High-pressure transitions of diopside and wollastonite: phase equilibria and thermochemistry of CaMgSi 2O 6, CaSiO 3 and CaSi 2O 5-CaTiSiO 5 system

NASA Astrophysics Data System (ADS)

Akaogi, M.; Yano, M.; Tejima, Y.; Iijima, M.; Kojitani, H.

2004-06-01

Phase transitions of CaMgSi 2O 6 diopside and CaSiO 3 wollastonite were examined at pressures to 23 GPa and temperatures to 2000 °C, using a Kawai-type multiavil apparatus. Enthalpies of high-pressure phases in CaSiO 3 and in the CaSi 2O 5-CaTiSiO 5 system were also measured by high-temperature calorimetry. At 17-18 GPa, diopside dissociates to CaSiO 3-rich perovskite + Mg-rich (Mg,Ca)SiO 3 tetragonal garnet (Gt) above about 1400 °C. The solubilities of CaSiO 3 in garnet and MgSiO 3 in perovskite increase with temperature. At 17-18 GPa below about 1400 °C, diopside dissociates to Ca-perovskite + β-Mg 2SiO 4 + stishovite. The Mg, Si-phases coexisting with Ca-perovskite change to γ-Mg 2SiO 4 + stishovite, to ilmenite, and finally to Mg-perovskite with increasing pressure. CaSiO 3 wollastonite transforms to the walstromite structure, and further dissociates to Ca 2SiO 4 larnite + CaSi 2O 5 titanite. The latter transition occurs at 9-11 GPa with a positive Clapeyron slope. At 1600 °C, larnite + titanite transform to CaSiO 3 perovskite at 14.6±0.6 GPa, calibrated against the α-β transition pressure of Mg 2SiO 4. The enthalpies of formation of CaSiO 3 walstromite and CaSi 2O 5 titanite from the mixture of CaO and SiO 2 quartz at 298 K have been determined as -76.1±2.8, and -27.8±2.1 kJ/mol, respectively. The latter was estimated from enthalpy measurements of titanite solid solutions in the system CaSi 2O 5-CaTiSiO 5, because CaSi 2O 5 titanite transforms to a triclinic phase upon decompression. The enthalpy difference between titanite and the triclinic phase is only 1.5±4.8 kJ/mol. Using these enthalpies of formation and those of larnite and CaSiO 3 perovskite, the transition boundaries in CaSiO 3 have been calculated. The calculated boundaries for the wollastonite-walstromite-larnite + titanite transitions are consistent with the experimental determinations within the errors. The calculated boundary between larnite + titanite and Ca-perovskite has a slope of 1.3-1.8(±0.4) MPa/K, and is located at a pressure about 2 GPa higher than that determined by [Am. Mineral. 79 (1994) 1219].

Ventral tegmental area disruption selectively affects CA1/CA2 but not CA3 place fields during a differential reward working memory task

PubMed Central

Martig, Adria K; Mizumori, Sheri JY

2010-01-01

Hippocampus (HPC) receives dopaminergic (DA) projections from the ventral tegmental area (VTA) and substantia nigra. These inputs appear to provide a modulatory signal that influences HPC dependent behaviors and place fields. We examined how efferent projections from VTA to HPC influence spatial working memory and place fields when the reward context changes. CA1 and CA3 process environmental context changes differently and VTA preferentially innervates CA1. Given these anatomical data and electrophysiological evidence that implicates DA in reward processing, we predicted that CA1 place fields would respond more strongly to both VTA disruption and changes in the reward context than CA3 place fields. Rats (N=9) were implanted with infusion cannula targeting VTA and recording tetrodes aimed at HPC. Then they were tested on a differential reward, win-shift working memory task. One recording session consisted of 5 baseline and 5 manipulation trials during which place cells in CA1/CA2 (N=167) and CA3 (N=94) were recorded. Prior to manipulation trials rats were infused with either baclofen or saline and then subjected to control or reward conditions during which the learned locations of large and small reward quantities were reversed. VTA disruption resulted in an increase in errors, and in CA1/CA2 place field reorganization. There were no changes in any measures of CA3 place field stability during VTA disruption. Reward manipulations did not affect performance or place field stability in CA1/CA2 or CA3; however, changes in the reward locations “rescued” performance and place field stability in CA1/CA2 when VTA activity was compromised, perhaps by trigging compensatory mechanisms. These data support the hypothesis that VTA contributes to spatial working memory performance perhaps specifically by maintaining place field stability selectively in CA1/CA2. PMID:20082295

Galectin-3 expression in hippocampal CA2 following transient forebrain ischemia and its inhibition by hypothermia or antiapoptotic agents

PubMed Central

Hisamatsu, Kenji; Kobayashi, Kazuhiro; Miyazaki, Tatsuhiko; Hirata, Akihiro; Hatano, Yuichiro; Tomita, Hiroyuki; Hara, Akira

2016-01-01

Recent evidence has suggested that the hippocampal CA2 region plays an important role in the recognition process. We have reported that ischemic damage in the hippocampal CA2 region following transient ischemia is caused by apoptosis, but the underlying mechanisms are still not clear. Galectin-3 is a β-galactosidase-binding lectin that is important in cell proliferation and apoptotic regulation. We have also reported that galectin-3 was expressed in activated microglia in the CA1 region 96 h after transient ischemia. The aim of this study is to determine the localization and time course of galectin-3 expression in the CA2 region following transient forebrain ischemia. Galectin-3 immunostaining was observed in both interior side of CA1 region and CA2 region in hippocampus 60 h after ischemic insult. At 66 h, galectin-3 was observed in the whole CA1 region adjacent to the CA2 region in the hippocampus. Both galectin-3 expression and neuronal cell death in the CA2 region were significantly inhibited by hypothermia and by apoptosis-inhibiting reagents. These results suggest that galectin-3 in the CA2 region is expressed independent of that in the CA1 region. Protection of the expression of galectin-3 in the CA2 region might contribute toward the survival of CA2 pyramidal neurons. PMID:26848998

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

PubMed

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

2017-08-25

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

Orai3 channel is the 2-APB-induced endoplasmic reticulum calcium leak.

PubMed

Leon-Aparicio, Daniel; Pacheco, Jonathan; Chavez-Reyes, Jesus; Galindo, Jose M; Valdes, Jesus; Vaca, Luis; Guerrero-Hernandez, Agustin

2017-07-01

We have studied in HeLa cells the molecular nature of the 2-APB induced ER Ca 2+ leak using synthetic Ca 2+ indicators that report changes in both the cytoplasmic ([Ca 2+ ] i ) and the luminal ER ([Ca 2+ ] ER ) Ca 2+ concentrations. We have tested the hypothesis that Orai channels participate in the 2-APB-induced ER Ca 2+ leak that was characterized in the companion paper. The expression of the dominant negative Orai1 E106A mutant, which has been reported to block the activity of all three types of Orai channels, inhibited the effect of 2-APB on the [Ca 2+ ] ER but did not decrease the ER Ca 2+ leak after thapsigargin (TG). Orai3 channel, but neither Orai1 nor Orai2, colocalizes with expressed IP 3 R and only Orai3 channel supported the 2-APB-induced ER Ca 2+ leak, while Orai1 and Orai2 inhibited this type of ER Ca 2+ leak. Decreasing the expression of Orai3 inhibited the 2-APB-induced ER Ca 2+ leak but did not modify the ER Ca 2+ leak revealed by inhibition of SERCA pumps with TG. However, reducing the expression of Orai3 channel resulted in larger [Ca 2+ ] i response after TG but only when the ER store had been overloaded with Ca 2+ by eliminating the acidic internal Ca 2+ store with bafilomycin. These data suggest that Orai3 channel does not participate in the TG-revealed ER Ca 2+ leak but forms an ER Ca 2+ leak channel that is limiting the overloading with Ca 2+ of the ER store. Copyright © 2017 Elsevier Ltd. All rights reserved.

K(Ca)3.1 channel downregulation and impaired endothelium-derived hyperpolarization-type relaxation in pulmonary arteries from chronically hypoxic rats.

PubMed

Kroigaard, Christel; Kudryavtseva, Olga; Dalsgaard, Thomas; Wandall-Frostholm, Christine; Olesen, Søren-Peter; Simonsen, Ulf

2013-04-01

Calcium-activated potassium channels of small (K(Ca)2, SK) and intermediate (K(Ca)3.1, IK) conductance are involved in endothelium-dependent relaxation of pulmonary arteries. We hypothesized that the function and expression of K(Ca)2 and K(Ca)3.1 increase as a compensatory mechanism to counteract hypoxia-induced pulmonary hypertension in rats. For functional studies, pulmonary arteries were mounted in microvascular myographs for isometric tension recordings. The K(Ca) channel expression was evaluated by immunoblotting and quantitative PCR. Although ACh induced similar relaxations, the ACh-induced relaxations were abolished by the combined inhibition of nitric oxide synthase (by L-nitro-arginine, L-NOARG), cyclo-oxygenase (by indomethacin) and soluble guanylate cyclase (by ODQ) in pulmonary arteries from hypoxic rats, whereas 20 ± 6% (n = 8) maximal relaxation in response to ACh persisted in arteries from normoxic rats. Inhibiting Na(+),K(+)-ATPase with ouabain or blocking K(Ca)2 and K(Ca)3.1 channels reduced the persisting ACh-induced relaxation. In the presence of L-NOARG and indomethacin, a novel K(Ca)2 and K(Ca)3.1 channel activator, NS4591, induced concentration- and endothelium-dependent relaxations, which were markedly reduced in arteries from chronically hypoxic rats compared with arteries from normoxic rats. The mRNA levels of K(Ca)2.3 and K(Ca)3.1 were unaltered, whereas K(Ca)2.3 protein expression was upregulated and K(Ca)3.1 protein expression downregulated in pulmonary arteries from rats exposed to hypoxia. In conclusion, endothelium-dependent relaxation was conserved in pulmonary arteries from chronically hypoxic rats, while endothelium-derived hyperpolarization (EDH)-type relaxation was impaired in chronically hypoxic pulmonary small arteries despite upregulation of K(Ca)2.3 channels. Since impaired EDH-type relaxation was accompanied by K(Ca)3.1 channel protein downregulation, these findings suggest that K(Ca)3.1 channels are important for the maintenance of EDH-type relaxation.

Modulation of voltage- and Ca2+-dependent gating of CaV1.3 L-type calcium channels by alternative splicing of a C-terminal regulatory domain.

PubMed

Singh, Anamika; Gebhart, Mathias; Fritsch, Reinhard; Sinnegger-Brauns, Martina J; Poggiani, Chiara; Hoda, Jean-Charles; Engel, Jutta; Romanin, Christoph; Striessnig, Jörg; Koschak, Alexandra

2008-07-25

Low voltage activation of Ca(V)1.3 L-type Ca(2+) channels controls excitability in sensory cells and central neurons as well as sinoatrial node pacemaking. Ca(V)1.3-mediated pacemaking determines neuronal vulnerability of dopaminergic striatal neurons affected in Parkinson disease. We have previously found that in Ca(V)1.4 L-type Ca(2+) channels, activation, voltage, and calcium-dependent inactivation are controlled by an intrinsic distal C-terminal modulator. Because alternative splicing in the Ca(V)1.3 alpha1 subunit C terminus gives rise to a long (Ca(V)1.3(42)) and a short form (Ca(V)1.3(42A)), we investigated if a C-terminal modulatory mechanism also controls Ca(V)1.3 gating. The biophysical properties of both splice variants were compared after heterologous expression together with beta3 and alpha2delta1 subunits in HEK-293 cells. Activation of calcium current through Ca(V)1.3(42A) channels was more pronounced at negative voltages, and inactivation was faster because of enhanced calcium-dependent inactivation. By investigating several Ca(V)1.3 channel truncations, we restricted the modulator activity to the last 116 amino acids of the C terminus. The resulting Ca(V)1.3(DeltaC116) channels showed gating properties similar to Ca(V)1.3(42A) that were reverted by co-expression of the corresponding C-terminal peptide C(116). Fluorescence resonance energy transfer experiments confirmed an intramolecular protein interaction in the C terminus of Ca(V)1.3 channels that also modulates calmodulin binding. These experiments revealed a novel mechanism of channel modulation enabling cells to tightly control Ca(V)1.3 channel activity by alternative splicing. The absence of the C-terminal modulator in short splice forms facilitates Ca(V)1.3 channel activation at lower voltages expected to favor Ca(V)1.3 activity at threshold voltages as required for modulation of neuronal firing behavior and sinoatrial node pacemaking.

Modulation of Ca(v)3.1 T-type Ca2+ channels by the ran binding protein RanBPM.

PubMed

Kim, Taehyun; Kim, Sunoh; Yun, Hyung-Mun; Chung, Kwang Chul; Han, Ye Sun; Shin, Hee-Sup; Rhim, Hyewhon

2009-01-02

In order to study the currently unknown cellular signaling pathways of Ca(v)3.1 T-type Ca(2+) channels (Ca(v)3.1 channels), we performed a yeast two-hybrid screening using intracellular domains of Ca(v)3.1 alpha1 subunit as bait. After screening the human brain cDNA library, several proteins, including RanBPM, were identified as interacting with Ca(v)3.1 channels. RanBPM was found to bind to the cytoplasmic intracellular loop between transmembrane domains I and II of Ca(v)3.1 channels. Using whole-cell patch-clamp techniques, we found that Ca(v)3.1 currents were increased by the expression of RanBPM in HEK293/Ca(v)3.1 cells. We next examined whether RanBPM affected the biophysical properties and plasma membrane expression of Ca(v)3.1 channels. Furthermore, we showed that the PKC activator inhibited Ca(v)3.1 currents, an effect that was abolished by the expression of RanBPM. These results suggest that RanBPM could be a key regulator of Ca(v)3.1 channel-mediated signaling pathways.

Effects of addition of Bi2Ca2Co2O y on the thermoelectric properties of Ca3Co4O9 polycrystalline ceramics

NASA Astrophysics Data System (ADS)

Feng, Ningbo; Liao, Y. W.; Lu, Y.; He, Y.; Jin, Y. R.; Liu, X. R.

2018-06-01

Thermoelectric properties of Ca3Co4O9 polycrystalline ceramics with sheet grains were optimized by adding Bi2Ca2Co2O y phase. Therefore, the (1 - x) Ca3Co4O9/ x Bi2Ca2Co2O y (0 ≤ x ≤ 1) composites were prepared. The phase constitution and micro-structure of the samples were analyzed by XRD and SEM, respectively. With the addition of Bi2Ca2Co2O y , the apparent density D a and the relative density D r of the samples continuously increases. When x ≤ 0.4, the electrical resistivity of the samples declines, however, when x ≥ 0.4, the electrical resistivity of the samples increases. The Seebeck coefficient of the samples grows with the increase of the x monotonously. The power factor of the 0.6 Ca3Co4O9/0.4 Bi2Ca2Co2O y samples reaches 0.24 mW m-1K-2 at 973 K. Thermal conductivity κ of the 0.6 Ca3Co4O9/0.4 Bi2Ca2Co2O y monotonously decreases with the temperature rising, achieving the minimum about 1.34 W m-1K-1 at 973 K. The ZT of 0.6 Ca3Co4O9/0.4 Bi2Ca2Co2O y composites gets to 0.18, which is comparable to that of most doped Ca3Co4O9 polycrystalline ceramics, implying higher ZT can be realized by combining the strategy of doping and introducing the Bi2Ca2Co2O y .

Calcium homeostasis in identified rat gonadotrophs.

PubMed Central

Tse, A; Tse, F W; Hille, B

1994-01-01

1. Whole-cell voltage clamp was used in conjunction with the fluorescent Ca2+ indicator indo-1 to measure extracellular Ca2+ entry and intracellular Ca2+ concentrations ([Ca2+]i) in rat gonadotrophs identified with the reverse haemolytic plaque assay. 2. Depolarizations to potentials more positive than -40 mV elicited inward Ca2+ current (ICa) and transient elevations of [Ca2+]i. 3. The relationship between [Ca2+]i elevations and Ca2+ entry with different Ca2+ buffer concentrations in the pipette showed that endogenous Ca2+ buffers normally bind approximately 99% of the Ca2+ entering the cell. 4. With [Ca2+]i elevations less than 500 nM, decay of [Ca2+]i could be approximated by an exponential whose time constant increased with the concentration of exogenous Ca2+ buffers. 5. Inhibitors of intracellular Ca(2+)-ATPases, thapsigargin, cyclopiazonic acid (CPA) and 2,5-di-(tert-butyl)-1,4-benzohydroquinone (BHQ), caused [Ca2+]i to rise. Application of BHQ during [Ca2+]i oscillations induced by gonadotrophin-releasing hormone (GnRH) terminated the oscillation in a slowly decaying elevation. BHQ slowed the decay of depolarization-induced [Ca2+]i elevations about 3-fold. 6. Taking into account the Ca2+ buffering properties of the cytoplasm permitted estimation of the fluxes and rate constants for Ca2+ movements in gonadotrophs. The intracellular store is a major determinant of Ca2+ homeostasis in gonadotrophs. PMID:7932239

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

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.

The series Bi2Sr2Ca(n-1) Cu(n)O(2n+4) (1 less than or equal to n less than or equal to 5): Phase stability and superconducting properties

NASA Technical Reports Server (NTRS)

Deguire, Mark R.; Bansal, Narottam P.; Farrell, David E.; Finan, Valerie; Kim, Cheol J.; Hills, Bethanie J.; Allen, Christopher J.

1989-01-01

Phase relations at 850 and 870 C, melting transitions in air, oxygen, and helium were studied for Bi(2.1)Sr(1.9) CuO6 and for the Bi2Sr2Ca(n-1) Cu(n)O(2n+4) for n = 1, 2, 3, 4, 5, and infinity (CaCuO2). Up to 870 C, the n = 2 composition resides in the compatibility tetrahedron bounded by Bi(2+x)(Sr,Ca)(3-y) Cu2O8, (Sr,Ca)14 Cu24O41, Ca2CuO3, and a Bi-Sr-Ca-O phase. The n is greater than or equal to 3 compositions reside in the compatibility tetrahedron Bi(2+x)(Sr,Ca)(3-y) Cu2O8 - (Sr,Ca)14 Cu24O41 - Ca2CuO3 - CuO up to 850 C. However, Bi(2+x)Sr(4-y) Cu3O10 forms for n is greater than or equal to 3 after extended heating at 870 C. Bi(2+x)Sr(2-y) CuO6 and Bi(2+x)(Sr,Ca)(3-y) Cu2O8 melt in air at 914 C and 895 C respectively. During melting, all of the compositions studied lose 1 to 2 percent by weight of oxygen from the reduction of copper. Bi(2+x)Sr(2-y) CuO6, Bi(2+n)(Sr,Ca)(3-y) Cu2O8, and Bi(2+x)(Sr,Ca)(4-y) Cu3O10 exhibit crystallographic alignment in a magnetic field, with the c-axes orienting parallel to the field.

New anticancer drug candidates sulfonamides as selective hCA IX or hCA XII inhibitors.

PubMed

Gul, Halise Inci; Yamali, Cem; Sakagami, Hiroshi; Angeli, Andrea; Leitans, Janis; Kazaks, Andris; Tars, Kaspars; Ozgun, Dilan Ozmen; Supuran, Claudiu T

2018-04-01

In this study, new 4-[3-(aryl)-5-substitutedphenyl-4,5-dihydro-1H-pyrazole-1-yl]benzensulfonamides (19-36) were synthesized and evaluated their cytotoxic/anticancer and CA inhibitory effects. According to results obtained, the compounds 34 (4-[5-(2,3,4-trimethoxyphenyl)-3-(thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1-yl] benzensulfonamide, Potency-Selectivity Expression (PSE) = 141) and 36 (4-[5-(3,4,5-trimethoxyphenyl)-3-(thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1-yl]benzensulfonamide, PSE = 54.5) were found the leader anticancer compounds with the highest PSE values. In CA inhibitory studies, the compounds 36 and 24 (4-[5-(3,4,5-trimethoxyphenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazole-1-yl]benzensulfonamide) were found the leader CA inhibitors depending on selectivity ratios. The compound 36 was a selective inhibitor of hCA XII isoenzyme (hCA I/hCA XII = 1250 and hCA II/hCA XII = 224) while the compound 24 was a selective inhibitor of hCA IX isoenzyme (hCA I/hCA IX = 161 and hCA II/hCA IX = 177). The compounds 24, 34, and 36 can be considered to develop new anticancer drug candidates. Copyright © 2018 Elsevier Inc. All rights reserved.

Role of L-type Ca2+ channel isoforms in the extinction of conditioned fear.

PubMed

Busquet, Perrine; Hetzenauer, Alfred; Sinnegger-Brauns, Martina J; Striessnig, Jörg; Singewald, Nicolas

2008-05-01

Dihydropyridine (DHP) L-type Ca(2+) channel (LTCC) antagonists, such as nifedipine, have been reported to impair the extinction of conditioned fear without interfering with its acquisition. Identification of the LTCC isoforms mediating this DHP effect is an essential basis to reveal their role as potential drug targets for the treatment of specific anxiety disorders. Ca(V)1.2 and Ca(V)1.3 are the predominant LTCCs in the mammalian brain. However, since no isoform-selective DHP blockers are available, their individual contribution to fear memory extinction is unknown. We used a novel mouse model expressing DHP-insensitive Ca(V)1.2 LTCCs (Ca(V)1.2DHP(-/-) mice) to address this question. In line with previous studies, wild-type (WT) mice treated with systemic nifedipine displayed markedly impaired fear extinction. This DHP effect was completely abolished in Ca(V)1.2DHP(-/-) mice, indicating that it is mediated by Ca(V)1.2, but not by Ca(V)1.3 LTCCs. Supporting this conclusion, Ca(V)1.3-deficient mice (Ca(V)1.3(-/-)) showed extinction identical to the respective WT mice. The inhibition of fear extinction was not observed after intracerebroventricular (i.c.v.) application of different doses of nifedipine, suggesting that this effect is secondary to inhibition of peripheral Ca(V)1.2 channels. The LTCC activator BayK, which lacks neurotoxic effects in Ca(V)1.2DHP(-/-) mice, did not influence the extinction time course. In summary, we demonstrate that LTCC signaling through the Ca(V)1.2 isoform of LTCCs interferes with fear memory extinction, presumably via a peripherally mediated mechanism. Activation of other LTCC isoforms (predominantly Ca(V)1.3) is not sufficient to accelerate extinction of conditioned fear in mice.

Role of L-type Ca2+ channel isoforms in the extinction of conditioned fear

PubMed Central

Busquet, Perrine; Hetzenauer, Alfred; Sinnegger-Brauns, Martina J.; Striessnig, Jörg; Singewald, Nicolas

2008-01-01

Dihydropyridine (DHP) L-type Ca2+ channel (LTCC) antagonists, such as nifedipine, have been reported to impair the extinction of conditioned fear without interfering with its acquisition. Identification of the LTCC isoforms mediating this DHP effect is an essential basis to reveal their role as potential drug targets for the treatment of specific anxiety disorders. CaV1.2 and CaV1.3 are the predominant LTCCs in the mammalian brain. However, since no isoform-selective DHP blockers are available, their individual contribution to fear memory extinction is unknown. We used a novel mouse model expressing DHP-insensitive CaV1.2 LTCCs (CaV1.2DHP−/− mice) to address this question. In line with previous studies, wild-type (WT) mice treated with systemic nifedipine displayed markedly impaired fear extinction. This DHP effect was completely abolished in CaV1.2DHP−/− mice, indicating that it is mediated by CaV1.2, but not by CaV1.3 LTCCs. Supporting this conclusion, CaV1.3-deficient mice (CaV1.3−/−) showed extinction identical to the respective WT mice. The inhibition of fear extinction was not observed after intracerebroventricular (i.c.v.) application of different doses of nifedipine, suggesting that this effect is secondary to inhibition of peripheral CaV1.2 channels. The LTCC activator BayK, which lacks neurotoxic effects in CaV1.2DHP−/− mice, did not influence the extinction time course. In summary, we demonstrate that LTCC signaling through the CaV1.2 isoform of LTCCs interferes with fear memory extinction, presumably via a peripherally mediated mechanism. Activation of other LTCC isoforms (predominantly CaV1.3) is not sufficient to accelerate extinction of conditioned fear in mice. PMID:18441296

Clomiphene, an ovulation-inducing agent, causes [Ca2+]i increases in human osteoblast-like cells.

PubMed

Chen, Y C; Wang, J L; Liu, C P; Cheng, J S; Chang, H T; Yuk-Keung, L; Su, W; Law, Y P; Chen, W C; Jan, C R

2001-06-30

The effect of clomiphene, an ovulation-inducing agent, on cytosolic free Ca2+ levels ([Ca2+]i) in MG63 human osteosarcoma cells was explored by using fura-2 as a Ca2+ indicator. Clomiphene at concentrations between 5-75 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 of 50 microM. The [Ca2+]i signal consisted of an initial rise and a sustained phase. Ca2+ removal reduced the Ca2+ signal by 40+/-10%. The [Ca2+]i increase induced by 50 microM clomiphene was inhibited by 80+/-5% by 10 microM nifedipine, but was insensitive to 50 microM La3+ or 10 microM verapamil. In Ca2+-free medium, pretreatment with 50 microM brefeldin A (to disrupt the Golgi complex Ca2+ store), 1 microM thapsigargin (to inhibit the endoplasmic reticulum Ca2+ pump), and carbonylcyanide m-chlorophenylhydrazone (CCCP; to uncouple mitochondria) inhibited 51+/-3% of 50 microM clomiphene-induced Ca2+ release; conversely, pretreatment with 50 microM clomiphene abolished the [Ca2+]i increase induced by thapsigargin, CCCP, and brefeldin A. The Ca2+ release-induced by 50 pM clomiphene was unchanged by inhibition of phospholipase C with 2 microM 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). Collectively, the results suggest that clomiphene increased [Ca2+]i, in osteoblast-like cells, by releasing intracellular Ca2+ in a phospholipase C-independent manner and by causing nifedipine-sensitive Ca2+ influx.

Loss of the Chloroplast Transit Peptide from an Ancestral C3 Carbonic Anhydrase Is Associated with C4 Evolution in the Grass Genus Neurachne1[OPEN

PubMed Central

Clayton, Harmony; Saladié, Montserrat; Sharwood, Robert; Macfarlane, Terry

2017-01-01

Neurachne is the only known grass lineage containing closely related C3, C3-C4 intermediate, and C4 species, making it an ideal taxon with which to study the evolution of C4 photosynthesis in the grasses. To begin dissecting the molecular changes that led to the evolution of C4 photosynthesis in this group, the complementary DNAs encoding four distinct β-carbonic anhydrase (CA) isoforms were characterized from leaf tissue of Neurachne munroi (C4), Neurachne minor (C3-C4), and Neurachne alopecuroidea (C3). Two genes (CA1 and CA2) each encode two different isoforms: CA1a/CA1b and CA2a/CA2b. Transcript analyses found that CA1 messenger RNAs were significantly more abundant than transcripts from the CA2 gene in the leaves of each species examined, constituting ∼99% of all β-CA transcripts measured. Localization experiments using green fluorescent protein fusion constructs showed that, while CA1b is a cytosolic CA in all three species, the CA1a proteins are differentially localized. The N. alopecuroidea and N. minor CA1a isoforms were imported into chloroplasts of Nicotiana benthamiana leaf cells, whereas N. munroi CA1a localized to the cytosol. Sequence analysis indicated an 11-amino acid deletion in the amino terminus of N. munroi CA1a relative to the C3 and C3-C4 proteins, suggesting that chloroplast targeting of CA1a is the ancestral state and that loss of a functional chloroplast transit peptide in N. munroi CA1a is associated with the evolution of C4 photosynthesis in Neurachne spp. Remarkably, this mechanism is homoplastic with the evolution of the C4-associated CA in the dicotyledonous genus Flaveria, although the actual mutations in the two lineages differ. PMID:28153918

Effect of sulfation on the surface activity of CaO for N2O decomposition

NASA Astrophysics Data System (ADS)

Wu, Lingnan; Hu, Xiaoying; Qin, Wu; Dong, Changqing; Yang, Yongping

2015-12-01

Limestone addition to circulating fluidized bed boilers for sulfur removal affects nitrous oxide (N2O) emission at the same time, but mechanism of how sulfation process influences the surface activity of CaO for N2O decomposition remains unclear. In this paper, we investigated the effect of sulfation on the surface properties and catalytic activity of CaO for N2O decomposition using density functional theory calculations. Sulfation of CaO (1 0 0) surface by the adsorption of a single gaseous SO2 or SO3 molecule forms stable local CaSO3 or CaSO4 on the CaO (1 0 0) surface with strong hybridization between the S atom of SOx and the surface O anion. The formed local CaSO3 increases the barrier energy of N2O decomposition from 0.989 eV (on the CaO (1 0 0) surface) to 1.340 eV, and further sulfation into local CaSO4 remarkably increases the barrier energy to 2.967 eV. Sulfation from CaSO3 into CaSO4 is therefore the crucial step for deactivating the surface activity for N2O decomposition. Completely sulfated CaSO4 (0 0 1) and (0 1 0) surfaces further validate the negligible catalytic ability of CaSO4 for N2O decomposition.

Cav 1.3 channels play a crucial role in the formation of paroxysmal depolarization shifts in cultured hippocampal neurons.

PubMed

Stiglbauer, Victoria; Hotka, Matej; Ruiß, Manuel; Hilber, Karlheinz; Boehm, Stefan; Kubista, Helmut

2017-05-01

An increase of neuronal Ca v 1.3 L-type calcium channels (LTCCs) has been observed in various animal models of epilepsy. However, LTCC inhibitors failed in clinical trials of epileptic treatment. There is compelling evidence that paroxysmal depolarization shifts (PDSs) involve Ca 2+ influx through LTCCs. PDSs represent a hallmark of epileptiform activity. In recent years, a probable epileptogenic role for PDSs has been proposed. However, the implication of the two neuronal LTCC isoforms, Ca v 1.2 and Ca v 1.3, in PDSs remained unknown. Moreover, Ca 2+ -dependent nonspecific cation (CAN) channels have also been suspected to contribute to PDSs. Nevertheless, direct experimental support of an important role of CAN channel activation in PDS formation is still lacking. Primary neuronal networks derived from dissociated hippocampal neurons were generated from mice expressing a dihydropyridine-insensitive Ca v 1.2 mutant (Ca v 1.2DHP -/- mice) or from Ca v 1.3 -/- knockout mice. To investigate the role of Ca v 1.2 and Ca v 1.3, perforated patch-clamp recordings were made of epileptiform activity, which was elicited using either bicuculline or caffeine. LTCC activity was modulated using the dihydropyridines Bay K 8644 (agonist) and isradipine (antagonist). Distinct PDS could be elicited upon LTCC potentiation in Ca v 1.2DHP -/- neurons but not in Ca v 1.3 -/- neurons. In contrast, when bicuculline led to long-lasting, seizure-like discharge events rather than PDS, these were prolonged in Ca v 1.3 -/- neurons but not in Ca v 1.2DHP -/- neurons. Because only the Ca v 1.2 isoform is functionally coupled to CAN channels in primary hippocampal networks, PDS formation does not require CAN channel activity. Our data suggest that the LTCC requirement of PDS relates primarily to Ca v 1.3 channels rather than to Ca v 1.2 channels and CAN channels in hippocampal neurons. Hence, Ca v 1.3 may represent a new therapeutic target for suppression of PDS development. The proposed epileptogenic role of PDSs may allow for a prophylactic rather than the unsuccessful seizure suppressing application of LTCC inhibitors. Wiley Periodicals, Inc. © 2017 International League Against Epilepsy.

Loss of the Chloroplast Transit Peptide from an Ancestral C3 Carbonic Anhydrase Is Associated with C4 Evolution in the Grass Genus Neurachne.

PubMed

Clayton, Harmony; Saladié, Montserrat; Rolland, Vivien; Sharwood, Robert; Macfarlane, Terry; Ludwig, Martha

2017-03-01

Neurachne is the only known grass lineage containing closely related C 3 , C 3 -C 4 intermediate, and C 4 species, making it an ideal taxon with which to study the evolution of C 4 photosynthesis in the grasses. To begin dissecting the molecular changes that led to the evolution of C 4 photosynthesis in this group, the complementary DNAs encoding four distinct β-carbonic anhydrase (CA) isoforms were characterized from leaf tissue of Neurachne munroi (C 4 ), Neurachne minor (C 3 -C 4 ), and Neurachne alopecuroidea (C 3 ). Two genes ( CA1 and CA2 ) each encode two different isoforms: CA1a/CA1b and CA2a/CA2b. Transcript analyses found that CA1 messenger RNAs were significantly more abundant than transcripts from the CA2 gene in the leaves of each species examined, constituting ∼99% of all β-CA transcripts measured. Localization experiments using green fluorescent protein fusion constructs showed that, while CA1b is a cytosolic CA in all three species, the CA1a proteins are differentially localized. The N. alopecuroidea and N. minor CA1a isoforms were imported into chloroplasts of Nicotiana benthamiana leaf cells, whereas N. munroi CA1a localized to the cytosol. Sequence analysis indicated an 11-amino acid deletion in the amino terminus of N. munroi CA1a relative to the C 3 and C 3 -C 4 proteins, suggesting that chloroplast targeting of CA1a is the ancestral state and that loss of a functional chloroplast transit peptide in N. munroi CA1a is associated with the evolution of C 4 photosynthesis in Neurachne spp. Remarkably, this mechanism is homoplastic with the evolution of the C 4 -associated CA in the dicotyledonous genus Flaveria , although the actual mutations in the two lineages differ. © 2017 American Society of Plant Biologists. All Rights Reserved.

Citrus bergamia Risso Elevates Intracellular Ca2+ in Human Vascular Endothelial Cells due to Release of Ca2+ from Primary Intracellular Stores

PubMed Central

Kang, Purum; Han, Seung Ho; Moon, Hea Kyung; Lee, Jeong-Min; Kim, Hyo-Keun; Min, Sun Seek; Seol, Geun Hee

2013-01-01

The purpose of the present study is to examine the effects of essential oil of Citrus bergamia Risso (bergamot, BEO) on intracellular Ca2+ in human umbilical vein endothelial cells. Fura-2 fluorescence was used to examine changes in intracellular Ca2+ concentration [Ca2+]i . In the presence of extracellular Ca2+, BEO increased [Ca2+]i , which was partially inhibited by a nonselective Ca2+ channel blocker La3+. In Ca2+-free extracellular solutions, BEO increased [Ca2+]i in a concentration-dependent manner, suggesting that BEO mobilizes intracellular Ca2+. BEO-induced [Ca2+]i increase was partially inhibited by a Ca2+-induced Ca2+ release inhibitor dantrolene, a phospholipase C inhibitor U73122, and an inositol 1,4,5-triphosphate (IP3)-gated Ca2+ channel blocker, 2-aminoethoxydiphenyl borane (2-APB). BEO also increased [Ca2+]i in the presence of carbonyl cyanide m-chlorophenylhydrazone, an inhibitor of mitochondrial Ca2+ uptake. In addition, store-operated Ca2+ entry (SOC) was potentiated by BEO. These results suggest that BEO mobilizes Ca2+ from primary intracellular stores via Ca2+-induced and IP3-mediated Ca2+ release and affect promotion of Ca2+ influx, likely via an SOC mechanism. PMID:24348719

Inositol trisphosphate receptor mediated spatiotemporal calcium signalling.

PubMed

Miyazaki, S

1995-04-01

Spatiotemporal Ca2+ signalling in the cytoplasm is currently understood as an excitation phenomenon by analogy with electrical excitation in the plasma membrane. In many cell types, Ca2+ waves and Ca2+ oscillations are mediated by inositol 1,4,5-trisphosphate (IP3) receptor/Ca2+ channels in the endoplasmic reticulum membrane, with positive feedback between cytosolic Ca2+ and IP3-induced Ca2+ release creating a regenerative process. Remarkable advances have been made in the past year in the analysis of subcellular Ca2+ microdomains using confocal microscopy and of Ca2+ influx pathways that are functionally coupled to IP3-induced Ca2+ release. Ca2+ signals can be conveyed into the nucleus and mitochondria. Ca2+ entry from outside the cell allows repetitive Ca2+ release by providing Ca2+ to refill the endoplasmic reticulum stores, thus giving rise to frequency-encoded Ca2+ signals.

Modeling Ca2+ Feedback on a Single Inositol 1,4,5-Trisphosphate Receptor and Its Modulation by Ca2+ Buffers

PubMed Central

Shuai, Jianwei; Pearson, John E.; Parker, Ian

2008-01-01

The inositol 1,4,5-trisphosphate receptor/channel (IP3R) is a major regulator of intracellular Ca2+ signaling, and liberates Ca2+ ions from the endoplasmic reticulum in response to binding at cytosolic sites for both IP3 and Ca2+. Although the steady-state gating properties of the IP3R have been extensively studied and modeled under conditions of fixed [IP3] and [Ca2+], little is known about how Ca2+ flux through a channel may modulate the gating of that same channel by feedback onto activating and inhibitory Ca2+ binding sites. We thus simulated the dynamics of Ca2+ self-feedback on monomeric and tetrameric IP3R models. A major conclusion is that self-activation depends crucially on stationary cytosolic Ca2+ buffers that slow the collapse of the local [Ca2+] microdomain after closure. This promotes burst-like reopenings by the rebinding of Ca2+ to the activating site; whereas inhibitory actions are substantially independent of stationary buffers but are strongly dependent on the location of the inhibitory Ca2+ binding site on the IP3R in relation to the channel pore. PMID:18641077

Inhibitory actions of synthesised polyamine spider toxins and their analogues on Ca2+-activated Cl- currents recorded from cultured DRG neurones from neonatal rats.

PubMed

Sutton, K G; Stapleton, S R; Scott, R H

1998-07-24

The whole cell variant of the patch clamp technique was used to investigate the actions of polyamine spider toxins and their analogues on high voltage-activated Ca2+ currents and Ca2+-activated Cl- currents (I(Cl(Ca))). The actions of synthesised FTX (putative natural toxin from the American funnel web spider), sFTX-3.3, Orn-FTX-3.3, Lys-FTX-3.3, and argiotoxin-636 on cultured dorsal root ganglion neurones from neonatal rats were investigated. Synthesised FTX (1 microM) inhibited I(Cl(Ca)) but did not inhibit high voltage-activated Ca2+ currents. In contrast, sFTX-3.3 (10 microM) inhibited both high voltage-activated Ca2+ currents and the associated I(Cl(Ca)) in near equal proportions. Argiotoxin-636 (1-10 microM) inhibited I(Cl(Ca)) evoked by Ca2+ entry through voltage-activated channels and by intracellular photorelease of Ca2+ from a caged precursor DM-nitrophen. This data indicates that synthesised FTX and argiotoxin-636 directly inhibit Ca2+-activated Cl- channels. In conclusion, the potency of polyamines as non-selective inhibitors of Ca2+ channels and Ca2+-activated Cl- channels is in part determined by the presence of a terminal arginine and this may involve an interaction between terminal guanidino groups and Ca2+ binding sites.

Effect of [6]-shogaol on cytosolic Ca2+ levels and proliferation in human oral cancer cells (OC2).

PubMed

Chen, Chung-Yi; Yang, Yu-Han; Kuo, Soong-Yu

2010-08-27

The effect of [6]-shogaol (1) on cytosolic free Ca(2+) concentrations ([Ca(2+)](i)) and viability has not been explored previously in oral epithelial cells. The present study has examined whether 1 alters [Ca(2+)](i) and viability in OC2 human oral cancer cells. Compound 1 at concentrations > or = 5 microM increased [Ca(2+)](i) in a concentration-dependent manner with a 50% effective concentration (EC(50)) value of 65 microM. The Ca(2+) signal was reduced substantially by removing extracellular Ca(2+). In a Ca(2+)-free medium, the 1-induced [Ca(2+)](i) elevation was mostly attenuated by depleting stored Ca(2+) with thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor). The [Ca(2+)](i) signal was inhibited by La(3+) but not by L-type Ca(2+) channel blockers. The elevation of [Ca(2+)](i) caused by 1 in a Ca(2+)-containing medium was not affected by modulation of protein kinase C activity, but was inhibited by 82% with the phospholipase A2 inhibitor aristolochic acid I (20 microM). U73122, a selective inhibitor of phospholipase C, abolished 1-induced [Ca(2+)](i) release. At concentrations of 5-100 microM, 1 killed cells in a concentration-dependent manner. These findings suggest that [6]-shogaol induces a significant rise in [Ca(2+)](i) in oral cancer OC2 cells by causing stored Ca(2+) release from the thapsigargin-sensitive endoplasmic reticulum pool in an inositol 1,4,5-trisphosphate-dependent manner and by inducing Ca(2+) influx via a phospholipase A2- and La(3+)-sensitive pathway.

Mineral sulphide-lime reactions and effect of CaO/C mole ratio during carbothermic reduction of complex mineral sulphides

NASA Astrophysics Data System (ADS)

Hara, Yotamu Stephen Rainford

2014-01-01

Mineral sulphide (MS)-lime (CaO) ion exchange reactions (MS + CaO = MO + CaS) and the effect of CaO/C mole ratio during carbothermic reduction (MS + CaO + C = M + CaS + CO(g)) were investigated for complex froth flotation mineral sulphide concentrates. Phases in the partially and fully reacted samples were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The primary phases during mineral sulphide-lime ion exchange reactions are Fe3O4, CaSO4 Cu2S, and CaS. A complex liquid phase of Ca2CuFeO3S forms during mineral sulphide-lime exchange reactions above 1173 K. The formation mechanisms of Ca2CuFeO3S liquid phase are determined by characterising the partially reacted samples. The reduction rate and extent of mineral sulphides in the presence of CaO and C increase with the increase in CaO/C ratio. The metallic phases are surrounded by the CaS rich phase at CaO/C > 1, but the metallic phases and CaS are found as separate phases at CaO/C < 1. Experimental results show that the stoichiometric ratio of carbon should be slightly higher than that of CaO. The reactions between CaO and gangue minerals (SiO2 and Al2O3) are only observed at CaO/C > 1 and the reacted samples are excessively sintered.

The contribution of inositol 1,4,5-trisphosphate and ryanodine receptors to agonist-induced Ca(2+) signaling of airway smooth muscle cells.

PubMed

Bai, Yan; Edelmann, Martin; Sanderson, Michael J

2009-08-01

The relative contribution of inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) and ryanodine receptors (RyRs) to agonist-induced Ca(2+) signaling in mouse airway smooth muscle cells (SMCs) was investigated in lung slices with phase-contrast or laser scanning microscopy. At room temperature (RT), methacholine (MCh) or 5-hydroxytryptamine (5-HT) induced Ca(2+) oscillations and an associated contraction in small airway SMCs. The subsequent exposure to an IP(3)R antagonist, 2-aminoethoxydiphenyl borate (2-APB), inhibited the Ca(2+) oscillations and induced airway relaxation in a concentration-dependent manner. 2-APB also inhibited Ca(2+) waves generated by the photolytic release of IP(3). However, the RyR antagonist ryanodine had no significant effect, at any concentration, on airway contraction or agonist- or IP(3)-induced Ca(2+) oscillations or Ca(2+) wave propagation. By contrast, a second RyR antagonist, tetracaine, relaxed agonist-contracted airways and inhibited agonist-induced Ca(2+) oscillations in a concentration-dependent manner. However, tetracaine did not affect IP(3)-induced Ca(2+) release or wave propagation nor the Ca(2+) content of SMC Ca(2+) stores as evaluated by Ca(2+)-release induced by caffeine. Conversely, both ryanodine and tetracaine completely blocked agonist-independent slow Ca(2+) oscillations induced by KCl. The inhibitory effects of 2-APB and absence of an effect of ryanodine on MCh-induced airway contraction or Ca(2+) oscillations of SMCs were also observed at 37 degrees C. In Ca(2+)-permeable SMCs, tetracaine inhibited agonist-induced contraction without affecting intracellular Ca(2+) levels indicating that relaxation also resulted from a reduction in Ca(2+) sensitivity. These results indicate that agonist-induced Ca(2+) oscillations in mouse small airway SMCs are primary mediated via IP(3)Rs and that tetracaine induces relaxation by both decreasing Ca(2+) sensitivity and inhibiting agonist-induced Ca(2+) oscillations via an IP(3)-dependent mechanism.

Differential expression and functional analysis of three calmodulin isoforms in germinating pea (Pisum sativum L.) seeds.

PubMed

Duval, Frédéric D; Renard, Michelle; Jaquinod, Michel; Biou, Valérie; Montrichard, Françoise; Macherel, David

2002-11-01

Implication of the ubiquitous, highly conserved, Ca2+ sensor calmodulin (CaM) in pea seed germination has been investigated. Mass spectrometry analysis of purified CaM revealed the coexistence in seeds of three protein isoforms, diverging from each other by single amino acid substitution in the N-terminal alpha-helix. CaM was shown to be encoded by a small multigenic family, and full-length cDNAs of the three isoforms (PsCaM1, 2 and 3) were isolated to allow the design of specific primers in more divergent 5' and 3' untranslated regions. Expression studies, performed by semiquantitative RT-PCR, demonstrated differential expression patterns of the three transcripts during germination. PsCaM1 and 2 were detected at different levels in dry axes and cotyledons, and they accumulated during imbibition and prior to radicle protrusion. In contrast, PsCaM3 appeared only upon radicle protrusion, then gradually increased in both tissues. To characterise the biochemical properties of the CaM isoforms, functional analyses were conducted in vitro using recombinant Strep-tagged proteins (CaM1-ST, CaM2-ST and CaM3-ST) expressed in Escherichia coli. Gel mobility shift assays revealed that CaM1-ST exhibited a stoichiometric binding of a synthetic amphiphilic CaM kinase II peptide while CaM2-ST and CaM3-ST affinities for the same peptide were reduced. Affinity differences were also observed for CaM isoform binding to Trp-3, an idealised helical CaM-binding peptide. However, the three proteins activated in the same way the CaM-dependent pea NAD kinase. Finally, the significance of the single substitutions upon CaM interaction with its targets is discussed in a structural context.

Cytosolic calcium homeostasis in bovine parathyroid cells and its modulation by protein kinase C.

PubMed Central

Racke, F K; Nemeth, E F

1993-01-01

1. The effects of protein kinase C (PKC) activators and inhibitors on the mechanisms regulating cytosolic Ca2+ homeostasis in dissociated bovine parathyroid cells loaded with fura-2 were examined. 2. Stepwise increases in the concentration of extracellular Ca2+ (from 0.5 to 2 or 3 mM) elicited transient followed by sustained increases in the concentration of intracellular free Ca2+ ([Ca2+]i). Cytosolic Ca2+ transients reflected the mobilization of intracellular Ca2+ and influx of extracellular Ca2+ whereas sustained increases in [Ca2+]i resulted from the influx of extracellular Ca2+. Brief (1-2 min) pretreatment with phorbol myristate acetate (PMA) shifted the concentration-response curve for extracellular Ca(2+)-induced cytosolic Ca2+ transients to the right without affecting the maximal response. Cytosolic Ca2+ transients elicited by extracellular Mg2+ were similarly affected by PMA. 3. These effects of PMA were mimicked by various other activators of PKC with the rank order of potency PMA > phorbol dibutyrate > bryostatin , > (-)indolactam V > mezerein. Isomers or analogues of these compounds that do not alter PKC activity (4 alpha-phorbols and (+)indolactam V) did not alter [Ca2+]i. 4. PKC activators depressed evoked increases in [Ca2+]i when influx of extracellular Ca2+ was blocked with Gd3+. Cytosolic Ca2+ transients elicited by extracellular Mg2+ in the absence of extracellular Ca2+ were similarly inhibited by PKC activators. Activation of PKC thus inhibits the mobilization of intracellular Ca2+ elicited by extracellular divalent cations. 5. Increases in the concentration of extracellular Ca2+ caused corresponding increases in the formation of [3H]inositol 1,4,5-trisphosphate ([3H]InsP3). Pretreatment with PMA shifted the concentration-response curve for extracellular Ca(2+)-induced [3H]InsP3 formation to the right without affecting the maximal response. 6. PKC activators also caused some depression of steady-state increases in [Ca2+]i elicited by extracellular Ca2+. In contrast, PMA did not affect increases in [Ca2+]i elicited by ionomycin or thapsigargin. 7. Ba2+ was used to monitor divalent cation influx. PMA decreased the rate of rise of the fluorescent signal elicited by extracellular Ba2+. 8. All these effects of PKC activators on [Ca2+]i were blocked or reversed by staurosporine at concentrations (30-100 nM) that inhibited PKC activity in parathyroid cells. Staurosporine alone potentiated cytosolic Ca2+ responses evoked by submaximal concentrations of extracellular divalent cations. 9. PKC thus depresses both the mobilization of intracellular Ca2+ and the influx of extracellular Ca2+ in parathyroid cells. The effects on [Ca2+]i provide evidence for a Ca2+ receptor on the surface of parathyroid cells that uses transmembrane signalling mechanisms common to some other Ca(2+)-mobilizing receptors.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8254504

Distribution of voltage-dependent and intracellular Ca2+ channels in submucosal neurons from rat distal colon.

PubMed

Rehn, Matthias; Bader, Sandra; Bell, Anna; Diener, Martin

2013-09-01

We recently observed a bradykinin-induced increase in the cytosolic Ca2+ concentration in submucosal neurons of rat colon, an increase inhibited by blockers of voltage-dependent Ca2+ (Ca(v)) channels. As the types of Ca(v) channels used by this part of the enteric nervous system are unknown, the expression of various Ca(v) subunits has been investigated in whole-mount submucosal preparations by immunohistochemistry. Submucosal neurons, identified by a neuronal marker (microtubule-associated protein 2), are immunoreactive for Ca(v)1.2, Ca(v)1.3 and Ca(v)2.2, expression being confirmed by reverse transcription plus the polymerase chain reaction. These data agree with previous observations that the inhibition of L- and N-type Ca2+ currents strongly inhibits the response to bradykinin. However, whole-cell patch-clamp experiments have revealed that bradykinin does not enhance Ca2+ inward currents under voltage-clamp conditions. Consequently, bradykinin does not directly interact with Ca(v) channels. Instead, the kinin-induced Ca2+ influx is caused indirectly by the membrane depolarization evoked by this peptide. As intracellular Ca2+ channels on Ca(2+)-storing organelles can also contribute to Ca2+ signaling, their expression has been investigated by imaging experiments and immunohistochemistry. Inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) have been functionally demonstrated in submucosal neurons loaded with the Ca(2+)-sensitive fluorescent dye, fura-2. Histamine, a typical agonist coupled to the phospholipase C pathway, induces an increase in the fura-2 signal ratio, which is suppressed by 2-aminophenylborate, a blocker of IP3 receptors. The expression of IP3R1 has been confirmed by immunohistochemistry. In contrast, ryanodine, tested over a wide concentration range, evokes no increase in the cytosolic Ca2+ concentration nor is there immunohistochemical evidence for the expression of ryanodine receptors in these neurons. Thus, rat submucosal neurons are equipped with various types of high-voltage activated Ca(v) channels and with IP3 receptors for intracellular Ca2+ signaling.

Dental enamel cells express functional SOCE channels

PubMed Central

Nurbaeva, Meerim K.; Eckstein, Miriam; Concepcion, Axel R.; Smith, Charles E.; Srikanth, Sonal; Paine, Michael L.; Gwack, Yousang; Hubbard, Michael J.; Feske, Stefan; Lacruz, Rodrigo S.

2015-01-01

Dental enamel formation requires large quantities of Ca2+ yet the mechanisms mediating Ca2+ dynamics in enamel cells are unclear. Store-operated Ca2+ entry (SOCE) channels are important Ca2+ influx mechanisms in many cells. SOCE involves release of Ca2+ from intracellular pools followed by Ca2+ entry. The best-characterized SOCE channels are the Ca2+ release-activated Ca2+ (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca2+ uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca2+ release mechanism. Passive depletion of ER Ca2+ stores with thapsigargin resulted in a significant raise in [Ca2+]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca2+ entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca2+ uptake in enamel formation. PMID:26515404

Dental enamel cells express functional SOCE channels.

PubMed

Nurbaeva, Meerim K; Eckstein, Miriam; Concepcion, Axel R; Smith, Charles E; Srikanth, Sonal; Paine, Michael L; Gwack, Yousang; Hubbard, Michael J; Feske, Stefan; Lacruz, Rodrigo S

2015-10-30

Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca(2+) release mechanism. Passive depletion of ER Ca(2+) stores with thapsigargin resulted in a significant raise in [Ca(2+)]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca(2+) entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca(2+) uptake in enamel formation.

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

PubMed

Willars, G B; Nahorski, S R

1995-03-01

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

Synthesis, biological evaluation, and docking studies of gigantol analogs as calmodulin inhibitors.

PubMed

Reyes-Ramírez, Adelfo; Leyte-Lugo, Martha; Figueroa, Mario; Serrano-Alba, Trinidad; González-Andrade, Martín; Mata, Rachel

2011-07-01

Several analogs of gigantol (1) were synthesized to evaluate their effect on the complexes Ca(2+)-calmodulin (CaM) and Ca(2+)-CaM-CaM sensitive phosphodiesterase 1 (PDE1). The compounds belong to four structural groups including, 1,2-diphenylethanes (2-11), diphenylmethanes (13-15), 1,3-diphenylpropenones (16-18), and 1,3-diphenylpropanes (20-22). In vitro enzymatic studies showed that all compounds except 11 inhibited the complex Ca(2+)-CaM-PDE1 with IC(50) values ranging from 9 to 146 μM. On the other hand, all analogs but 11, 12 and 15 quenched the extrinsic fluorescence of the CaM biosensor hCaM-M124C-mBBr to different extent, then revealing different affinities to CaM; their affinity constants (K(m)) values were in the range of 3-80 μM. Molecular modeling studies indicated that all these compounds bound to CaM at the same site that the classical inhibitors trifluoperazine (TFP) and chlorpromazine (CPZ). Some of these analogs could be worthy candidates for developing new anti-tumor, local anesthetics, antidepressants, antipsychotic, or smooth muscle relaxant drugs, with anti-CaM properties due to their good affinity to CaM and the straightforwardness of their synthesis. In addition they could be valuable tools for the study of Ca(2+)-CaM functions. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

The Contribution of L-Type Cav1.3 Channels to Retinal Light Responses.

PubMed

Shi, Liheng; Chang, Janet Ya-An; Yu, Fei; Ko, Michael L; Ko, Gladys Y-P

2017-01-01

L-type voltage-gated calcium channels (LTCCs) regulate tonic neurotransmitter release from sensory neurons including retinal photoreceptors. There are three types of LTCCs (Ca v 1.2, Ca v 1.3, and Ca v 1.4) expressed in the retina. While Ca v 1.2 is expressed in all retinal cells including the Müller glia and neurons, Ca v 1.3 and Ca v 1.4 are expressed in the retinal neurons with Ca v 1.4 exclusively expressed in the photoreceptor synaptic terminals. Mutations in the gene encoding Ca v 1.4 cause incomplete X-linked congenital stationary night blindness in humans. Even though Ca v 1.3 is present in the photoreceptor inner segments and the synaptic terminals in various vertebrate species, its role in vision is unclear, since genetic alterations in Ca v 1.3 are not associated with severe vision impairment in humans or in Ca v 1.3-null (Ca v 1.3 -/- ) mice. However, a failure to regulate Ca v 1.3 was found in a mouse model of Usher syndrome, the most common cause of combined deafness and blindness in humans, indicating that Ca v 1.3 may contribute to retinal function. In this report, we combined physiological and morphological data to demonstrate the role of Ca v 1.3 in retinal physiology and function that has been undervalued thus far. Through ex vivo and in vivo electroretinogram (ERG) recordings and immunohistochemical staining, we found that Ca v 1.3 plays a role in retinal light responses and synaptic plasticity. Pharmacological inhibition of Ca v 1.3 decreased ex vivo ERG a- and b-wave amplitudes. In Ca v 1.3 -/- mice, their dark-adapted ERG a-, b-wave, and oscillatory potential amplitudes were significantly dampened, and implicit times were delayed compared to the wild type (WT). Furthermore, the density of ribbon synapses was reduced in the outer plexiform layer of Ca v 1.3 -/- mice retinas. Hence, Ca v 1.3 plays a more prominent role in retinal physiology and function than previously reported.

Interaction of peridotite with Ca-rich carbonatite melt at 3.1 and 6.5 GPa: Implication for merwinite formation in upper mantle, and for the metasomatic origin of sublithospheric diamonds with Ca-rich suite of inclusions

NASA Astrophysics Data System (ADS)

Sharygin, Igor S.; Shatskiy, Anton; Litasov, Konstantin D.; Golovin, Alexander V.; Ohtani, Eiji; Pokhilenko, Nikolay P.

2018-03-01

We performed an experimental study, designed to reproduce the formation of an unusual merwinite + olivine-bearing mantle assemblage recently described as a part of a Ca-rich suite of inclusions in sublithospheric diamonds, through the interaction of peridotite with an alkali-rich Ca-carbonatite melt, derived from deeply subducted oceanic crust. In the first set of experiments, we studied the reaction between powdered Mg-silicates, olivine and orthopyroxene, and a model Ca-carbonate melt (molar Na:K:Ca = 1:1:2), in a homogeneous mixture, at 3.1 and 6.5 GPa. In these equilibration experiments, we observed the formation of a merwinite + olivine-bearing assemblage at 3.1 GPa and 1200 °C and at 6.5 GPa and 1300-1400 °C. The melts coexisting with this assemblage have a low Si and high Ca content (Ca# = molar 100 × Ca/(Ca + Mg) > 0.57). In the second set of experiments, we investigated reaction rims produced by interaction of the same Ca-carbonate melt (molar Na:K:Ca = 1:1:2) with Mg-silicate, olivine and orthopyroxene, single crystals at 3.1 GPa and 1300 °C and at 6.5 GPa and 1400 °C. The interaction of the Ca-carbonate melt with olivine leads to merwinite formation through the expected reaction: 2Mg2SiO4 (olivine) + 6CaCO3 (liquid) = Ca3MgSi2O8 (merwinite) + 3CaMg(CO3)2 (liquid). Thus, our experiments confirm the idea that merwinite in the upper mantle may originate via interaction of peridotite with Ca-rich carbonatite melt, and that diamonds hosting merwinite may have a metasomatic origin. It is remarkable that the interaction of the Ca-carbonate melt with orthopyroxene crystals does not produce merwinite both at 3.1 and 6.5 GPa. This indicates that olivine grain boundaries are preferable for merwinite formation in the upper mantle.

Alcohol Withdrawal-Induced Seizure Susceptibility is Associated with an Upregulation of CaV1.3 Channels in the Rat Inferior Colliculus

PubMed Central

Akinfiresoye, Luli R.; Allard, Joanne S.; Lovinger, David M.

2015-01-01

Background: We previously reported increased current density through L-type voltage-gated Ca2+ (CaV1) channels in inferior colliculus (IC) neurons during alcohol withdrawal. However, the molecular correlate of this increased CaV1 current is currently unknown. Methods: Rats received three daily doses of ethanol every 8 hours for 4 consecutive days; control rats received vehicle. The IC was dissected at various time intervals following alcohol withdrawal, and the mRNA and protein levels of the CaV1.3 and CaV1.2 α1 subunits were measured. In separate experiments, rats were tested for their susceptibility to alcohol withdrawal–induced seizures (AWS) 3, 24, and 48 hours after alcohol withdrawal. Results: In the alcohol-treated group, AWS were observed 24 hours after withdrawal; no seizures were observed at 3 or 48 hours. No seizures were observed at any time in the control-treated rats. Compared to control-treated rats, the mRNA level of the CaV1.3 α1 subunit was increased 1.4-fold, 1.9-fold, and 1.3-fold at 3, 24, and 48 hours, respectively. In contrast, the mRNA level of the CaV1.2 α1 subunit increased 1.5-fold and 1.4-fold at 24 and 48 hours, respectively. At 24 hours, Western blot analyses revealed that the levels of the CaV1.3 and CaV1.2 α1 subunits increased by 52% and 32%, respectively, 24 hours after alcohol withdrawal. In contrast, the CaV1.2 and CaV1.3 α1 subunits were not altered at either 3 or 48 hours during alcohol withdrawal. Conclusions: Expression of the CaV1.3 α1 subunit increased in parallel with AWS development, suggesting that altered L-type CaV1.3 channel expression is an important feature of AWS pathogenesis. PMID:25556199

Mouse osteoblastic cell line (MC3T3-E1) expresses extracellular calcium (Ca2+o)-sensing receptor and its agonists stimulate chemotaxis and proliferation of MC3T3-E1 cells

NASA Technical Reports Server (NTRS)

Yamaguchi, T.; Chattopadhyay, N.; Kifor, O.; Butters, R. R. Jr; Sugimoto, T.; Brown, E. M.; O'Malley, B. W. (Principal Investigator)

1998-01-01

The calcium-sensing receptor (CaR) is a G protein-coupled receptor that plays key roles in extracellular calcium ion (Ca2+o) homeostasis in parathyroid gland and kidney. Osteoblasts appear at sites of osteoclastic bone resorption during bone remodeling in the "reversal" phase following osteoclastic resorption and preceding bone formation. Bone resorption produces substantial local increases in Ca2+o that could provide a signal for osteoblasts in the vicinity, leading us to determine whether such osteoblasts express the CaR. In this study, we used the mouse osteoblastic, clonal cell line MC3T3-E1. Both immunocytochemistry and Western blot analysis, using an antiserum specific for the CaR, detected CaR protein in MC3T3-E1 cells. We also identified CaR transcripts in MC3T3-E1 cells by Northern analysis using a CaR-specific riboprobe and by reverse transcription-polymerase chain reaction with CaR-specific primers, followed by nucleotide sequencing of the amplified products. Exposure of MC3T3-E1 cells to high Ca2+o (up to 4.8 mM) or the polycationic CaR agonists, neomycin and gadolinium (Gd3+), stimulated both chemotaxis and DNA synthesis in MC3T3-E1 cells. Therefore, taken together, our data strongly suggest that the osteoblastic cell line MC3T3-E1 possesses both CaR protein and mRNA very similar, if not identical, to those in parathyroid and kidney. Furthermore, the CaR in these osteoblasts could play a key role in regulating bone turnover by stimulating the proliferation and migration of such cells to sites of bone resorption as a result of local release of Ca2+o.

Morphometric Parameters of Pyramidal Cells in CA1-CA4 Fields in the Hippocampus of Arctic Fox (Vulpes lagopus).

PubMed

Łuszczewska-Sierakowska, Iwona; Wawrzyniak-Gacek, Agata; Guz, Tomasz; Tatara, Marcin R; Charuta, Anna

2015-01-01

The aim of the study was a quantitative examination of neurons of hippocampal subfields (CA1-CA4) in mature male Arctic fox (Vulpes lagopus; syn. Alopex lagopus). The preparations were dyed using cresyl violet. Histological preparations were used to morphometricaly analyze the neurons of hippocampus. This analysis included the following parameters: average size of cells in μm, periphery of cells in μm, average cell area in μm2, percentage of cells in area and size of the largest and smallest cells in μm in CA1-CA4 fields. Morphometric observations show that the cells involved in hippocampal formation in polar fox in all layers CA1 -CA4 differ in size, shape, cell area and nucleus area. The size of the cell area in CA3 is the largest and fluctuates around 249.4 μm2, whereas in CA2 the cell area is 184.1 μm2. The cells of the CA2 field are densely arranged, pyramidal and contain a small amount of cytoplasm; their size fluctuates. Cells of CA2 and CA4 had the largest diameter of about 23.6 μm, whereas cells of the CA3 field had the smallest diameter of about 8.3 μm.

Buffer kinetics shape the spatiotemporal patterns of IP3-evoked Ca2+ signals

PubMed Central

Dargan, Sheila L; Parker, Ian

2003-01-01

Ca2+ liberation through inositol 1,4,5-trisphosphate receptors (IP3Rs) plays a universal role in cell regulation, and specificity of cell signalling is achieved through the spatiotemporal patterning of Ca2+ signals. IP3Rs display Ca2+-induced Ca2+ release (CICR), but are grouped in clusters so that regenerative Ca2+ signals may remain localized to individual clusters, or propagate globally between clusters by successive cycles of Ca2+ diffusion and CICR. We used confocal microscopy and photoreleased IP3 in Xenopus oocytes to study how these properties are modulated by mobile cytosolic Ca2+ buffers. EGTA (a buffer with slow ‘on-rate’) speeded Ca2+ signals and ‘balkanized’ Ca2+ waves by dissociating them into local signals. In contrast, BAPTA (a fast buffer with similar affinity) slowed Ca2+ responses and promoted ‘globalization’ of spatially uniform Ca2+ signals. These actions are likely to arise through differential effects on Ca2+ feedback within and between IP3R clusters, because Ca2+ signals evoked by influx through voltage-gated channels were little affected. We propose that cell-specific expression of Ca2+-binding proteins with distinct kinetics may shape the time course and spatial distribution of IP3-evoked Ca2+ signals for specific physiological roles. PMID:14555715

The influence of DOCA-salt hypertension and chronic administration of the FAAH inhibitor URB597 on KCa2.3/KCa3.1-EDH-type relaxation in rat small mesenteric arteries.

PubMed

Kloza, Monika; Baranowska-Kuczko, Marta; Malinowska, Barbara; Karpińska, Olga; Harasim-Symbor, Ewa; Kasacka, Irena; Kozłowska, Hanna

2017-12-01

The aim of this study was to examine the influence of deoxycorticosterone acetate-salt (DOCA-salt) hypertension and chronic treatment with the fatty acid amide hydrolase inhibitor, URB597, on small and intermediate conductance calcium-activated potassium channels and endothelium-dependent hyperpolarization (K Ca 2.3/K Ca 3.1-EDH) in rat small mesenteric arteries (sMAs). The EDH-type response was investigated, in endothelium-intact sMAs using a wire myograph, by examining acetylcholine-evoked vasorelaxation in the presence of N ω -nitro-L-arginine methyl ester and indomethacin (inhibitors of nitric oxide synthase and cyclooxygenase, respectively). In normo- and hypertension the efficacy of EDH-type relaxation was similar and inhibition of K Ca 2.3 and K Ca 3.1 by UCL1684 and TRAM-34, respectively, given alone or in combination, attenuated EDH-mediated vasorelaxation. K Ca 3.1 expression and NS309 (K Ca 2.3/K Ca 3.1 activator)-induced relaxation was reduced in sMAs of DOCA-salt rats. Endothelium denudation and incubation with UCL1684 and TRAM-34 attenuated the maximal NS309-evoked vasorelaxation in both groups. URB597 had no effect in functional studies, but increased the expression of K Ca 3.1 in the sMAs. K Ca 2.3/K Ca 3.1-EDH-mediated relaxation was maintained in the sMAs of DOCA-salt rats despite endothelial dysfunction and down-regulation of K Ca 3.1. Furthermore, K Ca 3.1 played a key role in the EDH-type dilator response of sMAs in normo- and hypertension. The hypotensive effect of URB597 is independent of K Ca 2.3/K Ca 3.1-EDH-type relaxation. Copyright © 2017 Elsevier Inc. All rights reserved.

Development of a histologically validated segmentation protocol for the hippocampal body.

PubMed

Steve, Trevor A; Yasuda, Clarissa L; Coras, Roland; Lail, Mohjevan; Blumcke, Ingmar; Livy, Daniel J; Malykhin, Nikolai; Gross, Donald W

2017-08-15

Recent findings have demonstrated that hippocampal subfields can be selectively affected in different disease states, which has led to efforts to segment the human hippocampus with in vivo magnetic resonance imaging (MRI). However, no studies have examined the histological accuracy of subfield segmentation protocols. The presence of MRI-visible anatomical landmarks with known correspondence to histology represents a fundamental prerequisite for in vivo hippocampal subfield segmentation. In the present study, we aimed to: 1) develop a novel method for hippocampal body segmentation, based on two MRI-visible anatomical landmarks (stratum lacunosum moleculare [SLM] & dentate gyrus [DG]), and assess its accuracy in comparison to the gold standard direct histological measurements; 2) quantify the accuracy of two published segmentation strategies in comparison to the histological gold standard; and 3) apply the novel method to ex vivo MRI and correlate the results with histology. Ultra-high resolution ex vivo MRI was performed on six whole cadaveric hippocampal specimens, which were then divided into 22 blocks and histologically processed. The hippocampal bodies were segmented into subfields based on histological criteria and subfield boundaries and areas were directly measured. A novel method was developed using mean percentage of the total SLM distance to define subfield boundaries. Boundary distances and subfield areas on histology were then determined using the novel method and compared to the gold standard histological measurements. The novel method was then used to determine ex vivo MRI measures of subfield boundaries and areas, which were compared to histological measurements. For direct histological measurements, the mean percentages of total SLM distance were: Subiculum/CA1 = 9.7%, CA1/CA2 = 78.4%, CA2/CA3 = 97.5%. When applied to histology, the novel method provided accurate measures for CA1/CA2 (ICC = 0.93) and CA2/CA3 (ICC = 0.97) boundaries, but not for the Subiculum/CA1 (ICC = -0.04) boundary. Accuracy was poorer using previous techniques for CA1/CA2 (maximum ICC = 0.85) and CA2/CA3 (maximum ICC = 0.88), with the previously reported techniques also performing poorly in defining the Subiculum/CA1 boundary (maximum ICC = 0.00). Ex vivo MRI measurements using the novel method were linearly related to direct measurements of SLM length (r 2 = 0.58), CA1/CA2 boundary (r 2 = 0.39) and CA2/CA3 boundary (r 2 = 0.47), but not for Subiculum/CA1 boundary (r 2 = 0.01). Subfield areas measured with the novel method on histology and ex vivo MRI were linearly related to gold standard histological measures for CA1, CA2, and CA3/CA4/DG. In this initial proof of concept study, we used ex vivo MRI and histology of cadaveric hippocampi to develop a novel segmentation protocol for the hippocampal body. The novel method utilized two anatomical landmarks, SLM & DG, and provided accurate measurements of CA1, CA2, and CA3/CA4/DG subfields in comparison to the gold standard histological measurements. The relationships demonstrated between histology and ex vivo MRI supports the potential feasibility of applying this method to in vivo MRI studies. Copyright © 2017. Published by Elsevier Inc.

Cell type-specific genetic and optogenetic tools reveal hippocampal CA2 circuits.

PubMed

Kohara, Keigo; Pignatelli, Michele; Rivest, Alexander J; Jung, Hae-Yoon; Kitamura, Takashi; Suh, Junghyup; Frank, Dominic; Kajikawa, Koichiro; Mise, Nathan; Obata, Yuichi; Wickersham, Ian R; Tonegawa, Susumu

2014-02-01

The formation and recall of episodic memory requires precise information processing by the entorhinal-hippocampal network. For several decades, the trisynaptic circuit entorhinal cortex layer II (ECII)→dentate gyrus→CA3→CA1 and the monosynaptic circuit ECIII→CA1 have been considered the primary substrates of the network responsible for learning and memory. Circuits linked to another hippocampal region, CA2, have only recently come to light. Using highly cell type-specific transgenic mouse lines, optogenetics and patch-clamp recordings, we found that dentate gyrus cells, long believed to not project to CA2, send functional monosynaptic inputs to CA2 pyramidal cells through abundant longitudinal projections. CA2 innervated CA1 to complete an alternate trisynaptic circuit, but, unlike CA3, projected preferentially to the deep, rather than to the superficial, sublayer of CA1. Furthermore, contrary to existing knowledge, ECIII did not project to CA2. Our results allow a deeper understanding of the biology of learning and memory.

Extracellular calcium-sensing-receptor (CaR)-mediated opening of an outward K(+) channel in murine MC3T3-E1 osteoblastic cells: evidence for expression of a functional CaR

NASA Technical Reports Server (NTRS)

Ye, C. P.; Yamaguchi, T.; Chattopadhyay, N.; Sanders, J. L.; Vassilev, P. M.; Brown, E. M.; O'Malley, B. W. (Principal Investigator)

2000-01-01

The existence in osteoblasts of the G-protein-coupled extracellular calcium (Ca(o)(2+))-sensing receptor (CaR) that was originally cloned from parathyroid and kidney remains controversial. In our recent studies, we utilized multiple detection methods to demonstrate the expression of CaR transcripts and protein in several osteoblastic cell lines, including murine MC3T3-E1 cells. Although we and others have shown that high Ca(o)(2+) and other polycationic CaR agonists modulate the function of MC3T3-E1 cells, none of these actions has been unequivocally shown to be mediated by the CaR. Previous investigations using neurons and lens epithelial cells have shown that activation of the CaR stimulates Ca(2+)-activated K(+) channels. Because osteoblastic cells express a similar type of channel, we have examined the effects of specific "calcimimetic" CaR activators on the activity of a Ca(2+)-activated K(+) channel in MC3T3-E1 cells as a way of showing that the CaR is not only expressed in those cells but is functionally active. Patch-clamp analysis in the cell-attached mode showed that raising Ca(o)(2+) from 0.75 to 2.75 mmol/L elicited about a fourfold increase in the open state probability (P(o)) of an outward K(+) channel with a conductance of approximately 92 pS. The selective calcimimetic CaR activator, NPS R-467 (0.5 micromol/L), evoked a similar activation of the channel, while its less active stereoisomer, NPSS-467 (0.5 micromol/L), did not. Thus, the CaR is not only expressed in MC3T3-E1 cells, but is also functionally coupled to the activity of a Ca(2+)-activated K(+) channel. This receptor, therefore, could transduce local or systemic changes in Ca(o)(2+) into changes in the activity of this ion channel and related physiological processes in these and perhaps other osteoblastic cells.

Suppression of Sleep Spindle Rhythmogenesis in Mice with Deletion of CaV3.2 and CaV3.3 T-type Ca(2+) Channels.

PubMed

Pellegrini, Chiara; Lecci, Sandro; Lüthi, Anita; Astori, Simone

2016-04-01

Low-threshold voltage-gated T-type Ca(2+) channels (T-channels or CaV3 channels) sustain oscillatory discharges of thalamocortical (TC) and nucleus Reticularis thalami (nRt) cells. The CaV3.3 subtype dominates nRt rhythmic bursting and mediates a substantial fraction of spindle power in the NREM sleep EEG. CaV3.2 channels are also found in nRt, but whether these contribute to nRt-dependent spindle generation is unexplored. We investigated thalamic rhythmogenesis in mice lacking this subtype in isolation (CaV3.2KO mice) or in concomitance with CaV3.3 deletion (CaV3.double-knockout (DKO) mice). We examined discharge characteristics of thalamic cells and intrathalamic evoked synaptic transmission in brain slices from wild-type, CaV3.2KO and CaV3.DKO mice through patch-clamp recordings. The sleep profile of freely behaving CaV3.2KO and CaV3.DKO mice was assessed by polysomnographic recordings. CaV3.2 channel deficiency left nRt discharge properties largely unaltered, but additional deletion of CaV3.3 channels fully abolished low-threshold whole-cell Ca(2+) currents and bursting, and suppressed burst-mediated inhibitory responses in TC cells. CaV3.DKO mice had more fragmented sleep, with shorter NREM sleep episodes and more frequent microarousals. The NREM sleep EEG power spectrum displayed a relative suppression of the σ frequency band (10-15 Hz), which was accompanied by an increase in the δ band (1-4 Hz). Consistent with previous findings, CaV3.3 channels dominate nRt rhythmogenesis, but the lack of CaV3.2 channels further aggravates neuronal, synaptic, and EEG deficits. Therefore, CaV3.2 channels can boost intrathalamic synaptic transmission, and might play a modulatory role adjusting the relative presence of NREM sleep EEG rhythms. © 2016 Associated Professional Sleep Societies, LLC.

Functional significance of the intermediate conductance Ca2+-activated K+ channel for the short-term survival of injured erythrocytes.

PubMed

Föller, Michael; Bobbala, Diwakar; Koka, Saisudha; Boini, Krishna M; Mahmud, Hasan; Kasinathan, Ravi S; Shumilina, Ekaterina; Amann, Kerstin; Beranek, Golo; Sausbier, Ulrike; Ruth, Peter; Sausbier, Matthias; Lang, Florian; Huber, Stephan M

2010-11-01

Increased cytosolic Ca(2+) concentrations activate Gardos K(+) channels in human erythrocytes with membrane hyperpolarization, efflux of K(+), Cl⁻, and osmotically obliged H₂O resulting in cell shrinkage, a phenomenon referred to as Gardos effect. We tested whether the Gardos effect delays colloid osmotic hemolysis of injured erythrocytes from mice lacking the Ca(2+)-activated K(+) channel K(Ca)3.1. To this end, we applied patch clamp and flow cytometry and determined in vitro as well as in vivo hemolysis. As a result, erythrocytes from K(Ca)3.1-deficient (K(Ca)3.1(-/-)) mice lacked Gardos channel activity and the Gardos effect. Blood parameters, reticulocyte count, or osmotic erythrocyte resistance, however, did not differ between K(Ca)3.1(-/-) mice and their wild-type littermates, suggesting low or absent Gardos channel activity in unstressed erythrocytes. Oxidative stress-induced Ca(2+) entry and phospholipid scrambling were significantly less pronounced in K(Ca)3.1(-/-) than in wild-type erythrocytes. Moreover, in vitro treatment with α-toxin from Staphylococcus aureus, which forms pores in the cellular membrane, resulted in significantly stronger hemolysis of K(Ca)3.1(-/-) than of wild-type erythrocytes. Intravenous injection of α-toxin induced more profound hemolysis in K(Ca)3.1(-/-) than in wild-type mice. Similarly, intra-peritoneal application of the redox-active substance phenylhydrazine, an agent for the induction of hemolytic anemia, was followed by a significantly stronger decrease of hematocrit in K(Ca)3.1(-/-) than in wild-type mice. Finally, malaria infection triggered the activation of K(Ca)3.1 and transient shrinkage of the infected erythrocytes. In conclusion, K(Ca)3.1 channel activity and Gardos effect counteract hemolysis of injured erythrocytes, thus decreasing hemoglobin release into circulating blood.

The effect of magnolol on Ca2+ homeostasis and its related physiology in human oral cancer cells.

PubMed

Hsieh, Shu-Feng; Chou, Chiang-Ting; Liang, Wei-Zhe; Kuo, Chun-Chi; Wang, Jue-Long; Hao, Lyh-Jyh; Jan, Chung-Ren

2018-05-01

Magnolol, a polyphenol compound from herbal medicines, was shown to alter physiology in various cell models. However, the effect of magnolol on Ca 2+ homeostasis and its related physiology in oral cancer cells is unclear. This study examined whether magnolol altered Ca 2+ signaling and cell viability in OC2 human oral cancer cells. Cytosolic Ca 2+ concentrations ([Ca 2+ ] i ) in suspended cells were measured by using the fluorescent Ca 2+ -sensitive dye fura-2. Cell viability was examined by 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay. Magnolol at concentrations of 20-100 μM induced [Ca 2+ ] i rises. Ca 2+ removal reduced the signal by approximately 50%. Magnolol (100 μM) induced Mn 2+ influx suggesting of Ca 2+ entry. Magnolol-induced Ca 2+ entry was partially suppressed by protein kinase C (PKC) regulators, and inhibitors of store-operated Ca 2+ channels. In Ca 2+ -free medium, treatment with the endoplasmic reticulum Ca 2+ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished magnolol-evoked [Ca 2+ ] i rises. Conversely, treatment with magnolol abolished BHQ-evoked [Ca 2+ ] i rises. Inhibition of phospholipase C (PLC) with U73122 partially inhibited magnolol-induced [Ca 2+ ] i rises. Magnolol at 20-100 μM decreased cell viability, which was not reversed by pretreatment with the Ca 2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in OC2 cells, magnolol induced [Ca 2+ ] i rises by evoking partially PLC-dependent Ca 2+ release from the endoplasmic reticulum and Ca 2+ entry via PKC-sensitive store-operated Ca 2+ entry. Magnolol also caused Ca 2+ -independent cell death. Therefore, magnolol-induced cytotoxicity may not be involved in activation mechanisms associated with intracellular Ca 2+ mobilization in oral cancer cells. Copyright © 2018. Published by Elsevier Ltd.

The CaV2.3 R-type voltage-gated Ca2+ channel in mouse sleep architecture.

PubMed

Siwek, Magdalena Elisabeth; Müller, Ralf; Henseler, Christina; Broich, Karl; Papazoglou, Anna; Weiergräber, Marco

2014-05-01

Voltage-gated Ca(2+) channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca(2+) channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca(2+) channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca(2+) channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3(-/-) mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca(2+) influx into RTN neurons can trigger small-conductance Ca(2+)-activated K(+)-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca(2+) channels in rodent sleep. The role of CaV2.3 Ca(2+) channels was analyzed in CaV2.3(-/-) mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3(-/-) mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca(2+) channel expression. The detailed mechanisms of SWS increase in CaV2.3(-/-) mice remain to be determined. Low-voltage activated CaV2.3 R-type Ca(2+) channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future.

A kinetic study of Ca-containing ions reacting with O, O2, CO2 and H2O: implications for calcium ion chemistry in the upper atmosphere.

PubMed

Broadley, Sarah; Vondrak, Tomas; Wright, Timothy G; Plane, John M C

2008-09-14

A series of gas-phase reactions involving molecular Ca-containing ions was studied by the pulsed laser ablation of a calcite target to produce Ca+ in a fast flow of He, followed by the addition of reagents downstream and detection of ions by quadrupole mass spectrometry. Most of the reactions that were studied are important for describing the chemistry of meteor-ablated calcium in the earth's upper atmosphere. The following rate coefficients were measured: k(CaO+ + O --> Ca+ + O2) = (4.2 +/- 2.8) x 10(-11) at 197 K and (6.3 +/- 3.0) x 10(-11) at 294 K; k(CaO+ + CO --> Ca+ + CO2, 294 K) = (2.8 +/- 1.5) x 10(-10); k(Ca+.CO2 + O2 --> CaO2+ + CO2, 294 K) = (1.2 +/- 0.5) x10(-10); k(Ca+.CO2 + H2O --> Ca+.H2O + CO2) = (13.0 +/- 4.0) x 10(-10); and k(Ca+.H2O + O2 --> CaO2+ + H2O, 294 K) = (4.0 +/- 2.5) x 10(-10) cm3 molecule(-1) s(-1). The quoted uncertainties are a combination of the 1 sigma standard errors in the kinetic data and the systematic errors in the models used to extract the rate coefficients. Rate coefficients were also obtained for the following recombination (also termed association) reactions in He bath gas: k(Ca+.CO2 + CO2 --> Ca+.(CO2)2, 294 K) = (2.6 +/- 1.0) x 10(-29); k(Ca+.H2O + H2O --> Ca+.(H2O)2) = (1.6 +/- 1.1) x 10(-27); and k(CaO2+ + O2 --> CaO2+.O2) < 1 x 10(-31) cm6 molecule(-2) s(-1). These recombination rate coefficients, as well as those for the ligand-switching reactions listed above, were then interpreted using a combination of high level quantum chemistry calculations and RRKM theory using an inverse Laplace transform solution of the master equation. The surprisingly slow reaction between CaO+ and O was explained using quantum chemistry calculations on the lowest 2A', 2A'' and 4A'' potential energy surfaces. These calculations indicate that reaction mostly occurs on the 2A' surface, leading to production of Ca+ (2S) + O2(1 Delta g). The importance of this reaction for controlling the lifetime of Ca+ in the upper mesosphere and lower thermosphere is then discussed.

Involvement of N-methyl-D-aspartate receptor subunits in zinc-mediated modification of CA1 long-term potentiation in the developing hippocampus.

PubMed

Takeda, Atsushi; Itagaki, Kosuke; Ando, Masaki; Oku, Naoto

2012-03-01

Zinc is an endogenous N-methyl-D-aspartate (NMDA) receptor blocker. It is possible that zinc-mediated modification of hippocampal CA1 long-term potentiation (LTP) is linked to the expression of NMDA receptor subunits, which varies with postnatal development. In the present study, the effect of ZnCl(2) and CaEDTA, a membrane-impermeable zinc chelator, on CA1 LTP induction was examined in hippocampal slices from immature (3-week-old) and young (6-week-old) rats. Tetanus (10-100 Hz, 1 sec)-induced CA1 LTP was more greatly enhanced in 3-week-old rats. CA1 LTP was inhibited in the presence of 2-amino-5-phosphonovalerate (APV), an NMDA receptor antagonist, and CaEDTA in 3-week-old rats, as in the case of 6-week-old rats reported previously. In 3-week-old rats, on the other hand, 5 μM ZnCl(2) attenuated NMDA receptor-mediated EPSPs more than in 6-week-old rats and significantly attenuated CA1 LTP. Moreover, 5 μM ZnCl(2) significantly attenuated CA1 LTP in the presence of (2R,4S)-4-(3-phosphonopropyl)-2-piperidinecarboxylic acid (PPPA), an NR2A antagonist, in 3-week-old rats, but not that in the presence of ifenprodil, an NR2B antagonist, suggesting that zinc-mediated attenuation of CA1 LTP is associated with the preferential expression of NR2B subunit in 3-week-old rats. In 6-week-old rats, however, 5 μM ZnCl(2) significantly potentiated CA1 LTP and also CA1 LTP in the presence of PPPA. The present study demonstrates that endogenous zinc may participate in the induction of CA1 LTP. It is likely that the changes in expression of NMDA receptor subunits are involved in the zinc-mediated modification of CA1 LTP in the developing hippocampus. Copyright © 2011 Wiley Periodicals, Inc.

Close Association of Carbonic Anhydrase (CA2a and CA15a), Na+/H+ Exchanger (Nhe3b), and Ammonia Transporter Rhcg1 in Zebrafish Ionocytes Responsible for Na+ Uptake

PubMed Central

Ito, Yusuke; Kobayashi, Sayako; Nakamura, Nobuhiro; Miyagi, Hisako; Esaki, Masahiro; Hoshijima, Kazuyuki; Hirose, Shigehisa

2013-01-01

Freshwater (FW) fishes actively absorb salt from their environment to tolerate low salinities. We previously reported that vacuolar-type H+-ATPase/mitochondrion-rich cells (H-MRCs) on the skin epithelium of zebrafish larvae (Danio rerio) are primary sites for Na+ uptake. In this study, in an attempt to clarify the mechanism for the Na+ uptake, we performed a systematic analysis of gene expression patterns of zebrafish carbonic anhydrase (CA) isoforms and found that, of 12 CA isoforms, CA2a and CA15a are highly expressed in H-MRCs at larval stages. The ca2a and ca15a mRNA expression were salinity-dependent; they were upregulated in 0.03 mM Na+ water whereas ca15a but not ca2a was down-regulated in 70 mM Na+ water. Immunohistochemistry demonstrated cytoplasmic distribution of CA2a and apical membrane localization of CA15a. Furthermore, cell surface immunofluorescence staining revealed external surface localization of CA15a. Depletion of either CA2a or CA15a expression by Morpholino antisense oligonucleotides resulted in a significant decrease in Na+ accumulation in H-MRCs. An in situ proximity ligation assay demonstrated a very close association of CA2a, CA15a, Na+/H+ exchanger 3b (Nhe3b), and Rhcg1 ammonia transporter in H-MRC. Our findings suggest that CA2a, CA15a, and Rhcg1 play a key role in Na+uptake under FW conditions by forming a transport metabolon with Nhe3b. PMID:23565095

The CaV2.3 R-Type Voltage-Gated Ca2+ Channel in Mouse Sleep Architecture

PubMed Central

Siwek, Magdalena Elisabeth; Müller, Ralf; Henseler, Christina; Broich, Karl; Papazoglou, Anna; Weiergräber, Marco

2014-01-01

Study Objectives: Voltage-gated Ca2+ channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca2+ channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca2+ channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca2+ channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3−/− mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca2+ influx into RTN neurons can trigger small-conductance Ca2+-activated K+-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca2+ channels in rodent sleep. Methods: The role of CaV2.3 Ca2+ channels was analyzed in CaV2.3−/− mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. Results: CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3−/− mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca2+ channel expression. The detailed mechanisms of SWS increase in CaV2.3−/− mice remain to be determined. Conclusions: Low-voltage activated CaV2.3 R-type Ca2+ channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future. Citation: Siwek ME, Müller R, Henseler C, Broich K, Papazoglou A, Weiergräber M. The CaV2.3 R-type voltage-gated Ca2+ channel in mouse sleep architecture. SLEEP 2014;37(5):881-892. PMID:24790266

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

PubMed

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

2009-01-01

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

Phase equilibria and crystal chemistry of the CaO–½Sm 2O 3–CoOz system at 885 °C in air

DOE PAGES

Wong-Ng, W.; Laws, W.; Lapidus, S. H.; ...

2015-06-27

The CaO–½Sm 2O 3–CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca 3$-$xSm x)Co 4O 9$-$z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca 3Co 2O 6 which consists of chains of alternating CoO 6 trigonal prisms and CoO 6 octahedra. Ca 3Co 2O 6 was found to be a point compound without the substitution of Sm on the Ca site. A solid solution region of distorted perovskite, (Sm 1$-$xCa x)CoO 3$-$z (0 ≤ x ≤ 0.22, space group Pnma)more » was established. The reported Sm 2CoO 4 phase was not observed at 885 °C, but a ternary Ca-doped oxide, (Sm 1+xCa 1$-$x)CoO 4$-$z (Bmab) where 0 < x ≤ 0.15 was found to be stable at this temperature. In the peripheral binary systems, Sm was not present in the Ca site of CaO, while a small solid solution region was identified for (Sm 1$-$xCa x)O(3 $-$z)/2 (0 ≤ x ≤ 0.075). Lastly, ten solid solution tie-line regions and six three-phase regions were determined in the CaO–½Sm 2O 3–CoO z system in air.« less

CD147 reinforces [Ca2+]i oscillations and promotes oncogenic progression in hepatocellular carcinoma.

PubMed

Tang, Juan; Guo, Yun-Shan; Yu, Xiao-Ling; Huang, Wan; Zheng, Ming; Zhou, Ying-Hui; Nan, Gang; Wang, Jian-Chao; Yang, Hai-Jiao; Yu, Jing-Min; Jiang, Jian-Li; Chen, Zhi-Nan

2015-10-27

Oscillations in intracellular Ca2+ concentrations ([Ca2+]i) mediate various cellular function. Although it is known that [Ca2+]i oscillations are susceptible to dysregulation in tumors, the tumor-specific regulators of [Ca2+]i oscillations are poorly characterized. We discovered that CD147 promotes hepatocellular carcinoma (HCC) metastasis and proliferation by enhancing the amplitude and frequency of [Ca2+]i oscillations in HCC cells. CD147 activates two distinct signaling pathways to regulate [Ca2+]i oscillations. By activating FAK-Src-IP3R1 signaling pathway, CD147 promotes Ca2+ release from endoplasmic reticulum (ER) and enhances the amplitude of [Ca2+]i oscillations. Furthermore, CD147 accelerates ER Ca2+refilling and enhances the frequency of [Ca2+]i oscillations through activating CaMKP-PAK1-PP2A-PLB-SERCA signaling pathway. Besides, CD147-promoted ER Ca2+ release and refilling are tightly regulated by changing [Ca2+]i. CD147 may activate IP3R1 channel under low [Ca2+]i conditions and CD147 may activate SERCA pump under high [Ca2+]i conditions. CD147 deletion suppresses HCC tumorigenesis and increases the survival rate of liver-specific CD147 knockout mice by regulating [Ca2+]i oscillations in vivo. Together, these results reveal that CD147 functions as a critical regulator of ER-dependent [Ca2+]i oscillations to promote oncogenic progression in HCC.

CD147 reinforces [Ca2+]i oscillations and promotes oncogenic progression in hepatocellular carcinoma

PubMed Central

Zheng, Ming; Zhou, Ying-Hui; Nan, Gang; Wang, Jian-Chao; Yang, Hai-Jiao; Yu, Jing-Min; Jiang, Jian-Li; Chen, Zhi-Nan

2015-01-01

Oscillations in intracellular Ca2+ concentrations ([Ca2+]i) mediate various cellular function. Although it is known that [Ca2+]i oscillations are susceptible to dysregulation in tumors, the tumor-specific regulators of [Ca2+]i oscillations are poorly characterized. We discovered that CD147 promotes hepatocellular carcinoma (HCC) metastasis and proliferation by enhancing the amplitude and frequency of [Ca2+]i oscillations in HCC cells. CD147 activates two distinct signaling pathways to regulate [Ca2+]i oscillations. By activating FAK-Src-IP3R1 signaling pathway, CD147 promotes Ca2+ release from endoplasmic reticulum (ER) and enhances the amplitude of [Ca2+]i oscillations. Furthermore, CD147 accelerates ER Ca2+ refilling and enhances the frequency of [Ca2+]i oscillations through activating CaMKP-PAK1-PP2A-PLB-SERCA signaling pathway. Besides, CD147-promoted ER Ca2+ release and refilling are tightly regulated by changing [Ca2+]i. CD147 may activate IP3R1 channel under low [Ca2+]i conditions and CD147 may activate SERCA pump under high [Ca2+]i conditions. CD147 deletion suppresses HCC tumorigenesis and increases the survival rate of liver-specific CD147 knockout mice by regulating [Ca2+]i oscillations in vivo. Together, these results reveal that CD147 functions as a critical regulator of ER-dependent [Ca2+]i oscillations to promote oncogenic progression in HCC. PMID:26498680

Functional reconstitution of the mitochondrial Ca2+/H+ antiporter Letm1.

PubMed

Tsai, Ming-Feng; Jiang, Dawei; Zhao, Linlin; Clapham, David; Miller, Christopher

2014-01-01

The leucine zipper, EF hand-containing transmembrane protein 1 (Letm1) gene encodes a mitochondrial inner membrane protein, whose depletion severely perturbs mitochondrial Ca(2+) and K(+) homeostasis. Here we expressed, purified, and reconstituted human Letm1 protein in liposomes. Using Ca(2+) fluorophore and (45)Ca(2+)-based assays, we demonstrate directly that Letm1 is a Ca(2+) transporter, with apparent affinities of cations in the sequence of Ca(2+) ≈ Mn(2+) > Gd(3+) ≈ La(3+) > Sr(2+) > Ba(2+), Mg(2+), K(+), Na(+). Kinetic analysis yields a Letm1 turnover rate of 2 Ca(2+)/s and a Km of ∼25 µM. Further experiments show that Letm1 mediates electroneutral 1 Ca(2+)/2 H(+) antiport. Letm1 is insensitive to ruthenium red, an inhibitor of the mitochondrial calcium uniporter, and CGP-37157, an inhibitor of the mitochondrial Na(+)/Ca(2+) exchanger. Functional properties of Letm1 described here are remarkably similar to those of the H(+)-dependent Ca(2+) transport mechanism identified in intact mitochondria.

CaV1.3 L-type Ca2+ channels modulate depression-like behaviour in mice independent of deaf phenotype.

PubMed

Busquet, Perrine; Nguyen, Ngoc Khoi; Schmid, Eduard; Tanimoto, Naoyuki; Seeliger, Mathias W; Ben-Yosef, Tamar; Mizuno, Fengxia; Akopian, Abram; Striessnig, Jörg; Singewald, Nicolas

2010-05-01

Mounting evidence suggests that voltage-gated L-type Ca2+ channels can modulate affective behaviour. We therefore explored the role of CaV1.3 L-type Ca2+ channels in depression- and anxiety-like behaviours using CaV1.3-deficient mice (CaV1.3-/-). We showed that CaV1.3-/- mice displayed less immobility in the forced swim test as well as in the tail suspension test, indicating an antidepressant-like phenotype. Locomotor activity in the home cage or a novel open-field test was not influenced. In the elevated plus maze (EPM), CaV1.3-/- mice entered the open arms more frequently and spent more time there indicating an anxiolytic-like phenotype which was, however, not supported in the stress-induced hyperthermia test. By performing parallel experiments in Claudin 14 knockout mice (Cldn14-/-), which like CaV1.3-/- mice are congenitally deaf, an influence of deafness on the antidepressant-like phenotype could be ruled out. On the other hand, a similar EPM behaviour indicative of an anxiolytic phenotype was also found in the Cldn14-/- animals. Using electroretinography and visual behavioural tasks we demonstrated that at least in mice, CaV1.3 channels do not significantly contribute to visual function. However, marked morphological changes were revealed in synaptic ribbons in the outer plexiform layer of CaV1.3-/- retinas by immunohistochemistry suggesting a possible role of this channel type in structural plasticity at the ribbon synapse. Taken together, our findings indicate that CaV1.3 L-type Ca2+ channels modulate depression-like behaviour but are not essential for visual function. The findings raise the possibility that selective modulation of CaV1.3 channels could be a promising new therapeutic concept for the treatment of mood disorders.

The inhibitory effects of phenolic Mannich bases on carbonic anhydrase I and II isoenzymes.

PubMed

Yamali, Cem; Tugrak, Mehtap; Gul, Halise Inci; Tanc, Muhammet; Supuran, Claudiu T

2016-12-01

Phenolic mono Mannich bases [2-[4-hydroxy-3-(aminomethyl)benzylidene]-2,3-dihydro-1H-inden-1-one (8-15)] and bis Mannich bases [2-[4-hydroxy-3,5-bis(aminomethyl)benzylidene]-2, 3-dihydro-1H-inden-1-one (2-7)] were synthesized starting from 2-(4-hydroxybenzylidene)-2, 3-dihydro-inden-1-one (1). This study was designed in order to investigate the carbonic anhydrase (CA, EC 4.2.1.1) inhibitory properties of a library of compounds incorporating the phenol functional group. All prepared compounds showed a low inhibition percentages on both human (h) isoforms hCA I and hCA II compared to the reference sulfonamide acetazolamide. Mannich bases 2-15 had lower inhibition percentages than the compound 1 on hCA I and hCA II, except compound 14, which is a Mannich base derivative of dipropylamine, which had a similar inhibitory power as compound 1 on hCA II. All compounds synthesized 1-15 were 1.3-1.9 times more effective on hCA II comparing with the effectivenes of the compounds on hCA I.

Differential Regulation of Multiple Steps in Inositol 1,4,5-Trisphosphate Signaling by Protein Kinase C Shapes Hormone-stimulated Ca2+ Oscillations*

PubMed Central

Bartlett, Paula J.; Metzger, Walson; Gaspers, Lawrence D.; Thomas, Andrew P.

2015-01-01

How Ca2+ oscillations are generated and fine-tuned to yield versatile downstream responses remains to be elucidated. In hepatocytes, G protein-coupled receptor-linked Ca2+ oscillations report signal strength via frequency, whereas Ca2+ spike amplitude and wave velocity remain constant. IP3 uncaging also triggers oscillatory Ca2+ release, but, in contrast to hormones, Ca2+ spike amplitude, width, and wave velocity were dependent on [IP3] and were not perturbed by phospholipase C (PLC) inhibition. These data indicate that oscillations elicited by IP3 uncaging are driven by the biphasic regulation of the IP3 receptor by Ca2+, and, unlike hormone-dependent responses, do not require PLC. Removal of extracellular Ca2+ did not perturb Ca2+ oscillations elicited by IP3 uncaging, indicating that reloading of endoplasmic reticulum stores via plasma membrane Ca2+ influx does not entrain the signal. Activation and inhibition of PKC attenuated hormone-induced Ca2+ oscillations but had no effect on Ca2+ increases induced by uncaging IP3. Importantly, PKC activation and inhibition differentially affected Ca2+ spike frequencies and kinetics. PKC activation amplifies negative feedback loops at the level of G protein-coupled receptor PLC activity and/or IP3 metabolism to attenuate IP3 levels and suppress the generation of Ca2+ oscillations. Inhibition of PKC relieves negative feedback regulation of IP3 accumulation and, thereby, shifts Ca2+ oscillations toward sustained responses or dramatically prolonged spikes. PKC down-regulation attenuates phenylephrine-induced Ca2+ wave velocity, whereas responses to IP3 uncaging are enhanced. The ability to assess Ca2+ responses in the absence of PLC activity indicates that IP3 receptor modulation by PKC regulates Ca2+ release and wave velocity. PMID:26078455

Control of Excitation/Inhibition Balance in a Hippocampal Circuit by Calcium Sensor Protein Regulation of Presynaptic Calcium Channels.

PubMed

Nanou, Evanthia; Lee, Amy; Catterall, William A

2018-05-02

Activity-dependent regulation controls the balance of synaptic excitation to inhibition in neural circuits, and disruption of this regulation impairs learning and memory and causes many neurological disorders. The molecular mechanisms underlying short-term synaptic plasticity are incompletely understood, and their role in inhibitory synapses remains uncertain. Here we show that regulation of voltage-gated calcium (Ca 2+ ) channel type 2.1 (Ca V 2.1) by neuronal Ca 2+ sensor (CaS) proteins controls synaptic plasticity and excitation/inhibition balance in a hippocampal circuit. Prevention of CaS protein regulation by introducing the IM-AA mutation in Ca V 2.1 channels in male and female mice impairs short-term synaptic facilitation at excitatory synapses of CA3 pyramidal neurons onto parvalbumin (PV)-expressing basket cells. In sharp contrast, the IM-AA mutation abolishes rapid synaptic depression in the inhibitory synapses of PV basket cells onto CA1 pyramidal neurons. These results show that CaS protein regulation of facilitation and inactivation of Ca V 2.1 channels controls the direction of short-term plasticity at these two synapses. Deletion of the CaS protein CaBP1/caldendrin also blocks rapid depression at PV-CA1 synapses, implicating its upregulation of inactivation of Ca V 2.1 channels in control of short-term synaptic plasticity at this inhibitory synapse. Studies of local-circuit function revealed reduced inhibition of CA1 pyramidal neurons by the disynaptic pathway from CA3 pyramidal cells via PV basket cells and greatly increased excitation/inhibition ratio of the direct excitatory input versus indirect inhibitory input from CA3 pyramidal neurons to CA1 pyramidal neurons. This striking defect in local-circuit function may contribute to the dramatic impairment of spatial learning and memory in IM-AA mice. SIGNIFICANCE STATEMENT Many forms of short-term synaptic plasticity in neuronal circuits rely on regulation of presynaptic voltage-gated Ca 2+ (Ca V ) channels. Regulation of Ca V 2.1 channels by neuronal calcium sensor (CaS) proteins controls short-term synaptic plasticity. Here we demonstrate a direct link between regulation of Ca V 2.1 channels and short-term synaptic plasticity in native hippocampal excitatory and inhibitory synapses. We also identify CaBP1/caldendrin as the calcium sensor interacting with Ca V 2.1 channels to mediate rapid synaptic depression in the inhibitory hippocampal synapses of parvalbumin-expressing basket cells to CA1 pyramidal cells. Disruption of this regulation causes altered short-term plasticity and impaired balance of hippocampal excitatory to inhibitory circuits. Copyright © 2018 the authors 0270-6474/18/384430-11$15.00/0.

Hypervitaminosis D mediates compensatory Ca2+ hyperabsorption in TRPV5 knockout mice.

PubMed

Renkema, Kirsten Y; Nijenhuis, Tom; van der Eerden, Bram C J; van der Kemp, Annemiete W C M; Weinans, Harrie; van Leeuwen, Johannes P T M; Bindels, René J M; Hoenderop, Joost G J

2005-11-01

Vitamin D plays an important role in Ca(2+) homeostasis by controlling Ca(2+) (re)absorption in intestine, kidney, and bone. The epithelial Ca(2+) channel TRPV5 mediates the Ca(2+) entry step in active Ca(2+) reabsorption. TRPV5 knockout (TRPV5(-/-)) mice show impaired Ca(2+) reabsorption, hypercalciuria, hypervitaminosis D, and intestinal hyperabsorption of Ca(2+). Moreover, these mice demonstrate upregulation of intestinal TRPV6 and calbindin-D(9K) expression compared with wild-type mice. For addressing the role of the observed hypervitaminosis D in the maintenance of Ca(2+) homeostasis and the regulation of expression levels of the Ca(2+) transport proteins in kidney and intestine, TRPV5/25-hydroxyvitamin-D(3)-1alpha-hydroxylase double knockout (TRPV5(-/-)/1alpha-OHase(-/-)) mice, which show undetectable serum 1,25(OH)(2)D(3) levels, were generated. TRPV5(-/-)/1alpha-OHase(-/-) mice displayed a significant hypocalcemia compared with wild-type mice (1.10 +/- 0.02 and 2.54 +/- 0.01 mM, respectively; P < 0.05). mRNA levels of renal calbindin-D(28K) (7 +/- 2%), calbindin-D(9K) (32 +/- 4%), Na(+)/Ca(2+) exchanger (12 +/- 2%), and intestinal TRPV6 (40 +/- 8%) and calbindin-D(9K) (26 +/- 4%) expression levels were decreased compared with wild-type mice. Hyperparathyroidism and rickets were present in TRPV5(-/-)/1alpha-OHase(-/-) mice, more pronounced than observed in single TRPV5 or 1alpha-OHase knockout mice. It is interesting that a renal Ca(2+) leak, as demonstrated in TRPV5(-/-) mice, persisted in TRPV5(-/-)/1alpha-OHase(-/-) mice, but a compensatory upregulation of intestinal Ca(2+) transporters was abolished. In conclusion, the elevation of serum 1,25(OH)(2)D(3) levels in TRPV5(-/-) mice is responsible for the upregulation of intestinal Ca(2+) transporters and Ca(2+) hyperabsorption. Hypervitaminosis D, therefore, is of crucial importance to maintain normocalcemia in impaired Ca(2+) reabsorption in TRPV5(-/-) mice.

The specific GTP requirement for inositol 1,4,5-trisphosphate-induced Ca2+ release from skinned vascular smooth muscle.

PubMed

Saida, K; Twort, C; van Breemen, C

1988-01-01

Exogenous GTP was required for the induction of Ca2+ release from smooth muscle SR by IP3 if endogenous GTP was depleted. NaN3 could function as a partial substitute for GTP as a cofactor for the IP3-induced Ca2+ release from the SR. In contrast to the IP3-induced Ca2+ release, caffeine-induced Ca2+ release from the SR did not require GTP. Pertussis toxin inhibited the IP3-induced Ca2+ release from the SR, whereas it had no effect on caffeine-induced Ca2+ release. These results indicate that in smooth muscle two different Ca2+ release-channels exist in the SR: (a) activated by IP3, and (b) activated by caffeine or Ca2+.

Increased hippocampal CA1 cerebral blood volume in schizophrenia

PubMed Central

Talati, Pratik; Rane, Swati; Kose, Samet; Blackford, Jennifer Urbano; Gore, John; Donahue, Manus J.; Heckers, Stephan

2014-01-01

Hippocampal hyperactivity has been proposed as a biomarker in schizophrenia. However, there is a debate whether the CA1 or the CA2/3 subfield is selectively affected. We studied 15 schizophrenia patients and 15 matched healthy control subjects with 3T steady state, gadolinium-enhanced, absolute cerebral blood volume (CBV) maps, perpendicular to the long axis of the hippocampus. The subfields of the hippocampal formation (subiculum, CA1, CA2/3, and hilus/dentate gyrus) were manually segmented to establish CBV values. Comparing anterior CA1 and CA2/3 CBV between patients and controls revealed a significant subfield-by-diagnosis interaction. This interaction was due to the combined effect of a trend of increased CA1 CBV (p = .06) and non-significantly decreased CA2/3 CBV (p = 0.14) in patients relative to healthy controls. These results support the emerging hypothesis of increased hippocampal activity as a biomarker of schizophrenia and highlight the importance of subfield-level investigations. PMID:25161901

Spontaneous Ca2+ spiking in a vascular smooth muscle cell line is independent of the release of intracellular Ca2+ stores.

PubMed

Byron, K L; Taylor, C W

1993-04-05

Monolayers of fura-2-loaded A7r5 cells, a cell line derived from rat embryonic aorta, generated spontaneous Ca2+ spikes that were synchronized within the cell population. These Ca2+ spikes were abolished by removal of extracellular Ca2+ or addition of nimodipine (50 nM), and their frequency was increased by depolarization with high K+ or by treatment with BAYK 8644 (1 microM), indicating that Ca2+ entry through L-type Ca2+ channels is required for Ca2+ spiking. Several lines of evidence indicate that mobilization of intracellular Ca2+ stores is not necessary for this Ca2+ spiking. 1) Ryanodine (0.1-50 microM) neither stimulated Ca2+ mobilization nor affected Ca2+ spiking; 2) the complex effects of caffeine were mimicked by theophylline, 8-bromo-cyclic adenosine 3':5'-monophosphate (8-bromo-cAMP), and forskolin, suggesting that the caffeine effects may be mediated by cAMP and not by ryanodine receptors; 3) prolonged incubation with thapsigargin (50 nM), which depletes intracellular Ca2+ stores, did not affect the frequency of Ca2+ spiking; 4) Ba2+ or Sr2+ could substitute for Ca2+ in the spike-generating mechanism even when intracellular stores were depleted of Ca2+. Under conditions where the sarcoplasmic reticulum (SR) contained Ca2+, Ba2+ spikes did not cause Ca2+ mobilization. The mechanisms involved in generating spontaneous Ca2+ spiking in A7r5 cells are therefore likely to reside in the sarcolemma and to operate independently of SR Ca2+ uptake and release.

Ca2+ release by inositol-trisphosphorothioate in isolated triads of rabbit skeletal muscle.

PubMed Central

Valdivia, C; Valdivia, H H; Potter, B V; Coronado, R

1990-01-01

The effectiveness of the nonmetabolizable second messenger analogue DL-myo-inositol 1,4,5-trisphosphorothioate (IPS3) described by Cooke, A. M., R. Gigg, and B. V. L. Potter, (1987b. Jour. Chem. Soc. Chem. Commun. 1525-1526.) was examined in triads purified from rabbit skeletal muscle. A Ca2+ electrode uptake-release assay was used to determine the size and sensitivity of the IPS3-releasable pool of Ca2+ in isolated triads. Uptake was initiated by 1 mM MgATP, pCa 5.8, pH 7.5 Release was initiated when the free Ca2+ had lowered to pCa approximately 7. We found that 5-25 microM myo-inositol 1,4,5-trisphosphate (IP3), and separately IPS3, consistently released 5-20% of the Ca2+ pool actively loaded into triads. Single channel recording was used to determine if ryanodine receptor Ca2+ release channels were affected by IPS3 at the same myoplasmic Ca2+ and IPS3 concentrations. Open probability of ryanodine receptor Ca2+ release channels was monitored in triads fused to bilayers over long periods (200 s) in the absence and following addition of 30 microM IPS3 to the same channel. At myoplasmic pCa approximately 7, IPS3 had no effect in the absence of MgATP (Po = 0.0094 +/- 0.001 in control and Po = 0.01 +/- 0.006 after IPS3) and slightly increased activity in the presence of 1 mM MgATP (Po = 0.024 +/- 0.03 in control and Po = 0.05 +/- 0.03 after IPS3). Equally small effects were observed at higher myoplasmic Ca2+. The onset of channel activation by IPS3 or IP3 was slow, on the time scale 20-60 s. We suggest that in isolated triads of rabbit skeletal muscle, IP3-induced release of stored Ca2+ is probably not mediated by the opening of Ca2+ release channels. PMID:2168221

A Store-Operated Ca2+ Influx Pathway in the Bag Cell Neurons of Aplysia

PubMed Central

Kachoei, Babak A.; Knox, Ronald J.; Uthuza, Didier; Levy, Simon; Kaczmarek, Leonard K.; Magoski, Neil S.

2010-01-01

Although store-operated Ca2+ influx has been well-studied in nonneuronal cells, an understanding of its nature in neurons remains poor. In the bag cell neurons of Aplysia californica, prior work has suggested that a Ca2+ entry pathway can be activated by Ca2+ store depletion. Using fura-based imaging of intracellular Ca2+ in cultured bag cell neurons, we now characterize this pathway as store-operated Ca2+ influx. In the absence of extracellular Ca2+, the endoplasmic reticulum Ca2+-ATPase inhibitors, cyclopiazonic acid (CPA) or thapsigargin, depleted intracellular stores and elevated intracellular free Ca2+. With the subsequent addition of extracellular Ca2+, a prominent Ca2+ influx was observed. The ryanodine receptor agonist, chloroethylphenol (CEP), also increased intracellular Ca2+ but did not initiate store-operated Ca2+ influx, despite overlap between CEP- and CPA-sensitive stores. Bafilomycin A, a vesicular H+-ATPase inhibitor, liberated intracellular Ca2+ from acidic stores and attenuated subsequent Ca2+ influx, presumably by replenishing CPA-depleted stores. Store-operated Ca2+ influx was partially blocked by low concentrations of La3+ or BTP2, and strongly inhibited by either 1-[b-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF-96365) or a high concentration of Ni2+. Regarding IP3 receptor blockers, 2-aminoethyldiphenyl borate, but not xestospongin C, prevented store-operated Ca2+ influx. However, jasplakinolide, an actin stabilizer reported to inhibit this pathway in smooth muscle cell lines, was ineffective. The bag cell neurons initiate reproductive behavior through a prolonged afterdischarge associated with intracellular Ca2+ release and neuropeptide secretion. Store-operated Ca2+ influx may serve to replenish stores depleted during the afterdischarge or participate in the release of peptide that triggers behavior. PMID:16885525

Description and crystal structure of albrechtschraufite, MgCa4F2[UO2(CO3)3]2ṡ17-18H2O

NASA Astrophysics Data System (ADS)

Mereiter, Kurt

2013-04-01

Albrechtschraufite, MgCa4F2[UO2(CO3)3]2ṡ17-18H2O, triclinic, space group Pī, a = 13.569(2), b = 13.419(2), c = 11.622(2) Å, α = 115.82(1), β = 107.61(1), γ = 92.84(1)° (structural unit cell, not reduced), V = 1774.6(5) Å3, Z = 2, D c = 2.69 g/cm3 (for 17.5 H2O), is a mineral that was found in small amounts with schröckingerite, NaCa3F[UO2(CO3)3](SO4)ṡ10H2O, on a museum specimen of uranium ore from Joachimsthal (Jáchymov), Czech Republic. The mineral forms small grain-like subhedral crystals (≤ 0.2 mm) that resemble in appearance liebigite, Ca2[UO2(CO3)3]ṡ ~ 11H2O. Colour pale yellow-green, luster vitreous, transparent, pale bluish green fluorescence under ultraviolet light. Optical data: Biaxial negative, nX = 1.511(2), nY = 1.550(2), nZ = 1.566(2), 2 V = 65(1)° ( λ = 589 nm), r < v weak. After qualitative tests had shown the presence of Ca, U, Mg, CO2 and H2O, the chemical formula was determined by a crystal structure analysis based on X-ray four-circle diffractometer data. The structure was later on refined with data from a CCD diffractometer to R1 = 0.0206 and wR2 = 0.0429 for 9,236 independent observed reflections. The crystal structure contains two independent [UO2(CO3)3]4- anions of which one is bonded to two Mg and six Ca while the second is bonded to only one Mg and three Ca. Magnesium forms a MgF2(Ocarbonate)3(H2O) octahedron that is linked via the F atoms with three Ca atoms so as to provide each F atom with a flat pyramidal coordination by one Mg and two Ca. Calcium is 7- and 8-coordinate forming CaFO6, CaF2O2(H2O)4, CaFO3(H2O)4 and CaO2(H2O)6 coordination polyhedra. The crystal structure is built up from MgCa3F2[UO2(CO3)3]ṡ8H2O layers parallel to (001) which are linked by Ca[UO2(CO3)3]ṡ5H2O moieties into a framework of the composition MgCa4F2[UO2(CO3)3]ṡ13H2O. Five additional water molecules are located in voids of the framework and show large displacement parameters. One of the water positions is partly vacant, leading to a total water content of 17-18H2O per formula unit. The MgCa3F2[UO2(CO3)3]ṡ8H2O layers are pseudosymmetric according to plane group symmetry cmm. The remaining constituents do not sustain this pseudosymmetry and make the entire structure truly triclinic. A characteristic paddle-wheel motif Ca[UO2(CO3)3]4Ca relates the structure of albrechtschraufite partly to that of andersonite and two synthetic alkali calcium uranyl tricarbonates.

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

PubMed

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

2008-11-01

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

Regulation of gene expression by dietary Ca2+ in kidneys of 25-hydroxyvitamin D3-1 alpha-hydroxylase knockout mice.

PubMed

Hoenderop, Joost G J; Chon, Helena; Gkika, Dimitra; Bluyssen, Hans A R; Holstege, Frank C P; St-Arnaud, Rene; Braam, Branko; Bindels, Rene J M

2004-02-01

Pseudovitamin D deficiency rickets (PDDR) is an autosomal disease, characterized by undetectable levels of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), rickets and secondary hyperparathyroidism. Mice in which the 25-hydroxyvitamin D3-1 alpha-hydroxylase (1 alpha-OHase) gene was inactivated, presented the same clinical phenotype as patients with PDDR. cDNA Microarray technology was used on kidneys of 1 alpha-OHase knockout mice to study the expression profile of renal genes in this Ca2+-related disorder. Genome wide molecular events that occur during the rescue of these mice by high dietary Ca2+ intake were studied by the use of 15K cDNA microarray chips. 1 alpha-OHase knockout mice fed a normal Ca2+ diet developed severe hypocalcemia, rickets and died with an average life span of 12 +/- 2 weeks. Intriguingly, 1 alpha-OHase-/- mice supplemented with an enriched Ca2+ diet were normocalcemic and not significantly different from wild-type mice. Inactivation of the 1 alpha-OHase gene resulted in a significant regulation of +/- 1000 genes, whereas dietary Ca2+ supplementation of the 1 alpha-OHase-/- mice revealed +/- 2000 controlled genes. Interestingly, 557 transcripts were regulated in both situations implicating the involvement in the dietary Ca2+-mediated rescue mechanism of the 1 alpha-OHase-/- mice. Conspicuous regulated genes encoded for signaling molecules like the PDZ-domain containing protein channel interacting protein, FK binding protein type 4, kinases, and importantly Ca2+ transporting proteins including the Na+-Ca2+ exchanger, calbindin-D28K and the Ca2+ sensor calmodulin. Dietary Ca2+ intake normalized disturbances in the Ca2+ homeostasis due to vitamin D deficiency that were accompanied by the regulation of a subset of renal genes, including well-known renal Ca2+ transport protein genes, but also genes not previously identified as playing a role in renal Ca2+ handling.

Phase equilibria and crystal chemistry of the CaO-1/2 >Nd2O3-CoOz system at 885 °C in air

NASA Astrophysics Data System (ADS)

Wong-Ng, W.; Laws, W.; Talley, K. R.; Huang, Q.; Yan, Y.; Martin, J.; Kaduk, J. A.

2014-07-01

The phase diagram of the CaO-1/2 >Nd2O3-CoOz system at 885 °C in air has been determined. The system consists of two calcium cobaltate compounds that have promising thermoelectric properties, namely, the 2D thermoelectric oxide solid solution, (Ca3-xNdx)Co4O9-z (0≤x≤0.5), which has a misfit layered structure, and Ca3Co2O6 which consists of 1D chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Nd on the Ca site. The reported Nd2CoO4 phase was not observed at 885 °C. A ternary (Ca1-xNd1+x)CoO4-z (x=0) phase, or (CaNdCo)O4-z, was found to be stable at this temperature. A solid solution region of distorted perovskite (Nd1-xCax)CoO3-z (0≤x≤0.25, space group Pnma) was established. In the peripheral binary systems, while a solid solution region was identified for (Nd1-xCax)2O3-z (0≤x≤0.2), Nd was not found to substitute in the Ca site of CaO. Six solid solution tie-line regions and six three-phase regions were determined in the CaO-Nd2O3-CoOz system in air.

Arachidonate-Regulated Ca2+ Influx in Human Airway Smooth Muscle

PubMed Central

Thompson, Michael A.; Prakash, Y. S.

2014-01-01

Plasma membrane Ca2+ influx, especially store-operated Ca2+ entry triggered by sarcoplasmic reticulum (SR) Ca2+ release, is a key component of intracellular calcium concentration ([Ca2+]i) regulation in airway smooth muscle (ASM). Agonist-induced Ca2+ oscillations in ASM that involve both influx and SR mechanisms have been previously demonstrated. In nonexcitable cells, [Ca2+]i oscillations involve Ca2+ influx via arachidonic acid (AA) –stimulated channels, which show similarities to store-operated Ca2+ entry, although their molecular identity remains undetermined. Little is known about AA-regulated Ca2+ channels or their regulation in ASM. In enzymatically dissociated human ASM cells loaded with the Ca2+ indicator, fura-2, AA (1–10 μM) triggered [Ca2+]i oscillations that were inhibited by removal of extracellular Ca2+. Other fatty acids, such as the diacylglycerol analog, 1-oleoyl-2-acetyl-SN-glycerol, oleic acid, and palmitic acid (10 μM each), failed to elicit similar [Ca2+]i responses. Preincubation with LaCl3 (1 μM or 1 mM) inhibited AA-induced oscillations. Inhibition of receptor-operated channels (SKF96,365 [10 μM]), lipoxygenase (zileuton [10 μM]), or cyclooxygenase (indomethacin [10 μM]) did not affect oscillation parameters. Inhibition of SR Ca2+ release (ryanodine [10 μM] or inositol 1,4,5-trisphosphate receptor inhibitor, xestospongin C [1 μM]) decreased [Ca2+]i oscillation frequency and amplitude. Small interfering RNA against caveolin-1, stromal interaction molecule 1, or Orai3 (20 nM each) reduced the frequency and amplitude of AA-induced [Ca2+]i oscillations. In ASM cells derived from individuals with asthma, AA increased oscillation amplitude, but not frequency. These results are highly suggestive of a novel AA-mediated Ca2+–regulatory mechanism in human ASM, reminiscent of agonist-induced oscillations. Given the role of AA in ASM intracellular signaling, especially with inflammation, AA-regulated Ca2+ channels could potentially contribute to increased [Ca2+]i in diseases such asthma. PMID:24471656

Microprocessor Realization of a Linear Predictive Vocoder. Appendix C. LPCM Detail Drawings and Layouts

DTIC Science & Technology

1977-02-07

CHG12 1 Dr.%VC 8 DB ILA8 DC1II 29 FTLE: FDS TAPIRWLST Al 1/19/77 16:1~2 H.I.T. LINCOLN LAB3ORATORY 1 DB116 DB16 D11G12 1 DI)V8 DD V,"R DWl 1 DBV16 DBV...5 CD27 CA27 CDC.6 CAC6 "F23 CD25 CA25 CD%.4 CAt4 IN ,7 F2’ C!ൠ CA24 CDV3 CA.^ ELI 11 CI)22 CA23 CP,2 CA,2 1D1.. CA22 CDI CA. 1 "FH𔃼 CD39 CA38 CD17...FC17 FE22 ,26 FC19 UE24 1 ’P27 FC19 F21 1 IP 29 FA V7 EF21 1 !p33* FA10 FF12" I %P32 FG𔄀 EE1 1 IP3 FG ’i^7 EF15 1 ’P 34 FGF12 Ffl2 1 1115FG ’ 1 F12

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.

Czochralski growth of 2 in. Ca3Ta(Ga,Al)3Si2O14 single crystals for piezoelectric applications

NASA Astrophysics Data System (ADS)

Yoshikawa, Akira; Shoji, Yasuhiro; Ohashi, Yuji; Yokota, Yuui; Chani, Valery I.; Kitahara, Masanori; Kudo, Tetsuo; Kamada, Kei; Kurosawa, Shunsuke; Medvedev, Andrey; Kochurikhin, Vladimir

2016-10-01

Growth of 2-in. diameter Al-substituted Ca3TaGa3Si2O14 crystals by Czochralski method is reported. The crystals were grown from the melt of Ca3TaGa1.5Al1.5Si2O14 composition and had langasite structure. No inclusions of secondary phases were detected in these crystals. The Ca3Ta(Ga,Al)3Si2O14 mixed crystals produced using non-substituted Ca3TaGa3Si2O14 seeds were defective. They had cracks and/or poly-crystalline structure. However, those grown on the seed of approximately Ca3TaGa1.5Al1.5Si2O14 composition were defect-free. Phase diagram of the Ca3TaGa3Si2O14-Ca3TaAl3Si2O14 pseudo-binary system and segregation phenomenon are discussed in some details. Homogeneity of the crystals was evaluated by measuring 2D-mapping of leaky surface acoustic wave (LSAW) velocities for Y-cut Ca3TaGa1.5Al1.5Si2O14 substrate. Although some inhomogeneities were observed due to slight variations in chemical composition, the crystal had acceptable homogeneity for applications in acoustic wave devices exhibiting the LSAW velocity variation within ±0.048%.

Parathyroid hormone enhances fluid shear-induced [Ca2+]i signaling in osteoblastic cells through activation of mechanosensitive and voltage-sensitive Ca2+ channels

NASA Technical Reports Server (NTRS)

Ryder, K. D.; Duncan, R. L.

2001-01-01

Osteoblasts respond to both fluid shear and parathyroid hormone (PTH) with a rapid increase in intracellular calcium concentration ([Ca2+]i). Because both stimuli modulate the kinetics of the mechanosensitive cation channel (MSCC), we postulated PTH would enhance the [Ca2+]i response to fluid shear by increasing the sensitivity of MSCCs. After a 3-minute preflow at 1 dyne/cm2, MC3T3-E1 cells were subjected to various levels of shear and changes in [Ca2+]i were assessed using Fura-2. Pretreatment with 50 nM bovine PTH(1-34) [bPTH(1-34)] significantly enhanced the shear magnitude-dependent increase in [Ca2+]i. Gadolinium (Gd3+), an MSCC blocker, significantly inhibited the mean peak [Ca2+]i response to shear and shear + bPTH(1-34). Nifedipine (Nif), an L-type voltage-sensitive Ca2+ channel (VSCC) blocker, also significantly reduced the [Ca2+]i response to shear + bPTH(1-34), but not to shear alone, suggesting VSCC activation plays an interactive role in the action of these stimuli together. Activation of either the protein kinase C (PKC) or protein kinase A (PKA) pathways with specific agonists indicated that PKC activation did not alter the Ca2+ response to shear, whereas PKA activation significantly increased the [Ca2+]i response to lower magnitudes of shear. bPTH(1-34), which activates both pathways, induced the greatest [Ca2+]i response at each level of shear, suggesting an interaction of these pathways in this response. These data indicate that PTH significantly enhances the [Ca2+]i response to shear primarily via PKA modulation of the MSCC and VSCC.

Synthesis and evaluation of new thiadiazole derivatives as potential inhibitors of human carbonic anhydrase isozymes (hCA-I and hCA-II).

PubMed

Altintop, Mehlika Dilek; Ozdemir, Ahmet; Kucukoglu, Kaan; Turan-Zitouni, Gulhan; Nadaroglu, Hayrunnisa; Kaplancikli, Zafer Asim

2015-02-01

2-[[5-(2,4-Difluoro/dichlorophenylamino)-1,3,4-thiadiazol-2-yl]thio] acetophenone derivatives (3a--s) were designed as human carbonic anhydrase isozymes (hCA-I and hCA-II) inhibitors and synthesized. hCA-I and hCA-II were purified from erythrocyte cells by the affinity chromatography. The inhibitory effects of 18 newly synthesized acetophenones on hydratase activity of these isoenzymes were studied in vitro. The average IC50 values of the new compounds for hydratase activity ranged from 0.033 to 0.14 μM for hCA-I and from 0.030 to 0.11 μM for hCA-II. Among the newly synthesized compounds, 2-[[5-(2,4-dichlorophenylamino)-1,3,4-thiadiazol-2-yl]thio]-4'-bromoacetophenone (3n) can be considered as a promising hCA-II inhibitor owing to its selective and potent inhibitory effect on hCA-II.

Disruption of the Gardos channel (KCa3.1) in mice causes subtle erythrocyte macrocytosis and progressive splenomegaly.

PubMed

Grgic, Ivica; Kaistha, Brajesh P; Paschen, Steffen; Kaistha, Anuradha; Busch, Christoph; Si, Han; Köhler, Kernt; Elsässer, Hans-Peter; Hoyer, Joachim; Köhler, Ralf

2009-06-01

Gardos channel, the erythrocyte Ca(2+)-activated K(+) channel (K(Ca)3.1), is considered a major regulator of red blood cell (RBC) volume by mediating efflux of potassium and thus cell dehydration and shrinkage. However, the functional importance of K(Ca)3.1 in RBC in vivo is incompletely understood. Here, we used K(Ca)3.1(-/-)-mice to investigate the consequences of K(Ca)3.1 deficiency for RBC indices, functions, and sequestration. RBCs of K(Ca)3.1(-/-)-mice of all ages were mildly macrocytic but their biconcave appearance being preserved. RBC number, total hemoglobin, and hematocrit were unchanged in the adult K(Ca)3.1(-/-)-mice and increased in the premature K(Ca)3.1(-/-)-mice. Filterability, Ca(2+)-dependent volume decrease and osmotic tolerance of RBCs lacking K(Ca)3.1 were noticeably reduced when compared to RBC of wild-type littermates. Deformability to increasing shear stress was unchanged. Strikingly, K(Ca)3.1(-/-)-mice developed progressive splenomegaly which was considerable ( approximately 200% of controls) in the >6-month-old mice and was paralleled by increased iron deposition in the aged mice presumably as a consequence of enhanced RBC sequestration. Daily injections of the K(Ca)3.1-blocker TRAM-34 (120 mg/kg) also produced mild splenomegaly in wild-type mice. We conclude that genetic deficit of erythroid K(Ca)3.1 causes mild RBC macrocytosis, presumably leading to reduced filterability, and impairs volume regulation. These RBC defects result in mild but progressive splenomegaly.

Suppression of Sleep Spindle Rhythmogenesis in Mice with Deletion of CaV3.2 and CaV3.3 T-type Ca2+ Channels

PubMed Central

Pellegrini, Chiara; Lecci, Sandro; Lüthi, Anita; Astori, Simone

2016-01-01

Study Objectives: Low-threshold voltage-gated T-type Ca2+ channels (T-channels or CaV3 channels) sustain oscillatory discharges of thalamocortical (TC) and nucleus Reticularis thalami (nRt) cells. The CaV3.3 subtype dominates nRt rhythmic bursting and mediates a substantial fraction of spindle power in the NREM sleep EEG. CaV3.2 channels are also found in nRt, but whether these contribute to nRt-dependent spindle generation is unexplored. We investigated thalamic rhythmogenesis in mice lacking this subtype in isolation (CaV3.2KO mice) or in concomitance with CaV3.3 deletion (CaV3.double-knockout (DKO) mice). Methods: We examined discharge characteristics of thalamic cells and intrathalamic evoked synaptic transmission in brain slices from wild-type, CaV3.2KO and CaV3.DKO mice through patch-clamp recordings. The sleep profile of freely behaving CaV3.2KO and CaV3.DKO mice was assessed by polysomnographic recordings. Results: CaV3.2 channel deficiency left nRt discharge properties largely unaltered, but additional deletion of CaV3.3 channels fully abolished low-threshold whole-cell Ca2+ currents and bursting, and suppressed burst-mediated inhibitory responses in TC cells. CaV3.DKO mice had more fragmented sleep, with shorter NREM sleep episodes and more frequent microarousals. The NREM sleep EEG power spectrum displayed a relative suppression of the σ frequency band (10–15 Hz), which was accompanied by an increase in the δ band (1–4 Hz). Conclusions: Consistent with previous findings, CaV3.3 channels dominate nRt rhythmogenesis, but the lack of CaV3.2 channels further aggravates neuronal, synaptic, and EEG deficits. Therefore, CaV3.2 channels can boost intrathalamic synaptic transmission, and might play a modulatory role adjusting the relative presence of NREM sleep EEG rhythms. Citation: Pellegrini C, Lecci S, Lüthi A, Astori S. Suppression of sleep spindle rhythmogenesis in mice with deletion of Cav3.2 and Cav3.3 T-type Ca2+ channels. SLEEP 2016;39(4):875–885. PMID:26612388

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

Chronic High Fructose Intake Reduces Serum 1,25 (OH)2D3 Levels in Calcium-Sufficient Rodents

PubMed Central

Douard, Veronique; Patel, Chirag; Lee, Jacklyn; Tharabenjasin, Phuntila; Williams, Edek; Fritton, J. Christopher; Sabbagh, Yves; Ferraris, Ronaldo P.

2014-01-01

Excessive fructose consumption inhibits adaptive increases in intestinal Ca2+ transport in lactating and weanling rats with increased Ca2+ requirements by preventing the increase in serum levels of 1,25(OH)2D3. Here we tested the hypothesis that chronic fructose intake decreases 1,25(OH)2D3 levels independent of increases in Ca2+ requirements. Adult mice fed for five wk a high glucose-low Ca2+ diet displayed expected compensatory increases in intestinal and renal Ca2+ transporter expression and activity, in renal CYP27B1 (coding for 1α-hydroxylase) expression as well as in serum 1,25(OH)2D3 levels, compared with mice fed isocaloric glucose- or fructose-normal Ca2+ diets. Replacing glucose with fructose prevented these increases in Ca2+ transporter, CYP27B1, and 1,25(OH)2D3 levels induced by a low Ca2+ diet. In adult mice fed for three mo a normal Ca2+ diet, renal expression of CYP27B1 and of CYP24A1 (24-hydroxylase) decreased and increased, respectively, when the carbohydrate source was fructose instead of glucose or starch. Intestinal and renal Ca2+ transporter activity and expression did not vary with dietary carbohydrate. To determine the time course of fructose effects, a high fructose or glucose diet with normal Ca2+ levels was fed to adult rats for three mo. Serum levels of 1,25(OH)2D3 decreased and of FGF23 increased significantly over time. Renal expression of CYP27B1 and serum levels of 1,25(OH)2D3 still decreased in fructose- compared to those in glucose-fed rats after three mo. Serum parathyroid hormone, Ca2+ and phosphate levels were normal and independent of dietary sugar as well as time of feeding. Thus, chronically high fructose intakes can decrease serum levels of 1,25(OH)2D3 in adult rodents experiencing no Ca2+ stress and fed sufficient levels of dietary Ca2+. This finding is highly significant because fructose constitutes a substantial portion of the average diet of Americans already deficient in vitamin D. PMID:24718641

Structural Diversities in Heterometallic Mn-Ca Cluster Chemistry from the Use of Salicylhydroxamic Acid: {MnIII4Ca2}, {MnII/III6Ca2}, {MnIII/IV8Ca}, and {MnIII8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex.

PubMed

Alaimo, Alysha A; Koumousi, Evangelia S; Cunha-Silva, Luís; McCormick, Laura J; Teat, Simon J; Psycharis, Vassilis; Raptopoulou, Catherine P; Mukherjee, Shreya; Li, Chaoran; Gupta, Sayak Das; Escuer, Albert; Christou, George; Stamatatos, Theocharis C

2017-09-05

One-pot reactions between the [Mn 3 O(O 2 CPh) 6 (py) x ] +/0 triangular precursors and either CaBr 2 ·xH 2 O or CaCl 2 ·6H 2 O, in the presence of salicylhydroxamic acid (shaH 2 ), have afforded the heterometallic complexes [Mn III 4 Ca 2 (O 2 CPh) 4 (shi) 4 (H 2 O) 3 (Me 2 CO)] (1) and (pyH)[Mn II 2 Mn III 4 Ca 2 Cl 2 (O 2 CPh) 7 (shi) 4 (py) 4 ] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO 3 ) 2 ·4H 2 O/Ca(NO 3 ) 2 ·4H 2 O and Mn(O 2 CPh) 2 ·2H 2 O/Ca(ClO 4 ) 2 ·4H 2 O "metal blends" and shaH 2 , in the presence of external base NEt 3 , led to the new complexes (NHEt 3 ) 2 [Mn III 4 Mn IV 4 Ca(OEt) 2 (shi) 10 (EtOH) 2 ] (3) and (NHEt 3 ) 4 [Mn III 8 Ca 2 (CO 3 ) 4 (shi) 8 ] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi 3- ), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH 2 , was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a Mn 4 Ca 2 octahedron bound to an additional Mn 2 unit, 3 consists of a Mn 8 "ring" surrounding a Ca II atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two Ca II atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

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

PubMed

Mead, Robert N; Mountjoy, Gavin

2006-07-27

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

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

PubMed Central

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

1996-01-01

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

Evaluation of serum CA27.29, CA15-3 and CEA in patients with breast cancer.

PubMed

Hou, M F; Chen, Y L; Tseng, T F; Lin, C M; Chen, M S; Huang, C J; Huang, Y S; Hsieh, J S; Huang, T J; Jong, S B; Huang, Y F

1999-09-01

The Truquant BR radioimmunoassay (RIA) using monoclonal antibody BR 27.29 to recognize a peptide sequence on the MUC-1 gene product for quantification of the CA 27.29 antigen in serum was used in this report to evaluate in 145 patients with breast cancer and compared the other conventional serum markers such as CA15-3 and CEA. The upper limit of normal (25 u/ml) was determined from CA27.29 values 12.4 +/- 4.1 u/ml (mean +/- 3 S.D.) for 112 female subjects apparently free of disease. The CA15-3 levels above 25 u/ml and CEA levels above 5 ng/ml were considered positive values. Thirty-seven cases of 145 patients studied had elevated CA 27.29 levels (sensitivity: 25.5%), 35 of 145 had positive CA15-3 levels (sensitivity 24.1%) and 27 of 145 patients had positive CEA levels (sensitivity: 18.6%) (p < 0.05). One hundred and ten cases of the breast cancer patients (75.8%) did not have metastatic disease. In this group CA 27.29 sensitivity was 6.4%, while CA15-3 sensitivity was 5.5% and CEA sensitivity was 4.5% (p > 0.05). Mean values were 10.2 +/- 9.2 u/ml for CA 27.29, 14.1 +/- 5.6 u/ml for CA 15-3 and 1.7 +/- 1.5 ng/ml for CEA. Thirty-five patients (24.2%) had metastatic disease. In this group CA 27.29 sensitivity was 85.7%, CA15-3 sensitivity was 82.8% and CEA sensitivity was 62.8% (p < 0.05). Mean values for CA27.29 was 152.6 +/- 131.6 u/ml, CA15-3 was 123.1 +/- 107.6 u/ml and 21.8 +/- 36.9 ng/ml of CEA. With regard to the correlation of three tumor markers with clinical stages, patients had significantly higher levels of CA27.29 than CEA, but they were similar to CA 15-3 in metastatic breast cancer. These results suggest CA27.29 to be more sensitive and specific than CEA, but that it is similar to CA15-3 for metastatic breast cancer detection and monitoring.

Multiple effects of ryanodine on intracellular free Ca2+ in smooth muscle cells from bovine and porcine coronary artery: modulation of sarcoplasmic reticulum function.

PubMed

Wagner-Mann, C; Hu, Q; Sturek, M

1992-04-01

1. The effects of ryanodine and caffeine on intracellular free Ca2+ concentration ([Ca2+]i) were studied by use of fura-2 microfluorometry in single smooth muscle cells freshly dispersed from bovine and porcine coronary artery. 2. Bovine and porcine cells demonstrated similar sensitivities to 10 min of exposure to ryanodine in physiological salt solution (PSS), as determined by comparable dose-dependent decreases in the subsequent [Ca2+]i transient induced by 5 mM caffeine. 3. Ryanodine (10 microM) caused a significant increase in [Ca2+]i to a plateau level 27 +/- 3% and 38 +/- 4% above baseline [Ca2+]i (baseline [Ca2+]i = [Ca2+]i at 0 min) in porcine and bovine cells, respectively, when bathed in PSS. In bovine cells the time required to reach 1/2 the plateau level was only 3 min versus 6 min for porcine cells. 4. The ryanodine-induced plateau increase in [Ca2+]i was 35 +/- 5% above baseline for bovine cells bathed in 0 Ca PSS (PSS including 10 microM EGTA with no added Ca2+), but only 7 +/- 3% above baseline in porcine cells during 10 min exposure to 10 microM ryanodine. In bovine cells [Ca2+]i showed proportional increases when extracellular Ca2+ was increased from the normal 2 mM Ca2+ PSS to 5 and 10 mM. 5. Cells pretreated with caffeine in 0 Ca PSS, which depleted the caffeine-sensitive sarcoplasmic reticulum Ca2+ store, showed no increase in [Ca2+]i when challenged with 10 microM ryanodine. The ryanodine-associated increase in [Ca2+]i, which was sustained in 0 Ca PSS during the 10 min ryanodine exposure in cells not pretreated with caffeine, suggests that ryanodine releases Ca2+ from the sarcoplasmic reticulum, but also inhibits Ca2+ efflux.6. Intracellular free Ba2+ ([Ba24],) was measured with fura-2 microfluorometry to define further the Ca2" efflux pathway inhibited by ryanodine; specifically, Ba2+ is not transported by the Ca2" pump, but will substitute for Ca2" in Na+-Ca24 exchange. In porcine cells pretreated with caffeine in 0 Ca PSS to deplete the caffeine-sensitive sarcoplasmic reticulum Ca2+ store, depolarization with 80 mM K4 in 2 mM external Ba24 caused a 100 +/- 6% increase in fura-2 fluorescence ([Ba2+]j). During the 17.5 min 0 Ca PSS recovery from depolarization, exposure to 10 microM ryanodine inhibited the removal of [Ba24]i by 69 + 3% when compared with control (0 Ca PSS without ryanodine).7. It was concluded that in bovine and porcine smooth muscle cells: (a) ryanodine (> 10 microM) releases Ca24 from the sarcoplasmic reticulum; (b) ryanodine ( 10O microM) decreases Ca24 efflux, probably by inhibition of Na+-Ca2+ exchange; (c) the sarcoplasmic reticulum Ca24 store may be larger in bovine than in porcine smooth muscle cells; thus, porcine cells have a relatively greater reliance on Ca24 influx to increase [Ca2+]i.

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.

Sarcoplasmic reticulum calcium release compared in slow-twitch and fast-twitch fibres of mouse muscle.

PubMed

Baylor, S M; Hollingworth, S

2003-08-15

Experiments were carried out to compare the amplitude and time course of Ca2+ release from the sarcoplasmic reticulum (SR) in intact slow-twitch and fast-twitch mouse fibres. Individual fibres within small bundles were injected with furaptra, a low-affinity, rapidly responding Ca2+ indicator. In response to a single action potential at 16 degrees C, the peak amplitude and half-duration of the change in myoplasmic free [Ca2+] (Delta[Ca2+]) differed significantly between fibre types (slow-twitch: peak amplitude, 9.4 +/- 1.0 microM (mean +/- S.E.M.); half-duration, 7.7 +/- 0.6 ms; fast-twitch: peak amplitude 18.5 +/- 0.5 microM; half-duration, 4.9 +/- 0.3 ms). SR Ca2+ release was estimated from Delta[Ca2+] with a computational model that calculated Ca2+ binding to the major myoplasmic Ca2+ buffers (troponin, ATP and parvalbumin); buffer concentrations and reaction rate constants were adjusted to reflect fibre-type differences. In response to an action potential, the total concentration of released Ca2+ (Delta[CaT]) and the peak rate of Ca2+ release ((d/dt)Delta[CaT]) differed about 3-fold between the fibre types (slow-twitch: Delta[CaT], 127 +/- 7 microM; (d/dt)Delta[CaT], 70 +/- 6 microM ms-1; fast-twitch: Delta[CaT], 346 +/- 6 microM; (d/dt)Delta[CaT], 212 +/- 4 microM ms-1). In contrast, the half-duration of (d/dt)Delta[CaT] was very similar in the two fibre types (slow-twitch, 1.8 +/- 0.1 ms; fast-twitch, 1.6 +/- 0.0 ms). When fibres were stimulated with a 5-shock train at 67 Hz, the peaks of (d/dt)Delta[CaT] in response to the second and subsequent shocks were much smaller than that due to the first shock; the later peaks, expressed as a fraction of the amplitude of the first peak, were similar in the two fibre types (slow-twitch, 0.2-0.3; fast-twitch, 0.1-0.3). The results support the conclusion that individual SR Ca2+ release units function similarly in slow-twitch and fast-twitch mammalian fibres.

Spectrum and Prevalence of CALM1-, CALM2-, and CALM3-Encoded Calmodulin (CaM) Variants in Long QT Syndrome (LQTS) and Functional Characterization of a Novel LQTS-Associated CaM Missense Variant, E141G

PubMed Central

Calvert, Melissa L.; Tester, David J.; Kryshtal, Dmytro; Hwang, Hyun Seok; Johnson, Christopher N.; Chazin, Walter J.; Loporcaro, Christina G.; Shah, Maully; Papez, Andrew L.; Lau, Yung R.; Kanter, Ronald; Knollmann, Bjorn C.; Ackerman, Michael J.

2016-01-01

Background Calmodulin (CaM) is encoded by three genes, CALM1, CALM2, and CALM3, all of which harbor pathogenic variants linked to long QT syndrome (LQTS) with early and severe expressivity. These LQTS-causative variants reduce CaM affinity to Ca2+ and alter the properties of the cardiac L-type calcium channel (CaV1.2). CaM also modulates NaV1.5 and the ryanodine receptor, RyR2. All of these interactions may play a role in disease pathogenesis. Here, we determine the spectrum and prevalence of pathogenic CaM variants in a cohort of genetically elusive LQTS, and functionally characterize the novel variants. Methods and Results Thirty-nine genetically elusive LQTS cases underwent whole exome sequencing to identify CaM variants. Non-synonymous CaM variants were overrepresented significantly in this heretofore LQTS cohort (15.4%) compared to exome aggregation consortium (0.04%; p<0.0001). When the clinical sequelae of these 6 CaM-positive cases was compared to the 33 CaM-negative cases, CaM-positive cases had a more severe phenotype with an average age of onset of 8 months, an average QTc of 679 ms, and a high prevalence of cardiac arrest. Functional characterization of one novel variant, E141G-CaM, revealed an 11-fold reduction in Ca2+ binding affinity and a functionally-dominant loss of inactivation in CaV1.2, mild accentuation in NaV1.5 late current, but no effect on intracellular RyR2-mediated calcium release. Conclusions Overall, 15% of our genetically elusive LQTS cohort harbored non-synonymous variants in CaM. Genetic testing of CALM1-3 should be pursued for individuals with LQTS, especially those with early childhood cardiac arrest, extreme QT prolongation, and a negative family history. PMID:26969752

The investigation of minoxidil-induced [Ca2+]i rises and non-Ca2+-triggered cell death in PC3 human prostate cancer cells.

PubMed

Chen, I-Shu; Chou, Chiang-Ting; Liu, Yuan-Yuarn; Yu, Chia-Cheng; Liang, Wei-Zhe; Kuo, Chun-Chi; Shieh, Pochuen; Kuo, Daih-Huang; Chen, Fu-An; Jan, Chung-Ren

2017-02-01

Minoxidil is clinically used to prevent hair loss. However, its effect on Ca 2+ homeostasis in prostate cancer cells is unclear. This study explored the effect of minoxidil on cytosolic-free Ca 2+ levels ([Ca 2+ ] i ) and cell viability in PC3 human prostate cancer cells. Minoxidil at concentrations between 200 and 800 μM evoked [Ca 2+ ] i rises in a concentration-dependent manner. This Ca 2+ signal was inhibited by 60% by removal of extracellular Ca 2+ . Minoxidil-induced Ca 2+ influx was confirmed by Mn 2+ -induced quench of fura-2 fluorescence. Pre-treatment with the protein kinase C (PKC) inhibitor GF109203X, PKC activator phorbol 12-myristate 13 acetate (PMA), nifedipine and SKF96365 inhibited minoxidil-induced Ca 2+ signal in Ca 2+ containing medium by 60%. Treatment with the endoplasmic reticulum Ca 2+ pump inhibitor 2,5-ditert-butylhydroquinone (BHQ) in Ca 2+ -free medium abolished minoxidil-induced [Ca 2+ ] i rises. Conversely, treatment with minoxidil abolished BHQ-induced [Ca 2+ ] i rises. Inhibition of phospholipase C (PLC) with U73122 abolished minoxidil-evoked [Ca 2+ ] i rises. Overnight treatment with minoxidil killed cells at concentrations of 200-600 μM in a concentration-dependent fashion. Chelation of cytosolic Ca 2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM (BAPTA/AM) did not prevent minoxidil's cytotoxicity. Together, in PC3 cells, minoxidil induced [Ca 2+ ] i rises that involved Ca 2+ entry through PKC-regulated store-operated Ca 2+ channels and PLC-dependent Ca 2+ release from the endoplasmic reticulum. Minoxidil-induced cytotoxicity in a Ca 2+ -independent manner.

Functional comparison of the reverse mode of Na+/Ca2+ exchangers NCX1.1 and NCX1.5 expressed in CHO cells.

PubMed

Long, Yan; Wang, Wei-ping; Yuan, Hui; Ma, Shi-ping; Feng, Nan; Wang, Ling; Wang, Xiao-liang

2013-05-01

To investigate the reverse mode function of Na(+)/Ca(2+) exchangers NCX1.1 and NCX1.5 expressed in CHO cells as well as their modulations by PKC and PKA. CHO-K1 cells were transfected with pcDNA3.1 (+) plasmid carrying cDNA of rat cardiac NCX1.1 and brain NCX1.5. The expression of NCX1.1 and NCX1.5 was examined using Western blot analysis. The intracellular Ca(2+) level ([Ca(2+)]i) was measured using Ca(2+) imaging. Whole-cell NCX currents were recorded using patch-clamp technique. Reverse mode NCX activity was elicited by perfusion with Na(+)-free medium. Ca(2+) paradox was induced by Ca(2+)-free EBSS medium, followed by Ca(2+)-containing solution (1.8 or 3.8 mmol/L CaCl2). The protein levels of NCX1.1 and NCX1.5 expressed in CHO cells had no significant difference. The reverse modes of NCX1.1 and NCX1.5 in CHO cells exhibited a transient increase of [Ca(2+)]i, which was followed by a Ca(2+) level plateau at higher external Ca(2+) concentrations. In contrast, the wild type CHO cells showed a steady increase of [Ca(2+)]i at higher external Ca(2+) concentrations. The PKC activator PMA (0.3-10 μmol/L) and PKA activator 8-Br-cAMP (10-100 μmol/L) significantly enhanced the reverse mode activity of NCX1.1 and NCX1.5 in CHO cells. NCX1.1 was 2.4-fold more sensitive to PKC activation than NCX1.5, whereas the sensitivity of the two NCX isoforms to PKA activation had no difference. Both PKC- and PKA-enhanced NCX reverse mode activities in CHO cells were suppressed by NCX inhibitor KB-R7943 (30 μmol/L). Both NCX1.1 and NCX1.5 are functional in regulating and maintaining stable [Ca(2+)]i in CHO cells and differentially regulated by PKA and PKC. The two NCX isoforms might be useful drug targets for heart and brain protection.

Functional roles and efficiencies of the thioredoxin boxes of calcium-binding proteins 1 and 2 in protein folding.

PubMed Central

Kramer, B; Ferrari, D M; Klappa, P; Pöhlmann, N; Söling, H D

2001-01-01

The rat luminal endoplasmic-recticulum calcium-binding proteins 1 and 2 (CaBP1 and CaBP2 respectively) are members of the protein disulphide-isomerase (PDI) family. They contain two and three thioredoxin boxes (Cys-Gly-His-Cys) respectively and, like PDI, may be involved in the folding of nascent proteins. We demonstrate here that CaBP1, similar to PDI and CaBP2, can complement the lethal phenotype of the disrupted Saccharomyces cerevisiae PDI gene, provided that the natural C-terminal Lys-Asp-Glu-Leu sequence is replaced by His-Asp-Glu-Leu. Both the in vitro RNase AIII-re-activation assays and in vivo pro-(carboxypeptidase Y) processing assays using CaBP1 and CaBP2 thioredoxin (trx)-box mutants revealed that, whereas the three trx boxes in CaBP2 seem to be functionally equivalent, the first trx box of CaBP1 is significantly more active than the second trx box. Furthermore, only about 65% re-activation of denatured reduced RNase AIII could be obtained with CaBP1 or CaBP2 compared with PDI, and the yield of PDI-catalysed reactions was significantly reduced in the presence of either CaBP1 or CaBP2. In contrast with PDI, neither CaBP1 nor CaBP2 could catalyse the renaturation of denatured glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is a redox-independent process, and neither protein had any effect on the PDI-catalysed refolding of GAPDH. Furthermore, although PDI can bind peptides via its b' domain, a property it shares with PDIp, the pancreas-specific PDI homologue, and although PDI can bind malfolded proteins such as 'scrambled' ribonuclease, no such interactions could be detected for CaBP2. We conclude that: (1) both CaBP2 and CaBP1 lack peptide-binding activity for GAPDH attributed to the C-terminal region of the a' domain of PDI; (2) CaBP2 lacks the general peptide-binding activity attributed to the b' domain of PDI; (3) interaction of CaBP2 with substrate (RNase AIII) is different from that of PDI and substrate; and (4) both CaBP2 and CaBP1 may promote oxidative folding by different kinetic pathways. PMID:11415439

In vitro and in vivo evaluation of zinc-modified ca-si-based ceramic coating for bone implants.

PubMed

Yu, Jiangming; Li, Kai; Zheng, Xuebin; He, Dannong; Ye, Xiaojian; Wang, Meiyan

2013-01-01

The host response to calcium silicate ceramic coatings is not always favorable because of their high dissolution rates, leading to high pH within the surrounding physiological environment. Recently, a zinc-incorporated calcium silicate-based ceramic Ca2ZnSi2O7 coating, developed on a Ti-6Al-4V substrate using plasma-spray technology, was found to exhibit improved chemical stability and biocompatibility. This study aimed to investigate and compare the in vitro response of osteoblastic MC3T3-E1 cells cultured on Ca2ZnSi2O7 coating, CaSiO3 coating, and uncoated Ti-6Al-4V titanium control at cellular and molecular level. Our results showed Ca2ZnSi2O7 coating enhanced MC3T3-E1 cell attachment, proliferation, and differentiation compared to CaSiO3 coating and control. In addition, Ca2ZnSi2O7 coating increased mRNA levels of osteoblast-related genes (alkaline phosphatase, procollagen α1(I), osteocalcin), insulin-like growth factor-I (IGF-I), and transforming growth factor-β1 (TGF-β1). The in vivo osteoconductive properties of Ca2ZnSi2O7 coating, compared to CaSiO3 coating and control, was investigated using a rabbit femur defect model. Histological and histomorphometrical analysis demonstrated new bone formation in direct contact with the Ca2ZnSi2O7 coating surface in absence of fibrous tissue and higher bone-implant contact rate (BIC) in the Ca2ZnSi2O7 coating group, indicating better biocompatibility and faster osseointegration than CaSiO3 coated and control implants. These results indicate Ca2ZnSi2O7 coated implants have applications in bone tissue regeneration, since they are biocompatible and able to osseointegrate with host bone.

Cav1.2, but not Cav1.3, L-type calcium channel subtype mediates nicotine-induced conditioned place preference in miceo.

PubMed

Liu, Yudan; Harding, Meghan; Dore, Jules; Chen, Xihua

2017-04-03

Nicotine use is one of the most common forms of drug addiction. Although L-type calcium channels (LTCCs) are involved in nicotine addiction, the contribution of the two primary LTCC subtypes (Ca v 1.2 and 1.3) is unknown. This study aims to determine the contribution of these two LTCC subtypes to nicotine-induced conditioned place preference (CPP) responses by using transgenic mouse models that do not express Ca v 1.3 (Ca v 1.3 -/- ) or contain a mutation in the dihydropyridine (DHP) site of the Ca v 1.2 (Ca v 1.2DHP -/- ). We found a hyperbolic dose dependent nicotine (0.1-1mg/kg; 0.5mg/kg optimum) effect on place preference in wild type (WT) mice, that could be prevented by the DHP LTCC blocker nifedipine pretreatment. Similarly, Ca v 1.3 -/- mice showed nicotine-induced place preference which was antagonized by nifedipine. In contrast, nifedipine pretreatment of Ca v 1.2DHP -/- mice had no effect on nicotine-induced CPP responses, suggesting an involvement of Ca v 1.2 subtype in the nicotine-induced CPP response. Nifedipine alone failed to produce either conditioned place aversion or CPP in WT mice. These results collectively indicate Ca v 1.2, but not Ca v 1.3 LTCC subtype regulates, at least in part, the reinforcing effects of nicotine use. Copyright © 2017 Elsevier Inc. All rights reserved.

The synthesis and crystal structure of α-Ca 3UO 6

NASA Astrophysics Data System (ADS)

Holc, J.; Golic̆, L.

1983-07-01

Single crystals of α-Ca 3UO 6 were grown from a UO 3CaCl 2CaO melt by the slow cooling method from 950°C. The crystal structure was determined by means of X-ray diffraction with R = 0.032 and Rw = 0.019. The structure of α-Ca 3UO 6 is of Mg 3TeO 6 type. α-Ca 3UO 6 is rhombohedral with a = 6.729 (1)Å, α = 90.30 (1)°, Z = 2, Dc = 4.955 g/cm 3, Dm = 4.79 g/cm 3, space group R overline3. Uranium and calcium atoms are six-coordinated. At 1200°C rhombohedral α-Ca 3UO 6 irreversibly transforms to monoclinic β-Ca 3UO 6.

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

PubMed Central

1990-01-01

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

Association between domestic water hardness, chlorine, and atopic dermatitis risk in early life: A population-based cross-sectional study.

PubMed

Perkin, Michael R; Craven, Joanna; Logan, Kirsty; Strachan, David; Marrs, Tom; Radulovic, Suzana; Campbell, Linda E; MacCallum, Stephanie F; McLean, W H Irwin; Lack, Gideon; Flohr, Carsten

2016-08-01

Domestic water hardness and chlorine have been suggested as important risk factors for atopic dermatitis (AD). We sought to examine the link between domestic water calcium carbonate (CaCO3) and chlorine concentrations, skin barrier dysfunction (increased transepidermal water loss), and AD in infancy. We recruited 1303 three-month-old infants from the general population and gathered data on domestic water CaCO3 (in milligrams per liter) and chlorine (Cl2; in milligrams per liter) concentrations from local water suppliers. At enrollment, infants were examined for AD and screened for filaggrin (FLG) skin barrier gene mutation status. Transepidermal water loss was measured on unaffected forearm skin. CaCO3 and chlorine levels were strongly correlated. A hybrid variable of greater than and less than median levels of CaCO3 and total chlorine was constructed: a baseline group of low CaCO3/low total chlorine (CaL/ClL), high CaCO3/low total chlorine (CaH/ClL), low CaCO3/high total chlorine (CaL/ClH) and high CaCO3/high total chlorine (CaH/ClH). Visible AD was more common in all 3 groups versus the baseline group: adjusted odds ratio (AOR) of 1.87 (95% CI, 1.25-2.80; P = .002) for the CaH/ClL group, AOR of 1.46 (95% CI, 0.97-2.21; P = .07) for the CaL/ClH, and AOR of 1.61 (95% CI, 1.09-2.38; P = .02) for the CaH/ClH group. The effect estimates were greater in children carrying FLG mutations, but formal interaction testing between water quality groups and filaggrin status was not statistically significant. High domestic water CaCO3 levels are associated with an increased risk of AD in infancy. The influence of increased total chlorine levels remains uncertain. An intervention trial is required to see whether installation of a domestic device to decrease CaCO3 levels around the time of birth can reduce this risk. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Trafficking of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid Receptor (AMPA) Receptor Subunit GluA2 from the Endoplasmic Reticulum Is Stimulated by a Complex Containing Ca2+/Calmodulin-activated Kinase II (CaMKII) and PICK1 Protein and by Release of Ca2+ from Internal Stores*

PubMed Central

Lu, Wei; Khatri, Latika; Ziff, Edward B.

2014-01-01

The GluA2 subunit of the AMPA receptor (AMPAR) dominantly blocks AMPAR Ca2+ permeability, and its trafficking to the synapse regulates AMPAR-dependent synapse Ca2+ permeability. Here we show that GluA2 trafficking from the endoplasmic reticulum (ER) to the plasma membrane of cultured hippocampal neurons requires Ca2+ release from internal stores, the activity of Ca2+/calmodulin activated kinase II (CaMKII), and GluA2 interaction with the PDZ protein, PICK1. We show that upon Ca2+ release from the ER via the IP3 and ryanodine receptors, CaMKII that is activated enters a complex that contains PICK1, dependent upon the PICK1 BAR (Bin-amphiphysin-Rvs) domain, and that interacts with the GluA2 C-terminal domain and stimulates GluA2 ER exit and surface trafficking. This study reveals a novel mechanism of regulation of trafficking of GluA2-containing receptors to the surface under the control of intracellular Ca2+ dynamics and CaMKII activity. PMID:24831007

Crystal structure and physical properties of new Ca{sub 2}TGe{sub 3} (T = Pd and Pt) germanides

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

Klimczuk, T., E-mail: tomasz.klimczuk@pg.gda.pl; Xie, Weiwei; Winiarski, M.J.

The crystallographic, electronic transport and thermal properties of Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3} are reported. The compounds crystalize in an ordered variant of the AlB{sub 2} crystal structure, in space group P6/mmm, with the lattice parameters a = 8.4876(4) Å/8.4503(5) Å and c = 4.1911(3) Å/4.2302(3) Å for Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3}, respectively. The resistivity data exhibit metallic behavior with residual-resistivity-ratios (RRR) of 13 for Ca{sub 2}PdGe{sub 3} and 6.5 for Ca{sub 2}PtGe{sub 3}. No superconducting transition is observed down to 0.4 K. Specific heat studies reveal similar values of the Debye temperatures and Sommerfeldmore » coefficients: Θ{sub D} = 298 K, γ = 4.1 mJ mol{sup −1} K{sup −2} and Θ{sub D} = 305 K, γ = 3.2 mJ mol{sup −1} K{sup −2} for Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3}, respectively. The low value of γ is in agreement with the electronic structure calculations.« less

A molecule-based genetic association approach implicates a range of voltage-gated calcium channels associated with schizophrenia.

PubMed

Li, Wen; Fan, Chun Chieh; Mäki-Marttunen, Tuomo; Thompson, Wesley K; Schork, Andrew J; Bettella, Francesco; Djurovic, Srdjan; Dale, Anders M; Andreassen, Ole A; Wang, Yunpeng

2018-06-01

Traditional genome-wide association studies (GWAS) have successfully detected genetic variants associated with schizophrenia. However, only a small fraction of heritability can be explained. Gene-set/pathway-based methods can overcome limitations arising from single nucleotide polymorphism (SNP)-based analysis, but most of them place constraints on size which may exclude highly specific and functional sets, like macromolecules. Voltage-gated calcium (Ca v ) channels, belonging to macromolecules, are composed of several subunits whose encoding genes are located far away or even on different chromosomes. We combined information about such molecules with GWAS data to investigate how functional channels associated with schizophrenia. We defined a biologically meaningful SNP-set based on channel structure and performed an association study by using a validated method: SNP-set (sequence) kernel association test. We identified eight subtypes of Ca v channels significantly associated with schizophrenia from a subsample of published data (N = 56,605), including the L-type channels (Ca v 1.1, Ca v 1.2, Ca v 1.3), P-/Q-type Ca v 2.1, N-type Ca v 2.2, R-type Ca v 2.3, T-type Ca v 3.1, and Ca v 3.3. Only genes from Ca v 1.2 and Ca v 3.3 have been implicated by the largest GWAS (N = 82,315). Each subtype of Ca v channels showed relatively high chip heritability, proportional to the size of its constituent gene regions. The results suggest that abnormalities of Ca v channels may play an important role in the pathophysiology of schizophrenia and these channels may represent appropriate drug targets for therapeutics. Analyzing subunit-encoding genes of a macromolecule in aggregate is a complementary way to identify more genetic variants of polygenic diseases. This study offers the potential of power for discovery the biological mechanisms of schizophrenia. © 2018 Wiley Periodicals, Inc.

Cellular characteristics of primary and immortal canine embryonic fibroblast cells.

PubMed

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

2004-08-31

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

Functional analysis of the omega-6 fatty acid desaturase (CaFAD2) gene family of the oil seed crop Crambe abyssinica

PubMed Central

2013-01-01

Background Crambe abyssinica produces high erucic acid (C22:1, 55-60%) in the seed oil, which can be further increased by reduction of polyunsaturated fatty acid (PUFA) levels. The omega-6 fatty acid desaturase enzyme (FAD2) is known to be involved in PUFA biosynthesis. In crambe, three CaFAD2 genes, CaFAD2-C1, CaFAD2-C2 and CaFAD2-C3 are expressed. Results The individual effect of each CaFAD2 gene on oil composition was investigated through studying transgenic lines (CaFAD2-RNAi) for differential expression levels in relation to the composition of seed-oil. Six first generation transgenic plants (T1) showed C18:1 increase (by 6% to 10.5%) and PUFA reduction (by 8.6% to 10.2%). The silencing effect in these T1-plants ranged from the moderate silencing (40% to 50% reduction) of all three CaFAD2 genes to strong silencing (95% reduction) of CaFAD2-C3 alone. The progeny of two T1-plants (WG4-4 and WG19-6) was further analysed. Four or five transgene insertions are characterized in the progeny (T2) of WG19-6 in contrast to a single insertion in the T2 progeny of WG4-4. For the individual T2-plants of both families (WG19-6 and WG4-4), seed-specific silencing of CaFAD2-C1 and CaFAD2-C2 was observed in several individual T2-plants but, on average in both families, the level of silencing of these genes was not significant. A significant reduction in expression level (P < 0.01) in both families was only observed for CaFAD2-C3 together with significantly different C18:1 and PUFA levels in oil. Conclusions CaFAD2-C3 expression is highly correlated to levels of C18:1 (r = -0.78) and PUFA (r = 0.75), which suggests that CaFAD2-C3 is the most important one for changing the oil composition of crambe. PMID:24083776

Seawater Mg/Ca controls polymorph mineralogy of microbial CaCO3: a potential proxy for calcite-aragonite seas in Precambrian time.

PubMed

Ries, J B; Anderson, M A; Hill, R T

2008-03-01

A previously published hydrothermal brine-river water mixing model driven by ocean crust production suggests that the molar Mg/Ca ratio of seawater (mMg/Ca(sw)) has varied significantly (approximately 1.0-5.2) over Precambrian time, resulting in six intervals of aragonite-favouring seas (mMg/Ca(sw) > 2) and five intervals of calcite-favouring seas (mMg/Ca(sw) < 2) since the Late Archaean. To evaluate the viability of microbial carbonates as mineralogical proxy for Precambrian calcite-aragonite seas, calcifying microbial marine biofilms were cultured in experimental seawaters formulated over the range of Mg/Ca ratios believed to have characterized Precambrian seawater. Biofilms cultured in experimental aragonite seawater (mMg/Ca(sw) = 5.2) precipitated primarily aragonite with lesser amounts of high-Mg calcite (mMg/Ca(calcite) = 0.16), while biofilms cultured in experimental calcite seawater (mMg/Ca(sw) = 1.5) precipitated exclusively lower magnesian calcite (mMg/Ca(calcite) = 0.06). Furthermore, Mg/Ca(calcite )varied proportionally with Mg/Ca(sw). This nearly abiotic mineralogical response of the biofilm CaCO3 to altered Mg/Ca(sw) is consistent with the assertion that biofilm calcification proceeds more through the elevation of , via metabolic removal of CO2 and/or H+, than through the elevation of Ca2+, which would alter the Mg/Ca ratio of the biofilm's calcifying fluid causing its pattern of CaCO3 polymorph precipitation (aragonite vs. calcite; Mg-incorporation in calcite) to deviate from that of abiotic calcification. If previous assertions are correct that the physicochemical properties of Precambrian seawater were such that Mg/Ca(sw) was the primary variable influencing CaCO3 polymorph mineralogy, then the observed response of the biofilms' CaCO3 polymorph mineralogy to variations in Mg/Ca(sw), combined with the ubiquity of such microbial carbonates in Precambrian strata, suggests that the original polymorph mineralogy and Mg/Ca(calcite )of well-preserved microbial carbonates may be an archive of calcite-aragonite seas throughout Precambrian time. These results invite a systematic evaluation of microbial carbonate primary mineralogy to empirically constrain Precambrian seawater Mg/Ca.

Cytoskeletal actin genes function downstream of HNF-3beta in ascidian notochord development.

PubMed

Jeffery, W R; Ewing, N; Machula, J; Olsen, C L; Swalla, B J

1998-11-01

We have examined the expression and regulation of cytoskeletal actin genes in ascidians with tailed (Molgula oculata) and tailless larvae (Molgula occulta). Four cDNA clones were isolated representing two pairs of orthologous cytoskeletal actin genes (CA1 and CA2), which encode proteins differing by five amino acids in the tailed and tailless species. The CA1 and CA2 genes are present in one or two copies, although several related genes may also be present in both species. Maternal CA1 and CA2 mRNA is present in small oocytes but transcript levels later decline, suggesting a role in early oogenesis. In the tailed species, embryonic CA1 and CA2 mRNAs first appear in the presumptive mesenchyme and muscle cells during gastrulation, subsequently accumulate in the presumptive notochord cells, and can be detected in these tissues through the tadpole stage. CA1 mRNAs accumulate initially in the same tissues in the tailless species but subsequently disappear, in concert with the arrest of notochord and tail development. In contrast, CA2 mRNAs were not detected in embryos of the tailless species. Fertilization of eggs of the tailless species with sperm of the tailed species, which restores the notochord and the tail, also results in the upregulation of CA1 and CA2 gene expression in hybrid embryos. Antisense oligodeoxynucleotide experiments suggest that CA1 and CA2 expression in the notochord, but not in the muscle cells, is dependent on prior expression of Mocc FHI, an ascidian HNF-3beta-like gene. The expression of the CA1 and CA2 genes in the notochord in the tailed species, downregulation in the tailless species, upregulation in interspecific hybrids, and dependence on HNF-3beta activity is consistent with a role of these genes in development of the ascidian notochord.

Multimodality of Ca2+ signaling in rat atrial myocytes.

PubMed

Morad, Martin; Javaheri, Ashkan; Risius, Tim; Belmonte, Steve

2005-06-01

It has been suggested that the multiplicity of Ca(2+) signaling pathways in atrial myocytes may contribute to the variability of its function. This article reports on a novel Ca(2+) signaling cascade initiated by mechanical forces induced by "puffing" of solution onto the myocytes. Ca(i) transients were measured in fura-2 acetoxymethyl (AM) loaded cells using alternating 340- and 410-nm excitation waves at 1.2 kHz. Pressurized puffs of bathing solutions, applied by an electronically controlled micro-barrel system, activated slowly (approximately 300 ms) developing Ca(i) transients that lasted 1,693 +/- 68 ms at room temperature. Subsequent second and third puffs, applied at approximately 20 s intervals activated significantly smaller or no Ca(i) transients. Puff-triggered Ca(i) transients could be reactivated once again following caffeine (10 mM)-induced release of Ca(2+) from sarcoplasmic reticulum (SR). Puff-triggered Ca(i) transients were independent of [Ca(2+)](o), and activation of voltage-gated Ca(2+) or cationic stretch channels or influx of Ca(2+) on Na(+)/Ca(2+)exchanger, because puffing solution containing no Ca(2+), 10 microM diltiazem, 1 mM Cd(2+), 5 mM Ni(2+), or 100 microM Gd(3+) failed to suppress them. Puff-triggered Ca(i) transients were enhanced in paced compared to quiescent myocytes. Electrically activated Ca(i) transients triggered during the time course of puff-induced transients were unaltered, suggesting functionally separate Ca(2+) pools. Contribution of inositol 1,4,5-triphosphate (IP(3))-gated or mitochondrial Ca(2+) pools or modulation of SR stores by nitric oxide/nitric oxide synthase (NO/NOS) signaling were evaluated using 0.5 to 500 microM 2-aminoethoxydiphenyl borate (2-APB) and 0.1 to 1 microM carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP), and 1 mM Nomega-Nitro-L-arginine methyl ester (L-NAME) and 7-nitroindizole, respectively. Only FCCP appeared to significantly suppress the puff-triggered Ca(i) transients. It was concluded that neither Ca(2+) influx nor depolarization was required for activation of this signaling pathway. These studies suggest that pressurized puffs of solutions activate a mechanically sensitive receptor, which signals in turn the release of Ca(2+) from a limited Ca(2+) store of mitochondria. How mechanical forces are sensed and transmitted to mitochondria to induce Ca(2+) release and what role such a Ca(2+) signaling pathway plays in the physiology or pathophysiology of the heart remain to be worked out.

Investigation of properties of the Ca2+ influx and of the Ca2+-activated K+ efflux (Gárdos effect) in vanadate-treated and ATP-depleted human red blood cells.

PubMed

Kaiserová, K; Lakatos, B; Peterajová, E; Orlický, J; Varecka, L'

2002-12-01

In this study the properties of the 45Ca2+ influx in human red blood cells (RBC) induced by NaVO3 or ATP-depletion were compared. Both NaVO3-induced and ATP-depletion-induced 45Ca2+ influxes were in the range 10(-6)-10(-5) mol Ca2+ x l(-1)cells x h(-1). The saturatability of ATP-depletion-induced 45Ca2+ influx with Ca2+ was much less pronounced than that of NaVO3-induced 45Ca2+ influx. The NaVO3-induced Ca2+ influx was sensitive to nifedipine (IC50 = 50 micromol/l) and Cu2+ (IC50 = 9 micromol/l) but these inhibitors had only a marginal effect when ATP-depletion was used as the Ca2+ influx inducer. On the other hand, polymyxin B (PXB) (1-5 mg/ml) strongly stimulated the ATP-depletion-induced 45Ca2+ influx whereas its effect on the NaVO3-induced Ca2+ influx was biphasic, with about 10% stimulation at lower PXB concentrations and an inhibition of 40% at higher concentrations. SDS-PAGE revealed that both NaVO3 and PXB induced changes in the protein phosphorylation pattern in the presence of Ca2+. NaVO3 stimulated the phosphorylation of several proteins and this effect was counteracted by PXB. The comparison of the kinetics and temperature dependencies of the Gárdos effect induced by NaVO3 and the ATP-depletion showed marked differences. The ability of NaVO3 to induce the Gárdos effect dramatically increased in ATP-depleted cells. These findings indicate that the 45Ca2+ influxes preceding the activation of the Ca2+-activated K+ efflux (Gárdos effect) stimulated by NaVO3 and by ATP-depletion, are mediated by different transport pathways. In addition, obtained results demonstrate that ATP-depletion and NaVO3-treatment exert additive action in triggering the Gárdos effect.

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

PubMed Central

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

1981-01-01

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

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.

Ca(2+) regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts

NASA Technical Reports Server (NTRS)

Chen, N. X.; Ryder, K. D.; Pavalko, F. M.; Turner, C. H.; Burr, D. B.; Qiu, J.; Duncan, R. L.

2000-01-01

Osteoblasts subjected to fluid shear increase the expression of the early response gene, c-fos, and the inducible isoform of cyclooxygenase, COX-2, two proteins linked to the anabolic response of bone to mechanical stimulation, in vivo. These increases in gene expression are dependent on shear-induced actin stress fiber formation. Here, we demonstrate that MC3T3-E1 osteoblast-like cells respond to shear with a rapid increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) that we postulate is important to subsequent cellular responses to shear. To test this hypothesis, MC3T3-E1 cells were grown on glass slides coated with fibronectin and subjected to laminar fluid flow (12 dyn/cm(2)). Before application of shear, cells were treated with two Ca(2+) channel inhibitors or various blockers of intracellular Ca(2+) release for 0. 5-1 h. Although gadolinium, a mechanosensitive channel blocker, significantly reduced the [Ca(2+)](i) response, neither gadolinium nor nifedipine, an L-type channel Ca(2+) channel blocker, were able to block shear-induced stress fiber formation and increase in c-fos and COX-2 in MC3T3-E1 cells. However, 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM, an intracellular Ca(2+) chelator, or thapsigargin, which empties intracellular Ca(2+) stores, completely inhibited stress fiber formation and c-fos/COX-2 production in sheared osteoblasts. Neomycin or U-73122 inhibition of phospholipase C, which mediates D-myo-inositol 1,4,5-trisphosphate (IP(3))-induced intracellular Ca(2+) release, also completely suppressed actin reorganization and c-fos/COX-2 production. Pretreatment of MC3T3-E1 cells with U-73343, the inactive isoform of U-73122, did not inhibit these shear-induced responses. These results suggest that IP(3)-mediated intracellular Ca(2+) release is required for modulating flow-induced responses in MC3T3-E1 cells.

Phospholipase C-β1 and β4 Contribute to Non-Genetic Cell-to-Cell Variability in Histamine-Induced Calcium Signals in HeLa Cells

PubMed Central

Ishida, Sachiko; Matsu-ura, Toru; Fukami, Kiyoko; Michikawa, Takayuki; Mikoshiba, Katsuhiko

2014-01-01

A uniform extracellular stimulus triggers cell-specific patterns of Ca2+ signals, even in genetically identical cell populations. However, the underlying mechanism that generates the cell-to-cell variability remains unknown. We monitored cytosolic inositol 1,4,5-trisphosphate (IP3) concentration changes using a fluorescent IP3 sensor in single HeLa cells showing different patterns of histamine-induced Ca2+ oscillations in terms of the time constant of Ca2+ spike amplitude decay and the Ca2+ oscillation frequency. HeLa cells stimulated with histamine exhibited a considerable variation in the temporal pattern of Ca2+ signals and we found that there were cell-specific IP3 dynamics depending on the patterns of Ca2+ signals. RT-PCR and western blot analyses showed that phospholipase C (PLC)-β1, -β3, -β4, -γ1, -δ3 and -ε were expressed at relatively high levels in HeLa cells. Small interfering RNA-mediated silencing of PLC isozymes revealed that PLC-β1 and PLC-β4 were specifically involved in the histamine-induced IP3 increases in HeLa cells. Modulation of IP3 dynamics by knockdown or overexpression of the isozymes PLC-β1 and PLC-β4 resulted in specific changes in the characteristics of Ca2+ oscillations, such as the time constant of the temporal changes in the Ca2+ spike amplitude and the Ca2+ oscillation frequency, within the range of the cell-to-cell variability found in wild-type cell populations. These findings indicate that the heterogeneity in the process of IP3 production, rather than IP3-induced Ca2+ release, can cause cell-to-cell variability in the patterns of Ca2+ signals and that PLC-β1 and PLC-β4 contribute to generate cell-specific Ca2+ signals evoked by G protein-coupled receptor stimulation. PMID:24475116

Effects of oral calcium supplementation on mineral and acid-base status, energy metabolites, and health of postpartum dairy cows.

PubMed

Martinez, N; Sinedino, L D P; Bisinotto, R S; Daetz, R; Lopera, C; Risco, C A; Galvão, K N; Thatcher, W W; Santos, J E P

2016-10-01

Two experiments were conducted to characterize blood concentrations of minerals and acid-base status after oral dosing of Ca salts and to determine the effects of oral Ca on mineral and metabolic status and incidence diseases. The hypotheses were that administration of oral Ca as CaCl2 and CaSO4 maintains blood total Ca (tCa) concentrations ≥2.125 mM and reduces the incidence of diseases in early lactation. In experiment 1, 18 Holstein cows on the day of calving were assigned to receive a single dose of 0, 43, or 86g of Ca as an oral bolus. Blood was sampled before and after treatments to characterize acid-base status and concentrations of minerals. In experiment 2, 450 Holstein cows considered of low (LRM; normal calving) or high risk (HRM; dystocia, twins, stillbirth, retained placenta, vulvo-vaginal laceration, or a combination of these) of metritis (primiparous-LRM=84; primiparous-HRM=84; multiparous-LRM=138; multiparous-HRM=138) on the day of calving were blocked by parity and then randomly assigned to control, no Ca supplementation; 86g of Ca on d 0 and 1 postpartum (CaS1); or 86g of Ca on d 0 and 1 postpartum followed by 43g/d on d 2 to 4 postpartum (CaS4). Blood was sampled before and 30 min after treatment on d 0, and 30 min after treatments on d 1 to 4, and d 7 and 10 for determination of concentrations of minerals and metabolites and blood acid-base responses. Disease incidence was evaluated for the first 30 DIM. Concentrations of ionized Ca (iCa) increased for 2h in cows supplemented with 43g of Ca and fewer than 8h in cows supplemented with 86g of Ca. The changes in iCa concentrations from pretreatment to 30 min after 86g of Ca supplemented on d 0 were 0.11±0.03 mM in multiparous cows and 0.25±0.03 mM in primiparous cows. Oral Ca reduced the incidence of subclinical hypocalcemia (SCH; tCa <2.125mM) in the first 4 d in the experiment (control=69.3%; CaS1=57.5%; CaS4=34.2%). Calcium supplementation decreased the prevalence of SCH on d 0 and 1 postpartum in all cows. Stopping oral Ca in CaS1 on d 1 postpartum, however, caused a rebound in SCH on d 2 to 4 postpartum in primiparous cows. Oral Ca increased the incidence of metritis (control=22.7%; CaS1=34.8%; CaS4=32.8%), primarily because of an increase in LRM primiparous cows (control=17.9%; CaS1=35.7%; CaS4=42.9%). Oral Ca increased morbidity in primiparous cows (control=38.1%; CaS1=61.8%; CaS4=60.3%) but had no effect on multiparous cows (control=38.2%; CaS1=35.1%; CaS4=30.1%). Large doses of oral Ca as salts of chloride and sulfate in the first days postpartum should be avoided in primiparous cows and used only in cows at risk of clinical hypocalcemia. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

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

PubMed Central

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

2012-01-01

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

The system Na2CO3-CaCO3 at 3 GPa

NASA Astrophysics Data System (ADS)

Podborodnikov, Ivan V.; Shatskiy, Anton; Arefiev, Anton V.; Rashchenko, Sergey V.; Chanyshev, Artem D.; Litasov, Konstantin D.

2018-04-01

It was suggested that alkali-alkaline earth carbonates may have a substantial role in petrological processes relevant to metasomatism and melting of the Earth's mantle. Because natrite, Na2CO3, Na-Ca carbonate (shortite and/or nyerereite), and calcite, CaCO3, have been recently reported from xenoliths of shallow mantle (110-115 km) origin, we performed experiments on phase relations in the system Na2CO3-CaCO3 at 3 GPa and 800-1300 °C. We found that the system has one intermediate compound, Na2Ca3(CO3)4, at 800 °C, and two intermediate compounds, Na2Ca(CO3)2 and Na2Ca3(CO3)4, at 850 °C. CaCO3 crystals recovered from experiments at 950 and 1000 °C are aragonite and calcite, respectively. Maximum solid solution of CaCO3 in Na2CO3 is 20 mol% at 850 °C. The Na-carbonate-Na2Ca(CO3)2 eutectic locates near 860 °C and 56 mol% Na2CO3. Na2Ca(CO3)2 melts incongruently near 880 °C to produce Na2Ca3(CO3)4 and a liquid containing about 51 mol% Na2CO3. Na2Ca3(CO3)4 disappears above 1000 °C via incongruent melting to calcite and a liquid containing about 43 mol% Na2CO3. At 1050 °C, the liquid, coexisting with Na-carbonate, contains 87 mol% Na2CO3. Na-carbonate remains solid up to 1150 °C and melts at 1200 °C. The Na2CO3 content in the liquid coexisting with calcite decreases to 15 mol% as temperature increases to 1300 °C. Considering the present and previous data, a range of the intermediate compounds on the liquidus of the Na2CO3-CaCO3 join changes as pressure increases in the following sequence: Na2Ca(CO3)2 (0.1 GPa) → Na2Ca(CO3)2, Na2Ca3(CO3)4 (3 GPa) → Na4Ca(CO3)3, Na2Ca3(CO3)4 (6 GPa). Thus, the Na2Ca(CO3)2 nyerereite stability field extends to the shallow mantle pressures. Consequently, findings of nyerereite among daughter phases in the melt inclusions in olivine from the sheared garnet peridotites are consistent with their mantle origin.

Epigallocatechin-3-gallate increases intracellular [Ca2+] in U87 cells mainly by influx of extracellular Ca2+ and partly by release of intracellular stores.

PubMed

Kim, Hee Jung; Yum, Keun Sang; Sung, Jong-Ho; Rhie, Duck-Joo; Kim, Myung-Jun; Min, Do Sik; Hahn, Sang June; Kim, Myung-Suk; Jo, Yang-Hyeok; Yoon, Shin Hee

2004-02-01

Green tea has been receiving considerable attention as a possible preventive agent against cancer and cardiovascular disease. Epigallocatechin-3-gallate (EGCG) is a major polyphenol component of green tea. Using digital calcium imaging and an assay for [3H]-inositol phosphates, we determined whether EGCG increases intracellular [Ca2+] ([Ca2+]i) in non-excitable human astrocytoma U87 cells. EGCG induced concentration-dependent increases in [Ca2+]i. The EGCG-induced [Ca2+]i increases were reduced to 20.9% of control by removal of extracellular Ca2+. The increases were also inhibited markedly by treatment with the non-specific Ca2+ channel inhibitors cobalt (3 mM) for 3 min and lanthanum (1 mM) for 5 min. The increases were not significantly inhibited by treatment for 10 min with the L-type Ca2+ channel blocker nifedipine (100 nM). Treatment with the inhibitor of endoplasmic reticulum Ca2+-ATPase thapsigargin (1 micro M) also significantly inhibited the EGCG-induced [Ca2+]i increases. Treatment for 15 min with the phospholipase C (PLC) inhibitor neomycin (300 micro M) attenuated the increases significantly, while the tyrosine kinase inhibitor genistein (30 micro M) had no effect. EGCG increased [3H]-inositol phosphates formation via PLC activation. Treatment for 10 min with mefenamic acid (100 micro M) and flufenamic acid (100 micro M), derivatives of diphenylamine-2-carboxylate, blocked the EGCG-induced [Ca2+]i increase in non-treated and thapsigargin-treated cells but indomethacin (100 micro M) did not affect the increases. Collectively, these data suggest that EGCG increases [Ca2+]i in non-excitable U87 cells mainly by eliciting influx of extracellular Ca2+ and partly by mobilizing intracellular Ca2+ stores by PLC activation. The EGCG-induced [Ca2+]i influx is mediated mainly through channels sensitive to diphenylamine-2-carboxylate derivatives.

Immunohistochemical Analysis of Activin Receptor-Like Kinase 1 (ACVRL1/ALK1) Expression in the Rat and Human Hippocampus: Decline in CA3 During Progression of Alzheimer's Disease.

PubMed

Adams, Stephanie L; Benayoun, Laurent; Tilton, Kathy; Mellott, Tiffany J; Seshadri, Sudha; Blusztajn, Jan Krzysztof; Delalle, Ivana

2018-01-01

The pathophysiology of Alzheimer's disease (AD) includes signaling defects mediated by the transforming growth factor β-bone morphogenetic protein-growth and differentiation factor (TGFβ-BMP-GDF) family of proteins. In animal models of AD, administration of BMP9/GDF2 improves memory and reduces amyloidosis. The best characterized type I receptor of BMP9 is ALK1. We characterized ALK1 expression in the hippocampus using immunohistochemistry. In the rat, ALK1 immunoreactivity was found in CA pyramidal neurons, most frequently and robustly in the CA2 and CA3 fields. In addition, there were sporadic ALK1-immunoreactive cells in the stratum oriens, mainly in CA1. The ALK1 expression pattern in human hippocampus was similar to that of rat. Pyramidal neurons within the CA2, CA3, and CA4 were strongly ALK1-immunoreactive in hippocampi of cognitively intact subjects with no neurofibrillary tangles. ALK1 signal was found in the axons of alveus and fimbria, and in the neuropil across CA fields. Relatively strongest ALK1 neuropil signal was observed in CA1 where pyramidal neurons were occasionally ALK1-immunoractive. As in the rat, horizontally oriented neurons in the stratum oriens of CA1 were both ALK1- and GAD67-immunoreactive. Analysis of ALK1 immunoreactivity across stages of AD pathology revealed that disease progression was characterized by overall reduction of the ALK1 signal in CA3 in advanced, but not early, stages of AD. These data suggest that the CA3 pyramidal neurons may remain responsive to the ALK1 ligands, e.g., BMP9, during initial stages of AD and that ALK1 may constitute a therapeutic target in early and moderate AD.

Altered thalamocortical rhythmicity and connectivity in mice lacking CaV3.1 T-type Ca2+ channels in unconsciousness

PubMed Central

Choi, Soonwook; Yu, Eunah; Lee, Seongwon; Llinás, Rodolfo R.

2015-01-01

In unconscious status (e.g., deep sleep and anesthetic unconsciousness) where cognitive functions are not generated there is still a significant level of brain activity present. Indeed, the electrophysiology of the unconscious brain is characterized by well-defined thalamocortical rhythmicity. Here we address the ionic basis for such thalamocortical rhythms during unconsciousness. In particular, we address the role of CaV3.1 T-type Ca2+ channels, which are richly expressed in thalamic neurons. Toward this aim, we examined the electrophysiological and behavioral phenotypes of mice lacking CaV3.1 channels (CaV3.1 knockout) during unconsciousness induced by ketamine or ethanol administration. Our findings indicate that CaV3.1 KO mice displayed attenuated low-frequency oscillations in thalamocortical loops, especially in the 1- to 4-Hz delta band, compared with control mice (CaV3.1 WT). Intriguingly, we also found that CaV3.1 KO mice exhibited augmented high-frequency oscillations during unconsciousness. In a behavioral measure of unconsciousness dynamics, CaV3.1 KO mice took longer to fall into the unconscious state than controls. In addition, such unconscious events had a shorter duration than those of control mice. The thalamocortical interaction level between mediodorsal thalamus and frontal cortex in CaV3.1 KO mice was significantly lower, especially for delta band oscillations, compared with that of CaV3.1 WT mice, during unconsciousness. These results suggest that the CaV3.1 channel is required for the generation of a given set of thalamocortical rhythms during unconsciousness. Further, that thalamocortical resonant neuronal activity supported by this channel is important for the control of vigilance states. PMID:26056284

Altered thalamocortical rhythmicity and connectivity in mice lacking CaV3.1 T-type Ca2+ channels in unconsciousness.

PubMed

Choi, Soonwook; Yu, Eunah; Lee, Seongwon; Llinás, Rodolfo R

2015-06-23

In unconscious status (e.g., deep sleep and anesthetic unconsciousness) where cognitive functions are not generated there is still a significant level of brain activity present. Indeed, the electrophysiology of the unconscious brain is characterized by well-defined thalamocortical rhythmicity. Here we address the ionic basis for such thalamocortical rhythms during unconsciousness. In particular, we address the role of CaV3.1 T-type Ca(2+) channels, which are richly expressed in thalamic neurons. Toward this aim, we examined the electrophysiological and behavioral phenotypes of mice lacking CaV3.1 channels (CaV3.1 knockout) during unconsciousness induced by ketamine or ethanol administration. Our findings indicate that CaV3.1 KO mice displayed attenuated low-frequency oscillations in thalamocortical loops, especially in the 1- to 4-Hz delta band, compared with control mice (CaV3.1 WT). Intriguingly, we also found that CaV3.1 KO mice exhibited augmented high-frequency oscillations during unconsciousness. In a behavioral measure of unconsciousness dynamics, CaV3.1 KO mice took longer to fall into the unconscious state than controls. In addition, such unconscious events had a shorter duration than those of control mice. The thalamocortical interaction level between mediodorsal thalamus and frontal cortex in CaV3.1 KO mice was significantly lower, especially for delta band oscillations, compared with that of CaV3.1 WT mice, during unconsciousness. These results suggest that the CaV3.1 channel is required for the generation of a given set of thalamocortical rhythms during unconsciousness. Further, that thalamocortical resonant neuronal activity supported by this channel is important for the control of vigilance states.

Interrelation between domain structures and polarization switching in hybrid improper ferroelectric Ca3(Mn,Ti)2O7

NASA Astrophysics Data System (ADS)

Gao, Bin; Huang, Fei-Ting; Wang, Yazhong; Kim, Jae-Wook; Wang, Lihai; Lim, Seong-Joon; Cheong, Sang-Wook

2017-05-01

Ca3Mn2O7 and Ca3Ti2O7 have been proposed as the prototypical hybrid improper ferroelectrics (HIFs), and a significant magnetoelectric (ME) coupling in magnetic Ca3Mn2O7 is, in fact, reported theoretically and experimentally. Although the switchability of polarization is confirmed in Ca3Ti2O7 and other non-magnetic HIFs, there is no report of switchable polarization in the isostructural Ca3Mn2O7. We constructed the phase diagram of Ca3Mn2-xTixO7 through our systematic study of a series of single crystalline Ca3Mn2-xTixO7 (x = 0, 0.1, 1, 1.5, and 2). Using transmission electron microscopy, we have unveiled the unique domain structure of Ca3Mn2O7: the high-density 90° stacking of a- and b-domains along the c-axis due to the phase transition through an intermediate Acca phase and the in-plane irregular wavy ferroelastic twin domains. The interrelation between domain structures and physical properties is unprecedented: the stacking along the c-axis prevents the switching of polarization and causes the irregular in-plane ferroelastic domain pattern. In addition, we have determined the magnetic phase diagram and found complex magnetism of Ca3Mn2O7 with isotropic canted moments. These results lead to negligible observable ME coupling in Ca3Mn2O7 and guide us to explore multiferroics with large ME coupling.

Carnosic acid prevents COL1A2 transcription through the reduction of Smad3 acetylation via the AMPKα1/SIRT1 pathway.

PubMed

Zhao, Yan; Shi, Xue; Ding, Chunchun; Feng, Dongcheng; Li, Yang; Hu, Yan; Wang, Li; Gao, Dongyan; Tian, Xiaofeng; Yao, Jihong

2018-01-15

Carnosic acid (CA), a major bioactive component in rosemary extract, has many biological and pharmaceutical activities. Smad3 acetylation can regulate the transcription of type I α2 collagen (COL1A2), which is the major component of the extracellular matrix (ECM). The aim of the current study was to evaluate whether CA inhibits COL1A2 transcription via the reduction of Smad3 acetylation against liver fibrosis. The results showed that CA treatment significantly suppressed COL1A2 transcription and markedly decreased the deposition of ECM induced by dimethylamine (DMN) in rats. Importantly, the suppression of COL1A2 transcription following CA treatment depended on the reduction of Smad3 acetylation via the activation of Sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide + (NAD + )-dependent deacetylase. SIRT1 siRNA increased the acetylation of Smad3 and blocked CA-down-regulated Smad3 deacetylation. Notably, CA-mediated AMP-activated protein kinase-α1 (AMPKα1) activation not only increased AMPKα1 phosphorylation but also increased SIRT1 expression, thus leading to a significant reduction in Smad3 acetylation. Furthermore, CA-mediated SIRT1 activation was inhibited by AMPKα1 siRNA. Collectively, CA can inhibit the transcription of COL1A2 through SIRT1-mediated Smad3 deacetylation, and the activation of SIRT1 by CA involves the AMPKα1/SIRT1 pathway in liver fibrosis. Copyright © 2017 Elsevier Inc. All rights reserved.

CaV 3.1 and CaV 3.3 account for T-type Ca2+ current in GH3 cells.

PubMed

Mudado, M A; Rodrigues, A L; Prado, V F; Beirão, P S L; Cruz, J S

2004-06-01

T-type Ca2+ channels are important for cell signaling by a variety of cells. We report here the electrophysiological and molecular characteristics of the whole-cell Ca2+ current in GH3 clonal pituitary cells. The current inactivation at 0 mV was described by a single exponential function with a time constant of 18.32 +/- 1.87 ms (N = 16). The I-V relationship measured with Ca2+ as a charge carrier was shifted to the left when we applied a conditioning pre-pulse of up to -120 mV, indicating that a low voltage-activated current may be present in GH3 cells. Transient currents were first activated at -50 mV and peaked around -20 mV. The half-maximal voltage activation and the slope factors for the two conditions are -35.02 +/- 2.4 and 6.7 +/- 0.3 mV (pre-pulse of -120 mV, N = 15), and -27.0 +/- 0.97 and 7.5 +/- 0.7 mV (pre-pulse of -40 mV, N = 9). The 8-mV shift in the activation mid-point was statistically significant (P < 0.05). The tail currents decayed bi-exponentially suggesting two different T-type Ca2+ channel populations. RT-PCR revealed the presence of alpha1G (CaV3.1) and alpha1I (CaV3.3) T-type Ca2+ channel mRNA transcripts.

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

PubMed

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

2017-11-26

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

STM/STS study of superconducting properties in Ca10(Pt4As8)(Fe2As2)5

NASA Astrophysics Data System (ADS)

Kim, Jisun; Nam, Hyoungdo; Li, Guorong; Karki, Amar; Shih, Chih-Kang; Zhang, Jiandi; Jin, Rongying; Plummer, E. W.

2014-03-01

Newly discovered iron-based superconductor, Ca10(Pt4As8)(Fe2As2)5 (Tc = 34 K) is studied using scanning tunneling microscopy/spectroscopy (STM/S). Given the symmetry of the crystal structure, several surface terminations are expected with roughly same probability: 1) Ca or partial Ca layer on top Fe2As2; 2) Ca or partial Ca layer on top Pt4As8 layer; 3) A Fe2As2 layer, and; 4) A Pt4As8layer.Surprisingly,Fe2As2 related layers (1 & 3) are rarely observed (less than 1%). Instead, we observe Pt4As8 layers separated by unit-cell-high (~ 1 nm) steps accompanied with Ca or partial Ca layer on top Pt4As8 layer (1 - 2 Å step height). Scanning tunneling spectroscopy reveals different spectra for each surface, with superconducting coherence peaks seen only on Ca layers. We argue that intermediary layers are proximity-coupled to superconducting Fe2As2 layers. The results from Ca10(Pt4As8)(Fe2As2)5 are discussed with the properties observed in other iron-based superconductors. Funded by NSF

Spontaneous Ca(2+) transients in interstitial cells of Cajal located within the deep muscular plexus of the murine small intestine.

PubMed

Baker, Salah A; Drumm, Bernard T; Saur, Dieter; Hennig, Grant W; Ward, Sean M; Sanders, Kenton M

2016-06-15

Interstitial cells of Cajal at the level of the deep muscular plexus (ICC-DMP) in the small intestine generate spontaneous Ca(2+) transients that consist of localized Ca(2+) events and limited propagating Ca(2+) waves. Ca(2+) transients in ICC-DMP display variable characteristics: from discrete, highly localized Ca(2+) transients to regionalized Ca(2+) waves with variable rates of occurrence, amplitude, duration and spatial spread. Ca(2+) transients fired stochastically, with no cellular or multicellular rhythmic activity being observed. No correlation was found between the firing sites in adjacent cells. Ca(2+) transients in ICC-DMP are suppressed by the ongoing release of inhibitory neurotransmitter(s). Functional intracellular Ca(2+) stores are essential for spontaneous Ca(2+) transients, and the sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) pump is necessary for maintenance of spontaneity. Ca(2+) release mechanisms involve both ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP3 Rs). Release from these channels is interdependent. ICC express transcripts of multiple RyRs and InsP3 Rs, with Itpr1 and Ryr2 subtypes displaying the highest expression. Interstitial cells of Cajal in the deep muscular plexus of the small intestine (ICC-DMP) are closely associated with varicosities of enteric motor neurons and generate responses contributing to neural regulation of intestinal motility. Responses of ICC-DMP are mediated by activation of Ca(2+) -activated Cl(-) channels; thus, Ca(2+) signalling is central to the behaviours of these cells. Confocal imaging was used to characterize the nature and mechanisms of Ca(2+) transients in ICC-DMP within intact jejunal muscles expressing a genetically encoded Ca(2+) indicator (GCaMP3) selectively in ICC. ICC-DMP displayed spontaneous Ca(2+) transients that ranged from discrete, localized events to waves that propagated over variable distances. The occurrence of Ca(2+) transients was highly variable, and it was determined that firing was stochastic in nature. Ca(2+) transients were tabulated in multiple cells within fields of view, and no correlation was found between the events in adjacent cells. TTX (1 μm) significantly increased the occurrence of Ca(2+) transients, suggesting that ICC-DMP contributes to the tonic inhibition conveyed by ongoing activity of inhibitory motor neurons. Ca(2+) transients were minimally affected after 12 min in Ca(2+) free solution, indicating these events do not depend immediately upon Ca(2+) influx. However, inhibitors of sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) pump and blockers of inositol triphosphate receptor (InsP3 R) and ryanodine receptor (RyR) channels blocked ICC Ca(2+) transients. These data suggest an interdependence between RyR and InsP3 R in the generation of Ca(2+) transients. Itpr1 and Ryr2 were the dominant transcripts expressed by ICC. These findings provide the first high-resolution recording of the subcellular Ca(2+) dynamics that control the behaviour of ICC-DMP in situ. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Spontaneous Ca2+ transients in interstitial cells of Cajal located within the deep muscular plexus of the murine small intestine

PubMed Central

Baker, Salah A.; Drumm, Bernard T.; Saur, Dieter; Hennig, Grant W.; Ward, Sean M.

2016-01-01

Key points Interstitial cells of Cajal at the level of the deep muscular plexus (ICC‐DMP) in the small intestine generate spontaneous Ca2+ transients that consist of localized Ca2+ events and limited propagating Ca2+ waves.Ca2+ transients in ICC‐DMP display variable characteristics: from discrete, highly localized Ca2+ transients to regionalized Ca2+ waves with variable rates of occurrence, amplitude, duration and spatial spread.Ca2+ transients fired stochastically, with no cellular or multicellular rhythmic activity being observed. No correlation was found between the firing sites in adjacent cells.Ca2+ transients in ICC‐DMP are suppressed by the ongoing release of inhibitory neurotransmitter(s).Functional intracellular Ca2+ stores are essential for spontaneous Ca2+ transients, and the sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) pump is necessary for maintenance of spontaneity.Ca2+ release mechanisms involve both ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP3Rs). Release from these channels is interdependent.ICC express transcripts of multiple RyRs and InsP3Rs, with Itpr1 and Ryr2 subtypes displaying the highest expression. Abstract Interstitial cells of Cajal in the deep muscular plexus of the small intestine (ICC‐DMP) are closely associated with varicosities of enteric motor neurons and generate responses contributing to neural regulation of intestinal motility. Responses of ICC‐DMP are mediated by activation of Ca2+‐activated Cl− channels; thus, Ca2+ signalling is central to the behaviours of these cells. Confocal imaging was used to characterize the nature and mechanisms of Ca2+ transients in ICC‐DMP within intact jejunal muscles expressing a genetically encoded Ca2+ indicator (GCaMP3) selectively in ICC. ICC‐DMP displayed spontaneous Ca2+ transients that ranged from discrete, localized events to waves that propagated over variable distances. The occurrence of Ca2+ transients was highly variable, and it was determined that firing was stochastic in nature. Ca2+ transients were tabulated in multiple cells within fields of view, and no correlation was found between the events in adjacent cells. TTX (1 μm) significantly increased the occurrence of Ca2+ transients, suggesting that ICC‐DMP contributes to the tonic inhibition conveyed by ongoing activity of inhibitory motor neurons. Ca2+ transients were minimally affected after 12 min in Ca2+ free solution, indicating these events do not depend immediately upon Ca2+ influx. However, inhibitors of sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) pump and blockers of inositol triphosphate receptor (InsP3R) and ryanodine receptor (RyR) channels blocked ICC Ca2+ transients. These data suggest an interdependence between RyR and InsP3R in the generation of Ca2+ transients. Itpr1 and Ryr2 were the dominant transcripts expressed by ICC. These findings provide the first high‐resolution recording of the subcellular Ca2+ dynamics that control the behaviour of ICC‐DMP in situ. PMID:26824875

β-Adrenergic induced SR Ca2+ leak is mediated by an Epac-NOS pathway.

PubMed

Pereira, Laëtitia; Bare, Dan J; Galice, Samuel; Shannon, Thomas R; Bers, Donald M

2017-07-01

Cardiac β-adrenergic receptors (β-AR) and Ca 2+ -Calmodulin dependent protein kinase (CaMKII) regulate both physiological and pathophysiological Ca 2+ signaling. Elevated diastolic Ca 2+ leak from the sarcoplasmic reticulum (SR) contributes to contractile dysfunction in heart failure and to arrhythmogenesis. β-AR activation is known to increase SR Ca 2+ leak via CaMKII-dependent phosphorylation of the ryanodine receptor. Two independent and reportedly parallel pathways have been implicated in this β-AR-CaMKII cascade, one involving exchange protein directly activated by cAMP (Epac2) and another involving nitric oxide synthase 1 (NOS1). Here we tested whether Epac and NOS function in a single series pathway to increase β-AR induced and CaMKII-dependent SR Ca 2+ leak. Leak was measured as both Ca 2+ spark frequency and tetracaine-induced shifts in SR Ca 2+ , in mouse and rabbit ventricular myocytes. Direct Epac activation by 8-CPT (8-(4-chlorophenylthio)-2'-O-methyl-cAMP) mimicked β-AR-induced SR Ca 2+ leak, and both were blocked by NOS inhibition. The same was true for myocyte CaMKII activation (assessed via a FRET-based reporter) and ryanodine receptor phosphorylation. Inhibitor and phosphorylation studies also implicated phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt) downstream of Epac and above NOS activation in this pathway. We conclude that these two independently characterized parallel pathways function mainly via a single series arrangement (β-AR-cAMP-Epac-PI3K-Akt-NOS1-CaMKII) to mediate increased SR Ca 2+ leak. Thus, for β-AR activation the cAMP-PKA branch effects inotropy and lusitropy (by effects on Ca 2+ current and SR Ca 2+ -ATPase), this cAMP-Epac-NOS pathway increases pathological diastolic SR Ca 2+ leak. This pathway distinction may allow novel SR Ca 2+ leak therapeutic targeting in treatment of arrhythmias in heart failure that spare the inotropic and lusitropic effects of the PKA branch. Copyright © 2017 Elsevier Ltd. All rights reserved.

Lung Beractant Increases Free Cytosolic Levels of Ca2+ in Human Lung Fibroblasts

PubMed Central

Guzmán-Silva, Alejandro; Vázquez de Lara, Luis G.; Torres-Jácome, Julián; Vargaz-Guadarrama, Ajelet; Flores-Flores, Marycruz; Pezzat Said, Elias; Lagunas-Martínez, Alfredo; Mendoza-Milla, Criselda; Tanzi, Franco; Moccia, Francesco; Berra-Romani, Roberto

2015-01-01

Beractant, a natural surfactant, induces an antifibrogenic phenotype and apoptosis in normal human lung fibroblasts (NHLF). As intracellular Ca2+ signalling has been related to programmed cell death, we aimed to assess the effect of beractant on intracellular Ca2+ concentration ([Ca2+]i) in NHLF in vitro. Cultured NHLF were loaded with Fura-2 AM (3 μM) and Ca2+ signals were recorded by microfluorimetric techniques. Beractant causes a concentration-dependent increase in [Ca2+]i with a EC50 of 0.82 μg/ml. The application of beractant, at a concentration of 500 μg/ml, which has been shown to exert an apoptotic effect in human fibroblasts, elicited different patterns of Ca2+ signals in NHLF: a) a single Ca2+ spike which could be followed by b) Ca2+ oscillations, c) a sustained Ca2+ plateau or d) a sustained plateau overlapped by Ca2+ oscillations. The amplitude and pattern of Ca2+ transients evoked by beractant were dependent on the resting [Ca2+]i. Pharmacological manipulation revealed that beractant activates a Ca2+ signal through Ca2+ release from intracellular stores mediated by phospholipase Cβ (PLCβ), Ca2+ release from inositol 1,4,5-trisphosphate receptors (IP3Rs) and Ca2+ influx via a store-operated pathway. Moreover, beractant-induced Ca2+ release was abolished by preventing membrane depolarization upon removal of extracellular Na+ and Ca2+. Finally, the inhibition of store-operated channels prevented beractant-induced NHLF apoptosis and downregulation of α1(I) procollagen expression. Therefore, beractant utilizes SOCE to exert its pro-apoptotic and antifibrinogenic effect on NHLF. PMID:26230503

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.

Formation process of micro arc oxidation coatings obtained in a sodium phytate containing solution with and without CaCO3 on binary Mg-1.0Ca alloy

NASA Astrophysics Data System (ADS)

Zhang, R. F.; Zhang, Y. Q.; Zhang, S. F.; B. Qu; Guo, S. B.; Xiang, J. H.

2015-01-01

Micro arc oxidation (MAO) is an effective method to improve the corrosion resistance of magnesium alloys. In order to reveal the influence of alloying element Ca and CaCO3 electrolyte on the formation process and chemical compositions of MAO coatings on binary Mg-1.0Ca alloy, anodic coatings after different anodizing times were prepared on binary Mg-1.0Ca alloy in a base solution containing 3 g/L sodium hydroxide and 15 g/L sodium phytate with and without addition of CaCO3. The coating formation was studied by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results show that Mg-1.0Ca alloy is composed of two phases, the Mg phase and Mg2Ca phase. After treating for 5 s, the coating began to develop and was preferentially formed on the area nearby Mg2Ca phase, which may be resulted from the intrinsic electronegative potential of the Mg phase than that of Mg2Ca phase. Anodic coatings unevenly covered the total surface after 20 s. After 80 s, the coatings were uniformly developed on Mg-1.0Ca alloy with micro pores. During MAO process, some sodium phytate molecules are hydrolyzed into inorganic phosphate. CaCO3 has minor influence on the calcium content of the obtained MAO coatings.

One- and three-time mild hypobaric hypoxia modifies expression of mitochondrial thioredoxin-2 in hippocampus of rat.

PubMed

Stroev, Sergey Alexandrovich; Tjulkova, Ekaterina Iosifovna; Samoilov, Michail Olegovich; Pelto-Huikko, Markku Tapio

2011-01-01

Our previous study demonstrated that preconditioning by 3-times repetitive mild hypoxia significantly augmented expression of mitochondrial thioredoxin-2 (Trx-2) at 3 h after subsequent acute severe hypoxia in rat hippocampus. However, it was unclear whether this augmentation was due to build up of Trx-2 by mild hypoxia before severe hypoxia or by modification of reaction to severe hypoxia itself. To answer on this question we study the expression level during and after preconditioning without subsequent severe hypoxia. Trx-2 expression was studied by immunocytochemistry 3 h and 24 h after first session and 3 h and 24 h after last session of 3-times (spaced at 24 h) mild hypobaric hypoxia (360 Torr, 2h). At 3 h after 1-time hypoxia (first session of 3-time hypoxia) the total number of Trx-2-immunoreactive cells (Nt) was significantly decreased in contrast with control in CA2, CA3 and DG. The number of cells with intensive expression of Trx-2 (Ni) was reduced in CA1 and CA3. At 24 h after the same 1-time hypoxia Nt was lower than in control and at 3 h time-point in all hippocampal areas studied (CA1, CA2, CA3 and DG); Ni was decreased only compared to control in CA1 and CA3. At 3 h after last session of 3-times hypoxia Nt and Ni were significantly down regulated in comparison with control only in CA1. At 24 h after it Nt was significantly decreased compared to control in CA1, CA2 and CA3 (in DG the decrease was not statistically significant) but in all areas was higher than at 24 h after 1-time hypoxia. Dynamics of Nt changes from 3-hours after single to 24-hours after triple moderate hypoxia had the wave phase character. These findings indicate that Trx-2 expression in most areas of hippocampus was decreased to 24 h after 3-time mild hypoxia. Thus the augmentation of Trx-2 expression in hippocampal neurons of preconditioned animals in response to subsequent severe hypoxia is caused obviously not by Trx-2 accumulation during preconditioning sessions but by modification of reaction to severe impact.

Insight into Ca-Substitution Effects on O3-Type NaNi1/3 Fe1/3 Mn1/3 O2 Cathode Materials for Sodium-Ion Batteries Application.

PubMed

Sun, Liqi; Xie, Yingying; Liao, Xiao-Zhen; Wang, Hong; Tan, Guoqiang; Chen, Zonghai; Ren, Yang; Gim, Jihyeon; Tang, Wan; He, Yu-Shi; Amine, Khalil; Ma, Zi-Feng

2018-04-18

O3-type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NaNFM) is well investigated as a promising cathode material for sodium-ion batteries (SIBs), but the cycling stability of NaNFM still needs to be improved by using novel electrolytes or optimizing their structure with the substitution of different elements sites. To enlarge the alkali-layer distance inside the layer structure of NaNFM may benefit Na + diffusion. Herein, the effect of Ca-substitution is reported in Na sites on the structural and electrochemical properties of Na 1- x Ca x /2 NFM (x = 0, 0.05, 0.1). X-ray diffraction (XRD) patterns of the prepared Na 1- x Ca x /2 NFM samples show single α-NaFeO 2 type phase with slightly increased alkali-layer distance as Ca content increases. The cycling stabilities of Ca-substituted samples are remarkably improved. The Na 0.9 Ca 0.05 Ni 1/3 Fe 1/3 Mn 1/3 O 2 (Na 0.9 Ca 0.05 NFM) cathode delivers a capacity of 116.3 mAh g -1 with capacity retention of 92% after 200 cycles at 1C rate. In operando XRD indicates a reversible structural evolution through an O3-P3-P3-O3 sequence of Na 0.9 Ca 0.05 NFM cathode during cycling. Compared to NaNMF, the Na 0.9 Ca 0.05 NFM cathode shows a wider voltage range in pure P3 phase state during the charge/discharge process and exhibits better structure recoverability after cycling. The superior cycling stability of Na 0.9 Ca 0.05 NFM makes it a promising material for practical applications in sodium-ion batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Calcium isotopic fractionation in mantle peridotites by melting and metasomatism and Ca isotope composition of the Bulk Silicate Earth

NASA Astrophysics Data System (ADS)

Kang, Jin-Ting; Ionov, Dmitri A.; Liu, Fang; Zhang, Chen-Lei; Golovin, Alexander V.; Qin, Li-Ping; Zhang, Zhao-Feng; Huang, Fang

2017-09-01

To better constrain the Ca isotopic composition of the Bulk Silicate Earth (BSE) and explore the Ca isotope fractionation in the mantle, we determined the Ca isotopic composition of 28 peridotite xenoliths from Mongolia, southern Siberia and the Siberian craton. The samples are divided in three chemical groups: (1) fertile, unmetasomatized lherzolites (3.7-4.7 wt.% Al2O3); (2) moderately melt-depleted peridotites (1.3-3.0 wt.% Al2O3) with no or very limited metasomatism (LREE-depleted cpx); (3) strongly metasomatized peridotites (LREE-enriched cpx and bulk rock) further divided in subgroups 3a (harzburgites, 0.1-1.0% Al2O3) and 3b (fertile lherzolites, 3.9-4.3% Al2O3). In Group 1, δ44/40Ca of fertile spinel and garnet peridotites, which experienced little or no melting and metasomatism, show a limited variation from 0.90 to 0.99‰ (relative to SRM 915a) and an average of 0.94 ± 0.05‰ (2SD, n = 14), which defines the Ca isotopic composition of the BSE. In Group 2, the δ44/40Ca is the highest for three rocks with the lowest Al2O3, i.e. the greatest melt extraction degrees (average 1.06 ± 0.04 ‰, i.e. ∼0.1‰ heavier than the BSE estimate). Simple modeling of modal melting shows that partial melting of the BSE with 103 ln ⁡αperidotite-melt ranging from 0.10 to 0.25 can explain the Group 2 data. By contrast, δ44/40Ca in eight out of nine metasomatized Group 3 peridotites are lower than the BSE estimate. The Group 3a harzburgites show the greatest δ44/40Ca variation range (0.25-0.96‰), with δ44/40Ca positively correlated with CaO and negatively correlated with Ce/Eu. Chemical evidence suggests that the residual, melt-depleted, low-Ca protoliths of the Group 3a harzburgites were metasomatized, likely by carbonate-rich melts/fluids. We argue that such fluids may have low (≤0.25‰) δ44/40Ca either because they contain recycled crustal components or because Ca isotopes, similar to trace elements and their ratios, may be fractionated by kinetic and/or chromatographic effects of melt percolation in the mantle. The δ44/40Ca in Group 3b lherzolites (0.83-0.89‰) are lower than in the BSE as well, but the effects of metasomatism on δ44/40Ca are smaller, possibly because of the high Ca contents in their protoliths and/or smaller δ44/40Ca differences between the protoliths and metasomatic agents. The BSE estimates based on fertile peridotites in this study fall in the δ44/40Ca ranges for oceanic and continental basalts, various meteorites (achondrites; carbonaceous, ordinary and enstatite chondrites), Mars, and the Moon. These results provide benchmarks for the application of Ca isotopes to planet formation, mantle evolution, and crustal recycling.

Calcium-dependent stoichiometries of the KCa2.2 (SK) intracellular domain/calmodulin complex in solution

PubMed Central

Halling, D. Brent; Kenrick, Sophia A.; Riggs, Austen F.

2014-01-01

Ca2+ activates SK Ca2+-activated K+ channels through the protein Ca2+ sensor, calmodulin (CaM). To understand how SK channels operate, it is necessary to determine how Ca2+ regulates CaM binding to its target on SK. Tagless, recombinant SK peptide (SKp), was purified for binding studies with CaM at low and high Ca2+ concentrations. Composition gradient multi-angle light scattering accurately measures the molar mass, stoichiometry, and affinity of protein complexes. In 2 mM Ca2+, SKp and CaM bind with three different stoichiometries that depend on the molar ratio of SKp:CaM in solution. These complexes include 28 kD 1SKp/1CaM, 39 kD 2SKp/1CaM, and 44 kD 1SKp/2CaM. A 2SKp/2CaM complex, observed in prior crystallographic studies, is absent. At <5 nM Ca2+, 1SKp/1CaM and 2SKp/1CaM were observed; however, 1SKp/2CaM was absent. Analytical ultracentrifugation was used to characterize the physical properties of the three SKp/CaM stoichiometries. In high Ca2+, the sedimentation coefficient is smaller for a 1SKp:1CaM solution than it is for either 2SKp:1CaM or 1SKp:2CaM. At low Ca2+ and at >100 µM protein concentrations, a molar excess of SKp over CaM causes aggregation. Aggregation is not observed in Ca2+ or with CaM in molar excess. In low Ca2+ both 1SKp:1CaM and 1SKp:2CaM solutions have similar sedimentation coefficients, which is consistent with the absence of a 1SKp/2CaM complex in low Ca2+. These results suggest that complexes with stoichiometries other than 2SKp/2CaM are important in gating. PMID:24420768

Calcium-dependent stoichiometries of the KCa2.2 (SK) intracellular domain/calmodulin complex in solution.

PubMed

Halling, D Brent; Kenrick, Sophia A; Riggs, Austen F; Aldrich, Richard W

2014-02-01

Ca(2+) activates SK Ca(2+)-activated K(+) channels through the protein Ca(2+) sensor, calmodulin (CaM). To understand how SK channels operate, it is necessary to determine how Ca(2+) regulates CaM binding to its target on SK. Tagless, recombinant SK peptide (SKp), was purified for binding studies with CaM at low and high Ca(2+) concentrations. Composition gradient multi-angle light scattering accurately measures the molar mass, stoichiometry, and affinity of protein complexes. In 2 mM Ca(2+), SKp and CaM bind with three different stoichiometries that depend on the molar ratio of SKp:CaM in solution. These complexes include 28 kD 1SKp/1CaM, 39 kD 2SKp/1CaM, and 44 kD 1SKp/2CaM. A 2SKp/2CaM complex, observed in prior crystallographic studies, is absent. At <5 nM Ca(2+), 1SKp/1CaM and 2SKp/1CaM were observed; however, 1SKp/2CaM was absent. Analytical ultracentrifugation was used to characterize the physical properties of the three SKp/CaM stoichiometries. In high Ca(2+), the sedimentation coefficient is smaller for a 1SKp:1CaM solution than it is for either 2SKp:1CaM or 1SKp:2CaM. At low Ca(2+) and at >100 µM protein concentrations, a molar excess of SKp over CaM causes aggregation. Aggregation is not observed in Ca(2+) or with CaM in molar excess. In low Ca(2+) both 1SKp:1CaM and 1SKp:2CaM solutions have similar sedimentation coefficients, which is consistent with the absence of a 1SKp/2CaM complex in low Ca(2+). These results suggest that complexes with stoichiometries other than 2SKp/2CaM are important in gating.

The influence of chemical agents on the level of ionized [Ca2+] in squid axons

PubMed Central

1985-01-01

Squid giant axons injected with either aequorin or arsenazo III and bathed in 3 mM Ca (Na) seawater were transferred to 3 mM Ca (K) seawater and the response of the aequorin light or the change in the absorbance of arsenazo III was followed. These experimental conditions were chosen because they measure the change in the rate of Na/Ca exchange in introducing Ca into the axon upon depolarization; [Ca]o is too low to effect a channel-based system of Ca entry. This procedure was applied to axons treated with a variety of compounds that have been implicated as inhibitors of Na/Ca exchange. The result obtained was that the substances tested could be placed in three groups. (a) Substances that were without effect on Ca entry effected by Na/Ca exchange were: D600 at 10-100 microM, nitrendipine at 1-5 microM, Ba2+ and Mg2+ at concentrations of 10-50 mM, lidocaine at 0.1-10 mM, cyanide at 2 mM, adriamycin at a concentration of 3 microM, chloradenosine at 35 microM, 2,4-diaminopyridine at 1 mM, Cs+ at 45-90 mM, and tetrodotoxin at 10(-7). (b) Substances that had a significant inhibitory effect on Na/Ca exchange were: Mn2+, Cd2+, and La3+ at 1-50 mM, and quinidine at 50 microM. (c) There were also blocking agents and biochemical inhibitors whose action appeared to be the inhibition of nonmitochondrial Ca buffering in axoplasm rather than an inhibition of Na/Ca exchange. These were the general anesthetic l-octanol at 0.1 mM and 1 mM orthovanadate plus apyrase. PMID:2410536

Microwave assisted synthesis of novel acridine-acetazolamide conjugates and investigation of their inhibition effects on human carbonic anhydrase isoforms hCA I, II, IV and VII.

PubMed

Ulus, Ramazan; Aday, Burak; Tanç, Muhammet; Supuran, Claudiu T; Kaya, Muharrem

2016-08-15

4-Amino-N-(5-sulfamoyl-1,3,4-thiadiazol-2-yl)benzamide was condensed with cyclic-1,3-diketones (dimedone and cyclohexane-1,3-dione) and aromatic aldehydes under microwave irradiation, leading to a series of acridine-acetazolamide conjugates. The new compounds were investigated as inhibitors of carbonic anhydrases (CA, EC 4.2.1.1), and more precisely cytosolic isoforms hCA I, II, VII and membrane-bound one hCA IV. All investigated isoforms were inhibited in low micromolar and nanomolar range by the new compounds. hCA IV and VII were inhibited with KIs in the range of 29.7-708.8nM (hCA IV), and of 1.3-90.7nM (hCA VII). For hCA I and II the KIs were in the range of 6.7-335.2nM (hCA I) and of 0.5-55.4nM (hCA II). The structure-activity relationships (SAR) for the inhibition of these isoforms with the acridine-acetazolamide conjugates reported here were delineated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Clofibric acid degradation in UV254/H2O2 process: effect of temperature.

PubMed

Li, Wenzhen; Lu, Shuguang; Qiu, Zhaofu; Lin, Kuangfei

2010-04-15

The degradation of clofibric acid (CA) in UV(254)/H(2)O(2) process under three temperature ranges, i.e. T1 (9.0-11.5 degrees C), T2 (19.0-21.0 degrees C) and T3 (29.0-30.0 degrees C) was investigated. The effects of solution constituents including NO(3)(-) and HCO(3)(-) anions, and humic acid (HA) on CA degradation were evaluated in Milli-Q waters. CA degradation behaviors were simulated with the pseudo-first-order kinetic model and the apparent rate constant (k(ap)) and half-life time (t(1/2)) were calculated. The results showed that higher temperature would favor CA degradation, and CA degradation was taken place mostly by indirect oxidation through the formation of OH radicals in UV(254)/H(2)O(2) process. In addition, the effects of both NO(3)(-) and HCO(3)(-) anions at two selected concentrations (1.0x10(-3) and 0.1 mol L(-1)) and HA (20 mg L(-1)) on CA degradation were investigated. The results showed that HA had negative effect on CA degradation, and this effect was much more apparent under low temperature condition. On the other hand, the inhibitive effect on CA degradation at both lower and higher concentrations of bicarbonate was observed, and this inhibitive effect was much more apparent at higher bicarbonate concentration and lower temperature condition. While, at higher nitrate concentration the inhibitive effect on CA degradation under three temperature ranges was observed, and with the temperature increase this negative effect was apparently weakened. However, at lower nitrate concentration a slightly positive effect on CA degradation was found under T2 and T3 conditions. Moreover, when using a real wastewater treatment plant (WWTP) effluent spiked with CA over 99% of CA removal could be achieved under 30 degrees C within only 15 min compared with 40 and 80 min under 20 and 10 degrees C respectively, suggesting a significant promotion in CA degradation under higher temperature condition. Therefore, it can be concluded that temperature plays an important role in CA degradation in UV/H(2)O(2) process. 2009 Elsevier B.V. All rights reserved.

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

PubMed

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

2014-02-01

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

Measurement of true ileal calcium digestibility in meat and bone meal for broiler chickens using the direct method.

PubMed

Anwar, M N; Ravindran, V; Morel, P C H; Ravindran, G; Cowieson, A J

2016-01-01

The objective of the study that is presented herein was to determine the true ileal calcium (Ca) digestibility in meat and bone meal (MBM) for broiler chickens using the direct method. Four MBM samples (coded as MBM-1, MBM-2, MBM-3 and MBM-4) were obtained and analyzed for nutrient composition, particle size distribution and bone to soft tissue ratio. The Ca concentrations of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 71, 118, 114 and 81 g/kg, respectively. The corresponding geometric mean particle diameters and bone to soft tissue ratios were 0.866, 0.622, 0.875 and 0.781 mm, and 1:1.49, 1:0.98, 1:0.92 and 1:1.35, respectively. Five experimental diets, including four diets with similar Ca concentration (8.3 g/kg) from each MBM and a Ca and phosphorus-free diet, were developed. Meat and bone meal served as the sole source of Ca in the MBM diets. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage) and offered from d 28 to 31 post-hatch. Apparent ileal Ca digestibility was calculated by the indicator method and corrected for ileal endogenous Ca losses to determine the true ileal Ca digestibility. Ileal endogenous Ca losses were determined to be 88 mg/kg dry matter intake. True ileal Ca digestibility coefficients of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 0.560, 0.446, 0.517 and 0.413, respectively. True Ca digestibility of MBM-1 was higher (P < 0.05) than MBM-2 and MBM-4 but similar (P > 0.05) to that of MBM-3. True Ca digestibility of MBM-2 was similar (P > 0.05) to MBM-3 and MBM-4, while that of MBM-3 was higher (P < 0.05) than MBM-4. These results demonstrated that the direct method can be used for the determination of true Ca digestibility in feed ingredients and that Ca in MBM is not highly available as often assumed. The variability in true Ca digestibility of MBM samples could not be attributed to Ca content, percentage bones or particle size. © 2015 Poultry Science Association Inc.

PCV2 induces apoptosis and modulates calcium homeostasis in piglet lymphocytes in vitro.

PubMed

Lv, Yingjun; Dai, Lei; Han, Huili; Zhang, Shuxia

2012-12-01

This study investigated the process of PCV2-induced apoptosis and the effect of PCV2 inoculation on calcium homeostasis in piglet lymphocytes in vitro. PCV2-inoculated lymphocytes exhibited chromatin condensation, chromatin segregation, the appearance of membrane-enclosed apoptotic bodies, and DNA fragmentation. Moreover, the proportion of apoptotic cells increased significantly in PCV2-inoculated lymphocytes compared with controls. These results demonstrate that PCV2 induces lymphocyte apoptosis. Some evidence suggests that an alteration in the intracellular free Ca2+ concentration ([Ca2+]i) could cause apoptosis. We measured elevated [Ca2+]i in PCV2-inoculated lymphocytes for 12 or 24 h compared with controls. Our results support that PCV2-induced apoptosis may be relative to [Ca2+]i. In addition, calmodulin (CaM) was increased in PCV2-inoculated lymphocytes for 12 h compared with controls. The amount of CaM-dependent protein kinase II (CaMKII) did not change with PCV2 inoculation. We infer that the increased [Ca2+]i can bind CaM protein, but functions independently of CaMKII. Inositol 1,4,5-trisphosphate receptor (IP3R)-1 mRNA expression increased with PCV2 inoculation, whereas plasma Ca2+-ATP4 mRNA expression decreased. A decreased Ca2+-ATP4 level may inhibit Ca2+ efflux, and the increased IP3R-1 may trigger Ca2+ release from the endoplasmic reticulum. Both of these changes may contribute to increased [Ca2+]i. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

PubMed

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

2014-03-15

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

Sarcoplasmic reticulum buffering of myoplasmic calcium in bovine coronary artery smooth muscle.

PubMed Central

Sturek, M; Kunda, K; Hu, Q

1992-01-01

1. We tested the hypothesis that the sarcoplasmic reticulum (SR) buffers (attenuates) the increase in averaged myoplasmic free [Ca2+] (Ca(im)) resulting from Ca2+ influx. 2. Fura-2 measurements of Ca(im) were obtained in single smooth muscle cells freshly dispersed from bovine coronary artery. 3. Caffeine (5 x 10(-3) M) elicited a transient increase in Ca(im) and depleted the SR Ca2+ store. In the continued presence of caffeine or 10(-5) M-ryanodine SR buffering of Ca(im) was inhibited. Subsequent exposure to high extracellular [K+] (greater than 30 mM, equimolar Na+ removal) elicited a 2-fold more rapid and 2-fold greater peak increase in Ca(im) than high K+ elicited when SR buffering of Ca(im) was normal. The augmented increase in Ca(im) was inhibited 35% by 10(-5) M-diltiazem, 65% by 2 x 10(-4) M-LaCl3, and 87% in Ca(2+)-free external solution. 4. When Ca(im) buffering capacity was increased by partially depleting the SR with a transient (1 min) exposure to caffeine, subsequent exposure to 80 nM-K+ solution increased Ca(im) almost 2-fold more slowly than 80 mM-K+ before depletion of Ca2+ from the SR. However, the influxing Ca2+ was sequestered by the SR and refilled it, as evident by the subsequent caffeine-induced Ca(im) transient being identical to the first. Increasing extracellular [K+] (thus, increasing depolarization and Na+ removal) caused proportional increases in Ca(im) and the subsequent caffeine-induced Ca(im) transients were proportionally larger, indicating a graded filling of the SR by Ca2+ influx. 5. Diltiazem (10(-5) M) inhibited the refilling of the SR achieved by 80 mM-K+, by 26%. Refilling was inhibited 76% by 80 mM-K+, Ca(2+)-free solution, indicating the fraction of refilling dependent on influx of Ca2+ through voltage-gated Ca2+ channels, leak channels, and other influx pathways. Mild depolarization with 35 mM-K+ (no Na+ removal) often caused no increase in Ca(im), but influx through voltage-gated Ca2+ channels occurred because the SR Ca2+ store was refilled. Also, 10(-5) M-diltiazem or 10(-6) M-TA3090 inhibited the refilling to levels attributable only to leak influx of Ca2+. 6. All data support our hypothesis that the SR significantly attenuates the amount of Ca2+ influx that accumulates to increase Ca(im).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1403813

In Vitro and In Vivo Evaluation of Zinc-Modified Ca–Si-Based Ceramic Coating for Bone Implants

PubMed Central

Zheng, Xuebin; He, Dannong; Ye, Xiaojian; Wang, Meiyan

2013-01-01

The host response to calcium silicate ceramic coatings is not always favorable because of their high dissolution rates, leading to high pH within the surrounding physiological environment. Recently, a zinc-incorporated calcium silicate-based ceramic Ca2ZnSi2O7 coating, developed on a Ti-6Al-4V substrate using plasma-spray technology, was found to exhibit improved chemical stability and biocompatibility. This study aimed to investigate and compare the in vitro response of osteoblastic MC3T3-E1 cells cultured on Ca2ZnSi2O7 coating, CaSiO3 coating, and uncoated Ti-6Al-4V titanium control at cellular and molecular level. Our results showed Ca2ZnSi2O7 coating enhanced MC3T3-E1 cell attachment, proliferation, and differentiation compared to CaSiO3 coating and control. In addition, Ca2ZnSi2O7 coating increased mRNA levels of osteoblast-related genes (alkaline phosphatase, procollagen α1(I), osteocalcin), insulin-like growth factor-I (IGF-I), and transforming growth factor-β1 (TGF-β1). The in vivo osteoconductive properties of Ca2ZnSi2O7 coating, compared to CaSiO3 coating and control, was investigated using a rabbit femur defect model. Histological and histomorphometrical analysis demonstrated new bone formation in direct contact with the Ca2ZnSi2O7 coating surface in absence of fibrous tissue and higher bone-implant contact rate (BIC) in the Ca2ZnSi2O7 coating group, indicating better biocompatibility and faster osseointegration than CaSiO3 coated and control implants. These results indicate Ca2ZnSi2O7 coated implants have applications in bone tissue regeneration, since they are biocompatible and able to osseointegrate with host bone. PMID:23483914

Mastoparan-Induced Intracellular Ca2+ Fluxes May Regulate Cell-to-Cell Communication in Plants.

PubMed

Tucker, E. B.; Boss, W. F.

1996-06-01

The relationship of Ca2+ and plasmodesmatal closure was examined in staminal hairs of Setcreasea purpurea by microinjecting cells with active mastoparan (Mas-7), inactive mastoparan (Mas-17), active inositol-1,4,5-trisphosphate (IP3), or inactive IP3. Calcium green dextran 10,000 was used to study cellular free Ca2+, and carboxyfluorescein was used to monitor plasmodesmatal closure. When Mas-7 was microinjected into the cytoplasm of cell 1 (the tip cell of a chain of cells), a rapid increase in calcium green dextran-10,000 fluorescence was observed in the cytoplasmic areas on both sides of the plasmodesmata connecting cells 1 and 2 during the same time that the diffusion of carboxyfluorescein through them was blocked. The inhibition of cell-to-cell diffusion was transient, and the closed plasmodesmata reopened within 30 s. The elevated Ca2+ level near plasmodesmata was also transient and returned to base level in about 1.5 min. The transient increase in Ca2+, once initiated in cell 1, repeated with an oscillatory period of 3 min. Elevated Ca2+ and oscillations of Ca2+ were also observed near interconnecting cell walls throughout the chain of cells, indicating that the signal had been transmitted. Previously, we reported that IP3 closed plasmodesmata; now we report that it stimulated Ca2+ and oscillations similar to Mas-7. The effect was specific for similar concentrations of Mas-7 over Mas-17 and active IP3 over inactive IP3. It is important that the Ca2+ channel blocker La3+ eliminated the responses from Mas-7 and IP3, indicating that an influx of Ca2+ was required. These results support the contention that plasmodesmata functioning is regulated via Ca2+ and that IP3 may be an intermediary between the stimulus and Ca2+ elevations.

Mastoparan-Induced Intracellular Ca2+ Fluxes May Regulate Cell-to-Cell Communication in Plants.

PubMed Central

Tucker, E. B.; Boss, W. F.

1996-01-01

The relationship of Ca2+ and plasmodesmatal closure was examined in staminal hairs of Setcreasea purpurea by microinjecting cells with active mastoparan (Mas-7), inactive mastoparan (Mas-17), active inositol-1,4,5-trisphosphate (IP3), or inactive IP3. Calcium green dextran 10,000 was used to study cellular free Ca2+, and carboxyfluorescein was used to monitor plasmodesmatal closure. When Mas-7 was microinjected into the cytoplasm of cell 1 (the tip cell of a chain of cells), a rapid increase in calcium green dextran-10,000 fluorescence was observed in the cytoplasmic areas on both sides of the plasmodesmata connecting cells 1 and 2 during the same time that the diffusion of carboxyfluorescein through them was blocked. The inhibition of cell-to-cell diffusion was transient, and the closed plasmodesmata reopened within 30 s. The elevated Ca2+ level near plasmodesmata was also transient and returned to base level in about 1.5 min. The transient increase in Ca2+, once initiated in cell 1, repeated with an oscillatory period of 3 min. Elevated Ca2+ and oscillations of Ca2+ were also observed near interconnecting cell walls throughout the chain of cells, indicating that the signal had been transmitted. Previously, we reported that IP3 closed plasmodesmata; now we report that it stimulated Ca2+ and oscillations similar to Mas-7. The effect was specific for similar concentrations of Mas-7 over Mas-17 and active IP3 over inactive IP3. It is important that the Ca2+ channel blocker La3+ eliminated the responses from Mas-7 and IP3, indicating that an influx of Ca2+ was required. These results support the contention that plasmodesmata functioning is regulated via Ca2+ and that IP3 may be an intermediary between the stimulus and Ca2+ elevations. PMID:12226302

The role of TRPP2 in agonist-induced gallbladder smooth muscle contraction.

PubMed

Zhong, Xingguo; Fu, Jie; Song, Kai; Xue, Nairui; Gong, Renhua; Sun, Dengqun; Luo, Huilai; He, Wenzhu; Pan, Xiang; Shen, Bing; Du, Juan

2016-04-01

TRPP2 channel protein belongs to the superfamily of transient receptor potential (TRP) channels and is widely expressed in various tissues, including smooth muscle in digestive gut. Accumulating evidence has demonstrated that TRPP2 can mediate Ca(2+) release from Ca(2+) stores. However, the functional role of TRPP2 in gallbladder smooth muscle contraction still remains unclear. In this study, we used Ca(2+) imaging and tension measurements to test agonist-induced intracellular Ca(2+) concentration increase and smooth muscle contraction of guinea pig gallbladder, respectively. When TRPP2 protein was knocked down in gallbladder muscle strips from guinea pig, carbachol (CCh)-evoked Ca(2+) release and extracellular Ca(2+) influx were reduced significantly, and gallbladder contractions induced by endothelin 1 and cholecystokinin were suppressed markedly as well. CCh-induced gallbladder contraction was markedly suppressed by pretreatment with U73122, which inhibits phospholipase C to terminate inositol 1,4,5-trisphosphate receptor (IP3) production, and 2-aminoethoxydiphenyl borate (2APB), which inhibits IP3 recepor (IP3R) to abolish IP3R-mediated Ca(2+) release. To confirm the role of Ca(2+) release in CCh-induced gallbladder contraction, we used thapsigargin (TG)-to deplete Ca(2+) stores via inhibiting sarco/endoplasmic reticulum Ca(2+)-ATPase and eliminate the role of store-operated Ca(2+) entry on the CCh-induced gallbladder contraction. Preincubation with 2 μmol L(-1) TG significantly decreased the CCh-induced gallbladder contraction. In addition, pretreatments with U73122, 2APB or TG abolished the difference of the CCh-induced gallbladder contraction between TRPP2 knockdown and control groups. We conclude that TRPP2 mediates Ca(2+) release from intracellular Ca(2+) stores, and has an essential role in agonist-induced gallbladder muscle contraction.

Ubiquitin Ligase RNF138 Promotes Episodic Ataxia Type 2-Associated Aberrant Degradation of Human Cav2.1 (P/Q-Type) Calcium Channels.

PubMed

Fu, Ssu-Ju; Jeng, Chung-Jiuan; Ma, Chia-Hao; Peng, Yi-Jheng; Lee, Chi-Ming; Fang, Ya-Ching; Lee, Yi-Ching; Tang, Sung-Chun; Hu, Meng-Chun; Tang, Chih-Yung

2017-03-01

Voltage-gated Ca V 2.1 channels comprise a pore-forming α 1A subunit with auxiliary α 2 δ and β subunits. Ca V 2.1 channels play an essential role in regulating synaptic signaling. Mutations in the human gene encoding the Ca V 2.1 subunit are associated with the cerebellar disease episodic ataxia type 2 (EA2). Several EA2-causing mutants exhibit impaired protein stability and exert dominant-negative suppression of Ca V 2.1 wild-type (WT) protein expression via aberrant proteasomal degradation. Here, we set out to delineate the protein degradation mechanism of human Ca V 2.1 subunit by identifying RNF138, an E3 ubiquitin ligase, as a novel Ca V 2.1-binding partner. In neurons, RNF138 and Ca V 2.1 coexist in the same protein complex and display notable subcellular colocalization at presynaptic and postsynaptic regions. Overexpression of RNF138 promotes polyubiquitination and accelerates protein turnover of Ca V 2.1. Disrupting endogenous RNF138 function with a mutant (RNF138-H36E) or shRNA infection significantly upregulates the Ca V 2.1 protein level and enhances Ca V 2.1 protein stability. Disrupting endogenous RNF138 function also effectively rescues the defective protein expression of EA2 mutants, as well as fully reversing EA2 mutant-induced excessive proteasomal degradation of Ca V 2.1 WT subunits. RNF138-H36E coexpression only partially restores the dominant-negative effect of EA2 mutants on Ca V 2.1 WT functional expression, which can be attributed to defective membrane trafficking of Ca V 2.1 WT in the presence of EA2 mutants. We propose that RNF138 plays a critical role in the homeostatic regulation of Ca V 2.1 protein level and functional expression and that RNF138 serves as the primary E3 ubiquitin ligase promoting EA2-associated aberrant degradation of human Ca V 2.1 subunits. SIGNIFICANCE STATEMENT Loss-of-function mutations in the human Ca V 2.1 subunit are linked to episodic ataxia type 2 (EA2), a dominantly inherited disease characterized by paroxysmal attacks of ataxia and nystagmus. EA2-causing mutants may exert dominant-negative effects on the Ca V 2.1 wild-type subunit via aberrant proteasomal degradation. The molecular nature of the Ca V 2.1 ubiquitin-proteasome degradation pathway is currently unknown. The present study reports the first identification of an E3 ubiquitin ligase for Ca V 2.1, RNF138. Ca V 2.1 protein stability is dynamically regulated by RNF138 and auxiliary α 2 δ and β subunits. We provide a proof of concept that protecting the human Ca V 2.1 subunit from excessive proteasomal degradation with specific interruption of endogenous RNF138 function may partially contribute to the future development of a novel therapeutic strategy for EA2 patients. Copyright © 2017 the authors 0270-6474/17/372485-19$15.00/0.

The 3R polymorph of CaSi{sub 2}

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

Nedumkandathil, Reji; Benson, Daryn E.; Grins, Jekabs

The Zintl phase CaSi{sub 2} commonly occurs in the 6R structure where puckered hexagon layers of Si atoms are stacked in an AA′BB′CC′ fashion. In this study we show that sintering of CaSi{sub 2} in a hydrogen atmosphere (30 bar) at temperatures between 200 and 700 °C transforms 6R-CaSi{sub 2} quantitatively into 3R-CaSi{sub 2}. In the 3R polymorph (space group R-3m (no. 166), a=3.8284(1), c=15.8966(4), Z=3) puckered hexagon layers are stacked in an ABC fashion. The volume per formula unit is about 3% larger compared to 6R-CaSi{sub 2}. First principles density functional calculations reveal that 6R and 3R-CaSi{sub 2} aremore » energetically degenerate at zero Kelvin. With increasing temperature 6R-CaSi{sub 2} stabilizes over 3R because of its higher entropy. This suggests that 3R-CaSi{sub 2} should revert to 6R at elevated temperatures, which however is not observed up to 800 °C. 3R-CaSi{sub 2} may be stabilized by small amounts of incorporated hydrogen and/or defects. - Graphical abstract: The common 6R form of CaSi{sub 2} can be transformed quantitatively into 3R-CaSi{sub 2} upon sintering in a hydrogen atmosphere. - Highlights: • Quantitative and reproducible bulk synthesis of the rare 3R polymorph of CaSi{sub 2}. • Clarification of the energetic relation between 3R and conventional 6R form. • 3R-CaSi{sub 2} is presumably stabilized by small amounts of incorporated hydrogen and/or defects.« less

Ca2+ cycling between sarcoplasmic reticulum and mitochondria in rabbit cardiac myocytes.

PubMed Central

Bassani, J W; Bassani, R A; Bers, D M

1993-01-01

1. Shortening and intracellular Ca2+ (Ca2+i) transients were measured in isolated rabbit ventricular myocytes during paired contractures induced by rapid application of 10 mM caffeine. 2. Caffeine-induced contractures relax despite maintained presence of caffeine. In control solution, a second phasic caffeine contracture failed to appear, unless the sarcoplasmic reticulum (SR) was refilled by a series of electrically stimulated twitches during the interval between caffeine exposures. 3. The relaxation of caffeine-induced contractures in 0 Na(+)-0 Ca2+ solution has previously been shown to rely on mitochondrial Ca2+ uptake and sarcolemmal Ca2(+)-ATPase. Thus, a second caffeine contracture (T2) while still in 0 Na(+)-0 Ca2+ was greatly reduced compared to the first one (T1). However, the amplitude of T2 increased exponentially with the time interval, attaining a maximum of approximately 50% of T1 for an interval of 180-300 s, with a time constant (tau) of 41.2 s. Similar results were found for Ca2+i transients (tau = 45 s). 4. Inhibition of the mitochondrial Ca2+ uptake by the oxidative phosphorylation uncoupler, FCCP during T1 dramatically depressed T2. On the other hand, inhibition of the sarcolemmal Ca2(+)-ATPase (by increasing extracellular Ca2+ concentration, [Ca2+]o) resulted in increase of T2. Spermine inclusion during T1 also increased T2, possibly by an increase of mitochondrial Ca2+ uptake. 5. We conclude that Ca2+ taken up by mitochondria during the decline of T1 moves back to the SR after caffeine is removed, with a tau approximately 40 s. 6. Partial intracellular Na+ depletion by prolonged (3 min) perfusion with 0 Na(+)-0 Ca2+ solution before T1 (a) accelerated relaxation and [Ca2+]i decline during T1, and (b) slowed, but did not abolish, the recovery of T2 as the interval was increased. This effect was particularly pronounced when choline was used instead of Li+ as the Na+ substitute. 7. We further conclude that the mitochondrial Na(+)-Ca2+ antiporter influences the rate of net Ca2+ uptake by mitochondria and is also important in Ca2+ efflux from mitochondria during rest. PMID:8387590

Ca2+ cycling between sarcoplasmic reticulum and mitochondria in rabbit cardiac myocytes.

PubMed

Bassani, J W; Bassani, R A; Bers, D M

1993-01-01

1. Shortening and intracellular Ca2+ (Ca2+i) transients were measured in isolated rabbit ventricular myocytes during paired contractures induced by rapid application of 10 mM caffeine. 2. Caffeine-induced contractures relax despite maintained presence of caffeine. In control solution, a second phasic caffeine contracture failed to appear, unless the sarcoplasmic reticulum (SR) was refilled by a series of electrically stimulated twitches during the interval between caffeine exposures. 3. The relaxation of caffeine-induced contractures in 0 Na(+)-0 Ca2+ solution has previously been shown to rely on mitochondrial Ca2+ uptake and sarcolemmal Ca2(+)-ATPase. Thus, a second caffeine contracture (T2) while still in 0 Na(+)-0 Ca2+ was greatly reduced compared to the first one (T1). However, the amplitude of T2 increased exponentially with the time interval, attaining a maximum of approximately 50% of T1 for an interval of 180-300 s, with a time constant (tau) of 41.2 s. Similar results were found for Ca2+i transients (tau = 45 s). 4. Inhibition of the mitochondrial Ca2+ uptake by the oxidative phosphorylation uncoupler, FCCP during T1 dramatically depressed T2. On the other hand, inhibition of the sarcolemmal Ca2(+)-ATPase (by increasing extracellular Ca2+ concentration, [Ca2+]o) resulted in increase of T2. Spermine inclusion during T1 also increased T2, possibly by an increase of mitochondrial Ca2+ uptake. 5. We conclude that Ca2+ taken up by mitochondria during the decline of T1 moves back to the SR after caffeine is removed, with a tau approximately 40 s. 6. Partial intracellular Na+ depletion by prolonged (3 min) perfusion with 0 Na(+)-0 Ca2+ solution before T1 (a) accelerated relaxation and [Ca2+]i decline during T1, and (b) slowed, but did not abolish, the recovery of T2 as the interval was increased. This effect was particularly pronounced when choline was used instead of Li+ as the Na+ substitute. 7. We further conclude that the mitochondrial Na(+)-Ca2+ antiporter influences the rate of net Ca2+ uptake by mitochondria and is also important in Ca2+ efflux from mitochondria during rest.

Can Polyphosphate Biochemistry Affect Biological Apatite Saturation?

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

Synthesis and thermoelectric property of Ca-doped n-type Bi85 Sb 15 alloy

NASA Astrophysics Data System (ADS)

Kadel, Kamal; Li, Wenzhi; Joshi, Giri; Ren, Zhifeng

2011-03-01

Bi 1-x Sb x (0.09 x 0.20) alloysaren - typesemiconductingmaterialsthatexhibitagoodthermoelectricpropertyatlowtemperature , around 80 K . InthepresentworkweinvestigatedthethermoelectricpropertiesofundopedBi 85 Sb 15 anddifferentCa - dopedBi 85 Sb 15 Ca x alloys (x = 0.5 , 2 , and 5) synthesizedviaarc - meltingfirstandfollowedbyballmillingandhotpressing . EffectofdifferentCadopinglevelsontransportpropertiesofBi 85 Sb 15 alloyshasbeeninvestigated . ItisfoundthatthermalconductivitydecreaseswithincreasingCa . ElectricaltransportmeasurementsshowthatpowerfactorincreaseswithdopinglevelofCauptoBi 85 Sb 15 Ca 2 andthendecreases , yieldingthemaximumvalueofpowerfactorof 3.8 × 10 -3 Wm -1 K -2 andZTof 0.39 atroomtemperatureforBi 85 Sb 15 Ca 2 . Properties at below room temperature will also be presented.

Cell-type specific circuit connectivity of hippocampal CA1 revealed through Cre-dependent rabies tracing

PubMed Central

Sun, Yanjun; Nguyen, Amanda; Nguyen, Joseph; Le, Luc; Saur, Dieter; Choi, Jiwon; Callaway, Edward M.; Xu, Xiangmin

2014-01-01

Summary We applied a new Cre-dependent, genetically modified rabies-based tracing system to map direct synaptic connections to CA1 excitatory and inhibitory neuron types in mouse hippocampus. We found common inputs to excitatory and inhibitory CA1 neurons from CA3, CA2, entorhinal cortex and the medial septum (MS), and unexpectedly also from the subiculum. Excitatory CA1 neurons receive inputs from both cholinergic and GABAergic MS neurons while inhibitory CA1 neurons receive a great majority of input from GABAergic MS neurons; both cell types also receive weaker input from glutamatergic MS neurons. Comparisons of inputs to CA1 PV+ interneurons versus SOM+ interneurons showed similar strengths of input from the subiculum, but PV+ interneurons receive much stronger input than SOM+ neurons from CA3, entorhinal cortex and MS. Differential input from CA3 to specific CA1 cell types was also demonstrated functionally using laser scanning photostimulation and whole cell recordings. PMID:24656815

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

PubMed

Su, J Y; Chang, Y I

1993-05-01

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

Calcium–calmodulin signalling pathway up-regulates glutamatergic synaptic function in non-pyramidal, fast spiking rat hippocampal CA1 neurons

PubMed Central

Wang, Jin-Hui; Kelly, Paul

2001-01-01

The role of Ca2+-calmodulin (CaM) signalling cascades in modulating glutamatergic synaptic transmission on CA1 non-pyramidal fast-spiking neurons was investigated using whole-cell recording and perfusion in rat hippocampal slices. Paired stimuli (PS), consisting of postsynaptic depolarization to 0 mV and presynaptic stimulation at 1 Hz for 30 s, enhanced excitatory postsynaptic currents (EPSCs) on non-pyramidal neurons in the stratum pyramidale (SP). The potentiation was reduced by the extracellular application of d-amino-5-phosphonovaleric acid (DAP-5, 40 μm), and blocked by the postsynaptic perfusion of 1,2-bis(2-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid (BAPTA, 10 mm), a CaM-binding peptide (100 μm) or CaMKII (281–301) (an autoinhibitory peptide of CaM-dependent protein kinases, 100 μm). The application of adenophostin, an agonist of inositol trisphosphate receptors (IP3Rs) that evokes Ca2+ release, into SP non-pyramidal neurons via the patch pipette (1 μm) enhanced EPSCs and occluded PS-induced synaptic potentiation. The co-application of BAPTA (10 mm) with adenophostin blocked synaptic potentiation. In addition, Ca2+-CaM (40:10 μm) induced synaptic potentiation, which occluded PS-induced potentiation and was attenuated by introducing CaMKII (281–301) (100 μm). EPSCs were sensitive to an antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR). Application of Ca2+-CaM into SP non-pyramidal neurons induced the emergence of AMPAR-mediated EPSCs that were not evoked by low stimulus intensity before perfusion. Ca2+-CaM also increased the amplitude and frequency of spontaneous EPSCs. A scavenger of nitric oxide, carboxy-PTIO (30 μm in slice-perfusion solution), did not affect these increases in sEPSCs. The magnitude of PS-, adenophostin- or Ca2+-CaM-induced synaptic potentiation in SP non-pyramidal neurons increased during postnatal development. These results indicate that Ca2+-CaM signalling pathways in CA1 SP non-pyramidal neurons up-regulate glutamatergic synaptic transmission probably through the conversion of inactive-to-active synapses. PMID:11389201

In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

PubMed

Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

2010-05-01

Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Basal activity of voltage-gated Ca(2+) channels controls the IP3-mediated contraction by α(1)-adrenoceptor stimulation of mouse aorta segments.

PubMed

Leloup, Arthur J; Van Hove, Cor E; De Meyer, Guido R Y; Schrijvers, Dorien M; Fransen, Paul

2015-08-05

α1-Adrenoceptor stimulation of mouse aorta causes intracellular Ca(2+) release from sarcoplasmic reticulum Ca(2+) stores via stimulation of inositoltriphosphate (IP3) receptors. It is hypothesized that this Ca(2+) release from the contractile and IP3-sensitive Ca(2+) store is under the continuous dynamic control of time-independent basal Ca(2+) influx via L-type voltage-gated Ca(2+) channels (LCC) residing in their window voltage range. Mouse aortic segments were α1-adrenoceptor stimulated with phenylephrine in the absence of external Ca(2+) (0Ca) to measure phasic isometric contractions. They gradually decreased with time in 0Ca, were inhibited with 2-aminoethoxydiphenyl borate, and declined with previous membrane potential hyperpolarization (levcromakalim) or with previous inhibition of LCC (diltiazem). Former basal stimulation of LCC with depolarization (15 mM K(+)) or with BAY K8644 increased the subsequent phasic contractions by phenylephrine in 0Ca. Although exogenous NO (diethylamine NONOate) reduced the phasic contractions by phenylephrine, stimulation of endothelial cells with acetylcholine in 0Ca failed to attenuate these phasic contractions. Finally, inhibition of the basal release of NO with N(Ω)-nitro-L-arginine methyl ester also attenuated the phasic contractions by phenylephrine. Results indicated that α1-adrenoceptor stimulation with phenylephrine causes phasic contractions, which are controlled by basal LCC and endothelial NO synthase activity. Endothelial NO release by acetylcholine was absent in 0Ca. Given the growing interest in the active regulation of arterial compliance, the dependence of contractile SR Ca(2+) store-refilling in basal conditions on the activity of LCC and basal eNOS may contribute to a more thorough understanding of physiological mechanisms leading to arterial stiffness. Copyright © 2015. Published by Elsevier B.V.

Enhancement of red emission intensity of Ca2Al2SiO7:Eu3+ phosphor by MoO3 doping or excess SiO2 addition for application to white LEDs

NASA Astrophysics Data System (ADS)

Jiao, H. Y.; LiMao, C. R.; Chen, Q.; Wang, P. Y.; Cai, R. C.

2018-01-01

Ca1.86Al2(Si1-xMox)O7:0.14Eu3+ and Ca1.86Al2Si1+yO7+2y:0.14 Eu3+ were synthesized by solid-state reaction. X-ray powder diffraction, excitation and emission spectra were used to investigate their structures and photoluminescence properties. The results shows that the phosphor Ca1.86Al2SiO7:0.14Eu3+ cannot be excited efficiently by light of 393 nm. The introduced Mo ion does not change the position of the excitation peak, but increases both the absorption at 400nm and the emission intensity of Eu3+. The intense red emitting phosphor Ca1.86Al2(Si0.95Mo0.05)O7:0.14Eu3+ was obtained, which has 67% enhanced luminous intensity compared to that of the undoped sample Ca1.86Al2SiO7:0.14Eu3+. Otherwise, SiO2 excess of non-stoichiometric phosphors Ca1.86Al2Si1+yO7+2y:0.14Eu3+ showed the characteristic pattern of a tetragonal structure with a small SiO2 concentration. The optimal phosphor of Ca1.86Al2Si1.1O7.2:0.14Eu3+ has a luminous intensity about two times higher than that of the original stoichiometric phosphor Ca1.86Al2SiO7:0.14Eu3+. We confirmed that the photoluminescence intensity of the obtained phosphors is fairly enhanced by excessive SiO2. The mechanism of this photoluminescence enhancement is discussed in this paper.

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

PubMed

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

2008-05-15

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

β-carbonic anhydrases play a role in salicylic acid perception in Arabidopsis

PubMed Central

Medina-Puche, Laura; Castelló, María José; Canet, Juan Vicente; Lamilla, Julián; Colombo, María Laura

2017-01-01

The plant hormone salicylic acid (SA) is required for defense responses. NON EXPRESSER OF PATHOGENESIS RELATED 1 (NPR1) and NON RECOGNITION OF BTH-4 (NRB4) are required for the response to SA in Arabidopsis (Arabidopsis thaliana). Here, we isolated several interactors of NRB4 using yeast two-hybrid assays. Two of these interactors, βCA1 and βCA2, are β-carbonic anhydrase family proteins. Since double mutant βca1 βca2 plants did not show any obvious phenotype, we investigated other βCAs and found that NRB4 also interacts with βCA3 and βCA4. Moreover, several βCAs interacted with NPR1 in yeast, including one that interacted in a SA-dependent manner. This interaction was abolished in loss-of-function alleles of NPR1. Interactions between βCAs and both NRB4 and NPR1 were also detected in planta, with evidence for a triple interaction, NRB4-βCA1-NPR1. The quintuple mutant βca1 βca2 βca3 βca4 βca6 showed partial insensitivity to SA. These findings suggest that one of the functions of carbonic anhydrases is to modulate the perception of SA in plants. PMID:28753666

Effects of calcium binding and of EDTA and CaEDTA on the clotting of bovine fibrinogen by thrombin.

PubMed

Perizzolo, K E; Sullivan, S; Waugh, D F

1985-03-01

Studies were carried out at pH 7.0 and gamma/2 0.15 before addition of CaCl2 or EDTA. Clotting time, tau, at 3.03 microM fibrinogen and 0.91 u/ml thrombin was determined for equilibrium systems. With added Ca2+, tau decreases, from tau 0 at 0 added Ca2+ (mean, 29.7 +/- 3 s), by approximately 3 s at 5 mM added Ca2+. With added EDTA, tau increases sigmoidally from tau 0 at 0 EDTA to a maximum (mean tau m = 142 +/- 23 s) at approximately 200 microM EDTA. tau then decreases slightly to a minimum at approximately 1.3 mM and finally increases to infinity at approximately 10 mM EDTA. Between 0 and 1.3 mM EDTA, effects on clotting time are completely reversed by adding Ca2+ and, after equilibration at 400 microM EDTA, tau is independent of EDTA concentration. Thus, up to 400 microM EDTA, effects on clotting time are attributed to decreasing fibrinogen bound Ca2+. Between 5 mM Ca2+ and 200 microM EDTA it is assumed that an equilibrium distribution of fibrinogen species having 3, 2, 1, or 0 bound calcium ions is established and that a clotting time is determined by the sum of products of species fractional abundance and pure species clotting time. Analysis indicates that pure species clotting times increase proportionately with decreasing Ca2+ binding, binding sites are nearly independent, and the microscopic association constant for the first bound Ca2+ is approximately 4.9 X 10(6) M-1. Effects of adding Ca2+ at times t1 after thrombin addition to systems initially equilibrated at 200 microM EDTA were determined. Analysis of the relation between tau and t1 indicates that as Ca2+ binding decreases, rate constants for release of B peptides decrease less than those for release of A peptides. As EDTA concentration is increased above 1.3 mM, inhibitory effects of EDTA and CaEDTA progressively increase.

Type 1 Inositol (1,4,5)-Trisphosphate Receptor Activates Ryanodine Receptor 1 to Mediate Calcium Spark Signaling in Adult Mammalian Skeletal Muscle*♦

PubMed Central

Tjondrokoesoemo, Andoria; Li, Na; Lin, Pei-Hui; Pan, Zui; Ferrante, Christopher J.; Shirokova, Natalia; Brotto, Marco; Weisleder, Noah; Ma, Jianjie

2013-01-01

Functional coupling between inositol (1,4,5)-trisphosphate receptor (IP3R) and ryanodine receptor (RyR) represents a critical component of intracellular Ca2+ signaling in many excitable cells; however, the role of this mechanism in skeletal muscle remains elusive. In skeletal muscle, RyR-mediated Ca2+ sparks are suppressed in resting conditions, whereas application of transient osmotic stress can trigger activation of Ca2+ sparks that are restricted to the periphery of the fiber. Here we show that onset of these spatially confined Ca2+ sparks involves interaction between activation of IP3R and RyR near the sarcolemmal membrane. Pharmacological prevention of IP3 production or inhibition of IP3R channel activity abolishes stress-induced Ca2+ sparks in skeletal muscle. Although genetic ablation of the type 2 IP3R does not appear to affect Ca2+ sparks in skeletal muscle, specific silencing of the type 1 IP3R leads to ablation of stress-induced Ca2+ sparks. Our data indicate that membrane-delimited signaling involving cross-talk between IP3R1 and RyR1 contributes to Ca2+ spark activation in skeletal muscle. PMID:23223241

High-pressure synthesis and structural, physical properties of CaIr1-xPtxO3 and CaIr1-xRhxO3

NASA Astrophysics Data System (ADS)

Hirai, S.; Bromiley, G. D.; Klemme, S.; Irifune, T.; Ohfuji, H.; Attfield, P.; Nishiyama, N.

2010-12-01

Since the discovery of the perovskite to post-perovskite transition in MgSiO3 in a laser-heated DAC, wide attention has been focussed on the post-perovskite phase of MgSiO3. This is because the post-perovskite phase is likely to play a key role in Earth’s lowermost mantle, and because the perovskite to post-perovskite transition can explain many features of the D” seismic discontinuity. While it is meaningful to conduct further studies of MgSiO3, the post-perovskite phase of MgSiO3 cannot be quenched to ambient pressure/temperature conditions. Thus, further studies must be conducted using analogue compounds of MgSiO3 post-perovskite, which are quenchable to ambient pressure/temperature conditions. The post-perovskite phase of MgSiO3 crystallizes in a layered structure with CaIrO3-structure. Therefore, it is useful to investigate compounds with CaIrO3-structure. There are only four quenchable oxides with CaIrO3-structure reported to date: CaIrO3, CaPtO3, CaRhO3 and CaRuO3. CaIrO3 can be synthesized at ambient pressure, whilst the other three oxides can only be obtained at high pressure/temperature conditions using a multi-anvil apparatus. Further studies on these materials have revealed structural phase transitions at high P-T and a metal-insulator transition by hole doping. In the case of CaIrO3, The post-perovskite phase of CaIrO3 synthesized at 2GPa, 1373K transforms into a perovskite phase at 2GPa, 1673K. In other words, the perovskite phase can be synthesized at temperatures higher than those needed for synthesizing the post-perovskite phase. This is also the case for CaRhO3 (6GPa, 1873K) and CaRuO3 (23GPa, 1343K), while CaPtO3 remained post-perovskite at higher temperatures. We have succeeded in synthesizing solid solutions between CaIrO3, CaPtO3 and CaRhO3. We have found the systematic change in structural and physical properties of post-perovskite oxides, with composition and P-T, which broadens the future opportunity for studying post-perovskite systems in terms of materials science applications. To our knowledge, this will be the first report on structural, magnetic and charge-transport properties of B-site substituted solid solutions of post-perovskite oxides with 4d/5d transition metals. High-quality polycrystalline samples of CaIr1-xPtxO3 and CaIr1-xRhxO3 have been obtained at high pressures, and structural, magnetic and charge-transport properties of the compounds will be reported. ODF analysis reveals that solutions of CaIrO3, CaPtO3 and CaRhO3 exhibit similar grain growth features to the mother compound, although growth in [0 1 0] plays a more dominant role than the growth in [0 0 1] for the solid solutions. CaIrO3 is a characteristic hard magnet suitable for applications such as magnetic recording, with TN = 108K. A new phase of CaIr1-xPtxO3 synthesized at a high P/T condition has Raman modes which resemble those of CaIrO3 perovskite, suggesting this phase has a perovskite structure.The instability of the perovskite phase of CaIr1-xPtxO3 reveals why the post-perovskite to peovskite phase transition has not been observed for CaPtO3 unlike the case for CaIrO3, CaRhO3 and CaRuO3.

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

PubMed

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

2008-08-08

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

Enhancement of the red emission in CaTiO 3:Pr 3+ by addition of rare earth oxides

NASA Astrophysics Data System (ADS)

Zhang, Xianmin; Zhang, Jiahua; Zhang, Xia; Chen, Li; Luo, Yongshi; Wang, Xiao-jun

2007-02-01

Enhancement of the 1D 2- 3H 4 red emission of CaTiO 3:Pr 3+ with addition of rare earth oxides Ln 2O 3 (Ln = Lu, La, Gd) is reported. Ca 2+ and Ti 4+ in CaTiO 3 can be substituted by Ln 3+ ions as donors and acceptors, respectively. Ca 2+ and Ti 4+ vacancies, as quenching centers in the host, are effectively suppressed by the self-compensation, leading to the increase of lifetimes and then the emission efficiency of 1D 2. The red fluorescence intensity for CaTiO 3:Pr 3+ phosphor co-doped with 5 mol% Lu 2O 3 is nearly 3 times greater than that of the Lu-free samples.

GTP requirement for inositol-1,4,5-trisphosphate-induced Ca2+ release from sarcoplasmic reticulum in smooth muscle.

PubMed

Saida, K; van Breemen, C

1987-05-14

We have examined inositol-1,4,5-trisphosphate (IP3)-induced Ca2+ release from the sarcoplasmic reticulum (SR) in the skinned vascular smooth muscle. The amount of Ca2+ in the SR was estimated indirectly by caffeine-induced contraction of the skinned preparation. The Ca2+ release from the SR by IP3 required GTP. A non-hydrolyzable analogue of GTP, guanosine 5'-(beta gamma-imido) triphosphate (GppNHp) could substitute for GTP in the IP3-induced Ca2+ release. These results suggest an involvement of GTP-binding protein in the mechanism of Ca2+ release from the SR by IP3 in smooth muscle.

Effects of S(+)-efonidipine on the rabbit sinus node action potential and calcium channel subunits Ca(V)1.2, Ca(V)1.3 and Ca(V)3.1.

PubMed

Tanaka, Hikaru; Namekata, Iyuki; Ogawa, Toru; Tsuneoka, Yayoi; Komikado, Chisa; Takahara, Akira; Iida-Tanaka, Naoko; Izumi-Nakaseko, Hiroko; Tsuru, Hiromichi; Adachi-Akahane, Satomi

2010-12-15

The effect of S(+)-efonidipine on sinus node action potential and calcium channel α-subunits was examined. The slope of the phase 4 depolarization of isolated rabbit sinus node tissue was significantly reduced by S(+)-efonidipine (1 μM), slightly reduced by nifedipine (1 μM), but was not affected by R(-)-efonidipine. S(+)-efonidipine (1 μM), inhibited the expressed Ca(V)1.2, Ca(V)1.3 and Ca(V)3.1 channel currents by 75.7%, 75.3% and 94.0%, nifedipine 84.0%, 43.2% and 14.9%, and R(-)-efonidipine 30.0%, 19.6% and 92.8%, respectively. Thus, the prolongation of the phase 4 depolarization of the rabbit sinus node by S(+)-efonidipine may be explained by blockade of the Ca(V)1.3 channel current. Copyright © 2010 Elsevier B.V. All rights reserved.

Experimental Determination of Solubilities of Tri-calcium Di-Citrate Tetrahydrate [Ca 3[C 3H 5O(COO) 3] 2•4H 2O] Earlandite in NaCl and MgCl 2 Solutions to High Ionic Strengths and Its Pitzer Model: Applications to Nuclear Waste Isolation and Other Low Temperature Environments

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

Xiong, Yongliang; Kirkes, Leslie Dawn; Westfall, Terry

In this study, solubility measurements on tri-calcium di-citrate tetrahydrate [Ca 3[C 3H 5O(COO) 3]2•4H 2O, abbreviated as Ca 3[Citrate] 2•4H 2O] as a function of ionic strength are conducted in NaCl solutions up to I = 5.0 mol•kg –1 and in MgCl 2 solutions up to I = 7.5 mol•kg –1, at room temperature (22.5 ± 0.5°C). The solubility constant (log Kmore » $$0\\atop{sp}$$) for Ca 3[Citrate] 2•4H 2O and formation constant (logβ$$0\\atop{1}$$) for Ca[C 3H 5O(COO) 3] –Ca 3[C 3H 5O(COO) 3] 2•4H 2O (earlandite) = 3Ca 2+ + 2[C 3H 5O(COO) 3] 3– + 4H 2O (1) Ca 2+ + [C 3H 5O(COO) 3] 3– = Ca[C 3H 5O(COO) 3] – (2) are determined as –18.11 ± 0.05 and 4.97 ± 0.05, respectively, based on the Pitzer model with a set of Pitzer parameters describing the specific interactions in NaCl and M gCl 2 media.« less

Stimulation-evoked Ca2+ signals in astrocytic processes at hippocampal CA3-CA1 synapses of adult mice are modulated by glutamate and ATP.

PubMed

Tang, Wannan; Szokol, Karolina; Jensen, Vidar; Enger, Rune; Trivedi, Chintan A; Hvalby, Øivind; Helm, P Johannes; Looger, Loren L; Sprengel, Rolf; Nagelhus, Erlend A

2015-02-18

To date, it has been difficult to reveal physiological Ca(2+) events occurring within the fine astrocytic processes of mature animals. The objective of the study was to explore whether neuronal activity evokes astrocytic Ca(2+) signals at glutamatergic synapses of adult mice. We stimulated the Schaffer collateral/commissural fibers in acute hippocampal slices from adult mice transduced with the genetically encoded Ca(2+) indicator GCaMP5E driven by the glial fibrillary acidic protein promoter. Two-photon imaging revealed global stimulation-evoked astrocytic Ca(2+) signals with distinct latencies, rise rates, and amplitudes in fine processes and somata. Specifically, the Ca(2+) signals in the processes were faster and of higher amplitude than those in the somata. A combination of P2 purinergic and group I/II metabotropic glutamate receptor (mGluR) antagonists reduced the amplitude of the Ca(2+) transients by 30-40% in both astrocytic compartments. Blockage of the mGluRs alone only modestly reduced the magnitude of the stimulation-evoked Ca(2+) signals in processes and failed to affect the somatic Ca(2+) response. Local application of group I or I/II mGluR agonists or adenosine triphosphate (ATP) elicited global astrocytic Ca(2+) signals that mimicked the stimulation-evoked astrocytic Ca(2+) responses. We conclude that stimulation-evoked Ca(2+) signals in astrocytic processes at CA3-CA1 synapses of adult mice (1) differ from those in astrocytic somata and (2) are modulated by glutamate and ATP. Copyright © 2015 the authors 0270-6474/15/353016-06$15.00/0.

Impact of anthropogenic CO2 on the CaCO3 system in the oceans.

PubMed

Feely, Richard A; Sabine, Christopher L; Lee, Kitack; Berelson, Will; Kleypas, Joanie; Fabry, Victoria J; Millero, Frank J

2004-07-16

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5 +/- 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3.

Cell culture alters Ca2+ entry pathways activated by store-depletion or hypoxia in canine pulmonary arterial smooth muscle cells.

PubMed

Ng, Lih Chyuan; Kyle, Barry D; Lennox, Alison R; Shen, Xiao-Ming; Hatton, William J; Hume, Joseph R

2008-01-01

Previous studies have shown that, in acutely dispersed canine pulmonary artery smooth muscle cells (PASMCs), depletion of both functionally independent inositol 1,4,5-trisphosphate (IP(3))- and ryanodine-sensitive Ca(2+) stores activates capacitative Ca(2+) entry (CCE). The present study aimed to determine if cell culture modifies intracellular Ca(2+) stores and alters Ca(2+) entry pathways caused by store depletion and hypoxia in canine PASMCs. Intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured in fura 2-loaded cells. Mn(2+) quench of fura 2 signal was performed to study divalent cation entry, and the effects of hypoxia were examined under oxygen tension of 15-18 mmHg. In acutely isolated PASMCs, depletion of IP(3)-sensitive Ca(2+) stores with cyclopiazonic acid (CPA) did not affect initial caffeine-induced intracellular Ca(2+) transients but abolished 5-HT-induced Ca(2+) transients. In contrast, CPA significantly reduced caffeine- and 5-HT-induced Ca(2+) transients in cultured PASMCs. In cultured PASMCs, store depletion or hypoxia caused a transient followed by a sustained rise in [Ca(2+)](i). The transient rise in [Ca(2+)](i) was partially inhibited by nifedipine, whereas the nifedipine-insensitive transient rise in [Ca(2+)](i) was inhibited by KB-R7943, a selective inhibitor of reverse mode Na(+)/Ca(2+) exchanger (NCX). The nifedipine-insensitive sustained rise in [Ca(2+)](i) was inhibited by SKF-96365, Ni(2+), La(3+), and Gd(3+). In addition, store depletion or hypoxia increased the rate of Mn(2+) quench of fura 2 fluorescence that was also inhibited by these blockers, exhibiting pharmacological properties characteristic of CCE. We conclude that cell culture of canine PASMCs reorganizes IP(3) and ryanodine receptors into a common intracellular Ca(2+) compartment, and depletion of this store or hypoxia activates voltage-operated Ca(2+) entry, reverse mode NCX, and CCE.

β-Cell Ca(2+) dynamics and function are compromised in aging.

PubMed

Barker, Christopher J; Li, Luosheng; Köhler, Martin; Berggren, Per-Olof

2015-01-01

Defects in pancreatic β-cell function and survival are key components in type 2 diabetes (T2D). An age-dependent deterioration in β-cell function has also been observed, but little is known about the molecular mechanisms behind this phenomenon. Our previous studies indicate that the regulation of cytoplasmic free Ca(2+) concentration ([Ca(2+)]i) may be critical and that this is dependent on the proper function of the mitochondria. The [Ca(2+)]i dynamics of the pancreatic β-cell are driven by an interplay between glucose-induced influx of extracellular Ca(2+) via voltage-dependent Ca(2+) channels and the inositol 1,4,5-trisphosphate (Ins(1,4,5)P3)-mediated liberation of Ca(2+) from intracellular stores. Our previous work has indicated a direct relationship between disruption of Ins(1,4,5)P3-mediated Ca(2+) regulation and loss of β-cell function, including disturbed [Ca(2+)]i dynamics and compromised insulin secretion. To investigate these processes in aging we used three mouse models, a premature aging mitochondrial mutator mouse, a mature aging phenotype (C57BL/6) and an aging-resistant phenotype (129). Our data suggest that age-dependent impairment in mitochondrial function leads to modest changes in [Ca(2+)]i dynamics in mouse β-cells, particularly in the pattern of [Ca(2+)]i oscillations. These changes are driven by modifications in both PLC/Ins(1,4,5)P3-mediated Ca(2+) mobilization from intracellular stores and decreased β-cell Ca(2+) influx over the plasma membrane. Our findings underscore an important concept, namely that even relatively small, time-dependent changes in β-cell signal-transduction result in compromised insulin release and in a diabetic phenotype. Copyright © 2014 Elsevier Ltd. All rights reserved.

ACUTE EFFECT OF ETHANOL ON HEPATIC RETICULAR G6Pase AND Ca2+ POOL

PubMed Central

Jacobs-Harper, Amy; Crumbly, Ashlee; Romani, Andrea

2012-01-01

Background Hydrolysis of glucose 6-phosphate via glucose 6-phosphatase enlarges the reticular Ca2+ pool of the hepatocyte. Exposure of liver cells to ethanol impairs reticular Ca2+ homeostasis. The present study investigated the effect of acute ethanol administration on glucose 6-phosphate supported Ca2+ accumulation in liver cells. Methods Total microsomes were isolated from rat livers acutely perfused with varying doses of ethanol (0.01%, 0.1%, or 1% v/v) for 8 minutes. Calcium uptake was assessed by 45Ca redistribution. Inorganic phosphate (Pi) formation was measured as an indicator of glucose 6-phosphatase hydrolytic activity. Results Glucose 6-phosphate-supported Ca2+ uptake decreased in a manner directly proportional to the dose of ethanol infused in the liver whereas Ca2+ uptake via SERCA pumps was decreased by ~25% only at the highest dose of alcohol administered. The reduced accumulation of Ca2+ within the microsomes resulted in a smaller IP3-induced Ca2+ release. Kinetic assessment of IP3 and passive Ca2+ release indicated a faster mobilization in microsomes from ethanol-treated livers, suggesting alcohol-induced alteration of Ca2+ releasing mechanisms. Pre-treatment of livers with chloromethiazole or dithio-threitol, but not 4-methyl-pyrazole prevented the inhibitory effect of ethanol on glucose 6-phosphatase activity and Ca2+ homeostasis. Conclusions Liver glucose 6-phosphatase activity and IP3-mediated Ca2+ release are rapidly inhibited following acute (8 min) exposure to ethanol, thus compromising the ability of the endoplasmic reticulum to dynamically modulate Ca2+ homeostasis in the hepatocyte. The protective effect of chloromethiazole and di-thio-threitol suggests that the inhibitory effect of ethanol is mediated through its metabolism via reticular cyP4502E1 and consequent free radicals formation. PMID:22958133

Localization of the cannabinoid CB1 receptor and the 2-AG synthesizing (DAGLα) and degrading (MAGL, FAAH) enzymes in cells expressing the Ca2+-binding proteins calbindin, calretinin, and parvalbumin in the adult rat hippocampus

PubMed Central

Rivera, Patricia; Arrabal, Sergio; Cifuentes, Manuel; Grondona, Jesús M.; Pérez-Martín, Margarita; Rubio, Leticia; Vargas, Antonio; Serrano, Antonia; Pavón, Francisco J.; Suárez, Juan; Rodríguez de Fonseca, Fernando

2014-01-01

The retrograde suppression of the synaptic transmission by the endocannabinoid sn-2-arachidonoylglycerol (2-AG) is mediated by the cannabinoid CB1 receptors and requires the elevation of intracellular Ca2+ and the activation of specific 2-AG synthesizing (i.e., DAGLα) enzymes. However, the anatomical organization of the neuronal substrates that express 2-AG/CB1 signaling system-related molecules associated with selective Ca2+-binding proteins (CaBPs) is still unknown. For this purpose, we used double-label immunofluorescence and confocal laser scanning microscopy for the characterization of the expression of the 2-AG/CB1 signaling system (CB1 receptor, DAGLα, MAGL, and FAAH) and the CaBPs calbindin D28k, calretinin, and parvalbumin in the rat hippocampus. CB1, DAGLα, and MAGL labeling was mainly localized in fibers and neuropil, which were differentially organized depending on the hippocampal CaBPs-expressing cells. CB+1 fiber terminals localized in all hippocampal principal cell layers were tightly attached to calbindin+ cells (granular and pyramidal neurons), and calretinin+ and parvalbumin+ interneurons. DAGLα neuropil labeling was selectively found surrounding calbindin+ principal cells in the dentate gyrus and CA1, and in the calretinin+ and parvalbumin+ interneurons in the pyramidal cell layers of the CA1/3 fields. MAGL+ terminals were only observed around CA1 calbindin+ pyramidal cells, CA1/3 calretinin+ interneurons and CA3 parvalbumin+ interneurons localized in the pyramidal cell layers. Interestingly, calbindin+ pyramidal cells expressed FAAH specifically in the CA1 field. The identification of anatomically related-neuronal substrates that expressed 2-AG/CB1 signaling system and selective CaBPs should be considered when analyzing the cannabinoid signaling associated with hippocampal functions. PMID:25018703

Highly efficient continuous-wave laser operation of LD-pumped Nd,Gd:CaF2 and Nd,Y:CaF2 crystals

NASA Astrophysics Data System (ADS)

Pang, Siyuan; Ma, Fengkai; Yu, Hao; Qian, Xiaobo; Jiang, Dapeng; Wu, Yongjing; Zhang, Feng; Liu, Jie; Xu, Jiayue; Su, Liangbi

2018-05-01

Spectroscopic properties of Nd:CaF2 crystals are investigated. The photoluminescence intensity in the near infrared region is drastically enhanced by co-doping Gd3+ ions and Y3+ in Nd:CaF2 crystals. Preliminary laser experiments are carried out with 0.3%Nd,5%Gd:CaF2 and 0.3%Nd,5%Y:CaF2 crystals under laser diode pumping; true continuous wave laser operation is achieved with slope efficiencies of 42% and 39%, respectively, and the maximum output power reaches 1.188 W.

Impact of mitochondrial Ca2+ cycling on pattern formation and stability.

PubMed

Falcke, M; Hudson, J L; Camacho, P; Lechleiter, J D

1999-07-01

Energization of mitochondria significantly alters the pattern of Ca2+ wave activity mediated by activation of the inositol (1,4,5) trisphosphate (IP3) receptor (IP3R) in Xenopus oocytes. The number of pulsatile foci is reduced and spiral Ca2+ waves are no longer observed. Rather, target patterns of Ca2+ release predominate, and when fragmented, fail to form spirals. Ca2+ wave velocity, amplitude, decay time, and periodicity are also increased. We have simulated these experimental findings by supplementing an existing mathematical model with a differential equation for mitochondrial Ca2+ uptake and release. Our calculations show that mitochondrial Ca2+ efflux plays a critical role in pattern formation by prolonging the recovery time of IP3Rs from a refractory state. We also show that under conditions of high energization of mitochondria, the Ca2+ dynamics can become bistable with a second stable stationary state of high resting Ca2+ concentration.

Arachidonic acid-induced Ca2+ entry and migration in a neuroendocrine cancer cell line.

PubMed

Goswamee, Priyodarshan; Pounardjian, Tamar; Giovannucci, David R

2018-01-01

Store-operated Ca 2+ entry (SOCE) has been implicated in the migration of some cancer cell lines. The canonical SOCE is defined as the Ca 2+ entry that occurs in response to near-maximal depletion of Ca 2+ within the endoplasmic reticulum. Alternatively, arachidonic acid (AA) has been shown to induce Ca 2+ entry in a store-independent manner through Orai1/Orai3 hetero-multimeric channels. However, the role of this AA-induced Ca 2+ entry pathway in cancer cell migration has not been adequately assessed. The present study investigated the involvement of AA-induced Ca 2+ entry in migration in BON cells, a model gastro-enteropancreatic neuroendocrine tumor (GEPNET) cell line using pharmacological and gene knockdown methods in combination with live cell fluorescence imaging and standard migration assays. We showed that both the store-dependent and AA-induced Ca 2+ entry modes could be selectively activated and that exogenous administration of AA resulted in Ca 2+ entry that was pharmacologically distinct from SOCE. Also, whereas homomeric Orai1-containing channels appeared to largely underlie SOCE, the AA-induced Ca 2+ entry channel required the expression of Orai3 as well as Orai1. Moreover, we showed that AA treatment enhanced the migration of BON cells and that this migration could be abrogated by selective inhibition of the AA-induced Ca 2+ entry. Taken together, these data revealed that an alternative Orai3-dependent Ca 2+ entry pathway is an important signal for GEPNET cell migration.

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

PubMed Central

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

1996-01-01

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

Muscarinic Ca2+ responses resistant to muscarinic antagonists at perisynaptic Schwann cells of the frog neuromuscular junction.

PubMed Central

Robitaille, R; Jahromi, B S; Charlton, M P

1997-01-01

1. Acetylcholine causes a rise of intracellular Ca2+ in perisynaptic Schwann cells (PSCs) of the frog neuromuscular junction. The signalling pathway was characterized using the fluorescent Ca2+ indicator fluo-3 and fluorescence microscopy. 2. Nicotinic antagonists had no effect on Ca2+ responses evoked by ACh and no Ca2+ responses were evoked with the nicotinic agonist nicotine. The muscarinic agonists muscarine and oxotremorine-M induced Ca2+ signals in PSCs. 3. Ca2+ responses remained unchanged when extracellular Ca2+ was removed, indicating that they are due to the release of Ca2+ from internal stores. Incubation with pertussis toxin did not alter the Ca2+ signals induced by muscarine, but did block depression of transmitter release induced by adenosine and prevented Ca2+ responses in PSCs induced by adenosine. 4. The general muscarinic antagonists atropine, quinuclidinyl benzilate and N-methyl-scopolamine failed to block Ca2+ responses to muscarinic agonists. Atropine (at 20,000-fold excess concentration) also failed to reduce the proportion of cells responding to a threshold muscarine concentration sufficient to cause responses in less than 50% of cells. Only the allosteric, non-specific blocker, gallamine (1-10 microM) was effective in blocking muscarine-induced Ca2+ responses. 5. In preparations denervated 7 days prior to experiments, low concentrations of atropine reversibly and completely blocked Ca2+ responses to muscarine. 6. The lack of blockade by general muscarinic antagonists in innervated, in situ preparations suggests that muscarinic Ca2+ responses at PSCs are not mediated by any of the five known muscarinic receptors or that post-translational modification prevented antagonist binding. Images Figure 2 Figure 3 Figure 4 Figure 6 Figure 7 PMID:9365908

Identification and characterization of calcium transporter gene family in finger millet in relation to grain calcium content.

PubMed

Singh, Uma M; Metwal, Mamta; Singh, Manoj; Taj, Gohar; Kumar, Anil

2015-07-15

Calcium (Ca) is an essential mineral for proper growth and development of plants as well as animals. In plants including cereals, calcium is deposited in seed during its development which is mediated by specialized Ca transporters. Common cereal seeds contain very low amounts of Ca while the finger millet (Eleusine coracana) contains exceptionally high amounts of Ca in seed. In order to understand the role of Ca transporters in grain Ca accumulation, developing seed transcriptome of two finger millet genotypes (GP-1, low Ca and GP-45 high Ca) differing in seed Ca content was sequenced using Illumina paired-end sequencing technology and members of Ca transporter gene family were identified. Out of 109,218 and 120,130 contigs, 86 and 81 contigs encoding Ca transporters were identified in GP-1 and GP-45, respectively. After removal of redundant sequences, a total of 19 sequences were confirmed as Ca transporter genes, which includes 11 Ca(2+) ATPases, 07 Ca(2+)/cation exchangers and 01 Ca(2+) channel. The differential expressions of all genes were analyzed from transcriptome data and it was observed that 9 and 3 genes were highly expressed in GP-45 and GP-1 genotypes respectively. Validation of transcriptome expression data of selected Ca transporter genes was performed on different stages of developing spikes of both genotypes grown under different concentrations of exogenous Ca. In both genotypes, significant correlation was observed between the expression of these genes, especially EcCaX3, and on the amount of Ca accumulated in seed. The positive correlation of seed mass with the amount of Ca concentration was also observed. The efficient Ca transport property and responsiveness of EcCAX3 towards exogenous Ca could be utilized in future biofortification program. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of Sodium Chloride, Potassium Chloride and Calcium Chloride on the Formation of α-Dicarbonyl Compounds, Furfurals and Development of Browning in Cookies during Baking.

PubMed

Kocadağlı, Tolgahan; Gökmen, Vural

2016-10-02

Effect of NaCl, KCl, CaCl2, NaHCO3, and NH4HCO3 on the formation of glucosone, 1-deoxyglucosone, 3-deoxyglucosone, glyoxal, methylglyoxal, diacetyl, 5-hydroxymethyl-2-furfural, 2-furfural and browning were investigated in cookies. Presence of 1.5% NaCl, 1% KCl, and 1% CaCl2 on flour basis had no effect on α-dicarbonyl compounds, except 1-deoxyglucosone increased in the presence of KCl and CaCl2. The increase in 5-hydroxymethyl-2-furfural formation in the presence of NaCl, KCl, and CaCl2 did not relate to 3-deoxyglucosone formation and pH changes. NaCl, KCl, and CaCl2 increased browning in cookies. Model reaction systems indicated that NaCl, KCl, and CaCl2 enhance browning by increasing furfurals in caramelization. NaCl, KCl, and CaCl2 decreased browning intensity in heated glucose-glycine system. Usage of CaCl2 in cookies may considerably increase furfurals but not α-dicarbonyl compounds. Sodium reduction can be obtained by replacement with potassium without sacrificing the desired consequences of caramelization in sugar rich bakeries.

Effect of metabolic and respiratory acidosis on intracellular calcium in osteoblasts.

PubMed

Frick, Kevin K; Bushinsky, David A

2010-08-01

In vivo, metabolic acidosis {decreased pH from decreased bicarbonate concentration ([HCO(3)(-)])} increases urine calcium (Ca) without increased intestinal Ca absorption, resulting in a loss of bone Ca. Conversely, respiratory acidosis [decreased pH from increased partial pressure of carbon dioxide (Pco(2))] does not appreciably alter Ca homeostasis. In cultured bone, chronic metabolic acidosis (Met) significantly increases cell-mediated net Ca efflux while isohydric respiratory acidosis (Resp) does not. The proton receptor, OGR1, appears critical for cell-mediated, metabolic acid-induced bone resorption. Perfusion of primary bone cells or OGR1-transfected Chinese hamster ovary (CHO) cells with Met induces transient peaks of intracellular Ca (Ca(i)). To determine whether Resp increases Ca(i), as does Met, we imaged Ca(i) in primary cultures of bone cells. pH for Met = 7.07 ([HCO(3)(-)] = 11.8 mM) and for Resp = 7.13 (Pco(2) = 88.4 mmHg) were similar and lower than neutral (7.41). Both Met and Resp induced a marked, transient increase in Ca(i) in individual bone cells; however, Met stimulated Ca(i) to a greater extent than Resp. We used OGR1-transfected CHO cells to determine whether OGR1 was responsible for the greater increase in Ca(i) in Met than Resp. Both Met and Resp induced a marked, transient increase in Ca(i) in OGR1-transfected CHO cells; however, in these cells Met was not different than Resp. Thus, the greater induction of Ca(i) by Met in primary bone cells is not a function of OGR1 alone, but must involve H(+) receptors other than OGR1, or pathways sensitive to Pco(2), HCO(3)(-), or total CO(2) that modify the effect of H(+) in primary bone cells.

Function of a STIM1 Homologue in C. elegans: Evidence that Store-operated Ca2+ Entry Is Not Essential for Oscillatory Ca2+ Signaling and ER Ca2+ Homeostasis

PubMed Central

Yan, Xiaohui; Xing, Juan; Lorin-Nebel, Catherine; Estevez, Ana Y.; Nehrke, Keith; Lamitina, Todd; Strange, Kevin

2006-01-01

1,4,5-trisphosphate (IP3)-dependent Ca2+ signaling regulates gonad function, fertility, and rhythmic posterior body wall muscle contraction (pBoc) required for defecation in Caenorhabditis elegans. Store-operated Ca2+ entry (SOCE) is activated during endoplasmic reticulum (ER) Ca2+ store depletion and is believed to be an essential and ubiquitous component of Ca2+ signaling pathways. SOCE is thought to function to refill Ca2+ stores and modulate Ca2+ signals. Recently, stromal interaction molecule 1 (STIM1) was identified as a putative ER Ca2+ sensor that regulates SOCE. We cloned a full-length C. elegans stim-1 cDNA that encodes a 530–amino acid protein with ∼21% sequence identity to human STIM1. Green fluorescent protein (GFP)–tagged STIM-1 is expressed in the intestine, gonad sheath cells, and spermatheca. Knockdown of stim-1 expression by RNA interference (RNAi) causes sterility due to loss of sheath cell and spermatheca contractile activity required for ovulation. Transgenic worms expressing a STIM-1 EF-hand mutant that constitutively activates SOCE in Drosophila and mammalian cells are sterile and exhibit severe pBoc arrhythmia. stim-1 RNAi dramatically reduces STIM-1∷GFP expression, suppresses the EF-hand mutation–induced pBoc arrhythmia, and inhibits intestinal store-operated Ca2+ (SOC) channels. However, stim-1 RNAi surprisingly has no effect on pBoc rhythm, which is controlled by intestinal oscillatory Ca2+ signaling, in wild type and IP3 signaling mutant worms, and has no effect on intestinal Ca2+ oscillations and waves. Depletion of intestinal Ca2+ stores by RNAi knockdown of the ER Ca2+ pump triggers the ER unfolded protein response (UPR). In contrast, stim-1 RNAi fails to induce the UPR. Our studies provide the first detailed characterization of STIM-1 function in an intact animal and suggest that SOCE is not essential for certain oscillatory Ca2+ signaling processes and for maintenance of store Ca2+ levels in C. elegans. These findings raise interesting and important questions regarding the function of SOCE and SOC channels under normal and pathophysiological conditions. PMID:16966474

Function of a STIM1 homologue in C. elegans: evidence that store-operated Ca2+ entry is not essential for oscillatory Ca2+ signaling and ER Ca2+ homeostasis.

PubMed

Yan, Xiaohui; Xing, Juan; Lorin-Nebel, Catherine; Estevez, Ana Y; Nehrke, Keith; Lamitina, Todd; Strange, Kevin

2006-10-01

1,4,5-trisphosphate (IP(3))-dependent Ca(2+) signaling regulates gonad function, fertility, and rhythmic posterior body wall muscle contraction (pBoc) required for defecation in Caenorhabditis elegans. Store-operated Ca(2+) entry (SOCE) is activated during endoplasmic reticulum (ER) Ca(2+) store depletion and is believed to be an essential and ubiquitous component of Ca(2+) signaling pathways. SOCE is thought to function to refill Ca(2+) stores and modulate Ca(2+) signals. Recently, stromal interaction molecule 1 (STIM1) was identified as a putative ER Ca(2+) sensor that regulates SOCE. We cloned a full-length C. elegans stim-1 cDNA that encodes a 530-amino acid protein with approximately 21% sequence identity to human STIM1. Green fluorescent protein (GFP)-tagged STIM-1 is expressed in the intestine, gonad sheath cells, and spermatheca. Knockdown of stim-1 expression by RNA interference (RNAi) causes sterility due to loss of sheath cell and spermatheca contractile activity required for ovulation. Transgenic worms expressing a STIM-1 EF-hand mutant that constitutively activates SOCE in Drosophila and mammalian cells are sterile and exhibit severe pBoc arrhythmia. stim-1 RNAi dramatically reduces STIM-1GFP expression, suppresses the EF-hand mutation-induced pBoc arrhythmia, and inhibits intestinal store-operated Ca(2+) (SOC) channels. However, stim-1 RNAi surprisingly has no effect on pBoc rhythm, which is controlled by intestinal oscillatory Ca(2+) signaling, in wild type and IP(3) signaling mutant worms, and has no effect on intestinal Ca(2+) oscillations and waves. Depletion of intestinal Ca(2+) stores by RNAi knockdown of the ER Ca(2+) pump triggers the ER unfolded protein response (UPR). In contrast, stim-1 RNAi fails to induce the UPR. Our studies provide the first detailed characterization of STIM-1 function in an intact animal and suggest that SOCE is not essential for certain oscillatory Ca(2+) signaling processes and for maintenance of store Ca(2+) levels in C. elegans. These findings raise interesting and important questions regarding the function of SOCE and SOC channels under normal and pathophysiological conditions.

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

PubMed Central

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

2006-01-01

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

Method of forming superconducting Tl-Ba-Ca-Cu-O films

DOEpatents

Wessels, Bruce W.; Marks, Tobin J.; Richeson, Darrin S.; Tonge, Lauren M.; Zhang, Jiming

1993-01-01

A method of forming a superconducting Tl-Ba-Ca-Cu-O film is disclosed, which comprises depositing a Ba-Ca-Cu-O film on a substrate by MOCVD, annealing the deposited film and heat-treating the annealed film in a closed circular vessel with TlBa.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x and cooling to form said superconducting film of TlO.sub.m Ba.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+2, wherein m=1,2 and n=1,2,3.

Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca2+ release during the quasi-steady level of release in twitch fibers from frog skeletal muscle

PubMed Central

Fénelon, Karine; Lamboley, Cédric R.H.; Carrier, Nicole

2012-01-01

Experiments were performed to characterize the properties of the intrinsic Ca2+ buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([CaT]SR and [Ca2+]SR) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca2+ indicator). Results indicate SR Ca2+ buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca2+. Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca2+]SR and [CaT]SR are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca2+ permeability of the SR, namely d[CaT]SR/dt ÷ [Ca2+]SR (denoted release permeability), in experiments in which only [CaT]SR or [Ca2+]SR is measured. In response to a voltage-clamp step to −20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ∼50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca2+ release of 2.3 SR Ca2+ release channels neighboring each channel activated by its associated voltage sensor. Release permeability at −60 mV increases as [CaT]SR decreases from its resting physiological level to ∼0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca2+]SR inhibits release when [CaT]SR declines to a low level. PMID:23008434

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

PubMed

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

2012-10-01

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

Regulation of RYR1 activity by Ca(2+) and calmodulin

NASA Technical Reports Server (NTRS)

Rodney, G. G.; Williams, B. Y.; Strasburg, G. M.; Beckingham, K.; Hamilton, S. L.

2000-01-01

The skeletal muscle calcium release channel (RYR1) is a Ca(2+)-binding protein that is regulated by another Ca(2+)-binding protein, calmodulin. The functional consequences of calmodulin's interaction with RYR1 are dependent on Ca(2+) concentration. At nanomolar Ca(2+) concentrations, calmodulin is an activator, but at micromolar Ca(2+) concentrations, calmodulin is an inhibitor of RYR1. This raises the question of whether the Ca(2+)-dependent effects of calmodulin on RYR1 function are due to Ca(2+) binding to calmodulin, RYR1, or both. To distinguish the effects of Ca(2+) binding to calmodulin from those of Ca(2+) binding to RYR1, a mutant calmodulin that cannot bind Ca(2+) was used to evaluate the effects of Ca(2+)-free calmodulin on Ca(2+)-bound RYR1. We demonstrate that Ca(2+)-free calmodulin enhances the affinity of RYR1 for Ca(2+) while Ca(2+) binding to calmodulin converts calmodulin from an activator to an inhibitor. Furthermore, Ca(2+) binding to RYR1 enhances its affinity for both Ca(2+)-free and Ca(2+)-bound calmodulin.

Short belt-like Ca 2 B 2 O 5 ·H 2 O nanostructures: Hydrothermal formation, FT-IR, thermal decomposition, and optical properties

NASA Astrophysics Data System (ADS)

Zhu, Wancheng; Zhang, Xiao; Wang, Xiaoli; Zhang, Heng; Zhang, Qiang; Xiang, Lan

2011-10-01

Uniform high crystallinity short belt-like Ca 2B 2O 5·H 2O nanostructures (nanobelts) were facilely synthesized through a room temperature coprecipitation of CaCl 2, H 3BO 3, and NaOH solutions, followed by a mild hydrothermal treatment (180 °C, 12.0 h). By a preferential growth parallel to the (1 0 0) planes, Ca 2B 2O 5·H 2O nanobelts with a length of 1-5 μm, a width of 100-400 nm, and a thickness of 55-90 nm were obtained. The calcination of the nanobelts at 500 °C for 2.0 h led to short Ca 2B 2O 5 nanobelts with well preserved 1D morphology. Calcination at 800 °C led to a mixture of Ca 2B 2O 5 and Ca 3B 2O 6. The products were with belt-like and quasi-polyhedron morphology, while they turned into pore-free micro-rod like and polyhedron morphology when the calcination was taken in the presence of NaCl. NaCl assisted high temperature calcination at 900 °C promoted the formation of Ca 3B 2O 6 in the products. When dispersed in deionized water or absolute ethanol, the Ca 2B 2O 5·H 2O nanobelts and Ca 2B 2O 5 nanobelts showed good transparency from the ultraviolet to the visible region. The as-synthesized Ca 2B 2O 5·H 2O and Ca 2B 2O 5 nanobelts can be employed as novel metal borate nanomaterials for further potential applications in the area of glass fibers, antiwear additive, ceramic coatings, and so on.

Modulation of K(Ca)3.1 channels by eicosanoids, omega-3 fatty acids, and molecular determinants.

PubMed

Kacik, Michael; Oliván-Viguera, Aida; Köhler, Ralf

2014-01-01

Cytochrome P450- and ω-hydrolase products (epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraeonic acid (20-HETE)), natural omega-3 fatty acids (ω3), and pentacyclic triterpenes have been proposed to contribute to a wide range of vaso-protective and anti-fibrotic/anti-cancer signaling pathways including the modulation of membrane ion channels. Here we studied the modulation of intermediate-conductance Ca(2+)/calmodulin-regulated K(+) channels (K(Ca)3.1) by EETs, 20-HETE, ω3, and pentacyclic triterpenes and the structural requirements of these fatty acids to exert channel blockade. We studied modulation of cloned human hK(Ca)3.1 and the mutant hK(Ca)3.1(V275A) in HEK-293 cells, of rK(Ca)3.1 in aortic endothelial cells, and of mK(Ca)3.1 in 3T3-fibroblasts by inside-out and whole-cell patch-clamp experiments, respectively. In inside-out patches, Ca(2+)-activated hK(Ca)3.1 were inhibited by the ω3, DHA and α-LA, and the ω6, AA, in the lower µmolar range and with similar potencies. 5,6-EET, 8,9-EET, 5,6-DiHETE, and saturated arachidic acid, had no appreciable effects. In contrast, 14,15-EET, its stable derivative, 14,15-EEZE, and 20-HETE produced channel inhibition. 11,12-EET displayed less inhibitory activity. The K(Ca)3.1(V275A) mutant channel was insensitive to any of the blocking EETs. Non-blocking 5,6-EET antagonized the inhibition caused by AA and augmented cloned hK(Ca)3.1 and rK(Ca)3.1 whole-cell currents. Pentacyclic triterpenes did not modulate K(Ca)3.1 currents. Inhibition of K(Ca)3.1 by EETs (14,15-EET), 20-HETE, and ω3 critically depended on the presence of electron double bonds and hydrophobicity within the 10 carbons preceding the carboxyl-head of the molecules. From the physiological perspective, metabolism of AA to non-blocking 5,6,- and 8,9-EET may cause AA-de-blockade and contribute to cellular signal transduction processes influenced by these fatty acids.

A molecular dynamics study of the atomic structure of (CaO)x(Al2O3)1-x glass with x = 0.625 close to the eutectic

NASA Astrophysics Data System (ADS)

Thomas, B. W. M.; Mead, R. N.; Mountjoy, G.

2006-05-01

Aluminate glasses are difficult to prepare as they do not contain traditional network formers, but they are promising materials for optical applications. The atomic structure of calcium aluminate glasses has been studied using several experimental techniques. The current study uses molecular dynamics to obtain a model of a (CaO)0.625(Al2O3)0.375 glass close to the eutectic. The glass consists of a tetrahedral alumina network with average network polymerization \\langle Q^{n}\\rangle of n = 3.3. Ca acts as a network modifier with average coordination of 6.2. Ca is typically coordinated to three bridging oxygens (Ob) and three non-bridging oxygens (Onb), with Ca-Onb bonds noticeably shorter than the Ca-Ob bonds. A new method of analysing modifier cation coordination is presented, which specifically shows the distribution of Ca coordination NCaO in terms of combinations of NCaOb and NCaOnb. Ob is most often coordinated to two Al plus two Ca, and Onb is most often coordinated to one Al plus three Ca. The typical coordinations of Ca, Ob, and Onb all have a noticeable similarity to those for the 5CaO·3Al2O3 crystal. The Ca-Ca distribution shows a clear similarity to that for (CaO)0.5(SiO2)0.5 glass, and this is attributed to the equal atomic number densities of Ca in these glasses.

Neuronal calcium wave propagation varies with changes in endoplasmic reticulum parameters: a computer model

PubMed Central

Neymotin, Samuel A.; McDougal, Robert A.; Sherif, Mohamed A.; Fall, Christopher P.; Hines, Michael L.; Lytton, William W.

2015-01-01

Calcium (Ca2+) waves provide a complement to neuronal electrical signaling, forming a key part of a neuron’s second messenger system. We developed a reaction-diffusion model of an apical dendrite with diffusible inositol triphosphate (IP3), diffusible Ca2+, IP3 receptors (IP3Rs), endoplasmic reticulum (ER) Ca2+ leak, and ER pump (SERCA) on ER. Ca2+ is released from ER stores via IP3Rs upon binding of IP3 and Ca2+. This results in Ca2+-induced-Ca2+-release (CICR) and increases Ca2+ spread. At least two modes of Ca2+ wave spread have been suggested: a continuous mode based on presumed relative homogeneity of ER within the cell; and a pseudo-saltatory model where Ca2+ regeneration occurs at discrete points with diffusion between them. We compared the effects of three patterns of hypothesized IP3R distribution: 1. continuous homogeneous ER, 2. hotspots with increased IP3R density (IP3R hotspots), 3. areas of increased ER density (ER stacks). All three modes produced Ca2+ waves with velocities similar to those measured in vitro (~50–90µm /sec). Continuous ER showed high sensitivity to IP3R density increases, with time to onset reduced and speed increased. Increases in SERCA density resulted in opposite effects. The measures were sensitive to changes in density and spacing of IP3R hotspots and stacks. Increasing the apparent diffusion coefficient of Ca2+ substantially increased wave speed. An extended electrochemical model, including voltage gated calcium channels and AMPA synapses, demonstrated that membrane priming via AMPA stimulation enhances subsequent Ca2+ wave amplitude and duration. Our modeling suggests that pharmacological targeting of IP3Rs and SERCA could allow modulation of Ca2+ wave propagation in diseases where Ca2+ dysregulation has been implicated. PMID:25734493

ZnT-1 enhances the activity and surface expression of T-type calcium channels through activation of Ras-ERK signaling.

PubMed

Mor, Merav; Beharier, Ofer; Levy, Shiri; Kahn, Joy; Dror, Shani; Blumenthal, Daniel; Gheber, Levi A; Peretz, Asher; Katz, Amos; Moran, Arie; Etzion, Yoram

2012-07-15

Zinc transporter-1 (ZnT-1) is a putative zinc transporter that confers cellular resistance from zinc toxicity. In addition, ZnT-1 has important regulatory functions, including inhibition of L-type calcium channels and activation of Raf-1 kinase. Here we studied the effects of ZnT-1 on the expression and function of T-type calcium channels. In Xenopus oocytes expressing voltage-gated calcium channel (CaV) 3.1 or CaV3.2, ZnT-1 enhanced the low-threshold calcium currents (I(caT)) to 182 ± 15 and 167.95 ± 9.27% of control, respectively (P < 0.005 for both channels). As expected, ZnT-1 also enhanced ERK phosphorylation. Coexpression of ZnT-1 and nonactive Raf-1 blocked the ZnT-1-mediated ERK phosphorylation and abolished the ZnT-1-induced augmentation of I(caT). In mammalian cells (Chinese hamster ovary), coexpression of CaV3.1 and ZnT-1 increased the I(caT) to 166.37 ± 6.37% compared with cells expressing CaV3.1 alone (P < 0.01). Interestingly, surface expression measurements using biotinylation or total internal reflection fluorescence microscopy indicated marked ZnT-1-induced enhancement of CaV3.1 surface expression. The MEK inhibitor PD-98059 abolished the ZnT-1-induced augmentation of surface expression of CaV3.1. In cultured murine cardiomyocytes (HL-1 cells), transient exposure to zinc, leading to enhanced ZnT-1 expression, also enhanced the surface expression of endogenous CaV3.1 channels. Consistently, in these cells, endothelin-1, a potent activator of Ras-ERK signaling, enhanced the surface expression of CaV3.1 channels in a PD-98059-sensitive manner. Our findings indicate that ZnT-1 enhances the activity of CaV3.1 and CaV3.2 through activation of Ras-ERK signaling. The augmentation of CaV3.1 currents by Ras-ERK activation is associated with enhanced trafficking of the channel to the plasma membrane.

Decreased store operated Ca2+ entry in dendritic cells isolated from mice expressing PKB/SGK-resistant GSK3.

PubMed

Schmid, Evi; Yan, Jing; Nurbaeva, Meerim K; Russo, Antonella; Yang, Wenting; Faggio, Caterina; Shumilina, Ekaterina; Lang, Florian

2014-01-01

Dendritic cells (DCs), key players of immunity, are regulated by glycogen synthase kinase GSK3. GSK3 activity is suppressed by PKB/Akt and SGK isoforms, which are in turn stimulated by the PI3K pathway. Exposure to bacterial lipopolysaccharides increases cytosolic Ca(2+)-concentration ([Ca(2+)]i), an effect augmented in DCs isolated from mutant mice expressing PKB/SGK-resistant GSK3α,β (gsk3(KI) ). Factors affecting [Ca(2+)]i include Ca(2+)-release from intracellular stores (CRIS), store-operated Ca(2+)-entry (SOCE) through STIM1/STIM2-regulated Orai1, K(+)-dependent Na(+)/Ca(2+)-exchangers (NCKX), K(+)-independent Na(+)/Ca(2+)-exchangers (NCX) and calbindin-D28k. The present study explored whether PKB/SGK-dependent GSK3α, β-activity impacts on CRIS, SOCE, NCKX, NCX or calbindin. DCs were isolated from gsk3(KI) mice and respective wild-type mice (gsk3(WT) ), [Ca(2+)]i estimated from Fura2 fluorescence, Orai1, STIM1, STIM2 as well as calbindin-D28k protein abundance determined by Western blotting and mRNA levels quantified by real time PCR. As a result, thapsigargin-induced CRIS and SOCE were significantly blunted by GSK3-inhibitors SB216763 (1-10 µM, 30 min) or GSK-XIII (10 µM, 30 min) but were significantly lower in gsk3(WT) than in gsk3(KI) DCs. Orai1, STIM1 and STIM2 protein abundance was significantly lower and calbindin-D28k abundance significantly higher in gsk3(KI) than in gsk3(WT) DCs. Activity of NCKX and NCX was significantly higher in gsk3(KI) than in gsk3(WT) DCs and was significantly increased by SB216763 (1 µM, 30 min) or GSK-XIII (10 µM, 30 min). Treatment of gsk3(WT) DCs with SB216763 (1 µM, 4-24 h) or GSK-XIII (10 µM, 4-24 h) did not significantly modify the protein abundance of Orai1, STIM1 and STIM2. The present observations point to a dual role of GSK3 in the regulation of Ca(2+) in DCs. Acute inhibition of GSK3 blunted the increase of [Ca(2+)]i following CRIS and SOCE and stimulated NCKX/NCX activity. However, expression of PKB/SGK-resistant GSK3α, β downregulated the increase of [Ca(2+)]i following CRIS and SOCE, an effect at least partially due to downregulation of Orai1, STIM1 and STIM2 expression as well as upregulation of Na(+)/Ca(2+)-exchanger activity and calbindin D28k expression.

Decreased Store Operated Ca2+ Entry in Dendritic Cells Isolated from Mice Expressing PKB/SGK-Resistant GSK3

PubMed Central

Nurbaeva, Meerim K.; Russo, Antonella; Yang, Wenting; Faggio, Caterina; Shumilina, Ekaterina; Lang, Florian

2014-01-01

Dendritic cells (DCs), key players of immunity, are regulated by glycogen synthase kinase GSK3. GSK3 activity is suppressed by PKB/Akt and SGK isoforms, which are in turn stimulated by the PI3K pathway. Exposure to bacterial lipopolysaccharides increases cytosolic Ca2+-concentration ([Ca2+]i), an effect augmented in DCs isolated from mutant mice expressing PKB/SGK-resistant GSK3α,β (gsk3KI). Factors affecting [Ca2+]i include Ca2+-release from intracellular stores (CRIS), store-operated Ca2+-entry (SOCE) through STIM1/STIM2-regulated Orai1, K+-dependent Na+/Ca2+-exchangers (NCKX), K+-independent Na+/Ca2+-exchangers (NCX) and calbindin-D28k. The present study explored whether PKB/SGK-dependent GSK3α, β-activity impacts on CRIS, SOCE, NCKX, NCX or calbindin. DCs were isolated from gsk3KI mice and respective wild-type mice (gsk3WT), [Ca2+]i estimated from Fura2 fluorescence, Orai1, STIM1, STIM2 as well as calbindin-D28k protein abundance determined by Western blotting and mRNA levels quantified by real time PCR. As a result, thapsigargin-induced CRIS and SOCE were significantly blunted by GSK3-inhibitors SB216763 (1–10 µM, 30 min) or GSK-XIII (10 µM, 30 min) but were significantly lower in gsk3WT than in gsk3KIDCs. Orai1, STIM1 and STIM2 protein abundance was significantly lower and calbindin-D28k abundance significantly higher in gsk3KI than in gsk3WTDCs. Activity of NCKX and NCX was significantly higher in gsk3KI than in gsk3WTDCs and was significantly increased by SB216763 (1 µM, 30 min) or GSK-XIII (10 µM, 30 min). Treatment of gsk3WT DCs with SB216763 (1 µM, 4–24 h) or GSK-XIII (10 µM, 4–24 h) did not significantly modify the protein abundance of Orai1, STIM1 and STIM2. The present observations point to a dual role of GSK3 in the regulation of Ca2+ in DCs. Acute inhibition of GSK3 blunted the increase of [Ca2+]i following CRIS and SOCE and stimulated NCKX/NCX activity. However, expression of PKB/SGK-resistant GSK3α, β downregulated the increase of [Ca2+]i following CRIS and SOCE, an effect at least partially due to downregulation of Orai1, STIM1 and STIM2 expression as well as upregulation of Na+/Ca2+-exchanger activity and calbindin D28k expression. PMID:24523925

The effect of calcium on aqueous uranium(VI) speciation and adsorption to ferrihydrite and quartz

USGS Publications Warehouse

Fox, P.M.; Davis, J.A.; Zachara, J.M.

2006-01-01

Recent studies of uranium(VI) geochemistry have focused on the potentially important role of the aqueous species, CaUO2 (CO3)32- and Ca2 UO2(CO3)30(aq), on inhibition of microbial reduction and uranium(VI) aqueous speciation in contaminated groundwater. However, to our knowledge, there have been no direct studies of the effects of these species on U(VI) adsorption by mineral phases. The sorption of U(VI) on quartz and ferrihydrite was investigated in NaNO3 solutions equilibrated with either ambient air (430 ppm CO2) or 2% CO2 in the presence of 0, 1.8, or 8.9 mM Ca2+. Under conditions where the Ca2UO2(CO3)30 (aq) species predominates U(VI) aqueous speciation, the presence of Ca in solution lowered U(VI) adsorption on quartz from 77% in the absence of Ca to 42% and 10% at Ca concentrations of 1.8 and 8.9 mM, respectively. U(VI) adsorption to ferrihydrite decreased from 83% in the absence of Ca to 57% in the presence of 1.8 mM Ca. Surface complexation model predictions that included the formation constant for aqueous Ca2UO2(CO3)30(aq) accurately simulated the effect of Ca2+ on U(VI) sorption onto quartz and ferrihydrite within the thermodynamic uncertainty of the stability constant value. This study confirms that Ca2+ can have a significant impact on the aqueous speciation of U(VI), and consequently, on the sorption and mobility of U(VI) in aquifers. ?? 2005 Elsevier Inc. All rights reserved.

The 15th Internatonal Conference Quality in Resarch (Qir) 2017 Preparation and Ionic Conductivity of Li3.9Ca0.1Ti5O12 Using Waste Chicken Eggshells as ca Source for Anode Material of Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Subhan, Achmad; Setiawan, Dedy; Ahmiatri Saptari, Sitti

2018-03-01

Li3.9Ca0.1Ti5O12 has been synthesized as anode material for lithium-ion batteries parallel with Li4Ti5O12 anode material using solid state reaction method in an air atmosphere. LiOH.H2O, TiO2, and waste chicken eggshells in the form of CaCO3 were chosen as sources of Li, Ti, and Ca respectively and prepared using stoichiometric. The phase structure, morphology, and electrochemical impedance of as-prepared samples were characterized using XRD, SEM, and EIS. The XRD characterization revealed that in Li3.9Ca0.1Ti5O12 sample, all amount of dopant had entered the lattice structure of Li4Ti5O12. The EDX image also detect the existence of Ca in the structure of Li3.9Ca0.1Ti5O12. The EIS characterization revealed that the Li3.9Ca0.1Ti5O12 sample had lower electrochemical impedance compared to the Li4Ti5O12 sample. The diffusion coefficient were obtained by Faraday’s method, and exhibited that the Li3.9Ca0.1Ti5O12 sample (1.46986 × 10-12 cm2/s) had higher ionic conductivity than the Li4Ti5O12 sample (4.40995 × 10-16 cm2/s). According to the cycle performance test, the Li3.9Ca0.1Ti5O12 sample also had higher charge-discharge capacity and stability compared to the Li4Ti5O12 sample.

Identification and Characterization of Four Azole-Resistant erg3 Mutants of Candida albicans▿

PubMed Central

Martel, Claire M.; Parker, Josie E.; Bader, Oliver; Weig, Michael; Gross, Uwe; Warrilow, Andrew G. S.; Rolley, Nicola; Kelly, Diane E.; Kelly, Steven L.

2010-01-01

Sterol analysis identified four Candida albicans erg3 mutants in which ergosta 7,22-dienol, indicative of perturbations in sterol Δ5,6-desaturase (Erg3p) activity, comprised >5% of the total sterol fraction. The erg3 mutants (CA12, CA488, CA490, and CA1008) were all resistant to fluconazole, voriconazole, itraconazole, ketoconazole, and clotrimazole under standard CLSI assay conditions (MIC values, ≥256, 16, 16, 8, and 1 μg ml−1, respectively). Importantly, CA12 and CA1008 retained an azole-resistant phenotype even when assayed in the presence of FK506, a multidrug efflux inhibitor. Conversely, CA488, CA490, and three comparator isolates (CA6, CA14, and CA177, in which ergosterol comprised >80% of the total sterol fraction and ergosta 7,22-dienol was undetectable) all displayed azole-sensitive phenotypes under efflux-inhibited assay conditions. Owing to their ergosterol content, CA6, CA14, and CA177 were highly sensitive to amphotericin B (MIC values, <0.25 μg ml−1); CA1008, in which ergosterol comprised <2% of the total sterol fraction, was less sensitive (MIC, 1 μg ml−1). CA1008 harbored multiple amino acid substitutions in Erg3p but only a single conserved polymorphism (E266D) in sterol 14α-demethylase (Erg11p). CA12 harbored one substitution (W332R) in Erg3p and no residue changes in Erg11p. CA488 and CA490 were found to harbor multiple residue changes in both Erg3p and Erg11p. The results suggest that missense mutations in ERG3 might arise in C. albicans more frequently than currently supposed and that the clinical significance of erg3 mutants, including those in which additional mechanisms also contribute to resistance, should not be discounted. PMID:20733039

Chronic renal failure induces cell death in rat hippocampal CA1 via upregulation of αCaMKII/NR2A synaptic complex and phosphorylated GluR1-containing AMPA receptor cascades.

PubMed

Kim, Jong Wan; Ha, Gyoung Yim; Jung, Yong Wook

2014-09-01

N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propinoic acid (AMPA) receptors bound to postsynaptic density-95 (PSD-95) and α isoform of calcium/calmodulin-dependent protein kinase II (αCaMKII) is fundamentally involved in the regulation of working memory. The aim of present study was to investigate the alterations of NMDA and AMPA receptors responsible for hippocampal synaptic dysfunction and selective neuronal cell death after chronic renal failure (CRF) which may be associated with impairment of working memory. Altered interactions between NMDA and AMPA receptors and PSD-95 and αCaMKII were analyzed in the cornu ammonis (CA) 1 and CA3/dentate gyrus (DG) subfields of the uremic rat hippocampi using the immunoblotting and immunoprecipitation methods. Uremia induced by CRF produced necrotic cell death and decreased neuronal nucleoli protein levels in the hippocampal CA1 subfield, but not in the CA3/DG subfields. The CA1 subfields of CRF rats exhibited significant decreases and increases, respectively, in the expressions of PSD-95/NR2B and αCaMKII/NR2A synaptic complex. Moreover, increased phosphorylation of glutamate receptor type 1 (GluR1) AMPA receptor at ser831 was observed in the CA1 subfield after CRF. These hippocampal CA1 neuronal vulnerability may be responsible for memory dysfunction after CRF as mediated by an increase in NR2A-containing NMDA receptors bound to αCaMKII and subsequent activation of GluR1-containing AMPA receptors caused by the phosphorylation of GluR1 at ser831.

A quantitative description of tubular system Ca(2+) handling in fast- and slow-twitch muscle fibres.

PubMed

Cully, Tanya R; Edwards, Joshua N; Murphy, Robyn M; Launikonis, Bradley S

2016-06-01

Current methods do not allow a quantitative description of Ca(2+) movements across the tubular (t-) system membrane without isolating the membranes from their native skeletal muscle fibre. Here we present a fluorescence-based method that allows determination of the t-system [Ca(2+) ] transients and derivation of t-system Ca(2+) fluxes in mechanically skinned skeletal muscle fibres. Differences in t-system Ca(2+) -handling properties between fast- and slow-twitch fibres from rat muscle are resolved for the first time using this new technique. The method can be used to study Ca(2+) handling of the t-system and allows direct comparisons of t-system Ca(2+) transients and Ca(2+) fluxes between groups of fibres and fibres from different strains of animals. The tubular (t-) system of skeletal muscle is an internalization of the plasma membrane that maintains a large Ca(2+) gradient and exchanges Ca(2+) between the extracellular and intracellular environments. Little is known of the Ca(2+) -handling properties of the t-system as the small Ca(2+) fluxes conducted are difficult to resolve with conventional methods. To advance knowledge in this area we calibrated t-system-trapped rhod-5N inside skinned fibres from rat and [Ca(2+) ]t-sys , allowing confocal measurements of Ca(2+) -dependent changes in rhod-5N fluorescence during rapid changes in the intracellular ionic environment to be converted to [Ca(2+) ] transients in the t-system ([Ca(2+) ]t-sys (t)). Furthermore, t-system Ca(2+) -buffering power was determined so that t-system Ca(2+) fluxes could be derived from [Ca(2+) ]t-sys (t). With this new approach, we show that rapid depletion of sarcoplasmic reticulum (SR) Ca(2+) induced a robust store-operated Ca(2+) entry (SOCE) in fast- and slow-twitch fibres, reducing [Ca(2+) ]t-sys to < 0.1 mm. The rapid activation of SOCE upon Ca(2+) release was consistent with the presence of STIM1L in both fibre types. Abruptly introducing internal solutions with 1 mm Mg(2+) and [Ca(2+) ]cyto (28 nm-1.3 μm) to Ca(2+) -depleted fibres generated t-system Ca(2+) uptake rates dependent on [Ca(2+) ]cyto with [Ca(2+) ]t-sys reaching final plateaus in the millimolar range. For the same [Ca(2+) ]cyto , t-system Ca(2+) fluxes of fast-twitch fibres were greater than that in slow-twitch fibres. In addition, simultaneous imaging of t-system and SR Ca(2+) signals indicated that both membrane compartments accumulated Ca(2+) at similar rates and that SOCE was activated early during SR Ca(2+) depletion. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

A quantitative description of tubular system Ca2+ handling in fast‐ and slow‐twitch muscle fibres

PubMed Central

Cully, Tanya R.; Edwards, Joshua N.; Murphy, Robyn M.

2016-01-01

Key points Current methods do not allow a quantitative description of Ca2+ movements across the tubular (t‐) system membrane without isolating the membranes from their native skeletal muscle fibre.Here we present a fluorescence‐based method that allows determination of the t‐system [Ca2+] transients and derivation of t‐system Ca2+ fluxes in mechanically skinned skeletal muscle fibres. Differences in t‐system Ca2+‐handling properties between fast‐ and slow‐twitch fibres from rat muscle are resolved for the first time using this new technique.The method can be used to study Ca2+ handling of the t‐system and allows direct comparisons of t‐system Ca2+ transients and Ca2+ fluxes between groups of fibres and fibres from different strains of animals. Abstract The tubular (t‐) system of skeletal muscle is an internalization of the plasma membrane that maintains a large Ca2+ gradient and exchanges Ca2+ between the extracellular and intracellular environments. Little is known of the Ca2+‐handling properties of the t‐system as the small Ca2+ fluxes conducted are difficult to resolve with conventional methods. To advance knowledge in this area we calibrated t‐system‐trapped rhod‐5N inside skinned fibres from rat and [Ca2+]t‐sys, allowing confocal measurements of Ca2+‐dependent changes in rhod‐5N fluorescence during rapid changes in the intracellular ionic environment to be converted to [Ca2+] transients in the t‐system ([Ca2+]t‐sys (t)). Furthermore, t‐system Ca2+‐buffering power was determined so that t‐system Ca2+ fluxes could be derived from [Ca2+]t‐sys (t). With this new approach, we show that rapid depletion of sarcoplasmic reticulum (SR) Ca2+ induced a robust store‐operated Ca2+ entry (SOCE) in fast‐ and slow‐twitch fibres, reducing [Ca2+]t‐sys to < 0.1 mm. The rapid activation of SOCE upon Ca2+ release was consistent with the presence of STIM1L in both fibre types. Abruptly introducing internal solutions with 1 mm Mg2+ and [Ca2+]cyto (28 nm–1.3 μm) to Ca2+‐depleted fibres generated t‐system Ca2+ uptake rates dependent on [Ca2+]cyto with [Ca2+]t‐sys reaching final plateaus in the millimolar range. For the same [Ca2+]cyto, t‐system Ca2+ fluxes of fast‐twitch fibres were greater than that in slow‐twitch fibres. In addition, simultaneous imaging of t‐system and SR Ca2+ signals indicated that both membrane compartments accumulated Ca2+ at similar rates and that SOCE was activated early during SR Ca2+ depletion. PMID:26775687

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

PubMed

Layhadi, Janice A; Fountain, Samuel J

2017-06-03

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

Caffeine alleviates the deterioration of Ca2+ release mechanisms and fragmentation of in vitro aged mouse eggs

PubMed Central

Zhang, Nan; Wakai, Takuya; Fissore, Rafael. A.

2011-01-01

The developmental competence of mammalian eggs is compromised by postovulatory aging. We and others found that in these eggs the intracellular calcium ([Ca2+]i) responses required for egg activation and initiation of development are altered. Nevertheless, the mechanism(s) underlying this defective Ca2+ release is not well known. Here, we investigated if the function of IP3R1, the major Ca2+ release channel at fertilization, was undermined in in vitro aged mouse eggs. We found that in aged eggs IP3R1 displayed reduced function, as many of the changes acquired during maturation that enhance IP3R1 Ca2+ conductivity such as phosphorylation, receptor reorganization and increased Ca2+ store content ([Ca2+]ER) were lost with increasing postovulatory time. IP3R1 fragmentation, possibly associated with the activation of caspase-3, was also observed in these eggs. Many of these changes were prevented when the postovulatory aging of eggs was carried out in the presence of caffeine, which minimized the decline in IP3R1 function and maintained [Ca2+]ER content. Caffeine also maintained mitochondrial membrane potential as measured by JC-1 fluorescence. We therefore conclude that [Ca2+]i responses in aged eggs are undermined by reduced IP3R1 sensitivity, decreased [Ca2+]ER and compromised mitochondrial function, and that addition of caffeine ameliorates most of these aging-associated changes. Understanding the molecular basis of the protective effects of caffeine will be useful in elucidating, and possibly reversing, the signaling pathway(s) compromised by in vitro culture of eggs. PMID:22095868

Calmodulin in complex with the first IQ motif of myosin-5a functions as an intact calcium sensor

PubMed Central

Shen, Mei; Zhang, Ning; Zheng, Sanduo; Zhang, Wen-Bo; Zhang, Hai-Man; Lu, Zekuan; Su, Qian Peter; Sun, Yujie; Li, Xiang-dong

2016-01-01

The motor function of vertebrate myosin-5a is inhibited by its tail in a Ca2+-dependent manner. We previously demonstrated that the calmodulin (CaM) bound to the first isoleucine-glutamine (IQ) motif (IQ1) of myosin-5a is responsible for the Ca2+-dependent regulation of myosin-5a. We have solved the crystal structure of a truncated myosin-5a containing the motor domain and IQ1 (MD-IQ1) complexed with Ca2+-bound CaM (Ca2+-CaM) at 2.5-Å resolution. Compared with the structure of the MD-IQ1 complexed with essential light chain (an equivalent of apo-CaM), MD-IQ1/Ca2+-CaM displays large conformational differences in IQ1/CaM and little difference in the motor domain. In the MD-IQ1/Ca2+-CaM structure, the N-lobe and the C-lobe of Ca2+-CaM adopt an open conformation and grip the C-terminal and the N-terminal portions of the IQ1, respectively. Remarkably, the interlobe linker of CaM in IQ1/Ca2+-CaM is in a position opposite that in IQ1/apo-CaM, suggesting that CaM flip-flops relative to the IQ1 during the Ca2+ transition. We demonstrated that CaM continuously associates with the IQ1 during the Ca2+ transition and that the binding of CaM to IQ1 increases Ca2+ affinity and substantially changes the kinetics of the Ca2+ transition, suggesting that the IQ1/CaM complex functions as an intact Ca2+ sensor responding to distinct calcium signals. PMID:27647889

Calmodulin in complex with the first IQ motif of myosin-5a functions as an intact calcium sensor.

PubMed

Shen, Mei; Zhang, Ning; Zheng, Sanduo; Zhang, Wen-Bo; Zhang, Hai-Man; Lu, Zekuan; Su, Qian Peter; Sun, Yujie; Ye, Keqiong; Li, Xiang-Dong

2016-10-04

The motor function of vertebrate myosin-5a is inhibited by its tail in a Ca 2+ -dependent manner. We previously demonstrated that the calmodulin (CaM) bound to the first isoleucine-glutamine (IQ) motif (IQ1) of myosin-5a is responsible for the Ca 2+ -dependent regulation of myosin-5a. We have solved the crystal structure of a truncated myosin-5a containing the motor domain and IQ1 (MD-IQ1) complexed with Ca 2+ -bound CaM (Ca 2+ -CaM) at 2.5-Å resolution. Compared with the structure of the MD-IQ1 complexed with essential light chain (an equivalent of apo-CaM), MD-IQ1/Ca 2+ -CaM displays large conformational differences in IQ1/CaM and little difference in the motor domain. In the MD-IQ1/Ca 2+ -CaM structure, the N-lobe and the C-lobe of Ca 2+ -CaM adopt an open conformation and grip the C-terminal and the N-terminal portions of the IQ1, respectively. Remarkably, the interlobe linker of CaM in IQ1/Ca 2+ -CaM is in a position opposite that in IQ1/apo-CaM, suggesting that CaM flip-flops relative to the IQ1 during the Ca 2+ transition. We demonstrated that CaM continuously associates with the IQ1 during the Ca 2+ transition and that the binding of CaM to IQ1 increases Ca 2+ affinity and substantially changes the kinetics of the Ca 2+ transition, suggesting that the IQ1/CaM complex functions as an intact Ca 2+ sensor responding to distinct calcium signals.

Role of Caspase-3 Cleaved IP3R1 on Ca2+ Homeostasis and Developmental Competence of Mouse Oocytes and Eggs

PubMed Central

Zhang, Nan; Fissore, Rafael. A.

2014-01-01

Apoptosis in most cell types is accompanied by altered Ca2+ homeostasis. During apoptosis, caspase-3 mediated cleavage of the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) generates a 95-kDa C-terminal fragment (C-IP3R1), which represents the channel domain of the receptor. Aged mouse eggs display abnormal Ca2+ homeostasis and express C-IP3R1, although whether or not C-IP3R1 expression contributes to Ca2+ misregulation or a decrease in developmental competency is unknown. We sought to answer these questions by injecting in mouse oocytes and eggs cRNAs encoding CIP3R1. We found that: 1) expression of C-IP3R1 in eggs lowered the Ca2+ content of the endoplasmic reticulum (ER), although, as C-IP3R1 is quickly degraded at this stage, its expression did not impair pre-implantation embryo development; 2) expression of CIP3R1 in eggs enhanced fragmentation associated with aging; 3) endogenous IP3R1 is required for aging associated apoptosis, as its down-regulation prevented fragmentation, and expression of C-IP3R1 in eggs with downregulated IP3R1 partly restored fragmentation; 4) C-IP3R1 expression in GV oocytes resulted in persistent levels of protein, which abolished the increase in the ER releasable Ca2+ pool that occurs during maturation, undermined the Ca2+ oscillatory ability of matured eggs and their activation potential. Collectively, this study supports a role for IP3R1 and C-IP3R1 in regulating Ca2+ homeostasis and the ER Ca2+ content during oocyte maturation. Nevertheless, the role of C-IP3R1 on Ca2+ homeostasis in aged eggs seems minor, as in MII eggs the majority of endogenous IP3R1 remains intact and C-IP3R1 undergoes rapid turnover. PMID:24692207

The exchanged EF-hands in calmodulin and troponin C chimeras impair the Ca²⁺-induced hydrophobicity and alter the interaction with Orai1: a spectroscopic, thermodynamic and kinetic study.

PubMed

Jensen, Drake; Reynolds, Nicole; Yang, Ya-Ping; Shakya, Shubha; Wang, Zhi-Qiang; Stuehr, Dennis J; Wei, Chin-Chuan

2015-02-15

Calmodulin (CaM) plays an important role in Ca(2+)-dependent signal transduction. Ca(2+) binding to CaM triggers a conformational change, forming a hydrophobic patch that is important for target protein recognition. CaM regulates a Ca(2+)-dependent inactivation process in store-operated Ca(2+) entry, by interacting Orai1. To understand the relationship between Ca(2+)-induced hydrophobicity and CaM/Orai interaction, chimera proteins constructed by exchanging EF-hands of CaM with those of Troponin C (TnC) are used as an informative probe to better understand the functionality of each EF-hand. ANS was used to assess the context of the induced hydrophobic surface on CaM and chimeras upon Ca(2+) binding. The exchanged EF-hands from TnC to CaM resulted in reduced hydrophobicity compared with wild-type CaM. ANS lifetime measurements indicated that there are two types of ANS molecules with rather distinct fluorescence lifetimes, each specifically corresponding to one lobe of CaM or chimeras. Thermodynamic studies indicated the interaction between CaM and a 24-residue peptide corresponding to the CaM-binding domain of Orail1 (Orai-CMBD) is a 1:2 CaM/Orai-CMBD binding, in which each peptide binding yields a similar enthalpy change (ΔH = -5.02 ± 0.13 kcal/mol) and binding affinity (K(a) = 8.92 ± 1.03 × 10(5) M(-1)). With the exchanged EF1 and EF2, the resulting chimeras noted as CaM(1TnC) and CaM(2TnC), displayed a two sequential binding mode with a one-order weaker binding affinity and lower ΔH than that of CaM, while CaM(3TnC) and CaM(4TnC) had similar binding thermodynamics as CaM. The dissociation rate constant for CaM/Orai-CMBD was determined to be 1.41 ± 0.08 s(-1) by rapid kinetics. Stern-Volmer plots of Orai-CMBD Trp76 indicated that the residue is located in a very hydrophobic environment but becomes more solvent accessible when EF1 and EF2 were exchanged. Using ANS dye to assess induced hydrophobicity showed that exchanging EFs for all Ca(2+)-bound chimeras impaired ANS fluorescence and/or binding affinity, consistent with general concepts about the inadequacy of hydrophobic exposure for chimeras. However, such ANS responses exhibited no correlation with the ability to interact with Orai-CMBD. Here, the model of 1:2 binding stoichiometry of CaM/Orai-CMBD established in solution supports the already published crystal structure.

Combined Raman and SEM study on CaF2 formed on/in enamel by APF treatments.

PubMed

Tsuda, H; Jongebloed, W L; Stokroos, I; Arends, J

1993-01-01

Raman spectra containing the distinct band at 322 cm-1 due to CaF2 or CaF2-like material formed in/on fluoridated bovine enamel were recorded using a micro-Raman spectrograph. Due to increasing levels of background fluorescence with increasing thickness of enamel, the Raman measurements were carried out on thin regions of wedged enamel sections. The distribution of the CaF2 or CaF2-like material was estimated using a simple model. The results indicate that 1/3 of the total CaF2 was concentrated within the narrow depth < 2 microns with high CaF2 concentrations (> 10 wt%), and that the majority of the CaF2 was distributed over the depths up to 26 microns (1 wt% CaF2). SEM observations on fractured fluoridated enamel confirmed that morphological changes were present in the depth range comparable to that of the high CaF2 concentration region expected from the Raman analysis. In deeper regions where lower concentration (< 10%) but a large amount of CaF2 was still expected, the SEM images failed to distinguish between the normal and fluoridated enamel. After KOH treatment, the Raman spectra did not show evidence of the CaF2 peak and the SEM micrographs also confirmed the removal of globules. The peak position of the Raman band of the CaF2 formed by the fluoridation was identical to that of pure CaF2. However, the linewidth was 23 cm-1 (FWHM) and a factor of 2 broader than that of pure CaF2 (12 cm-1). This implies that the lattice dynamics of the CaF2 formed by fluoridation is different from of pure CaF2, and that the material formed is 'CaF2-like' or 'disordered CaF2'.

Mg/Ca- Δ CO3porewater2- -temperature calibration for Globobulimina spp.: A sensitive paleothermometer for deep-sea temperature reconstruction

NASA Astrophysics Data System (ADS)

Weldeab, Syee; Arce, Adam; Kasten, Sabine

2016-03-01

Existing benthic foraminiferal Mg/Ca-temperature calibrations are surrounded by substantial uncertainties mainly due to low temperature sensitivity of Mg/Ca in most benthic foraminifers and the effect of carbonate ion concentration on benthic foraminiferal Mg/Ca. Here we present Mg/Ca analysis of Rose Bengal stained and exceptionally well-preserved tests of the infaunal benthic foraminifer Globobulimina spp. from 39 eastern equatorial Atlantic core top samples. Mg/Ca in Globobulimina spp. varies between 2.5 mmol/mol and 9.1 mmol/mol corresponding to bottom water temperatures (BWT) between 1.8 °C and 19.1 °C and Δ CO3pore water2- between 33.7 ± 4 and - 34.3 ± 4 μmol /kg in sediment depths between 1 and 10 cm. Mg/Ca and BWT are linearly correlated with a best fit of Mg/Ca [mmol/mol] = (0.36 ± 0.02) * BWT [°C] + 2.22 ± 0.19 (r2 = 0.92, p-value: 11 *10-20, and n = 39). Using total alkalinity and pH data of pore water samples from 64 Atlantic multi-corer sites, we obtained Δ CO3pore water2- data from the depth habitat range of Globobulimina spp. (≥1 cm ≤ 10 cm below sediment surface). We show that Δ CO3pore waterSUP>2- is significantly lower than and linearly co-varies with the ΔCO2-3 of the overlying bottom water: Δ CO3pore water2- = (0.67 ± 0.05) * Δ CO3bottom water2- - (39.84 ± 1.98); r2 = 0.75, p-value: 6 *10-20, n = 64. We found a Mg/Ca sensitivity of 0.009 ± 0.0044 mmol /mol per μmol/kg Δ CO3pore water2- and Mg/Ca temperature sensitivity of 0.32 ± 0.06 mmol /mol / °C after a correction for the Δ CO3pore water2- effect. This study provides a robust Mg/Ca-temperature calibration, highlights that Δ CO3pore water2- is spatially and most likely temporally variable, and contradicts the notion that infaunal foraminiferal Mg/Ca is relatively immune from ΔCO2-3 changes in the overlying bottom water. Furthermore, comparison of down core Mg/Ca data of Cibicides pachyderma and Globobulimina spp. demonstrates that the high temperature sensitivity of Mg/Ca in Globobulimina spp. presents a more robust paleothermometer to reconstruct past changes in the thermal state of the deep ocean.

Effect of temperature on the reaction pathway of calcium carbonate formation via precursor phases

NASA Astrophysics Data System (ADS)

Purgstaller, Bettina; Mavromatis, Vasileios; Konrad, Florian; Dietzel, Martin

2016-04-01

It has been earlier postulated that some biogenic and sedimentary calcium carbonate (CaCO3) minerals (e.g. calcite and aragonite) are secondary in origin and have originally formed via a metastable calcium carbonate precursor phase (e.g. amorphous CaCO3, [1-2]). Such formation pathways are likely affected by various physicochemical parameters including aqueous Mg and temperature. In an effort to improve our understanding on the formation mechanism of CaCO3 minerals, precipitation experiments were carried out by the addition of a 0.6 M (Ca,Mg)Cl2 solution at distinct Mg/Ca ratios (1/4 and 1/8) into a 1 M NaHCO3 solution under constant pH conditions(8.3 ±0.1). The formation of CaCO3 was systematically examined as a function of temperature (6, 12, 18 and 25 ±0.3° C). During the experimental runs mineral precipitation was monitored by in situ Raman spectroscopy as well as by continuous sampling and analyzing of precipitates and reactive solutions. The results revealed two pathways of CaCO3 formation depending on the initial Mg/Ca ratio and temperature: (i) In experiments with a Mg/Ca ratio of 1/4 at ≤ 12° C as well as in experiments with a Mg/Ca ratio of 1/8 at ≤ 18° C, ikaite (CaCO3 6H2O) acts as a precursor phase for aragonite formation. (ii) In contrast higher temperatures induced the formation of Mg-rich amorphous CaCO3 (Mg-ACC) which was subsequently transformed to Mg-rich calcite. In situ Raman spectra showed that the transformation of Mg-ACC to Mg-calcite occurs at a higher rate (˜ 8 min) compared to that of ikaite to aragonite (> 2 h). Thus, the formation of aragonite rather than of Mg-calcite occurs due to the slower release of Ca2+and CO32- ions into the Mg-rich reactive solution during retarded ikaite dissolution. This behavior is generally consistent with the observation that calcite precipitation is inhibited at elevated aqueous Mg/Ca ratios. [1] Addadi L., Raz S. and Weiner S. (2003) Advanced Materials 15, 959-970. [2] Rodriguez-Blanco J. D., Shaw S., Bots P., Roncal-Herrero T. and Benning L. G (2014) Geochimica et Cosmochimica Acta 127, 204-220

The Pepper RING-Type E3 Ligase CaAIRF1 Regulates ABA and Drought Signaling via CaADIP1 Protein Phosphatase Degradation.

PubMed

Lim, Chae Woo; Baek, Woonhee; Lee, Sung Chul

2017-04-01

Ubiquitin-mediated protein modification occurs at multiple steps of abscisic acid (ABA) signaling. Here, we sought proteins responsible for degradation of the pepper ( Capsicum annuum ) type 2C protein phosphatase CaADIP1 via the 26S proteasome system. We showed that the RING-type E3 ligase CaAIRF1 ( Capsicum annuum ADIP1 Interacting RING Finger Protein 1) interacts with and ubiquitinates CaADIP1. CaADIP1 degradation was slower in crude proteins from CaAIRF1 -silenced peppers than in those from control plants. CaAIRF1 -silenced pepper plants displayed reduced ABA sensitivity and decreased drought tolerance characterized by delayed stomatal closure and suppressed induction of ABA- and drought-responsive marker genes. In contrast, CaAIRF1 -overexpressing Arabidopsis ( Arabidopsis thaliana ) plants exhibited ABA-hypersensitive and drought-tolerant phenotypes. Moreover, in these plants, CaADIP1-induced ABA hyposensitivity was strongly suppressed by CaAIRF1 overexpression. Our findings highlight a potential new route for fine-tune regulation of ABA signaling in pepper via CaAIRF1 and CaADIP1. © 2017 American Society of Plant Biologists. All Rights Reserved.

A distinct entorhinal cortex to hippocampal CA1 direct circuit for olfactory associative learning.

PubMed

Li, Yiding; Xu, Jiamin; Liu, Yafeng; Zhu, Jia; Liu, Nan; Zeng, Wenbo; Huang, Ning; Rasch, Malte J; Jiang, Haifei; Gu, Xiang; Li, Xiang; Luo, Minhua; Li, Chengyu; Teng, Junlin; Chen, Jianguo; Zeng, Shaoqun; Lin, Longnian; Zhang, Xiaohui

2017-04-01

Lateral and medial parts of entorhinal cortex (EC) convey nonspatial 'what' and spatial 'where' information, respectively, into hippocampal CA1, via both the indirect EC layer 2→ hippocampal dentate gyrus→CA3→CA1 and the direct EC layer 3→CA1 paths. However, it remains elusive how the direct path transfers distinct information and contributes to hippocampal learning functions. Here we report that lateral EC projection neurons selectively form direct excitatory synapses onto a subpopulation of morphologically complex, calbindin-expressing pyramidal cells (PCs) in the dorsal CA1 (dCA1), while medial EC neurons uniformly innervate all dCA1 PCs. Optogenetically inactivating the distinct lateral EC-dCA1 connections or the postsynaptic dCA1 calbindin-expressing PC activity slows olfactory associative learning. Moreover, optetrode recordings reveal that dCA1 calbindin-expressing PCs develop more selective spiking responses to odor cues during learning. Thus, our results identify a direct lateral EC→dCA1 circuit that is required for olfactory associative learning.

Clustering of Ca2+ transients in interstitial cells of Cajal defines slow wave duration

PubMed Central

Drumm, Bernard T.; Hennig, Grant W.; Battersby, Matthew J.; Sung, Tae Sik

2017-01-01

Interstitial cells of Cajal (ICC) in the myenteric plexus region (ICC-MY) of the small intestine are pacemakers that generate rhythmic depolarizations known as slow waves. Slow waves depend on activation of Ca2+-activated Cl− channels (ANO1) in ICC, propagate actively within networks of ICC-MY, and conduct to smooth muscle cells where they generate action potentials and phasic contractions. Thus, mechanisms of Ca2+ regulation in ICC are fundamental to the motor patterns of the bowel. Here, we characterize the nature of Ca2+ transients in ICC-MY within intact muscles, using mice expressing a genetically encoded Ca2+ sensor, GCaMP3, in ICC. Ca2+ transients in ICC-MY display a complex firing pattern caused by localized Ca2+ release events arising from multiple sites in cell somata and processes. Ca2+ transients are clustered within the time course of slow waves but fire asynchronously during these clusters. The durations of Ca2+ transient clusters (CTCs) correspond to slow wave durations (plateau phase). Simultaneous imaging and intracellular electrical recordings revealed that the upstroke depolarization of slow waves precedes clusters of Ca2+ transients. Summation of CTCs results in relatively uniform Ca2+ responses from one slow wave to another. These Ca2+ transients are caused by Ca2+ release from intracellular stores and depend on ryanodine receptors as well as amplification from IP3 receptors. Reduced extracellular Ca2+ concentrations and T-type Ca2+ channel blockers decreased the number of firing sites and firing probability of Ca2+ transients. In summary, the fundamental electrical events of small intestinal muscles generated by ICC-MY depend on asynchronous firing of Ca2+ transients from multiple intracellular release sites. These events are organized into clusters by Ca2+ influx through T-type Ca2+ channels to sustain activation of ANO1 channels and generate the plateau phase of slow waves. PMID:28592421

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

PubMed Central

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

1995-01-01

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

Spatial information is preferentially processed by the distal part of CA3: implication for memory retrieval.

PubMed

Flasbeck, Vera; Atucha, Erika; Nakamura, Nozomu H; Yoshida, Motoharu; Sauvage, Magdalena M

2018-07-16

For the past decades, CA3 was considered as a single functional entity. However, strong differences between the proximal (close to the dentate gyrus) and the distal (close to CA2) parts of CA3 in terms of connectivity patterns, gene expression and electrophysiological properties suggest that it is not the case. We recently showed that proximal CA3 (together with distal CA1) preferentially deals with non-spatial information [1]. In contrast to proximal CA3, distal CA3 mainly receives and predominantly projects to spatially tuned areas. Here, we tested if distal CA3 preferentially processes spatial information, which would suggest a segregation of the spatial information along the proximodistal axis of CA3. We used a high-resolution imaging technique based on the detection of the expression of the immediate-early gene Arc, commonly used to map activity in the medial temporal lobe. We showed that distal CA3 is strongly recruited in a newly designed delayed nonmatching-to-location task with high memory demands in rats, while proximal CA3 is not. These results indicate a functional segregation of CA3 that mirrors the one reported in CA1, and suggest the existence of a distal CA3- proximal CA1 spatial subnetwork. These findings bring further evidence for the existence of 'specialized' spatial and non-spatial subnetworks segregated along the proximodistal axis of the hippocampus and put forward the 'segregated' view of information processing in the hippocampus as a reasonable alternative to the well-accepted 'integrated' view, according to which spatial and non-spatial information are systematically integrated in the hippocampus to form episodic memory. Copyright © 2018. Published by Elsevier B.V.

Calmodulin regulates Cav3 T-type channels at their gating brake

PubMed Central

Taiakina, Valentina; Monteil, Arnaud; Piazza, Michael; Guan, Wendy; Stephens, Robert F.; Dieckmann, Thorsten; Guillemette, Joseph Guy; Spafford, J. David

2017-01-01

Calcium (Cav1 and Cav2) and sodium channels possess homologous CaM-binding motifs, known as IQ motifs in their C termini, which associate with calmodulin (CaM), a universal calcium sensor. Cav3 T-type channels, which serve as pacemakers of the mammalian brain and heart, lack a C-terminal IQ motif. We illustrate that T-type channels associate with CaM using co-immunoprecipitation experiments and single particle cryo-electron microscopy. We demonstrate that protostome invertebrate (LCav3) and human Cav3.1, Cav3.2, and Cav3.3 T-type channels specifically associate with CaM at helix 2 of the gating brake in the I–II linker of the channels. Isothermal titration calorimetry results revealed that the gating brake and CaM bind each other with high-nanomolar affinity. We show that the gating brake assumes a helical conformation upon binding CaM, with associated conformational changes to both CaM lobes as indicated by amide chemical shifts of the amino acids of CaM in 1H-15N HSQC NMR spectra. Intact Ca2+-binding sites on CaM and an intact gating brake sequence (first 39 amino acids of the I–II linker) were required in Cav3.2 channels to prevent the runaway gating phenotype, a hyperpolarizing shift in voltage sensitivities and faster gating kinetics. We conclude that the presence of high-nanomolar affinity binding sites for CaM at its universal gating brake and its unique form of regulation via the tuning of the voltage range of activity could influence the participation of Cav3 T-type channels in heart and brain rhythms. Our findings may have implications for arrhythmia disorders arising from mutations in the gating brake or CaM. PMID:28972185

Fabrication of Hybrid Capsules via CaCO3 Crystallization on Degradable Coacervate Droplets.

PubMed

Komatsu, Syuuhei; Ikedo, Yui; Asoh, Taka-Aki; Ishihara, Ryo; Kikuchi, Akihiko

2018-04-03

Organic-inorganic CaCO 3 capsules were prepared by crystallization of CaCO 3 on Pickering emulsion prepared using coacervate droplets made from thermoresponsive and degradable poly(2-methylene-1,3-dioxepane- co-2-hydroxyethyl acrylate) (poly(MDO- co-HEA)) in sole aqueous medium. The diameters of CaCO 3 -based Pickering emulsion could be controlled by varying several parameters: diameter of CaCO 3 powders, initial polymer concentration, and copolymer composition. The CaCO 3 Pickering emulsion was able to load low-molecular-weight hydrophobic substances at temperatures above the lower critical solution temperature (LCST) due to formation of polymer-concentrated phases, i.e., coacervate droplets. The diameter of CaCO 3 capsules prepared by crystallization also depended on the diameter of the CaCO 3 Pickering emulsion. The CaCO 3 shell was composed of calcite-type crystals, the most stable polymorph among known CaCO 3 crystals. The facially prepared CaCO 3 capsules are valuable for use in functional biomaterials, such as drug delivery carriers and cell culture scaffolds for noninvasive bone-regenerative medicine.

Role of the K(Ca)3.1 K+ channel in auricular lymph node CD4+ T-lymphocyte function of the delayed-type hypersensitivity model.

PubMed

Ohya, Susumu; Nakamura, Erina; Horiba, Sayuri; Kito, Hiroaki; Matsui, Miki; Yamamura, Hisao; Imaizumi, Yuji

2013-07-01

The intermediate-conductance Ca(2+)-activated K(+) channel (K(Ca)3.1) modulates the Ca(2+) response through the control of the membrane potential in the immune system. We investigated the role of K(Ca)3.1 on the pathogenesis of delayed-type hypersensitivity (DTH) in auricular lymph node (ALN) CD4(+) T-lymphocytes of oxazolone (Ox)-induced DTH model mice. The expression patterns of K(Ca)3.1 and its possible transcriptional regulators were compared among ALN T-lymphocytes of three groups [non-sensitized (Ox-/-), Ox-sensitized, but non-challenged (Ox+/-) and Ox-sensitized and -challenged (Ox+/+)] using real-time polymerase chain reaction, Western blotting and flow cytometry. KCa 3.1 activity was measured by whole-cell patch clamp and the voltage-sensitive dye imaging. The effects of K(Ca)3.1 blockade were examined by the administration of selective K(Ca)3.1 blockers. Significant up-regulation of K(Ca)3.1a was observed in CD4(+) T-lymphocytes of Ox+/- and Ox+/+, without any evident changes in the expression of the dominant-negative form, K(Ca)3.1b. Negatively correlated with this, the repressor element-1 silencing transcription factor (REST) was significantly down-regulated. Pharmacological blockade of K(Ca)3.1 resulted in an accumulation of the CD4(+) T-lymphocytes of Ox+/+ at the G0/G1 phase of the cell cycle, and also significantly recovered not only the pathogenesis of DTH, but also the changes in the K(Ca)3.1 expression and activity in the CD4(+) T-lymphocytes of Ox+/- and Ox+/+. The up-regulation of K(Ca)3.1a in conjunction with the down-regulation of REST may be involved in CD4(+) T-lymphocyte proliferation in the ALNs of DTH model mice; and K(Ca)3.1 may be an important target for therapeutic intervention in allergy diseases such as DTH. © 2013 The British Pharmacological Society.

Ca Addition Effects on the Microstructure, Tensile and Corrosion Properties of Mg Matrix Alloy Containing 8 wt.% Mg2Si

NASA Astrophysics Data System (ADS)

Lotfpour, M.; Emamy, M.; Dehghanian, C.; Pourbahari, B.

2018-02-01

The microstructure, tensile properties and corrosion behavior of the Mg-8 wt.% Mg2Si-x%Ca alloy have been studied by the use of optical microscopy, scanning electron microscopy equipped with energy-dispersive spectroscopy, x-ray diffraction, standard tensile testing, polarization test and electrochemical impedance spectroscopy (EIS) measurements. Microstructural studies indicated that Ca modifies both primary and eutectic Mg2Si phase. It was found that the average size of primary Mg2Si particles is about 60 μm, which is dropped by about 82% in the alloy containing 0.05 wt.% Ca. By the addition of different Ca contents, Ca-rich intermetallics (i.e., CaSi2 and CaMgSi) were formed. The modification mechanism of adding Ca during solidification was found to be due to the strong effect of CaMgSi phase as a heterogonous nucleation site, apart from CaSi2 which was reported before, for Mg2Si intermetallics. Tensile testing results ascertained that Ca addition enhances both ultimate tensile strength (UTS) and elongation values. The optimum amount of Ca was found to be 0.1 wt.%, which improved UTS and elongation values from about 130 MPa and 2% to 165 MPa and 5.5%, whereas more Ca addition (i.e., 3 wt.%) reduced the tensile properties of the alloy to about 105 MPa and 1.8%, which can be due to the formation of CaMgSi intermetallics with deteriorating needle-like morphology. Polarization and EIS tests also showed that the Mg-3%Si-0.5%Ca alloy pronounces as the best anti-corrosion alloy. Nevertheless, further added Ca (up to 3 wt.%) deteriorated the corrosion resistance due to predominance of worse galvanic coupling effect stemmed from the presence of stronger CaMgSi cathode in comparison with Mg2Si. With higher Ca additions, an adverse effect was seen on corrosion resistance of the Mg-3%Si alloy, as a result of forming a weak film on the alloy specimen surface.

Experimental verification of a predicted novel microRNA located in human PIK3CA gene with a potential oncogenic function in colorectal cancer.

PubMed

Saleh, Ali Jason; Soltani, Bahram M; Dokanehiifard, Sadat; Medlej, Abdallah; Tavalaei, Mahmoud; Mowla, Seyed Javad

2016-10-01

PI3K/AKT signaling is involved in cell survival, proliferation, and migration. In this pathway, PI3Kα enzyme is composed of a regulatory protein encoded by p85 gene and a catalytic protein encoded by PIK3CA gene. Human PIK3CA locus is amplified in several cancers including lung and colorectal cancer (CRC). Therefore, microRNAs (miRNAs) that are encoded within the PIK3CA gene might have a role in cancer development. Here, we report a novel microRNA named PIK3CA-miR1 (EBI accession no. LN626315), which is located within PIK3CA gene. A DNA segment corresponding to PIK3CA-premir1 sequence was transfected in human cell lines that resulted in generation of mature exogenous PIK3CA-miR1. Following the overexpression of PIK3CA-miR1, its predicted target genes (APPL1 and TrkC) were significantly downregulated in the CRC-originated HCT116 and SW480 cell lines, detected by qRT-PCR. Then, dual luciferase assay supported the interaction of PIK3CA-miR1 with APPL1 and TrkC transcripts. Endogenous PIK3CA-miR1 expression was also detected in several cell lines (highly in HCT116 and SW480) and highly in CRC specimens. Consistently, overexpression of PIK3CA-premir1 in HCT116 and SW480 cells resulted in significant reduction of the sub-G1 cell distribution and apoptotic cell rate, as detected by flowcytometry, and resulted in increased cell proliferation, as detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. PIK3CA-miR1 overexpression also resulted in Wnt signaling upregulation detected by Top/Fop assay. Overall, accumulative evidences indicated the presence of a bona fide novel onco-miRNA encoded within the PIK3CA oncogene, which is highly expressed in colorectal cancer and has a survival effect in CRC-originated cells.

Simulation-based Assessment to Reliably Identify Key Resident Performance Attributes.

PubMed

Blum, Richard H; Muret-Wagstaff, Sharon L; Boulet, John R; Cooper, Jeffrey B; Petrusa, Emil R; Baker, Keith H; Davidyuk, Galina; Dearden, Jennifer L; Feinstein, David M; Jones, Stephanie B; Kimball, William R; Mitchell, John D; Nadelberg, Robert L; Wiser, Sarah H; Albrecht, Meredith A; Anastasi, Amanda K; Bose, Ruma R; Chang, Laura Y; Culley, Deborah J; Fisher, Lauren J; Grover, Meera; Klainer, Suzanne B; Kveraga, Rikante; Martel, Jeffrey P; McKenna, Shannon S; Minehart, Rebecca D; Mitchell, John D; Mountjoy, Jeremi R; Pawlowski, John B; Pilon, Robert N; Shook, Douglas C; Silver, David A; Warfield, Carol A; Zaleski, Katherine L

2018-04-01

Obtaining reliable and valid information on resident performance is critical to patient safety and training program improvement. The goals were to characterize important anesthesia resident performance gaps that are not typically evaluated, and to further validate scores from a multiscenario simulation-based assessment. Seven high-fidelity scenarios reflecting core anesthesiology skills were administered to 51 first-year residents (CA-1s) and 16 third-year residents (CA-3s) from three residency programs. Twenty trained attending anesthesiologists rated resident performances using a seven-point behaviorally anchored rating scale for five domains: (1) formulate a clear plan, (2) modify the plan under changing conditions, (3) communicate effectively, (4) identify performance improvement opportunities, and (5) recognize limits. A second rater assessed 10% of encounters. Scores and variances for each domain, each scenario, and the total were compared. Low domain ratings (1, 2) were examined in detail. Interrater agreement was 0.76; reliability of the seven-scenario assessment was r = 0.70. CA-3s had a significantly higher average total score (4.9 ± 1.1 vs. 4.6 ± 1.1, P = 0.01, effect size = 0.33). CA-3s significantly outscored CA-1s for five of seven scenarios and domains 1, 2, and 3. CA-1s had a significantly higher proportion of worrisome ratings than CA-3s (chi-square = 24.1, P < 0.01, effect size = 1.50). Ninety-eight percent of residents rated the simulations more educational than an average day in the operating room. Sensitivity of the assessment to CA-1 versus CA-3 performance differences for most scenarios and domains supports validity. No differences, by experience level, were detected for two domains associated with reflective practice. Smaller score variances for CA-3s likely reflect a training effect; however, worrisome performance scores for both CA-1s and CA-3s suggest room for improvement.

Thermoelectric properties of antiperovskite calcium oxides Ca{sub 3}PbO and Ca{sub 3}SnO

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

Okamoto, Y., E-mail: yokamoto@nuap.nagoya-u.ac.jp; Institute for Advanced Research, Nagoya University, Nagoya 464-8601; Sakamaki, A.

We report the thermoelectric properties of polycrystalline samples of Ca{sub 3}Pb{sub 1−x}Bi{sub x}O (x = 0, 0.1, 0.2) and Ca{sub 3}SnO, both crystallizing in a cubic antiperovskite-type structure. The Ca{sub 3}SnO sample shows metallic resistivity and its thermoelectric power approaches 100 μV K{sup −1} at room temperature, resulting in the thermoelectric power factor of Ca{sub 3}SnO being larger than that of Ca{sub 3}Pb{sub 1−x}Bi{sub x}O. On the basis of Hall and Sommerfeld coefficients, the Ca{sub 3}SnO sample is found to be a p-type metal with a carrier density of ∼10{sup 19 }cm{sup −3}, a mobility of ∼80 cm{sup 2} V{sup −1} s{sup −1}, both comparablemore » to those in degenerated semiconductors, and a moderately large hole carrier effective mass. The coexistence of moderately high mobility and large effective mass observed in Ca{sub 3}SnO, as well as possible emergence of a multivalley electronic structure with a small band gap at low-symmetry points in k-space, suggests that the antiperovskite Ca oxides have strong potential as a thermoelectric material.« less

Capsaicin stimulates the non-store-operated Ca{sup 2+} entry but inhibits the store-operated Ca{sup 2+} entry in neutrophils

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

Wang, J.-P.; Tseng, C.-S.; Sun, S.-P.

2005-12-01

Rat neutrophils express the mRNA encoding for transient receptor potential (TRP) V1. However, capsaicin-stimulated [Ca{sup 2+}]{sub i} elevation occurred only at high concentrations ({>=}100 {mu}M). This response was substantially decreased in a Ca{sup 2+}-free medium. Vanilloids displayed similar patterns of Ca{sup 2+} response with the rank order of potency as follows: scutigeral>resiniferatoxin>capsazepine>capsaicin=olvanil>isovelleral. Arachidonyl dopamine (AAD), an endogenous ligand for TRPV1, failed to desensitize the subsequent capsaicin challenge. Capsaicin-induced Ca{sup 2+} response was not affected by 8-bromo-cyclic ADP-ribose (8-Br-cADPR), the ryanodine receptor blocker, but was slightly attenuated by 1-[6-[17{beta}-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,= 5-dione (U-73122), the inhibitor of phospholipase C-coupled processes, 1-[{beta}-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF-96365), the blockermore » of receptor-gated and store-operated Ca{sup 2+} (SOC) channels, 2-aminoethyldiphenyl borate (2-APB), the blocker of D-myo-inositol 1,4,5-trisphospahte (IP{sub 3}) receptor and Ca{sup 2+} influx, and by ruthenium red, a blocker of TRPV channels, and enhanced by the Ca{sup 2+} channels blocker, cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL-12330A) and Na{sup +}-deprivation. In addition, capsaicin had no effect on the plasma membrane Ca{sup 2+}-ATPase activity or the production of nitric oxide (NO) and reactive oxygen intermediates (ROI) or on the total thiols content. Capsaicin ({>=}100 {mu}M) inhibited the cyclopiazonic acid (CPA)-induced store-operated Ca{sup 2+} entry (SOCE). In the absence of external Ca{sup 2+}, the robust Ca{sup 2+} entry after subsequent addition of Ca{sup 2+} was decreased by capsaicin in CPA-activated cells. Capsaicin alone increased the actin cytoskeleton, and also increased the actin filament content in cell activation with CPA. These results indicate that capsaicin activates a TRPV1-independent non-SOCE pathway in neutrophils. The reorganization of the actin cytoskeleton is probably involved in the capsaicin inhibition of SOCE.« less

Multiple C-terminal tail Ca2+/CaMs regulate CaV1.2 function but do not mediate channel dimerization

PubMed Central

Kim, Eun Young; Rumpf, Christine H; Van Petegem, Filip; Arant, Ryan J; Findeisen, Felix; Cooley, Elizabeth S; Isacoff, Ehud Y; Minor, Daniel L

2010-01-01

Interactions between voltage-gated calcium channels (CaVs) and calmodulin (CaM) modulate CaV function. In this study, we report the structure of a Ca2+/CaM CaV1.2 C-terminal tail complex that contains two PreIQ helices bridged by two Ca2+/CaMs and two Ca2+/CaM–IQ domain complexes. Sedimentation equilibrium experiments establish that the complex has a 2:1 Ca2+/CaM:C-terminal tail stoichiometry and does not form higher order assemblies. Moreover, subunit-counting experiments demonstrate that in live cell membranes CaV1.2s are monomers. Thus, contrary to previous proposals, the crystallographic dimer lacks physiological relevance. Isothermal titration calorimetry and biochemical experiments show that the two Ca2+/CaMs in the complex have different properties. Ca2+/CaM bound to the PreIQ C-region is labile, whereas Ca2+/CaM bound to the IQ domain is not. Furthermore, neither of lobes of apo-CaM interacts strongly with the PreIQ domain. Electrophysiological studies indicate that the PreIQ C-region has a role in calcium-dependent facilitation. Together, the data show that two Ca2+/CaMs can bind the CaV1.2 tail simultaneously and indicate a functional role for Ca2+/CaM at the C-region site. PMID:20953164

Multiple C-terminal tail Ca(2+)/CaMs regulate Ca(V)1.2 function but do not mediate channel dimerization.

PubMed

Kim, Eun Young; Rumpf, Christine H; Van Petegem, Filip; Arant, Ryan J; Findeisen, Felix; Cooley, Elizabeth S; Isacoff, Ehud Y; Minor, Daniel L

2010-12-01

Interactions between voltage-gated calcium channels (Ca(V)s) and calmodulin (CaM) modulate Ca(V) function. In this study, we report the structure of a Ca(2+)/CaM Ca(V)1.2 C-terminal tail complex that contains two PreIQ helices bridged by two Ca(2+)/CaMs and two Ca(2+)/CaM-IQ domain complexes. Sedimentation equilibrium experiments establish that the complex has a 2:1 Ca(2+)/CaM:C-terminal tail stoichiometry and does not form higher order assemblies. Moreover, subunit-counting experiments demonstrate that in live cell membranes Ca(V)1.2s are monomers. Thus, contrary to previous proposals, the crystallographic dimer lacks physiological relevance. Isothermal titration calorimetry and biochemical experiments show that the two Ca(2+)/CaMs in the complex have different properties. Ca(2+)/CaM bound to the PreIQ C-region is labile, whereas Ca(2+)/CaM bound to the IQ domain is not. Furthermore, neither of lobes of apo-CaM interacts strongly with the PreIQ domain. Electrophysiological studies indicate that the PreIQ C-region has a role in calcium-dependent facilitation. Together, the data show that two Ca(2+)/CaMs can bind the Ca(V)1.2 tail simultaneously and indicate a functional role for Ca(2+)/CaM at the C-region site.

Store-Operated Ca2+ Entry Does Not Control Proliferation in Primary Cultures of Human Metastatic Renal Cellular Carcinoma

PubMed Central

Turin, Ilaria; Potenza, Duilio Michele; Bottino, Cinzia; Glasnov, Toma N.; Ferulli, Federica; Mosca, Alessandra; Guerra, Germano; Rosti, Vittorio; Luinetti, Ombretta; Porta, Camillo; Pedrazzoli, Paolo

2014-01-01

Store-operated Ca2+ entry (SOCE) is activated following depletion of the inositol-1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pool to regulate proliferation in immortalized cell lines established from either primary or metastatic lesions. The molecular nature of SOCE may involve both Stim1, which senses Ca2+ levels within the endoplasmic reticulum (ER) Ca2+ reservoir, and a number of a Ca2+-permeable channels on the plasma membrane, including Orai1, Orai3, and members of the canonical transient receptor (TRPC1–7) family of ion channels. The present study was undertaken to assess whether SOCE is expressed and controls proliferation in primary cultures isolated from secondary lesions of heavily pretreated metastatic renal cell carcinoma (mRCC) patients. SOCE was induced following pharmacological depletion of the ER Ca2+ store, but not by InsP3-dependent Ca2+ release. Metastatic RCC cells express Stim1-2, Orai1–3, and TRPC1–7 transcripts and proteins. In these cells, SOCE was insensitive to BTP-2, 10 µM Gd3+ and Pyr6, while it was inhibited by 100 µM Gd3+, 2-APB, and carboxyamidotriazole (CAI). Neither Gd3+ nor 2-APB or CAI impaired mRCC cell proliferation. Consistently, no detectable Ca2+ signal was elicited by growth factor stimulation. Therefore, a functional SOCE is expressed but does not control proliferation of mRCC cells isolated from patients resistant to multikinase inhibitors. PMID:25126575

Microsomal Ca2+ flux modulation as an indicator of heavy metal toxicity.

PubMed

Pentyala, Srinivas; Ruggeri, Jeanine; Veerraju, Amulya; Yu, Zhangzhang; Bhatia, Anjori; Desaiah, Durisala; Vig, Parminder

2010-07-01

Inositol 1,4,5-trisphosphatee (IP3), an intracellular messenger, releases Ca2+ from microsomes. Ca2+ plays a major role in regulating various cellular events like neural transmission and regulation of hormones and growth factors. Aluminum (Al), lead (Pb) and mercury (Hg) were reported to alter Ca(2+)-regulated events thereby causing neurotoxicity. Hence, an attempt was made characterize IP3 mediated Ca2+ release from rat brain microsomes under the influence of Al, Pb and Hg. Different concentrations of metals were tested over a designated time scale and their effects on IP3 mediated Ca2+ release from microsomes were monitored using Fura-2 technique. All the three metals inhibited IP3 mediated Ca2+ release, Pb being more potent. The order of potency of these three metals was Pb>Hg>Al. Except for Al, both Hg and Pb independently released Ca2+ from microsomes. Re-uptake of Ca2+ into microsomes was inhibited by all the three metals, Pb being more potent. Microsomal Ca(2+)-ATPase activity was also inhibited by all the three metals. These results suggest that neurotoxicity exerted by Al, Pb and Hg may be due to the interference of these metals with IP3 mediated calcium release and also interfering with the microsomal Ca2+ sequestration mechanism. Differential effects of heavy metal induced changes in Ca2+ flux can be used as an index of relative toxicity.

Influence of Ce Doping on Structural and Transport Properties of Ca1- x Ce x MnO3 ( x=0.2) Manganite

NASA Astrophysics Data System (ADS)

Varshney, Dinesh; Mansuri, Irfan

2011-01-01

We have investigated structural, electric, magnetic and thermal transport properties of electron doped Ca1- x Ce x MnO3 ( x=0.2) manganites. The Cerium substitution for Ca2+causes electron doping into insulating CaMnO3 without e g electron. At room temperature the polycrystalline Ca0.8Ce0.2MnO3 is in the crystallographic orthorhombic structure, with Pnma space group symmetry from the refinement of x-ray powder diffraction patterns. The electrical resistivity data infers that Ca0.8Ce0.2MnO3 manganite is in the semiconducting phase. A smooth linear behavior of log plot values is obtained and is well fitted with adiabatic small polaron conduction model. Nearest-neighbor hopping of a small polaron leads to a mobility with a thermally activated form. The negative values of thermopower infer electron as carriers in Ca0.8Ce0.2MnO3. From susceptibility measurements the Ce doped CaMnO3 shows a transition from antiferromagnetic (AFM) to paramagnetic (PM) phase.

Probing the limit of magnesium uptake by β-tricalcium phosphate in biphasic mixtures formed from calcium deficient apatites

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

Kumar, P. Nandha; Mishra, Sandeep K.; Kannan, S., E-mail: para_kanna@yahoo.com

2015-11-15

A series of magnesium doped non-stoichiometric calcium deficient apatites were synthesized through an aqueous precipitation route. The resultant structural changes during heat treatment were investigated by X-ray diffraction, Raman and FT-IR spectroscopy and Rietveld refinement. The results confirmed the formation of biphasic mixtures comprising Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} and β-Ca{sub 3}(PO{sub 4}){sub 2} after heat treatment at 1000 °C with the preferential occupancy of Mg{sup 2+} at the crystal lattice of β-Ca{sub 3}(PO{sub 4}){sub 2}. The concentration of Mg{sup 2+} uptake in β-Ca{sub 3}(PO{sub 4}){sub 2} is limited till reaching the stoichiometric ratio of (Ca+Mg)/P=1.67 and beyond this stoichiometricmore » value [(Ca+Mg)/P>1.67], Mg{sup 2+} precipitates as Mg(OH){sub 2} and thereafter gets converted to MgO during heat treatment. Any kind of Mg{sup 2+} uptake in the crystal lattice of Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} is discarded from the investigation. - Highlights: • Aqueous co-precipitation of calcium deficient apatites with excess magnesium (Mg{sup 2+}) additions. • Heat treatments beyond 800 °C results in the formation of biphasic apatite mixtures. • Mg{sup 2+} gets accommodated at the β-Ca{sub 3}(PO{sub 4}){sub 2} lattice of biphasic mixtures. • Mg{sup 2+} additions exceeding stoichiometric value (Ca/P>1.67) results in its formation as MgO. • Mg{sup 2+} occupancy at β-Ca{sub 3}(PO{sub 4}){sub 2} lattice delays its allotropic conversion α-Ca{sub 3}(PO{sub 4}){sub 2} till 1350 °C.« less

Spatial Segregation and Interaction of Calcium Signalling Mechanisms in Rat Hippocampal CA1 Pyramidal Neurons

PubMed Central

Nakamura, Takeshi; Lasser-Ross, Nechama; Nakamura, Kyoko; Ross, William N

2002-01-01

Postsynaptic [Ca2+]i increases result from Ca2+ entry through ligand-gated channels, entry through voltage-gated channels, or release from intracellular stores. We found that these sources have distinct spatial distributions in hippocampal CA1 pyramidal neurons. Large amplitude regenerative release of Ca2+ from IP3-sensitive stores in the form of Ca2+ waves were found almost exclusively on the thick apical shaft. Smaller release events did not extend more than 15 μm into the oblique dendrites. These synaptically activated regenerative waves initiated at points where the stimulated oblique dendrites branch from the apical shaft. In contrast, NMDA receptor-mediated increases were observed predominantly in oblique dendrites where spines are found at high density. These [Ca2+]i increases were typically more than eight times larger than [Ca2+]i from this source on the main aspiny apical shaft. Ca2+ entry through voltage-gated channels, activated by backpropagating action potentials, was detected at all dendritic locations. These mechanisms were not independent. Ca2+ entry through NMDA receptor channels or voltage-gated channels (as previously demonstrated) synergistically enhanced Ca2+ release generated by mGluR mobilization of IP3. PMID:12205182

Quantification of the functional expression of the Ca2+ -activated K+ channel KCa 3.1 on microglia from adult human neocortical tissue.

PubMed

Blomster, Linda V; Strøbaek, Dorte; Hougaard, Charlotte; Klein, Jessica; Pinborg, Lars H; Mikkelsen, Jens D; Christophersen, Palle

2016-12-01

The K Ca 3.1 channel (KCNN4) is an important modulator of microglia responses in rodents, but no information exists on functional expression on microglia from human adults. We isolated and cultured microglia (max 1% astrocytes, no neurons or oligodendrocytes) from neocortex surgically removed from epilepsy patients and employed electrophysiological whole-cell measurements and selective pharmacological tools to elucidate functional expression of K Ca 3.1. The channel expression was demonstrated as a significant increase in the voltage-independent current by NS309, a K Ca 3.1/K Ca 2 activator, followed by full inhibition upon co-application with NS6180, a highly selective K Ca 3.1 inhibitor. A major fraction (79%) of unstimulated human microglia expressed K Ca 3.1, and the difference in current between full activation and inhibition (ΔK Ca 3.1) was estimated at 292 ± 48 pA at -40 mV (n = 75), which equals at least 585 channels per cell. Serial K Ca 3.1 activation/inhibition significantly hyperpolarized/depolarized the membrane potential. The isolated human microglia were potently activated by lipopolysaccharide (LPS) shown as a prominent increase in TNF-α production. However, incubation with LPS neither changed the K Ca 3.1 current nor the fraction of K Ca 3.1 expressing cells. In contrast, the anti-inflammatory cytokine IL-4 slightly increased the K Ca 3.1 current per cell, but as the membrane area also increased, there was no significant change in channel density. A large fraction of the microglia also expressed a voltage-dependent current sensitive to the K Ca 1.1 modulators NS1619 and Paxilline and an inward-rectifying current with the characteristics of a K ir channel. The high functional expression of K Ca 3.1 in microglia from epilepsy patients accentuates the need for further investigations of its role in neuropathological processes. GLIA 2016;64:2065-2078. © 2016 Wiley Periodicals, Inc.

Role of Cyclin E as an Early Event in Ovarian Carcinogenesis

DTIC Science & Technology

2012-04-01

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

Imaging Ca2+ with a Fluorescent Rhodol.

PubMed

Contractor, Alisha A; Miller, Evan W

2018-01-16

Ca 2+ mediates a host of biochemical and biophysical signaling processes in cells. The development of synthetic, Ca 2+ -sensitive fluorophores has played an instrumental role in our understanding of the temporal and spatial dynamics of Ca 2+ . Coupling Ca 2+ -selective ligands to fluorescent reporters has provided a wealth of excellent indicators that span the visible excitation and emission spectrum and possess Ca 2+ affinities suited to a variety of cellular contexts. One underdeveloped area is the use of hybrid rhodamine/fluorescein fluorophores, or rhodols, in the context of Ca 2+ sensing. Rhodols are bright and photostable and have good two-photon absorption cross sections (σ TPA ), making them excellent candidates for incorporation into Ca 2+ -sensing scaffolds. Here, we present the design, synthesis, and application of rhodol Ca 2+ sensor 1 (RCS-1), a chlorinated pyrrolidine-based rhodol. RCS-1 possesses a Ca 2+ binding constant of 240 nM and a 10-fold turn response to Ca 2+ . RCS-1 effectively absorbs infrared light and has a σ TPA of 76 GM at 840 nm, 3-fold greater than that of its fluorescein-based counterpart. The acetoxy-methyl ester of RCS-1 stains the cytosol of live cells, enabling observation of Ca 2+ fluctuations and cultured neurons using both one- and two-photon illumination. Together, these results demonstrate the utility of rhodol-based scaffolds for Ca 2+ sensing using two-photon illumination in neurons.

Effect of chloride channel inhibitors on cytosolic Ca2+ levels and Ca2+-activated K+ (Gardos) channel activity in human red blood cells.

PubMed

Kucherenko, Yuliya V; Wagner-Britz, Lisa; Bernhardt, Ingolf; Lang, Florian

2013-04-01

DIDS, NPPB, tannic acid (TA) and AO1 are widely used inhibitors of Cl(-) channels. Some Cl(-) channel inhibitors (NPPB, DIDS, niflumic acid) were shown to affect phosphatidylserine (PS) scrambling and, thus, the life span of human red blood cells (hRBCs). Since a number of publications suggest Ca(2+) dependence of PS scrambling, we explored whether inhibitors of Cl(-) channels (DIDS, NPPB) or of Ca(2+)-activated Cl(-) channels (DIDS, NPPB, TA, AO1) modified intracellular free Ca(2+) concentration ([Ca(2+)]i) and activity of Ca(2+)-activated K(+) (Gardos) channel in hRBCs. According to Fluo-3 fluorescence in flow cytometry, a short treatment (15 min, +37 °C) with Cl(-) channels inhibitors decreased [Ca(2+)]i in the following order: TA > AO1 > DIDS > NPPB. According to forward scatter, the decrease of [Ca(2+)]i was accompanied by a slight but significant increase in cell volume following DIDS, NPPB and AO1 treatments. TA treatment resulted in cell shrinkage. According to whole-cell patch-clamp experiments, TA activated and NPPB and AO1 inhibited Gardos channels. The Cl(-) channel blockers further modified the alterations of [Ca(2+)]i following ATP depletion (glucose deprivation, iodoacetic acid, 6-inosine), oxidative stress (1 mM t-BHP) and treatment with Ca(2+) ionophore ionomycin (1 μM). The ability of the Cl(-) channel inhibitors to modulate PS scrambling did not correlate with their influence on [Ca(2+)]i as TA and AO1 had a particularly strong decreasing effect on [Ca(2+)]i but at the same time enhanced PS exposure. In conclusion, Cl(-) channel inhibitors affect Gardos channels, influence Ca(2+) homeostasis and induce PS exposure of hRBCs by Ca(2+)-independent mechanisms.

STIM1 as a key regulator for Ca2+ homeostasis in skeletal-muscle development and function

PubMed Central

2011-01-01

Stromal interaction molecules (STIM) were identified as the endoplasmic-reticulum (ER) Ca2+ sensor controlling store-operated Ca2+ entry (SOCE) and Ca2+-release-activated Ca2+ (CRAC) channels in non-excitable cells. STIM proteins target Orai1-3, tetrameric Ca2+-permeable channels in the plasma membrane. Structure-function analysis revealed the molecular determinants and the key steps in the activation process of Orai by STIM. Recently, STIM1 was found to be expressed at high levels in skeletal muscle controlling muscle function and properties. Novel STIM targets besides Orai channels are emerging. Here, we will focus on the role of STIM1 in skeletal-muscle structure, development and function. The molecular mechanism underpinning skeletal-muscle physiology points toward an essential role for STIM1-controlled SOCE to drive Ca2+/calcineurin/nuclear factor of activated T cells (NFAT)-dependent morphogenetic remodeling programs and to support adequate sarcoplasmic-reticulum (SR) Ca2+-store filling. Also in our hands, STIM1 is transiently up-regulated during the initial phase of in vitro myogenesis of C2C12 cells. The molecular targets of STIM1 in these cells likely involve Orai channels and canonical transient receptor potential (TRPC) channels TRPC1 and TRPC3. The fast kinetics of SOCE activation in skeletal muscle seem to depend on the triad-junction formation, favoring a pre-localization and/or pre-formation of STIM1-protein complexes with the plasma-membrane Ca2+-influx channels. Moreover, Orai1-mediated Ca2+ influx seems to be essential for controlling the resting Ca2+ concentration and for proper SR Ca2+ filling. Hence, Ca2+ influx through STIM1-dependent activation of SOCE from the T-tubule system may recycle extracellular Ca2+ losses during muscle stimulation, thereby maintaining proper filling of the SR Ca2+ stores and muscle function. Importantly, mouse models for dystrophic pathologies, like Duchenne muscular dystrophy, point towards an enhanced Ca2+ influx through Orai1 and/or TRPC channels, leading to Ca2+-dependent apoptosis and muscle degeneration. In addition, human myopathies have been associated with dysfunctional SOCE. Immunodeficient patients harboring loss-of-function Orai1 mutations develop myopathies, while patients suffering from Duchenne muscular dystrophy display alterations in their Ca2+-handling proteins, including STIM proteins. In any case, the molecular determinants responsible for SOCE in human skeletal muscle and for dysregulated SOCE in patients of muscular dystrophy require further examination. PMID:21798093

Crystal structure and electrical conductivity of lanthanum-calcium chromites-titanates La 1-xCa xCr 1-yTi yO 3-δ ( x=0-1, y=0-1)

NASA Astrophysics Data System (ADS)

Vashook, V.; Vasylechko, L.; Zosel, J.; Gruner, W.; Ullmann, H.; Guth, U.

2004-10-01

Five series of perovskite-type compounds in the system La1-xCaxCr1-yTiyO3 with the nominal compositions y = 0 , x = 0 - 0.5 ; y = 0.2 , x = 0.2 - 0.8 ; y = 0.5 , x = 0.5 - 1.0 ; y = 0.8 , x = 0.6 - 1.0 and y = 1 , x = 0.8 - 1 were synthesized by a ceramic technique in air (final heating 1350 °C). On the basis of the X-ray analysis of the samples with (Ca/Ti)⩾1, the phase diagram of the CaTiO3-LaCrIIIO3-CaCrIVO3 quasi-ternary system was constructed. Extended solid solution with a wide homogeneity range is formed in the quasi-ternary system CaCrIVO3-CaTiO3-LaCrIIIO3. The solid solution La(1-x‧-y)Ca(x‧+y)CrIVx‧CrIII(1-x‧-y)TiyO3 exists by up to 0.6-0.7 mol fractions of CaCrIVO3 (x‧ < 0.6 - 0.7) at the experimental conditions. The crystal structure of the compounds is orthorhombic in the space group Pbnm at room temperature. The lattice parameters and the average interatomic distances of the samples within the solid solution ranges decrease uniformly with increasing Ca content. Outside the quasi-ternary system, the nominal compositions La0.1Ca0.9TiO3, La0.2Ca0.8TiO3, La0.4Ca0.6Cr0.2Ti0.8O3 and La0.3Ca0.7Cr0.2Ti0.8O3 in the system La1-xCaxCr1-yTiyO3 were found as single phases with an orthorhombic structure. In the temperature range between 850 and 1000 °C, the synthesized single-phase compositions are stable at pO2=6×10-16-0.21×105 Pa. Oxygen stoichiometry and electrical conductivity of the separate compounds were investigated as functions of temperature and oxygen partial pressure. The chemical stability of these oxides with respect to oxygen release during thermal dissociation decreases with increasing Ca-content. At 900 °C and oxygen partial pressure 1×10-15-0.21×105 Pa, the compounds with x > y (acceptor doped) are p-type semiconductors and those with x < y (donor doped) and x = y are n-type semiconductors. The type and level of electrical conductivity are functions of the concentration ratios of cations occupying the B-sites of the perovskite structures: [Cr3+]/[Cr4+] and [Ti4+]/[Ti3+]. The maximum electrical conductivity at 900 °C and pO2=10-15 Pa was found for the composition La0.1Ca0.9TiO3 (near 50 S/cm) and in air at 900 °C for La0.5Ca0.5CrO3 (close to 100 S/cm).

Muscarinic agonists and ATP increase the intracellular Ca2+ concentration in chick cochlear hair cells.

PubMed

Shigemoto, T; Ohmori, H

1990-01-01

1. Cholinergic muscarinic agonists applied by the pressure puff method increased intracellular Ca2+ concentration in Fura-2-loaded hair cells. The Ca2+ response outlasted the agonist application. 2. The Ca2+ response induced by acetylcholine (ACh) was ACh dose dependent with a KD of 200 microM. Desensitization was negligible, and almost identical Ca2+ responses were observed when two ACh puffs were separated by 150 s. The response was blocked by d-tubocurarine (dTC). The KD of dTC blocking was 500 microM when 100 microM-ACh induced the Ca2+ response. 3. The amplitude of the ACh-induced Ca2+ responses were potentiated to 3 times the control by incubation with calcitonin gene-related peptide (CGRP; 0.1-1 microM). CGRP did not affect the resting Ca2+ concentration. Glycine (100 microM) potentiated the ACh response to 1.4 times the control, and also increased the resting Ca2+ concentration slightly. 4. The ACh-induced Ca2+ response was suppressed by atropine. It was induced in Ca2(+)-free extracellular medium, and in Ca2(+)-free medium desensitization to a second ACh stimulation was significant. The amplitude of the second Ca2+ response was 44% of the first when two ACh puffs were separated by 117 s in Ca2+ free medium. 5. Muscarine and carbamylcholine induced similar Ca2+ responses, with KD values of 130 microM for muscarine and 340 microM for carbamylcholine. Desensitization of Ca2+ responses was negligible in both agonists. 6. ATP co-exists with ACh in some presynaptic nerve terminals (Burnstock, 1981). Puff-applied ATP (100 microM) generated a Ca2+ response with a rapid rising phase and a following slow phase. In Ca2(+)-free medium the rapid phase disappeared and only the slow phase was observed. The rapid phase is due to the influx of Ca2+ ions and the slow phase is due to a release of Ca2+ ions from an intracellular reservoir. Under voltage clamp ATP induced a fast inward current and a following slow outward current. 7. Nicotine, adenosine, glycine, GABA, glutamate and bradykinin did not induce Ca2+ responses in the hair cell. 8. ACh induced hyperpolarization of the hair cell membrane under current clamp, most probably by the activation of Ca2+ activated K+ conductance. Therefore, a cholinergic muscarinic receptor may mediate the inhibitory effects of efferent innervation observed in hair cells.

The role of luminal Ca2+ in the generation of Ca2+ waves in rat ventricular myocytes

PubMed Central

Lukyanenko, Valeriy; Subramanian, Saisunder; Györke, Inna; Wiesner, Theodore F; Györke, Sandor

1999-01-01

We used confocal Ca2+ imaging and fluo-3 to investigate the transition of localized Ca2+ releases induced by focal caffeine stimulation into propagating Ca2+ waves in isolated rat ventricular myocytes. Self-sustaining Ca2+ waves could be initiated when the cellular Ca2+ load was increased by elevating the extracellular [Ca2+] ([Ca2+]o) and they could also be initiated at normal Ca2+ loads when the sensitivity of the release sites to cytosolic Ca2+ was enhanced by low doses of caffeine. When we prevented the accumulation of extra Ca2+ in the luminal compartment of the sarcoplasmic reticulum (SR) with thapsigargin, focal caffeine pulses failed to trigger self-sustaining Ca2+ waves on elevation of [Ca2+]o. Inhibition of SR Ca2+ uptake by thapsigargin in cells already preloaded with Ca2+ above normal levels did not prevent local Ca2+ elevations from triggering propagating waves. Moreover, wave velocity increased by 20 %. Tetracaine (0·75 mM) caused transient complete inhibition of both local and propagating Ca2+ signals, followed by full recovery of the responses due to increased SR Ca2+ accumulation. Computer simulations using a numerical model with spatially distinct Ca2+ release sites suggested that increased amounts of releasable Ca2+ might not be sufficient to generate self-sustaining Ca2+ waves under conditions of Ca2+ overload unless the threshold of release site Ca2+ activation was set at relatively low levels (< 1·5 μM). We conclude that the potentiation of SR Ca2+ release channels by luminal Ca2+ is an important factor in Ca2+ wave generation. Wave propagation does not require the translocation of Ca2+ from the spreading wave front into the SR. Instead, it relies on luminal Ca2+ sensitizing Ca2+ release channels to cytosolic Ca2+. PMID:10373699

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.

The Use of Rietveld Technique to Study Phase Composition and Developments of Calcium Aluminate

NASA Astrophysics Data System (ADS)

Ridwan, I.; Asmi, D.

2008-03-01

The phase composition and development of calcium aluminates (CA, CA2, and CA6) processed by in-situ reaction sintering of Al2O3 and CaCO3 have been studied by Rietveld refinement technique. The formation of calcium aluminates is temperature-dependent. X-ray diffraction result revealed that the CA, CA2, and CA6 phases starts to develop at approximately 1000 °C, 1100 °C and 1375 °C, respectively. The relative phase compositions obtained from x-ray diffraction patterns for the α-Al2O3 phase decreased markedly with increasing temperature, i.e. from 86.0(1.1) wt% at 1000 °C to 34.7(0.4) wt% at 1400 °C. The wt% of CA decreased from 10.9(0.3)-1.9(0.2) wt% at 1100-1200 °C but disappeared at 1300 °C. The wt% of CA2 reached 36.0(0.7) wt% at 1300 °C and decreased to 18.5 (0.5) wt% at 1400 °C. The wt% CA6 increased markedly from 1375 to 1400 °C, i.e. 12.80(0.6)-47.3(0.9) wt%. The goodness of fit values is relatively low and the fluctuation in the difference plots shows a reasonable fit between the observed and the calculated plot.

Intrinsic cytosolic calcium buffering properties of single rat cardiac myocytes.

PubMed Central

Berlin, J R; Bassani, J W; Bers, D M

1994-01-01

Intracellular passive Ca2+, buffering was measured in voltage-clamped rat ventricular myocytes. Cells were loaded with indo-1 (K+ salt) to an estimated cytosolic concentration of 44 +/- 5 microM (Mean +/- SEM, n = 5), and accessible cell volume was estimated to be 24.5 +/- 3.6 pl. Ca2+ transport by the sarcoplasmic reticulum (SR) Ca-ATPase and sarcolemmal Na-Ca exchange was inhibited by treatment with thapsigargin and Na-free solutions, respectively. Extracellular [Ca2+] was maintained at 10 mM and, in some experiments, the mitochondrial uncoupler "1799" was used to assess the degree of mitochondrial Ca2+ uptake. To perform single cell titrations, intracellular Ca2+ ([Ca2+]i) was increased progressively by a train of depolarizing voltage clamp pulses from -40 to +10 mV. The total Ca2+ gain with each pulse was calculated by integration of the Ca current and then analyzed as a function of the rapid change in [Ca2+]i during the pulse. In the range of [Ca2+]i from 0.1 to 2 microM, overall cell buffering was well described as a single lumped Michaelis-Menten type species with an apparent dissociation constant, KD, of of 0.63 +/- 0.07 microM (n = 5) and a binding capacity, Bmax, of 162 +/- 15 mumol/l cell H2O. Correction for buffering attributable to cytosolic indo-1 gives intrinsic cytosolic Ca2+ buffering parameters of KD = 0.96 +/- 0.18 microM and Bmax = 123 +/- 18 mumol/l cell H2O. The fast Ca2+ buffering measured in this manner agrees reasonably with the characteristics of known rapid Ca buffers (e.g., troponin C, calmodulin, and SR Ca-ATPase), but is only about half of the total Ca2+ buffering measured at equilibrium. Inclusion of slow Ca buffers such as the Ca/Mg sites on troponin C and myosin can account for the differences between fast Ca2+ buffering in phase with the Ca current measured in the present experiments and equilibrium Ca2+ buffering. The present data indicate that a rapid rise of [Ca2+]i from 0.1 to 1 microM during a contraction requires approximately 50 microM Ca2+ to be added to the cytosol. PMID:7819510

Exogenous Calcium Alleviates Photoinhibition of PSII by Improving the Xanthophyll Cycle in Peanut (Arachis Hypogaea) Leaves during Heat Stress under High Irradiance

PubMed Central

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

2013-01-01

Peanut is one of the calciphilous plants. Calcium (Ca) serves as a ubiquitous central hub in a large number of signaling pathways. The effect of exogenous calcium nitrate [Ca(NO3)2] (6 mM) on the dissipation of excess excitation energy in the photosystem II (PSII) antenna, especially on the level of D1 protein and the xanthophyll cycle in peanut plants under heat (40°C) and high irradiance (HI) (1 200 µmol m−2 s−1) stress were investigated. Compared with the control plants [cultivated in 0 mM Ca(NO3)2 medium], the maximal photochemical efficiency of PSII (Fv/Fm) in Ca2+-treated plants showed a slighter decrease after 5 h of stress, accompanied by higher non-photochemical quenching (NPQ), higher expression of antioxidative genes and less reactive oxygen species (ROS) accumulation. Meanwhile, higher content of D1 protein and higher ratio of (A+Z)/(V+A+Z) were also detected in Ca2+-treated plants under such stress. These results showed that Ca2+ could help protect the peanut photosynthetic system from severe photoinhibition under heat and HI stress by accelerating the repair of D1 protein and improving the de-epoxidation ratio of the xanthophyll cycle. Furthermore, EGTA (a chelant of Ca ion), LaCl3 (a blocker of Ca2+ channel in cytoplasmic membrane), and CPZ [a calmodulin (CaM) antagonist] were used to analyze the effects of Ca2+/CaM on the variation of (A+Z)/(V+A+Z) (%) and the expression of violaxanthin de-epoxidase (VDE). The results indicated that CaM, an important component of the Ca2+ signal transduction pathway, mediated the expression of the VDE gene in the presence of Ca to improve the xanthophyll cycle. PMID:23940721

Estradiol up-regulates L-type Ca2+ channels via membrane-bound estrogen receptor/phosphoinositide-3-kinase/Akt/cAMP response element-binding protein signaling pathway.

PubMed

Yang, Xiaoyan; Mao, Xiaofang; Xu, Gao; Xing, Shasha; Chattopadhyay, Ansuman; Jin, Si; Salama, Guy

2018-05-01

In long QT syndrome type 2, women are more prone than men to the lethal arrhythmia torsades de pointes. We previously reported that 17β-estradiol (E2) up-regulates L-type Ca 2+ channels and current (I Ca,L ) (∼30%) in rabbit ventricular myocytes by a classic genomic mechanism mediated by estrogen receptor-α (ERα). In long QT syndrome type 2 (I Kr blockade or bradycardia), the higher Ca 2+ influx via I Ca,L causes Ca 2+ overload, spontaneous sarcoplasmic reticulum Ca 2+ release, and reactivation of I Ca,L that triggers early afterdepolarizations and torsades de pointes. The purpose of this study was to investigate the molecular mechanisms whereby E2 up-regulates I Ca,L , which are poorly understood. H9C2 and rat myocytes were incubated with E2 ± ER antagonist, or inhibitors of downstream transcription factors, for 24 hours, followed by western blots of Cav1.2α1C and voltage-clamp measurements of I Ca,L . Incubation of H9C2 cells with E2 (10-100 nM) increased I Ca,L density and Cav1.2α1C expression, which were suppressed by the ER antagonist ICI182,780 (1 μM). Enhanced I Ca,L and Cav1.2α1C expression by E2 was suppressed by inhibitors of phosphoinositide-3-kinase (Pi3K) (30 μM LY294002; P <.05) and Akt (5 μM MK2206) but not of mitogen-activated protein kinase (5 μM U0126) or protein kinase A (1 μM KT5720). E2 incubation increased p-CREB via the Pi3K/Akt pathway, reached a peak in 20 minutes (3-fold), and leveled off to 1.5-fold 24 hours later. Furthermore, a CREB decoy oligonucleotide inhibited E2-induced Cav1.2α1C expression, whereas membrane-impermeable E2 (E2-bovine serum albumin) was equally effective at Cav1.2α1C up-regulation as E2. Estradiol up-regulates Cav1.2α1C and I Ca,L via plasma membrane ER and by activating Pi3K, Akt, and CREB signaling. The promoter regions of the CACNA1C gene (human-rabbit-rat) contain adjacent/overlapping binding sites for p-CREB and ERα, which suggests a synergistic regulation by these pathways. Copyright © 2018 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Identification and Levels of 2′-Carboxyarabinitol in Leaves 1

PubMed Central

Moore, Brandon d.; Sharkey, Thomas D.; Kobza, John; Seemann, Jeffrey R.

1992-01-01

2′-Carboxyarabinitol 1-phosphate (CA1P) is a naturally occurring inhibitor of ribulose-1,5 bisphosphate carboxylase/oxygenase activity. A chloroplast phosphatase has previously been identified that degrades CA1P in vitro to carboxyarabinitol (CA) plus phosphate, but CA has not yet been detected in plants. Here, we detail procedures to isolate and assay CA from leaves and utilize mass spectrometry to demonstrate for the first time that CA is present in plants. CA was present in leaves of all 13 species examined, including those of C3, C4, and Crassulacean acid metabolism photosynthetic subgroups. CA was present both in species with high levels of CA1P (e.g. Phaseolus vulgaris, Lycopersicon esculentum, Beta vulgaris) as well as in species with low levels of CA1P (e.g. Spinacea oleracea, Triticum aestivum). CA levels in the light were sometimes greater than those in the dark. Bean leaves had the most CA of any species tested, with levels in the light approaching 1 micromole per milligram of chlorophyll. In illuminated bean leaves, about 63% of the CA is located outside the chloroplast. CA is one of only a few branched chain sugar acids to be identified from plants. PMID:16669072

Differential routes of Ca2+ influx in Swiss 3T3 fibroblasts in response to receptor stimulation.

PubMed Central

Miyakawa, T; Kojima, M; Ui, M

1998-01-01

Ca2+ influx into cells in response to stimulation of various receptors was studied with Swiss 3T3 fibroblasts. The mechanisms involved were found to be so diverse that they were classified into four groups, Type I to IV. Type-I influx occurred, via pertussis toxin-susceptible G-proteins, immediately after internal Ca2+ mobilization by bradykinin, thrombin, endothelin, vasopressin or angiotensin II. Type-II influx induced by bombesin differed from Type I in its insusceptibility to pertussis toxin treatment. Ca2+ influx induced by prostaglandin E1, referred to as Type-III influx, was unique in that phospholipase C was apparently not activated without extracellular Ca2+, strongly suggesting that the Ca2+ influx preceded and was responsible for InsP3 generation and internal Ca2+ mobilization. More Ca2+ entered the cells more slowly via the Type-IV route opened by platelet-derived and other growth factors. These types of Ca2+ influx could be differentiated by their different susceptibilities to protein kinase C maximally activated by 1 h of exposure of cells to PMA, which inhibited phospholipase Cbeta coupled to receptors involved in Type-I and -II influx but did not inhibit growth-factor-receptor-coupled phospholipase Cgamma. Type-I and -II Ca2+ influxes, together with store-operated influx induced by thapsigargin, were not directly inhibited by exposure of cells to PMA, but Type-III and -IV influxes were completely inhibited. In addition, stimulation of receptors involved in Type-I and -IV Ca2+ influx, but not Type-II and -III influx, led to phospholipase A2 activation in the presence of extracellular Ca2+. Inhibition of Type-I and -IV Ca2+ influxes by their respective inhibitors, diltiazem and nifedipine, resulted in abolition of phospholipase A2 activation induced by the respective receptor agonists, in agreement with the notion that Ca2+ influx via these routes is responsible for receptor-mediated phospholipase A2 activation. PMID:9405282

Differential routes of Ca2+ influx in Swiss 3T3 fibroblasts in response to receptor stimulation.

PubMed

Miyakawa, T; Kojima, M; Ui, M

1998-01-01

Ca2+ influx into cells in response to stimulation of various receptors was studied with Swiss 3T3 fibroblasts. The mechanisms involved were found to be so diverse that they were classified into four groups, Type I to IV. Type-I influx occurred, via pertussis toxin-susceptible G-proteins, immediately after internal Ca2+ mobilization by bradykinin, thrombin, endothelin, vasopressin or angiotensin II. Type-II influx induced by bombesin differed from Type I in its insusceptibility to pertussis toxin treatment. Ca2+ influx induced by prostaglandin E1, referred to as Type-III influx, was unique in that phospholipase C was apparently not activated without extracellular Ca2+, strongly suggesting that the Ca2+ influx preceded and was responsible for InsP3 generation and internal Ca2+ mobilization. More Ca2+ entered the cells more slowly via the Type-IV route opened by platelet-derived and other growth factors. These types of Ca2+ influx could be differentiated by their different susceptibilities to protein kinase C maximally activated by 1 h of exposure of cells to PMA, which inhibited phospholipase Cbeta coupled to receptors involved in Type-I and -II influx but did not inhibit growth-factor-receptor-coupled phospholipase Cgamma. Type-I and -II Ca2+ influxes, together with store-operated influx induced by thapsigargin, were not directly inhibited by exposure of cells to PMA, but Type-III and -IV influxes were completely inhibited. In addition, stimulation of receptors involved in Type-I and -IV Ca2+ influx, but not Type-II and -III influx, led to phospholipase A2 activation in the presence of extracellular Ca2+. Inhibition of Type-I and -IV Ca2+ influxes by their respective inhibitors, diltiazem and nifedipine, resulted in abolition of phospholipase A2 activation induced by the respective receptor agonists, in agreement with the notion that Ca2+ influx via these routes is responsible for receptor-mediated phospholipase A2 activation.

Investigation of the Effect of Some Optically Active Imine Compounds on the Enzyme Activities of hCA-I and hCA-II under In Vitro Conditions: An Experimental and Theoretical Study.

PubMed

Tektas, Osman; Akkemik, Ebru; Baykara, Haci

2016-06-01

Inhibitors of carbonic anhydrase (hCA; EC 4.2.1.1) are used as medicines for many diseases. Therefore, they are very important. In this study, a known series of Schiff bases were synthesized and their effects on the activities of hCA-I and hCA-II, which are cytosolic isoenzymes of carbonic anhydrase, were investigated under in vitro conditions. The synthesized compounds (H1, H2, H3, and H4) were found to cause inhibition on enzyme activities of hCA-1 and hCA-II. IC50 values of H1, H2, H3, and H4 compounds were 140, 88, 201, and 271 μM for hCA-I enzyme activity and 134, 251, 79, and 604 μM for hCA-II enzyme activity, respectively. The synthesized Schiff bases were characterized by several methods, including (1) H NMR, FT-IR, elemental analysis, and polarimetric measurements. Correlation coefficient square values (R(2) ) of comparison of the theoretical and experimental (1) H NMR shifts for H1, H2, H3, and H4 compounds were found as 0.9781, 0.9814, 0.9758, and 0.8635, respectively. © 2016 Wiley Periodicals, Inc.

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

Blanpied, G.D.

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

Hydrogen Sulfide Regulates Ca2+ Homeostasis Mediated by Concomitantly Produced Nitric Oxide via a Novel Synergistic Pathway in Exocrine Pancreas

PubMed Central

Moustafa, Amira

2014-01-01

Abstract Aim: The present study was designed to explore the effects of hydrogen sulfide (H2S) on Ca2+ homeostasis in rat pancreatic acini. Results: Sodium hydrosulfide (NaHS; an H2S donor) induced a biphasic increase in the intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner. The NaHS-induced [Ca2+]i elevation persisted with an EC50 of 73.3 μM in the absence of extracellular Ca2+ but was abolished by thapsigargin, indicating that both Ca2+ entry and Ca2+ release contributed to the increase. The [Ca2+]i increase was markedly inhibited in the presence of NG-monomethyl L-arginine or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), and diaminofluorescein-2/diaminofluorescein-2 triazole (DAF-2/DAF-2T) fluorometry demonstrated that nitric oxide (NO) was also produced by H2S in a dose-dependent manner with an EC50 of 64.8 μM, indicating that NO was involved in the H2S effect. The H2S-induced [Ca2+]i increase was inhibited by pretreatment with U73122, xestospongin C, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, KT5823, and GP2A, indicating that phospholipase C (PLC), the inositol 1,4,5-trisphosphate (IP3) receptor, soluble guanylate cyclase (sGC), protein kinase G (PKG), and Gq-protein play roles as intermediate components in the H2S-triggered intracellular signaling. Innovation: To our knowledge, our study is the first one highlighting the effect of H2S on intracellular Ca2+ dynamics in pancreatic acinar cells. Moreover, a novel cascade was presumed to function via the synergistic interaction between H2S and NO. Conclusion: We conclude that H2S affects [Ca2+]i homeostasis that is mediated by H2S-evoked NO production via an endothelial nitric oxide synthase (eNOS)-NO-sGC-cyclic guanosine monophosphate-PKG-Gq-protein-PLC-IP3 pathway to induce Ca2+ release, and this pathway is identical to the one we recently proposed for a sole effect of NO and the two gaseous molecules synergistically function to regulate Ca2+ homeostasis. Antioxid. Redox Signal. 20, 747–758. PMID:24138560

Expression and subcellular localization of the ryanodine receptor in rat pancreatic acinar cells.

PubMed Central

Leite, M F; Dranoff, J A; Gao, L; Nathanson, M H

1999-01-01

The ryanodine receptor (RyR) is the principal Ca2+-release channel in excitable cells, whereas the inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) is primarily responsible for Ca2+ release in non-excitable cells, including epithelia. RyR also is expressed in a number of non-excitable cell types, but is thought to serve as an auxiliary or alternative Ca2+-release pathway in those cells. Here we use reverse transcription PCR to show that a polarized epithelium, the pancreatic acinar cell, expresses the type 2, but not the type 1 or 3, isoform of RyR. We furthermore use immunochemistry to demonstrate that the type 2 RyR is distributed throughout the basolateral and, to a lesser extent, the apical region of the acinar cell, but is excluded from the trigger zone, where cytosolic Ca2+ signals originate in this cell type. Since propagation of Ca2+ waves in acinar cells is sensitive to ryanodine, caffeine and Ca2+, these findings suggest that Ca2+ waves in this cell type result from the co-ordinated release of Ca2+, first from InsP3Rs in the trigger zone, then from RyRs elsewhere in the cell. RyR may play a fundamental role in Ca2+ signalling in polarized epithelia, including for Ca2+ signals initiated by InsP3. PMID:9882629

Voltage inactivation of Ca2+ entry and secretion associated with N- and P/Q-type but not L-type Ca2+ channels of bovine chromaffin cells

PubMed Central

Villarroya, Mercedes; Olivares, Román; Ruíz, Ana; Cano-Abad, María F; de Pascual, Ricardo; Lomax, Richard B; López, Manuela G; Mayorgas, Inés; Gandía, Luis; García, Antonio G

1999-01-01

In this study we pose the question of why the bovine adrenal medullary chromaffin cell needs various subtypes (L, N, P, Q) of the neuronal high-voltage activated Ca2+ channels to control a given physiological function, i.e. the exocytotic release of catecholamines. One plausible hypothesis is that Ca2+ channel subtypes undergo different patterns of inactivation during cell depolarization. The net Ca2+ uptake (measured using 45Ca2+) into hyperpolarized cells (bathed in a nominally Ca2+-free solution containing 1·2 mM K+) after application of a Ca2+ pulse (5 s exposure to 100 mM K+ and 2 mM Ca2+), amounted to 0·65 ± 0·02 fmol cell−1; in depolarized cells (bathed in nominally Ca2+-free solution containing 100 mM K+) the net Ca2+ uptake was 0·16 ± 0·01 fmol cell−1. This was paralleled by a dramatic reduction of the increase in the cytosolic Ca2+ concentration, [Ca2+]i, caused by Ca2+ pulses applied to fura-2-loaded single cells, from 1181 ± 104 nM in hyperpolarized cells to 115 ± 9 nM in depolarized cells. A similar decrease was observed when studying catecholamine release. Secretion was decreased when K+ concentration was increased from 1·2 to 100 mM; the Ca2+ pulse caused, when comparing the extreme conditions, the secretion of 807 ± 35 nA of catecholamines in hyperpolarized cells and 220 ± 19 nA in depolarized cells. The inactivation by depolarization of Ca2+ entry and secretion occluded the blocking effects of combined ω-conotoxin GVIA (1 μM) and ω-agatoxin IVA (2 μM), thus suggesting that depolarization caused a selective inactivation of the N- and P/Q-type Ca2+ channels. This was strengthened by two additional findings: (i) nifedipine (3 μM), an L-type Ca2+ channel blocker, suppressed the fraction of Ca2+ entry (24 %) and secretion (27 %) left unblocked by depolarization; (ii) FPL64176 (3 μM), an L-type Ca2+ channel ‘activator’, dramatically enhanced the entry of Ca2+ and the secretory response in depolarized cells. In voltage-clamped cells, switching the holding potential from -80 to -40 mV promoted the loss of 80 % of the whole-cell inward Ca2+ channel current carried by 10 mM Ba2+ (IBa). The residual current was blocked by 80 % upon addition of 3 μM nifedipine and dramatically enhanced by 3 μM FPL64176. Thus, it seems that the N- and P/Q-subtypes of calcium channels are more prone to inactivation at depolarizing voltages than the L-subtype. We propose that this different inactivation might occur physiologically during different patterns of action potential firing, triggered by endogenously released acetylcholine under various stressful conditions. PMID:10087342

High-density lipoproteins induce a rapid and transient release of Ca2+ in cultured fibroblasts.

PubMed Central

Pörn, M I; Akerman, K E; Slotte, J P

1991-01-01

Several different cell types showed increased rates of proliferation and cholesterol mobilization in response to treatment with high-density lipoprotein (HDL). This would suggest that one main function of HDL is the activation of signal pathways in cells. In the current study we have used the fluorescent indicator fura-2 to monitor the level of cytosolic Ca2+ ([Ca2+]i) in human skin fibroblasts. Exposure of subconfluent as well as confluent fibroblasts to HDL3 (20-60 micrograms/ml) resulted in a rapid and transient increase in [Ca2+]i. Sequential additions of HDL3 resulted in diminished rises in [Ca2+]i. The transient rise in [Ca2+]i was observed with HDL prepared from plasma either by conventional ultracentrifugation or by precipitation with dextran sulphate. Chelation of the extracellular Ca2+ with EGTA prior to the addition of HDL3 did not prevent the HDL3-induced rise in [Ca2+]i, suggesting that the mobilized Ca2+ was derived mainly from intracellular stores. Covalent modification of the apoproteins of HDL3 with dimethyl suberimidate or tetranitromethane did not inhibit the HDL3-induced rise in [Ca2+]i. This indicates that the binding of HDL3 to cell surface receptors may not be necessary for the mobilization of intracellular Ca2+. Moreover, the Ca(2+)-releasing effect of HDL3 was not inhibited by the presence of albumin (1%, w/v) in the extracellular medium, suggesting that non-esterified fatty acids were not the cause of the increased [Ca2+]i. The exposure of fibroblasts to lysophosphatidic acid, a potent mitogen and Ca(2+)-releasing agent, before addition of HDL3 completely inhibited the HDL3-induced rise in [Ca2+]i. Furthermore, phorbol 12-myristate 13-acetate blocked the HDL3-induced rise in [Ca2+]i. The results of this study imply that exposure of cells to HDL generates an intracellular signal which is induced by a component of the lipid fraction. PMID:1930148

Cytoplasmic Calcium Increases in Response to Changes in the Gravity Vector in Hypocotyls and Petioles of Arabidopsis Seedlings1

PubMed Central

Toyota, Masatsugu; Furuichi, Takuya; Tatsumi, Hitoshi; Sokabe, Masahiro

2008-01-01

Plants respond to a large variety of environmental signals, including changes in the gravity vector (gravistimulation). In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation is known to increase the cytoplasmic free calcium concentration ([Ca2+]c). However, organs responsible for the [Ca2+]c increase and the underlying cellular/molecular mechanisms remain to be solved. In this study, using Arabidopsis seedlings expressing apoaequorin, a Ca2+-sensitive luminescent protein in combination with an ultrasensitive photon counting camera, we clarified the organs where [Ca2+]c increases in response to gravistimulation and characterized the physiological and pharmacological properties of the [Ca2+]c increase. When the seedlings were gravistimulated by turning 180°, they showed a transient biphasic [Ca2+]c increase in their hypocotyls and petioles. The second peak of the [Ca2+]c increase depended on the angle but not the speed of rotation, whereas the initial peak showed diametrically opposite characters. This suggests that the second [Ca2+]c increase is specific for changes in the gravity vector. The potential mechanosensitive Ca2+-permeable channel (MSCC) inhibitors Gd3+ and La3+, the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), and the endomembrane Ca2+-permeable channel inhibitor ruthenium red suppressed the second [Ca2+]c increase, suggesting that it arises from Ca2+ influx via putative MSCCs in the plasma membrane and Ca2+ release from intracellular Ca2+ stores. Moreover, the second [Ca2+]c increase was attenuated by actin-disrupting drugs cytochalasin B and latrunculin B but not by microtubule-disrupting drugs oryzalin and nocodazole, implying that actin filaments are partially involved in the hypothetical activation of Ca2+-permeable channels. These results suggest that the second [Ca2+]c increase via MSCCs is a gravity response in the hypocotyl and petiole of Arabidopsis seedlings. PMID:18055589

Synthesis and photoluminescence control of Ca{sub 10.5–1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+} phosphors by aliovalent cation substitution

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

Fan, Yanting; Tang, Miao; Qiu, Zhongxian

A range of Ca{sub 10.5-1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+}phosphors were synthesized by high temperature solid state method. Subsequently we studied the crystal structures and luminescent properties through X-ray diffraction, photoluminescence and photoluminescence excitation, diffuse reflection spectra, Raman spectra and decay curves systematically. Based on the special crystal structure ofβ-Ca{sub 3}(PO{sub 4}){sub 2}:Eu{sup 2+}, its emission undergoes a variation from violet–blue to cyan through introducing La{sup 3+}. The substitution of La{sup 3+} for Ca{sup 2+} could form some cation vacancies in Ca(4) sites according to the scheme 3Ca{sup 2+}= 2La{sup 3+}+ □ due to the different ion valence, which compels Eu{supmore » 2+} to migrate from Ca(4) site to other sites. Additionally, the formation of the cation vacancies can further reduce the thermal stability of phosphors. - Highlights: • Realizing photoluminescence control of Eu{sup 2+} by introducing relatively larger La{sup 3+} ion to replace the Ca{sup 2+} in β-Ca{sub 3}(PO{sub 4}){sub 2}:Eu{sup 2+} phosphor. • The mechanism of spectral control is proposed to be due to emptying of Ca{sup 2+} and migration of Eu{sup 2+}. • The thermal stability reduction is related to the formation of vacancies.« less

The development of binary Mg-Ca alloys for use as biodegradable materials within bone.

PubMed

Li, Zijian; Gu, Xunan; Lou, Siquan; Zheng, Yufeng

2008-04-01

Binary Mg-Ca alloys with various Ca contents were fabricated under different working conditions. X-ray diffraction (XRD) analysis and optical microscopy observations showed that Mg-xCa (x=1-3 wt%) alloys were composed of two phases, alpha (Mg) and Mg2Ca. The results of tensile tests and in vitro corrosion tests indicated that the mechanical properties could be adjusted by controlling the Ca content and processing treatment. The yield strength (YS), ultimate tensile strength (UTS) and elongation decreased with increasing Ca content. The UTS and elongation of as-cast Mg-1Ca alloy (71.38+/-3.01 MPa and 1.87+/-0.14%) were largely improved after hot rolling (166.7+/-3.01 MPa and 3+/-0.78%) and hot extrusion (239.63+/-7.21 MPa and 10.63+/-0.64%). The in vitro corrosion test in simulated body fluid (SBF) indicated that the microstructure and working history of Mg-xCa alloys strongly affected their corrosion behaviors. An increasing content of Mg2Ca phase led to a higher corrosion rate whereas hot rolling and hot extrusion could reduce it. The cytotoxicity evaluation using L-929 cells revealed that Mg-1Ca alloy did not induce toxicity to cells, and the viability of cells for Mg-1Ca alloy extraction medium was better than that of control. Moreover, Mg-1Ca alloy pins, with commercial pure Ti pins as control, were implanted into the left and right rabbit femoral shafts, respectively, and observed for 1, 2 and 3 months. High activity of osteoblast and osteocytes were observed around the Mg-1Ca alloy pins as shown by hematoxylin and eosin stained tissue sections. Radiographic examination revealed that the Mg-1Ca alloy pins gradually degraded in vivo within 90 days and the newly formed bone was clearly seen at month 3. Both the in vitro and in vivo corrosion suggested that a mixture of Mg(OH)2 and hydroxyapatite formed on the surface of Mg-1Ca alloy with the extension of immersion/implantation time. In addition, no significant difference (p>0.05) of serum magnesium was detected at different degradation stages. All these results revealed that Mg-1Ca alloy had the acceptable biocompatibility as a new kind of biodegradable implant material. Based on the above results, a solid alloy/liquid solution interface model was also proposed to interpret the biocorrosion process and the associated hydroxyapatite mineralization.

Selection of intracellular calcium patterns in a model with clustered Ca2+ release channels

NASA Astrophysics Data System (ADS)

Shuai, J. W.; Jung, P.

2003-03-01

A two-dimensional model is proposed for intracellular Ca2+ waves, which incorporates both the discrete nature of Ca2+ release sites in the endoplasmic reticulum membrane and the stochastic dynamics of the clustered inositol 1,4,5-triphosphate (IP3) receptors. Depending on the Ca2+ diffusion coefficient and concentration of IP3, various spontaneous Ca2+ patterns, such as calcium puffs, local waves, abortive waves, global oscillation, and tide waves, can be observed. We further investigate the speed of the global waves as a function of the IP3 concentration and the Ca2+ diffusion coefficient and under what conditions the spatially averaged Ca2+ response can be described by a simple set of ordinary differential equations.

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

PubMed

Lee, Jun-Yeop; Yun, Jong-Il

2013-07-21

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

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.

Intracellular Ca2+ regulation by the leech giant glial cell.

PubMed

Nett, W; Deitmer, J W

1998-02-15

1. We have measured the intracellular Ca2+ concentration, [Ca2+]i, and the intracellular Na+ concentration, [Na+]i, with the fluorescent dyes fura-2 (for Ca2+) and SBFI (for Na+) in situ in giant glial cells of the central nervous system of the leech Hirudo medicinalis. 2. The basal [Ca2+]i was 79 +/- 35 nM (n = 27) in cells voltage clamped at -70 to -80 mV, and 75 +/- 29 nM (mean +/- S.D., n = 82) in unclamped cells at a mean membrane potential of -67 +/- 6 mV. 3. Removal of external Na+ evoked a small reversible [Ca2+]i increase of 29 +/- 21 nM (n = 27) in cells voltage clamped at -70 to -80 mV, and of 35 +/- 18 nM (n = 37) in unclamped cells. This [Ca2+]i increase, and the time constant of the subsequent [Ca2+]i recovery after Na+ re-addition, did not change significantly with the holding potential between -110 and -60 mV. 4. The basal [Na+]i was 5.6 +/- 1.3 mM (n = 18). Increasing [Na+]i by inhibiting the Na+-K+ pump with 100 microM ouabain had no effect on the [Ca2+]i rise upon removal of external Na+. 5. The time course of recovery from a [Ca2+]i load mediated by voltage-dependent Ca2+ influx during depolarization in high K+ was unaffected by the removal of external Na+. 6. Cyclopiazonic acid (10 muM), an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a transient increase in [Ca2+]i of 28 +/- 11 nM (n = 5), and significantly slowed the recovery from imposed [Ca2+]i loads. 7. Iontophoretic injection of orthovanadate, an inhibitor of P-type ATPases including the plasma membrane Ca2+-ATPase, caused a persistent increase in the basal [Ca2+]i of 163 +/- 101 nM (n = 5) in standard saline, and of 427 +/- 338 nM in Na+-free saline (n = 5). Vanadate injection significantly slowed the recovery from [Ca2+]i loads. Removal of external Na+ during vanadate injection induced an additional, reversible [Ca2+]i increase of 254 +/- 64 nM (n = 3). 8. The results suggest that the low basal [Ca2+]i in these glial cells is predominantly maintained by a Ca2+-ATPase in the plasma membrane. This ATPase is also the main Ca2+ extruder after an intracellular Ca2+ load, while intracellular stores appear to contribute little to this recovery. A Na+-Ca2+ exchanger seems to play a minor role in the maintenance of basal [Ca2+]i in these cells, but becomes prominent when the plasma membrane Ca2+-ATPase is blocked.

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

PubMed

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

2016-04-01

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

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

PubMed

Schlegel, P; Gutzwiller, A

2017-10-01

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

The intermediate-conductance Ca2+ -activated K+ channel (KCa3.1) in vascular disease.

PubMed

Tharp, D L; Bowles, D K

2009-01-01

The intermediate-conductance Ca(2+)-activated K(+) channel (K(Ca)3.1) was first described by Gardos in erythrocytes and later confirmed to play a significant role in T-cell activation and the immune response. More recently, K(Ca)3.1 has been characterized in numerous cell types which contribute to the development of vascular disease, such as T-cells, B-cells, endothelial cells, fibroblasts, macrophages, and dedifferentiated smooth muscle cells (SMCs). Physiologically, K(Ca)3.1 has been demonstrated to play a role in acetylcholine and endothelium-derived hyperpolarizing factor (EDHF) induced hyperpolarization, and thus control of blood pressure. Pathophysiologically, K(Ca)3.1 contributes to proliferation of T-cells, B-cells, fibroblasts, and vascular SMCs, as well as the migration of SMCs and macrophages and platelet coagulation. Recent studies have indicated that blockade of K(Ca)3.1, by specific blockers such as TRAM-34, could prove to be an effective treatment for vascular disease by inhibiting T-cell activation as well as preventing proliferation and migration of macrophages, endothelial cells, and SMCs. This vasculoprotective potential of K(Ca)3.1 inhibition has been confirmed in both rodent and swine models of restenosis. In this review, we will discuss the physiological and pathophysiological role of K(Ca)3.1 in cells closely associated with vascular biology, and the effect of K(Ca)3.1 blockers on the initiation and progression of vascular disease.

Silencing of the Cav3.2 T-type calcium channel gene in sensory neurons demonstrates its major role in nociception.

PubMed

Bourinet, Emmanuel; Alloui, Abdelkrim; Monteil, Arnaud; Barrère, Christian; Couette, Brigitte; Poirot, Olivier; Pages, Anne; McRory, John; Snutch, Terrance P; Eschalier, Alain; Nargeot, Joël

2005-01-26

Analgesic therapies are still limited and sometimes poorly effective, therefore finding new targets for the development of innovative drugs is urgently needed. In order to validate the potential utility of blocking T-type calcium channels to reduce nociception, we explored the effects of intrathecally administered oligodeoxynucleotide antisenses, specific to the recently identified T-type calcium channel family (CaV3.1, CaV3.2, and CaV3.3), on reactions to noxious stimuli in healthy and mononeuropathic rats. Our results demonstrate that the antisense targeting CaV3.2 induced a knockdown of the CaV3.2 mRNA and protein expression as well as a large reduction of 'CaV3.2-like' T-type currents in nociceptive dorsal root ganglion neurons. Concomitantly, the antisense treatment resulted in major antinociceptive, anti-hyperalgesic, and anti-allodynic effects, suggesting that CaV3.2 plays a major pronociceptive role in acute and chronic pain states. Taken together, the results provide direct evidence linking CaV3.2 T-type channels to pain perception and suggest that CaV3.2 may offer a specific molecular target for the treatment of pain.

Turmeric extract inhibits apoptosis of hippocampal neurons of trimethyltin-exposed rats.

PubMed

Yuliani, S; Widyarini, S; Mustofa; Partadiredja, G

2017-01-01

The aim of the present study was to reveal the possible antiapoptotic effect of turmeric (Curcuma longa Linn.) on the hippocampal neurons of rats exposed to trimethyltin (TMT). Oxidative damage in the hippocampus can induce the apoptosis of neurons associated with the pathogenesis of dementiaMETHODS. The ethanolic turmeric extract and a citicoline (as positive control) solution were administered to the TMT-exposed rats for 28 days. The body weights of rats were recorded once a week. The hippocampal weights and imumunohistochemical expression of caspase 3 proteins in the CA1 and CA2-CA3 regions of the hippocampi were examined at the end of the experiment. Immunohistochemical analysis showed that the injection of TMT increased the expression of caspase 3 in the CA1 and CA2-CA3 regions of hippocampus. TMT also decreased the body and hippocampal weights. Furthermore, the administration of 200 mg/kg bw dose of turmeric extract decreased the caspase 3 expression in the CA2-CA3 pyramidal neurons but not in the CA1 neurons. It also prevented the decrease of the body and hippocampal weights. We suggest that the 200 mg/kg bw dose of turmeric extract may exert antiapoptotic effect on the hippocampal neurons of the TMT-exposed rats (Tab. 1, Fig. 3, Ref. 49).

Synaptically activated Ca2+ waves in layer 2/3 and layer 5 rat neocortical pyramidal neurons

PubMed Central

Larkum, Matthew E; Watanabe, Shigeo; Nakamura, Takeshi; Lasser-Ross, Nechama; Ross, William N

2003-01-01

Calcium waves in layer 2/3 and layer 5 neocortical somatosensory pyramidal neurons were examined in slices from 2- to 8-week-old rats. Repetitive synaptic stimulation evoked a delayed, all-or-none [Ca2+]i increase primarily on the main dendritic shaft. This component was blocked by 1 mm (R,S)-α-methyl-4-carboxyphenylglycine (MCPG), 10 μm ryanodine, 1 mg ml−1 internal heparin, and was not blocked by 400 μm internal Ruthenium Red, indicating that it was due to Ca2+ release from internal stores by inositol 1,4,5-trisphosphate (IP3) mobilized via activation of metabotropic glutamate receptors. Calcium waves were initiated on the apical shaft at sites between the soma to around the main branch point, mostly at insertion points of oblique dendrites, and spread in both directions along the shaft. In the proximal dendrites the peak amplitude of the resulting [Ca2+]i change was much larger than that evoked by a train of Na+ spikes. In distal dendrites the peak amplitude was comparable to the [Ca2+]i change due to a Ca2+ spike. IP3-mediated Ca2+ release also was observed in the presence of the metabotropic agonists t-ACPD and carbachol when backpropagating spikes were generated. Ca2+ entry through NMDA receptors was observed primarily on the oblique dendrites. The main differences between waves in neocortical neurons and in previously described hippocampal pyramidal neurons were, (a) Ca2+ waves in L5 neurons could be evoked further out along the main shaft, (b) Ca2+ waves extended slightly further out into the oblique dendrites and (c) higher concentrations of bath-applied t-ACPD and carbachol were required to generate Ca2+ release events by backpropagating action potentials. PMID:12692172

Effects of milk proteins on sperm binding to the zona pellucida and intracellular Ca(2+) concentration in stallion sperm.

PubMed

Coutinho da Silva, Marco A; Seidel, George E; Squires, Edward L; Graham, James K; Carnevale, Elaine M

2014-11-10

Objectives were to determine the effects of extracellular Ca(2+) and milk proteins on intracellular Ca(2+) concentrations in stallion sperm; and to determine the effects of single caseins on sperm binding to the zona pellucida (ZP). In Experiment I, sperm were incubated in media containing 2 or 4mM Ca(2+) and intracellular Ca(2+) concentration was determined after ionomycin treatment and long-term incubation (3h). Extracellular Ca(2+) concentrations (2 compared with 4mM) did not affect baseline intracellular Ca(2+) concentration of sperm. However, incubating sperm in a medium containing 4 compared with 2mM Ca(2+) resulted in greater (P<0.05) influx of Ca(2+) into sperm. In Experiment II, sperm incubated in media containing 1mg/mL of native phosphocaseinate (NP) or sodium caseinate (SC) showed similar baseline intracellular Ca(2+) and influx of Ca(2+) than control (TALP). In Experiment III, sperm-ZP binding assays were performed in TALP medium containing: no additions (TALP); 1mg/mL SC; 1 or 3mg/mL of α-casein; 1 or 3mg/mL of β-casein; and 1 or 3mg/mL of κ-casein. The number of stallion sperm bound to bovine ZP was greatest (P<0.05) when SC was used. Co-incubation in media containing single caseins (α-, β- or κ-casein) resulted in similar results to TALP; however, a dose effect (P<0.05) was observed for β- and κ-caseins. In conclusion, extracellular Ca(2+) concentration and milk proteins did not affect baseline intracellular calcium in stallion sperm. It appears that β- and κ-caseins may be responsible for enhancing sperm binding to ZP, but the mechanism remains unknown. Copyright © 2014 Elsevier B.V. All rights reserved.

Regulation of AMP-activated protein kinase by LKB1 and CaMKK in adipocytes.

PubMed

Gormand, Amélie; Henriksson, Emma; Ström, Kristoffer; Jensen, Thomas Elbenhardt; Sakamoto, Kei; Göransson, Olga

2011-05-01

AMP-activated protein kinase (AMPK) is a serine/threonine kinase that regulates cellular and whole body energy homeostasis. In adipose tissue, activation of AMPK has been demonstrated in response to a variety of extracellular stimuli. However, the upstream kinase that activates AMPK in adipocytes remains elusive. Previous studies have identified LKB1 as a major AMPK kinase in muscle, liver, and other tissues. In certain cell types, Ca(2+) /calmodulin-dependent protein kinase kinase β (CaMKKβ) has been shown to activate AMPK in response to increases of intracellular Ca(2+) levels. Our aim was to investigate if LKB1 and/or CaMKK function as AMPK kinases in adipocytes. We used adipose tissue and isolated adipocytes from mice in which the expression of LKB1 was reduced to 10-20% of that of wild-type (LKB1 hypomorphic mice). We show that adipocytes from LKB1 hypomorphic mice display a 40% decrease in basal AMPK activity and a decrease of AMPK activity in the presence of the AMPK activator phenformin. We also demonstrate that stimulation of 3T3L1 adipocytes with intracellular [Ca(2+) ]-raising agents results in an activation of the AMPK pathway. The inhibition of CaMKK isoforms, particularly CaMKKβ, by the inhibitor STO-609 or by siRNAs, blocked Ca(2+) -, but not phenformin-, AICAR-, or forskolin-induced activation of AMPK, indicating that CaMKK activated AMPK in response to Ca(2+) . Collectively, we show that LKB1 is required to maintain normal AMPK-signaling in non-stimulated adipocytes and in the presence of phenformin. In addition, we demonstrate the existence of a Ca(2+) /CaMKK signaling pathway that can also regulate the activity of AMPK in adipocytes. Copyright © 2011 Wiley-Liss, Inc.

SiO2 and CaF2 Behavior During Shielded Metal Arc Welding and Their Effect on Slag Detachability of the CaO-CaF2-SiO2 Type ENiCrFe-7-Covered Electrode

NASA Astrophysics Data System (ADS)

Wang, Huang; Qin, Renyao; He, Guo

2016-09-01

The metallurgical behavior during shielded metal arc welding (SMAW) and the slag detachability of the CaO-CaF2-SiO2 type ENiCrFe-7-covered electrodes was investigated. The results indicated that the slag detachability could be improved as the SiO2 in the flux coatings decreased. When the SiO2 in the flux coating was 10.9 pct, about 28.3 pct CaF2 resulted in the best slag detachability. The CaF2 and SiO2 in the flux coating interacted during SMAW to form gaseous SiF4 to be evacuated. In the reactions, one SiO2 consumed two CaF2, leading to the reduction of the ratio of CaF2/SiO2. After comparing the slag compositions, the best slag detachability was obtained at CaO:CaF2:SiO2 = 1.7:1.8:1, but the worst slag detachability appeared at CaO:CaF2:SiO2 = 1.3:0.9:1. The XRD analysis revealed that the oxides and fluorides in the slags preferred to gather together to form cuspidine and other complex phases. If the CaF2 was dominant in the slags, they intended to form homogenous porous microstructures that were relatively strong and would most likely detach from the weld metal in blocks, exhibiting good slag detachability. If the cuspidine phase was dominant, the slags exhibited a `rock strata'-like microstructure in the intergranular area. Such microstructure was very fragile and could be broken into fine powders that were easily embedded in the weld ripples, leading to slag adhesions. This work provides the researcher with a wealth of information and data, which will also be beneficial to the welding material producers and users.

Temperature-dependence of L-type Ca(2+) current in ventricular cardiomyocytes of the Alaska blackfish (Dallia pectoralis).

PubMed

Kubly, Kerry L; Stecyk, Jonathan A W

2015-12-01

To lend insight into the overwintering strategy of the Alaska blackfish (Dallia pectoralis), we acclimated fish to 15 or 5 °C and then utilized whole-cell patch clamp to characterize the effects of thermal acclimation and acute temperature change on the density and kinetics of ventricular L-type Ca(2+) current (I Ca). Peak I Ca density at 5 °C (-1.1 ± 0.1 pA pF(-1)) was 1/8th that at 15 °C (-8.8 ± 0.6 pA pF(-1)). However, alterations of the Ca(2+)- and voltage-dependent inactivation properties of L-type Ca(2+) channels partially compensated against the decrease. The time constant tau (τ) for the kinetics of inactivation of I Ca was ~4.5 times greater at 5 °C than at 15 °C, and the voltage for half-maximal inactivation was shifted from -23.3 ± 1.0 mV at 15 °C to -19.8 ± 1.2 mV at 5 °C. These modifications increase the open probability of the channel and culminate in an approximate doubling of the L-type Ca(2+) window current, which contributes to approximately 15% of the maximal Ca(2+) conductance at 5 °C. Consequently, the charge density of I Ca (Q Ca) and the total Ca(2+) transferred through the L-type Ca(2+) channels (Δ[Ca(2+)]) were not as severely reduced at 5 °C as compared to peak I Ca density. In combination, the results suggest that while the Alaska blackfish substantially down-regulates I Ca with acclimation to low temperature, there is sufficient compensation in the kinetics of the L-type Ca(2+) channel to support the level of cardiac performance required for the fish to remain active throughout the winter.

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

Magnolol and honokiol regulate the calcium-activated potassium channels signaling pathway in Enterotoxigenic Escherichia coli-induced diarrhea mice.

PubMed

Deng, Yanli; Han, Xuefeng; Tang, Shaoxun; Xiao, Wenjun; Tan, Zhiliang; Zhou, Chuanshe; Wang, Min; Kang, Jinghe

2015-05-15

To explore the regulatory mechanisms of magnolol and honokiol on calcium-activated potassium channels signaling pathway in Enterotoxigenic Escherichia coli (ETEC)-induced diarrhea mice, the concentrations of serum chloride ion (Cl(-)), sodium ion (Na(+)), potassium ion (K(+)) and calcium ion (Ca(2+)) were measured. Additionally, the mRNA expressions of calmodulin 1 (CaM), calcium/calmodulin-dependent protein kinase II alpha subunit (CaMKIIα) and beta subunit (CaMKIIβ), ryanodine receptor 1, inositol 1,4,5-trisphosphate receptors (IP3 receptors), protein kinases C (PKC), potassium intermediate/small conductance calcium-activated channels (SK) and potassium large conductance calcium-activated channels(BK)were determined. A diarrhea mouse model was established using ETEC suspensions (3.29×10(9)CFU/ml) at a dosage of 0.02ml/g live body weight (BW). Magnolol or honokiol was intragastrically administered at dosages of 100 (M100 or H100), 300 (M300 or H300) and 500 (M500 or H500) mg/kg BW according to a 3×3 factorial arrangement. Magnolol and honokiol increased the Cl(-) and K(+) concentrations, further, upregulated the CaM, BKα1 and BKβ3 mRNA levels but downregulated the IP3 receptors 1, PKC, SK1, SK2, SK3, SK4 and BKβ4 mRNA expressions. Magnolol and honokiol did not alter the CaMKIIα, CaMKIIβ, ryanodine receptor 1, IP3 receptor 2, IP3 receptor 3, BKβ1 and BKβ2 mRNA expressions. These results clarify that magnolol and honokiol, acting through Ca(2+) channel blockade, inhibit the activation of IP3 receptor 1 to regulate the IP3-Ca(2+) store release, activate CaM to inhibit SK channels, and effectively suppress PKC kinases to promote BKα1 and BKβ3 channels opening and BKβ4 channel closing, which modulates the intestinal ion secretion. Copyright © 2015 Elsevier B.V. All rights reserved.

The effect of oleuropein from olive leaf (Olea europaea) extract on Ca²⁺ homeostasis, cytotoxicity, cell cycle distribution and ROS signaling in HepG2 human hepatoma cells.

PubMed

Cheng, Jin-Shiung; Chou, Chiang-Ting; Liu, Yuan-Yuarn; Sun, Wei-Chih; Shieh, Pochuen; Kuo, Daih-Huang; Kuo, Chun-Chi; Jan, Chung-Ren; Liang, Wei-Zhe

2016-05-01

Oleuropein, a phenolic compound found in the olive leaf (Olea europaea), has been shown to have biological activities in different models. However, the effects of oleuropein on Ca(2+) homeostasis, cytotoxicity, cell cycle distribution and ROS signaling in liver cells have not been analyzed. Oleuropein induced [Ca(2+)]i rises only in HepG2 cells but not in AML12, HA22T or HA59T cells due to the different status of 3-hydroxy-3-methylglutaryl-CoA reductase expression. In HepG2 cells, this Ca(2+) signaling response was reduced by removing extracellular Ca(2+), and was inhibited by the store-operated Ca(2+) channel blockers 2-APB and SKF96365. In Ca(2+)-free medium, pretreatment with the ER Ca(2+) pump inhibitor thapsigargin abolished oleuropein-induced [Ca(2+)]i rises. Oleuropein induced cell cycle arrest which was associated with the regulation of p53, p21, CDK1 and cyclin B1 levels. Furthermore, oleuropein elevated intracellular ROS levels but reduced GSH levels. Treatment with the intracellular Ca(2+) chelator BAPTA-AM or the antioxidant NAC partially reversed oleuropein-induced cytotoxicity. Together, in HepG2 cells, oleuropein induced [Ca(2+)]i rises by releasing Ca(2+) from the ER and causing Ca(2+) influx through store-operated Ca(2+) channels. Moreover, oleuropein induced Ca(2+)-associated cytotoxicity that involved ROS signaling and cell cycle arrest. This compound may offer a potential therapy for treatment of human hepatoma. Copyright © 2016 Elsevier Ltd. All rights reserved.

Extracellular nucleotides potentiate the cytosolic Ca2+, but not cyclic adenosine 3', 5'-monophosphate response to parathyroid hormone in rat osteoblastic cells.

PubMed

Kaplan, A D; Reimer, W J; Feldman, R D; Dixon, S J

1995-04-01

Binding to PTH to its cell surface receptor activates both adenylyl cyclase and phospholipase-C, leading to elevation of cytosolic cAMP and free Ca2+. We have shown previously that extracellular nucleotides interact with P2U and P2Y subtypes of purinoceptor on osteoblastic cells, both linked to Ca2+ mobilization. In the present study, we investigated possible interactions between nucleotide and PTH signaling pathways in osteoblastic cells. The cytosolic free Ca2+ concentration ([Ca2+]i) of UMR-106 osteoblastic cells was monitored by fluorescence spectrophotometry. PTH (0.01-1 microM; bovine 1-84 or human 1-34) induced a small transient elevation of [Ca2+]i, lasting less than 1 min. A number of nucleotides, including ATP, UTP, and UDP, induced transient elevation of [Ca2+]i and potentiated the subsequent Ca2+ response to PTH. Of the nucleotides tested, UDP was the most effective at potentiating the PTH-induced Ca2+ transient. Treatment of cells with UDP (100 microM for 2.5 min), but not inorganic phosphate or uridine, reversibly potentiated the Ca2+ response to PTH (0.1 microM) by 11 +/- 2-fold (mean +/- SEM; n = 39). In contrast, UDP did not affect the cAMP response to PTH, indicating a selective action on Ca2+ signaling. Potentiation of the Ca2+ signal was still observed in the absence of extracellular Ca2+, establishing that nucleotides enhance PTH-induced release of Ca2+ from intracellular stores. Studies using selective purinoceptor agonists suggest that potentiation of PTH signaling is mediated by the P2U receptor subtype. In vivo, nucleotides released during trauma or inflammation may modulate PTH-induced Ca2+ signaling in osteoblasts.

Intracellular Ca2+ release and Ca2+ influx during regulatory volume decrease in IMCD cells.

PubMed

Tinel, H; Wehner, F; Sauer, H

1994-07-01

Volume changes and cytosolic Ca2+ concentration ([Ca2+]i) of inner medullary collecting duct (IMCD) cells under hypotonic stress were monitored by means of confocal laser scanning microscopy and fura 2 fluorescence, respectively. Reduction of extracellular osmolality from 600 to 300 mosmol/kgH2O by omission of sucrose led to an increase in cell volume within 1 min to 135 +/- 3% (n = 9), followed by a partial regulatory volume decrease (RVD) to 109 +/- 2% (n = 9) within the ensuring 5 min. In parallel, [Ca2+]i rose from 145 +/- 9 to 433 +/- 16 nmol/l (n = 9) and thereafter reached a lower steady state of 259 +/- 9 nmol/l. Under low-Ca2+ conditions (10 nmol/l) RVD was not impeded and reduction of osmolality evoked only a transient increase of [Ca2+]i by 182 +/- 22 nmol/l (n = 6). Preincubation with 100 mumol/l 8-(N,N-diethylamino)octyl-3,4,5-trimethoxy-benzoate hydrochloride (TMB-8) or 20 mmol/l caffeine, both effective inhibitors of Ca2+ release from intracellular stores, in low Ca2+ as well as in high Ca2+, inhibited the Ca2+ response and abolished RVD. The temporal relationship between Ca2+ release from intracellular stores and Ca2+ entry was analyzed by determining fura 2 quenching, using Mn2+ as a substitute for external Ca2+. Intracellular Ca2+ release preceded Mn2+ influx by 17 +/- 3 s (n = 10). Mn2+ influx persisted during the whole period of exposure to hypotonicity, indicating that there is no time-dependent Ca2+ channel inactivation. Preincubation with TMB-8 or caffeine reduced Mn2+ influx to the control level, indicating that activation of Ca2+ channels in the plasma membrane occurs via intracellular Ca2+ release.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium signalling in salivary gland physiology and dysfunction

PubMed Central

2015-01-01

Abstract Studies over the past four decades have established that Ca2+ is a critical factor in control of salivary gland function and have led to identification of the critical components of this process. The major ion transport mechanisms and ion channels that are involved in fluid secretion have also been established. The key event in activation of fluid secretion is an increase in [Ca2+]i triggered by inositol 1,4,5‐trisphosphate (IP3)‐induced release of Ca2+ from ER via the IP3 receptor (IP3R). IP3Rs determine the site of initiation and the pattern of the [Ca2+]i signal in the cell. However, Ca2+ entry into the cell is required to sustain the elevation of [Ca2+]i and fluid secretion and is mediated by the store‐operated Ca2+ entry (SOCE) mechanism. Orai1, TRPC1, TRPC3 and STIM1 have been identified as critical components of SOCE in these cells. Cells finely tune the generation and amplification of [Ca2+]i signals for regulation of cell function. An important emerging area is the concept that unregulated [Ca2+]i signals in cells can directly cause cell damage, dysfunction and disease. Alternatively, aberrant [Ca2+]i signals can also amplify and increase the rates of cell damage. Such defects in Ca2+ signalling have been described in salivary glands in conjunction with radiation‐induced loss of salivary gland function as well as in the salivary defects associated with the autoimmune exocrinopathy Sjögren's syndrome. Such defects have been associated with altered function or expression of key Ca2+ signalling components, such as STIM proteins and TRP channels. These studies offer new avenues for examining the mechanisms underlying the disease and development of novel clinical targets and therapeutic strategies. PMID:26592972

Calcium signalling in salivary gland physiology and dysfunction.

PubMed

Ambudkar, Indu S

2016-06-01

Studies over the past four decades have established that Ca(2+) is a critical factor in control of salivary gland function and have led to identification of the critical components of this process. The major ion transport mechanisms and ion channels that are involved in fluid secretion have also been established. The key event in activation of fluid secretion is an increase in [Ca(2+) ]i triggered by inositol 1,4,5-trisphosphate (IP3 )-induced release of Ca(2+) from ER via the IP3 receptor (IP3 R). IP3 Rs determine the site of initiation and the pattern of the [Ca(2+) ]i signal in the cell. However, Ca(2+) entry into the cell is required to sustain the elevation of [Ca(2+) ]i and fluid secretion and is mediated by the store-operated Ca(2+) entry (SOCE) mechanism. Orai1, TRPC1, TRPC3 and STIM1 have been identified as critical components of SOCE in these cells. Cells finely tune the generation and amplification of [Ca(2+) ]i signals for regulation of cell function. An important emerging area is the concept that unregulated [Ca(2+) ]i signals in cells can directly cause cell damage, dysfunction and disease. Alternatively, aberrant [Ca(2+) ]i signals can also amplify and increase the rates of cell damage. Such defects in Ca(2+) signalling have been described in salivary glands in conjunction with radiation-induced loss of salivary gland function as well as in the salivary defects associated with the autoimmune exocrinopathy Sjögren's syndrome. Such defects have been associated with altered function or expression of key Ca(2+) signalling components, such as STIM proteins and TRP channels. These studies offer new avenues for examining the mechanisms underlying the disease and development of novel clinical targets and therapeutic strategies. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Lowering glucose level elevates [Ca2+]i in hypothalamic arcuate nucleus NPY neurons through P/Q-type Ca2+ channel activation and GSK3β inhibition

PubMed Central

Chen, Yu; Zhou, Jun; Xie, Na; Huang, Chao; Zhang, Jun-qi; Hu, Zhuang-li; Ni, Lan; Jin, You; Wang, Fang; Chen, Jian-guo; Long, Li-hong

2012-01-01

Aim: To identify the mechanisms underlying the elevation of intracellular Ca2+ level ([Ca2+]i) induced by lowering extracellular glucose in rat hypothalamic arcuate nucleus NPY neurons. Methods: Primary cultures of hypothalamic arcuate nucleus (ARC) neurons were prepared from Sprague-Dawley rats. NPY neurons were identified with immunocytochemical method. [Ca2+]i was measured using fura-2 AM. Ca2+ current was recorded using whole-cell patch clamp recording. AMPK and GSK3β levels were measured using Western blot assay. Results: Lowering glucose level in the medium (from 10 to 1 mmol/L) induced a transient elevation of [Ca2+]i in ARC neurons, but not in hippocampal and cortical neurons. The low-glucose induced elevation of [Ca2+]i in ARC neurons depended on extracellular Ca2+, and was blocked by P/Q-type Ca2+channel blocker ω-agatoxin TK (100 nmol/L), but not by L-type Ca2+ channel blocker nifedipine (10 μmol/L) or N-type Ca2+channel blocker ω-conotoxin GVIA (300 nmol/L). Lowering glucose level increased the peak amplitude of high voltage-activated Ca2+ current in ARC neurons. The low-glucose induced elevation of [Ca2+]i in ARC neurons was blocked by the AMPK inhibitor compound C (20 μmol/L), and enhanced by the GSK3β inhibitor LiCl (10 mmol/L). Moreover, lowering glucose level induced the phosphorylation of AMPK and GSK3β, which was inhibited by compound C (20 μmol/L). Conclusion: Lowering glucose level enhances the activity of P/Q type Ca2+channels and elevates [Ca2+]i level in hypothalamic arcuate nucleus neurons via inhibition of GSK3β. PMID:22504905

Subpopulation of store-operated Ca2+ channels regulate Ca2+-induced Ca2+ release in non-excitable cells.

PubMed

Yao, Jian; Li, Qin; Chen, Jin; Muallem, Shmuel

2004-05-14

Ca2+-induced Ca2+ release (CICR) is a well characterized activity in skeletal and cardiac muscles mediated by the ryanodine receptors. The present study demonstrates CICR in the non-excitable parotid acinar cells, which resembles the mechanism described in cardiac myocytes. Partial depletion of internal Ca2+ stores leads to a minimal activation of Ca2+ influx. Ca2+ influx through this pathway results in an explosive mobilization of Ca2+ from the majority of the stores by CICR. Thus, stimulation of parotid acinar cells in Ca2+ -free medium with 0.5 microm carbachol releases approximately 5% of the Ca2+ mobilizable by 1 mm carbachol. Addition of external Ca2+ induced the same Ca2+ release observed in maximally stimulated cells. Similar results were obtained by a short treatment with 2.5-10 microm cyclopiazonic acid, an inhibitor of the sarco/endoplasmic reticulum Ca2+ ATPase pump. The Ca2+ release induced by the addition of external Ca2+ was largely independent of IP(3)Rs because it was reduced by only approximately 30% by the inhibition of the inositol 1,4,5-trisphosphate receptors with caffeine or heparin. Measurements of Ca2+ -activated outward current and [Ca2+](i) suggested that most CICR triggered by Ca2+ influx occurred away from the plasma membrane. Measurement of the response to several concentrations of cyclopiazonic acid revealed that Ca2+ influx that regulates CICR is associated with a selective portion of the internal Ca2+ pool. The minimal activation of Ca2+ influx by partial store depletion was confirmed by the measurement of Mn2+ influx. Inhibition of Ca2+ influx with SKF96365 or 2-aminoethoxydiphenyl borate prevented activation of CICR observed on addition of external Ca2+. These findings provide evidence for activation of CICR by Ca2+ influx in non-excitable cells, demonstrate a previously unrecognized role for Ca2+ influx in triggering CICR, and indicate that CICR in non-excitable cells resembles CICR in cardiac myocytes with the exception that in cardiac cells Ca2+ influx is mediated by voltage-regulated Ca2+ channels whereas in non-excitable cells Ca2+ influx is mediated by store-operated channels.

A plasma membrane-type Ca[sup 2+]-ATPase of 120 kilodaltons on the endoplasmic reticulum from carrot (Daucus carota) cells

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

Chen, F.H.; Ratterman, D.M.; Sze, H.

1993-06-01

Cytosolic Ca[sup 2+] levels are regulated in part by Ca[sup 2+]-pumping ATPases that export Ca[sup 2+] from the cytoplasm; The types and properties of Ca[sup 2+] pumps in plants are not well understood. The kinetic properties of a 120-kD phosphoenzyme (PE) intermediate formed during the reaction cycle of a Ca[sup 2+]-ATPase from suspension-cultured carrot (Daucus carota) cells are characterized. Only one Ca[sup 2+]-dependent phosphoprotein was formed when carrot membrane vesicles were incubated with [[gamma]-[sup 32]P]ATP. Formation of this 120-kD phosphoprotein was inhibited by vanadate, enhanced by La[sup 3+], and decreased by hydroxylamine, confirming its identification as an intermediate of amore » phosphorylated-type Ca[sup 2+]-translocating ATPase. The 120-kD Ca[sup 2+]-ATPase was most abundant in endoplasmic reticulum-enriched fractions, in which the Ca[sup 2+]-ATPase was estimated to be 0.1% of membrane protein. Direct quantitation of Ca[sup 2+]-dependent phosphoprotein was used to examine the kinetics of PE formation. PE formation exhibited a K[sub m] for Ca[sup 2+] of 1 to 2 [mu]m and a K[sub m] for ATP of 67 nm. Relative affinities of substrates, determined by competition experiments, were 0.075 [mu]m for ATP, 1 [mu]m for ADP, 100 [mu]m for ITP, and 250 [mu]m for GTP. Thapsigargin and cyclopiazonic acid, specific inhibitors of animal sarcoplasmic/endoplasmic reticulum Ca[sup 2+]-ATPase, had no effect on PE formation; erythrosin B inhibited with 50% inhibition at <0.1 [mu]m. Calmodulin (1 [mu]m) stimulated PE formation by 25%. The results indicate that the carrot 120-kD Ca[sup 2+]-ATPase is similar but not identical to animal plasma membrane-type Ca[sup 2+]-ATPase and yet is located on endomembranes, such as the endoplasmic reticulum. This type of Ca[sup 2+] pump may reside on the cortical endoplasmic reticulum, thought to play a major role in anchoring the cytoskeleton and in facilitating secretion. 34 refs., 9 figs., 3 tabs.« less

Chelating effect of citric acid is negligible for development of enamel erosions.

PubMed

Azadi-Schossig, Parastu; Becker, Klaus; Attin, Thomas

2016-09-01

Citric acid (CA) is a component in beverages responsible for dental erosion. The aim of this study was to examine the influence of CA with different pH, titratable acid and buffer capacity (ß), and the impact of the chelating effect of CA on development of enamel erosions. In a superfusion model, hydroxy apatite (HAp) dissolution of bovine enamel was measured in four experiments (EXP 1-4) with 27 experimental groups (n = 8 per group). The samples were superfused with different CA variations and respective controls. EXP-1: Dilution series of HCl (pH 2.15-3.02). EXP-2: Dilution series of natural CA (56-1.75 mmol l(-1); pH 2.15-3.02). EXP-3: CA solutions (56 and 14 mmol l(-1), ß: 39.7 and 10.2 mmol l(-1) pH(-1), respectively) with different titratable acidity at equal pH values. EXP-4: CA concentrations (56-1.75 mmol l(-1)) neutralized to pH 7. CA led to higher HAp-dissolution than HCl. With higher pH, the difference in HAp-dissolution rate between the two acids became increasingly smaller. At equal pH, HAp-dissolution was higher for the CA with the higher amount of titratable acid. However, no clear correlation between erosion and titratable acid or ß could be found. Only minimal amounts of HAp were dissolved by neutralized CA compared to CA with natural pH. Under the chosen conditions chelating effects of CA do not have a relevant influence of HAp-dissolution of enamel. Moreover, amount of HAp-dissolution by CA is not attributed to a single factor alone. The interplay between the different parameters of CA seems to be responsible for its erosive potential. The erosive potential of solutions containing citric acid with unknown concentrations could not be predicted using a single parameter alone, and should at best determined in experimental set-ups.

Effect of running exercise on the number of the neurons in the hippocampus of young transgenic APP/PS1 mice.

PubMed

Jiang, Lin; Ma, Jing; Zhang, Yi; Zhou, Chun-Ni; Zhang, Lei; Chao, Feng-Lei; Chen, Lin-Mu; Jiang, Rong; Wu, Hong; Tang, Yong

2018-08-01

To investigate the effect of running exercise on the number of the neurons in the hippocampus of young APP/PS1 mice, twenty 6-month-old male APP/ PS1 transgenic mice were randomly divided into the APP/PS1 control (AD control) group and the APP/PS1 running (AD running) group (10 mice per group), and ten wild-type mice of the littermate were regarded as the wild-type (WT) group. The AD running mice ran on motorized treadmill machiene for 4 months, while the WT mice and AD control mice were housed in standard condition without running. Then, Morris water maze tests (MWM) were used to assess the special learning and memory abilities of mice in three groups. The stereological methods were used to quantitatively evaluate the volume of the hippocampus, CA1/2, CA3 and the dentate gyrus (DG) and count the number of the neurons in CA1/2, CA3 and DG. We found that 4-month running effectively shortened the escape latency of young APP/PS1 control mice in MWM. More importantly, 4-month running effectively increased the volumes of the hippocampus, CA1/2, CA3 and DG and increased the number of neurons in CA1/2, CA3 and DG in young APP/PS1 mice. The present results suggested that 4-month running has significant beneficial effects on the spatial learning and memory capacities of young APP/PS1 mice and could delay the progress of atrophy of hippocampus and the neuron death in CA1/2, CA3 and DG in young APP/PS1 mice. Copyright © 2018 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2018-01-01

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

Ca2+ mobilization in the aortic endothelium in streptozotocin-induced diabetic and cholesterol-fed mice.

PubMed

Kamata, K; Nakajima, M

1998-04-01

1. Experiments were performed to compare Ca2+ mobilization in the aortic endothelium in streptozotocin (STZ)-induced diabetic and cholesterol-fed mice with that in age-matched controls. 2. The intracellular free Ca2+ ([Ca2+]i) in the fura PE-3 loaded endothelium of aortic rings was dose-dependently increased by cumulative administration of acetylcholine (ACh). ACh caused a transient rise in [Ca2+]i in Ca2+-free medium. The ACh-induced increase in [Ca2+]i in normal or Ca2+-free medium was significantly weaker in both STZ-induced diabetic and cholesterol-fed mice. 3. The weaker [Ca2+]i response in Ca2+-containing medium in STZ-induced diabetic and cholesterol-fed mice was normalized by chronic administration of cholestyramine. 4. The increased low density lipoprotein (LDL) levels seen in both STZ-induced diabetic and cholesterol-fed mice were normalized by the same chronic administration of cholestyramine (300 mg kg(-1), p.o. daily for 10 weeks). Chronic administration of cholestyramine had no effect on the plasma glucose level. 5. Lysophosphatidylcholine (LPC) decreased the [Ca2+]i responses to ACh in the aortic endothelium from normal mice. 6. These results suggest that ACh increases both Ca2+ influx and Ca2+ release from storage in the aortic endothelium. The weaker [Ca2+]i influx seen in the endothelium of aortae from both STZ-induced diabetic and cholesterol-fed mice was improved by the chronic administration of cholestyramine, and we suggest that this improvement is due, at least in part, to a lowering of the plasma LDL level. It is further suggested that LPC may have an important influence over Ca2+ mobilization in the endothelium.

Calcium-regulation of mitochondrial respiration maintains ATP homeostasis and requires ARALAR/AGC1-malate aspartate shuttle in intact cortical neurons.

PubMed

Llorente-Folch, Irene; Rueda, Carlos B; Amigo, Ignacio; del Arco, Araceli; Saheki, Takeyori; Pardo, Beatriz; Satrústegui, Jorgina

2013-08-28

Neuronal respiration is controlled by ATP demand and Ca2+ but the roles played by each are unknown, as any Ca2+ signal also impacts on ATP demand. Ca2+ can control mitochondrial function through Ca2+-regulated mitochondrial carriers, the aspartate-glutamate and ATP-Mg/Pi carriers, ARALAR/AGC1 and SCaMC-3, respectively, or in the matrix after Ca2+ transport through the Ca2+ uniporter. We have studied the role of Ca2+ signaling in the regulation of mitochondrial respiration in intact mouse cortical neurons in basal conditions and in response to increased workload caused by increases in [Na+]cyt (veratridine, high-K+ depolarization) and/or [Ca2+]cyt (carbachol). Respiration in nonstimulated neurons on 2.5-5 mm glucose depends on ARALAR-malate aspartate shuttle (MAS), with a 46% drop in aralar KO neurons. All stimulation conditions induced increased OCR (oxygen consumption rate) in the presence of Ca2+, which was prevented by BAPTA-AM loading (to preserve the workload), or in Ca2+-free medium (which also lowers cell workload). SCaMC-3 limits respiration only in response to high workloads and robust Ca2+ signals. In every condition tested Ca2+ activation of ARALAR-MAS was required to fully stimulate coupled respiration by promoting pyruvate entry into mitochondria. In aralar KO neurons, respiration was stimulated by veratridine, but not by KCl or carbachol, indicating that the Ca2+ uniporter pathway played a role in the first, but not in the second condition, even though KCl caused an increase in [Ca2+]mit. The results suggest a requirement for ARALAR-MAS in priming pyruvate entry in mitochondria as a step needed to activate respiration by Ca2+ in response to moderate workloads.

Postsynaptic density protein (PSD)-95 expression is markedly decreased in the hippocampal CA1 region after experimental ischemia-reperfusion injury.

PubMed

Yan, Bing Chun; Park, Joon Ha; Ahn, Ji Hyeon; Lee, Jae-Chul; Won, Moo-Ho; Kang, Il-Jun

2013-07-15

Synaptic plasticity is important for functional recovery after cerebral ischemic injury. In the present study, we investigated chronological change in the immunoreactivity of PSD-95, a kind of postsynaptic density protein, in the hippocampus proper (CA1-3 regions) after 5 min of transient cerebral ischemia in gerbils. PSD-95 immunoreactivity was observed in MAP-2-immunoreactive dendrites in the CA1-3 regions of the sham group. The PSD-95 immunoreactivity was shown as beaded structure in the MAP-2-immunoreactive dendrites. However, PSD-95 immunoreactivity began to be dramatically decreased in MAP-2-immunoreactive dendrites in the CA1 region, not CA2-3 region, at early time after ischemia-reperfusion. At 5 days after ischemia-reperfusion, MAP-2 immunoreactivity almost disappeared in the ischemic CA1 region, and PSD-95 immunoreactivity was much lower than that in the sham group. In brief, PSD-95 immunoreactivity in the CA1 dendrites was markedly decreased at early time after ischemia-reperfusion. We suggest that decreased PSD-95 immunoreactivity in the ischemic CA1 region may lead to a deficit of postsynaptic plasticity in the brain. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

Preparation of core-shell structured CaCO3 microspheres as rapid and recyclable adsorbent for anionic dyes

NASA Astrophysics Data System (ADS)

Zhao, Mengen; Chen, Zhenhua; Lv, Xinyan; Zhou, Kang; Zhang, Jie; Tian, Xiaohan; Ren, Xiuli; Mei, Xifan

2017-09-01

Core-shell structured CaCO3 microspheres (MSs) were prepared by a facile, one-pot method at room temperature. The adsorbent dosage and adsorption time of the obtained CaCO3 MSs were investigated. The results suggest that these CaCO3 MSs can rapidly and efficiently remove 99-100% of anionic dyes within the first 2 min. The obtained CaCO3 MSs have a high Brunauer-Emmett-Teller surface area (211.77 m2 g-1). In addition, the maximum adsorption capacity of the obtained CaCO3 MSs towards Congo red was 99.6 mg g-1. We also found that the core-shell structured CaCO3 MSs have a high recycling capability for removing dyes from water. Our results demonstrate that the prepared core-shell structured CaCO3 MSs can be used as an ideal, rapid, efficient and recyclable adsorbent to remove dyes from aqueous solution.

Regulation of IP 3 Receptors by IP 3 and Ca 2+

NASA Astrophysics Data System (ADS)

Taylor, Colin W.; Swatton, Jane E.

Inositol 1,4,5-trisphosphate ( IP 3) receptors are intracellular Ca 2+ channels that mediate release of Ca 2+ from intracellular stores. The channels are oligomeric assemblies of four subunits, each of which has an N-terminal IP 3-binding domain and each of which contributes to formation of the Ca 2+ channel. In mammals, three different genes encode IP 3 receptors subunits and the type 1 receptor (and perhaps the type 2 receptor) is also expressed as splice variants. Further diversity arises from assembly of the receptor in hetero- and homo-tetrameric channels. The subtypes differ in their expression and regulation, but they share the key property of being regulated by both IP3 and cytosolic Ca 2+. All three mammalian IP 3 subtypes, and probably also the IP 3 receptors expressed in invertebrates, are biphasically regulated by cytosolic Ca2+, although the underlying mechanisms appear to differ between subtypes. The interactions between IP 3 and Ca 2+ in controlling IP 3 receptor gating, and the physiological significance of such regulation will be reviewed.

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

PubMed Central

Findeisen, Felix; Minor, Daniel L.

2010-01-01

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

Experimental study of the Ca-Mg-Zn system using diffusion couples and key alloys

NASA Astrophysics Data System (ADS)

Zhang, Yi-Nan; Kevorkov, Dmytro; Bridier, Florent; Medraj, Mamoun

2011-03-01

Nine diffusion couples and 32 key samples were prepared to map the phase diagram of the Ca-Mg-Zn system. Phase relations and solubility limits were determined for binary and ternary compounds using scanning electron microscopy, electron probe microanalysis and x-ray diffraction (XRD). The crystal structure of the ternary compounds was studied by XRD and electron backscatter diffraction. Four ternary intermetallic (IM) compounds were identified in this system: Ca3MgxZn15-x (4.6<=x<=12 at 335 °C, IM1), Ca14.5Mg15.8Zn69.7 (IM2), Ca2Mg5Zn13 (IM3) and Ca1.5Mg55.3Zn43.2 (IM4). Three binary compounds were found to have extended solid solubility into ternary systems: CaZn11, CaZn13 and Mg2Ca form substitutional solid solutions where Mg substitutes for Zn atoms in the first two compounds, and Zn substitutes for both Ca and Mg atoms in Mg2Ca. The isothermal section of the Ca-Mg-Zn phase diagram at 335 °C was constructed on the basis of the obtained experimental results. The morphologies of the diffusion couples in the Ca-Mg-Zn phase diagram at 335 °C were studied. Depending on the terminal compositions of the diffusion couples, the two-phase regions in the diffusion zone have either a tooth-like morphology or contain a matrix phase with isolated and/or dendritic precipitates.

Involvement of Parkin in the ubiquitin proteasome system-mediated degradation of N-type voltage-gated Ca2+ channels.

PubMed

Grimaldo, Lizbeth; Sandoval, Alejandro; Garza-López, Edgar; Felix, Ricardo

2017-01-01

N-type calcium (CaV2.2) channels are widely expressed in the brain and the peripheral nervous system, where they play important roles in the regulation of transmitter release. Although CaV2.2 channel expression levels are precisely regulated, presently little is known regarding the molecules that mediate its synthesis and degradation. Previously, by using a combination of biochemical and functional analyses, we showed that the complex formed by the light chain 1 of the microtubule-associated protein 1B (LC1-MAP1B) and the ubiquitin-proteasome system (UPS) E2 enzyme UBE2L3, may interact with the CaV2.2 channels promoting ubiquitin-mediated degradation. The present report aims to gain further insights into the possible mechanism of degradation of the neuronal CaV2.2 channel by the UPS. First, we identified the enzymes UBE3A and Parkin, members of the UPS E3 ubiquitin ligase family, as novel CaV2.2 channel binding partners, although evidence to support a direct protein-protein interaction is not yet available. Immunoprecipitation assays confirmed the interaction between UBE3A and Parkin with CaV2.2 channels heterologously expressed in HEK-293 cells and in neural tissues. Parkin, but not UBE3A, overexpression led to a reduced CaV2.2 protein level and decreased current density. Electrophysiological recordings performed in the presence of MG132 prevented the actions of Parkin suggesting enhanced channel proteasomal degradation. Together these results unveil a novel functional coupling between Parkin and the CaV2.2 channels and provide a novel insight into the basic mechanisms of CaV channels protein quality control and functional expression.

Identification of expressed genes in cDNA library of hemocytes from the RLO-challenged oyster, Crassostrea ariakensis Gould with special functional implication of three complement-related fragments (CaC1q1, CaC1q2 and CaC3).

PubMed

Xu, Ting; Xie, Jiasong; Li, Jianming; Luo, Ming; Ye, Shigen; Wu, Xinzhong

2012-06-01

A SMARTer™ cDNA library of hemocyte from Rickettsia-like organism (RLO) challenged oyster, Crassostrea ariakensis Gould was constructed. Random clones (400) were selected and single-pass sequenced, resulted in 200 unique sequences containing 96 known genes and 104 unknown genes. The 96 known genes were categorized into 11 groups based on their biological process. Furthermore, we identified and characterized three complement-related fragments (CaC1q1, CaC1q2 and CaC3). Tissue distribution analysis revealed that all of three fragments were ubiquitously expressed in all tissues studied including hemocyte, gills, mantle, digestive glands, gonads and adductor muscle, while the highest level was seen in the hemocyte. Temporal expression profile in the hemocyte monolayers reveled that the mRNA expression levels of three fragments presented huge increase after the RLO incubation at 3 h and 6 h in post-challenge, respectively. And the maximal expression levels at 3 h in post-challenge are about 256, 104 and 64 times higher than the values detected in the control of CaC1q1, CaC1q2 and CaC3, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

Functional Roles of the Non-Catalytic Calcium-Binding Sites in the N-Terminal Domain of Human Peptidylarginine Deiminase 4

PubMed Central

Liu, Yi-Liang; Tsai, I-Chen; Chang, Chia-Wei; Liao, Ya-Fan; Liu, Guang-Yaw; Hung, Hui-Chih

2013-01-01

This study investigated the functional roles of the N-terminal Ca2+ ion-binding sites, in terms of enzyme catalysis and stability, of peptidylarginine deiminase 4 (PAD4). Amino acid residues located in the N-terminal Ca2+-binding site of PAD4 were mutated to disrupt the binding of Ca2+ ions. Kinetic data suggest that Asp155, Asp157 and Asp179, which directly coordinate Ca3 and Ca4, are essential for catalysis in PAD4. For D155A, D157A and D179A, the k cat/K m,BAEE values were 0.02, 0.63 and 0.01 s−1mM−1 (20.8 s−1mM−1 for WT), respectively. Asn153 and Asp176 are directly coordinated with Ca3 and indirectly coordinated with Ca5 via a water molecule. However, N153A displayed low enzymatic activity with a k cat value of 0.3 s−1 (13.3 s−1 for wild-type), whereas D176A retained some catalytic power with a k cat of 9.7 s−1. Asp168 is the direct ligand for Ca5, and Ca5 coordination by Glu252 is mediated by two water molecules. However, mutation of these two residues to Ala did not cause a reduction in the k cat/K m,BAEE values, which indicates that the binding of Ca5 may not be required for PAD4 enzymatic activity. The possible conformational changes of these PAD4 mutants were examined. Thermal stability analysis of the PAD4 mutants in the absence or presence of Ca2+ indicated that the conformational stability of the enzyme is highly dependent on Ca2+ ions. In addition, the results of urea-induced denaturation for the N153, D155, D157 and D179 series mutants further suggest that the binding of Ca2+ ions in the N-terminal Ca2+-binding site stabilizes the overall conformational stability of PAD4. Therefore, our data strongly suggest that the N-terminal Ca2+ ions play critical roles in the full activation of the PAD4 enzyme. PMID:23382808

Effect of prophylactic oral calcium supplementation on postpartum mineral status and markers of energy balance of multiparous Jersey cows.

PubMed

Valldecabres, A; Pires, J A A; Silva-Del-Río, N

2018-05-01

The effects of prophylactic oral Ca supplementation on blood mineral status and markers of energy balance were evaluated on 205 multiparous Jersey cows at a commercial dairy. Postpartum, cows were systematically assigned to control (n = 105) or oral Ca supplementation (CaOS; 50 to 60 g of Ca as boluses; n = 100) at 0 and 1 d in milk (DIM). Blood samples for analysis of serum minerals (Ca, P, Mg, K, Na, Fe, Zn, and Cu) were collected before and 1 h after treatment at 0 and 1 DIM, and at 2 DIM. Urine pH was measured immediately before and 1 h after treatment administration (n = 96). A subset of 74 cows was evaluated for plasma glucose and fatty acid concentrations at 0, 1, and 2 DIM. Cows were classified according to their initial calcemic status (Ca status) as normocalcemic (NC; serum Ca >2.12 mmol/L) or subclinically hypocalcemic (SCH; serum Ca ≤2.12 mmol/L). Average serum Ca concentration was higher in CaOS than control cows (2.12 vs. 2.06 mmol/L); this treatment effect was higher for SCH [CaOS (2.03 mmol/L); control (1.89 mmol/L)] than NC cows [CaOS (2.22 mmol/L); control (2.22 mmol/L)]. The incidence of subclinical hypocalcemia was lower for CaOS than control cows (53 vs. 65%); however, at 2 DIM the prevalence of subclinical hypocalcemia tended to be higher for CaOS cows, mostly because it was higher for CaOS-NC than control-NC cows (70 vs. 25%). Urine pH was lower for CaOS than control cows (6.10 vs. 7.04). Lower serum Mg concentration was detected for CaOS-SCH (1.06 mmol/L) than for control-SCH (1.10 mmol/L) cows. Cows in the CaOS group had higher serum K (4.68 vs. 4.53 mmol/L), lower plasma glucose (2.97 vs. 3.10 mmol/L), and at 2 DIM higher plasma fatty acid concentrations (0.43 vs. 0.35 mmol/L) than control cows. Our results showed that postpartum serum Ca concentration increases with oral Ca supplementation, but calcemic status influenced treatment response. Future studies should evaluate the long-term implications on production and reproduction of oral Ca supplementation in Jersey cows. The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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.

Resveratrol-induced autophagy is dependent on IP3Rs and on cytosolic Ca2.

PubMed

Luyten, Tomas; Welkenhuyzen, Kirsten; Roest, Gemma; Kania, Elzbieta; Wang, Liwei; Bittremieux, Mart; Yule, David I; Parys, Jan B; Bultynck, Geert

2017-06-01

Previous work revealed that intracellular Ca 2+ signals and the inositol 1,4,5-trisphosphate (IP 3 ) receptors (IP 3 R) are essential to increase autophagic flux in response to mTOR inhibition, induced by either nutrient starvation or rapamycin treatment. Here, we investigated whether autophagy induced by resveratrol, a polyphenolic phytochemical reported to trigger autophagy in a non-canonical way, also requires IP 3 Rs and Ca 2+ signaling. Resveratrol augmented autophagic flux in a time-dependent manner in HeLa cells. Importantly, autophagy induced by resveratrol (80μM, 2h) was completely abolished in the presence of 10μM BAPTA-AM, an intracellular Ca 2+ -chelating agent. To elucidate the IP 3 R's role in this process, we employed the recently established HEK 3KO cells lacking all three IP 3 R isoforms. In contrast to the HEK293 wt cells and to HEK 3KO cells re-expressing IP 3 R1, autophagic responses in HEK 3KO cells exposed to resveratrol were severely impaired. These altered autophagic responses could not be attributed to alterations in the mTOR/p70S6K pathway, since resveratrol-induced inhibition of S6 phosphorylation was not abrogated by chelating cytosolic Ca 2+ or by knocking out IP 3 Rs. Finally, we investigated whether resveratrol by itself induced Ca 2+ release. In permeabilized HeLa cells, resveratrol neither affected the sarco- and endoplasmic reticulum Ca 2+ ATPase (SERCA) activity nor the IP 3 -induced Ca 2+ release nor the basal Ca 2+ leak from the ER. Also, prolonged (4 h) treatment with 100μM resveratrol did not affect subsequent IP 3 -induced Ca 2+ release. However, in intact HeLa cells, although resveratrol did not elicit cytosolic Ca 2+ signals by itself, it acutely decreased the ER Ca 2+ -store content irrespective of the presence or absence of IP 3 Rs, leading to a dampened agonist-induced Ca 2+ signaling. In conclusion, these results reveal that IP 3 Rs and cytosolic Ca 2+ signaling are fundamentally important for driving autophagic flux, not only in response to mTOR inhibition but also in response to non-canonical autophagy inducers like resveratrol. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech. Copyright © 2017 Elsevier B.V. All rights reserved.

Complexation of the calcium cation with antamanide: an experimental and theoretical study

NASA Astrophysics Data System (ADS)

Makrlík, Emanuel; Böhm, Stanislav; Vaňura, Petr; Ruzza, Paolo

2015-06-01

By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Ca2+(aq) + 1 .Sr2+(nb) ? 1 .Ca2+(nb) + Sr2+(aq) occurring in the two-phase water-nitrobenzene system (1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Ca2+, 1 .Sr2+) = 1.6 ± 0.1. Further, the stability constant of the 1 .Ca2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1 .Ca2+) = 10.9 ± 0.2. Finally, applying quantum mechanical density functional level of theory calculations, the most probable structure of the cationic complex species 1 .Ca2+ was derived. In the resulting complex, the 'central' cation Ca2+ is bound by six strong bonding interactions to the corresponding six carbonyl oxygen atoms of the parent ligand 1. Besides, the whole 1 .Ca2+ complex structure is stabilised by two intramolecular hydrogen bonds. The interaction energy of the considered 1 .Ca2+ complex, involving the Boys-Bernardi counterpoise corrections of the basis set superposition error, was found to be -1219.3 kJ/mol, confirming the formation of this cationic species.

Expression of a Diverse Array of Ca2+-Activated K+ Channels (SK1/3, IK1, BK) that Functionally Couple to the Mechanosensitive TRPV4 Channel in the Collecting Duct System of Kidney.

PubMed

Li, Yue; Hu, Hongxiang; Butterworth, Michael B; Tian, Jin-Bin; Zhu, Michael X; O'Neil, Roger G

2016-01-01

The voltage- and Ca2+-activated, large conductance K+ channel (BK, maxi-K) is expressed in the collecting duct system of kidney where it underlies flow- and Ca2+-dependent K+ excretion. To determine if other Ca2+-activated K+ channels (KCa) may participate in this process, mouse kidney and the K+-secreting mouse cortical collecting duct (CCD) cell line, mCCDcl1, were assessed for TRPV4 and KCa channel expression and cross-talk. qPCR mRNA analysis and immunocytochemical staining demonstrated TRPV4 and KCa expression in mCCDcl1 cells and kidney connecting tubule (CNT) and CCD. Three subfamilies of KCa channels were revealed: the high Ca2+-binding affinity small-conductance SK channels, SK1and SK3, the intermediate conductance channel, IK1, and the low Ca2+-binding affinity, BK channel (BKα subunit). Apparent expression levels varied in CNT/CCD where analysis of CCD principal cells (PC) and intercalated cells (IC) demonstrated differential staining: SK1:PCIC, IK1:PC>IC, BKα:PC = IC, and TRPV4:PC>IC. Patch clamp analysis and fluorescence Ca2+ imaging of mCCDcl1 cells demonstrated potent TRPV4-mediated Ca2+ entry and strong functional cross-talk between TRPV4 and KCa channels. TRPV4-mediated Ca2+ influx activated each KCa channel, as evidenced by selective inhibition of KCa channels, with each active KCa channel enhancing Ca2+ entry (due to membrane hyperpolarization). Transepithelial electrical resistance (TEER) analysis of confluent mCCDcl1 cells grown on permeable supports further demonstrated this cross-talk where TRPV4 activation induce a decrease in TEER which was partially restored upon selective inhibition of each KCa channel. It is concluded that SK1/SK3 and IK1 are highly expressed along with BKα in CNT and CCD and are closely coupled to TRPV4 activation as observed in mCCDcl1 cells. The data support a model in CNT/CCD segments where strong cross talk between TRPV4-mediated Ca2+ influx and each KCa channel leads to enhance Ca2+ entry which will support activation of the low Ca2+-binding affinity BK channel to promote BK-mediated K+ secretion.

Role of extracellular and intracellular sources of Ca2+ in sarafotoxin S6b-induced contraction of strips of the rat aorta.

PubMed Central

Watanabe, C.; Hirano, K.; Kanaide, H.

1993-01-01

1. The effect of sarafotoxin S6b (sarafotoxin), a vasoconstrictor peptide, on cytosolic Ca2+ concentration ([Ca2+]i) and force in rat aortic strips loaded with fura-2 was determined by front-surface fluorometry. The objective was to elucidate the role of extracellular and intracellular Ca2+ in the mechanism of action of this peptide. 2. In the presence of extracellular 1.25 mM Ca2+, sarafotoxin induced a biphasic response consisting of an initial rapid increase in [Ca2+]i followed by a secondary sustained increase. Tension developed slowly but was sustained during the application of sarafotoxin. Diltiazem (10 nM-0.1 mM) partially inhibited both the increases in [Ca2+]i and tension. 3. In the presence of extracellular Ca2+, the force developed in relation to the increase in [Ca2+]i ([Ca2+]i-force relationship) observed with sarafotoxin was much greater than that observed upon K+ depolarization. In the presence of diltiazem the sarafotoxin-induced [Ca2+]i-force relationship was shifted even further to the left. 4. In the absence of extracellular Ca2+, sarafotoxin induced a transient increase in [Ca2+]i and a sustained contraction. Extending the incubation time in Ca(2+)-free physiological solution, resulted in smaller responses. However, after 60 min in Ca(2+)-free solution, sarafotoxin induced a sustained contraction but no change in [Ca2+]i. This residual contraction was inhibited by H-7, which is known to inhibit protein kinase C. 5. After treatment with caffeine to reduce intracellular stored Ca2+, sarafotoxin could still elicit increases in [Ca2+]i and in tension, showing that the caffeine-sensitive intracellular Ca2+ store partially overlaps with the sarafotoxin-sensitive store.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8428211

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

PubMed

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

2014-09-01

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

The ternary system K2SO4MgSO4CaSO4

USGS Publications Warehouse

Rowe, J.J.; Morey, G.W.; Silber, C.C.

1967-01-01

Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4??3MgSO4 (m.p. 1201??C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of ??-CaSO4 (anhydrite) to ??-CaSO4 at 1195??C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136??C and that of CaSO4 is 1462??C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4??2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4??2MgSO4 (langbeinite) and incongruently melting K2SO4??2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4??3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4??MgSO4??nCaSO4), K2SO4??3CaSO4 and K2SO4??CaSO4 were not found; (8) a minimum in the ternary system at: 740??C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882??C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880??, 67??5% MgSO4, 5% CaSO4, 27??5% K2SO4. ?? 1967.

Ca2+-independent Activation of Ca2+/Calmodulin-dependent Protein Kinase II Bound to the C-terminal Domain of CaV2.1 Calcium Channels*

PubMed Central

Magupalli, Venkat G.; Mochida, Sumiko; Yan, Jin; Jiang, Xin; Westenbroek, Ruth E.; Nairn, Angus C.; Scheuer, Todd; Catterall, William A.

2013-01-01

Ca2+/calmodulin-dependent protein kinase II (CaMKII) forms a major component of the postsynaptic density where its functions in synaptic plasticity are well established, but its presynaptic actions are poorly defined. Here we show that CaMKII binds directly to the C-terminal domain of CaV2.1 channels. Binding is enhanced by autophosphorylation, and the kinase-channel signaling complex persists after dephosphorylation and removal of the Ca2+/CaM stimulus. Autophosphorylated CaMKII can bind the CaV2.1 channel and synapsin-1 simultaneously. CaMKII binding to CaV2.1 channels induces Ca2+-independent activity of the kinase, which phosphorylates the enzyme itself as well as the neuronal substrate synapsin-1. Facilitation and inactivation of CaV2.1 channels by binding of Ca2+/CaM mediates short term synaptic plasticity in transfected superior cervical ganglion neurons, and these regulatory effects are prevented by a competing peptide and the endogenous brain inhibitor CaMKIIN, which blocks binding of CaMKII to CaV2.1 channels. These results define the functional properties of a signaling complex of CaMKII and CaV2.1 channels in which both binding partners are persistently activated by their association, and they further suggest that this complex is important in presynaptic terminals in regulating protein phosphorylation and short term synaptic plasticity. PMID:23255606

Neto Auxiliary Protein Interactions Regulate Kainate and NMDA Receptor Subunit Localization at Mossy Fiber–CA3 Pyramidal Cell Synapses

PubMed Central

Wyeth, Megan S.; Pelkey, Kenneth A.; Petralia, Ronald S.; Salter, Michael W.; McInnes, Roderick R.

2014-01-01

Neto1 and Neto2 auxiliary subunits coassemble with NMDA receptors (NMDARs) and kainate receptors (KARs) to modulate their function. In the hippocampus, Neto1 enhances the amplitude and prolongs the kinetics of KAR-mediated currents at mossy fiber (MF)–CA3 pyramidal cell synapses. However, whether Neto1 trafficks KARs to synapses or simply alters channel properties is unresolved. Therefore, postembedding electron microscopy was performed to investigate the localization of GluK2/3 subunits at MF–CA3 synapses in Neto-null mice. Postsynaptic GluK2/3 Immunogold labeling was substantially reduced in Neto-null mice compared with wild types. Moreover, spontaneous KAR-mediated synaptic currents and metabotropic KAR signaling were absent in CA3 pyramidal cells of Neto-null mice. A similar loss of ionotropic and metabotropic KAR function was observed in Neto1, but not Neto2, single knock-out mice, specifically implicating Neto1 in regulating CA3 pyramidal cell KAR localization and function. Additional controversy pertains to the role of Neto proteins in modulating synaptic NMDARs. While Immunogold labeling for GluN2A at MF–CA3 synapses was comparable between wild-type and Neto-null mice, labeling for postsynaptic GluN2B was robustly increased in Neto-null mice. Accordingly, NMDAR-mediated currents at MF–CA3 synapses exhibited increased sensitivity to a GluN2B-selective antagonist in Neto1 knockouts relative to wild types. Thus, despite preservation of the overall MF–CA3 synaptic NMDAR-mediated current, loss of Neto1 alters NMDAR subunit composition. These results confirm that Neto protein interactions regulate synaptic localization of KAR and NMDAR subunits at MF–CA3 synapses, with implications for both ionotropic and metabotropic glutamatergic recruitment of the CA3 network. PMID:24403160

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

PubMed

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

2014-05-15

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

Emptying of Intracellular Calcium Pool and Oxidative Stress Imbalance Are Associated with the Glyphosate-Induced Proliferation in Human Skin Keratinocytes HaCaT Cells

PubMed Central

George, Jasmine; Shukla, Yogeshwer

2013-01-01

We demonstrated that glyphosate possesses tumor promoting potential in mouse skin carcinogenesis and SOD 1, calcyclin (S100A6), and calgranulin B (S100A9) have been associated with this potential, although the mechanism is unclear. We aimed to clarify whether imbalance in between [Ca2+]i levels and oxidative stress is associated with glyphosate-induced proliferation in human keratinocytes HaCaT cells. The [Ca2+]i levels, ROS generation, and expressions of G1/S cyclins, IP3R1, S100A6, S100A9, and SOD 1, and apoptosis-related proteins were investigated upon glyphosate exposure in HaCaT cells. Glyphosate (0.1 mM) significantly induced proliferation, decreases [Ca2+]i, and increases ROS generation in HaCaT cells, whereas antioxidant N-acetyl-L-cysteine (NAC) pretreatment reverts these effects which directly indicated that glyphosate induced cell proliferation by lowering [Ca2+]i levels via ROS generation. Glyphosate also enhanced the expression of G1/S cyclins associated with a sharp decrease in G0/G1 and a corresponding increase in S-phases. Additionally, glyphosate also triggers S100A6/S100A9 expression and decreases IP3R1 and SOD 1 expressions in HaCaT cells. Notably, Ca2+ suppression also prevented apoptotic related events including Bax/Bcl-2 ratio and caspases activation. This study highlights that glyphosate promotes proliferation in HaCaT cells probably by disrupting the balance in between [Ca2+]i levels and oxidative stress which in turn facilitated the downregulation of mitochondrial apoptotic signaling pathways. PMID:24073338

Synchronization of calcium waves by mitochondrial substrates in Xenopus laevis oocytes

NASA Astrophysics Data System (ADS)

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

1995-10-01

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

Kinetics of Ca2+ binding to parvalbumin in bovine chromaffin cells: implications for [Ca2+] transients of neuronal dendrites

PubMed Central

Lee, Suk-Ho; Schwaller, Beat; Neher, Erwin

2000-01-01

The effect of parvalbumin (PV) on [Ca2+] transients was investigated by perfusing adrenal chromaffin cells with fura-2 and fluorescein isothiocyanate (FITC)-labelled PV. As PV diffused into cells, the decay of [Ca2+] transients was transformed from monophasic into biphasic. The proportion of the initial fast decay phase increased in parallel with the fluorescence intensity of FITC, indicating that PV is responsible for the initial fast decay phase.The relationship between the fast decay phase and the [Ca2+] level was investigated using depolarizing trains of stimuli. Within a train the relative amplitude of the fast decay phase was inversely dependent on the [Ca2+] level preceding a given stimulus.Based on these observations, we estimated the Ca2+ binding ratio of PV (κP), the apparent dissociation constant of PV for Ca2+ (Kdc,app), and the unbinding rate constant of Ca2+ from PV (kc-) in the cytosol of chromaffin cells. Assuming free [Mg2+] to be 0.14 mm, we obtained values of 51.4 ± 2.0 nm (n = 3) and 0.95 ± 0.026 s−1 (n = 3), for Kdc,app and kc-, respectively.With the parameters obtained in the perfusion study, we simulated [Ca2+] transients, using two different Ca2+ extrusion rates (γ) – 20 and 300 s−1– which represent typical values for chromaffin cells and neuronal dendrites, respectively. The simulation indicated that Ca2+ is pumped out before it is equilibrated with PV, when γ is comparable to the equilibration rates between PV and Ca2+, resulting in the fast decay phase of a biexponential [Ca2+] transient.From these results we conclude that Ca2+ buffers with slow kinetics, such as PV, may cause biexponential decays in [Ca2+] transients, thereby complicating the analysis of endogenous Ca2+ binding ratios (κS) based on time constants. Nevertheless, estimates of κS based on Ca2+ increments provide reasonable estimates for Ca2+ binding ratios before equilibration with PV. PMID:10835044

Carbachol induces Ca(2+)-dependent contraction via muscarinic M2 and M3 receptors in rat intestinal subepithelial myofibroblasts.

PubMed

Iwanaga, Koichi; Murata, Takahisa; Okada, Muneyoshi; Hori, Masatoshi; Ozaki, Hiroshi

2009-07-01

Intestinal myofibroblasts (IMFs) that exist adjacent to the basement membrane of intestines have contractility and contribute to physical barriers of the intestine. Nerve endings distribute adjacent to IMFs, suggesting neurotransmitters may influence IMFs motility; however, there is no direct evidence showing the interaction. Here, we isolated IMFs from rat colon and investigated the effect of acetylcholine on IMFs contractility. In the collagen gel contraction assay, carbachol (1 - 10 microM) and the muscarinic receptor agonist bethanechol (30 - 300 microM) dose-dependently induced IMFs contraction. Pretreatment with the muscarinic receptor antagonist atropine (1 - 10 nM) inhibited carbachol-induced contraction. In RT-PCR, mRNA expression of all muscarinic receptor subtypes (M(1) - M(5)) was detected in IMFs. Subsequently we found pretreatment with the muscarinic M(2) receptor antagonist 11-([2-[(diethylamino)methyl]-1-piperdinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX116) (10 and 30 nM) or the muscarinic M(3) receptor antagonist 4-diphenylacetoxy-N-methyl-piperidine (4-DAMP) (3 and 10 nM) dose-dependently inhibited carbachol-induced contraction. In Ca(2+) measurement, 1 - 10 microM carbachol and 30 - 300 microM bethanechol elevated the intracellular Ca(2+) concentration ([Ca(2+)](i)) in IMFs. Atropine (10 nM) eliminated carbachol-induced [Ca(2+)](i) elevation. The Ca(2+)-channel blocker LaCl(3) (3 microM) abolished carbachol-induced [Ca(2+)](i) elevation and contraction. Furthermore, AF-DX116 and 4-DAMP dose-dependently inhibited the carbachol-induced [Ca(2+)](i) elevation. These observations suggest that acetylcholine elicits Ca(2+)-dependent IMF contraction through muscarinic M(2) and M(3) receptors.

Cell-specific vacuolar calcium storage mediated by CAX1 regulates apoplastic calcium concentration, gas exchange, and plant productivity in Arabidopsis.

PubMed

Conn, Simon J; Gilliham, Matthew; Athman, Asmini; Schreiber, Andreas W; Baumann, Ute; Moller, Isabel; Cheng, Ning-Hui; Stancombe, Matthew A; Hirschi, Kendal D; Webb, Alex A R; Burton, Rachel; Kaiser, Brent N; Tyerman, Stephen D; Leigh, Roger A

2011-01-01

The physiological role and mechanism of nutrient storage within vacuoles of specific cell types is poorly understood. Transcript profiles from Arabidopsis thaliana leaf cells differing in calcium concentration ([Ca], epidermis <10 mM versus mesophyll >60 mM) were compared using a microarray screen and single-cell quantitative PCR. Three tonoplast-localized Ca(2+) transporters, CAX1 (Ca(2+)/H(+)-antiporter), ACA4, and ACA11 (Ca(2+)-ATPases), were identified as preferentially expressed in Ca-rich mesophyll. Analysis of respective loss-of-function mutants demonstrated that only a mutant that lacked expression of both CAX1 and CAX3, a gene ectopically expressed in leaves upon knockout of CAX1, had reduced mesophyll [Ca]. Reduced capacity for mesophyll Ca accumulation resulted in reduced cell wall extensibility, stomatal aperture, transpiration, CO(2) assimilation, and leaf growth rate; increased transcript abundance of other Ca(2+) transporter genes; altered expression of cell wall-modifying proteins, including members of the pectinmethylesterase, expansin, cellulose synthase, and polygalacturonase families; and higher pectin concentrations and thicker cell walls. We demonstrate that these phenotypes result from altered apoplastic free [Ca(2+)], which is threefold greater in cax1/cax3 than in wild-type plants. We establish CAX1 as a key regulator of apoplastic [Ca(2+)] through compartmentation into mesophyll vacuoles, a mechanism essential for optimal plant function and productivity.

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

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

Li, Yun; Lin, Xiaowen; Zhao, XueJun

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

Parallel activation of Ca(2+)-induced survival and death pathways in cardiomyocytes by sorbitol-induced hyperosmotic stress.

PubMed

Chiong, M; Parra, V; Eisner, V; Ibarra, C; Maldonado, C; Criollo, A; Bravo, R; Quiroga, C; Contreras, A; Vicencio, J M; Cea, P; Bucarey, J L; Molgó, J; Jaimovich, E; Hidalgo, C; Kroemer, G; Lavandero, S

2010-08-01

Hyperosmotic stress promotes rapid and pronounced apoptosis in cultured cardiomyocytes. Here, we investigated if Ca(2+) signals contribute to this response. Exposure of cardiomyocytes to sorbitol [600 mosmol (kg water)(-1)] elicited large and oscillatory intracellular Ca(2+) concentration increases. These Ca(2+) signals were inhibited by nifedipine, Cd(2+), U73122, xestospongin C and ryanodine, suggesting contributions from both Ca(2+) influx through voltage dependent L-type Ca(2+) channels plus Ca(2+) release from intracellular stores mediated by IP(3) receptors and ryanodine receptors. Hyperosmotic stress also increased mitochondrial Ca(2+) levels, promoted mitochondrial depolarization, reduced intracellular ATP content, and activated the transcriptional factor cyclic AMP responsive element binding protein (CREB), determined by increased CREB phosphorylation and electrophoretic mobility shift assays. Incubation with 1 mM EGTA to decrease extracellular [Ca(2+)] prevented cardiomyocyte apoptosis induced by hyperosmotic stress, while overexpression of an adenoviral dominant negative form of CREB abolished the cardioprotection provided by 1 mM EGTA. These results suggest that hyperosmotic stress induced by sorbitol, by increasing Ca(2+) influx and raising intracellular Ca(2+) concentration, activates Ca(2+) release from stores and causes cell death through mitochondrial function collapse. In addition, the present results suggest that the Ca(2+) increase induced by hyperosmotic stress promotes cell survival by recruiting CREB-mediated signaling. Thus, the fate of cardiomyocytes under hyperosmotic stress will depend on the balance between Ca(2+)-induced survival and death pathways.

Attenuated Ca(2+) release in a mouse model of limb girdle muscular dystrophy 2A.

PubMed

DiFranco, Marino; Kramerova, Irina; Vergara, Julio L; Spencer, Melissa Jan

2016-01-01

Mutations in CAPN3 cause limb girdle muscular dystrophy type 2A (LGMD2A), a progressive muscle wasting disease. CAPN3 is a non-lysosomal, Ca-dependent, muscle-specific proteinase. Ablation of CAPN3 (calpain-3 knockout (C3KO) mice) leads to reduced ryanodine receptor (RyR1) expression and abnormal Ca2+/calmodulin-dependent protein kinase II (Ca-CaMKII)-mediated signaling. We previously reported that Ca(2+) release measured by fura2-FF imaging in response to single action potential stimulation was reduced in old C3KO mice; however, the use of field stimulation prevented investigation of the mechanisms underlying this impairment. Furthermore, our prior studies were conducted on older animals, whose muscles showed advanced muscular dystrophy, which prevented us from establishing whether impaired Ca(2+) handling is an early feature of disease. In the current study, we sought to overcome these matters by studying single fibers isolated from young wild-type (WT) and C3KO mice using a low affinity calcium dye and high intracellular ethylene glycol-bis(2-aminoethylether)-n,n,n',n'-tetraacetic acid (EGTA) to measure Ca(2+) fluxes. Muscles were subjected to both current and voltage clamp conditions. Standard and confocal fluorescence microscopy was used to study Ca(2+) release in single fibers enzymatically isolated from hind limb muscles of wild-type and C3KO mice. Two microelectrode amplifier and experiments were performed under current or voltage clamp conditions. Calcium concentration changes were detected with an impermeant low affinity dye in the presence of high EGTA intracellular concentrations, and fluxes were calculated with a single compartment model. Standard Western blotting analysis was used to measure the concentration of RyR1 and the α subunit of the dihydropyridine (αDHPR) receptors. Data are presented as mean ± SEM and compared with the Student's test with significance set at p < 0.05. We found that the peak value of Ca(2+) fluxes elicited by single action potentials was significantly reduced by 15-20 % in C3KO fibers, but the kinetics was unaltered. Ca(2+) release elicited by tetanic stimulation was also impaired in C3KO fibers. Confocal studies confirmed that Ca(2+) release was similarly reduced in all triads of C3KO mice. Voltage clamp experiments revealed a normal voltage dependence of Ca(2+) release in C3KO mice but reduced peak Ca(2+) fluxes as with action potential stimulation. These findings concur with biochemical observations of reduced RyR1 and αDHPR levels in C3KO muscles and reduced mechanical output. Confocal studies revealed a similar decrease in Ca(2+) release at all triads consistent with a homogenous reduction of functional voltage activated Ca(2+) release sites. Overall, these results suggest that decreased Ca(2+) release is an early defect in calpainopathy and may contribute to the observed reduction of CaMKII activation in C3KO mice.

Folding units in calcium vector protein of amphioxus: Structural and functional properties of its amino- and carboxy-terminal halves.

PubMed

Baladi, S; Tsvetkov, P O; Petrova, T V; Takagi, T; Sakamoto, H; Lobachov, V M; Makarov, A A; Cox, J A

2001-04-01

Muscle of amphioxus contains large amounts of a four EF-hand Ca2+-binding protein, CaVP, and its target, CaVPT. To study the domain structure of CaVP and assess the structurally important determinants for its interaction with CaVPT, we expressed CaVP and its amino (N-CaVP) and carboxy-terminal halves (C-CaVP). The interactive properties of recombinant and wild-type CaVP are very similar, despite three post-translational modifications in the wild-type protein. N-CaVP does not bind Ca2+, shows a well-formed hydrophobic core, and melts at 44 degrees C. C-CaVP binds two Ca2+ with intrinsic dissociation constants of 0.22 and 140 microM (i.e., very similar to the entire CaVP). The metal-free domain in CaVP and C-CaVP shows no distinct melting transition, whereas its 1Ca2+ and 2Ca2+) forms melt in the 111 degrees -123 degrees C range, suggesting that C-CaVP and the carboxy- domain of CaVP are natively unfolded in the metal-free state and progressively gain structure upon binding of 1Ca2+ and 2Ca2+. Thermal denaturation studies provide evidence for interdomain interaction: the apo, 1Ca2+ and 2Ca2+ states of the carboxy-domain destabilize to different degrees the amino-domain. Only C-CaVP forms a Ca2+-dependent 1:1 complex with CaVPT. Our results suggest that the carboxy-terminal domain of CaVP interacts with CaVPT and that the amino-terminal lobe modulates this interaction.

Folding units in calcium vector protein of amphioxus: Structural and functional properties of its amino- and carboxy-terminal halves

PubMed Central

Baladi, Sibyl; Tsvetkov, Philipp O.; Petrova, Tatiana V.; Takagi, Takashi; Sakamoto, Hiroshi; Lobachov, Vladimir M.; Makarov, Alexander A.; Cox, Jos A.

2001-01-01

Muscle of amphioxus contains large amounts of a four EF-hand Ca2+-binding protein, CaVP, and its target, CaVPT. To study the domain structure of CaVP and assess the structurally important determinants for its interaction with CaVPT, we expressed CaVP and its amino (N-CaVP) and carboxy-terminal halves (C-CaVP). The interactive properties of recombinant and wild-type CaVP are very similar, despite three post-translational modifications in the wild-type protein. N-CaVP does not bind Ca2+, shows a well-formed hydrophobic core, and melts at 44°C. C-CaVP binds two Ca2+ with intrinsic dissociation constants of 0.22 and 140 μM (i.e., very similar to the entire CaVP). The metal-free domain in CaVP and C-CaVP shows no distinct melting transition, whereas its 1Ca2+ and 2Ca2+ forms melt in the 111°–123°C range, suggesting that C-CaVP and the carboxy- domain of CaVP are natively unfolded in the metal-free state and progressively gain structure upon binding of 1Ca2+ and 2Ca2+. Thermal denaturation studies provide evidence for interdomain interaction: the apo, 1Ca2+ and 2Ca2+ states of the carboxy-domain destabilize to different degrees the amino-domain. Only C-CaVP forms a Ca2+-dependent 1:1 complex with CaVPT. Our results suggest that the carboxy-terminal domain of CaVP interacts with CaVPT and that the amino-terminal lobe modulates this interaction. PMID:11274468

Impaired Compensation for Salt-Induced Urinary Calcium Loss in a Space Flight Model

NASA Technical Reports Server (NTRS)

Navidi, Meena; Harper, J. S.; Evans, J.; Fung, P.; Wolinsky, I.; Arnaud, S. B.; Wade, Charles E. (Technical Monitor)

1994-01-01

The loss of urinary calcium (UCa) induced by high sodium (HiNa) diets is compensated for by an increase in net intestinal Ca absorption (abs.). To determine the capacity of the intestine to absorb Ca in a space flight model in which the formation of 1,25-dihydroxyvitamin D (1,25-D) is suppressed, we induced Ca loss with HiNa diets (8%) and restricted dietary Ca (0.2%). In 200 g rats with hind limbs unloaded by tail suspension (S), we examined intestinal Ca abs. by direct measurement in the duodenum (everted gut sac or S/M), vitamin D receptors (VDR) and Ca balance. We also measured serum ionized calcium (ICa), pH, parathyroid hormone (PTH) and 1,25D. PTH was related to ICa (r = -0.44, p is less than 0.02), pH (r = -0.47, p is less than 0.02) and %Ca abs. (r = -0.40, p is less than 0.05). 1,25-D was related to %Ca abs. (r = 0.60, p is less than 0.001) but not VDR or S/M. Effects of the model were lower serum 1,25-D (110 +/- 59 vs. 199 +/- 80 pg/ml, p is less than 0.005), %Ca abs. (83 +/- 6.9 vs. 93 +/- 3.2, p is less than 0.03) and Ca balance (27 +/- 0.2 vs. 30 +/- 0.3 mg/d, p is less than 0.001) in S than controls (C). The HiNa diet increased UCa excretion from 2 to 13% of dietary Ca. Responses to HiNa diets, compared to normal Na, revealed no differences in 1,25-D, Ca abs. or VDR. Ca balances were lower in HiNa (27 +/- 0.3 vs. 30 +/- 0.4 mg/d, p is less than 0.001) in spite of higher Ca intakes. The failure of S rats fed HiNa diets to increase Ca abs. in response to Na-induced Ca loss appears to be related to suppressed 1,25-D in the space flight model, the cause of which remains obscure.

Modulation of Candida albicans virulence by bacterial biofilms on titanium surfaces.

PubMed

Cavalcanti, Yuri Wanderley; Wilson, Melanie; Lewis, Michael; Del-Bel-Cury, Altair Antoninha; da Silva, Wander José; Williams, David W

2016-01-01

Whilst Candida albicans occurs in peri-implant biofilms, its role in peri-implantitis remains unclear. This study therefore examined the virulence of C. albicans in mixed-species biofilms on titanium surfaces. Biofilms of C. albicans (Ca), C. albicans with streptococci (Streptococcus sanguinis, S. mutans) (Ca-Ss-Sm) and those incorporating Porphyromonas gingivalis (Ca-Pg and Ca-Ss-Sm-Pg) were developed. Expression of C. albicans genes associated with adhesion (ALS1, ALS3, HWP1) and hydrolytic enzymes (SAP2, SAP4, SAP6, PLD1) was measured and hyphal production by C. albicans quantified. Compared with Ca biofilms, significant (p<0.05) up-regulation of ALS3, HWP1, SAP2 and SAP6, and hyphal production occurred in biofilms containing streptococci (Ca-Ss-Sm). In Ca-Pg biofilms, down-regulation of HWP1 and SAP4 expression, with reduced hyphal production occurred. Ca-Ss-Sm-Pg biofilms had increased hyphal proportions and up-regulation of ALS3, SAP2 and SAP6. In conclusion, C. albicans expressed virulence factors in biofilms that could contribute to peri-implantitis, but this was dependent on associated bacterial species.

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

Ca2+ influx in the endothelial cells is required for the bradykinin-induced endothelium-dependent contraction in the porcine interlobar renal artery

PubMed Central

Ihara, Eikichi; Derkach, Dmitry N; Hirano, Katsuya; Nishimura, Junji; Nawata, Hajime; Kanaide, Hideo

2001-01-01

To determine the mechanism of bradykinin-induced production of endothelium-derived contracting factors, we monitored the changes in cytosolic Ca2+ concentration ([Ca2+]i) in in situ endothelial cells in porcine aortic valvular strips and the changes in [Ca2+]i of smooth muscle cells and force in porcine interlobar renal arterial strips using front-surface fluorometry of fura-2. In the presence of Nω-nitro-l-arginine methyl ester, bradykinin caused an endothelium-dependent transient elevation of [Ca2+]i and contraction in smooth muscle in the interlobar renal artery. This contraction was completely inhibited by a prostaglandin H2/thromboxane A2 receptor antagonist. In the absence of extracellular Ca2+, bradykinin failed to induce contraction. However, replenishing extracellular Ca2+ to 0.75 mm and higher induced an instantaneous contraction. However, replenishing Ca2+per se did not induce any contraction in the absence of bradykinin. Pretreatment with either 10−5m 1-(β-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenethyl)-1H-imidazole hydrochloride (SKF96365) or 0.2 mm Ni2+ abolished the contraction induced by bradykinin in the presence of extracellular Ca2+. Treatment with 10−5m indomethacin completely inhibited the contractile response induced by Ca2+ replenishment, regardless of the timing of its application, before or after the application of bradykinin. In endothelial cells in the valvular strips, bradykinin caused a transient [Ca2+]i elevation in the presence of 1.25 mm extracellular Ca2+, but [Ca2+]i returned to the resting level within 10 min. Neither 10−5m SKF96365 nor 0.2 mm Ni2+ had any effect on the peak [Ca2+]i elevation, but decreased [Ca2+]i in the declining phase. In the absence of extracellular Ca2+, bradykinin induced a transient [Ca2+]i elevation to a level similar to that seen in the presence of 1.25 mm extracellular Ca2+. However, [Ca2+]i then rapidly returned to the prestimulation level within 5 min. Subsequent Ca2+ replenishment to 0.75 mm and higher in the presence of bradykinin elevated [Ca2+]i to significantly higher levels than the resting level seen in the media containing 1.25 mm Ca2+. In conclusion, Ca2+ influx in the endothelial cells is essential for bradykinin to induce endothelium-dependent contraction in the porcine interlobar renal artery. PMID:11483701

Roles of Ca(v) channels and AHNAK1 in T cells: the beauty and the beast.

PubMed

Matza, Didi; Flavell, Richard A

2009-09-01

T lymphocytes require Ca2+ entry though the plasma membrane for their activation and function. Recently, several routes for Ca2+ entry through the T-cell plasma membrane after activation have been described. These include calcium release-activated channels (CRAC), transient receptor potential (TRP) channels, and inositol-1,4,5-trisphosphate receptors (IP3Rs). Herein we review the emergence of a fourth new route for Ca2+ entry, composed of Ca(v) channels (also known as L-type voltage-gated calcium channels) and the scaffold protein AHNAK1 (AHNAK/desmoyokin). Both helper (CD4+) and killer (CD8+) T cells express high levels of Ca(v)1 alpha1 subunits (alpha1S, alpha1C, alpha1D, and alpha1F) and AHNAK1 after their differentiation and require these molecules for Ca2+ entry during an immune response. In this article, we describe the observations and open questions that ultimately suggest the involvement of multiple consecutive routes for Ca2+ entry into lymphocytes, one of which may be mediated by Ca(v) channels and AHNAK1.

Effects of methyl p-hydroxybenzoate (methyl paraben) on Ca2+ concentration and histamine release in rat peritoneal mast cells

PubMed Central

Fukugasako, Sanae; Ito, Shinichi; Ikemoto, Yoshimi

2003-01-01

Mechanisms of methyl p-hydroxybenzoate (methyl paraben) action in allergic reactions were investigated by measuring the intracellular Ca2+ concentration ([Ca2+]i) and histamine release in rat peritoneal mast cells (RPMCs). In the presence or absence of extracellular Ca2+, methyl paraben (0.1–10 mM) increased [Ca2+]i, in a concentration-dependent manner. Under both the conditions, methyl paraben alone did not evoke histamine release. In RPMCs pretreated with a protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate (PMA) 3 and 10 nM), methyl paraben (0.3–3 mM) induced histamine release. However, a high concentration (10 mM) of the agent did not increase the histamine release. U73122 (0.1 and 0.5 μM), an inhibitor of phospholipase C (PLC), significantly inhibited the methyl paraben-induced histamine release in PMA-pretreated RPMCs. U73343 (0.5 μM), an inactive analogue of U73122, did not inhibit the histamine release caused by methyl paraben. In Ca2+-free solution, PLC inhibitors (U73122 0.1 and 0.5 μM, D609 1–10 μM) inhibited the methyl paraben-induced increase in [Ca2+]i, whereas U73343 (0.5 μM) did not. Xestospongin C (2–20 μM) and 2 aminoethoxydiphenyl borate (30 and 100 μM), blockers of the inositol 1,4,5-trisphosphate (IP3) receptor, inhibited the methyl paraben-induced increase in [Ca2+]i in Ca2+-free solution. In conclusion, methyl paraben causes an increase in [Ca2+]i, which may be due to release of Ca2+ from storage sites by IP3 via activation of PLC in RPMCs. In addition, methyl paraben possibly has some inhibitory effects on histamine release via unknown mechanisms. PMID:12770943

The role and mechanism of KCa3.1 channels in human monocyte migration induced by palmitic acid.

PubMed

Ma, Xiao-Zhen; Pang, Zheng-Da; Wang, Jun-Hong; Song, Zheng; Zhao, Li-Mei; Du, Xiao-Jun; Deng, Xiu-Ling

2018-05-21

Monocyte migration into diseased tissues contributes to the pathogenesis of diseases. Intermediate-conductance Ca 2+ -activated K + (K Ca 3.1) channels play an important role in cell migration. However, the role of K Ca 3.1 channels in mediating monocyte migration induced by palmitic acid (PA) is still unclear. Using cultured THP-1 cells and peripheral blood mononuclear cells from healthy subjects, we investigated the role and signaling mechanisms of K Ca 3.1 channels in mediating the migration induced by PA. Using methods of Western blotting analysis, RNA interference, cell migration assay and ELISA, we found that PA-treated monocytes exhibited increment of the protein levels of K Ca 3.1 channel and monocyte chemoattractant protein-1 (MCP-1), and the effects were reversed by co-incubation of PA with anti-TLR2/4 antibodies or by specific inhibitors of p38-MAPK, or NF-κB. In addition, PA increased monocyte migration, which was abolished by a specific K Ca 3.1 channel blocker, TRAM-34, or K Ca 3.1 small interfering RNA (siRNA). The expression and secretion of MCP-1 induced by PA was also similarly prevented by TRAM-34 and K Ca 3.1 siRNA. These results demonstrate for the first time that PA upregulates K Ca 3.1 channels through TLR2/4, p38-MAPK and NF-κB pathway to promote the expression of MCP-1, and then induce the trans-endothelial migration of monocytes. Copyright © 2018 Elsevier Inc. All rights reserved.

Essential role of carbonic anhydrase XII in secretory gland fluid and HCO3 (-) secretion revealed by disease causing human mutation.

PubMed

Hong, Jeong Hee; Muhammad, Emad; Zheng, Changyu; Hershkovitz, Eli; Alkrinawi, Soliman; Loewenthal, Neta; Parvari, Ruti; Muallem, Shmuel

2015-12-15

Fluid and HCO3 (-) secretion is essential for all epithelia; aberrant secretion is associated with several diseases. Carbonic anhydrase XII (CA12) is the key carbonic anhydrase in epithelial fluid and HCO3 (-) secretion and works by activating the ductal Cl(-) -HCO3 (-) exchanger AE2. Delivery of CA12 to salivary glands increases salivation in mice and of the human mutation CA12(E143K) markedly inhibits it. The human mutation CA12(E143K) causes disease due to aberrant CA12 glycosylation, and misfolding resulting in loss of AE2 activity. Aberrant epithelial fluid and HCO3 (-) secretion is associated with many diseases. The activity of HCO3 (-) transporters depends of HCO3 (-) availability that is determined by carbonic anhydrases (CAs). Which CAs are essential for epithelial function is unknown. CA12 stands out since the CA12(E143K) mutation causes salt wasting in sweat and dehydration in humans. Here, we report that expression of CA12 and of CA12(E143K) in mice salivary glands respectively increased and prominently inhibited ductal fluid secretion and salivation in vivo. CA12 markedly increases the activity and is the major HCO3 (-) supplier of ductal Cl(-) -HCO3 (-) exchanger AE2, but not of NBCe1-B. The E143K mutation alters CA12 glycosylation at N28 and N80, resulting in retention of the basolateral CA12 in the ER. Knockdown of AE2 and of CA12 inhibited pancreatic and salivary gland ductal AE2 activity and fluid secretion. Accordingly, patients homozygous for the CA12(E143K) mutation have a dry mouth, dry tongue phenotype. These findings reveal an unsuspected prominent role of CA12 in epithelial function, explain the disease and call for caution in the use of CA12 inhibitors in cancer treatment. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

In Vivo Epithelial Wound Repair Requires Mobilization of Endogenous Intracellular and Extracellular Calcium*

PubMed Central

Aihara, Eitaro; Hentz, Courtney L.; Korman, Abraham M.; Perry, Nicholas P. J.; Prasad, Vikram; Shull, Gary E.; Montrose, Marshall H.

2013-01-01

We report that a localized intracellular and extracellular Ca2+ mobilization occurs at the site of microscopic epithelial damage in vivo and is required to mediate tissue repair. Intravital confocal/two-photon microscopy continuously imaged the surgically exposed stomach mucosa of anesthetized mice while photodamage of gastric epithelial surface cells created a microscopic lesion that healed within 15 min. Transgenic mice with an intracellular Ca2+-sensitive protein (yellow cameleon 3.0) report that intracellular Ca2+ selectively increases in restituting gastric epithelial cells adjacent to the damaged cells. Pretreatment with U-73122, indomethacin, 2-aminoethoxydiphenylborane, or verapamil inhibits repair of the damage and also inhibits the intracellular Ca2+ increase. Confocal imaging of Fura-Red dye in luminal superfusate shows a localized extracellular Ca2+ increase at the gastric surface adjacent to the damage that temporally follows intracellular Ca2+ mobilization. Indomethacin and verapamil also inhibit the luminal Ca2+ increase. Intracellular Ca2+ chelation (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid/acetoxymethyl ester, BAPTA/AM) fully inhibits intracellular and luminal Ca2+ increases, whereas luminal calcium chelation (N-(2-hydroxyetheyl)-ethylendiamin-N,N,N′-triacetic acid trisodium, HEDTA) blocks the increase of luminal Ca2+ and unevenly inhibits late-phase intracellular Ca2+ mobilization. Both modes of Ca2+ chelation slow gastric repair. In plasma membrane Ca-ATPase 1+/− mice, but not plasma membrane Ca-ATPase 4−/− mice, there is slowed epithelial repair and a diminished gastric surface Ca2+ increase. We conclude that endogenous Ca2+, mobilized by signaling pathways and transmembrane Ca2+ transport, causes increased Ca2+ levels at the epithelial damage site that are essential to gastric epithelial cell restitution in vivo. PMID:24121509

In vivo epithelial wound repair requires mobilization of endogenous intracellular and extracellular calcium.

PubMed

Aihara, Eitaro; Hentz, Courtney L; Korman, Abraham M; Perry, Nicholas P J; Prasad, Vikram; Shull, Gary E; Montrose, Marshall H

2013-11-22

We report that a localized intracellular and extracellular Ca(2+) mobilization occurs at the site of microscopic epithelial damage in vivo and is required to mediate tissue repair. Intravital confocal/two-photon microscopy continuously imaged the surgically exposed stomach mucosa of anesthetized mice while photodamage of gastric epithelial surface cells created a microscopic lesion that healed within 15 min. Transgenic mice with an intracellular Ca(2+)-sensitive protein (yellow cameleon 3.0) report that intracellular Ca(2+) selectively increases in restituting gastric epithelial cells adjacent to the damaged cells. Pretreatment with U-73122, indomethacin, 2-aminoethoxydiphenylborane, or verapamil inhibits repair of the damage and also inhibits the intracellular Ca(2+) increase. Confocal imaging of Fura-Red dye in luminal superfusate shows a localized extracellular Ca(2+) increase at the gastric surface adjacent to the damage that temporally follows intracellular Ca(2+) mobilization. Indomethacin and verapamil also inhibit the luminal Ca(2+) increase. Intracellular Ca(2+) chelation (1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxymethyl ester, BAPTA/AM) fully inhibits intracellular and luminal Ca(2+) increases, whereas luminal calcium chelation (N-(2-hydroxyetheyl)-ethylendiamin-N,N,N'-triacetic acid trisodium, HEDTA) blocks the increase of luminal Ca(2+) and unevenly inhibits late-phase intracellular Ca(2+) mobilization. Both modes of Ca(2+) chelation slow gastric repair. In plasma membrane Ca-ATPase 1(+/-) mice, but not plasma membrane Ca-ATPase 4(-/-) mice, there is slowed epithelial repair and a diminished gastric surface Ca(2+) increase. We conclude that endogenous Ca(2+), mobilized by signaling pathways and transmembrane Ca(2+) transport, causes increased Ca(2+) levels at the epithelial damage site that are essential to gastric epithelial cell restitution in vivo.

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

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

Zhang, Tan; Taylor, Jackson; Jiang, Yang

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

A toxin fraction (FTX) from the funnel-web spider poison inhibits dihydropyridine-insensitive Ca2+ channels coupled to catecholamine release in bovine adrenal chromaffin cells.

PubMed

Duarte, C B; Rosario, L M; Sena, C M; Carvalho, A P

1993-03-01

In adrenal chromaffin cells, depolarization-evoked Ca2+ influx and catecholamine release are partially blocked by blockers of L-type voltage-sensitive Ca2+ channels. We have now evaluated the sensitivity of the dihydropyridine-resistant components of Ca2+ influx and catecholamine release to a toxin fraction (FTX) from the funnel-web spider poison, which is known to block P-type channels in mammalian neurons. FTX (1:4,000 dilution, with respect to the original fraction) inhibited K(+)-depolarization-induced Ca2+ influx by 50%, as monitored with fura-2, whereas nitrendipine (0.1-1 microM) and FTX (3:3), a synthetic FTX analogue (1 mM), blocked the [Ca2+]i transients by 35 and 30%, respectively. When tested together, FTX and nitrendipine reduced the [Ca2+]i transients by 70%. FTX or nitrendipine reduced adrenaline and noradrenaline release by approximately 80 and 70%, respectively, but both substances together abolished the K(+)-evoked catecholamine release, as measured by HPLC. The omega-conotoxin GVIA (0.5 microM) was without effect on K(+)-stimulated 45Ca2+ uptake. Our results indicate that FTX blocks dihydropyridine- and omega-conotoxin-insensitive Ca2+ channels that, together with L-type voltage-sensitive Ca2+ channels, are coupled to catecholamine release.

Thermoelectric properties of Ca(1-x-y)Dy(x)CeyMnO3 for power generation.

PubMed

Park, K; Lee, G W; Jung, J; Kim, S-J; Lim, Y-S; Choi, S-M; Seo, W-S

2011-08-01

The sintered Ca(1-x-y)Dy(x)CeyMnO3 bodies were a single phase with a perovskite structure without any impurity phases. The calculated crystallite sizes of the Ca(1-x-y)Dy(x)CeyMnO3 were in the range of 43.3 to 63.3 nm. The composition significantly affected their microstructural and thermoelectric characteristics. The doped Dy led to both an increase in the electrical conductivity as well as the absolute value of the Seebeck coefficient, resulting in an enhanced power factor. The highest power factor (5.1 x 10(-4) Wm(-1) K(-2)) was obtained for Ca(0.8)Dy(0.2)MnO3 at 800 degrees C. In this study, we systematically discussed the thermoelectric properties of the Ca(1-x-y)Dy(x)CeyMnO3, with respect to the substitution of Dy and/or Ce for Ca.

Fluorescence Resonance Energy Transfer-Sensitized Emission of Yellow Cameleon 3.60 Reveals Root Zone-Specific Calcium Signatures in Arabidopsis in Response to Aluminum and Other Trivalent Cations1[W][OA

PubMed Central

Rincón-Zachary, Magaly; Teaster, Neal D.; Sparks, J. Alan; Valster, Aline H.; Motes, Christy M.; Blancaflor, Elison B.

2010-01-01

Fluorescence resonance energy transfer-sensitized emission of the yellow cameleon 3.60 was used to study the dynamics of cytoplasmic calcium ([Ca2+]cyt) in different zones of living Arabidopsis (Arabidopsis thaliana) roots. Transient elevations of [Ca2+]cyt were observed in response to glutamic acid (Glu), ATP, and aluminum (Al3+). Each chemical induced a [Ca2+]cyt signature that differed among the three treatments in regard to the onset, duration, and shape of the response. Glu and ATP triggered patterns of [Ca2+]cyt increases that were similar among the different root zones, whereas Al3+ evoked [Ca2+]cyt transients that had monophasic and biphasic shapes, most notably in the root transition zone. The Al3+-induced [Ca2+]cyt increases generally started in the maturation zone and propagated toward the cap, while the earliest [Ca2+]cyt response after Glu or ATP treatment occurred in an area that encompassed the meristem and elongation zone. The biphasic [Ca2+]cyt signature resulting from Al3+ treatment originated mostly from cortical cells located at 300 to 500 μ m from the root tip, which could be triggered in part through ligand-gated Glu receptors. Lanthanum and gadolinium, cations commonly used as Ca2+ channel blockers, elicited [Ca2+]cyt responses similar to those induced by Al3+. The trivalent ion-induced [Ca2+]cyt signatures in roots of an Al3+-resistant and an Al3+-sensitive mutant were similar to those of wild-type plants, indicating that the early [Ca2+]cyt changes we report here may not be tightly linked to Al3+ toxicity but rather to a general response to trivalent cations. PMID:20053711

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

PubMed

Valéri, Antoine

2002-01-01

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

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

PubMed

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

2013-12-23

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

Regulation of mouse lung development by the extracellular calcium-sensing receptor, CaR

PubMed Central

Finney, Brenda A; del Moral, Pierre M; Wilkinson, William J; Cayzac, Sebastien; Cole, Martin; Warburton, David; Kemp, Paul J; Riccardi, Daniela

2008-01-01

Postnatal lung function is critically dependent upon optimal embryonic lung development. As the free ionized plasma calcium concentration ([Ca2+]o) of the fetus is higher than that of the adult, the process of lung development occurs in a hypercalcaemic environment. In the adult, [Ca2+]o is monitored by the G-protein coupled, extracellular calcium-sensing receptor (CaR), but neither its ontogeny nor its potential role in lung development are known. Here, we demonstrate that CaR is expressed in the mouse lung epithelium, and that its expression is developmentally regulated, with a peak of expression at embryonic day 12.5 (E12.5) and a subsequent decrease by E18, after which the receptor is absent. Experiments carried out using the lung explant culture model in vitro show that lung branching morphogenesis is sensitive to [Ca2+]o, being maximal at physiological adult [Ca2+]o (i.e. 1.0–1.3 mm) and lowest at the higher, fetal (i.e. 1.7 mm) [Ca2+]o. Administration of the specific CaR positive allosteric modulator, the calcimimetic R-568, mimics the suppressive effects of high [Ca2+]o on branching morphogenesis while both phospholipase C and PI3 kinase inhibition reverse these effects. CaR activation suppresses cell proliferation while it enhances intracellular calcium signalling, lung distension and fluid secretion. Conditions which are restrictive either to branching or to secretion can be rescued by manipulating [Ca2+]o in the culture medium. In conclusion, fetal Cao2+, acting through a developmentally regulated CaR, is an important extrinsic factor that modulates the intrinsic lung developmental programme. Our observations support a novel role for the CaR in preventing hyperplastic lung disease in utero. PMID:18955379

Roles of calcium/calmodulin-dependent kinase II in long-term memory formation in crickets.

PubMed

Mizunami, Makoto; Nemoto, Yuko; Terao, Kanta; Hamanaka, Yoshitaka; Matsumoto, Yukihisa

2014-01-01

Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a key molecule in many systems of learning and memory in vertebrates, but roles of CaMKII in invertebrates have not been characterized in detail. We have suggested that serial activation of NO/cGMP signaling, cyclic nucleotide-gated channel, Ca(2+)/CaM and cAMP signaling participates in long-term memory (LTM) formation in olfactory conditioning in crickets, and here we show participation of CaMKII in LTM formation and propose its site of action in the biochemical cascades. Crickets subjected to 3-trial conditioning to associate an odor with reward exhibited memory that lasts for a few days, which is characterized as protein synthesis-dependent LTM. In contrast, animals subjected to 1-trial conditioning exhibited memory that lasts for only several hours (mid-term memory, MTM). Injection of a CaMKII inhibitor prior to 3-trial conditioning impaired 1-day memory retention but not 1-hour memory retention, suggesting that CaMKII participates in LTM formation but not in MTM formation. Animals injected with a cGMP analogue, calcium ionophore or cAMP analogue prior to 1-trial conditioning exhibited 1-day retention, and co-injection of a CaMKII inhibitor impaired induction of LTM by the cGMP analogue or that by the calcium ionophore but not that by the cAMP analogue, suggesting that CaMKII is downstream of cGMP production and Ca(2+) influx and upstream of cAMP production in biochemical cascades for LTM formation. Animals injected with an adenylyl cyclase (AC) activator prior to 1-trial conditioning exhibited 1-day retention. Interestingly, a CaMKII inhibitor impaired LTM induction by the AC activator, although AC is expected to be a downstream target of CaMKII. The results suggest that CaMKII interacts with AC to facilitate cAMP production for LTM formation. We propose that CaMKII serves as a key molecule for interplay between Ca(2+) signaling and cAMP signaling for LTM formation, a new role of CaMKII in learning and memory.

Mg2+ activates the ryanodine receptor type 2 (RyR2) at intermediate Ca2+ concentrations.

PubMed

Chugun, Akihito; Sato, Osamu; Takeshima, Hiroshi; Ogawa, Yasuo

2007-01-01

To clarify whether activity of the ryanodine receptor type 2 (RyR2) is reduced in the sarcoplasmic reticulum (SR) of cardiac muscle, as is the case with the ryanodine receptor type 1 (RyR1), Ca(2+)-dependent [(3)H]ryanodine binding, a biochemical measure of Ca(2+)-induced Ca(2+) release (CICR), was determined using SR vesicle fractions isolated from rabbit and rat cardiac muscles. In the absence of an adenine nucleotide or caffeine, the rat SR showed a complicated Ca(2+) dependence, instead of the well-documented biphasic dependence of the rabbit SR. In the rat SR, [(3)H]ryanodine binding initially increased as [Ca(2+)] increased, with a plateau in the range of 10-100 microM Ca(2+), and thereafter further increased to an apparent peak around 1 mM Ca(2+), followed by a decrease. In the presence of these modulators, this complicated dependence prevailed, irrespective of the source. Addition of 0.3-1 mM Mg(2+) unexpectedly increased the binding two- to threefold and enhanced the affinity for [(3)H]ryanodine at 10-100 microM Ca(2+), resulting in the well-known biphasic dependence. In other words, the partial suppression of RyR2 is relieved by Mg(2+). Ca(2+) could be a substitute for Mg(2+). Mg(2+) also amplifies the responses of RyR2 to inhibitory and stimulatory modulators. This stimulating effect of Mg(2+) on RyR2 is entirely new, and is referred to as the third effect, in addition to the well-known dual inhibitory effects. This effect is critical to describe the role of RyR2 in excitation-contraction coupling of cardiac muscle, in view of the intracellular Mg(2+) concentration.

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

PubMed

Findeisen, Felix; Minor, Daniel L

2010-12-08

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

Ca2+ release triggered by nicotinate adenine dinucleotide phosphate in intact sea urchin eggs.

PubMed Central

Perez-Terzic, C M; Chini, E N; Shen, S S; Dousa, T P; Clapham, D E

1995-01-01

Nicotinate adenine dinucleotide phosphate (NAADP) was recently identified [Lee and Aarhus (1995) J. Biol. Chem. 270, 2152-2157; Chini, Beers and Dousa (1995) J. Biol. Chem. 270, 3116-3223] as a potent Ca(2+)-releasing agent in sea urchin egg homogenates. NAADP triggered Ca2+ release by a mechanism that was distinct from inositol 1,4,5-trisphosphate (InsP3)- and cyclic ADP-ribose (cADPR)-induced Ca2+ release. When NAADP was microinjected into intact sea urchin eggs it induced a dose-dependent increase in cytoplasmic free Ca2+ which was independent of the extracellular [Ca2+]. The Ca2+ waves elicited by microinjections of NAADP originated at the site of injection and swept across the cytosol. As previously found in sea urchin egg homogenates, NAADP-induced Ca2+ release in intact eggs was not blocked by heparin or by prior desensitization to InsP3 or cADPR. Thio-NADP, a specific inhibitor of the NAADP-induced Ca2+ release in sea urchin homogenates [Chini, Beers and Dousa (1995) J. Biol. Chem. 270, 3116-3223] blocked NAADP (but not InsP3 or cADPR) injection-induced Ca2+ release in intact sea urchin eggs. Finally, fertilization of sea urchin eggs abrogated subsequent NAADP-induced Ca2+ release, suggesting that the NAADP-sensitive Ca2+ pool may participate in the fertilization response. This study demonstrates that NAADP acts as a selective Ca(2+)-releasing agonist in intact cells. Images Figure 2 PMID:8554544

Pulsed Infrared Releases Ca2+ from the Endoplasmic Reticulum of Cultured Spiral Ganglion Neurons.

PubMed

Barrett, John N; Rincon, Samantha; Singh, Jayanti; Matthewman, Cristina; Pasos, Julio; Barrett, Ellen F; Rajguru, Suhrud M

2018-04-18

We investigated the effects of pulsed infrared radiation (IR, 1863 nm) stimulation on cytosolic [Ca 2+ ] in inner ear spiral ganglion neurons cultured from day 4 postnatal mice and loaded with a fluorescent Ca 2+ indicator (fluo-4, -5F or -5N). IR pulse trains (200 µs, 200-250 Hz, 2-5 s) delivered via an optical fiber coupled to IR source produced a rapid, transient temperature increase of 6-11ºC (above a baseline of 24-30 ºC) and evoked transient increases in both nuclear and cytosolic [Ca 2+ ] of 0.20 - 1.4 µM, with a simultaneous reduction of [Ca 2+ ] in regions containing endoplasmic reticulum (ER). IR-induced increases in cytosolic [Ca 2+ ] continued in medium containing no added Ca 2+ ({plus minus} Ca 2+ buffers) and low [Na + ], indicating that the [Ca 2+ ] increase was mediated by release from intracellular stores. Consistent with this hypothesis, the IR-induced [Ca 2+ ] response was prolonged and eventually blocked by inhibition of ER Ca-ATPase with cyclopiazonic acid, and was also inhibited by a high concentration of ryanodine and by inhibitors of IP 3 -mediated Ca 2+ release (xestospongin C and 2-APB). The thermal sensitivity of the response suggested involvement of warm-sensitive transient receptor potential (TRP) receptors. Immunostaining of the spiral ganglion demonstrated the presence of intracellular TRPV4 and TRPM2, and the IR-induced [Ca 2+ ] increase was inhibited by TRPV4 inhibitors (HC067047 and GSK2193874). These results suggest that the temperature-sensitivity of IR-induced [Ca 2+ ] elevations is conferred by TRP channels on ER membranes, which facilitate Ca 2+ efflux into the cytosol and initiate Ca 2+ -induced Ca 2+ -release via IP 3 and ryanodine receptors.

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

PubMed

Granados Sánchez, A M; Orejuela Zapata, J F

2018-05-25

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

Performance of residents and anesthesiologists in a simulation-based skill assessment.

PubMed

Murray, David J; Boulet, John R; Avidan, Michael; Kras, Joseph F; Henrichs, Bernadette; Woodhouse, Julie; Evers, Alex S

2007-11-01

Anesthesiologists and anesthesia residents are expected to acquire and maintain skills to manage a wide range of acute intraoperative anesthetic events. The purpose of this study was to determine whether an inventory of simulated intraoperative scenarios provided a reliable and valid measure of anesthesia residents' and anesthesiologists' skill. Twelve simulated acute intraoperative scenarios were designed to assess the performance of 64 residents and 35 anesthesiologists. The participants were divided into four groups based on their training and experience. There were 31 new CA-1, 12 advanced CA-1, and 22 CA-2/CA-3 residents as well as a group of 35 experienced anesthesiologists who participated in the assessment. Each participant managed a set of simulated events. The advanced CA-1 residents, CA-2/CA-3 residents, and 35 anesthesiologists managed 8 of 12 intraoperative simulation exercises. The 31 CA-1 residents each managed 3 intraoperative scenarios. The new CA-1 residents received lower scores on the simulated intraoperative events than the other groups of participants. The advanced CA-1 residents, CA-2/CA-3 residents, and anesthesiologists performed similarly on the overall assessment. There was a wide range of scores obtained by individuals in each group. A number of the exercises were difficult for the majority of participants to recognize and treat, but most events effectively discriminated among participants who achieved higher and lower overall scores. This simulation-based assessment provided a valid method to distinguish the skills of more experienced anesthesia residents and anesthesiologists from residents in early training. The overall score provided a reliable measure of a participant's ability to recognize and manage simulated acute intraoperative events. Additional studies are needed to determine whether these simulation-based assessments are valid measures of clinical performance.

Calcium feedback mechanisms regulate oscillatory activity of a TRP-like Ca2+ conductance in C. elegans intestinal cells

PubMed Central

Estevez, Ana Y; Strange, Kevin

2005-01-01

Inositol-1,4,5-trisphosphate (IP3)-dependent Ca2+ oscillations in Caenorhabditis elegans intestinal epithelial cells regulate the nematode defecation cycle. The role of plasma membrane ion channels in intestinal cell oscillatory Ca2+ signalling is unknown. We have shown previously that cultured intestinal cells express a Ca2+-selective conductance, IORCa, that is biophysically similar to TRPM7 currents. IORCa activates slowly and stabilizes when cells are patch clamped with pipette solutions containing 10 mm BAPTA and free Ca2+ concentrations of ∼17 nm. However, when BAPTA concentration is lowered to 1 mm, IORCa oscillates. Oscillations in channel activity induced simultaneous oscillations in cytoplasmic Ca2+ levels. Removal of extracellular Ca2+ inhibited IORCa oscillations, whereas readdition of Ca2+ to the bath caused a rapid and transient reactivation of the current. Experimental manoeuvres that elevated intracellular Ca2+ blocked current oscillations. Elevation of intracellular Ca2+ in the presence of 10 mm BAPTA to block IORCa oscillations led to a dose-dependent increase in the rate of current activation. At intracellular Ca2+ concentrations of 250 nm, current activation was transient. Patch pipette solutions buffered with 1–4 mm of either BAPTA or EGTA gave rise to similar patterns of IORCa oscillations. We conclude that changes in Ca2+ concentration close to the intracellular opening of the channel pore regulate channel activity. Low concentrations of Ca2+ activate the channel. As Ca2+ enters and accumulates near the pore mouth, channel activity is inhibited. Oscillating plasma membrane Ca2+ entry may play a role in generating intracellular Ca2+ oscillations that regulate the C. elegans defecation rhythm. PMID:15961418

Ca2+-driven intestinal HCO3− secretion and CaCO3 precipitation in the European flounder in vivo: influences on acid-base regulation and blood gas transport

PubMed Central

Cooper, Christopher A.; Whittamore, Jonathan M.

2010-01-01

Marine teleost fish continuously ingest seawater to prevent dehydration and their intestines absorb fluid by mechanisms linked to three separate driving forces: 1) cotransport of NaCl from the gut fluid; 2) bicarbonate (HCO3−) secretion and Cl− absorption via Cl−/HCO3− exchange fueled by metabolic CO2; and 3) alkaline precipitation of Ca2+ as insoluble CaCO3, which aids H2O absorption). The latter two processes involve high rates of epithelial HCO3− secretion stimulated by intestinal Ca2+ and can drive a major portion of water absorption. At higher salinities and ambient Ca2+ concentrations the osmoregulatory role of intestinal HCO3− secretion is amplified, but this has repercussions for other physiological processes, in particular, respiratory gas transport (as it is fueled by metabolic CO2) and acid-base regulation (as intestinal cells must export H+ into the blood to balance apical HCO3− secretion). The flounder intestine was perfused in vivo with salines containing 10, 40, or 90 mM Ca2+. Increasing the luminal Ca2+ concentration caused a large elevation in intestinal HCO3− production and excretion. Additionally, blood pH decreased (−0.13 pH units) and plasma partial pressure of CO2 (Pco2) levels were elevated (+1.16 mmHg) at the highest Ca perfusate level after 3 days of perfusion. Increasing the perfusate [Ca2+] also produced proportional increases in net acid excretion via the gills. When the net intestinal flux of all ions across the intestine was calculated, there was a greater absorption of anions than cations. This missing cation flux was assumed to be protons, which vary with an almost 1:1 relationship with net acid excretion via the gill. This study illustrates the intimate link between intestinal HCO3− production and osmoregulation with acid-base balance and respiratory gas exchange and the specific controlling role of ingested Ca2+ independent of any other ion or overall osmolality in marine teleost fish. PMID:20130227

Ca2+-driven intestinal HCO(3)(-) secretion and CaCO3 precipitation in the European flounder in vivo: influences on acid-base regulation and blood gas transport.

PubMed

Cooper, Christopher A; Whittamore, Jonathan M; Wilson, Rod W

2010-04-01

Marine teleost fish continuously ingest seawater to prevent dehydration and their intestines absorb fluid by mechanisms linked to three separate driving forces: 1) cotransport of NaCl from the gut fluid; 2) bicarbonate (HCO(3)(-)) secretion and Cl(-) absorption via Cl(-)/HCO(3)(-) exchange fueled by metabolic CO(2); and 3) alkaline precipitation of Ca(2+) as insoluble CaCO(3), which aids H(2)O absorption). The latter two processes involve high rates of epithelial HCO(3)(-) secretion stimulated by intestinal Ca(2+) and can drive a major portion of water absorption. At higher salinities and ambient Ca(2+) concentrations the osmoregulatory role of intestinal HCO(3)(-) secretion is amplified, but this has repercussions for other physiological processes, in particular, respiratory gas transport (as it is fueled by metabolic CO(2)) and acid-base regulation (as intestinal cells must export H(+) into the blood to balance apical HCO(3)(-) secretion). The flounder intestine was perfused in vivo with salines containing 10, 40, or 90 mM Ca(2+). Increasing the luminal Ca(2+) concentration caused a large elevation in intestinal HCO(3)(-) production and excretion. Additionally, blood pH decreased (-0.13 pH units) and plasma partial pressure of CO(2) (Pco(2)) levels were elevated (+1.16 mmHg) at the highest Ca perfusate level after 3 days of perfusion. Increasing the perfusate [Ca(2+)] also produced proportional increases in net acid excretion via the gills. When the net intestinal flux of all ions across the intestine was calculated, there was a greater absorption of anions than cations. This missing cation flux was assumed to be protons, which vary with an almost 1:1 relationship with net acid excretion via the gill. This study illustrates the intimate link between intestinal HCO(3)(-) production and osmoregulation with acid-base balance and respiratory gas exchange and the specific controlling role of ingested Ca(2+) independent of any other ion or overall osmolality in marine teleost fish.

Creation of a 3Mn/1Fe cluster in the oxygen-evolving complex of photosystem II and investigation of its functional activity.

PubMed

Semin, B К; Davletshina, L N; Seibert, M; Rubin, A B

2018-01-01

Extraction of Mn cations from the oxygen-evolving complex (OEC) of Ca-depleted PSII membranes (PSII[-Ca,4Mn]) by reductants like hydroquinone (H 2 Q) occurs with lower efficiency at acidic pH (2Mn/reaction center [RC] are extracted at pH5.7) than at neutral pH (3Mn/RC are extracted at pH6.5) [Semin et al. Photosynth. Res. 125 (2015) 95]. Fe(II) also extracts Mn cations from PSII(-Ca,4Mn), but only 2Mn/RC at pH6.5, forming a heteronuclear 2Mn/2Fe cluster [Semin and Seibert, J. Bioenerg. Biomembr. 48 (2016) 227]. Here we investigated the efficiency of Mn extraction by Fe(II) at acidic pH and found that Fe(II) cations can extract only 1Mn/RC from PSII(-Ca,4Mn) membranes at pH 5.7, forming a 3Mn/1Fe cluster. Also we found that the presence of Fe cations in a heteronuclear cluster (2Mn/2Fe) increases the resistance of the remaining Mn cations to H 2 Q action, since H 2 Q can extract Mn cations from homonuclear Mn clusters of PSII(-Ca,4Mn) and PSII(-Ca,2Mn) membranes but not from the heteronuclear cluster in PSII(-Ca,2Mn,2Fe) membranes. H 2 Q also cannot extract Mn from PSII membranes obtained by incubation of PSII(-Ca,4Mn) membranes with Fe(II) cations at pH5.7, which suggests the formation of a heteronuclear 3Mn/1Fe cluster in the OEC. Functional activity of PSII with a 3Mn/1Fe cluster was investigated. PSII preparations with a 3Mn/1Fe cluster in the OEC are able to photoreduce the exogenous electron acceptor 2,6-dichlorophenolindophenol, possibly due to incomplete oxidation of water molecules as is the case with PSII(-Ca,2Mn,2Fe) samples. However, in the contrast to PSII(-Ca,2Mn,2Fe) samples PSII(-Ca,3Mn,1Fe) membranes can evolve O 2 at a low rate in the presence of exogenous Ca 2+ (at about 27% of the rate of O 2 evolution in native PSII membranes). The explanation for this phenomenon (either water splitting and production of molecular O 2 by the 3Mn/1Fe cluster or apparent O 2 evolution due to minor contamination of PSII(3Mn,1Fe) samples with PSII(-Ca,4Mn) membranes) is discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

A forward genetic screen identifies a negative regulator of rapid Ca2+-dependent cell egress (MS1) in the intracellular parasite Toxoplasma gondii

PubMed Central

McCoy, James M.; Stewart, Rebecca J.; Uboldi, Alessandro D.; Li, Dongdi; Schröder, Jan; Scott, Nicollas E.; Papenfuss, Anthony T.; Lehane, Adele M.; Foster, Leonard J.

2017-01-01

Toxoplasma gondii, like all apicomplexan parasites, uses Ca2+ signaling pathways to activate gliding motility to power tissue dissemination and host cell invasion and egress. A group of “plant-like” Ca2+-dependent protein kinases (CDPKs) transduces cytosolic Ca2+ flux into enzymatic activity, but how they function is poorly understood. To investigate how Ca2+ signaling activates egress through CDPKs, we performed a forward genetic screen to isolate gain-of-function mutants from an egress-deficient cdpk3 knockout strain. We recovered mutants that regained the ability to egress from host cells that harbored mutations in the gene Suppressor of Ca2+-dependent Egress 1 (SCE1). Global phosphoproteomic analysis showed that SCE1 deletion restored many Δcdpk3-dependent phosphorylation events to near wild-type levels. We also show that CDPK3-dependent SCE1 phosphorylation is required to relieve its suppressive activity to potentiate egress. In summary, our work has uncovered a novel component and suppressor of Ca2+-dependent cell egress during Toxoplasma lytic growth. PMID:28258212

The human carbonic anhydrase isoenzymes I and II (hCA I and II) inhibition effects of trimethoxyindane derivatives.

PubMed

Taslimi, Parham; Gulcin, Ilhami; Ozgeris, Bunyamin; Goksu, Suleyman; Tumer, Ferhan; Alwasel, Saleh H; Supuran, Claudiu T

2016-01-01

Carbonic anhydrases (CAs, EC 4.2.1.1) had six genetically distinct families described to date in various organisms. There are 16 known CA isoforms in humans. Human CA isoenzymes I and II (hCA I and hCA II) are ubiquitous cytosolic isoforms. Acetylcholine esterase (AChE. EC 3.1.1.7) is a hydrolase that hydrolyzes the neurotransmitter acetylcholine relaying the signal from the nerve. In this study, some trimethoxyindane derivatives were investigated as inhibitors against the cytosolic hCA I and II isoenzymes, and AChE enzyme. Both hCA isozymes were inhibited by trimethoxyindane derivatives in the low nanomolar range. These compounds were good hCA I inhibitors (Kis in the range of 1.66-4.14 nM) and hCA II inhibitors (Kis of 1.37-3.12 nM) and perfect AChE inhibitors (Kis in the range of 1.87-7.53 nM) compared to acetazolamide as CA inhibitor (Ki: 6.76 nM for hCA I and Ki: 5.85 nM for hCA II) and Tacrine as AChE inhibitor (Ki: 7.64 nM).

Purified TPC Isoforms Form NAADP Receptors with Distinct Roles for Ca2+ Signaling and Endolysosomal Trafficking

PubMed Central

Ruas, Margarida; Rietdorf, Katja; Arredouani, Abdelilah; Davis, Lianne C.; Lloyd-Evans, Emyr; Koegel, Heidi; Funnell, Timothy M.; Morgan, Anthony J.; Ward, John A.; Watanabe, Keiko; Cheng, Xiaotong; Churchill, Grant C.; Zhu, Michael X.; Platt, Frances M.; Wessel, Gary M.; Parrington, John; Galione, Antony

2010-01-01

Summary Intracellular Ca2+ signals constitute key elements in signal transduction. Of the three major Ca2+ mobilizing messengers described, the most potent, nicotinic acid adenine dinucleotide phosphate (NAADP) is the least well understood in terms of its molecular targets [1]. Recently, we showed that heterologous expression of two-pore channel (TPC) proteins enhances NAADP-induced Ca2+ release, whereas the NAADP response was abolished in pancreatic beta cells from Tpcn2 gene knockout mice [2]. However, whether TPCs constitute native NAADP receptors is unclear. Here we show that immunopurified endogenous TPC complexes possess the hallmark properties ascribed to NAADP receptors, including nanomolar ligand affinity [3–5]. Our study also reveals important functional differences between the three TPC isoforms. Thus, TPC1 and TPC2 both mediate NAADP-induced Ca2+ release, but the subsequent amplification of this trigger Ca2+ by IP3Rs is more tightly coupled for TPC2. In contrast, TPC3 expression suppressed NAADP-induced Ca2+ release. Finally, increased TPC expression has dramatic and contrasting effects on endolysosomal structures and dynamics, implicating a role for NAADP in the regulation of vesicular trafficking. We propose that NAADP regulates endolysosomal Ca2+ storage and release via TPCs and coordinates endoplasmic reticulum Ca2+ release in a role that impacts on Ca2+ signaling in health and disease [6]. PMID:20346675

Purified TPC isoforms form NAADP receptors with distinct roles for Ca(2+) signaling and endolysosomal trafficking.

PubMed

Ruas, Margarida; Rietdorf, Katja; Arredouani, Abdelilah; Davis, Lianne C; Lloyd-Evans, Emyr; Koegel, Heidi; Funnell, Timothy M; Morgan, Anthony J; Ward, John A; Watanabe, Keiko; Cheng, Xiaotong; Churchill, Grant C; Zhu, Michael X; Platt, Frances M; Wessel, Gary M; Parrington, John; Galione, Antony

2010-04-27

Intracellular Ca(2+) signals constitute key elements in signal transduction. Of the three major Ca(2+) mobilizing messengers described, the most potent, nicotinic acid adenine dinucleotide phosphate (NAADP) is the least well understood in terms of its molecular targets [1]. Recently, we showed that heterologous expression of two-pore channel (TPC) proteins enhances NAADP-induced Ca(2+) release, whereas the NAADP response was abolished in pancreatic beta cells from Tpcn2 gene knockout mice [2]. However, whether TPCs constitute native NAADP receptors is unclear. Here we show that immunopurified endogenous TPC complexes possess the hallmark properties ascribed to NAADP receptors, including nanomolar ligand affinity [3-5]. Our study also reveals important functional differences between the three TPC isoforms. Thus, TPC1 and TPC2 both mediate NAADP-induced Ca(2+) release, but the subsequent amplification of this trigger Ca(2+) by IP(3)Rs is more tightly coupled for TPC2. In contrast, TPC3 expression suppressed NAADP-induced Ca(2+) release. Finally, increased TPC expression has dramatic and contrasting effects on endolysosomal structures and dynamics, implicating a role for NAADP in the regulation of vesicular trafficking. We propose that NAADP regulates endolysosomal Ca(2+) storage and release via TPCs and coordinates endoplasmic reticulum Ca(2+) release in a role that impacts on Ca(2+) signaling in health and disease [6]. Copyright © 2010 Elsevier Ltd. All rights reserved.

The effect of bulk composition on the solidus of carbonated eclogite from partial melting experiments at 3 GPa

NASA Astrophysics Data System (ADS)

Dasgupta, Rajdeep; Hirschmann, Marc M.; Dellas, Nikki

2005-05-01

To explore the effect of bulk composition on the solidus of carbonated eclogite, we determined near-solidus phase relations at 3 GPa for four different nominally anhydrous, carbonated eclogites. Starting materials (SLEC1, SLEC2, SLEC3, and SLEC4) were prepared by adding variable proportions and compositions of carbonate to a natural eclogite xenolith (66039B) from Salt Lake crater, Hawaii. Near-solidus partial melts for all bulk compositions are Fe Na calcio-dolomitic and coexist with garnet + clinopyroxene + ilmenite ± calcio-dolomitic solid solution. The solidus for SLEC1 (Ca#=100 × molar Ca/(Ca + Mg + FeT)=32, 1.63 wt% Na2O, and 5 wt% CO2) is bracketed between 1,050°C and 1,075°C (Dasgupta et al. in Earth Planet Sci Lett 227:73 85, 2004), whereas initial melting for SLEC3 (Ca# 41, 1.4 wt% Na2O, and 4.4 wt% CO2) is between 1,175°C and 1,200°C. The solidus for SLEC2 (Ca# 33, 1.75 wt% Na2O, and 15 wt% CO2) is estimated to be near 1,100°C and the solidus for SLEC3 (Ca# 37, 1.47 wt% Na2O, and 2.2 wt% CO2) is between 1,100°C and 1,125°C. Solidus temperatures increase with increasing Ca# of the bulk, owing to the strong influence of the calcite magnesite binary solidus-minimum on the solidus of carbonate bearing eclogite. Bulk compositions that produce near-solidus crystalline carbonate closer in composition to the minimum along the CaCO3-MgCO3 join have lower solidus temperatures. Variations in total CO2 have significant effect on the solidus if CO2 is added as CaCO3, but not if CO2 is added as a complex mixture that maintains the cationic ratios of the bulk-rock. Thus, as partial melting experiments necessarily have more CO2 than that likely to be found in natural carbonated eclogites, care must be taken to assure that the compositional shifts associated with excess CO2 do not unduly influence melting behavior. Near-solidus dolomite and calcite solid solutions have higher Ca/(Ca + Mg) than bulk eclogite compositions, owing to Ca Mg exchange equilibrium between carbonates and silicates. Carbonates in natural mantle eclogite, which have low bulk CO2 concentration, will have Ca/Mg buffered by reactions with silicates. Consequently, experiments with high bulk CO2 may not mimic natural carbonated eclogite phase equilibria unless care is taken to ensure that CO2 enrichment does not result in inappropriate equilibrium carbonate compositions. Compositions of eclogite-derived carbonate melt span the range of natural carbonatites from oceanic and continental settings. Ca#s of carbonatitic partial melts of eclogite vary significantly and overlap those of partial melts of carbonated lherzolite, however, for a constant Ca-content, Mg# of carbonatites derived from eclogitic sources are likely to be lower than the Mg# of those generated from peridotite.

The Endoplasmic Reticulum: A Central Player in Cell Signalling and Protein Synthesis

NASA Astrophysics Data System (ADS)

Llewelyn Roderick, H.; Berridge, Michael J.; Bootman, Martin D.

In addition to being the principle intracellular Ca 2+ store, the endoplasmic reticulum (ER) is the initial site of synthesis and folding of membrane and secretory proteins. These two roles of the ER are intimately linked. First, the function of many proteins involved in Ca 2+ handling are modulated by Ca 2+ and second, ER lumenal Ca 2+ modulates protein synthesis and folding. Within the ER, Ca 2+ is stored by low affinity high capacity Ca 2+ binding proteins and is maintained at a free concentration between 0.1 and 1 μM relative to 0.1 μM cytosolic Ca 2+. This concentration gradient is maintained by the action of the Sarco-Endoplasmic Reticulum ATPases (SERCa) which hydrolyse ATP to pump Ca 2+ into the ER. Following stimulation Ca 2+ is released from the ER through several classes of ligand gated channels. The most well characterized of these being the inositol 1,4,5-trisphosphate receptor ( IP 3 R) and the Ryanodine receptor (RyR) families of proteins. This release of Ca 2+ results in a drop of ER free Ca 2+ to levels as low as 10 μM. This decrease in lumenal Ca 2+ inhibits further release through the channels and increases the rate of re-sequestration of Ca 2+ into the ER by the SERCa pumps. Under these conditions, in addition to effects on Ca 2+ handling proteins, protein synthesis is inhibited, chaperones dissociate from their substrates, secondary modifications of proteins are inhibited and the retention of many proteins within the ER is lost. Furthermore, a signalling cascade resulting in the up-regulation of many proteins involved in protein folding and Ca 2+ homeostasis is initiated. This review will focus on the proteins involved in the regulation ER lumenal Ca 2+ and the role of ER lumenal Ca 2+ in cell signalling and protein synthesis.

Extracellular carbonic anhydrase in the dogfish, Squalus acanthias: a role in CO2 excretion.

PubMed

Gilmour, K M; Perry, S F; Bernier, N J; Henry, R P; Wood, C M

2001-01-01

In Pacific spiny dogfish (Squalus acanthias), plasma CO(2) reactions have access to plasma carbonic anhydrase (CA) and gill membrane-associated CA. The objectives of this study were to characterise the gill membrane-bound CA and investigate whether extracellular CA contributes significantly to CO(2) excretion in dogfish. A subcellular fraction containing membrane-associated CA activity was isolated from dogfish gills and incubated with phosphatidylinositol-specific phospholipase C. This treatment caused significant release of CA activity from its membrane association, a result consistent with identification of the dogfish gill membrane-bound CA as a type IV isozyme. Inhibition constants (K(i)) against acetazolamide and benzolamide were 4.2 and 3.5 nmol L(-1), respectively. Use of a low dose (1.3 mg kg(-1) or 13 micromol L(-1)) of benzolamide to selectively inhibit extracellular CA in vivo caused a significant 30%-60% reduction in the arterial-venous total CO(2) concentration difference, a significant increase in Pco(2) and an acidosis, without affecting blood flow or ventilation. No effect of benzolamide on any measure of CO(2) excretion was detected in rainbow trout (Oncorhynchus mykiss). These results indicate that extracellular CA contributes substantially to CO(2) excretion in the dogfish, an elasmobranch, and confirm that CA is not available to plasma CO(2) reactions in rainbow trout, a teleost.

Endothelial Ca+-activated K+ channels in normal and impaired EDHF-dilator responses--relevance to cardiovascular pathologies and drug discovery.

PubMed

Grgic, Ivica; Kaistha, Brajesh P; Hoyer, Joachim; Köhler, Ralf

2009-06-01

The arterial endothelium critically contributes to blood pressure control by releasing vasodilating autacoids such as nitric oxide, prostacyclin and a third factor or pathway termed 'endothelium-derived hyperpolarizing factor' (EDHF). The nature of EDHF and EDHF-signalling pathways is not fully understood yet. However, endothelial hyperpolarization mediated by the Ca(2+)-activated K(+) channels (K(Ca)) has been suggested to play a critical role in initializing EDHF-dilator responses in conduit and resistance-sized arteries of many species including humans. Endothelial K(Ca) currents are mediated by the two K(Ca) subtypes, intermediate-conductance K(Ca) (KCa3.1) (also known as, a.k.a. IK(Ca)) and small-conductance K(Ca) type 3 (KCa2.3) (a.k.a. SK(Ca)). In this review, we summarize current knowledge about endothelial KCa3.1 and KCa2.3 channels, their molecular and pharmacological properties and their specific roles in endothelial function and, particularly, in the EDHF-dilator response. In addition we focus on recent experimental evidences derived from KCa3.1- and/or KCa2.3-deficient mice that exhibit severe defects in EDHF signalling and elevated blood pressures, thus highlighting the importance of the KCa3.1/KCa2.3-EDHF-dilator system for blood pressure control. Moreover, we outline differential and overlapping roles of KCa3.1 and KCa2.3 for EDHF signalling as well as for nitric oxide synthesis and discuss recent evidence for a heterogeneous (sub) cellular distribution of KCa3.1 (at endothelial projections towards the smooth muscle) and KCa2.3 (at inter-endothelial borders and caveolae), which may explain their distinct roles for endothelial function. Finally, we summarize the interrelations of altered KCa3.1/KCa2.3 and EDHF system impairments with cardiovascular disease states such as hypertension, diabetes, dyslipidemia and atherosclerosis and discuss the therapeutic potential of KCa3.1/KCa2.3 openers as novel types of blood pressure-lowering drugs.

Thermoelectric transport properties of Ca3Co4- x Ni x O9+ δ oxide materials

NASA Astrophysics Data System (ADS)

Park, K.; Cha, J. S.; Nam, S. W.; Choi, S.-M.; Seo, W.-S.; Lee, S.; Lim, Y. S.

2016-01-01

Nano-sized Ca3Co4- x Ni x O9+ δ (0 ≤ x ≤ 0.3) thermoelectric powders are synthesized by using the solution combustion method, with aspartic acid as a combustion fuel. The synthesized Ca3Co4- x Ni x O9+ δ nano-sized powders exhibit a spherical-like shape and a smooth surface. Higher Ni content results in a smaller grain size and a higher porosity, resulting in a decrease in the electrical conductivity. However, the Seebeck coefficient of Ni-added Ca3Co4O9 is much higher than that of Ca3Co4O9. The highest power factor (1.4 × 10-4 Wm-1K-2), which is more than nine times larger than that of Ca3Co4O9, is attained for Ca3Co0.38Ni0.2O9+ δ at 800 °C. The addition of a small amount of Ni is highly effective in improving the thermoelectric properties of Ca3Co4O9. We believe that Ca3Co4- x Ni x O9+ δ is a potential p-type thermoelectric material for renewable energy conversion.

Site overview. Part 1 of 3part panorama with nos. CA27022 ...

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

Site overview. Part 1 of 3-part panorama with nos. CA-2702-2 and CA-2707-3. Southern LTA ship hangar (building 28; hangar no. 2 in distant center of photograph. Seen from roadway leading to northern LTA ship hangar (building 29; hangar no. 1) landing pad. Looking 208 SSW. - Marine Corps Air Station Tustin, East of Red Hill Avenue between Edinger Avenue & Barranca Parkway, Tustin, Orange County, CA

Site overview. Part 1 of 3part panorama with nos. CA27022 ...

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

Site overview. Part 1 of 3-part panorama with nos. CA-2702-2 and CA-2707-3. Southern LTA ship hangar (building 28; hangar no. 2 in distant center of photograph. Seen from roadway leading to northern LTA ship hangar (building 29; hangar no. 1) landing pad. Looking 208 SSW. - Marine Corps Air Station Tustin, Northern Lighter Than Air Ship Hangar, Meffett Avenue & Maxfield Street, Tustin, Orange County, CA

Calculated and measured [Ca(2+)] in buffers used to calibrate Ca(2+) macroelectrodes.

PubMed

McGuigan, John A S; Stumpff, Friederike

2013-05-01

The ionized concentration of calcium in physiological buffers ([Ca(2+)]) is normally calculated using either tabulated constants or software programs. To investigate the accuracy of such calculations, the [Ca(2+)] in EGTA [ethylene glycol-bis(β-aminoethylether)-N,N,N|,N|-tetraacetic acid], BAPTA [1,2-bis(o-aminophenoxy) ethane-N,N,N|,N|-tetraacetic acid], HEDTA [N-(2-hydroxyethyl)-ethylenediamine-N,N|,N|-triacetic acid], and NTA [N,N-bis(carboxymethyl)glycine] buffers was estimated using the ligand optimization method, and these measured values were compared with calculated values. All measurements overlapped in the pCa range of 3.51 (NTA) to 8.12 (EGTA). In all four buffer solutions, there was no correlation between measured and calculated values; the calculated values differed among themselves by factors varying from 1.3 (NTA) to 6.9 (EGTA). Independent measurements of EGTA purity and the apparent dissociation constants for HEDTA and NTA were not significantly different from the values estimated by the ligand optimization method, further substantiating the method. Using two calibration solutions of pCa 2.0 and 3.01 and seven buffers in the pCa range of 4.0-7.5, calibration of a Ca(2+) electrode over the pCa range of 2.0-7.5 became a routine procedure. It is proposed that such Ca(2+) calibration/buffer solutions be internationally defined and made commercially available to allow the precise measurement of [Ca(2+)] in biology. Copyright © 2013 Elsevier Inc. All rights reserved.

Stimulatory and inhibitory effects of PKC isozymes are mediated by serine/threonine PKC sites of the Cav2.3α1 subunits.

PubMed

Rajagopal, Senthilkumar; Burton, Brittney K; Fields, Blanche L; El, India O; Kamatchi, Ganesan L

2017-05-01

Protein kinase C (PKC) isozymes modulate voltage-gated calcium (Ca v ) currents through Ca v 2.2 and Ca v 2.3 channels by targeting serine/threonine (Ser/Thr) phosphorylation sites of Ca v α 1 subunits. Stimulatory (Thr-422, Ser-2108 and Ser-2132) and inhibitory (Ser-425) sites were identified in the Ca v 2.2α 1 subunits to PKCs βII and ε. In the current study, we investigated if the homologous sites of Ca v 2.3α 1 subunits (stimulatory: Thr-365, Ser-1995 and Ser-2011; inhibitory: Ser-369) behaved in similar manner. Several Ala and Asp mutants were constructed in Ca v 2.3α 1 subunits in such a way that the Ser/Thr sites can be examined in isolation. These mutants or WT Ca v 2.3α 1 along with auxiliary β 1b and α 2 /δ subunits were expressed in Xenopus oocytes and the effects of PKCs βII and ε studied on the barium current (I Ba ). Among these sites, stimulatory Thr-365 and Ser-1995 and inhibitory Ser-369 behaved similar to their homologs in Ca v 2.2α 1 subunits. Furthermore PKCs produced neither stimulation nor inhibition when stimulatory Thr-365 or Ser-1995 and inhibitory Ser-369 were present together. However, the PKCs potentiated the I Ba when two stimulatory sites, Thr-365 and Ser-1995 were present together, thus overcoming the inhibitory effect of Ser-369. Taken together net PKC effect may be the difference between the responses of the stimulatory and inhibitory sites. Copyright © 2017 Elsevier Inc. All rights reserved.

Investigations of the effect of nonmagnetic Ca substitution for magnetic Dy on spin-freezing in Dy₂Ti₂O₇.

PubMed

Anand, V K; Tennant, D A; Lake, B

2015-11-04

Physical properties of partially Ca substituted hole-doped Dy2Ti2O7 have been investigated by ac magnetic susceptibility χ(ac)(T), dc magnetic susceptibility χ(T), isothermal magnetization M(H) and heat capacity C(p)(T) measurements on Dy1.8Ca0.2Ti2O7. The spin-ice system Dy2Ti2O7 exhibits a spin-glass type freezing behavior near 16 K. Our frequency dependent χ(ac)(T) data of Dy1.8Ca0.2Ti2O7 show that the spin-freezing behavior is significantly influenced by Ca substitution. The effect of partial nonmagnetic Ca(2+) substitution for magnetic Dy(3+) is similar to the previous study on nonmagnetic isovalent Y(3+) substituted Dy(2-x)Y(x) Ti2O7 (for low levels of dilution), however the suppression of spin-freezing behavior is substantially stronger for Ca than Y. The Cole-Cole plot analysis reveals semicircular character and a single relaxation mode in Dy1.8Ca0.2Ti2O7 as for Dy2Ti2O7. No noticeable change in the insulating behavior of Dy2Ti2O7 results from the holes produced by 10% Ca(2+) substitution for Dy(3+) ions.

[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.

Down-regulation of CaV1.2 channels during hypertension: how fewer CaV1.2 channels allow more Ca2+ into hypertensive arterial smooth muscle

PubMed Central

Tajada, Sendoa; Cidad, Pilar; Colinas, Olaia; Santana, L Fernando; López-López, José R; Pérez-García, M Teresa

2013-01-01

Hypertension is a clinical syndrome characterized by increased arterial tone. Although the mechanisms are varied, the generally accepted view is that increased CaV1.2 channel function is a common feature of this pathological condition. Here, we investigated the mechanisms underlying vascular dysfunction in a mouse model of genetic hypertension. Contrary to expectation, we found that whole-cell CaV1.2 currents (ICa) were lower in hypertensive (BPH line) than normotensive (BPN line) myocytes. However, local CaV1.2 sparklet activity was higher in BPH cells, suggesting that the relatively low ICa in these cells was produced by a few hyperactive CaV1.2 channels. Furthermore, our data suggest that while the lower expression of the pore-forming α1c subunit of CaV1.2 currents underlies the lower ICa in BPH myocytes, the increased sparklet activity was due to a different composition in the auxiliary subunits of the CaV1.2 complexes. ICa currents in BPN cells were produced by channels composed of α1c/α2δ/β3 subunits, while in BPH myocytes currents were probably generated by the opening of channels formed by α1c/α2δ/β2 subunits. In addition, Ca2+ sparks evoked large conductance, Ca2+-activated K+ (BK) currents of lower magnitude in BPH than in BPN myocytes, because BK channels were less sensitive to Ca2+. Our data are consistent with a model in which a decrease in the global number of CaV1.2 currents coexist with the existence of a subpopulation of highly active channels that dominate the resting Ca2+ influx. The decrease in BK channel activity makes the hyperpolarizing brake ineffective and leads BPH myocytes to a more contracted resting state. PMID:24167226

(CaO)nIrO2 (n = 1, 2, 4) family: Chemical scissors effects of CaO on structural characteristics correlated to physical properties. Ab initio study

NASA Astrophysics Data System (ADS)

Matar, Samir F.; Etourneau, Jean

2017-11-01

Based on crystal chemistry analysis within Ca-Ir-O ternary, the generic (CaO)nIrO2 formula leading to CaIrO3 for n = 1, Ca2IrO4 for n = 2 and Ca4IrO6 for n = 4 actual chemical compounds show significant structural changes regarding the spatial arrangement of IrO6 octahedra whereby increasing amounts of CaO act as 'chemical scissor' decreasing the dimensionality of stacking octahedra from 3D (IrO2) to 0D (Ca4IrO6). This is accompanied by changes in the electronic structure investigated within density functional theory. Such changes are particularly exhibited by linear increase of Ir density of states at the Fermi level revealing increasing localization of d states with crystal field effects. Eventually only for Ca4IrO6 a magnetic instability occurs in non magnetic configuration. Spin polarized calculations lead to development of small magnitude but finite magnetization on Ir with M 0.50 μB totally polarized along minority spin channel ↓.

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

PubMed

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

2005-08-01

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

Disbalance of calcium regulation-related genes in broiler hearts induced by selenium deficiency.

PubMed

Zhang, Ziwei; Liu, Man; Guan, Zhenqiong; Yang, Jie; Liu, Zhonghua; Xu, Shiwen

2017-06-01

Dietary selenium (Se) deficiency may influence the calcium (Ca) homeostasis in broilers. Our objective was to investigate the effects of Se deficiency on Ca regulation-related genes in broiler hearts. In the present study, 1-day-old broilers were fed either a commercial diet (as control group) with 0.15 mg/kg Se or a Se-deficient diet (as L group) with 0.033 mg/kg Se for 35 days. We examined the mRNA expression levels of 15 Ca regulation-related genes (ITPR 1, ITPR 2, ITPR3, RyR2, RyR3, SERCA1s, SLC8A1, PMCA1, CACNA1S, TRPC1, TRPC3, stromal interacting molecule 1, ORAI1, calmodulin (CaLM) and calreticulin (CRT) in broiler hearts. Then, Kyoto Encyclopedia of Genes and Genomes analysis, protein-protein interactions (PPI) analysis and correlation analysis were performed to analyse the relationships between these genes. The results showed that the mRNA expression levels of ITPR 1, ITPR 2, RyR2, RyR3, SERCA1s, SLC8A1, PMCA1, CACNA1S, CaLM and CRT were generally decreased by Se deficiency, while mRNA expression levels of TRPC1, TRPC3, stromal interacting molecule 1, ORAI1 and ITPR3 were increased by Se deficiency. Kyoto Encyclopedia of Genes and Genomes and PPI analysis showed that these Ca regulation-related genes are involved in the Ca signalling pathway and a total of 15 PPIs with a combined score of >0.4 were obtained. In conclusion, the results demonstrated that Se deficiency might cause heart injury via modulating the Ca-related pathway genes, and then induce Ca 2+ overload in the heart of broilers.

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

PubMed

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

2004-11-03

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

Raman spectroscopy and x-ray diffraction of sp 3 CaC O 3 at lower mantle pressures

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

Lobanov, Sergey S.; Dong, Xiao; Martirosyan, Naira S.

The exceptional ability of carbon to form sp 2 and sp 3 bonding states leads to a great structural and chemical diversity of carbon-bearing phases at nonambient conditions. Here we use laser-heated diamond-anvil cells combined with synchrotron x-ray diffraction, Raman spectroscopy, and first-principles calculations to explore phase transitions in CaC O 3 at P > 40 GPa . We find that postaragonite CaC O 3 transforms to the previously predicted P 2 1 / c CaC O 3 with sp 3 -hybridized carbon at 105 GPa ( ~ 30 GPa higher than the theoretically predicted crossovermore » pressure). The lowest-enthalpy transition path to P2 1 / c CaC O 3 includes reoccurring sp 2 and sp 3 CaC O 3 intermediate phases and transition states, as revealed by our variable-cell nudged-elastic-band simulation. Raman spectra of P 2 1 / c CaC O 3 show an intense band at 1025 c m -1 , which we assign to the symmetric C-O stretching vibration based on empirical and first-principles calculations. This Raman band has a frequency that is ~ 20 % low-ymmetric C-O stretching in sp 2 CaC O 3 due to the C-O bond length increase across the sp 2 ~ sp 3 transition and can be used as a fingerprint of tetrahedrally coordinated carbon in other carbonates.« less

Trichloroethylene decomposition and in-situ dry sorption of Cl-products by calcium oxides prepared from hydrated limes.

PubMed

Gotoh, Yoshimi; Iwata, Goichi; Choh, Kyaw; Kubota, Mitsuhiro; Matsuda, Hitoki

2011-10-01

A comparison of CaOs produced by calcining two types of hydrated lime and calcium carbonate was made for decomposition of trichloroethylene and in-situ dry sorption of the decomposed Cl-products using a lab-scale gas flow type tubular packed bed reactor. About 20 mg of CaO sample was mixed with about 2 g of Al2O3 particles and packed in the reactor and allowed to react with a flowing standard gas containing 500 ppm of C2HCl3 (N2 balance) at 673 and 873 K, under the condition that the reaction of CaO with C2HCl3 might be completed within a few hours. It was found that no thermal decomposition of C2HCl3 at or below 673 K was observed in a reactor packed only with Al2O3 particles. However, a considerable amount of decomposition of C2HCl3 was obtained in a reactor packed with CaO and Al2O3, even at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)2 at 673 K, decomposition of 0.42 mol of C2HCl3 and in-situ absorption product of 0.53 mol of CaCl2 were obtained. At 873 K, about 46% of C2HCl3 was thermally decomposed. The total amount of C2HCl3 decomposed in CaO-Al2O3 particle bed at 873 K became nearly twice larger than that at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)2 at 873 K, decomposition of 0.59 mol of C2HCl3 and in-situ absorption product of 0.67 mol of CaCl2 were obtained. Small amounts of C2Cl2, C2Cl4, CCl4, etc. were detected during decomposition of C2HCl3 at 673 and 873 K. It was recognized that the data on decomposition of C2HCl3 as well as in-situ dry sorption of Cl-products in CaO particle bed were correlated with specific surface area of the CaO employed. Copyright © 2011 Elsevier Ltd. All rights reserved.

[Analysis on the change of genotype of enteroviruses associated hand, foot and mouth disease in Beijing during 2013 to 2014].

PubMed

Song, Qinwei; Huang, Hui; Deng, Jie; Zhao, Linqing; Deng, Li; Sun, Yu; Wang, Fang; Oian, Yuan; Zhu, Runan

2015-08-01

To analyze the genotype, epidemic pattern and the characteristics of the disease of enteroviruses during the epidemic season of hand, foot and mouth disease (HMFD) in children from 2013 to 2014 in Beijing to provide the scientific evidence for prevention and treatment of HFMD. During April to September in 2013 and March to October in 2014, a total of 977 throat swabs were collected from children who visited the Children's Hospital Affiliated to Capital Institute of Pediatrics, including 147 from patients with HFMD in 2013, 343 with HFMD, 201 with atypical HFMD, 83 with herpangina, 25 with fever with convulsions, 64 fever with rash and 114 with rash in 2014. Enteroviruses universal type (EV), Enteroviruses type 71 (EV71) and Coxsackievirus group A 16 (CA16) were detected by real-time RT-PCR respectively. The nucleic acid of specimens which were identified with non-EV71, non-CA16 was tested by nested PCR and analyzed by VP1 sequencing. The detection rate and epidemic pattern of different genotypes of enterovirus were analyzed among different age groups and between 2013 and 2014. Of 977 throat swabs, 80. 1% samples were detected positive for enteroviruses. The positive rates of CA16, EV71, CA6, CA10, CA4 and other EVs were 25. 6% (250/977), 18. 9% (185/977), 20. 0% (195/977), 5. 0% (49/977), 1.5% (15/977) and 9.1% (89/977), respectively. Twenty six of the 89 other EVs included CA2, CA5, CA8, CA9, CA12, CA14, CB2, CB5, E6, E9 and E25, each genotype of which was no more than 3. The nucleotide homologies shared among CA6, CA10 and CA4 strains between 2013 and 2014 were 94. 3% - 100%, 93. 8% - 99. 1% and 92.7% - 99. 8%, respectively. The positive rates of ≤1 year group were 71. 1% (106/149), which was lower than that of other age groups (all P <0. 05), but similar to that of >5 year group (χ2 =1. 181,P = 0. 277). In 2013, the positive rate of EV was 85. 7% (126/147) and the predominant genotype was CA6 54. 8% (69/126), followed by CA16 20. 6% (26/126) and EV71 11. 9% (15/126). In 2014, the positive rate of EV was 85. 4% (293/343) in the 343 children with HFMD, the predominant genotypes were CA16 with the positive rate of 42. 7% (125/293), EV71 with 38. 2% (112/293) and CA6 with only 11. 3% (33/293). In 2014, the positive rates of EV in 201 atypical HFMD, 83 herpangina, 25 fever with convulsions, 64 fever with rash and 114 rash were 83. 6% (168/201), 80. 7% (67/83), 76. 0% (19/25), 64. 1% (41/64) and 60. 5% (69/114), respectively. All genotypes of enteroviruses peaked mainly during May to August every year, but there were no obvious epidemiological pattern about each genotype. CA6 became the main causative agent of HFMD in 2013, however, CA16 and EV71 predominated again in 2014 in Beijing. The clinical manifestations caused by CA6, CA10, CA4 and other genotype of enteroviruses differed from EV71 and CA16. Besides EV71 and CA16, more attention should be paid to CA6, CA10, CA4 and other type of enteroviruses.

CaMKIIβ Association with the Actin Cytoskeleton Is Regulated by Alternative Splicing

PubMed Central

O'Leary, Heather; Lasda, Erika

2006-01-01

The Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII)β has morphogenic functions in neurons not shared by the α isoform. CaMKIIβ contains three exons (v1, v3, and v4) not present in the CaMKIIα gene, and two of these exons (v1 and v4) are subject to differential alternative splicing. We show here that CaMKIIβ, but not α, mediated bundling of F-actin filaments in vitro. Most importantly, inclusion of exon v1 was required for CaMKIIβ association with the F-actin cytoskeleton within cells. CaMKIIβe, which is the dominant variant around birth and lacks exon v1 sequences, failed to associate with F-actin. By contrast, CaMKIIβ′, which instead lacks exon v4, associated with F-actin as full-length CaMKIIβ. Previous studies with CaMKIIβ mutants have indicated a role of nonstimulated kinase activity in enhancing dendritic arborization. Here, we show that F-actin–targeted CaMKIIβ, but not α, was able to phosphorylate actin in vitro even by nonstimulated basal activity in absence of Ca2+/CaM. In rat pancreatic islets and in skeletal muscle, the actin-associated CaMKIIβ′ and βM were the predominant variants, respectively. Thus, cytoskeletal targeting may mediate functions of CaMKIIβ variants also outside the nervous system. PMID:16928958

Enhanced expression of extracellular calcium sensing receptor in monocyte-differentiated versus undifferentiated HL-60 cells: potential role in regulation of a nonselective cation channel

NASA Technical Reports Server (NTRS)

Yamaguchi, T.; Ye, C.; Chattopadhyay, N.; Sanders, J. L.; Vassilev, P. M.; Brown, E. M.; O'Malley, B. W. (Principal Investigator)

2000-01-01

Human promyelocytic leukemia cells (HL-60) have been used widely as a model for studying the differentiation of hematopoietic progenitor cells in vitro. After treatment with phorbol-12-myristate-13-acetate (PMA) or 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], HL-60 cells differentiate into cells with the phenotype of monocytes/macrophages. We previously showed that peripheral blood monocytes and the murine J774 monocytic cell line express the CaR, and myeloid progenitors in the bone marrow and myeloid cells in peripheral blood other than monocytes express lower levels of the CaR. Therefore, we investigated whether undifferentiated HL-60 cells express a functional G protein-coupled, extracellular calcium (Ca(2+)(o))-sensing receptor (CaR) and if the expression of the CaR increases as these cells differentiate along the monocytic lineage. The use of reverse transcription-polymerase chain reaction (RT-PCR) with CaR-specific primers, followed by sequencing of the amplified products, identified an authentic CaR transcript in undifferentiated HL-60 cells. Both immunocytochemistry and Western blot analysis using a CaR-specific antiserum detected low levels of CaR protein expression in undifferentiated HL-60 cells. The levels of CaR protein increased considerably following treatment of the cells with PMA (50 nM) or 1,25(OH)(2)D(3) (100 nM) for 5 days. Northern analysis using a CaR-specific riboprobe identified CaR transcripts in undifferentiated HL-60 cells, but CaR mRNA levels did not change appreciably after treatment with either agent, suggesting that upregulation of CaR protein occurs at a translational level. PMA-treated HL-60 cells expressed a nonselective cation channel (NCC), and the calcimimetic CaR activator, NPS R-467, but not its less active stereoisomer, NPS S-467, as well as the polycationic CaR agonist, neomycin, activated this NCC, demonstrating that the CaR expressed in these cells is functionally active. Therefore, HL-60 cells exhibit an increase in CaR protein expression, occurring at a translational level during their differentiation into cells with a monocyte/macrophage phenotype in response to treatment with PMA or 1, 25(OH)(2)D(3), which is functionally linked to activation of a nonselective cation channel.

Calcium homeostasis in the outer segments of retinal rods from the tiger salamander.

PubMed Central

Lagnado, L; Cervetto, L; McNaughton, P A

1992-01-01

1. The processes regulating intracellular calcium in the outer segments of salamander rods have been investigated. The main preparation used was the isolated rod loaded with the Ca(2+)-sensitive photoprotein aequorin, from which outer segment membrane current and free [Ca2+]i could be recorded simultaneously. Two other preparations were also used: outer segment membrane current was recorded from intact, isolated rods using a suction pipette, and from detached outer segments using a whole-cell pipette. 2. Measurements of free intracellular [Ca2+] in Ringer solution were obtained from two aequorin-loaded rods. Mean [Ca2+]i in darkness was 0.41 microM, and after a bright flash [Ca2+]i fell to below detectable levels ( < 0.3 microM). No release of intracellular Ca2+ by a bright flash of light could be detected ( < 0.2 microM). 3. Application of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) caused an increase in the size of the light-sensitive current and a rise in [Ca2+]i, but application of IBMX either when the light-sensitive channels had been closed by a bright light or in the absence of external Ca2+ caused no detectable rise in [Ca2+]i. It is concluded that IBMX increases [Ca2+]i by opening light-sensitive channels, and does not release Ca2+ from stores within the outer segment. 4. Removal of external Na+ caused a rise in [Ca2+]i to around 2 microM and completely suppressed the light-sensitive current. 5. The Na(+)-Ca2+, K+ exchange current in aequorin-loaded rods was activated in first-order manner by internal free calcium, with a mean Michaelis constant, KCa, of 1.6 microM. 6. The KCa of the Na(+)-Ca2+, K+ exchange was increased by elevating internal [Na+]. 7. The Michaelis relation between [Ca2+]i and the activity of the Na(+)-Ca2+, K+ exchange was used to calculate the change in [Ca2+]i occurring during the response to a bright light. In aequorin-loaded rods in Ringer solution the mean change in free [Ca2+]i after a bright flash was 0.34 microM. In these rods 10% of the dark current was carried by Ca2+. 8. Most of the calcium entering the outer segment was taken up rapidly and reversibly by buffer systems. The time constant of equilibration between free and rapidly bound Ca2+ was less than 20 ms. No slow component of calcium uptake was detected. 9. Two components of calcium buffering could be distinguished in the outer segments of aequorin-loaded rods.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1282928

Probing the limit of magnesium uptake by β-tricalcium phosphate in biphasic mixtures formed from calcium deficient apatites

NASA Astrophysics Data System (ADS)

Kumar, P. Nandha; Mishra, Sandeep K.; Kannan, S.

2015-11-01

A series of magnesium doped non-stoichiometric calcium deficient apatites were synthesized through an aqueous precipitation route. The resultant structural changes during heat treatment were investigated by X-ray diffraction, Raman and FT-IR spectroscopy and Rietveld refinement. The results confirmed the formation of biphasic mixtures comprising Ca10(PO4)6(OH)2 and β-Ca3(PO4)2 after heat treatment at 1000 °C with the preferential occupancy of Mg2+ at the crystal lattice of β-Ca3(PO4)2. The concentration of Mg2+ uptake in β-Ca3(PO4)2 is limited till reaching the stoichiometric ratio of (Ca+Mg)/P=1.67 and beyond this stoichiometric value [(Ca+Mg)/P>1.67], Mg2+ precipitates as Mg(OH)2 and thereafter gets converted to MgO during heat treatment. Any kind of Mg2+ uptake in the crystal lattice of Ca10(PO4)6(OH)2 is discarded from the investigation.

Thrombospondin-1 and Angiotensin II Inhibit Soluble Guanylyl Cyclase through an Increase in Intracellular Calcium Concentration

PubMed Central

Ramanathan, Saumya; Mazzalupo, Stacy; Boitano, Scott; Montfort, William R.

2011-01-01

Nitric Oxide (NO) regulates cardiovascular hemostasis by binding to soluble guanylyl cyclase (sGC), leading to cGMP production, reduced cytosolic calcium concentration ([Ca2+]i) and vasorelaxation. Thrombospondin-1 (TSP-1), a secreted matricellular protein, was recently discovered to inhibit NO signaling and sGC activity. Inhibition of sGC requires binding to cell-surface receptor CD47. Here, we show that a TSP-1 C-terminal fragment (E3CaG1) readily inhibits sGC in Jurkat T cells, and that inhibition requires an increase in [Ca2+]i. Using flow cytometry, we show that E3CaG1 binds directly to CD47 on the surface of Jurkat T cells. Using digital imaging microscopy on live cells, we further show that E3CaG1 binding results in a substantial increase in [Ca2+]i, up to 300 nM. Addition of angiotensin II, a potent vasoconstrictor known to increase [Ca2+]i, also strongly inhibits sGC activity. sGC isolated from calcium-treated cells or from cell-free lysates supplemented with Ca2+ remains inhibited, while addition of kinase inhibitor staurosporine prevents inhibition, indicating inhibition is likely due to phosphorylation. Inhibition is through an increase in Km for GTP, which rises to 834 µM for the NO-stimulated protein, a 13-fold increase over the uninhibited protein. Compounds YC-1 and BAY 41-2272, allosteric stimulators of sGC that are of interest for treating hypertension, overcome E3CaG1-mediated inhibition of NO-ligated sGC. Taken together, these data suggest that sGC not only lowers [Ca2+]i in response to NO, inducing vasodilation, but is also inhibited by high [Ca2+]i, providing a fine balance between signals for vasodilation and vasoconstriction. PMID:21823650

Life-threatening hemolytic anemia due to an autoanti-Pr cold agglutinin: evidence that glycophorin A antibodies may induce lipid bilayer exposure and cation permeability independent of agglutination.

PubMed

Brain, Michael C; Ruether, Bernard; Valentine, Karen; Brown, Christopher; ter Keurs, Henk

2010-02-01

The hemoglobin of a 29-year-old man fell below 35 g/L over 5 days, despite 14 units of red blood cells (RBCs), due to an anti-Pr cold agglutinin (CA). His hemolytic anemia necessitated respiratory support in intensive care for 4 weeks. The hemolysis was investigated by the effects on blood group-compatible RBCs of this anti-Pr and an anti-I CA and of a rabbit anti-human glycophorin A (GPA) immunoglobulin G (IgG) antibody on Ca(2+) permeability and of phosphatidylethanolamine (PE) exposure. 1) The anti-Pr CA (in a plasmapheresis product from the patient) was absorbed and eluted from RBC ghosts and its immunophenotype was determined by agarose electrophoresis and immunofixation. 2) Ca(2+) permeability was measured by the response of Fluo-3-labeled RBCs to addition of external Ca(2+). 3) Exposed PE was measured with streptavidin-labeled biotinylated peptide Ro 09-0198 (cinnamycin). 1) The patient's anti-Pr CA was a polyclonal IgG. 2) The anti-Pr and the rabbit anti-human glycophorin IgG, but not an anti-I CA, rapidly increased Ca(2+)-dependent fluorescence upon addition of external Ca(2+) in a fraction (15%-25%) of RBCs that also became positive for cinnamycin. 3) Trypsin treatment of RBCs reduced the Ca(2+) influx due to the anti-Pr IgG, but neither trypsin nor neuraminidase changed the responses to the rabbit anti-human GPA IgG. The anti-Pr CA and rabbit anti-human GPA increased exposure of PE and increased membrane Ca(2+) permeability that may have caused hemolysis. The difference in the responses to these antibodies to enzyme treatment of RBCs suggests that they react with different epitopes on GPA.

Efficiency of several leaching reagents on removal of Cu, Pb, Cd, and Zn from highly contaminated paddy soil.

PubMed

Gao, Ruili; Zhu, Pengfei; Guo, Guangguang; Hu, Hongqing; Zhu, Jun; Fu, Qingling

2016-11-01

The efficiency of five different single leaching reagents (tartaric acid (TA), citric acid (CA), CaCl 2 , FeCl 3 , EDTA) and two different composite leaching reagents (CA + FeCl 3 , CA + EDTA) on removing Cu, Pb, Zn, and Cd from contaminated paddy soil in Hunan Province (in China) was studied. The results indicated that the efficiencies of CA, FeCl 3 , and EDTA on extracting Cu, Pb, Cd, and Zn from soil were greater than that of TA and CaCl 2 , and their extraction efficiencies were EDTA ≥ FeCl 3 > CA. The efficiencies of CA + FeCl 3 on extracting Cu, Pb, Cd, and Zn were higher than that of single CA or FeCl 3 . The 25 mmol L -1 CA + 20 mmol L -1 FeCl 3 was a promising composite leaching reagent for paddy soil, and it could remove Cu (57.6 %), Pb (59.3 %), Cd (84.8 %), and Zn (28.0 %), respectively. With the same amount of leaching reagent, the efficiency of continuous leaching by several times was higher than that by once. In addition, the easily reducible and oxidizable fractions of heavy metals showed significant decrease during the process of leaching.

Dynamic Ca2+ signalling in rat arterial smooth muscle cells under the control of local renin–angiotensin system

PubMed Central

Asada, Yukinori; Yamazawa, Toshiko; Hirose, Kenzo; Takasaka, Tomonori; Iino, Masamitsu

1999-01-01

We visualized the changes in intracellular Ca2+ concentration ([Ca2+]i), using fluo-3 as an indicator, in individual smooth muscle cells within intact rat tail artery preparations. On average in about 45 % of the vascular smooth muscle cells we found spontaneous Ca2+ waves and oscillations (≈0.13 Hz), which we refer to here as Ca2+ ripples because the peak amplitude of [Ca2+]i was about one-seventh of that of Ca2+ oscillations evoked by noradrenaline. We also found another pattern of spontaneous Ca2+ transients often in groups of two to three cells. They were rarely observed and are referred to as Ca2+ flashes because their peak amplitude was nearly twice as large as that in noradrenaline-evoked responses. Sympathetic nerve activity was not considered responsible for the Ca2+ ripples, and they were abolished by inhibitors of either the Ca2+ pump in the sarcoplasmic reticulum (cyclopiazonic acid) or phospholipase C (U-73122). Both angiotensin antagonists ([Sar1,Ile8]-angiotensin II and losartan) and an angiotensin converting enzyme inhibitor (captopril) inhibited the Ca2+ ripples. The extracellular Ca2+-dependent tension borne by unstimulated arterial rings was reduced by the angiotensin antagonist by ≈50 %. These results indicate that the Ca2+ ripples are generated via inositol 1,4,5-trisphosphate-induced Ca2+ release from the intracellular Ca2+ stores in response to locally produced angiotensin II, which contributes to the maintenance of vascular tone. PMID:10581318

Carvedilol inhibits cADPR- and IP3-induced Ca2+ release.

PubMed

Morgan, Anthony J; Bampali, Konstantina; Ruas, Margarida; Factor, Cailley; Back, Thomas G; Chen, S R Wayne; Galione, Antony

2016-06-01

Spontaneous Ca 2+ waves, also termed store-overload-induced Ca 2+ release (SOICR), in cardiac cells can trigger ventricular arrhythmias especially in failing hearts. SOICR occurs when RyRs are activated by an increase in sarcoplasmic reticulum (SR) luminal Ca 2+ . Carvedilol is one of the most effective drugs for preventing arrhythmias in patients with heart failure. Furthermore, carvedilol analogues with minimal β-blocking activity also block SOICR showing that SOICR-inhibiting activity is distinct from that for β-block. We show here that carvedilol is a potent inhibitor of cADPR-induced Ca 2+ release in sea urchin egg homogenate. In addition, the carvedilol analog VK-II-86 with minimal β-blocking activity also suppresses cADPR-induced Ca 2+ release. Carvedilol appeared to be a non-competitive antagonist of cADPR and could also suppress Ca 2+ release by caffeine. These results are consistent with cADPR releasing Ca 2+ in sea urchin eggs by sensitizing RyRs to Ca 2+ involving a luminal Ca 2+ activation mechanism. In addition to action on the RyR, we also observed inhibition of inositol 1,4,5-trisphosphate (IP 3 )-induced Ca 2+ release by carvedilol suggesting a common mechanism between these evolutionarily related and conserved Ca 2+ release channels.

The Crystal Structure of GCAP3 Suggests Molecular Mechanism of GCAP–linked Cone Dystrophies

PubMed Central

Stephen, Ricardo; Palczewski, Krzysztof; Sousa, Marcelo C.

2014-01-01

Summary Absorption of light by visual pigments initiates the phototransduction pathway that results in degradation of the intracellular pool of cyclic–GMP (cGMP). This hydrolysis promotes the closing of cGMP–gated cation channels and consequent hyperpolarization of rod and cone photoreceptor cell membranes. Guanylate Cyclase Activating Proteins (GCAPs) are a family of proteins that regulate retinal guanylate cyclase (GC) activity in a Ca2+–dependent manner. At high [Ca2+], typical of the dark–adapted state (~500 nM), GCAPs inhibit retinal GCs. At the low [Ca2+] (~50 nM) that occur after the closing of cGMP-gated channels, GCAPs activate retinal GCs to replenish dark–state cGMP levels. Here, we report the crystal structure of unmyristoylated human GCAP3 with Ca2+ bound. GCAP3 is an EF–hand Ca2+–binding protein with Ca2+ bound to EF2, 3 and 4, while Ca2+ binding to EF–hand 1 is disabled. GCAP3 contains two domains with the EF–hand motifs arranged in a tandem array similar to GCAP2 and members of the recoverin subfamily of Ca2+–binding proteins. Residues not involved in Ca2+ binding, but conserved in all GCAPs, cluster around EF1 in the N–terminal domain and may represent the interface with GCs. Five point mutations in the closely related GCAP1 have been linked to the etiology of cone dystrophies. These residues are conserved in GCAP3 and the structure suggests important roles for these amino acids. We present a homology model of GCAP1 based on GCAP3 that offers insight into the molecular mechanism underlying the autosomal dominant cone dystrophies produced by GCAP1 mutations. PMID:16626734

The crystal structure of GCAP3 suggests molecular mechanism of GCAP-linked cone dystrophies.

PubMed

Stephen, Ricardo; Palczewski, Krzysztof; Sousa, Marcelo C

2006-06-02

Absorption of light by visual pigments initiates the phototransduction pathway that results in degradation of the intracellular pool of cyclic-GMP (cGMP). This hydrolysis promotes the closing of cGMP-gated cation channels and consequent hyperpolarization of rod and cone photoreceptor cell membranes. Guanylate cyclase-activating proteins (GCAPs) are a family of proteins that regulate retinal guanylate cyclase (GC) activity in a Ca2+-dependent manner. At high [Ca2+], typical of the dark-adapted state (approximately 500 nM), GCAPs inhibit retinal GCs. At the low [Ca2+] (approximately 50 nM) that occurs after the closing of cGMP-gated channels, GCAPs activate retinal GCs to replenish dark-state cGMP levels. Here, we report the crystal structure of unmyristoylated human GCAP3 with Ca2+ bound. GCAP3 is an EF-hand Ca2+-binding protein with Ca2+ bound to EF2, 3 and 4, while Ca2+ binding to EF-hand 1 is disabled. GCAP3 contains two domains with the EF-hand motifs arranged in a tandem array similar to GCAP2 and members of the recoverin subfamily of Ca2+-binding proteins. Residues not involved in Ca2+ binding, but conserved in all GCAPs, cluster around EF1 in the N-terminal domain and may represent the interface with GCs. Five point mutations in the closely related GCAP1 have been linked to the etiology of cone dystrophies. These residues are conserved in GCAP3 and the structure suggests important roles for these amino acids. We present a homology model of GCAP1 based on GCAP3 that offers insight into the molecular mechanism underlying the autosomal dominant cone dystrophies produced by GCAP1 mutations.

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.

CaCO3-III and CaCO3-VI, high-pressure polymorphs of calcite: Possible host structures for carbon in the Earth's mantle

NASA Astrophysics Data System (ADS)

Merlini, M.; Hanfland, M.; Crichton, W. A.

2012-06-01

Calcite, CaCO3, undergoes several high pressure phase transitions. We report here the crystal structure determination of the CaCO3-III and CaCO3-VI high-pressure polymorphs obtained by single-crystal synchrotron X-ray diffraction. This new technical development at synchrotron beamlines currently affords the possibility of collecting single-crystal data suitable for structure determination in-situ at non-ambient conditions, even after multiphase transitions. CaCO3-III, observed in the pressure range 2.5-15 GPa, is triclinic, and it presents two closely related structural modifications, one, CaCO3-III, with 50 atoms in the unit cell [a=6.281(1) Å, b=7.507(2) Å, c=12.516(3) Å, α=93.76(2)°, β=98.95(2)°, γ=106.49(2)°, V=555.26(20) Å3 at 2.8 GPa], the second, CaCO3-IIIb, with 20 atoms [a=6.144(3) Å, b=6.3715(14) Å, c=6.3759(15) Å, α= 93.84(2)°, β=107.34(3)°, γ=107.16(3)°, V=224.33(13) Å3 at 3.1 GPa]. Different pressure-time experimental paths can stabilise one or the other polymorph. Both structures are characterised by the presence of non-coplanar CO3 groups. The densities of CaCO3-III (2.99 g/cm3 at 2.8 GPa) and CaCO3-IIIb (2.96 g/cm3 at 3.1 GPa) are lower than aragonite, in agreement with the currently accepted view of aragonite as the thermodynamically stable Ca-carbonate phase at these pressures. The presence of different cation sites, with variable volume and coordination number (7-9), suggests however that these structures have the potential to accommodate cations with different sizes without introducing major structural strain. Indeed, this structure can be adopted by natural Ca-rich carbonates, which often exhibit compositions deviating from pure calcite. Mg-calcites are found both in nature (Frezzotti et al., 2011) and in experimental syntheses at conditions corresponding to deep subduction environments (Poli et al., 2009). At these conditions, the low pressure rhombohedral calcite structure is most unlikely to be stable, and, at the same time, Mg and Fe solubility in aragonite is hindered energetically in the 9-fold coordination site. Above 15 GPa, and up to the maximum pressure investigated (40 GPa), we observe the high-pressure polymorph CaCO3-VI, triclinic [a=3.3187(12) Å, b=4.8828(14) Å, c=5.5904(14) Å, α=103.30(2)°, β=94.73(2)°, γ=89.21(2)°, V=87.86(20) Å3 at 30.4 GPa] with 10 atoms in the unit cell. It is characterised by coplanar CO3 groups but the structure is no longer layered, as in the lower pressure polymorphs. The density of the CaCO3-VI structure (3.78 g/cm3 at 30.4 GPa) is higher than aragonite. For this reason it could be supposed that a region may exist where this polymorph replaces aragonite in the Earth's intermediate mantle. The lower coordination number for the Ca site [7+2] instead of [9] in aragonite suggests that this structure could be easily adopted by an extended solid-solution range from calcite towards the dolomite [CaMg(CO3)2]-ankerite [CaFe(CO3)2] compositional join. The transitions from calcite to CaCO3-III, CaCO3-IIIb and CaCO3-VI are perfectly reversible and after pressure release we always observe the calcite structure, with the sample recovered as a single-crystal. Indeed, it is highly unlikely that these structures can be observed in samples recovered from high-pressure environments.

Autophagy blockade sensitizes the anticancer activity of CA-4 via JNK-Bcl-2 pathway

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

Li, Yangling; Luo, Peihua; Wang, Jincheng

Combretastatin A-4 (CA-4) has already entered clinical trials of solid tumors over ten years. However, the limited anticancer activity and dose-dependent toxicity restrict its clinical application. Here, we offered convincing evidence that CA-4 induced autophagy in various cancer cells, which was demonstrated by acridine orange staining of intracellular acidic vesicles, the degradation of p62, the conversion of LC3-I to LC3-II and GFP-LC3 punctate fluorescence. Interestingly, CA-4-mediated apoptotic cell death was further potentiated by pretreatment with autophagy inhibitors (3-methyladenine and bafilomycin A1) or small interfering RNAs against the autophagic genes (Atg5 and Beclin 1). The enhanced anticancer activity of CA-4 andmore » 3-MA was further confirmed in the SGC-7901 xenograft tumor model. These findings suggested that CA-4-elicited autophagic response played a protective role that impeded the eventual cell death while autophagy inhibition was expected to improve chemotherapeutic efficacy of CA-4. Meanwhile, CA-4 treatment led to phosphorylation/activation of JNK and JNK-dependent phosphorylation of Bcl-2. Importantly, JNK inhibitor or JNK siRNA inhibited autophagy but promoted CA-4-induced apoptosis, indicating a key requirement of JNK-Bcl-2 pathway in the activation of autophagy by CA-4. We also identified that pretreatment of Bcl-2 inhibitor (ABT-737) could significantly enhance anticancer activity of CA-4 due to inhibition of autophagy. Taken together, our data suggested that the JNK-Bcl-2 pathway was considered as the critical regulator of CA-4-induced protective autophagy and a potential drug target for chemotherapeutic combination. - Highlights: • Autophagy inhibition could be a potential for combretastatin A-4 antitumor efficacy. • The JNK-Bcl-2 pathway plays a critical role in CA-4-induced autophagy. • ABT-737 enhances CA-4 anticancer activity due to inhibition of autophagy.« less

Dual regulation of Ca2+-dependent glutamate release from astrocytes: vesicular glutamate transporters and cytosolic glutamate levels.

PubMed

Ni, Yingchun; Parpura, Vladimir

2009-09-01

Vesicular glutamate transporters (VGLUTs) are responsible for vesicular glutamate storage and exocytotic glutamate release in neurons and astrocytes. Here, we selectively and efficiently overexpressed individual VGLUT proteins (VGLUT1, 2, or 3) in solitary astrocytes and studied their effects on mechanical stimulation-induced Ca2+-dependent glutamate release. Neither VGLUT1 nor VGLUT2 overexpression changed the amount of glutamate release, whereas overexpression of VGLUT3 significantly enhanced Ca2+-dependent glutamate release from astrocytes. None of the VGLUT overexpression affected mechanically induced intracellular Ca2+ increase. Inhibition of glutamine synthetase activity by L-methionine sulfoximine in astrocytes, which leads to increased cytosolic glutamate concentration, greatly increased their mechanically induced Ca2+-dependent glutamate release, without affecting intracellular Ca2+ dynamics. Taken together, these data indicate that both VGLUT3 and the cytosolic concentration of glutamate are key limiting factors in regulating the Ca2+-dependent release of glutamate from astrocytes.

Red wine polyphenols increase calcium in bovine aortic endothelial cells: a basis to elucidate signalling pathways leading to nitric oxide production

PubMed Central

Martin, Sophie; Andriambeloson, Emile; Takeda, Ken; Andriantsitohaina, Ramaroson

2002-01-01

The present study investigates the mechanisms by which polyphenolic compounds from red wine elicit Ca2+ mobilization in bovine aortic endothelial cells (BAECs). Two polyphenol-containing red wine extracts, red wine polyphenolic compounds (RWPC) and Provinols™, and delphinidin, an anthocyanin were used. RWPC stimulated a Ca2+-dependent release of nitric oxide (NO) from BAECs accounting for the relaxation of endothelium-denuded rat aortic rings as shown by cascade bioassay. RWPC, Provinols™ and delphinidin increased cytosolic free calcium ([Ca2+]i), by releasing Ca2+ from intracellular stores and by increasing Ca2+ entry. The RWPC-induced increase in [Ca2+]i was decreased by exposure to ryanodine (30 μM), whereas Provinols™ and delphinidin-induced increases in [Ca2+]i were decreased by bradykinin (0.1 μM) and thapsigargin (1 μM) pre-treatment. RWPC, Provinols™ and delphinidin-induced increases in [Ca2+]i were sensitive to inhibitors of phospholipase C (neomycin, 3 mM; U73122, 3 μM) and tyrosine kinase (herbimycin A, 1 μM). RWPC, Provinols™ and delphinidin induced herbimycin A (1 μM)-sensitive tyrosine phosphorylation of several intracellular proteins. Provinols™ released Ca2+ via both a cholera (CTX) and pertussis toxins (PTX)-sensitive pathway, whereas delphinidin released Ca2+ only via a PTX-sensitive mechanism. Our data contribute in defining the mechanisms of endothelial NO production caused by wine polyphenols including the increase in [Ca2+]i and the activation of tyrosine kinases. Furthermore, RWPC, Provinols™ and delphinidin display differences in the process leading to [Ca2+]i increases in endothelial cells illustrating multiple cellular targets of natural dietary polyphenolic compounds. PMID:11906973

Estrogen attenuates glutamate-induced cell death by inhibiting Ca2+ influx through L-type voltage-gated Ca2+ channels

PubMed Central

Sribnick, Eric A.; Del Re, Angelo M.; Ray, Swapan K.; Woodward, John J.; Banik, Naren L.

2009-01-01

Estrogen-mediated neuroprotection is observed in neurodegenerative disease and neurotrauama models; however, determining a mechanism for these effects has been difficult. We propose that estrogen may limit cell death in the nervous system tissue by inhibiting increases in intracellular free Ca2+. Here, we present data using VSC 4.1 cell line, a ventral spinal motoneuron and neuroblastoma hybrid cell line. Treatment with 1 mM glutamate for 24 h induced apoptosis. When cells were pre-treated with 100 nM 17β-estradiol (estrogen) for 1 h and then co-treated with glutamate, apoptotic death was significantly attenuated. Estrogen also prevented glutamate-mediated changes in resting membrane potential and membrane capacitance. Treatment with either 17α-estradiol or cell impermeable estrogen did not mimic the findings seen with estrogen. Glutamate treatment significantly increased both intracellular free Ca2+ and the activities of downstream proteases such as calpain and caspase-3. Estrogen attenuated both the increases in intracellular free Ca2+ and protease activities. In order to determine the pathway responsible for estrogen-mediated inhibition of these increases in intracellular free Ca2+, cells were treated with several Ca2+ entry inhibitors, but only the L-type Ca2+ channel blocker nifedipine demonstrated cytoprotective effects comparable to estrogen. To expand these findings, cells were treated with the L-type Ca2+ channel agonist FPL 64176, which increased both cell death and intracellular free Ca2+, and estrogen inhibited both effects. From these observations, we conclude that estrogen limits glutamate-induced cell death in VSC 4.1 cells through effects on L-type Ca2+ channels, inhibiting Ca2+ influx as well as activation of the pro-apoptotic proteases calpain and caspase-3. PMID:19389388

Effects of antimony substitution on bismuth based superconductors

NASA Technical Reports Server (NTRS)

Barrientos, Alfonso

1990-01-01

The effect of Sb substitution and simultaneous substitution of Pb and Sb on the superconducting transition temperatures in the BiSrCaCuO system is investigated. The 2:2:2:3 phase is of particular interest since any small increase in the transition temperature could be of great interest. More that 90 different samples were prepared based on 2:2:2:3 stoichiometry in the BiSrCaCuO system. After this preliminary attempt, four different families of samples were investigated. In the first family of samples, Bi was substituted by Sb to form Bi(1.9)Sb(0.1)Sr2Ca2Cu3O(y). The second group of samples were prepared by simultaneous addition of Pb and Sb with nominal composition Bi(1.8)Pb(0.1)Sb(0.1)Sr2Ca2Cu3O(y). The third and fourth groups were prepared to determine the effect created when the Pb concentration is increased with the nominal compositions being Bi(1.7)Pb(0.1)Sr2Ca2Cu3O(y) and Bi(1.6)Sb(0.1)Sr2Ca2Cu3O(y). The results of these investigations are presented with a discussion.

Calcium signaling in liver.

PubMed

Gaspers, Lawrence D; Thomas, Andrew P

2005-01-01

In hepatocytes, hormones linked to the formation of the second messenger inositol 1,4,5-trisphosphate (InsP3) evoke transient increases or spikes in cytosolic free calcium ([Ca2+]i), that increase in frequency with the agonist concentration. These oscillatory Ca2+ signals are thought to transmit the information encoded in the extracellular stimulus to down-stream Ca2+-sensitive metabolic processes. We have utilized both confocal and wide field fluorescence microscopy techniques to study the InsP3-dependent signaling pathway at the cellular and subcellular levels in the intact perfused liver. Typically InsP3-dependent [Ca2+]i spikes manifest as Ca2+ waves that propagate throughout the entire cytoplasm and nucleus, and in the intact liver these [Ca2+]i increases are conveyed through gap junctions to encompass entire lobular units. The translobular movement of Ca2+ provides a means to coordinate the function of metabolic zones of the lobule and thus, liver function. In this article, we describe the characteristics of agonist-evoked [Ca2+]i signals in the liver and discuss possible mechanisms to explain the propagation of intercellular Ca2+ waves in the intact organ.

Factors that reverse the persistent depolarization produced by deprivation of oxygen and glucose in rat hippocampal CA1 neurons in vitro.

PubMed

Yamamoto, S; Tanaka, E; Shoji, Y; Kudo, Y; Inokuchi, H; Higashi, H

1997-08-01

In CA1 pyramidal neurons in rat hippocampal tissue slices, superfusion with ischemia-simulating medium produced a rapid depolarization after 6 min of exposure. The membrane potential eventually reached 0 after 5 min (a persistent depolarization), even when oxygen and glucose were reintroduced. The role of various ions in the reversal of this persistent depolarization after reintroduction of oxygen and glucose was investigated. The peak of the persistent depolarization was decreased in solutions containing reduced Na+ or Ca2+ and in solutions containing Co2+ or Ni2+. In contrast, the depolarization was not affected by reduction of external K+ or Cl- or by addition of tetrodotoxin (TTX), flunarizine, or nifedipine. These results suggest that sustained Na+ and Ca2+ influxes produce the persistent depolarization. The membrane potential recovered after reintroduction of oxygen and glucose in low Ca2+, low Cl-, or K+-rich medium and in TTX- or tetraethylammonium-containing medium, but not in low Na+ or low K+ medium and in flunarizine- or nifedipine-containing medium. Either reduction in extracellular Ca2+ or addition of Co2+ was the most effective in promoting recovery from the persistent depolarization, suggesting that Ca2+ influx has a key role in causing the membrane dysfunction. The peak of the persistent depolarization was reduced by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), DL-2-amino-5-phosphonopentanoic acid (AP5), DL-amino-3-phosphonopropionic acid (AP3), or DL-amino-4-phosphonobutyric acid, suggesting that activation of non-N-methyl-D-aspartate (non-NMDA), NMDA, and metabotropic glutamate (Glu) receptors is involved in the generation and maintenance of the persistent depolarization. Among these Glu receptor antagonists, only CNQX or AP5 was able to reduce dose dependently the level of depolarization, suggesting that Ca2+ influx via both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate type II receptors and NMDA receptors contributes to the membrane dysfunction. trans-1-aminocyclopentane-1,3-dicarboxylic acid (t-ACPD) did not affect the peak potential of the persistent depolarization, but it dose-dependently restored the membrane potential. AP3 antagonized the protective action of t-ACPD. The membrane potential also recovered after reintroduction when the slice was pretreated by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester, ryanodol 3-(1H-pyrrole-2-carboxylate), 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride, and procaine, suggesting that raised [Ca2+]i from Ca2+-induced Ca2+ release pool contributes to the membrane dysfunction. It, therefore, is concluded that raised [Ca2+]i has a dominant role in causing irreversible changes. The increase in [Ca2+]i during the persistent depolarization may be the result of Ca2+ entry via both a leaky membrane and Glu-activated receptor channels as well as Ca2+ released from internal stores.

Theoretical study on the reaction mechanism of CH 4 with CaO

NASA Astrophysics Data System (ADS)

Yang, Hua-Qing; Hu, Chang-Wei; Qin, Song

2006-11-01

The reaction pathways and energetics for the reaction of methane with CaO are discussed on the singlet spin state potential energy surface at the B3LYP/6-311+G(2df,2p) and QCISD/6-311++G(3df,3pd)//B3LYP/6-311+G(2df,2p) levels of theory. The reaction of methane with CaO is proposed to proceed in the following reaction pathways: CaO + CH 4 → CaOCH 4 → [TS] → CaOH + CH 3, CaO + CH 4 → OCaCH 4 → [TS] → HOCaCH 3 → CaOH + CH 3 or [TS] → CaCH 3OH → Ca + CH 3OH, and OCaCH 4 → [TS] → HCaOCH 3 → CaOCH 3 + H or [TS] → CaCH 3OH → Ca + CH 3OH. The gas-phase methane-methanol conversion by CaO is suggested to proceed via two kinds of important reaction intermediates, HOCaCH 3 and HCaOCH 3, and the reaction pathway via the hydroxy intermediate (HOCaCH 3) is energetically more favorable than the other one via the methoxy intermediate (HCaOCH 3). The hydroxy intermediate HOCaCH 3 is predicted to be the energetically most preferred configuration in the reaction of CaO + CH 4. Meanwhile, these three product channels (CaOH + CH 3, CaOCH 3 + H and Ca + CH 3OH) are expected to compete with each other, and the formation of methyl radical is the most preferable pathway energetically. On the other hand, the intermediates HCaOCH 3 and HOCaCH 3 are predicted to be the energetically preferred configuration in the reaction of Ca + CH 3OH, which is precisely the reverse reaction of methane hydroxylation.

Modulated visible spectra properties of Pr:Ca1-xRxF2+x(R=Y, La, Gd) crystals

NASA Astrophysics Data System (ADS)

Yu, Hao; Qian, Xiaobo; Wu, Qinghui; Ma, Fengkai; Wang, Jingya; Xu, Jun; Su, Liangbi

2017-10-01

The spectroscopic properties of the 1.0 at.%Pr:Ca0.97R0.02F2.03(R=Y, La, Gd) crystals are investigated. X-diffraction and room temperature absorption spectra have been registered and analyzed. The emission spectra and decay curves of the crystals were obtained at room temperature. The photoluminescence intensity in the visible region is significantly enhanced by co-doping R3+ ions in Pr:CaF2 crystal. The different effects among the R3+ (Y3+, La3+ and Gd3+) regulating ions on the crystals were observed and compared. Pr:Ca0.97La0.02F2.03 and Pr:Ca0.97Y0.02F2.03 crystals have substantially strong emission at blue and orange region, while the Pr:Ca0.97Gd0.02F2.03 crystal is more suitable for the red emission emitting.

Zinc deficiency promotes cystitis-related bladder pain by enhancing function and expression of Cav3.2 in mice.

PubMed

Ozaki, Tomoka; Matsuoka, Junki; Tsubota, Maho; Tomita, Shiori; Sekiguchi, Fumiko; Minami, Takeshi; Kawabata, Atsufumi

2018-01-15

Ca v 3.2 T-type Ca 2+ channel activity is suppressed by zinc that binds to the extracellular histidine-191 of Ca v 3.2, and enhanced by H 2 S that interacts with zinc. Ca v 3.2 in nociceptors is upregulated in an activity-dependent manner. The enhanced Ca v 3.2 activity by H 2 S formed by the upregulated cystathionine-γ-lyase (CSE) is involved in the cyclophosphamide (CPA)-induced cystitis-related bladder pain in mice. We thus asked if zinc deficiency affects the cystitis-related bladder pain in mice by altering Ca v 3.2 function and/or expression. Dietary zinc deficiency for 2 weeks greatly decreased zinc concentrations in the plasma but not bladder tissue, and enhanced the bladder pain/referred hyperalgesia (BP/RH) following CPA at 200mg/kg, a subeffective dose, but not 400mg/kg, a maximal dose, an effect abolished by pharmacological blockade or gene silencing of Ca v 3.2. Acute zinc deficiency caused by systemic N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylendiamine (TPEN), a zinc chelator, mimicked the dietary zinc deficiency-induced Ca v 3.2-dependent promotion of BP/RH following CPA at 200mg/kg. CPA at 400mg/kg alone or TPEN plus CPA at 200mg/kg caused Ca v 3.2 overexpression accompanied by upregulation of Egr-1 and USP5, known to promote transcriptional expression and reduce proteasomal degradation of Ca v 3.2, respectively, in the dorsal root ganglia (DRG). The CSE inhibitor, β-cyano-l-alanine, prevented the BP/RH and upregulation of Ca v 3.2, Egr-1 and USP5 in DRG following TPEN plus CPA at 200mg/kg. Together, zinc deficiency promotes bladder pain accompanying CPA-induced cystitis by enhancing function and expression of Ca v 3.2 in nociceptors, suggesting a novel therapeutic avenue for treatment of bladder pain, such as zinc supplementation. Copyright © 2017 Elsevier B.V. All rights reserved.

Calcium-independent activation of extracellular signal-regulated kinases 1 and 2 by cyclic strain

NASA Technical Reports Server (NTRS)

Ikeda, M.; Takei, T.; Mills, I.; Sumpio, B. E.

1998-01-01

We have previously demonstrated that cyclic strain induces extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation in endothelial cells (EC). The aim of this study was to investigate the effect of Ca2+ on the activation of ERK1/2. Bovine aortic EC were pretreated with a chelator of extracellular Ca2+, ethylaneglycol-bis(aminoethylether)-tetra-acetate (EGTA), a depleter of Ca2+ pools, 2,5-Di-(tert-butyl)-1,4-benzohydroquinone (BHQ), or a Ca2+ channel blocker, GdCl3, and subjected to an average 10 % strain at a rate of 60 cycles/min for 10 min. BHQ and GdCl3 did not inhibit the strain-induced ERK1/2 activation. Chelation of normal extracellular Ca2+ (1.8 mM) medium with EGTA (3 mM) acutely stimulated baseline phosphorylation and activation of ERK1/2, thereby obscuring any strain-induced activation of ERK1/2. However, in EC preincubated for 24 hours in Ca2+-free medium, elevated baseline phosphorylation was minimally activated by EGTA (200 microM) such that cyclic strain stimulated ERK1/2 in the presence or absence of BHQ. These results suggest a Ca2+ independence of the ERK1/2 signaling pathway by cyclic strain. Copyright 1998 Academic Press.

The CLAVATA signaling pathway mediating stem cell fate in shoot meristems requires Ca(2+) as a secondary cytosolic messenger.

PubMed

Chou, Hsuan; Zhu, Yingfang; Ma, Yi; Berkowitz, Gerald A

2016-02-01

CLAVATA1 (CLV1) is a receptor protein expressed in the shoot apical meristem (SAM) that translates perception of a non-cell-autonomous CLAVATA3 (CLV3) peptide signal into altered stem cell fate. CLV3 reduces expression of WUSCHEL (WUS) and FANTASTIC FOUR 2 (FAF2) in the SAM. Expression of WUS and FAF2 leads to maintenance of undifferentiated stem cells in the SAM. CLV3 binding to CLV1 inhibits expression of these genes and controls stem cell fate in the SAM through an unidentified signaling pathway. Cytosolic Ca(2+) elevations, cyclic nucleotide (cGMP)-activated Ca(2+) channels, and cGMP have been linked to signaling downstream of receptors similar to CLV1. Hence, we hypothesized that cytosolic Ca(2+) elevation mediates the CLV3 ligand/CLV1 receptor signaling that controls meristem stem cell fate. CLV3 application to Arabidopsis seedlings results in elevation of cytosolic Ca(2+) and cGMP. CLV3 control of WUS was prevented in a genotype lacking a functional cGMP-activated Ca(2+) channel. In wild-type plants, CLV3 inhibition of WUS and FAF2 expression was impaired by treatment with either a Ca(2+) channel blocker or a guanylyl cyclase inhibitor. When CLV3-dependent repression of WUS is blocked, altered control of stem cell fate leads to an increase in SAM size; we observed a larger SAM size in seedlings treated with the Ca(2+) channel blocker. These results suggest that the CLV3 ligand/CLV1 receptor system initiates a signaling cascade that elevates cytosolic Ca(2+), and that this cytosolic secondary messenger is involved in the signal transduction cascade linking CLV3/CLV1 to control of gene expression and stem cell fate in the SAM. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Normocalcemia without hyperparathyroidism in vitamin D-deficient rats.

PubMed

Kollenkirchen, U; Fox, J; Walters, M R

1991-03-01

Despite numerous attempts, no reliable dietary regimen exists to achieve vitamin D deficiency (-D) in rats without attendant changes in plasma parathyroid hormone (PTH), Ca, or phosphate. This represents an important obstacle to proper investigations of the physiologic role(s) of vitamin D metabolites in the function of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] target tissues. This paper describes the successful development of such a diet, which uses a combination of high Ca content, properly controlled Ca/P ratio, and lactose. Normal weanling rats were fed diets containing A, 0.8% Ca, 0.5% P, +D3, or -D diets containing B, 0.8% Ca and 0.5% P; C, 2.0% Ca and 1.25% P; or D, 2.0% Ca, 1.25% P, and 20% lactose. After 6 diet weeks group D rats remained normocalcemic and normophosphatemic, but diet groups B and C became hypocalcemic (6.9 +/- 0.8 and 7.2 +/- 0.4 mg/dl, respectively). Thus high dietary Ca and P was incapable of maintaining normal plasma Ca levels in the absence of dietary lactose. The normocalcemia in group D was not maintained by elevated PTH secretion because N-terminal PTH levels were also normal (14 +/- 3 versus 20 +/- 5 pg/ml). In contrast, PTH levels were markedly elevated in hypocalcemic groups B and C (47 +/- 7 and 48 +/- 10 pg/ml, respectively). Plasma 25-OHD3 and 1,25-(OH)2D3 levels were reduced to less than 120 and less than 12 pg/ml, respectively, in all -D groups. Thus the high-Ca diet and the use of normal weanlings did not impede the development of vitamin D deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Proximal clustering between BK and CaV1.3 channels promotes functional coupling and BK channel activation at low voltage

PubMed Central

Vivas, Oscar; Moreno, Claudia M; Santana, Luis F; Hille, Bertil

2017-01-01

CaV-channel dependent activation of BK channels is critical for feedback control of both calcium influx and cell excitability. Here we addressed the functional and spatial interaction between BK and CaV1.3 channels, unique CaV1 channels that activate at low voltages. We found that when BK and CaV1.3 channels were co-expressed in the same cell, BK channels started activating near −50 mV, ~30 mV more negative than for activation of co-expressed BK and high-voltage activated CaV2.2 channels. In addition, single-molecule localization microscopy revealed striking clusters of CaV1.3 channels surrounding clusters of BK channels and forming a multi-channel complex both in a heterologous system and in rat hippocampal and sympathetic neurons. We propose that this spatial arrangement allows tight tracking between local BK channel activation and the gating of CaV1.3 channels at quite negative membrane potentials, facilitating the regulation of neuronal excitability at voltages close to the threshold to fire action potentials. DOI: http://dx.doi.org/10.7554/eLife.28029.001 PMID:28665272

Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

NASA Astrophysics Data System (ADS)

Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

2018-05-01

Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

Type-3 ryanodine receptors mediate hypoxia-, but not neurotransmitter-induced calcium release and contraction in pulmonary artery smooth muscle cells.

PubMed

Zheng, Yun-Min; Wang, Qing-Song; Rathore, Rakesh; Zhang, Wan-Hui; Mazurkiewicz, Joseph E; Sorrentino, Vincenzo; Singer, Harold A; Kotlikoff, Michael I; Wang, Yong-Xiao

2005-04-01

In this study we examined the expression of RyR subtypes and the role of RyRs in neurotransmitter- and hypoxia-induced Ca2+ release and contraction in pulmonary artery smooth muscle cells (PASMCs). Under perforated patch clamp conditions, maximal activation of RyRs with caffeine or inositol triphosphate receptors (IP3Rs) with noradrenaline induced equivalent increases in [Ca2+]i and Ca2+-activated Cl- currents in freshly isolated rat PASMCs. Following maximal IP3-induced Ca2+ release, neither caffeine nor chloro-m-cresol induced a response, whereas prior application of caffeine or chloro-m-cresol blocked IP3-induced Ca2+ release. In cultured human PASMCs, which lack functional expression of RyRs, caffeine failed to affect ATP-induced increases in [Ca2+]i in the presence and absence of extracellular Ca2+. The RyR antagonists ruthenium red, ryanodine, tetracaine, and dantrolene greatly inhibited submaximal noradrenaline- and hypoxia-induced Ca2+ release and contraction in freshly isolated rat PASMCs, but did not affect ATP-induced Ca2+ release in cultured human PASMCs. Real-time quantitative RT-PCR and immunofluorescence staining indicated similar expression of all three RyR subtypes (RyR1, RyR2, and RyR3) in freshly isolated rat PASMCs. In freshly isolated PASMCs from RyR3 knockout (RyR3-/-) mice, hypoxia-induced, but not submaximal noradrenaline-induced, Ca2+ release and contraction were significantly reduced. Ruthenium red and tetracaine can further inhibit hypoxic increase in [Ca2+]i in RyR3-/- mouse PASMCs. Collectively, our data suggest that (a) RyRs play an important role in submaximal noradrenaline- and hypoxia-induced Ca2+ release and contraction; (b) all three subtype RyRs are expressed; and (c) RyR3 gene knockout significantly inhibits hypoxia-, but not submaximal noradrenaline-induced Ca2+ and contractile responses in PASMCs.

Effects of elevated physiological temperatures on sarcoplasmic reticulum function in mechanically skinned muscle fibers of the rat.

PubMed

van der Poel, C; Stephenson, D G

2007-07-01

Properties of the sarcoplasmic reticulum (SR) with respect to Ca(2+) loading and release were measured in mechanically skinned fiber preparations from isolated extensor digitorum longus (EDL) muscles of the rat that were either kept at room temperature (23 degrees C) or exposed to temperatures in the upper physiological range for mammalian skeletal muscle (30 min at 40 or 43 degrees C). The ability of the SR to accumulate Ca(2+) was significantly reduced by a factor of 1.9-2.1 after the temperature treatments due to a marked increase in SR Ca(2+) leak, which persisted for at least 3 h after treatment. Results with blockers of Ca(2+) release channels (ruthenium red) and SR Ca(2+) pumps [2,5-di(tert-butyl)-1,4-hydroquinone] indicate that the increased Ca(2+) leak was not through the SR Ca(2+) release channel or the SR Ca(2+) pump, although it is possible that the leak pathway was via oligomerized Ca(2+) pump molecules. No significant change in the maximum SR Ca(2+)-ATPase activity was observed after the temperature treatment, although there was a tendency for a decrease in the SR Ca(2+)-ATPase. The observed changes in SR properties were fully prevented by the superoxide (O(2)(*-)) scavenger Tiron (20 mM), indicating that the production of O(2)(*-) at elevated temperatures is responsible for the increase in SR Ca(2+) leak. Results show that physiologically relevant elevated temperatures 1) induce lasting changes in SR properties with respect to Ca(2+) handling that contribute to a marked increase in the SR Ca(2+) leak and, consequently, to the reduction in the average coupling ratio between Ca(2+) transport and SR Ca(2+)-ATPase and muscle performance, and 2) that these changes are mediated by temperature-induced O(2)(*-) production.

Tetanic Ca2+ transient differences between slow- and fast-twitch mouse skeletal muscle fibres: a comprehensive experimental approach.

PubMed

Calderón, Juan C; Bolaños, Pura; Caputo, Carlo

2014-12-01

One hundred and eighty six enzymatically dissociated murine muscle fibres were loaded with Mag-Fluo-4 AM, and adhered to laminin, to evaluate the effect of modulating cytosolic Ca(2+) buffers and sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA), mitochondria, and Na(+)/Ca(2+) exchanger (NCX) on the differential tetanic Ca(2+) transient kinetics found in different fibre types. Tetanic Ca(2+) transients were classified as morphology type I (MT-I) or type II (MT-II) according to their shape. The first peak of the MT-I (n = 25) and MT-II (n = 23) tetanic Ca(2+) transients had an amplitude (∆F/F) of 0.41 ± 0.03 and 0.83 ± 0.05 and a rise time (ms) of 1.35 and 0.98, respectively. MT-I signals had a time constant of decay (τ1, ms) of 75.9 ± 4.2 while MT-II transients showed a double exponential decay with time constants of decay (τ1 and τ2, ms) of 18.3 ± 1.4 and 742.2 ± 130.3. Sarcoendoplasmic reticulum Ca(2+) ATPase inhibition demonstrated that the decay phase of the tetanic transients mostly rely on SERCA function. Adding Ca(2+) chelators in the AM form to MT-I fibres changed the morphology of the initial five peaks to a MT-II one, modifying the decay phase of the signal in a dose-dependent manner. Mitochondria and NCX function have a minor role in explaining differences in tetanic Ca(2+) transients among fibre types but still help in removing Ca(2+) from the cytosol in both MT-I and MT-II fibres. Cytoplasmic Ca(2+) buffering capacity and SERCA function explain most of the different kinetics found in tetanic Ca(2+) transients from different fibre types, but mitochondria and NCX have a measurable role in shaping tetanic Ca(2+) responses in both slow and fast-twitch muscle fibre types. We provided experimental evidence on the mechanisms that help understand the kinetics of tetanic Ca(2+) transients themselves and explain kinetic differences found among fibre types.

Inhibition of muscarinic-stimulated polyphosphoinositide hydrolysis and Ca2+ mobilization in cat iris sphincter smooth muscle cells by cAMP-elevating agents.

PubMed

Ding, K H; Husain, S; Akhtar, R A; Isales, C M; Abdel-Latif, A A

1997-09-01

The effects of carbachol (CCh) on inositol 1,4,5-trisphosphate (IP3) production and intracellular calcium ([Ca2+]i) mobilization, and their regulation by cAMP-elevating agents were investigated in SV-40 transformed cat iris sphincter smooth muscle (SV-CISM-2) cells. CCh produced time- and dose-dependent increases in IP3 production; the t1/2 and EC50 values were 68 s and 0.5 microM, respectively. The muscarinic agonist provoked a transient increase in [Ca2+]i which reached maximum within 77 s, and increased [Ca2+]i mobilization in a concentration-dependent manner with an EC50 of 1.4 microM. Thapsigargin, a Ca(2+)-pump inhibitor, caused a rapid rise in [Ca2+]i and subsequent addition of CCh was without effect. Both CCh-induced IP3 production and CCh-induced [Ca2+]i mobilization were more potently antagonized by 4-DAMP, an M3 muscarinic receptor antagonist, than by pirenzepine, an M1 receptor antagonist, suggesting that both responses are mediated through the M3 receptor subtype. Treatment of the cells with U73122, a phospholipase C (PLC) inhibitor, resulted in a concentration-dependent decrease in both CCh-stimulated IP3 production and [Ca2+]i mobilization. These data indicate close correlation between enhanced IP3 production and [Ca2+]i mobilization in these smooth muscle cells and suggest that the CCh-stimulated increase in [Ca2+]i could be mediated through increased IP3 production. Isoproterenol (ISO) inhibited CCh-induced IP3 production (IC50 = 80 nM) and [Ca2+]i mobilization (IC50 = 0.17 microM) in a concentration-dependent manner. Microsomal fractions isolated from SV-CISM-2 cells contained phospholipase C (PLC) which was stimulated by CCh (10 microM) and GTP gamma S (0.1 microM). Pretreatment of the cells with ISO or forskolin, 5 microM each, produced membrane fractions in which CCh-stimulated PLC activity was significantly attenuated. Furthermore, when microsomal fractions isolated from SV-CISM-2 cells were phosphorylated with Protein kinase A (PKA), the CCh- and GTP gamma S-stimulated IP3 production were significantly inhibited. It can be concluded from these studies that in SV-CISM-2 cells, activation of M3 muscarinic receptors results in stimulation of PLC-mediated PIP2 hydrolysis, generating IP3 which mobilizes [Ca2+]i. Furthermore, elevation of cAMP may inhibit IP3 production and [Ca2+]i mobilization through mechanisms involving PKA-dependent phosphorylation of PLC, G-proteins, IP3 receptor and/or IP3 metabolizing enzymes.

Functional Properties of a Newly Identified C-terminal Splice Variant of Cav1.3 L-type Ca2+ Channels*

PubMed Central

Bock, Gabriella; Gebhart, Mathias; Scharinger, Anja; Jangsangthong, Wanchana; Busquet, Perrine; Poggiani, Chiara; Sartori, Simone; Mangoni, Matteo E.; Sinnegger-Brauns, Martina J.; Herzig, Stefan; Striessnig, Jörg; Koschak, Alexandra

2011-01-01

An intramolecular interaction between a distal (DCRD) and a proximal regulatory domain (PCRD) within the C terminus of long Cav1.3 L-type Ca2+ channels (Cav1.3L) is a major determinant of their voltage- and Ca2+-dependent gating kinetics. Removal of these regulatory domains by alternative splicing generates Cav1.342A channels that activate at a more negative voltage range and exhibit more pronounced Ca2+-dependent inactivation. Here we describe the discovery of a novel short splice variant (Cav1.343S) that is expressed at high levels in the brain but not in the heart. It lacks the DCRD but, in contrast to Cav1.342A, still contains PCRD. When expressed together with α2δ1 and β3 subunits in tsA-201 cells, Cav1.343S also activated at more negative voltages like Cav1.342A but Ca2+-dependent inactivation was less pronounced. Single channel recordings revealed much higher channel open probabilities for both short splice variants as compared with Cav1.3L. The presence of the proximal C terminus in Cav1.343S channels preserved their modulation by distal C terminus-containing Cav1.3- and Cav1.2-derived C-terminal peptides. Removal of the C-terminal modulation by alternative splicing also induced a faster decay of Ca2+ influx during electrical activities mimicking trains of neuronal action potentials. Our findings extend the spectrum of functionally diverse Cav1.3 L-type channels produced by tissue-specific alternative splicing. This diversity may help to fine tune Ca2+ channel signaling and, in the case of short variants lacking a functional C-terminal modulation, prevent excessive Ca2+ accumulation during burst firing in neurons. This may be especially important in neurons that are affected by Ca2+-induced neurodegenerative processes. PMID:21998310

Enhanced pyruvate dehydrogenase activity improves cardiac outcomes in a murine model of cardiac arrest.

PubMed

Piao, Lin; Fang, Yong-Hu; Kubler, Manfred M; Donnino, Michael W; Sharp, Willard W

2017-01-01

Post-ischemic changes in cellular metabolism alter myocardial and neurological function. Pyruvate dehydrogenase (PDH), the limiting step in mitochondrial glucose oxidation, is inhibited by increased expression of PDH kinase (PDK) during ischemia/reperfusion injury. This results in decreased utilization of glucose to generate cellular ATP. Post-cardiac arrest (CA) hypothermia improves outcomes and alters metabolism, but its influence on PDH and PDK activity following CA are unknown. We hypothesized that therapeutic hypothermia (TH) following CA is associated with the inhibition of PDK activity and increased PDH activity. We further hypothesized that an inhibitor of PDK activity, dichloroacetate (DCA), would improve PDH activity and post-CA outcomes. Anesthetized and ventilated adult female C57BL/6 wild-type mice underwent a 12-minute KCl-induced CA followed by cardiopulmonary resuscitation. Compared to normothermic (37°C) CA controls, administering TH (30°C) improved overall survival (72-hour survival rate: 62.5% vs. 28.6%, P<0.001), post-resuscitation myocardial function (ejection fraction: 50.9±3.1% vs. 27.2±2.0%, P<0.001; aorta systolic pressure: 132.7±7.3 vs. 72.3±3.0 mmHg, P<0.001), and neurological scores at 72-hour post CA (9.5±1.3 vs. 5.4±1.3, P<0.05). In both heart and brain, CA increased lactate concentrations (1.9-fold and 3.1-fold increase, respectively, P<0.01), decreased PDH enzyme activity (24% and 50% reduction, respectively, P<0.01), and increased PDK protein expressions (1.2-fold and 1.9-fold, respectively, P<0.01). In contrast, post-CA treatment with TH normalized lactate concentrations (P<0.01 and P<0.05) and PDK expressions (P<0.001 and P<0.05), while increasing PDH activity (P<0.01 and P<0.01) in both the heart and brain. Additionally, treatment with DCA (0.2 mg/g body weight) 30 min prior to CA improved both myocardial hemodynamics 2 hours post-CA (aortic systolic pressure: 123±3 vs. 96±4 mmHg, P<0.001) and 72-hour survival rates (50% vs. 19%, P<0.05) in normothermic animals. Enhanced PDH activity in the setting of TH or DCA administration is associated with improved post-CA resuscitation outcomes. PDH is a promising therapeutic target for improving post-CA outcomes.

Carnosic Acid Alleviates BDL-Induced Liver Fibrosis through miR-29b-3p-Mediated Inhibition of the High-Mobility Group Box 1/Toll-Like Receptor 4 Signaling Pathway in Rats

PubMed Central

Zhang, Shuai; Wang, Zhecheng; Zhu, Jie; Xu, Ting; Zhao, Yan; Zhao, Huanyu; Tang, Fan; Li, Zhenlu; Zhou, Junjun; Gao, Dongyan; Tian, Xiaofeng; Yao, Jihong

2018-01-01

Fibrosis reflects a progression to liver cancer or cirrhosis of the liver. Recent studies have shown that high-mobility group box-1 (HMGB1) plays a major role in hepatic injury and fibrosis. Carnosic acid (CA), a compound extracted from rosemary, has been reported to alleviate alcoholic and non-alcoholic fatty liver injury. CA can also alleviate renal fibrosis. We hypothesized that CA might exert anti-liver fibrosis properties through an HMGB1-related pathway, and the results of the present study showed that CA treatment significantly protected against hepatic fibrosis in a bile duct ligation (BDL) rat model. CA reduced the liver expression of α-smooth muscle actin (α-SMA) and collagen 1 (Col-1). Importantly, we found that CA ameliorated the increase in HMGB1 and Toll-like receptor 4 (TLR4) caused by BDL, and inhibited NF-κB p65 nuclear translocation in fibrotic livers. In vitro, CA inhibited LX2 cell activation by inhibiting HMGB1/TLR4 signaling pathway. Furthermore, miR-29b-3p decreased HMGB1 expression, and a dual-luciferase assay validated these results. Moreover, CA down-regulated HMGB1 and inhibited LX2 cell activation, and these effects were significantly counteracted by antago-miR-29b-3p, indicating that the CA-mediated inhibition of HMGB1 expression might be miR-29b-3p dependent. Collectively, the results demonstrate that a miR-29b-3p/HMGB1/TLR4/NF-κB signaling pathway, which can be modulated by CA, is important in liver fibrosis, and indicate that CA might be a prospective therapeutic drug for liver fibrosis. PMID:29403377

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

PubMed

Hayashi, Teruo; Su, Tsung-Ping

2007-11-02

Communication between the endoplasmic reticulum (ER) and mitochondrion is important for bioenergetics and cellular survival. The ER supplies Ca(2+) directly to mitochondria via inositol 1,4,5-trisphosphate receptors (IP3Rs) at close contacts between the two organelles referred to as mitochondrion-associated ER membrane (MAM). We found here that the ER protein sigma-1 receptor (Sig-1R), which is implicated in neuroprotection, carcinogenesis, and neuroplasticity, is a Ca(2+)-sensitive and ligand-operated receptor chaperone at MAM. Normally, Sig-1Rs form a complex at MAM with another chaperone, BiP. Upon ER Ca(2+) depletion or via ligand stimulation, Sig-1Rs dissociate from BiP, leading to a prolonged Ca(2+) signaling into mitochondria via IP3Rs. Sig-1Rs can translocate under chronic ER stress. Increasing Sig-1Rs in cells counteracts ER stress response, whereas decreasing them enhances apoptosis. These results reveal that the orchestrated ER chaperone machinery at MAM, by sensing ER Ca(2+) concentrations, regulates ER-mitochondrial interorganellar Ca(2+) signaling and cell survival.

Dual-wavelength Nd:CaLnAlO4 lasers at 1.365 and 1.390 μm

NASA Astrophysics Data System (ADS)

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

2018-02-01

Tetragonal calcium rare-earth aluminates, CaLnAlO4, are attractive laser host crystals. The emission of Nd3+ ions at 1.3- 1.4 μm due to the 4F3/2 -> 4I13/2 transition is of interest for medicine, fiber optics, and light conversion. We report on compact Nd:CaLnAlO4 lasers using a plane-plane cavity. With an a-cut 0.8 at.% Nd:CaYAlO4 crystal diode-pumped at 802 nm, a maximum continuous-wave output power of 365 mW was achieved at 1.365 & 1.390 μm corresponding to the σ-polarization. The 4F3/2 -> 4I13/2 laser performance of the Nd:CaLnAlO4 crystals was compared to that from a monoclinic Nd:KGd(WO4)2. At the 4F3/2-> 4I11/2 transition (1.08 μm), a Nd:CaYAlO4 micro-laser generated multi-watt output (>4 W) with a slope efficiency of 39%.

Calcium ion as intracellular messenger and cellular toxin.

PubMed

Rasmussen, H; Barrett, P; Smallwood, J; Bollag, W; Isales, C

1990-03-01

Ca2+ serves a nearly universal intracellular messenger function in cell activation, but excess Ca2+ is also a cellular toxin. The possibility of Ca2+ intoxication is minimized by an elaborate autoregulatory system in which changes in Ca2+ influx rate across the plasma membrane are rapidly compensated for by parallel changes in Ca2+ efflux rate. By this mean, cellular Ca2+ homestasis is maintained so that minimal changes in total cell calcium and cytosolic Ca2+ concentration occur during sustained Ca2(+)-mediated responses. Rather than a sustained increase in cytosolic Ca2+ concentration, it is the localized cycling of Ca2+ across the plasma membrane that is the critically important Ca2+ messenger during the sustained phase of cellular responses mediated via surface receptors linked to the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 hydrolysis gives rise to inositol(1,4,5)trisphosphate (IP3) and diacylglycerol (DAG). The IP3 acts to release Ca2+ from an intracellular pool, thereby causing a transient rise in cytosolic Ca2+ concentration. This transient Ca2+ signal activates calmodulin-dependent protein kinases transiently, and hence, causes the transient phosphorylation of a subset of cellular proteins that mediate the initial phase of the response. The DAG brings about the association of protein kinase C (PKC) with the plasma membrane where a receptor-mediated increase in Ca2+ cycling across the membrane regulates PKC activity. The sustained phosphorylation of a second subset of proteins by PKC mediates the sustained phase of the response. Hence, Ca2+ serves as a messenger during both phases of the cellular response, but its cellular sites of action, its mechanisms of generation, and its molecular targets differ during the initial and sustained phases of the response.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium ion as intracellular messenger and cellular toxin.

PubMed Central

Rasmussen, H; Barrett, P; Smallwood, J; Bollag, W; Isales, C

1990-01-01

Ca2+ serves a nearly universal intracellular messenger function in cell activation, but excess Ca2+ is also a cellular toxin. The possibility of Ca2+ intoxication is minimized by an elaborate autoregulatory system in which changes in Ca2+ influx rate across the plasma membrane are rapidly compensated for by parallel changes in Ca2+ efflux rate. By this mean, cellular Ca2+ homestasis is maintained so that minimal changes in total cell calcium and cytosolic Ca2+ concentration occur during sustained Ca2(+)-mediated responses. Rather than a sustained increase in cytosolic Ca2+ concentration, it is the localized cycling of Ca2+ across the plasma membrane that is the critically important Ca2+ messenger during the sustained phase of cellular responses mediated via surface receptors linked to the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 hydrolysis gives rise to inositol(1,4,5)trisphosphate (IP3) and diacylglycerol (DAG). The IP3 acts to release Ca2+ from an intracellular pool, thereby causing a transient rise in cytosolic Ca2+ concentration. This transient Ca2+ signal activates calmodulin-dependent protein kinases transiently, and hence, causes the transient phosphorylation of a subset of cellular proteins that mediate the initial phase of the response. The DAG brings about the association of protein kinase C (PKC) with the plasma membrane where a receptor-mediated increase in Ca2+ cycling across the membrane regulates PKC activity. The sustained phosphorylation of a second subset of proteins by PKC mediates the sustained phase of the response. Hence, Ca2+ serves as a messenger during both phases of the cellular response, but its cellular sites of action, its mechanisms of generation, and its molecular targets differ during the initial and sustained phases of the response.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2190811

Effects of Neodymium and Calcium on the Thermal Stability of AZ71 Magnesium Alloys

NASA Astrophysics Data System (ADS)

Yue, Cheng-Feng; Huang, Shi-Jei; Chen, Jhewn-Kuang; Li, Hsien-Tsung; Chan, Kam-Shau

2018-03-01

The effects of an addition of 0-2 wt% Nd on thermal stability of 0-3 wt% Ca-containing modified AZ71 magnesium alloys was investigated. The ignition temperature was found to increase from that of AZ71, 574, to 825 °C with the addition of 0.5 wt% Ca and 1 wt% Nd. The ignition temperature was further increased to 1114 °C when 3 wt% Ca was added. The Ca- and Nd-added AZ71 was isothermally maintained at a temperature of 500 °C in air for 12 h. The MgO-CaO-Nd2O3 formed on the surface to improve the thermal stability of the AZ71-xCa-yNd alloys. While both the tensile strength and ductility decreased with the Ca concentration in the alloy, an addition of 1 wt% Nd was found able to alleviate the degradation effects of Ca on the tensile strength and ductility at 170 °C. Both solid solution formation and precipitation strengthening contributed to the increase in toughness. AZ71 containing 0.5-2 wt% Ca and 1 wt% Nd provides the optimum combination of ignition resistance and mechanical properties.

Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite.

PubMed

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

2016-08-01

Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite

NASA Astrophysics Data System (ADS)

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

2016-08-01

Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

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

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

Fallon, Jennifer L.; Baker, Mariah R.; Xiong, Liangwen

2009-11-10

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

Inflammation alters regional mitochondrial Ca²+ in human airway smooth muscle cells.

PubMed

Delmotte, Philippe; Yang, Binxia; Thompson, Michael A; Pabelick, Christina M; Prakash, Y S; Sieck, Gary C

2012-08-01

Regulation of cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) in airway smooth muscle (ASM) is a key aspect of airway contractility and can be modulated by inflammation. Mitochondria have tremendous potential for buffering [Ca(2+)](cyt), helping prevent Ca(2+) overload, and modulating other intracellular events. Here, compartmentalization of mitochondria to different cellular regions may subserve different roles. In the present study, we examined the role of Ca(2+) buffering by mitochondria and mitochondrial Ca(2+) transport mechanisms in the regulation of [Ca(2+)](cyt) in enzymatically dissociated human ASM cells upon exposure to the proinflammatory cytokines TNF-α and IL-13. Cells were loaded simultaneously with fluo-3 AM and rhod-2 AM, and [Ca(2+)](cyt) and mitochondrial Ca(2+) concentration ([Ca(2+)](mito)) were measured, respectively, using real-time two-color fluorescence microscopy in both the perinuclear and distal, perimembranous regions of cells. Histamine induced a rapid increase in both [Ca(2+)](cyt) and [Ca(2+)](mito), with a significant delay in the mitochondrial response. Inhibition of the mitochondrial Na(+)/Ca(2+) exchanger (1 μM CGP-37157) increased [Ca(2+)](mito) responses in perinuclear mitochondria but not distal mitochondria. Inhibition of the mitochondrial uniporter (1 μM Ru360) decreased [Ca(2+)](mito) responses in perinuclear and distal mitochondria. CGP-37157 and Ru360 significantly enhanced histamine-induced [Ca(2+)](cyt). TNF-α and IL-13 both increased [Ca(2+)](cyt), which was associated with decreased [Ca(2+)](mito) in the case of TNF-α but not IL-13. The effects of TNF-α on both [Ca(2+)](cyt) and [Ca(2+)](mito) were affected by CGP-37157 but not by Ru360. Overall, these data demonstrate that in human ASM cells, mitochondria buffer [Ca(2+)](cyt) after agonist stimulation and its enhancement by inflammation. The differential regulation of [Ca(2+)](mito) in different parts of ASM cells may serve to locally regulate Ca(2+) fluxes from intracellular sources versus the plasma membrane as well as respond to differential energy demands at these sites. We propose that such differential mitochondrial regulation, and its disruption, may play a role in airway hyperreactivity in diseases such as asthma, where [Ca(2+)](cyt) is increased.

Phase equilibria, crystal structures, and dielectric anomaly in the BaZrO 3-CaZrO 3 system

NASA Astrophysics Data System (ADS)

Levin, Igor; Amos, Tammy G.; Bell, Steven M.; Farber, Leon; Vanderah, Terrell A.; Roth, Robert S.; Toby, Brian H.

2003-11-01

Phase equilibria in the (1- x)BaZrO 3- xCaZrO 3 system were analyzed using a combination of X-ray and neutron powder diffraction, and transmission electron microscopy. The proposed phase diagram features two extended two-phase fields containing mixtures of a Ba-rich cubic phase and a tetragonal, or orthorhombic Ca-rich phase, all having perovskite-related structures. The symmetry differences in the Ca-rich phases are caused by different tilting patterns of the [ZrO 6] octahedra. In specimens quenched from 1650°C, CaZrO 3 dissolves only a few percent of Ba, whereas the solubility of Ca in BaZrO 3 is approximately 30 at% . The BaZrO 3-CaZrO 3 system features at least two tilting phase transitions, Pm3 m→ I4/ mcm and I4/ mcm→ Pbnm. Rietveld refinements of the Ba 0.8Ca 0.2ZrO 3 structure using variable-temperature neutron powder diffraction data confirmed that the Pm3 m→ I4/ mcm transition corresponds to a rotation of octahedra about one of the cubic axes; successive octahedra along this axis rotate in opposite directions. In situ variable-temperature electron diffraction studies indicated that the transition temperature increases with increasing Ca-substitution on the A-sites, from approximately -120°C at 5 at% Ca to 225°C at 20 at% Ca. Dielectric measurements revealed that the permittivity increases monotonically from 36 for BaZrO 3 to 53 for Ba 0.9Ca 0.1ZrO 3, and then decreases to 50 for Ba 0.8Ca 0.2ZrO 3. This later specimen was the Ca-richest composition for which pellets could be quenched from the single-phase cubic field with presently available equipment. Strongly non-monotonic behavior was also observed for the temperature coefficient of resonant frequency; however, in this case, the maximum occurred at a lower Ca concentration, 0.05⩽ x⩽0.1. The non-linear behavior of the dielectric properties was attributed to two competing structural effects: a positive effect associated with substitution of relatively small Ca cations on the A-sites, resulting in stretched Ca-O bonds, and a negative effect, related to the distortion of the A-site environment (bond strain relaxation) upon octahedral tilting.

Identification of Glycosylation Sites Essential for Surface Expression of the CaVα2δ1 Subunit and Modulation of the Cardiac CaV1.2 Channel Activity*

PubMed Central

Tétreault, Marie-Philippe; Bourdin, Benoîte; Briot, Julie; Segura, Emilie; Lesage, Sylvie; Fiset, Céline; Parent, Lucie

2016-01-01

Alteration in the L-type current density is one aspect of the electrical remodeling observed in patients suffering from cardiac arrhythmias. Changes in channel function could result from variations in the protein biogenesis, stability, post-translational modification, and/or trafficking in any of the regulatory subunits forming cardiac L-type Ca2+ channel complexes. CaVα2δ1 is potentially the most heavily N-glycosylated subunit in the cardiac L-type CaV1.2 channel complex. Here, we show that enzymatic removal of N-glycans produced a 50-kDa shift in the mobility of cardiac and recombinant CaVα2δ1 proteins. This change was also observed upon simultaneous mutation of the 16 Asn sites. Nonetheless, the mutation of only 6/16 sites was sufficient to significantly 1) reduce the steady-state cell surface fluorescence of CaVα2δ1 as characterized by two-color flow cytometry assays and confocal imaging; 2) decrease protein stability estimated from cycloheximide chase assays; and 3) prevent the CaVα2δ1-mediated increase in the peak current density and voltage-dependent gating of CaV1.2. Reversing the N348Q and N812Q mutations in the non-operational sextuplet Asn mutant protein partially restored CaVα2δ1 function. Single mutation N663Q and double mutations N348Q/N468Q, N348Q/N812Q, and N468Q/N812Q decreased protein stability/synthesis and nearly abolished steady-state cell surface density of CaVα2δ1 as well as the CaVα2δ1-induced up-regulation of L-type currents. These results demonstrate that Asn-663 and to a lesser extent Asn-348, Asn-468, and Asn-812 contribute to protein stability/synthesis of CaVα2δ1, and furthermore that N-glycosylation of CaVα2δ1 is essential to produce functional L-type Ca2+ channels. PMID:26742847

Origins of mass-dependent and mass-independent Ca isotope variations in meteoritic components and meteorites

NASA Astrophysics Data System (ADS)

Bermingham, K. R.; Gussone, N.; Mezger, K.; Krause, J.

2018-04-01

The Ca isotope composition of meteorites and their components may vary due to mass-dependent and/or -independent isotope effects. In order to evaluate the origin of these effects, five amoeboid olivine aggregates (AOAs), three calcium aluminum inclusions (CAIs), five chondrules (C), a dark inclusion from Allende (CV3), two dark fragments from North West Africa 753 (NWA 753; R3.9), and a whole rock sample of Orgueil (CI1) were analyzed. This is the first coupled mass-dependent and -independent Ca isotope dataset to include AOAs, a dark inclusion, and dark fragments. Where sample masses permit, Ca isotope data are reported with corresponding petrographic analyses and rare earth element (REE) relative abundance patterns. The CAIs and AOAs are enriched in light Ca isotopes (δ44/40Ca -5.32 to +0.72, where δ44/40Ca is reported relative to SRM 915a). Samples CAI 5 and AOA 1 have anomalous Group II REE patterns. These REE and δ44/40Ca data suggest that the CAI 5 and AOA 1 compositions were set via kinetic isotope fractionation during condensation and evaporation. The remaining samples show mass-dependent Ca isotope variations which cluster between δ44/40Ca +0.53 and +1.59, some of which are coupled with unfractionated REE abundance patterns. These meteoritic components likely formed through the coaccretion of the evaporative residue and condensate following Group II CAI formation or their chemical and isotopic signatures were decoupled (e.g., via nebular or parent-body alteration). The whole rock sample of Orgueil has a δ44/40Ca +0.67 ± 0.18 which is in agreement with most published data. Parent-body alteration, terrestrial alteration, and variable sampling of Ca-rich meteoritic components can have an effect on δ44/40Ca compositions in whole rock meteorites. Samples AOA 1, CAI 5, C 2, and C 4 display mass-independent 48/44Ca anomalies (ε48/44Ca +6 to +12) which are resolved from the standard composition. Other samples measured for these effects (AOA 5, CAI 1, CAI 2, C 3, D 1, D 2, D 3) possess the same 48/44Ca isotope composition as the standard within analytical uncertainty. These data indicate a heterogeneous distribution of 48Ca in the early solar nebula during formation of CAIs, AOAs, and chondrules. In a ε48/44Ca vs. δ44/40Ca plot, no strong correlation is evident which suggests that the thermal processing event which caused a heterogeneous distribution of ε48/44Ca in the solar nebula is unlikely to be directly related to the thermal processing event that caused coupled REE and Ca mass-dependent isotopic fractionation in meteoritic components.

Properties of spontaneous Ca2+ transients recorded from interstitial cells of Cajal-like cells of the rabbit urethra in situ

PubMed Central

Hashitani, Hikaru; Suzuki, Hikaru

2007-01-01

Interstitial cells of Cajal-like cells (ICC-LCs) in the urethra may act as electrical pacemakers of spontaneous contractions. However, their properties in situ and their interaction with neighbouring urethral smooth muscle cells (USMCs) remain to be elucidated. To further explore the physiological role of ICC-LCs, spontaneous changes in [Ca2+]i (Ca2+ transients) were visualized in fluo-4 loaded preparations of rabbit urethral smooth muscle. ICC-LCs were sparsely distributed, rather than forming an extensive network. Ca2+ transients in ICC-LCs had a lower frequency and a longer half-width than those of USMCs. ICC-LCs often exhibited Ca2+ transients synchronously with each other, but did not often show a close temporal relationship with Ca2+ transients in USMCs. Nicardipine (1 μm) suppressed Ca2+ transients in USMCs but not in ICC-LCs. Ca2+ transients in ICC-LCs were abolished by cyclopiazonic acid (10 μm), ryanodine (50 μm) and caffeine (10 mm) or by removing extracellular Ca2+, and inhibited by 2-aminoethoxydiphenyl borate (50 μm) and 3-morpholino-sydnonimine (SIN-1; 10 μm), but facilitated by increasing extracellular Ca2+ or phenylephrine (1–10 μm). These results indicated that Ca2+ transients in urethral ICC-LCs in situ rely on both Ca2+ release from intracellular Ca2+ stores and Ca2+ influx through non-L-type Ca2+ channel pathways. ICC-LCs may not act as a coordinated pacemaker electrical network as do ICC in the gastrointestinal (GI) tract. Rather they may randomly increase excitability of USMCs to maintain the tone of urethral smooth muscles. PMID:17615099

Nicergoline inhibits T-type Ca2+ channels in rat isolated hippocampal CA1 pyramidal neurones.

PubMed Central

Takahashi, K.; Akaike, N.

1990-01-01

1. The effects of nicergoline on the T- and L-type Ca2+ currents in pyramidal cells freshly isolated from rat hippocampal CA1 region were investigated by use of a 'concentration-clamp' technique. The technique combines a suction-pipette technique, which allows intracellular perfusion under a single-electrode voltage-clamp, and rapid exchange of extracellular solution within 2 ms. 2. T-type Ca2+ currents were evoked by step depolarizations from a holding potential of -100 mV to potentials more positive than -70 to -60 mV, and reached a peak at about -30 mV in the current-voltage relationship. Activation and inactivation of T-type Ca2+ currents were highly potential-dependent. 3. Nicergoline and other Ca2+ antagonists dose-dependently blocked the T-type Ca2+ channel with an order of potency nicardipine greater than nicergoline greater than diltiazem. 4. The L-type Ca2+ channel was also blocked in the order nicardipine greater than nicergoline greater than diltiazem, although the T-type Ca2+ channel was more sensitive to nicergoline. 5. The inhibitory effects of nicergoline and nicardipine on the T-type Ca2+ current were voltage-, time-, and use-dependent, and the inhibition increased with a decrease in the external Ca2+ concentration. Diltiazem showed only a use-dependent block. PMID:2169937

Nicergoline inhibits T-type Ca2+ channels in rat isolated hippocampal CA1 pyramidal neurones.

PubMed

Takahashi, K; Akaike, N

1990-08-01

1. The effects of nicergoline on the T- and L-type Ca2+ currents in pyramidal cells freshly isolated from rat hippocampal CA1 region were investigated by use of a 'concentration-clamp' technique. The technique combines a suction-pipette technique, which allows intracellular perfusion under a single-electrode voltage-clamp, and rapid exchange of extracellular solution within 2 ms. 2. T-type Ca2+ currents were evoked by step depolarizations from a holding potential of -100 mV to potentials more positive than -70 to -60 mV, and reached a peak at about -30 mV in the current-voltage relationship. Activation and inactivation of T-type Ca2+ currents were highly potential-dependent. 3. Nicergoline and other Ca2+ antagonists dose-dependently blocked the T-type Ca2+ channel with an order of potency nicardipine greater than nicergoline greater than diltiazem. 4. The L-type Ca2+ channel was also blocked in the order nicardipine greater than nicergoline greater than diltiazem, although the T-type Ca2+ channel was more sensitive to nicergoline. 5. The inhibitory effects of nicergoline and nicardipine on the T-type Ca2+ current were voltage-, time-, and use-dependent, and the inhibition increased with a decrease in the external Ca2+ concentration. Diltiazem showed only a use-dependent block.

DA-6034 Induces [Ca(2+)]i Increase in Epithelial Cells.

PubMed

Yang, Yu-Mi; Park, Soonhong; Ji, Hyewon; Kim, Tae-Im; Kim, Eung Kweon; Kang, Kyung Koo; Shin, Dong Min

2014-04-01

DA-6034, a eupatilin derivative of flavonoid, has shown potent effects on the protection of gastric mucosa and induced the increases in fluid and glycoprotein secretion in human and rat corneal and conjunctival cells, suggesting that it might be considered as a drug for the treatment of dry eye. However, whether DA-6034 induces Ca(2+) signaling and its underlying mechanism in epithelial cells are not known. In the present study, we investigated the mechanism for actions of DA-6034 in Ca(2+) signaling pathways of the epithelial cells (conjunctival and corneal cells) from human donor eyes and mouse salivary gland epithelial cells. DA-6034 activated Ca(2+)-activated Cl(-) channels (CaCCs) and increased intracellular calcium concentrations ([Ca(2+)]i) in primary cultured human conjunctival cells. DA-6034 also increased [Ca(2+)]i in mouse salivary gland cells and human corneal epithelial cells. [Ca(2+)]i increase of DA-6034 was dependent on the Ca(2+) entry from extracellular and Ca(2+) release from internal Ca(2+) stores. Interestingly, these effects of DA-6034 were related to ryanodine receptors (RyRs) but not phospholipase C/inositol 1,4,5-triphosphate (IP3) pathway and lysosomal Ca(2+) stores. These results suggest that DA-6034 induces Ca(2+) signaling via extracellular Ca(2+) entry and RyRs-sensitive Ca(2+) release from internal Ca(2+) stores in epithelial cells.

Monensin causes transient calcium ion influx into mouse splenic lymphocytes in a sodium ion-independent fashion.

PubMed

Satoh, Eiki; Satoh, Kiyohiro

2007-04-30

Monensin, a Na(+) ionophore, can increase cytosolic free Ca(2+) concentration ([Ca(2+)](i)) in many cell types, but no studies have investigated the mechanism underlying a monensin-induced increase in [Ca(2+)](i) in immune cells. In view of this, we investigated the effect of monensin on [Ca(2+)](i) and cytosolic free Na(+) concentration ([Na(+)](i)) in mouse splenic lymphocytes using a fluorescence Ca(2+) indicator, fura-2, and a fluorescence Na(+) indicator, sodium-binding benzofuran isophthalate (SBFI), respectively. Monensin (1-100 microM) caused transient and sustained increases in [Ca(2+)](i) and [Na(+)](i), respectively, in a concentration-dependent manner. The monensin-induced increase in [Ca(2+)](i) was abolished by the omission of extracellular Ca(2+) or 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF-96365, 100-150 microM), and was largely inhibited by Ni(2+) (2-5 mM). The omission of extracellular Na(+) failed to inhibit the monensin-induced increases in [Ca(2+)](i). Furthermore, tetrodotoxin (1-10 microM), 5-(N,N-dimethyl)-amiloride (DMA, 10-20 microM), 2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline (SEA0400, 3-10 microM), verapamil (10-200 microM), nifedipine (10-200 microM), omega-agatoxin IVA (0.2-10 microM), omega-conotoxin GVIA (1-10 microM), omega-conotoxin MVIIC (0.5-10 microM), and nordihydroguaiaretic acid (NDGA, 1-10 microM) had no effect on the increases in [Ca(2+)](i). Monensin-induced Mn(2+) influx into splenic lymphocytes. The Mn(2+) influx was completely inhibited by SKF-96365. These results suggest that monensin transiently increases [Ca(2+)](i) in mouse splenic lymphocytes by stimulating Ca(2+) entry via non-selective cation channels in a Na(+)-independent manner.

Ammon's Horn 2 (CA2) of the Hippocampus: A Long-Known Region with a New Potential Role in Neurodegeneration.

PubMed

Pang, Cindy Chi-Ching; Kiecker, Clemens; O'Brien, John T; Noble, Wendy; Chang, Raymond Chuen-Chung

2018-06-01

The hippocampus has a critical role in cognition and human memory and is one of the most studied structures in the brain. Despite more than 400 years of research, little is known about the Ammon's horn region cornu ammonis 2 (CA2) subfield in comparison to other subfield regions (CA1, CA3, and CA4). Recent findings have shown that CA2 plays a bigger role than previously thought. Here, we review understanding of hippocampus and CA2 ontogenesis, together with basic and clinical findings about the potential role of this region in neurodegenerative disease. The CA2 has widespread anatomical connectivity, unique signaling molecules, and intrinsic electrophysiological properties. Experimental studies using in vivo models found that the CA2 region has a role in cognition, especially in social memory and object recognition. In models of epilepsy and hypoxia, the CA2 exhibits higher resilience to cell death and hypoxia in comparison with neighboring regions, and while hippocampal atrophy remains poorly understood in Parkinson's disease (PD) and dementia with Lewy bodies (DLB), findings from postmortem PD brain demonstrates clear accumulation of α-synuclein pathology in CA2, and the CA2-CA3 region shows relatively more atrophy compared with other hippocampal subfields. Taken together, there is a growing body of evidence suggesting that the CA2 can be an ideal hallmark with which to differentiate different neurodegenerative stages of PD. Here, we summarize these recent data and provide new perspectives/ideas for future investigations to unravel the contribution of the CA2 to neurodegenerative diseases.

A “mix-and-match” approach to designing Ca2+ microdomains at membrane-contact sites

PubMed Central

Penny, Christopher J; Kilpatrick, Bethan S; Min Han, Jung; Sneyd, James; Patel, Sandip

2014-01-01

Ca2+ microdomains are critical for regulating cellular activity and often form at membrane contact sites. Such sites between lysosomes and the ER potentially provide a platform for signaling by the Ca2+ mobilizing messenger NAADP. However, at present we know little of how Ca2+ release events are coordinated at these experimentally intractable junctions. We therefore developed a computational model of lysosome-ER microdomains, which suggested that small leaks of Ca2+ from the lysosome couple to Ca2+-sensitive Ins(1,4,5)P3 receptors on the ER to generate global, microdomain-dependent Ca2+ signals. Here we discuss how the “mix-and-match” arrangement of different Ca2+ signaling proteins on the “source” and “target” membranes might generate functionally heterogeneous Ca2+ microdomains. PMID:25077010

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

PubMed Central

Loomis-Husselbee, J W; Dawson, A P

1993-01-01

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

Deficiency of MIP phosphatase induces a muscle disorder by disrupting Ca2+ homeostasis

PubMed Central

Shen, Jinhua; Yu, Wen-Mei; Brotto, Marco; Scherman, Joseph A.; Guo, Caiying; Stoddard, Christopher; Nosek, Thomas M.; Valdivia, Héctor H.; Qu, Cheng-Kui

2009-01-01

The intracellular Ca2+ ([Ca2+]i) level of skeletal muscles must be rapidly regulated during the excitation-contraction-relaxation process 1. However, the signaling components involved in such rapid Ca2+ movement are not fully understood. Here, we report that mice deficient in the novel phosphatidylinositol phosphate (PIP) phosphatase MIP displayed muscle weakness and fatigue. Muscles isolated from MIP−/− mice produced less contractile force, markedly prolonged relaxation, and exhibited exacerbated fatigue. Further analyses revealed that MIP deficiency resulted in spontaneous Ca2+ leak from the internal store — the sarcoplasmic reticulum (SR). This was attributed to the decreased metabolism/dephosphorylation and the subsequent accumulation of MIP substrates, especially PI(3,5)P2 and PI(3,4)P2. Furthermore, we found that PI(3,5)P2 and PI(3,4)P2 bound to and directly activated the Ca2+ release channel/ryanodine receptor (RyR1) of the SR. These studies provide the first evidence that finely controlled PIP levels in muscle cells are essential for maintaining Ca2+ homeostasis and muscle performance. PMID:19465920

Study on the site preference of Ca in superconducting oxides Bi{sub 2}Sr{sub 2−x}Ca{sub x}CuO{sub 6+δ} (0.1 ≤ x ≤ 1.0)

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

Sun, B.Z.; Zhou, S.L.; Wang, H.

2014-01-15

A series of compound with the nominal composition of Bi{sub 2}Sr{sub 2−x}Ca{sub x}CuO{sub 6+δ} (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) were synthesized by the sol–gel method. Constituent phases and crystal structure of samples were analyzed by X-ray diffraction. It can be found that the Ca-doped Bi-2201 system was composed of Bi-2201 phase containing Ca and a small quantity of Bi{sub 16}(Sr,Ca){sub 14}O{sub 38}. For Bi-2201 unit cell containing Ca, chemical component and site preference of Ca atoms were characterized systematically by transmission electron microscopy. With the introduction of Ca atoms, Sr-sites have been occupiedmore » partially by Ca{sup 2+} in Bi-2201 unit cell, which leads to a decrease in the lattice parameters c and b of the Bi-2201 phase when the Ca-content x is below 0.6. Two types of new orthorhombic lattices are formed in the substitution. One is a lattice with space group Pma2 as the two nearest neighbor Sr-sites in the same Sr–O layer are occupied by Ca{sup 2+}. Its lattice parameters can be characterized as a = 5.402 Å, b = 5.313 Å and c = 24.272 Å, respectively. When two nearest Sr ions of the second neighboring Sr–O layers are replaced by Ca{sup 2+} ions, the lattice with the space group Pmn2{sub 1} can be formed. Its lattice parameters are close to that of the previous. The modulation vector is lying in the a*–c* plane in the two new orthorhombic lattices (Pma2 and Pmn2{sub 1}). Bi/Ca-2201 lattice (with Ca) and Bi-2201 lattice (without Ca) coexist in the same Bi{sub 2}Sr{sub 2−x}Ca{sub x}CuO{sub 6}+{sub δ} grain, which can be described as an intergrowth structure.« less

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

PubMed

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

2014-07-18

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

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

PubMed Central

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

2014-01-01

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

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.

Store-operated Ca2+ entry is involved in transforming growth factor-β1 facilitated proliferation of rat airway smooth muscle cells.

PubMed

Gao, Ya-Dong; Zheng, Jun-Wen; Li, Ping; Cheng, Ming; Yang, Jiong

2013-06-01

To investigate the role and underlying mechanisms of store-operated Ca(2+) entry (SOCE) in mediating the promoting effect of transforming growth factor (TGF)-β1 on the proliferation of airway smooth muscle cells (ASMCs). Rat bronchial smooth muscle cells were cultured as we described previously. The intracellular Ca(2+) concentration ([Ca(2+)]i) of ASMCs was measured by laser confocal microscope Ca(2+) fluorescence imaging with Fluo-3/AM. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and p27 expression assay were used to determine the proliferation rate of ASMCs. We demonstrated that TGF-β1 (10 ng/ml) increased basal (Ca(2+)]i) level, [Ca(2+)]i rise induced by thapsigargin-induced Ca(2+) release and SOCE in rat ASMCs. This effect of TGF-β1 on SOCE was not inhibited by glucocorticoid dexamethasone (DXM, 100 nM), antioxidant α-tocopherol (100 μM), and intermediate-conductance Ca(2+)-activated K(+) channels (IKCa) inhibitor charybdotoxin (100 nM), suggesting that reactive oxygen species and IKCa channels might not mediate the effect of TGF-β1. TGF-β1 slightly increased the expression of Orai1 and STIM1, two important molecules involved in the molecule component and regulation of SOC channels, in the presence of 10% fetal bovine serum (FBS). The proliferation of ASMC stimulated with 2.5% FBS was promoted by TGF-β1, and partly inhibited by non-specific Ca(2+) channel blocker SKF-96365 (10 μM) and Ni(2+) (100 μM). DXM, α-tocopherol, and charybdotoxin had no effect on the proliferation promoted by TGF-β1. TGF-β1 promotes ASMC proliferation partly through increasing the expression and activity of SOC channels.

Effect of limestone particle size and calcium to non-phytate phosphorus ratio on true ileal calcium digestibility of limestone for broiler chickens.

PubMed

Anwar, M N; Ravindran, V; Morel, P C H; Ravindran, G; Cowieson, A J

2016-10-01

The purpose of this study was to determine the effect of limestone particle size and calcium (Ca) to non-phytate phosphorus (P) ratio on the true ileal Ca digestibility of limestone for broiler chickens. A limestone sample was passed through a set of sieves and separated into fine (<0.5 mm) and coarse (1-2 mm) particles. The analysed Ca concentration of both particle sizes was similar (420 g/kg). Six experimental diets were developed using each particle size with Ca:non-phytate P ratios of 1.5:1, 2.0:1 and 2.5:1, with ratios being adjusted by manipulating the dietary Ca concentrations. A Ca-free diet was also developed to determine the basal ileal endogenous Ca losses. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to 6 replicate cages (8 birds per cage) and fed from d 21 to 24 post hatch. Apparent ileal digestibility of Ca was calculated using the indicator method and corrected for basal endogenous losses to determine the true Ca digestibility. The basal ileal endogenous Ca losses were determined to be 127 mg/kg of dry matter intake. Increasing Ca:non-phytate P ratios reduced the true Ca digestibility of limestone. The true Ca digestibility coefficients of limestone with Ca:non-phytate P ratios of 1.5, 2.0 and 2.5 were 0.65, 0.57 and 0.49, respectively. Particle size of limestone had a marked effect on the Ca digestibility, with the digestibility being higher in coarse particles (0.71 vs. 0.43).

Inhibitory action of linoleamide and oleamide toward sarco/endoplasmic reticulum Ca2+-ATPase.

PubMed

Yamamoto, Sachiko; Takehara, Munenori; Ushimaru, Makoto

2017-01-01

SERCA maintains intracellular Ca 2+ homeostasis by sequestering cytosolic Ca 2+ into SR/ER stores. Two primary fatty acid amides (PFAAs), oleamide (18:1 9-cis ) and linoleamide (18:2 9,12-cis ), induce an increase in intracellular Ca 2+ levels, which might be caused by their inhibition of SERCA. Three major SERCA isoforms, rSERCA1a, hSERCA2b, and hSERCA3a, were individually overexpressed in COS-1 cells, and the inhibitory action of PFAAs on Ca 2+ -ATPase activity of SERCA was examined. The Ca 2+ -ATPase activity of each SERCA was inhibited in a concentration-dependent manner strongly by linoleamide (IC 50 15-53μM) and partially by oleamide (IC 50 8.3-34μM). Inhibition by other PFAAs, such as stearamide (18:0) and elaidamide (18:1 9-trans ), was hardly or slightly observed. With increasing dose, linoleamide decreased the apparent affinity for Ca 2+ and the apparent maximum velocity of Ca 2+ -ATPase activity of all SERCAs tested. Oleamide also lowered these values for hSERCA3a. Meanwhile, oleamide uniquely reduced the apparent Ca 2+ affinity of rSERCA1a and hSERCA2b: the reduction was considerably attenuated above certain concentrations of oleamide. The dissociation constants for SERCA interaction varied from 6 to 45μM in linoleamide and from 1.6 to 55μM in oleamide depending on the isoform. Linoleamide and oleamide inhibit SERCA activity in the micromolar concentration range, and in a different manner. Both amides mainly suppress SERCA activity by lowering the Ca 2+ affinity of the enzyme. Our findings imply a novel role of these PFAAs as modulators of intracellular Ca 2+ homeostasis via regulation of SERCA activity. Copyright © 2016 Elsevier B.V. All rights reserved.

Possibility of adjusting the photoluminescence spectrum of Ca scheelites to the emission spectrum of incandescent lamps: [ nCaWO4-(1- n)CaMoO4]: Eu3+ solid solutions

NASA Astrophysics Data System (ADS)

Bakovets, V. V.; Zolotova, E. S.; Antonova, O. V.; Korol'kov, I. V.; Yushina, I. V.

2016-12-01

The specific features of the photoluminescence of [ nCaWO4-(1- n)CaMoO4]:Eu3+ solid solutions with the scheelite structure are examined using X-ray phase analysis and photoluminescence, Raman scattering, and diffuse reflectance spectroscopy. The studied features are associated with a change in the long- and short-range orders of the crystal lattice upon variations in the composition of solutions in the range n = 0-1.0 (with a pitch of 0.2) at a concentration of red photoluminescence activator Eu3+ of 2 mol %. The mechanism of the modification of photoluminescence of solid solutions upon variations in their composition has been discussed. Anomalies in the variations in parameters of the crystal lattice, its short-range order, and luminescence spectra have been observed in the transition from pure compounds CaMoO4:Eu3+ and CaWO4:Eu3+ to solutions; the concentration of Eu3+ ions in the centrosymmetric localization increases (decreases) in the transition from the molybdate (tungstate). It has been demonstrated that the spectral radiant emittance of solid solution [0.4CaWO4-0.6CaMoO4]:Eu3+ (2 mol %) is the closest to that of an incandescent lamp.

Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) Activates Global and Heterogeneous Local Ca2+ Signals from NAADP- and Ryanodine Receptor-gated Ca2+ Stores in Pulmonary Arterial Myocytes*

PubMed Central

Jiang, Yong-Liang; Lin, Amanda H. Y.; Xia, Yang; Lee, Suengwon; Paudel, Omkar; Sun, Hui; Yang, Xiao-Ru; Ran, Pixin; Sham, James S. K.

2013-01-01

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca2+-mobilizing messenger that releases Ca2+ from endolysosomal organelles. Recent studies showed that NAADP-induced Ca2+ release is mediated by the two-pore channels (TPCs) TPC1 and TPC2. However, the expression of TPCs and the NAADP-induced local Ca2+ signals have not been examined in vascular smooth muscle. Here, we found that both TPC1 and TPC2 are expressed in rat pulmonary arterial smooth muscle cells (PASMCs), with TPC1 being the major subtype. Application of membrane-permeant NAADP acetoxymethyl ester to PASMCs elicited a biphasic increase in global [Ca2+]i, which was independent of extracellular Ca2+ and blocked by the NAADP antagonist Ned-19 or the vacuolar H+-ATPase inhibitor bafilomycin A1, indicating Ca2+ release from acidic endolysosomal Ca2+ stores. The Ca2+ response was unaffected by xestospongin C but was partially blocked by ryanodine or thapsigargin. NAADP triggered heterogeneous local Ca2+ signals, including a diffuse increase in cytosolic [Ca2+], Ca2+ sparks, Ca2+ bursts, and regenerative Ca2+ release. The diffuse Ca2+ increase and Ca2+ bursts were ryanodine-insensitive, presumably arising from different endolysosomal sources. Ca2+ sparks and regenerative Ca2+ release were inhibited by ryanodine, consistent with cross-activation of loosely coupled ryanodine receptors. Moreover, Ca2+ release stimulated by endothelin-1 was inhibited by Ned-19, ryanodine, or xestospongin C, suggesting that NAADP-mediated Ca2+ signals interact with both ryanodine and inositol 1,4,5-trisphosphate receptors during agonist stimulation. Our results show that NAADP mediates complex global and local Ca2+ signals. Depending on the physiological stimuli, these diverse Ca2+ signals may serve to regulate different cellular functions in PASMCs. PMID:23443655

Transcription of the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase type 3 gene, ATP2A3, is regulated by the calcineurin/NFAT pathway in endothelial cells

PubMed Central

Hadri, Lahouaria; Pavoine, Catherine; Lipskaia, Larissa; Yacoubi, Sabrina; Lompré, Anne-Marie

2005-01-01

Histamine, known to induce Ca2+ oscillations in endothelial cells, was used to alter Ca2+ cycling. Treatment of HUVEC (human umbilical-vein endothelial cell)-derived EA.hy926 cells with histamine for 1–3 days increased the levels of SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase) 3, but not of SERCA 2b, transcripts and proteins. Promoter-reporter gene assays demonstrated that this increase in expression was due to activation of SERCA 3 gene transcription. The effect of histamine was abolished by mepyramine, but not by cimetidine, indicating that the H1 receptor, but not the H2 receptor, was involved. The histamine-induced up-regulation of SERCA 3 was abolished by cyclosporin A and by VIVIT, a peptide that prevents calcineurin and NFAT (nuclear factor of activated T-cells) from interacting, indicating involvement of the calcineurin/NFAT pathway. Histamine also induced the nuclear translocation of NFAT. NFAT did not directly bind to the SERCA 3 promoter, but activated Ets-1 (E twenty-six-1), which drives the expression of the SERCA 3 gene. Finally, cells treated with histamine and loaded with fura 2 exhibited an improved capacity in eliminating high cytosolic Ca2+ concentrations, in accordance with an increase in activity of a low-affinity Ca2+-ATPase, like SERCA 3. Thus chronic treatment of endothelial cells with histamine up-regulates SERCA 3 transcription. The effect of histamine is mediated by the H1R (histamine 1 receptor) and involves activation of the calcineurin/NFAT pathway. By increasing the rate of Ca2+ sequestration, up-regulation of SERCA 3 counteracts the cytosolic increase in Ca2+ concentration. PMID:16250893

Spontaneous sarcoplasmic reticulum calcium release and extrusion from bovine, not porcine, coronary artery smooth muscle.

PubMed Central

Stehno-Bittel, L; Sturek, M

1992-01-01

1. We tested the hypothesis that the Ca(2+)-loaded sarcoplasmic reticulum (SR) of coronary artery smooth muscle spontaneously releases Ca2+ preferentially toward the sarcolemma to be extruded from the cell without increasing the average free myoplasmic [Ca2+] (Ca(im)) concentration. 2. The SR of bovine cells was Ca(2+)-loaded by depolarization-induced Ca2+ influx. Release (unloading) of Ca2+ from the SR during recovery from depolarization was determined by Fura-2 microfluorometry of Ca(im). The SR Ca2+ unloading was maximal following a long (14 min) recovery from depolarization, as shown by the 66% decrease in the peak caffeine-induced Ca(im) transient compared to the Ca(im) transient after a short (2 min) recovery. No increase in Ca(im) occurred during the long recovery. No unloading of the SR Ca2+ store was noted in porcine cells. 3. Approximately 80% of the outward K+ current in bovine and porcine cells was sensitive to subsarcolemmal Ca2+ (Ca(is)) concentrations. Whole-cell voltage clamp using pipette solutions with Ca2+ concentrations clamped between 0 and 1000 nM with Ca(2+)-EGTA or Ca(2+)-BAPTA buffers showed increasing K+ currents (normalized for cell membrane surface area) as a function of both membrane potential and Ca(is). Clamping of Ca(im) and Ca(is) was verified by the lack of changes in K+ current and Fura-2 ratio in response to Ca2+ influx, Ca(2+)-free external solution, or caffeine-induced Ca2+ release. At +30 to +50 mV the K+ current amplitude showed a similar sensitivity to Ca2+ as Fura-2. These data indicate that in this experimental preparation Ca(2+)-activated K+ current is a valid estimate of Ca(is). 4. Simultaneous Ca(im) and Ca(is) measurements in bovine cells which were not Ca(2+)-clamped (2 x 10(-4) M-EGTA pipette solution) showed that during the long recovery period the K+ current (reflecting Ca(is)) increased 55%, while Ca(im) did not change. 5. In quiescent bovine cells the Ca(is) was higher than Ca(im), while the higher resting Ca(is) gradient was not apparent in porcine cells. 6. The Ca(is) concentration was directly related to the amount of Ca2+ in the SR in bovine, but not porcine cells. Depletion of the SR in bovine cells by caffeine resulted in a 58% decrease in K+ current compared to the resting K+ current. 7. Caffeine-induced Ca2+ release caused an increase in Ca(is) which preceded the increase in Ca(im) by approximately 2 s.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1403820

Activation of the Ano1 (TMEM16A) chloride channel by calcium is not mediated by calmodulin

PubMed Central

Zhu, Jinqiu; Qu, Zhiqiang; Cui, Yuan-Yuan; Hartzell, H. Criss

2014-01-01

The Ca2+-activated Cl channel anoctamin-1 (Ano1; Tmem16A) plays a variety of physiological roles, including epithelial fluid secretion. Ano1 is activated by increases in intracellular Ca2+, but there is uncertainty whether Ca2+ binds directly to Ano1 or whether phosphorylation or additional Ca2+-binding subunits like calmodulin (CaM) are required. Here we show that CaM is not necessary for activation of Ano1 by Ca2+ for the following reasons. (a) Exogenous CaM has no effect on Ano1 currents in inside-out excised patches. (b) Overexpression of Ca2+-insensitive mutants of CaM have no effect on Ano1 currents, whereas they eliminate the current mediated by the small-conductance Ca2+-activated K+ (SK2) channel. (c) Ano1 does not coimmunoprecipitate with CaM, whereas SK2 does. Furthermore, Ano1 binds very weakly to CaM in pull-down assays. (d) Ano1 is activated in excised patches by low concentrations of Ba2+, which does not activate CaM. In addition, we conclude that reversible phosphorylation/dephosphorylation is not required for current activation by Ca2+ because the current can be repeatedly activated in excised patches in the absence of ATP or other high-energy compounds. Although Ano1 is blocked by the CaM inhibitor trifluoperazine (TFP), we propose that TFP inhibits the channel in a CaM-independent manner because TFP does not inhibit Ano1 when applied to the cytoplasmic side of excised patches. These experiments lead us to conclude that CaM is not required for activation of Ano1 by Ca2+. Although CaM is not required for channel opening by Ca2+, work of other investigators suggests that CaM may have effects in modulating the biophysical properties of the channel. PMID:24420770

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.

Purification of legumin-like proteins from Coffea arabica and Coffea racemosa seeds and their insecticidal properties toward cowpea weevil ( Callosobruchus maculatus ) (Coleoptera: Bruchidae).

PubMed

Coelho, Mirela Batista; Macedo, Maria Lígia Rodrigues; Marangoni, Sérgio; Silva, Desiree Soares da; Cesarino, Igor; Mazzafera, Paulo

2010-03-10

Legumin-like proteins from seeds of Coffea arabica (CaL-1 and CaL-2) and Coffea racemosa (CrL-1 and CrL-2) were characterized and isolated by gel filtration and reverse-phase chromatography. The insecticidal properties of the purified proteins were tested against Callosobruchus maculatus using artificial diets. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analyses indicated that CaL-1 is composed of two subunits of 33 and 24 kDa, while CaL-2, CrL-1, and CrL-2 were monomeric with a single band of 14 kDa. The LD(50) values were 0.5% (w/w) for CaL-1 and 0.3% (w/w) for CaL-2, CrL-1, and CrL-2. ED(50) at 0.3% was assessed for all protein concentrations. The legumin-like proteins were not digested by midgut homogenates of C. maculatus until 8 h of incubation. CaL-1 and CaL-2 ( C. arabica ) and CrL-1 and CrL-2 ( C. racemosa ) are chitin-binding proteins, and their insecticidal properties toward C. maculatus larvae might be related to their capacity to bind chitin present in the larval gut and their associated low digestibility.

Structure and Calcium Binding Properties of a Neuronal Calcium-Myristoyl Switch Protein, Visinin-Like Protein 3.

PubMed

Li, Congmin; Lim, Sunghyuk; Braunewell, Karl H; Ames, James B

2016-01-01

Visinin-like protein 3 (VILIP-3) belongs to a family of Ca2+-myristoyl switch proteins that regulate signal transduction in the brain and retina. Here we analyze Ca2+ binding, characterize Ca2+-induced conformational changes, and determine the NMR structure of myristoylated VILIP-3. Three Ca2+ bind cooperatively to VILIP-3 at EF2, EF3 and EF4 (KD = 0.52 μM and Hill slope of 1.8). NMR assignments, mutagenesis and structural analysis indicate that the covalently attached myristoyl group is solvent exposed in Ca2+-bound VILIP-3, whereas Ca2+-free VILIP-3 contains a sequestered myristoyl group that interacts with protein residues (E26, Y64, V68), which are distinct from myristate contacts seen in other Ca2+-myristoyl switch proteins. The myristoyl group in VILIP-3 forms an unusual L-shaped structure that places the C14 methyl group inside a shallow protein groove, in contrast to the much deeper myristoyl binding pockets observed for recoverin, NCS-1 and GCAP1. Thus, the myristoylated VILIP-3 protein structure determined in this study is quite different from those of other known myristoyl switch proteins (recoverin, NCS-1, and GCAP1). We propose that myristoylation serves to fine tune the three-dimensional structures of neuronal calcium sensor proteins as a means of generating functional diversity.

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

PubMed

Jolliff, J S; Mahan, D C

2013-06-01

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

Ischemic preconditioning improves mitochondrial tolerance to experimental calcium overload.

PubMed

Crestanello, Juan A; Doliba, Nicolai M; Babsky, Andriy M; Doliba, Natalia M; Niibori, Koki; Whitman, Glenn J R; Osbakken, Mary D

2002-04-01

Ca(2+) overload leads to mitochondrial uncoupling, decreased ATP synthesis, and myocardial dysfunction. Pharmacologically opening of mitochondrial K(ATP) channels decreases mitochondrial Ca(2+) uptake, improving mitochondrial function during Ca(2+) overload. Ischemic preconditioning (IPC), by activating mitochondrial K(ATP) channels, may attenuate mitochondrial Ca(2+) overload and improve mitochondrial function during reperfusion. The purpose of these experiments was to study the effect of IPC (1) on mitochondrial function and (2) on mitochondrial tolerance to experimental Ca(2+) overload. Rat hearts (n = 6/group) were subjected to (a) 30 min of equilibration, 25 min of ischemia, and 30 min of reperfusion (Control) or (b) two 5-min episodes of ischemic preconditioning, 25 min of ischemia, and 30 min of reperfusion (IPC). Developed pressure (DP) was measured. Heart mitochondria were isolated at end-Equilibration (end-EQ) and at end-Reperfusion (end-RP). Mitochondrial respiratory function (state 2, oxygen consumption with substrate only; state 3, oxygen consumption stimulated by ADP; state 4, oxygen consumption after cessation of ADP phosphorylation; respiratory control index (RCI, state 3/state 4); rate of oxidative phosphorylation (ADP/Deltat), and ADP:O ratio) was measured with polarography using alpha-ketoglutarate as a substrate in the presence of different Ca(2+) concentrations (0 to 5 x 10(-7) M) to simulate Ca(2+) overload. IPC improved DP at end-RP. IPC did not improve preischemic mitochondrial respiratory function or preischemic mitochondrial response to Ca(2+) loading. IPC improved state 3, ADP/Deltat, and RCI during RP. Low Ca(2+) levels (0.5 and 1 x 10(-7) M) stimulated mitochondrial function in both groups predominantly in IPC. The Control group showed evidence of mitochondrial uncoupling at lower Ca(2+) concentrations (1 x 10(-7) M). IPC preserved state 3 at high Ca(2+) concentrations. The cardioprotective effect of IPC results, in part, from preserving mitochondrial function during reperfusion and increasing mitochondrial tolerance to Ca(2+) loading at end-RP. Activation of mitochondrial K(ATP) channels by IPC and their improvement in Ca(2+) homeostasis during RP may be the mechanism underlying this protection.

The Ca2+ Status of the Endoplasmic Reticulum Is Altered by Induction of Calreticulin Expression in Transgenic Plants1

PubMed Central

Persson, Staffan; Wyatt, Sarah E.; Love, John; Thompson, William F.; Robertson, Dominique; Boss, Wendy F.

2001-01-01

To investigate the endoplasmic reticulum (ER) Ca2+ stores in plant cells, we generated tobacco (Nicotiana tabacum; NT1) suspension cells and Arabidopsis plants with altered levels of calreticulin (CRT), an ER-localized Ca2+-binding protein. NT1 cells and Arabidopsis plants were transformed with a maize (Zea mays) CRT gene in both sense and antisense orientations under the control of an Arabidopsis heat shock promoter. ER-enriched membrane fractions from NT1 cells were used to examine how altered expression of CRT affects Ca2+ uptake and release. We found that a 2.5-fold increase in CRT led to a 2-fold increase in ATP-dependent 45Ca2+ accumulation in the ER-enriched fraction compared with heat-shocked wild-type controls. Furthermore, after treatment with the Ca2+ ionophore ionomycin, ER microsomes from NT1 cells overproducing CRT showed a 2-fold increase in the amount of 45Ca2+ released, and a 2- to 3-fold increase in the amount of 45Ca2+ retained compared with wild type. These data indicate that altering the production of CRT affects the ER Ca2+ pool. In addition, CRT transgenic Arabidopsis plants were used to determine if altered CRT levels had any physiological effects. We found that the level of CRT in heat shock-induced CRT transgenic plants correlated positively with the retention of chlorophyll when the plants were transferred from Ca2+-containing medium to Ca2+-depleted medium. Together these data are consistent with the hypothesis that increasing CRT in the ER increases the ER Ca2+ stores and thereby enhances the survival of plants grown in low Ca2+ medium. PMID:11457960

Evaluation of ex-vivo 9.4T MRI in post-surgical specimens from temporal lobe epilepsy patients.

PubMed

Kwan, Benjamin Y M; Salehi, Fateme; Kope, Ryan; Lee, Donald H; Sharma, Manas; Hammond, Robert; Burneo, Jorge G; Steven, David; Peters, Terry; Khan, Ali R

2017-10-01

This study evaluates hippocampal pathology through usage of ultra-high field 9.4T ex-vivo imaging of resected surgical specimens in patients who have undergone temporal lobe epilepsy surgery. This is a retrospective interpretation of prospectively acquired data. MRI scanning of resected surgical specimens from patients who have undergone temporal lobe epilepsy surgery was performed on a 9.4T small bore Varian MR magnet. Structural images employed a balanced steady-state free precession sequence (TrueFISP). Six patients (3 females; 3 males) were included in this study with an average age at surgery of 40.7 years (range 20Y_"60) (one was used as a control reference). Two neuroradiologists qualitatively reviewed the ex-vivo MRIs of resected specimens while blinded to the histopathology reports for the ability to identify abnormal features in hippocampal subfield structures. The hippocampal subfields were reliably identified on the 9.4T ex-vivo scans in the hippocampal head region and hippocampal body region by both neuroradiologists in all 6 patients. There was high concordance to pathology for abnormalities detected in the CA1, CA2, CA3 and CA4 subfields. Detection of abnormalities in the dentate gyrus was also high with detection in 4 of 5 cases. The Cohen's kappa between the two neuroradiologists was calculated at 0.734 SE=0.102. Ex-vivo 9.4T specimen imaging can detect abnormalities in CA1, CA2, CA3, CA4 and DG in both the hippocampal head and body. There was good concordance between qualitative findings and histopathological abnormalities for CA1, CA2, CA3, CA4 and DG. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Calcium buffering properties of calbindin D28k and parvalbumin in rat sensory neurones.

PubMed Central

Chard, P S; Bleakman, D; Christakos, S; Fullmer, C S; Miller, R J

1993-01-01

1. We have examined the ability of the Ca(2+)-binding proteins (CABP) calbindin D28k and paravalbumin to modulate increases in the intracellular free Ca2+ concentration ([Ca2+]i), produced by brief depolarizations, in rat dorsal root ganglion (DRG) neurones. 2. In order to obtain good voltage control, we replated DRG neurones prior to performing these experiments. Immunocytochemical staining of these cells revealed that approximately 10% stained for CABPs. 3. Using fluorescently labelled parvalbumin, we demonstrated that in the whole-cell voltage clamp mode the protein freely entered the cell soma with a mean half-life t0.5 of 6 min 22 s +/- 54 s. 4. Analysis of the effects of calbindin D28k (370 microM) and parvalbumin (1 mM) on Ca2+ currents in the whole-cell voltage clamp mode, revealed that neither protein changed the rate of inactivation of the Ca2+ current or its rate of run-down. 5. Introducing either calbindin D28k (370 microM) or parvalbumin (1 mM) into the cell soma did not significantly alter the basal [Ca2+]i when compared to control cells. 6. Compared to control cells, both CABPs significantly reduced the peak [Ca2+]i obtained for a Ca2+ influx of an equivalent charge density, whereas lysozyme (1 mM), a protein with low affinity for Ca2+, failed to do so. 7. Calbindin D28k caused an 8-fold decrease in the rate of rise in [Ca2+]i and altered the kinetics of decay of [Ca2+]i to a single slow component. Parvalbumin also slowed the rate of rise in [Ca2+]i. Parvalbumin selectively increased a fast component in the decay of the Ca2+ signal. 8. These data demonstrate that both calbindin D28k and paravalbumin effectively buffer Ca2+ in a cellular environment and may therefore regulate Ca(2+)-dependent aspects of neuronal function. Images Fig. 1 PMID:8145149

Increases in intracellular calcium via activation of potentially multiple phospholipase C isozymes in mouse olfactory neurons

PubMed Central

Szebenyi, Steven A.; Ogura, Tatsuya; Sathyanesan, Aaron; AlMatrouk, Abdullah K.; Chang, Justin; Lin, Weihong

2014-01-01

Phospholipase C (PLC) and internal Ca2+ stores are involved in a variety of cellular functions. However, our understanding of PLC in mammalian olfactory sensory neurons (OSNs) is generally limited to its controversial role in odor transduction. Here we employed single-cell Ca2+ imaging and molecular approaches to investigate PLC-mediated Ca2+ responses and its isozyme gene transcript expression. We found that the pan-PLC activator m-3M3FBS (25 μM) induces intracellular Ca2+ increases in vast majority of isolated mouse OSNs tested. Both the response amplitude and percent responding cells depend on m-3M3FBS concentrations. In contrast, the inactive analog o-3M3FBS fails to induce Ca2+ responses. The m-3M3FBS-induced Ca2+ increase is blocked by the PLC inhibitor U73122, while its inactive analog U73433 has no effect. Removal of extracellular Ca2+ does not change significantly the m-3M3FBS-induced Ca2+ response amplitude. Additionally, in the absence of external Ca2+, we found that a subset of OSNs respond to an odorant mixture with small Ca2+ increases, which are significantly suppressed by U73122. Furthermore, using reverse transcription polymerase chain reaction and real-time quantitative polymerase chain reaction, we found that multiple PLC isozyme gene transcripts are expressed in olfactory turbinate tissue in various levels. Using RNA in situ hybridization analysis, we further show expression of β4, γ1, γ2 gene transcripts in OSNs. Taken together, our results establish that PLC isozymes are potent enzymes for mobilizing intracellular Ca2+ in mouse OSNs and provide molecular insight for PLC isozymes-mediated complex cell signaling and regulation in the peripheral olfactory epithelium. PMID:25374507

Transcription factor Sp1 regulates T-type Ca(2+) channel CaV 3.1 gene expression.

PubMed

González-Ramírez, Ricardo; Martínez-Hernández, Elizabeth; Sandoval, Alejandro; Felix, Ricardo

2014-05-01

Voltage-gated T-type Ca(2+) (CaV 3) channels mediate a number of physiological events in developing and mature cells, and are implicated in neurological and cardiovascular diseases. In mammals, there are three distinct T-channel genes (CACNA1G, CACNA1H, and CACNA1I) encoding proteins (CaV 3.1-CaV 3.3) that differ in their localization as well as in molecular, biophysical, and pharmacological properties. The CACNA1G is a large gene that contains 38 exons and is localized in chromosome 17q22. Only basic characteristics of the CACNA1G gene promoter region have been investigated classifying it as a TATA-less sequence containing several potential transcription factor-binding motifs. Here, we cloned and characterized a proximal promoter region and initiated the analysis of transcription factors that control CaV 3.1 channel expression using the murine Cacna1g gene as a model. We isolated a ∼1.5 kb 5'-upstream region of Cacna1g and verified its transcriptional activity in the mouse neuroblastoma N1E-115 cell line. In silico analysis revealed that this region possesses a TATA-less minimal promoter that includes two potential transcription start sites and four binding sites for the transcription factor Sp1. The ability of one of these sites to interact with the transcription factor was confirmed by electrophoretic mobility shift assays. Consistent with this, Sp1 over-expression enhanced promoter activity while siRNA-mediated Sp1 silencing significantly decreased the level of CaV 3.1 protein and reduced the amplitude of whole-cell T-type Ca(2+) currents expressed in the N1E-115 cells. These results provide new insights into the molecular mechanisms that control CaV 3.1 channel expression. © 2013 Wiley Periodicals, Inc.

Synaptically activated Ca2+ waves and NMDA spikes locally suppress voltage-dependent Ca2+ signalling in rat pyramidal cell dendrites

PubMed Central

Manita, Satoshi; Miyazaki, Kenichi; Ross, William N

2011-01-01

Abstract Postsynaptic [Ca2+]i changes contribute to several kinds of plasticity in pyramidal neurons. We examined the effects of synaptically activated Ca2+ waves and NMDA spikes on subsequent Ca2+ signalling in CA1 pyramidal cell dendrites in hippocampal slices. Tetanic synaptic stimulation evoked a localized Ca2+ wave in the primary apical dendrites. The [Ca2+]i increase from a backpropagating action potential (bAP) or subthreshold depolarization was reduced if it was generated immediately after the wave. The suppression had a recovery time of 30–60 s. The suppression only occurred where the wave was generated and was not due to a change in bAP amplitude or shape. The suppression also could be generated by Ca2+ waves evoked by uncaging IP3, showing that other signalling pathways activated by the synaptic tetanus were not required. The suppression was proportional to the amplitude of the [Ca2+]i change of the Ca2+ wave and was not blocked by a spectrum of kinase or phosphatase inhibitors, consistent with suppression due to Ca2+-dependent inactivation of Ca2+ channels. The waves also reduced the frequency and amplitude of spontaneous, localized Ca2+ release events in the dendrites by a different mechanism, probably by depleting the stores at the site of wave generation. The same synaptic tetanus often evoked NMDA spike-mediated [Ca2+]i increases in the oblique dendrites where Ca2+ waves do not propagate. These NMDA spikes suppressed the [Ca2+]i increase caused by bAPs in those regions. [Ca2+]i increases by Ca2+ entry through voltage-gated Ca2+ channels also suppressed the [Ca2+]i increases from subsequent bAPs in regions where the voltage-gated [Ca2+]i increases were largest, showing that all ways of raising [Ca2+]i could cause suppression. PMID:21844002

Spatio-temporal characterization imaging of Ca2+ oscillations in rat hippocampal neurons

NASA Astrophysics Data System (ADS)

Zhang, Zhihong; Lu, Jinling; Zhou, Wei; Liu, Rengang; Zeng, Shaoqun; Luo, Qingming

2001-08-01

Ca2+ is the most common signal transduction element in cells and plays critical rolls in neuronal development and plasticity. Ca2+ signals encode information in their oscillation frequency or amplitude and response time to regular cellular function. In this study, in order to reveal the spatio-temporal characterization of Ca2+ oscillations in rat hippocampal neurons, two kinds of Ca2+ fluorescent probes, yellow cameleons 2.1 (YC2.1) and Fluo-3, were used to monitor the change of the intracellular free Ca2+ concentration (]Ca2+[i). Spontaneous Ca2+ oscillations and glutamate elicited Ca2+ oscillations were observed with multi-photon excitation laser scan microscope (MPELSM) and confocal laser scan microscope (CLSM). The observation showed that the spatio- temporal characterization of either spontaneous or glutamate provoked Ca2+ oscillations had difference between the neurites and somata in individual nerons, especially in some distal end of neurites. The result indicated that Ca2+ oscillations were most important signal transduction pattern in neuronal development and activation. The spatio-temporal characterization of difference of Ca2+ signals between the distal endo of neurites and the somata might be associated with the distribution of ionotropic receptor and metabotropic glutamate receptors, and Ca2+ response mechanism mediated by two kinds of glutamate receptor. Ca2+ signal elicited by glutamate in the distal end of neurites appeared more complex and generated faster than that in the somata. It was suggested that Ca2+ signal in glutamate stimulated hippacamal neurons first generated from the distal end of neurites and then transduted to the somata. The complicated Ca2+ signal characterization in the distal end of neurites might be associated with neuronal activitation, neurotransmitter releasing, and other functions of neurons.

Actin cytoskeleton modulates calcium signaling during maturation of starfish oocytes.

PubMed

Kyozuka, Keiichiro; Chun, Jong T; Puppo, Agostina; Gragnaniello, Gianni; Garante, Ezio; Santella, Luigia

2008-08-15

Before successful fertilization can occur, oocytes must undergo meiotic maturation. In starfish, this can be achieved in vitro by applying 1-methyladenine (1-MA). The immediate response to 1-MA is the fast Ca2+ release in the cell cortex. Here, we show that this Ca2+ wave always initiates in the vegetal hemisphere and propagates through the cortex, which is the space immediately under the plasma membrane. We have observed that alteration of the cortical actin cytoskeleton by latrunculin-A and jasplakinolide can potently affect the Ca2+ waves triggered by 1-MA. This indicates that the cortical actin cytoskeleton modulates Ca2+ release during meiotic maturation. The Ca2+ wave was inhibited by the classical antagonists of the InsP(3)-linked Ca2+ signaling pathway, U73122 and heparin. To our surprise, however, these two inhibitors induced remarkable actin hyper-polymerization in the cell cortex, suggesting that their inhibitory effect on Ca2+ release may be attributed to the perturbation of the cortical actin cytoskeleton. In post-meiotic eggs, U73122 and jasplakinolide blocked the elevation of the vitelline layer by uncaged InsP(3), despite the massive release of Ca2+, implying that exocytosis of the cortical granules requires not only a Ca2+ rise, but also regulation of the cortical actin cytoskeleton. Our results suggest that the cortical actin cytoskeleton of starfish oocytes plays critical roles both in generating Ca2+ signals and in regulating cortical granule exocytosis.

Role of Na+/Ca2+ Exchangers in Therapy Resistance of Medulloblastoma Cells.

PubMed

Pelzl, Lisann; Hosseinzadeh, Zohreh; Al-Maghout, Tamer; Singh, Yogesh; Sahu, Itishri; Bissinger, Rosi; Schmidt, Sebastian; Alkahtani, Saad; Stournaras, Christos; Toulany, Mahmoud; Lang, Florian

2017-01-01

Alterations of cytosolic Ca2+-activity ([Ca2+]i) are decisive in the regulation of tumor cell proliferation, migration and survival. Transport processes participating in the regulation of [Ca2+]i include Ca2+ extrusion through K+-independent (NCX) and/or K+-dependent (NCKX) Na+/Ca2+-exchangers. The present study thus explored whether medulloblastoma cells express Na+/Ca2+-exchangers, whether expression differs between therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells, and whether Na+/Ca2+-exchangers participate in the regulation of cell survival. In therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells transcript levels were estimated by RT-PCR, protein abundance by Western blotting, cytosolic Ca2+-activity ([Ca2+]i) from Fura-2-fluorescence, Na+/ Ca2+-exchanger activity from the increase of [Ca2+]i (Δ[Ca2+]i) and from whole cell current (Ica) following abrupt replacement of Na+ containing (130 mM) and Ca2+ free by Na+ free and Ca2+ containing (2 mM) extracellular perfusate as well as cell death from PI -staining and annexin-V binding in flow cytometry. The transcript levels of NCX3, NCKX2, and NCKX5, protein abundance of NCX3, slope and peak of Δ[Ca2+]i as well as Ica were significantly lower in therapy sensitive D283 than in therapy resistant UW228-3 medulloblastoma cells. The Na+/Ca2+-exchanger inhibitor KB-R7943 (10 µM) significantly blunted Δ[Ca2+]i, and augmented the ionizing radiation-induced apoptosis but did not significantly modify clonogenicity of medulloblastoma cells. Apoptosis was further enhanced by NCX3 silencing. Na+/Ca2+-exchanger activity significantly counteracts apoptosis but does not significantly affect clonogenicity after radiation of medulloblastoma cells. © 2017 The Author(s). Published by S. Karger AG, Basel.

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

DTIC Science & Technology

2010-04-01

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

Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

NASA Astrophysics Data System (ADS)

Park, Kyeongsoon; Lee, Ga Won

2011-10-01

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.

Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

PubMed Central

2011-01-01

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature. PMID:21974984

Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process.

PubMed

Park, Kyeongsoon; Lee, Ga Won

2011-10-05

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.

Contraction produced by intracellular injection of calcium, strontium, and barium in the single crayfish muscle fibers.

PubMed

Matsumura, M; Mashima, H

1976-01-01

Ca ions were ionophoretically injected through an intracellular microelectrode into the single muscle fiber of a crayfish, and the resulting contraction sphere was observed under a microscope and photographed with a movie camera. The minimum contraction produced by the threshold current involved usually three or four, sometimes two, sarcomers on both sides of the injecting pipette but contraction involving only one sarcomere was not observered. The rheobase of the Ca-injecting current was 3.2 X 10(-9) A. The strength-duration curves were determined for Ca-, Sr-, and Ba-injecting currents; all fitted a similar hyperbolic equation. The threshold amount of Ca above rheobasic injection was 2.1 X 10(-15)mol, and the ratios between threshold amounts were Ca: Sr: Ba=1: 1.9: 3.0. The effects of Ca and Sr were additive for the contraction. More current was required for the Ca-injection to produce the contraction in the K-depolarized-or 15mM-procaine-treated muscle, although less current was sufficient for the muscle treated with 0.5-1.0 mM of caffeine. The participation of the Ca-induced Ca release mechanism in the contraction produced by Ca injection and the role of Sr or Ba as a substitute for Ca were discussed.

UV and VUV photolysis vs. UV/H2O2 and VUV/H2O2, treatment for removal of clofibric acid from aqueous solution.

PubMed

Li, Wenzhen; Lu, Shuguang; Qiu, Zhaofu; Lin, Kuangfei

2011-07-01

Clofibric acid (CA), a metabolite of lipid regulators, was investigated in ultra-pure water and sewage treatment plant (STP) effluent at 10 degrees C under UV, vacuum UV (VUV), UV/H2O2 and VUV/H2O2 processes. The influences of NO3-, HCO3- and humic acid (HA) on CA photolysis in all processes were examined. The results showed that all the experimental data well fitted the pseudo-first-order kinetic model, and the apparent rate constant (k(ap)) and half-life time (t(1/2)) were calculated accordingly. Direct photolysis of CA through UV irradiation was the main process, compared with the indirect oxidation of CA due to the slight generation of hydroxyl radicals dissociated from water molecules under UV irradiation below 200 nm monochromatic wavelength emission. In contrast, indirect oxidation was the main CA degradation mechanism in UV/H2O2 and VUV/H2O2, and VUV/H2O2 was the most effective process for CA degradation. The addition of 20 mg L(-1) HA could significantly inhibit CA degradation, whereas, except for UV irradiation, the inhibitive effects of NO3- and HCO3- (1.0 x 10(-3) and 0.1 mol L(-1), respectively) on CA degradation were observed in all processes, and their adverse effects were more significant in UV/H2O2 and VUV/H2O2 processes, particularly at the high NO3- and HCO3- concentrations. The degradation rate decreased 1.8-4.9-fold when these processes were applied to a real STP effluent owing to the presence of complex constituents. Of the four processes, VUV/H2O2 was the most effective, and the CA removal efficiency reached over 99% after 40 min in contrast to 80 min in both the UV/H2O2 and VUV processes and 240 min in the UV process.

Role of calbindin-D9k in buffering cytosolic free Ca2+ ions in pig duodenal enterocytes.

PubMed

Schröder, B; Schlumbohm, C; Kaune, R; Breves, G

1996-05-01

1. The aim of the present study was to test whether the vitamin D-dependent Ca(2+)-binding protein calbindin-D9k could function as an important cytosolic Ca2+ buffer in duodenal enterocytes while facilitating transepithelial active transport of Ca2+ ions. For the investigations we used dual-wavelength, fluorescence ratio imaging, with fura-2 as the Ca(2+)-sensitive dye, to measure changes in cytosolic concentrations of free Ca2+ ions ([Ca2+]i) in isolated pig duodenal enterocytes affected by different cytosolic calbindin-D9k concentrations. 2. Epithelial cells were obtained from weaned piglets with normal calbindin-D9k concentrations (con-piglets), from piglets with low calbindin-D9k levels due to inherited calcitriol deficiency caused by defective renal 25-hydroxycholecalciferol D3-1 alpha-hydroxylase activity (def-piglets), and from piglets with reconstituted calbindin-D9k concentrations, i.e. def-animals treated with high doses of vitamin D3 which elevated plasma calcitriol levels by extrarenal production (def-D3-piglets). Basal levels of [Ca2+]i ranged between 170 and 205 nM and did not differ significantly between the groups. 3. After addition of 5 mM theophylline, the [Ca2+]i in enterocytes from con-piglets doubled during the 10 min incubation. This effect, however, was three times higher in enterocytes from def-piglets compared with those from con-piglets. Similar results were obtained after 4 min incubation of enterocytes from con- and def-piglets in the presence of 1 microM ionomycin. In preparations from def-D3-piglets, ionomycin-induced increases in [Ca2+]i were significantly lower compared with enterocytes from def-piglets and were not different from the control values. 4. From the results, substantial support is given for the hypothesis that one of the major functions of mucosal calbindin-D9k is the effective buffering of Ca2+ ions.

Role of calbindin-D9k in buffering cytosolic free Ca2+ ions in pig duodenal enterocytes.

PubMed Central

Schröder, B; Schlumbohm, C; Kaune, R; Breves, G

1996-01-01

1. The aim of the present study was to test whether the vitamin D-dependent Ca(2+)-binding protein calbindin-D9k could function as an important cytosolic Ca2+ buffer in duodenal enterocytes while facilitating transepithelial active transport of Ca2+ ions. For the investigations we used dual-wavelength, fluorescence ratio imaging, with fura-2 as the Ca(2+)-sensitive dye, to measure changes in cytosolic concentrations of free Ca2+ ions ([Ca2+]i) in isolated pig duodenal enterocytes affected by different cytosolic calbindin-D9k concentrations. 2. Epithelial cells were obtained from weaned piglets with normal calbindin-D9k concentrations (con-piglets), from piglets with low calbindin-D9k levels due to inherited calcitriol deficiency caused by defective renal 25-hydroxycholecalciferol D3-1 alpha-hydroxylase activity (def-piglets), and from piglets with reconstituted calbindin-D9k concentrations, i.e. def-animals treated with high doses of vitamin D3 which elevated plasma calcitriol levels by extrarenal production (def-D3-piglets). Basal levels of [Ca2+]i ranged between 170 and 205 nM and did not differ significantly between the groups. 3. After addition of 5 mM theophylline, the [Ca2+]i in enterocytes from con-piglets doubled during the 10 min incubation. This effect, however, was three times higher in enterocytes from def-piglets compared with those from con-piglets. Similar results were obtained after 4 min incubation of enterocytes from con- and def-piglets in the presence of 1 microM ionomycin. In preparations from def-D3-piglets, ionomycin-induced increases in [Ca2+]i were significantly lower compared with enterocytes from def-piglets and were not different from the control values. 4. From the results, substantial support is given for the hypothesis that one of the major functions of mucosal calbindin-D9k is the effective buffering of Ca2+ ions. PMID:8734984

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

Preterm infants fed nutrient-enriched formula until 6 months show improved growth and development.

PubMed

Jeon, Ga Won; Jung, Yu Jin; Koh, Sun Young; Lee, Yeon Kyung; Kim, Kyung Ah; Shin, Son Moon; Kim, Sung Shin; Shim, Jae Won; Chang, Yun Sil; Park, Won Soon

2011-10-01

The purpose of the present study was to determine the effect of feeding nutrient-enriched preterm formula to preterm infants until 6 months' corrected age (CA) on growth and development in the first 18 months of life. Very low-birthweight preterm infants were fed preterm formula until term (40 weeks CA). Infants were then assigned to one of three groups and were fed term formula until 6 months' CA (group 1, n= 29); preterm formula to 3 months' CA and then term formula to 6 months' CA (group 2, n= 30); or preterm formula until 6 months' CA (group 3, n= 31). Anthropometry was performed at term, 3, 6, 9, 12, 15, and at s18 months' CA. Mental and psychomotor development were assessed using the Bayley Scales of Infant Development II at 18 months' CA. Although body weight, length, head circumference and z score for CA at term in group 3 were significantly lower than those of groups 1 and 2, growth rates of these parameters were significantly higher in group 3 up to 18 months CA', as compared to groups 1 and 2. The mental developmental index and psychomotor developmental index of the Bayley test were not significantly different between the three groups. Very low-birthweight preterm infants fed nutrient-enriched preterm formula until 6 months' CA demonstrated significantly improved growth rates for bodyweight, length and head circumference, and comparable mental and psychomotor development throughout the first 18 months of life. © 2011 The Authors. Pediatrics International © 2011 Japan Pediatric Society.

Lithiation-induced zinc clustering of Zn 3, Zn 12, and Zn 18 units in Zintl-like Ca ~30Li 3+xZn 60-x (x=0.44-1.38)

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

Lin, Qisheng

2014-11-14

Zinc clusters are not common for binary intermetallics with relatively low zinc content, but this work shows that zinc clustering can be triggered by lithiation, as exemplified by Ca ~30Li 3+xZn 60-x, P6/mmm, Z = 1, which can be directly converted from CaZn 2. Two end members of the solid solution (x = 0.44 and 1.38) were established and structurally characterized by single-crystal X-ray diffraction analyses: Ca 30Li 3.44(6)Zn59.56(6), a = 15.4651(9) Å, c = 9.3898(3) Å; Ca 30.45(2)Li 4.38(6)Zn 58.62(6), a = 15.524(3) Å, c = 9.413(2) Å. The structures of Ca ~30Li 3+xZn 60-x feature a condensed anionicmore » network of Zn3 triangles, lithium-centered Zn12 icosahedra, and arachno-(Zn,Li)18 tubular clusters that are surrounded respectively by Ca 14, Ca 20, and Ca 30 polyhedra. These polyhedra share faces and form a clathrate-like cationic framework. The specific occupation of lithium in the structure is consistent with theoretical “coloring” analyses. Analysis by the linear muffin-tin orbital (LMTO) method within the atomic sphere approximation reveals that Ca ~30Li 3+xZn 60-x is a metallic, Zintl-like phase with an open-shell electronic structure. The contribution of Ca–Zn polar covalent interactions is about 41%.« less

Ultrasound-targeted microbubble destruction of calcium channel subunit α 1D siRNA inhibits breast cancer via G protein-coupled receptor 30.

PubMed

Ji, Yanlei; Han, Zhen; Shao, Limei; Zhao, Yuehuan

2016-10-01

Estrogen has been closely associated with breast cancer. Several studies reported that Ca2+ signal and Ca2+ channels act in estrogen-modulated non-genomic pathway of breast cancer, however little was revealed on the function of L-type Ca2+ channels. The L-type Ca2+ channel subunit α 1D, named Cav1.3 was found in breast cancer cells. We aimed to investigate the expression and activity of Cav1.3 in human breast cancer, and reveal the effect of estrogen in regulating the expression of Cav1.3. The qRT-PCR and western blotting were employed to show that Cav1.3 was highly expressed in breast cancer tissues. E2 exposure rapidly upregulated the expression of Cav1.3 in dosage- and time-dependent manner, and promoted Ca2+ influx. The silencing of G protein-coupled estrogen receptor 30 (GPER1/GPR30) using siRNA transfection inhibited the upregulation of Cav1.3 and Ca2+ influx induced by E2. Moreover, the inhibition of Cav1.3 by siRNA transfection suppressed E2-induced second peak of Ca2+ signal, the expression of p-ERK1/2, and the cell proliferation. Ultrasound-targeted microbubble destruction (UTMD) of Cav1.3 siRNA was used in MCF-7 cells in vitro and in the tumor xenografts mice in vivo. The application of UTMD significantly suppressed the tumor growth and promoted the survival rate. In conclusion, E2 upregulated the expression of Cav1.3 for Ca2+ influx to promote the expression of p-ERK1/2 for cell proliferation. The study confirmed that the mechanism of E2 inducing the expression of Cav1.3 through a non-genomic pathway, and highlighted that UTMD of Cav1.3 siRNA is a powerful promising technology for breast cancer gene therapy.

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

PubMed Central

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

2010-01-01

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

Peroxisome proliferation activation receptor alpha modulation of Ca2+-regulated exocytosis via arachidonic acid in guinea-pig antral mucous cells.

PubMed

Sawabe, Yukinori; Shimamoto, Chikao; Sakai, Akiko; Kuwabara, Hiroko; Saad, Adel H; Nakano, Takashi; Takitani, Kimitaka; Tamai, Hiroshi; Mori, Hiroshi; Marunaka, Yoshinori; Nakahari, Takashi

2010-08-01

Indomethacin (IDM, 10 microm), not aspirin (ASA; 10 microm), enhanced the Ca(2+)-regulated exocytosis stimulated by 1 microm acetylcholine (ACh) in guinea-pig antral mucous cells. Indomethacin inhibits prostaglandin G/H (PGG/H) and 15R-hydroperoxy-eicosatetraenoic acid (15R-HPETE) production from arachidonic acid (AA), while ASA inhibits PGG/H production but accelerates 15R-HPETE production. This suggests that IDM accumulates AA. Arachidonic acid (2 microm) enhanced Ca(2+)-regulated exocytosis in antral mucous cells to a similar extent to IDM. Moreover, a stable analogue of AA, arachidonyltrifluoromethyl ketone (AACOCF(3)), also enhanced Ca(2+)-regulated exocytosis, indicating that AA, not products from AA, enhances Ca(2+)-regulated exocytosis. We hypothesized that AA activates peroxisome proliferation activation receptor alpha (PPARalpha), because AA is a natural ligand for PPARalpha. A PPARalpha agonist (WY14643; 1 microm) enhanced Ca(2+)-regulated exocytosis, and a PPARalpha blocker (MK886; 50 microm) abolished the enhancement of Ca(2+)-regulated exocytosis induced by AA, IDM, AACOCF(3) and WY14643. Western blotting and immunohistochemical examinations demonstrated that PPARalpha exists in antral mucous cells. Moreover, MK886 decreased the frequency of Ca(2+)-regulated exocytosis activated by 1 microm ACh or 2 microm thapsigargin alone by 25-30%. Thus, ACh stimulates AA accumulation via an [Ca(2+)](i) increase, which activates PPARalpha, leading to enhancement of Ca(2+)-regulated exocytosis in antral mucous cells. A novel autocrine mechanism mediated via PPARalpha enhances Ca(2+)-regulated exocytosis in guinea-pig antral mucous cells.

Relationship between depolarization-induced force responses and Ca2+ content in skeletal muscle fibres of rat and toad.

PubMed

Owen, V J; Lamb, G D; Stephenson, D G; Fryer, M W

1997-02-01

1. The relationship between the total Ca2+ content of a muscle fibre and the magnitude of the force response to depolarization was examined in mechanically skinned fibres from the iliofibularis muscle of the toad and the extensor digitorum longus muscle of the rat. The response to depolarization in each skinned fibre was assessed either at the endogenous level of Ca2+ content or after depleting the fibre of Ca2+ to some degree. Ca2+ content was determined by a fibre lysing technique. 2. In both muscle types, the total Ca2+ content could be reduced from the endogenous level of approximately 1.3 mmol l-1 (expressed relative to intact fibre volume) to approximately 0.25 mmol l-1 by either depolarization or caffeine application in the presence of Ca2+ chelators, showing that the great majority of the Ca2+ was stored in the sarcoplasmic reticulum (SR). Chelation of Ca2+ in the transverse tubular (T-) system, either by exposure of fibres to EGTA before skinning or by permeabilizing the T-system with saponin after skinning, reduced the lower limit of Ca2+ content to < or = 0.12 mmol l-1, indicating that 10-20% of the total fibre Ca2+ resided in the T-system. 3. In toad fibres, both the peak and the area (i.e. time integral) of the force response to depolarization were reduced by any reduction in SR Ca2+ content, with both decreasing to zero in an approximately linear manner as the SR Ca2+ content was reduced to < 15% of the endogenous level. In rat fibres, the peak size of the force response was less affected by small decreases in SR content, but both the peak and area of the response decreased to zero with greater depletion. In partially depleted toad fibres, inhibition of SR Ca2+ uptake potentiated the force response to depolarization almost 2-fold. 4. The results show that in this skinned fibre preparation: (a) T-system depolarization and caffeine application can each virtually fully deplete the SR of Ca2+, irrespective of any putative inhibitory effect of SR depletion on channel activation; (b) all of the endogenous level of SR Ca2+ must be released in order to produce a maximal response to depolarization; and (c) a substantial part (approximately 40%) of the Ca2+ released by a depolarization is normally taken back into the SR before it can contribute to force production.

Relationship between depolarization-induced force responses and Ca2+ content in skeletal muscle fibres of rat and toad.

PubMed Central

Owen, V J; Lamb, G D; Stephenson, D G; Fryer, M W

1997-01-01

1. The relationship between the total Ca2+ content of a muscle fibre and the magnitude of the force response to depolarization was examined in mechanically skinned fibres from the iliofibularis muscle of the toad and the extensor digitorum longus muscle of the rat. The response to depolarization in each skinned fibre was assessed either at the endogenous level of Ca2+ content or after depleting the fibre of Ca2+ to some degree. Ca2+ content was determined by a fibre lysing technique. 2. In both muscle types, the total Ca2+ content could be reduced from the endogenous level of approximately 1.3 mmol l-1 (expressed relative to intact fibre volume) to approximately 0.25 mmol l-1 by either depolarization or caffeine application in the presence of Ca2+ chelators, showing that the great majority of the Ca2+ was stored in the sarcoplasmic reticulum (SR). Chelation of Ca2+ in the transverse tubular (T-) system, either by exposure of fibres to EGTA before skinning or by permeabilizing the T-system with saponin after skinning, reduced the lower limit of Ca2+ content to < or = 0.12 mmol l-1, indicating that 10-20% of the total fibre Ca2+ resided in the T-system. 3. In toad fibres, both the peak and the area (i.e. time integral) of the force response to depolarization were reduced by any reduction in SR Ca2+ content, with both decreasing to zero in an approximately linear manner as the SR Ca2+ content was reduced to < 15% of the endogenous level. In rat fibres, the peak size of the force response was less affected by small decreases in SR content, but both the peak and area of the response decreased to zero with greater depletion. In partially depleted toad fibres, inhibition of SR Ca2+ uptake potentiated the force response to depolarization almost 2-fold. 4. The results show that in this skinned fibre preparation: (a) T-system depolarization and caffeine application can each virtually fully deplete the SR of Ca2+, irrespective of any putative inhibitory effect of SR depletion on channel activation; (b) all of the endogenous level of SR Ca2+ must be released in order to produce a maximal response to depolarization; and (c) a substantial part (approximately 40%) of the Ca2+ released by a depolarization is normally taken back into the SR before it can contribute to force production. PMID:9051571

Assembly and Properties of Heterobimetallic CoII/III/CaII Complexes with Aquo and Hydroxo Ligands

PubMed Central

Lacy, David C.; Park, Young Jun; Ziller, Joseph W.; Yano, Junko; Borovik, A. S.

2012-01-01

The use of water as a reagent in redox-driven reactions is advantageous because it is abundant and environmentally compatible. The conversion of water to dioxygen in photosynthesis illustrates one example, in which a redox-inactive CaII ion and four manganese ions are required for function. In this report we describe the stepwise formation of two new heterobimetallic complexes containing CoII/III and CaII ions, and either hydroxo or aquo ligands. The preparation of a 4-coordinate CoII synthon was achieved with the tripodal ligand, N,N′,N″-[2,2′,2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido, [MST]3−. Water binds to [CoIIMST]− to form the 5-coordinate [CoIIMST(OH2)]− complex that was used to prepare the CoII/CaII complex [CoIIMST(μ-OH2)CaII⊂15-crown-5(OH2)]+ ([CoII(μ-OH2)CaIIOH2]+). [CoII(μ-OH2)CaOH2]+ contained two aquo ligands, one bonded to the CaII ion and one bridging between the two metal ions and thus represents an unusual example of a heterobimetallic complex containing 2 aquo ligands spanning different metal ions. Both aquo ligands formed intramolecular hydrogen bonds with the [MST]3− ligand. [CoIIMST(OH2)]− was oxidized to form [CoIIIMST(OH2)] that was further converted to [CoIIIMST(μ-OH)CaII⊂15-crown-5]+ ([CoIII(μ-OH)CaII]+) in the presence of base and CaIIOTf2/15-crown-5. [CoIII(μ-OH)CaII]+ was also synthesized from the oxidation of [CoIIMST]− with PhIO in the presence of CaIIOTf2/15-crown-5. Allowing [CoIII(μ-OH)CaII]+ to react with diphenylhydrazine afforded [CoII(μ-OH2)CaIIOH2]+ and azobenzene. Additionally, the characterization of [CoIII(μ-OH)CaII]+ provides another formulation for the previously reported CoIV–oxo complex, [(TMG3tren)CoIV(μ-O)ScIII(OTf)3]2+ to one that instead could contain a CoIII–OH unit. PMID:22998407

Mechanisms of reoxygenation-induced calcium overload in cultured chick embryo heart cells

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

Murphy, J.G.; Smith, T.W.; Marsh, J.D.

1988-06-01

We examined mechanisms by which Ca enters cultured myocardial cells during posthypoxic reoxygenation. Monolayer cultures of chick embryo ventricular cells were prepared from hearts 10 days in ovo. Cells were exposed to hypoxic conditions (PO/sub 2/ less than 1.5 Torr), and /sup 45/Ca uptake during subsequent reoxygenation was then examined in the absence and presence of modulators of Ca channel-dependent Ca entry and Na-Ca exchange. Modulation of Ca entry by free radical-scavenging enzymes was also examined. Hypoxia for 120 min followed by reoxygenation increased Ca content from 1.9 to 6.1 nmol/mg protein (P less than 0.05) at 30 min. Verapamilmore » (10(-5) M) added before reoxygenation reduced Ca overload to 3.1 +/- 0.2 nmol/mg protein (P less than 0.05), but both verapamil and BAY K 8644 were without effect on modulating Ca entry if added 30 min after reoxygenation. /sup 24/Na content of cells increased from 70 nmol/mg protein in control cells to 157 nmol/mg protein (P less than 0.05) after hypoxia and reoxygenation, favoring Ca entry via Na-Ca exchange. Dichlorobenzamil significantly ameliorated reoxygenation-induced Ca overload, as did catalase and superoxide dismutase. We conclude that reoxygenation-induced Ca overload is unlikely to occur via the Ca channel. It occurs in part via Na-Ca exchange and is substantially ameliorated by enzymatic O/sub 2/ free radical scavengers.« less

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

PubMed Central

Chang, Chi-Lun; Liou, Jen

2016-01-01

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

Effect of 1,25-dihydroxyvitamin D3 on plasma concentrations of calcium-binding protein in normal and rachitic (vitamin D-dependent rickets type I) pigs.

PubMed

Maunder, E M; Pillay, A V; Care, A D

1987-10-01

An i.v. injection of calcitriol (1,25-(OH)2D3) had no effect within 2.5 h on plasma concentrations of calbindin-D9K (vitamin D-induced calcium-binding protein; CaBP) in hypocalcaemic pigs with inherited vitamin D-dependent rickets type I or in their normocalcaemic siblings or half-siblings. Three days later the plasma concentration of CaBP had doubled in the hypocalcaemic pigs, but was unaltered in the normocalcaemic siblings and half-siblings. Following daily i.v. injections of 1,25-(OH)2D3 for a further 5 days (days 4-8) plasma concentrations of CaBP increased in both the hypocalcaemic (days 4-8) and normocalcaemic (day 8) pigs, the effect being more rapid and greater in the hypocalcaemic 1,25-(OH)2D3-deficient animals. An i.v. injection of 1,25-(OH)2D3 to pure Yucatan pigs also had no effect on plasma concentrations of CaBP within 1.5 h, but in the following 1 h there was some indication of an increase in plasma CaBP levels. In contrast to the normal pigs, insulin-induced hypoglycaemia did not lead to a peak in plasma CaBP concentrations in the hypocalcaemic pigs. There was also no change in the plasma concentrations of 1,25-(OH)2D3 associated with the peak in plasma CaBP following insulin-induced hypoglycaemia in normocalcaemic pigs. These results suggest that changes in plasma concentrations of 1,25-(OH)2D3 are not directly involved in mediating the increase in plasma CaBP which follows hypoglycaemia induced by insulin in normal pigs, although 1,25-(OH)2D3 probably plays a permissive role.

Synthesis of the new compound CaFe(CO 3) 2 and experimental constraints on the (Ca,Fe)CO 3 join

NASA Astrophysics Data System (ADS)

Davidson, Paula M.; Symmes, Gregory H.; Cohen, Barbara A.; Reeder, Richard J.; Lindsley, Donald H.

1993-12-01

Synthesis of the new (disordered) compound CaFe(CO 3) 2 has been achieved with the use of Fe-substituted CaCO 3(Cc ss) + Ca-substituted FeCO 3(Sid ss) as starting materials, and high CO 2 pressures. High pressure (20-30 kbar) is needed to stabilize FeCO 3 to sufficiently high temperatures for disordered CaFe(CO 3) 2 to form. Experiments provide reversed compositions of coexisting disordered phases in the CaFe join and locate the solvus temperature for CaFe(C) 3) 2 between 815 and 845°C at 30 kbars. Calculated phase relations predict that the stability of ordered CaFe(CO 3) 2 is limited to T < ˜450°C by the breakdown to Cc ss + Sid ss. A comparison of the unit-cell volume measured for disordered CaFe(CO 3) 2 vs. that estimated for ordered CaFe(CO 3) 2 suggests that increasing pressure stabilizes the disordered phase.

Rational design of a conformation-switchable Ca2+- and Tb3+-binding protein without the use of multiple coupled metal-binding sites.

PubMed

Li, Shunyi; Yang, Wei; Maniccia, Anna W; Barrow, Doyle; Tjong, Harianto; Zhou, Huan-Xiang; Yang, Jenny J

2008-10-01

Ca2+, as a messenger of signal transduction, regulates numerous target molecules via Ca2+-induced conformational changes. Investigation into the determinants for Ca2+-induced conformational change is often impeded by cooperativity between multiple metal-binding sites or protein oligomerization in naturally occurring proteins. To dissect the relative contributions of key determinants for Ca2+-dependent conformational changes, we report the design of a single-site Ca2+-binding protein (CD2.trigger) created by altering charged residues at an electrostatically sensitive location on the surface of the host protein rat Cluster of Differentiation 2 (CD2).CD2.trigger binds to Tb3+ and Ca2+ with dissociation constants of 0.3 +/- 0.1 and 90 +/- 25 microM, respectively. This protein is largely unfolded in the absence of metal ions at physiological pH, but Tb3+ or Ca2+ binding results in folding of the native-like conformation. Neutralization of the charged coordination residues, either by mutation or protonation, similarly induces folding of the protein. The control of a major conformational change by a single Ca2+ ion, achieved on a protein designed without reliance on sequence similarity to known Ca2+-dependent proteins and coupled metal-binding sites, represents an important step in the design of trigger proteins.

Carbon dioxide "trapped" in a β-carbonic anhydrase

DOE PAGES

Aggarwal, Mayank; Chua, Teck Khiang; Pinard, Melissa A.; ...

2015-10-12

Carbonic anhydrases (CAs) are enzymes that catalyze the hydration/ dehydration of CO 2/HCO 3 - with rates approaching diffusion-controlled limits (k cat/K M ~ 10 8 M –1s –1). Here, this family of enzymes has evolved disparate protein folds that all perform the same reaction at near catalytic perfection. Presented here is a structural study of a beta-CA (psCA3) expressed in Pseudomonas aeruginosa, in complex with CO 2, using pressurized cryocooled crystallography. The structure has been refined to 1.6 angstrom resolution with R cryst and R free values of 17.3 and 19.9%, respectively, and is compared with the α-CA, humanmore » CA isoform II (hCA II), the only other CA to have CO 2, captured in its active site. Despite the lack of structural similarity between psCA3 and hCA II, the CO 2, binding orientation relative to the zinc-bound solvent is identical. In addition, a second CO 2, binding site was located at the dimer interface of psCA3. Interestingly, all β-CAs function as dirners or higher-order oligomeric states, and the CO 2, bound at the interface may contribute to the allosteric nature of this family of enzymes or may be a convenient alternative binding site as this pocket has been previously shown to be a promiscuous site for a variety of ligands, including bicarbonate, sulfate, and phosphate ions.« less

Activation of the Ca2+-sensing receptor increases renal claudin-14 expression and urinary Ca2+ excretion

PubMed Central

Dimke, Henrik; Desai, Prajakta; Borovac, Jelena; Lau, Alyssa; Pan, Wanling; Alexander, R. Todd

2016-01-01

Kidney stones are a prevalent clinical condition imposing a large economic burden on the health-care system. Hypercalciuria remains the major risk factor for development of a Ca2+-containing stone. The kidney’s ability to alter Ca2+ excretion in response to changes in serum Ca2+ is in part mediated by the Ca2+-sensing receptor (CaSR). Recent studies revealed renal claudin-14 (Cldn14) expression localized to the thick ascending limb (TAL) and its expression to be regulated via the CaSR. We find that Cldn14 expression is increased by high dietary Ca2+ intake and by elevated serum Ca2+ levels induced by prolonged 1,25-dihydroxyvitamin D3 administration. Consistent with this, activation of the CaSR in vivo via administration of the calcimimetic cinacalcet hydrochloride led to a 40-fold increase in Cldn14 mRNA. Moreover, overexpression of Cldn14 in two separate cell culture models decreased paracellular Ca2+ flux by preferentially decreasing cation permeability, thereby increasing transepithelial resistance. These data support the existence of a mechanism whereby activation of the CaSR in the TAL increases Cldn14 expression, which in turn blocks the paracellular reabsorption of Ca2+. This molecular mechanism likely facilitates renal Ca2+ losses in response to elevated serum Ca2+. Moreover, dys-regulation of the newly described CaSR-Cldn14 axis likely contributes to the development of hypercalciuria and kidney stones. PMID:23283989

Characterizing Pyroxene Reaction Space in Calcium-Aluminum Rich Inclusions: Oxidation During CAI Rim Formation

NASA Astrophysics Data System (ADS)

Dyl, K. A.; Young, E. D.

2009-12-01

We define the reaction space that controls changes in pyroxene composition in CAIs and Wark-Lovering (WL) rims in an oxidizing solar nebula. Ti-rich pyroxenes in CAIs record a sub-solar oxygen fugacity (Ti3+/Ti4+~1.5). WL rim pyroxenes in the CAI Leoville 144A have a distinctly lower oxidation state.This difference supports WL rim condensation in an environment of increasing O2(g) and Mg(g) (Simon et al. 2005). We used the following phase components to identify four linearly independent reactions (Thompson 1982): diopside, CaTs (Al2Mg-1Si-1), T3 (Ti3+AlMg-1Si-1), T4 (Ti4+Al2Mg-1Si-2), En (MgCa-1), perovskite, O(g), Mg(g), SiO(g), and Ca(g). Compositional variation in this system is dominated by two reactions. The first is oxidation of Ti3+ via reaction with O and Mg in the gas phase: 1.5 O(g) + Mg(g) → ¼ Di + [Ti4+Mg3/4Ti3+-1Ca-1/4Si-1/2] (1). Pyroxene is produced and En is introduced. The second reaction (2) is perovskite formation. It is observed in the WL rim of Leoville 144A, and experiments confirm that an elevated Ti component converts pyroxene to perovskite(Gupta et al. 1973). MgCa-1 is the third linearly independent reaction (3). They combine to give: ½ Di + x Ca(g)→ x Mg(g)+ Pv + [Mg1/2-xSiTi4+-1Ca-1/2+x](2,3). Unlike (1), pyroxene is consumed in this reaction. The parameter x defines the extent of Mg-Ca exchange. When x > 0.5, WL rim formation occurs in an environment where Mg is volatile and Ca condenses. The reaction space defined by reactions (1) and (2,3) describes the transition from CAI interior to WL rims. WL rim pyroxene Ti contents, [CaTs], and Ca < 1 pfu are all explained in this space. The fourth linearly independent reaction is SiO(g):1/8 Di + ¼ Mg(g)→ ¾ SiO(g) + [Mg3/8Ca1/8Ti4+Ti3+-1Si-1/2](4). Silica reduction forms Ti4+, releasing SiO(g). (4) does not describe the oxidation of Ti3+ in WL rim pyroxene, but (1) - (4) results in En formation directly from the gas phase. This may explain WL rim analyses that have Si contents in excess of those predicted from reactions (1) and (2,3). Simon et al. (2005) EPSL 41, 272-283; Thompson (1982)Rev. Min. 10, 33-52; Gupta et al. (1973) Contr. Mineral. Petrol. 41, 333-344 Reaction space for CAI pyroxene. Pyroxenes plotted using titanium contents.

CRAC channel activity in C. elegans is mediated by Orai1 and STIM1 homologues and is essential for ovulation and fertility

PubMed Central

Lorin-Nebel, Catherine; Xing, Juan; Yan, Xiaohui; Strange, Kevin

2007-01-01

The Ca2+ release-activated Ca2+ (CRAC) channel is a plasma membrane Ca2+ entry pathway activated by endoplasmic reticulum (ER) Ca2+ store depletion. STIM1 proteins function as ER Ca2+ sensors and regulate CRAC channel activation. Recent studies have demonstrated that CRAC channels are encoded by the human Orai1 gene and a homologous Drosophila gene. C. elegans intestinal cells express a store-operated Ca2+ channel (SOCC) regulated by STIM-1. We cloned a full-length C. elegans cDNA that encodes a 293 amino acid protein, ORAI-1, homologous to human and Drosophila Orai1 proteins. ORAI-1 GFP reporters are co-expressed with STIM-1 in the gonad and intestine. Inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ signalling regulates C. elegans gonad function, fertility and rhythmic posterior body wall muscle contraction (pBoc) required for defecation. RNA interference (RNAi) silencing of orai-1 expression phenocopies stim-1 knockdown and causes sterility and prevents intestinal cell SOCC activation, but has no effect on pBoc or intestinal Ca2+ signalling. Orai-1 RNAi suppresses pBoc defects induced by intestinal expression of a STIM-1 Ca2+-binding mutant, indicating that the proteins function in a common pathway. Co-expression of stim-1 and orai-1 cDNAs in HEK293 cells induces large inwardly rectifying cation currents activated by ER Ca2+ depletion. The properties of this current recapitulate those of the native SOCC current. We conclude that C. elegans expresses bona fide CRAC channels that require the function of Orai1- and STIM1-related proteins. CRAC channels thus arose very early in animal evolution. In C. elegans, CRAC channels do not play obligate roles in all IP3-dependent signalling processes and ER Ca2+ homeostasis. Instead, we suggest that CRAC channels carry out highly specialized and cell-specific signalling roles and that they may function as a failsafe mechanism to prevent Ca2+ store depletion under pathophysiological and stress conditions. PMID:17218360

46 CFR 7.125 - Point Vincente, CA to Point Conception, CA.

Code of Federal Regulations, 2010 CFR

2010-10-01

... BOUNDARY LINES Pacific Coast § 7.125 Point Vincente, CA to Point Conception, CA. (a) A line drawn from Redondo Beach East Jetty Light “2” to Redondo Beach West Jetty Light “3”. (b) A line drawn from Marina Del... 46 Shipping 1 2010-10-01 2010-10-01 false Point Vincente, CA to Point Conception, CA. 7.125...

46 CFR 7.125 - Point Vincente, CA to Point Conception, CA.

Code of Federal Regulations, 2012 CFR

2012-10-01

... BOUNDARY LINES Pacific Coast § 7.125 Point Vincente, CA to Point Conception, CA. (a) A line drawn from Redondo Beach East Jetty Light “2” to Redondo Beach West Jetty Light “3”. (b) A line drawn from Marina Del... 46 Shipping 1 2012-10-01 2012-10-01 false Point Vincente, CA to Point Conception, CA. 7.125...

46 CFR 7.125 - Point Vincente, CA to Point Conception, CA.

Code of Federal Regulations, 2013 CFR

2013-10-01

... BOUNDARY LINES Pacific Coast § 7.125 Point Vincente, CA to Point Conception, CA. (a) A line drawn from Redondo Beach East Jetty Light “2” to Redondo Beach West Jetty Light “3”. (b) A line drawn from Marina Del... 46 Shipping 1 2013-10-01 2013-10-01 false Point Vincente, CA to Point Conception, CA. 7.125...

46 CFR 7.125 - Point Vincente, CA to Point Conception, CA.

Code of Federal Regulations, 2014 CFR

2014-10-01

... BOUNDARY LINES Pacific Coast § 7.125 Point Vincente, CA to Point Conception, CA. (a) A line drawn from Redondo Beach East Jetty Light “2” to Redondo Beach West Jetty Light “3”. (b) A line drawn from Marina Del... 46 Shipping 1 2014-10-01 2014-10-01 false Point Vincente, CA to Point Conception, CA. 7.125...

46 CFR 7.125 - Point Vincente, CA to Point Conception, CA.

Code of Federal Regulations, 2011 CFR

2011-10-01

... BOUNDARY LINES Pacific Coast § 7.125 Point Vincente, CA to Point Conception, CA. (a) A line drawn from Redondo Beach East Jetty Light “2” to Redondo Beach West Jetty Light “3”. (b) A line drawn from Marina Del... 46 Shipping 1 2011-10-01 2011-10-01 false Point Vincente, CA to Point Conception, CA. 7.125...