke, G.; Shuai, J.W.

    2010-01-01

    Abstract We study Ca2+ release through single and clustered IP3 receptor channels on the ER membrane under presence of buffer proteins. Our computational scheme couples reaction-diffusion equations and a Markovian channel model and allows our investigating the effects of buffer proteins on local calcium concentrations and channel gating. We find transient and stationary elevations of calcium concentrations around active channels and show how they determine release amplitude. Transient calcium domains occur after closing of isolated channels and constitute an important part of the channel's feedback. They cause repeated openings (bursts) and mediate increased release due to Ca2+ buffering by immobile proteins. Stationary domains occur during prolonged activity of clustered channels, where the spatial proximity of IP3Rs produces a distinct [Ca2+] scale (0.5–10 μM), which is smaller than channel pore concentrations (>100 μM) but larger than transient levels. While immobile buffer affects transient levels only, mobile buffers in general reduce both transient and stationary domains, giving rise to Ca2+ evacuation and biphasic modulation of release amplitude. Our findings explain recent experiments in oocytes and provide a general framework for the understanding of calcium signals. PMID:20655827

  12. The association of metabotropic glutamate receptor type 5 with the neuronal Ca2+-binding protein 2 modulates receptor function.

    Science.gov (United States)

    Canela, Laia; Fernández-Dueñas, Víctor; Albergaria, Catarina; Watanabe, Masahiko; Lluís, Carme; Mallol, Josefa; Canela, Enric I; Franco, Rafael; Luján, Rafael; Ciruela, Francisco

    2009-10-01

    Metabotropic glutamate (mGlu) receptors mediate in part the CNS effects of glutamate. These receptors interact with a large array of intracellular proteins in which the final role is to regulate receptor function. Here, using co-immunoprecipitation and pull-down experiments we showed a close and specific interaction between mGlu(5) receptor and NECAB2 in both transfected human embryonic kidney cells and rat hippocampus. Interestingly, in pull-down experiments increasing concentrations of calcium drastically reduced the ability of these two proteins to interact, suggesting that NECAB2 binds to mGlu(5) receptor in a calcium-regulated manner. Immunoelectron microscopy detection of NECAB2 and mGlu(5) receptor in the rat hippocampal formation indicated that both proteins are codistributed in the same subcellular compartment of pyramidal cells. In addition, the NECAB2/mGlu(5) receptor interaction regulated mGlu(5b)-mediated activation of both inositol phosphate accumulation and the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway. Overall, these findings indicate that NECAB2 by its physical interaction with mGlu(5b) receptor modulates receptor function.

  13. Acute Cocaine Induces Fast Activation of D1 Receptor and Progressive Deactivation of D2 Receptor Strial Neurons: In Vivo Optical Microprobe [Ca2+]i Imaging

    International Nuclear Information System (INIS)

    Du, C.; Luo, Z.; Volkow, N.D.; Heintz, N.; Pan, Y.; Du, C.

    2011-01-01

    Cocaine induces fast dopamine increases in brain striatal regions, which are recognized to underlie its rewarding effects. Both dopamine D1 and D2 receptors are involved in cocaine's reward but the dynamic downstream consequences of cocaine effects in striatum are not fully understood. Here we used transgenic mice expressing EGFP under the control of either the D1 receptor (D1R) or the D2 receptor (D2R) gene and microprobe optical imaging to assess the dynamic changes in intracellular calcium ([Ca 2+ ] i ) responses (used as marker of neuronal activation) to acute cocaine in vivo separately for D1R- versus D2R-expressing neurons in striatum. Acute cocaine (8 mg/kg, i.p.) rapidly increased [Ca 2+ ] i in D1R-expressing neurons (10.6 ± 3.2%) in striatum within 8.3 ± 2.3 min after cocaine administration after which the increases plateaued; these fast [Ca 2+ ] i increases were blocked by pretreatment with a D1R antagonist (SCH23390). In contrast, cocaine induced progressive decreases in [Ca 2+ ] i in D2R-expressing neurons (10.4 ± 5.8%) continuously throughout the 30 min that followed cocaine administration; these slower [Ca 2+ ] i decreases were blocked by pretreatment with a D2R antagonist (raclopride). Since activation of striatal D1R-expressing neurons (direct-pathway) enhances cocaine reward, whereas activation of D2R expressing neurons suppresses it (indirect-pathway) (Lobo et al., 2010), this suggests that cocaine's rewarding effects entail both its fast stimulation ofD1R (resulting in abrupt activation of direct-pathway neurons) and a slower stimulation of D2R (resulting in longer-lasting deactivation of indirect-pathway neurons). We also provide direct in vivo evidence of D2R and D1R interactions in the striatal responses to acute cocaine administration.

  14. Phase diagram study for the PbO-ZnO-CaO-SiO_2 -“Fe_2O_3 ” system in air with CaO/SiO_2 in 1.1 and PbO/(CaO+SiO_2) in 2.4 weight ratios

    International Nuclear Information System (INIS)

    Lopez-Rodriguez, Josue; Romero-Serrano, Antonio; Hernandez-Ramirez, Aurelio; Cruz-Ramirez, Alejandro; Almaguer-Guzman, Isaias; Benavides-Perez, Ricardo; Flores-Favela, Manuel

    2017-01-01

    An experimental study on the phase equilibrium and the liquidus isotherms for the PbO-ZnO-CaO-SiO_2 -“Fe_2O_3 ” system with CaO/SiO_2 in 1.1 and PbO/(CaO+SiO_2) in 2.4 weight ratios, respectively, was carried out in the temperature range 1100-1300 deg C (1373-1573 K). High temperature phases were determined by the equilibrium-quenching method. Results are presented in the form of pseudo-ternary sections “Fe_2O_3 ”-ZnO-(PbO+CaO+SiO_2). X-Ray diffraction (XRD) and SEM-EDS results showed that the phase equilibria in this system are dominated by the high melting temperature spinel and zincite phases. It was observed that if the system is at a temperature below 1300 deg C and the total (Fe_2O_3 + ZnO) is greater than 20 wt%, spinel and/or zincite will be present in the slag system. As an application of the phase diagram, the liquid phase compositions below the liquidus surface were estimated, then their viscosities were calculated using FACTSage software. (author)

  15. Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF2-CaO-SiO2-based slags

    Science.gov (United States)

    Duan, Sheng-chao; Li, Chuang; Guo, Han-jie; Guo, Jing; Han, Shao-wei; Yang, Wen-sheng

    2018-04-01

    The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO-SiO2-MgO-FeO-MnO-Al2O3-TiO2-CaF2 was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step (RCS) for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide (MnO), the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol-1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the "specific reaction interface" (SRI) value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

  16. The emerging role of promiscuous 7TM receptors as chemosensors for food intake

    DEFF Research Database (Denmark)

    Wellendorph, Petrine; Johansen, Lars Dan; Bräuner-Osborne, Hans

    2010-01-01

    review, we describe the molecular mechanisms of nutrient-sensing of the calcium-sensing receptor (CaR), the G protein-coupled receptor family C, group 6, subtype A (GPRC6A), and the taste1 receptor T1R1/T1R3-sensing L-a-amino acids; the carbohydrate-sensing T1R2/T1R3 receptor; the proteolytic degradation......In recent years, several highly promiscuous seven transmembrane (7TM) receptors have been cloned and characterized of which many are activated broadly by amino acids, proteolytic degradation products, carbohydrates, or free fatty acids (FFAs) and are expressed in taste tissue, the gastrointestinal...

  17. CaMKII Regulation of Cardiac Ryanodine Receptors and Inositol Triphosphate Receptors

    Directory of Open Access Journals (Sweden)

    Emmanuel eCamors

    2014-05-01

    Full Text Available Ryanodine receptors (RyRs and inositol triphosphate receptors (InsP3Rs are structurally related intracellular calcium release channels that participate in multiple primary or secondary amplified Ca2+ signals, triggering muscle contraction and oscillatory Ca2+ waves, or activating transcription factors. In the heart, RyRs play an indisputable role in the process of excitation-contraction coupling as the main pathway for Ca2+ release from sarcoplasmic reticulum (SR, and a less prominent role in the process of excitation-transcription coupling. Conversely, InsP3Rs are believed to contribute in subtle ways, only, to contraction of the heart, and in more important ways to regulation of transcription factors. Because uncontrolled activity of either RyRs or InsP3Rs may elicit life-threatening arrhythmogenic and/or remodeling Ca2+ signals, regulation of their activity is of paramount importance for normal cardiac function. Due to their structural similarity, many regulatory factors, accessory proteins, and posttranslational processes are equivalent for RyRs and InsP3Rs. Here we discuss regulation of RyRs and InsP3Rs by CaMKII phosphorylation, but touch on other kinases whenever appropriate. CaMKII is emerging as a powerful modulator of RyR and InsP3R activity but interestingly, some of the complexities and controversies surrounding phosphorylation of RyRs also apply to InsP3Rs, and a clear-cut effect of CaMKII on either channel eludes investigators for now. Nevertheless, some effects of CaMKII on global cellular activity, such as SR Ca2+ leak or force-frequency potentiation, appear clear now, and this constrains the limits of the controversies and permits a more tractable approach to elucidate the effects of phosphorylation at the single channel level.

  18. Store-operated calcium entry is required for sustained contraction and Ca2+ oscillations of airway smooth muscle.

    Science.gov (United States)

    Chen, Jun; Sanderson, Michael J

    2017-05-15

    Airway hyper-responsiveness in asthma is driven by excessive contraction of airway smooth muscle cells (ASMCs). Agonist-induced Ca 2+ oscillations underlie this contraction of ASMCs and the magnitude of this contraction is proportional to the Ca 2+ oscillation frequency. Sustained contraction and Ca 2+ oscillations require an influx of extracellular Ca 2+ , although the mechanisms and pathways mediating this Ca 2+ influx during agonist-induced ASMC contraction are not well defined. By inhibiting store-operated calcium entry (SOCE) or voltage-gated Ca 2+ channels (VGCCs), we show that SOCE, rather than Ca 2+ influx via VGCCs, provides the major Ca 2+ entry pathway into ASMCs to sustain ASMCs contraction and Ca 2+ oscillations. SOCE may therefore serve as a potential target for new bronchodilators to reduce airway hyper-responsiveness in asthma. Asthma is characterized by airway hyper-responsiveness: the excessive contraction of airway smooth muscle. The extent of this airway contraction is proportional to the frequency of Ca 2+ oscillations within airway smooth muscle cells (ASMCs). Sustained Ca 2+ oscillations require a Ca 2+ influx to replenish Ca 2+ losses across the plasma membrane. Our previous studies implied store-operated calcium entry (SOCE) as the major pathway for this Ca 2+ influx. In the present study, we explore this hypothesis, by examining the effects of SOCE inhibitors (GSK7975A and GSK5498A) as well as L-type voltage-gated Ca 2+ channel inhibitors (nifedipine and nimodipine) on airway contraction and Ca 2+ oscillations and SOCE-mediated Ca 2+ influx in ASMCs within mouse precision-cut lung slices. We found that both GSK7975A and GSK5498A were able to fully relax methacholine-induced airway contraction by abolishing the Ca 2+ oscillations, in a manner similar to that observed in zero extracellular Ca 2+ ([Ca 2+ ] e ). In addition, GSK7975A and GSK5498A inhibited increases in intracellular Ca 2+ ([Ca 2+ ] i ) in ASMCs with depleted Ca 2+ -stores in

  19. CaMKII in sinoatrial node physiology and dysfunction

    Directory of Open Access Journals (Sweden)

    Yuejin eWu

    2014-03-01

    Full Text Available The calcium and calmodulin dependent protein kinase II (CaMKII is present in sinoatrial node (SAN pacemaker cells and is required for physiological fight or flight SAN beating rate responses. Inhibition of CaMKII in SAN does not affect baseline heart rate, but reduces heart rate increases in response to physiological stress. CaMKII senses intracellular calcium (Ca2+ changes, oxidation status and hyperglycemia to phosphorylate substrates that regulate Ca2+-sensitive proteins, such as L-type Ca2+ channels, phospholamban (PLN, and cardiac ryanodine receptors (RyR2. All of these substrates are involved in the SAN pacemaking mechanism. Excessive CaMKII activity, as occurs under pathological conditions such as heart failure, ischemia and diabetes, can promote intracellular Ca2+ overload and reactive oxygen species (ROS production. Oxidation of CaMKII (ox-CaMKII locks CaMKII into a constitutively active configuration that contributes to SAN cell apoptosis and fibrosis. This ox-CaMKII-mediated loss of functional SAN cells contributes to sinoatrial node dysfunction (SND and sudden death. Thus, CaMKII has emerged as a central regulator of physiological SAN responses and a key determinant of SND.

  20. Proton Environments in Biomimetic Calcium Phosphates Formed from Mesoporous Bioactive CaO-SiO2-P2O5 Glasses in Vitro: Insights from Solid-State NMR.

    Science.gov (United States)

    Mathew, Renny; Turdean-Ionescu, Claudia; Yu, Yang; Stevensson, Baltzar; Izquierdo-Barba, Isabel; García, Ana; Arcos, Daniel; Vallet-Regí, María; Edén, Mattias

    2017-06-22

    When exposed to body fluids, mesoporous bioactive glasses (MBGs) of the CaO-SiO 2 -P 2 O 5 system develop a bone-bonding surface layer that initially consists of amorphous calcium phosphate (ACP), which transforms into hydroxy-carbonate apatite (HCA) with a very similar composition as bone/dentin mineral. Information from various 1 H-based solid-state nuclear magnetic resonance (NMR) experiments was combined to elucidate the evolution of the proton speciations both at the MBG surface and within each ACP/HCA constituent of the biomimetic phosphate layer formed when each of three MBGs with distinct Ca, Si, and P contents was immersed in a simulated body fluid (SBF) for variable periods between 15 min and 30 days. Directly excited magic-angle-spinning (MAS) 1 H NMR spectra mainly reflect the MBG component, whose surface is rich in water and silanol (SiOH) moieties. Double-quantum-single-quantum correlation 1 H NMR experimentation at fast MAS revealed their interatomic proximities. The comparatively minor H species of each ACP and HCA component were probed selectively by heteronuclear 1 H- 31 P NMR experimentation. The initially prevailing ACP phase comprises H 2 O and "nonapatitic" HPO 4 2- /PO 4 3- groups, whereas for prolonged MBG soaking over days, a well-progressed ACP → HCA transformation was evidenced by a dominating O 1 H resonance from HCA. We show that 1 H-detected 1 H → 31 P cross-polarization NMR is markedly more sensitive than utilizing powder X-ray diffraction or 31 P NMR for detecting the onset of HCA formation, notably so for P-bearing (M)BGs. In relation to the long-standing controversy as to whether bone mineral comprises ACP and/or forms via an ACP precursor, we discuss a recently accepted structural core-shell picture of both synthetic and biological HCA, highlighting the close relationship between the disordered surface layer and ACP.

  1. Absorption of labelled calcium-45Ca by prawn from sea water

    International Nuclear Information System (INIS)

    Deshimaru, Osamu; Kuroki, Katsunobu; Sakamoto, Syuichi; Yone, Yasuo.

    1978-01-01

    In connection with the previous study of the mineral requirements of prawn, Penaeus japonicus, the absorption of radioactive calcium- 45 Ca from surrounding sea water by the prawn fed on a diet without supplemental calcium was compared with that of the prawn fed on a calcium-supplemented diet. The surrounding sea water was prepared to contain labelled calcium- 45 Ca-CaCl 2 . The prawn were first fed on each test diet in ordinary sea water, and one hour after the final mealtime were transferred to sea water in which 45 Ca-CaCl 2 was dissolved. One, four, and twentythree hours later, the prawn were analyzed for the radioactivity incorporated into their bodies. The radioactivity of 45 Ca accumulated in the prawn gradually increased with the lapse of time, and the group fed on the diet without supplemental calcium exhibited faster absorption and higher activity of 45 Ca than the group fed on the diet with calcium. (author)

  2. Calcium Regulation and Bone Mineral Metabolism in Elderly Patients with Chronic Kidney Disease

    Directory of Open Access Journals (Sweden)

    Vickram Tejwani

    2013-05-01

    Full Text Available The elderly chronic kidney disease (CKD population is growing. Both aging and CKD can disrupt calcium (Ca2+ homeostasis and cause alterations of multiple Ca2+-regulatory mechanisms, including parathyroid hormone, vitamin D, fibroblast growth factor-23/Klotho, calcium-sensing receptor and Ca2+-phosphate product. These alterations can be deleterious to bone mineral metabolism and soft tissue health, leading to metabolic bone disease and vascular calcification and aging, termed CKD-mineral and bone disorder (MBD. CKD-MBD is associated with morbid clinical outcomes, including fracture, cardiovascular events and all-cause mortality. In this paper, we comprehensively review Ca2+ regulation and bone mineral metabolism, with a special emphasis on elderly CKD patients. We also present the current treatment-guidelines and management options for CKD-MBD.

  3. [Interaction between TRPC1 and STIM1 in calcium sensing receptor mediated calcium influx and nitric oxide production in human umbilical vein endothelial cells].

    Science.gov (United States)

    Wang, L M; Zhong, H; Tang, N; Pang, L J; Zhang, C J; He, F

    2017-11-24

    Objective: To investigate the interaction of Ca(2+) protein TRPC1 and STIM1 in extracellular Ca(2+) -sensing receptor (CaR)-induced extracellular Ca(2+) influx and the production of nitric oxide (NO). Methods: Human umbilical vein endothelial cells (HUVECs) were cultured and incubated with CaR agonist spermine (activating store-operates cation channels (SOC) and receptor-operated channels (ROC)), CaR negative allosteric modulator Calhex231 (blocking SOC, activating ROC) and ROC analogue TPA (activating ROC, blocking SOC), protein kinase C (PKC) inhibitor Ro31-8220, PKCs and PKCμ inhibitor Go6967(activate SOC, blocking ROC), respectively. The interaction of TRPC1 and STIM1 was determined using the immunofluorescence methods. The interaction between TRPC1 and STIM1 were examined by Co-immuno precipitation. The HUVECs were divided into: TRPC1 and STIM1 short hairpin RNA group (shTRPC1+ shSTIM1 group), vehicle-TRPC1+ vehicle-STIM1 group and control group. The cells were incubated with four different treatments under the action of above mentioned interventions, intracellular Ca(2+) concentration ([Ca(2+) ](i)) was detected using the fluorescence Ca(2+) indicator Fura-2/AM, the production of NO was determined by DAF-FM. Results: (1) The expression of TRPC1 and STIM1 proteins levels in HUVECs: Under the confocal microscope, TRPC1 and STIM1 protein expression showed masculine gender, both located in cytoplasm in the normal control group. Post incubation with Calhex231+ TPA, Ro31-8220 and Go6967, TRPC1 and STIM1 positioned in cytoplasm was significantly reduced, and the combined TRPC1 and STIM1 was also significantly reduced. (2) The interaction of TRPC1 and STIM1 in HUVECs: The relative ratios of Calhex231+ TPA+ Spermine+ Ca(2+) group, Ro31-8220+ Spermine+ Ca(2+) group and Go6976+ Spermine+ Ca(2+) group STIM1/TRPC1 and TRPC1/STIM1 were as follows: (25.98±2.17)% and (44.10±4.01)%, (20.85±1.01)% and (46.31±3.47)%, (23.88±2.05)% and (39.65±2.91)%, which were

  4. Activity of RE/sub 2/O/sub 3/ in liquid La/sub 2/O/sub 3/-Al/sub 2/O/sub 3/-CaF/sub 2/ and Ce/sub 2/O/sub 3/-CaO-CaF/sub 2/ slags

    International Nuclear Information System (INIS)

    Changzhen, W.; Shuqing, Y.; Qieng, D.

    1985-01-01

    In the course of electro-slag refining, if the slag contains rare earth oxides, the amount of rare earth introduced to the steel depends on the composition of the slag and other conditions. The main aim of this investigation is to study the activity of RE/sub 2/O/sub 3/ in the electro-slags of various compositions. One is the La/sub 2/O/sub 3/-CaO-CaF/sub 2/ ternary slag system and the other is the Ce/sub 2/O/sub 3/-CaO-CaF/sub 2/ slag system. The iso-activity diagram for RE/sub 2/O/sub 3/ and the liquid boundary for slags system were estimated

  5. Oxide meets silicide. Synthesis and single-crystal structure of Ca{sub 21}SrSi{sub 24}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Reckeweg, Olaf; DiSalvo, Francis J. [Cornell Univ., Ithaca, NY (United States). Dept. of Chemistry and Chemical Biology

    2017-06-01

    A few black, rectangular thin plates of Ca{sub 21}SrSi{sub 24}O{sub 2} were obtained by serendipity in a solid-state reaction of calcium metal, strontium chloride and silicon powder at 1200 K for 2 days designed to produce 'Ca{sub 2}SrCl{sub 2}[Si{sub 3}]'. The title compound forms next to some CaSi and some remaining educts. Ca{sub 21}SrSi{sub 24}O{sub 2} crystallizes in the monoclinic space group C2/m (no. 12) with unit cell parameters of a=1895.2(2), b=450.63(5) and c=1397.33(18) pm and β=112.008(7) (Z=1). The title compound shows planar, eight-membered, kinked Si{sub 8} chains with Si-Si distances between 241.4 and 245.0 pm indicating bonding interactions and kinked 'rope ladders' connecting the chains with interatomic Si-Si distances in the range 268.1-274.7 pm. Embedded in between these silicon substructures are columns of oxygen centered, apex sharing [(Ca{sub 1-x} Sr{sub x}){sub 6/2}O] octahedra and calcium ions.

  6. Thermodinamically stable phases in the CaO-SiO2-Al2O3-CaSO4-H2O closed system at 25 ºC. Application to cementitious systems

    Directory of Open Access Journals (Sweden)

    Blanco-Varela, M. T.

    2009-06-01

    Full Text Available One of the chief causes of cement and concrete deterioration is the loss of durability prompted by sulphate attack. The existing standards call for long test periods (2- 12 months. Thermodynamic modelling is a particularly appropriate technique for studying systems that only reach equilibrium in the long term. Used in the present study to establish the fields of thermodynamic stability for the phases in the CaO-SiO2-Al2O3-CaSO4-H2O system at 25 ºC. According to the model, gypsum is stable at sulphate ion concentrations of 1.23e-2 mol/kg and over, while ettringite exhibits stability at concentrations ranging from 7.64e-6 to 1.54e-2 mol/kg. Ettringite is compatible with all system phases except SH and gypsum only with ettringite, the C-S-H gels, AH3 and SH. None of the calcium aluminates or silicoaluminates in the system is compatible with gypsum: in its presence, they all decompose to cement deteriorating ettringite. Finally, the model revealed that the maximum sulphate concentration at which C-S-H gel is stable is slightly higher in systems with than without Al2O3.Uno de los principales problemas asociados al deterioro de cementos y hormigones es la pérdida de durabilidad por ataque de sulfatos. La normativa existente requiere largos tiempos de ensayo (2-12 meses. La modelización termodinámica es una técnica particularmente adecuada para el estudio de sistemas que alcanzan el equilibrio en tiempos largos. Aplicando esta metodología se han establecido los campos de estabilidad termodinámica de las fases del sistema CaO-SiO2-Al2O3-CaSO4-H2O a 25 ºC. El yeso es estable a partir de la [SO42-] = 1,23e-2 mol/kg, y la ettringita es estable en un rango de [SO42-] = 7,64e-6 -1,54e-2 mol/kg. La ettringita es compatible con todas las fases del sistema excepto con SH y el yeso sólo con la ettringita, los geles C-S-H, el AH3 y el SH. Ninguno de los aluminatos o silicoaluminatos cálcicos son compatibles con el yeso, en su presencia se descomponen

  7. Molecular pharmacology of promiscuous seven transmembrane receptors sensing organic nutrients.

    Science.gov (United States)

    Wellendorph, Petrine; Johansen, Lars Dan; Bräuner-Osborne, Hans

    2009-09-01

    A number of highly promiscuous seven transmembrane (7TM) receptors have been cloned and characterized within the last few years. It is noteworthy that many of these receptors are activated broadly by amino acids, proteolytic degradation products, carbohydrates, or free fatty acids and are expressed in taste tissue, the gastrointestinal tract, endocrine glands, adipose tissue, and/or kidney. These receptors thus hold the potential to act as sensors of food intake, regulating, for example, release of incretin hormones from the gut, insulin/glucagon from the pancreas, and leptin from adipose tissue. The promiscuous tendency in ligand recognition of these receptors is in contrast to the typical specific interaction with one physiological agonist seen for most receptors, which challenges the classic "lock-and-key" concept. We here review the molecular mechanisms of nutrient sensing of the calcium-sensing receptor, the G protein-coupled receptor family C, group 6, subtype A (GPRC6A), and the taste1 receptor T1R1/T1R3, which are sensing L-alpha-amino acids, the carbohydrate-sensing T1R2/T1R3 receptor, the proteolytic degradation product sensor GPR93 (also termed GPR92), and the free fatty acid (FFA) sensing receptors FFA1, FFA2, FFA3, GPR84, and GPR120. The involvement of the individual receptors in sensing of food intake has been validated to different degrees because of limited availability of specific pharmacological tools and/or receptor knockout mice. However, as a group, the receptors represent potential drug targets, to treat, for example, type II diabetes by mimicking food intake by potent agonists or positive allosteric modulators. The ligand-receptor interactions of the promiscuous receptors of organic nutrients thus remain an interesting subject of emerging functional importance.

  8. Defect Study of MgO-CaO Material Doped with CeO2

    Directory of Open Access Journals (Sweden)

    Han Zhang

    2013-01-01

    Full Text Available MgO-CaO refractories were prepared using analytical reagent chemicals of Ca(OH2 and Mg(OH2 as starting materials and CeO2 as dopant, then sintered at 1650°C for 3 h. The effect of CeO2 powders on the defect of MgO-CaO refractories was investigated. The sample characterizations were analyzed by the techniques of XRD and SEM. According to the results, with the addition of CeO2, the lattice constant of CaO increased, and the bulk density of the samples increased while apparent porosity decreased. The densification of MgO-CaO refractories was promoted obviously. In the sintering process, MgO grains grew faster than CaO, pores at the MgO-CaO grain boundaries decreased while pores in the MgO grains increased gradually, and no pores were observed in the CaO grains. The nature of the CeO2 promoting densification lies in the substitution and solution with CaO. Ce4+ approaches into CaO lattices, which enlarges the vacancy concentration of Ca2+ and accelerates the diffusion of Ca2+.

  9. Sweet taste receptor expressed in pancreatic beta-cells activates the calcium and cyclic AMP signaling systems and stimulates insulin secretion.

    Directory of Open Access Journals (Sweden)

    Yuko Nakagawa

    Full Text Available BACKGROUND: Sweet taste receptor is expressed in the taste buds and enteroendocrine cells acting as a sugar sensor. We investigated the expression and function of the sweet taste receptor in MIN6 cells and mouse islets. METHODOLOGY/PRINCIPAL FINDINGS: The expression of the sweet taste receptor was determined by RT-PCR and immunohistochemistry. Changes in cytoplasmic Ca(2+ ([Ca(2+](c and cAMP ([cAMP](c were monitored in MIN6 cells using fura-2 and Epac1-camps. Activation of protein kinase C was monitored by measuring translocation of MARCKS-GFP. Insulin was measured by radioimmunoassay. mRNA for T1R2, T1R3, and gustducin was expressed in MIN6 cells. In these cells, artificial sweeteners such as sucralose, succharin, and acesulfame-K increased insulin secretion and augmented secretion induced by glucose. Sucralose increased biphasic increase in [Ca(2+](c. The second sustained phase was blocked by removal of extracellular calcium and addition of nifedipine. An inhibitor of inositol(1, 4, 5-trisphophate receptor, 2-aminoethoxydiphenyl borate, blocked both phases of [Ca(2+](c response. The effect of sucralose on [Ca(2+](c was inhibited by gurmarin, an inhibitor of the sweet taste receptor, but not affected by a G(q inhibitor. Sucralose also induced sustained elevation of [cAMP](c, which was only partially inhibited by removal of extracellular calcium and nifedipine. Finally, mouse islets expressed T1R2 and T1R3, and artificial sweeteners stimulated insulin secretion. CONCLUSIONS: Sweet taste receptor is expressed in beta-cells, and activation of this receptor induces insulin secretion by Ca(2+ and cAMP-dependent mechanisms.

  10. Characterization and evaluation of antibacterial activity of plant mediated calcium oxide (CaO) nanoparticles by employing Mentha pipertia extract

    Science.gov (United States)

    Ijaz, Umber; Bhatti, Ijaz Ahmed; Mirza, Saima; Ashar, Ambreen

    2017-10-01

    The antibacterial activity of green synthesized calcium oxide nanoparticles was investigated using leaf extract of Mentha piperita in this study. The synthesized nanomaterial was subjected to characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive x-ray spectroscopy (EDX). The SEM images showed agglomeration of disc shaped nanoparticles, and FTIR and EDX spectroscopy indicated intensive peaks for calcium ions and oxygen. Subsequently, the potential of nanoscale CaO was also evaluated for antimicrobial index against E. coli using the well diffusion method. A maximum zone of inhibition up to 42 mm was observed when 100 µg ml-1 material was loaded with inoculum size 50 µl of E. coli in sunlight exposure of 5 h. The experimental conditions were optimized using a central composite design using a response surface methodology. The maximum antimicrobial index of the CaO nanoparticle was 6 mm as a result of the optimized response. Furthermore, the minimum inhibitory concentration of the CaO nanoparticle showed 25 µg ml-1, an effective initial concentration for E.coli removal. The results revealed that the CaO nanocomposite synthesized via a green route was a promising candidate for the removal of E. coli present in drinking water, which is an important fecal indicator.

  11. PGC-1α accelerates cytosolic Ca2+ clearance without disturbing Ca2+ homeostasis in cardiac myocytes

    International Nuclear Information System (INIS)

    Chen, Min; Wang, Yanru; Qu, Aijuan

    2010-01-01

    Energy metabolism and Ca 2+ handling serve critical roles in cardiac physiology and pathophysiology. Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) is a multi-functional coactivator that is involved in the regulation of cardiac mitochondrial functional capacity and cellular energy metabolism. However, the regulation of PGC-1α in cardiac Ca 2+ signaling has not been fully elucidated. To address this issue, we combined confocal line-scan imaging with off-line imaging processing to characterize calcium signaling in cultured adult rat ventricular myocytes expressing PGC-1α via adenoviral transduction. Our data shows that overexpressing PGC-1α improved myocyte contractility without increasing the amplitude of Ca 2+ transients, suggesting that myofilament sensitivity to Ca 2+ increased. Interestingly, the decay kinetics of global Ca 2+ transients and Ca 2+ waves accelerated in PGC-1α-expressing cells, but the decay rate of caffeine-elicited Ca 2+ transients showed no significant change. This suggests that sarcoplasmic reticulum (SR) Ca 2+ -ATPase (SERCA2a), but not Na + /Ca 2+ exchange (NCX) contribute to PGC-1α-induced cytosolic Ca 2+ clearance. Furthermore, PGC-1α induced the expression of SERCA2a in cultured cardiac myocytes. Importantly, overexpressing PGC-1α did not disturb cardiac Ca 2+ homeostasis, because SR Ca 2+ load and the propensity for Ca 2+ waves remained unchanged. These data suggest that PGC-1α can ameliorate cardiac Ca 2+ cycling and improve cardiac work output in response to physiological stress. Unraveling the PGC-1α-calcium handing pathway sheds new light on the role of PGC-1α in the therapy of cardiac diseases.

  12. Neuronal Calcium Sensor-1 Binds the D2 Dopamine Receptor and G-protein-coupled Receptor Kinase 1 (GRK1) Peptides Using Different Modes of Interactions.

    Science.gov (United States)

    Pandalaneni, Sravan; Karuppiah, Vijaykumar; Saleem, Muhammad; Haynes, Lee P; Burgoyne, Robert D; Mayans, Olga; Derrick, Jeremy P; Lian, Lu-Yun

    2015-07-24

    Neuronal calcium sensor-1 (NCS-1) is the primordial member of the neuronal calcium sensor family of EF-hand Ca(2+)-binding proteins. It interacts with both the G-protein-coupled receptor (GPCR) dopamine D2 receptor (D2R), regulating its internalization and surface expression, and the cognate kinases GRK1 and GRK2. Determination of the crystal structures of Ca(2+)/NCS-1 alone and in complex with peptides derived from D2R and GRK1 reveals that the differential recognition is facilitated by the conformational flexibility of the C-lobe-binding site. We find that two copies of the D2R peptide bind within the hydrophobic crevice on Ca(2+)/NCS-1, but only one copy of the GRK1 peptide binds. The different binding modes are made possible by the C-lobe-binding site of NCS-1, which adopts alternative conformations in each complex. C-terminal residues Ser-178-Val-190 act in concert with the flexible EF3/EF4 loop region to effectively form different peptide-binding sites. In the Ca(2+)/NCS-1·D2R peptide complex, the C-terminal region adopts a 310 helix-turn-310 helix, whereas in the GRK1 peptide complex it forms an α-helix. Removal of Ser-178-Val-190 generated a C-terminal truncation mutant that formed a dimer, indicating that the NCS-1 C-terminal region prevents NCS-1 oligomerization. We propose that the flexible nature of the C-terminal region is essential to allow it to modulate its protein-binding sites and adapt its conformation to accommodate both ligands. This appears to be driven by the variability of the conformation of the C-lobe-binding site, which has ramifications for the target specificity and diversity of NCS-1. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. The superconductor (Tl,Hg,Ca)2(Ba,Sr)2(Ca,Sr,Tl)Cu2O7.6

    International Nuclear Information System (INIS)

    Valldor, M.; Bryntse, I.; Morawski, A.

    2002-01-01

    In the title 2212-type superconductor (thallium mercury calcium barium strontium copper oxide), which contains both Tl and Hg in the charge reservoir (CR), Sr is located at both alkali-earth (AE) metal sites. Ca enters the CR at the same time as Tl shares the smaller AE site, which increases the apical Cu-Cu distance significantly. The structure causes the superconducting Cu-O layers to become significantly puckered. (orig.)

  14. Up-regulation of Ca2+/CaMKII/CREB signaling in salicylate-induced tinnitus in rats.

    Science.gov (United States)

    Zhao, Jiuhan; Wang, Biao; Wang, Xiaohong; Shang, Xiuli

    2018-02-09

    The purpose of the study was to investigate the changes of Ca 2+ /calmodulin-dependent protein kinases II (CaMKII)/cAMP response element-binding protein (CREB) signaling pathway in a rat tinnitus model. Eighteen Wistar rats were randomly divided into three groups: normal control (NC), normal saline (NS), and tinnitus model (TM) groups. Tinnitus model was induced by intraperitoneal injection of salicylate. The concentration of intracellular calcium level in auditory cortex cells was determined using Fura-2 acetoxymethyl ester (Fura-2 AM) method with fluorospectrophotometer. Expressions of calmodulin (CaM), N-methyl-D-aspartate receptor 2B subunit (NR2B), calcium-calmodulin kinase II (CaMKII), and cAMP response element-binding protein (CREB) were detected with Western blot. Tinnitus model was successfully established by the intraperitoneal administration of salicylate in rats. Compared with rats in NC and NS groups, salicylate administration significantly elevated CaM, NR2B, phospho-CaMKII and phospho-CREB expression in auditory cortex from tinnitus model group (p salicylate administration causes tinnitus symptoms and elevates Ca 2+ /CaMKII/CREB signaling pathway in auditory cortex cells. Our study likely provides a new understanding of the development of tinnitus.

  15. Analysis and effects of cytosolic free calcium increases in response to elicitors in Nicotiana plumbaginifolia cells.

    Science.gov (United States)

    Lecourieux, David; Mazars, Christian; Pauly, Nicolas; Ranjeva, Raoul; Pugin, Alain

    2002-10-01

    Cell suspensions obtained from Nicotiana plumbaginifolia plants stably expressing the apoaequorin gene were used to analyze changes in cytosolic free calcium concentrations ([Ca(2+)](cyt)) in response to elicitors of plant defenses, particularly cryptogein and oligogalacturonides. The calcium signatures differ in lag time, peak time, intensity, and duration. The intensities of both signatures depend on elicitor concentration and extracellular calcium concentration. Cryptogein signature is characterized by a long-sustained [Ca(2+)](cyt) increase that should be responsible for sustained mitogen-activated protein kinase activation, microtubule depolymerization, defense gene activation, and cell death. The [Ca(2+)](cyt) increase in elicitor-treated cells first results from a calcium influx, which in turns leads to calcium release from internal stores and additional Ca(2+) influx. H(2)O(2) resulting from the calcium-dependent activation of the NADPH oxidase also participates in [Ca(2+)](cyt) increase and may activate calcium channels from the plasma membrane. Competition assays with different elicitins demonstrate that [Ca(2+)](cyt) increase is mediated by cryptogein-receptor interaction.

  16. Opposing Roles of Calcium and Intracellular ATP on Gating of the Purinergic P2X2 Receptor Channel

    Directory of Open Access Journals (Sweden)

    Milos B. Rokic

    2018-04-01

    Full Text Available P2X2 receptors (P2X2R exhibit a slow desensitization during the initial ATP application and a progressive, calcium-dependent increase in rates of desensitization during repetitive stimulation. This pattern is observed in whole-cell recordings from cells expressing recombinant and native P2X2R. However, desensitization is not observed in perforated-patched cells and in two-electrode voltage clamped oocytes. Addition of ATP, but not ATPγS or GTP, in the pipette solution also abolishes progressive desensitization, whereas intracellular injection of apyrase facilitates receptor desensitization. Experiments with injection of alkaline phosphatase or addition of staurosporine and ATP in the intracellular solution suggest a role for a phosphorylation-dephosphorylation in receptor desensitization. Mutation of residues that are potential phosphorylation sites identified a critical role of the S363 residue in the intracellular ATP action. These findings indicate that intracellular calcium and ATP have opposing effects on P2X2R gating: calcium allosterically facilitates receptor desensitization and ATP covalently prevents the action of calcium. Single cell measurements further revealed that intracellular calcium stays elevated after washout in P2X2R-expressing cells and the blockade of mitochondrial sodium/calcium exchanger lowers calcium concentrations during washout periods to basal levels, suggesting a role of mitochondria in this process. Therefore, the metabolic state of the cell can influence P2X2R gating.

  17. Characterisation of the interaction of the C-terminus of the dopamine D2 receptor with neuronal calcium sensor-1.

    Directory of Open Access Journals (Sweden)

    Lu-Yun Lian

    Full Text Available NCS-1 is a member of the neuronal calcium sensor (NCS family of EF-hand Ca(2+ binding proteins which has been implicated in several physiological functions including regulation of neurotransmitter release, membrane traffic, voltage gated Ca(2+ channels, neuronal development, synaptic plasticity, and learning. NCS-1 binds to the dopamine D2 receptor, potentially affecting its internalisation and controlling dopamine D2 receptor surface expression. The D2 receptor binds NCS-1 via a short 16-residue cytoplasmic C-terminal tail. We have used NMR and fluorescence spectroscopy to characterise the interactions between the NCS-1/Ca(2+ and D2 peptide. The data show that NCS-1 binds D2 peptide with a K(d of ∼14.3 µM and stoichiometry of peptide binding to NCS-1 of 2:1. NMR chemical shift mapping confirms that D2 peptide binds to the large, solvent-exposed hydrophobic groove, on one face of the NCS-1 molecule, with residues affected by the presence of the peptide spanning both the N and C-terminal portions of the protein. The NMR and mutagenesis data further show that movement of the C-terminal helix 11 of NCS-1 to fully expose the hydrophobic groove is important for D2 peptide binding. Molecular docking using restraints derived from the NMR chemical shift data, together with the experimentally-derived stoichiometry, produced a model of the complex between NCS-1 and the dopamine receptor, in which two molecules of the receptor are able to simultaneously bind to the NCS-1 monomer.

  18. Bioactivity of gel-glass powders in the CaO-SiO2 system: a comparison with ternary (CaO-P2O5-SiO2) and quaternary glasses (SiO2-CaO-P2O5-Na2O).

    Science.gov (United States)

    Saravanapavan, Priya; Jones, Julian R; Pryce, Russell S; Hench, Larry L

    2003-07-01

    Bioactive glasses react chemically with body fluids in a manner that is compatible with the repair processes of the tissues. This results in the formation of an interfacial bond between the glasses and living tissue. Bioactive glasses also stimulate bone-cell proliferation. This behavior is dependent on the chemical composition as well as the surface texture of the glasses. It has been recently reported that gel-derived monolith specimens in the binary SiO2 - CaO are bioactive over a similar molar range of SiO2 content as the previously studied ternary CaO-P2O5-SiO2 system. In this report, the preparation and bioactivity of the binary gel-glass powder with 70 mol % SiO2 is discussed and its bioactivity is compared with the melt-derived 45S5 (quaternary) Bioglass and sol-gel-derived 58S (ternary) bioactive gel-glass compositions. Dissolution kinetic parameters K(1) and K(2) were also computed based on the silicon release for all glass powders. It was shown that the simple two-component SiO2-CaO gel-glass powder is bioactive with comparable dissolution rates as the clinically used melt-derived 45S5 Bioglass powder and extensively studied sol-gel-derived 58S gel-glass powder. Copyright 2003 Wiley Periodicals, Inc.

  19. One Dimensional Finite Element Method Approach to Study Effect of Ryanodine Receptor and Serca Pump on Calcium Distribution in Oocytes

    Science.gov (United States)

    Naik, Parvaiz Ahmad; Pardasani, Kamal Raj

    2013-11-01

    Oocyte is a female gametocyte or germ cell involved in reproduction. Calcium ions (Ca2+) impact nearly all aspects of cellular life as they play an important role in a variety of cellular functions. Calcium ions contributes to egg activation upon fertilization. Since it is the internal stores which provide most of the calcium signal, much attention has been focused on the intracellular channels. There are mainly two types of calcium channels which release calcium from the internal stores to the cytoplasm in many cell types. These channels are IP3-Receptor and Ryanodine Receptor (RyR). Further it is essential to maintain low cytosolic calcium concentration, the cell engages the Serco/Endoplasmic reticulum Ca2+ ATPases (SERCA) present on the ER or SR membrane for the re-uptake of cytosolic calcium at the expense of ATP hydrolysis. In view of above an attempt has been made to study the effect of the Ryanodine receptor (RyR) and the SERCA pump on the calcium distribution in oocytes. The main aim of this paper is to study the calcium concentration in absence and presence of these parameters. The FEM is used to solve the proposed Mathematical model under appreciate initial and boundary conditions. The program has been developed in MATLAB 7.10 for the entire problem to get numerical results.

  20. 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.

  1. Air Plasma-Sprayed La2Zr2O7-SrZrO3 Composite Thermal Barrier Coating Subjected to CaO-MgO-Al2O3-SiO2 (CMAS)

    Science.gov (United States)

    Cai, Lili; Ma, Wen; Ma, Bole; Guo, Feng; Chen, Weidong; Dong, Hongying; Shuang, Yingchai

    2017-08-01

    La2Zr2O7-SrZrO3 composite thermal barrier coatings (TBCs) were prepared by air plasma spray (APS). The La2Zr2O7-SrZrO3 composite TBCs covered with calcium-magnesium-aluminum-silicate (CMAS) powder, as well as the powder mixture of CMAS and spray-dried La2Zr2O7-SrZrO3 composite powder, were heat-treated at 1250 °C in air for 1, 4, 8, and 12 h. The phase constituents and microstructures of the reaction products were characterized by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Experimental results showed that the La2Zr2O7-SrZrO3 composite TBCs had higher CMAS resistance than 8YSZ coating. A dense new layer developed between CMAS and La2Zr2O7-SrZrO3 composite TBCs during interaction, and this new layer consisted mostly of apatite (Ca2La8(SiO4)6O2) and c-ZrO2. The newly developed layer effectively protected the La2Zr2O7-SrZrO3 composite TBCs from further CMAS attack.

  2. Mechanism of a strong rise of Tc due to the calcium doping in Y1-xCaxBa2Cu2.8Zn0.2Oy

    International Nuclear Information System (INIS)

    Martynova, O.A.; Potapov, D.V.; Gasumyants, V.E.; Vladimirskaya, E.V.

    2011-01-01

    Highlights: → Calcium is observed to restore superconductivity in Y 1-x Ca x Ba 2 Cu 2.8 Zn 0.2 O y . → Parameters of the band spectrum and charge-carrier system are determined. → The calcium doping is shown to give a noticeable contribution to the DOS function. → The mechanism of calcium effect on T c in doped YBa 2 Cu 3 O y is discussed. - Abstract: The normal-state transport properties and the critical temperature, T c , for three series of Y 1-x Ca x Ba 2 Cu 2.8 Zn 0.2 O y (x = 0-0.2) samples with different oxygen content have been investigated and discussed in comparison with results for other calcium-doped YBa 2 Cu 3 O y . We have observed the calcium doping to restore the superconductivity in the YBa 2 Cu 3 O y system even in case of the preliminary T c suppression by the direct destruction of the CuO 2 planes due to a preliminary doping by zinc. The T c value rises strongly with increasing calcium content and this rise becomes faster for the oxygen-reduced series. Based on a narrow-band model, the parameters of the band spectrum structure and the charge-carrier system in the normal state were determined from the analysis of the thermopower temperature dependences in order to reveal the mechanism of the T c rise under the Ca influence. It is shown that the T c increase in Y 1-x Ca x Ba 2 Cu 2.8 Zn 0.2 O y is related to the direct Ca ions effect. The mechanism of the calcium influence on the T c value is discussed with respect to the Ca-induced conduction band modification. The calcium doping in Y 1-x Ca x Ba 2 Cu 2.8 Zn 0.2 O y is shown to give a noticeable contribution to the density-of-states function leading to a strong rise in its value at the Fermi level that results in a restoration of the superconducting properties.

  3. Synthesis, structural, spectroscopic and thermoanalytical study of sol–gel derived SiO{sub 2}–CaO–P{sub 2}O{sub 5} gel and ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Catauro, Michelina, E-mail: michelina.catauro@unina2.it [Department of Industrial and Information Engineering, Second University of Naples, via Roma 29, Aversa (CE) (Italy); Dell’Era, Alessandro [Department D.M.E., ‘Guglielmo Marconi’ University, via Plinio 44, Roma (Italy); Vecchio Ciprioti, Stefano, E-mail: stefano.vecchio@uniroma1.it [Department S.B.A.I., Sapienza University of Rome, via del Castro Laurenziano 7, Roma (Italy)

    2016-02-10

    Highlights: • Four different SiO{sub 2}–CaO–P{sub 2}O{sub 5} gel-glasses were synthesized by the sol–gel method. • FTIR, XRD, SEM-EDS and TG/DTA techniques were used to fully characterize the gels. • Integral isoconversional OFW method was used to study dehydration kinetics. • Appropriate temperatures of 600 and 1200 °C were chosen to thermally treat them. • All amorphous gels at 1200 °C crystallize as wollastonite and pseudowollastonite. - Abstract: In the present work bioactive powders of the ternary SiO{sub 2CaO·P{sub 2}O{sub 5} systems, which differ in the Ca/P molar ratio, were synthesized by means of a sol–gel route, using tetraethyl orthosilicate (TEOS, Si(OC{sub 2}H{sub 5}){sub 4}), calcium nitrate tetrahydrate (Ca(NO{sub 3}){sub 2}·4H{sub 2}O) and triethyl phosphate (TEP, OP(OC{sub 2}H{sub 5}){sub 3}) as precursors of SiO{sub 2}, CaO and P{sub 2}O{sub 5}, respectively. In order to investigate the influence of the relative amount of each phase (in this study: SiO{sub 2}, CaO and P{sub 2}O{sub 5}) the thermal properties of the synthesized gel-glass materials were studied as a function of the Ca/P molar ratio using thermogravimetric and differential thermal analysis (TG/DTA). After dehydration (in a single step), described from a kinetic point of view as a simple water evaporation without rupture of chemical bonds, all gels undergo a complex multi-step decomposition with endo and exothermic effects, followed by crystallization of calcium silicate phases at about 950 °C. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy, coupled with energy dispersive spectroscopy (SEM/EDS), allowed us to detect the chemical modifications induced by modifying the Ca/P molar ratio and the sintering. This process is obtained by thermal treatment of the gel-glass precursors after analyzing their thermal behavior in the temperature range 600–1000 °C, with the aim to convert them into

  4. Piezoelectric and electromechanical properties of ultrahigh temperature CaBi2Nb2O9 ceramics

    International Nuclear Information System (INIS)

    Wang, Jin-Feng; Zhang, Shujun; Shrout, Thomas R.; Wang, Chun-Ming

    2009-01-01

    The piezoelectric, dielectric, and electromechanical properties of the (KCe) co-substituted calcium bismuth niobate (CaBi 2 Nb 2 O 9 , CBN) were investigated. The piezoelectric activities of CBN ceramics were significantly enhanced and the dielectric loss tan δ decreased by (KCe) substitution. The Ca 0.9 (KCe) 0.05 Bi 2 Nb 2 O 9 ceramics possess the optimal piezoelectric properties, and the piezoelectric coefficient (d 33 ), Curie temperature (T C ), and electromechanical coupling factors (k p and k t ) were found to be 16 pC/N, 868 C, 8.6%, and 23.8%, respectively. The excellent dielectric and electromechanical spectra, together with the high piezoelectric activities and ultrahigh Curie temperature, make CBN ceramics promising candidates for high temperature piezoelectric applications. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Phase equilibria and crystal chemistry of the CaO-½Gd2O3-CoOz system at 885 °C in air

    Science.gov (United States)

    Wong-Ng, W.; Laws, W.; Lapidus, S. H.; Ribaud, L.; Kaduk, J. A.

    2017-10-01

    The CaO-½Gd2O3-CoOz system prepared at 885 °C in air consists of two thermoelectric calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xGdx)Co4O9-z (0 ≤ x ≤ 0.42) which has a misfit layered structure, and the 1D Ca3Co2O6 compound which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound. In the peripheral binary systems, Gd was not present in the Ca site of CaO, while a small solid solution region was identified for (Gd1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.075). A solid solution region of distorted perovskite, (Gd1-xCax)CoO3-z (0 ≤ x ≤ 0.24, space group Pnma) was established. The structure of a member of the solid solution, (Gd0.92Ca0.08)CoO3-z, was determined using high resolution synchrotron radiation. A ternary oxide compound CaGdCoO4-z which has an orthorhombic structure (Bmab) was found to be stable at this temperature. Five solid solution tie-line regions and six three-phase regions were determined in the CaO-½Gd2O3-CoOz system. A comparison of the phase diagrams of the CaO-½R2O3-CoOz (R = La, Sm and Gd) systems is provided.

  6. The study of skeletal calcium metabolism with 41Ca and 45Ca

    Science.gov (United States)

    Freeman, Stewart P. H. T.; Beck, Belinda; Bierman, June M.; Caffee, Marc W.; Heaney, Robert P.; Holloway, Leah; Marcus, Robert; Southon, John R.; Vogel, John S.

    2000-10-01

    The living skeleton can be labeled for life by the administration of radiologically trivial amounts of 41Ca tracer. After initial elimination of tracer from the readily exchangeable calcium pools subsequent skeletal calcium turnover maintains and modulates the urine 41Ca content. Uniquely, bone calcium metabolism may then be studied with tracer in near equilibrium with the body's calcium and resorbing calcium directly measured by accelerator mass spectrometry (AMS) of excreta. Our experiments with 25 41Ca labeled subjects demonstrate excellent diurnal stability and remarkable response to intervention of the urine signal. Thus the tracer method may prove a competitive means of measuring the effects of antiresorptive osteoporosis treatments, for therapy development or even clinical monitoring. Novel studies of long-term skeletal evolution are also possible. We realize that routinely administered short-lived calcium radiotracers contain 41Ca impurities and that thousands of experimental participants have been historically inadvertently 41Ca labeled. The 41Ca urine index might now rapidly further be characterized by contemporary measurements of these one-time subjects, and with their by now thoroughly skeleton-equilibrated tracer they might be ideal participants in other new experiments. We are also investigating 45Ca AMS. It may prove preferable to label the skeleton with this radiotracer already familiar to bioscientists, but new to AMS.

  7. 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

  8. Lipophilic Chemicals from Diesel Exhaust Particles Trigger Calcium Response in Human Endothelial Cells via Aryl Hydrocarbon Receptor Non-Genomic Signalling

    Directory of Open Access Journals (Sweden)

    Bendik C. Brinchmann

    2018-05-01

    Full Text Available Exposure to diesel exhaust particles (DEPs affects endothelial function and may contribute to the development of atherosclerosis and vasomotor dysfunction. As intracellular calcium concentration [Ca2+]i is considered important in myoendothelial signalling, we explored the effects of extractable organic matter from DEPs (DEP-EOM on [Ca2+]i and membrane microstructure in endothelial cells. DEP-EOM of increasing polarity was obtained by pressurized sequential extraction of DEPs with n-hexane (n-Hex-EOM, dichloromethane (DCM-EOM, methanol, and water. Chemical analysis revealed that the majority of organic matter was extracted by the n-Hex- and DCM-EOM, with polycyclic aromatic hydrocarbons primarily occurring in n-Hex-EOM. The concentration of calcium was measured in human microvascular endothelial cells (HMEC-1 using micro-spectrofluorometry. The lipophilic n-Hex-EOM and DCM-EOM, but not the more polar methanol- and water-soluble extracts, induced rapid [Ca2+]i increases in HMEC-1. n-Hex-EOM triggered [Ca2+]i increase from intracellular stores, followed by extracellular calcium influx consistent with store operated calcium entry (SOCE. By contrast, the less lipophilic DCM-EOM triggered [Ca2+]i increase via extracellular influx alone, resembling receptor operated calcium entry (ROCE. Both extracts increased [Ca2+]i via aryl hydrocarbon receptor (AhR non-genomic signalling, verified by pharmacological inhibition and RNA-interference. Moreover, DCM-EOM appeared to induce an AhR-dependent reduction in the global plasma membrane order, as visualized by confocal fluorescence microscopy. DCM-EOM-triggered [Ca2+]i increase and membrane alterations were attenuated by the membrane stabilizing lipid cholesterol. In conclusion, lipophilic constituents of DEPs extracted by n-hexane and DCM seem to induce rapid AhR-dependent [Ca2+]i increase in HMEC-1 endothelial cells, possibly involving both ROCE and SOCE-mediated mechanisms. The semi-lipophilic fraction

  9. Ca2+ and voltage dependence of cardiac ryanodine receptor channel block by sphingosylphosphorylcholine.

    Science.gov (United States)

    Yasukochi, Midori; Uehara, Akira; Kobayashi, Sei; Berlin, Joshua R

    2003-03-01

    The effect of sphingosylphosphorylcholine (SPC) on the cytoplasmic Ca(2+) and voltage dependence of channel gating by cardiac ryanodine receptors (RyR) was examined in lipid bilayer experiments. Micromolar concentrations of the lysosphingolipid SPC added to cis solutions rapidly and reversibly decreased the single-channel open probability (P(o)) of reconstituted RyR channels. The SPC-induced decrease in P(o) was marked by an increase in mean closed time and burst-like channel gating. Gating kinetics during intraburst periods were unchanged from those observed in the absence of the sphingolipid, although SPC induced a long-lived closed state that appeared to explain the observed decrease in channel P(o). SPC effects were observed over a broad range of cis [Ca(2+)] but were not competitive with Ca(2+). Interestingly, the sphingolipid-induced, long-lived closed state displayed voltage-dependent kinetics, even though other channel gating kinetics were not sensitive to voltage. Assuming SPC effects represent channel blockade, these results suggest that the blocking rate is independent of voltage whereas the unblocking rate is voltage dependent. Together, these results suggest that SPC binds directly to the cytoplasmic side of the RyR protein in a location in or near the membrane dielectric, but distinct from cytoplasmic Ca(2+) binding sites on the protein.

  10. 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.

  11. Crystal structures and thermal decomposition of permanganates AE[MnO_4]_2 . n H_2O with the heavy alkaline earth elements (AE=Ca, Sr and Ba)

    International Nuclear Information System (INIS)

    Henning, Harald; Bauchert, Joerg M.; Conrad, Maurice; Schleid, Thomas

    2017-01-01

    Reexamination of the syntheses and crystal structures as well as studies of the thermal decomposition of the heavy alkaline earth metal permanganates Ca[MnO_4]_2 . 4 H_2O, Sr[MnO_4]_2 . 3 H_2O and Ba[MnO_4]_2 are the focus of this work. As an alternative to the very inelegant Muthmann method, established for the synthesis of Ba[MnO_4]_2 a long time ago, we employed a cation-exchange column loaded with Ba"2"+ cations and passed through an aqueous potassium-permanganate solution. We later used this alternative also with strontium- and calcium-loaded columns and all the compounds synthesized this way were indistinguishable from the products of the established methods. Ca[MnO_4]_2 . 4 H_2O exhibiting [CaO_8] polyhedra crystallizes in the orthorhombic space group Pccn with the lattice parameters a=1397.15(9), b=554.06(4) and c=1338.97(9) pm with Z=4, whereas Sr[MnO_4]_2 . 3 H_2O with [SrO_1_0] polyhedra adopts the cubic space group P2_13 with a=964.19(7) pm and Z=4. So the harder the AE"2"+ cation, the higher its demand for hydration in aqueous solution. Consequently, the crystal structure of Ba[MnO_4]_2 in the orthorhombic space group Fddd with a=742.36(5), b=1191.23(7) and c=1477.14(9) pm with Z=8 lacks any crystal water, but contains [BaO_1_2] polyhedra. During the thermal decomposition of Ca[MnO_4]_2 . 4 H_2O, the compound expels up to two water molecules of hydration, before the crystal structure collapses after the loss of the third H_2O molecule at 157 C. The crystal structure of Sr[MnO_4]_2 . 3 H_2O breaks down after the expulsion of the third water molecule as well, but this already occurs at 148 C. For both the calcium and the strontium permanganate samples, orthobixbyite-type α-Mn_2O_3 and the oxomanganates(III,IV) AEMn_3O_6 (AE=Ca and Sr) remain as final decomposition products at 800 C next to amorphous phases. On the other hand, the already anhydrous Ba[MnO_4]_2 thermally decomposes to hollandite-type BaMn_8O_1_6 and BaMnO_3 at 800 C.

  12. TRPM2, calcium and neurodegenerative diseases

    Science.gov (United States)

    Xie, Yu-Feng; MacDonald, John F; Jackson, Michael F

    2010-01-01

    NMDA receptor overactivation triggers intracellular Ca2+ dysregulation, which has long been thought to be critical for initiating excitotoxic cell death cascades associated with stroke and neurodegenerative disease. The inability of NMDA receptor antagonists to afford neuroprotection in clinical stroke trials has led to a re-evaluation of excitotoxic models of cell death and has focused research efforts towards identifying additional Ca2+ influx pathways. Recent studies indicate that TRPM2, a member of the TRPM subfamily of Ca2+-permeant, non-selective cation channel, plays an important role in mediating cellular responses to a wide range of stimuli that, under certain situations, can induce cell death. These include reactive oxygen and nitrogen species, tumour necrosis factor as well as soluble oli-gomers of amyloid beta. However, the molecular basis of TRPM2 channel involvement in these processes is not fully understood. In this review, we summarize recent studies about the regulation of TRPM2, its interaction with calcium and the possible implications for neurodegenerative diseases. PMID:21383889

  13. PEG/CaFe{sub 2}O{sub 4} nanocomposite: Structural, morphological, magnetic and thermal analyses

    Energy Technology Data Exchange (ETDEWEB)

    Khanna, Lavanya, E-mail: lavanshya@yahoo.co.in; Verma, Narendra K., E-mail: nkverma@thapar.edu

    2013-10-15

    The coating of Polyethylene Glycol (PEG) on calcium ferrite (CaFe{sub 2}O{sub 4}) nanoparticles has been reported in the present study. The X-ray diffraction pattern revealed the formation of orthorhombic structure of bare CaFe{sub 2}O{sub 4} nanoparticles, which was also retained after the PEG coating, along with additional characteristic peaks of PEG at 19° and 23°. The rings of CaFe{sub 2}O{sub 4} nanoparticles were identified by the selected area electron diffraction pattern. The characteristic bands of PEG as observed in its Fourier transform infrared spectrum were also present in PEG coated CaFe{sub 2}O{sub 4} nanoparticles, hence confirming its presence. In the thermal gravimetric studies, the complete thermal decomposition of PEG occurred in a one step process, but in case of PEG coated CaFe{sub 2}O{sub 4} nanoparticles, the decomposition took place at a higher temperature owing to the formation of covalent bonds of PEG with CaFe{sub 2}O{sub 4} nanoparticles. The presence of PEG on CaFe{sub 2}O{sub 4} nanoparticles, spherical formation of PEG coated CaFe{sub 2}O{sub 4} nanoparticles and reduced agglomeration in the CaFe{sub 2}O{sub 4} nanoparticles were revealed by high resolution transmission electron microscope, transmission electron microscope and scanning electron microscope studies, respectively. In vibrating sample magnetometer analysis, both bare as well as coated CaFe{sub 2}O{sub 4} nanoparticles exhibited superparamagnetic behavior. However, a drop in the magnetic saturation value was observed from 36.76 emu/g for CaFe{sub 2}O{sub 4} nanoparticles to 6.74 emu/g for PEG coated CaFe{sub 2}O{sub 4} nanoparticles, due to the formation of magnetically dead layer of PEG. In ZFC and FC analyses, superparamagnetic behavior with blocking temperature for bare and coated nanoparticles has been observed at ∼40 K and ∼60 K, respectively. The increase in the blocking temperature is attributed to the increase in the particle size after PEG coating.

  14. Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y1.5Ba2-xCaxCu3Oy superconductors

    International Nuclear Information System (INIS)

    Park, S.D.; Kim, H.J.; Park, B.J.; Han, Y.H.; Jun, B.-H.; Lee, J.S.; Kim, C.-J.

    2011-01-01

    We study effects of calcium doping in melt processed Y123 superconductors. We examine a superconducting transition temperature and current density. A transition temperature and current density decreases by calcium doping. Calcium doping leads to coarseing of Y211 particles. Y211 refining effect by CeO 2 is disappreared by calcium doping. The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y 1.5 Ba 2-x Ca x Cu 3 O y superconductors was studied in terms of calcium content (X ca ). YBa 2-x Ca x Cu 3 O 7-δ (X ca = 0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa 2-x Ca x Cu 3 O 7-δ powders were mixed with 0.25 mole Y 2 O 3 powder and 1 wt.% CeO 2 as Y 2 BaCuO 5 (Y211) refiner, and finally made into Y 1 . 5 Ba 2-x Ca x Cu 3 O y (Y1.5) + 1 wt.% CeO 2 composition. The single Y123 growth on the top surface was observed up to X ca = 0.1, while the multiple Y123 growth was observed at X ca ≥ 0.1. The superconducting transition temperature (T c ) and critical current density (J c ) of TSMG processed Y1.5 samples were inversely proportional to X ca . The Y211 size increased with increasing X ca due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO 2 was observed in the calcium doped samples. The T c and J c decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

  15. Conotoxins as Tools to Understand the Physiological Function of Voltage-Gated Calcium (CaV Channels

    Directory of Open Access Journals (Sweden)

    David Ramírez

    2017-10-01

    Full Text Available Voltage-gated calcium (CaV channels are widely expressed and are essential for the completion of multiple physiological processes. Close regulation of their activity by specific inhibitors and agonists become fundamental to understand their role in cellular homeostasis as well as in human tissues and organs. CaV channels are divided into two groups depending on the membrane potential required to activate them: High-voltage activated (HVA, CaV1.1–1.4; CaV2.1–2.3 and Low-voltage activated (LVA, CaV3.1–3.3. HVA channels are highly expressed in brain (neurons, heart, and adrenal medulla (chromaffin cells, among others, and are also classified into subtypes which can be distinguished using pharmacological approaches. Cone snails are marine gastropods that capture their prey by injecting venom, “conopeptides”, which cause paralysis in a few seconds. A subset of conopeptides called conotoxins are relatively small polypeptides, rich in disulfide bonds, that target ion channels, transporters and receptors localized at the neuromuscular system of the animal target. In this review, we describe the structure and properties of conotoxins that selectively block HVA calcium channels. We compare their potency on several HVA channel subtypes, emphasizing neuronal calcium channels. Lastly, we analyze recent advances in the therapeutic use of conotoxins for medical treatments.

  16. Piezoelectrically-induced stress-luminescence phenomenon in CaAl{sub 2}O{sub 4}:Eu{sup 2+}

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Yongbin [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Wu, Zheng, E-mail: wuzheng@zjnu.cn [College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004 (China); Jia, Yanmin, E-mail: ymjia@zjnu.edu.cn [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Liu, Yongsheng [Department of Physics, Shanghai University of Electric Power, Shanghai 200090 (China)

    2015-10-15

    Piezoelectrically-induced stress-luminescence in the CaAl{sub 2}O{sub 4}:Eu{sup 2+} was investigated. Blue light that was visible to the naked eye could be observed in the dark when a pulse force of ∼7.7 kN was applied to the sample. The intensity of the stress-luminescence strongly depended on the magnitude of the applied force during a pulse cycle. The intensity decreased with repetitive application of pulse stress and was completely recovered after irradiation with ultraviolet light. It is suggested that the stress-luminescence effect in CaAl{sub 2}O{sub 4}:Eu{sup 2+} arises from the piezoelectrically-induced de-trapping of the charge carriers. A CaAl{sub 2}O{sub 4}:Eu{sup 2+} ceramic that exhibits a stress-luminescence effect has potential applications in smart stress optically-sensing devices. - Highlights: • The strong induced stress-luminescence in CaAl{sub 2}O{sub 4}:Eu{sup 2+} was observed. • The stress-luminescent intensity strongly depends on the magnitude of force. • The stress-luminescence could be completely recovered after the UV irradiation. • The strong stress-luminescent effect is potential in stress-light sensors.

  17. Removal of arsenic from water by Friedel's salt (FS: 3CaO·Al2OCaCl2·10H2O).

    Science.gov (United States)

    Zhang, Danni; Jia, Yongfeng; Ma, Jiayu; Li, Zhibao

    2011-11-15

    Low levels of arsenic can be effectively removed from water by adsorption onto various materials and searching for low-cost, high-efficiency new adsorbents has been a hot topic in recent years. In the present study, the performance of Friedel's salt (FS: 3CaO·Al(2)O(3)·CaCl(2)·10H(2)O), a layered double hydroxide (LDHs), as an adsorbent for arsenic removal from aqueous solution was investigated. Friedel's salt was synthesized at lower temperature (50°C) compared to traditional autoclave methods by reaction of calcium chloride with sodium aluminate. Kinetic study revealed that adsorption of arsenate by Friedel's salt was fast in the first 12h and equilibrium was achieved within 48 h. The adsorption kinetics are well described by second-order Lageren equation. The adsorption capacity of the synthesized sorbent for arsenate at pH 4 and 7 calculated from Langmuir adsorption isotherms was 11.85 and 7.80 mg/g, respectively. Phosphate and silicate markedly decreased the removal of arsenate, especially at higher pH, but sulfate was found to suppress arsenate adsorption at lower pH and the adverse effect was disappeared at pH ≥ 6. Common metal cations (Ca(2+), Mg(2+)) enhanced arsenate adsorption. The results suggest that Friedel's salt is a potential cost-effective adsorbent for arsenate removal in water treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Effect of inhibition of microsomal Ca(2+)-ATPase on cytoplasmic calcium and enzyme secretion in pancreatic acini.

    Science.gov (United States)

    Metz, D C; Pradhan, T K; Mrozinski, J E; Jensen, R T; Turner, R J; Patto, R J; Gardner, J D

    1994-01-13

    We used thapsigargin (TG), 2,5-di-tert-butyl-1,4-benzohydroquinone (BHQ) and cyclopiazonic acid (CPA), each of which inhibits microsomal Ca(2+)-ATPase, to evaluate the effects of this inhibition on cytoplasmic free calcium ([Ca2+]i) and secretagogue-stimulated enzyme secretion in rat pancreatic acini. Using single-cell microspectrofluorimetry of fura-2-loaded acini we found that all three agents caused a sustained increase in [Ca2+]i by mobilizing calcium from inositol-(1,4,5)-trisphosphate-sensitive intracellular calcium stores and by promoting influx of extracellular calcium. Concentrations of all three agents that increased [Ca2+]i potentiated the stimulation of enzyme secretion caused by secretagogues that activate adenylate cyclase but inhibited the stimulation of enzyme secretion caused by secretagogues that activate phospholipase C. With BHQ, potentiation of adenylate cyclase-mediated enzyme secretion occurred immediately whereas inhibition of phospholipase C-mediated enzyme secretion occurred only after several min of incubation. In addition, the effects of BHQ and CPA on both [Ca2+]i and secretagogue-stimulated enzyme secretion were reversed completely by washing whereas the actions of TG could not be reversed by washing. Concentrations of BHQ in excess of those that caused maximal changes in [Ca2+]i inhibited all modes of stimulated enzyme secretion by a mechanism that was apparently unrelated to changes in [Ca2+]i. Finally, in contrast to the findings with TG and BHQ, CPA inhibited bombesin-stimulated enzyme secretion over a range of concentrations that was at least 10-fold lower than the range of concentrations over which CPA potentiated VIP-stimulated enzyme secretion.

  19. Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

    Science.gov (United States)

    Li, H C; Wang, D G; Meng, X G; Chen, C Z

    2014-06-01

    A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. About LTCC materials in the substance system of CaO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}; Ueber LTCC-Werkstoffe aus dem Stoffsystem CaO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Gemeinert, Marion

    2009-09-01

    Glass ceramic composites made of glassy and crystalline powders offer numerous possibilities for modifying materials properties e.g. sintering behaviour, thermal expansion coefficient, mechanical behaviour, chemical durability, dielectric properties and surface quality for special use. Glass ceramic composite powders can be used for the production of ceramic green tapes which are processed by LTCC (Low Temperature Co-fired Ceramics)- technology to form ceramic multilayers for electronic packaging in microsystems. During free sintering of LTCC-multilayers a lateral shrinkage occurs which is connected with a comparatively high shrinkage tolerance. Different sintering technologies are used to avoid the lateral shrinkage. A new possibility to achieve a zero lateral shrinkage is given by use of a self-constrained laminate. Therefore a multilayer is produced of two different materials for inner and outer layers, showing different sintering temperatures ({delta}T>50 K). Object of this dissertation was the development of LTCC-materials, which can be used for inner layers of a self-constrained laminate to reduce the lateral shrinkage nearly to zero. Therefore LTCC-materials in the field of CaO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}, which can be sintered below 800 C, were investigated. Starting from the development of adapted glasses based on calcium lanthanium borate- and calcium lanthanium alumoborate glasses glass ceramic composites were produced by the addition of corundum powder. The composites crystallize during the sintering process almost completely. Lanthanum borate crystallizes from the glassy phase and calcium alumoborate and calcium alumoborate oxide respectively is formed by a chemical solid state reaction of the residual glassy phase, which is enriched by calcium borate, and the corundum. The proportional relation of the new crystalline phases determines the thermal and dielectric properties of the material. The most important formed new

  1. Combined effects of adsorption and photocatalysis by hybrid TiO2/ZnO-calcium alginate beads for the removal of copper

    Institute of Scientific and Technical Information of China (English)

    Devagi Kanakaraju; Shantini Ravichandar; Ying Chin Lim

    2017-01-01

    The use of nanosized titanium dioxide (TiO2) and zinc oxide (ZnO) in the suspension form during treatment makes the recovering and recycling of photocatalysts difficult.Hence,supported photocatalysts are preferred for practical water treatment applications.This study was conducted to investigate the efficiency of calcium alginate (CaAlg) beads that were immobilized with hybrid photocatalysts,TiO2/ZnO to form TiO2/ZnO-CaAlg.Theseimmobilized beads,with three different mass ratios of TiO2:ZnO (1∶1,1∶2,and 2∶1) were used to remove Cu(Ⅱ) in aqueous solutions in the presence of ultraviolet light.These beads were subjected to three cycles of photocatalytic treatment with different initial Cu(Ⅱ) concentrations (10-80 ppm).EDX spectra have confirmed the inclusion of Ti and Zn on the surface of the CaAlg beads.Meanwhile,the surface morphology of the beads as determined using SEM,has indicated differences of before and after the photocatalytic treatment of Cu(Ⅱ).Among all three,the equivalent mass ratio TiO2/ZnO-CaAlg beads have shown the best performance in removing Cu(Ⅱ) during all three recycling experiments.Those TiO2/ZnO-CaAlg beads have also shown consistent removal of Cu,ranging from 7.14-62.0 ppm (first cycle) for initial concentrations of 10-80 ppm.In comparison,bare CaAlg was only able to remove 6.9-48 ppm of similar initial Cu concentrations.Thus,the potential use of TiO2/ZnO-CaAlg beads as environmentally friendly composite material can be further extended for heavy metal removal from contaminated water.

  2. Biodiesel production from soybean and Jatropha oils by magnetic CaFe2O4–Ca2Fe2O5-based catalyst

    International Nuclear Information System (INIS)

    Xue, Bao-jin; Luo, Jia; Zhang, Fan; Fang, Zhen

    2014-01-01

    Heterogeneous CaFe 2 O 4 –Ca 2 Fe 2 O 5 -based catalyst with weak magnetism was prepared by co-precipitation and calcination. It was characterized by various techniques including X-ray diffraction, X-ray photoelectron spectroscopy and temperature programmed desorption method. Its active components were identified as mainly Ca–Fe composite oxides such as CaFe 2 O 4 for transesterification. The magnetism was further strengthened by reducing its component of Fe 2 O 3 to Fe 3 O 4 –Fe under H 2 atmosphere for better magnetic separation. Both catalysts were used for the catalytic transesterification of soybean and Jatropha oils to biodiesel. The highest biodiesel yields for soybean oil of 85.4% and 83.5% were obtained over the weak and strong magnetic catalysts, respectively under the optimized conditions (373 K, 30 min, 15/1 methanol/oil molar ratio and 4 wt% catalyst). The catalysts could be recycled three times. Biodiesel production from pretreated Jatropha oil was tested with the magnetic CaFe 2 O 4 –Ca 2 Fe 2 O 5 –Fe 3 O 4 –Fe catalyst, and 78.2% biodiesel yield was obtained. The magnetic CaFe 2 O 4 –Ca 2 Fe 2 O 5 -based catalyst shows a potential application for the green production of biodiesel. - Highlights: • Magnetic catalyst was prepared by co-precipitation, calcination and reduction. • The catalyst was composed of CaFe 2 O 4 –Ca 2 Fe 2 O 5 –Fe 3 O 4 –Fe. • Biodiesel yields of 83.5% and 78.2% were achieved for soybean and Jatropha oils. • The catalyst was easily separated by a magnet and used for three cycles

  3. Crystal structures of coordination polymers from CaI2 and proline

    Directory of Open Access Journals (Sweden)

    Kevin Lamberts

    2015-06-01

    Full Text Available Completing our reports concerning the reaction products from calcium halides and the amino acid proline, two different solids were found for the reaction of l- and dl-proline with CaI2. The enantiopure amino acid yields the one-dimensional coordination polymer catena-poly[[aqua-μ3-l-proline-tetra-μ2-l-proline-dicalcium] tetraiodide 1.7-hydrate], {[Ca2(C5H9NO25(H2O]I4·1.7H2O}n, (1, with two independent Ca2+ cations in characteristic seven- and eightfold coordination. Five symmetry-independent zwitterionic l-proline molecules bridge the metal sites into a cationic polymer. Racemic proline forms with Ca2+ cations heterochiral chains of the one-dimensional polymer catena-poly[[diaquadi-μ2-dl-proline-calcium] diiodide], {[Ca(C5H9NO22(H2O2]I2}n, (2. The centrosymmetric structure is built by one Ca2+ cation that is bridged towards its symmetry equivalents by two zwitterionic proline molecules. In both structures, the iodide ions remain non-coordinating and hydrogen bonds are formed between these counter-anions, the amino groups, coordinating and co-crystallized water molecules. While the overall composition of (1 and (2 is in line with other structures from calcium halides and amino acids, the diversity of the carboxylate coordination geometry is quite surprising.

  4. MicroRNA-145 suppresses ROS-induced Ca2+ overload of cardiomyocytes by targeting CaMKIIδ

    International Nuclear Information System (INIS)

    Cha, Min-Ji; Jang, Jin-Kyung; Ham, Onju; Song, Byeong-Wook; Lee, Se-Yeon; Lee, Chang Yeon; Park, Jun-Hee; Lee, Jiyun; Seo, Hyang-Hee; Choi, Eunhyun; Jeon, Woo-min; Hwang, Hye Jin; Shin, Hyun-Taek

    2013-01-01

    Highlights: •CaMKIIδ mediates H 2 O 2 -induced Ca 2+ overload in cardiomyocytes. •miR-145 can inhibit Ca 2+ overload. •A luciferase assay confirms that miR-145 functions as a CaMKIIδ-targeting miRNA. •Overexpression of miR-145 regulates CaMKIIδ-related genes and ameliorates apoptosis. -- Abstract: A change in intracellular free calcium (Ca 2+ ) is a common signaling mechanism of reperfusion-induced cardiomyocyte death. Calcium/calmodulin dependent protein kinase II (CaMKII) is a critical regulator of Ca 2+ signaling and mediates signaling pathways responsible for functions in the heart including hypertrophy, apoptosis, arrhythmia, and heart disease. MicroRNAs (miRNA) are involved in the regulation of cell response, including survival, proliferation, apoptosis, and development. However, the roles of miRNAs in Ca 2+ -mediated apoptosis of cardiomyocytes are uncertain. Here, we determined the potential role of miRNA in the regulation of CaMKII dependent apoptosis and explored its underlying mechanism. To determine the potential roles of miRNAs in H 2 O 2 -mediated Ca 2+ overload, we selected and tested 6 putative miRNAs that targeted CaMKIIδ, and showed that miR-145 represses CaMKIIδ protein expression and Ca 2+ overload. We confirmed CaMKIIδ as a direct downstream target of miR-145. Furthermore, miR-145 regulates Ca 2+ -related signals and ameliorates apoptosis. This study demonstrates that miR-145 regulates reactive oxygen species (ROS)-induced Ca 2+ overload in cardiomyocytes. Thus, miR-145 affects ROS-mediated gene regulation and cellular injury responses

  5. How calcium makes endocytic receptors attractive

    DEFF Research Database (Denmark)

    Andersen, Christian B F; Moestrup, Søren K

    2014-01-01

    of the receptor. Endosomal acidification and calcium efflux lead to the essential ligand-receptor affinity switch and separation. Recent data, including crystal structures of receptor-ligand complexes, now reveal how calcium, in different types of domain scaffolds, functions in a common way as a removable...... 'lynchpin' that stabilizes favorable positioning of ligand-attractive receptor residues. In addition to explaining how calcium depletion can cause ligand-receptor dissociation, the new data add further insight into how acidification contributes to dissociation through structural changes that affect...... the receptor calcium sites....

  6. Zoledronate complexes. III. Two zoledronate complexes with alkaline earth metals: [Mg(C(5)H(9)N(2)O(7)P(2))(2)(H(2)O)(2)] and [Ca(C(5)H(8)N(2)O(7)P(2))(H(2)O)](n).

    Science.gov (United States)

    Freire, Eleonora; Vega, Daniel R; Baggio, Ricardo

    2010-06-01

    Diaquabis[dihydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonato-kappa(2)O,O']magnesium(II), [Mg(C(5)H(9)N(2)O(7)P(2))(2)(H(2)O)(2)], consists of isolated dimeric units built up around an inversion centre and tightly interconnected by hydrogen bonding. The Mg(II) cation resides at the symmetry centre, surrounded in a rather regular octahedral geometry by two chelating zwitterionic zoledronate(1-) [or dihydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonate] anions and two water molecules, in a pattern already found in a few reported isologues where the anion is bound to transition metals (Co, Zn and Ni). catena-Poly[[aquacalcium(II)]-mu(3)-[hydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonato]-kappa(5)O:O,O':O',O''], [Ca(C(5)H(8)N(2)O(7)P(2))(H(2)O)](n), consists instead of a Ca(II) cation in a general position, a zwitterionic zoledronate(2-) anion and a coordinated water molecule. The geometry around the Ca(II) atom, provided by six bisphosphonate O atoms and one water ligand, is that of a pentagonal bipyramid with the Ca(II) atom displaced by 0.19 A out of the equatorial plane. These Ca(II) coordination polyhedra are ;threaded' by the 2(1) axis so that successive polyhedra share edges of their pentagonal basal planes. This results in a strongly coupled rhomboidal Ca(2)-O(2) chain which runs along [010]. These chains are in turn linked by an apical O atom from a -PO(3) group in a neighbouring chain. This O-atom, shared between chains, generates strong covalently bonded planar arrays parallel to (100). Finally, these sheets are linked by hydrogen bonds into a three-dimensional structure. Owing to the extreme affinity of zoledronic acid for bone tissue, in general, and with calcium as one of the major constituents of bone, it is expected that this structure will be useful in modelling some of the biologically interesting processes in which the drug takes part.

  7. Phase diagram study for the PbO-ZnO-CaO-SiO{sub 2} -“Fe{sub 2}O{sub 3} ” system in air with CaO/SiO{sub 2} in 1.1 and PbO/(CaO+SiO{sub 2}) in 2.4 weight ratios

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Rodriguez, Josue; Romero-Serrano, Antonio; Hernandez-Ramirez, Aurelio; Cruz-Ramirez, Alejandro, E-mail: romeroipn@hotmail.com [Instituto Politecnico Nacional-ESIQIE, Zacatenco, Mexico City (Mexico); Almaguer-Guzman, Isaias; Benavides-Perez, Ricardo; Flores-Favela, Manuel [Servicios Administrativos Penoles S.A de C.V., Torreon, Coahuila (Mexico)

    2017-07-15

    An experimental study on the phase equilibrium and the liquidus isotherms for the PbO-ZnO-CaO-SiO{sub 2} -“Fe{sub 2}O{sub 3} ” system with CaO/SiO{sub 2} in 1.1 and PbO/(CaO+SiO{sub 2}) in 2.4 weight ratios, respectively, was carried out in the temperature range 1100-1300 deg C (1373-1573 K). High temperature phases were determined by the equilibrium-quenching method. Results are presented in the form of pseudo-ternary sections “Fe{sub 2}O{sub 3} ”-ZnO-(PbO+CaO+SiO{sub 2}). X-Ray diffraction (XRD) and SEM-EDS results showed that the phase equilibria in this system are dominated by the high melting temperature spinel and zincite phases. It was observed that if the system is at a temperature below 1300 deg C and the total (Fe{sub 2}O{sub 3} + ZnO) is greater than 20 wt%, spinel and/or zincite will be present in the slag system. As an application of the phase diagram, the liquid phase compositions below the liquidus surface were estimated, then their viscosities were calculated using FACTSage software. (author)

  8. Structural and sensing characteristics of Gd2Ti2O7, Er2TiO5 and Lu2Ti2O7 sensing membrane electrolyte–insulator–semiconductor for bio-sensing applications

    International Nuclear Information System (INIS)

    Pan, Tung-Ming; Liao, Pei-You; Chang, Kung-Yuan; Chi, Lifeng

    2013-01-01

    Highlights: ► The structural and sensing properties of Gd 2 Ti 2 O 7 , Er 2 TiO 5 and Lu 2 Ti 2 O 7 sensing films grown on Si substrates by reactive co-sputtering. ► The EIS device incorporating a Lu 2 Ti 2 O 7 sensing film exhibited a higher sensitivity, a larger drift rate, a higher hysteresis voltage, and a larger hysteresis gap than other sensing films. ► The impedance effect of EIS sensors has been investigated using C–V method. -- Abstract: This paper describes the structural and sensing characteristics of Gd 2 Ti 2 O 7 , Er 2 TiO 5 , and Lu 2 Ti 2 O 7 sensing membranes deposited on Si substrates through reactive co-sputtering for electrolyte–insulator–semiconductor (EIS) pH sensors. In this work, the structural properties of Gd 2 Ti 2 O 7 , Er 2 TiO 5 , and Lu 2 Ti 2 O 7 membranes were investigated by X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. The observed structural properties were then correlated with the resulting pH sensing performances. The EIS device incorporating a Lu 2 Ti 2 O 7 sensing film exhibited a higher sensitivity (59.32 mV pH −1 ), a larger drift rate (0.55 mV h −1 ), a higher hysteresis voltage (5 mV), and a larger hysteresis gap (∼70 mV) compared to those of the other sensing films. This result is attributed to the higher surface roughness and the formation of a thicker interfacial layer at the oxide–Si interface. Furthermore, the impedance effect of EIS sensors has been investigated using capacitance–voltage (C–V) method (frequency-dependent C–V curves). From the impedance spectroscopy analysis, we find that the diameter of a semicircle of an EIS sensor becomes smaller due to a gradual decrease in the bulk resistance of the device with degree of pH value

  9. Decreasing extracellular Na+ concentration triggers inositol polyphosphate production and Ca2+ mobilization

    International Nuclear Information System (INIS)

    Smith, J.B.; Dwyer, S.D.; Smith, L.

    1989-01-01

    Removing extracellular Na+ (Na+o) evoked a large increase in cytosolic free Ca2+ concentration ([Ca2+]i in human skin fibroblasts. Decreasing [Na+]o from 120 to 14 mM caused the half-maximal peak increase in [Ca2+]i. Removing Na+o strongly stimulated 45 Ca2+ efflux and decreased total cell Ca2+ by about 40%. Bradykinin caused changes in [Ca2+]i, total Ca2+, and 45 Ca2+ fluxes similar to those evoked by removing Na+o. Prior stimulation of the cells with bradykinin prevented Na+o removal from increasing [Ca2+]i and vice versa. Na+o removal rapidly increased [ 3 H]inositol polyphosphate production. Loading the cells with Na+ had no effect on the increase in 45 Ca2+ efflux produced by Na+o removal. Therefore, decreasing [Na+]o probably stimulates a receptor(s) which is sensitive to extracellular, not intracellular, Na+. Removing Na+o also mobilized intracellular Ca2+ in smooth muscle and endothelial cells cultured from human umbilical and dog coronary arteries, respectively

  10. Glycine Receptor Activation Impairs ATP-Induced Calcium Transients in Cultured Cortical Astrocytes

    Directory of Open Access Journals (Sweden)

    Tatiana P. Morais

    2018-01-01

    Full Text Available In central nervous system, glycine receptor (GlyR is mostly expressed in the spinal cord and brainstem, but glycinergic transmission related elements have also been identified in the brain. Astrocytes are active elements at the tripartite synapse, being responsible for the maintenance of brain homeostasis and for the fine-tuning of synaptic activity. These cells communicate, spontaneously or in response to a stimulus, by elevations in their cytosolic calcium (calcium transients, Ca2+T that can be propagated to other cells. How these Ca2+T are negatively modulated is yet poorly understood. In this work, we evaluated GlyR expression and its role on calcium signaling modulation in rat brain astrocytes. We first proved that GlyR, predominantly subunits α2 and β, was expressed in brain astrocytes and its localization was confirmed in the cytoplasm and astrocytic processes by immunohistochemistry assays. Calcium imaging experiments in cultured astrocytes showed that glycine (500 μM, a GlyR agonist, caused a concentration-dependent reduction in ATP-induced Ca2+T, an effect abolished by the GlyR antagonist, strychnine (0.8 μM, as well as by nocodazole (1 μM, known to impair GlyR anchorage to the plasma membrane. This effect was mimicked by activation of GABAAR, another Cl--permeable channel. In summary, we demonstrated that GlyR activation in astrocytes mediates an inhibitory effect upon ATP induced Ca2+T, which most probably involves changes in membrane permeability to Cl- and requires GlyR anchorage at the plasma membrane. GlyR in astrocytes may thus be part of a mechanism to modulate astrocyte-to-neuron communication.

  11. Preparation and bioactivity of micro-arc oxidized calcium phosphate coatings

    International Nuclear Information System (INIS)

    Pan, Y.K.; Chen, C.Z.; Wang, D.G.; Lin, Z.Q.

    2013-01-01

    Calcium phosphate (CaP) coatings were prepared on ZK60 magnesium alloy by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH 3 COO) 2 Ca·H 2 O) and disodium hydrogen phosphate dodecahydrate (Na 2 HPO 4 ·12H 2 O). Scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDX) and X-ray diffractometer (XRD) were employed to characterize the microstructure, elemental distribution and phase composition of the CaP coatings respectively. Simulated body fluid (SBF) immersion test was used to evaluate the coating degradability and bioactivity. After 30 days of SBF immersion, the CaP coatings effectively reduce the degradation rate. The surfaces of CaP coatings are covered by a new layer formed of numerous needle-like, spherical and columned calcium phosphates. SEM, EDX and XRD results suggest that these calcium phosphates are bioactive calcium phosphate phases such as hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HA) and calcium pyrophosphates (Ca 2 P 2 O 7 , CPP). The formation of these calcium phosphates indicates that the CaP coatings have bioactivity. - Highlights: • Bioactive CaP coatings are successfully formed on ZK60 magnesium alloy. • CaP coatings consist of MgO, MgF 2 , CaO, CaF 2 and Ca 3 (PO 4 ) 2 . • Needle-like, spherical and columned calcium phosphates formed in SBF. • CaP coatings exhibit bioactivity and low corrosion rate

  12. Ca2+ handling abnormalities in early-onset muscle diseases: Novel concepts and perspectives.

    NARCIS (Netherlands)

    Treves, S.; Jungbluth, H.; Voermans, N.C.; Muntoni, F.; Zorzato, F.

    2017-01-01

    The physiological process by which Ca2+ is released from the sarcoplasmic reticulum is called excitation-contraction coupling; it is initiated by an action potential which travels deep into the muscle fiber where it is sensed by the dihydropyridine receptor, a voltage sensing L-type Ca2+channel

  13. Simulation of the effect of rogue ryanodine receptors on a calcium wave in ventricular myocytes with heart failure

    International Nuclear Information System (INIS)

    Lu, Luyao; Xia, Ling; Ye, Xuesong; Cheng, Heping

    2010-01-01

    Calcium homeostasis is considered to be one of the most important factors for the contraction and relaxation of the heart muscle. However, under some pathological conditions, such as heart failure (HF), calcium homeostasis is disordered, and spontaneous waves may occur. In this study, we developed a mathematical model of formation and propagation of a calcium wave based upon a governing system of diffusion–reaction equations presented by Izu et al (2001 Biophys. J. 80 103–20) and integrated non-clustered or 'rogue' ryanodine receptors (rogue RyRs) into a two-dimensional (2D) model of ventricular myocytes isolated from failing hearts in which sarcoplasmic reticulum (SR) Ca 2+ pools are partially unloaded. The model was then used to simulate the effect of rogue RyRs on initiation and propagation of the calcium wave in ventricular myocytes with HF. Our simulation results show that rogue RyRs can amplify the diastolic SR Ca 2+ leak in the form of Ca 2+ quarks, increase the probability of occurrence of spontaneous Ca 2+ waves even with smaller SR Ca 2+ stores, accelerate Ca 2+ wave propagation, and hence lead to delayed afterdepolarizations (DADs) and cardiac arrhythmia in the diseased heart. This investigation suggests that incorporating rogue RyRs in the Ca 2+ wave model under HF conditions provides a new view of Ca 2+ dynamics that could not be mimicked by adjusting traditional parameters involved in Ca 2+ release units and other ion channels, and contributes to understanding the underlying mechanism of HF

  14. Simulation of the effect of rogue ryanodine receptors on a calcium wave in ventricular myocytes with heart failure

    Science.gov (United States)

    Lu, Luyao; Xia, Ling; Ye, Xuesong; Cheng, Heping

    2010-06-01

    Calcium homeostasis is considered to be one of the most important factors for the contraction and relaxation of the heart muscle. However, under some pathological conditions, such as heart failure (HF), calcium homeostasis is disordered, and spontaneous waves may occur. In this study, we developed a mathematical model of formation and propagation of a calcium wave based upon a governing system of diffusion-reaction equations presented by Izu et al (2001 Biophys. J. 80 103-20) and integrated non-clustered or 'rogue' ryanodine receptors (rogue RyRs) into a two-dimensional (2D) model of ventricular myocytes isolated from failing hearts in which sarcoplasmic reticulum (SR) Ca2+ pools are partially unloaded. The model was then used to simulate the effect of rogue RyRs on initiation and propagation of the calcium wave in ventricular myocytes with HF. Our simulation results show that rogue RyRs can amplify the diastolic SR Ca2+ leak in the form of Ca2+ quarks, increase the probability of occurrence of spontaneous Ca2+ waves even with smaller SR Ca2+ stores, accelerate Ca2+ wave propagation, and hence lead to delayed afterdepolarizations (DADs) and cardiac arrhythmia in the diseased heart. This investigation suggests that incorporating rogue RyRs in the Ca2+ wave model under HF conditions provides a new view of Ca2+ dynamics that could not be mimicked by adjusting traditional parameters involved in Ca2+ release units and other ion channels, and contributes to understanding the underlying mechanism of HF.

  15. Acute Cocaine Induces Fast Activation of D1 Receptor and Progressive Deactivation of D2 Receptor Strial Neurons: In Vivo Optical Microprobe [Ca(superscript)2+]subscript)i Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Du, C.; Luo, Z.; Volkow, N.D.; Heintz, N.; Pan, Y.; Du, C.

    2011-09-14

    Cocaine induces fast dopamine increases in brain striatal regions, which are recognized to underlie its rewarding effects. Both dopamine D1 and D2 receptors are involved in cocaine's reward but the dynamic downstream consequences of cocaine effects in striatum are not fully understood. Here we used transgenic mice expressing EGFP under the control of either the D1 receptor (D1R) or the D2 receptor (D2R) gene and microprobe optical imaging to assess the dynamic changes in intracellular calcium ([Ca{sup 2+}]{sub i} ) responses (used as marker of neuronal activation) to acute cocaine in vivo separately for D1R- versus D2R-expressing neurons in striatum. Acute cocaine (8 mg/kg, i.p.) rapidly increased [Ca{sup 2+}]{sub i} in D1R-expressing neurons (10.6 {+-} 3.2%) in striatum within 8.3 {+-} 2.3 min after cocaine administration after which the increases plateaued; these fast [Ca{sup 2+}]{sub i} increases were blocked by pretreatment with a D1R antagonist (SCH23390). In contrast, cocaine induced progressive decreases in [Ca{sup 2+}]{sub i} in D2R-expressing neurons (10.4 {+-} 5.8%) continuously throughout the 30 min that followed cocaine administration; these slower [Ca{sup 2+}]{sub i} decreases were blocked by pretreatment with a D2R antagonist (raclopride). Since activation of striatal D1R-expressing neurons (direct-pathway) enhances cocaine reward, whereas activation of D2R expressing neurons suppresses it (indirect-pathway) (Lobo et al., 2010), this suggests that cocaine's rewarding effects entail both its fast stimulation ofD1R (resulting in abrupt activation of direct-pathway neurons) and a slower stimulation of D2R (resulting in longer-lasting deactivation of indirect-pathway neurons). We also provide direct in vivo evidence of D2R and D1R interactions in the striatal responses to acute cocaine administration.

  16. Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

    Science.gov (United States)

    Agathopoulos, S; Tulyaganov, D U; Ventura, J M G; Kannan, S; Karakassides, M A; Ferreira, J M F

    2006-03-01

    New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

  17. Description and crystal structure of albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Mereiter, K. [Vienna Univ. of Technology (Austria). Inst. of Chemical Technologies and Analytics

    2013-04-15

    Albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O, triclinic, space group P anti 1, a = 13.569(2), b = 13.419(2), c = 11.622(2) Aa, α = 115.82(1), β = 107.61(1), γ = 92.84(1) (structural unit cell, not reduced), V = 1774.6(5) Aa{sup 3}, Z = 2, Dc = 2.69 g/cm{sup 3} (for 17.5 H{sub 2}O), is a mineral that was found in small amounts with schroeckingerite, NaCa{sub 3}F[UO{sub 2}(CO{sub 3}){sub 3}](SO{sub 4}).10H{sub 2}O, on a museum specimen of uranium ore from Joachimsthal (Jachymov), Czech Republic. The mineral forms small grain-like subhedral crystals (= 0.2 mm) that resemble in appearance liebigite, Ca{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]. ∝ 11H{sub 2}O. Colour pale yellow-green, luster vitreous, transparent, pale bluish green fluorescence under ultraviolet light. Optical data: Biaxial negative, nX = 1.511(2), nY = 1.550(2), nZ = 1.566(2), 2V = 65(1) (λ = 589 nm), r < v weak. After qualitative tests had shown the presence of Ca, U, Mg, CO{sub 2} and H{sub 2}O, the chemical formula was determined by a crystal structure analysis based on X-ray four-circle diffractometer data. The structure was later on refined with data from a CCD diffractometer to R1 = 0.0206 and wR2 = 0.0429 for 9,236 independent observed reflections. The crystal structure contains two independent [UO{sub 2}(CO{sub 3}){sub 3}]{sup 4-} anions of which one is bonded to two Mg and six Ca while the second is bonded to only one Mg and three Ca. Magnesium forms a MgF{sub 2}(O{sub carbonate}){sub 3}(H{sub 2}O) octahedron that is linked via the F atoms with three Ca atoms so as to provide each F atom with a flat pyramidal coordination by one Mg and two Ca. Calcium is 7- and 8-coordinate forming CaFO{sub 6}, CaF{sub 2}O{sub 2}(H{sub 2}O){sub 4}, CaFO{sub 3}(H{sub 2}O){sub 4} and CaO{sub 2}(H{sub 2}O){sub 6} coordination polyhedra. The crystal structure is built up from MgCa{sub 3}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}].8H{sub 2}O layers parallel to (001) which

  18. PGC-1{alpha} accelerates cytosolic Ca{sup 2+} clearance without disturbing Ca{sup 2+} homeostasis in cardiac myocytes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Min, E-mail: chenminyx@gmail.com [Institute of Molecular Medicine, State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871 (China); Yunnan Centers for Diseases Prevention and Control, Kunming 650022 (China); Wang, Yanru [Institute of Molecular Medicine, State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871 (China); Qu, Aijuan [Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States)

    2010-06-11

    Energy metabolism and Ca{sup 2+} handling serve critical roles in cardiac physiology and pathophysiology. Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1{alpha}) is a multi-functional coactivator that is involved in the regulation of cardiac mitochondrial functional capacity and cellular energy metabolism. However, the regulation of PGC-1{alpha} in cardiac Ca{sup 2+} signaling has not been fully elucidated. To address this issue, we combined confocal line-scan imaging with off-line imaging processing to characterize calcium signaling in cultured adult rat ventricular myocytes expressing PGC-1{alpha} via adenoviral transduction. Our data shows that overexpressing PGC-1{alpha} improved myocyte contractility without increasing the amplitude of Ca{sup 2+} transients, suggesting that myofilament sensitivity to Ca{sup 2+} increased. Interestingly, the decay kinetics of global Ca{sup 2+} transients and Ca{sup 2+} waves accelerated in PGC-1{alpha}-expressing cells, but the decay rate of caffeine-elicited Ca{sup 2+} transients showed no significant change. This suggests that sarcoplasmic reticulum (SR) Ca{sup 2+}-ATPase (SERCA2a), but not Na{sup +}/Ca{sup 2+} exchange (NCX) contribute to PGC-1{alpha}-induced cytosolic Ca{sup 2+} clearance. Furthermore, PGC-1{alpha} induced the expression of SERCA2a in cultured cardiac myocytes. Importantly, overexpressing PGC-1{alpha} did not disturb cardiac Ca{sup 2+} homeostasis, because SR Ca{sup 2+} load and the propensity for Ca{sup 2+} waves remained unchanged. These data suggest that PGC-1{alpha} can ameliorate cardiac Ca{sup 2+} cycling and improve cardiac work output in response to physiological stress. Unraveling the PGC-1{alpha}-calcium handing pathway sheds new light on the role of PGC-1{alpha} in the therapy of cardiac diseases.

  19. 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.

  20. Tensión superficial, viscosidad y densidad de algunas escorias CaO-Al2O3

    Directory of Open Access Journals (Sweden)

    Oliveira, F. A.

    1999-04-01

    Full Text Available The metallurgical concepts with regard to the structures and properties of calcium aluminate melts have been based upon analogies within ternary CaO-Al2O3-SiO2 systems. In this work the results of surface tension, density and viscosity of some calcium aluminate slags, in the temperature range of 1500 to 1600°C are presented and the results are discussed based upon recent structural characterisation results of crystalline aluminates. The compositional range investigated was from 45 to 53 weight-% alumina. The results indicate a reduction in density as the molar ratio CaO-Al2O3 decreases. Surface tension falls on increasing either the molar ratio CaO-Al2O3 or temperature. Conversely, viscosity increases with increasing molar ratio CaO-Al2O3 and decreasing temperature. The compositional dependence of both surface tension and viscosity data may be associated with the presence of some aluminium ions in octahedral co-ordination, and a concept of surface behaviour is proposed which involves surface activity of aluminate anions containing aluminium ions in a reduced valence state, such as Al2+.

    Los conceptos metalúrgicos con respecto a la estructura y propiedades de los aluminatos de calcio, están predominantemente basados en analogías con el sistema ternario CaO-Al2O3-SiO2. En este trabajo se presentan y discuten los resultados de medidas de tensión superficial, densidad y viscosidad de algunas escorias de aluminato de calcio, en la franja de temperatura entre 1.500 y 1.650°C, a la luz de investigaciones recientes sobre caracterización de la estructura vítrea de aluminatos y alumino- silicatos. La faja de composición investigada fue de 45 a 52% en peso de alúmina. Los resultados indican una reducción en la densidad con la disminución de la razón molar CaO: Al2O3. La

  1. Long-term potentiation in the CA1 hippocampus induced by NR2A subunit-containing NMDA glutamate receptors is mediated by Ras-GRF2/Erk map kinase signaling.

    Directory of Open Access Journals (Sweden)

    Shan-xue Jin

    Full Text Available BACKGROUND: NMDA-type glutamate receptors (NMDARs are major contributors to long-term potentiation (LTP, a form of synaptic plasticity implicated in the process of learning and memory. These receptors consist of calcium-permeating NR1 and multiple regulatory NR2 subunits. A majority of studies show that both NR2A and NR2B-containing NMDARs can contribute to LTP, but their unique contributions to this form of synaptic plasticity remain poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we show that NR2A and NR2B-containing receptors promote LTP differently in the CA1 hippocampus of 1-month old mice, with the NR2A receptors functioning through Ras-GRF2 and its downstream effector, Erk Map kinase, and NR2B receptors functioning independently of these signaling molecules. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that NR2A-, but not NR2B, containing NMDA receptors induce LTP in pyramidal neurons of the CA1 hippocampus from 1 month old mice through Ras-GRF2 and Erk. This difference add new significance to the observation that the relative levels of these NMDAR subtypes is regulated in neurons, such that NR2A-containing receptors become more prominent late in postnatal development, after sensory experience and synaptic activity.

  2. Mechanisms of intragastric pH sensing.

    Science.gov (United States)

    Goo, Tyralee; Akiba, Yasutada; Kaunitz, Jonathan D

    2010-12-01

    Luminal amino acids and lack of luminal acidity as a result of acid neutralization by intragastric foodstuffs are powerful signals for acid secretion. Although the hormonal and neural pathways underlying this regulatory mechanism are well understood, the nature of the gastric luminal pH sensor has been enigmatic. In clinical studies, high pH, tryptic peptides, and luminal divalent metals (Ca(2+) and Mg(2+)) increase gastrin release and acid production. The calcium-sensing receptor (CaSR), first described in the parathyroid gland but expressed on gastric G cells, is a logical candidate for the gastric acid sensor. Because CaSR ligands include amino acids and divalent metals, and because extracellular pH affects ligand binding in the pH range of the gastric content, its pH, metal, and nutrient-sensing functions are consistent with physiologic observations. The CaSR is thus an attractive candidate for the gastric luminal sensor that is part of the neuroendocrine negative regulatory loop for acid secretion.

  3. Evaluation of TeO2 content on the optical and spectroscopic properties of Yb3 +-doped calcium borotellurite glasses

    Science.gov (United States)

    Lima, A. M. O.; Gomes, J. F.; Hegeto, F. L.; Medina, A. N.; Steimacher, A.; Barboza, M. J.

    2018-03-01

    This paper reports the synthesis and the characterization of Yb3 +-doped calcium borotellurite (CaBTeX) glasses with composition 10CaF2-(29.5 - 0.4x)CaO-(60 - 0.6x)B2O3-xTeO2-0.5Yb2O3 (x = 10, 16, 22, 31 and 54 mol%). The results of XRD confirm the amorphous character of all the samples. The density, molar volume, refractive index and electronic polarizability values show an increase with TeO2 content. Otherwise, the optical band gap energy shows a decrease with the increase of TeO2 content. The replacement of CaO and B2O3 by TeO2 changes the glass structure, which decreases the excited Yb3 +/cm3 and, consequently, the luminescence intensity. The temperature dependence of luminescence was studied for all the samples up to 420 K. The fluorescence lifetime does not change significantly due to TeO2 addition. In addition, absorption and emission cross section were calculated and present high values as compared to other tellurite and phosphate glasses.

  4. Preparation and bioactivity of micro-arc oxidized calcium phosphate coatings

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Y.K. [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Ji' nan, Shandong 250061 (China); School of Materials Science and Engineering, Shandong University, Ji' nan, Shandong 250061 (China); Chen, C.Z., E-mail: czchen@sdu.edu.cn [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Ji' nan, Shandong 250061 (China); School of Materials Science and Engineering, Shandong University, Ji' nan, Shandong 250061 (China); Wang, D.G.; Lin, Z.Q. [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Ji' nan, Shandong 250061 (China); School of Materials Science and Engineering, Shandong University, Ji' nan, Shandong 250061 (China)

    2013-09-16

    Calcium phosphate (CaP) coatings were prepared on ZK60 magnesium alloy by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH{sub 3}COO){sub 2}Ca·H{sub 2}O) and disodium hydrogen phosphate dodecahydrate (Na{sub 2}HPO{sub 4}·12H{sub 2}O). Scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDX) and X-ray diffractometer (XRD) were employed to characterize the microstructure, elemental distribution and phase composition of the CaP coatings respectively. Simulated body fluid (SBF) immersion test was used to evaluate the coating degradability and bioactivity. After 30 days of SBF immersion, the CaP coatings effectively reduce the degradation rate. The surfaces of CaP coatings are covered by a new layer formed of numerous needle-like, spherical and columned calcium phosphates. SEM, EDX and XRD results suggest that these calcium phosphates are bioactive calcium phosphate phases such as hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, HA) and calcium pyrophosphates (Ca{sub 2}P{sub 2}O{sub 7}, CPP). The formation of these calcium phosphates indicates that the CaP coatings have bioactivity. - Highlights: • Bioactive CaP coatings are successfully formed on ZK60 magnesium alloy. • CaP coatings consist of MgO, MgF{sub 2}, CaO, CaF{sub 2} and Ca{sub 3}(PO{sub 4}){sub 2}. • Needle-like, spherical and columned calcium phosphates formed in SBF. • CaP coatings exhibit bioactivity and low corrosion rate.

  5. New vanadium oxides with perovskite type structure: AThV/sub 2/O/sub 6/ (A=Ca,Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Vidyasagar, K; Gopalakrishnan, J

    1982-07-01

    New perovskite oxides of the formula AThV/sub 2/O/sub 6/ (A=Ca,Sr) have been prepared by reduction of the corresponding AThV/sub 2/O/sub 8/ under hydrogen atmosphere. CaThV/sub 2/O/sub 6/ crystallizes in an orthorhombic LaVO/sub 3/ type structure, while the strontium compound exhibiting cation-deficient nonstoichiometry. SrThsub(1-x)V/sub 2/O/sub 6/ (x approx. 0.4), is cubic. The magnetic susceptibility behaviour of the calcium compound is similar to that of V/sup 3 +/ perovskites, while the strontium compound exhibits a large increase in susceptibility below 130K, the behaviour being likely to be associated with the mixed-valence character of vanadium.

  6. Synaptically released zinc triggers metabotropic signaling via a zinc-sensing receptor in the hippocampus.

    Science.gov (United States)

    Besser, Limor; Chorin, Ehud; Sekler, Israel; Silverman, William F; Atkin, Stan; Russell, James T; Hershfinkel, Michal

    2009-03-04

    Zn(2+) is coreleased with glutamate from mossy fiber terminals and can influence synaptic function. Here, we demonstrate that synaptically released Zn(2+) activates a selective postsynaptic Zn(2+)-sensing receptor (ZnR) in the CA3 region of the hippocampus. ZnR activation induced intracellular release of Ca(2+), as well as phosphorylation of extracellular-regulated kinase and Ca(2+)/calmodulin kinase II. Blockade of synaptic transmission by tetrodotoxin or CdCl inhibited the ZnR-mediated Ca(2+) rises. The responses mediated by ZnR were largely attenuated by the extracellular Zn(2+) chelator, CaEDTA, and in slices from mice lacking vesicular Zn(2+), suggesting that synaptically released Zn(2+) triggers the metabotropic activity. Knockdown of the expression of the orphan G-protein-coupled receptor 39 (GPR39) attenuated ZnR activity in a neuronal cell line. Importantly, we observed widespread GPR39 labeling in CA3 neurons, suggesting a role for this receptor in mediating ZnR signaling in the hippocampus. Our results describe a unique role for synaptic Zn(2+) acting as the physiological ligand of a metabotropic receptor and provide a novel pathway by which synaptic Zn(2+) can regulate neuronal function.

  7. Probing cycle stability and reversibility in thermochemical energy storage – CaC_2O_4·H_2O as perfect match?

    International Nuclear Information System (INIS)

    Knoll, Christian; Müller, Danny; Artner, Werner; Welch, Jan M.; Werner, Andreas; Harasek, Michael; Weinberger, Peter

    2017-01-01

    Highlights: • CaC_2O_4·H_2O dehydration is fully reversible between 25 °C and 200 °C. • Isothermal cycling between hydrate and anhydrate phase can be triggered by the water vapour concentration. • High reaction rates and full reversibility demonstrated over 100 cycles. • Material shows no ageing effects or reactivity decrease. - Abstract: The dehydration and subsequent rehydration of calcium oxalate monohydrate has yet to find application in thermochemical energy storage. Unlike for many other salt hydrates, complete reversibility of the dehydration-rehydration reaction was observed. Additionally, it was found that the rehydration temperature is strongly affected by the water vapour concentration: Full reversibility is not only achieved at room-temperature, but, depending on the water vapour concentration, at up to 200 °C. This allows isothermal switching of the material between charging and discharging by a change of the H_2O-partial pressure. Cycle stability of the material was tested by a long-term stress experiment involving 100 charging and discharging cycles. No signs of material fatigue or reactivity loss were found. In-situ powder X-ray diffraction showed complete rehydration of the material within 300 s. The experimental findings indicate that the CaC_2O_4·H_2O/CaC_2O_4 system is perfectly suited for technical application as a thermochemical energy storage medium.

  8. Effects of Calcium Source on Biochemical Properties of Microbial CaCO3 Precipitation.

    Science.gov (United States)

    Xu, Jing; Du, Yali; Jiang, Zhengwu; She, Anming

    2015-01-01

    The biochemical properties of CaCO3 precipitation induced by Sporosarcina pasteurii, an ureolytic type microorganism, were investigated. Effects of calcium source on the precipitation process were examined, since calcium source plays a key role in microbiologically induced mineralization. Regardless of the calcium source type, three distinct stages in the precipitation process were identified by Ca(2+), NH4 (+), pH and cell density monitoring. Compared with stage 1 and 3, stage 2 was considered as the most critical part since biotic CaCO3 precipitation occurs during this stage. Kinetics studies showed that the microbial CaCO3 precipitation rate for calcium lactate was over twice of that for calcium nitrate, indicating that calcium lactate is more beneficial for the cell activity, which in turn determines urease production and CaCO3 precipitation. X-ray diffraction analysis confirmed the CaCO3 crystal as calcite, although scanning electron microscopy revealed a difference in crystal size and morphology if calcium source was different. The findings of this paper further suggest a promising application of microbiologically induced CaCO3 precipitation in remediation of surface and cracks of porous media, e.g., cement-based composites, particularly by using organic source of calcium lactate.

  9. Development of calcium-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in cultured neocortical neurons visualized by cobalt staining

    DEFF Research Database (Denmark)

    Jensen, J B; Schousboe, A; Pickering, D S

    1998-01-01

    The developmental expression of calcium (Ca2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors in cultured neocortical neurons was evaluated by using cobalt uptake, a histochemical method that identifies cells expressing Ca2+-permeable, non-N-methyl-D-aspartate...

  10. Synthetic, spectroscopic and structural studies on 4-aminobenzoate complexes of divalent alkaline earth metals: x-ray crystal structures of [[Mg(H2O)6] (4-aba)2].2H2O and [Ca(H2O)2(4-aba)2] (4-aba=4-aminobenzoate)

    International Nuclear Information System (INIS)

    Murugavel, Ramaswamy; Karambelkar, Vivek V.; Anantharaman, Ganapathi

    2000-01-01

    Reactions between MCl 2 .nH 2 O (M = Mg, Ca, Sr, and Ba) and 4-aminobenzoic acid (4-abaH) result in the formation of complexes [(Mg(H 2 O) 6 )(4-aba) 2 ) .2H 2 O (I), [Ca(4-aba) 2 (H2 O ) 2 ] (2), [Sr(4-aba) 2 (H2 O ) 2 ] (3), and [Ba(4-aba) 2 Cl] (4), respectively. The new compounds 1 and 2, as well as the previously reported 3 and 4 form an extended intra- and intermolecular hydrogen bonded network in the solid-state. The compounds have been characterized by elemental analysis, pH measurements, thermogravimetric studies, and IR, NMR, and UV-Vis spectroscopy. The solid state structures of the molecules 1 and 2 have been determined by single crystal x-ray diffraction studies. In the case of magnesium complex 1, the dipositively charged Mg cation is surrounded by six water molecules and the two 4-aminobenzoate ligands show no direct bonding to the metal ion. The calcium ion in 2 is octa-coordinated with direct coordination of the 4-aminobenzoate ligands to the metal ion. The Ca-Ca separation in the polymeric chain of 2 is 3.9047(5) A. (author)

  11. Iron mediates N-methyl-D-aspartate receptor-dependent stimulation of calcium-induced pathways and hippocampal synaptic plasticity.

    Science.gov (United States)

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

    2011-04-15

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

  12. Synthesis, bioactivity and preliminary biocompatibility studies of glasses in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2.

    Science.gov (United States)

    Tulyaganov, D U; Agathopoulos, S; Valerio, P; Balamurugan, A; Saranti, A; Karakassides, M A; Ferreira, J M F

    2011-02-01

    New compositions of bioactive glasses are proposed in the CaO-MgO-SiO(2)-Na(2)O-P(2)O(5)-CaF(2) system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO(4)) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts' cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C).

  13. Formation of ternary CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) complexes under neutral to weakly alkaline conditions.

    Science.gov (United States)

    Lee, Jun-Yeop; Yun, Jong-Il

    2013-07-21

    The chemical behavior of ternary Ca-UO2-CO3 complexes was investigated by using time-resolved laser fluorescence spectroscopy (TRLFS) in combination with EDTA complexation at pH 7-9. A novel TRLFS revealed two distinct fluorescence lifetimes of 12.7 ± 0.2 ns and 29.2 ± 0.4 ns for uranyl complexes which were formed increasingly dependent upon the calcium ion concentration, even though nearly indistinguishable fluorescence peak shapes and positions were measured for both Ca-UO2-CO3 complexes. For identifying the stoichiometric number of complexed calcium ions, slope analysis in terms of relative fluorescence intensity versus calcium concentration was employed in a combination with the complexation reaction of CaEDTA(2-) by adding EDTA. The formation of CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) was identified under given conditions and their formation constants were determined at I = 0.1 M Na/HClO4 medium, and extrapolated to infinitely dilute solution using specific ion interaction theory (SIT). As a result, the formation constants for CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) were found to be log β113(0) = 27.27 ± 0.14 and log β213(0) = 29.81 ± 0.19, respectively, providing that the ternary Ca-UO2-CO3 complexes were predominant uranium(vi) species at neutral to weakly alkaline pH in the presence of Ca(2+) and CO3(2-) ions.

  14. Late calcium EDTA rescues hippocampal CA1 neurons from global ischemia-induced death.

    Science.gov (United States)

    Calderone, Agata; Jover, Teresa; Mashiko, Toshihiro; Noh, Kyung-min; Tanaka, Hidenobu; Bennett, Michael V L; Zukin, R Suzanne

    2004-11-03

    Transient global ischemia induces a delayed rise in intracellular Zn2+, which may be mediated via glutamate receptor 2 (GluR2)-lacking AMPA receptors (AMPARs), and selective, delayed death of hippocampal CA1 neurons. The molecular mechanisms underlying Zn2+ toxicity in vivo are not well delineated. Here we show the striking finding that intraventricular injection of the high-affinity Zn2+ chelator calcium EDTA (CaEDTA) at 30 min before ischemia (early CaEDTA) or at 48-60 hr (late CaEDTA), but not 3-6 hr, after ischemia, afforded robust protection of CA1 neurons in approximately 50% (late CaEDTA) to 75% (early CaEDTA) of animals. We also show that Zn2+ acts via temporally distinct mechanisms to promote neuronal death. Early CaEDTA attenuated ischemia-induced GluR2 mRNA and protein downregulation (and, by inference, formation of Zn2+-permeable AMPARs), the delayed rise in Zn2+, and neuronal death. These findings suggest that Zn2+ acts at step(s) upstream from GluR2 gene downregulation and implicate Zn2+ in transcriptional regulation and/or GluR2 mRNA stability. Early CaEDTA also blocked mitochondrial release of cytochrome c and Smac/DIABLO (second mitochondria-derived activator of caspases/direct inhibitor of apoptosis protein-binding protein with low pI), caspase-3 activity (but not procaspase-3 cleavage), p75NTR induction, and DNA fragmentation. These findings indicate that CaEDTA preserves the functional integrity of the mitochondrial outer membrane and arrests the caspase death cascade. Late injection of CaEDTA at a time when GluR2 is downregulated and caspase is activated inhibited the delayed rise in Zn2+, p75NTR induction, DNA fragmentation, and cell death. The finding of neuroprotection by late CaEDTA administration has striking implications for intervention in the delayed neuronal death associated with global ischemia.

  15. 40 CFR 721.10012 - Manganate (MnO21-), calcium (2:1).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Manganate (MnO21-), calcium (2:1). 721... Substances § 721.10012 Manganate (MnO21-), calcium (2:1). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganate (MnO2 1 -), calcium (2:1) (PMN P...

  16. KChIP2 regulates the cardiac Ca2+ transient and myocyte contractility by targeting ryanodine receptor activity.

    Directory of Open Access Journals (Sweden)

    Drew M Nassal

    Full Text Available Pathologic electrical remodeling and attenuated cardiac contractility are featured characteristics of heart failure. Coinciding with these remodeling events is a loss of the K+ channel interacting protein, KChIP2. While, KChIP2 enhances the expression and stability of the Kv4 family of potassium channels, leading to a more pronounced transient outward K+ current, Ito,f, the guinea pig myocardium is unique in that Kv4 expression is absent, while KChIP2 expression is preserved, suggesting alternative consequences to KChIP2 loss. Therefore, KChIP2 was acutely silenced in isolated guinea pig myocytes, which led to significant reductions in the Ca2+ transient amplitude and prolongation of the transient duration. This change was reinforced by a decline in sarcomeric shortening. Notably, these results were unexpected when considering previous observations showing enhanced ICa,L and prolonged action potential duration following KChIP2 loss, suggesting a disruption of fundamental Ca2+ handling proteins. Evaluation of SERCA2a, phospholamban, RyR, and sodium calcium exchanger identified no change in protein expression. However, assessment of Ca2+ spark activity showed reduced spark frequency and prolonged Ca2+ decay following KChIP2 loss, suggesting an altered state of RyR activity. These changes were associated with a delocalization of the ryanodine receptor activator, presenilin, away from sarcomeric banding to more diffuse distribution, suggesting that RyR open probability are a target of KChIP2 loss mediated by a dissociation of presenilin. Typically, prolonged action potential duration and enhanced Ca2+ entry would augment cardiac contractility, but here we see KChIP2 fundamentally disrupts Ca2+ release events and compromises myocyte contraction. This novel role targeting presenilin localization and RyR activity reveals a significance for KChIP2 loss that reflects adverse remodeling observed in cardiac disease settings.

  17. New calcium-selective smart contrast agents for magnetic resonance imaging.

    Science.gov (United States)

    Verma, Kirti Dhingra; Forgács, Attila; Uh, Hyounsoo; Beyerlein, Michael; Maier, Martin E; Petoud, Stéphane; Botta, Mauro; Logothetis, Nikos K

    2013-12-23

    Calcium plays a vital role in the human body and especially in the central nervous system. Precise maintenance of Ca(2+) levels is very crucial for normal cell physiology and health. The deregulation of calcium homeostasis can lead to neuronal cell death and brain damage. To study this functional role played by Ca(2+) in the brain noninvasively by using magnetic resonance imaging, we have synthesized a new set of Ca(2+) -sensitive smart contrast agents (CAs). The agents were found to be highly selective to Ca(2+) in the presence of other competitive anions and cations in buffer and in physiological fluids. The structure of CAs comprises Gd(3+)-DO3A (DO3A=1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane) coupled to a Ca(2+) chelator o-amino phenol-N,N,O-triacetate (APTRA). The agents are designed to sense Ca(2+) present in extracellular fluid of the brain where its concentration is relatively high, that is, 1.2-0.8 mM. The determined dissociation constant of the CAs to Ca(2+) falls in the range required to sense and report changes in extracellular Ca(2+) levels followed by an increase in neural activity. In buffer, with the addition of Ca(2+) the increase in relaxivity ranged from 100-157%, the highest ever known for any T1-based Ca(2+)-sensitive smart CA. The CAs were analyzed extensively by the measurement of luminescence lifetime measurement on Tb(3+) analogues, nuclear magnetic relaxation dispersion (NMRD), and (17)O NMR transverse relaxation and shift experiments. The results obtained confirmed that the large relaxivity enhancement observed upon Ca(2+) addition is due to the increase of the hydration state of the complexes together with the slowing down of the molecular rotation and the retention of a significant contribution of the water molecules of the second sphere of hydration. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Investigation of CaO-CO₂ reaction kinetics by in-situ XRD using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Biasin, A.; Segre, C. U.; Salviulo, G.; Zorzi, F.; Strumendo, M. [Padova; (IIT)

    2015-02-05

    In this work, in-situ synchrotron radiation x-ray powder diffraction (SR-XRPD), performed at the Advanced Photon Source (APS) facilities of the Argonne National Laboratory, was applied to investigate the CaO–CO2 reaction. A set of CO2 absorption experiments were conducted in a high temperature reaction capillary with a controlled atmosphere (CO2 partial pressure of 1 bar), in the temperature range between 450 °C and 750 °C using CaO based sorbents obtained by calcination of commercial calcium carbonate. The evolution of the crystalline phases during CO2 uptake by the CaO solid sorbents was monitored for a carbonation time of 20 min as a function of the carbonation temperature and of the calcination conditions. The Rietveld refinement method was applied to estimate the calcium oxide conversion during the reaction progress and the average size of the initial (at the beginning of carbonation) calcium oxide crystallites. The measured average initial carbonation rate (in terms of conversion time derivative) of 0.280 s-1 (±13.2% standard deviation) is significantly higher than the values obtained by thermo-gravimetric analysis and reported thus far in the literature. Additionally, a dependence of the conversion versus time curves on the initial calcium oxide crystallite size was observed and a linear relationship between the initial CaO crystallite size and the calcium oxide final conversion was identified.

  19. The effects of 3,4-methylenedioxymethamphetamine (MDMA) on nicotinic receptors: Intracellular calcium increase, calpain/caspase 3 activation, and functional upregulation

    International Nuclear Information System (INIS)

    Garcia-Rates, Sara; Camarasa, Jordi; Sanchez-Garcia, Ana I.; Gandia, Luis; Escubedo, Elena; Pubill, David

    2010-01-01

    Previous work by our group demonstrated that homomeric α7 nicotinic acetylcholine receptors (nAChR) play a role in the neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA), as well as the binding affinity of this drug to these receptors. Here we studied the effect of MDMA on the activation of nAChR subtypes, the consequent calcium mobilization, and calpain/caspase 3 activation because prolonged Ca 2+ increase could contribute to cytotoxicity. As techniques, we used fluorimetry in Fluo-4-loaded PC12 cells and electrophysiology in Xenopus oocytes. MDMA produced a rapid and sustained increase in calcium without reaching the maximum effect induced by ACh. It also concentration-dependently inhibited the response induced by ACh, nicotine, and the specific α7 agonist PNU 282987 with IC 50 values in the low micromolar range. Similarly, MDMA induced inward currents in Xenopus oocytes transfected with human α7 but not with α4β2 nAChR and inhibited ACh-induced currents in both receptors in a concentration-dependent manner. The calcium response was inhibited by methyllycaconitine (MLA) and α-bungarotoxin but not by dihydro-β-erythroidine. These results therefore indicate that MDMA acts as a partial agonist on α7 nAChRs and as an antagonist on the heteromeric subtypes. Subsequently, calcium-induced Ca 2+ release from the endoplasmic reticulum and entry through voltage-operated calcium channels are also implicated as proved using specific antagonists. In addition, treatment with MDMA for 24 h significantly increased basal Ca 2+ levels and induced an increase in α-spectrin breakdown products, which indicates that calpain and caspase 3 were activated. These effects were inhibited by pretreatment with MLA. Moreover, pretreatment with MDMA induced functional upregulation of calcium responses to specific agonists of both heteromeric and α7 nAChR. Sustained calcium entry and calpain activation could favor the activation of Ca 2+ -dependent enzymes such as

  20. Beta-Estradiol Regulates Voltage-Gated Calcium Channels and Estrogen Receptors in Telocytes from Human Myometrium

    Directory of Open Access Journals (Sweden)

    Adela Banciu

    2018-05-01

    Full Text Available Voltage-gated calcium channels and estrogen receptors are essential players in uterine physiology, and their association with different calcium signaling pathways contributes to healthy and pathological conditions of the uterine myometrium. Among the properties of the various cell subtypes present in human uterine myometrium, there is increasing evidence that calcium oscillations in telocytes (TCs contribute to contractile activity and pregnancy. Our study aimed to evaluate the effects of beta-estradiol on voltage-gated calcium channels and estrogen receptors in TCs from human uterine myometrium and to understand their role in pregnancy. For this purpose, we employed patch-clamp recordings, ratiometric Fura-2-based calcium imaging analysis, and qRT-PCR techniques for the analysis of cultured human myometrial TCs derived from pregnant and non-pregnant uterine samples. In human myometrial TCs from both non-pregnant and pregnant uterus, we evidenced by qRT-PCR the presence of genes encoding for voltage-gated calcium channels (Cav3.1, Ca3.2, Cav3.3, Cav2.1, estrogen receptors (ESR1, ESR2, GPR30, and nuclear receptor coactivator 3 (NCOA3. Pregnancy significantly upregulated Cav3.1 and downregulated Cav3.2, Cav3.3, ESR1, ESR2, and NCOA3, compared to the non-pregnant condition. Beta-estradiol treatment (24 h, 10, 100, 1000 nM downregulated Cav3.2, Cav3.3, Cav1.2, ESR1, ESR2, GRP30, and NCOA3 in TCs from human pregnant uterine myometrium. We also confirmed the functional expression of voltage-gated calcium channels by patch-clamp recordings and calcium imaging analysis of TCs from pregnant human myometrium by perfusing with BAY K8644, which induced calcium influx through these channels. Additionally, we demonstrated that beta-estradiol (1000 nM antagonized the effect of BAY K8644 (2.5 or 5 µM in the same preparations. In conclusion, we evidenced the presence of voltage-gated calcium channels and estrogen receptors in TCs from non-pregnant and pregnant

  1. Beta-Estradiol Regulates Voltage-Gated Calcium Channels and Estrogen Receptors in Telocytes from Human Myometrium.

    Science.gov (United States)

    Banciu, Adela; Banciu, Daniel Dumitru; Mustaciosu, Cosmin Catalin; Radu, Mihai; Cretoiu, Dragos; Xiao, Junjie; Cretoiu, Sanda Maria; Suciu, Nicolae; Radu, Beatrice Mihaela

    2018-05-09

    Voltage-gated calcium channels and estrogen receptors are essential players in uterine physiology, and their association with different calcium signaling pathways contributes to healthy and pathological conditions of the uterine myometrium. Among the properties of the various cell subtypes present in human uterine myometrium, there is increasing evidence that calcium oscillations in telocytes (TCs) contribute to contractile activity and pregnancy. Our study aimed to evaluate the effects of beta-estradiol on voltage-gated calcium channels and estrogen receptors in TCs from human uterine myometrium and to understand their role in pregnancy. For this purpose, we employed patch-clamp recordings, ratiometric Fura-2-based calcium imaging analysis, and qRT-PCR techniques for the analysis of cultured human myometrial TCs derived from pregnant and non-pregnant uterine samples. In human myometrial TCs from both non-pregnant and pregnant uterus, we evidenced by qRT-PCR the presence of genes encoding for voltage-gated calcium channels (Cav3.1, Ca3.2, Cav3.3, Cav2.1), estrogen receptors (ESR1, ESR2, GPR30), and nuclear receptor coactivator 3 (NCOA3). Pregnancy significantly upregulated Cav3.1 and downregulated Cav3.2, Cav3.3, ESR1, ESR2, and NCOA3, compared to the non-pregnant condition. Beta-estradiol treatment (24 h, 10, 100, 1000 nM) downregulated Cav3.2, Cav3.3, Cav1.2, ESR1, ESR2, GRP30, and NCOA3 in TCs from human pregnant uterine myometrium. We also confirmed the functional expression of voltage-gated calcium channels by patch-clamp recordings and calcium imaging analysis of TCs from pregnant human myometrium by perfusing with BAY K8644, which induced calcium influx through these channels. Additionally, we demonstrated that beta-estradiol (1000 nM) antagonized the effect of BAY K8644 (2.5 or 5 µM) in the same preparations. In conclusion, we evidenced the presence of voltage-gated calcium channels and estrogen receptors in TCs from non-pregnant and pregnant human uterine

  2. Ceramic powders of CaZrO3. Preparation and sintering

    International Nuclear Information System (INIS)

    Tamborenea, S.; Coronel, A.; Mazzoni, A.D.; Aglietti, E.F.

    2003-01-01

    Calcium zirconate (CaZrO 3 ) is a compound belonging to the perovskite family of the A 2+ B 4+ O 3 6- type with orthorhombic crystalline structure (distorted perovskite).CaZrO 3 is used in the manufacture of sensors of oxygen, humidity, hydrogen and hydrocarbides.Additionally, it is also being studied for the manufacture of thermistors.The calcium zirconate preparation by solid state reaction from stoichiometric mixtures of CaCO 3 and ZrO 2 is studied.The formation reaction was followed by thermal analysis techniques (DTA-TG-DTG) and X-ray diffraction (XRD).The different behaviour of the mixtures was studied according to the milling type employed.It could be observed a shift of some peaks, mainly of TG (gravimetry) with a tendency to a temperature decrease.These changes are mainly influenced by the amorphization effects on the carbonate and by the mixing caused by the milling type used.The powder (CaZrO 3 ) was isostatically pressed obtaining then green densities of 50% of the theoretical one.Sintering was made in air between 1300 and 1600degC at times between 0 and 240.Densities reached were between 90 and 95% increasing with the temperature and the sintering time

  3. Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

    Science.gov (United States)

    Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

    2017-06-01

    We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

  4. Role of post-translational modifications on structure, function and pharmacology of class C G protein-coupled receptors

    DEFF Research Database (Denmark)

    Nørskov-Lauritsen, Lenea; Bräuner-Osborne, Hans

    2015-01-01

    taste receptors (T1R1-3), one calcium-sensing (CaS) receptor, one GPCR, class C, group 6, subtype A (GPRC6) receptor, and seven orphan receptors. G protein-coupled receptors undergo a number of post-translational modifications, which regulate their structure, function and/or pharmacology. Here, we...

  5. Pd- and Ca-doped iron oxide for ethanol vapor sensing

    International Nuclear Information System (INIS)

    Neri, G.; Bonavita, A.; Ipsale, S.; Rizzo, G.; Baratto, C.; Faglia, G.; Sberveglieri, G.

    2007-01-01

    Iron oxide thin films doped with Ca and Pd, prepared by a liquid-phase deposition method (LPD) from aqueous solution, have been investigated as potential ethanol gas sensors. SEM and XRD analyses were used to characterize Fe 2 O 3 LPD films. Hematite (α-Fe 2 O 3 ), having an average crystallite size in the range between 20 and 30 nm, was the only crystalline phase detected on all undoped and doped films. The electrical response towards ethanol (100-500 ppm) has been studied in the temperature range of 300-500 deg. C. Both Ca and Pd promoters have shown a positive effect on the sensitivity of Fe 2 O 3 films at the lower temperature investigated, whereas at higher temperature the undoped Fe 2 O 3 film has shown better performances. The sensing properties of undoped and doped Fe 2 O 3 thin films towards different interfering gases like NO 2 , CO and NH 3 have been also investigated, showing that the selectivity to ethanol benefits of the Ca addition

  6. Influence of relation CaO/SiO{sub 2} mixtures of anhydrous cement and mineral additives on the formation of CSH and combat the retrogression; Influencia da relacao CaO/SiO{sub 2} de misturas anidras de cimento e aditivos minerais na formacao do C-S-H e no combate a retrogressao

    Energy Technology Data Exchange (ETDEWEB)

    Anjos, Marcos A.S. [Instituto Federal de Educacao, Ciencia e Tecnologia do Rio Grande do Norte (IFRN), Natal, RN (Brazil); Martinelli, Antonio E.; Melo, Dulce M.A.; Souza, Pablo P.D. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil); Renovato, Tiago

    2012-07-01

    Temperatures above de 110 deg C cause cracks in the cement placed on the annular, and lost of hydraulic insulation; this crack is occasioned by the phenomenon of retrogression of the compressive resistance due to the conversion of the hydrated calcium silicate in phases calcium-rich, caused by the high temperatures in the wells. This paper presents the results of an experimental study aimed to investigate the influence of the molar ratio of different mixtures CaO/SiO{sub 2} Portland cement (CP) and minerals additives in the formation of CSH and retrogression of cement slurries subjected to high temperature and pressure. For both cement slurries were formulated with the addition of sugarcane biomass waste, silica flour and metakaolin in different concentrations of additives. The results of compressive strength and XRD showed that the use of cement slurries with molar ratio CaO/SiO{sub 2} near one can minimize the effect of retrogression when pulps are subjected to temperatures of 280 deg C and 17.2 MPa. (author)

  7. Glucose-Dependent Insulin Secretion in Pancreatic β-Cell Islets from Male Rats Requires Ca2+ Release via ROS-Stimulated Ryanodine Receptors.

    Directory of Open Access Journals (Sweden)

    Paola Llanos

    Full Text Available Glucose-stimulated insulin secretion (GSIS from pancreatic β-cells requires an increase in intracellular free Ca2+ concentration ([Ca2+]. Glucose uptake into β-cells promotes Ca2+ influx and reactive oxygen species (ROS generation. In other cell types, Ca2+ and ROS jointly induce Ca2+ release mediated by ryanodine receptor (RyR channels. Therefore, we explored here if RyR-mediated Ca2+ release contributes to GSIS in β-cell islets isolated from male rats. Stimulatory glucose increased islet insulin secretion, and promoted ROS generation in islets and dissociated β-cells. Conventional PCR assays and immunostaining confirmed that β-cells express RyR2, the cardiac RyR isoform. Extended incubation of β-cell islets with inhibitory ryanodine suppressed GSIS; so did the antioxidant N-acetyl cysteine (NAC, which also decreased insulin secretion induced by glucose plus caffeine. Inhibitory ryanodine or NAC did not affect insulin secretion induced by glucose plus carbachol, which engages inositol 1,4,5-trisphosphate receptors. Incubation of islets with H2O2 in basal glucose increased insulin secretion 2-fold. Inhibitory ryanodine significantly decreased H2O2-stimulated insulin secretion and prevented the 4.5-fold increase of cytoplasmic [Ca2+] produced by incubation of dissociated β-cells with H2O2. Addition of stimulatory glucose or H2O2 (in basal glucose to β-cells disaggregated from islets increased RyR2 S-glutathionylation to similar levels, measured by a proximity ligation assay; in contrast, NAC significantly reduced the RyR2 S-glutathionylation increase produced by stimulatory glucose. We propose that RyR2-mediated Ca2+ release, induced by the concomitant increases in [Ca2+] and ROS produced by stimulatory glucose, is an essential step in GSIS.

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

    Science.gov (United States)

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

    2014-09-11

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

  9. 40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214, CAS...

  10. MicroRNA-145 suppresses ROS-induced Ca{sup 2+} overload of cardiomyocytes by targeting CaMKIIδ

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Min-Ji [Cardiovascular Research Institute, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Jang, Jin-Kyung [College of Pharmacy, Sookmyung Women’s University, 52 HyoChangWon-Gil, Yongsan-ku, Seoul 140-742 (Korea, Republic of); Ham, Onju; Song, Byeong-Wook; Lee, Se-Yeon [Cardiovascular Research Institute, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Lee, Chang Yeon; Park, Jun-Hee [Department of Integrated Omics for Biomedical Sciences, Graduate School, Yonsei University, 50 Yonsei-ro, Seodamun-gu, Seoul 120-759 (Korea, Republic of); Lee, Jiyun; Seo, Hyang-Hee [Cardiovascular Research Institute, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Choi, Eunhyun [Severance Integrative Research Institute for Cerebral and Cardiovascular Disease, Yonsei University Health System, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Jeon, Woo-min [Department of Animal Resource, Sahmyook University, Seoul 139-742 (Korea, Republic of); Hwang, Hye Jin [Cardiovascular Research Institute, Yonsei University College of Medicine, 250 Seongsanno, Seodamun-gu, Seoul 120-752 (Korea, Republic of); Shin, Hyun-Taek [College of Pharmacy, Sookmyung Women’s University, 52 HyoChangWon-Gil, Yongsan-ku, Seoul 140-742 (Korea, Republic of); and others

    2013-06-14

    Highlights: •CaMKIIδ mediates H{sub 2}O{sub 2}-induced Ca{sup 2+} overload in cardiomyocytes. •miR-145 can inhibit Ca{sup 2+} overload. •A luciferase assay confirms that miR-145 functions as a CaMKIIδ-targeting miRNA. •Overexpression of miR-145 regulates CaMKIIδ-related genes and ameliorates apoptosis. -- Abstract: A change in intracellular free calcium (Ca{sup 2+}) is a common signaling mechanism of reperfusion-induced cardiomyocyte death. Calcium/calmodulin dependent protein kinase II (CaMKII) is a critical regulator of Ca{sup 2+} signaling and mediates signaling pathways responsible for functions in the heart including hypertrophy, apoptosis, arrhythmia, and heart disease. MicroRNAs (miRNA) are involved in the regulation of cell response, including survival, proliferation, apoptosis, and development. However, the roles of miRNAs in Ca{sup 2+}-mediated apoptosis of cardiomyocytes are uncertain. Here, we determined the potential role of miRNA in the regulation of CaMKII dependent apoptosis and explored its underlying mechanism. To determine the potential roles of miRNAs in H{sub 2}O{sub 2}-mediated Ca{sup 2+} overload, we selected and tested 6 putative miRNAs that targeted CaMKIIδ, and showed that miR-145 represses CaMKIIδ protein expression and Ca{sup 2+} overload. We confirmed CaMKIIδ as a direct downstream target of miR-145. Furthermore, miR-145 regulates Ca{sup 2+}-related signals and ameliorates apoptosis. This study demonstrates that miR-145 regulates reactive oxygen species (ROS)-induced Ca{sup 2+} overload in cardiomyocytes. Thus, miR-145 affects ROS-mediated gene regulation and cellular injury responses.

  11. Ontogenic and sexual differences in pituitary GnRH receptors and intracellular Ca2+ mobilization induced by GnRH.

    Science.gov (United States)

    Lacau-Mengido, I M; González Iglesias, A; Lux-Lantos, V; Libertun, C; Becú-Villalobos, D

    1998-04-01

    a decrease in the magnitude of intracellular, Ca2+ mobilization induced by GnRH (10(-8) to 10(-10) M) from 15-30 d of age, even though the concentration of GnRH receptors did not change in the same period. In conclusion, the present results suggest that high sensitivity to GnRH, which has been described in the female infantile rat, may be related to elevated concentration of hypophyseal receptors coupled to an increase of intracellular calcium response to GnRH, both parameters decreasing as the rat matures. In males, the greater sensitivity that has been described for GnRH at 30 d in comparison to 15 d is paralleled by an increase in the total number of GnRH receptors per pituitary (and not in their concentration), but not in an increase in the magnitude of Ca2+ mobilization induced by GnRH. On the other hand, neonatal sexual organization of the hypothalamus is involved in the differential expression of GnRH receptors, but does not modulate mobilization of intracellular Ca2+ induced by the decapeptide.

  12. Calcium titanate (CaTiO{sub 3}) dielectrics prepared by plasma spray and post-deposition thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ctibor, Pavel [Materials Engineering Department, Institute of Plasma Physics ASCR, v.v.i., Za Slovankou 3, Prague 8 (Czech Republic); Kotlan, Jiri, E-mail: kotlan@ipp.cas.cz [Materials Engineering Department, Institute of Plasma Physics ASCR, v.v.i., Za Slovankou 3, Prague 8 (Czech Republic); Department of Electrotechnology, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Prague 6 (Czech Republic); Pala, Zdenek [Materials Engineering Department, Institute of Plasma Physics ASCR, v.v.i., Za Slovankou 3, Prague 8 (Czech Republic); Sedlacek, Josef [Department of Electrotechnology, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Prague 6 (Czech Republic); Hajkova, Zuzana; Grygar, Tomas Matys [Institute of Inorganic Chemistry ASCR, v.v.i., Husinec-Rez 1001, Rez (Czech Republic)

    2015-12-15

    Highlights: • Calcium titanate was sprayed by two different plasma spray systems. • Significant improvement of dielectric properties after annealing was observed. • Calcium titanate self-supporting parts can be fabricated by plasma spraying. - Abstract: This paper studies calcium titanate (CaTiO{sub 3}) dielectrics prepared by plasma spray technology. A water stabilized plasma gun (WSP) as well as a widely used gas stabilized plasma gun (GSP) were employed in this study to deposit three sample sets at different spray conditions. Prepared specimens were annealed in air at atmospheric pressure for 2 h at various temperatures from 530 to 1170 °C. X-ray diffraction (XRD), Raman spectroscopy and porosity measurements were used for sample characterization. Dielectric spectroscopy was applied to obtain relative permittivity, conductivity and loss factor frequency dependence. Band gap energy was estimated from reflectance measurements. The work is focused on the explanation of changes in microstructure and properties of a plasma sprayed deposit after thermal annealing. Obtained results show significant improvement of dielectric properties after thermal annealing.

  13. Preparation of 45 Ca (HDEHP)n and (C8H15O2)2 samples for liquid scintillation counting, compared to 45CaCl2 results

    International Nuclear Information System (INIS)

    Rodriguez Barquero, L.; Los Arcos Merino, J.M.; Grau Malonda, A.

    1994-01-01

    A procedure for preparation of liquid scintillation counting organic samples of the Di-2-ethylhexyl phosphate calcium complex and the 2-ethyhexanoate calcium salt, labelled with ''45 Ca, is described. The chemical quench, the counting stability and spectral evolution of both compounds is studied in six scintillators, Toluene, Toluene-alcohol, Dioxane-napthalhene, Hisafe II, Ultima-Gold and Instagel, and compared to results obtained from a commercial solution of ''45 CaCl 2

  14. Synthesis, characterization and in vitro bioactivity of sol-gel-derived SiO2-CaO-P2O5-MgO bioglass

    International Nuclear Information System (INIS)

    Saboori, A.; Rabiee, M.; Moztarzadeh, F.; Sheikhi, M.; Tahriri, M.; Karimi, M.

    2009-01-01

    In this study, the synthesis of SiO 2 -CaO-P 2 O 5 -MgO bioactive glass was performed by the sol-gel method. Sol-gel-derived bioglass material was produced both in powder and in discs form by uniaxial pressing, followed by sintering at 700 deg. C. The obtained material was evaluated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses. The biocompatibility evaluation of the formed glass was assessed through in vitro cell culture [alkaline phosphatase (AP) activity of osteoblasts] experiments and immersion studies in simulated body fluid (SBF) for different time intervals while monitoring the pH changes and the concentration of calcium, phosphorus and magnesium in the SBF medium. The SEM, XRD and FTIR studies were conducted before and after soaking of the material in SBF. At first, an amorphous calcium phosphate was formed; after 7 days this surface consisted of deposited crystalline apatite. The present investigation also revealed that the sol-gel derived quaternary bioglass system has the ability to support the growth of human fetal osteoblastic cells (hFOB 1.19). Finally, this material proved to be non-toxic and compatible for the proposed work in segmental defects in the goat model in vivo

  15. Aberrant Splicing Induced by Dysregulated Rbfox2 Produces Enhanced Function of CaV1.2 Calcium Channel and Vascular Myogenic Tone in Hypertension.

    Science.gov (United States)

    Zhou, Yingying; Fan, Jia; Zhu, Huayuan; Ji, Li; Fan, Wenyong; Kapoor, Isha; Wang, Yue; Wang, Yuan; Zhu, Guoqing; Wang, Juejin

    2017-12-01

    Calcium influx from activated voltage-gated calcium channel Ca V 1.2 in vascular smooth muscle cells is indispensable for maintaining myogenic tone and blood pressure. The function of Ca V 1.2 channel can be optimized by alternative splicing, one of post-transcriptional modification mechanisms. The splicing factor Rbfox2 is known to regulate the Ca V 1.2 pre-mRNA alternative splicing events during neuronal development. However, Rbfox2's roles in modulating the key function of vascular Ca V 1.2 channel and in the pathogenesis of hypertension remain elusive. Here, we report that the proportion of Ca V 1.2 channels with alternative exon 9* is increased by 10.3%, whereas that with alternative exon 33 is decreased by 10.5% in hypertensive arteries. Surprisingly, the expression level of Rbfox2 is increased ≈3-folds, presumably because of the upregulation of a dominant-negative isoform of Rbfox2. In vascular smooth muscle cells, we find that knockdown of Rbfox2 dynamically increases alternative exon 9*, whereas decreases exon 33 inclusion of Ca V 1.2 channels. By patch-clamp studies, we show that diminished Rbfox2-induced alternative splicing shifts the steady-state activation and inactivation curves of vascular Ca V 1.2 calcium channel to hyperpolarization, which makes the window current potential to more negative. Moreover, siRNA-mediated knockdown of Rbfox2 increases the pressure-induced vascular myogenic tone of rat mesenteric artery. Taken together, our data indicate that Rbfox2 modulates the functions of vascular Ca V 1.2 calcium channel by dynamically regulating the expressions of alternative exons 9* and 33, which in turn affects the vascular myogenic tone. Therefore, our work suggests a key role for Rbfox2 in hypertension, which provides a rational basis for designing antihypertensive therapies. © 2017 American Heart Association, Inc.

  16. Effect of titanium and calcium oxide additions on Zr2O2 polymorphism during Al2O3+Zr2O2 mixture fusion

    International Nuclear Information System (INIS)

    Gladkov, V.E.; Zhekhanova, N.B.; Fotiev, A.A.; Viktorov, V.V.; Ivashinnikov, V.T.; Zubov, A.S.

    1985-01-01

    The effect of titanium and calcium containing additions introduced into the Al 2 O 3 +ZrO 2 melt on the phase composition and temperature ranges of ZrO 2 polymorphous transformation in the material is investigated. It is shown that introducing sponge titanium into the 70Al 2 O 3 +30ZrO 2 prepared composition melt (mass. %) with its subsequent intensive cooling one can conserve upto room temperatures 50-70% of ZrO 2 metastable tetragonal modification and therefore reduce the volume changes causing metal cracking. Calcium oxide doping stabilizes the ZrO 2 cubic modification and reduces α-Al 2 O 3 content due to formation of aluminates

  17. The FERONIA Receptor Kinase Maintains Cell-Wall Integrity during Salt Stress through Ca2+ Signaling.

    Science.gov (United States)

    Feng, Wei; Kita, Daniel; Peaucelle, Alexis; Cartwright, Heather N; Doan, Vinh; Duan, Qiaohong; Liu, Ming-Che; Maman, Jacob; Steinhorst, Leonie; Schmitz-Thom, Ina; Yvon, Robert; Kudla, Jörg; Wu, Hen-Ming; Cheung, Alice Y; Dinneny, José R

    2018-03-05

    Cells maintain integrity despite changes in their mechanical properties elicited during growth and environmental stress. How cells sense their physical state and compensate for cell-wall damage is poorly understood, particularly in plants. Here we report that FERONIA (FER), a plasma-membrane-localized receptor kinase from Arabidopsis, is necessary for the recovery of root growth after exposure to high salinity, a widespread soil stress. The extracellular domain of FER displays tandem regions of homology with malectin, an animal protein known to bind di-glucose in vitro and important for protein quality control in the endoplasmic reticulum. The presence of malectin-like domains in FER and related receptor kinases has led to widespread speculation that they interact with cell-wall polysaccharides and can potentially serve a wall-sensing function. Results reported here show that salinity causes softening of the cell wall and that FER is necessary to sense these defects. When this function is disrupted in the fer mutant, root cells explode dramatically during growth recovery. Similar defects are observed in the mur1 mutant, which disrupts pectin cross-linking. Furthermore, fer cell-wall integrity defects can be rescued by treatment with calcium and borate, which also facilitate pectin cross-linking. Sensing of these salinity-induced wall defects might therefore be a direct consequence of physical interaction between the extracellular domain of FER and pectin. FER-dependent signaling elicits cell-specific calcium transients that maintain cell-wall integrity during salt stress. These results reveal a novel extracellular toxicity of salinity, and identify FER as a sensor of damage to the pectin-associated wall. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. 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 2CaO·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 2CaO·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.

  19. Brief communication: ikaite (CaCO3*6H2O) discovered in Arctic sea ice

    Science.gov (United States)

    Dieckmann, G. S.; Nehrke, G.; Uhlig, C.; Göttlicher, J.; Gerland, S.; Granskog, M. A.; Thomas, D. N.

    2010-02-01

    We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3*6H2O) in sea ice from the Arctic (Kongsfjorden, Svalbard). This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This finding is an important step in the quest to quantify its impact on the sea ice driven carbon cycle and should in the future enable improvement parametrization sea ice carbon models.

  20. Synaptically evoked Ca2+ release from intracellular stores is not influenced by vesicular zinc in CA3 hippocampal pyramidal neurones.

    Science.gov (United States)

    Evstratova, Alesya; Tóth, Katalin

    2011-12-01

    The co-release of neuromodulatory substances in combination with classic neurotransmitters such as glutamate and GABA from individual presynaptic nerve terminals has the capacity to dramatically influence synaptic efficacy and plasticity. At hippocampal mossy fibre synapses vesicular zinc is suggested to serve as a cotransmitter capable of regulating calcium release from internal stores in postsynaptic CA3 pyramidal cells. Here we investigated this possibility using combined intracellular ratiometric calcium imaging and patch-clamp recording techniques. In acute hippocampal slices a brief train of mossy fibre stimulation produced a large, delayed postsynaptic Ca(2+) wave that was spatially restricted to the proximal apical dendrites of CA3 pyramidal cells within stratum lucidum. This calcium increase was sensitive to intracellularly applied heparin indicating reliance upon release from internal stores and was triggered by activation of both group I metabotropic glutamate and NMDA receptors. Importantly, treatment of slices with the membrane-impermeant zinc chelator CaEDTA did not influence the synaptically evoked postsynaptic Ca(2+) waves. Moreover, mossy fibre stimulus evoked postsynaptic Ca(2+) signals were not significantly different between wild-type and zinc transporter 3 (ZnT3) knock-out animals. Considered together our data do not support a role for vesicular zinc in regulating mossy fibre evoked Ca(2+) release from CA3 pyramidal cell internal stores.

  1. Calcium phosphate–gold nanoparticles nanocomposite for protein adsorption and mediator-free H2O2 biosensor construction

    International Nuclear Information System (INIS)

    Xu Qin; Lu Guiju; Bian XiaoJun; Jin Gendi; Wang Wei; Hu Xiaoya; Wang Yang; Yang Zhanjun

    2012-01-01

    This work reports a new method for the preparation and application of a kind of biocompatible calcium phosphate–gold nanoparticles (Ca 3 (PO 4 ) 2 –AuNPs) nanocomposite. UV–vis spectroscopy and transmittance electron microscopy (TEM) have been used to monitor the formation process of the nanocomposite and to examine the interaction between calcium phosphate and gold nanoparticles (AuNPs). The nanocomposite has multiple sites and improved conductivity which make it suitable for the binding of proteins to construct electrochemical sensors. Myoglobin (Mb) adsorbed on the nanocomposite retained its native structure which was proved by Fourier transform infrared spectroscopy (FTIR). Direct electron transfer between the adsorbed Mb and the electrode was observed. Further results demonstrated that the adsorbed Mb has good electrocatalytic activity towards the reduction of H 2 O 2 in the absence of any mediator. Highlights: ► Using gelatin modified gold nanoparticles to prepare needle-like calcium phosphate. ► Calcium phosphate provides multiple sites for protein adsorption. ► Gold nanoparticles act as electron tunneling. ► Myoglobin adsorbed on the material showed direct electrochemistry and good catalysis.

  2. P2Y1 receptor antagonists mitigate oxygen and glucose deprivation‑induced astrocyte injury.

    Science.gov (United States)

    Guo, Hui; Liu, Zhong-Qiang; Zhou, Hui; Wang, Zhi-Ling; Tao, Yu-Hong; Tong, Yu

    2018-01-01

    The aim of the present study was to elucidate the effects of blocking the calcium signaling pathway of astrocytes (ASs) on oxygen and glucose deprivation (OGD)‑induced AS injury. The association between the changes in the concentrations of AS‑derived transmitter ATP and glutamic acid, and the changes in calcium signaling under the challenge of OGD were investigated. The cortical ASs of Sprague Dawley rats were cultured to establish the OGD models of ASs. The extracellular concentrations of ATP and glutamic acid in the normal group and the OGD group were detected, and the intracellular concentration of calcium ions (Ca2+) was detected. The effects of 2'‑deoxy‑N6‑methyl adenosine 3', 5'‑diphosphate diammonium salt (MRS2179), a P2Y1 receptor antagonist, on the release of calcium and glutamic acid of ASs under the condition of OGD were observed. The OGD challenge induced the release of glutamic acid and ATP by ASs in a time‑dependent manner, whereas elevation in the concentration of glutamic acid lagged behind that of the ATP and Ca2+. The concentration of Ca2+ inside ASs peaked 16 h after OGD, following which the concentration of Ca2+ was decreased. The effects of elevated release of glutamic acid by ASs when challenged by OGD may be blocked by MRS2179, a P2Y1 receptor antagonist. Furthermore, MRS2179 may significantly mitigate OGD‑induced AS injury and increase cell survival. The ASs of rats cultured in vitro expressed P2Y1 receptors, which may inhibit excessive elevation in the concentration of intracellular Ca2+. Avoidance of intracellular calcium overload and the excessive release of glutamic acid may be an important reason why MRS2179 mitigates OGD‑induced AS injury.

  3. Intercellular calcium signaling occurs between human osteoblasts and osteoclasts and requires activation of osteoclast P2X7 receptors

    DEFF Research Database (Denmark)

    Jørgensen, Niklas R; Henriksen, Zanne; Sørensen, Ole

    2002-01-01

    that human osteoclasts expressed functional P2Y1 receptors, but, unexpectedly, desensitization of P2Y1 did not block calcium signaling to osteoclasts. We also found that osteoclasts expressed functional P2X7 receptors and showed that pharmacological inhibition of these receptors blocked calcium signaling...

  4. Study the effect of sintering temperature on structural, microstructural and electromagnetic properties of 10% Ca-doped Mn_0_._6Zn_0_._4Fe_2O_4

    International Nuclear Information System (INIS)

    Rahaman, Md. D.; Dalim Mia, Md.; Khan, M.N.I.; Akther Hossain, A.K.M.

    2016-01-01

    Calcium doped manganese–zinc ferrite having the nominal composition Mn_0_._6_−_xCa_xZn_0_._4Fe_2O_4 (x=0.0, 0.1) were prepared via the conventional solid-state sintering method, which were sintered at 1150, 1200 and 1250 °C for 5 h. The microstructure and surface morphology were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscope (SEM). XRD patterns revealed the formation of pure spinel phase ferrites with α-Fe_2O_3 impurity phase. FTIR spectra showed two absorption bands (ν_1 and ν_2) attributed to stretching vibration of tetrahedral and octahedral complex Fe"3"+–O"2"−, respectively. SEM micrographs displayed non-homogeneous grains of polyhedral shape but with increased grain size along with the increase of sintering temperature. Pure and calcium doped samples exhibit the highest dielectric constant at 1250 °C. Calcium doped sample has lower dielectric constant as compared to the pristine sample which is attributed to the retardation in electron exchange mechanism caused by lockup among iron and calcium ion. The dielectric loss peaks in pristine sample is attributed to the hopping frequency of Fe"2"+/Fe"3"+ between the tetrahedral and octahedral sites nearly equal to the frequency of the applied field. Calcium doped sample exhibits improved AC conductivity compare to the undoped sample at 1200 °C and 1250 °C because the electron hopping between Fe"3"+ and Fe"2"+ increases as the migration of Fe"3"+ to the B-sites increases with the occupancy of Ca"2"+ in the A-sites. Complex impedance spectra revealed that the conduction process is mainly attributed due to the processes which are associated with the grain and grain boundary in pristine sample and in calcium doped sample is associated with the grain only at 1150 and 1200 °C. Calcium substituted sample has lower permeability than that of pristine sample because Ca"2"+ can segregate the grain boundaries and creates an insulating

  5. Crystallization kinetics of bioactive glasses in the ZnO-Na2O-CaO-SiO2 system.

    Science.gov (United States)

    Malavasi, Gianluca; Lusvardi, Gigliola; Pedone, Alfonso; Menziani, Maria Cristina; Dappiaggi, Monica; Gualtieri, Alessandro; Menabue, Ledi

    2007-08-30

    The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.68, where x is the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using both nonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na(2)CaSi(2)O(6) phase, whereas the Na(2)ZnSiO(4) crystalline phase is obtained from the Zn-rich glass, in addition to Na(2)CaSi(2)O(6). The activation energy (Ea) for the crystallization of the Na(2)O.CaO.2SiO(2) glass is 193 +/- 10 and 203 +/- 5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from the isothermal method is 1 at low temperature (530 degrees C), and its value increases linearly with temperature increase up to 2 at 607 degrees C. For the crystallization of Na(2)CaSi(2)O(6) from the Zn-containing glass, higher values of both the crystallization temperature (667 and 661 degrees C) and Ea (223 +/- 10 and 211 +/- 5 kJ/mol) have been found from the isothermal and nonisothermal methods, respectively. The Na(2)ZnSiO(4) crystalline phase crystallizes at lower temperature with respect to Na(2)CaSi(2)O(6), and the Ea value is 266 +/- 20 and 245 +/- 15 kJ/mol from the isothermal and nonisothermal methods, respectively. The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, it causes an increase of Ea for the Na diffusion process, determined using MD simulations, and consequently an overall increase of Ea for the crystallization process of Na(2)CaSi(2)O(6). Our results show good agreement between the Ea and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determination of the temperature

  6. Oxalic acid decreases calcium absorption in rats

    International Nuclear Information System (INIS)

    Weaver, C.M.; Martin, B.R.; Ebner, J.S.; Krueger, C.A.

    1987-01-01

    Calcium absorption from salts and foods intrinsically labeled with 45 Ca was determined in the rat model. Calcium bioavailability was nearly 10 times greater for low oxalate kale, CaCO 3 and CaCl 2 than from CaC 2 O 4 (calcium oxalate) and spinach (high in oxalates). Extrinsic and intrinsic labeling techniques gave a similar assessment of calcium bioavailability from kale but not from spinach

  7. Protein-induced satiation and the calcium-sensing receptor

    OpenAIRE

    Ojha,Utkarsh

    2018-01-01

    Utkarsh Ojha Faculty of Medicine, Imperial College School of Medicine, Imperial College London, London, UK Abstract: Obesity is a major global health issue. High-protein diets have been shown to be associated with weight loss and satiety. The precise mechanism by which protein-rich diets promote weight loss remains unclear. Evidence suggests amino acids, formed as a consequence of protein digestion, are sensed by specific receptors on L-cells in the gastrointestinal (GI) tract. These L-cells ...

  8. Oxygen-coupled Redox Regulation of the Skeletal Muscle Ryanodine Receptor/Ca2+ Release Channel (RyR1)

    Science.gov (United States)

    Sun, Qi-An; Wang, Benlian; Miyagi, Masaru; Hess, Douglas T.; Stamler, Jonathan S.

    2013-01-01

    In mammalian skeletal muscle, Ca2+ release from the sarcoplasmic reticulum (SR) through the ryanodine receptor/Ca2+-release channel RyR1 can be enhanced by S-oxidation or S-nitrosylation of separate Cys residues, which are allosterically linked. S-Oxidation of RyR1 is coupled to muscle oxygen tension (pO2) through O2-dependent production of hydrogen peroxide by SR-resident NADPH oxidase 4. In isolated SR (SR vesicles), an average of six to eight Cys thiols/RyR1 monomer are reversibly oxidized at high (21% O2) versus low pO2 (1% O2), but their identity among the 100 Cys residues/RyR1 monomer is unknown. Here we use isotope-coded affinity tag labeling and mass spectrometry (yielding 93% coverage of RyR1 Cys residues) to identify 13 Cys residues subject to pO2-coupled S-oxidation in SR vesicles. Eight additional Cys residues are oxidized at high versus low pO2 only when NADPH levels are supplemented to enhance NADPH oxidase 4 activity. pO2-sensitive Cys residues were largely non-overlapping with those identified previously as hyperreactive by administration of exogenous reagents (three of 21) or as S-nitrosylated. Cys residues subject to pO2-coupled oxidation are distributed widely within the cytoplasmic domain of RyR1 in multiple functional domains implicated in RyR1 activity-regulating interactions with the L-type Ca2+ channel (dihydropyridine receptor) and FK506-binding protein 12 as well as in “hot spot” regions containing sites of mutation implicated in malignant hyperthermia and central core disease. pO2-coupled disulfide formation was identified, whereas neither S-glutathionylated nor sulfenamide-modified Cys residues were observed. Thus, physiological redox regulation of RyR1 by endogenously generated hydrogen peroxide is exerted through dynamic disulfide formation involving multiple Cys residues. PMID:23798702

  9. Receptor model for the molecular basis of tissue selectivity of 1,4-dihydropyridine calcium channel drugs

    Science.gov (United States)

    Langs, David A.; Strong, Phyllis D.; Triggle, David J.

    1990-09-01

    Our analysis of the solid state conformations of nifedipine [dimethyl 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinecarboxylate] and its 1,4-dihydropyridine (1,4-DHP) analogues produced a cartoon description of the important interactions between these drugs and their voltage-dependent calcium channel receptor. In the present study a molecular-level detailed model of the 1,4-DHP receptor binding site has been built from the published amino acid sequence of the 215-1 subunit of the voltage-dependent calcium channel isolated from rabbit skeletal muscle transverse tubule membranes. The voltage-sensing component of the channel described in this work differs from others reported for the homologous sodium channel in that it incorporates a water structure and a staggered, rather than eclipsed, hydrogen bonded S4 helix conformation. The major recognition surfaces of the receptor lie in helical grooves on the S4 or voltagesensing α-helix that is positioned in the center of the bundle of transmembrane helices that define each of the four calcium channel domains. Multiple binding clefts defined by Arg-X-X-Arg-P-X-X-S `reading frames' exist on the S4 strand. The tissue selectivity of nifedipine and its analogues may arise, in part, from conservative changes in the amino acid residues at the P and S positions of the reading frame that define the ester-binding regions of receptors from different tissues. The crystal structures of two tissue-selective nifedipine analogues, nimodipine [isopropyl (2-methoxyethyl) 1,4-dihydro-2,6- dimethyl-4-(3-nitrophenyl)-3,5-pyridinecarboxylate] and nitrendipine [ethyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinecarboxylate] are reported. Nimodipine was observed to have an unusual ester side chain conformation that enhances the fit to the proposed ester-sensing region of the receptor.

  10. Qualidade de carambolas azedas cv. 'Golden Star' tratadas com CaCl2 por imersão e armazenadas sob refrigeração Quality of starfruit cv 'Golden Star' treated with CaCl2 and stored under refrigerated conditions

    Directory of Open Access Journals (Sweden)

    Leandro Camargo Neves

    2004-04-01

    Full Text Available No presente trabalho, avaliou-se o efeito de diferentes concentrações de CaCl2 aplicadas na pós-colheita de carambolas cv. 'Golden Star, durante o armazenamento refrigerado (AR. Os frutos colhidos fisiologicamente maturos foram selecionados pela ausência de defeitos e imersos em soluções de CaCl2, em diferentes concentrações, em temperatura ambiente (22 °C por 20 minutos. Após aplicação dos tratamentos T1 - controle (0% de CaCl2; T2 - CaCl2 a 1%; T3 - CaCl2 a 2%; T4 - CaCl2 a 3%, e T5 - CaCl2 a 4%, os frutos foram colocados em câmara frigorífica, por 35 dias, a 12 ± 0,5ºC e 95 ± 3%, e mais 3 dias a 22 ± 3°C e 72 ± 5% de umidade relativa (UR. 24 horas após a colheita e a cada sete dias, amostras foram retiradas da AR, mantidas por 12 horas em condições ambiente (22 ± 3°C e 72 ± 5% UR e analisadas quanto ao teor de cálcio na polpa, perda de massa fresca, coloração da epiderme, firmeza de polpa (FP, sólidos solúveis totais (SST, acidez total titulável (ATT e a ocorrência de distúrbios fisiológicos. Ao final do experimento, foi feita uma análise sensorial. Observou-se que os frutos imersos em solução de CaCl2 a 2% apresentaram menor perda de massa fresca e maior firmeza de polpa. As carambolas deste tratamento também não apresentaram manchas e podridões e foram preferidas pelos julgadores no teste de preferência. Os sólidos solúveis totais, a acidez total titulável e a coloraçãoo apresentaram diferença estatística entre os tratamentos. Na análise de teores de cálcio adsorvido pelos frutos, determinou-se que quanto, maior a concentração da solução de CaCl2 aplicada, maior a concentração de cálcio presente na polpa.In the present work were evaluated the effects of different CaCl2 concentrations applied after harvest on starfruit cv. Golden Star, during refrigerated storage (RS. The fruits were harvested at physiological maturity stage, selected free of defects and immersed for 20 minutes at

  11. Transcription factor CREB is involved in CaSR-mediated cytoskeleton gene expression.

    Science.gov (United States)

    Huang, Shuaishuai; Ren, Yu; Wang, Ping; Li, Yanyuan; Wang, Xue; Zhuang, Haihui; Fang, Rong; Wang, Yuduo; Liu, Ningsheng; Hehir, Michael; Zhou, Jeff X

    2015-03-01

    Our previous studies illustrated that a steady increase of intracellular calcium concentration ([Ca2+]i) was important for maintaining microtubules (MTs) rearrangement in apoptotic cells. However, little is known about the effect of calcium sensing receptor (CaSR)-mediated increase in [Ca2+]i on cytoskeleton gene expression. We examined the impact of taxol or CaSR agonist/antagonist on the regulation of [Ca2+]i concentration, cytoskeleton arrangement, phosphorylated CREB and cytoskeleton gene expressions in HeLa cells with dominant negative plasmid of CREB (PM). This study demonstrated that Gdcl3 (a specific CaSR agonist) evoked a rapid increase of [Ca2+]i, formed a rigid bundle of MTs which surrounded the nucleus and decreased the cytoskeleton gene expressions in HeLa cells. These effects were rescued by addition of NPS2390 (a specific CaSR antagonist). Moreover, CaSR activity affected cytoskeleton gene expression through transcription factor CREB. Histoscores of pCREB immunoreactivity in tissues of cervical adenocarcinoma, renal clear cell carcinoma, and diffuse large B-cell lymphoma were markedly increased compared with non malignant tissue. These data demonstrate, for the first time, that CaSR-mediated increase in [Ca2+]i probably modulate cytoskeleton organization and gene expression via transcription factor. © 2014 Wiley Periodicals, Inc.

  12. CaBr2 hydrolysis for HBr production using a direct sparging contactor

    International Nuclear Information System (INIS)

    Doctor, R.D.; Yang, J.; Panchal, Ch.B.; Lottes, St.A.; Lyczkowski, R.W.

    2010-01-01

    We investigated a novel, continuous hybrid cycle for hydrogen production employing both heat and electricity. Calcium bromide (CaBr 2 ) hydrolysis, which is endothermic, generates hydrogen bromide (HBr), and this is electrolysed to produce hydrogen. CaBr 2 hydrolysis at 1050 K is endothermic with a 181.5 KJ/mol heat of reaction and the free energy change is positive at 99.6 kJ/mol. What makes this hydrolysis reaction attractive is both its rate and the fact that well over half the thermodynamic requirements for water-splitting free energy of ΔG T = 285.8 KJ/mol are supplied at this stage using heat rather than electricity. These experiments provide support for a second order hydrolysis reaction in CaBr 2 forming a complex involving CaBr 2 and CaO and the system appears to be: 3CaBr 2 + H 2 O → (CaBr 2 ) 2 .CaO + 2HBr. This reaction is highly endothermic and the complex also includes some water of hydration. COMSOL TM multi-physics modelling of sparging steam into a calcium bromide melt guided the design of an experiment using a mullite tube (ID 70 mm) capable of holding 0.3-0.5 kg (1.5-2.5 10 -3 kmol) CaBr 2 forming a melt with a maximum 0.08 m depth. Half of the experiments employed packings. Sparging steam at a steam rate of 0.02-0.04 mol/mol of CaBr 2 per minute into this molten bath promptly yielded HBr in a stable operation that converted up to 19 mol% of the calcium bromide. The kinetic constant derived from the experimental data was kinetic constant was 2.17 10 -12 kmol s -1 m -2 MPa -1 for the hydrolysis reaction. (authors)

  13. Optochemokine Tandem for Light-Control of Intracellular Ca2.

    Directory of Open Access Journals (Sweden)

    Katrin Feldbauer

    Full Text Available An optochemokine tandem was developed to control the release of calcium from endosomes into the cytosol by light and to analyze the internalization kinetics of G-protein coupled receptors (GPCRs by electrophysiology. A previously constructed rhodopsin tandem was re-engineered to combine the light-gated Ca2+-permeable cation channel Channelrhodopsin-2(L132C, CatCh, with the chemokine receptor CXCR4 in a functional tandem protein tCXCR4/CatCh. The GPCR was used as a shuttle protein to displace CatCh from the plasma membrane into intracellular areas. As shown by patch-clamp measurements and confocal laser scanning microscopy, heterologously expressed tCXCR4/CatCh was internalized via the endocytic SDF1/CXCR4 signaling pathway. The kinetics of internalization could be followed electrophysiologically via the amplitude of the CatCh signal. The light-induced release of Ca2+ by tandem endosomes into the cytosol via CatCh was visualized using the Ca2+-sensitive dyes rhod2 and rhod2-AM showing an increase of intracellular Ca2+ in response to light.

  14. Hydroxyl and calcium ions diffusion from endodontic materials through roots of primary teeth - in vitro study Avaliação in vitro da difusão de íons Ca+2 e OH- de materiais endodônticos em dentes decíduos

    Directory of Open Access Journals (Sweden)

    Ana Cristina Gerent Petry Nunes

    2005-06-01

    Full Text Available The purpose of this research was to evaluate the diffusion of calcium (Ca+2 and hydroxyl (OH- ions from materials with a calcium hydroxide base - Ca(OH2 through the intact roots of deciduous teeth. This diffusion of ions is important for periapical healing. Forty-six deciduous teeth were selected and instrumented to their working length with #40 files. The teeth were washed during cleaning and shaping with a 1% sodium hypochlorite (NaOCl solution. The canals were dried with paper points. The teeth were divided into 4 groups based on the sealer type, with 10 specimens in each group. A fifth group of 6 teeth without sealer constituted the control group. The materials used as sealers were: Ca(OH2 paste associated to propylene glycol (CaPE thickened at the proportion of 2:1 w/v; UFSC (Federal University of Santa Catarina paste - a mixture of 0.3g of zinc oxide with 0.3g of Ca(OH2 with 0.2ml of olive oil 1:1 w/w; Vitapex® and Sealapex®. The coronal access was sealed with a glass ionomer after the root had been filled with each sealer. A one-third apical surface and foramen was hard-pressed with Araldite®. The teeth were stored individually in flasks containing saline solution at 37ºC and 100% humidity. The OH- and Ca+2 ions diffusion levels were determined using a pH meter and an atomic absorption spectrometer. Data were collected at 48 hours and at intervals of 7, 30, 45 and 60 days. Statistical analysis was performed using ANOVA to compare groups. In the pH evaluation, the CaPE group presented the largest OH- ions diffusion, which peaked at sixty days (p=0.0309, when compared to the other groups (pO objetivo desta pesquisa foi avaliar a difusão de íons Ca+2 e OH- de materiais endodônticos a base hidróxido de cálcio - Ca(OH2, através da raiz intacta de dentes decíduos. 46 dentes decíduos foram selecionados e instrumentados em seu comprimento de trabalho até a lima # 40, e irrigados durante o preparo com solução de hipoclorito de s

  15. Natural CaO-TiO2-SiO2 based ceramics

    Directory of Open Access Journals (Sweden)

    Jelena Pantić

    2011-06-01

    Full Text Available Lešnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method, the aim of this work was to study the structure of the sphene from the Lešnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lešnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.0021.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.0010.995 Si4+1.024 O2-5.

  16. Electrophysical properties of calcium vanadates

    International Nuclear Information System (INIS)

    Krasnenko, T.I.; Fotiev, A.A.

    1983-01-01

    Electrophysical properties of calcium vanadates are studied for the case of alteration of external parameters of the medium (PO 2 , T). It is lshown that structural transformations bring about changes in the nature of electrophysical properties of Ca 2 V 2 O 7 , Ca 3 (VO 4 ) 2 , this being the reason for charge redistribution in anion groupings. It is obvious, that the general conductivity of calcium methavanadate is mainly caused by ion transport. Ca(VO 3 ) 2 possesses amphoteric character of semiconducting properties: the type of conductivity changes from ''p'' to ''n'' with temperature increase. Polytherms of conductivity and sums of ion numbers of Ca 2 V 2 O 7 transition are given. It is established that calcium pyrovanadate has a mixed electron-ion conductivity

  17. Early-life seizures alter synaptic calcium-permeable AMPA receptor function and plasticity

    Science.gov (United States)

    Lippman-Bell, Jocelyn J.; Zhou, Chengwen; Sun, Hongyu; Feske, Joel S.; Jensen, Frances E.

    2016-01-01

    Calcium (Ca2+)-mediated1 signaling pathways are critical to synaptic plasticity. In adults, the NMDA glutamate receptor (NMDAR) represents a major route for activity-dependent synaptic Ca2+ entry. However, during neonatal development, when synaptic plasticity is high, many AMPA glutamate receptors (AMPARs) are also permeable to Ca2+ (CP-AMPAR) due to low GluA2 subunit expression, providing an additional route for activity- and glutamate-dependent Ca2+ influx and subsequent signaling. Therefore, altered hippocampal Ca2+ signaling may represent an age-specific pathogenic mechanism. We thus aimed to assess Ca2+ responses 48 hours after hypoxia-induced neonatal seizures (HS) in postnatal day (P)10 rats, a post-seizure time point at which we previously reported LTP attenuation. We found that Ca2+ responses were higher in brain slices from post-HS rats than in controls and this increase was CP-AMPAR-dependent. To determine whether synaptic CP-AMPAR expression was also altered post-HS, we assessed the expression of GluA2 at hippocampal synapses and the expression of long-term depression (LTD), which has been linked to the presence of synaptic GluA2. Here we report a decrease 48 hours after HS in synaptic GluA2 expression at synapses and LTD in hippocampal CA1. Given the potentially critical role of AMPAR trafficking in disease progression, we aimed to establish whether post-seizure in vivo AMPAR antagonist treatment prevented the enhanced Ca2+ responses, changes in GluA2 synaptic expression, and diminished LTD. We found that NBQX treatment prevents all three of these post-seizure consequences, further supporting a critical role for AMPARs as an age-specific therapeutic target. PMID:27521497

  18. Microstructure, Thermal, Mechanical, and Dielectric Properties of BaO-CaO-Al2O3-B2O3-SiO2 Glass-Ceramics

    Science.gov (United States)

    Li, Bo; Bian, Haibo; Fang, Yi

    2017-12-01

    BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) glass-ceramics were prepared via the method of controlled crystallization. The effect of CaO modification on the microstructure, phase evolution, as well as thermal, mechanical, and dielectric properties was investigated. XRD identified that quartz is the major crystal phase; cristobalite and bazirite are the minor crystal phases. Moreover, the increase of CaO could inhibit the phase transformation from quartz to cristobalite, but excessive CaO would increase the porosity of the ceramics. Additionally, with increasing the amount of CaO, the thermal expansion curve tends to be linear, and subsequently the CTE value decreases gradually, which is attributed to the decrease of cristobalite with high CTE and the formation of CaSiO3 with low CTE. The results indicated that a moderate amount of CaO helps attaining excellent mechanical, thermal, and dielectric properties, that is, the specimen with 9 wt% CaO sintered at 950 °C has a high CTE value (11.5 × 10-6/°C), a high flexural strength (165.7 MPa), and good dielectric properties (ɛr = 6.2, tanδ = 1.8 × 10-4, ρ = 4.6 × 1011 Ω•cm).

  19. Preparation of CaO/Fly ash as a catalyst inhibitor for transesterification process off palm oil in biodiesel production

    Science.gov (United States)

    Helwani, Z.; Fatra, W.; Saputra, E.; Maulana, R.

    2018-03-01

    A palm fly ash supported calcium oxide (CaO) catalyst was prepared and used in transesterification from off-grade palm oil for biodiesel production. The catalyst synthesized by loading CaO of calcium nitrate tetrahydrate (Ca(NO3)2.4H2O) into fly ash through impregnation method. The optimum catalyst preparation conditions were determined by influence of calcination temperature and weight ratio of Ca(NO3)2.4H2O and fly ash. Catalyst with highest catalytic activity was achieved when calcined at 800 °C and proportion of Ca(NO3)2.4H2O to fly ash is 80:20. Under the conditions of oil : methanol ratio of 1:6, catalyst dosage of 6 wt% and temperature of 70 °C for 2 h, the biodiesel yield reaches to 71.77%. CaO, SiO2, Ca(OH)2 and Ca2SiO4 were found in the catalyst through X-ray diffraction (XRD) while the basic strength of the catalyst H_ in the range 9.3 – 11. Surface area of the developed catalyst is 24.342 m2/g through Brunauer-Emmett-Teller (BET). Characteristics of biodiesel such as density, kinematic viscosity, acid value, flash point has been matched with standard for biodiesel specification of Indonesia.

  20. Large conductance Ca2+-activated K+ (BK channel: Activation by Ca2+ and voltage

    Directory of Open Access Journals (Sweden)

    RAMÓN LATORRE

    2006-01-01

    Full Text Available Large conductance Ca2+-activated K+ (BK channels belong to the S4 superfamily of K+ channels that include voltage-dependent K+ (Kv channels characterized by having six (S1-S6 transmembrane domains and a positively charged S4 domain. As Kv channels, BK channels contain a S4 domain, but they have an extra (S0 transmembrane domain that leads to an external NH2-terminus. The BK channel is activated by internal Ca2+, and using chimeric channels and mutagenesis, three distinct Ca2+-dependent regulatory mechanisms with different divalent cation selectivity have been identified in its large COOH-terminus. Two of these putative Ca2+-binding domains activate the BK channel when cytoplasmic Ca2+ reaches micromolar concentrations, and a low Ca2+ affinity mechanism may be involved in the physiological regulation by Mg2+. The presence in the BK channel of multiple Ca2+-binding sites explains the huge Ca2+ concentration range (0.1 μM-100 μM in which the divalent cation influences channel gating. BK channels are also voltage-dependent, and all the experimental evidence points toward the S4 domain as the domain in charge of sensing the voltage. Calcium can open BK channels when all the voltage sensors are in their resting configuration, and voltage is able to activate channels in the complete absence of Ca2+. Therefore, Ca2+ and voltage act independently to enhance channel opening, and this behavior can be explained using a two-tiered allosteric gating mechanism.

  1. Shock Compression Response of Calcium Fluoride (CaF2)

    Science.gov (United States)

    Root, Seth

    2017-06-01

    The fluorite crystal structure is a textbook lattice that is observed for many systems, such as CaF2, Mg2 Si, and CeO2. Specifically, CaF2 is a useful material for studying the fluorite system because it is readily available as a single crystal. Under static compression, CaF2 is known to have at least three solid phases: fluorite, cotunnite, and a Ni2 In phase. Along the Hugoniot CaF2 undergoes a fluorite to cotunnite phase transition, however, at higher shock pressures it is unknown whether CaF2 undergoes another solid phase transition or melts directly from the cotunnite phase. In this work, we conducted planar shock compression experiments on CaF2 using Sandia's Z-machine and a two-stage light gun up to 900 GPa. In addition, we use density functional theory (DFT) based quantum molecular dynamics (QMD) simulations to provide insight into the CaF2 state along the Hugoniot. In collaboration with: Michael Desjarlais, Ray Lemke, Patricia Kalita, Scott Alexander, Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL850.

  2. Simultaneous decontamination of cross-polluted soils with heavy metals and PCBs using a nano-metallic Ca/CaO dispersion mixture.

    Science.gov (United States)

    Mallampati, Srinivasa Reddy; Mitoma, Yoshiharu; Okuda, Tetsuji; Sakita, Shogo; Simion, Cristian

    2014-01-01

    In the present work, we investigated the use of nano-metallic calcium (Ca) and calcium oxide (CaO) dispersion mixture for the simultaneous remediation of contaminated soils with both heavy metals (As, Cd, Cr, and Pb) and polychlorinated biphenyls (PCBs). Regardless of soil moisture content, nano-metallic Ca/CaO dispersion mixture achieved about 95-99% of heavy metal immobilization by a simple grinding process. During the same treatment, reasonable PCB hydrodechlorination efficiencies were obtained (up to 97%), though higher hydrodechlorination efficiency by preliminary drying of soil was observed.

  3. Determination of Mo- and Ca-isotope ratios in Ca100MoO4 crystal for AMoRE-I experiment

    Science.gov (United States)

    Karki, S.; Aryal, P.; Kim, H. J.; Kim, Y. D.; Park, H. K.

    2018-01-01

    The first phase of the AMoRE (Advanced Mo-based Rare process Experiment) is to search for neutrinoless double-beta decay of 100Mo with calcium molybdate (Ca100MoO4) crystals enriched in 100Mo and depleted in 48Ca using a cryogenic technique at Yangyang underground laboratory in Korea. It is important to know 100Mo- and 48Ca-isotope ratios in Ca100MoO4 crystal to estimate half-life of 100Mo decays and to 2 νββ background from 48Ca. We employed the ICP-MS (Inductive Coupled Plasma Mass Spectrometer) to measure 100Mo- and 48Ca-isotope ratios in Ca100MoO4 crystal. The measured results for 100Mo- and 48Ca-isotope ratios in the crystal are (94 . 6 ± 2 . 8) % and (0 . 00211 ± 0 . 00006) %, respectively, where errors are included both statistical and systematic uncertainties.

  4. EGF suppresses hydrogen peroxide induced Ca2+ influx by inhibiting L-type channel activity in cultured human corneal endothelial cells.

    Science.gov (United States)

    Mergler, Stefan; Pleyer, Uwe; Reinach, Peter; Bednarz, Jürgen; Dannowski, Haike; Engelmann, Katrin; Hartmann, Christian; Yousif, Tarik

    2005-02-01

    Endogenous generated hydrogen peroxide during eye bank storage limits viability. We determined in cultured human corneal endothelial cells (HCEC) whether: (1) this oxidant induces elevations in intracellular calcium concentration [Ca2+]i; (2) epidermal growth factor (EGF) medium supplementation has a protective effect against peroxide mediated rises in [Ca2+]i. Whereas pathophysiological concentrations of H2O2 (10 mM) induced irreversible large increases in [Ca2+]i, lower concentrations (up to 1 mM) had smaller effects, which were further reduced by exposure to either 5 microM nifedipine or EGF (10 ng ml(-1)). EGF had a larger protective effect against H2O2-induced rises in [Ca2+]i than nifedipine. In addition, icilin, the agonist for the temperature sensitive transient receptor potential protein, TRPM8, had complex dose-dependent effects (i.e. 10 and 50 microM) on [Ca2+]i. At 10 microM, it reversibly elevated [Ca2+]i whereas at 50 microM an opposite effect occurred suggesting complex effects of temperature on endothelial viability. Taken together, H2O2 induces rises in [Ca2+]i that occur through increases in Ca2+ permeation along plasma membrane pathways that include L-type Ca2+ channels as well as other EGF-sensitive pathways. As EGF overcomes H2O2-induced rises in [Ca2+]i, its presence during eye bank storage could improve the outcome of corneal transplant surgery.

  5. Effect of cerium oxide doping on the performance of CaO-based sorbents during calcium looping cycles.

    Science.gov (United States)

    Wang, Shengping; Fan, Shasha; Fan, Lijing; Zhao, Yujun; Ma, Xinbin

    2015-04-21

    A series of CaO-based sorbents were synthesized through a sol-gel method and doped with different amounts of CeO2. The sorbent with a Ca/Ce molar ratio of 15:1 showed an excellent absorption capacity (0.59 gCO2/g sorbent) and a remarkable cycle durability (up to 18 cycles). The admirable capture performance of CaCe-15 was ascribed to its special morphology formed by the doping of CeO2 and the well-distributed CeO2 particles. The sorbents doped with CeO2 possessed a loose shell-connected cross-linking structure, which was beneficial for the contact between CaO and CO2. CaO and CeO2 were dispersed homogeneously, and the existence of CeO2 also decreased the grain size of CaO. The well-dispersed CeO2, which could act as a barrier, effectively prevented the CaO crystallite from growing and sintering, thus the sorbent exhibited outstanding stability. The doping of CeO2 also improved the carbonation rate of the sorbent, resulting in a high capacity in a short period of time.

  6. A rice tonoplastic calcium exchanger, OsCCX2 mediates Ca2+/cation transport in yeast

    Science.gov (United States)

    Yadav, Akhilesh K.; Shankar, Alka; Jha, Saroj K.; Kanwar, Poonam; Pandey, Amita; Pandey, Girdhar K.

    2015-01-01

    In plant cell, cations gradient in cellular compartments is maintained by synergistic action of various exchangers, pumps and channels. The Arabidopsis exchanger family members (AtCCX3 and AtCCX5) were previously studied and belong to CaCA (calcium cation exchangers) superfamily while none of the rice CCXs has been functionally characterized for their cation transport activities till date. Rice genome encode four CCXs and only OsCCX2 transcript showed differential expression under abiotic stresses and Ca2+ starvation conditions. The OsCCX2 localized to tonoplast and suppresses the Ca2+ sensitivity of K667 (low affinity Ca2+ uptake deficient) yeast mutant under excess CaCl2 conditions. In contrast to AtCCXs, OsCCX2 expressing K667 yeast cells show tolerance towards excess Na+, Li+, Fe2+, Zn2+ and Co2+ and suggest its ability to transport both mono as well as divalent cations in yeast. Additionally, in contrast to previously characterized AtCCXs, OsCCX2 is unable to complement yeast trk1trk2 double mutant suggesting inability to transport K+ in yeast system. These finding suggest that OsCCX2 having distinct metal transport properties than previously characterized plant CCXs. OsCCX2 can be used as potential candidate for enhancing the abiotic stress tolerance in plants as well as for phytoremediation of heavy metal polluted soil. PMID:26607171

  7. 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.

  8. 21 CFR 184.1193 - Calcium chloride.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium chloride. 184.1193 Section 184.1193 Food... Specific Substances Affirmed as GRAS § 184.1193 Calcium chloride. (a) Calcium chloride (CaCl2·2H2O, CAS Reg. No. 10035-04-8) or anhydrous calcium chloride (CaCl2, CAS Reg. No. 10043-52-4) may be commercially...

  9. Comparative Study of Electronic Structure and Magnetic Properties of Osmate Double Perovskites: Ca2FeOsO6 versus Ca2Co(Ni)OsO6

    Science.gov (United States)

    Samanta, Kartik; Saha-Dasgupta, Tanusri

    2018-04-01

    Employing density functional theory, we study the trend in the electronic and magnetic properties of 3d-5d double perovskites, upon varying the 3d element for a fixed choice of 5d element, namely Ca2BOsO6 (B = Fe/Co/Ni). While all three compounds are reported to be ferrimagnets, the magnetic transition temperature of Ca2FeOsO6 is reported to be 2-2.4 times larger than that of Ca2CoOsO6 or Ca2NiOsO6. Our first-principles study provides microscopic insight into this trend. This trend is found to be caused by the downward shift in the position of d level energies of the B site element with respect to that of the Os t2g level upon moving across the 3d series from Fe to Co and Ni. This in turn changes the nominal valence of the Os ion from 5+ in Ca2FeOsO6 to 6+ in Ca2CoOsO6 and Ca2NiOsO6, resulting in differing superexchange paths between Ca2FeOsO6 and Ca2Co(Ni)OsO6, and additionally enabling the hybridization-mechanism-driven magnetism in Ca2FeOsO6. These together significantly enhance the magnetic transition temperature in Ca2FeOsO6 compared with that in Ca2Co(Ni)OsO6.

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

    African Journals Online (AJOL)

    Application of slow release calcium carbide (CaC2) to the soil are thought to improve plant growth and yield through the generation of acetylene, which inhibits nitrification, thereby reducing nitrogen losses which may be converted to physiologically significant concentrations of the plant growth regulator ethylene. The effects ...

  11. Solidification and Immobilization of Heavy metals in Soil using with nano-metallic Ca/CaO Dispersion Mixture

    Directory of Open Access Journals (Sweden)

    Mallampati S. R.

    2013-04-01

    Full Text Available In the present work, the use of nano-metallic calcium (Ca and calcium oxide (CaO dispersion mixture for the immobilization of heavy metals (As, Cd, Cr and Pb in soil was investigated. With simple grinding, 85-90% of heavy metals immobilization could be achieved, while it could be enhanced to 98-100% by grinding with the addition of nano-metallic Ca/CaO dispersion mixture. By SEM-EDS elemental maps as well as semi-quantitative analysis observed that the amount of As, Cd, Cr and Pb measurable on soil particle surface decreases after nano-metallic Ca/CaO treatment. The leachable heavy metals concentrations were reduced, to the concentration lower than the Japan soil elution standard regulatory threshold, i. e., < 0.01 mg/l for As, Cd and Pb and 0.05mg/l for Cr. Whereas, the effect of soil moisture and pH on heavy metals immobilization was not much influenced. The results suggest that nano-metallic Ca/CaO mixture is suitable to be used for the gentle immobilization of heavy metals contaminated soil at normal moisture conditions.

  12. Fracto- mechanoluminescence and thermoluminescence properties of orange-red emitting Eu3+ doped Ca2Al2SiO7 phosphors

    International Nuclear Information System (INIS)

    Tiwari, Geetanjali; Brahme, Nameeta; Sharma, Ravi; Bisen, D.P.; Sao, Sanjay K.; Khare, Ayush

    2017-01-01

    The suitability of nano-structured Ca 2 Al 2 SiO 7 :Eu 3+ phosphors for thermoluminescence and mechanoluminescence dosimeter were investigated. Europium doped di-calcium di-aluminum silicate phosphor was synthesised by the combustion assisted method and annealed at 1100 °C for 4 h in reducing and oxidizing environments. The prepared Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX), photoluminescence (PL) and decay characteristics. The phase structure of sintered phosphor has akermanite type which belongs to the tetragonal crystallography; this structure is a member of the melilite group and forms a layered compound. The chemical composition of the sintered Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was confirmed by EDX spectra. Mechanoluminescence (ML) and thermoluminescence (TL) studies revealed that the ML and TL intensity increases with activator concentration. Optimum ML was observed for the sample having 2 mol% of Eu ions. The TL intensity of Ca 2 Al 2 SiO 7 :Eu 3+ was recorded for different exposure times of γ -irradiation and it was observed that TL intensity is maximum for γ dose of 1770 Gy. The PL spectra indicated that Ca 2 Al 2 SiO 7 :Eu 3+ could be excited effectively by near ultraviolet (NUV) light and exhibited bright orange-red emission with excellent colour stability. CIE colour coordinates of the prepared Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was found suitable as orange-red light emitting phosphor with a CIE value of (x=0.6142, y=0.3849) and correlated colour temperature (CCT) is 1250 K. Therefore, it is considered to be a new promising orange-red emitting phosphor for white light emitting diode (LED) application.

  13. Study of solid state interactions in the systems ZnFe2O4 - CaO, ZnFe2O4 - MgO and zinc cake with CaO and MgO

    Directory of Open Access Journals (Sweden)

    Peltekov A.B.

    2013-01-01

    Full Text Available The solid state interactions of CaO and MgO with synthetic and industrial ZnFe2O4 (in zinc cake have been studied using chemical, XRD analysis and Mössbauer spectroscopy. The exchange reactions in the systems ZnFe2O4 - CaO and ZnFe2O4 - MgO have been investigated in the range of 850-1200ºC and duration up to 180 min. It has been established that Ca2+ and Mg2+ ions exchange Zn2+ in ferrite partially and the solubility of zinc in a 7% sulfuric acid solution increases. The possibilities for utilization of the obtained results in zinc hydrometallurgy have been discussed.

  14. Ca{sup 2+} ion sensing by a piperidin-4-one derivative and the effect of β-cyclodextrin complexation on the sensing

    Energy Technology Data Exchange (ETDEWEB)

    Sumithra, M.; Sivaraj, R.; Selvan, G. Tamil; Selvakumar, P. Mosae; Enoch, Israel V.M.V., E-mail: drisraelenoch@gmail.com

    2017-05-15

    In this paper, we report the turn-on fluorescence based Ca{sup 2+} ion sensing by an anthracene piperidin-4-one derivative. The compound is obtained using a simple two step synthesis. The compound is characterized using NMR and mass spectral methods. The host-guest complex formation of the compound with β-cyclodextrin is prepared and characterized using fluorescence and 2D ROESY spectroscopy. The compound forms the inclusion complex with a 1:1 stoichiometry. The structure of the host-guest complex is proposed. The Ca{sup 2+} ion selectivity of the compound in its free form and cyclodextrin-bound forms are studied. In both the forms, the piperidin-4-one derivative senses Ca{sup 2+} and in the case of the cyclodextrin encapsulated form it shows a better competitive binding of Ca{sup 2+} in the presence of other metal ions. - Highlights: •An anthracene iminoderivative of 3-methyl-2,6-diphenylpiperidin-4-one is synthesized. •The anthracene moiety of the compound is encapsulated by β-Cyclodextrin. •The compound senses Ca{sup 2+} ion both in water and β-CD media. •β-CD molecule does not interrupt the Ca{sup 2+} ion binding.

  15. Apo states of calmodulin and CaBP1 control CaV1 voltage-gated calcium channel function through direct competition for the IQ domain.

    Science.gov (United States)

    Findeisen, Felix; Rumpf, Christine H; Minor, Daniel L

    2013-09-09

    In neurons, binding of calmodulin (CaM) or calcium-binding protein 1 (CaBP1) to the CaV1 (L-type) voltage-gated calcium channel IQ domain endows the channel with diametrically opposed properties. CaM causes calcium-dependent inactivation and limits calcium entry, whereas CaBP1 blocks calcium-dependent inactivation (CDI) and allows sustained calcium influx. Here, we combine isothermal titration calorimetry with cell-based functional measurements and mathematical modeling to show that these calcium sensors behave in a competitive manner that is explained quantitatively by their apo-state binding affinities for the IQ domain. This competition can be completely blocked by covalent tethering of CaM to the channel. Further, we show that Ca(2+)/CaM has a sub-picomolar affinity for the IQ domain that is achieved without drastic alteration of calcium-binding properties. The observation that the apo forms of CaM and CaBP1 compete with each other demonstrates a simple mechanism for direct modulation of CaV1 function and suggests a means by which excitable cells may dynamically tune CaV activity. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

  16. Pharmacological analysis of calcium antagonist receptors

    International Nuclear Information System (INIS)

    Reynolds, I.J.

    1987-01-01

    This work focuses on two aspects of the action of calcium antagonist drugs, namely, the interaction of drugs with receptors for verapamil-like calcium antagonists, and the interactions of drugs with voltage-sensitive calcium fluxes in rat brain synaptosomes. From binding studies I have found that the ligand of choice for labeling the verapamil receptor is (-)[ 3 H]desmethoxy-verapamil. This drug labels potently, reversibly and stereoselectively two receptors in membranes prepared from rat brain and rabbit skeletal muscle tissues. In equilibrium studies dihydropyridine calcium antagonists interact in a non-competitive fashion, while many non-DHPs are apparently competitive. In-depth kinetic studies in skeletal muscle membranes indicate that the two receptors are linked in a negative heterotropic fashion, and that low-affinity binding of (-) [ 3 H]desmethoxy-verapamil may be to the diltiazem receptor. However, these studies were not able to distinguish between the hypothesis that diltiazem binds to spatially separate, allosterically coupled receptors, and the hypothesis that diltiazem binds to a subsite of the verapamil receptor

  17. Use of CaO as an activator for producing a price-competitive non-cement structural binder using ground granulated blast furnace slag

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Sik; Jun, Yubin; Lee, Changha, E-mail: clee@unist.ac.kr; Oh, Jae Eun, E-mail: ohjaeeun@unist.ac.kr

    2013-12-15

    The use of calcium oxide (CaO) demonstrates a superior potential for the activation of ground granulated blast furnace slag (GGBFS), and it produces a higher mechanical strength than calcium hydroxide [Ca(OH){sub 2}]. The mechanical strength differences between CaO- and Ca(OH){sub 2}-activated GGBFS binders are explored using isothermal calorimetry, powder X-ray diffraction, thermogravimetric and differential thermal analysis (TGA and DTA) as well as compressive strength testing. Calcium silicate hydrate (C–S–H), Ca(OH){sub 2} and a hydrotalcite-like phase are found as reaction products in all samples. The TGA and DTA results indicate that the use of CaO produces more C–S–H, although this is not likely to be the primary cause of higher strength development in the CaO-activated GGBFS. Rather, other factors such as porosity may govern the strength at a higher order of magnitude. Significant reduction of Ca(OH){sub 2} occurs only with the use of Ca(OH){sub 2}, followed by the formation of carbonate (CaCO{sub 3}), indicating carbonation. -- Highlights: •CaO showed a better potential for the activation of GGBFS than Ca(OH){sub 2}. •Strength test, XRD, TGA/DTA and isothermal calorimetry are used. •C-S-H, Ca(OH){sub 2}, and a hydrotalcite-like phase are found in all samples. •The use of Ca(OH){sub 2} causes some degree of carbonation.

  18. Pembuatan La0,8Ca0,2MnO3 sebagai Katoda pada Solid Oxide Fuel Cell (SOFC dan Karakteristiknya

    Directory of Open Access Journals (Sweden)

    Riska Ekawati

    2007-06-01

    Full Text Available The making of La0,8Ca0,2MnO3 cathode material of solid oxide fuel cell from lanthanum oxide (La2O3, calcium oxide (CaO, and manganese carbonate hydrate (MnCO3.H2O has been done using tape casting method. Time of firing the La0,8Ca0,2MnO3 varied. The values of t = 30 minutes, 60 minutes and 120 minutes. Microstructure of these materials was analyzed and characterized by means of their electric conductivity, XRD (x ray diffraction and SEM (scanning electron microscope. It is found that formulated micro structure is orthorhombic. The result of measurement shows that density is in linear (positive correlation with increasing of holding time of firing, porosity and coefficient of thermal expansion is negatively correlated with density and electric conductivity is in linear (positive correlation with increase density.

  19. Fabrication and evaluation of osteoblastic differentiation of human mesenchymal stem cells on novel CaO-SiO2-P2O5-B2O3 glass-ceramics.

    Science.gov (United States)

    Lee, Jae Hyup; Seo, Jun-Hyuk; Lee, Kyung Mee; Ryu, Hyun-Seung; Baek, Hae-Ri

    2013-07-01

    Apatite-wollastonite glass-ceramics have high mechanical strength, and CaO-SiO2 -B2 O3 glass-ceramics showed excellent bioactivity and high biodegradability. A new type of CaO-SiO2 -P2 O5 -B2 O3 system of bioactive glass-ceramics (BGS-7) was fabricated, and the effect and usefulness was evaluated via bioactivity using simulated body fluid and human mesenchymal stem cells (hMSCs). The purpose of this study was to compare BGS-7 and hydroxyapatite (HA) using hMSCs in order to evaluate the bioactivity of BGS-7 and its possibility as a bone graft extender. Alkaline phosphatase (ALP) staining, ALP activity, cell proliferation 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, Alizarin Red-S (AR-S) staining, calcium levels, the mRNA expression of ALP, osteocalcin, osteopontin, and runt-related transcription factor 2 (runx-2) using reverse-transcription polymerase chain reaction (RT-PCR) and the protein expression of osteocalcin and runx-2 using Western blot were measured by transplanting hMSC onto a tissue culture plate, HA, and BGS-7. The ALP staining and AR-S staining of BGS-7 was greater than that of HA and control. The ALP value of BGS-7 was significantly higher than that of HA and control. The MTS results showed that BGS-7 had a higher value than the groups transplanted onto HA and control on day 15. The calcium level was higher than the control in both HA and BGS-7, and was especially high in BGS-7. There were more mineral products on BGS-7 than on the HA when analyzed by scanning electron microscopy. The mRNA expression of ALP, osteopontin, osteocalcin, and runx-2 were higher on BGS-7 than on HA and the control when analyzed by RT-PCR. The relative gene expression of osteopontin and runx-2 were found to be higher on BGS-7 than on HA and the control by Western blot. Accordingly, it is predicted that BGS-7 would have high biocompatibility and good osteoconductivity, and presents a possibility as a new

  20. Study of CO2 cyclic absorption stability of CaO-based sorbents derived from lime mud purified by sucrose method.

    Science.gov (United States)

    Ma, AiHua; Jia, QingMing; Su, HongYing; Zhi, YunFei; Tian, Na; Wu, Jing; Shan, ShaoYun

    2016-02-01

    Using lime mud (LM) purified by sucrose method, derived from paper-making industry, as calcium precursor, and using mineral rejects-bauxite-tailings (BTs) from aluminum production as dopant, the CaO-based sorbents for high-temperature CO2 capture were prepared. Effects of BTs content, precalcining time, and temperature on CO2 cyclic absorption stability were illustrated. The cyclic carbonation behavior was investigated in a thermogravimetric analyzer (TGA). Phase composition and morphologies were analyzed by XRD and SEM. The results reflected that the as-synthesized CaO-based sorbent doped with 10 wt% BTs showed a superior CO2 cyclic absorption-desorption conversion during multiple cycles, with conversion being >38 % after 50 cycles. Occurrence of Ca12Al14O33 phase during precalcination was probably responsible for the excellent CO2 cyclic stability.

  1. Molecular genetic analysis of the calcium sensing receptor gene in patients clinically suspected to have familial hypocalciuric hypercalcemia: phenotypic variation and mutation spectrum in a Danish population

    DEFF Research Database (Denmark)

    Nissen, Peter H; Christensen, Signe E; Heickendorff, Lene

    2007-01-01

    CONTEXT: The autosomal dominantly inherited condition familial hypocalciuric hypercalcemia (FHH) is characterized by elevated plasma calcium levels, relative or absolute hypocalciuria, and normal to moderately elevated plasma PTH. The condition is difficult to distinguish clinically from primary...... hyperparathyroidism and is caused by inactivating mutations in the calcium sensing receptor (CASR) gene. OBJECTIVE: We sought to define the mutation spectrum of the CASR gene in a Danish FHH population and to establish genotype-phenotype relationships regarding the different mutations. DESIGN AND PARTICIPANTS...

  2. Optical anisotropy of Bi2Sr2CaCu2O8

    Science.gov (United States)

    Kim, J. H.; Bozovic, I.; Mitzi, D. B.; Kapitulnik, A.; Harris, J. S., Jr.

    1990-04-01

    The optical anisotropy of Bi2Sr2CaCu2O8 in the 0.08-0.5-eV region is investigated by polarized reflectance measurements on single crystals. A very large anisotropy is found in this spectral region. The in-plane reflectance exhibits metallic behavior, while the c-axis reflectance exhibits insulatorlike behavior. This result is consistent with the large anisotropy found in the resistivity of Bi2Sr2CaCu2O8. Our spectroscopic data suggest that Bi2Sr2CaCu2O8 is a quasi-two-dimensional metal similar to La2-xSrxCuO4.

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

    OpenAIRE

    Aldes Lesbani; Sabat Okta Ceria Sitompul; Risfidian Mohadi; Nurlisa Hidayati

    2016-01-01

    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...

  4. Effect of Ca, Sr and Ba on the structure, morphology and electrical properties of (Co,Sb)-doped SnO{sub 2} varistors

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar-Martínez, J.A., E-mail: josue.aguilarm@uanl.mx [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, Centro de Investigación e Innovación en Ingeniería Aeronáutica (CIIIA), Carretera a Salinas Victoria km. 2.3, C.P. 66600 Apodaca, N.L. (Mexico); Rodríguez, Edén [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, Av. Universidad S/N, Cd. Universitaria, C.P. 66451 San Nicolás de los Garza, N.L. (Mexico); García-Villarreal, S.; Falcon-Franco, L. [Universidad Autónoma de Coahuila, Facultad de Metalurgia, Carr. 57, Km 4.5, C.P. 25710 Monclova, Coah. (Mexico); Hernández, M.B. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, Av. Universidad S/N, Cd. Universitaria, C.P. 66451 San Nicolás de los Garza, N.L. (Mexico)

    2015-03-01

    In this work, the effect of calcium (Ca), barium (Ba) and strontium (Sr) additions on the microstructure and electrical properties of SnO{sub 2}-Co{sub 3}O{sub 4}-Sb{sub 2}O{sub 5} ceramic varistors was investigated. It was found that the calcium addition promotes densification and grain growth. Ceramics with calcium addition exhibit the lowest electric field at a fixed current density (10{sup −3} A cm{sup −2}). The addition of strontium shows a similar effect on microstructure and current-voltage characteristics. However, barium addition causes porosity increase, grain size reduction, changes in the grain morphology (from approximately equiaxed to elongated grains) and the electric field at a fixed current density showed almost no change. Consequently, Ba-containing SnO{sub 2}-based ceramics cannot be considered as attractive candidates for low-voltage varistors. - Highlights: • The calcium and Strontium addition promotes densification and grain growth. • Barium addition causes porosity increase, grain size reduction and changes in the grain morphology. • Ceramics with calcium addition exhibit the lowest electric field. • Ceramics with calcium addition can be considered as promising materials for low-voltage varistors.

  5. Effect of sulfation on the surface activity of CaO for N2O decomposition

    International Nuclear Information System (INIS)

    Wu, Lingnan; Hu, Xiaoying; Qin, Wu; Dong, Changqing; Yang, Yongping

    2015-01-01

    Graphical abstract: - Highlights: • Sulfation of CaO (1 0 0) surface greatly deactivates its surface activity for N 2 O decomposition. • An increase of sulfation degree leads to a decrease of CaO surface activity for N 2 O decomposition. • Sulfation from CaSO 3 into CaSO 4 is the crucial step for deactivating the surface activity for N 2 O decomposition. • The electronic interaction CaO (1 0 0)/CaSO 4 (0 0 1) interface is limited to the bottom layer of CaSO 4 (0 0 1) and the top layer of CaO (1 0 0). • CaSO 4 (0 0 1) and (0 1 0) surfaces show negligible catalytic ability for N 2 O decomposition. - Abstract: Limestone addition to circulating fluidized bed boilers for sulfur removal affects nitrous oxide (N 2 O) emission at the same time, but mechanism of how sulfation process influences the surface activity of CaO for N 2 O decomposition remains unclear. In this paper, we investigated the effect of sulfation on the surface properties and catalytic activity of CaO for N 2 O decomposition using density functional theory calculations. Sulfation of CaO (1 0 0) surface by the adsorption of a single gaseous SO 2 or SO 3 molecule forms stable local CaSO 3 or CaSO 4 on the CaO (1 0 0) surface with strong hybridization between the S atom of SO x and the surface O anion. The formed local CaSO 3 increases the barrier energy of N 2 O decomposition from 0.989 eV (on the CaO (1 0 0) surface) to 1.340 eV, and further sulfation into local CaSO 4 remarkably increases the barrier energy to 2.967 eV. Sulfation from CaSO 3 into CaSO 4 is therefore the crucial step for deactivating the surface activity for N 2 O decomposition. Completely sulfated CaSO 4 (0 0 1) and (0 1 0) surfaces further validate the negligible catalytic ability of CaSO 4 for N 2 O decomposition.

  6. A molecular dynamics study of the atomic structure of (CaO)x(Al2O3)1-x glass with x = 0.625 close to the eutectic

    Science.gov (United States)

    Thomas, B. W. M.; Mead, R. N.; Mountjoy, G.

    2006-05-01

    Aluminate glasses are difficult to prepare as they do not contain traditional network formers, but they are promising materials for optical applications. The atomic structure of calcium aluminate glasses has been studied using several experimental techniques. The current study uses molecular dynamics to obtain a model of a (CaO)0.625(Al2O3)0.375 glass close to the eutectic. The glass consists of a tetrahedral alumina network with average network polymerization \\langle Q^{n}\\rangle of n = 3.3. Ca acts as a network modifier with average coordination of 6.2. Ca is typically coordinated to three bridging oxygens (Ob) and three non-bridging oxygens (Onb), with Ca-Onb bonds noticeably shorter than the Ca-Ob bonds. A new method of analysing modifier cation coordination is presented, which specifically shows the distribution of Ca coordination NCaO in terms of combinations of NCaOb and NCaOnb. Ob is most often coordinated to two Al plus two Ca, and Onb is most often coordinated to one Al plus three Ca. The typical coordinations of Ca, Ob, and Onb all have a noticeable similarity to those for the 5CaO·3Al2O3 crystal. The Ca-Ca distribution shows a clear similarity to that for (CaO)0.5(SiO2)0.5 glass, and this is attributed to the equal atomic number densities of Ca in these glasses.

  7. 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

  8. Calculation of self-absorption coefficients of calcium resonance lines in the case of a CaCl2-water plasma

    International Nuclear Information System (INIS)

    Hannachi, R.; Cressault, Y.; Teulet, Ph.; Gleizes, A.; Lakhdar, Z. Ben

    2008-01-01

    The resonance escape factors for the lines emitted by a neutral calcium atom Ca I at 4226.73 A and of ionic calcium Ca II at 3933.66 A and at 3968.47 A are calculated assuming a Voigt profile and in the case of CaCl 2 -water plasma. The dependence of the escape factor on the optical thickness f 0 from the line center which itself depends on the two main spectral line shape broadening mechanisms (pressure and Doppler effects) are considered. The variation of the resonance escape factors with the temperature, the CaCl 2 molar proportion and the size of the plasma are also investigated. This calculation is useful for the application of Laser-Induced Breakdown Spectroscopy in the quantitative analysis of elemental composition. Its application allows us to reduce the non-linearities in the relation between resonance lines intensities of calcium in our case and its concentration

  9. Thermodynamic modeling of the CaO-SiO2-CaCO3-HCaCO2O closed and open system at 25ºC

    Directory of Open Access Journals (Sweden)

    Martínez-Ramírez, S.

    2003-06-01

    Full Text Available This paper reports on a thermodynamic calculation-based study of the CaO-SiOCaCO2-CaCOCaCO3-HCaCO2O closed system at 25 °C, conducted to determine the range of carbonate ion concentrations at which each phase of the system is stable. Portlandite (CH and the CSH gel were found to be stable for carbonate ion concentrations of less than or equal to 7.62 X 10-3 mM/kg and 1.62 x 10-2 mM/kg, respectively. The CSH gel was found to remain stable in the system at pH values ranging from 10.18 to 10.48. In the CaO-SiO2-H2O open system at 25 °C, likewise studied, with PCO2 held constant at atmospheric values, only hydrated silica (SH and calcite were found to be stable.En este trabajo se estudia el sistema CaO2-CaCO3-H2O, cerrado y a 25 ºC a través de cálculos termodinámicos, y se determina el rango de concentración de ion carbonato en el que son estables cada una de las fases del sistema. Se concluye que la portlandita (CH y el gel CSH son estables para concentraciones de ion carbonato iguales o inferiores a 7,62 X 10-3 niM/kg y 1,62 x 10-2 mM/kg respectivamente. El rango de pH en el que el gel CSH es estable en el sistema es 10,18-10,48. También se estudia el sistema CaO-SiO2-H2O a 25 °C, en sistema abierto a PCO2 constante e igual a la de dicho gas en la atmósfera, encontrando que solo la sílice hidratada (SH y la calcita son estables en dicho sistema.

  10. Structure determinations for Ca3Ti2O7, Ca4Ti3O10, Ca3.6Sr0.4Ti3O10 and a refinement of Sr3Ti2O7

    International Nuclear Information System (INIS)

    Elcombe, M.M.; Kisi, E.H.; Hawkins, K.D.; White, T.J.; Goodman, P.; Matheson, S.

    1991-01-01

    The structures of the orthorhombic Ruddlesden-Popper (A n+1 B n X 3n+1 ) phases Ca 3 Ti 2 O 7 (n=2) refined from neutron powder diffraction data at λ=1.893 A. They consist of coherent intergrowths of perovskite (CaTiO 3 ) blocks, n TiO 6 octahedra thick, with single layers of CaO having a distorted NaCl configuration. TiO 6 octahedra are tilted and distorted in a very similar fashion to those in CaTiO 3 (n=∞). This fact was used to determine the space groups of the layered structures. Convergent-beam electron diffraction patterns are best matched by calculations in the above space groups which are thus confirmed. Octahedral tilt angles increase slightly in the sequence n=2, 3, ∞. Strontium addition reduces the octahedral tilt angles because of preferential substitution of Sr on the Ca sites within the perovskite blocks of Ca 4 Ti 3 O 10 . The algorithm used to produce starting models for structure refinements is thought to be generally applicable to Ruddlesden-Popper and possibly other layered perovskite structures. It furnishes the predictions: (a) all n-even compounds in the Ca n+1 Ti n O 3n+1 series will have space group Ccm2 1 , (b) all n-odd compounds in this series will have space group Pcab, (c) all A n+1 B n X 3n+1 series for which the n=∞ end member (ABX 3 ) is isostructural with CaTiO 3 will be isostructural with the compounds reported above (e.g. Ca n+1 Zr n O 3n+1 ). (orig./WL)

  11. In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

    Science.gov (United States)

    Riaz, Madeeha; Zia, Rehana; Saleemi, Farhat; Bashir, Farooq; Hossain, Tousif; Kayani, Zohra

    2014-09-01

    Zinc is an essential trace element that stimulates bone formation but it is also known as an inhibitor of apatite crystal growth. In this work addition of ZnO to SiO2-CaO-P2O5-Na2O-CaF2 glass-ceramic system was made by conventional melt-quenching technique. DSC curves showed that the addition of ZnO moved the endothermic and exothermic peaks to lower temperatures. X-ray diffraction analysis did not reveal any additional phase caused by ZnO addition and showed the presence of wollastonite and hydroxyapatite crystalline phases only in all the glass-ceramic samples. As bio-implant apatite forming ability is an essential condition, the surface reactivity of the prepared glass-ceramic specimens was studied in vitro in Kokubo's simulated body fluid (SBF) [1] with ion concentration nearly equal to human blood plasma for 30 days at 37 °C under static condition. Atomic absorption spectroscopy (AAS) was used to study the changes in element concentrations in soaking solutions and XRD, FT-IR and SEM were used to elucidate surface properties of prepared glass-ceramics, which confirmed the formation of HCAp on the surface of all glass-ceramics. It was found that the addition of ZnO had a positive effect on bioactivity of glass-ceramics and made it a potential candidate for restoration of damaged bones.

  12. Ca 2+ signaling by plant Arabidopsis thaliana Pep peptides depends on AtPepR1, a receptor with guanylyl cyclase activity, and cGMP-activated Ca 2+ channels

    KAUST Repository

    Qia, Zhi

    2010-11-18

    A family of peptide signaling molecules (AtPeps) and their plasma membrane receptor AtPepR1 are known to act in pathogendefense signaling cascades in plants. Little is currently known about the molecular mechanisms that link these signaling peptides and their receptor, a leucine-rich repeat receptor-like kinase, to downstream pathogen-defense responses. We identify some cellular activities of these molecules that provide the context for a model for their action in signaling cascades. AtPeps activate plasma membrane inwardly conducting Ca 2+ permeable channels in mesophyll cells, resulting in cytosolic Ca 2+ elevation. This activity is dependent on their receptor as well as a cyclic nucleotide-gated channel (CNGC2). We also show that the leucine-rich repeat receptor- like kinase receptor AtPepR1 has guanylyl cyclase activity, generating cGMP from GTP, and that cGMP can activate CNGC2- dependent cytosolic Ca 2+ elevation. AtPep-dependent expression of pathogen-defense genes (PDF1.2, MPK3, and WRKY33) is mediated by the Ca 2+ signaling pathway associated with AtPep peptides and their receptor. The work presented here indicates that extracellular AtPeps, which can act as danger-associated molecular patterns, signal by interaction with their receptor, AtPepR1, a plasma membrane protein that can generate cGMP. Downstream from AtPep and AtPepR1 in a signaling cascade, the cGMP-activated channel CNGC2 is involved in AtPep- and AtPepR1-dependent inward Ca 2+ conductance and resulting cytosolic Ca 2+ elevation. The signaling cascade initiated by AtPeps leads to expression of pathogen- defense genes in a Ca 2+-dependent manner.

  13. Apo-states of calmodulin and CaBP1 control CaV1 voltage-gated calcium channel function through direct competition for the IQ domain

    Science.gov (United States)

    Findeisen, Felix; Rumpf, Christine; Minor, Daniel L.

    2013-01-01

    In neurons, binding of calmodulin (CaM) or calcium-binding protein 1 (CaBP1) to the CaV1 (L-type) voltage-gated calcium channel IQ domain endows the channel with diametrically opposed properties. CaM causes calcium-dependent inactivation (CDI) and limits calcium entry, whereas CaBP1 blocks CDI and allows sustained calcium influx. Here, we combine isothermal titration calorimetry (ITC) with cell-based functional measurements and mathematical modeling to show that these calcium sensors behave in a competitive manner that is explained quantitatively by their apo-state binding affinities for the IQ domain. This competition can be completely blocked by covalent tethering of CaM to the channel. Further, we show that Ca2+/CaM has a sub-picomolar affinity for the IQ domain that is achieved without drastic alteration of calcium binding properties. The observation that the apo-forms of CaM and CaBP1 compete with each other demonstrates a simple mechanism for direct modulation of CaV1 function and suggests a means by which excitable cells may dynamically tune CaV activity. PMID:23811053

  14. Effect of Sulfur in Steel on Transient Evolution of Inclusions During Calcium Treatment

    Science.gov (United States)

    Liu, Yang; Zhang, Lifeng; Zhang, Ying; Duan, Haojian; Ren, Ying; Yang, Wen

    2018-04-01

    In the current study, the effect of S content in the molten steel on inclusions during calcium treatment was studied using an induction furnace. The calcium in steel decreased from 48 to 2 ppm, and the sulfur in steel changed a little with time. When sulfur content in steel was as low as 25 ppm during calcium treatment, inclusions shifted from CaO-Al2O3-CaS to Al2O3-CaO with about 35 pct CaO. When the sulfur increased over 90 ppm, more CaS-CaO formed just after the addition of calcium, and then the CaS content decreased from over 45 pct to lower than 15 pct and inclusions were mostly Al2O3-CaO-CaS and Al2O3-CaO with a high Al2O3 content. Thermodynamic calculation predicted the variation of the composition of inclusions, indicating good agreement with the measurement, while a certain deviation existed, especially for heats with 90 and 180 ppm sulfur. A reaction model was proposed for the formation of CaO and CaS, which considered the reaction between calcium vapor bubbles in the zone and the dissolved oxygen and sulfur in the molten steel, as described by a Langmuir-type adsorption isotherm with a reaction occurring on the remaining vacant sites. The variation of transient CaS inclusions was discussed based on the thermodynamic calculation and the morphology evolution of typical inclusions containing CaS.

  15. Aequorin chimeras as valuable tool in the measurement of Ca2+ concentration during cadmium injury

    International Nuclear Information System (INIS)

    Biagioli, M.; Pinton, P.; Scudiero, R.; Ragghianti, M.; Bucci, S.; Rizzuto, R.

    2005-01-01

    The ability of cadmium to disrupt calcium homeostasis has been known since a long time, but the precise cellular targets of its toxic action are still debated. A great problem in the interpretation of data has been associated with the ability of cadmium to strongly bind traditional calcium probes. Aequorin, the well-characterized calcium-sensitive photoprotein, was used as intracellular calcium indicator during cadmium injury in NIH 3T3 murine fibroblasts. NIH 3T3 cells were transfected with a cDNA construct containing aequorin fused to a truncated glutamate receptor, which directs the probe to the outer surface of intracellular membranes. At first, we tested if different cadmium concentrations were able to modify the rate of light emission by aequorin showing that cadmium concentrations 2+ /Ca 2+ interference. To directly investigate the role of Cd 2+ in Ca 2+ homeostasis, we have started to selectively measure the free Ca 2+ concentration in different cell compartments. Here, we report that cadmium reduces the transient free calcium signal after stimulation of cells with bradykinin. Further studies are in progress to clarify the role of mitochondria and endoplasmic reticulum in cadmium-induced alterations of Ca 2+ homeostasis in order to link signal transduction modifications with the onset of apoptosis induced by cadmium exposure

  16. Hydrogen peroxide homeostasis: activation of plant catalase by calcium/calmodulin

    Science.gov (United States)

    Yang, T.; Poovaiah, B. W.

    2002-01-01

    Environmental stimuli such as UV, pathogen attack, and gravity can induce rapid changes in hydrogen peroxide (H(2)O(2)) levels, leading to a variety of physiological responses in plants. Catalase, which is involved in the degradation of H(2)O(2) into water and oxygen, is the major H(2)O(2)-scavenging enzyme in all aerobic organisms. A close interaction exists between intracellular H(2)O(2) and cytosolic calcium in response to biotic and abiotic stresses. Studies indicate that an increase in cytosolic calcium boosts the generation of H(2)O(2). Here we report that calmodulin (CaM), a ubiquitous calcium-binding protein, binds to and activates some plant catalases in the presence of calcium, but calcium/CaM does not have any effect on bacterial, fungal, bovine, or human catalase. These results document that calcium/CaM can down-regulate H(2)O(2) levels in plants by stimulating the catalytic activity of plant catalase. Furthermore, these results provide evidence indicating that calcium has dual functions in regulating H(2)O(2) homeostasis, which in turn influences redox signaling in response to environmental signals in plants.

  17. Purification and reconstitution of the calcium antagonist receptor of the voltage-sensitive calcium channel

    International Nuclear Information System (INIS)

    Curtis, B.M.

    1986-01-01

    Treatment with digitonin solubilized the calcium antagonist receptor as a stable complex with [ 3 H]nitrendipine from rat brain membranes. The solubilized complex retains allosteric coupling to binding sites for diltiazem, verapamil, and inorganic calcium antagonist sites. The calcium antagonist receptor from cardiac sarcolemma and the transverse-tubule membrane of skeletal muscle is also efficiently solubilized with digitonin and the receptor in all three tissues is a large glycoprotein with a sedimentation coefficient of 20 S. The T-tubule calcium antagonist receptor complex was extensively purified by a combination of chromatography on WGA-Sepharose, ion exchange chromatography, and sedimentation on sucrose gradients to yield preparations estimated to be 41% homogeneous by specific activity and 63% homogeneous by SDS gel electrophoresis. Analysis of SDS gels detect three polypeptides termed α(Mr 135,000), β(Mr 50,000), and γ(Mr 32,000) as noncovalently associated subunits of the calcium antagonist receptor. The α and γ subunits are glycosylated polypeptides, and the molecular weight of the core polypeptides are 108,000 and 24,000 respectively. The calcium antagonist receptor was reconstituted into a phospholipid bilayer by adding CHAPS and exogeneous lipid to the purified receptor followed by rapid detergent removal. This procedure resulted in the incorporation of 45% of the calcium antagonist receptor into closed phospholipid vesicles. Data suggests that the α, β, and γ subunits of the T-tubule calcium antagonist receptor are sufficient to form a functional calcium channel

  18. Calcium signalling silencing in atrial fibrillation.

    Science.gov (United States)

    Greiser, Maura

    2017-06-15

    Subcellular calcium signalling silencing is a novel and distinct cellular and molecular adaptive response to rapid cardiac activation. Calcium signalling silencing develops during short-term sustained rapid atrial activation as seen clinically during paroxysmal atrial fibrillation (AF). It is the first 'anti-arrhythmic' adaptive response in the setting of AF and appears to counteract the maladaptive changes that lead to intracellular Ca 2+ signalling instability and Ca 2+ -based arrhythmogenicity. Calcium signalling silencing results in a failed propagation of the [Ca 2+ ] i signal to the myocyte centre both in patients with AF and in a rabbit model. This adaptive mechanism leads to a substantial reduction in the expression levels of calcium release channels (ryanodine receptors, RyR2) in the sarcoplasmic reticulum, and the frequency of Ca 2+ sparks and arrhythmogenic Ca 2+ waves remains low. Less Ca 2+ release per [Ca 2+ ] i transient, increased fast Ca 2+ buffering strength, shortened action potentials and reduced L-type Ca 2+ current contribute to a substantial reduction of intracellular [Na + ]. These features of Ca 2+ signalling silencing are distinct and in contrast to the changes attributed to Ca 2+ -based arrhythmogenicity. Some features of Ca 2+ signalling silencing prevail in human AF suggesting that the Ca 2+ signalling 'phenotype' in AF is a sum of Ca 2+ stabilizing (Ca 2+ signalling silencing) and Ca 2+ destabilizing (arrhythmogenic unstable Ca 2+ signalling) factors. Calcium signalling silencing is a part of the mechanisms that contribute to the natural progression of AF and may limit the role of Ca 2+ -based arrhythmogenicity after the onset of AF. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

  19. PENGUKURAN NILAI DIELEKTRIK MATERIAL CALCIUM COPPER TITANAT ( CaCu3Ti4O12 MENGGUNAKAN SPEKTROSKOPI IMPEDANSI TERKOMPUTERISASI

    Directory of Open Access Journals (Sweden)

    Widodo Budi Kurniawan

    2017-05-01

    ABSTRACT   The measurement of the complex dielectric constant and the magnitude of the capacitor impedances of the ceramic materials Calcium Copper Titanate CaCu3Ti4O12 (CCTO with purity of 99% has been done by using the method of computerized impedance spectroscopy in the frequency range 5 kHz - 120 kHz. The highest dielectric constant of the material was found to be 745 at 5 kHz in the sample sintered 7000C and the highest impedance of capacitor occured in CCTO sample non sintered that is 150434Ω. The results showed that complex dielectric constant and impedance of the capacitor of the material under study was frequency dependent.   Keywords : impedance spectroscopy, CaCu3Ti4O12,complex dielectric constant and impedance of capacitor

  20. Calcium transport in sealed vesicles from red beet (Beta vulgaris L.) storage tissue. II. Characterization of 45Ca2+ uptake into plasma membrane vesicles

    International Nuclear Information System (INIS)

    Giannini, J.L.; Ruiz-Cristin, J.; Briskin, D.P.

    1987-01-01

    Calcium uptake was examined in sealed plasma membrane vesicles isolated from red beet (Beta vulgaris L.) storage tissue using 45 Ca 2+ . Uptake of 45 Ca 2+ by the vesicles was ATP-dependent and radiotracer accumulated by the vesicles could be released by the addition of the calcium ionophore A23187. The uptake was stimulated by gramicidin D but slightly inhibited by carbonylcyanide m-chlorophenylhydrazone. Although the latter result might suggest some degree of indirect coupling of 45 Ca 2+ uptake to ATP utilization via ΔμH + , no evidence for a secondary H + /Ca 2+ antiport in this vesicle system could be found. Following the imposition of an acid-interior pH gradient, proton efflux from the vesicle was not enhanced by the addition of Ca 2+ and an imposed pH gradient could not drive 45 Ca 2+ uptake. Optimal uptake of 45 Ca 2+ occurred broadly between pH 7.0 and 7.5 and the transport was inhibited by orthovanadate, N,N'-dicyclohexylcarbodiimide, and diethylstilbestrol but insensitive to nitrate and azide. The dependence of 45 Ca 2+ uptake on both calcium and Mg:ATP concentration demonstrated saturation kinetics with K/sub m/ values of 6 micromolar and 0.37 millimolar, respectively. While ATP was the preferred substrate for driving 45 Ca 2+ uptake, GTP could drive transport at about 50% of the level observed for ATP. The results of this study demonstrate the presence of a unique primary calcium transport system associated with the plasma membrane which could drive calcium efflux from the plant cell

  1. 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

  2. Mechanism of Ca2+/calmodulin-dependent kinase II regulation of AMPA receptor gating

    DEFF Research Database (Denmark)

    Kristensen, Anders Skov; Jenkins, Meagan A; Banke, Tue G

    2011-01-01

    The function, trafficking and synaptic signaling of AMPA receptors are tightly regulated by phosphorylation. Ca(2+)/calmodulin-dependent kinase II (CaMKII) phosphorylates the GluA1 AMPA receptor subunit at Ser831 to increase single-channel conductance. We show that CaMKII increases the conductanc...

  3. A common behaviour of thermoelectric layered cobaltites: incommensurate spin density wave states in [Ca2Co4/3Cu2/3O4]0.62[CoO2] and [Ca2CoO3]0.62[CoO2

    International Nuclear Information System (INIS)

    Sugiyama, J; Brewer, J H; Ansaldo, E J; Itahara, H; Dohmae, K; Xia, C; Seno, Y; Hitti, B; Tani, T

    2003-01-01

    Magnetism of a misfit layered cobaltite [Ca 2 Co 4/3 Cu 2/3 O 4 ] x RS [CoO 2 ] (x ∼ 0.62, RS denotes a rocksalt-type block) was investigated by a positive muon spin rotation and relaxation (μ + SR) experiment. A transition to an incommensurate (IC) spin density wave (SDW) state was found below 180 K (= T C on ); and a clear oscillation due to a static internal magnetic field was observed below 140 K(= T C ). Furthermore, an anisotropic behaviour of the zero-field μ + SR experiment indicated that the IC-SDW lies in the a-b plane, with oscillating moments directed along the c axis. These results were quite similar to those for the related compound [Ca 2 CoO 3 ] 0.62 RS [CoO 2 ], i.e., Ca 3 Co 4 O 9 . Since the IC-SDW field in [Ca 2 Co 4/3 Cu 2/3 O 4 ] 0.62 RS [CoO 2 ] was approximately the same as those in pure and doped [Ca 2 CoO 3 ] 0.62 RS [CoO 2 ], it was concluded that the IC-SDW exists in the [CoO 2 ] planes

  4. Crystal structures and thermal decomposition of permanganates AE[MnO{sub 4}]{sub 2} . n H{sub 2}O with the heavy alkaline earth elements (AE=Ca, Sr and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Henning, Harald; Bauchert, Joerg M.; Conrad, Maurice; Schleid, Thomas [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

    2017-10-01

    Reexamination of the syntheses and crystal structures as well as studies of the thermal decomposition of the heavy alkaline earth metal permanganates Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O, Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O and Ba[MnO{sub 4}]{sub 2} are the focus of this work. As an alternative to the very inelegant Muthmann method, established for the synthesis of Ba[MnO{sub 4}]{sub 2} a long time ago, we employed a cation-exchange column loaded with Ba{sup 2+} cations and passed through an aqueous potassium-permanganate solution. We later used this alternative also with strontium- and calcium-loaded columns and all the compounds synthesized this way were indistinguishable from the products of the established methods. Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O exhibiting [CaO{sub 8}] polyhedra crystallizes in the orthorhombic space group Pccn with the lattice parameters a=1397.15(9), b=554.06(4) and c=1338.97(9) pm with Z=4, whereas Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O with [SrO{sub 10}] polyhedra adopts the cubic space group P2{sub 1}3 with a=964.19(7) pm and Z=4. So the harder the AE{sup 2+} cation, the higher its demand for hydration in aqueous solution. Consequently, the crystal structure of Ba[MnO{sub 4}]{sub 2} in the orthorhombic space group Fddd with a=742.36(5), b=1191.23(7) and c=1477.14(9) pm with Z=8 lacks any crystal water, but contains [BaO{sub 12}] polyhedra. During the thermal decomposition of Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O, the compound expels up to two water molecules of hydration, before the crystal structure collapses after the loss of the third H{sub 2}O molecule at 157 C. The crystal structure of Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O breaks down after the expulsion of the third water molecule as well, but this already occurs at 148 C. For both the calcium and the strontium permanganate samples, orthobixbyite-type α-Mn{sub 2}O{sub 3} and the oxomanganates(III,IV) AEMn{sub 3}O{sub 6} (AE=Ca and Sr) remain as final decomposition products at 800 C

  5. Synthesis, cytotoxicity, and hydroxyapatite formation in 27-Tris-SBF for sol-gel based CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses.

    Science.gov (United States)

    Kaur, Gurbinder; Pickrell, G; Kimsawatde, G; Homa, D; Allbee, H A; Sriranganathan, N

    2014-03-18

    CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses were prepared via an optimized sol-gel method. The current investigation was focused on producing novel zinc based calcium phosphoborosilicate glasses and to evaluate their mechanical, rheological, and biocompatible properties. The morphology and composition of these glasses were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The particle size, mechanical and flexural strength was also determined. Furthermore, the zeta potential of all the glasses were determined to estimate their flocculation tendency. The thermal analysis and weight loss measurements were carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) respectively. For assessing the in-vitro bioactive character of synthesized glasses, the ability for apatite formation on their surface upon their immersion in simulated body fluid (SBF) was checked using SEM and pH measurements. MTS assay cytotoxicity assay and live-dead cell viability test were conducted on J774A.1 cells murine macrophage cells for different glass concentrations.

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

    International Nuclear Information System (INIS)

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

    1992-01-01

    The high-resolution Ca L 2,3 x-ray-absorption near-edge-structure (XANES) spectrum of a Bi 2 Sr 2 CaCu 2 O 8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200x200 μm 2 . The Ca L 2,3 XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF 2 . Good agreement between the calculated and experimental crystal-field splitting Δ f of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O(in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, we have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO 2 planes separated by the Ca ions

  7. Experimental Study Of Precipitation Competition Of Ca(OH)2 And Mg(OH)2 On MSF Desalination Condition

    International Nuclear Information System (INIS)

    Sumijanto

    2001-01-01

    Competition study has been carried out by using sea water simulation containing of 142 on deposit ppm of bicarbonate ion, 400 ppm of calcium ion and 1272 ppm of magnesium ion. Experiment was performed by heating sample at temperature 50, 60, 70, 80, and 90 C for 30 minutes. Precipitation competition of Ca(OHh and Mg(OHh was analyzed by reduction of calcium and magnesium ion. Experiment data showed information that at the temperature bellow 800 o C CaCO 3 precipitation was more dominant, meanwhile above than 80 o C precipitation Mg(OH) 2 was more dominant. This competition occurred because at temperature more than 80 o C rate of hydroxyl ion formation and Mg(OH) 2 recipitation was greater than CaCO 3 precipitation and at temperature bellow 80 o C rate of hydrolysis carbonate ion was less than thermal decomposition bicarbonates ion

  8. Synthetic peptides corresponding to human follicle-stimulating hormone (hFSH)-beta-(1-15) and hFSH-beta-(51-65) induce uptake of 45Ca++ by liposomes: evidence for calcium-conducting transmembrane channel formation

    Energy Technology Data Exchange (ETDEWEB)

    Grasso, P.; Santa-Coloma, T.A.; Reichert, L.E. Jr. (Department of Biochemistry, Albany Medical College, New York, NY (USA))

    1991-06-01

    We have previously described FSH receptor-mediated influx of 45Ca++ in cultured Sertoli cells from immature rats and receptor-enriched proteoliposomes via activation of voltage-sensitive and voltage-independent calcium channels. We have further shown that this effect of FSH does not require cholera toxin- or pertussis toxin-sensitive guanine nucleotide binding protein or activation of adenylate cyclase. In the present study, we have identified regions of human FSH-beta-subunit which appear to be involved in mediating calcium influx. We screened 11 overlapping peptide amides representing the entire primary structure of hFSH-beta-subunit for their effects on 45Ca++ flux in FSH receptor-enriched proteoliposomes. hFSH-beta-(1-15) and hFSH-beta-(51-65) induced uptake of 45Ca++ in a concentration-related manner. This effect of hFSH-beta-(1-15) and hFSH-beta-(51-65) was also observed in liposomes lacking incorporated FSH receptor. Reducing membrane fluidity by incubating liposomes (containing no receptor) with hFSH-beta-(1-15) or hFSH-beta-(51-65) at temperatures lower than the transition temperatures of their constituent phospholipids resulted in no significant (P greater than 0.05) difference in 45Ca++ uptake. The effectiveness of the calcium ionophore A23187, however, was abolished. Ruthenium red, a voltage-independent calcium channel antagonist, was able to completely block uptake of 45Ca++ induced by hFSH-beta-(1-15) and hFSH-beta-(51-65) whereas nifedipine, a calcium channel blocker specific for L-type voltage-sensitive calcium channels, was without effect. These results suggest that in addition to its effect on voltage-sensitive calcium channel activity, interaction of FSH with its receptor may induce formation of transmembrane aqueous channels which also facilitate influx of extracellular calcium.

  9. Adenosine A2A receptor-dependent proliferation of pulmonary endothelial cells is mediated through calcium mobilization, PI3-kinase and ERK1/2 pathways

    International Nuclear Information System (INIS)

    Ahmad, Aftab; Schaack, Jerome B.; White, Carl W.; Ahmad, Shama

    2013-01-01

    Highlights: •A 2A receptor-induced pulmonary endothelial growth is mediated by PI3K and ERK1/2. •Cytosolic calcium mobilization is also critical for pulmonary endothelial growth. •Effectors of A 2A receptor, like tyrosine kinases and cAMP increase PI3K/Akt signaling. •Activation of A 2A receptor can contribute to vascular remodeling. -- Abstract: Hypoxia and HIF-2α-dependent A 2A receptor expression and activation increase proliferation of human lung microvascular endothelial cells (HLMVECs). This study was undertaken to investigate the signaling mechanisms that mediate the proliferative effects of A 2A receptor. A 2A receptor-mediated proliferation of HLMVECs was inhibited by intracellular calcium chelation, and by specific inhibitors of ERK1/2 and PI3-kinase (PI3K). The adenosine A 2A receptor agonist CGS21680 caused intracellular calcium mobilization in controls and, to a greater extent, in A 2A receptor-overexpressing HLMVECs. Adenoviral-mediated A 2A receptor overexpression as well as receptor activation by CGS21680 caused increased PI3K activity and Akt phosphorylation. Cells overexpressing A 2A receptor also manifested enhanced ERK1/2 phosphorylation upon CGS21680 treatment. A 2A receptor activation also caused enhanced cAMP production. Likewise, treatment with 8Br-cAMP increased PI3K activity. Hence A 2A receptor-mediated cAMP production and PI3K and Akt phosphorylation are potential mediators of the A 2A -mediated proliferative response of HLMVECs. Cytosolic calcium mobilization and ERK1/2 phosphorylation are other critical effectors of HLMVEC proliferation and growth. These studies underscore the importance of adenosine A 2A receptor in activation of survival and proliferative pathways in pulmonary endothelial cells that are mediated through PI3K/Akt and ERK1/2 pathways

  10. Synthesis and X-ray diffraction studies of dysprosium-calcium ferrites Dy1-xCaxFeO3-y (0≤x≤2/3)

    International Nuclear Information System (INIS)

    Li, J.; Song, D.; Su, Z.; Wang, T.M.

    1997-01-01

    Samples of dysprosium-calcium ferrites Dy 1-x Ca x FeO 3-y with x ranging from 0 to 2/3 were novelly prepared in air by solid state reaction and characterized by X-ray powder diffraction. These samples are single-phased orthorhombic perovskite-type compounds belonging to the space group D 2h 16 -Pbnm. The lattice constants of the Dy 1-x Ca x FeO 3-y samples have been refined by Cohen's least-squares method. The initial substitution of Ca for Dy leads to a decrease of the lattice constants. Further substitution of Ca for Dy has hardly any influence on the lattice dimensions. (orig.)

  11. 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.

  12. The crystallization behaviour and bioactivity of wollastonite glass-ceramic based on Na2O–K2O–CaO–SiO2–F glass system

    Directory of Open Access Journals (Sweden)

    S.M. Salman

    2015-09-01

    Full Text Available The study concerns about the crystallization behaviour and in vitro bioactivity of a glass-ceramic prepared from a series of glasses in the Na2O–K2O–CaO–SiO2–F system. A minor amount of cerium oxide was also added instead of calcium oxide in some selective glass batches. The main crystalline phases, formed after the appropriate heat treatments, were wollastonite solid solution and pseudo-wollastonite-like phases. There is a preferential tendency for wollastonite (CaSiO3 to accommodate K, Na, F, and Ce ions in its structure forming wollastonite solid solution with variable formulas. The bioactivity of the resulting crystalline materials was examined in vitro by immersion in simulated body fluid at 37 °C. An increase of the surface bioactivity of glass-ceramic with the Na2O/K2O replacement was observed which is attributed to the augmentation solubility of the crystalline sample. On the other hand, the bioactivity of the crystalline sample with CeO2/CaO replacement was improved by the crystallization of pseudo-wollastonite phase together with wollastonite solid solution phase.

  13. Calcium in pollen-pistil interaction in 'Petunia hybrida Hat'. Pt. 3. Localization of Ca2+ ions and Ca2+-ATPase in pollinated pistil

    International Nuclear Information System (INIS)

    Bednarska, E.; Butowt, R.

    1995-01-01

    Studies were carried out of Ca 2+ and Ca 2+ -ATPase localization in pollinated (6 and 48 h after pollination) pistils of 'Petunia hybrida'. The results were confronted with Ca 2+ localization in mature pollen grain and in unpollinated pistil. It has been found that after pollination the number of Ca 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 2+ were found in the organelles of the tip cytoplasm and in the external pectin cell wall. Studies with the use of 45 Ca 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 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 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 2+ -ATPase. (author). 30 refs, 19 figs

  14. Effects of Y2O3 on crystallization kinetics of SiO2-Al2O3-CaO-CaF2 oxy-fluoride glass-ceramic system

    Directory of Open Access Journals (Sweden)

    M. Soleymani Zarabad

    Full Text Available Differential thermal analysis (DTA patterns of SiO2-Al2O3-CaO-CaF2 oxy-fluoride glass system with adding different amounts of Y2O3 from 0.5 (wt% to 1.5 (wt% have been studied under isochronal circumstances. It is concluded that, the crystallization of the glasses is a process controlled by Avrami nucleation, three dimensional diffusion controlled growth and anisotropic growth impingement mode. Afterwards, the effective activation energy Qp, growth exponent, nucleation activation energy QN, and growth activation energy QG, have been determined and were in the range of 283–321 kJ mol−1, 2.05–2.25, 190–249 kJ mol−1 and 325–349 kJ mol−1, respectively. Qp, QN, QG and np are increased with increase of Y2O3 amount, which is related to the network forming role of Y2O3 in these systems. Keywords: Oxy-fluoride glass-ceramics, Activation energy, Crystallization mechanism, Growth exponent

  15. Investigation of electrochemical reduction of GeO2 to Ge in molten CaCl2-NaCl

    International Nuclear Information System (INIS)

    Rong, Liangbin; He, Rui; Wang, Zhiyong; Peng, Junjun; Jin, Xianbo; Chen, George Z.

    2014-01-01

    Electrochemical reduction of solid GeO 2 has been investigated in the mixed CaCl 2 -NaCl melt at 1023 K for developing a more efficient process for preparation of Ge. Cyclic voltammetry and potentiostatic electrolysis were applied to study the GeO 2 -loaded metallic cavity electrode. In addition, porous GeO 2 pellets were reduced by potentiostatic and constant cell voltage electrolysis with a graphite anode, and the electrolysis products were analyzed by powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometry, focusing on understanding the reduction mechanism and the impact of electrode potential on the product purity. It was found that the reduction of GeO 2 to Ge occurred at a potential of about -0.50 V (vs. Ag/Ag + ), but generating various calcium germanates simultaneously, whose reduction was a little more difficult and needed a potential more negative than -1.00 V. However, if the cathode potential exceeded -1.60 V, Ca (or Na) - Ge intermetallic compounds might form. These results gave an appropriate potential range between -1.10 and -1.40 V for the production of pure germanium. Rapid electrolysis of GeO 2 to pure Ge has been realized at a cell voltage of 2.5 V with a current efficiency of about 92%

  16. Calcium looping technology using improved stability nanostructured sorbent for cyclic CO{sub 2} capture

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Cong; Zheng, Ying; Ding, Ning; Zheng, Chu-guang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

    2013-07-01

    One of the post-combustion CO{sub 2} capture technologies that have sufficiently been proved to be the best candidates for practical large scale post-combustion application is the calcium looping cycle. However, the CO{sub 2} capture capacity of a calcium-based sorbent derived from natural limestone decays through long-term cyclic utilization; thus, the development of novel sorbents to achieve a high CO{sub 2} capture capacity is an critical challenge for the calcium looping cycle technology. In this paper, we report the preparation and character of a new calcium-based sorbent produced via the combustion of a dry gel. The results show that the novel calcium-based sorbent has a much higher residual carbonation conversion as well as a better performance of anti-sintering when compared with the calcium-based sorbent derived from commercial micrometer grade CaCO{sub 3} and nanometer grade CaCO{sub 3}. It is reasonable to propose that the different final carbonation performances are induced by their different pore structures and BET surface areas rather than by different particle sizes. Compared with the commercial nano CaO, the morphology of the new sorbent shows a more rough porous appearance with hollow nanostructure. During carbonation, CO{sub 2} diffused more easily through the hollow structure than through a solid structure to reach the unreacted CaO. Besides, there is less chance for the hollow nanostructured particles to be merged together during the high temperature reactions.

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

    Energy Technology Data Exchange (ETDEWEB)

    Borg, A; King, P L; Pianetta, P; Lindau, I; Mitzi, D B

    1992-01-01

    The high-resolution Ca L(2,3) x-ray-absorption near-edge-structure (XANES) spectrum of a Bi2Sr2CaCu2O8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200x200 micrometers square. The Ca L(2,3) XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF2. Good agreement between the calculated and experimental crystal-field splitting Delta f of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O (in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, the authors have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO2 planes separated by the Ca ions.

  18. Brief Communication: Ikaite (CaCO3·6H2O) discovered in Arctic sea ice

    Science.gov (United States)

    Dieckmann, G. S.; Nehrke, G.; Uhlig, C.; Göttlicher, J.; Gerland, S.; Granskog, M. A.; Thomas, D. N.

    2010-05-01

    We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3·6H2O) in sea ice from the Arctic (Kongsfjorden, Svalbard) as confirmed by morphology and indirectly by X-ray diffraction as well as XANES spectroscopy of its amorophous decomposition product. This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This observation is an important step in the quest to quantify its impact on the sea ice driven carbon cycle.

  19. The GluR2 hypothesis: Ca(++)-permeable AMPA receptors in delayed neurodegeneration

    NARCIS (Netherlands)

    Bennett, M. V.; Pellegrini-Giampietro, D. E.; Gorter, J. A.; Aronica, E.; Connor, J. A.; Zukin, R. S.

    1996-01-01

    Increased glutamate-receptor-mediated Ca++ influx is considered an important factor underlying delayed neurodegeneration following ischemia or seizures. Until recently, the NMDA receptor was the only glutamate receptor known to be Ca(++)-permeable. It is now well established that glutamate receptors

  20. Oxytocin receptors expressed and coupled to Ca2+ signalling in a human vascular smooth muscle cell line.

    Science.gov (United States)

    Yazawa, H; Hirasawa, A; Horie, K; Saita, Y; Iida, E; Honda, K; Tsujimoto, G

    1996-03-01

    1. In a human vascular smooth muscle cell line (HVSMC), binding experiments with [3H]-arginine8-vasopressin (AVP) have shown the existence of a homogeneous population of binding sites with affinity (Kd value) of 0.65 nM and a maximum number of binding sites (Bmax) of 122 fmol mg-1 protein. 2. Nonlabelled compounds compete for [3H]-AVP binding in the HVSMC membrane with an order of potency of oxytocin > lyspressin > or = AVP > Thr4, Gly7-oxytocin > (beta-mercapto-beta-beta-cyclopentamethylenepropionyl-O-Me Tyr2, Arg8) vasopressin > desmopressin > OPC21268 > OPC31260. This order was markedly different from that observed in rat vascular smooth muscle cells (A10), a well-established V1A receptor system. 3. In HVSMC both oxytocin and AVP increased inositol 1,4,5-trisphosphate (IP3) production and [Ca2+]i response, but the efficacy of the responses was greater for oxytocin than AVP. 4. Reverse transcription-polymerase chain reaction (RT-PCR) assay detected only oxytocin receptor but not V1A or V2 receptors in HVSMC, whereas only V1A receptors were found in A10 cells. 5. In conclusion, in HVSMC only oxytocin receptors are expressed among the vasopressin receptor family, and they coupled to phosphatidyl inositol (PI) turnover/Ca2+ signalling. This unexpected observation should provide new insight into the functional role of the oxytocin receptor in a human vascular smooth muscle cell line.

  1. Interactions between calcium and phosphorus in the regulation of the production of fibroblast growth factor 23 in vivo

    Science.gov (United States)

    Quinn, Stephen J.; Thomsen, Alex R. B.; Pang, Jian L.; Kantham, Lakshmi; Bräuner-Osborne, Hans; Pollak, Martin; Goltzman, David

    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 D3 [1,25(OH)2D3] despite no change in FGF23, suggesting direct regulation of 1,25(OH)2D3 synthesis by serum phosphorus. Calcium-mediated increases in serum FGF23 required a threshold level of serum phosphorus of about 5 mg/dl. Analogously, phosphorus-elicited increases in FGF23 were markedly blunted if serum calcium was less than 8 mg/dl. The best correlation between calcium and phosphorus and serum FGF23 was found between FGF23 and the calcium × phosphorus product. Since calcium stimulated FGF23 production in the PTH-CaSR DKO mice, this effect cannot be mediated by the full-length CaSR. Thus the regulation of FGF23 by both calcium and phosphorus appears to be fundamentally important in coordinating the serum levels of both mineral ions and ensuring that the calcium × phosphorus product remains within a physiological range. PMID:23233539

  2. Gas Sensing Properties of ZnO-SnO2 Nanostructures.

    Science.gov (United States)

    Chen, Weigen; Li, Qianzhu; Xu, Lingna; Zeng, Wen

    2015-02-01

    One-dimensional (1D) semiconductor metal oxide nanostructures have attracted increasing attention in electrochemistry, optics, magnetic, and gas sensing fields for the good properties. N-type low dimensional semiconducting oxides such as SnO2 and ZnO have been known for the detection of inflammable or toxic gases. In this paper, we fabricated the ZnO-SnO2 and SnO2 nanoparticles by hydrothermal synthesis. Microstructure characterization was performed using X-ray diffraction (XRD) and surface morphologies for both the pristine and doped samples were observed using field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Then we made thin film gas sensor to study the gas sensing properties of ZnO-SnO2 and SnO2 gas sensor to H2 and CO. A systematic comparison study reveals an enhanced gas sensing performance for the sensor made of SnO2 and ZnO toward H2 and CO over that of the commonly applied undecorated SnO2 nanoparticles. The improved gas sensing properties are attributed to the size of grains and pronounced electron transfer between the compound nanostructures and the absorbed oxygen species as well as to the heterojunctions of the ZnO nanoparticles to the SnO2 nanoparticles, which provide additional reaction rooms. The results represent an advance of compound nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials, offering a new avenue and direction to detect gases of interest based on composite tin oxide nanoparticles.

  3. Calcium homeostasis modulator (CALHM) ion channels.

    Science.gov (United States)

    Ma, Zhongming; Tanis, Jessica E; Taruno, Akiyuki; Foskett, J Kevin

    2016-03-01

    Calcium homeostasis modulator 1 (CALHM1), formerly known as FAM26C, was recently identified as a physiologically important plasma membrane ion channel. CALHM1 and its Caenorhabditis elegans homolog, CLHM-1, are regulated by membrane voltage and extracellular Ca(