Composition and distribution of elements and ultrastructural topography of a human cardiac calculus.

PubMed

Cheng, Ching-Li; Chang, Hsiao-Huang; Huang, Pei-Jung; Chu, Yu-Ting; Lin, Shan-Yang

2013-04-01

Trace elements (TEs) may contribute to the formation of calculi or stones or be involved in the aetiopathogenesis of stone diseases. The compositions and spatial distribution of elements from the inner nucleus to outer crust of the cardiac calculus were investigated by energy-dispersive X-ray fluorescence (EDXRF) spectrometer. The surface topograph, distribution map of elements, elemental and chemical compositions were also determined by environmental scanning electron microscope (ESEM)-energy-dispersive X-ray (EDX) analysis. Twenty-five elements were identifiable from 18 positions on the cardiac calculus by EDXRF spectrometer, in which the highest concentrations of toxic TEs (Ni, Pt, Hg, Sn, Pb, W, Au, Al, Si) and higher levels of essential TEs (Ca, Sr, Cr, P) were detected. A moderate positive Pearson's correlation between TEs concentrations of Mg, Ca or P and location differences from centre to periphery in the cardiac calculus was observed. A positive correlation was also found for Ca/Zn and Ca/Cu, indicating the gradual increase of calcium concentration from inner nucleus to outer crust of cardiac calculus. The drop-like nodules/crystals on the surface of petrous part of cardiac calculus were observed from ESEM analysis. ESEM-EDX analysis determined the calculus to be predominantly composed of calcium hydroxyapatite and cholesterol, as indicated by the petrous surface and drop-like nodules/crystals, respectively. This composition was confirmed using a portable Raman analyser. The spatial distribution analysis indicated a gradual increase in Mg, P and Ca concentrations from the inner nucleus to the outer crust of the cardiac calculus. The major chemical compositions of calcium hydroxyapatite and cholesterol were detected on this cardiac calculus.

Mineral contents and their solubility on calcium carbonat calcite nanocrystals from cockle shell powder (Anadara granosa Linn)

NASA Astrophysics Data System (ADS)

Widyastuti, S.; Pramushinta, I. A.

2018-03-01

Prepared and characterized calcium carbonat calcite nanocrystals improves solubility. Calcium carbonat calcite nanocrystals were synthesized using precipitation method from the waste of blood clam cockle shells (Anadara granosa Linn). This study was conducted to analyze mineral composition of nanocrystals calcium carbonat calcite cockle (Anadara granosa) shell for calcium fortification of food applications and to evaluate the solubilities of Calsium and Phospor. The sample of nanocrystals from cockle shells was evaluated to determine the content of 11 macro-and micro-elements. These elements are Calcium (Ca), Magnesium (Mg), Sodium (Na), Phosphorus (P), Potassium (K), Ferrum (Fe), Copper (Cu), Nickel (Ni), Zink (Zn), Boron (B) and Silica (Si)). Cockleshell powders were found to contain toxic elements below detectable levels. The solubilities of Calcium and Phospor were p<0.05.

Calcium ketoglutarate versus calcium acetate for treatment of hyperphosphataemia in patients on maintenance haemodialysis: a cross-over study.

PubMed

Birck, R; Zimmermann, E; Wassmer, S; Nowack, R; van der Woude, F J

1999-06-01

Since dietary restrictions and phosphorus removal by haemodialysis (HD) are not sufficient to control serum phosphate (s-phosphate) levels in dialysis patients the use of oral phosphate binders is mandatory. Calcium ketoglutarate (CaKE) is an analogue of glutamic acid exerting phosphate binding properties. Therefore we compared this substance to calcium acetate (CaAC) in a 24-weeks open cross-over trial in 28 maintenance HD patients. Medications and HD prescriptions were kept unchanged during the trial. Following 2 weeks of withdrawal of phosphate binders, patients were randomly assigned to one of the calcium salts for 12 weeks; after a second withdrawal of 2 weeks, all patients were shifted to the other treatment for another 12 weeks. All patients received equimolar doses of CaKE and CaAC with respect to the amount of prescribed elemental calcium. Treatment with CaAC and CaKE significantly reduced s-phosphate levels after 4 weeks (CaAC 1.95+/-0.6 vs. 2.4+/-0.53 mmol/l, P = 0.004; CaKE 1.95+/-0.4 vs. 2.47+/-0.63 mmol/l, P = 0.0001) reaching a virtually stable plateau over the remaining observation time without significant differences between the groups. The incidence of hypercalcaemia defined as a serum calcium level > or =2.8 mmol/l was significantly higher in CaAC than in CaKE treated patients (n = 8 vs. n = 1, P = 0.03). There were no significant differences in serum intact parathyroid hormone (PTH) bicarbonate, albumin or calcitriol levels between the groups after 12 weeks treatment. We conclude that CaKE is as effective as CaAC for treatment of hyperphosphataemia in chronic HD patients and may be particularly helpful in patients who are prone to develop hypercalcaemia.

Synthesis and characterization of nano-sized CaCO3 in purified diet

NASA Astrophysics Data System (ADS)

Mulyaningsih, N. N.; Tresnasari, D. R.; Ramahwati, M. R.; Juwono, A. L.; Soejoko, D. S.; Astuti, D. A.

2017-07-01

The growth and development of animals depend strongly on the balanced nutrition in the diet. This research aims is to characterize the weight variations of nano-sized calcium carbonate (CaCO3) in purified diet that to be fed to animal model of rat. The nano-sized CaCO3 was prepared by milling the calcium carbonate particles for 20 hours at a rotation speed of 1000 rpm and resulting particle size in a range of 2-50 nm. Nano-sized CaCO3 added to purified diet to the four formulas that were identified as normal diet (N), deficiency calcium (DC), rich in calcium (RC), and poor calcium (PC) with containing in nano-sized CaCO3 much as 0.50 %, 0.00 %, 0.75 % and 0.25 % respectively. The nutritional content of the purified diet was proximate analyzed, it resulted as followed moisture, ash, fat, protein, crude fiber. The quantities of chemical element were analyzed by atomic absorption spectrometry (AAS), it resulted iron, magnesium, potassium and calcium. The results showed that N diet (Ca: 16,914.29 ppm) were suggested for healthy rats and RC diet (Ca: 33,696.13 ppm) for conditioned osteoporosis rats. The crystalline phases of the samples that were examined by X-ray diffraction showed that crystalline phase increased with the increasing concentration of CaCO3.

Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste.

PubMed

de Beer, M; Doucet, F J; Maree, J P; Liebenberg, L

2015-12-01

We recently showed that the production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste by thermally reducing the waste into calcium sulphide (CaS) followed by its direct aqueous carbonation yielded low-grade carbonate products (i.e. <90 mass% as CaCO3). In this study, we used the insight gained from our previous work and developed an indirect aqueous CaS carbonation process for the production of high-grade CaCO3 (i.e. >99 mass% as CaCO3) or precipitated calcium carbonate (PCC). The process used an acid gas (H2S) to improve the aqueous dissolution of CaS, which is otherwise poorly soluble. The carbonate product was primarily calcite (99.5%) with traces of quartz (0.5%). Calcite was the only CaCO3 polymorph obtained; no vaterite or aragonite was detected. The product was made up of micron-size particles, which were further characterised by XRD, TGA, SEM, BET and true density. Results showed that about 0.37 ton of high-grade PCC can be produced from 1.0 ton of gypsum waste, and generates about 0.19 ton of residue, a reduction of 80% from original waste gypsum mass to mass of residue that needs to be discarded off. The use of gypsum waste as primary material in replacement of mined limestone for the production of PPC could alleviate waste disposal problems, along with converting significant volumes of waste materials into marketable commodities. Copyright © 2015 Elsevier Ltd. All rights reserved.

Determination of Ca content of coral skeleton by analyte additive method using the LIBS technique

NASA Astrophysics Data System (ADS)

Haider, A. F. M. Y.; Khan, Z. H.

2012-09-01

Laser-induced breakdown spectroscopic (LIBS) technique was used to study the elemental profile of coral skeletons. Apart from calcium and carbon, which are the main elemental constituents of coral skeleton, elements like Sr, Na, Mg, Li, Si, Cu, Ti, K, Mn, Zn, Ba, Mo, Br and Fe were detected in the coral skeletons from the Inani Beach and the Saint Martin's island of Bangladesh and the coral from the Philippines. In addition to the qualitative analysis, the quantitative analysis of the main elemental constituent, calcium (Ca), was done. The result shows the presence of (36.15±1.43)% by weight of Ca in the coral skeleton collected from the Inani Beach, Cox's Bazar, Bangladesh. It was determined by using six calibration curves, drawn for six emission lines of Ca I (428.301 nm, 428.936 nm, 431.865 nm, 443.544 nm, 443.569 nm, and 445.589 nm), by standard analyte additive method. Also from AAS measurement the percentage content of Ca in the same sample of coral skeleton obtained was 39.87% by weight which compares fairly well with the result obtained by the analyte additive method.

A new process for converting SO2 to sulfur without generating secondary pollutants through reactions involving CaS and CaSO4.

PubMed

Sohn, H Y; Kim, Byung-Su

2002-07-01

Nonferrous smelters and coal gasification processes generate environmentally harmful sulfur dioxide streams, most of which are treated to produce sulfuric acid with the accompanying problems of market shortage and transportation difficulties. Some sulfur dioxide streams are scrubbed with an alkali solution or a solid substance such as limestone or dolomite, which in turn generates wastes that pose other pollution problems. While the conversion of sulfur dioxide to elemental sulfur has many environmental advantages, no processes exist that are environmentally acceptable and economically viable. A new method for converting sulfur dioxide to elemental sulfur by a cyclic process involving calcium sulfide and calcium sulfate without generating solid wastes has been developed. In this process, calcium sulfate pellets as the starting raw material are reduced by a suitable reducing agent such as hydrogen to produce calcium sulfide pellets, which are used to reduce sulfur dioxide producing elemental sulfur vapor and calcium sulfate. The latter is then reduced to regenerate calcium sulfide. Thermodynamic analysis and experimental results indicated that the CaS-SO2 reaction produces mainly sulfur vapor and solid calcium sulfate and that the gaseous product from the CaSO4-H2 reaction is mainly water vapor. The rates of the two reactions are reasonably rapid in the temperature range 1000-1100 K, and, importantly, the physical strengths and reactivities of the pellets are maintained largely unchanged up to the tenth cycle, the last cycle tested in this work. Sulfur dioxide-containing streams from certain sources, such as the regenerator off-gas from an integrated gasification combined cycle desulfurization unit and new sulfide smelting plants, contain much higher partial pressures of SO2. In these cases, the rate of the first reaction is expected to be proportionally higher than in the test conditions reported in this paper.

Ca2+–calmodulin-dependent protein kinase II represses cardiac transcription of the L-type calcium channel α1C-subunit gene (Cacna1c) by DREAM translocation

PubMed Central

Ronkainen, Jarkko J; Hänninen, Sandra L; Korhonen, Topi; Koivumäki, Jussi T; Skoumal, Reka; Rautio, Sini; Ronkainen, Veli-Pekka; Tavi, Pasi

2011-01-01

Abstract Recent studies have demonstrated that changes in the activity of calcium–calmodulin-dependent protein kinase II (CaMKII) induce a unique cardiomyocyte phenotype through the regulation of specific genes involved in excitation–contraction (E–C)-coupling. To explain the transcriptional effects of CaMKII we identified a novel CaMKII-dependent pathway for controlling the expression of the pore-forming α-subunit (Cav1.2) of the L-type calcium channel (LTCC) in cardiac myocytes. We show that overexpression of either cytosolic (δC) or nuclear (δB) CaMKII isoforms selectively downregulate the expression of the Cav1.2. Pharmacological inhibition of CaMKII activity induced measurable changes in LTCC current density and subsequent changes in cardiomyocyte calcium signalling in less than 24 h. The effect of CaMKII on the α1C-subunit gene (Cacna1c) promoter was abolished by deletion of the downstream regulatory element (DRE), which binds transcriptional repressor DREAM/calsenilin/KChIP3. Imaging DREAM–GFP (green fluorescent protein)-expressing cardiomyocytes showed that CaMKII potentiates the calcium-induced nuclear translocation of DREAM. Thereby CaMKII increases DREAM binding to the DRE consensus sequence of the endogenous Cacna1c gene. By mathematical modelling we demonstrate that the LTCC downregulation through the Ca2+–CaMKII–DREAM cascade constitutes a physiological feedback mechanism enabling cardiomyocytes to adjust the calcium intrusion through LTCCs to the amount of intracellular calcium detected by CaMKII. PMID:21486818

Determination of the calcium elemental abundance for 43 flares from SMM-XRP solar X-ray spectra

NASA Astrophysics Data System (ADS)

Lemen, J. R.; Sylwester, J.; Bentley, R. D.

The helium and lithium-like X-ray transitions of Ca XVIII-XIX have been used to make an absolute measurement of the coronal calcium elemental abundance relative to hydrogen (ACa) in solar flares. Cooling phase spectra of 43 flares obtained in channel 1 of the Bent Crystal Spectrometer on the Solar Maximum Mission have been analyzed. The abundance is determined from the intensity ratio of the Ca XIX resonance line (1S0 - 1P1) and nearby continuum. Attempts to correlate the ACa measurements with other observable features are discussed.

In Silico Analysis of Expression Data for Identification of Genes Involved in Spatial Accumulation of Calcium in Developing Seeds of Rice

PubMed Central

Goel, Anshita; Gaur, Vikram S.; Arora, Sandeep; Gupta, Sanjay

2012-01-01

Abstract The calcium (Ca2+) transporters, like Ca2+ channels, Ca2+ ATPases, and Ca2+ exchangers, are instrumental for signaling and transport. However, the mechanism by which they orchestrate the accumulation of Ca2+ in grain filling has not yet been investigated. Hence the present study was designed to identify the potential calcium transporter genes that may be responsible for the spatial accumulation of calcium during grain filling. In silico expression analyses were performed to identify Ca2+ transporters that predominantly express during the different developmental stages of Oryza sativa. A total of 13 unique calcium transporters (7 from massively parallel signature sequencing [MPSS] data analysis, and 9 from microarray analysis) were identified. Analysis of variance (ANOVA) revealed differential expression of the transporters across tissues, and principal component analysis (PCA) exhibited their seed-specific distinctive expression profile. Interestingly, Ca2+ exchanger genes are highly expressed in the initial stages, whereas some Ca2+ ATPase genes are highly expressed throughout seed development. Furthermore, analysis of the cis-elements located in the promoter region of the subset of 13 genes suggested that Dof proteins play essential roles in regulating the expression of Ca2+ transporter genes during rice seed development. Based on these results, we developed a hypothetical model explaining the transport and tissue specific distribution of calcium in developing cereal seeds. The model may be extrapolated to understand the mechanism behind the exceptionally high level of calcium accumulation seen in grains like finger millet. PMID:22734689

Intra-amniotic administration (Gallus gallus) of cicer arietinum and lens culinaris prebiotics extracts and duck egg white peptides affects calcium status and intestinal functionality

USDA-ARS?s Scientific Manuscript database

Calcium (Ca) is one of the most abundant inorganic elements in the human body and has many important physiological roles. Prebiotics and bioactive peptides are two important substances used to promote calcium uptake. However, the difference in mechanisms of the calcium uptake from these two suppleme...

Calcium oxalate druses affect leaf optical properties in selenium-treated Fagopyrum tataricum.

PubMed

Golob, Aleksandra; Stibilj, Vekoslava; Nečemer, Marijan; Kump, Peter; Kreft, Ivan; Hočevar, Anja; Gaberščik, Alenka; Germ, Mateja

2018-03-01

Plants of the genus Fagopyrum contain high levels of crystalline calcium oxalate (CaOx) deposits, or druses, that can affect the leaf optical properties. As selenium has been shown to modify the uptake and accumulation of metabolically important elements such as calcium, we hypothesised that the numbers of druses can be altered by selenium treatment, and this would affect the leaf optical properties. Tartary buckwheat (Fagopyrum tataricum Gaertn.) was grown outdoors in an experimental field. At the beginning of flowering, plants were foliarly sprayed with sodium selenate solution at 10 mg selenium L -1 or only with water. Plant morphological, biochemical, physiological and optical properties were examined, along with leaf elemental composition and content. Se spraying did not affect leaf biochemical and functional properties. However, it increased leaf thickness and the contents of Se in the leaves, and decreased the density of calcium oxalate druses in the leaves. Except Se content, Se spraying did not affect contents of other elements in leaves, including total calcium per dry mass of leaf tissue. Redundancy analysis showed that of all parameters tested, only the calcium oxalate druses parameters were significant in explaining the variability of the leaf reflectance and transmittance spectra. The density of CaOx druses positively correlated with the reflectance in the blue, green, yellow and UV-B regions of the spectrum, while the area of CaOx druses per mm 2 of leaf transection area positively correlated with the transmittance in the green and yellow regions of the spectrum. Copyright © 2018 Elsevier B.V. All rights reserved.

Calcium, essential for health

PubMed

Martínez de Victoria, Emilio

2016-07-12

Calcium (Ca) is the most abundant mineral element in our body. It accounts for about 2% of body weight. The functions of calcium are: a) functions skeletal and b) regulatory functions. Bone consists of a protein matrix that mineralizes mainly with calcium (the most abundant), phosphate and magnesium, for it is essential an adequate dietary intake of Ca, phosphorus and vitamin D. The ionic Ca (Ca2+) is essential to maintain and / or perform different specialized functions of, virtually, all body cells cellular. Because of its important functions Ca2+ must be closely regulated, keeping plasma concentrations within narrow ranges. For this reason there is an accurate response against hypocalcemia or hypercalcemia in which the parathormone, calcitriol, calcitonin and vitamin K are involved. Ca intakes in the Spanish population are low in a significant percentage of the older adult’s population, especially in women. The main source of Ca in the diet is milk and milk derivatives. Green leafy vegetables, fruits and legumes can be important sources of Ca in a Mediterranean dietary pattern. The bioavailability of dietary Ca depends on physiological and dietary factors. Physiological include age, physiological status (gestation and lactation) Ca and vitamin D status and disease. Several studies relate Ca intake in the diet and various diseases, such as osteoporosis, cancer, cardiovascular disease and obesity.

Stabilizing function for myristoyl group revealed by the crystal structure of a neuronal calcium sensor, guanylate cyclase-activating protein 1.

PubMed

Stephen, Ricardo; Bereta, Grzegorz; Golczak, Marcin; Palczewski, Krzysztof; Sousa, Marcelo Carlos

2007-11-01

Guanylate cyclase-activating proteins (GCAPs) are Ca(2+)-binding proteins myristoylated at the N terminus that regulate guanylate cyclases in photoreceptor cells and belong to the family of neuronal calcium sensors (NCS). Many NCS proteins display a recoverin-like "calcium-myristoyl switch" whereby the myristoyl group, buried inside the protein in the Ca(2+)-free state, becomes fully exposed upon Ca(2+) binding. Here we present a 2.0 A resolution crystal structure of myristoylated GCAP1 with Ca(2+) bound. The acyl group is buried inside Ca(2+)-bound GCAP1. This is in sharp contrast to Ca(2+)-bound recoverin, where the myristoyl group is solvent exposed. Furthermore, we provide direct evidence that the acyl group in GCAP1 remains buried in the Ca(2+)-free state and does not undergo switching. A pronounced kink in the C-terminal helix and the presence of the myristoyl group allow clustering of sequence elements crucial for GCAP1 activity.

Stabilizing Function for Myristoyl Group Revealed by the Crystal Structure of a Neuronal Calcium Sensor, Guanylate Cyclase-Activating Protein 1

PubMed Central

Stephen, Ricardo; Bereta, Grzegorz; Golczak, Marcin; Palczewski, Krzysztof; Sousa, Marcelo Carlos

2008-01-01

SUMMARY Guanylate cyclase-activating proteins (GCAPs) are Ca2+-binding proteins myristoylated at the N terminus that regulate guanylate cyclases in photoreceptor cells and belong to the family of neuronal calcium sensors (NCS). Many NCS proteins display a recoverin-like “calcium-myristoyl switch” whereby the myristoyl group, buried inside the protein in the Ca2+-free state, becomes fully exposed upon Ca2+ binding. Here we present a 2.0 Å resolution crystal structure of myristoylated GCAP1 with Ca2+ bound. The acyl group is buried inside Ca2+-bound GCAP1. This is in sharp contrast to Ca2+-bound recoverin, where the myristoyl group is solvent exposed. Furthermore, we provide direct evidence that the acyl group in GCAP1 remains buried in the Ca2+-free state and does not undergo switching. A pronounced kink in the C-terminal helix and the presence of the myristoyl group allow clustering of sequence elements crucial for GCAP1 activity. PMID:17997965

Identifying calcium sources at an acid deposition-impacted spruce forest: a strontium isotope, alkaline earth element multi-tracer approach

Treesearch

Thomas D. Bullen; Scott W. Bailey

2005-01-01

Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources. but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration...

Mg/Ca, Sr/Ca and Ca isotope ratios in benthonic foraminifers related to test structure, mineralogy and environmental controls

NASA Astrophysics Data System (ADS)

Gussone, Nikolaus; Filipsson, Helena L.; Kuhnert, Henning

2016-01-01

We analysed Mg/Ca, Sr/Ca and Ca isotope ratios of benthonic foraminifers from sediment core tops retrieved during several research cruises in the Atlantic Ocean, in order to improve the understanding of isotope fractionation and element partitioning resulting from biomineralisation processes and changes in ambient conditions. Species include foraminifers secreting tests composed of hyaline low magnesium calcite, porcelaneous high magnesium calcite as well as aragonite. Our results demonstrate systematic isotope fractionation and element partitioning patterns specific for these foraminiferal groups. Calcium isotope fractionation is similar in porcelaneous and hyaline calcite tests and both groups demonstrate the previously described anomaly with enrichment of heavy isotopes around 3-4 °C (Gussone and Filipsson, 2010). Calcium isotope ratios of the aragonitic species Hoeglundina elegans, on the other hand, are about 0.4‰ lighter compared to the calcitic species, which is in general agreement with stronger fractionation in inorganic aragonite compared to calcite. However, the low and strongly variable Sr content suggests additional processes during test formation, and we propose that transmembrane ion transport or a precursor phase to aragonite may be involved. Porcelaneous tests, composed of high Mg calcite, incorporate higher amounts of Sr compared to hyaline low Mg calcite, in agreement with inorganic calcite systematics, but also porcelaneous tests with reduced Mg/Ca show high Sr/Ca. While calcium isotopes, Sr/Ca and Mg/Ca in benthonic foraminifers primarily appear to fractionate and partition with a dominant inorganic control, δ44/40Ca temperature and growth rate dependencies of benthonic foraminifer tests favour a dominant contribution of light Ca by transmembrane transport relative to unfractionated seawater Ca to the calcifying fluid, thus controlling the formation of foraminiferal δ44/40Ca and Sr/Ca proxy signals.

Enzyme-accelerated and structure-guided crystallization of calcium carbonate: role of the carbonic anhydrase in the homologous system.

PubMed

Müller, Werner E G; Schlossmacher, Ute; Schröder, Heinz C; Lieberwirth, Ingo; Glasser, Gunnar; Korzhev, Michael; Neufurth, Meik; Wang, Xiaohong

2014-01-01

The calcareous spicules from sponges, e.g. from Sycon raphanus, are composed of almost pure calcium carbonate. In order to elucidate the formation of those structural skeletal elements, the function of the enzyme carbonic anhydrase (CA), isolated from this species, during the in vitro calcium carbonate-based spicule formation, was investigated. It is shown that the recombinant sponge CA substantially accelerates calcium carbonate formation in the in vitro diffusion assay. A stoichiometric calculation revealed that the turnover rate of the sponge CA during the calcification process amounts to 25 CO2s(-1) × molecule CA(-1). During this enzymatically driven process, initially pat-like particles are formed that are subsequently transformed to rhomboid/rhombohedroid crystals with a dimension of ~50 μm. The CA-catalyzed particles are smaller than those which are formed in the absence of the enzyme. The Martens hardness of the particles formed is ~4 GPa, a value which had been determined for other biogenic calcites. This conclusion is corroborated by energy-dispersive X-ray spectroscopy, which revealed that the particles synthesized are composed predominantly of the elements calcium, oxygen and carbon. Surprising was the finding, obtained by light and scanning electron microscopy, that the newly formed calcitic crystals associate with the calcareous spicules from S. raphanus in a highly ordered manner; the calcitic crystals almost perfectly arrange in an array orientation along the two opposing planes of the spicules, leaving the other two plane arrays uncovered. It is concluded that the CA is a key enzyme controlling the calcium carbonate biomineralization process, which directs the newly formed particles to existing calcareous spicular structures. It is expected that with the given tools new bioinspired materials can be fabricated. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Leaching mechanisms of constituents from fly ash under the influence of humic acid.

PubMed

Zhao, Shengxin; Chen, Zhonglin; Shen, Jimin; Kang, Jing; Zhang, Jin; Shen, Yanqing

2017-01-05

As a low-cost material for adsorption, FA is one of the most efficient adsorbents of HA. However, the leaching of elements from FA is problematic during utilization in water treatment. In this investigation, the potential leaching behaviors of Calcium, Arsenic, Born, Chromium, and other elements from FA in HA solution were studied via batch test. The data show that HA had an effect on the leaching of each element of FA, depending on the pH, the initial concentration of HA and the addition of calcium oxide (CaO). The Langmuir isotherm could better fit the equilibrium data in different initial concentrations of HA from 10 to 100mg/L. Because of the interaction between HA and the FA leaching elements, multi-layer adsorption occurred when the initial concentration of HA was more than 100mg/L. The pH and free CaO content played major roles in HA adsorption and FA leaching. Using SEM and XRD to characterize the solid of FA being mixed with CaO treated in solution, the results demonstrated that the reaction between FA and CaO could generate crystal minerals, such as portlandite, gismondine, ettringite (AFt) and calcite, which effectively restrained the leaching of elements, reduced secondary pollution. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of Trace Elements in Rat Bronchoalveolar Lavage Fluid by Inductively Coupled Plasma Mass Spectrometry.

PubMed

Qamar, Wajhul; Al-Ghadeer, Abdul Rahman; Ali, Raisuddin; Abuelizz, Hatem A

2017-08-01

The main objective was to determine the elemental profile of the lung lining fluid of rats which are used as model animals in various experiments. Lung lining fluid elemental constitution obtained after bronchoalveolar lavage fluid (BALF) was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the biological trace elements along with calcium and magnesium. BALF was collected from healthy rats using a tracheal cannula. However, cells in BALF were counted to monitor any underlying inflammatory lung condition. Cell free BALF samples were processed and analyzed for the elements including magnesium (Mg), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), selenium (Se), bromine (Br), and iodine (I). In view of this, calcium concentration was the highest (6318.08 ± 3094.3 μg/L) and copper concentration was the lowest (0.89 ± 0.21 μg/L). The detected elements, from high to low concentration, include Ca > Mg > Fe > Br > I > Cr > Ni > Zn > Mn > Se > Cu. Pearson's correlation analysis revealed no significant correlation between cell count and concentration of any of the element detected in BALF. Correlation analysis also revealed significant positive correlation among Fe, I, Cr, Ni, and Mn. Ca was found to be correlated negatively with Cu and positively with Se. Br and Mg found to be positively correlated with each other. Zn remained the only element that was not found to be correlated with any of the elements in the rat BALF.

Increased calcium absorption from synthetic stable amorphous calcium carbonate: double-blind randomized crossover clinical trial in postmenopausal women.

PubMed

Vaisman, Nachum; Shaltiel, Galit; Daniely, Michal; Meiron, Oren E; Shechter, Assaf; Abrams, Steven A; Niv, Eva; Shapira, Yami; Sagi, Amir

2014-10-01

Calcium supplementation is a widely recognized strategy for achieving adequate calcium intake. We designed this blinded, randomized, crossover interventional trial to compare the bioavailability of a new stable synthetic amorphous calcium carbonate (ACC) with that of crystalline calcium carbonate (CCC) using the dual stable isotope technique. The study was conducted in the Unit of Clinical Nutrition, Tel Aviv Sourasky Medical Center, Israel. The study population included 15 early postmenopausal women aged 54.9 ± 2.8 (mean ± SD) years with no history of major medical illness or metabolic bone disorder, excess calcium intake, or vitamin D deficiency. Standardized breakfast was followed by randomly provided CCC or ACC capsules containing 192 mg elemental calcium labeled with 44Ca at intervals of at least 3 weeks. After swallowing the capsules, intravenous CaCl2 labeled with 42Ca on was administered on each occasion. Fractional calcium absorption (FCA) of ACC and CCC was calculated from the 24-hour urine collection following calcium administration. The results indicated that FCA of ACC was doubled (± 0.96 SD) on average compared to that of CCC (p < 0.02). The higher absorption of the synthetic stable ACC may serve as a more efficacious way of calcium supplementation. © 2014 American Society for Bone and Mineral Research.

A methodology for quantifying trace elements in the exoskeletons of Florida stone crab (Menippe mercenaria) larvae using inductively coupled plasma optical emission spectrometry (ICP–OES)

USGS Publications Warehouse

Gravinese, Philip M.; Flannery, Jennifer A.; Toth, Lauren T.

2016-11-23

The larvae of the Florida stone crab, Menippe mercenaria, migrate through a variety of habitats as they develop and, therefore, experience a broad range of environmental conditions through ontogeny. Environmental variability experienced by the larvae may result in distinct elemental signatures within the exoskeletons, which could provide a tool for tracking the environmental history of larval stone crab populations. A method was developed to examine trace-element ratios, specifically magnesium-to-calcium (Mg/Ca) and strontium-to-calcium (Sr/Ca) ratios, in the exoskeletons of M. mercenaria larvae. Two developmental stages of stone crab larvae were analyzed—stage III and stage V. Specimens were reared in a laboratory environment under stable conditions to quantify the average ratios of Mg/Ca and Sr/Ca of larval stone crab exoskeletons and to determine if the ratios differed through ontogeny. The elemental compositions (Ca, Mg, and Sr) in samples of stage III larvae (n = 50 per sample) from 11 different broods (mean Sr/Ca = 5.916 ± 0.161 millimole per mole [mmol mol−1]; mean Mg/Ca = 218.275 ± 59.957 mmol mol−1) and stage V larvae (n = 10 per sample) from 12 different broods (mean Sr/Ca = 6.110 ± 0.300 mmol mol−1; mean Mg/Ca = 267.081 ± 67.211 mmol mol–1) were measured using inductively coupled plasma optical emission spectrometry (ICP–OES). The ratio of Sr/Ca significantly increased from stage III to stage V larvae, suggesting an ontogenic shift in Sr/Ca ratios between larval stages. The ratio of Mg/Ca did not change significantly between larval stages, but variability among broods was high. The method used to examine the trace-element ratios provided robust, highly reproducible estimates of Sr/Ca and Mg/Ca ratios in the larvae of M. mercenaria, demonstrating that ICP–OES can be used to determine the trace-element composition of chitinous organisms like the Florida stone crab.

Calcium-43 chemical shift and electric field gradient tensor interplay: a sensitive probe of structure, polymorphism, and hydration.

PubMed

Widdifield, Cory M; Moudrakovski, Igor; Bryce, David L

2014-07-14

Calcium is the 5th most abundant element on earth, and is found in numerous biological tissues, proteins, materials, and increasingly in catalysts. However, due to a number of unfavourable nuclear properties, such as a low magnetogyric ratio, very low natural abundance, and its nuclear electric quadrupole moment, development of solid-state (43)Ca NMR has been constrained relative to similar nuclides. In this study, 12 commonly-available calcium compounds are analyzed via(43)Ca solid-state NMR and the information which may be obtained by the measurement of both the (43)Ca electric field gradient (EFG) and chemical shift tensors (the latter of which are extremely rare with only a handful of literature examples) is discussed. Combined with density functional theory (DFT) computations, this 'tensor interplay' is, for the first time for (43)Ca, illustrated to be diagnostic in distinguishing polymorphs (e.g., calcium formate), and the degree of hydration (e.g., CaCl2·2H2O and calcium tartrate tetrahydrate). For Ca(OH)2, we outline the first example of (1)H to (43)Ca cross-polarization on a sample at natural abundance in (43)Ca. Using prior knowledge of the relationship between the isotropic calcium chemical shift and the calcium quadrupolar coupling constant (CQ) with coordination number, we postulate the coordination number in a sample of calcium levulinate dihydrate, which does not have a known crystal structure. Natural samples of CaCO3 (aragonite polymorph) are used to show that the synthetic structure is present in nature. Gauge-including projector augmented-wave (GIPAW) DFT computations using accepted crystal structures for many of these systems generally result in calculated NMR tensor parameters which are in very good agreement with the experimental observations. This combination of (43)Ca NMR measurements with GIPAW DFT ultimately allows us to establish clear correlations between various solid-state (43)Ca NMR observables and selected structural parameters, such as unit cell dimensions and average Ca-O bond distances.

Minor element partitioning and mineralogy in limpets from the Ischia CO2 vent site

NASA Astrophysics Data System (ADS)

Langer, Gerald; Sadekov, Aleksey; Nehrke, Gernot; Baggini, Cecilia; Rodolfo-Metalpa, Riccardo; Hall-Spencer, Jason; Bijma, Jelle; Elderfield, Henry

2015-04-01

Specimens of the patellogastropod limpet Patella caerulea were collected within and outside a CO2 vent site at Ischia, Italy. The shells were sectioned transversally and scanned for polymorph distribution by means of confocal Raman microscopy. Minor element to calcium ratios were measured using laser-ablation-inductively-coupled-plasma-mass-spectroscopy (LA-ICPMS). Mg/Ca, Sr/Ca, and Li/Ca ratios were determined in calcitic as well as aragonitic parts of the shells. This approach allows for investigating the effects of the polymorph and the seawater carbonate chemistry on minor element partitioning separately.

Transcriptome Wide Identification and Validation of Calcium Sensor Gene Family in the Developing Spikes of Finger Millet Genotypes for Elucidating Its Role in Grain Calcium Accumulation

PubMed Central

Singh, Uma M.; Chandra, Muktesh; Shankhdhar, Shailesh C.; Kumar, Anil

2014-01-01

Background In finger millet, calcium is one of the important and abundant mineral elements. The molecular mechanisms involved in calcium accumulation in plants remains poorly understood. Transcriptome sequencing of genetically diverse genotypes of finger millet differing in grain calcium content will help in understanding the trait. Principal Finding In this study, the transcriptome sequencing of spike tissues of two genotypes of finger millet differing in their grain calcium content, were performed for the first time. Out of 109,218 contigs, 78 contigs in case of GP-1 (Low Ca genotype) and out of 120,130 contigs 76 contigs in case of GP-45 (High Ca genotype), were identified as calcium sensor genes. Through in silico analysis all 82 unique calcium sensor genes were classified into eight calcium sensor gene family viz., CaM & CaMLs, CBLs, CIPKs, CRKs, PEPRKs, CDPKs, CaMKs and CCaMK. Out of 82 genes, 12 were found diverse from the rice orthologs. The differential expression analysis on the basis of FPKM value resulted in 24 genes highly expressed in GP-45 and 11 genes highly expressed in GP-1. Ten of the 35 differentially expressed genes could be assigned to three documented pathways involved mainly in stress responses. Furthermore, validation of selected calcium sensor responder genes was also performed by qPCR, in developing spikes of both genotypes grown on different concentration of exogenous calcium. Conclusion Through de novo transcriptome data assembly and analysis, we reported the comprehensive identification and functional characterization of calcium sensor gene family. The calcium sensor gene family identified and characterized in this study will facilitate in understanding the molecular basis of calcium accumulation and development of calcium biofortified crops. Moreover, this study also supported that identification and characterization of gene family through Illumina paired-end sequencing is a potential tool for generating the genomic information of gene family in non-model species. PMID:25157851

Transcriptome wide identification and validation of calcium sensor gene family in the developing spikes of finger millet genotypes for elucidating its role in grain calcium accumulation.

PubMed

Singh, Uma M; Chandra, Muktesh; Shankhdhar, Shailesh C; Kumar, Anil

2014-01-01

In finger millet, calcium is one of the important and abundant mineral elements. The molecular mechanisms involved in calcium accumulation in plants remains poorly understood. Transcriptome sequencing of genetically diverse genotypes of finger millet differing in grain calcium content will help in understanding the trait. In this study, the transcriptome sequencing of spike tissues of two genotypes of finger millet differing in their grain calcium content, were performed for the first time. Out of 109,218 contigs, 78 contigs in case of GP-1 (Low Ca genotype) and out of 120,130 contigs 76 contigs in case of GP-45 (High Ca genotype), were identified as calcium sensor genes. Through in silico analysis all 82 unique calcium sensor genes were classified into eight calcium sensor gene family viz., CaM & CaMLs, CBLs, CIPKs, CRKs, PEPRKs, CDPKs, CaMKs and CCaMK. Out of 82 genes, 12 were found diverse from the rice orthologs. The differential expression analysis on the basis of FPKM value resulted in 24 genes highly expressed in GP-45 and 11 genes highly expressed in GP-1. Ten of the 35 differentially expressed genes could be assigned to three documented pathways involved mainly in stress responses. Furthermore, validation of selected calcium sensor responder genes was also performed by qPCR, in developing spikes of both genotypes grown on different concentration of exogenous calcium. Through de novo transcriptome data assembly and analysis, we reported the comprehensive identification and functional characterization of calcium sensor gene family. The calcium sensor gene family identified and characterized in this study will facilitate in understanding the molecular basis of calcium accumulation and development of calcium biofortified crops. Moreover, this study also supported that identification and characterization of gene family through Illumina paired-end sequencing is a potential tool for generating the genomic information of gene family in non-model species.

Methamphetamine acutely inhibits voltage-gated calcium channels but chronically up-regulates L-type channels.

PubMed

Andres, Marilou A; Cooke, Ian M; Bellinger, Frederick P; Berry, Marla J; Zaporteza, Maribel M; Rueli, Rachel H; Barayuga, Stephanie M; Chang, Linda

2015-07-01

In neurons, calcium (Ca(2+) ) channels regulate a wide variety of functions ranging from synaptic transmission to gene expression. They also induce neuroplastic changes that alter gene expression following psychostimulant administration. Ca(2+) channel blockers have been considered as potential therapeutic agents for the treatment of methamphetamine (METH) dependence because of their ability to reduce drug craving among METH users. Here, we studied the effects of METH exposure on voltage-gated Ca(2+) channels using SH-SY5Y cells as a model of dopaminergic neurons. We found that METH has different short- and long-term effects. A short-term effect involves immediate (< 5 min) direct inhibition of Ca(2+) ion movements through Ca(2+) channels. Longer exposure to METH (20 min or 48 h) selectively up-regulates the expression of only the CACNA1C gene, thus increasing the number of L-type Ca(2+) channels. This up-regulation of CACNA1C is associated with the expression of the cAMP-responsive element-binding protein (CREB), a known regulator of CACNA1C gene expression, and the MYC gene, which encodes a transcription factor that putatively binds to a site proximal to the CACNA1C gene transcription initiation site. The short-term inhibition of Ca(2+) ion movement and later, the up-regulation of Ca(2+) channel gene expression together suggest the operation of cAMP-responsive element-binding protein- and C-MYC-mediated mechanisms to compensate for Ca(2+) channel inhibition by METH. Increased Ca(2+) current density and subsequent increased intracellular Ca(2+) may contribute to the neurodegeneration accompanying chronic METH abuse. Methamphetamine (METH) exposure has both short- and long-term effects. Acutely, methamphetamine directly inhibits voltage-gated calcium channels. Chronically, neurons compensate by up-regulating the L-type Ca(2+) channel gene, CACNA1C. This compensatory mechanism is mediated by transcription factors C-MYC and CREB, in which CREB is linked to the dopamine D1 receptor signaling pathway. These findings suggest Ca(2+) -mediated neurotoxicity owing to over-expression of calcium channels. © 2015 International Society for Neurochemistry.

Mineralization of gellan gum hydrogels with calcium and magnesium carbonates by alternate soaking in solutions of calcium/magnesium and carbonate ion solutions.

PubMed

Lopez-Heredia, Marco A; Łapa, Agata; Reczyńska, Katarzyna; Pietryga, Krzysztof; Balcaen, Lieve; Mendes, Ana C; Schaubroeck, David; Van Der Voort, Pascal; Dokupil, Agnieszka; Plis, Agnieszka; Stevens, Chris V; Parakhonskiy, Bogdan V; Samal, Sangram Keshari; Vanhaecke, Frank; Chai, Feng; Chronakis, Ioannis S; Blanchemain, Nicolas; Pamuła, Elżbieta; Skirtach, Andre G; Douglas, Timothy E L

2018-04-27

Mineralization of hydrogels is desirable prior to applications in bone regeneration. CaCO 3 is a widely used bone regeneration material and Mg, when used as a component of calcium phosphate biomaterials, has promoted bone-forming cell adhesion and proliferation and bone regeneration. In this study, gellan gum (GG) hydrogels were mineralized with carbonates containing different amounts of calcium (Ca) and magnesium (Mg) by alternate soaking in, firstly, a calcium and/or magnesium ion solution and, secondly, a carbonate ion solution. This alternate soaking cycle was repeated five times. Five different calcium and/or magnesium ion solutions, containing different molar ratios of Ca to Mg ranging from Mg-free to Ca-free were compared. Carbonate mineral formed in all sample groups subjected to the Ca:Mg elemental ratio in the carbonate mineral formed was higher than in the respective mineralizing solution. Mineral formed in the absence of Mg was predominantly CaCO 3 in the form of a mixture of calcite and vaterite. Increasing the Mg content in the mineral formed led to the formation of magnesian calcite, decreased the total amount of the mineral formed and its crystallinity. Hydrogel mineralization and increasing Mg content in mineral formed did not obviously improve proliferation of MC3T3-E1 osteoblast-like cells or differentiation after 7 days. This article is protected by copyright. All rights reserved.

Calcium phosphate supplementation increases faecal Lactobacillus spp. in a randomised trial of young adults.

PubMed

Dahl, W J; Ford, A L; Coppola, J A; Lopez, D; Combs, W; Rohani, A; Ukhanova, M; Culpepper, T; Tompkins, T A; Christman, M; Mai, V

2016-02-01

The aim of the studies was to determine the effects of calcium carbonate and calcium phosphate supplementation on faecal Lactobacillus spp., with and without a probiotic supplement, in healthy adults. Study 1 comprised of a randomised, double-blind, crossover design; participants (n=15) received 2 capsules/d of 250 mg elemental calcium as calcium carbonate (Ca1) and calcium phosphate (Ca2) each for 2-week periods, with 2-week baseline and washout periods. Study 2 was a randomised, double-blind, crossover design; participants (n=17) received 2 capsules/d of Lactobacillus helveticus R0052 and Lactobacillus rhamnosus R0011 (probiotic) alone, the probiotic with 2 capsules/d of Ca1, and probiotic with 2 capsules/d of Ca2 each for 2-week periods with 2-week baseline and washout periods. In both studies, stools were collected during the baseline, intervention and washout periods for Lactobacillus spp. quantification and qPCR analyses. Participants completed daily questionnaires of stool frequency and compliance. In Study 1, neither calcium supplement influenced viable counts of resident Lactobacillus spp., genome equivalents of lactic acid bacteria or stool frequency. In Study 2, faecal Lactobacillus spp. counts were significantly enhanced from baseline when the probiotic was administered with Ca2 (4.83±0.30, 5.79±0.31) (P=0.02), but not with Ca1 (4.98±0.31) or with the probiotic alone (5.36±0.31, 5.55±0.29) (not significant). Detection of L. helveticus R0052 and L. rhamnosus R0011 was significantly increased with all treatments, but did not differ among treatments. There were no changes in weekly stool frequency. Calcium phosphate co-administration may increase gastrointestinal survival of orally-administered Lactobacillus spp.

Rotational spectra of the X 2Sigma(+) states of CaH and CaD

NASA Technical Reports Server (NTRS)

Frum, C. I.; Oh, J. J.; Cohen, E. A.; Pickett, H. M.

1993-01-01

The rotational spectra of the 2Sigma(2+) ground states of calcium monohydride and monodeuteride have been recorded in absorption between 250 and 700 GHz. The gas phase free radicals have been produced in a ceramic furnace by the reaction of elemental calcium with molecular hydrogen or deuterium in the presence of an electrical discharge. The molecular constants including the rotational constant, centrifugal distortion constants, spin-rotation constants, and magnetic hyperfine interaction constants have been extracted from the spectra.

Calcium plus vitamin D supplementation and height loss: findings from the Women's Health Initiative Calcium and Vitamin D clinical trial.

PubMed

Crandall, Carolyn J; Aragaki, Aaron K; LeBoff, Meryl S; Li, Wenjun; Wactawski-Wende, Jean; Cauley, Jane A; Margolis, Karen L; Manson, JoAnn E

2016-12-01

The aim of this study was to determine the associations between calcium + vitamin D supplementation (vs placebo) and height loss in 36,282 participants of the Women's Health Initiative Calcium and Vitamin D trial. Post hoc analysis of data from a double-blind randomized controlled trial of 1,000 mg of elemental calcium as calcium carbonate with 400 IU of vitamin D3 daily (CaD) or placebo in postmenopausal women at 40 US clinical centers. Height was measured annually (mean follow-up 5.9 y) with a stadiometer. Average height loss was 1.28 mm/y among participants assigned to CaD versus 1.26 mm/y for women assigned to placebo (P = 0.35). Effect modification of the CaD intervention was not observed by age, race/ethnicity, or baseline intake of calcium or vitamin D. Randomization to the CaD group did not reduce the risk of clinical height loss (loss of ≥1.5 inches [3.8 cm]: hazard ratio (95% CI) = 1.00 (0.81, 1.23). A strong association (P < 0.001) was observed between age group and height loss. When we censored follow-up data in participants who became nonadherent to study pills, the results were similar to those of our primary analysis. Compared with placebo, the CaD supplement used in this trial did not prevent height loss in healthy postmenopausal women.

Transition of spiral calcium waves between multiple stable patterns can be triggered by a single calcium spark in a fire-diffuse-fire model

PubMed Central

Tang, Ai-Hui; Wang, Shi-Qiang

2009-01-01

Spiral patterns have been found in various nonequilibrium systems. The Ca2+-induced Ca2+ release system in single cardiac cells is unique for highly discrete reaction elements, each giving rise to a Ca2+ spark upon excitation. We imaged the spiral Ca2+ waves in isolated cardiac cells and numerically studied the effect of system excitability on spiral patterns using a two-dimensional fire-diffuse-fire model. We found that under certain conditions, the system was able to display multiple stable patterns of spiral waves, each exhibiting different periods and distinct routines of spiral tips. Transition between these different patterns could be triggered by an internal fluctuation in the form of a single Ca2+ spark. PMID:19792039

Transition of spiral calcium waves between multiple stable patterns can be triggered by a single calcium spark in a fire-diffuse-fire model.

PubMed

Tang, Ai-Hui; Wang, Shi-Qiang

2009-09-01

Spiral patterns have been found in various nonequilibrium systems. The Ca(2+)-induced Ca(2+) release system in single cardiac cells is unique for highly discrete reaction elements, each giving rise to a Ca(2+) spark upon excitation. We imaged the spiral Ca(2+) waves in isolated cardiac cells and numerically studied the effect of system excitability on spiral patterns using a two-dimensional fire-diffuse-fire model. We found that under certain conditions, the system was able to display multiple stable patterns of spiral waves, each exhibiting different periods and distinct routines of spiral tips. Transition between these different patterns could be triggered by an internal fluctuation in the form of a single Ca(2+) spark.

Micro-topography and reactivity of implant surfaces: an in vitro study in simulated body fluid (SBF).

PubMed

Gandolfi, M G; Taddei, P; Siboni, F; Perrotti, V; Iezzi, G; Piattelli, A; Prati, C

2015-02-01

The creation of micro-textured dental implant surfaces possessing a stimulating activity represents a challenge in implant dentistry; particularly, the formation of a thin, biologically active, calcium-phosphate layer on their surface could help to strengthen the bond to the surrounding bone. The aim of the present study was to characterize in terms of macrostructure, micro-topography and reactivity in simulated body fluid (SBF), the surface of titanium (Ti) implants blasted with TiO2 particles, acid etched with hydrofluoric acid, and activated with Ca and Mg-containing nanoparticles. Sandblasted and acid-etched implants were analyzed by ESEM-EDX (environmental scanning electron microscope with energy dispersive X-ray system) to study the micromorphology of the surface and to perform elemental X-ray microanalysis (microchemical analyses) and element mapping. ESEM-EDX analyses were performed at time 0 and after a 28-day soaking period in SBF Hank's balanced salt solution (HBSS) following ISO 23317 (implants for surgery—in vitro evaluation for apatite-forming ability of implant materials). Microchemical analyses (weight % and atomic %) and element mapping were carried out to evaluate the relative element content, element distribution, and calcium/phosphorus (Ca/P) atomic ratio. Raman spectroscopy was used to assess the possible presence of impurities due to manufacturing and to investigate the phases formed upon HBSS soaking. Micro-morphological analyses showed a micro-textured, highly rough surface with microgrooves. Microchemical analyses showed compositional differences among the apical, middle, and distal thirds. The micro-Raman analyses of the as-received implant showed the presence of amorphous Ti oxide and traces of anatase, calcite, and a carbonaceous material derived from the decomposition of an organic component of lipidic nature (presumably used as lubricant). A uniform layer of Ca-poor calcium phosphates (CaPs) (Ca/P ratio <1.47) was observed after soaking in HBSS; the detection of the 961 cm⁻¹ Raman band confirms this finding. These implants showed a micro-textured surface supporting the formation of CaPs when immersed in SBF. These properties may likely favor bone anchorage and healing by stimulation of mineralizing cells.

Postural stabilizing effect of alfacalcidol and active absorbable algal calcium (AAA Ca) compared with calcium carbonate assessed by computerized posturography.

PubMed

Fujita, Takuo; Nakamura, Shoji; Ohue, Mutsumi; Fujii, Yoshio; Miyauchi, Akimitsu; Takagi, Yasuyuki; Tsugeno, Hirofumi

2007-01-01

Sway and postural instability have drawn attention as a risk factor for osteoporotic fracture, in addition to low bone mineral density (BMD) and poor bone quality. In view of the fracture-reducing effect of alfacalcidol and active absorbable algal calcium (AAA Ca) not readily explained by rather mild increases of BMD, attempts were made to evaluate postural stabilizing effect of alfacalcidol, AAA Ca, and calcium carbonate (CaCO(3)) by computerized posturography. Track of the gravity center was analyzed to calculate parameters related to tract length, track range, and track density to express the degree of sway before and after supplementation in 126 subjects ranging in age between 20 and 81 years randomly divided into four groups. Supplementation with AAA Ca containing 900 mg elemental Ca (group A), no calcium (group B), CaCO(3) also containing 900 mg elemental Ca (group C), or alfacalcidol (group D) continued daily for 12 months. For each parameter, the ratio closed eye value/open eye value (Romberg ratio) was calculated to detect aggravation of sway by eye closure. Age, parameters of Ca and P, and proportions of subjects with fracture and those with low BMD showed no marked deviation among the groups. With eyes open, significant decreases of a track range parameter (REC) from group B was noted in groups A (P = 0.0397) and D (P = 0.0296), but not in group C according to multiple comparison by Scheffe, indicating superior postural stabilizing effect of A and D over C. In the first 2 months, a significant fall was already evident in REC from group B in group D (P = 0.0120) with eyes open. Paired comparison of sway parameters before and after supplementation revealed a significant increase of track density parameter (LNGA), indicating sway control efficiency and a significant decrease of REC in groups A and D compared to group B with eyes open. With eyes closed, only group A showed a significant improvement from group B (P = 0.0456; Fig. 1), with a significant shortening on paired After/Before comparison (P = 0.0142; Fig. 2). Computerized posturography appears to be useful in analyzing sway phenomena especially as to the effects of vitamin D and various Ca preparations.

Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

PubMed

Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

2014-02-01

The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

A randomized clinical trial of the effects of supplemental calcium and vitamin D3 on markers of their metabolism in normal mucosa of colorectal adenoma patients.

PubMed

Ahearn, Thomas U; McCullough, Marjorie L; Flanders, W Dana; Long, Qi; Sidelnikov, Eduard; Fedirko, Veronika; Daniel, Carrie R; Rutherford, Robin E; Shaukat, Aasma; Bostick, Roberd M

2011-01-15

In cancer cell lines and rodent models, calcium and vitamin D favorably modulate cell proliferation, differentiation, and apoptosis in colonic epithelia. These effects may be modulated by local expression of the calcium receptor (CaR), the vitamin D receptor (VDR), and the P450 cytochromes, CYP27B1 and CYP24A1; however, they have yet to be investigated in humans. To address this gap, we conducted a randomized, double-blinded, placebo-controlled 2×2 factorial clinical trial. Patients with at least one pathology-confirmed colorectal adenoma were treated with 2 g/d elemental calcium and/or 800 IU/d vitamin D3 versus placebo over 6 months (n=92; 23 per group). CaR, VDR, CYP27B1, and CYP24A1 expression and distribution in biopsies of normal appearing rectal mucosa were detected by standardized, automated immunohistochemistry and quantified by image analysis. In the calcium-supplemented group, CaR expression increased 27% (P=0.03) and CYP24A1 expression decreased 21% (P=0.79). In the vitamin D3-supplemented group, CaR expression increased 39% (P=0.01) and CYP27B1 expression increased 159% (P=0.06). In patients supplemented with both calcium and vitamin D3, VDR expression increased 19% (P=0.13) and CaR expression increased 24% (P=0.05). These results provide mechanistic support for further investigation of calcium and vitamin D3 as chemopreventive agents against colorectal neoplasms, and CaR, VDR, CYP27B1, and CYP24A1 as modifiable, preneoplastic risk biomarkers for colorectal neoplasms. © 2010 AACR.

Derivation of ionization balance for calcium XVIII/XIX using XRP solar X-ray data

NASA Astrophysics Data System (ADS)

Antonucci, E.; Gabriel, A. H.; Doyle, J. G.; Dubau, J.; Faucher, P.; Jordan, C.; Veck, N.

1984-04-01

Spectra of calcium from solar flares are used in an attempt to derive an ionization balance for Ca XVIII/Ca XIX. The isothermal assumption inherent in this derivation is shown not to introduce errors, by modelling a number of hypothetical nonisothermal plasmas. The unresolved blend of calcium and argon lines prevents a definitive determination of the results, owing to uncertainties in the ratio of abundances of these elements. The resulting ionization balance curves are presented as a function of the solar argon/calcium abundance ratio. The theoretical ionization balance of Doyle and Raymond is consistent with the data. To within the expected accuracy of the atomic theories, there is no reason to assume that the flare plasma is other than close to steady-state ionization balance.

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

PubMed Central

Morais, Tatiana P.; Coelho, David; Vaz, Sandra H.; Sebastião, Ana M.; Valente, Cláudia A.

2018-01-01

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. PMID:29386993

Constraining Calcium Production in Novae

NASA Astrophysics Data System (ADS)

Tiwari, Pranjal; C. Fry, C. Wrede Team; A. Chen, J. Liang Collaboration; S. Bishop, T. Faestermann, D. Seiler Collaboration; R. Hertenberger, H. Wirth Collaboration

2017-09-01

Calcium is an element that can be produced by thermonuclear reactions in the hottest classical novae. There are discrepancies between the abundance of Calcium observed in novae and expectations based on astrophysical models. Unbound states 1 MeV above the proton threshold affect the production of Calcium in nova models because they act as resonances in the 38 K(p , γ) 39 Ca reaction present. This work describes an experiment to measure the energies of the excited states of 39 Ca . We will bombard a thin target of 40 Ca with a beam of 22 MeV deuterons, resulting in tritons and 39Ca. We will use a Q3D magnetic spectrograph from the MLL in Garching, Germany to momenta analyze the tritons to observe the excitation energies of the resulting 39 Ca states. Simulations have been run to determine the optimal spectrograph settings. We decided to use a chemically stable target composed of CaF2 , doing so resulted in an extra contaminant, Fluorine, which is dealt with by measuring the background from a LiF target. These simulations have led to settings and targets that will result in the observation of the 39 Ca states of interest with minimal interference from contaminants. Preliminary results from this experiment will be presented. National Sciences and Engineering Research Council of Canada and U.S. National Science Foundation.

Modification of Ca isotope and trace metal composition of the major matrices involved in shell formation of Mytilus edulis

NASA Astrophysics Data System (ADS)

Heinemann, Agnes; Fietzke, Jan; Eisenhauer, Anton; Zumholz, Karsten

2008-01-01

In this study we present the first combined investigation into the composition of the major matrices involved in calcification processes (surrounding water, extrapallial fluid, aragonite, and calcite) of Mytilus edulis with respect to their calcium isotope (δ44/40Ca) and elemental compositions (Sr/Ca and Mg/Ca). Our aim was to examine the suitability of Mytilus edulis as a proxy archive and to contribute to the understanding of the process of biomineralization. Mytilus edulis specimens were live collected from the Schwentine Estuary, Kiel Fjord, and North Sea (Sylt). δ44/40Ca was determined by thermal ionization mass spectrometry (TIMS) accompanied by measurements of Mg/Ca and Sr/Ca using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The elemental and isotopic compositions of the investigated matrices showed systematic offsets. The carbonates are strongly depleted in their magnesium and strontium concentrations and fractionated toward lighter calcium isotope compositions relative to the surrounding Schwentine Estuary water. The opposite is observed for the extrapallial fluid (EPF). Our findings extend the results of previous studies reporting a strong biological control and the interaction of different environmental conditions influencing biomineralization. Future studies should focus on the temporal development of the interrelation between the different matrices.

Calcium Isotopic Compositions of Forearc Sediments from DSDP Site 144

NASA Astrophysics Data System (ADS)

Zhang, Z.; Zhu, H.; Nan, X.; Li, X.; Huang, F.

2016-12-01

It is important to investigate calcium isotopic compositions of reservoirs of the Earth for better application of Ca isotopes into studies of a variety of geochemical problems. Because Ca isotopic compositions for igneous rocks and carbonates are increasingly reported, this maybe bring new requirements on carefully understanding the isotopic compositions of subducted marine sediments. Marine sediments mainly contains carbonates and clays, controlling the compositions of slab-derived materials which are added to the mantle wedge. Obviously, it could have different elemental and calcium isotopic compositions with marine carbonate. Thus, it could also put biases on calcium isotopic signatures of basalts resulted from recycling oceanic carbonate into the mantle. Here, we report calcium isotopic compositions of 17 sediment samples from Deep Sea Drilling Project (DSDP) site 144 (09°27.23' N, 54°20.52' W) which is located about 400 km north of Surinam on the northern flank of the Demerara Rise with a water depth of 2957 meters. These samples have CaO contents ranging from 14.56 wt.% to 41.46 wt.% with an average of 29.61 ± 18.21 (2SD), δ44/40Ca ranges from 0.19 to 0.58 (relative to SRM915a) with an average of 0.40 ± 0.22 (2SD). These carbonate-rich sediments can be used to represent an endmember with high CaO content and low δ44/40Ca, which could modify chemical composition of the upper mantle and subduction zone lavas if they are recycled to the convective mantle during subduction. The positive linear correlation between CaO and δ44/40Ca in the sediments cannot be explained by a simple mixing between marine carbonate and clay. Instead, δ44/40Ca of these samples roughly increase from the Upper Cretaceous to the Early Oligocene, which might reflect the evolution of calcium isotopic compositions of seawater through time.

Hybrid calcium phosphate coatings for implants

NASA Astrophysics Data System (ADS)

Malchikhina, Alena I.; Shesterikov, Evgeny V.; Bolbasov, Evgeny N.; Ignatov, Viktor P.; Tverdokhlebov, Sergei I.

2016-08-01

Monophasic biomaterials cannot provide all the necessary functions of bones or other calcined tissues. It is necessary to create for cancer patients the multiphase materials with the structure and composition simulating the natural bone. Such materials are classified as hybrid, obtained by a combination of chemically different components. The paper presents the physical, chemical and biological studies of coatings produced by hybrid technologies (HT), which combine primer layer and calcium phosphate (CaP) coating. The first HT type combines the method of vacuum arc titanium primer layer deposition on a stainless steel substrate with the following micro-arc oxidation (MAO) in phosphoric acid solution with addition of calcium compounds to achieve high supersaturated state. MAO CaP coatings feature high porosity (2-8%, pore size 5-7 µm) and surface morphology with the thickness greater than 5 µm. The thickness of Ti primer layer is 5-40 µm. Amorphous MAO CaP coating micro-hardness was measured at maximum normal load Fmax = 300 mN. It was 3.1 ± 0.8 GPa, surface layer elasticity modulus E = 110 ± 20 GPa, roughness Ra = 0.9 ± 0.1 µm, Rz = 7.5 ± 0.2 µm, which is less than the titanium primer layer roughness. Hybrid MAO CaP coating is biocompatible, able to form calcium phosphates from supersaturated body fluid (SBF) solution and also stimulates osteoinduction processes. The second HT type includes the oxide layer formation by thermal oxidation and then CaP target radio frequency magnetron sputtering (RFMS). Oxide-RFMS CaP coating is a thin dense coating with good adhesion to the substrate material, which can be used for metal implants. The RFMS CaP coating has thickness 1.6 ± 0.1 µm and consists of main target elements calcium and phosphorus and Ca/P ratio 2.4. The second HT type can form calcium phosphates from SBF solution. In vivo study shows that hybrid RFMS CaP coating is biocompatible and produces fibrointegration processes.

Vitamin D treatment in calcium-deficiency rickets: a randomised controlled trial.

PubMed

Thacher, Tom D; Fischer, Philip R; Pettifor, John M

2014-09-01

To determine whether children with calcium-deficiency rickets have a better response to treatment with vitamin D and calcium than with calcium alone. Randomised controlled trial. Jos University Teaching Hospital, Jos, Nigeria. Nigerian children with active rickets treated with calcium carbonate as limestone (approximately 938 mg elemental calcium twice daily) were, in addition, randomised to receive either oral vitamin D2 50,000 IU (Ca+D, n=44) or placebo (Ca, n=28) monthly for 24 weeks. Achievement of a 10-point radiographic severity score ≤1.5 and serum alkaline phosphatase ≤350 U/L. The median (range) age of enrolled children was 46 (15-102) months, and baseline characteristics were similar in the two groups. Mean (±SD) 25-hydroxyvitamin D (25(OH)D) was 30.2±13.2 nmol/L at baseline, and 29 (43%) had values <30 nmol/L. Baseline alkaline phosphatase and radiographic scores were unrelated to vitamin D status. Of the 68 children (94% of original cohort) who completed 24 weeks of treatment, 29 (67%) in the Ca+D group and 11 (44%) in the Ca group achieved the primary outcome (p=0.06). Baseline 25(OH)D did not alter treatment group effects (p=0.99 for interaction). At the end of 24 weeks, 25(OH)D values were 55.4±17.0 nmol/L and 37.9±20.0 nmol/L in the Ca+D and Ca groups, respectively, (p<0.001). In the Ca+D and Ca groups, the final 25(OH)D concentration was greater in those who achieved the primary outcome (56.4±17.2 nmol/L) than in those who did not (37.7±18.5 nmol/L, p<0.001). In children with calcium-deficiency rickets, there is a trend for vitamin D to improve the response to treatment with calcium carbonate as limestone, independent of baseline 25(OH)D concentrations. ClinicalTrials.gov NCT00949832. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Changes in calcium and iron levels in the brains of rats during kainate induced epilepsy

NASA Astrophysics Data System (ADS)

Ren, Min-Qin; Ong, Wei-Yi; Makjanic, Jagoda; Watt, Frank

1999-10-01

Epilepsy is a recurrent disorder of cerebral function characterised by sudden brief attacks of altered consciousness, motor activity or sensory phenomena, and affects approximately 1% of the population. Kainic acid injection induces neuronal degeneration in rats, is associated with glial hypertrophy and proliferation in the CA3-CA4 fields of hippocampal complex, and is a model for temporal lobe epilepsy. In this study we have applied Nuclear Microscopy to the investigation of the elemental changes within the hippocampus and the cortex areas of the rat brain following kainate injection. Analyses of unstained freeze dried tissue sections taken at 1 day and 1, 2, 3 and 4 weeks following injection were carried out using the Nuclear Microscopy facility at the Research Centre for Nuclear Microscopy, National University of Singapore. Quantitative analysis and elemental mapping indicates that there are significant changes in the calcium levels and distributions in the hippocampus as early as 1 day following injection. Preliminary results indicate a rapid increase in cellular calcium. High levels of calcium can activate calcium dependent proteins and phospholipases. Activation of phospholipase A 2 can be harmful to surrounding neurons through free radical damage. In addition to observed increases in calcium, there was evidence of increases in iron levels. This is consistent with measurements in other degenerative brain disorders, and may signal a late surge in free radical production.

Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications.

PubMed

Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari; Declercq, Heidi A; Schaubroeck, David; Mendes, Ana C; der Voort, Pascal Van; Dokupil, Agnieszka; Plis, Agnieszka; De Schamphelaere, Karel; Chronakis, Ioannis S; Pamuła, Elżbieta; Skirtach, Andre G

2017-12-01

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO 3 ) has been successfully applied as a bone regeneration material, but hydrogel-CaCO 3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO 3 , Mg-enriched CaCO 3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium:magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO 3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Otolith edge fingerprints as approach for stock identification of Genidens barbus

NASA Astrophysics Data System (ADS)

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

2017-07-01

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

The Mercury exosphere after MESSENGER

NASA Astrophysics Data System (ADS)

Killen, Rosemary; McClintock, William; Vervack, Ronald; Merkel, Aimee; Burger, Matthew; Cassidy, Timothy; Sarantos, Menelaos

2016-07-01

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft observed sodium, calcium and magnesium emisison in Mercury's exosphere on a near-daily basis for >16 Mercury years. The MASCS observations showed that calcium in Mercury's exosphere is persistently concentrated in the dawn hemisphere and is of extreme temperature (>50,000 K). The column abundance varies seasonally, and is extremely repeatable each Mercury year. In addition, the calcium exhibits a persistent maximum not at perihelion but 20° after perihelion, an enhancement that was shown to be coincident with the probable intersection of Mercury's orbit with a dust stream originating at Comet Encke. Any mechanism producing the Mercurian Ca exosphere must explain the facts that the Ca is extremely hot, that it is seen almost exclusively on the dawnside of the planet, and that its content varies seasonally, not sporadically. Energization of the Ca atoms was suggested to originate through dissociation of Ca-bearing molecules ejected by meteoritic impacts. Magnesium was also observed on a daily basis throughout the MESSENGER orbital phase. Mg has its own spatial and temporal pattern, peaking at mid-morning instead of early morning like Ca, and exhibiting a warm thermal profile, about 5000 K, unlike the extreme temperature of Ca which is an order of magnitude hotter. Although Mercury's sodium exosphere has been observed from the ground for many decades, the MASCS observations showed that, like calcium, the sodium exosphere is dominated by seasonal variations, not sporadic variations. However a conundrum exists as to why ground-based observations show highly variable high-latitude variations that eluded the MASCS. The origin of a persistent south polar enhancement has not been explained. The more volatile element, Na, is again colder, about 1200 K, but not thermally accommodated to the surface temperature. A combination of source processes is surmised for this element, dominated by photon-stimulated desorption. Sporadic and high latitude enhancements persistently seen from the Earth have eluded measurement from orbit, possibly due to the geometry of the observations. One discovery still not fully explained is the observation that ionized calcium is almost as dense in the anti-sunward near tail as neutral calcium. The reason is most probably due to magnetospheric convection, but further work is needed to confirm this. Other weakly emitting species such as aluminum were observed sporadically, but most often near the dawn terminator.

Women’s Health Initiative Clinical Trials: Interaction of calcium plus vitamin D and Hormone Therapy

PubMed Central

Robbins, John A; Aragaki, Aaron; Crandall, Carolyn J; Manson, Joann E; Carbone, Laura; Jackson, Rebecca; Lewis, Cora E.; Johnson, Karen C.; Sarto, Gloria; Stefanick, Marcia L; Wactawski-Wende, Jean

2013-01-01

Objective To test the added value of Calcium and vitamin D (CaD) for fracture prevention among women taking postmenopausal hormone therapy (HT). Methods A prospective, partial-factorial design, randomized controlled double blind trial amongst Women’s Health Initiative post-menopausal participants, ages 50–79, at 40 centers in the US, with 7.1 years average follow-up. 27,347 women were randomized to HT (conjugated estrogen 0.625 mg alone, or CEE 0.625 mg daily plus medroxyprogesterone acetate 2.5mg) and 36,282 women randomized to either 1000mg elemental calcium (carbonate) plus 400 IU of vitamin D3 daily each compared to placebo. A total of 16,089 women were in both arms. The predefined outcomes were adjudicated hip fractures and measured bone mineral density. Results Interaction between HT and CaD on hip fracture (P-interaction = 0.01) was shown. The effect of CaD was stronger among women assigned to HT (HR, 0.59; 95%CI, 0.38–0.93) than placebo (HR, 1.20; 95%CI, 0.85, 1.69). The effect of HT on hip fracture was stronger among women assigned to active CaD (HR, 0.43; 0.28–0.66) than placebo (HR, 0.87; 95%CI, 0.60–1.26). CaD supplementation enhanced the anti-fracture effect of the HT at all levels of personal calcium intake. There was no interaction of HT and CaD on change in hip or spine BMD. Conclusions Postmenopausal women at normal risk of hip fracture on HT, supplementation with CaD significantly reduced incident hip fracture beyond HT alone; at all levels of personal baseline total calcium intake. PMID:23799356

Superresolution Modeling of Calcium Release in the Heart

PubMed Central

Walker, Mark A.; Williams, George S.B.; Kohl, Tobias; Lehnart, Stephan E.; Jafri, M. Saleet; Greenstein, Joseph L.; Lederer, W.J.; Winslow, Raimond L.

2014-01-01

Stable calcium-induced calcium release (CICR) is critical for maintaining normal cellular contraction during cardiac excitation-contraction coupling. The fundamental element of CICR in the heart is the calcium (Ca2+) spark, which arises from a cluster of ryanodine receptors (RyR). Opening of these RyR clusters is triggered to produce a local, regenerative release of Ca2+ from the sarcoplasmic reticulum (SR). The Ca2+ leak out of the SR is an important process for cellular Ca2+ management, and it is critically influenced by spark fidelity, i.e., the probability that a spontaneous RyR opening triggers a Ca2+ spark. Here, we present a detailed, three-dimensional model of a cardiac Ca2+ release unit that incorporates diffusion, intracellular buffering systems, and stochastically gated ion channels. The model exhibits realistic Ca2+ sparks and robust Ca2+ spark termination across a wide range of geometries and conditions. Furthermore, the model captures the details of Ca2+ spark and nonspark-based SR Ca2+ leak, and it produces normal excitation-contraction coupling gain. We show that SR luminal Ca2+-dependent regulation of the RyR is not critical for spark termination, but it can explain the exponential rise in the SR Ca2+ leak-load relationship demonstrated in previous experimental work. Perturbations to subspace dimensions, which have been observed in experimental models of disease, strongly alter Ca2+ spark dynamics. In addition, we find that the structure of RyR clusters also influences Ca2+ release properties due to variations in inter-RyR coupling via local subspace Ca2+ concentration ([Ca2+]ss). These results are illustrated for RyR clusters based on super-resolution stimulated emission depletion microscopy. Finally, we present a believed-novel approach by which the spark fidelity of a RyR cluster can be predicted from structural information of the cluster using the maximum eigenvalue of its adjacency matrix. These results provide critical insights into CICR dynamics in heart, under normal and pathological conditions. PMID:25517166

Ion-Doped Silicate Bioceramic Coating of Ti-Based Implant

PubMed Central

Mohammadi, Hossein; Sepantafar, Mohammadmajid

2016-01-01

Titanium and its alloy are known as important load-bearing biomaterials. The major drawbacks of these metals are fibrous formation and low corrosion rate after implantation. The surface modification of biomedical implants through various methods such as plasma spray improves their osseointegration and clinical lifetime. Different materials have been already used as coatings on biomedical implant, including calcium phosphates and bioglass. However, these materials have been reported to have limited clinical success. The excellent bioactivity of calcium silicate (Ca-Si) has been also regarded as coating material. However, their high degradation rate and low mechanical strength limit their further coating application. Trace element modification of (Ca-Si) bioceramics is a promising method, which improves their mechanical strength and chemical stability. In this review, the potential of trace element-modified silicate coatings on better bone formation of titanium implant is investigated. PMID:26979401

Surface integrity and corrosion performance of biomedical magnesium-calcium alloy processed by hybrid dry cutting-finish burnishing.

PubMed

Salahshoor, M; Li, C; Liu, Z Y; Fang, X Y; Guo, Y B

2018-02-01

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive orthopedic biomaterial compared to permanent metallic alloys. However, the critical issue is that MgCa alloy corrodes too fast in the human organism. Compared to dry cutting, the synergistic dry cutting-finish burnishing can significantly improve corrosion performance of MgCa0.8 (wt%) alloy by producing a superior surface integrity including good surface finish, high compressive hook-shaped residual stress profile, extended strain hardening in subsurface, and little change of grain size. A FEA model was developed to understand the plastic deformation of MgCa materials during burnishing process. The measured polarization curves, surface micrographs, and element distributions of the corroded surfaces by burnishing show an increasing and uniform corrosion resistance to simulated body fluid. Copyright © 2017 Elsevier Ltd. All rights reserved.

Correlations between elements in the fur of wild animals.

PubMed

Długaszek, Maria; Kopczyński, Krzysztof

2014-07-01

There is little data on the elemental composition of wild animals fur. In the paper, an attempt has been made to evaluate the concentration of elements in the fur of roe deer, wild boar and hare. The contents of following elements: calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), lead (Pb), cadmium (Cd), aluminium (Al), chromium (Cr), nickel (Ni) were determined by atomic absorption spectrometry method. Their content was in the range 0.01 (Cd) to 1,519 (Ca) μg/g. Correlations between the content of Mn, Al, Ca, Pb, Cr, Ni in the fur of animals, liver and muscle tissues were found. Thus it can be assumed that the fur of wild animals can provide an information on the bioavailability of elements and environmental exposure and can be considered as an useful biomarker in animals and environmental studies, although research on this subject should be continued.

μX-ray fluorescence analysis of traces and calcium phosphate phases on tooth tartar interfaces using synchrotron radiation

NASA Astrophysics Data System (ADS)

Abraham, J. A.; Grenón, M. S.; Sánchez, H. J.; Valentinuzzi, M. C.; Perez, C. A.

2007-07-01

Hard dental tissues like dentine and cementum with calcified deposits (dental calculi) were studied in several human dental pieces of adult individuals from the same geographic region. A couple of cross cuts were performed at dental root level resulting in a planar slice with calculus and dental tissue exposed for analysis. The elemental content along a linear path crossing the dentine-cementum-tartar interfaces and also all over a surface was measured by X-ray fluorescence microanalysis using synchrotron radiation (μSRXRF). The concentration of elemental traces like K, V, Cu, Zn, As, Br and Sr showed different features on the analyzed regions. The possible connections with the dynamic of mineralization and biological implications are discussed. The concentrations of major elements Ca and P were also determined and the measured Ca/P molar ratio was used to estimate the average composition of calcium phosphate phases in the measured points. A deeper knowledge of the variations of the elemental compositions and the changes of the different phases will help to a better understanding of the scarcely known mechanism of calculus growing.

Intra-Amniotic Administration (Gallus gallus) of Cicer arietinum and Lens culinaris Prebiotics Extracts and Duck Egg White Peptides Affects Calcium Status and Intestinal Functionality

PubMed Central

Hou, Tao; Glahn, Raymond P.; Tako, Elad

2017-01-01

Calcium (Ca) is one of the most abundant inorganic elements in the human body and has many important physiological roles. Prebiotics and bioactive peptides are two important substances used to promote calcium uptake. However, the difference in mechanisms of the calcium uptake from these two supplements is not clear. By using the Gallus gallus model and the intra-amniotic administration procedure, the aim of this study was to investigate whether Ca status, intestinal functionality, and health-promoting bacterial populations were affected by prebiotics extracted from chickpea and lentil, and duck egg white peptides (DPs). Eleven groups (non-injected; 18 MΩ H2O; 4 mmol/L CaCl2; 50 mg/mL chickpea + 4 mmol/L CaCl2; 50 mg/mL lentil + 4 mmol/L CaCl2; 40 mg/mL DPs + 4 mmol/L CaCl2; 5 mg/mL Val-Ser-Glu-Glu (VSEE) + 4 mmol/L CaCl2; 50 mg/mL chickpea; 50 mg/mL lentil; 40 mg/mL DPs; 5 mg/mL VSEE) were utilized. Upon hatch, blood, cecum, small intestine, liver and bone were collected for assessment of serum bone alkaline phosphate level (BALP), the relative abundance of intestinal microflora, expression of Ca-related genes, brush border membrane (BBM) functional genes, and liver and bone mineral levels, respectively. The BALP level increased in the presence of lentil, DPs and VSEE (p < 0.05). The relative abundance of probiotics increased significantly (p < 0.05) by VSEE + Ca and chickpea. The expression of CalbindinD9k (Ca transporter) increased (p < 0.05) in Ca, chickpea + Ca and lentil + Ca groups. In addition, the brush border membrane functionality genes expressions increased (p < 0.05) by the chickpea or lentil extracts. Prebiotics and DPs beneficially affected the intestinal microflora and duodenal villus surface area. This research expands the understanding of the prebiotics’ properties of chickpea and lentil extracts, and peptides’ effects on calcium metabolism and gut health. PMID:28754012

Intra-Amniotic Administration (Gallus gallus) of Cicer arietinum and Lens culinaris Prebiotics Extracts and Duck Egg White Peptides Affects Calcium Status and Intestinal Functionality.

PubMed

Hou, Tao; Kolba, Nikolai; Glahn, Raymond P; Tako, Elad

2017-07-21

Calcium (Ca) is one of the most abundant inorganic elements in the human body and has many important physiological roles. Prebiotics and bioactive peptides are two important substances used to promote calcium uptake. However, the difference in mechanisms of the calcium uptake from these two supplements is not clear. By using the Gallus gallus model and the intra-amniotic administration procedure, the aim of this study was to investigate whether Ca status, intestinal functionality, and health-promoting bacterial populations were affected by prebiotics extracted from chickpea and lentil, and duck egg white peptides (DPs). Eleven groups (non-injected; 18 MΩ H₂O; 4 mmol/L CaCl₂; 50 mg/mL chickpea + 4 mmol/L CaCl₂; 50 mg/mL lentil + 4 mmol/L CaCl₂; 40 mg/mL DPs + 4 mmol/L CaCl₂; 5 mg/mL Val-Ser-Glu-Glu (VSEE) + 4 mmol/L CaCl₂; 50 mg/mL chickpea; 50 mg/mL lentil; 40 mg/mL DPs; 5 mg/mL VSEE) were utilized. Upon hatch, blood, cecum, small intestine, liver and bone were collected for assessment of serum bone alkaline phosphate level (BALP), the relative abundance of intestinal microflora, expression of Ca-related genes, brush border membrane (BBM) functional genes, and liver and bone mineral levels, respectively. The BALP level increased in the presence of lentil, DPs and VSEE ( p < 0.05). The relative abundance of probiotics increased significantly ( p < 0.05) by VSEE + Ca and chickpea. The expression of CalbindinD9k (Ca transporter) increased ( p < 0.05) in Ca, chickpea + Ca and lentil + Ca groups. In addition, the brush border membrane functionality genes expressions increased ( p < 0.05) by the chickpea or lentil extracts. Prebiotics and DPs beneficially affected the intestinal microflora and duodenal villus surface area. This research expands the understanding of the prebiotics' properties of chickpea and lentil extracts, and peptides' effects on calcium metabolism and gut health.

Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading (TED)

PubMed Central

Samtleben, Samira; Jaepel, Juliane; Fecher, Caroline; Andreska, Thomas; Rehberg, Markus; Blum, Robert

2013-01-01

Visualization of calcium dynamics is important to understand the role of calcium in cell physiology. To examine calcium dynamics, synthetic fluorescent Ca2+ indictors have become popular. Here we demonstrate TED (= targeted-esterase induced dye loading), a method to improve the release of Ca2+ indicator dyes in the ER lumen of different cell types. To date, TED was used in cell lines, glial cells, and neurons in vitro. TED bases on efficient, recombinant targeting of a high carboxylesterase activity to the ER lumen using vector-constructs that express Carboxylesterases (CES). The latest TED vectors contain a core element of CES2 fused to a red fluorescent protein, thus enabling simultaneous two-color imaging. The dynamics of free calcium in the ER are imaged in one color, while the corresponding ER structure appears in red. At the beginning of the procedure, cells are transduced with a lentivirus. Subsequently, the infected cells are seeded on coverslips to finally enable live cell imaging. Then, living cells are incubated with the acetoxymethyl ester (AM-ester) form of low-affinity Ca2+ indicators, for instance Fluo5N-AM, Mag-Fluo4-AM, or Mag-Fura2-AM. The esterase activity in the ER cleaves off hydrophobic side chains from the AM form of the Ca2+ indicator and a hydrophilic fluorescent dye/Ca2+ complex is formed and trapped in the ER lumen. After dye loading, the cells are analyzed at an inverted confocal laser scanning microscope. Cells are continuously perfused with Ringer-like solutions and the ER calcium dynamics are directly visualized by time-lapse imaging. Calcium release from the ER is identified by a decrease in fluorescence intensity in regions of interest, whereas the refilling of the ER calcium store produces an increase in fluorescence intensity. Finally, the change in fluorescent intensity over time is determined by calculation of ΔF/F0. PMID:23685703

Direct imaging of ER calcium with targeted-esterase induced dye loading (TED).

PubMed

Samtleben, Samira; Jaepel, Juliane; Fecher, Caroline; Andreska, Thomas; Rehberg, Markus; Blum, Robert

2013-05-07

Visualization of calcium dynamics is important to understand the role of calcium in cell physiology. To examine calcium dynamics, synthetic fluorescent Ca(2+) indictors have become popular. Here we demonstrate TED (= targeted-esterase induced dye loading), a method to improve the release of Ca(2+) indicator dyes in the ER lumen of different cell types. To date, TED was used in cell lines, glial cells, and neurons in vitro. TED bases on efficient, recombinant targeting of a high carboxylesterase activity to the ER lumen using vector-constructs that express Carboxylesterases (CES). The latest TED vectors contain a core element of CES2 fused to a red fluorescent protein, thus enabling simultaneous two-color imaging. The dynamics of free calcium in the ER are imaged in one color, while the corresponding ER structure appears in red. At the beginning of the procedure, cells are transduced with a lentivirus. Subsequently, the infected cells are seeded on coverslips to finally enable live cell imaging. Then, living cells are incubated with the acetoxymethyl ester (AM-ester) form of low-affinity Ca(2+) indicators, for instance Fluo5N-AM, Mag-Fluo4-AM, or Mag-Fura2-AM. The esterase activity in the ER cleaves off hydrophobic side chains from the AM form of the Ca(2+) indicator and a hydrophilic fluorescent dye/Ca(2+) complex is formed and trapped in the ER lumen. After dye loading, the cells are analyzed at an inverted confocal laser scanning microscope. Cells are continuously perfused with Ringer-like solutions and the ER calcium dynamics are directly visualized by time-lapse imaging. Calcium release from the ER is identified by a decrease in fluorescence intensity in regions of interest, whereas the refilling of the ER calcium store produces an increase in fluorescence intensity. Finally, the change in fluorescent intensity over time is determined by calculation of ΔF/F0.

Calcium-rich biochar from the pyrolysis of crab shell for phosphorus removal.

PubMed

Dai, Lichun; Tan, Furong; Li, Hong; Zhu, Nengmin; He, Mingxiong; Zhu, Qili; Hu, Guoquan; Wang, Li; Zhao, Jie

2017-08-01

Calcium-rich biochars (CRB) prepared through pyrolysis of crab shell at various temperatures were characterized for physicochemical properties and P removal potential. Elemental analysis showed that CRB was rich in calcium (22.91%-36.14%), while poor in carbon (25.21%-9.08%). FTIR, XRD and TG analyses showed that calcite-based CRB was prepared at temperature ≤600 °C, while lime-based CRB was prepared at temperature ≥700 °C. Phosphorus removal experiment showed that P removal efficiencies in 80 mg P/L phosphate solution and biogas effluent ranged from 26% to 11%, respectively, to about 100% and 63%, respectively, depending on the pyrolysis temperature of the resulting biochar. Specifically, compared to common used CaCO 3 and Ca(OH) 2 , P removal potential of calcite-based CRB was much higher than that of CaCO 3 ; while that of lime-based CRB was close to that of Ca(OH) 2 . These results suggested that CRB was competent for P removal/recovery from wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Effect of cadmium stress on physiological characteristics of garlic seedlings and the alleviation effects of exogenous calcium].

PubMed

Li, He; Lian, Hai-feng; Liu, Shi-qi; Yu, Xin-hui; Sun, Ya-li; Guo, Hui-ping

2015-04-01

In the experiment, the effects of exogenous cadmium (Cd2+) and calcium (Ca2+) in nutrient solution on growth, photosynthetic characteristics, enzymes activities, main mineral elements absorption of garlic seedlings were studied. The results showed that cadmium could obviously inhibit the growth of garlic seedlings, decrease the pigment contents and photosynthetic parameters (P(n), E, g(s)) of leaves, reduced the enzymes (SOD, POD, CAT) activities and increase the MDA content of leaves, and also could reduce the N, P, K, Ca, Mg contents and increase the Cd content of roots. The growth was promoted after adding exogenous calcium to garlic seedlings under cadmium stress, which reflected that the morphological indexes were increased at first and then decreased with the increase of exogenous calcium concentrations, and were maximized when the exogenous calcium was 2 or 3 mmol x L(-1). At the same time, the pigment contents and photosynthetic parameters (P(n), E, g(s)) of leaves showed a similar tendency with the morphological indexes, and they were the highest when the exogenous calcium was 2 or 3 mmol x L(-1). In addition, adding exogenous calcium to garlic seedlings under cadmium stress enhanced the enzymes (SOD, POD, CAT) activities and decreased the MDA content of leaves, also added the N, P, K, Ca, Mg contents and reduced the Cd content of roots, and the effect was best when the exogenous calcium concentration was 2 or 3 mmol x L(-1).

Nuclear BK Channels Regulate Gene Expression via the Control of Nuclear Calcium Signaling

PubMed Central

Li, Boxing; Jie, Wei; Huang, Lianyan; Wei, Peng; Li, Shuji; Luo, Zhengyi; Friedman, Allyson K.; Meredith, Andrea L.; Han, Ming-Hu; Zhu, Xin-Hong; Gao, Tian-Ming

2014-01-01

Ion channels are essential for the regulation of neuronal functions. The significance of plasma membrane, mitochondrial, endoplasmic reticulum, and lysosomal ion channels in the regulation of Ca2+ is well established. In contrast, surprisingly less is known about the function of ion channels on the nuclear envelope (NE). Here we demonstrate the presence of functional large-conductance, calcium-activated potassium channels (BK channels) on the NE of rodent hippocampal neurons. Functionally blockade of nuclear BK channels (nBK channels) induces NE-derived Ca2+ release, nucleoplasmic Ca2+ elevation, and cAMP response element binding protein (CREB)-dependent transcription. More importantly, blockade of nBK channels regulates nuclear Ca2+-sensitive gene expression and promotes dendritic arborization in a nuclear Ca2+-dependent manner. These results suggest that nBK channel functions as a molecular linker between neuronal activity and nuclear Ca2+ to convey the signals from synapse to nucleus and is a new modulator for synaptic activity-dependent neuronal functions at the NE level. PMID:24952642

Calcium channel-dependent molecular maturation of photoreceptor synapses.

PubMed

Zabouri, Nawal; Haverkamp, Silke

2013-01-01

Several studies have shown the importance of calcium channels in the development and/or maturation of synapses. The Ca(V)1.4(α(1F)) knockout mouse is a unique model to study the role of calcium channels in photoreceptor synapse formation. It features abnormal ribbon synapses and aberrant cone morphology. We investigated the expression and targeting of several key elements of ribbon synapses and analyzed the cone morphology in the Ca(V)1.4(α(1F)) knockout retina. Our data demonstrate that most abnormalities occur after eye opening. Indeed, scaffolding proteins such as Bassoon and RIM2 are properly targeted at first, but their expression and localization are not maintained in adulthood. This indicates that either calcium or the Ca(V)1.4 channel, or both are necessary for the maintenance of their normal expression and distribution in photoreceptors. Other proteins, such as Veli3 and PSD-95, also display abnormal expression in rods prior to eye opening. Conversely, vesicle related proteins appear normal. Our data demonstrate that the Ca(V)1.4 channel is important for maintaining scaffolding proteins in the ribbon synapse but less vital for proteins related to vesicular release. This study also confirms that in adult retinae, cones show developmental features such as sprouting and synaptogenesis. Overall we present evidence that in the absence of the Ca(V)1.4 channel, photoreceptor synapses remain immature and are unable to stabilize.

Effects of phosphates on microstructure and bioactivity of micro-arc oxidized calcium phosphate coatings on Mg-Zn-Zr magnesium alloy.

PubMed

Pan, Y K; Chen, C Z; Wang, D G; Zhao, T G

2013-09-01

Calcium phosphate (CaP) coatings were prepared on Mg-Zn-Zr magnesium alloy by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH3COO)2Ca·H2O) and different phosphates (i.e. disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), sodium phosphate (Na3PO4·H2O) and sodium hexametaphosphate((NaPO3)6)). Scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray diffractometer (XRD) were employed to characterize the microstructure, elemental distribution and phase composition of the CaP coatings. Simulated body fluid (SBF) immersion test was used to evaluate the coating bioactivity and degradability. Systemic toxicity test was used to evaluate the coating biocompatibility. Fluoride ion selective electrode (ISE) was used to measure F(-) ions concentration during 30 days SBF immersion. The CaP coatings effectively reduced the corrosion rate and the surfaces of CaP coatings were covered by a new layer formed of numerous needle-like and scale-like apatites. The formation of these calcium phosphate apatites indicates that the coatings have excellent bioactivity. The coatings formed in (NaPO3)6-containging electrolyte exhibit thicker thickness, higher adhesive strength, slower degradation rate, better apatite-inducing ability and biocompatibility. Copyright © 2013 Elsevier B.V. All rights reserved.

Helix A Stabilization Precedes Amino-terminal Lobe Activation upon Calcium Binding to Calmodulin

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

Chen, Baowei; Lowry, David; Mayer, M. Uljana

2008-08-09

The structural coupling between opposing domains of CaM was investigated using the conformationally sensitive biarsenical probe 4,5-bis(1,3,2-dithioarsolan-2-yl)-resorufin (ReAsH), which upon binding to an engineered tetracysteine binding motif near the end of helix A (Thr-5 to Phe-19) becomes highly fluorescent. Changes in conformation and dynamics are reflective of the native CaM structure, as there is no change in the 1H- 15N HSQC NMR spectrum in comparison to wild-type CaM. We find evidence of a conformational intermediate associated with CaM activation, where calcium occupancy of sites in the amino-terminal and carboxyl-terminal lobes of CaM differentially affect the fluorescence intensity of bound ReAsH.more » Insight into the structure of the conformational intermediate is possible from a consideration of calcium-dependent changes in rates of ReAsH binding and helix A mobility, which respectively distinguish secondary structural changes associated with helix A stabilization from the tertiary structural reorganization of the amino-terminal lobe of CaM necessary for high-affinity binding to target proteins. Helix A stabilization is associated with calcium occupancy of sites in the carboxyl-terminal lobe (Kd = 0.36 ± 0.04 μM), which results in a reduction in the rate of ReAsH binding from 4900 M -1 sec -1 to 370 M -1 sec -1. In comparison, tertiary structural changes involving helix A and other structural elements in the amino-terminal lobe requires calcium-occupancy of amino-terminal sites (Kd = 18 ± 3 μM). Observed secondary and tertiary structural changes involving helix A in response to the sequential calcium occupancy of carboxyl- and amino-terminal lobe calcium binding sites suggest an important involvement of helix A in mediating the structural coupling between the opposing domains of CaM. These results are discussed in terms of a model in which carboxyl-terminal lobe calcium activation induces secondary structural changes within the interdomain linker that release helix A, thereby facilitating the formation of calcium binding sites in the amino-terminal lobe and linked tertiary structural rearrangements to form a high-affinity binding cleft that can associate with target proteins.« less

Calcium Biofortification: Three Pronged Molecular Approaches for Dissecting Complex Trait of Calcium Nutrition in Finger Millet (Eleusine coracana) for Devising Strategies of Enrichment of Food Crops

PubMed Central

Sharma, Divya; Jamra, Gautam; Singh, Uma M.; Sood, Salej; Kumar, Anil

2017-01-01

Calcium is an essential macronutrient for plants and animals and plays an indispensable role in structure and signaling. Low dietary intake of calcium in humans has been epidemiologically linked to various diseases which can have serious health consequences over time. Major staple food-grains are poor source of calcium, however, finger millet [Eleusine coracana (L.) Gaertn.], an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Understanding the existing genetic variation as well as molecular mechanisms underlying the uptake, transport, accumulation of calcium ions (Ca2+) in grains is of utmost importance for development of calcium bio-fortified crops. In this review, we have discussed molecular mechanisms involved in calcium accumulation and transport thoroughly, emphasized the role of molecular breeding, functional genomics and transgenic approaches to understand the intricate mechanism of calcium nutrition in finger millet. The objective is to provide a comprehensive up to date account of molecular mechanisms regulating calcium nutrition and highlight the significance of bio-fortification through identification of potential candidate genes and regulatory elements from finger millet to alleviate calcium malnutrition. Hence, finger millet could be used as a model system for explaining the mechanism of elevated calcium (Ca2+) accumulation in its grains and could pave way for development of nutraceuticals or designer crops. PMID:28144246

Calcium Biofortification: Three Pronged Molecular Approaches for Dissecting Complex Trait of Calcium Nutrition in Finger Millet (Eleusine coracana) for Devising Strategies of Enrichment of Food Crops.

PubMed

Sharma, Divya; Jamra, Gautam; Singh, Uma M; Sood, Salej; Kumar, Anil

2016-01-01

Calcium is an essential macronutrient for plants and animals and plays an indispensable role in structure and signaling. Low dietary intake of calcium in humans has been epidemiologically linked to various diseases which can have serious health consequences over time. Major staple food-grains are poor source of calcium, however, finger millet [ Eleusine coracana (L.) Gaertn.], an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Understanding the existing genetic variation as well as molecular mechanisms underlying the uptake, transport, accumulation of calcium ions (Ca 2+ ) in grains is of utmost importance for development of calcium bio-fortified crops. In this review, we have discussed molecular mechanisms involved in calcium accumulation and transport thoroughly, emphasized the role of molecular breeding, functional genomics and transgenic approaches to understand the intricate mechanism of calcium nutrition in finger millet. The objective is to provide a comprehensive up to date account of molecular mechanisms regulating calcium nutrition and highlight the significance of bio-fortification through identification of potential candidate genes and regulatory elements from finger millet to alleviate calcium malnutrition. Hence, finger millet could be used as a model system for explaining the mechanism of elevated calcium (Ca 2+ ) accumulation in its grains and could pave way for development of nutraceuticals or designer crops.

Characterization of calcium isotopes in natural and synthetic barite

USGS Publications Warehouse

Griffith, E.M.; Schauble, E.A.; Bullen, T.D.; Paytan, A.

2008-01-01

The mineral barite (BaSO4) accommodates calcium in its crystal lattice, providing an archive of Ca-isotopes in the highly stable sulfate mineral. Holocene marine (pelagic) barite samples from the major ocean basins are isotopically indistinguishable from each other (??44/40Ca = -2.01 ?? 0.15???) but are different from hydrothermal and cold seep barite samples (??44/40Ca = -4.13 to -2.72???). Laboratory precipitated (synthetic) barite samples are more depleted in the heavy Ca-isotopes than pelagic marine barite and span a range of Ca-isotope compositions, ??44/40Ca = -3.42 to -2.40???. Temperature, saturation state, a Ba2 + / a SO42 -, and aCa2+/aBa2+ each influence the fractionation of Ca-isotopes in synthetic barite; however, the fractionation in marine barite samples is not strongly related to any measured environmental parameter. First-principles lattice dynamical modeling predicts that at equilibrium Ca-substituted barite will have much lower 44Ca/40Ca than calcite, by -9??? at 0 ??C and -8??? at 25 ??C. Based on this model, none of the measured barite samples appear to be in isotopic equilibrium with their parent solutions, although as predicted they do record lower ??44/40Ca values than seawater and calcite. Kinetic fractionation processes therefore most likely control the extent of isotopic fractionation exhibited in barite. Potential fractionation mechanisms include factors influencing Ca2+ substitution for Ba2+ in barite (e.g. ionic strength and trace element concentration of the solution, competing complexation reactions, precipitation or growth rate, temperature, pressure, and saturation state) as well as nucleation and crystal growth rates. These factors should be considered when investigating controls on isotopic fractionation of Ca2+ and other elements in inorganic and biogenic minerals. ?? 2008 Elsevier Ltd.

ANOMALOUS RELATIVE AR/CA CORONAL ABUNDANCES OBSERVED BY THE HINODE/EUV IMAGING SPECTROMETER NEAR SUNSPOTS

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

Doschek, G. A.; Warren, H. P.; Feldman, U.

2015-07-20

In determining the element abundance of argon (a high first ionization potential; FIP element) relative to calcium (a low FIP element) in flares, unexpectedly high intensities of two Ar xiv lines (194.40, 187.96 Å) relative to a Ca xiv line (193.87 Å) intensity were found in small (a few arcseconds) regions near sunspots in flare spectra recorded by the Extreme-ultraviolet Imaging Spectrometer on the Hinode spacecraft. In the most extreme case the Ar xiv line intensity relative to the Ca xiv intensity was 7 times the value expected from the photospheric abundance ratio, which is about 30 times the abundancemore » of argon relative to calcium in active regions, i.e., the measured Ar/Ca abundance ratio is about 10 instead of 0.37 as in active regions. The Ar xiv and Ca xiv lines are formed near 3.4 MK and have very similar contribution functions. This is the first observation of the inverse FIP effect in the Sun. Other regions show increases of 2–3 over photospheric abundances, or just photospheric abundances. This phenomenon appears to occur rarely and only over small areas of flares away from the regions containing multi-million degree plasma, but more work is needed to quantify the occurrences and their locations. In the bright hot regions of flares the Ar/Ca abundance ratio is coronal, i.e., the same as in active regions. In this Letter we show three examples of the inverse FIP effect.« less

Constraints on Ca/Sr as a Proxy for Calcium in Forest Ecosystems

NASA Astrophysics Data System (ADS)

Hoff, C. J.; Hobbie, E. A.; Hallett, R.; Colpaert, J.; Bryce, J. G.

2004-05-01

Calcium is a key plant nutrient and important base cation in ecosystems. Our current efforts to quantify Ca cycling in ecosystems rely on indirect proxies, e.g., Ca/Sr or Sr isotopic systems (1). An important assumption in these applications is that the elemental ratio of calcium to strontium faithfully represents calcium cycling and that little fractionation occurs through biogeochemical and physiological processes. However, several researchers have reported variations in Ca/Sr, e.g. among different tree tissues (2) and during weathering processes (3), raising doubts about the suitability of the proxy. To address the question of reliability, we measured Ca/Sr values in a culture study in which Scots pines were grown at low or high nutrient supply rates (3% per day or 5% per day). Because mycorrhizal fungi are intimately involved in plant nutrient supply, plants were also grown either uncolonized or colonized with one of two different species of mycorrhizal fungi (Suillus luteus and Thelephora terrestris). Our preliminary results indicate that Ca/Sr values differ between high and low nutrient treatments, root and foliage, and mycorrhizal treatments. In individual seedlings, roots have lower Ca/Sr than foliage by absolute factors of 2-5. The magnitude of the effect is apparently determined by a combination of environmental factors including both the nutrient and mycorrhizal treatments. These results indicate that Ca and Sr are partitioned differently between nutrient and mycorrhizal treatments and between plant fractions despite the common nutrient broth and substrate. Thus, Ca/Sr values alone are not reliable tracers of Ca within an ecosystem because of partitioning of Ca and Sr during nutrient transport within the plant-mycorrhizal system. We are presently refining analytical techniques and conducting leachate experiments to improve the quantification of this Ca/Sr fractionation. We are also exploring the use of isotopic tracers to study calcium biogeochemical cycling in forest ecosystems. (1) Blum, J.D., et al. 2002. Nature 417: 729-731. (2) Bailey, S.W., et al. 1996. Water Resources Research 32: 707-719. (3) Vitousek, P.M., et al. 1999. Oecologia 121: 255- 259.

Modeling CICR in rat ventricular myocytes: voltage clamp studies

PubMed Central

2010-01-01

Background The past thirty-five years have seen an intense search for the molecular mechanisms underlying calcium-induced calcium-release (CICR) in cardiac myocytes, with voltage clamp (VC) studies being the leading tool employed. Several VC protocols including lowering of extracellular calcium to affect Ca2+ loading of the sarcoplasmic reticulum (SR), and administration of blockers caffeine and thapsigargin have been utilized to probe the phenomena surrounding SR Ca2+ release. Here, we develop a deterministic mathematical model of a rat ventricular myocyte under VC conditions, to better understand mechanisms underlying the response of an isolated cell to calcium perturbation. Motivation for the study was to pinpoint key control variables influencing CICR and examine the role of CICR in the context of a physiological control system regulating cytosolic Ca2+ concentration ([Ca2+]myo). Methods The cell model consists of an electrical-equivalent model for the cell membrane and a fluid-compartment model describing the flux of ionic species between the extracellular and several intracellular compartments (cell cytosol, SR and the dyadic coupling unit (DCU), in which resides the mechanistic basis of CICR). The DCU is described as a controller-actuator mechanism, internally stabilized by negative feedback control of the unit's two diametrically-opposed Ca2+ channels (trigger-channel and release-channel). It releases Ca2+ flux into the cyto-plasm and is in turn enclosed within a negative feedback loop involving the SERCA pump, regulating[Ca2+]myo. Results Our model reproduces measured VC data published by several laboratories, and generates graded Ca2+ release at high Ca2+ gain in a homeostatically-controlled environment where [Ca2+]myo is precisely regulated. We elucidate the importance of the DCU elements in this process, particularly the role of the ryanodine receptor in controlling SR Ca2+ release, its activation by trigger Ca2+, and its refractory characteristics mediated by the luminal SR Ca2+ sensor. Proper functioning of the DCU, sodium-calcium exchangers and SERCA pump are important in achieving negative feedback control and hence Ca2+ homeostasis. Conclusions We examine the role of the above Ca2+ regulating mechanisms in handling various types of induced disturbances in Ca2+ levels by quantifying cellular Ca2+ balance. Our model provides biophysically-based explanations of phenomena associated with CICR generating useful and testable hypotheses. PMID:21062495

Dual mechanochemical immobilization of heavy metals and decomposition of halogenated compounds in automobile shredder residue using a nano-sized metallic calcium reagent.

PubMed

Mallampati, Srinivasa Reddy; Lee, Byoung Ho; Mitoma, Yoshiharu; Simion, Cristian

2016-11-01

Simultaneous immobilization of heavy metals and decomposition of halogenated organic compounds in different fractions of automobile shredder residue (ASR) were achieved with a nano-sized metallic calcium through a 60-min ball milling treatment. Heavy metal (HM) immobilization and chlorinated/brominated compound (CBC) decomposition efficiencies both reached 90-100 %, after ball milling with nanometallic calcium/calcium oxide (Ca/CaO) dispersion, regardless of ASR particle size (1.0, 0.45-1.0, and 0.250 mm). Concentrations of leachable HMs substantially decreased to a level lower than the regulatory standard limits (Co and Cd 0.3 mg L -1 ; Cr 1.5 mg L -1 ; Fe, Pb, and Zn 3.0 mg L -1 ; Mn and Ni 1 mg L -1 ) proposed by the Korean hazardous waste elution standard regulatory threshold. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) element maps/spectra showed that while the amounts of HMs and CBCs detectable in ASR significantly decreased, the calcium mass percentage increased. X-ray powder diffraction (XRD) patterns indicate that the main fraction of enclosed/bound materials on ASR includes Ca-associated crystalline complexes that remarkably inhibit HM desorption and simultaneously transform dangerous CBCs into harmless compounds. The use of a nanometallic Ca/CaO mixture in a mechanochemical process to treat hazardous ASR (dry conditions) is an innovative approach to remediate cross-contaminated residues with heavy metals and halogenated compounds.

Kcnip1 a Ca²⁺-dependent transcriptional repressor regulates the size of the neural plate in Xenopus.

PubMed

Néant, Isabelle; Mellström, Britt; Gonzalez, Paz; Naranjo, Jose R; Moreau, Marc; Leclerc, Catherine

2015-09-01

In amphibian embryos, our previous work has demonstrated that calcium transients occurring in the dorsal ectoderm at the onset of gastrulation are necessary and sufficient to engage the ectodermal cells into a neural fate by inducing neural specific genes. Some of these genes are direct targets of calcium. Here we search for a direct transcriptional mechanism by which calcium signals are acting. The only known mechanism responsible for a direct action of calcium on gene transcription involves an EF-hand Ca²⁺ binding protein which belongs to a group of four proteins (Kcnip1 to 4). Kcnip protein can act in a Ca²⁺-dependent manner as a transcriptional repressor by binding to a specific DNA sequence, the Downstream Regulatory Element (DRE) site. In Xenopus, among the four kcnips, we show that only kcnip1 is timely and spatially present in the presumptive neural territories and is able to bind DRE sites in a Ca²⁺-dependent manner. The loss of function of kcnip1 results in the expansion of the neural plate through an increased proliferation of neural progenitors. Later on, this leads to an impairment in the development of anterior neural structures. We propose that, in the embryo, at the onset of neurogenesis Kcnip1 is the Ca²⁺-dependent transcriptional repressor that controls the size of the neural plate. This article is part of a Special Issue entitled: 13th European Symposium on Calcium. Copyright © 2014. Published by Elsevier B.V.

A ROS-Assisted Calcium Wave Dependent on the AtRBOHD NADPH Oxidase and TPC1 Cation Channel Propagates the Systemic Response to Salt Stress.

PubMed

Evans, Matthew J; Choi, Won-Gyu; Gilroy, Simon; Morris, Richard J

2016-07-01

Plants exhibit rapid, systemic signaling systems that allow them to coordinate physiological and developmental responses throughout the plant body, even to highly localized and quickly changing environmental stresses. The propagation of these signals is thought to include processes ranging from electrical and hydraulic networks to waves of reactive oxygen species (ROS) and cytoplasmic Ca(2+) traveling throughout the plant. For the Ca(2+) wave system, the involvement of the vacuolar ion channel TWO PORE CHANNEL1 (TPC1) has been reported. However, the precise role of this channel and the mechanism of cell-to-cell propagation of the wave have remained largely undefined. Here, we use the fire-diffuse-fire model to analyze the behavior of a Ca(2+) wave originating from Ca(2+) release involving the TPC1 channel in Arabidopsis (Arabidopsis thaliana). We conclude that a Ca(2+) diffusion-dominated calcium-induced calcium-release mechanism is insufficient to explain the observed wave transmission speeds. The addition of a ROS-triggered element, however, is able to quantitatively reproduce the observed transmission characteristics. The treatment of roots with the ROS scavenger ascorbate and the NADPH oxidase inhibitor diphenyliodonium and analysis of Ca(2+) wave propagation in the Arabidopsis respiratory burst oxidase homolog D (AtrbohD) knockout background all led to reductions in Ca(2+) wave transmission speeds consistent with this model. Furthermore, imaging of extracellular ROS production revealed a systemic spread of ROS release that is dependent on both AtRBOHD and TPC1 These results suggest that, in the root, plant systemic signaling is supported by a ROS-assisted calcium-induced calcium-release mechanism intimately involving ROS production by AtRBOHD and Ca(2+) release dependent on the vacuolar channel TPC1. © 2016 American Society of Plant Biologists. All Rights Reserved.

Reactions of calcium orthosilicate and barium zirconate with oxides and sulfates of various elements

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.

1979-01-01

Calcium orthosilicate and barium zirconate were evaluated as the insulation layer of thermal barrier coatings for air cooled gas turbine components. Their reactions with various oxides and sulfates were studied at 1100 C and 1300 C for times ranging up to 400 and 200 hours, respectively. These oxides and sulfates represent potential impurities or additives in gas turbine fuels and in turbine combustion air, as well as elements of potential bond coat alloys. The phase compositions of the reaction products were determined by X-ray diffraction analysis. BaZrO3 and 2CaO-SiO2 both reacted with P2O5, V2O5, Cr2O3, Al2O3, and SiO2. In addition, 2CaO-SiO2 reacted with Na2O, BaO, MgO, and CoO and BaZrO3 reacted with Fe2O3.

Testing the chondrule-rich accretion model for planetary embryos using calcium isotopes

NASA Astrophysics Data System (ADS)

Amsellem, Elsa; Moynier, Frédéric; Pringle, Emily A.; Bouvier, Audrey; Chen, Heng; Day, James M. D.

2017-07-01

Understanding the composition of raw materials that formed the Earth is a crucial step towards understanding the formation of terrestrial planets and their bulk composition. Calcium is the fifth most abundant element in terrestrial planets and, therefore, is a key element with which to trace planetary composition. However, in order to use Ca isotopes as a tracer of Earth's accretion history, it is first necessary to understand the isotopic behavior of Ca during the earliest stages of planetary formation. Chondrites are some of the oldest materials of the Solar System, and the study of their isotopic composition enables understanding of how and in what conditions the Solar System formed. Here we present Ca isotope data for a suite of bulk chondrites as well as Allende (CV) chondrules. We show that most groups of carbonaceous chondrites (CV, CI, CR and CM) are significantly enriched in the lighter Ca isotopes (δ 44 / 40 Ca = + 0.1 to + 0.93 ‰) compared with bulk silicate Earth (δ 44 / 40 Ca = + 1.05 ± 0.04 ‰, Huang et al., 2010) or Mars, while enstatite chondrites are indistinguishable from Earth in Ca isotope composition (δ 44 / 40 Ca = + 0.91 to + 1.06 ‰). Chondrules from Allende are enriched in the heavier isotopes of Ca compared to the bulk and the matrix of the meteorite (δ 44 / 40 Ca = + 1.00 to + 1.21 ‰). This implies that Earth and Mars have Ca isotope compositions that are distinct from most carbonaceous chondrites but that may be like chondrules. This Ca isotopic similarity between Earth, Mars, and chondrules is permissive of recent dynamical models of planetary formation that propose a chondrule-rich accretion model for planetary embryos.

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

Bosche, Bert, E-mail: bert.bosche@uk-essen.de; Max Planck Institute for Neurological Research with Klaus-Joachim-Zülch Laboratories of the Max Planck Society and the Medical Faculty of the University of Cologne; Schäfer, Matthias, E-mail: matthias.schaefer@sanofi.com

Highlights: •We investigate free calcium as a central signalling element in endothelial cells. •Inhibition of glycolysis with 2-deoxy-D-glucose reduces cellular ATP. •This manoeuvre leads to a biphasic increase and overload of free calcium. •Pre-treatment with lithium for 24 h abolishes both phases of the calcium increase. •This provides a new strategy to protect endothelial calcium homeostasis and barrier function. -- Abstract: Cytosolic free calcium concentration ([Ca{sup 2+}]{sub i}) is a central signalling element for the maintenance of endothelial barrier function. Under physiological conditions, it is controlled within narrow limits. Metabolic inhibition during ischemia/reperfusion, however, induces [Ca{sup 2+}]{sub i} overload, whichmore » results in barrier failure. In a model of cultured porcine aortic endothelial monolayers (EC), we addressed the question of whether [Ca{sup 2+}]{sub i} overload can be prevented by lithium treatment. [Ca{sup 2+}]{sub i} and ATP were analysed using Fura-2 and HPLC, respectively. The combined inhibition of glycolytic and mitochondrial ATP synthesis by 2-desoxy-D-glucose (5 mM; 2-DG) plus sodium cyanide (5 mM; NaCN) caused a significant decrease in cellular ATP content (14 ± 1 nmol/mg protein vs. 18 ± 1 nmol/mg protein in the control, n = 6 culture dishes, P < 0.05), an increase in [Ca{sup 2+}]{sub i} (278 ± 24 nM vs. 71 ± 2 nM in the control, n = 60 cells, P < 0.05), and the formation of gaps between adjacent EC. These observations indicate that there is impaired barrier function at an early state of metabolic inhibition. Glycolytic inhibition alone by 10 mM 2-DG led to a similar decrease in ATP content (14 ± 2 nmol/mg vs. 18 ± 1 nmol/mg in the control, P < 0.05) with a delay of 5 min. The [Ca{sup 2+}]{sub i} response of EC was biphasic with a peak after 1 min (183 ± 6 nM vs. 71 ± 1 nM, n = 60 cells, P < 0.05) followed by a sustained increase in [Ca{sup 2+}]{sub i}. A 24-h pre-treatment with 10 mM of lithium chloride before the inhibition of ATP synthesis abolished both phases of the 2-DG-induced [Ca{sup 2+}]{sub i} increase. This effect was not observed when lithium chloride was added simultaneously with 2-DG. We conclude that lithium chloride abolishes the injurious [Ca{sup 2+}]{sub i} overload in EC and that this most likely occurs by preventing inositol 3-phosphate-sensitive Ca{sup 2+}-release from the endoplasmic reticulum. Though further research is needed, these findings provide a novel option for therapeutic strategies to protect the endothelium against imminent barrier failure.« less

Alleviation of cadmium toxicity in Brassica juncea L. (Czern. & Coss.) by calcium application involves various physiological and biochemical strategies.

PubMed

Ahmad, Parvaiz; Sarwat, Maryam; Bhat, Nazir Ahmad; Wani, Mohd Rafiq; Kazi, Alvina Gul; Tran, Lam-Son Phan

2015-01-01

Calcium (Ca) plays important role in plant development and response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effect of Ca (50 mM) in controlling cadmium (Cd) uptake in mustard (Brassica juncea L.) plants exposed to toxic levels of Cd (200 mg L(-1) and 300 mg L(-1)). The Cd treatment showed substantial decrease in plant height, root length, dry weight, pigments and protein content. Application of Ca improved the growth and biomass yield of the Cd-stressed mustard seedlings. More importantly, the oil content of mustard seeds of Cd-stressed plants was also enhanced with Ca treatment. Proline was significantly increased in mustard plants under Cd stress, and exogenously sprayed Ca was found to have a positive impact on proline content in Cd-stressed plants. Different concentrations of Cd increased lipid peroxidation but the application of Ca minimized it to appreciable level in Cd-treated plants. Excessive Cd treatment enhanced the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase and glutathione reductase, which were further enhanced by the addition of Ca. Additionally, Cd stress caused reduced uptake of essential elements and increased Cd accumulation in roots and shoots. However, application of Ca enhanced the concentration of essential elements and decreased Cd accumulation in Cd-stressed plants. Our results indicated that application of Ca enables mustard plant to withstand the deleterious effect of Cd, resulting in improved growth and seed quality of mustard plants.

Distribution of calcium (Ca) and magnesium (Mg) in the leaves of Brassica rapa under varying exogenous Ca and Mg supply.

PubMed

Rios, Juan Jose; Lochlainn, Seosamh O; Devonshire, Jean; Graham, Neil S; Hammond, John P; King, Graham J; White, Philip J; Kurup, Smita; Broadley, Martin R

2012-05-01

Leafy vegetable Brassica crops are an important source of dietary calcium (Ca) and magnesium (Mg) and represent potential targets for increasing leaf Ca and Mg concentrations through agronomy or breeding. Although the internal distribution of Ca and Mg within leaves affects the accumulation of these elements, such data are not available for Brassica. The aim of this study was to characterize the internal distribution of Ca and Mg in the leaves of a vegetable Brassica and to determine the effects of altered exogenous Ca and Mg supply on this distribution. Brassica rapa ssp. trilocularis 'R-o-18' was grown at four different Ca:Mg treatments for 21 d in a controlled environment. Concentrations of Ca and Mg were determined in fully expanded leaves using inductively coupled plasma-mass spectrometry (ICP-MS). Internal distributions of Ca and Mg were determined in transverse leaf sections at the base and apex of leaves using energy-dispersive X-ray spectroscopy (EDS) with cryo-scanning electron microscopy (cryo-SEM). Leaf Ca and Mg concentrations were greatest in palisade and spongy mesophyll cells, respectively, although this was dependent on exogenous supply. Calcium accumulation in palisade mesophyll cells was enhanced slightly under high Mg supply; in contrast, Mg accumulation in spongy mesophyll cells was not affected by Ca supply. The results are consistent with Arabidopsis thaliana and other Brassicaceae, providing phenotypic evidence that conserved mechanisms regulate leaf Ca and Mg distribution at a cellular scale. The future study of Arabidopsis gene orthologues in mutants of this reference B. rapa genotype will improve our understanding of Ca and Mg homeostasis in plants and may provide a model-to-crop translation pathway for targeted breeding.

Calcium-regulated nuclear enzymes: potential mediators of phytochrome-induced changes in nuclear metabolism?

NASA Technical Reports Server (NTRS)

Roux, S. J.

1992-01-01

Calcium ions have been proposed to serve as important regulatory elements in stimulus-response coupling for phytochrome responses. An important test of this hypothesis will be to identify specific targets of calcium action that are required for some growth or development process induced by the photoactivated form of phytochrome (Pfr). Initial studies have revealed that there are at least two enzymes in pea nuclei that are stimulated by Pfr in a Ca(2+)-dependent fashion, a calmodulin-regulated nucleoside triphosphatase and a calmodulin-independent but Ca(2+)-dependent protein kinase. The nucleoside triphosphatase appears to be associated with the nuclear envelope, while the protein kinase co-purifies with a nuclear fraction highly enriched for chromatin. This short review summarizes the latest findings on these enzymes and relates them to what is known about Pfr-regulated nuclear metabolism.

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

NASA Astrophysics Data System (ADS)

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.

Fluoride Alters Serum Elemental (Calcium, Magnesium, Copper, and Zinc) Homeostasis Along with Erythrocyte Carbonic Anhydrase Activity in Fluorosis Endemic Villages and Restores on Supply of Safe Drinking Water in School-Going Children of Nalgonda District, India.

PubMed

Khandare, Arjun L; Validandi, Vakdevi; Boiroju, Naveen

2018-02-17

The present study aimed to determine the serum trace elements (copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg)) along with erythrocyte carbonic anhydrase (CA) activity and effect of intervention with safe drinking water for 5 years in the school children of fluorosis endemic area. For this purpose, three categories of villages were selected based on drinking water fluoride (F): Category I (control, F = 1.68 mg/L), category II (affected F = 3.77 mg/L), and category III (intervention village) where initial drinking water F was 4.51 mg/L, and since the last 5 years, they were drinking water containing < 1.0 mg/L F. The results revealed that urinary F was significantly (P < 0.05) higher in category II compared to categories I and III. A significant (P < 0.05) increase in serum Cu and Mg was observed in category II compared to category I. Serum Zn and Ca was significantly (P < 0.05) decreased in categories II and III compared to category I. The erythrocyte CA activity was decreased in the category II compared to category I. However, in the category III, erythrocyte CA activity was comparable to the control group. In conclusion, F exposure altered elemental homeostasis which has restored to some extent on intervention by safe drinking water for 5 years in school-going children.

Quadrupole collectivity in 42Ca from low-energy Coulomb excitation with AGATA

NASA Astrophysics Data System (ADS)

Hadyńska-Klęk, K.; Napiorkowski, P. J.; Zielińska, M.; Srebrny, J.; Maj, A.; Azaiez, F.; Valiente Dobón, J. J.; Kicińska-Habior, M.; Nowacki, F.; Naïdja, H.; Bounthong, B.; Rodríguez, T. R.; de Angelis, G.; Abraham, T.; Anil Kumar, G.; Bazzacco, D.; Bellato, M.; Bortolato, D.; Bednarczyk, P.; Benzoni, G.; Berti, L.; Birkenbach, B.; Bruyneel, B.; Brambilla, S.; Camera, F.; Chavas, J.; Cederwall, B.; Charles, L.; Ciemała, M.; Cocconi, P.; Coleman-Smith, P.; Colombo, A.; Corsi, A.; Crespi, F. C. L.; Cullen, D. M.; Czermak, A.; Désesquelles, P.; Doherty, D. T.; Dulny, B.; Eberth, J.; Farnea, E.; Fornal, B.; Franchoo, S.; Gadea, A.; Giaz, A.; Gottardo, A.; Grave, X.; Grębosz, J.; Görgen, A.; Gulmini, M.; Habermann, T.; Hess, H.; Isocrate, R.; Iwanicki, J.; Jaworski, G.; Judson, D. S.; Jungclaus, A.; Karkour, N.; Kmiecik, M.; Karpiński, D.; Kisieliński, M.; Kondratyev, N.; Korichi, A.; Komorowska, M.; Kowalczyk, M.; Korten, W.; Krzysiek, M.; Lehaut, G.; Leoni, S.; Ljungvall, J.; Lopez-Martens, A.; Lunardi, S.; Maron, G.; Mazurek, K.; Menegazzo, R.; Mengoni, D.; Merchán, E.; Męczyński, W.; Michelagnoli, C.; Million, B.; Myalski, S.; Napoli, D. R.; Niikura, M.; Obertelli, A.; Özmen, S. F.; Palacz, M.; Próchniak, L.; Pullia, A.; Quintana, B.; Rampazzo, G.; Recchia, F.; Redon, N.; Reiter, P.; Rosso, D.; Rusek, K.; Sahin, E.; Salsac, M.-D.; Söderström, P.-A.; Stefan, I.; Stézowski, O.; Styczeń, J.; Theisen, Ch.; Toniolo, N.; Ur, C. A.; Wadsworth, R.; Wasilewska, B.; Wiens, A.; Wood, J. L.; Wrzosek-Lipska, K.; Ziębliński, M.

2018-02-01

A Coulomb-excitation experiment to study electromagnetic properties of 42Ca was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in 42Ca were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E 2 matrix elements coupling six low-lying states in 42Ca, including the diagonal E 2 matrix elements of 21+ and 22+ states, were determined using the least-squares code gosia. The obtained set of reduced E 2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 01,2 + and 21,2 + states, as well as triaxiality for 01,2 + states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in 42Ca. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in 42Ca.

Harnessing Finger Millet to Combat Calcium Deficiency in Humans: Challenges and Prospects.

PubMed

Puranik, Swati; Kam, Jason; Sahu, Pranav P; Yadav, Rama; Srivastava, Rakesh K; Ojulong, Henry; Yadav, Rattan

2017-01-01

Humans require more than 20 mineral elements for healthy body function. Calcium (Ca), one of the essential macromineral, is required in relatively large quantities in the diet for maintaining a sound overall health. Young children, pregnant and nursing women in marginalized and poorest regions of the world, are at highest risk of Ca malnutrition. Elderly population is another group of people most commonly affected by Ca deficiency mainly in the form of osteoporosis and osteopenia. Improved dietary intake of Ca may be the most cost-effective way to meet such deficiencies. Finger millet [ Eleusine coracana (L.) Gaertn.], a crop with inherently higher Ca content in its grain, is an excellent candidate for understanding genetic mechanisms associated with Ca accumulation in grain crops. Such knowledge will also contribute toward increasing Ca contents in other staple crops consumed on daily basis using plant-breeding (also known as biofortification) methods. However, developing Ca-biofortified finger millet to reach nutritional acceptability faces various challenges. These include identifying and translating the high grain Ca content to an adequately bioavailable form so as to have a positive impact on Ca malnutrition. In this review, we assess some recent advancements and challenges for enrichment of its Ca value and present possible inter-disciplinary prospects for advancing the actual impact of Ca-biofortified finger millet.

Harnessing Finger Millet to Combat Calcium Deficiency in Humans: Challenges and Prospects

PubMed Central

Puranik, Swati; Kam, Jason; Sahu, Pranav P.; Yadav, Rama; Srivastava, Rakesh K.; Ojulong, Henry; Yadav, Rattan

2017-01-01

Humans require more than 20 mineral elements for healthy body function. Calcium (Ca), one of the essential macromineral, is required in relatively large quantities in the diet for maintaining a sound overall health. Young children, pregnant and nursing women in marginalized and poorest regions of the world, are at highest risk of Ca malnutrition. Elderly population is another group of people most commonly affected by Ca deficiency mainly in the form of osteoporosis and osteopenia. Improved dietary intake of Ca may be the most cost-effective way to meet such deficiencies. Finger millet [Eleusine coracana (L.) Gaertn.], a crop with inherently higher Ca content in its grain, is an excellent candidate for understanding genetic mechanisms associated with Ca accumulation in grain crops. Such knowledge will also contribute toward increasing Ca contents in other staple crops consumed on daily basis using plant-breeding (also known as biofortification) methods. However, developing Ca-biofortified finger millet to reach nutritional acceptability faces various challenges. These include identifying and translating the high grain Ca content to an adequately bioavailable form so as to have a positive impact on Ca malnutrition. In this review, we assess some recent advancements and challenges for enrichment of its Ca value and present possible inter-disciplinary prospects for advancing the actual impact of Ca-biofortified finger millet. PMID:28798761

Ryanodine receptors regulate arterial diameter and wall [Ca2+] in cerebral arteries of rat via Ca2+-dependent K+ channels

PubMed Central

Knot, Harm J; Standen, Nicholas B; Nelson, Mark T

1998-01-01

The effects of inhibitors of ryanodine-sensitive calcium release (RyR) channels in the sarcoplasmic reticulum (SR) and Ca2+-dependent potassium (KCa) channels on the membrane potential, intracellular [Ca2+], and diameters of small pressurized (60 mmHg) cerebral arteries (100–200 μm) were studied using digital fluorescence video imaging of arterial diameter and wall [Ca2+], combined with microelectrode measurements of arterial membrane potential. Ryanodine (10 μm), an inhibitor of RyR channels, depolarized by 9 mV, increased intracellular [Ca2+] by 46 nm and constricted pressurized (to 60 mmHg) arteries with myogenic tone by 44 μm (∼22 %). Iberiotoxin (100 nm), a blocker of KCa channels, under the same conditions, depolarized the arteries by 10 mV, increased arterial wall calcium by 51 nm, and constricted by 37 μm (∼19 %). The effects of ryanodine and iberiotoxin were not additive and were blocked by inhibitors of voltage-dependent Ca2+ channels. Caffeine (10 mm), an activator of RyR channels, transiently increased arterial wall [Ca2+] by 136 ± 9 nm in control arteries and by 158 ± 12 nm in the presence of iberiotoxin. Caffeine was relatively ineffective in the presence of ryanodine, increasing [calcium] by 18 ± 5 nm. In the presence of blockers of voltage-dependent Ca2+ channels (nimodipine, diltiazem), ryanodine and inhibitors of the SR calcium ATPase (thapsigargin, cyclopiazonic acid) were without effect on arterial wall [Ca2+] and diameter. These results suggest that local Ca2+ release originating from RyR channels (Ca2+ sparks) in the SR of arterial smooth muscle regulates myogenic tone in cerebral arteries solely through activation of KCa channels, which regulate membrane potential through tonic hyperpolarization, thus limiting Ca2+ entry through L-type voltage-dependent Ca2+ channels. KCa channels therefore act as a negative feedback control element regulating arterial diameter through a reduction in global intracellular free [Ca2+]. PMID:9490841

Synthesis and Molecular Structure of a Novel Compound Containing a Carbonate-Bridged Hexacalcium Cluster Cation Assembled on a Trimeric Trititanium(IV)-Substituted Wells-Dawson Polyoxometalate.

PubMed

Hoshino, Takahiro; Isobe, Rina; Kaneko, Takuya; Matsuki, Yusuke; Nomiya, Kenji

2017-08-21

A novel compound containing a hexacalcium cluster cation, one carbonate anion, and one calcium cation assembled on a trimeric trititanium(IV)-substituted Wells-Dawson polyoxometalate (POM), [{Ca 6 (CO 3 )(μ 3 -OH)(OH 2 ) 18 }(P 2 W 15 Ti 3 O 61 ) 3 Ca(OH 2 ) 3 ] 19- (Ca 7 Ti 9 Trimer), was obtained as the Na 7 Ca 6 salt (NaCa-Ca 7 Ti 9 Trimer) by the reaction of calcium chloride with the monomeric trititanium(IV)-substituted Wells-Dawson POM species "[P 2 W 15 Ti 3 O 59 (OH) 3 ] 9- " (Ti 3 Monomer). Ti 3 Monomer was generated in situ under basic conditions from the separately prepared tetrameric species with bridging Ti(OH 2 ) 3 groups and an encapsulated Cl - ion, [{P 2 W 15 Ti 3 O 59 (OH) 3 } 4 {μ 3 -Ti(H 2 O) 3 } 4 Cl] 21- (Ti 16 Tetramer). The Na 7 Ca 6 salt of Ca 7 Ti 9 Trimer was characterized by complete elemental analysis, thermogravimetric (TG) and differential thermal analyses (DTA), FTIR, single-crystal X-ray structure analysis, and solution 183 W and 31 P NMR spectroscopy. X-ray crystallography revealed that the [Ca 6 (CO 3 )(μ 3 -OH)(OH 2 ) 18 ] 9+ cluster cation was composed of six calcium cations linked by one μ 6 -carbonato anion and one μ 3 -OH - anion. The cluster cation was assembled, together with one calcium ion, on a trimeric species composed of three tri-Ti(IV)-substituted Wells-Dawson subunits linked by Ti-O-Ti bonds. Ca 7 Ti 9 Trimer is an unprecedented POM species containing an alkaline-earth-metal cluster cation and is the first example of alkaline-earth-metal ions clustered around a titanium(IV)-substituted POM.

Apo calmodulin binding to the L-type voltage-gated calcium channel Ca{sub v}1.2 IQ peptide

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

Lian Luyun; Myatt, Daniel; Kitmitto, Ashraf

2007-02-16

The influx of calcium through the L-type voltage-gated calcium channels (LTCCs) is the trigger for the process of calcium-induced calcium release (CICR) from the sarcoplasmic recticulum, an essential step for cardiac contraction. There are two feedback mechanisms that regulate LTCC activity: calcium-dependent inactivation (CDI) and calcium-dependent facilitation (CDF), both of which are mediated by calmodulin (CaM) binding. The IQ domain (aa 1645-1668) housed within the cytoplasmic domain of the LTCC Ca{sub v}1.2 subunit has been shown to bind both calcium-loaded (Ca{sup 2+}CaM ) and calcium-free CaM (apoCaM). Here, we provide new data for the structural basis for the interaction ofmore » apoCaM with the IQ peptide using NMR, revealing that the apoCaM C-lobe residues are most significantly perturbed upon complex formation. In addition, we have employed transmission electron microscopy of purified LTCC complexes which shows that both apoCaM and Ca{sup 2+}CaM can bind to the intact channel.« less

The Actions of Calcium on Hair Bundle Mechanics in Mammalian Cochlear Hair Cells

PubMed Central

Beurg, Maryline; Nam, Jong-Hoon; Crawford, Andrew; Fettiplace, Robert

2008-01-01

Sound stimuli excite cochlear hair cells by vibration of each hair bundle, which opens mechanotransducer (MT) channels. We have measured hair-bundle mechanics in isolated rat cochleas by stimulation with flexible glass fibers and simultaneous recording of the MT current. Both inner and outer hair-cell bundles exhibited force-displacement relationships with a nonlinearity that reflects a time-dependent reduction in stiffness. The nonlinearity was abolished, and hair-bundle stiffness increased, by maneuvers that diminished calcium influx through the MT channels: lowering extracellular calcium, blocking the MT current with dihydrostreptomycin, or depolarizing to positive potentials. To simulate the effects of Ca2+, we constructed a finite-element model of the outer hair cell bundle that incorporates the gating-spring hypothesis for MT channel activation. Four calcium ions were assumed to bind to the MT channel, making it harder to open, and, in addition, Ca2+ was posited to cause either a channel release or a decrease in the gating-spring stiffness. Both mechanisms produced Ca2+ effects on adaptation and bundle mechanics comparable to those measured experimentally. We suggest that fast adaptation and force generation by the hair bundle may stem from the action of Ca2+ on the channel complex and do not necessarily require the direct involvement of a myosin motor. The significance of these results for cochlear transduction and amplification are discussed. PMID:18178649

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

PubMed

Zimmermann, E; Wassmer, S; Steudle, V

1996-01-01

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

Characterization of calcium deposition induced by Synechocystis sp. PCC6803 in BG11 culture medium

NASA Astrophysics Data System (ADS)

Yan, Huaxiao; Han, Zuozhen; Zhao, Hui; Zhou, Shixue; Chi, Naijie; Han, Mei; Kou, Xiaoyan; Zhang, Yan; Xu, Linlin; Tian, Chenchen; Qin, Song

2014-05-01

Calcium carbonate (CaCO3) crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 (inoculated BG11). In this study, the features of calcium carbonate deposition were investigated. Inoculated BG11 in different calcium ion concentrations was used for the experimental group, while the BG11 culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium (Ca), carbon (C), oxygen (O), phosphorus (P), iron (Fe), copper (Cu), zinc (Zn), and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BG11 culture media. There may be more calcium-containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.

Auger electron spectroscopy for the determination of sex and age related Ca/P ratio at different bone sites

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

Balatsoukas, Ioannis; Kourkoumelis, Nikolaos; Tzaphlidou, Margaret

The Ca/P ratio of normal cortical and trabecular rat bone was measured by Auger electron spectroscopy (AES). Semiquantitative analysis was carried out using ratio techniques to draw conclusions on how age, sex and bone site affect the relative composition of calcium and phosphorus. Results show that Ca/P ratio is not sex dependent; quite the opposite, bone sites exhibit variations in elemental stoichiometry where femoral sections demonstrate higher Ca/P ratio than rear and front tibias. Age-related changes are more distinct for cortical bone in comparison with the trabecular bone. The latter's Ca/P ratio remains unaffected from all the parameters under study.more » This study confirms that AES is able to successfully quantify bone mineral main elements when certain critical points, related to the experimental conditions, are addressed effectively.« less

Measuring calcium, potassium, and nitrate in plant nutrient solutions using ion-selective electrodes in hydroponic greenhouse of some vegetables.

PubMed

Vardar, Gökay; Altıkatoğlu, Melda; Ortaç, Deniz; Cemek, Mustafa; Işıldak, İbrahim

2015-01-01

Generally, the life cycle of plants depends on the uptake of essential nutrients in a balanced manner and on toxic elements being under a certain concentration. Lack of control of nutrient levels in nutrient solution can result in reduced plant growth and undesired conditions such as blossom-end rot. In this study, sensitivity and selectivity tests for various polyvinylchloride (PVC)-based ion-selective membranes were conducted to identify those suitable for measuring typical concentration ranges of macronutrients, that is, NO(3-), K(+), and Ca(2+), in hydroponic solutions. The sensitivity and selectivity of PVC-membrane-based ion-selective sensors prepared with tetradodecylammoniumnitrate for NO(3-), valinomycin for K(+), and Ca ionophore IV for Ca(2+) were found to be satisfactory for measuring NO(3-), K(+), and Ca(2+) ions in nutrient solutions over typical ranges of hydroponic concentrations. Potassium, calcium, and nitrate levels that were utilized by cucumber and tomato seedlings in the greenhouse were different. The findings show that tomato plants consumed less amounts of nitrate than cucumber plants over the first 2 months of their growth. We also found that the potassium intake was higher than other nutritional elements tested for all plants. © 2014 International Union of Biochemistry and Molecular Biology, Inc.

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

PubMed Central

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

Apo states of calmodulin and CaBP1 control CaV1 voltage-gated calcium channel function through direct competition for the IQ domain.

PubMed

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.

Barium and calcium analyses in sediment cores using µ-XRF core scanners

NASA Astrophysics Data System (ADS)

Acar, Dursun; Çaǧatay, Namık; Genç, S. Can; Eriş, K. Kadir; Sarı, Erol; Uçarkus, Gülsen

2017-04-01

Barium and Ca are used as proxies for organic productivity in paleooceanographic studies. With its heavy atomic weight (137.33 u), barium is easily detectable in small concentrations (several ppm levels) in marine sediments using XRF methods, including the analysis by µ-XRF core scanners. Calcium has an intermediate atomic weight (40.078 u) but is a major element in the earth's crust and in sediments and sedimentary rocks, and hence it is easily detectable by µ-XRF techniques. Normally, µ-XRF elemental analysis of cores are carried out using split half cores or 1-2 cm thich u-channels with an original moisture. Sediment cores show variation in different water content (and porosity) along their length. This in turn results in variation in the XRF counts of the elements and causes error in the elemental concentrations. We tried µ-XRF elemental analysis of split half cores, subsampled as 1 cm thick u-channels with original moisture and 0.3 mm-thin film slices of the core with original wet sample and after air drying with humidity protector mylar film. We found considerable increase in counts of most elements, and in particular for Ba and Ca, when we used 0.3 mm thin film, dried slice. In the case of Ba, the counts increased about three times that of the analysis made with wet and 1 cm thick u-channels. The higher Ba and Ca counts are mainly due to the possible precipitation of Ba as barite and Ca as gypsum from oxidation of Fe-sulphides and the evaporation of pore waters. The secondary barite and gypsum precipitation would be especially serious in unoxic sediment units, such as sapropels, with considerable Fe-sulphides and bio-barite.It is therefore suggested that reseachers should be cautious of such secondary precipitation on core surfaces when analyzing cores that have long been exposed to the atmospheric conditions.

Apo-states of calmodulin and CaBP1 control CaV1 voltage-gated calcium channel function through direct competition for the IQ domain

PubMed Central

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

[Apatite-forming ability of pure titanium implant after micro-arc oxidation treatment].

PubMed

Tian, Zhihui; Zhang, Yu; Wang, Lichao; Nan, Kaihui

2013-10-01

To investigate the apatite forming ability of pure titanium implant after micro-arc oxidation treatment in simulated body fluid (SBF) and obtain implants with calcium phosphate (Ca-P) layers. The implants were immersed in (SBF) after micro-arc oxidation treatment for different time lengths, and their apatite forming ability and the morphology and constituents of the Ca-P layers formed on the sample surface were analyzed using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive electron probe. After immersion in SBF, large quantities of Ca-P layers were induced on the surface of the samples. The Ca-P layers were composed of octacalcium phosphate and carbonated hydroxyapatite, and the crystals showed a plate-like morphology with an oriented growth. The implants with micro-arc oxidation treatment show good apatite forming ability on the surface with rich calcium and phosphorus elements. The formed layers are composed of bone-like apatite including octacalcium phosphate and carbonated hydroxyapatite.

Soil salination indicators

USDA-ARS?s Scientific Manuscript database

Salts are naturally present in soils, and many salt elements are essential nutrients for plants. The most common soluble salts in soil include major cations of sodium (Na+), magnesium (Mg2+), calcium (Ca2+), potassium (K+), and anions of chloride (Cl-), sulfate (SO42-), bicarbonate (HCO3-) and carbo...

Two Dimensional Finite Element Model to Study Calcium Distribution in Oocytes

NASA Astrophysics Data System (ADS)

Naik, Parvaiz Ahmad; Pardasani, Kamal Raj

2015-06-01

Cytosolic free calcium concentration is a key regulatory factor and perhaps the most widely used means of controlling cellular function. Calcium can enter cells through different pathways which are activated by specific stimuli including membrane depolarization, chemical signals and calcium depletion of intracellular stores. One of the important components of oocyte maturation is differentiation of the Ca2+ signaling machinery which is essential for egg activation after fertilization. Eggs acquire the ability to produce the fertilization-specific calcium signal during oocyte maturation. The calcium concentration patterns required during different stages of oocyte maturation are still not completely known. Also the mechanisms involved in calcium dynamics in oocyte cell are still not well understood. In view of above a two dimensional FEM model has been proposed to study calcium distribution in an oocyte cell. The parameters such as buffers, ryanodine receptor, SERCA pump and voltage gated calcium channel are incorporated in the model. Based on the biophysical conditions the initial and boundary conditions have been framed. The model is transformed into variational form and Ritz finite element method has been employed to obtain the solution. A program has been developed in MATLAB 7.10 for the entire problem and executed to obtain numerical results. The numerical results have been used to study the effect of buffers, RyR, SERCA pump and VGCC on calcium distribution in an oocyte cell.

Structural and functional characterization of a calcium-activated cation channel from Tsukamurella paurometabola

NASA Astrophysics Data System (ADS)

Dhakshnamoorthy, Balasundaresan; Rohaim, Ahmed; Rui, Huan; Blachowicz, Lydia; Roux, Benoît

2016-09-01

The selectivity filter is an essential functional element of K+ channels that is highly conserved both in terms of its primary sequence and its three-dimensional structure. Here, we investigate the properties of an ion channel from the Gram-positive bacterium Tsukamurella paurometabola with a selectivity filter formed by an uncommon proline-rich sequence. Electrophysiological recordings show that it is a non-selective cation channel and that its activity depends on Ca2+ concentration. In the crystal structure, the selectivity filter adopts a novel conformation with Ca2+ ions bound within the filter near the pore helix where they are coordinated by backbone oxygen atoms, a recurrent motif found in multiple proteins. The binding of Ca2+ ion in the selectivity filter controls the widening of the pore as shown in crystal structures and in molecular dynamics simulations. The structural, functional and computational data provide a characterization of this calcium-gated cationic channel.

Anomalous REE patterns in unequilibrated enstatite chondrites: Evidence and implications

NASA Technical Reports Server (NTRS)

Crozaz, Ghislaine; Hsu, Weibiao

1993-01-01

We present here a study of Rare Earth Element (REE) microdistributions in unequilibrated enstatite chondrites (EOC's). Although the whole rock REE contents are similar in both unequilibrated and equilibrated chondrites, the host minerals of these refractory elements are different. In the least equilibrated ordinary chondrites (UOC's), the REE reside mainly in glass whereas, in their more equilibrated counterparts, the bulk of the REE is in calcium phosphate, a metamorphic mineral that formed by oxidation of phosphorous originally contained in metal. In the smaller group of enstatite (E) chondrites, calcium phosphate is absent and the phase that contains the highest REE concentrations is a minor mineral, CaS (oldhamite), which contains approximately 50 percent of the total Ca present. In E chondrites, elements typically considered to be lithophiles (such as Ca and Mn) occur in sulfides rather than silicates. This indicates formation under extremely reducing conditions, thus in a region of the solar nebula distinct from those that supplied the more abundant ordinary and carbonaceous chondrites. Previously, we observed a variety of REE patterns in the oldhamite of UEC's; they range from almost flat to some with pronounced positive Eu and Yb anomalies. Here, we searched for complementary REE patterns in other minerals from E chondrites and found them in the major mineral, enstatite. Whenever Eu and Yb anomalies are present in this mineral, they are always negative.

Calcium/vitamin D supplementation, serum 25-hydroxyvitamin D concentrations, and cholesterol profiles in the Women's Health Initiative calcium/vitamin D randomized trial.

PubMed

Schnatz, Peter F; Jiang, Xuezhi; Vila-Wright, Sharon; Aragaki, Aaron K; Nudy, Matthew; O'Sullivan, David M; Jackson, Rebecca; LeBlanc, Erin; Robinson, Jennifer G; Shikany, James M; Womack, Catherine R; Martin, Lisa W; Neuhouser, Marian L; Vitolins, Mara Z; Song, Yiqing; Kritchevsky, Stephen; Manson, JoAnn E

2014-08-01

The objective of this study was to evaluate whether increased serum 25-hydroxyvitamin D3 (25OHD3) concentrations, in response to calcium/vitamin D (CaD) supplementation, are associated with improved lipids in postmenopausal women. The parent trial was a double-blind, randomized, placebo-controlled, parallel-group trial designed to test the effects of CaD supplementation (1,000 mg of elemental calcium + 400 IU of vitamin D3 daily) versus placebo in postmenopausal women. Women from the general community, including multiple sites in the United States, were enrolled between 1993 and 1998. This cohort included 300 white, 200 African-American, and 100 Hispanic participants who were randomly selected from the Women's Health Initiative CaD trial. Serum 25OHD3 and lipid (fasting plasma triglycerides [TG], high-density lipoprotein cholesterol [HDL-C], and calculated low-density lipoprotein cholesterol [LDL-C]) levels were assessed before and after CaD randomization. There was a 38% increase in mean serum 25OHD3 concentrations after 2 years (95% CI, 1.29-1.47, P < 0.001) for women randomized to CaD (24.3 ng/mL postrandomization mean) compared with placebo (18.2 ng/mL). Women randomized to CaD had a 4.46-mg/dL mean decrease in LDL-C (P = 0.03). Higher concentrations of 25OHD3 were associated with higher HDL-C levels (P = 0.003), along with lower LDL-C and TG levels (P = 0.02 and P < 0.001, respectively). Supplemental CaD significantly increases 25OHD3 concentrations and decreases LDL-C. Women with higher 25OHD3 concentrations have more favorable lipid profiles, including increased HDL-C, lower LDL-C, and lower TG. These results support the hypothesis that higher concentrations of 25OHD3, in response to CaD supplementation, are associated with improved LDL-C.

Comparative Proteomic Analysis Reveals the Effects of Exogenous Calcium against Acid Rain Stress in Liquidambar formosana Hance Leaves.

PubMed

Hu, Wen-Jun; Wu, Qian; Liu, Xiang; Shen, Zhi-Jun; Chen, Juan; Liu, Ting-Wu; Chen, Juan; Zhu, Chun-Quan; Wu, Fei-Hua; Chen, Lin; Wei, Jia; Qiu, Xiao-Yun; Shen, Guo-Xin; Zheng, Hai-Lei

2016-01-04

Acid rain (AR) impacts forest health by leaching calcium (Ca) away from soils and plants. Ca is an essential element and participates in various plant physiological responses. In the present study, the protective role of exogenous Ca in alleviating AR stress in Liquidambar formosana Hance at the physiological and proteomic levels was examined. Our results showed that low Ca condition resulted in the chlorophyll content and photosynthesis decreasing significantly in L. formosana leaves; however, these effects could be reversed by high Ca supplementation. Further proteomic analyses successfully identified 81 differentially expressed proteins in AR-treated L. formosana under different Ca levels. In particular, some of the proteins are involved in primary metabolism, photosynthesis, energy production, antioxidant defense, transcription, and translation. Moreover, quantitative real time polymerase chain reaction (qRT-PCR) results indicated that low Ca significantly increased the expression level of the investigated Ca-related genes, which can be reversed by high Ca supplementation under AR stress. Further, Western blotting analysis revealed that exogenous Ca supply reduced AR damage by elevating the expression of proteins involved in the Calvin cycle, reactive oxygen species (ROS) scavenging system. These findings allowed us to better understand how woody plants respond to AR stress at various Ca levels and the protective role of exogenous Ca against AR stress in forest tree species.

A new mechanism for calcium loss in forest-floor soils

USGS Publications Warehouse

Lawrence, G.B.; David, M.B.; Shortle, W.C.

1995-01-01

CALCIUM is the fifth most abundant element in trees, and is an essential component for wood formation and the maintenance of cell walls. Depletion of Ca from the rooting zone can result in acidification of soil1 and surface water2 and possibly growth decline and dieback of red spruce3,4. During the past six decades, concentrations of root-available Ca (exchangeable and acid-ex tract able forms) in forest-floor soils have decreased in the northeastern United States5,6. Both net forest growth and acid deposition have been put forth as mechanisms that can account for this Ca depletion5,6. Here, however, we present data collected in red spruce forests in the northeastern United States that are inconsistent with either of these mechanisms. We propose that aluminium, mobilized in the mineral soil by acid deposition, is transported into the forest floor in a reactive form that reduces storage of Ca, and thus its availability for root uptake. This results in potential stress to trees and, by increasing the demand for Ca, also decreases neutralization of drainage waters, thereby leading to acidification of lakes and streams.

Calcium influx through the TRPV1 channel of endothelial cells (ECs) correlates with a stronger adhesion between monocytes and ECs.

PubMed

Himi, N; Hamaguchi, A; Hashimoto, K; Koga, T; Narita, K; Miyamoto, O

2012-01-01

Atherosclerosis is thought to be initiated by the transendothelial migration of monocytes. In the early stage of this process, the adhesion of monocytes to endothelial cells is supported by an increase in the intracellular concentration of calcium ion ([Ca(2+)]i) in endothelial cells. However, the main source of Ca(2+) has been unclear. In this study, the changes in ionic transmittance and [Ca(2+)]i due to the adhesion of monocytes were continuously measured by an electrophysiological technique and fluorescent imaging. Especially, we focused on transient receptor potential vanilloid channel 1 (TRPV1) as a Ca(2+) channel that could influence the adhesion of monocytes. Whole-cell current was continuously recorded in human umbilical vein endothelial cells (HUVECs) by a patch electrode. The adhesion of monocytes (THP-1) induced a transient inward current in HUVECs, as well as an elevation of [Ca(2+)]i. This inward element was abolished by the application of 100 nM SB366,791, a selective antagonist of TRPV1 channel. Furthermore, SB366,791 significantly decreased the number of THP-1 cells that adhered to HUVECs (control: 231 ± 38, SB366,791: 96 ± 16 cells/mm2). These results suggest that an inward calcium current via the TRPV1 channels of endothelial cells correlates with a stronger adhesion between monocytes and endothelial cells.

Towards bio monitoring of toxic (lead) and essential elements in whole blood from 1- to 72-month old children: a cross-sectional study.

PubMed

Kang-Sheng, Liu; Xiao-Dong, Mao; Juan, Shi; Chun-Fan, Dai; Pingqing, Gu

2015-06-01

Minerals such as zinc, copper, selenium, calcium, and magnesium are essential for normal human development and functioning of the body. They have been found to play important roles in immuno-physiologic functions. The study is to evaluate the distribution and correlation of nonessential (lead) and essential elements in whole blood from 1- to 72-month old children. The cross-sectional study was performed in 1551 children. Six element concentrations, including copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg), iron (Fe) and lead (Pb) in the blood were determined by atomic absorption spectrometry. Distributions and correlations of trace elements in different age groups were analyzed and compared. A Pearson correlation controlled for age and gender was used to assess the relationship of non essential (lead) and essential elements. Levels of copper and magnesium were 18.09 ± 4.42 µmol/L and 1.42 ± 0.12 mmol/L, respectively. 6.04% of all children showed copper levels below the normal threshold, the levels of Magnesium were stable in different age groups. Though the overall mean blood zinc and iron concentrations (61.19 ± 11.30 µmol/L and 8.24 ± 0.59 mmol/L, respectively) gradually increased with age and the overall deficiency levels (24.1% and 36.0%, respectively) decreased with age, zinc and iron deficiencies were still very stable. Controlling for gender and age, significant positive correlations were found when comparing copper to zinc, calcium, magnesium, and iron ((r = 0.333, 0.241, 0.417, 0.314 ,p < 0.01); zinc to magnesium and iron (r = 0.440, 0.497p < 0.01); and magnesium to Calcium and iron (r = 0.349, 0.645, p < 0.01). The overall mean blood lead levels (41.16 ± 16.10) were relatively unstable among different age groups. The prevalence of lead intoxication in all children was 1.3% .Calcium levels decreased gradually with age, with an overall concentration of 1.78 ± 0.13 mmol/L. Significant negative correlations were also noted between Pb and Zn, Fe (r = -0.179, -0.124.p < 0.01) .The importance of calcium deficiency and supplementation is well realized, but the severity of iron and zinc deficiency is not well recorded. The degree of lead intoxication in all the children studied was low; The established reference intervals for Cu, Zn, Ca and Mg provide an important guidance for the reasonable supplementation of essential elements during different age groups.

Atmospheric parameters and magnesium and calcium NLTE abundances for a sample of 16 ultra metal-poor stars

NASA Astrophysics Data System (ADS)

Sitnova, Tatyana; Mashonkina, Lyudmila; Ezzeddine, Rana; Frebel, Anna

2018-06-01

The most metal-poor stars provide important observational clues to the astrophysical objects that enriched the primordial gas with heavy elements. Accurate atmospheric parameters is a prerequisite of determination of accurate abundances. We present atmospheric parameters and abundances of calcium and magnesium for a sample of 16 ultra-metal poor (UMP) stars. In spectra of UMP stars, iron is represented only by lines of Fe I, while calcium is represented with lines of Ca I and Ca II, which can be used for determination/checking of effective temperature and surface gravity. Accurate calculations of synthetic spectra of UMP stars require non-local thermodynamic equilibrium (NLTE) treatment of line formation, since deviations from LTE grow with metallicity decreasing. The method of atmospheric parameter determination is based on NLTE analysis of lines of Ca I and Ca II, multi-band photometry, and isochrones. The method was tested in advance with the ultra metal-poor giant CD-38 245, where, in addition, trigonometric parallax measurements from Gaia DR1 and lines of Fe I and Fe II are available. Using photometric Teff = 4900 K and distance based log g = 2.0 for CD-38 245, we derived consistent within error bars NLTE abundances from Fe I and Fe II and Ca I and Ca II, while LTE leads to a discrepancy of 0.6 dex between Ca I and Ca II. We determined NLTE and LTE abundances of magnesium and calcium in 16 stars of the sample. For the majority of stars, as expected, [Ca/Mg] NLTE abundance ratios are close to 0, while LTE leads to systematically higher [Ca/Mg], by up to 0.3 dex, and larger spread of [Ca/Mg] for different stars. Three stars of our sample are strongly enhanced in magnesium, with [Mg/Ca] of 1.3 dex. It is worth noting that, for these three stars, we got very similar [Mg/Ca] of 1.30, 1.45, and 1.29, in contrast to the data from the literature, where, for the same stars, [Mg/Ca] vary from 0.7 to 1.4. Very similar [Mg/Ca] abundance ratios of these stars argue that their abundances originate from a similar nucleosynthetic event.

High-precision measurement of variations in calcium isotope ratios in urine by multiple collector inductively coupled plasma mass spectrometry

USGS Publications Warehouse

Morgan, J.L.L.; Gordon, G.W.; Arrua, R.C.; Skulan, J.L.; Anbar, A.D.; Bullen, T.D.

2011-01-01

We describe a new chemical separation method to isolate Ca from other matrix elements in biological samples, developed with the long-term goal of making high-precision measurement of natural stable Ca isotope variations a clinically applicable tool to assess bone mineral balance. A new two-column procedure utilizing HBr achieves the purity required to accurately and precisely measure two Ca isotope ratios (44Ca/42Ca and 44Ca/43Ca) on a Neptune multiple collector inductively coupled plasma mass spectrometer (MC-ICPMS) in urine. Purification requirements for Sr, Ti, and K (Ca/Sr > 10000; Ca/Ti > 10000000; and Ca/K > 10) were determined by addition of these elements to Ca standards of known isotopic composition. Accuracy was determined by (1) comparing Ca isotope results for samples and standards to published data obtained using thermal ionization mass spectrometry (TIMS), (2) adding a Ca standard of known isotopic composition to a urine sample purified of Ca, and (3) analyzing mixtures of urine samples and standards in varying proportions. The accuracy and precision of δ44/42Ca measurements of purified samples containing 25 μg of Ca can be determined with typical errors less than ±0.2‰ (2σ).

Variation of calcium, copper and iron levels in serum, bile and stone samples of patients having different types of gallstone: A comparative study.

PubMed

Khan, Mustafa; Kazi, Tasneem Gul; Afridi, Hassan Imran; Sirajuddin; Bilal, Muhammad; Akhtar, Asma; Khan, Sabir; Kadar, Salma

2017-08-01

Epidemiological data among the human population has shown a significantly increased incidence of gallstone (GS) disease worldwide. It was studied that some essential (calcium) and transition elements (iron and copper) in bile play an important role in the development of GS. The estimation of calcium, copper and iron were carried out in the serum, gall bladder bile and different types of GS (cholesterol, mixed and pigmented) of 172 patients, age ranged 20-55years. For comparative purpose age matched referents not suffering from GS diseases were also selected. Biliary concentrations of calcium (Ca), iron (Fe) and copper (Cu) were correlated with their concentrations in serum and different types of GS samples. The ratio of Ca, Fe and Cu in bile with serum was also calculated. Understudy metals were determined by flame atomic absorption spectroscopy after acid decomposition of matrices of selected samples. The Ca concentrations in serum samples were significantly higher in patients with pigmented GS as compared to controls (p<0.005), whereas for patients having cholesterol and mixed GS the concentrations were on the lower side. Biliary Ca concentrations of patients were found to be higher than controls, but difference was significant for pigmented GS patients (p>0.001). The contents of Cu and Fe in serum and bile of all patients (except female cholesterol GS patient have low serum iron concentration) were found to be higher than control, but difference was significant in those patients who have pigmented GS. The concentration of Ca, Fe and Cu in different types GS were found in the order, Pigmented>mixed>cholesterol. The bile/serum ratio for Ca, Cu and Fe was found to be significantly higher in pigmented GS patients. Gall bladder bile was slightly alkaline in patients as compared to referents. The density of bile was found to be higher in patients as compared to the referents. Various functional groups present in different types of GS samples were confirmed by Fourier transform infra-red spectroscopy. The higher density and pH of bile, elevated concentrations of transition elements in all types of biological samples (serum, bile and GS), could be an important factor for the formation of different types of GS. Copyright © 2017 Elsevier B.V. All rights reserved.

Vitamin D and calcium supplementation and one-year change in mammographic density in the Women’s Health Initiative Calcium and Vitamin D Trial

PubMed Central

Bertone-Johnson, Elizabeth R.; McTiernan, Anne; Thomson, Cynthia A.; Wactawski-Wende, Jean; Aragaki, Aaron K.; Rohan, Thomas E.; Vitolins, Mara Z.; Tamimi, Rulla M.; Johnson, Karen C.; Lane, Dorothy; Rexrode, Kathryn M.; Peck, Jennifer D.; Chlebowski, Rowan T.; Sarto, Gloria; Manson, JoAnn E.

2012-01-01

Background Calcium and vitamin D may be inversely related to breast cancer risk, in part by affecting mammographic density. However, results from previous, mostly cross-sectional studies have been mixed, and there have been few randomized clinical trials of the effect of calcium and vitamin D supplementation on change in mammographic density. Methods We assessed the effect of one year of supplementation on mammographic density in 330 postmenopausal women enrolled in the Women’s Health Initiative Hormone Therapy (HT) and Calcium and Vitamin D (CaD) trials. Women were randomized to receive 1000 mg/day of elemental calcium carbonate plus 400 IU/day of vitamin D3 or placebo. Results After approximately one year, mammographic density decreased 2% in the CaD supplementation group and increased 1% in the placebo group (ratio of means = 0.97; 95% confidence interval (CI) = 0.81–1.17). Results suggested potential interaction by HT use (P = 0.08). Among women randomized to HT placebo, the ratio of mean density comparing CaD supplementation and placebo groups was 0.82 (95%CI = 0.61–1.11) vs. 1.16 (95%CI = 0.92–1.45) in women randomized to active HT. In sensitivity analyses limited to women taking ≥80% of study supplements, ratios were 0.67 (95%CI = 0.41–1.07) in women not assigned to HT and 1.07 (95%CI = 0.79–1.47) women assigned to HT. Conclusions We observed no overall effect of vitamin D and calcium supplementation on mammographic density after one year. Impact Potential interaction between these nutrients and estrogen as related to mammographic density warrants further study. PMID:22253296

Calcium Isotopes in Foraminifera Shells: Evaluation for Paleo-temperature Reconstruction

NASA Astrophysics Data System (ADS)

Paytan, A.; Revello, C. A.; Bullen, T. D.

2002-12-01

The Ca stable isotope ratio of foraminifera shells has been suggested as a potential paleo-temperature proxy and has recently been applied in several studies to reconstruct glacial interglacial fluctuations in seawater temperatures. The major advantage of using Ca isotopes for paleo-temperature reconstruction is the relatively long residence time of Ca in the ocean. Thus, no spatial or temporal change in the Ca isotopic composition of seawater is expected over time scales much shorter than a million years. Moreover, since Ca is a major constituent of carbonate, and an isotopic ratio rather than an element concentration or element-element ratio (e.g. Mg/Ca, Sr/Ca) is measured, the Ca isotope proxy is much less likely to be affected by post depositional diagenetic alteration. However, preliminary results indicate that kinetic effects might largely control the Ca isotope fractionation involved in calcite shell formation. Before this new and exciting proxy can be utilized routinely, a better understanding of the parameters controlling Ca isotope fractionation in carbonate minerals in general and in foraminifera and other carbonate-secreting organisms is required. We have measured the Ca stable isotope ratio of several foraminifera species from core top sediments from two well-studied sites to determine the inter-species and within-species variability in Ca isotopes. We assess the effects of water temperature, calcification rate, and vital effects on the Ca stable isotope ratio of modern foraminifera and evaluate the potential of this proxy for paleo-temperature reconstruction.

Laser-induced breakdown spectroscopy (LIBS) analysis of calcium ions dissolved in water using filter paper substrates: an ideal internal standard for precision improvement.

PubMed

Choi, Daewoong; Gong, Yongdeuk; Nam, Sang-Ho; Han, Song-Hee; Yoo, Jonghyun; Lee, Yonghoon

2014-01-01

We report an approach for selecting an internal standard to improve the precision of laser-induced breakdown spectroscopy (LIBS) analysis for determining calcium (Ca) concentration in water. The dissolved Ca(2+) ions were pre-concentrated on filter paper by evaporating water. The filter paper was dried and analyzed using LIBS. By adding strontium chloride to sample solutions and using a Sr II line at 407.771 nm for the intensity normalization of Ca II lines at 393.366 or 396.847 nm, the analysis precision could be significantly improved. The Ca II and Sr II line intensities were mapped across the filter paper, and they showed a strong positive shot-to-shot correlation with the same spatial distribution on the filter paper surface. We applied this analysis approach for the measurement of Ca(2+) in tap, bottled, and ground water samples. The Ca(2+) concentrations determined using LIBS are in good agreement with those obtained from flame atomic absorption spectrometry. Finally, we suggest a homologous relation of the strongest emission lines of period 4 and 5 elements in groups IA and IIA based on their similar electronic structures. Our results indicate that the LIBS can be effectively applied for liquid analysis at the sub-parts per million level with high precision using a simple drying of liquid solutions on filter paper and the use of the correct internal standard elements with the similar valence electronic structure with respect to the analytes of interest.

Calcium carbonate crystals promote calcium oxalate crystallization by heterogeneous or epitaxial nucleation: possible involvement in the control of urinary lithogenesis.

PubMed

Geider, S; Dussol, B; Nitsche, S; Veesler, S; Berthézène, P; Dupuy, P; Astier, J P; Boistelle, R; Berland, Y; Dagorn, J C; Verdier, J M

1996-07-01

A large proportion of urinary stones have calcium oxalate (CaOx) as the major mineral phase. In these stones, CaOx is generally associated with minor amounts of other calcium salts. Several reports showing the presence of calcium carbonate (CaCO3) and calcium phosphate in renal stones suggested that crystals of those salts might be present in the early steps of stone formation. Such crystals might therefore promote CaOx crystallization from supersaturated urine by providing an appropriate substrate for heterogeneous nucleation. That possibility was investigated by seeding a metastable solution of 45Ca oxalate with vaterite or calcite crystallites. Accretion of CaOx was monitored by 45Ca incorporation. We showed that (1) seeds of vaterite (the hexagonal polymorph of CaCO3) and calcite (the rhomboedric form) could initiate calcium oxalate crystal growth; (2) in the presence of lithostathine, an inhibitor of CaCO3 crystal growth, such accretion was not observed. In addition, scanning electron microscopy demonstrated that growth occurred by epitaxy onto calcite seeds whereas no special orientation was observed onto vaterite. It was concluded that calcium carbonate crystals promote crystallization of calcium oxalate and that inhibitors controlling calcium carbonate crystal formation in Henle's loop might play an important role in the prevention of calcium oxalate stone formation.

Calcium distribution in Amoeba proteus

PubMed Central

1979-01-01

A preliminary investigation of the distribution of cellular calcium in Amoeba proteus was undertaken. Total cellular calcium under control conditions was found to be 4.59 mmol/kg of cells. When the external Ca++ concentration is increased from the control level of 0.03 to 20 mM, a net Ca++ influx results with a new steady-state cellular calcium level being achieved in integral of 3 h. At steady state the amount of calcium per unit weight of cells is higher than the amount of calcium per unit weight of external solution when the external concentration of Ca++ is below 10 mM. At external Ca++ concentrations above this level, total cellular calcium approaches the medium level of Ca++. Steady- state calcium exchange in Amoeba proteus was determined with 45Ca. There is an immediate and rapid exchange of integral of 0.84 mmol/kg of cells or 18% of the total cellular calcium with the labelled Ca++. Following this initial exchange, there was very little if any further exchange observed. Most of this exchanged calcium could be eliminated from the cell with 1 mM La+++, suggesting that the exchanged calcium is associated with the surface of the cell. Increase in either the external Ca++ concentration of pH raise the amount of exchangeable calcium associated with the cell. Calcium may be associated with the cell surface as a co-ion in the diffuse double layer or bound to fixed negative sites on the surface of the cell. If Ca++-binding sites do exist on the cell surface, there may be more than one type and they may have different dissociation constants. The cytoplasmic Ca++ ion activity is probably maintained at very low levels. PMID:512628

Characterization of nanoscopic calcium fluoride films

NASA Astrophysics Data System (ADS)

Rehmer, A.; Kemnitz, E.

2016-09-01

Nano metal fluorides are appropriate materials for different applications e.g. heterogeneous catalysis, ceramic materials for laser applications and antireflective layers on glass, respectively. An easy way to synthesize such nano metal fluorides is the fluorolytic sol-gel synthesis which was developed some few years ago for HS-AlF3 [1] and MgF2.[2] CaF2 exhibits similar optical properties as MgF2, and thus, is a promising candidate for antireflective (AR) coatings. That means, CaF2 exhibits a lower refractive index (n500 = 1.44) as compared to common soda lime glass (n500 = 1.53). Hence, we present an easy synthesis approach toward nanoscaled CaF2 sols to fabricate finally AR-CaF2 films by dip coating. Irrespective of the choice of the calcium precursor, the CaF2 films are porous in comparison to thin dense CaF2 films which are generated by physical vapor deposition. The characterization of CaF2 films was performed by different analytical methods like HR-SEM, XPS, EDX, EP (ellipsometric porosimetry), DLS (dynamic light scattering) and CA (contact angle measurement). Beside the good optical and mechanical properties, we have investigated the surface properties of CaF2 films on glass and silicon wafer e.g. surface morphology with elemental composition, open porosity, zeta potentials at the surfaces as well as the free energy of interaction between water and the CaF2 film.

Isolation, characterization and immunolocalization of a seed dominant CaM from finger millet (Eleusine coracana L. Gartn.) for studying its functional role in differential accumulation of calcium in developing grains.

PubMed

Kumar, Anil; Mirza, Neelofar; Charan, Tara; Sharma, Netrapal; Gaur, Vikram Singh

2014-03-01

To understand the exceptional high grain calcium accumulation in finger millet grains, a calmodulin (CaM) gene that is strongly expressed during developing spikes of high grain calcium genotype was further characterized. Using 5'-3' RACE, the full-length CaM open reading frame (ORF) was isolated and the deduced protein sequence showed the presence of four characteristic EF motifs. Phylogenetic analysis showed that the finger millet CaM (Eleusine coracana calmodulin [EcCaM]) was identical to the rice CaM 1-1. Southern hybridization showed the presence of at least four copies of CaM gene that might be located on different regions of the finger millet "AABB" genome. Immunodetection using monospecific polyclonal anti-EcCaM antibodies revealed that EcCaM is localized in the embryo and aleurone layer and accumulates in higher amounts in high grain calcium genotype compared to the low grain calcium genotype. Furthermore, in silico analysis showed that EcCaM interacts with aquaporin which indicates that calcium is probably delivered to developing spike via mass flow of water. These results indicate that higher expression of CaM might cause greater stimulation of the downstream calcium transport machinery operative in the aleurone layer leading to the higher calcium accumulation in the grains of high grain calcium genotype.

The role of CAX1 and CAX3 in elemental distribution and abundance in Arabidopsis seed

USDA-ARS?s Scientific Manuscript database

The ability to alter nutrient partitioning within plant cells is poorly understood. In Arabidopsis (Arabidopsis thaliana), a family of endomembrane cation exchangers (CAXs) transports Ca(2+) and other cations. However, experiments have not focused on how the distribution and partitioning of calcium ...

Significance of Ca-soap formation for calcium absorption in the rat.

PubMed Central

Gacs, G; Barltrop, D

1977-01-01

The significance of calcium soap formation in the inhibition of calcium absorption has been studied in rats. 47Ca labelled soaps of fatty acids were introduced into the duodenum and the absorption of calcium measured after four hours in a whole body counter. The absorption of calcium was inversely correlated with the chain length of the fatty acid varying from 1% for Ca-stearate to 60% for Ca-hexanoate. Increasing the degree of unsaturation of the fatty acid was accompanied by increased calcium absorption. The availability of calcium for absorption from the soaps was correlated with their solubility in 1% aqueous Na-tauroglycocholate. The percentages of calcium as soap in the small intestine and the faeces after intragastric administration of calcium and fats were similar, which suggests that the faecal content of calcium soaps is an index of intestinal soap formation. Soap formation was negligible when CaCl2 was given with tristearate, triolaeate, or tridecanoate and no depression of calcium absorption was observed. Calcium absorption was markedly impaired by the addition of phosphates at a Ca/P ratio of 1:1 irrespective of the presence of neutral fats. Stearic acid resulted in significant soap formation and reduced calcium absorption. The degree of Ca-soap formation and the inhibition of calcium absorption were well correlated. The results suggest that, although calcium soap formation may markedly depress calcium absorption in the rat, no significant soap formation takes place when fats are given in the form of triglycerides. PMID:838405

Ectopic expression of phloem motor protein pea forisome PsSEO-F1 enhances salinity stress tolerance in tobacco.

PubMed

Srivastava, Vineet Kumar; Raikwar, Shailendra; Tuteja, Renu; Tuteja, Narendra

2016-05-01

PsSEOF-1 binds to calcium and its expression is upregulated by salinity treatment. PsSEOF - 1 -overexpressing transgenic tobacco showed enhanced salinity stress tolerance by maintaining cellular ion homeostasis and modulating ROS-scavenging pathway. Calcium (Ca(2+)) plays important role in growth, development and stress tolerance in plants. Cellular Ca(2+) homeostasis is achieved by the collective action of channels, pumps, antiporters and by Ca(2+) chelators present in the cell like calcium-binding proteins. Forisomes are ATP-independent mechanically active motor proteins known to function in wound sealing of injured sieve elements of phloem tissue. The Ca(2+)-binding activity of forisome and its role in abiotic stress signaling were largely unknown. Here we report the Ca(2+)-binding activity of pea forisome (PsSEO-F1) and its novel function in promoting salinity tolerance in transgenic tobacco. Native PsSEO-F1 promoter positively responded in salinity stress as confirmed using GUS reporter. Overexpression of PsSEO-F1 tobacco plants confers salinity tolerance by alleviating ionic toxicity and increased ROS scavenging activity which probably results in reduced membrane damage and improved yield under salinity stress. Evaluation of several physiological indices shows an increase in relative water content, electrolyte leakage, proline accumulation and chlorophyll content in transgenic lines as compared with null-segregant control. Expression of several genes involved in cellular homeostasis is perturbed by PsSEO-F1 overexpression. These findings suggest that PsSEO-F1 provides salinity tolerance through cellular Ca(2+) homeostasis which in turn modulates ROS machinery providing indirect link between Ca(2+) and ROS signaling under salinity-induced perturbation. PsSEO-F1 most likely functions in salinity stress tolerance by improving antioxidant machinery and mitigating ion toxicity in transgenic lines. This finding should make an important contribution in our better understanding of the significance of calcium signaling in phloem tissue leading to salinity stress tolerance.

Seasonal Trends and Inter-Individual Heterogeneity: A multi-species record of Mg, Sr, Ba, & Mn in Planktic Foraminifera from the Modern Cariaco Basin

NASA Astrophysics Data System (ADS)

Davis, C. V.; Thunell, R.; Astor, Y. M.

2017-12-01

The trace element to calcium ratios (TE/Ca) of planktic foraminifera shells are a valuable tool for paleoceanographic reconstructions, and represent a combination of environmental, ecological and biological signals. We present here a three-year record (2010-2013) of TE/Ca (Mg, Sr, Ba, Mn) from four species of foraminifera (Orbulina universa, Globigerina ruber, Globigerinella siphonifera, and Globorotalia menardii) collected by plankton tow in the modern Cariaco basin. Each tow is paired with in situ measurements of water column properties, allowing a direct comparison between shell geochemistry and calcification environment. A combination of Laser Ablation and solution ICP-MS analyses are used to document seasonality, primarily due to the alternating influence of wind-driven coastal upwelling and riverine inputs, in shell TE/Ca. Individual shell data further allows for the quantification of trace element heterogeneity among individual shells within single tows. All TE/Ca ratios vary temporally and show inter-individual variability within single tows. The spread in TE/Ca differs between element and species, with Mg/Ca ratios being the most variable. Despite this, Mg/Ca still tracks temperature changes in G. ruber, O. universa, and G. menardii, with G. ruber most closely reproducing sea surface temperature. Some species show chamber-to-chamber differences in trace element ratios, with G. ruber Mg/Ca and Ba/Ca decreasing in younger chambers (but not other elements) and Mg/Ca, Mn/Ca and Ba/Ca decreasing in younger chambers in G. siphonifera. We find the original Mn/Ca to be variable both temporally and between species, with G. menardii in some samples having extremely high ratios (100 μmol/mol). Assessing seasonal trends and environmental drivers of TE/Ca variability and quantifying the extent of inter-individual heterogeneity in these species will inform the use of their shells as geochemical proxies.

Calcium-Dependent Energetics of Calmodulin Domain Interactions with Regulatory Regions of the Ryanodine Receptor Type 1 (RyR1)

PubMed Central

Newman, Rhonda A.; Sorensen, Brenda R.; Kilpatrick, Adina M.; Shea, Madeline A.

2014-01-01

Calmodulin (CaM) plays a vital role in calcium homeostasis by allosterically modulating intracellular calcium channels including the homo-tetrameric human Ryanodine Receptor Type 1 (hRyR1). Apo (calcium-free) CaM activates hRyR1 while calcium-saturated CaM inhibits it. Two CaM-binding regions (residues 1975–1999 and 3614–3643) identified in each RyR1 monomer were proposed to allow CaM to bridge adjacent RyR1 subunits. We explored the distinct roles of CaM domains by using fluorescence anisotropy to determine the affinity of CaM1–148 (full-length), CaM1–80 (N-domain) and CaM76–148 (C-domain) for peptides encompassing hRyR1 residues 1975–1999 or 3614–3643. Both CaM1–148 and CaM76–148 associated in a calcium-independent manner with similar affinities for hRyR1(3614–3643)p while CaM1–80 required calcium and bound ~250-fold more weakly. Association of CaM1–148, CaM1–80 and CaM76–148 with hRyR1(1975–1999)p was much less favorable than with hRyR1(3614–3643)p; differences between the two CaM domains were smaller. Equilibrium calcium titrations monitored by steady-state fluorescence demonstrated that both hRyR1 peptides increased the calcium-binding affinity of both CaM domains. These thermodynamic properties support a prior model in which the CaM C-domain associates with RyR1(3614–3643) at low levels of calcium, positioning CaM to rapidly respond to calcium efflux. However, the affinity of the N-domain of CaM for hRyR1(1975–1999)p is insufficient to explain a model in which CaM bridges adjacent RyR1 subunits within the tetramer. This indicates that other protein factors or properties of the tertiary or quaternary structure of hRyR1 contribute to the energetics of CaM-mediated regulation. PMID:25145833

Interaction of Nanostructured Calcium Silicate Hydrate with Ibuprofen Drug Molecules: X-ray Absorption Near Edge Structure (XANES) Study at the Ca, Si and O K-edge

NASA Astrophysics Data System (ADS)

Guo, X. X.; Sham, T. K.; Zhu, Y. J.; Hu, Y. F.

2013-04-01

Mesoporous calcium silicate hydrate (CSH) nanostructure has been proven to be bioactive and biocompatible, and has a bright future in the application of bone treatment among other applications. X-ray absorption near edge structure (XANES) is a powerful tool for the study of the interactions of calcium silicate hydrates with drug molecules because it is element specific and it probes the unoccupied electronic states. Herein, we report the use of the calcium, silicon and oxygen K-edge XANES spectroscopy to identify how drug molecules interact with different groups in calcium silicate hydrate mesoporous nano-carriers with different morphologies. Significant changes are observed in XANES spectra after drug loading into the calcium silicate hydrate system, especially at the Si and O K-edge. The implications of these findings are discussed.

Ca2+/Calmodulin-dependent kinase II signaling causes skeletal overgrowth and premature chondrocyte maturation.

PubMed

Taschner, Michael J; Rafigh, Mehran; Lampert, Fabienne; Schnaiter, Simon; Hartmann, Christine

2008-05-01

The long bones of vertebrate limbs originate from cartilage templates and are formed by the process of endochondral ossification. This process requires that chondrocytes undergo a progressive maturation from proliferating to postmitotic prehypertrophic to mature, hypertrophic chondrocytes. Coordinated control of proliferation and maturation regulates growth of the skeletal elements. Various signals and pathways have been implicated in orchestrating these processes, but the underlying intracellular molecular mechanisms are often not entirely known. Here we demonstrated in the chick using replication-competent retroviruses that constitutive activation of Calcium/Calmodulin-dependent kinase II (CaMKII) in the developing wing resulted in elongation of skeletal elements associated with premature differentiation of chondrocytes. The premature maturation of chondrocytes was a cell-autonomous effect of constitutive CaMKII signaling associated with down-regulation of cell-cycle regulators and up-regulation of chondrocyte maturation markers. In contrast, the elongation of the skeletal elements resulted from a non-cell autonomous up-regulation of the Indian hedgehog responsive gene encoding Parathyroid-hormone-related peptide. Reduction of endogenous CaMKII activity by overexpressing an inhibitory peptide resulted in shortening of the skeletal elements associated with a delay in chondrocyte maturation. Thus, CaMKII is an essential component of intracellular signaling pathways regulating chondrocyte maturation.

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

PubMed Central

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

The Content of Structural and Trace Elements in the Knee Joint Tissues.

PubMed

Roczniak, Wojciech; Brodziak-Dopierała, Barbara; Cipora, Elżbieta; Mitko, Krzysztof; Jakóbik-Kolon, Agata; Konieczny, Magdalena; Babuśka-Roczniak, Magdalena

2017-11-23

Many elements are responsible for the balance in bone tissue, including those which constitute a substantial proportion of bone mass, i.e., calcium, phosphorus and magnesium, as well as minor elements such as strontium. In addition, toxic elements acquired via occupational and environmental exposure, e.g., Pb, are included in the basic bone tissue composition. The study objective was to determine the content of strontium, lead, calcium, phosphorus, sodium and magnesium in chosen components of the knee joint, i.e., tibia, femur and meniscus. The levels of Sr, Pb, Ca, P, Na and Mg were the highest in the tibia in both men and women, whereas the lowest in the meniscus. It should be noted that the levels of these elements were by far higher in the tibia and femur as compared to the meniscus. In the components of the knee joint, the level of strontium showed the greatest variation. Significant statistical differences were found between men and women only in the content of lead.

The Content of Structural and Trace Elements in the Knee Joint Tissues

PubMed Central

Roczniak, Wojciech; Brodziak-Dopierała, Barbara; Cipora, Elżbieta; Mitko, Krzysztof; Jakóbik-Kolon, Agata; Konieczny, Magdalena; Babuśka-Roczniak, Magdalena

2017-01-01

Many elements are responsible for the balance in bone tissue, including those which constitute a substantial proportion of bone mass, i.e., calcium, phosphorus and magnesium, as well as minor elements such as strontium. In addition, toxic elements acquired via occupational and environmental exposure, e.g., Pb, are included in the basic bone tissue composition. The study objective was to determine the content of strontium, lead, calcium, phosphorus, sodium and magnesium in chosen components of the knee joint, i.e., tibia, femur and meniscus. The levels of Sr, Pb, Ca, P, Na and Mg were the highest in the tibia in both men and women, whereas the lowest in the meniscus. It should be noted that the levels of these elements were by far higher in the tibia and femur as compared to the meniscus. In the components of the knee joint, the level of strontium showed the greatest variation. Significant statistical differences were found between men and women only in the content of lead. PMID:29168758

Allosteric Effects of the Anti-Psychotic Drug Trifluoperazine on the Energetics of Calcium Binding by Calmodulin

PubMed Central

Feldkamp, Michael D.; O'Donnell, Susan E.; Yu, Liping; Shea, Madeline A.

2010-01-01

Trifluoperazine (TFP; Stelazine™) is an antagonist of calmodulin (CaM), an essential regulator of calcium-dependent signal transduction. Reports differ regarding whether, or where, TFP binds to apo CaM. Three crystallographic structures (1CTR, 1A29, 1LIN) show TFP bound to (Ca2+)4-CaM in ratios of 1, 2 or 4 TFP per CaM. In all of these, CaM domains adopt the “open” conformation seen in CaM-kinase complexes having increased calcium affinity. Most reports suggest TFP also increases calcium affinity of CaM. To compare TFP binding to apo CaM and (Ca2+)4-CaM, and explore differential effects on the N- and C-domains of CaM, stoichiometric TFP titrations of CaM were monitored by 15N-HSQC NMR. Two TFP bound to apo CaM, while four bound to (Ca2+)4-CaM. In both cases, the preferred site was in the C-domain. During the titrations, biphasic responses for some resonances suggested inter-site interactions. TFP-binding sites in apo CaM appeared distinct from those in (Ca2+)4-CaM. In equilibrium calcium titrations at defined ratios of TFP:CaM, TFP reduced calcium affinity at most levels tested; this is similar to the effect of many IQ-motifs on CaM. However, at the highest level tested, TFP raised the calcium affinity of the N-domain of CaM. A model of conformational switching is proposed to explain how TFP can exert opposing allosteric effects on calcium affinity by binding to different sites in the “closed”, “semi-open” and “open” domains of CaM. In physiological processes, apo CaM, as well as (Ca2+)4-CaM, needs to be considered a potential target of drug action. PMID:20544963

Physicochemical fabrication of antibacterial calcium phosphate submicrospheres with dispersed silver nanoparticles via coprecipitation and photoreduction under laser irradiation.

PubMed

Nakamura, Maki; Oyane, Ayako; Shimizu, Yoshiki; Miyata, Saori; Saeki, Ayumi; Miyaji, Hirofumi

2016-12-01

We achieved rapid, surfactant-free, and one-pot fabrication of antibacterial calcium phosphate (CaP) submicrospheres containing silver nanoparticles by combining physical laser and chemical coprecipitation processes. In this physicochemical process, weak pulsed laser irradiation (20min) was performed on a labile CaP reaction mixture supplemented with silver ions as a light-absorbing agent. The silver content in the submicrospheres was controlled for a wide range (Ag/P elemental ratio varied from 0.60 to 62.0) by tuning the initial concentration of silver ions (from 5 to 20mM) in the CaP reaction mixture. At the silver concentration of 5mM, we obtained unique nanocomposite particles: CaP submicrospheres (average diameter of approximately 500nm) containing metallic silver nanoparticles dispersed throughout, as a result of CaP and silver coprecipitation with simultaneous photoreduction of silver ions and spheroidization of the coprecipitates. These CaP submicrospheres containing silver nanoparticles (ca. 0.3mg silver per 1mg submicrospheres) exhibited antibacterial activity against major pathogenic oral bacteria, i.e., Streptococcus mutans, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis. Moreover, the CaP submicrospheres dissolved and neutralized the acidic environment generated by Streptococcus mutans, demonstrating their potential as acid-neutralizing and remineralizing agents. The present process and resulting antibacterial CaP-based submicrospheres are expected to be useful in dental healthcare and infection control. Nano- and microsized spheres of calcium phosphate (CaP) containing silver nanoparticles have great potential in dental applications. Conventional fabrication processes were time-consuming or weak regarding the size/shape control of the spheres. In this study, we achieved a simple (one-pot), rapid (20-min irradiation), and surfactant-free fabrication of CaP submicrospheres containing silver nanoparticles by pulsed laser irradiation to a mixture of calcium, phosphate, and silver ion solutions. The resulting CaP submicrospheres contained metallic silver nanoparticles dispersed throughout in a sequence of reactions: CaP and silver coprecipitation, laser-induced melting and spheroidization of the coprecipitates, and photoreduction of silver ions. These submicrospheres showed antibacterial activity against oral bacteria and acid-neutralizing property in the bacterial suspension, and hence are worth considering for dental applications. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Authentication of two samples of ancient Chinese coins with component element depth analysis by confocal 3D XRF

NASA Astrophysics Data System (ADS)

Zhou, Peng; Liu, Zhiguo; Lin, Xiaoyan; Liu, Xin; Ye, Lei; Wang, Xingyi; Pan, Kai; Li, Yude

2018-05-01

Two samples of ancient Chinese coins were analyzed with a confocal three-dimensional micro-X-ray fluoroscope. The depth distributions of elemental iron (Fe), calcium (Ca) and copper (Cu) were obtained based on this non-destructive measurement method. One coin, named "Chongning Tongbao", was certified as genuine in accordance with the available archaeological data, whereas another coin, named "Zhenglong Yuanbao", was identified as a reproduction.

Responses of plant calmodulin to endocytosis induced by rare earth elements.

PubMed

Wang, Lihong; Cheng, Mengzhu; Chu, Yunxia; Li, Xiaodong; Chen, David D Y; Huang, Xiaohua; Zhou, Qing

2016-07-01

The wide application of rare earth elements (REEs) have led to their diffusion and accumulation in the environment. The activation of endocytosis is the primary response of plant cells to REEs. Calmodulin (CaM), as an important substance in calcium (Ca) signaling systems, regulating almost all of the physiological activities in plants, such as cellular metabolism, cell growth and division. However, the response of CaM to endocytosis activated by REEs remains unknown. By using immunofluorescence labeling and a confocal laser scanning microscope, we found that trivalent lanthanum [La(III)], an REE ion, affected the expression of CaM in endocytosis. Using circular dichroism, X-ray photoelectron spectroscopy and computer simulations, we demonstrated that a low concentration of La(III) could interact with extracellular CaM by electrostatic attraction and was then bound to two Ca-binding sites of CaM, making the molecular structure more compact and orderly, whereas a high concentration of La(III) could be coordinated with cytoplasmic CaM or bound to other Ca-binding sites, making the molecular structure more loose and disorderly. Our results provide a reference for revealing the action mechanisms of REEs in plant cells. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

PubMed

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.

Simultaneous removal of SO2 and trace As2O3 from flue gas: mechanism, kinetics study, and effect of main gases on arsenic capture.

PubMed

Li, Yuzhong; Tong, Huiling; Zhuo, Yuqun; Li, Yan; Xu, Xuchang

2007-04-15

Sulfur dioxide (SO2) and trace elements are pollutants derived from coal combustion. This study focuses on the simultaneous removal of S02 and trace arsenic oxide (As2O3) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range. Experiments have been performed on a thermogravimetric analyzer (TGA). The interaction mechanism between As2O3 and CaO is studied via XRD detection. Calcium arsenate [Ca3(AsO4)2] is found to be the reaction product in the range of 600-1000 degrees C. The ability of CaO to absorb As2O3 increases with the increasing temperature over the range of 400-1000 degrees C. Through kinetics analysis, it has been found that the rate constant of arsenate reaction is much higher than that of sulfate reaction. SO2 presence does not affect the trace arsenic capture either in the initial reaction stage when CaO conversion is relatively low or in the later stage when CaO conversion is very high. The product of sulfate reaction, CaS04, is proven to be able to absorb As2O3. The coexisting CO2 does not weaken the trace arsenic capture either.

Biomineralisation by earthworms - an investigation into the stability and distribution of amorphous calcium carbonate.

PubMed

Hodson, Mark E; Benning, Liane G; Demarchi, Bea; Penkman, Kirsty E H; Rodriguez-Blanco, Juan D; Schofield, Paul F; Versteegh, Emma A A

Many biominerals form from amorphous calcium carbonate (ACC), but this phase is highly unstable when synthesised in its pure form inorganically. Several species of earthworm secrete calcium carbonate granules which contain highly stable ACC. We analysed the milky fluid from which granules form and solid granules for amino acid (by liquid chromatography) and functional group (by Fourier transform infrared (FTIR) spectroscopy) compositions. Granule elemental composition was determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and electron microprobe analysis (EMPA). Mass of ACC present in solid granules was quantified using FTIR and compared to granule elemental and amino acid compositions. Bulk analysis of granules was of powdered bulk material. Spatially resolved analysis was of thin sections of granules using synchrotron-based μ-FTIR and EMPA electron microprobe analysis. The milky fluid from which granules form is amino acid-rich (≤ 136 ± 3 nmol mg -1 (n = 3; ± std dev) per individual amino acid); the CaCO 3 phase present is ACC. Even four years after production, granules contain ACC. No correlation exists between mass of ACC present and granule elemental composition. Granule amino acid concentrations correlate well with ACC content (r ≥ 0.7, p ≤ 0.05) consistent with a role for amino acids (or the proteins they make up) in ACC stabilisation. Intra-granule variation in ACC (RSD = 16%) and amino acid concentration (RSD = 22-35%) was high for granules produced by the same earthworm. Maps of ACC distribution produced using synchrotron-based μ-FTIR mapping of granule thin sections and the relative intensity of the ν 2 : ν 4 peak ratio, cluster analysis and component regression using ACC and calcite standards showed similar spatial distributions of likely ACC-rich and calcite-rich areas. We could not identify organic peaks in the μ-FTIR spectra and thus could not determine whether ACC-rich domains also had relatively high amino acid concentrations. No correlation exists between ACC distribution and elemental concentrations determined by EMPA. ACC present in earthworm CaCO 3 granules is highly stable. Our results suggest a role for amino acids (or proteins) in this stability. We see no evidence for stabilisation of ACC by incorporation of inorganic components. Graphical abstractSynchrotron-based μ-FTIR mapping was used to determine the spatial distribution of amorphous calcium carbonate in earthworm-produced CaCO 3 granules.

An overview of techniques for the measurement of calcium distribution, calcium fluxes, and cytosolic free calcium in mammalian cells.

PubMed Central

Borle, A B

1990-01-01

An array of techniques can be used to study cell calcium metabolism that comprises several calcium compartments and many types of transport systems such as ion channels, ATP-dependent pumps, and antiporters. The measurement of total cell calcium brings little information of value since 60 to 80% of total cell calcium is actually bound to the extracellular glycocalyx. Cell fractionation and differential centrifugation have been used to study intracellular Ca2+ compartmentalization, but the methods suffer from the possibility of Ca2+ loss or redistribution among cell fractions. Steady-state kinetic analyses of 45Ca uptake or desaturation curves have been used to study the distribution of Ca2+ among various kinetic pools in living cells and their rate of Ca2+ exchange, but the analyses are constrained by many limitations. Nonsteady-state tracer studies can provide information about rapid changes in calcium influx or efflux in and out of the cell. Zero-time kinetics of 45Ca uptake can detect instantaneous changes in calcium influx, while 45Ca fractional efflux ratio, can detect rapid stimulations or inhibitions of calcium efflux out of cells. Permeabilized cells have been successfully used to gauge the relative role of intracellular organelles in controlling [Ca2+]i. The measurement of the cytosolic ionized calcium ([Ca2+]i) is undoubtedly the most important and, physiologically, the most relevant method available. The choice of the appropriate calcium indicator, fluorescent, bioluminescent, metallochromic, or Ca2(+)-sensitive microelectrodes depends on the cell type and the magnitude and time constant of the event under study. Each probe has specific assets and drawbacks. The study of plasma membrane vesicles derived from baso-lateral or apical plasmalemma can also bring important information on the (Ca2(+)-Mg2+) ATPase-dependent calcium pump and on the kinetics and stoichiometry of the Na(+)-Ca2+ antiporter. The best strategy to study cell calcium metabolism is to use several different methods that focus on a specific problem from widely different angles. PMID:2190818

High precision calcium isotope analysis using 42Ca-48Ca double-spike TIMS technique

NASA Astrophysics Data System (ADS)

Feng, L.; Zhou, L.; Gao, S.; Tong, S. Y.; Zhou, M. L.

2014-12-01

Double spike techniques are widely used for determining calcium isotopic compositions of natural samples. The most important factor controlling precision of the double spike technique is the choice of appropriate spike isotope pair, the composition of double spikes and the ratio of spike to sample（CSp/CN）. We propose an optimal 42Ca-48Ca double spike protocol which yields the best internal precision for calcium isotopic composition determinations among all kinds of spike pairs and various spike compositions and ratios of spike to sample, as predicted by linear error propagation method. It is suggested to use spike composition of 42Ca/(42Ca+48Ca) = 0.44 mol/mol and CSp/(CN+ CSp)= 0.12mol/mol because it takes both advantages of the largest mass dispersion between 42Ca and 48Ca (14%) and lowest spike cost. Spiked samples were purified by pass through homemade micro-column filled with Ca special resin. K, Ti and other interference elements were completely separated, while 100% calcium was recovered with negligible blank. Data collection includes integration time, idle time, focus and peakcenter frequency, which were all carefully designed for the highest internal precision and lowest analysis time. All beams were automatically measured in a sequence by Triton TIMS so as to eliminate difference of analytical conditions between samples and standards, and also to increase the analytical throughputs. The typical internal precision of 100 duty cycles for one beam is 0.012‒0.015 ‰ (2δSEM), which agrees well with the predicted internal precision of 0.0124 ‰ (2δSEM). Our methods improve internal precisions by a factor of 2‒10 compared to previous methods of determination of calcium isotopic compositions by double spike TIMS. We analyzed NIST SRM 915a, NIST SRM 915b and Pacific Seawater as well as interspersed geological samples during two months. The obtained average δ44/40Ca (all relative to NIST SRM 915a) is 0.02 ± 0.02 ‰ (n=28), 0.72±0.04 ‰ (n=10) and 1.93±0.03 ‰ (n=21) for NIST SRM 915a, NIST SRM 915b and Pacific Seawater, respectively. The long-term reproducibility is 0.10‰ (2 δSD), which is comparable to the best external precision of 0.04 ‰ (2 δSD) of previous methods, but our sample throughputs are doubled with significant reduction in amount of spike used for single samples.

Fabrication and characterization of magnesium and calcium trimesate complexes via ion-exchange and one-pot self-assembly reaction

NASA Astrophysics Data System (ADS)

Ozer, Demet; Oztas, Nursen Altuntas; Köse, Dursun A.; Şahin, Onur

2018-03-01

Using two different synthesis methods, two diversified magnesium and calcium complexes were successfully prepared. When the ion exchange method was used, C9H14MgO11.H2O and C18H30Ca3O24 complexes were obtained. When the one-pot self-assembly reaction was used, C18H34Mg3O26.4H2O and C9H12CaO10 complexes were produced. The structural characterizations were performed by using X-ray diffraction, FT-IR and elemental analyses. Thermal behavior of complexes were also determined via TGA method. The both complexes of magnesium and calcium trimesate have micro and mesoporosity with low porosity because of hydrogen bonds. Then hydrogen storage capacities of complexes were also determined. The differences in synthesis method result in the differences on complexes structure, morphology (shape, particle size and specific surface area) and hydrogen storage capacities.

Risk of calcium oxalate nephrolithiasis in postmenopausal women supplemented with calcium or combined calcium and estrogen.

PubMed

Domrongkitchaiporn, Somnuek; Ongphiphadhanakul, Boonsong; Stitchantrakul, Wasana; Chansirikarn, Sirinthorn; Puavilai, Gobchai; Rajatanavin, Rajata

2002-02-26

Recent studies showed that postmenopausal women lost less bone mass when supplemented with calcium or estrogen therapy. However, the safety of the treatments in terms of the risk of calcium oxalate stone formation is unknown. We therefore conducted this study to determine the alteration in calcium oxalate supersaturation after calcium supplement or after combined calcium and estrogen therapy in postmenopausal osteoporotic women. Fifty-six postmenopausal women were enrolled in this study. All subjects were more than 10 years postmenopausal with vertebral or femoral osteoporosis by bone mineral density criteria. They were randomly allocated to receive either 625 mg of calcium carbonate (250 mg of elemental calcium) at the end of a meal three times a day (group A, n=26) or calcium carbonate in the same manner plus 0.625 mg/day of conjugated equine estrogen and 5 mg medrogestone acetate from day 1-12 each month (group B, n=30). The age (mean +/- S.E.M.) was 66.3 +/- 1.2 and 65.1 +/- 1.1 years, weight 54.1 +/- 1.2 and 55.3 +/- 2.1 kg, in group A and group B, respectively. Urine specimens (24-h) were collected at baseline and 3 months after treatment for the determination of calcium oxalate saturation by using Tiselius's index (AP(CaOx)) and calcium/citrate ratio. After 3 months of treatment, there was no significant alteration from baseline for urinary excretion of calcium, citrate and oxalate. Urinary phosphate excretion was significantly reduced (6.3 +/- 0.7 vs. 5.1 +/- 0.7 mmol/day for group A and 8.2 +/- 0.9 vs. 5.8 +/- 0.7 mmol/day for group B, P<0.05), whereas net alkaline absorption was significantly elevated (10.1 +/- 3.6 vs. 20.1 +/- 4.4 meq/day for group A and 4.8 +/- 3.2 vs. 19.9 +/- 3.6 meq/day for group B, P<0.05). Calcium/citrate ratio and AP(CaOx) determined at baseline were not different from the corresponding values after treatment in both groups; calcium/citrate: 10.1 +/- 3.1 vs. 10.1 +/- 2.5 for group A and 9.3 +/- 1.8 vs. 11.9 +/- 2.5 for group B and AP(CaOx): 1.1 +/- 0.1 vs. 1.3 +/- 0.2 for group A and 1.2 +/- 0.2 vs. 1.1 +/- 0.1 for group B. There were eight and nine patients with high AP(CaOx), or >2, at baseline and after treatment, respectively. Calcium supplement with a meal or combined calcium supplement and estrogen therapy is not associated with a significant increased risk of calcium oxalate stone formation in the majority of postmenopausal osteoporotic patients. Determination of urinary saturation for calcium oxalate after calcium and estrogen supplements, especially at the initial phase of treatment, may be helpful in the avoidance of nephrolithiasis.

Ca:Mg:Zn:CO3 and Ca:Mg:CO3-tri- and bi-elemental carbonate microparticles for novel injectable self-gelling hydrogel-microparticle composites for tissue regeneration.

PubMed

Douglas, Timothy E L; Sobczyk, Katarzyna; Łapa, Agata; Włodarczyk, Katarzyna; Brackman, Gilles; Vidiasheva, Irina; Reczyńska, Katarzyna; Pietryga, Krzysztof; Schaubroeck, David; Bliznuk, Vitaliy; Voort, Pascal Van Der; Declercq, Heidi A; Bulcke, Jan Van den; Samal, Sangram Keshari; Khalenkow, Dmitry; Parakhonskiy, Bogdan V; Van Acker, Joris; Coenye, Tom; Lewandowska-Szumieł, Małgorzata; Pamuła, Elżbieta; Skirtach, Andre G

2017-03-24

Injectable composites for tissue regeneration can be developed by dispersion of inorganic microparticles and cells in a hydrogel phase. In this study, multifunctional carbonate microparticles containing different amounts of calcium, magnesium and zinc were mixed with solutions of gellan gum (GG), an anionic polysaccharide, to form injectable hydrogel-microparticle composites, containing Zn, Ca and Mg. Zn and Ca were incorporated into microparticle preparations to a greater extent than Mg. Microparticle groups were heterogeneous and contained microparticles of differing shape and elemental composition. Zn-rich microparticles were 'star shaped' and appeared to consist of small crystallites, while Zn-poor, Ca- and Mg-rich microparticles were irregular in shape and appeared to contain lager crystallites. Zn-free microparticle groups exhibited the best cytocompatibility and, unexpectedly, Zn-free composites showed the highest antibacterial activity towards methicilin-resistant Staphylococcus aureus. Composites containing Zn-free microparticles were cytocompatible and therefore appear most suitable for applications as an injectable biomaterial. This study proves the principle of creating bi- and tri-elemental microparticles to induce the gelation of GG to create injectable hydrogel-microparticle composites.

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

NASA Technical Reports Server (NTRS)

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

1997-01-01

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

Nitrogen enrichment regulates calcium sources in forests

USGS Publications Warehouse

Hynicka, Justin D.; Pett-Ridge, Julie C.; Perakis, Steven

2016-01-01

Nitrogen (N) is a key nutrient that shapes cycles of other essential elements in forests, including calcium (Ca). When N availability exceeds ecosystem demands, excess N can stimulate Ca leaching and deplete Ca from soils. Over the long term, these processes may alter the proportion of available Ca that is derived from atmospheric deposition vs. bedrock weathering, which has fundamental consequences for ecosystem properties and nutrient supply. We evaluated how landscape variation in soil N, reflecting long-term legacies of biological N fixation, influenced plant and soil Ca availability and ecosystem Ca sources across 22 temperate forests in Oregon. We also examined interactions between soil N and bedrock Ca using soil N gradients on contrasting basaltic vs. sedimentary bedrock that differed 17-fold in underlying Ca content. We found that low-N forests on Ca-rich basaltic bedrock relied strongly on Ca from weathering, but that soil N enrichment depleted readily weatherable mineral Ca and shifted forest reliance toward atmospheric Ca. Forests on Ca-poor sedimentary bedrock relied more consistently on atmospheric Ca across all levels of soil N enrichment. The broad importance of atmospheric Ca was unexpected given active regional uplift and erosion that are thought to rejuvenate weathering supply of soil minerals. Despite different Ca sources to forests on basaltic vs. sedimentary bedrock, we observed consistent declines in plant and soil Ca availability with increasing N, regardless of the Ca content of underlying bedrock. Thus, traditional measures of Ca availability in foliage and soil exchangeable pools may poorly reflect long-term Ca sources that sustain soil fertility. We conclude that long-term soil N enrichment can deplete available Ca and cause forests to rely increasingly on Ca from atmospheric deposition, which may limit ecosystem Ca supply in an increasingly N-rich world.

CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle

NASA Astrophysics Data System (ADS)

Nestola, F.; Korolev, N.; Kopylova, M.; Rotiroti, N.; Pearson, D. G.; Pamato, M. G.; Alvaro, M.; Peruzzo, L.; Gurney, J. J.; Moore, A. E.; Davidson, J.

2018-03-01

Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth’s mantle. Discoveries of some of these minerals in ‘super-deep’ diamonds—formed between two hundred and about one thousand kilometres into the lower mantle—have confirmed part of this picture. A notable exception is the high-pressure perovskite-structured polymorph of calcium silicate (CaSiO3). This mineral—expected to be the fourth most abundant in the Earth—has not previously been found in nature. Being the dominant host for calcium and, owing to its accommodating crystal structure, the major sink for heat-producing elements (potassium, uranium and thorium) in the transition zone and lower mantle, it is critical to establish its presence. Here we report the discovery of the perovskite-structured polymorph of CaSiO3 in a diamond from South African Cullinan kimberlite. The mineral is intergrown with about six per cent calcium titanate (CaTiO3). The titanium-rich composition of this inclusion indicates a bulk composition consistent with derivation from basaltic oceanic crust subducted to pressures equivalent to those present at the depths of the uppermost lower mantle. The relatively ‘heavy’ carbon isotopic composition of the surrounding diamond, together with the pristine high-pressure CaSiO3 structure, provides evidence for the recycling of oceanic crust and surficial carbon to lower-mantle depths.

Leaching characteristics of calcium-based compounds in MSWI Residues: From the viewpoint of clogging risk

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

Xia, Yi; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092; Zhang, Hua, E-mail: zhanghua_tj@tongji.edu.cn

Highlights: • The leaching behavior of Ca-based compounds commonly in MSWI residues was studied. • pH is the crucial factor for calcium leaching process. • CaCO{sub 3} was the most sensitive to leaching temperature and Ca{sub 3}(PO{sub 4}){sub 2} was the least. • Ca leaching of MSWIBA and SAPCR attributed to CaCO{sub 3} and Ca{sub 3}(PO{sub 4}){sub 2} respectively. • Potential clogging ability of MSWI residues leachate in open air was calculated. - Abstract: Leachate collection system (LCS) clogging caused by calcium precipitation would be disadvantageous to landfill stability and operation. Meanwhile, calcium-based compounds are the main constituents in bothmore » municipal solid waste incineration bottom ash (MSWIBA) and stabilized air pollution control residues (SAPCR), which would increase the risk of LCS clogging once these calcium-rich residues were disposed in landfills. The leaching behaviors of calcium from the four compounds and municipal solid waste incineration (MSWI) residues were studied, and the influencing factors on leaching were discussed. The results showed that pH was the crucial factor in the calcium leaching process. CaCO{sub 3} and CaSiO{sub 3} began leaching when the leachate pH decreased to less than 7 and 10, respectively, while Ca{sub 3}(PO{sub 4}){sub 2} leached at pH < 12. CaSO{sub 4} could hardly dissolve in the experimental conditions. Moreover, the sequence of the leaching rate for the different calcium-based compounds is as follows: CaSiO{sub 3} > Ca{sub 3}(PO{sub 4}){sub 2} > CaCO{sub 3}. The calcium leaching from the MSWIBA and SAPCR separately started from pH < 7 and pH < 12, resulting from CaCO{sub 3} and Ca{sub 3}(PO{sub 4}){sub 2} leaching respectively, which was proven by the X-ray diffraction results. Based on the leaching characteristics of the different calcium compounds and the mineral phase of calcium in the incineration residues, simulated computation of their clogging potential was conducted, providing the theoretical basis for the risk assessment pertaining to LCS clogging in landfills.« less

Determination of calcium to phosphate elemental ratio in natural hydroxypatite using LIBS

NASA Astrophysics Data System (ADS)

Mazalan, Elham; Chaudhary, Kashif; Haider, Zuhaib; Hadi, Siti Fatimah Abd; Ali, Jalil

2018-05-01

In this work, laser induced breakdown spectroscopy (LIBS) is employed for determination of calcium to phosphate (Ca/P) ratio in hydroxyapatite (HA) extracted from animal bones. HA was extracted from the biological bones of lamb, bovine, and fish separately. Fresh bones were boiled in deuterium-depleted water (DDW) for 4 hours and immersed it in acetone for 15 hours followed by drying process in the oven. Dried bones were heated at 600 °C and crushed into powder form which was then mixed with potassium bromide (KBr) in a known quantity. The mixture for each sample was palletized into pellets of identical mass using a hydraulic press. The palletized samples of HA extracted from the bones were ablated with 10 ns Q-switched Nd-YAG laser pulses having an energy of 320 mJ/pulse. The optical emissions produced from the laser induced plasma were recorded. Ca and P emission lines are identified and the Ca/P is calculated. Ca/P ratio by LIBS analysis has been verified by EDX measurements and are found in good agreement.

Calcium bioavailability and kinetics of calcium ascorbate and calcium acetate in rats.

PubMed

Cai, Jianwei; Zhang, Qinmin; Wastney, Meryl E; Weaver, Connie M

2004-01-01

The objective was to investigate the bioavailability and mechanism of calcium absorption of calcium ascorbate (ASC) and calcium acetate (AC). A series of studies was performed in adult Sprague-Dawley male rats. In the first study, each group of rats (n = 10/group) was assigned to one of the five test meals labeled with (45)Ca: (i) 25 mg calcium as heated ASC or (ii) unheated ASC, (iii) 25 mg calcium as unheated AC, (iv) 3.6 mg Ca as unheated ASC, or (v) unheated AC. Femur uptake indicated better calcium bioavailability from ASC than AC at both calcium loads. A 5-min heat treatment partly reduced bioavailability of ASC. Kinetic studies were performed to further investigate the mechanism of superior calcium bioavailability from ASC. Two groups of rats (n = 10/group) received oral doses of 25 mg Ca as ASC or AC. Each dose contained 20 micro Ci (45)Ca. Two additional groups of rats (n = 10/group) received an intravenous injection (iv) of 10 micro Ci (45)Ca after receiving an unlabeled oral dose of 25 mg calcium as ASC or AC. Sequential blood samples were collected over 48 hrs. Urine and fecal samples were collected every 12 hrs for 48 hrs and were analyzed for total calcium and (45)Ca content. Total calcium and (45)Ca from serum, urine, and feces were fitted by a compartment kinetics model with saturable and nonsaturable absorption pathways by WinSAAM (Windows-based Simulation Analysis and Modeling). The difference in calcium bioavailability between the two salts was due to differences in saturable rather than passive intestinal absorption and not to endogenous secretion or calcium deposition rate. The higher bioavailability of calcium ascorbate was due to a longer transit time in the small intestine compared with ASC.

Diagnosis and assessment of skeletal related disease using calcium 41

DOEpatents

Hillegonds, Darren J [Oakland, CA; Vogel, John S [San Jose, CA; Fitzgerald, Robert L [Encinitas, CA; Deftos, Leonard J [Del Mar, CA; Herold, David [Del Mar, CA; Burton, Douglas W [San Diego, CA

2012-05-15

A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

Diagnosis and assessment of skeletal related disease using calcium 41

DOEpatents

Hillegonds, Darren J.; Vogel, John S.; Fitzgerald, Robert L.; Deftos, Leonard J.; Herold, David; Burton, Douglas W.

2013-03-05

A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

Evaluation of heavy metals in hazardous automobile shredder residue thermal residue and immobilization with novel nano-size calcium dispersed reagent.

PubMed

Lee, Chi-Hyeon; Truc, Nguyen Thi Thanh; Lee, Byeong-Kyu; Mitoma, Yoshiharu; Mallampati, Srinivasa Reddy

2015-10-15

This study was conducted to synthesize and apply a nano-size calcium dispersed reagent as an immobilization material for heavy metal-contaminated automobile shredder residues (ASR) dust/thermal residues in dry condition. Simple mixing with a nanometallic Ca/CaO/PO4 dispersion mixture immobilized 95-100% of heavy metals in ASR dust/thermal residues (including bottom ash, cavity ash, boiler and bag filter ash). The quantity of heavy metals leached from thermal residues after treatment by nanometallic Ca/CaO/PO4 was lower than the Korean standard regulatory limit for hazardous waste landfills. The morphology and elemental composition of the nanometallic Ca/CaO-treated ASR residue were characterized by field emission scanning election microscopy combined with electron dispersive spectroscopy (FE-SEM/EDS). The results indicated that the amounts of heavy metals detectable on the ASR thermal residue surface decreased and the Ca/PO4 mass percent increased. X-ray diffraction (XRD) pattern analysis indicated that the main fraction of enclosed/bound materials on ASR residue included Ca/PO4- associated crystalline complexes, and that immobile Ca/PO4 salts remarkably inhibited the desorption of heavy metals from ASR residues. These results support the potential use of nanometallic Ca/CaO/PO4 as a simple, suitable and highly efficient material for the gentle immobilization of heavy metals in hazardous ASR thermal residue in dry condition. Copyright © 2015 Elsevier B.V. All rights reserved.

Alleviating effects of calcium on cobalt toxicity in two barley genotypes differing in cobalt tolerance.

PubMed

Lwalaba, Jonas Lwalaba Wa; Zvobgo, Gerald; Fu, Liangbo; Zhang, Xuelei; Mwamba, Theodore Mulembo; Muhammad, Noor; Mundende, Robert Prince Mukobo; Zhang, Guoping

2017-05-01

Cobalt (Co) contamination in soils is becoming a severe issue in environment safety and crop production. Calcium (Ca) , as a macro-nutrient element, shows the antagonism with many divalent heavy metals and the capacity of alleviating oxidative stress in plants. In this study, the protective role of Ca in alleviating Co stress was hydroponically investigated using two barley genotypes differing in Co toxicity tolerance. Barley seedlings exposed to 100µM Co showed the significant reduction in growth and photosynthetic rate, and the dramatic increase in the contents of reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH) and oxidized glutathione (GSSG), and the activities of anti-oxidative enzymes, with Ea52 (Co-sensitive) being much more affected than Yan66 (Co-tolerant). Addition of Ca in growth medium alleviated Co toxicity by reducing Co uptake and enhancing the antioxidant capacity. The effect of Ca in alleviating Co toxicity was much greater in Yan66 than in Ea52. The results indicate that the alleviation of Co toxicity in barley plants by Ca is attributed to the reduced Co uptake and enhanced antioxidant capacity. Copyright © 2017 Elsevier Inc. All rights reserved.

Identifying calcium sources at an acid deposition-impacted spruce forest: A strontium isotope, alkaline earth element multi-tracer approach

USGS Publications Warehouse

Bullen, T.D.; Bailey, S.W.

2005-01-01

Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured 87Sr/86Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87Sr/86Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87Sr/86Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible alternative explanations of aspects of the observed trends, the chemical buffering capacity of the forest floor-biomass pool limits their effectiveness as causal mechanisms. ?? Springer 2005.

Mechanisms of calcium sequestration by isolated Malpighian tubules of the house cricket Acheta domesticus.

PubMed

Browne, Austin; O'Donnell, Michael J

2018-01-01

Hemolymph calcium homeostasis in insects is achieved by the Malpighian tubules, primarily by sequestering excess Ca 2+ within internal calcium stores (Ca-rich granules) most often located within type I (principal) tubule cells. Using both the scanning ion-selective electrode technique and the Ramsay secretion assay this study provides the first measurements of basolateral and transepithelial Ca 2+ fluxes across the Malpighian tubules of an Orthopteran insect, the house cricket Acheta domesticus. Ca 2+ transport was specific to midtubule segments, where 97% of the Ca 2+ entering the tubule is sequestered within intracellular calcium stores and the remaining 3% is secreted into the lumen. Antagonists of voltage-gated (L-type) calcium channels decreased Ca 2+ influx ≥fivefold in adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated tubules, suggesting basolateral Ca 2+ influx is facilitated by voltage-gated Ca 2+ channels. Increasing fluid secretion through manipulation of intracellular levels of cAMP or Ca 2+ had opposite effects on tubule Ca 2+ transport. The adenylyl cyclase-cAMP-PKA pathway promotes Ca 2+ sequestration whereas both 5-hydroxytryptamine and thapsigargin inhibited sequestration. Our results suggest that the midtubules of Acheta domesticus are dynamic calcium stores, which maintain hemolymph calcium concentration by manipulating rates of Ca 2+ sequestration through stimulatory (cAMP) and inhibitory (Ca 2+ ) regulatory pathways. © 2017 Wiley Periodicals, Inc.

Contrasting calcium localization and speciation in leaves of Medicago trunculata mutant COD5 analyzed via synchrotron X-ray techniques

USDA-ARS?s Scientific Manuscript database

Oxalate-producing plants accumulate calcium oxalate crystals (CaOx(C)) in the range of 3-80%(w/w) of their dry weight, reducing calcium (Ca) bioavailability. The calcium oxalate deficient 5 (cod5) mutant of Medicago truncatula has been previously shown to contain similar Ca, but lower oxalate and Ca...

Calcium Plus Vitamin D Supplementation and the Risk of Nonmelanoma and Melanoma Skin Cancer: Post Hoc Analyses of the Women's Health Initiative Randomized Controlled Trial

PubMed Central

Tang, Jean Y.; Fu, Teresa; LeBlanc, Erin; Manson, JoAnn E.; Feldman, David; Linos, Eleni; Vitolins, Mara Z.; Zeitouni, Nathalie C.; Larson, Joseph; Stefanick, Marcia L.

2011-01-01

Purpose In light of inverse relationships reported in observational studies of vitamin D intake and serum 25-hydroxyvitamin D levels with risk of nonmelanoma skin cancer (NMSC) and melanoma, we evaluated the effects of vitamin D combined with calcium supplementation on skin cancer in a randomized placebo-controlled trial. Methods Postmenopausal women age 50 to 79 years (N = 36,282) enrolled onto the Women's Health Initiative (WHI) calcium/vitamin D clinical trial were randomly assigned to receive 1,000 mg of elemental calcium plus 400 IU of vitamin D3 (CaD) daily or placebo for a mean follow-up period of 7.0 years. NMSC and melanoma skin cancers were ascertained by annual self-report; melanoma skin cancers underwent physician adjudication. Results Neither incident NMSC nor melanoma rates differed between treatment (hazard ratio [HR], 1.02; 95% CI, 0.95 to 1.07) and placebo groups (HR, 0.86; 95% CI, 0.64 to 1.16). In subgroup analyses, women with history of NMSC assigned to CaD had a reduced risk of melanoma versus those receiving placebo (HR, 0.43; 95% CI, 0.21 to 0.90; Pinteraction = .038), which was not observed in women without history of NMSC. Conclusion Vitamin D supplementation at a relatively low dose plus calcium did not reduce the overall incidence of NMSC or melanoma. However, in women with history of NMSC, CaD supplementation reduced melanoma risk, suggesting a potential role for calcium and vitamin D supplements in this high-risk group. Results from this post hoc subgroup analysis should be interpreted with caution but warrant additional investigation. PMID:21709199

Multi-Functions of Carbonated Calcium Deficient Hydroxyapatite (CDHA)

NASA Astrophysics Data System (ADS)

Zhou, Huan

Natural bone is a complex composite mainly constituted of inorganic minerals and organic collagen molecules. Calcium phosphate (CaP) based materials have been proposed as the predominant bone substitute for bone tissue engineering applications due to their chemical similarity to bone mineral. Amorphous carbonated calcium deficient hydroxyapatite (CDHA) is an important compound among CaP materials because of the amorphous crystallite structure. The presence of extra ions in its lattice structure not only influences cell attachment and proliferation of osteoblasts, but also helps in bone metabolism. Biomimetic coating approach is the most widely used approach to produce CDHA coatings to implant. It is a process using simulated body fluid (SBF) to deposit bone-like CDHA coating to various material surfaces. The CDHA formation mechanism, SBF compositions and reacting conditions of biomimetic coating have already been sufficiently studied and compared in the past 20 years. It is an attempt in this thesis to explore new applications of SBF in biomedical research, focusing on different biomaterial applications: 1) based on the low temperature reaction condition of SBF, bisphosphonate incorporated CDHA coatings were deposited onto Ti6Al4V surface for the treatment of osteoporosis; 2) amorphous calcium phosphate nanospheres with extra elements in the lattice structure were prepared by a novel microwave assisted approach, providing a new potential of CaP materials production; 3) CDHA particles formed in SBF can be used as great fillers with biopolymers for preparing biocomposites for biomedical applications; 4) based on the high activity of CDHA amorphous structure and the stabilization ability of ethanol, yttrium and europium doped calcium phosphates were prepared using CDHA as a sacrificing template. In the end, future work based on these observations in the thesis is addressed, including areas of drug delivery, biocomposite fabrication and preparation of functionalized calcium phosphate materials.

Cavβ2 transcription start site variants modulate calcium handling in newborn rat cardiomyocytes.

PubMed

Moreno, Cristian; Hermosilla, Tamara; Morales, Danna; Encina, Matías; Torres-Díaz, Leandro; Díaz, Pablo; Sarmiento, Daniela; Simon, Felipe; Varela, Diego

2015-12-01

In the heart, the main pathway for calcium influx is mediated by L-type calcium channels, a multi-subunit complex composed of the pore-forming subunit CaV1.2 and the auxiliary subunits CaVα2δ1 and CaVβ2. To date, five distinct CaVβ2 transcriptional start site (TSS) variants (CaVβ2a-e) varying only in the composition and length of the N-terminal domain have been described, each of them granting distinct biophysical properties to the L-type current. However, the physiological role of these variants in Ca(2+) handling in the native tissue has not been explored. Our results show that four of these variants are present in neonatal rat cardiomyocytes. The contribution of those CaVβ2 TSS variants on endogenous L-type current and Ca(2+) handling was explored by adenoviral-mediated overexpression of each CaVβ2 variant in cultured newborn rat cardiomyocytes. As expected, all CaVβ2 TSS variants increased L-type current density and produced distinctive changes on L-type calcium channel (LTCC) current activation and inactivation kinetics. The characteristics of the induced calcium transients were dependent on the TSS variant overexpressed. Moreover, the amplitude of the calcium transients varied depending on the subunit involved, being higher in cardiomyocytes transduced with CaVβ2a and smaller in CaVβ2d. Interestingly, the contribution of Ca(2+) influx and Ca(2+) release on total calcium transients, as well as the sarcoplasmic calcium content, was found to be TSS-variant-dependent. Remarkably, determination of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) messenger RNA (mRNA) abundance and cell size change indicates that CaVβ2 TSS variants modulate the cardiomyocyte hypertrophic state. In summary, we demonstrate that expression of individual CaVβ2 TSS variants regulates calcium handling in cardiomyocytes and, consequently, has significant repercussion in the development of hypertrophy.

Divergent biophysical properties, gating mechanisms, and possible functions of the two skeletal muscle Ca(V)1.1 calcium channel splice variants.

PubMed

Tuluc, Petronel; Flucher, Bernhard E

2011-12-01

Voltage-gated calcium channels are multi-subunit protein complexes that specifically allow calcium ions to enter the cell in response to membrane depolarization. But, for many years it seemed that the skeletal muscle calcium channel Ca(V)1.1 is the exception. The classical splice variant Ca(V)1.1a activates slowly, has a very small current amplitude and poor voltage sensitivity. In fact adult muscle fibers work perfectly well even in the absence of calcium influx. Recently a new splice variant of the skeletal muscle calcium channel Ca(V)1.1e has been characterized. The lack of the 19 amino acid exon 29 in this splice variant results in a rapidly activating calcium channel with high current amplitude and good voltage sensitivity. Ca(V)1.1e is the dominant channel in embryonic muscle, where the expression of this high calcium-conducting Ca(V)1.1 isoform readily explains developmental processes depending on L-type calcium currents. Moreover, the availability of these two structurally similar but functionally distinct channel variants facilitates the analysis of the molecular mechanisms underlying the unique current properties of the classical Ca(V)1.1a channel.

NeuroCa: integrated framework for systematic analysis of spatiotemporal neuronal activity patterns from large-scale optical recording data

PubMed Central

Jang, Min Jee; Nam, Yoonkey

2015-01-01

Abstract. Optical recording facilitates monitoring the activity of a large neural network at the cellular scale, but the analysis and interpretation of the collected data remain challenging. Here, we present a MATLAB-based toolbox, named NeuroCa, for the automated processing and quantitative analysis of large-scale calcium imaging data. Our tool includes several computational algorithms to extract the calcium spike trains of individual neurons from the calcium imaging data in an automatic fashion. Two algorithms were developed to decompose the imaging data into the activity of individual cells and subsequently detect calcium spikes from each neuronal signal. Applying our method to dense networks in dissociated cultures, we were able to obtain the calcium spike trains of ∼1000 neurons in a few minutes. Further analyses using these data permitted the quantification of neuronal responses to chemical stimuli as well as functional mapping of spatiotemporal patterns in neuronal firing within the spontaneous, synchronous activity of a large network. These results demonstrate that our method not only automates time-consuming, labor-intensive tasks in the analysis of neural data obtained using optical recording techniques but also provides a systematic way to visualize and quantify the collective dynamics of a network in terms of its cellular elements. PMID:26229973

Common Genetic Denominators for Ca++-Based Skeleton in Metazoa: Role of Osteoclast-Stimulating Factor and of Carbonic Anhydrase in a Calcareous Sponge

PubMed Central

Müller, Werner E. G.; Wang, Xiaohong; Grebenjuk, Vlad A.; Korzhev, Michael; Wiens, Matthias; Schloßmacher, Ute; Schröder, Heinz C.

2012-01-01

Calcium-based matrices serve predominantly as inorganic, hard skeletal systems in Metazoa from calcareous sponges [phylum Porifera; class Calcarea] to proto- and deuterostomian multicellular animals. The calcareous sponges form their skeletal elements, the spicules, from amorphous calcium carbonate (ACC). Treatment of spicules from Sycon raphanus with sodium hypochlorite (NaOCl) results in the disintegration of the ACC in those skeletal elements. Until now a distinct protein/enzyme involved in ACC metabolism could not been identified in those animals. We applied the technique of phage display combinatorial libraries to identify oligopeptides that bind to NaOCl-treated spicules: those oligopeptides allowed us to detect proteins that bind to those spicules. Two molecules have been identified, the (putative) enzyme carbonic anhydrase and the (putative) osteoclast-stimulating factor (OSTF), that are involved in the catabolism of ACC. The complete cDNAs were isolated and the recombinant proteins were prepared to raise antibodies. In turn, immunofluorescence staining of tissue slices and qPCR analyses have been performed. The data show that sponges, cultivated under standard condition (10 mM CaCl2) show low levels of transcripts/proteins for carbonic anhydrase or OSTF, compared to those animals that had been cultivated under Ca2+-depletion condition (1 mM CaCl2). Our data identify with the carbonic anhydrase and the OSTF the first two molecules which remain conserved in cells, potentially involved in Ca-based skeletal dissolution, from sponges (sclerocytes) to human (osteoclast). PMID:22506035

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

USGS Publications Warehouse

Dauer, Jenny M.; Perakis, Steven S.

2014-01-01

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

The grapevine VvCAX3 is a cation/H+ exchanger involved in vacuolar Ca2+ homeostasis.

PubMed

Martins, Viviana; Carneiro, Filipa; Conde, Carlos; Sottomayor, Mariana; Gerós, Hernâni

2017-12-01

The grapevine VvCAX3 mediates calcium transport in the vacuole and is mostly expressed in green grape berries and upregulated by Ca 2+ , Na + and methyl jasmonate. Calcium is an essential plant nutrient with important regulatory and structural roles in the berries of grapevine (Vitis vinifera L.). On the other hand, the proton-cation exchanger CAX proteins have been shown to impact Ca 2+ homeostasis with important consequences for fruit integrity and resistance to biotic/abiotic stress. Here, the CAX gene found in transcriptomic databases as having one of the highest expressions in grapevine tissues, VvCAX3, was cloned and functionally characterized. Heterologous expression in yeast showed that a truncated version of VvCAX3 lacking its NNR autoinhibitory domain (sCAX3) restored the ability of the yeast strain to grow in 100-200 mM Ca 2+ , demonstrating a role in Ca 2+ transport. The truncated VvCAX3 was further shown to be involved in the transport of Na + , Li + , Mn 2+ and Cu 2+ in yeast cells. Subcellular localization studies using fluorescently tagged proteins confirmed VvCAX3 as a tonoplast transporter. VvCAX3 is expressed in grapevine stems, leaves, roots, and berries, especially at pea size, decreasing gradually throughout development, in parallel with the pattern of calcium accumulation in the fruit. The transcript abundance of VvCAX3 was shown to be regulated by methyl jasmonate (MeJA), Ca 2+ , and Na + in grape cell suspensions, and the VvCAX3 promotor contains several predicted cis-acting elements related to developmental and stress response processes. As a whole, the results obtained add new insights on the mechanisms involved in calcium homeostasis and intracellular compartmentation in grapevine, and indicate that VvCAX3 may be an interesting target towards the development of strategies for enhancement of grape berry properties.

Crystal-chemistry of alteration products of vitrified wastes: Implications on the retention of polluting elements

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

Sterpenich, Jerome

2008-07-01

Alteration products of vitrified wastes coming from the incineration of household refuse (MSW) are described. Two vitrified wastes containing 50% and 70% of fly ash and a synthetic stained-glass with a composition close to that of an ancient glass (medieval stained-glass) were altered under different pH conditions (1, 5.5 corresponding to demineralized water and 10) during 181 days. Under acidic condition, the alteration layer is made of an amorphous hydrated silica gel impoverished in most of the initial elements. A minor phase MPO{sub 4} . nH{sub 2}O, where M represents Fe, Ti, Al, Ca and K cations, also constitutes themore » altered layer of the synthetic stained-glass. Under neutral and basic conditions, the altered layer is made of an amorphous hydrated silica gel and a crystallized calcium phosphate phase. The silica gel is depleted in alkalis and alkali-earth elements but contains significant amounts of aluminium, magnesium and transition elements, whereas the calcium phosphate is a hydroxylapatite-like phase with P-Si substitutions and a Ca/P ratio depending on the pH of the solution. This study shows: (i) the strong influence of pH conditions on the crystal-chemistry of alteration products and thus on the mechanisms of weathering resulting in different trapping of polluting elements, and (ii) that glass alteration does not necessary produce thermodynamically stable phases which has to be taken into account for the prediction of the long-term behavior.« less

Primary inhibition of hypocotyl growth and phototropism depend differently on phototropin-mediated increases in cytoplasmic calcium induced by blue light.

PubMed

Folta, Kevin M; Lieg, Erin J; Durham, Tessa; Spalding, Edgar P

2003-12-01

The phototropin photoreceptors transduce blue-light signals into several physiological and developmental responses in plants. A transient rise in cytoplasmic calcium (Ca2+) that begins within seconds of phototropin 1 (phot1) excitation is believed to be an important element in the transduction pathways leading to one or more of the phot1-dependent responses. The goal of the present work was to determine whether the Ca2+ response was necessary for (a). the inhibition of hypocotyl elongation that develops within minutes of the irradiation, and (b). hypocotyl phototropism (curved growth of the stem in response to asymmetric illumination). After determining that pulses of light delivering photon fluences of between 1 and 1000 micromol m-2 induced growth inhibition mediated by phot1 without significant interference from other photosensory pathways, the effect of blocking the Ca2+ rise was assessed. Treatment of seedlings with a Ca2+ chelator prevented the rise in cytoplasmic Ca2+ and prevented phot1-mediated growth inhibition. However, the same chelator treatment did not impair phot1-mediated phototropism. Thus, it appears that the early, transient rise in cytoplasmic Ca2+ is an important intermediary process in at least one but not all phot1-signaling pathways.

Primary Inhibition of Hypocotyl Growth and Phototropism Depend Differently on Phototropin-Mediated Increases in Cytoplasmic Calcium Induced by Blue Light1

PubMed Central

Folta, Kevin M.; Lieg, Erin J.; Durham, Tessa; Spalding, Edgar P.

2003-01-01

The phototropin photoreceptors transduce blue-light signals into several physiological and developmental responses in plants. A transient rise in cytoplasmic calcium (Ca2+) that begins within seconds of phototropin 1 (phot1) excitation is believed to be an important element in the transduction pathways leading to one or more of the phot1-dependent responses. The goal of the present work was to determine whether the Ca2+ response was necessary for (a) the inhibition of hypocotyl elongation that develops within minutes of the irradiation, and (b) hypocotyl phototropism (curved growth of the stem in response to asymmetric illumination). After determining that pulses of light delivering photon fluences of between 1 and 1,000 μmol m-2 induced growth inhibition mediated by phot1 without significant interference from other photosensory pathways, the effect of blocking the Ca2+ rise was assessed. Treatment of seedlings with a Ca2+ chelator prevented the rise in cytoplasmic Ca2+ and prevented phot1-mediated growth inhibition. However, the same chelator treatment did not impair phot1-mediated phototropism. Thus, it appears that the early, transient rise in cytoplasmic Ca2+ is an important intermediary process in at least one but not all phot1-signaling pathways. PMID:14645723

Calcium - Magnesium imbalance implicated in benign prostatic hyperplasia and restoration by a phytotherapeutic drug - Croton membranaceus Müll.Arg.

PubMed

Asare, George Awuku; Ngala, Robert A; Afriyie, Daniel; Adjei, Samuel; Nyarko, Adriana; Anang-Quartey, Yvonne; Asiedu, Bernice; Doku, Derek; Amoah, Brodrick Y; Bentum, Kennedy; Musah, Iddi; Mossanda, Kensese

2017-03-11

Calcium (Ca)- magnesium (Mg) imbalance is implicated in prostate cancer. Ca/Mg ratio increases or decreases with proliferation or apoptosis, respectively. The study examined whether this Ca/Mg imbalance exists in BPH patients and the effect of a phytotherapeutic drug on the Ca/Mg ratio. Thirty (30) BPH patients who used the ethanolic root extract of Croton membranaceus (60 mg/day) for 3 months were examined for serum Ca, Mg, phosphate, parathyroid hormone (PTH), vitamin D, prostate specific antigen (PSA) levels and renal function tests (RFT) before (BT) and after treatment (AT) alongside thirty (30) controls. Twenty (20) trace element including Mg and Ca were determined in the drug by neutron activation analysis (NAA). RFT, PTH and vitamin D for BT, AT and controls (C) were normal. Mean PSA was 1.0 ± 0.64 (C), 27.9 ± 19.0 (BT) and 16.2 ± 11.8 ng/mL (AT) (p = 0.002). Mg, Ca/Mg ratio BT, AT and control were significantly different (p = 0.0001, respectively). After treatment, Mg and Ca/Mg ratio were not different from controls. The prevalence of Ca/Mg imbalance was 80% (BT), 13.3% (AT) and 3.3% (control group). Ca/Mg ratio imbalance is associated with BPH. This has previously not been demonstrated. The imbalance was significantly corrected after treatment with the phytotherapeutic drug.

First evidence on phloem transport of nanoscale calcium oxide in groundnut using solution culture technique

NASA Astrophysics Data System (ADS)

Deepa, Manchala; Sudhakar, Palagiri; Nagamadhuri, Kandula Venkata; Balakrishna Reddy, Kota; Giridhara Krishna, Thimmavajjula; Prasad, Tollamadugu Naga Venkata Krishna Vara

2015-06-01

Nanoscale materials, whose size typically falls below 100 nm, exhibit novel chemical, physical and biological properties which are different from their bulk counterparts. In the present investigation, we demonstrated that nanoscale calcium oxide particles (n-CaO) could transport through phloem tissue of groundnut unlike the corresponding bulk materials. n-CaO particles are prepared using sol-gel method. The size of the as prepared n-CaO measured (69.9 nm) using transmission electron microscopic technique (TEM). Results of the hydroponics experiment using solution culture technique revealed that foliar application of n-CaO at different concentrations (10, 50, 100, 500, 1,000 ppm) on groundnut plants confirmed the entry of calcium into leaves and stems through phloem compared to bulk source of calcium sprayed (CaO and CaNO3). After spraying of n-CaO, calcium content in roots, shoots and leaves significantly increased. Based on visual scoring of calcium deficiency correction and calcium content in plant parts, we may establish the fact that nanoscale calcium oxide particles (size 69.9 nm) could move through phloem tissue in groundnut. This is the first report on phloem transport of nanoscale calcium oxide particles in plants and this result points to the use of nanoscale calcium oxide particles as calcium source to the plants through foliar application, agricultural crops in particular, as bulk calcium application through foliar nutrition is restricted due to its non-mobility in phloem.

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

Medina, J., E-mail: judit.medina@cenim.csic.es

The effects of calcium, manganese and cerium-rich mischmetal additions on the microstructure and texture of the extruded Mg−6Zn−1Y (wt.%) alloy have been investigated. The microstructure of the alloys consisted of a magnesium matrix embedding second phase particles aligned along the extrusion direction. The nature and volume fraction of the second phases depended on the alloying element. Thus, Ce-rich mischmetal promoted the formation of T-phase while calcium additions resulted in the formation of a ternary Mg−Zn−Ca compound. Only, manganese additions did not affect the existence of the I-phase present in the ternary alloy. The texture was measured and it was foundmore » that calcium addition has a significant effect weakening the extrusion texture. - Highlights: •In-situ HEXRD and DSC techniques are employed to identify phase transformations. •The existence of I-phase is not altered by manganese addition to Mg93Zn6Y1 (wt.%). •Calcium addition promotes Mg{sub 6}Zn{sub 3}Ca{sub 2} formation instead of I-phase. •Mischmetal addition induces the formation of coarse T-phase particles. •Texture depends on the nature of second phases and therefore of the extrusion pressure.« less

Transcriptional expression analysis of genes involved in regulation of calcium translocation and storage in finger millet (Eleusine coracana L. Gartn.).

PubMed

Mirza, Neelofar; Taj, Gohar; Arora, Sandeep; Kumar, Anil

2014-10-25

Finger millet (Eleusine coracana) variably accumulates calcium in different tissues, due to differential expression of genes involved in uptake, translocation and accumulation of calcium. Ca(2+)/H(+) antiporter (CAX1), two pore channel (TPC1), CaM-stimulated type IIB Ca(2+) ATPase and two CaM dependent protein kinase (CaMK1 and 2) homologs were studied in finger millet. Two genotypes GP-45 and GP-1 (high and low calcium accumulating, respectively) were used to understand the role of these genes in differential calcium accumulation. For most of the genes higher expression was found in the high calcium accumulating genotype. CAX1 was strongly expressed in the late stages of spike development and could be responsible for accumulating high concentrations of calcium in seeds. TPC1 and Ca(2+) ATPase homologs recorded strong expression in the root, stem and developing spike and signify their role in calcium uptake and translocation, respectively. Calmodulin showed strong expression and a similar expression pattern to the type IIB ATPase in the developing spike only and indicating developing spike or even seed specific isoform of CaM affecting the activity of downstream target of calcium transportation. Interestingly, CaMK1 and CaMK2 had expression patterns similar to ATPase and TPC1 in various tissues raising a possibility of their respective regulation via CaM kinase. Expression pattern of 14-3-3 gene was observed to be similar to CAX1 gene in leaf and developing spike inferring a surprising possibility of CAX1 regulation through 14-3-3 protein. Our results provide a molecular insight for explaining the mechanism of calcium accumulation in finger millet. Copyright © 2014 Elsevier B.V. All rights reserved.

Cameleon calcium indicator reports cytoplasmic calcium dynamics in Arabidopsis guard cells

NASA Technical Reports Server (NTRS)

Allen, G. J.; Kwak, J. M.; Chu, S. P.; Llopis, J.; Tsien, R. Y.; Harper, J. F.; Schroeder, J. I.; Evans, M. L. (Principal Investigator)

1999-01-01

Cytoplasmic free calcium ([Ca2+]cyt) acts as a stimulus-induced second messenger in plant cells and multiple signal transduction pathways regulate [Ca2+]cyt in stomatal guard cells. Measuring [Ca2+]cyt in guard cells has previously required loading of calcium-sensitive dyes using invasive and technically difficult micro-injection techniques. To circumvent these problems, we have constitutively expressed the pH-independent, green fluorescent protein-based calcium indicator yellow cameleon 2.1 in Arabidopsis thaliana (Miyawaki et al. 1999; Proc. Natl. Acad. Sci. USA 96, 2135-2140). This yellow cameleon calcium indicator was expressed in guard cells and accumulated predominantly in the cytoplasm. Fluorescence ratio imaging of yellow cameleon 2.1 allowed time-dependent measurements of [Ca2+]cyt in Arabidopsis guard cells. Application of extracellular calcium or the hormone abscisic acid (ABA) induced repetitive [Ca2+]cyt transients in guard cells. [Ca2+]cyt changes could be semi-quantitatively determined following correction of the calibration procedure for chloroplast autofluorescence. Extracellular calcium induced repetitive [Ca2+]cyt transients with peak values of up to approximately 1.5 microM, whereas ABA-induced [Ca2+]cyt transients had peak values up to approximately 0.6 microM. These values are similar to stimulus-induced [Ca2+]cyt changes previously reported in plant cells using ratiometric dyes or aequorin. In some guard cells perfused with low extracellular KCl concentrations, spontaneous calcium transients were observed. As yellow cameleon 2.1 was expressed in all guard cells, [Ca2+]cyt was measured independently in the two guard cells of single stomates for the first time. ABA-induced, calcium-induced or spontaneous [Ca2+]cyt increases were not necessarily synchronized in the two guard cells. Overall, these data demonstrate that that GFP-based cameleon calcium indicators are suitable to measure [Ca2+]cyt changes in guard cells and enable the pattern of [Ca2+]cyt dynamics to be measured with a high level of reproducibility in Arabidopsis cells. This technical advance in combination with cell biological and molecular genetic approaches will become an invaluable tool in the dissection of plant cell signal transduction pathways.

Leaching characteristics of calcium-based compounds in MSWI Residues: From the viewpoint of clogging risk.

PubMed

Xia, Yi; Zhang, Hua; Phoungthong, Khamphe; Shi, Dong-Xiao; Shen, Wen-Hui; Shao, Li-Ming; He, Pin-Jing

2015-08-01

Leachate collection system (LCS) clogging caused by calcium precipitation would be disadvantageous to landfill stability and operation. Meanwhile, calcium-based compounds are the main constituents in both municipal solid waste incineration bottom ash (MSWIBA) and stabilized air pollution control residues (SAPCR), which would increase the risk of LCS clogging once these calcium-rich residues were disposed in landfills. The leaching behaviors of calcium from the four compounds and municipal solid waste incineration (MSWI) residues were studied, and the influencing factors on leaching were discussed. The results showed that pH was the crucial factor in the calcium leaching process. CaCO3 and CaSiO3 began leaching when the leachate pH decreased to less than 7 and 10, respectively, while Ca3(PO4)2 leached at pH<12. CaSO4 could hardly dissolve in the experimental conditions. Moreover, the sequence of the leaching rate for the different calcium-based compounds is as follows: CaSiO3>Ca3(PO4)2>CaCO3. The calcium leaching from the MSWIBA and SAPCR separately started from pH<7 and pH<12, resulting from CaCO3 and Ca3(PO4)2 leaching respectively, which was proven by the X-ray diffraction results. Based on the leaching characteristics of the different calcium compounds and the mineral phase of calcium in the incineration residues, simulated computation of their clogging potential was conducted, providing the theoretical basis for the risk assessment pertaining to LCS clogging in landfills. Copyright © 2015 Elsevier Ltd. All rights reserved.

Zoned chondrules in Semarkona: Evidence for high-and low-temperature processing

USGS Publications Warehouse

Grossman, J.N.; Alexander, C.M. O'D.; Wang, Jingyuan; Brearley, A.J.

2002-01-01

At least 15% of the low-FeO chondrules in Semarkona (LL3.0) have mesostases that are concentrically zoned in Na, with enrichments near the outer margins. We have studied zoned chondrules using electron microprobe methods (x-ray mapping plus quantitative analysis), ion micropobe analysis for trace elements and hydrogen isotopes, cathodoluminescence imaging, and transmission electron microscopy in order to determine what these objects can tell us about the environment in which chondrules formed and evolved. Mesostases in these chondrules are strongly zoned in all moderately volatile elements and H (interpreted as water). Calcium is depleted in areas of volatile enrichment. Titanium and Cr generally decrease toward the chondrule surfaces, whereas Al and Si may either increase or decrease, generally in opposite directions to one another; Mn follows Na in some chondrules but not in others; Fe and Mg are unzoned. D/H ratios increase in the water-rich areas of zoned chondrules. Mesostasis shows cathodoluminescence zoning in most zoned chondrules, with the brightest yellow color near the outside. Mesostasis in zoned chondrules appears to be glassy, with no evidence for devitrification. Systematic variations in zoning patterns among pyroxene- and olivine-rich chondrules may indicate that fractionation of low- and high-Ca pyroxene played some role in Ti, Cr, Mn, Si, Al, and some Ca zoning. But direct condensation of elements into hot chondrules, secondary melting of late condensates into the outer portions of chondrules, and subsolidus diffusion of elements into warm chondrules cannot account for the sub-parallel zoning profiles of many elements, the presence of H2O, or elemental abundance patterns. Zoning of moderately volatile elements and Ca may have been produced by hydration of chondrule glass without devitrification during aqueous alteration on the parent asteroid. This could have induced structural changes in the glass allowing rapid diffusion and exchange of elements between altered glass and surrounding matrix and rim material. Calcium was mainly lost during this process, and other nonvolatile elements may have been mobile as well. Some unzoned, low-FeO chondrules appear to have fully altered mesostasis.

The Study of Carious Teeth by Laser-Induced Breakdown Spectroscopy

NASA Astrophysics Data System (ADS)

Hamzaoui, S.; Nouir, R.; Jaidene, N.

2017-03-01

The aim of this work is a multi-component analysis of the element composition of the enamel and carious parts of teeth and the quantification of enamel demineralization using laser-induced breakdown spectroscopy (LIBS). For each tooth the P/Ca ratios of the emission line intensities in the enamel part and those in the carious regions were compared. Since zinc is a trace element, the same procedure was performed for Zn/Ca ratios in the enamel and carious parts. These comparisons showed that the mineral loss from carious lesions occurs at different rates for the studied elements. Calcium has the highest casualty rate. On the other hand, the zinc level diminishes also in the carious region but at a lower rate. The lines were obtained from plume plasma emission generated on the enamel and carious regions.

Effects of calcium antagonists on isolated bovine cerebral arteries: inhibition of constriction and calcium-45 uptake induced by potassium or serotonin

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

Wendling, W.W.; Harakal, C.

1987-05-01

The purpose of this study was to determine the mechanisms by which organic calcium channel blockers inhibit cerebral vasoconstriction. Isolated bovine middle cerebral arteries were cut into rings to measure contractility or into strips to measure radioactive calcium (/sup 45/Ca) influx and efflux. Calcium channel blockers (10(-5) M verapamil or 3.3 X 10(-7) M nifedipine) and calcium-deficient solutions all produced near-maximal inhibition of both potassium- and serotonin-induced constriction. In calcium-deficient solutions containing potassium or serotonin, verapamil and nifedipine each blocked subsequent calcium-induced constriction in a competitive manner. Potassium and serotonin significantly increased /sup 45/Ca uptake into cerebral artery strips duringmore » 5 minutes of /sup 45/Ca loading; for potassium /sup 45/Ca uptake increased from 62 to 188 nmol/g, and for serotonin from 65 to 102 nmol/g. Verapamil or nifedipine had no effect on basal /sup 45/Ca uptake but significantly blocked the increase in /sup 45/Ca uptake induced by potassium or serotonin. Potassium, and to a lesser extent serotonin, each induced a brief increase in the rate of /sup 45/Ca efflux into calcium-deficient solutions. Verapamil or nifedipine had no effect on basal or potassium-stimulated /sup 45/Ca efflux. The results demonstrate that verapamil and nifedipine block /sup 45/Ca uptake through both potential-operated (potassium) and receptor-operated (serotonin) channels in bovine middle cerebral arteries.« less

Calcium/calmodulin-dependent serine protein kinase CASK modulates the L-type calcium current.

PubMed

Nafzger, Sabine; Rougier, Jean-Sebastien

2017-01-01

The L-type voltage-gated calcium channel Ca v 1.2 mediates the calcium influx into cells upon membrane depolarization. The list of cardiopathies associated to Ca v 1.2 dysfunctions highlights the importance of this channel in cardiac physiology. Calcium/calmodulin-dependent serine protein kinase (CASK), expressed in cardiac cells, has been identified as a regulator of Ca v 2.2 channels in neurons, but no experiments have been performed to investigate its role in Ca v 1.2 regulation. Full length or the distal C-terminal truncated of the pore-forming Ca v 1.2 channel (Ca v 1.2α1c), both present in cardiac cells, were expressed in TsA-201 cells. In addition, a shRNA silencer, or scramble as negative control, of CASK was co-transfected in order to silence CASK endogenously expressed. Three days post-transfection, the barium current was increased only for the truncated form without alteration of the steady state activation and inactivation biophysical properties. The calcium current, however, was increased after CASK silencing with both types of Ca v 1.2α1c subunits suggesting that, in absence of calcium, the distal C-terminal counteracts the CASK effect. Biochemistry experiments did not reveals neither an alteration of Ca v 1.2 channel protein expression after CASK silencing nor an interaction between Ca v 1.2α1c subunits and CASK. Nevertheless, after CASK silencing, single calcium channel recordings have shown an increase of the voltage-gated calcium channel Ca v 1.2 open probability explaining the increase of the whole-cell current. This study suggests CASK as a novel regulator of Ca v 1.2 via a modulation of the voltage-gated calcium channel Ca v 1.2 open probability. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structure of a prokaryotic sodium channel pore reveals essential gating elements and an outer ion binding site common to eukaryotic channels

PubMed Central

Shaya, David; Findeisen, Felix; Abderemane-Ali, Fayal; Arrigoni, Cristina; Wong, Stephanie; Nurva, Shailika Reddy; Loussouarn, Gildas; Minor, Daniel L.

2013-01-01

Voltage-gated sodium channels (NaVs) are central elements of cellular excitation. Notwithstanding advances from recent bacterial NaV (BacNaV) structures, key questions about gating and ion selectivity remain. Here, we present a closed conformation of NaVAe1p, a pore-only BacNaV derived from NaVAe1, a BacNaV from the arsenite oxidizer Alkalilimnicola ehrlichei found in Mono Lake, California, that provides insight into both fundamental properties. The structure reveals a pore domain in which the pore-lining S6 helix connects to a helical cytoplasmic tail. Electrophysiological studies of full-length BacNaVs show that two elements defined by the NaVAe1p structure, an S6 activation gate position and the cytoplasmic tail ‘neck’, are central to BacNaV gating. The structure also reveals the selectivity filter ion entry site, termed the ‘outer ion’ site. Comparison with mammalian voltage-gated calcium channel (CaV) selectivity filters, together with functional studies shows that this site forms a previously unknown determinant of CaV high affinity calcium binding. Our findings underscore commonalities between BacNaVs and eukaryotic voltage-gated channels and provide a framework for understanding gating and ion permeation in this superfamily. PMID:24120938

Transgenic plants with increased calcium stores

NASA Technical Reports Server (NTRS)

Robertson, Dominique (Inventor); Wyatt, Sarah (Inventor); Tsou, Pei-Lan (Inventor); Boss, Wendy (Inventor)

2004-01-01

The present invention provides transgenic plants over-expressing a transgene encoding a calcium-binding protein or peptide (CaBP). Preferably, the CaBP is a calcium storage protein and over-expression thereof does not have undue adverse effects on calcium homeostasis or biochemical pathways that are regulated by calcium. In preferred embodiments, the CaBP is calreticulin (CRT) or calsequestrin. In more preferred embodiments, the CaBP is the C-domain of CRT, a fragment of the C-domain, or multimers of the foregoing. In other preferred embodiments, the CaBP is localized to the endoplasmic reticulum by operatively associating the transgene encoding the CaBP with an endoplasmic reticulum localization peptide. Alternatively, the CaBP is targeted to any other sub-cellular compartment that permits the calcium to be stored in a form that is biologically available to the plant. Also provided are methods of producing plants with desirable phenotypic traits by transformation of the plant with a transgene encoding a CaBP. Such phenotypic traits include increased calcium storage, enhanced resistance to calcium-limiting conditions, enhanced growth and viability, increased disease and stress resistance, enhanced flower and fruit production, reduced senescence, and a decreased need for fertilizer production. Further provided are plants with enhanced nutritional value as human food or animal feed.

Synchrotron-induced X-ray fluorescence from rat bone and lumber vertebra of different age groups

NASA Astrophysics Data System (ADS)

Rao, Donepudi V.; Swapna, Medasani; Cesareo, Roberto; Brunetti, Antonio; Akatsuka, Tako; Yuasa, Tetsuya; Takeda, Tohoru; Tromba, Giuliana; Gigante, Giovanni E.

2009-02-01

The fluorescence spectra from rat bones of different age groups (8, 56 and 78 weeks) and lumber vertebra were measured with 8, 10 and 12 keV synchrotron X-rays. We have utilized the new hard X-ray micro-spectroscopy beamline facility, X27A, available at NSLS with a primary beam spot size of the order of ˜10 μm. With this spatial resolution and high flux throughput, X-ray fluorescent intensities for Ca and other trace elements were measured using a liquid-nitrogen-cooled 13-element energy-dispersive high-purity germanium detector. Regarding the lumber vertebra, we acquired the fluorescence spectra from the left, right and middle portions and calcium accumulation was evaluated and compared with the other samples. We have identified the major trace elements of Ca, Ni, Fe and Zn and minor trace elements of Ti, Cr and Mn in the sample. The percentage of scattered radiation and trace element contributions from these samples were highlighted at different energies.

Effects of adrenalectomy on the alpha-adrenergic regulation of cytosolic free calcium in hepatocytes

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

Freudenrich, C.C.; Borle, A.B.

1988-06-25

We have previously published that bilateral adrenalectomy in the rat reduces the Ca2+-mediated alpha-adrenergic activation of hepatic glycogenolysis, while it increases the cellular calcium content of hepatocytes. In the experiments presented here, the concentration of cytosolic free calcium (Ca2+i) at rest and in response to epinephrine was measured in aequorin-loaded hepatocytes isolated from sham and adrenalectomized male rats. We found that in adrenalectomized rats the resting Ca2+i was elevated, the rise in Ca2+i evoked by epinephrine was reduced, and the rise in /sup 45/Ca efflux that follows such stimulation was depressed. Furthermore, the slope of the relationship between Ca2+i andmore » calcium efflux was decreased 60% in adrenalectomized. Adrenalectomy did not change Ca2+ release from intracellular calcium pools in response to IP3 in saponin-permeabilized hepatocytes. The EC50 for inositol 1,4,5-triphosphate and the maximal Ca2+ released were similar in both sham and adrenalectomized animals. Finally, the liver calmodulin content determined by radioimmunoassay was not significantly different between sham and adrenalectomized rats. These results suggest that 1) adrenalectomy reduces calcium efflux from the hepatocyte, probably by an effect on the plasma membrane (Ca2+-Mg2+)-ATPase-dependent Ca2+ pump and thus alters cellular calcium homeostasis; 2) adrenalectomy decreases the rise in Ca2+i in response to epinephrine; 3) this decreased rise in Ca2+i is not due to defects in the intracellular Ca2+ storage and mobilization processes; and 4) the effects of adrenalectomy on cellular calcium metabolism and on alpha-adrenergic activation of glycogenolysis are not caused by a reduction in soluble calmodulin.« less

Calcium deprivation increases the palatability of calcium solutions in rats.

PubMed

McCaughey, Stuart A; Forestell, Catherine A; Tordoff, Michael G

2005-02-15

Calcium-deprived rats have elevated intakes of CaCl2, other calcium salts, and some non-calcium compounds. We used taste reactivity to examine the effects of calcium deprivation on the palatability of CaCl2 and other solutions. Nine male Sprague-Dawley rats were calcium-deprived by maintenance on a low-calcium diet, and eight replete rats were used as controls. All rats were videotaped during intraoral infusion of the following solutions: 30 and 300 mM CaCl2, 30 mM calcium lactate, 100 and 600 mM NaCl, 30 mM MgCl2, 1 mM quinine.HCl, 2.5 mM sodium saccharin, and deionized water. We counted individual orofacial and somatic movements elicited by the infusions and used them to calculate total ingestive and aversive scores. Relative to controls, calcium-deprived rats gave a significantly larger number of tongue protrusions and had higher total ingestive scores for CaCl2, calcium lactate, NaCl, and MgCl2. Our results suggest that CaCl2, calcium lactate, NaCl, and MgCl2 taste more palatable to rats when they are calcium-deprived than replete, and this may be responsible for the increased intake of these solutions following calcium deprivation.

Microstructural analysis of biodegradable Mg-0.9Ca-1.2Zr alloy

NASA Astrophysics Data System (ADS)

Istrate, B.; Munteanu, C.; Geanta, V.; Baltatu, S.; Focsaneanu, S.; Earar, K.

2016-08-01

Magnesium alloys have applications in aerospace and medical applications as biodegradable orthopedic implants. Alloying with biocompatible elements, such as calcium or zirconium contribute to refining the the microstructure and improves corrosion resistance with the formation of an eutectic compound - Mg2Ca at boundary alpha-Mg grains. The purpose of this paper is to present the microstructure throw optical and scanning electron methods and phase and constituents identification with X-ray analysis. The results showed the presence of alpha-Mg grains with formation of a mechanical compound - Mg2Ca and appearance of alpha- Zr phase relatively uniformly distributed in nests.

Backbone and side-chain resonance assignments of (Ca2+)4-calmodulin bound to beta calcineurin A CaMBD peptide.

PubMed

Fowler, C Andrew; Núñez Hernandez, Maria F; O'Donnell, Susan E; Yu, Liping; Shea, Madeline A

2017-10-01

Calcineurin (CaN) is a heterodimeric and highly conserved serine/threonine phosphatase (PP2B) that plays a critical role in coupling calcium signals to physiological processes including embryonic cardiac development, NF-AT-regulated gene expression in immune responses, and apoptosis. The catalytic subunit (CaN A ) has three isoforms (α, β, and γ,) in humans and seven isoforms in Paramecium. In all eukaryotes, the EF-hand protein calmodulin (CaM) regulates CaN activity in a calcium-dependent manner. The N- and C-domains of CaM (CaM N and CaM C ) recognize a CaM-binding domain (CaMBD) within an intrinsically disordered region of CaN A that precedes the auto-inhibitory domain (AID) of CaN A . Here we present nearly complete 1 H, 13 C, and 15 N resonance assignments of (Ca 2+ ) 4 -CaM bound to a peptide containing the CaMBD sequence in the beta isoform of CaN A (βCaN A -CaMBDp). Its secondary structure elements predicted from the assigned chemical shifts were in good agreement with those observed in the high-resolution structures of (Ca 2+ ) 4 -CaM bound to CaMBDs of multiple enzymes. Based on the reported literature, the CaMBD of the α isoform of CaN A can bind to CaM in two opposing orientations which may influence the regulatory function of CaM. Because a high resolution structure of (Ca 2+ ) 4 -CaM bound to βCaN A -CaMBDp has not been reported, our studies serve as a starting point for determining the solution structure of this complex. This will demonstrate the preferred orientation of (Ca 2+ ) 4 -CaM on the CaMBD as well as the orientations of CaM N and CaM C relative to each other and to the AID of βCaN A .

Experimental Comparison of Calcium Sulfate (CaSO(4)) Scale Deposition on Coated Carbon Steel and Titanium Surfaces

NASA Astrophysics Data System (ADS)

Al-Otaibi, Dhawi AbdulRahman

Calcium Sulfate (CaSO4) deposit reduces heat exchange in heat transfer equipment which adversely affects the equipment performance and plant production. This experimental study was conducted by using the Rotating Cylinder Electrode (RCE) equipment available in the university's Center for Engineering Research (CER/RI) to study and compare the effect of solution hydrodynamics on Calcium Sulfate (CaSO4) scale deposition on coated carbon steel and titanium surfaces. In addition, the Scanning Electron Microscopic was used to examine the morphology and distribution of Calcium Sulfate (CaSO 4) crystals deposited on titanium metal surfaces. In this study, the rotational speed was varied from 100 to 2000 RPM to study the behavior of Calcium Sulfate (CaSO4) accumulation on both materials. Based on the experimental results, Calcium Sulfate (CaSO4) scale obtained in the present study was almost constant on coated carbon steel in which the rate of scale deposition is equal to the rate of scale removal. However, the deposition of Calcium Sulfate (CaSO4) observed on titanium material was increased as the speed increased.

A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean

NASA Astrophysics Data System (ADS)

Battaglia, Gianna; Steinacher, Marco; Joos, Fortunat

2016-05-01

The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 export fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Monte Carlo scheme to construct a 1000-member ensemble with the Bern3D ocean model. Ensemble results are constrained by comparing simulated and observation-based fields of excess dissolved calcium carbonate (TA*). The minerals calcite and aragonite are modelled explicitly and ocean-sediment fluxes are considered. For local dissolution rates, either a strong or a weak dependency on CaCO3 saturation is assumed. In addition, there is the option to have saturation-independent dissolution above the saturation horizon. The median (and 68 % confidence interval) of the constrained model ensemble for global biogenic CaCO3 export is 0.90 (0.72-1.05) Gt C yr-1, that is within the lower half of previously published estimates (0.4-1.8 Gt C yr-1). The spatial pattern of CaCO3 export is broadly consistent with earlier assessments. Export is large in the Southern Ocean, the tropical Indo-Pacific, the northern Pacific and relatively small in the Atlantic. The constrained results are robust across a range of diapycnal mixing coefficients and, thus, ocean circulation strengths. Modelled ocean circulation and transport timescales for the different set-ups were further evaluated with CFC11 and radiocarbon observations. Parameters and mechanisms governing dissolution are hardly constrained by either the TA* data or the current compilation of CaCO3 flux measurements such that model realisations with and without saturation-dependent dissolution achieve skill. We suggest applying saturation-independent dissolution rates in Earth system models to minimise computational costs.

Activation of the edema factor of Bacillus anthracis by calmodulin: evidence of an interplay between the EF-calmodulin interaction and calcium binding.

PubMed

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

2010-10-06

Calmodulin (CaM) is a remarkably flexible protein which can bind multiple targets in response to changes in intracellular calcium concentration. It contains four calcium-binding sites, arranged in two globular domains. The calcium affinity of CaM N-terminal domain (N-CaM) is dramatically reduced when the complex with the edema factor (EF) of Bacillus anthracis is formed. Here, an atomic explanation for this reduced affinity is proposed through molecular dynamics simulations and free energy perturbation calculations of the EF-CaM complex starting from different crystallographic models. The simulations show that electrostatic interactions between CaM and EF disfavor the opening of N-CaM domains usually induced by calcium binding. Relative calcium affinities of the N-CaM binding sites are probed by free energy perturbation, and dissociation probabilities are evaluated with locally enhanced sampling simulations. We show that EF impairs calcium binding on N-CaM through a direct conformational restraint on Site 1, by an indirect destabilization of Site 2, and by reducing the cooperativity between the two sites. Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

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

PubMed

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.

Analysis and Effects of Cytosolic Free Calcium Increases in Response to Elicitors in Nicotiana plumbaginifolia Cells

PubMed Central

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

2002-01-01

Cell suspensions obtained from Nicotiana plumbaginifolia plants stably expressing the apoaequorin gene were used to analyze changes in cytosolic free calcium concentrations ([Ca2+]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 [Ca2+]cyt increase that should be responsible for sustained mitogen-activated protein kinase activation, microtubule depolymerization, defense gene activation, and cell death. The [Ca2+]cyt increase in elicitor-treated cells first results from a calcium influx, which in turns leads to calcium release from internal stores and additional Ca2+ influx. H2O2 resulting from the calcium-dependent activation of the NADPH oxidase also participates in [Ca2+]cyt increase and may activate calcium channels from the plasma membrane. Competition assays with different elicitins demonstrate that [Ca2+]cyt increase is mediated by cryptogein–receptor interaction. PMID:12368509

Calcium-independent metal-ion catalytic mechanism of anthrax edema factor

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

Shen, Yuequan; Zhukovskaya, Natalia L.; Guo, Qing

2009-11-18

Edema factor (EF), a key anthrax exotoxin, has an anthrax protective antigen-binding domain (PABD) and a calmodulin (CaM)-activated adenylyl cyclase domain. Here, we report the crystal structures of CaM-bound EF, revealing the architecture of EF PABD. CaM has N- and C-terminal domains and each domain can bind two calcium ions. Calcium binding induces the conformational change of CaM from closed to open. Structures of the EF-CaM complex show how EF locks the N-terminal domain of CaM into a closed conformation regardless of its calcium-loading state. This represents a mechanism of how CaM effector alters the calcium affinity of CaM andmore » uncouples the conformational change of CaM from calcium loading. Furthermore, structures of EF-CaM complexed with nucleotides show that EF uses two-metal-ion catalysis, a prevalent mechanism in DNA and RNA polymerases. A histidine (H351) further facilitates the catalysis of EF by activating a water to deprotonate 3'OH of ATP. Mammalian adenylyl cyclases share no structural similarity with EF and they also use two-metal-ion catalysis, suggesting the catalytic mechanism-driven convergent evolution of two structurally diverse adenylyl cyclases.« less

A case of gain-of-function mutation in calcium-sensing receptor: supplemental hydration is required for renal protection.

PubMed

Suzuki, M; Aso, T; Sato, T; Michimata, M; Kazama, I; Saiki, H; Hatano, R; Ejima, Y; Miyama, N; Sato, A; Matsubara, M

2005-06-01

The calcium-sensing receptor (CaSR) regulates the extracellular calcium level, mainly by controlling parathyroid hormon secretion and renal calcium reabsorption. In gain-of-function CaSR mutations, the genetic abnormalities increase CaSR activity leading to the development of such clinical manifestations as hypercalciuric hypocalcemia and hypoparathyroidism. We report a Japanese case of CaSR gain-of-function mutation and represent a therapeutic intervention based on the functional characteristics of CaSR in renal tubule. DNA sequence analysis revealed a heterozygous G to T mutation identified in a 12-year-old Japanese girl presenting with sporadic onset of hypercalciuric hypocalcemia and hypoparathyroidism. The mutation is located in the N-terminal extracellular domain of the CaSR gene, one of the most important parts for the three-dimensional construction of the receptor, resulting in the substitution of phenylalanine for cysteine at amino acid 131 (C131F) in exon 3. Based on the diagnosis of the gain-of-function mutation in the CaSR, oral hydrochlorothiazide administration and supplemental hydration were started in addition to calcium supplementation. The combination therapy of thiazide and supplemental hydration markedly reduced both renal calcium excretion and urinary calcium concentration from 0.4-0.7 to less than 0.1 mg/mg (urinary calcium/creatinine ratio) and from 10-15 to 3-5 mg/dl (urinary calcium concentration), respectively. This therapy stopped the progression of renal calcification during the follow-up period. Supplemental hydration should be considered essential for the following reasons: (1) calcium supplementation activates the CaSR in the kidney and suppresses renal urinary concentrating ability, (2) the thiazide has a diuretic effect, (3) as calcium supplementation increases renal calcium excretion, the supplemental hydration decreases urinary calcium concentration by increasing urinary volume, thereby diminishing the risk of intratubular crystallization of calcium ion.

Calcium-41 as a long-term biological tracer for bone resorption

NASA Astrophysics Data System (ADS)

Elmore, David; Bhattacharyya, Maryka H.; Sacco-Gibson, Nancy; Peterson, David P.

1990-12-01

The use of 41Ca (half-life 1 × 10 5 yr) as a tracer for studying calcium metabolism in living systems is compared to the shorter-lived radionuclides 45Ca (165 d) and 47Ca (45 d) and the stable isotopes 42Ca and 44Ca. The feasibility of using accelerator mass spectrometry (AMS) measurements of 41Ca for studying multi-year calcium resorption in humans was tested as part of a companion study that used 45Ca to measure the effects of dietary cadmium on calcium metabolism in dogs. It was shown that Ca resorbed from prelabeled bones correlates well with 45Ca for a period of 28 weeks. The advantage of 41Ca is that, even with a negligible radiation dose, it can be measured by AMS long after the 45Ca becomes unmeasurable.

Anthrax and the geochemistry of soils in the contiguous United States

USGS Publications Warehouse

Griffin, Dale W.; Silvestri, Erin E.; Bowling, Charlena Y.; Boe, Timothy; Smith, David B.; Nichols, Tonya L.

2014-01-01

Soil geochemical data from sample sites in counties that reported occurrences of anthrax in wildlife and livestock since 2000 were evaluated against counties within the same states (MN, MT, ND, NV, OR, SD and TX) that did not report occurrences. These data identified the elements, calcium (Ca), manganese (Mn), phosphorus (P) and strontium (Sr), as having statistically significant differences in concentrations between county type (anthrax occurrence versus no occurrence). Tentative threshold values of the lowest concentrations of each of these elements (Ca = 0.43 wt %, Mn = 142 mg/kg, P = 180 mg/kg and Sr = 51 mg/kg) and average concentrations (Ca = 1.3 wt %, Mn = 463 mg/kg, P = 580 mg/kg and Sr = 170 mg/kg) were identified from anthrax-positive counties as prospective investigative tools in determining whether an outbreak had “potential” or was “likely” at any given geographic location in the contiguous United States.

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

Code of Federal Regulations, 2010 CFR

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...

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

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 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...

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

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 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...

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

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 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...

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

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 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...

Biogeochemical Relationships of a Subtropical Dry Forest on Karst

Treesearch

E. Medina; E. Cuevas; H. Marcano-Vega; E. Meléndez-Ackerman; E.H. Helmer

2017-01-01

Tropical dry forests on calcareous substrate constitute the main vegetation cover in many islands of the Caribbean. Dry climate and nutrient scarcity in those environments are ideal to investigate the potential role of high levels of soil calcium (Ca) in regulating plant selection and productivity. We analyzed the elemental composition of soil, loose litter, and leaf...

Spin-gapless and half-metallic ferromagnetism in potassium and calcium δ-doped GaN digital magnetic heterostructures for possible spintronic applications: insights from first principles

NASA Astrophysics Data System (ADS)

Du, Jiangtao; Dong, Shengjie; Zhou, Baozeng; Zhao, Hui; Feng, Liefeng

2017-04-01

The reports previously issued predominantly paid attention to the d-block magnetic elements δ-doped digital magnetic materials. In this work, GaN δ-doped with non-magnetic main group s-block elements K and Ca as digital magnetic heterostructures were purposed and explored theoretically. We found that K- and Ca-embedded GaN digital alloys exhibit spin-gapless and half-metallic ferromagnetic characteristics, respectively. All compounds obey the Slater-Pauling rule with diverse electronic and magnetic properties. For these digital ferromagnetic heterostructures, spin polarization occurs in nitrogen within a confined space around the δ-doped layer, demonstrating a hole-mediated two-dimensional magnetic phenomenon.

Long-term evolution of highly alkaline steel slag drainage waters.

PubMed

Riley, Alex L; Mayes, William M

2015-07-01

The disposal of slag generated by the steel industry can have negative consequences upon the surrounding aquatic environment by the generation of high pH waters, leaching of potentially problematic trace metals, and rapid rates of calcite precipitation which smother benthic habitats. A 36-year dataset was collated from the long-term ambient monitoring of physicochemical parameters and elemental concentrations of samples from two steel slag leachate-affected watercourses in northern England. Waters were typified by elevated pH (>10), high alkalinity, and were rich in dissolved metals (e.g. calcium (Ca), aluminium (Al), and zinc (Zn)). Long-term trend analysis was performed upon pH, alkalinity, and Ca concentration which, in addition to Ca flux calculations, were used to highlight the longevity of pollution arising as a result of the dumping and subsequent leaching of steel slags. Declines in calcium and alkalinity have been modest over the monitoring period and not accompanied by significant declines in water pH. If the monotonic trends of decline in alkalinity and calcium continue in the largest of the receiving streams, it will be in the region of 50-80 years before calcite precipitation would be expected to be close to baseline levels, where ecological impacts would be negligible.

Indian Summer Monsoon dynamics during Termination II and MIS 5e

NASA Astrophysics Data System (ADS)

Magiera, Matthias; Erhardt, Andrea M.; Hartland, Adam; Kwiecien, Ola; Cheng, Hai; Immenhauser, Adrian; Turchyn, Alexandra; Breitenbach, Sebastian F. M.

2017-04-01

The interpretation of speleothem oxygen isotope ratios (δ18O) as proxy for Indian Summer Monsoon (ISM) dynamics is ambiguous, due to multiple influencing factors. Here we combine δ18O and calcium isotope δ44Ca analyses with elemental data to delineate regional shifts in moisture source, local rainfall amount, and changes in ISM intensity and length during Termination II and MIS 5e. Oxygen isotope ratios reflect a mixed signal of moisture source dynamics and rainfall amount; δ44Ca and Mg/Ca ratios are interpreted as proxies for local effective moisture and prior calcite precipitation (PCP) in the epikarst. The age of stalagmite MAW-3 from Mawmluh Cave, NE India, is constraint by six U-series dates. 108 samples, obtained at 0.4 mm resolution from the 70 mm long speleothem sample, have been analysed for δ18O, δ44Ca and Mg/Ca. Oxygen isotope ratios were measured on a ThermoFisher Scientific MAT 253 at Ruhr-University Bochum. Elemental ratios were measured on a quadrupole ICP-MS at Waikato University. Calcium isotope ratios were analyzed on a ThermoFisher Scientific Triton at University of Cambridge. MAW-3 grew from 136 kyrs BP to 96 kyrs BP, covering Termination II and MIS 5e. Oxygen isotope values are high (ca. +0.91 ‰) during Termination II, reach a minimum during MIS 5e (-3.5 ‰), and rise again to -0.2 ‰ at the end of MIS 5e. Calcium isotope ratios range from -0.32 ‰ to -0.70 ‰ and show a positive correlation (R2= 0.7) with δ18O. High δ18O values during Termination II reflect reduced atmospheric circulation and/or a proximal moisture source (Bay of Bengal), implying lowered ISM intensity. A positive correlation of δ18O with δ44Ca suggests concurrent changes of moisture source location and local rainfall amount, with a proximal moisture source and reduced effective rainfall during periods of weak ISM. Elevated Mg/Ca ratios at such intervals corroborate PCP occurrence, which reflects dry conditions. The beginning of MIS 5e (ca. 132 kyrs BP) is marked by a rapid change to lower δ18O and δ44Ca, suggesting increased local infiltration with increasing ISM rainfall, and a concurrent change to a more distal moisture source. The MAW-3 multi-proxy record compares well with reconstructions from China and northern India, the latter being more depleted, due to Rayleigh fractionation. We suggest that multi-proxy analyses of δ18O, δ44Ca and Mg/Ca greatly help to delineate regional circulation pattern and local effective moisture dynamics in monsoonal settings.

Structures of Ca(V) Ca**2+/CaM-IQ Domain Complexes Reveal Binding Modes That Underlie Calcium-Dependent Inactivation And Facilitation

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

Kim, E.Y.; Rumpf, C.H.; Fujiwara, Y.

2009-05-20

Calcium influx drives two opposing voltage-activated calcium channel (Ca{sub V}) self-modulatory processes: calcium-dependent inactivation (CDI) and calcium-dependent facilitation (CDF). Specific Ca{sup 2+}/calmodulin (Ca{sup 2+}/CaM) lobes produce CDI and CDF through interactions with the Ca{sub V}{alpha}{sub 1} subunit IQ domain. Curiously, Ca{sup 2+}/CaM lobe modulation polarity appears inverted between Ca{sub V}1s and Ca{sub V}2s. Here, we present crystal structures of Ca{sub V}2.1, Ca{sub V}2.2, and Ca{sub V}2.3 Ca{sup 2+}/CaM-IQ domain complexes. All display binding orientations opposite to Ca{sub V}1.2 with a physical reversal of the CaM lobe positions relative to the IQ {alpha}-helix. Titration calorimetry reveals lobe competition for a high-affinitymore » site common to Ca{sub V}1 and Ca{sub V}2 IQ domains that is occupied by the CDI lobe in the structures. Electrophysiological experiments demonstrate that the N-terminal Ca{sub V}2 Ca{sup 2+}/C-lobe anchors affect CDF. Together, the data unveil the remarkable structural plasticity at the heart of Ca{sub V} feedback modulation and indicate that Ca{sub V}1 and Ca{sub V}2 IQ domains bear a dedicated CDF site that exchanges Ca{sup 2+}/CaM lobe occupants.« less

Interactions between calcium and phosphorus in the regulation of the production of fibroblast growth factor 23 in vivo

PubMed Central

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

Biocalcite, a multifunctional inorganic polymer: Building block for calcareous sponge spicules and bioseed for the synthesis of calcium phosphate-based bone

PubMed Central

Schröder, Heinz C; Müller, Werner E G

2014-01-01

Summary Calcium carbonate is the material that builds up the spicules of the calcareous sponges. Recent results revealed that the calcium carbonate/biocalcite-based spicular skeleton of these animals is formed through an enzymatic mechanism, such as the skeleton of the siliceous sponges, evolutionarily the oldest animals that consist of biosilica. The enzyme that mediates the calcium carbonate deposition has been identified as a carbonic anhydrase (CA) and has been cloned from the calcareous sponge species Sycon raphanus. Calcium carbonate deposits are also found in vertebrate bones besides the main constituent, calcium phosphate/hydroxyapatite (HA). Evidence has been presented that during the initial phase of HA synthesis poorly crystalline carbonated apatite is deposited. Recent data summarized here indicate that during early bone formation calcium carbonate deposits enzymatically formed by CA, act as potential bioseeds for the precipitation of calcium phosphate mineral onto bone-forming osteoblasts. Two different calcium carbonate phases have been found during CA-driven enzymatic calcium carbonate deposition in in vitro assays: calcite crystals and round-shaped vaterite deposits. The CA provides a new target of potential anabolic agents for treatment of bone diseases; a first CA activator stimulating the CA-driven calcium carbonate deposition has been identified. In addition, the CA-driven calcium carbonate crystal formation can be frozen at the vaterite state in the presence of silintaphin-2, an aspartic acid/glutamic acid-rich sponge-specific protein. The discovery that calcium carbonate crystals act as bioseeds in human bone formation may allow the development of novel biomimetic scaffolds for bone tissue engineering. Na-alginate hydrogels, enriched with biosilica, have recently been demonstrated as a suitable matrix to embed bone forming cells for rapid prototyping bioprinting/3D cell printing applications. PMID:24991497

Biocalcite, a multifunctional inorganic polymer: Building block for calcareous sponge spicules and bioseed for the synthesis of calcium phosphate-based bone.

PubMed

Wang, Xiaohong; Schröder, Heinz C; Müller, Werner E G

2014-01-01

Calcium carbonate is the material that builds up the spicules of the calcareous sponges. Recent results revealed that the calcium carbonate/biocalcite-based spicular skeleton of these animals is formed through an enzymatic mechanism, such as the skeleton of the siliceous sponges, evolutionarily the oldest animals that consist of biosilica. The enzyme that mediates the calcium carbonate deposition has been identified as a carbonic anhydrase (CA) and has been cloned from the calcareous sponge species Sycon raphanus. Calcium carbonate deposits are also found in vertebrate bones besides the main constituent, calcium phosphate/hydroxyapatite (HA). Evidence has been presented that during the initial phase of HA synthesis poorly crystalline carbonated apatite is deposited. Recent data summarized here indicate that during early bone formation calcium carbonate deposits enzymatically formed by CA, act as potential bioseeds for the precipitation of calcium phosphate mineral onto bone-forming osteoblasts. Two different calcium carbonate phases have been found during CA-driven enzymatic calcium carbonate deposition in in vitro assays: calcite crystals and round-shaped vaterite deposits. The CA provides a new target of potential anabolic agents for treatment of bone diseases; a first CA activator stimulating the CA-driven calcium carbonate deposition has been identified. In addition, the CA-driven calcium carbonate crystal formation can be frozen at the vaterite state in the presence of silintaphin-2, an aspartic acid/glutamic acid-rich sponge-specific protein. The discovery that calcium carbonate crystals act as bioseeds in human bone formation may allow the development of novel biomimetic scaffolds for bone tissue engineering. Na-alginate hydrogels, enriched with biosilica, have recently been demonstrated as a suitable matrix to embed bone forming cells for rapid prototyping bioprinting/3D cell printing applications.

Hybrid systems analysis of the control of burst duration by low-voltage-activated calcium current in leech heart interneurons.

PubMed

Olypher, Andrey; Cymbalyuk, Gennady; Calabrese, Ronald L

2006-12-01

The leech heartbeat CPG is paced by the alternating bursting of pairs of mutually inhibitory heart interneurons that form elemental half-center oscillators. We explore the control of burst duration in heart interneurons using a hybrid system, where a living, pharmacologically isolated, heart interneuron is connected with artificial synapses to a model heart interneuron running in real-time, by focusing on a low-voltage-activated (LVA) calcium current I(CaS). The transition from silence to bursting in this half-center oscillator occurs when the spike frequency of the bursting interneuron declines to a critical level, f(Final), at which the inhibited interneuron escapes owing to a build-up of the hyperpolarization-activated cation current, I(h). We varied I(CaS) inactivation time constant either in the living heart interneuron or in the model heart interneuron. In both cases, varying I(CaS) inactivation time constant did not affect f(Final) of either interneuron, but in the varied interneuron, the time constant of decline of spike frequency during bursts to f(Final) and thus the burst duration varied directly and nearly linearly with I(CaS) inactivation time constant. Bursts of the opposite, nonvaried interneuron did not change. We show also that control of burst duration by I(CaS) inactivation does not require synaptic interaction by reconstituting autonomous bursting in synaptically isolated living interneurons with injected I(CaS). Therefore inactivation of LVA calcium current is critically important for setting burst duration and thus period in a heart interneuron half-center oscillator and is potentially a general intrinsic mechanism for regulating burst duration in neurons.

Magnesium stable isotope ecology using mammal tooth enamel

NASA Astrophysics Data System (ADS)

Martin, Jeremy E.; Vance, Derek; Balter, Vincent

2015-01-01

Geochemical inferences on ancient diet using bone and enamel apatite rely mainly on carbon isotope ratios (δ13C) and to a lesser extent on strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) elemental ratios. Recent developments in nontraditional stable isotopes provide an unprecedented opportunity to use additional paleodietary proxies to disentangle complex diets such as omnivory. Of particular relevance for paleodietary reconstruction are metals present in large quantity in bone and enamel apatite, providing that biologically mediated fractionation processes are constrained. Calcium isotope ratios (δ44Ca) meet these criteria but exhibit complex ecological patterning. Stable magnesium isotope ratios (δ26Mg) also meet these criteria but a comprehensive understanding of its variability awaits new isotopic data. Here, 11 extant mammal species of known ecology from a single locality in equatorial Africa were sampled for tooth enamel and, together with vegetation and feces, analyzed for δ26Mg, δ13C, Sr/Ca, and Ba/Ca ratios. The results demonstrate that δ26Mg incorporated in tooth enamel becomes heavier from strict herbivores to omnivores/faunivores. Using data from experimentally raised sheep, we suggest that this 26Mg enrichment up the trophic chain is due to a 26Mg enrichment in muscle relative to bone. Notably, it is possible to distinguish omnivores from herbivores, using δ26Mg coupled to Ba/Ca ratios. The potential effects of metabolic and dietary changes on the enamel δ26Mg composition remain to be explored but, in the future, multiproxy approaches would permit a substantial refinement of dietary behaviors or enable accurate trophic reconstruction despite specimen-limited sampling, as is often the case for fossil assemblages.

[Contents of calcium, phosphorus and aluminum in central nervous system, liver and kidney of rabbits with experimental atherosclerosis--scavenger effects of vinpocetine on the deposition of elements].

PubMed

Yasui, M; Yano, I; Ota, K; Oshima, A

1990-04-01

The aims in this study were designed to clarify the contents of calcium (Ca), phosphorus (P) and aluminum (Al) in central nervous system (CNS), liver and kidney of rabbits with atherosclerosis experimentally induced by cholesterol-rich diet, and investigate scavenger effect of 14-ethoxycarbonyl-(3 alpha, 16 alpha-ethyl)-14,15-eburnamenine (vinpocetine) on the deposition of these elements in CNS and soft tissues of experimental atherosclerosis. Sixteen male rabbits were divided into 4 groups. Each group was fed with standard diet (Group A), standard diet containing 1.5% cholesterol (Group B), standard diet containing 1.5% cholesterol plus oral administration of 3 mg/kg/day vinpocetine (Group C), and standard diet containing 1.5% cholesterol plus administration of 10 mg/kg/day vinpocetine (Group D). After 3 months' feeding, experimental atherosclerosis was produced with a modified method of Kritchevsky et al in rabbits of Groups B, C and D. Blood was collected by cardiocentesis under the anesthesia of ether and then rabbits sacrificed to remove CNS and other tissues. The blood was stood for 1 hour at room temperature and separated by centrifugation at 3000 rpm for 10 min to determine serum total cholesterol, phospholipids, HDL-cholesterol, peroxide lipid, NEFA and calcium levels. Ca, P and Al contents in the frontal lobe, pons, cerebellum, spinal cord, liver and kidney were determined by neutron activation analysis. Ca contents of CNS, liver and kidney in Group B significantly increased than those of Group A (p less than 0.01), and significantly decreased in Groups C and D compared with those of Group B (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The Different Facets of Extracellular Calcium Sensors: Old and New Concepts in Calcium-Sensing Receptor Signalling and Pharmacology

PubMed Central

2018-01-01

The current interest of the scientific community for research in the field of calcium sensing in general and on the calcium-sensing Receptor (CaR) in particular is demonstrated by the still increasing number of papers published on this topic. The extracellular calcium-sensing receptor is the best-known G-protein-coupled receptor (GPCR) able to sense external Ca2+ changes. Widely recognized as a fundamental player in systemic Ca2+ homeostasis, the CaR is ubiquitously expressed in the human body where it activates multiple signalling pathways. In this review, old and new notions regarding the mechanisms by which extracellular Ca2+ microdomains are created and the tools available to measure them are analyzed. After a survey of the main signalling pathways triggered by the CaR, a special attention is reserved for the emerging concepts regarding CaR function in the heart, CaR trafficking and pharmacology. Finally, an overview on other Ca2+ sensors is provided. PMID:29584660

Systems Modeling of Ca2+ Homeostasis and Mobilization in Platelets Mediated by IP3 and Store-Operated Ca2+ Entry

PubMed Central

Dolan, Andrew T.; Diamond, Scott L.

2014-01-01

Resting platelets maintain a stable level of low cytoplasmic calcium ([Ca2+]cyt) and high dense tubular system calcium ([Ca2+]dts). During thrombosis, activators cause a transient rise in inositol trisphosphate (IP3) to trigger calcium mobilization from stores and elevation of [Ca2+]cyt. Another major source of [Ca2+]cyt elevation is store-operated calcium entry (SOCE) through plasmalemmal calcium channels that open in response to store depletion as [Ca2+]dts drops. A 34-species systems model employed kinetics describing IP3-receptor, DTS-plasmalemma puncta formation, SOCE via assembly of STIM1 and Orai1, and the plasmalemma and sarco/endoplasmic reticulum Ca2+-ATPases. Four constraints were imposed: calcium homeostasis before activation; stable in zero extracellular calcium; IP3-activatable; and functional SOCE. Using a Monte Carlo method to sample three unknown parameters and nine initial concentrations in a 12-dimensional space near measured or expected values, we found that model configurations that were responsive to stimuli and demonstrated significant SOCE required high inner membrane electric potential (>−70 mV) and low resting IP3 concentrations. The absence of puncta in resting cells was required to prevent spontaneous store depletion in calcium-free media. Ten-fold increases in IP3 caused saturated calcium mobilization. This systems model represents a critical step in being able to predict platelets’ phenotypes during hemostasis or thrombosis. PMID:24806937

Calcium transport in turtle bladder

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

Sabatini, S.; Kurtzman, N.A.

1987-12-01

Unidirectional {sup 45}Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (J{sup net}{sub Ca}) was secretory (serosa to mucosa). Ouabain reversed J{sup net}{sub Ca} to an absorptive flux. Amiloride reduced both fluxes such that J{sup net}{sub Ca} was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, J{sup net}{sub Ca} decreased to approximately one-third of control value but remained secretory. When ouabain was added under short-circuit conditions, J{sup net}{sub Ca} was similar inmore » magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue {sup 45}Ca content was {approx equal}30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca{sup 2+}-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na{sup +}-K{sup +}-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.« less

CaMKII activity is essential for improvement of memory-related behaviors by chronic rivastigmine treatment.

PubMed

Moriguchi, Shigeki; Tagashira, Hideaki; Sasaki, Yuzuru; Yeh, Jay Z; Sakagami, Hiroyuki; Narahashi, Toshio; Fukunaga, Kohji

2014-03-01

Because the cholinergic system is down-regulated in the brain of Alzheimer's disease patients, cognitive deficits in Alzheimer's disease patients are significantly improved by rivastigmine treatment. To address the mechanism underlying rivastigmine-induced memory improvements, we chronically treated olfactory bulbectomized (OBX) mice with rivastigmine. The chronic rivastigmine treatments for 12-13 days starting at 10 days after OBX operation significantly improved memory-related behaviors assessed by Y-maze task, novel object recognition task, passive avoidance task, and Barnes maze task, whereas the single rivastigmine treatment failed to improve the memory. Consistent with the improved memory-related behaviors, long-term potentiation in the hippocampal CA1 region was markedly restored by rivastigmine treatments. In immunoblotting analyses, the reductions of calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation and calcium/calmodulin-dependent protein kinase IV (CaMKIV) phosphorylation in the CA1 region in OBX mice were significantly restored by rivastigmine treatments. In addition, phosphorylation of AMPAR subunit glutamate receptor 1 (GluA1) (Ser-831) and cAMP-responsive element-binding protein (Ser-133) as downstream targets of CaMKII and CaMKIV, respectively, in the CA1 region was also significantly restored by chronic rivastigmine treatments. Finally, we confirmed that rivastigmine-induced improvements of memory-related behaviors and long-term potentiation were not obtained in CaMKIIα(+/-) mice. On the other hand, CaMKIV(-/-) mice did not exhibit the cognitive impairments. Taken together, the stimulation of CaMKII activity in the hippocampus is essential for rivastigmine-induced memory improvement in OBX mice. © 2013 International Society for Neurochemistry.

Calcium Isotope Fractionation during Carbonate Weathering in the Northern Guangdong, South China

NASA Astrophysics Data System (ADS)

Liu, F.; Mao, G.; Wei, G.; Zhang, Z.

2017-12-01

CO2 is consumed during the weathering of carbonates, whereas carbonates are precipitated rapidly in the oceans, which are pivotal to modulate atmospheric CO2, oceanic pH and climate. Calcium carbonate in limestone is one of the largest reservoirs of carbon at the Earth's surface, so calcium is an important element that links the lithosphere, hydrosphere, biosphere, and the atmosphere. Compared with silicate rocks, carbonate rocks have more rapid rates of physical and chemical erosions, so the carbonate weathering will respond more quickly to the climatic changes. In the southeast of China, enormous of carbonate rocks are widely distributed. Due to the influence of the subtropical monsoon climate, the rocks experienced strong chemical weathering and pedogenic process, resulting in red weathering crust of carbonate rocks. This type of weathering crust is geochemistry-sensitive and ecology-vulnerable, which can provide important insights into the recycle of supergene geochemistry in the karst areas. In this study, we report calcium isotopic compositions of saprolites from a weathering profile developed on argillaceous carbonate rocks in northern Guangdong, South China. The acid-leachable fraction, which was extracted by 1N hydrochloride acid, showed limited variation of δ44/40Ca(NIST 915a) spanning from 0.55 ± 0.06‰ (2SD) to 0.72 ± 0.05‰ (2SD) despite CaO content ranging from 0.01 wt.% to 45.7 wt.%, implying that Ca isotope didn't fractionate much which may due to the congruent dissolution of limestone minerals. In contrast, radiogenic 87Sr/86Sr ratios of the whole rocks changed with depth from 0.710086 ± 6 (2SE) at the base rock to 0.722164± 8 (2SE) at the top-soil, which are possibly attributed to the mixing effect between carbonate and silicate fractions. Sr is an analogue for Ca due to its similar ionic size and charge; however, these two systems can differ in certain respects. The coupled study of Ca and Sr will be helpful to verify sources of Ca and the global Ca and C cycles.

Cellular roles of neuronal calcium sensor-1 and calcium/calmodulin-dependent kinases in fungi.

PubMed

Tamuli, Ranjan; Kumar, Ravi; Deka, Rekha

2011-04-01

The neuronal calcium sensor-1 (NCS-1) possesses a consensus signal for N-terminal myristoylation and four EF-hand Ca(2+)-binding sites, and mediates the effects of cytosolic Ca(2+). Minute changes in free intracellular Ca(2+) are quickly transformed into changes in the activity of several kinases including calcium/calmodulin-dependent protein kinases (Ca(2+)/CaMKs) that are involved in regulating many eukaryotic cell functions. However, our current knowledge of NCS-1 and Ca(2+)/CaMKs comes mostly from studies of the mammalian enzymes. Thus far very few fungal homologues of NCS-1 and Ca(2+)/CaMKs have been characterized and little is known about their cellular roles. In this minireview, we describe the known sequences, interactions with target proteins and cellular roles of NCS-1 and Ca(2+)/CaMKs in fungi. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intracellular Calcium Mobilization in Response to Ion Channel Regulators via a Calcium-Induced Calcium Release Mechanism

PubMed Central

Petrou, Terry; Olsen, Hervør L.; Thrasivoulou, Christopher; Masters, John R.; Ashmore, Jonathan F.

2017-01-01

Free intracellular calcium ([Ca2+]i), in addition to being an important second messenger, is a key regulator of many cellular processes including cell membrane potential, proliferation, and apoptosis. In many cases, the mobilization of [Ca2+]i is controlled by intracellular store activation and calcium influx. We have investigated the effect of several ion channel modulators, which have been used to treat a range of human diseases, on [Ca2+]i release, by ratiometric calcium imaging. We show that six such modulators [amiodarone (Ami), dofetilide, furosemide (Fur), minoxidil (Min), loxapine (Lox), and Nicorandil] initiate release of [Ca2+]i in prostate and breast cancer cell lines, PC3 and MCF7, respectively. Whole-cell currents in PC3 cells were inhibited by the compounds tested in patch-clamp experiments in a concentration-dependent manner. In all cases [Ca2+]i was increased by modulator concentrations comparable to those used clinically. The increase in [Ca2+]i in response to Ami, Fur, Lox, and Min was reduced significantly (P < 0.01) when the external calcium was reduced to nM concentration by chelation with EGTA. The data suggest that many ion channel regulators mobilize [Ca2+]i. We suggest a mechanism whereby calcium-induced calcium release is implicated; such a mechanism may be important for understanding the action of these compounds. PMID:27980039

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

PubMed

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

2014-01-01

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

Effect of Sulfur in Steel on Transient Evolution of Inclusions During Calcium Treatment

NASA Astrophysics Data System (ADS)

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.

Is bone equally responsive to calcium and vitamin D intake from food vs. supplements? Use of (41)calcium tracer kinetic model.

PubMed

Rogers, Tara S; Garrod, Marjorie G; Peerson, Janet M; Hillegonds, Darren J; Buchholz, Bruce A; Demmer, Elieke; Richardson, Christine; Gertz, Erik R; Van Loan, Marta D

2016-12-01

Few interventions directly compare equivalent calcium and vitamin D from dairy vs. supplements on the same bone outcomes. The radioisotope calcium-41 ((41)Ca) holds promise as a tracer method to directly measure changes in bone resorption with differing dietary interventions. Using (41)Ca tracer methodology, determine if 4 servings/day of dairy foods results in greater (41)Ca retention than an equivalent amount of calcium and vitamin D from supplements. Secondary objective was to evaluate the time course for the change in (41)Ca retention. In this crossover trial, postmenopausal women (n = 12) were dosed orally with 100 nCi of (41)Ca and after a 180 day equilibration period received dairy (4 servings/day of milk or yogurt; ~ 1300 mg calcium, 400 IU cholecalciferol (vitamin D3/day)) or supplement treatments (1200 mg calcium carbonate/day and 400 IU vitamin D3/day) in random order. Treatments lasted 6 weeks separated by a 6 week washout (WO). Calcium was extracted from weekly 24 h urine collections; accelerator mass spectrometry (AMS) was used to determine the (41/40)Ca ratio. Primary outcome was change in (41/40)Ca excretion. Secondary outcome was the time course for change in (41)Ca excretion during intervention and WO periods. The (41/40)Ca ratio decreased significantly over time during both treatments; there was no difference between treatments. Both treatments demonstrated a significant retention of (41)Ca within 1-2 weeks (p = 0.0007 and p < 0.001 for dairy and supplements, respectively). WO demonstrated a significant decrease (p = 0.0024) in (41)Ca retention within 1-2 weeks, back to pre-intervention levels. These data demonstrate that urinary (41)Ca retention is increased with an increase in calcium and vitamin D intake regardless of the source of calcium, and the increased retention occurs within 1-2 weeks.

The site of net absorption of Ca from the intestinal tract of growing pigs and effect of phytic acid, Ca level and Ca source on Ca digestibility.

PubMed

González-Vega, J Caroline; Walk, Carrie L; Liu, Yanhong; Stein, Hans H

2014-01-01

An experiment was conducted to test the hypothesis that the standardised digestibility of Ca in calcium carbonate and Lithothamnium calcareum Ca is not different regardless of the level of dietary Ca, and that phytic acid affects the digestibility of Ca in these two ingredients to the same degree. The objectives were to determine where in the intestinal tract Ca absorption takes place and if there are measurable quantities of basal endogenous Ca fluxes in the stomach, small intestine or large intestine. Diets contained calcium carbonate or L. calcareum Ca as the sole source of Ca, 0% or 1% phytic acid and 0.4% or 0.8% Ca. A Ca-free diet was also formulated and used to measure endogenous fluxes and losses of Ca. Nine growing pigs (initial body weight 23.8 ± 1.3 kg) were cannulated in the duodenum and in the distal ileum, and faecal, ileal and duodenal samples were collected. Duodenal endogenous fluxes of Ca were greater (p < 0.05) than ileal endogenous fluxes and total tract endogenous losses of Ca, but ileal endogenous fluxes were less (p < 0.05) than total tract endogenous losses. Standardised digestibility of Ca was not affected by the level of phytic acid, but decreased (p < 0.05) as Ca level increased in L. calcareum Ca diets, but that was not the case if calcium carbonate was the source of Ca (interaction, p < 0.05). The standardised duodenal digestibility (SDD), standardised ileal digestibility (SID) and standardised total tract digestibility (STTD) of Ca were not different if calcium carbonate was the source of dietary Ca. However, the STTD of Ca in L. calcareum Ca was greater (p < 0.05) than the SID and SDD of Ca. The SDD, SID and STTD of Ca in calcium carbonate were greater (p < 0.05) than those of L. calcareum Ca. In conclusion, under the conditions of this experiment, standardised digestibility of Ca is not affected by the level of phytic acid, but may be affected by dietary Ca level depending on the Ca source. Calcium from calcium carbonate is mostly absorbed before the duodenum, but Ca from L. calcareum Ca is mostly absorbed in the jejunum and ileum.

Preparation and characterization of porous bioceramic layers on pure titanium surfaces obtained by micro-arc oxidation process

NASA Astrophysics Data System (ADS)

Chien, Chi-Sheng; Hung, Yu-Chien; Hong, Ting-Fu; Wu, Chung-Chun; Kuo, Tsung-Yuan; Lee, Tzer-Min; Liao, Tze-Yuan; Lin, Huan-Chang; Chuang, Cheng-Hsin

2017-03-01

Fluorapatite (FA) has better chemical and thermal stability than hydroxyapatite (HA), and has thus attracted significant interest for biomaterial applications in recent years. In this study, porous bioceramic layers were prepared on pure titanium surfaces using a micro-arc oxidation (MAO) technique with an applied voltage of 450 V and an oxidation time of 5 min. The MAO process was performed using three different electrolyte solutions containing calcium fluoride (CaF2), calcium acetate monohydrate (Ca(CH3COO)2·H2O), and sodium phosphate monobasic dihydrate (NaH2PO4·2H2O) mixed in ratios of 0:2:1, 1:1:1, and 2:0:1, respectively. The surface morphology, composition, micro-hardness, porosity, and biological properties of the various MAO coatings were examined and compared. The results showed that as the CaF2/Ca(CH3COO)2·H2O ratio increased, the elemental composition of the MAO coating transformed from HA, A-TiO2 (Anatase) and R-TiO2 (Rutile); to A-TiO2, R-TiO2, and a small amount of HA; and finally A-TiO2, R-TiO2, CaF2, TiP2O5, and FA. The change in elemental composition was accompanied by a higher micro-hardness and a lower porosity. The coatings exhibited a similar in vitro bioactivity performance during immersion in simulated body fluid for 7-28 days. Furthermore, for in initial in vitro biocompatibility tests performed for 24 h using Dulbecco's Modified Eagle Medium (DMEM) supplement containing 10%Fetal bovine serum, the attachment and spreading of osteoblast-like osteosarcoma MG63 cells were found to increase slightly with an increasing CaF2/Ca(CH3COO)2·H2O ratio. In general, the results presented in this study show that all three MAO coatings possess a certain degree of in vitro bioactivity and biocompatibility.

Calcium triggers reversal of calmodulin on nested anti-parallel sites in the IQ motif of the neuronal voltage-dependent sodium channel NaV1.2.

PubMed

Hovey, Liam; Fowler, C Andrew; Mahling, Ryan; Lin, Zesen; Miller, Mark Stephen; Marx, Dagan C; Yoder, Jesse B; Kim, Elaine H; Tefft, Kristin M; Waite, Brett C; Feldkamp, Michael D; Yu, Liping; Shea, Madeline A

2017-05-01

Several members of the voltage-gated sodium channel family are regulated by calmodulin (CaM) and ionic calcium. The neuronal voltage-gated sodium channel Na V 1.2 contains binding sites for both apo (calcium-depleted) and calcium-saturated CaM. We have determined equilibrium dissociation constants for rat Na V 1.2 IQ motif [IQRAYRRYLLK] binding to apo CaM (~3nM) and (Ca 2+ ) 4 -CaM (~85nM), showing that apo CaM binding is favored by 30-fold. For both apo and (Ca 2+ ) 4 -CaM, NMR demonstrated that Na V 1.2 IQ motif peptide (Na V 1.2 IQp ) exclusively made contacts with C-domain residues of CaM (CaM C ). To understand how calcium triggers conformational change at the CaM-IQ interface, we determined a solution structure (2M5E.pdb) of (Ca 2+ ) 2 -CaM C bound to Na V 1.2 IQp . The polarity of (Ca 2+ ) 2 -CaM C relative to the IQ motif was opposite to that seen in apo CaM C -Na v 1.2 IQp (2KXW), revealing that CaM C recognizes nested, anti-parallel sites in Na v 1.2 IQp . Reversal of CaM may require transient release from the IQ motif during calcium binding, and facilitate a re-orientation of CaM N allowing interactions with non-IQ Na V 1.2 residues or auxiliary regulatory proteins interacting in the vicinity of the IQ motif. Copyright © 2017 Elsevier B.V. All rights reserved.

Data on PKO biodiesel production using CaO catalyst from Turkey bones.

PubMed

Ayoola, A A; Fayomi, O S I; Usoro, I F

2018-08-01

In this research paper the production of biodiesel from palm kernel oil (PKO) using CaO obtained from waste turkey bones (WTB) and analytical grade calcium oxide was investigated. Treated WTB was reduced to fine particulate size of <150 µm and then calcinated at 800 °C for 3 h to increase its catalytic activity by its conversion from Calcium phosphate hydroxide (Ca 10 P 6 O 26 H 2 ) to CaO. X-ray diffraction (XRD) and X-ray fluorescent (XRF) analysis of the analytical grade CaO, uncalcined and calcined WTB were carried out to establish their elemental chemical composition. The transesterification reaction between the triglyceride of palm kernel oil (PKO) and methanol was carried out at a constant agitation speed of 600 rpm and temperature of 65 °C, with varied methanol to oil molar ratio (8-14), catalyst concentration (1-7 wt/wt%) and the reaction time (1-3 h). Minitab 17 software (using response surface method) was employed for the design of experiment and statistical analysis required in the transesterification process of biodiesel production. The qualities of the biodiesel produced were assessed and the results obtained showed conformity of the biodiesel produced to the ASTM standard for biodiesel.

Hunting increases phosphorylation of calcium/calmodulin-dependent protein kinase type II in adult barn owls.

PubMed

Nichols, Grant S; DeBello, William M

2015-01-01

Juvenile barn owls readily adapt to prismatic spectacles, whereas adult owls living under standard aviary conditions do not. We previously demonstrated that phosphorylation of the cyclic-AMP response element-binding protein (CREB) provides a readout of the instructive signals that guide plasticity in juveniles. Here we investigated phosphorylation of calcium/calmodulin-dependent protein kinase II (pCaMKII) in both juveniles and adults. In contrast to CREB, we found no differences in pCaMKII expression between prism-wearing and control juveniles within the external nucleus of the inferior colliculus (ICX), the major site of plasticity. For prism-wearing adults that hunted live mice and are capable of adaptation, expression of pCaMKII was increased relative to prism-wearing adults that fed passively on dead mice and are not capable of adaptation. This effect did not bear the hallmarks of instructive information: it was not localized to rostral ICX and did not exhibit a patchy distribution reflecting discrete bimodal stimuli. These data are consistent with a role for CaMKII as a permissive rather than an instructive factor. In addition, the paucity of pCaMKII expression in passively fed adults suggests that the permissive default setting is "off" in adults.

A Calcium Sensor-Regulated Protein Kinase, CALCINEURIN B-LIKE PROTEIN-INTERACTING PROTEIN KINASE19, Is Required for Pollen Tube Growth and Polarity1[OPEN

PubMed Central

Zhou, Liming; Lan, Wenzhi; Chen, Binqing; Fang, Wei; Luan, Sheng

2015-01-01

Calcium plays an essential role in pollen tube tip growth. However, little is known concerning the molecular basis of the signaling pathways involved. Here, we identified Arabidopsis (Arabidopsis thaliana) CALCINEURIN B-LIKE PROTEIN-INTERACTING PROTEIN KINASE19 (CIPK19) as an important element to pollen tube growth through a functional survey for CIPK family members. The CIPK19 gene was specifically expressed in pollen grains and pollen tubes, and its overexpression induced severe loss of polarity in pollen tube growth. In the CIPK19 loss-of-function mutant, tube growth and polarity were significantly impaired, as demonstrated by both in vitro and in vivo pollen tube growth assays. Genetic analysis indicated that disruption of CIPK19 resulted in a male-specific transmission defect. Furthermore, loss of polarity induced by CIPK19 overexpression was associated with elevated cytosolic Ca2+ throughout the bulging tip, whereas LaCl3, a Ca2+ influx blocker, rescued CIPK19 overexpression-induced growth inhibition. Our results suggest that CIPK19 may be involved in maintaining Ca2+ homeostasis through its potential function in the modulation of Ca2+ influx. PMID:25713341

Yeast respond to hypotonic shock with a calcium pulse

NASA Technical Reports Server (NTRS)

Batiza, A. F.; Schulz, T.; Masson, P. H.

1996-01-01

We have used the transgenic AEQUORIN calcium reporter system to monitor the cytosolic calcium ([Ca2+]cyt) response of Saccharomyces cerevisiae to hypotonic shock. Such a shock generates an almost immediate and transient rise in [Ca2+]cyt which is eliminated by gadolinium, a blocker of stretch-activated channels. In addition, this transient rise in [Ca2+]cyt is initially insensitive to 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), an extracellular calcium chelator. However, BAPTA abruptly attenuates the maintenance of that transient rise. These data show that hypotonic shock generates a stretch-activated channel-dependent calcium pulse in yeast. They also suggest that the immediate calcium influx is primarily generated from intracellular stores, and that a sustained increase in [Ca2+]cyt depends upon extracellular calcium.

Mapping Calcium Rich Ejecta in Two Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Fesen, Robert

2016-10-01

Type Ia supernovae (SNe Ia) are thermonuclear explosions of white dwarfs (WDs) in close binary systems with either a non-degenerate or WD companion. SN Ia explosion computations are quite challenging, involving a complex interplay of turbulent hydrodynamics, nuclear burning, conduction, radiative transfer in iron-group rich material and possibly magnetic fields leading to significant uncertainties. Several key questions about expansion asymmetries and the overall characteristics of SNe Ia could be resolved if one could obtain direct observations of the internal kinematics and elemental distributions of young SN Ia remnants.We propose to use WFC3/UVIS to obtain images of the normal Type Ia supernova remnant 0519-69.0 and the overluminous Type Ia supernova remnant 0509-67.5 in the LMC. The Ca II on-band F390M filter and off-band F336W and FQ422M filters will be used to determine the spatial extent and density distributions of the Ca-rich ejecta via resonance line absorption. Differences in the observed on and off band Ca II fluxes for LMC stars located behind these young 400 - 600 yr old remnants will yield calcium column density estimates for multiple lines-of-sight within these remnants. These results will be compared to the calcium distribution seen in SN 1885, a subluminous SN Ia in M31, already imaged by HST.The resulting calcium density distribution maps for both a normal and overluminous SN Ia events will provide powerful insights regarding the structure and kinematics of calcium-rich ejecta in three different type Ia subclass events, and unique empirical data with which to test current SN Ia explosion models.

Depletion of intracellular calcium stores facilitates the influx of extracellular calcium in platelet derived growth factor stimulated A172 glioblastoma cells.

PubMed

Vereb, G; Szöllösi, J; Mátyus, L; Balázs, M; Hyun, W C; Feuerstein, B G

1996-05-01

Calcium signaling in non-excitable cells is the consequence of calcium release from intracellular stores, at times followed by entry of extracellular calcium through the plasma membrane. To study whether entry of calcium depends upon the level of saturation of intracellular stores, we measured calcium channel opening in the plasma membrane of single confluent A172 glioblastoma cells stimulated with platelet derived growth factor (PDGF) and/or bradykinin (BK). We monitored the entry of extracellular calcium by measuring manganese quenching of Indo-1 fluorescence. PDGF raised intracellular calcium concentration ([Ca2+]i) after a dose-dependent delay (tdel) and then opened calcium channels after a dose-independent delay (tch). At higher doses (> 3 nM), BK increased [Ca2+]i after a tdel approximately 0 s, and tch decreased inversely with both dose and peak [Ca2+]i. Experiments with thapsigargin (TG), BK, and PDGF indicated that BK and PDGF share intracellular Ca2+ pools that are sensitive to TG. When these stores were depleted by treatment with BK and intracellular BAPTA, tdel did not change, but tch fell to almost 0 s in PDGF stimulated cells, indicating that depletion of calcium stores affects calcium channel opening in the plasma membrane. Our data support the capacitative model for calcium channel opening and the steady-state model describing quantal Ca2+ release from intracellular stores.

Disruption of the IS6-AID linker affects voltage-gated calcium channel inactivation and facilitation.

PubMed

Findeisen, Felix; Minor, Daniel L

2009-03-01

Two processes dominate voltage-gated calcium channel (Ca(V)) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The Ca(V)beta/Ca(V)alpha(1)-I-II loop and Ca(2+)/calmodulin (CaM)/Ca(V)alpha(1)-C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6-alpha-interaction domain (AID) linker provides a rigid connection between the pore and Ca(V)beta/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate Ca(V)1.2 (L-type) and Ca(V)2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt Ca(V)beta/I-II association sharply decelerate CDI and reduce a second Ca(2+)/CaM/Ca(V)alpha(1)-C-terminal-mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, Ca(V)beta and the IS6-AID linker, are essential for calcium-dependent modulation, and that both Ca(V)beta-dependent and CaM-dependent components couple to the pore by a common mechanism requiring Ca(V)beta and an intact IS6-AID linker.

Disruption of the IS6-AID Linker Affects Voltage-gated Calcium Channel Inactivation and Facilitation

PubMed Central

Findeisen, Felix

2009-01-01

Two processes dominate voltage-gated calcium channel (CaV) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The CaVβ/CaVα1-I-II loop and Ca2+/calmodulin (CaM)/CaVα1–C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6–α-interaction domain (AID) linker provides a rigid connection between the pore and CaVβ/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate CaV1.2 (L-type) and CaV2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt CaVβ/I-II association sharply decelerate CDI and reduce a second Ca2+/CaM/CaVα1–C-terminal–mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, CaVβ and the IS6-AID linker, are essential for calcium-dependent modulation, and that both CaVβ-dependent and CaM-dependent components couple to the pore by a common mechanism requiring CaVβ and an intact IS6-AID linker. PMID:19237593

Calcium signalling silencing in atrial fibrillation.

PubMed

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.

Plating and stripping calcium in an organic electrolyte

NASA Astrophysics Data System (ADS)

Wang, Da; Gao, Xiangwen; Chen, Yuhui; Jin, Liyu; Kuss, Christian; Bruce, Peter G.

2018-01-01

There is considerable interest in multivalent cation batteries, such as those based on magnesium, calcium or aluminium. Most attention has focused on magnesium. In all cases the metal anode represents a significant challenge. Recent work has shown that calcium can be plated and stripped, but only at elevated temperatures, 75 to 100 °C, with small capacities, typically 0.165 mAh cm-2, and accompanied by significant side reactions. Here we demonstrate that calcium can be plated and stripped at room temperature with capacities of 1 mAh cm-2 at a rate of 1 mA cm-2, with low polarization (~100 mV) and in excess of 50 cycles. The dominant product is calcium, accompanied by a small amount of CaH2 that forms by reaction between the deposited calcium and the electrolyte, Ca(BH4)2 in tetrahydrofuran (THF). This occurs in preference to the reactions which take place in most electrolyte solutions forming CaCO3, Ca(OH)2 and calcium alkoxides, and normally terminate the electrochemistry. The CaH2 protects the calcium metal at open circuit. Although this work does not solve all the problems of calcium as an anode in calcium-ion batteries, it does demonstrate that significant quantities of calcium can be plated and stripped at room temperature with low polarization.

Effect of phosphorus and calcium on zinc metabolism in man

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

Spencer, H.; Kramer, L.; Lesniak, M.

The effect of phosphorus on zinc metabolism was studied in adult men receiving different calcium intakes ranging from 200 to 2000 mg/day. The diet and urinary and fecal excretions were analyzed for Zn, P and Ca. Metabolic balances of these elements were determined for several weeks in each study phase. In control studies the dietary intake was 800 mg/day and in the experimental studies it was increased to 2000 mg/day by adding sodium glycerophosphate to the constant diet. The dietary Zn intake averaged 14.5 mg/day in the different studies. These studies have shown that increasing the P intake by amore » factor of 2.5, from 800 to 2000 mg/day, did not affect urinary or fecal Zn excretions nor the Zn balance. Similar results were obtained on increasing the Ca intake from 200 to 2000 mg/day.« less

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

PubMed Central

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

Mechanism of Calcium Lactate Facilitating Phytic Acid Degradation in Soybean during Germination.

PubMed

Hui, Qianru; Yang, Runqiang; Shen, Chang; Zhou, Yulin; Gu, Zhenxin

2016-07-13

Calcium lactate facilitates the growth and phytic acid degradation of soybean sprouts, but the mechanism is unclear. In this study, calcium lactate (Ca) and calcium lactate with lanthanum chloride (Ca+La) were used to treat soybean sprouts to reveal the relevant mechanism. Results showed that the phytic acid content decreased and the availability of phosphorus increased under Ca treatment. This must be due to the enhancement of enzyme activity related to phytic acid degradation. In addition, the energy metabolism was accelerated by Ca treatment. The energy status and energy metabolism-associated enzyme activity also increased. However, the transmembrane transport of calcium was inhibited by La(3+) and concentrated in intercellular space or between the cell wall and cell membrane; thus, Ca+La treatment showed reverse results compared with those of Ca treatment. Interestingly, gene expression did not vary in accordance with their enzyme activity. These results demonstrated that calcium lactate increased the rate of phytic acid degradation by enhancing growth, phosphorus metabolism, and energy metabolism.

Optimization of calcium concentration of saliva with phosphoryl oligosaccharides of calcium (POs-Ca) for enamel remineralization in vitro.

PubMed

Tanaka, Tomoko; Kobayashi, Takatsugu; Takii, Hiroshi; Kamasaka, Hiroshi; Ohta, Noboru; Matsuo, Tatsuhito; Yagi, Naoto; Kuriki, Takashi

2013-02-01

Phosphoryl oligosaccharides of calcium (POs-Ca) are highly soluble calcium source made from potato starch. The aim of this study was to investigate the optimal concentrations of POs-Ca for the remineralization of subsurface enamel lesions in vitro. Demineralized bovine enamel slabs (n=5) were remineralized in vitro for 24h at 37°C with artificial saliva (AS) containing 0-0.74% POs-Ca to adjust the Ca/P ratio to 0.4-3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n=11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl2-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann-Whitney U-test. The highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2±7.4%) was significantly higher than that for AS containing CaCl2 (12.5±11.3%) (mean±SD, p<0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7±10.9%) was also significantly higher than that for AS containing CaCl2 (23.1±13.5%) (p<0.05). The restored crystallites were oriented in the same directions as in sound enamel. POs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multiple, disparate roles for calcium signaling in apoptosis of human prostate and cervical cancer cells exposed to diindolylmethane.

PubMed

Savino, John A; Evans, Jodi F; Rabinowitz, Dorianne; Auborn, Karen J; Carter, Timothy H

2006-03-01

Diindolylmethane (DIM), derived from indole-3-carbinol in cruciferous vegetables, causes growth arrest and apoptosis of cancer cells in vitro. DIM also induces endoplasmic reticulum (ER) stress, and thapsigargin, a specific inhibitor of the sarcoplasmic reticulum/ER calcium-dependent ATPase, enhances this effect. We asked whether elevated cytosolic free calcium [Ca2+]i is required for cytotoxicity of DIM and thapsigargin in two cancer cells lines (C33A, from cervix, and DU145, from prostate). [Ca2+]i was measured in real-time by FURA-2 fluorescence. We tested whether DIM, thapsigargin, and DIM + thapsigargin cause apoptosis, measured by nucleosome release, under conditions that prevented elevation of [Ca2+]i, using both cell-permeable and cell-impermeable forms of the specific calcium chelator BAPTA. DIM, like thapsigargin, rapidly mobilized ER calcium. C33A and DU145 responded differently to perturbations in Ca2+ homeostasis, suggesting that DIM induces apoptosis by different mechanisms in these two cell lines and/or that calcium mobilization also activates different survival pathways in C33A and DU145. Apoptosis in C33A was independent of increased [Ca2+]i, suggesting that depletion of ER Ca2+ stores may be sufficient for cell killing, whereas apoptosis in DU145 required elevated [Ca2+]i for full response. Inhibitor studies using cyclosporin A and KN93 showed that Ca2+ signaling is important for cell survival but the characteristics of this response also differed in the two cell lines. Our results underscore the complex and variable nature of cellular responses to disrupted Ca2+ homeostasis and suggest that alteration Ca2+ homeostasis in the ER can induce cellular apoptosis by both calcium-dependent and calcium-independent mechanisms.

Ordering of calcium and vacancies in calcium catapleiite CaZr[Si{sub 3}O{sub 9}] • 2H{sub 2}O

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

Aksenov, S. M., E-mail: aks.crys@gmail.com; Portnov, A. M.; Chukanov, N. V.

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{sub 0.97}Na{sub 0.02}Zr{sub 1.01}Si{sub 3}O{sub 9} • 2H{sub 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{sup 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 themore » final R = 2.91%. The structure of calcium catapleiite under study is based on the microporous heteropolyhedral framework formed by ZrO{sub 6} octahedra and threemembered silicon–oxygen rings [Si{sub 3}O{sub 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{sup 2+} cationic conduction.« less

Extracellular calcium elicits a chemokinetic response from monocytes in vitro and in vivo

NASA Technical Reports Server (NTRS)

Olszak, I. T.; Poznansky, M. C.; Evans, R. H.; Olson, D.; Kos, C.; Pollak, M. R.; Brown, E. M.; Scadden, D. T.; O'Malley, B. W. (Principal Investigator)

2000-01-01

Recruitment of macrophages to sites of cell death is critical for induction of an immunologic response. Calcium concentrations in extracellular fluids vary markedly, and are particularly high at sites of injury or infection. We hypothesized that extracellular calcium participates in modulating the immune response, perhaps acting via the seven-transmembrane calcium-sensing receptor (CaR) on mature monocytes/macrophages. We observed a dose-dependent increase in monocyte chemotaxis in response to extracellular calcium or the selective allosteric CaR activator NPS R-467. In contrast, monocytes derived from mice deficient in CaR lacked the normal chemotactic response to a calcium gradient. Notably, CaR activation of monocytes bearing the receptor synergistically augmented the transmigration response of monocytes to the chemokine MCP-1 in association with increased cell-surface expression of its cognate receptor, CCR2. Conversely, stimulation of monocytes with MCP-1 or SDF-1alpha reciprocally increased CaR expression, suggesting a dual-enhancing interaction of Ca(2+) with chemokines in recruiting inflammatory cells. Subcutaneous administration in mice of Ca(2+), MCP-1, or (more potently) the combination of Ca(2+) and MCP-1, elicited an inflammatory infiltrate consisting of monocytes/macrophages. Thus extracellular calcium functions as an ionic chemokinetic agent capable of modulating the innate immune response in vivo and in vitro by direct and indirect actions on monocytic cells. Calcium deposition may be both consequence and cause of chronic inflammatory changes at sites of injury, infection, and atherosclerosis.

Fluoride Binding to Dental Biofilm Bacteria: Synergistic Effect with Calcium Questioned.

PubMed

Nóbrega, Diego Figueiredo; Leitão, Tarcísio Jorge; Cury, Jaime Aparecido; Tenuta, Livia Maria Andaló

2018-06-06

It has been suggested that fluoride binding to dental biofilm is enhanced when more bacterial calcium binding sites are available. However, this was only observed at high calcium and fluoride concentrations (i.e., when CaF2 precipitation may have occurred). We assessed fluoride binding to Streptococcus mutans pellets treated with calcium and fluoride at concentrations allowing CaF2 precipitation or not. Increasing calcium concentration resulted in a linear increase (p < 0.01) in fluoride concentration only in the pellets in which CaF2 precipitated. The results suggest that CaF2 precipitation, rather than bacterially bound fluoride, is responsible for the increase in fluoride binding to dental biofilm with the increase in calcium availability. © 2018 S. Karger AG, Basel.

Calcium-mediated signaling and calmodulin-dependent kinase regulate hepatocyte-inducible nitric oxide synthase expression.

PubMed

Zhang, Baochun; Crankshaw, Will; Nesemeier, Ryan; Patel, Jay; Nweze, Ikenna; Lakshmanan, Jaganathan; Harbrecht, Brian G

2015-02-01

Induced nitric oxide synthase (iNOS) is induced in hepatocytes by shock and inflammatory stimuli. Excessive NO from iNOS mediates shock-induced hepatic injury and death, so understanding the regulation of iNOS will help elucidate the pathophysiology of septic shock. In vitro, cytokines induce iNOS expression through activation of signaling pathways including mitogen-activated protein kinases and nuclear factor κB. Cytokines also induce calcium (Ca(2+)) mobilization and activate calcium-mediated intracellular signaling pathways, typically through activation of calmodulin-dependent kinases (CaMK). Calcium regulates NO production in macrophages but the role of calcium and calcium-mediated signaling in hepatocyte iNOS expression has not been defined. Primary rat hepatocytes were isolated, cultured, and induced to produce NO with proinflammatory cytokines. Calcium mobilization and Ca(2+)-mediated signaling were altered with ionophore, Ca(2+) channel blockers, and inhibitors of CaMK. The Ca(2+) ionophore A23187 suppressed cytokine-stimulated NO production, whereas Ethylene glycol tetraacetic acid and nifedipine increased NO production, iNOS messenger RNA, and iNOS protein expression. Inhibition of CaMK with KN93 and CBD increased NO production but the calcineurin inhibitor FK 506 decreased iNOS expression. These data demonstrate that calcium-mediated signaling regulates hepatocyte iNOS expression and does so through a mechanism independent of calcineurin. Changes in intracellular calcium levels may regulate iNOS expression during hepatic inflammation induced by proinflammatory cytokines. Copyright © 2015 Elsevier Inc. All rights reserved.

Expression of voltage-activated calcium channels in the early zebrafish embryo.

PubMed

Sanhueza, Dayán; Montoya, Andro; Sierralta, Jimena; Kukuljan, Manuel

2009-05-01

Increases in cytosolic calcium concentrations regulate many cellular processes, including aspects of early development. Calcium release from intracellular stores and calcium entry through non-voltage-gated channels account for signalling in non-excitable cells, whereas voltage-gated calcium channels (CaV) are important in excitable cells. We report the expression of multiple transcripts of CaV, identified by its homology to other species, in the early embryo of the zebrafish, Danio rerio, at stages prior to the differentiation of excitable cells. CaV mRNAs and proteins were detected as early as the 2-cell stages, which indicate that they arise from both maternal and zygotic transcription. Exposure of embryos to pharmacological blockers of CaV does not perturb early development significantly, although late effects are appreciable. These results suggest that CaV may have a role in calcium homeostasis and control of cellular process during early embryonic development.

Calcium polysulphide, its applications and emerging risk of environmental pollution-a review article.

PubMed

Dahlawi, Saad Mohammed; Siddiqui, Samreen

2017-01-01

Easy availability, preparation technique, and economic value make calcium polysulphide (CaS x ) a very useful inorganic chemical for various field and industrial applications. In this article, disparate applications of CaS x solution have been reviewed to suggest potential and future consolidation. This article also encompasses the physiochemical properties and production of CaS x solution, with critical appraisal on research focusing on CaS x application in agriculture industries and removal of potentially toxic elements (PTEs) from the environment. The kinetics of CaS x , technical issues associated with optimization of its dosage and environmental fate is also discussed in detail. This study covers almost all of the peer-reviewed research that has been performed since 1914. Some of the critiques in this article include the lack of integration between the exposure effect and the efficiency of treatment method, effects of oxidizing environments on the long-term performance of CaS x solution, and kinetics of CaS x solution with the PTEs. The working model of CaS x with PTEs is still system dependent, and therefore cannot be used with other applications. The kinetics of CaS x is described in detail with various phase stoichiometric reactions. Environmental fate is discussed based on applications, government reports, peer-reviewed articles and kinetics of CaS x , which provides a clear picture of emerging contaminants in the environment in relation to the insect resistance and ecotoxicology. Real time, lab based research articles are needed to identify toxicity limits of CaS x in environment in order to describe its effective permissible limit in environmental system. This review article provides a risk assessment of environmental pollution by CaS x based on its physicochemical characteristic, stoichiometry, kinetics, field, and industrial applications.

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

PubMed Central

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

First-Row Transition Metal Doping in Calcium Phosphate Bioceramics: A Detailed Crystallographic Study

PubMed Central

Renaudin, Guillaume; Gomes, Sandrine; Nedelec, Jean-Marie

2017-01-01

Doped calcium phosphate bioceramics are promising materials for bone repair surgery because of their chemical resemblance to the mineral constituent of bone. Among these materials, BCP samples composed of hydroxyapatite (Ca10(PO4)6(OH)2) and β-TCP (Ca3(PO4)2) present a mineral analogy with the nano-multi-substituted hydroxyapatite bio-mineral part of bones. At the same time, doping can be used to tune the biological properties of these ceramics. This paper presents a general overview of the doping mechanisms of BCP samples using cations from the first-row transition metals (from manganese to zinc), with respect to the applied sintering temperature. The results enable the preparation of doped synthetic BCP that can be used to tailor biological properties, in particular by tuning the release amounts upon interaction with biological fluids. Intermediate sintering temperatures stabilize the doping elements in the more soluble β-TCP phase, which favors quick and easy release upon integration in the biological environment, whereas higher sintering temperatures locate the doping elements in the weakly soluble HAp phase, enabling a slow and continuous supply of the bio-inspired properties. An interstitial doping mechanism in the HAp hexagonal channel is observed for the six investigated cations (Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) with specific characteristics involving a shift away from the center of the hexagonal channel (Fe3+, Co2+), cationic oxidation (Mn3+, Co3+), and also cationic reduction (Cu+). The complete crystallochemical study highlights a complex HAp doping mechanism, mainly realized by an interstitial process combined with calcium substitution for the larger cations of the series leading to potentially calcium deficient HAp. PMID:28772452

High-Resolution Synchrotron Radiation Imaging of Trace Metal Elemental Concentrations in Porites Coral

NASA Astrophysics Data System (ADS)

Cirino, M.; Dunbar, R. B.; Tangri, N.; Mehta, A.

2014-12-01

We investigated the use of synchrotron radiation for elemental imaging within the skeleton of a Porites coral from American Samoa to explore the fine-scale structure of strontium to calcium (Sr/Ca) variability. The use of a synchrotron for coral paleoclimate analysis is relatively new. The method provides a high resolution, two-dimensional elemental map of a coral surface. The aragonitic skeleton of Porites sp. colonies has been widely used for paleoclimate reconstruction as the oxygen isotope ratio (δ18O) signal varies with both sea surface temperature (SST) and sea surface salinity (SSS). Sr/Ca has been used in previous studies in conjunction with δ18O to deconvolve SST from SSS, as Sr/Ca in the coral skeleton varies with SST, but not SSS. However, recent studies suggest that in some cases Sr/Ca variability in coral does not reliably reflect changes in SST. We sought to address this puzzle by investigating Sr/Ca variability in Porites corals at a very fine spatial scale while also demonstrating the suitability of the synchrotron as a coral analysis tool. We also considered Sr/Ca variability as it pertains to the coral's structural elements. The Stanford Linear Accelerator Center synchrotron station generates collimated x-rays in the energy range of 4500-45000 eV with beam diameters as small as 20 μm. Synchrotron imaging allows faster and higher-resolution Sr/Ca analysis than does inductively coupled plasma mass spectrometry (ICP-MS). It also is capable of mapping spatial distributions of many elements, which aids in the development of a multiproxy approach to paleoclimate reconstruction. Imaging and analysis of the Porites coral using synchrotron radiation revealed an intricate sub-seasonal Sr/Ca signal, possibly correlating to a sub-monthly resolution. This signal, which seems unrelated to SST, dominates the annual signal.

Extracellular Calcium Has Multiple Targets to Control Cell Proliferation.

PubMed

Capiod, Thierry

2016-01-01

Calcium channels and the two G-protein coupled receptors sensing extracellular calcium, calcium-sensing receptor (CaSR) and GPRC6a, are the two main means by which extracellular calcium can signal to cells and regulate many cellular processes including cell proliferation, migration and invasion of tumoral cells. Many intracellular signaling pathways are sensitive to cytosolic calcium rises and conversely intracellular signaling pathways can modulate calcium channel expression and activity. Calcium channels are undoubtedly involved in the former while the CaSR and GPRC6a are most likely to interfere with the latter. As for neurotransmitters, calcium ions use plasma membrane channels and GPCR to trigger cytosolic free calcium concentration rises and intracellular signaling and regulatory pathways activation. Calcium sensing GPCR, CaSR and GPRC6a, allow a supplemental degree of control and as for metabotropic receptors, they not only modulate calcium channel expression but they may also control calcium-dependent K+ channels. The multiplicity of intracellular signaling pathways involved, their sensitivity to local and global intracellular calcium increase and to CaSR and GPRC6a stimulation, the presence of membrane signalplex, all this confers the cells the plasticity they need to convert the effects of extracellular calcium into complex physiological responses and therefore determine their fate.

Effects of microbial phytase on apparent and standardized total tract digestibility of calcium in calcium supplements fed to growing pigs.

PubMed

González-Vega, J C; Walk, C L; Stein, H H

2015-05-01

An experiment was conducted to test the hypothesis that differences in the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of Ca exist among Ca supplements and that inclusion of microbial phytase increases the ATTD and STTD of Ca. One hundred and four growing barrows (average initial BW of 17.73 ± 2.53 kg) were allotted to a randomized complete block design with 13 dietary treatments and 8 pigs per treatment. A basal diet containing corn, cornstarch, potato protein isolate, soybean oil, calcium carbonate, monosodium phosphate, vitamins, and minerals was formulated. Five additional diets were formulated by adding monocalcium phosphate (MCP), dicalcium phosphate (DCP), calcium carbonate, Lithothamnium calcareum Ca, or a high-Ca sugar beet co-product to the basal diet at the expense of cornstarch. Six additional diets that were similar to the previous 6 diets with the exception that they also contained 500 units per kilogram of microbial phytase were also formulated. A Ca-free diet was used to determine basal endogenous losses of Ca. Feces were collected using the marker-to-marker approach. Results indicated that regardless of inclusion of microbial phytase, MCP had the greatest (P < 0.05) ATTD and STTD of Ca. The ATTD and STTD of Ca in DCP were greater (P < 0.05) than in calcium carbonate, L. calcareumC a, or in the sugar beet co-product, but no differences were observed among the ATTD and STTD of Ca in calcium carbonate, L. calcareum Ca, or sugar beet co-product. Inclusion of microbial phytase increased (P < 0.05) the ATTD and STTD of Ca in the diets, but this was not the case in the Ca supplements. Regardless of inclusion of microbial phytase, the ATTD of P was greater ( P< 0.05) in pigs fed basal, MCP, or DCP diets than in pigs fed calcium carbonate, L. calcareum Ca, or the sugar beet co-product, but pigs fed calcium carbonate diets had greater ( P< 0.05) ATTD of P than pigs fed L. calcareumCa or the sugar beet co-product. Regardless of Ca source, inclusion of microbial phytase increased (P < 0.001) the ATTD of P. In conclusion, MCP has the greatest ATTD and STTD of Ca among the calcium supplements used in this experiment, followed by DCP. Basal, MCP, and DCP diets had greater ATTD of P than the other diets, and inclusion of microbial phytase increased the ATTD and STTD of Ca and the ATTD of P in the diets.

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

PubMed

Protti, D A; Uchitel, O D

1997-08-01

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

Natural and anthropogenic drivers of calcium depletion in a northern forest during the last millennium.

PubMed

Leys, Bérangère A; Likens, Gene E; Johnson, Chris E; Craine, Joseph M; Lacroix, Brice; McLauchlan, Kendra K

2016-06-21

The pace and degree of nutrient limitation are among the most critical uncertainties in predicting terrestrial ecosystem responses to global change. In the northeastern United States, forest growth has recently declined along with decreased soil calcium (Ca) availability, suggesting that acid rain has depleted soil Ca to the point where it may be a limiting nutrient. However, it is unknown whether the past 60 y of changes in Ca availability are strictly anthropogenic or partly a natural consequence of long-term ecosystem development. Here, we report a high-resolution millennial-scale record of Ca and 16 other elements from the sediments of Mirror Lake, a 15-ha lake in the White Mountains of New Hampshire surrounded by northern hardwood forest. We found that sedimentary Ca concentrations had been declining steadily for 900 y before regional Euro-American settlement. This Ca decline was not a result of serial episodic disturbances but instead the gradual weathering of soils and soil Ca availability. As Ca availability was declining, nitrogen availability concurrently was increasing. These data indicate that nutrient availability on base-poor, parent materials is sensitive to acidifying processes on millennial timescales. Forest harvesting and acid rain in the postsettlement period mobilized significant amounts of Ca from watershed soils, but these effects were exacerbated by the long-term pattern. Shifting nutrient limitation can potentially occur within 10,000 y of ecosystem development, which alters our assessments of the speed and trajectory of nutrient limitation in forests, and could require reformulation of global models of forest productivity.

Natural and anthropogenic drivers of calcium depletion in a northern forest during the last millennium

PubMed Central

Leys, Bérangère A.; Likens, Gene E.; Craine, Joseph M.; Lacroix, Brice; McLauchlan, Kendra K.

2016-01-01

The pace and degree of nutrient limitation are among the most critical uncertainties in predicting terrestrial ecosystem responses to global change. In the northeastern United States, forest growth has recently declined along with decreased soil calcium (Ca) availability, suggesting that acid rain has depleted soil Ca to the point where it may be a limiting nutrient. However, it is unknown whether the past 60 y of changes in Ca availability are strictly anthropogenic or partly a natural consequence of long-term ecosystem development. Here, we report a high-resolution millennial-scale record of Ca and 16 other elements from the sediments of Mirror Lake, a 15-ha lake in the White Mountains of New Hampshire surrounded by northern hardwood forest. We found that sedimentary Ca concentrations had been declining steadily for 900 y before regional Euro-American settlement. This Ca decline was not a result of serial episodic disturbances but instead the gradual weathering of soils and soil Ca availability. As Ca availability was declining, nitrogen availability concurrently was increasing. These data indicate that nutrient availability on base-poor, parent materials is sensitive to acidifying processes on millennial timescales. Forest harvesting and acid rain in the postsettlement period mobilized significant amounts of Ca from watershed soils, but these effects were exacerbated by the long-term pattern. Shifting nutrient limitation can potentially occur within 10,000 y of ecosystem development, which alters our assessments of the speed and trajectory of nutrient limitation in forests, and could require reformulation of global models of forest productivity. PMID:27298361

The onset of calcium carbonate nucleation: a density functional theory molecular dynamics and hybrid microsolvation/continuum study.

PubMed

Di Tommaso, Devis; de Leeuw, Nora H

2008-06-12

Density functional theory (Perdew-Burke-Ernzerhof) based methods have been used to study the structure and hydration environment of the building blocks of CaCO 3 in aqueous solutions of calcium bicarbonate and calcium carbonate. Car-Parrinello molecular dynamics simulations of Ca(2+)/CO3(2-) and Ca (2+)/HCO3(-) in explicit water were performed to investigate the formation of CaCO3 and the hydration shell of the solvated hetero-ion pair. Our simulations show that the formation of the monomer of CaCO3 occurs with an associative mechanism and that the dominant building block of calcium (bi)carbonate in aqueous solution is Ca[eta(1)-(H)CO3](H2O)5, i.e., the preferred hydration number is five, while the (bi)carbonate is coordinated to the calcium in a monodentate mode. This result agrees with static calculations, where a hybrid approach using a combination of explicit solvent molecules and a polarizable continuum model has been applied to compute the solvation free energies of calcium bicarbonate species. Furthermore, the discrete-continuum calculations predict that the Ca(HCO3)2 and Ca(HCO3)3(-) species are stable in an aqueous environment preferentially as Ca(HCO3)2(H2O)4 and Ca(HCO3)3(H2O)2(-), respectively.

Structure of a prokaryotic sodium channel pore reveals essential gating elements and an outer ion binding site common to eukaryotic channels.

PubMed

Shaya, David; Findeisen, Felix; Abderemane-Ali, Fayal; Arrigoni, Cristina; Wong, Stephanie; Nurva, Shailika Reddy; Loussouarn, Gildas; Minor, Daniel L

2014-01-23

Voltage-gated sodium channels (NaVs) are central elements of cellular excitation. Notwithstanding advances from recent bacterial NaV (BacNaV) structures, key questions about gating and ion selectivity remain. Here, we present a closed conformation of NaVAe1p, a pore-only BacNaV derived from NaVAe1, a BacNaV from the arsenite oxidizer Alkalilimnicola ehrlichei found in Mono Lake, California, that provides insight into both fundamental properties. The structure reveals a pore domain in which the pore-lining S6 helix connects to a helical cytoplasmic tail. Electrophysiological studies of full-length BacNaVs show that two elements defined by the NaVAe1p structure, an S6 activation gate position and the cytoplasmic tail "neck", are central to BacNaV gating. The structure also reveals the selectivity filter ion entry site, termed the "outer ion" site. Comparison with mammalian voltage-gated calcium channel (CaV) selectivity filters, together with functional studies, shows that this site forms a previously unknown determinant of CaV high-affinity calcium binding. Our findings underscore commonalities between BacNaVs and eukaryotic voltage-gated channels and provide a framework for understanding gating and ion permeation in this superfamily. © 2013. Published by Elsevier Ltd. All rights reserved.

Disruption of Calcium Homeostasis During Exercise as a Mediator of Bone Metabolism

DTIC Science & Technology

2015-10-01

Meeting of the American College of Sports Medicine (Appendix A). 15. SUBJECT TERMS calcium homeostasis, exercise, bone resorption, parathyroid hormone ... hormone (PTH). PTH can defend serum Ca by reducing urinary Ca excretion, increasing intestinal Ca absorption, and increasing mobilization of skeletal Ca...certain conditions. It is our contention that disruptions in calcium homeostasis during exercise lead to increases in parathyroid hormone (PTH) and

Transient Evolution of Nonmetallic Inclusions During Calcium Treatment of Molten Steel

NASA Astrophysics Data System (ADS)

Zhang, Lifeng; Liu, Yang; Zhang, Ying; Yang, Wen; Chen, Wei

2018-06-01

The transient evolution of nonmetallic inclusions after calcium addition in pipeline steels was investigated with a vacuum induction furnace. Samples were taken at 1, 5, 10, 15, and 20 minutes after calcium treatment in both MgO and Al2O3 crucibles. It was found that the total oxygen and the number density of inclusions were increased during calcium modification, while they were dropped to a low level in the last tapped sample. Due to the evaporation of calcium, inclusions were transferred from CaO-CaS to Al2O3-CaO-CaS, and then to Al2O3-CaO. The decomposition of CaS was highly dependent on the decrease of the total calcium and the increase of the total oxygen in the steel. Thermodynamic calculation was performed to predict the composition of inclusions considering the effect of the total oxygen and the total calcium and was validated by measurement. The relationship between the content of Al2O3 in inclusions and the ratio of the total calcium and the total oxygen in steels was measured and compared with the calculated one using thermodynamic software Factsage 7.0. The mass-transfer coefficient of the dissolved calcium in the steel was estimated in the range of 2.35 × 10-4 to 3.53 × 10-4 m/s.

Altervalent substitution of sodium for calcium in biogenic calcite and aragonite

NASA Astrophysics Data System (ADS)

Yoshimura, Toshihiro; Tamenori, Yusuke; Suzuki, Atsushi; Kawahata, Hodaka; Iwasaki, Nozomu; Hasegawa, Hiroshi; Nguyen, Luan T.; Kuroyanagi, Azumi; Yamazaki, Toshitsugu; Kuroda, Junichiro; Ohkouchi, Naohiko

2017-04-01

Sodium concentrations in biogenic CaCO3 are several thousands of parts per million, and, on a molar basis, Na is among the most abundant constituent minor element in these carbonates. Nevertheless, the chemical form of Na in CaCO3 is not well constrained. We used synchrotron X-ray spectroscopy to identify the dominant molecular host sites for Na in biogenic calcite and aragonite precipitated by corals, bivalves, and foraminifera. We also used the K-edge X-ray absorption near-edge structure to investigate the chemical environment of Na in biogenic calcium carbonates and identify the altervalent substitution of Na into Ca sites in the lattice structures of calcite and aragonite. Minor cation and anion concentrations in biogenic CaCO3 suggest that the principal substitution mechanism involves charge compensation through the creation of CO32- vacancies. The mostly homogeneous Na concentrations in the skeletal microstructures of the various biota we examined indicate that environmental and biological controls, such as temperature, skeletal microstructure, and calcification rates, have only minor influences on skeletal Na concentrations. A decrease of Na:Ca ratios with increasing age of foraminiferal shells picked from a Quaternary sediment core, indicates progressive release of Na, which suggests that structurally-substituted Na in biogenic CaCO3 is readily leached during burial diagenesis. Whereas the sediment that undergo diagenesis release some Na back to the water column, sodium co-precipitation in biogenic CaCO3 serves as a potential sink of Na for the ocean.

Synthesis of highly efficient CaO-based, self-stabilizing CO2 sorbents via structure-reforming of steel slag.

PubMed

Tian, Sicong; Jiang, Jianguo; Yan, Feng; Li, Kaimin; Chen, Xuejing

2015-06-16

Capturing anthropogenic CO2 in a cost-effective and highly efficient manner is one of the most challenging issues faced by scientists today. Herein, we report a novel structure-reforming approach to convert steel slag, a cheap, abundant, and nontoxic calcium-rich industrial waste, as the only feedstock into superior CaO-based, self-stabilizing CO2 sorbents. The CO2 capture capacity of all the steel slag-derived sorbents was improved more than 10-fold compared to the raw slag, with the maximum uptake of CO2 achieving at 0.50 gCO2 gsorbent(-1). Additionally, the initial steel slag-derived sorbent could retain 0.25 gCO2 gsorbent(-1), that is, a decay rate of only 12% over 30 carbonation-calcination cycles, the excellent self-stabilizing property allowed it to significantly outperform conventional CaO, and match with most of the existing synthetic CaO-based sorbents. A synergistic effect that facilitated CO2 capture by CaO-based sorbents was clearly recognized when Mg and Al, the most common elements in steel slag, coexisted with CaO in the forms of MgO and Al2O3, respectively. During the calcium looping process, MgO served as a well spacer to increase the porosity of sorbents together with Al2O3 serving as a durable stabilizer to coresist the sintering of CaCO3 grains at high temperatures.

Analysis of human nails by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Hosseinimakarem, Zahra; Tavassoli, Seyed Hassan

2011-05-01

Laser-induced breakdown spectroscopy (LIBS) is applied to analyze human fingernails using nanosecond laser pulses. Measurements on 45 nail samples are carried out and 14 key species are identified. The elements detected with the present system are: Al, C, Ca, Fe, H, K, Mg, N, Na, O, Si, Sr, Ti as well as CN molecule. Sixty three emission lines have been identified in the spectrum that are dominated by calcium lines. A discriminant function analysis is used to discriminate among different genders and age groups. This analysis demonstrates efficient discrimination among these groups. The mean concentration of each element is compared between different groups. Correlation between concentrations of elements in fingernails is calculated. A strong correlation is found between sodium and potassium while calcium and magnesium levels are inversely correlated. A case report on high levels of sodium and potassium in patients with hyperthyroidism is presented. It is shown that LIBS could be a promising technique for the analysis of nails and therefore identification of health problems.

Serum ionized calcium in dogs with chronic renal failure and metabolic acidosis.

PubMed

Kogika, Marcia M; Lustoza, Marcio D; Notomi, Marcia K; Wirthl, Vera A B F; Mirandola, Regina M S; Hagiwara, Mitika K

2006-12-01

Chronic renal failure (CRF) is a common disease in dogs, and many metabolic disorders can be observed, including metabolic acidosis and calcium and phosphorus disturbances. Acidosis may change the ionized calcium (i-Ca) fraction, usually increasing its concentration. In this study we evaluated the influence of acidosis on the serum concentration of i-Ca in dogs with CRF and metabolic acidosis. Dogs were studied in 2 groups: group I (control group = 40 clinically normal dogs) and group II (25 dogs with CRF and metabolic acidosis). Serum i-Ca was measured by an ion-selective electrode method; other biochemical analytes were measured using routine methods. The i-Ca concentration was significantly lower in dogs in group II than in group I; 56% of the dogs in group II were hypocalcemic. Hypocalcemia was observed in only 8% of dogs in group II when based on total calcium (t-Ca) concentration. No correlation between pH and i-Ca concentration was observed. A slight but significant correlation was detected between i-Ca and serum phosphorus concentration (r = -.284; P = .022), as well as between serum t-Ca and i-Ca concentration (r = .497; P < .0001). The i-Ca concentration in dogs with CRF and metabolic acidosis varied widely from that of t-Ca, showing the importance of determining the biologically active form of calcium. Metabolic acidosis did not influence the increase in i-Ca concentration, so other factors besides acidosis in CRF might alter the i-Ca fraction, such as hyperphosphatemia and other compounds that may form complexes with calcium.

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

PubMed

Najafpour, Mohammad Mahdi

2011-06-01

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

Novel Peptide with Specific Calcium-Binding Capacity from Schizochytrium sp. Protein Hydrolysates and Calcium Bioavailability in Caco-2 Cells

PubMed Central

Cai, Xixi; Lin, Jiaping; Wang, Shaoyun

2016-01-01

Peptide-calcium can probably be a suitable supplement to improve calcium absorption in the human body. In this study, a specific peptide Phe-Tyr (FY) with calcium-binding capacity was purified from Schizochytrium sp. protein hydrolysates through gel filtration chromatography and reversed phase HPLC. The calcium-binding capacity of FY reached 128.77 ± 2.57 μg/mg. Results of ultraviolet spectroscopy, fluorescence spectroscopy, and infrared spectroscopy showed that carboxyl groups, amino groups, and amido groups were the major chelating sites. FY-Ca exhibited excellent thermal stability and solubility, which were beneficial to be absorbed and transported in the basic intestinal tract of the human body. Moreover, the calcium bioavailability in Caco-2 cells showed that FY-Ca could enhance calcium uptake efficiency by more than three times when compared with CaCl2, and protect calcium ions against dietary inhibitors, such as tannic acid, oxalate, phytate, and Zn2+. Our findings further the progress of algae-based peptide-calcium, suggesting that FY-Ca has the potential to be developed as functionally nutraceutical additives. PMID:28036002

Coupled nitrogen and calcium cycles in forests of the Oregon Coast Range

USGS Publications Warehouse

Perakis, S.S.; Maguire, D.A.; Bullen, T.D.; Cromack, K.; Waring, R.H.; Boyle, J.R.

2006-01-01

Nitrogen (N) is a critical limiting nutrient that regulates plant productivity and the cycling of other essential elements in forests. We measured foliar and soil nutrients in 22 young Douglas-fir stands in the Oregon Coast Range to examine patterns of nutrient availability across a gradient of N-poor to N-rich soils. N in surface mineral soil ranged from 0.15 to 1.05% N, and was positively related to a doubling of foliar N across sites. Foliar N in half of the sites exceeded 1.4% N, which is considered above the threshold of N-limitation in coastal Oregon Douglas-fir. Available nitrate increased five-fold across this gradient, whereas exchangeable magnesium (Mg) and calcium (Ca) in soils declined, suggesting that nitrate leaching influences base cation availability more than soil parent material across our sites. Natural abundance strontium isotopes (87Sr/86Sr) of a single site indicated that 97% of available base cations can originate from atmospheric inputs of marine aerosols, with negligible contributions from weathering. Low annual inputs of Ca relative to Douglas-fir growth requirements may explain why foliar Ca concentrations are highly sensitive to variations in soil Ca across our sites. Natural abundance calcium isotopes (??44Ca) in exchangeable and acid leachable pools of surface soil measured at a single site showed 1 per mil depletion relative to deep soil, suggesting strong Ca recycling to meet tree demands. Overall, the biogeochemical response of these Douglas-fir forests to gradients in soil N is similar to changes associated with chronic N deposition in more polluted temperate regions, and raises the possibility that Ca may be deficient on excessively N-rich sites. We conclude that wide gradients in soil N can drive non-linear changes in base-cation biogeochemistry, particularly as forests cross a threshold from N-limitation to N-saturation. The most acute changes may occur in forests where base cations are derived principally from atmospheric inputs. ?? 2006 Springer Science+Business Media, Inc.

Trichomes of Tobacco Excrete Zinc as Zinc-Substituted Calcium Carbonate and Other Zinc-Containing Compounds1[W

PubMed Central

Sarret, Géraldine; Harada, Emiko; Choi, Yong-Eui; Isaure, Marie-Pierre; Geoffroy, Nicolas; Fakra, Sirine; Marcus, Matthew A.; Birschwilks, Mandy; Clemens, Stephan; Manceau, Alain

2006-01-01

Tobacco (Nicotiana tabacum L. cv Xanthi) plants were exposed to toxic levels of zinc (Zn). Zn exposure resulted in toxicity signs in plants, and these damages were partly reduced by a calcium (Ca) supplement. Confocal imaging of intracellular Zn using Zinquin showed that Zn was preferentially accumulated in trichomes. Exposure to Zn and Zn + Ca increased the trichome density and induced the production of Ca/Zn mineral grains on the head cells of trichomes. These grains were aggregates of submicrometer-sized crystals and poorly crystalline material and contained Ca as major element, along with subordinate amounts of Zn, manganese, potassium, chlorine, phosphorus, silicon, and magnesium. Micro x-ray diffraction revealed that the large majority of the grains were composed essentially of metal-substituted calcite (CaCO3). CaCO3 polymorphs (aragonite and vaterite) and CaC2O4 (Ca oxalate) mono- and dihydrate also were identified, either as an admixture to calcite or in separate grains. Some grains did not diffract, although they contained Ca, suggesting the presence of amorphous form of Ca. The presence of Zn-substituted calcite was confirmed by Zn K-edge micro-extended x-ray absorption fine structure spectroscopy. Zn bound to organic compounds and Zn-containing silica and phosphate were also identified by this technique. The proportion of Zn-substituted calcite relative to the other species increased with Ca exposure. The production of Zn-containing biogenic calcite and other Zn compounds through the trichomes is a novel mechanism involved in Zn detoxification. This study illustrates the potential of laterally resolved x-ray synchrotron radiation techniques to study biomineralization and metal homeostasis processes in plants. PMID:16731580

Molecular and biochemical evidence for the involvement of calcium/calmodulin in auxin action

NASA Technical Reports Server (NTRS)

Yang, T.; Poovaiah, B. W.

2000-01-01

The use of (35)S-labeled calmodulin (CaM) to screen a corn root cDNA expression library has led to the isolation of a CaM-binding protein, encoded by a cDNA with sequence similarity to small auxin up RNAs (SAURs), a class of early auxin-responsive genes. The cDNA designated as ZmSAUR1 (Zea mays SAURs) was expressed in Escherichia coli, and the recombinant protein was purified by CaM affinity chromatography. The CaM binding assay revealed that the recombinant protein binds to CaM in a calcium-dependent manner. Deletion analysis revealed that the CaM binding site was located at the NH(2)-terminal domain. A synthetic peptide of amino acids 20-45, corresponding to the potential CaM binding region, was used for calcium-dependent mobility shift assays. The synthetic peptide formed a stable complex with CaM only in the presence of calcium. The CaM affinity assay indicated that ZmSAUR1 binds to CaM with high affinity (K(d) approximately 15 nM) in a calcium-dependent manner. Comparison of the NH(2)-terminal portions of all of the characterized SAURs revealed that they all contain a stretch of the basic alpha-amphiphilic helix similar to the CaM binding region of ZmSAUR1. CaM binds to the two synthetic peptides from the NH(2)-terminal regions of Arabidopsis SAUR-AC1 and soybean 10A5, suggesting that this is a general phenomenon for all SAURs. Northern analysis was carried out using the total RNA isolated from auxin-treated corn coleoptile segments. ZmSAUR1 gene expression began within 10 min, increased rapidly between 10 and 60 min, and peaked around 60 min after 10 microM alpha-naphthaleneacetic acid treatment. These results indicate that ZmSAUR1 is an early auxin-responsive gene. The CaM antagonist N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide hydrochloride inhibited the auxin-induced cell elongation but not the auxin-induced expression of ZmSAUR1. This suggests that calcium/CaM do not regulate ZmSAUR1 at the transcriptional level. CaM binding to ZmSAUR1 in a calcium-dependent manner suggests that calcium/CaM regulate ZmSAUR1 at the post-translational level. Our data provide the first direct evidence for the involvement of calcium/CaM-mediated signaling in auxin-mediated signal transduction.

The effects of thermal stimuli on intracellular calcium change and histamine releases in rat basophilic leukemia mast cells

NASA Astrophysics Data System (ADS)

Wu, Zu-Hui; Zhu, Dan; Chen, Ji-Yao; Zhou, Lu-Wei

2012-05-01

The effects of thermal stimuli on rat basophilic leukemia mast cells were studied. The cells in calcium-contained or calcium-free buffers were thermally stimulated in the temperature range of 25-60 °C. The corresponding calcium ion concentration in cells [Ca2+]i as well as the released histamine from cells was measured with fluorescence staining methods. The ruthenium red (RR), a block of membrane calcium channels (transient receptor potential family V (TRPV)), was used in experiments. Under the stimulus of 25-50 °C, no significant difference on [Ca2+]i was found between these three groups of the cells in calcium-contained buffer without or with RR and cells in calcium-free saline, indicating that the increased calcium in cytosol did not result from the extracellular buffer but came from the intracellular calcium stores. The [Ca2+]i continuously increased under the temperature of 50-60 °C, but the RR and calcium-free saline can obviously diminish the [Ca2+]i increase at these high temperatures, reflecting that the opening of the TRPV2 channels leads to a calcium influx resulting in the [Ca2+]i increment. The histamine release also became significant in these cases. Since the released histamine is a well-known mediator for the microcirculation promotion, the histamine release from mast cells could be one of the mechanisms of thermal therapy.

Synthesis of CaCu3Ti4O12 by modified Sol-gel method with Hydrothermal process

NASA Astrophysics Data System (ADS)

Masingboon, C.; Rungruang, S.

2017-09-01

CaCu3Ti4O12 powders were synthesized by modified Sol-gel method with Hydrothermal process using Ca(NO3)2· 4H2O, Cu(NO3)2·3H2O, Ti(OC3H7)4 and freshly extracted egg white (ovalbumin) in aqueous medium. The precursor was calcined at 800, 900 and 1000 °C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, TEM and EDX. The XRD results indicated that all calcined samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CaTiO3, CuO and TiO2. TEM micrographs showed particle size 100 - 500 nm and EDX results showed elements of CaCu3Ti4O12 powders have calcium, copper, titanium and oxygen.

Monthly Strontium/Calcium oscillations in symbiotic coral aragonite: Biological effects limiting the precision of the paleotemperature proxy

USGS Publications Warehouse

Meibom, A.; Stage, M.; Wooden, J.; Constantz, B.R.; Dunbar, R.B.; Owen, A.; Grumet, N.; Bacon, C.R.; Chamberlain, C.P.

2003-01-01

In thermodynamic equilibrium with sea water the Sr/Ca ratio of aragonite varies predictably with temperature and the Sr/Ca ratio in coral have thus become a frequently used proxy for past Sea Surface Temperature (SST). However, biological effects can offset the Sr/Ca ratio from its equilibrium value. We report high spatial resolution ion microprobe analyses of well defined skeletal elements in the reef-building coral Porites lutea that reveal distinct monthly oscillations in the Sr/Ca ratio, with an amplitude in excess of ten percent. The extreme Sr/Ca variations, which we propose result from metabolic changes synchronous with the lunar cycle, introduce variability in Sr/Ca measurements based on conventional sampling techniques well beyond the analytical precision. These variations can limit the accuracy of Sr/Ca paleothermometry by conventional sampling techniques to about 2??C. Our results may help explain the notorious difficulties involved in obtaining an accurate and consistent calibration of the Sr/Ca vs. SST relationship.

Calcium signaling and cell proliferation.

PubMed

Pinto, Mauro Cunha Xavier; Kihara, Alexandre Hiroaki; Goulart, Vânia A M; Tonelli, Fernanda M P; Gomes, Katia N; Ulrich, Henning; Resende, Rodrigo R

2015-11-01

Cell proliferation is orchestrated through diverse proteins related to calcium (Ca(2+)) signaling inside the cell. Cellular Ca(2+) influx that occurs first by various mechanisms at the plasma membrane, is then followed by absorption of Ca(2+) ions by mitochondria and endoplasmic reticulum, and, finally, there is a connection of calcium stores to the nucleus. Experimental evidence indicates that the fluctuation of Ca(2+) from the endoplasmic reticulum provides a pivotal and physiological role for cell proliferation. Ca(2+) depletion in the endoplasmatic reticulum triggers Ca(2+) influx across the plasma membrane in an phenomenon called store-operated calcium entries (SOCEs). SOCE is activated through a complex interplay between a Ca(2+) sensor, denominated STIM, localized in the endoplasmic reticulum and a Ca(2+) channel at the cell membrane, denominated Orai. The interplay between STIM and Orai proteins with cell membrane receptors and their role in cell proliferation is discussed in this review. Copyright © 2015 Elsevier Inc. All rights reserved.

Calcium movements during pigment aggregation in freshwater shrimp chromatophores.

PubMed

Ribeiro, Márcia; McNamara, John Campbell

2007-02-01

Pigment granule migration within crustacean chromatophores provides an excellent model with which to investigate cytoplasmic movements, given the antagonistic, neurosecretory peptide regulation of granule translocation, and the absence of innervation in these large, brightly colored cells. Red pigment-concentrating hormone (RPCH) induces pigment aggregation in shrimp chromatophores via an increase in intracellular Ca2+; however, how this increase is brought about is not known. To examine the putative Ca2+ movements leading to pigment translocation in red, ovarian chromatophores of the freshwater shrimp, Macrobrachium olfersii, this study manipulates intra- and extracellular Ca2+ employing ER Ca2+-ATPase inhibitors, ryanodine-sensitive, ER Ca2+ channel blockers, and EDTA/EGTA-buffered A23187/Ca2+-containing salines. Our findings reveal that during pigment aggregation, cytosolic Ca2+ apparently increases from an intracellular source, the abundant SER, loaded by the SERCA and released through ryanodine-sensitive receptor/channels, triggered by capacitative calcium influx and/or calcium-induced calcium release mechanisms. Aggregation also depends on external calcium, which may modulate RPCH/receptor coupling. Such calcium-regulated pigment movements form the basis of a complex system of chromatic adaptation, which confers selective advantages like camouflage and protection against ultra-violet radiation to this palaemonid shrimp.

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

PubMed Central

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

Effects of adrenalectomy on the control and adrenergic regulation of cytosolic free calcium in hepatocytes

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

Freudenrich, C.C.

1987-01-01

The purpose of this study was to investigate the effects of adrenalectomy on the control and ..cap alpha..-adrenergic regulation of the concentration of cytosolic free calcium (Ca/sub i/) in hepatocytes. In hepatocytes isolated from adrenalectomized (adx) and sham-operated male rats 7-1 days after surgery, Ca/sub i/ at rest and in response to epinephrine (EPI) was measured with the calcium-sensitive photoprotein aequorin, /sup 45/Ca efflux was measured, and Ca/sup 2 +/ release from intracellular stores in response to inositol triphosphate (IP/sub 3/) was measured in saponin-permeabilized cells. Liver calmodulin content was also assayed by radioimmunoassay. It was found in adx ratsmore » that the resting Ca/sub i/ was elevated, the rise in Ca/sub i/ during EPI stimulation was reduced at physiological EPI concentrations, and the rise in calcium efflux evoked by EPI was reduced. Furthermore, the slope of the relationship between Ca/sub i/ and calcium efflux was reduced 60% in adx. Adx did not alter the characteristics of Ca/sup 2 +/ release from intracellular calcium pools in response to IP/sub 3/ in permeabilized cells. Finally, the liver calmodulin contents were not significantly different between the 2 groups.« less

Effect of the calcium to phosphorus ratio on the setting properties of calcium phosphate bone cements.

PubMed

Vlad, M D; Gómez, S; Barracó, M; López, J; Fernández, E

2012-09-01

α-Tricalcium phosphate (α-TCP) has become the main reactant of most experimental and commercial ceramic bone cements. It has calcium-to-phosphorus (Ca/P) ratio of 1.50. The present study expands and reports on the microstructures and mechanical properties of calcium phosphate (CP) cements containing sintered monolithic reactants obtained in the interval 1.29 < Ca/P < 1.77. The study focuses on their cement setting and hardening properties as well as on their microstructure and crystal phase evolution. The results showed that: (a) CP-cements made with reactants with Ca/P ratio other than 1.50 have longer setting and lower hardening properties; (b) CP-cements reactivity was clearly affected by the Ca/P ratio of the starting reactant; (c) reactants with Ca/P < 1.50 were composed of several phases, calcium pyrophosphate and α- and β-TCP. Similarly, reactants with Ca/P > 1.50 were composed of α-TCP, tetracalcium phosphate and hydroxyapatite; (d) only the reactant with Ca/P = 1.50 was monophasic and was made of α-TCP, which transformed during the setting into calcium deficient hydroxyapatite; (e) CP-cements developed different crystal microstructures with specific features depending on the Ca/P ratio of the starting reactant.

Effects of Astragalus membranaceus with supplemental calcium on bone mineral density and bone metabolism in calcium-deficient ovariectomized rats.

PubMed

Kang, Se-Chan; Kim, Hee Jung; Kim, Mi-Hyun

2013-01-01

It has been reported that Astragalus membranaceus, an Asian traditional herb, has an estrogenic effect in vitro. To examine the possible role of A. membranaceus extract with supplemental calcium (Ca) on bone status in calcium-deficient (LCa) ovariectomized (OVX) rats, a total of 48 female rats were divided into six groups: (1) normal control, (2) sham operation with LCa (sham-LCa), (3) OVX with LCa (OVX-LCa), (4) A. membranaceus supplementation with OVX-LCa (OVX-MLCa), (5) Ca supplementation with OVX (OVX-Ca), and (6) A. membranaceus and Ca supplementation with OVX (OVX-MCa). A. membranaceus ethanol extract (500 mg/kg BW) and/or Ca (800 mg/kg BW) were administered orally for 8 weeks along with a Ca-deficient diet. Results revealed that Ca supplementation with or without A. membranaceus extract significantly improved bone mineral density, biomechanical strength, and ash weight of the femur and tibia in OVX rats. High Ca with A. membranaceus combination supplementation significantly increased the ash weight of the femur and tibia and decreased urinary Ca excretion compared with supplementation of Ca alone. Uterine weight was not changed by A. membranaceus administration in OVX rats. These results suggest that A. membranaceus extract combined with supplemental Ca may be more protective against the Ca loss of bone than A. membranaceus or supplementation of Ca alone in calcium-insufficient postmenopausal women.

Particle size of calcium carbonate does not affect apparent and standardized total tract digestibility of calcium, retention of calcium, or growth performance of growing pigs.

PubMed

Merriman, L A; Stein, H H

2016-09-01

Two experiments were conducted to evaluate particle size of calcium carbonate used in diets fed to growing pigs. Experiment 1 was conducted to determine apparent total tract digestibility (ATTD), standardized total tract digestibility (STTD), and retention of Ca among diets containing calcium carbonate produced to different particle sizes, and Exp. 2 was conducted to determine if growth performance of weanling pigs is affected by particle size of calcium carbonate. In Exp. 1, 4 diets based on corn and potato protein isolate were formulated to contain 0.70% Ca and 0.33% standardized total tract digestible P, but the calcium carbonate used in the diets was ground to 4 different particle sizes (200, 500, 700, or 1,125 μm). A Ca-free diet was formulated to determine basal endogenous losses of Ca. In Exp. 2, 4 diets were based on corn and soybean meal and the only difference among diets was that each diet contained calcium carbonate ground to the 4 particle sizes used in Exp. 1. In Exp. 1, 40 barrows (15.42 ± 0.70 kg initial BW) were allotted to the 5 diets with 8 replicate pigs per diet using a randomized complete block design, and in Exp. 2, 128 pigs with an initial BW of 9.61 ± 0.09 kg were randomly allotted to 4 experimental diets. Results of Exp. 1 indicated that basal endogenous losses of Ca were 0.329 g/kg DMI. The ATTD of Ca was 70.0 ± 3.2, 74.3 ± 2.7, 70.0 ± 2.9, and 72.1 ± 2.7 and the STTD of Ca was 74.2 ± 3.2, 78.5 ± 2.7, 74.1 ± 2.9, and 76.2 ± 2.7 for calcium carbonate ground to 200, 500, 700, or 1,125 μm, respectively. Retention of Ca was 67.4 ± 3.1, 70.4 ± 2.6, 63.9 ± 2.8, and 67.2 ± 2.2 for diets containing calcium carbonate ground to 200, 500, 700, or 1,125 μm, respectively. There were no differences among diets for ATTD of Ca, STTD of Ca, or retention of Ca. The ATTD of P was 64.5 ± 1.7, 66.8 ± 2.6, 64.2 ± 3.0, and 63.2 ± 1.7% and retention of P was 61.4 ± 1.4, 63.8 ± 2.8, 61.9 ± 2.8, and 60.9 ± 1.5 for diets containing calcium carbonate ground to 200, 500, 700, or 1,125 μm, respectively. Neither ATTD of P nor retention of P was influenced by the particle size of calcium carbonate. Results of Exp. 2 indicated that ADG, ADFI, and G:F were not impacted by the particle size of calcium carbonate. In conclusion, particle size of calcium carbonate did not affect ATTD of Ca, STTD of Ca, or retention of Ca; ATTD of P or retention of P; or growth performance of pigs. Any particle size of calcium carbonate in the range from 200 to 1,125 μm can therefore be used in diets fed to pigs.

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

PubMed

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.

Calmodulin Activation by Calcium Transients in the Postsynaptic Density of Dendritic Spines

PubMed Central

Keller, Daniel X.; Franks, Kevin M.; Bartol, Thomas M.; Sejnowski, Terrence J.

2008-01-01

The entry of calcium into dendritic spines can trigger a sequence of biochemical reactions that begins with the activation of calmodulin (CaM) and ends with long-term changes to synaptic strengths. The degree of activation of CaM can depend on highly local elevations in the concentration of calcium and the duration of transient increases in calcium concentration. Accurate measurement of these local changes in calcium is difficult because the spaces are so small and the numbers of molecules are so low. We have therefore developed a Monte Carlo model of intracellular calcium dynamics within the spine that included calcium binding proteins, calcium transporters and ion channels activated by voltage and glutamate binding. The model reproduced optical recordings using calcium indicator dyes and showed that without the dye the free intracellular calcium concentration transient was much higher than predicted from the fluorescent signal. Excitatory postsynaptic potentials induced large, long-lasting calcium gradients across the postsynaptic density, which activated CaM. When glutamate was released at the synapse 10 ms before an action potential occurred, simulating activity patterns that strengthen hippocampal synapses, the calcium gradient and activation of CaM in the postsynaptic density were much greater than when the order was reversed, a condition that decreases synaptic strengths, suggesting a possible mechanism underlying the induction of long-term changes in synaptic strength. The spatial and temporal mechanisms for selectivity in CaM activation demonstrated here could be used in other signaling pathways. PMID:18446197

Calcium fertilization increases the concentration of calcium in sapwood and calcium oxalate in foliage of red spruce

Treesearch

Kevin T. Smith; Walter C. Shortle; Jon H. Connolly; Rakesh Minocha; Jody Jellison

2009-01-01

Calcium cycling plays a key role in the health and productivity of red spruce forests in the northeastern US. A portion of the flowpath of calcium within forests includes translocation as Ca2+ in sapwood and accumulation as crystals of calcium oxalate in foliage. Concentrations of Ca in these tree tissues have been used as markers of...

A microstructural study of the degradation and calcium release from hydroxyapatite-calcium oxide ceramics made by infiltration.

PubMed

Zhang, Qinghao; Schmelzer, Eva; Gerlach, Jörg C; Nettleship, Ian

2017-04-01

Hydroxyapatite pellets, partially densified in a low-temperature heat treatment, were infiltrated with calcium nitrate solution followed by in-situ precipitation of Ca(OH) 2 and CaCO 3 . The infiltrated bodies were then densified to high relative density and the calcium carbonate transformed to calcium oxide during sintering and resulted in biphasic hydroxyapatite-CaO ceramics. This work investigated the influence of the infiltration on surface morphology, weight change, and microstructural-level degradation caused by exposure to saline at pH=7.4 and a temperature of 20°C. The CaO rendered the materials more susceptible to degradation, and released calcium into the saline faster than single phase, calcium deficient hydroxyapatite (HA) that were used as a control. In consequence, these ceramics could be used to release calcium into the culture microenvironments of bone tissue or bone marrow cells next to a scaffold surface. Copyright © 2016 Elsevier B.V. All rights reserved.

SLP-2 negatively modulates mitochondrial sodium-calcium exchange.

PubMed

Da Cruz, Sandrine; De Marchi, Umberto; Frieden, Maud; Parone, Philippe A; Martinou, Jean-Claude; Demaurex, Nicolas

2010-01-01

Mitochondria play a major role in cellular calcium homeostasis. Despite decades of studies, the molecules that mediate and regulate the transport of calcium ions in and out of the mitochondrial matrix remain unknown. Here, we investigate whether SLP-2, an inner membrane mitochondrial protein of unknown function, modulates the activity of mitochondrial Ca(2+) transporters. In HeLa cells depleted of SLP-2, the amplitude and duration of mitochondrial Ca(2+) elevations evoked by agonists were decreased compared to control cells. SLP-2 depletion increased the rates of calcium extrusion from mitochondria. This effect disappeared upon Na(+) removal or addition of CGP-37157, an inhibitor of the mitochondrial Na(+)/Ca(2+) exchanger, and persisted in permeabilized cells exposed to a fixed cytosolic Na(+) and Ca(2+) concentration. The rates of mitochondrial Ca(2+) extrusion were prolonged in SLP-2 over-expressing cells, independently of the amplitude of mitochondrial Ca(2+) elevations. The amplitude of cytosolic Ca(2+) elevations was increased by SLP-2 depletion and decreased by SLP-2 over-expression. These data show that SLP-2 modulates mitochondrial calcium extrusion, thereby altering the ability of mitochondria to buffer Ca(2+) and to shape cytosolic Ca(2+) signals. 2009 Elsevier Ltd. All rights reserved.

Inhibition of recombinant Ca(v)3.1 (alpha(1G)) T-type calcium channels by the antipsychotic drug clozapine.

PubMed

Choi, Kee-Hyun; Rhim, Hyewhon

2010-01-25

Low voltage-activated T-type calcium channels are involved in the regulation of the neuronal excitability, and could be subject to many antipsychotic drugs. The effects of clozapine, an atypical antipsychotic drug, on recombinant Ca(v)3.1 T-type calcium channels heterologously expressed in human embryonic kidney 293 cells were examined using whole-cell patch-clamp recordings. At a standard holding potential of -100 mV, clozapine inhibited Ca(v)3.1 currents with an IC(50) value of 23.7+/-1.3 microM in a use-dependent manner. However, 10 microM clozapine inhibited more than 50% of the Ca(v)3.1 currents in recordings at a more physiologically relevant holding potential of -75 mV. Clozapine caused a significant hyperpolarizing shift in the steady-state inactivation curve of the Ca(v)3.1 channels, which is presumably the main mechanism accounting for the inhibition of the Ca(v)3.1 currents. In addition, clozapine slowed Ca(v)3.1 deactivation and inactivation kinetics but not activation kinetics. Clozapine-induced changes in deactivation and inactivation rates of the Ca(v)3.1 channel gating would likely facilitate calcium influx via Ca(v)3.1 T-type calcium channels. Thus, clozapine may exert its therapeutic and/or side effects by altering cell's excitability and firing properties through actions on T-type calcium channels.

Novel calcium recognition constructions in proteins: Calcium blade and EF-hand zone

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

Denesyuk, Alexander I., E-mail: adenesyu@abo.fi; Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino 142290; Permyakov, Sergei E.

Metal ions can regulate various cell processes being first, second or third messengers, and some of them, especially transition metal ions, take part in catalysis in many enzymes. As an intracellular ion, Ca{sup 2+} is involved in many cellular functions from fertilization and contraction, cell differentiation and proliferation, to apoptosis and cancer. Here, we have identified and described two novel calcium recognition environments in proteins: the calcium blade zone and the EF-hand zone, common to 12 and 8 different protein families, respectively. Each of the two environments contains three distinct structural elements: (a) the well-known characteristic Dx[DN]xDG motif; (b) anmore » adjacent structurally identical segment, which binds metal ion in the same way between the calcium blade zone and the EF-hand zone; and (c) the following structurally variable segment, which distinguishes the calcium blade zone from the EF-hand zone. Both zones have sequence insertions between the last residue of the zone and calcium-binding residues in positions V or VI. The long insertion often connects the active and the calcium-binding sites in proteins. Using the structurally identical segments as an anchor, we were able to construct the classical calmodulin type EF-hand calcium-binding site out of two different calcium-binding motifs from two unrelated proteins.« less

Thermodynamic properties of calcium-bismuth alloys determined by emf measurements

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

Kim, H; Boysen, DA; Bradwell, DJ

2012-01-15

The thermodynamic properties of Ca-Bi alloys were determined by electromotive force (emf) measurements to assess the suitability of Ca-Bi electrodes for electrochemical energy storage applications. Emf was measured at ambient pressure as a function of temperature between 723 K and 1173 K using a Ca(s)vertical bar CaF2(s)vertical bar Ca(in Bi) cell for twenty different Ca-Bi alloys spanning the entire range of composition from chi(Ca) = 0 to 1. Reported are the temperature-independent partial molar entropy and enthalpy of calcium for each Ca-Bi alloy. Also given are the measured activities of calcium, the excess partial molar Gibbs energy of bismuth estimatedmore » from the Gibbs-Duhem equation, and the integral change in Gibbs energy for each Ca-Bi alloy at 873 K, 973 K, and 1073 K. Calcium activities at 973 K were found to be nearly constant at a value a(Ca) = 1 x 10(-8) over the composition range chi(Ca) = 0.32-0.56, yielding an emf of similar to 0.77 V. Above chi(Ca) = 0.62 and coincident with Ca5Bi3 formation, the calcium activity approached unity. The Ca-Bi system was also characterized by differential scanning calorimetry over the entire range of composition. Based upon these data along with the emf measurements, a revised Ca-Bi binary phase diagram is proposed. (C) 2011 Elsevier Ltd. All rights reserved.« less

Thermodynamic Linkage Between Calmodulin Domains Binding Calcium and Contiguous Sites in the C-Terminal Tail of CaV1.2

PubMed Central

Evans, T. Idil Apak; Hell, Johannes; Shea, Madeline A.

2011-01-01

Calmodulin (CaM) binding to the intracellular C-terminal tail (CTT) of the cardiac L-type Ca2+ channel (CaV1.2) regulates Ca2+ entry by recognizing sites that contribute to negative feedback mechanisms for channel closing. CaM associates with CaV1.2 under low resting [Ca2+], but is poised to change conformation and position when intracellular [Ca2+] rises. CaM binding Ca2+, and the domains of CaM binding the CTT are linked thermodynamic functions. To better understand regulation, we determined the energetics of CaM domains binding to peptides representing pre-IQ sites A1588, and C1614 and the IQ motif studied as overlapping peptides IQ1644 and IQ′1650 as well as their effect on calcium binding. (Ca2+)4-CaM bound to all four peptides very favorably (Kd ≤ 2 nM). Linkage analysis showed that IQ1644–1670 bound with a Kd ~1 pM. In the pre-IQ region, (Ca2+)2-N-domain bound preferentially to A1588, while (Ca2+)2-C-domain preferred C1614. When bound to C1614, calcium binding in the N-domain affected the tertiary conformation of the C-domain. Based on the thermodynamics, we propose a structural mechanism for calcium-dependent conformational change in which the linker between CTT sites A and C buckles to form an A-C hairpin that is bridged by calcium-saturated CaM. PMID:21757287

The Incredible, Embryological Egg: Calcium and Strontium Isotopes Recapitulate Ontogeny

NASA Astrophysics Data System (ADS)

Gordon, G. W.; Skulan, J. L.

2011-12-01

Embryological development reflects evolutionary history. Understanding the processes of fetal growth is important for curing human birth defects and predicting damage to ecosystems from environmental insults. Tracing enzymatic and hormonal gradients during development, and correlating them to genetic cues dominate modern embryology. Previous work done tracing the mass transfer of elements has generally been limited to isotope spikes in vitro. Natural mass-dependent Ca and Sr isotopic ratios and radiogenic Sr isotopes have the potential to reveal both source and biochemical mechanism information about processes in vivo, but have not previously been extensively explored. The process when a hen lays a fertilized egg that becomes a chick includes formation and dissolution of calcium phosphate (bone) and calcium carbonate (shell). Skulan and DePaolo (1999) showed that chickens have 2% δ44/42Ca between a hen's bones and an egg white; this span represents more than 80% of the entire range of natural Ca isotope variation and illustrates there is significant variation to investigate. A striking feature of archosaurian development that also occurs in many mammals, including humans, is mass transfer of calcium from mother to embryo. The yolk of the domestic hen matures over 7-9 days, but the albumen, shell membranes and shell form in less than 20 hours. Domestic laying hens are at the physiological limit of egg production and selective breeding is no longer an effective method of increasing egg production. 60-75% of the shell's ~1.5 g of calcium comes from dietary sources, while 25-40% comes from the hen's medullary bone. Medullary bone is spicules formed in the marrow of long bones, and is a store of dietary calcium rapidly available for eggshell secretion. During in ovo development, the embryo's skeleton is formed from calcium in the yolk and by bulk dissolution of the eggshell's inner aspect via carbonic anhydrase in a process that has an effect on bone density similar to that caused by osteoporosis in humans. For both mass-dependent Ca and Sr isotopes, the isotopic value of the albumen is the highest natural value yet measured. The offset between the δ88/86Sr values of the albumen and shell is 0.45%, less than half that of the δ44/42Ca offset value (1.29%), as predicted by the relative mass differences. However, the yolk is 0.35% heavier than the shell in δ44/42Ca but 0.70% lighter in δ88/86Sr. In addition, the 87Sr/86Sr value of the shell (0.70854 ±0.000012, 2σ) is statistically the same as the albumen (0.70856 ±0.000018), but slightly offset from the yolk (0.70830 ±0.000014). The apparent decoupling of Ca and Sr, and the radiogenic offset between yolk and shell, may reflect differences in the residence time of calcium and strontium in different reproductive organs, as well as the contribution of medullary bone to shell formation. In addition, it may also reflect differential discrimination against Sr versus Ca in oviduct and uterus. Further studies could extend to thinning eggshells in wild avian populations, biochemical mechanisms of bone formation, and the mechanism of strontium ranelate in the treatment of osteoporosis.

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

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

Li, Xuerun, E-mail: xuerunli@163.com; Zhang, Yu; Shen, Xiaodong, E-mail: xdshen@njut.edu.cn

The formation kinetics of tricalcium aluminate (C{sub 3}A) and calcium sulfate yielding calcium sulfoaluminate (C{sub 4}A{sub 3}more » $$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C{sub 3}A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca{sub 3}Al{sub 2}O{sub 6} + CaSO{sub 4} → Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 6CaO was the primary reaction < 1350 °C with and activation energy of 231 ± 42 kJ/mol; while the decomposition reaction 2Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 10CaO → 6Ca{sub 3}Al{sub 2}O{sub 6} + 2SO{sub 2} ↑ + O{sub 2} ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C{sub 4}A{sub 3}$$ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C{sub 4}A{sub 3}$ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca{sup 2+} and SO{sub 4}{sup 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{sub 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.« less

Calcium-43 chemical shift tensors as probes of calcium binding environments. Insight into the structure of the vaterite CaCO3 polymorph by 43Ca solid-state NMR spectroscopy.

PubMed

Bryce, David L; Bultz, Elijah B; Aebi, Dominic

2008-07-23

Natural-abundance (43)Ca solid-state NMR spectroscopy at 21.1 T and gauge-including projector-augmented-wave (GIPAW) DFT calculations are developed as tools to provide insight into calcium binding environments, with special emphasis on the calcium chemical shift (CS) tensor. The first complete analysis of a (43)Ca solid-state NMR spectrum, including the relative orientation of the CS and electric field gradient (EFG) tensors, is reported for calcite. GIPAW calculations of the (43)Ca CS and EFG tensors for a series of small molecules are shown to reproduce experimental trends; for example, the trend in available solid-state chemical shifts is reproduced with a correlation coefficient of 0.983. The results strongly suggest the utility of the calcium CS tensor as a novel probe of calcium binding environments in a range of calcium-containing materials. For example, for three polymorphs of CaCO3 the CS tensor span ranges from 8 to 70 ppm and the symmetry around calcium is manifested differently in the CS tensor as compared with the EFG tensor. The advantages of characterizing the CS tensor are particularly evident in very high magnetic fields where the effect of calcium CS anisotropy is augmented in hertz while the effect of second-order quadrupolar broadening is often obscured for (43)Ca because of its small quadrupole moment. Finally, as an application of the combined experimental-theoretical approach, the solid-state structure of the vaterite polymorph of calcium carbonate is probed and we conclude that the hexagonal P6(3)/mmc space group provides a better representation of the structure than does the orthorhombic Pbnm space group, thereby demonstrating the utility of (43)Ca solid-state NMR as a complementary tool to X-ray crystallographic methods.

CaMKII Signaling Stimulates Mef2c Activity In Vitro but Only Minimally Affects Murine Long Bone Development in vivo

PubMed Central

Amara, Chandra S.; Fabritius, Christine; Houben, Astrid; Wolff, Lena I.; Hartmann, Christine

2017-01-01

The long bones of vertebrate limbs form by endochondral ossification, whereby mesenchymal cells differentiate into chondrogenic progenitors, which then differentiate into chondrocytes. Chondrocytes undergo further differentiation from proliferating to prehypertrophic, and finally to hypertrophic chondrocytes. Several signaling pathways and transcription factors regulate this process. Previously, we and others have shown in chicken that overexpression of an activated form of Calcium/calmodulin-dependent kinase II (CaMKII) results in ectopic chondrocyte maturation. Here, we show that this is not the case in the mouse. Although, in vitro Mef2c activity was upregulated by about 55-fold in response to expression of an activated form of CaMKII (DACaMKII), transgenic mice that expressed a dominant-active form of CaMKII under the control of the Col2a1 regulatory elements display only a very transient and mild phenotype. Here, only the onset of chondrocyte hypertrophy at E12.5 is accelerated. It is also this early step in chondrocyte differentiation that is temporarily delayed around E13.5 in transgenic mice expressing the peptide inhibitor CaM-KIIN from rat (rKIIN) under the control of the Col2a1 regulatory elements. Yet, ultimately DACaMKII, as well as rKIIN transgenic mice are born with completely normal skeletal elements with regard to their length and growth plate organization. Hence, our in vivo analysis suggests that CaMKII signaling plays a minor role in chondrocyte maturation in mice. PMID:28361052

Synthesis of sodium caseinate-calcium carbonate microspheres and their mineralization to bone-like apatite

NASA Astrophysics Data System (ADS)

Xu, Zhewu; Liang, Guobin; Jin, Lin; Wang, Zhenling; Xing, Chao; Jiange, Qing; Zhang, Zhiguang

2014-06-01

Phosphoproteins can induce and stabilize calcium carbonate (CaCO3) vaterite, which has desirable features for high reactivity. The purpose of this study was to synthesize bioactive CaCO3 microspheres for bone regeneration. Sodium caseinate (NaCas)-containing CaCO3 microspheres, with the crystal phase of vaterite, were synthesized by fast precipitation in an aqueous solution of CaCl2, Na2CO3, and 2 mg/mL of NaCas. The uniform microspheres exhibited rougher surfaces and lower negative charges than CaCO3 particles without NaCas addition. Fourier-transform infrared spectroscopy (FT-IR) of the microspheres showed characteristic peaks or bands corresponding to phosphate and hydroxyl groups. Thermogravimetric analysis (TGA) curves exhibited approximately 5% weight loss below 600 °C due to the decomposition of NaCas. Scanning electron microscope (SEM) images showed lath-like hydroxyapatite (HAp) on the surface after soaking in simulated body fluid (SBF) at 37 °C for 5 and 10 days. Energy dispersive X-ray spectrometry (EDS) revealed that the agglomerates were composed of Ca, C, O, P, Na, and Mg elements, and the Ca/P ratios ranged from 1.53 to 1.56. X-ray diffraction (XRD) patterns exhibited peaks characteristic of hydroxyapatite. The results of this study demonstrated that the addition of NaCas induced the formation of vaterite microspheres which possesses an enhanced apatite formation after soaking in SBF at 37 °C for 5 and 10 days. These NaCas-CaCO3 microspheres may be a potential biomaterial for bone regeneration.

Environmental Controls on Mg/Ca in Neogloboquadrina incompta: A Core-Top Study From the Subpolar North Atlantic

NASA Astrophysics Data System (ADS)

Morley, Audrey; Babila, Tali L.; Wright, James; Ninnemann, Ulysses; Kleiven, Kikki; Irvali, Nil; Rosenthal, Yair

2017-12-01

Magnesium/calcium paleothermometry is an established tool for reconstructing past surface and deep-sea temperatures. However, our understanding of nonthermal environmental controls on the uptake of Mg into the calcitic lattice of foraminiferal tests remains limited. Here we present a combined analysis of multiple trace element/calcium ratios and stable isotope (δ18O and δ13C) geochemistry on the subpolar planktonic foraminifera Neogloboquadrina incompta to assess the validity of Mg/Ca as a proxy for surface ocean temperature. We identify small size-specific offsets in Mg/Ca and δ18Oc values for N. incompta that are consistent with depth habitat migration patterns throughout the life cycle of this species. Additionally, an assessment of nonthermal controls on Mg/Ca values reveals that (1) the presence of volcanic ash, (2) the addition of high-Mg abiotic overgrowths, and (3) ambient seawater carbonate chemistry can have a significant impact on the Mg/Ca-to-temperature relationship. For carbonate-ion concentrations of values > 200 μmol kg-1, we find that temperature exerts the dominant control on Mg/Ca values, while at values < 200 μmol kg-1 the carbonate-ion concentration of seawater increases the uptake of Mg, thereby resulting in higher-than-expected Mg/Ca values at low temperatures. We propose two independent correction schemes to remove the effects of volcanic ash and carbonate-ion concentration on Mg/Ca values in N. incompta within the calibration data set. Applying the corrections improves the fidelity of past ocean temperature reconstructions.

Spectral identifiers from roasting process of Arabica and Robusta green beans using Laser-Induced Breakdown Spectroscopy (LIBS)

NASA Astrophysics Data System (ADS)

Wirani, Ayu Puspa; Nasution, Aulia; Suyanto, Hery

2016-11-01

Coffee (Coffea spp.) is one of the most widely consumed beverages in the world. World coffee consumption is around 70% comes from Arabica, 26% from Robusta , and the rest 4% from other varieties. Coffee beverages characteristics are related to chemical compositions of its roasted beans. Usually testing of coffee quality is subjectively tasted by an experienced coffee tester. An objective quantitative technique to analyze the chemical contents of coffee beans using LIBS will be reported in this paper. Optimum experimental conditions was using of 120 mJ of laser energy and delay time 1 μs. Elements contained in coffee beans are Ca, W, Sr, Mg, Na, H, K, O, Rb, and Be. The Calcium (Ca) is the main element in the coffee beans. Roasting process will cause the emission intensity of Ca decreased by 42.45%. In addition, discriminant analysis was used to distinguish the arabica and robusta variants, either in its green and roasted coffee beans. Observed identifier elements are Ca, W, Sr, and Mg. Overall chemical composition of roasted coffee beans are affected by many factors, such as the composition of the soil, the location, the weather in the neighborhood of its plantation, and the post-harvesting process of the green coffee beans (drying, storage, fermentation, and roasting methods used).

Macro elemental analysis of food samples by nuclear analytical technique

NASA Astrophysics Data System (ADS)

Syahfitri, W. Y. N.; Kurniawati, S.; Adventini, N.; Damastuti, E.; Lestiani, D. D.

2017-06-01

Energy-dispersive X-ray fluorescence (EDXRF) spectrometry is a non-destructive, rapid, multi elemental, accurate, and environment friendly analysis compared with other detection methods. Thus, EDXRF spectrometry is applicable for food inspection. The macro elements calcium and potassium constitute important nutrients required by the human body for optimal physiological functions. Therefore, the determination of Ca and K content in various foods needs to be done. The aim of this work is to demonstrate the applicability of EDXRF for food analysis. The analytical performance of non-destructive EDXRF was compared with other analytical techniques; neutron activation analysis and atomic absorption spectrometry. Comparison of methods performed as cross checking results of the analysis and to overcome the limitations of the three methods. Analysis results showed that Ca found in food using EDXRF and AAS were not significantly different with p-value 0.9687, whereas p-value of K between EDXRF and NAA is 0.6575. The correlation between those results was also examined. The Pearson correlations for Ca and K were 0.9871 and 0.9558, respectively. Method validation using SRM NIST 1548a Typical Diet was also applied. The results showed good agreement between methods; therefore EDXRF method can be used as an alternative method for the determination of Ca and K in food samples.

Using MRI to detect and differentiate calcium oxalate and calcium hydroxyapatite crystals in air-bubble-free phantom

PubMed Central

Mustafi, Devkumar; Fan, Xiaobing; Peng, Bo; Foxley, Sean; Palgen, Jeremy; Newstead, Gillian M.

2015-01-01

Calcium oxalate (CaOX) crystals and calcium hydroxyapatite (CaHA) crystals were commonly associated with breast benign and malignant lesions, respectively. In this research, CaOX (n = 6) and CaHA (n = 6) crystals in air-bubble-free agarose phantom were studied and characterized by using MRI at 9.4 Tesla scanner. Calcium micro-crystals sizes ranged from 200 – 500 microns were made with either 99% pure CaOX or CaHA powder and embedded in agar to mimic the dimensions and calcium content of breast microcalcifications in vivo. MRI data were acquired with high spatial resolution T2-weighted (T2W) images and gradient echo images with five different echo times (TEs). The crystals areas were determined by setting the threshold relative to agarose signal. The ratio of crystals areas were calculated by the measurements from gradient echo images divided by T2W images. Then the ratios as a function of TE were fitted with the radical function. The results showed that the blooming artifacts due to magnetic susceptibility between agar and CaHA crystals were more than twice as large as the susceptibility in CaOX crystals (p < 0.05). In addition, larger bright rings were observed on gradient echo images around CaHA crystals compared to CaOX crystals. Our results suggest that MRI may provide useful information regarding breast microcalcifications by evaluating the apparent area of crystals ratios obtained between gradient echo and T2W images. PMID:26392170

Phototropins Function in High-Intensity Blue Light-Induced Hypocotyl Phototropism in Arabidopsis by Altering Cytosolic Calcium1[C][W][OA

PubMed Central

Zhao, Xiang; Wang, Yan-Liang; Qiao, Xin-Rong; Wang, Jin; Wang, Lin-Dan; Xu, Chang-Shui; Zhang, Xiao

2013-01-01

Phototropins (phot1 and phot2), the blue light receptors in plants, regulate hypocotyl phototropism in a fluence-dependent manner. Especially under high fluence rates of blue light (HBL), the redundant function mediated by both phot1 and phot2 drastically restricts the understanding of the roles of phot2. Here, systematic analysis of phototropin-related mutants and overexpression transgenic lines revealed that HBL specifically induced a transient increase in cytosolic Ca2+ concentration ([Ca2+]cyt) in Arabidopsis (Arabidopsis thaliana) hypocotyls and that the increase in [Ca2+]cyt was primarily attributed to phot2. Pharmacological and genetic experiments illustrated that HBL-induced Ca2+ increases were modulated differently by phot1 and phot2. Phot2 mediated the HBL-induced increase in [Ca2+]cyt mainly by an inner store-dependent Ca2+-release pathway, not by activating plasma membrane Ca2+ channels. Further analysis showed that the increase in [Ca2+]cyt was possibly responsible for HBL-induced hypocotyl phototropism. An inhibitor of auxin efflux carrier exhibited significant inhibitions of both phototropism and increases in [Ca2+]cyt, which indicates that polar auxin transport is possibly involved in HBL-induced responses. Moreover, PHYTOCHROME KINASE SUBSTRATE1 (PKS1), the phototropin-related signaling element identified, interacted physically with phototropins, auxin efflux carrier PIN-FORMED1 and calcium-binding protein CALMODULIN4, in vitro and in vivo, respectively, and HBL-induced phototropism was impaired in pks multiple mutants, indicating the role of the PKS family in HBL-induced phototropism. Together, these results provide new insights into the functions of phototropins and highlight a potential integration point through which Ca2+ signaling-related HBL modulates hypocotyl phototropic responses. PMID:23674105

Phototropins function in high-intensity blue light-induced hypocotyl phototropism in Arabidopsis by altering cytosolic calcium.

PubMed

Zhao, Xiang; Wang, Yan-Liang; Qiao, Xin-Rong; Wang, Jin; Wang, Lin-Dan; Xu, Chang-Shui; Zhang, Xiao

2013-07-01

Phototropins (phot1 and phot2), the blue light receptors in plants, regulate hypocotyl phototropism in a fluence-dependent manner. Especially under high fluence rates of blue light (HBL), the redundant function mediated by both phot1 and phot2 drastically restricts the understanding of the roles of phot2. Here, systematic analysis of phototropin-related mutants and overexpression transgenic lines revealed that HBL specifically induced a transient increase in cytosolic Ca(2+) concentration ([Ca(2+)]cyt) in Arabidopsis (Arabidopsis thaliana) hypocotyls and that the increase in [Ca(2+)]cyt was primarily attributed to phot2. Pharmacological and genetic experiments illustrated that HBL-induced Ca(2+) increases were modulated differently by phot1 and phot2. Phot2 mediated the HBL-induced increase in [Ca(2+)]cyt mainly by an inner store-dependent Ca(2+)-release pathway, not by activating plasma membrane Ca(2+) channels. Further analysis showed that the increase in [Ca(2+)]cyt was possibly responsible for HBL-induced hypocotyl phototropism. An inhibitor of auxin efflux carrier exhibited significant inhibitions of both phototropism and increases in [Ca(2+)]cyt, which indicates that polar auxin transport is possibly involved in HBL-induced responses. Moreover, PHYTOCHROME KINASE SUBSTRATE1 (PKS1), the phototropin-related signaling element identified, interacted physically with phototropins, auxin efflux carrier PIN-FORMED1 and calcium-binding protein CALMODULIN4, in vitro and in vivo, respectively, and HBL-induced phototropism was impaired in pks multiple mutants, indicating the role of the PKS family in HBL-induced phototropism. Together, these results provide new insights into the functions of phototropins and highlight a potential integration point through which Ca(2+) signaling-related HBL modulates hypocotyl phototropic responses.

A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean

NASA Astrophysics Data System (ADS)

Battaglia, G.; Steinacher, M.; Joos, F.

2015-12-01

The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally-constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Latin-Hypercube scheme to construct a 1000 member ensemble with the Bern3D ocean model. Ensemble results are constrained by comparing simulated and observation-based fields of excess dissolved calcium carbonate (TA*). The minerals calcite and aragonite are modelled explicitly and ocean-sediment fluxes are considered. For local dissolution rates either a strong, a weak or no dependency on CaCO3 saturation is assumed. Median (68 % confidence interval) global CaCO3 export is 0.82 (0.67-0.98) Gt PIC yr-1, within the lower half of previously published estimates (0.4-1.8 Gt PIC yr-1). The spatial pattern of CaCO3 export is broadly consistent with earlier assessments. Export is large in the Southern Ocean, the tropical Indo-Pacific, the northern Pacific and relatively small in the Atlantic. Dissolution within the 200 to 1500 m depth range (0.33; 0.26-0.40 Gt PIC yr-1) is substantially lower than inferred from the TA*-CFC age method (1 ± 0.5 Gt PIC yr-1). The latter estimate is likely biased high as the TA*-CFC method neglects transport. The constrained results are robust across a range of diapycnal mixing coefficients and, thus, ocean circulation strengths. Modelled ocean circulation and transport time scales for the different setups were further evaluated with CFC11 and radiocarbon observations. Parameters and mechanisms governing dissolution are hardly constrained by either the TA* data or the current compilation of CaCO3 flux measurements such that model realisations with and without saturation-dependent dissolution achieve skill. We suggest to apply saturation-independent dissolution rates in Earth System Models to minimise computational costs.

Using Calcium Isotopic Composition of Calcium Carbonate Veins to Assess the Roles of Vein Formation and Seafloor Alteration in Regulation of the Carbon Cycle

NASA Astrophysics Data System (ADS)

Chen, F.; Coggon, R. M.; Teagle, D. A. H.; Turchyn, A. V.

2016-12-01

Calcium carbonate vein formation in the oceanic crust has been proposed as a climate-sensitive feedback mechanism that regulates the carbon cycle on million-year timescales. The suggestion has been that higher pCO2 levels may drive changes in ocean temperature and pH that increase seafloor alteration, releasing more calcium from oceanic basalt. This results in more removal of carbon from Earth's surface through calcium carbonate formation, which includes calcium carbonate vein formation in oceanic crust. The importance of this feedback mechanism remains enigmatic. Measurements of the δ44Ca of calcium carbonate veins in the oceanic crust may constrain the sources of calcium and timing of vein formation. Seawater and basalt are the only sources present shortly after crustal formation, whereas other sources, such as anhydrite dissolution and sedimentary carbonates become available when the crust ages, at which point carbonate veins may form far from the ridge axis. We report the calcium isotopic composition of 65 calcium carbonate veins, ranging from 108 to 1.2 million years old, in hydrothermally altered basalt from the Mid-Atlantic and Juan de Fuca ridges. We also present 43 δ44Ca measurements of 5.9 million year old basalts and dikes from the Costa Rica Rift that have undergone hydrothermal alteration over a range of conditions in upper crust. The δ44Ca of the calcium carbonate veins ranges from -1.59 to 1.01‰ (versus Bulk Silicate Earth), whereas the δ44Ca of altered basalts ranges from -0.18 to 0.28‰. Depth and temperature of formation seem to be major influences on calcium carbonate vein δ44Ca, with veins formed at cool, shallower depths having higher δ44Ca, closer to seawater. In contrast, we note no temporal variation in δ44Ca of calcium carbonate veins when comparing samples from older and younger crust. The majority of veins (54 out of 65) have δ44Ca between that of seawater and basalt, which implies that they may have formed quite soon after crustal formation before other sources of calcium became available. We conclude that calcium carbonate vein formation may derive a significant fraction of calcium from seafloor alteration of basalts. This may cause rates of carbonate vein formation to be sensitive to aspects of ocean chemistry that vary due to changing climate conditions.

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

PubMed Central

Letz, Saskia; Haag, Christine; Schulze, Egbert; Frank-Raue, Karin; Raue, Friedhelm; Hofner, Benjamin; Mayr, Bernhard; Schöfl, Christof

2014-01-01

Introduction 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. Methods 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. Results 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. Conclusion 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. PMID:25506941

Functional and molecular features of the calmodulin-interacting protein IQCG required for haematopoiesis in zebrafish.

PubMed

Chen, Li-Ting; Liang, Wen-Xue; Chen, Shuo; Li, Ren-Ke; Tan, Jue-Ling; Xu, Peng-Fei; Luo, Liu-Fei; Wang, Lei; Yu, Shan-He; Meng, Guoyu; Li, Keqin Kathy; Liu, Ting-Xi; Chen, Zhu; Chen, Sai-Juan

2014-05-02

We previously reported a fusion protein NUP98-IQCG in an acute leukaemia, which functions as an aberrant regulator of transcriptional expression, yet the structure and function of IQCG have not been characterized. Here we use zebrafish to investigate the role of iqcg in haematopoietic development, and find that the numbers of haematopoietic stem cells and multilineage-differentiated cells are reduced in iqcg-deficient embryos. Mechanistically, IQCG binds to calmodulin (CaM) and acts as a molecule upstream of CaM-dependent kinase IV (CaMKIV). Crystal structures of complexes between CaM and IQ domain of IQCG reveal dual CaM-binding footprints in this motif, and provide a structural basis for a higher CaM-IQCG affinity when deprived of calcium. The results collectively allow us to understand IQCG-mediated calcium signalling in haematopoiesis, and propose a model in which IQCG stores CaM at low cytoplasmic calcium concentrations, and releases CaM to activate CaMKIV when calcium level rises.

Calcium and stretch activation modulate power generation in Drosophila flight muscle.

PubMed

Wang, Qian; Zhao, Cuiping; Swank, Douglas M

2011-11-02

Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca(2+)]). In vivo myoplasmic calcium levels in Drosophila flight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca(2+)] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinned Drosophila asynchronous flight muscle fibers increased with increasing [Ca(2+)]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca(2+)] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca(2+)]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca(2+)]. However, calcium tension saturated at slightly lower [Ca(2+)] than stretch-activated tension, such that as [Ca(2+)] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca(2+)] is the main mechanism by which power is varied during flight. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Free-calcium distribution and calcium pulses in rat peripheral macrophages

NASA Astrophysics Data System (ADS)

Yu, Yanhua; Xing, Da; Tang, Yonghong; Jin, Ying

2000-10-01

With Laser Confocal Scanning Microscope (LCSM) system, three aspects of characteristics of free cytoplasmic calcium in rat peripheral macrophages are studied. One is the Ca2+ concentration in different area in the same cell. Second is the Ca2+ concentration in the same area in different dividing stage. Third is the feature of calcium pulses evoked by Kcl or pH changing. The results show that even in one cell, the evolution of the Ca2+ concentration is not the same in a different area. In the same area, the nucleolus Ca2+ concentration in division breaking stage is much higher than that in division stage. From the experiment phenomena, we conclude that Kcl itself can not evoke calcium pulses in the unexcitable macrophage, but the change of pH can trig calcium pulses in the same cells.

Ternary alkali-metal and transition metal or metalloid acetylides as alkali-metal intercalation electrodes for batteries

DOEpatents

Nemeth, Karoly; Srajer, George; Harkay, Katherine C; Terdik, Joseph Z

2015-02-10

Novel intercalation electrode materials including ternary acetylides of chemical formula: A.sub.nMC.sub.2 where A is alkali or alkaline-earth element; M is transition metal or metalloid element; C.sub.2 is reference to the acetylide ion; n is an integer that is 0, 1, 2, 3 or 4 when A is alkali element and 0, 1, or 2 when A is alkaline-earth element. The alkali elements are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr). The alkaline-earth elements are Berilium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). M is a transition metal that is any element in groups 3 through 12 inclusive on the Periodic Table of Elements (elements 21 (Sc) to element 30 (Zn)). In another exemplary embodiment, M is a metalloid element.

Development, characterization and dissolution behavior of calcium-aluminoborate glass wasteforms to immobilize rare-earth oxides.

PubMed

Kim, Miae; Corkhill, Claire L; Hyatt, Neil C; Heo, Jong

2018-03-28

Calcium-aluminoborate (CAB) glasses were developed to sequester new waste compositions made of several rare-earth oxides generated from the pyrochemical reprocessing of spent nuclear fuel. Several important wasteform properties such as waste loading, processability and chemical durability were evaluated. The maximum waste loading of the CAB compositions was determined to be ~56.8 wt%. Viscosity and the electrical conductivity of the CAB melt at 1300 °C were 7.817 Pa·s and 0.4603 S/cm, respectively, which satisfies the conditions for commercial cold-crucible induction melting (CCIM) process. Addition of rare-earth oxides to CAB glasses resulted in dramatic decreases in the elemental releases of B and Ca in aqueous dissolution experiments. Normalized elemental releases from product consistency standard chemical durability test were <3.62·10 -5  g·m -2 for Nd, 0.009 g·m -2 for Al, 0.067 g·m -2 for B and 0.073 g·m -2 for Ca (at 90, after 7 days, for SA/V = 2000m -1 ); all meet European and US regulation limits. After 20 d of dissolution, a hydrated alteration layer of ~ 200-nm-thick, Ca-depleted and Nd-rich, was formed at the surface of CAB glasses with 20 mol% Nd 2 O 3 whereas boehmite [AlO(OH)] secondary crystalline phases were formed in pure CAB glass that contained no Nd 2 O 3 .

Resorption kinetics of four hydroxyapatite-based ceramics by particle induced X-ray emission and neutron activation analysis

NASA Astrophysics Data System (ADS)

Jallot, E.; Irigaray, J. L.; Oudadesse, H.; Brun, V.; Weber, G.; Frayssinet, P.

1999-05-01

From the viewpoint of hard tissue response to implant materials, calcium phosphates are probably the most compatible materials presently known. During the last few years, much attention has been paid to hydroxyapatite and β-tricalcium phosphate as potential biomaterials for bone substitute. A good implantation of biomaterials in the skeleton is to reach full integration of non-living implant with living bone. The aim of this study is to compare the resorption kinetics of four kinds of calcium phosphate ceramics: hydroxyapatite (Ca{10}(PO4)6(OH)2), hydroxyapatite doped with manganese or zinc and a composite material of 75% hydroxyapatite and 25% β-tricalcium phosphate (Ca3(PO4)2). Cylinders (5 6 mm in diameter) of these ceramics were packed into holes made in the femur diaphysis of mature ovine. At 2, 4, 8, 12, 16, 20, 28, 36 and 48 weeks after the operation, bone/implant interface was embedded in polymethylmethacrylate. We used the PIXE method (particle induced X-ray emission) to measure the distribution of mineral elements (Ca, P, Sr, Zn, Mn and Fe) at the bone/implant interface. At 4, 8, 16, 28 and 48 weeks after implantation we studied a biopsy of the ceramics by neutron activation method. Then, we have a global measurement of mineral elements in the biomaterial. The results showed that the resorption kinetics of hydroxyapatite doped with zinc was faster than that of the three other bioceramics.

Mineral density volume gradients in normal and diseased human tissues

DOE PAGES

Djomehri, Sabra I.; Candell, Susan; Case, Thomas; ...

2015-04-09

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-raymore » fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095mg/cc, bone: 570-1415mg/cc, cementum: 1240-1340mg/cc, dentin: 1480-1590mg/cc, cementum affected by periodontitis: 1100-1220mg/cc, hypomineralized carious dentin: 345-1450mg/cc, hypermineralized carious dentin: 1815-2740mg/cc, and dental calculus: 1290-1770mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.« less

Mineral density volume gradients in normal and diseased human tissues

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

Djomehri, Sabra I.; Candell, Susan; Case, Thomas

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-raymore » fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095mg/cc, bone: 570-1415mg/cc, cementum: 1240-1340mg/cc, dentin: 1480-1590mg/cc, cementum affected by periodontitis: 1100-1220mg/cc, hypomineralized carious dentin: 345-1450mg/cc, hypermineralized carious dentin: 1815-2740mg/cc, and dental calculus: 1290-1770mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.« less

Mineral density volume gradients in normal and diseased human tissues.

PubMed

Djomehri, Sabra I; Candell, Susan; Case, Thomas; Browning, Alyssa; Marshall, Grayson W; Yun, Wenbing; Lau, S H; Webb, Samuel; Ho, Sunita P

2015-01-01

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095 mg/cc, bone: 570-1415 mg/cc, cementum: 1240-1340 mg/cc, dentin: 1480-1590 mg/cc, cementum affected by periodontitis: 1100-1220 mg/cc, hypomineralized carious dentin: 345-1450 mg/cc, hypermineralized carious dentin: 1815-2740 mg/cc, and dental calculus: 1290-1770 mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.

Mineral Density Volume Gradients in Normal and Diseased Human Tissues

PubMed Central

Djomehri, Sabra I.; Candell, Susan; Case, Thomas; Browning, Alyssa; Marshall, Grayson W.; Yun, Wenbing; Lau, S. H.; Webb, Samuel; Ho, Sunita P.

2015-01-01

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095mg/cc, bone: 570-1415mg/cc, cementum: 1240-1340mg/cc, dentin: 1480-1590mg/cc, cementum affected by periodontitis: 1100-1220mg/cc, hypomineralized carious dentin: 345-1450mg/cc, hypermineralized carious dentin: 1815-2740mg/cc, and dental calculus: 1290-1770mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations. PMID:25856386

Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors

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

Baumann, O.; Walz, B.; Somlyo, A.V.

Honey bee photoreceptors contain large sacs of endoplasmic reticulum (ER) that can be located unequivocally in freeze-dried cryosections. The elemental compositon of the ER was determined by electron probe x-ray microanalysis and was visualized in high-resolution x-ray maps. In the ER of dark-adapted photoreceptors, the Ca concentration was 47.5 {plus minus} 1.1 mmol/kg (dry weight). During a 3-sec nonsaturating light stimulus, {approximately}50% of the Ca content was released from the ER. Light stimulation also caused a highly significant increase in the Mg content of the ER; the ratio of Mg uptake to Ca released was {approximately}0.7. Our results show unambiguouslymore » that the ER is the source of Ca{sup 2+} release during cell stimulation and suggest the Mg{sup 2+} can nearly balance the charge movement of Ca{sup 2+}.« less

Calcium phosphate coatings modified with zinc- or copper- incorporation on Ti-40Nb alloy

NASA Astrophysics Data System (ADS)

Komarova, E. G.; Sedelnikova, M. B.; Sharkeev, Yu P.; Kazakbaeva, A. A.; Glukhov, I. A.; Khimich, M. A.

2017-05-01

The influence of the microarc oxidation parameters and electrolyte composition on the structure, properties and composition of CaP coatings modified with Zn- or Cu- incorporation on the Ti-40mas.%Nb (Ti-40Nb) alloy was investigated. The linear growth of thickness, roughness, and size of structural elements with process voltage increasing has been revealed. It was shown that the CaP coatings have the low contact angles with liquids and, consequently, high free surface energy. This indicates a high hydrophilicity of the coatings. X-ray diffraction analysis showed that the coatings have X-ray amorphous structure. The increase of the process voltage leads to the formation of such crystalline phases as CaHPO4 and β-Ca2P2O7 in the coatings. The maximum Ca/P atomic ratio was equal to 0.4, and Zn or Cu contents was equal to 0.3 or 0.2 at.%, respectively.

21 CFR 184.1193 - Calcium chloride.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false 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...

21 CFR 184.1193 - Calcium chloride.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false 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...

21 CFR 184.1193 - Calcium chloride.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium chloride. 184.1193 Section 184.1193 Food... 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 obtained as a byproduct in...

Calcium isotope ratios in animal and human bone

NASA Astrophysics Data System (ADS)

Reynard, L. M.; Henderson, G. M.; Hedges, R. E. M.

2010-07-01

Calcium isotopes in tissues are thought to be influenced by an individual's diet, reflecting parameters such as trophic level and dairy consumption, but this has not been carefully assessed. We report the calcium isotope ratios (δ 44/42Ca) of modern and archaeological animal and human bone ( n = 216). Modern sheep raised at the same location show 0.14 ± 0.08‰ higher δ 44/42Ca in females than in males, which we attribute to lactation by the ewes. In the archaeological bone samples the calcium isotope ratios of the herbivorous fauna vary by location. At a single site, the archaeological fauna do not show a trophic level effect. Humans have lower δ 44/42Ca than the mean site fauna by 0.22 ± 0.22‰, and the humans have a greater δ 44/42Ca range than the animals. No effect of sex or age on the calcium isotope ratios was found, and intra-individual skeletal δ 44/42Ca variability is negligible. We rule out dairy consumption as the main cause of the lower human δ 44/42Ca, based on results from sites pre-dating animal domestication and dairy availability, and suggest instead that individual physiology and calcium intake may be important in determining bone calcium isotope ratios.

The effect of crystal structure of TiO2 nanotubes on the formation of calcium phosphate coatings during biomimetic deposition

NASA Astrophysics Data System (ADS)

Liu, Yi; Kim, Sun; McLeod, John A.; Li, Jun; Guo, Xiaoxuan; Sham, Tsun-Kong; Liu, Lijia

2017-02-01

The crystallization process of bioactive calcium phosphate (CaP) species via biomimetic deposition onto anodic TiO2 nanotubes is investigated. The porous surface of nanostructured TiO2 provides an ideal substrate for CaP crystallization. The compositions of CaP coatings are studied using X-ray absorption near-edge structures (XANES) at the Ca K-edge. Using detection modes with different probing depths, both the surface of the CaP coating and the CaP-TiO2 interface are simultaneously analyzed. Calcium phosphate (CaP) species, such as hydroxyapatite (HAp), octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O, OCP), brushite (CaHPO4·2H2O, DCPD), and amorphous calcium phosphate (ACP), are found in the CaP coatings. TiO2 nanotubes of amorphous and anatase phases are comparatively studied to determine their effect on the efficiency of CaP formation and the phase transformation among CaP species in prolonged deposition time. It is found the composition of CaP coating has a strong dependency on the crystal structure of TiO2 substrate and the kinetics (deposition time).

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

PubMed

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.

Effects of dietary calcium on atherosclerosis, aortic calcification, and icterus in rabbits fed a supplemental cholesterol diet.

PubMed

Hsu, Howard H T; Culley, Nathan C

2006-06-23

Vascular calcification is implicated in myocardial infarction, instability and rigidity of the aortic wall, and bioprosthetic failures. Although an increase in the calcium (Ca) content in atherogenic diets has been shown to decrease atherosclerosis in rabbits, whether Ca supplementation and deficiency can affect atherosclerosis-related aortic calcification remains unknown. New Zealand White male rabbit littermates were fed an atherogenic diet containing 0.5% cholesterol and 2% peanut oil. The Ca content of the diet, which normally contains 1%, was adjusted to 0.5 or 3%. Segments of thoracic aortas were dissected from rabbits for histological evaluations and Ca and Pi determinations. Rabbits with calcium supplementation were maintained for 4 months, whereas those with calcium deficiency were maintained for 2 1/2 months due to severe icterus beyond this stage. The ratios of intimal to medial areas and calcified to intimal areas were used to semi-quantify lesion accumulation and calcification, respectively. Icterus was estimated from the extent of yellowing of the skin, sclera, and mucous membranes along with gross evidence of hepatic lipidosis and/or biliary obstructions. Statistical analysis of 16 matched littermates shows that Ca supplementation significantly decreased the lesions by 41% (p < 0.05) and markedly inhibited calcification by 62% (p < 0.05). Statistical analysis of 11 matched littermates shows that Ca deficiency significantly increased the lesions by 2.7-fold (p < 0.05) and that the diet caused a small but significant calcification not seen in the sibling groups with normal dietary Ca. Ca supplementation caused a significant 30% decrease in serum cholesterol (p < 0.05). Calcium deficiency increased serum cholesterol by 57% (p < 0.001). Serum cholesterol and LDL-cholesterol levels in Ca deficient rabbits were 2-fold higher than those with high Ca diets. Ca supplementation decreased soluble Ca and Pi content in aortas, suggesting that this effect may underlie the effects of Ca supplementation on calcification. Calcium deficiency increased icterus by 33% (p < 0.05), which may affect hepatic clearance of cholesterol, while calcium supplementation decreased it by 43% (p < 0.001). Ca supplementation to an atherogenic diet inhibits atherosclerosis, aortic calcification, and icterus, whereas a Ca deficient-diet promotes them.

Controls on dripwater chemistry of Oregon Caves National Monument, northwestern United States

NASA Astrophysics Data System (ADS)

Rushdi, Ahmed I.; Ersek, Vasile; Mix, Alan C.; Clark, Peter U.

2018-02-01

Cave dripwater chemistry of Oregon Caves National Monument (OCNM) was studied, where the parameters pH, total alkalinity, calcium, magnesium, strontium, sodium and barium were analyzed at quasi-monthly intervals from 2005 to 2007. Different statistical analyses have been used to investigate the variability of the chemical parameters in the different sites in the OCNM cave system. The dripwater varies in response to seasonal changes in rainfall. The drip rates range from zero in summer to continuous flow in winter, closely following the rainfall intensity. Spatial variations of dripwater chemistry, which is nonlinearly related to dripwater discharge likely, reflect the chemical composition of bedrock and overlying soil, and the residence time of the ground water within the aquifer. The residence time of infiltrated water in bedrock cracks control the dissolution carbonate bedrock, reprecipitation of calcium carbonate and the degree of saturation of dripwater with respect to calcium carbonate minerals. Spatiotemporal fluctuations of dripwater Mg/Ca and Sr/Ca ratios are controlled by dissolution of carbonate bedrock and the degree of calcite reprecipitation in bedrock cracks. This suggests that trace elements in speleothem deposits at the OCNM may serve as paleoclimatological proxies for precipitation, if interpreted within the context of understanding local bedrock chemistry.

Occurrence and characterisation of calcium oxalate crystals in stems and fruits of Hylocereus costaricensis and Selenicereus megalanthus (Cactaceae: Hylocereeae).

PubMed

Viñas, María; Jiménez, Víctor M

2016-10-01

Detailed description about occurrence of calcium oxalate (CaOx) crystals in the edible vine cactus species Hylocereus costaricensis and Selenicereus megalanthus is scarce. Therefore, we evaluated and characterized the presence, morphology and composition of CaOx crystals in both species. Crystals were isolated from greenhouse and in vitro vegetative stems, and from ripe fruit peels and pulp by enzymatic digestion and density centrifugation and quantified with a haemocytometer. Morphologies were studied using scanning electron microscopy, elemental composition with energy-dispersive X-ray spectroscopy and salt composition with X-ray powder diffraction. Analyses conducted confirmed that isolated crystals were exclusively composed by CaOx, both mono- and dihydrated. Highest crystal contents were measured in greenhouse stems, followed by the fruit peels. While very few crystals were quantified in in vitro plants, they were not detected in the fruit pulp at all, which is of advantage for its human consumption and could be linked to mechanisms of seed dispersal through animals. Different crystal morphologies were observed, sometimes varying between genotypes and tissues analysed. This is the first work known to the authors with a detailed characterization of CaOx crystals in vine cacti. Copyright © 2016 Elsevier Ltd. All rights reserved.

Phytate/calcium molar ratio does not predict accessibility of calcium in ready-to-eat dishes.

PubMed

Erba, Daniela; Manini, Federica; Meroni, Erika; Casiraghi, Maria C

2017-08-01

Phytic acid (PA), a naturally occurring compound of plant food, is generally considered to affect mineral bioavailability. The aim of this study was to investigate the reliability of the PA/calcium molar ratio as a predictive factor of calcium accessibility in composed dishes and their ingredients. Dishes were chosen whose ingredients were rich in Ca (milk or cheese) or in PA (whole-wheat cereals) in order to consider a range of PA/Ca ratios (from 0 to 2.4) and measure Ca solubility using an in vitro approach. The amounts of soluble Ca in composed dishes were consistent with the sum of soluble Ca from ingredients (three out of five meals) or higher. Among whole-wheat products, bread showed higher Ca accessibility (71%, PA/Ca = 1.1) than biscuits (23%, PA/Ca = 0.9) and pasta (15%, PA/Ca = 1.5), and among Ca-rich ingredients, semi-skimmed milk displayed higher Ca accessibility (64%) than sliced cheese (50%) and Parmesan (38%). No significant correlation between the PA/Ca ratio and Ca accessibility was found (P = 0.077). The reliability of the PA/Ca ratio for predicting the availability of calcium in composed dishes is unsatisfactory; data emphasized the importance of the overall food matrix influence on mineral accessibility. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Calcium-Enhanced Twitching Motility in Xylella fastidiosa Is Linked to a Single PilY1 Homolog

PubMed Central

Cruz, Luisa F.; Parker, Jennifer K.; Cobine, Paul A.

2014-01-01

The plant-pathogenic bacterium Xylella fastidiosa is restricted to the xylem vessel environment, where mineral nutrients are transported through the plant host; therefore, changes in the concentrations of these elements likely impact the growth and virulence of this bacterium. Twitching motility, dependent on type IV pili (TFP), is required for movement against the transpiration stream that results in basipetal colonization. We previously demonstrated that calcium (Ca) increases the motility of X. fastidiosa, although the mechanism was unknown. PilY1 is a TFP structural protein recently shown to bind Ca and to regulate twitching and adhesion in bacterial pathogens of humans. Sequence analysis identified three pilY1 homologs in X. fastidiosa (PD0023, PD0502, and PD1611), one of which (PD1611) contains a Ca-binding motif. Separate deletions of PD0023 and PD1611 resulted in mutants that still showed twitching motility and were not impaired in attachment or biofilm formation. However, the response of increased twitching at higher Ca concentrations was lost in the pilY1-1611 mutant. Ca does not modulate the expression of any of the X. fastidiosa PilY1 homologs, although it increases the expression of the retraction ATPase pilT during active movement. The evidence presented here suggests functional differences between the PilY1 homologs, which may provide X. fastidiosa with an adaptive advantage in environments with high Ca concentrations, such as xylem sap. PMID:25217013

Calcium-Enhanced Twitching Motility in Xylella fastidiosa Is Linked to a Single PilY1 Homolog.

PubMed

Cruz, Luisa F; Parker, Jennifer K; Cobine, Paul A; De La Fuente, Leonardo

2014-12-01

The plant-pathogenic bacterium Xylella fastidiosa is restricted to the xylem vessel environment, where mineral nutrients are transported through the plant host; therefore, changes in the concentrations of these elements likely impact the growth and virulence of this bacterium. Twitching motility, dependent on type IV pili (TFP), is required for movement against the transpiration stream that results in basipetal colonization. We previously demonstrated that calcium (Ca) increases the motility of X. fastidiosa, although the mechanism was unknown. PilY1 is a TFP structural protein recently shown to bind Ca and to regulate twitching and adhesion in bacterial pathogens of humans. Sequence analysis identified three pilY1 homologs in X. fastidiosa (PD0023, PD0502, and PD1611), one of which (PD1611) contains a Ca-binding motif. Separate deletions of PD0023 and PD1611 resulted in mutants that still showed twitching motility and were not impaired in attachment or biofilm formation. However, the response of increased twitching at higher Ca concentrations was lost in the pilY1-1611 mutant. Ca does not modulate the expression of any of the X. fastidiosa PilY1 homologs, although it increases the expression of the retraction ATPase pilT during active movement. The evidence presented here suggests functional differences between the PilY1 homologs, which may provide X. fastidiosa with an adaptive advantage in environments with high Ca concentrations, such as xylem sap. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Calcium Isotope Analysis with "Peak Cut" Method on Column Chemistry

NASA Astrophysics Data System (ADS)

Zhu, H.; Zhang, Z.; Liu, F.; Li, X.

2017-12-01

To eliminate isobaric interferences from elemental and molecular isobars (e.g., 40K+, 48Ti+, 88Sr2+, 24Mg16O+, 27Al16O+) on Ca isotopes during mass determination, samples should be purified through ion-exchange column chemistry before analysis. However, large Ca isotopic fractionation has been observed during column chemistry (Russell and Papanastassiou, 1978; Zhu et al., 2016). Therefore, full recovery during column chemistry is greatly needed, otherwise uncertainties would be caused by poor recovery (Zhu et al., 2016). Generally, matrix effects could be enhanced by full recovery, as other elements might overlap with Ca cut during column chemistry. Matrix effects and full recovery are difficult to balance and both need to be considered for high-precision analysis of stable Ca isotopes. Here, we investigate the influence of poor recovery on δ44/40Ca using TIMS with the double spike technique. The δ44/40Ca values of IAPSO seawater, ML3B-G and BHVO-2 in different Ca subcats (e.g., 0-20, 20-40, 40-60, 60-80, 80-100%) with 20% Ca recovery on column chemistry display limited variation after correction by the 42Ca-43Ca double spike technique with the exponential law. Notably, δ44/40Ca of each Ca subcut is quite consistent with δ44/40Ca of Ca cut with full recovery within error. Our results indicate that the 42Ca-43Ca double spike technique can simultaneously correct both of the Ca isotopic fractionation that occurred during column chemistry and thermal ionization mass spectrometry (TIMS) determination properly, because both of the isotopic fractionation occurred during analysis follow the exponential law well. Therefore, we propose the "peak cut" method on Ca column chemistry for samples with complex matrix effects. Briefly, for samples with low Ca contents, we can add the double spike before column chemistry, and only collect the middle of the Ca eluate and abandon the both sides of Ca eluate that might overlap with other elements (e.g., K, Sr). This method would eliminate matrix effects and improve efficiency for the column chemistry.

Rapid frequency‐dependent changes in free mitochondrial calcium concentration in rat cardiac myocytes

PubMed Central

Wüst, Rob C. I.; Helmes, Michiel; Martin, Jody L.; van der Wardt, Thomas J. T.; Musters, René J. P.; van der Velden, Jolanda

2017-01-01

Key points Calcium ions regulate mitochondrial ATP production and contractile activity and thus play a pivotal role in matching energy supply and demand in cardiac muscle.The magnitude and kinetics of the changes in free mitochondrial calcium concentration in cardiac myocytes are largely unknown.Rapid stimulation frequency‐dependent increases but relatively slow decreases in free mitochondrial calcium concentration were observed in rat cardiac myocytes. This asymmetry caused a rise in the mitochondrial calcium concentration with stimulation frequency.These results provide insight into the mechanisms of mitochondrial calcium uptake and release that are important in healthy and diseased myocardium. Abstract Calcium ions regulate mitochondrial ATP production and contractile activity and thus play a pivotal role in matching energy supply and demand in cardiac muscle. Little is known about the magnitude and kinetics of the changes in free mitochondrial calcium concentration in cardiomyocytes. Using adenoviral infection, a ratiometric mitochondrially targeted Förster resonance energy transfer (FRET)‐based calcium indicator (4mtD3cpv, MitoCam) was expressed in cultured adult rat cardiomyocytes and the free mitochondrial calcium concentration ([Ca2+]m) was measured at different stimulation frequencies (0.1–4 Hz) and external calcium concentrations (1.8–3.6 mm) at 37°C. Cytosolic calcium concentrations were assessed under the same experimental conditions in separate experiments using Fura‐4AM. The increases in [Ca2+]m during electrical stimulation at 0.1 Hz were rapid (rise time = 49 ± 2 ms), while the decreases in [Ca2+]m occurred more slowly (decay half time = 1.17 ± 0.07 s). Model calculations confirmed that this asymmetry caused the rise in [Ca2+]m during diastole observed at elevated stimulation frequencies. Inhibition of the mitochondrial sodium–calcium exchanger (mNCE) resulted in a rise in [Ca2+]m at baseline and, paradoxically, in an acceleration of Ca2+ release. In conclusion: rapid increases in [Ca2+]m allow for fast adjustment of mitochondrial ATP production to increases in myocardial demand on a beat‐to‐beat basis and mitochondrial calcium release depends on mNCE activity and mitochondrial calcium buffering. PMID:28028811

Bio-inspired voltage-dependent calcium channel blockers.

PubMed

Yang, Tingting; He, Lin-Ling; Chen, Ming; Fang, Kun; Colecraft, Henry M

2013-01-01

Ca(2+) influx via voltage-dependent CaV1/CaV2 channels couples electrical signals to biological responses in excitable cells. CaV1/CaV2 channel blockers have broad biotechnological and therapeutic applications. Here we report a general method for developing novel genetically encoded calcium channel blockers inspired by Rem, a small G-protein that constitutively inhibits CaV1/CaV2 channels. We show that diverse cytosolic proteins (CaVβ, 14-3-3, calmodulin and CaMKII) that bind pore-forming α1-subunits can be converted into calcium channel blockers with tunable selectivity, kinetics and potency, simply by anchoring them to the plasma membrane. We term this method 'channel inactivation induced by membrane-tethering of an associated protein' (ChIMP). ChIMP is potentially extendable to small-molecule drug discovery, as engineering FK506-binding protein into intracellular sites within CaV1.2-α1C permits heterodimerization-initiated channel inhibition with rapamycin. The results reveal a universal method for developing novel calcium channel blockers that may be extended to develop probes for a broad cohort of unrelated ion channels.

Adjustment of ionized calcium concentration for serum pH is not a valid marker of calcium homeostasis: implications for identifying individuals at risk of calcium metabolic disorders.

PubMed

Lam, Virginie; Dhaliwal, Satvinder S; Mamo, John C

2013-05-01

Ionized calcium (iCa) is the biologically active form of this micronutrient. Serum determination of iCa is measured via ion-electrode potentiometry (IEP) and reporting iCa relative to pH 7.4 is normally utilized to avoid the potential confounding effects of ex vivo changes to serum pH. Adjustment of iCa for pH has not been adequately justified. In this study, utilizing carefully standardized protocols for blood collection, the preparation of serum and controlling time of collection-to-analysis, we determined serum iCa and pH utilizing an IEP-analyser hosted at an accredited diagnostic laboratory. Regression analysis of unadjusted-iCa (iCa(raw)) concentration versus pH was described by linear regression and accounted for 37% of serum iCa(raw) variability. iCa(raw) was then expressed at pH 7.4 by either adjusting iCa(raw) based on the linear regression equation describing the association of iCa with serum pH (iCa(regr)) or using IEP coded published normative equations (iCa(pub)). iCa(regr) was comparable to iCa(raw), indicating that blood collection and processing methodologies were sound. However, iCa(pub) yielded values that were significantly lower than iCa(raw). iCa(pub) did not identify 15% subjects who had greater than desirable serum concentration of iCa based on iCa(raw). Sixty percent of subjects with low levels of iCa(raw) were also not detected by iCa(pub). Determination of the kappa value measure of agreement for iCa(raw) versus iCa(pub) showed relatively poor concordance (κ = 0.42). With simple protocols that avoid sampling artefacts, expressing iCa(raw) is likely to be a more valid and physiologically relevant marker of calcium homeostasis than is iCa(pub).

Dependence of Ca outflow and depression of frog myocardium contraction on ryodipine concentration.

PubMed

Narusevicius, E; Gendviliene, V; Macianskiene, R; Hmelj-Dunai, G; Velena, A; Duburs, G

1988-02-01

The effect of ryodipine on calcium outflow from tissues, on contraction force, the duration of action potentials and the relaxation phase time-constant in the contraction cycles of myocardial strips was studied using frog heart preparations. It was found that calcium outflow (delta Ca) as a function on ryodipine concentration can be represented as: (formula; see text) A linear correlation exists between Ca2+, contraction blocking and the shortening of the action potential in the presence of various ryodipine concentrations. Ryodipine (10(-5) mol/l) decreased the relaxation time-constant by about 20% as compared to controls. It was concluded that calcium outflow from myocardial tissues in response to ryodipine is due to blockade of calcium entry into the cells and their output through the Na+--Ca2+ exchange system. Frog heart myocardial contractions are essentially under the control of calcium entry through sarcolemmal calcium channels.

Calcium-dependent molecular fMRI using a magnetic nanosensor.

PubMed

Okada, Satoshi; Bartelle, Benjamin B; Li, Nan; Breton-Provencher, Vincent; Lee, Jiyoung J; Rodriguez, Elisenda; Melican, James; Sur, Mriganka; Jasanoff, Alan

2018-06-01

Calcium ions are ubiquitous signalling molecules in all multicellular organisms, where they mediate diverse aspects of intracellular and extracellular communication over widely varying temporal and spatial scales 1 . Though techniques to map calcium-related activity at a high resolution by optical means are well established, there is currently no reliable method to measure calcium dynamics over large volumes in intact tissue 2 . Here, we address this need by introducing a family of magnetic calcium-responsive nanoparticles (MaCaReNas) that can be detected by magnetic resonance imaging (MRI). MaCaReNas respond within seconds to [Ca 2+ ] changes in the 0.1-1.0 mM range, suitable for monitoring extracellular calcium signalling processes in the brain. We show that the probes permit the repeated detection of brain activation in response to diverse stimuli in vivo. MaCaReNas thus provide a tool for calcium-activity mapping in deep tissue and offer a precedent for the development of further nanoparticle-based sensors for dynamic molecular imaging with MRI.

Calcium and organic matter removal by carbonation process with waste incineration flue gas towards improvement of leachate biotreatment performance.

PubMed

Zhang, Cheng; Zhu, Xuedong; Wu, Liang; Li, Qingtao; Liu, Jianyong; Qian, Guangren

2017-09-01

Municipal solid wastes incineration (MSWI) flue gas was employed as the carbon source for in-situ calcium removal from MSWI leachate. Calcium removal efficiency was 95-97% with pH of 10.0-11.0 over 100min of flue gas aeration, with both bound Ca and free Ca being removed effectively. The fluorescence intensity of tryptophan, protein-like and humic acid-like compounds increased after carbonation process. The decrease of bound Ca with the increase of precipitate indicated that calcium was mainly converted to calcium carbonate precipitate. It suggested that the interaction between dissolved organic matter and Ca 2+ was weakened. Moreover, 10-16% of chemical oxygen demand removal and the decrease of ultraviolet absorption at 254nm indicated that some organics, especially aromatic compound decreased via adsorption onto the surface of calcium carbonate. The results indicate that introduce of waste incineration flue gas could be a feasible way for calcium removal from leachate. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calcium-dependent molecular fMRI using a magnetic nanosensor

NASA Astrophysics Data System (ADS)

Okada, Satoshi; Bartelle, Benjamin B.; Li, Nan; Breton-Provencher, Vincent; Lee, Jiyoung J.; Rodriguez, Elisenda; Melican, James; Sur, Mriganka; Jasanoff, Alan

2018-06-01

Calcium ions are ubiquitous signalling molecules in all multicellular organisms, where they mediate diverse aspects of intracellular and extracellular communication over widely varying temporal and spatial scales1. Though techniques to map calcium-related activity at a high resolution by optical means are well established, there is currently no reliable method to measure calcium dynamics over large volumes in intact tissue2. Here, we address this need by introducing a family of magnetic calcium-responsive nanoparticles (MaCaReNas) that can be detected by magnetic resonance imaging (MRI). MaCaReNas respond within seconds to [Ca2+] changes in the 0.1-1.0 mM range, suitable for monitoring extracellular calcium signalling processes in the brain. We show that the probes permit the repeated detection of brain activation in response to diverse stimuli in vivo. MaCaReNas thus provide a tool for calcium-activity mapping in deep tissue and offer a precedent for the development of further nanoparticle-based sensors for dynamic molecular imaging with MRI.

Extracellular calcium- and magnesium-mediated regulation of passive calcium transport across Caco-2 monolayers.

PubMed

Davies, Sarah L; Gibbons, Claire E; Steward, Martin C; Ward, Donald T

2008-10-01

The calcium-sensing receptor (CaR) is expressed on intestinal epithelial serosal membrane and in Caco-2 cells. In renal epithelium, CaR expressed on the basolateral membrane acts to limit excess tubular Ca2+ reabsorption. Therefore, here we investigated whether extracellular calcium (Ca(o)2+) can regulate active or passive 45Ca2+ transport across differentiated Caco-2 monolayers via CaR-dependent or CaR-independent mechanisms. Raising the Ca(o)2+ concentration from 0.8 to 1.6 mM increased transepithelial electrical resistance (TER) and decreased passive Ca2+ permeability but failed to alter active Ca2+ transport. The Ca(o)2+ effect on TER was rapid, sustained and concentration-dependent. Increasing basolateral Mg2+ concentration increased TER and inhibited both passive and active Ca2+ transport, whereas spermine and the CaR-selective calcimimetic NPS R-467 were without effect. We conclude that small increases in divalent cation concentration elicit CaR-independent increases in TER and inhibit passive Ca2+ transport across Caco-2 monolayers, most probably through a direct effect on tight junction permeability. Whilst it is known that the complete removal of Ca(o)2+ lowers TER, here we show that Ca(o)2+ addition actually increases TER in a concentration-dependent manner. Therefore, such Ca(o)2+-sensitivity could modulate intestinal solute transport including the limiting of excess Ca2+ absorption.

Decomposition of polychlorinated biphenyls in soil with a dispersion mixture of metallic calcium and calcium oxide.

PubMed

Mitoma, Yoshiharu; Mallampati, Srinivasa Reddy; Miyata, Hideaki; Kakeda, Mitsunori

2013-02-01

This study describes the decomposition of polychlorinated biphenyls (PCBs) in soil with dispersion mixtures of metallic calcium (Ca) and calcium oxide (CaO) at different temperatures. In these experiments, naturally moisturized and contaminated soil (1.0 g [31 ppm PCBs]), CaO (dried 2.0 wt%), and metallic Ca (0.01 g [0.25 mmol]) were introduced into a stainless steel pressure reactor under 0.1 MPa N(2) gas. The mixtures were stirred magnetically and heated at 260, 280, and 300 °C, respectively. Soil treatment with metallic Ca and CaO under various temperature conditions is extremely effective for degrading existing PCBs. Decomposition resulted from dechlorination (DC). Initial moisture in soil acted as a hydrogen source during stirring. Soil moisture can be beneficial for hydrodechlorination in the presence of metallic Ca and CaO. Furthermore, metallic Ca and CaO can greatly increase the number of collisions and mutual refinement. Treatment at 260, 280, and 300 °C combined with metallic Ca and CaO is effective for the decomposition (approximately 95 % DC) of PCBs in soil under natural moisture conditions.

Vitamin D receptor displays DNA binding and transactivation as a heterodimer with the retinoid X receptor, but not with the thyroid hormone receptor.

PubMed

Thompson, P D; Hsieh, J C; Whitfield, G K; Haussler, C A; Jurutka, P W; Galligan, M A; Tillman, J B; Spindler, S R; Haussler, M R

1999-12-01

The vitamin D receptor (VDR) is a transcription factor believed to function as a heterodimer with the retinoid X receptor (RXR). However, it was reported [Schräder et al., 1994] that, on putative vitamin D response elements (VDREs) within the rat 9k and mouse 28k calcium binding protein genes (rCaBP 9k and mCaBP 28k), VDR and thyroid hormone receptor (TR) form heterodimers that transactivate in response to both 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and triiodothyronine (T(3)). We, therefore, examined associations of these receptors on the putative rCaBP 9k and mCaBP 28k VDREs, as well as on established VDREs from the rat osteocalcin (rOC) and mouse osteopontin (mOP) genes, plus the thyroid hormone response element (TRE) from the rat myosin heavy chain (rMHC) gene. In gel mobility shift assays, we found no evidence for VDR-TR heterodimer interaction with any tested element. Further, employing these hormone response elements linked to reporter genes in transfected cells, VDR and TR mediated responses to their cognate ligands only from the rOC/mOP and rMHC elements, respectively, while the CaBP elements were unresponsive to any combination of ligand(s). Utilizing the rOC and mOP VDREs, two distinct repressive actions of TR on VDR-mediated signaling were demonstrated: a T(3)-independent action, presumably via direct TR-RXR competition for DNA binding, and a T(3)-dependent repression, likely by diversion of limiting RXR from VDR-RXR toward the formation of TR-RXR heterodimers. The relative importance of these two mechanisms differed in a response element-specific manner. These results may provide a partial explanation for the observed association between hyperthyroidism and bone demineralization/osteoporosis. Copyright 1999 Wiley-Liss, Inc.

Electrochemical investigation of lead-calcium alloys in sulphuric acid

NASA Astrophysics Data System (ADS)

Bass, K.; Ellis, S. R.; Johnson, M.; Hampson, N. A.

The hydrogen evolution reaction from, and the cycle life (Pb /ar PbSO 4) of, a series of lead-calcium alloys (0 - 0.2 wt.% Ca) in sulphuric acid hav The exchange current density and Tafel slope for the H.R.E. increase with Ca content up to 0.05 wt.% then decrease to a value approaching that of pure The observed results are explained by: (i) preferential adsorption of calcium ions at the electrode surface; (ii) incorporation of Ca, to form a supersaturated solution, with alloys containing < 0.075 wt.% Ca; (iii) formation of an insoluble, non-conducting layer of calcium sulphate on the high content alloy.

Mass dependence of calcium isotope fractionations in crown-ether resin chromatography.

PubMed

Fujii, Yasuhiko; Nomura, Masao; Kaneshiki, Tositaka; Sakuma, Yoichi; Suzuki, Tatsuya; Umehara, Saori; Kishimoto, Tadahumi

2010-06-01

Benzo 18-crown-6-ether resin was synthesised by the phenol condensation polymerisation process in porous silica beads, of which particle diameter was ca 60micro Calcium adsorption chromatography was performed with the synthesised resin packed in a glass column. The effluent was sampled in fractions, and the isotopic abundance ratios of (42)Ca, (43)Ca, (44)Ca, and (48)Ca against (40)Ca were measured by a thermo-ionisation mass spectrometer. The enrichment of heavier calcium isotopes was observed at the front boundary of calcium adsorption chromatogram. The mass dependence of mutual separation of calcium isotopes was analysed by using the three-isotope-plots method. The slopes of three-isotope-plots indicate the relative values of mutual separation coefficients for concerned isotopic pairs. The results have shown the normal mass dependence; isotope fractionation is proportional to the reduced mass difference, (M - M')/MM', where M and M' are masses of heavy and light isotope, respectively. The mass dependence clarifies that the isotope fractionations are originated from molecular vibration. The observed separation coefficient epsilon is 3.1x10(-3) for the pair of (40)Ca and (48)Ca. Productivity of enriched (48)Ca by crown-ether-resin was discussed as the function of the separation coefficient and the height equivalent to the theoretical plate.

Carbon-Based Solid-State Calcium Ion-Selective Microelectrode and Scanning Electrochemical Microscopy: A Quantitative Study of pH-Dependent Release of Calcium Ions from Bioactive Glass.

PubMed

Ummadi, Jyothir Ganesh; Downs, Corey J; Joshi, Vrushali S; Ferracane, Jack L; Koley, Dipankar

2016-03-15

Solid-state ion-selective electrodes are used as scanning electrochemical microscope (SECM) probes because of their inherent fast response time and ease of miniaturization. In this study, we report the development of a solid-state, low-poly(vinyl chloride), carbon-based calcium ion-selective microelectrode (Ca(2+)-ISME), 25 μm in diameter, capable of performing an amperometric approach curve and serving as a potentiometric sensor. The Ca(2+)-ISME has a broad linear response range of 5 μM to 200 mM with a near Nernstian slope of 28 mV/log[a(Ca(2+))]. The calculated detection limit for Ca(2+)-ISME is 1 μM. The selectivity coefficients of this Ca(2+)-ISME are log K(Ca(2+),A) = -5.88, -5.54, and -6.31 for Mg(2+), Na(+), and K(+), respectively. We used this new type of Ca(2+)-ISME as an SECM probe to quantitatively map the chemical microenvironment produced by a model substrate, bioactive glass (BAG). In acidic conditions (pH 4.5), BAG was found to increase the calcium ion concentration from 0.7 mM ([Ca(2+)] in artificial saliva) to 1.4 mM at 20 μm above the surface. In addition, a solid-state dual SECM pH probe was used to correlate the release of calcium ions with the change in local pH. Three-dimensional pH and calcium ion distribution mapping were also obtained by using these solid-state probes. The quantitative mapping of pH and Ca(2+) above the BAG elucidates the effectiveness of BAG in neutralizing and releasing calcium ions in acidic conditions.

Hybrid zero valent iron (ZVI)/H2O2 oxidation process for landfill leachate treatment with novel nanosize metallic calcium/iron composite.

PubMed

Lee, Son Dong; Mallampati, Srinivasa Reddy; Lee, Byoung Ho

2017-04-01

A novel nanosize metallic calcium/iron dispersed reagent was synthesized and tested as coagulant/catalyst in a hybrid zero valent iron (ZVI)/H 2 O 2 oxidation process to treat leachate. Two different types of leachates, one from municipal solid waste (MSW) tipping hall (MSWIL) and second from an MSW landfill site (MSWLL), were collected and characterized. The morphology, elemental composition, and mineral phases of the nano-Ca/CaO and nano-Fe/Ca/CaO were characterized by scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS) and x-ray powder diffraction (XRD) analysis. The coagulation process with 2.5 g L -1 nano-Ca/CaO attained 64.0, 56.0, and 20.7% removal of color, chemical oxygen demand (COD), and total suspended solids (TSS) in MSWLL. With only 1.0 g L -1 of nano-Fe/Ca/CaO, relatively high color, COD and TSS removal was achieved in MSWLL at 67.5, 60.2, and 37.7%, respectively. The heavy metal removal efficiency reached 91-99% after treatment with nano-Fe/Ca/CaO in both leachate samples. The coupling process, using 1.0 g L -1 of nano-Fe/Ca/CaO and 20 mM H 2 O 2 doses, achieved enhancement removal of color, COD, and TSS, up to 95%, 96%, and 66%, respectively, without initial pH control. After this treatment, the color, COD, TSS, and heavy metals were significantly decreased, fitting the Korean discharge regulation limit. A hybrid coupled zero valent iron (ZVI)/H 2 O 2 oxidation process with novel nanosized metallic calcium/iron dispersed reagent proved to be a suitable treatment for dealing with leachate samples. Conventional treatments (biological or physicochemical) are not sufficient anymore to reach the level of purification needed to fully reduce the negative impact of landfill leachates on the environment. This implies that new treatment alternatives species must be proposed. A coupled zero valent iron (ZVI)/H 2 O 2 oxidation process proved to be a suitable treatment for dealing with leachate samples. Coagulation with nFe/Ca/CaO allows 91-99% of heavy metals removal. The coupled coagulation-oxidation process by nFe/Ca/CaO reveals excellent ability to treat leachate. After coupled treatment the color, COD, and TSS were also much lower than the discharge regulation limit.

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

PubMed

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

2015-09-01

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

Calmodulins from Schistosoma mansoni: Biochemical analysis and interaction with IQ-motifs from voltage-gated calcium channels.

PubMed

Thomas, Charlotte M; Timson, David J

2018-05-17

The trematode Schistosoma mansoni is a causative agent of schistosomiasis, the second most common parasitic disease of humans after malaria. Calcium homeostasis and calcium-mediated signalling pathways are of particular interest in this species. The drug of choice for treating schistosomiasis, praziquantel, disrupts the regulation of calcium uptake and there is interest in exploiting calcium-mediated processes for future drug discovery. Calmodulin is a calcium sensing protein, present in most eukaryotes. It is a critical regulator of processes as diverse as muscle contraction, cell division and, partly through interaction with voltage-gated calcium channels, intra-cellular calcium concentrations. S. mansoni expresses two highly similar calmodulins - SmCaM1 and SmCaM2. Both proteins interact with calcium, manganese, cadmium (II), iron (II) and lead ions in native gel electrophoresis. These ions also cause conformational changes in the proteins resulting in the exposure of a more hydrophobic surface (as demonstrated by anilinonaphthalene-8-sulfonate fluorescence assays). The proteins are primarily dimeric in the absence of calcium ions, but monomeric in the presence of this ion. Both SmCaM1 and SmCaM2 interact with a peptide corresponding to an IQ-motif derived from the α-subunit of the voltage-gated calcium channel SmCa v 1B (residues 1923-1945). Both proteins bound with slightly higher affinity in the presence of calcium ions. However, there was no difference between the affinities of the two proteins for the peptide. This interaction could be antagonised by chlorpromazine and trifluoperazine, but not praziquantel or thiamylal. Interestingly no interaction could be detected with the other three IQ-motifs identified in S. mansoni voltage-gated ion calcium channels. Copyright © 2018 Elsevier Ltd. All rights reserved.

Hydrocarbon-soluble calcium hydride: a "worker-bee" in calcium chemistry.

PubMed

Spielmann, Jan; Harder, Sjoerd

2007-01-01

The reactivity of the hydrocarbon-soluble calcium hydride complex [{CaH(dipp-nacnac)(thf)}(2)] (1; dipp-nacnac=CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)) with a large variety of substrates has been investigated. Addition of 1 to C=O and C=N functionalities gave easy access to calcium alkoxide and amide complexes. Similarly, reduction of the C[triple chemical bond]N bond in a cyanide or an isocyanide resulted in the first calcium aldimide complexes [Ca{N=C(H)R}(dipp-nacnac)] and [Ca{C(H)=NR}(dipp-nacnac)], respectively. Complexation of 1 with borane or alane Lewis acids gave the borates and alanates as contact ion pairs. In reaction with epoxides, nucleophilic ring-opening is observed as the major reaction. The high reactivity of hydrocarbon-soluble 1 with most functional groups contrasts strongly with that of insoluble CaH(2), which is essentially inert and is used as a common drying agent. Crystal structures of the following products are presented: [{Ca{OC(H)Ph(2)}(dipp-nacnac)}(2)], [{Ca{N=C(H)Ph}(dipp-nacnac)}(2)], [{Ca{C(H)=NC(Me)(2)CH(2)C(Me)(3)}(dipp-nacnac)}(2)], [{Ca{C(H)=NCy}(dipp-nacnac)}(2)], [Ca(dipp-nacnac)(thf)](+)[H(2)BC(8)H(14)](-) and [{Ca(OCy)(dipp-nacnac)}(2)]. The generally smooth and clean conversions of 1 with a variety of substrates and the stability of most intermediates against ligand exchange make 1 a valuable key precursor in the syntheses of a wide variety of beta-diketiminate calcium complexes.

Dissolved Strontium and Barium in Fresh and Saltwater: a 2-year Study in the Calcasieu River to the Gulf of Mexico

NASA Astrophysics Data System (ADS)

He, S.; Xu, Y. J.

2016-02-01

Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. As sea level rise continues, many estuarine rivers face saltwater intrusion, which may cause changes in mobility and distribution of these metals upstream. Despite intensive research on metal adsorption and desorption in marine systems, knowledge of the spatiotemporal distribution of these elements along estuarine rivers is still limited. In this study, we conducted an intensive monitoring of Sr and Ba dynamics along an 88-km long estuary, the Calcasieu River, which has been strongly affected by saltwater intrusion. Over the period from May 2013 to July 2015, we collected monthly water samples and performed in-situ water quality measurements at six sites from the upstream to the river mouth. Water samples were analyzed for dissolved Sr, Ba, and Ca concentrations. In-situ measurements of salinity, pH, water temperature, dissolved oxygen concentration, and specific conductance were taken. Our preliminary data showed that the Sr and Ca concentrations and the Sr/Ca ratio all increased significantly with decreasing distance to the Gulf of Mexico, while the Ba/Ca ratio decreased with decreasing distance to the Gulf. The spatial variation in Ba concentration was marginal. The Sr and Ca concentrations and ratios were positively related to salinity, while Ba/Ca was negatively related to salinity. All the elemental concentrations and ratios had considerable seasonal and interannual variations. There were significant differences among sampling months for all the elemental concentrations and ratios (p<0.05), and there were significant differences among sampling years for the Sr and Ca concentrations and the Ba/Ca ratio (p<0.05).

Efficacy of a Calcium Sucrose Phosphate Based Toothpaste in Elevating the Level of Calcium, Phosphate Ions in Saliva and Reducing Plaque: A Clinical Trial

PubMed Central

Menon, Leena Unnikrishnan; Varma, R. Balagopal; Kumaran, Parvathy; Xavier, Arun Mamachan; Govinda, Bhat Sangeetha; Kumar, J. Suresh

2018-01-01

Aim: To evaluate and compare the efficacy of “calcium sucrose phosphate” (CaSP) toothpaste (Enafix 5%) with ordinarily used calcium, phosphate-containing toothpaste in elevating the level of calcium, phosphate ions in saliva. Secondary aims were to evaluate substantivity and plaque-reducing ability of CaSP toothpaste. Materials and Methods: Thirty study participants of age group 6–13 years were divided into two groups: Group X (Control group) was made to continue brushing with their regularly used calcium, phosphate-containing toothpaste and Group Y (Test group) was allotted CaSP toothpaste. 1 ml of unstimulated saliva was periodically collected from both groups to determine any alteration in the salivary calcium, phosphate level. Parameters such as substantivity and plaque-reducing ability of CaSP toothpaste were also evaluated. Salivary mineral's intergroup comparison was evaluated by Student's t-test while its intragroup comparison along with the plaque amount variation in Group Y was evaluated by ANOVA and Tukey's post hoc test. Results: Group Y showed an increase in the salivary calcium level though not statistically significant. The increase was pronounced in samples collected on day 1. Group Y showed a consistent level of calcium, phosphate in samples collected immediately and 6 h postbrushing, indicating its substantivity. In addition, Group Y had an impact in reducing the plaque level when the 1st-month plaque score was compared with the 12th-month score. Conclusion: CaSP leads to an increase in the salivary calcium level though it was not statistically significant. Supervised brushing and dietary habits showed a positive effect on both the groups. CaSP toothpaste also showed substantivity and plaque-reducing ability.

Supplementing a low-protein diet with dibasic amino acids increases urinary calcium excretion in young women.

PubMed

Bihuniak, Jessica D; Sullivan, Rebecca R; Simpson, Christine A; Caseria, Donna M; Huedo-Medina, Tania B; O'Brien, Kimberly O; Kerstetter, Jane E; Insogna, Karl L

2014-03-01

Increasing dietary protein within a physiologic range stimulates intestinal calcium absorption, but it is not known if specific amino acids or dietary protein as a whole are responsible for this effect. Therefore, we selectively supplemented a low-protein (0.7 g/kg) diet with either the calcium-sensing receptor-activating amino acids (CaSR-AAAs) L-tryptophan, L-phenylalanine, and L-histidine, or the dibasic amino acids (DAAs) L-arginine and L-lysine, to achieve intakes comparable to the content of a high-protein diet (2.1 g/kg) and measured intestinal calcium absorption. Fourteen young women took part in a placebo-controlled, double-blind, crossover feeding trial in which each participant ingested a 6-d low-protein diet supplemented with CaSR-AAAs, DAAs, or methylcellulose capsules (control) after an 11-d adjustment period. All participants ingested all 3 diets in random order. Intestinal calcium absorption was measured between days 5 and 6 using dual-stable calcium isotopes ((42)Ca, (43)Ca, and (44)Ca). There was no difference in calcium absorption between the diet supplemented with CaSR-AAAs (22.9 ± 2.0%) and the control diet (22.3 ± 1.4%) (P = 0.64). However, calcium absorption tended to be greater during the DAA supplementation period (25.2 ± 1.4%) compared with the control diet period (22.3 ± 1.4%) (P < 0.10). Larger and longer clinical trials are needed to clarify the possible benefit of arginine and lysine on calcium absorption.

SBIR Phase I final report, Sensor for direct, rapid and complete elemental analysis of coal

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

Liu, Chunyi

This Final Report is the result of the DOE SBIR Phase I assistance agreement No: DE-FOA-0001619 awarded to Applied Spectra, Inc. During the nine-month Phase I effort, we successfully demonstrated the ability to quantify rare-earth elements (REE) in coal using LIBS (Laser Induced Breakdown Spectroscopy) along with other elements of interest such as silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), titanium (Ti) and iron (Fe). In addition to elemental quantification, eighteen different coal types could be classified with 100% certainty using their LIBS spectrum. High-resolution LA-ICP-MS surface mapping showed a correlation between REE and other prevalent elementsmore » such as aluminum, silicon, and titanium.« less

The Influence of Calcium Chloride Deicing Salt on Phase Changes and Damage Development in Cementitious Materials.

PubMed

Farnam, Yaghoob; Dick, Sarah; Wiese, Andrew; Davis, Jeffrey; Bentz, Dale; Weiss, Jason

2015-11-01

The conventional CaCl 2 -H 2 O phase diagram is often used to describe how calcium chloride behaves when it is used on a concrete pavement undergoing freeze-thaw damage. However, the chemistry of the concrete can alter the appropriateness of using the CaCl 2 -H 2 O phase diagram. This study shows that the Ca(OH) 2 present in a hydrated portland cement can interact with CaCl 2 solution creating a behavior that is similar to that observed in isoplethal sections of a ternary phase diagram for a Ca(OH) 2 -CaCl 2 -H 2 O system. As such, it is suggested that such isoplethal sections provide a reasonable model that can be used to describe the behavior of concrete exposed to CaCl 2 solution as the temperature changes. Specifically, the Ca(OH) 2 can react with CaCl 2 and H 2 O resulting in the formation of calcium oxychloride. The formation of the calcium oxychloride is expansive and can produce damage in concrete at temperatures above freezing. Its formation can also cause a significant decrease in fluid ingress into concrete. For solutions with CaCl 2 concentrations greater than about 11.3 % (by mass), it is found that calcium oxychloride forms rapidly and is stable at room temperature (23 °C).

The Influence of Calcium Chloride Deicing Salt on Phase Changes and Damage Development in Cementitious Materials

PubMed Central

Farnam, Yaghoob; Dick, Sarah; Wiese, Andrew; Davis, Jeffrey; Bentz, Dale; Weiss, Jason

2015-01-01

The conventional CaCl2-H2O phase diagram is often used to describe how calcium chloride behaves when it is used on a concrete pavement undergoing freeze-thaw damage. However, the chemistry of the concrete can alter the appropriateness of using the CaCl2-H2O phase diagram. This study shows that the Ca(OH)2 present in a hydrated portland cement can interact with CaCl2 solution creating a behavior that is similar to that observed in isoplethal sections of a ternary phase diagram for a Ca(OH)2-CaCl2-H2O system. As such, it is suggested that such isoplethal sections provide a reasonable model that can be used to describe the behavior of concrete exposed to CaCl2 solution as the temperature changes. Specifically, the Ca(OH)2 can react with CaCl2 and H2O resulting in the formation of calcium oxychloride. The formation of the calcium oxychloride is expansive and can produce damage in concrete at temperatures above freezing. Its formation can also cause a significant decrease in fluid ingress into concrete. For solutions with CaCl2 concentrations greater than about 11.3 % (by mass), it is found that calcium oxychloride forms rapidly and is stable at room temperature (23 °C). PMID:26692655

Assessment and clinical course of hypocalcemia in critical illness

PubMed Central

2013-01-01

Introduction Hypocalcemia is common in critically ill patients. However, its clinical course during the early days of admission and the role of calcium supplementation remain uncertain, and the assessment of calcium status is inconsistent. We aimed to establish the course of hypocalcemia during the early days of critical illness in relation to mortality and to assess the impact of calcium supplementation on calcium normalization and mortality. Methods Data were collected on 1,038 admissions to the critical care units of a tertiary care hospital. One gram of calcium gluconate was administered intravenously once daily to patients with adjusted calcium (AdjCa) <2.2 mmol/L. Demographic and outcome data were compared in normocalcemic (ionized calcium, iCa, 1.1-1.3 mmol/L) and mildly and severely hypocalcemic patients (iCa 0.9-1.1 mmol/L and <0.9 mmol/L, respectively). The change in iCa concentrations was monitored during the first four days of admission and comparisons between groups were made using Repeated Measures ANOVA. Comparisons of normalization and outcome were made between hypocalcemic patients who did and did not receive calcium replacement according to the local protocol. The suitability of AdjCa to predict low iCa was determined by analyzing sensitivity, specificity and receiver operating characteristic (ROC) curves. Multivariate logistic regression was performed to determine associations of other electrolyte derangements with hypocalcemia. Results 55.2% of patients were hypocalcemic on admission; 6.2% severely so. Severely hypocalcemic patients required critical care for longer (P = 0.001) compared to normocalcemic or mildly hypocalcemic patients, but there was no difference in mortality between groups (P = 0.48). iCa levels normalized within four days in most, with no difference in normalization between those who died and survived (P = 0.35). Severely hypocalcemic patients who failed to normalize their iCa by day 4 had double the mortality (38% vs. 19%, P = 0.15). Neither iCa normalization nor survival were superior in hypocalcemic patients receiving supplementation on admission. AdjCa <2.2 mmol/L had a sensitivity of 78.2% and specificity of 63.3% for predicting iCa <1.1 mmol/L. Low magnesium, sodium and albumin were independently associated with hypocalcemia on admission. Conclusions Hypocalcemia usually normalizes within the first four days after admission to ICU and failure to normalize in severely hypocalcemic patients may be associated with increased mortality. Calcium replacement appears not to improve normalization or mortality. AdjCa is not a good surrogate of iCa in an ICU setting. PMID:23734769

Characterization of sea cucumber (stichopus japonicus) ovum hydrolysates: calcium chelation, solubility and absorption into intestinal epithelial cells.

PubMed

Sun, Na; Cui, Pengbo; Lin, Songyi; Yu, Cuiping; Tang, Yue; Wei, Ye; Xiong, Youling; Wu, Haitao

2017-10-01

Sea cucumber (Stichopus japonicus) ovum hydrolysates (SCOHs) chelated with calcium were produced to investigate the characteristics of calcium binding and solubility, as well as to study any effects on calcium absorption by human intestinal epithelial cells. The results of the present study show that the calcium-binding capacity of SCOHs depended greatly on the type of proteases. The maximum level of Ca binding (0.38 mmol L -1 ) occurred when trypsin was used, with a peptide yield of 85.7%. Investigation of the possible chelating modes between SCOHs and calcium ions indicated that calcium ions bound to SCOHs primarily via interactions with carboxyl oxygen and amino nitrogen atoms of Glu and Asp and also that the phosphoserine residues might be also responsible for SCOH-calcium chelation. Moreover, SCOH-calcium complexes maintained the solubility of calcium under simulated gastrointestinal digestion, regardless of the presence of dietary components such as oxalate. Furthermore, SCOH-Ca led to higher peak intracellular [Ca 2+ ] i in both Caco-2 cells (338.3 nmol L -1 versus 269.6 nmol L -1 ) and HT-29 cells (373.9 nmol L -1 versus 271.7 nmol L -1 ) than casein phosphopeptide-Ca. Carboxyl oxygen and amino nitrogen atoms in the SCOHs could bind calcium ions, forming SCOH-calcium complexes. These complexes improved calcium solubility under simulated gastrointestinal digestion and also promoted calcium absorption in Caco-2 and HT-29 cells. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Thermal degradation of hexachlorobenzene in the presence of calcium oxide at 340-400 °C.

PubMed

Yin, Keqing; Gao, Xingbao; Sun, Yifei; Zheng, Lei; Wang, Wei

2013-11-01

Hexachlorobenzene (HCB) in the milligram range was co-heated with calcium oxide (CaO) powder in sealed glass ampoules at 340-400 °C. The heated samples were characterized and analyzed by Raman spectroscopy, elemental analysis, gas chromatography/mass spectrometry, ion chromatography, and thermal/optical carbon analysis. The degradation products of HCB were studied at different temperatures and heated times. The amorphous carbon was firstly quantitatively evaluated and was thought to be important fate of the C element of HCB. The yield of amorphous carbon in products increased with heating time, for samples treated for 8h at 340, 380 °C and 400 °C, the value were 17.5%, 34.8% and 50.2%, respectively. After identification of the dechlorination products, the HCB degradation on CaO at 340-400 °C was supposed to through dechlorination/polymerization pathway, which is induced by electron transfer, generate chloride ions and form high-molecular weight intermediates with significant levels of both hydrogen and chlorine, and finally form amorphous carbon. Higher temperature was beneficial for the dechlorination/polymerization efficiency. The results are helpful for clarifying the reaction mechanism for thermal degradation of chlorinated aromatics in alkaline matrices. Copyright © 2013 Elsevier Ltd. All rights reserved.

Multi-spectroscopic analysis of cholesterol gallstone using TOF-SIMS, FTIR and UV-Vis spectroscopy

NASA Astrophysics Data System (ADS)

Jaswal, Brij Bir S.; Kumar, Vinay; Swart, H. C.; Sharma, Jitendra; Rai, Pradeep K.; Singh, Vivek K.

2015-10-01

For the first time, spatial distribution of major and trace elements has been studied in cholesterol gallstones using time-of-flight secondary mass ion mass spectrometry (TOF-SIMS). The TOF-SIMS has been used to study the elemental constituents of the center and surface parts of the gallstone sample. We have classified the gallstone sample using Fourier transform spectroscopy. The detected elements in cholesterol gallstone sample were carbon (C), hydrogen (H), calcium (Ca), sodium (Na), potassium (K), strontium (Sr), copper (Cu), iron (Fe), chromium (Cr), mercury (Hg) and lead (Pb). The detected molecules in the cholesterol gallstone were CH3 +, CO3 +, CaCO3 + and C3H+. Our results revealed that the contents of these elements in cholesterol gallstone were higher in the center part than that in the surface part. In the present paper, we have also presented the UV-Vis spectroscopic studies of the center and surface parts of the gallstone sample which indicated the presence of a higher content of cholesterol in the surface part and bilirubin in the center part.

Calcium-based biomaterials for diagnosis, treatment, and theranostics.

PubMed

Qi, Chao; Lin, Jing; Fu, Lian-Hua; Huang, Peng

2018-01-22

Calcium-based (CaXs) biomaterials including calcium phosphates, calcium carbonates, calcium silicate and calcium fluoride have been widely utilized in the biomedical field owing to their excellent biocompatibility and biodegradability. In recent years, CaXs biomaterials have been strategically integrated with imaging contrast agents and therapeutic agents for various molecular imaging modalities including fluorescence imaging, magnetic resonance imaging, ultrasound imaging or multimodal imaging, as well as for various therapeutic approaches including chemotherapy, gene therapy, hyperthermia therapy, photodynamic therapy, radiation therapy, or combination therapy, even imaging-guided therapy. Compared with other inorganic biomaterials such as silica-, carbon-, and gold-based biomaterials, CaXs biomaterials can dissolve into nontoxic ions and participate in the normal metabolism of organisms. Thus, they offer safer clinical solutions for disease theranostics. This review focuses on the state-of-the-art progress in CaXs biomaterials, which covers from their categories, characteristics and preparation methods to their bioapplications including diagnosis, treatment, and theranostics. Moreover, the current trends and key problems as well as the future prospects and challenges of CaXs biomaterials are also discussed at the end.

Recognition of spectral identifier from green coffee beans of arabica and robusta varieties using laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Anggraeni, Karina; Nasution, Aulia; Suyanto, Hery

2016-11-01

Coffee is one of the world's commodity that is cultivated in more than 50 countries. Production of coffee in Indonesia is positioned of fourth rank in the world, after Brazil, Vietnam, and Colombia. There are two varieties of coffee grown in Indonesia, i.e. the arabica and robusta. The chemical compositions between arabica and robusta are different each other. A trained coffee tester can distinguish these differences from its taste, but it is very subjective. Laser-Induced Breakdown Spectroscopy (LIBS) is a spectroscopic technique based on the analysis of micro-plasma induced on the surface sample after being shot with a laser pulse. In this study, elemental spectra acquired using Laser-Induced Breakdown Spectroscopy (LIBS) technique were analysed to differentate between green coffee beans of arabica and robusta, which are collected from plantations in Malang, Bondowoso, Prigen, and Pasuruan. Results show that optimum conditions for acquiring spectra from green coffee beans using LIBS are at 120 mJ of laser energy and 1,0 μs of delay time. Green coffee beans of arabica and robusta contain some elements such as Ca, W, Sr, Mg, Be, Na, H, N, K, Rb, and O. Discriminant analysis method was then applied to distinguish the green beans of arabica and robusta coffee. Element identifiers of green coffee beans are Ca, W, Mg, Be, Na, and Sr. The abundant element in green coffee beans is Calcium (Ca), and depth-profile testing shows that Ca is homogeneous inside the beans.

Calcium Efflux Systems in Stress Signaling and Adaptation in Plants

PubMed Central

Bose, Jayakumar; Pottosin, Igor I.; Shabala, Stanislav S.; Palmgren, Michael G.; Shabala, Sergey

2011-01-01

Transient cytosolic calcium ([Ca2+]cyt) elevation is an ubiquitous denominator of the signaling network when plants are exposed to literally every known abiotic and biotic stress. These stress-induced [Ca2+]cyt elevations vary in magnitude, frequency, and shape, depending on the severity of the stress as well the type of stress experienced. This creates a unique stress-specific calcium “signature” that is then decoded by signal transduction networks. While most published papers have been focused predominantly on the role of Ca2+ influx mechanisms to shaping [Ca2+]cyt signatures, restoration of the basal [Ca2+]cyt levels is impossible without both cytosolic Ca2+ buffering and efficient Ca2+ efflux mechanisms removing excess Ca2+ from cytosol, to reload Ca2+ stores and to terminate Ca2+ signaling. This is the topic of the current review. The molecular identity of two major types of Ca2+ efflux systems, Ca2+-ATPase pumps and Ca2+/H+ exchangers, is described, and their regulatory modes are analyzed in detail. The spatial and temporal organization of calcium signaling networks is described, and the importance of existence of intracellular calcium microdomains is discussed. Experimental evidence for the role of Ca2+ efflux systems in plant responses to a range of abiotic and biotic factors is summarized. Contribution of Ca2+-ATPase pumps and Ca2+/H+ exchangers in shaping [Ca2+]cyt signatures is then modeled by using a four-component model (plasma- and endo-membrane-based Ca2+-permeable channels and efflux systems) taking into account the cytosolic Ca2+ buffering. It is concluded that physiologically relevant variations in the activity of Ca2+-ATPase pumps and Ca2+/H+ exchangers are sufficient to fully describe all the reported experimental evidence and determine the shape of [Ca2+]cyt signatures in response to environmental stimuli, emphasizing the crucial role these active efflux systems play in plant adaptive responses to environment. PMID:22639615

Large Calcium Isotopic Variation in Peridotitic Xenoliths from North China Craton

NASA Astrophysics Data System (ADS)

Huang, S.; Zhao, X.; Zhang, Z.

2016-12-01

Calcium is the fifth most abundant element in the Earth. The Ca isotopic composition of the Earth is important in many aspects, ranging from tracing the Ca cycle on the Earth to comparing the Earth to other terrestrial planets. There is large mass-dependent Ca isotopic variation, measured as δ44/40Ca relative to a standard sample, in terrestrial igneous rocks: about 2 per mil in silicate rocks, compared to 3 per mil in carbonates. Therefore, a good understanding of the Ca isotopic variation in igneous rocks is necessary. Here we report Ca isotopic data on a series of peridotitic xenoliths from North China Craton (NCC). There is about 1 per mil δ44/40Ca variation in these NCC peridotites: The highest δ44/40Ca is close to typical mantle values, and the lowest δ44/40Ca is found in an Fe-rich peridotite, -1.13 relative to normal mantle (or -0.08 on the SRM 915a scale). This represents the lowest δ44/40Ca value ever reported for igneous rocks. Combined with published Fe isotopic data on the same samples, our data show a positive linear correlation between δ44/40Ca and δ57/54Fe in NCC peridotites. This trend is inconsistent with mixing a low-δ44/40Ca and -δ57/54Fe sedimentary component with a normal mantle component. Rather, it is best explained as the result of kinetic isotopic effect caused by melt-peridotite reaction on a time scale of several hundreds of years. In detail, basaltic melt reacts with peridotite, replaces orthopyroxene with clinopyroxene, and increases the Fo number of olivine. Consistent with this interpretation, our on-going Mg isotopic study shows that low-δ44/40Ca and -δ57/54Fe NCC peridotites also have heavier Mg isotopes compared to normal mantle. Our study shows that mantle metasomatism plays an important role generating stable isotopic variations within the Earth's mantle.

Milling assisted synthesis of calcium zirconate СаZrО3

NASA Astrophysics Data System (ADS)

Kalinkin, A. M.; Nevedomskii, V. N.; Kalinkina, E. V.; Balyakin, K. V.

2014-08-01

Monophase calcium zirconate (CaZrO3) has been prepared from the equimolar ZrO2 + CaCO3 mixture by two-step synthesis process. In the first step, mechanical treatment of the mixture is performed in an AGO-2 planetary ball mill. In the second step, the milled mixture is annealed to form calcium zirconate. High-energy ball milling of the (ZrO2+CaCO3) mixture results in decrease in the temperature of CaZrO3 formation during annealing at 950 °C. The enhancement of CaZrO3 synthesis is due to accumulation of excess energy by the reagents, decreasing the particle size and notable increase in the interphase area because of “smearing” of CaCO3 on ZrO2 particles during milling. Nanocrystalline calcium zirconate has been produced by controlling the annealing temperature and time.

Arctigenin exhibits relaxation effect on bronchus by affecting transmembrane flow of calcium.

PubMed

Zhao, Zhenying; Yin, Yongqiang; Wang, Zengyong; Fang, Runping; Wu, Hong; Jiang, Min; Bai, Gang; Luo, Guo'an

2013-12-01

Arctigenin, a lignan extract from Arctium lappa (L.), exhibits anti-inflammation, antioxidation, vasodilator effects, etc. However, the effects of arctigenin on bronchus relaxation are not well investigated. This study aimed to investigate how arctigenin regulates bronchus tone and calcium ion (Ca(2+)) flow. Trachea strips of guinea pigs were prepared for testing the relaxation effect of arctigenin to acetylcholine, histamine, KCl, and CaCl2, respectively. Furthermore, L-type calcium channel currents were detected by patch-clamp, and intracellular Ca(2+) concentration was detected by confocal microscopy. The results showed that arctigenin exhibited relaxation effect on tracheae to different constrictors, and this was related to decreasing cytoplasmic Ca(2+) concentration by inhibiting Ca(2+) influx partly through L-type calcium channel as well as promoting Ca(2+) efflux. In summary, this study provides new insight into the mechanisms by which arctigenin exhibits relaxation effect on bronchus and suggests its potential use for airway disease therapy.

Environmental Impact on Fossil Record for Palaecological Reconstruction Studies

NASA Astrophysics Data System (ADS)

Paraskevi, Chantzi; Elissavet, Dotsika; Brunella, Raco; Konstadinos, Albanakis; Anastasia, Poutouki; Eleni, Samarztidou

2016-10-01

Paleoecological studies have an important role in understanding past environmental, dietary and/or societal changes however require the authentic signature of fossil materials. Therefore, a significant part of these studies concerns the isolation of the material authentic matrix. Bone hydroxyapatite from different animal species from the archaeological site of Dispilio in Kastoria Lake basin in northern Greece has been subjected to mineral analysis in order to detect if there are suitable for palaoecological studies. Calcium, phosphorus, oxygen and hydrogen are the main components of bones resulting rigidity, hardness and compressive strength of their structure. However different bone structure resulting different calcium- phosphate phases and different compositions, including Ca/P ratios. These disparities may be attributable to different physiological characteristic, conditions under which the bones were formed or burial environment. Trace element analysis (Ca/P, Sr/P, Fe/Mn) concluded that treated fossil bones retained their biochemical signal without any strong influence by soil remains however without suggesting that no chemical alteration have been occurred.

Study of composition change and agglomeration of flue gas cleaning residue from a fluidized bed waste incinerator.

PubMed

Lievens, P; Verbinnen, B; Bollaert, P; Alderweireldt, N; Mertens, G; Elsen, J; Vandecasteele, C

2011-10-01

Blocking of the collection hoppers of the baghouse filters in a fluidized bed incinerator for co-incineration of high calorific industrial solid waste and sludge was observed. The composition of the flue gas cleaning residue (FGCR), both from a blocked hopper and from a normal hopper, was investigated by (differential) thermogravimetric analysis, quantitative X-ray powder diffraction and wet chemical analysis. The lower elemental carbon concentration and the higher calcium carbonate concentration of the agglomerated sample was the result of oxidation of carbon and subsequent reaction of CO2 with CaO. The evolved heat causes a temperature increase, with the decomposition of CaOHCl as a consequence. The formation of calcite and calcium chloride and the evolution of heat caused agglomeration of the FGCR. Activated lignite coke was replaced by another adsorption agent with less carbon, so the auto-ignition temperature increased; since then no further block formation has occurred.

Calmodulin-dependent gating of Ca(v)1.2 calcium channels in the absence of Ca(v)beta subunits.

PubMed

Ravindran, Arippa; Lao, Qi Zong; Harry, Jo Beth; Abrahimi, Parwiz; Kobrinsky, Evgeny; Soldatov, Nikolai M

2008-06-10

It is generally accepted that to generate calcium currents in response to depolarization, Ca(v)1.2 calcium channels require association of the pore-forming alpha(1C) subunit with accessory Ca(v)beta and alpha(2)delta subunits. A single calmodulin (CaM) molecule is tethered to the C-terminal alpha(1C)-LA/IQ region and mediates Ca2+-dependent inactivation of the channel. Ca(v)beta subunits are stably associated with the alpha(1C)-interaction domain site of the cytoplasmic linker between internal repeats I and II and also interact dynamically, in a Ca2+-dependent manner, with the alpha(1C)-IQ region. Here, we describe a surprising discovery that coexpression of exogenous CaM (CaM(ex)) with alpha(1C)/alpha(2)delta in COS1 cells in the absence of Ca(v)beta subunits stimulates the plasma membrane targeting of alpha(1C), facilitates calcium channel gating, and supports Ca2+-dependent inactivation. Neither real-time PCR with primers complementary to monkey Ca(v)beta subunits nor coimmunoprecipitation analysis with exogenous alpha(1C) revealed an induction of endogenous Ca(v)beta subunits that could be linked to the effect of CaM(ex). Coexpression of a calcium-insensitive CaM mutant CaM(1234) also facilitated gating of Ca(v)beta-free Ca(v)1.2 channels but did not support Ca2+-dependent inactivation. Our results show there is a functional matchup between CaM(ex) and Ca(v)beta subunits that, in the absence of Ca(v)beta, renders Ca2+ channel gating facilitated by CaM molecules other than the one tethered to LA/IQ to support Ca2+-dependent inactivation. Thus, coexpression of CaM(ex) creates conditions when the channel gating, voltage- and Ca2+-dependent inactivation, and plasma-membrane targeting occur in the absence of Ca(v)beta. We suggest that CaM(ex) affects specific Ca(v)beta-free conformations of the channel that are not available to endogenous CaM.

Real-time Recording of Cytosolic Calcium Levels in Arabidopsis thaliana Cell Cultures during Parabolic Flights

NASA Astrophysics Data System (ADS)

Neef, Maren; Ecke, Margret; Hampp, Rüdiger

2015-07-01

In plants, like in other organisms, calcium (Ca2+) is an important second messenger which participates in the conversion of environmental signals into molecular responses. There is increasing evidence, that sensing of changes in gravitation or reorientation of tissues is an example for such signaling cascades in which Ca2+ is involved. In order to determine g-dependent changes in the cytosolic calcium (Ca^{2+}_{ {cyt}}) concentration of plant cells, semisolid transgenic callus cell cultures of Arabidopsis thaliana (A.t.), expressing the calcium sensor YC3.6 (cameleon), were exposed to g-forces between 1.8 g and μ g during parabolic flights. Using such cells, intracellular calcium transients can be monitored by FRET in vivo and in real-time. Interestingly we observed a slight decrease of the Ca^{2+}_{ {cyt}} level during the hypergravity phases of a parabola but a significant increase of the Ca^{2+}_{ {cyt}} concentration during microgravity. Application of known Ca2+ inhibitors and antagonists yielded the following effects: nifedipine (Ca2+ channel blocker) showed no effect, whereas LaCl3, GdCl3 (both inhibitors of uptake at the plasma membrane), DPI (inhibitor of NADP oxidase), and DMSO (solvent) diminished the gravity-alteration-related Ca^{2+}_{ {cyt}} response. EGTA (binding of Ca2+) and eosin yellow (inhibitor of a plasma membrane-located Ca2+ pump) suppressed the respective Ca^{2+}_{ {cyt}} changes entirely. We thus conclude that the significant increase in Ca^{2+}_{ {cyt}} under microgravity is largely due to extracellular Ca2+ sources.

Restricting calcium currents is required for correct fiber type specification in skeletal muscle

PubMed Central

Sultana, Nasreen; Dienes, Beatrix; Benedetti, Ariane; Tuluc, Petronel; Szentesi, Peter; Sztretye, Monika; Rainer, Johannes; Hess, Michael W.; Schwarzer, Christoph; Obermair, Gerald J.; Csernoch, Laszlo

2016-01-01

ABSTRACT Skeletal muscle excitation-contraction (EC) coupling is independent of calcium influx. In fact, alternative splicing of the voltage-gated calcium channel CaV1.1 actively suppresses calcium currents in mature muscle. Whether this is necessary for normal development and function of muscle is not known. However, splicing defects that cause aberrant expression of the calcium-conducting developmental CaV1.1e splice variant correlate with muscle weakness in myotonic dystrophy. Here, we deleted CaV1.1 (Cacna1s) exon 29 in mice. These mice displayed normal overall motor performance, although grip force and voluntary running were reduced. Continued expression of the developmental CaV1.1e splice variant in adult mice caused increased calcium influx during EC coupling, altered calcium homeostasis, and spontaneous calcium sparklets in isolated muscle fibers. Contractile force was reduced and endurance enhanced. Key regulators of fiber type specification were dysregulated and the fiber type composition was shifted toward slower fibers. However, oxidative enzyme activity and mitochondrial content declined. These findings indicate that limiting calcium influx during skeletal muscle EC coupling is important for the secondary function of the calcium signal in the activity-dependent regulation of fiber type composition and to prevent muscle disease. PMID:26965373

Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

PubMed

Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

2012-12-18

The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.

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

NASA Astrophysics Data System (ADS)

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.

Administration of Inulin-Supplemented Gluten-Free Diet Modified Calcium Absorption and Caecal Microbiota in Rats in a Calcium-Dependent Manner.

PubMed

Krupa-Kozak, Urszula; Markiewicz, Lidia H; Lamparski, Grzegorz; Juśkiewicz, Jerzy

2017-07-06

In coeliac disease (CD), the risk of adverse calcium balance and reduced bone density is induced mainly by the disease, but also by a gluten-free diet (GFD), the only accepted CD therapy. Prebiotics through the beneficial impact on intestinal microbiota may stimulate calcium (Ca) absorption. In the present study, we hypothesised that the dietary inulin in GFD would influence positively the intestinal microbiota, and by that will stimulate the absorption of calcium (Ca), especially in the conditions of Ca malnutrition. In a six-weeks nutritional experiment on growing a significant ( p < 0.05) luminal acidification, decrease in ammonia concentration and stimulation of short chain fatty acids formation indicated inulin-mediated beneficial effects on the caecal microbiota. However, the effect of inulin on characteristics of intestinal microbiota and mineral utilization depended on the dietary Ca intake from GFDs. Inulin stimulated bifidobacteria, in particular B. animalis species, only if a recommended amount of Ca was provided. Most benefits to mineral utilization from inulin consumption were seen in rats fed Ca-restricted GFD where it increased the relative Ca absorption. Administration of inulin to a GFDs could be a promising dietary strategy for beneficial modulation of intestinal ecosystem and by that for the improvement the Ca absorption.

Plasma membrane calcium ATPases: From generic Ca(2+) sump pumps to versatile systems for fine-tuning cellular Ca(2.).

PubMed

Strehler, Emanuel E

2015-04-24

The plasma membrane calcium ATPases (PMCAs) are ATP-driven primary ion pumps found in all eukaryotic cells. They are the major high-affinity calcium extrusion system for expulsion of Ca(2+) ions from the cytosol and help restore the low resting levels of intracellular [Ca(2+)] following the temporary elevation of Ca(2+) generated during Ca(2+) signaling. Due to their essential role in the maintenance of cellular Ca(2+) homeostasis they were initially thought to be "sump pumps" for Ca(2+) removal needed by all cells to avoid eventual calcium overload. The discovery of multiple PMCA isoforms and alternatively spliced variants cast doubt on this simplistic assumption, and revealed instead that PMCAs are integral components of highly regulated multi-protein complexes fulfilling specific roles in calcium-dependent signaling originating at the plasma membrane. Biochemical, genetic, and physiological studies in gene-manipulated and mutant animals demonstrate the important role played by specific PMCAs in distinct diseases including those affecting the peripheral and central nervous system, cardiovascular disease, and osteoporosis. Human PMCA gene mutations and allelic variants associated with specific disorders continue to be discovered and underline the crucial role of different PMCAs in particular cells, tissues and organs. Copyright © 2015 Elsevier Inc. All rights reserved.

[Fluorine removal efficiency of organic-calcium during coal combustion].

PubMed

Liu, Jing; Liu, Jian-Zhong; Zhou, Jun-Hu; Xiao, Hai-Ping; Cen, Ke-Fa

2006-08-01

Effectiveness of calcium magnesium acetate (CMA) and calcium acetate(CA) as feasible HF capture were studied by means of fixed bed tube furnaces. The effects of temperature, particle diameter and Ca/S molar ratio on the fluorine removal efficiency were studied. By contract with CaCO3 at the same condition, we find that the HF capture effectiveness of those sorbents is superior to CaCO3, especially at high temperature. At 1 000 - 1 100 degrees C, the efficiency of fluorine removal during coal combustion of CMA is 1.68 - 1.74 times as that of CaCO3; the efficiency of fluorine removal during coal combustion of CA is 1.28 - 1.37 times as that of CaCO3.

Impact of calcium and TOC on biological acidification assessment in Norwegian rivers.

PubMed

Schneider, Susanne C

2011-02-15

Acidification continues to be a major impact in freshwaters of northern Europe, and the biotic response to chemical recovery from acidification is often not a straightforward process. The focus on biological recovery is relevant within the context of the EU Water Framework Directive, where a biological monitoring system is needed that detects differences in fauna and flora compared to undisturbed reference conditions. In order to verify true reference sites for biological analyses, expected river pH is modeled based on Ca and TOC, and 94% of variability in pH at reference sites is explained by Ca alone, while 98% is explained by a combination of Ca and TOC. Based on 59 samples from 28 reference sites, compared to 547 samples from 285 non-reference sites, the impact of calcium and total organic carbon (TOC) on benthic algae species composition, expressed as acidification index periphyton (AIP), is analyzed. Rivers with a high Ca concentration have a naturally higher AIP, and TOC affects reference AIP only at low Ca concentrations. Four biological river types are needed for assessment of river acidification in Norway based on benthic algae: very calcium-poor, humic rivers (Ca<1 mg/l and TOC>2 mg/l); very calcium-poor, clear rivers (Ca<1 mg/l and TOC<2 mg/l); calcium-poor rivers (Ca between 1 and 4 mg/l); moderately calcium rich rivers (Ca>4 mg/l). A biological assessment system for river acidification in Norway based on benthic algae is presented, following the demands of the Water Framework Directive. Copyright © 2010 Elsevier B.V. All rights reserved.

Calcium kinetics during bed rest with artificial gravity and exercise countermeasures

PubMed Central

Smith, S. M.; Castaneda-Sceppa, C.; O’Brien, K. O.; Abrams, S. A.; Gillman, P.; Brooks, N. E.; Cloutier, G. J.; Heer, M.; Zwart, S. R.; Wastney, M. E.

2015-01-01

Summary We assessed the potential for countermeasures to lessen the loss of bone calcium during bed rest. Subjects ingested less calcium during bed rest, and with artificial gravity, they also absorbed less calcium. With exercise, they excreted less calcium. To retain bone during bed rest, calcium intake needs to be maintained. Introduction This study aims to assess the potential for artificial gravity (AG) and exercise (EX) to mitigate loss of bone calcium during space flight. Methods We performed two studies: (1) a 21-day bed rest (BR) study with subjects receiving 1 h/day AG (n=8) or no AG (n=7) and (2) a 28-day BR study with 1 h/day resistance EX (n=10) or no EX (n=3). In both studies, stable isotopes of Ca were administered orally and intravenously, at baseline and after 10 days of BR, and blood, urine, and feces were sampled for up to 14 days post dosing. Tracers were measured using thermal ionization mass spectrometry. Data were analyzed by compartmental modeling. Results Less Ca was absorbed during BR, resulting in lower Ca balance in BR+AG (−6.04±3.38 mmol/day, P=0.023). However, Ca balance did not change with BR+EX, even though absorbed Ca decreased and urinary Ca excretion increased, because endogenous excretion decreased, and there was a trend for increased bone deposition (P=0.06). Urinary N-telopeptide excretion increased in controls during BR, but not in the EX group. Markers of bone formation were not different between treatment groups for either study. Ca intake decreased during BR (by 5.4 mmol/day in the AG study and 2.8 mmol/day in the EX study), resulting in lower absorbed Ca. Conclusions During BR (or space flight), Ca intake needs to be maintained or even increased with countermeasures such as exercise, to enable maintenance of bone Ca. PMID:24861908

Application of Quantitative Analytical Electron Microscopy to the Mineral Content of Insect Cuticle

NASA Astrophysics Data System (ADS)

Rasch, Ron; Cribb, Bronwen W.; Barry, John; Palmer, Christopher M.

2003-04-01

Quantification of calcium in the cuticle of the fly larva Exeretonevra angustifrons was undertaken at the micron scale using wavelength dispersive X-ray microanalysis, analytical standards, and a full matrix correction. Calcium and phosphorus were found to be present in the exoskeleton in a ratio that indicates amorphous calcium phosphate. This was confirmed through electron diffraction of the calcium-containing tissue. Due to the pragmatic difficulties of measuring light elements, it is not uncommon in the field of entomology to neglect the use of matrix corrections when performing microanalysis of bulk insect specimens. To determine, firstly, whether such a strategy affects the outcome and secondly, which matrix correction is preferable, phi-rho (z) and ZAF matrix corrections were contrasted with each other and without matrix correction. The best estimate of the mineral phase was found to be given by using the phi-rho (z) correction. When no correction was made, the ratio of Ca to P fell outside the range for amorphous calcium phosphate, possibly leading to flawed interpretation of the mineral form when used on its own.

The Institute of Medicine, the Food and Drug Administration, and the calcium conundrum.

PubMed

Neupane, Shristi; Knohl, Stephen J

2014-08-01

In the present article we aim to bring forward the apparent disconnect between two US government-sponsored entities - the Institute of Medicine (IOM) and the Food and Drug Administration (FDA) - regarding the safe upper limit of Ca intake. In light of the 2011 US Congress-appointed IOM report indicating an upper limit of elemental Ca intake of 2000-2500 mg/d in adults (based on age group), it is perplexing that the FDA has not yet required a change on the labelling of over-the-counter Ca-containing antacids, some of which indicate an upper limit of elemental Ca intake of 2800-3000 mg/d. Even more concerning is that Ca intake is rarely from supplementation in isolation. National Health and Nutrition Examination Survey (NHANES) data from 2003-2006 indicate that mean dietary Ca intakes for males ranged from 871 to 1266 mg/d and for females from 748 to 968 mg/d depending on the age group. The estimated total Ca (diet + supplements) intake exceeded the upper limit in 5 % of the population older than 50 years. Furthermore, NHANES data from 1999-2000 indicate that when Ca is taken as part of an antacid preparation, patients often fail to report this as Ca intake. Thus, individuals taking the maximum allowable dose of supplemental Ca as antacids are at high risk for complications associated with excess Ca intake. Our hope is that by describing Ca homeostasis and highlighting the risks and dangers of Ca overload, the FDA will align its recommendation with the IOM and solve the current Ca conundrum in the USA for the sake of patient safety.

Calcium Signals: The Lead Currency of Plant Information Processing

PubMed Central

Kudla, Jörg; Batistič, Oliver; Hashimoto, Kenji

2010-01-01

Ca2+ signals are core transducers and regulators in many adaptation and developmental processes of plants. Ca2+ signals are represented by stimulus-specific signatures that result from the concerted action of channels, pumps, and carriers that shape temporally and spatially defined Ca2+ elevations. Cellular Ca2+ signals are decoded and transmitted by a toolkit of Ca2+ binding proteins that relay this information into downstream responses. Major transduction routes of Ca2+ signaling involve Ca2+-regulated kinases mediating phosphorylation events that orchestrate downstream responses or comprise regulation of gene expression via Ca2+-regulated transcription factors and Ca2+-responsive promoter elements. Here, we review some of the remarkable progress that has been made in recent years, especially in identifying critical components functioning in Ca2+ signal transduction, both at the single-cell and multicellular level. Despite impressive progress in our understanding of the processing of Ca2+ signals during the past years, the elucidation of the exact mechanistic principles that underlie the specific recognition and conversion of the cellular Ca2+ currency into defined changes in protein–protein interaction, protein phosphorylation, and gene expression and thereby establish the specificity in stimulus response coupling remain to be explored. PMID:20354197

Interactions of endoplasmic reticulum and mitochondria Ca2+ stores with capacitative calcium entry

PubMed Central

Huang, Hsueh-Meei; Chen, Huan-Lian; Gibson, Gary E.

2014-01-01

Thiamine dependent enzymes are diminished in Alzheimer’s disease (AD). Thiamine deficiency in vitro and in rodents is a useful model of this reduction. Thiamine interacts with cellular calcium stores. To directly test the relevance of the thiamine dependent changes to dynamic processes in AD, the interactions must be studied in cells from patients with AD. These studies employed fibroblasts. Mitochondrial dysfunction including reductions in thiamine dependent enzymes and abnormalities in calcium homeostasis and oxidative processes occur in fibroblasts from Alzheimer’s Disease (AD) patients. Bombesin-releasable calcium stores (BRCS) from the endoplasmic reticulum (ER) are exaggerated in fibroblasts from patients with AD bearing a presenilin-1 (PS-1) mutation and in control fibroblasts treated with oxidants. ER calcium regulates calcium entry into the cell through capacitative calcium entry (CCE), which is reduced in fibroblasts and neurons from mice bearing PS-1 mutations. Under physiological conditions, mitochondria and ER play important and interactive roles in the regulation of Ca2+ homeostasis. Thus, the interactions of mitochondria and oxidants with CCE were tested. Inhibition of ER Ca2+-ATPase by cyclopiazonic acid (CPA) stimulates CCE. CPA-induced CCE was diminished by inhibition of mitochondrial Ca2+ export (−60%) or import (−40%). Different aspects of mitochondrial Ca2+ coupled to CPA-induced-CCE were sensitive to select oxidants. The effects were very different when CCE was examined in the presence of InsP3, a physiological regulator of ER calcium release, and subsequent CCE. CCE under these conditions was only mildly reduced (20–25%) by inhibition of mitochondrial Ca2+ export, and inhibition of mitochondrial Ca2+ uptake exaggerated CCE (+53%). However, t-BHP reversed both abnormalities. The results suggest that in the presence of InsP3, mitochondria buffer the local Ca2+ released from ER following rapid activation of InsP3R and serve as a negative feedback to the CCE. The results suggest that mitochondrial Ca2+ modifies the depletion and refilling mechanism of ER Ca2+ stores. PMID:24748364

Resveratrol-induced antinociception is involved in calcium channels and calcium/caffeine-sensitive pools.

PubMed

Pan, Xiaoyu; Chen, Jiechun; Wang, Weijie; Chen, Ling; Wang, Lin; Ma, Quan; Zhang, Jianbo; Chen, Lichao; Wang, Gang; Zhang, Meixi; Wu, Hao; Cheng, Ruochuan

2017-02-07

Resveratrol has been widely investigated for its potential health properties, although little is known about its mechanism in vivo. Previous studies have indicated that resveratrol produces antinociceptive effects in mice. Calcium channels and calcium/caffeine-sensitive pools are reported to be associated with analgesic effect. The present study was to explore the involvement of Ca2+ channel and calcium/caffeine-sensitive pools in the antinociceptive response of resveratrol. Tail-flick test was used to assess antinociception in mice treated with resveratrol or the combinations of resveratrol with MK 801, nimodipine, CaCl2, ryanodine and ethylene glycol tetraacetic acid (EGTA), respectively. The Ca2+/calmodulin-dependent protein kinase II (CaMKII) and brain-derived neurotrophic factor (BDNF) levels in the spinal cord were also investigated when treated with the above drugs. The results showed that resveratrol increased the tail flick latency in the tail-flick test, in dose-dependent manner. N-methyl-D-aspartate (NMDA) glutamate receptor antagonist MK 801 potentiated the antinociceptive effects of sub-threshold dose of resveratrol at 10 mg/kg. Ca2+ channel blocker, however, abolished the antinociceptive effects of resveratrol. In contrast to these results, EGTA or ryanodine treatment (i.c.v.) potentiated resveratrol-induced antinociception. There was a significant decrease in p-CaMKII and an increase in BDNF expression in the spinal cord when combined with MK 801, nimodipine, ryanodine and EGTA. While an increase in p-CaMKII level and a decrease in BDNF expression were observed when high dose of resveratrol combined with CaCl2. These findings suggest that resveratrol exhibits the antinociceptive effects by inhibition of calcium channels and calcium/caffeine-sensitive pools.

Expression of the high capacity calcium-binding domain of calreticulin increases bioavailable calcium stores in plants

NASA Technical Reports Server (NTRS)

Wyatt, Sarah E.; Tsou, Pei-Lan; Robertson, Dominique; Brown, C. S. (Principal Investigator)

2002-01-01

Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca2+-transport and storage pathways that include Ca2+ buffering proteins in the lumen of intracellular compartments. To date, most research has focused on the role of transporters in regulating cytosolic calcium. We used a reverse genetics approach to modulate calcium stores in the lumen of the endoplasmic reticulum. Our goals were two-fold: to use the low affinity, high capacity Ca2+ binding characteristics of the C-domain of calreticulin to selectively increase Ca2+ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. The C-domain of calreticulin is a highly acidic region that binds 20-50 moles of Ca2+ per mole of protein and has been shown to be the major site of Ca2+ storage within the endoplasmic reticulum of plant cells. A 377-bp fragment encoding the C-domain and ER retention signal from the maize calreticulin gene was fused to a gene for the green fluorescent protein and expressed in Arabidopsis under the control of a heat shock promoter. Following induction on normal medium, the C-domain transformants showed delayed loss of chlorophyll after transfer to calcium depleted medium when compared to seedlings transformed with green fluorescent protein alone. Total calcium measurements showed a 9-35% increase for induced C-domain transformants compared to controls. The data suggest that ectopic expression of the calreticulin C-domain increases Ca2+ stores, and that this Ca2+ reserve can be used by the plant in times of stress.

Crystallization and preliminary crystallographic analysis of calcium-binding protein-2 from Entamoeba histolytica and its complexes with strontium and the IQ1 motif of myosin V

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

Gourinath, S., E-mail: sgourinath@mail.jnu.ac.in; Padhan, Narendra; Alam, Neelima

2005-04-01

Calcium-binding protein-2 (EhCaBP2) crystals were grown using MPD as a precipitant. EhCaBP2 also crystallized in complex with strontium (replacing calcium) at similar conditions. Preliminary data for EhCaBP2 crystals in complex with an IQ motif are also reported. Calcium plays a pivotal role in the pathogenesis of amoebiasis, a major disease caused by Entamoeba histolytica. Two domains with four canonical EF-hand-containing calcium-binding proteins (CaBPs) have been identified from E. histolytica. Even though they have very high sequence similarity, these bind to different target proteins in a Ca{sup 2+}-dependent manner, leading to different functional pathways. Calcium-binding protein-2 (EhCaBP2) crystals were grown usingmore » MPD as a precipitant. The crystals belong to space group P2{sub 1}, with unit-cell parameters a = 111.74, b = 68.83, c = 113.25 Å, β = 116.7°. EhCaBP2 also crystallized in complex with strontium (replacing calcium) at similar conditions. The crystals belong to space group P2{sub 1}, with unit-cell parameters a = 69.18, b = 112.03, c = 93.42 Å, β = 92.8°. Preliminary data for EhCaBP2 crystals in complex with an IQ motif are also reported. This complex was crystallized with MPD and ethanol as precipitating agents. These crystals belong to space group P2{sub 1}, with unit-cell parameters a = 60.5, b = 69.86, c = 86.5 Å, β = 97.9°.« less

Autophosphorylation-based calcium (Ca2+) sensitivity priming and Ca2+/Calmodulin inhibition of Arabidopsis thaliana Ca2+-dependent protein kinase 28 (CPK28)

USDA-ARS?s Scientific Manuscript database

Plant calcium (Ca2+) dependent protein kinases (CPKs) are composed of a dual specificity (Ser/Thr and Tyr) kinase domain tethered to a Calmodulin-like domain (CLD) via an autoinhibitory junction (J) and represent the primary Ca2+-dependent protein kinase activities in plant systems. While regulation...

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

NASA Astrophysics Data System (ADS)

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.

Imaging calcium sparks in cardiac myocytes.

PubMed

Guatimosim, Silvia; Guatimosim, Cristina; Song, Long-Sheng

2011-01-01

Calcium ions play fundamental roles in many cellular processes in virtually all type of cells. The use of Ca(2+) sensitive fluorescent indicators has proven to be an indispensable tool for studying the spatio-temporal dynamics of intracellular calcium ([Ca(2+)](i)). With the aid of laser scanning confocal microscopy and new generation of Ca(2+) indicators, highly localized, short-lived Ca(2+) signals, namely Ca(2+) sparks, were revealed as elementary Ca(2+) release events during excitation-contraction coupling in cardiomyocytes. Since the discovery of Ca(2+) sparks in 1993, the demonstration of dynamic Ca(2+) micro-domains in living cardiomyocytes has revolutionized our understanding of Ca(2+)-mediated signal transduction in normal and diseased hearts. In this chapter, we have described a commonly used method for recording local and global Ca(2+) signals in cardiomyocytes using the fluorescent indicator fluo-4 acetoxymethyl (AM) and laser scanning confocal microscopy.

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

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

Angiotensin II stimulates calcium-dependent activation of c-Jun N-terminal kinase.

PubMed Central

Zohn, I E; Yu, H; Li, X; Cox, A D; Earp, H S

1995-01-01

In GN4 rat liver epithelial cells, angiotensin II (Ang II) and other agonists which activate phospholipase C stimulate tyrosine kinase activity in a calcium-dependent, protein kinase C (PKC)-independent manner. Since Ang II also produces a proliferative response in these cells, we investigated downstream signaling elements traditionally linked to growth control by tyrosine kinases. First, Ang II, like epidermal growth factor (EGF), stimulated AP-1 binding activity in a PKC-independent manner. Because increases in AP-1 can reflect induction of c-Jun and c-Fos, we examined the activity of the mitogen-activated protein (MAP) kinase family members Erk-1 and -2 and the c-Jun N-terminal kinase (JNK), which are known to influence c-Jun and c-Fos transcription. Ang II stimulated MAP kinase (MAPK) activity but only approximately 50% as effectively as EGF; again, these effects were independent of PKC. Ang II also produced a 50- to 200-fold activation of JNK in a PKC-independent manner. Unlike its smaller effect on MAPK, Ang II was approximately four- to sixfold more potent in activating JNK than EGF was. Although others had reported a lack of calcium ionophore-stimulated JNK activity in lymphocytes and several other cell lines, we examined the role of calcium in GN4 cells. The following results suggest that JNK activation in rat liver epithelial cells is at least partially Ca(2+) dependent: (i) norepinephrine and vasopressin hormones that increase inositol 1,4,5-triphosphate stimulated JNK; (ii) both thapsigargin, a compound that produces an intracellular Ca(2+) signal, and Ca(2+) ionophores stimulated a dramatic increase in JNK activity (up to 200-fold); (iii) extracellular Ca(2+) chelation with ethylene glycol tetraacetic acid (EGTA) inhibited JNK activation by ionophore and intracellular chelation with 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl-ester (BAPTA-AM) partially inhibited JNK activation by Ang II or thapsigargin; and (iv) JNK activation by Ang II was inhibited by pretreatment of cells with thapsigargin and EGTA, a procedure which depletes intracellular Ca(2+) stores. JNK activation following Ang II stimulation did not involve calmodulin; either W-7 nor calmidizolium, in concentrations sufficient to inhibit Ca(2+)/calmodulin-dependent kinase II, blocked JNK activation by Ang II. In contrast, genistein, in concentrations sufficient to inhibit Ca(2+)-dependent tyrosine phosphorylation, prevented Ang II and thapsigargin-induced JNK activation. In summary, in GN4 rat liver epithelial cells, Ang II stimulates JNK via a novel Ca(2+)-dependent pathway. The inhibition by genistein suggest that Ca(2+)-dependent tyrosine phosphorylation may modulate the JNK pathway in a cell type-specific manner, particularly in cells with a readily detectable Ca(2+)-regulated tyrosine kinase. PMID:7565768

Fluoride-induced enhancement of diffusion in streptococcal model plaque biofilms.

PubMed

Rose, R K; Turner, S J

1998-01-01

It has been demonstrated that fluoride decreases the calcium-binding affinity of Streptococcus mutans and approximately doubles the calcium-binding capacity. To investigate the effect of this mechanism on calcium mobility in plaque, 45Ca flux was measured from a condensed films of S. mutans into tracer-free solution. Bacteria were suspended in pH 7.0 or 5.0 buffer including 0, 5, 10, 15 or 20 mmol/l Ca2+ carrier, with or without 5 mmol/l F- and with 45Ca and 3H-inulin. The appearance of 45Ca and 3H-inulin in carrier-containing but initially tracer-free buffer was measured and extracellular fraction (Ve) and bound calcium were calculated. As the ratio (R) of bound to free Ca2+ approached zero at high [Ca2+], the measured diffusion coefficient (rDe) approached the effective diffusion coefficient (De), such that: rDe = De/(1+R). Fluoride increased the rate of calcium diffusion by a reduction in the binding affinity. This work demonstrates that fluoride significantly increases mobility in plaque; this may increase the rate at which calcium is transported between plaque and an underlying lesion and so promote remineralization. This mechanism could also increase the penetration of bacteriocides and suggests a novel method for biofilm treatment.

Induction of defence gene expression by oligogalacturonic acid requires increases in both cytosolic calcium and hydrogen peroxide in Arabidopsis thaliana.

PubMed

Hu, Xiang Yang; Neill, Steven J; Cai, Wei Ming; Tang, Zhang Cheng

2004-06-01

Responses to oligogalacturonic acid (OGA) were determined in transgenic Arabidopsis thaliana seedlings expressing the calcium reporter protein aequorin. OGA stimulated a rapid, substantial and transient increase in the concentration of cytosolic calcium ([Ca2+]cyt) that peaked after ca. 15 s. This increase was dose-dependent, saturating at ca. 50 ug Gal equiv/ml of OGA. OGA also stimulated a rapid generation of H2O2. A small, rapid increase in H2O2 content was followed by a much larger oxidative burst, with H2O2 content peaking after ca. 60 min and declining thereafter. Induction of the oxidative burst by OGA was also dose-dependent, with a maximum response again being achieved at ca. 50 ug Gal equiv/mL. Inhibitors of calcium fluxes inhibited both increases in [Ca2+]cyt and [H2O2], whereas inhibitors of NADPH oxidase blocked only the oxidative burst. OGA increased strongly the expression of the defence-related genes CHS, GST, PAL and PR-1. This induction was suppressed by inhibitors of calcium flux or NADPH oxidase, indicating that increases in both cytosolic calcium and H2O2 are required for OGA-induced gene expression.

Laser induced fluorescence spectroscopy of the Ca dimer deposited on helium and mixed helium/xenon clusters

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

Gaveau, Marc-André; Pothier, Christophe; Briant, Marc

2014-12-09

We study how the laser induced fluorescence spectroscopy of the calcium dimer deposited on pure helium clusters is modified by the addition of xenon atoms. In the wavelength range between 365 and 385 nm, the Ca dimer is excited from its ground state up to two excited electronic states leading to its photodissociation in Ca({sup 1}P)+Ca({sup 1}S): this process is monitored by recording the Ca({sup 1}P) fluorescence at 422.7nm. One of these electronic states of Ca{sub 2} is a diexcited one correlating to the Ca(4s4p{sup 3}P(+Ca(4s3d{sup 3}D), the other one is a repulsive state correlating to the Ca(4s4p1P)+Ca(4s21S) asymptote, accountingmore » for the dissociation of Ca{sub 2} and the observation of the subsequent Ca({sup 1}P) emission. On pure helium clusters, the fluorescence exhibits the calcium atomic resonance line Ca({sup 1}S←{sup 1}P) at 422.7 nm (23652 cm{sup −1}) assigned to ejected calcium, and a narrow red sided band corresponding to calcium that remains solvated on the helium cluster. When adding xenon atoms to the helium clusters, the intensity of these two features decreases and a new spectral band appears on the red side of calcium resonance line; the intensity and the red shift of this component increase along with the xenon quantity deposited on the helium cluster: it is assigned to the emission of Ca({sup 1}P) associated with the small xenon aggregate embedded inside the helium cluster.« less

The plasma membrane protein Rch1 and the Golgi/ER calcium pump Pmr1 have an additive effect on filamentation in Candida albicans.

PubMed

Jiang, Linghuo; Xu, Dayong; Hameed, Ahsan; Fang, Tianshu; Bakr Ahmad Fazili, Abu; Asghar, Faiza

2018-06-01

Pmr1 is the Golgi/ER calcium pump, while Rch1 is a newly identified negative regulator of calcium influx in the plasma membrane of yeast cells. We show here that CaRch1 plays a dominant role over CaPmr1 in response of Candida albicans to SDS and tunicamycin stresses, while CaPmr1 has a major role in cell wall stress. Deletion of CaRCH1 increases the calcium/calcineurin signaling level in cells lacking CaPMR1. Calcineurin function is required for the role of CaRch1 in SDS stresses, while it is required for the function of CaPmr1 under all conditions examined. Disruption of CaRCH1 alone does not reduce the cell wall chitin, mannan or β-glucan content, but lack of CaRCH1 slightly decreases the chitin content of cells lacking CaPMR1. Furthermore, CaRch1 and CaPmr1 have an additive effect on filamentation of C. albicans cells in vitro. Cells lacking both CaRCH1 and CaPMR1 and cells lacking CaPMR1 alone show a similar degree of virulence attenuation, being much more attenuated than cells lacking CaRCH1 alone. Therefore, CaRch1 genetically interacts with CaPmr1 in the regulation of in vitro filamentation in C. albicans. Copyright © 2018 Elsevier Inc. All rights reserved.

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

PubMed

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.

Natural calcium isotonic composition of urine as a marker of bone mineral balance

USGS Publications Warehouse

Skulan, J.; Bullen, T.; Anbar, A.D.; Puzas, J.E.; Shackelford, L.; LeBlanc, A.; Smith, S.M.

2007-01-01

Background: We investigated whether changes in the natural isotopic composition of calcium in human urine track changes in net bone mineral balance, as predicted by a model of calcium isotopic behavior in vertebrates. If so, isotopic analysis of natural urine or blood calcium could be used to monitor short-term changes in bone mineral balance that cannot be detected with other techniques. Methods: Calcium isotopic compositions are expressed as ??44Ca, or the difference in parts per thousand between the 44Ca/40Ca of a sample and the 44Ca/ 40Ca of a standard reference material. ??44Ca was measured in urine samples from 10 persons who participated in a study of the effectiveness of countermeasures to bone loss in spaceflight, in which 17 weeks of bed rest was used to induce bone loss. Study participants were assigned to 1 of 3 treatment groups: controls received no treatment, one treatment group received alendronate, and another group performed resistive exercise. Measurements were made on urine samples collected before, at 2 or 3 points during, and after bed rest. Results: Urine ??44Ca values during bed rest were lower in controls than in individuals treated with alendronate (P <0.05, ANOVA) or exercise (P <0.05), and lower than the control group baseline (P <0.05, Mest). Results were consistent with the model and with biochemical and bone mineral density data. Conclusion: Results confirm the predicted relationship between bone mineral balance and calcium isotopes, suggesting that calcium isotopic analysis of urine might be refined into a clinical and research tool. ?? 2007 American Association for Clinical Chemistry.

Natural calcium isotopic composition of urine as a marker of bone mineral balance.

PubMed

Skulan, Joseph; Bullen, Thomas; Anbar, Ariel D; Puzas, J Edward; Shackelford, Linda; LeBlanc, Adrian; Smith, Scott M

2007-06-01

We investigated whether changes in the natural isotopic composition of calcium in human urine track changes in net bone mineral balance, as predicted by a model of calcium isotopic behavior in vertebrates. If so, isotopic analysis of natural urine or blood calcium could be used to monitor short-term changes in bone mineral balance that cannot be detected with other techniques. Calcium isotopic compositions are expressed as delta(44)Ca, or the difference in parts per thousand between the (44)Ca/(40)Ca of a sample and the (44)Ca/(40)Ca of a standard reference material. delta(44)Ca was measured in urine samples from 10 persons who participated in a study of the effectiveness of countermeasures to bone loss in spaceflight, in which 17 weeks of bed rest was used to induce bone loss. Study participants were assigned to 1 of 3 treatment groups: controls received no treatment, one treatment group received alendronate, and another group performed resistive exercise. Measurements were made on urine samples collected before, at 2 or 3 points during, and after bed rest. Urine delta(44)Ca values during bed rest were lower in controls than in individuals treated with alendronate (P <0.05, ANOVA) or exercise (P <0.05), and lower than the control group baseline (P <0.05, t-test). Results were consistent with the model and with biochemical and bone mineral density data. Results confirm the predicted relationship between bone mineral balance and calcium isotopes, suggesting that calcium isotopic analysis of urine might be refined into a clinical and research tool.

Cholinergic Neurons Mediate CaMKII-Dependent Enhancement of Courtship Suppression

ERIC Educational Resources Information Center

Mehren, Jennifer E.; Griffith, Leslie C.

2006-01-01

In "Drosophila," calcium/calmodulin-dependent protein kinase II (CaMKII) activity is crucial in associative courtship conditioning for both memory formation and suppression of courtship during training with a mated female. We have previously shown that increasing levels of constitutively active CaMKII, but not calcium-dependent CaMKII, in a subset…

Physiological implications of anthropogenic environmental calcium depletion

Treesearch

Catherine H. Borer; Paul G. Schaberg; Donald H. DeHayes; Gary J. Hawley

2001-01-01

Recent evidence indicates that numerous anthropogenic factors can deplete calcium (Ca) from forested ecosystems. Although it is difficult to quantify the extent of this depletion, some reports indicate that the magnitude of Ca losses may be substantial. The potential for Ca depletion raises important questions about tree health. Only a fraction of foliar Ca is...

Nano-rod Ca-decorated sludge derived carbon for removal of phosphorus.

PubMed

Kong, Lingjun; Han, Meina; Shih, Kaimin; Su, Minhua; Diao, Zenghui; Long, Jianyou; Chen, Diyun; Hou, Li'an; Peng, Yan

2018-02-01

Recovering phosphorus (P) from waste streams takes the unique advantage in simultaneously addressing the crisis of eutrophication and the shortage of P resource. A novel calcium decorated sludge carbon (Ca-SC) was developed from dyeing industry wastewater treatment sludge by decorating calcium (Ca) to effectively adsorb phosphorus from solution. The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques were used to characterize the Ca-SCs, followed by isotherm and kinetic sorption experiments. A preferred design with CaCO 3 to sludge mass ratio of 1:2 was found to have a sorption capacity of 116.82 mg/g for phosphorus. This work reveals the crucial role of well-dispersed nano-rod calcium on the Ca-SC surface for the sorption of phosphorus. Moreover, the decoration of nano-rod calcium was found to further promote the uptake of phosphorus through the formation of hydroxylapatite (Ca 5 (PO 4 ) 3 (OH)). Thus, the development of decorated Ca-SC for sorption of phosphorus is very important in solving the P pollution and resource loss. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calcium transport in gill cells of Ucides cordatus, a mangrove crab living in variable salinity environments.

PubMed

Leite, V P; Zanotto, F P

2013-10-01

Crustaceans show discontinuous growth and have been used as a model system for studying cellular mechanisms of calcium transport, which is the main mineral found in their exoskeleton. Ucides cordatus, a mangrove crab, is naturally exposed to fluctuations in calcium and salinity. To study calcium transport in this species during isosmotic conditions, dissociated gill cells were marked with fluo-3 and intracellular Ca(2+) change was followed by adding extracellular Ca(2+) as CaCl2 (0, 0.1, 0.25, 0.50, 1.0 and 5mM), together with different inhibitors. For control gill cells, Ca(2+) transport followed Michaelis-Menten kinetics with Vmax=0.137±0.001 ∆Ca(2+)i (μM×22.10(4)cells(-1)×180s(-1); N=4; r(2)=0.99); Km=0.989±0.027mM. The use of different inhibitors for gill cells showed that amiloride (Na(+)/Ca(2+) exchange inhibitor) inhibited 80% of Ca(2+) transport in gill cells (Vmax). KB-R, an inhibitor of Ca influx in vertebrates, similarly caused a decrease in Ca(2+) transport and verapamil (Ca(2+) channel inhibitor) had no effect on Ca(2+) transport, while nifedipine (another Ca(2+) channel inhibitor) caused a 20% decrease in Ca(2+) affinity compared to control values. Ouabain, on the other hand, caused no change in Ca(2+) transport, while vanadate increased the concentration of intracellular calcium through inhibition of Ca(2+) efflux probably through the plasma membrane Ca(2+)-ATPase. Results show that transport kinetics for Ca(2+) in these crabs under isosmotic conditions is lower compared to a hyper-regulator freshwater crab Dilocarcinus pagei studied earlier using fluorescent Ca(2+) probes. These kinds of studies will help understanding the comparative mechanisms underlying the evolution of Ca transport in crabs living in different environments. © 2013.

Damage development, phase changes, transport properties, and freeze-thaw performance of cementitious materials exposed to chloride based salts

NASA Astrophysics Data System (ADS)

Farnam, Yaghoob

Recently, there has been a dramatic increase in premature deterioration in concrete pavements and flat works that are exposed to chloride based salts. Chloride based salts can cause damage and deterioration in concrete due to the combination of factors which include: increased saturation, ice formation, salt crystallization, osmotic pressure, corrosion in steel reinforcement, and/or deleterious chemical reactions. This thesis discusses how chloride based salts interact with cementitious materials to (1) develop damage in concrete, (2) create new chemical phases in concrete, (3) alter transport properties of concrete, and (4) change the concrete freeze-thaw performance. A longitudinal guarded comparative calorimeter (LGCC) was developed to simultaneously measure heat flow, damage development, and phase changes in mortar samples exposed to sodium chloride (NaCl), calcium chloride (CaCl 2), and magnesium chloride (MgCl2) under thermal cycling. Acoustic emission and electrical resistivity measurements were used in conjunction with the LGCC to assess damage development and electrical response of mortar samples during cooling and heating. A low-temperature differential scanning calorimetry (LT-DSC) was used to evaluate the chemical interaction that occurs between the constituents of cementitious materials (i.e., pore solution, calcium hydroxide, and hydrated cement paste) and salts. Salts were observed to alter the classical phase diagram for a salt-water system which has been conventionally used to interpret the freeze-thaw behavior in concrete. An additional chemical phase change was observed for a concrete-salt-water system resulting in severe damage in cementitious materials. In a cementitious system exposed to NaCl, the chemical phase change occurs at a temperature range between -6 °C and 8 °C due to the presence of calcium sulfoaluminate phases in concrete. As a result, concrete exposed to NaCl can experience additional freeze-thaw cycles due to the chemical phase change creating cracks and damage to concrete under freezing and thawing. In a cementitious system exposed to CaCl2, the chemical phase change is mainly due to the presence of calcium hydroxide (CH) in concrete. Calcium hydroxide can react with CaCl2 solution producing calcium oxychloride. Calcium oxychloride forms at room temperature (i.e., 23 °C) for CaCl 2 salt concentrations at or above ~ 12 % by mass in the solution creating expansion and degradation in concrete. In a cementitious system exposed to MgCl2, it was observed that MgCl2 can be entirely consumed in concrete by reacting with CH and produce CaCl2. As such, it followed a response that is more similar to the concrete-CaCl2-water system than that of the MgCl2-water phase diagram. Formation of calcium/magnesium oxychloride is most likely the main source of the chemical phase change (which can cause damage) in concrete exposed to MgCl2. During the LGCC testing for CaCl2 and MgCl2 salts, it was found that the chemical reactions occur rapidly (~ 10 min) and can cause a significant decrease in subsequent fluid ingress into exposed concrete in comparison to NaCl. Isothermal calorimetry, fluid absorption, oxygen permeability, oxygen diffusivity, and X-ray fluorescence testing showed that the formation of calcium oxychloride in concrete exposed to CaCl2 and MgCl 2 can block or fill in the concrete pores on the surface of the specimen; thereby decreasing the CaCl2 and MgCl2 fluid ingress into the concrete. To mitigate the damage and degradation due to the chemical phase transition, two approaches were evaluated: (1) use of a cementitious binder that does not react with salts, and (2) use of a new practical technology to melt ice and snow, thereby decreasing the demand for deicing salt usage. For the first approach, carbonated calcium silicate based cement (CCSC) was used and the CCSC mortar showed a promising performance and resistance to salt degradation than an ordinary portland mortar does. For the second approach, phase change materials (PCM), including paraffin oil and methyl laurate, were used to store heat in concrete elements and release the stored heat during cooling to reduce ice formation and snow accumulation on the surface of concrete. PCM approach also showed a promising performance in melting ice and snow, thereby decreasing the demand for salt usage.

Ca4As3 – a new binary calcium arsenide

PubMed Central

Hoffmann, Andrea V.; Hlukhyy, Viktor; Fässler, Thomas F.

2015-01-01

The crystal structure of the binary compound tetra­calcium triarsenide, Ca4As3, was investigated by single-crystal X-ray diffraction. Ca4As3 crystallizes in the Ba4P3 structure type and is thus a homologue of isotypic Sr4As3. The unit cell contains 32 Ca2+ cations, 16 As3− isolated anions and four centrosymmetric [As2]4– dumbbells. The As atoms in each of the dumbbells are connected by a single bond, thus this calcium arsenide is a Zintl phase. PMID:26870427

21 CFR 184.1230 - Calcium sulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium sulfate. 184.1230 Section 184.1230 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT... GRAS § 184.1230 Calcium sulfate. (a) Calcium sulfate (CaSO4, CAS Reg. No. 7778-18-9 or CaSO4·2H2O, CAS...

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

PubMed

Gregório, Sílvia F; Fuentes, Juan

2018-04-04

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.

Proteinaceous and oligosaccharidic elicitors induce different calcium signatures in the nucleus of tobacco cells.

PubMed

Lecourieux, David; Lamotte, Olivier; Bourque, Stéphane; Wendehenne, David; Mazars, Christian; Ranjeva, Raoul; Pugin, Alain

2005-12-01

We previously reported elevated cytosolic calcium levels in tobacco cells in response to elicitors [D. Lecourieux, C. Mazars, N. Pauly, R. Ranjeva, A. Pugin, Analysis and effects of cytosolic free calcium elevations in response to elicitors in Nicotiana plumbaginifolia cells, Plant Cell 14 (2002) 2627-2641]. These data suggested that in response to elicitors, Ca2+, as a second messenger, was involved in both systemic acquired resistance (RSA) and/or hypersensitive response (HR) depending on calcium signature. Here, we used transformed tobacco cells with apoaequorin expressed in the nucleus to monitor changes in free nuclear calcium concentrations ([Ca2+](nuc)) in response to elicitors. Two types of elicitors are compared: proteins leading to necrosis including four elicitins and harpin, and non-necrotic elicitors including flagellin (flg22) and two oligosaccharidic elicitors, namely the oligogalacturonides (OGs) and the beta-1,3-glucan laminarin. Our data indicate that the proteinaceous elicitors induced a pronounced and sustainable [Ca2+](nuc) elevation, relative to the small effects of oligosaccharidic elicitors. This [Ca2+](nuc) elevation, which seems insufficient to induce cell death, is unlikely to result directly from the diffusion of calcium from the cytosol. The [Ca2+](nuc) rise depends on free cytosolic calcium, IP3, and active oxygen species (AOS) but is independent of nitric oxide.

Effects of various forms of calcium on body weight and bone turnover markers in women participating in a weight loss program.

PubMed

Wagner, Ginger; Kindrick, Shirley; Hertzler, Steven; DiSilvestro, Robert A

2007-10-01

This study examined the effects of calcium intake on body weight, body fat, and markers of bone turnover in pre-menopausal adult women undergoing a 12 week weight loss program of diet and exercise. Subjects were prescribed a 12 week diet with a 500 Kcal restriction containing about 750 mg calcium/day, exercised 3 times/week, and were given either placebo capsules, capsules of calcium lactate or calcium phosphate (daily dose about 800 mg calcium), or low fat milk (daily dose about 800 mg calcium). Subjects completed and returned daily diet diaries weekly. Daily calcium intake in mg from diet records + supplement assignment was: 788 +/- 175 (placebo), 1698 +/- 210 (Ca lactate), 1566 +/- 250 (Ca phosphate), 1514 +/- 225 (milk)(no significant differences among the calcium and milk groups). Each group had statistically significant changes in body weight (p < 0.01), but there were no significant differences among groups for the weight loss: 5.8 +/- 0.8 kg (placebo), 4.1 +/- 0.7 kg (Ca lactate), 5.4 +/- 1.3 kg (Ca phosphate), 4.2 +/- 0.8 kg (milk). Body fat was changed significantly in each group (p < 0.01), with milk group showing a little less change than the other groups. Serum bone specific alkaline phophatase activity, a bone synthesis marker, increased similarly in all groups (p < 0.001 within groups, no significance for changes among groups). In contrast, the Ca lactate group, but not other groups, had a drop in urine values for alpha helical peptide, a bone resorption marker (p < 0.05). For the conditions of this study, increased calcium intake, by supplement or milk, did not enhance loss of body weight or fat, though calcium lactate supplementation lowered values for a marker of bone degradation.

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

PubMed Central

Sánchez, Gina; Hidalgo, Cecilia; Donoso, Paulina

2003-01-01

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

Elemental composition of four farmed fish produced in Portugal.

PubMed

Lourenço, Helena M; Afonso, Cláudia; Anacleto, Patrícia; Martins, Maria F; Nunes, Maria L; Lino, Ana R

2012-11-01

Farmed gilthead sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax), rainbow trout (Oncorhynchus mykiss) and turbot (Psetta maxima) produced in Portugal were analysed in order to characterize their elemental composition. Atomic absorption (flame and cold vapour) and molecular absorption spectrometry techniques were used to determine all the studied elements. Similar patterns of macro, trace and ultra trace elements were observed for all fish species. The main elements were potassium (K), sodium (Na), phosphorus (P), magnesium (Mg) and calcium (Ca), followed by zinc (Zn), iron (Fe), copper (Cu), chromium (Cr), manganese (Mn) and nickel (Ni). Cadmium (Cd), mercury (Hg) and lead (Pb) concentrations, obtained in this study, allow concluding that these species do not present a hazard for human consumption. In addition, they contain almost all essential elements at concentrations sufficient to suit the dietary reference intake. Nevertheless, P. maxima nutritious trace element content is relatively low compared with the other three species.

High affinity binding of amyloid β-peptide to calmodulin: Structural and functional implications.

PubMed

Corbacho, Isaac; Berrocal, María; Török, Katalin; Mata, Ana M; Gutierrez-Merino, Carlos

2017-05-13

Amyloid β-peptides (Aβ) are a major hallmark of Alzheimer's disease (AD) and their neurotoxicity develop with cytosolic calcium dysregulation. On the other hand, calmodulin (CaM), a protein which plays a major multifunctional role in neuronal calcium signaling, has been shown to be involved in the regulation of non-amyloidogenic processing of amyloid β precursor protein (APP). Using fluorescent 6-bromoacetyl-2-dimethylaminonaphthalene derivatives of CaM, Badan-CaM, and human amyloid β(1-42) HiLyte™-Fluor555, we show in this work that Aβ binds with high affinity to CaM through the neurotoxic Aβ25-35 domain. In addition, the affinity of Aβ for calcium-saturated CaM conformation is approximately 20-fold higher than for CaM conformation in the absence of calcium (apo-CaM). Moreover, the value of K d of 0.98 ± 0.11 nM obtained for Aβ1-42 dissociation from CaM saturated by calcium points out that CaM is one of the cellular targets with highest affinity for neurotoxic Aβ peptides. A major functional consequence of Aβ-CaM interaction is that it slowdowns Aβ fibrillation. The novel and high affinity interaction between calmodulin and Aβ shown in this work opens a yet-unexplored gateway to further understand the neurotoxic effect of Aβ in different neural cells and also to address the potential of calmodulin and calmodulin-derived peptides as therapeutic agents in AD. Copyright © 2017 Elsevier Inc. All rights reserved.

Heat Treatment of Closed-Cell A356 + 4 wt.%Cu + 2 wt.%Ca Foam and Its Effect on the Foam Mechanical Behavior

NASA Astrophysics Data System (ADS)

Mirbagheri, S. M. H.; Vali, H.; Soltani, H.

2017-01-01

In this investigation, aluminum-silicon alloy foam is developed by adding certain amounts of copper and calcium elements in A356 alloy. Addition of 4 wt.%Cu + 2 wt.%Ca to the melt changed bubbles morphology from ellipsoid to spherical by decreasing Reynolds number and increasing Bond number. Compression behavior and energy absorption of the foams are assessed before and after aging. Solid solution treatment and aging lead to the best mechanical properties with 170% enhancement in yield strength and 185% improvement in energy absorption capacity as compared to non-heat-treated foams. The metallographic observations showed that bubbles geometry and structure in the A356 + 4wt.% Cu + 2 wt.%Ca foam are more homogeneous than the A356 foam.

Recognition of β-calcineurin by the domains of calmodulin: thermodynamic and structural evidence for distinct roles.

PubMed

O'Donnell, Susan E; Yu, Liping; Fowler, C Andrew; Shea, Madeline A

2011-03-01

Calcineurin (CaN, PP2B, PPP3), a heterodimeric Ca(2+)-calmodulin-dependent Ser/Thr phosphatase, regulates swimming in Paramecia, stress responses in yeast, and T-cell activation and cardiac hypertrophy in humans. Calcium binding to CaN(B) (the regulatory subunit) triggers conformational change in CaN(A) (the catalytic subunit). Two isoforms of CaN(A) (α, β) are both abundant in brain and heart and activated by calcium-saturated calmodulin (CaM). The individual contribution of each domain of CaM to regulation of calcineurin is not known. Hydrodynamic analyses of (Ca(2+))₄-CaM(1-148) bound to βCaNp, a peptide representing its CaM-binding domain, indicated a 1:1 stoichiometry. βCaNp binding to CaM increased the affinity of calcium for the N- and C-domains equally, thus preserving intrinsic domain differences, and the preference of calcium for sites III and IV. The equilibrium constants for individual calcium-saturated CaM domains dissociating from βCaNp were ∼1 μM. A limiting K(d) ≤ 1 nM was measured directly for full-length CaM, while thermodynamic linkage analysis indicated that it was approximately 1 pM. βCaNp binding to ¹⁵N-(Ca(2+))₄-CaM(1-148) monitored by ¹⁵N/¹HN HSQC NMR showed that association perturbed the N-domain of CaM more than its C-domain. NMR resonance assignments of CaM and βCaNp, and interpretation of intermolecular NOEs observed in the ¹³C-edited and ¹²C-¹⁴N-filtered 3D NOESY spectrum indicated anti-parallel binding. The sole aromatic residue (Phe) located near the βCaNp C-terminus was in close contact with several residues of the N-domain of CaM outside the hydrophobic cleft. These structural and thermodynamic properties would permit the domains of CaM to have distinct physiological roles in regulating activation of βCaN. Copyright © 2010 Wiley-Liss, Inc.

Calcium signaling in immune cells

PubMed Central

Vig, Monika; Kinet, Jean-Pierre

2010-01-01

Calcium acts as a second messenger in many cell types, including lymphocytes. Resting lymphocytes maintain a low concentration of Ca2+. However, engagement of antigen receptors induces calcium influx from the extracellular space by several routes. A chief mechanism of Ca2+ entry in lymphocytes is through store-operated calcium (SOC) channels. The identification of two important molecular components of SOC channels, CRACM1 (the pore-forming subunit) and STIM1 (the sensor of stored calcium), has allowed genetic and molecular manipulation of the SOC entry pathway. In this review, we highlight advances in the understanding of Ca2+ signaling in lymphocytes with special emphasis on SOC entry. We also discuss outstanding questions and probable future directions of the field. PMID:19088738

A ryanodine receptor-dependent Ca(i)(2+) asymmetry at Hensen's node mediates avian lateral identity.

PubMed

Garic-Stankovic, Ana; Hernandez, Marcos; Flentke, George R; Zile, Maija H; Smith, Susan M

2008-10-01

In mouse, the establishment of left-right (LR) asymmetry requires intracellular calcium (Ca(i)(2+)) enrichment on the left of the node. The use of Ca(i)(2+) asymmetry by other vertebrates, and its origins and relationship to other laterality effectors are largely unknown. Additionally, the architecture of Hensen's node raises doubts as to whether Ca(i)(2+) asymmetry is a broadly conserved mechanism to achieve laterality. We report here that the avian embryo uses a left-side enriched Ca(i)(2+) asymmetry across Hensen's node to govern its lateral identity. Elevated Ca(i)(2+) was first detected along the anterior node at early HH4, and its emergence and left-side enrichment by HH5 required both ryanodine receptor (RyR) activity and extracellular calcium, implicating calcium-induced calcium release (CICR) as the novel source of the Ca(i)(2+). Targeted manipulation of node Ca(i)(2+) randomized heart laterality and affected nodal expression. Bifurcation of the Ca(i)(2+) field by the emerging prechordal plate may permit the independent regulation of LR Ca(i)(2+) levels. To the left of the node, RyR/CICR and H(+)V-ATPase activity sustained elevated Ca(i)(2+). On the right, Ca(i)(2+) levels were actively repressed through the activities of H(+)K(+) ATPase and serotonin-dependent signaling, thus identifying a novel mechanism for the known effects of serotonin on laterality. Vitamin A-deficient quail have a high incidence of situs inversus hearts and had a reversed calcium asymmetry. Thus, Ca(i)(2+) asymmetry across the node represents a more broadly conserved mechanism for laterality among amniotes than had been previously believed.

Physiological implications of seasonal variation in membrane-associated calcium in red spruce mesophyll cells

Treesearch

D.H. DeHayes; P.G. Schaberg; G.J. Hawley; C.H. Borer; J.R. Cumming; J.R. Strimbeck

1997-01-01

We examined the pattern of seasonal variation in total foliar calcium (Ca) pools and plasma membrane-associated Ca (mCa) in mesophyll cells of current-year and 1-year-old needles of red spruce (Picea rubens Sarg.) and the relationship between mCa and total foliar Ca on an individual plant and seasonal basis. Foliar samples were collected from...

Role of Mitochondrial Ca2+ in the Regulation of Cellular Energetics

PubMed Central

Glancy, Brian; Balaban, Robert S.

2012-01-01

Calcium is an important signaling molecule involved in the regulation of many cellular functions. The large free energy in the Ca2+ ion membrane gradients make Ca2+ signaling inherently sensitive to the available cellular free energy, primarily in the form of ATP. In addition, Ca2+ regulates many cellular ATP consuming reactions such as muscle contraction, exocytosis, biosynthesis and neuronal signaling. Thus, Ca2+ becomes a logical candidate as a signaling molecule to modulate ATP hydrolysis and synthesis during changes in numerous forms of cellular work. Mitochondria are the primary source of aerobic energy production in mammalian cells and also maintain a large Ca2+ gradient across their inner membrane providing a signaling potential for this molecule. The demonstrated link between cytosolic and mitochondrial [Ca2+], identification of transport mechanisms as well as proximity of mitochondria to Ca2+ release sites further supports the notion that Ca2+ can be an important signaling molecule in the energy metabolism interplay of the cytosol with the mitochondria. Here we review sites within the mitochondria where Ca2+ plays a role in the regulation of ATP generation and potentially contributes to the orchestration of the cellular metabolic homeostasis. Early work on isolated enzymes pointed to several matrix dehydrogenases that are stimulated by Ca2+, which were confirmed in the intact mitochondrion as well as cellular and in vivo systems. However, studies in these intact systems suggested a more expansive influence of Ca2+ on mitochondrial energy conversion. Numerous non-invasive approaches monitoring NADH, mitochondrial membrane potential, oxygen consumption and workloads suggest significant Ca2+ effects on other elements of NADH generation as well as downstream elements of oxidative phosphorylation including the F1FO-ATPase and the cytochrome chain. These other potential elements of Ca2+ modification of mitochondrial energy conversion will be the focus of this review. Though most of specific molecular mechanisms have yet to be elucidated, it is clear that Ca2+ provides a balanced activation of mitochondrial energy metabolism which exceeds the alteration of dehydrogenases alone. PMID:22443365

Ca isotope fractionation and Sr/Ca partitioning associated with anhydrite formation at mid-ocean ridge hydrothermal systems: An experimental approach

NASA Astrophysics Data System (ADS)

Syverson, D. D.; Scheuermann, P.; Pester, N. J.; Higgins, J. A.; Seyfried, W. E., Jr.

2016-12-01

The elemental and isotopic mass balance of Ca and Sr between seawater and basalt at mid-ocean ridge (MOR) hydrothermal systems is an integrated reflection of the various physiochemical processes, which induce chemical exchange, in the subseafloor. Specifically, the processes of anhydrite precipitation and recrystallization are recognized to be important controls on governing the Ca and Sr elemental and isotope compositions of high temperature vent fluids, however, few experimental data exist to constrain these geochemical effects. Thus, to better understand the associated Sr/Ca partitioning and Ca isotope fractionation and rate of exchange between anhydrite and dissolved constituents, anhydrite precipitation and recrystallization experiments were performed at 175, 250, and 350°C and 500 bar at chemical conditions indicative of active MOR hydrothermal systems. The experimental data suggest that upon entrainment of seawater into MOR hydrothermal systems, anhydrite will precipitate rapidly and discriminate against the heavy isotopes of Ca (Δ44/40Ca(Anh-Fluid) = -0.68 - -0.25 ‰), whereas Sr/Ca partitioning depends on the saturation state of the evolving hydrothermal fluid with respect to anhydrite at each PTX (KD(Anh-Fluid) = 1.24 - 0.55). Coupling experimental constraints with the temperature gradient inferred for high temperature MOR hydrothermal systems in the oceanic crust, data suggest that the Ca isotope and Sr elemental composition of anhydrite formed near the seafloor will be influenced by disequilibrium effects, while, at higher temperatures further into the oceanic crust, anhydrite will be representative of equilibrium Sr/Ca partitioning and Ca isotope fractionation conditions. These experimental observations are consistent with analyzed Sr/Ca and Ca isotope compositions of anhydrites and vent fluids sampled from modern MOR hydrothermal systems1,2 and can be used to further constrain the geochemical effects of hydrothermal circulation in the oceanic crust throughout Earth's history. 1 Tivey, M. K. Generation of Seafloor Hydrothermal Deposits. Oceanography 20, 50-66 (2007).2 Amini, M. et al. Calcium isotope (δ44/40Ca) fractionation along hydrothermal pathways, Logatchev field (Mid-Atlantic Ridge, 14°45'N). Geochimica et Cosmochimica Acta 72, 4107-4122 (2008).

Alterations in cytosol free calcium in horseradish roots simultaneously exposed to lanthanum(III) and acid rain.

PubMed

Zhang, Xuanbo; Wang, Lihong; Zhou, Anhua; Zhou, Qing; Huang, Xiaohua

2016-04-01

The extensive use of rare earth elements (REEs) has increased their environmental levels. REE pollution concomitant with acid rain in many agricultural regions can affect crop growth. Cytosol free calcium ions (Ca(2+)) play an important role in almost all cellular activities. However, no data have been reported regarding the role of cytosol free Ca(2+) in plant roots simultaneously exposed to REE and acid rain. In this study, the effects of exposures to lanthanum(III) and acid rain, independently and in combination, on cytosol free Ca(2+) levels, root activity, metal contents, biomass, cytosol pH and La contents in horseradish roots were investigated. The simultaneous exposures to La(III) and acid rain increased or decreased the cytosol free Ca(2+) levels, depending on the concentration of La(III), and these effects were more evident than independent exposure to La(III) or acid rain. In combined exposures, cytosol free Ca(2+) played an important role in the regulation of root activity, metal contents and biomass. These roles were closely related to La(III) dose, acid rain strength and treatment mode (independent exposure or simultaneous exposure). A low concentration of La(III) (20 mg L(-1)) could alleviate the adverse effects on the roots caused by acid rain, and the combined exposures at higher concentrations of La(III) and acid rain had synergic effects on the roots. Copyright © 2015 Elsevier Inc. All rights reserved.

Fast calcium and voltage-sensitive dye imaging in enteric neurones reveal calcium peaks associated with single action potential discharge.

PubMed

Michel, K; Michaelis, M; Mazzuoli, G; Mueller, K; Vanden Berghe, P; Schemann, M

2011-12-15

Slow changes in [Ca(2+)](i) reflect increased neuronal activity. Our study demonstrates that single-trial fast [Ca(2+)](i) imaging (≥200 Hz sampling rate) revealed peaks each of which are associated with single spike discharge recorded by consecutive voltage-sensitive dye (VSD) imaging in enteric neurones and nerve fibres. Fast [Ca(2+)](i) imaging also revealed subthreshold fast excitatory postsynaptic potentials. Nicotine-evoked [Ca(2+)](i) peaks were reduced by -conotoxin and blocked by ruthenium red or tetrodotoxin. Fast [Ca(2+)](i) imaging can be used to directly record single action potentials in enteric neurones. [Ca(2+)](i) peaks required opening of voltage-gated sodium and calcium channels as well as Ca(2+) release from intracellular stores.

Preparation and bioavailability of calcium-chelating peptide complex from tilapia skin hydrolysates.

PubMed

Chen, Jun; Qiu, Xujian; Hao, Gengxin; Zhang, Meng; Weng, Wuyin

2017-11-01

With the continuous improvement in material life, the generation of fish by-products and the market demand for calcium supplements have been increasing in China. Therefore a calcium-chelating peptide complex (CPC) from tilapia skins was prepared and its effect on calcium (Ca)-deficient mice was investigated. The molecular weight distribution of CPC mainly ranged from 2000 to 180 Da, and its contents of complete amino acids and free amino acids were 85.30 and 8.67% (w/w) respectively. Scanning electron microscopy images and Fourier transform infrared data revealed that Ca crystals were bound with gelatin hydrolysates via interaction between Ca ions and NH/CN groups. When Ca-deficient mice were fed CPC and CaCO 3 respectively for 4 weeks, no significant differences in serum biochemistry or bone mineral density were found. However, the length, weight, Ca content and hydroxyproline content of the femur, Ca absorption and body weight gain of mice fed CPC were significantly higher than those of mice fed CaCO 3 . It is concluded that the prepared CPC could promote bone formation via better bioavailability of Ca and an increase in bone collagen. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Modulation of polyepoxysuccinic acid on crystallization of calcium oxalate

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

Zhang, Yanqing; Tang, Yongming, E-mail: tangym@njtech.edu.cn; Xu, Jinqiu

The influence of polyepoxysuccinic acid (PESA) on the phase composition and crystal morphology of calcium oxalate was investigated in this paper. It was found that the presence of PESA inhibited the growth of the monoclinic calcium oxalate monohydrate (COM) crystal and promoted the nucleation of the tetragonal calcium oxalate dihydrate (COD). In addition, with the increase in PESA concentration, the aggregation of COD crystals was reduced but the particle size was increased. Under the conditions of low calcium-to-oxalate ratio and high CaOx concentration, PESA could not effectively stabilize the formation of COD. Based on molecular dynamic simulations, the adsorption ofmore » PESA on CaOx crystal faces was confirmed. - Graphical abstract: Introduction of PESA into crystallization solutions promotes the formation of calcium oxalate dehydrate and modifies the morphology of crystals. - Highlights: • PESA induces the formation of COD at low supersaturation. • Establishment of Ca-rich surface augments the adsorption of PESA. • At Ca/Ox=0.5 PESA cannot induce the formation of COD compared with Ca/Ox=2. • Interaction of PESA with COM faces is stronger than that with COD faces.« less

Preparation of hydroxyapatite/collagen injectable bone paste with an anti-washout property utilizing sodium alginate. Part 1: influences of excess supplementation of calcium compounds.

PubMed

Sato, Taira; Kikuchi, Masanori; Aizawa, Mamoru

2017-03-01

The anti-washout property, viscosity, and cytocompatibility to an osteoblastic cell line, MG-63, of anti-washout pastes were investigated. Mixing a hydroxyapatite/collagen bone-like nanocomposite (HAp/Col), an aqueous solution of sodium alginate (Na-Alg), which is a paste hardening and lubricant agent, and supplementation of calcium carbonate or calcium citrate (Ca-Cit) as a calcium resource for the hardening reaction realized an injectable bone paste. Adding Ca-Cit at a concentration greater than eight times the Ca 2+ ion concentration to Na-Alg improved the anti-washout property. Although the viscosity test indicated a gradual increase in the paste viscosity as the calcium compounds increased, pastes with excess supplementation of calcium compounds exhibited injectability through a syringe with a 1.8 mm inner diameter, realizing an injectable bone filler. Furthermore, the anti-washout pastes with Ca-Cit had almost the same cell proliferation rate as that of the HAp/Col dense body. Therefore, HAp/Col injectable anti-washout pastes composed of the HAp/Col, Na-Alg, and Ca-Cit are potential candidates for bioresorbable bone filler pastes.

Calcination of calcium carbonate and blend therefor

DOEpatents

Mallow, William A.; Dziuk, Jr., Jerome J.

1989-01-01

A method for calcination of a calcium carbonate material comprising heating the calcium carbonate material to a temperature and for a time sufficient to calcine the material to the degree desired while in the presence of a catalyst; said catalyst comprising at least one fused salt having the formula MCO.sub.3.CaCO.sub.3.CaO.H.sub.2 O.sub.x, wherein M is an alkali metal and x is 0 to 1 and formed by fusing MCO.sub.3 and CaCO.sub.3 in a molar ratio of about 1:2 to 2:1, and a blend adapted to be heated to CaO comprising a calcium carbonate material and at least one such fused salt.

Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells

PubMed Central

Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu

2016-01-01

This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium–yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium–yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200–500 nm in the long axis and 100–300 nm in the short axis, and a Ca/P atomic ratio of 1.5–1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor. PMID:25917827

Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells.

PubMed

Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu; Liu, Huinan

2015-05-01

This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium-yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium-yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200-500 nm in the long axis and 100-300 nm in the short axis, and a Ca/P atomic ratio of 1.5-1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor.

Regulation of axonal and dendritic growth by the extracellular calcium-sensing receptor (CaSR)

PubMed Central

Vizard, Thomas N.; O'Keeffe, Gerard W.; Gutierrez, Humberto; Kos, Claudine H.; Riccardi, Daniela; Davies, Alun M.

2009-01-01

The extracellular calcium-sensing receptor (CaSR) monitors the systemic extracellular free ionized calcium level ([Ca2+]o) in organs involved in systemic [Ca2+]o homeostasis. However, the CaSR is also expressed in the nervous system where its role is unknown. Here we find high levels of the CaSR in perinatal mouse sympathetic neurons when their axons are innervating and branching extensively in their targets. Manipulating CaSR function in these neurons by varying [Ca2+]o, using CaSR agonists and antagonists or expressing a dominant-negative CaSR markedly affects neurite growth in vitro Sympathetic neurons lacking the CaSR have smaller neurite arbors in vitro, and sympathetic innervation density is reduced in CaSR-deficient mice in vivo. Hippocampal pyramidal neurons, which also express the CaSR, have smaller dendrites when transfected with dominant-negative CaSR in postnatal organotypic cultures. Our findings reveal a crucial role for the CaSR in regulating the growth of neural processes in the peripheral and central nervous systems. PMID:18223649

Subthreshold membrane potential oscillations in inferior olive neurons are dynamically regulated by P/Q- and T-type calcium channels: a study in mutant mice.

PubMed

Choi, Soonwook; Yu, Eunah; Kim, Daesoo; Urbano, Francisco J; Makarenko, Vladimir; Shin, Hee-Sup; Llinás, Rodolfo R

2010-08-15

The role of P/Q- and T-type calcium channels in the rhythmic oscillatory behaviour of inferior olive (IO) neurons was investigated in mutant mice. Mice lacking either the CaV2.1 gene of the pore-forming alpha1A subunit for P/Q-type calcium channel, or the CaV3.1 gene of the pore-forming alpha1G subunit for T-type calcium channel were used. In vitro intracellular recording from IO neurons reveals that the amplitude and frequency of sinusoidal subthreshold oscillations (SSTOs) were reduced in the CaV2.1-/- mice. In the CaV3.1-/- mice, IO neurons also showed altered patterns of SSTOs and the probability of SSTO generation was significantly lower (15%, 5 of 34 neurons) than that of wild-type (78%, 31 of 40 neurons) or CaV2.1-/- mice (73%, 22 of 30 neurons). In addition, the low-threshold calcium spike and the sustained endogenous oscillation following rebound potentials were absent in IO neurons from CaV3.1-/- mice. Moreover, the phase-reset dynamics of oscillatory properties of single neurons and neuronal clusters in IO were remarkably altered in both CaV2.1-/- and CaV3.1-/- mice. These results suggest that both alpha1A P/Q- and alpha1G T-type calcium channels are required for the dynamic control of neuronal oscillations in the IO. These findings were supported by results from a mathematical IO neuronal model that incorporated T and P/Q channel kinetics.

Calcium Homeostasis and Cone Signaling Are Regulated by Interactions between Calcium Stores and Plasma Membrane Ion Channels

PubMed Central

Bartoletti, Theodore M.; Huang, Wei; Akopian, Abram; Thoreson, Wallace B.; Krizaj, David

2009-01-01

Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca2+ entry (SOCE) to Ca2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca2+ channels. Exposure to MRS 1845 resulted in ∼40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse. PMID:19696927

Mechanism and evolution of calcium transport across the plant plasma membrane

USDA-ARS?s Scientific Manuscript database

Calcium is an essential plant nutrient, thus the influx of Ca(2+) into plant cells is a critical process. In addition, the efflux of Ca(2+) out of a cell is important to prevent toxicity resulting from Ca(2+) excess, and to modulate levels of cytosolic Ca(2+) required for signaling functions. Bioc...

Dietary Protein and Calcium Interact to Influence Calcium Retention: A Controlled Feeding Study

USDA-ARS?s Scientific Manuscript database

Objective: To test the effect of dietary protein on Ca (Ca) retention at low and high Ca intakes. Methods: In a randomized, controlled feeding study with a 2x2 factorial crossover design, healthy post-menopausal women (n=27), consumed either ~675 or ~1510 mg Ca/d, with both low and high protein (pro...

Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition

NASA Astrophysics Data System (ADS)

Posavec, Lidija; Knijnenburg, Jesper T. N.; Hilty, Florentine M.; Krumeich, Frank; Pratsinis, Sotiris E.; Zimmermann, Michael B.

2016-10-01

Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO3) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO3 made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO3 and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO3, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca2P2O7 with increasing hydroxyapatite content at higher Ca:P. Aging of powders with Ca:P = 1.0 and 1.5 for over 500 days gradually increased particle size (but less than for CaCO3) without a change in phase composition or crystallinity. In 0.01 M H3PO4 calcium phosphate nanopowders dissolved ≈4 times more Ca than micronsized compounds and about twice more Ca than CaCO3 nanopowders, confirming that nanosizing and/or amorphous structuring sharply increases Ca powder dissolution. Because higher Ca solubility in vitro generally leads to greater absorption in vivo, these novel FASP-made Ca nanostructured compounds may prove useful for nutrition applications, including supplementation and/or food fortification.

Effect of calcium phosphate and vitamin D₃ supplementation on bone remodelling and metabolism of calcium, phosphorus, magnesium and iron.

PubMed

Trautvetter, Ulrike; Neef, Nadja; Leiterer, Matthias; Kiehntopf, Michael; Kratzsch, Jürgen; Jahreis, Gerhard

2014-01-17

The aim of the present study was to determine the effect of calcium phosphate and/or vitamin D₃ on bone and mineral metabolism. Sixty omnivorous healthy subjects participated in the double-blind, placebo-controlled parallel designed study. Supplements were tricalcium phosphate (CaP) and cholecalciferol (vitamin D₃). At the beginning of the study (baseline), all subjects documented their normal nutritional habits in a dietary record for three successive days. After baseline, subjects were allocated to three intervention groups: CaP (additional 1 g calcium/d), vitamin D₃ (additional 10 μg/d) and CaP + vitamin D₃. In the first two weeks, all groups consumed placebo bread, and afterwards, for eight weeks, the test bread according to the intervention group. In the last week of each study period (baseline, placebo, after four and eight weeks of intervention), a faecal (three days) and a urine (24 h) collection and a fasting blood sampling took place. Calcium, phosphorus, magnesium and iron were determined in faeces, urine and blood. Bone formation and resorption markers were analysed in blood and urine. After four and eight weeks, CaP and CaP + vitamin D₃ supplementations increased faecal excretion of calcium and phosphorus significantly compared to placebo. Due to the vitamin D₃ supplementations (vitamin D₃, CaP + vitamin D₃), the plasma 25-(OH)D concentration significantly increased after eight weeks compared to placebo. The additional application of CaP led to a significant increase of the 25-(OH)D concentration already after four weeks. Bone resorption and bone formation markers were not influenced by any intervention. Supplementation with daily 10 μg vitamin D₃ significantly increases plasma 25-(OH)D concentration. The combination with daily 1 g calcium (as CaP) has a further increasing effect on the 25-(OH)D concentration. Both CaP alone and in combination with vitamin D₃ have no beneficial effect on bone remodelling markers and on the metabolism of calcium, phosphorus, magnesium and iron. NCT01297023.

Subcellular localization of calcium and Ca-ATPase activity during nuclear maturation in Bufo arenarum oocytes.

PubMed

Ramos, Inés; Cisint, Susana B; Crespo, Claudia A; Medina, Marcela F; Fernández, Silvia N

2009-08-01

The localization of calcium and Ca-ATPase activity in Bufo arenarum oocytes was investigated by ultracytochemical techniques during progesterone-induced nuclear maturation, under in vitro conditions. No Ca2+ deposits were detected in either control oocytes or progesterone-treated ones for 1-2 h. At the time when nuclear migration started, electron dense deposits of Ca2+ were visible in vesicles, endoplasmic reticulum cisternae and in the space between the annulate lamellae membranes. Furthermore, Ca-ATPase activity was also detected in these membrane structures. As maturation progressed, the cation deposits were observed in the cytomembrane structures, which underwent an important reorganization and redistribution. Thus, they moved from the subcortex and became located predominantly in the oocyte cortex area when nuclear maturation ended. Ca2+ stores were observed in vesicles surrounding or between the cortical granules, which are aligned close to the plasma membrane. The positive Ca-ATPase reaction in these membrane structures could indicate that the calcium deposit is an ATP-dependent process. Our results suggest that during oocyte maturation calcium would be stored in membrane structures where it remains available for release at the time of fertilization. Data obtained under our experimental conditions indicate that calcium from the extracellular medium would be important for the oocyte maturation process.

On the nature and origin of the oxalate package in Solanum sisymbriifolium anthers.

PubMed

Burrieza, Hernán Pablo; López-Fernández, María Paula; Láinez, Verónica; Montenegro, Teresita; Maldonado, Sara

2010-11-01

This is a detailed study carried out in Solanum sisymbriifolium Lam. on the development of the circular cell cluster (CCC) during crystal deposition, as well as the composition of the crystals. Light microscopy and scanning and transmission electron microscopy (TEM) were used to characterize tissue throughout anther development. Energy dispersive X-ray analysis (EDAX) allowed the determination of the elemental composition of crystals that form in the CCC region, and infrared and x-ray diffraction analysis were used to specify the crystal salt composition. TEM analysis revealed that the crystals originated simultaneously within the vacuoles in association with a paracrystalline protein. Prior to the appearance of protein within vacuoles, protein paracrystals were visible in both rough endoplasmic reticulum and vesicles with ribosomes on their membranes. In vacuoles, paracrystals constitute nucleation sites for druse crystals formation. EDAX revealed that C, O, and Ca were the main elements, and K, Cl, Mg, P, S, and Si, the minor elements. X-ray powder diffraction of crystals detected the predominant presence of calcium oxalate, but also vestiges of calcite, quartz, and sylvite. The calcium oxalate coexisted in the three chemical forms, that is, whewellite, weddellite, and caoxite. Infrared spectrophotometry identified bands that characterize O-C-O, H-O, C-H bonds, all of calcium oxalate, and Si-O-Si, of quartz. These results were compared with studies of anthers carried out in other Solanaceae genera.

The calcium-sensing receptor regulates mammary gland parathyroid hormone–related protein production and calcium transport

PubMed Central

VanHouten, Joshua; Dann, Pamela; McGeoch, Grace; Brown, Edward M.; Krapcho, Karen; Neville, Margaret; Wysolmerski, John J.

2004-01-01

The transfer of calcium from mother to milk during lactation is poorly understood. In this report, we demonstrate that parathyroid hormone–related protein (PTHrP) production and calcium transport in mammary epithelial cells are regulated by extracellular calcium acting through the calcium-sensing receptor (CaR). The CaR becomes expressed on mammary epithelial cells at the transition from pregnancy to lactation. Increasing concentrations of calcium, neomycin, and a calcimimetic compound suppress PTHrP secretion by mammary epithelial cells in vitro, whereas in vivo, systemic hypocalcemia increases PTHrP production, an effect that can be prevented by treatment with a calcimimetic. Hypocalcemia also reduces overall milk production and calcium content, while increasing milk osmolality and protein concentrations. The changes in milk calcium content, milk osmolality, and milk protein concentration were mitigated by calcimimetic infusions. Finally, in a three-dimensional culture system that recapitulates the lactating alveolus, activation of the basolateral CaR increases transcellular calcium transport independent of its effect on PTHrP. We conclude that the lactating mammary gland can sense calcium and adjusts its secretion of calcium, PTHrP, and perhaps water in response to changes in extracellular calcium concentration. We believe this defines a homeostatic system that helps to match milk production to the availability of calcium. PMID:14966569

Energy response of CaSO4:Dy teflon TLD disk dosimeters to photons and electrons.

PubMed

Sharada, K S

1983-01-01

The photon energy response of CaSO4:Dy teflon disk dosimeters used widely in radiation dosimetry is computed using the energy absorption coefficient values for calcium, sulfur, oxygen, and carbon taken from J. H. Hubbell's tables. For fluorine, the energy absorption coefficients were obtained from the values given by F. H. Attix for CaF2 and Ca. The energy response of the radiation-monitoring disk for the range of 10 keV to 10 MeV, relative to air, is computed and plotted. The response is maximum between 20 and 30 keV and then gradually falls to a constant at 200 keV to 10 MeV. This computed response for different energies is compared with the experimental TL response of the dosimeter. The electron energy response of these TLD disks is computed using the stopping-power values for the different component elements. The electron stopping power for sulfur and calcium from 10 keV to 10 MeV is computed using the Bethe-Bloch formula. Those for oxygen and carbon are taken from the tables given by M. J. Berger and S. M. Seltzer. For fluorine, the values are computed from those for Li and LiF given in the same tables. This calculated response is compared with the experimental beta response of the TL dosimeter.

[Involvement of interaction between TRPC1 and Orai1 in calcium sensing receptor-mediated calcium influx and nitric oxide generation in human umbilical vein endothelial cells].

PubMed

Wang, La-Mei; Tang, Na; Zhong, Hua; Pang, Li-Juan; Zhang, Chun-Jun; He, Fang

2018-06-25

The present study was to investigate the role of the interaction between canonical transient receptor potential channel 1 (TRPC1) and calcium release-activated calcium modulator 1 (Orai1) in extracellular Ca 2+ -sensing receptor (CaR)-induced extracellular Ca 2+ influx and nitric oxide (NO) production. Human umbilical vein endothelial cells (HUVECs) were incubated with CaR agonist Spermine [activating store-operated calcium channels (SOC) and receptor-operated calcium channels (ROC)] alone or in combination with the following reagents: CaR negative allosteric modulator Calhex231 plus ROC analogue TPA (activating ROC and blocking SOC), Ro31-8220 (PKC inhibitor that activates SOC and blocks ROC) or Go6967 (PKCs and PKCµ inhibitor that activates SOC and blocks ROC). The protein expressions and co-localization of TRPC1 and Orai1 were determined using immunofluorescent staining. The interaction between TRPC1 and Orai1 was examined by co-immunoprecipitation. We silenced the expressions of their genes in the HUVECs by transfection of constructed TRPC1 and Orai1 shRNA plasmids. Intracellular Ca 2+ concentration ([Ca 2+ ] i ) was detected using Ca 2+ indicator Fura-2/AM, and NO production was determined by DAF-FM staining. The results showed that TRPC1 and Orai1 protein expressions were co-located on the cell membrane of the HUVECs. Compared with Spermine+Ca 2+ group, Calhex231+ TPA+Spermine+Ca 2+ , Ro31-8220+Spermine+Ca 2+ and Go6976+Spermine+Ca 2+ groups exhibited down-regulated protein expressions of TRPC1 and Orai1 in cytoplasm and decreased co-localization on the cell membrane. Co-immunoprecipitation results showed that the interaction between TRPC1 and Orai1 was reduced by Calhex231 plus TPA, Ro31-8220 or Go6976 addition in the Spermine-stimulated HUVECs. Double knockdown of Trpc1 and Orai1 genes significantly decreased [Ca 2+ ] i level and NO production in all of the Spermine+Ca 2+ , Calhex231+TPA+Spermine+Ca 2+ , Ro31-8220+Spermine+Ca 2+ and Go6976+Spermine+Ca 2+ groups. These results suggest that TRPC1/Orai1 may form a complex that mediates Ca 2+ influx and No production via SOC and ROC activation.

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

PubMed Central

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

2012-01-01

SUMMARY 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 HCs 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. PMID:22503562

Skin Barrier and Calcium.

PubMed

Lee, Sang Eun; Lee, Seung Hun

2018-06-01

Epidermal barrier formation and the maintenance of barrier homeostasis are essential to protect us from the external environments and organisms. Moreover, impaired keratinocytes differentiation and dysfunctional skin barrier can be the primary causes or aggravating factors for many inflammatory skin diseases including atopic dermatitis and psoriasis. Therefore, understanding the regulation mechanisms of keratinocytes differentiation and skin barrier homeostasis is important to understand many skin diseases and establish an effective treatment strategy. Calcium ions (Ca 2+ ) and their concentration gradient in the epidermis are essential in regulating many skin functions, including keratinocyte differentiation, skin barrier formation, and permeability barrier homeostasis. Recent studies have suggested that the intracellular Ca 2+ stores such as the endoplasmic reticulum (ER) are the major components that form the epidermal calcium gradient and the ER calcium homeostasis is crucial for regulating keratinocytes differentiation, intercellular junction formation, antimicrobial barrier, and permeability barrier homeostasis. Thus, both Ca 2+ release from intracellular stores, such as the ER and Ca 2+ influx mechanisms are important in skin barrier. In addition, growing evidences identified the functional existence and the role of many types of calcium channels which mediate calcium flux in keratinocytes. In this review, the origin of epidermal calcium gradient and their role in the formation and regulation of skin barrier are focused. We also focus on the role of ER calcium homeostasis in skin barrier. Furthermore, the distribution and role of epidermal calcium channels, including transient receptor potential channels, store-operated calcium entry channel Orai1, and voltage-gated calcium channels in skin barrier are discussed.

Trace element study in scallop shells by laser ablation ICP-MS: the example of Ba/Ca ratios

NASA Astrophysics Data System (ADS)

Lorrain, A.; Pécheyran, C.; Paulet, Y.-M.; Chauvaud, L.; Amouroux, D.; Krupp, E.; Donard, O.

2003-04-01

As scallop shells grow incrementally at a rate of one line per day, environmental changes could then be evidenced on a daily basis. As an example for trace element incorporation studies, barium is a geochemical tracer that can be directly related to oceanic primary productivity. Hence, monitoring Ba/Ca variations in a scallop shell should give information about phytoplanktonic events encountered day by day during its life. The very high spatial resolution (typically 40 - 200 µm) and the high elemental sensitivity required can only be achieved by the combination of laser ablation coupled to inductively coupled plasma mass spectrometry. This study demonstrates that Laser ablation coupled to ICP-MS determination is a relevant tool for high resolution distribution measurement of trace elements in calcite matrix. The ablation strategy related to single line rastering and calcium normalisation were found to be the best analytical conditions in terms of reproducibility and sensitivity. The knowledge of P. maximus growth rings periodicity (daily), combined with LA-ICP-MS micro analysis allows the acquisition of time dated profiles with high spatial and thus temporal resolution. This resolution makes P. maximus a potential tool for environmental reconstruction and especially for accurate calibration of proxies. However, the relations among Ba/Ca peaks and phytoplanktonic events differed according to the animals and some inter-annual discrepancies complexify the interpretation.

Localized intracellular calcium signaling in muscle: calcium sparks and calcium quarks.

PubMed

Niggli, E

1999-01-01

Subcellularly localized Ca2+ signals in cardiac and skeletal muscle have recently been identified as elementary Ca2+ signaling events. The signals, termed Ca2+ sparks and Ca2+ quarks, represent openings of Ca2+ release channels located in the membrane of the sarcoplasmic reticulum (SR). In cardiac muscle, the revolutionary discovery of Ca2+ sparks has allowed the development of a fundamentally different concept for the amplification of Ca2+ signals by Ca(2+)-induced Ca2+ release. In such a system, a graded amplification of the triggering Ca2+ signal entering the myocyte via L-type Ca2+ channels is accomplished by a recruitment process whereby individual SR Ca2+ release units are locally controlled by L-type Ca2+ channels. In skeletal muscle, the initial SR Ca2+ release is governed by voltage-sensors but subsequently activates additional Ca2+ sparks by Ca(2+)-induced Ca2+ release from the SR. Results from studies on elementary Ca2+ release events will improve our knowledge of muscle Ca2+ signaling at all levels of complexity, from the molecule to normal cellular function, and from the regulation of cardiac and skeletal muscle force to the pathophysiology of excitation-contraction coupling.

Klotho Prevents Renal Calcium Loss

PubMed Central

Alexander, R. Todd; Woudenberg-Vrenken, Titia E.; Buurman, Jan; Dijkman, Henry; van der Eerden, Bram C. J.; van Leeuwen, Johannes P.T.M.; Bindels, René J.

2009-01-01

Disturbed calcium (Ca2+) homeostasis, which is implicit to the aging phenotype of klotho-deficient mice, has been attributed to altered vitamin D metabolism, but alternative possibilities exist. We hypothesized that failed tubular Ca2+ absorption is primary, which causes increased urinary Ca2+ excretion, leading to elevated 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and its sequelae. Here, we assessed intestinal Ca2+ absorption, bone densitometry, renal Ca2+ excretion, and renal morphology via energy-dispersive x-ray microanalysis in wild-type and klotho−/− mice. We observed elevated serum Ca2+ and fractional excretion of Ca2+ (FECa) in klotho−/− mice. Klotho−/− mice also showed intestinal Ca2+ hyperabsorption, osteopenia, and renal precipitation of calcium-phosphate. Duodenal mRNA levels of transient receptor potential vanilloid 6 (TRPV6) and calbindin-D9K increased. In the kidney, klotho−/− mice exhibited increased expression of TRPV5 and decreased expression of the sodium/calcium exchanger (NCX1) and calbindin-D28K, implying a failure to absorb Ca2+ through the distal convoluted tubule/connecting tubule (DCT/CNT) via TRPV5. Gene and protein expression of the vitamin D receptor (VDR), 25-hydroxyvitamin D-1-α-hydroxylase (1αOHase), and calbindin-D9K excluded renal vitamin D resistance. By modulating the diet, we showed that the renal Ca2+ wasting was not secondary to hypercalcemia and/or hypervitaminosis D. In summary, these findings illustrate a primary defect in tubular Ca2+ handling that contributes to the precipitation of calcium-phosphate in DCT/CNT. This highlights the importance of klotho to the prevention of renal Ca2+ loss, secondary hypervitaminosis D, osteopenia, and nephrocalcinosis. PMID:19713312

Calcium-phosphate and parathyroid intradialytic profiles: A potential aid for tailoring the dialysate calcium content of patients on different hemodialysis schedules.

PubMed

Ferraresi, Martina; Pia, Anna; Guzzo, Gabriella; Vigotti, Federica Neve; Mongilardi, Elena; Nazha, Marta; Aroasio, Emiliano; Gonella, Cinzia; Avagnina, Paolo; Piccoli, Giorgina Barbara

2015-10-01

Severe hyperparathyroidism is a challenge on hemodialysis. The definition of dialysate calcium (Ca) is a pending issue with renewed importance in cases of individualized dialysis schedules and of portable home dialysis machines with low-flow dialysate. Direct measurement of calcium mass transfer is complex and is imprecisely reflected by differences in start-to-end of dialysis Ca levels. The study was performed in a dialysis unit dedicated to home hemodialysis and to critical patients with wide use of daily and tailored schedules. The Ca-phosphate (P)-parathyroid hormone (PTH) profile includes creatinine, urea, total and ionized Ca, albumin, sodium, potassium, P, PTH levels at start, mid, and end of dialysis. "Severe" secondary hyperparathyroidism was defined as PTH > 300 pg/mL for ≥3 months. Four schedules were tested: conventional dialysis (polysulfone dialyzer 1.8-2.1 m(2) ), with dialysate Ca 1.5 or 1.75 mmol/L, NxStage (Ca 1.5 mmol/L), and NxStage plus intradialytic Ca infusion. Dosages of vitamin D, calcium, phosphate binders, and Ca mimetic agents were adjusted monthly. Eighty Ca-P-PTH profiles were collected in 12 patients. Serum phosphate was efficiently reduced by all techniques. No differences in start-to-end PTH and Ca levels on dialysis were observed in patients with PTH levels < 300 pg/mL. Conversely, Ca levels in "severe" secondary hyperparathyroid patients significantly increased and PTH decreased during dialysis on all schedules except on Nxstage (P < 0.05). Our data support the need for tailored dialysate Ca content, even on "low-flow" daily home dialysis, in "severe" secondary hyperparathyroid patients in order to increase the therapeutic potentials of the new dialysis techniques. © 2015 International Society for Hemodialysis.

Low-level laser irradiation modulates brain-derived neurotrophic factor mRNA transcription through calcium-dependent activation of the ERK/CREB pathway.

PubMed

Yan, Xiaodong; Liu, Juanfang; Zhang, Zhengping; Li, Wenhao; Sun, Siguo; Zhao, Jian; Dong, Xin; Qian, Jixian; Sun, Honghui

2017-01-01

Low-level laser (LLL) irradiation has been reported to promote neuronal differentiation, but the mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) has been confirmed to be one of the most important neurotrophic factors because it is critical for the differentiation and survival of neurons during development. Thus, this study aimed to investigate the effects of LLL irradiation on Bdnf messenger RNA (mRNA) transcription and the molecular pathway involved in LLL-induced Bdnf mRNA transcription in cultured dorsal root ganglion neurons (DRGNs) using Ca 2+ imaging, pharmacological detections, RNA interference, immunocytochemistry assay, Western blot, and qPCR analysis. We show here that LLL induced increases in the [Ca 2+ ] i level, Bdnf mRNA transcription, cAMP-response element-binding protein (CREB) phosphorylation, and extracellular signal-regulated kinase (ERK) phosphorylation, mediated by Ca 2+ release via inositol triphosphate receptor (IP3R)-sensitive calcium (Ca 2+ ) stores. Blockade of Ca 2+ increase suppressed Bdnf mRNA transcription, CREB phosphorylation, and ERK phosphorylation. Downregulation of phosphorylated (p)-CREB reduced Bdnf mRNA transcription triggered by LLL. Furthermore, blockade of ERK using PD98059 inhibitor reduced p-CREB and Bdnf mRNA transcription induced by LLL. Taken together, these findings establish the Ca 2+ -ERK-CREB cascade as a potential signaling pathway involved in LLL-induced Bdnf mRNA transcription. To our knowledge, this is the first report of the mechanisms of Ca 2+ -dependent Bdnf mRNA transcription triggered by LLL. These findings may help further explore the complex molecular signaling networks in LLL-triggered nerve regeneration in vivo and may also provide experimental evidence for the development of LLL for clinical applications.

Compositional variations at ultra-structure length scales in coral skeleton

NASA Astrophysics Data System (ADS)

Meibom, Anders; Cuif, Jean-Pierre; Houlbreque, Fanny; Mostefaoui, Smail; Dauphin, Yannicke; Meibom, Karin L.; Dunbar, Robert

2008-03-01

Distributions of Mg and Sr in the skeletons of a deep-sea coral ( Caryophyllia ambrosia) and a shallow-water, reef-building coral ( Pavona clavus) have been obtained with a spatial resolution of 150 nm, using the NanoSIMS ion microprobe at the Muséum National d'Histoire Naturelle in Paris. These trace element analyses focus on the two primary ultra-structural components in the skeleton: centers of calcification (COC) and fibrous aragonite. In fibrous aragonite, the trace element variations are typically on the order of 10% or more, on length scales on the order of 1-10 μm. Sr/Ca and Mg/Ca variations are not correlated. However, Mg/Ca variations in Pavona are strongly correlated with the layered organization of the skeleton. These data allow for a direct comparison of trace element variations in zooxanthellate and non-zooxanthellate corals. In both corals, all trace elements show variations far beyond what can be attributed to variations in the marine environment. Furthermore, the observed trace element variations in the fibrous (bulk) part of the skeletons are not related to the activity of zooxanthellae, but result from other biological activity in the coral organism. To a large degree, this biological forcing is independent of the ambient marine environment, which is essentially constant on the growth timescales considered here. Finally, we discuss the possible detection of a new high-Mg calcium carbonate phase, which appears to be present in both deep-sea and reef-building corals and is neither aragonite nor calcite.

Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

NASA Astrophysics Data System (ADS)

Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.

2017-10-01

Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of appendages results in a decrease in Mg/Ca. BSE imaging and WDS elemental mapping provided evidence for cementation, facilitated by microbial-boring as the primary cause of increasing Sr/Ca. These novel proxies hold advantages over taphonomic measures and further provide a rapid method to infer sediment transport pathways within back-reef environments.

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

PubMed

Martínez, Javier; Moreno, Juan J

2005-09-01

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

L-Histidine sensing by calcium sensing receptor inhibits voltage-dependent calcium channel activity and insulin secretion in β-cells

PubMed Central

Parkash, Jai; Asotra, Kamlesh

2011-01-01

Aims Our goal was to test the hypothesis that the histidine-induced activation of calcium sensing receptor (CaR) can regulate calcium channel activity of L-type voltage dependent calcium channel (VDCC) due to increased spatial interaction between CaR and VDCC in β-cells and thus modulate glucose-induced insulin secretion. Main methods Rat insulinoma (RINr1046-38) insulin-producing β-cells were cultured in RPMI-1640 medium on 25 mm diameter glass coverslips in six-well culture plates in a 5% CO2 incubator at 37°C. The intracellular calcium concentration, [Ca2+]i, was determined by ratio fluorescence microscopy using Fura-2AM. The spatial interactions between CaR and L-type VDCC in β-cells were measured by immunofluorescence confocal microscopy using a Nikon C1 laser scanning confocal microscope. The insulin release was determined by enzyme-linked immunosorbent assay (ELISA). Key findings The additions of increasing concentrations of L-histidine along with 10 mM glucose resulted in 57% decrease in [Ca2+]i. The confocal fluorescence imaging data showed 5.59 to 8.62-fold increase in colocalization correlation coefficient between CaR and VDCC in β-cells exposed to L-histidine thereby indicating increased membrane delimited spatial interactions between these two membrane proteins. The insulin ELISA data showed 54% decrease in 1st phase of glucose-induced insulin secretion in β-cells exposed to increasing concentrations of L-histidine. Significance L-histidine-induced increased spatial interaction of CaR with VDCC can inhibit calcium channel activity of VDCC and consequently regulate glucose-induced insulin secretion by β-cells. The L-type VDCC could therefore be potential therapeutic target in diabetes. PMID:21219913

The Calmodulin-Binding, Short Linear Motif, NSCaTE Is Conserved in L-Type Channel Ancestors of Vertebrate Cav1.2 and Cav1.3 Channels

PubMed Central

Taiakina, Valentina; Boone, Adrienne N.; Fux, Julia; Senatore, Adriano; Weber-Adrian, Danielle

2013-01-01

NSCaTE is a short linear motif of (xWxxx(I or L)xxxx), composed of residues with a high helix-forming propensity within a mostly disordered N-terminus that is conserved in L-type calcium channels from protostome invertebrates to humans. NSCaTE is an optional, lower affinity and calcium-sensitive binding site for calmodulin (CaM) which competes for CaM binding with a more ancient, C-terminal IQ domain on L-type channels. CaM bound to N- and C- terminal tails serve as dual detectors to changing intracellular Ca2+ concentrations, promoting calcium-dependent inactivation of L-type calcium channels. NSCaTE is absent in some arthropod species, and is also lacking in vertebrate L-type isoforms, Cav1.1 and Cav1.4 channels. The pervasiveness of a methionine just downstream from NSCaTE suggests that L-type channels could generate alternative N-termini lacking NSCaTE through the choice of translational start sites. Long N-terminus with an NSCaTE motif in L-type calcium channel homolog LCav1 from pond snail Lymnaea stagnalis has a faster calcium-dependent inactivation than a shortened N-termini lacking NSCaTE. NSCaTE effects are present in low concentrations of internal buffer (0.5 mM EGTA), but disappears in high buffer conditions (10 mM EGTA). Snail and mammalian NSCaTE have an alpha-helical propensity upon binding Ca2+-CaM and can saturate both CaM N-terminal and C-terminal domains in the absence of a competing IQ motif. NSCaTE evolved in ancestors of the first animals with internal organs for promoting a more rapid, calcium-sensitive inactivation of L-type channels. PMID:23626724

Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial.

PubMed

Lappe, Joan M; Travers-Gustafson, Dianne; Davies, K Michael; Recker, Robert R; Heaney, Robert P

2007-06-01

Numerous observational studies have found supplemental calcium and vitamin D to be associated with reduced risk of common cancers. However, interventional studies to test this effect are lacking. The purpose of this analysis was to determine the efficacy of calcium alone and calcium plus vitamin D in reducing incident cancer risk of all types. This was a 4-y, population-based, double-blind, randomized placebo-controlled trial. The primary outcome was fracture incidence, and the principal secondary outcome was cancer incidence. The subjects were 1179 community-dwelling women randomly selected from the population of healthy postmenopausal women aged >55 y in a 9-county rural area of Nebraska centered at latitude 41.4 degrees N. Subjects were randomly assigned to receive 1400-1500 mg supplemental calcium/d alone (Ca-only), supplemental calcium plus 1100 IU vitamin D3/d (Ca + D), or placebo. When analyzed by intention to treat, cancer incidence was lower in the Ca + D women than in the placebo control subjects (P < 0.03). With the use of logistic regression, the unadjusted relative risks (RR) of incident cancer in the Ca + D and Ca-only groups were 0.402 (P = 0.01) and 0.532 (P = 0.06), respectively. When analysis was confined to cancers diagnosed after the first 12 mo, RR for the Ca + D group fell to 0.232 (CI: 0.09, 0.60; P < 0.005) but did not change significantly for the Ca-only group. In multiple logistic regression models, both treatment and serum 25-hydroxyvitamin D concentrations were significant, independent predictors of cancer risk. Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00352170.

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

DTIC Science & Technology

2010-02-01

Metallurgist. 45, 267, 2001. 10. Dodero, M. "Electrolytic Preparation of Calcium Silicide ," Compt. Rend.. 198, 1593, 1934. 11. Dodero, M...Allqem. Chem.. 242, 117, 1939. 13. Yamaguchi, Y. and Hayakawa, Y., "The Preparation of Calcium Silicide by Reacting Solid Silicon Carbide and...SYNTHESIS OF CALCIUM SILICIDE (CaSi2) BY ROTARY ATOMIZATION Paul E. Anderson Kin Yee Eugene Homentowski Gartung Cheng Neha Mehta Gary Chen U.S

New evidence about the relationship between water channel activity and calcium in salinity-stressed pepper plants.

PubMed

Cabañero, Francisco J; Martínez-Ballesta, M Carmen; Teruel, José A; Carvajal, Micaela

2006-02-01

This study, of how Ca2+ availability (intracellular, extracellular or linked to the membrane) influences the functionality of aquaporins of pepper (Capsicum annuum L.) plants grown under salinity stress, was carried out in plants treated with NaCl (50 mM), CaCl2 (10 mM), and CaCl2 (10 mM) + NaCl (50 mM). For this, water transport through the plasma membrane of isolated protoplasts, and the involvement of aquaporins and calcium (extracellular, intracellular and linked to the membrane) has been determined. After these treatments, it could be seen that the calcium concentration was reduced in the apoplast, in the cells and on the plasma membrane of roots of pepper plants grown under saline conditions; these concentrations were increased or restored when extra calcium was added to the nutrient solution. Protoplasts extracted from plants grown under Ca2+ starvation showed no aquaporin functionality. However, for the protoplasts to which calcium was added, an increase of aquaporin functionality of the plasma membrane was observed [osmotic water permeability (Pf) inhibition after Hg addition]. Interestingly, when verapamil (a Ca2+ channel blocker) was added, no functionality was observed, even when Ca2+ was added with verapamil. Therefore, calcium seems to be involved in plasma membrane aquaporin regulation via a chain of processes within the cell but not by alteration of the stability of the plasma membrane.

Calcium balance in dialysis is best managed by adjusting dialysate calcium guided by kinetic modeling of the interrelationship between calcium intake, dose of vitamin D analogues and the dialysate calcium concentration.

PubMed

Gotch, Frank; Levin, Nathan W; Kotanko, Peter

2010-01-01

Calcium mass balance (Ca(MB)) is determined by the difference between Ca absorbed between dialyses (Ca(Abs)) and the Ca removed during dialysis (J(d)Ca(2+)). A mathematical model to quantify (1) Ca(Abs) as a function of Ca intake (Ca(INT)) and the doses of vitamin D analogues, and (2) J(d)Ca(2+) as a function of Ca(2+) dialysance, the mean plasma Ca(2+) ((M)C(pi)Ca(2+)) minus dialysate Ca(2+) (C(di)Ca(2+)), ultrafiltration rate (Q(f)) and treatment time is developed in this paper. The model revealed a basic design flaw in clinical studies of Ca-based as opposed to non-Ca-based binders in that C(di)Ca(2+) must be reduced with the Ca-based binders in order to avoid a positive Ca(MB) relative to the non-Ca-based binders. The model was also used to analyze Ca(MB) in 320 Renal Research Institute hemodialysis patients and showed that all patients irrespective of type of binder were in positive Ca(MB) between dialyses (mean +/- SD 160 +/- 67 mg/day) with current doses of vitamin D analogues prescribed. Calculation of the optimal C(di)Ca(2+) for the 320 Renal Research Institute patients revealed that in virtually all instances, the C(di)Ca(2+) required for neutral Ca(MB), where Ca removal during dialysis was equal to Ca accumulation between dialyses, was less than 2.50 mEq/l and averaged about 2.00 mEq/l. This sharply contradicts the recent KDIGO (Kidney Disease: Improving Global Outcomes) Clinical Practice Guideline for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease - Mineral and Bone Disorder, that suggests a C(di)Ca(2+) of 2.5-3.0 mEq/l. Review of the KDIGO work group discussions shows that this discrepancy stems from the unwarranted work group assumption that intradialytic Ca(MB) is zero. We strongly believe that this guideline for dialysate Ca(2+) is inappropriate and should be modified to more realistically reflect the needs of dialysis patients. Copyright (c) 2010 S. Karger AG, Basel.

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

PubMed

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, p<10 -5 ). The main biological processes affected by [Ca 2+ ] o were DNA replication, cell division, and regulation of transcription. All factors involved in DNA replication-licensing were significantly downregulated by [Ca 2+ ] o . Furthermore, we show that the calcium-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.

A Comparative Study of Ion Diffusion from Calcium Hydroxide with Various Herbal Pastes through Dentin

PubMed Central

Dhirawani, Rajesh B; Marya, Jayant; Dhirawani, Vrinda; Kumar, Vijayendra

2017-01-01

Aim The aim of this study was to evaluate the diffusion ability of ions through dentinal tubules of different nonalcoholic calcium hydroxide-containing herbal pastes and compare it with the calcium hydroxide paste prepared with saline. Materials and methods A total of 36 single-rooted premolar teeth were used in this study. The tooth crowns were removed and the root canals were prepared. Depending on the vehicle to be used for preparing calcium hydroxide pastes, six groups were made: Group I: Ca(OH)2 saline paste (control group), group II: Ca(OH)2 papaya latex paste, group III: Ca(OH)2 coconut water paste, group IV: Ca(OH)2 Ashwagandha (Withania somnifera) paste, group V: Ca(OH)2 Tulsi (Ocimum tenuiflorum) paste, and group VI: Ca(OH)2 garlic (Allium sativum) paste. After biomechanical preparation, calcium hydroxide herbal paste dressings were applied and sealed with resin-based cement. The teeth were placed in containers with deionized water, and the pH of the water was measured at regular intervals over 3, 24, 72, and 168 hours. Results We observed that all herbal pastes allowed the diffusion of ions, but pastes prepared with Ashwagandha and papaya latex showed more ion diffusion after 168 hours and marked increase in pH, depicting better support for calcium hydroxide action. Conclusion We conclude that Ashwagandha and papaya latex allow better diffusion of calcium hydroxide through den-tinal tubules, thus enhancing its action, and advise its use as a vehicle for placing intracanal medicament. How to cite this article Dausage P, Dhirawani RB, Marya J, Dhirawani V, Kumar V. A Comparative Study of Ion Diffusion from Calcium Hydroxide with Various Herbal Pastes through Dentin. Int J Clin Pediatr Dent 2017;10(1):41-44. PMID:28377654

Calcium plus vitamin D supplementation and lung cancer incidence among postmenopausal women in the Women's Health Initiative.

PubMed

Tao, Meng-Hua; Dai, Qi; Chen, Shande; Freudenheim, Jo L; Rohan, Thomas; Wakelee, Heather; Datta, Mridul; Wactawski-Wende, Jean

2017-08-01

Magnesium and calcium are antagonistic in many physiologic processes. However, few studies have investigated the associations of supplemental calcium with lung cancer risk taking this antagonism into account. We evaluated the effect of calcium and vitamin D supplementation on lung cancer incidence and explored whether the ratio of baseline calcium to magnesium (Ca:Mg) intake modifies the association in the Women's Health Initiative (WHI) calcium plus vitamin D supplementation (CaD) trial. The intervention phase of the WHI CaD was a double-blinded, randomized, placebo-controlled trial in 36,382 postmenopausal women aged 50-79 years, recruited at 40U.S. centers. Post-intervention follow-up continued among 29,862 (86%) of the surviving participants. Risk of lung cancer in association with CaD supplementation was evaluated using proportional hazard regression models. After 11 years' cumulative follow-up, there were 207 lung cancers (incidence 0.11% per year) in the supplement arm and 241 (0.12%) in the placebo arm (hazard ratio (HR) for the intervention, 0.91; 95% confidence interval (CI), 0.71-1.17). Subgroup analyses suggested that the HR for lung cancer varied by baseline Ca:Mg intake ratio among women who were current smokers at enrollment (p=0.04 for interaction). Over the entire follow-up period, calcium and vitamin D supplementation did not reduce lung cancer incidence among postmenopausal women. In exploratory analyses, an interaction was found for the baseline Ca:Mg intake ratio on lung cancer among current smokers at the trial entry. This findings need to be further studied for the role of calcium with magnesium in lung carcinogenesis in current smokers. Copyright © 2017 Elsevier B.V. All rights reserved.

[Human calcium channelopathies. Voltage-gated Ca(2+) channels in etiology, pathogenesis, and pharmacotherapy of neurologic disorders].

PubMed

Weiergräber, M; Hescheler, J; Schneider, T

2008-04-01

Voltage-gated calcium channels are key components in a variety of physiological processes. Within the last decade an increasing number of voltage-gated Ca(2+) channelopathies in both humans and animal models has been described, most of which are related to the neurologic and muscular system. In humans, mutations were found in L-type Ca(v)1.2 and Ca(v)1.4 Ca(2+) channels as well as the non-L-type Ca(v)2.1 and T-type Ca(v)3.2 channels, resulting in altered electrophysiologic properties. Based on their widespread distribution within the CNS, voltage-gated calcium channels are of particular importance in the etiology and pathogenesis of various forms of epilepsy and neuropsychiatric disorders. In this review we characterise the different human Ca(2+) channelopathies known so far, further illuminating basic pathophysiologic mechanisms and clinical aspects.

Synthesis of calcium superoxide

NASA Technical Reports Server (NTRS)

Rewick, R. T.; Blucher, W. G.; Estacio, P. L.

1972-01-01

Efforts to prepare Ca(O2) sub 2 from reactions of calcium compounds with 100% O3 and with O(D-1) atoms generated by photolysis of O3 at 2537 A are described. Samples of Ca(OH) sub 2, CaO, CaO2, Ca metal, and mixtures containing suspected impurities to promote reaction have been treated with excess O3 under static and flow conditions in the presence and absence of UV irradiation. Studies with KO2 suggest that the superoxide anion is stable to radiation at 2537 A but reacts with oxygen atoms generated by the photolysis of O3 to form KO3. Calcium superoxide is expected to behave in an analogous.

Controls on foliar nutrient and aluminium concentrations in a tropical tree flora: phylogeny, soil chemistry and interactions among elements.

PubMed

Metali, Faizah; Abu Salim, Kamariah; Tennakoon, Kushan; Burslem, David F R P

2015-01-01

Foliar elemental concentrations are predictors of life-history variation and contribute to spatial patterns in biogeochemical cycling. We examined the contributions of habitat association, local soil environment, and elemental interactions to variation in foliar elemental concentrations in tropical trees using methods that account for phylogeny. We sampled top-soils and leaves of 58 tropical trees in heath forest (HF) on nutrient-poor sand and mixed dipterocarp forest (MDF) on nutrient-rich clay soils. A phylogenetic generalized least squares method was used to determine how foliar nutrient and aluminium (Al) concentrations varied in response to habitat distribution, soil chemistry and other elemental concentrations. Foliar nitrogen (N) and Al concentrations were greater for specialists of MDF than for specialists of HF, while foliar calcium (Ca) concentrations showed the opposite trend. Foliar magnesium (Mg) concentrations were lower for generalists than for MDF specialists. Foliar element concentrations were correlated with fine-scale variation in soil chemistry in phylogenetically controlled analyses across species, but there was limited within-species plasticity in foliar elemental concentrations. Among Al accumulators, foliar Al concentration was positively associated with foliar Ca and Mg concentrations, and negatively associated with foliar phosphorus (P) concentrations. The Al-accumulation trait and relationships between foliar elemental and Al concentrations may contribute to species habitat partitioning and ecosystem-level differences in biogeochemical cycles. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Function of endoplasmic reticulum calcium ATPase in innate immunity-mediated programmed cell death

PubMed Central

Zhu, Xiaohong; Caplan, Jeffrey; Mamillapalli, Padmavathi; Czymmek, Kirk; Dinesh-Kumar, Savithramma P

2010-01-01

Programmed cell death (PCD) initiated at the pathogen-infected sites during the plant innate immune response is thought to prevent the development of disease. Here, we describe the identification and characterization of an ER-localized type IIB Ca2+-ATPase (NbCA1) that function as a regulator of PCD. Silencing of NbCA1 accelerates viral immune receptor N- and fungal-immune receptor Cf9-mediated PCD, as well as non-host pathogen Pseudomonas syringae pv. tomato DC3000 and the general elicitor cryptogein-induced cell death. The accelerated PCD rescues loss-of-resistance phenotype of Rar1, HSP90-silenced plants, but not SGT1-silenced plants. Using a genetically encoded calcium sensor, we show that downregulation of NbCA1 results in the modulation of intracellular calcium signalling in response to cryptogein elicitor. We further show that NbCAM1 and NbrbohB function as downstream calcium decoders in N-immune receptor-mediated PCD. Our results indicate that ER-Ca2+-ATPase is a component of the calcium efflux pathway that controls PCD during an innate immune response. PMID:20075858

Synthesis and characterization of superparamagnetic iron oxide nanoparticles as calcium-responsive MRI contrast agents

NASA Astrophysics Data System (ADS)

Xu, Pengfei; Shen, Zhiwei; Zhang, Baolin; Wang, Jun; Wu, Renhua

2016-12-01

Superparamagnetic iron oxide nanoparticles (SPIONs) as T2 contrast agents have great potential to sense calcium ion (Ca2+) using magnetic resonance imaging (MRI). Here we prepared calcium-responsive SPIONs for MRI, formed by combining poly(ethylene glycol) (PEG) and polyethylenimine (PEI) coated iron oxide nanoparticle (PEI/PEG-SPIONs) contrast agents with the straightforward calcium-sensing compound EGTA (ethylene glycol tetraacetic acid). EGTA was conjugated onto PEI/PEG-SPIONs using EDC/sulfo-NHS method. EGTA-SPIONs were characterized using TEM, XPS, DSL, TGA and SQUIID. DSL results show that the SPIONs aggregate in the presence of Ca2+. MRI analyses indicate that the water proton T2 relaxation rates in HEPES suspensions of the EGTA-SPIONs significantly increase with the calcium concentration because the SPIONs aggregate in the presence of Ca2+. The T2 values decreased 25% when Ca2+ concentration decreased from 1.2 to 0.8 mM. The aggregation of EGTA-SPIONs could be reversed by EDTA. EGTA-SPIONs have potential as smart contrast agents for Ca2+-sensitive MRI.

Synthesis of β-Calcium Pyrophosphate by sol-gel method

NASA Astrophysics Data System (ADS)

Windarti, T.; Taslimah; Haris, A.; Astuti, Y.; Darmawan, A.

2017-02-01

Beta calcium pyrophosphate [β-CPP, β-Ca2P2O7] can be used as bone graft extender in posterolateral lumbar fusion. In this research, β-CPP was synthesized by sol-gel method using phosphorus pentaoxide [P2O5] and calcium nitrate tetrahydrate [Ca(NO3)2.4H2O] as phosphorus and calcium precursors. The reaction was carried out in ethanol medium with Ca/P ratio of 1.67. After 21 hours of reaction and 20 hours of drying at 80°C, white powder of amorphous calcium phosphate (ACP) was produced. Transformation of ACP to β-CPP was undertaken by firring at 400-800°C for 8 hours. Transformations of amorphous to microcrystalline, semicrystalline and crystalline structures occur at 400, 600 and 800°C, respectively. The β-CPP with the crystallite size of 61.71 nm, Ca/P ratio of 0.89 and Ca/O ratio of 0.21 was achieved by firing at 800°C. Morphology changes due to firing in which irregular shape of β-CPP at 400° changed to regular cuboid at 600 °C and above.

Effect of aluminum on bidirectional calcium flux in rat everted intestinal sacs.

PubMed

Adler, A J; Zara, C; Berlyne, G M

1989-09-01

The effect of aluminum on intestinal calcium absorption was determined in male Sprague-Dawley rats using an everted intestinal sac technique. Bidirectional calcium flux in the duodena and ilea of normal rats was assessed by means of dual calcium isotopes. Two micromolar aluminum significantly inhibited net calcium absorption (J net) in the duodenum through suppression of mucosato-serosa flux (J m----s). Jm----s was reduced from 2.21 +/- 0.50 mumol Ca.h-1.g wet wt-1 in controls to 0.93 +/- 0.35 mumol Ca.h-1.g-1 in aluminum exposed sacs, and Jnet was reduced from 1.88 +/- 0.14 mumol Ca.h-1.g-1 to 0.55 +/- 0.41 mumol Ca.h-1.g-1 (P less than 0.001). Serosa-to-mucosa calcium flux (Js----m) was not similarly influenced by aluminum. Inhibition of Jm----s occurred whether aluminum was initially present on the mucosal or serosal side of the duodenal sac and inhibition of Jnet calcium by 2 muM A1 occurred at all ambient concentrations of calcium studied. In the ileum, aluminum had no effect on any component of calcium flux. Aluminum did not induce any suppression of glucose transport in either the duodenum or ileum, suggesting that the effect on calcium transport is relatively specific. These results suggest that aluminum inhibits calcium absorption in the duodenum through an effect on active mucosa-to-serosa transport, but has no effect on ileal calcium absorption, which in the rat is not mediated by an active process.

Beneficial use of meat and bone meal combustion residue: "an efficient low cost material to remove lead from aqueous effluent".

PubMed

Deydier, Eric; Guilet, Richard; Sharrock, Patrick

2003-07-04

Meat and bone meal (MBM) combustion residues, a natural apatite-rich substance, was evaluated as a low cost substitute for hydroxyapatite in lead sequestration from water effluents. The thermal behaviour of crude meat and bone meal was followed by TGA and 24% inorganic residue was collected. The resulting ashes were characterised by powder X-ray diffraction (XRD), particle size distribution, specific surface area (BET), and elemental analysis confirming apatite contents, with high level of phosphate (56.3%) and calcium (36.8%). Mechanism and kinetics of lead removal by this bioinorganic material were investigated and compared to mechanisms and kinetics involved with synthetic apatite. Batch metal removal experiments were carried out with 500 and 1500ppm (mg/kg) Pb(2+) solutions. Lead concentration, calcium and pH were monitored. We observed that the mechanism is similar to that occurring for pure apatite, and involved both surface complexation and calcium hydroyapatite (CaHA), Ca(10)(PO(4))(6)(OH)(2), dissolution followed by less soluble Pb(10)(PO(4))(6)(OH)(2) precipitation, as confirmed by XRD analysis of ashes after incubation with lead solution. Our results show that this natural apatite-rich material removes in a few minutes a large quantity of lead (275mg/g capacity) which remains however lower than the theoretical maximum capacity (if calcium were totally substituted by lead). Meat and bone meal combustion residues represent a valuable alternative apatite source for environmental application.

Disruption of the vacuolar calcium-ATPases in arabidopsis results in the activation of a salicylic acid-dependent programmed cell death pathway

USDA-ARS?s Scientific Manuscript database

Calcium (Ca2+) signals regulate many aspects of plant development, including the Hypersensitive Response (HR) that triggers a programmed cell death response to protect a plant from a pathogen. A transient increase in cytosolic Ca2+ ([Ca2+]cyt ) results from Ca2+ entry from the apoplast or release fr...

Chronic alcohol feeding potentiates hormone-induced calcium signalling in hepatocytes.

PubMed

Bartlett, Paula J; Antony, Anil Noronha; Agarwal, Amit; Hilly, Mauricette; Prince, Victoria L; Combettes, Laurent; Hoek, Jan B; Gaspers, Lawrence D

2017-05-15

Chronic alcohol consumption causes a spectrum of liver diseases, but the pathogenic mechanisms driving the onset and progression of disease are not clearly defined. We show that chronic alcohol feeding sensitizes rat hepatocytes to Ca 2+ -mobilizing hormones resulting in a leftward shift in the concentration-response relationship and the transition from oscillatory to more sustained and prolonged Ca 2+ increases. Our data demonstrate that alcohol-dependent adaptation in the Ca 2+ signalling pathway occurs at the level of hormone-induced inositol 1,4,5 trisphosphate (IP 3 ) production and does not involve changes in the sensitivity of the IP 3 receptor or size of internal Ca 2+ stores. We suggest that prolonged and aberrant hormone-evoked Ca 2+ increases may stimulate the production of mitochondrial reactive oxygen species and contribute to alcohol-induced hepatocyte injury. ABSTRACT: 'Adaptive' responses of the liver to chronic alcohol consumption may underlie the development of cell and tissue injury. Alcohol administration can perturb multiple signalling pathways including phosphoinositide-dependent cytosolic calcium ([Ca 2+ ] i ) increases, which can adversely affect mitochondrial Ca 2+ levels, reactive oxygen species production and energy metabolism. Our data indicate that chronic alcohol feeding induces a leftward shift in the dose-response for Ca 2+ -mobilizing hormones resulting in more sustained and prolonged [Ca 2+ ] i increases in both cultured hepatocytes and hepatocytes within the intact perfused liver. Ca 2+ increases were initiated at lower hormone concentrations, and intercellular calcium wave propagation rates were faster in alcoholics compared to controls. Acute alcohol treatment (25 mm) completely inhibited hormone-induced calcium increases in control livers, but not after chronic alcohol-feeding, suggesting desensitization to the inhibitory actions of ethanol. Hormone-induced inositol 1,4,5 trisphosphate (IP 3 ) accumulation and phospholipase C (PLC) activity were significantly potentiated in hepatocytes from alcohol-fed rats compared to controls. Removal of extracellular calcium, or chelation of intracellular calcium did not normalize the differences in hormone-stimulated PLC activity, indicating calcium-dependent PLCs are not upregulated by alcohol. We propose that the liver 'adapts' to chronic alcohol exposure by increasing hormone-dependent IP 3 formation, leading to aberrant calcium increases, which may contribute to hepatocyte injury. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Silicene-terminated surface of calcium and strontium disilicides: properties and comparison with bulk structures by computational methods

NASA Astrophysics Data System (ADS)

Brázda, Petr; Mutombo, Pingo; Ondráček, Martin; Corrêa, Cinthia Antunes; Kopeček, Jaromír; Palatinus, Lukáš

2018-05-01

The bulk and surface structures of calcium and strontium disilicides are investigated by computational methods using density functional theory. The investigated structures are R6, R3 and P1-CaSi2 and P1-SrSi2. The investigated properties are the cleavage energy at the silicene sheet, buckling of the bulk and surface silicene layers, charge transfer from calcium to silicon, band structure of bulk and surface-terminated structures and adsorption energies on H atoms and H2 molecules on the silicene-terminated surface of the R3 phase. The cleavage energy at the silicene surface is low in all cases. Structures P1-CaSi2 and R3-CaSi2 contain silicene sheets with different coordination to Ca, while R6-CaSi2 contains both types of the sheets. It is shown that the properties of the two types of silicene-like sheets in R6-CaSi2 are similar to those of the corresponding sheets in P1-CaSi2 and R3-CaSi2, and the thermodynamically stable R6 phase is a good candidate for experimental investigation of silicene-terminated surface in calcium disilicide.

Effects of zearalenone on calcium homeostasis of splenic lymphocytes of chickens in vitro.

PubMed

Wang, Y C; Deng, J L; Xu, S W; Peng, X; Zuo, Z C; Cui, H M; Wang, Y; Ren, Z H

2012-08-01

Zearalenone (ZEA) is an estrogenic mycotoxin. It is produced by several Fusarium species and can contaminate food and feed. To investigate the role of calcium homeostasis in ZEA-induced toxicity of poultry and elucidate its cytotoxic mechanism, splenic lymphocytes isolated from chickens were exposed to ZEA (0-25 μg/mL) for 48 h. The intracellular calcium concentration ([Ca2+]i), pH, calmodulin (CaM) mRNA levels, and Na+/K+-ATPase activities and Ca2+-ATPase activities were detected by the fluorescent dyes Fluo-3/AM and BCECF/AM, quantitative real-time PCR, and chromatometry. Supernatant CaM concentrations were simultaneously detected by ELISA. As the ZEA exposure concentration increased, the [Ca2+]i and CaM mRNA levels gradually increased, while intracellular pH, CaM concentrations of supernatants, and intracellular Na+,K+-ATPase and Ca2+-ATPase activities gradually decreased in a dose-dependent manner. There were significant differences (P<0.05 or P<0.01) between the treatment groups and the control group. These results indicate that ZEA cytotoxicity arises by causing an imbalance in calcium homeostasis and intracellular acidification in lymphocytes.

Role of magnesium on the biomimetic deposition of calcium phosphate

NASA Astrophysics Data System (ADS)

Sarma, Bimal K.; Sarma, Bikash

2016-10-01

Biomimetic depositions of calcium phosphate (CaP) are carried out using simulated body fluid (SBF), calcifying solution and newly developed magnesium containing calcifying solution. Calcium phosphate has a rich phase diagram and is well known for its excellent biocompatibility and bioactivity. The most common phase is hydroxyapatite (HAp), an integral component of human bone and tooth, widely used in orthopedic and dental applications. In addition, calcium phosphate nanoparticles show promise for the targeted drug delivery. The doping of calcium phosphate by magnesium, zinc, strontium etc. can change the protein uptake by CaP nanocrystals. This work describes the role of magnesium on the nucleation and growth of CaP on Ti and its oxide substrates. X-ray diffraction studies confirm formation of HAp nanocrystals which closely resemble the structure of bone apatite when grown using SBF and calcifying solution. It has been observed that magnesium plays crucial role in the nucleation and growth of calcium phosphate. A low magnesium level enhances the crystallinity of HAp while higher magnesium content leads to the formation of amorphous calcium phosphate (ACP) phase. Interestingly, the deposition of ACP phase is rapid when magnesium ion concentration in the solution is 40% of calcium plus magnesium ions concentration. Moreover, high magnesium content alters the morphology of CaP films.

Quantitative analysis of the expression and distribution of calcium channel alpha 1 subunit mRNA in the atria and ventricles of the rat heart.

PubMed

Larsen, Janice K; Mitchell, Jennifer W; Best, Philip M

2002-05-01

Two distinct calcium currents are present in mammalian cardiac myocytes. Utilizing quantitative RT-PCR methods, we have analysed the expression patterns and abundance of four calcium channel alpha 1 subunit mRNAs in different regions of the rat heart and compared them to the known density of calcium currents recorded from rat atria. Our results show that Ca(V)1.2 is the most abundant of the four alpha 1 subunit transcripts in the rat heart. The Ca(V)1.2 message is more abundant in ventricle than in atria and does not vary in expression as a function of developmental age. Ca(V)2.3, Ca(V)3.1 and Ca(V)3.2 mRNAs are 10-100 times less abundant than Ca(V)1.2. Interestingly, Ca(V)2.3, Ca(V)3.1 and Ca(V)3.2 are expressed in both atria and ventricle. The abundance of atrial Ca(V)3.1 mRNA does not change significantly during development and remains high in older animals. In contrast, levels of atrial Ca(V)3.2 mRNA are high in embryonic tissue and at 3- and 4-weeks postnatal but become undetectable at 5 weeks. Expression of atrial Ca(V)2.3 mRNA is highest at 4-weeks postnatal and then declines gradually. We have previously documented that the LVA calcium current density is highest within 4-5 weeks after birth and then declines gradually reaching less than 30% of its maximal value at 12-14 weeks. The complex relationship between atrial LVA current density and the abundance of Ca(V)2.3, Ca(V)3.1 and Ca(V)3.2 mRNA suggests that their contribution to the cardiac LVA current may vary as a function of postnatal age. Copyright 2002 Academic Press.

Calcium carbonate precipitation by heterotrophic bacteria isolated from biofilms formed on deteriorated ignimbrite stones: influence of calcium on EPS production and biofilm formation by these isolates.

PubMed

López-Moreno, Angélica; Sepúlveda-Sánchez, José David; Mercedes Alonso Guzmán, Elia Mercedes; Le Borgne, Sylvie

2014-01-01

Heterotrophic CaCO3-precipitating bacteria were isolated from biofilms on deteriorated ignimbrites, siliceous acidic rocks, from Morelia Cathedral (Mexico) and identified as Enterobacter cancerogenus (22e), Bacillus sp. (32a) and Bacillus subtilis (52g). In solid medium, 22e and 32a precipitated calcite and vaterite while 52g produced calcite. Urease activity was detected in these isolates and CaCO3 precipitation increased in the presence of urea in the liquid medium. In the presence of calcium, EPS production decreased in 22e and 32a and increased in 52g. Under laboratory conditions, ignimbrite colonization by these isolates only occurred in the presence of calcium and no CaCO3 was precipitated. Calcium may therefore be important for biofilm formation on stones. The importance of the type of stone, here a siliceous stone, on biological colonization is emphasized. This calcium effect has not been reported on calcareous materials. The importance of the effect of calcium on EPS production and biofilm formation is discussed in relation to other applications of CaCO3 precipitation by bacteria.

Calcium-controlled conformational choreography in the N-terminal half of adseverin

NASA Astrophysics Data System (ADS)

Chumnarnsilpa, Sakesit; Robinson, Robert C.; Grimes, Jonathan M.; Leyrat, Cedric

2015-09-01

Adseverin is a member of the calcium-regulated gelsolin superfamily of actin-binding proteins. Here we report the crystal structure of the calcium-free N-terminal half of adseverin (iA1-A3) and the Ca2+-bound structure of A3, which reveal structural similarities and differences with gelsolin. Solution small-angle X-ray scattering combined with ensemble optimization revealed a dynamic Ca2+-dependent equilibrium between inactive, intermediate and active conformations. Increasing calcium concentrations progressively shift this equilibrium from a main population of inactive conformation to the active form. Molecular dynamics simulations of iA1-A3 provided insights into Ca2+-induced destabilization, implicating a critical role for the A2 type II calcium-binding site and the A2A3 linker in the activation process. Finally, mutations that disrupt the A1/A3 interface increase Ca2+-independent F-actin severing by A1-A3, albeit at a lower efficiency than observed for gelsolin domains G1-G3. Together, these data address the calcium dependency of A1-A3 activity in relation to the calcium-independent activity of G1-G3.

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

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

Feng, Shan-Li; Sun, Ming-Rui; Li, Ting-Ting

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 andmore » 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} increased the expression of TRPC3 mRNA and protein, which were reversed by SKF96365 but not by inhibitors of the L-type channels and the Na{sup +}/Ca{sup 2+} exchangers. However, GdCl{sub 3} had no obvious effect on the expression of TRPC1 protein. These results suggested that CaR stimulation induced activation of TRP channels and promoted the expression of TRPC3, but not TRPC1, that sustained the increased [Ca{sup 2+}]{sub i}.« less

In vivo Post-Cardiac Arrest Myocardial Dysfunction is Supported by CaMKII-Mediated Calcium Long-Term Potentiation and Mitigated by Alda-1, an Agonist of Aldehyde Dehydrogenase Type 2

PubMed Central

Downey, Peter; Zalewski, Adrian; Rubio, Gabriel R.; Liu, Jing; Homburger, Julian R.; Grunwald, Zachary; Qi, Wei; Bollensdorff, Christian; Thanaporn, Porama; Ali, Ayyaz; Riemer, Kirk; Kohl, Peter; Mochly-Rosen, Daria; Gerstenfeld, Edward; Large, Stephen; Ali, Ziad; Ashley, Euan

2016-01-01

Background Survival after sudden cardiac arrest is limited by post-arrest myocardial dysfunction but understanding of this phenomenon is constrained by lack of data from a physiological model of disease. In this study, we established an in vivo model of cardiac arrest and resuscitation, characterized the biology of the associated myocardial dysfunction, and tested novel therapeutic strategies. Methods We developed rodent models of in vivo post-arrest myocardial dysfunction using extra-corporeal membrane oxygenation (ECMO) resuscitation followed by invasive hemodynamics measurement. In post-arrest isolated cardiomyocytes, we assessed mechanical load and Ca2+ induced Ca2+ release (CICR) simultaneously using the micro-carbon-fiber technique and observed reduced function and myofilament calcium sensitivity. We used a novel-designed fiber optic catheter imaging system, and a genetically encoded calcium sensor GCaMP6f, to image CICR in vivo. Results We found potentiation of CICR in isolated cells from this ECMO model and also in cells isolated from an ischemia-reperfusion Langendorff model perfused with oxygenated blood from an arrested animal, but not when reperfused in saline. We established that CICR potentiation begins in vivo. The augmented CICR observed post-arrest was mediated by the activation of Ca2+/calmodulin kinase II (CaMKII). Increased phosphorylation of CaMKII, phospholamban and ryanodine receptor 2 (RyR2) was detected in the post-arrest period. Exogenous adrenergic activation in vivo recapitulated Ca2+ potentiation but was associated with lesser CaMKII activation. Since oxidative stress and aldehydic adduct formation were high post arrest, we tested a small molecule activator of aldehyde dehydrogenase type 2, Alda-1, which reduced oxidative stress, restored calcium and CaMKII homeostasis, and improved cardiac function and post-arrest outcome in vivo. Conclusions Cardiac arrest and reperfusion lead to CaMKII activation and calcium long-term potentiation which support cardiomyocyte contractility in the face of impaired post-ischemic myofilament calcium sensitivity. Alda-1 mitigates these effects, normalizes calcium cycling and improves outcome. PMID:27582424

CASK regulates CaMKII autophosphorylation in neuronal growth, calcium signaling, and learning

PubMed Central

Gillespie, John M.; Hodge, James J. L.

2013-01-01

Calcium (Ca2+)/calmodulin (CaM)-dependent kinase II (CaMKII) activity plays a fundamental role in learning and memory. A key feature of CaMKII in memory formation is its ability to be regulated by autophosphorylation, which switches its activity on and off during synaptic plasticity. The synaptic scaffolding protein CASK (calcium (Ca2+)/calmodulin (CaM) associated serine kinase) is also important for learning and memory, as mutations in CASK result in intellectual disability and neurological defects in humans. We show that in Drosophila larvae, CASK interacts with CaMKII to control neuronal growth and calcium signaling. Furthermore, deletion of the CaMK-like and L27 domains of CASK (CASK β null) or expression of overactive CaMKII (T287D) produced similar effects on synaptic growth and Ca2+ signaling. CASK overexpression rescues the effects of CaMKII overactivity, consistent with the notion that CASK and CaMKII act in a common pathway that controls these neuronal processes. The reduction in Ca2+ signaling observed in the CASK β null mutant caused a decrease in vesicle trafficking at synapses. In addition, the decrease in Ca2+ signaling in CASK mutants was associated with an increase in Ether-à-go-go (EAG) potassium (K+) channel localization to synapses. Reducing EAG restored the decrease in Ca2+ signaling observed in CASK mutants to the level of wildtype, suggesting that CASK regulates Ca2+ signaling via EAG. CASK knockdown reduced both appetitive associative learning and odor evoked Ca2+ responses in Drosophila mushroom bodies, which are the learning centers of Drosophila. Expression of human CASK in Drosophila rescued the effect of CASK deletion on the activity state of CaMKII, suggesting that human CASK may also regulate CaMKII autophosphorylation. PMID:24062638

Fortified tuna bone powder supplementation increases bone mineral density of lactating rats and their offspring.

PubMed

Suntornsaratoon, Panan; Charoenphandhu, Narattaphol; Krishnamra, Nateetip

2018-03-01

Breastfeeding leads to bone calcium loss for milk production, resulting in progressive maternal osteopenia. Calcium supplement from natural sources has been postulated to be more beneficial to bone health than purified CaCO 3 because natural sources also contain other nutrients such as certain amino acids that might enhance calcium metabolism. Herein, we examined the effect of calcium supplementation from tuna bone powder and CaCO 3 on bones of dams and the offspring. Both forms of calcium supplement, i.e. tuna bone powder and CaCO 3 , increased maternal bone mineral density (BMD). However, bone histomorphometry revealed that only tuna bone had beneficial effect on maternal bone microstructure, i.e. increased bone formation, decreased bone resorption and increased in bone volume. Regarding the mechanical properties, the decreased ultimate load in non-supplement lactating mothers was restored to the load seen in nulliparous animals by calcium supplementation. Moreover, both tuna bone and CaCO 3 supplementation in mothers led to increased milk calcium concentration and consequently increased BMD in the growing offspring. Calcium supplement from tuna bone powder was effective in preventing maternal osteopenia. Tuna bone, which is a readily available fishing industrial waste, is a good alternative source of calcium supplement that increases BMD in both lactating mothers and the neonates. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Sulfhydryl oxidation modifies the calcium dependence of ryanodine-sensitive calcium channels of excitable cells.

PubMed Central

Marengo, J J; Hidalgo, C; Bull, R

1998-01-01

The calcium dependence of ryanodine-sensitive single calcium channels was studied after fusing with planar lipid bilayers sarcoendoplasmic reticulum vesicles isolated from excitable tissues. Native channels from mammalian or amphibian skeletal muscle displayed three different calcium dependencies, cardiac (C), mammalian skeletal (MS), and low fractional open times (low Po), as reported for channels from brain cortex. Native channels from cardiac muscle presented only the MS and C dependencies. Channels with the MS or low Po behaviors showed bell-shaped calcium dependencies, but the latter had fractional open times of <0.1 at all [Ca2+]. Channels with C calcium dependence were activated by [Ca2+] < 10 microM and were not inhibited by increasing cis [Ca2+] up to 0.5 mM. After oxidation with 2,2'-dithiodipyridine or thimerosal, channels with low Po or MS dependencies increased their activity. These channels modified their calcium dependencies sequentially, from low Po to MS and C, or from MS to C. Reduction with glutathione of channels with C dependence (native or oxidized) decreased their fractional open times in 0.5 mM cis [Ca2+], from near unity to 0.1-0.3. These results show that all native channels displayed at least two calcium dependencies regardless of their origin, and that these changed after treatment with redox reagents. PMID:9512024

Enthalpies of formation of CaAl4O7 and CaAl12O19 (hibonite) by high temperature, alkali borate solution calorimetry

NASA Technical Reports Server (NTRS)

Geiger, C. A.; Kleppa, O. J.; Grossman, L.; Mysen, B. O.; Lattimer, J. M.

1988-01-01

Enthalpies of formation were determined for two calcium aluminate phases, CaAl4O7 and CaAl12O19, using high-temperature alkali borate solution calorimetry. The aluminates were synthesized by multiple-cycle heating and grinding stoichiometric mixtures of CaCO3 and Al2O3, and the products were characteized by X-ray diffraction and SEM microbeam analysis. The data on impurities (CaAl4O7 was found to be about 89.00 percent pure by weight and the CaAl12O19 samples about 91.48 percent pure) were used to correct the heat of solution values of the synthetic products. The enthalpies of formation, at 1063 K, from oxides, were found to be equal to -(25.6 + or - 4.7) kJ/g.f.w. for CaAl4O7 and -(33.0 + or - 9.7) kJ/g.f.w. for CaAl12O19; the respective standard enthalpies of formation from elements, at 298 K, were estimated to be -4007 + or - 5.2 kJ/g.f.w. and -10,722 + or - 12 kJ/g.f.w.

When Isolated at Full Receptivity, in Vitro Fertilized Wheat (Triticum aestivum, L.) Egg Cells Reveal [Ca2+]cyt Oscillation of Intracellular Origin

PubMed Central

Pónya, Zsolt; Corsi, Ilaria; Hoffmann, Richárd; Kovács, Melinda; Dobosy, Anikó; Kovács, Attila Zoltán; Cresti, Mauro; Barnabás, Beáta

2014-01-01

During in vitro fertilization of wheat (Triticum aestivum, L.) in egg cells isolated at various developmental stages, changes in cytosolic free calcium ([Ca2+]cyt) were observed. The dynamics of [Ca2+]cyt elevation varied, reflecting the difference in the developmental stage of the eggs used. [Ca2+]cyt oscillation was exclusively observed in fertile, mature egg cells fused with the sperm cell. To determine how [Ca2+]cyt oscillation in mature egg cells is generated, egg cells were incubated in thapsigargin, which proved to be a specific inhibitor of the endoplasmic reticulum (ER) Ca2+-ATPase in wheat egg cells. In unfertilized egg cells, the addition of thapsigargin caused an abrupt transient increase in [Ca2+]cyt in the absence of extracellular Ca2+, suggesting that an influx pathway for Ca2+ is activated by thapsigargin. The [Ca2+]cyt oscillation seemed to require the filling of an intracellular calcium store for the onset of which, calcium influx through the plasma membrane appeared essential. This was demonstrated by omitting extracellular calcium from (or adding GdCl3 to) the fusion medium, which prevented [Ca2+]cyt oscillation in mature egg cells fused with the sperm. Combined, these data permit the hypothesis that the first sperm-induced transient increase in [Ca2+]cyt depletes an intracellular Ca2+ store, triggering an increase in plasma membrane Ca2+ permeability, and this enhanced Ca2+ influx results in [Ca2+]cyt oscillation. PMID:25535074

The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to l-phenylalanine in acutely isolated intestinal I cells

PubMed Central

Liou, Alice P.; Sei, Yoshitatsu; Zhao, Xilin; Feng, Jianying; Lu, Xinping; Thomas, Craig; Pechhold, Susanne; Raybould, Helen E.

2011-01-01

The extracellular calcium-sensing receptor (CaSR) has recently been recognized as an l-amino acid sensor and has been implicated in mediating cholecystokinin (CCK) secretion in response to aromatic amino acids. We investigated whether direct detection of l-phenylalanine (l-Phe) by CaSR results in CCK secretion in the native I cell. Fluorescence-activated cell sorting of duodenal I cells from CCK-enhanced green fluorescent protein (eGFP) transgenic mice demonstrated CaSR gene expression. Immunostaining of fixed and fresh duodenal tissue sections confirmed CaSR protein expression. Intracellular calcium fluxes were CaSR dependent, stereoselective for l-Phe over d-Phe, and responsive to type II calcimimetic cinacalcet in CCK-eGFP cells. Additionally, CCK secretion by an isolated I cell population was increased by 30 and 62% in response to l-Phe in the presence of physiological (1.26 mM) and superphysiological (2.5 mM) extracellular calcium concentrations, respectively. While the deletion of CaSR from CCK-eGFP cells did not affect basal CCK secretion, the effect of l-Phe or cinacalcet on intracellular calcium flux was lost. In fact, both secretagogues, as well as superphysiological Ca2+, evoked an unexpected 20–30% decrease in CCK secretion compared with basal secretion in CaSR−/− CCK-eGFP cells. CCK secretion in response to KCl or tryptone was unaffected by the absence of CaSR. The present data suggest that CaSR is required for hormone secretion in the specific response to l-Phe by the native I cell, and that a receptor-mediated mechanism may inhibit hormone secretion in the absence of a fully functional CaSR. PMID:21252045

Calcium dependence of rapid auxin action in maize roots

NASA Technical Reports Server (NTRS)

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

1986-01-01

We investigated the interaction of Ca2+ and auxin on root elongation in seedlings of Zea mays L. The seedlings were raised either in the presence of Ca2+ (high calcium; HC = imbibed and raised in 10 millimolar CaCl2), in the absence of additional Ca2+ (intermediate calcium; IC = imbibed and raised in distilled H2O, calcium supply from seed only), or without additional Ca2+ and subsequently depleting them of Ca2+ (low calcium; LC = imbibed and raised in distilled H2O and subsequently treated with 1 millimolar ethyleneglycol-bis-[beta-aminoethylether]-N,N,N',N'-tetraacetic acid [EGTA]). Exposure of roots of either HC or IC seedlings to auxin concentrations from 0.1 to 10 micromolar resulted in strong inhibition of elongation. In roots of LC seedlings, on the other hand, auxin concentrations as high as 10 micromolar caused only slight inhibition of elongation. Adding 0.5 millimolar Ca2+ to LC roots in the presence of IAA allowed normal expression of the inhibitory action of the hormone. Inhibition of elongation in IC roots by indoleacetic acid was reversible upon treatment of the roots with 1 millimolar EGTA. The inhibitory action of auxin could then be re-established by supplying 0.5 millimolar Ca2+. The data indicate that Ca2+ may be necessary to the growth-regulating action of auxin. The significance of this finding is discussed with respect to the potential role of Ca2+ as a second messenger of auxin action and the relevance of this model to recent evidence for gravi-induced redistribution of Ca2+ and its role in establishing gravitropic curvature.

Effect of Noopept on Dynamics of Intracellular Calcium in Neurons of Cultured Rat Hippocampal Slices.

PubMed

Kolbaev, S N; Aleksandrova, O P; Sharonova, I N; Skrebitsky, V G

2018-01-01

A neuroprotective and nootropic drug Noopept increased the frequency of spontaneous calcium transients in neurons of CA1 radial layer in cultured rat hippocampal slices. In contrast, the drug exerted no significant effect on intracellular calcium concentration and its dynamics in neurons of hippocampal CA1 pyramidal layer.

Amyotrophic lateral sclerosis immunoglobulins increase intracellular calcium in a motoneuron cell line.

PubMed

Colom, L V; Alexianu, M E; Mosier, D R; Smith, R G; Appel, S H

1997-08-01

A hybrid motoneuron cell line (VSC4.1) was used as a model system to study the relationship between alterations in intracellular calcium and subsequent cell death induced by immunoglobulin fractions purified from sera of patients with ALS. Using fluo-3 fluorescence imaging, immunoglobulins from 8 of 10 patients with ALS were found to induce transient increases in intracellular calcium ([Ca2+]i) in differentiated VSC4.1 cells. These transient [Ca2+]i increases required extracellular calcium entry through voltage-gated calcium channels sensitive to synthetic FTX and to high concentrations (>1 microM) of omega-agatoxin IVa. The incidence of transient [Ca2+]i increases induced by ALS immunoglobulins correlated with the extent of cytotoxicity induced by the same ALS immunoglobulins in parallel cultures of VSC4.1 cells. Furthermore, manipulations which blocked transient [Ca2+]i increases (addition of synthetic FTX or omega-agatoxin IVa) also inhibited the cytotoxic effects of ALS immunoglobulins. No transient calcium increases were observed in VSC4.1 cells following addition of immunoglobulins from 7 neurologic disease control patients. However, transient [Ca2+]i increases were observed following addition of immunoglobulins from 4 of 5 patients with myasthenia gravis (MG). The [Ca2+]i changes induced by MG immunoglobulins were not blocked by s-FTX, suggesting that they result from a different mechanism than those induced by ALS immunoglobulins. These results suggest that immunoglobulins from patients with ALS can induce transient increases in intracellular calcium in a motoneuron cell line, which may represent early events in the cascade of processes leading to injury and death of susceptible cells.

Hake fish bone as a calcium source for efficient bone mineralization.

PubMed

Flammini, Lisa; Martuzzi, Francesca; Vivo, Valentina; Ghirri, Alessia; Salomi, Enrico; Bignetti, Enrico; Barocelli, Elisabetta

2016-01-01

Calcium is recognized as an essential nutritional factor for bone health. An adequate intake is important to achieve or maintain optimal bone mass in particular during growth and old age. The aim of the present study was to evaluate the efficiency of hake fish bone (HBF) as a calcium source for bone mineralization: in vitro on osteosarcoma SaOS-2 cells, cultured in Ca-free osteogenic medium (OM) and in vivo on young growing rats fed a low-calcium diet. Lithotame (L), a Ca supplement derived from Lithothamnium calcareum, was used as control. In vitro experiments showed that HBF supplementation provided bone mineralization similar to standard OM, whereas L supplementation showed lower activity. In vivo low-Ca HBF-added and L-added diet similarly affected bone deposition. Physico-chemical parameters concerning bone mineralization, such as femur breaking force, tibia density and calcium/phosphorus mineral content, had beneficial effects from both Ca supplementations, in the absence of any evident adverse effect. We conclude HBF derived from by-product from the fish industry is a good calcium supplier with comparable efficacy to L.

Biogas recirculation for simultaneous calcium removal and biogas purification within an expanded granular sludge bed system treating leachate.

PubMed

Luo, Jinghuan; Lu, Xueqin; Liu, Jianyong; Qian, Guangren; Lu, Yongsheng

2014-12-01

Biogas, generated from an expanded granular sludge bed (EGSB) reactor treating municipal solid waste (MSW) leachate, was recirculated for calcium removal from the leachate via a carbonation process with simultaneous biogas purification. Batch trials were performed to optimize the solution pH and imported biogas (CO2) for CaCO3 precipitation. With applicable pH of 10-11 obtained, continuous trials achieved final calcium concentrations of 181-375 mg/L (removal efficiencies≈92.8-96.5%) in the leachate and methane contents of 87.1-91.4% (purification efficiencies≈65.4-82.2%) in the biogas. Calcium-balance study indicates that 23-986 mg Ca/d was released from the bio-system under the carbonized condition where CaCO3 precipitating was moved outside the bioreactor, whereas 7918-9517 mg Ca/d was trapped into the system for the controlled one. These findings demonstrate that carbonation removal of calcium by biogas recirculation could be a promising alternative to pretreat calcium-rich MSW leachate and synergistically to improve methane content. Copyright © 2014 Elsevier Ltd. All rights reserved.

Anthropogenic calcium depletion: a unique threat to forest ecosystem health?

Treesearch

Paul G. Schaberg; Donald H. DeHayes; Gary J. Hawley

2001-01-01

Numerous anthropogenic factors can deplete calcium (Ca) from forest ecosystems. Because an adequate supply of Ca is needed to support fundamental biological functions, including cell membrane stability and stress response, the potential for Ca deficiency following the individual, cumulative, or potentially synergistic, influences of anthropogenic factors raises...

Calcium from salmon and cod bone is well absorbed in young healthy men: a double-blinded randomised crossover design.

PubMed

Malde, Marian K; Bügel, Susanne; Kristensen, Mette; Malde, Ketil; Graff, Ingvild E; Pedersen, Jan I

2010-07-20

Calcium (Ca) - fortified foods are likely to play an important role in helping the consumer achieve an adequate Ca intake, especially for persons with a low intake of dairy products. Fish bones have a high Ca content, and huge quantities of this raw material are available as a by-product from the fish industry. Previously, emphasis has been on producing high quality products from fish by-products by use of bacterial proteases. However, documentation of the nutritional value of the enzymatically rinsed Ca-rich bone fraction remains unexplored. The objective of the present study was to assess the bioavailability of calcium in bones of Atlantic salmon (oily fish) and Atlantic cod (lean fish) in a double-blinded randomised crossover design. Ca absorption was measured in 10 healthy young men using 47Ca whole body counting after ingestion of a test meal extrinsically labelled with the 47Ca isotope. The three test meals contained 800 mg of Ca from three different calcium sources: cod bones, salmon bones and control (CaCO3). Mean Ca absorption (+/- SEE) from the three different Ca sources were 21.9 +/- 1.7%, 22.5 +/- 1.7% and 27.4 +/- 1.8% for cod bones, salmon bones, and control (CaCO3), respectively. We conclude that bones from Atlantic salmon and Atlantic cod are suitable as natural Ca sources in e.g. functional foods or as supplements.

Calcium from salmon and cod bone is well absorbed in young healthy men: a double-blinded randomised crossover design

PubMed Central

2010-01-01

Background Calcium (Ca) - fortified foods are likely to play an important role in helping the consumer achieve an adequate Ca intake, especially for persons with a low intake of dairy products. Fish bones have a high Ca content, and huge quantities of this raw material are available as a by-product from the fish industry. Previously, emphasis has been on producing high quality products from fish by-products by use of bacterial proteases. However, documentation of the nutritional value of the enzymatically rinsed Ca-rich bone fraction remains unexplored. The objective of the present study was to assess the bioavailability of calcium in bones of Atlantic salmon (oily fish) and Atlantic cod (lean fish) in a double-blinded randomised crossover design. Methods Ca absorption was measured in 10 healthy young men using 47Ca whole body counting after ingestion of a test meal extrinsically labelled with the 47Ca isotope. The three test meals contained 800 mg of Ca from three different calcium sources: cod bones, salmon bones and control (CaCO3). Results Mean Ca absorption (± SEE) from the three different Ca sources were 21.9 ± 1.7%, 22.5 ± 1.7% and 27.4 ± 1.8% for cod bones, salmon bones, and control (CaCO3), respectively. Conclusion We conclude that bones from Atlantic salmon and Atlantic cod are suitable as natural Ca sources in e.g. functional foods or as supplements. PMID:20646299

Printability of calcium phosphate: calcium sulfate powders for the application of tissue engineered bone scaffolds using the 3D printing technique.

PubMed

Zhou, Zuoxin; Buchanan, Fraser; Mitchell, Christina; Dunne, Nicholas

2014-05-01

In this study, calcium phosphate (CaP) powders were blended with a three-dimensional printing (3DP) calcium sulfate (CaSO4)-based powder and the resulting composite powders were printed with a water-based binder using the 3DP technology. Application of a water-based binder ensured the manufacture of CaP:CaSO4 constructs on a reliable and repeatable basis, without long term damage of the printhead. Printability of CaP:CaSO4 powders was quantitatively assessed by investigating the key 3DP process parameters, i.e. in-process powder bed packing, drop penetration behavior and the quality of printed solid constructs. Effects of particle size, CaP:CaSO4 ratio and CaP powder type on the 3DP process were considered. The drop penetration technique was used to reliably identify powder formulations that could be potentially used for the application of tissue engineered bone scaffolds using the 3DP technique. Significant improvements (p<0.05) in the 3DP process parameters were found for CaP (30-110 μm):CaSO4 powders compared to CaP (<20 μm):CaSO4 powders. Higher compressive strength was obtained for the powders with the higher CaP:CaSO4 ratio. Hydroxyapatite (HA):CaSO4 powders showed better results than beta-tricalcium phosphate (β-TCP):CaSO4 powders. Solid and porous constructs were manufactured using the 3DP technique from the optimized CaP:CaSO4 powder formulations. High-quality printed constructs were manufactured, which exhibited appropriate green compressive strength and a high level of printing accuracy. Copyright © 2014 Elsevier B.V. All rights reserved.

Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel

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

Gaudioso, Christelle; Carlier, Edmond; Youssouf, Fahamoe

2011-07-29

Highlights: {yields} Both Ca{sup ++}-Calmodulin (CaM) and Ca{sup ++}-free CaM bind to the C-terminal region of Nav1.1. {yields} Ca{sup ++} and CaM have both opposite and convergent effects on I{sub Nav1.1}. {yields} Ca{sup ++}-CaM modulates I{sub Nav1.1} amplitude. {yields} CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. {yields} Ca{sup ++} alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channelmore » expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca{sup ++} depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca{sup ++} could bind the Nav1.1 C-terminal region with micromolar affinity.« less

Osteoclast cytosolic calcium, regulated by voltage-gated calcium channels and extracellular calcium, controls podosome assembly and bone resorption

NASA Technical Reports Server (NTRS)

Miyauchi, A.; Hruska, K. A.; Greenfield, E. M.; Duncan, R.; Alvarez, J.; Barattolo, R.; Colucci, S.; Zambonin-Zallone, A.; Teitelbaum, S. L.; Teti, A.

1990-01-01

The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5 X 10(-6) M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+ ([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10(-5) M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggests the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e) reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.

Subthreshold membrane potential oscillations in inferior olive neurons are dynamically regulated by P/Q- and T-type calcium channels: a study in mutant mice

PubMed Central

Choi, Soonwook; Yu, Eunah; Kim, Daesoo; Urbano, Francisco J; Makarenko, Vladimir; Shin, Hee-Sup; Llinás, Rodolfo R

2010-01-01

The role of P/Q- and T-type calcium channels in the rhythmic oscillatory behaviour of inferior olive (IO) neurons was investigated in mutant mice. Mice lacking either the CaV2.1 gene of the pore-forming α1A subunit for P/Q-type calcium channel, or the CaV3.1 gene of the pore-forming α1G subunit for T-type calcium channel were used. In vitro intracellular recording from IO neurons reveals that the amplitude and frequency of sinusoidal subthreshold oscillations (SSTOs) were reduced in the CaV2.1−/− mice. In the CaV3.1−/− mice, IO neurons also showed altered patterns of SSTOs and the probability of SSTO generation was significantly lower (15%, 5 of 34 neurons) than that of wild-type (78%, 31 of 40 neurons) or CaV2.1−/− mice (73%, 22 of 30 neurons). In addition, the low-threshold calcium spike and the sustained endogenous oscillation following rebound potentials were absent in IO neurons from CaV3.1−/− mice. Moreover, the phase-reset dynamics of oscillatory properties of single neurons and neuronal clusters in IO were remarkably altered in both CaV2.1−/− and CaV3.1−/− mice. These results suggest that both α1A P/Q- and α1G T-type calcium channels are required for the dynamic control of neuronal oscillations in the IO. These findings were supported by results from a mathematical IO neuronal model that incorporated T and P/Q channel kinetics. PMID:20547676

Influence of calcium ions on the crystallization of sodium bicarbonate

NASA Astrophysics Data System (ADS)

Zhu, Yi; Demilie, Paul; Davoine, Perrine; Cartage, Thierry; Delplancke-Ogletree, Marie-Paule

2005-02-01

In industrial crystallization of sodium bicarbonate (sodium hydrogenocarbonate), the presence of calcium ions in solutions is unavoidable due to the production process. The understanding of the Ca 2+ role in NaHCO 3 crystallization would be helpful for improving the quality of the final products. The influence of calcium ions on NaHCO 3 crystallization was investigated in a 5-l mixed suspension mixed product removal crystallizer under controlled conditions. A density meter was used for continuous supersaturation monitoring. After a steady state had been reached, different CaCl 2 amounts were added at a constant flow rate. It was found that limited calcium ion levels in the system reduce drastically the nucleation frequency of NaHCO 3 and has a limited influence on crystal growth rate. The supersaturation measurements and other methods confirmed this phenomenon. The relationship between the Ca 2+ influence on NaHCO 3 crystallization, the calcium carbonate solubility and its metastable zone in concentrated NaHCO 3 solution was established. In fact, Ca 2+ has a maximum effect on NaHCO 3 crystallization kinetics when the saturation of calcium carbonate in NaHCO 3 solution has been reached, and the effect is constant in the metastable zone. The excess of Ca 2+ precipitates in NaHCO 3 solution as CaCO 3, as observed by energy dispersive X-ray and X-ray diffraction. This explained why an increasing Ca 2+ concentration in the solution has a limited influence on NaHCO 3 crystal size distribution and habit, but decreases the crystal purity. It is also confirmed that an impurity as Ca 2+ has no influence on the equilibrium NaHCO 3-Na 2CO 3.

Divergent calcium signaling in RBCs from Tropidurus torquatus (Squamata – Tropiduridae) strengthen classification in lizard evolution

PubMed Central

Beraldo, Flávio H; Garcia, Célia RS

2007-01-01

Background We have previously reported that a Teiid lizard red blood cells (RBCs) such as Ameiva ameiva and Tupinambis merianae controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na+/H+ ionophore monensin, K+/H+ ionophore nigericin and the H+ pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca2+ from intracellular stores upon ATP addition. Results Here we report, that RBCs from the tropidurid lizard Tropidurus torquatus store Ca2+ in endoplasmic reticulum (ER) pool but unlike in the referred Teiidae, these cells do not store calcium in monensin-nigericin sensitive pools. Moreover, mitochondria from T. torquatus RBCs accumulate Ca2+. Addition of ATP to a calcium-free medium does not increase the [Ca2+]c levels, however in a calcium medium we observe an increase in cytosolic calcium. This is an indication that purinergic receptors in these cells are P2X-like. Conclusion T. torquatus RBCs present different mechanisms from Teiid lizard red blood cells (RBCs), for controlling its intracellular calcium levels. At T. torquatus the ion is only stored at endoplasmic reticulum and mitochondria. Moreover activation of purinergic receptor, P2X type, was able to induce an influx of calcium from extracelullar medium. These studies contribute to the understanding of the evolution of calcium homeostasis and signaling in nucleated RBCs. PMID:17716375

Divergent calcium signaling in RBCs from Tropidurus torquatus (Squamata--Tropiduridae) strengthen classification in lizard evolution.

PubMed

Beraldo, Flávio H; Garcia, Célia R S

2007-08-23

We have previously reported that a Teiid lizard red blood cells (RBCs) such as Ameiva ameiva and Tupinambis merianae controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na+/H+ ionophore monensin, K+/H+ ionophore nigericin and the H+ pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca2+ from intracellular stores upon ATP addition. Here we report, that RBCs from the tropidurid lizard Tropidurus torquatus store Ca2+ in endoplasmic reticulum (ER) pool but unlike in the referred Teiidae, these cells do not store calcium in monensin-nigericin sensitive pools. Moreover, mitochondria from T. torquatus RBCs accumulate Ca2+. Addition of ATP to a calcium-free medium does not increase the [Ca2+]c levels, however in a calcium medium we observe an increase in cytosolic calcium. This is an indication that purinergic receptors in these cells are P2X-like. T. torquatus RBCs present different mechanisms from Teiid lizard red blood cells (RBCs), for controlling its intracellular calcium levels. At T. torquatus the ion is only stored at endoplasmic reticulum and mitochondria. Moreover activation of purinergic receptor, P2X type, was able to induce an influx of calcium from extracellular medium. These studies contribute to the understanding of the evolution of calcium homeostasis and signaling in nucleated RBCs.

Nuclear Calcium Buffering Capacity Shapes Neuronal Architecture*

PubMed Central

Mauceri, Daniela; Hagenston, Anna M.; Schramm, Kathrin; Weiss, Ursula; Bading, Hilmar

2015-01-01

Calcium-binding proteins (CaBPs) such as parvalbumin are part of the cellular calcium buffering system that determines intracellular calcium diffusion and influences the spatiotemporal dynamics of calcium signals. In neurons, CaBPs are primarily localized to the cytosol and function, for example, in nerve terminals in short-term synaptic plasticity. However, CaBPs are also expressed in the cell nucleus, suggesting that they modulate nuclear calcium signals, which are key regulators of neuronal gene expression. Here we show that the calcium buffering capacity of the cell nucleus in mouse hippocampal neurons regulates neuronal architecture by modulating the expression levels of VEGFD and the complement factor C1q-c, two nuclear calcium-regulated genes that control dendrite geometry and spine density, respectively. Increasing the levels of nuclear calcium buffers by means of expression of a nuclearly targeted form of parvalbumin fused to mCherry (PV.NLS-mC) led to a reduction in VEGFD expression and, as a result, to a decrease in total dendritic length and complexity. In contrast, mRNA levels of the synapse pruning factor C1q-c were increased in neurons expressing PV.NLS-mC, causing a reduction in the density and size of dendritic spines. Our results establish a close link between nuclear calcium buffering capacity and the transcription of genes that determine neuronal structure. They suggest that the development of cognitive deficits observed in neurological conditions associated with CaBP deregulation may reflect the loss of necessary structural features of dendrites and spines. PMID:26231212